酶催化明胶原位凝固成型陶瓷坯体的研究上

采用天然高分子凝胶进行陶瓷原位凝固成型具有有机物加入量少、无毒等优点.本文讨论了一种新的凝胶化工艺用以成型陶瓷坯体,其原理是利用尿素作为氢键阻断剂,阻止热明胶溶液冷却时的凝胶化转变.待球磨、真空除泡等工艺操作完成后,再加入尿酶使尿素分解,明胶大分子重新获得氢键结合能力,在室温下完成凝胶化转变,形成网络结构,实现原位凝固成型.该成型方法可获得表面光洁,内部均匀的陶瓷坯体.     

酶催化明胶原位凝固成型陶瓷坯体的研究

采用天然高分子凝胶进行陶瓷原位凝固成型具有机物加入量少，无毒等优点。本文讨论了一种新的凝胶化工艺用以成型陶瓷坯体，其原理是利用尿素作为氢键阻断剂，阻止热明胶溶胶溶胶冷却时的凝胶化转变。待球磨，真空除泡等工艺操作完成后，再加入尿酶使尿素分解，明胶大分子重新获得氢键结合能力，在室温下完成凝胶化转变，形成网络结构，实现原位凝固成型。该成型方法可获得表面光洁，内部均匀的陶瓷坯体。     

PCRBSC材料的原位凝固成型制备

依据淀粉颗粒的水中润胀吸水，在加热时产生糊化的特性，实现了一种新的陶瓷原位凝固成型方法。在固相含量接近50％(体积分数)的SiC陶瓷料浆中引入约3％(质量分数)的淀粉，用水溶加热的方法可以原位凝固成型各种形态的SiC陶瓷部件，获得致密、均匀的PCRBSC和RBSC坯体。经真空渗硅，制备出微现结构均匀，性能良好的SiC材料。     

高分子多糖凝胶在高性能陶瓷原位凝固成型中的应用

简要介绍了高性能陶瓷原位凝固成型技术的发展,重点介绍了琼脂糖、明胶、果胶和淀粉等高分子多糖的凝胶特性以及这些多糖凝胶应用于高性能陶瓷原位凝固成型时,对悬浮浆料的流变性能和成型坯体性能的影响.     

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。     

用改性淀粉原位凝固成型制备Al2O3陶瓷

陶瓷凝胶注模成型工艺是一种新颖的成型工艺,它将高分子化学单体聚合的思路引入到陶瓷的成型工艺中.本文用改性淀粉原位凝胶注模成型技术制备了具有较高强度和均匀性良好的氧化铝陶瓷坯体.研究了氧化铝陶瓷的凝胶注模成型工艺中低粘度高固相体积分数浓悬浮体的制备、浓悬浮体的固化、成型坯体的显微结构及性能.     

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。     

计算机辅助无模成型陶瓷部件坯体的工艺

本专利涉及陶瓷材料制造技术。其特征在于首先将海藻酸钠制备成水溶液,然后加入陶瓷粉料和分散剂混合球磨,球磨后的陶瓷浆料室温下除泡。将浆料以一定的厚度铺展在成型工作平台上,在计算机指令下按照部件的CAD模型有选择地在浆料上喷上凝胶剂,引发浆料局部凝胶,然后在已经凝胶的浆料层上通过刮刀再铺上一层新的浆料。不断重复上述过程,直到整个陶瓷部件坯体建造完成。陶瓷坯体经过清洗、干燥后,烧结得到成品。利用本发明工艺成型的陶瓷部件不需要模具,自动化程度高,尺寸准确,工艺周期短,坯体有机物含量低,密度高,内部均匀性好,采用的原料…     

直接凝固注模成型Si_3N_4及SiC陶瓷──基本原理及工艺过程

直接凝固注模成型（ｄｉｒｅｃｔｃｏａｇｕｌａｔｉｏｎｃａｓｔｉｎｇ，ＤＣＣ）是一种崭新的（准）净尺寸陶瓷成型方法。本文报道了采用此法成型Ｓｉ_３Ｎ_４及ＳｉＣ陶瓷的基本原理和工艺过程。ＤＣＣ成型工艺过程为把高固相含量低粘度的陶瓷浆料浇注到无孔模具中，事先加入到浆料中的生物酶及化学物质通过改变浆料的ｐＨ或电解质浓度来改变浆料的胶体化学行为，从而使浆料原位凝固，得到有足够脱模强度的陶瓷坯体。ＤＣＣ成型的特点为坯体密度高（理论密度的５５％～７０％），坯体均匀，不用或只需少量的有机添加剂（少于１％），可成型大尺寸、复杂形状、高可靠性的陶瓷部件。     

