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关键词： Room temperature FLC mixture   Silver nanoparticles   Nanocomposite   Spontaneous polarization   Switching time  

摘要： We have investigated the effect of doping of a small amount of silver nanoparticles (AgNPs) on the physicochemical properties of a room temperature ferroelectric liquid crystal mixture. Polarizing optical microscopy, differential scanning calorimetry, synchrotron X-ray diffraction, dielectric and electro-optic studies showed that the inclusion of AgNPs greatly influences the phase transition temperatures, structural, dielectric, and electro-optic properties. Doping slightly decreases the SmC-SmA* and SmA*-Iso transition temperatures signifying decreased ordering which is also reflected in reduced tilt angles. The Goldstone mode dielectric increment of the nanocomposite increases twofold but the critical frequency decreases slightly. Spontaneous polarization of the mixture also increases significantly in the presence of AgNPs whereas the conductivity decreases indicating trapping of ions by the nanoparticles. Goldstone mode rotational viscosity decreases and as a result of which the switching time also decreases by 88 As making the nano doped mixture more suitable for practical applications. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 征订工作   物理化学学报   学术刊物   中国化学会   交叉学科   工程学院   人物专访   学报编辑部  

摘要： 2021年全国报刊杂志征订工作已经开始,敬请向贵单位推荐订阅2021年《物理化学学报》。《物理化学学报》是由中国科学技术协会主管,中国化学会和北京大学共同主办,北京大学化学与分子工程学院学报编辑部编辑出版的学术刊物。设有"亮点""当期推荐""通讯""展望""专论""综述""论文""人物专访"等栏目,报导物理化学学科及交叉学科的基础研究及应用研究的创新成果。

关键词： 信息技术   网络教学平台   物理化学  

摘要： 通过网络教学平台,建立"教学团队"和"班级课程群"将信息技术应用于物理化学教学中,结合物理化学学科特点,探讨适用于物理化学教学的信息化教学模式,促进现代化信息技术与物理化学教学的深度融合。

关键词： Sorption   Layers   Physical and chemical properties   Clay   Extraction  

摘要： Heterogeneity in physical and chemical properties is a common characteristic in a subsurface environment. This study investigated the effect of physico-chemical heterogeneity on arsenic (As) sorption and reactive transport under water extraction in a layered system with preferential flow paths. A flume experiment was performed to derive the spatio-temporal data of As reactive transport. The results indicated that the heterogeneous system significantly accelerated downward (vertical direction) As migration as a coupled effect of physical and chemical heterogeneity that led to fast As transport with low As sorption along the preferential flow paths. The results also indicated that such a heterogeneity effect was driven by water extraction that enhanced the downward groundwater flow along the preferential flow paths. Numerical simulations were performed by matching the experimental results to provide insights into the dominant processes controlling the As migration in the heterogeneous systems. The simulation results highlighted the importance of the kinetic oxidation of mineral-bonded Fe(II) to Fe(III) in the clay matrix that dynamically increased As sorption affinity and retarded As reactive transport. A coupled model of reactive transport along the preferential flow paths, sorption-retarded diffusion from the preferential flow paths into the clay matrixes, and reactions that change sorption affinity in the matrix was required to describe the As reactive transport systems with physico-chemical heterogeneities. The results have strong implications for understanding and modeling As downward migration from shallow to deep aquifers under groundwater pumping conditions in field systems with inherent heterogeneity.

关键词： 乙酸乙酯   双液系   气-液平衡   相图  

摘要： 通过对相关文献的分析及资料的查阅,总结了作为学生实验用双液系气-液平衡相图体系的选择要点。本文选用环己烷-乙酸乙酯双液系,进行气-液相图绘制。经实验证明,笔者认为此体系是一个适合本科教学开展的物理化学实验。

关键词： 物理化学   静电喷雾技术   RDX/NC/Al   复合炸药   热分解性能  

摘要： 为改善环三次甲基三硝基胺(RDX)的能量密度和反应速率,采用静电喷雾法制备了RDX/NC/Al复合炸药;通过扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)对产品的形貌、结构进行分析,利用透射电镜法对纳米Al进行活性分析,采用热重-差示扫描量热(TG-DSC)对产品热性能进行了分析,同时测定了其机械感度,并用高速摄影仪分析其燃烧过程。结果表明,采用静电喷雾法制得的RDX/NC/Al复合炸药的粒径范围为60~170nm,以团聚微球的形式存在,3种原料之间的复合为物理复合,纳米Al粉的铝质量分数约为74.89%;与原料RDX相比,RDX/NC/Al复合炸药的活化能提高了25.11kJ/mol,热爆炸临界温度提高了2.4℃,两者的等动力学温度为214.69℃,撞击感度和摩擦感度分别大于40J和360N,降感效果明显。表明RDX/NC/Al复合炸药的燃烧性能较好,具有较短的点火延迟时间和较高的燃烧速率,以及较好的安全性能。

关键词： 物理化学   课程思政   立德树人  

摘要： 就物理化学热力学、动力学、相平衡、表面活性剂等部分知识点教学过程中思政元素的融入进行探索,以期在教学过程中践行立德树人的理念。

关键词： 征订工作   物理化学学报   学术刊物   中国化学会   交叉学科   工程学院   人物专访   学报编辑部  

摘要： 2021年全国报刊杂志征订工作已经开始,敬请向贵单位推荐订阅2021年《物理化学学报》。《物理化学学报》是由中国科学技术协会主管,中国化学会和北京大学共同主办,北京大学化学与分子工程学院学报编辑部编辑出版的学术刊物。设有"亮点"、"当期推荐"、"通讯"、"展望"、"专论"、"综述"、"论文"、"人物专访"等栏目,报导物理化学学科及交叉学科的基础研究及应用研究的创新成果。

关键词： 物理化学   线上线下   四位一体模式   混合式教学  

摘要： 物理化学是化学化工、生物医药等理工科的专业必修课程,具有理论性强、注重公式推演和理论联系实际等特点。现有的教学安排无法满足课程的全面开展,利用线上线下混合教学模式,借助网络教学平台可以充实课程资料,丰富教学体验。依托超星学习通平台,通过建立"教学评改"四位一体的教学模式,推进物理化学课程教学改革的高效开展。

关键词： Black soldier fly (BSF)   Hermetia illucens   Chitin   Acid detergent fiber (ADF)   Acid detergent lignin (ADL)  

摘要： This study aims to valorize chitin polymer from the side stream of an insect farm and to determine the chitin content, and its physicochemical properties obtained from different processing steps in the insect farm (Adult Black Soldier Fly insect, Puparia, and Flake). We used an acid-base method (using 1 M HCl and 1 M NaOH) as a conventional technique and the acid detergent fiber (ADF) with acid detergent lignin (ADL) methods. The chitin samples are then characterized for thermal stability (TGA-DTA), crystallinity (XRD), chemical compounds (FTIR), and C/N content, and the results were compared to the commercial shrimp chitin. The Puparia had the highest chitin content of 21-33%, followed by the Flake 20-28% and the Adult insect with 7-13% chitin, depending on the extraction method. The chitin yield from ADF-ADL method was on par with the conventional method, while the ADF results were approximately 3-10% higher than the ADF-ADL results. The insect farm side stream is an abundant rich source of high-quality chitin with physiochemical properties comparable with the commercially available shrimp derived chitin. (C) 2020 Elsevier Ltd. All rights reserved.