球磨-转喷微注法制备纳米Al2O3颗粒/Al(7075)复合材料的组织及磨损特性

采用球磨-转喷微注相结合的新工艺制备纳米Al₂O₃颗粒(Al₂O_3p)/Al(7075)复合材料,设计一种转喷微注装置,该装置能将连续、微量的纳米Al₂O_3p注入到Al熔体中。观察纳米Al₂O₃增强相对Al(7075)基体合金材料微观组织的影响,并测试Al(7075)基体和纳米Al₂O_3p/Al(7075)复合材料的磨损特性。对纳米Al₂O_3p/Al(7075)复合材料和Al(7075)基体在不同载荷(15 N、25 N和35 N)下的磨损特性进行对比研究。结果表明:球磨-转喷微注法制备的纳米Al₂O_3p/Al(7075)复合材料晶粒较小,且增强相在基体中分布均匀且结合良好;随着载荷增大,纳米Al₂O_3p/Al(7075)复合材料磨损量的上升趋势慢于Al(7075)基体。载荷为35 N时,纳米Al₂O_3p/Al(7075)复合材料的磨损量较Al(7075)基体少,磨屑尺寸较小,其耐磨性能明显改善,这主要得益于纳米Al₂O_3p的支撑作用和材料的细晶强化作用。      

Friction and wear of Synfluo 180XF wax and nano-Al2O3 filled Nomex fabric composites

Nomex fabric composites filled with the particulates of Synfluo 180XF wax (SFW) and nano-Al₂O₃ was prepared by dip-coating of Nomex fabric in a phenolic resin containing particulates to be incorporated and the successive curing. The friction and wear performance of the pure and filled Nomex fabric composites sliding against AISI-1045 steel in a pin-on-disk configuration were evaluated on a Xuanwu-III high temperature friction and wear tester. The microstructure of the composites, and the morphologies of the worn surfaces and the morphologies of counterpart steel pins were analyzed by means of scanning electron microscopy. And the elemental plane distribution of Al on the cross-section of the Nomex fabric composites filled with nano-Al₂O₃ was analyzed with an energy dispersive X-ray analyzer (EDAX). The results showed that the addition of Synfluo 180XF wax in composites have the potential to increase wear resistance and friction reduction of Nomex fabric composites, and the addition of the nano-Al₂O₃ with the optimum mass fraction in composites can improve the anti-wear ability of the composites. Besides the self-properties of the filler, the character of the microstructure of the Nomex fabric composites filled with different particles, coupled with the character of the transfer film, largely accounts for the improved anti-wear and friction-reducing abilities of the filled Nomex fabric composites as compared with the unfilled one.     

纳米Al2O3及酚酞聚芳醚酮改性环氧复合材料性能

通过机械分散技术制备了纳米Al₂O₃ /环氧、酚酞聚芳醚酮/环氧和纳米Al₂O₃/ 酚酞聚芳醚酮/环氧复合材料,并对比研究了其拉伸模量、拉伸强度、断裂性能和热性能。结果表明：纳米Al₂O₃及酚酞聚芳醚酮在环氧树脂中呈均匀的分散状态;纳米Al₂O₃使环氧树脂拉伸模量增加,使拉伸强度先增后降;酚酞聚芳醚酮使环氧树脂拉伸模量略微下降,对拉伸强度影响不明显;纳米Al₂O₃/酚酞聚芳醚酮/环氧三元复配体系的拉伸模量和拉伸强度呈非单调变化的趋势;纳米Al₂O₃和酚酞聚芳醚酮对环氧树脂均有增韧作用,三元复配体系增韧效果更明显,表现出协同增韧效果;高含量纳米Al₂O₃降低了环氧树脂的初始分解温度,而其余填料对环氧树脂热稳定性具有改善作用,填料均使环氧树脂玻璃化转变温度有所降低。     

Microstructure of Al2O3 nanocrystalline/cobalt-based alloy composite coatings by laser deposition

Composite coatings, made of nano-Al₂O₃/cobalt-based alloy, produced by a 5-kW CO₂ laser on Ni-based superalloy were investigated. The coatings were examined to reveal their microstructure using optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffraction instrument. The results showed that some equilibrium or non-equilibrium phases, such as γ-Co, Cr₂₃C₆, CoAl₂O₄, Al₂O₃ and ε-Co existed in the coatings. Fine and short dendritic microstructure and columnar to equiaxed transition occurred by adding nano-Al₂O₃ particle. With the increase of nano-materials (1%, mass fraction), fully equiaxed crystallization appeared. These were contributed to that nano-Al₂O₃ particles acted as new nucleation site and rapid solidification of the melted pool. The results also showed inhomogeneous dispersion of nano-Al₂O₃ that resulted in the formation of ε-Co phase in the coatings. The sub-microstructure of the clad was stacking fault. The mechanism of formation of equiaxed grains was also analyzed.     

