纳米钙钛矿LaxSr1-xFe1-yCoyO3复合氧化物的制备和表征

用甘氨酸-硝酸盐燃烧合成法，制备La_xSr_1-xFe_1-yCo_yO₃复合氧化物的陶瓷粉末，对该钙钛矿型氧化物进行了XRD、IR、紫外漫反射光谱及循环伏安曲线分析。结果表明：该复合氧化物粉体平均晶粒为15.3～29.8 nm,为立方和正交晶系。该氧电极具有双功能催化特性，但不完全可逆。对水溶液染料进行光解实验，利用紫外-可见、人工神经网络光度法研究La_xSr_1-xFe_1-yCo_yO₃的催化性能。结果表明：CO²⁺的加入可使La_xSr_1-xFeO₃的光催化活性有所提高，B位离子(Fe³⁺，CO²⁺)改变与加入，使La_xSr_1-xFe_1-yCo_yO₃(x=0.7，0.3；y=0.3，0.9，1)光催化活性高于La_xSr_1-xFeO₃。同时，对5种染料进行紫外光解，在0.75 h，脱色率大于91%，并为动力学一级反应。     

Ce1－xNdxO2－δ固溶体的电子顺磁共振谱和阻抗谱的研究

利用溶胶-凝胶方法在800 ℃焙烧10 h后, 合成了固溶体Ce_1－xNd_xO_2－δ (x＝0.05～0.55), X射线衍射(XRD)测试表明固溶体已经形成立方萤石结构; 电子顺磁共振谱(EPR)研究表明在固溶体Ce_1－xNd_xO_2－δ中随着掺杂量x的增大, Ce^3＋离子含量减少, 说明掺杂Nd^3＋离子可以抑制Ce^4＋的还原; 交流阻抗谱的测量表明固溶体Ce_0.9Nd_0.1O_2－d 具有离子导电特性, 600和700 ℃时的电导率分别为4.25×10^－3和1.12×10^－2 S•cm^－1, 活化能为0.68 eV.     

LixNi0.5Co0.5O2的态密度计算及电化学性能研究

>为获得综合性能更好的锂离子二次电池正极材料, 分析了Co掺杂对Li_xNiO₂电化学性能的影响. 采用密度泛函DFT理论对Li_xNiO₂和Li_xNi_0.5Co_0.5O₂的平均放电电压和态密度进行了计算. 同时, 用共沉淀法制备了Li_xNiO₂和Li_xNi_0.5Co_0.5O₂锂离子二次电池正极材料, 并对其进行了XRD结构分析和恒流充放电测试. 实验和计算结果表明: 随锂离子嵌入正极(电池放电), 电池的电压逐渐降低, 材料的态密度峰向低能量方向移动; 与Li_xNiO₂相比, Li_xNi_0.5Co_0.5O₂的电压平台相对较高(当0.25≤x≤0.5), 而且在Li^＋嵌/脱时, Li_xNi_0.5Co_0.5O₂的结构变化相对较小; Co离子的掺入, 减小了NiO₆八面体的畸变度, 使材料的电化学稳定性得以提高. 在钴掺杂镍酸锂体系中, NiO₆和CoO₆具有相互的稳定作用.     

掺镍型层状LixNiyMn1-yO2正极材料的合成与电性能研究

A kind of cathode material of layered Li_xNi_yMn_1-yO₂ characterized with the O2 type has been synthesized by a simple method. Its precursor Na_xNi_yMn_1-yO₂ has been prepared from manganese dioxide， nickel hydroxide and sodium carbonate at high temperature in air and quickly cooled in cold water， then it has been exchanged by the melted LiNO₃ at 300～400℃ in air. The effects of calcine-temperature for the precursors and its compositions (the content of Na and Ni) on the electrochemical properties of the material Li_xNi_yMn_1-yO₂ have been investingated by XRD and electrochemical tests. The results show that the sample Li_0.7Ni_0.3Mn_0.7O₂， has the best electrochemical properties which shows only one charge-discharge potential stage of 2.8～3.0V and has a high specific capacity over 180mAh·g^-1 cycled between 2.0～4.20V. A significant structure transformation to the spinal-type phase has not been found in the charge-discharge cycling and the discharge specific capacity around 165mAh·g^-1 has re-mained after the 20th cyclings for the material.     

LixNi0.8-yCo0.2ZnyOp的合成及电化学性能研究

A series of single-phase Li_xNi_0.8-yCo_0.2Zn_yO_p(0.96 ≤x≤ 1.10， 0 ≤y≤ 0.05， 2 ≤p≤ 2(1+y) ) (different in the y values) were synthesized by a two-step solid state reaction method， in which LiOH·H₂O， Zn-doped spherical Ni(OH)₂ and Co₂O₃ were used as the precursors. The ICP-AES analyses proved that the Zn-doped compounds synthesized had the nonstoichiometric form. The results of the XRD， SEM identified that the uniform particles of the as-prepared materials having a good layered structure were fine， narrowly distributed and well crystallized. The electrochemical performance test was carried out and the results showed that the as-prepared Zn-doped materials had not only a high capacity， but also a better cycling stability characterization than the un-doped one. The Li_1.06Ni_0.75Co_0.22Zn_0.03O_2.03 material has an initial reversible capacity as high as 160.5mAh·g^-1; and a first discharge efficiency 89.2%， and exhibits satisfactory cyclic stability with 90% retainable capacity after 50 cycles.     

层状O2结构锂锰氧化物Li0.60[MgxCoyMn1-x-y]O2的制备及结构表征

本文采用离子交换法分别制备了双复合锂锰氧化物Li_0.60[Mg_xMn_1-x]O₂(0.05 ≤ x ≤ 0.15)和三复合锂锰氧化物Li_0.60[Mg_xCo_yMn_1-x-y]O₂(x=0.05，0.05 ≤      

Ba0.4Sr0.6Co1-xFexO3-δ系阴极材料的制备和表征

采用甘氨酸-硝酸盐(GNP)法合成了中温固体氧化物燃料电池阴极材料Ba_0.4Sr_0.6Co_1-xFe_xO_3-δ(x=0.0～0.8)系列粉体。利用XRD和SEM对材料的结构和微观形貌进行分析,用直流四端子法测量了烧结陶瓷体在中温(450～800 ℃)范围内的电导率。结果表明,制备的样品为单一钙钛矿相,随着Fe含量增加,XRD衍射峰值向高角度方向稍有偏移。电导率随着温度及Fe含量的变化出现极大值,在x＜0.2时,Ba_0.4Sr_0.6Co_1-xFe_xO_3-δ系列烧结体在中温(450～800 ℃)区的电导率,随Fe掺入量的增大而增大,x=0.2样品的电导率最高,800 ℃时达244.7 S·cm^-1,远超过文献报道值,进一步增大Fe含量导电性能变差。     

La1-xSrxCoO3（x=0，0.2，0.4，0.6，0.8）钙钛矿型氧化物的催化性能及改性

通过溶胶-凝胶法制备出A位Sr掺杂的钙钛矿型氧化物La_1-xSr_xCoO₃（x=0,0.2,0.4,0.6,0.8）,并将其作为催化剂应用于双功能氧电极中。测试结果表明,A位Sr的掺杂的La_1-xSr_xCoO₃比LaCoO₃具有更高的电催化活性,并且La_0.6Sr_0.4CoO₃在氧还原和氧析出反应中均表现出最优的催化性能,最大电流密度分别达到0.244 A·cm^-2（-0.6 V vs Hg/HgO）和0.303 A·cm^-2（1 V vs Hg/HgO）。为进一步提高催化剂的催化活性,将水热法制备的α-MnO₂纳米管与La_0.6Sr_0.4CoO₃复合作为双功能催化剂。当α-MnO₂的质量分数为40%时,比起单一的α-MnO₂或钙钛矿氧化物,α-MnO₂/La_0.6Sr_0.4CoO₃复合材料表现出协同效应,有更好的双功能电催化活性,使双效氧电极具有更好的电化学性能及稳定性。     

稀土钠钨青铜化合物NaxLayWO3结构与导电性的理论研究

使用密度泛函理论研究了稀土钠钨青铜化合物的结构和导电性质. 在实验晶体结构数据的基础上构建Na_xWO₃和Na_xLa_yWO₃的模型分子, 优化其几何结构, 并与实验值比较. 在此基础上计算了化合物的能带结构和电子能态密度. 通过这些研究探讨当La^3＋取代Na_xWO₃的中心Na^＋后对结构和导电性的影响. 计算结果表明La^3＋的取代并没有改变结构的空间对称性, 但却使晶格参数和体积略有增大; 取代使电子结构发生了变化, 在费米面附近, 能带相互交叠更加密集, 电子出现的几率增加, 从而增加了其导电性. 这可能是掺杂后La^3＋的4f和5d电子的贡献使电子轨道杂化作用增强, 电子云密度分布重排的结果.     

复合氧化物LaxSr1-xFe1-yNiyO3光电催化活性研究

用甘氨酸-硝酸盐燃烧法,制备纳米晶体LaxSr1-xFe1-yN iyO3,并对其进行了XRD、SEM、EDS结构分析。制备了双功能氧电极,在通氧或不通氧的条件下测试了循环伏安曲线。合成的LaxSr1-xFe1-yN iyO3复合氧化物,在汞灯激发光源下,对5种有机染料进行了脱色催化降解反应;利用红外、紫外-可见以及人工神经网络光度法研究LaxSr1-xFe1-yN iyO3的催化性能。结果表明:LaxSr1-xFe1-yN iyO3(x=0.3,0.7;y=0.1,0.25,0.6)复合氧化物具有较强光催化特性,为动力学一级反应。     

Ce1-xNixO2/Al2O3/FeCrAl催化剂的制备及其甲烷催化燃烧性能

以FeCrA l合金薄片为基体,A l2O3为过渡载体,Ce1-xN ixO2(x=0.1-0.3)、CeO2和N iO为活性组分,制备了Ce1-xN ixO2/A l2O3/FeCrA l、CeO2/A l2O3/FeCrA l和N iO/A l2O3/FeCrA l金属基整体式催化剂,在固定床微型反应器中评价了催化剂的甲烷催化燃烧性能,用SEM、XRD、TPR等方法对催化剂的物相、表面形貌和氧化还原性进行了表征.结果表明,Ce1-xN ixO2在催化剂表面的分散性比CeO2和N iO要好;Ce1-xN ixO2/A l2O3/FeCrA l(x=0.1-0.3)催化剂具有好的催化活性和高温稳定性,CeO2/A l2O3/FeCrA l和N iO/A l2O3/FeCrA l催化剂有好的初活性但高温稳定性较差;活性组分与A l2O3和FeCrA l金属基体之间存在较强的相互作用.     

金属并联电解制备LiCo_xNi_(1-x)O_2正极材料

应用钴、镍金属并联电解法制备锂离子电池正极材料.电解反应时,调节流过钴、镍电极上的电流比值及控制合适的电流密度,可生成均匀的CoxNi1-x(OH)2前驱体.研究表明,该法简单且无污染.合成的LiCo0.3Ni0.7O2正极材料充放电的容量较高,循环稳定性也较好,其初始放电容量为163mAh/g,经过50次充放电循环后放电容量仍可保持140mAh/g.     

具有一级磁相变的不同系列NiMnGa合金其电子浓度对相变温度的影响

分析了具有一级磁相变的Ni2 x yMn1-xGa1-y,Ni2 xMn1-xGa两个合金系列中,合金电子浓度e/a对结构和磁转变温度的影响。对于Ni2 x yMn1-xGa1-y系列合金,随着电子浓度的增加,马氏体相变温度TM增大,居里温度TC减小,在e/a=7.68处相交,继续增加e/a,TM和TC同时减小;而对于Ni2 xMn1-xGa系列合金,随x的增加,电子浓度增加,TM增大,TC减小,在e/a=7.635处相交,x继续增大,TM和TC仍然缓慢增加。不同NiMnGa合金系列中TM,TC与合金的e/a之间不同的变化关系说明,e/a对TM和TC的影响在不同的NiMnGa合金系列中是相同的。     

SOLID STATE CHEMISTRY OF La_(1-x)Li_(x)MnO_3 AND RELATED COMPOUND

A series of perovskite type oxides La_(1-x)A_(x)MnO_3(x=0.1 for A=Li,Na,K;x=0.1～0.5 for A=Li)have been prepared by impregnation.Experimental results showed that the substitution of La~(3 ) by Li~ inLaMnO_(3 ?) greatly increased the selectivity to ethane and ethylene for theoxidative coupling of methane.Temperature-programmed desorption of oxygenproved the presence of oxygen vacancies in the oxide lattice.The higher Mn~(4 )/Mn_t ratio in oxide made the formation of oxygen vacancies easier on the oxidesurface.The general formula of the oxides is La_(1-x)Li_(x)Mn＇V＇_(y)O_(3-y),V=vacancy.     

