硫化钐中硫和钐的分离与测定

研究了一种可同时测定硫化钐中硫和钐含量的方法。硫化钐样品经氢氧化钠、过氧化钠熔融,将负二价硫全部氧化为正六价,经两次氨水分离,滤液在pH值为2~5的条件下,煮沸加入氯化钡溶液沉淀硫酸根,计算硫含量;氨水分离两次后的氢氧化钐沉淀经盐酸酸化后,用EDTA标准溶液滴定,测定钐含量。通过正交实验确定了熔样条件为550 ℃熔融10 min,氯化钡溶液沉淀硫酸根时沉淀不需陈化;由方差分析得出氨水分离次数和沉淀pH值为影响实验结果的显著因素,进一步试验确定氨水分离次数为2次、沉淀时pH值为2~5;此外,通过实验证明方法采用镍坩埚熔样所引入的镍并不影响测定结果。按实验方法对硫化钐样品进行精密度考察,硫和钐测定结果的相对标准偏差(RSD)分别为0.73%、0.18%;加标回收试验表明,硫和钐的回收率分别在101%~103%、100%~102%之间。采用实验方法对两个硫化钐样品进行测定,并分别与氯化钡滴定法测定硫及草酸盐重量法测定钐的结果进行对照,吻合较好。实验方法相比单元素测定法,避免了重复熔样,减少了样品预处理过程,实现了硫和钐的联合测定,可用于日常生产分析。     

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.     

Effect of samarium oxide on structural,optical and electrical properties of some alumino-borate glasses with constant copper chloride

The glass system under study was prepared and examined using the melt quenching procedures and XRD to emphasize the amorphous nature,respectively.Transmittance of the prepared solid glass system was performed by a spectrophotometer in wavelengths from 190 to 1099 nm.Using traditional techniques and standard formulas,the density,molar volume,refractive index,optical band gap and the optical filter characteristics were determined,then the influence of samarium oxide on some properties like the structure and optical,also the electrical properties were dissected.A novel formula was proposed to estimate the refractive index from the optical energy gap.The obtained samples are good optical filters especially the sample that contains 0.8 mol% of Sm_2 O_3.Also this sample has the utmost density,the least molar volume,the maximum transmittance,least refractive index,the highest optical band gap and the least dc conductivity.     

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.     

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.     

铁矿粉烧结基础特性之同化性研究进展

烧结矿在中国高炉的入炉炉料中所占比例为70%左右,烧结工序能耗占钢铁生产能耗的8%～10%,合理优化烧结配矿过程有利于钢铁企业增产降耗。利用铁矿粉烧结高温基础特性指导优化配矿更符合生产实际,基础特性中的同化性反映铁矿粉与CaO熔剂形成液相的难易程度,影响烧结矿的矿物组成、冷态性能及冶金性能,近年来相关研究取得了较大的进展。首先总结了铁矿粉同化性的研究历程,以及当前同化性检测的方法及设备,探讨了各种方法的优缺点,随后分析了不同铁矿粉化学成分等对最低同化温度的影响。结果表明,随着SiO₂、Al₂O₃含量的增加,最低同化温度先降低后升高;MgO、(Al₂O₃+SiO₂+MgO)含量的增加使最低同化温度升高。对不同含铁矿物而言,一般表现为褐铁矿同化性优于赤铁矿,磁铁矿的同化性最差。最后,在前人研究的基础上,基于烧结工艺、优化配矿以及实践经验,总结并探讨了现阶段存在的问题,并尝试提出了未来相关研究的方向。     

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...     

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.