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•Lightweight and flexible silicone rubber foams with gradient structure were firstly prepared.•The shielding network of composite foam was enhanced through density-induced effect.•The ...conductivity of the composite foam can reach up to 279.3 S/m at 0.51 vol% Ag.•The composite foam displays an EMI SE of 30.5 dB at thickness of only 0.7 mm.•The silicon rubber foams present excellent EMI SE stability after 1000 bending.
Flexible and efficient electromagnetic interference (EMI) shielding materials are urgently needed to satisfy the requirements for electromagnetic (EM) protection with the rapid popularization of wearable and the second generation of flexible electronic technology. Herein, lightweight and flexible silicone rubber/silver (Ag) plated hollow glass microspheres (HGMs) EMI shielding composite foam with gradient structure was prepared through supercritical carbon dioxide (scCO2) foaming technology. The composite foam displays an EMI SE of 30.5 dB at thickness of 0.7 mm and exhibits excellent EMI shielding stability under 1000 times bending. The electrical conductivity of the composite foam can reach up to 279.3 S/m at the Ag content of only 0.51 vol% due to the density-induced effect and the effective decorating of Ag particles on the surface of HGMs, which results in the selective distribution of Ag particles on the upper surface of foam, thereby enhancing the conductive network. The ability of composite foam to consume EM wave was further improved and the reflection EMI shielding effectiveness (SE) and reflection power coefficient (R) were reduced by 3.4 dB and 0.22 respectively because of the magnetic loss caused by Fe3O4@MWCNTs nanoparticles and the absorption originated by multiple reflections inside the cells. Furthermore, the EMI SE of the three-layer composite foam is as high as 59.39 dB, while the R value is only 0.59 at thickness of 2.0 mm. The gradient structure design and selective dispersion of conductive fillers provide a new insight into the preparation of EMI shielding composites. These composite foams have great potential applications in the field of EMI protection in wearable, intelligent and precision electronic devices.
Photochromic molecules are well-established colourants in the manufacturing of niche products, providing reversible colour change effects when irradiated with ultraviolet (UV) light. The high ...material cost of such speciality dyes along with the general high carbon footprint and extensive water consumption of textile products necessitates resource-efficient production processes. The use of supercritical CO2 (scCO2) dyeing technique enables the economic production of textile high-end products, where a uniform through colouration is desired. This study investigates the potential application of two commercial photochromic dyes based on spirooxazine (Sea Green – SO-SG) and naphthopyran (Ruby Red – NP-RR) to polyester fabric using scCO2 dyeing technique and examines their photochromic behaviour. The dyeing was carried out at 120 °C and 25 MPa for 1 h. The photochromic performance was evaluated using a specially designed online colour measurement system capable of simultaneous UV irradiation and continuous measurement of photochromic colour change even after the shutdown of the UV source. The colour yields (K/S values), photoswitching rates and durability against washing were the main parameters examined. The results showed that scCO2 dyed photochromic polyester fabrics exhibited reversible colour changing properties upon UV exposure and removal. The samples dyed with SO-SG demonstrated a comparable degree of photo-colouration, lower background colour, faster colouration and decolouration speeds, but inferior wash fastness compared with NP-RR dyed samples. Particularly, the same class of dyes applied by scCO2 dyeing showed faster fading rates compared with conventionally dyed and screen printed samples. This study shows that scCO2 dyeing method is a potential alternative to develop uniformly coloured photochromic textiles providing excellent photochromic performance with additional economic and environmental benefits.
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•Resource-efficient production of UV sensing fabrics using scCO2 dyeing technology.•Evaluation of colour performance of commercial photochromic dyes on fabric.•Photocolourability, switching rates, and durability towards washing were examined.•ScCO2 dyed fabrics exhibit superior colour performance compared to conventional dyeing.•Widened scope of application of scCO2 technology with potential for smart textiles.
Carbon dioxide (CO2) is an alternative working fluid to water for hydraulic fracturing in shale reservoirs. It offers advantages as a substitute for the use of large quantities of potable water and ...for the concurrent sequestration of CO2, however sorption and swelling effects, and their impact on permeability may be detrimental and are undefined. Hence, it is of great importance to understand the mechanism of supercritical carbon dioxide fracturing in shale and its effect on shale permeability enhancement. We conduct hydraulic fracturing experiments on shale samples using both water (H2O) and supercritical carbon dioxide (Sc-CO2) as fracturing fluids to explore the surface characteristics and permeability evolution of fluid-driven fractures. We use profilometry to measure the roughness and complexity of the resulting fracture surfaces and measure the permeability of the fractures. Results indicate that: (1) Sc-CO2 fracturing creates fractures with larger tortuosity relative to H2O fracturing (macroscale); (2) the topography of Sc-CO2 fracture surfaces is more rough and complex compared to that of H2O fractured surfaces; (3) larger mineral grains are removed and relocated from induced fracture surfaces by Sc-CO2 fracturing – these acting as micro proppants that result in a larger fracture aperture; (4) correspondingly, the permeability of shale fractures increases by ∼5 orders of magnitude with Sc-CO2 fracturing and this enhancement is ∼3 orders of magnitude higher than that by traditional hydraulic fracturing. This observation potentially validates the feasibility of Sc-CO2 as a fracturing fluid for the stimulation of shale reservoirs.
