Y_2O_3掺杂对17Ni/(NiFe_2O_4-10NiO)金属陶瓷高温氧化性能的影响

氩气气氛保护下采用气压烧结技术制备掺杂Y2O3的17Ni/(NiFe2O4-10NiO)金属陶瓷惰性阳极,在电解温度(960℃)下,对材料进行抗高温氧化性能研究。采用SEM分析材料及氧化产物的各物相分布情况、氧化形貌,并利用XRD进行成分分析。结果表明,金属陶瓷阳极的氧化动力曲线均大致符合抛物线规律;掺杂适量的Y2O3对金属相的分散有一定作用,并能有效抑制烧结试样及氧化物的孔洞生成,从而显著改善该金属陶瓷的抗高温氧化性能,其中,当Y2O3掺杂量为0.5%时,材料抗高温氧化性能最好,30 h后单位面积氧化增重量仅为10.6591 mg/cm2。     

掺杂MnO2对铁酸镍陶瓷惰性阳极性能的影响

为了提高铝电解惰性阳极材料的性能，尝试在合成铁酸镍陶瓷阳极的过程中掺杂一定量MnO2. 采用高温固相反应法在1200℃下烧结6 h，制备了掺杂MnO2的铁酸镍阳极材料. 对掺杂试样进行X射线衍射分析，并且研究了掺杂MnO2对材料密度、导电性及抗弯强度和抗热震性的影响. 研究结果表明，掺杂MnO2后未形成新相，MnO2与NiFe2O4形成固溶体，Mn4+离子取代了部分Fe3+离子，材料仍是镍铁尖晶石结构；掺杂MnO2后，NiFe2O4的晶格产生畸变，说明MnO2促进了烧结，提高了材料的密度；并且由于Mn4+离子取代Fe3+离子，产生阳离子空位，改善了铁酸镍阳极的导电性. 同时MnO2对改善试样的抗弯强度及抗热震性也有明显作用.     

MnO2添加剂对镍铁尖晶石基惰性阳极耐腐蚀性的影响

以氧化物NiO和Fe2O3为原料,添加氧化物MnO2,采用高温固相烧结法制备了NiFe2O4基惰性阳极材料,采用失重法测量了阳极试样的静态热腐蚀速率,并对其腐蚀机理进行了初步探讨. 实验结果表明,添加2%(ω) MnO2粉末的惰性阳极试样的静态热腐蚀速率最低. 由于掺杂的MnO2在晶界处富集,熔盐对晶粒的腐蚀首先在晶界处发生反应生成Mn2AlO4相,而Mn2AlO4相结构致密,冰晶石熔盐通过该相向NiFe2O4尖晶石晶粒内扩散速度减慢,从而降低了腐蚀速率.     

镍铝尖晶石基铝用惰性阳极导电性的初步研究

以减轻惰性阳极材料对铝液的污染为目的 ,选用NiAl2 O4合成尖晶石作为陶瓷相 ,加入金属铜、镍以提高材料的导电性 ,采用粉末冶金的方法制备金属陶瓷型铝用惰性阳极。对惰性阳极试样的一些理化指标进行了测定 ,着重研究了试样的电导率随温度变化的规律。在试样制备条件一般、烧成试样气孔率较高的情况下 ,试样的电导率达到 2S·m-1,电导率还有进一步提高的空间     

铝电解用金属基惰性阳极材料的研究进展

对铝电解惰性阳极的优势及阳极材料的要求进行了说明.简要介绍了国内外在铝电解工业用惰性阳极材料研究方面的最新进展,重点阐述了惰性阳极材料中的金属基惰性阳极和金属陶瓷惰性阳极的种类及性能,金属陶瓷复合材料具有良好的导电性、抗氧化和耐腐蚀性能,指出了惰性阳极的研究方向-氧化物掺杂金属陶瓷阳极.     

