竹节状碳纳米管有序阵列的合成和表征

用1,4-偶氮二异丁基腈作碳源,以载有催化剂Co的多孔Al₂O₃膜作模板,用化学气相沉积法在较低温度(600℃)下方便地制得了单分散碳纳米管有序阵列。透射电子显微分析表明,所得碳纳米管的形态为竹节形状,端口是闭合的,这和同样用Al₂O₃膜作模板但以乙烯或乙炔作碳源热分解制得的中空碳纳米管的情形明显不同。对该纳米管的生成机理进行了初步探讨。     

变浓度无有机模板剂合成ZSM-5沸石分子筛膜

报道了无有机模板剂制备出15 nm的ZSM-5分子筛，并以其为晶种浸涂在多孔α-Al₂O₃陶瓷管外表面，再用先浓后稀的无有机模板剂的晶化液水热合成出ZSM-5分子筛膜的新方法。晶种和晶化液的物质的量组成为12Na₂O∶100SiO₂∶2Al₂O₃∶(2 500～5 000)H₂O。XRD分析表明α-Al₂O₃陶     

Al2O3-ZrO2复合膜的制备与表征

以异丙醇铝和氧氯化锆为原料,用溶胶-凝胶法在Al₂O₃中空纤维上制备了Al₂O₃-ZrO₂复合膜。应用TG、DTA、XRD、SEM等测试手段对复合膜的热稳定性、结构、形貌进行了表征。结果表明复合膜的热稳定性比单一由氧化铝或氧化锆制成的膜有显著的提高,在1100℃之前,复合膜以t-ZrO₂存在,1200℃时,出现了m-ZrO₂和α-Al₂O₃相。扫描电镜分析表明,膜表面完整、无缺陷。气体渗透实验进一步表明所得膜具有一定的气体选择性,0.3MPa和0.5MPa下对氮气和氩气的分离因子α分别为1.191和1.185,和氮气与氩气的理论分离因子(α=1.194)相当,说明气体通过膜的扩散以Knudsen扩散传质为主。用等温氮气吸附实验测定了非担载膜的孔径大小和分布,最可几孔径约为4.3nm。     

TiO2微粒功能化多孔Al2O3膜的光电化学研究

用恒电位法制备了多孔Al₂O₃薄膜, 通过在Al₂O₃薄膜孔内水蒸汽水解钛酸异丙酯生成了锐钛矿型TiO₂微粒, 制备出了Al₂O₃与TiO₂微粒的复合薄膜. 用XRD, SEM, 光电化学方法进行了研究. 实验表明: 该复合薄膜具有光电转换特性, 在光催化、光电化学太阳能转换中具有应用价值.     

氢分离与CO催化甲烷化双功能型钯复合膜

以多孔Al₂O₃陶瓷为基体材料, 采用浸渍法担载NiO后用2B铅笔修饰NiO/Al₂O₃表面, 通过化学镀法沉积约5 μm厚的金属钯, 还原后成功制得Pd/Pencil/Ni/Al₂O₃膜. 为进行对比, 还制备了未担载镍的Pd/Pencil/Al₂O₃膜. 膜的表面和断面形貌分别采用扫描电镜和金相显微镜观测, 膜的透氢动力学通过H₂/N₂单气体法测试, 并以成分为H₂ 77.8%, CO 5.2%, CO₂ 13.5%和CH₄ 3.5%的原料氢测定了膜的氢分离效果. 结果表明, 未载镍的Pd/Pencil/Al₂O₃膜只具有氢分离作用, 而Pd/Pencil/Ni/Al₂O₃膜还可以有效地将钯膜泄漏的CO和CO₂转化为甲烷, 因而成为双功能型钯膜. 这种双功能膜尤其适用于面向质子交换膜燃料电池(PEMFC)的氢气分离, 既有效解决了PEMFC对氢燃料中CO格外敏感的难题, 又提高了对钯膜缺陷的容忍度, 因而延长了钯膜的使用寿命.     

