Pub Date : 2020-11-30DOI: 10.21303/2585-6847.2020.001504
A. Bolotnikova
The superconducting cuprate Y3Ba5Cu8Ox was obtained with the help of sol-gel technology (sample C), co-precipitation of hydroxocarbonates (sample B) and solid-phase synthesis methods (A). Based on the results of scanning electron microscopy and methods based on the analysis of X-ray diffraction data: the Williamson-Hall construction and the Scherrer formula, features of the microstructure of the synthesized samples are established. The smallest particle size has a sample that has been synthesized by the sol-gel method. The tendency to aggregation and sedimentation for this sample is the smallest. The sample obtained by the co-precipitation method has larger grains and a higher tendency to aggregate. The size of the microparticles and the tendency to aggregate for the sample synthesized by the solid-phase method are greatest. The morphology of particles was studied using three methods: SEM, Scherrer and Williamson-Hall formulas and the following results were found: particle size depends on the synthesis method, but a relatively narrow size distribution within one synthesis method remains, the value of crystal lattice microdeformation for samples increases in a line: C sample– A sample– B sample. Thus, the work was carried out for determining the size, structure and morphology of superconducting phases. It expands knowledge in the field of research of superconducting compounds
{"title":"Determination of the Sizes of Particles of Superconducting Cuprate Y3Ba5Cu8OX by Means of Different Methods","authors":"A. Bolotnikova","doi":"10.21303/2585-6847.2020.001504","DOIUrl":"https://doi.org/10.21303/2585-6847.2020.001504","url":null,"abstract":"The superconducting cuprate Y3Ba5Cu8Ox was obtained with the help of sol-gel technology (sample C), co-precipitation of hydroxocarbonates (sample B) and solid-phase synthesis methods (A). Based on the results of scanning electron microscopy and methods based on the analysis of X-ray diffraction data: the Williamson-Hall construction and the Scherrer formula, features of the microstructure of the synthesized samples are established. The smallest particle size has a sample that has been synthesized by the sol-gel method. The tendency to aggregation and sedimentation for this sample is the smallest. The sample obtained by the co-precipitation method has larger grains and a higher tendency to aggregate. The size of the microparticles and the tendency to aggregate for the sample synthesized by the solid-phase method are greatest. The morphology of particles was studied using three methods: SEM, Scherrer and Williamson-Hall formulas and the following results were found: particle size depends on the synthesis method, but a relatively narrow size distribution within one synthesis method remains, the value of crystal lattice microdeformation for samples increases in a line: C sample– A sample– B sample. Thus, the work was carried out for determining the size, structure and morphology of superconducting phases. It expands knowledge in the field of research of superconducting compounds","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85218978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Se-Ho Kim, Xue Zhang, K. Schweinar, I. S. Souza Filho, K. Angenendt, Yan Ma, D. Vogel, L. Stephenson, A. El-Zoka, J. Mianroodi, M. Rohwerder, B. Gault, D. Raabe
Steel is the most important material class in terms of volume and environmental impact. While it is a sustainability enabler, for instance through lightweight design and magnetic devices, its primary production is not. Iron is reduced from ores by carbon, causing 30% of the global CO2 emissions in manufacturing, qualifying it as the largest single industrial greenhouse gas emission source. Hydrogen is an attractive alternative reductant. Although this reaction has been studied for decades, its kinetics is not well understood, particularly the wustite reduction step, which is much slower than hematite reduction. Some rate limiting factors of this reaction depend on the microstructure and local chemistry. Here, we report on a multi-scale structure and composition analysis of iron reduced from hematite with pure H2, reaching down to near-atomic scale. The microstructure after reduction consists of nearly pure iron crystals, containing inherited and acquired pores and cracks. We observe several types of lattice defects that accelerate mass transport inbound (hydrogen) and outbound (oxygen) as well as chemical impurities in the form of oxide islands that were not reduced. With this study, we aim to open the perspective in the field of carbon-neutral iron production from macroscopic processing towards the underlying microscopic reduction mechanisms and kinetics.
