Fe2O3、Cr2O3掺杂对4YSZ导电性能的影响

用柠檬酸溶胶-凝胶法制备了分别掺Fe2O3和Cr2O3的4YSZ前驱体凝胶,凝胶在500℃预烧,压制成圆片状后在1 300℃煅烧2 h得到所需试样;分别研究Fe2O3、Cr2O3的不同掺量对试样的烧结性能、电导率的影响。结果表明掺Fe2O3可提高试样的电导率和烧结性能;掺Cr2O3可提高试样的低温电导率,但使试样的烧结性能下降。     

磁性纳米Fe3O4的研究进展

简单介绍纳米Fe3O4的制备方法,表征手段、应用进展。制备方法通常有化学共沉淀法、沉淀氧化法、溶胶法、微乳液法等。其应用范围主要包括在磁性密封、生物医学、微波吸收、催化剂等一些领域。     

Fe3O4超细磁粉生产技术

北京理工大学逸夫科技交流中心近日向社会推出Fe3O4 超细磁粉生产技术。据介绍 ,这种超细磁粉因兼有磁性和超细粒子的特性而在许多领域得到了广泛的应用 ,如用于制备复印机显影剂、磁性油墨、透明颜料等。北京理工大学化工与材料学院采用成本低廉、设备简单、重复性好的化学法制备Fe3O4 超细磁粉 ,所制备的磁粉粒度均匀 ,其粒径大小、粒子形态、比饱和磁化强度、矫顽力等多种参数皆可根据使用需要予以调整。该制备技术已通过中试生产 ,以该技术生产的Fe3O4 超细磁粉已被用于复印机显影剂的生产。在该技术基础上 ,通过对生产工艺参数的调…     

锰锌铁氧体中Fe2O3、Mn3O4和ZnO的匹配

简单介绍了锰锌铁氧体制造过程中所用主要原材料氧化铁,四氧化三锰,氧化锌等的物理、化学性能,并讨论了彼此之间的相容性和有关匹配问题。     

Transformation of α-Fe2O3 to Fe3O4 Realized by Mechanochemical Reaction of α-Fe2O3 and SrCO3

A transformation from ??-Fe₂O₃ with rhombohedral structure to Fe₃O₄ with spinel face-centered cubic (fcc) structure was realized by ball milling the mixture of SrCO₃ and ??-Fe₂O₃ powders with molar ratio of 1:3 under ambient air in the current work, but it was not observed by ball milling the ??-Fe₂O₃ powders. The transformation is due to a mechanochemical reaction between SrCO₃ and ??-Fe₂O₃ in the milling process, and the ??-Fe₂O₃ catalyzes the decomposition of SrCO₃, while the decomposition promotes the transformation of ??-Fe₂O₃ to Fe₃O₄. X-ray diffraction, X-ray photoelectron spectrometry, and magnetic measurements indicate that the transformation finishes completely upon milling of 120?hours, and the mixture milled for 120?hours consists of Fe₃O₄ and a Sr element. However, Sr does not incorporate into the Fe₃O₄ but exists in grain boundary of the Fe₃O₄ in a form of a Sr-O bond. It is found that the product obtained by ball milling the mixture is different from that prepared by sintering the mixture at atmospheric pressure, which product is SrFeO_2.97 with cubic structure. The mechanism of the transformation and origin of difference in products obtained in the ball milling and sintering processes are also discussed in the current work.     

超微Fe3O4胶体粒子的制备

本文研究了不同碱类和搅拌速度对生成的Ｆｅ３Ｏ４磁性胶体微料形貌和磁性能的影响，证明按ＮａＯＨ、ＮＨ４ＯＨ、ＮＨ４ＨＣＯ３、Ｎａ２ＣＯ３的次序、饱和磁化强度依次降低；而随转速加快，矫顽力增加，上述研究结果为工业制备Ｆｅ３Ｏ４磁性胶体微料节依据。     

Determination of standard gibbs energies of formation of Fe2Mo3O12, Fe2Mo3O8, Fe2MoO4, and FeMoO4 of the Fe-Mo-O ternary system and μ phase of the Fe-Mo binary system by electromotive force measurement using a Y2O3-stabilized ZrO2 solid electrolyte

