This study deals with the durability of composites based on polyamide 6.6 (PA6.6) in a humid environment, and more especially, with the loss of fracture properties. It is known that PA6.6 undergoes ...plasticization in the presence of water, but hydrolysis also occurs. This hydrolysis leads to a sharp decline in fracture properties in resin. The aim of this study is thus to understand the behavior of two PA6.6-based composites, one containing short glass fibers and the other both glass fibers and a rubber. The results showed the transition from ductile to brittle behavior as a function of hydrolysis time in resin. For composites, the drop in elongation breaking with the macromolecular chain length was linear for all ageing conditions considered here without marked transition. The results presented here can be used for lifetime prediction of PA6.6-based composites in a humid environment.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The characterisation of in-plane shear behaviour during textile reinforcement forming is one of the most important factors to insure the quality of the preforms before resin impregnation. All ...experimental and numerical studies on the in-plane shear behaviour concern orthogonally fabrics, interlaced by weaving or stitched for NCF preforms. In the present work, the in-plane shear behaviour of non-orthogonally interlaced fabrics manufactured by braiding is studied. Braided fabrics are widely used as textile reinforcements to manufacture advanced composite parts. Due to the non-symmetric structure of braided reinforcements, it is necessary to study this shear behaviour not only in axial direction but also in transversal direction. A geometric criterion and an analytical model for in-plane shearing characterisation by the bias-extension test are developed firstly for any textile structure. Then, two types of fabrics, Flax/PA12 and E-glass braided fabrics, are performed in bias-extension tests for validating the theoretical model. Analytical and experimental results present a good agreement that demonstrates the bias-extension test can be used to characterise the in-plane shear behaviour of braided reinforcements. Moreover, the in-plane shear behaviour of the braided samples with different ratios of length to width is also discussed to analyse the influence of the dimension ratio on tested samples. The results show that varying dimension ratio does not change the shear moment/shear angle behaviour but could affect the shear load/displacement behaviour.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Glaciers in polar regions are sensitive to climate and ocean changes and can thin rapidly as a consequence of global warming. Digital Elevation Models (DEMs) from remote sensing observations have ...been widely used to detect changes in polar glaciers. DEMs from Terrestrial Radar Interferometer (TRI) have recently been used for high frequency glacier change and glacier-ocean interaction studies. However, it is unclear whether TRI DEM over a large study area can be combined directly with remote sensing observations to investigate glacier changes as well as the accuracy of TRI DEM at far range. In this study, we deployed a TRI close to Helheim Glacier, East Greenland and generated DEMs using TRI and satellite laser altimetry. We analyzed the accuracy of the TRI DEM using theoretical calculations, comparisons based on repeat observations, and comparisons with a high accurate ArcticDEM. The validation results suggest that for stable ground surfaces, the uncertainty (standard deviation) is <5 m at range < 9.8 km. Averaging across time (e.g. one hour) decreases the uncertainty almost linearly with range, over 0.5 m to 1.2 m when the range increases from 7.0 km to 10.0 km. Increasing the correlation coefficient threshold for phase unwrapping does not significantly reduce uncertainty. TRI DEMs are influenced by systematic error at far range primarily due to coarse azimuth resolution and phase unwrapping difficulties in discontinuous interferograms. As the absolute accuracy of TRI DEMs is not uniformly distributed in the range direction (farther points have worse uncertainty), our findings indicate that TRI DEMs within range of 10 km can reach <5 m uncertainty, which can be compared with DEMs obtained from remote sensing satellites to detect glacier thinning.
•A method to generate TRI DEM referring to WGS-84 ellipsoid is presented.•Averaging across time decreases the DEM uncertainty almost linearly with range.•Increasing correlation coefficient threshold does not significantly improve TRI DEM.•Large uncertainty at far range is caused by coarser azimuth resolution and discontinuous interferogram.•TRI DEMs with range < 10 km have <5 m uncertainty and can match satellite observations.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Although glass has been manufactured and used for millennia, the understanding that the mechanism of their formation is distinct from that of the more common polycrystalline arrived only a few ...decades ago.
•We analyze common household recycling policies for metals, glass, and plastics.•Our data were collected during a 2006 national survey of 2136 U.S. households.•The main recycling drivers are ...perceived obstacles/benefits and curbside recycling.•Moral considerations, nearby drop-off recycling centers and bottle bills also matter.•Socio-demographic characteristics and trash marginal pricing only play a small role.
This paper analyzes a unique dataset collected during a 2006 national survey of U.S. households to explore the effectiveness of common household recycling policies for metals, glass, and plastics: curbside recycling, drop-off recycling, deposit–refund systems (bottle bills), and marginal pricing for household waste. After estimating either generalized ordered logit or multinomial logit models, we find that the most important determinants of household recycling are people's attitudes toward recycling. Our results also suggest that omitting internal variables (perceived recycling obstacles and benefits as well as moral considerations) may bias policy coefficients. Socio-economic variables are typically not statistically significant, with the exceptions of young adults and of African Americans who tend to recycle less than others. Policies with the largest odds ratios are curbside recycling (which is further strengthened if recycling is mandatory), followed by the presence of drop-off collection centers nearby. Bottle bills are also statistically significant but their odds ratios are smaller, possibly because refunds are relatively small and typically do not change for years. Finally, marginal pricing appears to have a limited impact on recycling. These results suggest avenues for improving household recycling at a time when recycling rates appear to be plateauing.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A coral-like film of nickel@nickel sulfide (Ni@NiS) was obtained on a conducting glass through an electrochemical method, in which the Ni functioned as a template. Three types of Ni thin films were ...electrodeposited on fluorine-doped tin oxide (FTO) substrates by a pulse current technique at the passed charge densities of 100, 200, and 300 mC cm −2 , which rendered custard apple-like, coral-like, and cracked nanostructures, respectively. Subsequently, nickel sulfide films were coated on these Ni films by using a pulse potential technique. Due to the template effect of the Ni films, the composite films of Ni@NiS also assumed the same structures as those of their nickel templates. In each case of the films the particle of the film assumed a core–shell structure. The Ni@NiS coated FTO glasses were used as the counter electrodes for dye-sensitized solar cells (DSSCs). The DSSC with the coral-like Ni@NiS film on its counter electrode exhibits the highest power conversion efficiency ( η ) of 7.84%, while the DSSC with platinum film on its counter electrode shows an η of 8.11%. The coral-like Ni@NiS film exhibits multiple functions, i.e. , large surface area, high conductivity, and great electrocatalytic ability for iodine/triiodine (I − /I 3 − ) reduction. X-ray photoelectron spectroscopy (XPS), X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), and four-point probe technique were used to characterize the films. The photovoltaic parameters are substantiated using incident photon-to-current conversion efficiency (IPCE) curves, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization plots. The IPCE curves were further used to calculate theoretical short-current densities of the cells.
