水合稀土三氯醋酸盐的合成及脱水热焓的测定

本文合成了稀土三氯醋酸盐,用化学分析、热重法和五氧化二磷真空干燥脱水法对其组成进行了测定。除三水合三氯醋酸镧外,其它皆为未见报道的新水合物Ln(CCl_3COO)_3·XH_2O(Ln=Eu,x=2.5; Ln=Ce、Nd、Sm、Gd,x=2; Ln=Pr,x=1.5)。用X射线粉末衍射法测定了化合物的衍射数据。用TG、DTG和DTA热分析研究了水合盐的脱水过程,并用DSC法测定了水合盐在各脱水阶段的脱水热焓值.     

六水合硝酸镧和六水合硝酸铈的热分解

本文采用TG、DTA和DSC法研究了La(NO_3)_3·6H_2O和Ce(NO_3)_3·6H_2O的热分解,并通过IR和X—射线法对反应物、中间产物和最后产物进行了鉴别,发现六水合物均经多个步骤脱水生成无水盐。生成的无水硝酸镧又经一系列中间产物的分解过程最后变成La_2O_3;而生成的无水Ce(NO_3)_3则直接分解成最终产物CeO_2。     

水合稀土二氯醋酸盐的合成及热分解研究

合成了La,Ce,Nd,Sm,Eu,Gd二氯醋酸盐,经化学分析,热重法和五氧化二磷真空千燥脱水法确定组成为Ln(CHCl2COO)3.nH2O(n=2,Ln=La,Ce,Nd;n=1.5,Ln=Sm;n=1.25,Ln=Eu;n=1,Ln=Gd),它们均属新水合物.用DTA-TG-DTG并用技术并辅以化学分析和红外光谱技术研究了其热分解机理,实验证明,由室温至600℃范围内,它们均发生三步主要反应:水合盐脱水变为无水盐;无水盐分解为中间产物,Ln2(OH)Cl5.3H2O[Eu盐分解为Eu2(OH)Cl5.2H2O];中间产物进一步分解为LnOCl[Ce盐为CeO2].并观察到无水盐和氯氧化物形成温度皆与原子序数呈现镧系"双一双效应".     

BaTiO3基PTCR陶瓷材料的Sol-Gel制备方法的改进

正电阻-温度系数;溶胶-凝胶法;纳米粉体;BaTiO3基PTCR陶瓷材料的Sol-Gel制备方法的改进     

一个半水合和五水合醋酸镧的脱水过程及脱水焓测定

醋酸镧已报道三种水合物:LaAc₃·1.5H₂O(Ⅰ)^[1,2]、LaAc₃·5H₂O(Ⅱ)^[3]和LaAc₃·H₂O(Ⅲ)^[4],迄今尚未见(Ⅰ)和(Ⅱ)的脱水焓数据发表,我们继(Ⅲ)的研究工作后,采用新的合成方法制得了(Ⅰ)和(Ⅱ),并采用DTA-TG-DTG联用技术和DSC技术分别对这两种水合物进行了脱水过程及脱水焓的测定。测得(Ⅰ)和(Ⅱ)的脱水过程分别为:     

水合稀土一氯醋酸盐的合成及其脱水热的测定

本文合成了La-Ga七种一氯醋酸盐的水合物,经元素分析、热重法和P₂O₅真空脱水法确定其组成为Ln(CH₂ClCOO)₃·xH₂O(x=1.5,Ln=La,Ce,Pr,Sm,Eu;x=2,Ln=Nd,Gd)。用X-射线衍射测得其粉末衍射数据;用DTA-TG-DTG联用技术研究了水合盐的脱水过程;用DSC法测得各盐的脱水热值。     

PTCR纳米陶瓷粉及其烧结体的制备

The PTCR(positive temperature coefficient of resistance) nanosized ceramic powder was prepared by Sol-Gel process and characterized by XRD, DSC, SEM and BET techniques. The results showed that the nanopowder has an average crystallite size of 35nm with sphere-shaped, whose specific surface area is 27.80m²·g^-1 and the crystal structure is abnormal cubical perovskite phase at room temperature. In addition, the nanopowder was pressed into pellets and then sintered according to improved technique which was built based on the data of thermal analysis of the PTCR green-compact to yield PTCR ceramic materials with peculiar microstructure and higher properties, which has a resistivity at room temperature of ～20Ω·cm, a temperature coefficient of resistivity of ～19%·℃^-1, a withstand voltage intensity of >160V·mm^-1 and a resistivity jump of >10⁵.     

Y掺杂Ba0.90Sr0.08Ca0.02TiO3固溶体纳米晶粒尺寸 对其晶体结构的影响

The title nanocrystalline powders were prepared by sol-gel method, the influences of grain size on crystal structure were investigated by XRD and DSC techniques.The experiment results show that the tetragonal ferroelectric phase content of the powders and the Curie temperature Tc are increased with the increase of grain size.When the grain size is less than 34.7nm, crystal structure of the particle changes into cubic paraelectric phase and the transition of ferro-paraelectric phase disappears as well.     

水合氯代醋酸镧和水合氯代醋酸钕的脱水焓测定

镧、钕二元素的水合氯代醋酸盐的脱水过程及其焓变值至今尚未见工作报道。我们合成了上述六种水合氯代醋酸盐,经化学分析及热重法对其成分及水合分子数进行了测定,确定其组成为:La(CH_2ClCOO)_3·1.5H_2O,La(CHCl_2COO)_3·2H_2O,La(CCl_3COO)_3·3H_2O,Nd(CH_2ClCOO)_3·2H_2O,Nd(CHCl_2COO)_3·2H_2O和Nd(CCl_3COO)_3·2H_2O。用DTA—TG—DTG联用技术研究了脱水过程,并采用DSC法     

差示扫描量热法测定热效应

本文采用差示扫描量热法(DSC)除测得了碳酸氢铵分解热为41.52±0.46KCal·mole~(-1)和一水合磷酸二氢钙脱水热为14.69±0.26KCal·mole~(-1)外,还测得了P—(4—正戊基—1—环已基)—苯甲酸—P′—氰基—苯酯液晶由晶体向向列相转变的热焓、熔融熵及由向列相转变为各向同性液体的转变热焓、清亮熵,它们的值分剐为21.28KJ·mole~(-1),55.69J·mole~(-1)。K~(-1),1.06KJ·mole~(-1)和2.13J·mole·K~(-1)。由该法测得上述所有热效应的值,其精密度和准确度均在2%以内。