Au-Ag-Si钎料合金的初步研究

针对目前熔点在450～500℃范围内的电子器件用钎料的空缺，通过分析Au-Ag-Si系三元相图，并根据其存在的共晶单变量线e1e2，制备了几种熔化温度在400～500℃的共晶钎料合金，并对其钎焊性和加工性能进行了初步的研究。DTA分析发现，合金的熔点在所选定的合金成分范围内随Ag含量的增加而升高。此钎料与Ni板浸润性较好；将钎料合金铸锭热轧后表明该合金作为可加工的实用钎料是合适的。同时，初步探讨了Cu元素对于Au-Ag-Si系合金的熔化特性和塑性变形能力的影响，结果表明Cu对于改善合金的加工性能和缩小固液相间距具有重要的意义。     

Evaluation about wettability,water absorption or swelling of excipients through various methods and the correlation between these parameters and tablet disintegration

Objective: To evaluate parameters about wettability, water absorption or swelling of excipients in forms of powders or dosage through various methods systematically and explore its correlation with tablet disintegration.

Material and methods: The water penetration and swelling of powders with different proportions of excipients including microcrystalline cellulose (MCC), mannitol, low-substituted hydroxypropyl cellulose (L-HPC), crospolyvinylpyrrolidone (PVPP), carboxymethyl starch sodium (CMS-Na), croscarmellose sodium (CCMC-Na) and magnesium stearate (MgSt) were determined by Washburn capillary rise. Both contact angle of water on the excipient compacts and surface swelling volume were measured by sessile drop technique. Moreover, the test about water absorption and swelling of compacts was fulfilled by a modified method. Eventually, the disintegration of tablets with or without loratadine was performed according to the method described in USP.

Results and discussion: These parameters were successfully identified by the methods above, which proved that excipient wettability or swelling properties varied with the structure of excipients. For example, MgSt could improve the water uptake, while impeded tablet swelling. Furthermore, in the present study it is verified that tablet disintegration was closely related to these parameters, especially wetting rate and initial water absorption rate. The higher wetting rate of water on tablet or initial water absorption rate, the faster swelling it be, resulting in the shorter tablet disintegration time.

Conclusion: The methods utilized in the present study were feasible and effective. The disintegration of tablets did relate to these parameters, especially wetting rate and initial water absorption rate.     

Joining of Cf/SiBCN composite with CuPd-V filler alloy

Two compositions of CuPd-V system filler alloy were designed for joining the Cf/SiBCN composite. Their dynamic wettability on the Cf/SiBCN composite was studied with the sessile drop method. The CuPd-8 V alloy exhibited a contact angle of 57° after holding at 1170℃ for 30 min, whereas for CuPd-13 V alloy,a lower contact angle of 28°can be achieved after heating at 1200 ℃ for 20 min. Sound C_f/SiBCN joints were successfully produced using the latter filler alloy under the brazing condition of(1170-1230)℃for 10 min. The results showed that the active element V strongly diffused to the surface of Cf/SiBCN composite, with the formation of V_2 C/VN reaction layer. The microstructure in the central part of the joint brazed at 1200 ℃ was characterized by the V_2 C/VN particles distributing scatteringly in CuPd matrix. The corresponding joints showed the maximum three-point bend strength of 82.4 MPa at room temperature.When the testing temperature was increased to 600 0 C, the joint strength was even elevated to 108.8 MPa.Furthermore, the joints exhibited the strength of 92.4 MPa and 39.8 MPa at 800 ℃ and 900 ℃, respectively.     

Wettability-patterned microchip for emerging biomedical materials and technologies

Microchip has long been studied and facilitated recent investigations in multiple biomedical and material fields. The advances in functional materials triggered several leaps in the development of microchip technology. Microarray chip, benefiting from micropatterning and nucleic acid nanotechnology, was firstly introduced around 1980 and rapidly facilitated genomics, proteomics, and biodetections. In the following generation, the microfluidic chips, raised from microelectromechanical systems (MEMS) and soft lithography, are revolutionizing several areas like biology, material fabrication, energy, and environmental science. More recently, the advances in materials fabrication keep expanding the frontiers of microchip platforms, like nanoscale fabrications and flexible device manufacturing. One of the most promising platforms is the wettability-patterned materials inspired by ubiquitous natural wetting creatures such as lotus leaf, spider silk, and Stenocara beetles. The unique property of handling liquids with no sophisticated equipment potentially facilitated the current microchip platform by combining the merits of microarray and microfluidics, and in turn, benefits material communities and beyond. In this featured article, we briefly introduce the state of art technologies to fabricate wettability-patterned chips and highlight some proof-of-concept demonstration of its emerging applications in material and biomedical science. We also give an outlook on its further developments including machine-learning micropattern manufacturing technology and reveal its potentiality to revolute several scientific areas.     

