Nonisothermal crystallization kinetics and stability of leucite and kalsilite from K2O-Al2O3-SiO2 glasses

The crystallization mechanisms and elemental stability of leucite and kalsilite formed from K₂O-Al₂O₃-SiO₂ glasses were investigated by X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Raman spectroscopy and differential scanning calorimetry (DSC). Glass samples with compositions along the leucite-kalsilite tie-line were produced by melt processing and were then heat-treated at 850, 950, and 1250°C for times ranging from 5 minutes to 1000 hours. Kalsilite is an unstable phase that behaves as an intermediate precursor to leucite. Crystalline materials in which kalsilite is the major phase lose potassium upon prolonged heat treatment (1000 hours at 1250°C), in contrast to those with leucite, in which little or no compositional alteration is detected. The formation of leucite from stoichiometric kalsilite is accompanied by the formation of potassium-doped alumina. The activation energies for leucite and kalsilite crystallization, determined via application of the Kissinger equation to thermal analysis data, were 579 and 548 kJ/mol, respectively. Finally, production of pure leucite can be achieved with more favorable crystallization kinetics when starting with off-stoichiometric compositions.     

Effect of Fe2O3 content on the electrical resistivity of aluminous porcelain applied to electrical insulators

In general, the presence of Fe₂O₃ is claimed to reduce the insulating behavior of electrical porcelains, even if a rigorous proof has not yet been reported. The purpose of this study was to evaluate the real influence of Fe₂O₃ content on the electrical resistivity of a standard aluminous porcelain widely used in insulators. The electrical resistivity for the composition with 3 wt% Fe₂O₃ was higher than those found for standard aluminous porcelain, which was discussed in terms of the concentration of glassy and mullite phases. A reduction in the electrical resistivity was only observed in porcelain samples containing over 3 wt% Fe₂O₃. The presence of hematite phase was considered responsible for this reduction. These results suggest that low-cost raw materials with greater Fe₂O₃ content should not extensively affect the insulating properties and could therefore be used in manufacturing aluminous electrical porcelain.     

In situ polymerized Fe2O3@PPy/chitosan hydrogels as a hydratable skeleton for solar-driven evaporation

The world population is severely affected by water scarcity, and it is an alarming issue that needs to be addressed urgently. Seawater desalination by solar-driven evaporation is a promising technique to produce clean water. However, it is energy intensive and directs to a low water yield under natural sunlight. Therefore, the developments of new photothermal materials can reduce required energy for desired evaporation rates for efficient freshwater yield. Indeed, chitosan and polypyrrole-based polymers are natural cationic copolymers, and their nanocomposites present well deal of interest for hydrogel structures due to their hydratable skeletons, and solar-absorbing nature. Here, we report in situ polymerized Fe₂O₃@PPy/chitosan hydrogels as lightweight evaporation structures for solar-powered evaporation under brine solutions (3.5 wt%). The polymeric network of Fe₂O₃@PPy/chitosan hydrogels builds in cross-linked macroporous water channels, self-floating, and a wide range of omnidirectional solar absorption (96%). The state-of-the-art evaporation experiments demonstrate an efficient evaporation rate of water (1.80 kg m^–2 h^–1) and enhanced solar-to-vapor conversion efficiency (91%) as compared to other carbon-based evaporation structures, excluding heat losses under 1 kW m^–2 (one sun). Of note, the ultra-black hydrogel surface stored enough thermal energy (39.6°C) under one sun solar irradiance due to the cationic polymeric network of Fe₂O₃@PPy/chitosan. A single-step process for a freshwater supply that has been purified from various contaminants shows the potential of this device for real-world applications.     

磺基水杨酸分光光度法测定三氧化二铁

针对低铁含量（w（Fe2O3）0.5％～1.5％）的云南磷矿石,采用磺基水杨酸分光光度法测定Fe2O3,可获得准确的分析结果,标准偏差为0.03％,且分析过程简便.     

Na2O-Al2O3-Fe2O3系烧结过程中铝、铁的反应行为

以Al2O3, Fe2O3和Na2CO3为原料,对Na2O-Al2O3-Fe2O3系烧结过程中的反应行为进行了详细研究. 基于溶出率与时间、温度的关系,证明Na2O×Al2O3和Na2O×Fe2O3的生成反应动力学都服从Zhuralev-Lesokin-Tempelman模型,表观活化能分别为186.59和80.92 kJ/mol,表明Na2O×Fe2O3比Na2O×Al2O3在动力学上更易形成;Al2O3易与Na2O×Fe2O3反应形成Na2O×Al2O3和Fe2O3,在1273 K烧结30 min,所得熟料Al2O3溶出率达98.51%;Fe2O3对Na2O×Al2O3的形成有双重作用,在1273 K下可加速Na2O×Al2O3的形成,超过1323 K,促使Na2O×Al2O3分解成Na2O和b-Al2O3,且随着温度升高或时间延长,分解程度增高,从而导致熟料中Al2O3溶出率显著降低.     

