骨架结构对SiC/Al双连续相复合材料的影响

用挤压铸造法制备了不同结构的SiC泡沫增强ZL109双连续相复合材料,研究了增强体骨架结构(筋的结构、泡沫孔和体积分数)对复合材料压缩性能和弯曲性能的影响。结果表明:SiC泡沫增强体的筋的结构影响了界面的结合,影响了材料的压缩性能;当筋具有三明治结构时,复合材料的强度最大;当筋具有双层结构时,复合材料的强度最低;随着SiC泡沫孔径的增大,复合材料的压缩强度、弹性模量和屈服强度都有所提高,材料的屈服应变减小,弯曲强度先升高后降低,弯曲强度在泡沫孔径为1.5 mm时达到最大值;复合材料的压缩强度随着增强体体积分数的增大而提高,屈服应变随着体积分数的增大而减小。     

裂解温度对聚硅氧烷转化Cf/Si-O-C复合材料界面结构和弯曲强度的影响

以聚硅氧烷为先驱体,采用先驱体转化法制备碳纤维二维编织布增强Si-O-C复合材料(Cf/Si-O-C),探讨了裂解温度对材料界面结构和弯曲强度的影响.研究发现,当倒数第二周期的裂解温度从1 100℃提高到1 400℃时,可以弱化纤维/基体的界面结合强度,从而提高材料的弯曲强度.     

SiC泡沫陶瓷/SiCp混杂增强Al基复合材料的性能

以SiC泡沫陶瓷和SiC颗粒(7、15、20 μm)为混合增强体,用挤压铸造法制备出SiC泡沫陶瓷/SiCp混杂增强Al基复合材料,研究了SiCp颗粒尺寸对复合材料压缩强度和弯曲性能的影响,以及金属基体的韧性对复合材料压缩行为的影响.结果表明,随着SiC颗粒尺寸的增大,复合材料的压缩强度和弯曲强度降低,最大挠度减小,这是因为随着SiC颗粒尺寸的增大,颗粒间距随之增大,SiC颗粒的强度降低,使SiC颗粒的增强效果减弱.随着基体韧性的提高,复合材料的塑性变形明显增大,但压缩强度和模量降低.     

体积分数对Wf／Zr基非晶复合材料准静态压缩特性的影响

系统研究了体积分数对钨丝增强Zr基非晶复合材料力学性能的影响。结果显示，在钨丝体积分数〈50％时，复合材料以剪切方式断裂为主，压缩强度和塑性应变随着体积分数的增加而增加；在体积分数≥50％时，复合材料以弯曲和劈开方式断裂为主，压缩强度随着体积分数的增加而继续增加，而塑性应变则开始降低。分析表明，钨丝体积分数的变化通过影响剪切带的形成而引起材料的力学性能发生变化。     

浇注温度对Cu/Ni水套材料界面结合特性的影响

利用固-液复合法制备了一种预埋纯镍管的新型Cu/Ni水套材料,采用金相、扫描电镜、显微硬度和剪切强度测试,重点分析不同浇注温度下铸铜水套材料的基体与顸埋镍管的界面结合特性,如界面原子扩散行为、显微硬度、结合强度等.结果表明,在1 100℃、1 200℃和1 300℃3个浇注温度下,随着浇注温度的升高,界面处扩散层厚度增加,显微硬度增大;当浇注温度过高(1 300℃)时,镍管表面易于附着铜基体中析出的微小气孔,降低界面的结合强度,在1 200℃浇注温度下获得了约为162 MPa的最佳界面剪切强度.     

铸造工艺对自生Mg2Si/Al-20Si复合材料组织及性能的影响

采用熔体直接反应法制备了Mg2Si/Al-20Si复合材料,研究了不同浇注温度、冷却强度对该原位自生复合材料组织及性能的影响.结果表明,浇注温度为750 ℃时,复合材料中Mg2Si和初晶Si晶粒均匀细小,力学性能较好;在过低或过高的浇注温度时,复合材料中Mg2Si和初晶Si晶粒变粗大,力学性显著降低.同时,随着冷却强度的增加,复合材料的力学性显著增强.     

浇注温度对304不锈钢/纯铝复合材料界面组织及性能的影响

采用热浸镀铝工艺对不锈钢管表面进行镀铝处理，再用固-液复合铸造法制备304不锈钢/纯铝管状复合材料，用SEM观察复合界面的微观形貌，结合EDS与XRD物相检测对复合材料结合界面的物相成分与分布进行分析，并测试其显微硬度、抗拉强度和剪切强度。结果发现，随着浇注温度提高，界面处裂纹消失，结合层厚度逐渐增加。界面处形成金属间化合物，主要以FeAl₃和Fe₂Al₅相为主，Fe和Al的含量在界面附近呈现相反的阶梯梯度分布，且存在一个稳定的台阶。随浇注温度升高，纯铝基体的硬度基本保持稳定，304不锈钢基体的硬度有所降低。抗拉强度和剪切强度都呈现出先上升后下降的趋势，当浇注温度为740℃时抗拉强度和剪切强度均达到最大，分别为512.3 MPa和41.6 MPa。     