Wetting behaviour of Y2O3/AlN additive on SiC ceramics

The wetting of SiC plate by Y₂O₃/AlN additive was analysed using the sessile drop method. The wetting behaviour was observed by image capture system using a CCD camera during the heating, in argon atmosphere. The contact angle was measured as a function of temperature and time. After the wetting test the SiC plus additive samples were cut in order to observe the thickness plate cross section. The additive area and the interface between SiC and additive were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The wetting of SiC by Y₂O₃/AlN is influenced by the presence of a solid phase in some of the additive drops that depends mainly on the additive composition and consequently on the temperature. The measured contact angles were below 7°, reaching 0° for Y₂O₃/AlN additive tested at the eutectic composition, indicating a very good wettability of Y₂O₃/AlN on the SiC.     

Studies on the controlled morphology and wettability of polystyrene surfaces by electrospinning or electrospraying

Polystyrene (PS) surfaces with various morphologies have been produced by electrospinning or electrospraying, such as beads with different sizes and shapes, bead-on-string structures with different aspect ratios of the beads and fibers with different diameters and shapes. Both the solution properties and the electrospinning conditions affected the PS surface morphology obtained. The results of water contact angle (CA) measurement indicated that the surface morphology could affect the wettability distinctively. It was found that CA values of PS surfaces comprised merely fibers were in the range of 140°-150°. The CA values of PS surfaces comprised bead-on-string structures were usually about 150°. However, the CA values of PS surfaces consisted of particles could reach up to 160°, which shows a superhydrophobic property. A bilayer fibers-on-beads surface was verified to be stable and superhydrophobic.     

Al2O3-W复合材料的抗渣蚀性能

在埋炭条件下,以金属铝粉、氧化钨及刚玉为原料,对以铝热反应为基础制备的Al2O3-W复合材料的抗渣性能进行了研究.结果表明Al2O3-W复合材料的抗渣性能随金属钨含量的增加而改善.金属钨和渣较差的润湿性是一个重要因素,而氧化铝和熔渣的反应机理和常规刚玉质材料的抗渣蚀机理一致.金属钨和渣中被还原的铁相反应生成高熔点相Fe7W6,增加了液相的粘度,抑制了熔渣的侵蚀和渗透.     

水平井润湿性反转堵水的数值模拟研究

水平井堵水技术是提高水平井原油采收率的一项关键技术,通过对毛管压力方程的分析,明确了水平井润湿反转堵水的机理,建立了水平井润湿反转的模型,并运用数值模拟方法证明了润湿反转堵水的可行性。     

Efficacy of multi-mode adhesive systems on dentin wettability and microtensile bond strength of resin composite

Purpose: To evaluate the wetting ability and the microtensile bond strength of adhesive systems in various depths of dentin. Materials and Method: 48 extracted human molars cut in half in buccolingual direction. Buccal and lingual surfaces were used to obtain deep (n = 48) and superficial (n = 48) dentin. Groups were divided into 4 subgroups: Self-etch (CSE), etch&rinse (SB), multi-mode self-etch (SAU) and multimode etch&rinse (EAU) adhesive systems. 3 consecutive contact-angle measurements were obtained: T0- 3 μl drop of distilled water on dentin; T1-Droplet of the adhesive; T2- Distilled water after polymerization of the adhesive. After composite build-ups, microtensile measurements were performed. Contact angle data were analysed with analysis of variance for repeated measures. Bond strength data were analyzed by repeated measures analysis of variance, comparisons were made according to the logarithmic values (p < 0.05). Results: The difference between groups was not significant regardless of dentin depth for all measurements (p < 0.05). All groups except CSE enhanced the wetting ability of the adhesive but reduced the wetting ability of distilled water after application of the adhesive (p < 0.05). Regarding adhesive systems, the groups showed no significant difference between bond strengths to various depths of dentin except SAU (p > 0.05); in SAU, bond strength to deep dentine were significantly higher than superficial dentin (p < 0.05). Regarding adhesives’ bond strength, CSE showed significantly greater values than the other groups (p < 0.05). Conclusion: The cavity depth does not affect the bonding ability for all adhesive systems; self-etch adhesive systems might be a better choice since different adhesives may influence the wetting ability and microtensile bond strength of the dentin substrates.     

Synthesis and characterization of ceramic nanoparticles reinforced lead-free solder

Sn-0.7Cu is among the least expensive types of lead-free solders available. However, its poor mechanical properties have limited its application. In this study, Sn-Cu lead-free solder reinforced with amorphous silica (SiO₂) nanoparticles was synthesized through powder metallurgy route. Desired mixtures of raw materials was mechanically milled, compressed, sintered and extruded to prepare bulk solder samples. The samples were characterized by optical and electron microscopy as well as mechanical tests. The results showed that mechanical properties were increased by addition of SiO₂ nanoparticles to the solder matrix. Addition of 1.5 wt% ceramic reinforcement to the composite increased tensile, yield and compressive strengths up to 27%, 23% and 41%, respectively, compared to those of the monolithic sample. In addition, the ceramic nanoparticles caused an up to 50% decrease in the wetting angle between the substrate and the nanocomposite solder.