水热法制备SnO2/α-Fe2O3纳米复合材料

用α-Fe2O3纳米粒子作为前驱物,以SnC l4和NaOH作为反应试剂,通过简单的水热法制备了SnO2/α-Fe2O3纳米复合材料。SnO2/α-Fe2O3纳米复合材料具有有趣的形貌:直径约为20nm的SnO2纳米棒以α-Fe2O3纳米粒子为中心向四周辐射生长。利用X-ray粉末衍射(XRD),透射电镜(TEM)和扫描电镜(SEM)等测试手段对样品的成份、结构、形貌和尺寸进行了表征,初步探讨了SnO2/α-Fe2O3纳米复合材料的形成机理。     

球形α-Fe2O3纳米粉体的超声水解法合成与表征

0引言纳米Fe2O3因在磁性、气敏、催化、染料、抗腐蚀等领域显示出广阔的应用前景而备受瞩目[1￣3]。Fe2O3存在α-Fe2O3、β-Fe2O3、γ-Fe2O3、ε-Fe2O3等多种构型,它们在性能上差异较大,如α-Fe2O3具有良好的磁性和气敏性,可用作气敏材料和磁记录材料;γ-Fe2O3具有独特的电、磁、光等性质而在信息存贮器、彩色显像管、生物处理、磁制冷等方面得到广泛应用。由于其各种应用都与性能有直接关系,所以研究Fe2O3的制备方法具有重要意义。尽管不少学者采用溶胶-凝胶法[4]、电化学合成法[5]、微波辐射法[6]、燃烧合成法[7]、水热法等[8]不…     

碳纳米管/氧化锌纳米复合材料的制备及其形貌控制

0引言碳纳米管(CNT)优良的力学、电学、热学性能使其在材料、储能、传感等许多领域都有广泛的应用前景,近年来,以碳纳米管为载体制备的纳米复合材料因其独特的应用潜力而受到广泛关注:彭峰等[1]用FeSO4-H2O2体系修饰碳纳米管,成功地制备了由碳纳米管负载的Fe2O3催化剂;Chen等[2]用溶胶凝胶法制备了CNT/SnO复合材料,作为Li离子电池阴极材料,测试表明它的电化学性能比单独的CNT和SnO材料都有所增强;Jitianu等[3]用溶胶凝胶和水热方法得到不同形貌的TiO2/CNT复合结构,这种新型的纳米复合材料在光催化方面有着重要的应用前景。纳米Z…     

复合固体超强酸SO2-4/TiO2-Fe2O3催化合成丁酸异丁酯

采用溶胶-凝胶法制备的复合固体超强酸催化剂SO2-4/TiO2-Fe2O3催化合成丁酸异丁酯[1],结果表明物质的量比n(Ti)∶n(Fe)＝2∶1时催化剂活性最高,这与文献结果[2]有所不同.     

碳网封装Fe3O4/还原氧化石墨烯锂离子电池负极材料

通过简单有效的溶剂热法将Fe3 O4颗粒与氧化石墨烯(GO)进行复合,得到Fe3 O4/GO复合材料.将Fe3 O4/GO与葡萄糖进行碾磨.在高温下将GO还原成还原氧化石墨烯(rGO)的同时在Fe3 O4/rGO表面制备网状结构的导电碳层,得到三维网络传输结构C/Fe3 O4/rGO复合材料.由碳网和还原氧化石墨烯组成...     

醋酸钾溶液体系中α-Fe_2O_3纳米微球的离子液体辅助合成及气敏性能研究

以Fe Cl3·6H2O和CH3COOK为反应物,以离子液体1-丁基-3-甲基咪唑氯化物([Bmim]Cl)为结构导向剂和表面活性剂,采用水热合成法在150℃反应8 h制备出结晶度好、形貌规整,直径为10~30 nm的α-Fe2O3纳米微球.考察了[Bmim]Cl的添加量对氧化铁形貌和气敏性能的影响.气敏性能测试结果表明:当离子液体添加量为12 mmol时,α-Fe2O3纳米微球对乙醇的气敏性能最佳.在工作温度为300℃时,对50μL/L乙醇的灵敏度达到7.56,是不添加离子液体时制备的α-Fe2O3的5.6倍,在10~200μL/L的检测范围内灵敏度与浓度具有良好的线性关系(R=98.8%),并且具有良好的选择性和稳定性.本文还详细探讨了α-Fe2O3纳米微球对乙醇的敏感机理,以及工作温度对其气敏性能的影响.     

