氧化锆气凝胶研究进展

氧化锆气凝胶以其优异的性能受到人们广泛的关注。本文综述了氧化锆气凝胶的制备工艺、掺杂改性工艺、SiO2-ZrO2复合气凝胶、纤维增强氧化锆气凝胶的研究进展以及氧化锆气凝胶的应用。最后,对氧化锆气凝胶的发展方向进行了探讨。     

凝胶推进剂的由来与发展

简介了凝胶（Ｇｅｌ）的基本概念；综述和评说了凝胶推进剂的发展概况；提出了实现先进的凝胶推进剂的关键技术在于寻找高效能的凝胶 剂，以及合适的制造工艺和与之相适应的新型发动机。     

凝胶注模成型工艺的研究进展

系统地介绍了凝胶注模成型工艺十余年来的研究进展 ,重点介绍了HMAM工艺和TRG(热可逆转变凝胶注模成型 )两种新型工艺 ,并列举了凝胶注模成型工艺在金属和无机非金属材料方面的应用。最后提出了凝胶注模成型工艺需注意和解决的问题 ,并展望了其未来发展前景。     

凝胶注模制备多孔陶瓷的研究进展

凝胶注模是将传统的陶瓷粉体成型与有机物原位聚合相结合的一种新型成型工艺,为制备高性能、复杂结构的多孔陶瓷提供了一条新途径.在阐述凝胶注模工艺原理的基础上,综述了凝胶注模结合不同成孔方法制备多孔陶瓷的成孔机制以及最新研究进展,并展望了凝胶注模制备多孔陶瓷的发展趋势.     

石棉绒增强SiO2气凝胶隔热材料常压工艺研究

气凝胶是一种优质隔热材料.本文以石棉绒纤维作为气凝胶的增强材料,以水玻璃为硅源,通过常压干燥工艺进行SiO2气凝胶块体保温隔热材料的制备.研究了湿凝胶制备工艺流程及洗涤工艺对气凝胶材料结构及性能的影响.研究发现,以石棉绒为增强材料常压制备SiO2湿凝胶的最佳制备工艺为:在水、纤维和分散剂配制的纤维分散悬浮液中首先加入乙醇搅拌均匀,然后与水玻璃和氟硅酸钠配制的水玻璃凝胶液搅拌混合,再注模固化;在固化湿凝胶的洗涤和溶剂置换工艺中,以水为洗涤溶剂效果好,产品性能高.以石棉绒为增强材料,采用常压干燥工艺制备的SiO2气凝胶隔热材料具有收缩率小,产品规整,密度小,孔隙率高,及较好的强度和隔热性能.     

间甲酚甲醛气凝胶炭化工艺的研究

以间甲酚为原料,经溶胶－凝胶合成,酸洗老化,超临界干燥得到有机气凝胶、进一步炭化得炭气凝胶。采用正交试验方法重点考虑了炭化工艺条件对炭气凝胶结构和性能的影响。     

陶瓷原位凝胶注模成形技术的发展

对凝胶注模成形技术的各种凝胶体系进行了系统介绍，并对这些新凝胶体系的凝胶化原理、工艺过程及应用特点进行了较全面的分析和比较。指出了目前存在的问题及发展趋势。     

熔石英陶瓷凝胶注模成型的凝胶固化过程及其影响因素

凝胶固化过程在凝胶注模成型工艺中是形成坯体和得到较高性能熔石英陶瓷的基础。本文通过对凝胶注模成型凝胶固化过程的研究,不仅从理论上讨论了料浆凝胶固化的反应机理,而且讨论了固化温度、固相体积含量以及引发剂含量对凝胶固化过程及所成坯体性能的影响。     

溶胶--凝胶技术的研究进展

溶胶—凝胶技术的化学过程根据原料不同可以分为有机工艺和无机工艺。以有机工艺为重点介绍了溶胶起始原料的选择、溶胶—凝胶法的原理及工艺过程、溶胶的制备、凝胶的干燥与干凝胶的热处理整个工艺过程，指出了有机工艺与无机工艺的区别。简述了溶胶—凝胶法应用的近期进展以及该方法的优缺点，并对发展前景作了展望。     

用闽西膨润土制备无机凝胶技术的研究

膨润土凝胶广泛应用于精细化工、轻工日化、医药等领域,是一种高附加值的深加工产品。本文研究了用闽西膨润土制备无机凝胶的技术,阐述了无机凝胶的制备工艺和闽西铝(氢)基膨润土的工艺特点,并对工艺过程进行了概括总结。     

N-羟甲基丙烯酰胺聚合体系注凝成型纳米氮化硅陶瓷

注凝成型工艺中通常使用的单体丙烯酰胺是一种神经毒素,它阻止了注凝成型工艺的进一步发展,为此,通过实验研究了一种廉价、低毒N-羟甲基丙烯酰胺单体注凝成型体系及该体系形成凝胶时的用量、温度、预混液的pH值等对凝胶时间和凝胶强度的影响.结果表明:N-羟甲基丙烯酰胺聚合体系在无交联剂时仍能形成凝胶;在固相体积分数为40%纳米氮化硅陶瓷粉体的料浆中仅需质量分数的3%的N-羟甲基丙烯酰胺单体即可通过注凝成型得到可用于机械加工的坯体,完全可以代替丙烯酰胺应用于注凝成型工艺中.     

