The effect of the catalyst height on the morphology of diamond crystal is investigated by means of temperature gradient growth(TGG) under high pressure and high temperature(HPHT) conditions with using a Ni-based catal...The effect of the catalyst height on the morphology of diamond crystal is investigated by means of temperature gradient growth(TGG) under high pressure and high temperature(HPHT) conditions with using a Ni-based catalyst in this article. The experimental results show that the morphology of diamond changes from an octahedral shape to a cuboctahedral shape as the catalyst height rises. Moreover, the finite element method(FEM) is used to simulate the temperature field of the melted catalyst/solvent. The results show that the temperature at the location of the seed diamond continues to decrease with the increase of catalyst height, which is conducive to changing the morphology of diamond. This work provides a new way to change the diamond crystal morphology.展开更多
The high pressure and high temperature(HPHT) method is successfully used to synthesize jadeite in a temperature range of 1000℃–1400℃ under a pressure of 3.5 GPa. The initial raw materials are Na_2SiO_3·9H_2O a...The high pressure and high temperature(HPHT) method is successfully used to synthesize jadeite in a temperature range of 1000℃–1400℃ under a pressure of 3.5 GPa. The initial raw materials are Na_2SiO_3·9H_2O and Al_2(SiO_3)_3.Through the HPHT method, the amorphous glass material is entirely converted into crystalline jadeite. We can obtain the good-quality jadeite by optimizing the reaction pressure and temperature. The measurements of x-ray diffraction(XRD),scanning electron microscopy(SEM), Fourier-transform infrared(FTIR) and Raman scattering indicate that the properties of synthesized jadeite at 1260℃ under 3.5 GPa are extremely similar to those of the natural jadeite. What is more, the results will be valuable for understanding the formation process of natural jadeite. This work also reveals the mechanism for metamorphism of magma in the earth.展开更多
Fe\-2O 3 /Al\-2O 3 nanocomposites prepared by using the sol-gel technique were reduced in H\-2 atmosphere at different temperatures, and the corresponding Fe/Al2O3 nanocomposites were obtained after the reduction of F...Fe\-2O 3 /Al\-2O 3 nanocomposites prepared by using the sol-gel technique were reduced in H\-2 atmosphere at different temperatures, and the corresponding Fe/Al2O3 nanocomposites were obtained after the reduction of Fe\-2O 3 /Al\-2O 3 nanocomposites at 1173 K. The structures and properties of the specimens were studied by X-ray diffraction（XRD）, Mssbauer spectroscopy（MS）, and vibrating sample magnetometry（VSM）. The results show that the reduction temperature has a significant influence on the structure, the grain size, and the magnetic properties of the specimens.展开更多
Polycrystalline Cu_(2)Se bulk materials were synthesized by high-pressure and high-temperature(HPHT)technique.The effects of synthetic temperature and pressure on the thermoelectric properties of Cu_(2)Se materials we...Polycrystalline Cu_(2)Se bulk materials were synthesized by high-pressure and high-temperature(HPHT)technique.The effects of synthetic temperature and pressure on the thermoelectric properties of Cu_(2)Se materials were investigated.The results indicate that both synthetic temperature and pressure determine the microstructure and thermoelectric performance of Cu2Se compounds.The increase of synthetic temperature can effectively enhance the electrical conductivity and decrease the lattice thermal conductivity.A two-fold improvement in the power factor is obtained at synthetic temperature of 1000℃ compared to that obtained at room temperature.All b-Cu2Se samples exhibit low and temperatureindependent lattice thermal conductivity ranging from 0.3 to 0.5 Wm^(-1)K^(-1) due to the intrinsic superionic feature and the abundant lattice defects produced at high pressure.A maximum zT of 1.19 at 723 K was obtained for the sample synthesized at 3 GPa and 1000℃.These findings indicate that HPHT technology is an efficient approach to synthesize Cu_(2)Se-based bulk materials.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51172089)the Program for New Century Excellent Talents in University,the Natural Science Foundation of Guizhou Provincial Education Department(Grant No.KY[2013]183)the Collaborative Fund of Science and Technology Office of Guizhou Province,China(Grant No.LH[2015]7232)
文摘The effect of the catalyst height on the morphology of diamond crystal is investigated by means of temperature gradient growth(TGG) under high pressure and high temperature(HPHT) conditions with using a Ni-based catalyst in this article. The experimental results show that the morphology of diamond changes from an octahedral shape to a cuboctahedral shape as the catalyst height rises. Moreover, the finite element method(FEM) is used to simulate the temperature field of the melted catalyst/solvent. The results show that the temperature at the location of the seed diamond continues to decrease with the increase of catalyst height, which is conducive to changing the morphology of diamond. This work provides a new way to change the diamond crystal morphology.
