Tape Casting Slip Preparation by in Situ Polymerization

The present work describes the polymerization of methylmethacrylate monomer into polymethylmethacrylate (PMMA), in the presence of either coarse or ultrafine alumina powder. The flexibility of the material was modified by addition of either butylbenzyl phthalate (S-160), or butylacrylate (BA) monomer as plasticizers. It was found that BA is more compatible than S-160 in the PMMA system. A density of 97%–99% was reached with ultrafine alumina. The maximum tensile strength of the green and sintered tapes was 10 and 140 MPa, respectively. Due to improved homogeneity in the polymerized slip, the sintered tapes prepared by in situ polymerization were stronger and denser than those prepared by conventional blending of commercial PMMA.     

Non-metal Catalysts for Dioxygen Reduction in an Acidic Electrolyte

Active non-metal catalysts for the Oxygen Reduction Reaction (ORR) were prepared by decomposition of acetonitrile vapor at 900°C over a pure alumina support, and supports containing 2 wt% Fe or 2 wt% Ni on alumina. The exposed alumina and metal in the samples were subsequently washed away with HF acid to purify the solid carbon material. The sample prepared with iron was the most active sample for the ORR, with only 100 mV greater overpotential than a commercial 20 wt% Pt / Vulcan Carbon catalyst. However, nitrogen-containing carbon deposited on pure alumina (which contained less than 1 ppm metal contamination) was also quite active, demonstrating that platinum or iron is not required for ORR activity. Characterization by XPS and TEM revealed that the more active samples had nanostructured carbon with more edge plane exposure than the less active tube structures formed from the nickel sample.     

Wear behavior and microstructure of alumina-mullite-zirconia composites prepared by a novel method: Coating of zircon powder by aluminum alkoxide

The formation of the mullite phase is the main challenge in the preparation of alumina-mullite-zirconia (AMZ) composites. To overcome this limitation, a novel method based on the coating of zircon powder with aluminum alkoxide was proposed in this study. Reaction sintering of alumina and coated zircon was carried out at 1630 °C for 3 h. The microstructural, physical, mechanical, and tribological properties of samples were compared with the conventional AMZ composites prepared by common mixing of alumina and zircon. The microstructural analysis indicated the higher alumina phase of the sample prepared with the conventional method. On contrary, the samples prepared with the proposed method included higher percentages of mullite phase. In terms of mechanical properties, the conventional AMZ samples performed better. However, due to the beneficial effect of the mullite phase in tribological applications, the samples prepared with this new method show superior wear resistance. Especially, the samples prepared from 30 wt% aluminum alkoxide exhibited the best wear resistance. The delamination and adhesive wear mechanisms govern the wear process.     

Preparation of acrylic acid grafted polypropylene nonwoven fabric by photoinduced graft polymerization with preabsorption of monomer solution

We improved photoinduced graft polymerization by absorbing the monomer solution onto the substrate (Ab‐type) instead of immersing the substrate in the monomer solution (Im‐type) before photoirradiation to yield a more practical and effective grafting system. With this system, acrylic acid (AA) was effectively grafted onto polypropylene (PP) nonwoven fabric. The maximum degree of grafting obtainable was restricted by the amount of monomer preabsorbed onto the PP fabric. However, we effectively enhanced the degree of grafting by increasing the monomer concentration, adding trimethylolpropane triacrylate (TMPTA) to the monomer solution, and repeating the photoirradiation with supplementation of the monomer solution. The net availability of the monomer for graft polymerization was 50% or greater; this increased to 90% or greater with the addition of TMPTA and was much higher than for conventional Im‐type photografting (≤13%). Fourier transform infrared spectra, scanning electron microscopy morphology observations, and the adsorption–regeneration properties confirmed that the PP‐g‐AA fabric prepared by the improved Ab‐type photografting method had comparable qualities to those of fabric prepared by conventional Im‐type photografting. Thus, the improved Ab‐type photografting system provides potential for the preparation of graft adsorbents on a large scale at a competitive cost with a continuous reactor, such as a conveyer belt system, instead of a batch reactor. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of novel optically active polyesters with high thermal stability