钙钛矿型La1+X/2Sr1-x/2Co1-xCuxO3催化CO氧化活性与表征

The catalytic activity and the reactive properties of perovskite-type oxides catalysts La(1+x/2)Sr(1-x/2)Co1-xCuxO3 for CO oxidation reaction were investigated. Results showed that the catalytic activity for CO oxidation reached to a maximum when x＝0.4. The temperature for complete CO oxidation under atmospheric and experimental conditions was 168℃. According to the stoicheometry of catalyst, all catalysts were oxygen defect compounds. The active oxygen species on this catalyst was the adsorbed oxygen which was adsorbed on the surface lattice oxygen defect. It was also found that Co4+ existed in the catalysts and the sufrace active oxygen species was caused by the Co4+. It was concluded that CO oxidation reaction on this catalyst was carried out by the valence change between Co3+ and Co4+ which was adjusted by the adsorbed oxygen.     

双钙钛矿Sr_2FeMn_(1-x)Co_xO_6催化剂的制备及其催化性能

通过溶胶凝胶法制备了一系列双钙钛矿催化剂Sr_2FeMn_(1-x)Co_xO_6(x=0.1,0.3,0.5,0.7,0.9),其结构经XRD,BET,H_2-TPR和SEM表征。以催化甲烷燃烧为模板反应,考察掺杂不同量Co~(2+)对Sr_2FeMn_(1-x)Co_xO_6催化性能的影响。结果表明:催化剂经800℃焙烧后可形成完整的双钙钛矿晶型,且Co离子掺杂量不同其催化活性不同,当Co离子掺杂量为0.3时,催化剂Sr_2FeMn_(0.7)Co_(0.3)O_6具有较高的催化活性,样品比表面积为9m~2·g~(-1),起燃温度T_(10%)为442℃,T_(90%)为654℃,Fe~(3+)、Mn~(2+)、Co~(2+)之间有一定协同作用。     

A1掺杂量对正极材料LiNi_(1/3)Co_(2/3-x)A1_xO_2结构和电化学性能的影响

以共沉淀法合成的前驱体Ni_(1/3)Co_(2/3-x)Al_x(OH)_2与低共熔锂盐0.38LiOH·H_2O-0.62LiNO_3制备了锂离子电池正极材料LiNi_(1/3)Co_(2/3-x)Al_xO_2(x=1/12,1/3,1/2,7/12).采用X射线衍射(XRD)、扫描电镜(SEM)和电化学性能测试对其结构、形貌和电化学性质进行表征.结果表明,LiNi_(1/3)Co_(2/3-x)Al_xO_2在1/12≤x≤1/3范围内可以保持单一的六方层状a-NaFeO_2结构,当A1掺杂量(x)高于1/3时,会出现杂相.其中,LiNi_(1/3)Co_(1/3)Al_(1/3)O_2结晶程度最高,阳离子混排效应最小,并且颗粒小而均匀,振实密度可以达到2.88 g·cm~(-3),首次放电容量为151.5 mAh·g~(-1),循环50次后放电容量保持在91.4%,在1C和2C倍率下放电容量仍可达到133.7和120.9 mAh·g~(-1)     

甲烷氧化偶联Ti-La-Li系混合氧化物催化剂

研究了Ti-La-Li三元氧化物的组成、结构及其对甲烷氧化偶联反应的催化性能；用XRD、IR、XPS和SEM等方法对催化剂进行表征，结果表明：在LiTi_xLa_(1-x)O_2系列催化剂中，随x值的不同，可生成LaTi_(1－y)Li_yO_(3-λ)、Li_2TiO_3、La_(0.66)TiO_(2.993)、La_2O_3和Li_(1.33)Ti_(1.66)O_4几种物相，其中，钙钛矿到三元复合氧化物LaTi_(1-y)Li_yO_(3-λ)是甲烷氧化偶联反应的主要活性相，活性位Li~＋-O~－-Ti~(3＋)的形成是活性提高的主要原因．Li_2TiO_3和La_(0.66)TiO_(2.993)是深度氧化活性相，而Li_(1.33)Ti_(1.66)O_4既无偶联活性，也无深度氧化活性．