Understanding CO_2 decomposition by thermal plasma with supersonic expansion quench

CO_2 pyrolysis by thermal plasma was investigated,and a high conversion rate of 33% and energy efficiency of 17% were obtained.The high performance benefited from a novel quenching method,which synergizes the converging nozzle and cooling tube.To understand the synergy effect,a computational fluid dynamics simulation was carried out.A quick quenching rate of 10~7Ks(-1) could be expected when the pyrolysis gas temperature decreased from more than 3000 to 1000 K.According to the simulation results,the quenching mechanism was discussed as follows: first,the compressible fluid was adiabatically expanded in the converging nozzle and accelerated to sonic speed,and parts of the heat energy converted to convective kinetic energy; second,the sonic fluid jet into the cooling tube formed a strong eddy,which greatly enhanced the heat transfer between the inverse-flowing fluid and cooling tube.These two mechanisms ensure a quick quenching to prevent the reverse reaction of CO_2 pyrolysis gas when it flows out from the thermal plasma reactor.     

Investigation of operating parameters on CO2 splitting by dielectric barrier discharge plasma

Experiments of CO2 splitting by dielectric barrier discharge (DBD) plasma were carried out,and the influence of CO2 flow rate,plasma power,discharge voltage,discharge frequency on CO2 conversion and process energy efficiency were investigated.It was shown that the absolute quantity of CO2 decomposed was only proportional to the amount of conductive electrons across the discharge gap,and the electron amount was proportional to the discharge power;the energy efficiency of CO2 conversion was almost a constant at a lower level,which was limited by CO2 inherent discharge character that determined a constant gap electric field strength.This was the main reason why CO2 conversion rate decreased as the CO2 flow rate increase and process energy efficiency was decreased a little as applied frequency increased.Therefore,one can improve the CO2 conversion by less feed flow rate or larger discharge power in DBD plasma,but the energy efficiency is difficult to improve.     

Experimental Research on Plasma Induced by TEA CO2 Laser Propulsion

Results in the air-breathing propulsion experiments with a parabolic light craft and a self-made UV-preionized 100 J TEA CO2 laser device are presented. Air disturbance and the spectrum of the plasma after the interaction of pulsed laser radiation with the light craft were studied. It was found that the focal length of the parabolic light craft had a significant effect on the air-disturbance. Two shock waves were detected for the longer focal length, while only one shock wave detected for the short focal length. The spectrum of the laser-induced plasma, the distribution of the characteristic lines, and the temporal behaviors of the air plasma were studied in detail. The results showed that, the evolution of the laser-induced plasma lasted 20μs, and the plasma spectrum would reach the maximum intensity at 7μs.     

Growth of 4 diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters,and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230-380 K.The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra.Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples,respectively.TC,as high as 1950 ± 230 W m-1 K-1 at room temperature,is measured for the most perfect material.A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.     

Recent Development of CO_2 Reforming of CH_4 by “Arc” Plasma

This paper presents a brief overview of CO_2 reforming of CH_4(CRM) by various forms of "arc" plasma, which is more suitable to CRM, and the energy efficiency is used to evaluate different plasma processes specifically. According to the reported results, the arc thermal plasma with binode exhibited better performance. Moreover, the plasma CRM process was compared with the reported plasma steam reforming of CH_4(SRM) process, and the results showed that the former process has advantages on energy efficiency and CH_4 consumption. Additionally,it is believed that the plasma CRM process would be competitive with the conventional SRM process in both energy efficiency and CO_2 emission once the heat management is emphasized and the renewable power is used. Finally, a concept of plasma reactor for industrial application is proposed.     

Plasma-assisted Co/Zr-metal organic framework catalysis of CO_2 hydrogenation:influence of Co precursors

In this study, Co/Zr-metal organic framework(MOF) precursors were obtained by a roomtemperature liquid-phase precipitation method and the equivalent-volume impregnation method,respectively, using a Zr-MOF as the support, and Co/Zr-MOF-M and Co/Zr-MOF-N catalysts were prepared after calcination in a hydrogen–argon mixture gases(V_(Ar):V_(H_2)= 9: 1) at 350 °C for 2 h. The catalytic activities of the prepared samples for CO_2 methanation under atmosphericpressure cold plasma were studied. The results showed that Co/Zr-MOF-M had a good synergistic effect with cold plasma. At a discharge power of 13.0 W, V_(H_2):V_(CO_2)= 4: 1 and a gas flow rate of 30 ml·min~(-1), the CO_2 conversion was 58.9% and the CH_4 selectivity reached 94.7%,which was higher than for Co/Zr-MOF-N under plasma(CO_2 conversion 24.8%, CH_4 selectivity 9.8%). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N_2 adsorption and desorption(Brunauer–Emmett–Teller) and x-ray photoelectron spectroscopy analysis results showed that Co/Zr-MOF-M and Co/Zr-MOF-N retained a good Zr-MOF framework structure, and the Co oxide was uniformly dispersed on the surface of the Zr-MOF. Compared with Co/Zr-MOF-N, the Co/Zr-MOF-M catalyst has a larger specific surface area and higher Co~(2+)/Cototaland Co/Zr ratios. Additionally, the Co oxide in Co/ZrMOF-M is distributed on the surface of the Zr-MOF in the form of porous particles, which may be the main reason why the catalytic activity of Co/Zr-MOF-M is higher than that of Co/ZrMOF-N.     

