Microstructures,mechanical properties and corrosion resistance of sprayed Ca–P coating for micropatterning carbon/carbon substrate surface

Carbon/carbon (C/C) surface micropatterning is a method of modifying the surface into the complete and regular geometry. In this work, we introduce a positive effect on bonding strength between sprayed Ca–P coating and surface micropatterning C/C substrate. Interestingly, C/C substrate coated by Ca–P coating provides textured surface for a new bone ingrowth. The sprayed Ca–P coating is then subjected to microwave-hydrothermal (MH) treatment with the aim of eliminating surface defects and obtaining a uniform purity phase. These objectives were achieved in our previous study by the MH method. The molar ratio of Ca/P in the coatings is nearly close to 1, which is far below that of Ca/P for hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA, 1.67). The purpose of this article is to transform the phases in the sprayed Ca–P coating, which owns the better bioactivity and high corrosion resistance. In order to raise the molar ratio of Ca/P, the coatings are treated under high-temperature (around 700 °C). They are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and a fourier transform infrared spectra (FTIR). The bonding strength (coating/substrate), biological activity and corrosion resistance of the coatings are investigated. The resulting coatings own the different microstructures and phase compositions from the original sprayed Ca–P coating. Especially, results show that the shear strength of the sprayed Ca–P coating deposited on surface micropatterning C/C substrate increases by 61% which is more than that of the coating on non-surface micropatterning C/C substrate. Additionally, high-temperature treated coating presents a good biological activity and an excellent corrosion resistance of current density (1.3078 × 10^-6 A/cm²) and potential (−0.17 V_SCE).     

超音速大气等离子喷涂TiB2-SiC涂层的抗氧化性及耐熔盐腐蚀性能

采用超音速大气等离子喷涂制备全包覆TiB₂-SiC涂层,研究了TiB₂-SiC涂层在400和800 ℃的氧化性能,并探究其氧化机理。对TiB₂-SiC涂层在900 ℃下的抗铝熔盐腐蚀性能进行研究,并探讨其耐熔盐腐蚀机理。结果表明,超音速大气等离子喷涂制备的TiB₂-SiC涂层具有良好的抗氧化性,在400 ℃的氧化速率常数为1.92×10^-5 mg²·cm^-4·s^-1,在800 ℃的氧化速率常数为1.82×10^-4 mg²·cm^-4·s^-1。超音速大气等离子喷涂制备的TiB₂-SiC涂层在900 ℃下具有良好的抗熔盐腐蚀性能,熔盐腐蚀后TiB₂-SiC涂层都保持致密结构,未发生涂层的开裂及剥落。     

Effect of Y2O3 on the oxidation properties of ZrSi2/SiC coating prepared by SAPS on the carbon-carbon composites

In order to improve the oxidation resistance of carbon-carbon (C/C) composites at high temperature, different content of Y₂O₃ modified ZrSi₂/SiC coating for C/C composites were prepared by pack cementation and supersonic atmosphere plasma spraying (SAPS). Microstructure observation and phase identification of the coatings were analyzed by SEM, XRD, DSC/TG and EDS. Experimental results shown that the coating with 10?wt% Y₂O₃ effectively protected C/C composites from oxidation at 1500?°C in air for 301?h with a mass loss of 0.13% and experienced 18 thermal shock times from room temperature (RT) to 1500?°C. First, Y₂O₃ could restrain the phase transition of ZrO₂ to reduce the formation of thermal stresses of the coating; second, the random distribution of ZrO₂ ceramic particles and the formation of ZrSiO₄ enhanced the stability of the SiO₂; third, the formation of Y₂Si₂O₇ and Y₂SiO₅ could relieve the thermal mismatch between ZrSi₂-Y₂O₃ outer layer and the inner layer.     

A comparison of hydrogen storage technologies for solar-powered stand-alone power supplies: A photovoltaic system sizing approach

This paper compares the performance of three different solar based technologies for a stand-alone power supply (SAPS) using different methods to address the seasonal variability of solar insolation—(i) photovoltaic (PV) panels with battery storage; (ii) PV panels with electrolyser and hydrogen (_H2)$({\mathrm{H}}_2)$ storage; and (iii) photoelectrolytic (PE) dissociation of water for _H2${\mathrm{H}}_2$ generation and storage. The system size is determined at three different Australian locations with greatly varying latitudes—Darwin (12^°S${12}^{°}\mathrm{S}$), Melbourne (38^°S${38}^{°}\mathrm{S}$) and Macquarie Island (55^°S${55}^{°}\mathrm{S}$). While the PV/electrolyser system requires fewer PV panels compared to the PV/battery scenario due to the seasonal storage ability of _H2${\mathrm{H}}_2$, the final number of PV modules is only marginally less at the highest latitude due to the lower energy recovery efficiency of _H2${\mathrm{H}}_2$ compared to batteries. For the PE technology, an upper limit on the cost of such a system is obtained if it is to be competitive with the existing PV/battery technology.     

