聚苯乙烯-SiO2/NiFe2O4磁性微球的制备与表征

以NiFe2O4纳米粒子作磁性载体、苯乙烯(ST)、正硅酸乙酯(TEOS)为原料,KH-570为交联剂,采用乳液聚合法制备了聚苯乙烯-SiO2/NiFe2O4磁性微球材料。通过VSM、FT-IR、SEM、TG-DTA、溶剂抽提等方法对磁性微球材料进行了测试。制备的NiFe2O4粒子为面心立方结构,NiFe2O4纳米颗粒及聚苯乙烯-SiO2/NiFe2O4磁性微球具有超顺磁性。聚苯乙烯-SiO2/NiFe2O4磁性微球以SiO2/NiFe2O4为核、PS为壳,通过KH-570接枝到SiO2/NiFe2O4上,核壳间以共价键相接的包覆型纳米粒子,平均直径为100nm左右,具有良好的热稳定性和耐溶剂性能。热重(TG)分析表明,磁性聚苯乙烯微球磁性物质质量分数为28.8%。     

Fe-Ni/NiFe_2O_4纳米复合颗粒的制备与磁性研究

结合共沉淀法和氢气还原法成功制备出FeNi/NiFe2O4纳米复合颗粒,所制备的纳米复合颗粒包含NiFe2O4和Fe-Ni合金,其中Fe-Ni合金具有体心立方和面心立方两种结构。用XRD和TEM对所得样品进行结构分析。用SQUID测量样品在室温时的磁滞回线,发现Fe-Ni/NiFe2O4纳米复合颗粒的矫顽力和饱和磁化强度与制备态NiFe2O4纳米颗粒相比随着退火时间的增加呈现出逐渐增加的趋势。为了进一步研究所制备的纳米复合颗粒的磁性特征,测量退火时间相同而退火温度不同的两个样品在零磁场冷却(ZFC)和带磁场冷却(FC)条件下的M-T曲线。     

共沉淀法制备纳米Fe3O4及其对橙黄Ⅱ的降解

通过共沉淀法制备Fe3O4纳米颗粒,采用X射线衍射(XRD)、扫描电子显微镜(SEM)和比表面孔隙分析(BET)对样品进行表征。以合成的纳米Fe3O4催化H2O2氧化降解橙黄Ⅱ,考察了共沉淀法制备过程中的Fe2+/Fe3+的摩尔比、反应温度、pH值、Fe离子浓度等因素对Fe3O4催化性能的影响。结果表明在Fe2+/Fe3+的摩尔比为3∶4、反应温度80℃、pH值为10、Fe离子浓度为0.1mol·L-1的条件下制备出的Fe3O4纳米颗粒催化活性最高,其粒径为20nm左右。并且未干燥的磁流体对橙黄Ⅱ的降解效率明显高于Fe3O4粉体。     

Fe2O3纳米粒子的醋酸改性对其催化高氯酸铵热分解的影响

利用表面改性法对Fe2O3纳米粒子进行醋酸改性,用TEM和纳米粒度测试仪对Fe2O3纳米粒子进行了形貌和粒度表征,用FTIR和XPS对改性后的Fe2O3纳米粒子进行了结构表征,用DTA研究了醋酸改性处理对Fe2O3纳米粒子的高氯酸铵(AP)热分解催化性能的影响.结果表明,用凝胶-溶胶法制备了平均粒径为40nm,窄粒度分布的Fe2O3纳米粒子,醋酸改性处理改善了Fe2O3纳米粒子的分散性.FTIR和XPS结果表明,Fe2O3纳米粒子与醋酸分子发生了化学键合.DTA结果表明,Fe2O3纳米粒子的醋酸改性能提高Fe2O3纳米粒子的AP热分解催化性能;随着Fe2O3纳米粒子含量的增加,醋酸改性的效果越明显.     

乙二醇体系中纳米Cu2O的制备及其性能研究

以Cu(NO3)2为原料,乙二醇为溶剂和还原剂,制备了不同形貌的纳米Cu2O.通过X射线衍射,透射电子显微镜对产物进行了表征,并用热分析法考察了纳米Cu2O对高氯酸铵热分解的催化作用.结果表明,在乙二醇体系中少量水的加入对产物的形貌有着重要的影响.当加入少量水时,产物形貌由不规则状变为短棒状.不同形貌的纳米Cu2O均能强烈催化高氯酸铵的热分解,分散性较好的Cu2O使高氯酸铵的高温分解温度下降了约104℃,分解放热量由590J/g增至1450J/g.     

