Microstructure and interracial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy （SEM）, electron probe microscopy an...Microstructure and interracial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy （SEM）, electron probe microscopy analysis （EPMA）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. The interracial reaction layer thickness of joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of Al2O3 particulate was also studied. The experimental results indicated although there were Al2O3 particulates added into active filler metals, the time dependence of interracial layer growth of joints brazed with active composite filler material is t^1/2 as described by Fickian law as the joints brazed with conventional active filler metal.展开更多
Bi2(Te,Se)3 alloys are conventional commercial thermoelectric materials for solid-state refrigeration around room temperature.In recent years,much attention has been paid to various advanced thermoelectric composite m...Bi2(Te,Se)3 alloys are conventional commercial thermoelectric materials for solid-state refrigeration around room temperature.In recent years,much attention has been paid to various advanced thermoelectric composite materials due to the unique thermoelectric properties.In this work,Bi2Se3/TiO2 composites were prepared by hot pressing the plate-like Bi2Se3 powders coated in situ with hydrolyzed hytetabutyl-n-butyl titanate(TNBT),and therefore numerous TiO2 in micrometer size could be formed on the interface of Bi2Se3 grains.The carrier concentration in Bi2Se3 matrix is optimized subject to the addition of n-type semiconductor TiO2,contributing to a significant improved power factor.In the meantime,the lattice thermal conductivity is also suppressed due to the enhanced phonon scattering at Bi2Se3/TiO2 interface and amorphous TiO2 particles.As a consequence,a peak figure of merit(zT)of 0.41 is obtained at 525 K in Bi2Se3/15 mol%TiO2 composites,nearly 50%augment over the pristine Bi2Se3 binary compound.展开更多
A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was emplo...A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.展开更多
W-2 wt.%Y2O3 composite material with uniform distribution of yttrium element was fabricated through processes of mechanical alloying （MA） and spark plasma sintering （SPS）. The relevant productions were characteriz...W-2 wt.%Y2O3 composite material with uniform distribution of yttrium element was fabricated through processes of mechanical alloying （MA） and spark plasma sintering （SPS）. The relevant productions were characterized by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The XRD showed that the W-2 wt.%Y2O3 composite powder, including tungsten matrix and Y2O3 particles, was refined to nanometer sizes during the MA process. The SEM and TEM micrographs showed that the MA produced composite powder presented a lamellar morphology and contained many dislocations and microcracks. The EDS showed that the Y and O elements were uniformly distributed in the W matrix after mechanically alloying for 15 h. The W-2 wt.%Y2O3 composite material with uniform distribution of yttrium was obtained by sintering of the MA produced composite powder.展开更多
A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon...A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon - carbon double bonds systems and reusability. Furthermore, XPS and IR spectra shouted that active component in the composite catalysts is atomic Pd(0). An addition of a small amount of Fe2O3 has a promotive action upon hydrogenation activity of the catalysts, which indicated that there are some strong interactions (electron transfer) between Pd(0) and Fe(Ⅲ) species. Based on these results, a possible catalytic hydrogenation mechanism was also suggested.展开更多
目的通过等离子喷涂工艺,在油气管道X70管线钢表面制备出Cr2O3/TiO2高温氧化物陶瓷复合涂层,研究该涂层的微观组织与电化学性能。方法采用9MC Plasma Control Unit等离子喷涂系统,基于线切割尺寸为40mm×24mm×6mm的X70管线钢...目的通过等离子喷涂工艺,在油气管道X70管线钢表面制备出Cr2O3/TiO2高温氧化物陶瓷复合涂层,研究该涂层的微观组织与电化学性能。方法采用9MC Plasma Control Unit等离子喷涂系统,基于线切割尺寸为40mm×24mm×6mm的X70管线钢基体表面,沉积Cr2O3/TiO2高温氧化物陶瓷复合涂层。利用金相显微镜和扫描电子显微镜观察该复合涂层的微观组织与形貌,利用X射线衍射仪分析该复合涂层的物相组成,利用电化学工作站测定该复合涂层的电化学腐蚀性能。结果Cr2O3/TiO2高温氧化物陶瓷复合涂层由完全熔化区和半熔化区双态组成,呈典型的等离子喷涂层状结构,层与层之间结合较紧密,分布着富Cr2O3沉积区与富TiO2沉积区,无相变产生,完全熔融的TiO2液相可嵌入到未完全熔融的Cr2O3结构间隙中形成固溶结构。经电化学腐蚀性能测试,其自腐蚀电位介于-0.4^-0.3V之间,高于X70管线钢基体的自腐蚀电位-0.6^-0.5V,腐蚀倾向滞后,表现出好的抗腐蚀性能。结论研究选取的等离子喷涂参数较合适,并成功制备出了能明显提高油气管道X70管线钢抗电化学腐蚀性且组织分布均匀的Cr2O3/TiO2高温氧化物陶瓷复合涂层。展开更多
