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31.
Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O3 at high pH, 03/H202, O3/UV and H2O2/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O3/UV process, the effect of the H202:03 ratio in the O3/H2O2 process, and the impact of the low extinction coefficient of H2O2 in the H202/UV process. 相似文献
32.
A novel micromachined single wall carbon nanotube (SWCNT) reinforced nanocrystalline tin dioxide gas sensor has been developed. The presence of SWCNT in SnO2 matrix was realized by a spin-on sol–gel process. The SWCNT/SnO2 sensor's sensitivity for hydrogen detection has greatly increased by a factor of three, in comparison to that of pure SnO2 sensor. The novel sensor also lowers the working temperature, response time and recovery time. The greatly improved performances are mainly attributed to the effective gas accessing nano passes through SWCNT plus the smaller distance between adjacent gas accessing boundaries formed by the distribution of tiny SWCNTs. Therefore, both the spatial requirement (D ≤ 2L, D is the distance between adjacent gas accessing boundaries and L is the space charge layer thickness) and surficial requirement (adequate gas activation area) are met and the maximum inherent sensitivity of SnO2 is achieved. 相似文献
33.
新能源制氢系统是提升风能、太阳能等新能源发电消纳的有效途径。目前国内外关于电解槽能量管理的相关研究以单电解槽为主。单电解槽能量管理未考虑电解槽非线性的工作特性,难以兼顾多个电解槽制氢效率,影响系统经济性。论文针对含有多电解槽新能源制氢系统的能量管理问题进行了研究。以新能源消纳率、经济收益、制氢率为目标,考虑单个电解槽运行特性及生产约束等条件,建立包含风电、光伏、蓄电池、电解槽多个模块的能量管理优化模型,并采用SPEA2算法求解多目标优化问题。仿真研究表明,所提能量管理策略能够实现新能源发电的100%消纳,单位制氢效益可提升5.15%。因此,多电解槽制氢系统进行有效的能量管理有助于提高制氢效率,有效克服单电解槽运行及能量管理的不足。 相似文献
34.
The effects of alloy 718 microstructure on hydrogen embrittlement susceptibility and tensile fracture mode were assessed through slow strain rate tensile testing and fracture surface analysis. Alloy 718 was annealed and aged to produce microstructures with variations in grain size and amount of grain boundary precipitates. Furthermore, the different ageing conditions likely resulted in differences in volume fractions and sizes of γ′ and γ′′ precipitates. The extent of grain boundary precipitation had the strongest effect on hydrogen embrittlement susceptibility, while grain size did not have any significant effect. Hydrogen embrittlement susceptibility was also correlated with differences in strength level, which was primarily controlled by the γ′ and γ′′ precipitate populations. 相似文献
35.
《材料科学技术学报》2019,35(10):2213-2219
The effect of grain size (in the range from 4 μm to 12 μm) on the hydrogen embrittlement (HE) of 304 austenitic stainless steel (ASS) was studied. HE susceptibility result shows that HE resistance increases with grain refinement. Electron backscattered diffraction kernel average misorientation (EBSD-KAM) mapping shows that the strain localization can be mitigated by grain refinement. Hence, strain localization sites which act as highways for hydrogen diffusion and preferred crack initiation sites can be reduced along with grain refinement, leading to a high HE resistance. Meanwhile, grain size shows no influence on the strain induced martensite (SIM) transformation during the hydrogen charging slow strain tensile test (SSRT). Hence, the SIM formed during hydrogen charging SSRT is not responsible for the different HE resistance of 304 ASSs with various grain sizes. Hydrogen diffusion is supposed to be controlled by a competition between short-circuit diffusion along random grain boundary (RGB) and hydrogen trapping at dislocations, leading to a maximum hydrogen diffusion coefficient in the 304 ASS with an average grain size of 8 μm. 相似文献
36.
D. ZilliAuthor VitaeP.R. BonelliAuthor Vitae A.L. CukiermanAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(1):169-176
Multi-walled carbon nanotubes (MWCNTs) are successfully processed in the form of thin films (buckypapers), and their morphology and electrical behaviour are characterized. The MWCNTs are synthesized by the floating catalyst chemical vapour deposition process. The effects of a sequence of treatments applied for MWCNTs purification on the buckypapers electrical behaviour are also examined. Nanocomposite thin films constituted of pristine and purified MWCNTs and Pd nanoparticles are prepared in order to evaluate their viability as H2 sensors at room temperature. For this purpose, the electrical resistance of the nanocomposite films in atmospheres with different H2 concentrations, is determined. Scanning electron microscopy (SEM) images show that the buckypapers and the nanocomposite films are 2D structures constituted by randomly oriented MWCNTs. The buckypapers present a semiconductor-like electrical behaviour as determined by the standard four point method. Room temperature resistivity values of around 10−3 Ω m are assessed. Nanocomposite films show different electrical behaviour depending on the purification treatment applied to the MWCNTs employed. Furthermore, the electrical resistance of the nanocomposite films is found to increase when the measurements are performed in H2 atmosphere. Values of H2 sensitivity at room temperature of the nanocomposite films up to 2.15% are determined for H2 average concentration higher than 350 ppm with short recovery time. 相似文献
37.
