THE RELATIVE INFLUENCE OF DIELECTRIC AND OTHER DRYING TECHNIQUES ON THE PHYSICO - MECHANICAL PROPERTIES OF A PHARMACEUTICAL TABLET EXCIPIENT. PARTI: COMPACTION CHARACTERISTICS.

The relative Influence of nine techniques for drying wet granulated microcrystal-lline cellulose (MCC) on the subsequent compaction characteristics was studied In terms of the tensile strength and corrected work of failure of the tablets. Wet granulation resulted in a substantial decrease in compatibility. However, the drying technique used was found to affect the degree of loss in compatibility. In general, microwave-vacuum drying using the “high” process type resulted in the production of granules with the highest compatibility followed by freeze drying and fluidized bed drying. Granules dried under ambient conditions, and granules tray dried to “just dry” or “over dried” conditions resulted In tablets possessing approximately comparable compatibilites, with the poorest compaction characteristics being exhibited by vacuum dried granules, in addition It was found that use of a “low” drying process type during microwave- vacuum drying yielded granules with inferior compaction characteristics to those dried by the “high” process type. Radio frequency drying was found to yield granules which produced tablets having slightly inferior tensile strength to tray dried material, although the tablet work of failure values were comparable. The effect of drying technique on the subsequent compaction characteristics was not found to be directly related to the moisture content of the granules.     

微波介质陶瓷的界面特性及其对介电性能的影响

详细地总结了界面的偏析、扩散和润湿性对微波介电性能的影响机理。并评述了粉末的初始状态、烧结工艺、添加剂(掺杂)和烧结方法等因素对材料界面特性的影响，进而影响到材料介电性能的研究进展。最后指出了在微波介质陶瓷界面研究领域面临的问题及今后的发展方向。     

INFLUENCE OF DRYING CONDITIONS ON THE RHEOLOGICAL PROPERTIES OF PRUNES

Rheological properties of rehydrated prunes were obtained applying compression-relaxation tests by using a Texture Analyzer TAXT2i. A mathematical development was adopted to determine the stress and area, along the deformation. Experimental data of stress versus time was fitted by using three different rheological models: generalized Maxwell, Normand & Peleg and Maxwell. Results showed that generalized Maxwell model can be used to describe the viscoelastic behavior of the samples. The rheological parameters obtained indicated that prunes exhibited elastic behavior more pronounced at low moisture content and drying air temperature. At high moisture content and temperature the sample became a more viscous and less rigid.     

INFLUENCE OF DRYING CONDITIONS ON THE RHEOLOGICAL PROPERTIES OF PRUNES

ABSTRACT

Rheological properties of rehydrated prunes were obtained applying compression–relaxation tests by using a Texture Analyzer TAXT2i. A mathematical development was adopted to determine the stress and area, along the deformation. Experimental data of stress versus time was fitted by using three different rheological models: generalized Maxwell, Normand & Peleg and Maxwell. Results showed that generalized Maxwell model can be used to describe the viscoelastic behavior of the samples. The rheological parameters obtained indicated that prunes exhibited elastic behavior more pronounced at low moisture content and drying air temperature. At high moisture content and temperature the sample became a more viscous and less rigid.     

烧成制度对BaTiO3介电性能的影响

烧成制度对BaTiO3质PTC陶瓷的介电性能有重要影响,详细讨论了烧成温度、保温时间、冷却速度以及烧结气氛等因素对BaTiO3质陶瓷室温电阻和PTC效应的影响,并对其影响机制给出了合理解释。研究结果表明,陶瓷的半导化与烧成温度密切相关,适当保温对传质有很大影响,冷却速度和烧结气氛对室温电阻和PTC效应有一定影响。     

气隙长度和纺丝速度对Lyocell纤维性能的影响

本文详细探讨了以NMMO作溶剂时,纤维素溶液纺丝工艺的三个重要工艺参数──气隙长度、纺丝速度和拉伸比对Lyocell纤维性能的影响。本文以大量的实验数据表明:随着气隙长度的增加,纤维的强度和伸长都有所增加;随着纺丝速度的提高,纤维的伸长减少,初始模量增大,而纤维的强度则随纺丝速度的提高而增加到一峰值后,再下降,强度最大时纺丝速度约为50m/min;在泵供量相同的条件下,拉伸比对纤维性能的影响同纺丝速度对纤维性能影响的趋势相同。     