TiC/AZ91D镁基复合材料高温压缩变形行为

利用自发渗透原位合成法制备了不同体积分数的TiC增强AZ91D镁基复合材料,研究了不同压缩应变速率以及不同变形温度下复合材料的热变形行为,计算分析了不同温度下应变速率敏感指数(m)和表观激活能(Q)与TiC含量的关系．结果表明：TiC／AZ91D复合材料压缩流变应力随TiC含量的增加而升高;TiC含量相同时,流变应力随温度升高或初始应变速率减小而降低．m值随变形温度升高而增大;变形温度以及压缩应变速率相同时,m值随TiC含量升高而增大．Q值依赖于温度、应变速率和TiC含量及其分布,不同条件下其高温变形机制有所差异．     

Cf/SiC制动材料弯曲性能的研究

以短碳纤维为增强体,以树脂为粘结剂,运用模压成型-无压烧结法制备Cf/SiC陶瓷制动材料.研究了烧结助剂含量、烧结温度、碳纤维长度和碳纤维体积分数对该复合材料弯曲强度性能的影响.结果表明:随着烧结助剂含量的增加,Cf/SiC制动材料的密度先增加后减小,抗弯强度也先增加后减小;随着烧结温度的增加,Cf/SiC制动材料的弯曲强度先增大后减小;随着碳纤维长度的增加,材料的弯曲强度先增大后减小,当碳纤维含量分别为5％、10％、15％时,该复合材料的弯曲强度先增大后减小.     

放电等离子烧结TiB/Ti-1.5Fe-2.25Mo复合材料的微观组织与力学性能

采用放电等离子烧结技术原位合成了TiB增强Ti?1.5Fe?2.25Mo复合材料,研究了烧结温度对复合材料微观组织和力学性能的影响规律。结果表明,随着烧结温度的升高,钛合金中 TiB 晶须的长细比迅速减小;然而,复合材料的相对密度及TiB的体积含量随着烧结温度的升高而不断增大。由于TiB晶须长细比的减小会导致复合材料强度的降低,而复合材料的相对密度及TiB体积含量的增大又会带来复合材料强度的增加,因此,在这两种因素的共同作用下,最终导致 TiB/Ti?1.5Fe?2.25Mo复合材料的弯曲强度随着烧结温度的升高而缓慢增大。在烧结温度为1150°C 时,TiB/Ti?1.5Fe?2.25Mo复合材料具有最大的弯曲强度1596 MPa。     

Structural, mechanical and corrosion properties of TiOxNy/ZrOxNy multilayer coatings

Results on the deposition and characterization of TiO_xN_y/ZrO_xN_y multilayers, with bilayer periods of 20 and 400 nm, are presented. The coatings were deposited on TiNiNb alloy substrates by the pulsed magnetron sputtering method. The elemental composition, hardness, adhesion and corrosion resistance of the coatings were analyzed.As resulted from the XPS analysis, the individual layers consisted of a mixture of titanium or zirconium oxynitrides and corresponding oxides. X-ray analysis revealed that the coatings were amorphous. Only slight differences between the microhardness and adhesion values of the coatings with small and large bilayer period Λ were found. The experiments also showed that the multilayered coatings improved the corrosion resistance of the uncoated alloy and reduced the amount of ion release in artificial body fluids.     

MOCVD growth and characterizations of BxAl1−xAs and BxAl1−x−yInyAs alloys

Zinc-blende B_xAl_1−xAs and B_xAl_1−x−yIn_yAs alloys have been grown on exactly oriented (0 0 1)GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). The influence of susceptor coating, growth temperature and gas-phase boron mole fraction on boron incorporation into AlAs has been comprehensively investigated. It has been found that boron incorporation into AlAs could be enhanced and the optimal growth temperature range of B_xAl_1−xAs alloys changed from 580 °C to 610 °C when SiC-coated graphite susceptors were replaced by the non-coated ones. In this study, the maximum boron composition x of 2.8% was achieved for the pseudomorphically strained B_xAl_1−xAs alloys. AFM measurements show that RMS roughness of B_xAl_1−xAs alloys increased sharply with the increase of gas-phase boron mole fraction. Raman spectra of B_xAl_1−xAs alloys show a linear increase of the BAs shift with boron composition x. Based on BAlAs deposition, bulk B_xAl_1−x−yIn_yAs (x = 1.9%) quaternary alloy was grown lattice-matched to GaAs successfully. Moreover, 10-period BAlAs/GaAs and BAlInAs/GaAs MQW heterostructures were also demonstrated.     

High strength and good ductility of casting Al-Cu alloy modified by PrxOy and LaxOy

A modified Al-Cu alloy with high tensile strength and ductility of about 574.0 MPa and 10.4%, respectively, was obtained by adding multiple rare earth oxides (Pr_xO_y and La_xO_y) as modifier. Compared with the unmodified Al-Cu alloy, the tensile strength and ductility of the modified sample were increased by 24.3% and 42.5%, respectively. The improvement both in the strength and ductility may attribute to the finer crystal grains and dendrites, more homogeneously distributed θ′ phase precipitates and the intermetallic compounds formed at the crystal grain boundaries as well as in the space of the dendrites.     