20vol%体积分数纳米Al2O3颗粒增强铝基复合材料的高温压缩性能

为提高铝基材料的高温力学性能以满足其在573 K以上用于航空航天装备结构件的性能需求,采用高能球磨结合真空热压烧结工艺制备了体积分数高达20vol%的纳米Al₂O₃颗粒(146 nm)增强铝基复合材料,对其微观结构和高温压缩性能进行了研究。结果表明：纳米Al₂O₃颗粒均匀分散于超细晶铝基体中,且复合材料完全致密;该复合材料具有优异的高温压缩性能：应变速率为0.001/s时,473 K时压缩强度高达380 MPa,即使673 K时依然高达250 MPa,比其他传统铝基材料提高至少1倍;通过对其流变应力进行基于热激活的本构模型拟合可以发现,该复合材料具有高的应力指数(30)和表观激活能(204.02 kJ/mol)。这是由于高体积分数纳米颗粒能够有效钉扎晶界,并与铝基体形成热稳定的界面结合,显著提高复合材料的组织热稳定性,而且在变形过程中与晶界有效阻碍位错运动,显著提高复合材料的热变形门槛应力(在473～673 K时为190.6～328.4 MPa),其热变形过程可以由亚结构不变模型进行解释。     

热障涂层陶瓷层材料LnMgAl11O19(Ln=La,Nd)粉体的性能

用共沉淀法制备LaMgAl₁₁O₁₉粉体,证明了提高沉淀温度和pH值可使前驱粉体的性能明显提高。应用差热分析和X射线法研究了磁铅石相的生成温度和粉体的结晶度;使用Scherrer 公式并结合XRD谱计算了晶粒尺寸;用扫描电镜观察了各工艺参数的前驱粉体在1500℃时效5 h后的形貌;使用Malvern ZEN3600粒度仪和Manual measurement软件分析了粉体硬团聚的尺寸分布;用Nd₂O₃, Gd₂O₃, Sm₂O₃替代La₂O₃,研究了制备多种镁基六铝酸盐粉体的可行性。结果表明：在pH值为11.5、沉淀温度为60℃条件下制备的前驱粉体,其完全相变为纯LaMgAl₁₁O₁₉粉体的初始温度为1440℃,比在常温下沉淀的前驱粉体降低了150℃,磁铅石相的生成效率明显提高。在1500℃时效5 h的粉体其晶粒为纳米尺度。提高沉淀温度和pH值有利于减小晶粒尺寸和降低粉体的热导率。采用相同工艺参数可制备出纯NdMgAl₁₁O₁₉粉体,其晶粒尺寸略大于LaMgAl₁₁O₁₉粉体的尺寸。     

Al2O3/环氧树脂-氰酸酯复合材料反应动力学及力学性能

以双酚A型环氧树脂(E51)和双酚A型氰酸酯(BCE)为原料,研究E51改性BCE共固化反应机制。同时,以E51-BCE为基体树脂,溶胶-凝胶法(Sol-Gel)自制Al2O3为增强体,制备Al2O3改性E51-BCE (Al2O3/E51-BCE)复合材料。通过非等温DSC确定了E51-BCE体系的固化工艺及固化反应动力学,并根据Kissinger法和Ozawa法求得体系的表观活化能分别为66.13 kJ/mol和69.46 kJ/mol。利用红外光谱跟踪固化体系在起始固化温度为160℃、 180℃时的反应历程,结果表明:起始固化温度在160℃时,以E51与BCE直接反应为主;起始固化温度在180℃时, BCE反应活性提高,以BCE自聚反应为主,生成三嗪环的速率加快,少量的BCE直接与E51反应生成恶唑啉结构。对Sol-Gel法自制Al2O3进行FTIR和TEM表征,结果表明:Al2O3为短纤维状的晶体,表面含有少量羟基。SEM结果显示:Al2O3为分散相,与基体间界面模糊, Al2O3/E51-BCE复合材料的脆断面裂纹不规则,为典型的韧性断裂;当Al2O3掺杂量为3wt%时, Al2O3在基体中分散均匀, Al2O3/E51-BCE复合材料的冲击强度和弯曲模量分别为24.2 kJ/m2和2.54 GPa,比基体树脂的冲击强度和弯曲模量分别提高53.65%和22.12%,力学性能得到明显改善。     

