纳米铁酸锌的制备与应用

以乙酰丙酮铁(Fe(acac)3)和一水合乙酰丙酮锌(Zn(acac)2.H2O)为主要原料,用均匀共沉淀法制备ZnFe2O4纳米晶粒。XRD表明,这是由细小的晶种组成的粒径在70-100nm的ZnFe2O4晶体颗粒。再利用甲基丙烯酸甲酯(MMA)分散乳液聚合,得到粒径在30-70nm具有核壳结构的纳米ZnFe2O4/PMMA复合粒子。     

聚吡咯-二氧化钛自组装复合膜的制备及其光电转换性质

通过原位自组装技术制备了聚吡咯-二氧化钛纳米复合膜,利用紫外-可见光谱、红外光谱、原子力显微镜、电化学循环伏安等方法对所制备的复合膜进行了表征.与利用原位自组装技术制备的聚吡咯膜相比较,由于在复合膜中聚吡咯和TiO2纳米粒子之间的相互作用,复合膜π→π*跃迁吸收峰发生蓝移,氧化还原峰的位置向负电位方向移动.沉积在导电玻璃ITO表面的该纳米复合膜在可见光下表现出一定的光电转换性质.     

纳米晶铁酸锌和铁酸镧的合成与表征

用硬脂酸凝胶法制备了尖晶石型ZnFe2O4和钙钛矿型LaFeO3纳米晶，通过热重差热（TG-DTA）、X射线粉末衍射（XRD）、透射电镜（TEM）和BET比表面吸附，对纳米粒子的组成、结构、形貌、粒径进行了分析和表征．     

超声波化学法制备纳米铁酸锌粉末的影响因素

超声辐射Fe(NO3)3·9H2O、不同锌盐和脲的混合水溶液得到前驱体,再经过高温焙烧得到纳米ZnFe2O4粉末.得到的纳米ZnFe2O4粉末用X射线衍射(XRD),傅立叶转换红外光谱(FT-IR)表征得到确认.系统研究了超声波化学法制备纳米铁酸锌粉末工艺中不同锌盐、超声波辐射时间、焙烧温度和焙烧时间等影响因素,结果表明:Fe(NO3)3·9H2O与Zn(NO3)2·6H2O为原料,超声波辐射为4h,焙烧温度为950q℃,焙烧时间为14h可制备结晶良好、分散性好、粒度小于100nm的尖晶石型铁酸锌粉末.     

方酸菁功能材料修饰纳米晶TiO2薄膜电极的光电转换性能研究

考察了三种方酸菁染料修饰的米晶ＴｉＯ２薄膜电极表面应用于光电化学太阳能电池进行光电转换的情况,发现它们的光电化学性能参数按照Ｓｑ３〉Ｓｑ２〉Ｓｑ１的顺序,随着染料在纳米晶ＴｉＯ２上吸附力的增强而提高,其中,Ｓｑ３的光电转换效率为２．１７％,它在６５０ｎｍ处的最高单色光光电流效率ＩＰＣＥ值达到６．２％,表明方酸菁是一类优良的光电转换功能材料。     

铁酸锌纳米晶体的制备及表面光伏特性研究

采用偶合的共沉淀法和水热法相结合的方法,制备出ZnFe2O4纳米晶体,并利用DRS、XRD、FTIR、TEM等技术对其结构和谱学特性进行了研究,并在其基础上利用表面光电压谱(SPS)深入探讨了所制样品的表面光伏特性,研究表明样品具有较窄的禁带宽度,晶型为正尖晶石型结构,大小均匀(7nm),无团聚,表面光伏特性研究显示ZnFe2O4纳米晶体具有明显的表面和量子限域效应,有一定的捕获电子能力,在外加电场下光伏响应变化明显,在正电场下有一个最佳响应值,而当负电场达到一定值时,外电场的光伏响应将占据主导地位.     

