Fabrication of sub-micron 3-D structure using duo-mold UV-RIL process

3-D polymeric micro- and nano-structures were fabricated by the reversal imprint lithography technique using nano-patterned molds. A surface-treated quartz mold and a water-soluble poly vinyl alcohol (PVA) mold were used to make dual-side patterned, 2-D polymeric, micro- and nano-structures. First, UV-curable, polymeric resin was dropped onto the quartz mold, which was then covered with the PVA mold. The two stacked molds were pressed and exposed to UV-light to cure the resin. The cured polymeric resin (the reversal layer) was easily released from the quartz mold, because the surface of the latter was treated with an anti-stiction layer. The reversal layer, bound to the PVA mold, was transferred to a Si substrate by applying a thin layer of a UV-curable bonding agent. After bonding the reversal layer, the PVA mold was selectively removed by dipping in water. As a result, the dual-side patterned, thin polymeric 2-D structure was formed on the silicon substrate and, by repeating this process, 2-D nano-structures were stacked to form a 3-D nano-structure. By making use of the anti-stiction-treated, quartz mold and the water-soluble characteristic of the PVA material, the reliable release of the reversal layer was achieved.     

Comparison of imaging quality between linear sampling method and time reversal in microwave imaging problems

This research investigated imaging quality of two important methods widely used in electromagnetic inverse scattering problems. The algorithms, time reversal (TR) and linear sampling method (LSM), were compared for resolution of point imaging and a correlation indicator to determine image quality. Comparisons were made in single- and multifrequency modes for 2D scenarios in free-space. Comparisons revealed that resolution of TR is much better than LSM. In order to compare the total reconstructed images, several cases were considered to determine a comprehensive conclusion. The simulations were done based on experimental data. In this case, comparisons showed that in the term of correlation indicator, LSM surpasses TR.     

Dielectric surface-polarity tuning and enhanced operation stability of solution-processed organic field-effect transistors

The electrical performance of triethylsilylethynyl anthradithiophene (TES-ADT) organic field-effect transistors (OFETs) was significantly affected by dielectric surface polarity controlled by grafting hexamethyldisilazane and dimethyl chlorosilane-terminated polystyrene (PS-Si(CH₃)₂Cl) to 300-nm-thick SiO₂ dielectrics. On the untreated and treated SiO₂ dielectrics, solvent–vapor annealed TES-ADT films contained millimeter-sized crystals with low grain boundaries (GBs). The operation and bias stability of OFETs containing similar crystalline structures of TES-ADT could be significantly increased with a decrease in dielectric surface polarity. Among dielectrics with similar capacitances (10.5–11 nF cm⁻²) and surface roughnesses (0.40–0.44 nm), the TES-ADT/PS-grafted dielectric interface contained the fewest trap sites and therefore the OFET produced using it had low-voltage operation and a charge-carrier mobility ∼1.32 cm² V⁻¹ s⁻¹, on–off current ratio >10⁶, threshold voltage ∼0 V, and long-term operation stability under negative bias stress.     

Colloidal properties of polymerizable counterion surfmers solutions based on alkylamino 2-acrylamido-2-methylpropanesulfonates in different solvents

Three polymerizable surfactants (surfmers) bearing 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as polymerizable group in the counterion have been designed, synthesized, and their micelle-forming properties have been investigated in different solvents. Solutions of dodecylammonium (DDA-AMPS), cetylammonium (CA-AMPS), and cetyltrimethylammonium (CTA-AMPS) 2-acrylamido-2-methylpropanesulfonates were studied in water, water–dioxane mixtures in a whole range of components ratios, and xylene. The solutions were investigated by capillary and rotational viscometry, conductometry, and small-angle neutron scattering; aggregates adsorbed from the solutions on as-split mica were studied by atomic force microscopy (AFM). The surfmers follow general regularities of surfactant behavior in aqueous solutions. Decrease in polarity of the media with an increase in dioxane content in water–dioxane mixtures leads to disappearance of direct micelles. At low water content (below 5%) the surfmers form reverse micelles in the mixtures. The surfmers form reverse micelles in low polarity solvents, such as xylene, which should affect the polymerization results.     

