Oscillating drop experiments allow the surface tension and viscosity of high temperature and highly reactive melts to be measured without an interface contacting the surface of the molten sample. Surface oscillations are induced by varying the electromagnetic field. The oscillations are measured to determine the surface tension and viscosity from the frequency and damping of the oscillations, respectively. The damping of the oscillations is, however, sensitive to the flow conditions within the melt. Recent advances have allowed transient magnetohydrodynamic models to calculate changes in the internal flow in response to variations in the magnetic field, much like those used to induce surface oscillations. These models show that the excitation pulse drives rapid acceleration within the melt. While the fluid flow may accelerate to speeds above the laminar-turbulent transition, the flow speeds are not sustained for sufficient time periods to allow turbulent flow to develop. Following the excitation pulse, the flow rapidly slows and quickly returns to the conditions present before the excitation pulse.
{"title":"The effects of the excitation pulse on flow in electromagnetic levitation experiments","authors":"G. Bracker, R. Hyers","doi":"10.32908/hthp.v52.1301","DOIUrl":"https://doi.org/10.32908/hthp.v52.1301","url":null,"abstract":"Oscillating drop experiments allow the surface tension and viscosity of high temperature and highly reactive melts to be measured without an interface contacting the surface of the molten sample. Surface oscillations are induced by varying the electromagnetic field. The oscillations are measured to determine the surface tension and viscosity from the frequency and damping of the oscillations, respectively. The damping of the oscillations is, however, sensitive to the flow conditions within the melt. Recent advances have allowed transient magnetohydrodynamic models to calculate changes in the internal flow in response to variations in the magnetic field, much like those used to induce surface oscillations. These models show that the excitation pulse drives rapid acceleration within the melt. While the fluid flow may accelerate to speeds above the laminar-turbulent transition, the flow speeds are not sustained for sufficient time periods to allow turbulent flow to develop. Following the excitation pulse, the flow rapidly slows and quickly returns to the conditions present before the excitation pulse.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. P. Kreuzer, Fan Yang, S. Szabó, Z. Evenson, A. Meyer, W. Petry
We investigate the atomic dynamics of a Cu-rich Cu76Ti24 alloy between 1223 K and 1453 K using the quasi-elastic neutron scattering technique. The obtained mean Cu/Ti self-diffusion coefficient D exhibits an Arrhenius-like temperature dependence with an activation energy of 0.46�0.02 eV per atom. Compared with those of the pure elements at a given temperature, D is slower than that for pure Cu, but similar to pure Ti. This slowing down of the liquid dynamics upon alloying has been observed for most binary alloy systems. However, in this study, the packing fraction of the Cu-Ti alloy is lower than that of the pure elements, which can be explained by the positive excess volume of the Cu-Ti system. Therefore, the compositional dependence of the atomic dynamics cannot be linked to a macroscopic packing argument. Only, the atomic dynamics is not correlated with an increase of the average packing fraction of the melt.