氧化铝-g-聚丙烯酰胺复合磨粒的制备及表征

为提高α-Al₂O₃磨粒在水基介质中的分散稳定性，采用接枝聚合方法制备了Al₂O₃-g-聚丙烯酰胺复合粒子。采用FTIR、XPS、TOF-SIMS、激光粒度仪、SEM、沉降试验等对氧化铝复合粒子结构及分散性能等进行了表征。结果表明，聚丙烯酰胺以化学键形式接枝到Al₂O₃粒子表面，形成聚丙烯酰胺为壳，Al₂O₃为核的复合磨粒;接枝改性后的Al₂O₃粒子分散性明显提高，并且其分散性与Al₂O₃表面接枝量密切相关。     

硅源量和晶化时间对SAPO-34分子筛结构和性能的影响

以吗啡啉为模板剂合成了SAPO-34分子筛，研究了晶化液SiO₂/Al₂O₃比(硅源量)的影响。当SiO₂/Al₂O₃ ≥ 0.6时，能合成出纯净的SAPO-34分子筛;SiO₂/Al₂O₃=1.0时，分子筛骨架中出现“硅岛”结构，此时合成的分子筛样品具有最高的(乙烯+丙烯)选择性。继续增大硅铝比对(乙烯+丙烯     

Al2O3催化剂结构对催化臭氧化活性的影响

以Al₂O₃为催化剂催化臭氧化处理邻苯二甲酸二甲酯. 通过XRD、比表面积、孔结构、FTIR和活性评价等方法对催化剂的物化性质及催化活性进行了研究, 考察了焙烧温度、成型粒径对催化剂活性的影响. 结果表明, Al₂O₃催化剂对臭氧化降解邻苯二甲酸二甲酯具有很高的催化活性, 反应120 min后, 总有机碳(TOC)的去除率从单独臭氧氧化的23.9%提高到55.1%; 焙烧温度对催化剂的活性具有很大的影响, 600 ℃催化剂催化活性最高; 随着焙烧温度的升高, Al₂O₃晶型经历了从γ-Al₂O₃到θ-Al₂O₃到α-Al₂O₃的转变, 催化剂的比表面积、焙烧得到的孔容逐渐变小, 晶体粒径变大, 表面•OH数量减少, 催化活性下降. Al₂O₃成型粒径的减小, 提高了催化剂的外比表面积, 减小了内部传质扩散的影响, 从而提高了催化活性.     

T型分子筛膜的合成、表征与渗透汽化性能

采用二次生长法,在不锈钢、α-Al₂O₃和莫来石多孔管状支撑体上分别合成了高渗透汽化性能的T型分子筛膜。考察了合成条件如合成时间、n(SiO₂)/n(Al₂O₃)、n(H₂O)/n(Al₂O₃)和硅源等对T型分子筛膜形成和分离性能的影响。通过XRD和SEM表征了膜的晶相和形貌。     

间歇式水热合成制备丝光沸石膜及其异丙醇脱水应用

采用市售廉价大孔α-Al₂O₃管作为基质材料，通过热浸渍法在管外表面涂敷晶种，随后在无模板剂体系下，利用新型的间歇式水热合成法制备丝光沸石膜。对比了传统加热和间歇式加热对丝光沸石膜形貌、结构及渗透蒸发异丙醇脱水分离性能的差异。考察了合成液中Na₂O/SiO₂、SiO₂/Al₂O₃和NaF/SiO₂物质的量之比在间歇式水热合成下对丝光沸石膜的影响。研究结果表明，当合成液中Na₂O/SiO₂、SiO₂/Al₂O₃和NaF/SiO₂物质的量之比分别为0.24、16.7和0.25时，制备的丝光沸石膜渗透蒸发异丙醇脱水分离性能最佳，在75℃下，对异丙醇/水(9∶1，w/w)的渗透通量达5.60 kg·m^-2·h^-1，水对异丙醇的分离因数大于10 000。     

Solid surface and field catalysed interface formation of colloidal Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript> during Al anodizing affecting the kinetics and mechanism of development and structure of porous oxides

