容量法测定金合金中的金

对重铬酸钾滴定过量硫酸亚铁返滴定法测定金合金中金的主要问题做了探讨和实验.拟定了简便、准确的测定方法,方法的重现性好,金含量为60%～99%时的相对标准偏差＜0.2%.     

Ce在黄K金中的分布及对铸态组织影响

研究了在黄色金合金中添加不同含量微量稀土元素Ce对合金的影响,包含稀土元素Ce的黄色金合金的中间合金中,稀土在中间合金中除少量固溶在合金基体中外,其余与合金元素反应生成化合物相CeAg6在晶间析出。在金合金中,这些稀土化合物相在熔炼过程中熔入合金熔液中,当Ce含量低于固溶度时,Ce基本上均匀固溶在合金基体中,随Ce含量增加,Ce与金反应生成析出相Au51Ce14在枝晶间隙析出。当微量稀土添加到彩色金合金中时,合金晶粒及铸态组织均得到明显细化。当稀土含量增加到0．5％时,合金发生明显变质作用。微量稀土添加黄彩色金合金中,随稀土添加,合金液相温度区间增大。凝固过程中溶质再分配,造成固液界面前沿成分过冷度增大是稀土在彩色金合金中主要的晶粒细化机理。     

火试金测定锡铅金锑合金中金含量

对锡含量高的Sn-Pb-Au-Sb合金中金含量的火试金测定,作者采用熔炼、灰吹手段,解决了Sn干扰测定结果的问题.具体的作法是,用碳酸钠和硼砂配制成混合熔剂,将该混合熔剂与合金试样混合,经高温熔炼,使Sn转变成锡酸钠造渣而不进入铅扣,试样经灰吹富集形成Au-Ag合金.用硝酸分Ag,重量法测Au.合成样回收率99.93%～100.09%,相对标准偏（RSD%）为0.369%.     

永磁场对金合金二次枝晶臂间距和析出相的影响

将旋转永磁场应用于金合金的制备过程中,研究不同转速永磁场对金合金二次枝晶臂间距和析出相的影响规律,同时探讨其机理。结果表明:旋转永磁场可以使金合金凝固组织明显细化,显著降低了合金的二次枝晶臂间距,但过高的永磁体转速使合金熔体的集肤效应显著增大,减小了永磁场的作用范围,使熔体心部磁感应强度减小,二次枝晶臂间距反而增大。对金合金施加永磁搅拌提高了枝晶间富金相的面积分数,转速300 r/min时金合金富金相含量最多,为5.07%,比未施加永磁搅拌的金合金高出近59.4%。     

不同金锡合金中金含量的火试金测定

当金锡合金中锡含量超过35%,直接进行灰吹时,金、银合粒松散,不聚珠,灰皿中存在灰吹残留渣,导致火试金测定结果偏低。对高含量样品,研究采用熔炼-灰吹的操作可去除锡干扰,得到完整的合粒。对不同含量的样品宜选择不同的分金硝酸浓度。根据不同含量采用不同的操作步骤,测定金锡合金中金的加标回收率为99.74%~100.27%,方法精密度(RSD)为0.021%~0.127%。     

金及金合金的主要应用现状

综述了金及其合金的主要应用领域:饰品用金、钎焊料用金、电接触材料用金、金在电子工业中的应用、牙科用金、金在医药中的应用、金在高科技产品中的应用.还介绍了金在这些应用领域中的研究发展现状及发展趋势.     

火试金分析中退火工艺的研究

研究了火试金分析过程中退火工艺对检测结果的影响,分别采用扫描电镜和显微硬度仪研究了不同退火条件下金银合金的组织结构和力学性能。结果表明,火枪退火和炉内退火对金含量的检测影响不大,两种退火方式下的金银合金具有相似的微区结构和力学性能。炉内退火操作条件可为400℃退火10 min,或500℃退火5 min以上。     

铜基仿金合金

为了寻找金的代用品,长期以来研究者竞相研制铜基仿金合金以满足制造较大的金色艺术品。文中阐述了研制铜基仿金合金的原理及其金色度和抗变色性的测试方法,分别叙述了铝、锌、锡、铟、硅、镍、稀土等元素对合金金色度和抗变色性的影响。鉴于各研究者得出的合金化学成分相差极大,最后提供了较为合理的铜基仿金合金的化学成分。     

