Tungsten Carbide and Vanadium Carbide Nanopowders Synthesis in DC Plasma Reactor

Air–methane and nitrogen–hydrogen DC thermal plasma confined flows were used to synthesize tungsten carbide and vanadium carbide nanopowders. The influence of input process parameters such as C/W and C/V molar ratio, plasma jet chemical composition, plasma jet enthalpy, and reactants flow rates on the average nanoparticle size, chemical and crystallographic phase compositions were investigated. During post heat treatment, the synthesized MeC_1?x nanopowders were fully carburized to monocarbides WC and VC with particles size less than 80 and 40 nm correspondently.     

Behavior of nitrided and carburized AISI 904 L stainless steels under severe light ion beam irradiation with plasma focus

Superaustenitic stainless steels have become of growing interest in industrial and technological fields, but there is not a complete understanding on their fundamental properties and their performances. For this paper, AISI 904 L superaustenitic samples were nitrided and carburized in order to study the expanded austenite stability under severe deuterium and helium ion bombardment. Surface treatments were conducted using pulsed plasma glow discharges in a low pressure atmosphere, and a dense plasma focus device was used to irradiate the samples. Characterization techniques used were focused ion beam/SEM, energy‐dispersive X‐ray spectroscopy, and grazing incidence X‐ray diffraction. Our results showed in carburized samples lattice expansion growth with the time treatment, but in nitrided samples, an expanded austenite reduction with time treatment was observed due to the formation of nitride nanoagglomerates. Moreover, this ion impingement provoked surface melting and a severe collision cascade, and a damaged bead located under the craters composed solely of minor alloying atoms. Furthermore, nitrided samples were more stable following ion bombardment than the carburized ones. When helium ions were used, the loss of expansion (triggered by diffusion processes of N or C to deeper regions) was more pronounced in the expanded austenite, but when deuterium ions were used to bombard the sample, there was a crystallite development of stressed austenite, which provoked a diffraction peak arousal at 43.3°. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of acidic centers on supported Mo2C catalysts

The acidic properties of both HZSM-5 and SiO₂ supported MoO₃ and carburized MoO₃ have been investigated by FTIR spectroscopy. Deposition of Mo caused the consumption of Brønsted acidic OH groups of HZSM-5 as shown by the changes in the ν(OH) region of the spectra and also by pyridine and low temperature CO adsorption measurements. Carburization of the sample did not result in regeneration of acidic OH groups of the zeolite. Mo reacted with OH groups during its deposition on SiO₂. The results of both pyridine and CO adsorption measurements did not indicate the generation of Brønsted acidic sites on MoO₃/SiO₂ and carburized MoO₃/SiO₂. Lewis acid sites are formed, however, upon the deposition of Mo. Carburization led to stronger Lewis centers, which are probably the active sites—together with the carbide phase—in methane aromatization on MoO₃/SiO₂.     

Thermal Behaviour of Perfluoropolyether w/o Percolative Microemulsions

The thermal properties of a perfluoropolyether (PFPE) W/O microemulsion were investigated by Differential Scanning Calorimetry (DSC) both on freezing the liquid samples and upon their melting. PFPE systems as a function of increasing volume fraction (Φ=water+surfactant/total), were studied along a dilution line with a water/surfactant molar ratio W/S=11. The percolative nature of these systems emerged directly from the spreading of the exothermic peaks associated with the freezing of the dispersed phase. This behaviour was found to depend on whether the starting temperature of the DSC measure was at, below or above the percolative threshold temperature of the given sample. A low temperature 'needle-like' peak was found around 143 K, immediately after the glass transition due to the oil continuous phase. The low temperature peak was also present in other percolative, three-component microemulsions. The higher order phase transition at the percolation temperature was also evidenced. This revised version was published online in August 2006 with corrections to the Cover Date.     

