Structural role and coordination environment of Fe in Fe2O3–PbO–SiO2–Na2O composite glasses

The structural role, coordination geometry and valence of Fe in a series of Fe₂O₃–PbO–SiO₂–Na₂O glasses are studied by means of Fe-K-NEXAFS and EXAFS spectroscopies. Parameters for the study are the concentration of the Fe and Pb-oxides, the SiO₂/Na₂O ratio and the cast temperature. The EXAFS and NEXAFS results reveal that the role of Fe³⁺ depends on the concentration of Fe₂O₃. More specifically, in most of the studied quaternary systems, the Fe³⁺ ion is a glass former, i.e. the Fe atoms belong to FeO₄ tetrahedra that participate in the formation of the glassy network. The role of Fe as an intermediate oxide is identified only in one sample with 20 wt% Fe₂O₃, where ～80 at.% of the Fe atoms are tetrahedrally coordinated with O atoms, while the remaining ～20 at.% of the Fe atoms occupy octahedral sites. It is also revealed that the tetrahedral coordination of Fe in the vitreous matrix is destroyed when a number of parameters is altered, such as the T_cast, the (Fe + Si)/O and the SiO₂/Na₂O ratio.     

Glass forming region and physical properties in the system P2O5-Na2O–Fe2O3

The glass forming region of the system P₂O₅–Na₂O–Fe₂O₃ was determined, using phosphate salts as precursor materials. The glasses were produced in non-wetting gold/platinum crucibles in order to avoid contamination. Glass formation was confirmed using XRD and the final composition determined using EDX. The glass forming region was found to be relatively short at 50% P₂O₅ content in comparison to both lower and higher P₂O₅ content. As expected, the inclusion of Fe₂O₃ had a significant effect on both glass transition temperature and density with a peak seen at around 30 mol% Fe₂O₃. This coincides with previously reported abrupt structural changes in the glass. The inclusion of Na₂O has little effect on the glass transition temperature but causes a small increase in density.     

Fe2O3-CO3O4共掺杂MgO-Al2O3-SiO2体系的红外辐射性能研究

采用固相反应法制备Fe2O3-Co3O4共掺杂MgO-Al2O3-SiO2体系的复合陶瓷材料,并通过XRD、SEM、XPS以及红外辐射测试等方法研究了样品的结晶行为与红外辐射性能.结果表明:Fe2 O3和Co3 O4共掺杂MgO-Al2 O3-SiO2体系后离子分布改变并生成混合尖晶石,从而引起品格畸变,从而有效提高材料的红外辐射性能.材料的红外发射率与其晶格畸变程度具有相同的变化趋势,并随Fe2 O3与Co3O4质量之比(R)的增加呈非线性变化.当R=3∶2时,材料在8 ～ 14 μm波段的辐射率可达0.92.     

Fe2O3对MgO-Al2O3-SiO2系微晶玻璃介电性能的影响

以化学纯试剂为原料采用高温熔融法制备MgO-Al2O3-SiO2 (MAS)系微晶玻璃,利用差热分析仪(DSC)、X射线衍射(XRD)、电子扫描显微镜(SEM)以及介电检测等手段对Fe2O3在MAS系微晶玻璃中介电性能的影响进行探究.结果表明:Fe2O3有降低微晶玻璃核化和晶化温度的作用;随着Fe2O3的加入,试样的主晶相由堇青石向镁铝尖晶石转变,试样的介电常数和介电损耗逐渐减小并且电阻率增高;当Fe2O3的添加量大于6;时,微晶玻璃的介电性能变化不大,趋于稳定.     

