Varistor ceramics of ZnO Bi 2O 3 TiO 2 Sb 2O 3 system have been fabricated by introducing pre fabricated ZnO seed grains with different size distributions respectively. The results show that the varistor properties we...Varistor ceramics of ZnO Bi 2O 3 TiO 2 Sb 2O 3 system have been fabricated by introducing pre fabricated ZnO seed grains with different size distributions respectively. The results show that the varistor properties were significantly influenced by the size of introduced seed grains, and introducing larger seed grains is more advantageous to the modification of microstructure and the improvement of varistor properties. The varistor properties were considerably improved with a moderately increased sintering temperature or time, whereas degraded apparently when the sintering temperature or time was excessively increased. Compared with the sintering time, the sintering temperature plays a more critical role in determining the varistor properties. By introducing pre fabricated ZnO seed grains into the original powders, low voltage ZnO varistor ceramics possessing the desired electrical properties have been produced with a sintering temperature of about 1 210 ℃ and a sintering temperature of 2～2.5 h. [展开更多
The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag（NS） and blast furnace slag（BFS） with a small amount of quartz sand was investigated.A modified melting method which ...The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag（NS） and blast furnace slag（BFS） with a small amount of quartz sand was investigated.A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process.The results show that the iron-rich system has much lower melting temperature,glass transition temperature（Tg）,and glass crystallization temperature（Tc）,which can result in a further energy-saving process.The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918°C.The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample.The crystallization process can be completed in a few minutes.A distinct boundary between the crystallized part and the non-crystallized part exists during the process.In the non-crystallized part showing a black colour,some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to Tc.In the crystallized part showing a khaki colour,a compact structure is formed by augite crystals.展开更多
With the help of scanning electronic microscopy and X-ray diffraction, the relationships of microstructure characteristics, phase assemblage, and fracture micrograph of Al2O3/ZrO2 laminated ceramics were studied. Comp...With the help of scanning electronic microscopy and X-ray diffraction, the relationships of microstructure characteristics, phase assemblage, and fracture micrograph of Al2O3/ZrO2 laminated ceramics were studied. Compared with monolithic Al2O3/ZrO2 ceramics, the existence of surface compressive stresses greatly restrained the growth of ZrO2 and Al2O3 grains at high sinter temperature, fined the grain size, and increased the content of metastable t-ZrO2, which made the fracture transformation energy quantity 70% higher than that of the monolithic ceramics. The trans-granular and inter-granular fracture features were observed in the surface and center layers, which further verified that transformation toughening is the main mechanism, whereas, micro-crack toughening is helpful for enhancing fracture toughness.展开更多
（1 - x）PbZr0.54Tio.4603-xKNbO3 （0 〈 x 〈 25mo1%） （abbreviated as PZT-xKN） piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225℃ for 30 min. The influence of KNbO3 co...（1 - x）PbZr0.54Tio.4603-xKNbO3 （0 〈 x 〈 25mo1%） （abbreviated as PZT-xKN） piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225℃ for 30 min. The influence of KNbO3 content on the crystal structure and electrical properties of the PZT-xKN piezoelectric ceramics was studied. Samples with 0 〈 x 0.20 show a pure peroskite structure, indicating that ul KNbOdiffused ito the crystal lattice of PZT to form a single solid solution in this compositional range. A second Pb3Nb4013 phase is observed in the PZT-0.25KN sample, showing that the maximum solid solubility of KNbO3 in PZT matrix ceramic is less than 25mo1%. Compared with pure PZT piezoelectric ceramics, samples containing KNbO3 have smaller crystal grains. PZT-0.15KN exhibits excellent piezoelectric properties with d33 ： 209 pC/N.展开更多
