LiMn2O4表面包覆Li4Ti5O12的制备及倍率特性

采用固相法合成了尖晶石型LiMn₂O₄，并通过溶胶-凝胶法制备了不同物质的量的百分比含量Li₄Ti₅O₁₂包覆的正极材料。X-射线衍射和扫描电镜结果表明，Li₄Ti₅O₁₂微粒包覆在LiMn₂O₄的表面没有产生晶体结构的变化。实验电池在室温下，以1C，2C和5C倍率作充放电循环测试；结果表明，与未包覆的LiMn₂O₄相比，表面包覆Li₄Ti₅O₁₂微粒的正极材料在高倍率下具有更好的循环稳定性。     

Li4Ti5O12/(Ag+C)电极材料的固相合成及电化学性能

以Li₂CO₃,TiO₂为原料,葡萄糖为碳源,采用固相煅烧工艺合成了亚微米级的Li₄Ti₅O₁₂/C复合负极材料。并将之与AgNO₃复合,采用固相方法制备出了Ag表面修饰的Li₄Ti₅O₁₂/(Ag+C)复合材料。采用XRD、SEM和TEM测试方法对材料的微结构进行了表征。结果表明,C的存在对Ag单质在Li₄Ti₅O₁₂/C颗粒表面的大量形成起到了积极的促进作用,从而很大程度地提高了Li₄Ti₅O₁₂/C的电导率,因此有效地改善了其电化学性能。在1C倍率下,Li₄Ti₅O₁₂/(Ag+C)复合材料的首次放电容量达到了164 mAh·g^-1。     

Ni0.8Co0.15Al0.05C2O4@Graphene的合成及电化学性能研究

过渡金属氧化物/石墨烯复合材料具有优异的电化学性能被广泛应用在锂离子电池中。本文以硫酸镍、硫酸钴、硫酸铝、草酸为原料按一定的物质的量比配制成溶液,在120°C的条件下水热反应12小时,得到多元过渡金属氧化物前驱体Ni_0.8Co_0.15Al_0.05C₂O₄(NCA-C₂O₄);该前驱体经聚烯丙基胺盐酸盐修饰后,与氧化石墨烯进行复合并还原得到石墨烯包覆的多元过渡金属氧化物/石墨烯负极材料Ni_0.8Co_0.15Al_0.05C₂O₄@Graphene(NCA-C₂O₄@G)。对材料的结构、形貌和电化学性质进行了表征。扫描电镜测试结果显示样品粒度均一,具有两端不规则长方体形貌。电化学性能测试结果表明：石墨烯包覆后的NCA-C₂O₄@G充放电容量高于前驱体NCA-C₂O₄,NCA-C₂O₄@G复合材料在0.1C电流密度 (1C=1000 mAh/g)下首次放电比容量为1956 mA h/g;经过0.1C、0.2C、0.5C、1C、2C高倍率循环后,当测试电流密度恢复至100 mA/g时,复合材料比容量可迅速回升至720 mA h/g,并在随后50次循环中比容量保持稳定,显示出良好的循环稳定性和倍率性能。     

Y2O3∶C陶瓷的发光性能

采用传统陶瓷制备工艺制备了C掺杂的Y₂O₃多晶陶瓷;研究了Y₂O₃∶C陶瓷的光谱性能,发现在403 nm有明显的发射峰。通过对其激发光谱的研究,表明它们是由F⁺和F色心造成的。本文还研究了Y₂O₃∶C陶瓷的热释光和光释光性能。用2个指数衰变函数拟合光衰变曲线得到的衰变时间常数τ₁=(4.66±0.27)s,τ₂=(23.31±1.03) s。     

Li4Ti5O12/(Cu+C)复合材料的制备及电化学性能

以Li₄Ti₅O₁₂,Cu(CH₃COO)₂·H₂O和C₆H₁₂O₆为前驱体,化学沉积与热分解结合合成锂离子电池负极材料Li₄Ti₅O₁₂/(Cu+C)。采用X-射线衍射(XRD)、扫描电子显微镜(SEM)、恒流充放电、循环伏安和电化学阻抗方法表征样品的结构、形貌和电化学性能。结果表明,Li₄Ti₅O₁₂表面包覆的Cu与C提高了Li₄Ti₅O₁₂电极材料的导电率,其循环性能和倍率性能得到有效地改善。在0.5C、1C和3C倍率下,经过50次充放电循环,放电比容量分别为168.2、160、140.6 mAh·g^-1,其容量保持率分别为88.7%、84.4%、71.2%。电化学阻抗测试表明,表面包覆的Cu与C使其电荷转移阻抗大幅度减少。     

