超细La2O3纳米粉末制备过程的电子显微镜动态观察

用超高压透射电子显微镜原位加热动态观察的方法研究从非晶氢氧化镧转变为纳米级氧化镧超细粉过程中显微组织和结构的变化。电子衍射花样证实在试样被加热到４００℃以上时转变为氧化镧纳米粉，其颗粒尺寸为２０￣５０ｎｍ。     

球形La2O3∶Eu纳米晶的制备及其发光特性

近年来纳米材料的发展及纳米材料所具有的特异的光学性质,使得纳米发光材料引起越来越多的关注。La2O3结构简单,易于合成,价格便宜．因此以La2O3为基质的发光材料已有很多报道。Mekittric等研究认为,发光材料的形貌,如颗粒度、形状、结晶性等．是影响发光效率的一个重要因素．球形颗粒可以提高其密堆性．从而能有效地提高产品的发光亮度。     

纳米晶LaMnO3及La1-xSrxMnO3的合成及其催化氧化性能

纳米晶ＬａＭｎＯ３及Ｌａ１－ｘＳｒｘＭｎＯ３的合成及其催化氧化性能刘源秦永宁（天津大学化工系，天津３０００７２）韩森（天津大学化工系一碳化工国家重点实验室，天津３０００７２）关键词纳米晶，钙钛矿型复合氧化物，一氧化碳，催化氧化，超临界干燥分类号Ｏ６４...     

纳米Sm2O3掺杂CeO2粉末的制备和性能表征

以Ce2(CO3)3和Sm2O3为原料, 用改进的氨水-双氧水沉淀法制备了CeO2和(CeO2)0.8为基质(Sm2O3)0.2的纳米粉末.对干燥后的氢氧化物进行了TG/DSC热分析, 约650 ℃时Ce(OH)4完全转变为CeO2.XRD分析表明, 650 ℃焙烧的粉末为萤石结构, 说明Sm2O3已固溶到CeO2中.经TEM测试, 粉体颗粒大小在5～10 nm之间, BET测试的平均颗粒尺寸为11.2 nm.由TEM照片还可以看出粉体具有良好的分散性, 且无硬团聚体存在.     

一种由La2O3水化制备棒状La（OH）3的简便方法

通过本体氧化物在常压沸腾水中的水化处理制备了具有棒状外型的氢氧化镧。XRD衍射图显示在短时间内可以得到六方相氢氧化镧，表明其水化过程是相当快的。所得氢氧化镧几乎完全呈针状和棒状外型，其宽度为2-3μm，长为5-8μm。对棒状氢氧化镧的形成机制作了适当解释，并通过煅烧该氢氧化镧微米棒得到了类似外形的氧化镧。该方法比水热法更易于实现工业化应用。     

La2（C2O4）3纳米微粒的摩擦学行为研究

纳米摩擦学是９０年代摩擦学研究最活跃的领域之一［１］。稀土元素由于具有４ｆ电子特性,使其元素及其化合物具有许多特殊的性能［２～８］。本研究采用吸附共沉淀表面修饰法制备了烷基磷酸盐修饰的Ｌａ２（Ｃ２Ｏ４）３纳米微粒,并将其分散于润滑基础油中考察其摩擦学行为。利用有机脂肪链的减摩、纳米微粒的抗磨以及稀土元素的特殊作用,提高润滑油的摩擦学性能,拓宽稀土化合物在润滑材料领域的应用。１　实验部分１１　表面修饰Ｌａ２（Ｃ２Ｏ４）３纳米微粒的制备在醇水混合溶剂中,加入一定量的烷基磷酸吡啶盐（自制）和草酸盐…     

La2O3掺杂TiO2光催化剂的制备和性能

采用溶胶-凝胶法制备了La2O3掺杂TiO2纳米光催化剂，并通过XRD、TEM、BET和XPS等手段进行了表征．掺入La2O3后，阻止了TiO2从锐钛矿晶型向金红石晶型的转变，使TiO2的粒径减小，比表面积增大．以甲基橙为光催化降解反应模型化合物，考察了光催化剂的活性．测定了甲基橙在纯TiO2和La2O3掺杂TiO2光催化剂上的吸附常数．考察了pH、H2O2对降解性能的影响．讨论了光催化活性与催化剂性质的关系．     

La3+掺杂对γ-Fe2O3纳米粒子相转变的抑制作用

超细γ-Fe2O3是一种在高科技领域中得到广泛应用的功能材料,可以作为磁性材料应用于电子、计算机等领域,也可以作为气敏材料,制成稳定性好、选择性和灵敏度高的气敏传感器;同时还可作为催化材料,应用于石油化工及环保领域。但是,γ-Fe2O3属于亚稳相,在300℃时就有向更为稳定的α-Fe2O3相转化的趋势,影响了其在较高温度下的使用。因此,探索新的合成方法,     

席夫碱盐燃烧法制备纳米Er2O3晶体

以硝酸铒和席夫碱为原料，制备席夫碱盐络合物。使用燃烧合成的方法制备了Er2O3纳米晶体。采用傅立叶变换红外光谱(FT—IR)分析了反应历程。使用x射线衍射分析仪(XRD)进行了物相分析及粒径计算。使用透射电镜(TEM)观察了粉体的形貌。结果表明，生成相为单一的立方晶系。纳米晶体晶粒分布不均匀，没有明显的硬团聚现象发生。荧光试验表明，其发射谱在1．54μm处出现发射峰，同时在1．54μm两侧出现肩峰。     

Preparation and characterization of nanocrystalline ZnO by direct precipitation method

Nanocrystalline ZnO was prepared with ZnCl₂·2H₂O and (NH₄)₂CO₃ as raw materials by direct precipitation method. The precursor was proved to be [Zn₅(OH)₆(CO₃)₂] by TG-DTG-DTA and IR analysis. This precursor was calcined at 300°C for 1, 2 and 3 hours respectively, and then the nanocrystalline ZnO of different grain size were obtained. The nanocrystalline ZnO was characterized using X-ray diffraction (XRD), TEM and Brunner-Emmett-Teller method (BET). Experimental results for nanocrystalline ZnO showed that the minimum size was about 8nm, the maximum was about 15 nm and the mean grain size was 12 nm, the surface area was 80.56 m²/g and the purity was 99.9% when the precursor was calcined at 300°C for 2 h. __________ Translated from Journal of Inner Mongolia Normal University (Natural Science Edition), 2006, 35(1) (in Chinese)     

氧化镧催化剂上的低温甲烷氧化偶联反应

 采用沉淀法制备了氧化镧催化剂,并考察其催化低温甲烷氧化偶联反应的性能. 催化剂性能测试结果表明,在723 K, CH4/O2摩尔比=3和GHSV=7500 ml/(g·h)的条件下,甲烷的转化率和C2的选择性分别达26.6%和40.8%, 比商品化氧化镧催化剂的启动温度低100 K. 催化剂的表征结果表明,沉淀法制备的氧化镧催化剂与商品化的氧化镧催化剂都为六方晶相的氧化镧,但前者具有较大的比表面积,并且在598 K处出现一个明显的O2脱附峰.     

La2NiO4／Al2O3催化剂上CH4／CO2的重整

 通过溶胶－凝胶方法制备了尖晶石结构的La2NiO4／Al2O3催化剂，采用BET，XRD和TG表征了催化剂的孔分布、比表面积、体相组成以及凝胶样品的热失重和热分解过程．将催化剂应用于CH4／CO2重整反应制合成气，考察了惰性气体和反应温度对转化率、选择性以及积碳的影响．结果表明，在高空速（GHSV＝4．8×104ml／（g·h））下，CH4和CO2转化率分别为51％和60％，CO和H2的选择性约为98％和92％，惰性气体He的引入明显地提高了CH4和CO2的转化率．     

Preparation of nanocrystalline anatase TiO2 using basic sol-gel method

Nanocrystalline titanium dioxide particles with anatase structure and high thermal stability have been synthesized using the basic sol-gel method. The particle size and morphology were refined under hydrothermal conditions in the presence of different concentrations of tetramethylammonium hydroxide (TMAH) at 210°C and 230°C. XRD and TEM analysis showed that the TiO₂ particles obtained were homogeneous and monodispersive at low contents of TMAH. All intense peaks, clearly observed in the XRD patterns, were assigned to the anatase phase and no rutile phase was observed. At high contents of TMAH, nanoscale small (10–30 nm) and larger (>100 nm) TiO₂ particles were one-pot synthesized. The nanocrystalline TiO₂ particles synthesized by this method have good thermal stability. With the sintering temperature of up to 650°C, all the XRD peaks maintained good agreement with the anatase reference data.     

碳酸氢铵沉淀法制备氧化钇粉体时反应条件对产物粒度的影响

研究了碳酸氢铵沉淀法的反应条件对氧化钇粒度的影响,探讨了粒度变化规律。发现在沉淀反应中,晶型碳酸钇铵的形成与否是影响氧化钇粒度的关键因素。在较低的反应温度下,当碳酸氢铵和氯化钇的浓度大于0.25mol·L-1,摩尔比大于5,陈化时间大于60min时得到碳酸钇铵沉淀,经煅烧可获得粒度(D50)大于1μm的氧化钇。当反应物浓度较低、摩尔比小,陈化时间较短时得到无定型碳酸钇沉淀,煅烧沉淀可获得粒度(D50)小于0.5μm的氧化钇。实验证明选择适当的沉淀反应条件,可制备D50在0.3～10μm范围内的不同粒度级别的氧化钇粉体。     