琼脂糖凝胶注模成型制备氧化铝陶瓷的研究

本文利用琼脂糖做凝胶剂,对凝胶注模成型所需的水性无毒氧化铝陶瓷浆料进行了正交实验,分析了各因素对凝胶注模成型浆料制备的影响,经实验确定了形成较好琼脂糖凝胶注模成型的技术条件,所得陶瓷坯体具有较高的强度和较好的表面质量。     

Gelation forming of ceramic compacts using agarose

Abstract

The development of a cast forming process for ceramics based on agarose gelation is described and the properties of green and sintered bodies are presented. For this process, a warm alumina slurry containing more than 50 vol.-% solids loading and ～1 wt-% agarose binder (Al₂O₃ basis) is cast into a relatively cold, non-porous mould, resulting in a tough green body formed by gelation (37°C) of the agarose molecules. The green compacts show uniform density distribution, with precise dimensions and very smooth surfaces. After drying, they can be sintered directly without special binder burn out procedures. Complex ceramic parts with thick and thin cross-sections can be formed. The process is illustrated for the preparation of a turbine rotor component.     

Improved consolidation of alumina by agarose gelation

A great effort has been devoted to develop low-cost effective forming methods for the production of complex-shaped parts. One of the most promising processes is low-pressure injection moulding in water in which a slurry gelates in the presence of a thermogelling binder. For this technique agarose has been found to be a suitable gelling additive. This work deals with the manufacturing of alumina by agarose gelation. For such purpose the rheological behaviour of aqueous alumina slips is studied as a function of the polyelectrolyte concentration, the solid loading and the temperature, in order to reproduce the injection conditions. The gelation behaviour of agarose solutions is studied from rheological measurements. Two different routes for preparing the injection slip are studied, the first by adding agarose as a solid powder and then heating the slurry, and the second by preparing independently the slurry and the agarose solution and further mixing at temperatures higher than 60°C. This second route demonstrates to be suitable for obtaining reliable alumina parts with a green density of 58% of theoretical and a sintered density of 98.7% of theoretical, significantly higher than the values reported in previous works.     

Aqueous injection moulding of silicon nitride

The fabrication of pressureless sintered silicon nitride parts by low pressure injection moulding of aqueous slurries is described. A basic requirement for this process is the preparation of a stable suspension with high solids content and appropriate rheological properties. The temperature has also a determining role in the stability conditions of the slip. In this work the effect of temperature on the rheological behaviour of silicon nitride aqueous slips was studied taking into account slip parameters such as the type and concentration of deflocculant, pH, ageing, etc. Once the stability conditions were determined, the effect of a gelling agent (agarose) on the slip rheology was also studied in order to optimize the injection conditions. The rheological behaviour of slips containing 1 wt.% agarose was studied as a function of temperature as well as the influence of sintering aids. Injection moulding was performed at temperatures of 60–65°C and a pressure of 0.4 MPa. Final densities of about 90% theoretical are obtained after sintering at 1750°C in N₂ flow.     

环氧氯丙烷活化琼脂糖凝胶过程强化及性能评价

环氧氯丙烷的低水溶性和活化过程中环氧基水解制约了高活化效率的获得. 通过引入亲水性有机试剂二甲基亚砜,研究了提高Sepharose CL-6B介质环氧基活化密度的方法. 研究结果显示,二甲基亚砜溶剂体系消除了琼脂糖凝胶与环氧氯丙烷之间的相界面,形成了均相反应体系,强化了活化反应. 在10%(j)环氧氯丙烷、0.8 mol/L氢氧化钠及反应时间2.5 h的优化条件下,环氧基活化密度可达100 mmol/mL以上. 上述活化过程对介质的性能没有明显影响. 活化介质对5-氨基吲哚的偶联密度达到95.3 mmol/mL,较常规活化方法提高75%以上.     

Cu micropatterning on n-Si(1 1 1) by selective electrochemical deposition using an agarose stamp

Electrochemical wet stamping (E-WETS) was applied for selective deposition of Cu on n-Si(1 1 1) using an agarose stamp. The agarose stamp was first prepared by molding against a master with an array of depressions using its property of plasticity. Cu microstructures were then fabricated directly by preferential electrochemical deposition involving contact between the stamp and a n-Si(1 1 1) workpiece. The gel stamp behaves as a current flow channel between the working electrode and the counter electrode. Furthermore, it simultaneously supplies electrolyte to preferential parts of the n-Si surface. Cu microstructures complementary of those on the master were patterned on the workpiece. The lateral deviation of the fabricated microstructures from those on the master was approximately 0.6%.     

