B4C—Al2O3复合材料的组织结构及力学性能

Ｂ４Ｃ基体中掺加不同量的Ａｌ２Ｏ３在１８５０℃,３５ＭＰａ压力下,热压燃结,利用ＸＲＤ,ＳＥＭ、ＥＤＡＸ,ＳＥＮＢ等方法对试样的组织结构及力学性能进行研究,结果表明：Ａｌ２Ｏ３掺加不仅降低了热压烧结温度,促进了烧结致密化,获得９６％以上的相对密度而且提高了纯Ｂ４Ｃ材料的力学性能。Ｂ４Ｃ－２０％ｖｏｌ Ａｌ２Ｏ３的Ｋｉｃ值达５．４３ＭＰａ·ｍ＾１／２,弯曲强度为３７０．４ＭＰａ;Ｂ４Ｃ－３０％ｖｏｌ     

添加Al2O3对B4C材料热压烧结行为的研究

Ｂ４Ｃ粉末通常需在２０００℃以上的高温烧结才能获得较高的密度。本文利用Ａｌ２Ｏ３作为添加剂,在真空气氛３５ＭＰａ压力下烧结,成功地降低了Ｂ４Ｃ材料的烧结温度,可在１８５０℃获得９８％的相对密度。工提高的主要原因是在１８００℃以上,Ａｌ２Ｏ３成为液相及Ｂ４Ｃ与Ａｌ２Ｏ３反应形成的ＡｌＢ１２Ｃ２,促进了致密化过程。     

纳米Ni_3Al/Al_2O_3复合陶瓷的制备及性能

利用氢电弧等离子体法制备了纳米Ni3Al金属间化合物,并以此为弥散相,以氧化铝为基体,采用热压烧结工艺在1 450℃下制得纳米Ni3Al/Al2O3复合陶瓷,并研究其力学性能和微观结构。结果表明:加入纳米Ni3Al的复合陶瓷断裂韧性比纯氧化铝陶瓷有了明显提高,当加入质量分数5%纳米Ni3Al时,断裂韧性最高达12.1 MPa.m1/2。利用扫描电子显微镜观察试样的断口形貌,分析陶瓷的微观结构发现:随着纳米Ni3Al含量的增加,片状晶数量逐渐降低,说明纳米Ni3Al质量分数的加入抑制了片晶的生长。     

直接氧化法制备Al_2O_3／A1复合材料氧化生长动力学研究

系统分析了Ｍｇ含量、Ｓｉ含量、高温保温湿度和高温保温时间对直接氧化法制备Ａｌ２０３／Ａ１复合材料氧化生长物重量及其中Ａｌ２Ｏ３；百分含量的影响规律，确定了上述工艺参数的最佳取值范围，并从理论上深入分析了所得影响规律的成因①．     

Microstructure and mechanical property evolution of friction stir welded(B_4C+Al_2O_3)/Al composites designed for neutron absorbing materials

(B_4C+Al_2O_3)/Al composite designed for the dry storage of spent nuclear fuels was fabricated and then subjected to friction stir welding, at a welding speed of 100 mm/min and rotation rates of 400–800 r/min. Sound joints were obtained under all welding parameters; however, significant softening occurred in the nugget zone(NZ) for all the joints. Therefore, all the joints exhibited significantly decreased strength at both room temperature and high temperature compared with the base metal, with the joints fracturing in the NZs. Rotation rate exhibited no obvious effect on the tensile strength of the joints, but led to increased elongation as the result of the broadened NZs. The detailed microstructural examinations indicated that the welding thermomechanical effect broke up the near 3D amorphous Al_2O_3 netlike structure distributed at the Al grain boundaries, caused the coarsening of Al grains, and the agglomeration and crystallization of amorphous Al_2O_3, thereby resulting in the softening of the NZs and the reduction in the joint strength. Consequently, inhibiting the breakup and crystallization of 3D amorphous Al_2O_3 netlike structure is the key factor to improve the joint strength of the(B_4C+Al_2O_3)/Al composite.     