{"title":"Influence of Microstructure and Atomic-Scale Chemistry on Iron Ore Reduction with Hydrogen at 700°C","authors":"Se-Ho Kim, Xue Zhang, K. Schweinar, I. S. Souza Filho, K. Angenendt, Yan Ma, D. Vogel, L. Stephenson, A. El-Zoka, J. Mianroodi, M. Rohwerder, B. Gault, D. Raabe","doi":"10.2139/ssrn.3726295","DOIUrl":"https://doi.org/10.2139/ssrn.3726295","url":null,"abstract":"Steel is the most important material class in terms of volume and environmental impact. While it is a sustainability enabler, for instance through lightweight design and magnetic devices, its primary production is not. Iron is reduced from ores by carbon, causing 30% of the global CO2 emissions in manufacturing, qualifying it as the largest single industrial greenhouse gas emission source. Hydrogen is an attractive alternative reductant. Although this reaction has been studied for decades, its kinetics is not well understood, particularly the wustite reduction step, which is much slower than hematite reduction. Some rate limiting factors of this reaction depend on the microstructure and local chemistry. Here, we report on a multi-scale structure and composition analysis of iron reduced from hematite with pure H2, reaching down to near-atomic scale. The microstructure after reduction consists of nearly pure iron crystals, containing inherited and acquired pores and cracks. We observe several types of lattice defects that accelerate mass transport inbound (hydrogen) and outbound (oxygen) as well as chemical impurities in the form of oxide islands that were not reduced. With this study, we aim to open the perspective in the field of carbon-neutral iron production from macroscopic processing towards the underlying microscopic reduction mechanisms and kinetics.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83404794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sudhanshu Nahata, M. Moradi, Y. Picard, N. Kota, O. B. Ozdoganlar
Abstract Mechanical removal of metal induces deformation and changes to microstructural characteristics of the newly created surfaces. The mode and extent of deformation can be difficult to predict since it depends on the local crystallographic orientation, which varies significantly for polycrystalline metals. In this work, we analyzed the deformation mode and extent beneath machined surfaces of different crystallographic orientations. This was accomplished by orthogonal micromachining of single-crystal aluminum along six different crystallographic orientations orthogonal to the sample [111] zone-axis, followed by electron backscatter diffraction (EBSD) analysis to evaluate the resulting subsurface microstructure and crystal lattice rotation. The results indicate that differences in the initial material crystallographic orientation produce significant variations in the depth of deformation (compared to the uncut chip thickness), the degree of grain refinement and the extent of lattice rotations. We grouped the orientation as “hard” or “soft” based on the measured cutting force. The soft orientations exhibit deformation modes consisting of shear bands and lattice rotations; whereas hard orientations exhibit deformation modes consistent with strain hardening: localized dynamic recrystallization, highly entangled dislocations and minimal crystal lattice rotations. The depth of subsurface deformation for some orientations was extensive, reaching depths far greater than the uncut chip thicknesses. Overall, we conclude that the cutting force required to machine a given orientation does provide some insight on the local deformation mode, and orientations can be easier or harder to machine based on local susceptibility to shear and lattice rotation.