利用准弹性中子散射技术研究了富cu Cu76Ti24合金在1223k和1453k之间的原子动力学。得到的Cu/Ti平均自扩散系数D表现出类似阿伦尼乌斯的温度依赖性，活化能为0.46 ~ 0.02 eV /原子。在一定温度下，与纯元素相比，D比纯Cu慢，但与纯Ti相似。在大多数二元合金体系中，已经观察到这种合金化过程中液体动力学的减慢。然而，在本研究中，Cu-Ti合金的填充分数低于纯元素，这可以解释为Cu-Ti体系的正过剩体积。因此，原子动力学的组分依赖性不能与宏观堆积论证联系起来。只是，原子动力学与熔体平均堆积分数的增加无关。
{"title":"Relationship of the atomic dynamics and excess volume of a copper rich Cu76Ti24 alloy melt","authors":"L. P. Kreuzer, Fan Yang, S. Szabó, Z. Evenson, A. Meyer, W. Petry","doi":"10.32908/hthp.v52.1353","DOIUrl":"https://doi.org/10.32908/hthp.v52.1353","url":null,"abstract":"We investigate the atomic dynamics of a Cu-rich Cu76Ti24 alloy between 1223 K and 1453 K using the quasi-elastic neutron scattering technique. The obtained mean Cu/Ti self-diffusion coefficient D exhibits an Arrhenius-like temperature dependence with an activation energy of 0.46�0.02 eV per atom. Compared with those of the pure elements at a given temperature, D is slower than that for pure Cu, but similar to pure Ti. This slowing down of the liquid dynamics upon alloying has been observed for most binary alloy systems. However, in this study, the packing fraction of the Cu-Ti alloy is lower than that of the pure elements, which can be explained by the positive excess volume of the Cu-Ti system. Therefore, the compositional dependence of the atomic dynamics cannot be linked to a macroscopic packing argument. Only, the atomic dynamics is not correlated with an increase of the average packing fraction of the melt.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electromagnetic Levitation in reduced gravity has demonstrated great utility in the measurement of thermophysical properties and the study of solidification of metallic melts. Internal flow in the liquid metal samples is a critical parameter in many of these experiments. For example, turbulent flow in the sample prevents measurement of viscosity by the oscillating droplet method, as the measured damping of oscillations is a property of the flow and not of the fluid. In solidification, it has been demonstrated that internal flow changes the lifetime of the metastable phase in stainless steels by almost two orders of magnitude over the experimentally accessible range. For these experiments, the flow was quantified by CFD models; however, these models require as an experimental input whether the flow is laminar or turbulent. To date, the only study of the transition to turbulence in EML comes from experiments on the Space Shuttle in 1997 on MSL-1 TEMPUS on a palladium-silicon alloy. On each melting cycle, tracer particles reveal the laminar or turbulent nature of the flow. However, this phenomenon was only noticed and examined after the flight, so observations are available only for a very narrow range of conditions. As these results were the only ones available, they have been boldly extrapolated to conditions far from the original experiment. Furthermore, while evidence from measurements on germanium shows that the positioner alone can drive turbulent flow, there are no available measurements of the turbulent transition in positioner-dominated flows. On a more fundamental level, EML flows are constrained by the free surface of the drop, like the walls of internal flows. However, the free surface of the EML drop does not support shear stresses, unlike the walls in internal flows. Better quantification of the transition to turbulence in EML flows may lead to insights into the nature of turbulence and turbulent transition. Closing this gap requires a combination of experiments and models that will quantify the turbulent transition over as wide a range of experimental conditions as possible in ISS-EML. Modeling results are presented here; experiments are planned for ISS-EML Batch 4, estimated for 2024.
{"title":"Accessible ranges of turbulent and transitional flow in electromagnetic levitation experiments","authors":"A. K. Pauls, G. Bracker, R. Hyers","doi":"10.32908/hthp.v52.1331","DOIUrl":"https://doi.org/10.32908/hthp.v52.1331","url":null,"abstract":"Electromagnetic Levitation in reduced gravity has demonstrated great utility in the measurement of thermophysical properties and the study of solidification of metallic melts. Internal flow in the liquid metal samples is a critical parameter in many of these experiments. For example, turbulent flow in the sample prevents measurement of viscosity by the oscillating droplet method, as the measured damping of oscillations is a property of the flow and not of the fluid. In solidification, it has been demonstrated that internal flow changes the lifetime of the metastable phase in stainless steels by almost two orders of magnitude over the experimentally accessible range. For these experiments, the flow was quantified by CFD models; however, these models require as an experimental input whether the flow is laminar or turbulent. To date, the only study of the transition to turbulence in EML comes from experiments on the Space Shuttle in 1997 on MSL-1 TEMPUS on a palladium-silicon alloy. On each melting cycle, tracer particles reveal the laminar or turbulent nature of the flow. However, this phenomenon was only noticed and examined after the flight, so observations are available only for a very narrow range of conditions. As these results were the only ones available, they have been boldly extrapolated to conditions far from the original experiment. Furthermore, while evidence from measurements on germanium shows that the positioner alone can drive turbulent flow, there are no available measurements of the turbulent transition in positioner-dominated flows. On a more fundamental level, EML flows are constrained by the free surface of the drop, like the walls of internal flows. However, the free surface of the EML drop does not support shear stresses, unlike the walls in internal flows. Better quantification of the transition to turbulence in EML flows may lead to insights into the nature of turbulence and turbulent transition. Closing this gap requires a combination of experiments and models that will quantify the turbulent transition over as wide a range of experimental conditions as possible in ISS-EML. Modeling results are presented here; experiments are planned for ISS-EML Batch 4, estimated for 2024.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ryohei Sato, Ryo Ishiwata, S. Taguchi, Masahito Watanabe
We proposed the determination method of the normal spectral emissivity of molten oxides using a combination of immiscible molten oxides and liquid metals. We can determine the normal spectral emissivity of molten oxide from the ratio of the normal spectral radiance of molten oxides andliquid metals, using a commercially available pyrometer combined with an electromagnetic levitation system. In the present study, we measured the normal spectral emissivity of a molten oxide sample from SiO2-CaOFeO (SCF) ternary system and FeO using liquid Fe as the reference liquid metal. The normal spectral emissivity of the molten SCF sample with the composition of SiO2:CaO:FeO = 20:20:60 mass % was determined to be 0.78±0.01 and that of molten FeO to be 0.68 ± 0.03. Based on these results, we have discussed the relationship between the normal spectral emissivity and the electrical conductivity of molten oxides.