Microstructure and Tribological Behavior of Al_2O_3 Particle Reinforced Al Matrix Composites Fabricated by Spark Plasma Sintering

Nanoparticles and microparticles reinforced Al matrix composites were fabricated by spark plasma sintering, and the microstructure and tribological properties were investigated systemically. The nano-Al_2O_3 particle and micro-Al_2O_3 particle uniformly dispersed in Al matrix composites. The introduction of nanoparticles is beneficial to the decrease of friction coefficient and wear rate, while microparticles are responsible to the high friction coefficient, resulting in the abrasive wear. With the introduction of both nanoparticles and microparticles, their synergic effect will lead to the variation of tribological behavior.     

Al2O3-SiO2溶胶对莫来石耐火材料性能的影响

采用溶胶-凝胶法制备Al2O3-SiO2溶胶粉末,用制备好的Al2O3-SiO2溶胶粉末作为结合剂合成莫来石耐火材料。研究Al2O3,SiO2和Al2O3-SiO2溶胶的不同配比对莫来石耐火材料性能的影响。结果表明：在不加入Al2O3情况下,SiO2微粉的加入量在77％～87％范围内逐渐增加时,耐火材料的体积密度增大,显气孔率降低,吸水率变化不明显;当加入30％的SiO2微粉时,随着Al2O3微粉加入量在52％～62％范围内逐渐增加,试样的体积密度先增后减,在加入量为57％时达到最高;当Al2O3-SiO2粉末加入量2％～4％时,显气孔率逐渐上升,体积密度也增加,当加入量超过5％时,耐火材料的体积密度下降,显气孔率逐渐上升。     

Al2O3／ZL108复合材料凝固界面的研究

利用挤压铸造制备Ａｌ２Ｏ３／ＺＬ１０８复合材料，研究了氧化铝纤维／铝合金基体的界面，结果表明，在复合材料中，纤维与基体之间的界面层，合金元素通过适当的化学反应可形成尖晶石，有利于纤维与基体的结合，试样断口分析表明，复合材料的界面结构状况良好，可传递足够的载荷到纤维上，发挥其增强作用。     

Al2O3对PbTe微观结构和热电性能的影响

为研究Al2O3对PbTe微观结构和热电性能的影响,在Tl0.02Pb0.98Te材料中添加纳米Al2O3粉末,用高能球磨加热压方法制备了Tl0.02Pb0.98Te样品,并对样品进行实验分析。结果表明:添加纳米Al2O3粉末有效地强化了样品高温机械性能;同时,纳米Al2O3颗粒弥散分布在晶界,阻止热压过程中晶粒长大,使晶粒尺寸降低了约50倍;晶粒细化后界面增多,能更好地散射长波长声子;由于晶格热导率降低了约20%,Tl0.02Pb0.98Te(Al2O3)0.06样品的ZT在723 K时达到1.3。     

Al2O3／ZA12复合材料凝固组织的研究

利用挤压铸造制备了Ａｌ２Ｏ３／ＺＡ１２复合材料,研究了其凝固组织。结果表明,复合材料的基体组织细小,合金元素通过适当的化学反应可改善纤维与基体的结合;在凝固过程中,Ａｌ２Ｏ３纤维可作为ＺＡ１２中共晶体非自发形核的衬底,纤维／基体界面上的硅在共晶体的共生生长过程中起了领先相作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变组成。     

Influence of Adding Ti Powder in Preform on Microstructure and Mechanical Properties of Al_2O_3p/Steel Composites by Squeeze Casting