Realizing high efficiency and large-area sterilization by a rotating plasma jet device

By tilting a plasma jet and rotating 360°, a large-area can be scanned and sterilized in a short time. Compared with the previous array device, this pipe has the significant advantages of high sterilization uniformity and low gas consumption. Firstly, a rotatable plasma jet device, which can control the swing and rotation of a jet pipe, is designed, and a corresponding theoretical model is established to guide the experiment. Secondly, with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) as the target bacteria, the device achieves a short sterilization time of 158 s—the minimum sterilization flow of S. aureus and E. coli is 0.8 slm and 0.6 slm, respectively. The device is compared with an array plasma sterilization device in terms of sterilization speed and gas consumption. The results show that the device is not only better than an array plasma sterilization device with respect to scanning uniformity, but also far less than the array plasma sterilization device in gas consumption of 5 slm. Therefore, the device has great potential in applications involving efficient, large-area sterilization.     

Morphology of irradiated PMMA membranes prepared by phase inversion with supercritical CO2

Poly （methyl methacrylate） （PMMA） pellets are irradiated using 60Co gamma-ray in air and successfully formed by hot pressing at constant conditions. The irradiated PMMA membranes are prepared by supercritical carbon dioxide （scCO2） as a physical blowing agent using the pressure quench method. Effects of foaming conditions such as adsorbed dose, saturation temperature, pressure on the morphology and cell size of the microcellular PMMA membranes are investigated in detail. The results showed that the irradiated PMMA membranes possess spherically closed-cell structure with uniform cell size. They have a high cell density compared with virgin PMMA. The cell size uniformity becomes poor at dose lower than 10 kGy, but increases with the dose at dose higher than 10 kGy. The mean cell diameter is less than 10 μm and the cell density increases with increasing dose. The average cell size of irradiated PMMA membranes decreases and cell density increases with increased saturation temperature and pressure. The changes in morphology of membranes are attributed to the gamma-ray radiation and scCO2 synergistic effect.     

Degradation of tetracycline in water by gas-liquid plasma in conjunction with rGO-TiO2 nanocomposite

Tetracycline(TC)is an antibiotic mainly used in livestock production and respiratory infection.Traditional methods are not effective in removing TC from solution.In this study,TC was degraded by gas-liquid plasma in the presence of rGO-TiO2 in solution.The rGO-TiO2 was prepared by modified hummers and hydrothermal method.The electrical and optical properties of the gas-liquid discharge plasma were studied and the produced long-lived reactive species were analyzed by spectrophotometer.The degradation efficiency of TC was improved by 41.4％after plasma treatment for 12 min in presence of 30 mg l-1 rGO-TiO2 compared to that with plasma alone.The degradation efficiency increased with increasing discharge power,but as the initial concentration was increased from 20 to 80 mg l-1,the degradation efficiency of TC decreased.The initial pH had no significant effect on the degradation of TC.The intermediate products were determined by UV-vis spectrophotometry and ESI(+)-MS,and the degradation mechanism was analyzed.The reactive species,including O3,OH,and H2O2,etc.,produced in the plasma/catalyst system attracted electron-rich functional groups(amino group,aromatic ring,and double bond).Therefore,the gas-liquid plasma/catalyst system could be an effective and promising method for pharmaceutical wastewater treatment in future.     