以Fe2P2O7为前驱体制备LiFePO4及其电化学性能

以磷铁废渣（Fe_1.5P）和温室效应气体CO₂为原料,以磷酸为补充磷源合成磷酸铁锂（LiFePO₄）的前驱体Fe₂P₂O₇,并研究了其合成过程对LiFePO₄正极材料储能性能的影响。采用SEM观察了LiFePO₄的表面形貌,采用XRD分析了LiFePO₄和Fe₂P₂O₇的晶体结构。进一步对该方法进行优化,发现Fe_1.5P与磷酸混合物（n_Fe1.5P：n_H3PO4=1：1）在800℃热处理6 h合成的Fe₂P₂O₇对应的LiFePO₄/C电化学性能最好,在0.1C,0.2C,0.5C和1C倍率下的容量分别可达130,126,117和108 mAh·g^-1。     

以Fe2P2O7为前驱体制备LiFePO4及其电化学性能

以磷铁废渣（Fe_1.5P）和温室效应气体CO₂为原料,以磷酸为补充磷源合成磷酸铁锂（LiFePO₄）的前驱体Fe₂P₂O₇,并研究了其合成过程对LiFePO₄正极材料储能性能的影响。采用SEM观察了LiFePO₄的表面形貌,采用XRD分析了LiFePO₄和Fe₂P₂O₇的晶体结构。进一步对该方法进行优化,发现Fe_1.5P与磷酸混合物（n_Fe1.5P：n_H3PO4=1：1）在800℃热处理6 h合成的Fe₂P₂O₇对应的LiFePO₄/C电化学性能最好,在0.1C,0.2C,0.5C和1C倍率下的容量分别可达130,126,117和108 mAh·g^-1。该方法具有成本低廉,减少碳排放和环境友好等特点,为LiFePO₄正极材料的生产提出了一种新的工艺。     

纳米Ce1—xMnxO2催化剂上乙醇催化氧化发光研究

研究了纳米Ce_1—xMn_xO₂上乙醇催化氧化发光特性, 重点考察了反应温度和催化剂组成(Ce/Mn比)对发光强度的影响规律. 为研究催化发光机理, 在相近的反应条件下考察了纳米Ce_1—xMn_xO₂上乙醇催化氧化反应的活性和选择性. 结果表明: 催化发光强度与催化反应中生成CH₃CHO的产率有很好的顺变关系, 表明CH₃CHO是导致C₂H₅OH分子在纳米Ce_1—xMn_xO₂催化剂上氧化发光的“活性分子”.     

CeO2表面修饰提高锂离子电池正极材料LiNi0.80Co0.15Al0.05O2的循环及存储性能

采用共沉淀法制备锂离子电池正极材料LiNi_0.8Co_0.15Al_0.05O₂。通过溶胶凝胶法对LiNi_0.8Co_0.15Al_0.05O₂材料进行表面修饰提高循环和存储性能,包覆后的材料经过600℃热处理4 h。测试结果显示,0.2C下,CeO₂包覆量为0.02%(物质的量比)时首次放电比容量为182.44 mAh·g^-1,与未包覆样品相比没有下降;同时包覆后拥有更优的容量保持率,在2.75~4.3 V,0.5C下,100次循环后容量保持达到85.96%。包覆CeO₂不仅可以阻止电极与电解液之间的副反应,而且高氧化性CeO₂包覆层可以提前与电解液反应,从而消耗电解液中痕量的水和HF,保护内部活性材料。     

锂离子电池正极材料层状LiNi1/2Mn1/2O2的制备与表征

用一种简单的共沉淀法制备出了层状LiNi_1/2Mn_1/2O₂材料，并且用XRD、SEM、循环充放电、循环伏安(CV)和电化学阻抗谱(EIS)等方法对材料进行了表征测试。首先，用共沉淀法制备氢氧化镍和氢氧化锰的混合物;然后，对共沉淀溶液进行预氧化来制备前驱体;最后，用预氧化的前驱体合成了LiNi_1/2Mn_1/2O₂材料。SEM和XRD测试结果分别表明:LiNi_1/2Mn_1/2O₂材料是粒径范围在100～200 nm之间的球形粒子，并且具有非常好的层状结构。循环充放电表明:在空气中900 ℃下合成时间为9 h的材料，在充放电截止电压为2.8～4.6 V的情况下，经过40次循环，材料的容量可以稳定地保持在140 mAh·g^-1左右。循环伏安曲线表明:在锂的初始脱嵌和入嵌过程中存在不可逆相变。电化学阻抗谱测试表明LiNi_1/2Mn_1/2O₂具有很好的锂离子扩散能力。     

Effect of CO on surface oxidation of uranium metal

The surface reactions of uranium metal with carbon monoxide at 25 and 200 °C have been studied by X-ray photoelectron spectroscopy (XPS); respectively. Adsorption of carbon monoxide on the surface layer of uranium metal leads to partial reduction of surface oxide and results in U4f photoelectron peak shifting to the lower binding energy. The content of oxygen in the surface oxide is decreased and O1s/O4f ratio decreases with increasing the exposure of carbon monoxide. The investigation indicates the surface layer of uranium metal has resistance to further oxidation in the atmosphere of carbon monoxide.     

