专利信息

一种水基流延制备陶瓷薄膜的方法一种水基流延制备陶瓷薄膜的方法，属于陶瓷薄膜的制备领域。本发明采用水作为流延工艺中的唯一溶剂，采用聚乙烯醇（PVA）和聚乙烯基吡咯烷酮（PVP）为粘结剂，加入量是PVP占PVA和PVP的总质量百分比为10%～30%；选用丙二醇为塑性剂，丙二醇和PVA的质量比为1∶4～1∶1。本发明提出的流延工艺很易实现，工艺过程也易于控制，不仅适用于Al2O3为代表的氧化物粉体，而且适用于SiC、Si3N4、TiC等非氧化物流延法制膜。利用反应诱导凝胶化制备陶瓷素坯的方法一种利用反应诱导凝胶化制备陶瓷素坯的方法，…     

影响陶瓷材料流延成型的关键因素

成型是制备功能陶瓷的关键环节，而流延成型技术是制备高性能超薄陶瓷的关键技术。本文对流延成型的流程进行详细介绍，比较了水基流延成型技术与有机流延成型技术的优缺点；在流延成型过程中，浆料制备、流延膜厚度以及流延膜的干燥等因素影响着流延成品的质量，概述了对这些因素作出的要求。     

凝胶铸技术在陶瓷成型应用中的新发展

凝胶铸模(Gel—casting)是九十年代由美国橡树岭国家实验室提出的一种近净尺寸陶瓷成型技术。由于该方法制备的陶瓷坯体强度高、有机物含量较少(2—4wt％)、工艺简便、可操作性强,因此得到广泛的研究与应用。本文综述了该技术在研究和应用上取得的新的进展。主要包括以下三个方面：(1)克服凝胶铸过程中因氧阻聚而使与空气接触部分的坯体表面产生起皮剥落的现象。与国外采用氮气保护方法不同,现采用化学方法只须在浆料中加入少量添加剂就可达到此目的。(2)凝胶铸技术应用可从微米级、亚微米级陶瓷粉料的成型扩展到粗颗粒(10μm-1000μm)体系的陶瓷和高级耐火材料,已在氮化硅结合碳化硅,重结晶碳化硅等材料的成型制备中取得较好效果。(3)将凝胶铸与流延成型结合,发展了一种新的水基凝胶流延成型工艺,该方法可成型0．1～1．0mm厚各种陶瓷薄片,包括氧化铝陶瓷基板、电子陶瓷层片等材料。     

平面波导YAG/Yb:YAG/YAG透明陶瓷的制备与离子扩散行为

以高纯Y_2O_3、α-Al_2O_3和Yb_2O_3粉体为原料,采用非水基流延成型并结合真空反应烧结制备了平面波导YAG/10%Yb:YAG/YAG(YAG=Y_3Al_5O_(12))透明陶瓷。通过扫描电子显微镜表征了原料粉体、流延膜、素坯和陶瓷的微观形貌。采用分光光度计测试了陶瓷的直线光透过率。采用X射线能谱线扫描测试了Y和Yb元素在陶瓷断面处的扩散分布。研究表明:流延成型工艺可以获得均匀致密的流延膜和素坯结构,并且1 775℃真空烧结30 h后的陶瓷样品在可见光波段的直线光透过率接近80%,在1 100 nm处透过率高达81.5%,其中Y和Yb离子的体扩散系数(Dv)分别是5.79×10~(–15)和7.16×10~(–15),晶界扩散系数(D_g)分别为2.25×10~(–7)和2.20×10~(–7)。     

陶瓷材料流延成型工艺的研究进展

流延成型是制备电子器件用陶瓷基板的关键技术，本文系统地论述了流延浆料的组成，如陶瓷粉末、溶剂、分散剂、粘结剂、增塑剂以及其他添加剂，并且介绍了这些组分的功能以及选择的原则；概述了致密陶瓷材料与多孔陶瓷材料的几种新型流延成型工艺的研究现状，如流延-温压成型工艺、凝胶流延成型工艺、等静压流延成型工艺、流延-冷冻法与相转化流延法等；根据流延技术的最新研究成果，对流延成型技术进行展望，并提出了一些见解     

水基流延工艺制备陶瓷材料的研究

流延法作为制备片层材料的重要工艺已经被陶瓷研究者广泛应用.但是,有机流延体系带来的环境污染、毒性及易燃性等问题已被社会所关注.因此,研究无毒、无污染的水基流延工艺已得到材料界的广泛重视.本文主要概述了国内外水基流延工艺的研究现状,重点介绍了PVA体系、丙烯酰胺凝胶流延体系、纤维素类粘结剂体系及乳胶体系的不同特点;从粘结剂、分散剂、增塑剂等多个角度分析了影响水基流延工艺的技术因素,并提出了很好的解决方法,最后介绍了乳胶体系水基流延工艺在制备片状或层状陶瓷材料方面的应用.     

