Under servitization (one paradigm of non-ownership-transfer) business model such as sharing, a manufacturer is responsible not only for product design but also for maintenance. This paper deals with ...joint decision of product quality and maintenance under servitization. A model minimising total cost is formulated to obtain the optimal product quality, maintenance effort and maintenance times. We find that the total cost first decreases then increases with product quality, maintenance effort and maintenance times. Moderate quality and maintenance effort level are the best for the manufacturer, because too high or too low quality and effort cause too high total cost. However, preventive maintenance should be implemented as many times as possible until the failure cost is reduced to zero as long as each maintenance can save cost. Moreover, in the optimal joint decision, the product quality, maintenance effort and maintenance times are negatively correlated in pairs. In addition, we explore the impact of unit failure cost, product lifecycle, production cost, maintenance cost, and failure intensity on the manufacturer's optimal decisions. In extensions, we further take penalty cost, exponential failure distribution, discount rate, and customer usage into account. This paper provides insight for the manufacturer to jointly consider product design and maintenance under servitization.
With the trend of integration and miniaturization of stretchable electronics, thermal management has been a crucial issue. Developing novel materials with high thermal conductivity (TC) and ...flexibility is urgent. Herein, we report a stretchable polydimethylsiloxane (PDMS)/boron nitride nanosheet (BNNS)@spherical aluminum oxide (Al2O3) composite with high TC and electrical insulation prepared by a two‐step strategy of sucrose‐template and hot‐pressing. An effective foam‐pressing route benefits the composites to form a three‐dimensional thermally conductive networks, improving the in‐plane TC value of the resultant composite to 4.03 W/(mK) at the filler mass fraction of 35.7 wt% and enhancing to 4.66 W/(mK) under 40% stretching ratio. Meanwhile, the composites can be restored to their former state and retain thermally conductive stability with repeated bending and twisting tests. Moreover, the composites were applied in LED with stretching, exhibiting good heat dissipation performance. These results demonstrate this PDMS composite can be potentially utilized as a high‐performance material to solve thermal management problems in flexible electronics.
Highlights
The heat conduction network is prepared by sucrose‐template and hot‐pressing.
BNNS@P‐Al2O3 fillers are self‐assembled via the electrostatic interaction.
The composites exhibit good thermal conduction and superior flexibility.
The thermal conductivity of the composite increases after stretching.
The composites can retain thermal conductive stability after deformation.
Schematic diagram of thermal conductivity pathway formation in BNNS@P‐Al2O3/PDMS composite.
Nitrogen dioxide (NO2) emission has severe impact on human health and the ecological environment and effective monitoring of NO2 requires the detection limit (limit of detection) of several ...parts‐per‐billion (ppb). All organic semiconductor‐based NO2 sensors fail to reach such a level. In this work, using an ion‐in‐conjugation inspired‐polymer (poly(3,3′‐diaminobenzidine‐squarine, noted as PDBS) as the sensory material, NO2 can be detected as low as 1 ppb, which is the lowest among all reported organic NO2 sensors. In addition, the sensor has high sensitivity, good reversibility, and long‐time stability with a period longer than 120 d. Theoretical calculations reveal that PDBS offers unreacted amine and zwitterionic groups, which can offer both the H‐bonding and ion‐dipole interaction to NO2. The moderate binding energies (≈0.6 eV) offer high sensitivity, selectivity as well as good reversibility. The results demonstrate that the ion‐in‐conjugation can be employed to greatly improve sensitivity and selectivity in organic gas sensors by inducing both H‐bonding and ion‐dipole attraction.
An ion‐in‐conjugation inspired‐polymer (poly(3,3′‐diaminobenzidine‐squarine)) is employed as in chemiresistor to detect NO2 as low as 1 ppb, which is the lowest among all reported organic NO2 sensors.
With the electronic device advancing to miniaturization, higher integration and flexibility, flexible polymer composites with high thermal conductivity are desirable for efficient removal of ...accumulated heat to maintain normal operation of electronics. In this work, a polydimethylsiloxane/boron nitride nanosheets (PDMS/BNNS) foam scaffold was prepared by the sugar-templated method, and the corresponding PDMS/BNNS composites were manufactured with vacuum-assisted PDMS impregnation and curing. The PDMS/BNNS composites exhibit a three-dimensional (3D) BNNS interconnected network with curved BNNS pathways due to the intensive compression during hot-pressing curing, providing thermally conductive network and corresponding prestrains for deformable application. The PDMS/BNNS composites finally can achieve a high thermal conductivity of 7.55 W m−1 K−1 in the in-plane direction and 1.12 W m−1 K−1 in the through-plane direction with 25 vol% BNNS, which represent 153% and 78% increases over the composites prepared by randomly mixing method, respectively. In addition, the composite still maintains superior heat dissipation property under repeated stretching and bending conditions, which indicates a broad and bright application for thermal management in flexible electronic devices.