{"title":"Measurement of the Normal Spectral Emissivity of Molten Oxide Using an Electromagnetically Levitated Complex Droplet of Molten Oxide and Liquid Fe","authors":"Ryohei Sato, Ryo Ishiwata, S. Taguchi, Masahito Watanabe","doi":"10.32908/hthp.v52.1433","DOIUrl":"https://doi.org/10.32908/hthp.v52.1433","url":null,"abstract":"We proposed the determination method of the normal spectral emissivity of molten oxides using a combination of immiscible molten oxides and liquid metals. We can determine the normal spectral emissivity of molten oxide from the ratio of the normal spectral radiance of molten oxides andliquid metals, using a commercially available pyrometer combined with an electromagnetic levitation system. In the present study, we measured the normal spectral emissivity of a molten oxide sample from SiO2-CaOFeO (SCF) ternary system and FeO using liquid Fe as the reference liquid metal. The normal spectral emissivity of the molten SCF sample with the composition of SiO2:CaO:FeO = 20:20:60 mass % was determined to be 0.78±0.01 and that of molten FeO to be 0.68 ± 0.03. Based on these results, we have discussed the relationship between the normal spectral emissivity and the electrical conductivity of molten oxides.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ultrasonic transducer is an indispensably critical component for sound velocity measurement. With the increasing demand of high-temperature ultrasonic dual mode transducer applicable to cubic-anvil apparatus, where experiments of high-pressure and high-temperature sound velocity are routinely conducted, a PZT-based ultrasonic dual mode transducer was presented in this study. It was made of a sandwich of two PZT piezoceramic wafers, the upper one generating P-waves and the lower one generating S-waves. The transducer was directly bonded onto a WC anvil of cubic-anvil apparatus using high-temperature adhesive, and then heated in an oven while measuring the bottom echoes from the WC anvil. The results showed that the high-temperature transducer could work up to 140 °C. The transducer features low cost, easy fabricating, and highquality signals, and so we believe it is useful for sound velocity measurement at high temperatures in cubic-anvil apparatus.
