Effect of Hydrothermal Time,pH, and Alkali on Crystal Phase and Morphology of Manganese Oxides

γ‐MnOOH nanowires and Mn₃O₄ nanoparticles were prepared in the hydrothermal process. The effect of hydrothermal time, pH, and alkali on morphology and composition of manganese oxides was investigated. The results of XRD, TEM, and SEM showed that the γ‐MnOOH prepared in shorter hydrothermal time was a mixture of nanocubes and nanowires, while in longer hydrothermal time was pure nanowires. Interestingly, increasing the pH of the reaction system from 8 to 10, the mixture of γ‐MnOOH nanowires and Mn₃O₄ nanoparticles was obtained. Alkali types also were discussed in directing the reaction and crystallization of manganese oxides. The product was pure γ‐MnOOH when using NaOH in the system, but a mixture of Mn₃O₄ and γ‐MnOOH was obtained when using NH₃ · H₂O.     

Control of Catalytic Activity Via Porosity,Chemical Composition,and Morphology of Nanostructured Porous Manganese Oxide Materials

This review concerns a summary of synthesis, characterization, and applications of octahedral molecular sieve (OMS) materials. These OMS systems have been the focus of our research program for over 20 years. This review primarily covers the past 10 years with an emphasis on the most recent developments in this area. Some current areas of concern include the systematic synthesis of well ordered materials, control of particle sizes, generation of nano‐size particles, and development of new synthetic methods like pulse laser deposition and epitaxial growth of oxidic materials. Applications include use of OMS in environmental catalysis, adsorption, clean energy materials, activation of the Greenhouse gas carbon dioxide, and selective oxidations. OMS catalysts are outstanding selective oxidation catalysts and can also drive total oxidations. The highly selective of OMS systems may be related to redox cycling and redox catalysis.     

水热处理对二氧化锰电容性能的影响

采用化学共沉淀法制备了二氧化锰。XRD测试表明，产物为α-MnO₂和γ-MnO₂无定形粉末，经水热处理后的二氧化锰晶化程度增加，为α-MnO₂和γ-MnO₂混晶相结构。电化学测试表明，二氧化锰单电极比容量达252.72 F·g^-1。经水热处理后单电极比容量达到299.15 F·g^-1，比处理前的提高18.37%。经400次循环后，水热处理后的样品比容量衰减极小。     

甲壳胺的结晶度和结晶形态

首次制得非晶甲壳胺样品,并给出了根据X射线衍射图精确计算甲壳胺结晶度的公式,计算得知甲壳胺的结晶度随脱酰度的增加(74%～85%)而增加,发现甲壳胺的结晶结构和结晶形态与制样条件有关。     

结晶碳酸钕的水热合成、外观形貌及其组成

Crystalline neodymium carbonates were prepared by treating the amorphous precipitate formed from the reaction between neodymium chloride and ammonium bicarbonate under hydrothermal condition. Their composition, morphology and crystal phase were identified by means of elemental analysis, SEM and XRD. It was found that Nd₂(CO₃)₃·2.5H₂O with tengerite-type structure and sheet morphology was obtained when the feed molar ratio(FMR=n_(NH4)2CO2/n_NdCl3)was 2 or 1.8 and hydrothermally treated at 150 ℃ for 12h. However, orthogonal NdOHCO₃ particles agglomerated with long rod crystals were formed when lowering FMR to 1.5 under the same hydrothermal condition. Phase transformation from tengerite-type Nd₂(CO₃)₃·2.5H₂O to orthogonal NdOHCO₃ was occurred when increasing hydrothermal temperature or prolonging hydrothermal time, which is beneficial to the preparation of neodymium hydroxyl-carbonate with neodymium oxide content higher than 70%.     