Overall kinetic and potentiometric studies of the growth of porous anodic alumina films in saturated H₂SO₄+Al₂(SO₄)₃ electrolyte showed non-saturation conditions inside the pores and supersaturation conditions at the pore surface/electrolyte interface where the field and the solid surface catalyse the formation of colloidal Al₂(SO₄)₃ micelles. Suitable high-strength field thermodynamically sustained electrochemical and chemical kinetic equations were formulated. It was shown that the diameter and surface fraction of charge exchange at the pore bases, the real pore wall surface fraction where oxide dissolution occurs, and its rate are strongly affected by the conditions. The mechanism of growth and structure of the films are quite different from those in H₂SO₄. A mechanism of regular film growth is imposed and the critical current density, above which pitting appears, strongly increases. The formulated theory may predict improved or new Al anodizing technologies. Electronic Publication     

Formulation of a holistic model for the kinetics of steady state growth of porous anodic alumina films

A holistic model for the kinetics of steady state growth of porous anodic alumina films in oxalic acid, H₂C₂O₄, solution was developed not necessarily requiring the adoption of any ‘a priori’ mechanism of porous film growth. By this model the effect of anodising conditions on the transport numbers of Al³⁺ cations and O²⁻ anions across the barrier layer was revealed. The cation (anion) transport number decreased (increased) with current density, increased (decreased) with temperature and was unaffected by the concentration of electrolyte or pH. A complementary atomistic-ionic kinetic model was developed that fully justified these results and showed that the activation distances of Al³⁺ and O²⁻ transport are comparable, but the activation energy of Al³⁺ transport is lower mainly due to the much smaller size of Al³⁺. The validity of the model was tested on the basis of SEM observations, while structural features and the rate of pore wall dissolution were determined.     

Interface physicochemical processes controlling sulphate anion incorporation in porous anodic alumina and their dependence on the thermodynamic and transport properties of cations

Aluminium was anodised in H₂SO₄, LiHSO₄, NaHSO₄, KHSO₄, Mg(HSO₄)₂ and Al(HSO₄)₃ electrolytes. The kinetics of growth of porous anodic alumina films and of the pore wall oxide dissolution during anodisation was studied. Based on the derived kinetic parameters, suitable physicochemical processes in the barrier layer electrolyte interface controlling the anion incorporation in the barrier layer were suggested and relevant models were formulated. According to these processes Al³⁺ and H⁺ ions are rejected from the pore base surface in the attached double layer, where Al³⁺ ions are solvated, and are transferred to the pore filling solution. The strongly different mobilities of Al³⁺ and H⁺ and the necessary space negative charge density distribution in the double layer result in similar concentration distributions of Al³⁺ and anions inside it, which differ strongly from that of H⁺. These Al³⁺ and anion concentrations increase with decreasing mobility of the main cations in the solution which depends on their hydration enthalpy and transport mechanism. The concentration of incorporated anions inside both a thin surface layer of the barrier layer and the double layer vary similarly. For identical surface density and base diameter of pores the decrease of the above mobility reinforces anion incorporation.     

Surface characteristics of anodic oxide films fabricated in acid and neutral electrolytes on Ti–10V–2Fe–3Al alloy

Anodic oxide films were fabricated on Ti–10V–2Fe–3Al alloy in acid (H₂SO₄/H₃PO₄) and neutral environmental friendly (C₄H₄O₆Na₂) electrolytes. The morphology, roughness, crystalline structure of the anodic oxide film were characterized by using scanning electron microscopy, atomic force microscopy, Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results showed that the oxide film fabricated in H₂SO₄/H₃PO₄ electrolyte had a porous structure and the thickness of the film was 3.5 µm. The oxide film fabricated in C₄H₄O₆Na₂ electrolyte presented a nonporous structure that sustained the evident microstructure of the substrate, and the thickness of the film was 6.0 µm. The surface average roughness values of the two types of films were 245 nm and 166 nm, respectively. The phase of the anodic oxide films consisted mainly of anatase and rutile. EIS results showed that the film fabricated in C₄H₄O₆Na₂ electrolyte had higher impedance of the outer layer, while the film fabricated in H₂SO₄/H₃PO₄ electrolyte had higher impedance of the inner layer. Moreover, we attempt to explain the differences in the anodizing kinetics, structure and electrochemical impedance of anodic oxide films by the different films growth processes in the two types of electrolytes. Copyright © 2012 John Wiley & Sons, Ltd.     

Aluminium anodising in low acidity sulphate baths: growth mechanism and nanostructure of porous anodic films

Overall kinetic and chronopotentiometric studies were performed during Al anodising in H₂SO₄, 0–5% w/v, bath solutions pure and saturated by Al₂(SO₄)₃. Peculiarities in film growth mechanism and nanostructure in these cases appeared, like significant differences of porosity and its dependence on film thickness, different critical current density above which pitting appears, salt deposition on pitted surface regions in saturated bath, etc. The different conditions inside pores are responsible for this behaviour like almost depletion of H⁺ during a long initial transient stage in the first case, supersaturation and formation of Al₂(SO₄)₃ nanoparticle micelles on pore surface in the second case, etc. Differences in film growth mechanism also appeared between these and alike baths at higher acidity. Anodising in low acidity saturated baths shows superiority for growing low porosity films at specific conditions. New technologies may be suggested to produce optimal films of desired structure.     

Improvement of the oxidation behavior of Ti1-xAlxN hard coatings by optimization of the Ti/Al ratio

The oxidation behavior of cubic Ti_1-xAl_xN films was improved by decreasing the Ti/Al ratio from 50/50 in the direction of the phase transition between cubic and hexagonal structure. Metastable, polycrystalline, single-phase Ti_1-xAl_xN films were deposited on high speed steel (HSS) substrates by reactive magnetron sputtering ion plating (MSIP). The composition of the bulk was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). A Ti_1-xAl_xN film with a Ti/Al atomic ratio of 38/62 was deposited in cubic NaCl structure, whereas a further decrease of the Ti/Al ratio down to 27/73 led to a two-phase film with both cubic and hexagonal constituents. The Ti_0.38Al_0.62N film was oxidized in synthetic air for 1 h at 800?°C. The oxidic overlayer was analyzed by X-ray photoelectron spectroscopy (XPS) sputter depth profiling, EPMA crater edge linescan analysis, and secondary neutrals mass spectroscopy (SNMS). Scanning electron microscopy (SEM) micrographs of the cross sectional fracture were taken for morphological examination. With higher Ti content, the Ti_1-xAl_xN formed a TiO_2-x rich sublayer beneath an Al₂O₃ rich toplayer, whereas the oxide layer on the Ti_0.38Al_0.62N film consisted of pure Al₂O₃. The thickness of the oxide layer was determined to 60–80 nm, about a quarter of the oxide layer thickness detected on Ti_0.5Al_0.5N films. The absence of a TiO_2-x sublayer was also confirmed by XRD. The results show a distinct improvement of the oxidation resistance of cubic Ti_1-xAl_xN films by increasing the Al content from x = 0.5 to 0.62, whereas a further increase leads to the hexagonal structure, which is less suitable for tribological applications due to its tendency to form cracks during oxidation.     

Investigation of the incorporation of electrolyte anions in porous anodic Al2O3 films by employing a suitable probe catalytic reaction

A new method has been developed capable of describing the incorporation of electrolyte anions along the pore wall surface and across both the barrier layer and the pore wall oxide after the establishment of the steady state of growth of porous anodic Al₂O₃ where other methods cannot be applied to obtain reliable results. The knowledge of the nature/composition of anodic oxides as regards the incorporation of species like electrolyte anions is of specific importance for both the understanding of the electrochemical mechanism of oxide production and growth and the scientific and technological applications of porous anodic Al₂O₃ films. The method consists of the selection and use of a suitable catalytic probe reaction on porous anodic oxides at thicknesses varying from a value near zero up to the maximum limiting thickness and the treatment of the experimental reaction rate results by a properly developed mathematical formalism. This method was employed in anodic Al₂O₃ films prepared in H₂SO₄ anodizing electrolyte at a constant bath temperature and different current densities using as a probe reaction the decomposition of HCOOH on these oxides, which is almost exclusively a dehydration reaction, at relatively high reaction temperatures, 350 °C and 390 °C, where the effect of other species except SO₄ ²⁻ incorporated in the oxide on the reaction rate is eliminated. It has been shown that the fraction of the intercrystallite surfaces occupied by SO₄ ²⁻ follows a parabola-like distribution. It has a significant value at the pore base surface, depending on the current density, then it passes through a maximum along the pore wall surface and across both the barrier layer and the pore walls near the pore bases at positions depending on the current density and then becomes almost zero at the mouths of the pores of the oxide with the maximum limiting thickness and at both the Al₂O₃/Al interface and cell boundaries. The maximum value of the surface coverage is almost independent of the current density and is always near 1, showing an almost complete saturation of intercrystalline surfaces at these positions. The above distribution of surface coverage predicts a qualitatively similar distribution of the SO₄ ²⁻ bulk concentration across both the barrier layer and pore wall oxide around the pore bases. The method may be improved and developed further either for a more detailed investigation of the above films or to investigate films prepared in other pore-forming electrolytes. Received: 30 July 1998 / Accepted: 30 September 1998     