{"title":"PZT-based high-temperature ultrasonic dual mode transducer applicable to cubic-anvil apparatus for sound velocity measurement","authors":"Wei Song, Chang Su, Shuai Wang, Yonggang Liu","doi":"10.32908/hthp.v52.1317","DOIUrl":"https://doi.org/10.32908/hthp.v52.1317","url":null,"abstract":"The ultrasonic transducer is an indispensably critical component for sound velocity measurement. With the increasing demand of high-temperature ultrasonic dual mode transducer applicable to cubic-anvil apparatus, where experiments of high-pressure and high-temperature sound velocity are routinely conducted, a PZT-based ultrasonic dual mode transducer was presented in this study. It was made of a sandwich of two PZT piezoceramic wafers, the upper one generating P-waves and the lower one generating S-waves. The transducer was directly bonded onto a WC anvil of cubic-anvil apparatus using high-temperature adhesive, and then heated in an oven while measuring the bottom echoes from the WC anvil. The results showed that the high-temperature transducer could work up to 140 °C. The transducer features low cost, easy fabricating, and highquality signals, and so we believe it is useful for sound velocity measurement at high temperatures in cubic-anvil apparatus.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135711010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A simple unified thermodynamic approach is developed to determine the effect of size on Raman frequency of nanomaterials. The model approach is based on the Bond energy model developed to determine cohesive energy of nanomaterials with respect to bulk material. The model formulation includes the size, dimension and shape of nanomaterial. The model approach is obtained extending the relation used to determine the effect of size and shape on Debye temperature of nanomaterials. Raman Frequency variation with size is studied for Si, CdSe, InP, CeO2, SnO2, ZnO nanocrystals. It is noted from the model calculations that Raman frequency of nanocrystals drop with decrease in the size at nano level resulting in Raman red shift. The experimental data of previous workers is found in good agreement with model results. The approach is further used to determine the Raman frequency variation with size and shape in nanoparticles and nanowires of varied shapes and nanofilms. Depending on the surface atoms to volume ratio in nanomaterials of varied shapes, variation in Raman frequency is studied and good consistency with the available data confirms the validity of the formulation.
{"title":"Impact of variation in size, shape and dimension of nanomaterial on Debye temperature and Raman frequency","authors":"Monika Goyal","doi":"10.32908/hthp.v52.1369","DOIUrl":"https://doi.org/10.32908/hthp.v52.1369","url":null,"abstract":"A simple unified thermodynamic approach is developed to determine the effect of size on Raman frequency of nanomaterials. The model approach is based on the Bond energy model developed to determine cohesive energy of nanomaterials with respect to bulk material. The model formulation includes the size, dimension and shape of nanomaterial. The model approach is obtained extending the relation used to determine the effect of size and shape on Debye temperature of nanomaterials. Raman Frequency variation with size is studied for Si, CdSe, InP, CeO2, SnO2, ZnO nanocrystals. It is noted from the model calculations that Raman frequency of nanocrystals drop with decrease in the size at nano level resulting in Raman red shift. The experimental data of previous workers is found in good agreement with model results. The approach is further used to determine the Raman frequency variation with size and shape in nanoparticles and nanowires of varied shapes and nanofilms. Depending on the surface atoms to volume ratio in nanomaterials of varied shapes, variation in Raman frequency is studied and good consistency with the available data confirms the validity of the formulation.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135712617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Systematical experimental data on density, molar volume and the surface tension, measured in electromagnetic levitation, has been summarized for the liquid Ti-V system. The optical dilatometry method as well as the oscillating drop technique have been employed to investigate the temperature- and compositional dependence. A linear decrease in density and surface tension with increasing temperature has been observed for all investigated compositions. Pure Vanadium shows hereby the highest density and surface tension while pure titanium shows the lowest density and surface tension respectively. Therefore, the density and surface tension decrease with increasing titanium content, however not linear. Since no excess quantities were available, simple models could be employed to cover the complete liquid Ti-V system. Experimental data as well as the corresponding linear fits are presented.