To improve the mechanical properties of alumina particulates reinforced steel matrix composite, Ti powder was added into the alumina preform, a 5140 steel matrix composite was fabricated by squeeze casting, and the influences of Ti powder on the microstructure, hardness and bending strength of the composite were investigated, compared with the composite without adding Ti powder. Applied Ti powder and alumina particulates were 10-25 μm and 100-180 μm in size, respectively. Both composites were successfully fabricated, however Ti powder addition increased the infiltration thickness of the composite. In the Ti contained composite, a TiC film in micron scale is formed on the surface of alumina particles, many TiC aggregates are dispersed in the steel matrix without obvious remaining Ti powder. The hardness and the three-point bending strength of the composite reach 49.5 HRC and 1 018 MPa, respectively, which are 17.9% and 52.4% higher than those of the composite in the absence of Ti addition. Fracture morphology shows that the debonding of alumina particulates is eliminated for the composite in the presence of Ti addition. Sessile drop test shows the average wetting angle between 5140 steel and that of Ti coated Al_2O_3 is about 82.15°, much lower than the wetting angle 150° between steel and pure Al_2O_3. Therefore, the increase in the mechanical properties of the composite is attributed to the improvement of Al_2O_3 p/steel interface wetting and bonding by adding Ti powder in the preform.     

Na_2O/B_2O_3对硼硅酸盐玻璃结构与性能的影响

硼硅酸盐玻璃具有非常优异的性能。采用熔融冷却法制备了不同Na2O含量的高硼硅酸盐玻璃。主要探讨R(R=Na2O/B2O3)对硼硅酸盐玻璃结构和性能的影响。通过红外光谱分析了硼硅酸盐玻璃在不同R的情况下的结构变化,测试了玻璃的密度、热震性、化学稳定性和力学性能。研究结果表明:随着R的增大,硼硅酸盐玻璃结构中出现了[BO3]转变为[BO4]的现象,并且在R=0.5时,出现了结构变化的极值点。硼硅酸盐玻璃的化学稳定性受玻璃结构的影响,R对耐酸、耐水性能影响不大,但随着R的增大,其耐碱性显著下降。硼硅酸盐玻璃的力学性能与玻璃的结构有关,即与[BO3]、[BO4]及[SiO4]的比例有关。随着R的增加,硼硅酸盐玻璃的弯曲强度及硬度呈现先增大后减小的趋势,且在R=0.5处产生最大值,分别为69.5MPa、6.94GPa。     

Dielectric Properties of Polytetrafluoroethylene/CaCu_3Ti_4O_(12) Composites

Polymer-based composite was investigated by embedding calcium copper titanate(CaCu_3Ti_4O_(12); CCTO) fillers into polytetrafluoroethylene(PTFE) matrix. The dielectric performances of the composite were investigated within the frequency range from 100 Hz to 1 MHz. It is indicated that dielectric permittivity(ε) and dielectric loss(tanδ) increase gradually as the filler content increases. Dielectric permittivity for the composite with 50 vol% CCTO filler loading is 33.5, approximately 16 times higher than that of pure PTFE(ε = 2.1) at 100 Hz. As the frequency increases, the dielectric loss decreases rapidly and reaches stability, and then remains low when the frequency rises to 1 MHz. The values for dielectric permittivity and dielectric loss in the microwave frequency(8-13 GHz) are lower than that in low frequency of 10 kHz for the composites because of different polarization modes. Several theoretical models were implemented to compare the experimental results with the theoretical calculations and the modified Lichtenecker equation was found to fit the best.     

Mechanical Properties and Microstructure of Al_2O_3/SiC Composite Ceramics for Solar Heat Absorber

Al_2O_3/SiC composite ceramics were prepared from α-Al_2O_3 and SiC by a pressureless sinter method in this study.The effect of SiC contents on the mechanic properties,phase compositions and microstructure is studied.Experimental results show that the vickers hardness,wear resistance and thermal conductivity of the samples increase with the increase in the SiC content,and the hardness of the sample reaches 16.22 GPa,and thermal conductivity of the sample reaches 25.41 W/(m.K) at room temperature when the SiC content is 20 wt%(B5) and the sintering temperature is at 1 640 ℃.Higher hardness means higher scour resistance,and it indicates that the B5 material is expected to be used for the solar heat absorber of third generation solar thermal generation.The results indicate the mechanism of improving mechanical properties of Al_2O_3/SiC composite ceramics:SiC plays a role in grain refinement that the grain of SiC inhibits the grain growth of Al_2O_3,while the addition of SiC changes the fracture mode from the intergranular to the intergranular-transgranular.     

