通过不同的纳米尺寸Y TZP形成悬浮液的流变性的研究外文翻译资料

 2022-12-11 20:03:23

Rheology Study of Suspension Formed by Different Nano-sizeY-TZP

Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

( Manuscript received October 18, 1996, in revised form February 24, 1997

The theological properties of slurries formed by different nano-size Y-TZP have been studied.

The viscosity is sensitive to solid loading especially for high solid content level. The dispersant

NH4PAA can improve the flowability efficiently. The smaller ceramic particles need to adsorb

more dispersant to the flowability. Under the same solid content, the smaller the particles, the

higher the viscosity of its slurry.

1. Introduction

The dispersion of ceramic powder is of considerable importance in plastic-forming processes, e.g., slipcasting, injection molding and gelcasting}l}2}.Low suspension viscosity and high solid loading rate are the two conflicting requirements which can be controlled by the adding of dispersant and the selection of particle size distribution as well as other parameters.The theological behaviour of ceramic suspensions con troll the solid loading as well as the forming properties of a green bodyl3}4}. The production of nanocompos-ites would require understanding of the behaviour of slurries forming the green body, especially for thoseFormed finer powder mixtures in colloidal state. Inthis paper, the theological properties of slurries withvarious particle size were observed by measuring the change in viscosity. The influence of the surface area on the viscosity is also discussed.

Table 1 Properties of three powders

Powder I (9000C) II (7000C) III (4500C)

SSA/(mz/g) 18.3 48.1 81.9

grain size/nm 27.3 10.4 6.0

(BET)

grain size/nm 36.8 24.1 10.0

(TEM)

2. Experimental

2.1 Slurry preparation

3Y-TZP powder was prepared by chemical copre-cipitation method and calcinated at 9000C (No.I),7000C (No.II) a,nd 4500C (No.III) respectively. Ta-ble 1 summarizes the physical properties of these pow-ders. A polyelectrolyte dispersant used in the prepa-ration of dispersed Y-TZP slurries was the ammonium salt of polyacrylic acid (abbreviated as NH4PAA)with molecular weight as about 3000. The suspen-sion was transferred into a plastic bottle which wasloaded with zirconia grinding media, then agitated by a turbomixer for 8 h.

2.2 Rheological measurements

Rheological characteristics of the Y-TZP suspen-sions were determined using cylindrical measuring system on rotational viscosimeter (Model Rheomat260, Mettler Toledo AG, Switzerland). To eliminate artifacts from different treatments during the filling procedure, the samples were presheared for 3 min,followed 5 min at rest. Several modes of tests were available.

3.1 Influence of solid content and the amount of dispersant

The viscosity behaviour of powder I with different weight fractions is shown in Fig.l. The relaxation test was carried out at shear rate of 40 s-1, the testing re-suits are listed in Table 2. When the solid content is raised from 49% to 57.5%, the viscosity rises only4.4 mPa-s. But when the solid content is raised from57.5% to 65%, the viscosity increases greatly, almost8 times. That means the viscosity is sensitive to solid content especially from high solid loading level. This is the reason why it is very difficult to prepare the flowable slurry above 80% of zirconia powder. From

Table 2, we can see that with the increase of solid loading the viscosity modulus rises drastically.

By comparing the two columns 3 and 4 in Table2, it is obtained that with the addtion of more dispersant, the yield stress drops from 640 mPa to 48 mPa.In general, a yield stress appearing in the flow curve of a concentrated slurry would be caused by a rigidstructure formed the particle-particle attractive in-teraction. The adding of dispersant forms the repul-sive effect on particles, making the attractive forcedecrease. Other parameters such as viscosity, relax-ation time and elasticity modulus are also decreased.The addition of dispersant NH4PAA can effectivelyimprove the flowability of Y-TZP slurry.

3.2lnfluence of particle size on the viscosity of slurries

Keeping the solid content as 49 wt pct, and the dispersant as 1.12 wt pct (relative to the weight of the powder), we get the flow curve (Fig.2) of slurries formed by different nano-size Y-TZP. The behaviour of the shear stress as a function of shear rate can be fitted the where k is the fluid factor and n is the flow exponent. The three kinds of slurries show reduction in apparent viscosity with increasing shear rate. That is characterized with pseudoplasticity and indicates thixotropic theology. With decreasing of particle size,the fluid factor rises drastically, k of powder I, II an III is 795, 6139 and 7381 respectively. Keeping the shear rate at 40 s-1, the viscosity is 31.0, 204 and269 mPa.s for powder I, II and III respectively. This means under the same condition, provided that the dispersant form a monolayer of polymer on the particles, the smaller the particles, the bigger the effective volume. Although the net solid content of the three kinds of slurries is the same, the smaller powders need more water to be wet and they hold more space than the coarser powder. So the smaller powder has higher viscosity.

