Volume Fractions of Tantalum Carbides Deduced from the Ta Contents in the Matrix of Three 1250°C–Aged Cobalt–Based Alloys; Comparison with Thermodynamic Calculations
Some superalloys for service at high temperature under stresses are strengthened by tantalum carbides. Their creep resistance depends on the quantity of TaC and this is the reason why it is often important to control the volume fraction of these carbides in the microstructure. Metallographic preparation followed by electron imaging and surface fraction measurements by image analysis is a frequent way for that. Another possibility is to deduce the mass fraction of TaC, and after their volume fraction, from the chemical composition of the matrix when the alloys are only double–phased, on the {matrix + TaC} type. In this work three alloys – chemically designed to be made exclusively of matrix and TaC – were elaborated and isothermally exposed to an elevated temperature for a duration long enough to allow the alloys being at their thermodynamic equilibria. The chemical compositions of the alloy and of its matrix were measured and the results allowed evaluating their TaC mass fractions which were converted in volume fractions. The obtained TaC fractions were compared to results issued from thermodynamic calculations. Good agreement was found for the three alloys, and this allowed to exploit the used software and thermodynamic database to explore further the microstructures at the same high temperature, notably to know the conditions on the Co, Ni, Cr, Ta and C contents to keep the {matrix + TaC} structure and to avoid any possible partial melting.
The industry of ultrafine and nanopowder materials requires new methods for their production and hardware equipment for engineering processes. Among them there is plasmachemical synthesis of powder materials with the use of electric arc generators of low-temperature plasma. Plasma heating of initial inputs allows evaporation of almost any material and performance of the required chemical reactions in the gas phase with following vapor condensation to the nanodisperse solid phase. Considering the capacities of plasma generators and plasmachemical reactors achieved for today (many hundreds of kilowatts), we can expect that productivity by the desired product can be hundreds of kilograms per hour. Moreover, the plasma equipment demonstrates high universality relative to the initial materials, possible synthesis of complex powders and continuous conditions of operatingprocedure. The developed electric-arc plasmatrons and reactors allow different high-temperature processes, including powder processing in plasma flows . Now the most common constructions ofplasma reactors are the direct-flow ones with co-axial plasmatron and the three-jet ones with three plasmatrons tilted at 30–45° relative to the reactor axis and located in 120° intervals on the water-cooled upper lid. The plasmatron with sectioned inter-electrode insertion and shaped outlet nozzle-electrode ensure diffuse glow of the anode region of the arc discharge, what leads to the uniform temperature field and flow velocity at the nozzle edge. These parameters of the plasma jet have a good impact on reproducibility of powder processing, high coefficient of initial material use and production of powder with the given physical-chemical properties. Application of the three-jet plasmachemical reactor ensures the uniform temperature field along the reaction zone, allows easy control of productivity due
FlowVision CFD - Verification Calculations as per CFD FlowVision Code for Sod...capvidia
Application of FlowVision CFD Software for Analytical Validation of Sodium-Cooled Fast Reactor Structure Components
Verification of LMS (Liquid Metals Sodium) Turbulent Heat Transfer Model
Streaming and Mixing of Coolant Flows within "OKBM Afrikantov, BN-600 Reactor with Integral Layout of Equipment
Direct alloying of steel a review of studies at lab and industrial scaleJorge Madias
The direct alloying of the steel is attractive as it minimizes alloying cost, total energy consumption and CO2 emissions, compared with ferroalloys. This allying technique is in use for high alloyed (stainless), low alloyed and carbon steel. The elements reviewed include chromium, nickel, molybdenum, vanadium and manganese. Raw materials used to this purpose are lump ores, ore fines, special slags, self-reducing briquettes and others. For the development of this technique, tools like thermodynamic modelling, testing in induction furnaces of several scales and industrial tests have been instrumental. This paper summarizes the fundamental and industrial efforts carried out to develop and employ direct alloying in Japan, Russia, China and other steelmaking countries
This paper presents information about fast warm cathode for microwave tubes applications. Its mechanical profile and thermal characteristics are discussed.
Reduction of cold start emissions in automotive catalytic converter using the...Asheesh Padiyar
Catalytic converters are used to convert harmful exhaust gases like CO, NOx and unburnt hydrocarbons released by
internal combustion engine of automobiles into less harmful gases like CO2, H2O and N2. During the start-up of engine run, catalytic converters suffer cold start problems as the catalyst does not remain active in cold conditions. This results in emission of unconverted harmful gases into the atmosphere. This work attempts to eliminate cold start problems using a heat storage system to keep the catalytic converter hot even under engine off conditions. A eutectic alloy of Mg-Zn-Al is used as the Phase Change Material (PCM) to store the heat around the catalyst. This alloy has high latent heat of fusion, high specific heat, suitable melting point and high thermal stability. Mg-Zn-Al eutectic alloy changes its state between liquid and solid on application and removal of heat. Thus this phase change material acts as a heat storage mechanism in the catalytic converter. Catalytic converter design also involves Rockwool insulation in order to aid longer heat storage. This thermal energy storage system as a combination of PCM and insulation, keeps the catalytic converter hot for several hours even after the engine is shut of
Thermal Barrier Coating For Gas Turbine EnginesNelsonkandulna
This presentation describes the thermal barrier coating process, its anatomy, types, material selection, failure, and characterization. Thermal barrier coatings (TBCs) were introduced to protect the external surface of gas turbine engine components from thermal resistance and thereby decrease the temperature of the metal surfaces. Yttria stabilized zirconia (YSZ) is one of the most popular and widely used TBC materials as it provides the best performance in high-temperature zones such as diesel engines and gas turbines. The columnar microstructure of YSZ coating provides excellent strain tolerance and adhesion to the coating. Gas turbines are used to power aircraft, trains, ships, electrical generators, pumps, gas compressors, and tanks.
