高比表面积砂状氧化铝制备研究进展

比表面积是砂状Al_2O_3的重要参数,对产品的溶解性能、吸氟能力等特性有显著影响。介绍了影响Al_2O_3比表面积的微观孔结构因素,分析了铝酸钠溶液分解过程和氢氧化铝煅烧过程的调控措施对砂状Al_2O_3产品形貌、粒度、比表面积等参数的影响,概述了外场强化、改变溶液体系等新的制备技术及其产品性能。指出各种强化技术可与现行生产工艺相匹配,为产出冶金级砂状Al_2O_3和化学品活性Al_2O_3等不同种类的高比表面积产品提供了新的途径。认为突破强度随比表面积增大而降低这一瓶颈并开发出高质量的砂状Al_2O_3依然是今后的一个研究热点。     

碳分法制备氢氧化铝过程的研究

以偏铝酸钠溶液和二氧化碳气体为原料,成功地制备了不同晶型的氢氧化铝纳米粉末.叙述了实验过程中工艺条件对产品粒度、形貌和晶型等方面的影响.采用TEM、SEM、XRD分析表征了产品的形貌、粒度和晶型,结果表明,产品分别为片状三水氢氧化铝、纤维状的-水拟薄水铝石和无定形的三水氢氧化铝.     

氢氧化铝粉体粒度测量技术

氧化铝生产工艺分解过程中氢氧化铝粒度检测的结果对分解系统的稳定和产品氧化铝的粒度控制有着非常重要的意义。氢氧化铝粒度的测定方法很多,目前用来监测粒度的方法有筛分法、马尔文激光粒度法、库尔特全自动颗粒粒度分析、颗粒计数器分析等,综合各种分析结果可得到氢氧化铝的全粒度分布情况。     

单槽碳分生产非冶金用氢氧化铝的研究

通过对加种子单槽碳分的试验室试验及工业试验 ,找到了单槽碳分生产非冶金用氢氧化铝合适的生产条件 ,使产品性能达到了非冶金用氢氧化铝的使用要求。使用单槽分解后能减少大生产波动对多品种生产的影响 ,提高产品质量和产量。     

Elzone 5382颗粒计数器测定氢氧化铝粒度方法的探讨

以Elzone 5382颗粒计数器为主要分析设备,对如何准确地测定氢氧化铝粒度分布进行了分析讨论.通过试验证明,此方法分析结果较为准确、稳定,能够起到指导砂状氧化铝生产控制的目的.     

单槽碳分生产非冶金和氢氧化铝的研究

通过对加种子单槽碳分的试验室试验及工业试验，找到了单槽碳分生产非冶金用氢氧化铝合适的生产条件，使产品性能达到了非冶金用氢氧化铝的使用要求，使用单槽分解后能减少大生产波动对多品种生产的影响，提高产品质量和产量。     

铝酸钠溶液中超细氢氧化铝制备的研究进展

简要介绍了各种以铝盐为原料制备超细氢氧化铝粉方法的优缺点。以铝酸钠溶液为原料,结合拜耳法和烧结法生产氧化铝的工艺,阐述了碳分法、种分法制备氢氧化铝的机理以及晶种制备方法、溶液制备方法、溶液组成和分解制度等对超细氢氧化铝纯度、白度和粒度分布等的影响规律。烧结法溶液产品白度高,但碳分产品结晶差、粒度分布宽,生产成本高,而以拜耳法溶液为原料种分的氢氧化铝结晶好、粒度分布易控制,但产品白度低。国外拜耳法溶液浓度较低,相比之下我国高浓度溶液仍需在溶液净化、种分机理等方面进行深入研究,以提高产品质量,开发更多产品。     

两段种子分解法制备超细氢氧化铝微粉工艺研究

研究成功了制取非晶质高活性种子的方法,活性晶种能够破坏铝酸纳溶液的稳定性,诱导出一个突然自发产生超细氢氧化铝晶粒的过程。采用两段分解工艺制备了超细氢氧化铝,研究了种子比、温度、精液中苛性Na2O与Al2O3分子比αK的影响。控制分解过程既有次生晶核的生成又要保持一部分晶粒适当长大。超细氢氧化铝产品粒度保持在1.5～2μm范围,产品比表面积4m3/g左右。     