Kinetic study of the nitric oxide oxidation between 288 and 323 K,under pressure,focus on the oxygen influence on the reaction rate constant

The sequestration of carbon dioxide fumes from oxyfuel combustion is used to reduce significantly the carbon dioxide emissions from coal-fired power plants. Impurities like nitric oxide, present in the fumes, can cause technical difficulties during the capture, the treatment, the transport, and the storage steps of the CO₂ fumes. The purpose of this study is to better understand the oxidation of nitric oxide under pressure in the presence of carbon dioxide and in the experimental condition of flue gas treatment. This reaction is known to be a third-order reaction, two order in nitric oxide and first order in oxygen. To examine the effect of the temperature, the pressure and the volume fraction of oxygen on the rate constant of oxidation, k₁, an autoclave is used. The first experiment studies the influence of the temperature between 288 and 323 K. The results found are in the form of an Arrhenius-type equation: k₁ = 810 exp^(620/T) and are in agreement with the literature. Carbon dioxide does not seem to have an influence on the rate constant, whereas our experimental measurements indicate an influence of the volume fraction of oxygen. The rate constant decreases when the oxygen volume fraction increases by up to 10%. Then the rate constant remains constant. This observation allows us to conclude that the mechanism involving the mechanism with a dimer of NO as an intermediate is more likely to be the mechanism involved in the nitric oxide oxidation in our experimental conditions: high pressure and ambient temperature. The rate constant k₂, k_–2, and k₃ were also estimated in these conditions.     

Chemical shifts in uranium Auger transitions

Uranium metal and uranium dioxide surfaces have been examined using Auger electron spectroscopy. An essentially oxide free uranium surface can be produced by heating the metal to 800°C in a vacuum of ≈ 1 × 10⁻⁸ NM⁻² while subsequent oxidation is shown to produce chemical shifts in the uranium Auger peak positions.     

The back-titration of chemisorbed atomic oxygen on copper by carbon monoxide investigated by microcalorimetry and transient kinetics

The back-titration of atomic oxygen chemisorbed on metallic copper using carbon monoxide is investigated by microcalorimetry. Results from simulations based on a microkinetic model of the back-titration are used for processing of microcalorimetric data. In addition, surface oxidation of copper by nitrous oxide is investigated by microcalorimetry. The results are compared with results obtained by nitrous oxide reactive frontal chromatography and by static oxygen adsorption studied by microcalorimetry. The heat of adsorption of nitrous oxide on copper amounts to 304 kJ mol⁻¹, and the heat of adsorption of carbon monoxide on surfaceoxidized copper is in the range from 120 to 70 kJ mol⁻¹.     

An overview of studies on the highly dispersed uranium oxide species occluded within mesoporous MCM-41 and MCM-48 host materials

In this article we have consolidated our recent studies on anchoring of uranyl groups and encapsulation of highly dispersed nano-particles of -U₃O₈ in mesoporous MCM samples. The size of uranium oxide crystallites and the binding of uranyl groups at framework sites of host matrix depended on the preparation method, viz. wet impregnation, exchange of template cations, and the hydrothermal route. These uranium species contributed individually to the catalytic oxidation of organic molecules, such as methanol, toluene and benzyl alcohol; the uranyl groups playing a more important role at lower reaction temperatures. Also, the size and the lattice oxygen of uranium oxide crystallites played a vital role, not only in the lowering of reaction onset temperature but also in deciding the nature and the reactivity of the transient surface species formed during the oxidation of above mentioned organics. For instance, the results of in situ IR spectroscopy experiments have shown that while larger-size U₃O₈ crystallites help in the growth of certain oxymethylene (–OCH₂) and polymerized oxymethylene (–OCH₂)_n species, adsorption of methanol on smaller size particles helped in the additional formation of formate-type complexes. Thus, a relationship was found between the size of uranium oxide crystallites, the nature of the transient species formed and the catalytic conversion of methanol to form CO₂, CO and methane. In addition, the uranyl ions anchored within the pore system of host matrix are found to serve as efficient heterogeneous photocatalysts for the sunlight-assisted deep oxidation of organic molecules in the vapor phase and at room temperature. The reaction mechanisms, accounting for the catalytic properties of occluded UO_x species without and in the presence of radiation, are discussed in the light of the above mentioned results.     

