Heat transfer at the metal/substrate interface during solidification of Pb-Sn solder alloys

Heat transfer analysis during the solidification of lead, tin, and two lead-base solder alloys against two different chill materials (steel and copper) was carried out with and without flux coating on the chill surface. Temperatures at two known locations inside the chill and casting were recorded as the casting started solidifying, and the acquired chill temperature data were used for solving a one-dimensional heat conduction equation inversely to yield the metal/chill interfacial heat flux and chill surface temperature as a function of time. The initial heat flux was high due to good contact at the metal/chill interface. As the casting started solidifying, there was a reduction in the heat flux due to the nonconforming contact at the interface. Chills with flux coating resulted in finer microstructures near the solder/substrate interface compared to those obtained with uncoated chills. The fineness of the microstructure also increased when copper was used as the chill material. The estimated total heat flow was found to be higher with flux-coated and copper chills. This was in good agreement with the finer microstructures obtained near the solder/chill interfacial region for solidification against copper chills and chills with flux coating on their surface.     

不同间隙下硼钢板-模具界面换热系数的反演

确定不同条件下板料-模具界面的换热系数对控制硼钢板在热成形中的局部冷却速率、获得组织性能呈区域性分布的构件具有重要意义,还可为热成形过程精确数值仿真提供可靠的热边界条件。设计了简单、有效的实验装置以模拟硼钢板热成形中不同单边间隙下板料与模具间的传热状态,其中测温点处的温度变化仅与板料-模具界面换热系数相关,从而为界面换热系数的准确反演提供了保障。建立了界面换热系数的有限元优化模型,反演获得了不同间隙下B1500HS板与H13模具钢之间的换热系数,发现其随间隙的增大呈指数函数式减小,并对反演获得的界面换热系数进行了实验验证。     

Origin of charge transfer complex resulting in Ohmic contact at the C60/Cu interface

The conducting charge transfer complex formed on the C₆₀/Cu interface after heat treatment was investigated by using density functional theory. We optimized the geometries of the C₆₀ and C₆₀–Cu complexes. Then, a comparison of the valence band spectrum with the simulated density of states revealed detailed molecular properties. We confirm that the C₆₀–Cu complex layer formed at the C₆₀/Cu interface enhances charge transfer. The conducting complex creates both an occupied gap state and unoccupied states between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of C₆₀. These states lead to the formation of Ohmic contact between the C₆₀ layer and the Cu layer.     

Equivalent heat transfer coefficient at casting/Cu mould interface and temperature field simulation

1　INTRODUCTIONThesolidifiedmicrostructuresofalloysdependontheirsolidifyingprocesswhoseprimarycharacteristicsarethetemperaturedropofthesuperheatedmeltandthere leaseofthelatentheat.Sothestudyontheheattransferduringthesolidificationprocessistheessentialprobleminthesolidificationtheorystudy .Theresearchersworkingonthenumericalsimulationofthesolidificationprocessallknowthattheinterfacialheattransfercoefficientatthecasting/mouldisavariablechangingwithtime .Thusthedeterminationoftheinterfacialh…     

Charge transfer complexes between sulphur and polyacetylene-like materials

We describe preliminary results concerning the use of new conjugated polymeric materials, obtained from the reaction of sulphur with chemically dehydrochlorinated polyvinylchloride, as electrodes in electrochemical cells which present remarkable characteristics.     

TiC硬质合金/碳钢爆炸焊接复合板界面微观组织

用透射电镜、扫描电镜和X射线能谱仪对TiC硬质合金/碳钢爆炸焊接复合板界面微观组织和相组成进行分析.结果表明,界面上有一断续的熔合层,层厚约10μm,层内为尺寸位于几十个～几百个纳米之间的纳米或亚微米超细晶粒,组成相为铁素体、奥氏体和少量TiC.在界面附近碳钢侧可以看到明显的流线状组织特征,铁索体具有板条状马氏体的结构特征,珠光体层片间距减小,呈流线分布.焊接过程中Ti向钢中扩散15μm左右.     

