Structure of the right-handed helical crystal ribbon and multilevel fibrils in a tube fiber from a coir fiber

A coir fiber is composed of many tube fibers with large hollows that align in parallel. SEM observation has shown that the tube fiber existing in a coir fiber is packed by a right-handed helix crystal ribbon, and its length/diameter ratio is lower than that of the crystal ribbon by 1–2 orders of magnitude. Based on the results of TEM, the diameter of protofibrils extracted from coir fibers is 6–10 nm, while that of the microfibrils is 20–40 nm, and the length/diameter ratios of protofibrils and microfibrils are 50–250 and 25–150, respectively. According to these observed results, the packing models of the right-handed helix crystal ribbon and its multilevel fibrils have been derived and further verified through the calculation and comparison of both the crystallinity in volume and whisker sizes obtained by means of X-ray diffraction analysis.     

A New Discovery of Calcium Phosphate Urinary Stones Formation Induced by Melamine: Nanocrystalline Assembly Mechanism

Melamine (Mel), a contaminant that has received much attention in recent years, has been adulterated into milk powder, causing a large number of infants suffering from kidney stone disease. To study the process and mechanism of calcium phosphate (CaP) stone formation induced by Mel, we simulated the formation process of CaP stones and studied the effect of Mel on crystallization in aqueous and synthetic urine systems, respectively. Ion selective electrode method was used to study the thermodynamic parameters and reaction rate of the crystallization process. It was firstly discovered that Mel could induce the formation of CaP crystals significantly under weak acidic urine conditions in which CaP cannot be stably present, so it may cause people to produce CaP stones. Thermodynamic parameter and reaction rate analysis indicated that Mel could increase the reaction tendency and accelerate the formation of CaP crystals, which was achieved by two process of electrostatic adsorption and release of calcium ions. This research is expected to provide scientific guidance for the prevention and treatment of Mel‐related stones.     

双极性碳纳米管薄膜晶体管构建及电性能研究

本文用聚 (PFO-BT)分离的半导体碳纳米管作为有源层,通过气溶胶喷墨打印技术在刚性基体上构建出底栅结构的碳纳米管薄膜晶体管器件。用钛酸钡复合材料封装后,碳纳米管薄膜晶体管表现出很好的双极性、较高的开关比和零回滞特性,同时阈值电压能够控制在0 V附近。通过两个双极性薄膜晶体管连接而成的反相器表现出零回滞、高电压增益(V_dd=1.5 V时,其增益可达到35)和大噪声容限(V_dd=1 V时,最大噪声容限为0.44 V)。     

SnO纳米晶须的制备及其性能表征

以SnCl2·2H2O为主要原料, Na2CO3 为矿化剂,十六烷基三甲基溴化铵为表面活性剂,采用压力热晶法,在160~200℃成功地制备出分散性好、晶型完整、结构稳定的氧化亚锡纳米晶须,并用透射电子显微镜、电子衍射、X射线衍射等技术手段对氧化亚锡纳米晶须的结构和形貌进行表征.表征结果显示,制得的SnO晶须具有棒状外观结构,其直径和长度分别为10~40、100~400nm. 实验还考察了反应时间、体系压力等条件对产物结构和形貌的影响,实验结果表明,增加压力和延长反应时间都有利于四方晶型氧化亚锡晶须的形成. 同时探论了四方晶型氧化亚锡纳米晶的须形成机理,初步认为其形成过程是一个成核并沿晶格延伸生长的过程.     

Epoxy matrix composites reinforced with purified carbon nanotubes for thermal management applications

The role of carbon nanotube purification treatment as a means to improve the thermal properties of polymer matrix composites was investigated. Particular emphasis was placed on clarifying the processing‐property relationship in polymer composites for thermal management applications. The results indicated that purification treatment is critical to the thermal properties of derived polymer composites. Purification treatment can yield a twofold increase in composite thermal conductivity because of improved effectiveness in interfacial interaction and increased chemical purity of the filler. However, there is a trade‐off between the benefits and disadvantages associated with purification treatment, particularly when thermal and electrical properties are both concerned. Purification treatment gives rise to a sharp decrease in composite electrical conductivity by at least two orders of magnitude because of the lack of an effective percolating network. The effect of purification treatment on composite electrical properties is more significant than on its thermal properties.     

纳/微米二硫化钼的化学制备及其催化加氢脱硫应用

二硫化钼(MoS2)是典型的层状过渡金属硫化物,因其在加氢催化、润滑、光电领域的广泛应用而备受关注。纳/微米材料由于特殊的微观结构而表现出很多优异的性质,因此具有特定形貌和结构的MoS2纳/微米材料的合成及性能研究对层状无机化合物的发展有重要意义。针对近年不断涌现的有关纳/微米MoS2及其在相关领域应用的报道,本文综述了MoS2的化学制备方法,主要介绍了基于热分解法、硫化法、水热/溶剂热法、液相沉淀法及新颖的物理化学联合技术等制备具有不同形貌和性能的纳/微米级MoS2及其复合材料,讨论了反应条件对产物形貌和性能的影响,评述了各种方法的特点。此外,简要介绍了非负载型和负载型MoS2催化剂在油品加氢脱硫方面的应用,并展望了其发展方向和应用前景。     

关于可压液晶方程组的能量有界性

考察可压液晶方程组有关能量的基本性质.证明了只要初始能量有界,此系统的能量就是一个与时间无关的有界量.