Ti3AlC2-Al2O3/TiAl3复合材料在Al液中的熔蚀-磨损行为及其交互作用机制

通过对比分析Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在纯腐蚀、纯磨损及熔蚀-磨损三种条件下的材料流失特征,研究了Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中的熔蚀-磨损行为及熔蚀与磨损的交互作用机制。结果表明,Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中的熔蚀-磨损体积损失比H13钢的体积损失低了两个数量级,随着载荷和转速的上升,Ti₃AlC₂-Al₂O₃/TiAl₃复合材料的磨损由磨粒磨损逐渐向黏着磨损转变。Ti₃AlC₂-Al₂O₃/TiAl₃复合材料的熔蚀、磨损交互作用率的最大值为47.5%,在低载荷或低转速条件下由于铝熔体的润滑作用,Ti₃AlC₂-Al₂O₃/TiAl₃复合材料甚至表现出负的交互作用。这一方面是由于Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中腐蚀时不生成其它界面产物,而仅为极少量Ti元素的溶解;另一方面则是由于TiAl₃基体与Al₂O₃二者所形成的空间网络状结构改善了Ti₃AlC₂-Al₂O₃/TiAl₃复合材料在Al液中的耐磨损性能。      

CNTs添加对Cu-Al2O3复合材料耐电弧侵蚀性能的影响

Cu-Al₂O₃复合材料具有优异的传导性能和力学性能,在耐磨材料领域具有广阔的应用前景。为进一步提升电摩擦条件下复合材料的耐电弧侵蚀性能,本文采用内氧化法与粉末冶金法相结合制备了不同碳纳米管(CNTs)含量的CNTs/Cu-Al₂O₃复合材料,观察了CNTs/Cu-Al₂O₃复合材料中增强相的分布及其与基体界面结合情况,研究了添加不同含量CNTs对Cu-Al₂O₃复合材料传导性能和力学性能的影响,重点探究了CNTs/Cu-Al₂O₃复合材料的耐电弧侵蚀机制。结果表明：原位生成的纳米Al2O3颗粒钉扎位错及对CNTs分布具有调控作用,使CNTs弥散分布在铜基体中。与Cu-Al₂O₃复合材料相比,CNTs/Cu-Al₂O₃复合材料燃弧时间和燃弧能量明显降低,波动更平稳。在电弧侵蚀过程中,...     

亚微米级Al2O3颗粒增强LD2铝合金复合材料的拉伸性能与强化机制

为克服颗粒增强铝基复合材料的强度低、脆性大、机械加工难等问题, 选用平均直径为0.15Lm, 细小且接近圆形的Al₂O₃颗粒增强LD2铝合金, 对其铸态材料和挤压材料的室温及高温拉伸性能进行了考察和组织分析, 结果发现: 颗粒尺寸小到亚微米级之后, 材料的组织中极难观察到位错, 增强机制也有所变化。在30～ 40% 体积率的挤压材上得到了640～ 760M Pa 拉伸强度和8. 6～2% 的延伸率, 增强率达到了212% , 获得了高强度、高塑性、易加工性的复合材料。      

片状纳米Al2O3/环氧树脂复合材料的制备及性能

采用水热法制备片状纳米Al₂O₃,经过偶联剂改性后与环氧树脂复合,通过溶液混合法制备了不同填充量的片状纳米Al₂O₃/环氧树脂复合材料,研究了片状纳米Al₂O₃用量对片状纳米Al₂O₃/环氧树脂复合材料介电性能和热性能的影响,利用SEM对复合材料的断口形貌进行了表征。结果表明: 片状纳米Al₂O₃在环氧树脂基体中分散良好;随着片状纳米Al₂O₃填充量的增加,复合材料的起始热分解温度升高、介电强度增大,当片状纳米Al₂O₃的填充量为7wt%时,复合材料的介电强度为 29.58 kV/mm,比纯环氧树脂的介电强度提高了30%;复合材料的介电常数(3.8~4.5)和介电损耗(0.015)比纯环氧树脂稍有增大,但仍维持在较好的介电性能范围内。     

