铝电解用NiFe2O4-10NiO基陶瓷铁元素优先腐蚀研究

在高温熔盐电解质78.07%Na3AlF6-9.5%AlF3-5.0%CaF2-7.43%Al2O3中对NiFe2O4-10NiO基陶瓷进行了电解腐蚀性能研究,结果发现烧结后的陶瓷NiFe2O4相中的Fe/Ni比为2.211～2.89,且NiO相的Fe/Ni比为0.136～0.34,而电解腐蚀后NiFe2O4相中的Fe/Ni比为2.07～2.335,且NiO相中Fe/Ni比为0.120～0.195,说明在电解腐蚀过程中Fe元素发生了优先腐蚀。铁元素在电解过程中发生优先腐蚀的原因可能是化学腐蚀和电化学腐蚀共同作用的结果。     

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。     

NiFe2O4/Ag复合材料的制备及其耐蚀和导电性能

以Fe2O3、NiO和Ag2O为主要原料,采用固相烧结工艺制备了NiFe2O4/Ag复合材料,用X射线衍射和扫描电子显微镜对材料的组成和微观结构进行了研究,并测量了样品在冰晶石熔盐中的静态热腐蚀速率及其高温电导率.结果表明,复合材料由NiO、NiFe2O4尖晶石和Ag三相组成.随着Ag2O含量的增多,复合材料的致密化程度先增加而后降低,当Ag2O含量为6%时,试样的致密化程度最高.Ag2O的加入在不提高试样在冰晶石熔盐中的静态热腐蚀速率的前提下,提高了试样的高温电导率.     

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℃。     

核壳结构SrFe12O19NiFe2O4复合纳米粉体的吸波性能

以Fe(NO₃)₃、 Ni(NO₃)₂和Sr(NO₃)₂为主要原料, 通过两步柠檬酸盐溶胶-凝胶法, 制备出核-壳结构SrFe₁₂O₁₉-NiFe₂O₄磁性纳米复合粉体。采用XRD、 TEM、 VSM及矢量网络分析仪对合成的粉体的结构、 形貌及吸波性能进行了分析研究。结果表明, 复合粉体的相结构与NiFe₂O₄含量有关, 当SrFe₁₂O₁₉与NiFe₂O₄的质量比为1∶2、 烧结温度为1050℃时, 复合纳米粉体的相与NiFe₂O₄接近, 核-壳结构SrFe₁₂O₁₉-NiFe₂O₄纳米复合粉体的饱和磁化强度(M_s)(51.4 emu/g)比单体SrFe₁₂O₁₉纳米粉体 (42.6 emu/g)的大; 但矫顽力(H_c) (336 Oe)比单体SrFe₁₂O₁₉纳米粉体的小, 在SrFe₁₂O₁₉ 与NiFe₂O₄的矫顽力5395～160 Oe之间。在频率为8～18 GHz范围内, 微波吸收逐渐增强, 当频率为12 GHz时, SrFe₁₂O₁₉-NiFe₂O₄纳米复合粉体的微波吸收达到最大值-9.7 dB, 是一种性能优良的吸波材料。      

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.     

Fe对(Cu-Ni-Fe)-xNiFe2O4复合惰性阳极低温铝电解成膜机制的影响

以高温固相合成的NiFe_2O_4和Cu,Ni,Fe金属粉为原料,采用冷压烧结法制备不同合金相含量的(Cu-Ni-Fe)-xNiFe_2O_4(x=50,60,70,80,质量分数/%,下同)金属基复合惰性阳极材料,研究合金相中Fe元素对(Cu-Ni-Fe)-xNiFe_2O_4金属基复合惰性阳极材料烧结和电解过程中基体成分与微观组织的影响,发现合金相中的Ni,Fe及NiFe_2O_4陶瓷相在烧结和电解过程中发生了可逆的氧化还原反应,使得NiFe_2O_4相发生解离和再生成。对(Cu-Ni-Fe)-xNiFe_2O_4金属基复合惰性阳极材料进行了低温电解性能测试,研究其在电解过程中的成膜过程和腐蚀行为。结果表明:(Cu-Ni-Fe)-xNiFe_2O_4金属基复合惰性阳极材料电解过程中电压稳定,铝液杂质含量低于0.7%(质量分数),有望解决金属陶瓷阳极热稳定性差的问题,是理想的惰性阳极材料。     

