Chromatography using a water stationary phase and a carbon dioxide mobile phase

A novel chromatographic separation method is introduced which employs water (saturated with CO(2)) as a stationary phase and CO(2) (saturated with water) as a mobile phase. Since water and CO(2) have little miscibility, conditions can be attained that create a stationary phase of water lining the inside of an uncoated stainless steel capillary. Because altering temperature and pressure can change both the density of the mobile phase and the polarity of the stationary phase, these experimental parameters offer good flexibility for optimizing separations and allow for different gradient programmed separation options. Further, since this method is free of organic stationary and mobile phase components, it is environmentally compatible and allows the use of universal flame ionization detection. This system offers very good sample capacity, peak symmetry, and retention time reproducibility (～1% RSD run-to-run, ～4% RSD day-to-day). Analytes such as alcohols, carboxylic acids, phenols, and tocopherols are employed to investigate this relatively inexpensive and robust method. As an application, the system is used to quantify ethanol in alcoholic beverages and biofuel and to analyze caffeine levels in drinks. In all cases, quantitative results are obtained with quick throughput times and often little need for sample preparation.     

Influence of austenitising temperature on kinetics of phase transformations in medium carbon TRIP steel

Abstract

Comprehensive, dilatometric studies of the kinetic transformations of undercooled austenite in medium carbon TRansformation Induced Plasticity (TRIP) steel during cooling from the temperature range of 750–1030°C were carried out. Selection of austenitising temperatures was based on the knowledge of the critical temperatures. The influence of the austenitising temperature on the formation ranges of new phases and microstructural constituents during continuous cooling was determined. It was also shown that the annealing of the investigated steel at the lowest temperature resulted in the strongest lowering of Ms temperature as well as in the lowering hardenability. Based on the analysis of the stated relationships, modifications of the annealing, adapted to the investigated steel chemical composition, were proposed.     

Influence of titanium on the static recrystallization of a medium carbon microalloyed steel

Static recrystallization kinetics of three medium carbon steels, microalloyed with vanadium and titanium (titanium varied from 0.003 to 0.039% in weight), were studied by hot torsion test simulation. A higher recrystallization time was observed in the steel with 0.019 wt% Ti. This difference in recrystallization time was checked by metallographic observations and mechanical softening. This time shift implies different activation energies, which were calculated by the time needed to obtain a 50% recrystallized structure and also by solving the Zener-Hollomon equation. Evolution of the kinetics of recrystallization as a function of temperature was also studied. In addition, the critical allowable temperature for a fully recrystallized structure was investigated.     

表面态对纳米晶BaTiO3介电性能的影响

采用硬脂酸凝胶法制备了粒度均匀的纳米晶BaTiO3，用X射线衍射分析、红外光谱分析、透射电子显微镜对产物进行了表征，研究了表面态与介电性能。结果表明，BaTiO3纳米材料表面的不完整性主要是氧空位造成的，暴露在粒子表面的是一些金属离子，随着晶粒尺寸的减小，氧空位缺陷的浓度增加，极化增强，纳米材料的这种表面状态对其介电性能有重要影响，使其静态介电常数远比常规材料的大。     

Review Environmentally friendly coatings using carbon dioxide as the carrier medium

The use of supercritical or liquid carbon dioxide as a medium for delivering coating systems is attracting much interest because of concerns over the environmental effects of volatile organic compound (VOC) emissions from conventional coatings. Significant reductions in VOC emissions can be achieved by replacing some or all of the organic solvent by CO₂ in spray coatings. Technical and commercial benefits are also claimed for these systems, including improved coating efficiency and operating cost savings. In this review, the range of current and potential applications achievable using CO₂-based coatings is discussed. In addition to spray coatings onto a variety of substrate surfaces, CO₂ processes can be used to produce controlled particle size powders for use in powder coatings and also for the coating of preformed particles such as metal powders and pharmaceuticals for controlled release in drug delivery. Use of CO₂ in spin coating and microlithography offers the potential for significant waste reduction. Specific substrates where use of CO₂ can be beneficial include the treatment of building stone and wood treatment. CO₂ can aid surface impregnation of substrates because of its high diffusivity and the potential for substrate swelling.     

Influence of homogeneous condensation on the gasdynamics and radiation of a free carbon dioxide jet

The influence of homogeneous condensation on the gasdynamics and radiation of carbon dioxide gas during jet expansion into a vacuum is investigated experimentally and theoretically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 1, pp. 5–10, July, 1985.     