纳米固体超强酸SO2-4/Fe2O3催化合成尼泊金酸丁酯

以纳米固体超强酸SO2-4/Fe2O3为催化剂,催化尼泊金酸与正丁醇的酯化反应,合成尼泊金酸丁酯.较适宜的反应条件为:尼泊金酸25 mmol,n(尼泊金酸):n(正丁醇)=1:4,催化剂加入量为反应物总质量的2%,甲苯5 mL,温度(122～124)℃,反应4 h,酯化率达92.4%.     

三氧化二铁超细粉末的制备

以含三价铁离子的酸性溶液为源物质，采用溶胶-凝胶法制备三氧化二铁超细粉末，在650℃下焙烧后得到Fe2O3超细粉末，用X射线衍射(XRD)对粒子进行表征，结果表明该超细粉末达到纳米级，其平均粒径达23nm。     

Fe2O3中空微球的制备与表征

以自制碳球为模板,FeCl3为原料,经水解、高温煅烧,制备出粒径约为250 nm的Fe2O3中空微球。用X-射线衍射（XRD）、透射电镜（TEM）等现代测试手段对Fe2O3中空微球样品的结构、形貌进行了表征;并考察了煅烧时间的变化对所制备的Fe2O3中空微球的晶型及形貌的影响。     

三氧化二铁着色的云母钛珠光颜料的制备

对三氧化二铁着色的云母钛珠光颜料的制备工艺进行了研究。最佳反应条件为：ｐＨ２～４，反应温度９０℃，三氯化铁与尿素的重量比为１∶３～１∶５。三氧化二铁沉积量１％～３％时颜料成金色，大于４％呈红色     

PVA/Fe2O3磁敏感性水凝胶的制备及性能

采用循环冷冻-解冻方法制备了聚乙烯醇(PVA)/Fe2O3磁敏感性水凝胶. 考察了水凝胶的力学性能、溶胀性能和磁敏感性,并用扫描电镜观察了其表面形貌. 结果表明,当Fe2O3含量为1%(w)时,水凝胶的力学性能最好;水凝胶的溶胀度和脱水率随时间增加有相似的变化趋势,都随磁性粒子含量升高而降低;溶胀性能降低其交联程度增加;PVA和Fe2O3相容性较好;水凝胶在3000 Oe的磁场强度下达到饱和,呈现出很强的顺磁性,磁滞损耗较多,表明具有较好的磁敏感性.     

Fe/Al2O3梯度涂层的制备与性能

采用喷涂法和溶胶-凝胶法相结合的工艺制备钢基Fe/Al2O3梯度涂层复合材料,并对其性能进行分析。结果表明：Fe/Al2O3梯度涂层与钢基体的界面结合强度较高,达21.2MPa;涂层与基体以及涂层与涂层之间没有明显的界面,实现了良好结合。涂层的表面硬度要比钢基体高4-5倍;Fe/Al2O3梯度涂层主要由α-Al2O3、AlFeO3、Al2Fe2O3和Al3Fe5O3物相组成。     

纳米固体超强酸SO2-4/Fe2O3催化合成正丁酸异戊酯的研究

采用纳米固体超强酸SO2-4/Fe2O3为催化剂,以正丁酸和异戊醇为原料,催化合成正丁酸异戊酯.较适宜反应条件为:正丁酸150 mmol,n(酸):n(醇)=1:1.2,催化剂300 mg(占反应物总量1%),于150～160 ℃回流反应3 h,产率达96.30%.     

试述煤灰中Fe2O3测定的几点改进意见

利用标准煤样的结果作对照，对煤样分析标准中的一些操作步骤作了尝试性的改进，最终获得快速、准确的实验结果。     

纳米Fe2O3的有机表面改性及表征

研究了纳米Fe2O3，有机表面改性的影响因素，确定了最优改性剂和改性条件。采用红外光谱（FT-IR）、热分析（TG）、透射电镜（TEM）和分散性实验对表面改性前后的纳米Fe2O3，进行了表征。实验结果表明，以硬脂酸为改性剂、用量为15％、pH值为8、改性时间为2h时，改性后的纳米Fe2O3的亲油化度达到89．47％。红外光谱和热分析显示，硬脂酸以化学键合的方式结合在纳米Fe2O3的表面，其质量分数约为11％。透射电镜（TEM）和分散性实验表明，经硬脂酸有机表面改性的纳米Fe2O3，具有亲油疏水性能，能较好地分散于有机溶剂二甲苯中。     