经Fe(NO3)3处理的Fe3O4纳米微粒分析

Fe3O4纳米微粒是一种制备磁性液体的重要组成部分。但Fe3O4纳米微粒不稳定,极易氧化成γ-Fe2O3,其磁化强度也会明显降低[1-2]。铁氧体还易为酸溶解,化学反应式为:MFe2O4 8H M2 2Fe3 4H2O式中M为Fe、Co、Mn等二价金属。在Massart法制备酸性离子型磁性液体的方法中,采用了Fe(NO     

基于溶液配位化学过程调控的中空单晶氧化铁纳米材料

本文简要综述了本课题组近年来在单晶氧化铁空心纳米结构制备与生长机理研究方面的相关工作.通过采用磷酸根与硫酸根的双阴离子调节,结合反应时间、反应温度等条件的改变,实现了对α-Fe2O3单晶空心纳米结构形貌、尺寸和表面结构的良好调控,并提出一种针对非层状结构纳米环/纳米管新颖生长机理,即"配位辅助的定向溶解机理".以所制备的α-Fe2O3为前驱体,采用气相还原方法,成功制备得到了系列单晶Fe3O4和γ-Fe2O3管状及环状纳米结构,并对单个Fe3O4纳米环的磁学行为进行了考察.     

纳米化Fe2O3粉体的制备与表征

采用分析纯FeCl3·6H2O和NH3·H2O为主要原料,以均匀沉淀法制备了Fe2O3纳米粉体.通过X射线衍射(XRD)、红外光谱(IR)、扫描电子显微镜(SEM)及差热分析(DTA)等手段研究了热处理温度、分散剂、反应pH值对Fe2O3相变、结构、形貌及纳米属性的影响.结果表明:纳米化增大了Fe2O3的表面能,γ-Fe2O3转变为α-Fe2O3的温度仅为238.2 ℃,比常规粉体降低了约312 ℃;由于量子尺寸效应和表面效应,使用分散剂后α-Fe2O3纳米粉体的分散性、均匀性得到改善,粒径下降,Fe-O键伸缩及弯曲振动IR吸收频率发生蓝移;尤其是硬脂酸钠分散后α-Fe2O3的Fe-O伸缩、弯曲振动吸收频率分别蓝移11.57、10.93 cm-1;获得了液相均匀沉淀法制备Fe(OH)3纳米粉体的最佳工艺条件.     

3D α-Fe_2O_3/掺氮石墨烯/碳纳米管复合材料及其储锂性能

针对α-Fe2O3负极在充放电过程中存在的体积膨胀及首次库伦效率低等主要问题,本文采用简单的水热法制备出具有三维多孔结构的α-Fe2O3/掺氮石墨烯(N-GNS)/碳纳米管(CNTs)复合材料。XRD,SEM,TEM及XPS等测试结果表明碳纳米管成功插入到掺氮石墨烯片层间,暴露N-GNS表面的晶格缺陷,为α-Fe2O3晶体生长提供了大量成核位点。粒径大小为30~70 nm的α-Fe2O3颗粒均匀锚定于N-GNS/CNTs三维复合碳载体内进行高效储锂反应。电化学测试结果显示,这种三维复合结构有效改善了α-Fe2O3/GNS负极的电化学性能。     

