This document summarizes a method for preparing carbon-supported magnesium nanoparticles using melt infiltration. Molten magnesium is infiltrated into various types of nanoporous carbon supports, including graphite, activated carbon, and ordered mesoporous carbon. The magnesium crystallizes within the nanopores of the carbon, resulting in magnesium nanoparticles ranging in size from 2-5 nm down to less than 2 nm. Up to 15 wt% magnesium nanoparticles can be supported on the carbon without forming bulk magnesium particles. These composite materials may enable improved hydrogen storage properties due to nanosizing effects and interactions between the magnesium and carbon support.
The document summarizes a study on the photo-oxidative degradation of p-nitrophenol (PNP), a toxic and refractory organic pollutant, using hydrogen peroxide (H2O2) as an oxidizing agent and ultraviolet (UV) light. The degradation of PNP was found to be faster with a combination of UV light and H2O2 compared to using either method alone. A higher intensity 125W UV lamp achieved complete degradation within 2 hours, while an 8W lamp required 5 hours. Degradation rate increased under neutral to alkaline conditions compared to acidic pH. Hydroxyl radicals generated from the UV-induced photolysis of H2O2 were the primary oxidizing agents that attacked
One Pot Hydrothermal Synthesis Characterizations Of Silver Nanoparticles On R...IOSRJAC
Graphene-based nanocomposite have significant applicability in catalysis, electronics, medicine, and energy. In this report silver nanoparticles (AgNPs) with Reduced Graphene Oxide (RGO) - nanocomposite was prepared by a one-pot hydrothermal process using silver nitrate as a precursor. Under hydrothermal process Graphene oxide (GO) was reduced to reduced graphene oxide (RGO), without using chemical reagents. As synthesized (Ag-RGO) nanocomposite was characterized by XRD, UV Vis-spectroscopy, Scanning electron microscope, and Raman spectroscopy. Antimicrobial activities of the composite were investigated against both Gram-positive and Gram-negative bacteria. The results demonstrate that Ag-RGO nanocomposite was a strong bactericide against Gram-negative bacteria. Antioxidant activity was evaluated for bare GO, Ag and Ag-RGO nanocomposite by DPPH radical scavenging assay. It was observed that Ag/RGO nanocomposite has enhanced antioxidant activity than bare GO and Ag.
Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Productijtsrd
A condensation product CP was successfully synthesized from reaction of dimethyl amino benzaldehyde and aniline giving yields of 80 . The compound was characterized by Fourier Transform Infrared FTIR Spectroscopy. The corrosion inhibiting property of the CP on mild steel in HCl solution were investigated by the weight loss measurements, electrochemical impedance spectroscopy EIS and linear polarization resistance LPR . The concentrations of CP were varied from 1 x 10 3 M to 5 x 10 3 M. The inhibition efficiencies obtained from all the methods employed were in good agreement where the percentage of inhibition efficiencies increased with concentration of CP. Results showed that CP was the better inhibitor with inhibition efficiency of 90 at 5 x 10 3 M additive concentration. This is likely due to the effect of its large molecular size, higher number of electroactive heteroatoms and bigger p electron cloud of the conjugated double bond system. Ganesha Achary "Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Product" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30869.pdf Paper Url :https://www.ijtsrd.com/chemistry/physical-chemistry/30869/corrosion-inhibition-of-mild-steel-in-hcl-medium-by-a-condensation-product/ganesha-achary
The document discusses using forward osmosis (FO) to treat reverse osmosis concentrate (ROC) from water treatment plants. It examines using FO alone and with granular activated carbon (GAC) pretreatment to reduce the volume of ROC and remove organic micropollutants. Five steps of FO using 2-3M NaCl as the draw solution reduced the ROC volume to 8%. FO rejected some organic micropollutants but GAC pretreatment followed by FO removed almost all organic micropollutants from the ROC. Reducing the pH of the ROC feed solution arrested flux decline caused by fouling during FO.
Isotherm Modeling and Thermodynamic Study of the Adsorption of Toxic Metal by...CrimsonpublishersEAES
Isotherm Modeling and Thermodynamic Study of the Adsorption of Toxic Metal by the Apricot Stone by Moussa Abbas*, Tounsia Aksil and Mohamed Trari in Environmental Analysis & Ecology Studies
Synthesis, spectroscopic, magnetic properties and superoxide dismutase (SOD) ...IOSR Journals
Three new ternary copper(II) complexes formulated as [Cu(HIda)(bipy)] 1; [Cu(HIda)(phen)] 2; [Cu(HIda)(dmp)] 3; where HIda =N-(2-hydroxyethyl)-2- iminodiacetic acid ; bipy = 2, 2’- bipyridine; phen = 1,10- phenanthroline; dmp = 2,9-dimethyl 1,10-phenanthroline, have been synthesized and characterized by partial elemental analysis, FAB-mass (m/z), EPR, UV-visible and CV measurements. The magnetic and spectroscopic data of all these complexes 1-3 indicate distorted octahedral geometry. The EPR spectra of these complexes in frozen DMSO solutions showed a single at g ca. 2. The trend in g-value (g||>g>2.0023) suggests that the unpaired electron on copper (II) has dx2–y2 character. The SOD activities of the complexes have been investigated. Antibacterial and antifungal activity of these complexes were also measured and discussed.
This document summarizes research on using various catalysts to promote the dehydrogenation of cyclohexane to produce hydrogen gas. Key findings include:
- Monometallic silver (Ag) catalysts supported on activated carbon cloth showed increasing hydrogen evolution rates with increasing Ag loading up to 10 wt%, but rates decreased at 15 wt% loading likely due to poorer dispersion.
- Bimetallic catalysts with 1 wt% noble metals (platinum, palladium, rhodium) promoted on 10 wt% Ag/ACC showed enhanced hydrogen evolution rates compared to the monometallic Ag catalyst. In particular, a 10 wt% Ag-1 wt% Pt catalyst produced hydrogen at twice the rate of the 10 wt%
This document summarizes research on the catalytic hydrogenation of aqueous nitrate over iron/carbon (Fe/C) catalysts. Key points:
- Batch and continuous reactor experiments show that Fe/C catalysts can effectively reduce nitrate in water to nitrogen gas with high selectivity and activity. Up to 2.9 mmol/gmetal/min nitrate reduction rate was achieved in batch tests.
- Column studies demonstrate the catalyst can reduce nitrate levels below 5 ppm from an initial 100 ppm concentration, with a breakthrough capacity of over 530 bed volumes to reach 45 mg/L.
- Characterization with XRD, SEM-EDAX and XPS confirms the presence of iron dispersed on the
The document summarizes a study on the photo-oxidative degradation of p-nitrophenol (PNP), a toxic and refractory organic pollutant, using hydrogen peroxide (H2O2) as an oxidizing agent and ultraviolet (UV) light. The degradation of PNP was found to be faster with a combination of UV light and H2O2 compared to using either method alone. A higher intensity 125W UV lamp achieved complete degradation within 2 hours, while an 8W lamp required 5 hours. Degradation rate increased under neutral to alkaline conditions compared to acidic pH. Hydroxyl radicals generated from the UV-induced photolysis of H2O2 were the primary oxidizing agents that attacked
One Pot Hydrothermal Synthesis Characterizations Of Silver Nanoparticles On R...IOSRJAC
Graphene-based nanocomposite have significant applicability in catalysis, electronics, medicine, and energy. In this report silver nanoparticles (AgNPs) with Reduced Graphene Oxide (RGO) - nanocomposite was prepared by a one-pot hydrothermal process using silver nitrate as a precursor. Under hydrothermal process Graphene oxide (GO) was reduced to reduced graphene oxide (RGO), without using chemical reagents. As synthesized (Ag-RGO) nanocomposite was characterized by XRD, UV Vis-spectroscopy, Scanning electron microscope, and Raman spectroscopy. Antimicrobial activities of the composite were investigated against both Gram-positive and Gram-negative bacteria. The results demonstrate that Ag-RGO nanocomposite was a strong bactericide against Gram-negative bacteria. Antioxidant activity was evaluated for bare GO, Ag and Ag-RGO nanocomposite by DPPH radical scavenging assay. It was observed that Ag/RGO nanocomposite has enhanced antioxidant activity than bare GO and Ag.
Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Productijtsrd
A condensation product CP was successfully synthesized from reaction of dimethyl amino benzaldehyde and aniline giving yields of 80 . The compound was characterized by Fourier Transform Infrared FTIR Spectroscopy. The corrosion inhibiting property of the CP on mild steel in HCl solution were investigated by the weight loss measurements, electrochemical impedance spectroscopy EIS and linear polarization resistance LPR . The concentrations of CP were varied from 1 x 10 3 M to 5 x 10 3 M. The inhibition efficiencies obtained from all the methods employed were in good agreement where the percentage of inhibition efficiencies increased with concentration of CP. Results showed that CP was the better inhibitor with inhibition efficiency of 90 at 5 x 10 3 M additive concentration. This is likely due to the effect of its large molecular size, higher number of electroactive heteroatoms and bigger p electron cloud of the conjugated double bond system. Ganesha Achary "Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Product" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30869.pdf Paper Url :https://www.ijtsrd.com/chemistry/physical-chemistry/30869/corrosion-inhibition-of-mild-steel-in-hcl-medium-by-a-condensation-product/ganesha-achary
The document discusses using forward osmosis (FO) to treat reverse osmosis concentrate (ROC) from water treatment plants. It examines using FO alone and with granular activated carbon (GAC) pretreatment to reduce the volume of ROC and remove organic micropollutants. Five steps of FO using 2-3M NaCl as the draw solution reduced the ROC volume to 8%. FO rejected some organic micropollutants but GAC pretreatment followed by FO removed almost all organic micropollutants from the ROC. Reducing the pH of the ROC feed solution arrested flux decline caused by fouling during FO.
Isotherm Modeling and Thermodynamic Study of the Adsorption of Toxic Metal by...CrimsonpublishersEAES
Isotherm Modeling and Thermodynamic Study of the Adsorption of Toxic Metal by the Apricot Stone by Moussa Abbas*, Tounsia Aksil and Mohamed Trari in Environmental Analysis & Ecology Studies
Synthesis, spectroscopic, magnetic properties and superoxide dismutase (SOD) ...IOSR Journals
Three new ternary copper(II) complexes formulated as [Cu(HIda)(bipy)] 1; [Cu(HIda)(phen)] 2; [Cu(HIda)(dmp)] 3; where HIda =N-(2-hydroxyethyl)-2- iminodiacetic acid ; bipy = 2, 2’- bipyridine; phen = 1,10- phenanthroline; dmp = 2,9-dimethyl 1,10-phenanthroline, have been synthesized and characterized by partial elemental analysis, FAB-mass (m/z), EPR, UV-visible and CV measurements. The magnetic and spectroscopic data of all these complexes 1-3 indicate distorted octahedral geometry. The EPR spectra of these complexes in frozen DMSO solutions showed a single at g ca. 2. The trend in g-value (g||>g>2.0023) suggests that the unpaired electron on copper (II) has dx2–y2 character. The SOD activities of the complexes have been investigated. Antibacterial and antifungal activity of these complexes were also measured and discussed.
This document summarizes research on using various catalysts to promote the dehydrogenation of cyclohexane to produce hydrogen gas. Key findings include:
- Monometallic silver (Ag) catalysts supported on activated carbon cloth showed increasing hydrogen evolution rates with increasing Ag loading up to 10 wt%, but rates decreased at 15 wt% loading likely due to poorer dispersion.
- Bimetallic catalysts with 1 wt% noble metals (platinum, palladium, rhodium) promoted on 10 wt% Ag/ACC showed enhanced hydrogen evolution rates compared to the monometallic Ag catalyst. In particular, a 10 wt% Ag-1 wt% Pt catalyst produced hydrogen at twice the rate of the 10 wt%
This document summarizes research on the catalytic hydrogenation of aqueous nitrate over iron/carbon (Fe/C) catalysts. Key points:
- Batch and continuous reactor experiments show that Fe/C catalysts can effectively reduce nitrate in water to nitrogen gas with high selectivity and activity. Up to 2.9 mmol/gmetal/min nitrate reduction rate was achieved in batch tests.
- Column studies demonstrate the catalyst can reduce nitrate levels below 5 ppm from an initial 100 ppm concentration, with a breakthrough capacity of over 530 bed volumes to reach 45 mg/L.
- Characterization with XRD, SEM-EDAX and XPS confirms the presence of iron dispersed on the
Investigative studies on the inhibitive effects of Newbouldialaevis extracts ...researchinventy
The inhibitive effects ofNewbouldiaLaevis (NL) leaf extract and magnetic field on copper corrosion in 0.5M H2SO4 aqueous solution were investigated experimentally by gravimetric technique and theoretically using Quantum Chemical calculations. The results show that both NL and the magnetic field caused reduction in corrosion rate. The inhibition efficiency increased with concentration. The magnetic field caused greater increase in the inhibition efficiency. Temperature increase caused a decrease in inhibition efficiency. The activation energy is low and oscillates, possibly due to error factor from non-linearity of the Arrhenius plot. Among the tested isotherms, Langmuir has the highest correlation coefficient of 0.9963 and 0.7935 with and without magnet field respectively. The magnetic field increased the change in free energy, caused the reaction to become spontaneous, one mole of the inhibitor to replace 4 moles of water mole while reducing the number of monolayer of the inhibitor on the metal. The quantum chemical calculations performed on newbouldiaquinone and lapacholconstituents of NL showed that lapachol contributed more to the inhibition efficiency due its low binding energy, high dipole moment, chemical softness and fractional electron transfer. The magnetic field and temperature played opposite roles.
Corrosion Inhibition of Carbon Steel in Chloride and Sulfate SolutionsIJERA Editor
The document discusses corrosion inhibition of carbon steel in chloride and sulfate solutions. It studies using a combination of dichromate, molybdate, and nitrite inhibitors to provide high corrosion inhibition. Testing involved immersing steel coupons in synthetic solutions with chloride and sulfate ions and measuring corrosion rates. Results found that a combination of 1 ppm sodium dichromate, 250 ppm sodium molybdate, and 50 ppm sodium nitrite provided the best corrosion inhibition while meeting environmental regulations. Further testing examined the effects of changing inhibitor concentrations and environmental parameters like chloride concentration, rotation speed, and pH. The inhibitor combination performed well except being sensitive to increases in sulfate concentration.
This document provides an overview of coupling reactions, specifically palladium-catalyzed cross coupling reactions. It discusses the types of coupling reactions, including heterocouplings and homocouplings. Reductive elimination and beta hydride elimination are important reaction mechanisms. Organometallic reagents like organolithium and organomagnesium compounds are commonly used in coupling reactions. Examples of coupling reactions discussed include the Heck, Suzuki, and Stille reactions, and the mechanisms of the Heck reaction are outlined in steps of oxidative addition, π complex formation, insertion, and elimination.
SYNTHESIS AND CHARACTERIZATION OF KAOLINITE COATED WITH CU-OXIDE AND ITS EFFE...Premier Publishers
This document summarizes a study that synthesized copper oxide coated kaolinite to remove mercury ions from aqueous solution. Kaolinite was characterized and then coated with copper oxide via precipitation and thermal treatment. The coated material was then tested for removing mercury ions from water. Key findings include:
1) The copper oxide coated kaolinite was characterized through various analyses which confirmed the coating and composition.
2) Reactivity experiments determined the proton coefficient was 0.89, indicating decreased proton consumption compared to uncoated kaolinite.