Gelation process in low-toxic gelcasting systems

Gelcasting has been recognized as a very high-potential method in fabricating complex three-dimensional ceramic parts. The main component of the original gelcasting system (i.e. acrylamide) is a neurotoxic and industry is reluctant to use gelcasting instead of the other ceramic forming methods. Hence, developing of gelcasting systems with similar or superior properties to the original system and low toxicity is required. In this study, gelation kinetics of acrylic acid-based system as a low-toxic gelcasting system were investigated and compared with the original acrylamide-based system, using the Taguchi statistical method.Statistical analysis showed that in both of the gelcasting systems, initiator and accelerator concentrations had the strongest effects on the gelation behaviour. Also, monofunctional monomers had the same effects on the gelation behaviour in both of the gelcasting systems. Between the rest variables (ceramic loading level and crosslinker concentration) a counter interacting term existed which caused to weak the pure effects of these variables on the gelation behaviour of gelcasting systems. In the acrylic acid-based system, unlike the original one, the precise monitoring of the idle time was possible. In this system, in spite of very low activity in the gelcasting process all of the undesirable neurotoxic effects of the original gelcasting system were omitted.     

Defect-free drying of large fine-particle zirconia compacts prepared by gelcasting method

In this work, drying of bodies prepared by gelcasting fine submicrometre-sized zirconia particles was studied and a drying process for defect-free bodies with large cross-sections was proposed. It was found that the cracking of large bodies could be prevented by reducing the monomer content and using appropriate non-volatile cosolvents. Glycerol and polyethylene glycols with different molecular weights were used as non-volatile cosolvents in aqueous ceramic suspensions. The complex effects of the individual cosolvents on the gelcasting process and, in particular, on the drying step were investigated and explained. The applicability of individual cosolvents for the gelcasting process were discussed and their optimal use was indicated.     

α-Al2O3悬浮体的流变性及凝胶注模成型工艺的研究

陶瓷凝胶注模型工艺是一种新颖的成型工艺,具有很好的应用前景。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,可制备高强度、高均匀性的陶瓷坯体。     

Development of ethylene glycol-based gelcasting for the preparation of highly porous SiC ceramics

Aqueous gelcasting is inappropriate for the preparation of highly porous ceramics, due to the large drying shrinkage of green bodies caused by the high surface tension of water. To solve this problem, non-aqueous gelcasting using organic solvents with much lower surface tension was developed. However, for most organic solvents, the precipitation polymerization of gels led to the low strength of green bodies, which was inconvenient for the fabrication of large size workpieces. In this work, a novel ethylene glycol-based gelcasting was developed to prepare highly porous SiC ceramics. Ethylene glycol induced the solution polymerization of gels and increased the strength of green bodies effectively. In addition, the high flexibility of the ethylene glycol-based gels could release the inner stress in the drying process. Highly porous SiC ceramics with large size were successfully prepared by the optimized gelcasting method.     

注凝成型(gelcasting)工艺及其新发展

简要概括了注凝成型的工艺过程及其特点,着重介绍了低毒性凝胶系统的选择、注凝成型技术的扩大应用2个方面.分析了注凝成型现阶段存在的问题,并指出了新的发展方向.     

Porous YSZ ceramics by water-based gelcasting

Gelcasting, as a novel method to form ceramic bodies, has been successfully developed to fabricate porous YSZ ceramics with an open porosity of 33.1–50.3%, mean pore size of 0.66–0.98 μm and the nitrogen permeability of 215–438 m³/m².bar.h. In order to further illustrate the features of this water-based gelcasting process to prepare porous ceramics, the same YSZ powders were blended with the same additives, and then cold pressed and sintered at the same conditions employed for gelcasting process. Compared with the cold pressed samples, the gelcast bodies exhibit higher open porosity, lower closed porosity, relatively larger pore size and thus higher gas permeability. Therefore, the developed gelcasting process is a very effective method to fabricate porous ceramics for filters or supports.     

Study on Gelcasting of Fused Silica Glass Using Glutinous Rice Flour as Binder

Gelcasting is a colloidal processing method for fabricating high-strength and complex shape ceramic green bodies. However, industry has been reluctant to use the gelcasting technique because the most commonly used gel, acrylamide (AM), is a neurotoxin. Here, we report an attempt at the gelcasting of fused silica glass using a natural and nontoxic gel, glutinous rice flour (GRF) as binder. The GRF-based aqueous system was found to behave excellently in the gelcasting process. Flexural strength of fused silica green bodies solidified with only 3 wt% GRF is up to 11.87 MPa. Bulk density and flexural strength of fused silica glass sintered at 1275 °C are 1.75 g/cm³ and 47.02 MPa, respectively.