钽粉中碳的来源及其对电性能影响的研究

主要介绍了钽粉中碳杂质的来源以及不同碳含量对钽粉电性能的影响,重点分析了不同碳含量对钽粉电性能的影响,并提出了有效控制钽粉中碳杂质含量的建议,以求达到降低钽粉中碳杂质含量的目的。     

氟钽酸钾中控制碳量原因及剔除方法

简述了碳对冶炼金属钽粉的影响，进而阐述氟钽酸钾中碳含量必须受到的控制的原因，以及湿法钽铌冶炼剔除碳的方法。     

真空碳脱氧回收废钽工艺研究

分析了真空碳脱除钽中氧的热力学条件，研究了保温温度、保温时间对真空碳脱氧效果的影响，用碳处理废钽的工业扩大试验获得了含Ｏ０．１７％、Ｃ０．０３％的合格冶金级钽粉。     

真空热处理炉炉况对钽粉碳含量影响因素分析

分析了真空热处理炉炉况管理对钽粉碳含量的影响因素,重点分析了不同热处理温度、真空阀加装限位、油扩散泵冷凝壁冷却水连接方式,油扩散泵关闭维持泵后不同管道真空、扩散泵障板冷却方式、油扩散泵壁不同回水温度对钽粉碳含量的影响。研究表明较高的烧结温度能够有效地降低钽粉中的碳含量,可提高真空炉空载烘炉温度;真空炉真空阀未加装限位器较加装限位器生产钽粉碳含量明显偏高,真空炉的真空阀需加装限位器有效实现阀门的连锁开启关闭;油扩散泵冷凝壁冷却水连接方式采用下进上出的方式生产钽粉的碳含量明显偏高,油扩散泵冷凝壁冷却水应采用上进下出的方式;扩散泵前级管道在关闭维持泵6h后的管道压力越大碳含量越高,应保证扩散泵的管道在一定压力范围内;油扩散泵障板处采用氟利昂制冷的碳含量较采用水冷的碳含量明显偏低;扩散泵泵壁出口温度偏高,可在扩散泵泵壁出口端增加增加泵,有效碳解决了出口温度偏高、真空炉生产钽粉的碳含量偏高的问题。     

电容器级钽粉的生坯强度

用电容器级钽粉压成活于制作于固体电解电容器阳极的坯块。压缩测定其生坯强度。研究了钽粉中非金属杂质的含量,钽粉的比表面积,存放时间,松装密度,钽粉粒度分布,颗粒开头及颗粒强度对生坯强度的影响。     

高氧钽粉配碳生产低氧钽条的工艺研究

对高氧钽粉生产低氧钽条工艺进行了研究,结果表明：采用高氧钽粉配碳预烧结、还原的方法可以生产出低氧优质钽条,与镁处理法相比,该法工艺简单、节能降耗,经济效益明显。     

碳还原法制取高压、高比容(63V 2800μFV/g)钽粉的研究

本文对碳还原法生产高压、高比容(63V 2800μFV/g)钽粉的工艺过程进行了研究,对工艺技术条件及所产钽粉的性能也作了较为详细的介绍。     

表面活性剂在钽粉球磨工艺中的应用研究

介绍了一种钽粉湿式球磨的方法,通过向球磨介质中加入表面活性剂对钽粉进行球磨,获得片状钽粉,在减少了球磨时间的同时,所得片状钽粉粒度更为均匀,且钽粉金属杂质含量更低,最终产品的耐击穿性能提高,漏电流得到改善。     

从片状钽电容器的发展看我国钽工业面临的形势和侨务

本文首先剖析了国外钽电容器及钽粉的发展状况，指出，随着电子工业的飞速发展，片状钽电容器、钽粉工业也得到了长足的进步，从发展观点看，钽产品的市场前景可观；其次，本文总结分析了我国钽工业技术产品发展现状及同国外的差距；最后，论述了促使我国钽工业技术进步，应重视的实际问题和该行业的任务     

