This document summarizes research on the electrical and thermal properties of a natural polymetal ore from Egypt after sintering treatments. The ore contains zinc, lead, iron, calcium, magnesium, and silica. Samples were sintered at temperatures from 573 to 1273 K for 4 hours. Analysis found the sintered ore exhibited semiconducting behavior with increasing electrical conductivity at higher temperatures. Electron hopping between iron ions was identified as the main conduction mechanism. Higher sintering temperatures promoted the formation of magnetite, increasing crystallinity and improving electrical properties for potential thermotechnological applications.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
— Heat exchangers included in air conditioning systems for aircraft are produced by brazing stamped thin alloys sheets made of nickel-based alloys, Alloy 600 and Ni 201, or stainless steel, AISI 444. Separation metal sheets and locking bars of Alloy 625 are used to complete the system. The brazing filler metal, mainly composed of nickel, manganese, silicon and copper, is referred as BNi-8. In order to control brazing process, a good knowledge of both the brazing filler metal metallurgical behavior and of the interaction with the base metal is essential. The study of the brazing filler metal melting behavior in itself reveals that the melting point is highly dependent on the chemical composition and especially on silicon content. Microstructures analysis showed the presence of several phases with significant differences in terms of mechanical properties at a small scale which could induce local embrittlement. Interactions between the brazing filler metal and the different alloys constitutive of the assembly induce chemical composition evolutions related to the local configuration of the assembly. Dissolution and interdiffusion processes as well as chemical exchanges with the furnace environment occur. Finally, due to this set of phenomena, significant brazing defects can affect the mechanical integrity of the component.
Effects of thermo mechanical simulation on the corrosion of steelJaideep Adusumelli
Performed numerous stress-strain elasticity tests along with impact test under controlled temperature and stress factors.
then the corrosion properties were studied based on the microstructures and corrosion current graphs.
A facile method to prepare CdO-Mn3O4 nanocompositeIOSR Journals
CdO-Mn3O4 nanocomposite has been prepared by a simple solvothermal method using a domestic microwave oven. Cadmium acetate, manganese acetate and urea were used as the precursors and ethylene glycol as the solvent. The as-prepared sample was annealed for 1 hour in each case at different temperatures, viz. 100, 200 and 300°C. The as-prepared and annealed samples were characterized by X-ray diffraction and scanning electron microscopic analyses. Results indicate that annealing at 300°C is required to get the sample with high phase purity and homogeneity. The present study indicates that the method adopted can be considered as an economical and scalable one to prepare the proposed nanocomposite with reduced size, phase purity and homogeneity.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
— Heat exchangers included in air conditioning systems for aircraft are produced by brazing stamped thin alloys sheets made of nickel-based alloys, Alloy 600 and Ni 201, or stainless steel, AISI 444. Separation metal sheets and locking bars of Alloy 625 are used to complete the system. The brazing filler metal, mainly composed of nickel, manganese, silicon and copper, is referred as BNi-8. In order to control brazing process, a good knowledge of both the brazing filler metal metallurgical behavior and of the interaction with the base metal is essential. The study of the brazing filler metal melting behavior in itself reveals that the melting point is highly dependent on the chemical composition and especially on silicon content. Microstructures analysis showed the presence of several phases with significant differences in terms of mechanical properties at a small scale which could induce local embrittlement. Interactions between the brazing filler metal and the different alloys constitutive of the assembly induce chemical composition evolutions related to the local configuration of the assembly. Dissolution and interdiffusion processes as well as chemical exchanges with the furnace environment occur. Finally, due to this set of phenomena, significant brazing defects can affect the mechanical integrity of the component.
Effects of thermo mechanical simulation on the corrosion of steelJaideep Adusumelli
Performed numerous stress-strain elasticity tests along with impact test under controlled temperature and stress factors.
then the corrosion properties were studied based on the microstructures and corrosion current graphs.
A facile method to prepare CdO-Mn3O4 nanocompositeIOSR Journals
CdO-Mn3O4 nanocomposite has been prepared by a simple solvothermal method using a domestic microwave oven. Cadmium acetate, manganese acetate and urea were used as the precursors and ethylene glycol as the solvent. The as-prepared sample was annealed for 1 hour in each case at different temperatures, viz. 100, 200 and 300°C. The as-prepared and annealed samples were characterized by X-ray diffraction and scanning electron microscopic analyses. Results indicate that annealing at 300°C is required to get the sample with high phase purity and homogeneity. The present study indicates that the method adopted can be considered as an economical and scalable one to prepare the proposed nanocomposite with reduced size, phase purity and homogeneity.
Surfactant-assisted Hydrothermal Synthesis of Ceria-Zirconia Nanostructured M...IOSR Journals
CeO2–ZrO2 oxides were prepared by the surfactant-templated method using cetyl trimethyl ammonium bromide (CTAB) as template and modified with chromium nitrate. These were characterized by XRD, FT-IR, TEM, SEM, BET and TPD-CO2. The XRD data showed that as prepared CeO2-ZrO2 powder particles have single phase cubic fluorite structure. HRTEM shows mesoscopic ordering. Average particle size is 12-13 nm as calculated from particle histogram. The nitrogen adsorption/desorption isotherm were classified to be type IV isotherm, typical of mesoporous material. The presence of uni-modal mesopores are confirmed by the pore size distribution which shows pore distribution at around 60 A°. Catalytic activity was studied towards liquid-phase oxidation of benzene.
Sinthesis and Properties of Marble-Like Glass-Ceramics Using of Ash from Ther...Scientific Review SR
Color marble-like glass-ceramic materials were obtained through thermal treatment of glasses of the system CaO-Al2O3-SiO2 by using natural materials with the introduction of waste materials - ash from thermal power plants (TPP). The melting of the glass batch was in corundum crucibles at 1450oC with an isothermal hold of 60 min. The glasses obtained was fritted in distilled water and dried for 6 hours at 100oC, then completely crushed and divided into fractions with grain size of 0.8 mm, 1.0 mm, 2 mm, 2.5 mm and over 2.5 mm. It was found that the use of ash from TPP lead to higher values of degree of transformation (crystallization) than using base composition. Values of Avramy parameter’s in the range n=1,0 ÷ 1,6 are showed that crystallization of the glass frit is largely heterogeneous and crystal growing starts from the surface. The introduction of ash from TPP to native glasses carry out to significant reduction of energy of crystallization by Ес=289 kJ/mol to Ec=221 kJ/mol. The glass-ceramic materials were obtained through a one stage crystallization - 1050÷1070оС and an isothermal hold of 60 min., colored white, yellow brown to dark brown. The main crystalline phase in glass-ceramics is β-vollastonite with needle habit, size of crystals - ĺ = 40 ÷ 120 μm and d <5 μm in quantities 37 ÷ 42%. As secondary phases depending on the amount of ash have been identified - the anorthite, gehlenite and α-quartz with prismatic habit were appeared. The obtained glass-ceramic materials have a marble-like effect and technical parameters compared with natural granite and marble and have higher values of density, micro hardness, speed grinding, bending strength and chemical resistance. That’s why they can be used in construction such as lining materials.
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
Study the effect of Mn2+ ions on the ac electrical properties of some iron do...IJRES Journal
Oxide glasses doped with transition metal ions are of high interest because of their variant applications in both science and technology fields. However, the normal melt quench method have used to prepared some iron doped phosphate glasses according the following molecular formula: (65-x) mol% P2O5 - 20 mol% Na2O - 15 mol% Fe2O3 - x mol% MnO, Where x= 0, 5,10, 20, 25. The room temperature Mössbauer Effect ME Spectra used to characterized the glassy state homogeneity of these glasses. ME spectra show, for all glasses, no magnetic field participate which mean good glassy state formation. The ac electrical transport properties were also measured, as function of temperature up to 500k. It was found that the ac conductivity increased with the gradual increase of Mn2+ cations, while the electrical activation energy decreased.
