摘 要

注凝成型技术是一种近净尺寸的陶瓷成型技术，其中丙烯酰胺（AM）单体注凝成型体系具备工艺简便、坯体质量好等优点，已被广泛应用。但丙烯酰胺具有强神经毒性，有害于人体健康，因此许多低毒、无毒单体胶凝体系相继被开发。但这些体系因工艺复杂、坯体强度低等问题难以发展应用，所以低毒单体胶凝体系的改性研究具有重大意义。本文选用低毒的DMAA胶凝体系注凝成型制备氧化铝陶瓷，并首次将纤维素纳米晶（CNC）引入陶瓷制备技术，探讨CNC添加量对氧化铝坯体及烧结后样品性能的影响。本课题采用了XRD和SEM等测试手段探究了材料组成、制备工艺、结构和性能之间的关系。

以CNC为添加剂，探究了CNC添加量对DMAA单体注凝体系中氧化铝凝胶坯体力学性能的影响规律，并分析作用机理，结果表明：坯体干燥收缩率随CNC的添加而逐渐降低，一方面CNC表面的羟基具有锁水效应，水分子产生塑化作用，导致收缩率变小，另一方面，CNC会使料浆黏度增加，分子间结合力提高，坯体尺寸趋于稳定；CNC为细棒状刚性纳米材料，具有高强度与高弹性模量，可抑制微裂纹的扩展，当CNC含量为0.2wt%时，坯体抗折强度提高23%，而含量继续增大时，料浆黏度升高，导致应力集中，强度不再提高。将坯体分别置于氩气和空气两种气氛中烧结，探究了CNC添加量和烧结气氛对烧成样品物理性能的影响，结果表明：烧成样品抗折强度高达270MPa，CNC高温烧结转变成为碳，对样品吸水率、气孔率、体积密度和抗折强度基本无影响，不会显著提高样品强度，也不存在降低效应，但能大幅提高热导率；氩气烧结时，未排胶残留的有机物很难排出，对烧成强度有负面影响，使空气烧结的样品性能略优于氩气烧结。

关键词：注凝成型；纤维素纳米晶；低毒胶凝体系；物理性能

Abstract

Gel-casting is a kind of near net size ceramic forming technology. Among them, the acrylamide (AM) monomer gel system has advantages such as simple process, good quality of green body ,and has been widely used. However, acrylamide has strong neurotoxicity and is harmful to human health, so many low toxic and non-toxic monomer gel systems have been developed. But these systems are difficult to develop because of the complex process and the low strength of the green body. Therefore, it is of great significance to study the modification of low toxic monomer gel system. In this paper, low toxic DMAA gel system was chosen to prepare alumina ceramic by gel-casting, and the cellulose nanocrystal (CNC) was first introduced into the ceramic preparation technology to explore the effect of CNC addition on the properties of alumina body and sintered samples. The relationships between the chemical composition, preparation process, structure and properties have been investigated by XRD, SEM, etc.

The influence of CNC content on the mechanical properties of alumina gel body in DMAA monomer coagulation system was investigated by using CNC as additive, and the mechanism was analyzed. The results show that the drying shrinkage of the green body decreases gradually with CNC addition. On the one hand, the hydroxyl on the surface of CNC has the effect of water locking, and water molecules cause plasticization, resulting in smaller shrinkage. On the other hand, CNC will increase the viscosity of the slurry, the intermolecular bonding force increases, and the size of green body tends to be stable. CNC can inhibit the expansion of micro cracks because it is a kind of rigid thin rod structure nano materials with high strength and high modulus of elasticity. When the CNC content was 0.2wt%, the bending strength of green body increased by 23%; when the CNC content continued to increase, the viscosity of slurry increased, leading to stress concentration, so strength is no longer improved.

The bodies were sintered in two atmospheres of argon and air respectively, and the influences of CNC addition and sintering atmosphere on the physical properties of fired samples were investigated. The results indicated that the bending strength of sintered samples was as high as 270MPa, and the CNC became carbon at high temperature, which has no effect on the water absorption, porosity, bulk density and bending strength. It does not significantly increase the sample strength, nor has a reduction effect, but can substantially improve the thermal conductivity. When sintering atmosphere is argon, the residual organic matter is difficult to discharge, which has a negative effect on the sintering strength, thus the sample sintered by air is slightly better than argon sintering.

Key Words：Gel-casting; cellulose nanocrystals; low toxic gel system; physical properties

目 录

摘 要 I

Abstract II

目 录 IV

第1章 绪论 1

1.1 课题研究的目的及意义 1

1.2 注凝成型的研究进展 2

1.2.1 低毒凝胶体系的国内外研究进展 3

1.2.2 无毒凝胶体系的国内外研究进展 3

1.3 纤维素纳米晶的研究进展 3

1.3.1 纤维素纳米晶的制备方法 4

1.3.2 纤维素纳米晶在复合材料中的应用 4

1.4 本课题研究的主要内容 5

第2章 纤维素纳米晶对注凝成型陶瓷坯体力学性能的影响 6

2.1 实验 6

2.1.1 实验原料、试剂与主要仪器 6

2.1.2 样品制备 7

2.1.3 性能测试与表征 8

2.2 结果分析与讨论 9

2.2.1 坯体的干燥收缩分析 9

2.2.2 坯体的抗折强度分析 10

2.2.3 坯体的相组成分析 11

2.3 本章小结 12

第3章 纤维素纳米晶对注凝成型陶瓷物理性能的影响 13

3.1 实验 13

3.1.1 样品制备 13

3.1.2 性能测试与表征 13

3.2 结果分析与讨论 15

3.2.1 样品的烧成收缩分析 15

3.2.2 样品的吸水率、气孔率、体积密度和抗折强度分析 16

3.2.3 样品的热物理性能分析 18

3.2.4 样品的断面显微结构分析 19

3.3 本章小结 20

第4章 全文结论及展望 22

4.1 全文结论 22

4.2 展望 22

参考文献 23

致 谢 25

第1章 绪论

在科学技术不断进步的二十一世纪，材料、信息与能源被誉为现代文明的三大支柱，不断推动着人类社会的前进。其中，材料是当代文明和高新技术发展的物质基础，材料科学也始终是各国学者的研究热点。随着科技的迅猛发展，人们在传统材料的基础上，开发出各式各样的新材料，其研发水平已成为衡量一个地区科技进步的重要标志。

特种陶瓷，也称高性能陶瓷，作为新材料中的重要一员，凭借其独特的性能而普遍应用于化工、冶炼、电子、医学、激光等众多领域，对新型产业的发展起着重要作用。因此，世界各国对特种陶瓷材料日益重视起来，不惜投入大量财力、物力进行研究开发^[1]。氧化铝陶瓷耐磨性好，抗化学腐蚀，具备高强度、高韧性和良好的机械性能，由于这些优良特性在各行业中运用甚广，已成为高性能陶瓷材料中产量最大，应用最为广泛的陶瓷^[2-3]。