填料对环氧树脂混凝土力学性能影响

研究了填料对环氧树脂胶粘剂和树脂混凝土力学性能的影响。碳化硼、氧化铝、水泥和氧化锌均可提高胶粘剂、树脂混凝土强度,其中碳化硼提高幅度最大,因而填料在树脂混凝土中具有重要作用。     

THE EFFECT OF MECHANICAL PRESSURE ON THE IMBIBITIONAL AND DRYING PROPERTIES OF SOME CERAMIC CLAYS,II*

The apparatus and technique used in a study of the permeable-pressing characteristics of ceramic clays, described in a previous paper with the same title, were used in making a detailed study of the effect of molding pressure on the properties of permeablepressed disks of Florida and Delaware kaolins, The effect of initially high preswres on the properties of disks made at low pressures was investigated, and the rate of water removal was studied. The permeable-pressing characteristics of mixtures of clays and nonplastics were investigated at high and low pressures and the firing properties of permeable-pressed clay disks made in the previous investigation were determined. Further work with larger disks is in progress.     

硅灰石的表面改性对其填充PTFE复合材料摩擦学性能和力学性能的影响

利用钛酸酯偶联剂、硅烷偶联荆和硬脂酸对硅灰石进行表面改性,并对改性后的硅灰石进行类似与聚四氟乙烯(PTFE)复合加工过程中的热处理,测量其处理前后填料与水的接触角的变化,同时还考察了3种改性剂对PTFE/硅灰石复合材料的摩擦学性能和力学性能的影响.结果表明,硅烷偶联剂改性的硅灰石经过热处理后与水的接触角由64.5°增加到126.5°,表面能接近PTFE基体,相比其它改性荆能够更有效地提高复合材料的摩擦学性能和力学性能.     

加工方法对工程陶瓷力学性能影响的试验研究

工程陶瓷的力学性能受材料本体和表面状况的共同影响。加工方法对材料的表面状况有较大的影响,因此,陶瓷材料的力学性能也受加工方法的影响。本文利用三点弯曲试验的方法,通过Weibull分布模型的特征参数比较了不同加工方法对材料力学性能的影响。     

烧结助剂对多孔氮化硅陶瓷的力学性能及介电性能的影响

通过添加烧结助剂,采用常压烧结工艺制备出不同气孔率(19%～54%)的氮化硅陶瓷.采用Archimedes法、三点弯曲法和Vickers硬度测试法测量了材料的密度、气孔率、抗弯强度及硬度.用X射线衍射及扫描电镜检测了相组成和显微结构.用谐振腔法测试了氮化硅陶瓷在10.2 GHz的介电特性.结果表明:材料具有优良的介电性能.随着烧结助剂的减少,样品中气孔率增加,力学性能有所下降,介电常数和介电损耗降低.添加Lu2O3所制备的氮化硅陶瓷的力学性能和介电性能优于添加Eu2O3或Y2O3制备的氮化硅陶瓷.当气孔率高于50%时,多孔氮化硅陶瓷(添加入5%的Y2O3或Lu2O3,或Eu2O3,质量分数)的抗弯强度可达170 MPa,介电常数为3.0～3.2,介电损耗为0.000 6～0.002.     

增容剂对HDPE／AS合金流变和力学性能的影响

研究了增容剂氯化聚乙烯接枝（丙烯腈／苯乙烯）共聚物对ＨＤＰＥ／ＡＳ共混体系加工流变性能和力学性能的影响。增容剂使共混体系的塑化时间减少,且随着增容剂用量的增加,共混体系的平衡扭矩和拉伸强度增大,而断裂伸长率在ＨＤＰＥ／ＡＳ／ＰＥ－Ｃ－ｇ－ＡＳ＝８０／２０／４时出现极大值;螺杆转速的增加使共混体系的平衡扭矩增大。     

真空紫外和质子辐照对BaO-TiO_2系微波介质陶瓷介电性能的影响

考察了几种BaO -TiO2 系微波介质陶瓷材料在真空环境中经紫外和质子辐照后的介电性能变化。结果表明 ,辐照后材料表面均出现发灰黑色现象。材料的介电性能变化规律与材料的组成、初始原料的形态及处理条件密切相关 ,即质子辐照后的试样的介电常数均有提高 ,提高幅度在 10 %左右。紫外线辐照后不含稀土元素试样的介电常数会略有提高 ,而含稀土元素试样的介电常数呈下降趋势。除由纳米粉制成的BaTi4O9 5 %Pr(摩尔分数 )试样外 ,经质子和紫外辐照后试样的介质损耗都增大 ,且质子辐照后试样的介质损耗增大的程度比紫外辐照后试样的大     

