NiFe2O4-M金属陶瓷惰性阳极成分设计的热力学分析

NiFe2O4-M金属陶瓷惰性阳极由氧化物陶瓷相和金属相组成.多数美国专利认为Fe,Ni,Cu,Co,Ti,Cr,Mn,Al,Pd,Ag,V,Zr,Y,La,Ta,Nb,Sc,Hf,Ca,Sn,Zn等21种金属均适合作为上述阳极的金属相成分.但文中的热力学详细分析计算结果表明:在上述前8种金属中,仅有Cu,Ni 2种适...     

SiCw增强NiFe2O4基惰性阳极材料的力学性能

为改善铝电解惰性阳极用NiFe2O4尖晶石材料存在的不足,采用固态合成法制备了SiCw/NiFe2O4复合材料. 研究了SiCw添加量对体积密度、气孔率、冲击韧性、热震性等力学性能的影响,并与纯NiFe2O4尖晶石对比,利用扫描电子显微镜观察显微组织,分析了其性能差异的原因. 实验结果表明,添加SiCw可以显著改善NiFe2O4尖晶石的力学性能,含2% SiCw的试样冲击韧性比尖晶石提高了近65%;添加量为3%时抗弯强度比NiFe2O4尖晶石基体强度提高了近42%,经一次热震后强度保持率可提高15%,综合考虑SiCw添加量以3%为宜.     

铝电解用金属基惰性阳极材料的研究进展

对铝电解惰性阳极的优势及阳极材料的要求进行了说明.简要介绍了国内外在铝电解工业用惰性阳极材料研究方面的最新进展,重点阐述了惰性阳极材料中的金属基惰性阳极和金属陶瓷惰性阳极的种类及性能,金属陶瓷复合材料具有良好的导电性、抗氧化和耐腐蚀性能,指出了惰性阳极的研究方向-氧化物掺杂金属陶瓷阳极.     

铝电解惰性阳极材料选择的研究进展

论述了传统碳素阳极的缺点及使用惰性阳极的意义,提出了惰性阳极材料应符合的要求,重点阐述了国内外对金属氧化物陶瓷阳极、金属陶瓷阳极、金属阳极的研究成果并总结了以上三类惰性阳极有待进一步解决的主要问题。     

镍铁尖晶石基金属陶瓷惰性阳极的电解腐蚀行为

采用粉末冶金法制备了10%Ag-NiFe2O4/NiO金属陶瓷惰性阳极,阳极为圆柱形,直径50 mm,高15 mm. 在960℃下进行电流密度为0.8 A/cm2的铝电解实验,电解时间为10 h. 研究了阳极在Na3AlF6-5%CaF2-5%Al2O3熔体中的腐蚀行为. 电解后的阳极外观尺寸略有变化,但没有发生阳极肿胀及阳极表面起层、剥离的现象,表现出较好的耐腐蚀性. 计算得到阳极腐蚀率为1.5′10-4 g/(cm2·h),折算为13 mm/a. 电解所得铝的纯度在92%~93%之间. 对腐蚀后阳极的表面分析发现,陶瓷相中Ni和Fe组元并不以化学计量数溶解,陶瓷组元的Fe2O3比NiO优先溶解进入电解质. 正对阴极的阳极表面和背对阴极的阳极表面氧元素的含量不同,前者中氧元素多于后者,说明在阳极正对阴极的表面发生析氧反应更剧烈一些,一部分新生态的氧与阳极表面的金属发生氧化反应生成Ag3O4. 对腐蚀后阳极断面进行分析发现,电解质渗透进入阳极内部,与陶瓷基体离解产生的Fe2O3发生反应,生成FeF3沉积在阳极的空隙中.     

ZrO2(f)-NiFe2O4惰性阳极在冰晶石熔盐中的腐蚀行为

以NiO和Fe2O3为原料,采用固相烧结法合成了NiFe2O4尖晶石,通过添加ZrO2纤维[ZrO2(f)]制备了ZrO2(f)-NiFe2O4惰性阳极材料. 采用失重法测量了阳极试样在冰晶石熔盐中的静态热腐蚀率和电解腐蚀率,并对腐蚀机理进行了探讨. 结果表明,ZrO2(f)添加量由0增加至4%(w)时,阳极试样的气孔率从4.9%上升到5.8%,导致其静态热腐蚀率由3.8 mg/(cm2×h)增大到4.3 mg/(cm2×h);在电场作用下,氧化物在冰晶石熔盐中的溶解反应受到抑制,含3%(w) ZrO2(f)阳极试样的电解腐蚀率为2.2 mg/(cm2×h),远小于其静态腐蚀率,腐蚀均为物理化学溶解过程;高温下ZrO2(f)在冰晶石熔盐中稳定性良好,可作为铝电解NiFe2O4基惰性阳极的强韧化材料.     