电感耦合等离子体原子发射光谱(ICP-AES)法测定铸造用硅砂中的Fe2O3、Al2O3、CaO、MgO、TiO2、K2O、Na2O

建立了电感耦合等离子体原子发射光谱(ICP-AES)法测定铸造用硅砂中Fe_2O_3、Al_2O_3、CaO、MgO、TiO_2、K_2O、Na_2O的方法。研究了溶样方法的选择优化,采用硝酸、氢氟酸溶样,冒高氯酸处理,通过元素分析线的选择,基体和共存元素影响的消除,在最佳的仪器分析条件下得出了方法的线性范围、相关系数及检出限。用硅砂3个梯度含量的标准物质的分析结果评价方法的准确度和精密度。方法的检出限Fe为0.012μg/mL、Al为0.032μg/mL、Ca为0.27μg/mL、Mg为0.003 2μg/mL、Ti为0.002 1μg/mL、K为0.16μg/mL,Na为0.000 44μg/mL。5次数据的相对标准偏差说明方法稳定性较好。方法适用于铸造用硅砂中Fe_2O_3、Al_2O_3、CaO、MgO、TiO_2、K_2O、Na_2O含量的测定。     

Nitroformonitrile oxide

Two methods for the generation of nitroformonitrile oxide (NFNO) were proposed, namely, by dehydration of dinitromethane and by nitration of 2-methyl-1-nitro-1-propene. NFNO was identified as its cyclodimerization product, dinitrofuroxan.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 722–726, April, 1995.     

整体式三氧化钨/氧化石墨烯气凝胶增强可见光光催化氧化NO性能（英文）

近年来,光催化技术在去除以NO为代表的诸多室内气体污染物方面展现出巨大的潜力.单质铋和铋系氧化物,非金属氧化物以及钙钛矿等众多半导体光催化材料均具有优异的NO降解效率,但很难控制氧化产物.因而会生成大量毒性更强的中间产物NO2造成二次污染.因此,寻求一种清洁、高效,且具有良好选择性的光催化材料成为了亟待解决的问题.六方相三氧化钨(h-WO_3)的价带位置较正,氧化电位较高,具有很强的氧化能力,是一种良好的氧化性光催化半导体材料.然而,WO_3催化材料多为粉末状,不仅容易团聚,难以回收利用并且会堵塞检测气路.同时,WO_3本身存在的电子-空穴复合率高,弱的可见光响应性等问题使其光催化活性较低.因而,制备具有良好可见光响应,高电子-空穴分离效率的一体化WO_3材料是其广泛应用前急需解决的问题.而石墨烯气凝胶是理想的催化剂载体,其较高的比表面积以及多孔状结构可有效地增加催化剂的暴露面积,提升催化剂利用率;更重要的是,氧化石墨烯(GO)具有极高的导电率,可作为电子受体加速电子-空穴对的分离而提升光催化活性.因此,以GO作为基体材料,构建WO_3/GO气凝胶一体化材料有良好的应用前景.然而,现在还鲜见有关宏观WO_3/GO气凝胶光催化降解NO的报道.本文以偏钨酸铵为钨源,利用体积分数为25%的冰醋酸在180ⅹC条件下制备六方相三氧化钨.通过机械搅拌以及冷冻干燥法制备WO_3/GO气凝胶.经光催化氧化NO测试发现其可见光下降解率可达51%,是WO_3粉体的3.3倍,并且NO_2生成率仅为0.5%,远远低于其他相关光催化材料.采用了X射线衍射(XRD),透射电镜(TEM),X射线光电子能谱(XPS),紫外-漫反射分光光度计(UV-DRS),傅里叶红外光谱(FTIR)和荧光光谱(PL)等手段研究了其光催化性能提高的原因.XRD测试显示,复合材料主体为h-WO_3,说明GO的引入并未破坏材料晶体结构;TEM和BET测试发现,在加入GO之后h-WO_3分散性变好,比表面积变大,从而可暴露更多的光催化活性位点.UV-DRS吸收光谱可以看到WO_3/GO气凝胶材料的吸收边发生了显著的红移,其禁带宽度从3.44 eV减小到3.16 eV,这可能是GO影响了WO_3的能带结构所致.同时PL结果表明,引入了GO之后,气凝胶材料的非辐射跃迁程度明显减小表明其电子-空穴对的复合得到了显著抑制,电子迁移显著加强.综合以上结果,可以得到WO_3/GO光催化性能提升以及良好的产物选择性的原因.首先,三维气凝胶材料的结构提升了催化剂的有效利用率,较大的比表面积暴露了更多的活性位点.其次,GO的引入减小了复合材料的禁带宽度,并使其吸光性能有所改善,产生了更多的光生电子和空穴.最后,GO本身极高的导电性,使光生电子-空穴对得以有效的分离,一方面,电子通过GO迅速转移到材料表面来参与光催化反应;另一方面,电子的快速转移抑制了电子-空穴对的复合,进而提高光催化性能,而且较正的价带位置保证了NO较为彻底的氧化为NO3–.因此,相比传统粉末WO_3催化材料,一体化的WO_3/GO气凝胶不仅显著提升了NO降解率,同时严格抑制了毒副产物NO2的生成,同时更具有容易回收利用,不存在二次污染的优点.综上所述,WO_3/GO一体化气凝胶光催化材料有望在环境净化与能源领域表现出良好的应用前景.     

