STEM nanoanalysis of Au/Pt/Ti-Si3N4 interfacial defects and reactions during local stress of SiGe HBTs

Nanoscaled materials are attractive building blocks for hierarchical assembly of functional nanodevices, which exhibit diverse performances and simultaneous functions. We innovatively fabricated semiconductor nano-probes of tapered ZnS nanowires through melting and solidifying by electro-thermal process; and then, as-prepared nano-probes can manipulate nanomaterials including semiconductor/metal nanowires and nanoparticles through sufficiently electrostatic force to the desired location without structurally and functionally damage. With some advantages of high precision and large domain, we can move and position and interconnect individual nanowires for contracting nanodevices. Interestingly, by the manipulating technique, the nanodevice made of three vertically interconnecting nanowires, i.e., diode, was realized and showed an excellent electrical property. This technique may be useful to fabricate electronic devices based on the nanowires' moving, positioning, and interconnecting and may overcome fundamental limitations of conventional mechanical fabrication.     

Selective deposition of Pt on Au nanoparticles using hydrogen presorbed into Au nanoparticles during NaBH4 treatment

A facile chemical method to prepare a Pt layer selectively on Au nanoparticles is developed. The hydrogen presorbed into Au nanoparticles during NaBH₄ treatment leads to the formation of a thin Pt layer on Au nanoparticles. The Pt-coated Au nanoparticles exhibit significantly improved electrocatalytic activity for the electrooxidation of formic acid.     

Microstructure and mechanical characterization of Si3N4/nickel-based superalloy joints with Ti/Au/Ni interlayers

The Si₃N₄ ceramic was joined to nickel-based superalloy via partial transient liquid phase bonding with Ti/Au/Ni interlayers. The interfacial microstructure and strength of joints were examined by methods of scanning electron microscopy, transmission electron microscopy, X-ray diffraction and a three-point flexural test. The results revealed the joint between Si₃N₄ and Ni interlayer consisted of TiN layer, Au-rich phase, Ni-rich phase and tiny TiO phase. The highest flexural strength of 211?MPa was achieved at room temperature, and the high-temperature strength of joints reached up to 117?MPa when testing at 1073?K. Post-bonding treatment indicated the joint strength of 120?MPa was obtained after annealing in air at 1073?K for 100?h, which exhibited superior oxidation resistant.     

Microstructural evolution and interfacial reactions between Ti and ZrO2/CaTiO3 composites

Various proportions of ZrO₂/CaTiO₃ powders were mixed and hot pressed at 1500°C/30 min for Ti casting. The hot-pressed ZrO₂/CaTiO₃ composites were reacted with pure Ti at 1700°C/10 min in Ar. The interfacial reaction between Ti and ZrO₂/CaTiO₃ composites was investigated through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The ZrO₂/CaTiO₃ composites with less than 10 vol.%, CaTiO₃, and a minor amount of residual TiO₂ were found. When the content of ZrO₂ was increased to larger than 10 vol.%, two Ca₂Zr₅Ti₂O₁₆ and CaZrTi₂O₇ phases appeared in the composites. The amount of CaTiO₃ and CaZrTi₂O₇ in the composites gradually decreased as the amount of ZrO₂ increased. When Ti came in contact with ZrO₂/CaTiO₃ composites with less than 10 vol.% ZrO₂, the resulting eutectic reaction produced a liquid phase and induced melting. When ZrO₂ was increased to more than 30 vol.% in the composites, Ca₂Zr₅Ti₂O₁₆ and CaZrTi₂O₇ changed completely to CaZrO₃, Ti₂O, CaO, and ZrO₂. With more than 30 vol.% ZrO₂, no other reaction phases occurred in the Ti side after contact with the ZrO₂/CaTiO₃ composites, which is conducive for producing ceramic composites for Ti casting applications.     

POM/EVA/CaCO3复合材料拉伸载荷下界面应力的数值模拟

应用ANSYS软件对聚甲醛(POM)/乙烯-乙酸乙烯共聚物(EVA)/CaC03拉伸过程中界面应力及其分布进行了数值模拟,以考察相邻的EVA粒子与CaCO3粒子之间的相互作用对界面应力及其分布的影响.EVA粒子与CaCO3粒子之间存在明显的应力集中,尤其是CaCO3粒子靠近EVA粒子的一侧;两粒子的最大剪切应力都偏离了...     