激光粒度分析仪测定氢氧化铝细颗粒方法的探讨

针对马尔文2000型激光粒度分析仪在氢氧化铝分析中对25μm粒径以下细颗粒的分析不太敏感，难以满足氧化铝生产分解过程对粒度控制的要求，对试验样品采用一些非常规的特殊处理方法，以提高细小颗粒在处理过样品中所占的体积百分比；研究了不同的样品处理方式对分析结果的影响。试验结果表明，只有对洗涤、过滤后的湿样进行分析，才能对分解料浆样品中的细颗粒的粒度分布进行准确地分析，得到满足试验和生产过程控制精度的结果。     

机械活化对钾长石颗粒表面特征的影响

采用机械活化并添加碱性助剂的方法，将钾长石进行粉碎加工，综合研究钾长石粒度分布、比表面积、表面粗糙度、颗粒形貌及相互关系；分别以激光粒度分析仪、比表面积仪测定颗粒大小、表面积，计算表面粗糙度，定量化表征颗粒特性变化；分析机械活化过程中表面积与粒度关系，以及不同碱性助剂对钾长石粉体特性的影响；研究提升钾长石颗粒活性的工艺方法、控制因素及影响机理。结果表明：无论是干法还是湿法研磨加工均能提高钾长石的比表面积和粗糙度，但湿法加工对提高比表面积和粗糙度效率更高，加入碱性添加剂及其盐类则降低比表面积与粗糙度。     

Improved microstructure and magnetic properties of iron-cobalt nanowire via an ac electrodeposition with a multistep voltage

Highly ordered porous alumina templates prepared by a two-step anodization are widely utilized as the matrix to assemble nanowires. Usually, an ac electrodeposition with a constant voltage is employed to deposit the metal nanowires on the porous alumina template due to its simple electrodeposition process. However, the nanowires deposited under a constant voltage include many defects in the microstructure, e.g. the hole to weaken its physical properties. Recently, we used an ac electrodeposition with a multistep voltage to deposit a cobalt nanowire with less microstructure defects to enhance its magnetic properties. In this letter, we further investigate the microstructure and magnetic properties of the iron-cobalt nanowire via an ac electrodeposition with a multistep voltage on the porous alumina template. Such a FeCo nanowire has the more uniform crystalline microstructure than that of deposited under a constant voltage and thus the magnetic properties are improved. Our results indicate that an ac electrodeposition with a multistep voltage is an effective way to fabricate the nanowires on the porous alumina template.     

Al2O3基陶瓷材料增韧的研究进展

Al_2O_3基陶瓷材料具有高的化学稳定性,有较好的应用前景,但其脆性限制了它的推广应用,对氧化铝陶瓷进行增韧是解决其脆性问题的一条重要途径。简要介绍了目前氧化铝陶瓷的增韧方法和增韧机理,综述了氧化铝陶瓷增韧的研究现状,分析了氧化铝陶瓷增韧研究中存在的主要问题,展望了氧化铝陶瓷增韧的发展方向,提出了原位生长及复合增韧是高性能Al_2O_3基陶瓷材料的研究重点。     

Effect of adsorption behaviour of polyelectrolytes on fluidity and packing ability of aqueous graphite slurries

The effect of surface hydrophobicity on the adsorption behaviour of polyelectrolytes is investigated using graphite and alumina powder slurries. Graphite slurries containing carboxymethylcellulose (CMC) have a relatively low apparent viscosity and afford a sediment with a relatively high packing fraction as compared to that obtained when using sodium polyacrylate (Na-PAA) as a dispersant, although both have the same functional group. As a greater amount of CMC is adsorbed, it is concluded that its adsorption mechanism involves hydrophobic interaction, thus making it a better dispersant for hydrophobic powders in aqueous media. In contrast, Na-PAA is more effective in dispersing relatively hydrophilic powders such as alumina, as it adsorbs mainly through electrostatic interactions.     

Preparation and characterization of P(VDF-TrFE)/Al2O3 nanocomposite

Hybrid nanocomposites based on crystalline nanoparticles dispersed in polymer matrix have been widely studied in the past few years because of the ability of these materials to combine the properties of organic polymer and inorganic nanoparticles. The aim of this work is to tune the mechanical properties of a piezoelectric polymer by adding nanoparticles to the matrix. In this paper, alumina nanoparticles were dispersed in the copolymer P(VDF-TrFE), which exhibits high piezoelectric coefficient after polarization under high electric field without needing stretching during the polarization process. Transmission electron microscopy and scanning electron microscopy demonstrate the high rate of welldispersed nanoparticles with 10% of alumina nanoparticles added to the matrix. Piezoelectric measurements indicate that P(VDF-TrFE) may be filled by up to 10 wt% of alumina while retaining its high piezoelectric properties and increasing its elastic constant by more than 20%, measured by Brillouin spectroscopy. This work opens a wide range of applications using nanoparticles with nonlinear optical, pyroelectric, magnetic, or ferroelectric properties.     