R. ThangamuthuAuthor VitaeYu-Ching PanAuthor Vitae Shen-Ming ChenAuthor Vitae 《Sensors and actuators. B, Chemical》2011,151(2):377-383
The present work describes the electrocatalytic behavior of phosphotungstate-doped glutaraldehyde-cross-linked poly-l-lysine (PLL-GA-PW) film electrode towards reduction of hydrogen peroxide (H2O2) in acidic medium. The modified electrode was prepared by means of electrostatically trapping the phosphotungstate anion into the cationic PLL-GA coating on glassy carbon electrode. The PLL-GA-PW film electrode showed excellent electrocatalytic activity towards H2O2 reduction in 0.1 M H2SO4. Under the optimized conditions, the electrochemical sensor exhibited a linear response for H2O2 concentration over the range 2.5 × 10−6 to 6.85 × 10−3 M with a sensitivity of 1.69 μA mM−1. The curvature in the calibration curve at high concentration is explained in terms of Michaelis-Menten (MM) saturation kinetics, and the kinetics parameters calculated by three different methods were compared. The PLL-GA-PW film electrode did not respond to potential interferents such as dopamine, ascorbic acid and uric acid. This unique feature of PLL-GA-PW film electrode allowed selective determination of H2O2. Finally, the proposed electrochemical sensor was successfully applied to determine H2O2 in commercially available antiseptic solution and soft-contact lenses cleaning solution and the method has been validated using independent estimation by classical potassium permanganate titration method. Major advantages of the method are simple electrode fabrication, stability and high selectivity towards hydrogen peroxide. 相似文献
38.
Da ChenAuthor Vitae Jing Jing WangAuthor VitaeDe Hua LiAuthor Vitae Yan XuAuthor Vitae 《Sensors and actuators. B, Chemical》2011,159(1):234-237
We present an application of the Pd-functionalized film bulk acoustic resonator for hydrogen detection. The resonator consisted of an AlN piezoelectric stack and a Bragg reflector has a working resonance near 2.23 GHz and a high performance. A 50 nm thick Pd film was coated on the top electrode as a specific layer to capture hydrogen. The absorption of hydrogen can trigger changes of elastic properties of the Pd layer, which affects the resonance frequency of the resonator. The experimental results show that the Pd-functionalized film bulk acoustic resonator can yield a rapid, sensitive, reversible and reproducible response to hydrogen in the concentrations from 0.3% to 2%. The advantages of this sensor, including the simple fabrication process, ease of detection method, rapid response and high sensitivity and working at room temperature, make this promising in the early alarm of hydrogen leaking. 相似文献
39.
This paper investigates the use of artificial intelligent models as virtual sensors to predict relevant emissions such as
carbon dioxide, carbon monoxide, unburnt hydrocarbons and oxides of nitrogen for a hydrogen powered car. The virtual sensors
are developed by means of application of various Artificial Intelligent (AI) models namely; AI software built at the University
of Tasmania, back-propagation neural networks with Levenberg–Marquardt algorithm, and adaptive neuro-fuzzy inference systems.
These predictions are based on the study of qualitative and quantitative effects of engine process parameters such as mass
airflow, engine speed, air-to-fuel ratio, exhaust gas temperature and engine power on the harmful exhaust gas emissions. All
AI models show good predictive capability in estimating the emissions. However, excellent accuracy is achieved when using
back-propagation neural networks with Levenberg–Marquardt algorithm in estimating emissions for various hydrogen engine operating
conditions with the predicted values less than 6% of percentage average root mean square error. 相似文献
40.
Self-association (i.e. interchain aggregation) behavior of atactic poly(ethacrylic acid) PEA in dilute aqueous solution as function of degree-of-neutralization by Na+ counter-ions (i.e. charge fraction f) was investigated by molecular dynamics simulations. Aggregation is found to occur in the range 0 ≤ f ≤0.7 in agreement with experimental results compared at specified polymer concentration Cp = 0.36 mol/l in dilute solution. The macromolecular solution was characterized and analysed for radius-of-gyration, torsion angle distribution, inter and intra-molecular hydrogen bonds, radial distribution functions of intermolecular and inter-atomic pairs, inter-chain contacts and solvation enthalpy. The PEA chains form aggregate through attractive inter-chain interaction via hydrogen bonding, in the range f < 0.7, in agreement with experimental observation. The numbers of inter-chain contacts decreases with f. A critical structural transition occurs at f = 0.7, observed via simulations for the first time, in Rg as well as inter-chain H-bonds. The inter-chain distance increases with f due to repulsive interactions between COO− groups on the chains. PEA-PEA electrostatic interactions dominant solvation enthalpy. The PEA solvation enthalpy becomes increasingly favorable with increase in f. The transition enthalpy change, in going from uncharged (acid) state to fully charged state (f = 1) is unfavorable towards aggregate formation. 相似文献