The caloric effects under combined applications of magnetic field and hydrostatic pressure to a MnCoSi meta-magnet were investigated. Under a magnetic field change of 0–5 T, the maximum magnetic entropy change was enhanced by 35.7% when a 3.2kbar hydrostatic pressure was applied, and the cooling temperature span was extended by 60 K when a hydrostatic pressure of 9.7 kbar was applied. The coupled caloric entropy change, which originates from the coupling between the magnetism and volume, was calculated and accounted for the enhanced entropy change of MnCoSi. The present work facilitates the use of MnCoSi as a solid-state refrigerant and also enriches the investigation of the multicaloric effect under multiple external fields.
Graphical abstractOrganic/inorganic thermoelectric composites have played an important role in the development of new, green, and renewable energy sources with potential applications in efficient thermal management, flexible electronics, and bioelectronics. Electrochemical syntheses, including electropolymerization, electrochemical deposition, electrochemical doping, electrochemical post-processing, etc., require no addition of surfactants or oxidants, the products of which are easy to separate and purify, providing clean, efficient, and facile routes for the preparation of organic thermoelectric materials and their composites. In this review, the preparation, properties, and applications of organic/inorganic thermoelectric composites from electrochemical synthesis were reviewed in detail, offering a perspective on the recent advances in the field.
Graphical abstractExtension of corrosion inhibitors from traditional molecular-scale to nanoscale will not only be significant to develop green and efficient inhibitors, but also supplement the discipline system of corrosion inhibitors. However, many research on the interfacial behavior of nano-inhibitors have ignored the special colloidal properties of nanoparticles and show no obvious differences with traditional inhibitors. In this study, graphene oxide (GO) was functionalized with polydopamine (PDA) via covalent modifications and self-polymerization, and GO-PDA was studied as a corrosion inhibitor of carbon steel in HCl solution. Diversified measurements confirmed that GO-PDA can effectively protect carbon steel from corrosion, and the inhibition efficiency almost reached 90% at 100 mg/L. Interfering factors including immersion time and concentration were investigated. The lamellar nanoparticles adsorbed on the surface of carbon steel have formed a hydrophobic film in micro-nano structures. The transition from a negative charge on the GO surface to a positively charged GO-PDA contributed to adsorption at the interface. An initial model of nano-inhibitor was established to explicate the inhibition mechanism.
Graphical abstractAquivion membrane displays improved properties as compared to Nafion membrane, partly due to shorter side chains. However, some improvements are still necessary for proton exchange membrane fuel cell to operate at low relative humidity. To overcome this drawback, the addition of clay nanoparticle into the Aquivion matrix can be considered. In this study, different composite membranes have been prepared mixing short-side-chain PFSA (perfluorosulfonic acid) Aquivion and selectively modified halloysite nanotubes for PEMFC low relative humidity operation. Halloysites were grafted with fluorinated groups, sulfonated groups, or perfluoro-sulfonated groups on inner or outer surface of the tubes. The obtained composite membranes showed improved properties, especially higher water uptake associated with reduced swelling and better mechanical strength compared to pristine Aquivion membrane and commercially available Nafion HP used as reference. The best performance in this study was obtained with Aquivion loaded with 5 wt% of pretreated perfluoro-sulfonated halloysite. The composite membrane, referred to as Aq/pHNT-SF5, displayed the largest water uptake and proton conductivity among the panel of membranes tested. The chemical stability was not affected by the presence of halloysite in the Aquivion matrix.
Graphical abstractNovel thermal nanoparticles [hollow mesoporous silica nanospheres (HMSNs)–poly (N-isopropyl acrylamide-acrylic acid) PNIPAM-AA] were developed with Ag nanoparticles (AgNps) as the core, mesoporous silica nanoparticles as the layer, and thermally responsive polymers PNIPAM-AA as the shell. The AgNps had good photothermal effects, PNIPAM-AA was responsive to temperature, the combination of AgNps and PNIPAM-AA could be used as a photothermal-responsive switch for drug release, and HMSNs greatly increased the drug loading of the carrier. The samples were characterized by means of scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, and UV–Vis absorption spectra. The results showed that Ag@HMSN nanoparticles possessed a uniform diameter (330 nm), high specific surface area (822.45 m2/g), and mesoporous pore size (2.75 nm). Using ibuprofen (IBU) as a model drug, the release process was monitored under in vitro conditions to investigate its release characteristics at different temperatures. The results showed that the nanoparticles had a significant regulatory effect on IBU release.
