流延成型法制备三氧化二铝陶瓷膜基体 (Ⅰ)浆体的制备和流延成型

采用水基浆体流延成型法制备陶瓷膜基体。讨论了分散剂、乳胶液粘结剂、塑化剂对三氧化二铝浆体流动性、韧性和机械强度的影响。实验结果表明 :不加乳液粘结剂 ,分散剂质量分数 0 1 %时 ,浆体的流动性较好 ;采用醋丙和苯丙乳液作粘结剂 ,分散剂质量分数 0 3 %时 ,浆体的流动性好 ,粘度较低 ,适合流延成型 ;用醋叔乳液作粘结剂 ,分散剂质量分数 0 7%时 ,浆体的流动性最好 ,但浆体粘度较高 ;用苯丙乳液粘结剂和邻苯二甲酸二丁酯塑化剂并用 (塑化剂质量分数 1 % ) ,得到的生坯具有较好的塑性、韧性和机械强度。     

Preparation and properties of multi-wall carbon nanotube/SiC composites by aqueous tape casting

MWCNTS/SiC composites were fabricated by aqueous tape casting. High solid content (50 vol%) SiC slurries with sintering additives and multi-wall carbon nanotubes (MWCNTs) as reinforcements were prepared using Tetramethylammonium hydroxide as the dispersant. The stability of MWCNTs/SiC slur-ries was studied and characterized in terms of zeta potential and rheology measurements. The relative density of the composite was about 98% after hot-pressing at 1850℃ (at 25 MPa in Ar for 30 min). The hardness of the composites decreased with the increase in MWCNTs content. The flexural strength and the fracture toughness were 742.17 MPa and 4.63 MPa·m1/2, respectively when the MWCNTs content was 0.25 wt%. Further increase in MWCNTs content to 0.50 wt% did not lead to the increase in mechanical properties. Most of MWCNTs were found to be located at SiC grain boundaries and the pull out of the MWCNTs was observed.     

氧化铝陶瓷凝胶注模成型影响因素的研究

探讨陶瓷凝胶注模成型的机理和特点，研究固相体积含量、pH值、分散剂等对制备低粘度、高固相体积含量的氧化铝陶瓷悬浮液的影响。实验结果表明，固相体积分数为55％浆料的粘度可以满足注模的需要，坯体抗弯强度可达30Mpa。控制pH值为9左右，加入8％的PMAA-NH4分散剂，可制得粘度低、流动性好适宜于复杂形状制品注模的陶瓷浆料。     

ZnO导电陶瓷的制备及电性能研究

采用注浆成型法制得ZnO导电陶瓷 ,通过添加Al2 O3、Cr2 O3、Fe2 O3、La2 O3,探讨了各添加剂对ZnO陶瓷电性能的影响。结果表明 ,聚丙烯酸胺 (PMMA)是ZnO粉体良好的分散剂 ,其质量分数在 0 3%时可得到低粘度、高固含量的ZnO悬浮体。各种氧化物添加剂的添加量对ZnO陶瓷的室温电阻率及电阻温度特性具有较大的影响。随着Al2 O3添加量的增加 ,ZnO陶瓷体的电阻率先略微减小然后增大 ;添加Cr2 O3与添加Al2 O3的效果相反 ;随着Fe2 O3、La2 O3添加量的增加 ,ZnO陶瓷体的电阻率增大。添加Al2 O3、Cr2 O3、Fe2 O3、La2O3的ZnO陶瓷呈现负电阻温度特性。     

Viscosity of kaolin slurries: Effects of dispersant and urea-intercalation

Good fluidity (low viscosity) of highly concentrated kaolin is highly needed in paper-coating industry. We put forward an effective route to improve the viscosity concentration of Beihai kaolin slurries. The effects of various factors such as solid content, pH, dispersant content, and urea-intercalation on the viscosity of kaolin slurries were investigated. The results revealed that the viscosity of kaolin slurries significantly decreased with decreasing solid content or with increasing pH and dispersant content. It was worth noting that urea-intercalation was proven to be an efficient method for promoting the dispersion of highly concentrated kaolin as compared with adding dispersant. The intercalation ratio of urea-intercalated kaolin was increased from 17.36% with 2% of urea addition to 81.30% with 6% of urea addition. Meanwhile, the viscosity concentration of raw kaolin slurry was improved from 65.0% to 70.13% after the intercalation of urea with 6% addition, which was attributed to finer particle size, increased pH value and more negative charges of urea-intercalated kaolin. Therefore, the route is effective to improve the dispersion of highly concentrated kaolin for paper-coating.     

