稀土在球铁和蠕铁中的作用

通过对稀土在球铁和蠕铁中作用的研究得出稀土蠕化能力比镁强,蠕化剂应以稀土为主同时含少量镁,镁的球化能力比稀土强,球化剂应以镁为主同时含少量稀土的结论。“球铁中含适量稀土可降低球化所需的残余镁量,使石墨球数增加,白口倾向和壁厚敏感性减小,同时能减少氧化夹渣和消除干扰元素的影响。     

稀土对AM50力学性能及高温蠕变的影响

对Y和富La稀土对镁合金AM50微观组织、铸态力学性能和蠕变性能的影响进行了研究.研究结果表明: AM50中加入Y和富La稀土能有效地细化晶粒,由于显微组织的改善,使得AM50合金的室温和高温力学性能均有一定的提高,并明显地改善了AM50镁合金的抗蠕变性能.填加稀土可以在AM50合金晶界处生成稳定的铝稀土化合物,可以明显提高镁合金AM50的常温及高温(150 ℃)力学性能.与加入富La稀土的AM50相比,加入Y提高力学性能及蠕变抗力的作用更明显.     

稀土、钾、钠微合金化铁素体基体蠕墨铸铁玻璃模具材质的研究

介绍了稀土、钾、钠微合金化蠕墨铸铁玻璃模具材质的组织特点，探讨了铸造工艺对模具本体双层石墨形成的影响，总结了稀土残留量和钾、钠微合金化元素与模具材质力学性能和高温性能之间的关系。结果表明：这种模具材质具有较好的尺寸稳定性，较高的抗氧化疲劳能力，其使用寿命是原铸铁模具使用寿命的5倍，达到62万次／模。具有很好的应用推广价值。     

高性能镁-稀土结构材料的研制、开发与应用

由于镁合金具有低的密度-质轻、高比刚度、卓越的机械性能、高的硬度及良好的铸造性能, 近几十年来镁合金的应用一直是自动化工业的目标之一. 然而, 高温特殊用途, 例如在发动机上的应用, 通常的镁合金就受到了限制, 因为在高温下它们的强度和抗蠕变性能都比较差. 由于镁-稀土合金增加了材料的抗拉强度、延展性及抗蠕变性能, 稀土加入后形成镁-稀土合金就可以满足高温应用的要求. 本文就我国丰富的镁和稀土资源评述了国内外镁-稀土合金的研制、开发与应用状况及发展趋势, 同时结合我国相关单位的研究进展, 对我国镁-稀土合金的发展提出了建议.     

蠕墨铸铁生产新方法的研究

采用稀土氧化物固态渣饼为脱硫剂和变质剂,在吹氩条件下对高硫(s=0.10％)过共晶铁水进行变质处理以生产蠕墨铸铁。在1380℃、1410℃和1450℃下均获得成功。在1450℃下处理约30分钟其成功率为90％。获得的蠕铁碳当量CE约为5％,RE约为0.01％。金相显微镜和电子显微镜观察结果表明蠕墨形貌和Ⅲ型石墨蠕墨基本一致。对脱硫反应和稀土氧化物还原反应进行了讨论和热力学计算,上述反应在本实验条件下在热力学上都是可行的。实验结果和热力学计算都表明固态渣饼在变质处理过程中可以重复使用。     

含纳米稀土、铁复合粒子润滑油的摩擦学性能

选择了吐温(Tween)-60、司本(Span)-20、司本(Span)-80和聚醚表面活性剂,配制了纳米稀土(RE)和铁粒子的复合润滑油.采用透射电子显微镜(TEM)观察、测定了纳米稀土、铁粒子形貌和粒径.采用磨损试验机测试了含纳米稀土、铁复合粒子润滑油的摩擦学性能.结果表明纳米稀土与纳米铁粒子比例为11,总浓度为0.6%时该润滑油具有最佳的抗磨、减摩性能.并探讨了其抗磨、减摩机制.     

含稀土抗蠕变压铸镁合金的开发

针对商用压铸镁合金抗高温蠕变性能较差的现状，开发了抗高温蠕变压铸镁合金，其开发的目的是针对大马力柴油发动机汽缸罩盖，其抗高温蠕变性能应该能够保障其在150℃条件下稳定工作，而且其成本的增加应该控制在AZ91D合金成本的15％以内。讨论了稀土元素Ce，Y，Nd及Ca和Si的添加对压铸镁合金在常温拉伸性能以150℃条件下的蠕变行为、显微组织的影响，以及对表面处理和腐蚀试验的影响，并进行了实际产品的压铸牛产。试验结果表明，所开发的抗蠕变压铸镁合金具有应用于汽车动力系统部件的制造并大幅度减轻重量的潜力。     

