An historical collection of more than one hundred samples of minerals and ore, used in the second half of the XVIII century was found and acquired during Munich Mineralientage 2014. The samples contained in numbered g...An historical collection of more than one hundred samples of minerals and ore, used in the second half of the XVIII century was found and acquired during Munich Mineralientage 2014. The samples contained in numbered glass vials but lacking description, were prepared for teaching purpose about determinative mineralogy and ore recognition. All samples were analysed and identified. The identification effort drove the authors along a historical excursus about the didactics of mineralogy and the dry method analysis, nowadays neglected.展开更多
Lattice parameters of lead titanate were precisely re-determined in thetemperature range of-150-950 deg C by high precision XRPD measurements. It was clarified that therewas no any evidence for a new phase transition ...Lattice parameters of lead titanate were precisely re-determined in thetemperature range of-150-950 deg C by high precision XRPD measurements. It was clarified that therewas no any evidence for a new phase transition at low tempera-lures. Tetragonal distortion straindecreases with temperature increasing. A novel thermal expansion was observed, positive thermalexpansion from -150 deg C to room temperature (RT) and above 490 deg C, and the negative thermalexpansion in the temperature range of RT-490 deg C. A big jump of thermal expansion coefficient isattributed to the tetragonal-cubic phase transition. A rationalization for the negative thermalexpansion of PbTiO_3 is due to the decrease of anion-anion repulsion as polyhedra become moreregular at heating. The mechanisms of positive and negative thermal expansions were elucidated asthe same nature in the homogenous tetragonal phase at present case.展开更多
The polymorphism characteristics of p-tert-octyl phenol was studied.It was found that after thermal treatment of differential scanning calorimetry(DSC), the melting point of p-tert-octyl phenol sample was about 75.0℃...The polymorphism characteristics of p-tert-octyl phenol was studied.It was found that after thermal treatment of differential scanning calorimetry(DSC), the melting point of p-tert-octyl phenol sample was about 75.0℃,lower than that of the untreated original sample which was 85.4℃.The fusion enthalpy of p-tert-octyl phenol decreased with increasing cooling rate of the thermal treatment.The samples before and after the thermal treatment of DSC were analyzed with DSC, FTIR spectroscopy,and powder X-ray diffraction.The results showed that through the thermal treatment, p-tert-octyl phenol generated a new crystalline form with a lower melting point and lower fusion enthalpy.The solid stability of the polymorphs was further studied.It was found that the two polymorphs belonged to monotropy.The α form with a higher melting point was stable at temperatures below its melting point.The β form with a lower melting point was metastable, which could convert into the α form at a low temperature.展开更多
X-射线粉末衍射仪(X-ray power diffractometer,XRPD)是一种非常重要的材料分析测试仪,它在许多学科和领域都有着广泛的的应用。目前在高校中,X-射线粉末衍射仪已经成为样品表征的必备仪器,其应用于科学研究的同时并逐步应用在实验教学...X-射线粉末衍射仪(X-ray power diffractometer,XRPD)是一种非常重要的材料分析测试仪,它在许多学科和领域都有着广泛的的应用。目前在高校中,X-射线粉末衍射仪已经成为样品表征的必备仪器,其应用于科学研究的同时并逐步应用在实验教学、课程改革和人才培养。该仪器在测试过程中对各种参数的设置对测试结果有很大的影响,本文以Al_2O_3粉末作为研究对象初步探究X-射线粉末衍射仪各种参数设置如电压、电流、扫描速度及扫描步长对其测试结果的影响并对各种参数进行优化。展开更多
文摘An historical collection of more than one hundred samples of minerals and ore, used in the second half of the XVIII century was found and acquired during Munich Mineralientage 2014. The samples contained in numbered glass vials but lacking description, were prepared for teaching purpose about determinative mineralogy and ore recognition. All samples were analysed and identified. The identification effort drove the authors along a historical excursus about the didactics of mineralogy and the dry method analysis, nowadays neglected.
基金This work is financially supported by Natural Science Foundation of Beijing(No.2032010)National Natural Science Foundation of China(No.20171006)Funds of Ministry of Education of China for Training Ph.D.Candidates (No.2001008005)
文摘Lattice parameters of lead titanate were precisely re-determined in thetemperature range of-150-950 deg C by high precision XRPD measurements. It was clarified that therewas no any evidence for a new phase transition at low tempera-lures. Tetragonal distortion straindecreases with temperature increasing. A novel thermal expansion was observed, positive thermalexpansion from -150 deg C to room temperature (RT) and above 490 deg C, and the negative thermalexpansion in the temperature range of RT-490 deg C. A big jump of thermal expansion coefficient isattributed to the tetragonal-cubic phase transition. A rationalization for the negative thermalexpansion of PbTiO_3 is due to the decrease of anion-anion repulsion as polyhedra become moreregular at heating. The mechanisms of positive and negative thermal expansions were elucidated asthe same nature in the homogenous tetragonal phase at present case.
文摘The polymorphism characteristics of p-tert-octyl phenol was studied.It was found that after thermal treatment of differential scanning calorimetry(DSC), the melting point of p-tert-octyl phenol sample was about 75.0℃,lower than that of the untreated original sample which was 85.4℃.The fusion enthalpy of p-tert-octyl phenol decreased with increasing cooling rate of the thermal treatment.The samples before and after the thermal treatment of DSC were analyzed with DSC, FTIR spectroscopy,and powder X-ray diffraction.The results showed that through the thermal treatment, p-tert-octyl phenol generated a new crystalline form with a lower melting point and lower fusion enthalpy.The solid stability of the polymorphs was further studied.It was found that the two polymorphs belonged to monotropy.The α form with a higher melting point was stable at temperatures below its melting point.The β form with a lower melting point was metastable, which could convert into the α form at a low temperature.
文摘X-射线粉末衍射仪(X-ray power diffractometer,XRPD)是一种非常重要的材料分析测试仪,它在许多学科和领域都有着广泛的的应用。目前在高校中,X-射线粉末衍射仪已经成为样品表征的必备仪器,其应用于科学研究的同时并逐步应用在实验教学、课程改革和人才培养。该仪器在测试过程中对各种参数的设置对测试结果有很大的影响,本文以Al_2O_3粉末作为研究对象初步探究X-射线粉末衍射仪各种参数设置如电压、电流、扫描速度及扫描步长对其测试结果的影响并对各种参数进行优化。
