不同氧化铝引入料对高铝玻璃熔制与性能的影响

采用高温熔融法制备了高铝玻璃,在玻璃料中分别采用α-Al2O3、γ-Al2O3、Al(OH)3三种不同的氧化铝引入料,利用高温热台进行熔制观测对比。再对三种晶型的氧化铝及其所熔制玻璃进行了DSC分析,并利用红外与热膨胀仪对比分析了三种氧化铝引入料对高铝玻璃的熔制过程、结构、性能等影响。     

γ-Al2O3和α-Al2O3与其对应的氢氧化物对合成尖晶石的影响

以γ-Al2O3(勃姆石在700℃保温4 h热处理后的产物)、α-Al2O3(Al(OH)3在1 400℃保温4 h热处理后的产物)、勃姆石、Al(OH)3为原料,与轻烧MgO按n(Al2O3):n(MgO)=1的组成配料并制备试样,研究了在800～1 600 ℃下不同氧化铝及其对应的氢氧化物对合成尖晶石的影响.结果表明:γ-Al2O3和α-Al2O3分别同与其对应的氢氧化物为原料的试样具有相似的烧结性能;且以氢氧化物为原料比以氢氧化物煅烧后所得的氧化物为原料更有利于尖晶石的生成,但不利于尖晶石的致密化.     

氧化铝基载体组成对钴基催化剂结构和费-托合成催化性能的影响

以γ-Al2O3为原料制备Ni-γ-Al2O3、Zn-γ-Al2O3和Al2O3载体,并采用等容浸渍法制备了钴基费-托合成用催化剂。结果表明:高温焙烧使氧化铝晶型和孔结构发生较大变化;镍添加后在载体表面形成高分散的氧化镍物种;而锌添加后与载体发生反应生成了铝酸锌;负载型催化剂中,四氧化三钴粒径大小主要取决于载体孔结构。CoPt/γ-Al2O3、CoPt/Zn-γ-Al2O3、CoPt/Ni-γ-Al2O3具有相近的费-托合成催化性能,而CoPt/Al2O3呈现出最高的催化活性和最低的甲烷选择性。表明,钴物种粒径和载体结构是影响催化剂费-托合成催化性能的主要因素。     

激光重熔等离子喷涂Al2O3陶瓷层的相转变

研究了锌铝基Al2O3陶瓷层激光重熔区内陶瓷相的转变。采用METCO 4MP等离子喷涂机对基体材料表面喷涂氧化铝(Al2O3的质量分数为99％)陶瓷层。采用上海光学精密机械研究所HJ-4工业用横流CO2激光器进行激光重熔。通过X射线衍射分析和透射电镜对Al2O3陶瓷的微观结构、成分和分布的研究，得到以下结论：在等离子喷涂过程中，喷涂层中陶瓷相发生。α-Al2O3→γ-Al2O3 α-Al2O3的转变。激光重熔后，试样表层的原α-Al2O3陶瓷相、γ-Al2O3陶瓷相均转变为δ-Al2O3陶瓷相，为体心四方结构．熔池区陶瓷相主要分布在表层，次表层和过渡区。     

氧化铝粒体在κ-至α-相变过程的发育现象

本研究观察以三水铝矿石[(Gibbsite,Al(OH)3)]为原料获得之氧化铝微粒在κ-至α-相变过程中之粒体成长行为.相变过程存在临界晶径与基础晶径现象.前者之大小对κ-与α-相均约为35nm,后者则为60 nm.由于所得α-Al2O3粒体存有原始粉末粒体的外型,因此如要由三水氧化铝获得奈米级(小于100 nm)α-Al2O3粉末,则于热处理前应将三水氧化铝先行细化.     

