Ge_4Se_(96)红外玻璃的热力学性能

通过融熔-淬冷法制备了Ge_4Se_(96)硫系玻璃块状试样,利用等温步阶方法(stepwise method)测定其DSC曲线,并采用新算法对Ge_4Se_(96)玻璃的比热进行了分析计算。通过比热算出Gibbs自由能变化△G和熵变△S,得到了△G和△S随温度变化的曲线,确定了Kauzmann温度Tk。采用热机械分析(TMA)确定了Ge_4Se_(96)玻璃的应变点、退火点、玻璃转变点、屈服点和软化点的特征温度。结果表明,Ge_4Se_(96)的玻璃化转变温度Tg是52℃,平均热膨胀系数是△L/L0=(0.0557T-1.7576)/10~3,Kauzmann温度T_k=233.5 K。     

多组元替换Zr-Al-Ni-Cu-Ag金属玻璃的热稳定性和晶化行为

为提高金属玻璃的热稳定性并获得大过冷液相区,研究了成分为Zr_65-x(Al_0.21Ni_0.29Cu_0.04Ag_0.46)_35+x（x=0,7.5,15.0,22.5）的金属玻璃,重点分析了组分浓度对合金热稳定性、热诱导沉淀相以及力学性能的影响。结果表明,随着合金组分浓度的增加,非晶漫散射峰的峰位向更高角度偏移,出现了玻璃转变现象。随着玻璃转变温度（T_g）和晶化温度（T_x）增加,液相线温度（T_l）降低,导致T_x和T_g之间的温度差（ΔT_x）减小,约化玻璃转变温度（T_rg）增大。此外,形核激活能（E_x）和长大激活能（E_p1）随着溶质浓度的增加而增加。初晶从四方Zr₂Ni、Zr₂(Cu, Ag)、ZrAg和六方Zr₅Al₃相的组合转变为单一四方ZrAg相,维氏硬度呈现出增加的趋势。通过研究,发现了具有141 K过冷液相区（ΔT_x）和高热稳定性的新型金属玻璃Zr_65-x(Al_0.21Ni_0.29Cu_0.04Ag_0.46)_35+x（x=7.5）,且具有较强的抵抗晶化的特性。本研究采用的多组元替换策略对提高金属玻璃的热稳定性具有重要意义。     

Hf对Zr-Al-Ni-Cu金属玻璃弛豫行为的影响

通过测定快淬态和退火态比热与温度的关系,研究了Hf元素对Zr₇₀Al_7.5Ni₈Cu_14.5（70Zr）、Zr₅₅Al₁₀Ni₅Cu₃₀（55Zr）和(Zr_0.75Hf_0.25)₆₅Al_7.5Ni₁₀Cu_17.5（65Zr_0.75Hf_0.25）厘米级金属玻璃焓和硬度弛豫的影响。结果显示：70Zr和55Zr合金的结构弛豫表现为单峰现象,在退火温度（T_a）接近玻璃转变温度（T_g）时出现弛豫峰;而65Zr_0.75Hf_0.25合金的结构弛豫表现为双峰现象,分别在523和648 K（接近T_g）时出现焓弛豫峰。70Zr和55Zr合金在T_g温度附近出现明显的单峰弛豫行为,表明合金在T_g之前的整个温度范围内具有较高的抵抗退火诱导结构弛豫的能力;另一方面,65Zr_0.75Hf_0.25合金在523 K附近出现一个弛豫子峰,可能是由于Zr-Hf原子对的键合性较弱,混合焓接近于零,随后在T_g附近出现明显的主弛豫。65Zr_0.75Hf_0.25和(Zr_0.5Hf_0.5)₆₅Al_7.5Ni₁₀Cu_17.5（65Zr_0.5Hf_0.5）合金的硬度也表现出类似的双峰现象,导致第一峰的T_a与焓弛豫峰的T_a一致。结果表明,满足非晶形成三原则的Zr、Al、Ni和Cu组成的类二十面体中程有序结构在低T_a温度下保持稳定;只有背离非晶形成三原则的65Zr_0.75Hf_0.25和65Zr_0.5Hf_0.5金属玻璃焓弛豫和硬度弛豫出现了双峰,表明形成大块金属玻璃非必要组元的增加将导致合金结构在低温退火过程中的不稳定性。     