3) Kinetic studies found maximum 85% mercury adsorption after 12 hours, with mass transfer rates lower than for uncoated kaolinite, possibly due to blocked reaction sites on the
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Characterization of Semi-Interpenetrated Network Alginate/Gelatin Wound Dress...UniversitasGadjahMada
Gel contraction of alginate during ionic crosslinking at sol phase was reduced by blending with gelatin solution due to intermolecular interaction and chain entanglement. The semi-interpenetrated network (semi-IPN) of wound dressing hydrogels were prepared by overlaid alginate/gelatin blend with 1.0% (w/w) CaCl2 solution under ambient temperature for 2 h. Results showed that gel contraction was significantly reduced with increasing gelatin content i.e. from 40.5 ± 5.8% for pure alginate to as low as 5.8 ± 1.2% for alginate/gelatin of 1:7 (w/w). It seems that gelatin successfully inhibited alginate chains mobility during their network re-arrangement by a Ca2+ cation. The FTIR spectra of hydrogels showed a combination of characteristic vibration of alginate and gelatin. Increasing gelatin content also significantly improved elasticity and tensile strength at break of dried hydrogels. Swelling kinetics of dried hydrogels were fitted with Schott’s second-order power-law model. Increasing gelatin fraction increased the swelling rate while decreased the swelling at equilibrium. Their absorptive capacity was of the interval for management of moderate to heavily exudating wound.
This document describes a study that synthesized γ-alumina nanotubes using a hydrothermal method and used them to support iron, cobalt, and nickel Fischer-Tropsch catalysts. Characterization showed the alumina nanotubes had a surface area of 203.73 m2/g. The three catalysts were prepared by wet impregnation and showed different catalytic behaviors. Nickel catalyst had the highest activity, followed by cobalt then iron catalyst, based on measurements of acidity, reducibility, active sites, and CO conversion in Fischer-Tropsch testing.
This document summarizes a study that used response surface methodology to optimize the removal of Zn2+ ions from aqueous solution using a novel biochar-alginate composite adsorbent. The researchers developed a quadratic model to predict Zn2+ removal based on initial Zn2+ concentration, adsorbent dose, and temperature. Their analysis found that initial Zn2+ concentration and adsorbent dose had the largest effect on removal efficiency. The optimum conditions for maximum 85% removal were determined to be an initial Zn2+ concentration of 43.18 mg/L, adsorbent dose of 0.062 g, and temperature of 313.5 K.
Electrochemical investigations on the inhibition behaviorAliKarimi127
This document discusses the corrosion inhibition properties of di(Resacetophenone) 1,2 cyclohexandiimine (R DACH) Schiff base on steel in 1 M HCl solution. Electrochemical measurements including potentiodynamic polarization, electrochemical impedance spectroscopy, and chronoamperometry were used to evaluate the inhibition efficiency of R DACH at different concentrations and temperatures. The results showed that R DACH is an effective corrosion inhibitor for steel, with inhibition efficiency increasing with increasing concentration. Adsorption of the inhibitor followed the Langmuir isotherm. Activation energy and thermodynamic parameters like enthalpy, entropy, and Gibbs free energy of adsorption were calculated from corrosion currents at different temperatures and
This document summarizes the preparation, characterization, and antimicrobial activities of mixed ligand complexes of Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) with a Schiff base ligand derived from cephalexin drug and 4(dimethylamino)benzaldehyde combined with nicotinamide. The ligand and complexes were characterized using various analytical techniques. The complexes were found to be non-electrolytes with octahedral geometry. Antimicrobial testing showed the complexes had antibacterial activity against Staphylococcus aureus and Escherichia coli.
Preparation , characterization and antimicrobial activities of mixed ligand c...Alexander Decker
This document describes the preparation, characterization, and antimicrobial activities of mixed ligand complexes of Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) with a Schiff base ligand derived from cephalexin drug and 4(dimethylamino)benzaldehyde combined with nicotinamide. The ligand and complexes were characterized using techniques such as NMR, FT-IR, UV-Vis, elemental analysis, conductivity measurements, and magnetic susceptibility. The complexes showed octahedral geometry and were found to be non-electrolytes. The complexes and free ligand were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli.
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.
The document discusses various applications of nanomaterials in catalysis. It begins by introducing different types of catalysts and how nanocatalysts combine advantages of homogeneous and heterogeneous systems by having a high surface area like homogeneous catalysts while also being easily separable like heterogeneous catalysts. Several examples of nanocatalyst applications are then summarized in areas like water purification, biodiesel production, drug delivery, fuel cells, environmental protection, and solar cells. The document emphasizes how nanocatalysts provide benefits like high activity, selectivity, stability, and being energy efficient.
This study investigated the effects of spermine NONOate (a nitric oxide donor), ATP, and sodium/potassium buffer environment on the thermal stability of human hemoglobin using circular dichroism spectroscopy. The main findings were:
1) Spermine NONOate decreased the unfolding temperature of hemoglobin irrespective of buffer composition.
2) ATP increased the unfolding temperature by 3°C in both sodium and potassium buffers.
3) The effects of ATP and nitric oxide depended strongly on the specific buffer ionic composition.
Chemical reduction technique for the synthesis of nickel nanoparticlesIJERA Editor
Chemical reduction technique was used to synthesize nickel powder using hydrazine hydrate as reducing agent,
nickel chloride hexahydrate as precursor and polyvinylpyrrolidone (PVP) as capping agent in ethylene glycol
medium. Experiments were carried out with mole ratios 13:1 and 20:1 of hydrazine to nickel chloride
hexahydrate by keeping the amounts of ethylene glycol and NaOH as constant. Variation of capping agent
concentration and temperature was also studied. X-ray diffraction (XRD) analysis was performed and the crystal
size was calculated using Debye-Scherrer equation. XRD peaks where corresponds to that of the face-centered
cubic nickel crystals, in accordance with the literature. Likewise, no oxygen peaks were found in XRD pattern,
which confirm the absence of oxide formation in nickel. Morphological studies were performed using scanning
electron microscopy (SEM) and the elemental composition was determined using energy dispersive X-ray
analysis. The elemental composition was found to be nickel with small traces of oxygen.
The document evaluates the corrosion inhibition of carbon steel in saline solutions using gluconate, zinc sulfate, and green clay eluate. Electrochemical measurements using the Tafel polarization technique show that sodium gluconate alone provides substantial corrosion inhibition in 0.5% NaCl solution, acting primarily through an anodic mechanism. However, pitting corrosion can still occur. The combination of gluconate and green clay eluate provides better inhibition of both general and localized corrosion at 84.9% efficiency. In 3.5% NaCl solution, which is more aggressive, 4g/L of gluconate alone inhibits 65.35% of corrosion. The addition of zinc sulfate or green clay eluate to gluconate mixtures provides further
Study of the Influence of Nickel Content and Reaction Temperature on Glycerol...IJRESJOURNAL
ABSTRACT: La2O3-SiO2-supported nickel catalysts were evaluated in glycerol steam reforming. The samples (30wt% La and 5, 10 and 15wt% of Ni on 70wt% commercial SiO2), prepared by the simultaneous impregnation method, were characterized by EDX, nitrogen physisorption, XRD, in-situ XRD, XANES and TPR. The analyses revealed NiO species weakly interact with the support and the different metallic surface areas of the catalysts. Catalytic tests were performed in a fixed bed reactor at 600oC and 15Ni catalyst, which showed the best performance, was also evaluated at 500oC and 700oC. According to the results, the Ni content on the catalyst surface interferes in the distribution of gaseous products H2, CO, CO2 and CH4. The increase in the Ni content increases the carbon formation during reaction. The reaction temperature affected the catalytic performance and the best results were obtained with the 15Ni catalyst at 600oC, which was also tested for 20 hours for the analysis of its stability.
Ultrasound In organic reaction and Supercritical Liquidsal mamun
This document discusses various applications of ultrasound and supercritical fluids in organic chemistry. It begins by defining ultrasound and describing how it is used to accelerate organic reactions by increasing reaction rates and product yields. Specific examples of heterocycle synthesis and other reaction types improved by ultrasound are provided. The document then defines supercritical fluids as substances above their critical point where distinct liquid and gas phases do not exist. Common supercritical fluids of carbon dioxide and water are noted. Applications of supercritical fluids discussed include extraction, dry cleaning, chromatography, chemical reactions, and biodiesel production.