MICROSTRUCTURAL CHARACTERIZATION AND HOT EROSION BEHAVIOR OF CRC-NICR COATED ...IAEME Publication
Erosion behavior of the High Velocity Oxygen Fuel (HVOF) deposited CrC - NiCr coating on stainless steel was evaluated. Th e solid particle erosion stu dy was conducted using an air jet erosion test rig at a velocity 60m/sec and impingement angle 60 ° , 75 ° and 90 ° , on HVOF spray coated steel at 600 ° C. Microstructure, chemical composition, phases present in the coating on the steel substrate was studied by using Scanning Electron Microscope (SEM) and X - Ray Diffraction method. The Hardness is gradually increasing with increasing content of Cr 3 C 2 particles in all three samples. The erosion mechanism of coatings was also discussed and erosion rate is maximum at impingement angle 75 °
. One of the methods used to surface hardening of ductile iron is chilled cast iron. Chill as the fast cooling rate in the mold during solidification and chill thickness greatly affects the thickness of the hardness layer. The main material used is ductile iron, and the chill material is SS 304. Casting uses the sand casting method. Before pouring, the chill plate has been inserted onto the surface of the pattern that has been formed in the mold, then the chill plate is preheated at 700OC. Pouring was carried out at a melting temperature of 1400OC, and then cooled with argon and O2 sprays into the mold in solidification conditions at exactly 700OC. The results analyzed were the microstructure, hardness value, and the hardness of the thickness layer. This chill coolant will absorb heat very quickly and the Cr and Ni alloy will diffuse to the specimen surface to stabilize the ferrite and austenite phases in the final solidification. The particles on the hard surface have Ferro carbide M7C3, which is in the form of cementite and martensitic phases so that to categorized as white cast iron structure formed on the surface with an area around 1.5-3mm has a hardness of 61-65HRC. But in the center area is 31-49HRC
Characterization and Dielectric Study of Mihaliccik Tremoliteijtsrd
The natural tremolite Ca2Mg5Si8O22 OH 2 was obtained from Mihaliccik district of Eskisehir, Turkey 39.8787N 31.3806E . It is a part of the amphibole family of silicate minerals. All the phases were described by X ray diffraction XRD , energy dispersive spectroscopy EDXRF , Raman, and Fourier transform infrared spectroscopy FTIR . The natural tremolite specimen used in this study includes mostly 54.4 SiO2, 22.82 MgO, 15.04 CaO, and 1.45 Al2O3. The natural tremolite sample used for the present investigation was not pure. The impurity was calcite. The FTIR spectrum and the Raman spectrum were recorded for natural tremolite sample in the range of 4000 and 350 cm 1 and 4000 and 70 cm 1 at room temperature, respectively. The natural tremolite and fired tremolite samples were prepared for this investigation. Dielectric measurements were realized in the 3 kHz ' 1 MHz frequency region and at the room temperature by using HP4192A LF Impedance Analyzer. The dielectric parameters of the samples were obtained the conclusions of the study were explained and given to be used for further investigations in some industrial productions. Ertugrul Izci "Characterization and Dielectric Study of Mihaliccik Tremolite" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-1 , December 2019, URL: https://www.ijtsrd.com/papers/ijtsrd29671.pdf Paper URL: https://www.ijtsrd.com/engineering/mineral-and-metallurgical-engineering/29671/characterization-and-dielectric-study-of-mihaliccik-tremolite/ertugrul-izci
ELECTRODEPOSITION OF TITANIUM AND ITS DIOXIDE FROM ILMENITE Al Baha University
The aim of the present work was to develop a simple and rapid electrolytic extraction process of titanium [l-3] and its dioxide from the ilmenite ore of the Eastern Desert. The ore mother liquor used for the electrolysis process is either produced by direct leaching with 98% H,SO, (S/L = 1 : 15), 35% HCl (S/L = 1: 20) and alkaline digestion with caustic soda in a ball-mill autoclave at 175°C under a pressure of 9.5 kg cmP2, or it is prepared through the fusion method using NaOH or Na,S,O, separately as fluxes at 600-700°C.
EXPERIMENTAL
Surfactant-assisted Hydrothermal Synthesis of Ceria-Zirconia Nanostructured M...IOSR Journals
CeO2–ZrO2 oxides were prepared by the surfactant-templated method using cetyl trimethyl ammonium bromide (CTAB) as template and modified with chromium nitrate. These were characterized by XRD, FT-IR, TEM, SEM, BET and TPD-CO2. The XRD data showed that as prepared CeO2-ZrO2 powder particles have single phase cubic fluorite structure. HRTEM shows mesoscopic ordering. Average particle size is 12-13 nm as calculated from particle histogram. The nitrogen adsorption/desorption isotherm were classified to be type IV isotherm, typical of mesoporous material. The presence of uni-modal mesopores are confirmed by the pore size distribution which shows pore distribution at around 60 A°. Catalytic activity was studied towards liquid-phase oxidation of benzene.
Sinthesis and Properties of Marble-Like Glass-Ceramics Using of Ash from Ther...Scientific Review SR
Color marble-like glass-ceramic materials were obtained through thermal treatment of glasses of the system CaO-Al2O3-SiO2 by using natural materials with the introduction of waste materials - ash from thermal power plants (TPP). The melting of the glass batch was in corundum crucibles at 1450oC with an isothermal hold of 60 min. The glasses obtained was fritted in distilled water and dried for 6 hours at 100oC, then completely crushed and divided into fractions with grain size of 0.8 mm, 1.0 mm, 2 mm, 2.5 mm and over 2.5 mm. It was found that the use of ash from TPP lead to higher values of degree of transformation (crystallization) than using base composition. Values of Avramy parameter’s in the range n=1,0 ÷ 1,6 are showed that crystallization of the glass frit is largely heterogeneous and crystal growing starts from the surface. The introduction of ash from TPP to native glasses carry out to significant reduction of energy of crystallization by Ес=289 kJ/mol to Ec=221 kJ/mol. The glass-ceramic materials were obtained through a one stage crystallization - 1050÷1070оС and an isothermal hold of 60 min., colored white, yellow brown to dark brown. The main crystalline phase in glass-ceramics is β-vollastonite with needle habit, size of crystals - ĺ = 40 ÷ 120 μm and d <5 μm in quantities 37 ÷ 42%. As secondary phases depending on the amount of ash have been identified - the anorthite, gehlenite and α-quartz with prismatic habit were appeared. The obtained glass-ceramic materials have a marble-like effect and technical parameters compared with natural granite and marble and have higher values of density, micro hardness, speed grinding, bending strength and chemical resistance. That’s why they can be used in construction such as lining materials.
The International Journal of Engineering and Science (The IJES)theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
Study the effect of Mn2+ ions on the ac electrical properties of some iron do...IJRES Journal
Oxide glasses doped with transition metal ions are of high interest because of their variant applications in both science and technology fields. However, the normal melt quench method have used to prepared some iron doped phosphate glasses according the following molecular formula: (65-x) mol% P2O5 - 20 mol% Na2O - 15 mol% Fe2O3 - x mol% MnO, Where x= 0, 5,10, 20, 25. The room temperature Mössbauer Effect ME Spectra used to characterized the glassy state homogeneity of these glasses. ME spectra show, for all glasses, no magnetic field participate which mean good glassy state formation. The ac electrical transport properties were also measured, as function of temperature up to 500k. It was found that the ac conductivity increased with the gradual increase of Mn2+ cations, while the electrical activation energy decreased.
