Conversion of chemical energy in an explosive by a magnetohydrodynamic method

Conclusions In this paper, we examined different practical methods for realizing the MHD method for converting chemical energy of a condensed explosive into pulsed electrical energy. It was shown that explosive MHD generators, which are compact sources of powerful pulses of electrical energy, are characterized by their relative simplicity, autonomy, and maneuverability of firing and they are capable of operating in the frequency-periodic mode. The moderate, compared to MC generator, weight-size characteristics of the generator (1 J/g, 1 J/cm³) are the necessary tradeoff for the new operational quality, namely, the nondestructibility of the setup.At the present time, a considerable amount of experimental information has been accumulated on the study of processes that determine the efficiency of the generator. Based on this information, a number of projects have been proposed for explosive MHD generators in the megajoule range. Practical experience has been gained in creating frequency-periodic action generators as well as autonomous setups using superconducting magnetic systems. The increase in the operational efficiency of an explosive MHD generator is primarily related to increasing the magnetic Reynolds number of the flow, which can be attained, in particular, by using different schemes for accumulating the energy of the explosion. The use of a metallic liner, which expands under the pressure of the detonation products, in an explosive MHD generator is, in the practical sense, apparently hopeless.The general information available in the literature on the parameters and properties of explosive MHD generators give a basis for concluding that this generator is a promising source of powerful energy pulses. In a certain range of parameters, it can be an alternative to the use of storage batteries, inductive accumulator, and an explosive magnetic generator, and according to a number of indicators (nondestructibility, autonomy, frequency-periodic operational mode) has advantages over them.Moscow and Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 18, No. 5, pp. 3–20, September–October, 1982.     

络合萃取法分离发酵液中丙酸

利用络合萃取法对模拟溶液和发酵液中的丙酸分离进行研究。络合剂、稀释剂筛选结果表明:选用甲基三辛基氯化胺(MTAC)为络合剂、正辛醇为稀释剂时,萃取受pH值和无机阴离子影响较小,对丙酸具有较高的选择性。以1.2mol/L的MTAC为萃取有机相,有机相/水相(体积比)为3的条件下,萃取15min即能达到平衡;该系统适用于较高浓度丙酸发酵液萃取,经4级萃取丙酸萃取率达86.2%。     

络合萃取法处理高浓度有机废水

介绍了高浓度有机废水的来源和处理现状。提出了高浓度有机废水的络合萃取处理方法的研究方向。阐述了络合萃取法处理高浓度有机废水的高效性     

Mercuriation and thalliation of polymers prepared using 2-vinylthiophene: Conversion of products into polymers containing thienylboronic acid residues

2-Vinylthiophene was homopolymerised and copolymerised with styrene and/or divinylbenzene using benzoyl peroxide as the initiator. The various polymeric products reacted smoothly with mercury(II) acetate or trifluoroacetate in tetrahydrofuran to give mercuriated polymers. Several of the polymers were treated with thallium(iii) trifluoroacetate in methylene chloride but the only polymer that was satisfactorily thalliated was the linear homopolymer, poly(vinylthiophene). Several of the mercuriated polymers were reacted with iodine to give polymers containing iodothiophene residues. Examples of mercuriated and thalliated polymers were reacted with borane to give polymer-supported organ-oboranes which, on treatment with water, gave polymers containing thienylboronic acid residues. It has been demonstrated that the latter polymers can serve as polymer-supported protecting groups for diols.     

Nanoscale mechanical properties of polymers irradiated by UV

The application of depth sensing nanoindentation to determine mechanical properties of three different polymers is described in this work using three different techniques to calibrate the measurement system. The nano-hardness and the elastic indentation modulus of polyvinyl chloride, polyethylene oxide and polyacrylic acid were inferred from nanomechanical tests, and the influence of ultraviolet irradiation on the mechanical properties of measured polymers is studied. A multicycling test—a sequence of several loading and unloading procedures—allowed the measurement of changes in the sample viscoelasticity. The nano-hardness of the polymers is shown to increase with radiation dose while the viscoelasticity decreases.     