微乳液法制备NiFe_2O_4/SiO_2核壳纳米复合粒子

用微乳液法制备了以NiFe2O4为核,SiO2为包覆层的核壳型纳米复合粒子NiFe2O4/SiO2。用XRD,FT-IR,SEM,TEM和EDS等技术手段对样品的结构和微观形貌进行了表征,用VSM测试了样品的磁性能。结果表明,合成的纳米复合材料的NiFe2O4/SiO2平均粒径为约40 nm,饱和磁化强度为12.97 emu/g。与未包覆的NiFe2O4相比,NiFe2O4/SiO2团聚趋势减弱,其饱和磁化强度下降,矫顽力基本不变,仍保持了良好的超顺磁性。     

单分散Fe3O4@SiO2/Au复合纳米颗粒的制备

制备了尺寸为30nm,具有磁响应的单分散Fe3O4@SiO2/Au核壳纳米颗粒,并研究其光学性质。首先利用热分解法制备油酸修饰的Fe3O4纳米粒子,再用反相微乳法制备Fe3O4@SiO2纳米粒子,最后利用表面修饰的氨基还原性,获得Fe3O4@SiO2/Au核壳复合纳米颗粒。分别用TEM、XRD、Zeta电位与粒度分析仪对产物形貌、结构、表面电位和粒径分布进行表征,用紫外-可见分光光度计对光学性质进行了测试。     

片状磁性纳米TiO2/SiO2/NiFe2O4制备及光催化性能

以锐钛矿磁性纳米TiO2/SiO2/NiFe2O4(TSN)为原料,采用水热法制备了片状磁性纳米TSN.利用XRD、TEM等技术对样品进行了表征.水热法处理后核壳结构的TSN部分转变为片状,催化剂磁性增强.以亚甲基兰溶液为模拟水样测试了样品的光催化性能,考察了催化剂加入量、反应时间、pH值等因素的影响.实验表明:片状磁性纳米TSN光催化性能明显优于粒状TSN.片状TSN具有良好的吸附性能,提高了光催化反应的初始速率.用于处理亚甲基兰废水时受pH值的影响较小,1小时的脱色率在90%以上.     

金属相20Ni-80Cu表面包覆NiFe2O4尖晶石对15（20Ni-80Cu）/85（NiFe2O4-10NiO）金属陶瓷腐蚀性能的研究

金属陶瓷金属相优先腐蚀是目前惰性阳极工业化难点之一,在金属相表面包覆NiFe2O4尖晶石来提高其耐高温熔盐腐蚀性能。包覆实验结果显示,包覆后的颗粒尺寸为2～5μm,且有团聚现象,金属相20Ni-80Cu表面除形成NiFe2O4尖晶石外,可能还含有NiFe2O4-x、Cu2O、NiO、CuxNi1-x、NiyFe1-yFe2O4-a和NizFe1-zO。腐蚀实验表明,金属表面包覆10%、20%、30%、40%和50%NiFe2O4尖晶石后制备的金属陶瓷惰性阳极样品其金属腐蚀层厚度都在20～50μm,其年腐蚀率分别为1.89、1.73、1.65、1.58和2.03cm/a,未包覆金属陶瓷惰性阳极金属腐蚀层厚度为200μm和年腐蚀率为4.15cm/a,说明金属表面包覆NiFe2O4尖晶石能提高惰性阳极的抗熔盐腐蚀性能。     

低温固相反应工艺对NiFe_2O_4纳米粉体形貌的影响

为了改善NiFe2O4纳米粉体气敏性,采用低温固相反应法制备了不同形貌的NiFe2O4纳米粉体.以FeSO4·7H2O、NiSO4·6H2O和NaOH作为反应物,充分研磨制备前驱体,通过先抽滤后600℃热处理和先600℃热处理后抽滤制备了两种NiFe2O4纳米粉体,通过X射线衍射和扫描电镜考察了不同制备工艺对纳米晶粒尺寸及形貌的影响.XRD和SEM分析结果表明:两种制备工艺均能生成NiFe2O4尖晶石相.先抽滤后热处理制备的NiFe2O4纳米粉体颗粒尺寸约为80nm,颗粒呈立方体结构.而先热处理后抽滤制备的NiFe2O4纳米粉体,由于热处理过程中存在Na2SO4相,使得NiFe2O4纳米粉体颗粒呈圆形片状结构分布,颗粒尺寸为50nm,厚度约10nm.     