Preparation and characterization of highly photoactive nanocrystalline TiO_2 powders by solvent evaporation- induced crystallization method

Highly photoactive bi-phase nanocrystalline TiO2 photocatalyst was prepared by a solvent evaporation-induced crystallization (SEIC) method, and calcined at different temperatures. The obtained TiO2 photocatalyst was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results show that solvent evaporation can promote the crystallization and phase transformation of TiO2 at 100℃. When calcination temperatures are below 600℃, the prepared TiO2 powders show bimodal pore size distributions in the mesoporous region. At 700℃, the pore size distributions exhibit monomodal distribution of the inter-aggregated pores due to the collapse of the intra-aggregated pores. At 100℃, the obtained TiO2 photocatalyst by this method shows good photocatalytic activity, and at 400℃, its photocatalytic activity exceeds that of Degussa P25. This may be attributed to the fact t     

La2O2S∶Mn2+荧光粉的微波合成及其荧光特性

Using La₂(SO₄)3 and the active carbon powder as reactants, La₂O₂S∶Mn²⁺ red phosphor was synthesized by microwave radiation method. The phosphor was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), laser-diffraction size analyzer and fluorospectrophotometer. The XRD analysis showed that the phosphor was pure phase La₂O₂S. The phosphor of La₂O₂S∶Mn²⁺ showed hexagonal crystal structure with diverse shapes, such as spherical and rod, with average particle size of 10.22 μm. The emission and excitation spectra of the phosphor were determined by fluorospectrophotometer and the results showed that the excitation spectrum of the phosphor under 600 nm emission wavelength was excitation bands between 250 nm and 350 nm with a peak value of 303 nm. Then ,when exicited under UV 303 nm, the phosphor showed broad band emission of 550~700 nm with a peak at 607 nm. In addition, the optimal effects were obtained for the phosphor preparation when the concentration of the activator Mn²⁺ was x_Mn=0.01, the ratio of C and O (n_C / n_O) in the reactants was 0.6∶1, and the time of reaction was about 1 h. La₂O₂S∶Mn²⁺ has strong absorption of UV spectrum and can emit bright red light.     

液相沉淀法制备纳米ZnO粉体的研究

现有制备纳米ZnO的方法大多需要较特殊的设备和严格的反应条件[1 4] 。笔者采用液相沉淀法,首先以草酸为沉淀剂直接从硫酸锌水溶液中沉淀出前驱体ZnC2 O4·2H2 O ,然后经过滤、洗涤、干燥和焙烧分解,制得了平均晶体粒径为2 5nm的ZnO粉体。此方法操作简单、反应条件温和、易于控制。但沉淀在洗涤过滤和干燥时易产生团聚现象[7] 。为此采取以稀草酸溶液对制得的前驱体进行超声洗涤和1 2 0℃真空干燥的措施,明显提高了粉体的分散性能。1　实验部分1 1　主要仪器及试剂Zn(SO4) 2 和H2 C2 O4·2H2 O(A .R .)。KS 2 5 0E型超声波清洗仪…     

Methane Conversion Over Sr2+/La2O3 Catalyst Modified with Nickel and Copper

Methane transformation over Ni and Cu modified Sr²⁺/La₂O₃ catalysts has been studied. These species favor formation of reducible mixed oxides and change the surface reactivity of the Sr²⁺/La₂O₃ system, modifying the reaction mechanism, since Sr²⁺/La₂O₃ favors methane oxidative coupling but with copper methane combustion is favored and nickel favors partial oxidation.     

Cu/La/CeO2-Al2O3的制备及其对丙烯选择性还原NO的催化活性

将Al(NO3)3-Ce(NO3)3混合溶液滴入到NH4HCO3-NH3.H2O混合溶液中,采用共沉淀法制备了CeO2-Al2O3复合载体.采用等体积浸渍法分别浸渍助剂La和活性组分Cu,制备了Cu/La/CeO2-Al2O3催化剂.考察了催化剂在富氧条件下对丙烯选择性还原NO反应的催化活性,并借助扫描电镜、原子力显微镜、X射线衍射、比表面积测定、红外光谱、热重分析、X射线光电子能谱和程序升温还原等方法研究了催化剂活性与结构之间的关系.结果表明,CeO2-Al2O3复合载体能显著增大催化剂的比表面积和孔径,增加表面Lewis酸酸量,改善催化剂的还原性能;助剂La能进一步增大催化剂的比表面积和孔径,增加表面Br nsted酸酸量,显著提高催化剂的热稳定性;催化剂的粒径较小,对丙烯选择性还原NO反应具有较高的催化活性,最高催化活性时的温度较低.