The industry of ultrafine and nanopowder materials requires new methods for their production and hardware equipment for engineering processes. Among them there is plasmachemical synthesis of powder materials with the use of electric arc generators of low-temperature plasma. Plasma heating of initial inputs allows evaporation of almost any material and performance of the required chemical reactions in the gas phase with following vapor condensation to the nanodisperse solid phase. Considering the capacities of plasma generators and plasmachemical reactors achieved for today (many hundreds of kilowatts), we can expect that productivity by the desired product can be hundreds of kilograms per hour. Moreover, the plasma equipment demonstrates high universality relative to the initial materials, possible synthesis of complex powders and continuous conditions of operatingprocedure. The developed electric-arc plasmatrons and reactors allow different high-temperature processes, including powder processing in plasma flows . Now the most common constructions ofplasma reactors are the direct-flow ones with co-axial plasmatron and the three-jet ones with three plasmatrons tilted at 30–45° relative to the reactor axis and located in 120° intervals on the water-cooled upper lid. The plasmatron with sectioned inter-electrode insertion and shaped outlet nozzle-electrode ensure diffuse glow of the anode region of the arc discharge, what leads to the uniform temperature field and flow velocity at the nozzle edge. These parameters of the plasma jet have a good impact on reproducibility of powder processing, high coefficient of initial material use and production of powder with the given physical-chemical properties. Application of the three-jet plasmachemical reactor ensures the uniform temperature field along the reaction zone, allows easy control of productivity due
FlowVision CFD - Verification Calculations as per CFD FlowVision Code for Sod...capvidia
Application of FlowVision CFD Software for Analytical Validation of Sodium-Cooled Fast Reactor Structure Components
Verification of LMS (Liquid Metals Sodium) Turbulent Heat Transfer Model
Streaming and Mixing of Coolant Flows within "OKBM Afrikantov, BN-600 Reactor with Integral Layout of Equipment
Direct alloying of steel a review of studies at lab and industrial scaleJorge Madias
The direct alloying of the steel is attractive as it minimizes alloying cost, total energy consumption and CO2 emissions, compared with ferroalloys. This allying technique is in use for high alloyed (stainless), low alloyed and carbon steel. The elements reviewed include chromium, nickel, molybdenum, vanadium and manganese. Raw materials used to this purpose are lump ores, ore fines, special slags, self-reducing briquettes and others. For the development of this technique, tools like thermodynamic modelling, testing in induction furnaces of several scales and industrial tests have been instrumental. This paper summarizes the fundamental and industrial efforts carried out to develop and employ direct alloying in Japan, Russia, China and other steelmaking countries
Similar to Volume Fractions of Tantalum Carbides Deduced from the Ta Contents in the Matrix of Three 1250°C–Aged Cobalt–Based Alloys; Comparison with Thermodynamic Calculations
This paper presents information about fast warm cathode for microwave tubes applications. Its mechanical profile and thermal characteristics are discussed.
Reduction of cold start emissions in automotive catalytic converter using the...Asheesh Padiyar
Catalytic converters are used to convert harmful exhaust gases like CO, NOx and unburnt hydrocarbons released by
internal combustion engine of automobiles into less harmful gases like CO2, H2O and N2. During the start-up of engine run, catalytic converters suffer cold start problems as the catalyst does not remain active in cold conditions. This results in emission of unconverted harmful gases into the atmosphere. This work attempts to eliminate cold start problems using a heat storage system to keep the catalytic converter hot even under engine off conditions. A eutectic alloy of Mg-Zn-Al is used as the Phase Change Material (PCM) to store the heat around the catalyst. This alloy has high latent heat of fusion, high specific heat, suitable melting point and high thermal stability. Mg-Zn-Al eutectic alloy changes its state between liquid and solid on application and removal of heat. Thus this phase change material acts as a heat storage mechanism in the catalytic converter. Catalytic converter design also involves Rockwool insulation in order to aid longer heat storage. This thermal energy storage system as a combination of PCM and insulation, keeps the catalytic converter hot for several hours even after the engine is shut of
Thermal Barrier Coating For Gas Turbine EnginesNelsonkandulna
This presentation describes the thermal barrier coating process, its anatomy, types, material selection, failure, and characterization. Thermal barrier coatings (TBCs) were introduced to protect the external surface of gas turbine engine components from thermal resistance and thereby decrease the temperature of the metal surfaces. Yttria stabilized zirconia (YSZ) is one of the most popular and widely used TBC materials as it provides the best performance in high-temperature zones such as diesel engines and gas turbines. The columnar microstructure of YSZ coating provides excellent strain tolerance and adhesion to the coating. Gas turbines are used to power aircraft, trains, ships, electrical generators, pumps, gas compressors, and tanks.
Post processing of SLM Ti-6Al-4V Alloy in accordance with AMS 4928 standardsIJERD Editor
This Research work was done to find out the impact of AMS 4928 standard heat treatment on
Selective Laser Melted (SLM) Ti-6Al-4V Grade 23 alloy. Ti-6Al-4V Grade 23 is an Extra Low Interstitial
version of Ti alloy with lower impurities and is α+β type alloy at room temperature. SLM is one type of method
in Additive Manufacturing based on Powder bed system. Each powder layer of few microns is coated and a laser
beam is scanned to melt the metal powder according to the specification of the part and subsequently moved
downwards layer by layer. The test coupons were first heat treated according to the above mentioned standard.
The tensile testing and the microstructural analysis were done to compare the results with that of mentioned in
the AMS 4928.The yield stress andPercentage elongation in the test coupons achieved are better than the
minimum requirement by AMS 4928 standard. Coarse lamellar grain structures were obtained with no
continuous network of alpha at prior beta grain boundaries.
Plasma Technique for Quickest IronmakingZohaib Akbar
The production of Liquid Iron by Orbitting plasma technique in a few micro seconds using fine ore such as Taconite(Fe3O4) Concentrates coupled with other technological advancement is a significant breakthrough for quality and cost-effective production of Ironmaking.
Deposition of ni ti n coatings by a plasma assisted mocvd using an organometa...tshankar20134
Titanium nitride (TiN)/nickel (Ni) composite coatings were synthesized by plasma assisted metal-organic
chemical vapour deposition (PAMOCVD) using organo-metallic and metal-organic complexes namely dichlorobis(5-
cyclopentadienyl)titanium (IV) for titanium and N,N'-ethylene-bis(2,4-pentanedion-iminoato)nickel(II) for nickel. The
growth of such films was investigated in nitrogen (N2) plasma environment in the substrate temperature range of 450-
550ºC at a deposition pressure of 0.5-1 mbar. Prior to the deposition of films, the Ti precursor was subjected to the
equilibrium vapour pressure measurements by employing TG/DTA in transpiration mode, which led to the value of 109.2
± 5.6 kJ mol-1 for the standard enthalpy of sublimation (Ho
sub). The phase identification using glancing incidence x-ray
diffraction showed Ni/TiN is a nanocomposite coating containing nanocrystals of Ni and TiN with face centered cubic
structure. Scanning electron microscopy revealed a uniform surface morphology of the films, while chemical analysis by
energy dispersive analysis confirmed the presence of titanium, nickel and nitrogen in the composite films.