Al_2O_3对铋硼酸盐玻璃结构和性能的影响

通过FTIR、Raman、~(27)Al NMR、XRD、DSC等测试方法,研究了Al_2O_3含量对Bi_2O_3-B_2O_3-ZnO-SiO_2-Al_2O_3系统低熔点封接玻璃结构及热性能的影响。结果表明:玻璃转变温度及软化温度随着Al_2O_3含量的增加逐渐降低。当Al_2O_3含量≤3%时Al_2O_3在玻璃中主要以[AlO_4]四面体结构存在,充当网络结构形成体,热膨胀系数减小;当Al_2O_3含量3%时Al_2O_3在玻璃中主要以[AlO_6]八面体结构存在,破坏玻璃网络结构,热膨胀系数增大。当Al_2O_3含量为7%时,样品析出ZnAl_2O_4晶体,热膨胀系数随之减小。综上所述,当Al_2O_3含量为3%时,该系统低熔点玻璃具有较低的特征温度及较低的热膨胀系数且可避免高铋含量玻璃的析晶。     

B_2O_3—Al_2O_3—PbO玻璃组成和物化性质的研究

本文研究了B_2O_3—Al_2O_3—PbO玻璃中引入La2O3、SiO2、Sb2O3、Ga2O3后，TF光学玻璃化学稳定性及相对部分色散Pg·F。论证了B2O3－Al2O3－PbO光学玻璃光学性质，化学稳定性和结构关系。TF光学玻璃在3．5L铂坩埚中熔制。     

SiCp/AI 复合材料的显微组织与常规力学性能研究

本文研究了流变铸造法制备的 SiCp/LY12和 SiCp/5083Al 复合材料中SiC 颗粒的分布情况,发现在特定的工艺条件下,只有当 SiC 颗粒的体积分数处在一定的范围内。复合材料才能获得良好的 SiC 颗粒分布均匀性:另外,加工工艺对SiC 颗粒的分布也将产生影响.研究结果表明,不同体积分数的 SiC 颗粒均使复合材料的屈服强度得到提高,除时效态 SiCp/LY12复合材料外,其余复合材料的抗拉强度也得到提高,但复合材科的冲击韧性却大大下降。     

Al2O3／Zn合金复合材料凝固组织的扫描电镜观察

利用扫描电子显微镜（ＳＥＭ）观察了铸造Ａｌ２Ｏ３／Ｚｎ合金复合材料的凝固组织，研究了复合材料凝固组织的一般特征．研究结果表明，复合材料的组织致密，纤维分布均匀，基体晶粒细小；在复合材料的凝固过程中，氧化铝纤维可作为Ｚｎ合金共晶体非自发形核的衬底，纤维／基体界面上的硅在共晶体的共生生长过程中起了领先相作用，导致了复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两部分组成．     

PA11/Al_2O_3涂覆汽车花键轴研究

研究了PA11/纳米Al2O3复合材料的摩擦性能。考察了纳米Al2O3含量及速率对材料摩擦系数和磨耗性能的影响,进行了涂覆花键轴的台架试验和道路行驶试验,并与尼龙11进行对比。结果表明,复合材料中纳米Al2O3为9%时材料的耐磨性能最好。SEM图片表明复合材料的磨损机理从纯PA11材料的粘着磨损转为轻微的磨粒磨损和粘着磨损。尼龙11与纳米Al2O3复合材料能明显提高花键轴的使用寿命。     

添加Li2O对BAS玻璃陶瓷相变和性能的影响

研究了溶胶─凝胶法合成的含Ｌｉ２Ｏ的ＢＡＳ凝胶玻璃的晶化行为及Ｌｉ２Ｏ加入量对ＢＡＳ玻璃陶瓷性能的影响规律。结果表明，不含Ｌｉ２Ｏ的ＢＡＳ凝胶玻璃晶化处理后获得主晶相为六方钡长石的ＢＡＳ玻璃陶瓷，加入Ｌｉ２Ｏ后，促进六方钡长石向单斜钡长石转变。