A new optically active diacid (DA) was prepared by nucleophilic substitution reaction of R‐(−)‐mandelic acid with terephthaloyl chloride in the presence of potassium hydroxide. This DA named terephthalic acid bis(carboxyphenylmethyl) ester was used as a monomer for the preparation of related optically active polyesters. Polycondensation of DA with different aromatic diols, including hydroquinone, 1,5‐dihydroxy naphthalene, 1,4‐dihydroxy anthraquinone, 1,8‐dihydroxy anthraquinone, 2,4‐dihydroxy benzophenone, and bisphenol A, in the presence of 4‐toluenesulfonyl chloride using high temperature solution method led to preparation of different polyesters. The prepared monomer and all the polymers were characterized by conventional methods. Thermal and physical properties of the polyesters, including thermal stability, thermal behavior, solution viscosity, and solubility behavior, in addition to optical activity were studied. The optically active polyesters showed high thermal stability, whereas the presence of bulky groups improved their solubility. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Catalytic oxidation of CO over Ag-Co/alumina catalysts

Low-loading silver cobalt catalysts on alumina for the catalytic oxidation of carbon monoxide were synthesized following different preparation methods: the single-step sol-gel method and the impregnation method. A catalyst synthesized by the single-step sol-gel method gave high surface area values. The activities of alumina-supported silver-cobalt catalysts were studied to obtain the effects of the calcination temperature, metal loading, and preparation methods on CO oxidation at low temperature. The catalysts prepared by impregnation metals on the alumina synthesized by the sol-gel method gave the best activity for the CO oxidation. Catalytic activity conversion of (5 wt% Ag-5 wt% Co)/Al 2 O 3 catalysts prepared by the sol-gel-impregnation method reached 100% at 200°C. Increasing silver loading over the catalysts gave rise to more active catalysts. The sol-gel catalysts had poor activity at low temperature.     

Influence of Pd Precursor and Method of Preparation on Hydrodechlorination Activity of Alumina Supported Palladium Catalysts

A series of alumina supported Pd catalysts were prepared by the novel deposition-precipitation method adopting the chloride precursor (DP-Cl) of Pd and varying the metal content from 0.25 to 1.0 wt%. The catalytic properties of prepared catalysts were studied by various characterization techniques such as N₂ adsorption, CO chemisorption, TPR, XRD, XPS, and TEM techniques. The activity and stability of the catalysts were evaluated for the gas phase hydrodechlorination (HDC) of chlorobenzene operating at atmospheric pressure. At 1 wt% of Pd the catalyst showed higher chlorobenzene conversion with good stability when tested for a period of 25 h, whereas the other catalysts exhibited a loss in activity with time. In order to elucidate the exceptional activity and stability of this catalyst, a few more catalysts with 1 wt% Pd were prepared by impregnation technique and also using a non-chloride precursor, palladium nitrate. The 1 wt% DP-Cl catalyst again was found to be the best among the others. The activity and stability of the DP-Cl catalyst was also found to be superior to two low-dispersed catalysts, each with 10 wt% Pd, prepared by conventional impregnation method using the chloride and nitrate as the precursors. The characterization results reveal that the high activity and stability of the DP-Cl catalyst is related to the formation of electron deficient Pd species and its stabilization in the octahedral vacancies of alumina.     

Preparation and Characterisation of Ag/Alumina Catalysts for the Removal of NOx Emissions Under Oxygen Rich Conditions

A highly active silver/alumina catalyst for continuous reduction of NO to nitrogen with octane under lean conditions was prepared. The effect of impregnation time and precursor concentration on the catalyst activity was investigated. The catalyst was characterized by means of XRF, H₂-TPR, and UV–Vis to correlate recorded results with different preparation methods. UV–Vis measurements indicated that the highest and most stable activity is obtained with Ag/alumina exhibiting predominantly mono-atomically dispersed silver.     

