添加剂对氧化铝陶瓷性能的影响

根据作用机理的不同,可以把添加剂分为2类:生成液相,这类添加剂如SiO2、MgO、CaO、SrO、BaO等碱土金属氧化物,在晶界形成低熔点的玻璃相,促进烧结,电性能良好,适于制备电子陶瓷;生成固溶体,这类添加剂如Cr2O3、Fe2O3、TiO2、MnO等,它们与氧化铝基体形成置换固溶体,降低烧结温度,同时降低陶瓷的体积电阻率,适于有力学要求的场合。     

烧结助剂对95氧化铝瓷性能的影响

采用正交实验,X射线衍射分析、电子显微镜及视频显微镜分析,研究了MgO-CaO-SiO2与TiO2烧结助剂及烧成温度对95氧化铝瓷的密度和洛氏硬度等性质的影响.结果表明:添加5％的MgO-CaO-SiO2,同时添加1.0％的Ti02,可实现95氧化铝瓷试样在1520℃时及常压下达到致密烧结,获得的试样吸水率为0.07％,体积密度为3.64g/cm3,洛氏硬度为90,相比其它常压烧结方法制备的95氧化铝瓷的烧结温度降低了约150℃.     

添加剂自增韧氧化铝陶瓷的若干研究进展

评述了近年来国内外对添加剂自增韧氧化铝陶瓷的研究，总结了国内外关于TiO2影响氧化铝晶粒生长的诸多不同观点，分析了氧化铝晶粒异向生长与氧化铝陶瓷的自增韧机理。     

比体积表面能对纳米氧化铝晶粒成长的影响

以表面能观点观察纳米级晶粒的成长现象.实验对3种晶径介于10～20 nm的θ-Al2O3粉末,以3种压力单轴压成型制成生坯,以获得单位体积内所含粉末粒体数目,或单位体积内粉体比表面积量(即比体积表面积,σv)不同的生坯样品.以热差分析获得θ-Al2O3粗化到达相变临界晶径的温度Tp,再透过Tp温度与σv及堆积密度fp的关系分析θ晶粒成长.结果显示,不受晶径或σv不同的影响,θ晶粒成长速率接近定值.晶粒系统具有同一σv值者将在同一温度开始成长,σv越大开始成长温度越低.而具有同一堆积密度者将在同一温度到达相变临界晶径.同时在成长过程中,粗晶粒有等细晶粒成长至同一体表面积后再一起成长(等比体积表面积成长)的现象.     

增钙渣和混合材与水泥比表面积的关系

根据小磨试验和生产实际推导出粒化增钙液态渣复合硅酸盐水泥强度与熟料强度、混合材掺量、比表面积之间的关系式,此式可用于水泥粉磨主要工艺参数的计算与控制.     

加工对一些塑料添加剂影响的研究

聚碳酸酯(PC)和丙烯腈-丁二烯-苯乙烯共聚物(ABS)是两种广泛应用的热塑性工程塑料。在这项研究中,一种PC树酯和一种ABS树脂在不同温度下加工或加工多次。用流变仪来进行模拟加工。为研究加工对树脂中添加剂的影响,用气相色谱-质谱(GC-MS)来分析加工前后树脂的提取液。研究结果表明加工中添加剂会因分解和转化失去,特别是在高温下加工或加工几个周期后。     

Effect of Surface Impurities on the Microstructure Development during Sintering of Alumina

Microstructural evolution during sintering of alumina powder compacts prepared by cold isostatic pressing (CIP) was monitored. For CIP, rubber molds lubricated with silicone oil were used so that a very small amount of impurity was introduced to the surface of the powder compacts. During sintering at 1600°C, grain growth in the surface region was inhibited up to sintering for 1 h, but subsequently abnormal grain growth occurred. In the inner region, however, the grains grew uniformly without abnormal grain growth. Impurities that initially drag the boundary migration but form liquid at the end are suggested to cause abnormal grain growth.     

