High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al-TiO2-C system by changing the size,distribution state and wet ability of reactants.Reaction temperature charact...High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al-TiO2-C system by changing the size,distribution state and wet ability of reactants.Reaction temperature characters（reaction ignition time,ignition temperature time.the maximum temperature and temperature rising rate）were changed by different milling time.The longer the milling time.the earlier the reaction.the quicker the temperature rise and the higher the maximum temperature.When the milling time exceeded 10 hours,the reactivity of reactants was so high that the synthetic reaction could take place at 850℃ directly without a long time pretreatment at 670℃.The microstructure of synthetic composites became uniform and the reinforced particles（TiC and α-Al2O3）became fine with milling time increasing.展开更多
Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced ...Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced using different processing parameters, including powder size, laser power, scanning speed and hatch distance. Results showed that the pre-alloyed powders ranging from 45 to 75 lm were more applicable to SLM with less balling tendency, in comparison with those between 75 and 180 lm. The increase in linear energy density（LED） resulted in the decrease in contact angle and the increase in the width of single track as well as its penetration depth into the substrate. Smaller hatch distance leaded to a larger remelted part of the former track and a higher volumetric laser energy density. With a thickness of 75.6 lm, an interfacial intermediate layer, enriched in Ti and depleted in Nb, Si, Cr and Al, was formed between the SLM part and the Ti6Al4V substrate. The mechanisms of the elimination of balling phenomenon by employing a higher LED and the interfacial bonding characteristics between Nb–Si-based alloys via SLM and the Ti6Al4V substrate were discussed.展开更多
The growth character and microstructure of high-T_c supereonducting YBCO thin films deposited on vari- ous substrates have been studied by X-ray diffraction, TEM and SEM.The results show that when the substrate temper...The growth character and microstructure of high-T_c supereonducting YBCO thin films deposited on vari- ous substrates have been studied by X-ray diffraction, TEM and SEM.The results show that when the substrate temperaturc is around 700～800℃ the films have a highly oriented texture with c-axis pependicular to the substrate. The structure of the single crystalline YBCO films grown epitaxially at optimal substrate tem- perature of 800℃ has been established by X-ray diffraction using Seemann-Bohlin geometry (SB). Brentano-Bragg geometry(BB),transmission Laue method and TEM. The lattice matching required for epitaxial growth is achievcd by azimuthal adjustment of the film plane with respect to the substrate plane. The sperior growth is demonstrated by film properties such as critical current density(2.4×10~6 A /cm^2,3.4× 10~6 A/cm^2 and 4.7×l0~6 A/cm^2) for films deposited on YSZ[(Zr(Y)O_2],SrTiO_3 and LaAIO_3 respectively at 77 K and zero fie1d.展开更多
文摘High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al-TiO2-C system by changing the size,distribution state and wet ability of reactants.Reaction temperature characters（reaction ignition time,ignition temperature time.the maximum temperature and temperature rising rate）were changed by different milling time.The longer the milling time.the earlier the reaction.the quicker the temperature rise and the higher the maximum temperature.When the milling time exceeded 10 hours,the reactivity of reactants was so high that the synthetic reaction could take place at 850℃ directly without a long time pretreatment at 670℃.The microstructure of synthetic composites became uniform and the reinforced particles（TiC and α-Al2O3）became fine with milling time increasing.
基金supported financially by the National Natural Science Foundation of China (Nos. 51471013 and 51571004)
文摘Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced using different processing parameters, including powder size, laser power, scanning speed and hatch distance. Results showed that the pre-alloyed powders ranging from 45 to 75 lm were more applicable to SLM with less balling tendency, in comparison with those between 75 and 180 lm. The increase in linear energy density（LED） resulted in the decrease in contact angle and the increase in the width of single track as well as its penetration depth into the substrate. Smaller hatch distance leaded to a larger remelted part of the former track and a higher volumetric laser energy density. With a thickness of 75.6 lm, an interfacial intermediate layer, enriched in Ti and depleted in Nb, Si, Cr and Al, was formed between the SLM part and the Ti6Al4V substrate. The mechanisms of the elimination of balling phenomenon by employing a higher LED and the interfacial bonding characteristics between Nb–Si-based alloys via SLM and the Ti6Al4V substrate were discussed.
文摘The growth character and microstructure of high-T_c supereonducting YBCO thin films deposited on vari- ous substrates have been studied by X-ray diffraction, TEM and SEM.The results show that when the substrate temperaturc is around 700～800℃ the films have a highly oriented texture with c-axis pependicular to the substrate. The structure of the single crystalline YBCO films grown epitaxially at optimal substrate tem- perature of 800℃ has been established by X-ray diffraction using Seemann-Bohlin geometry (SB). Brentano-Bragg geometry(BB),transmission Laue method and TEM. The lattice matching required for epitaxial growth is achievcd by azimuthal adjustment of the film plane with respect to the substrate plane. The sperior growth is demonstrated by film properties such as critical current density(2.4×10~6 A /cm^2,3.4× 10~6 A/cm^2 and 4.7×l0~6 A/cm^2) for films deposited on YSZ[(Zr(Y)O_2],SrTiO_3 and LaAIO_3 respectively at 77 K and zero fie1d.