Production and properties of high purity TeO2− WO3−(La2O3, Bi2O3) and TeO2− ZnO−Na2O−Bi2O3 glasses

TeO₂–WO₃ (TW), TeO₂–WO₃–La₂O₃ (TWL), TeO₂–WO₃–La₂O₃–Bi₂O₃ (TWLB) and TeO₂–ZnO–Na₂O–Bi₂O₃ (TZNB) glasses were produced by high-purity oxide mixtures melting in platinum or gold crucible at 800 °C in the atmosphere of purified oxygen. The total content of Cu, Mn, Fe, Co and Ni impurities was not more than 0.1–0.5 ppm wt in the initial oxides and glasses. The stability of TZNB glasses to crystallization, characterized by (T_x ? T_g) value more than 150 °C, was demonstrated by DSC measurements at heating rate 10 K/min. In the case of La₂O₃-containing glasses the thermal effects of both crystallization and fusion of the crystallized phases were not observed. The hydroxyl groups absorption coefficients of pure tellurite glasses at the maximum of the absorption band (λ ~ 3 μm) were in the region of 0.012–0.001 cm^?1. The optical absorption losses, measured by the laser calorimetry method at λ = 1.56 and 1.97 μm, did not exceed 100 dB/km.     

Fe2O3微球的制备及其表征

本文采用阳离子交换树脂为模板,通过离子交换、高温焙烧等过程制备了Fe2O3微球.采用X射线衍射、红外光谱、扫描电镜、X射线能量散射谱仪等分析方法对产物进行了表征.结果表明:所制备的微球直径在300～500 μm之间,微球表面由α-Fe2O3颗粒有序排列组成.     

Magnetite nanoparticles prepared by the crystallization of Na2O–Fe2O3–B2O3–SiO2 glasses

A glass with the composition of 35Na₂O–24Fe₂O₃–20B₂O₃–20SiO₂–1ZnO (mol%) was melted, quenched, using a twin roller technique, and subsequently heat treated in the range 485–750 °C for 1–2 h. This led to the crystallization of magnetite as the sole or the major crystalline phase.Heat treatment at lower temperatures resulted in the crystallization of magnetite crystals 7–20 nm in diameter, whereas heat treatment at higher temperatures produced higher quantities of magnetite and much larger crystals. The room temperature magnetization and coercive force values were in the range of 6–57 emu g^? 1 and 0–120 Oe, respectively for the heat treated glasses.     

Fe2O3掺杂对MgO-Al2O3-SiO2系玻璃析晶和性能的影响

采用高温熔融法和两步法微晶热处理制备了MgO-Al2O3-SiO2系堇青石微晶玻璃和铁尖晶石微晶玻璃.利用DSC分析、X射线衍射、FTIR和扫描电子显微镜等手段研究了Fe2O3对玻璃的析晶性能、显微结构和物理性能的影响.结果表明,Fe2 O3的加入可有效降低析晶活化能,促进晶体的析出.当Fe2O3含量达到7.44;时,主晶相由堇青石变为铁尖晶石.Fe2O3掺杂使样品的介电常数由3.2增大至5.8、热膨胀系数由1.941× 10-7增大至7.74×10-6、维氏硬度由7.131GPa增大至11.655 GPa,同时介电损耗由0.05降低至0.015.     

Crystal and molecular structure of complex compound [Fe3O(CH3COO)6(H2O)3]2[ZnCl4] ⋅ 2H2O

The X-ray crystal structure of trinuclear iron acetate [Fe₃O(CH₃COO)₆(H₂O)₃]₂ [ZnCl₄] ? 2H₂O was determined. The crystal has a ionic structure. It is monoclinic, a = 25.363(7), b = 14.533(4), c = 15.692(4) Å, β = 103.11(2)°, space group _C2/c, and R = 0.0685. The structure of the cationic complex [Fe₃O(CH₃COO)₆(H₂O)₃]⁺ is typical of trinuclear iron(III) compounds containing a μ₃-O bridge: the iron atoms are situated at the vertices of an almost equilateral triangle with the O atom at the center. Each Fe atom is coordinated by four O atoms of bridging carboxy groups, the μ₃-bridging O atom, and the water molecule in the trans position to the latter O atom. Mössbauer spectroscopy evidence indicates the high-spin state (_S = 5/2) of the iron(III) ions.     

