尺寸可控氢氧化镧纳米棒的水热合成及表征

以硝酸镧为镧源、三乙胺为碱源和络合剂,通过简便的水热法成功合成了大量均一的氢氧化镧纳米棒。详细研究了三乙胺的用量、表面活性剂、反应温度和时间对产物形貌及尺寸的影响。基于实验结果,提出了氢氧化镧纳米棒的形成机理。同时制备了稀土掺杂的氢氧化镧纳米棒。利用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）和高分辨透射电子显微镜（HRTEM）对所得产物的物相、结构和形貌进行了表征分析。     

水热微乳法合成La(OH)3纳米棒的形貌控制研究

自1991年Iijima发现碳纳米管以来,一维纳米材料如纳米管、纳米线、纳米棒和纳米纤维等由于其具有独特的光、电、磁等性质及其潜在的应用前景而引起全世界的广泛关注,一维纳米材料的制备方法有化学气相沉积法、溶胶一凝胶法、催化剂辅助法、固相化学反应法、模板法、溶剂热法、微乳法和水热,微乳法等,其中水热,微乳法是近年来兴起的一种很有发展前途的制备一维纳米材料的方法。     

Mechanism of corrosion inhibition of AA2024 by rare-earth compounds

The mechanism of corrosion protection of the widely used 2024-T3 aluminum alloy by cerium and lanthanum inhibitors in chloride media is described in detail in the present work. The corrosion process was investigated by means of scanning Kelvin probe force microscopy (SKPFM), in situ atomic force microscopy, and scanning electron microscopy coupled with energy dispersive spectroscopy. Employment of the high-resolution and in situ techniques results in a deep understanding of the details of the physical chemistry and mechanisms of the corrosion processes. The applicability of the SKPFM for mechanistic analysis of the effect of different corrosion inhibitors is demonstrated for the first time. The inhibitors under study show sufficient hindering of the localized corrosion processes especially in the case of pitting formation located around the intermetallic S-phase particles. The main role of Ce(3+) and La(3+) in the corrosion protection is formation of hydroxide deposits on S-phase inclusions buffering the local increase of pH, which is responsible for the acceleration of the intermetallics dealloying. The formed hydroxide precipitates can also act as a diffusion barrier hindering the corrosion processes in active zones. Cerium nitrate exhibits higher inhibition efficiency in comparison with lanthanum nitrate. The higher effect in the case of cerium is obtained due to lower solubility of the respective hydroxide. A detailed mechanism of the corrosion process and its inhibition is proposed based on thermodynamic analysis.     

La(Oxin)3·3H2O纳米晶的一步固相化学合成及表征

La(Oxin)3·3H2O;纳米晶;超声波;固相化学合成;结构表征     

溴氢氧化镧的合成及结构

在常温常压下由溴氧化镧与水蒸汽反应合成了溴氢氧化镧,用示差热分析和热失重分析方法研究了溴氢氧化镧的热分解过程--在空气中于360-405℃,在氮气流中于315-347℃热分解,脱水后生成溴氧化镧。用粉末X射线衍射确定了本实验所合成的溴氢氧化镧(La(OH)₂Br)的晶体结构,是斜方晶系,a=8.9064Å,b=13.024Å,c=5.5630Å。讨论了溴氢氧化镧的有关化学性质。     

Hydrothermal synthesis of nickel hydroxide nanostructures in mixed solvents of water and alcohol

Nickel hydroxide nanosheets and flowers have been hydrothermally synthesized using Ni(CH₃COO)₂·4H₂O in mixed solvents of ethylene glycol (EG) or ethanol and deionized water at 200 °C for different time. The phase and morphology of the obtained products can be controlled by adjusting the experimental parameters, including the hydrothermal time and the volume ratio of water to EG or ethanol. The possible reaction mechanism and growth of the nanosheets and nanoflowers are discussed based on the experimental results. Porous nickel oxide nanosheets are obtained by heating nickel hydroxide nanosheets in air at 400 °C. The products were characterized by using various methods including X-ray diffraction (XRD), fourier transform infrared (FTIR), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), field emission scanning electron microscopy (FESEM). The electrochemical property of β-Ni(OH)₂ nanosheets was investigated through the cyclic voltammogram (CV) measurement.     

Zn3(OH)2V2O7·2H2O纳米片的水热制备

采用硝酸锌、五氧化二钒和氢氧化钠作为反应物,通过一个简单的CTAB辅助的水热方法制备了Zn₃(OH)₂V₂O₇·2H₂O纳米片。运用XRD,ICP-AES,FTIR,HRTEM,EDS,FE-SEM对产物的晶相和形貌进行了表征。结果表明CTAB在控制产物的形貌、尺寸分布和自组装过程中起着关键作用。同时我们研究了产物的晶体生长行为和自组装过程。     

Zn3(OH)2V2O7·2H2O纳米片的水热制备

采用硝酸锌、五氧化二钒和氢氧化钠作为反应物,通过一个简单的CTAB辅助的水热方法制备了Zn3(OH)2V2O7·2H2O纳米片.运用XRD,ICP-AES,FTIR,HRTEM,EDS,FE-SEM对产物的晶相和形貌进行了表征.结果表明CTAB在控制产物的形貌、尺寸分布和自组装过程中起着关键作用.同时我们研究了产物的晶体生长行为和自组装过程.     