稀土La2O3掺杂对TiO2光催化性能的影响

本文通过对稀土氧化镧不同掺杂量,不同锻烧温度的样品光催化活性的研究显示,适量的稀土氧化镧掺杂有利于提高TiO_2的光催化活性;而关于稀土镧提高TiO_2光催化活性的机理有异于有关报道。     

镁合金微弧氧化边角烧蚀的ANSYS仿真研究

采用有限元分析软件ANSYS建立了微弧氧化时AZ40M镁合金试样、辅助阳极及周围电解液环境的有限元模型,对其进行静电场中电场强度与焦耳热的有限元模拟,得出试样设置辅助阳极前后的电场强度及焦耳热分布云图,分析辅助阳极对试样表面电场强度均匀性的影响。将模拟结果与实际试验结果进行对比,认为辅助阳极的设置可以有效解决微弧氧化过程中边缘烧蚀的问题。     

改性镧系钙钛矿催化剂强化挥发性有机物催化氧化的研究进展

钙钛矿因其结构稳定并具有优异的物化性质,近年来在催化剂方面的应用受到了广泛关注。本文综述了采用不同方法对镧系钙钛矿进行改性来增强催化剂的活性、抗毒性、稳定性和选择性的研究进展;分析了镧系钙钛矿的结构、表面参数、活性氧和低温还原性对于挥发性有机物转化效率的影响,重点阐述了通过优选钙钛矿的制备方法、制备负载型钙钛矿和掺杂型钙钛矿等改性方法来提高镧系钙钛矿催化剂的性能,由此展望了未来改性镧系钙钛矿催化剂的研究方向：采用非金属元素掺杂或多种强化方法结合制备高效催化剂、利用催化燃烧协同光催化氧化转化挥发性有机物、进一步通过实验和仿真模拟制备理想钙钛矿催化剂催化氧化多种挥发性有机物混合物以满足工业化需求。     

铝电解用炭素阳极抗氧化涂层的性能研究

采用过渡层、阻挡层、封填层相结合的具有协同作用的涂层结构形式,涂覆在炭素阳极表面以阻止(减少)氧化性气体与碳阳极接触,从而阻止(减少)阳极的消耗。通过对单一涂层结构和功能组合层结构的氧化失重率测试分析以及涂层表面形貌的SEM分析对比结果表明,采用最优配方制备的复合结构涂层阳极,可使氧化损失比裸样(未涂覆抗氧化涂层试样)减少70%左右,抗氧化效果显著。     

铋和镧共掺杂二氧化钛半导体的制备与光催化性能研究

采用溶胶-凝胶法制备了纯的TiO2和铋镧共掺杂的TiO2光催化剂,以活性黑KN-B为模型降解物,考察了铋单掺杂和铋镧共掺杂对TiO2光催化剂的活性影响,研究了催化剂投加量、染料初始质量浓度、溶液pH对活性黑KN-B降解率的影响.结果表明,铋掺杂的TiO2光催化活性高于TiO2,而适量铋镧共掺杂TiO2光催化活性进一步提高,最佳掺杂比是0.5％的Bi和0.2％的La.当铋镧共掺杂TiO2催化剂投加量为2.0 g·L-1,初始质量浓度为40 mg·L-1,pH为2.2时,活性黑KN-B在125W高压汞灯光照下20min后的降解率可达100％.     

锰铬体掺杂对氧化铝陶瓷绝缘子性能的影响

为改善氧化铝陶瓷绝缘子的沿面耐压能力开展体掺杂实验研究。以95％(质量分数,下同)氧化铝陶瓷瓷料为基料,选择Cr2O3和MnCO3作为添加剂制备掺杂样品,并对该陶瓷样品进行了性能参数测试及沿面耐压、体击穿、金属化等实验研究。结果表明：与目前常用的95％氧化铝陶瓷相比,锰铬掺杂氧化铝陶瓷具有更优越的表面性能。同一条件下,掺杂样品沿面耐压能力更强。采用新设计金属化配方及工艺,锰铬掺杂瓷样品金属化效果更佳。同时,体掺杂对氧化铝陶瓷体性能(体耐压水平、抗折强度等)没有十分明显的影响。进一步分析表明：锰铬掺杂降低了氧化铝陶瓷的表面电阻率和表面二次电子发射系数,从而使其具有更强的沿面绝缘能力。此外,在对陶瓷样品组成结构分析的基础上,就锰铬掺杂对氧化铝陶瓷的改性机理进行了探讨。     

