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关键词： 物理化学   化学热力学   化学动力学   界面现象   知识框架体系  

摘要： 物理化学作为一门实验科学,它的理论体系完全建立在实验研究的基础之上,有着非常严谨完整的知识体系。我们在教学课程中,注重从专业自身的特色着手,帮助学生学习和掌握物理化学的理论框架,掌握科学的学习方法,以物理化学的理论框架为基础结合专业特色合理筛选教学内容,优化课堂教学效果。物理化学课程教学中注意培养学生的科学文化修养,提升教学境界,培养学生尊重科学事实、严密完整的科学思维能力,这样必然对培养创新性思维这样一个宏观教学目标提出一个很好的培养模式。

关键词： 物理化学   类球形AP   CMDB推进剂   燃速   机械感度   热分解   分散均匀性  

摘要： 为了降低含超细AP的AP-CMDB推进剂的机械感度,将类球形超细AP加至CMDB推进剂中,通过扫描电子显微镜获得了推进剂的断面微观形貌;分别研究了类球形超细AP对推进剂密度、力学性能、燃烧性能和机械感度的影响。结果表明,类球形AP表面较光滑,在推进剂中分散较均匀,但与双基组分间存在部分界面脱粘现象;添加类球形超细AP对AP-CMDB推进剂的密度没有影响;可以有效提高推进剂的燃速,含类球形AP的AP-CMDB推进剂在10MPa时燃速从60.12mm/s提高至63.03mm/s;大幅降低推进剂的机械感度,特性落高(H50)提高了15.7cm,摩擦感度(P)降低了32%;但同时降低了推进剂的抗冲强度,-40℃时抗冲强度从5.22kJ/m^2降至4.12kJ/m^2,其原因与类球形AP的热分解性能、表面形貌、分散均匀性及与双基组分间的界面情况有关。

关键词： Phosphorus  

摘要： Phosphorus is a finite resource essential for global food production. However, excessive loss to river systems from diffuse sources (typically agricultural) and point sources (*** water treatment works and industrial effluent) can lead to negative environmental impacts, including changes to diatom and invertebrate community structure. Current environmental quality standards for phosphorus in the UK have been based on reactive phosphorus, which is poorly defined and comprises an unknown proportion of soluble reactive phosphorus and chemically extractable particulate phosphorus. This research assesses the influencing factors that may control soluble reactive phosphorus concentrations in rivers, including dissolved iron, as well as partitioning processes associated with the presence of total suspended solids, and questions the reliability of the assumptions used when setting environmental quality standards. The extensive phosphorus speciation monitoring carried out across a wide geographic area of England and Wales shows that not all phosphorus as measured by the molybdenum blue method is either soluble or necessarily bioavailable, particularly at concentrations in the range in which the Environmental Quality Standard for 'Good' status (typically less than 100 mu g P L-1) has been set. Phosphorus speciation can change due to physico-chemical processes which vary spatially and/or temporally, including precipitation with iron and partitioning with suspended solids.

关键词： 化学现象   《物理化学》   物理现象   方法探究   物理化学教学   演绎方法   重要基础课   物理学  

摘要： 物理化学是从物理现象和化学现象的联系人手,采用物理的实验方法和数学的演绎方法研究化学现象基本规律的一门科学。该课程是化学、化工、材料等专业学生必修的重要基础课,需要学生具有一定的化学和物理学的基础知识,是一门逻辑性较强的实用课程,一直以来受到广大师生的高度重视。

关键词： 物理化学实验   教学安排   模块化实验  

摘要： 物理化学实验是普通高等院校化学实验课程体系中的一门理论性与实践性均较强的重要课程,物理化学实验安排工作合理与否与实验课教学效果密切相关。本文对物理化学实验教学安排中存在的问题进行了讨论,并提出了应对方法。提出对原有实验教学体系进行重组,对提高普通高等院校学生化学技能是一种非常有益的尝试,符合全面推进素质教育及培养应用型创新人才培养的要求。

关键词： OBE理念   物理化学实验课   课程建设   教学方法  

摘要： OBE(Outcomes-Based Education)理念在高校教育教学中的应用是社会的现实需求。文章分析了OBE理念在物理化学实验课中的应用基础。从人才培养目标、课程体系和评价机制方面深入阐述了以目标为导向的材料类专业物理化学实验课的课程建设。探索并设计了在OBE理念下物理化学实验课的互联网+、动态调整、实时优化教育教学方法,有效保障学生获得学习成果,为国家和行业需要培养应用型人才。

关键词： Phosphoric acid   Phosphogypsum   Scales   Sludge   Natural radionuclides   Heavy metals   Radiological risks  