Versatile PEG-derivatized phosphine oxide ligands for water-dispersible metal oxide nanocrystals

We report the simple synthesis of poly(ethylene glycol)(PEG)-derivatized phosphine oxide ligands for water-dispersible metal oxide nanocrystals.     

Copper oxide nanocrystals

It is well-known that inorganic nanocrystals are a benchmark model for nanotechnology, given that the tunability of optical properties and the stabilization of specific phases are uniquely possible at the nanoscale. Copper (I) oxide (Cu(2)O) is a metal oxide semiconductor with promising applications in solar energy conversion and catalysis. To understand the Cu/Cu(2)O/CuO system at the nanoscale, we have developed a method for preparing highly uniform monodisperse nanocrystals of Cu(2)O. The procedure also serves to demonstrate our development of a generalized method for the synthesis of transition metal oxide nanocrystals. Cu nanocrystals are initially formed and subsequently oxidized to form highly crystalline Cu(2)O. The volume change during phase transformation can induce crystal twinning. Absorption in the visible region of the spectrum gave evidence for the presence of a thin, epitaxial layer of CuO, which is blue-shifted, and appears to increase in energy as a function of decreasing particle size. XPS confirmed the thin layer of CuO, calculated to have a thickness of approximately 5 A. We note that the copper (I) oxide phase is surprisingly well-stabilized at this length scale.     

Pristine graphite oxide

Graphite oxide (GO) is a lamellar substance with an ambiguous structure due to material complexity. Recently published GO-related studies employ only one out of several existing models to interpret the experimental data. Because the models are different, this leads to confusion in understanding the nature of the observed phenomena. Lessening the structural ambiguity would lead to further developments in functionalization and use of GO. Here, we show that the structure and properties of GO depend significantly on the quenching and purification procedures, rather than, as is commonly thought, on the type of graphite used or oxidation protocol. We introduce a new purification protocol that produces a product that we refer to as pristine GO (pGO) in contrast to the commonly known material that we will refer to as conventional GO (cGO). We explain the differences between pGO and cGO by transformations caused by reaction with water. We produce ultraviolet-visible spectroscopic, Fourier transform infrared spectroscopic, solid-state nuclear magnetic resonance spectroscopic, thermogravimetric, and scanning electron microscopic analytical evidence for the structure of pGO. This work provides a new explanation for the acidity of GO solutions and allows us to add critical details to existing GO models.     

Graphene oxide nanocolloids

Graphene oxide (GO) nanocolloids-sheets with lateral dimension smaller than 100 nm-were synthesized by chemical exfoliation of graphite nanofibers, in which the graphene planes are coin-stacked along the length of the nanofibers. Since the upper size limit is predetermined by the diameter of the nanofiber precursor, the size distribution of the GO nanosheets is much more uniform than that of common GO synthesized from graphite powders. The size can be further tuned by the oxidation time. Compared to the micrometer-sized, regular GO sheets, nano GO has very similar spectroscopic characteristics and chemical properties but very different solution properties, such as surface activity and colloidal stability. Due to higher charge density originating from their higher edge-to-area ratios, aqueous GO nanocolloids are significantly more stable. Dispersions of GO nanocolloids can sustain high-speed centrifugation and remain stable even after chemical reduction, which would result in aggregates for regular GO. Therefore, nano GO can act as a better dispersing agent for insoluble materials (e.g., carbon nanotubes) in water, creating a more stable colloidal dispersion.