Evaluation of Vaporized Hydrogen Peroxide Fumigation as a Method for the Bio-decontamination of the High Efficiency Particulate Air Filter Unit

Objective To evaluate the performance of vaporized hydrogen peroxide （VHP） for the bio-decontamination of the high efficiency particulate air （HEPA） filter unit. Methods Self-made or commercially available bioindicators were placed at designated locations in the HEPA filter unit under VHP fumigation. The spores on coupons were then extracted by 0.5 h submergence in eluent followed by 200- time violent knocks. Results Due to the presence of HEPA filter in the box, spore recovery from coupons placed at the bottom of the filter downstream was significantly higher than that from coupons placed at the other locations. The gap of decontamination efficiency between the top and the bottom of the filter downstream became narrower with the exposure time extended. The decontamination efficiency of the bottom of the filter downstream only improved gently with the injection rate of H202 increased and the decontamination efficiency decreased instead when the injection rate exceeded 2.5 g/min. The commercially available bioindicators were competent to indicate the disinfection efficiency of VHP for the HEPA filter unit. Conclusion The HEPA filter unit is more difficult than common enclosure to decontaminate using VHP fumigation. Complete decontamination can be achieved by extending fumigation time. VHP fumigation can be applied for in-situ biodecontamination of the HEPA filter unit as an alternative method to formaldehyde fumigation.

Electrocatalytic Activity of Ni/C Electrodes Prepared by Metal Vapor Synthesis For Hydrogen Evolution in Alkaline Solution

The metal vapor synthesis (MVS) methed was used to prepare activatedcarbon supported nickel electrode. The electrocatalytic activity of the electrode forhydrogen evolution reaction(HGR) in alkaline solution was studied. Cathodicpolarization curves showed the electrocatalytic activity of Ni/C electrode prepared byMVS method was higher than that of the one prepared by conventional method.

Identification of Model Parameters of Vaporized Hydrogen Peroxide Decomposi-tion Flux on Building Materials for Compu-tational Fluid Dynamics

To maintain healthy and sanitary indoor air quality, development of effective decontamination measures for the indoor environment is important and hydrogen peroxide is often used as decontamination agent in healthcare environment. In this study, we focused on the decomposition phenomena of vaporized hydrogen peroxide on wall surfaces in indoor environment and discussed a wall surface decomposition model for vaporized hydrogen peroxide using computational fluid dynamics to simulate the concentration distributions of vaporized hydrogen peroxide. A major drawback to using numerical simulations is the lack of sufficient data on boundary conditions for various types of building materials and hence. We also conducted the fundamental chamber experiment to identify the model parameters of wall surface decomposition model for targeting five types of building materials.

Smooth Surface Morphology of Hydrogenated Amorphous Silicon Film Prepared by Plasma Enhanced Chemical Vapor Deposition

Influence of the parameters of plasma enhanced chemical vapor deposition （PECVD） on the surface morphology of hydrogenated amorphous silicon （α-Si：H） film was investigated. The root-mean-square （RMS） roughness of the film was measured by atomic force microscope （AFM） and the relevant results were analyzed using the surface smoothing mechanism of film deposition. It is shown that an α-Si：H film with smooth surface morphology can be obtained by increasing the PH3/N2 gas flow rate for 10% in a high frequency （HF） mode. For high power, however, the surface morphology of the film will deteriorate when the Sill4 gas flow rate increases. Furthermore, optimized parameters of PECVD for growing the film with smooth surface were obtained to be Sill4：25 sccm （standard cubic centimeters per minute）, At： 275 sccm, 10%PH3/N2：2 sccm, HF power： 15 W, pressure： 0.9 Torr and temperature： 350℃. In addition, for in thick fihn deposition on silicon substrate, a N20 and NH3 preprocessing method is proposed to suppress the formation of gas bubbles.

Selective Area Growth and Characterization of GaN Nanorods Fabricated by Adjusting the Hydrogen Flow Rate and Growth Temperature with Metal Organic Chemical Vapor Deposition

CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.

Synthesis of Carbon Nanotubes by Catalytic Chemical Vapor Deposition Using Hydrogen Storage Alloy as A Catalyst

Carbon nanotubes (CNTs) were synthesized by catalytic chemical vapor deposition and using the alkali-reducing pretreated hydrogen storage alloy (MlNi(4.0)Co(0.6)Al(0.4)) powder as a catalyst. It was found that the surface modification of the alloy was effective to provide the catalytic active sires for CNTs growth. The Ni- and Go-clusters on the surface of the treated alloy were dominant for the growth of CNTs. The composite of CNTs with the hydrogen storage alloy has the potential to be used as a new type of hydrogen storage material without further purification.

