Firstly,the relation between the coefficient of thermal expansion(CTE)and the volume fraction of TiO_(2) was investigated, and also the influence of relative density of ceramic on the CTE was studied.The results show ...Firstly,the relation between the coefficient of thermal expansion(CTE)and the volume fraction of TiO_(2) was investigated, and also the influence of relative density of ceramic on the CTE was studied.The results show that the volume fraction of TiO_(2) and the relative density both make influence on the CTE of ZrO_(2)-TiO_(2) ceramic.According to the results,the ZrO_(2)-TiO_(2)(volume fraction of TiO_(2) is 27%)ceramic die with the similar CTE(8.92×10^(-6) ℃^(-1))to Ti6Al4V was fabricated.Secondly,to evaluate the dimensional accuracy of the workpiece superplastically formed,the Ti6Al4V impression experiment was performed.The result shows that the dimensional inaccuracy of workpiece is 0.003.Thirdly,in order to evaluate the practicability,the experiment of superplastic forming Ti6Al4V using ZrO_(2)-TiO_(2) cylinder ceramic die was carried out.The Ti6Al4V cylinder shows good shape retention and surface quality,and high dimensional accuracy.The ceramic dies seem to be adequate for superplastic forming the high accuracy Ti6Al4V, and the trials have confirmed the potential of the ZrO_(2)-TiO_(2) ceramic die.展开更多
Cordierite honeycomb ceramics was treated with 1.5 M HNO3 , followed with 1.5 M NaOH at 93 ℃. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal ...Cordierite honeycomb ceramics was treated with 1.5 M HNO3 , followed with 1.5 M NaOH at 93 ℃. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal expansion （CTE） caused by heat treatment, a phenomenon observed in samples treated solely with acid. Inductively coupled plasma （ICP） analysis results reveal that the alkali treatment preferentially dissolved ＂free＂ SiO2 left in the acid-treated samples, which is considered to be a key factor responsible for the CTE rebounding.展开更多
Beryllium aluminum cyclosilicate, an ore of beryllium was reinforced in Aluminum matrix to fabricate Al-beryl composites using powder metallurgy. Effect of the content of beryllium aluminum cyclosilicate on microstruc...Beryllium aluminum cyclosilicate, an ore of beryllium was reinforced in Aluminum matrix to fabricate Al-beryl composites using powder metallurgy. Effect of the content of beryllium aluminum cyclosilicate on microstructural hardness and thermal expansion was studied. The coefficient of thermal expansion of Al-beryl composite was measured in the temperature range between 50oC to 360oC using dilatometer and was theoretically studied using thermo-elastic models, and these models were used to explain abnormalities observed experimentally. The hardness of Al-beryl metal matrix composites increased with the increase in beryl percentage. Vacuum sintering of Al-beryl metal matrix composites at 600oC inhibited excellent bonding between the matrix and the particulate increasing the strength of the composite. The result shows the CTE significantly increased with increasing temperature but decreased with increasing reinforcement. At higher temperatures, CTE of Al-beryl metal matrix composites with 5 wt%, 10 wt% and 15 wt% of beryllium aluminum cyclosilicate was 21 ppm/K, 18.2 ppm/K, and 16.8 ppm/K. The CTE values were found to be comparable with theoretical results. The turner model showed conformance with experimental results, was well suited to the experimental results.展开更多
The gamma quanta attenuation studies have been carried out to determine mass attenuation coefficients of 7041, 7075 and 7095 wrought aluminum alloys. The temperature dependence of linear attenuation coefficient, densi...The gamma quanta attenuation studies have been carried out to determine mass attenuation coefficients of 7041, 7075 and 7095 wrought aluminum alloys. The temperature dependence of linear attenuation coefficient, density and thermal expansion of these wrought aluminum alloys in the temperature range 300 K - 850 K have been reported. The measurements were done by using a gamma ray densitometer designed and fabricated in our laboratory. The data on variation of density and linear thermal expansion with temperature have been represented by linear equations. Volume thermal expansion coefficients have been reported.展开更多