Untersuchung der Anfangsstadien der Oxidation einer NiCr23-Legierung mit AES/XPS

Summary The initial stage of oxidation of NiCr23 at room-temperature and oxygen pressures between 10^–6 and 10^–5 Pa has been studied by AES and XPS. The composition of the surface during oxygen exposure was followed by continuously recording the Auger peaks of Ni (61 eV), Cr (529 eV) and O (510 eV). Photoelectron spectra from Ni 2p3/2, Cr 2p3/2 and O 1s were measured after different oxygen exposures to characterize the chemical state. The thicknesses of the oxide layers were determined by angleresolved AES. The elemental in-depth distribution was obtained by sputter depth profiling. The results are explained by an initially preferential oxidation of Cr together with an oxygen-induced segregation of Cr, followed by enrichment and oxidation of Ni at the surface. The thickness of the oxide after an exposure with 200 Langmuir oxygen was 1.3 nm, while for pure Ni it was only 0.63 nm     

Surface characterization and electrical property of carbon fibers modified by air oxidation

Polyacrylonitrile‐based carbon fibers were modified by oxidation in air, and a systematic study of surface groups and surface resistance at different treated temperatures was made. Progressive fiber weight loss occurred with increasing extents of air oxidation, and it was approximately proportional to the extent of air oxidation from the onset of oxidation up to 400 °C. At this point 4.4% of the initial fiber weight had been lost. A faster loss of weight occurred as the extent of air oxidation increased from 400 °C to 700 °C. X‐ray photoelectron spectroscopy studies (C 1s and O 1s) indicated that the oxygen/carbon atomic ratio rose rapidly from 2.64% (as‐received carbon fiber) to 42.83% as the oxidation temperature was increased to 400 °C. Fourier transform infrared spectra showed the relative intensity of the peaks at about 3440 cm^?1 from ―OH stretching vibrations and at 1634 cm^?1 from ―C?O stretching vibrations increased significantly at 400 °C. FESEM micrographs showed that as‐received fibers show relatively smooth surface. With oxidation temperature increasing, the fiber surface was rougher. The surface resistance of treated carbon fibers decreased obviously with increasing oxidation temperatures. The most decrease was about 100% at 400 °C. Copyright © 2014 John Wiley & Sons, Ltd.     

CO在Ag掺杂的氧化锰八面体分子筛上吸附的TAP研究

利用产物瞬时分析反应器中进行的单脉冲实验, 考察了393～493 K温度范围内CO在Ag掺杂的氧化锰八面体分子筛上的吸附行为. 实验表明: CO在催化剂表面发生化学吸附, 并与晶格氧反应生成CO₂. 通过对该过程反应物及产物脉冲响应曲线的模拟, 得到了各基元反应的动力学参数. CO和CO₂在该催化剂表面的脱附活化能分别为83和31 kJ/mol, CO与晶格氧的反应活化能为116 kJ/mol.     

Al (110) surface oxide thermal stability in ultrahigh vacuum

This research characterizes the stability of the Al₂O₃ surface oxide on Al (110) as a function of temperature and within an ultrahigh vacuum environment (p < 5 × 10^?12 Torr). Auger electron spectroscopy and temperature desorption spectroscopy were used to correlate the change in oxygen and carbon surface concentration. The surface oxide was observed to remain stable up to 350–400 °C. Above this temperature, the oxide began to dissociate resulting in a CO desorption peak at 425 °C followed by extensive dissolution of the C and O into the Al bulk. A second and much smaller CO desorption peak was observed at 590 °C in concert with complete oxide breakdown and the virtual disappearance of surface carbon and oxygen. Extrapolation of the Auger electron spectral ratios of C_KLL and O_KLL peaks to the sum of the Al⁰_LVV and Al³⁺_LVV peak suggests that the surface concentration of each approaches zero at ~640 °C. The predominant mechanism for reduction of the surface oxide occurs by dissolution into the bulk instead of desorption. Copyright © 2013 John Wiley & Sons, Ltd.     

The oxidation of carbon monoxide on iron oxide

The oxidation of CO on α-Fe₂O₃ was studied in a flow reactor. The conversion was complete at 650–660 K. The catalytic activity of iron oxide was higher than that of the ferrite-containing xMgOyFe₂O₃ catalyst. The adsorption of CO on iron oxide and the kinetics of interaction of carbon monoxide with oxygen atomically adsorbed on the surface of α-Fe₂O₃ were studied. The kinetic parameters of the oxidation of CO are evidence of the participation of adsorbed oxygen atoms, whose binding energy on the surface of α-Fe₂O₃ is lower than that on the surface of the magnesium ferrite-containing catalyst.