氢化锆表面CO2反应层结构分析

利用CO2、P与ZrH2反应生成约3—5μm厚的薄膜,用扫描电镜对薄膜横截面进行形貌观察;用X光电子能谱和X射线衍射对反应层表面进行分析。分析结果证明,所得到的氢化锆表面反应层致密,与基体结合良好．具有阻挡氢的能力;反应层中含有Zr、C、O等元素;除baddeleyite结构的ZrO2以外．还有具有C—H键和O-H键的物质。     

Fast inactivation of microbes and degradation of organic compounds dissolved in water by thermal plasma

The multifunctionality and the advantages of thermal plasma for the fast inactivation of viable cells and degradation of organic compounds dissolved in waste water are presented.A complete bacterial inactivation process was observed and studied using a thermal plasma treatment source with very short application times,in particular for Staphylococcus aureus bundle spore survival.The survival curves and analyses of the experimental data of the initial and final densities of S.aureus bacteria show a dramatic inhibitory effect of the plasma discharge on the residual bacteria survival ratio.As the exposure time increased,the inactivation process rate increased for direct exposure more than it did for indirect exposure.The evaluation of direct and indirect exposure was based on the analysis of the ultraviolet spectrum from the absorbance spectra of the organic compound dye called benzene sulfonate(C_(16)H_(11)N_2Na O_4S)and of viable cells called S.aureus.Organic compounds were degraded and viable cells were killed in a short time by thermal plasma.Moreover,analyses of total carbon,total organic carbon,and total inorganic carbon showed a fast decrease in organically bound carbon,however,this was not as fast as the absorbance spectra revealed by the exposure time increasing more for direct exposure than indirect exposure.After 100 s of exposure to the organic compound dye the removal had a maximun of 40%for samples with indirect exposure to the plasma and a maximum of 90%for samples with the direct exposure.For both samples,where some organic contaminants still remained in treated water,four electrolytes(KCl,Na Cl,Na_2SO_4,and CH_3COONa)were added to be effective for complete sterilization,reaching a purity of 100%.A proposal is made for an optimized thermal plasma water purification system(TPWPS)to improve fast inactivation of microbes and the degradation of organic compounds dissolved in water(especially for direct exposure rather than indirect exposure)using a hybrid plasma torch with an electrical power of 125 kW(500 V–250 A)producing a high-temperature(10 000 K–19 000 K)plasma jet with a maximum gas consumption of 28 mg s~(-1).     

因子分析技术在铀与CO,O2反应俄歇分析中的运用

运用因子分析技术和Multipak软件中的TFA功能对铀分别在CO和O2气氛中的俄歇谱进行了处理。分析表明,因子分析方法能有效地解决C（KLL）和U（LMM）俄歇峰中的重峰问题,并能从原始数据中剥离出纯组元;同时还清楚地表明,铀与CO在300℃作用1h后,在其表面形成了铀的碳化物（或碳氧化物）;对铀在低压氧气中的氧化反应,用因子分析技术获得了金属态和氧化态的铀元素随氧气暴露剂量的变化情况,清楚地显示了氧化膜生长的3个阶段。     

[99mTc(CO)3]+ labeled histidine derivative containing 4-nitroimidazole: Synthesis, biodistribution as a tumor hypoxia imaging agent

A novel histidine derivative containing 4-nitroimidazole, (S)-2-(4-((4-nitro-lH-imidazol-l-yl) methyl) benzamido) -3- (1H- imidazol-4-yl)propanoic acid (His-NI), was synthesized and labeled with [99mTc(CO)3(H2O)3]+. The tricarbonyl technetium complex, the 99mTc(CO)3-His-NI, showed a 99% yield under mild conditions at a low His-NI ligand concentration of 10-4mol·L-1, and its biodistribution in mice bearing S180 tumor had a selective accumulation in tumor (2.01±0.40 %ID/g at 1 h postinjection) and a slow clearance. The tumor/muscle ratio was 1.64 at 1 h, 3.10 at 4 h, and 3.88 at 24 h, indicating that the 99mTc(CO)3-His-NI has a potential to image tumor hypoxia.     

氢化锆表面CO2反应层XPS分析

通过X射线光电子能谱分析了经过700℃加热前后的用CO2反应法制备的氢化锆表面反应层中一定深度(100nm、200nm和300nm)的C、O和Zr的化学态,并用相对灵敏度因子法对X射线光电子能谱分析结果进行了计算分析.结果表明:700℃加热前的膜层中含有C、O和Zr以及C-H键和-OH键;经过700℃加热以后,氢化锆表面氢渗透阻挡层中不仅有C-H键和-OH键,而且还出现了-COOH,与H结合的C、O量增大.     

Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor.The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis.The parameters influencing the thermal stress in the sputter process are analyzed,such as coating and substrate properties,temperature and Young's modulus.This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness,temperature and Young's modulus.However,this relationship is inversed with coating thickness.In addition,the rough substrate surface can increase the thermal stress in the process of coating deposition.The adhesive strength between the coating and the substrate is evaluated by the shear stress.Due to the higher compressive shear stress,the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating.Furthermore,the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.     