Research Paper Presentation by Ariful IslamArifulIslam665
The document summarizes a research presentation on the synthesis and characterization of new zinc, copper, and nickel complexes based on an imine ligand containing a 2-aminothiophenol moiety. Specifically, it describes the synthesis of a tridentate Schiff base ligand and its dimeric complexes with zinc, copper, and nickel ions. It then discusses the various techniques used to characterize the ligand and complexes, including IR spectroscopy, UV-Vis spectroscopy, NMR spectroscopy, conductivity measurements, computational modeling, and X-ray crystallography. The key findings are that the complexes were stable in solid and solution states, with the ligand acting as a tridentate chelating agent, and DFT calculations provided insights into their frontier
This document discusses an investigation into using polyvinyl pyrrolidone (PVP) as a corrosion inhibitor for carbon steel in hydrochloric acid solutions. Electrochemical methods like electrochemical impedance spectroscopy and potentiodynamic polarization, as well as gravimetric methods, were used to study the corrosion inhibition. The results showed that PVP inhibits corrosion by adsorbing onto the carbon steel surface, forming a protective film. PVP was found to be a mixed-type inhibitor that reduced both the anodic and cathodic reaction rates. Inhibition efficiency increased with increasing PVP concentration and temperature, ranging from 56-90% depending on the method. The adsorption of PVP fit the Langmuir is
The document summarizes a study on using palladium supported on hydrotalcite as a heterogeneous catalyst for the Suzuki cross-coupling reaction. Various palladium salts were tested as catalysts with different bases and temperatures. PdCl2 supported on hydrotalcite with potassium carbonate as the base provided the best results, with conversions comparable to homogeneous catalysts at temperatures above 90°C. The catalyst was characterized and found to have a palladium content of 1% without changing the structure of the hydrotalcite support. It was an effective catalyst for the reaction, with higher temperatures, bromobenzene, and chlorobenzene providing better conversions than other conditions tested.
Paladio soportado sobre hidrotalcita como un catalizador para la reacción de ...52900339
This document summarizes a study on using palladium supported on hydrotalcite as a catalyst for the Suzuki cross-coupling reaction. Three palladium catalysts were prepared using different palladium salts and hydrotalcite as support. The catalysts were tested in the Suzuki reaction of phenylboronic acid and bromobenzene with various bases. Potassium carbonate provided the best results. The PdCl2-hydrotalcite catalyst gave the highest conversion. Increasing the temperature improved conversion. The catalyst also showed activity for chloro- and fluorobenzenes. The reaction was found to be heterogeneous and the catalyst could be reused after reactivation.
Investigative studies on the inhibitive effects of Newbouldialaevis extracts ...researchinventy
The inhibitive effects ofNewbouldiaLaevis (NL) leaf extract and magnetic field on copper corrosion in 0.5M H2SO4 aqueous solution were investigated experimentally by gravimetric technique and theoretically using Quantum Chemical calculations. The results show that both NL and the magnetic field caused reduction in corrosion rate. The inhibition efficiency increased with concentration. The magnetic field caused greater increase in the inhibition efficiency. Temperature increase caused a decrease in inhibition efficiency. The activation energy is low and oscillates, possibly due to error factor from non-linearity of the Arrhenius plot. Among the tested isotherms, Langmuir has the highest correlation coefficient of 0.9963 and 0.7935 with and without magnet field respectively. The magnetic field increased the change in free energy, caused the reaction to become spontaneous, one mole of the inhibitor to replace 4 moles of water mole while reducing the number of monolayer of the inhibitor on the metal. The quantum chemical calculations performed on newbouldiaquinone and lapacholconstituents of NL showed that lapachol contributed more to the inhibition efficiency due its low binding energy, high dipole moment, chemical softness and fractional electron transfer. The magnetic field and temperature played opposite roles.
Corrosion Inhibition of Carbon Steel in Chloride and Sulfate SolutionsIJERA Editor
The document discusses corrosion inhibition of carbon steel in chloride and sulfate solutions. It studies using a combination of dichromate, molybdate, and nitrite inhibitors to provide high corrosion inhibition. Testing involved immersing steel coupons in synthetic solutions with chloride and sulfate ions and measuring corrosion rates. Results found that a combination of 1 ppm sodium dichromate, 250 ppm sodium molybdate, and 50 ppm sodium nitrite provided the best corrosion inhibition while meeting environmental regulations. Further testing examined the effects of changing inhibitor concentrations and environmental parameters like chloride concentration, rotation speed, and pH. The inhibitor combination performed well except being sensitive to increases in sulfate concentration.
This document provides an overview of coupling reactions, specifically palladium-catalyzed cross coupling reactions. It discusses the types of coupling reactions, including heterocouplings and homocouplings. Reductive elimination and beta hydride elimination are important reaction mechanisms. Organometallic reagents like organolithium and organomagnesium compounds are commonly used in coupling reactions. Examples of coupling reactions discussed include the Heck, Suzuki, and Stille reactions, and the mechanisms of the Heck reaction are outlined in steps of oxidative addition, π complex formation, insertion, and elimination.
SYNTHESIS AND CHARACTERIZATION OF KAOLINITE COATED WITH CU-OXIDE AND ITS EFFE...Premier Publishers
This document summarizes a study that synthesized copper oxide coated kaolinite to remove mercury ions from aqueous solution. Kaolinite was characterized and then coated with copper oxide via precipitation and thermal treatment. The coated material was then tested for removing mercury ions from water. Key findings include:
1) The copper oxide coated kaolinite was characterized through various analyses which confirmed the coating and composition.
2) Reactivity experiments determined the proton coefficient was 0.89, indicating decreased proton consumption compared to uncoated kaolinite.
3) Kinetic studies found maximum 85% mercury adsorption after 12 hours, with mass transfer rates lower than for uncoated kaolinite, possibly due to blocked reaction sites on the
Nitrogen-doped graphene-supported copper complex: a novel photocatalyst for C...Pawan Kumar
A copper(II) complex grafted to nitrogen-doped graphene (GrN700–CuC) was synthesized and then
demonstrated as an efficient photocatalyst for CO2 reduction into methanol under visible light irradiation
using a DMF/water mixture. The chemical and microstructural features of GrN700–CuC nanosheets were
studied by FTIR, XPS, XRD and HRTEM analyses. Owing to its truly heterogeneous nature, GrN700–CuC
could be easily recovered after the photocatalytic reaction and showed efficient recyclability for
subsequent runs.
Characterization of Semi-Interpenetrated Network Alginate/Gelatin Wound Dress...UniversitasGadjahMada
Gel contraction of alginate during ionic crosslinking at sol phase was reduced by blending with gelatin solution due to intermolecular interaction and chain entanglement. The semi-interpenetrated network (semi-IPN) of wound dressing hydrogels were prepared by overlaid alginate/gelatin blend with 1.0% (w/w) CaCl2 solution under ambient temperature for 2 h. Results showed that gel contraction was significantly reduced with increasing gelatin content i.e. from 40.5 ± 5.8% for pure alginate to as low as 5.8 ± 1.2% for alginate/gelatin of 1:7 (w/w). It seems that gelatin successfully inhibited alginate chains mobility during their network re-arrangement by a Ca2+ cation. The FTIR spectra of hydrogels showed a combination of characteristic vibration of alginate and gelatin. Increasing gelatin content also significantly improved elasticity and tensile strength at break of dried hydrogels. Swelling kinetics of dried hydrogels were fitted with Schott’s second-order power-law model. Increasing gelatin fraction increased the swelling rate while decreased the swelling at equilibrium. Their absorptive capacity was of the interval for management of moderate to heavily exudating wound.
This document describes a study that synthesized γ-alumina nanotubes using a hydrothermal method and used them to support iron, cobalt, and nickel Fischer-Tropsch catalysts. Characterization showed the alumina nanotubes had a surface area of 203.73 m2/g. The three catalysts were prepared by wet impregnation and showed different catalytic behaviors. Nickel catalyst had the highest activity, followed by cobalt then iron catalyst, based on measurements of acidity, reducibility, active sites, and CO conversion in Fischer-Tropsch testing.