The work covers a novel approach to the description of the phenomenon of thermal expansion of solids. The reason for undertaking the scientific quest is presented to follow with the analysis of existing knowledge on t...The work covers a novel approach to the description of the phenomenon of thermal expansion of solids. The reason for undertaking the scientific quest is presented to follow with the analysis of existing knowledge on the characteristics of phenomenon of thermal expansion of bodies being in the state of aggregation. A critical approach to the existing law of the linear thermal expansion is given. The paper presents an adequate approach to this considered phenomenon. The description provides parametric and functional characteristics of this phenomenon. The relationships of the coefficients of linear expansion on temperature for particular interstate zones, as well as the initial coefficients related to these zones, are presented. In the summary a synthesis of all actions and considerations with the directions to the adequate knowledge with advantage on the subjected phenomenon has been performed. It regards also to the latest thermal characteristics of solids, referred to the phase transformations. All they are realized by dilatometric studies together with determination of curves of thermal expansions of solids.展开更多
High-entropy pyrosilicate element selection is relatively blind, and the thermal expansion coefficient (CTE) of traditional β-type pyrosilicate is not adjustable, making it difficult to meet the requirements of vario...High-entropy pyrosilicate element selection is relatively blind, and the thermal expansion coefficient (CTE) of traditional β-type pyrosilicate is not adjustable, making it difficult to meet the requirements of various types of ceramic matrix composites (CMCs). The following study aimed to develop a universal rule for high-entropy pyrosilicate element selection and to achieve directional control of the thermal expansion coefficient of high-entropy pyrosilicate. The current study investigates a high-entropy design method for obtaining pyrosilicates with stable β-phase and γ-phase by introducing various rare-earth (RE) cations. The solid-phase method was used to create 12 different types of high-entropy pyrosilicates with 4–6 components. The high-entropy pyrosilicates gradually transformed from β-phase to γ-phase with an increase in the average radius of RE^(3+) ions ( r¯(RE^(3+))). The nine pyrosilicates with a small r¯(RE^(3+)) preserve β-phase or γ-phase stability at room temperature to the maximum of 1400 ℃. The intrinsic relationship between the thermal expansion coefficient, phase structure, and RE–O bond length has also been found. This study provides the theoretical background for designing high-entropy pyrosilicates from the perspective of r¯(RE^(3+)). The theoretical guidance makes it easier to synthesize high-entropy pyrosilicates with stable β-phase or γ-phase for the use in environmental barrier coatings (EBCs). The thermal expansion coefficient of γ-type high-entropy pyrosilicate can be altered through component design to match various types of CMCs.展开更多
The coefficients of linear thermal expansions （CLEs） of magnetic elements Fe, Co and Ni were assessed from experimental information using theoretical models combined with MATLAB calculations. Model parameters can be...The coefficients of linear thermal expansions （CLEs） of magnetic elements Fe, Co and Ni were assessed from experimental information using theoretical models combined with MATLAB calculations. Model parameters can be determined accurately, and the assessed data are in good agreement with the experimental results. To facilitate the assessments, theories of thermal expansion were applied to separate CLEs into its nonmagnetic and magnetic components. The calculations of nonmagnetic contribution to CLEs were based on the modified Gruineisen- Debye model, in which the Debye temperature was regarded as an undetermined constant. In order to put the prediction of CLEs at the magnetic transition region on a sound physical basis, two kinds of theoretical models were innovatively used to calculate the magnetic contribution to CLEs, i.e., the Bragg-Williams model and the Fermi-Dirac distribution function. Model parameters were evaluated from experimental data using least square method. Detailed comparisons were made with the published experimental data and the calculated total CLEs. A satisfactory agreement is reached.展开更多