The development of low-voltage ZnO varistor ceramics containing TiO2 is presented in this report. The varistor properties of ZnO ceramics with different compositions were measured, and microstructure of the ceramics w...The development of low-voltage ZnO varistor ceramics containing TiO2 is presented in this report. The varistor properties of ZnO ceramics with different compositions were measured, and microstructure of the ceramics was investigated by XRD and SEM. The results show that the addition of TiO2 is beneficial to the decrease of varistor voltage (V1mA). whereas it leads to the recession of nonlinear coefficient (α) and leakage current (lL). The varistor properties of ZnO ceramics containing TiO2 can be effectively improved by introducing moderate amount of pre-fabricated ZnO seed grains. The behaviors of TiO2 and seed grains, as well as the mechanisms by which TiO2 and seed grains influence varistor properties, are discussed.展开更多
Manganese-doped Ba（0.925）Ca（0.075）TiO3 lead-free piezoelectric ceramics（abbreviated as BCT）with high mechanical quality factor were synthesized by conventional solid-state reaction method.The effects of excess B...Manganese-doped Ba（0.925）Ca（0.075）TiO3 lead-free piezoelectric ceramics（abbreviated as BCT）with high mechanical quality factor were synthesized by conventional solid-state reaction method.The effects of excess Ba on the crystal structure,microstructure,and electrical properties of the ceramics were systematically investigated.X-ray diffraction and Raman spectra revealed that Ca^2＋ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol%extra Ba^2＋ions were added after sintering.The grain size of the ceramics was decreased by adding extra Ba^2＋ions.The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%.High piezoelectric coefficients（d（33）=150-190 pC/N）and high mechanical quality factors（Qm=1 000-1 200）were obtained in the ceramics when the excess of Ba was between 0.5 mol%and 1 mol%.These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.展开更多
Microstructural evolutions of ceramic grain growth at atomistic scale were modeled. The simulation was preceded with Monte-Carlo method, using Visual C++ and OpenGL languages. Realistic images in series were monitored...Microstructural evolutions of ceramic grain growth at atomistic scale were modeled. The simulation was preceded with Monte-Carlo method, using Visual C++ and OpenGL languages. Realistic images in series were monitored both in two d imensions and three dimensions. Simulated image of grain growth in this series i s presented in left figure with N 0=25, r=0.40 nm, α=0.1, T=1 300 ℃, and P 0=50 %. It was seen that the average grain size increases wit h the time of grain growth. It is in good agreement with that of practical BST c eramics. The average grain area versus grain growth time is shown in right figur e. It is clear that the kinetic exponents of grain growth are not constant durin g the process of microstructural evolution. The kinetic exponents are smaller ( m≈0.5) at the early stages of growth and larger (m≈8) at the later sta ges, which are in agreement with reported results.展开更多
Microstructural evolutions of ceramic grain growth we re dynamically demonstrated with 3D graphical display techniques. Based on the p rinciples of grain growth in ceramics, the data of coordination in different ato m...Microstructural evolutions of ceramic grain growth we re dynamically demonstrated with 3D graphical display techniques. Based on the p rinciples of grain growth in ceramics, the data of coordination in different ato ms were calculated with Monte-Carlo method at atomistic scale. Realistic images in three-dimension were displayed onto two-dimension monitor by projection, i llumination and atomization, using Visual C++ and OpenGL languages. Different small spheres were used to model different kind of atoms, which filled within a fictitious cube. The radius and coordination for different atoms were then determined according to corresponding ratios by using of perspective projec tion of OpenGL languages. The applications of illuminating, texturizing and at omization techniques enhanced greatly the stereo effect of images.展开更多
Bismuth (Bi) and lanthanum (La) doped lead manganese antimoine zirconate titanate (PZMST) ceramic powders have been synthesized by high temperature solid-state reaction method. Preliminary X-ray structural analysis of...Bismuth (Bi) and lanthanum (La) doped lead manganese antimoine zirconate titanate (PZMST) ceramic powders have been synthesized by high temperature solid-state reaction method. Preliminary X-ray structural analysis of the compounds shows the formation of tetragonal structure. Scanning electron micrographs (SEM) shows a uniform grain distribution and grain size of the order of ~2.28 μm. Detailed dielectric studies of the Pb0.95(La1-z Biz)0.05[(Zr0.6Ti0.4)0.95(Mn1/3Sb2/3)0.05]O3 samples as a function of the temperature (from 25°C to 450°C) at frequency 1 kHz suggest that the compounds undergo a diffuse phase transition. The transition temperature shifts increase with increasing the Bi ratio. Diffusivity (γ) study of phase transition of these compounds provided its value from 1.59 to 1.78 indicating the degree of the disordering in the system.展开更多
