碳化硅木质陶瓷的显微结构及力学性能

以汉麻秆芯碳化后的碳粉为原料,分别采用注浆和干压成型工艺制备素坯,通过反应烧结制备出碳化硅木质陶瓷.研究了注浆成型工艺中悬浮稳定剂的种类和添加量对浆料性能的影响.采用激光共聚焦显微镜、扫描电子显微镜和X射线衍射仪等分析了碳化硅木质陶瓷的显微结构、物相组成及力学性能.结果表明:采用注浆成型制备的碳化硅木质陶瓷力学性能优异,实测的游离硅含量同理论计算结果一致,说明渗硅过程中硅碳反应充分,烧结体显微硬度、弯曲强度、弹性模量和断裂韧性分别为22.3 GPa、397 MPa、290 GPa和3.0 MPa·m1/2.     

全废瓷料原位凝固成型制备建筑陶瓷的研究

通过瓜尔豆胶原位凝固成型技术制备建筑陶瓷,分别以废瓷粉、瓜尔豆胶和聚羧酸为原料,经原位凝固成型工艺制得陶瓷坯体,通过高温烧结制备建筑陶瓷样品。研究了瓜尔豆胶添加量对浆料流变性能的影响,并对瓜尔豆胶添加量对生坯和烧结性能影响进行分析。结果表明:通过添加0.35~0.55 wt%瓜尔豆胶可实现全废瓷料原位凝固成型,并可以制备具有高强度、低收缩率的瓷质建筑陶瓷烧结样品。     

干压结合冷等静压成形对陶瓷力学性能的影响

本文通过研究在不同压力下进行干压结合冷等静压成形过程对陶瓷素坯体和烧结体的结构、性能的影响,得出了最佳的成形工艺条件,即干压压力为20T、冷等静压压力为200MPa。     

亚微米高纯透明氧化铝陶瓷材料的制备方法

该技术属于透明氧化铝陶瓷材料制备技术领域。其特征在于它依次含有如下的步骤:用干压加冷等静压的成型工艺把α-Al2O3粉末成型;然后对这些坯体使用无压预烧结:无压预烧结的温度为1200～1350℃,时间为30～480min;把预烧结后的坯体置入热等静压炉中进行后处理,处理温度为1150～1350℃,压力为140～190MPa,保温保压的时间为30～60min,用Ar气作保护气,得到的陶瓷体相对密度大于99.9%;最后对烧结出的陶瓷体进行平面磨制和抛光。它不用加任何添加剂,工艺简单;采用低温烧结,能耗低;尤其是晶粒尺寸小于1μm,故称为亚微米氧化铝陶瓷。因而具有较高…     

固含量对凝胶注模成型碳化硅陶瓷性能的影响

碳化硅陶瓷具有优良的性能,广泛应用于各个领域。凝胶注模成型是通过有机单体的聚合反应实现原位固化的成型方法。成型的坯体具有结构均匀、致密度高、强度大等特点。本文采用凝胶注模成型工艺和无压烧结制备了碳化硅陶瓷材料,研究了固含量对无压烧结碳化硅陶瓷微观结构和性能的影响。研究结果表明:随着固含量的增加,碳化硅料浆的粘度值逐渐增加,流动性变差,而制得的碳化硅陶瓷弯曲强度和断裂韧性随固含量的增加而增加。     

淀粉原位凝固成型纯碳反应烧结碳化硅坯体的研究

研究了一种新的陶瓷原位凝固成型方法，其原理是依据淀粉颗粒在水中润胀吸水，在加热时产生糊化的特性。在固相体积分数接近50％的碳粉料浆中引入约3％质量分数的淀粉，用水浴加热期化的方法即可原位凝固成型各种形状的陶瓷部件，获得致密、均匀的坯体。研究了淀粉-碳粉料浆的流变学特性，单纯淀粉呈现膨胀型流动，含淀粉的碳粉料浆悬浮液的表观粘度随淀粉的加入量的增加而提高。料浆中淀粉的加入量应控制在原料干基质量的1％-5％范围内，料浆分散条件为中性。研究了淀粉原位凝固成型的机理以及对素坯结构的影响。     

直接凝胶凝固成型SiC(M,Y)-Al2O3复合陶瓷材料的研究(Ⅱ)基本原理及工艺过程研究

本文研究了一种新的陶瓷原位凝固成型技术 (直接凝胶凝固成型 )的基本原理和工艺过程 ,找出了影响成型工艺的基本因素 ,并且利用该成型技术制备出强度和密度较高 ,且密度均匀性好的坯体。     