Photoinduced electron transfer at an ITO/C60 trapped in a thin polypyrrole film interface

The photoelectrochemical properties of C₆₀ entrapped in thin, functionalized polypyrrole films coated on indium-tin oxide (ITO) electrodes have been examined. A stable photocurrent is observed in the presence of an irreversible electron donor (ascorbic acid) in solution. Results suggest the coexistence of monomers and aggregates of C₆₀ in the polymeric matrix.     

Surface state density at the semiconductor-glass interface

An investigative technique for the determination of the surface state density (SSD) at the semiconductor-lead-borosilicate-glass interface is proposed. It is shown that this technique involving differentiation of the C-V dependence is a more precise and less labor-consuming method, which shows the uniqueness of the solution.     

C-scan and L-scan generated images of the concrete/GFRP composite interface

Glass Fiber Reinforced Plastics (GFRP) are fast becoming a viable new construction material. They are being used for rehabilitating old concrete structures—columns, beams, slabs and walls—by gluing the composite plate to the concrete surface. Proper attachment between the GFRP plate and the concrete surface is necessary for efficient use of GFRP composites to increase the strength of the rehabilitated structures. Delamination between the rehabilitated structure and the GFRP plate significantly reduces the strength of the reinforced structure. Hence, delamination defects, if present at the interface, should be detected as soon as possible. In this paper, two ultrasonic techniques to detect delamination defects between the GFRP plate and the concrete surface are presented. One technique uses longitudinal waves or P-waves and the second technique uses Lamb waves. It is found that both techniques can detect the defect when used properly. However, Lamb waves give a better image quality of the defect than longitudinal waves.     

Heat transfer coefficient on external mold surface at high pressure and application to metal-matrix composite casting

A relationship is established between the heat transfer coefficient on the external surface of a mold and the ambient temperature and pressure within the operating range typical of pressure-infiltration casting of metal-matrix composites. This relationship is based on existing data and correlation for the thermo-physical properties of the ambient nitrogen. The predicted temperature profiles are in good agreement with the experimental data obtained for a metal-matrix composite casting process. The application of the established relationship is carried beyond the experimental evidence to predict the solidification pattern in the pressure-casting system.     

High strength bimetallic composite material fabricated by electroslag casting and characteristics of its composite interface

Bimetallic composite material of bainitic steel and PD3 steel was produced with electroslag casting process, and element distribution of its composite interface was investigated by theoretical calculation and energy dispersive spectrometer(EDS). Results show that the tensile strength(1,450 MPa), hardness(HRC 41-47) and impact toughness(94.7J·cm~(-2)) of bainitic steel were comparatively high, while its elongation was slightly low(4.0%). Tensile strength(1,100 MPa), hardness(HRC 31) and elongation(7.72%) of the interface were also relatively high, but its impact toughness was low at 20.4 J·cm~(-2). Results of theoretical calculation of the element distribution in the interface region were basically consistent with that of EDS. Therefore, electroslag casting is a practical process to produce bimetallic composite material of bainitic steel and PD3 steel, and theoretical calculation also is a feasible method to study element distribution of their interface.     

Si粉微合金化对钢-铝复合材料界面的影响

采用粉末轧制工艺,在界面添加4％ Si粉进行界面微合金化调控,成功制备出界面结合良好的钢-铝复合材料.研究了界面微合金化设计、扩散退火处理工艺对钢-铝复合材料界面区元素扩散、生成物相的影响规律,探讨了元素Si界面调控的作用机理.结果表明:添加4％ Si粉界面微合金设计,在500℃扩散退火,保温1h热处理工艺下,复合材料界面未出现金属间化合物,600℃扩散退火,保温1h热处理工艺下,仅出现少量化合物Fe2Al5,Si粉界面微合金化处理能延缓界面化合物相生成,使生成Fe2Al5相的扩散温度向高温推移;Si扩散固溶到Fe、Al基体中形成连续固溶体,提高了界面两侧物理及力学性能的连续性,改善复合材料的界面结合.     

