Strain-softening behavior of an Fe-6.5 wt%Si alloy during warm deformation and its applications

An Fe-6.5 wt%Si alloy with columnar grains was compressed at a temperature below its recrystallization temperature. The Vickers hardness and structure of the alloy before and after deformation were investigated. The results showed that with an increase in the degree of deformation, Vickers hardness of the alloy initially increased rapidly and then decreased slowly, indicating that the alloy had a strain-softening behavior after a large deformation. Meanwhile, the work-hardening exponent of the alloy decreased significantly. Transmission electron microscopy confirmed that the decrease of the order degree was responsible for the strain-softening behavior of the deformed alloy. Applying its softening behavior, the Fe-6.5 wt%Si alloy with columnar grains was rolled at 400 °C and then at room temperature. An Fe-6.5 wt%Si thin strip with thickness of 0.20 mm was fabricated. The surface of the strip was bright and had no obvious edge cracks.     

Coating of TiB2 dispersed Ti50Ni50 superelastic alloy layer onto Ti-6Al-4V alloy by spark and resistance sintering

The spark and resistance sintering (SRS) of a mixture of Ti, Ni, and TiB₂ powders was carried out to form a TiB₂ dispersed TiNi alloy layer onto a Ti-6Al-4V alloy substrate. The strength and delamination resistance of the surface layer were evaluated by three-point bending tests. The results showed that the bending strength of the specimen with the TiNi alloy surface layer without TiB₂ particles sintered at 1273 K was low because the crack initiation occurred at an early stage of loading in a thick interface layer containing brittle Ti-Ti₂Ni eutectic. By decreasing the sintering temperature to 1200 K, the bending strength increased and the crack initiation occurred from the surface because the interface layer was thin and did not contain the brittle Ti-Ti₂Ni eutectic. For the specimens with TiB₂ dispersed TiNi surface layer that was sintered at 1273 K, the bending strength was larger than that of the specimens with TiNi surface layer because the interface layer does not contain the Ti-Ti₂Ni eutectic and compressive residual stress generated in the surface layer during cooling process after SRS suppresses the crack initiation on the surface. The coating of TiB₂ dispersed TiNi alloy onto titanium alloys by SRS provides strong interface to prevent delamination of the surface layer, strong surface due to residual compressive stress, and wear-resistant surface due to the existence of hard TiB₂ particles and superelastic deformation of TiNi matrix.     

亚共晶Al-Cu系激光引燃自蔓延合金微观表征及性能研究

对亚共晶Al-Cu粉末压坯,通过不同功率进行激光引燃自蔓延烧结。用OM、SEM、XRD进行微观组织表征,并对烧结合金进行耐磨等性能测试。结果表明：烧结后物相由CuAlO2、Al4Cu9、Al2O3等构成,组织为树枝状晶和胞状晶相间分布。在激光输出功率为950W,烧结后密度最大,为2.8101g/cm3,致密性达到最高点,耐磨性最佳,相对失重为3.66%。     

BN—SF和BN—HF型皮革涂饰用树脂乳液的研究

本文介绍了用丙烯酸酯类单体与其他单体为原料,通过多元乳液共聚制备BN-SF和BN-HF两种新型皮革涂饰用高分子乳液的方法。并对所得胶乳及胶膜的物化性能进行了测试。论文还讨论了单体的配比,乳化剂的变化对乳液及胶膜性能的影响。实验表明这两类涂饰材料综合性能优良,贮存稳定性好。粒度范围为0.05～0.15)μm。经国内有关厂家成批量应用后表明该材料对皮革的涂饰效果好,涂层性能优良。     

Self-Adhesive Polydimethylsiloxane Foam Materials Decorated with MXene/Cellulose Nanofiber Interconnected Network for Versatile Functionalities

Polydimethylsiloxanes (PDMS) foam as one of next-generation polymer foam materials shows poor surface adhesion and limited functionality, which greatly restricts its potential applications. Fabrication of advanced PDMS foam materials with multiple functionalities remains a critical challenge. In this study, unprecedented self-adhesive PDMS foam materials are reported with worm-like rough structure and reactive groups for fabricating multifunctional PDMS foam nanocomposites decorated with MXene/cellulose nanofiber (MXene/CNF) interconnected network by a facile silicone foaming and dip-coating strategy followed by silane surface modification. Interestingly, such self-adhesive PDMS foam produces strong interfacial adhesion with the hybrid MXene/CNF nano-coatings. Consequently, the optimized PDMS foam nanocomposites have excellent surface super-hydrophobicity (water contact angle of ≈159^o), tunable electrical conductivity (from 10⁻⁸ to 10 S m⁻¹), stable compressive cyclic reliability in both wide-temperature range (from −20 to 200 ^oC) and complex environments (acid, sodium, and alkali conditions), outstanding flame resistance (LOI value of >27% and low smoke production rate), good thermal insulating performance and reliable strain sensing in various stress modes and complex environmental conditions. It provides a new route for the rational design and development of advanced PDMS foam nanocomposites with versatile multifunctionalities for various promising applications such as intelligent healthcare monitoring and fire-safe thermal insulation.     

