氧化铜对碳酸钙热分解动力学过程的影响

利用热重分析和差式扫描量热仪测定了CaCO3试样和在CaCO3试样中加入质量分数(下同)为1．0％CuO试样的热解动力学行为。应用Coats and Redfern方程得出2种试样的活化能。X射线衍射扫描电镜、能谱分析等方法分析了掺入CuO后CaCO3在600～1100℃的7个温度保温0．5h所得分解产物的组成及微观形貌。结果表明：CuO的加入能降低CaCO3的分解温度,并降低其活化能值,当CuO掺入量为1％时,CaCO3的起始分解温度和表观活化能比参比样分别下降了12℃和10kJ／mol。研究还表明：CuO与CaO反应形成了CaCu2O3和Ca2CuO3 2个中间化合物,该体系在1000～1050℃产生液相。     

掺杂对含硫铝酸钙矿物硅酸盐水泥烧成的影响

研究了CuO,P2O5对含硫铝酸钙矿物硅酸盐水泥熟料的易烧性及矿物形成的影响.借助化学分析测定了水泥熟料中游离氧化钙(f-CaO)及C4A3S矿物的含量,用X射线衍射分析了熟料矿物组成,并采用透射电镜(TEM)研究了CuO对C3S晶体结构的影响.结果表明:生料中掺入少量的CuO和P2O5能改善水泥生料的易烧性,促进f-CaO的吸收;CuO能促进C3S矿物产生调制结构.当CuO掺入量超过0.5%时,不利于C4A3S矿物形成;P2O5的掺入则有利于C4A3S的形成.     

掺杂CuO对C4A3(S)矿物形成的影响

研究了掺杂CuO对C4A3(S)矿物形成的影响.结果表明:在1300℃保温1 h,3 h的煅烧条件下,掺杂一定量的CuO,能使C4A3S的形成量增加,但当CuO掺加质量分数超过0.3%时,C4A3(S)含量会降低,保温时间延长对C4A3(S)的形成不利.IR分析结果表明:CuO使C4A3(S)的晶格发生了畸变.在石膏晶型转变前,掺杂适量的CuO可以促进C4A3(S)的形成,同时可以使C4A3(S)的形成温度降低,而且CuO的掺入会使石膏的分解温度降低,过量还会促进石膏的分解.     

不同SO3掺量下C3S矿物的形成

通过化学分析,应用等温煅烧的方法对不同SO3掺量为(0%,1%,2%,3%,3.5%,5%)的C3S矿物形成过程从动力学角度进行了系统探讨.通过拟合得到了C3S矿物形成的动力学模型,并根据该动力学模型对不同SO3掺量下C3S矿物形成的速率常数进行了计算.结果表明:在1450℃,不同SO3掺量下,C3S矿物形成由三维球形对称扩散动力学模型f(a)=(1-3√(x+y)2控制;随着SO3加入量的增加,C3S矿物形成的速率常数呈非线性变化;从游离CaO的含量和反应速率常数的角度来说,SO3的加入有利于C3S的形成.并且SO3加入量的增加有利于C3S的多相体M1的稳定.     

MgO对硫铁铝酸钡钙矿物的合成及性能的影响

用X射线衍射、扫描电子显微镜和综合热分析等研究了MgO对硫铁铝酸钡钙矿物1.75CaO·1.25BaO·2Al2O3·Fe2O3·CaSO4(C2.75B1.25A2F S)的合成及性能的影响,并测试了水化样品的抗压强度.结果表明:适量的MgO可降低CaCO3的分解温度,当MgO掺入质量分数为1%时,C2.75B1.25A2FS矿物形成的温度最低,矿物熟料中f-CaO的质量分数最低,仅为0.22%.水化物,28 d时的抗压强度达到最高,为104.2MPa.当MgO的掺量在0.3%～1%时,熟料晶体结晶状况相对较好,晶粒细小,晶界明显,轮廓清晰.     