3.3 Relationship between viscosity and specific surface area(SSA)

From Fig.3 ,we can see that if the solid content is less than 49 wt pct, the viscosity does not change greatly with SSA. The volume of the powder is much lower compared to that of the solvent. There is enough water between particles to act as moving reagent, so the viscosity changes a little. When the solid content is 65 wt pct, the viscosity increases with SSA expone

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通过不同的纳米尺寸Y TZP形成悬浮液的流变性的研究

（中国科学院上海陶瓷研究所，上海200050）

（手稿于1996年10月18日收到，1997年2月24日修订）

通过不同的纳米Y-TZP形成浆料的流变特性进行了研究。粘度对固体含量很敏感，特别是固体含量高的物体。分散剂聚丙烯酸铵可有效改善流动性。较小的陶瓷颗粒需要吸附更多的流动性分散剂。在相同的固体含量，较小的颗粒，浆料粘度高。

1、简介

陶瓷粉体的分散的过程。例如，注浆成形相当重视，分为注射成型和凝胶注模成型。低的悬浮液的粘度和高固体负荷率都可通过添加分散剂和颗粒尺寸分布的选择以及其他参数的控制这两个相互矛盾的要求的。陶瓷悬浮液的固相控制巨大的流变性能以及坯体的性能。对纳米复合材料的生产中需要泥浆成形坯体的行为的理解，特别是对于细粉的混合物在胶体状态。本文对不同粒径、泥浆流变性能的测量粘度的变化进行观察。还讨论了表面面积对粘度的影响。

表三1种粉末的性质

II（7000c） III（4500C）

（低温）

SSA /（MZ／g）18.3 48.1 81.9

晶粒尺寸/纳米10.4 6 27.3

（比表面）

晶粒尺寸/纳米24.1 10 36.8

（透射电镜）

2、实验

2.1泥浆制备

采用化学共沉淀法制备和烧结3Y-TZP粉末低温分别是（no.i），7000c（no.ii）、Nd 4500C（no.iii）。表1总结了这些粉末的物理性能。一种用于分散Y-TZP浆料的制备聚电解质分散剂聚丙烯酸铵（简称NH4PAA），分子量约为3000。该悬架被转移到一个塑料瓶，上装了各种氧化锆研磨介质，然后用叶轮式混合器搅拌8小时。

2.2流变测量

使用旋转粘度计圆柱测量系统测定了Y-TZP悬浮形式的流变特性（R型，旋转粘度260，瑞士梅特勒-托利多公司）。消除伪影的不同处理的填充过程中，样品被重剪切 3 分钟左右，然后在休息5分钟，几种模式的测试可这样进行。

3、结果与分析

3.1固体含量和分散剂用量的影响

粉末用不同质量分数的粘度特性如Fig.l.表示，进行在40 s-1的剪切率的松弛试验，试验结果列于表2。当固体含量从49%提高到57.5%，粘度上升，仅4.4 mPa.但当固体含量提高f从57.5～65%，粘度大大增加，几乎达到8倍以上。这意味着粘度是敏感的固体含量，特别是从高固体负荷水平。这就是为什么它是很难制备氧化锆粉80%以上的可流动的浆料。

表2，我们可以看到，随着固体加载的增加，粘度模量急剧上升。通过比较两列在表3和4，证明了具有更多的分散剂的加入，屈服应力下降640～48 MPa，屈服应力出现在一个集中的浆料流动曲线将由 一个刚性引起的结构形成的粒子的吸引力相互作用来体现。加入分散剂形成的粒子的斥力西伯效应，使有吸引力的压力下降。其他参数，如粘度、松弛时间和弹性模量也有所降低。分散剂聚丙烯酸铵的加入可以有效地提高Y-TZP浆料的流动性。

3.2、粒度对浆料粘度的影响

保持固含量为49%，与分散剂为1.12%（相对于粉末的重量），我们得到的流量曲线（图2）浆料的不同纳米Y-TZP形成。作为剪切速率的函数的剪切应力的行为，可以安装在何处的流体因子和氮是流动指数。三种浆料显示随着剪切速率的增加，表观粘度降低。具有假塑性，表明触变理论。随着颗粒粒径的减小，液体的因子急剧上升，粉末的钾，Ⅱ为795，6139和7381。保持在40 s-1的剪切速率，粉末粘度分别为31，204 和269 MPa用I，II和III表示。这意味着在相同的条件下，所提供的分散剂形成一个单层的聚合物上的颗粒，较小的颗粒，更大的有效体积。虽然三种浆料的净固含量是相同的，较小的粉体需要更多的水，所以他们拥有更多的空间比粗粉。因此，较小的粉末具有较高的粘度。

3.3粘度和比表面积之间的关系（SSA）

从图中，我们可以看到，如果固体含量低于49%，粘度不随SSA大大改变。和粉末的体积相比，溶剂的粒子之间有足够的水作为移动的试剂，所以粘度变化不大。当固含量为65%，粘度与SSA成倍增加。高SSA微粒需要吸附更多的分散剂是流动的。事实上，用粉末煅烧450.C形成可流动的浆料的上限是65%，700.C为重量百分比和900C粉末为上限是PCT含量获得高固相含量，控制粒度分布的一个明智的办法。

4、结论

（1）形成不同的纳米Y-TZP浆料是特别为高固相含量水平的固体含量的敏感，在我们的测试中，PCT水平高于60wt固体含量。

（2）加入分散剂聚丙烯酸铵可有效改善浆体的流动性。

（3）粉体粒度对浆料流变性能的影响。在相同固载下，颗粒越小，其浆的粘度越高。为了具有相似的流动性、较小的颗粒具有高SSA需要吸附更多的分散剂。

（图以原文为主，部分图由于难处理没给出来，敬请原谅，请参照原文）

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