Absorption of acrylates and polysilazanes in the far UVC and the VUV regions

A simple but reliable method was developed for the determination of wavelength-dependent absorption coefficients in the vacuum-UV (VUV) spectral range 160 nm < λ < 195 nm.     

The Use of Surface Analysis Techniques to Determine the Route of Manufacture of Tablet Dosage Forms

ABSTRACT

Analytical methods for determining the manufacturing process of tablet dosage forms have not been previously reported. The use of surface analysis techniques in particular X-ray Photoelectron Spectroscopy and Time of Flight Secondary Ionization Mass Spectrometry will be described and a model proposed which allows the prediction of the route of manufacture in calcium phosphate and cellulosic-based tablet formulations. Results of the application of this model to evaluate prototype tablet formulations prepared by wet granulation or direct compression will be reported. Strengths and limitations of the model will be discussed.     

基于憎水迁移性测试的复合绝缘子老化特性

憎水迁移性作为复合绝缘子状态评价和老化程度判断的关键参数,有着重要的研究意义。为此,以在我国南方地区运行多年的直流复合绝缘子为研究对象,采用静态接触角法进行了系统的憎水迁移性测试,同时应用傅里叶变换红外光谱和X射线光电子能谱分析深入探究了硅橡胶材料的微观结构变化。研究结果表明:绝缘子伞裙上表面的边沿憎水迁移性最差,根部憎水迁移性最好,绝缘子不同方位的憎水迁移性也有所差异;老化最为严重的边沿褪色位置有机官能团含量大幅下降,Si元素和C元素减少、Al元素增加,并且检测出硅橡胶体系交联度的明显上升。上述憎水迁移性以及微观分析的研究结果可为直流复合绝缘子老化机制和老化程度评估提供依据。     

变热流条件下XPS板辐射引燃特性试验研究

为研究XPS保温板在变化热流作用下的引燃特性,对10组变热流条件下2.2,4.5cm厚XPS保温板辐射引燃特性进行了试验.测量了XPS保温板表面接受到的热辐射强度、引燃时间、表面温度以及质量损失速率.结果表明：0.0194kW/（m2·s）热流变化率不足以引燃XPS保温板试样;当热流变化率大于0.0373kW/（m2·s）时,在热流的作用下XPS保温板表面温度逐渐升高;当温度达到临界着火点时,XPS保温板瞬间燃烧,发出耀眼火焰和黑色浓烟,同时温度闪升至970.5℃左右;当有焰燃烧结束时,表面温度突降,燃烧过程结束;在有焰燃烧阶段,XPS板质量呈线性递减;临界着火点温度为336.0~387.0℃,且XPS保温板引燃时间与热流变化率具有乘幂关系,幂指数约为-0.765.     

“Dark hole” cure in Ba4.2Nd9.2Ti18O54 microwave dielectric ceramics

Large size Ba_4.2Nd_9.2Ti₁₈O₅₄ (BNT) ceramics doped with MnCO₃, CuO and CoO were prepared by the conventional solid-state method. Only a single BaNd₂Ti₄O₁₂ phase was formed in all samples. No second phase was found in the XRD patterns. The bulk density increases slightly because of the dopants. The SEM results showed that the grain size of Mn²⁺and Cu²⁺-doped BNT ceramics became larger with the increasing amount of dopants. The permittivity of all samples stays the same. However, the Q×f value of BNT ceramics increases by doping, especially with Mn²⁺ ions. The conductivity of BNT ceramic doped with Mn²⁺(0.5 mol‰) under high temperature is lower than that without doping. There are fewer defects in Mn²⁺-doped BNT ceramics. The XPS results indicated that Ti reduction was suppressed in BNT ceramics doped with 0.5 mol‰ Mn²⁺. BNT ceramics doped with 0.5 mol‰ Mn²⁺ ions sintered at 1320 °C for 2 h exhibited good microwave dielectric properties, with ε_r=88.67, Q×f=7408 GHz and τf = 82.98 ppm/°C.     

Friction and Wear Behavior of Single-Phase Fe2B Bulk under Dry Sliding Condition

The effects of normal load and velocity on the friction and wear behavior of single-phase Fe₂B bulk have been investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Results indicate that the friction coefficient and wear rate both decrease at first and then increase with increasing load and velocity, respectively. Attributed to the formation of a lamellar film on the Fe₂B surface, the lowest friction coefficient and wear rate are obtained at a velocity of 0.2 m/s under a load of 12 N. The dynamic friction coefficients under loads of 4 and 12 N are around 0.8 in the initial steady stage and then decrease to about 0.6, whereas the friction coefficient at 20 N shows no obvious change and remains around 0.82. The lubricating film consisting of Fe₂O₃, B₂O₃, SiO₂, and H₃BO₃ reduces the friction coefficient at 0.2 m/s under a load of 12 N.     