掺杂CuO对C_4A_3矿物形成的影响

研究了掺杂CuO对C4A3矿物形成的影响。结果表明:在1300℃保温1h,3h的煅烧条件下,掺杂一定量的CuO,能使C4A3的形成量增加,但当CuO掺加质量分数超过0.3%时,C4A3含量会降低,保温时间延长对C4A3的形成不利。IR分析结果表明:CuO使C4A3的晶格发生了畸变。在石膏晶型转变前,掺杂适量的CuO可以促进C4A3的形成,同时可以使C4A3的形成温度降低,而且CuO的掺入会使石膏的分解温度降低,过量还会促进石膏的分解。     

CuO对C3S亚晶尺寸及晶型的影响

以Ca(OH)2、SiO2化学纯为原料,分别掺入不同质量分数的CuO制备不同晶型组成的C3S,运用相图分析、XRD、IR测试方法及MDI jade5.0软件对C3S亚晶生长、晶型转变过程进行研究。结果表明:由CaO-CuO、CuO-SiO2二元相图分析,CuO促进CaO-SiO2固相反应效应明显;C3S经CuO掺杂后,其晶型转变和亚晶成长均受到影响。当CuO掺量小于1.5%时,C3S亚晶尺寸减小趋势明显,大于1.5%时,减小趋势减缓。且C3S晶型随掺量变化先由T型向R型转换,但掺量大于2.0%时,R型又逐步转换为MⅠ型。同时IR分析表明,818 cm-1、999 cm-1谱带处的先减弱后增强及497 cm-1伸缩振动平移先增大后减小,均说明C3S晶体对称性先增大后减小的变化趋势。     

氧化铜对硅酸三钙和硫铝酸钙矿物形成及共存的影响

研究了CuO对含硫铝酸钙矿物硅酸盐水泥中硅酸三钙（C3S）和硫铝酸钙（C4A3S）矿物形成及共存的影响。借助化学分析和X射线衍射内标法分别测定了水泥熟料中C3S及C4A3S矿物的含量。用X射线衍射仪分析了熟料矿物组成,并采用差热分析和透射电镜分别研究了CuO对熟料形成特性和C3S晶体结构的影响。研究结果表明：生料中掺入生料质量0．1％的CuO,能降低水泥熟料的烧成温度。促进C3S和C4A3S两种矿物相互共存．提高熟料的强度。过量的CuO亦会降低C4A3S矿物的分解温度。     

SO3掺杂对高镁熟料Alite晶型和水化性能的影响

文章探讨了SO3对高镁水泥熟料中C3S晶型的调控以及对该熟料水化性能的影响。通过X射线衍射对熟料矿物含量和C3S的晶型进行表征并测试了熟料的净浆强度及结合水。研究表明:当SO3的掺量为1%、2%时不会对C3S的形成带来阻碍,样品中f-CaO含量均小于1%。在该熟料中,阿利特以M3型为主,多为细小的晶体,SO3的掺入能够稳定M1型的阿利特。1%~2%SO3的掺入能促进熟料的水化,提高熟料的中后期强度,当掺量为2%时3、28d净浆抗压强度分别提高8%和5%。水化程度随着SO3掺量的增加而增加,水化产物中含有大量的钙钒石。     

二氧化锰对含硫铝酸钙矿物硅酸盐水泥熟料相平衡共存的影响

借助X射线衍射定量分析及化学分析法,系统研究了MnO2对含硫铝酸钙矿物(3CaO·3Al2O3·CaSO4,C4A3)硅酸盐水泥熟料中阿利特和硫铝酸钙矿物形成及共存温度范围的影响。结果表明:在生料中掺入0.1%(质量分数)MnO2,可以加速CaCO3的分解,提高CaCO3的分解速率,促进熟料煅烧过程中固相反应的提前及水泥熟料烧成过程中f-CaO的吸收,同时,增加了液相量,加速熟料的烧成,使C4A3S矿物分解温度提高了100℃,使体系中阿利特和硫铝酸钙两者的共存温度范围扩大了57℃。     

Effect of dual liquid phase sintering aids on the densification and microstructure of low temperature sintered alumina ceramics

Alumina ceramics was prepared by pressureless sintering technology in which a CuO–TiO₂–Bi₂O₃ mixture (0–4.0 wt% Bi₂O₃ and 4.0 wt% CuO and TiO₂) was added as dual liquid phase sintering aids. The phase compositions, microstructural feature, and sintering behaviour of the alumina ceramics were analyzed. The results showed that adding 2.5 wt% Bi₂O₃ to alumina ceramics can increase the contribution rate of initial stage of sintering to the sintering process. The relative density of the sample reached 97.63% after sintering at 1200 °C for 90 min. Measurements from differential scanning calorimetry, with the addition of CuO–TiO₂–Bi₂O_3, demonstrated the formation of two liquid phase points, 827.4 and 936.8 °C. Notably, the solid solution temperature of TiO₂ and Al₂O₃ ceramics diminished thanks to the dual liquid phase sintering aids, and at the same time the activation energy required also dropped from 368.96 to 137.31 kJ/mol. Research indicates that the combined action of dual liquid phase sintering and solid-state reaction sintering has promoted the densification of alumina ceramics during the sintering process while at the same time inhibiting the growth of abnormal grains so that a homogeneous microstructure can be formed.     

