Uptake of the alkalis K and Na by calcium silicate hydrate (C-S-H) and calcium alumina silicate hydrate (C-A-S-H) of molar Ca/Si ratios=0.6 to 1.6 and molar Al/Si ratio=0 or 0.05 has been studied at ...20°C. Alkalis are thought to be bound in the interlayer space of C-A-S-H and show preferred uptake by lower Ca/Si ratios and by higher alkali concentrations. A consequence of alkali uptake into C-A-S-H is a rearrangement of the C-A-S-H structure. Less calcium is present in the interlayer and shorter silica chains are observed for the same molar Ca/Si ratio.
No significant difference was observed between sodium and potassium uptake. Equilibration times of 91days to 1year or the solid phase being either C-S-H or C-A-S-H had seemingly no effect on alkali uptake.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We present a method for high temperature stabilization of bulk amorphous aluminium oxide. The stabilization is achieved by dispersing polysilane dendritic molecules in aluminium hydroxide gel, which ...upon thermal treatment gives amorphous aluminium oxide stable up to 900 °C. The dispersed macromolecules covalently bind to the alumina matrix and induce homogeneously distributed strain fields that keep the alumina amorphous. The thermal conversion of the precursor system was followed by thermogravimetry with an evolved gas analysis, infrared spectroscopy and 29Si NMR. The amorphous structure of aluminium oxide was confirmed with an X-ray and electron diffraction. Additionally, the amorphous state was supported by presence of penta-coordinated aluminium detected by 27Al NMR and a low bandgap measured by a UV–visible absorption spectroscopy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A constitutive model for the stress–strain responses over the range of temperatures and strain rates when dynamic strain ageing prevails.•Decreasing/increasing strain rate sensitivity with plastic ...straining inside/outside the PLC domain.•A novel and consistent interpretation of all jerky flow scenarios.•Numerical prediction and experimental validation of the PLC domain.
Uniaxial tension tests at strain rates from 10−4 to 10−1s−1 and temperatures from 298 to 418 K are performed to study the dynamic strain ageing (DSA) of an AA5182-O sheet. Digital image correlation (DIC) is used to obtain the stress-strain curves and characterize the heterogenous deformations. A constitutive model based on the mechanical threshold stress (MTS) framework is then proposed and used to calculate the stress–strain response at different strain rates and temperatures. The modified MTS model captures the dependence of the strain rate sensitivity (SRS) on strain, temperature and strain rate both inside and outside the Portevin–Le Chatelier (PLC) domain. Special attention is paid to re-interpret the occurrence of stress serrations. It is found that the competition between work hardening and DSA leads to different jerky flow scenarios. The modified MTS model is used to predict the PLC domain as a function of strain rate and temperature. To further test the validity of the model at various temperatures and alloys, it is also approximately calibrated to Ni-based superalloys, for which it captures earlier reported behaviour at elevated temperatures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Pretreatment of produced water using ceramic membrane is considered promising due to its excellent separation performance and thermal and mechanical stabilities, however, the high cost of ceramic ...membranes discourages industries for large scale applications. The purpose of this work is to fabricate ceramic hollow fibre membranes from alumina-spinel composite powder synthesized from low-cost aluminium dross waste for the pretreatment of oily saline produced water. The hollow fibre membranes were prepared via phase inversion-based extrusion and sintering technique. Aluminium dross (less than 50 µm) was subjected to pre-treatment via water leaching and calcination, resulting in alumina (Al2O3) and spinel (MgAl2O4) as major constituents. Subsequently, the as-prepared alumina-spinel composite powder was used as a ceramic material in fabricating the hollow fibres. The effect of sintering temperatures on the morphology, crystalline phase, pore size and porosity, mechanical properties, and removal efficiencies of the alumina-spinel composite hollow fibre membranes were investigated. The microfiltration test of the hollow fibres was assessed using produced-water feed of 200 mg L−1 at 1 bar. The hollow fibre sintered at 1275 °C offers 92.41% rejection percentage of oil, the highest after 50 min of stable flux. Furthermore, turbidity was found to decrease from 378 NTU to 28.5 and 22.5 NTU for hollow fibres sintered at 1250 and 1275 °C after 2 h of filtration. In this work, the alumina-spinel composite hollow fibre membranes are found to be an effective tool as an alternative for the pretreatment of oily saline produced water.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Low level of influence of laser scan speed in SLM on the microstructure and grain size in Sc- and Zr- modified AlMg alloys.•Precipitation of Al3(Scx Zr1-x) particles occurs at low laser scan speeds. ...At high scan speeds Sc and Zr is in solid solution.•Zener pinning by Al3Sc particles and further features stabilize the microstructure against grain growth AM-processing.