{"title":"Micromachining Imposed Subsurface Plastic Deformation in Single-Crystal Aluminum","authors":"Sudhanshu Nahata, M. Moradi, Y. Picard, N. Kota, O. B. Ozdoganlar","doi":"10.2139/ssrn.3618731","DOIUrl":"https://doi.org/10.2139/ssrn.3618731","url":null,"abstract":"Abstract Mechanical removal of metal induces deformation and changes to microstructural characteristics of the newly created surfaces. The mode and extent of deformation can be difficult to predict since it depends on the local crystallographic orientation, which varies significantly for polycrystalline metals. In this work, we analyzed the deformation mode and extent beneath machined surfaces of different crystallographic orientations. This was accomplished by orthogonal micromachining of single-crystal aluminum along six different crystallographic orientations orthogonal to the sample [111] zone-axis, followed by electron backscatter diffraction (EBSD) analysis to evaluate the resulting subsurface microstructure and crystal lattice rotation. The results indicate that differences in the initial material crystallographic orientation produce significant variations in the depth of deformation (compared to the uncut chip thickness), the degree of grain refinement and the extent of lattice rotations. We grouped the orientation as “hard” or “soft” based on the measured cutting force. The soft orientations exhibit deformation modes consisting of shear bands and lattice rotations; whereas hard orientations exhibit deformation modes consistent with strain hardening: localized dynamic recrystallization, highly entangled dislocations and minimal crystal lattice rotations. The depth of subsurface deformation for some orientations was extensive, reaching depths far greater than the uncut chip thicknesses. Overall, we conclude that the cutting force required to machine a given orientation does provide some insight on the local deformation mode, and orientations can be easier or harder to machine based on local susceptibility to shear and lattice rotation.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81906909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Loevenich, M. Trippe, J. Brimmers, C. Brecher, S. Stark, D. Krueger
Geared turbofans increase the efficiency of aircraft engines. By decoupling the fan and low- ressure turbine, both components can be operated at their optimum speed. Due to the high number of flight hours and the high turbine speeds of n > 10,000 rpm, the number of load cycles at the gear teeth of the planetary gear unit is significantly higher than the conventional fatigue strength of gear teeth. The planetary gears under fully reversed bending load are particularly susceptible to tooth root fractures. Pulsator test rigs are not suitable for testing tooth root load capacity under fully reversed bending load. The concept of a modified 3-shaft backto-back test rig was set up to cope with this challenge. A back-to-back test rig consists of a test and reference gearbox, which are connected by shafts to form a closed power circuit. In order to perform the investigation efficiently, the test rig is operated at a speed of n > 12,000 rpm with a recirculating power of P > 5 MW. This performance class results in special requirements for the test rig design. The roller bearing arrangements normally used for back-to-back test rigs no longer offer sufficient load carrying capacity, so that a changeover to journal bearings is necessary. This leads to high power losses of the bearings of P ≈ 200 kW and oil quantities of Q ≈ 450 l/min on the cooling and bearing lubrication side. The journal bearings of the gearboxes have a decisive disadvantage. Starting under load is not possible. Therefore, a hydraulic load unit was designed which allows load application at operating speed. In the reference gearbox, this unit shifts two helical gears on a spline shaft, which are slanted in opposite directions, towards each other, so that a torsional load is generated in the test gearbox by means of a closed power circuit. The two displaceable helical gears represent the greatest challenge from a manufacturing point of view. In order to achieve an even load distribution on both gears, they must be manufactured very precisely to each other and to the spline profile. In the report, the focus is set on the double helical reference gearbox including the axial load unit. Besides the design of the components the requirements regarding manufacturing are analysed and possible manufacturing chains are discussed.
