喷涂Al／SiC复合材料的制备与组织分析

采用等离子喷涂技术和亚音速火焰喷涂技术制备了高性能Al／SiC复合材料。利用OM，SEM，TEM，XRD等仪器详细分析了上述两种技术制备的Al／SiC复合材料微观组织。结果显示，亚音速火焰喷涂技术和等离子喷涂技术均可制备出SiC体积分数大于50％的Al／SiC复合材料，所制备的Al／SiC复合材料组织致密、颗粒均匀分布、SiC颗粒和Al之间的界面结合良好。XRD研究表明，等离子喷涂Al／SiC复合材料中存在着Al，SiC，晶体Si等相。亚音速火焰喷涂Al／SiC复合材料中的相是由Al，SiC和少量的Al2O3组成。与等离子喷涂相比，亚音速火焰喷涂Al／SiC复合材料的孔隙率较高，氧化程度较高。此外等离子喷涂Al／SiC复合材料中有一定量纳米尺度的晶粒和颗粒。     

SDS／Vc／H2O微乳液中纳米金的合成

在SDS／Vc／H2O微乳液中用0．001mol·L^-1HAuCl4溶液代替组分水，以Vc作还原剂制备纳米金。紫外一可见光谱和扫描电镜实验结果表明，所制备的金纳米粒子的粒径在5-20nm之间；在固定SDS／Vc的质量比为50／50条件下，粒子的粒径随微乳液中HAuCl4（aq）含量的增加而增加。初步探讨了在SDS／Vc／H2O微乳液中合成纳米金的机制。     

纳米ATO／PP复合材料的结构与导电性能

分别采用超声波辅助溶液共混和熔融共混的方式制备了ATO／PP复合材料，采用扫描电镜对比分析了复合材料的微观相态结构及导电性能，采用广角X衍射及偏光显微镜研究了纳米ATO的加入对PP结晶性能的影响。结果表明：采用溶液混合并用超声辅助分散的方法使纳米ATO在PP基体中分散良好，在纳米ATO含量较低的情况下就可以获导电性能良好的复合材料；纳米ATO的加入起到了异相成核作用，使PP晶粒细化，但ATO的加入没有改变PP的结晶形态，ATO／PP纳米复合材料的结晶形态仍属于α晶型。     

n?SiO2的表面改性及其增强环氧树脂复合材料的性能

纳米粒子在聚合物中均匀、稳定分散,是纳米复合材料具有优良性能的前提。文中通过选择表面活性剂改性纳米SiO2,提高纳米粒子在环氧树脂中的分散性,制备出不同含量的n–SiO2/环氧树脂聚合物复合材料,探讨了纳米SiO2对复合材料强度的影响规律。研究结果表明:改性后的纳米SiO2粒子在聚合物体系中呈单分散状态,均匀分布的纳米粒子与基体结合紧密,其在基体中起到了物理交联点的作用,对剪切力的抵抗能力增强,提高了复合材料的综合性能。加入6%质量分数的纳米粒子,复合材料的拉伸剪切强度可提高35.1%。     

纳米银/环氧树脂复合材料的制备及其介电性能的研究

采用紫外辐照还原的方法制备了纳米银粒子，研究了保护剂的添加、辐照强度和溶液配比等因素对纳米银粒子尺寸的影响。TEM反映出银粒子分散均匀，其粒度约为20nm。将制备出的纳米银与环氧树脂混合固化形成纳米复合电介质，研究了这种复合材料的介电性能：室温下复合材料的体积电阻率和工频击穿场强随着纳米银粒子的加入有所提高，介质损耗略有降低，而介电常数变化不大。结果表明，纳米银粒子能够提高基体聚合物的介电性能。这一现象可用库仑阻塞机制解释。     

NiO／BaTiO3陶瓷复合材料制备与介电性能研究

以纳米NiO和BaTiO3粉为原料，在1100～1200℃烧结温度条件下，制备了NiO／BaTiO3陶瓷复合材料，研究了复合材料的介电性能。结果表明，随NiO加入量的增加，复合材料的介电常数和介电损耗随之降低，而且在10MHz频率附近，复合材料出现了较强的共振吸收现象。     

多壁纳米碳管／Cu基复合材料的摩擦磨损特性

利用销－盘式磨损试验机研究了粉末冶金法制备的多壁纳米碳管／Cu基复合材料的稳态摩擦磨损行为,并用扫描电镜分析了复合材料的磨损形貌。结果表明：多壁纳米碳管／Cu基复合材料具有较小的摩擦系数,并随纳米碳管质量分数的增加而逐渐降低;由于复合材料中纳米碳管的增强和减摩作用,在低载荷和中等载荷作用下,随着纳米碳管质量分数的增加,复合材料的磨损率减小;而在高载荷作用下,由于发生表面开裂和片状层剥落,含纳米碳管质量分数高的复合材料的磨损率增高。     