Effective manipulations of thermal expansion and conductivity are significant for improving operational performances of protective coatings,thermoelectric,and radiators.This work uncovers determinant mechanisms of the...Effective manipulations of thermal expansion and conductivity are significant for improving operational performances of protective coatings,thermoelectric,and radiators.This work uncovers determinant mechanisms of the thermal expansion and conductivity of symbiotic ScTaO_(4)/SmTaO_(4) composites as thermal/environmental barrier coatings(T/EBCs),and we consider the effects of interface stress and thermal resistance.The weak bonding and interface stress among composite grains manipulate coefficient of thermal expansion(CTE)stretching from 6.4×10^(−6) to 10.7×10^(−6) K^(−1) at 1300℃,which gets close to that of substrates in T/EBC systems.The multiscale effects,including phonon scattering at the interface,mitigation of the phonon speed(vp),and lattice point defects,synergistically depress phonon thermal transports,and we estimate the proportions of different parts.The interface thermal resistance(R)reduces the thermal conductivity(k)by depressing phonon speed and scattering phonons because of different acoustic properties and weak bonding between symbiotic ScTaO_(4) and SmTaO_(4) ceramics in the composites.This study proves that CTE of tantalates can be artificially regulated to match those of different substrates to expand their applications,and the uncovered multiscale effects can be used to manipulate thermal transports of various materials.展开更多
Effect of kyanite addition on properties of plastic refractories that based on Chinese calcined flint clay were investigated with the Chinese calcined flint clay as raw materials, aluminum sulfate and fireclay as bind...Effect of kyanite addition on properties of plastic refractories that based on Chinese calcined flint clay were investigated with the Chinese calcined flint clay as raw materials, aluminum sulfate and fireclay as binding systems. After 24 h curing after demoulding and another 24 h curing at 110 ℃, the specimens were heat-treated at 1000, 1300 and 1500℃ for 3 h, respectively. Thepermanent linear change, bulk density, modulus of rupture, clod crushing strength, thermal expansion coefficient and thermal shock resistance were examined. The results show that the shrinkage of plastic refractory decreased with increasing kyanite addition after heat-treated at 1000 and 1300℃ , and its expansivity increased with increasing kyanite addition after heat-treated at 1500 ℃. The strength can be increased when kyanite was added into the plastic refractory. The thermal expansion coefficient and the expansivity were increased, and the shrinkage can be reduced at high temperature when kyanite addition was more than 10%. On the condition of this experiment, the thermal shock resistance of plastic refractory was the best when kyanite addition is w(kyanite)=10%.展开更多
Mg-Gd-Y-Zr alloy castings are widely used in the aerospace field owing to their high strength and excellent creep resistance.The castability of these alloys is also an important consideration for engineering applicati...Mg-Gd-Y-Zr alloy castings are widely used in the aerospace field owing to their high strength and excellent creep resistance.The castability of these alloys is also an important consideration for engineering application.Thus,the hot tearing susceptibilities(HTSs)of Mg-10Gd-1Y-1Zn-0.5Zr(VW91)alloy and Mg-10Gd-2Y-1Zn-0.5Zr(VW92)alloy are investigated with a constrained rod casting(CRC)mold.The microstructures and fracture surface are characterized by optical microscope and scanning electron microscope.The results unveil that the HTS of VW92alloy is lower than that of VW91 alloy.The microstructures indicate that obvious tears can be observed in VW91 alloy,while the tears in VW92 alloy are tiny.The tear feeding and healing by eutectic are also observed in VW91 and VW92alloys.Therefore,the lower hot tearing susceptibility of VW92 alloy is mainly attributed to the high amount of eutectic which feeds and heals tears.Besides,the effects of the coefficient of thermal expansion(CTE)and the fluidity of VW91 and VW92 alloys on their HTSs are discussed.展开更多