Low band gap Schiff base polymers obtained by complexation with Lewis acids

Two Schiff base polymers were prepared from the respective monomers by condensation method using toluene and N-methyl-2-pyrrolidinone as solvent. They were complexed with Al(III), In(III), and Cu(II) trifluoromethane sulfonates (triflates), and AlCl₃ Lewis acids and characterized by FT-IR, UV–Vis spectroscopy, and scanning electron microscopy (SEM). Homogeneous films were prepared by spin coating in the presence and absence of Lewis acids. Polymer–Lewis acid interaction was confirmed by FT-IR, UV–Vis spectroscopy, and SEM. Lewis acid composition in polymers was determined by FT-IR spectroscopy. Absorption spectra of these conjugated Schiff base polymer complexes exhibited smaller optical band gap than pristine polymers. These variations ranged from 2.4 to 1.4 and 3.3 to 2.0 eV. Absorption depends on the Lewis acid in the polymer and band gap on the nature of the metal incorporated in the polymeric backbone. Solubility increased by complexation. The obtained complexes were soluble in trifluoroacetic and formic acids and in m-cresol. Polymer–Lewis acid solutions in m-cresol were stable for 98 h; the others remained stable over several months. The results of this study revealed that optical, solubility, and band-gap properties of conjugated Schiff base polymers can be modified by Lewis acids and these could be studied by optoelectronics.     

Influence of chemical structure of hardener on mechanical and adhesive properties of epoxy polymers

The mechanical and adhesive properties of epoxy formulations based on diglycidyl ether of bisphenol A cured with various aliphatic amines were evaluated in the glass state. Impact and uniaxial compression tests were used to determine the impact energy, elastic modulus and yield stress, respectively. The adhesion tests were carried out in steel–steel joints using single‐lap shear, T‐peel, and impact adhesive joints geometry. The better mechanical and adhesive behavior of the networks is obtained when exists high flexibility of chain between crosslink and/or high elastic modulus. The 1‐(2‐aminoethyl)piperazine epoxy network presents the best adhesive properties, high flexibility, and the largest impact energy. However, it possesses low elastic modulus and yield stress. Also, exhibits increases in peel strength and impact energy while reductions in lap shear strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Control of electrical properties of polymers by chemical modification

This article reviews the use of chemical modification of preformed polymers as a means of tailoring their electrical properties. Specifically, triboelectric charging, photoconductivity and dark conductivity are considered.     

Estimation of polymer crystallinity by dynamic mechanical techniques

Dynamic mechanical techniques can be used for a rapid estimation of polymer crystallinity with an accuracy of better than ±20%. The advantage of our proposed procedure is that it is absolute and the crystallinity can be instantaneously estimated when the dynamic mechanical analysis (DMA) data is available. A serious limitation is its applicability to crystallizable polymers (e.g., a quenched nylon 6) where higher values are obtained due to crystallization during the DMA experiment. Another limitation is that our technique cannot be applied to as polymerized samples, e.g., powders or pellets; only fabricated products such as films, fibers, or plaques are suitable for this determination using DMA. Using a variety of polymer systems, the underlying principle, advantages, disadvantages, and recommendations on crystallinity evaluation by DMA are presented. At present we consider this method to be more of a different approach rather than value it as a crystallinity measurement technique, especially for quenched polymers.     

Dynamic mechanical properties of polymers

A technique, employing samples in the form of tuning forks, to measure the mechanical properties of polymers is presented. Results for low density polyethylene, polypropylene, and polycarbonates are shown. A large transition is observed for polypropylene at approximately +10°C and a small transition at ?100°C for the polycarbonates. Polycarbonate data has also been obtained from 20 to 150°C, at approximately 70 cps. Effects of time, temperature, and history are presented.     

化工系统消纳可再生能源的电-氢协调储能系统优化设计

针对可再生能源发电间歇性和波动性与化工过程系统氢气需求波动性协调匹配的问题,本文以电-氢储能系统总费用最小为目标,建立了可再生能源发电与化工生产中加氢系统耦合的电-氢协调储能系统优化设计模型,以确定电-氢协调储能系统的最优容量配置和功率调度方案。采用典型案例研究了可再生能源渗透率和电-氢储能系统构成对电-氢储能优化设计和运行特性的影响。研究表明:当化工系统的氢气需求全部由可再生能源发电制氢提供时,在系统中同时采用电池和氢气储罐储能可有效地降低系统的总费用;在该系统中,电池可用于平抑短期内发电侧和负荷侧的波动,氢气储罐可平衡发电侧和负荷侧长期的不匹配;随着可再生能源渗透率的增加,系统的总费用显著增大;为了维持外购氢气流率的稳定,系统中需要增加电解槽和储能系统的容量以解决发电侧和负荷侧的波动和不匹配问题。     

Quantification of the complexation of protein with neutral water borne polymer by fluorescence spectroscopy

The complexation of bovine serum albumin (BSA) with poly(N-isopropylacrylamide) (PNIPAM) in an aqueous system (pH 7) has been investigated by means of fluorescence spectroscopy. Through analyzing the change of fluorescence intensity of protein chromophores caused by complexation, a quantitative mathematical equation has been established and the average number of bound proteins per neutral polymer (n_b) can be calculated accurately without destroying the dynamic equilibrium of aqueous complex system. At the same time, with the help of this equation, the extreme value of n_b can also be calculated when PNIPAM concentration is low enough. Compared with traditional calculation methods, this method has the advantages of rapid detectability, high sensitivity, accuracy and extensive applicability. Thus, it is a better way to study the complexation of protein with polymer.     