MICROSTRUCTURAL CHARACTERIZATION AND HOT EROSION BEHAVIOR OF CRC-NICR COATED ...IAEME Publication
Erosion behavior of the High Velocity Oxygen Fuel (HVOF) deposited CrC - NiCr coating on stainless steel was evaluated. Th e solid particle erosion stu dy was conducted using an air jet erosion test rig at a velocity 60m/sec and impingement angle 60 ° , 75 ° and 90 ° , on HVOF spray coated steel at 600 ° C. Microstructure, chemical composition, phases present in the coating on the steel substrate was studied by using Scanning Electron Microscope (SEM) and X - Ray Diffraction method. The Hardness is gradually increasing with increasing content of Cr 3 C 2 particles in all three samples. The erosion mechanism of coatings was also discussed and erosion rate is maximum at impingement angle 75 °
. One of the methods used to surface hardening of ductile iron is chilled cast iron. Chill as the fast cooling rate in the mold during solidification and chill thickness greatly affects the thickness of the hardness layer. The main material used is ductile iron, and the chill material is SS 304. Casting uses the sand casting method. Before pouring, the chill plate has been inserted onto the surface of the pattern that has been formed in the mold, then the chill plate is preheated at 700OC. Pouring was carried out at a melting temperature of 1400OC, and then cooled with argon and O2 sprays into the mold in solidification conditions at exactly 700OC. The results analyzed were the microstructure, hardness value, and the hardness of the thickness layer. This chill coolant will absorb heat very quickly and the Cr and Ni alloy will diffuse to the specimen surface to stabilize the ferrite and austenite phases in the final solidification. The particles on the hard surface have Ferro carbide M7C3, which is in the form of cementite and martensitic phases so that to categorized as white cast iron structure formed on the surface with an area around 1.5-3mm has a hardness of 61-65HRC. But in the center area is 31-49HRC
Characterization and Dielectric Study of Mihaliccik Tremoliteijtsrd
The natural tremolite Ca2Mg5Si8O22 OH 2 was obtained from Mihaliccik district of Eskisehir, Turkey 39.8787N 31.3806E . It is a part of the amphibole family of silicate minerals. All the phases were described by X ray diffraction XRD , energy dispersive spectroscopy EDXRF , Raman, and Fourier transform infrared spectroscopy FTIR . The natural tremolite specimen used in this study includes mostly 54.4 SiO2, 22.82 MgO, 15.04 CaO, and 1.45 Al2O3. The natural tremolite sample used for the present investigation was not pure. The impurity was calcite. The FTIR spectrum and the Raman spectrum were recorded for natural tremolite sample in the range of 4000 and 350 cm 1 and 4000 and 70 cm 1 at room temperature, respectively. The natural tremolite and fired tremolite samples were prepared for this investigation. Dielectric measurements were realized in the 3 kHz ' 1 MHz frequency region and at the room temperature by using HP4192A LF Impedance Analyzer. The dielectric parameters of the samples were obtained the conclusions of the study were explained and given to be used for further investigations in some industrial productions. Ertugrul Izci "Characterization and Dielectric Study of Mihaliccik Tremolite" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-1 , December 2019, URL: https://www.ijtsrd.com/papers/ijtsrd29671.pdf Paper URL: https://www.ijtsrd.com/engineering/mineral-and-metallurgical-engineering/29671/characterization-and-dielectric-study-of-mihaliccik-tremolite/ertugrul-izci
ELECTRODEPOSITION OF TITANIUM AND ITS DIOXIDE FROM ILMENITE Al Baha University
The aim of the present work was to develop a simple and rapid electrolytic extraction process of titanium [l-3] and its dioxide from the ilmenite ore of the Eastern Desert. The ore mother liquor used for the electrolysis process is either produced by direct leaching with 98% H,SO, (S/L = 1 : 15), 35% HCl (S/L = 1: 20) and alkaline digestion with caustic soda in a ball-mill autoclave at 175°C under a pressure of 9.5 kg cmP2, or it is prepared through the fusion method using NaOH or Na,S,O, separately as fluxes at 600-700°C.
EXPERIMENTAL
BAOJ Chemistry is a peer reviewed journal the presents latest papers and articles in the domain of chemistry. This journal meets holistically the information needs of chemists, pharmacists, micro-biologists, and other members of the scientific community. Authors can publish their papers and articles relating to different aspects of chemistry: Amino acids study, Bioactive plant products, Bio-organic chemistry, Chemical Engineering, Chemoenzymatic and enantioselective synthesis of organic compounds, Combinatorial chemistry, Computational chemistry, Enzymes in organic synthesis, Heterocyclic compounds, In organic Chemistry, Industrial Chemistry, Medicinal chemistry, Metal-catalyzed asymmetric reactions, Modelling of materials, Molecular modelling and drug design, Natural products, Nature of materials research, Organic reaction mechanism, Peptides and proteins, Physical Chemistry, Physicochemical aspects of their fabrication, Phyto-chemistry, Practical organic chemistry, Properties and app
Семантическая обработка медицинских данных в задачах диагностики и управления...Alexandre Prozoroff
Семантическая обработка медицинских данных в задачах диагностики и управления лечебным процессом в медицине критических состояний.
Semantic processing medical data in diagnosing problems and management of medical process in critical care medicine.
معنى كلمة «ملائكة» في الكتاب المقدس؟
* معناها الأول واحدٌ في اللغات العبرية واليونانية والعربية وهو «رسول». واستُعملت في الكتاب المقدس لكل ما يستخدمه الله لإجراء مقاصده وإعلان ذاته وقوته، فجاءت فيه بمعنى «رسول عادي» (أي 1: 4 و1صم 11: 3 ولو 7: 24 و9: 52). وجاءت بمعنى «نبي» (إش 42: 19 وحج 1: 13 وملا 3: 1) وبمعنى «كاهن» (ملا 2: 7) وبمعنى «خادم العهد الجديد» (رؤ 1: 20). واستُعملت أيضاً لغير العاقل كعمود السحاب (خر 14: 19) والرياح (مز 104: 4). وسُمّي الأقنوم الثاني من الثالوث الأقدس «ملاك حضرته» و«ملاك العهد» (إش 63: 9 وملا 3: 1). وسُمّيت الأوبئة «ملائكة أشرار» (مز 78: 49) ودعا بولس الشوكة في جسده «ملاك الشيطان» (2كو 12: 7). ولكن كلمة «ملاك» اشتهرت باستعمالها للأرواح السماوية الذين يستخدمهم الله ليُجروا إرادته (مت 25: 31) فعُرفوا باسم «ملائكة الله»
Inhibitive properties, thermodynamic, kinetics and quantum
chemical calculations of polydentate Schiff base compounds
as corrosion inhibitors for iron in acidic and alkaline media
Electro-Thermal and Semiconductivity Behaviour of Natural Sintered Complex Ca...Al Baha University
The electrical
conductivity (휎), thermal conductivity (퐾) and thermoelectric power coefficient (훼) have been investigated as a function of applied
temperature for the sintered ore materials. The electrical conduction is mainly achieved by free electrons near or in conduction
band or n-type. As the sintering temperature (푇s) increases the conduction of the ore is also increased due to the recombination
process taking place between the electrons and holes. Electrons hopping between Fe2+ and Fe3+ are the main charge carriers.The
formation of Fe3O4 at high sintering temperature acts as an active mineralizer, thus inducing an increased degree of crystallinity
and a more ordered crystal structure is produced.
Madkour 1986-journal of-chemical_technology_and_biotechnologyAl Baha University
Thermodynamic Studies on Sulphate Roasting for Zinc Electrowinning from Carbonate Ore
The bulk of the work consists of a theoretical study of the possibility of submitting Umm-Gheig carbonate ore to sulphate roasting. The use of the admixture with pyrites is to enable a carbonate ore to be treated in a similar way to a sulphide ore, and by doing so, to produce a roasted product capable of being treated by orthodox zinc electrowinning methods using sulphate solutions. Thermodynamic studies have been made to find the optimum conditions for sulphate roasting, in either normal air or enriched 36% oxygen air. The results obtained from the experimental work at different roasting temperatures in a tube furnace indicated that a maximum dissolu- tion of 91.2% Zn with a 17.9% Fe could be obtained at a roasting temperature of 650°C for 4 h, followed by leaching in 4% H2S04 (by vol.) at 60°C. The results of the electron microscopic investigation confirmed by metal value data given in the ASTM cards coincide well with results given by chemical analysis
Thermoluminescence Study of Mineral Ivory SodaIJCMESJOURNAL
The present paper reports the thermoluminescence characteristics of Ivory Soda mineral collected from Bhor Ghats near Sangamalner, Nasik Distric, Maharasta. The TL of as received minerals at varies heat treatment was recorded and also 15Gy beta dose was given to each sample prior to TL recording. TL of as received specimen (NTL) annealed for 1 hour and quenched from 200, 400, 600 and 800oC. The Ivory Soda mineral displayed a well resolved sharp peak around 140oC and 145oC for AQ from 600 and 800oC. XRD and TGA of Ivory Soda mineral were reported.
Particulate Sintering of Iron Ore and Empirical Analysis of Sintering Time Ba...IOSR Journals
Particulate sintering of iron ore has been carried out using the necessary ingredients. Empirical
analysis of the sintering time based on the coke breeze input concentration and ignition temperature were also
successfully obtained through first principle application of a derived model which functioned as a evaluative
tool. The derived model;
S = (√T)0.95 + 0.0012α
indicates that amongst ignition temperature and coke breeze input, sintering time is more significantly affected
by the coke breeze input concentration. This is based on the higher correlation it makes with sintering time
compared to applied ignition temperature, all other process parameters being constant. The validity of the
model was rooted in the core expression S – Kα ≈ (√T )N where both sides of the expression are correspondingly
approximately almost equal. Sintering time per unit rise in the operated ignition temperature as obtained from
experiment, derived model and regression model were evaluated as 0.0169, 0.0128 and 0.0159 mins. / 0C
respectively. Similarly, sintering time per unit coke breeze input concentration as obtained from experiment,
derived model and regression model were evaluated as 4.0, 3.0183 and 3.7537 mins./ % respectively indicating a
significant proximate agreement and validity of the model. The standard error (STEYX) incurred in predicting
sintering time for each value of the ignition temperature and coke breeze input concentration considered, as
obtained from the experiment, derived model and regression model are 1.6646, 0.7678 and 2.98 x10-5 % as well
as 2.2128, 1.0264 and 1.2379% respectively. The maximum deviation of mode-predicted results from the
corresponding experimental values was less than 11%.
