Influence of polymer on cement hydration in SBR-modified cement pastes

The influence of styrene-butadiene rubber (SBR) latex on cement hydrates Ca(OH)₂, ettringite, C₄AH₁₃ and C-S-H gel and the degree of cement hydration is studied by means of several measure methods. The results of DSC and XRD show that the Ca(OH)₂ content in wet-cured SBR-modified cement pastes increases with polymer-cement ratio (P/C) and reaches a maximum when P/C is 5%, 10% and 10% for the pastes hydrated for 3 d, 7 d and 28 d, respectively. With wet cure, appropriate addition of SBR promotes the hydration of cement, while the effect of SBR on the content of Ca(OH)₂ and the degree of cement hydration is not remarkable in mixed-cured SBR-modified cement pastes. XRD results illustrate that SBR accelerates the reaction of calcium aluminate with gypsum, and thus enhances the formation and stability of the ettringite and inhibits the formation of C₄AH₁₃. The structure of aluminum-oxide and silicon-oxide polyhedron is characterized by ²⁷Al and ²⁹Si solid state NMR spectrum method, which shows that tetrahedron and octahedron are the main forms of aluminum-oxide polyhedrons in SBR-modified cement pastes. There are only [SiO₄]⁴⁻ tetrahedron monomer and dimer in the modified pastes hydrated for 3 d, but there appears three-tetrahedron polymer in the modified pastes hydrated for 28 d. The effect of low SBR dosage on the structure of aluminum-oxide and silicon-oxide polyhedron is slight. However, the combination of Al³⁺ with [SiO₄]⁴⁻ is restrained when P/C is above 15%, and the structure of Al³⁺ is changed obviously. Meantime, the polymerization of the [SiO₄]⁴⁻ tetrahedron in C-S-H gel is controlled.     

硬质合金表面热阴极离子镀TiN涂层抗氧化性研究

利用热阴极离子镀技术在牌号为ZK1的硬质合金表面镀制TiN硬质涂层,并在300℃至700℃空气环境下进行抗氧化实验。运用XRD和XPS对涂层进行微观结构和成分的分析,并用SEM进行涂层断口的观察,最后采用显微硬度计和自动划痕仪分別对涂层的显微硬度和膜基结合力进行了检测。实验结果表明,涂层厚度约为5μm,涂层成分以TiN为主,平均显微硬度达2388HV,结合力最大达85N。随着氧化温度的升高,在涂层表面先后形成了TiNxOy、TiO2,涂层的显微硬度和膜基结合力都呈下降趋势并在550℃处剧烈下降。     

闪锌矿BxAl1-xAs合金的LP-MOCVD生长研究

利用低压金属有机化学气相沉积(LP-MOCVD)生长工艺,采用三乙基硼(TEB)源,在GaAs(001)衬底上生长了B并入比为0.4%～4.4%的一系列BxAl1-xAs合金。实验结果表明,BxAl1-xAs的最优生长温度为580℃;当生长温度为550℃和610℃时,BxAl1-xAs中B并入比都会下降,550℃时B并入比下降更为显著。在580℃最优生长温度下,B并入比随着TEB摩尔流量增加而提高,且B并入比从临界值2.1%增加至最大值4.4%时,DCXRDω-2θ扫描BxAl1-xAs衍射峰的半高宽值从51.8 arcsec升高到204.7 arcsec,原子力显微镜(AFM)测试表面粗糙度从2.469 nm增大到29.086 nm,说明B并入比超过临界值后BxAl1-xAs晶体质量已经逐渐严重恶化。     

制备温度和压力对纳米氧化锆相组成的影响

利用压力[CD*2/3]热液法制备纳米氧化锆粉体,考察不同温度和压力下的制备工艺条件,以及采用XRD分析经过热处理后粉体的相组成和晶粒的长大倾向.结果表明,制备出的氧化锆粉体平均粒径约15 nm,粉体在600℃、800℃、1 000℃热处理1 h后,晶粒随温度长大趋势较小,抗老化能力较好.     

水热温度对玻璃纤维增强HAp-CS涂层的影响

为了制备出结合强度较好的生物涂层,采用水热电泳法在碳/碳复合材料表面成功制备了玻璃微纤维增强的羟基磷灰石——壳聚糖(g(f)/HAp-CS)复合涂层,用x-射线衍射仪、透射电子显微镜、扫描电子显微镜、能谱分析仪、红外傅里叶变换分析仪等测试手段对涂层进行了测试和表征,主要研究了水热沉积温度对复合涂层中HAp晶相和涂层显微结构的影响以及HAp涂层的沉积动力学.结果表明:采用玻璃微纤维增强的HAp-CS涂层,致密性和均匀性有了很大提高,显著减少了复合涂层表面的裂纹;随着水热温度的升高,涂层中HAp的衍射峰逐渐增强,表面形貌得到了有效改善,涂层的致密性和均匀性显著提高;涂层的沉积速率随水热温度的升高而加快,其沉积活化能为14.63kJ/mol.     