{"title":"Experimental study of density, molar volume and surface tension of the liquid Ti-V system measured in electromagnetic levitation","authors":"B. Reiplinger, Y. Plevachuk, J. Brillo","doi":"10.32908/hthp.v52.1355","DOIUrl":"https://doi.org/10.32908/hthp.v52.1355","url":null,"abstract":"Systematical experimental data on density, molar volume and the surface tension, measured in electromagnetic levitation, has been summarized for the liquid Ti-V system. The optical dilatometry method as well as the oscillating drop technique have been employed to investigate the temperature- and compositional dependence. A linear decrease in density and surface tension with increasing temperature has been observed for all investigated compositions. Pure Vanadium shows hereby the highest density and surface tension while pure titanium shows the lowest density and surface tension respectively. Therefore, the density and surface tension decrease with increasing titanium content, however not linear. Since no excess quantities were available, simple models could be employed to cover the complete liquid Ti-V system. Experimental data as well as the corresponding linear fits are presented.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Cavaliere, F. Marone, C. Cozzo, K. Buchanan, C. Lorrette, M. Pouchon
Modern industry has become increasingly reliant on composite materials for a variety of applications, and the nuclear industry is no exception to this. Among the materials being researched as Enhanced Accident Tolerant Fuels, ceramic matrix composites such as SiC-fiber-reinforced SiC (SiCf/SiC) figure as some prime candidates due to their excellent high temperature performances. SiCf/SiC so far shows adequate nuclear, mechanical and chemical properties; still, the thermal properties need further investigation. The thermal behavior of a material is an important factor for its performance as a nuclear fuel cladding, i.e. the first barrier encapsulating the fuel pellets. Many features determine the resulting properties of composite materials, such as matrix and fiber reinforcement properties and orientation, void fraction, and pore morphology. This study establishes a methodology to study the physical properties of composite materials and applies it to SiCf/SiC. A FEM model is used to characterize the thermal properties of a fundamental SiCf/SiC element, referred to as a �unit cell�, with the objective of accurately predicting the thermal properties of this complex class of materials where experimental data is often difficult to obtain. The unit cell is built based on data acquired with high-resolution tomographic microscopy performed at the TOMCAT beamline of the Swiss Light Source. By using phase-retrieval prior to tomographic reconstruction, the pores, fibers and matrix that compose the material can be distinguished in the data analysis. The separated information is processed to obtain geometrical information about the individual pores and fibers, which is then used to parametrize them as cylindrical objects. This allows constructing a FEM model of a cubic unit cell that is used to extract the effective thermal properties of SiCf/SiC. The analysis scheme includes steady-state and dynamic thermal transport simulations, which yield directional effective thermal conductivity and diffusivity values, respectively. Both modes of analysis show isotropic thermal conductivity values in the range of 71 W/m/K at room temperature, more than three times that of currently employed nuclear cladding materials. Combining these results with the data on the larger structural features of the material will lead to realistic results on the macroscopic thermal properties.
{"title":"FEM heat transfer modelling with tomography-based SiCf/SiC unit cell","authors":"A. Cavaliere, F. Marone, C. Cozzo, K. Buchanan, C. Lorrette, M. Pouchon","doi":"10.32908/hthp.v52.1281","DOIUrl":"https://doi.org/10.32908/hthp.v52.1281","url":null,"abstract":"Modern industry has become increasingly reliant on composite materials for a variety of applications, and the nuclear industry is no exception to this. Among the materials being researched as Enhanced Accident Tolerant Fuels, ceramic matrix composites such as SiC-fiber-reinforced SiC (SiCf/SiC) figure as some prime candidates due to their excellent high temperature performances. SiCf/SiC so far shows adequate nuclear, mechanical and chemical properties; still, the thermal properties need further investigation. The thermal behavior of a material is an important factor for its performance as a nuclear fuel cladding, i.e. the first barrier encapsulating the fuel pellets. Many features determine the resulting properties of composite materials, such as matrix and fiber reinforcement properties and orientation, void fraction, and pore morphology. This study establishes a methodology to study the physical properties of composite materials and applies it to SiCf/SiC. A FEM model is used to characterize the thermal properties of a fundamental SiCf/SiC element, referred to as a �unit cell�, with the objective of accurately predicting the thermal properties of this complex class of materials where experimental data is often difficult to obtain. The unit cell is built based on data acquired with high-resolution tomographic microscopy performed at the TOMCAT beamline of the Swiss Light Source. By using phase-retrieval prior to tomographic reconstruction, the pores, fibers and matrix that compose the material can be distinguished in the data analysis. The separated information is processed to obtain geometrical information about the individual pores and fibers, which is then used to parametrize them as cylindrical objects. This allows constructing a FEM model of a cubic unit cell that is used to extract the effective thermal properties of SiCf/SiC. The analysis scheme includes steady-state and dynamic thermal transport simulations, which yield directional effective thermal conductivity and diffusivity values, respectively. Both modes of analysis show isotropic thermal conductivity values in the range of 71 W/m/K at room temperature, more than three times that of currently employed nuclear cladding materials. Combining these results with the data on the larger structural features of the material will lead to realistic results on the macroscopic thermal properties.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study; the structural, electronic and mechanical properties of sodium borohydride (NaBH4) compound were studied under high hydrostatic pressure from 0 to 300 GPa using the generalized gradient approach (GGA) within the framework of density functional theory (DFT). In the study, the NaBH4 compound transformed from the tetragonal structure with the space group P42 /nmc to the triclinic structure with the space group with the effect of gradually increasing pressure. Enthalpy and total energy calculations were performed to observe the agreement of the study with the experimental results. As a result of the calculations, it was concluded that a phase transition of the NaBH4 compound occurred at approximately 22.6 GPa from the tetragonal structure to the triclinic structure. In addition, the electronic properties of the NaBH4 compound were investigated and 6.22 and 4.95 eV band gaps were obtained for the P42 /nmc and phases, respectively.