NiFe_2O_4/T-ZnO_w复合材料的制备及磁性能

采用化学镀法在四角氧化锌晶须(T-ZnO_W)表面包覆NiFe_2O_4镀层,制备了NiFe_2O_4/T-ZnO_W复合材料。利用X射线衍射仪、扫描电镜、能谱分析仪、振动样品磁强计对镀覆前后T-ZnOw的结构、形貌等进行了表征。结果表明,化学镀覆后,在T-ZnO_W表面包覆了致密的尖晶石型NiFe_2O_4镀层,T-ZnO_W针尖部位生成的镀层厚度比根部薄。NiFe_2O_4/T-ZnO_W复合材料具有软磁特性。随着退火温度的升高,复合材料的饱和磁化强度和矫顽力逐渐升高,在800℃达到最高。     

微波吸收复合材料Ag/NiFe2-xCexO4的制备与表征

用水热法分别制备了镍铁氧体粉末(NiFe2O4)及其单质银复合、Ce^3+掺杂镍铁氧体粉末(Ag/NiFe2-xCexO4)复合物。用粉末X射线衍射仪(XRD)、扫描电子显微镜(SEM)、振动样品磁强计(VSM)和矢量网络分析仪(VAN)等分别表征了产物的结构、形貌、电磁性能。结果表明,水热法一步可制备出Ag/NiFe2-xCexO4复合物,Ag/NiFe2-xCexO4复合物的组分之间存在一定的相互作用;通过银单质复合与铈离子掺杂对铁氧体的比饱和磁化强度影响较大,但对矫顽力影响不大。与单一组分相比,Ag/NiFe2-xCexO4复合物表现出更优良的微波吸收性能,当x=0.08时,s11(Ag/NiFe1.92Ce0.08O4)=-22.80 dB,s12(Ag/NiFe1.92Ce0.08O4)=-4.04 dB。通过掺杂与复合其介电损耗和磁损耗都有提高,介电损耗提高更明显,是颇具应用前景的微波吸收材料。     

XRD分析TiO_2和MnO_2添加剂对固相合成NiFe_2O_4过程的影响

在1173和1273K以NiO和Fe2O3为原料,以TiO2和MnO2为添加剂,固相合成了NiFe2O4,用XRD和SEM对试样进行了表征,建立了NiFe2O4特征衍射峰强度与合成时间的关系。没有添加剂时,将温度从1173K提高到1273K时,合成NiFe2O4的反应速度并没有增加;在原料中加入0.5%(质量分数)TiO2,合成NiFe2O4的反应速率随着温度的升高而增加;用1%(质量分数)MnO2作为添加剂后,合成NiFe2O4的反应速率显著升高,扫描电镜结果证实添加TiO2和MnO2提高了试样的致密度,改善了其烧结性能。用零级反应动力学方程求得合成NiFe2O4反应的速率系数。     

海绵状NiFe2O4团簇的合成与表征

以乙醇-水为混合溶剂,六亚甲基四胺(HMTA)与聚乙烯吡咯烷酮(PVP)为添加剂,通过溶剂热法合成海绵状的镍铁氧体(NiFe2O4)团簇,并对其进行了XRD、VSM、SEM、TEM、BET与ICP表征。结果表明,在反应体系中同时引入PVP与HMTA时,合成的海绵状NiFe2O4团簇具有尖晶石晶体结构,晶粒均匀细小,比饱和磁化强度为57.30emu/g,比表面积与孔容分别为91.57m2/g、0.26cm3/g。     

磁性钛硅分子筛催化剂的结构解析

采用预涂和水热法在尖晶石铁酸镍的表面包覆钛硅分子筛(TS-1),制备了易于磁分离的磁性TS-1催化剂。利用透射电镜(TEM)、EDS能谱、X射线衍射分析(XRD)、紫外-可见光谱(UVVis)、红外光谱(IR)和振动样品磁强计(VSM)等手段多角度对磁性TS-1催化剂的壳层结构进行表征解析。结果表明磁性TS-1催化剂颗粒直径约150nm,是具有MFI骨架结构的壳核型复合催化剂,它具有催化活性和磁分离的双重功能。     

Synthesis of Ag@TiO2/NiFe2O4 ternary nanostructures and evaluation of their photocatalytic activities

Journal of Materials Science: Materials in Electronics - Synthesis and characterization of novel and ternary photocatalysts Ag@TiO2/NiFe2O4 for the three potential applications, such as...     