Phase transitions and polymorphism of cocoa butter

The polymorphism and phase transitions of cocoa butter (CB) have been reexamined separately by differential scanning calorimetry (DSC) and X-ray diffraction as a function of temperature (XRDT) at scanning rates between 0.1 to 5°C/min and 0.1 to 2°C/min, respectively. A new instrument, which allowed simultaneous DSC and XRDT recordings from the same sample by taking advantage of the high-energy flux of a synchrotron, was employed for characterization of the intermediate phase transitions. These techniques allowed us to confirm the existence of the six polymorphic forms of CB (called I to VI) by in situ characterization of their formation in the DSC + XRDT sample holder. A detailed study of Form I structure led us to propose a liquid-crystal organization in which some of the chains displayed sharp long-spacing lines (d₀₀₁=52.6±0.5 Å) and a β′ organization (4.19 and 3.77 Å), while the others remained unordered with broad scattering (maxima at about 112 and 36.5 Å). The organization of this liquid crystalline phase is compared to that of fat and oil liquids. This liquid crystalline phase progressively transformed on heating into a more stable phase (Form II, α type, d₀₀₁=48.5±0.5 Å and short-spacing at 4.22 Å). Form III was only observed in a sharp temperature domain through its specific short-spacings. The existence of the six species has been essentially related to the crystallization of monounsaturated triacylglycerols (TAG), while trisaturated species were found partly solid-soluble in these six polymorphic forms. An insoluble fraction crystallized independently of the polymorphism of the monounsaturated TAG in a separate phase with long-spacings that were either of the α (49.6±0.5 Å) or β (44.2±0.5 Å) form. In mixture with Form V, this fraction melts and solubilizes in the liquid phase at 37.5°C. Isolation of these high-melting crystals shows a melting point of about 50°C. High-performance liquid chromatography analysis of this fraction confirmed an increase from 3.0 to 11.3% of saturated TAG and their association with part of the 1,3-stearoyl-2-oleoylglycerol preferentially to 1-palmitoyl-2-oleoyl-3-stearoylglycerol and (1,3-palmitoyl-2-oleoylglycerol).     

氧化铁对硫铝酸钙矿物形成的影响

借助化学分析方法、X射线衍射、差示扫描量热法等测试手段研究了Fe2O3对无水硫铝酸钙矿物(C4A3S)形成过程的影响.研究表明:掺杂Fe2O3可促进熟料中游离氧化钙(f-CaO)的吸收,增加液相量,改善C4A3-S矿物生料的易烧性;不掺杂Fe2O3的矿物生料,C4A3-S单矿物在850℃以下几乎不生成,在1 000℃开始大量生成,在1 300℃达到最高值;掺杂1?2O3的试样中C4A3S含量与不掺杂试样在同温度下达到最大值,但绝对含量有一定幅度的下降;掺杂3%及5?2O3的试样中C4A3S含量在1 350℃达到最大值,达到最大值的时间比原来延迟0.5h,并且绝对含量有较大幅度的下降;掺杂Fe2O3的试样在1 200℃至1400℃时,Fe3 和C4A3-S中的Al3 发生置换,使Fe3 固熔到C4A3-S中形成固熔体C4(A0.95F0.05)6O12(SO4).     

液相烧结氧化铝陶瓷及其烧结动力学分析

研究了CuO TiO2复相添加剂对Al2O3陶瓷烧结性能、显微结构的影响以及添加剂形成液相时Al2O3陶瓷的烧结动力学.结果显示:添加剂的加入明显地促进了Al2O3陶瓷的烧结致密度.添加剂含量对致密有明显影响,含量越高,烧结速率越快.当添加剂(CuO TiO2)为2%(质量分数),CuO/TiO2质量比为1/2时,Al2O3样品致密度最高.添加剂的存在使Al2O3晶粒发生较快生长,晶粒形貌为等轴状.通过等温烧结动力学,确定掺杂Al2O3陶瓷烧结激活能为25.2kJ/mol,表明可能是氧离子和铝离子在液相中的扩散作用控制了烧结过程.     