Effect of sintering time on the particle size and dielectric properties of La...ijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
The Effect of Bed Thickness and Cooling Time on the Rate of Copper Slag Cooli...CrimsonPublishersAMMS
The Effect of Bed Thickness and Cooling Time
on the Rate of Copper Slag Cooling, Case Study:Khatoonabad Copper Smelter Plant by Esmaeil Rahimi and Neda Mohaghegh in Aspects in Mining & Mineral Science
Annealing and Microstructural Characterization of Tin-Oxide Based Thick Film ...Anis Rahman
Abstract. The sheet resistance of tin oxide based thick-film resistors exhibits two regions of temperature dependence,
described by hopping (23°C-200°C) and diffusion mechanisms (200°C-350°C), respectively.
Annealing these samples causes the sheet resistance to increase in both regions. In the post-annealed samples,
the hopping conduction range is extended by 50°C (23°C-250°C) while the hopping parameter, To, is decreased by
more than 50%. The activation energy of diffusion (0.60 eV) is the same for both pre- and post annealed samples, but
the magnitude of resistance in the diffusion controlled region is increased significantly as a result of annealing. These
changes are explained in terms of a net decrease in the concentration of tin ions in the glass matrix. From a careful
microstructural study it was found that a conduction path composed of tin-oxide grains or their clusters in contact
with each other does not exist in the present system. HREM micrographs showed the presence of nanocrystalline
tin-oxide particles in the glass phase separating the tin-oxide grain clusters. Estimated average separation between
the nanocrystals in 4 nm, consistent with a variable-range hopping conduction via the dissolved tin ions in the glass
matrix.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Selective Oxidation of Cyclohexene, Toluene and Ethyl Benzene Catalyzed by Bi...Iranian Chemical Society
Bis-(L-tyrosinato)copper(II) was reacted with 3-(chloropropyl)-trimethoxysilane functionalized silica that has infused magnetite to yield a magnetically separable catalyst in which the copper carboxylate is covalently linked to the silica matrix through the silane linkage. The immobilized catalyst has been characterized by spectroscopic studies (such as FT-IR, EPR, Magnetic Measurement, SEM) and chemical analyses. The immobilized catalytic system functions as an efficient heterogeneous catalyst for oxidation of cyclohexene, toluene and ethyl benzene in the presence of hydrogen peroxide (as an oxidant) and sodium bicarbonate (a co-catalyst). The reaction conditions have been optimized for solvent, temperature and amount of oxidant and catalyst. Comparison of the encapsulated catalyst with the corresponding homogeneous catalyst showed that the heterogeneous catalyst had higher activity and selectivity than the homogeneous catalyst. The immobilized catalyst could be readily recovered from the reaction mixture by using a simple magnet, and reused up to five times without any loss of activity.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Effect of Ytterbium Substitution on the Structural and Magnetic Properties of...ijtsrd
A series of ytterbium substituted Zinc ferrites Zn YbxFe1 x 2O4 with x=0.0000, 0.0125, 0.0250, 0.0375, 0.0500 was synthesized by the solid state method. The structural characterizations of all the prepared samples were done by using X ray diffraction XRD . These studies confirmed the formation of single phase structure in all compositions. The increase in the value of lattice parameter with increase in ytterbium concentration suggests the expansion of unit cell. Crystallinity and the crystallite size are observed to increase with the concentration of Ytterbium. The substitution of ytterbium strongly influences the magnetic characteristics and this is confirmed from the magnetization measurements at room temperature. Zar Zar Myint Aung "Effect of Ytterbium Substitution on the Structural and Magnetic Properties of Nanocrystalline Zinc Ferrite" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd27826.pdf Paper URL: https://www.ijtsrd.com/physics/other/27826/effect-of-ytterbium-substitution-on-the-structural-and-magnetic-properties-of-nanocrystalline-zinc-ferrite/zar-zar-myint-aung
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
A brief information about the SCOP protein database used in bioinformatics.
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Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
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Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
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Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
1. Loutfy H. Madkour
335
Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010, 335-346
SEMICONDUCTIVITY BEHAVIOUR OF EGYPTIAN NATURAL SINTERED ORE
FOR THERMOTECHNOLOGICAL APPLICATIONS
Loutfy H. Madkour
Chemistry Department, Faculty of Sciences and Arts,
Al-Kamil, King Abdul-Aziz University,
P.O. Box 80207 Jeddah 21589,
Kingdom of Saudi Arabia
E-mail: loutfy.madkour@yahoo.com
lmadkour@kau.edu.sa
ABSTRACT
The polymetal (Zn, Pb, Fe, Ca, Mg, Cd, Ba, Ni, Ti, and SiO2) complex Umm-Gheig carbonate ore is subjected to
sintering treatment at 573, 773, 973 and 1273 K, respectively, for four hours. Chemical, spectral, X-ray and differential
thermal analyses are applied for the native ore as well as for the samples preheated and sintered. The I-V characteristics,
bulk density (Db), percent shrinkage (% S), activation energy (Ea) and energy gap (Eg) are established for the sintered ore.
The electrical conductivity (s), thermal conductivity (K) and thermoelectric power coefficient (α) have been investigated
as a function of applied temperature for the sintered ore materials. The electrical and thermal measurements show that
the sintered ore has semiconductivity behaviour with temperature. The electrical conduction is mainly achieved by elec-
trons or n-type. As the sintering temperature (Ts) increases the conduction of the ore is also increased owning to the
recombination process taking place between the electrons and holes. Electrons hopping between Fe2+
and Fe3+
are the
main charge carriers. The formation of Fe3
O4
at high sintering temperature acts as an active mineralizer, thus inducing an
increased degree of crystallinity and the more ordered crystal structure is produced.
Keywords: polymetal ore, sintering treatment, semiconductivity behaviour.
Received 05 May 2009
Accepted 22 July 2010
INTRODUCTION
The polymetal deposits of the Red Sea ore belt
(a zone extending NW-SE for a distance of 130 km)
represent a complex morphogenetic type of mineral-
ization [1]. The chief minerals are hydrozincite, zinc
blende, smithsonite and cerussite, while silica and car-
bonates constitute the bulk of the gangue. The investi-
gated sample contains 30.7 % Zn, 7.99 % Pb, 5.05 % Fe
and 6.58 % SiO2
. The minerals present in the complex
ore are often so closely intergrown that it is either dif-
ficult to obtain suitable high-grade concentrates at high
recoveries [2] by physical methods, or the recovery of
metals from the respective concentrates is poor.
Madkour et al. [3-8] investigated experimentally the
thermochemistry of the complex ores roasting, with giv-
ing some theoretical thermodynamic calculations, for
the recovery of metal value. It is possible to control the
calcine composition by controlling the temperature and
air-solid ratio. It is very important for the understand-
ing of properties and conduction mechanism of ZnO
[9-11].
The solid state sintering is classical method for
obtaining of materials with wide application possibili-
ties, as microwave materials [12], ferrite materials [13]
and others. In this sense, the aim of the present work is
2. Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010
336
to investigate the electrical and thermal properties of
the natural polymetal complex ore on a series of sinter-
ing temperatures : 573, 773, 973 and 1273 K, respec-
tively, as well as to directly examine the semiconductivity
behaviour of the material, obtained by solid state sin-
tering that may have thermotechnological applications.
EXPERIMENTAL
Sampling
Mineralized horizone ore (500 kg) was crushed
to 100 % minus 1.0 mm. The ore samples are finally
mixed in an agate mortar to ensure homogeneous dis-
tribution. Discs of 1.1 cm in diameter and 0.15 cm thick-
ness were pressed at about 500 kg cm-2
in a steel die
using hydraulic press. The pressed discs were then sin-
tered at 573, 773, 973 and 1273 K, respectively, for
four hours under atmospheric pressure. The discs were
polished and coated on both flat surfaces with graphite
paste for electrical measurements.
