Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. I...Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. In this work, a novel high-entropy(HE) rare-earth phosphate monazite ceramic (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is designed and successfully synthesized. This new type of HE rare-earth phosphate monazite exhibits good chemical compatibility with Al2O3, without reaction with Al2O3 as high as 1600℃ in air. Moreover, the thermal expansion coefficient(TEC) of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4(8.9 × 10^-6/℃ at 300–1000℃) is close to that of Al2O3. The thermal conductivity of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 at room temperature is as low as 2.08 W·m^-1·K^-1, which is about 42% lower than that of La PO4. Good chemical compatibility, close TEC to that of Al2O3, and low thermal conductivity indicate that HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is suitable as a candidate EBC/TBC material and an interphase for Al2O3 f/Al2O3 composites.展开更多
By using ZnSO47H2O and NaOH as raw materials, C18H29NaO3S (DBS) as assistant, ZnO nanorods were synthesized directly in aqueous solution at low-temperature. TG-DSC, XRD, TEM and HRTEM results show that the crystal pha...By using ZnSO47H2O and NaOH as raw materials, C18H29NaO3S (DBS) as assistant, ZnO nanorods were synthesized directly in aqueous solution at low-temperature. TG-DSC, XRD, TEM and HRTEM results show that the crystal phase of the as-prepared ZnO nanorods has a hexagonal wurtzite structure with diameter from 30 to 50 nm and length up to 500 nm. The crystals grow along [001] direction. The mechanism for the ZnO nanorods growth was also discussed.展开更多
This review covers the major reactions involved in the solution synthesis of nanomaterials.It was designed to classify the traditional strategies such as precipitation,reduction,seed growth,etching,and so on into two ...This review covers the major reactions involved in the solution synthesis of nanomaterials.It was designed to classify the traditional strategies such as precipitation,reduction,seed growth,etching,and so on into two basic processes which are termed as bottom-up and top-down routines.The discussion is focused on the basic mechanism and principles during the nudeation and growth of nanocrystals,especially in the solution system.This review also presents a prediction for how to utilize these intrinsic processes to artificially construct the desired specific and functional nanostructures.We try to describe the most directive and effective way to control the structures of nanocrystals for researchers who can master the major reaction mechanism and grasp the basic technologies in synthetic nanoscience.展开更多
Ultrafine Fe3O4 powder was successfully synthesized via a novel ageing process from a precursor FeO（OH）, which was the hydrolysate of FeCl3 in the urea solution. The structure of as-synthesized powder was characteri...Ultrafine Fe3O4 powder was successfully synthesized via a novel ageing process from a precursor FeO（OH）, which was the hydrolysate of FeCl3 in the urea solution. The structure of as-synthesized powder was characterized by X-ray diffraction （XRD）, and the morphology of these nanoparticles was investigated using a transmission electron microscope （TEM）. Pure phase Fe3O4 was obtained and the mean diameter of these nanoparticles was about 21 nm.Furthermore, the study indicated that the precursor FeO（OH） played an important role in the formation of Fe3O4 nanoparticles. The mechanism was also discussed.展开更多
This paper proposes a novel method relating to the recycling of waste lead ash originated from procedure of lead alloy production.The spent lead ash was first disposed by acetic acid leaching system,where lead ash str...This paper proposes a novel method relating to the recycling of waste lead ash originated from procedure of lead alloy production.The spent lead ash was first disposed by acetic acid leaching system,where lead ash structure wrapping impurities would be destroyed.The synthesis of lead oxide products was conducted at a lower temperature of 90℃.The effect of molar ratio of CH3 COOH to lead content of the ash on leaching efficiency was studied through the acetic acid leaching system.The results demonstrate that 84.6%of lead could be obtained in the leaching solution,while merely 0.7%of Fe blend in solution within a leaching time of 120 min.In the stage of lead oxide synthesis from leaching solution,the yield of lead oxide products could reach up to 94.4%when the molar ratio of NaOH to lead in filtrate was 2.5.This novel green method could shed light on the reuse of lead from exhausted ash with a much more convenient and environmentally friendly procedure.展开更多
We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune...We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune the carrier concentration of the nanocomposites. Due to the Se doping, the thermoelectric figure of merit （ZT） of the nanocomposites is significantly enhanced due to the increased power factor and reduced thermal conductivity. We also find that thermal transport in our hot-pressed pellets is anisotropic, which results in different thermal conductivities along the in-plane and cross-plane directions. Theoretical calculations for both electronic and thermal transport are carried out to establish fundamental understanding of the material system and provide directions for further ZT optimization with adjustments to carrier concentration and mobility.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51672064 and U1435206)
文摘Low thermal conductivity, matched thermal expansion coefficient and good compatibility are general requirements for the environmental/thermal barrier coatings(EBCs/TBCs) and interphases for Al2O3 f/Al2O3 composites. In this work, a novel high-entropy(HE) rare-earth phosphate monazite ceramic (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is designed and successfully synthesized. This new type of HE rare-earth phosphate monazite exhibits good chemical compatibility with Al2O3, without reaction with Al2O3 as high as 1600℃ in air. Moreover, the thermal expansion coefficient(TEC) of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4(8.9 × 10^-6/℃ at 300–1000℃) is close to that of Al2O3. The thermal conductivity of HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 at room temperature is as low as 2.08 W·m^-1·K^-1, which is about 42% lower than that of La PO4. Good chemical compatibility, close TEC to that of Al2O3, and low thermal conductivity indicate that HE (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)PO4 is suitable as a candidate EBC/TBC material and an interphase for Al2O3 f/Al2O3 composites.