MgSO4·5Mg(OH)2·3H2O的水热合成及反应时间对其形貌的影响

Both whisker and nanometer MgSO₄·5Mg(OH)₂·3H₂O(MOS) were prepared by hydrothermal method at 140℃ for different times， using NaOH and MgSO₄·7H₂O as raw materials. The MgSO₄·5Mg(OH)₂·3H₂O part- icles were characterized by powder X-ray diffraction(XRD)，thermal analysis(TGA-DSC)， infrared spectroscopy(FT-IR)，transmission electron microscopy(SEM) and scanning electron microscopy(TEM). The size distribution in whisker-like and nanocrystalline materials are in the range of 10～50μm and 10～20nm respectively. The whisker MOS is metastable phase in MgSO₄-NaOH-H₂O system at 140℃，whereas nanometer MOS is stable phase.     

水热法合成羟基磷灰石的结构和形貌

羟基磷灰石是一种微溶于水的弱碱性磷酸钙盐 (Ｃａ10 (ＰＯ4 ) 6 (ＯＨ) 2 ,ＨＡ) [1] ,多用于人体硬组织(骨、牙 )的修复替换[2 ] 。与人类骨骼相比 ,致密羟基磷灰石仍然表现出较低的力学性能[3] 。由于针棒状的晶体具有较低的位错密度 ,较高的抗拉性能[4 ] 。近年来 ,针状或棒状羟基磷灰石的合成已引起广泛关注。合成ＨＡ的方法有固态反应法[5] 、液相沉淀法[6 ] 、溶胶 凝胶法[7,8] 及溅射法[9] 等 ,但只有少数几种方法能够对产物的形貌进行控制。虽然采用水热法在 2 0 0℃和 2ＭＰａ下合成了羟基磷灰石晶须[10 ] ,但实验步骤较为复杂 ,…     

MgSO_4·5Mg(OH)_2·3H_2O的水热合成及反应时间对其形貌的影响(英文)

０IntroductionWhiskerswithhighaspectratiohavebeenexten－sivelyusedascompositematerialsinalloys，ceramics，cementandplastic犤１～５犦，sincetheyhavespecificdesirepropertiessuchashighmeltingpoint，lowdensityandhighmodulus犤６犦．Magnesiumoxysulfate（MOS）com－poundshowsthehighcrystallinityandaspectratiotomakeitapotentialreinforcingmaterialforplastics，resinandrubber犤７，８犦．Inpastyears，MgSO４·５Mg（OH）２·３H２Ohasbeensynthesizedbyhydrothermalreactionusingmagnesiumhydroxideandmagnesium…     

Antimony‐Doped Tin Oxide Nanocrystals: Synthesis and Solubility Behavior in Organic Solvents

The right mix : SnO₂:Sb nanocrystals (NCs) can be solubilized into organic solvents with a suitable solvent/surfactant combination to achieve a stable colloid (see picture). A single synthesis route and different solvent/amphiphilic molecule pairs are used to obtain soluble NC colloids, instead of requiring several syntheses to obtain soluble NCs in different solvents.

     

Electrochemically Prepared Manganese Oxide as a Cathode Material for a Microbial Fuel Cell

This work describes the construction of a mediatorless microbial fuel cell (MFC) using the microorganism Acetobacter aceti as the biocatalyst in the anode compartment with glucose as a fuel. The periplasmic membrane bound pyrroloquinoline quinone (PQQ) containing enzymes of these genera provide fast and highly efficient oxidation of a wide variety of substrates and helps in the direct routing of electrons to the anode. We describe our preliminary findings with regard to the use of electrochemically deposited manganese oxide films on carbon substrates as cathode materials in MFCs. Manganese oxide was electrochemically deposited on carbon paper in the presence and in the absence of the surfactant, sodium lauryl sulfate (SLS). Electrochemical characterizations of the electrodeposited films are carried out by cyclic voltammetry and impedance spectroscopy. Structural characterization of the film is carried out by XRD, XPS, and SEM. The XPS studies reveal that the presence of Mn⁴⁺ (as MnO₂) in the absence of SLS and Mn^3+/2+ (as Mn₃O₄or Mn₂O₃ or MnOOH) ion in the presence of SLS. The power output obtained from MnO₂ cathode was 666 ± 9 mW m^?3 and it is the highest value reported for MFCs with cubical configuration with the same cathode.     

