Durability issues and service lifetime prediction of electrochromic windows for buildings applications

In general, the purposes of this paper are to elucidate the crucial importance of durability and service lifetime prediction (SLP) for electrochromic windows (ECWs) and to present an outline for developing a SLP methodology for ECWs. The specific objectives are (a) to illustrate the generic nature of SLP for several types of solar energy conversion or energy conservation devices, (b) to summarize the major durability issues associated with ECWs, (c) to justify using SLP in the triad of cost, performance, and durability rather than just durability, (d) to define and explain the seven major elements that constitute a generic SLP methodology, (e) to provide background for implementing the SLP methodology for ECWs, including the complexity of the potential degradation mechanisms, and (f) to provide an outline of studies using ECWs for improving the durability of ECW materials and predicting a service lifetime for ECWs using the SLP methodology outlined in objective (d). Our major conclusions are that substantial R&Dis necessary to understand the factors that limit ECW durability, and that it is possible to predict the service lifetime of ECWs.     

纤维种类对超高性能混凝土电杆性能的影响研究

为研究聚丙烯纤维(PP纤维)、耐碱玻璃纤维(BX纤维)、钢纤维(GX纤维)对超高性能混凝土(UHPC)电杆力学性能和耐久性能的影响,在前期掺量优选试验基础上,采用卧式离心工艺成型了规格为?190×12×M×BY的UHPC电杆,并进行了力学性能和耐久性能试验.结果表明:不同纤维种类对UHPC折压比的影响从高到底依次为:G...     

Adhesion improvement of poly (vinyl alcohol) coating on silicon substrate

The adhesion of the biocompatible hydrophilic polymer, poly (vinyl alcohol) to a model substrate, silicon, was investigated. Contact angle measurements were used to reveal the effect of various substrate cleaning procedures including sonication and UV-ozone treatment prior to casting a 35 μm coating. Raman microspectrometry and X-ray reflectometry were used to characterise the composition and the thickness of PVA thin films. The use of mechanical abrasion of the substrate followed by a 131 nm primer layer of PVA in combination with vacuum treatment at temperatures higher than the glass transition temperature (T_g = 80 °C) provided the best resistance to delamination as demonstrated by visual observation during prolonged immersion of the coatings in water.     

Highly conductive alumina/NCN composites electrodes fabricated by gelcasting and reduction-sintering—An electrochemical behavior study in aggressive environments

A novel highly conductive alumina/nano-carbon network composites (alumina/NCN composites) was fabricated by gelcasting and reduction-sintering method under argon atmosphere. The electrochemical behaviors of the alumina/NCN composites were studied systematically in some aggressive solutions (HCl, H₂SO₄, HNO₃, NaOH, and KOH), using potentiodynamic polarization and chronoamperometry and X-ray diffraction and SEM observations. The results showed that the electrochemical stability and reproducibility of the composite electrodes in these diluted acids and alkalis were very good and had, in some extent, an electro-catalytic activity toward formation of hydrogen evolution and reduction of dissolved oxygen in aqueous solutions in comparison with a commercial graphite electrode. In addition, the pyrolyzed nano-carbon contents, size, and shape in the alumina matrix, have greatly effects on the electrochemical performances and electrode reactions in these solutions. It is found that the minimal residual carbon content of 0.62 wt.% in the matrix is enough to improve electrochemical performances and avoid to loss the ceramics physical properties at the same time. When the additional potential in all the tested electrolytes was at +1700 mV (vs. SCE), alumina particles at the electrode surface were not observed to dissolve into solution in this case, indicating the material being suitable for electrodes in aggressive solutions.     

Effects of a combined admixture of slag powder and thermally treated flue gas desulphurization (FGD) gypsum on the compressive strength and durability of concrete

In this paper, the effects of a combined admixture of slag powder and thermally treated flue gas desulphurization (FGD) gypsum on the compressive strength and durability of concrete were explored. The gypsum was baked at a proper temperature of 200°C for 60 min; it was then mixed with slag powder to form the type-G slag powder in which SO₃ content was controlled at the optimum ratio of 3.5%. Concretes containing the type-G slag powder or ordinary slag powder were further contrasted on the compressive strength and durability. The results showed that the compressive strength, resistance to chloride, and resistance to gas permeability of concrete with the type-G slag powder were higher than that with ordinary slag powder. Additionally, there were no negative effects on concrete against sulfate attack. The combination of the two byproducts, slag powder and thermally treated FGD gypsum, provided synergistic benefits above that of ordinary slag powder alone.     