Ag-NiFe2O4金属陶瓷性能研究

为改善铝电解惰性阳极用NiFe2O4尖晶石材料存在的不足,制备了不同金属Ag含量的Ag-NiFe2O4金属陶瓷,利用扫描电子显微镜观察显微组织,由X射线衍射分析化学成分,研究了Ag-NiFe2O4试样的体积密度、热震性、导电率以及腐蚀速率,并与纯NiFe2O4尖晶石对比,分析了其性能差异的原因.试验结果表明,金属的Ag加入显著改善了抗热震性,含10%Ag试样的导电能力比纯NiFe2O4尖晶石提高了30%,综合考虑Ag含量为15%试样性能最好.     

磁性纳米TiO2／NiFe2O4光催化复合材料的制备及表征

采用均匀沉淀法在磁性NiFe2O4表面包覆TiO2,制备了一种新型纳米TiO2／NiFe2O4光催化复合材料。通过改变Ti和Ni物质量之比确定了复合材料最佳钛镍比,用X射线衍射、透射电镜、UV—vis漫反射、BET、TG—DSC、磁力学测试等手段对复合材料进行了表征,以甲基橙的水溶液为模拟污染物,评价样品的光催化性能：该复合材料在光照2h后,甲基橙的脱色率可达98．5％,是一种在可见光范围内有响应、便于回收、可重复使用的高效光催化剂。     

Tuning the exchange bias in NiFe/Fe-oxide bilayers by way of different Fe-oxide based mixtures made with an ion-beam deposition technique

We have investigated the structural and magnetic properties of ion-beam deposited polycrystalline NiFe (25 nm)/Fe-oxide (35 nm) bilayers. A film prepared with an assist beam O2 to Ar gas ratio of 0% during deposition had a bottom layer that consisted of pure b.c.c. Fe (a = 2.87 A) whereas films prepared with 19%O2/Ar and 35%O2/Ar had either Fe3O4 (a = 8.47 angstroms) or alpha-Fe2O3 (a = 5.04 angstroms, c = 13.86 angstroms) bottom layers, respectively. Cross-sectional transmission electron microscopy revealed a smooth interface between the top nano-columnar NiFe and bottom nano-columnar Fe-oxide layer for all films. At room temperature, the observed coercivity (Hc approximately 25 Oe) for a film prepared with 19% O2/Ar indicates the existence of a magnetically hard ferrimagnetic Fe3O4 phase that is enhancing the plain NiFe (Hc approximately 2 Oe) by way of exchange coupling. A significant amount of exchange bias is observed below 50 K, and at 10 K the size of exchange bias hysteresis loops shift increases with increasing oxygen in the films. Furthermore, the strongest exchange coupling (H(ex) approximately 135 Oe at 10 K) is with alpha-Fe2O3 (35% O2/Ar) as the bottom film layer. This indicates that the pure antiferromagnetic phases work better than ferrimagnetic phases when in contact with ferromagnetic NiFe. H(ex) (T) is well described by an effective AF domain wall energy that creates an exchange field with a (1 - T/T(crit)) temperature dependence. Hc (T) exhibits three distinct regimes of constant temperature that may indicate the existence of different AF spin populations that couple to the FM layer at different temperatures.     