This article explored the influence of molding density of TiO<sub>2</sub> varistor-ceramic on densification of ceramic body and grain growth. By the main phase and second phase analysis of TiO<sub>2&...This article explored the influence of molding density of TiO<sub>2</sub> varistor-ceramic on densification of ceramic body and grain growth. By the main phase and second phase analysis of TiO<sub>2</sub> varistor-ceramic through XRD and EDAX, the effects of the second phrase on TiO<sub>2</sub> varistor-ceramic were studied. Grain size and its distribution were observed through scanning electron microscope and the density of porcelain body was measured. The effects of grain size, distribution and density of ceramic body on electrical property of TiO<sub>2</sub> varistor-ceramic were the focus issue for analysis. The increased molding density would improve the densifying of magnetic body to some extent and promote grain growth.展开更多
Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average gra...Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average grain size and guaranteed the reliability,while the bigger-grained powder enhanced the dielectric constant.Various percentages of bigger-grained BT powder were introduced to balance the average grain size and the dielectric constant.As the proportion of bigger grains increased,the dielectric constant(εr)improved significantly.The room-temperatureεr of 25%bigger-grain mixed BT(2623)was~50%higher than that of the sample with a similar average grain size without grain grading.The ceramic mixed with 15%bigger-grained BT showed comprehensive dielectric performance,which met the EIA X5R standard and provided a considerableεr of 1841 along with a low dielectric loss of 0.78%.Notably,the average grain size was 90 nm,which favors the applications in ultra-thin multilayer ceramic capacitors.展开更多
It is well known that the grain size of high-entropy ceramics is quite small owing to the sluggish diffusion effect. However, abnormal grain growth often occurs in high-entropy pseudobrookite ceramics, ultimately resu...It is well known that the grain size of high-entropy ceramics is quite small owing to the sluggish diffusion effect. However, abnormal grain growth often occurs in high-entropy pseudobrookite ceramics, ultimately resulting in the formation of many abnormally grown grains with a grain size as large as 50 μm. To study this phenomenon, the grain growth behavior of high-entropy pseudobrookite ceramics was systematically investigated in this paper. The results demonstrate that the starting material powders first react with each other to form a high-entropy intermediate phase and calcined TiO_(2) powders (TiO_(2)-1100 ℃), and then as the sintering temperature increases, the formed high-entropy intermediate phase further reacts with TiO_(2)-1100 ℃ to form high-entropy pseudobrookite ceramics. Thus, in this system, in addition to the sluggish diffusion effect, the grain sizes of the high-entropy intermediate phase and TiO_(2)-1100 ℃ also affect the morphology of high-entropy pseudobrookite. Compared to nanosized TiO_(2), micron-sized TiO_(2) has a lower sintering activity. Therefore, the high-entropy intermediate phases (Mg,Co,Ni,Zn)TiO_(3) and TiO_(2)-1100 ℃ prepared with micron-sized starting materials exhibit lower grain sizes, finally resulting in the formation of high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) with small grain sizes. Moreover, nano-indentation and thermal conductivity tests were carried out on high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) with different morphologies. The results show that the hardness of high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) increases from 6.05 to 9.95 GPa as the grain size increases, whereas the thermal conductivity decreases from 2.091±0.006 to 1.583±0.006 W·m^(−1)·K^(−1). All these results indicate that high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) with a small grain size is a potential material for thermal protection.展开更多
The nanosize AIN particles were prepared by evaporation-condensation method in DC arc nitrogen plasma. Aluminium of high purity (99. 999%) was evaporated and nitrided in nitro-gen plasma by use of high temperature and...The nanosize AIN particles were prepared by evaporation-condensation method in DC arc nitrogen plasma. Aluminium of high purity (99. 999%) was evaporated and nitrided in nitro-gen plasma by use of high temperature and high re-activity of plasma gas. The purity of nanosize AIN particles is more than 98% (wt%) and the average particle size is about 50nm. The grain growth of nanosize AlN particle is also studied. The results show that the nanosize AlN particle begins to grow up at 900℃ and the grain growth increase rapidly at 1100℃. When the temperature is increased to 1600℃, the surface of nanosize AIN particle has been sintered softly. Results will be beneficial to pre-pare AIN ceramics.展开更多