18K金首饰中镍释放量与耐蚀性的关系

采用氧气乙炔火枪制备了4种镍含量分别为0%、2.5%、5%和8%的18K金合金,用扫描电子显微镜、能谱仪、电感耦合等离子发射光谱仪、电化学工作站和热膨胀仪研究了样品在人工汗液中的镍释放和耐腐蚀行为。研究发现,镍释放量与合金的耐腐蚀性负相关;耐腐蚀性与加工条件有关,与镍含量也存在一定的相关性;镍含量增加,原子间结合力减弱,耐腐蚀能力下降,镍释放量增加。     

Au-Ni合金作为直接甲酸燃料电池阳极催化剂的研究

采用氩弧熔炼法制备Au-Ni合金催化剂.采用循环伏安和计时电流曲线研究甲酸在Au-Ni合金催化剂上的电催化氧化性能,结果与单质金作对比.结果表明,根据氧化主峰电位及电流密度的比较,Au-Ni合金具有比单质Au更好的催化活性.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Effects of Sub-zero Celsius Treatment and Tempering on the Stability of Retained Austenite in Bearing Steel

In this work, the influence of sub-zero Celsius treatment and tempering on the mechanical and thermal stability of retained austenite in bearing steel were assessed by tensile test and DSC. Compared with traditional quenched and tempered treatment, sub-zero Celsius treatment obviously decreases the volume fraction of retained austenite. Moreover, the mechanical stability of retained austenite was enhanced due to the accumulation of compressive stresses in retained austenite after sub-zero Celsius treatment and tempering. Meanwhile, the morphology of retained austenite changed from film-like to blocky with austenitization temperature increasing, and the mechanical stability of film-like retained austenite is higher than that of blocky one. The DSC results showed that the activation energy of retained austenite decomposition slightly increased through sub-zero Celsius treatment and tempering. This result may probably be ascribed to partitioning of carbon during tempering. However, the temperature at which retained austenite starts to decompose is unchanged.     

Influence of Fe on Microstructure and Mechanical Properties in Pdoped Ni–Cr–Fe Alloys

The influence of Fe on the microstructure and mechanical properties of P-doped Ni–Cr–Fe alloys has been investigated.Results showed that increasing Fe content refined the dendrite microstructure and enhanced the solubility of P in as-cast alloys. The change of microhardness in different dendrite regions was attributed to the segregation of P atoms in solid solution state, which had strengthening effects. Increasing Fe contents from 15.2 to 60.7 wt% reduced the yield strength and tensile strength but had little influence on the elongation of alloys. The stress rupture life of alloys after heat treatment decreased with the increment of Fe contents, and the failure fracture modes transferred from transgranular to intergranular fracture mode. The change of fracture modes was due to the weakness of grain boundaries caused by the increment of Fe.In addition, the precipitation of M_(23)C_6 was believed to be related to the segregation of P toward grain boundaries, which led to the fluctuation of carbon and chromium atoms near the grain boundaries in alloys with low Fe contents. Consequently, the increment of Fe decreased the strength of matrix and changed the existence of P atoms and the precipitates at grain boundaries.     

Microstructure and Mechanical Properties of Intercritical Heat-affected Zone of X80 Pipeline Steel in Simulated In-Service Welding

The intercritical heat-affected zone(ICHAZ) of X80 pipeline steel was simulated by using the Gleeble-3500thermal/mechanical simulator according to the thermal cycle of in-service welding.The microstructures of ICHAZ with different cooling rates were examined,and the hardness,the toughness and corresponding fractography were investigated.Results show that untransformed bainite and ferrite as well as retransformed fine bainite and martensite–austenite(M–A)constituents constitute the microstructure of ICHAZ.The two different morphologies of M–A constituents are stringer and block.Second phase particles which mainly composed of Ti,Nb,C,Fe and Cu coarsened in ICHAZ.Compared with normal welding condition,the toughness of ICHAZ is poor when the cooling time is short under in-service welding condition because of the large area fraction and size of M–A constituents that connect into chains and distribute at the grain boundaries.The Vickers hardness of ICHAZ that decreases with the increase in the cooling time is independent with the area fraction of M–A constituents.     

