Microstructure of Alumina Composites Containing Niobium and Niobium Aluminides

The microstructures of niobium-based alumina composites prepared by pressureless sintering of compacts of attrition milled Al₂O₃, Nb, and Al powder mixtures were studied. The addition of a small amount of Al is assumed to assist in rapid sintering. X-ray diffraction analyses show that Al₂O₃, Nb, NbO, and the intermetallics AlNb₂ and AlNb₃ are present in the composites. Electron microscopy studies confirm the existence of these phases and reveal dense, fine-grained (≤500 nm) composites. Al₂O₃ and Nb grains form the matrix. NbO occurs as grains and additionally as small particles within Al₂O₃ grains and at Al₂O₃/Al₂O₃ grain boundaries. The intermetallic AlNb₂ and AlNb₃ phases do not exceed 300 nm in size if they occur at grain boundaries, and possess even smaller dimensions when occluded within Al₂O₃ grains or located at Al₂O₃ triple junctions. While the niobium intermetallics are expected to form during the heating cycle before reaching the sintering temperature, the NbO is assumed to form during the cooling cycle due to precipitation of oxygen dissolved in the niobium.     

氧化铌/木质活性碳纤维复合材料的结构性能表征

以木质活性碳纤维(ACHF)为载体,通过浸渍草酸铌以及改变煅烧温度,制备出不同煅烧温度(400、600和800℃)下的氧化钯/木质活性碳纤维(Nb2O5/ACHF).采用扫描电镜(SEM)、X射线衍射(XRD)、X光电子能谱(XPS)和全自动比表面积与孔径分析(BET)仪对制备的氧化铌/木质活性碳纤维结构、表面孔径等进...     

Synthesis and Morphology of Niobium Monocarbide Whiskers

Niobium monocarbide (NbC) whiskers were successfully synthesized by heating mixtures of niobium oxide (Nb₂O₅) powder and carbon black in an argon atmosphere to temperatures in excess of 1100°C. The whiskers were mainly cuboid or cycloid needles with a square-pyramid-shaped tip and were 0.1-2.0 µm in width and 5-100 µm in length. The particular shape of the whiskers and the very low impurity levels detected suggest that the NbC whiskers grew via a solid-vapor growth process.     

铌酸钾的合成、表征及性能研究

相比于PZT等铅基压电陶瓷,碱金属铌酸盐陶瓷具有下列特点:介电常数小,压电性高,频率常数大,密度小,因此多年来常被作为电光材料。铌酸钾作为一种典型的铌酸盐化合物,具有良好的催化活性、选择性及稳定性,本文系统介绍了铌酸钾粉体的性质,制备方法、表征以及性能研究的现状。     

Synthesis and Characterization of Nanocrystalline Niobium Nitride Powders

Nanocrystalline NbN powder was synthesized by the direct nitridation of amorphous Nb₂O₅ powder with high BET surface area. X-ray diffractometry analysis indicated that the cubic-phase NbN powder could be obtained by nitridation at 650°–800°C for 3–8 h. Transmission electron microscopy images showed that the particle sizes were in the range of 15–40 nm. The effect of the nitridation temperature and holding time on the powder properties was discussed.     

Synthesis of New Nanocrystalline Titanium–Niobium Oxynitride Powders

New titanium–niobium oxynitride (Ti_{1− z} Nb _z O _x N _y ) powders were synthesized by ammonolysis of nanosized TiO₂/Nb₂O₅ composite powders at 700°–900°C for 5 h. The products were characterized by X-ray diffraction (XRD), chemical analysis, and transmission electron microscopy. The results indicated that the as-synthesized powders were pure cubic structures with sizes of 30–60 nm. With increasing value of z , XRD peaks of Ti_{1− z} Nb _z O _x N _y powders tended to shift toward low 2θ angle and the cell parameter showed a linear increase.     