Chemical analysis
Analysis [14] of the ore sample was carried out at
the Egyptian Geological Survey and Mining Authority.
Thermal analysis
Analysis for the native ore sample was carried
out by means of a MOM derivatograph with á-Al2
O3
as
reference. The powdered ore sample was heated at the
rate of 10°C/min up to 1000°C (constant sensitivities:
DTA, 1/10, TG; 200 and DTG, 1/15). Differential ther-
mal analysis (DTA) of the investigated sintered ore
sample was carried out using a Schimadzu XD-3-ther-
mal analyzer.
X-ray analysis
The X-ray powder diffraction pattern was ob-
tained using CuKα
radiation and nickel filter. A Phillips
X-ray PW 1729 diffractometer has been used in the
range 2θ = 12-80.
Infrared spectra
The infrared spectra (KBr discs) were recorded
on a Perkin-Elmer 1430 Ratio Recording spectropho-
tometer and a Perkin-Elmer 683 spectrophotometer.
Electrical measurements
The I-U characteristic measurements were ob-
tained with a digital multimeter type KIETHLEY 130
A, as a voltameter and as milliampermeter. The digital
thermometer was used to measure the temperature with
an accuracy of ±0.1°C. The essential electric circuit is
shown in Fig. 1.
The apparatus used for the thermal measurements
[15] is shown in Fig. 2. It consists of a sample holder
held on three iron rods. The sample holder consists of a
stainless steel bar which is fixed in the central axis of
tubular stainless steel furnace working with a heater.
The central steel bar, copper leads thermocouple wires
and heater connections are insulated from the holder
base plate by a ceramic disc. Various wires and thermo-
couples are connected to the outside by means of cop-
per leads through teflon tubes. The sample S is slightly
Fig. 1. Essential electric circuit.
Fig. 2. Cross-section of the apparatus used for thermal
measurements.
3. Loutfy H. Madkour
337
pressed by means of a small load placed on its top just
to maintain good contact between the sample surfaces
and the two copper electrodes. A metal jacket cooled
with water through a copper coil placed around it, rests
on an annular vacuum rubber ring fixed to the base
plate. The degree of vacuum was 10-3
mm Hg, and the
heat leak due to convection was practically negligible.
The thermal conductivity K was measured at different
temperatures (30-240°C). This was achieved by con-
trolling the furnace heater to maintain constant tem-
perature at the lower surface of the sample and then the
temperature gradient was measured.
RESULTS AND DISCUSSION
Chemical composition and analysis
The investigated Umm-Gheig native ore sample
was found to contain 59.76 % ZnCO3
, 6.02 % PbCO3
,
4.86 % PbSO4
, 5.05 % Fe, 4.84 % CaO, 6.58 % SiO2
and 2.58 % MgO as given in Table 1. Thus, the natural
ore is considered as zinc concentrate. Its constituents
of FeO and Fe2
O3
are relatively high.
Furthermore, the chemical analysis made on the
sintered ore sample (after sintering at 1273 K for 4 h)
indicates the increase of Fe3
O4
content at the expense
of both originally present FeO and Fe2
O3
content.
Thermal analysis
Fig. 3a displays the differential thermal analysis
(DTA), thermogravimetry (TG) and derivative
thermogravimetry (DTG) of the native ore sample. The
arrangement of minerals [16,17] according to their abun-
dance is as follows: hydrozincite [Zn5
(CO3
)2
(OH)6
]; zinc
blende(ZnS);smithsonite(ZnCO3
) and cerussite (PbCO3
).
The total loss on ignition in mass percent at 1100°C is
28.22 %. It can be seen that the native ore sample dis-
plays two endothermic peaks at 280°C and 370°C, re-
spectively. This is assigned to loss of humidity content
or physically combined water. Further temperature rise
displays a whole intense broad exothermic hump cov-
ering the temperature range 400-550°C peaking at 500°C
for the strongest one. This is due to collective phase
changes [16], corresponding to the following reactions:
Table 1. Chemical and spectral analysis of native Umm-Gheig natural complex polymetal ore.
Content Content Content
Component (%) Component (%) Element (parts 10
-6
)
SiO2 6.58 Zn 30.70 Cd 800
A12O3 0.83 Pb 7.99 Ti 0.06
Fe 5.05 PbSO4 4.86 Ba 400
MgO 2.58 PbCO3 6.02 Ni 40
CaO 4.84 ZnCO3 59.76 Co -
SO4
2- 1.28 Moisture 0.97 Ag -
L.O.I.* 28.22 Au -
* Loss on ignition in weight percent at 1100oC.
Fig. 3. Thermal analysis of: (a) the native ore sample, (b)
sintered ore samples for 4 h at 573 K (B), 773 K (C), 973 K
(D) and 1273 K (E).
4. Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010
338
Fe2
O3
400oC Fe3
O4
(magnetite)
FeO
450oC
Fe2
O3
(hematite)
Fe2
O3
500oC
Fe3
O4
(magnetite)
It is important to note that the native present
Fe2
O3
(hematite) and the formed Fe3
O4
(magnetite) may
act as catalyst, for the subsequent oxidation and oxygen
uptake of FeO giving Fe2
O3
and latter on for the forma-
tion of Fe3
O4
as a final product. Besides it acts as an
active mineralizer, thus inducing an increased degree
of crystallinity [18] which often appears after the ap-
plied sintering treatment at 573, 773, 973 and 1273 K,
respectively. The broad exothermic peak covering the
temperature range 630-750°C peaking at 690°C for the
strongest one corresponds to the decomposition of the
original present metal carbonates and sulphates into the
corresponding oxides.
Differential thermal analysis for the ore samples
preheated and sintered at temperatures 573, 773, 973
and 1273 K, respectively, for hours is shown in Fig. 3 b.
DTA for the sintered ore indicates the oxidation of vari-
ous metal carbonates and sulphates present in the na-
tive ore into the corresponding metal oxides.
X-ray analysis
X-ray differaction studies ensured the chemical
composition of the native Umm-Gheig natural ore and
samples preheated and sintered at 573 - 1273 K, re-
spectively, as shown in Fig. 4. The X-ray diffraction
pattern of raw material sample (Fig. 4a) displays the
essential characteristic peaks for ZnCO3
(2θ = 33.70,
25.10, 51.25, 37.80, 46.40, 41.60 and 61.40). The es-
sential characteristic peaks for PbCO3
are: (2θ = 25.80,
36.40, 43.80, 29.00, 49.20, 36.40 and 47.30). The es-
sential characteristic peaks for PbSO4
are : (2θ = 29.50,
26.80, 44.50, 27.40 and 22.10). The essential charac-
teristic peaks for [Zn5
(CO3
)2
(OH)6
] are: (2θ = 36.40,
33.70, 29.00, 25.10, 30.70 and 16.80). X-ray powder
diffraction data shows that galena is mainly converted
to cerussite. After sintering treatment at 573, 773, 973
and 1273 K for four hours respectively, the X-ray dif-
fraction pattern of sintered ore samples (Fig. 4b-e) dis-
plays the characteristic deflection peaks for different
metal oxides formed as follows: ZnO (2θ = 36.10, 31.70
and 33.80). PbO (2θ = 29.10, 31.60, 32.15, 48.70 and
45.60). PbO2
(2θ = 28.15, 49.55 and 22.80. Pb2
O3
(2θ
= 29.50, 29.60 and 27.40). Pb3
O4
(2θ = 26.20, 31.60
and 32.15). FeO (2θ = 41.95, 36.20 and 61.00). Fe2
O3
(2θ = 33.50, 35.60 and 54.20). Fe3
O4
(2θ = 35.60, 62.40
and 29.60).
The X-ray diffraction studies of sintered ore
samples at higher sintering temperatures (Fig. 4) en-
sured a spinel phase formation (x Fe2
O4
) where, x = Zn
or Pb. The essential characteristic peaks for spinel
ZnFe2
O4
and PbFe2
O4
are: (2θ = 35.00, 29.60, 62.05,
56.60 ) and (2θ = 32.40, 46.00, 56.80, 74.40 and 67.40),
respectively. Furthermore, there is no indication for the
appearance of reflection peaks characteristics for the
carbonate mineral or sulphate composition which origi-
nally present in the native ore before sintering processes
at 573-1273 K. This is due to the thermal decomposi-
tion of the chief minerals present, into the correspond-
ing metal oxides.