陶瓷成型新方法及其应用的研究

介绍和讨论了作为一种借助酶催化化学反应实现原位凝固的崭新近净尺寸陶瓷成型概念的直接凝固注浆成型方法与技术，以及通过与陶瓷粉料混合形成浓悬浮胶体的有机单体在加人偶联剂、催化剂和引发剂后的聚合反应促成原位聚合凝固的注疑成型方法与技术。利用这两种成型技术可以获得均匀、无密度梯度的近净尺寸坯体和致密陶瓷制品。这里也简单介绍和讨论了喷墨打印成型技术。它是一种利用计算机控制实现多层打印、逐层叠加制出三维陶瓷坯体的计算机辅助制造(CAM)陶瓷的成型新技术。     

陶瓷直接凝固注模成型（DCC）原理及应用

直接凝固注模成型是一种崭新的净尺寸陶瓷成型概念，其基本过程是通过酶催化底物的化学反应改变，ｐＨ值至等电点（ＩＥＰ）或增加盐离子浓度，使双电层稳定的陶瓷浓悬浮体实现原位凝固，得到均匀，无密度梯度的坯体，然后干燥（无需脱脂）烧结致密化，本文详细讨论了这种成型工艺的原理和应用研究成果。     

传统硅酸盐泥浆的胶凝注浆成型工艺

研究了固相质量含量达76%～78%的硅酸盐陶瓷泥浆的制备方法。探讨了在上述高浓度泥浆中加入硫铝酸钙后泥浆的流变学性质的变化,硫铝酸钙在水中水解引起溶液电导率的变化,硅酸盐泥浆以及其主要组成成分的ζ电位随泥浆pH值的变化。在此基础上结合成型坯体的SEM形貌观察,提出了添加硫铝酸钙促使硅酸盐泥浆凝固的机理是钙离子向泥浆中释放,使泥浆的离子强度增大,引起泥浆中胶体颗粒的凝聚。以此为基础开发出泥浆的胶凝注浆成型工艺。通过测定成型素坯不同部位的孔隙半径分布,表明用该工艺成型的素坯内部密度分布均匀。     

刚玉瓷成形工艺与断裂韧性K_(IC)的关系

用不同的成形工艺制备氧化铝陶瓷,测量其抗弯强度、断裂韧性等主要力学性能;并讨论了不同的成形工艺与其主要力学性能尤其是断裂韧性K_(IC)的关系。     

Silicon Carbide Platelet/Alumina Composites: I, Effect of Forming Technique on Platelet Orientation

SiC-platelet-reinforced Al₂O₃-matrix composites were made by three different forming techniques, i.e., slip casting, tape casting, and dry compaction of a granulated powder. All samples were densified with hot pressing at 1650°C and 25 MPa for 0.5 h. The orientation of SiC platelets in the composites was studied before and after hot pressing using optical microscopy and a pole figure X-ray device. X-ray diffraction of the (0006) plane of silicon carbide (6H) was used to analyze the degree of preferred orientation. It was found that both tape casting and die pressing could give rise to preferred orientation in green bodies with the faces of SiC platelets parallel to the tape faces or perpendicular to the pressing direction, respectively. The preferred orientation in die-pressed samples also showed an increase with the increase of the compaction stress; however, this reached a saturation level at about 70 MPa in a similar way to the green density. Samples formed by slip casting gave a platelet orientation close to a random one in the green body. After hot pressing, preferred orientation was observed in both slip-cast and tape-cast samples with the faces of SiC platelets perpendicular to the direction of hot pressing. The effect of platelet size on the orientation was also investigated. The preferred orientation in platelet composites was found to yield higher toughness than the random state.     

Influence of forming methods on the microstructure of 3Y-TZP specimens

Nanosized 3Y-TZP powders with particle size of 10–40 nm were formed by gelcasting, dry pressing and cold isostatic pressing. The influence of particle size as well as forming methods on the microstructure and mechanical properties of specimens were investigated. Both SEM images and the analysis on pore size distribution reveal that the gelcast sample possessed more homogenous microstructure. 3Y-TZP powders with particle size of 10 nm have been gelcast with green density as 37.5% of theory and sintered density as high as 96% was achieved. Its fracture toughness was up to 11.9 MPa m^1/2 and the hardness value HV₁₀ is of 15.2 GPa. The difference of microstructure and mechanical properties is explained in terms of the differences in grain size and the forming methods.     

