李一冰
,
Ali Jawad
,
Aimal Khan
,
卢小艳
,
陈朱琦
,
刘卫东
,
尹国川
催化学报
doi:10.1016/S1872-2067(15)61092-0
近年来,环境污染特别是水的严重污染使其治理成为一个极具挑战性的课题.各种污染物复杂的化学成分和催化剂在处理过程中的浸出、寿命及成本等问题是导致众多氧化催化剂难以实际应用的主要原因.相对而言, H2O2是一种活性氧含量高、清洁并可在温和条件下使用的氧化剂,在各种高级氧化技术中受到广泛关注.而碳酸氢盐是一种弱碱性物质,在自然界及水体系中广泛存在,且无明显毒害.它可活化 H2O2,加快其氧化各种有机物,并在废水处理领域开始受到关注.该体系的明显优势在于处理体系始终处于微碱性环境,可以有效避免金属氧化物催化剂在处理过程中由于体系酸化而带来的催化剂流失,从而延长催化剂寿命,降低催化剂成本.
本文采用浸渍法制备了一种双金属铜、钴氧化物催化剂及相关的对照催化剂体系,利用碳酸氢盐活化 H2O2用于降解苯酚模拟废水.通过各种空白实验发现,负载于γ-Al2O3表面的钴、铜氧化物催化剂 CuO?Co3O4@γ-Al2O3具有最好的催化降解活性,而 CuO@γ-Al2O3, Co3O4@γ-Al2O3, CuO?Co3O4及 CuO和 Co3O4的物理混合物均表现出较差的催化性能.由此可见,在 CuO?Co3O4@γ-Al2O3催化剂中,铜、钴离子在苯酚降解过程中存在协同效应,这可能与催化剂中钴、铜金属离子的相互作用相关. X射线衍射和 X射线光电子能谱结果表明,反应前后 CuO?Co3O4@γ-Al2O3催化剂中金属的氧化状态并未发生改变,在使用过程中钴离子的浸出率可以忽略,铜离子的浸岀率也仅有0.6 ppm.荧光分析实验和自由基捕获实验表明,只有添加?O2-和?OH的捕获剂能明显抑制降解反应,因而推测该反应体系对有机物的降解是一个自由基氧化过程,起关键作用的可能是?O2-和?OH.
关键词:
协同效应
,
苯酚降解
,
铜/钴氧化物催化剂
,
机理研究
,
碳酸氢盐活化的过氧化氢
Ali Jawad
,
陈朱琦
,
尹国川
催化学报
doi:10.1016/S1872-2067(15)61100-7
水污染问题已成为影响我国可持续发展的关键问题之一，为有效提高现有污水处理的效率及其回收利用，各种催化氧化技术受到了广泛的关注。目前发展的各类高级氧化技术在实际的应用过程中明显受到了氧化剂的利用率、催化剂的浸出、寿命及成本等问题的严重限制。因此基于新的理念、发展新的催化氧化技术仍然受到广泛的关注。
最近几年，利用碳酸氢盐活化过氧化氢，应用于有机废水的降解逐渐受到环境催化领域的关注。碳酸氢盐本身是一种低毒性、广泛存在于环境及生物体系的化学物质，通过它活化过氧化氢产生过碳酸氢盐氧化剂，该氧化剂能够直接氧化有机物。同时，在各种过渡金属催化剂的存在下，通过该过碳酸氢盐可以形成氧化能力更强的各种自由基(如羟基自由基等) ；及高价态的过渡金属离子参与有机废水的降解。虽然传统认为碳酸盐及碳酸氢盐对高级氧化法降解有机废水不利，原因是认为它们能捕捉羟基自由基，形成氧化能力更低的碳酸根自由基。现有的研究已充分表明，较低浓度的碳酸氢盐能够加快有机废水的氧化降解，而且通常比单独使用过氧化氢效率更高，这些新的发现已明显突破了传统意义上对碳酸氢盐作用的理解。更为重要的是，在微量碳酸氢盐的存在下，其产生的微碱性环境极大地消除了负载型氧化物催化剂在废水降解过程中的金属离子流失、从而极大地延长了催化剂的寿命。该缺点是各种基于过渡金属氧化物催化剂的高级氧化技术难以广泛推广的关键性挑战，原因是随着氧化降解的进行，废水体系由于有机酸的生成而逐渐酸化，进而引发氧化物催化剂的酸溶而流失。在这点上，碳酸氢盐活化过氧化氢系统由于其天然的微碱性环境体现出了其明显的优势。
本文即是在本课题组工作基础上，对该领域内国内外研究进展加以总结，以期获得国内外同行的进一步关注。综述的主要内容包括：(1)碳酸氢氧活化过氧化氢的相关知识介绍，(2)均相碳酸氢氧活化过氧化氢降解有机废水的研究进展，(3)基于金属氧化物催化剂的碳酸氢氧活化过氧化氢降解有机废水的研究进展，和(4)碳酸氢盐在其他高级氧化技术中的应用。虽然基于碳酸氢氧活化过氧化氢降解有机废水的研究还处于早期探索阶段，还有很多基础科学问题如降解机理等值得进一步探索，期望通过该综述的介绍能够让同行对碳酸氢氧活化过氧化氢降解有机废水有一个比较全面的了解，进而推动该研究方向的发展，为有机废水的催化处理提供新的机会。
关键词:
废水处理
,
碳酸氢盐活化过氧化氢
,
催化剂浸出
,
污染降解
,
催化氧化
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(16)64373-X
