新型纳米Al2O3强化铜基复合材料的制备及其摩擦学性能

纳米复合材料是目前的研究热点,采用热压烧结法制备了纳米Al2O3颗粒强化铜基复合材料。采用阿基米德排水法测试了复合材料的致密度,采用硬度计测试其硬度,采用表面三维形貌仪测量其磨损体积并观察磨痕的三维形貌;采用摩擦磨损试验机研究了复合材料的摩擦磨损性能并分析其磨损机制;采用扫描电镜及能谱仪观察复合材料磨损前后的表面形貌、分析磨痕的化学成分;研究了工艺参数及Al2O3含量对复合材料性能的影响。结果表明:复合材料的最佳热压制备工艺为热压温度900℃,热压压力27.5 MPa,保温时间2 h,所得铜基复合材料的相对致密度达99.03%;随Al2O3含量增加,复合材料的硬度增加,耐磨性先升高后降低;Al2O3含量为2%时,复合材料磨损量最少,相对耐磨性为3.13,硬度较纯铜提高了35.5%;随Al2O3含量的增加,铜基复合材料的磨损机制从以黏着磨损为主转变为以磨粒磨损为主。     

单壁纳米碳管增强纳米铝基复合材料的制备

将用氢电弧法制备的单壁纳米碳管（SWNTs）提纯后与纳米Al粉体混合，在室温下冷压成型，再在260～480℃真空热压处理，制备出相对密度大于90%，SWNTs弥散分布于纳米Al基体中的单壁纳米管增强纳米复合材料，含量为2.5%（质量分数）的SWNTs对纳米Al基体的增强效果约为55%，SWNTs/纳米Al复合材料的硬度随热压温度的升高而增加，热压温度为380℃时硬度达到峰值2.21GPa，大约是粗晶Al的15倍，比同样温度热压出来的纳米Al块体的硬度高36.4%。     

木基免拆保温建筑模板制备及其性能研究

以木材加工剩余物碎料和自制无机胶粘剂为原料,通过热压工艺制备木基免拆保温建筑模板。研究了施胶量、热压时间、热压温度及板材密度对其性能的影响。结果表明,试验范围内,随着施胶量、密度的增大,木基免拆保温建筑模板的抗折强度、弹性模量、软化系数、导热系数逐渐增大,抗冻性能增强;随着热压温度、热压时间的增加,木基免拆建筑模板的抗折强度、弹性模量、软化系数先增大后减少,导热系数逐渐下降,抗冻性能先上升后下降。通过分析获得木基免拆保温建筑模板优化制板工艺参数:密度为0.9g/cm3,施胶量为65%,热压温度为120℃,热压时间为12min。     

WC-40%Al2O3复合粉末二步热压烧结

以高能球磨机械合金化制得的WC-40%Al₂O₃复合粉末为原料,采用二步热压烧结法制备复合块体。首先将粉末坯体在压力条件下加热到较高的温度 T₁,获得相对致密的坯体结构,此时存在临界的可收缩气孔,然后将其保温在一个相对较低的温度 T₂,通过低温保温实现致密化。由于烧结过程温度相对较低,晶粒长大被有效抑制。采用XRD、SEM、扫描探针（SPM）对复合材料的物相、微观结构进行表征,并进行正交实验分析第二步烧结温度以及保温时间对复合块体微观组织和力学性能影响。结果表明：当 T₁=1600 ℃、T₂=1450 ℃保温6 h时,WC-40%Al₂O₃复合材料成形致密度达到99.03%,维氏硬度和断裂韧性分别为18.36 GPa和10.4 MPa·m^1/2,抗弯强度为1162.1 MPa.     