MD simulations of radiation effects in Ti-Al based structural intermetallicsRoman Voskoboynikov
You need to download the pdf file to see the embedded video clips. The presentation was given at 15th International Conference 'Materials for Innovative Energy: Development, Characterization and Application', 23-27 October 2017, NRNU MEPhI, Moscow, Russia
Remaining life assessment of refinery furnace tubes using finite element methodBarhm Mohamad
Crude oil heater 9Cre-1Mo steel tubes from a refinery plant were studied, after 5 years of service at nominally 650 Cº and 3 bar, to predict their remnant lives. The investigation included dimensional, hardness and tensile measurements in addition to accelerated stress rupture tests between 650 Cº and 700 Cº and microstructural examination. Tube specimens were taken from two sections, the overheated side and the side which only saw the nominal operating temperature. The method employed involved the prediction of the increase in temperature with increasing sediment deposition during the operating life times using an FEM model. In addition the predicted temperatures are used to derive appropriate creep properties at relevant temperatures in a 3D pipe FEM creep analysis to predict the pipe deformation rate. All compare well with the actual service exposed pipe measurements and layer deposition. The overheated side revealed a small loss of creep strength in a stress rupture test. A layer of sediment (appr. 10 mm thickness) consisting basically of sintered carbon (coke) spread over the inside of the tube was acting as a thermal barrier causing the temperature to rise above 650 Cº. Analysis for the overheated side predicted an upper bound temperature of 800 Cº and a life of about 50 h suggesting that failure by creep rupture could occur rapidly in the sediment region.
Highly stable pt–ru nanoparticles supported on three dimensional cubic ordere...tshankar20134
Similar to Volume Fractions of Tantalum Carbides Deduced from the Ta Contents in the Matrix of Three 1250°C–Aged Cobalt–Based Alloys; Comparison with Thermodynamic Calculations (20)
Scientific Management of Equipment in Medical Innovation LaboratoryScientific Review SR
Aim; To solve the problem of innovation laboratory instrument management and improve laboratory management level. Method; It is necessary to do an excellent job in managing innovative laboratory equipment by improving the equipment management system, functional division management, appointment registration, and strengthening the construction of management teams to guarantee the cultivation of innovation and entrepreneurship capabilities of undergraduates. Results; The number of innovative experimental projects approved and the number of project groups that the laboratory can accept at the same time was increased significantly. The utilization rate of laboratory equipment has increased, and the vacancy rate has decreased. Conclusion; Excellent instrument management can significantly improve the efficiency of scientific research in the innovation laboratory.
Internationalization and Sustainable Operations: A Broad Investigation of Chi...Scientific Review SR
We investigate if internationalization behaviors encourage sustainable operations of China’s manufacturing firms due to their substantial impact on climate change and special governance modes, and organize a heterogeneity test to clarify what kind of internationalization behaviors can robustly influence such operations. We find that firms with abundant assets and heavy-polluting feature are more committed to sustainable operations. Getting close to international sustainability standards, international auditing standards, and international business all improve sustainable operations. Heterogeneity test further shows that compared with international standards, the positive impact of international business on sustainable operation lacks a robustness, which responds to an argument that for one country, international business acts as a double-edged sword. Overall, this paper reveals internationalization as a key indicator significantly influencing economic, ecological, and social spheres in manufacturing sectors of emerging markets, and complying with well-accepted international standards can be significantly embodied in a more optimistic sustainable operations. However, how to deal with international business in a right manner is a research highlight worthy of ongoing discussion. We focus on different types of internationalization behaviors, and this indicator can theoretically inspire future study to dialectically evaluate the role of internationalization in addressing sustainability problems in emerging markets’ pillar industries.
Mechanical Engineering in Ancient Egypt, Part 92: Tomb Inscription During the...Scientific Review SR
This work is based on a previously published hypothesis which proposed that the solid matter of the universe can be represented as a vibrational wave of energy propagating over an ether or matrix through a mechanism that scrambles the degree of duality in matter: x% localized (solid), y% delocalized (wave). The main purpose of this paper is to present a two-dimensional approximation of the three-dimensional structure of the shape of the energy distribution of an atomic orbital to propose a mechanism through which the orbital can be transported as a vibration from a point A to point B in the matrix. This process requires cycles or oscillations of mounting-dismounting-remounting in which what travels from point A to point B is the energy forming the orbital and not the solid matter that it can form. The atomic seven-dimensional f orbital of hydrogen-like atoms is used as a model to show an analogy to the transformations that it can be submitted to when transported over the matrix.
Usability Engineering, Human Computer Interaction and Allied Sciences: With R...Scientific Review SR
Human Computer Interaction is actually responsible for the designing of the computing technologies keeping in mind the aspects of Interaction. Some of the fields viz. Man-Machine Interaction (MMI), User Experience Designing, User Experience Design, Human Centered Designing etc and importantly all these systems and technologies are dedicated to the designing of interface of various tools and systems such as computers, laptops, electronic systems, smart phones etc. Information Technology field is growing rapidly and there are various technologies are increasing viz. Big Data Management, Cloud Computing, Green Computing, Data Science, Internet of Things (IoT), HCI, Usability Engineering etc. Usability Engineering is gaining as a field of study as well and dedicated in creation of the higher usability and user friendliness of the electronic tools and products. In this field few aspects and technologies are most important and emerging viz. Human cognition, behavioral Research Methods, Quantitative techniques etc for the development of usability systems. Designing, implementation, usability even in multimedia material viz. audio-video may also practice in the Usability Engineering and allied fields. Wireframes including few other prototypes are required in maintaining of the better and healthy man and machine interaction. As the field is growing therefore, it is applicable in other sectors and allied areas and among these agriculture is important one. In agricultural sector different applications of information technologies are increasing and among this Usability Engineering and HCI are important one. In pre production and also in post production; directly and indirectly this technology is emerging and growing. This paper talks about the basics of this technologies and also its current and future technologies with reference to academic potentialities of this branch in Agricultural Informatics programs.
Concentration Distribution and Ecological Risk Assessment of Polycyclic Aroma...Scientific Review SR
The ecological risk assessment of 16 USEPA priority polycyclic aromatic hydrocarbon (PAHs) in water and sediments of Kolo creek, Niger Delta Nigeria was assessed the samples were collected from November, 2018 to June, 2019 from seven locations (A-G) along the creek. The samples were extracted using standard methods and analyzed using gas chromatography (model: HP5890 S). The concentrations of the PAHs in the water and sediment samples ranged between 0.000 - 9.239 µ/L and .002 – 374.35µg/Kg respectively. All the compounds analyzed were detected in all the sampling places, even area far from the flow stations. Hence, the urban runoffs, sewage discharges, and agricultural activities are implicated. Four rings hydrocarbon were present in higher concentration when compared to other PAHs in all sampling sites, with benz (a)anthracene having the highest values in both matrixes. Similarly, lower molecular weight (LMW) PAHs were present in lower concentrations in all sampling sites and they are known to exhibit higher lethal toxicity than the larger PAHs. HMW were present in high concentrations than LMW and are persistent in the environment as a result of their increase resistance to oxidation, reduction and vaporization as molecular weight increases. Similarly, The PAFs of the investigated creek is less than 5%, suggesting existences of minor ecological risks that are insignificance. However, the TEQs detected in high molecular weight showed that there is possibility of cancer to those who may be exposed to the bottom sediment. The indices measured in this habitat may put more pressures to the aquatic organisms and cause drastic changes to their ecosystem which may lead to species extinction.