Au/Fe3O4纳米复合材料的制备及其催化性能

通过将金纳米粒子铆接到Fe3O4载体表面,制得了Au/Fe3O4纳米复合粒子。首先以对苯二酚为还原剂还原HAuCl4制得球形金纳米粒子;然后采用溶剂热法制备Fe3O4磁性纳米颗粒,并用巯基丙酸(MPA)对其修饰;最后通过MPA与金纳米粒子之间的相互作用,将金纳米颗粒固定到Fe3O4表面。采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)和振动样品磁强计(VSM)和紫外-可见分光光度计(UV-vis)对所制备材料进行形貌、晶型、磁性和催化性能的表征。结果表明,金纳米颗粒成功包覆在Fe3O4表面,所得到的Au/Fe3O4复合纳米材料具有单分散性和超顺磁性,并且对NaBH4还原对硝基苯酚(4-NP)制备对氨基苯酚(4-AP)的反应显示出优良的催化性能。     

Fe3O4/Au/Fe3O4 nanoflowers exhibiting tunable saturation magnetization and enhanced bioconjugation

Composite nanoparticles have proved to be promising in a wide range of biotechnological applications. In this paper, we report on a facile method to synthesize novel Fe(3)O(4)/Au/Fe(3)O(4) nanoparticles (nanoflowers) that integrate hybrid components and surface types. We demonstrate that relative to conventional nanoparticles with core/shell configuration, such nanoflowers not only retain their surface plasmon property but also allow for 170% increase in the saturation magnetization and 23% increase in the conjugation efficiency due to the synergistic co-operation between the hierarchical structures. Moreover, we demonstrate that the magnetic properties of such composite nanoparticles can be tuned by controlling the size of additional petals (Fe(3)O(4) phase). These novel building blocks could open up novel and exciting vistas in nanomedicine for broad applications such as biosensing, cancer diagnostics and therapeutics, targeted delivery, and imaging.     

Effect of interfacial mixing by N+ implantation on the adhesion and friction of Ti film on Si3N4

A thin ion-plated Ti film on sintered Si₃N₄ was implanted with 110 keV N⁺ at doses of 1 x 10¹⁶ to 3 x 10¹⁷ ions cm^-2 and a substrate temperature of 60°C. The adhesion of the ion-plated Ti film and the N⁺-implanted films on Si₃N₄ was examined using a scratch tester and a scanning electron microscope. The interfacial chemistry of the N⁺-implanted Ti/Sl₃N₄ specimens was examined using sample tilting diffraction (STD), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). It was found that at a dose of 3 x 10¹⁷ N⁺ cm^-2, the critical load for the scratch test on the N⁺-implanted Ti film/Si₃N₄ substrate increased from 10.8 to 50.0 N; consequently, the implanted films were not easily removed by interfacial failure as in the case of the unimplanted one. AES indicated that N⁺ implantation produced substantial interfacial mixing and interfacial grading in the Ti/Si₃N₄ system. The STD and XPS analyses revealed that a Ti_xN (x = 1, 2) compound was formed by N⁺ implantation. The combination of these effects in the N⁺implanted Ti/Si₃N₄ specimen provided an increased adhesion that was approximately 4.6 times that of the unimplanted system. In addition, the hydrocarbon adsorbed in the near-surface region of Ti films reduced the adhesion component of friction between the metal and the N⁺-implanted specimen.     

Si3N4/Si3N4扩散连接的力学性能研究

采用热压法进行氮化硅陶瓷材料的扩散连接.结果表明:在1520℃,15MPa,60min条件下,氮化硅连接体的最高强度为448.6MPa,超过母材强度;平均连接强度为401.5MPa,为母材强度的96%.     

Microstructure and mechanical properties of Si3N4f/Si3N4 composites with different coatings

The Si₃N₄ coating and Si₃N₄ coating with Si₃N₄ whiskers as reinforcement (Si₃N_4w-Si₃N₄) were prepared by chemical vapor deposition (CVD) on two-dimensional silicon nitride fiber reinforced silicon nitride ceramic matrix composites (2D Si₃N_4f/Si₃N₄ composites). The effects of process parameters of as-prepared coating including the preparation temperature and volume fraction of Si₃N_4w on the microstructure and mechanical properties of the composites were investigated. Compared with Si₃N₄ coating, Si₃N_4w-Si₃N₄ coating shows more significant effect on the strength and toughness of the composites, and both strengthening and toughening mechanism were analyzed.     