Room temperature preparation of highly crosslinked microgels

A series of highly crosslinked microgels has been prepared at room temperature via photoinitiated polymerisation in dilute solution using methyl methacrylate (MMA) and ethylene dimethacrylate (EDMA), respectively as non-functional monomer and crosslinker in N,N-dimethylformamide (DMF) as a solvent. The effect of monomer concentration and EDMA/MMA ratio on the yield, molecular weight and microgel size was studied and the data were compared to those previously obtained for microgels of similar composition prepared by thermal initiation. This mild polymerisation method yields better results compared to the more conventional thermal method, since it allows higher monomer concentrations to be employed as well as a better microgel size control. Consequently, the method can be advantageously used for the preparation of highly crosslinked microgels with improved properties, particularly useful, e.g. for molecular imprinting applications.     

A combination of Ag/alumina and Ag modified ZSM-5 to remove NOx and CO during lean conditions

Single and bi-metallic silver modified ZSM-5 catalysts were synthesized using different methods of preparation, characterized by several techniques and tested in simulated diesel conditions. Additionally the catalytic behaviour of the most active catalyst, containing 5 wt.% Ag and prepared by impregnation (5Ag(Imp)-H-ZSM-5), was studied over a broad temperature range with two reducing agents (octane and propene). To correlate the catalytic activity of the prepared catalysts with preparation parameters the materials were characterized by XRD, SEM, N₂-physisorption, octane/propene-TPD, EPR and ICP techniques. A dual bed system consisting of Ag/alumina and the most active zeolitic material (5Ag(Imp)-H-ZSM-5) was shown not only to substantially enhance the activity of Ag/alumina in the low temperature region, but also to completely oxidize the CO and unburned hydrocarbons.     

载镍金属有序介孔氧化铝催化一氧化碳 甲烷化反应性能研究

采用传统浸渍法制备出两种负载镍金属有序介孔氧化铝,并采用BET法比表面积测定、X射线衍射 （XRD）、程序升温还原（TPR）、X射线光电子能谱分析（XPS）、透射电镜（TEM）、电感耦合等离子体发射光谱仪（ICP-OES）等多种测试技术对合成的催化剂进行表征。通过一氧化碳甲烷化反应测定其催化活性并与负载镍金属普通氧化铝进行对比。实验结果表明,镍在两种有序介孔氧化铝上主要呈两种形态,即氧化镍和偏铝酸镍。合成的介孔氧化铝比普通氧化铝镍负载量大且分散性好,这主要归结于其具有的高比表面积（300~500 m²/g）及窄孔径分布（4~ 10 nm）的稳定有序结构。催化结果表明：由于具有较高的镍负载量及较好的镍金属分散性能,因而负载镍金属有序介孔氧化铝比普通氧化铝具有较好的催化活性。     

共沉淀法制备Ni/Al2O3催化剂的研究

油脂加氢催化剂是以金属镍为活性组分、氧化铝为载体制备的Ni/Al2O3催化剂。在制备催化剂过程中,其合成条件直接影响着催化剂的最终活性。以工业硝酸镍、碳酸钠和自制氧化铝粉为原料,利用共沉淀的方法制备加氢催化剂,考察了反应温度、反应时间、反应液pH及反应过程中搅拌转速对催化剂活性的影响。通过实验数据汇总分析,最终确定制备Ni/Al2O3油脂加氢催化剂的最佳条件：反应温度为85 ℃、反应结束时溶液pH=8.0、反应时间为1.5 h、搅拌转速为600 r/min。在此条件下制备的Ni/Al2O3催化剂,经棕榈油加氢评价后测定的碘值最低。     