纺织用陶瓷摩擦盘的研制

采用预烧氧化铝、细磨原料、引入Y2O3、聚乙烯醇添加剂、机加工等工艺措施，研制出纺织用陶瓷摩擦盘，其理化性能达到了进口产品的水平，满足使用要求。预烧氧化铝温度在1500～1530℃，使γ-Al2O3转化为α-Al2O3，赋予产品良好的性能；料浆细度控制在3μm以下，促进制品固相烧结；引入Y2O3添加剂促进液相烧结；引入聚乙烯醇添加剂赋予产品良好的工艺性能。     

铝质原料对多孔针状莫来石合成的影响

采用铝质原料和粘土为主要原料,通过原位固相反应烧结制备多孔针状莫来石陶瓷材料。利用XRD、SEM、EDS能谱分析等研究了Al(OH)3、γ-Al2O3、α-Al2O3等三种不同铝质原料对制备的针状莫来石多孔材料物相组成、微观结构和微区元素分布的影响。结果表明:不同铝质原料对针状莫来石的形成有着明显影响。在1400℃保温2h烧成后,以Al(OH)3为铝质原料制备的多孔材料中莫来石晶相含量可达88.77%,而采用α-Al2O3和γ-Al2O3时,莫来石晶相含量分别仅为55.65%,76.78%。采用三种不同铝质原料合成的针状莫来石长径比相近,但以Al(OH)3为铝质原料合成的莫来石晶体发育得更充分,且更有利于提高制备的针状莫来石多孔陶瓷的孔隙率和抗弯强度。     

煅烧α-Al（OH）3和K2SO4混合粉末制备片晶α-Al2O3的研究

片晶α-Al2O3是一种重要的陶瓷材料,在低温下制备尺寸可控的片晶α-Al2O3具有重要的意义。通过机械球磨α-Al(OH)3和K2SO4混合粉末,然后在900℃下煅烧混合粉末,制备了片晶α-Al2O3。研究了球磨转速和混合粉末中K/Al物质的量比对所得产物晶体结构及形貌的影响。结果表明,高球磨转速能有效促进γ-Al2O3向α-Al2O3的相变过程,并导致片晶α-Al2O3的平均直径减小;K/Al物质的量比对γ-Al2O3的相变过程有很大影响。研究发现,K2SO4能够有效促进γ-Al2O3向α-Al2O3的相变;片晶α-Al2O3的生成和液相的K3Al(SO4)3有关。     

pH值对沉淀法制备Al_2O_3相转变的影响

为获得Al2O3粉体,以Al(NO3)3为原料,NH3.H2O为沉淀剂,采用液相化学沉淀法,在不同pH值下制备了Al(OH)3前驱体,并利用TEM,XRD,TGA等分析手段对前驱体进行了表征。pH=5时前驱体的相转变主要是由非晶Al(OH)3→非晶Al2O3→α-Al2O3;pH=9及pH=11前驱体的相转变主要是由Al(OH)3→γ-Al2O3→θ-Al2O3→α-Al2O3。XRD结果表明,低pH值时制备的Al(OH)3更容易转化为α-Al2O3稳定相。pH=5时前驱体在1 100℃就可转变为α-Al2O3稳定相,而pH=9和pH=11时制备的前驱体则分别需在1 150℃和1 200℃才能转变为α-AlO。研究表明,pH值对制备的前驱体的物相、形貌、相转变都有很大影响。     

制备高纯度α-Al_2O_3粉体的工艺研究

以硝酸铝和碳酸铵为原料,采用化学沉淀法,在不同硝酸铝浓度下制备Al2O3的前驱体Al(OH)3,再经不同温度煅烧得到Al2O3粉体。利用TG-DTG、XRD、BET及SEM等分析手段对粉体的性能进行了表征。结果表明,煅烧温度对Al2O3的晶型有着重要的影响,硝酸铝浓度为0.1 mol/L时制备出的粉体分散性较好,经1 200℃煅烧能制备出纯度较高的形貌类似球形的α-Al2O3粉体。     

板状氧化铝增强氧化铝陶瓷

采用控制氧化铝显微结构的方法，通过向氧化铝材料中引入不同粒径的板状氧化铝颗粒，同时采用超细粉为初始原料来改善氧化铝陶瓷的力学性能。氧化铝试样于1550℃和1600℃下烧成并加入MgO和Y2O3来抑制晶粒的过分长大。实验结果表明：加入板状氧化铝颗粒后，氧化铝材料的抗折强度得到明显提高。     

Hydraulic Alumina Binder for Extrusion of Alumina Ceramics

The present work describes the effect of hydraulic alumina (HA) as a new inorganic binder on extrusion of alumina ceramics. The addition of a small amount of HA imparted significant flowability and rigidity to the extruded alumina. Under optimum processing conditions such as amounts of HA and water, and curing period, alumina rods and tubes were successfully extruded using a single screw extruder. Sintered specimens have achieved a relative density of 97% after sintering at 1600°C for 2 h. Dense alumina samples prepared using organic and inorganic binders had similar mechanical properties, that is, Young's modulus >380 GPa and H _v>2000. These results suggest that HA is a new kind of inorganic binder applicable to the extrusion of ceramics.     