Assessment of the Coliform Bacterial Load of Some Drinking Water Sources in D...Scientific Review SR
Drinking water samples from 5 sachet water companies, 3 boreholes and 2 taps, collected from different locations of Dutse Metropolis of Jigawa State, Nigeria were analysed for coliform bacterial counts using the Membrane Filtration Technique. All the samples contained some amounts of total coliforms, but mostly within permissible levels. Thirty three percent (33%) of the samples from borehole, 60% from sachet water and 100% from the taps contained faecal coliforms, which indicates contamination. Cultures of the faecal coliforms obtained were morphologically identified using the gram-staining procedure and some series of biochemical tests were carried out in order to identify the organisms. The identified organisms were Escherichia coli (E. coli), Klebsiella sp. and Citrobacter sp. Presence of coliforms above the regulatory set standards indicates contamination and un-safeness of the water for drinking. Presence of organisms such as E. coli, Klebsiella sp. and Citrobacter sp. necessitates improvement in monitoring and water hygiene practices to improve the quality of drinking water in the study area.
Bio Inspired Self-Curing Composite: A Leap into Augmented EnactmentScientific Review SR
Relentless progress has been made on composite materials, their manufacturing processes and their structural design in past few decades. Nevertheless, the approval of composite materials in all engineering disciplines is constrained due to its susceptibility to various kinds of defects during manufacturing stage viz porosity, foreign body inclusion, incorrect fiber volume, bonding defect, fiber misalignment, ply misalignment, incorrect curing cycle, wavy fiber, ply cracking, delamination, fiber microstructural defects etc. Hence there was a requirement of techniques to somehow overcome these defects during the service life of composites being used in various structures and equipment. This promising field of research has made great progress over the past several years, but many procedural encounters are still to be overcome, and there exists a great need for focused research to address several areas of concern. On the other hand, nature has materials that have curing potential and repair strategies ensuring their survival. Sustained development in the field will produce new curing chemistries that possess greater stability, faster kinetics. Tailor-made placement of curing agents is dynamic research subject at the cutting edge of self-curing. New bio-imitative curing agents are closely connected to vascular networks. The purpose of this technical paper is to sort the methodology in line with ongoing research efforts in composites. A perspective on current and future self-curing approaches using this biomimetic technique is offered.
Influence of Information and Communication Technology (ICT) in Tourism Sector...Scientific Review SR
Nepal is a country blessed with natural beauty, diverse culture, majestic Himalayas, religious destination which attracts thousands of tourists every year making the tourism industry progressive to flourish. Information Communication Technology (ICT) proves to be an effective tool for strengthening the tourism industry. Thus, the purpose of this research study is to analyze about the past scenario of tourism industry, advent of ICT in tourism industry, positive impacts of ICT in tourism industry through in-depth interview with tourism experts and people who have worked for tourism since decades. This study is a form of qualitative research where narrative inquiry has been selected and the scenario has been analyzed through themes developed from the narratives. The result reveals that the emerging technology brings positive impacts to tourism industry assisting branding, promotion of the country, enhancing networks through communication and easily booking tours. The proper utilization of ICT helps to welcome tourists and to give identity of our country Nepal to the world.
Reinforcement of Bakelite Moulding Powder in Acrylonitrile Butadiene Rubber (...Scientific Review SR
The influences of two phenolic resins, that is, cashew nut oil modified phenol-formaldehyde resin (CN-m-PF) and Bakelite moulding powder (BMP), on properties of carbon black filled acrylonitrile butadiene rubber (NBR) were investigated and compared. Processability, cure characteristics, mechanical properties, thermal ageing resistance, and oil resistance of the NBR filled with various contents of phenolic resins (0-60 phr) were determined. The addition of both resins leads to a prolonged cure time with a greater value of torque difference. Regardless of the resin type, the improvement of compound processability and the enhancement of modulus and hardness of the NBR vulcanisates are observed with increasing resin content. However, many mechanical properties such as tensile strength, elongation at break and abrasion resistance are deteriorated. Thermal ageing resistance of the NBR vulcanisate is slightly improved in the presence of both resins, probably due to the dilution of NBR with the high heat-resistant phenol-formaldehyde resins. Results also disclose that all NBR vulcanisates demonstrate excellent oil resistance, regardless of the resin type and content. At any given resin content, CN-m-PF gives a better processability, higher stiffness and greater mechanical properties than BMP. However, due to its lower cost, BMP can be used to enhance stiffness of NBR vulcanisates without the risk of processing problem.
Toxic Effect of Glyphosate-Pesticide on Lipid Peroxidation Superoxide Dismuta...Scientific Review SR
The oxidative stress indices lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) in juvenile Clarias gariepinus (average weight 200.15 g) exposed to sub - lethal dose 2.40mg/L and 4.98mg/L of glyphosate was investigated over a period of days 1,5,10 and 15 in three replicates. The colorimetric analysis showed increase in lipid peroxidation from 4.55 ±2.14a1 to 12.12± 10.00a1at 2.40mg/L but remain the same at 4.98mg/L (4.55±2.14a1) compared with control (3.03±0.01a1 to 1.51±2.14b1) from day 1 to 15. The SOD activity decreased significantly with time and concentration compared with control. The Catalase activity at day 15 decreased to 0.17±0.05a1 in 2.40mg/L but further increased to 0.28±0.05b1 in 4.98mg/L compared to 0.28±0.02a1 catalase activity as control. The result suggests that glyphosate induce oxidative stress that may overwhelm the antioxidant system in juvenile catfish especially at higher concentrations with long exposure.
Wheeled robots are often utilized for various remote sensing and telerobotic applications because of their ability to navigate through dynamic environments, mostly under the partial control of a human operator. To make these robots capable to traverse through terrains of rough and uneven topography, their driving mechanisms and controllers must be very efficient at producing and controlling large mechanical power with great precision in real-time, however small the robot may be. This paper discusses an approach for designing a quad-wheeled robot, which is wirelessly controlled with a personal computer (PC) by medium-range radio frequency (RF) transceiver, to navigate through unpaved paths with little or no difficulty. An efficient servo-controlled Ackerman steering mechanism and a high-torque driving power-train were developed. The robot’s controller is programmed to receive and respond to RF control signals from the PC to perform the desired motions. The dynamics of the robot’s drivetrain is modeled and analyzed on MATLAB to predict its performances. The robot was tested on various topographies to determine its physical capabilities. Results show that the robot is capable of non-holonomically constrained motions on rough and uneven terrains.
Geometrical Analysis and Design of Tension-Actuated Ackermann Steering System...Scientific Review SR
The tension-actuated steering system is a vehicular steering design that comprises a motorized gear system, pulleys, inelastic string, main steering bar, and a strain gauge. This development is aimed to produce a steering design that could enhance the efficiency of steering systems in quad-wheeled (i.e. four-wheeled) robots. In this work, the steering system of conventional passenger vehicles and existing quad-wheeled robots are reviewed and their technical deficiencies are improved based on cost, power and production factors. Thus, the tension-actuated steering system is proposed as a solution for mechanizing steering functions in quad-wheeled robots. It is expected that this work will stimulate interest and enthusiasm.
