Structure and superconducting properties of layered perovskite-like compounds Y1 ? 2xCaxPrxBa2Cu3Oy and Y1 ? xBa2PrxCu3 ? xZnxOy

The conditions of preparation of Y_{1 − x} Pr _x Ba₂Cu_{3 − x} Zn _x O _y and Y_{1 − 2x} Ca _x Pr _x Ba₂Cu₃O _y solid solutions with an Y-123-type structure in the orthorhombic crystal system by the method of solid-phase chemical reactions have been determined. The concentration dependences of the unit cell parameters for these solid solutions have been established. The temperature dependences of the resistivity of the synthesized compounds have been investigated, the critical temperatures of the superconducting transition have been determined, and their variation as a function of the type and content of the introduced dopants has been analyzed. It has been demonstrated that, in the Y_{1 − x} Pr _x Ba₂Cu_{3 − x} Zn _x O _y samples, individual dopants have a combined effect on the suppression of the superconducting properties, whereas in the Y_{1 − 2x} Ca _x Pr _x Ba₂Cu₃O _y samples, calcium and praseodymium ions interact with each other when they are simultaneously introduced into the yttrium sublattice.     

CuO-Co3O4-CeO2/CeO2-Al2O3催化剂脱除CO性能研究

以CeO₂-Al₂O₃为载体,采用等体积浸渍法制备CuO-Co₃O₄-CeO₂/CeO₂-Al₂O₃催化剂,通过X射线衍射(XRD)、氢气程序升温还原(H₂-TPR)、氢气等温还原(H₂-TIR)、CO脱除性能评价等方法,考察预还原温度、反应温度、液相空速对CO脱除性能的影响。结果表明：催化剂在160℃下预还原可以获得37.3%的还原度,有效提高活性Cu⁺的数量,进而提高CO脱除性能;在液相丙烯中微量CO脱除反应中,反应温度升高、液相空速减小有利于提高CO脱除性能,当反应温度不低于50℃,液相空速不高于8 h^-1时,CO体积分数可脱除至0.03 mL/m³以下。在50℃、3 MPa,液相空速为8 h^-1的反应条件下,CuO-Co₃O     

Characterization of MgMnxFe2?xO4 as a possible cathode material for electrochemical reduction of NOx

Spinel-type oxides of MgMn _x Fe_2−x O₄, x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, were synthesized as a solid state reaction and characterized with dilatometry and resistivity measurements up to 1000 °C. Results showed a general decrease of the linear expansion and an increase in conductivity as a function of the Mn content. Point electrodes were analyzed from 300 to 600 °C in a pseudo-three-electrode setup in 1% NO, 1% NO₂, and 10% O₂ using cyclic voltammetry. The activities in O₂ were in general very low whereas the activities in NO were slightly higher. The activities in NO₂ were for all materials much higher than the activities in O₂. Even though Mn tends to decrease the activity of the materials, current ratios of I_NOx/I_O2I_{{\rm NO}_{x}}/I_{{\rm O}_2} have relatively high values in both NO and NO₂.     

Electrochemical properties of Li1?z(Ni1?yFey)1+zO2 synthesized by the combustion method in an air atmosphere

For the syntheses of LiNi_1−y Fe _y O₂ (0.000 ≤ y ≤ 0.300), mixtures of the starting materials with the desired compositions were preheated in an air atmosphere at 400 °C for 30 min and calcined in air at 700 °C for 48 h. The phases appearing in the intermediate reaction steps for the formation of lithium nickel oxide are deduced from the DTA analysis. XRD analysis, FE-SEM observation, FTIR analysis and electrochemical measurement were performed for the synthesized Li_1−z (Ni_1−y Fe _y )_1+z O₂ (0.000 ≤ y ≤ 0.300) samples. The samples of Li_1−z (Ni_1−y Fe _y )_1+z O₂ with y = 0.025 and 0.050 have higher first discharge capacities than Li_1−z (Ni_1−y Fe _y )_1+z O₂ with y = 0.000 and better or similar cycling performance at the 0.1 C rate in the voltage range of 2.7–4.2 V. Similar results have not previously been reported except for Co-substituted LiNiO₂. The sample Li_1−z (Ni_0.975Fe_0.025)_1+z O₂ has the highest first discharge capacity (176.5 mAh g⁻¹). Rietveld refinement of the XRD patterns of LiNi_1−y Fe _y O₂ (0.000 < y ≤ 0.100) from a starting structure model [Li,Ni]_3b[Li,Ni,Fe]_3a[O₂]_6c showed that cation disordering occurred in the samples.     

