Integrated analytical techniques for the study of ancient Greek polychromy

The materials used in the decoration of three painted astragaloi (knucklebones) from the Koroneia cave (Greece) were investigated by means of sequential application of non-destructive and destructive techniques: optical microscopy, environmental scanning electron microscopy coupled with X-ray microanalysis (ESEM-EDX), Fourier transform infrared spectroscopy (FTIR) with micro-attenuated total reflection (μ-ATR) technique, high performance liquid chromatography (HPLC) coupled with UV-fluorescence and gas chromatography-mass spectrometry (GC-MS) were used.The main results highlighted that the three astragaloi were prepared with a ground of ochre or iron clay and painted with a proteinaceous matter such as binder egg tempera. Both FTIR and GC-MS agree in the detection of lipids that can be related to egg. Organic dyestuffs identified as madder lake and shellfish purple were used together with inorganic pigments.     

Animal glues in mixtures of natural binding media used in artistic and historic objects: identification by capillary zone electrophoresis

Animal glues were often used in historic and artistic objects, e.g. as paint ground, as binders for pigments, or as adhesives. The sources were egg, casein, or different collagens. For restoration and conservation purposes it is important to know which kind of animal glue a museum object contains. Capillary electrophoresis can deliver such information, because it enables differentiation among the three proteinaceous glue classes according to their different amino acid patterns after hydrolysis. This work deals with the most relevant problem in practice, whether this identification is obstructed by the presence of other binders, with which they are mixed in many real samples; in particular, interference from plant gums and drying oils was investigated. Capillary electrophoresis of the hydrolysates (after reaction with 6 mol L^–1 HCl) was performed with an acidic background electrolyte consisting of chloroacetic acid (51.9 mmol L^–1) adjusted with LiOH to pH 2.26. The underivatised analytes were detected with a contactless conductivity detector. It was found that the constituents of the plant gums (monosaccharides) or drying oils (long-chain fatty acids and short-chain dicarboxylic acids) never interfered with identification of the animal glues, as shown for artificial mixtures of the different binders even at tenfold excess over the animal glue, and for egg tempera samples. The method was used to identify the filling material from a statue from the eighteenth century.     

Phase change materials based on low-density polyethylene/paraffin wax blends

Phase change materials, based on low-density polyethylene blended with soft and hard paraffin waxes respectively, were studied in this paper. DSC, DMA, TGA and SEM were employed to determine the structure and properties of the blends. The blends were able to absorb large amounts of heat energy due to melting of paraffin wax, whereas the LDPE matrix kept the material in a compact shape on macroscopic level. The hard paraffin wax was, however, much more miscible with LDPE because of co-crystallization than the soft paraffin wax. LDPE blended with hard paraffin wax degrades in just one step, while blends containing soft paraffin wax degrade in two distinguishable steps. SEM showed completely different morphology for the two paraffin waxes and confirmed the lower miscibility of LDPE and soft paraffin wax. DMA analyses demonstrated the toughening effect of the waxes on the polymer matrix. This technique was also used to follow the thermal expansion as well as the dimensional stability of the samples during thermal cycling. The most visible expansion could be seen in the first cycle, probably due to a totally different thermal history of the sample. With further cycling the dimensions stabilized after two and four cycles for soft and hard paraffin wax, respectively. Controlled force ramp testing on DMA confirmed poor material strength of the blends containing soft wax, especially at temperatures above wax melting.     

Effect of Different Binders on the Combustion Properties of Lignite. Part II. Effect on kinetics

In this research kinetic analysis of the Tuncbilek lignite and its mixture with different binders (molasses, CMC, sulphide liquor, heavy crude oil, sodium silicate,cornstarch, lime, peridur, bentonite, cement and poly(vinyl-acetate)) were analysed by thermogravimetric (TG/DTG) methods. Two different kinetic models (Arrhenius and Coats–Redfern) were used to determine the activation energies of the samples studied. The concept of weighed mean activation energy was applied to determine the overall reactivity of the samples. It was observed that molasses, CMC, heavy crude oil, peridur, bentonite and poly(acetate) decreased the activation energy of the coal sample, whereas, all other binders increased the activation energy of the coal sample. This revised version was published online in July 2006 with corrections to the Cover Date.     

