Preparation and characterization of cellulose and konjac glucomannan blend film from ionic liquid

Blend films from cellulose and konjac glucomannan (KGM) in room temperature ionic liquid 1‐allyl‐3‐methylimidazolium chloride were satisfactorily prepared by coagulating with water. The composition of the blend films was gravimetrically analyzed, and the compatibility of the two natural polymers was characterized by Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction. The results indicate good compatibility and strong interactions between cellulose and KGM, resulting in almost no loss of the water‐soluble KGM from the blend films even after the water coagulating and washing. However, microstructure analyses portrayed phase separations in the blend films, namely, egg‐like new phase particles were embedded in a continuous matrix base (MB). Phase diagram analysis and differential scanning calorimetry of the phase inversion coagulation process suggest that relative low molecular mass part of both cellulose and KGM formed the continuous MB, whereas the egg‐like new phase particles were super patterns of relative high molecular mass of both polymers, which played an important role in strengthening the blend material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1686–1694, 2009     

Experimental study on combustion characteristics of diesel–hydrogen dual-fuel engine

As a clean and sustainable energy source, hydrogen is widely considered as an engine fuel by top researchers. In view of the fact that the uneven fuel mixture of diesel fuel deteriorated the combustion and emissions process, it is expected to adopt diesel and hydrogen dual-fuel combustion technology to optimize combustion and heat release of diesel engine. In this study, experiments are carried out on a diesel engine and the combustion characteristics of the engine with different hydrogen ratios (RH) are compared. It has been found that hydrogen addition is conducive to accelerate the heat release rate and improve the thermal efficiency. Specifically, compared with pure diesel conditions, the peak pressure increased by 7.7% and the cumulative heat release rate increased by 3.7% under the condition of RH of 20%. Moreover, although the effect on the ignition delay period is not clear, the higher RH brings about earlier heat release center and more cumulative heat release while enhancing the heat release of premixed combustion reducing the diffusion combustion and post-combustion.

     

Preparation of a liquid boron‐modified polycarbosilane and its ceramic conversion to dense SiC ceramics

A boron‐modified ethynylhydridopolycarbosilane (B‐EHPCS) was successfully prepared via the hydroboration reaction of ethynylhydridopolycarbosilane (EHPCS) with 9‐borabicyclo‐[3.3.1]nonane (9‐BBN). The as‐synthesized B‐EHPCS with a branched structure was characterized by means of gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). The structural evolution of ceramic conversion of B‐EHPCS was investigated by solid‐state NMR. The ¹³C magic angle spinning (MAS) NMR results indicated that the C?C and C?C groups of B‐EHPCS take part in the hydrosilation cross‐linking at a relatively low temperature (170°C). According to the ²⁹Si MAS NMR analysis, the CSiH₃ end groups are most reactive hydride functionality involved in the hydrosilation cross‐linking. With increasing curing temperature, the C₂SiH₂ and CSiH₃ units are completely consumed, while C₃SiH units remain even after curing at 600°C. The TGA results show the 1200°C ceramic yield of B‐EHPCS reaches 86%, which is 10% higher than that of the parent EHPCS (76%). At high temperatures, the introduction of <1 wt% boron significantly inhibits silicon carbide (SiC) crystallization. The 1800°C ceramics derived from B‐EHPCS are found to be significantly denser than that from EHPCS. Copyright © 2010 John Wiley & Sons, Ltd.     

Vertical transport of subwavelength localized surface electromagnetic modes

Transport of subwavelength electromagnetic (EM) energy has been achieved through near‐field coupling of highly confined surface EM modes supported by plasmonic nanoparticles, in a configuration usually on a two‐dimensional (2D) substrate. Vertical transport of similar modes along the third dimension, on the other hand, can bring more flexibility in designs of functional photonic devices, but this phenomenon has not been observed in reality. In this paper, designer (or spoof) surface plasmon resonators (‘plasmonic meta‐atoms’) are stacked in the direction vertical to their individual planes in demonstrating vertical transport of subwavelength localized surface EM modes. The dispersion relation of this vertical transport is determined from coupled‐mode theory and is verified with a near‐field transmission spectrum and field mapping with a microwave near‐field scanning stage. This work extends the near‐field coupled resonator optical waveguide (CROW) theory into the vertical direction, and may find applications in novel three‐dimensional slow‐light structures, filters, and photonic circuits.

