机械热化学法制备的Mo-Cu复合粉末及其性能

钼酸铵热解氧化物与铜粉经过球磨混合后,在H2气氛下进行共还原,制得Mo-30Cu复合粉末,利用X射线衍射、SEM等测试分析手段对复合粉末进行表征,研究粉末的压制行为和烧结性能,并研究烧结温度对Mo-Cu合金的致密度、热导率和电导率的影响。结果表明:采用机械-热化学法可以制备出颗粒均匀的Mo-Cu复合粉末,该粉末具有良好的压制性;随烧结温度的升高,Mo-Cu合金的致密度、热导率和电导率提高,经1 280℃烧结后,合金的致密度可达99%以上,显微组织分布均匀,合金的热导率最高达到196.5(W.m-1.K-1),电导率达50.5 IACS。     

MAC粉烧结性能的研究及工业实践

针对MAC矿粉在唐钢烧结中使用的可行性开展了铁矿粉物理化学性能、烧结性能的试验研究,通过生产试验,确定了MAC矿粉在烧结混料中的适宜配比.     

Effects of the penetration temperature on structure and electrical conductivity of samarium modified BaTiO3 powders

Gaseous penetration technique was adopted to improve the electrical conductivity of BaTiO3 powders and the effects of penetration temperature on the structure and electrical conductivity of Sm-modified BaTiO3 powders were studied.It was observed that the penetration of Sm made the resistivity of BaTiO3 powders decrease with the increase in the penetration temperature and decreased to the lowest point of 4.20×102 ?·m when the penetration temperature was 950 oC.The relationship curve of the temperature and resistivity of the samples was also established preliminarily to get the mathematical expression by the fitting method.Through X-ray diffraction (XRD) analysis,the new phases of Sm2O3 and Ba4Ti2O27 were detected.It was indicated that intricate reactions related to Sm took place during the penetration process and led to the Ti-rich state of the system.The Fourier transform infrared (FTIR) spectrum illustrated that the bonds of Ti–O octahedron was strengthened by substitution of Sm3+ at Ti4+ sites,which led to the growth of Ti:Ba ratio.The analysis results of scanning electron microscopy (SEM) indicated that the particle size of Sm-modified BaTiO3 powders progressed with the penetration temperature increasing.     

改善铁矿烧结透气性的节能装置

烧结的混合料中透气不足,则煤燃烧速度慢且不充分,放热少,影响产量和质量;如果透气过多、过快,烧的时间不够,同样影响产量和质量.松料器和透气板可使混合料中空气量适度、分布均匀,煤燃烧充分,提高产量和质量,降低煤耗.     

Character of electrical resistivity variation in the sintering of ultrafine powders

Conclusions As a result of oxidation of compacts from nickel and copper UFPs, their electrical resistivities may vary within a wide range. During the vacuum sintering of nickel and copper UFPs changes in electrical resistivity are recorded before densification. During heating the electrical resistivity of compacts may fall at a rate of up to half an order a minute. Measurements of and L/L during repeated heating-and-cooling cycles reveal increases in the electrical resistivity and elongation of specimens, which may be linked with elastic after-effect phenomena. A small rise in electrical resistivity during heating to 100C may also be brought about by elastic stress relaxation. An increase in electrical resistivity accompanied by shrinkage during a rise in temperature after isothermal sintering is indicative of rupture of contacts during densification; the extent of this process, which may be linked with sliding of whole particles relative to one another, diminishes with rise in temperature.Translated from Poroshkovaya Metallurgiya, No. 2(266), pp. 24–28, February, 1985.     

Microstructural changes in Mo steels during sintering and effect on electrical conductivity

Abstract

An electrical conductivity measurement method was used for studying the sintering mechanism and microstructural changes of low alloyed PM Mo steels in a temperature range between 600-1300°C. The influences of alloying method (elemental or prealloyed), Mo content (1·5 and 3·5 wt-%), and sintering temperature were investigated. The results show that the effects of, for example, formation of Mo carbide(s), ferrite-austenite phase transformation, as well as liquid phase formation during heating of the steel compacts can be detected by the technique cited. Mo dissolution during sintering of compacts from mixed powders results in a decrease of the conductivity with increasing sintering temperature while compacts from Fe-Mo prealloyed powders exhibit the standard behaviour of higher conductivity after sintering at higher temperature. Moreover, the relationship between Mo dissolution, formation of sintered contacts, and mechanical properties was demonstrated to assess the viability of the conductivity measurement method for studying the sintering behaviour of PM materials and its influence on physical and mechanical properties. An approach was also demonstrated for relating the conductivity to the microstructural parameters, e.g. total porosity and contiguity between solid phase, that would be useful for predicting relative changes in mechanical properties dependent on porosity and pore morphology.     

Synthesis and crystal structure of novel samarium coordination polymer derived from sulfonic acid ligand

The self-assembly of HL(L=[5-(ethoxycarbonyl)-4-phenyl-3,4-dihydropyrimidin-2(1H)-one-6-yl]methanesulfonate) with Sm(ClO4)3·6H2O yielded a 2D coordination polymer {[SmL3(H2O)2]·4H2O}n(1).Its crystallographic data indicated that it belonged to a triclinic system,space group P-1,a=1.42233(8),b=1.47155(8),c=1.53868(9) nm,α=8.62710(10),β=6.35250(10),γ=71.5790(10)°,V=2.7241(3) nm3,Z=2,R1=0.0693,wR2=0.1054.X-ray analysis revealed that the local coordination environment around Sm(III) was a slightly distorted dodecahedron in which Sm center was eight-coordinate geometry with eight oxygen atoms from three sulfonic groups,three carbonyl groups and two aqua ligands.Each L-acted as a bidentate spacer to link two Sm centers,resulted in the formation of a 2D hexagonally grid network.The discrete 2D planes in 1 were assembled into a 3D supramolecular network via strong hydrogen bonds among noncoordinated aqua O atoms,coordinated aqua O atoms,and noncoordinated O atoms of sulfonic groups and carbonyl groups.Furthermore,this metal-organic polymer exhibited strong photoluminescence maximized at 379 nm upon 274 nm excitation in the solid state at room temperature.     