Formation and Transport of Atomic Hydrogen in Hot-Filament Chemical Vapor Deposition Reactors

In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant is hydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers for heat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phase heat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature and H concentration distributions between the filament and the substrate. Examination of the relative importance of homogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecular hydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociation rates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the literature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociation rates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lower effective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heat transfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.

Study of filament performance in heat transfer and hydrogen dissociation in diamond chemical vapor deposition

Hot-filament chemical vapor deposition ( HFCVD) is a promising method for commercial production of diamond films. Filament performance in heat transfer and hydrogen decomposition in reactive environment was investigated. Power consumption by the filament in vacuum, helium and 2% CH4/H2 was experimentally determined in temperature range 1300℃-2200℃. Filament heat transfer mechanism in C-H reactive environment was calculated and analyzed. The result shows that due to surface carburization and slight carbon deposition, radiation in stead of hydrogen dissociation, becomes the largest contributor to power consumption. Filament-surface dissociation of H2 was observed at temperatures below 1873K, demonstrating the feasibility of diamond growth at low filament temperatures. The effective activation energies of hydrogen dissociation on several clean refractory flaments were derived from power consumption data in literatures. They are all lower than that of thermal dissociation of hydrogen revealing the nature of catalytic dissociation of hydrogen on filament surface. Observation of substrate temperature suggested a weaker role of atomic hydrogen recombination in heating substrates in C-H environment than in pure hydrogen.

塔什库尔干河流域河谷大气降水同位素特征与水汽输送路径

利用塔什库尔干河流域河谷2018年9月—2020年5月的降水事件的大气降水同位素数据,以及流域河谷代表性气象站点温度、降水、相对湿度等气象资料,分析降水中δ^(18)O、δ^(2)H和氘盈余(d-excess)变化特征,探讨影响因素,并基于拉格朗日后向轨迹模型(HYSPLIT)追踪解析流域河谷大气降水的水汽输送路径。结果表明:(1)降水δ^(2)H、δ^(18)O值总体上呈现夏季富集、冬季贫化的季节变化特征,且具有显著的温度效应(1.33‰·℃^(-1)),但未见显著雨量效应;(2)局地大气降水线方程为δ^(2)H=7.63δ^(18)O-3.55,呈现出显著的干旱气候特征;(3)HYSPLIT模拟结果表明研究流域降水水汽主要受西风环流和局地水汽再循环影响,其中夏半年局地水汽蒸发占比54.09%,冬半年西方路径中较长距离输送占比45.53%。8月源自印度洋的水汽可绕过青藏高原到达研究区域。成果可为塔什库尔干河流域水资源管理和气候应对提供参考依据。

温湿度对燃料电池质子膜气体透过率的影响

燃料电池质子膜的气体渗透不仅会降低燃料电池的燃料利用率,还会直接影响燃料电池的性能和使用寿命,因此气体透过率成为评价膜性能的重要指标。为模拟电池膜运行条件下的氢气渗透状况,提高电池膜气体渗透检测效率,采用压差法-气相色谱仪联用技术以及电磁加热-水蒸气增湿手段对不同型号的燃料电池质子膜进行氢气透过率测试,研究了不同温度、湿度条件对燃料电池质子膜氢气透过率的影响。同时,气相色谱选用耐水解型色谱柱,同步实现了不同温、湿度条件下水蒸气透过率的检测。结果表明,温度对燃料电池质子膜氢气透过率有显著影响。不同型号燃料电池膜的氢气透过率均随温度的上升呈指数型增长。在较低温度下,相对湿度与氢气透过率呈线性依赖。高温条件下氢气透过率随湿度升高而增长的趋势变缓。在不同温湿度条件下,水蒸气的渗透与氢气渗透的变化规律相似,随温度和湿度升高而增长。通过多种技术串联,建立相对完善的燃料电池膜氢气渗透检测体系,实现不同气体的同步检测,弥补国标测试方法的不足。