文摘Varistor ceramics of ZnO Bi 2O 3 TiO 2 Sb 2O 3 system have been fabricated by introducing pre fabricated ZnO seed grains with different size distributions respectively. The results show that the varistor properties were significantly influenced by the size of introduced seed grains, and introducing larger seed grains is more advantageous to the modification of microstructure and the improvement of varistor properties. The varistor properties were considerably improved with a moderately increased sintering temperature or time, whereas degraded apparently when the sintering temperature or time was excessively increased. Compared with the sintering time, the sintering temperature plays a more critical role in determining the varistor properties. By introducing pre fabricated ZnO seed grains into the original powders, low voltage ZnO varistor ceramics possessing the desired electrical properties have been produced with a sintering temperature of about 1 210 ℃ and a sintering temperature of 2～2.5 h. [
文摘The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag（NS） and blast furnace slag（BFS） with a small amount of quartz sand was investigated.A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process.The results show that the iron-rich system has much lower melting temperature,glass transition temperature（Tg）,and glass crystallization temperature（Tc）,which can result in a further energy-saving process.The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918°C.The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample.The crystallization process can be completed in a few minutes.A distinct boundary between the crystallized part and the non-crystallized part exists during the process.In the non-crystallized part showing a black colour,some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to Tc.In the crystallized part showing a khaki colour,a compact structure is formed by augite crystals.
基金This work was financially supported by the National Natural Science Foundation of China (No.59995440).
文摘With the help of scanning electronic microscopy and X-ray diffraction, the relationships of microstructure characteristics, phase assemblage, and fracture micrograph of Al2O3/ZrO2 laminated ceramics were studied. Compared with monolithic Al2O3/ZrO2 ceramics, the existence of surface compressive stresses greatly restrained the growth of ZrO2 and Al2O3 grains at high sinter temperature, fined the grain size, and increased the content of metastable t-ZrO2, which made the fracture transformation energy quantity 70% higher than that of the monolithic ceramics. The trans-granular and inter-granular fracture features were observed in the surface and center layers, which further verified that transformation toughening is the main mechanism, whereas, micro-crack toughening is helpful for enhancing fracture toughness.
基金financially supported by the Program of University-Industry Cooperation supported by the Ministry of Education and Guangdong Province of China (No.2008B090500262)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No. 20090006110010)
文摘（1 - x）PbZr0.54Tio.4603-xKNbO3 （0 〈 x 〈 25mo1%） （abbreviated as PZT-xKN） piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225℃ for 30 min. The influence of KNbO3 content on the crystal structure and electrical properties of the PZT-xKN piezoelectric ceramics was studied. Samples with 0 〈 x 0.20 show a pure peroskite structure, indicating that ul KNbOdiffused ito the crystal lattice of PZT to form a single solid solution in this compositional range. A second Pb3Nb4013 phase is observed in the PZT-0.25KN sample, showing that the maximum solid solubility of KNbO3 in PZT matrix ceramic is less than 25mo1%. Compared with pure PZT piezoelectric ceramics, samples containing KNbO3 have smaller crystal grains. PZT-0.15KN exhibits excellent piezoelectric properties with d33 ： 209 pC/N.
基金Funded by the science fund of Wuhan University of Technology.
文摘The development of low-voltage ZnO varistor ceramics containing TiO2 is presented in this report. The varistor properties of ZnO ceramics with different compositions were measured, and microstructure of the ceramics was investigated by XRD and SEM. The results show that the addition of TiO2 is beneficial to the decrease of varistor voltage (V1mA). whereas it leads to the recession of nonlinear coefficient (α) and leakage current (lL). The varistor properties of ZnO ceramics containing TiO2 can be effectively improved by introducing moderate amount of pre-fabricated ZnO seed grains. The behaviors of TiO2 and seed grains, as well as the mechanisms by which TiO2 and seed grains influence varistor properties, are discussed.