In this study,the Cr2O3/C@TiO2 composite was synthesized via the calcination of yolk–shell MIL-101@TiO2.The composite presented core–shell structure,where Cr-doped TiO2 and Cr2O3/C were the shell and core,respective...In this study,the Cr2O3/C@TiO2 composite was synthesized via the calcination of yolk–shell MIL-101@TiO2.The composite presented core–shell structure,where Cr-doped TiO2 and Cr2O3/C were the shell and core,respectively.The introduction of Cr^3+and Cr2O3/C,which were derived from the calcination of MIL-101,in the composite enhanced its visible light absorbing ability and lowered the recombination rate of the photogenerated electrons and holes.The large surface area of the Cr2O3/C@TiO2 composite provided numerous active sites for the photoreduction reaction.Consequently,the photocatalytic performance of the composite for the production of H2 was better than that of pure TiO2.Under the irradiation of a 300 W Xe arc lamp,the H2 production rate of the Cr2O3/C@TiO2 composite that was calcined at 500°C was 446μmol h−1 g−1,which was approximately four times higher than that of pristine TiO2 nanoparticles.Moreover,the composite exhibited the high H2 production rate of 25.5μmol h−1 g−1 under visible light irradiation(λ>420 nm).The high photocatalytic performance of Cr2O3/C@TiO2 could be attributed to its wide visible light photoresponse range and efficient separation of photogenerated electrons and holes.This paper offers some insights into the design of a novel efficient photocatalyst for water-splitting applications.展开更多
ZA22/Al2O3 composites were prepared by means of squeeze casting process. The effects of Ce on the ultimate tensile strength (UTS), impact toughness, and hardness of the composites were studied. The results show that b...ZA22/Al2O3 composites were prepared by means of squeeze casting process. The effects of Ce on the ultimate tensile strength (UTS), impact toughness, and hardness of the composites were studied. The results show that both the UTS and the hardness are improved and the impact toughness is decreased with the increase of the volume fraction of fibers (Vf). After Ce is added ,UTS (Vf>15%) and the hardness are improved at room temperature because of the modification of Ce, but the impact toughness and UTS at elevated temperature are lowered.The filtered action of the fiber preform results in that the influence of the amount of Ce added from 0. 1 wt% to 0. 5 wt% on the mechanical properties of the composites can be ignored.展开更多
基金the National Natural Science Foundation of China(Grant No.50075019) the Visiting Scholar Foundation of Key Lab.in University of China
文摘Microstructure and interracial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy （SEM）, electron probe microscopy analysis （EPMA）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. The interracial reaction layer thickness of joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of Al2O3 particulate was also studied. The experimental results indicated although there were Al2O3 particulates added into active filler metals, the time dependence of interracial layer growth of joints brazed with active composite filler material is t^1/2 as described by Fickian law as the joints brazed with conventional active filler metal.
基金financially supported by the National Natural Science Foundation of China(Nos.51871199 and 61534001)。
文摘Bi2(Te,Se)3 alloys are conventional commercial thermoelectric materials for solid-state refrigeration around room temperature.In recent years,much attention has been paid to various advanced thermoelectric composite materials due to the unique thermoelectric properties.In this work,Bi2Se3/TiO2 composites were prepared by hot pressing the plate-like Bi2Se3 powders coated in situ with hydrolyzed hytetabutyl-n-butyl titanate(TNBT),and therefore numerous TiO2 in micrometer size could be formed on the interface of Bi2Se3 grains.The carrier concentration in Bi2Se3 matrix is optimized subject to the addition of n-type semiconductor TiO2,contributing to a significant improved power factor.In the meantime,the lattice thermal conductivity is also suppressed due to the enhanced phonon scattering at Bi2Se3/TiO2 interface and amorphous TiO2 particles.As a consequence,a peak figure of merit(zT)of 0.41 is obtained at 525 K in Bi2Se3/15 mol%TiO2 composites,nearly 50%augment over the pristine Bi2Se3 binary compound.
文摘A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.