基金supported by the National Natural Science Foundation of China(Grant Nos.51172089 and 51171070)the Graduate Innovation Fund of Jilin University,China(Grant No.2016065)
文摘The high pressure and high temperature(HPHT) method is successfully used to synthesize jadeite in a temperature range of 1000℃–1400℃ under a pressure of 3.5 GPa. The initial raw materials are Na_2SiO_3·9H_2O and Al_2(SiO_3)_3.Through the HPHT method, the amorphous glass material is entirely converted into crystalline jadeite. We can obtain the good-quality jadeite by optimizing the reaction pressure and temperature. The measurements of x-ray diffraction(XRD),scanning electron microscopy(SEM), Fourier-transform infrared(FTIR) and Raman scattering indicate that the properties of synthesized jadeite at 1260℃ under 3.5 GPa are extremely similar to those of the natural jadeite. What is more, the results will be valuable for understanding the formation process of natural jadeite. This work also reveals the mechanism for metamorphism of magma in the earth.
基金Supported by the Jilin Distinguished Young Scholars'Program(No.20020118) and the National Key Laboratory of SuperhardMaterials, Jilin University(No. 2002006)
文摘Fe\-2O 3 /Al\-2O 3 nanocomposites prepared by using the sol-gel technique were reduced in H\-2 atmosphere at different temperatures, and the corresponding Fe/Al2O3 nanocomposites were obtained after the reduction of Fe\-2O 3 /Al\-2O 3 nanocomposites at 1173 K. The structures and properties of the specimens were studied by X-ray diffraction（XRD）, Mssbauer spectroscopy（MS）, and vibrating sample magnetometry（VSM）. The results show that the reduction temperature has a significant influence on the structure, the grain size, and the magnetic properties of the specimens.
基金the National Natural Science Foundation of China(No.11704340,11804305 and 51171070)the Project of Jilin Science and Technology Development Plan(Project No.20170101045JC)+1 种基金the China Postdoctoral Science Foundation(No.2017M620303 and 2017M622360)the Key Research Project of Higher Education Institution of Henan Province(No.19A140006).
文摘Polycrystalline Cu_(2)Se bulk materials were synthesized by high-pressure and high-temperature(HPHT)technique.The effects of synthetic temperature and pressure on the thermoelectric properties of Cu_(2)Se materials were investigated.The results indicate that both synthetic temperature and pressure determine the microstructure and thermoelectric performance of Cu2Se compounds.The increase of synthetic temperature can effectively enhance the electrical conductivity and decrease the lattice thermal conductivity.A two-fold improvement in the power factor is obtained at synthetic temperature of 1000℃ compared to that obtained at room temperature.All b-Cu2Se samples exhibit low and temperatureindependent lattice thermal conductivity ranging from 0.3 to 0.5 Wm^(-1)K^(-1) due to the intrinsic superionic feature and the abundant lattice defects produced at high pressure.A maximum zT of 1.19 at 723 K was obtained for the sample synthesized at 3 GPa and 1000℃.These findings indicate that HPHT technology is an efficient approach to synthesize Cu_(2)Se-based bulk materials.