Infrared spectra
The IR frequencies of the native Umm-Gheig
ore sample (a) and the sintered ore samples (b-e) along
with their assignments are given in Fig. 5. The bands at
1677-1632 cm-1
are assigned to the ν C=O groups.
Metallic carbonyls absorb in the 1984 cm-1
region [19].
Silicates give absorption bands in the 1168-915 cm-1
Fig.4. X-ray diffraction pattern for the native ore sample
(A) and sintered ore samples for 4 hrs. at 573 K (B), 773 K
(C), 973 K (D), and 1273 K (E).
5. Loutfy H. Madkour
339
range. Appearance of new bands in the frequency re-
gion at 332 - 328 cm-1
(Fig. 5b-d) is due to stretching
vibration bands of metal oxide (M-O) bonds, where M
= Zn, Pb or Fe. The existence of water molecules within
the co-ordination sphere of the hydrated ore samples is
supported by the presence of absorption bands in the
region 3889-3422 cm-1
and 1116-1073 cm-1
in the spec-
tra of the ore due to (OH) stretching, HOH deformation
and H2
O rocking [20].
Effect of sintering temperature on the bulk density
(Db) and shrinkage (% S)
The measured diameter of the sintered ore discs
is decreased as the sintering temperature increases,
therefore the percent shrinkage (% S) of the sintered
ore samples is consequently increased with increasing
the sintering temperature (Fig. 6). The bulk density Db
is also measured for the different sintered ore discs and
the data is plotted as a function of the sintering tem-
perature Ts
as represented in Fig. 6. The results show
that, the bulk density as well as the percentage shrink-
age are increased gradually with increasing the studied
sintering temperature from 573-1273 K. This behaviour
may be due to the more intensive diffusion process [21]
is occurring at high sintering temperature, leading to
the reduction of the porosity. As a result of this con-
traction, the crystal structure becomes compactness and
rigid at high sintering temperature. The observed small
Fig.5. Infrared spectra of the native ore sample (A) and
sintered ore samples for 4 hrs. at 573 K (B), 773 K (C), 973 K
(D) and 1273 K (E).
Fig. 6. Effect of sintering temperature Ts
on the bulk density
Db
and shrinkage (% S) of the ore samples.
Fig. 7. D.C. current voltage characteristic of sintered ore
samples.
6. Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010
340
values of Db
and (% S) at lower sintering temperatures
can be attributed to the limited rearrangement of the
crystal lattice structure through the movement of grain
boundaries [22].
Temperature dependence of electrical properties
The I-V characteristics have been measured on
the sintered ore samples at the studied different sinter-
ing temperatures ranging from 573-1273 K, respectively,
as shown in Fig. 7. It can be seen that the I vs. U plots
are on the whole, straight lines at all different sintering
temperatures. The plot is converted also to ln I vs. ln U,
as represented in Fig. 8. It is evident that at the applied
dc voltages an ohmic relationship (α = 1) is obtained
for all sintered samples with the exception of the ore
sample sintered at 773 K. The behaviour is called the
current-ohmic range. But for the case of sintered sample
at 773 K, the nonohmic relation, I ≡Uα
, holds good.
The parameter α which essentially defines the non-ohmic
nature of the material is equals to 1.52 and 1.95 for the
lower and upper branches lines, respectively. The non-
ohmic region (α > 1) in the I-U curves, arises due to
the space-charge effects and is termed as space-charge-
limited current (SCLC) region. These observations show
that the I-U characteristics provide the best understand-
ing of the conduction mechanism in the ore samples.
The tested ore material may be considered to be com-
posed of layers with different conductivities and thick-
nesses in series with each other. The well-conducting
grains, having thickness d1
, conductivity σ1
and permit-
tivity ε1
are separated by a thin layer of poorly conduct-
ing grain boundaries (GB) having thickness d2
, conduc-
tivity σ2
and permittivity ε2
. It is reasonable to assume
that σ1
>> σ2
. If U1
and U2
are the dc voltage drops
across the grain and the GB, respectively, then U = U1
+
U2
is the externally applies dc voltage. The voltage drop
will take place mainly across the grain boundary (i.e. U ≅
Sintering
temperature
(K)
Resistivity
( 10
7
. . cm)
573
773
973
1273
73.84
21.10 (before Vc) and 8.43 (after Vc)
11.75
11.09
Table 2. The electrical resistivity (r) as a function of sin-
tering temperature.
Fig. 8. Logarithmic current voltage characteristic of sintered ore samples.
7. Loutfy H. Madkour
341
U2
). If the current (i Ω1
) through the grain is only ohmic
and the current through the GB is ohmic (i Ω2
) as well as
space-charge limited (iscl
), the total current I = i Ω1
+ iΩ2
+
iscl
. The total current in the ore solid can be approxi-
mated as iΩ2
<< iscl
≅ I. Thus, the I-U characteristic
in the nonohmic region is given by iscl
≅ U2
α
. The space-
charge-limited current is determined mainly by the num-
ber of free charge carriers available in the grain-bound-
ary layers. At the applied dc voltages on the ore samples,
i.e. before the non-ohmic region (at 773 K sintered ore
sample) the current is purely ohmic (α = 1). In this region
the total current through the ore solid is iscl
<<i Ω2
≅ i, and
hence an ohmic relation holds. According to this theory
[23], the I-U curves are consisting of three parts :
• low-current ohmic range, for the sintered ore
at 1273 K (α = 0.93);
• scl-current range or the non-ohmic range, for
the sintered ore at 773 K (αI
= 1.52, αU
= 1.95), where
(αl
and αu
), represent the values of á at lower and up-
per, respectively;
• high-current ohmic range for the sintered ore
at 573 K and (α=1).
The broken line of I-U characteristic for the
tested sintered ore sample at 773 K shows that the criti-
cal voltage Uc
at which the line is broken is 15 volts.
The dependence of the electrical resistivity of the
sintered ore samples on the applied sintering tempera-
ture is given in Table 2. The obtained data indicates
that the resistivity of the sintered ore samples decreases
as the sintering temperature increases for the samples.
Electrical conductivity versus temperature char-
acteristics (lnσ - 1/T) of all the investigated samples
were measured and represented in Fig. 9. From the typi-
cal log σ vs. 1/T characteristics, as shown in Fig. 9, it is
seen that the sintered ore samples had a good
semicoductivity behaviour with increasing the applied
temperature from 430-550 K according to a Boltzmann-
distribution [24] :
σ = σo
exp(-Ea
/kT)
The parameter σo
, which is given by the inter-
cept of the line at 1/T = 0 is called the pre-exponential
factor or the frequency factor, kB
is the Boltzmann con-
stant and T is the absolute temperature. However, it is
worth anticipating the interpretation of the activation
energy Ea
for the electric conduction in eV, which is
motivated by writing the above equation as:
lnσ = lnσo
- Ea
/k.T
There we shall see that the activation energy Ea
represents the minimum energy necessary for a molecule
in the sample to possess in order to react. Ea
is calculated
from the slope of the straight line of this plot (Fig. 9).
The values of activation energy Ea
are plotted as a func-
tion of the sintering temperature. Ts
as shown in Fig. 10.
The experimental results in Figs. 9 and 10 indicate that
the electrical conductivity increases and consequently the
activation energies are decreased with increasing the sin-
tering temperature. The obtained data of either electrical
conductivity (Fig. 9) and/or activation energy (Fig. 10)
are in a good agreement with those obtained from the
previous studies of the resistivity values as given in Table
2. Also, the results obtained are in good agreement with
other work [25] and can be explained on the basis that
the propagation of lattice imperfection decreases and
the more ordered crystal structure is produced.
Fig.9. Temperature dependence of electrical conductivity
s for sintered ore samples.
Fig.10. Effect of sintering temperature on the activation
energy Ea for electrical conductivity of the ore samples.
8. Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010
342
Thus, all the investigated sintered ore samples
have semiconductivity properties. Generally, in a semi-
conductor material the outer electrons or valence elec-
trons are normally stable, i.e. bound to their atoms and
not free to move. But when heat is applied or an impu-
rity (a doping element) that serves to raise energy is
incorporated, the application of a voltage will cause
displacement of valence electrons in the material, i.e.
turn then into charge carriers. So, an electric current in
a sintered ore semiconductor may be induced and var-
ied over a wide range only under the action of external
influence, such as heat and doping. The higher the tem-
perature, the greater the number of free electrons and
the larger the conduction current in the semiconductor.