增强物理交联提升聚乙烯醇耐湿耐热性能

利用玉米淀粉(CS)和桃胶(PG)协同改性聚乙烯醇(PVA)法,制备了PVA/CS/PG复合膜,考察了PVA分子量、不同CS添加量以及PG添加量(在相同CS添加量条件下)对PVA/CS/PG复合膜耐湿、耐热性能的影响。结果表明:CS与PG的羟基与PVA发生了氢键相互作用,PVA/CS/PG复合膜的晶粒尺寸减小,交联密度增加。同时,随着CS和PG含量的增加,复合膜的网格尺寸逐渐减小,热稳定性能提升。水蒸气透过测试表明,当w(CS)=2%和w(PG)=2%时,PG/CS/PVA复合膜含水率较未处理原膜提升了11.5%,水蒸气透过率下降了43%。

液氢贮罐内过热蒸气不同质量流量泄放过程模拟

以液氢工厂中贮存液氢的液氢贮罐为研究对象,选择液氢、气液相界面、蒸气三个区域合适的控制方程,建立了可模拟从自增压到泄放后回到初始压力过程的三区模型。模拟了充液率为50%的10 m3液氢贮罐从自增压-泄放后回到初始压力的周期过程。在特定泄放时间,不同泄放质量流量条件下,对比了液氢贮罐内贮罐压力、饱和液氢和过热蒸气的质量流量和温度以及液氢体积随时间的变化特性。结果表明:泄放过热蒸气质量流量大小随泄放时间增大不断减小;泄压时间越短,泄放后过热蒸气温度越接近初始温度;进入泄放阶段,蒸发液氢质量流量发生了明显激增,增大幅度随泄放时间增大而减小。

过氧化氢气体检测仪校准技术初探

过氧化氢气体具有优异的灭菌效果,被广泛应用于各行各业,但其检测仪缺乏有效校准技术和方法。由于该气体稳定性较差,因此,本文根据各种应用条件下的浓度限值规定、传感器类型和量程,分析了校准技术的不足,研制了过氧化氢气体高效动态校准装置,并进行实验验证。结果表明:标准装置的示值误差较小,可为该检测仪的校准技术提供参考。

Structural evolution and optical characterization in argon diluted Si:H thin films obtained by plasma enhanced chemical vapor deposition

The structural evolution and optical characterization of hydrogenated silicon(Si:H) thin films obtained by conventional radio frequency(RF) plasma enhanced chemical vapor deposition(PECVD) through decomposition of silane diluted with argon were studied by X-ray diffractometry(XRD),Fourier transform infrared(FTIR) spectroscopy,Raman spectroscopy,transmission electron microscopy(TEM),and ultraviolet and visible(UV-vis) spectroscopy,respectively.The influence of argon dilution on the optical properties of the thin films was also studied.It is found that argon as dilution gas plays a significant role in the growth of nano-crystal grains and amorphous network in Si:H thin films.The structural evolution of the thin films with different argon dilution ratios is observed and it is suggested that argon plasma leads to the nanocrystallization in the thin films during the deposition process.The nanocrystallization initiating at a relatively low dilution ratio is also observed.With the increase of argon portion in the mixed precursor gases,nano-crystal grains in the thin films evolve regularly.The structural evolution is explained by a proposed model based on the energy exchange between the argon plasma constituted with Ar* and Ar+ radicals and the growth regions of the thin films.It is observed that both the absorption of UV-vis light and the optical gap decrease with the increase of dilution ratio.

不同剂量汽化过氧化氢和消毒时间对A2生物安全柜消毒效果的研究

过氧化氢是一种高效的消毒剂,对结构比较复杂的生物安全柜通过汽化过氧化氢进行消毒是目前首选的方法。然而在不同的消毒条件下,消毒剂的使用剂量和消毒时间是消毒效果的主要因素。文章通过使用不同剂量的过氧化氢,利用特定汽化设备进行汽化,在不同消杀时间的条件下,用嗜热脂肪芽孢杆菌作为生物指示剂,探索对A2生物安全柜的消毒情况进行探索。通过本实验研究,得到了有效消毒A2生物安全柜的汽化过氧化氢的使用剂量和消毒时间,这为规范进行A2生物安全柜的有效消毒提供参考值,保证生物安全柜的使用安全。