Zirconium stabilized Ba0.5Sr0.5(Co0.8−xZrx)Fe0.2O3−α perovskite hollow fibre membranes for oxygen separation

Ba_0.5Sr_0.5(Co_0.8−xZr_x)Fe_0.2O_3−α (x = 0.0–0.3) (BSCZxF) ceramic powders were synthesized via an improved EDTA-citric acid complexing method. The BSCZxF (x = 0.05, 0.1, 0.2) perovskite hollow fibre membranes were fabricated from the powders through a phase-version/sintering technique. The oxygen permeation properties of the hollow fibre membranes were measured under air/He gradients at 700–950 °C. Experimental results have shown that the composites with x = 0.05–0.20 Zr-doping content exhibit pure cubic perovskite structure but the BSCZ_0.30F oxide contains impurity phases. Due to the substitution of zirconium in Co sites, the phase stability, the mechanical strength and the densification properties of the BSCZxF hollow fibre membranes are improved noticeably. However, the oxygen permeation flux of the BSCZxF membranes decreases with increased activation energy as the Zr-doping content is increased from 0.05 to 0.20. The suitable Zr-doping content should be around x = 0.1 in order to obtain both high permeation fluxes and high permeation stability.     

H2O2/Fe2(MoO4)3体系中H2O2吸附分解及NO氧化行为的DFT研究

为阐明H₂O₂/Fe₂(MoO₄)₃体系脱硝过程中H₂O₂吸附分解及NO氧化行为，基于DFT方法首次计算了H₂O₂和NO分子单独及二者同时在Fe₂(MoO₄)₃表面的吸附构型，并通过考察吸附能、Mulliken电荷及氧化路径等特性揭示H₂O₂催化分解和NO氧化的微观机制。结果表明：H₂O₂在Fe₂(MoO₄)₃表面易分解为活性自由基，而NO则以分子形式吸附；H₂O₂和NO共吸附时，H₂O₂优先吸附于催化剂表面并随后分解，NO则分别被H₂O₂分解产...     

La2O3/AC催化剂在CO同时还原SO2和NO反应中的性能

以改性活性炭为载体,采用等体积浸渍法制备了La₂O₃/AC催化剂。采用XRD和BET手段对催化剂进行表征,使用微型固定床反应器考察催化剂的脱硫脱硝活性。结果表明,La₂O₃/AC催化剂对CO同时还原SO₂和NO具有良好活性,负载质量分数10%的La₂O₃/AC催化剂活性较好,SO₂和NO转化率达到90%的反应温度最低,分别为335 ℃和325 ℃;载体与活性组分之间存在协同作用,引入活性炭载体能够降低反应温度并提高催化活性。     

Fe/γ-Al2O3催化剂上CO同时还原NO和SO2研究

研究了不同载体(γ-Al₂O₃、HZSM-5、TiO₂、SiO₂和MgO)负载Fe催化剂上CO还原NO反应及CO同时还原NO和SO₂反应。结果表明,Fe/γ-Al₂O₃催化剂对CO与NO反应具有良好的催化活性,但随着反应时间的延长,催化剂很快失活;在CO和NO反应中加入SO₂,可以明显改善Fe/γ-Al₂O₃催化剂对CO还原NO反应的活性稳定性;O₂和H₂O对催化剂活性的影响较大,CO₂对催化剂的影响较小。XRD结果表明,FeS₂是催化剂的活性中心,在CO与NO反应后,FeS₂转变为催化惰性的Fe₇S₈而导致催化剂活性下降;在CO与NO及SO₂反应体系中引入O₂后,Fe/γ-Al₂O₃催化剂上的活性组分FeS2被氧化为Fe₂O₃,导致催化剂失活。     

ICP-AES法测定矾土中Fe2O3、TiO2和SiO2

采用四硼酸锂熔融试样,电感耦合等离子体原子发射光谱法(ICP-AES法)测定矾土中Fe2 O3、TiO2和SiO2。通过对熔样方法选择、铝基体以及背景的研究,确定了分析条件。结果表明,该法具有良好的精密度和准确性,回收率在94%～108%。     

纳米TiO2/SiO2复合食品抗菌材料

以水玻璃和Ti(SO4)2为原料,制备出了多孔的纳米TiO2/SiO2复合粒子,在后处理过程中,利用无机包覆剂溶解度随温度的变化,在复合粒子表面包覆了一层无机结晶膜,经热处理除去包覆剂后,得到了以单分散纳米复合粒子组成的复合微粉.对复合微粉进行比表面和孔容测试,并运用XRD和TEM进行了表征,发现TiO2以12.6nm的纳米晶粒的形式被多孔的SiO2包覆,所形成的复合粒子则约为20nm.为了了解复合微粒的灭菌效果,运用纳米TiO2和复合粉末对4种保健食品进行对照灭菌实验,两个月以后,测得含复合微粒的样品中的菌落总数为50～120个/g,是相应保健食品企业标准许可菌落数的0.25%～0.7%,为相应空白样和纳米TiO2粉样品菌落数的0.52%～0.97%和33.3%～83.3%.     