g-C3N4的改性策略以及g-C3N4/Ti3C2异质结研究进展

石墨相氮化碳（g-C₃N₄）禁带宽度约为2.7 eV,具有可见光响应能力。由于其良好的热和化学稳定性,且形貌和化学结构可调,在光催化领域应用广泛。但由于其带隙宽,对可见光响应范围窄,且光生载流子的复合率高,导致其光催化效率低,可通过改性来改善。本文综述了对g-C₃N₄形貌调控、掺杂和构建异质结等改性策略,以及g-C₃N₄/Ti₃C₂异质结的作用机理、制备方法和在光催化析氢、有机物降解及合成等领域的应用。     

Research progress on modification strategy of g-C3N4 and g-C3N4/Ti3C2 heterojunction

Graphite phase carbon nitride (g-C₃N₄) is a kind of metal-free semiconductor material with a forbidden band width of about 2.7 eV and has visible light response capability. Attributed to its good thermal and chemical stability, adjustable morphology and chemical structure, it is widely used in the field of photocatalysis. However, due to its low specific surface area and wide band gap, its response range to visible light is narrow and the recombination rate of photogenerated carriers is high, resulting in a low photocatalytic efficiency, which can be effectively improved by modification. The two-dimensional material Ti₃C₂ has a narrower band gap compared with other semiconductor materials, and the heterogeneous junction between Ti₃C₂ and g-C₃N₄ is expected to obtain a wider range of visible light absorption and higher photocatalytic efficiency. This article reviews the modification methods of g-C₃N₄ including morphology control, doping and constructing heterojunctions, as well as the action mechanism, preparation methods and applications of g-C₃N₄/Ti₃C₂ heterojunction in photocatalytic hydrogen evolution, organics degradation and synthesis, etc.     

Pt dispersion effects during NOx storage and reduction on Pt/BaO/Al2O3 catalysts

This study provides insight into the effect of Pt dispersion on the overall rate and product distribution during NOx storage and reduction. The storage and reduction performance of Pt/BaO/A₂O₃ monoliths with varied Pt dispersion (3%, 8%, and 50%) and fixed Pt (2.48 wt.%) and BaO (13.0 wt.%) loadings is reported. At low temperature (<200 °C), the differences in storage and reduction activity were the largest between the three catalysts. The amount of NOx stored increased with increased dispersion, as did the amount of stored NOx that was reduced. These trends are attributed to larger Pt surface area and Pt–BaO interfacial perimeter, the latter of which enhances the spillover of surface species between the precious metal and storage components. At high temperature (370 °C), the stored NOx was almost completely regenerated for the three catalysts. However, the regeneration of the 3% dispersion catalyst was much slower, suggesting a rate limitation involving the reverse spillover of stored NOx to Pt and/or of adsorbed hydrogen from Pt to BaO. The results indicate that the catalyst dispersion and operating conditions may be tuned to achieve the desired ammonia selectivity. For the aerobic regeneration feed, the most (net) NH₃ was generated by the 50% dispersion catalyst at the lowest temperature (125 °C), by the 3% dispersion catalyst at the highest temperature (340 °C), and by the 8% dispersion catalyst at the intermediate temperatures (170–290 °C). Similar trends were observed for the net production of NH₃ with an anaerobic regeneration feed. A phenomenological picture is proposed that describes the effects of Pt dispersion consistent with the established spatio-temporal behavior of the lean NOx trap.     

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

We compare the activity and relevant gold species of nanostructured gold–cerium oxide and gold–iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH ≥12. Both parent and leached catalysts were investigated. The activity of the leached gold–iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H₂ up to 400 °C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold–ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV–Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.     

Enhanced interfacial electronic transfer of BiVO4 coupled with 2D g-C3N4 for visible-light photocatalytic performance

A BiVO₄/2D g-C₃N₄ direct dual semiconductor photocatalytic system has been fabricated via electrostatic self-assembly method of BiVO₄ microparticle and g-C₃N₄ nanosheet. According to experimental measurements and first-principle calculations, the formation of built-in electric field and the opposite band bending around the interface region in BiVO₄/2D g-C₃N₄ as well as the intimate contact between BiVO₄ and 2D g-C₃N₄ will lead to high separation efficiency of charge carriers. More importantly, the intensity of bulid-in electric field is greatly enhanced due to the ultrathin nanosheet structure of 2D g-C₃N₄. As a result, BiVO₄/2D g-C₃N₄ exhibits excellent photocatalytic performance with the 93.0% Rhodamine B (RhB) removal after 40 min visible light irradiation, and the photocatalytic reaction rate is about 22.7 and 10.3 times as high as that of BiVO₄ and 2D g-C₃N₄, respectively. In addition, BiVO₄/2D g-C₃N₄ also displays enhanced photocatalytic performance in the degradation of tetracycline (TC). It is expected that this work may provide insights into the understanding the significant role of built-in electric field in heterostructure and fabricating highly efficient direct dual semiconductor systems.     

