Modulation on the electrical and optical properties of Na and Rh co-doped Ruddlesden-Popper layered Ca3Ti2O7

Layered perovskite Ca_2.91Na_0.09Ti_2-xRh_xO₇ (x?=?0.00, 0.02, 0.04, 0.06) were synthesized by a conventional solid-state reaction. Room temperature ferroelectricity has been confirmed. The remanent polarization increases with an increase of Rh content, which is due to a larger oxygen octahedral distortion by Rh doping. The coercive field increases with Rh doping as the pinning effect of oxygen vacancies reduce the mobility of domain wall. Remanent polarization and coercive field are caused by different mechanisms, so it is possible to modulate them independently to meet the requirement of application in ferroelectric field. The concentration of oxygen vacancy increased with Rh doping, leading to the significant increase of leakage current density. The bandgap of samples doped with Rh drastically decrease and the visible light response of the sample was improved by Rh doping due to the formation of impurity energy levels within the band gap.

     

AN EXPERIMENTAL-NUMERICAL METHOD FOR MEASURING CRACK PROPAGATING VELOCITIES UNDER STRESS WAVE LOADING

An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application.     

国内聚乙烯产品结构变化对α-烯烃发展的影响

论述了线型聚乙烯(HDPE/LLDPE)产品与α–烯烃的关系,分析了国内线型聚乙烯的供需增长、产品结构变化及α–烯烃在聚乙烯生产中的主要应用,提出随着国家经济"双循环"时代来临,聚乙烯产品结构的调整必将驱动对α–烯烃共聚单体(尤其是1–己烯和1–辛烯)的需求,对于促进高碳α–烯烃的国产化及产业发展有显著推动作用.     

Synergistic inhibition between o-phenanthroline and chloride ion for steel corrosion in sulphuric acid

The corrosion inhibition of cold rolled steel in 0.5 M sulphuric acid in the presence of o-phenanthroline and sodium chloride (NaCl) has been investigated by using weight loss and electrochemical techniques. The experimental data suggest that the inhibition efficiency increases with increasing NaCl concentration in the presence of 0.0002 M o-phenanthroline, but decreases with increasing temperature. A synergistic effect is observed when o-phenanthroline and chloride ions are used together to prevent cold rolled steel corrosion in 0.5 M sulphuric acid. The polarization curves showed that the complex of o-phenanthroline and NaCl acts as a mixed type inhibitor. The experimental results suggested that the presence of chloride ions in the solution stabilized the adsorption of o-phenanthroline molecules on the metal surface and improved the inhibition efficiency of o-phenanthroline. The adsorption of the complex accords with the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy have been calculated by employing thermodynamic equations. Kinetic parameters such as apparent activation energy and pre-exponential factor have been calculated and discussed.     

Preparation and properties of nanosize MnZn ferrite from δ-FeOOH

Ferrous ion was transformed into feroxyhyte (δ-FeOOH) by oxidation. Then, manganese sulfate and zinc sulfate in some ratio were added to the feroxyhyte solution. The co-precipitation was boiling reflux conditions sometime under constant stirring. The nanosize MnZn ferrite powder was formed. The mechanism of preparation of the nanosize MnZn ferrite was discussed, and the formation of feroxyhyte which was playing a key role during the process was mentioned. The properties of powder was tested by means of X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results show that the samples of spherical particles about 20 nm, which have characteristics of ferrimagnetism, has larger saturation magnetization, but the remanent magnetization and coercivity are comparatively smaller. The spinel MnZn ferrite nanosize powder was successfully prepared from δ-FeOOH at low temperature, with low-carbon steel and peroxide as main material.     

圆柱体相贯线上的圆角表示方法

在机械设计中，圆柱体相贯线上的圆角表示方法是CAD和计算机辅助设计中的难题，所有的CAD／CAM软件都没有这一功能，多数使用者采用的是各种近似方法。本文介绍了严密精确的设计和几何造型方法，可用于大型铸锻件和重型机械的CAD和计算机辅助设计。     

高层住宅结构设计

主要介绍长沙梦泽园高层住宅从基础到上部楼层各部位的结构设计,以及在设计、施工过程中所考虑的一些问题及处理方法。     

Effect of surface free energy on the adhesion of biofouling and crystalline fouling

Pipelines and heat exchangers using seawater as coolant suffer from biofouling. Biofouling not only reduces heat transfer performance significantly, but also causes considerable pressure drop, calling for higher pumping requirements. It would be much more desirable if surfaces with an inherently lower stickability for biofouling could be developed. In this paper, a cost-effective autocatalytic graded Ni-Cu-P-PTFE composite coating with corrosion-resistant properties was applied to reduce biofouling formation. The experimental results showed that the surface free energy of the Ni-Cu-P-PTFE coatings, which were altered by changing the PTFE content in the coatings, had a significant influence on the adhesion of microbial and mineral deposits. The Ni-Cu-P-PTFE coatings with defined surface free energy reduced the adhesion of these deposits significantly. The anti-bacterial mechanism of the composite coatings was explained with the extended DLVO theory.     

建筑供排水用聚丙烯管道(PP-R)特性简析

PP -R管道具有质轻、连接方便、良好耐热性和较小导热系数、耐腐蚀且管道阻力小等优点 ,属绿色产品 ,本文对施工过程中就PP -R管与混凝土的粘结不密、抗紫外性能差等问题提出了相应的处理措施