Charge transfer complexes in silicon-organic photoconductors with admixtures of acceptor molecules

The absorption spectra of the solutions of polysilanes (poly(methylphenylsilane) (PMPS) and poly(dihexylsilane) (PDHS)) with various acceptors (tetracyanoquinodimetane, tetracyano-naphtoquinodimetane and trinitrofluorenone) were investigated. It is shown that several new broad bands in visible region arise in the absorption spectra of polysilanes with addition of acceptors, which is accompanied by changes in the color of the solutions. These new bands are attributed to formation of charge transfer complexes (CT-complexes) between σ-donor (polysilane) and π-acceptor, i.e. polysilanes with admixture of acceptors can be used both as transport layers and photogeneration ones. The possible nature of the structure of the absorption bands of these CT-complexes is discussed.     

Charge transfer in PDI-derived systems studied with light-induced electron spin resonance

Dissymmetrical perylene-3,4,9,10-tetracarboxydiimide building block (PDI) was used to obtain the dyads with fullerene (PDI-C₆₀) and tetrathiafulvalene (PDI-TTF). Photoinduced electron transfer in these dyads was investigated with light-induced electron spin resonance (LESR) spectroscopy. The LESR signals of the samples in CHCl₃ solutions were recorded in the dark and under light illumination, at room temperature and at about 80 K. It was stated that the LESR signal increases stepwise with the incident light and decreases slowly when the light is switched off. The photogeneration of PDI⁺, TTF⁻ and C₆₀⁻ ion-radicals was observed and analyzed. The principal parameters of the LESR lines of the ion-radicals are determined.     

Thermal grooving at the interface between alumina and monazite

Interfaces of Al₂O₃ (sapphire) and LaPO₄ (La-monazite) have been separated by fracture to reveal boundary grooving effects analogous to surface grooves that develop at high temperature on a polycrystalline body wherever a grain boundary intersects the surface. Atomic force microscope measurements are used to form images from matching sides of a separated interface and to compare groove profiles with the solution of Mullins.     

Charge regulation by ferromagnetic metal/LiF spin-polarized interface for high-performance Li metal anodes

The interfacial characteristics of the Li metal anode(LMA) play a crucial role in its overall performance.Despite various materials being applied to modify the interface,a comprehensive understanding of their specific mechanisms remains to be investigated.Herein,we have prepared carbon cloth(CC) frameworks with their surfaces modified using ferromagnetic metal/LiF heterogeneous films(T^M-LiF-CC) as the substrate for LMA,which exhibit superior electrochemical performance.Utilizing ferro...     

液固包覆法制备Al-Pb层状复合材料及其界面研究

利用键参数函数理论分析了第三组元Bi或Sn作为Al-Pb非混溶体系实现冶金结合一体化的可行性,并采用液-固包覆成型的方法制得了Al-Bi-Pb及Al-Sn-Pb层状复合材料,通过SEM、EDS等检测手段分析研究试样的显微组织,并讨论了界面的扩散现象.结果表明:第三组元Bi或sn的引入将Al、Pb的混合焓△Hmin降低到零以下,在扩散动力学作用驱使下使各元素间在界面处发生了迁移和互扩散,形成了成分调控区,表现为一条状的均质固溶体带,实现了Al与Pb之间的冶金结合.     

氧化铝基复合陶瓷-金属钎焊界面的热应力

用Ag-Cu-Ti钎料钎焊SiCw／Al2O3复合陶瓷和金属时，陶瓷与钎料发生化学反应，在陶瓷表面形成由TiO、TiC等物相组成的反应层。采用有限元法，对SiCw／Al2O3复合陶瓷／反应层界面的热应力进行了计算。结果表明，复合陶瓷／反应层界面的残余应力变化急剧，最大拉应力位于晶须、基体和反应层交界处；晶须内部及其表面存在较高的双向压应力，Al2O3基体主要承受垂直于界面的拉应力；SiC晶须／反应层界面及其附近的反应产物TiC内具有较高的平行于界面的拉应力，当连接界面承受剪力作用时，SiC晶须／反应层界面和TiC处极易破坏。借助TEM和SEM观察了复合陶瓷／反应层界面区的精细结构和剪切断口形貌，并利用计算结果对观察到的现象进行了分析。