The γ-ray densitometer has been designed and fabricated in our laboratory and carried out studies on temperature dependent γ-ray attenuation and thermo physical properties of NaCl, NaBr and NaF. The linear attenuati...The γ-ray densitometer has been designed and fabricated in our laboratory and carried out studies on temperature dependent γ-ray attenuation and thermo physical properties of NaCl, NaBr and NaF. The linear attenuation coefficients (μl) for the pellets of NaCl, NaBr and NaF as a function of temperature have been determined. The coefficients of temperature dependence of density have been reported. The variation of density and thermal expansion of NaCl, NaBr and NaF in the temperature range of 300 K - 1000 K have been studied and compared with results available in the literature. The temperature dependence of density and thermal expansion has been represented by linear equations. Volume thermal expansion coefficients have been reported.展开更多
文摘Firstly,the relation between the coefficient of thermal expansion(CTE)and the volume fraction of TiO_(2) was investigated, and also the influence of relative density of ceramic on the CTE was studied.The results show that the volume fraction of TiO_(2) and the relative density both make influence on the CTE of ZrO_(2)-TiO_(2) ceramic.According to the results,the ZrO_(2)-TiO_(2)(volume fraction of TiO_(2) is 27%)ceramic die with the similar CTE(8.92×10^(-6) ℃^(-1))to Ti6Al4V was fabricated.Secondly,to evaluate the dimensional accuracy of the workpiece superplastically formed,the Ti6Al4V impression experiment was performed.The result shows that the dimensional inaccuracy of workpiece is 0.003.Thirdly,in order to evaluate the practicability,the experiment of superplastic forming Ti6Al4V using ZrO_(2)-TiO_(2) cylinder ceramic die was carried out.The Ti6Al4V cylinder shows good shape retention and surface quality,and high dimensional accuracy.The ceramic dies seem to be adequate for superplastic forming the high accuracy Ti6Al4V, and the trials have confirmed the potential of the ZrO_(2)-TiO_(2) ceramic die.
基金Funded bythe International Cooperation Project of Jiangsu Prov-ince(No.BZ2001043)
文摘Cordierite honeycomb ceramics was treated with 1.5 M HNO3 , followed with 1.5 M NaOH at 93 ℃. The combination of acid treatment with alkali treatment significantly diminished the rebounding of coefficient of thermal expansion （CTE） caused by heat treatment, a phenomenon observed in samples treated solely with acid. Inductively coupled plasma （ICP） analysis results reveal that the alkali treatment preferentially dissolved ＂free＂ SiO2 left in the acid-treated samples, which is considered to be a key factor responsible for the CTE rebounding.
文摘Beryllium aluminum cyclosilicate, an ore of beryllium was reinforced in Aluminum matrix to fabricate Al-beryl composites using powder metallurgy. Effect of the content of beryllium aluminum cyclosilicate on microstructural hardness and thermal expansion was studied. The coefficient of thermal expansion of Al-beryl composite was measured in the temperature range between 50oC to 360oC using dilatometer and was theoretically studied using thermo-elastic models, and these models were used to explain abnormalities observed experimentally. The hardness of Al-beryl metal matrix composites increased with the increase in beryl percentage. Vacuum sintering of Al-beryl metal matrix composites at 600oC inhibited excellent bonding between the matrix and the particulate increasing the strength of the composite. The result shows the CTE significantly increased with increasing temperature but decreased with increasing reinforcement. At higher temperatures, CTE of Al-beryl metal matrix composites with 5 wt%, 10 wt% and 15 wt% of beryllium aluminum cyclosilicate was 21 ppm/K, 18.2 ppm/K, and 16.8 ppm/K. The CTE values were found to be comparable with theoretical results. The turner model showed conformance with experimental results, was well suited to the experimental results.
文摘The gamma quanta attenuation studies have been carried out to determine mass attenuation coefficients of 7041, 7075 and 7095 wrought aluminum alloys. The temperature dependence of linear attenuation coefficient, density and thermal expansion of these wrought aluminum alloys in the temperature range 300 K - 850 K have been reported. The measurements were done by using a gamma ray densitometer designed and fabricated in our laboratory. The data on variation of density and linear thermal expansion with temperature have been represented by linear equations. Volume thermal expansion coefficients have been reported.