锂离子电池硅基负极及其相关材料

锂离子电池是目前电脑、通讯、消费电子品以及未来电动车动力系统的主要能源。硅基负极材料因其具有较高理论比容量(4200 mAh·g^-1,为石墨10倍以上),被视为最理想的下一代锂离子电池负极材料。然而硅负极在充放电过程中巨大的体积膨胀造成极片材料的粉化脱落、SEI膜的持续增长、正极锂离子的不断消耗,以及现有商业化粘结剂与硅表面较弱的相互作用等诸多缺陷,造成电池容量快速的衰减,阻碍了硅基材料在锂离子电池中的商业化应用。本文对硅基负极材料及其相关电池材料,如硅材料结构、粘结剂、电解液及添加剂等,进行了系统全面的总结。最后对硅基材料目前研究进展和未来发展方向做出总结与评述,以期为下一代硅基电池体系发展提供参考。     

Phase behavior, conformations, thermodynamic properties, and molecular motion of multicomponent paraffin waxes: A Raman spectroscopy study

Variable-temperature (72–20 °C) studies of Raman spectra (3100–800 cm⁻¹) and thermal analysis of multicomponent paraffin wax have been carried out. The disorder–order transition under liquid–solid transition was observed and their temperature ranges were obtained through the S_lateral order parameter as a function of temperature. From 56 to 43 °C, the paraffin undergoes a conformational state transition of non-extended chain state (NECS) to extended chain state (ECS). The enthalpy and entropy change for the transition obtained by van’t Hoff analysis were 214.286 ± 21 kJ/mol and 0.661 ± 0.066 kJ/mol/K, respectively. The enthalpy determined by differential scanning calorimetry (DSC) was 52.165 ± 5.2 kJ/mol, which is smaller than the van’t Hoff enthalpy due to larger effective non-extended chain state. The variation of Raman spectra with decreasing temperature presents the structure evolution and molecular motion during the crystallization of paraffin wax.     

A comparative analysis of moisture transport models as applied to an epoxy binder

The results of experimental and theoretical investigations into the kinetics of moisture sorption by a neat epoxy resin obtained from RAE Industries (Reapox 520, D523) are reported. The sorption process was realized in atmospheres with a constant relative humidity of 33, 53, 75, 84, and 97% and a temperature of 50°C. The results obtained showed that the diffusion behavior of epoxy resin did not obey Fick’s law under the experimental conditions considered. Consequently, the application of a non-Fickian diffusion model was necessary. For this purpose, two-phase moisture sorption models, a model with a time-dependent diffusivity, a two-phase material model, as well as relaxation and convection models of anomalous diffusion, were considered. The model parameters were obtained from the approximation of experimental sorption data. A comparative analysis of the sorption models was performed, and the specific features of their applications were estimated. The two-phase material model and the model with varying diffusivity were found to be the most suitable ones due to a good agreement between calculation results and experimental data and the rather small (three or four) number of parameters, which make them more flexible and physically more justified than the classical Fick’s model with its two parameters. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 555–570, July–August, 2007.     

Synthesis of CdSe/CdS with a simple non-TOP-based route

A convenient and non-TOP-based route for the synthesis of core-shell CdSe/CdS quantum dots (QDs) is developed for the first time. Simple reagents, such as cadmium oxide, selenium powder, sodium sulfide, paraffin and oleic acid with obvious advantages are used to replace organometallics. This simple route allows the preparation of a series of core-shell CdSe/CdS QDs emitting in a wide wavelength range (from 510 to 615 nm). After passivation of CdSe by CdS shell using sodium sulfide as the source of sulfur at 80 °C, the quantum yields (QYs) are improved from 15-30% to 35-50% and remained stable at least for 4 months. A narrow bandwidth (FWHM<50 nm) indicates that the as-prepared QDs have uniform size distribution, desirable dispersibility and good fluorescence properties. The whole procedure can be carried out either open to air or under nitrogen atmosphere, which is simpler, greener and cheaper as compared with TOP-based route.     

Influence of Moisture on the Structure and Properties of the Interphase Layer of a Composite Based on an Epoxy Binder with a Disperse Filler

Properties of a model composite based on an ED-22 epoxy binder, cured with polyprophylene polyamine, and disperse LiF crystals as a filler were investigated by the methods of dilatometry and X-ray diffractometry. It was established that the density of cross-links of the epoxy binder in the interphase layer was lower than in a block specimen. Therefore, the thermal expansion of the composite on heating to 120°C, in terms of that of the binder, grew significantly with the degree of filling ϕ, and the water uptake also increased at the initial stage. The presence of absorbed water led to considerable changes in the structure and properties of the composite interphase: the binder became more cross-linked, its structural ordering decreased, the thermal expansion at heating diminished by a factor of 3. 7 (at ϕ = 50%), and the glass-transition temperature increased. As a result of long-term action of moisture, changes in the internal stresses had an extreme character.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 535–544, July–August, 2005.     

水性黏结剂海藻酸钠和果胶酸钠对锂离子电池石墨负极电化学性能的影响

利用循环伏安和恒电流充放电测试,结合扫描电镜观测,研究了水性黏结剂海藻酸钠和果胶酸钠对石墨负极电化学性能的影响.结果表明,石墨负极在这两种黏结剂中均可以进行有效的嵌锂脱锂循环,且电化学循环性能较好,50次循环后可逆比容量损失不超过5%.两种水性黏结剂在改善石墨电极的嵌脱锂循环性能方面具有较好的发展前景.