连续碳纤维复合材料热压成型工艺条件优化研究

以连续碳纤维为增强体,以聚酰胺(PA)为基体,运用平板硫化机热压成型的方法制备连续碳纤维增强热塑性复合材料。对热压温度、热压压力、热压时间和保温时间等成型工艺参数进行考察,通过正交试验设计,研究热压成型工艺参数对复合材料力学性能的影响并分析各参数的影响程度,确定了较优的生产工艺条件,从而具备制得高性能碳纤维复合材料的热压成型工艺条件。     

铟锡氧化物陶瓷靶材热等静压致密化研究

用化学共常常法制备了铟锡氧化物（ＩＴＯ）复合粉末。粉末经冷等静压成型后进行热等静压致密化。热等静压时采用碳钢作包套,采用铜箔作隔层,实验研究了热等静压工艺参数－保温温度、保压压力和保温时间对ＩＴＯ陶瓷靶材致密化的影响。实验结果表明：靶材的相对密度在大约１０００℃处有一峰值;相对密度随压力增加而增加;当保温温度较低时,适当处长保温时间有利于提高密度;当保温温度较高时,延长保温时间反而使密度降低,分析     

AlN-堇青石玻璃复合材料的介电性能

为了研究热压温度和AlN含量对AlN-堇青石玻璃复合材料烧结和介电性能的影响,采用真空热压方法在900~1000℃低温烧结制备AlN-堇青石玻璃复合材料.利用X射线衍射、扫描电镜和阻抗分析仪对复合材料的微结构和介电性能进行了研究.结果表明,随着热压温度的提高,复合材料的相对密度增加,复合材料的介电常数和介电损耗减少;在一定的热压温度下,复合材料的介电常数和介电损耗随着AlN引入量的增加而增加.从复合材料的相组成和结构角度对以上结果予以解释,提高热压温度和增加α-堇青石数量均有利于降低复合材料的介电常数和介电损耗.制备的复合材料具有低的介电常数(5.6~6.5)和低的介电损耗(≤10-3),有望用于微电子封装领域.     

用废纸与木片制备复合包装材料的热压工艺研究

热压温度与热压时间是热压工艺的主要参数,是影响废纸－木材复合材料物理力学性能的重要因素.为了获得较好的热压工艺条件,以杨木刨花为原料,废纸为补充原料,异氰酸酯改性的脲醛树脂为胶黏剂,生产了废纸－木材复合材料,并测试了热压温度与热压时间对废纸－木材复合材料物理力学性能的影响.试验结果表明：随着热压时间的延长,废纸－木材复合材料的物理力学性能相应地提高;在140～170 ℃的热压温度范围内,升高热压温度有助于提高废纸－木材复合材料的物理力学性能.废纸－木材复合材料较适宜的热压工艺条件为：热压时间为每mm板厚30 s,热压温度为170 ℃.     

制备工艺对热压烧结SiC/SiC复合材料结构与性能的影响

采用纳米SiC和亚微米SiC粉料作为基体形成原料,通过热压烧结技术制备了SiC/SiC 复合材料.研究了粉料颗粒、烧结温度、烧结压力对复合材料显微结构和各种性能的影响.结果显示,采用纳米碳化硅粉体可有效降低烧结温度,促进复合材料的致密化过程,在1780℃、20MPa条件下可获得性能优良的复合材料.而采用亚微米SiC粉体,复合材料的致密化过程需要较高的温度,但随着密度的增加,基体与纤维之间的作用力增强,不利于性能的提高.     

AIN-堇青石玻璃复合材料的介电性能

为了研究热压温度和AIN含量对AIN-堇青石玻璃复合材料烧结和介电性能的影响,采用真空热压方法在900～1000℃低温烧结制备AIN-堇青石玻璃复合材料,利用X射线衍射、扫描电镜和阻抗分析仪对复合材料的微结构和介电性能进行了研究,结果表明,随着热压温度的提高,复合材料的相对密度增加,复合材料的介电常数和介电损耗减少;在一定的热压温度下,复合材料的介电常数和介电损耗随着AIN引入量的增加而增加,从复合材料的相组成和结构角度对以上结果予以解释,提高热压温度和增加α-堇青石数量均有利于降低复合材料的介电常数和介电损耗,.制备的复合材料具有低的介电常数(5.6～6.5)和低的介电损耗(≤10-3),有望用于微电子封装领域.     