纳米铁酸盐的制备研究 低温催化相转化法合成纳米级铁酸锌及表征

以ZnSO4.7H2O和FeCl3.6H2O为原料，在微量相转化催化剂存在下，利用沸腾回流的液相法制备了纳米铁酸锌微晶，当反应物总浓度高达1．2mol.L^-1时，仍可获得粒径＜20nm均匀粒子，研究了初始PH值对产物组成的影响，使用XRD、TEM、IR及磁强仪对产物进行了表征，并测定了所得产物的密度及比表面。     

铁酸锌纳米强化氨水发生过程实验研究

本文提出一种可直接测试有、无纳米氨水溶液氨气发生量的氨水纳米降膜发生实验装置,通过实验对比分析了0%~0.5%质量浓度的纳米和分散剂、25%~40%质量浓度的氨水以及加热水温度对氨气发生率和相对发生率的影响。研究表明:添加合适质量分数的铁酸锌(ZnFe_2O_4)和十二烷基苯磺酸钠(SDBS)配制的氨水纳米流体可以增加氨气发生率。当氨水基液质量浓度为25%~40%时,添加质量分数分别为0.1%的ZnFe_2O_4和0.05%的SDBS,氨气发生率比原相应浓度的氨水基液约增加60%。但只添加分散剂SDBS会对氨气发生产生一定的抑制作用。选择分散剂用量时需兼顾分散稳定性和对发生起正或副作用,以达到最优效果。因此将纳米应用于吸收式制冷系统以提高系统的COP具有较广阔的前景。     

石墨烯-铁酸铋纳米晶复合材料的制备及其催化性能研究

BiFeO3(BFO)是一种新型可回收光响应催化剂,但较高的光生电子/空穴对复合率和较低的量子产率限制了其实际应用.本研究通过水热法制备出还原氧化石墨烯-BFO(RGO-BFO)纳米晶复合材料,表征与测试结果表明,相比于BFO颗粒,复合材料的禁带宽度Eg为2.0 eV,降低约10％;40 min对亚甲基蓝吸附-催化效率...     

可磁分离ZnFe2O4-TiO2/还原氧化石墨烯复合材料的制备及光催化性能

以TiO2(P25)、 Fe(NO3)3·9H2O、 Zn(NO3)2·6H2O和氧化石墨烯(GO)为原料,通过一步溶剂热法合成可磁分离的ZnFe2O4-TiO2/还原氧化石墨烯(rGO)复合材料。采用UV-Vis、 Raman、 XRD、 SEM和EDS对ZnFe2O4-TiO2/rGO复合材料进行表征,并研究不同rGO比例的ZnFe2O4-TiO2/rGO对模拟染料废水亚甲基蓝(MB)的光催化降解性能。GO在溶剂热反应过程中,被还原成rGO。由于ZnFe2O4和rGO的加入,不仅使ZnFe2O4-TiO2/rGO实现对可见光的吸收,而且使其具有磁性,便于分离和回收利用。当GO质量分数为5wt%时, ZnFe2O4-TiO2/rGO显现出对MB最佳的光催化活性, 60 min光照后的降解率达到99.1%。通过光催化活性物种捕获实验得出ZnFe2O4-TiO2/rGO复合材料降解MB的过程中,活性物种主要为·OH和·O2-, TiO2导带(CB)中的光生电子(e+)转移到ZnFe2O4的价带(VB),遵循Z型转移机制。光催化剂稳定性实验表明, ZnFe2O4-TiO2/rGO复合材料具有优越的稳定性,可作为太阳光照射下降解有机染料的光催化剂。     

Photoelectrochemical property of ZnFe2O4/TiO2 double-layered films

ZnFe₂O₄/TiO₂ double-layered films on indium-tin oxide (ITO) substrate were prepared by a dip-coating method, and the optical absorption and photocurrent of the as-prepared films were measured. In the double-layered films, the onset of fundamental absorption edge shifts to a longer wavelength, and even shifts to a longer wavelength than that of ZnFe₂O₄-only film as the ZnFe₂O₄ layer thickness increases. Application of the coupled photoanodes double-layered films composed of ZnFe₂O₄ and TiO₂ can obviously increase the photocurrent. It was found that the photocurrent density of ZnFe₂O₄/TiO₂ double-layered films first increased and then decreased with increasing the ZnFe₂O₄ layer thickness. A five-fold increase in the photocurrent density was obtained compared with TiO₂-only films under optimum condition.     