SiC添加物对高铝质浇注料的作用

研究了SiC添加物对高铝质低水泥浇注料的作用。首先，研究了不同的混台比例以确定最佳SiC量。在初步的一些试验后，选择了由20％SiC、5％高铝水泥（Al2O3 70％)、8％活性氧化铝组成的20SIC，通过添加石墨研究了抗侵蚀性。由于在氧化气氛下烧结，高C添加对机械性能有负作用。使用金属铝以阻止氧化作用。将3％C添加到混合物中以改进抗侵蚀性，并测定了与温度和烧结气氛相关的强度损失。高SiC和C含量降低了抗氧化性，导致强度损失。在还原气氛下，强度损失降低，在实验室试验结束时，给出了最终结果。     

耐高温高比表面积氧化铝的制备及其性能

氧化铝作为一种常用的催化剂载体,在化工和环保行业有着非常广泛的应用。比表面积和高温稳定性是决定氧化铝性能的关键指标。因此,优化制备方法,开发新型添加剂,提高氧化铝的高温稳定性和比表面积,使其能够更好地满足工业化应用需要具有重要意义。详细介绍了耐高温高比表面积氧化铝的制备方法、结构改性及其在催化反应中的作用,并对目前的研究情况进行了展望。     

Low-Temperature Sintering of Alumina with Liquid-Forming Additives

Simultaneous application of colloidal processing and liquid-forming additives to alumina resulted in a sintered density of >99% in 1 h at a temperature as low as 1070°C for a commercial high-purity alumina powder at a total dopant level of 2 mol%. The additives were 0.9% CuO + 0.9% TiO₂+ 0.1% B₂O₃+ 0.1% MgO. At higher temperatures or after prolonged sintering, the doped alumina ceramic developed a duplex microstructure containing large elongated grains and exhibited a relatively high fracture toughness of ∼ 3.8 MPa · m^1/2 as compared to a value of ∼ 2.6 MPa · m^1/2 for the undoped alumina.     

球磨助剂对氧化铝粉末细度及90氧化铝陶瓷烧结温度的影响

本文以十二烷基苯磺酸钠、OP-10和吐温80作为氧化铝粉末中的球磨助剂，探讨了不同球磨助剂及其用量对氧化铝粉末的球磨效率及对90氧化铝陶瓷烧结温度的影响。结果表明，阴离子表面活性剂十二烷基苯磺酸钠的助磨效果最佳，OP-10次之，吐温作用不大。球磨助剂通过分散、润滑、劈裂等作用强化了球磨效果，可缩短球磨时间，并提高了球磨物料的细度，使氧化铝粉体的烧结活性增强。在相同的工艺条件下，加入球磨助剂可使90氧化铝陶瓷的烧结温度降低60℃以上。     

Effect of Surface Flaw Size on Fracture Strength of Alumina Ceramics

Semielliptical surface flaws of different sizes were introduced into Al₂O₃ by Knoop microhardness indentation. The specimens were fractured by four-point bending and the profiles of the indentation flaws were determined by observing the fracture surfaces with a scanning electron microscope. The relation between the indentation flaw size and the fracture strength could be well explained by applying the fracture-mechanics analysis for semielliptical surface flaw in bending. The calculated values of the as-indented critical stress intensity factor, K_IC, were lower than previously reported presumably because of the influence of the residual stresses produced by the indenter.     

Effect of Processing Parameters on the Surface Area of Freeze-Dried and Spray-Dried Alumina

The effect of variations in calcination temperature and time, solution concentration, and spraying pressure on the surface area of alumina was studied. Increasing the calcination temperature and time results in a decrease in surface area, whereas increasing the solution concentration and spraying pressure for a given nozzle diameter increases the surface area.     

CaTiO3添加剂对氧化铝陶瓷烧结、显微结构及微波介电性能的影响

CaTiO3添加剂通过湿法球磨与Al2O3粉料混合,并通过无压烧结制备了氧化铝陶瓷,研究了CaTiO3添加剂对氧化铝陶瓷烧结性能、相组成、显微结构和微波介电性能的影响.CaTiO3可以使Al2O3的烧结温度降低至1450℃,但在该温度下烧结的样品由于CaTiO3的加入会产生CaAl12O19第二相.样品中存在大、小两种晶粒,根据EDS能谱分析,大晶粒主要是CaAl12O19,而小晶粒为Al2O3和CaAl12O19的混合相.添加CaTiO3有利于Al2O3陶瓷介电常数的提高,1450℃下掺杂2.5wt％ CaTiO3的氧化铝陶瓷具有较好的烧结性能和微波介电性能,相对密度可达到97.74％,εr～10.86,Q×f～ 8061 GHz.     