The characterisation of paper-composite porcelain in a green state

A porcelain body traditionally used to produce ceramic art and design objects was re-formulated using additional waste paper. The aim of this study was to develop knowledge into the technological properties of paper-composite porcelain in its green state, for use within the traditional practices of ceramic art and design production.Characterisation was made by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Two different production methods used by potters, slip casting and free-hand pressing, were used.The presence of the paper fibre, the paper type and the content amount are the important factors in strengthening development. Significant differences were found in relation to the content amount of paper fibre, between the mother porcelain body and the different content amount of paper fibre in the paper-composite porcelain body.     

Near‐Net‐Shaping Methods for Ceramic Elements of (Body) Armor Systems

Shape‐forming techniques which may be useful in producing components for body armor are reviewed. The techniques are classified in three general categories, dry, wet, and plastic. The different shaping techniques are compared based on key parameters including shape limitations, rate of production, cost, and safety. The techniques are evaluated as to their suitability to be used to produce different body armor components such as breast plates, deltoid, shin and knee protection, and helmets. Dry‐pressing is the current standard for producing “relatively flat” components such as breast plates, but performance is limited by the inherent problem associated with dry‐pressing, namely, the difficulty in producing homogeneous green bodies because of agglomerates in the powder. Plastic processing has the potential to be useful to produce more reliable “flat” components with improved performance due to high shear mixing breaking up agglomerates. Wet (colloidal) processing techniques such as gelcasting and freeze casting may be useful to produce components with high curvature and more complex shape such as helmets. Tiles or segments may be combined to produce shaped components with increased flexibility.     

Pressureless sinterability of slip cast silicon nitride bodies prepared from coprecipitation-coated powders

The sinterability of compositions from different powder preparation methods (coprecipitation-coating of Si₃N₄ powder or mechanical mixing of Si₃N₄ with Y₂O₃ and Al₂O₃) and compaction routes (dry pressing or slip casting) was compared. Both the coating method and the slip casting process improved silicon nitride sinterability over the mechanical mixing method and dry pressing route. However, the minimisation of powder agglomeration in the green bodies achieved by slip casting is more determinant to the sintering behaviour than the homogeneous distribution of the sintering additives around the Si₃N₄ offered by the coated powder. The coating powder method in combination with the slip casting process is the most favourable processing route, leading to a homogeneous and fully dense microstructure by pressureless sintering at a relatively low temperature of 1750°C. This technique produced materials with hardness of 15·2 GPa, fracture toughness of 7 MPa  m^1/2 and flexural bending strength of 910 MPa.     

Characterisation of the green machinability of AlN powder compacts

The aim of this work is to study the machinability of aluminium nitride green bodies obtained from dry pressing of spray-dried granules. The characterisation of the green machinability of ceramics is not easy. Indeed, to date, no conventional mechanical test able to represent the machining behaviour of green powder ceramic compacts. Therefore, the first target of this work is to determine possible correlations between mechanical properties, microstructure and machinability and to propose suitable tests. Three types of aluminium nitride granules are investigated. Two of theses types of granules are commercial grades using a thermoplastic binder: a conventional grade for pressing and a specific grade especially developed for green machining. The third grade is under development and uses a thermoset binder. From this work it appears that the compacts containing the thermoset binder exhibit simultaneously the highest mechanical properties and the best behaviour at machining. The good machinability has been correlated to a high work of fracture together with a transgranular mode of fracture of the material.     

固体氧化物燃料电池的制备工艺

介绍了不同形状和类型的固体氧化物燃料电池的各结构部件的常用制备工艺方法,包括:用于平板式支撑体制备的干压法和流延成型法,制备平板膜的涂刷、丝网印刷、离心沉积和旋涂法,管式支撑体制备的注浆成型、挤出成型、热压注、浸涂、凝胶铸模和相转换法,以及用于管式膜制备的涂刷、浸涂、料浆喷涂、电化学气相沉积和热喷涂法。针对每种工艺方法,介绍了其原理和基本工艺操作流程及其在固体氧化物燃料电池制备中的应用,讨论了工艺影响因素。     

胶原蛋白流延薄膜的研制

采用流延成型法将胶原蛋白水溶液进行流延、凝固、后处理、干燥等工序制备出了胶原蛋白薄膜;测试了胶原蛋白薄膜的红外光谱和拉伸强度、断裂强度、断裂伸长率等力学性能;讨论了后处理液质量浓度、后处理时间对胶原蛋白薄膜力学性能的影响.结果表明:胶原蛋白分子间发生了交联反应;随着后处理时间延长和后处理液质量浓度增大,胶原蛋白薄膜的拉伸强度、断裂强度和断裂伸长率等力学性能得到改善和提高;对经过后处理的胶原蛋白薄膜进行浸水后,其耐水性有明显提高.红外光谱说明胶原蛋白分子间发生了交联.