A Study of Propensity Score on Influencing Factors of Length of Stay in Hospi...Scientific Review SR
Background: Burns are a global public health problem, which are universal and can happen to anyone. Because the physical functions in children and adults are different, the confounding factors are easy to affect the results of study. Objective: In this study, we aimed to explore influencing factors of the length of hospital stay (LOS) when the confounding factors were excluded by Propensity Score (PS) in children and adults. Methods: Patients hospitalized for burn from 2014 to 2016 were retrieved from the medical record system of a general biggest hospital in Zunyi. A database was established to analyze the influencing factors of LOS between children and adults by the PS. Results A total of 465 children (61.7% males) and 327 (69.7% males) adults were recruited. The average age was 3.61±3.57 years and 42.48±14.76 years in children and adults with burns respectively. Before PS matching, low age and skin grafting were the protective factors for LOS (Hazard Ratio [HR]=0.993 and 0.339). The risk factors of LOS were male (HR=1.234), the burn depth and total body surface area (TBSA), and burn etiology (HR=1.497). After PS matching, only skin grafting (HR=0.080) and treatment within 24 hours (HR=1.865) were the common influencing factors of LOS. Conclusion the confounding factors were excluded by the PS method, and skin grafting was still a protective factor of LOS for both children and adults. The results provide a reference for the promotion of skin grafting to reduce LOS in burn patients.
Concrete is one of the reliable, durable, economical and acceptable construction materials among the building and construction stakeholders worldwide. Performance of concrete could be threatened especially reinforced concrete by some processes such as corrosion, sulfate attack among others. Corrosion of reinforcement in reinforced concrete can be induced by carbonation process. Even though carbonation initiates corrosion, it has been gathered that carbonation could still be of immense benefits to building and construction industries if its mechanism of operation is understudied. This research work has therefore investigated the effect of carbonation on some selected mechanical properties of concrete such as compressive strength, flexural strength, water absorption and weight changes. Concrete cubes and beams of M15 grade with 0.5 % water-cement ratio were prepared and subjected to accelerated carbonation. Their compressive strength, flexural strength, water absorption and weight changes were determined in accordance with the relevant standards. The outcomes show that carbonation improves all the mechanical properties investigated. The use of carbonation can be positively explored in reinforced concrete provided there is adequate nominal cover.
Biogas Synthesis as Means of Solid Waste Management in Kampala, UgandaScientific Review SR
Cattle dung, cooked food waste, and chicken droppings mixed with coffee husks have been used separately and also as mixtures to form anaerobic digestion slurries in a bid to treat to degrade the organic fractions of these wastes and recycle the bio-fertilizer after recovering biogas. Single and mixed substrate slurries evolved significant quantities of methane within 27days together with reduced mass of soil conditioner. The volume of biogas formed in cogeneration mixtures were higher than for single substrate digestion due to the C/N ratio shifting to near 30:1 as a result of mixing. So degradation of organic pollutants was higher in mixed substrate digestion mixtures. Our study yielded average volumes ranging from 315 to 435+ 5.65.mL/L which was in agreement with what is in literature. Digestion of cattle dung, cooked waste foods, and droppings of chicken and mixed substrate slurries using sludge inoculums was very effective in degrading solid waste from homes, thus detoxifying it to bio-fertilizers. Although both single and mixed substrate digestion of waste yielded high enough volumes of biogas; digestion of slurry of mixed organic solid waste substrates is better method of waste management. Digestion of garbage from Kampala should be tested at macro levels at both ambient and mesophilic temperatures. There is need to try out the garbage digestion experiments in the semi-arid towns as well as very cold towns in Uganda.
The Influence of Partial Replacement of Some Selected Pozzolans on the Drying...Scientific Review SR
Concrete is prone to cracking and one of the major causes of cracking is drying shrinkage of the hardened concrete. This research work was carried out to study the influence of partial replacement of some selected pozzolans on the drying shrinkage of concrete. Four pozzolans used in this study, were made to replace cement at various percentages resulting in various concrete mixes. Setting time test was conducted for the various cement mixes using Vicat’s apparatus and drying shrinkage test was done for the concrete test specimens. The results of the setting time indicate that partial replacement of pozzolans with ordinary Portland cement increases both the initial and final setting time of cement as the percentage replacement increases. Similarly, drying shrinkage results show that concrete made with Groundnut Shell Ash (GSA) and Locust Bean Pod Ash (LBA) at 12% replacement will have a stable and better shrinkage resistance than the control at both 56 days and 90 days. Meanwhile, the control concrete gives a better drying shrinkage at 28 days curing. In conclusion, the results show that pozzolanas [Bamboo Leaves Ash (BLA), Locust Bean Pod Ash (LBA), Sugarcane Bagasse Ash (SBA) and Groundnut Shell Ash (GSA)] can successfully replace cement up to 12% without necessarily affecting the shrinkage ability of the produced concrete. It also shows that Groundnut Shell Ash (GSA), Locust Bean Pod Ash (LBA) and Bamboo Leaves Ash (BLA) are more resistance to drying shrinkage than the control.
Study on the Granulation of FLY Ash from Thermal Power StationScientific Review SR
The effect of the type and amount of binding substance on the yield and strength of granules prepared from fly ash was studied. The highest yield of granules was achieved with clayish slip used as binder. The granules obtained are brittle, with compression strength 0,1МРа. The apparent density of the sintered granulates was in the range1200-1500kg/m3 and the total porosity was 55-40%.
Machining Versus Molding Tolerances in Manufacturing Automotive Sealing SystemsScientific Review SR
The automotive industry has been at the forefront of converting traditional metal parts to plastics. The latter surely offer greater design freedom, opportunity for consolidation, fewer assembly operations, reduced secondary finishing, weight reduction, lower total system costs, a range of properties tailored to specific applications, the ability to withstand temperatures, immunity to most chemicals and corrosive environments. They offer processing in many colors, electrical non-conductivity (insulation from electrical shocks), good thermal breaks (“warmth-to-the-touch”), and low sound transmission (tendency to muffle noise). Nonetheless, plastics have only tapped an estimated 15% of their tremendous potential to replace metals. This is particularly to increase with newer high-performance plastics, increasing sophistication in alloying and blending technologies, and use of computer-aided design and engineering (CAD/CAE) systems. The latter enable engineers to visualize complex parts and molding tools more effectively and faster than ever before. This article identifies fundamental steps and requirements to conduct an efficient and successful conversion of metallic parts to plastics, reviewing the replacement design process from concept to production; an under-the-hood rear retainer for Ford Motor Company is detailed as a case study.
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.