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Additive processing via Selective Laser Melting (SLM) of Sc- and Zr-modified Al-Mg alloys (commercially known as Scalmalloy®) provides significant advantages over traditional 4xxx casting alloys. This is due to the high strength and ductility at very low mechanical anisotropy, which is a result of the alloys' very fine-grained microstructure combined with weak texture in the build-up direction. Next to their advantageous mechanical properties, the reliability of alloys processed by additive manufacturing is of great importance. Variations in microstructural features due to the use of different in processing parameters (e.g. laser scan speed) are well known for traditional alloys. This study analyses the influence of varying laser scan speeds on the static mechanical properties of SLM-processed Scalmalloy®, and discusses the evolving microstructure and precipitation of nm-sized Al3Sc particles at the correspondingly different energy inputs. It is found that by about doubling the laser scan speed the peak grain sizes in the fine-grained regions decrease from 1.1μm to 600nm, whereas in the coarse grained region almost no influence is observed. Al3Sc particles are only precipitated during processing at low scan speeds due to the corresponding high laser energy input, or by the intrinsic heat treatment from subsequent layers being built.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Many researchers are seeking simple and successful solutions to increase the output from the solar distiller. In this research work, reflective mirrors and reflective aluminium foil sheet were fixed ...on inner surfaces of the single-slope solar distiller, leading to more water production. The presence of reflective mirrors and reflective aluminium foil sheet on inner surfaces of the solar distillate permits the reflection of solar radiation falling inside the basin. Experiments were carried out on three stills: the first distiller is conventional solar still with black painted walls (CSS-BPW); the second distiller is conventional solar still with reflective aluminium foil sheet walls (CSS-RAFW); and the third distiller is conventional solar still with reflective glass mirror walls (CSS-RGMW). The maximum total drinking water productions from the CSS, CSS-RAFW and the CSS-RGMW are 3.41, 5.1 and 5.54 kg/m
2
, respectively. Compared to the CSS-BPW, the production of drinking water was increased by 68.57% when using the reflective glass mirrors and 48.57% when using the reflective aluminium foil sheet.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Alloying technology usually improves the mechanical properties of alloys; however, the high cost of alloying elements limits their wider applicability to conventional cast aluminium alloys. In this ...work, a novel high-strength, ductile, and low-cost Al–11Si–3Cu alloy microalloyed with minor Sr + Sc was developed and shown to improve the ultimate tensile strength and elongation relative to the majority of developed Al–Si-(Cu) alloys to date. Atom probe tomography (APT) reconstruction showed that Sc atoms existed separately instead of being enriched with Al and Sr atoms in eutectic Si, which indicated that the growth of eutectic Si in different crystallographic directions was inhibited. Many interactive stacking fault planes were formed in the novel alloy, which, as a series of barriers, effectively prevented dislocations from passing through, thereby providing a significant boost to the alloy strength. Moreover, a large number of Al3Sc and AlSi2Sc2 nano-precipitates exerted positive effects on the alloy strength by effectively slowing the dislocation movement. In addition, the strengthening mechanisms of the novel high-strength ductility Al–11Si–3Cu alloy are discussed.
•A novel high strength-ductility Al alloy was developed by minor content of Sr and Sc micro-alloying.•The distribution of micro-alloyed atoms in the novel alloys were analyzed by APT.•The Sc and Sr atoms inhibited the growth of eutectic Si in different directions.•Many stacking faults, Al3Sc and AlSi2Sc2 nanoparticles are formed in the alloy.•Effect of eutectic refining, stacking fault and nanoparticle strengthen are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
There is a significant demand for improved design and performance of gas sensors today. A fiber optic gas sensor based on light detection from a side-polished clad modified optical fiber (Evanescent ...mode) coated with nanocystalline aluminium oxide (Al2O3) is proposed for detecting VOCs such as acetone, methanol, ammonia, and ethanol gases. It is observed that there is an increase in the output light intensity for evanescent mode with an increase in the gas concentration, whereas a decrease in the transmission mode (light received from the end of fibre). The sensor exhibits excellent gas sensitivity and selectivity towards acetone gas in the evanescent mode. The normalized gas sensitivity for acetone was 603 × 10−3 /kPa in the evanescent mode and 29 × 10−3 /kPa in transmission mode, which is about 20 times better at sensitivity in evanescent mode compared to transmission mode. The dynamic characteristics of the sensor were also studied. A theoretical model for light dynamics in the optical fiber during gas sensing and its correspondence with sensing mechanism has been discussed.
•Gas sensing of Al2O3 coated optical fiber sensor in evanescent mode and transmission mode were studied for VOCs at RT.•The gas sensitivity for acetone was 603 x 10-3 /kPa in the evanescent mode and 29 x 10-3 /kPa in transmission mode.•Sensitivity is about 20 times better in evanescent mode compared to transmission mode.•Dynamic response and response of the sensor to change in humidity, temperature, and coating thickness were studied.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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