Dynamic Compaction of Pure Copper Powder Using Pulsed Magnetic Force

The compaction of pure Cu powder was carried out through a series of experiments using dynamic magnetic pulse compaction, and the effects of process parameters, such as discharge energy and compacting direction, on the homogeneity and the compaction density of compacted specimens were presented and discussed. The results indicated that the compaction density of specimens increased with the augment of discharge voltage and time. During unidirectional compaction, there was a density gradient along the loading direction in the compacted specimen, and the minimum compaction density was localized to the center of the bottom of the specimen. The larger the aspect ratio of a powder body, the higher the compaction density of the compacted specimen. And high conductivity drivers were beneficial to the increase of the compaction density. The iterative and the double direction compaction were efficient means to manufacture the homogeneous and high-density powder parts.     

保元汤提取物对“阳虚”小鼠的免疫药理作用

目的 研究保元汤提取物对“阳虚”小鼠的免疫药理作用。方法 用氢化可的松制备“阳虚”模型;巨噬细胞吞噬作用和C 3b 受体的检测分别用MTT 法和YC 花环形成实验;T 淋巴细胞转化实验用M TT 掺入法。结果 保元汤提取物给“阳虚”小鼠灌胃给药二周后, 观察其免疫药理作用, 结果发现, 两个剂量组皆能阻止“阳虚” 小鼠体重、WBC、胸腺重和胸腺指数, 以及脾重和脾指数的降低, 尤以大剂量组(IDA 组)明显。并且具有恢复其T 细胞转化率和巨噬细胞吞噬率和YC 花环形成率的作用。结论 保元汤提取物具有拮抗“阳虚”小鼠的免疫抑制作用。     

PRECIPITATION SELECTIVITY AND GROWTH OF PEROVSKITE PHASE FROM TITANIUM BEARING BLAST FURNACE SLAG

The effects of transformation of slag composition and additive agents on the morphology, the precipitation behavior, the crystal growth, and the volume fraction (VF) of perovskite (CaO·¤TiO_2) crystal in the Ti-bearing blast furnace slags were investigated. As the morphology of perovskite is dispersed in molten slags, the crystal growth mechanism of the melting of fine dendrites and the coarsening of large grains exist throughout the solidification of molten slags. With the increase of CaO and Fe_2O_3 content, VF of perovskite obviously increases. However, high basicity leads to the viscosity of slag, which results in the reduction of the average equivalent diameter (AED). The experimental results showed that the presence of the additives CaF_2 and MnO efficiently decreased the viscosity of the slags, and obviously improved the morphology of perovskite and promoted its growth.     

Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

铝-镓合金的生产工艺

氢气是干净的新能源,铝和水反应制取氢的成本低廉.但是,铝和水反应制取氢的过程中,反应生成物Al2O3在铝表面形成致密的保护膜,使反应不能持续进行.镓可以破坏铝表面的保护膜,使铝和水制取氢反应得以持续进行.镓分两次和铝熔体混合,制成铝-镓合金.     

Effects of Tungsten and Boron Contents on Crystallization Temperature and Microhardness of Tungsten Based Metallic Glasses

Effects of tungsten and boron contents on the thermal properties and microhardness of W-Fe-B metallic glass system were studied. Thin foils, with thicknesses of 20 and 100 μm, of the alloys were produced by piston and anvil method in an arc furnace. The structures of the foils were investigated by X-ray diffraction. Thermal stabilities of the alloys were examined by using differential scanning calorimetry. 20-μm- thick foils of all the alloys were determined to be fully amorphous, but crystalline phases were detected in the 100-μm-thick foils. It was found that crystallization temperatures of the alloys are between 1060 and 1177 K. Tungsten and boron content increases improve the crystallization temperature and microhardness of the alloys significantly, but deteriorate the glass forming ability of the alloys. It was also observed that for constant Fe content, increasing tungsten content to the level higher than that of boron content does not result in any further improvement in crystallization temperature, but improves glass forming ability significantly. The alloy containing highest total amount of tungsten and boron, W₃₅Fe₃₅B₃₀, has the highest crystallization temperature, 1177 K, and microhardness, 1634 HV.