A Physical Philosophy for Approaching the True and Then the Beautiful: Princi...Scientific Review SR
Physics demands not only the beautiful but also the true. The true is the first, and the beautiful is the second. The philosophy of physics should emphasize the true and then the beautiful. After reviewing three kind of main hypotheses beyond standard model, and based on experimental and observational evidences, three physical principles and three philosophical rules are suggested, namely P1-action principle, P2-duality principle, P3-equivalence principle, and R1-logic harmony, R2-minimum hypotheses, R3-maximum hopes. It is revealed that there are no supersymmetry and dark sectors because the space and time for the existence of unknown particles resemble impossible.
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.
Richard's entangled aventures in wonderlandRichard 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.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
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.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Volume Fractions of Tantalum Carbides Deduced from the Ta Contents in the Matrix of Three 1250°C–Aged Cobalt–Based Alloys; Comparison with Thermodynamic Calculations
2. Scientific Review
54
matrix are close to the ones calculated by a thermodynamic equilibria solver tool, this one mechanically leads to the
good mass or volume fractions. The Thermo–Calc software working with a database designed to well represent the
equilibrium states of the alloys of the studied family, will be tested. In case of good predictions it will appear as a
possible useful tool to track other sources of risk of mechanical weakening in addition to carbides disappearance: the
proximity of a liquid state.
2. Material and Method
2.1. Names Chemical Compositions and Fabrication of the Considered Alloys
The three alloys are all based on cobalt and they were all wished to contain 25 weight percent of chromium to
resist oxidation by hot gases as well as corrosion by hot aggressive liquid substances. They were designed to respect
the atomic equivalence between carbon and tantalum to promote the formatikon of TaC carbides exclusively (no
more carbon atoms than tantalum atoms in order to avoid the formation of chromium carbides). Knowing that 0.4
wt.% of carbon is a good compromise between the need of efficient carbides–strengthening and the necessity to
maintain a good toughness, the tantalum content was rated to fit this carbon content: same atomic content between C
and Ta, as is to say a weight content in Ta equal to fifteen times the C one (i. e. 6 wt.% Ta for 0.4 wt.%C). A fifth
element was added to two of the three alloys – nickel – with two contents: about 14 wt.%Ni and about 27 wt.%Ni.
This element, often added to cobalt–based alloys to control their tendency to change of crystalline network in case of
thermal cycling (Hexagonal Compact to Face Centered Cubic and inversely), may have also an influence of the TaC
stability and of the refractoriness of the alloys.
The “CCC” alloy, Co(bal.)–25Cr–0.4C–6Ta, the “CCn” alloy, Co(bal.)–14Ni–25Cr–0.4C–6Ta, and the “Cnn”
alloy, Co(bal.)–27Ni–25Cr–0.4C–6Ta, were all produced as 40 grams–weighing compact ingots, from pure elements
(purity > 99.9%, provider: Alfa Aesar) and using a high frequency induction furnace (manufacturer: CELES,
France). Heating, melting, 5 minutes–stay in the liquid state, liquid state cooling, solidification, solid state cooling
were done in an inert atmosphere made of 300–500 mbars of pure argon.
2.2. Microstructure and Chemical Characterization
Each ingot was cut to obtain, on the one hand, a sample for the examination of its as–cast microstructure and, on
the other hand, a sample to expose at high temperature. The first one was embedded in a cold resin system (resin and
hardener from ESCIL, France), ground (SiC papers from 240 to 1200#, water–washed and ethanol–dried, and
polished (1µm–hard particles on a rotating textile disk) until a mirror–like state was obtained. The obtained
metallographic sample was submitted to electronic examination using a Scanning Electron Microscope (SEM) in
Back Scattered Electrons (BSE) mode to control, and to Energy Dispersion Spectrometry (EDS), to control the
obtained microstructures and the chemical composition, respectively. The second sample was ground with 1200#
SiC paper and exposed to heat during 70 hours at 1250°C constantly. After return to ambient temperature this second
sample was prepared as described before in the case of the as–cast sample. Its microstructure was examined using
the SEM in BSE mode to observe the microstructures evolution of during the long stage at elevated temperature, in
particular to verify if the microstructure – certainly modified – is still of the same type as in the as–cast condition:
double–phased with matrix and TaC carbides only. EDS spot analysis were carried out in the matrix (assumed to be
chemically homogeneous after the stabilization at 1250°C). Five EDS measurements were performed and the results
led to an average value and a standard deviation one.
2.3. Comparison with Thermodynamic Calculations; Determination of the TaC Fractions
The Thermo–Calc software (version N) and a home–made thermodynamic database (the SSOL database
enriched with the description of several sub-systems involving tantalum: Co – Ta [11], Ni – Ta [12], Cr – Ta [13], Cr
– Ni – Ta [14], Co – Ta – C [15] and Ni-Ta-C [16] was used to predict the metallurgical state of the three alloys at
1250°C from their chemical compositions, and notably to know the chemical composition of the matrix, its Ta
content in particular.
The Ta contents in the matrix were exploited to determine the mass fractions of TaC carbides, according to the
first one of the two following equations. The corresponding TaC volume fraction was deduced from the TaC mass
fraction according to the second equation.
fTaC
mass
= {MTaC × (gTa
all
– gTa
mat
)} / {MTa – MTaC ×gTa
mat
} (eq.1)
fTaC
vol
= {fTaC
mass
/ TaC} / {(1 – fTaC
mass
)/mat + fTaC
mass
/TaC) (eq. 2)
In these equations, fTaC
mass
is the mass fraction of TaC, MTaC is the molar mass of TaC (globally 181g/mol +
12g/mol = 193 g/mol), gTa
all
is the Ta weight content in the whole alloy (6 wt.%), gTa
mat
is the Ta weight content in
the matrix (determined by EDS), MTa is the molar mass of tantalum (181 g/mol), fTaC
vol
is the mass fraction of TaC,
TaC is the volume mass of the TaC carbide (14.3 g/cm3
) and mat is the volume mass of the matrix (estimated at 9
g/cm3
).
2.4. Exploration of the 1250°C–Isothermal Section for Different Couples of Varying
Elements
In case of representativeness good enough of the thermodynamic predictions new calculations will be possibly
carried out to exploit this tool for exploring the metallurgical states of alloys derived from the three ones for more
extended variations of pairs of elements taken among Ni, Cr, Ta and C (with Ni at the expense of Co). Such
3. Scientific Review
55
calculations may play the role of very useful guidelines for the design of alloy, by indicating in which [wt.%Emin,
wt.%Emax] × [wt.%E’min, wt.%E’max] frames – with (E, E’) ϵ {Ni} × {Cr, Ta, C} – the {matrix + TaC} double-phased
state exists at 1250°C (possible service temperature of some of these alloys), and which (E, E’) combinations are to
avoid (absence of TaC, partial presence of liquid…).