SUB-OPTIMAL MASK SEARCH IN SAPS

Abstract

In this paper, a new and very simple algorithm for mask search in SAPS (System Approach Problem Solver) is introduced to illustrate a sub-optimal approach. It is intended to be used as an alternative of the optimal mask optimization present in previous versions of SAPS.

The algorithm described in this paper illustrates the general use of non-optimal search strategies. It is based on the hill-climbing strategy and as such it is not exponential as in all known previous versions of SAPS, but polynomial in nature. This results in an improved executing speed; very complex systems that were intractable with previous versions of SAPS can be handled with additional flexibility. The previous (exponential) algorithm is also implemented. Hence, comparisons and benchmarks are possible because of the same object-oriented environment. The main focus in this paper will lie on the justification for sub-optimal mask search techniques and its illustration with the algorithm     

Degradation of gas-liquid gliding arc discharge on Acid Orange II

The effects of pH value, initial concentration of dye solution and temperature on the degradation efficiency of Acid Orange II (AO7) using gas-liquid gliding arc discharge were investigated. The influences of pH value and temperature on degradation efficiency were not apparent. Increasing initial solution concentration caused the decrease of degradation rate and the increase of absolute degradation quantity. Considering energy efficiency and absolute degradation quantity, the gas-liquid gliding arc discharge is fit for treating high concentration organic wastewater. A possible mineralization pathway was proposed through the analysis of intermediate products detected by gas chromatograph coupled with mass spectrophotometer (GC-MS) and ion chromatograph (IC). Hydroxyl radicals reacted with the azo linkage-bearing carbon of a hydroxy-substituted ring, leading to the cleavage of -C-N- and degradation of AO7. The solution biodegradability was significantly improved (BOD(5)/COD from 0.02 to 0.43). The toxicity of intermediate products was lower than that of the initial Acid Orange II.     

Treatment of acidic coal mine drainage: design and operational challenges of successive alkalinity producing systems

Successive alkalinity producing systems (SAPS) provide a popular bioremediation alternative to anoxic limestone drains for acid mine drainage treatment. This paper reviews the designing of SAPS and then discusses the performance of an existing SAPS-based system in Hanchang coal mine of Kangwon province of Korea. The results indicate that sulfate reduction ceased in the VFR within the first year of operation, implying that metal hydroxide precipitation and adsorption prevailed over metal sulfide formation and precipitation.     

超音速等离子喷涂抗冲蚀 7YSZ 热障涂层

针对热障涂层在航空发动机低压涡轮导向叶片上应用时易发生冲蚀的问题,使用超音速等离子喷涂(SAPS)方法制备了7%氧化钇稳定氧化锆(7YSZ)热障涂层,对比普通等离子喷涂7YSZ涂层进行了研究。结果表明SAPS涂层熔化效果更好、微观结构更致密且呈小孔隙弥散分布。涂层的结合力、显微硬度、抗热震性能和抗高温冲蚀效果更好。两种涂层的隔热性能在薄涂层时(厚度150μm)相差不大,在厚度达到200μm时SAPS涂层会有降低。     

A comparison of PV/electrolyser and photoelectrolytic technologies for use in solar to hydrogen energy storage systems

The approach of using hydrogen for an energy store to offset seasonal variations in solar energy is one very much at the periphery of current renewable energy system design. Nonetheless, its inherent advantages for long term storage in stand alone power systems warrant further detailed investigation. This paper provides a comparative overview of the very disparate technologies within two generic approaches to achieving this goal. These are: photovoltaic (PV) powered electrolysis of water and direct photoelectrolytic (PE) generation of hydrogen from water. Comparison of these is difficult, however, the paper compares devices of similar material system and structure within each generic scheme. PV/electrolysis is the more mature technology but there is still a wide range of potential ‘solar to hydrogen’ efficiencies. A figure of about 9% is estimated for comparison, with justification given. The comparative figure for PE is more difficult to judge because of even more disparate approaches to specific problems of sufficient photovoltage and stability, but an approximate comparative figure of 5% is estimated. Thus making PV/electrolysis more appropriate at present. Nonetheless, inherent advantages of simplicity of system design and potential robustness mean that PE may become more appropriate as the technology develops.     

等离子喷涂致密La0.6Sr0.4Co0.2Fe0.8O3-δ透氧膜氧传输行为的研究

本文采用超音速等离子喷涂(SAPS)和等离子物理气相沉积方法(PS-PVD)制备了结构致密的钙钛矿型(ABO₃)La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(LSCF)透氧膜。利用氧程序升温脱附(O₂-TPD)、XPS等手段,比较了两种膜在200-900℃间氧物种在表面及体相中的传递变化情况。O₂-TPD结果显示：SAPS膜的物理吸附氧脱附量、化学吸附氧脱附量和晶格氧脱附量分别超过PS-PVD膜的2倍、3倍和6倍;而XPS结果显示：SAPS膜表面吸附氧与晶格氧O1s峰面积比也高于PS-PVD膜。以上结果表明SAPS膜对氧具有更好的吸附及解离能力、更多的本征氧空位及更高的空位生成能力。