电解铝用阳极材料的研究进展

介绍了国内外铝电解惰性阳极方面较有影响的研究工作,探讨了金属氧化物陶瓷惰性阳极、金属合金惰性阳极和金属陶瓷惰性阳极选材问题,并对惰性阳极在研究和应用中出现的一些问题进行了分析,阐述了惰性阳极将会取代碳素阳极。     

添加剂对金属陶瓷惰性阳极电解腐蚀的影响

采用粉末冶金法制备了无添加剂和添加V2O5的Ag-NiFe2O4/NiO金属陶瓷惰性阳极.铝电解试验在960 ℃进行,电流密度为0.5 A/cm2,电解时间为8 h,研究了无添加剂和添加2.0%(质量分数,下同)V2O5的Ag-NiFe2O4/NiO样品在Na3AlF6-5?F2-5%Al2O3熔体中的腐蚀行为.研究表明:无添加剂的样品有较明显的腐蚀迹象,而添加2.0%V2O5的样品腐蚀后尺寸略有变化,表现出很好的耐腐蚀性.对腐蚀后样品的表面进行扫描电镜/能量色散X射线分析发现:在添加剂V2O5的作用下,Fe2O3在冰晶石中的溶解速率减小,从而抑制了陶瓷基体的溶解.另外,无添加剂样品表面各元素分布不均匀,说明无添加剂的样品在电解过程中发生选择性腐蚀,晶界等薄弱部位先被腐蚀.而添加了2.0%V2O5的样品中各元素分布均匀,说明V2O5增强了晶界的稳定性,提高了材料抗电解质的腐蚀能力.     

NiFe2O4催化剂的制备及稠油降黏性能的研究

稠油黏度高、流动性差和开采成本高是各大油田面临的问题之一.采用水热法制备了NiFe2 O4纳米催化剂,通过XRD和黏温流变仪进行了表征.结果表明,在热裂解分解反应中加入NiFe2 O4后,重油的黏度降黏率达到80％以上.     

Y2O3掺杂对17Ni/(NiFe2O4-10NiO)金属陶瓷高温氧化性能的影响

氩气气氛保护下采用气压烧结技术制备掺杂Y2O3的17Ni/(NiFe2O4-10NiO)金属陶瓷惰性阳极,在电解温度(960℃)下,对材料进行抗高温氧化性能研究.采用SEM分析材料及氧化产物的各物相分布情况、氧化形貌,并利用XRD进行成分分析.结果表明,金属陶瓷阳极的氧化动力曲线均大致符合抛物线规律;掺杂适量的Y2 O3对金属相的分散有一定作用,并能有效抑制烧结试样及氧化物的孔洞生成,从而显著改善该金属陶瓷的抗高温氧化性能,其中,当Y2 O3掺杂量为0.5％时,材料抗高温氧化性能最好,30 h后单位面积氧化增重量仅为10.6591 mg/cm2.     

NiFe2O4基金属陶瓷的研制

采用传统粉末冶金技术冷压烧结法制备了Cu-NiFe2O4金属陶瓷板状惰性阳极。采用DTA-TG分析和XRD等方法研究了惰性阳极制备工艺、物相组成。采用电镜等方法研究了镍铁尖晶石材料结构及性能的关系。并测定了该材料的电导率,结果证明,Cu-NiFe2O4金属陶瓷呈现出半导体导电性质,在960℃时,电导率超过了40Ω-1·cm-1。     

CoFe2O4/NiFe2O4 S-scheme composite for photocatalytic decomposition of antibiotic contaminants

Keeping in view of the hazardous application of tetracycline hydrochloride antibiotic, an efficient CoFe₂O₄/NiFe₂O₄ heterojunction photocatalyst has been prepared hydrothermally by combining CoFe₂O₄ and NiFe₂O₄ nanoplates. The CoFe₂O₄/NiFe₂O₄ composite with the improved photocatalytic activity can be employed for removal of tetracycline hydrochloride antibiotic, comparing to the bare CoFe₂O₄ and NiFe₂O₄. The optimized sample 5%-CoFe₂O₄/NiFe₂O₄ shows the high photocatalytic degrading tetracycline with 76.1% removal efficiency in 60 min. These improved photocatalytic activities are attributed to the extended visible light absorption and enhanced charge separation following S-scheme route as confirmed from photoluminescence and electrochemical studies. From the charge trapping experiments, it is confirmed that superoxide radical and holes in the valence band of NiFe₂O₄ with high thermodynamic energies are responsible for the photodegradation of the target pollutant. This work provides sufficient attention towards the preparation of low cost materials for the removal of highly hazardous pollutants being present in water.     