Hydrothermal synthesis of superconductors Ba1−xKxBiO3 and double perovskites Ba1−xKxBi1−yNayO3

Superconductors Ba_1−xK_xBiO₃ and body-centered double perovskites Ba_1−xK_xBi_1−yNa_yO₃ have been selectively synthesized by a facile hydrothermal route. The appropriate ratio and adding sequence of initial reagents, alkalinity, reaction temperature and time are the critical factors that influence the crystal growth of the compounds. The purity and homogeneity of the crystals were detected by the ICP, SEM, EDX and TEM studies. Magnetic measurements show that the superconducting transition temperatures T_C of Ba_1−xK_xBiO₃ decrease from 22 K (for x = 0.35) to 8 K (for x = 0.55) with increasing the K doping level.     

铸造CAD／CAE／ES／PDM／ERP一体化及集成技术研究

详细阐述了支持铸造工艺设计、工艺优化、工艺信息管理、企业管理的系统研究与应用特点,在此基础上提出了基于PDM平台的铸造CAD／CAE／ES／PDM／ERP一体化框架体系,在华铸实验室现有软件体系（华铸CAE／CAD／PDM／ERP）及应用的基础上,设计与实现了一体化系统关键点及其集成技术。最后,以若干实际案例来证明本研究一体化系统的实用性。     

生物医用NiTi形状记忆合金腐蚀研究进展

镍钛形状记忆合金(NiTi-SMA)具有较好的耐腐蚀和机械性能,在口腔和临床医学中有着大量而广泛的应用。NiTi-SMA腐蚀后释放Ni²⁺会引发细胞毒性和过敏反应,进一步提高NiTi-SMA的耐蚀性是目前生物医学材料领域发展的核心之一。本文对近年来国内外有关口腔医学和临床医学中常用NiTi-SMA的腐蚀研究现状进行了总结,同时也对NiTi-SMA增材制造及表面改性技术进行了评述,以期为开发高性能抗腐蚀生物医用NiTi-SMA提供一定的指导意义。     

Li掺杂Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3高熵陶瓷的制备及介电性能研究

近年来,在高熵合金基础上发展起来的高熵陶瓷逐渐引起了研究者的广泛关注,其出现为开发高性能的无机非金属材料提供了新的设计思路。本文采用固相法制备了BaMO3基钙钛矿型高熵陶瓷Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%),并研究了Li含量对高熵陶瓷物相结构、微观形貌及介电性能的影响。结果表明,Li含量对陶瓷结构的影响不大,陶瓷均保持立方钙钛矿结构,且无杂相产生;陶瓷的晶粒尺寸相对较均匀。当x = 0时,即B位七元等摩尔比Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3高熵陶瓷,其介电常数达到了最大值2920 (@100 Hz),相较于已报道的不掺Li的六元高熵钙钛矿陶瓷Ba(Ti1/6Sn1/6Zr1/6Hf1/6Nb1/6Ga1/6)O3提升了近50倍。     

Thermoelectric properties of Sn1−x−yTiySbxO2 ceramics

Thermoelectric properties of Sn_1−x−yTi_y Sb_xO₂ ceramics were investigated in detail. The addition of Sb into SnO₂ matrix increased the electric conductivity, σ. The increase in the σ value should be caused by the increase in the carrier concentration. The Seebeck coefficients of all the samples were negative, which means that these samples have n-type conduction. The samples of this study have porous structure. The maximum Z value of all the samples measured in this study was 2.4 × 10⁻⁵ K⁻¹.     

Ti/Mn(0.8-x)SnxIr0.2O2电极的电容性能研究

采用热分解法制备了Ti/Mn_(0.8-x)SnxIr_0.2O_2三元氧化物电极材料。通过扫描电子显微镜,X射线衍射、循环伏安和交流阻抗谱等分析了Ti/Mn_(0.8-x)Sn_xIr_0.2O_2电极材料的组织结构和电容性能。结果表明:随SnO_2含量增加,氧化物涂层中正方结构Mn_3O_4相逐渐减少,正方结构SnO_2相逐渐增加。与锰铱二元氧化物相比,SnO_2的加入可明显改善电极材料在0~0.5 V区间的电流响应,并促进氧化锰活性的发挥,但在一定程度上也抑制了氧化铱的活性。SnO_2的加入也改变了电极材料的电荷转移电阻、弛豫时间常数、以及不同频率下的电容响应速度。相比其它电极材料,Ti/Ir_0.2Mn_0.6Sn_0.2O_2电极材料在低频范围(≤1 Hz)有更好的电容响应和更高的活性,因而获得最高的比电容值。     

Magnetic phase diagrams of the TbRh2−xPdxPdxSi2 and TbRu2−xPdxSi2 systems

The a.c. susceptibility and high field magnetization on TbRh_2−xPd_xPd_xSi₂ and TbRu_2−xPd_xSi₂ compounds were investigated up to 140 kOe. The (T,x) magnetic phase diagrams were determined. For both systems, an increase in the Pd content causes a decrease in the Néel temperature and changes the magnetization curves.