This document summarizes a study that used response surface methodology to optimize the removal of Zn2+ ions from aqueous solution using a novel biochar-alginate composite adsorbent. The researchers developed a quadratic model to predict Zn2+ removal based on initial Zn2+ concentration, adsorbent dose, and temperature. Their analysis found that initial Zn2+ concentration and adsorbent dose had the largest effect on removal efficiency. The optimum conditions for maximum 85% removal were determined to be an initial Zn2+ concentration of 43.18 mg/L, adsorbent dose of 0.062 g, and temperature of 313.5 K.
Electrochemical investigations on the inhibition behaviorAliKarimi127
This document discusses the corrosion inhibition properties of di(Resacetophenone) 1,2 cyclohexandiimine (R DACH) Schiff base on steel in 1 M HCl solution. Electrochemical measurements including potentiodynamic polarization, electrochemical impedance spectroscopy, and chronoamperometry were used to evaluate the inhibition efficiency of R DACH at different concentrations and temperatures. The results showed that R DACH is an effective corrosion inhibitor for steel, with inhibition efficiency increasing with increasing concentration. Adsorption of the inhibitor followed the Langmuir isotherm. Activation energy and thermodynamic parameters like enthalpy, entropy, and Gibbs free energy of adsorption were calculated from corrosion currents at different temperatures and
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Preparation , characterization and antimicrobial activities of mixed ligand c...Alexander Decker
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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.
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cubic nickel crystals, in accordance with the literature. Likewise, no oxygen peaks were found in XRD pattern,
which confirm the absence of oxide formation in nickel. Morphological studies were performed using scanning
electron microscopy (SEM) and the elemental composition was determined using energy dispersive X-ray
analysis. The elemental composition was found to be nickel with small traces of oxygen.
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Carbon corrosion and platinum nanoparticles ripening under open circuit poten...
The Preparation of Carbon-Supported Magnesium Nanoparticles
1. The Preparation of Carbon-Supported Magnesium Nanoparticles
using Melt Infiltration
Petra E. de Jongh,†,
* Rudy W. P. Wagemans,†
Tamara M. Eggenhuisen,†
Bibi S. Dauvillier,†
Paul B. Radstake,†
Johannes. D. Meeldijk,‡
John W. Geus,‡
and
Krijn P. de Jong†,
*
Inorganic Chemistry and Catalysis, Department of Chemistry, and Electron Microscopy Utrecht,
Department of Biology, Utrecht UniVersity, 3584 CA Utrecht, The Netherlands
ReceiVed August 6, 2007. ReVised Manuscript ReceiVed September 17, 2007
Magnesium dihydride contains 7.7 wt % hydrogen. However, its application for hydrogen storage is
impeded by its high stability and slow kinetics. Bringing the size of Mg(H2) into the nanometer range
will not only enhance the reaction rates but has also been theoretically predicted to change the
thermodynamic stability and destabilize the MgH2 with respect to Mg. However, the preparation of such
small particles is a major challenge. We identified a method to prepare large amounts of nanometer-
sized nonoxidized magnesium crystallites. The method is based on infiltration of nanoporous carbon
with molten magnesium. The size of the Mg crystallites is directly influenced by the pore size of the
carbon and can be varied from 2–5 to less than 2 nm. The majority of the nanocrystallites is not oxidized
after preparation. No bulk magnesium was detected in the samples with nanoparticle loadings up to 15
wt % on carbon. These 3D supported nanomaterials present interesting systems to study how nanosizing
and support interaction can steer the hydrogen sorption properties of metal hydrides.
Introduction
For hydrogen storage on board vehicles, the reversible
reaction of H2 with metals at near-ambient pressures and
temperatures may lead to compact systems with adequate
gravimetric storage densities if the main material components
are light metals.1,2
However, the reversibility and kinetics
are often limiting features. Kinetics and reversibility can be
improved by doping the material with a small amount of
catalyst and decreasing the crystallite size.3–7
If the material
is to absorb and desorb H2 near 1 atm and near fuel-cell
operating temperatures (roughly between 50 and 150 °C),
the enthalpy of decomposition (≡ -∆Hf
0
) should be in the
range of 42–55 kJ/mol of H2.2,8
Unfortunately, ∆Hf
0
is not
in the desired range for any of the primary metal hydrides
that meet gravimetric storage density criteria. Most hydrides,
such as NaH, LiH, and MgH2, are far too stable as bulk
materials to enable reasonable H2 pressures below 150 °C.8
Magnesium has been considered as one of the most
promising materials for hydrogen storage. It is light and
abundant, and magnesium dihydride contains 7.7 wt %
hydrogen. However, a major impediment toward practical
use is its large enthalpy of decomposition of 75 kJ/mol of
H2, which translates into an equilibrium temperature at 1
bar H2 pressure of 288 °C. In practice, sorption temperatures
of 300–400 °C are needed because of kinetic limitations,
especially if no catalyst is present and passivation by surface
oxidation has occurred.5
These temperatures can be lowered
by adding an extra compound that forms an alloy or
compound with the magnesium, thereby decreasing the
stability difference between the metal and the metal
hydride.8–10
However, for these increasingly complex sys-
tems, reversibility is often an issue because of mass-transport
limitations and phase segregation. Theoretical calculations
suggested that the hydrogen desorption enthalpy for pure
MgH2 also may be lower, namely, in systems with physical
confinement, small crystallites, or thin layers.11–15
Quantum-
chemical calculations showed that if the crystallite size is
reduced, MgH2 destabilizes faster than Mg. As a result, for
sufficiently reduced crystallite sizes (below 1 to 2 nm), the
absolute value of ∆Hf
0
decreases dramatically; for 0.9 nm
* To whom correspondence should be addressed. E-mail: p.e.dejongh@uu.nl;
k.p.dejong@uu.nl (P.E.d.J.).
†
Department of Chemistry, Utrecht University.
‡
Department of Biology, Utrecht University.
(1) Schlapbach, L.; Züttel, A. Nature 2001, 414, 353.
(2) http://www.eere.energy.gov/hydrogenandfuelcells/storage/storage_
challenges.html.
(3) Huot, H.; Liang, G.; Schulz, R. Appl. Phys. A: Mater. Sci. Process.
2001, 72, 187.
(4) Bogdanovic, B.; Schwickardi, M. J. Alloys Compd. 1997, 1, 253.
(5) Zaluski, L.; Zaluska, A.; Ström-Olsen, J. O. Appl. Phys. A: Mater.
Sci. Process. 2001, 72, 157.
(6) Oelerich, W.; Klassen, T.; Bormann, R. J. Alloys Compd. 2001, 315,
237.
(7) Baldé, C. P.; Hereijgers, B. P. C.; Bitter, J. H.; de Jong, K. P. Angew.
Chem., Int. Ed. 2006, 45, 3501.
(8) Alapati, S. V.; Johnson, J. K.; Sholl, D. S. J. Phys. Chem. B 2006,
110, 8769.
(9) Vajo, J. J.; Mertens, F.; Alm, C. C.; Bowman, R. C.; Fultz, B. J. Phys.
Chem. B 2004, 108, 13977.
(10) Dornheim, M.; Doppiu, S.; Barkhordarian, G.; Boesenberg, U.;
Klassen, T.; Gutfleisch, O.; Bormann, R. Scr. Mater. 2007, 56, 841.
(11) Liang, J. J.; Kung, W. C. J. Phys. Chem. B 2005, 109, 17837.
(12) Wagemans, R. W. P.; van Lenthe, J. H.; de Jongh, P. E.; van Dillen,
A. J.; de Jong, K. P. J. Am. Chem. Soc. 2005, 127, 16675.
(13) Liang, J. J. Appl. Phys. A: Mater. Sci. Process. 2005, 80, 173.
(14) Cheung, S.; Deng, W.-Q.; van Duin, A. C. T.; Goddard, W. A. J.