Synthesis, characterization and catalytic activity of CdO nanocrystals

In this paper, we report the synthesis of nanocrystalline cadmium oxide (CdO) and its characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Its catalytic activity was investigated on the thermal decomposition of 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), ammonium perchlorate (AP), hydroxyl terminated polybutadiene (HTPB) and composite solid propellants (CSPs) using thermogravimetric analysis (TG), simultaneous thermogravimerty and differential scanning calorimetry (TG-DSC) and ignition delay measurements. Kinetics of thermal decomposition of AP + CdO has also been investigated using model free (isoconversional) and model-fitting approaches which have been applied to data for isothermal TG decomposition. All these studies show enhancement in the rate of decomposition of AP, HTPB and CSPs but no effect on HMX. The burning rate of CSPs has also been found to be increased with CdO nanocrystals.     

Synthesis and characterization of KNd2Ti3O9.5 nanocrystal and its catalytic effect on decomposition of ammonium perchlorate

A novel kind of perovskite type oxide KNd₂Ti₃O_9.5 nanocrystals with an average size of 12 nm were successfully fabricated by a stearic acid sol–gel method (SAM) using Ti(OBu)₄, KOH, Nd₂O₃ and stearic acid as the raw materials. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the products. The catalytic effect of the KNd₂Ti₃O_9.5 nanoparticles on thermal decomposition of ammonium perchlorate (AP) was investigated by differential thermal analysis (DTA) and thermal gravimetry (TG) experiments. Results indicated that the obtained KNd₂Ti₃O_9.5 nanocrystals took on cubic structure and presented both good dispersibility and uniform crystallite size. Also, they have an intense catalytic effect on the thermal decomposition of AP. Adding 2% of KNd₂Ti₃O_9.5 nanoparticles to AP can obviously decrease the thermal decomposition temperature of AP by 50 °C, increase the heat of decomposition from 590 J g⁻¹ to 1659 J g⁻¹ and obviously quicken the decomposition reaction rate.     

Cu/Fe hydrotalcite derived mixed oxides as new catalyst for thermal decomposition of ammonium perchlorate

Cu/Fe mixed oxides (Cu/Fe-MOs) were prepared by calcination of Cu/Fe hydrotalcite (Cu/Fe-HT) precursors. They were used as new catalyst for thermal decomposition of ammonium perchlorate (AP) and their catalytic activity was studied by thermal gravimetric and differential thermal analysis. With the addition of 4 wt.% Cu/Fe-MOs, thermal decomposition of AP was accelerated by 104 °C. Higher catalyst addition favors further decomposition of AP. The catalytic activity order is: Cu/Fe-MOs-500 > Cu/Fe-MOs-800 > CuO·Fe₂O₃. The proposed catalytic mechanism is the presence of O₂⁻ on the surface of Cu/Fe-MOs which can simplify thermal decomposition of AP.     

Nano-metal oxide: potential catalyst on thermal decomposition of ammonium perchlorate

In this review, an attempt to collect the summarised data of literature on catalytic effect of nano-oxides, such as mono oxides, mixed oxide, binary and ternary ferrites and rare earth metal oxides on the thermal decomposition of ammonium perchlorate (AP) is made. Influence of size effect of oxides on thermal decomposition of AP and comparison of bulk and nanosized oxides is also discussed here. Several experimental results revealed that due to small size and large surface area nanosized metal oxides are more potential catalysts on thermal decomposition of AP compared to their bulk size oxides.     

Preparation of nanometer CuFe2O4 by auto-combustion and its catalytic activity on the thermal decomposition of ammonium perchlorate

Nanometer copper ferrite was synthesized by auto-combustion method using cupric nitrate, ferric nitrate and malic acid as raw materials. The precursor and as-burnt sample were characterized by X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) . Average particle size of sample is 26nm. The catalytic performance of nanometer CuFe₂O₄ on the thermal decomposition of ammonium perchlorate (AP) was investigated by DTA. The results show that the nanometer CuFe₂O₄ has high a catalytic activity, and the thermal decomposition temperature of AP shift 105 °C downward with the effect of nanometer copper ferrite. When the content of CuFe₂O₄ comes to 5%, the catalytic performance is the best.     