化学法测定催化裂化催化剂中金属含量

催化裂化催化剂中金属含量是评价催化剂性能的重要指标之一。为准确测定其金属含量,实验应用压力溶弹在高温高压下将样品熔融,经过滤、洗涤,得到滤液,使用乙二胺四乙酸配位滴定法测定其中氧化铝含量,电感耦合等离子体原子发射光谱仪(ICP-OES)测定氧化稀土(镧或铈)、铁和钠含量。通过与X射线荧光光谱仪(XRF)测定结果进行比较以及多次重复实验,得到测定结果的相对标准偏差(RSD)分别为氧化铝0. 01%、氧化钠0. 04%、氧化稀土0. 1%、铁0. 02%。加标回收率为97. 8%～105. 0%。结果证明,该实验方法可行,且不依附于X射线荧光光谱仪,分析成本低,具有一定的推广价值。     

Thermal properties of homogenous lanthanum hexaaluminate/alumina composite ceramics

Lanthanum hexaaluminate has the potential to be applied in thermal barrier coatings due to its relative low thermal conductivity and low sinterability at temperatures higher than 1100 °C. One of the main problems in developing this material as a thermal barrier coating is difficulty in controlling the microstructure in order to combine the low thermal conductivity with high structural reliability.The idea behind this study was to take advantage simultaneously of the low thermal conductivity of lanthanum hexaaluminate and of the high mechanical properties of alumina by developing alumina-rich and lanthanum hexaaluminate-rich alumina/lanthanum hexaaluminate ceramic composites. The thermal properties of the alumina/hexaaluminate ceramic composites were compared as a function of temperature and lanthanum hexaaluminate content (20–80 vol.%). The results showed that the alumina/lanthanum hexaaluminate ceramic composites have sufficient low thermal conductivity to be used in thermal barrier coatings.     

Influence of oxide dopants on the wetting of doped graphite by cryolite/alumina melts

In the aluminium smelting industry, the wetting of the electrolyte on the carbon anode is an important property associated with the onset of the anode effect. The effect of dopants on the wettability of the anode was investigated in this study. The carbon material selected was graphite. The composition of the cryolite/alumina melts varied between a very low alumina content and 6 wt.% alumina. The sessile drop approach was adopted to measure the contact angle between the melt and the graphite at 1030 °C. The influence of oxide dopants, chromium III oxide and alumina, in the graphite on the wettability was studied. The wettability on a pure graphite surface depends to a small extent on the liquid surface tension but mostly on the liquid–solid interfacial tension that varies with the concentration of alumina in the liquid. The wettability on an oxide doped graphite surface depends on the dissolution of the oxide in the melt that changes the liquid–solid interfacial tension. The alumina dissolution has a double effect on the liquid–solid interfacial tension: the chemical reaction as well as the change in the oxy-anions concentration at the interface decrease the interfacial tension.     

3D imaging and quantification of interfaces in SOFC anodes

Solid oxide fuel cells (SOFCs) are functional electrochemical conversion devices whose performance is strongly dependent on electrode microstructure. Both the performance and lifetime of these electrochemical devices can be considerably enhanced by the ability to design better electrodes. Data acquired from high resolution 3D imaging techniques were used in the quantification of two electrode structures of different compositions. The quantified nickel-based anode data through the analysis of particle sizes with their metal–metal and ceramic–ceramic neck sizes, metal–ceramic interface sizes, volume fractions, and triple-phase boundary densities, demonstrate it is possible to understand how microstructure contributes to differences observed in electrochemical and mechanical performance; facilitating optimisation of electrode micro/nano structure towards improved performance. In doing so, new insights are gained that could be used to develop better electrodes.     