Phys. Chem. A 2005, 109, 851.
(15) Bérube, V.; Radtke, G.; Dresselhaus, M.; Chen, G. Int. J. Hydrogen
Res. 2007, 31, 637.
AChem. Mater. XXXX, xxx, 000–000
10.1021/cm702205v CCC: $37.00 XXXX American Chemical Society
Published on Web 10/26/2007
2. MgH2 crystallites, the enthalpy of decomposition is only 63
kJ/mol (200 °C theoretical equilibrium at 1 bar H2 pressure)
and could be reduced further for smaller particles.12
It has
also been predicted that encapsulation of Mg(H2) in a
nanoscale scaffold can considerably lower the decomposition
enthalpy of the hydride because of physical confinement.13
Furthermore, it is known, for instance, for interstitial hydrides
such as Pd, that stress within the material can influence the
hydrogen sorption properties; recently, destabilization of the
hydrides because of stress in Mg–Ti thin film systems was
reported.16
Hence, the possibility to prepare nanometer-sized
particles of magnesium, interacting with or confined by a
substrate or matrix, would yield interesting systems to
investigate the option to lower the H2 desorption temperature
for relatively stable metal hydrides.
Nanostructuring hydrogen storage materials by ball-milling
to improve kinetics and distribute dopants to the system is
common practice,17,18
but this method typically produces
micrometer-sized particles consisting of crystal grains with
a minimum size of 10–15 nm. Furthermore, during hydrogen
cycling, the crystal grain size rapidly increases to 50–100
nm.17
It is far from trivial to obtain smaller particles than
this and stabilize nanosized particles during cycling. Wet-
chemical synthesis of Mg nanoparticles in liquid ammonia
has been reported, but these experiments have not been
followed up.19
With gas-phase techniques, generally only
small amounts can be produced, and it is virtually impossible
to prevent significant oxidation.20,21
Very recently, Chen and
co-workers reported on the gas-phase growth of unsupported
magnesium nanorods that displayed enhanced hydrogen-
sorption kinetics.22,23
However, the minimum diameter of
these rods was 30–50 nanometers. In this paper, we report
on a method to prepare large quantities of 3D carbon-
supported metallic magnesium with crystallite sizes on the
order of a few nanometers.
Experimental Section
We prepared magnesium nanoparticles by infiltration of
nanoporous carbon with molten magnesium. Different types of
nanoporous carbons (particle size typically 20–50 µm) were
explored: Cmeso (high-surface area-graphite HSAG500-RC085
with mainly 2–3 nm pores, purity 99.9%, obtained from Timcal
Ltd., Bodio, Switzerland); microporous activated carbon, 99.5%
purity, without (ACmicro ) extrudate R2030CO2) or with 10 at
% oxygen (ACmicro-O ) granulate 990721) (both obtained from
Norit Nederland BV The Netherlands); ACm + m (activated carbon
containing both micro- and mesopores and ∼10 at % O, extrudate
ROZ 3 A8332 obtained from Norit Nederland BV, The Neth-
erlands); and ordered mesoporous carbon without (OMC) or with
(OMC_N) a significant amount of nitrogen, prepared as described
below. The ACmicro-O was pretreated with an aqueous 25 wt %
ammonia solution for 1 h under reflux, washed, and dried.
Ordered mesoporous carbon was obtained following Ryoo et al. 24
SBA-15 was synthesized by dissolving 8 g of the block copolymer
ethyleneoxide20–propyleneoxide70–ethyleneoxide20 (P123 Pluronic)
in 60 g of H2O and 240 g of an aqueous solution of 2 M HCl, and
slowly adding 17 g of tetra-ethyl-orthosilicate (TEOS, Acros
Organics) at 40 °C while stirring. The solution was rested for 20 h
at 40 °C, aged at 80 °C for 48 h, filtered, and dried at 120 °C. The
sample was calcined at 550 °C for 6 h. The carbon replica without
nitrogen was prepared by impregnation of 1 g of a dry SBA-15 in
vacuum with 0.7 mL of an oxalic acid solution in furfuryl alcohol
with a molar ratio of 0.0044:1. The furfuryl alcohol was polym-
erized by heating at 80 °C for 16 h in air. Carbonization was
achieved by heating under a N2 flow: first, for 6 h at 150 °C, and
then for 30 min at 300 °C (ramp 1 °C/min), and finally, for 4 h at
850 °C (ramp 1 °C/min). The nitrogen-containing carbon replica
was prepared via chemical vapor deposition using acetonitrile.25
For 2 h, an Ar stream of 30 mL/min was bubbled through CH3CN
at 30 °C before entering a fixed bed reactor with 0.5 g of SBA-15
at 900 °C. To remove the silica, we refluxed the composites in 300
mL of aqueous 1 M KOH solution for 2 h at room temperature;
they were then filtered and washed three times with 1 M KOH
(aq). After this procedure was repeated, the sample was washed
with water until the pH was neutral and dried overnight at 90 °C.
All nanoporous carbons were ground in a mortar, dried at 400 °C,
and stored under N2 in a glovebox (Mbraun Labmaster I30, ∼1
ppm H2O, ∼1 ppm O2).
MgH2 was obtained as a powder from Goldschmidt GmbH (∼35
µm Tego Magnan). In a typical experiment, after being dried, 1 g
of carbon was mixed with 500 mg of MgH2 of similar particle size
in a mortar. In an exploratory experiment, 1 g of ACm + m was
mixed with 500 mg of Mg and pressed for 15 min at 100 °C with
104
kg/cm2
to provide intimate contact between the carbon and
magnesium. Five hundred milligrams of the mixture was placed in
a flash-dried alumina cup (20 × 20 × 50 mm) and transported
under a nitrogen atmosphere to a tube furnace. The quartz tubes (ø
50 × 1000 mm) in the tube furnace (Thermolyne 79300) were
predried at 100 °C under an Ar flow (300 mL/min). To limit the
evaporation of magnesium, we placed the sample cup in a narrow
alumina tube (ø 30 × 60 mm) inside the quartz tube. A cup with
sacrificial MgH2 was placed in the gas stream just before the sample
as an oxygen and water scavenger. The sample was heated to 625
°C at 2.5 °C/min and kept there for 10 min before heating further
to 666 °C at 1 °C/min with an Ar flow of 30 mL/min. After 10
min just above the melting point of magnesium, the samples were
slowly cooled to room temperature. Around 350 °C, H2 was
introduced to replace Ar in the gas stream. After preparation, all
samples were stored and handled under nitrogen.
Scanning electron micrographs (SEM) were obtained using a
Philips XL30S FEG electron microscope equipped with embedded
EDAX and low kilovolt backscatter detectors. Powder samples were
applied dry to a conducting sticky carbon film on the sample holder.
The samples were briefly exposed to air upon transfer into the
electron microscopes. The TEM samples were prepared by dipping
a TEM substrate (consisting of a holey carbon film on a copper
grid) in the nanocomposite powder and shaking off excess material.
TEM analysis was performed using an FEI Tecnai 20 FEG
(16) Borsa, D. M.; Gremaud, R.; Baldi, A.; Schreuders, H.; Rector, J. H.;
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B Chem. Mater., Vol. xxx, No. xx, XXXX Jongh et al.
3. microscope operating at 200 kV. In bright field, virtually no contrast
between carbon and magnesium was observed and hence dark-field
imaging was used. To enhance detection of the nanoscale magne-
sium crystallites, we employed the dynamic conical dark-field mode
(for more details, see the Supporting Information). X-ray diffraction
patterns were collected with a Bruker-AXS D8 diffractometer
equipped with a Co-KR12 source (λ ) 1.78897 Å). The sample
holder was filled in the glovebox and closed airtight with a
hemispherical X-ray transparent lid. Data were collected from 20
to 80° 2θ with a step size of 0.034° 2θ for approximately 20 min
per sample. XRD was used in a semiquantitative manner to estimate
the total amount of crystalline bulk Mg (for details, see the
Supporting Information). N2 physisorption isotherms were recorded
with a Micromeritics TriStar 3000 apparatus at 77 K. Before
measurements, the samples were dried at 250 or 300 °C under a
He flow for 10 h. Single-point total pore volumes were determined
at p/p0 ) 0.995, and pore size distributions were determined from
the adsorption branch of the isotherms via the BJH method for pores
between 2 and 50 nm. Pore volumes were measured before and
after magnesium infiltration and after removal of magnesium. To
remove the magnesium species from the composite, we mildly acid
leached the sample by boiling it under reflux for 1 h in a 1 M
aqueous HCl solution, followed by washing and drying.