{"title":"Electronic, elastic and pressure-induced phase transitions of tetragonal NaBH4 under high pressure","authors":"Ç. Yamçıçıer","doi":"10.32908/hthp.v52.1285","DOIUrl":"https://doi.org/10.32908/hthp.v52.1285","url":null,"abstract":"In this study; the structural, electronic and mechanical properties of sodium borohydride (NaBH4) compound were studied under high hydrostatic pressure from 0 to 300 GPa using the generalized gradient approach (GGA) within the framework of density functional theory (DFT). In the study, the NaBH4 compound transformed from the tetragonal structure with the space group P42 /nmc to the triclinic structure with the space group with the effect of gradually increasing pressure. Enthalpy and total energy calculations were performed to observe the agreement of the study with the experimental results. As a result of the calculations, it was concluded that a phase transition of the NaBH4 compound occurred at approximately 22.6 GPa from the tetragonal structure to the triclinic structure. In addition, the electronic properties of the NaBH4 compound were investigated and 6.22 and 4.95 eV band gaps were obtained for the P42 /nmc and phases, respectively.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jannatun Nawer, T. Ishikawa, H. Oda, Chihiro Koyama, Hideki Saruwatari, M. SanSoucie, Brandon Philips, St�phane Goss�, M. Mohr, M. Kolbe, D. Matson
Density, thermal expansion coefficient, surface tension and viscosity of Ni-based CMSX-4� Plus have been measured for a range of liquid temperature by utilizing two Electrostatic levitation (ESL) facilities. Ground-based tests were conducted using the NASA MSFC ESL facility in Ultra High Vacuum and space-based tests were conducted using JAXA ELF in a 172 kPa Argon gas atmosphere. The measured values were compared to the available literature data from various other facilities. This study focuses on a detailed uncertainty analysis of the experimental data to measure the accuracy and precision of the measured properties using Guide to the expression of Uncertainty Measurement (GUM) principles. The findings from this study have been used to quantify the performance of the two ESL facilities.
{"title":"A quantitative comparison of thermophysical property measurement of CMSX-4� Plus (SLS) in microgravity and terrestrial environments","authors":"Jannatun Nawer, T. Ishikawa, H. Oda, Chihiro Koyama, Hideki Saruwatari, M. SanSoucie, Brandon Philips, St�phane Goss�, M. Mohr, M. Kolbe, D. Matson","doi":"10.32908/hthp.v52.1407","DOIUrl":"https://doi.org/10.32908/hthp.v52.1407","url":null,"abstract":"Density, thermal expansion coefficient, surface tension and viscosity of Ni-based CMSX-4� Plus have been measured for a range of liquid temperature by utilizing two Electrostatic levitation (ESL) facilities. Ground-based tests were conducted using the NASA MSFC ESL facility in Ultra High Vacuum and space-based tests were conducted using JAXA ELF in a 172 kPa Argon gas atmosphere. The measured values were compared to the available literature data from various other facilities. This study focuses on a detailed uncertainty analysis of the experimental data to measure the accuracy and precision of the measured properties using Guide to the expression of Uncertainty Measurement (GUM) principles. The findings from this study have been used to quantify the performance of the two ESL facilities.","PeriodicalId":12983,"journal":{"name":"High Temperatures-high Pressures","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69443240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：