水性体系中超细镍粉的液相还原制备

采用快捷、温和的液相还原法,在水溶液中,以氢氧化钠为pH值调节剂,利用水合肼的还原作用将氯化镍还原得到超细镍粉．利用扫描电镜（SEM）及X射线衍射（XRD）的表征手段研究了反应条件对超细镍粉微观结构的影响．结果表明,所得到的产物是纯的面心立方结构的镍材料,颗粒的尺寸介于200～500nm之间,且分布较为均匀．     

A simple solvothermal route towards the morphological control of ZnO and tuning of its optical and photocatalytic properties

ZnO nanoparticles with different morphologies were solvothermally synthesized by controlling the alkali (sodium hydroxide) concentration in an isopropanol solution. The products were characterized by means of powder X-ray diffraction, UV-visible absorption spectra, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The morphologies of the formed ZnO nanocrystals were dependent on the concentration of the alkali, and with increases of sodium hydroxide concentration, the ZnO nanocrystals evolved from rod to hexagonal bipyramid, and then to a flower-like nanostructure. The flower-like nanostructure resulted from the etching of the hexagonal bipyramid by the excess alkali. The photoluminescence and photocatalytic properties of the prepared ZnO were investigated. The difference of green emission among the ZnO nanocrystals indicated that a higher sodium hydroxide concentration led to a higher level of defects. The size, the surface structure and defects in the ZnO nanocrystals affected its photo-degradation characteristics.     

A close look at silver oxide colloid for surface-enhanced Raman scattering

A silver oxide hydrosol has been prepared by reacting silver nitrate with sodium hydroxide in an aqueous solution. The colloidal particle composition and particle size have been characterized by X-ray diffractometry and transmittance electron microscopy. We have demonstrated that the sol is surface-enhanced Raman scattering active. One major advantage of this sol is the absence of the spectral interference arising from reaction products of the sol formation process. The mechanism of surface-enhanced Raman scattering activity is essentially contributed by the silver particles generated from the photochemical process during the laser excitation.     

一步法水热合成 TiO2纳米线及其光催化性能

以钛酸丁酯和异丙醇为原料, 采用一步法在NaOH溶液中水解后直接进行水热反应, 经焙烧处理, 得到TiO2纳米线. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)和能谱分析(EDX)对产物进行了形貌、结构及成分的表征. 考察了不同水热温度、碱液浓度、水热反应时间及焙烧温度等因素对产物的影响. 结果表明, 获得较好形貌TiO2纳米线的最佳水热温度、碱液浓度和水热反应时间分别是180 ℃, 10 mol/L和24 h. 所得TiO2纳米线焙烧至950 ℃时仍为锐钛矿相, 说明本文制备方法迟滞了TiO2纳米线由锐钛矿相向金红石相的转变. 以甲基橙为目标降解物, 采用紫外-可见分光光度计研究了未掺杂和铕掺杂TiO2纳米线(Eu-TiO2)的光催化性能. 结果显示, 最佳掺铕量(摩尔分数)为1.6%. 在300 W紫外灯照射60 min时, 此掺铕量的TiO2纳米线对甲基橙溶液的降解率是未掺杂样品的1.5倍.     

Effect of thermal annealing on the kinetics of rehydroxylation of Eu3+:La2O3 nanocrystals

Europium-doped lanthanum oxide (5 mol % Eu(3+):La(2)O(3)) was prepared by calcining europium-doped lanthanum hydroxide (5 mol % Eu(3+):La(OH)(3)) previously synthesized by a simple hydrothermal method. Interestingly, we observed different emission Eu(3+) signatures depending on the phase of the host (lanthanum oxide or hydroxide) by cathodoluminescence. Taking into account that lanthanum oxide easily rehydroxylates in air, for the first time, we report the use of cathodoluminiscence as a novel characterization technique to follow the lanthanum oxide rehydroxylation reaction versus time according to different annealing procedures. Additionally, differential thermal-thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques were used to identify the phases formed from the Eu(3+):La(OH)(3) depending on temperature and to study the evolution of La(2)O(3) to La(OH)(3) versus time. The results showed that the higher the temperature and the longer the annealing time, the higher the resistance to rehydroxylation of the Eu(3+):La(2)O(3) sample.     

形貌可控的LaPO4:Eu3+荧光粉的制备与发光性能研究

分别以硝酸镧、多聚磷酸和磷酸二氢钠为原料,在无任何添加剂和模板的条件下,采用水热法分别合成微纳米球和纳米棒两种形貌的磷酸镧.通过场发射-扫描电子显微镜(FE-SEM),X射线衍射(XRD),红外光谱(FTIR)和荧光光谱(PL)等测试手段对以上不同形貌的样品的相结构以及微观形貌进行表征.FE-SEM测试结果表明:当以多聚磷酸为磷源时,在酸性条件下可以得到平均粒径约为2μm左右的磷酸镧微球;而当以磷酸二氢钠磷源时,在酸性条件下则可以得到纳米棒;两者的分散性良好.XRD测试结果表明:两种不同形貌的样品均为单斜晶系结构.荧光光谱分析可知:Eu3+的掺杂浓度相同时,球状样品的发光强度远大于棒状样品.     

Reduction of organic halides with lanthanum metal: a novel generation method of alkyl radicals

Results of the reaction of alkyl halides with lanthanum metal have been shown. The reduction of alkyl iodide with 1/3 equiv of lanthanum metal efficiently proceeded to give the corresponding reductive dimerized products along with the formation of reduction and dehydroiodination products. In the case of alkyl bromides and chlorides, the reaction did not proceed under the same reaction conditions as that of alkyl iodides; however, the reaction was dramatically promoted by the addition of a catalytic amount of iodine. A reaction pathway including alkyl radicals was suggested.     

Nanobelt formation of magnesium hydroxide sulfate hydrate via a soft chemistry process

The nanobelt formation of magnesium hydroxide sulfate hydrate (MHSH) via a soft chemistry approach using carbonate salt and magnesium sulfate as reactants was successfully demonstrated. X-ray diffraction (XRD), energy dispersion X-ray spectra (EDS), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis revealed that the MHSH nanobelts possessed a thin belt structure (approximately 50 nm in thickness) and a rectangular cross profile (approximately 200 nm in width). The MHSH nanobelts suffered decomposition under electron beam irradiation during TEM observation and formed MgO with the pristine nanobelt morphology preserved. The formation process of the MHSH nanobelts was studied by tracking the morphology of the MHSH nanobelts during the reaction. A possible chemical reaction mechanism is proposed.     

Sorption of phosphate ions with materials based on titanium and lanthanum hydroxides

The possibility of preparing lanthanum(III) hydroxide and a 1:1 mixture of lanthanum(III) hydroxide with hydrated titania by precipitation from aqueous solutions was explored. The maximal sorption capacities of the mixture with respect to phosphate ions in acid and alkaline media were determined. The mechanism by which phosphates are removed was elucidated by IR spectroscopy.     

Chemical recycling of carbon fibre reinforced epoxy resin composites in subcritical water: Synergistic effect of phenol and KOH on the decomposition efficiency

The combination of phenol and potassium hydroxide (KOH) was used to chemically recycle carbon fibre reinforced epoxy resin cured with 4,4′-diaminodiphenylmethane in subcritical water. This combination had a synergistic effect on decomposing this kind of epoxy resin. The main decomposition products from the epoxy resin were identified by means of GC-MS, and a possible free-radical reaction mechanism for the decomposition of epoxy resin is proposed. The recovered carbon fibres were characterized using single fibre tensile tests, scanning electron microscopy and X-ray photoelectron spectroscopy. Compared to virgin carbon fibres after sizing removal, the surface compositions of the recovered carbon fibres had little change and the tensile strength of the recovered carbon fibres was well retained.     

Ru/SBA-15的制备及其对水煤气变换反应的催化作用

制备了中孔分子筛SBA-15,以SBA-15为载体采用真空浸渍法制备了负载型Ru基水煤气变换反应的催化剂。利用透射电子显微镜、X-射线粉末衍射等方法对样品进行了表征。结果表明,合成的SBA-15分子筛孔径约为8 nm,粒径约为1 nm的Ru纳米粒子均匀分布在分子筛孔道中,添加适量的La2O3助剂可以显著提高催化剂的低温活性。当Ru和La2O3的负载量分别为4%和8%时,R4L8/SBA-15催化剂对CO转化率在255℃和265℃下分别达到56%和98%。     

A simple mixed-solvothermal route for LaPO4 nanorods: synthesis, characterization, affecting factors and PL properties of LaPO4:Ce3+

In this paper, LaPO(4) nanorods have been successfully synthesized via a simple water-ethyleneglycol (H(2)O-EG) mixed-solvothermal route, employing lanthanum nitrate (La(NO(3))(3)·xH(2)O) as a La(3+) ion source and monobasic sodium phosphate (NaH(2)PO(4)·2H(2)O) as a PO(4)(3-) ion source. The as-obtained products were characterized by means of X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), (high resolution) transmission electron microscopy (HR/TEM), selected area electron diffraction (SAED) and field emission scanning electron microscopy (FESEM). Some factors influencing the formation of LaPO(4) nanorods, including the reaction temperature, the volume ratio of water/EG and the original amount of H(2)PO(4)(-) ions, were investigated. Experiments showed that the volume ratio of water/EG and the original amount of H(2)PO(4)(-) ions could markedly affect the morphology of the final product.