Results and Discussion
Detection of Nanoscale Magnesium. Because of the non-
polar nature of the carbon, molten magnesium is not a priori
expected to wet a carbon surface.26
We investigated different
options to improve the wetting: surface modification of the
carbons with nitrogen or oxygen, and forcing metallic
magnesium into the porous carbon by pressing at elevated
temperature before the melt-infiltration process. However,
even for some high-purity nanoporous carbons, we observed
spontaneous infiltration with molten magnesium, and the
formation of nanostructured magnesium upon cooling as will
be discussed below. See the Supporting Information for
details on the carbon morphologies.
To verify the presence of nanostructured Mg in the
carbon matrix, we employed transmission electron mi-
croscopy (TEM) combined with energy-dispersive X-ray
analysis (EDX). Typical results for ACm + m-, Cmeso-, and
ACmicro-based samples containing 25–35 wt % Mg are
shown in Figure 1 A–C respectively. The bright-field mode
(left panels) shows the disordered structure of the carbon,
but no larger crystallites. Because of the similarity in
atomic weight, it is not possible to distinguish magnesium
from carbon. However, in the dark-field mode (right
panels), small crystallites (bright spots) could be made
visible. The contrast was enhanced by using the dynamical
conical dark-field mode, choosing the beam angle such
that electrons diffracted because of interaction with
graphitelike material were not detected (for details, see
the Supporting Information). EDX confirmed that signifi-
cant amounts of Mg were present inside the porous carbon
particles. The average size of the nanocrystallites de-
creased from a few nanometers for ACm + m, to ∼2 nm
for Cmeso to less than 1–2 nanometers for ACmicro-based
samples, in accordance with the decreasing pore size of
the carbons.
Extent of Oxidation of the Nanocrystallites. Mg nano-
particles are extremely sensitive to oxidation, as was
evidenced by the immediate heat production and red glow
of the samples upon exposure to air after synthesis and
cooling down under inert atmosphere. To reduce the ox-
idation sensitivity, we made it the standard procedure to
replace the Ar atmosphere with hydrogen during the
cooling after melt-infiltration. As the hydrogen pressure
is modest, it is not expected that all magnesium is
hydrided. We tentatively ascribe the protective effect to
the formation of a surface hydride layer.27
It is a challenge
to determine and quantify which Mg species are present
in the samples. The presence of Mg carbides is unlikely;
their formation has been reported only in the presence of
a carbon source that readily decomposes at the melting
temperature of magnesium, such as pentane.28,29
However,
aside from Mg, MgH2 could also be present (either as
particles or as surface layer) as a result of interaction with
H2 during sample preparation. Furthermore, Mg(OH)2 and/
or MgO could have been formed because of oxidation.
Although the total diffraction intensity from the crystallites
was high enough to visualize them using dynamical
conical dark-field microscopy, the rings were not intense
(26) Dujardin, E.; Ebbesen, T. W.; Hiura, H.; Tanigaki, K. Science 1994,
265, 1850.
(27) For clarity, we will simply refer to the nanoparticles as “Mg
nanoparticles” in the remainder of the manuscript, although it is clear
that some oxidized or hydride magnesium species might be present
as well.
(28) Keiser, E. H.; McMaster, L. J. Am. Chem. Soc. 1910, 32, 388.
(29) Novák, J. Z. Phys. Chem. 1911, 73, 513.
Figure 1. Bright-field (left) and dark-field (right) mode transmission electron
micrographs for nanocomposites prepared from (A) 33 wt % Mg/ACm+m
contacted by hot pressing (B) 25 wt % MgH2/Cmeso and (C) 25 wt % MgH2/
ACmicro. Scale bar size is 20 nm. (D) EDX results for Cmeso- (left) and
ACmicro-based (right) samples.
CChem. Mater., Vol. xxx, No. xx, XXXXC-Supported Mg Nanoparticles Using Melt Infiltration
4. and sharp enough to determined which Mg species were
present; only the diffraction rings due to carbon were
identified. Hence, we used TEM-EDX analysis to deter-
mine the elemental composition of the Mg–C nanocom-
posites on selected areas of the sample where only small
crystallites inside porous carbon were found. From the
raw EDX data (two examples are shown in Figure 1D) it
was evident that the nanoporous carbon particles contained
a significant amount of Mg atoms, and that furthermore
carbon, oxygen, and copper, and Si because of the TEM
grid and film were present. Unfortunately, it is not possible
to reliably access the C:Mg atomic ratio of the nanocom-
posite particles (and hence the local Mg loading), as the
samples are mounted onto a carbon film for TEM analysis.
To obtain quantitative atomic ratios for the other elements,
we have to correct the raw data, most importantly for the
absorption of low-energy radiation by the detector win-
dow. For our instrument, the correction multiplication
factors for the elements C, O, and Mg are 6.3, 2.0, and
1.1. As it is essential to determine the Mg:O ratio, we
verified this correction factor by analyzing MgO crystal-
lites (produced by flame-burning of metallic magnesium
wire), and our data confirmed the microscope manufacturer
correction specifications.
Using the O:Mg elemental ratio, it is possible to determine
whether the majority of the nanocrystalline Mg present is
oxidized or not. Sometimes virtually no oxygen was detected
in the selected part of the sample (see right frame of Figure
1D), but typically a small amount of oxygen was detected
(see left frame of Figure 1D). Part of this oxygen usually
originated from the TEM grid films, which mainly contained
carbon, but often also some silicon and oxygen. Although
in a typical case as presented in the left frame of Figure 1D
it is not possible to unequivocally calculate the part of the
Mg that is not oxidized, a best and worst case scenario can
be constructed. The worst case scenario assumes that the
grid films do not contribute to the oxygen signal. Then, if
the O signal would be entirely due to the formation of MgO,
a minimum of 50% of the magnesium would still be present
in metallic (or hydride) form. If not MgO but Mg(OH)2 was
formed, then 70% of the Mg would still be present in
nonoxidized form. In the best case scenario, all Si detected
is present as SiO2 contamination of the grid film. In this case,
magnesium is not significantly oxidized. In general, we found
a strong correlation between the amount of oxygen in the
samples and the time that they had been stored. For samples
stored for a long time and/or exposed to air, the O:Mg ratio
was always close to 2, suggesting that the magnesium species
is converted into Mg(OH)2 upon oxidation at room temper-
ature. However, it is clear that for freshly prepared samples,
a major fraction of the nanocrystalline Mg in the samples is
not oxidized shortly after preparation, not even after brief
exposure to air.
Interaction between the Carbon Matrix and the Mol-
ten Magnesium. Although TEM/EDX is a powerful technique
to visualize Mg nanocrystallites, bulk analysis techniques are
essential to obtain statistically relevant data. We used N2
physisorption to yield information on the extent of Mg infiltra-
tion by comparing pore volumes and pore size distributions
before and after contacting the C with molten Mg. An overview
of the results is given in Table 1. Figure 2 shows the mesopore
volume distributions, normalized to the weight of the carbon.
Weight changes caused by Mg evaporation and oxidation were
either negligible or compensated one other, as no significant
weight change was detected upon melt infiltration. All samples
showed significant pore volume losses in the range of up to 10
nm pore diameter, which is consistent with an extended
interaction between the magnesium and the nanoporous carbon.
Furthermore, for smaller pores, larger relative pore volume
losses occurred.
