Eco-friendly approach for preparation of hybrid silica aerogel via freeze drying method

Journal of Materials Science - In this paper, an eco-friendly method of producing hybrid silica aerogels by freeze-drying method (FD) is proposed. In the freeze-drying system, deionized water was...     

有机元素检测仪器在石油化工行业的需求和应用现状

本文通过对国内外石油及石化产品分析检测相关标准技术的调研与收集,以及相关检测仪器特点的分析,对目前包括润滑油、汽油、柴油、煤油、石蜡、石化聚合物、原油等样品类型,共计80个样品在现有仪器上进行测试,使用标准方法对样品中碳、氢、氮、硫元素进行检测,获取样品的检测时间、含量结果、仪器条件等参数,为相关仪器检测提供数据基础.     

Modification of the wood-plastic composite for enhancement of formaldehyde clearance and the 3D printing application

As the formaldehyde is one of the main indoor pollutants, the purpose of this study is to effectively remove indoor formaldehyde pollution by using environmentally friendly 3D printing ornaments. The wood 3D printing filaments cellulose/polylactic acid composite (Cellu/P) was selected as the starting material, and 3-aminopropyltriethoxysilane (APTES) was used for chemical modification to obtain a series of cellulose composite materials with amino groups. The modified composite materials (APTES@Cellu/P) were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, thermogravimetric analysis, and mechanical tests, and a formaldehyde removal experiment was performed. The feasibility of 3D printing was evaluated, and the process of 3D printing-functionalized customized ornaments was proposed, and then a school emblem was used for modeling, printing, and surface modification. Compared with the commercially traditional activated carbon, 3D printing-customized ornaments of APTES@Cellu/P material has a better formaldehyde removal effect, and can even avoid the secondary pollution that is common to the activated carbon.     

A new strategy to reduce edge chipping using stress wave impedance matching

To restrain edge chipping and elucidate its mechanism during machining, the initiation of edge chipping was investigated in this study from the propagation properties of stress waves in the fractured media. Three technological principles of the support for chipping suppression were proposed to reduce the intensity of reflected extension waves, namely, the wave impedance matching, the smaller residual gap and the higher viscosity of the gap filler between the workpiece and the support. As demonstrated from the experimental results, using brass support with non-solid epoxy gap filler can significantly restrain the edge chipping of pressureless sintered silicon carbide during grinding.     

Matrix Manipulation of Directly-Synthesized PbS Quantum Dot Inks Enabled by Coordination Engineering

The direct-synthesis of conductive PbS quantum dot (QD) ink is facile, scalable, and low-cost, boosting the future commercialization of optoelectronics based on colloidal QDs. However, manipulating the QD matrix structures still is a challenge, which limits the corresponding QD solar cell performance. Here, for the first time a coordination-engineering strategy to finely adjust the matrix thickness around the QDs is presented, in which halogen salts are introduced into the reaction to convert the excessive insulating lead iodide into soluble iodoplumbate species. As a result, the obtained QD film exhibits shrunk insulating shells, leading to higher charge carrier transport and superior surface passivation compared to the control devices. A significantly improved power-conversion efficiency from 10.52% to 12.12% can be achieved after the matrix engineering. Therefore, the work shows high significance in promoting the practical application of directly synthesized PbS QD inks in large-area low-cost optoelectronic devices.     

Preparation of transparent BaSO4 nanodispersions by high-gravity reactive precipitation combined with surface modification for transparent X-ray shielding nanocomposite films

BaSO₄ nanoparticles as important functional materials have attracted considerable research interests, due to their X-rays barrier and absorption properties. However, most of BaSO₄ nanoparticles prepared by traditional technology are nanopowders with broad size distribution and poor dispersibility, which may greatly limit their applications. To the best of our knowledge, the synthesis of transparent BaSO₄ nanodispersions was rarely reported. Here, we firstly present a novel and efficient method to prepare transparent and stable BaSO₄ nanodispersions with a relatively small particle size around 10 to 17 nm using a precipitation method in a rotating packed bed (RPB), followed by a modification treatment using stearic acid. Compared with the BaSO₄ prepared in a traditional stirred tank, the product prepared using an RPB has much smaller particle size and narrower size distribution. More importantly, by using RPB, the reaction time can be significantly decreased from 20 min to 18 s. Furthermore, the transparent BaSO₄-polyvinyl butyral nanocomposite films with good X-ray shielding performance can be easily fabricated. We believe that the stable BaSO₄ nanodispersions may have a wide range of applications for transparent composite materials and coatings with X-ray shielding performance for future research.     

Effects of the joining process on the microstructure and properties of liquid-phase-sintered SiC-SiC joints formed with Ti foil

The joining of liquid-phase sintered SiC (LPS-SiC) ceramics was conducted using spark plasma sintering (SPS), through solid state diffusion bonding, with Ti-metal foil as a joining interlayer. Samples were joined at 1400 °C, under applied pressures of either 10 or 30 MPa, and with different atmospheres (argon, Ar, vs. vacuum). It was demonstrated that the shear strength of the joints increased with an increase in the applied joining pressure. The joining atmosphere also affected on both the microstructure and shear strength of the SiC joints. The composition and microstructure of the interlayer were examined to understand the mechanism. As a result, a SiC-SiC joining with a good mechanical performance could be achieved under an Ar environment, which in turn could provide a cost-effective approach and greatly widen the applications of SiC ceramic components with complex shape.     

TLCD基础隔震框架结构的减振控制研究

为了避免和减轻由过大隔震层位移引起的损害,对基础隔震框架结构装设调频液柱阻尼器(tuned liquid column damper,简称TLCD)后混合系统的减振效果进行研究。建立了单层和多层混合控制系统在地震作用下的运动方程,采用TLCD-结构体系转化为调频质量阻尼器(tuned mass damper,简称TMD)-结构体系的等效方法,利用TMD参数优化公式,得到单个TLCD初始设计参数,并采用状态空间方程得到多个TLCD最优设计参数。通过对某8层基础隔震结构进行模拟,证明了该理论设计方法的合理性。该混合结构不仅可以减小隔震层位移和加速度,而且对上部结构位移和加速度反应都能更有效的控制。