Performance investigation of Li2O–Al2O3–4SiO2 based glass–ceramics with B2O3, Na3AlF6 and Na2O fluxes

Influence of single fluxes (10 wt.% B₂O₃), bi-component fluxes (4 wt.% B₂O₃ + 6 wt.% Na₃AlF₆), and complex fluxes (4 wt.% B₂O₃ + 4 wt.% Na₃AlF₆ + 2 wt.% Na₂O) on the thermal kinetic parameters, microstructure, flexural strength and coefficient of thermal expansion (CTE) of Li₂O–Al₂O₃–4SiO₂ (LAS) glass–ceramics was investigated through differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that complex fluxes could efficiently decrease transition temperature (T_g) and crystallization temperature (T_p), and accelerate the formation of needle-like β-spodumene crystals which benefit high flexural strength. The homogeneous LAS glass–ceramic (sample C₃) which has a high strength of 132.4 MPa and low CTE (100–650 °C) of 2.74 × 10^? 6/°C is obtained by doping of the initial LAS glass by complex fluxes of 4 wt.% B₂O₃, 4 wt.% Na₃AlF₆, and 2 wt.% Na₂O, nucleating at 630 °C/120 min and then crystallized at 780 °C/120 min. It is worthy of further investigation as a bonder of diamond composite material due to its outstanding prosperities.     

Fe2O3对CaO-Al2O3-MgO-SiO2系微晶玻璃析晶及断裂特性的影响

采用熔融法,利用纯化学试剂制备了CaO-A12O3-MgO-SiO2 (CAMS)系微晶玻璃,利用DTA、XRD、拉曼光谱仪等研究了Fe2O3对微晶玻璃析晶特性的影响规律,微晶玻璃的物化性能由抗折强度、杨氏模量、剪切模量、泊松比、维氏硬度等进行评价.结果表明,微晶玻璃的析晶特性随着Fe2 O3含量的增加而增强,对应母体玻璃中首先出现富铁相,进而促进辉石主晶相的析出.微晶玻璃的断裂特性及裂纹扩展方式均随析晶度的提高得到明显改善.但过量的Fe2O3添加则对微晶玻璃的析晶特性无明显影响,反而降低了玻璃相的致密性.微晶玻璃的耐酸性、抗折强度、杨氏模量及剪切模量均呈现先增加后降低的趋势,微晶玻璃的Fe2 O3含量为6.6wt;时综合性能最优.     

Growth, structure, and properties of ferroelectric—ferroelastic— superionic K3Nb3B2O12 and K3−x NaxNb3B2O12 crystals

The potassium niobate-borate K₃Nb₃B₂O₁₂ (KNB) crystals and their solid solutions with partial substitution of potassium by sodium (KNB: Na) are grown from flux and their physical properties are studied. The specific feature of the crystals grown is a complicated polymorphism and the unique combination of ferroelectric and ferroelastic properties with superionic conductivity with respect to potassium ions.     

Fe2O3含量对SiO2-Al2O3-MgO-F系微晶玻璃析晶特征的影响

为研究Fe2O3含量对SiO2-Al2O3-MgO-F系微晶玻璃析晶特征的影响,采用高温熔融法制备不同Fe2O3含量的基础玻璃,利用差示扫描量热仪(DSC)、x射线衍射(XRD)及扫描电子显微镜(SEM)分别研究此基础玻璃的热效应、相组成及组织形貌.结果表明:在不同Fe2O3含量的样品中析出的晶相主要有云母、ZrO2莫来石及柱晶石,Fe2O3含量超过0.5;时莫来石相消失.随着Fe2O3含量的增加,云母的析出量逐渐提高,且晶体尺寸逐渐变大.但是当样品中Fe2O3含量超过0.8;时,云母晶体析出量反而减少且晶体尺寸变小.     

Nuclear magnetic resonance studies of the glasses in the system K2OB2O3P2O5

B¹¹ NMR spectra have been used to study the structure of glasses in the system K₂OB₂O₃P₂O₅. The results indicate that the glasses do not contain an appreciable number of boron atoms in BO₃ units with one or two non-bridging oxygens. The fraction N₄ of boron atoms in BO₄ units is measured and analyzed according to a structural model containing the following elements. (1) If the binary borophosphate system forms glasses, they consist of a borophosphate (BPO₄) network and a borate network for K<1, or a borophosphate (BPO₄) network and a phosphate network for K>1, where K = mol.% P₂O₅/mol.% B₂O₃. (2) The conversion rates of BO₄ units (i.e. the rate of production or destruction by added oxygens) in the borate network and the borophosphate (BPO₄) network are given as (+2) and (?0.38), respectively. (3) K⁺¹ ions are proportionally shared between the two networks; (i.e. between the borate and borophosphate (BPO₄) networks for K<1, and between the phosphate and borophosphate (BPO₄) networks for K>1).     