3. Results and Discussion
The alloys were successfully elaborated and cutting did not reveal the existence of not molten parts. Samples
resulting from ingots cutting were ready for further investigations and tests: EDS and microstructure control and
exposure at elevated temperature.
3.1. Obtained Chemical Compositions and Microstructures
The chemical compositions of the three alloys are displayed in Table 1, well fit with the targeted contents in
nickel and chromium. The tantalum contents are, as usual when EDS is used for such type of alloys, a little
overestimated: the real Ta contents, necessarily slightly lower than the values given by EDS, are in good agreement
with what was wished. Concerning the carbon content, it cannot be specified by EDS because this element is rather
light and, in addition, present in too low quantity in the alloys. It is supposed to be correctly respected, by
considering the density of the obtained TaC population.
Table-1.Chemical compositions of the obtained alloys (average ± standard deviation from five full frame ×250 EDS analyses); *: carbon cannot
be analyzed; it is supposed to be well respected
Alloys (×250) wt.% CCC CCn Cnn
Co Bal. Bal. Bal.
Ni / 13.1 ±0.2 25.5±0.4
Cr 25.2 ±0.5 26.2 ±0.3 25.7 ±0.5
Ta 7.7 ±0.5 7.9 ±0.4 7.7 ±0.2
C 0.4* 0.4* 0.4*
The microstructures of the alloys in their as–cast states are illustrated by SEM/BSE micrographs in Figure 1.
They are all double–phased, composed of a dendritic matrix and tantalum carbides precipitated in the interdendritic
spaces, obviously during a eutectic reaction transforming the residual liquid in a second matrix part and TaC
carbides closely imbricated.
These alloys were exposed at 1250°C for 70 hours. Figure 2 shows how microstructures have evolved during
this heat exposure. Obviously TaC fragmentation and coalescence modified a little the carbides network.
3.2. Qualitative Comparisons with Calculated Theoretical Microstructures
The three alloys are positioned in the isopleth section of the {Co, Ni, Cr, C, Ta, temperature T} diagram
calculated with Thermo–Calc for the {25wt.%Cr, 0.4wt.%C, 6 wt.%Ta, pressure P = 100 kPa}–fixed conditions
(Figure 3). According to this figure, the “CCC” and “CCn” alloys would be composed at 1250°C of matrix and TaC
phase only. The “Cnn” alloy should contain also Cr7C3 carbides, but in much lower quantity than TaC as suggested
to its position much closer to the double–phased {matrix + TaC} domain than to the {matrix + M7C3} one. In
addition one can also remark that 1250°C is just a little lower than the solidus temperature. The same observations
(double–phased or triple–phase states, proximity of solidus) can be done in 1250°C–isothermal sections such as in
Figure 4 where Ni (at the expense of Co) and Ta vary at constant T, P, other contents.
Figure-1. As–cast microstructures of the three alloys
4. Scientific Review
56
Figure-2. Microstructures of the three alloys aged at 1250°C
Figure-3. Positions of the three alloys in the isopleth section at {25 wt.%Cr, 0.4wt.%C and 6 wt.%Ta} of the quinary {Co, Ni, Cr, C, Ta} system;
diagram computed with Thermo–Calc
Figure-4. Positions of the three alloys in the 1250°C–isothermal section at {25 wt.%Cr and 0.4wt.%C} of the quinary {Co, Ni, Cr, C, Ta} system
with varying contents in Ni(Co) and Ta, computed with Thermo–Calc
LIQUID
FCC + TaC
FCC + TaC + M23C6
FCC + TaC + M7C3
LIQ + FCC
LIQ + FCC + TaC
FCC+TaC+M7C3+M23C6
: CCC
: CCn
: Cnn
FCC + TaC
FCC + TaC + M7C3
FCC + TaC+ LIQ
: CCC : CCn : Cnn
5. Scientific Review
57
3.3. Quantitative Comparisons with Calculated Theoretical Microstructures
Table 2 gathers the chemical compositions of the matrix of the three alloys after homogenization and
thermodynamic stabilization at 1250°C, according to Thermo–Calc calculations and really measured by EDS spot
analysis. There is very good agreement between the two sets of values. This is notably true for tantalum for which
the calculated Ta content is, in the three cases, located in the intervals defined by average Ta content ± standard
deviation.
Table-2. Comparison of the calculated and EDS–measured chemical compositions of the matrixes of the 1250°C–aged alloys (EDS: average ±
standard deviation from five full frame ×250 analyses)
Matrix at 1250°C wt.% CCC CCn Cnn
Ni (Th-C) / 14.44 28.85
Ni (EDS) / 14.1 ±0.3 27.2 ±0.4
Cr (Th-C) 26.30 26.29 26.02
Cr (EDS) 27.0 ±0.3 27.7 ±0.3 27.2 ±0.2
Ta (Th-C) 1.40 1.42 1.78
Ta (EDS) 1.6 ±0.2 1.5 ±0.2 1.6 ±0.2
C (Th-C) 0.09 0.09 0.09
C (EDS) Cannot be measured by EDS
The calculated Ta weight contents as well as the measured ones were interpreted in term of mass fractions of
TaC carbides according to (eq.1), which were converted into volume fractions according to (eq.2). The obtained
volume fractions are given in Table 3. In the case of the volume fractions coming from the EDS results, three values
were deduced: one for the average measured Ta content, one for this average value with standard deviation added,
and one for the average value with the standard deviation subtracted. In each case the TaC volume fraction derived
from the calculated TaC mass fraction is located between the two experimental extreme values. There is thus also
good agreement between experimental and calculations.
Table-3. Comparison of the volume fractions of TaC deduced from the mass fractions calculated by Thermo–Calc, with the TaC volume fractions
deduced from the mass fractions deduced from the EDS–measured Ta contents in the matrixes of the 1250°C–aged alloys (1: average Ta in
matrix - , 2: average Ta in matrix, 3: average Ta in matrix + ; = standard deviation)
Alloys TaC surf.% CCC CCn Cnn
Thermo-Calc
(deduced from this mass.%)
3.17 vol.%
(5.00 mass.%)
3.15 vol.%
(4.98 mass.%)
2.92 vol.%
(4.62 mass.%)
1250°C-aged
vol.% TaC
from wt.%Ta in matrix (EDS )
3.19 vol.%(1)
3.06 vol.%(2)
2.92 vol.%(3)
3.26 vol.%(1)
3.13 vol.%(2)
2.99 vol.%(3)
3.19 vol.%(1)
3.06 vol.%(2)
2.92 vol.%(3)
3.4. Visualization of the Deduced Volume Fractions
To verify whether these values of volume fractions well represent the TaC population as it can be seen by
metallographic observation some examples of SEM/BSE micrographs were treated to become groups of black or
white pixels depending on the grey level of each pixel of the micrographs. This was done by rating the grey level
threshold in order to reach the previously volume fractions of TaC, and finally by comparing the initial micrograph
and the binarized one. Results are given in Figure 5 for the “CCC” alloy, in Figure 6 for the “CCn” alloy and in
Figure 7 for the “Cnn” alloy. It appears that, by choosing the threshold which allows obtaining surface fractions of
TaC (white pixels) close to the volume fractions resulting from the conversion of the mass fractions deduced from
Ta contents in matrix measured EDS – or from calculated mass fractions since calculated and EDS–deduced mass
fractions are very close to one another – the figures formed by the white pixels are globally superimposed.