基金Funded by the National Natural Science Foundation of China(No.51672220)the 111 Program(No.B08040)of MOE+3 种基金the National Defense Science Foundation(No.32102060303)the Xi’an Science and Technology Foundation(Nos.2017XAKJCGZH-10 and 2017086CG-RC049-XBGY005)the Shaanxi Provincial Science Foundation(No.2017KW-018)the NPU Gaofeng Project(No.17GH020824)of China
文摘Manganese-doped Ba（0.925）Ca（0.075）TiO3 lead-free piezoelectric ceramics（abbreviated as BCT）with high mechanical quality factor were synthesized by conventional solid-state reaction method.The effects of excess Ba on the crystal structure,microstructure,and electrical properties of the ceramics were systematically investigated.X-ray diffraction and Raman spectra revealed that Ca^2＋ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol%extra Ba^2＋ions were added after sintering.The grain size of the ceramics was decreased by adding extra Ba^2＋ions.The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%.High piezoelectric coefficients（d（33）=150-190 pC/N）and high mechanical quality factors（Qm=1 000-1 200）were obtained in the ceramics when the excess of Ba was between 0.5 mol%and 1 mol%.These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.
文摘Microstructural evolutions of ceramic grain growth at atomistic scale were modeled. The simulation was preceded with Monte-Carlo method, using Visual C++ and OpenGL languages. Realistic images in series were monitored both in two d imensions and three dimensions. Simulated image of grain growth in this series i s presented in left figure with N 0=25, r=0.40 nm, α=0.1, T=1 300 ℃, and P 0=50 %. It was seen that the average grain size increases wit h the time of grain growth. It is in good agreement with that of practical BST c eramics. The average grain area versus grain growth time is shown in right figur e. It is clear that the kinetic exponents of grain growth are not constant durin g the process of microstructural evolution. The kinetic exponents are smaller ( m≈0.5) at the early stages of growth and larger (m≈8) at the later sta ges, which are in agreement with reported results.
文摘Microstructural evolutions of ceramic grain growth we re dynamically demonstrated with 3D graphical display techniques. Based on the p rinciples of grain growth in ceramics, the data of coordination in different ato ms were calculated with Monte-Carlo method at atomistic scale. Realistic images in three-dimension were displayed onto two-dimension monitor by projection, i llumination and atomization, using Visual C++ and OpenGL languages. Different small spheres were used to model different kind of atoms, which filled within a fictitious cube. The radius and coordination for different atoms were then determined according to corresponding ratios by using of perspective projec tion of OpenGL languages. The applications of illuminating, texturizing and at omization techniques enhanced greatly the stereo effect of images.
文摘Bismuth (Bi) and lanthanum (La) doped lead manganese antimoine zirconate titanate (PZMST) ceramic powders have been synthesized by high temperature solid-state reaction method. Preliminary X-ray structural analysis of the compounds shows the formation of tetragonal structure. Scanning electron micrographs (SEM) shows a uniform grain distribution and grain size of the order of ~2.28 μm. Detailed dielectric studies of the Pb0.95(La1-z Biz)0.05[(Zr0.6Ti0.4)0.95(Mn1/3Sb2/3)0.05]O3 samples as a function of the temperature (from 25°C to 450°C) at frequency 1 kHz suggest that the compounds undergo a diffuse phase transition. The transition temperature shifts increase with increasing the Bi ratio. Diffusivity (γ) study of phase transition of these compounds provided its value from 1.59 to 1.78 indicating the degree of the disordering in the system.
文摘This article explored the influence of molding density of TiO<sub>2</sub> varistor-ceramic on densification of ceramic body and grain growth. By the main phase and second phase analysis of TiO<sub>2</sub> varistor-ceramic through XRD and EDAX, the effects of the second phrase on TiO<sub>2</sub> varistor-ceramic were studied. Grain size and its distribution were observed through scanning electron microscope and the density of porcelain body was measured. The effects of grain size, distribution and density of ceramic body on electrical property of TiO<sub>2</sub> varistor-ceramic were the focus issue for analysis. The increased molding density would improve the densifying of magnetic body to some extent and promote grain growth.