负载型碳氧化钼催化剂的制备及其二苯并噻吩的HDS活性

通过XRD物相分析和利用小型在线质谱仪,对负载的或体相的氧化钼利用正己烷作为碳源,进行程序升温碳化考察,对所制备的负载型催化剂进行了二苯并噻吩（DBT）加氢脱硫（HDS）活性评价。实验发现,与采用甲烷相比,采用正己烷作为碳源进行碳化可以适当降低碳化所需要的温度,但对于HDS反应来说,并不是碳化越完全催化效果越好。对30%MoO3/γ-Al2O3进行碳化时,碳化原料组成为正己烷/氢气＝0.025（摩尔比）,在620℃碳化1ｈ所得催化剂具有比较好的DBT HDS活性。讨论了制备因素对HDS活性的影响。     

影响环氧树脂E-44相反转乳化的因素

研究了乳化剂的HLB值、乳化剂浓度、乳化温度、搅拌强度对环氧树脂E-44相反转乳化中临界含水量Rf值与乳状液稳定性的影响,探讨了环氧树脂E-44相反转机理。实验结果表明环氧树脂E-44从W/O向O/W相反转的发生与乳化剂的HLB值与浓度、乳化温度、搅拌强度等因素都有关,其Rf值随着乳化条件的不同是动态变化的。     

Practical aspects of carbon content determination in carburized steels by EPMA.

The carbon contents in carburized steels were investigated by electron probe microanalysis (EPMA) for a range of carbon levels in the solid solution less than 1 wt%. This article describes the difficulties encountered with the classic analytical procedure using the k ratio of X-ray intensities and the phi(rhoz) model. Here, a suitable calibration curve method is presented with emphasis on the metallographic study of standard specimens and on the carbon decontamination of samples.     

碳化钼催化剂加氢脱氮性能研究

MoO3在CH4/H2气氛中程序升温还原碳化反应制备了Mo2C催化剂,用XRD、BET、SEM、XPS进行了表征。以吡啶/环己烷溶液为模型化合物,在高压微反装置上评价了碳化钼催化剂的吡啶加氢脱氮性能。结果表明,MoO3在CH4/H2气氛中程序升温至675℃可制得高纯度的β-Mo2C,SEM表征其形貌为板块状颗粒,平均粒径约3.9μm,比表面积达到了10.7m2/g,高于其前驱体MoO3 的2.7倍。在反应压力3.0MPa,空速为8h－1,H2/原料液体积比为500∶1,体积分数为5%的吡啶/环己烷溶液中,碳化钼催化剂在340℃下的吡啶加氢脱氮转化率达到了86.30%,高于相应MoS2约8%。随还原碳化温度的升高,碳化钼催化剂的比表面积降低,表面积炭增多,导致其吡啶加氢脱氮活性下降。确定的碳化钼催化剂的合成条件以还原碳化温度675℃、还原碳化气体空速1.8×104h－1左右较为适宜。     

Ni–Mo2C supported on alumina as a substitute for Ni–Mo reduced catalysts supported on alumina material for dry reforming of methane

In this study, alumina-supported NiMo catalysts were carburized to obtain alumina-supported nickel–molybdenum carbides as potential catalysts for dry reforming of methane. The typical carbide was compared with a low carburized material (in 5% H₂/CH₄) and a reduced NiMo catalyst. It was shown that the passivated alumina-supported NiMo catalysts by carbon lead to higher reactivity, selectivity, and stability for dry methane reforming reaction.     

p－Si上电沉积Ni－W合金薄膜

利用恒电流沉积法，在ｐ－Ｓｉ上制备出不同Ｗ含量和不同结构的Ｎｉ－Ｗ薄膜，研究了镀液温度，ｐＨ值，电流密度对镀层组成的影响，结果表明，提高温度有利于获得高Ｗ含量的合金．随着镀层中Ｗ含量的增加，Ｎｉ面心立方晶格ｆ．ｃ．ｃ发生正畸变，晶粒平均尺寸变小，当Ｗ含量达到５６％以上时，晶粒小于２ｎｍ，薄膜呈非晶态结构．     

Zum chemischen Transport von Wolfram mit HgBr2 – Experimente und Modellrechnungen

On the Chemical Transport of Tungsten using HgBr₂ – Experiments and Thermochemical Calculations Using HgBr₂ as transport agent tungsten migrates in a temperature gradient from the region of higher temperature to the lower temperature (e.g. 1 000 → 900°C). The transport rates were measured for various transport agent concentrations (0.64 ? C(HgBr₂) ? 11.74 mg/cm³; T? = 950°C) and for various mean transport temperatures (800 ? T? ? 1 040°C). Under these conditions tungsten crystals were observed in the sink region. To observe the influence of tungsten dioxide (contamination of the tungsten powder) on the transport behaviour of tungsten, experiments with W/WO₂ as starting materials were performed. According to model calculations the following endothermic reactions are important for the migration of tungsten: In the presence of H₂O or WO₂ other equilibria play a role, too. Using a special “transport balance” we observed a delay of deposition of tungsten (e.g. T? = 800°C; 15 h delay of deposition) with W and W/WO₂ as starting materials. The heterogeneous and homogeneous equilibria will be discussed and an explanation for the non equilibrium transport behaviour of tungsten will be given.     