磁铅石结构LaMgAl11O19粉体制备及其晶格热膨胀

采用反向化学共沉淀-高温煅烧法制备了镁基六铝酸镧(LaMgAl₁₁O₁₉)粉体。利用X射线衍射、场发射扫描电子显微镜、高温原位X射线衍射及Rietveld晶体结构精修法对粉体的物相组成、显微形貌、晶体结构及晶格热膨胀行为进行了研究。结果表明,反向化学共沉淀制备的氢氧化物前驱体经1600 ℃热处理后完全转变为磁铅石结构的LaMgAl₁₁O₁₉,呈规则六方板片状,晶面光滑平整。采用高温原位XRD技术及Rietveld晶体结构精修系统研究了镁基六铝酸镧材料的晶格热膨胀行为。随着温度的升高,镁基六铝酸镧(LaMgAl₁₁O₁₉)晶格热膨胀表现出各向异性,晶胞参数a和c随温度变化关系为：a_T=5.5821+1.625×10_-5T+1.757×10_-8T₂+4.24×10_-12T₃,c_T=21.9189+1.1952×10_-4T+4.587×10_-8T₂+5.463×10_-11T₃。室温~1300 ℃,//a平均热膨胀系数为8.42×10_-6/℃,//c平均热膨胀系数为12.54×10_-6/℃。La-O键各向异性热膨胀是LaMgAl₁₁O₁₉晶格热膨胀各向异性的主要原因。     

热电Bi2Te3/Bi2Se3纳米“弹簧”材料的电化学组装

为了探索制备具有高热电优值的一维纳米材料,采用脉冲电化学技术制备了一种热电Bi₂Te₃/Bi₂Se₃多层纳米线材料。对电沉积过程的监测结果表明,电沉积过程中体系电阻不断增大,随着电沉积的不断进行,体系电阻增大幅度越来越小。对电沉积产物进行退火处理,然后溶解掉模板,进行XRD测试,结果表明,所制备的产物是Bi₂Te₃/Bi₂Se₃,同时,有很多“卫星峰”出现在衍射图上,表明所制备的材料具有超晶格结构。运用FE-SEM、TEM对产物形貌进行分析,结果发现,所制备的材料是像“弹簧”一样形状的Bi₂Te₃/Bi₂Se₃多层纳米线。通过对脉冲时间的调节,可以实现对多层纳米线周期的调制。     

四元Mg2Si0.27Ge0.05Sn0.65Sb0.03固溶体的热电性能

通过氧化硼助熔剂法和放电等离子烧结技术制备了Mg_2(1+x)Si_0.27Ge_0.05Sn_0.65Sb_0.03 (x = 0.05, 0.08)四元固溶体热电材料。测量了在300 K - 800 K 的温度区间内测试了所有四元固溶体试样的塞贝克系数、电导率和热导率。研究结果表明随着温度的升高电导率单调降低而塞贝克系数单调升高,所有样品的晶格热导率明显高于通过Abeles模型计算所得到的理论值。最高无量纲热电优值出现在x=0.08样品中,在800 K时达到最高值1.0.     

内生型(Ti0.474Zr0.34Cu0.06Be0.126)100 - x Fe x (x=0, 2)金属玻璃基复合材料的动态力学行为

为了解内生β-Ti相的Zr/Ti基金属玻璃复合材料的动态力学性能和热力学稳定性,采用力学弛豫谱研究了(Ti_0.474Zr_0.34- Cu_0.06Be_0.126)_100-xFe_x（x=0,2）金属玻璃复合材料。通过引入Fe元素,提高了β-Ti相的稳定性。此外,还发现了一个异常的内耗峰,这是由于在亚稳的β-Ti相中析出ω-Ti所引起的。在玻璃化转变温度T_g以下,由于相变和非晶基体部分结晶的耦合效应,2种金属玻璃复合材料的储能模量均表现出异常过冲行为。所得结果为更好地理解内生亚稳β-Ti型金属玻璃复合材料的复杂动态力学弛豫行为提供了借鉴。     