可见光响应氧化铁复合TiO2光催化剂的制备及其性能研究

以尿素铁(Ⅲ)配合物和钛酸四丁酯为前驱物,采用注入法制备了不同Fe2O3复合比的TiO2纳米粉体,通过DTATG 、XRD、XPS和UV-Vis的测试,表征其物相结构、样品表面元素存在形式和光谱学性质;并以甲基橙光降解反应为探针反应,分别以紫外光和可见光为光源测试其光催化活性.结果表明,复合Fe2O3后的TiO2纳米粉体为锐钛矿型,样品表面铁元素主要以Fe(Ⅲ)形式存在,并且其UV-Vis光谱吸收曲线有明显的红移现象;Fe2O3的复合明显提高了TiO2光催化剂的紫外和可见光催化活性;Fe2O3的最佳复合比为1 mol％.     

凝聚剂对氧化铁悬浮液流变性的影响

应用LVDV-Ⅲ+型可编程流变仪测定了凝聚剂对氧化铁悬浮液的流变特性的影响。实验结果表明,高价凝聚剂对于悬浮液颗粒的凝聚能力要比低价凝聚剂更加明显;随着凝聚剂浓度的增加,悬浮液颗粒的凝聚程度也相应增加;凝聚剂种类的不同,对于悬浮液流变性能的影响也不同,高价凝聚剂对于悬浮液流变性能的影响比低价凝聚剂大。在相同剪切速率下,添加高价凝聚剂悬浮液的表观粘度和剪切应力都大于添加低价凝聚剂悬浮液的表观粘度和剪切应力;凝聚剂浓度的不同,对于悬浮液流变性能的影响也不同。在相同剪切速率下,添加高浓度凝聚剂悬浮液的表观粘度和剪切应力都大于添加低浓度凝聚剂悬浮液的表观粘度和剪切应力,增加凝聚剂浓度对提高悬浮液粘着性能具有积极意义。     

双壳层中空Fe_2O_3微球的制备与性能研究

文章采用C微球为模板,通过多次包覆的方法成功制备出双壳层中空Fe2O3微球,并推断了其形成机理和研究了其性能。结果表明,双壳层中空Fe2O3微球具有较高的比表面积,在催化剂、纳米吸附剂、气体传感器等领域具有重要的潜在应用价值。     

单分散Fe3O4@nSiO2@mSiO2复合微球的制备及磁性的研究

以FeCl3作为铁源,乙二醇作为溶剂,采用溶剂热法合成单分散Fe3O4微球。通过调节铁源的浓度,改变Fe3O4的粒径(250～1 000 nm)以及磁特性(Ms:51.0～83.1 emu/g;Hc:82.2～165.6 Oe)。并采用改进的Stber法在Fe3O4微球表面包覆不同厚度的SiO2(35～150 nm),以进行其表面的修饰。,对Fe3O4@nSiO2@mSiO2微球的表面进行聚乙烯亚胺修饰以改善其亲水性和表面偶联性。寻找合适于生物细胞载体的磁珠的制备工艺。     

钇掺杂三氧化二铁催化剂的脱硝性能研究

为提升三氧化二铁(Fe₂O₃)催化剂的脱硝性能,扩展催化剂的活性温度窗口,采用共沉淀法引入助剂钇(Y)元素对Fe₂O₃催化剂进行改性。通过X射线衍射(XRD)、氮气等温吸-脱附(N₂-BET)、X射线光电子能谱(XPS)、氨气程序升温脱附(NH₃-TPD)、氢气程序升温还原(H₂-TPR)等表征方法对样品进行了表征分析。XRD和N₂-BET结果表明,Y的掺杂使催化剂结构发生变化,比表面积增加、孔径减小。XPS和NH₃-TPD结果证明,Y掺杂Fe₂O₃具有更多的表面吸附氧(O_Ⅰ)、Fe²⁺以及更多的酸量。H₂-TPR结果表明,Y的掺杂使催化剂的氧化还原能力略有下降。测试了不同含量Y掺杂的Fe₂O₃催化剂在150～400℃的脱硝性能,其中Fe<...     

纳米Fe3O4颗粒的制备及应用

介绍了纳米Fe3O4颗粒的制备方法,这包括化学共沉淀法、沉淀氧化法、微乳液法、水热法、机器研磨法、多元醇法、超声沉淀法、溶胶-凝胶法等,并比较了各种制备方法的特点;在此基础上,进一步论述了纳米Fe3O4颗粒在生物医学、导电磁性材料、催化剂以及磁记录材料中的应用进展。