Thus, electrical conduction [26] in all semiconductors
is mainly by electrons or n-type. Since the electrons
that participate in conduction are the semiconductor’s
own electrons, its conduction is called intrinsic.
The atoms that lost their electrons turn into posi-
tive-charge ions bound and unable to move. The va-
cancy left by the electron in the outer ring of the atom
is called a hole. An electron set free from the neighbor-
ing atom may fill the vacancy by moving to the hole
and leaving instead a hole in its atom thereby turning it
into a positively charged ion. The application of an elec-
tric current to a semiconductor will cause electrons to
move from atom to atom in one direction and leave
holes in the opposite direction. The hole is generally
regarded as a positive particle equal in charge to the
electron. The seeming movement of holes in the direc-
tion opposite to that of electrons is called hole current.
The electric conduction in the semiconductor, condi-
tioned by this current, hole or p-type conduction.
The movement of electrons in one direction
and of holes in the opposite determines intrinsic elec-
trical conduction in a semiconductor, because the charge
carriers (electrons and holes) belong to the
semiconductor’s own atoms. In this case, the conduc-
tion current I consists of the electron Ie and hole Ih
current components, i.e. I = Ie
+ Ih
.
With intrinsic conduction, concentration of elec-
trons (Ne
) and of holes (Nh
) are equal. However, Ie
> Ih
because the mobility of electron is higher than that of
hole. The mobility of a charge carrier is the ratio of the
velocity of electron ve
or of hole vh
to the electric field
strength E in the semiconductor. Then, the electron
mobility µe
= ve
/E and hole mobility µh
= vh
/E.
In that way, mobility indicates the distance electron
or hole covers per second in a field of strength E = 1V/cm.
Considering the aforementioned, expressions for the
electron and hole current components may be written
as [26].
Ie
= Ne
eve
= Ne
eµe
E
Ih
= Nh
evh
= Nh
eµe
E
where e is the charge of electron or hole and E is the
electric field strength.
The conduction current in a semiconductor is:
I = Ie
+ Ih
= Ne
eve
+ Nh
evh
= Ne
eµe
E + Nh
eµh
E
With intrinsic conduction, concentration of elec-
trons is equal to that of holes in semiconductor, i.e.
Ne
= Nh
= N
and
I = Ne
(µe
+ µh
)E
In a pure (intrinsic) semiconductor impurities
constitute not more than 10-11
%.
The investigated natural Umm-Gheig sintered ore
containing the iron atoms as impurities of a valency
higher than the semiconductor’s material tend to give
electrons thereby increasing the electron density. They
play therole of donors. Thus, the atoms of iron impuri-
ties present originally in the native ore can modify its
electrical properties. For example, to obtain a semi-
conductor that will exhibit n-type conduction. This leads
to the formation of some Fe2+
ions from Fe3+
ions. The
polarization of the ferrite is determined by local dis-
placement [23] of electrons in the direction of an ap-
plied electric field, which is due to the electron exchange
interaction: Fe2+
Fe3+
+ e-
The energy gap Eg
which is defined as the energy
required for separating the highest-filled or valence band
(VB) from the conduction band (CB) is equal twice [27]
activation energy, i.e. Eg
= 2 Ea
.
Sintering
temperature
(K)
Activation
energy
Ea (eV)
Energy gap
Eg (eV)
573
773
973
1273
0.850
0.825
0.760
0.580
1.70
1.65
1.52
1.16
Table 3.The effect of sintering temperature (Ts) on Ea
and Eg values.
9. Loutfy H. Madkour
343
The values of Ea
and Eg
for the investigated semi-
conductor sintered ore samples are calculated and given
in Table 3.
Temperature dependence of thermal conductivity (K)
The coefficient of thermal conductivity of the sin-
tered ore samples was estimated using the formula :
Q = I V/J = K A dT/dX
where Q is the quantity of heat per unit time trans-
ferred through the sample of thickness dX, J- the Joule’s
coefficient, I, U, dT/dX, A are the current in amperes,
voltage across the heater in volts, temperature gradient
(degree/m) and sample area (m2
), respectively.
The heat transport through lattice vibrations
(phonons) is mainly important for insulators and semi-
conductors. The thermal conductivity of the sintered
ore sample crystals has contributions from two compo-
nent [28], lattice vibration (phonons), and the carriers
(electrons).
K = Kph
+ Ke
If we consider the heat conduction by electron
carriers due to the presence of Fe2+
and Fe3+
impuri-
ties, the temperature gradient will cause a carrier con-
centration gradient, this results in a diffusion current
which transports heat energy. At temperatures lower than
the Debye temperature, the inelastic scattering processes
become important thus a strongly affecting the thermal
conductivity. In this range there is a sharp drop in phonon
concentration with rising temperature, leading to a sharp
increase in K which becomes proportional to T3
. But at
temperatures higher than the Debye temperature, the
scattering processes must be responsible for the ther-
mal resistance and the elastic scattering is dominant
since the phonon contribution to the thermal conduc-
tivity is relatively small compared with the electron
contribution.
The measured thermal conductivity is approxi-
mately equal to the contribution from electrons. In this
range K is inversely proportional to the temperature
(K ≡T-1
).
The temperature dependence of K for the inves-
tigated sintered ore samples is shown in Fig. 11. A sharp
rising of thermal conductivity with rising temperature
can be observed up to the transition temperature. The
concentration of phonons decreases with rising tempera-
ture leading to a consequent decrease in lattice vibra-
tions. This decrease of lattice vibration gives diminish-
ing to lattice scattering causing an increase in the mean
free path which would result in an increase of K.
Thus, the thermal conductivity K increases at
low temperature due to the increase of modes of vibra-
tion of crystal lattice and the responsible for conduc-
tion is the phonons up to Debye temperature. Above
the transition temperature or Debye temperature the
concentration of phonons increases with rising tempera-
ture leading to lattice scattering causing a decrease in the
mean free path which would result in a decrease of K. As
shown in Fig. 11 the values of thermal conductivity K
increase as the sintering temperature of the tested sin-
tered ore samples is also increased. As the sintering
temperature increases the material becomes more dense
and the pores are decreased. The pores act as scattering
centers of phonons, so the decreasing of pores causes
the observed increasing of the thermal conduction K.
The maximum values of thermal conductivity of the
tested ore samples sintered at 573, 773 and 973 K were
as follows: 180, 210 and 390 K (W/m deg) x 10-3
, re-
spectively, as shown in Fig. 11. The results obtained
from thermal conductivity K measurements are in a
good agreement with those obtained from the previous
electrical conductivity σ studies.
The thermoelectric power coefficient α was mea-
sured experimentally for the investigated sintered ore
Fig.11. Temperature dependence of thermal conductivity
K for sintered ore samples.
10. Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010
344
samples as a function of temperature. The α measured
was of negative values, showed that the main charge
carriers are electrons hopping between Fe2+
and Fe3+
ions which are present originally in the material as im-
purities (called dopants). Dopant or doping Fe ele-
ment whose atoms tends to give electrons to the semi-
conductor thereby increasing the electron density and
called donor. Iron impurities modify the electrical and
thermal properties to obtain a semiconductor that will
exhibit n-type conduction. It is clear that the electrons
constituting the iron impurity conduction are the chief
charge carrier in the investigated semiconductor sin-
tered ore material. Finally, the conduction current in
the investigated semiconductor sintered ore samples is
the sum of electronic and hole currents, but electronic
current is many times that of hole current.
Efficient solar conversion requires materials with
band gaps [29] of 1.3±0.3 eV i.e. absorption of light in
the spectral range of 250-1000 nm. Considerable atten-
tion has been given in the recent years to the application
[30, 31] of semiconductor colloids, powders and films
for conversion of solar energy into electricity and chemical
energy. The concentration of current carriers and hence
the semiconductivity increases with increasing tempera-
ture according to a Boltzmann distribution [24]. Thus,
the obtained experimental energy gap values Eg
of the
sintered ore samples under consideration as shown in
Table 3 are suitable and optimum for using the tested
natural sintered ore material as a highly absorbing semi-
conductor in the photoelectrochemical systems and
thermo-technological applications as suggested in the
following techniques:
(1) Nitrogen reduction to ammonia by photosen-
sitized [32] electron transfer from dispersed ore oxides
(Fe2
O3
, PbO2
, ZnO) doped TiO2
semiconductor particles.
(2) Semiconductors in water treatment [33].