     

Novel hierarchical microparticles super-assembled from nanoparticles with the induction of casein micelles

Inspired by the high light-harvesting properties of typical butterfly wings, ceramic WO₃ butterfly wings with hierarchical structures of bio-butterfly wings was fabricated using a template of PapilioParis butterfly wings through a sol–gel method. The effect of calcination temperatures on the structures of the ceramic butterfly wings was investigated and the results showed that the WO₃ butterfly wing replica calcined at 550 °C (WO₃ replica-550) is a single phase and has a high crystallinity and relatively fine hierarchical structure. The average grain size of WO₃ replica-550 and WO₃ powder are around 32.6 and 42.2 nm, respectively. Compared with pure WO₃ powder, WO₃ replica-550 demonstrated a higher light-harvesting capability in the region from 460 to 700 nm and more importantly the higher charge separation rate, as evidenced by electron paramagnetic resonance measurements. Photocatalytic O₂ evolutions from water were investigated on the ceramic butterfly wings and pure WO₃ powder under visible light (λ > 420 nm). The results showed that the amount of O₂ produced from WO₃ replica-550 is 50 % higher than that of the pure WO₃ powder. The improved photocatalytic performance of WO₃ replica-550 is attributed to the quasi-honeycomb structure inherited from the PapilioParis butterfly wings, providing both high light-harvesting efficiency and efficient charge transport through the WO₃.     

造价低廉的圆柱形空间吸声体的设计与应用

本文通过空间吸声体的造价分析，分析了所设计的以镀锌电焊网为骨架的一种圆柱形空间吸声体，这种空间吸声体结构简单，造价低廉，比常规做法节省资金约５０％，将这种吸声体用于济南铁路体育馆的声学改造工程，收到了良好效果。     

消声室自由声场的CAD及其某些结果的讨论

本文介绍了作者运用文献（３）中消声室自由声场的镜象法计算公式消声室自由声场的ＣＡＤ，根据这个软件计算出来的几点关于消声室自由声场的结果，可能值得建筑师和应用声学工作者们注意。     

共价有机框架分子印迹聚合物复合材料的制备及其用于牛奶中痕量诺氟沙星的选择性富集北大核心CSCD

诺氟沙星(NFX)作为一种常见的喹诺酮类兽药,被广泛应用于畜牧业中,但其会残留在动物体内,进而对人体健康造成危害,为此有许多国家和组织均对NFX残留量进行了严格限制。为实现对复杂体系中痕量NFX残留的准确与可靠分析,该文制备了一种以共价有机框架(COFs)为载体的分子印迹聚合物(MIPs)。首先,在室温条件下,以金属三氟酸盐为催化剂,对苯二甲醛和3,3′-二氨基联苯为原料快速合成了“席夫碱”型共价有机框架(DP-COF)。然后将NFX、甲基丙烯酸、乙二醇二甲基丙烯酸酯与DP-COF混合,利用偶氮二异丁腈引发聚合反应,即可得到DP-COF@MIPs。整个制备过程条件温和,耗时仅5 h。采用场发射扫描电镜、傅里叶红外光谱、X射线衍射仪、BET比表面积测试仪等对其进行了表征。结果证实成功制备出了DP-COF@MIPs,该材料表面粗糙,拥有介孔范围的孔径(17.79 nm)。通过吸附实验、重复使用性实验对材料性能进行评估,结果表明该材料表观吸附容量高达41.57 mg/g,对NFX具有良好的特异性和选择性识别能力,且重复使用率令人满意。结合HPLC-UV-Vis,实现对牛奶样品中痕量NFX的检测。在3个加标水平下(0.03、0.1、0.3 mg/L),平均回收率为88.8%~92.9%,相对标准偏差小于1.7%。结果表明,该方法可以实现在复杂基质中对兽药残留高选择性、高灵敏度及准确性的检测。