稀土对变形铅黄铜高温性能的影响

通过高温拉神试验,研究了稀土元素对不同铅含量的变形铅黄铜高温性能的影响。结果表明:添加微量稀土可较显著提高合金的高温延伸率,对最大流动应力无显著影响。采用扫描电镜、定量金相、结构分析等检测手段,研究了稀土对合金微观组织结构的影响。同时,探讨了稀土的作用机理。     

满足欧Ⅲ排放标准的汽油车中偶催化剂

 制备了高性能稀土储氧材料Ce0.5Zr0.4Y0.1O2和镧稳定的氧化铝(La-Al2O3), 并以此为基础制备了中偶汽油车尾气净化催化剂. 经老化前后的性能检测证实,稀土储氧材料具有优异的织构性能和储氧性能且高温稳定性优良; La-Al2O3具有优异的织构性能及优异的抗高温老化性能. 中偶催化剂对HC, CO和NOx具有优异的低温活性、抗高温老化性能和低的劣化系数. 捷达-MT型汽油车排放检测表明该催化剂能够满足欧Ⅲ排放标准.     

高温镍氢动力电池用镍电极的研究

镍电极在高温充电过程中由于析氧而使充电效率不高,添加稀土化合物可以提高析氧过电位从而抑制氧气的析出,可以显著提高活性物质高温性能.本文选用稀土氧化物Y2O3、Yb2O3、Lu2O3作为添加剂,研究其对镍电极高温性能的影响,并将添加Y2O3与未添加稀土添加剂的电池进行高温性能作比较.研究发现:稀土添加剂可以抑制镍电极充电过程中氧气的析出,提高高温充电效率;同时减少活化周期,降低电池制造成本;另外,添加Lu2O3的正极高温活性物质比容量最高,添加氧化钇的正极高温充电效率最高,且成本最低,最具市场潜力.     

稀土变质及热处理对耐磨铸铁冲击疲劳性能的影响

采用金相显微镜、扫描电镜观察了经冲击疲劳试验后耐磨铸铁中碳化物的形貌、疲劳裂纹的萌生与扩展,测定了稀土含量及加热温度与裂纹的长度和裂纹扩展之间的关系曲线,在此基础上探讨了稀土变质及热处理对耐磨铸铁冲击疲劳性能的影响.结果表明: 稀土能推迟裂纹萌生的时间,降低裂纹扩展速率,提高其冲击疲劳抗力.当稀土与热处理共同作用时,效果更显著.其原因主要归于网状共晶碳化物形态与分布的改变.     

Calibration of a quenching and deformation differential dilatometer upon heating and cooling: Thermal expansion of Fe and Fe-Ni alloys

Dilatometry is a technique for precise measurement of thermal dilatation of materials during heating or cooling. A procedure has been presented for calibration of a differential dilatometer operating with electromagnetic heating for metallic specimens both upon heating and cooling as well as under uniaxial compressive and tensile loading. The dilation signal has been calibrated for both heating and cooling and for uniaxial loading (compressive and tensile) using platinum or iron reference specimens, for which recommended dilational data are available. The ferro- to paramagnetic transition (characterised by the Curie temperature) of pure iron or iron-based alloys has been adopted to calibrate the temperature in the dilatometric measurement under different loading modes during heating and cooling. On this basis calibrated data for the thermal expansion coefficients of Fe and Fe-Ni alloys have been obtained.     

稀土对高铬铸铁碳化物形态及相变动力学的影响

研究了稀土元素对高铬铸铁中碳化物的影响，并对加稀土、不加稀土的高铬铸铁试样的连续冷却转变（ＣＣＴ）曲线进行了测定。结果表明，稀土元素能破碎高铬铸铁中的碳化物，使碳化物由网状、长条状向岛状、块状过渡。同时，稀土元素提高了高铬铸铁的固态相变温度并缩短了贝氏体的孕育期。     

Structures and Properties of Cast Irons Reinforced by Trace Addition of Modified SiC Nanopowders

"To improve the performance of traditional cast iron, trance amount of surface modified nanometer SiC powders were added into the melted iron. The microstructures, the mechanical properties, as well as the wear resistance were investigated. The trace addition of SiC nano-powders were active due to the presence of structural defects arising from the treatment, they were eoient in affecting not only the generation and growth of crystals but also change the morphology of graphite. On the other hand, the addition of SiC nanopowders as heterogeneous seedings in the crystallization of liquid metals lead to the changing of supercooling temperature, so the ratio of ferrite and pearlite was changed. The mechanical characteristics and wear resistance were enhanced as a result of the improved graphite shape and changed matrix composition caused by the trace addition of SiC nanopowders (in amounts of about 0.01% mass). The strengthening mechanism and the free gap between powders were also discussed. It is suggested that the tensile strength, toughness, as well as the wear resistance can be improved simultaneously, which indicates the novel strengthening technology by trace addition of nanopowders is promising to extend to large-scale industrial production."     