甲烷自热重整制氢热力学分析

为了优化甲烷自热重整制氢过程的反应条件，运用吉布斯自由能最小化方法对过程进行了热力学计算，研究了重整过程的反应温度、空碳比、水碳比对平衡组成的影响。模拟结果表明,适宜的水碳比为2.5～3.5，空碳比2.0～3.5，重整温度700℃～850℃，每摩尔甲烷生成2.17mol～2.23mol氢；以水碳比1.5为例，对不同空碳比下的组分的产生和转化的机理进行了分析。     

FORMATION OF MULTIPLE EMULSIONS IN A FOUR-COMPONENT SYSTEM CONTAINING NONIONIC SURFACTANTS

ABSTRACT

W/O/W and O/W/O multiple emulsions have been found in systems consisting of water, light mineral oil, and two nonionic surfactants (Span 80 and Tween 20).No specific order of addition of the components or pre-mixing was followed. Following gentle agitation at 25°, 35° and 45° for 48?hours, W/O/W emulsions were found at water contents above 30%, while 0/W/O emulsions generally appeared below 60% water.W/0 and 0/W emulsions, micellar phases and liquid crystalline phases were also observed at various compositions. The multiple emulsion regions decreased in size as temperature increased and the areas and positions of the other phases were also temperature dependent.     

污泥对神府煤灰熔点的影响

研究了神府煤（A）、污泥（W1）、改性污泥（W2）以及煤污泥混合物（AW1、AW2）的灰熔融特性,发现W1、W2分别加入神府煤中可以不同程度地降低煤的灰熔点。W1添加30.74g时,污泥煤灰的熔融温度降到最低,流动温度（FT）降幅程度达到63℃;W2加量为51.23g时,FT降低82℃。通过XRD分析了煤、污泥及混合物中的矿物质组分,并比较了AW1、AW2混合灰在不同特征温度下矿物质的形态演变。结果表明,W1加入A中后,生成了新的矿物质氯磷灰石,并且降低了石英、硬石膏、赤铁矿这三种主要矿物质的转化温度,从而降低了煤的灰熔点;W2降低煤灰熔点的主要原因在于W2中有大量的金属钠离子,混合灰在不同特征温度下主要发生钠类矿物质的转变。     

Phase transitions and microstructure of emulsion systems prepared with acylglycerols/zinc stearate emulsifier

The emulsification processes, during which acylglycerols/zinc stearate emulsifier, water, and oil phase formed ternary systems, such as water-in-oil (W/O) emulsions, oil-in-water (O/W) dispersions, and unstable oil-water mixtures, were investigated in order to characterize the progressive transformations of the dispersed systems. The type, structure, and phase transitions of the systems were found to be determined by temperature and water phase content. Crystallization of the emulsifier caused the destabilization and subsequent phase inversion of the emulsions studied, at a temperature of 60-61 degrees C. The observed destabilization was temporary and led, at lower temperature, to W/O emulsions, "O/W + O" systems, or O/W dispersions, depending on the water content. Simultaneous emulsification and cooling of 20-50 wt % water systems resulted in the formation of stable W/O emulsions that contained a number of large water droplets with dispersed oil globules inside them ("W/O + O/W/O"). In water-rich systems (60-80 wt % of water), crystallization of the emulsifier was found to influence the formation of crystalline vesicle structures that coexisted, in the external water phase, with globules of crystallized oil phase. Results of calorimetric, rheological, and light scattering experiments, for the O/W dispersions obtained, indicate the possible transition of a monostearoylglycerol-based alpha-crystalline gel phase to a coagel state, in these multicomponent systems.     

W2N／C催化剂加氢脱氮的研究

制备了加氢脱氮高活性催化剂Ｗ２Ｎ／Ｃ，探讨了氮化温度对催化剂活性的影响，考察了Ｗ２Ｎ／Ｃ催化剂上吡啶的加氢脱氮规律，提出了在该催化剂上吡啶加氢脱氮反应机理。     

络合作用对重油加氢处理催化剂性能的影响

以Ni、W为催化剂的活性金属组分,考察在金属组分浸渍液中加入有机络合剂对催化剂性质及加氢脱硫、脱氮性能的影响。结果表明,络合剂与金属组分共浸渍更有利于金属组分的分散;提高络合剂用量,既有利于提高主活性金属组分WO₃在载体表面的分散,又能促进六配位八面体Ni物种及高加氢活性相NiWO₃的形成;焙烧温度具有调变催化剂金属组分分散性及酸性的双重作用,在适宜的焙烧温度下制得的催化剂具有较好的酸性及加氢活性,主要表现为较高的加氢脱硫及脱氮活性。     

Microemulsion of Tween‐80/n‐Butylalcohol/H2O System and Its Entrapment Efficiency of ATRA

Microemulsion of Tween‐80/n‐butylalcohol/H₂O system was prepared, and the microemulsion region as well as the influence of temperature and concentration of NaCl on the region were determined with ternary diagrams. The O/W, W/O, and B.C. regions were divided by the conductance method. The particle diameters of microemulsions with different NaCl concentrations or microemulsion‐enveloping all‐trans retinoic acid (ATRA) were measured with dynamic light scattering in O/W region. The release rate of ATRA was studied with dialysis a bag‐ultraviolet spectrophotometers and the anticancer activity of ATRA in microemulsion was investigated with cancer cells H446. Results showed that O/W microemulsion forms when water content is over 64% in the mixture. The influences of temperature and salinity on microemulsion region were very slight, and even the particle diameter decreased very little with increasing salt and ATRA concentrations. The microemulsion‐enveloping ATRA possessed eminent sustaining release efficiencys and the efficiency was further confirmed with the growth inhibitory effect test on human cancer cells H446.     

Induction of instability in water-in-oil-in-water double emulsions by freeze-thaw cycling

Individual water-in-oil-in-water (W1/O/W2) double-emulsion globules loaded with fluorescently labeled bovine serum albumin (FITC-BSA) were optically monitored within cylindrical capillaries during freeze-thaw cycling. Coalescence of internal aqueous droplets (W1) and external aqueous phase (W2), termed external coalescence, was not observed before or during freezing of the oil phase (O). On the other hand, this instability mechanism was readily promoted during thawing. This realization confirms the previously suggested potential of W1/O/W2 double emulsions to trigger release upon oil thawing and demonstrates that it is a direct result of globule breakage through external coalescence. The presented results also identified a threshold in the relative W1 droplet size above which instability occurred, while smaller droplets remained unperturbed and therefore indicate that optimization of the delivery can be achieved by tuning the size of W1 droplets. In addition, we propose a possible explanation for the occurrence of instability during oil thawing and its dependence on the size of W1 droplets. Because this alternative globule-breakage mechanism simply uses temperature increase (solid-to-liquid-phase transition) as external stimulus, W1/O/W2 double-emulsion delivery systems can be easily tailored by choosing an oil phase with the appropriate phase-transition temperature.     

Liquid phase mononitration of chlorobenzene over WOx/ZrO2: A study of catalyst and reaction parameters

To study the effect of W concentration and activation temperature of the catalysts a series of WO_x/ZrO₂ samples with varying concentration of W (10–25 wt.%) were prepared and activated at 650/750 °C. XRD of sample shows 15 wt.% W stabilizes the tetragonal phase of zirconia up to 750 °C. Above and less than 15 wt.% shows peaks corresponding to monoclinic WO₃ and monoclinic ZrO₂, respectively. Further, the tungsten modification stabilizes the specific surface area of ZrO₂. There is an increase in the surface area observed up to 15 wt.% W, which declines on further increase in the concentration. The NH₃ TPD confirms the presence of acid sites with varying strength from the broad desorption profile. The 15 wt.% W and activated at 750 °C shows maximum acidity. The results of the nitration reaction of chlorobezene imply the 15 wt.% W and activation at 750 °C shows maximum activity. Not only yield, a better para-selectivity is also achieved with WO_x/ZrO₂ samples. Effect of activation temperature, W concentration and reaction parameters such as reaction temperature, reaction time, the presence of solvent and solvent free medium on activity and selectivity are studied in details.