Effects of Specific Surface Area and Impurities of Reactive Alumina on Properties of Corundum Based Castables

Effects of specific surface area and tiny amount of impurities of reactive alumina on the workability,sintering and high temperature mechanical strength of corundum based castables were investigated. The results show that the presence of reactive alumina with high specific surface area leads to accelerating of the hydration of calcium aluminate cement,thus shortening the working time and setting time of the castables,which can be ascribed that the critical energy barrier for stable nuclei of hydration products of cement can be reduced by the high specific surface area of reactive alumina. The sintering of the corundum based castables can be accelerated by the reactive alumina with high specific surface area and high amount of impurities, however, the reactive alumina with too high specific surface area and impurities can also lead to noticeable shrinkage of castables. In addition,high temperature mechanical strength of corundum based castables can be decreased by the higher amount of trace impurities of reactive alumina due to formation of lowmelting phase at high temperatures.     

利用铝型材厂污泥和硝酸研制的活性氧化铝比表面与孔结构研究

采用硝酸作为粘结剂,通过煅烧铝型材厂污泥研制球状活性氧化铝,用氮气等温吸附(77K)方法测量BET比表面积和孔结构.通过添加不同浓度、不同用量的硝酸,探讨在不同煅烧温度和保温时间下制备的活性氧化铝的各项性能指标.结果表明,加入一定浓度与用量的硝酸可以提高试样的比表面积,但会降低试样的孔容.综合硝酸浓度与用量以及热处理条件对试样的影响,确定硝酸的最佳浓度为13%,最佳用量为31%,最佳的煅烧温度为500℃,最佳保温时间为8h,这样制备的活性氧化铝比表面积和孔容分别达到283m2/g和0 56 cm3/g,平均孔径为6.8nm.     

TiO2-CAS 添加剂对氧化铝陶瓷密度和显微结构的影响

研究了单独引入TiO2、CAS(CaO-Al2O3-SiO2)及协同引入TiO2和CAS时 3 种情形对氧化铝材料显微结构影响.实验表明,单独引入TiO2时,随添加量从0.15%(质量分数,下同)增加到0.60%,Al2O3样品的晶粒形貌由正常生长逐渐向异向生长和异常长大转变;而单独引入CAS,即使添加量达到2.0%,Al2O3晶粒也没有出现异向生长和异常长大;实验还表明,在添加TiO2,同时引入CAS时,可以有效抑制TiO2添加所引起的Al2O3晶粒异常长大和异向生长.对 CAS 添加剂抑制晶粒异常长大和异向生长的原因进行了讨论.     

无机粉体改性效果对比表面积的影响

分别利用钛酸酯偶联剂(NDZ-311)、磷酸酯偶联剂(FX-1)、铝酸酯偶联剂(L-2)和硅烷偶联剂(KH-560)对滑石粉(Talc)进行表面改性,并利用力学性能与比表面积(BET)等测试方法研究了改性Talc对PP复合体系性能的影响,发现BET极大值点与力学性能极大值点呈对应关系,因此可利用比表面积测定来定性或定量地反映偶联剂对无机粉体的改性效果。SEM结果表明:改性后Talc在基体中的分散度得到提高,并能更好地与基体结合。     

Effect of Powder Surface Chemistry on the Stability of Concentrated Aqueous Dispersions of Alumina

The surface chemistry differences between two alumina powders is shown to have a significant effect on the properties of concentrated aqueous dispersions of the powders. The initial dispersion pH and magnitude and sign of the initial mobility of the particles (determined by acoustophoresis) are different for the two powders because of differences in surface impurity contents. As a result, the two powders require different amounts of dispersant to achieve stability in dispersions near their isoelectric points. The surface chemistry differences between these two aluminas illustrate the importance of examining ceramic dispersion properties at the concentrations used in processing the material.