Preparation of SnO<Subscript>2</Subscript>/C biomorphic materials by biotemplating from ramie fibres

A new SnO₂/C biomorphic material has been prepared by molding into a composite billet and carbothermal-reduction under vacuum from ramie fibres/Sn(OH)₄ precursors. The phase composition and microstructure of the prepared materials were characterized. The effects of the carbonization temperature, holding time and other factors on the crystal structure, morphology and ingredients of the prepared samples were discussed. The results showed that the sintering temperature and holding time have significant effects on the final products. When the sintering temperature reached 480°C, the SnO₂/C biomorphic materials were synthesized successfully.     

热压烧结增强Ca3Co4O9多晶的c轴择优织构和电输运性质的研究

分别采用常压固相反应和进一步的真空热压烧结法制备了Ca_3Co_4O_9多晶块材,通过XRD、SEM、致密度、电阻率-温度曲线、霍尔效应测试,对比研究了热压烧结对多晶织构和电输运性质的影响。结果表明两种方法制备的多晶样品均为c轴择优,经热压烧结后多晶的择优织构显著增强,致密度增大,但真空烧结使样品中氧的化学计量比不足,结晶质量略有下降。热压烧结后多晶的面内电阻率显著下降,其室温电阻率约为常压烧结样品的1/7,且电阻率随温度的降低而增大,这主要是由于热压样品晶粒沿(00l)择优排列显著增强,使沿材料ab面内的电输运占优,且晶界和缺陷散射减弱使Co~(4+)载流子迁移率增大。     

Effect of sintering temperature on microstructures and mechanical properties of spark plasma sintered nanocrystalline aluminum

Organic-coated aluminum nano-powders were consolidated by spark plasma sintering technique with low initial pressure of 1 MPa and high holding pressure of 300 MPa at different sintering temperature. The effect of sintering temperature on microstructures and mechanical properties of the compact bulks was investigated. The results indicate that both the density and the strain of the nanocrystalline aluminum increase with an increase in sintering temperature. However, the micro-hardness, compressive strength and tensile stress of the compact bulks increase initially and then decrease with increasing sintering temperature. The nanocrystalline aluminum sintered at 773 K has the highest micro-hardness of 3.06 GPa, the best compressive strength of 665 MPa and the supreme tensile stress of 282 MPa. A rapid grain growth of nanocrystalline aluminum sintered at 823 K leads to a decrease in micro-hardness, compressive strength and tensile stress. After annealing, a remarkable increase in strain and a slight rise in strength were obtained due to the relief of the residual stress in nanocrystalline Al and the formation of composite structure.     

SDC电解质致密化研究

以共沉淀-喷雾干燥法制备的Ce0.8 Sm0.2 O1.9(SDC)粉体为原料,模压成型后高温烧结获得SDC电解质陶瓷片.研究模压成型过程中加压时间、压力大小以及烧结温度对烧结体致密度的影响,利用XRD和SEM分别对不同烧结温度获得的烧结体结构和表面形貌进行分析.研究表明,压力30MPa、加压时间30min后获得的坯体,随着烧结温度的升高,烧结体致密度呈上升趋势,烧结温度达到1450℃时进入烧结后期,烧结体具有较高的致密度.此外,通过测定烧结过程中坯体收缩率,对SDC电解质陶瓷片的烧结动力学进行了研究,从而确定SDC电解质致密化的烧结温度为1300～1500℃.     

Microstructure development and dielectric properties of fast-fired BaTiO3 ceramics

The technique of zone sintering was applied to three BaTiO₃ source materials; studies were made in air, oxygen and vacuum. The optimum firing conditions suggested for the zone sintering of these materials were a temperature of 1450° C and a time in the hot zone of 5 min. The temperature dependence of the dielectric constant could be closely related to the firing conditions and material microstructure. Lower room-temperature dielectric constants and lower Curie temperatures were found as the holding time in the hot zone was increased, yielding larger grained structures.     