钽粉坯块强度的测试

介绍了测定钽粉坯块强度的方法,用坯块强度直观地描述钽粉的成型性。试验结果表明:钽粉的成型性主要是由钽粉的平均粒径和颗粒形状决定的,也与某些杂质含量有关。     

C/C基体密度对C/C-SiC-ZrC复合材料性能的影响

分别以密度为1.26 g/cm~3和1.46 g/cm~3的C/C复合材料作为基体材料,用有机硅和乙酸锆作为先驱体,采用先驱体浸渍裂解法(precursor infiltration pyrolysis,PIP)制备C/C-SiC-ZrC复合材料,利用X射线衍射仪(XRD)、扫描电镜(SEM)和能谱分析(EDS)等检测手段分析该复合材料的成分和微观结构,研究C/C基体密度对材料抗压强度、线膨胀系数以及抗烧蚀性能的影响。结果表明,C/C基体密度为1.46 g/cm~3时C/C-SiC-ZrC复合材料的抗压强度较高(146.36 MPa)、线膨胀系数较小。C/C基体密度为1.26 g/cm~3的C/C-SiC-ZrC复合材料具有更优的抗烧蚀性能,经过30 s烧蚀后,其质量烧蚀率和线烧蚀率分别为-2.9×10-4g/s和1.7×10-3 mm/s,这主要是因为C/C基体密度较低时,材料中的陶瓷含量更高,当烧蚀发生时,能更快地在材料表面形成SiO_2-ZrO_2氧化物薄膜,从而减缓材料内部基体的进一步烧蚀。     

快速更换连铸中间包水口的应用实践

高效化连铸的实现，必须对其浇注过程中的每一个环节进行严格的控制，否则将直接影响到连铸的产品质量，快速更换水口技术的应用从根本上解决了困扰连铸实现连铸的难题，而且是提高连铸机经济效益的有效途径。     

纤维体积分数对炭/炭复合材料性能的影响

通过对不同纤维体积分数的炭/炭复合材料进行力学性能,导热、导电性能试验,分析了纤维体积分数对炭/炭复合材料性能的影响.结果表明,初始坯体的纤维体积分数对炭/炭复合材料的力学性能影响较大;导热、导电性能则与材料内部结构有关而与纤维体积分数的关系不大.当预制坯体的纤维体积分数在25％～30％时,炭/炭复合材料的力学、导热、导电性能为最好.     

Evidence for the involvement of arginine 462 and the flanking sequence of human C4 beta-chain in mediating C5 binding to the C4b subcomponent of the classical complement pathway C5 convertase

Replacement of human C4 beta-chain residue arginine 458 by tryptophan, a substitution that occurs naturally in the hemolytically inactive A6 allotype of C4, totally abrogates the molecule's ability to act as a C5 binding subunit of the classical pathway C5 convertase. Hydropathy plots predict R458 to be within a hydrophilic segment extending from residue 455 to 469 and having the sequence SIERPDSRPPRVGDT. To further assess the potential involvement of this segment in the C5 binding function of C4, we have engineered "ala-scan" mutants through this segment, concentrating predominantly on charged residues, and analyzed their functional profiles. C4B isotype mutant proteins S455A (0.7), E457A (1.1), R458A (0.3), D460A (0.2), R462A (0.0), R465A (0.6), and D468A (0.3) displayed the relative to wild-type hemolytic activities indicated in the parentheses. In all cases, the hemolytic defect was accounted for solely at the C5 convertase stage. The total absence of C5 binding activity in the R462A mutant suggests a requirement for the guanidinium group per se, because mutants with a charge-conservative lysine or a relatively isosteric methionine at this position were also completely inactive. In contrast, the inactivity of the C4A6-like R458W mutant is probably caused by the intolerance of tryptophan in a hydrophilic segment, as substitution of R458 by alanine or methionine yielded recombinant molecules that retained 30% and 60% of wild-type hemolytic activity, respectively. Taken together, the mutagenesis results strongly imply that residues in the 455-469 segment contribute to the C5 binding site in C4; however, the conformational context of the segment appears to be crucial, as a synthetic peptide corresponding to this segment displayed no ability to inhibit C5 binding to surface-bound C4b.     

浸渍工艺对炭/炭复合材料力学性能的影响

通过对浸渍前后C/C复合材料抗弯性能、剪切性能和耐压性能的比较,分析了浸渍工艺过程对C/C复合材料力学性能的影响.浸渍工艺使C/C复合材料力学性能有明显改善:抗弯强度由浸渍前的101MPa提高到浸渍后的159 MPa,剪切强度由浸渍前的8.6 MPa提高到浸渍后的12.1MP,抗压强度由浸渍前的82 MPa提高到浸渍后的136 MPa.浸渍前后C/C复合材料断口的扫描电镜照片分析可得出浸渍工艺的炭生长层有与CVD工艺类似的微现结构的结论.     

A kinetic nephelometric method for the assay of serum C3 and C4

A two-point, fixed interval kinetic, nephelometric method for the immunoassay of serum C3 and serum C4 using a laser-modified, centrifugal fast analyzer is described. The procedure shows a precision of 2.45 percent (coefficient of variation, C.V.) for C3 at a mean concentration of 151 mg per dl and 3.65 percent (C.V.) for C4 at a mean concentration of 26.6 mg per dl. The kinetic method was found to give a satisfactory correlation with a continuous flow immunonephelometric procedure.     