Effect of strain on ferroelectric and magnetic behavior in Pb(Zr0.52Ti0.48)O3-based magnetoelectric heterostructures

In this paper, the "sandwich" structured magnetoelectric composite films of Pb(Zr0.52Ti0.48)O3/ NiFe2O4/Pb(Zr0.52Ti0.48)O3 and Pb(Zr0.52Ti0.48)O3/CoFe2O4/Pb(Zr0.52Ti0.48)O3 are epitaxially grown on SrRuO3/SrTiO3 substrates by pulsed-laser deposition. The crystalline quality and microstructures of these heterostructures are investigated by X-ray diffraction technique. The effects of strain on the ferroelectric, magnetic and magnetoelectric coupling properties of these thin films are systematically studied. The results show that the strain effect induced by lattice mismatch between the ferroelectric/ferromagnetic layers plays an important role in the ferroelectric and magnetic properties of these composite films. Compared to the strained Pb(Zr0.52Ti0.48)O3/ CoFe2O4/Pb(Zr0.52Ti0.48)O3 heterostructure, improved ferroelectric properties with an out-of-plane polarization (2P(r)) of 34.2 microC/cm2 and electric coercivity field of 158 kV/cm are obtained in the strain-free Pb(Zr0.52Ti0.48)O3/NiFe2O4/Pb(Zr0.52Ti0.48)O3 heterostructure. The ME measurement results not only show that the strain induced by lattice mismatch has great influence on the ME behavior, but also provide an understanding of the multilayers with full control over the interface structure at the atomic-scale.     

NiFe2O4纳米晶的制备及表面效应对其比饱和磁化强度的影响

以FeSO4*7H2O和NiSO4*7H2O为原料,首先制备出颗粒细小的碱式碳酸盐前驱体,在300～700℃焙烧1h后,制备出铁酸镍纳米晶,粒径为8～54nm,粒度均匀。通过测量它的比饱和磁化强度σs与比表面积Sa,得出经验公式σs(Sa)=σs(∞)(1-aSa),运用非共线磁结构理论很好地解释了上述经验公式,并得到纳米晶的非共线表面层的厚度。,A basic carbonate precursor with very fine particles was synthesied by using FeSO4*7H2O and NiSO4*7H2O, and NiFe2O4 nanocrystallites were then obtained by calcining the precursor. The results of XRD and TEM analysis show the NiFe2O4 nanocrystallites with spherical shape are even, and their average diameters increase from 8nm to 54nm when the precursor is calcined at 300—700℃ for 1h. Their specific saturation magnetization σs and specific surface area Sa were measured. A empirical formula σs(Sa)=σs(∞)(1-aSa)was obtained which can be interpreted very well by a noncollinear magnetic structure model, and the value of the canted-layer thickness was deduced.     

TiO2和WO3复合掺杂金属陶瓷的致密化及抗高温氧化性

采用真空烧结技术制备TiO_2和WO_3复合掺杂17Ni/(NiFe_2O_4-10NiO)金属陶瓷试样,研究TiO_2和WO_3复合掺杂剂对试样物相组成、显微组织、烧结致密化和抗高温氧化性的影响。结果表明:TiO_2和WO_3复合掺杂后无新相生成,而是固溶到NiFe_2O_4晶格中,产生晶格畸变和空位,使致密度提高;TiO_2和WO_3复合掺杂有利于17Ni/(NiFe2O_4-10NiO)金属陶瓷形成更加致密的具有氧化保护性的致密层,阻碍金属Ni向外迁移,提高试样的抗高温氧化性,其中TiO_2和WO_3复合掺杂量为2%(比例为3∶1)和3%(比例为1∶3)时,试样的抗高温氧化性最好,其氧化30h后的氧化层厚度大约为80μm,比未掺杂试样降低了38.46%。     

Effect of Ni+2-substituted Fe2TiO5 on the H2-reduction and CO2 Catalytic Decomposition Reactions at 500℃

CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas,high activity nanosized Ni 2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method.The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 (iron titanate) phase that has a nanocrystallite size of ～80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases (～80 nm)NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only.Samples with Ni 2=0 shows the lowest reduction extent (20%); as the extent of Ni 2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis (TGA) experiments. The oxidation of the H2-reduced Ni 2 substituted Fe2TiO5 at 500℃ was investigated. As Ni 2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of oxidized samples show also the presence of carbon in the sample containing Ni 2＞0, which appears in the form of nanotubes (25 nm).