•Sc-CO2 fracturing creates fractures with larger tortuosity.•Sc-CO2 fracturing creates fracture surfaces with a larger roughness and complexity.•Sc-CO2 fracturing increases shale permeability by five orders of magnitude.•Mineral grains are peeled from fracture surface by Sc-CO2 fracturing.
This paper presents optimization of a supercritical carbon dioxide Brayton cycle for three types of 300-MWth small modular reactors (SMRs); a pressurized water reactor (PWR), a sodium-cooled fast ...reactor (SFR) and a high-temperature gas-cooled reactor (HTGR). The parameters of the pressure ratio and the flow split fraction were examined for sensitivity analysis and optimization of cycle. The optimized cycle efficiencies of PWR, SFR, and HTGR were 30.6%, 46.38%, and 50.04%, respectively. Key components, i.e. turbomachinery and heat exchangers for the SMRs were designed to develop the optimized cycles. The cycle thermal efficiency was improved by using investigating the effects of the channel shape (zigzag, s-shape, airfoil fin) of the printed circuit heat exchangers (PCHEs) on the pressure drop. The study indicated that using airfoil fin type PCHE may increase the cycle thermal efficiency by about 1.0% in comparison with zigzag type PCHE. The effect of turbomachinery efficiencies on the cycle thermal efficiency were investigated.
•Thermodynamic analysis model for S-CO2 Brayton cycle was developed.•Sensitivity analysis of S-CO2 Brayton cycle coupled with three turbine inlet temperature were performed.•Optimum operating conditions and preliminary design of component were obtained for three turbine inlet conditions.•The effects of channel shape of PCHE were investigated for further improvement of cycle thermal efficiency.•The effects of turbomachinery efficiencies on the cycle thermal efficiency were investigated.
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•Solubility of imatinib mesylate in SC-CO2 was measured for the first time.•Temperature ranges of (308.2–338.2) K and pressure of (120–270) bar were used.•A new empirical model was ...proposed to correlate solubility of pharmaceutical compounds.•Models accuracy were evaluated by statistical criteria of (AARD %), (Radj) and F- value.•Results indicate superiority of the proposed model compared to the similar models and literature.
For the first time, solubility of imatinib mesylate (as a paradigm for cancer chemotherapy) in SC-CO2 was determined. Experiments were performed at operating temperatures and pressures of 308.2–338.2 K and 120–270 bar, respectively. Two different groups of methods including (1) three equations of state (EoSs), namely Soave–Redlich–Kwong (SRK), Pazuki et al. (PAZ), and Haghtalab et al. (HKM) with vdW2 mixing rule and (2) six density-based semi-empirical models were applied to correlate the solubility data of imatinib mesylate. The calculated results indicated the superiority of HKM EoS over other models. Then, a new, comprehensive empirical model with six adjustable parameters was proposed and compared with existing empirical models. The superiority of this model was confirmed by experimental solubility data of imatinib mesylate and 25 solubility datasets published in the literature. The proposed model could correlate the experimental solubility of imatinib mesylate with satisfactory accuracy.
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•A sustainable approach to fabrication of multifunctional PET has been investigated.•PET fabric has been successfully dyed with curcumin without mordant.•Excellent color strength, ...levelness, and fastness properties were achieved.•The dyed PET fabric demonstrated multiple functionalities.
This study presents a sustainable approach to the fabrication of multifunctional polyester fabric with bioactive natural colourant curcumin through a water free supercritical CO2 dyeing technique. A simple dyeing process was carried out in which curcumin powder dye was directly applied to polyester fabric in scCO2 medium without involving mordant chemicals and fabric pre-treatment procedures. The colour, bioactivity, and durability properties of the dyed samples were characterized. Results showed that the colour strength increases when the dye concentration increases and higher colour strength (K/S value above 17) could be achieved using low curcumin concentration (ca. 0.75 % owf). Moreover, the dyed fabrics displayed desirable antimicrobial, antioxidant, and UV-protection activities with acceptable colour fastness to washing and rubbing. This study opens a new view towards the sustainable fabrication of coloured and bioactive polyester fabric using curcumin via a resource-efficient and eco-friendly scCO2 dyeing technique.
Solubility measurement of a solid solute in supercritical fluid (SCF) is considered as a primary step in micro- and nano-sized particles production through SCF technology. In this work, for the first ...time, solubility of Lansoprazole (LPZ) in supercritical carbon dioxide (SC–CO2) was determined at pressures and temperatures ranging within 12–27 MPa and 308.2–338.2 K, respectively. Under the applied conditions, mole fractions were obtained in the range of 1.15 × 10−5 to 7.36 × 10−4. For correlating the drug solubility, six semi-empirical models and two equations of state (EoSs), i.e., Peng–Robinson (PR) as a cubic EoS and SAFT-VR as a non-cubic EoSs were applied. Results showed the highest accuracy for “Reddy and Garlapati” model among semi-empirical models with AARDz of 7.36%. Furthermore, SAFT-VR EoS with AARD of 6.65 proved a very good priority than PR EoS and displayed the highest precision compared to all empirical models. This could be a promising application of SAFT equations to predict the thermodynamic behavior of SCFs.