纸浆漂白过程流中非过程铁元素的表征

以新制铁和陈化铁模拟纸浆漂白过程流中的非过程铁元素,研究了非过程铁元素存在颗粒的粒径大小和分布、表面形态和物象组成.研究发现,新制铁胶体颗粒以纳米级存在(210～250 nm),并随体系pH值增加而增加,其密度和体积分布呈双峰分布.70 ℃水浴加热1 h后,新制铁胶体颗粒粒径明显增加,pH 13时达到1 620 nm.陈化铁颗粒粒径较大,高达10 μm.IR、XRD、SEM-EDS分析表明,以新制铁形式的非过程铁胶体颗粒没有结晶成分存在,其宏观分子式为Fe29.1O17.2(OH)52.9;以陈化铁形式存在的非过程铁胶体颗粒主要以Fe2O3晶体存在,其宏观分子式为Fe34.7O38.8(OH)26.5.     

Microstructure of Pd/CeO2 catalyst: Effect of high temperature reduction in hydrogen

The effect of high temperature reduction (HTR) in hydrogen (up to 1180 K) on the microstructure of 9 wt.-% Pd/CeO₂ catalyst was studied by HRTEM and XRD methods. Reduction of the catalyst at or above 973 K caused severe recrystallization of CeO₂ and Pd with simultaneous strong interaction between the two components appearing as three phenomena: epitaxial growth of small Pd particles on CeO₂ (most frequently with [111]Pd[111]CeO₂); decoration of large Pd particles with ordered CeO₂ overlayer and expansion of the lattice parameter of Pd (by 2.1%). The origin of the Pd lattice expansion is discussed and diffusion of Ce species into the Pd lattice seems to be the most probable one. HTR caused also phase transformations in the ceria support. At 973 K and 1100 K, whole CeO₂ was transformed into oxygen deficient CeO_x phase exhibiting the same or similar structure but with expanded lattice parameter (by 2.8%). At 1180 K most ceria was transformed into hexagonal A-Ce₂₃. The CeO_x phase appeared to be stable in hydrogen and in vacuum at room temperature, but upon exposure to air at room temperature it rapidly reoxidised to CeO₂. Ce₂O₃ also reoxidised to CeO₂ but much slower. Another consequence of HTR at or above 773 K was formation of pits in CeO₂ crystallites, mainly on (112)-type crystal faces. The pits (1–10 nm) exhibited well defined walls parallel to CeO₂ lattice fringes and they could possibly constitute nucleation sites for strongly bonded, epitaxial oriented Pd particles.     

邯郸膨润土的特征研究

采用化学成分分析、X-射线衍射分析、红外光谱、差热分析和扫描电镜等分析方法,研究了邯郸膨润土的特征。分析结果显示,邯郸膨润土是一典型的钙基膨润土,蒙脱石含量50%左右。进行人工钠化改性所获得的膨润土具有天然钠基膨润土同样的特性。     

Teaching and Learning Crystal structures through Virtual Reality based systems

Teaching and learning through Virtual Reality(VR) is an emerging technology in the last few years. In this article, the development and use of a VR based teaching–learning system for crystal structures are discussed. The VR system is designed as a lab environment where a user can do experiments related to crystal structures. The VR system is designed in Unity,¹ and Oculus Rift S² is used as a VR headset. Currently, the system consists of three phases; in the first phase user can visualize the crystal lattice structures, wherein the second one a user can visualize the light interaction with the crystal lattice structure using a virtual torch ray. The third phase is the X-ray Diffraction (XRD) experiment. In this phase, users can perform the XRD experiment in the lab environment by taking a random crystal from a crystal dispenser machine and placing it in the X-ray machine which identifies the chosen crystalline material and analyses the unit cell. The incident ray colour changes when there is a peak found in the crystal for a better understanding of the user. There is also an interactive display where users can increase/decrease the angles of the radiation and also lock and unlock the experiment to view the diffraction plot for the crystal structure. In many cases, it was found that XRD and the crystal structure is available in the course syllabus but there are no experiments to enhance their learning. Therefore an experiment with 39 participants was performed where the maximum participants are new to crystallography. The study was conducted in two phases; in the first phase, participants are asked to watch video tutorials of the topic followed by questionnaires; in the second phase participants are asked to do the VR based experiment and followed by questionnaires related to overall study and experiment. From the analysis of the study we found that everyone found VR based teaching methods are better than traditional book/video studies. Study results give an average score of 56.74% in comparison to VR based learning approach with an average score of 93.81%. Participants who took part in the experiment found the experience interactive and motivating and found it helpful to learn elusive concepts, which can be learned when simulated. For example, one participant wrote: “The VR experience was surreal and was easy to control. Lucid user experience. Got a view of XRD like never seen before”.     

超细矿粉对混凝土界面区硫酸盐腐蚀的影响

为了研究骨料与水泥石界面区(ITZ)的组成及结构对混凝土抗硫酸盐腐蚀性能的影响,利用紫外分光光度计绘制了硫酸钠溶液浸泡混凝土试样的SO2-4浸入浓度/深度曲线,并辅以扫描电镜(SEM)和电子探针能谱(EDS)等对ITZ进行观测;同时利用XRD定量分析研究了混凝土本体相和界面相的水化产物富集的差异.结果表明:Ca(OH)2、钙矾石(AFt)等晶体富集于硫酸钠溶液浸泡后试样的ITZ,引起AFt二次结晶型的硫酸盐腐蚀破坏.在适量石膏的激发下,掺入超细矿粉(GGBS)可阻止AFt转变成单硫型水化硫铝酸钙(AFm),减少AFt二次结晶的生成,明显提高抗硫酸盐侵蚀能力,试样的同深度硫酸根浓度最低,抗硫酸盐侵蚀性能最好.