掺杂纳米SnO_2-Al_2O_3/Cu新型电触头复合材料的制备及耐磨性能

为满足低压电器对于高品质电触头材料的迫切需求,同时保护稀缺资源、降低电触头成本,采用粉末冶金工艺制备了掺杂纳米SnO_2-Al_2O_3/Cu新型电触头复合材料,并对其电导率、硬度及耐磨性能进行了研究。结果表明:复烧与冷变形工艺均可显著提高复合材料的烧结质量、密度、电导率与硬度。随着纳米Al_2O_3及掺杂纳米SnO_2颗粒的总含量增加,掺杂纳米SnO_2-Al_2O_3/Cu电触头复合材料的硬度与耐磨性能表现出了相同的变化规律,即先升高后降低。当纳米Al_2O_3及掺杂纳米SnO_2颗粒的总含量为0.80wt%时,复合材料的硬度与耐磨性能均达到最优;而当纳米Al_2O_3及掺杂纳米SnO_2颗粒的总含量保持0.80wt%不变时,随纳米Al_2O_3颗粒的含量增加,掺杂纳米SnO_2-Al_2O_3/Cu电触头复合材料的硬度与耐磨性能改善;当掺杂纳米SnO_2颗粒的含量为0时,复合材料的耐磨性能达到了最优。因此较之掺杂纳米SnO_2颗粒,纳米Al_2O_3颗粒对掺杂纳米SnO_2-Al_2O_3/Cu电触头复合材料的耐磨性能有更显著的提高作用。     

Microstructure and mechanical performances of ZTA/LaAl11O18 composite prepared by a heterogeneous precipitation method

Al₂O₃ composite combinatively strengthened by ZrO₂ and in situ formed LaAl₁₁O₁₈ was prepared by a heterogeneous precipitation method. The sintering temperature was significantly lowered in comparison with monolithic Al₂O₃. ZrO₂ and LaAl₁₁O₁₈ inhibited Al₂O₃ grain growth, forming fine and uniform microstructure in the material. SEM showed that increasing numbers of Al₂O₃ and LaAl₁₁O₁₈ grains fractured transgranularly, because of the strengthened grain boundary by residual thermal stress. X-ray diffraction revealed that ZrO₂ was exclusively in tetragonal symmetry (t-ZrO₂) and did not transformed to m-ZrO₂ under the fracture stress. The strength of the material was about 1 GPa, almost doubled over that of monolithic Al₂O₃.     

稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻性能的影响

采用低温固相化学反应法制备了Pr₂O₃掺杂的ZnO纳米复合粉体, 并用此粉体在不同烧结温度下制备了高压ZnO压敏电阻。采用X射线衍射、 比表面测试、 透射电镜、 扫描电镜等手段对制备的ZnO纳米复合粉体及高压ZnO压敏电阻进行了表征, 并与未掺杂ZnO压敏电阻进行了对比研究, 探讨了稀土氧化物Pr₂O₃掺杂对高压ZnO压敏电阻电性能的影响机制。结果表明: 较低的烧结温度(1030～1130 ℃)时, 掺杂的稀土氧化物Pr₂O₃偏析于ZnO晶界中, 有活化晶界、 促使晶粒生长的作用; 同时, Pr₂O₃掺杂导致1080 ℃烧结的ZnO压敏陶瓷体中晶体相互交织形成晶界织构, 比未掺杂的更均匀和致密, 这有助于高压ZnO压敏电阻晶界性能的改善, 从而提高其综合电性能。当烧结温度为1080 ℃时, Pr₂O₃掺杂的高压ZnO压敏电阻的综合电性能最佳: 电位梯度为864.39 V/mm, 非线性系数为28.75, 漏电流为35 μA。     

Eu3+、Dy3+和Er3+对制备堇青石晶相转变的对比表征

以菱镁矿风化石、工业Al₂O₃和SiO₂微粉为原料, 固相反应烧结合成制备堇青石。通过在反应物中分别加入不同含量的Eu₂O₃、Dy₂O₃和Er₂O₃, 研究分析和对比了Eu³⁺、Dy³⁺和Er³⁺对堇青石晶相组成、晶粒大小、晶胞常数、结晶度及显微结构的影响。采用XRD和SEM表征试样中的晶相和显微结构, 利用X'Pert Plus软件对结晶相的晶胞参数和结晶度进行分析, 采用半定量法对试样晶相组成进行计算, 利用Scherrer公式计算堇青石的晶粒大小。结果表明: 由于Eu₂O₃、Dy₂O₃和Er₂O₃的加入, 通过固相反应烧结所得堇青石试样中出现了莫来石相, Eu³⁺、Dy³⁺和Er³⁺对Mg²⁺的置换作用改变了堇青石相晶格常数和晶胞体积。随着添加剂含量的增加, 堇青石结构中液相量增加, 相对结晶度降低, 常温致密度提高, 堇青石晶粒粒径减小。综合对比分析, Eu₂O₃对堇青石晶相转变的影响程度最弱, Er₂O₃对堇青石晶相转变的影响程度最强, 对提高合成堇青石的烧结性和热震稳定性效果最好。     