摘要： The industry devoted to the production of phosphoric acid by using as raw material sedimentary phosphate rock (PR) is considered as a NORM activity (Naturally Occurring Radioactive Materials), due to the high levels of U-series radionuclides contained in this ore, which are 1-2 orders of magnitude higher than those in unperturbed soils. This fact allowed us to develop a deep characterization of the raw materials, wastes, main intermediate materials, and final products obtained at a typical phosphoric acid factory. The elemental composition (major, minor and trace elements), radionuclide concentrations, grain size distribution, mineralogy and micro-structural composition were analyzed. The aim of this characterization was to obtain information for operators and maintenance personnel involved in cleanup and waste management operations. The highest concentrations of some heavy metals and radionuclide activity concentrations were found in the "scales" (or internal incrustations)from the pipes that carry either phosphoric acid (PA) or the phosphogypsum waste (PG). The highest concentrations where found for Ra-226 and K-40,with values up to 9 and 5 Bq g(-1), respectively. In addition, high concentrations of many toxic heavy metals and trace elements, such as Cd, Cr, Ni, Sr, Y, V, Zn, Th, and U, were found in some sludge samples. The shielding effect of the containers/vessels/pipes has an essential role in the measured external dose in the intermediate products. The radiological implications of natural radionuclides with higher activity showed that if the maximum particulate matter concentration established in the Spanish regulation is verified, and taking into account the most conservative scenario, the annual limit of 1 mSv y(-1) is not exceeded. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Gelatin   Pullulan   Potassium sorbate   Mechanical properties   DSC  

摘要： Edible films based on pullulan/gelatin (PUL/GEL) blends (100/0, 75/25, 50/50, 25/75, and 0/100) incorporated with various concentrations (0, 0.5, 1, 2%) of potassium sorbate (KS) were prepared and characterized. The results showed that the mixing of PUL and GEL solutions led to a phase separation. At ratio PUL:GEL = 50:50 the polymers segregated into the biggest microscopic domains. The incorporation of KS resulted in an increase in the size of microparticles. The crystallinity and tensile strength increased as the GEL content in the films increased. As proven by findings of wide-angle X-ray diffraction, the amorphous nature of PUL-rich films was converted to semi-crystalline-like, possibly as a result of reflection of the recrystallized KS. On the other hand, the KS decreased the crystalline character of the GEL-rich films. The incorporation of KS reduced the glass transition temperature, suggesting that the preservative acted as plasticizer for the films. Consequently, the KS reduced mechanical strength and stiffness and improved stretchability of the films. Additionally, the KS increased the pH, UVB-barrier capacity, and moisture absorption properties (at water activities >0.52). After the KS addition, the GEL-containing films showed a much more intensive yellowing compared to the pure PUL films. Furthermore, the increase in GEL concentration favored the recrystallization of KS.

关键词： Shrinkage stress   Physical properties   Volumetric shrinkage   Degree of conversion  

摘要： New photocurable "Phene" like monomers Hexaethylene glycol bis(carbamate-isoproply-alpha-methylstyrene) (HEPhene) and Triethylene glycol bis(carbamate-isoproply-alpha-methylstyrene) (TE-Phene) were synthesized and incorporated into Bis-GMA/TEGDMA with the aim of reducing polymerization shrinkage without detriment to the physical and handling properties of the resin composites. Phene like monomers (HE/TE-Phene) were synthesized through a one-step reaction route, and their structures were confirmed by FT-IR and 1H-NMR spectra. HE/TE-Phene were incorporated into Bis-GMA/TEGDMA (50/50,wt/wt) with a series of mass fraction (from 0 wt.% to 40 wt.%). Experimental resin composites were prepared by mixing 29 wt.% of resin matrix to 71 wt.% of particulate-fillers. Degree of conversion (DC) was determined by FT-IR analysis. The volumetric shrinkage (VS) was calculated as a buoyancy change in distilled water by means of the Archimedes principle. Polymerization shrinkage-stress (SS) was measured using the tensilometer technique. The flexural strength (FS), modulus (FM), and fracture toughness (FT) were measured using a three-point bending setup. Viscosity was analyzed with a rotating disk rheometer. Water sorption and solubility were also measured. ANOVA analysis showed that DC (after 40 s), VS, and SS were in a trend of decreasing with the increasing of HE/TE-Phene concentration. In general, the experimental resin composites had comparable FT, FS and FM (p > 0.05) when the mass fraction of HE/TE-Phene in resin matrix was not more than 30 wt.%. The overall tested properties prove that including HE/TE-Phene up to 30 wt.% into Bis-GMA/TEGDMA resin could be potentially useful in the formulation of lowshrinkage resin composites.

关键词： Okara   Dietary fiber   Cavitation jet   Microstructure  

摘要： The ability of cavitation jet processing to alter the structural and physicochemical properties of dietary fiber extracted from okara was examined. The impact of processing time (0 to 15 min) on the morphology and composition of the dietary fiber was monitored using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Atomic force microscopy (AFM), and Scanning electron microscopy (SEM). The water holding, oil holding, and swelling capacities of the okara dietary fibers were measured, which increased after processing, reaching values of 10.0 +/- 0.2 g/g, 5.04 +/- 0.07 g/g, and 13.9 +/- 0.4 mL/g, respectively after 10 min. Cavitation jet processing had little impact on the total dietary fiber content, but increased soluble dietary fiber content more than 5-fold, which led to a pronounced increase in the shear viscosity. FTIR and XRD indicated that intermolecular hydrogen bonds and crystalline structures within the dietary fibers were disrupted by cavitation jet processing, while AFM and SEM indicated that there were appreciable changes in microstructure.