流延工艺对生瓷带结构和微波特性的影响

基于低温共烧陶瓷技术流延工艺的特点,通过研究粘合剂、分散剂和增塑剂等在浆料体系中的力学效应对生瓷带中陶瓷成分颗粒的几何排列及所产生的孔隙排斥等力学特性的影响,以及优化热处理温度对生瓷带的质量损失、延展率和拉伸强度的关系,深入分析了流延过程的关键技术及工艺参数对生瓷带结构和微波特性的影响。研究后提出:通过调整流延浆化浆料中粘合剂、分散剂和增塑剂配比,采用梯度缓变的热处理烘干温度曲线和消除生瓷带累积应力等方法,可明显改善流延工艺过程,最终获得质量稳定、可靠性高和功能满足于微波应用要求的生瓷带。     

原料合金化及烧结方式对NiTi合金性能的影响

镍钛形状记忆合金因具有优良的形状记忆效应、超弹性和良好的生物相容性而被广泛地运用于各个领域。本文研究原料粉末合金化及烧结方式对烧结体结构和性能的影响,分别以金属镍/钛混合粉及镍钛合金粉为原料,通过凝胶注模成形得到生坯,再以不同的烧结方式获得NiTi合金,利用X射线衍射仪和扫描电镜等设备,对原料粉末及烧结体的结构和性能进行分析。结果表明:相对于镍钛混合粉,以NiTi合金粉为原料制备出的NiTi合金组织中NiTi相含量更多;采用热等静压方法在1 050 ℃、9 MPa气压值的条件下,烧结4 h,制备出致密度达到91.5%、密度为5.9 g/cm3的合金,比真空烧结制备出的合金的密度值高出约0.5 g/cm3;同时热等静压烧结出合金的平均硬度值为226.2 HV,比真空烧结出合金硬度高出约33.6 HV。采热等静压的烧结方式能促进烧结过程中合金的致密化,大幅度提高凝胶注模成形制备NiTi合金的密度。     

高致密氧化镁陶瓷的凝胶注模成型

探讨了高致密氧化镁陶瓷水基凝胶注模成型工艺,研究了预烧处理温度对原料的水化活性、粒度及比表面积的影响;同时研究了预烧处理温度、分散剂及固含量等对MgO陶瓷浆料流变学性能的影响。通过DSC-60A热分析仪对MgO陶瓷素坯进行热分析,制定了合适的烧结制度;用SSX-550观察了烧结体的微观形貌。结果表明,MgO粉体随着预烧处理温度的升高,水化活性降低,粒度增大,比表面积降低。在1 350℃处理后的MgO粉活性最低,当分散剂的加入量为3%时,可制备出固含量为54%、黏度低于200mPa.s的流动性良好的稳定浆料。MgO烧结体的密度可达到理论密度的98.32%,且烧结体宏观无缺陷,微观结构均匀致密。     

透气性多孔陶瓷材料制备工艺的研究

以硅酸乙脂水解液为粘结剂,以莫来石、铁粉为原料,通过粉浆浇注、干燥及烧结等工艺过程,制备了多孔透气性莫来石基陶瓷材料。研究了成型及干燥工艺对成型坯体质量及烧结体性能的影响。     

覆膜金属粉末变长线扫描激光烧结成型特性

介绍了利用变长线扫描激光烧结技术制造金属零件的基本原理。在线扫描激光烧结成型实验装置上对覆膜９８Ｆｅ２Ｎｉ合金粉末进行了烧结成型试验,研究了铺粉厚度、预热温度、激光功率、扫描速度及扫描方向等工艺参数对烧结成型性能的影响关系。     