The standard Gibbs energies of formation of Fe₂Mo₃O₁₂, Fe₂Mo₃O₈, FeMoO₄, and Fe₂MoO₄ of the Fe-Mo-O ternary system and the μ phase of the Fe-Mo binary system have been determined by measuring electromotive forces of galvanic cells having an Y₂O₃-stabilized ZrO₂ solid electrolyte. The results are as follows: $$\begin{gathered} \Delta _f G^\circ (FeMoO_4 )/kJ \cdot mol^{ - 1} = - 1053.5 + 0.2983(T/K) \pm 0.4 \hfill \\ Temperature range: 1112 to 1339 K \hfill \\ \Delta _f G^\circ (Fe_2 Mo_3 O_8 )/kJ \cdot mol^{ - 1} = - 2347 + 0.6814(T/K) \pm 1 \hfill \\ Temperature range: 1112 to 1339 K \hfill \\ \Delta _f G^\circ (Fe_2 Mo_3 O_{12} )/kJ \cdot mol^{ - 1} = - 2993 + 0.9105(T/K) \pm 2 \hfill \\ Temperature range: 1040 to 1145 K \hfill \\ \Delta _f G^\circ (Fe_{0.58} Mo_{0.42} )/kJ \cdot mol^{ - 1} = - 18.7 + 0.0117(T/K) \pm 0.1 \hfill \\ Temperature range: 1162 to 1223 K \hfill \\ \Delta _f G^\circ (Fe_2 MoO_4 )/kJ \cdot mol^{ - 1} = - 1174 + 0.342(T/K) \pm 1 \hfill \\ Temperature range: 1243 to 1466 K \hfill \\ \end{gathered} $$ where the standard pressure is 1 bar (100 kPa).     

循环伏安法测定溶液中Fe3+和Fe2+浓度比

采用循环伏安法（CV）测定铁泥制备Fe3O4过程中Fe3+与Fe2+浓度比值的变化,为该工艺过程提供方便、快捷的监测方法。在实验条件下,溶液中的Fe3+与Fe2+组成可逆的氧化还原体系,产生一对峰形良好的氧化还原峰。对影响峰电流的扫描速度、pH值及干扰离子等因素进行考察,结果表明,扫描速度在0.002~0.01 V/s、pH在1.5~2.5时对氧化峰电流及还原峰电流没有影响;溶液中存在的SO42-离子在实验范围内对体系基本无干扰。Fe3+的浓度在0.000 8～0.008 4 mol/L呈线性关系,相关系数为0.999 9,相对标准偏差(n=7)在 0.70%~2.0%之间。该法与标准重铬酸钾滴定法对比,相对误差为1.7%。     

Effect of Fe2O3 Loading Amount on Catalytic Properties of Monolithic Fe2O3/Ce0.67Zr0.33O2 -Al2O3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.     

Fe3O4纳米粒子的合成与表征

以P123胶束作为"纳米反应器",采用水溶液法合成了Fe3O4纳米粒子.采用场发射扫描电子显微镜(FE-SEM)、X射线衍射仪(XRD)、傅立叶变换红外光谱(FTIR)和样品振动磁强计等现代化分析测试手段对产物的形貌、结构和磁性进行了测试表征.结果表明,合成的Fe3O4纳米粒子粒径大小在30～120 nm可控,它们在常温下是超顺磁性的且具有较高的饱和磁化强度.所合成的纳米铁氧体磁性材料在信息存储、生物医药和催化等领域具有重要的理论研究价值和广阔的应用前景.     

Fe2O3催化煤粉燃烧的动力学

采用WCT-2C型微机热重分析天平以及非等温燃烧的方法对汉阳煤的燃烧特性及其反应动力学参数进行详细分析.研究了不同Fe2O3配比对试样的着火温度、燃烧速率最大时温度、燃尽温度和最大燃烧速率等的影响,计算出煤粉燃烧反应的动力学参数活化能Ea.试验结果表明:试样燃烧的的活化能呈现“V”形,Fe2 O3配比为3％(质量分数,下同)时催化作用最明显,超过3％后随着配比的增加催化作用减弱.     