Synthesis,characterisation and catalytic activity of cadmium cobaltite nanoparticles: part 87

In this paper, we report the synthesis of cadmium cobaltite nanoparticles (CCNs) and their characterisation by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The particles are spherical in shape and the average particle size is of the order of 20–30 nm. Its catalytic activity was investigated through the thermal decomposition of ammonium perchlorate (AP), composite solid propellants (CSPs), 5-nitro-2,4-dihydro-3H-1,2,4-triazole-3-one (NTO) and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) using thermogravimetry (TG), TG coupled with differential scanning calorimetry (TG-DSC) and ignition delay measurements. The kinetics of thermal decomposition of AP + CCNs has also been investigated using isoconversional and model-fitting approaches, which have been applied to data for isothermal TG decomposition. The burning rate of CSPs was considerably enhanced by these nanoparticles. The ignition delays and activation energies are found to decrease when CCNs were incorporated in the system. The addition of CCNs to AP led to a shifting of the high-temperature decomposition peak towards lower temperature. All these studies show enhancement in the rate of decomposition of AP, NTO, HMX and CSPs.     

Spindly cobalt ferrite nanocrystals: preparation, characterization and magnetic properties

In this paper we describe the preparation of homogeneously needle-shaped cobalt ferrite (CoFe(2)O(4)) nanocrystals on a large scale through the smooth decomposition of urea and the resulting co-precipitation of Co(2+) and Fe(3+) in oleic acid micelles. Furthermore, we found that other ferrite nanocrystals with a needle-like shape, such as zinc ferrite (ZnFe(2)O(4)) and nickel ferrite (NiFe(2)O(4)), can be prepared by the same process. Needle-shaped CoFe(2)O(4) nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellent stability and the formed colloid does not produce any precipitations after two months, which is of prime importance if these materials are applied in magnetic fluids. X-ray diffraction (XRD) measurements were used to characterize the phase and component of the co-precipitation products, and demonstrate that they are spinel ferrite with a cubic symmetry. Transmission electron microscopy (TEM) observation showed that all the nanocrystals present a needle-like shape with a 22?nm short axis and an aspect ratio of around?6. Varying the concentration of oleic acid did not bring about any obvious influence on the size distribution and shapes of CoFe(2)O(4). The magnetic properties of the needle-shaped CoFe(2)O(4) nanocrystals were evaluated by using a vibrating sample magnetometer (VSM), electron paramagnetic resonance (EPR), and a M?ssbauer spectrometer, and the results all demonstrated that CoFe(2)O(4) nanocrystals were superparamagnetic at room temperature.     

纳米金刚石负载Fe2O3的制备及其对高氯酸氨的热分解催化作用

对纳米金刚石（ND）进行羧基化处理以提高其分散性,然后采用沉淀法制备了羧基化ND负载Fe₂O₃的催化剂。利用XRD、TG、BET和TEM对该负载型催化剂进行表征,通过DSC研究其对高氯酸铵(AP)热分解的催化作用。结果表明:ND经过羧基化处理后,在水中的分散性大幅度提高。沉淀法制备了直径5 nm、长50 nm的Fe₂O₃包裹或附着于ND的负载型复合催化剂,该催化剂对AP高温热分解的催化效果优于单一的Fe₂O₃或ND。当Fe₂O₃和ND的质量比为5∶1、在AP中添加质量分数2%的复合催化剂时,AP的高温分解峰温降低约30 ℃,ND负载Fe₂O₃催化剂具有一定的协同催化作用。     

Preparation and characterization of rice-shaped MnO2/CNTs composite and superior catalytic activity on thermal decomposition of ammonium perchlorate

Manganese dioxides (MnO₂) were successfully deposited on carbon nanotubes (CNTs) surface by redox reaction between potassium permanganate and CNTs. The characterization results showed that the MnO₂ exhibited the rice-shaped nanostructure with about 5～10 nm in width and 10～30 nm in the length on CNTs. The solvothermal temperature of composite can greatly affected its morphology and structure to improve the thermal catalytic on ammonium perchlorate (AP) decomposition. Compared with other samples, the prepared composite at 120°C exhibited superior catalytic performance, as 3wt% of composite added in AP, the second exothermic peak temperature decreased by 160.2°C and the apparent release heat of the thermal decomposition of AP which is four times of that of pure AP. A possible mechanism for formation the rice shaped MnO₂/CNTs composite is also presented.