NH4HF2 氟化Al2O3 制备无水AlF3 研究

采用热重-差热分析（TG-DTA）方法对不同NH₄HF₂/Al₂O₃质量比的Al₂O₃+NH₄HF₂混合物的热行为进行了分析,确定了DTA曲线的临界温度。进一步分析了各临界温度前后直接热处理所得产物的形貌和物相。结果表明,质量比对临界反应温度和反应过程没有影响。氟化反应在室温下以(NH₄)₃AlF₆的形成开始,在162.3~162.8 ℃时占主导地位,在180 ℃左右完成。进一步热处理后,(NH₄)₃AlF₆在249.8~250.1 ℃分解为NH₄AlF₄,在356.8~357.7 ℃分解为β-AlF₃;随后β-AlF₃在400~650 ℃向α-AlF₃转变。     

玻璃形成能力及稳定性三角形判定准则

根据降温过程的玻璃形成能力（GFA）和升温过程的玻璃稳定性（GS）,构建了以伪四特征参数组合为顶点的判定玻璃形成能力和稳定性的三角形（Tri-FAS）,从而推导出判定GFA&GS的准则：G-FAS=T_g/T_l+T_x/T_l+T_x/T_g（T_x为起始结晶温度;T_l为液体温度;T_g为玻璃化转变温度）,并从降温过程非晶化与晶化之间的竞争关系和准则各组成项对准则的均衡贡献两个方面进行了修订：G-FAS_m=T_g/(1.5T_x)+T_x/T_l+T_x/T_g和G-FAS_m′=T_g/T_l+T_x/T_l+(T_x/T_g)^a (a≈1.5±0.2)。讨论了G-FAS与临界冷却速率R_c、G-FAS与T_xg（T_xg反映了玻璃的过冷液区,T_xg=T_x/T_g）的相关性,分别能够反映GFA和GS。通过大量金属玻璃和其他玻璃形成体从GFA和GS两方面对判定准则的有效性进行了评估,结果显示：该判定准则无论是GFA方面还是GS方面,在不同玻璃形成体系中均可靠有效,具有广泛应用性。提出的Tri-FAS和G-FAS判定准则在玻璃的生产和实际应用过程中具有指导作用。     

G3合金在高温高H2S/CO2环境下临界点蚀温度研究

利用恒电位极化和EIS技术研究G3合金在高温高H₂S/CO₂分压环境下的临界点蚀温度。结果表明,利用恒电位极化技术测试G3合金在高温高H₂S/CO₂分压环境下的临界点蚀温度为58.5℃,而利用EIS方法测试得到G3合金在模拟环境下的临界点蚀温度在50-60℃之间,分别利用恒电位极化和EIS方法测试所得G3合金在模拟环境下的的临界点蚀温度基本一致。     

X-ray diffraction study of Ba0.985Na0.015Ti0.985Nb0.015O3, Ba0.6Na0.4Ti0.6Nb0.4O3 and Ba0.3Na0.7Ti0.3Nb0.7O3 compositions

The Ba_0.985Na_0.015Ti_0.985Nb_0.015O₃, Ba_0.6Na_0.4Ti_0.6Nb_0.4O₃ and Ba_0.3Na_0.7Ti_0.3Nb_0.7O₃ compositions of the (1 − x) BaTiO₃–xNaNbO₃ (BTNNx) system have been studied by X-ray diffraction and by measurements of dielectric properties. The specimens with composition BTNN (x = 0.015, 0.40 and 0.70) have been refined by the JANA program from X-ray powder diffraction data. Ceramic samples with composition (1 − x) BaTiO₃ + xNaNbO₃ (where x = 0.015, 0.40 and 0.70) were prepared by calcinations from appropriate mixture of BaCO₃, TiO₂, Na₂CO₃ and Nb₂O₅. The calcined powder was sintered at temperature range 1200–1400 °C. As the composition x increased from 0.015 (and 0.70), the ferroelectric ceramics (x = 0.015, FE) with tetragonal phase changed to the ferroelectric relaxors (RFE, x = 0.40). RFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to 180 K) due to a frustration between RFE and FE state. These ceramics present the classical ferroelectric character when 0 ≤ x < 0.075 and 0.55 < x ≤ 1 and relaxor character when 0.075 ≤ x ≤ 0.55.     