Na2SO4辅助水热合成SnO2纳米晶

系统地研究了以SnCl₄·5H₂O为原料，以Na₂SO₄为矿化剂，采用水热法在较低温度下和较短的反应时间内制备结晶良好并均匀分散的SnO₂纳米晶。采用X射线衍射(XRD)、透射电子显微镜(TEM)、红外光谱(IR)等技术对水热反应的晶化过程进行了分析。结果表明：在Na₂SO₄存在的情况下，在120 ℃反应4 h 即可制备得到晶粒细小，分散性能良好的SnO₂纳米晶。XRD衍射峰峰宽随水热温度的升高或反应时间的延长而变窄，结晶性提高。TEM结果表明产物颗粒小、分散性能良好。水热反应温度和反应时间对产物结晶度和粒径有明显的影响。对Na₂SO₄在反应过程中的作用机理进行了分析。     

水热合成法对纳米氧化锡粉体粒径和形貌的控制研究

利用氯化锡和氨水作为反应试剂,通过水热合成技术制备了近球形,棒状,椭球形,六角形等粉体形貌和粒径范围从4 nm至120 nm的纳米氧化锡粉体,并对水热合成条件对粉体的粒径和形貌的影响进行了研究。所制备的粉体的XRD分析结果显示,合成温度在160 ℃以上并且合成时间在3 h以上,粉体全部具有氧化锡晶体结构。利用透射电镜对粉体的粒径和形貌观察发现,二氧化锡粉体的形貌和粒径可通过改变溶液的浓度,合成温度与合成时间进行有效的控制,其中合成温度与溶液浓度不仅可以控制合成粉体的粒径,而且可以控制粉体的形貌。     

水热法生长方式对ZnO纳米棒阵列结构和性能的影响

本文系统地比较了三种方式制备的ZnO纳米棒阵列的结构和性能的异同.根据水热法生长液中碱来源的不同,ZnO纳米棒阵列的生长方式分为三种:N方式(氨水)、H方式(六次甲基四胺)和NH方式(两次N方式和一次H方式).通过扫描电子显微镜,对这三种方式生长的ZnO纳米棒阵列形貌进行了表征.此外,利用X射线衍射仪、透射电子显微镜和激光拉曼光谱对ZnO的结晶性能进行比较.结果表明,ZnO纳米棒阵列的取向性N≈NH>H,ZnO的晶体质量H>NH>N.NH方式综合N方式和H方式的优势,得到了取向性和晶体质量优良的ZnO纳米棒阵列.这将为在进一步应用中有效地选择ZnO纳米棒阵列的制备方式提供重要信息.     

聚偏氟乙烯取向薄膜的结晶形态

本文用小角激光散射法研究了聚偏氟乙烯薄膜在拉伸取向过程中晶体形态及结构的变化。拉伸使球晶形变为椭球,同时伴随着局部熔融与重结晶过程,散射图案由原来的四叶瓣发展为八叶瓣。红外测量及X-射线衍射分析表明,拉伸引起分子链构象改变,使晶型发生了转变。     

不同晶型和形貌MnO2纳米材料的可控制备

以KMnO4为锰源, 采用水热技术在180 ℃条件下于不同种类酸溶液中可控制备了α-, β-, δ-MnO2, 系统研究了 K＋, H＋及阴离子对制备产物MnO2晶型和形貌的影响. 研究结果表明, K＋与H＋在反应体系中对于制备产物晶相的生成形成竞争性影响, 其量的大小对制备产物晶型具有控制作用, 高浓度K＋离子有助于生成α-MnO2, 而高浓度的H＋有利于生成β-MnO2; 阴离子的种类和浓度对制备产物MnO2的晶型和形貌无显著影响. 在对制备产物进行XRD, SEM和元素分析的基础上, 提出了不同晶型和形貌MnO2的可能形成机理.     

Effect of crystallization temperature on the crystalline phase content and morphology of poly(vinylidene fluoride)

The effect of temperature on the crystallization of α, β, and γ phases of PVDF from dimethylacetamide (DMA) solution was studied. Variation in the crystallinity content of these three phases was obtained as a function of temperature using infrared spectroscopy, differential scanning calorimetry (DSC) and x-ray diffraction techniques. Such variation is related to the dependence of the crystallization rate of each phase with temperature, and allowed a better understanding of some results found in the literature about the crystallization and interconversion of these phases. Micrographs of samples present morphologies that corroborate with the proposed explanations. © 1994 John Wiley & Sons, Inc.     