Hydrophobic coating of surfaces by plasma polymerization in an RF plasma reactor with an outer planar electrode: synthesis,characterization and biocompatibility

This paper presents the plasma polymerization of poly(hexafluorobutyl acrylate)(PHFBA) thin films on different substrates in an RF plasma reactor with an outer planar electrode. This reactor configuration allows?large area uniformity and fast processing times. Deposition rates of up to60 nm min-1were observed. The influence?of plasma power and substrate temperature on the?deposition rate, structure and wettability of the as-deposited films was?investigated. It was observed that better hydrophobicity was obtained at high plasma power and in low temperature conditions. PHFBA thin films deposited on electrospun poly(acrylonitrile) fiber mats under such conditions resulted in superhydrophobic surfaces with?contact angle values greater than 150°.In?vitro cell studies using human epithelial cells demonstrated the non-toxic nature of the?plasma-polymerized PHFBA films.     

不同LET辐射对HepG2肝癌细胞的辐射敏感性与周期阻滞的影响

本工作研究不同LET射线辐照对HepG2肝癌细胞辐射敏感性、周期进程和凋亡的影响,为重离子治疗癌症的临床应用积累基础数据.以0、0.5、1、2、4、8Gy剂量的12C6 离子及X射线分别照射处于指数生长期的HepG2细胞,用克隆形成率测定细胞辐射敏感性,通过流式细胞术测定细胞DNA含量以确定各时相细胞的比例及细胞凋亡情况.实验结果显示,12C6 离子辐照所致的HepG2细胞存活率明显低于X射线.随着吸收剂量的增加和修复时间的延长,12C6 离子能导致更显著的细胞S期阻滞、G2/M期阻滞延迟和细胞凋亡.说明与X射线相比,12C6 离子辐照能更有效地杀伤HepG2肝癌细胞并诱导其凋亡.     

Application of dielectric barrier discharge (DBD) plasma packed with glass and ceramic pellets for SO2 removal at ambient temperature: optimization and modeling using response surface methodology

Air pollution is a major health problem in developing countries and has adverse effects on human health and the environment. Non-thermal plasma is an effective air pollution treatment technology. In this research, the performance of a dielectric barrier discharge (DBD) plasma reactor packed with glass and ceramic pellets was evaluated in the removal of SO₂ as a major air pollutant from air in ambient temperature. The response surface methodology was used to evaluate the effect of three key parameters (concentration of gas, gas flow rate, and voltage) as well as their simultaneous effects and interactions on the SO₂ removal process. Reduced cubic models were derived to predict the SO₂ removal efficiency (RE) and energy yield (EY). Analysis of variance results showed that the packed-bed reactors (PBRs) studied were more energy efficient and had a high SO₂ RE which was at least four times more than that of the non-packed reactor. Moreover, the results showed that the performance of ceramic pellets was better than that of glass pellets in PBRs. This may be due to the porous surface of ceramic pellets which allows the formation of microdischarges in the fine cavities of a porous surface when placed in a plasma discharge zone. The maximum SO₂ RE and EY were obtained at 94% and 0.81 g kWh⁻¹, respectively under the optimal conditions of a concentration of gas of 750 ppm, a gas flow rate of 2 l min⁻¹, and a voltage of 18 kV, which were achieved by the DBD plasma packed with ceramic pellets. Finally, the results of the model's predictions and the experiments showed good agreement.     

α/γ相比率调控对超音速等离子喷涂Al2O3阻氚涂层微结构及性能的影响

采用超音速等离子喷涂技术在中国低活化马氏体钢表面制备不同α/γ相比率的Al₂O₃阻氚涂层,研究了α/γ相比率调控对Al₂O₃涂层微观结构、力学性能和耐电化学腐蚀性能的影响。利用掠入射X射线衍射（GIXRD）和扫描电子显微镜（SEM）表征Al₂O₃涂层的微观结构、粘结拉伸试验法和纳米压痕仪表征涂层的力学性能、动电位极化曲线法测试涂层的耐电化学腐蚀性能。研究结果显示：通过调控特征喷涂参数（CPSP）,Al₂O₃涂层中α相含量从78.6%至24.4%可控调节,且孔隙率从2.8%降低至1.5%;α相含量为78.6%的Al₂O₃涂层硬度为(11.500±0.575) GPa,约为高γ相含量(75.6%)涂层的2倍;且高α相含量(78.6%)涂层的腐蚀电流密度较高γ相含量(75.6%)涂层的腐蚀电流密度低1个数量级。以上结果表明,高α相含量(78.6%)的Al₂O₃涂层具有更优异的力学性能、耐电化学腐蚀性能以及耐Cl^-扩散穿透能力,具有应用于聚变堆结构材料表面阻氚涂层的潜能。