Durability of concrete — Degradation phenomena involving detrimental chemical reactions

While interacting with its service environment, concrete often undergoes significant alterations that often have significant adverse consequences on its engineering properties. As a result, the durability of hydrated cement systems and their constituent phases has received significant attention from scientists and engineers. Cement paste deterioration by detrimental chemical reactions is discussed. First, the mechanisms that govern the transport of ions, moisture and gas are described. Then, different chemical degradation phenomena are reviewed. Microstructural alterations resulting from exposure to chlorides and carbon dioxide are discussed. Sulfate attack from external sources is described including processes resulting in the formation of ettringite and thaumasite. The mineralogy of Portland cement is sensitive to temperature and thermal cycling, particularly during the early hydration period.     

Approximate migration coefficient of percolated interfacial transition zone by using the accelerated chloride migration test

In this study, the electrochemical technique is applied to accelerate chloride ion migration in cement-based material to estimate its migration coefficient. In order to investigate the chloride migration coefficient of percolated interfacial transition zone (ITZ) on the chloride migration coefficient of specimen, specimens with cylindrical aggregates of the same height as the specimen were cast and tested. In this study, the volume fraction of aggregate is constant and the varied lateral surface area of the aggregate cylinder was obtained by using different diameters and number of aggregate. The chloride migration coefficient of cement-based material was determined experimentally as a function of the lateral surface area of aggregate. A model obtained for the migration coefficient of cement-based material and the regression analysis are used to determine the approximate chloride migration coefficient of the percolated ITZ. Based on the experimental and regression analytical results, the approximate percolated ITZ migration coefficient is 40.6, 35.5, and 37.8 times of the altered migration coefficient of matrix mortar for the water/cement (w/c) ratio of 0.35, 0.45, and 0.55, respectively.     

涂层硬质合金刀片切削性能的试验研究

对涂层硬质合金刀片与未涂层硬质合金刀片进行了切削力、刀具磨损及刀具耐用度的对比试验，并做了摩擦系数的计算，论述了涂层硬质合金刀具的优越性能、实际使用价值及推广意义。     

Depletion of Antioxidants from a HDPE Geomembrane in a Composite Liner

The results of two series of accelerated aging tests are reported. Both series of tests were conducted at temperatures of 85, 70, 55, and 26°C over a period of about 3?years. In the simulated liner series, the top of the geomembrane was covered with a geotextile (protection) layer that was exposed to simulated municipal solid waste (MSW) landfill leachate while the bottom of the geomembrane was in contact with a hydrated geosynthetic clay liner. In the immersion series, the geomembrane was immersed in the simulated MSW leachate, and hence, both sides were exposed to leachate. The results from oxidative induction time tests indicate that the antioxidant depletion is about 2.2–4.8 times faster for the leachate immersed geomembrane than for geomembrane in a composite liner. The higher rates are attributed to the higher extraction of antioxidants from two sides of the geomembrane immersed in leachate. The measured antioxidant depletion rates are extrapolated to a range of temperatures (0–60°C) using Arrhenius modeling. At a liner temperature of 35°C, the calculated time for the depletion of antioxidants is about 40?years for a geomembrane in a composite liner compared to 10?years if it is simply immersed in leachate. These tests suggest that to obtain realistic estimates of geomembrane service life one needs data from tests that simulate the expected field conditions and that prediction based on immersion tests may underestimate the service life.     

Effects of MEA fabrication method on durability of polymer electrolyte membrane fuel cells

To study the effects of fabrication methods on the durability of polymer electrolyte membrane fuel cells (PEMFCs), membrane-electrode assemblies (MEAs) were fabricated using a conventional method, a catalyst-coated membrane (CCM) method, and a CCM-hot pressed method. Single cells assembled with the prepared MEAs were operated galvanostatically at 600 mA cm⁻² for 1000 h for the conventional MEA and the CCM MEA and for 500 h for the CCM-hot pressed MEA. During operation, i-V curves, impedance spectra, and cyclic voltammograms were measured roughly every 100 h. Before and after long-term operation, the physical and chemical characteristics of the MEAs were analyzed using mercury porosimetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and Fourier transformation infrared spectroscopy (FTIR). Under the operating conditions, the CCM MEA exhibited the lowest degradation rate as well as the highest initial performance.