3.5. Exploration of the Predictable Variations in Microstructure at 1250°C
The calculations performed by Thermo–Calc associated to the home–made thermodynamic database have
shown a good representativeness of the real microstructures at 1250°C of three alloys. It was decided to use this
thermodynamic modeling tool to study the consequences of more or less limited changes in the weight contents of
Ni, Cr, Ta and C. Three 1250°C–isothermal sections of the quinary system were computed. The section obtained by
varying the Ni and Cr contents simultaneously is given in Figure 8, the one obtained by simultaneously varying the
Ni and Ta contents is given in Figure 9 and the one with the contents in Ni and C varying at the same time is given
in Figure 10.
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58
Figure-5. Threshold rating for retrieving the TaC surface fraction in the CCC alloy deduced from the EDS–measured Ta content in matrix
Figure-6. Threshold rating for retrieving the TaC surface fraction in the CCn alloy deduced from the EDS–measured Ta content in matrix
Figure-7. Threshold rating for retrieving the TaC surface fraction in the CCn alloy deduced from the EDS–measured Ta content in matrix
7. Scientific Review
59
Figure-8. 1250°C–isothermal section at {25 wt.%Cr and 0.4wt.%C} of the quinary {Co, Ni, Cr, C, Ta} system with varying contents in Ni(Co)
and Ta (up to 10 wt.%) computed with Thermo–Calc with the positions of the three alloys; proximity with a {solid + liquid} domain, notably for
the Cnn alloy
Figure 8 shows clearly that, for 1250°C, any increase in Ta content favors the existence of TaC carbides at the
expense of the Cr7C3 carbides, and also that adding more and more nickel inversely favors Cr7C3 at the expense of
TaC. In absence of nickel – and for 0.4 wt.%C – the boundary between the {matrix + TaC + Cr7C3} domain and the
{matrix + TaC} one is stuck on 6wt.%Ta (Ta content threshold being very close to 5.8wt.%Ta, more precisely). This
well corresponds to the atomic equivalence between C and Ta. But, when more en more nickel is present, the need in
Ta for preserving the double–phased {matrix + TaC} state is increased. For instance, for 30wt.%Ni, 8wt.%Ta or
more is compulsory for maintaining this {matrix + TaC} microstructure. On the low Ta side, the Ta content
threshold of TaC appearance is about 0.8wt.%Ta in absence of Ni, but this threshold increases with the Ni content.
For instance, when the alloy contains 40 wt.%Ni, at least 3 wt.%Ta are required to allow the presence of first TaC
carbides in addition to the Cr7C3} carbides. To finish with Figure 8, one can remark that in case of simultaneous high
contents in Ni (e.g. 40 wt.%) and in Ta (e.g. 10 wt.%) the alloy ought to be partly molten at 1250°C. Increases in Ni
and in Ta seem decreasing the refractoriness of the alloy.
In Figure 9 there is a wide domain where the alloys are double–phased {matrix + TaC} at 1250°C. This is only
above the line joining the (0 wt.%Ni, 37 wt.%Cr) and (40 wt.%Ni, 17wt.%Cr) points, that chromium carbides may
be present in addition to the TaC carbides: Cr23C6 on the left (Co–rich side) and Cr7C3 on the right (Ni–richer side).
In case of contents in Ni and Cr simultaneously too high, liquid may be present.
Figure-9. 1250°C–isothermal section at {6 wt.%Ta and 0.4wt.%C} of the quinary {Co, Ni, Cr, C, Ta} system with varying contents in Ni(Co)
and Cr (up to 40 wt.%) computed with Thermo–Calc with the positions of the three alloys; proximity with a {solid + liquid} domain, notably for
the Cnn alloy
: CCC : CCn : Cnn
FCC + TaC
FCC + TaC + M7C3
FCC + M7C3
alloys partly or
totally LIQUID
: CCC : CCn : Cnn
FCC + TaC
FCC + TaC +
M23C6
FCC + TaC +
M7C3
alloys partly or
totally LIQUID
8. Scientific Review
60
In Figure 10, for given contents in Cr (25wt.%) and Ta (6wt.%) the carbon content appears as influencing factor
for both the carbides population type and the alloy’s refractoriness. High carbon promotes the formation of Cr7C3 in
addition to TaC while, for low C contents, the carbon atoms are monopolized by tantalum atoms, which leave
nothing to chromium. Carbon seems favoring the refractoriness of the alloys. This was not really expected and thus a
little surprising since carbon favors carbides which are of a eutectic type for carbon contents not too high.
Figure-10. 1250°C–isothermal section at {25 wt.%Cr and 6 wt.%Ta} of the quinary {Co, Ni, Cr, C, Ta} system with varying contents in Ni(Co)
and C (up to 1 wt.%) computed with Thermo–Calc with the positions of the three alloys; proximity with a {solid + liquid} domain, notably for the
Cnn alloy
4. Conclusion
The knowledge of the quantity of carbides able to stay present at high temperature in the microstructure of a
superalloy, the mechanical strength of which is based on hardening by these particles, is of great importance to
predict the lifetime of components made of this superalloy. In the case of conventionally cast carbides-strengthened
cobalt–based superalloys, exploiting the high morphological stability of primary tantalum carbides is well
recognized solution to allow uses for rather long times at elevated temperature. However TaC carbides must be
present with volume fractions high enough, not only in the as–cast condition but also at the service temperature.
Verifications can be done on artificially high temperature aged superalloys but metallography limited to imaging can
be not accurate enough. Furthermore it can lead to dangerous overestimation of the TaC fractions, because of their
very bright tint when observed in electron microscopy. In this work it was attempted to deduce TaC volume fractions
from TaC mass fractions, themselves deduced from Ta contents in matrix. The obtained results demonstrate that this
way is rather efficient. In addition, the experimentally obtained values of Ta content in matrix for thermodynamic
equilibrium at 1250°C allowed testing a home–made database designed to be exploited by Thermo–Calc. The good
correspondence between measured values and calculated values showed that the database was rather accurate for
predicting microstructures at 1250°C. This allowed carrying out different types of calculations / isothermal sections
of diagrams, potentially helpful for choosing alloy’s composition for reaching the wished microstructures and for
avoiding partial molten states.
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L+F
L+F+T
FCC + TaC
FCC + TaC + M7C3
alloys partly or
totally LIQUID
: CCC : CCn : Cnn
9. Scientific Review
61
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