Influence of structural and dielectric anisotropy on the dielectrophoresis of single-walled carbon nanotubes

We report on a carbon nanotube network which is composed of aligned metallic and randomly oriented semiconducting single-walled carbon nanotubes. The material is formed by using a novel radio frequency dielectrophoresis setup, which generates very large dielectrophoretic force fields and allows dielectrophoretic assembling of nanotube films up to 100 nm thickness. Polarization dependent absorption measurements provide experimental evidence for the electronic type specific alignment behavior. We explain the experimental data with an advanced model for nanotube dielectrophoresis, which explicitly takes into account both the longitudinal and transversal polarizability. On the basis of this model, we calculate the dielectrophoretic force fields and show that semiconducting nanotubes deposit under very large fields due to their transversal polarizability even for high field frequencies.     

Influence of physical state of intercalating agents on intercalation process of high speed airflow pretreated montmorillonite in supercritical carbon dioxide

The work aimed at studying the effect of scCO₂ processing technology on basal spacing, surface morphology and thermal stability of sodium montmorillonite (MMT) that were pretreated with high speed airflow pulverization method and then modified using myristyltrimethylammonium bromide (MTAB) and tetradecyltrihexylphosphonium chloride (TDTHP) with scCO₂ as the medium. X-ray diffraction (XRD) showed that physical state of intercalating agents played an important role on the intercalation process in scCO₂. Solid-state MTAB could hardly intercalate into the interlayer of pretreated MMT (PMMT), though addition of co-solvent benefited the intercalation to some extent. However, liquid TDTHP could intercalate into the interlayer of PMMT easily even without co-solvent and the basal spacing of TDTHP-modified PMMT was larger than that of MTAB-modified PMMT. Scanning electron micrographic (SEM) showed the large compact structure for MMT broke into small random structures after airflow processing and some smaller tactoids and more dispersed structures can be observed for both MTAB-modified PMMT and TDTHP-modified PMMT compared to unprocessed MMT. For TDTHP–PMMT, many clay platelets that were separated from the tactoidal structure and more dispersed structure were observed, which may be helpful for MMT exfoliation and dispersion in polymers. Thermogravimetric analysis (TG) demonstrated that TDTHP-modified PMMT was up to 100 °C more stable than MTAB-modified PMMT. These results are very important and relevant to the preparation and application of MMT/polymer nanocomposites.     

CO2的浓度含量对超声波气体流量计的精度影响

文章设计了实验用以测试CO2的浓度含量对超声波气体流量计测量精度的影响，实验结果表明，由于在流量计中采用了“过零电平检测”、“随机多次测量声时后平均”等技术措施，即使在CO2的浓度较高的情况下，流量计依然可以保持在较高的测量精度。     

二氧化碳对空分装置安全运行的影响

以一套空分装置运行实际情况 ,说明二氧化碳对空分安全运行的严重影响 ;当装置内有大量富聚的二氧化碳存在时 ,即使主冷凝蒸发器液氧中总碳含量在 1 0 0× 1 0 - 6 以下 ,也很容易导致主冷凝蒸发器爆炸泄漏的发生 ;提出影响空分安全运行的四个方面     

Effect of carbon monoxide and sulphur dioxide on the oxidation state of copper in zeolite

A study is made of the reduction and oxidation of Cu²⁺ in CuNaY zeolites by CO and SO₂, using electron spin resonance. It is observed that the Cu⁺ or Cu^o formed by the reduction of Cu²⁺ with CO can be reoxidized to Cu²⁺ by SO₂ at 400°C. SO₂ can also reduce a fraction of the Cu²⁺ sites in the Cu-exchanged zeolites. SO₂ decomposes and forms elemental S under experimental conditions on the zeolite.     

Crack extension force in a dielectric medium

The authors' previously derived path-independent integral [1], which is related to the energy-release rate, is evaluated for a crack placed in an infinite dielectric medium subjected to a far field uniaxial tension and an external electric field. The governing equations and boundary conditions for a fully nonlinear elastic dielectric are linearized to a quasi-linear form. Electric field quantities are then decomposed into a rigid body state and a deformed state. This leads to a set of linear differential equations, boundary conditions and constitutive relations. An integral transform technique is used to obtain the solution in closed form. From this solution the crack extension force is evaluated.     