流延成型法制备三氧化二铝陶瓷膜基体(Ⅱ)——陶瓷膜基体的性能及结构表征

以苯丙乳胶液为粘接剂,水为分散介质,采用流延成型法制备了氧化铝陶瓷膜生坯体。通过对生坯体烧结后气孔率及断裂强度的测定,讨论了烧结温度及粘接剂含量对气孔率和断裂强度的影响。结果表明,随烧结温度的升高,基体的断裂强度增加,而气孔率有降低的趋势。在同一烧结温度下,随着粘结剂含量的增加,基体的气孔率增加,在添加了增稠剂羟乙基纤维素(HEC)后,气孔率进一步增加,但增加量不大,并且导致浆体粘度增加,不易流延成型。通过对不同烧结温度的基体的扫描电镜观察发现,氧化铝粒子分布比较均匀,随着温度的升高,晶粒明显长大,致密性提高,气孔率下降。     

Rheologic behavior and PIM processing of WC-TiC-Co powder feedstock

An improved wax-based binder was developed for the powder injection molding (PIM) of WC-TiC-Co cemented carbides. The critical powder loading and the rheologic behavior of the feedstock were determined. It was found that the critical powder loading could achieve up to 62.5% (volume fraction) and the feedstock exhibited a pseudo-plastic flow behavior. The injection molding,debinding and sintering processes were studied. The dimension deviation of the sintered samples could be controlled in the range of _ 0.2% with the optimized processing parameters and the mechanical properties were better than or equivalent to those of the same alloy made by conventional press-sintering process.     

含有定向排列颗粒的氮化硅陶瓷各向异性研究

通过添加α—Si3N4晶须,利用流延成型和热压烧结技术制备舍有定向排列颗粒、各向异性的Si3N4陶瓷。研究α-Si3N4相在流延膜及烧结块体中的分布状态,并通过XRD、SEM和力学性能对流延膜和烧结块体的各向异性进行表征。结果表明,1550℃下烧结制备的块体T（与流延方向平行的平面）、N（与流延方向垂直的平面）、P（侧面）三个面的I（210）／I（102）值与等轴状α-Si3N4粉体的相应值比较,其中T面的值较大,N面和P面的值较小;在T面的显微结构中存在平行于流延方向排列的大颗粒;试样不同面的力学性能（断裂韧性和抗弯强度）中,T面最好,P面次之,N面最差;I（210）／I（102）值、显微结构、力学性能测试结果表明所制备的氮化硅陶瓷存在各向异性。     

流延法制备FeNiMnO4热敏陶瓷薄片

采用有机溶剂浆料系统的流延成型工艺制备了FeNiMnO4热敏陶瓷薄片.通过优化粉体的特性、浆料组成和流延条件,制得的陶瓷薄片厚度为～0.2 mm,表面平整光洁,微结构均匀,密度高达～96%.     

Lu3Al5O12：Ce3+超细粉体的制备及其性能研究

在LuAG：Ce3+闪烁陶瓷的制备中,粉体的性能对陶瓷的透明度有重要影响,提出了采用满足透明陶瓷闪烁体需求的Lu3Al5O12：Ce3+（LuAG：Ce3+）超细粉体制备方法。以CeO2,Lu2O3为原料,NH4HCO3为沉淀剂,聚乙二醇（PEG200）为分散剂,采用共沉淀法在一定温度下灼烧制备Lu3Al5O12：Ce3+（LuAG：Ce3+）超细粉体。通过X射线衍射分析（XRD）、荧光分光光度计（PL）和扫描电子显微镜（SEM）等表征样品的结构与性能。研究分散剂、不同Ce3+掺杂浓度、烧结温度对晶相形成和发光性能的影响。共沉淀法制备粉体的工艺简单,所需烧结温度较低,得到粉体粒径小。结果表明,加入分散剂后的前驱体在1300℃下煅烧2h获得的粉体颗粒均匀,相纯度高,分散性好,制备的LuAG：Ce3+粉体在460nm的蓝光激发下发出505nm的绿光。     