耦合蒸气冷却屏的真空多层绝热结构对液氢储罐自增压过程的影响机制研究

基于MATLAB,构建了一种考虑氢储罐真空多层绝热结构、蒸气冷却屏和内部流体域的瞬态仿真模型。引入了无量纲的蒸气消耗因子η_(c)、休眠期延长因子η_(s)和单位因子η,η_(c)代表冷却屏在储存全周期蒸气的消耗量,η_(s)代表采用冷却屏时休眠期相对于未采用时休眠期的延长量,η是η_(s)与η_(c)的比值,代表冷却屏屏蔽漏热的能力。研究了冷却屏的无量纲位置、η_(c)、流量和开启时刻对η_(s)和η的影响。结果表明,在冷却屏开启时段不变时,使得η_(s)最大化的冷却屏最佳位置是0.622;当冷却屏位置是0.622,η_(c)从0.0640降至0.0128,η增大34.7%,但是当冷却屏的设置偏离最佳位置越远,降低η_(c)使得η增大的幅度越小;固定η_(c)和蒸气冷却屏的开启时长,η_(s)随着开启时刻的推迟先增大后减小,当冷却屏的位置是0.622,使η_(s)最大的开启时刻是第23.26天。

银川平原夏半年不同等级降雨水汽输送机制

全球气候变暖加速了区域水循环,改变了水汽的传输路径,了解不同等级降雨稳定同位素特征及水汽来源为水资源的利用及旱涝灾害的防治提供依据。基于2018—2020年夏半年(5—10月)采集的银川平原降雨样品,研究不同等级降雨中氢氧稳定同位素的变化特征及其二次蒸发效应,并利用后向轨迹模型及水汽通量等方法分析降雨的水汽来源及潜在蒸发源区。结果表明:银川平原夏半年不同等级降雨稳定同位素随着降雨等级的增加而偏负,小雨氘盈余(d-excess)值偏负而中雨和大雨偏正,大气降水线斜率和截距随着雨量级的增加呈现出递减的规律。二次蒸发作用的强弱随气温升高而增大,随降雨量、相对湿度和雨滴直径增大而减弱。西风水汽为银川平原夏半年降雨的主控水汽,同时小雨、中雨、大雨还分别受到陆地蒸发水汽、大西洋水汽及太平洋水汽的影响。潜在蒸发源区对小雨影响较大,主要位于研究区周边及北部、南部和东南部地区;中雨潜在蒸发源区主要分布在研究区周边地区及其西北部和东南部;大雨主要分布在研究区周边及东南部地区。

Thermodynamic Analysis of Chemical Vapor Deposition of BCl_3-NH_3-SiCl_4-H_2-Ar System

The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reactants, deposition temperature and total pressure) on the distribution regions of solid phase products were analyzed based on the diagrams. The results show that:(a) Solid phase products are mainly affected by deposition temperature. The area of BN+Si3N4 phase increases with the temperature rising from 650 to 900 ℃, and decreases with the temperature rising from 900 to 1 200 ℃;(b) When temperature and total pressure are constants, BN+Si3N4 phase exists at a high partial pressure of NH3;(c) The effect of total system pressure is correlated to deposition temperature. The temperature ranging from 700 to 900 ℃ under low total pressure is the optimum condition for the deposition.(d) Appropriate kinetic parameters can be determined based on the results of thermodynamic calculation. Si–B–N coating is obtained via low pressure chemical vapor deposition. The analysis by X-ray photoelectron spectroscopy indicates that B–N and Si–N are the main chemical bonds of the coating.

液氢储罐蒸气冷却屏多层绝热性能分析

针对液氢存储时由于与环境温差大而导致的漏热较大的问题,建立耦合蒸气冷却屏的多层绝热结构的传热模型,同时引入氢仲正转化进一步降低液氢储罐漏热,采用MATLAB自编程方法,分析多层绝热结构、仲正转化、蒸气冷却屏个数及排列方式对绝热结构性能的影响。研究结果表明:单个蒸气冷却屏的加入使多层绝热性能得到大幅提升,净热流密度最多下降61.3%,最佳屏位出现在绝热结构中心附近;氢仲正转化的加入能够使结构的绝热性能进一步提升,净热流密度最多下降11.1%;串联型蒸气冷却屏的绝热性能明显优于并联型蒸气冷却屏;当蒸气冷却屏数量由1增加至3时,净热流密度分别降低22.8%和10.9%。研究结果可为液氢储罐耦合蒸气冷却屏的多层绝热结构的设计和优化提供理论参考。