Formation of Superhydrophobic Alumina Coating Films with High Transparency on Polymer Substrates by the Sol-Gel Method

Transparent, superhydrophobic coating films have been prepared on polymer substrates at low temperatures through the sol-gel method. Al₂O₃ gel films were prepared on poly(ethylene terephthalate) substrates from Al(O-sec-C₄H₉)₃ chemically modified with ethyl acetoacetate. A small roughness of about 20–50 nm was found to form on the surface of the Al₂O₃ gel films dried at room temperature and then immersed in hot water at 60°C. The electron diffraction measurements have shown that this roughened surface consists of pseudoboehmite nanocrystals. The coating of hydrolyzed fluoroalkyltrimethoxysilane on the Al₂O₃ gel films with the small roughness produced transparent, superhydrophobic films with contact angle for water larger than 150°.     

Aluminium anodising in ultra-dense sulfate baths: discovery by overall kinetic and potentiometric studies of the critical role of interface colloidal Al2(SO4)3 nanoparticles in the mechanism of growth and nanostructure of porous oxide coatings

The solubility of Al₂(SO₄)₃ in H₂SO₄ at different concentrations was determined and showed a minimum at 95% w/v. Overall kinetic and potentiometric studies of Al anodising were performed in large ranges of concentrations of saturated H₂SO₄ solutions and current densities. During anodising quasi-steady-state supersaturation and unsaturation conditions for concentrations below and above 95% w/v dominate in the pore-filling solution affecting those in the oxide–electrolyte interface. Interface colloidal Al₂(SO₄)₃ nanoparticles form occupying surface fractions increasing with salt concentration, supersaturation, field strength in the pore base surface and current density increase and temperature decrease. These control the mechanism and kinetics of growth and structural parameters of films and impose the growth of non-pitted uniform films up to current densities higher than in unsaturated baths, more effectively under supersaturation conditions. Well-defined peaks of structural parameters appear depending on thickness and current. Thus optimal regularly grown films of desired nanostructure and the introduction of new anodising technologies can be achieved.     

Trimetallic NiMoW/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> hydrotreating catalyst based on H<Subscript>4</Subscript>SiMo<Subscript>3</Subscript>W<Subscript>9</Subscript>O<Subscript>40</Subscript> mixed heteropoly acid

Trimetallic NiMoW/Al₂O₃ catalyst was prepared using mixed H₄SiMo₃W₉O₄₀ heteropoly acid of Keggin structure and nickel citrate. Bimetallic NiMo/Al₂O₃ and NiW/Al₂O₃ catalysts based on H₄SiMo₁₂O₄₀ and H₄SiW₁₂O₄₀, respectively, were synthesized as reference samples. The use of mixed H₄SiMo₃W₉O₄₀ heteropoly acid as an oxide precursor allows the tungsten sulfidation degree and the degree of promotion of active phase particles to be increased. The hydrodesulfurization activity is enhanced as compared to NiW/Al₂O₃ catalyst. The synergistic enhancement of the activity of the NiMo₃W₉/Al₂O₃ catalyst relative to the bimetallic analogs is probably caused by formation of new mixed promoted active sites for direct desulfurization.