{"title":"Design and Manufacturing Strategy of a Back-to-Back Test Rig for Investigation of Ultra High Cycle Fatigue Strength Regarding Tooth Root Strength in Aerospace Applications","authors":"J. Loevenich, M. Trippe, J. Brimmers, C. Brecher, S. Stark, D. Krueger","doi":"10.2139/ssrn.3724213","DOIUrl":"https://doi.org/10.2139/ssrn.3724213","url":null,"abstract":"Geared turbofans increase the efficiency of aircraft engines. By decoupling the fan and low- ressure turbine, both components can be operated at their optimum speed. Due to the high number of flight hours and the high turbine speeds of n > 10,000 rpm, the number of load cycles at the gear teeth of the planetary gear unit is significantly higher than the conventional fatigue strength of gear teeth. The planetary gears under fully reversed bending load are particularly susceptible to tooth root fractures. Pulsator test rigs are not suitable for testing tooth root load capacity under fully reversed bending load. The concept of a modified 3-shaft backto-back test rig was set up to cope with this challenge. A back-to-back test rig consists of a test and reference gearbox, which are connected by shafts to form a closed power circuit. In order to perform the investigation efficiently, the test rig is operated at a speed of n > 12,000 rpm with a recirculating power of P > 5 MW. This performance class results in special requirements for the test rig design. The roller bearing arrangements normally used for back-to-back test rigs no longer offer sufficient load carrying capacity, so that a changeover to journal bearings is necessary. This leads to high power losses of the bearings of P ≈ 200 kW and oil quantities of Q ≈ 450 l/min on the cooling and bearing lubrication side. The journal bearings of the gearboxes have a decisive disadvantage. Starting under load is not possible. Therefore, a hydraulic load unit was designed which allows load application at operating speed. In the reference gearbox, this unit shifts two helical gears on a spline shaft, which are slanted in opposite directions, towards each other, so that a torsional load is generated in the test gearbox by means of a closed power circuit. The two displaceable helical gears represent the greatest challenge from a manufacturing point of view. In order to achieve an even load distribution on both gears, they must be manufactured very precisely to each other and to the spline profile. In the report, the focus is set on the double helical reference gearbox including the axial load unit. Besides the design of the components the requirements regarding manufacturing are analysed and possible manufacturing chains are discussed.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88746136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-31DOI: 10.15587/2706-5448.2020.214781
N. Dmytriieva, I. Agafonova, Nina Bostan
The object of reseaerch is concrete samples modified with ash-containing fillers and plasticizers. As practice shows, the use of secondary resources is an important issue in the field of construction and entails significant savings. The issue is also considered from the point of view of environmental protection. The study is aimed at determining the effect of modification of concrete with ash-containing waste on the strength characteristics using the example of the hydroelectric power station of the Dnistrovska PSPS (Sokyriany district, Chernivtsi region, Ukraine). The main hypothesis of the study is the assumption that varying components such as fly ash, water glass, and superplasticizers will make it possible to obtain concrete with specified strength characteristics. To achieve the aim, the authors decided to use in the study the superplasticizer SikaPlast-520N and BETO-plast, Portland cement M400 and sands of the quarries of the Parkan and Suklei regions (Moldova). According to the plan of the experiment, studies of the influence of hardening conditions on the structure and properties of modified concrete samples were carried out. Destructive testing of samples was carried out in the laboratory directly on a hydraulic press.
The results of experiments without the addition of liquid glass and the introduction of a minimum amount of fly ash and experiments with the introduction of a minimum amount of fly ash and the addition of 3 % water glass are presented. To determine the dynamics of strength gain, tests were carried out on 7, 14 and 28 days. The presented results of the study of the samples on day 7 show a gain of more than 50 % strength. This indicates the possibility of reducing the curing period of structural concrete in the formwork system. A more complete and objective idea of the quality of concrete is possible while taking into account the average strength of concrete and its homogeneity.
Today, there is no unified theory that can relate the different properties of cement and filler to the final properties of a composite material. The issue of modifying concrete compositions when using fine aggregate from other quarries requires additional research. At the same time, the results of the experiment show that the use of microfillers based on wastes from the Dnistrovska PSPS provide ample opportunities not only for saving binders, but also for improving the physical, mechanical and operational characteristics of concrete.