A hierarchically porous bioactive glass-ceramic microsphere with enhanced bioactivity and good biocompatibility was fabricated via electro spraying technique assisted with non-solvent induced phase ...inversion. The electro sprayed bioactive glass (ESBG) microspheres were 20 ± 5 μm in diameter, and composed of four characteristic pores: <200 nm, 200–500 nm, 500–1000 nm and >1000 nm. The influences of sintering temperatures (600 °C-1000 °C) on the microstructure, crystalline phase and the related in vitro bioactivity of the samples were investigated. All the ESBG microspheres possessed bioactivity, and the earliest apatite deposition time (3 h) occurred in the samples sintered at 1000 °C owing to the highly porous structure and the formation of wollastonite. The in vitro cytotoxicity was evaluated via CCK-8 assay using MC3T3-E1 cells, revealing the good biocompatibility as well. These results suggest that the ESBG microsphere is a promising material for bone tissue engineering.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Classical microcontact printing and polymer pen lithography (PPL) involve ink transfer to substrates using solid elastomeric stamps. Ink depletion thus limits the number of successive stamping steps ...without reinking. Porous stamps developed to overcome this limitation are used only for manual proof‐of‐principle experiments. Here, porous composite stamps for scanner‐based capillary stamping (SCS) that can be mounted on automated printing devices designed for PPL are developed. Porous SCS composite stamps consist of a rigid controlled porous silica glass (CPG) layer and a porous polymeric stamping layer. The latter can be topographically structured with contact elements by replication molding. The mechanical stabilization by the CPG layer ensures that the contact elements are coplanar. SCS allows automated, continuous, high‐throughput patterning enabled by ink supply through the porous SCS composite stamps. Even after more than 800 consecutive stamp–substrate contacts without reinking (the porous SCS composite stamps themselves are used as ink reservoirs), ink microdroplets are deposited without deterioration of the pattern quality. However, SCS also allows supply of additional ink during ongoing stamping operations through the pore systems of the porous SCS composite stamps. SCS can easily be adapted for multi‐ink patterning and may pave the way for further upscaling of contact lithography.
Porous composite stamps for scanner‐based capillary stamping that can be mounted on automated printing devices designed for polymer pen lithography are developed. Automated, continuous, high‐throughput patterning is enabled by ink supply through the porous composite stamps.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Display omitted
•Novel method by Flash DSC to measure the delay time for crystallization is proposed.•Delay time for marginal Al-based metallic glasses are precisely determined.•Minor-alloying effect ...on delay time and glass formation ability are studied.
The delay time for primary crystallization plays an important role in the understanding of the transport and nucleation behaviors during crystallization in metallic glasses. In this work, a novel method via Flash DSC is demonstrated to measure the delay time for primary crystallization in Al-based metallic glasses. In a typical Al-based metallic glass of Al87Y7Fe6, the delay times were established corresponding to different temperatures. Transmission electron microscopy tests before and after delay time were conducted to further verify the validity of the measured delay time. The effect of a 1 at.% substitution by Cu on the delay time of Al88Y7Fe5 was investigated to determine the effect of minor alloying on the glass formation ability. The significant changes in the primary crystallization temperatures were demonstrated to be directly related to the corresponding changes in the delay time. The results indicate that minor alloying that is designed to increase the delay time is an effective strategy to enhance the glass formation ability.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Highly active electrocatalysts with good long term stability are vital for the commercialization of metal air batteries and alkaline fuel cells which involve the oxygen reduction reaction (ORR) at ...the cathode end. Herein, we developed a pulsed laser deposition (PLD) technique for the precise fabrication of silver-copper metallic glass (AgCu-MG) electrocatalysts. This PLD technique provides excellent control over the surface microtopography along with high flexibility for the deposition of different compositions of silver-copper metallic glass electrocatalysts onto nickel foam. Among all investigated Ag-based catalysts, AgCu-MG catalysts exhibit high electrocatalytic activity with a half-wave potential of 0.67 V (vs. RHE) which can be in situ enhanced by dealloying treatment in N sub(2) saturated 0.1 M KOH solution. In situ dealloying of the AgCu-MG provides exceptional ORR catalytic activity with a half-wave potential of 0.78 V (vs. RHE) at 1600 rpm, which is comparable to 0.81 V (vs. RHE) of commercial Pt/C-20%. The AgCu-MG electrocatalyst showed excellent long-term stability in rechargeable zinc-air batteries. After 1000 charge-discharge cycles at 20 mA cm super(-2), the discharge voltage of batteries was stable at 1.0 V demonstrating the potential application of AgCu-MG as an alternative to Pt/C-20% in zinc-air batteries and alkaline fuel cells.
PDF
