Al-Al_2O_3结构件钎缝处的剪切应力分布与热膨胀匹配

采用有限元数值模拟方法研究了冷却过程在Al Al2 O3 异种材料结构件钎缝处导致的剪切应力分布。计算结果表明 :最大剪切应力位于钎缝圆角处和靠近钎缝圆角的Al2 O3 陶瓷 /Cu镀层金属界面处 ,同时中间层合金的热膨胀系数与Al的热膨胀系数相匹配时 ,可以最大限度减小剪切应力     

钎缝圆角几何形状对Al-Al_2O_3钎焊件剪切应力分布的影响

异种材料连接结构中由于被连接材料的热膨胀系数不匹配 ,焊后冷却过程将在钎焊件内部导致较大的应力。同时 ,钎缝圆角几何形状对这一热应力分布有重要影响。本文采用有限元数值模拟方法研究了钎缝圆角几何形状对Al-Al2 O3 异种材料钎焊件内部剪切应力分布的影响。计算结果表明 ,钎缝圆角的最佳几何形状为钎缝伸出长度略大于钎缝高度的凹型。     

钎缝圆角几何形状对Al-Al2O3钎焊件剪切应力分布的影响

异种材料连接结构中由于被连接材料的热膨胀系数不匹配,焊后冷却过程将在钎焊件内部导致较大的应力。同时,钎缝圆角几何形状对这一热应力分布有重要影响。本文采用有限元数值模拟方法研究了钎缝圆几何形状对Al-Al2O3异种材料钎焊件内部剪切应力分布的影响。计算结果表明,钎缝圆角的最佳几何形状为钎缝伸出长度略大于钎缝高度的凹型。     

Al2O3P／Cu基复合材料与Nb钎焊研究

采用Ag-20Cu-5Ti对Al2O3P／Cu基复合材料与Nb的钎焊性进行了初步探讨。研究表明，通过在钎料中加入活性元素Ti，可以减少和消除钎缝中的Al2O3P颗粒，避免Al2O3P颗粒在钎缝中的聚集，实现离子共价键Al2O3P向类金属键TiO转化，从而提高钎缝基体与颗粒相之间的匹配性。     

复合钎料钎焊Al_2O_3接头剪切应力场的数值模拟

对Al2O3颗粒增强复合钎料钎焊Al2O3/Al2O3接头的残余应力场进行了数值模拟,分析了Al2O3陶瓷颗粒的加入对陶瓷接头残余剪切应力的影响.模拟发现,陶瓷接头的最大应力位于陶瓷-钎缝界面,陶瓷颗粒的加入对钎焊接头应力起到了缓解作用,其缓解程度随陶瓷颗粒体积分数的增加而增大;在陶瓷颗粒百分比一定的情况下,钎缝厚度的...     

Al2O3/Cu基复合材料与Nb的钎焊

采用Ag—20Cu—5Ti对Al2O3／Cu基复合材料与Nb的钎焊性进行了初步探讨。研究表明,通过在钎料中加入活性元素Ti,可以减少和消除钎缝中的Al2O3,颗粒,避免Al2O3颗粒在钎缝中的聚集,实现离子共价键Al2O3向类金属键TiO转化,从而提高钎缝基体与颗粒相之间的匹配性。     

弥散强化铜基复合材料钎焊接头强度

从冶金方面就如何改善Al2O3P颗粒与钎缝的化学相容性及工艺参数对钎焊接头力学性能的影响进行了初步探讨。研究结果表明。当保温时间较短时，由于钎缝中含有较多的Al2O3P颗粒相，且有偏聚的趋势，钎焊接头强度较低；延长保温时间，钎料中活性组元Ti与Al2O3P颗粒反应，可以有效控制Al2O3P含量，从而减缓其不利影响，使钎焊接头强度大幅度提高。     

Al2O3弥散强化铜与T2铜的真空钎焊研究

用Ag-Cu-Ti钎料对Al2O3弥散强化铜与T2铜进行真空钎焊.研究了钎焊温度和保温时间对钎焊接头组织和性能的影响.结果表明:温度过低,钎料与母材相互冶金作用不强,结合不紧密;温度过高和保温时间过长,钎料向Al2O3弥散强化铜中毛细渗入严重,钎缝出现虚焊,接头强度下降.钎缝组织主要为Cu的同溶体与Ag的同溶体.     

Al2O3P/Al复合材料钎焊的试验研究

针对Al2O3P/Al复合材料，选用铝基HL401作钎料，选用QJ201为钎剂，在炉中氩气保护下进行钎焊．试验研究了其焊接工艺参数对接头强度的影响。试验表明：采用炉中氩气保护下钎焊Al2O3P/Al复合材料完全可行，用所选择的合适的钎料和钎剂，在优化的工艺参数条件下可获得优质的焊接接头。     

AgCu+nano-Al_2O_3复合钎料钎焊TC4合金与Al_2O_3陶瓷:界面结构及接头性能

通过向Ag Cu共晶钎料中添加nano-Al2O3增强相(2%,质量分数)并采用高能球磨的方法获得了Ag Cu+nano-Al2O3复合钎料(Ag Cu C钎料)。采用Ag Cu C钎料实现了TC4合金与Al2O3陶瓷的高质量钎焊连接,确定了TC4/Ag Cu C/Al2O3钎焊接头的典型界面组织结构为:TC4/α-Ti+Ti2Cu扩散层/Ti3Cu4层/Ag(s,s)+Ti3Cu4+Ti Cu/Ti3Cu4层/Ti3(Cu,Al)3O层/Al2O3。Nano-Al2O3的添加抑制了钎缝中连续的Ti-Cu化合物层的生长,同时在钎缝中形成了颗粒状Ti-Cu化合物相增强的Ag基复合材料,改善了钎焊接头的界面组织。随着钎焊温度的升高,各反应层厚度逐渐增加,颗粒状Ti-Cu化合物不断长大,Ag基复合材料组织逐渐细小。当钎焊温度T=920℃,保温时间t=10 min时接头抗剪强度达到最大为67.8 MPa,典型断口分析表明:压剪过程中,裂纹起源于钎角处并沿钎缝扩展后转入Al2O3陶瓷,最终在Al2O3陶瓷母材侧发生断裂。     

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。     

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.     

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.     

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。     

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.     

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。     

Synthesis and electrochemical properties of LiNi0.4Mn1.5Cr0.1O4 and Li4Ti5O12

Spinel compound LiNi_0.4Mn_1.5Cr_0.1O₄ (LNMCO) and Li₄Ti₅O₁₂ (LTO) were synthesized by the sol-gel method and the solid-state method, respectively. The particle sizes of the products LiNi_0.4Mn_1.5Cr_0.1O₄ and Li₄Ti₅O₁₂ were 0.5 to 2 um and 0.5 to 0.8 um, respectively. All samples exhibited excellent electrochemical properties. A LiNi_0.4Mn_1.5Cr_0.1O₄/Li₄Ti₅O₁₂ (LNMCO/LTO) cell was fabricated and was demonstrated to exhibit good electrochemical properties at the high current rate of 1 C. When the specific capacity was determined based on the mass of the LNMCO cathode, the LNMCO/LTO cell delivered 125 mAh g⁻¹ at 1 C and 77 mAh g⁻¹ at 5 C. The capacity retentions after 30 cycles were 94.4 % and 83.1 %, respectively.