{"title":"Research for Modification of Concrete With Ash-Containing Waste of Dnistrovska PSPS (Ukraine)","authors":"N. Dmytriieva, I. Agafonova, Nina Bostan","doi":"10.15587/2706-5448.2020.214781","DOIUrl":"https://doi.org/10.15587/2706-5448.2020.214781","url":null,"abstract":"The object of reseaerch is concrete samples modified with ash-containing fillers and plasticizers. As practice shows, the use of secondary resources is an important issue in the field of construction and entails significant savings. The issue is also considered from the point of view of environmental protection. The study is aimed at determining the effect of modification of concrete with ash-containing waste on the strength characteristics using the example of the hydroelectric power station of the Dnistrovska PSPS (Sokyriany district, Chernivtsi region, Ukraine). The main hypothesis of the study is the assumption that varying components such as fly ash, water glass, and superplasticizers will make it possible to obtain concrete with specified strength characteristics. To achieve the aim, the authors decided to use in the study the superplasticizer SikaPlast-520N and BETO-plast, Portland cement M400 and sands of the quarries of the Parkan and Suklei regions (Moldova). According to the plan of the experiment, studies of the influence of hardening conditions on the structure and properties of modified concrete samples were carried out. Destructive testing of samples was carried out in the laboratory directly on a hydraulic press.<br><br>The results of experiments without the addition of liquid glass and the introduction of a minimum amount of fly ash and experiments with the introduction of a minimum amount of fly ash and the addition of 3 % water glass are presented. To determine the dynamics of strength gain, tests were carried out on 7, 14 and 28 days. The presented results of the study of the samples on day 7 show a gain of more than 50 % strength. This indicates the possibility of reducing the curing period of structural concrete in the formwork system. A more complete and objective idea of the quality of concrete is possible while taking into account the average strength of concrete and its homogeneity.<br><br>Today, there is no unified theory that can relate the different properties of cement and filler to the final properties of a composite material. The issue of modifying concrete compositions when using fine aggregate from other quarries requires additional research. At the same time, the results of the experiment show that the use of microfillers based on wastes from the Dnistrovska PSPS provide ample opportunities not only for saving binders, but also for improving the physical, mechanical and operational characteristics of concrete.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73217104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
When machining duplex steel 1.4462 the choice of the hard coating of the cutting tool plays a major role due to the high process temperatures, caused by relatively low thermal conductivity of this material. Hard coatings can have different thermo-physical properties, e. g. thermal conductivity and specific heat capacity. Thus, they influence the process temperatures in the shear zones and have an impact on the chip formation. For a mechanisms-oriented tool development it is necessary to understand these influences. Experimental cutting tests based on a linearorthogonal kinematic are a suitable method for an experimental approach. A challenge with experimental methods is to vary the thermo-physical properties of the coatings without changing the friction effects in the contact areas of the tool and workpiece at the same time. An unwanted change of the friction leads to superimposed effects and difficulties during the interpretation of the influence of the thermo-physical properties. This work discusses the influence of two different wear protection layers on the behavior of an austenitic-ferritic duplex steel during linearorthogonal cutting experiments. In the investigations, one monolayer coating (TiAlN) and one multilayer coating (TiN-TiCN-Al2O3) were examined. The experiments were carried out under different cutting conditions and wear conditions of the tools to generate various friction conditions. In the results analysis, focus is mainly given to the cutting and feed forces as well as the chip thickness values. The experimental results are supplemented with analytical analyses to understand the influence of thermo-physical properties of coatings and interfacial effects caused by friction.
{"title":"Investigation of the Influence of Different Hard Coatings on Chip Formation and Process Forces When Machining Duplex Steel 1.4462","authors":"A. Glavas, B. Thimm, T. Teppernegg, C. Czettl","doi":"10.2139/ssrn.3722050","DOIUrl":"https://doi.org/10.2139/ssrn.3722050","url":null,"abstract":"When machining duplex steel 1.4462 the choice of the hard coating of the cutting tool plays a major role due to the high process temperatures, caused by relatively low thermal conductivity of this material. Hard coatings can have different thermo-physical properties, e. g. thermal conductivity and specific heat capacity. Thus, they influence the process temperatures in the shear zones and have an impact on the chip formation. For a mechanisms-oriented tool development it is necessary to understand these influences. Experimental cutting tests based on a linearorthogonal kinematic are a suitable method for an experimental approach. A challenge with experimental methods is to vary the thermo-physical properties of the coatings without changing the friction effects in the contact areas of the tool and workpiece at the same time. An unwanted change of the friction leads to superimposed effects and difficulties during the interpretation of the influence of the thermo-physical properties. This work discusses the influence of two different wear protection layers on the behavior of an austenitic-ferritic duplex steel during linearorthogonal cutting experiments. In the investigations, one monolayer coating (TiAlN) and one multilayer coating (TiN-TiCN-Al2O3) were examined. The experiments were carried out under different cutting conditions and wear conditions of the tools to generate various friction conditions. In the results analysis, focus is mainly given to the cutting and feed forces as well as the chip thickness values. The experimental results are supplemented with analytical analyses to understand the influence of thermo-physical properties of coatings and interfacial effects caused by friction.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72789759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-23DOI: 10.15587/1729-4061.2020.214399
D. Starokadomsky, D. Rassokhin, A. Ishchenko, N. Sigareva, M. Reshetnyk
This paper reports the results of studying epoxy compositions with gypsum taken in the form of dispersed powders in the original and water-hardened form. The exact pattern has been shown in the way the introduction of a gypsum additive in the amount of 50 % by weight affects the strength, chemical stability, and morphology of the composites.