纳米晶ZnFe2O4薄膜的制备及其丙酮气体敏感性能研究

以尖晶石结构ZnFe2O4材料为研究对象,以可溶性无机盐为原料,利用溶胶-凝胶技术在Al2O3基片上制备了ZnFe2O4薄膜,研究其对低浓度丙酮气体的敏感特性.通过DTA,TG,XRD及SEM分析手段对制膜过程及薄膜形态进行了表征.研究发现,采用柠檬酸作为络合剂的无机盐原料溶液-溶胶-凝胶(ISG)工艺,在700℃烧结温度下,可以得到覆盖良好、结构均匀、晶粒尺寸约在100nm的尖晶石结构ZnFe2O4薄膜.通过该薄膜对丙酮气敏特性测试表明,ZnFe2O4材料对丙酮具有较好的敏感性,在550℃的操作温度下,材料对丙酮气体敏灵敏度为8,响应与恢复时间小于5s.     

Synthesis and properties of ZnFe2O4 replica with biological hierarchical structure

ZnFe₂O₄ replica with biological hierarchical structure was synthesized from Papilio paris by a sol–gel method followed by calcination. The crystallographic structure and morphology of the obtained samples were characterized by X-ray diffraction, field-emission scanning electron microscope, and transmittance electron microscope. The results showed that the hierarchical structures were retained in the ZFO replica of spinel structure. The magnetic behavior of such novel products was measured by a vibrating sample magnetometer. A superparamagnetism-like behavior was observed due to nanostructuration size effects. In addition, the ZFO replica with “quasi-honeycomb-like structure” showed a much higher specific capacitance of 279.4 F g⁻¹ at 10 mV s⁻¹ in comparison with ZFO powder of 137.3 F g⁻¹, attributing to the significantly increased surface area. These results demonstrated that ZFO replica is a promising candidate for novel magnetic devices and supercapacitors.     

Structural stability of ZnFe2O4 nanoparticles under different annealing conditions

We study the structural stability of surfactant coated ZnFe₂O₄ (ZF) nanoparticles of average particle size 10 nm annealed under different environments. The X-ray diffraction studies in oleic acid coated ZF (OC-ZF) show distinctly different phase transitions under different annealing conditions. The OC-ZF is reduced to α-Fe/ZnO phase under vacuum while it forms FeO/ZnO under argon whereas the ZnFe₂O₄ phase remains stable under air annealing. The simultaneous thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) coupled mass spectra (MS) in OC-ZF under argon atmosphere suggests that the residual carbon removes oxygen from the lattice to reduce the ZnFe₂O₄ phase into FeO/ZnO during argon annealing. Apart from CO and CO₂ gas evolution at high temperature under argon annealing, creation of oxygen vacancies due to the random removal of oxygen under vacuum annealing, leads to direct interaction between Fe–Fe and the formation of metal Fe. It appears that the residual carbon aids the reduction of ZF and the formation of α-Fe/ZnO during vacuum annealing. After annealing at 1000 °C in vacuum, the magnetization is increased abruptly from 13.8 to 106.5 emu g⁻¹. In sharp contrast, the air and argon annealed samples show a diminished magnetization of 1 emu g⁻¹. The field cooled (FC) and zero FC magnetization of vacuum and argon annealed samples exhibit superparamagnetic and spin-glass type behavior respectively. Our results offer possibilities to switch a magnetically inactive material to an active one.     