Study of Electromagnetic Properties of Fabricated NiFe2O4/Polyurethane Nanocomposites

Nickel ferrite loaded (NiFe₂O₄) segmented polyurethane (SPU) nanocomposites prepared by melt mixing method using microcompounder at temperature 185 °C in recirculation mode to ensure proper dispersion and distribution of nanoparticles at optimized residency time of 5 min. Three different weight percentages of nanocomposites (3, 5, and 10 wt %) was prepared and studied the electromagnetic property of nanocomposites obtained from complex permittivity and permeability. The effect of nanofiller (NiFe₂O₄) has been studied to assess their thermal properties using thermogravimetric analysis, differential scanning calorimetry, and thermomechanical analysis. The nanocomposites (NiFe₂O₄/SPU) have further been studied using FE-SEM, and the micrographs show embedded NiFe₂O₄ filler uniformly dispersed in SPU matrix without agglomeration (size 20–40 nm). It is also evident that further loading of nanofiller resulted in saturation effect yielding no applicable change in thermal behavior and revealed lesser melting enthalpy due to the coalescence of the nanofillers. X-ray diffraction and vibrating sample magnetometer also support the formation of the nanocomposite. The electric and magnetic properties of NiFe₂O₄ incorporated nanocomposite (NiFe₂O₄/SPU) may have potential application in microwave absorption. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48645.     

Light-modulated ferromagnetism of strained NiFe2O4 nanocrystals

Light provides a potential approach to modulate magnetism due to the low energy consumption, which could be used for the development of optical-magnetic coupling devices, data storage technology and quantum computation technology. In this work, NiFe₂O₄ nanocrystals with inverse spinel structure confined in non-magnetic Al₂O₃ film are synthesized. Based on theoretical calculation and experimental validation, it is revealed that the NiFe₂O₄ nanocrystals experience compressive strain from Al₂O₃ film. The compressive strain can be partially relaxed, leading to the formation of disorder layers at the surfaces of strained NiFe₂O₄ nanocrystals, which provide an ideal platform to modulate magnetism optically. A remarkable light-modulated ferromagnetism in the strained NiFe₂O₄ nanocrystals is observed. This work demonstrates a novel approach to optically engineer the ferromagnetic properties for applications in next generation of magnetic nano-devices.     

铁酸镍纳米晶体材料的制备

以ＦｅＳＯ４·７Ｈ２Ｏ和ＮｉＳＯ４·７Ｈ２Ｏ为原料,首先制备出晶粒细小的碱式碳酸盐前驱体,在３００～７００℃焙烧１ｈ后,制备出ＮｉＦｅ２Ｏ４纳米晶体材料。经ＸＲＤ和ＴＥＭ检测,粒径为３～１８ｎｍ,粒度均匀。     

Synthesis and characterization of monodisperse NiFe2O4 nanoparticles

Narrow size distribution nickel ferrite nanoparticles with average particle size of around 6 nm has been synthesized via rapid thermo-decomposition method in the presence of oleylamine in solution which acted as neutralizing, stabilizing and reducing agent OAm coated NiFe₂O₄ NPs. X-ray powder diffraction (XRD), Fourier Transform Infrared Spectra (FT-IR), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), Vibrating Simple Magnetometer (VSM) and also Mössbauer Spectroscopy were used for structural, morphological, spectroscopic and magnetic characterization of the product. The XRD analysis revealed the formation of single phase nickel ferrite with Fd-3m space group. Both FT-IR and TGA analyses confirmed the formation of desired nanocomposite. FT-IR analysis also showed characteristic IR absorption bands of the spinel nickel ferrite phase and oleylamine. TEM and SEM analysis showed that product have almost spherical structural morphology. TEM images showed that NiFe₂O₄ nanoparticles have narrow size distribution and Energy Dispersive X-ray (EDX) analysis confirmed the presence of metal ions in the required stoichiometric ratio. Superparamagnetic property of the product was confirmed by VSM. From ⁵⁷Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values have been determined. The Mössbauer spectra for OAm coated NiFe₂O₄ NPs. is consisting of one paramagnetic central doublets and one magnetic Zeeman sextet. Finally, the synthetic procedure can be extended to the preparation of high quality metal or alloy nanoparticles.     

Mo-Al2O3金属陶瓷与绝缘陶瓷共烧实验研究

探讨Mo-Al2O3金属陶瓷与氧化铝绝缘陶瓷共烧制备技术,利用陶瓷料浆收缩率内外差．通过热压铸成形方法制备稳固结合的共烧坯体,经高温氢炉烧成．成功制得金属陶瓷与氧化铝陶瓷共烧体．经氦质谱仪检漏测试,其漏气率小于10^-13Pa·m^3／s。