Under conventional heat treatment (60‒110 °C) of the hardened composites, the maximum stress at compression σm and the elasticity module at compression Ес, as well as wear resistance, decrease after the introduction of gypsums (of both types). At the same time, after a hard (destructive) heating at 250‒260 °C, the elasticity module Ес of the hardened composites increases. The maximum stress at compression σm is also increased. The same applies to the wear resistance, which grows especially noticeably after 250 °C.
The micro-hardness after filling is prone to increase but the fragility of epoxy-gypsum composites does not make it possible to measure it when a punch (a steel hemisphere) penetrates it deeper than 20 µm. However, after the heat treatment at 250‒260 °C, the unfilled polymer, on the contrary, is embrittled while the filled ones are plasticized, thus showing a high micro-hardness at significant (30‒50 µm) immersion.
The composites with gypsum, in contrast to the unfilled ones, do not disintegrate in acetone and retain integrity at any aging duration (up to 75 days and beyond). In this case, the original gypsum produces a composite with less swelling in acetone than the hardened gypsum. Based on the data from atomic-strength microscopy (ASM) microscopy, the morphologies of the non-filled composite, the composites with the hardened gypsum and original gypsum are different. The original gypsum forms a composite with a more pronounced (possibly crystalline) filler structure; the morphology for the hardened composite reflects the distribution of inert particles; for the unfilled composite (H-composite), only pores are visible against the background of a relatively smooth relief.
{"title":"Strength and Chemical Resistance of Composites Based on Epoxy Resins, Filled With Gypsum in the Original and Waterhardened Forms","authors":"D. Starokadomsky, D. Rassokhin, A. Ishchenko, N. Sigareva, M. Reshetnyk","doi":"10.15587/1729-4061.2020.214399","DOIUrl":"https://doi.org/10.15587/1729-4061.2020.214399","url":null,"abstract":"This paper reports the results of studying epoxy compositions with gypsum taken in the form of dispersed powders in the original and water-hardened form. The exact pattern has been shown in the way the introduction of a gypsum additive in the amount of 50 % by weight affects the strength, chemical stability, and morphology of the composites.<br><br>Under conventional heat treatment (60‒110 °C) of the hardened composites, the maximum stress at compression σm and the elasticity module at compression Ес, as well as wear resistance, decrease after the introduction of gypsums (of both types). At the same time, after a hard (destructive) heating at 250‒260 °C, the elasticity module Ес of the hardened composites increases. The maximum stress at compression σm is also increased. The same applies to the wear resistance, which grows especially noticeably after 250 °C.<br><br>The micro-hardness after filling is prone to increase but the fragility of epoxy-gypsum composites does not make it possible to measure it when a punch (a steel hemisphere) penetrates it deeper than 20 µm. However, after the heat treatment at 250‒260 °C, the unfilled polymer, on the contrary, is embrittled while the filled ones are plasticized, thus showing a high micro-hardness at significant (30‒50 µm) immersion.<br><br>The composites with gypsum, in contrast to the unfilled ones, do not disintegrate in acetone and retain integrity at any aging duration (up to 75 days and beyond). In this case, the original gypsum produces a composite with less swelling in acetone than the hardened gypsum. Based on the data from atomic-strength microscopy (ASM) microscopy, the morphologies of the non-filled composite, the composites with the hardened gypsum and original gypsum are different. The original gypsum forms a composite with a more pronounced (possibly crystalline) filler structure; the morphology for the hardened composite reflects the distribution of inert particles; for the unfilled composite (H-composite), only pores are visible against the background of a relatively smooth relief.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81380495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. V. Haag, David Edwards, C. Henager, W. Setyawan, Jing Wang, M. Murayama