提出了一种从氧化铝中提取原铝的新方法。该方法的原理基于如下化学反应：AlI3+(3/2)Zn=Al+(3/2)ZnI2。首先通过氧化铝的碳热氯化反应得到氯化铝(AlCl3)，然后通过氯化铝和碘化钙的交换反应(AlCl3+CaI2→AlI3+CaCl2)得到碘化铝。在实验室条件下对这些反应进行了研究，同时对一些回收主要化学试剂的反应进行了研究(Cl2, ZnI2→Zn, CaCl2→CaI2)。采用XRD和SEM对反应产物的相组成及形貌进行分析。采用总自由能最小方法对化学反应平衡进行计算。结果表明，采用非电解方法，可以在没有非常高的温度和可消耗的化学试剂的条件下，从氧化铝中有效地提取铝。与当今采用燃煤发电提供电力的铝电解厂相比，本方法所产生的单位碳消耗和 CO2大气排放可以降低一半以上。
关键词:
铝
,
铝合金
,
氯化物
,
碘化物
,
锌
,
碘
,
高速冶金
Journal of Alloys and Compounds
Interdiffusion coefficients within the beta-phase region of the nickel-cobalt-chromium-aluminum (Ni-Co-Cr-Al) quaternary system were estimated by square root diffusivity analysis. The obtained results indicated that the cross interdiffusion coefficients D(ij) (i not equal j, i, j = Al, Cr, Co) other than D(AlCo), were less than the main interdiffusion coefficients Do (i = j), and that the values of D(Ali) were greater than those of D(Cri) and D(Coi). This finding suggests that the addition of chromium decreases the interdiffusion coefficients of aluminum and cobalt, but the addition of cobalt did not cause an obvious change in the interdiffusion coefficients of aluminum and chromium in the beta-phase region. The different effects associated with the additions of chromium and cobalt were qualitatively discussed in light of the relationship between the thermodynamic properties of the system and Wagner's interaction parameter. The results revealed that the different effects could be ascribed to the stronger thermodynamic interactions between aluminum and cobalt compared to that between aluminum and chromium. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Diffusion;NiAl phase;Electron microprobe;multicomponent diffusion couples;square root diffusivity;transfer-matrix method;zero-flux planes;intermetallic compound;coefficients;ternary;nickel;alloys;fe
陈小庆
,
孙利杰
,
邬小鹏
,
钟泽
,
傅竹西
功能材料
用MOCVD方法在Si基片上生长了Al掺杂的SiC薄膜,发现三甲基铝(TMA)源载气流量与硅烷流量之比的大小,会决定薄膜的导电类型.用XPS方法测试样品后发现,TMA载气流量与硅烷流量比直接影响Al原子在SiC薄膜中的含量.Al含量在1.5%以下,Al原子在SiC薄膜中主要以填隙形式(Ali)存在,薄膜显示出n型;而Al含量在1.5%～3%之间的时候,Al原子主要以替位Si(AlSi)的形式存在,薄膜显示出p型.继续增加掺杂源的流量,所得SiC薄膜结晶质量会变得较差,电阻也变得较高.