Preparation,Morphology, and Structure of Thermotropic Liquid Crystalline Polyester-imide/Phenol-formaldehyde Resin Blends

As a novel toughening agent, thermotropic liquid crystalline polymers (TLCPs) possess excellent properties of high strength, high modulus, low expanding coefficient, and high thermal stability. In this study, a thermotropic liquid crystalline poly(ester-imide) derived from N,N’-hexane-1,6-diylbis(tri-millitimide) (IA6), p-hydroxylbenzoic acid (PHB), and 4,4’-dihydroxybenzophenone (DHBP) was synthesized by the Higashi's direct polycondensation method. The structure and properties of the TLCP were studied using Fourier transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetic analyses (TGA), polarized light microscopy (POM), and wide angle X-ray diffraction (WAXD). The results revealed that the synthesized polyester-imide is a nematic TLCP with good thermal stability and its starting decomposition temperature is up to 439°C. Additionally, polymer blends of phenol-formaldehyde (PF) resin with different contents of polyester-imide were prepared and characterized by POM and WAXD. POM results demonstrated that two-step blending is an ideal method for blending TLCP and PF resin. By this method, continuous filamentous stripes can be clearly observed at 230°C for TLCP/PF blend of 10 wt% poly(ester-imide).     

Thermally Induced Growth of ZnO Nanocrystals on Mixed Metal Oxide Surfaces

An in situ method for the growth of ZnO nanocrystals on Zn/Al mixed metal oxide (MMO) surfaces is presented. The key to this method is the thermal treatment of Zn/Al layered double hydroxides (Zn/Al LDHs) in the presence of nitrate anions, which results in partial demixing of the LDH/MMO structure and the subsequent crystallization of ZnO crystals on the surface of the forming MMO layers. In a first experimental series, thermal treatment of Zn/Al LDHs with different fractions of nitrate and carbonate in the interlayer space was examined by thermogravimetry coupled with mass spectrometry (TG‐MS) and in situ XRD. In a second experimental series, Zn/Al LDHs with only carbonate in the interlayer space were thermally treated in the presence of different amounts of an external nitrate source (NH₄NO₃). All obtained Zn/Al MMO samples were analysed by electron microscopy, nitrogen physisorption and powder X‐ray diffraction. The gas phase formed during nitrate decomposition turned out to be responsible for the formation of crystalline ZnO nanoparticles. Accordingly, both interlayer nitrate and the presence of ammonium nitrate led to the formation of supported ZnO nanocrystals with mean diameters between 100 and 400 nm, and both methods offer the possibility to tailor the amount and size of the ZnO crystals by means of the amount of nitrate.     

Impacts of Hydrothermal Treatments on the Morphology,Structural Characteristics,and In Vitro Digestibility of Water Caltrop Starch

The influence of hydrothermal treatments on the structural properties and digestibility of water caltrop starch was investigated. Scanning electron microscopy (SEM) showed some small dents on the surface of starch granules for samples treated with heat moisture treatment (HMT), but not for samples treated with annealing (ANN) which generally showed smoother surfaces. The gelatinization temperature of starch was generally increased by hydrothermal treatments, accompanied by a trend of decreasing breakdown viscosity. These results implied the improvement of thermal and shearing stability, particularly for HMT in comparison to ANN. After being cooked, the native and ANN-modified water caltrop starch granules were essentially burst or destroyed. On the other hand, the margin of starch granules modified by HMT and dual hydrothermal treatments remained clear with some channels inside the starch granules. X-ray diffraction revealed that the crystalline pattern of water caltrop starch changed from the C_A-type to the A-type and the relative crystallinity reduced with increasing moisture levels of HMT. Results of ANN-modified water caltrop starch were mostly similar to those of the native one. Moreover, water caltrop starch modified with HMT20 and dual modification contained a pronouncedly higher resistant starch content. These results suggested that HMT, ANN, and dual modification effectively modified the functional properties of water caltrop starch.