Abstract Tungsten heavy alloys (WHAs) are a type of ductile phase toughened alloy that are becoming increasingly interesting as an alternative to polycrystalline tungsten for fusion reactor plasma facing material components due to their balanced strength and ductility. To justify their use in the extremely harsh environment of a fusion reactor, understanding detailed microstructural features of WHAs associated with their mechanical property changes is necessary. A 90W-7Ni-3Fe WHA alloy has been chosen to investigate the effect of thermomechanical treatment and microstructural manipulation on the overall effectiveness of deformation accommodation in these bi-phase metallic composites. Both in-situ tensile testing and 3D microstructural analysis of the samples reveal a predominance of microcracking at tungsten grain boundaries that are blunted and arrested by the ductile phase, while there remains little to no instances of interfacial debonding. Thermomechanical treatment of this alloy is found to alter the spherical brittle phase domains into elongated plates, drastically reducing the ductile phase connectivity, and changing the nature of material deformation. Characterization of the ductile phase toughening mechanisms in these materials has provided deeper insight into the underlying physics governing material behavior in these alloys; revealing a surprising interfacial strength between the different phases.
{"title":"Characterization of Ductile Phase Toughening Mechanisms in a Hot-Rolled Tungsten Heavy Alloy","authors":"J. V. Haag, David Edwards, C. Henager, W. Setyawan, Jing Wang, M. Murayama","doi":"10.2139/ssrn.3683518","DOIUrl":"https://doi.org/10.2139/ssrn.3683518","url":null,"abstract":"Abstract Tungsten heavy alloys (WHAs) are a type of ductile phase toughened alloy that are becoming increasingly interesting as an alternative to polycrystalline tungsten for fusion reactor plasma facing material components due to their balanced strength and ductility. To justify their use in the extremely harsh environment of a fusion reactor, understanding detailed microstructural features of WHAs associated with their mechanical property changes is necessary. A 90W-7Ni-3Fe WHA alloy has been chosen to investigate the effect of thermomechanical treatment and microstructural manipulation on the overall effectiveness of deformation accommodation in these bi-phase metallic composites. Both in-situ tensile testing and 3D microstructural analysis of the samples reveal a predominance of microcracking at tungsten grain boundaries that are blunted and arrested by the ductile phase, while there remains little to no instances of interfacial debonding. Thermomechanical treatment of this alloy is found to alter the spherical brittle phase domains into elongated plates, drastically reducing the ductile phase connectivity, and changing the nature of material deformation. Characterization of the ductile phase toughening mechanisms in these materials has provided deeper insight into the underlying physics governing material behavior in these alloys; revealing a surprising interfacial strength between the different phases.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85845113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Spiridigliozzi, C. Ferone, R. Cioffi, G. Dell’Agli
Abstract High-Entropy Oxides (HEOs) are a totally new class of ceramic materials that have recently attracted many scientific attentions. However, the huge intrinsic complexity and the massive number of possible combinations characterizing such systems make it hard to predict a priori their properties and their crystal structures. Moreover, the idea of designing and engineering new materials by using entropy as a driving force is conceptually exciting and intellectually stimulating. Thus, we acknowledged that predicting and synthesizing unknown entropy-stabilized single-phases of a given formula in a given crystal structure could be of great interest to the HEOs research community and, through a systematic study of 18 samples of equimolar 5-component Rare Earths-based oxides, we were able to elaborate a simple and effective predictive model to design HEOs stabilized in a single-phase fluorite-like structure. The novelty of our model, other than its simplicity and immediacy, consists in pointing out that the “dispersion” of the cationic radii of the involved elements of a certain system (expressed in terms of their standard deviation) is crucial for stabilizing fluorite-structured HEOs. Definitely, for systems owning standard deviations of the involved elements cationic radii (coordination VIII) distribution higher than 0.095, single-phase fluorite-structured systems are formed; otherwise, for s