Influence of roasting temperature on reactions between ferruginous blende and copper(II) oxide

Thermal treatment in an oxidizing atmosphere of a mixture of raw blende (ZnS) and copper(II) oxide enhanced the formation of a mixed ferrite phase at temperature about 600°C. The composition established at 900°C was approximately (0.8 ZnO · 0.2 CuO)Fe₂O₃. For the mixture ZnS–CuO, with 5 to 15% CuO by weight, less than 15% copper was involved in the formation of the spinel phase. The increasing copper content in the mixture, roasted above 1000°C, favoured solubilization of iron, even in a weakly acid medium.     

Low-Temperature Sintering and Piezoelectric Properties of CuO-Added 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 Ceramics

The sintering temperature of 0.95(Na_0.5K_0.5)NbO₃–0.05BaTiO₃ (NKN–BT) ceramics needs to be decreased below 1000°C to prevent Na₂O evaporation, which can cause difficulties in poling and may eventually degrade their piezoelectric properties. NKN–BT ceramics containing CuO were well sintered at 950°C with grain growth. Poling was easy for all specimens. Densification and grain growth were explained by the formation of a liquid phase. The addition of CuO improved the piezoelectric properties by increasing the grain size and density. High piezoelectric properties of d ₃₃=230 pC/N, k _p=37%, and ɛ₃^T/ɛ₀=1150 were obtained from the specimen containing 1.0 mol% of CuO synthesized by the conventional solid-state method.     

Analysis of reactions during sintering of CuO-doped 3Y-TZP nano-powder composites

3Y-TZP (yttria-doped tetragonal zirconia) and CuO nano powders were prepared by co-precipitation and copper oxalate complexation–precipitation techniques, respectively. During sintering of powder compacts (8 mol% CuO-doped 3Y-TZP) of this two-phase system several solid-state reactions clearly influence densification behaviour. These reactions were analysed by several techniques like XPS, DSC/TGA and high-temperature XRD. A strong dissolution of CuO in the 3Y-TZP matrix occurs below 600 °C, resulting in significant enrichment of CuO in a 3Y-TZP grain-boundary layer with a thickness of several nanometres. This “transient” liquid phase strongly enhances densification. Around 860 °C a solid-state reaction between CuO and yttria as segregated to the 3Y-TZP grain boundaries occurs, forming Y₂Cu₂O₅. This solid-state reaction induces the formation of the thermodynamic stable monoclinic zirconia phase. The formation of this solid phase also retards densification. Using this knowledge of microstructural development during sintering it was possible to obtain a dense nano–nano composite with a grain size of only 120 nm after sintering at 960 °C.     

Effects of CuO Doping on the Microstructural and Dielectric Properties of Ba0.6Sr0.4TiO3 Ceramics

This study investigates the effect of CuO on the sintering behavior, dielectric properties, and microstructures of Ba_0.6Sr_0.4TiO₃ (BST) ceramics. The ceramics were sintered in air at temperatures ranging from 1000° to 1230°C. It is found that a small amount of added CuO (0.6 mol%) can significantly increase the density and improve the dielectric properties of BST ceramics. Doped BST ceramics can be sintered to a density >95% of the theoretical density at 1150°C. scanning electron microscopic observations show that the BST grain sizes increase with increasing amounts of CuO. No secondary phases in the BST ceramics are observed using X-ray diffraction pattern for CuO additions up to 0.9 mol%. However, compositional analysis using transmission electron microscopy-EDX for the BST ceramics with 0.9 mol% CuO sintered at 1150°C showed that a small level of secondary phase formation is present. On the other hand, large dislocations are observed for BST with 0.6 mol% CuO addition as a result of lattice distortion, which creates the vacancy condensation because of the atomic mismatch in the solid solutions. Optimal CuO doping concentrations can reduce the loss tangents of BST that can also ensure a high dielectric constant. When the doping concentration of CuO is 0.6 mol% and the ceramic is sintered at 1150°C, the BST ceramic has the following properties at 1 MHz: dielectric constant=4094, tan δ=0.55%.