BaTiO3瓷粉水基流延成型的研究

本文以BaTiO3瓷粉为原料，聚丙烯酸酯类水性粘合剂为载体，通过水基流延成型成功制备了20-25μm的电子陶瓷素坯膜；研究了水性粘合剂对浆料的流变性、流延素坯膜的力学性能及微观结构的影响。结果表明，水性粘合剂的用量为10％时，流延素坯膜的综合性能较好．BaTiO3在粘合剂中分散均匀。     

流延法在Si3N4块体及Si3N4/BN层状材料制备中的应用

本采用流延法制备了Si3N4块体及Si3N4/BN层状材料,流延法已经在陶瓷的制备工艺中得到了广泛的应用,但是很少用于Si3N4体系,尤其是水基流延法。用流法制备Si3N4/BN层状材料时,可以较为容易地控制坯片的厚度,得到性能稳定的层状材料。     

钙长石陶瓷基片的水基流延成型工艺研究

采用水基流延成型钙长石陶瓷基片坯体,研究分散剂、pH值、粘结剂及塑化剂对浆料流动性能的影响.实验结果表明:当浆料中固相含量为48vol%时,以聚丙烯酸胺为分散剂,浆料的pH值10,粘结剂含量为6.0wt%～8wt%时,增塑剂含量为4wt%～6wt%时,可以制备出稳定性良好、流动性适宜的钙长石流延浆料.通过SEM可以看出,高分子膜均匀包覆在钙长石颗粒表面,并且钙长石颗粒分布均匀,没有明显较大的孔隙.     

氮化硅流延膜的制备

流延成型是一种制备高质量陶瓷基片的成型方法.氮化硅是一种高热导率的材料,有望在电子基片领域获得应用.本文利用流延成型制备了具有较好柔韧性和一定强度的氮化硅流延素坯膜.研究了无水乙醇、无水乙醇/丁酮作为溶剂时对浆料粘度的影响.通过优化流延浆料添加剂的各种配比,得出了适合氮化硅粉体(SN-E10)流延的最佳配方.     

Effect of Unfired Tape Porosity on Surface Film Formation by Dip Coating

Thin ceramic layers have been fabricated by dipping green tapes of alumina, formed by the doctor-blade casting method, into aqueous slurries containing mixtures of alumina and either unstabilized zirconia (MZ–ZrO₂) or mullite. It was observed that the formation of a thin layer on the surface of the tape is governed by both liquid entrainment and slip-casting mechanisms, and was accelerated by increasing the withdrawal rate, immersion time, or volume fraction of solids in the slurry used for dip coating. By modifying these parameters, layers as thin as 2 μm and as thick as 108 μm were easily formed. Layer formation was found to be strongly influenced by the structure of the tape surface. Layers formed on the top surface of the tape were found to be as much as 48% thicker than those formed on the bottom surface. This difference appears to be related to the smaller amount of porosity on the bottom surface of the tape. Evidence suggests that the polymer binder, used for doctor-blade casting, concentrated on the bottom of the tape as evaporation occurred from the top surface. The lower porosity on the bottom reduced the casting rate during dip coating and produced significantly thinner layers, relative to the top surface.     

Preparation and electrical properties of multilayer ZnO varistors with water-based tape casting

Multilayer ZnO varistors were prepared by water-based tape casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the tape casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for tape casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based tape casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based tape casting display comparable good electrical properties to those prepared by solvent-based tape casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based tape casting is suitable for the manufacture of high performance multilayer ZnO varistors.     

Effect of plasma treatment of polymeric tape carriers on wetting behaviour of aqueous ceramic tape casting slurry

Due to environmental and health aspects, aqueous ceramic slurries are preferred to traditional organic solvent systems in tape casting. An important obstacle associated with the high surface energy of water is poor wetting of aqueous ceramic slurries on polymeric tape carriers. Therefore, we measured the contact angles of an aqueous epoxy-based ceramic slurry on polyethylene terephtalate (PET), polypropylene (PP), polymethyl methacrylate (PMMA), and aluminium-coated polyethylene terephtalate (PET-Al) films and investigated approaches to improving their wetting. We evaluated the effect of plasma treatment of the tape carrier surface on the wetting behaviour and compared it with the effect of adding non-ionic amphiphilic surfactants to the ceramic slurry. The treatment of the tape carrier surface by low-temperature plasma substantially improved the wetting behaviour of aqueous ceramic slurry. The lowest contact angle of 31° was obtained on the PET film. Although the addition of non-ionic surfactants improved both the wetting behaviour of the slurry and the detachment of the polymeric carrier from the ceramic tape even better than the plasma treatment of the carrier surface did, the plasma-treated carriers still present a useful alternative to the surfactants. In the case of the plasma-treated PET carrier the surfactants could be fully eliminated and potential drawbacks related to the use of surfactants could be prevented.     