Magnetic, electrical and plastic properties of Fe76Nb2Si13B9, Fe75Ag1Nb2Si13B9 and Fe75Cu1Nb2Si13B9 amorphous alloys

Influence of 1 h annealing in vacuum on magnetic, electrical and plastic properties of Fe₇₆Nb₂Si₁₃B₉, Fe₇₅Ag₁Nb₂Si₁₃B₉ and Fe₇₅Cu₁Nb₂Si₁₃B₉ melt spun ribbons were carefully investigated. It was shown that in all cases soft magnetic properties can be significantly enhanced by applying 1-h annealing at characteristic temperatures T_op. This optimization annealing causes that permeability increases more than 15-times and magnetic losses (tangent of loss angle) achieves a minimum in relation to the as quenched state. Using structural examinations (X-ray and HRTEM) it was shown that for the Fe₇₅Cu₁Nb₂Si₁₃B₉ alloy the optimized microstructure corresponds to a nanocrystalline αFe(Si) phase whereas in other alloys to a relaxed amorphous phase free of iron nanograins. As a consequence of this fact the Fe₇₆Nb₂Si₁₃B₉ and Fe₇₅Ag₁Nb₂Si₁₃B₉ alloys show higher plasticity in comparison to the nanocrystalline Fe₇₅Cu₁Nb₂Si₁₃B₉ alloy. Temperatures of the first stage of crystallization, and related diffusion parameters were determined using measurements of resistivity versus temperature with different heating rates.     

Fe2+-Ni2+-NH3-NH4+-C2O42-H2O体系的沉淀配合平衡热力学

针对草酸盐配位共沉淀热分解还原法制备超细铁镍合金粉过程中Fe2+-Ni2+-NH3-NH4+-C2O42--H2O体系的溶液平衡建立热力学分析模型,并根据模型进行相关计算,揭示反应体系中各物质随pH值、氨及草酸浓度的变化关系。结果表明:溶液中的Fe主要以[Fe(C2O4)n]2 2n络合物形式存在,而铁氨络合物含量很低。当氨含量较低时,溶液中的Ni主要以[Ni(C2O4)n]2 2n存在;氨含量较高时,在酸性条件下,溶液中的Ni主要以[Ni(C2O4)n]2 2n存在,在碱性条件下,则主要以[Ni(NH3)n]2+存在。低pH值下,Ni的沉淀率较Fe的高,而高pH值下,Ni的沉淀率则较Fe的低。     

New Zr6CoAs2-type compounds: Y6CoBi2, Ho6CoBi2 and Tm6CoBi2

Results of a powder X-ray diffraction investigation of new ternary compounds are reported. The compounds Y₆CoBi₂ [a=0.8312(1) nm, c=0.4144(1) nm], Ho₆CoBi₂ [a=0.8246(2) nm, c=0.4095(1) nm], and Tm₆CoBi₂ [a=0.8155(2) nm, c=0.4066(1) nm] crystallize in the hexagonal Zr₆CoAs₂-type structure (space group P6b2m No. 189). The Zr₆CoAs₂-type structure is a superstructure of the Fe₂P-type structure.     

Thermodynamics and phase diagrams in the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3

We applied our model to the enthalpy of mixing data of the binary systems Na₂O-SiO₂, Na₂O-GeO₂, Na₂O-B₂O₃, Li₂O-B₂O₃, CaO-B₂O₃, SrO-B₂O₃, and BaO-B₂O₃. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO₂, CaO-Al₂O₃, PbO-B₂O₃, PbO-SiO₂, ZnO-B₂O₃, and ZnO-SiO₂ systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.     