Influence of the properties of hydrated solid phase surfaces on the effect of a density change in a dispersed medium

The role of exchange cations in the formation of the structure of a dispersed medium on hydrated surfaces of montmorillonite is shown.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 3, pp. 449–457, March, 1977.     

Influence of carbon dioxide shielding gas on microstructure and corrosion property of welds

The microstructures and corrosion properties of weld joints are studied during 10 kW high power fiber laser welding of 304 stainless steel with shielding gases of 100 % argon, 80 % argon containing 20 % carbon dioxide and 100 % carbon dioxide, respectively. As the content of carbon dioxide in argon shielding gas increases from 0 % to 20 % then to 100 % during 10 kW high power fibre laser welding, the interdendritic δ‐ferrite in weld joints changes from lathy, short strip and trivial structures to thick‐long strip with short secondary dendrite arms then to skeletal‐network structure. Oxide inclusions, observed in 100 % carbon dioxide shielded weld, promote the formation of the skeletal‐network structure of δ‐ferrite and the homogenization of chromium and nickel in weld joint. The 100 % argon shielded weld joint has a highest initial corrosion current density, the 80 % argon containing 20 % carbon dioxide shielded weld has a lowest pitting potential, while the 100 % carbon dioxide shielded weld has a highest initial corrosion potential. The microstructures and element distribution play important role in determining the corrosion properties of the weld joints.     

Influence of pressurized carbon dioxide on ketoprofen-incorporated hot-melt extruded low molecular weight hydroxypropylcellulose

Objectives: The aim of the current research project was to investigate the effect of pressurized carbon dioxide (P-CO₂) on the physico-mechanical properties of ketoprofen (KTP)-incorporated hydroxypropylcellulose (HPC) (Klucel? ELF, EF, and LF) produced using hot-melt extrusion (HME) techniques and to assess the plasticization effect of P-CO₂ on the various polymers tested.

Methods: The physico-mechanical properties of extrudates with and without injection of P-CO₂ were examined and compared with extrudates with the addition of 5% liquid plasticizer of propylene glycol (PG). The extrudates were milled and compressed into tablets. Tablet characteristics of the extrudates with and without injection of P-CO₂ were evaluated.

Results and conclusion: P-CO₂ acted as a plasticizer for tested polymers, which allowed for the reduction in extrusion processing temperature. The microscopic morphology of the extrudates was changed to a foam-like structure due to the expansion of the CO₂ at the extrusion die. The foamy extrudates demonstrated enhanced KTP release compared with the extrudates processed without P-CO₂ due to the increase of porosity and surface area of those extrudates. Furthermore, the hardness of the tablets prepared by foamy extrudates was increased and the percent friability was decreased. Thus, the good binding properties and compressibility of the extrudates were positively influenced by utilizing P-CO₂ processing.     

Influence of dielectric constant of polymerization medium on processability and ammonia gas sensing properties of polyaniline

Polyaniline (PANI) was synthesized by the oxidation of aniline hydrochloride in the presence of ammonium persulphate and hydrochloric acid. The polymerization reaction was carried out in several batches in different solvent media by changing the volume ratio of N,N -dimethyl formamide (DMF) and water as binary solvent mixture. The dielectric constant of the polymerization medium for each batch reaction was determined by measuring the capacitance with change in frequency. The UV spectra of the synthesized polyaniline solutions helped us to optimize the ratio of the binary solvent to get sufficient polymer growth and processability. Thin film of processable polyaniline was then deposited on glass slides coated with polyvinyl alcohol (PVA) crosslinked with maleic anhydride (MA). FTIR and XRD studies of the coated film were also done. AFM studies further helped in the morphological study of the film deposited. Finally, conductivity and ammonia gas-sensing property of the polyaniline film were also studied.     

Propagation of Bessel beams from a dielectric to a conducting medium

Recently, the use of Bessel beams in evaluating the possibility of using them for a new generation of ground penetrating radar systems has been considered. Therefore, an analysis of the propagation of Bessel beams in conducting media is worthwhile. We present here an analysis of this type. Specifically, for normal incidence we analyze the propagation of a Bessel beam coming from a perfect dielectric and impinging on a conducting medium, i.e., the propagation of a Bessel beam generated by refracted inhomogeneous waves. The remarkable and unexpected result is that the incident Bessel beam does not change its shape even when propagating in the conducting medium.