铝电解惰性阳极材料选择的研究进展

论述了传统碳素阳极的缺点及使用惰性阳极的意义,提出了惰性阳极材料应符合的要求,重点阐述了国内外对金属氧化物陶瓷阳极、金属陶瓷阳极、金属阳极的研究成果并总结了以上三类惰性阳极有待进一步解决的主要问题。     

氧化铝气凝胶的研究进展

Al2O3气凝胶以其独特性质受到人们的广泛关注.本文就Al2O3气凝胶的结构、性质和制备方法进行了综述,制备方法包括铝醇盐的一步法、两步法和无机铝盐的滴加环氧丙烷法,其中滴加环氧丙烷法是制备高性能Al2O3气凝胶非常有发展潜力的方法之一.同时还介绍了纤维增强气凝胶、多组分及掺杂改性气凝胶.     

Effect of Metal Oxide Additions on the High-Temperature Electrical Conductivity of Alumina

Several metal oxide additions were made to typical 99 and 96% alumina compositions to study their effect on the electrical conductivity of alumina from 500° to 1400°C. The metal oxide additions investigated were CO₂O₃, Cr₂O₃, CuO, Fe₂O₃, MnO₂, NiO, and TiO₂. Using a guarded two-probe technique, dc resistivities were measured on nonporous ceramic specimens. Additions of 0.5 to 2 mole % Co₂O₃, 2 mole % CuO, 1 mole % Fe₂O₃, or 2 mole % NiO to either a 96 or a 99% alumina composition increased the electrical resistivity. The addition of 1 mole % Cr₂O₃ to either a 96 or a 99% alumina showed practically no change in the resistivity. All changes in resistivity seemed to be structure dependent.     

Sr2−XLaXMgMoO6 and Sr2−XLaXMgNbO6 for Use as Sulfur‐Tolerant Anodes Without a Buffer Layer

The objective of this effort is to synthesize and characterize a series of lanthanum‐(La) doped Sr₂MgMoO₆ (SMMO) and La‐doped Sr₂MgNbO₆ (SMNO) anode materials which can be used in combination with lanthanum‐containing electrolytes to mitigate the effects of lanthanum poisoning in solid oxide fuel cells (SOFCs). Currently, an La_0.4Ce_0.6O_1.8 (LDC) buffer layer is used with many perovskite‐based anode materials to prevent La diffusion into the anode from the La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 (LSGM) electrolyte which can create a resistive La species that impedes electrochemical performance. The LDC buffer layer, with diminished electronic conductivity, adds an extra level of complexity in the SOFC manufacturing process. Further, this extraneous layer presents an added experimental challenge when assessing anode material performance. Overall electrochemical performance could be improved if the resistive buffer layer could be removed, thereby allowing the anode material to have direct contact with the electrolyte. To accomplish this, a new class of anode materials was synthesized with the goal of balancing “La” chemical potential between these neighboring materials. La‐doped SMMO and SMNO were prepared and studied. It was hypothesized that by incorporating La into the anode, the gradient of chemical activity between the anode and electrolyte would decrease, which would prevent La diffusion. These anode materials were synthesized via a sol–gel methodology and characterized with X‐ray diffraction to assess phase purity. The conductivity of the materials was analyzed in the presence of both H₂ and 100 ppm H₂S/H₂ to determine the stability and performance of these materials during device operation. The stability experiments demonstrated that 40% La‐doped SMNO is stable in all pertinent environments while not reacting with the LSGM electrolyte.     

Cyanoethylation of alcohols over solid base catalysts

Cyanoethylation of alcohols with acrylonitrile to form 3-alkoxypropanenitriles proceeds effectively over solid base catalysts such as alkaline metal oxides and hydroxides, lanthanum oxide, and alumina supported potassium fluoride and hydroxide at a reaction temperature below 323 K. The order of the reactivity of alcohols varied with the types of catalyst. With magnesium hydroxide and calcium hydroxide, the reactivity of alcohol decreased: methanol>ethanol>2-propanol, while with the alkaline earth oxides, lanthanum oxide, and alumina supported KOH and KF, the reactivity order was opposite. The reactivity orders are interpreted by the acidity of alcohol combined with the basic strength of the catalysts. The catalytic activity of solid base catalysts were scarcely affected by exposure of the catalyst to air before use for the reaction.