平板状阳极氧化铝催化剂在煤油水蒸汽重整中的催化性能

在草酸溶液中对一种铝基板(Al/Fe-Ni-Cr alloy/Al)采用阳极氧化技术制备了氧化铝多孔膜,考察了扩孔处理、水热处理和焙烧处理对氧化铝膜比表面积的影响,并用FE-SEM、BET等研究了氧化铝膜的微观形态及结构。采用这种材料作为载体通过浸渍法制备了负载钌质量分数1.0%的钌基催化剂Ru/Al,并在固定床反应器上研究Ru/Al催化剂在煤油水蒸汽重整中的催化性能。结果表明,在氧化铝多孔膜载体制备过程中,扩孔处理能有效扩大膜孔,水热处理能让多孔膜形成更为复杂的多孔结构,并极大地提高多孔膜的比表面积。在空气中750℃焙烧50 h后,多孔膜的比表面积仍能维持在原来的60%。催化剂性能测试结果表明,与对比剂Ru A相比,在活性实验中虽然两者活性相似,但在加速劣化实验中,采用阳极氧化技术制备的催化剂Ru/Al比Ru A更稳定。工业应用中对这种载体仍需要改良以减弱烧结程度,因为在水蒸汽气氛于750℃焙烧50 h后,载体的比表面积只有原来的38%。     

Selective hydrogenation of sunflower oil over Ni catalysts

This work focuses on the influence of the support and the preparation method on the activity and selectivity of nickel catalysts in the hydrogenation of sunflower oil. Catalysts were prepared over silica and alumina supports following the incipient wetness impregnation and deposition-precipitation techniques. The activation process was followed by temperature-programmed reduction (TPR). Precipitation-deposition method allowed a stronger metal-support interaction than incipient wetness impregnation. A precipitation-deposition time of 14 h (which allowed a Ni loading of about 20wt%) was deemed as the most adequate from the standpoint of high specific surface area and strong Ni-support interaction. The selectivity to oleic acid was not affected by the preparation method, but it was significantly influenced by the type of support. In this regard, the catalysts prepared on silica are more active and produce less saturated fatty acids.     

Fluorinated copolyimides prepared by one-shot and stepwise monomer addition method

Copolyimides containing a hexafluoropropylidene group are prepared by the stepwise monomer addition method as well as the conventional one shot method. The stepwise addition method goes through an oligomeric imide prepolymer. The molecular weight distribution of the prepolymers approximately follows the Flory's statistical distribution in the fluorinated imide prepolymer. Except for the final molecular weight, the conventional one-shot method does not give a significant difference in the copolymer character from the stepwise method, indicating that the segmental distribution in the copolyimides is practically statistical in the present monomer combination. The observed difference in the molecular weight by the preparation method may be related to the reactivity difference of the two monomer pairs. © 1995 John Wiley & Sons, Inc.     

Conducting poly(<Emphasis Type="Italic">N</Emphasis>-(1-Naphthyl) ethylene-diamine dihydrochloride) electropolymerization,characterization and electroanalytical applications

Uniform conducting polymer films of poly(N-(1-Naphthyl) ethylene-diamine dihydrochloride), PNED, were prepared conveniently and reproducibly by the anodic oxidation of the monomer, N-(1-Naphthyl) ethylene-diamine dihydrochloride, NED, in an acidic aqueous solution using the conventional potentiodynamic technique. The different parameters influencing the preparation conditions like monomer concentration, solvent constitution, scan range, scan rate, scan repetition, rotation speed of the working electrode and the type of the substrate were investigated and the optimum preparation conditions are specified. The stability of the prepared films was tested in both aqueous and non-aqueous media. The characteristics of the polymer films and their electrochemical activity towards catalyzing some technologically promising redox reactions were also examined. The films were found to be very stable in aqueous solutions and in some organic solvents like acetone, acetonitrile, and chloroform and dimethyl sulfoxide. The film stability was found to depend on the solution pH. The polymer films were capable of catalyzing the redox processes of several natural products and amino acids e.g. vitamin C and glycine. The polymer film possesses electrochromic properties and the color of the film changes from purple to violet to dark blue and then to brown according to the preparation and/or polarization conditions. The electrochromic properties are related to polaron formation, which subsequently oxidizes to diimine species followed by the oxidation of the aromatic ring. The mechanism of the polymerization process was investigated and discussed. The process involves deprotonation reactions and a head-to-tail coupling of the oxidized monomer with cation radicals. An erratum to this article can be found at     

Catalytic selective reduction of NO with propylene over Cu-Al2O3 catalysts: influence of catalyst preparation method