关键词:
3C-SiC
,
SiC:Al
,
MOCVD
,
导电类型
Acta Materialia
Porous Ni-Ti shape-memory alloys (SMAs) have attracted a great deal of attention recently because they have a similar microstructure to human bone and have significant prospects in medical applications. In the present study, equiatomic porous Ni-Ti SMAs, especially those with an unusual kind of linear-aligned elongated pore structure, have been successfully prepared by self-propagating high-temperature synthesis (SHS) using elemental nickel and titanium powders. The porous Ni-Ti SMAs thus obtained have an open porous structure with about 60 vol.% porosity, and the channel size is about 400 mu m. The corresponding microstructural characteristics and the effect of preheating temperature on the microstructure have been investigated. It is found that the combustion temperature increases with increasing preheating temperature and results in melting of the NiTi compound above 450 degrees C. Moreover, the preheating temperature has been shown to have a significant effect on the microstructure of the SHS-synthesized porous Ni-Ti SMAs, and the mechanism of anisotropy in pole structure is attributed to the convective flows of Liquid and argon during combustion. (C) 2000 Acm Metallurgica Inc. Published by Elsevier Science Ltd. Ali rights reserved.
关键词:
self-propagating high-temperature synthesis (SHS);porous Ni-Ti;shape-memory alloys;combustion synthesis
Acta Materialia
Cyclic deformation behavior and surface deformation features of [011] multiple-slip-oriented single crystals were investigated at constant plastic shear strain amplitude (gamma(pl)) in the range of 1.1x10(-4)- 7.2 x 10(-3) at room temperature in air. It was revealed that the cyclic deformation characteristic of [011] copper single crystal is quite different from that of [001] and [(1) over bar 11] multiple-slip-oriented copper single crystals. The [011] crystal exhibits a rather low initial hardening rate, which does not increase notably even under higher plastic strain amplitudes. The cyclic stress-strain (CSS) curve of the [011] crystal exhibit a clear plateau region over the range of plastic strain amplitude investigated. Surface observations indicated that the primary persistent slip bands (PSBs) already occur under a lower strain amplitude of 1.1x10(-4), but the operation of secondary slip was strongly suppressed by the corresponding dislocation interactions even at high strain amplitudes. This slip characteristic was suggested to be associated with the occurrence of the plateau region. When gamma(pl)greater than or equal to 2.5 x 10(-3), two types of deformation bands (DBI and DBII) formed on the specimen surface and their habit planes are perpendicular to each other strictly. An analysis based on the classical crystallographic deformation geometry was proposed to interpret the existence of an irreversible rotation of crystal in single crystal subjected to symmetrical push-pull loading. This phenomenon is assumed to be an essential reason for the formation of DBI and DBII. When gamma(pl)greater than or equal to 5.0 x 10(-3) another type of deformation band (DBIII) was observed on the specimen surface and its habit plane is exactly (001) with the maximum shear stress acting on it. The favorable macroscopic state of stress may be responsible for the formation of DBIII, giving rise to the cyclic softening in the cyclically deformed [011] copper single crystals at high strain amplitudes (y(pl) greater than or equal to 5.0 x 10(-3)). (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. Ali rights reserved.
关键词:
dislocation-structures;fatigue damage;behavior;amplitude;localization