Effects of Sintering Process Conditions on Size Shrinkages of Low-Temperature Co-Fired Ceramic Substrate

The effects of sintering process conditions on the size shrinkages of low-temperature co-fired ceramic (LTCC) substrate were investigated. The process variables investigated were thickness of the stacked raw tapes, lamination pressure, lamination-pressure holding time, pre-heating time, debinding time, sintering dwell time, and sintering temperature ramp. Results revealed that the size shrinkage percentage of the LTCC samples in the lateral directions was always smaller than that in the thickness direction. The lateral shrinkage deviations were less than 2.1% for all the experiments conducted in this study. Pre-heating time, lamination-pressure holding time, debinding time, sintering dwell time and sintering temperature ramp had almost no effects on the lateral size shrinkage of the LTCC samples, and the average of the lateral shrinkage values was 15.3%, with a standard deviation of 0.17%. Lamination pressure and stacked raw-tape thickness had effects on the lateral size shrinkage of the LTCC samples, and empirical equations for calculation of the size shrinkage values were obtained by curve fitting.     

Investigation of Sintering Technology for Composite of Stainless Steel and Partially Stabilized Zirconia

The sintering technology for mixed powedered extrusion rods of different proportions of stainless steel to magnesia partially stabilized zirconia(PSZ) was investigated..The effects of some sintering parameters including holding time ,atmosphere and protective gas pressure on shrinkage,relative density,micostructure,micro-Vickers hardness and compression strength of sintered samples were mainly researched.The experimental results are as follows(1)The shrinkage and the relative density of the sintered samples decrease as increasing stainless steel content in the composite,except for the xase containing 90 percent of stainless steel;(2)The porosity in PSZ matrix rises as increasing the stainless steel content in the composite;(3)Longer sintering holding time ,higher sintering vacuum and gas-pressure sintering process not only enhance the relative density ,but also improve microstructure of composite;(4)Micre-Vickers hardness of PSZ matrix decreases as increasing stainless steel content,while that of stainless steel particles in sintered samples varies unnoticeably.     

聚苯乙烯/CeO2纳米复合微球的粒径及其影响因素

采用原位悬浮聚合法制备了聚苯乙烯/CeO2纳米复合微球。讨论了引发剂浓度、CeO2纳米粒子含量、分散剂聚乙烯醇浓度及复配分散剂等对纳米复合微球粒径及其分布的影响。结果表明,随着引发剂浓度和CeO2纳米粒子含量的增加,纳米复合微球粒径变小,粒径分布变窄;随着复配分散剂中聚甲基丙烯酸钠含量的增加,粒子粒径变小,粒径分别变窄。制得的聚苯乙烯/CeO2纳米复合微球粒径可控。     

Microstructure characteristic, mechanical properties and sintering mechanism of nanocrystalline copper obtained by SPS process

Nano-sized copper powder with an average size of 50 nm fabricated by chemical reduction method of hydrazine hydrate was consolidated using spark plasma sintering (SPS) method. The relationship between the sintering temperature and relative density of the nanocrystalline bulk copper was studied, the microstructure and the mechanical properties were examined, and the sintering mechanism was discussed. It was concluded that the nanocrystalline copper with a relative density greater than 99% and the yield strength of nearly 650 MPa could be fabricated by SPS process with the holding pressure of 600 MPa, sintering temperature of 350 °C, holding time of 5 min, and heating rate of 100 °C/min. Both refinement of the grains and formation of the extensive nanoscale twins in the NC bulk copper are the main factors to strengthen the metal.     

TiB2/FeMo陶瓷的显微结构与力学性能

以Fe-Mo为助烧剂，通过热压制备了TiB2陶瓷．研究了烧结温度、烧结时间对材料显微结构和力学性能的影响，分析了烧结致密化过程．实验结果表明，随着热压烧结温度升高，材料抗弯强度、洛氏硬度出现峰值，热压烧结时间延长，抗弯强度有所下降．液相烧结的重排阶段致密化速率最快．