新型复合材料在骨伤科的应用

传统石膏绷带是用于帮助骨伤病人固定肢体的材料,但由于其具有质量重、不透气等缺点,给病人带来诸多不便。随着科技的发展,新型复合材料以其轻质高强、对X射线透明等优点开始逐渐取代传统石膏绷带,在医疗领域得到应用。文中系统地阐述了新型玻璃纤维医用高分子绷带、夹板及柔韧型高分子绷带的特点和应用。     

Reaction-Bonded Niobium Carbide on Graphite via a Novel Solution Impregnation Process

A simple and rapid process has been developed that allows the preparation of NbC-C composite rods. Graphite rods are impregnated with an ethanolic solution of NbOCl₂ and resistively fired (> 1900°C) under an argon atmosphere. The final composite product is found to contain residual carbon particles within a NbC-C matrix.     

新型石蜡基复合材料的研究进展

石蜡基复合材料具有不同的组成和结构,包括氧化物/石蜡、单质/石蜡、聚合物/石蜡等二元复合材料以及石蜡基三元复合材料。它们具有优异的物理和化学性质,在众多领域里显示出广阔的应用前景,如润滑与摩擦学、储能材料和传感器等领域。制备具有新颖组成和结构的石蜡基复合材料及其应用研究已经成为复合材料领域的研究前沿和热点之一。综述了新型石蜡基复合材料的组成、制备以及应用的研究进展,探讨了该研究领域亟待解决的问题以及今后可能的发展前景。     

Synthesis of Niobium(V)-Stabilized Tetragonal Zirconia Nanocrystalline Powders

The polymer precursor method is very useful to prepare Nb⁵⁺-stabilized nanocrystalline powders of t -ZrO₂. The precursor solution is composed of zirconium oxalate, niobium tartrate, and poly(vinyl alcohol), which help to form a network matrix to disperse the metal ions homogeneously. Nb⁵⁺ is an effective agent to stabilize t -ZrO₂, and ease of formation of the tetragonal phase increases with increasing dopant concentration. Thermal stability of t -phase is found up to 1700°C having 15 mol% Nb⁵⁺, prepared at 600°C with particle sizes of 35 ± 5 nm.     

丁腈橡胶/聚氨酯复合材料用相容剂的合成及复合材料的性能研究

利用端羟基液体丁腈橡胶（HTBN）分别与二苯基甲烷二异氰酸酯（MDI）和对氯苯基异氰酸酯（4CPI）反应制备HTBN-聚氨酯（PU）和HTBN-4CPI两系列相容剂,研究其对采用机械共混法制备的丁腈橡胶（NBR）/PU复合材料性能的影响。结果表明：加入相容剂后,NBR和PU的相容性得到有效改善,NBR/PU复合材料的拉伸强度和储能模量增大,磨耗性能提高,当HTBN-4CPI质量分数为0.98%时,NBR/PU复合材料的拉伸强度和储能模量最大,磨耗性能最佳,其中拉伸强度增大35%,磨耗量减小56%。     

Synthesis and Characterization of Novel Polyurethane Composites Based on Hybrid Inorganic/Organic Phosphazene‐Containing Microspheres

Novel polyurethane (PU) composites were prepared, based on hybrid inorganic/organic phosphazene‐containing microspheres. The FT‐IR spectra have shown that the microspheres have been linked with PU matrix. The microstructure of the composites is investigated by SEM. In comparison with PU, the glass transition temperatures and thermal stability of the composites are increased. The results from tensile testing of the composites have indicated that tensile strength is improved and elongation at break is almost invariable. The investigation on the surface properties of the composites showed that the water contact angles are obviously increased by adding 2 and 4 wt.‐% microspheres to the matrix.

     

Synthesis and Application of Novel Nano Fe-BTC/GO Composites as Highly Efficient Photocatalysts in the Dye Degradation

Topics in Catalysis - Nano Fe-BTC/graphene oxide (GO) composites were successfully synthesized by hydrothermal treatment with a microwave-assisted method. Samples were characterized by X-ray...     