Three factors can contribute to loss of pore volume:
pore filling, pore blocking, or destruction of the porous
nature of the carbon. To exclude the last possibility, we
leached Mg from the nanocomposite with diluted hydro-
chloric acid. In all cases, almost all of the original pore
volume was recovered. It is difficult to distinguish between
pore filling and blocking, but it is illustrative to compare
the loss of pore volume with the volume of the added Mg
(Table 1). For the nanocomposite samples that contained
a significant amount of oxygen (OMC, OMC_N, ACm + m, and
ACmicro_O), the loss of pore volume was usually greater than
the volume of the added Mg. It is not surprising that these
samples suffer from pore blocking, as molten Mg readily
reacts with oxygen impurities to form solid MgO, which
would block the pores and stop the further flow of molten
Mg. For the high-purity carbons (Cmeso and ACmicro), no
evidence of pore blocking was found. However, this does
not necessarily mean that all Mg has penetrated the pores, it
is possible that part of the magnesium has blocked a large
pore volume, whereas the rest is still present as bulk Mg. In
general, it can be concluded that there is a sufficient interaction
between molten magnesium and the carbon to bring about
Table 1. Overview of the Total Carbon Pore Volumes Determined
from N2 Physisorption before and after Melt Infiltration with 25 or
36 wt % MgH2
sample
original
pore volume
(cm3
/g[C])
pore volume
after infiltration
(cm3
/g[C])
difference
(cm3
/g[C])
added Mg
volume
(cm3
/g[C])
OMC 0.768 0.114 -0.654 0.177
OMC_N 0.543 0.217 -0.326 0.177
ACmicro-O 0.482 0.186 -0.296 0.263
ACM+M 0.514 0.318 -0.196 0.263
ACmicro 0.450 0.324 -0.126 0.177
Cmeso 0.649 0.567 -0.082 0.177
Figure 2. Carbon pore volume distributions before (—*—) and after (—•—)
melt infiltration, and after removal of the Mg(O) by leaching (—O—) for
nanocomposites based on (A) OMC_N, (B) OMC, (C) ACm+m, and (D)
Cmeso. The nanocomposites were prepared with 36 wt % MgH2 (C) or 25
wt % MgH2 (A, B, D).
D Chem. Mater., Vol. xxx, No. xx, XXXX Jongh et al.
5. capillary flow to at least partly fill pores with a diameter of 10
nm or smaller.
Quantification of the Nano versus Bulk Phase. To assess
how much magnesium had penetrated into the carbon, we
varied the magnesium loading for a given carbon matrix.
For samples based on Cmeso, Figure 3 compares N2 phys-
isorption results as a function of loading with semiquanti-
tative XRD analysis of the bulk magnesium content (see the
Supporting Information for details). Also, the volume of the
added Mg is indicated. For low loadings, the loss of pore
volume increases linearly with increasing magnesium load-
ing. Furthermore, with XRD, no bulk magnesium is detected
for loadings below 10–15 wt %. This combination of results
suggests that at these loadings, (nearly) all of the Mg was
involved in pore filling.30
At higher loadings (for this type
of carbon, >10–15 wt%), the loss of pore volume levels off
and a linearly increasing amount of bulk Mg is detected with
increasing loading. This suggests that above a critical loading,
all extra Mg added remains as bulk material in the sample,
but that below this loading, all added magnesium will be in
nanocrystalline or amorphous form after preparation of the
composite material.
Additional evidence comes from scanning electron mi-
croscopy. Figure 4 shows the morphology of nanocomposites
based on Cmeso after addition of 33.3 wt% (left frame) and
10.8 wt% (right frame) of MgH2 and heat treatment. To
enhance the contrast between Mg and C, we detected only
backscattered electrons (BSE). In both cases, the original
morphology of the carbon was retained. Additionally, for
the loading of 33.3 wt%, 20–50 µm, often faceted particles
are found, which by EDX could be identified as magnesium
crystallites. On the other hand, for the 10.8 wt% loaded
sample, no such Mg-rich particles or crystallites were
detected, neither using BSE imaging nor in a higher
magnification using EDX.
The “critical loading” below which no bulk Mg was
detected varied with the type of carbon: for the nanocom-
posite based on Cmeso, it was between 10 and 15 wt %,
whereas for ACmicro-based composites, it was between 15
and 20 wt %. It is at this stage not yet clear what is the
origin of the filling of only a specific fraction of the pores.
Keeping the samples above the melting point of magnesium
longer than 10 min during synthesis did not increase the pore
volume loss. The fact that the amount of pore volume loss
becomes independent of the amount of Mg added at high
loadings suggests that the cause is not poor mixing of MgH2
and C in the starting phase. Furthermore, experiments in
which the contact was forced by pressing the physical
mixture before melt infiltration, or by ball-milling, did not
give a significant increase in pore volume loss. N2 phys-
isorption results shown in Figure 2 prove that there is a strong
interaction only between the molten magnesium and pores
smaller than 10 nm and that the smaller the pores, the higher
the degree of pore filling. However, not all very small pores
are filled. A tentative explanation is that, related to the three-
dimensional character of the pores, part of the smaller pores
can be accessed only via larger ones, which because of a
lower effective driving force (capillary suction) are not filled
with molten magnesium.
Conclusion
We prepared nanometer-sized Mg in carbon matrices. For
oxygen-containing carbons, pore blocking was found, indi-
cating, as expected, reaction between the molten magnesium
and the oxygen groups on the carbon. However, several high-
purity nanoporous carbons were spontaneously infiltrated by
the molten magnesium. For freshly prepared samples, it was
proven that the majority of the nanoscale magnesium was
not oxidized. The smaller the pores, the higher the degree
of pore filling; only for pores with a diameter up to 10 nm
was a significant fraction of the pores filled with Mg after
preparation. However, only a certain fraction of the smallest
pores was filled, depending on the type of carbon. The size
of the crystallites varied from 2–5 to below 2 nm by choosing
carbons with different pore size distributions. As far as we
know, this is the first time that results on the preparation of
gram amounts of nanometer-sized nonoxidized magnesium
particles are reported. Favorable hydrogen sorption properties
are predicted for such small Mg nanocrystallites; we will
discuss the H2 sorption kinetics and thermodynamics in a
future publication. The reported preparation route is very
promising for obtaining systems in which nanosizing and
substrate interaction can be used to steer the hydrogen
sorption properties of light metal hydrides.
Acknowledgment. This research was funded by Utrecht
University and ACTS (Project 053.61.502). P.B.R. acknowl-
edges financial support from a Casimir Grant (018.001.001).
(30) The pore volume loss seems even somewhat higher than the volume
of the added Mg. This could indicated a minor degree of pore blocking,
but more likely it is due to partial oxidation of Mg to Mg(OH)2, which
has a larger molar volume.
Figure 3. Comparison between the total loss of carbon pore volume as
measured by N2 physisorption (—•—), and the amount of bulk Mg detected
with XRD (—O—) as a function of initial Mg/C loading for samples based
on Cmeso. The amount of Mg added is also indicated (dashed line).
Figure 4. Backscattered electron (BSE) scanning electron micrographs of
nanocomposites based on Cmeso with different loadings, respectively, 33.3
(left frame) and 10.8 wt % MgH2 (right frame).
EChem. Mater., Vol. xxx, No. xx, XXXXC-Supported Mg Nanoparticles Using Melt Infiltration
6. We thank Ad Mens for the physisorption measurements, Marjan
Versluis-Helder for the SEM measurements, and Hans Geerlings
from Shell Research and Technology Centre Amsterdam for
stimulating discussions. Furthermore, we are grateful to Timcal
Ltd. (Bodio, Switzerland) and Norit Nederland BV (The
Netherlands) for providing the high-surface-area graphite and
porous carbons, respectively.
Supporting Information Available: SEM characterization of
the carbon morphologies, explanation of and details on the
dynamical conical dark field imaging technique for TEM, and details
on the quantification of the XRD results (PDF). This material is
available free of charge via the Internet at http://pubs.acs.org.
CM702205V
F Chem. Mater., Vol. xxx, No. xx, XXXX Jongh et al.