镁砂中Fe2O3、Al2O3、P2O5、TiO2的联合测定

镁砂产品检验中,采用碱熔融法共同预处理样品,在同一母液中,联合测定铁、铝、磷、钛的含量,缩短了检测时间。通过分别控制各元素的显色酸度,各元素线性良好,测得的Fe2O3、Al2O3、P2O5、TiO2的相对标准偏差分别小于1.11%、2.78%、4.84%、5.88%。实验结果表明,方法的准确度和精密度都较高。     

球磨Fe_3O_4+Al制备Fe/α-Al_2O_3及选择刻蚀Fe制备α-Al_2O_3

本研究以Al粉和Fe_3O_4粉末为原料,采用机械诱发自蔓延方法制备α-Al_2O_3和Fe混合粉末,然后对产物进行分离和提纯,并得到纯净的α-Al_2O_3粉末。本研究中主要应用了球磨技术、X射线衍射分析技术、超声清洗技术、扫描电镜技术等先进设备和技术。     

用pH计测定溶液中H2O2、Fe3+和Cr6+的质量浓度

用 p H计测定溶液中某些离子的质量浓度 ,一般都是将 p H计与离子选择电极配合使用。如用氟离子选择电极与 p H计配合可测定溶液中 F- 的浓度。p H计一般用于测定溶液的 p H值和电位值。但经研究认为 ,与滴定装置配合 ,用数字显示p H计作为滴定终点显示仪 ,不用指示剂可测定溶液中的一些成分或离子的浓度。这里将一些应用实例简要介绍如下。1 .在铀的 H2 O2 沉淀中 ,由于 H2 O2 溶液在杂质或光的作用下很溶液发生催化分解 ,所以对沉淀剂及沉淀母液中 H2 O2 的量的测定极为重要。为此我们开发出了一种用 p H计作为滴定终点电位显示仪 ,…     

Al/Fe2O3反应合成材料热力学

运用CALPHAD技术，基于多组元多相复杂平衡体系的吉布斯自由能最小化原理，用大型集成数据库F^*A^*C^*T系统，考察了铝和氧化铁经典反应体系的热力学规律。针对材料的反应合成技术，计算了化学计量铝和氧化铁体系以及各种产物中物种的相变情况；分析了原料初始温度、配料比和SiO2含量对绝热温度和平衡组成的影响。     

Fe3O4纳米级超微粉末的制备试验

分析了讨论了以共沉淀制备Ｆｅ３Ｏ４纳米级超微粉末时，不同反应条件对产物粒径与磁学性能的影响，确定了较为合适的工艺参数，所制备的Ｆｅ３Ｏ４超微粉末，粒径分布均匀，平均粒径约为１１．８ｎｍ，比饱和磁化强度达７１．６ｃｍｕ／ｇ。     

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In order to understand the effects of various iron oxides on the properties of melts, viscosity, density as well as sulphide capacities of slag system containing FeOx were summarized and discussed. It is indicated that either thermophysical or thermochemical properties would be modified accordingly with the valence change of iron oxides. Fe2+ and Fe3+ have different functions in slag. Fe2+ existed as a network-breaker, which resulted in the decreasing of viscosity and increasing of sulphide capacities with increasing addition of FeO. However, Fe3+ commonly would occupy the tetrahedron and octahedron positions, and play a network-former role, consequently, cause the viscosity of melts increasing etc. Direct investigations of slag structure or valence state of iron in the melt also support the regular patterns derived indirectly from the various physical-chemical properties. Meanwhile, these patterns of slag system including iron oxides also offer a good reference to the study of other transition melt oxides in slag system.     

Thermodynamic properties of the MgAl2O4−MnAl2O4 spinel solid solution

The thermodynamic properties of the MgAl₂O₄−MnAl₂O₄ system are required for calculating the deoxidation equilibrium of molten iron and nickel containing magnesium, manganese, and aluminum. The thermodynamic properties of the MgAl₂O₄−MnAl₂O₄ spinel solid solution have been determined by equilibrating it with silver at known oxygen partial pressures. The free energy of formation of MnAl₂O₄ from its oxide components at 1673 and 1823 K was found to be −30.6 and −28.2 kJ/mol, respectively. It was observed that the MgAl₂O₄−MnAl₂O₄ spinel solid solution exhibited small negative deviations from ideal behavior at 1673 and 1823 K. The excess partial free energies of MgAl₂O₄, , and MnAl₂O₄, , at 1673 and 1823 K are expressed asG