Synthesis and photocatalytic property of Ce-doped SnO2

Pure SnO₂ and Ce-doped (1%, 4%, 7%, 10% in mass ratio) SnO₂ powders were prepared by a simple sol-gel method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) specific surface area analyzers. Results showed that the 7% Ce-doped sample has a particle size of 0.1-0.3 μm with a narrow particle size distribution while the pure SnO₂ was consisted of large agglomerated particles with a diameter up to several micrometers. When used as the catalyst to degrade methyl orange (MO), the 7% Ce-doped sample showed best photocatalytic property. These properties can be attributed to the large surface area and small particle size of the 7% Ce-doped sample.     

Reflectivity of powders and valence state of samarium in its selenides of variable composition

Translated from Poroshkovaya Metallurgiya, No. 12(312), pp. 58–61, December, 1988.     

甘氨酸硝酸盐法制备超细Mo-Cu粉末及烧结

以四水合钼酸铵（（NH4）6Mo7O24·4H2O）、硝酸铜（Cu（NO3）2·3H2O）、甘氨酸和乙二胺为原料采用甘氨酸硝酸盐法（GNP）制备前驱体粉末,经过700℃氢气还原2 h得到Mo-Cu 复合粉末,经压制后进行真空烧结,研究不同烧结温度对Mo-Cu 烧结体性能的影响.结果表明：甘氨酸-硝酸盐法（GNP）制备的超细Mo-Cu 复合粉末形状规则、大小均匀、钼铜两相弥散分布,颗粒大小平均为50~80 nm.在950~1250℃范围内,随着烧结温度的升高,烧结体的硬度增大,致密度、电导率和热导率在1150℃达到最大值.     

烧结条件与组成对含Cr粉末冶金钢力学性能的影响

对先进铁基粉末冶金材料的期望,已导致开发了更接近模拟锻钢组成的合金.像Cr等传统锻钢合金化元素,已用于提高力学性能与淬透性,而且成本可行.过去在粉末冶金中避免用铬是因为与氧相关的问题,但现在较新的合金系都含有这种元素.尽管这些合金可提供良好的力学性能与生产总成本可行,但这些合金的适当烧结仍是关键性问题.将介绍烧结条件与...     

Polymer-encapsulated Sm-doped nano-hydroxylapatite and its antibacterial property

Hydroxylapatite（HAp）,owing to its excellent biocompatibility,is a promising carrier for lanthanide ions to encourage antibacterial activity.However,hydroxylapatite powder would still require modification to ensure the optimal integration of antibacterial characteristics.In this study,Sm-doped nano-hydroxylapatite（SmHAp） was synthesized by spontaneous mineralization of amorphous SmHAp precursors,which ensures a homogeneous distribution of Sm³⁺ within bulk SmHAp.Powder X-ray diffraction and its Pawley fitting results for SmHAp indicate the lattice substitution of Ca²⁺ with Sm³⁺,resulting in the lattice distortion in SmHAp compared to pure HAp.Meanwhile,polymer-encapsulated Sm-doped nano-hydroxylapatite composite（p＿SmHAp） was synthesized by a dual-step polymerization involving UV curing of an outer crust and heat treatment for bulk reaction completion.Irgacure 2959 and a toluene solution of AIBN were used as catalysts for the radical polymerization process.The antibacterial property of p＿SmHAp was evaluated by observing the growth of Sporosarcina pasteurii（ATCC 11859） both in the solid and the liquid medium,correlating with the Sm fraction and SmHAp's crystallinity in p＿SmHAp.These bacteriostatic rings' diameters exceed 20 mm,demonstrating that p＿SmHAp with a SmHAP/p＿SmHAp mass ratio of 0.1 and Sm/（Ca+Sm） molar ratio of 0.05-0.1 effectively releases Sm³⁺,serving as a strong antibacterial agent.     

固相烧结低钨含量W-Ni-Fe合金的微观结构与力学性能

采用固相烧结工艺(1 300℃保温1 h)制备低钨含量(质量分数为60%~80%)的W-Ni-Fe合金,测定合金的抗拉强度、抗压强度和伸长率,利用金相显微镜观察合金的显微组织,并通过扫描电镜(SEM)观察合金断口形貌,研究钨含量对固相烧结W-Ni-Fe合金力学性能与微观结构的影响。结果表明:随钨含量降低,合金的孔隙率和平均孔径减小,抗拉强度增大,伸长率显著提高,抗压强度变化不大。W含量为60%~80%的W-Ni-Fe合金,其孔隙率为17.8%~21.4%,抗拉强度为231~262 MPa,抗压强度2 450~2 550 MPa,伸长率为0.3%~2.3%,压拉比为9.45~11.04,都能满足易碎型穿甲弹弹芯材料的性能要求。