纳米SiC对C/C复合材料石墨化与抗氧化性能的影响规律

本文制备纳米SiC基体改性的SiC-C/C复合材料,利用X射线衍射技术、高分辨率透射电镜等研究SiC对碳材料的石墨化度的影响.纳米SiC能够显著促进碳基体材料的石墨化度,同时通过高分辨率透射电镜在纳米SiC颗粒周围观测到明显的石墨化结构,并且距离SiC越近,碳基体的石墨化程度越高.通过静态氧化实验研究SiC-C/C复合材料的抗氧化性能.结果表明,随着SiC加入量的增加复合材料的抗氧化性显著提高,纳米SiC在高温下生成较为均匀的SiO₂保护层,覆盖在碳材料的表面,阻碍氧气与碳材料的接触,并且SiC含量越高,形成的保护层越厚,抗氧化能力越强.      

Sn-C and Al-Sn-C phase diagrams and thermodynamic properties of C in the alloys: 1550 °C to 2300 °C

In research conducted by the United States Bureau of Mines, the Sn-C and Al-Sn-C phase diagrams were determined over the temperature range of 1550 °C to 2300 °C by chemical anal-ysis of alloys saturated with carbon within sealed graphite crucibles. Carbon forms a dilute solution in tin described by log [at. pct C] = 2.9767-12,082.35/T, whereT is temperature in Kelvin. Isothermal sections for the ternary system were determined at intervals of 150 °C over the range of temperatures investigated. The univariant points on the 1700 °C, 1850 °C, and 2000 °C isotherms were determined by metallographic examination of rapidly cooled alloys to be about 34Al-66Sn-0.1C, 49.7Al-49.7Sn-0.5C, and 70Al-27Sn-2.8C, respectively, where all concentrations are atomic percent. Graphite and A1₄C₃ (decomposition temperature 2156 °C) were the only solid phases observed at these temperatures. The excess partial Gibbs energy for dissolved C in liquid Al-Sn-C solutions in equilibrium with C, as calculated from the experi-mental solubilities, is G _C ^e = -RT ln x = y²[176.860 - 55.42T - (224,200 - 110.84T)x] + (231,400 - 18.700T)z₂ + yz[151,860 - 8.423T + (19,400 - 8.4867)z + (56,100 - 57.6577)yz - (39,800 - 40.904T)yz²], J/g · atom where R is the gas constant,T is the temperature in Kelvin, andx, y, and z are the atomic fractions of C, Al, and Sn, respectively. The equation also is a good approximation for liquid solutions in equilibrium with A1₄C₃ within about 100 °C of the decomposition temperature.     

Alternative pathway of complement: recruitment of precursor properdin by the labile C3/C5 convertase and the potentiation of the pathway

In this study the physiological role of properdin and the differential subunit composition of the solid phase enzymes of the pathway have been explored. Cell-bound C3 and C5 convertase differ in their C3b requirement. Apparently one molecule of C3b is sufficient to allow formation of C3 convertase (C3b,B), whereas two or more are required for generation of C5 convertase (C3bn,B). This conclusion was drawn from results indicating the critical role of the spacial distribution of C3b molecules on the cell surface in enzyme formation. While the C3/C5 convertase is fully capable of acting on C5 and thereby initiating the assembly of the cytolytic membrane attack complex, it is exceedingly labile and vulnerable to destruction by the C3b inactivator. It is the apparent role of properdin to confer a degree of stability upon the labile enzyme and to protect its C3 convertase function against enzymatic destruction. To achieve these effects, precursor properdin (pre-P) is recruited in a binding-activation reaction by the labile C3/C5 convertase. Multiple C3b molecules appear to be needed for the formation of properdin-activating principle. Three modes of regulation have been described, which involve spontaneous dissociation enzymatic degradation by C3b inactivator and disassembly by beta1H. The functional differences of pre-P and activated properdin (P) were delineated, pre-P displaying a weak affinity for C3b and P the capacity of strong interaction, P generating a soluble C3 convertase in serum and pre-P being unable to do so. Because of the profound differences between native pre-P and the laboratory product P, the question was raised as to whether soluble P represents an unphysiological form of the protein. On the basis of this and other studies, the conclusion was reached that in vitro properdin recruitment constitutes the terminal event of the properdin pathway, and that properdin augments the function of C3/C5 convertase without changing its substrate specificity.