文摘By using ZnSO47H2O and NaOH as raw materials, C18H29NaO3S (DBS) as assistant, ZnO nanorods were synthesized directly in aqueous solution at low-temperature. TG-DSC, XRD, TEM and HRTEM results show that the crystal phase of the as-prepared ZnO nanorods has a hexagonal wurtzite structure with diameter from 30 to 50 nm and length up to 500 nm. The crystals grow along [001] direction. The mechanism for the ZnO nanorods growth was also discussed.
基金supported by the Fundamental Research Funds for the Central Universities(WK2060190043 and WK2060190053)the National Natural Science Foundation of China(21521091,21131004,21390393,U1463202 and 21522107)
文摘This review covers the major reactions involved in the solution synthesis of nanomaterials.It was designed to classify the traditional strategies such as precipitation,reduction,seed growth,etching,and so on into two basic processes which are termed as bottom-up and top-down routines.The discussion is focused on the basic mechanism and principles during the nudeation and growth of nanocrystals,especially in the solution system.This review also presents a prediction for how to utilize these intrinsic processes to artificially construct the desired specific and functional nanostructures.We try to describe the most directive and effective way to control the structures of nanocrystals for researchers who can master the major reaction mechanism and grasp the basic technologies in synthetic nanoscience.
文摘Ultrafine Fe3O4 powder was successfully synthesized via a novel ageing process from a precursor FeO（OH）, which was the hydrolysate of FeCl3 in the urea solution. The structure of as-synthesized powder was characterized by X-ray diffraction （XRD）, and the morphology of these nanoparticles was investigated using a transmission electron microscope （TEM）. Pure phase Fe3O4 was obtained and the mean diameter of these nanoparticles was about 21 nm.Furthermore, the study indicated that the precursor FeO（OH） played an important role in the formation of Fe3O4 nanoparticles. The mechanism was also discussed.
基金Supported by the China Postdoctoral Science Foundation(2018M632799)the Education Department of Henan Province Science Research Program(18B610008,19A610010)the Henan province Key Research and Development and Promotion(182102311033)
文摘This paper proposes a novel method relating to the recycling of waste lead ash originated from procedure of lead alloy production.The spent lead ash was first disposed by acetic acid leaching system,where lead ash structure wrapping impurities would be destroyed.The synthesis of lead oxide products was conducted at a lower temperature of 90℃.The effect of molar ratio of CH3 COOH to lead content of the ash on leaching efficiency was studied through the acetic acid leaching system.The results demonstrate that 84.6%of lead could be obtained in the leaching solution,while merely 0.7%of Fe blend in solution within a leaching time of 120 min.In the stage of lead oxide synthesis from leaching solution,the yield of lead oxide products could reach up to 94.4%when the molar ratio of NaOH to lead in filtrate was 2.5.This novel green method could shed light on the reuse of lead from exhausted ash with a much more convenient and environmentally friendly procedure.
基金H. Y. F. thanks Scott Finefrock and Tianyue Gao for the help in Hall measurement. H. Y. F. and Y. W. acknowledge the use of the hot press setup in Prof. Chin-The Sun＇s lab at Purdue University. H. Y. F. and Y. W. acknowledge Air Force Office of Scientific Research （No. FA9550-12-1-0061）. T. L. F. and X. L. R. acknowledge the partial support from National Science Foundation （No. 1150948）.
文摘We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune the carrier concentration of the nanocomposites. Due to the Se doping, the thermoelectric figure of merit （ZT） of the nanocomposites is significantly enhanced due to the increased power factor and reduced thermal conductivity. We also find that thermal transport in our hot-pressed pellets is anisotropic, which results in different thermal conductivities along the in-plane and cross-plane directions. Theoretical calculations for both electronic and thermal transport are carried out to establish fundamental understanding of the material system and provide directions for further ZT optimization with adjustments to carrier concentration and mobility.