NO reduction to N₂ by C₃H₆ was investigated and compared over Cu-Al₂O₃ catalysts prepared by four different methods, namely, the conventional impregnation, co-precipitation, evaporation of a mixed aqueous solution, and xerogel methods. It was found that the catalyst preparation method as well as the Cu content exerts a significant influence on catalyst activity. For the catalysts prepared by the first three preparation methods, with the increase of Cu content from 5 to 15 wt%, the maximum NO reduction conversion decreased slightly, but the temperature for the maximum NO reduction also decreased. For the xerogel Cu-Al₂O₃, there was a significant decrease in NO reduction conversion with the increase of Cu content from 5 to 10 wt%. In the absence of water vapour, the Cu-Al₂O₃ catalyst prepared by the impregnation method exhibited the highest activity toward NO reduction. The purity of alumina support was found to be a crucial factor to the activity of the Cu-Al₂O₃ catalyst prepared by impregnation. In the presence of water vapour, a substantial decrease in NO conversion was observed for the Cu-Al₂O₃ catalysts prepared by the first three methods, especially for the impregnated Cu-Al₂O₃ catalyst. In contrast, the presence of water vapour showed only a minor influence on the xerogel 5 wt% Cu-Al₂O₃ and it showed the highest activity for NO reduction in the presence of 20% water vapour. The xerogel 5 wt% Cu-Al₂O₃ catalyst was also found to be less affected by a 5 wt% sulfate deposition than the Cu-Al₂O₃ catalysts prepared by other methods.     

Near-net shape manufacture of macroporous nanosized alumina monolith by aqueous gel casting method

A potentially near-net-shape manufacturing procedure for macroporous alumina monoliths with 20%-75% porosity was presented by gel casting of nano γ-Al₂O₃. Although monolith obtained by nano alumina had a high surface area and low sintering temperature, an optimum fraction of micron alumina needed to be added to achieve the proper rheological and mechanical properties of slurries. The preparation parameters including alumina loading, sintering temperature, monomer concentration, and the fraction of nano alumina were investigated. The green densities ranging from 0.66 to 0.86 g cm⁻³ were obtained by raising alumina loading from 10 to 20 vol%. Depending on the monomer concentration and sintering temperature, the mean pore size ranging from 45 to 412 nm, total porosity (20%–75%), and open porosity varying from 12% to 89% were obtained. The sintered density (from 0.95 to 3.15 g cm⁻³) and compressive strength (CS) (from 4.2 to 31.46 MPa) were suitable for use in different fields.     

Novel freeze-casting fabrication of aligned lamellar porous alumina with a centrosymmetric structure

A novel freeze-casting method is used to fabricate aligned lamellar porous alumina with a centrosymmetric structure from aqueous alumina slurries. Two cold fronts oriented perpendicularly to each other, originating from the bottom and side of the cylindrical copper mold, induce the growth of ice crystals in specific directions along the radius of the cylindrical mold. Lamellar channels of porous alumina are arranged centrosymmetrically along the radial axis. The pore distribution of the currently prepared porous ceramics is more regular when compared with that of porous ceramics prepared by conventional freeze casting. This affords porous ceramics with improved mechanical properties and stability. The current method addresses the issue of partial failure as induced by the randomly distributed channels in lamellar porous ceramics.     

Polyhedral alumina foam

The presented paper reports on the results of preparation of alumina foam with ideal polyhedral shapes of bubbles-pores. The foam was prepared by direct foaming method using partially hydrophobized Al₂O₃ particles, where dodecylbenzenesulfonic acid was used as a hydrophobization agent. A polyhedral shape of the bubbles was achieved by “water procedure”, in which the alumina foam prepared by the direct foaming method was poured into twice its volume of water and mixed. After the mixing was stopped, the particles with an inadequate contact angle were washed out from the system of the alumina foam by draining. The foam was formed only from particles which were physically bound in the lamellas and the bubbles were arranged in ideal polyhedral shapes. The water procedure increases the foam stability, allowing for preparation of alumina foams with porosity of 99 %.