THE EFFECT OF MECHANICAL PRESSURE ON THE IMBIBITIONAL AND DRYING PROPERTIES OF SOME CERAMIC CLAYS,I*

A number of ceramic clays in the plastic condition were held between water-permeable pistons under mechanical pressure of from 200 to 20,000 pounds per square inch in contact with water at atmospheric pressure until equilibrium was reached; the water in the pistons was removed by compressed air, the pressure released. and the moisture content, density, drying shrinkage, and other properties of the clays determined. In every case, the moisture content and drying shrinkage decreased with increasing pressure and with some clays at high pressures expansion occurred on drying. Rather complete data are given for a number of clays and their theoretical and practical significance is discussed.     

水解/接枝处理对F-12纤维/环氧复合材料力学性能的影响

采用氢氧化钾稀溶液对F-12纤维进行表面处理,将—COOK离子对引入到F-12纤维表面,进而引发不同接枝单体的接枝,并分析了不同接枝单体和接枝时间等对F-12纤维拉伸强度及其环氧复合材料层间剪切强度的影响。研究表明,在温和条件下将—COOK离子对引入到F-12纤维表面,引发环氧氯丙烷接枝,可以提高F-12纤维/环氧复合材料的层间剪切强度。     

锆元素不同掺杂方式对钛酸钡陶瓷介电性能的影响

研究了锆元素不同掺杂方式对钛酸钡陶瓷介电性能的影响.采用固相法制备出掺杂比例为1mol%的zrO<,2>-BaO和ZrO<,2>两种掺杂方式的钛酸钡陶瓷样品,对其进行多方面的表征.实验结果表明.ZrO<,2>-BaO掺杂与ZrO<,2>掺杂的钛酸钡晶格常数、介电性能会发生不同的变化,这是由锆元素不同掺杂情况对钛酸钡的作...     

添加剂对3Y-TZP材料烧结行为及力学性能的影响

在3Y－TZP（tetragonal zirconia polycrystals stabilized,3% Y2O3，摩尔分数）中，采用CAS（CaO-Al2O3-SiO2)玻璃粉料为添加剂，使材料在较低的温度下烧结致密，并具有较好的力学性能，发现液相烧结是使试样的烧结温度显著降低的主要原因。探讨了添加剂对试样的烧结特性及力学性能的影响。与加入LAS添加剂的试样相比，CAS试样的抗弯强度好高，而断裂韧性要差，分析了造成这种力学性能的原因。     

孔隙率对复合材料单向板横向力学性能的影响

在考虑纤维和孔隙随机分布的情况下,通过随机算法生成包含孔隙的代表性体积单元Representative Volume Element(RVE)。对生成的RVE建立有限元模型,引入基体的塑性本构模型和界面的双线性本构模型,采用有限元方法研究了孔隙率对碳纤维/环氧树脂复合材料单向板横向力学性能的影响。研究显示,孔隙随机分布对横向力学性能的影响不是很大;当孔隙率不超过临界值时,孔隙对横向力学性能的影响相对较小;当孔隙率超过临界值后,材料横向弹性模量、横向拉伸强度和横向压缩强度都会有较大的下降。     

Fe2O3对陶瓷墙地砖吸水率和力学性能的影响

研究了Fe2O3对陶瓷墙地砖的吸水率和力学性能的影响。采用排水法测定了陶瓷的吸水率,采用三点抗弯法测定了陶瓷的抗弯强度。结果表明：在适当的烧成制度下,当Fe2O3加入量小于3wt％时,陶瓷的吸水率小于0．1％,Fe2O3的加入量小于5wt％的情况下,陶瓷抗弯强度随着Fe2O3含量的增加而增加。加入2wt％到6wt％的Fe2O3的陶瓷强度比没有外加Fe2O3的陶瓷强度提高了30％以上。     

凝固浴浓度对Lyocell纤维性能及最大纺丝速度的影响

探讨了Lyocell纤维纺丝工艺中凝固浴浓度对最大纺丝速度及纤维相对强度、断裂伸长、初始模量的影响.结果表明:随着凝固浴浓度增大,最大纺丝速度减小;而在凝固浴浓度为10%时,纤维的相对强度和初始模量为最大,延伸度则为最小.