文摘The work covers a novel approach to the description of the phenomenon of thermal expansion of solids. The reason for undertaking the scientific quest is presented to follow with the analysis of existing knowledge on the characteristics of phenomenon of thermal expansion of bodies being in the state of aggregation. A critical approach to the existing law of the linear thermal expansion is given. The paper presents an adequate approach to this considered phenomenon. The description provides parametric and functional characteristics of this phenomenon. The relationships of the coefficients of linear expansion on temperature for particular interstate zones, as well as the initial coefficients related to these zones, are presented. In the summary a synthesis of all actions and considerations with the directions to the adequate knowledge with advantage on the subjected phenomenon has been performed. It regards also to the latest thermal characteristics of solids, referred to the phase transformations. All they are realized by dilatometric studies together with determination of curves of thermal expansions of solids.
基金supported by the Instrument and Equipment Development,Chinese Academy of Sciences(YJKYYQ20210030)Shanghai Science and Technology Innovation Action Plan(21142201100).
文摘High-entropy pyrosilicate element selection is relatively blind, and the thermal expansion coefficient (CTE) of traditional β-type pyrosilicate is not adjustable, making it difficult to meet the requirements of various types of ceramic matrix composites (CMCs). The following study aimed to develop a universal rule for high-entropy pyrosilicate element selection and to achieve directional control of the thermal expansion coefficient of high-entropy pyrosilicate. The current study investigates a high-entropy design method for obtaining pyrosilicates with stable β-phase and γ-phase by introducing various rare-earth (RE) cations. The solid-phase method was used to create 12 different types of high-entropy pyrosilicates with 4–6 components. The high-entropy pyrosilicates gradually transformed from β-phase to γ-phase with an increase in the average radius of RE^(3+) ions ( r¯(RE^(3+))). The nine pyrosilicates with a small r¯(RE^(3+)) preserve β-phase or γ-phase stability at room temperature to the maximum of 1400 ℃. The intrinsic relationship between the thermal expansion coefficient, phase structure, and RE–O bond length has also been found. This study provides the theoretical background for designing high-entropy pyrosilicates from the perspective of r¯(RE^(3+)). The theoretical guidance makes it easier to synthesize high-entropy pyrosilicates with stable β-phase or γ-phase for the use in environmental barrier coatings (EBCs). The thermal expansion coefficient of γ-type high-entropy pyrosilicate can be altered through component design to match various types of CMCs.
基金financially supported by China Postdoctoral Science Foundation(No.2009045110)
文摘The coefficients of linear thermal expansions （CLEs） of magnetic elements Fe, Co and Ni were assessed from experimental information using theoretical models combined with MATLAB calculations. Model parameters can be determined accurately, and the assessed data are in good agreement with the experimental results. To facilitate the assessments, theories of thermal expansion were applied to separate CLEs into its nonmagnetic and magnetic components. The calculations of nonmagnetic contribution to CLEs were based on the modified Gruineisen- Debye model, in which the Debye temperature was regarded as an undetermined constant. In order to put the prediction of CLEs at the magnetic transition region on a sound physical basis, two kinds of theoretical models were innovatively used to calculate the magnetic contribution to CLEs, i.e., the Bragg-Williams model and the Fermi-Dirac distribution function. Model parameters were evaluated from experimental data using least square method. Detailed comparisons were made with the published experimental data and the calculated total CLEs. A satisfactory agreement is reached.
基金Thanks for the supports from the National Natural Science Foundation of China(No.91960103)National Key Research and Development Program of China(No.2022YFB3708600)+1 种基金the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province(No.202102AB080019-1)the Top Innovative Talents of Graduate Students of Kunming University of Science and Technology。
文摘Effective manipulations of thermal expansion and conductivity are significant for improving operational performances of protective coatings,thermoelectric,and radiators.This work uncovers determinant mechanisms of the thermal expansion and conductivity of symbiotic ScTaO_(4)/SmTaO_(4) composites as thermal/environmental barrier coatings(T/EBCs),and we consider the effects of interface stress and thermal resistance.The weak bonding and interface stress among composite grains manipulate coefficient of thermal expansion(CTE)stretching from 6.4×10^(−6) to 10.7×10^(−6) K^(−1) at 1300℃,which gets close to that of substrates in T/EBC systems.The multiscale effects,including phonon scattering at the interface,mitigation of the phonon speed(vp),and lattice point defects,synergistically depress phonon thermal transports,and we estimate the proportions of different parts.The interface thermal resistance(R)reduces the thermal conductivity(k)by depressing phonon speed and scattering phonons because of different acoustic properties and weak bonding between symbiotic ScTaO_(4) and SmTaO_(4) ceramics in the composites.This study proves that CTE of tantalates can be artificially regulated to match those of different substrates to expand their applications,and the uncovered multiscale effects can be used to manipulate thermal transports of various materials.