钻头齿面堆焊用硬质合金耐磨性试验

为了选择更合适的钻头齿面强化材料,对多种粒度的球状烧结碳化钨和粒状铸造碳化钨堆焊层分别作了磨料磨损试验,以评价其抗磨性能。用 Ｎｉ 基合金作钎料,在高真空度下将硬质合金颗粒焊至２０ Ｎｉ４ Ｍｏ 表面。试验采用多种冲击能量,磨料介质为石英砂、水和少量悬浮剂,用天平称出磨损失重。结果表明：球状烧结碳化钨或不同类型和粒度混合的碳化钨堆焊层都比现行采用的粒状铸造碳化钨具有更好的抗冲击磨料磨损能力。用球状烧结碳化钨代替粒状铸造碳化钨作钢齿钻头齿面堆焊材料是提高齿面强化效果的有效途径。     

STUDY ON PREPARATION OF YBa_2Cu_3O_(7-x) ULTRAFINE POWDERS BY SOL-GEL PROCESS

The ultrafine powders of YBa_2Cu_3O_(7-x) withthe size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization ofYBa_2Cu_3O_(7-x) in the Sol-Gel synthetic reaction has bee studied.The particle size,pruity,sintering activity and superconductingproperties of YBa_2Cu_3O_(7-x)prepared by Sol-Gel method are betterthan by solid state reaction.     

水泥窑用方镁石-铁铝尖晶石砖的性能研究

以电熔镁砂、铁粉、氧化铁粉和α-Al2O3粉为原料,制备方镁石-铁铝尖晶石砖,研究了烧结温度和铁加入量对方镁石-铁铝尖晶石砖性能的影响,采用XRD和SEM对试样的物相组成和显微结构进行了分析和表征。结果表明,提高烧结温度有利于方镁石-铁铝尖晶石砖性能的提高,1500℃烧成的试样最致密,综合性能较好,增大铁加入量不利于方镁石-铁铝尖晶石砖性能的提高。与直接结合镁铬砖相比,方镁石-铁铝尖晶石砖的常温耐压强度、抗折强度和热震稳定性较好,挂窑皮性和抗侵蚀性与其相近。     

Aqueous Tape Casting Process with Styrene-acrylic Latex Binder

A commercial styrene-acrylic latex binder has been investigated as a good binder for aqueous Al2O3 suspensions tape-casting process. This paper focuses on the forming film mechanism of latex binder, the rheological behaviors of the suspensions, physical properties of green tapes and drying process of aqueous slurries with latex binder system. The drying process of the alumina suspensions is shown to follow a two-stage mechanism ( the first stage : evaporation controlled process ; and the second stage : diffusion controlled process ). During the drying stage of the suspensions, the compressive force presses the latex particles arid makes them be distorted, which results in cross-linking structure in co.acted latex particles of the solidified tapes. A smooth-surface and high-strength green tape was fabricated by aqueous tape casting with latex binder system. The results from the SEM images of the crossing section microstrueture of green tapes show that the latex is a very suitable binder for aqueous tape casting.     

基于SLS的叶轮精密铸造工艺及性能

为提升叶轮零件的铸造质量,将3D打印模样与石膏型精密铸造相结合,对模样的成型位置及浸蜡工艺进行分析,利用选区激光烧结技术 (SLS) 制得高质量叶轮模样,基于顺序凝固和排气优良设计顶注式横浇道 – 内浇道式浇注系统,经ProCAST软件模拟验证设计方案的合理性,最后通过真空加压浇注成功得到合格铸件,并分析T5热处理对铸件力学性能的影响。结果表明：SLS可与石膏型铸造良好结合,3D打印模样的力学性能取决于受力面是否为打印面,浸蜡可明显提升模样的力学性能;铸件经T5热处理后,其抗拉强度和布氏硬度分别从184 MPa和57 HB上升至330 MPa和109 HB,共晶硅的熔断和钝化是力学性能提升的主要原因。