Al2O3掺杂BaTi0.85Sn0.15O3陶瓷的制备及性能表征

通过传统固相二次烧结法来制备x wt% Al₂O₃（x=0、1.0、1.5）/BaTi_0.85Sn_0.15O₃（BTS）陶瓷。研究了掺杂不同含量Al₂O₃对BTS陶瓷的微观结构、介电性能及挠曲电性能的影响。结果表明,掺杂Al₂O₃的BTS陶瓷不改变陶瓷的晶体结构,仍为标准钙钛矿结构晶型;Al₂O₃的掺入能够有效降低晶粒尺寸,具有明显的细晶作用。随着Al₂O₃含量的增大,Al₂O₃/BTS陶瓷的介电常数减小,介电损耗得到明显改善,居里峰逐渐宽化且向温度高的方向偏移。Al₂O₃/BTS陶瓷的挠曲电系数随着Al₂O₃含量的增加和测试环境温度的升高均减小。此外,Al₂O₃/BTS陶瓷的挠曲电系数和介电常数之间存在一种近线性关系,但当温度非常接近于居里温度时,这种线性关系减弱。     

Ni0.5Co0.5Fe2O4铁氧体/氰酸酯-环氧树脂复合材料的制备和性能

采用水热法合成Ni_0.5Co_0.5Fe₂O₄铁氧体,并应用于氰酸酯-环氧树脂（CE-EP）复合材料的增韧改性,研究Ni_0.5Co_0.5Fe₂O₄铁氧体对CE-EP固化反应、力学性能及热稳定性的影响。XRD和SEM结果表明,所合成的Ni_0.5Co_0.5Fe₂O₄铁氧体结晶性好、纯净、呈块状,粒径约为20 nm。性能研究表明,Ni_0.5Co_0.5Fe₂O₄铁氧体的加入对CE和EP间的固化反应速度影响不大,且不会改变树脂基体的固化反应机制。与纯CE-EP树脂体系相比,Ni_0.5Co_0.5Fe₂O₄铁氧体/CE-EP复合材料在保持CE-EP玻璃化转变温度（T_g）的基础上明显改善了其韧性,当Ni_0.5Co_0.5Fe₂O₄铁氧体质量分数为3wt%时,其冲击强度和弯曲强度达到最大值,较纯CE-EP树脂基体分别提高了65%和30.3%;但其热分解温度略有降低,可能是由于Ni_0.5Co_0.5Fe₂O₄铁氧体对CE-EP树脂基体高温分解的催化作用造成的。      

纳米Al2O3和TiO2改性有机硅涂层对304不锈钢高温氧化行为的影响

本文以纳米Al₂O₃和TiO₂为主要填料,采用物理混合方法制备了两种纳米改性有机硅涂料,将涂料喷涂于马口铁和304不锈钢表面并室温干燥,获得了两种涂层样品。测试了两种涂层的常规机械性能,研究了600℃空气中涂层对304不锈钢抗氧化性能的影响。结果表明：两种涂层均具有良好的附着力、柔韧性和耐冲击性能。两种涂层均能有效减缓304不锈钢在600℃下的氧化;当纳米Al₂O₃和TiO₂含量比例为4:1时,纳米改性有机硅涂层对304不锈钢的防护效果最佳。     

Synthesis and characterization of Zn/Al2O3 nanocomposite by mechanical alloying

In this study, fabrication and characterization of zinc-based metal matrix nanocomposite reinforced by Al₂O₃ particles was investigated. Aluminum and zinc oxide powder mixture was milled in a planetary ball mill in order to produce Zn/Al₂O₃ nanocomposite. The structural evaluation milled and annealed powders studied by X-ray diffraction, SEM observation and hardness measurement. The zinc crystallite size estimated with broadening of XRD peaks by Williamson-Hall formula. The zinc oxide was found to react with Al through a rapid self-sustaining combustion reaction process. As a result a zinc matrix composite reinforced by Al₂O₃ particulate was formed. The microhardness value of produced nanocomposite powder was about 350 HV which was 10–15 times higher than the microhardness of pure zinc (20–30 HV).     

IR spectra of VO2 and V2O3

IR spectra of the tetragonal modification of VO₂ and of the trigonal form of V₂O₃ are recorded at room temperature and compared with that of V₂O₅. The investigated samples of the two lower-valent vanadium oxides, obtained on temperature-programmed reduction treatment, were also characterized with diffuse reflectance and electron-paramagnetic resonance spectra. The effect of atmospheric oxygen on these materials was revealed with XPS measurements and also studied with IR spectra.