Effects of Ni and TiN Coatings on the Alumina/Heat-Resistant Steel Interface Properties

Ni and TiN coatings on alumina particles were achieved using a chemical vapor deposition (CVD) method. The coated alumina was then used as raw materials to prepare alumina/heat-resistant steel (HRS) composites. The effects of Ni/TiN coatings on the alumina/HRS interface strength and oxidation resistance at elevated temperature were investigated. It is found that the both coatings can improve the alumina/HRS interface bonding strength and Ni coating has a more significant effect. For the composite made from Ni-coated alumina and HRS, the interface exhibited a better oxidation resistance due to the dissolution of Ni coating into the HRS matrix. However, the composite of TiN-coated alumina/HRS has a poor oxidation resistance behavior because TiN still existed on the alumina/HRS interface.     

表面活性剂辅助水热热分解法制备介孔氧化铝纤维

以PEG(Mn=20000)为模板导向剂, 尿素为沉淀剂, 采用水热热分解法制备了纳米介孔结构的氧化铝纤维, 并对其吸附性能进行了研究. 通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、热释重仪(TGA)和N2等温脱附-吸附分析, 考察了介孔氧化铝纤维的相态、结构、形貌、比表面积和介孔特征. 采用选择性催化还原(SCR)烟气脱硝装置对其吸附性能进行了研究. 结果表明：以PEG为模板, 采用简单的水热法就可得到直径(200～300)nm×(8～10)μm的碳酸铝铵纤维; 经900℃煅烧2h得到比表面积为316m²/g、平均孔径为2.5nm的η-Al₂O₃介孔纤维, 形貌基本不发生变化; SCR烟气脱硝测试显示, 相比商品氧化铝粉末, 合成的氧化铝介孔纤维有着更强的吸附性能, 它的脱硝效率较之商品氧化铝粉末约提高了15%.     

Shock deformation of coarse grain alumina above Hugoniot elastic limit

Symmetric shock experiments were conducted on a 10 μm grain size coarse alumina ceramic with a gas gun to identify its Hugoniot elastic limit (HEL). To understand the damage initiation and their subsequent growth mechanisms in coarse grain alumina subjected to shock impact at levels much above the HEL, additional asymmetric shock recovery experiments with the same gas gun were then deliberately conducted on the same alumina at shock pressure levels more than three times as high as the HEL and the fragments collected by a dedicated catcher system. Detailed characterization of the shock recovered alumina fragments by X-ray diffraction, nanoindentation, scanning electron microscopy, field emission scanning electron microscopy and transmission electron microscopy were utilized to understand the nature and process of failure initiation, incubational growth, coalescence and propagation leading to fragmentation. Based on these data a new qualitative damage model was developed to explain the deformation mechanism.     

特种氧化铝生产研究开发现状及其展望

介绍了特种氧化铝的分类、性质及国内外生产规模并分析其迅速发展的原因；重点介绍了特种氧化铝的应用、制备方法和研究进展，并对特种氧化铝的研究开发趋势提出了新的展望。     

Freestanding Alumina Membrane by Double-Layer Anodization

A novel method has been developed for fabricating full or partial freestanding anodic alumina. In our method a sacrificial metal layer is introduced between an Al film and a Si₃N₄ substrate. A freestanding alumina film at wafer scale is successfully achieved by anodizing the double metal layer, during which the alumina is spontaneously stripped off the Si₃N₄ substrate due to the anodic oxidation of the sacrificial layer. The barrier oxide of the alumina film is effectively removed either by H₃PO₄ dissolution or by CF₄ reactive ion etching. The freestanding alumina film is utilized as a contact mask to transfer its nanoporous pattern to a Si substrate. By patterning the sacrificial metal layer with contact lithography, a partial freestanding alumina film is successfully achieved on the silicon chip, producing a unique micro/nanofluidic channel. Compared with previous techniques, the method reported here is advantageous for its simplicity and flexibility