Thermal and electric transport properties of (60−x)V2O5–xAs2O3–20Fe2O3–10CaO–10Li2O unconventional glassy system

This paper presents the results of kinematical studies of glass transition and crystallization in the unconventional glassy system (60?x)V₂O₅–xAs₂O₃–20Fe₂O₃–10CaO–10Li₂O (x = 0, 10, 20, 30, 40 mol%) using differential scanning calorimetry (DSC). The glass transition temperatures (T_g), the onset crystallization temperatures (T_c), and the peak temperatures of crystallization (T_p) were found to be dependent on the compositions and the heating rates. From the dependence on heating rates of (T_g) and (T_p) the activation energy for glass transition (E_g) and the activation energy for crystallization (E_c) are calculated. The thermal stability of (60?x)V₂O₅–xAs₂O₃–20Fe₂O₃–10CaO–10Li₂O was evaluated in term of, criteria ΔT = T_c ? T_g. All the results confirm that the thermal stability increase with increasing As₂O₃ contents. From the electric–dielectric measurements it was found that, σ_dc, σ_ac(ω) and θ_D/2 decrease with increasing As₂O₃ contents. It is also observed that the dielectric constant (ε₁(ω)) and the loss factor (tan δ) decrease with increasing As₂O₃ contents in this glass system.     

微波辐射沉淀法制备碳纳米管负载均分散Fe2O3

本文研究了微波辐射沉淀法制备碳纳米管负载Fe2O3粒子.实验表明,采用微波辐射并加入十二烷基苯磺酸钠作为表面活性剂,可在较短时间内,制备出碳纳米管负载均分散的Fe2O3粒子,并对一系列影响因素进行了理论分析.     

Structure,magnetic and IR studies of copper(II) diphenylphosphate dihydrate,Cu(DPhP)2·(H2O)2

The title compound has been synthesized, and characterized by means of X-ray, magnetic, and IR-spectroscopic measurements.The crystals of Cu(DPhP)₂(H₂O)₂(DPhP=diphenylphosphate) are monoclinic, space groupI2/c witha=24.126(6),b=8.510(2),c=12.333(3) Å,=90.73(5)° andZ=4. The structure was solved by the heavy-atom technique, and refined by full-matrix least-squares calculations to a finalR of 0.040 for 1494 reflections.The complex is centrosymmetric, and the Cu atom at a center of symmetry is four-fold coordinated with two oxygen atoms from two phosphate groups and two water molecules. The coordination about the Cu atom is square-planar, with Cu-O and Cu-O(W) distances 1.926(3) and 1.912(3) Å, respectively.The O(2) phosphate oxygen is an acceptor of two H bonds; one of them is an intramolecular O(W)-H(2)O(2) of 2.714(4) Å, and the other is an intermolecularO(W)-H(1)O(2ⁱ) of 2.667(4) Å. Their presence is also deduced from the IR spectrum of this compound at 3250 and 3000 cm^–1, respectively.The calculated magnetic moment value of 1.92 B.M. corresponds to that of the monomeric copper(II) complexes including those of some alkyl phosphates.     

Bi2O3掺杂Sm0.5Sr0.5CoO3-δ的制备与光学性能研究

采用固相法制备(Sm1-xBix)05Sr05CoO3-δ (0≤x≤0.5),研究不同Bi3+掺杂浓度对材料的晶体结构、表面形貌与光学性能的影响.结果表明,当掺量0≤x(Bi3+)≤0.2,材料为单一纯相的钙钛矿结构;当掺量0.3≤x≤0.5,材料主相仍保持着钙钛矿结构,同时出现杂相CoO与Sr0.5CoBi0.5Ox.(Sm1-xBix)05Sr05CoO3-δ平均粒径随着Bi3+掺量的增加由1.98 μm增大为9.77 μm,晶粒形状由多边形状变为方块状;光学测试表明,随着Bi3+浓度的增加,材料的光学吸收率由0.73增大到0.87,发射率由0.34增大到0.80.