Al2O3-Sm2O3-CeO2电解质的性能（英文）

采用溶胶-凝胶法和低温燃烧技术制备Ce1-xSmxO2（x=0,0.1,0.2,0.3）和掺杂Sm和（2%-8%）Al2O3的二氧化铈;研究其合成、结构、致密化、导电性和热膨胀等性能,并利用XRD研究其结构和相组成。结果表明,于1300°C烧结球团,获得致密的陶瓷,于1250°C在Ce0.8Sm0.2O0.2中加入2%和4%的Al2O3以促进烧结。利用扫描电子显微镜观察烧结后球团的表面形貌,使用双探针交流阻抗谱研究总离子电导率。     

电弧喷涂制备Fe65Cr20Mo7B3.5SiMn1.5W3涂层

在Q235低碳钢板上利用电弧喷涂工艺进行喷涂,以制得Fe65Cr20Mo7B3.5SiMn1.5W3涂层。喷涂材料为自行配制的丝材,按照35%的填充率将配好的粉填充到U型不锈钢外皮中,经过多道拉拔、挤压工艺制成Φ2mm的粉芯丝材。采用X射线衍射仪、扫描电镜、能谱分析仪、透射电镜对涂层的物相和组织形貌及成分进行了表征;采用差示扫描量热仪、显微硬度仪等设备对涂层的热稳定性及显微硬度进行了检测和分析。试验结果表明:涂层组织形貌呈典型的层状组织结构,由变形良好的带状粒子相互搭接堆积而成。涂层含有50.63%的非晶相,同时含有纳米级的晶相。涂层组织均匀、结构致密、孔隙率低,并且涂层硬度高达1040.5HV0.3,属硬质涂层,具有良好的热稳定性。     

Sinterability and dielectric properties of Ba0.55Sr0.4Ca0.05TiO3-CaTiSiO5-Mg2TiO4 composite ceramics

The composite ceramics of Ba_0.55Sr_0.4Ca_0.05TiO₃-CaTiSiO₅-Mg₂TiO₄ (BSCT-CTS-MT) were prepared by the conventional solid-state route. The sintering performance, phase structures, morphologies, and dielectric properties of the composite ceramics were investigated. The BSCT-CTS-MT ceramics were sintered at 1100 °C and possessed dense microstructure. The dielectric constant was tailored from 1196 to 141 as the amount of Mg₂TiO₄ increased from 0 to 50 wt%. The dielectric constant and dielectric loss of 40 wt% Ba_0.55Sr_0.4Ca_0.05TiO₃-10 wt% CaTiSiO₅-50 wt% Mg₂TiO₄ was 141 and 0.0020, respectively, and the tunability was 8.64% under a DC electric field of 8.0 kV/cm. The Curie peaks were broadened and depressed after the addition of CaTiSiO₅. The optimistic dielectric properties made it a promising candidate for the application of tunable capacitors and phase shifters.     

Zur Kenntnis von RbBa3Ca4Cu3V7O28

Single crystals of RbBa₃Ca₄Cu₃V₇O₂₈ were prepared above the melting point of the reaction mixture. It crystallizes with hexagonal symmetry, space group C_6V⁴-P6₃mc, a 11.1751, c 12.434 Å, Z = 2. RbBa₃Ca₄Cu₃V₇O₂₈ is the second member of a new structure type of the copper-oxovanadates. Ba²⁺ shows an unusual 12-fold coordination. The two calcium positions are coordinated by trigonal prisms and octahedra respectively. The copper coordination is characterized by a stretched square pyramid. The Cu²⁺ ions are outside the centre nearly in plane of the pyramids.

Zusammenfassung

Einkristalle von RbBa₃Ca₄Cu₃V₇O₂₈ wurden oberhalb des Schmelzpunktes der Reaktionsmischung erhalten. Die Verbindung kristallisiert hexagonal, Raumgruppe C_6V⁴-P6₃mc, a 11.1751, c 12.434 Å, Z = 2. RbBa₃Ca₄Cu₃V₇O₂₈ ist das zweite Beispiel für einen neuen Strukturtyp der Kupfer-Oxovanadate, mit 12-fach koordinierten Ba²⁺ -Ionen. Die zwei Calciumpositionen sind trigonal prismatisch bzw. oktaedrisch koordiniert. Die Koordination der Cu²⁺-Ionen ist durch eine gestreckte Pyramide charakterisiert. Cu²⁺ ist auβerhalb des Polyederzentrums nahezu in der quadratischen Fläche der Pyramide angeordnet.