Quasi-cube ZnFe2O4 nanocrystals: Hydrothermal synthesis and photocatalytic activity with TiO2 (Degussa P25) as nanocomposite

The fabrication and photocatalytic application of zinc ferrite nanocrystals were reported. Quasi-cube ZnFe₂O₄ nanocrystals with typical small sizes of 5-15 nm were successfully synthesized by a facile hydrothermal approach. ZnFe₂O₄/P25 nanocomposite was prepared by physically grinding the ZnFe₂O₄ nanocrystals with TiO₂ (commercial Degussa P25) at ambient temperature, and it exhibited excellent photocatalytic activity for the mineralization of Rhodamine B. UV-vis measurement and photocatalytic test results showed that ZnFe₂O₄ nanocrystals exhibited effective band-gap coupling to P25 nanopowders by simply physical grinding without any surface modification or high-energy balling, which is usually adopted in conventional mixture process. This phenomenon can be attributed to the high surface activities of the as-obtained tiny ZnFe₂O₄ nanocrystals and commercial P25 nanoparticles. It may imply that the mixing process of composite materials would be simplified by further lowering the grain sizes of their component particles.     

ZnFe2O4 thin films from a single source precursor by aerosol assisted chemical vapour deposition

A single source heterobimetallic complex [Fe₂(acac)₄(dmaeH)₂][ZnCl₄] (1) (acac = 2,4-pentanedionate, dmaeH = N,N-dimethylaminoethanol), was synthesized in high yield. The complex was analyzed by melting point, Fourier transfer infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The structure of the cation was established by single crystal X-ray analysis on a derivative, [Fe₂(acac)₄(dmaeH)₂][ZnCl₃(THF)]₂·THF (1a) (THF = tetrahydrofuran). TGA analysis showed that complex (1) undergoes facile thermal decomposition at 450 °C to give ZnFe₂O₄ residue. In-house designed aerosol assisted chemical vapour deposition equipment was used to deposit thin films of ZnFe₂O₄ on fluorine doped SnO₂ coated conducting glass substrate at 450 °C. X-ray diffraction analysis proved the formation of crystalline ZnFe₂O₄ phase and scanning electron microscopy revealed the film morphology with well defined crystalline particles evenly distributed in the range 150-200 nm. The indirect and direct bandgap energies of the thin films were estimated to be 1.76 and 2.10 eV, respectively.     

Microstructure and mechanical properties of MgO-Al2O3-SiO2-TiO2 glass-ceramics

Crystallization sequences of MgO-Al₂O₃-SiO₂-TiO₂ system glass were investigated by means of DTA, XRD, SEM and EDS. The mechanical properties of samples, including density, microhardness and elastic modulus, were characterized as well. The relationship between crystalline phases, heat treatment methods and mechanical properties is discussed. The results have shown that: the glass first underwent extensive phase separation into titanium-rich droplets in a silica-rich matrix, then magnesium aluminotitanate (MAT) initially precipitated in the droplet phase. With the crystallization temperature increased, β-quartz_ss, sapphirine, α-quartz_ss, α-cordierite and cristobalite made their appearance successively. When the glass was heated at 1100 °C for 2 h, the maximum elastic modulus of 137 GPa (accompanied by a microhardness of 8.5 GPa and a density of 2.924 g/cm³) was obtained.     

ZnFe2O4纳米球的制备及其对丙酮的气敏性能研究

丙酮被广泛应用于工业和实验室,对丙酮浓度的检测十分重要。ZnFe₂O₄是一种尖晶石型三元金属氧化物,气敏性能优良,可广泛应用于气体传感器。本文采用简单的一步水热法制备了球状的ZnFe₂O₄气敏材料。通过XRD、XPS、SEM、TEM、N2吸附-解析仪对材料的形貌结构、化学组成、比表面积等进行分析,并以丙酮为目标气体对其气敏性能进行了综合研究。结果表明,ZnFe₂O₄纳米球是由纳米粒子自组装而成,有较大的比表面积;该ZnFe₂O₄基气体传感器在最佳工作温度150℃下对丙酮的灵敏度为65.74,并具有出色的选择性、稳定性、重复性,但随着湿度的增加其气敏性能逐渐降低。