Influence of Green Formulation and Pyrolyzable Particulates on the Porous Microstructure and Sintering Characteristics of Tape Cast Ceramics

Porous morphology and total porosity produced in sintered ceramic tapes was controlled by the amount and distribution of pyrolyzable graphite particles added to a colloidal suspension during a tape casting operation. A conceptual model of the green tape microstructure was used to explain the influence of graphite and tape formulation on sintering characteristics. The creation of a connected, open porous network in the sintered body was the result of graphite particle percolation within the green body. Additional voidage introduced by particle bridging was the source of excess porosity and also resulted in a bimodal pore size distribution. Sintering shrinkage was determined by the ceramic packing density, which was primarily determined by the tape formulation.     

Gel-tape casting as a novel method for the production of flexible fine-grained alumina sheets

The paper reports on the development of a new aqueous gel-tape casting method for processing nanosized powders into thin fine-grained sheets with a high relative density after sintering. The method was based on casting a low-viscosity slurry into a tape, using the doctor-blade method and gelling the slurry after the casting. The gelled tape was removed from the tape carrier without any solvent evaporation and the drying of the gelled tape was performed later in a climate box under controlled temperature and humidity. The epoxy-based ceramic slurry could be prepared with a solid loading of 42 vol.%. Ceramic sheets with flat and smooth surfaces were prepared in a thickness range from 0.08 to 0.4 mm after sintering. The sintered sheets reached a relative density of 99.4%, with an average grain size of about 1.1 μm. The strength and flexibility of alumina sheets were investigated and discussed.     

The effect of tape casting operational parameters on the quality of adjacently graded ceramic film

For small length tape casting of ceramic slurries varying green film thickness is often a problem. To optimise this, the following parameters were investigated: single blade, double blade, using a pump system and a modelled speed change mode have been analysed. Advantages and limitations of every method are described here. The tape casting experiments were built to be generic in order to allow the control of various processing conditions.From these results, the single-blade technique was chosen for a study of side-by-side tape casting. The influence of the geometric parameters of partitioning the casting tank into chambers, on the quality of graded tape was studied. Tape casting experiments at different speeds and partition tongue lengths in combination with rheological tests revealed that high casting speeds and absence of the partition under the blade are detrimental to the formation of the smooth well-controlled interface between the co-cast slurries, required for most of applications.     

Functionally Graded Ceramics Fabricated with Side‐by‐Side Tape Casting for Use in Magnetic Refrigeration

Functionally graded ceramic tapes have been fabricated by a side‐by‐side tape casting technique. This study shows the possibility and describes the main principles of adjacent coflow of slurries resulting in formation of thin plates of graded ceramic material. Results showed that the small variations of solvent and binder system concentrations have a substantial effect on slurry viscosity. Varying these parameters showed that side‐by‐side tape casting with a well‐defined interface area is possible for slurries with viscosities above 3500 mPa s at a casting shear rate of 3.3 s^?1. As it was expected, the choice of de‐bindering and sintering regimes significantly influences crack formation, and a three‐step heating programme was found to result in tapes of the highest quality. The interface regions of green graded tapes were investigated structurally by scanning electron microscopy; for a distinct identification of the interface region and analysing the degree of cross‐interface diffusion, the isothermal entropy change was measured by a vibrating sample magnetometer as the magnetic transition temperature (Curie temperature) is very sensitive to the dopant level in ceramics. Also the purpose of developing this graded ceramic tape casting was applications of these specific magnetocaloric properties within the magnetic refrigeration technology.     

流延法制备陶瓷薄片的研究进展

流延成型是一种目前使用较广泛,能够获得高质量、超薄型陶瓷薄片的成型方法.本文论述了流延成型时有机物(包括溶剂、分散剂、粘结剂、增塑剂等)的选择原则、浆料的制备以及流延工艺过程,并对影响流延膜厚度和流延膜质量的因素进行了分析讨论,同时提出了改进流延膜质量的措施.