Several consolidation cycles were performed to study the impact of processing parameters on void content, ultrasonic NDT and mechanical performance of CF/PEEK composites. A series of +45/−454S ...laminates were manufactured by out-of-autoclave technologies including vacuum bag only, hot-press, and automatic lay-up with in-situ consolidation. A range of porosity between 0 and 19% of void content was assessed by varying the processing temperature from 340 to 500 °C and pressure from 0.25 to 1.5 MPa. Void content, shape and location were characterized by using C-scan, matrix digestion and 2D microscopy. Mechanical characterization including in-plane shear and interlaminar shear testing was performed. The results show a critical void content where properties start to decrease at a given drop-off rate. The results suggest that each processing technology should have its own quality control criteria. The proposed methodology is useful for engineering applications of thermoplastic composites and the creation of NDT acceptance criteria.
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•The energy performance of a solar-powered VMD plant was evaluated.•The effect of the applied vacuum pressure on the specific energy consumption was demonstrated.•The effect of solar ...radiation on the energy performance of the installation was analyzed.•The impact of recycling hot cooling water used for steam condensation on SEC, GOR and daily production was discussed.
In this paper, a study of the energy performance of a solar powered vacuum membrane distillation was investigated on four typical days that represent the four seasons of the year namely: the equinoxes (March 21st and September 21st) and the solstices (June 21st and December 21st), through the widely used energy criteria such as specific energy consumption, gained output ratio and heat recovery factor. The results indicate that the energy performance of the process is strongly linked to the solar irradiation and as long as the VMD is coupled with solar energy, the process could be competitive with industrialized desalination technologies such as RO, MSF and MED. Besides, the effect of the applied vacuum level on the specific energy consumption was examined. Obviously, the results reveal that for minimum SEEC an optimal vacuum pressure is between 5000 and 10000 Pa. As well a technique to optimize the energy performance by recycling hot cooling water, used for steam condensation, was discussed. An amelioration of about 35%, 26% and 31%, during the hottest day (June 21st) and of about 22%, 19% and 21%, during the coldest (December 21st) in the GOR, the SEC and the daily production could be achieved.
Industry is facing the management of geometrical deviations along the entire lifecycle of the product. It is helped by digital twin tools that may minimise the geometrical deviations from nominal of ...products. The new digital twin tools allow to manage geometrical variations through a set of steps fully related by modern information and communication technologies that establish a continuous and unambiguous flow of information among the different steps of this digital process along the whole product lifecycle. They are based on data coming from manufacturing, assembly and inspection. The available large data sets from manufacturing and inspection allow to develop new and more accurate simulation models that realistically consider form deviations and process signature, i.e. the pattern left by the manufacturing process on the produced part surfaces. The present work introduces a digital twin tool to support the lightweight design of assemblies in composite material. It establishes a continuous and unambiguous flow of variation information from the part design to assembly, passing through manufacturing by considering the manufacturing signature. It was applied to a case study and the obtained results agree with the experimental ones.
Membrane crystallization (MCr) is emerging as an interesting candidate to extract additional freshwater and raw materials from high-concentrated solutions. Traditionally, MCr has been carried out by ...using polymeric membranes that have limited chemical and mechanical stability. These shortcomings can be overcome by using ceramic membranes. The current study describes the preparation and testing of two hydrophobic ceramic membranes synthesized trough sol-gel process, and combined phase-inversion and sintering method. The first membrane (CM-L) was synthesized by coating hydrophobic polymethylsilsesquioxane aerogels on alumina membrane supports via a sol-gel process. The membrane showed stable hydrophobic character in membrane distillation and crystallization tests but very low flux. To obtain high flux, a second type (CM-S) membrane was prepared by applying Fluoroalkylsilanes (FAS) (1H, 1H, 2H, 2H‑perfluorooctyltriethoxysilane) hydrophobic agent at the relatively thin and more porous as-sintered alumina hollow fibers. The suitability of both membranes for MCr process was analyzed by crystallizing NaCl and LiCl. By using 1 M NaCl and 13 M LiCl aqueous solutions, and under the same operative conditions, CM-S membrane exhibited average flux higher than CM-L membrane. The performance of both the membranes, in terms of hydrophobic character, remained stable throughout the performed tests.
•Novel ceramic membranes for MCr/MD process•Influence of membrane characteristics on MCr process•Membrane assisted crystallization in desalination
Metal halide perovskite solar cells (PSCs) currently attract enormous research interest because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication costs, but their ...practical development is hampered by difficulties in achieving high performance with large-size devices. We devised a simple vacuum flash—assisted solution processing method to obtain shiny, smooth, crystalline perovskite films of high electronic quality over large areas. This enabled us to fabricate solar cells with an aperture area exceeding 1 square centimeter, a maximum efficiency of 20.5%, and a certified PCE of 19.6%. By contrast, the best certified PCE to date is 15.6% for PSCs of similar size. We demonstrate that the reproducibility of the method is excellent and that the cells show virtually no hysteresis. Our approach enables the realization of highly efficient large-area PSCs for practical deployment.