稀土—氮复合孕育剂对灰铸铁石墨组织的影响

采用主碳当量灰铸铁作为试验材料，以孕育处理的方式加入稀土和氮，研究了稀土，氮及二者复合能对石墨数量和石墨表面形貌的影响。试验结果表明，稀土和氮，特别是它们复合加入，使石墨百分含量减少；氮和氮与稀土复合孕育使灰铸铁的石墨表面变粗糙，且端部有钝化现象。     

灰铸铁石墨形态的自动分类

在所提取的纹理特征的基础上,使用误差后向传播神经网络构建了一种优化的人工神经网络人顺。实现了灰铸铁石墨态的自动分类。用于描述石墨形态特征由分形维,粗细参数和二维自回归系数共同组成。该法成功地将人工神经网络引入了对灰铸铁石墨形态的分类,相对于传统人工目测法是一种很大的进步,而神经网络分类器的优化方法对其它神经网络模型的构也具有一定参考价值。     

SIMS Analysis of the wear of boron nitride tools for the machining of compacted graphite iron and grey cast iron

Cubic boron nitride (cBN) is a common material for tools for the machining of cast irons at high cutting speed. During the machining of compacted graphite iron (CGI) in continuous cutting the wear of the cBN tools was found to be significantly higher compared to the machining of grey cast iron. This is possibly a result of a heating of the tool surface during the cutting of CGI. One possible reason for the wear is diffusion of some elements from the cutting tool into the CGI or from the CGI into the cutting tool. SIMS measurements were carried out which prove the existence of such diffusion processes. A static model experiment has been performed by heating cBN tools to 700 °C while in contact with CGI or cast iron (CI). SIMS depth profiles of the cBN tools and of CGI/CI show that there is a diffusion of several elements in both directions (B, W and Ti from the cBN tools into the CGI or CI, Fe and Si from the CGI or CI samples into the cBN) up to a depth of 20 μm. Received: 18 March 1999 / Revised: 16 June 1999 / Accepted: 18 June 1999     

Low percolation conductive graphite flakes-filled poly(urethane-imide) composites with high thermal stability via imidization self-foaming structure

In the study, the conductive graphite flakes filled poly(urethane-imide) composites (PUI/GFs) with high performance were constructed by the thermal imidization self-foaming reaction. It was found that the foaming action could promote the redistribution of GFs during curing process and the formation of stable linear conductive pathways. The percolation threshold of PUI/GFs composites was lowered from 1.26 wt% (2000 mesh GFs) or 0.86 wt% (1000 mesh GFs) to 0.79 wt% (500 mesh GFs), which were relatively low percolation thresholds for polymer/GFs composites so far. When the content of 500 mesh GFs was 4.0 wt%, the electrical conductivity of the composite was as high as 3.96 × 10^?1 S/m. Also, a poly(urethane-imide) (PUI) matrix with excellent thermal stability (T_d10%: 334.97 °C) and mechanical properties (elongation at break: 324.52%, tensile strength: 15.88 MPa) was obtained by introducing the rigid aromatic heterocycle into the polyurethane (PU) hard segments. Moreover, the zero temperature coefficient of resistivity for the composites was observed at the temperature range from 30 °C to 200 °C. Consequently, PUI/GFs composites may provide the novel strategy for considerable conductive materials with high thermal stability in electrical conductivity.     

Heated graphite cylinder electrodes

A new heated graphite cylinder electrode (HGCE) has been successfully fabricated, which arrangement is similar to that of the heated metal (Pt or Au) wire electrode invented by Grundler. The cylinders’ diameters range from ca. 95 to 300 μm obtained by grinding the commercial available pencil graphite. HGCEs demonstrate rapid responses to the heating up and high thermal stability during being continuously heated. Predictions for the temperature rise at the electrode surface based on an empirical model for a natural laminar flow at heated cylinders are in good agreement with the experimental results. The temperature rise at HGCEs was found to be strongly dependent on the square of heating currents, the diameter and the temperature coefficient of the specific resistance of the graphite cylinders, and less dependent on the bulk solution temperature. It is indicated the temperature rise at HGCEs was linearly changed with the reciprocal of the square of the cylinder diameter as the heating currents were given. The evolution from peak-shaped to sigmoid-shaped voltammograms was manifested at HGCEs as the temperature increased from 20 to 95 °C. The compatible between biological substances and graphite electrodes might facilitate studies on the electrochemical behavior of them at HGCEs.     

Effect of synthesis parameters on characteristics of expanded graphite

Effect of synthesis parameters on the characteristics of expanded graphite were studied. The starting sample, intercalated graphite, was treated by several methods: thermal shock (400, 1000°C) and programmed heating (400–700°C). The samples were examined by scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, and low-temperature nitrogen adsorption. The programmed-heating method yields better texture characteristics as compared with the thermal shock. The programmed-heating method was used to obtain high-quality expanded graphite with high specific surface area (299 m² g^–1) at a comparatively moderate temperature of 400°C.