PHBV微球／磷酸钙骨水泥复合材料研究

采用在磷酸钙骨水泥中添加一定量的PHBV微球来制备在初期有较高的抗压强度，而后随着PHBV微球的降解，在磷酸钙骨水泥基体中形成三维孔隙结构的PHBV微球／磷酸钙骨水泥复合材料。选用的骨水泥的固相成分以α-TCP为主，液相成分为NaH2PO4／Na2HPO4、KH2PO4/K2HPO4缓冲溶液，PHBV微球直径为100μm～300μm，主要研究不同的固化液，固液比以及PHBV微球添加量对PHBV／磷酸钙骨水泥复合材料抗压强度等性能的影响，制备出凝固时间在15min-30min，具备一定可注射性，抗压强度达到10MPa～30MPa的PHBV微球／磷酸钙骨水泥复合材料。最终制备的PHBV微球／磷酸钙骨水泥复合材料能够满足骨修复材料的要求。     

纳米-相变陶瓷复合材料的有效刚度

含纳米纤维和相变粒子的陶瓷复合材料具有较大的断裂韧性和较高的塑性形变行为，其组织结构以含纳米纤维的棒状复合体为基体，并在棒状复合体周围分布有少量的可产生相变的二相粒子。本文在Mori-Tanaka方法和有效自洽法的基础上提出复合材料刚度预报的随机二相胞元法。首先应用Mori-Tanaka方法计算出棒状复合体的刚度，考虑棒状复合体方位的随机性，根据复相陶瓷基体的应变均值，计算出复合材料基体的有效弹性模量和泊松比，复相陶瓷材料基体为各向同性体。最后将相变粒子看作夹杂在基体中的颗粒，计算出陶瓷复合材料的等效刚度。复相陶瓷的弹性模量随二相组元体积分数的增加而下降且略低于用混合律求解的结果，说明纳米纤维和相变粒子之间的相互作用降低了弹性模量；复相陶瓷的泊松比随二相组元体积分数的增加而下降且略高于用混合律求解的结果，说明纳米纤维和相变粒子之间的相互作用提高了泊松比。     

纳米ZrO2/Pt复合材料的高温性能及高温断口分析

用“胶体共混法”制备纳米ZrO2／Pt粉体,再通过粉末冶金的方法制备出纳米ZrO2／Pt复合材料。通过正交试验方法对各影响条件进行了优选,测试了在最佳条件下制备的纳米ZrO2／Pt复合材料的高温性能,并对其高温拉伸断口及高温蠕变断口进行了分析。     

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.     

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。     

Ag/LaNixCo1-xO3触点材料的制备及电接触性能研究

本文运用溶胶-凝胶燃烧法合成了双钙钛矿型LaNixCo1-xO3(LNCO)纳米材料,利用粉末冶金和热挤压技术制备了相应的Ag/LNCO触点材料及元件样品。重点考察了不同Ni、Co含量对Ag/LNCO触点材料微观结构、物相组成、物理性能、力学性能及电寿命服役能力的影响,对其电弧侵蚀失效行为进行了研究,并与SnO2粉体增强Ag基触点材料进行对比。结果表明:溶胶凝胶法合成的LNCO纳米颗粒粒径为20-30 nm,经粉末冶金工艺制备的Ag/LaNi0.5Co0.5O3触点材料电学性能和电寿命都优于Ag/SnO2触点材料,其电阻率低至2.10 μΩ?cm,电寿命性能达到51287次。表明Ag/LaNi0.5Co0.5O3触点材料性能较佳,是一种可以取代Ag/CdO的新型触点材料。     

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.     

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.     

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.     

Si3N4/Ti/Cu/Ni/Cu/Ti/Si3N4二次部分瞬间液相连接强度

采用Ti/Cu／Ni中间层对Si3N4陶瓷进行二次部分瞬间液相(PTLP)连接，研究连接工艺参数对Si3N4／Ti/Cu／Ni连接强度的影响，同时研究了连接强度随试验温度的变化规律。结果表明，在该试验条件下，室温连接强度随着二次连接温度的提高和二次保温时间的延长而提高，改变连接工艺参数对Si3N4／Ti/Cu／Ni二次PTLP连接界面反应层厚度无明显影响；连接强度在试验温度400℃时达到最大，随后随试验温度升高，连接强度降低，但在800℃前，其高温强度具有很好的稳定性。     

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.