Ag3PO4/g-C3N4复合材料制备及其光催化性能

采用原位沉淀法制备了Ag3PO4/g-C3N4复合材料，利用XRD、SEM、TEM、UV-Vis DRS和PL等技术对其进行表征。结果显示，g-C3N4呈现二维片状结构，Ag3PO4为立方晶相的类球状结构，且均匀分布在g-C3N4表面。以亚甲基蓝（MB）为模拟污染物，考察g-C3N4与Ag3PO4的不同摩尔比对MB降解率的影响。结果表明，在Ag3PO4/g-C3N4的摩尔比为1:0.7时，Ag3PO4/g-C3N4复合材料的光催化活性最佳，可见光照30 min后MB降解率即达到100%。光催化剂稳定性较好，重复使用5次，MB降解率仍达到85.24%。降解机理研究表明，h 和e-是降解MB的主要活性物质。     

Hydrodechlorination of CCl4 over Pt/γ-Al2O3 prepared from different Pt precursors

The platinum particle size on γ-Al₂O₃ prepared from different platinum precursors such as Pt(NH₃)₂(NO₂)₂, H₂PtCl₆, and K₂PtCl₆, and its effect on hydrodechlorination (HDC) of CCl₄ with the variation of calcination temperatures was investigated. It concomitantly affects the products distribution and catalytic stability in HDC of CCl₄. To verify the effects of platinum particle size with different platinum precursors on the product distribution, the catalysts have been characterized by HRTEM and CO chemisorption, FT-IR, and TP methods (TPR, TPD and TPSR). The catalysts with small platinum particles, which possess low coordination number and electron-deficient character, favor the complete dechlorination of CCl₄ and produce CH₄ more selectively. It could be due to the strong adsorption strength of CCl₄ or the decreased activation energy of surface intermediates on small platinum particles. FT-IR studies reveal that the maximum peak position of linear-bonded CO shifted to the higher frequency with the increase of platinum particle size in all catalysts prepared from three different platinum precursors. While the selectivity to CH₄ increased with the decrease in the platinum particle size, the total amount of carbonaceous species on the platinum particles was enhanced. The larger the platinum particle, the higher the selectivity to CHCl₃ was obtained in all tested catalysts under the non-deactivating condition.     

Effect of long-term oxidation on creep and failure of Si3N4 and Si3N4/SiC nanocomposites

The high-temperature mechanical behaviour of an Si₃N₄/SiC nanocomposite and its monolithic Si₃N₄ reference material was studied after long-term oxidation treatments intended to simulate future operating conditions in a severe environment. Creep and failure at elevated temperature were significantly affected, in the direction of increased brittleness. The transition stress between the ductile range present at low stresses and the brittle range existing at high stresses was shifted to distinctly lower values. The creep resistance in the low-stress range was increased by the oxidation treatment. The failure time under a given stress was drastically reduced; this was attributed to an increased sensitivity to subcritical crack growth. The failure stress for a given failure time was decreased by about half. The phenomena are explained in terms of a purification of the intergranular phase and by the formation of surface defects and of a uniformly distributed pore population.     

Pt/C催化加氢3-氯-4-甲基硝基苯制备3-氯-4-甲基苯胺

3-氯-4-甲基苯胺是合成有机颜料、染料和农药的重要有机中间体。以3-氯-4-甲基硝基苯为原料,1%Pt/C为催化剂,低压催化加氢制备3-氯-4-甲基苯胺,考察不同溶剂、反应压力、反应温度和催化剂用量对产物收率的影响。结果表明,在3-氯-4-甲基硝基苯10 g、溶剂甲醇用量30 m L、1%Pt/C催化剂用量0.04 g、反应温度80℃和反应压力1.0 MPa条件下,3-氯-4-甲基苯胺收率99.08%,脱氯率0.2%,催化剂可重复使用5次。     

Ag3PO4/g-C3N4复合材料的制备及其光催化性能

以硝酸银和三聚氰胺为原料,采用原位沉淀法制备了Ag3PO4/g-C3N4复合材料,利用XRD、SEM、TEM、UV-Vis DRS和PL等技术对其进行了表征.结果显示,g-C3N4呈二维片状结构,Ag3PO4为立方晶相的类球状结构,且均匀分布在g-C3N4表面.以亚甲基蓝(MB)为模拟污染物,考察g-C3N4与Ag3P...