Grafting polymers onto carbon black surface by trapping polymer radicals

Polystyrene, poly(styrene-co-maleic anhydride), poly[styrene-co-(4-vinylpyridine)] and poly(4-vinylpyridine) with well-defined molecular weights and polydispersities were synthesized using 4-hydroxyl-2,2,6,6-tetramethylpiperidin-1-oxyl (HTEMPO)-mediated radical polymerization initiated by azobisisobutyronitrile or benzoyl peroxide. The resultant polymers were grafted onto carbon black surface through a radical trapping reaction at 130 °C in DMF. ¹H NMR, TGA, TEM, AFM, DSC and dynamic light scattering were used to characterize the carbon black grafted with polymers. It was found that the carbon black grafted with polystyrene and poly(styrene-co-maleic anhydride) could be dispersed in THF, chloroform, dichloromethane, DMF, etc., and the carbon black grafted with poly(4-vinylpyridine) and poly[styrene-co-(4-vinylpyridine)] could be well dispersed in ethanol.     

Heat distortion and mechanical properties of polymers by thermal-mechanical analysis

Polymer properties were measured as a function of temperature at 5 and 10°C per minute heating rates and as a function of time at constant temperature, using the Du Pont 940 thermal-mechanical analyzer. Data are reported on deflection temperature under load, vicat softening temperature, and creep properties. These results have been correlated with ASTM values. These tests require short times and are applicable to thermoplastics, thermosets, and elastomers.     

Topographical and chemical characterization of polymer surfaces modified by physical and chemical processes

Nanoscale changes to the surface of polymeric materials enables changes in materials' adhesion, wettability, printability, chemical functionality, and bioactivity, while maintaining desirable bulk properties. Polymer surface modification is therefore used in applications such as antimicrobial or non‐fouling materials, biosensors, and active packaging. The range of available modification and analytical techniques used across laboratories prevents accurate comparison of techniques in terms of their effects on surface chemistry and topography. It was therefore our goal to evaluate the effects of four surface modification techniques (chromic acid, piranha solution, ultraviolet irradiation, and oxygen plasma) on polyethylene films. Changes in surface chemistry and topography were quantified using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), contact angle measurement, and direct measurement of available surface carboxylic acids. Roughness increased in the order: piranha (57.7 nm); oxygen plasma (76.3 nm); UV irradiation (76.4 nm); chromic acid (120 nm). Hydrophobicity decreased in the order: piranha (77.20), chromic acid (73.50), oxygen plasma (61.70), UV irradiation (58.70). Functionalization (by IR absorbance intensity between 1680–1780 cm⁻¹) increased in the order: oxygen plasma (0.06), piranha (0.09), chromic acid (0.34), UV irradiation (0.50). By analyzing these methods using consistent analytical techniques, side‐by‐side comparisons have been accurately made. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

生物质废弃物水热分解产化学品的技术进展

生物质是一种来源丰富的可再生资源,利用生物质废弃物产化学品已经成为研究热点。水热技术分解生物质废弃物能够产生有机酸等高附加值化学品,对于生物质废弃物的资源化利用具有重要价值。本文介绍了生物质废弃物水热分解技术及其产化学品的进展,以期为生物质废弃物的高效资源化利用提供参考。     

Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property

Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO₃ (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 μW/cm² (49.79 μW/cm³) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.     

On the mechanical ageing of polymers

The breaking of the polymers under operational conditions is a result of the simultaneous action of oxygen, humidity, and mechanical stresses. The mechanical ageing of a longtime life of the model polymer materials was investigated in function of the applied static stress. It was established that the time required for the breaking of the model polymers varies regularly as a function of the magnitude of the applied force. Expressed graphically, this dependence is S-shaped. The action of the mechanical stress alters the tension of the valence bonds, hence also the vibration frequency, and consequently the energy term in the Arrhenius equation. The assumption that mechanical stress alters only the activation energy of the breaking processes does not lead to a dependence between longtime life and stress which corresponds to actual observations.