O1/A1/O2/A2工艺处理焦化废水试验研究

通过对短程硝化反硝化工艺的研究,开发了好氧/厌氧/好氧/缺氧(O1/A1/O2/A2)生物脱氮新工艺并用于焦化废水的处理。考察了NH4+-N、COD、TN对反应器运行效果影响。结果表明,当进水COD平均为3 012.9 mg/L,NH4+-N、TN、挥发酚、总氰平均质量浓度分别为590.5、608.4、361.8、34.5 mg/L;出水COD平均为81.7 mg/L,出水NH4+-N、TN、挥发酚、总氰的平均质量浓度分别为0.1、9.9、0.1、0.1 mg/L,出水指标达到国家污水综合排放一级标准,A/O工艺处理这种焦化废水TN偏高,而用O1/A1/O2/A2工艺可以解决这一问题,实现了TN脱除。考察了温度、DO、pH对短程硝化影响。结果表明,在DO质量浓度为1.0～1.5 mg/L、温度在30～35℃、pH 7.5～8.0,系统能够进行稳定短程硝化反硝化。     

MoS2/TiO2光催化降解甲基红

利用硫化钠与钼酸钠为原料,通过盐酸酸化,在TiO2上沉积MoS2纳米片。利用甲基红为降解对象,研究合成的片状纳米MoS2/TiO2复合物的光催化性能。结果显示该复合物具有优良的光催化降解甲基红的性能;催化剂用量、甲基红初始浓度与初始pH等条件对甲基红降解存在明显影响。该催化剂在重复使用3次时,甲基红2 h的脱色率接近65%,表明催化剂具有较好的重复使用性能。     

γ-Fe2O3空心球/Fe-N-C宽电位窗口选择性电催化还原CO2为CO的研究

Fe-N-C材料是一类重要的电催化还原CO₂为CO的催化剂,但其只能在较正的电位和较窄的电位窗口实现CO的高选择性,不能满足串联催化中CO被进一步还原的要求。因此,以高纯Fe(phen)₃Cl₂(phen=1,10-邻菲罗啉)晶体和ZIF-8为前驱体,通过热解得到新颖的Fe-N-C担载γ-Fe₂O₃空心球材料。利用SEM、HR-TEM、XRD、XPS等对催化剂进行表征,并对其电催化还原CO₂的性能进行测试。结果表明,该催化剂在-0.5～-1.1 V(相对于可逆氢电极)宽电位窗口表现出优异的CO选择性(CO的法拉第效率大于97%),且在-0.6 V连续电解2 h后电流密度和CO的法拉第效率均基本保持不变,表现出卓越的稳定性。     

TiO2基催化剂还原CO2研究进展

能源危机和环境污染是当今世界发展面临的两大挑战,如何有效缓解煤、石油等不可再生化石资源过度消耗所引发的能源危机,以及由此造成CO₂过量排放引起的温室效应问题,是当前人类发展亟待解决的重大科学问题之一。基于此,本文综述了近年来以TiO₂为光催化剂,以绿色、清洁的太阳光能催化还原CO₂成低价态含碳燃料(如CH₄、CH₃OH、HCHO、HCOOH、C₂H₅OH等)研究进展。在TiO₂光还原CO₂机理基础上,对元素掺杂、半导体复合与染料敏化、高活性晶面调控、低维纳米结构设计、助催化剂、Z型结构设计和单原子催化等方法来提高光还原CO₂反应效率和选择性进行分析,并指出目前研究存在的关键问题和未来CO₂光还原的发展方向。     

稀土掺杂TiO2光催化还原CO2

采用溶胶-凝胶法制备了稀土掺杂TiO₂纳米光催化剂,并应用于光催化还原CO₂/H₂O体系中。通过XRD对光催化性能进行表征,研究稀土离子掺杂和焙烧温度对光催化性能的影响。结果表明,稀土La和Ce的加入可以抑制TiO2的晶相转变,提高光催化性能。催化剂800 ℃焙烧可达到最好的光催化活性,在反应时间7 h、CO₂流量200 mL·min^-1和反应液中NaOH与Na₂SO₃浓度均为0.10 mol·L^-1条件下,甲醇产率高达315.49 μmol·g^-1。并对稀土掺杂TiO₂催化剂光催化还原CO₂的机理进行了探究。     

ZrB2质与TiB2质耐火材料

介绍了ZrB     

TiO2/SiO2/NiFe2O4介孔材料的制备和电磁特性

NiFe2O4纳米粒子做磁性载体,苯乙烯、正硅酸乙酯为原料,KH-570为交联剂,采用乳液聚合法制备了PS/SiO2/NiFe2O4磁性微球材料。以PS/SiO2/NiFe2O4磁性微球为核,十二烷基磺酸钠和聚乙烯吡咯烷酮作模板剂,钛酸丁酯做钛源,制备得到多层介孔复合微粒TiO2/SiO2/NiFe2O4。通过XRD、SEM对磁性复合微粒的结构进行了表征,结果表明,TiO2/SiO2/NiFe2O4是具有核壳结构的中空介孔微粒。采用矢量网络分析仪测试了NiFe2O4、SiO2/NiFe2O4、TiO2/NiFe2O4、TiO2/SiO2/NiFe2O4复合材料的微波电磁参数,SiO2、TiO2对磁性微粒的电磁参数有明显的改善,可较好的解决吸波涂层设计中的阻抗匹配问题。