Friction and Wear Reduction Mechanism of Polyalkylene Glycol-Based Engine Oils

Polyalkylene glycols (PAG) have been explored as a possible base stock for engine oil formulation. The friction, wear, and load-carrying capacity of five different PAG chemistries were evaluated either as a base stock or as formulated oils in pure sliding and sliding-rolling conditions using various laboratory bench test rigs operating under boundary and mixed lubrication regimes. The results were compared against GF-5 SAE 5W-20 and a mineral-based oil. The wear surfaces were also characterized using various surface-sensitive techniques for analysis of tribofilms to understand the mechanism of friction reduction. The results indicated that PAG oils show lower friction/traction coefficients and improved load-carrying capability, depending on the formulation, than those of the GF-5 SAE 5W-20 and mineral-based oil. The adsorption of PAG molecules on the surface appeared to be responsible for the lower friction characteristics.     

Surface modifications of activated carbon by gamma irradiation

Four commercial activated carbons with different chemical and textural characteristics were modified by gamma irradiation under five different conditions: irradiated in absence of water, in presence of ultrapure water, in ultrapure water at pH = 1.0 and 1000 mg L⁻¹ Cl⁻, in ultrapure water at pH = 7.5 and 1000 mg L⁻¹ Br⁻, and in ultrapure water at pH = 12.5 and 1000 mg L⁻¹ NO₃⁻. Changes in surface chemistry were studied by X-ray photoelectron spectroscopy; pH of point of zero charge, total acidic groups and total basic groups, which were determined by assessment with HCl and NaOH; and textural changes were determined by obtaining the corresponding adsorption isotherms of N₂ and CO₂. Outcomes show that the activated carbon surface chemistry can be modified by gamma irradiation and that the changes depend on the irradiation conditions. Modifications in the sp² hybridization of the surface carbons suggest that the irradiated carbons undergo graphitization. Measurements of structural parameters indicate that the irradiation treatment does not modify the textural properties of the carbons. Finally, studies of pristine and irradiated activated carbons using diffuse reflectance spectroscopy with the Kubelka–Munk function revealed a reduction in band gap energy in the irradiated carbons associated with an increase in sp² hybridization of the carbon atoms.     

Role of activated carbon on micropollutans degradation by ionizing radiation

The objective of this study was to analyze the influence of the presence of activated carbon on the degradation of the triiodinated contrast medium diatrizoate (DTZ) by the simultaneous use of gamma radiation and activated carbon. Four commercial activated carbons (Ceca, Witco, Sorbo, and Merck) with different textural and chemical characteristics were used for this purpose. The percentage DTZ removal obtained was considerably higher with the gamma radiation/activated carbon (GM/AC) system than with radiolysis in the absence of activated carbon, and it depended on the specific activated carbon employed. First, we optimized the amount of activated carbon required to maximize the amount of DTZ removed by the GM/AC system (0.06 g). The degradation constants were higher with the GM/AC system than with radiolysis alone, evidencing a synergic effect that favors pollutant removal. This synergic effect is independent of the textural but not the chemical characteristics of the activated carbon, observing a higher synergic activity for carbons with a higher surface content of oxygen, specifically quinone groups. We also highlight that the synergic effect of the activated carbon requires adsorbent–adsorbate electrostatic interaction and is absent when this interaction is hindered.     

青铜器保护机理与工艺研究

从青铜器的小孔腐蚀机理出发,以电镀Cu-Sn-Pb合金多孔镀层作为模拟试片,采用电化学工作站定量测定腐蚀电阻的方法,研制出以苯骈三氮唑(BTA)为主钝化剂的乙醇型缓蚀保护剂,可将试片的腐蚀电阻提高2个数量级,达到107Ω.采用氩离子溅射纵向刻蚀和光电子能谱(XPS)相结合测试了缓蚀膜层成分的纵向分布,呈现较稳定的成分结构.应用保护剂成功地对郑州博物馆战国青铜釜和汉代青铜饰品2件文物进行了保护处理,处理后颜色微有加深,基本保持了文物的绿锈原貌. 