基金supported by Ministry of Science and Technology of China through The Key Area Research Plan of Guangdong(Grant No.2019B010937001)High-end MLCC Key Project supported by Guangdong Fenghua Advanced Technology Holding Co.,Ltd.(No.20212001429)+1 种基金the National Key Research and Development Program of China(No.2017YFB0406302)the National Natural Science Foundation of China(No.52032005).
文摘Four BT-based ceramic samples were prepared using a grain grading approach.The bigger-grained(~100 nm)and smaller-grained(~70 nm)BaTiO_(3)(BT)powders were mixed.The smaller-grained BT powder controlled the average grain size and guaranteed the reliability,while the bigger-grained powder enhanced the dielectric constant.Various percentages of bigger-grained BT powder were introduced to balance the average grain size and the dielectric constant.As the proportion of bigger grains increased,the dielectric constant(εr)improved significantly.The room-temperatureεr of 25%bigger-grain mixed BT(2623)was~50%higher than that of the sample with a similar average grain size without grain grading.The ceramic mixed with 15%bigger-grained BT showed comprehensive dielectric performance,which met the EIA X5R standard and provided a considerableεr of 1841 along with a low dielectric loss of 0.78%.Notably,the average grain size was 90 nm,which favors the applications in ultra-thin multilayer ceramic capacitors.
基金financial support from the National Key R&D Program of China(No.2023YFB3711200)the National Natural Science Foundation of China(No.52172072).
文摘It is well known that the grain size of high-entropy ceramics is quite small owing to the sluggish diffusion effect. However, abnormal grain growth often occurs in high-entropy pseudobrookite ceramics, ultimately resulting in the formation of many abnormally grown grains with a grain size as large as 50 μm. To study this phenomenon, the grain growth behavior of high-entropy pseudobrookite ceramics was systematically investigated in this paper. The results demonstrate that the starting material powders first react with each other to form a high-entropy intermediate phase and calcined TiO_(2) powders (TiO_(2)-1100 ℃), and then as the sintering temperature increases, the formed high-entropy intermediate phase further reacts with TiO_(2)-1100 ℃ to form high-entropy pseudobrookite ceramics. Thus, in this system, in addition to the sluggish diffusion effect, the grain sizes of the high-entropy intermediate phase and TiO_(2)-1100 ℃ also affect the morphology of high-entropy pseudobrookite. Compared to nanosized TiO_(2), micron-sized TiO_(2) has a lower sintering activity. Therefore, the high-entropy intermediate phases (Mg,Co,Ni,Zn)TiO_(3) and TiO_(2)-1100 ℃ prepared with micron-sized starting materials exhibit lower grain sizes, finally resulting in the formation of high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) with small grain sizes. Moreover, nano-indentation and thermal conductivity tests were carried out on high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) with different morphologies. The results show that the hardness of high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) increases from 6.05 to 9.95 GPa as the grain size increases, whereas the thermal conductivity decreases from 2.091±0.006 to 1.583±0.006 W·m^(−1)·K^(−1). All these results indicate that high-entropy (Mg,Co,Ni,Zn)Ti_(2)O_(5) with a small grain size is a potential material for thermal protection.
文摘The nanosize AIN particles were prepared by evaporation-condensation method in DC arc nitrogen plasma. Aluminium of high purity (99. 999%) was evaporated and nitrided in nitro-gen plasma by use of high temperature and high re-activity of plasma gas. The purity of nanosize AIN particles is more than 98% (wt%) and the average particle size is about 50nm. The grain growth of nanosize AlN particle is also studied. The results show that the nanosize AlN particle begins to grow up at 900℃ and the grain growth increase rapidly at 1100℃. When the temperature is increased to 1600℃, the surface of nanosize AIN particle has been sintered softly. Results will be beneficial to pre-pare AIN ceramics.