文摘W-2 wt.%Y2O3 composite material with uniform distribution of yttrium element was fabricated through processes of mechanical alloying （MA） and spark plasma sintering （SPS）. The relevant productions were characterized by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The XRD showed that the W-2 wt.%Y2O3 composite powder, including tungsten matrix and Y2O3 particles, was refined to nanometer sizes during the MA process. The SEM and TEM micrographs showed that the MA produced composite powder presented a lamellar morphology and contained many dislocations and microcracks. The EDS showed that the Y and O elements were uniformly distributed in the W matrix after mechanically alloying for 15 h. The W-2 wt.%Y2O3 composite material with uniform distribution of yttrium was obtained by sintering of the MA produced composite powder.
文摘A series of polymer- supported Pd -Fe2O3 composite catalysts were prepared and their hydrogenation property mas investigated. It was found that the above catalysts have good catalytic hydrogenation activity for carbon - carbon double bonds systems and reusability. Furthermore, XPS and IR spectra shouted that active component in the composite catalysts is atomic Pd(0). An addition of a small amount of Fe2O3 has a promotive action upon hydrogenation activity of the catalysts, which indicated that there are some strong interactions (electron transfer) between Pd(0) and Fe(Ⅲ) species. Based on these results, a possible catalytic hydrogenation mechanism was also suggested.
文摘目的通过等离子喷涂工艺,在油气管道X70管线钢表面制备出Cr2O3/TiO2高温氧化物陶瓷复合涂层,研究该涂层的微观组织与电化学性能。方法采用9MC Plasma Control Unit等离子喷涂系统,基于线切割尺寸为40mm×24mm×6mm的X70管线钢基体表面,沉积Cr2O3/TiO2高温氧化物陶瓷复合涂层。利用金相显微镜和扫描电子显微镜观察该复合涂层的微观组织与形貌,利用X射线衍射仪分析该复合涂层的物相组成,利用电化学工作站测定该复合涂层的电化学腐蚀性能。结果Cr2O3/TiO2高温氧化物陶瓷复合涂层由完全熔化区和半熔化区双态组成,呈典型的等离子喷涂层状结构,层与层之间结合较紧密,分布着富Cr2O3沉积区与富TiO2沉积区,无相变产生,完全熔融的TiO2液相可嵌入到未完全熔融的Cr2O3结构间隙中形成固溶结构。经电化学腐蚀性能测试,其自腐蚀电位介于-0.4^-0.3V之间,高于X70管线钢基体的自腐蚀电位-0.6^-0.5V,腐蚀倾向滞后,表现出好的抗腐蚀性能。结论研究选取的等离子喷涂参数较合适,并成功制备出了能明显提高油气管道X70管线钢抗电化学腐蚀性且组织分布均匀的Cr2O3/TiO2高温氧化物陶瓷复合涂层。
文摘In this study,the Cr2O3/C@TiO2 composite was synthesized via the calcination of yolk–shell MIL-101@TiO2.The composite presented core–shell structure,where Cr-doped TiO2 and Cr2O3/C were the shell and core,respectively.The introduction of Cr^3+and Cr2O3/C,which were derived from the calcination of MIL-101,in the composite enhanced its visible light absorbing ability and lowered the recombination rate of the photogenerated electrons and holes.The large surface area of the Cr2O3/C@TiO2 composite provided numerous active sites for the photoreduction reaction.Consequently,the photocatalytic performance of the composite for the production of H2 was better than that of pure TiO2.Under the irradiation of a 300 W Xe arc lamp,the H2 production rate of the Cr2O3/C@TiO2 composite that was calcined at 500°C was 446μmol h−1 g−1,which was approximately four times higher than that of pristine TiO2 nanoparticles.Moreover,the composite exhibited the high H2 production rate of 25.5μmol h−1 g−1 under visible light irradiation(λ>420 nm).The high photocatalytic performance of Cr2O3/C@TiO2 could be attributed to its wide visible light photoresponse range and efficient separation of photogenerated electrons and holes.This paper offers some insights into the design of a novel efficient photocatalyst for water-splitting applications.
文摘ZA22/Al2O3 composites were prepared by means of squeeze casting process. The effects of Ce on the ultimate tensile strength (UTS), impact toughness, and hardness of the composites were studied. The results show that both the UTS and the hardness are improved and the impact toughness is decreased with the increase of the volume fraction of fibers (Vf). After Ce is added ,UTS (Vf>15%) and the hardness are improved at room temperature because of the modification of Ce, but the impact toughness and UTS at elevated temperature are lowered.The filtered action of the fiber preform results in that the influence of the amount of Ce added from 0. 1 wt% to 0. 5 wt% on the mechanical properties of the composites can be ignored.