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•Solubility of Lansoprazole in SC-CO2 was measured for the first time.•Temperature and pressure ranges of 308.2–338.2 K & 12–27 MPa were investigated.•Experimental data was correlated by semiempirical models.•Experimental data was also correlated by PR and SAFT-VR equations of state.•SAFT-VR EoS provided accurate predictions and was superior to PR cubic EoS.
Economic and environmental disadvantages of conventional cutting fluids based on mineral oil drive the research for alternative methods such as dry cutting, cutting with alternative cutting fluids ...and/or minimum quantity lubrication. Oil-in-air minimum quantity lubrication is a frequently discussed method in literature. However, this technique only provides lubrication without sufficient cooling and is therefore often combined with cryogenic fluids such as liquid nitrogen. In recent research, the use of minimum quantity lubrication combined with supercritical carbon dioxide is used. This research focus on processes with geometrically defined cutting edges. The relevant literature can therefore not describe the use of minimum quantity lubrication combined with supercritical carbon dioxide in cutting-fluid-intense processes such as grinding. Regarding this research gap, a conducted feasibility study is presented in this paper as first approach to understand the potentials and barriers using supercritical carbon dioxide in surface grinding processes. In a novel MQL-scCO2 grinding application, the research includes the evaluation of a nozzle application, grinding forces, surface roughnesses, cutting power and the grinding wheel clogging using supercritical carbon dioxide in grinding. It was found that the use of supercritical carbon dioxide in combination with minimum quantity lubrication overall leads to lower or similar forces and cutting power compared to conventional cooling lubrication with emulsion. It was also determined that, in its current state of development, the surface roughness increases. Hence, further research is needed, specifically in the topics of an optimized nozzle construction, thermal analysis and dressing characteristics. A simplified evaluation of energy performance indicators shows a potential to cleaner production compared to a conventional system.
•MQL + scCO2 system has great potential as cutting fluid alternative.•Forces and cutting power can be reduced for MQL + scCO2 in surface grinding.•Surface roughness of the workpiece is higher for MQL + scCO2 compared to emulsion.•scCO2 system requires significantly less energy compared to an emulsion system.•Performance of MQL + scCO2 is strongly depended on the nozzle setup.
Concentrated solar power (CSP) plants with thermal energy storage (TES) system are emerging as one kind of the most promising power plants in the future renewable energy system, since they can supply ...dispatchable and low-cost electricity with abundant but intermittent solar energy. In order to significantly reduce the levelized cost of electricity (LCOE) of the present commercial CSP plants, the next generation CSP technology with higher process temperature and energy efficiency is being developed. The TES system in the next generation CSP plants works with new TES materials at higher temperatures (> 565 °C) compared to that with the commercial nitrate salt mixtures. This paper reviews recent progress in research and development of the next generation CSP and TES technology. Emphasis is given on the advanced TES technology based on molten chloride salt mixtures such as MgCl2/NaCl/KCl which has similar thermo-physical properties as the commercial nitrate salt mixtures, higher thermal stability (> 800 °C), and lower costs (< 0.35 USD∙kg−1). Recent progress in the selection/optimization of chloride salts, determination of molten chloride salt properties, and corrosion control of construction materials (e.g., alloys) in molten chlorides is reviewed.
Ti6Al4V alloy is a typical difficult-to-cut material. In order to improve its machinability and realize cleaner production, eco-friendly cooling/lubrication techniques are applied. Therefore, this ...study aims to investigate the tool wear, surface topography, cutting torque, and surface profile in side milling Ti6Al4V under four sustainable conditions, i.e., dry, supercritical carbon dioxide (scCO2), scCO2 with antifreeze water based minimum quantity lubrication (scCO2-WMQL), and scCO2 with oil-on-water based MQL (scCO2-OoWMQL) conditions. A theoretical model of flank wear width VB with average prediction error 15.87% is established. scCO2-OoWMQL reduces VB by 67.2% compared to scCO2 alone due to improved lubricity. Detailed characteristics of machined surface profile are investigated using continuous wavelet transform. The performance of scCO2-OoWMQL as a new sustainable and efficient cooling/lubrication technique is superior to scCO2 alone.
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•scCO2 with MQL as an efficient coolant/lubricant is used in milling Ti6Al4V.•A theoretical model of VB with average prediction error 15.87% is established.•Tool wear causes the cutting torque to lag behind the rotation angle continuously.•Milled surface profile is characterized using continuous wavelet transform.•Performance of scCO2 with MQL is superior to scCO2 alone due to improved lubrication.
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