不同极性抗氧化剂对油包水乳液氧化稳定性的影响

以富含多不饱和脂肪酸(UPFA)的核桃油为油相,采用超高压微射流均质机制备油包水(W/O)乳液,分别添加非极性抗氧化剂α-生育酚及其极性对应物—6-羟基-2,5,7,8-四甲基色烷-2-羧酸(Trolox)于乳液中,45℃避光保存,检测乳液初级氧化产物—脂质氢过氧化物与次级氧化产物-顶空己醛含量,探究抗氧化剂极性对W/O乳液稳定性影响。结果表明,10~1000μM,α-生育酚与Trolox对W/O乳液脂质氢过氧化物和己醛的形成都具有抑制作用,其中Trolox抗氧化性随浓度的增大而提升,而较高浓度的α-生育酚(500~1000μM)反而降低其对脂质氢过氧化物的抑制作用;α-生育酚分布于乳液油水界面浓度小于极性抗氧化剂Trolox,导致非极性抗氧化剂α-生育酚活性低于极性抗氧化剂Trolox;乳液水相pH 3.0时,Trolox抗氧化性高于水相pH 7.0,水相pH通过影响Trolox在W/O乳液各相分布,从而影响其抗氧化性。     

Effect of post weld heat treatment on properties of variable polarity TIG welded AA2219 aluminium alloy joints

AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas (VPTIG) welding process and the effects of post weld heat treatment (PWHT) on the tensile properties, microstructure and fatigue behaviour of the welded joints were investigated. The VPTIG welding process was adopted because it could meet the need of cathode cleaning and meanwhile it could reduce the deterioration of tungsten electrode furthest. The welded samples were divided into as-welded (AW) sample and PWHT sample. The PWHT method used on the samples was solution treatment (535 °C, 30 min), water quenching and artificial aging (175 °C, 12 h). The experimental results show that, compared with the AW samples, the microstructure characteristics and mechanical properties of the AA2219 joints after PWHT were significantly improved. The improvement of yield strength, ultimate tensile strength, and fatigue strength are 42.6%, 43.1% and 18.4%, respectively.     

Optimization of HPVP-GTAW process parameters for Al-Mg aluminum alloy welded joints

Optimization of hybrid ultrahigh frequency pulse variable polarity gas tungsten arc welding （HPVP-GTAW） process was carried out to obtain the optimum weld characteristics of 5AO6-HX4 aluminum-magnesium alloy sheets of 3 mm thickness. The square butt joints were produced by HPVP-GTA W process, the microstructure and mechanical properties were systematically investigated. It is observed that the process parameters influence the weld microstructure and mechanical properties significantly. Weld microstructure is mainly composed of grid a （A1） solid solution, with a large number of intermetallic （ Mg2Al3 ） precipitates distributed in the matrix. The amount of ~ （ Mg2Al3 ） precipitates has an obvious difference with different parameters. Compared with that of the base material, tensile strength of 5AO6-HX4 alloy welded joints has a certain reduction, as well as the elongation and reduction of area. The optimized welding process parameters for 5A06-HX4 alloy sheets are presented.     

基于逆向设计的异型金刚石砂轮设计流程分析与应用

随着石材制品向着高档化、异型化、艺术化的发展,个性化的定制、小批量的生产是石材制品加工发展的必然趋势,异型金刚石砂轮的设计则是实现石材异型化加工的关键。我们以实际建筑设计中的异型石材为例,应用逆向设计的方法,根据建筑设计效果图,反求设计出异型砂轮的外形尺寸,并结合金刚石砂轮的制造工艺对异型砂轮的设计提出了改良措施。最终实现从建设效果图到砂轮外形的逆向设计流程。研究成果为异型金刚石砂轮的设计方法提供了参考依据。     

基于LabVIEW的VPPA焊接信号采集分析系统

在实验室原有的变极性等离子焊接试验系统上,利用虚拟仪器软件LabVIEW设计了焊接电信号采集与分析系统,包括电流电压信号采集、滤波、概率统计以及频谱分析等焊接电特性参数采集与分析模块。通过焊接试验,对具有高低频调制脉冲功能的变极性等离子焊接系统进行信号检测与分析,比较分析了不同高低频时电弧电流波形以及频谱的不同。实验结果表明,该数据采集分析系统工作稳定,数据完整可靠,具有主要的信号分析功能。