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Developing highly efficient and multifunctional membranes toward oil adsorption and oil/water separation is of significance in oily wastewater treatment. Herein, a novel electrospun composite ...membrane with dual-scaled porous structure and nanoraised structure on each fiber was fabricated through electrospinning using biodegradable polylactide (PLA) and magnetic γ-Fe2O3 nanoparticles. The PLA/γ-Fe2O3 composite membranes show high porosity (>90%), superhydrophobic and superlipophilic performances with CH2I2 contact angle of 0°, good water adhesion ability like water droplets on a petal surface, excellent anti-icing performance, and good mechanical properties with a tensile strength of 1.31 MPa and a tensile modulus of 11.65 MPa. The superlipophilicity and dual-scaled porous structure endow the composite membranes with ultrahigh oil adsorption capacity up to 268.6 g/g toward motor oil. Furthermore, the composite membranes also show high oil permeation flux up to 2925 L/m2 h under the force of gravity. Even for oil/water emulsion, the composite membranes have high separation efficiency. We expect that the PLA/γ-Fe2O3 composite membranes can be used in oily wastewater treatment under various conditions through one-off adsorption or continuous oil/water separation, especially under low environmental temperature condition.
Chirality is an asymmetric property widely found in nature. Here, we propose and demonstrate experimentally the spontaneous emergence of chirality in an on-chip ultrahigh-Q whispering-gallery ...microresonator, without broken parity or time-reversal symmetry. This counterintuitive effect arises due to the inherent Kerr-nonlinearity-modulated coupling between clockwise and counterclockwise propagating waves. Above an input threshold of a few hundred microwatts, the initial chiral symmetry is broken spontaneously, and the counterpropagating output ratio exceeds 20∶1 with bidirectional inputs. The spontaneous chirality in an on-chip microresonator holds great potential in studies of fundamental physics and applied photonic devices.
•Novel phase change materials (PCMs) with anisotropic structure have been developed.•High latent heat, thermal conductivity and encapsulation ability are achieved.•The PCMs exhibit high efficiency in ...solar/electrical energy application.
Phase change materials (PCMs) exhibit great potential applications in many fields, such as energy-saving building, solar energy harvesting, waste heat utilization, constant temperature protection and thermal management of microelectronic devices. In this work, we proposed a facile and novel method to prepare the composite PCMs. Through the combination of pre-refrigeration and freeze-drying techniques using the microcrystalline cellulose (MCC)/graphene nanoplatelets (GNPs) hydrogels, which were firstly prepared through solution compounding, gelling and solvent exchanging successively, the porous MCC/GNP aerogels with highly oriented stacking of MCC/GNP were successfully obtained. The composite PCMs based on the highly anisotropic MCC/GNP aerogel and polyethylene glycol (PEG) exhibited relatively high thermal conductivity (1.03 W/mK) at low GNP content (1.51 wt%), high latent heat (182.6 J/g) which was 99.84% of pure PEG, excellent encapsulation ability and mechanical stability. Further results showed that the composite PCMs exhibited excellent solar energy harvesting/electrical energy transformation, storage and release abilities. In addition, a simple heating device was designed to verify the application of the composite PCMs as the temperature protection element. The measurements showed that the presence of the PCMs prevented the rapidly rising of temperature during the heating process while maintained the temperature at relatively high level in a long time during the cooling process.
•Flexible PCM composites were prepared by infiltrating 3D MXene-coated melamine scaffold with PEG.•The PCM composites possessed high phase change enthalpy (194.1 J g−1) and dimension retention ratio ...(90%).•The solar-thermal conversion efficiency was 92.7% with the incorporation of MXene network.•The PCM composites exhibited an excellent light-actuated shape memory performance.•An application of light-driven and flexible heat eye-patch was proposed.
The liquid leakage, low light absorption capability and strong rigidity severely limit large-scale applications of phase change materials (PCMs). In this work, novel PCM composites with good encapsulation property, superior solar-to-thermal conversion efficiency and shape memory function were fabricated by introducing MXene-coated melamine foam (MF@MXene) into poly(ethylene glycol) (PEG). The MF@MXene/PEG composites showed satisfactory dimension retention ratio (90%) and phase change enthalpy (194.1 Jg−1). The three-dimensional MXene network constructed along the MF skeleton imparted the PCM composites with the ability to absorb and store the solar-energy as latent heat. Sunlight irradiation measurements suggested that the solar-thermal conversion efficiency reached 92.7%. Moreover, combining the resilience of MF@MXene sponge and the phase transition of PEG, the PCM composites exhibited remarkable shape fixation and recovery effects. A flexible heat eye-patch was further developed, which could be closely attached on human eyes and provided long-time thermal comfort within a stable temperature range.
•A new design of solar thermoelectric generator is proposed.•The design combines the segmented materials and asymmetric legs.•The output power is enhanced by 19–21%, as compared with the conventional ...design.•A simple analytical model is developed to predict the optimal leg length ratio.
In this work, a novel solar thermoelectric generator (TEG) design is proposed to enhance its output power and conversion efficiency. It combines segmented thermoelectric materials and asymmetrical legs with variable cross-sectional area along the leg length. A three-dimensional multiphysics thermoelectric model is employed to examine the performance of the new design. The optimal leg length ratio of two segmented materials (P1 and P2 materials) and the optimal cross-sectional area ratio of cold end to hot end are determined. In comparison with using P1 and P2 materials, the results show that the segmented design increases the output power by 14.9% and 16.6%, respectively, when the leg length ratio is optimized. When the asymmetrical legs are introduced to the segmented design, the output power can be additionally increased by 4.21%, as compared with the optimal segmented design. Moreover, a simple analytical model is proposed to predict the optimal leg length ratio of two thermoelectric materials for the present new design. The proposed model can be reduced to the existing models when the leg cross-sectional area ratio of cold end to hot end is equal to 1. Thus, the model can be considered as a generalized model, which can evaluate the optimal leg length ratio for the segmented design with any leg shape. Based on the model, the optimal leg length ratio should make the interface temperature between the two materials equal to the temperature of intersection point of their ZT (figure of merit) curves. Theoretically, this conclusion can be extended to any leg shape with a constant or variable cross-sectional area. The present simulations verify the theoretical prediction of the optimal leg length ratio.
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•2D S-scheme BC-20 catalysts for efficient activation of PMS under visible light.•The BC-20 + vis + PMS system exhibits an ultra-fast degradation rate for CIP.•In situ XPS confirms ...electron transport paths in heterojunctions.•Excellent carrier separation and transport in BC-20 + vis + PMS system.
Organic pollutants, such as ciprofloxacin (CIP), are ubiquitously detected in wastewater. However, their removal remains a challenge for conventional wastewater treatment technologies. Photocatalysis and peroxymonosulfate activation coupling are considered a promising strategy for the removal of recalcitrant organic pollutants. However, identifying optimal photocatalysts that can effectively couple with peroxymonosulfate activation and induce synergistic degradation of organic pollutants remains a challenge to be addressed. In this work, a novel S-scheme inorganic–organic heterojunction BiVO4/Cu-TCPP (BC) was fabricated. In situ X-ray photoelectron spectrum showed that the strong internal electric field of the S-scheme heterojunctions enabled efficient carrier transport. The generated photogenerated electrons could activate the peroxymonosulfate, which further promoted the separation of the carriers. The BC-vis-peroxymonosulfate system achieved 93.1% ciprofloxacin removal in 10 min with apparent rate constants k of 0.2426 min−1, which is larger than most reported peroxymonosulfate systems. Electron paramagnetic resonance spectra and liquid chromatography mass spectrometry demonstrated that the synergistic coupling of S-scheme heterojunction with peroxymonosulfate activation significantly improved the catalytic activity of the reaction system and enabled rapid CIP removal via both radical and nonradical pathways. The BC-vis-peroxymonosulfate system demonstrated ultra-fast removal of other quinolone antibiotics and organic pollutants and strong environmental adaptability under various conditions, suggesting its great potential for practical application. This study provides new insights for the design of efficient S-scheme heterojunction coupled peroxymonosulfate activation for environmental remediation.
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