Gelation of water-based PZT slurries in the presence of ammonium polyacrylate using agarose

Gel casting is a suitable near net shape-forming technique based on the solidification of aqueous suspensions for the production of green parts with interesting economic and environmental benefits. In the present work, PZT-5 suspensions in aqueous media were successfully prepared using ammonium polyacrylate (PAA-NH₄) as the dispersing agent. The gelation of the 46–48 vol.% PZT suspensions in aqueous media based on agarose was studied by measuring the height of the samples before and after demoulding. The study found that the suitable amount condition for development of the green parts made was achieved at 0.082–0.19 wt.% agarose (based on dry solid). The density of the green body produced at the optimum content of agarose was determined. A very uniform part with green density of 52% and 55% before and after drying, respectively, was developed. Small shrinkage was measured after drying and heat treating at 550 °C. Sintered samples at 1250 and 1285 °C showed a theoretical density of 99% with an even smaller shrinkage of 16.2%. The dielectric constant and longitudinal piezoelectric charge coefficients, d₃₃, of the selected samples were 2550 and 680 pC/N, respectively.     

New Aqueous Injection Molding Process for Ceramic Powders

An aqueous injection molding process based on the gelling properties of certain naturally occurring polysaccharides, in particular agar, and its purified derivative, agarose, is described. The materials form nonviscous solutions at temperatures near 100°C which solidify to rigid gels upon cooling below the so-called gel point temperature, 37°C. Gels formed by these materials are strong, nominally 1500 g/cm² for agar and 2500 g/cm² for agarose at 3 wt% concentration. Molded parts can be dried and fired without use of absorbent powders or special debinding operations of any kind.     

Preparation of genipin‐fixed agarose hydrogel

Genipin, a naturally occurring crosslinker, was employed to modify agarose in aqueous medium at pH ～ 7 at ambient conditions. The physical and rheological properties were studied. The genipin‐fixed agarose hydrogel (0.8 wt % genipin with respect to the polysaccharide) having the maximum swelling capacity was obtained after 85‐h crosslinking reaction. The reaction mixture developed a dark blue color with the passage of time, indicating thereby the progress of the crosslinking reaction in presence of genipin. The maximum swelling of the genipin‐fixed agarose hydrogel in acidic medium at pH 1.2 was ～ 48 g/g, whereas the parent polysaccharide agarose achieved equilibrium swelling state at 6 g/g. The genipin‐fixed agarose showed 30% weight loss in Ringer's solution, while the agarose polysaccharide exhibited ～ 50% weight loss in the same medium, both after 60 days. The thermogravimetric analysis studies revealed enhanced thermal stability of the genipin‐fixed agarose hydrogel. In view of the enhanced stability and swelling capacity of the genipin‐fixed agarose compared to agarose, the value added polysaccharide may be useful in new applications as super absorbents and in biomedical applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 290–296, 2007     

模板剂对共沉淀法合成纳米羟基磷灰石粉体形貌的影响

采用共沉淀法,以Ca(NO3)2.4H2O和(NH4)2HPO4为反应体系,分别添加硫酸软骨素、琼脂糖和天门冬氨酸作为模板剂,引入生物矿化作用,合成了不同形貌的纳米羟基磷灰石粉体。采用X射线衍射法和透射电子显微镜分析了合成产物的晶相结构和粉体形貌。结果表明3种模板剂作用下合成的样品都是纯相的纳米羟基磷灰石。在添加硫酸软骨素(≥0.2%,质量分数,下同)或琼脂糖(1.0%)的条件下,当反应体系钙磷比(钙与磷的摩尔比)为1.67,反应pH值为11.0,纳米羟基磷灰石的形貌分别是梭形短片状和纤维丝状。当天门冬氨酸浓度为2.0%时,若反应体系钙磷比为1.62,反应pH值为10.0,其形貌为类球状;若反应体系钙磷比为1.72,反应pH值为8.5,其形貌则为片状。     

Functionalization of porous agarose film with single‐walled carbon nanotubes as excellent electrochemical interface materials

Three‐dimensional (3D) agarose gel network could be readily modified with single‐walled carbon nanotubes (SWNTs) through their noncovalent interactions. Because of the embedded SWNT network, the agarose‐SWNT film fabricated by the gel‐drying method well maintained its in‐plane shape and size. Compared with pure agarose film, the maximum strain at break and strength of agarose‐SWNT film could be increased by 67.2% and 24%, respectively. More importantly, modifying the bare glass carbon electrode (GCE) with agarose‐SWNT film, we observed 12 times increase in dopamine (DA) electrochemical peak current, and 2.6 times increase in the case of potassium ferricyanide (K₃Fe(CN)₆). The porous 3D agarose network interpenetrated with high‐conductivity SWNT network might contribute to the excellent electrochemical interface property. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers