Wire-mesh honeycomb catalysts for selective catalytic reduction of NO with NH3

Both flat and corrugated wire mesh sheets were coated with aluminum powder by using electrophoretic deposition (EPD) method. Controlled thermal sintering of coated samples yielded uniform porous aluminum layer with a thickness of 100 μm that was attached firmly on the wire meshes. Subsequent controlled calcination formed a finite thickness of Al₂O₃ layer on the outer surface of each deposited aluminum particles, which resulted in the formation of Al₂O₃/Al double-layered composite particles that were attached firmly on the wire surface to form a certain thickness of porous layer. A rectangular-shaped wire-mesh honeycomb (WMH) module with triangular-shaped channels was manufactured by packing alternately the flat sheet and corrugated sheet of the Al₂O₃/Al-coated wire meshes. This WMH was further coated with V₂O₅-MoO₃-WO₃ catalyst by wash-coating method to be applied for the selective catalytic reduction (SCR) of NO with NH₃. With an optimized catalyst loading of 16 wt%, WMH catalyst module shows more than 90% NO conversion at 240 °C and almost complete NO conversion at temperatures higher than 300 °C at GHSV 5,000 h⁻¹. When compared with conventional ceramic honeycomb catalyst, WMH catalyst gives NO conversion higher by 20% due to reduced mass transfer resistance by the existence of three dimensional opening holes in WMH.     

Formation of Fe(III)-containing mackinawite from hydroxysulphate green rust by sulphate reducing bacteria

The interactions between Fe(II–III) hydroxysulphate GR() and sulphate reducing bacteria (SRB) were studied. The considered SRB, Desulfovibrio desulfuricans subsp. aestuarii ATCC 29578, were added with GR() to culture media. Different conditions were envisioned, corresponding to various concentrations of bacteria, various sources of sulphate (dissolved  + GR() or GR() alone) and various atmospheres (N₂:H₂ or N₂:CO₂:H₂). In the first part of the study, CO₂ was deliberately omitted so as to avoid the formation of carbonated compounds, and GR() was the only source of sulphate. Cell concentration increases from 4 × 10⁷ to 7 × 10⁸ cells/mL in 2 weeks. The evolution with time of the iron compounds, monitored by Raman spectroscopy and X-ray diffraction, showed the progressive formation of a FeS compound, the Fe(III)-containing mackinawite. This result is consistent with the association GR()/SRB/FeS observed in rust layers formed on steel in seawater. In the presence of CO₂ and additional dissolved sulphate species, a rapid growth of the bacteria could be observed, leading to the total transformation of GR() into mackinawite, found in three physico-chemical states (nanocrystalline, crystalline stoichiometric FeS and Fe(III)-containing), and siderite FeCO₃.     

Influence of manganese on iron oxyhydroxides and oxides formed in aqueous solution

Structural analysis techniques such as X-ray diffraction and anomalous X-ray scattering were used for characterizing the influence of manganese on iron oxyhydroxides and oxides formed from green rust (GR) in an aqueous solution. The results showed that the formation of Fe₃O₄ was enhanced by the addition of manganese ions during the conversion of GR2 to α-FeOOH and Fe₃O₄. The results obtained from anomalous X-ray scattering showed that manganese was present both in α-FeOOH and Fe₃O₄ particles. The incorporation of manganese in α-FeOOH appears to induce the distortion of the atomic-scale structure of α-FeOOH particles formed in an aqueous solution.     

Electrochemical behaviour of stainless steels in media containing iron-oxidizing bacteria (IOB) by corrosion process modeling

Localized corrosion mechanism of stainless steel (SS) types UNS S30403 and UNS 31603 in the presence of iron-oxidizing bacteria Sphaerotilus spp. isolated from rust deposits was studied electrochemically. OCP transient, cyclic anodic and cathodic potentiodynamic polarization curves were measured on steel electrodes through their exposure to 3% NaCl solution supplemented with Sphaerotilus culture. The exposure period was composed of three parts: (a) 5 days incubation of steel electrodes in sterile 3% NaCl solution; (b) addition of 3 days-old Sphaerotilus culture to 3% NaCl at 3:2 v/v ratio with subsequent electrodes exposure for 11 days up to complete sedimentation of ferric oxides and (c) subsequent exposure of electrodes for 14 days in upper and bottom (sediments layer) fractions of the experimental medium. The results revealed an instantaneous gradual shift of the transient potential of both steels towards negative potentials from steady-state value of −0.15 V to −0.35 to −0.42 V (SCE) during the whole exposure interval since IOB culture addition into sterile 3% NaCl solution.No evidence of pitting corrosion was found on SS samples subsequent to their exposure to sterile 3% NaCl solution, though in the presence of IOB culture, numerous pits were revealed on 304 L steels specimens exposed to iron hydroxides sediments layer. Electrochemical characteristics (OCP or corrosion potential - E_CORR, breakdown potential - E_BD, repassivation potential - E_RP, passivation current - i_PASS) periodically measured by cyclic polarization method, allowed monitoring the electrochemical behavior changes of experimental SS and to establish the initiation of pitting corrosion in the presence of IOB, resulting in crevice effect caused by biogenic ferric oxides deposits precipitated on steel surface. Overall, steel 316L demonstrated higher resistance to pitting corrosion compared to 304L.     

A New Slicing Procedure for Rapid Prototyping Systems

The current slicing rule of most rapid prototyping (RP) systems cannot ensure unilateral tolerances on the whole prototype and often results in problems of overcut and undercut on the same part. This drawback leads to unsatisfactory precision of the part in post processing. In order to reduce the above problems, a new slicing method is proposed in this paper. Based on the geometry information in a stereolithography (STL) file, an algorithm is developed. The appropriate slicing rule is selected according to the inner product of the normal vector and working direction of the part, together with the function of the part to be manufactured. The STL file is cut into 2D sections and an accurate contour is calculated. After the slicing computation, an appropriate working path is produced. The rules proposed in this paper have been verified. This work contributes to the improvement of slicing rules in existing RP systems, especially in systems using uniform thickness slicing. It also improves manufacturing efficiency and working tolerances.     

环氧树脂复合涂层耐用磨性的研究

研究了石墨含量对环氧树脂复合涂层的滚动摩损性能的影响.结果表明,随石墨含量的增加,涂层的滚动磨损量减少.在砂粒高速冲刷时,石墨存在反而使冲刷性能恶化.随石墨含量增加,低角度冲刷时磨损量增加的更快.     

SPM用于超精加工领域的重要性及特殊性

讨论了扫描针显微镜作为一种显微工具的优势和不足,介绍了把ＳＰＭ应用于超精密加工检测领域所要注意的问题,指出纳米级加工机理的研究将依赖于ＳＰＭ的复合化及多功能化,只有实现了加工与检测的一体化才能正确评价加工方法及工艺参数的优化选择,从而引导超精密加工的发展。     

采用面向对象技术设计实现逻辑链路控制和适配协议

逻辑链路控制和适配协议是蓝牙协议栈中数据链路层的一部分。利用面向对象的分析和设计思想,应用标准建模语言的建模技术,对L2CAP协议进行了设计和实现。     

网络管理信息模型研究

文章在比较现有的各种信息模型的基础上,分别对网络层和业务层的信息模型给出了基基本的被管对象,对各层信息模型之间的关系进行了讨论,并探讨了从语义角度改善信息模型,为智能化提供支持。     

界面反应引起弥散型燃料的芯体结构演化

在反应堆运行工况下,Ｕ３Ｓｉ２－Ａｌ弥散型燃料的燃料颗粒与基体的界面相互扩散形成反应层,从而导致芯体结构的演化。本文根据Ｍｏｎｔｅ－Ｃａｒｌｏ原理建立了弥散型燃料芯体的模拟方法,并用该方法模拟了燃料相体积分散为４３％和具有一定尺寸分布的球形燃料颗粒在芯片中的空间随机排列。