文摘Effect of kyanite addition on properties of plastic refractories that based on Chinese calcined flint clay were investigated with the Chinese calcined flint clay as raw materials, aluminum sulfate and fireclay as binding systems. After 24 h curing after demoulding and another 24 h curing at 110 ℃, the specimens were heat-treated at 1000, 1300 and 1500℃ for 3 h, respectively. Thepermanent linear change, bulk density, modulus of rupture, clod crushing strength, thermal expansion coefficient and thermal shock resistance were examined. The results show that the shrinkage of plastic refractory decreased with increasing kyanite addition after heat-treated at 1000 and 1300℃ , and its expansivity increased with increasing kyanite addition after heat-treated at 1500 ℃. The strength can be increased when kyanite was added into the plastic refractory. The thermal expansion coefficient and the expansivity were increased, and the shrinkage can be reduced at high temperature when kyanite addition was more than 10%. On the condition of this experiment, the thermal shock resistance of plastic refractory was the best when kyanite addition is w(kyanite)=10%.
基金the Key Research and Development Program of Zhejiang of China(No.2021C01086)the National Natural Science Foundation of China(No.52071036)the Interdisciplinary and Team Building Program of Central Universities,China(No.2020CDJQY-A002,2021CDJCGJ009)。
文摘Mg-Gd-Y-Zr alloy castings are widely used in the aerospace field owing to their high strength and excellent creep resistance.The castability of these alloys is also an important consideration for engineering application.Thus,the hot tearing susceptibilities(HTSs)of Mg-10Gd-1Y-1Zn-0.5Zr(VW91)alloy and Mg-10Gd-2Y-1Zn-0.5Zr(VW92)alloy are investigated with a constrained rod casting(CRC)mold.The microstructures and fracture surface are characterized by optical microscope and scanning electron microscope.The results unveil that the HTS of VW92alloy is lower than that of VW91 alloy.The microstructures indicate that obvious tears can be observed in VW91 alloy,while the tears in VW92 alloy are tiny.The tear feeding and healing by eutectic are also observed in VW91 and VW92alloys.Therefore,the lower hot tearing susceptibility of VW92 alloy is mainly attributed to the high amount of eutectic which feeds and heals tears.Besides,the effects of the coefficient of thermal expansion(CTE)and the fluidity of VW91 and VW92 alloys on their HTSs are discussed.
文摘The γ-ray densitometer has been designed and fabricated in our laboratory and carried out studies on temperature dependent γ-ray attenuation and thermo physical properties of NaCl, NaBr and NaF. The linear attenuation coefficients (μl) for the pellets of NaCl, NaBr and NaF as a function of temperature have been determined. The coefficients of temperature dependence of density have been reported. The variation of density and thermal expansion of NaCl, NaBr and NaF in the temperature range of 300 K - 1000 K have been studied and compared with results available in the literature. The temperature dependence of density and thermal expansion has been represented by linear equations. Volume thermal expansion coefficients have been reported.
基金financially supported by the Major Special Projects in Anhui Province,China(No.202003c08020005)the Key Projects in Hunan Province,China(No.2020GK2045)+1 种基金the Science and Technology Innovation Program of Hunan Province,China(No.2021RC4036)Postgraduate Scientific Research Innovation Project of Hunan Province,China(No.CX20211079)。