Constrained Densification Kinetics of Alumina/Borosilicate Glass + Alumina/Alumina Sandwich Structure

The densification kinetics and mechanism of a low-temperature cofirable borosilicate glass (BSG) + alumina during the constrained sintering of a sandwich structure of alumina/(BSG + alumina)/alumina has been studied. The densification kinetics becomes slower when the BSG + alumina tape is constrained during firing. However, a viscous flow-controlling mechanism of the BSG also is still operative during free and constrained sintering. The densification behavior of constrained sintering can be mathematically described by free sintering, using the viscous analogy for the constitutive equations of a porous sintering glass.     

Porous Alumina Films with Width-Controllable Alumina Stripes

Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.     

Alpha Alumina Formation in Alum-Derived Gamma Alumina

The formation of alpha alumina in gamma alumina obtained from ammonium alum was studied at 1150°C. The transformation occurs by a nucleation and growth process, preceded by an incubation time. Mechanical treatments of the gamma alumina markedly increase the density of nuclei and hence the transformation rate. The alpha alumina forms in porous colonies consisting of a single crystal with an interconnected wormy morphology.     

影响氧化铝及其水合物白度测定的因素

本文就影响氧化铝及其水合物白度的诸因素中,以大量的数据侧重地展示了十年来仪器类及同种仪器台间差给测定结果带来的影响,标准白板、滤光片波长、白度公式的选择均会影响白度值,进而介绍了国际著名的甘茨(GANZ)公式。建议铝行业要建立标准并以α-Al_2O_3作为基准物质。文中大量的统计数字证明了碱石灰烧结法这一独特工艺制得的氧化铝、氢氧化铝具有理想白与喜爱白的特征。     

氧化铝粉体对氧化铝陶瓷制品性能的影响

研究了Al2O3粉体对α－Al2O3为主晶相的Al2O3陶瓷性能的影响。结果表明：粉体纯度、粉体的粒度及粉体中α－Al2O3含量对产品的性能影响较大,而Al2O3粉体的加入量影响产品的体积密度及强度,对耐磨影响不明显。     

High-Strength Alumina/Alumina:Calcium-Hexaluminate Layer Composites

The strength degradation of alumina/alumina:calcium-hexaluminate/alumina trilayers, after damage from Hertzian contacts, is evaluated. Relative to the monolithic alumina and alumina:calcium-hexaluminate constituent layer materials, the trilayers show markedly improved strength retention in the damaged state at high contact loads. The outer, fine-grained alumina layers are classically brittle, characterized by cone cracking, whereas the inner alumina:calcium hexaluminate layer is essentially quasi-plastic, with a well-defined "yield" zone that consists of distributed microdamage. The improved strength behavior of the trilayer composite is rationalized in terms of a synergistic interaction between the contact-induced deformation modes in the two layers, with each mode partially ne-gating the effectiveness of the other as a source of failure. This result offers the prospect of hybrid structures with hard outer layers, to provide wear resistance, and soft, tough underlayers, to inhibit brittle fracture.     

Gelcasting of Alumina

Gelcasting is a novel method for molding ceramic powder based on a synthesis of concepts derived from traditional ceramics and polymer chemistry. Gelcasting of alumina is described in this paper. The process is based on the in situ polymerization of acrylamide monomers as the setting mechanism for forming the green body. It has the following features: slurries with high solids loading and low viscosity (1.8 Pa·s at 62 vol% solids), dried bodies containing less than 4 wt% binder, and the ability to fabricate complex-shaped bodies.     

Thermoluminescence of Alumina

Results of measurements of thermoluminescence for γ-irradiated pure, and magnesia-doped alumina ceramics are presented. A self-consistent method of glow curve analysis led to results differing from those previously reported in the literature, with smaller trapping energies and realistic attempt-frequency factors.