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.     

聚苯乙烯/纳米SiO2复合颗粒制备与表征

为改善二氧化硅(SiO2)纳米粒子与聚合物基体间的亲和性,使SiO2表面功能化,将硅烷偶联剂KH-570引入C=C基团,采用乳液聚合方法在纳米SiO2粒子表面接枝苯乙烯(St)单体,实现了纳米二氧化硅表面的聚苯乙烯(PS)高分子包覆改性,制备了具有核/壳结构的SiO2-PS复合纳米粒子,产物的单体转化率和接枝效率在80%以上.研究了二氧化硅含量和偶联剂用量对聚合反应的单体转化率和接枝效率的影响,探讨了偶联剂的作用机理,利用FT-IR、TEM、TG对SiO2-PS复合粒子的表面结构进行了表征.结果表明,复合粒子具有明显的核壳结构,壳层厚度在20nm左右,乳液聚合过程可有效使二氧化硅的团聚体剥离呈纳米级颗粒.     

NiFe2O4纳米粒子的水热合成及表征

以Ni(NO3)2·6H2O和Fe(NO3)3·9H2O为主要原料,在聚乙二醇(PEG)存在下,采用水热法制备了磁性NiFe2O4纳米粒子,用X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁场计(VSM)等分析方法对样品进行了表征.结果表明:水热法合成的NiFe2O4纳米粒子为尖晶石结构,粒度分布均匀,为方形形貌,粒子直径范围在50～60nm;比饱和磁化强度为25.83emu/g,剩磁为6.167emu/g,矫顽力达85.87Oe.     

反相乳液界面合成中空Fe3O4/SiO2磁性微胶囊

报道了一种简单合成中空Fe3O4/SiO2磁性微胶囊的方法,即以反相乳液的水滴作为形成中空结构的软模板,通过界面溶胶-凝胶过程,制备中空Fe3O4/SiO2磁性微胶囊。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、选区电子衍射(SAED)、多晶粉末X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)及磁滞回线测量等手段对样品的结构和性质进行表征和研究。XRD、SAED和FTIR分析结果表明,微胶囊由SiO2和Fe3O4磁性纳米粒子(MPs)组成。SEM和TEM观察结果表明,微胶囊具有中空结构,且SiO2壳层具有多孔特性。磁性能检测结果表明,微胶囊具有超顺磁性和磁响应性。通过对比实验,提出SiO2界面异相成核的中空磁性微胶囊的形成机理。     

核壳型磁载TiO2/CoFe2O4光催化剂的制备与性能研究

纳米TiO2是一种高效的光催化剂,为了解决TiO2纳米颗粒从悬浮体系中分离回收难的问题,可将其包覆于磁性微球之外,借助于磁场的作用实现快速有效地分离.以尖晶石型CoFe2O4为磁核,制备了核壳型纳米磁性TiO2/CoFe2O4光催化剂,通过水浴恒温条件、热处理温度的改变,以及工艺的调整优化了催化剂的制备工艺.采用XRD和TEM分析了催化剂的结构与形貌.研究发现,水浴90℃恒温2h、600℃热处理后的TiO2/CoFe2O4在降解TNT时表现出了较高的催化活性.表明合适的反应时间和热处理温度是影响催化剂活性的关键因素.     

Fe3O4 包覆聚苯乙烯磁性微球的制备及性能

为研究一种应用于磁稳定流化床反应器的新型高分子磁性微球的制备方法及性能,采用悬浮聚合法制备了Fe_3O_4纳米粒子包覆聚苯乙烯磁性微球,研究了搅拌速率、加入磁性Fe_3O_4纳米粒子的时间等因素对复合微球粒径及性能的影响,运用扫描电子显微镜(SEM)、X射线衍射(XRD)、振动样品磁强计(VSM)、热重(TGA)等测试手段,表征了磁性聚苯乙烯微球的形貌特征、结构、粒径、磁学性能及Fe_3O_4的包覆量.实验结果表明:在搅拌转速为600 r/min,80℃保温10 min加入修饰Fe_3O_4纳米粒子,制备所得的磁性聚苯乙烯微球为粒径分布均匀的球状微粒;Fe_3O_4的包覆量达到5%,最高饱和磁化强度为3.73 emu/g,具有较好的超顺磁性,可应用于磁稳定流化床反应器.     