(3) Colloidal semiconductors in photovoltaic sys-
tems [27,34]. As known from the Schottky barrier theory,
the low bias potential region might be controlled by re-
combination and trapping of electrons in the depletion
region [35]. These processes occur most effectively in
localized states energetically centered in the mid-gap
position leading to a. recombination current proportional
to [exp (qV/2kT)-1][36,37].
(4) It is often necessary that semiconductor mate-
rials be exclusively of n- or p-type for many industrial
applications, e.g. for semiconductor-based rectifiers to
rectify alternating current into pulsating direct current.
Thus a system of two semiconductors with different types
of electric conduction resists reverse current flow. This
property is highly valued for semiconductor rectifiers.
Fusing together the two types forms a p-n junction that
has the property of rectifying alternating current. If we
apply an a.c. voltage to such a system of two semicon-
ductors, the p-n junction will pass the current of only
one half-cycle of voltage. In crystal diodes the p-n junc-
tion are used chiefly for rectifiers applications.
(5) Thermo-electric generation is essentially the
same as the energy conversion and heat pumping (when
a semiconductor material is used thermoelectrically as a
heat pump) with p-type and n-type materials.
(6) Partial illumination of a semiconductor induces
a photo emf between the illuminated and unilluminated
areas of the material surface. This phenomenon is used for
making sources of electric power, such as photovoltaic
cells and solar batteries, semiconductor devices capable
of solar-to-electric energy conversion.
CONCLUSIONS
The obtained results from the electron microscopic
investigation for the either native ore and/or for the ore
after sintering treatment confirmed by metal value data
given in the ASTM. cards coincide well with those given
by chemical analysis.
From the observations of I-U characteristics,
ln σ vs. 1/T and K vs. T behaviours of the investigated
natural sintered ore samples, we can summarize the fol-
lowing conclusions.
• The sintered ore material had a good
semiconductivity behaviour with increasing temperature.
• The semiconductor sintered ore exhibits n-type
conduction.
• Both values of Ea
and Eg
in eV decrease with
increasing the applied sintering temperature from 573 to
1273 K. Consequently the electrical conductivity σ in-
creases in the same range of the studied sintering tem-
peratures.
• The thermal phonon scattering and lattice vi-
bration scattering are responsible of thermal conductiv-
ity K for the behaviour of the material at changing tem-
peratures.
11. Loutfy H. Madkour
345
• The measurements for electrical, thermal and
semiconductivity behaviour of the investigated material,
obtained by solid state sintering, suppose its
thermotechnological industrial applications.
REFERENCES
1. A.H. Sabet, V.B. Tsogoev, V.P. Bordonosov, V.A.
Beloshitsky, D.N. Kuznetsove, H.A. El-Hakim, An-
nals of the Geological Survey of Egypt According to
Contract VI. 1980, 1976.
2. A.M. Eid, M.M. Abd EI-Rehime, Metallurgical Re-
search on Zn-Pb Oxidised Ore of Umm-Gheig De-
posit, Eastern Desert Geological Survey and Mineral
Research Department, Egypt, 1963, 22.
3.P.V.Viswanathan,B.V.S.Yedavalli,S.R.Srinivasan,P.P.
Bhatnagar,SymposiumonRecentDevelopmentinNon-
Ferrous Metals Technology, v. II, Copper, 1968.
4. H.H. Kellogg, A Critical Review of Sulphation Equi-
libria, Trans. Metallurgical Society of A.I.M.E., 1964,
230 and 1622.
5. G.R. Smithson Jr, J.E. Hanway Jr, Bench Scal Devel-
opment of a Sulphation Process for Complex Sul-
phide Ores Trans. Metallurgical Society of A.I.M.E.,
1962, 224 and 827.
6. F. Taha, S.E. Afifi, L.H. Madkour, J. Tabbin Institute
for Metallurgical Studies, (T.I.M.S.), 1982, 47.
7. A.P. Snernikar, V.M. Yurenko, Laboratory Studies
on the Hydrometalurgical Treatment of Cu-Pb-Zn
Intermediate Products, Russian Journal of Non-Fer-
rous Metals, 11, 1965, 77.
8. L.H. Madkour, Thermodynamic Studies on Sulphate
Roasting for Zinc Electrowinning from Carbonate
Ore, J. Chem. Tech. Biotechnol., 36, 1985, 197.
9. M. Tao et al., J. Appl. Phys., 61, 1987, 1562.
10. E. Omisson, G.L.J. Dunlop, J. Appl. Phys., 66, 1989,
3666.
11. Z. Feng, Cao Zechun, J. Appl. Phys., 80, 2, 1996,1033.
12. V. Parvanova, I. Iliev, L. Ilkov, Synthesis and mi-
crowave properties of doped zinc titanate,
J.Univ.Chem. Tech.Met.(Sofia), 41, 4, 2006, 461-
466.
13. B. Boyanov, Synthesis and determination of Curie
temperature of ferrites from the systems BaO-CoO-
ZrO2
-Fe2
O3
and BaO-NiO-ZrO2
-Fe2
O3
, J. Univ.
Chem. Tech. Met. (Sofia), 41, 1, 2006, 61-64.
14. E. Merck, Complexometric Assay Methods With
Titriplex, Merck, Darmstadt 1971, 3rd ed.
15. A.A. Awad Ghani, , M.A. Ahmed, Proc. Math and
Phys. Soc. Egypt, 1976, 12, 93.
16. D.N. Todor, Thermal Analysis of Minerals, Abacus
Press, 1976.
17. L.H. Madkour, Recommended Flowsheets for the
Electrolytic Extraction of Lead and Zinc from Red
Sea Polymetal Ore. J. Chem. Tech. Biotechnol., 35A,
1985, 108-114.
18. L.H. Madkour, M.M. Abou-Sekkina, O.M. Hemeda,
Thermo-Physical Studies on Ilmenite Ore for Mass
Production of Ceramic Capacitors, J. Erzmetall 49,
5, 1996, 309.
19. L.J. Bellamy, The Infrared Spectra of Complex
Molecules, Third edition, 1975, Chapman and Hall
Ltd., London.
20. K. Nakamoto, Infrared Spectra of Inorganic and
Coordination Compounds, Wiley, New York, 1970.
21. P.J. Jorgensen, Sintering and Related Phenomena,
Ed. G.G. Kuczynski, Hooton, N.A., Gibbon, C.F.
Gordan & Breach. New York, 1967, 40.
22. H. Schmalzried, Solid State Reactions, Verlage
Chemie Weinheim Bergstr, Academic press: INC,
New York and London, 1974.
23. B.K. Kuanr, G.B.J. Srivastava, J. Appl. Phys., 75,
10, 1994, 6115.
24. J.O. Williams, Adv. Phys. Org. Chem., 16, 1978, 159.
25. D.W. Strickler, W.G.J. Carlson, J. Amer. Ceramic
Soc., 48, 6, 1965, 286.
26. N. Nikulin, Fundamentals of Electrical Materials,
Mir Publishers, Moscow, 1988.
27. K. Büker, N. Alonso-Vante, H.J. Tributsch, Appl.
Phys., 72, 12, 1992, 5721.
28. J.S. Blakmore, in Solid State Physics, 2nd edition,
Mir Publisher, 1988, p. 118, 169.
29. R. Memming, Electrochim. Acta, 25, 1980, 77.
30. M. Grätzel, Heterogeneous Photochemical Electron
Transfer, Boca, Raton F.L: CRC Press, 1989.
31. P.V. Kamat, in: Kinetics and Catalysis in Microhetero-
geneousSystems,M.Grätzel,K.Kalyanasundaram,(Eds.)
Marcel Dekker, New York, 1991, 375.
32. P.P. Radford, C.G.J. Francis, J. Chem. Soc. Chem.
Commun., 1983, 1520.
33. M. Grätzel, in: Modern Aspects of Electrochemis-
try, R.E. White, J.O’M. Bockris, B.E. Conway, (Eds.),
Plenum Press, New York, 1983.
34. P. Bogdanoff, N. Alonso-Vante, J. Electroanal. Chem.,
12. Journal of the University of Chemical Technology and Metallurgy, 45, 3, 2010
346
1994, 379, 415.
35. E.H. Rhoderick, R.H. Williams, Metal-Semiconduc-
tor Contacts, 2nd
ed., C1arendon, Oxford, 1988.
36. W. Shockley, T.W. Road, Phys. Rev., 87, 1952, 835.
37. A.S. Grove, Physics and Technology of Semicon-
ductors Devices, Wiley, New York, 1967.