Spatial dependence of Raman frequencies in ordered and disordered monolayer graphene

A micro-Raman investigation was carried out on several flakes of monolayer (1 L) graphene obtained by the micro-mechanical exfoliation technique and, then, put on a c-Si wafer coated by a SiO₂ thin film. Some of the 1 L zones show a remarkable dispersion of the 2D-overtone wavenumber as a function of the position within the graphene sheet, and, in some case, a significant broadening of the E_2g phonon (G band) is associated to this wavenumber shift of 2D-band. Such effects were studied, in particular, for a 1 L zone characterized by a rather strong lattice disorder, as revealed by the strong D/G band intensity ratio, and for other zones quite ordered, showing a vanishing intensity of the D band. Moreover, by moving along different directions within 1 L graphene sheets, different trends for 2D wavenumber and E_2g phonon bandwidth vs. position were observed. All these reported behaviours are explained in terms of different distributions of intrinsic uniaxial strain occurring within the 1 L graphene sheets.     

Can Dentin Surfaces Be Bonded Safely With Ozone and Boric Acid?

The aim of this study is to evaluate the effect of different cavity disinfectants on shear bond strength. In this study, 60 caries-free human molar teeth were used. Smooth dentin surfaces were revealed by cutting occlusal enamel and a standard smear layer was obtained by using 600-grid sandpaper. Specimens were randomly assigned to four groups according to the disinfectant used: Group 1: Control (no disinfectant); Group 2: Ozone; Group 3: Chlorhexidine, Group 4: Boric acid. Specimens were bonded using S3 Plus Bond and the composite buildups were created by using composite resin according to the manufacturer’s instructions. After specimens were kept for 24 h, at 37 °C in distilled water, the shear bond strength test was measured with a universal test machine. The highest bond strength values were observed in the control group. The bond strength was significantly lower in the chlorhexidine, and boric acid-treated groups than it was in the control group (respectively, p = 0.046 and p = 0.028); however, no significant difference in the bond strength was observed between the ozone group and the control group (p = 0.444). The ozone group was detected as having the best shear bond strength values in groups which were applied to cavity disinfectants.     

Synthesis and characterization of neodymium doped ceria nanocrystalline ceramic structures

In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the hybrid polymers solution of their composite precursor was put forward. Calcined and sintered nanopowders were characterized by FT-IR, XRD, BET, SEM, and AFM techniques. According to the XRD analysis, the obtained powders are single phase and independent of the dopant concentration in the range investigated. The crystallite sizes were calculated using Scherrer equation. Moreover, lattice parameters, dislocation densities and microstrain values were calculated. BET results show that the increase of the neodymium doped content decrease the surface area of the composite powders, confirming the highly ordered micro and mesostructure. SEM and AFM results show that the samples have spherical grains. According to the surface roughness measurements, the increase in the amount of neodymium and the decrease in the amount of cerium decreased the surface roughness.     

二(巯基乙酸)钡的合成及其应用性能研究

以巯基乙酸和氢氧化钡等为原料合成了二 (巯基乙酸 )钡 ,试验选择了其优惠工艺条件。对产品进行了红外光谱分析及其物化常数的检测 ,并研究了它与有机锑复配时在聚氯乙烯 (PVC)塑料中的热稳定性能。     

风景园林科技"十五"计划及2015年发展规划

简要回顾、分析、总结近２０年来中国风景园林科技发展状况，提出行业科技“十五”及２０１５年发展目标。     

固体绝缘材料真空干燥的瞬态湿分迁移

固体绝缘材料是电气行业的主要原材料，真空处理工艺是改善其性能的关键技术之一。本文分析了真空干燥过程中湿分的非稳态迁移机理，为民工产品的真空处理工艺提供了理论依据。     

全自动石油油管（套管）静水压试验装置的改进

介绍了一种适用于石油油管、套管进行静水压试验的全自动试验装置。其适用管径为φ60－φ180mm（上至更大管径），长度8－11m（或8.5－11.5m及其他尺寸）；可试压力为0－100MPA，循环周期不大于150s；工作方式为单机单根或单机双根；密封方式为径向外抱式强制密封。介绍了其总体设计方案、配套情况及主要技术特点。