纳米NiFe2O4的制备及其对高氯酸铵的热分解催化性能

采用水热法制备出纯相的NiFe2O4纳米颗粒。利用X射线衍射仪(XRD),透射电镜(TEM)和傅里叶变换红外光谱仪(FT-IR)对样品进行了表征,并运用热分析法和质谱仪研究了样品对高氯酸铵的热分解催化性能。结果表明,制备的NiFe2O4纳米颗粒粒径约为5.0nm,对高氯酸铵的热分解具有很高的催化活性。当NiFe2O4纳米颗粒的添加量达到10%时,对高氯酸铵的热分解催化性能最好,可使高氯酸铵的高温分解温度降低89.8℃。     

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。     

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。     

SnO2/Fe3O4磁性光催化微纳米材料的制备与性能研究

以磁性纳米颗粒Fe3O4为核,SnCl4.5H2O、氨水、无水乙醇为原料,采用液相共沉淀法在Fe3O4表面包覆一层SnO2光催化剂。采用X射线衍射仪(XRD)及扫描电镜(SEM)分析了其成分和表面形貌。结果显示:Fe3O4纳米颗粒在实验过程中发生了团聚,尺寸增大;当Fe3O4与SnCl4.5H2O物质的量比为(1∶2)～(1∶4)时,SnO2能被较好地包覆在Fe3O4表面,形成核-壳结构的SnO2/Fe3O4复合光催化材料;600℃热处理能够形成结晶性良好的SnO2晶体,但此时Fe3O4转变为Fe2O3,失去了磁性。     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Thermal diffusion in binary mixtures H2-CCl2F2 and H2-CHClF2

Thermal diffusion coefficients were measured in two gaseous mixtures, in which one component was close to the critical temperature, in the pressure range (19.6–127.4)·10⁴ N/m² and at a freon concentration of 0.25–0.8.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Radial GRIN glasses in Li2O-Na2O-Al2O3-TiO2-SiO2 systems

A series of GRIN glass rods have been developed in Li2O-Na2O-Al2O3-TiO2-SiO2 systems. Negative radial refractive index profiles were generated by exchanging Na+ for Li+ ions in these glass rods. It has been observed that TiO2 plays a vital role in increase in the profile depth and maximum change in the refractive index because of its ambivalent nature. Change in the refractive index can be further increased by increasing the concentration of exchanging cation in the base glass.     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.     

Si_2N_2O-Al_2O_3-La_2O_3和Si_2N_2O-Al_2O_3-CaO系统的亚固相关系

本文给出了 Si_2N_2O-Al_2O_3-La_2O_3和 Si_2N_2O-Al_2O_3-CaO 系统的亚固相图。实验结果表明:在 Si_2N_2O-Al_2O_3-CaO 系统中有一个未知结构的新化合物 CaO·Si_2N_2O,在3CaO·Si_2N_2O 和3CaO·Al_2O_3两化合物之间形成连续立方固溶体。而 Si_2N_2O-Al_2O_3-La_2O_3系统中则没有发现新化合物。在两个系统的富 Si_2N_2O区,过量的 Si_2N_2O 与 La_2O_3和 CaO 分别反应形成 Si_3N_4与 La_(10)[SiO_4]_(?)N_2(H-相)(和 CaSiO_3。所研究的这两个三元系统中,分别形成了如下几个四元相容性区。在 Si_2N_2O-Al_2O_3-La_2O_3系统内有:H-Si_3N_4-La_2O_3·Si_2N_2O-La_2O_3·Al_2O_3;H-Si_3N_4-La_2O_3·Al_2O_3-La_2O_3·11 Al_2O_3;H-Si_3N_4-La_2O_3·11 Al_2O_3-Al_2O_3;H-Si_3N_4-Al_2O_3-O′s.s;H-Si_3N_4-O′s.s-Si_2N_2O在 Si_2N_2O-Al_2O_3-CaO 系统内有:Si_3N_4-CaSiO_3-CaO·Si_2N_2O-3CaO·Al_2O_3;Si_3N_3-CaSiO_3-3CaO·Al_2O_3-2CaO·Al_2O_3·SiO_(?);Si_(?)N_(?)-CaSiO_3-2CaO·Al_2O_3·SiO_2-Al_2O_3;Si_3N_4-CaSiO_3-Al_2O_(?)-O′s.s;Si_3N_4-CaSiO_3-O′s.s-Si_(?)N_(?)O