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•Membrane contactors with renewable CO2 absorbents are used for biogas upgrading.•Mass transfer resistance in the membrane contactor for biogas upgrading is studied.•Temperature has ...little effect on CO2 absorption rates of the renewable absorbents.•Biogas upgrading performance is highly dependent on the gas and liquid flow rates.•This study paves a new way to use renewable absorbents for carbon minimization.
This study employs novel renewable absorbents derived from biogas slurry (BS) for biogas upgrading via membrane contactors. CO2 absorption capacity of biogas slurry can be enhanced by adding alkali solutions, vacuum regeneration or vacuum membrane distillation (VMD). These methods are used to produce four types of renewable CO2 solvents, including vacuum regenerated BS, recovered aqueous ammonia (RAA) from BS by VMD, calcium oxide treated BS and potassium hydroxide treated BS. These renewable absorbents for CO2 capture from biogas by membrane contactors are investigated. CO2 removal efficiency reduces but absorption rates increase with the rise in CO2 volume fraction in the feed gas stream. Absorption temperature has a limited effect on CO2 absorption rates of the renewable absorbents. RAA shows the best CO2 absorption performance among the four types of renewable absorbents in the membrane contactor. RAA flowing on the tube side leads to a 50% higher CO2 removal efficiency compared with RAA on the shell side. At low gas flow rates, partial absorbents and hollow fibers may not be utilized. Thus, selection of membrane module parameters, including the length of module, the number of hollow fibers, biogas flow rates and absorption performance, should be carefully considered when using membrane contactors for biogas upgrading.
To investigate the effect of RDX on the explosion reaction mechanism of FOX-7 based aluminized explosives in vacuum environment, the explosion field temperature of FOX-7 based aluminized explosives ...and RDX/FOX-7 based aluminized explosives were measured in an isolated explosion chamber. The results show that adding RDX would increase the equilibrium temperature of explosion field of FOX-7-based aluminized explosives. The equilibrium temperature of FOX-7-based aluminized explosives and RDX/FOX-7-based aluminized explosives increases first and then decreases with the increasing of Al content, which shows the highest equilibrium temperature as the Al content is 30%. When the Al content is less than 25%, the explosion peak temperature of FOX-7-based aluminized explosives would increased by adding RDX, and when the aluminium content is more than 30%, the explosion peak temperature of FOX-7-based aluminized explosives can be reduced by adding RDX.
The C 1s signal from ubiquitous carbon contamination on samples forming during air exposure, so called adventitious carbon (AdC) layers, is the most common binding energy (BE) reference in X‐ray ...photoelectron spectroscopy studies. We demonstrate here, by using a series of transition‐metal nitride films with different AdC coverage, that the BE of the C 1s peak EBF
varies by as much as 1.44 eV. This is a factor of 10 more than the typical resolvable difference between two chemical states of the same element, which makes BE referencing against the C 1s peak highly unreliable. Surprisingly, we find that C 1s shifts correlate to changes in sample work function ϕSA
, such that the sum EBF+ϕSA
is constant at 289.50±0.15 eV, irrespective of materials system and air exposure time, indicating vacuum level alignment. This discovery allows for significantly better accuracy of chemical state determination than offered by the conventional methods. Our findings are not specific to nitrides and likely apply to all systems in which charge transfer at the AdC/substrate interface is negligible.
Zeros matter: The C 1s signal from adventitious carbon (AdC) is the most common binding energy (BE) reference in X‐ray photoelectron spectroscopy. It is shown here that the BE of the C 1s peak EBF
is substrate dependent, which makes BE referencing highly unreliable. Surprisingly, C 1s shifts correlate to changes in the sample work function ϕSA
, such that the sum EBF+ϕSA
is constant irrespective of the materials system and air exposure time, indicating vacuum level alignment. This discovery allows for significantly better accuracy of chemical state determination.
We present a comprehensive first-principles study of the electronic structure of 51 semiconducting monolayer transition-metal dichalcogenides and -oxides in the 2H and 1T hexagonal phases. The ...quasiparticle (QP) band structures with spin–orbit coupling are calculated in the G0W0 approximation, and comparison is made with different density functional theory descriptions. Pitfalls related to the convergence of GW calculations for two-dimensional (2D) materials are discussed together with possible solutions. The monolayer band edge positions relative to vacuum are used to estimate the band alignment at various heterostructure interfaces. The sensitivity of the band structures to the in-plane lattice constant is analyzed and rationalized in terms of the electronic structure. Finally, the q-dependent dielectric functions and effective electron and hole masses are obtained from the QP band structure and used as input to a 2D hydrogenic model to estimate exciton binding energies. Throughout the paper we focus on trends and correlations in the electronic structure rather than detailed analysis of specific materials. All the computed data is available in an open database.
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