Highly Crystalline Soluble Acene Crystal Arrays for Organic Transistors: Mechanism of Crystal Growth During Dip‐Coating

The preparation of uniform large‐area highly crystalline organic semiconductor thin films that show outstanding carrier mobilities remains a challenge in the field of organic electronics, including organic field‐effect transistors. Quantitative control over the drying speed during dip‐coating permits optimization of the organic semiconductor film formation, although the kinetics of crystallization at the air–solution–substrate contact line are still not well understood. Here, we report the facile one‐step growth of self‐aligning, highly crystalline soluble acene crystal arrays that exhibit excellent field‐effect mobilities (up to 1.5 cm V^?1 s^?1) via an optimized dip‐coating process. We discover that optimized acene crystals grew at a particular substrate lifting‐rate in the presence of low boiling point solvents, such as dichloromethane (b.p. of 40.0 °C) or chloroform (b.p. of 60.4 °C). Variable‐temperature dip‐coating experiments using various solvents and lift rates are performed to elucidate the crystallization behavior. This bottom‐up study of soluble acene crystal growth during dip‐coating provides conditions under which one may obtain uniform organic semiconductor crystal arrays with high crystallinity and mobilities over large substrate areas, regardless of the substrate geometry (wafer substrates or cylinder‐shaped substrates).     

1310nm大功率高偏振度量子阱超辐射发光二极管

设计并制备了一种斜条脊波导结构压应变高偏振度多量子阱超辐射发光二极管.设计的脊波导出光面TiO2/SiO2四层宽带增透膜的TE模式反射率约为10-6,分析了脊波导角度偏差和膜层厚度偏差对增透膜反射率的影响.实验结果表明,在250 mA直流电流驱动下,所设计的超辐射发光二极管芯片单管输出功率可达22.7 mW,出射光谱FWHM约为37.3 nm,光谱纹波系数低于0.15 dB,TE模式输出光强占主导,偏振度约为19.2 dB.     

Improvement in open circuit voltage of n‐ZnO/p‐Si solar cell by using amorphous‐ZnO at the interface

Several research groups are currently working on n‐ZnO/p‐Si heterojunction solar cell, and recently, Pietruszka et al [Sol. Energ. Mat. Sol. Cells 147 (2016) 164‐170] has reported the highest efficiency of 7.1% for this structure. The main challenge is to enhance the open circuit voltage up to theoretically predicted value of >0.6 V. This paper reports >20% improvement in open circuit voltage of n‐ZnO/p‐Si solar cell by depositing amorphous‐ZnO at the interface at room temperature that possibly improves the passivation and/or avoids oxide formation at the interface during ZnO deposition. Two other materials, aluminum nitride and amorphous‐Si, have also been used as buffer layers to evaluate their effect on suppression of interface states. Furthermore, additional advantage of ZnO as an antireflector has been experimentally verified for different thicknesses of ZnO film.     

Understanding the Meniscus‐Guided Coating Parameters in Organic Field‐Effect‐Transistor Fabrications

Meniscus‐guided coating (MGC) is mainly applicable on the soluble organic semiconductors with strong π–π overlap for achieving single‐crystalline organic thin films and high‐performance organic field‐effect‐transistors (OFETs). In this work, four elementary factors including shearing speed (v), solute concentration (c), deposition temperature (T), and solvent boiling point (T_b) are unified to analyze crystal growth behavior in the meniscus‐guided coating. By carefully varying and studying these four key factors, it is confirmed that v is the thickness regulation factor, while c is proportional to crystal growth rate. The MGC crystal growth rate is also correlated to latent heat (L) of solvents and deposition temperature in an Arrhenius form. The latent heat of solvents is proportional to T_b. The OFET channels grown by the optimized MGC parameters show uniform crystal morphology (Roughness R_q < 0.25 nm) with decent carrier mobilities (average µ = 5.88 cm² V^?1 s^?1 and highest µ = 7.68 cm² V^?1 s^?1). The studies provide a generalized formula to estimate the effects of these fabrication parameters, which can serve as crystal growth guidelines for the MGC approach. It is also an important cornerstone towards scaling up the OFETs for the sophisticated organic circuits or mass production.     

工艺参数对激光冲击微造型效果的影响

激光表面织构(LST)是一种广泛应用的表面微造型方法,然而其主要缺点是消融过程会导致材料熔化、断裂以及改变表面微观组织。基于激光冲击强化(LSP)技术在Al7075表面开展微凹坑造型研究,其特点是既能克服激光表面织构的缺点,又能继承激光冲击强化的优点。使用AxioCSM700真彩色共聚焦扫描显微镜和VeccoWYKO表面形貌仪观察微凹坑的几何形貌,用HXD-1000TMSC/LCD MH-VK双压头显微硬度计测量微凹坑的内部以及周围表面的硬度。实验结果表明,微凹坑的直径和深度随激光的脉冲能量、冲击次数、离焦量、约束层K9玻璃厚度的变化呈现一定的变化规律;微凹坑的影响区域,沿着凹坑径向方向硬度逐渐增加,中心位置硬度最大,这有利于提高材料的抗磨损能力。