Cyclic Fatigue Life‐ and Crack‐Growth Behavior of Zirconia–Niobium Composites

A 3Y‐TZP/Nb composite fabricated by Hot‐pressing (HP) sintering with well‐distributed lamellar/flake–shaped metal particles (20 vol% fraction) has been studied under cyclic loading. Fatigue life was determined for the ceramic/metal composite as well as for monolithic zirconia to compare the sensitivities of both materials to cyclic stresses. In both cases, the fatigue test was performed according to ISO 6872. It was found that the 3Y‐TZP/Nb composite exhibits fatigue behavior which was compared with monolithic zirconia. The growth of fatigue cracks influences the bridging actions of the metallic grains and causes significant degradation in the mechanical properties of the composite material.     

Novel Process for the Preparation of Fiber-Reinforced Ceramic-Matrix Composites

A procedure for the reproducible production of monofilament/powder composites has been developed. The process consists of making a slurry of the powder in a solventless ultraviolet-curing resin, and coating the fiber with this slurry in a continuous process whereby the coating solidifies immediately after leaving the coater. The fast curing prevents the breakup of coating into globules, which usually occurs with monofilaments. This technique can be applied to any composite using continuous filaments and matrices available in the form of particulate precursors. The application of the technique for preparing a silicon carbide monofilament/glass composite is demonstrated.     

Combustion Synthesis of Silicon Nitride-Silicon Carbide Composites

The feasibility of synthesizing silicon nitride-silicon carbide composites by self-propagating high-temperature reactions is demonstrated. Various mixtures of silicon, silicon nitride, and carbon powders were ignited under a nitrogen pressure of 30 atm (∼ 3 MPa), to produce a wide composition range of Si₃N₄-SiC powder products. Products containing up to 17 vol% of SiC, after being attrition milled, could be hot-pressed to full density under 1700°C, 3000 psi (∼ 21 MPa) with 4 wt% of Y₂O₃. The microhardness and fracture toughness of these composites were superior to those of the pure β-Si₃N₄ matrix material and compared very well with the properties of "traditionally" prepared composites.     

Glass-Reinforced Composites Based on a Novel Oligoimide-Epoxy Resin System

A novel matrix resin system, oligoimide-epoxy resin, has been developed to prepare glass fiber reinforced composites. Benzidine bismaleimide-diaminodiphenyl methane (BBM-DDM) and ethyl-ene bismaieimide-diaminodiphenyl methane (EBM-DDM) oligo-mers having more —NH₂ groups were prepared through the Michael addition reaction. These oligoimides were used for curing of commercial epoxy resin (i.e., diglycidyl ether of bisphenol-A) at 120°–140°C to fabricate crosslinked oligoimide-epoxy resin glass fiber reinforced composites without the evolution of byproduct. The fabricated composites (i.e., laminates) were characterized by their chemical resistance and mechanical properties.     

3,4-二氯苯胺的合成新工艺

以邻二氟苯为原料,经硝化、还原两步合成3,4-二氟苯胺。混酸的组成为2:1(硫酸:硝酸),硝酸与邻二氯苯的摩尔比为1.6:1,反应温度为60℃-70℃,3,4-二氯硝基苯的收率为90.43%;用铁粉作还原剂,其反应最佳条件为邻二氯苯:氯化氨:铁粉的摩尔比为1:2.73:4.3,3,4-二氯苯胺收率达99%,并经FT—IR进行了表征。     

环氧虫啶的合成新工艺

介绍了一种环氧虫啶的合成新方法。以硝基二氯乙烯为原料,先通过硝化得到二甲氧基硝基乙烯,经环合反应合成硝基亚甲基咪唑烷,再经过缩合反应制得重要中间体氯吡啶硝基亚甲基咪唑烷,最后与丁二醛通过成环反应合成环氧虫啶。该合成工艺原料易得,操作简便,反应条件温和,产品含量97%,具有工业化应用前景。关键词:环氧虫啶;丁二醛;     

新型喹诺酮类衍生物的合成

以4-硝基愈创木酚、乙氧甲叉基丙二酸二乙酯、2-琉基苯并噻唑等为原料,经烃化、还原、缩合、环合、水解、缩合酰化等反应合成了2个喹诺酮-3-甲酰胺类衍生物、2个喹诺酮-3-甲酸硫酯类衍生物,化合物结构经核磁氢谱、质谱确证,结构未见文献报道,为新型喹诺酮类小分子药物的研究提供了化合物基础.