{"title":"A Simple and Effective Predictor to Design Novel Fluorite-Structured High Entropy Oxides (HEOs)","authors":"L. Spiridigliozzi, C. Ferone, R. Cioffi, G. Dell’Agli","doi":"10.2139/ssrn.3688785","DOIUrl":"https://doi.org/10.2139/ssrn.3688785","url":null,"abstract":"Abstract High-Entropy Oxides (HEOs) are a totally new class of ceramic materials that have recently attracted many scientific attentions. However, the huge intrinsic complexity and the massive number of possible combinations characterizing such systems make it hard to predict a priori their properties and their crystal structures. Moreover, the idea of designing and engineering new materials by using entropy as a driving force is conceptually exciting and intellectually stimulating. Thus, we acknowledged that predicting and synthesizing unknown entropy-stabilized single-phases of a given formula in a given crystal structure could be of great interest to the HEOs research community and, through a systematic study of 18 samples of equimolar 5-component Rare Earths-based oxides, we were able to elaborate a simple and effective predictive model to design HEOs stabilized in a single-phase fluorite-like structure. The novelty of our model, other than its simplicity and immediacy, consists in pointing out that the “dispersion” of the cationic radii of the involved elements of a certain system (expressed in terms of their standard deviation) is crucial for stabilizing fluorite-structured HEOs. Definitely, for systems owning standard deviations of the involved elements cationic radii (coordination VIII) distribution higher than 0.095, single-phase fluorite-structured systems are formed; otherwise, for s","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84612817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Chawake, Lavanya Raman, P. Ramasamy, P. Ghosh, F. Spieckermann, C. Gammer, B. S. Murty, R. S. Kottada, J. Eckert
Abstract A composite of two different medium entropy alloys (MEAs, i.e., CoCrFeNi and AlCoCrFe) was synthesized using ball milling and spark plasma sintering. The composite microstructure contains a homogenous distribution of fcc and bcc phases with submicron-sized grains and exhibits excellent microstructural and phase stability even after 100 h heat treatment at 800 °C. The composite provides a combination of high compressive strength, adequate plastic strain, and multiple strain-hardening stages at room temperature. This first exploratory study on a MEA composite can be used as a template to other systems and illustrates the feasibility of combining two or more MEAs.
{"title":"Composite of Medium Entropy Alloys Synthesized Using Spark Plasma Sintering","authors":"N. Chawake, Lavanya Raman, P. Ramasamy, P. Ghosh, F. Spieckermann, C. Gammer, B. S. Murty, R. S. Kottada, J. Eckert","doi":"10.2139/ssrn.3680365","DOIUrl":"https://doi.org/10.2139/ssrn.3680365","url":null,"abstract":"Abstract A composite of two different medium entropy alloys (MEAs, i.e., CoCrFeNi and AlCoCrFe) was synthesized using ball milling and spark plasma sintering. The composite microstructure contains a homogenous distribution of fcc and bcc phases with submicron-sized grains and exhibits excellent microstructural and phase stability even after 100 h heat treatment at 800 °C. The composite provides a combination of high compressive strength, adequate plastic strain, and multiple strain-hardening stages at room temperature. This first exploratory study on a MEA composite can be used as a template to other systems and illustrates the feasibility of combining two or more MEAs.","PeriodicalId":18300,"journal":{"name":"MatSciRN: Other Materials Processing & Manufacturing (Topic)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81425946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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