Graphical abstractHybrid organic–inorganic nanocomposites are great candidates for display and illumination systems due to improved optoelectronic properties and photostability. This work endeavours towards the scientific study of the influence of defect-induced zinc oxide nanoparticles (ZnO) on the optical characteristics of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). ZnO nanoparticles consist of many vacancies which facilitate light emission across the visible region. The green defective emission occurring due to the presence of oxygen vacancies in ZnO was used to re-excite MEH-PPV and hence, improve the luminescence quantum efficiency. The photostability of the nanocomposite was enhanced through charge transfer (prevents the formation of superoxides) and energy transfer (reduces the non-radiative decay) mechanisms.
Graphical abstractIn this study, poly(L-lactic acid) (PLA)/low molar mass alkali lignin (aL) (1%, 5% and 10% w/w) composites were prepared primarily for a comprehensive understanding of the effect of aL on their antimicrobial properties, biocompatibility and cytotoxic behavior. The properties were evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetry and X-ray diffraction. The mechanical, water vapor barrier properties and photodegradability were analyzed as well. The results showed a significant inhibiting effect of aL on the crystallization behavior of PLA, increased water barrier properties (up to 73%) and photodegradability. PLA/aL composites showed a tenfold reduction in Gram-positive bacteria viability, very good cellular response and very low cytotoxicity levels, thus validating these materials as non-cytotoxic and with high potential to be used as food packaging.
Graphical abstractIn view of the disadvantages of concentration polarization and trade-off effects in the application of membrane in desalination field, oxide-nano graphene oxide/polyamide (O-NGO/PA) loose intermediate layer and PA ultra-thin dense layer were introduced to fabricate PA/O-NGO/polyphenylene sulfide composite membrane with sandwich structure via multi-step interfacial polymerization (MS-IP) method. The selective permeation mechanism of ultrathin layer produced by different aqueous monomers (PIP and MPD) was studied, the effect of its physicochemical structure on the relief of concentration polarization phenomenon and the breakthrough of trade-off effect was analyzed. The ultra-thin and dense PA layer mainly played the role of interception and shortened the water molecular penetration path. In the retention test of metal salt solution, compared with the rough surface, it was found that the smooth surface was more conducive to the diffusion of intercepted metal ions into the feed solution, thus alleviating the concentration polarization phenomenon.
Graphical abstractIn this critical note, the thermal stability behavior of ultra-fine grained (UFG) and nano-structured (NS) metals and alloys produced through severe plastic deformation (SPD) techniques is reviewed. For this case, the common engineering metals with body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP) crystal structures such as aluminum, copper, nickel, magnesium, steel, titanium, and their relating alloys were assessed. Microstructural evolution in these severely deformed materials following post-processing annealing treatment was investigated for various times and temperatures below the recrystallization point. The microstructure development reported in the literature was studied in terms of the stable grain structures correlated with different levels of plastic straining. The stacking fault energy (SFE) is noted to be a key issue which has a critical influence in predicting the coalescence or coarsening behavior of ultra-fine and nanoscale grains after SPD treatment by controlling the cross-slip phenomenon for screw dislocations.
Graphical AbstractRescuing the compromised function of periodontal ligament stem cells (PDLSCs) due to hyperglycemia-induced oxidative stress and reducing the risk of postoperative infection around the interface of scaffold materials are of prime importance for periodontal regeneration in diabetes mellitus. To this end, a facile and green approach for the establishment of surfaces with antioxidative and antibacterial properties was developed in this work. Briefly, the surfaces of polystyrene (PS) plate were pre-modified with polydopamine and then coated with a genipin crosslinked layer-by-layer (LbL) assembly, which was established by using the antibacterial polyelectrolytes carboxymethyl chitosan (CMC) and polylysine (PLL) as building block. Metformin as an antioxidative agent was incorporated into the discrete nanolayers to achieve sustainable release. Our research showed that metformin-loaded LbL assembly presented favorable cytocompatibility. The released metformin could partially rescue the impaired osteogenic function of human PDLSCs induced by high glucose in vitro. Meanwhile, owing to the antibacterial activity of CMC and PLL, the colonization of common pathogenic bacteria related to periodontal disease could be disturbed on the surface of developed coatings. Accordingly, the presented strategy for surface functionalization of materials in our study holds a promising potential for periodontal regeneration application in diabetic patients.
Graphical abstractWe review the literature describing the use of interleaves to increase interlaminar fracture toughness in fibre-reinforced polymer composites and hence to improve damage tolerance. From an analysis of data provided in the literature from the use of microfibre and nanofibre interleaves, we show that the performance of these widely researched systems is clearly differentiated when plotted against the mean coverage of the interleaf. Using a simple analysis, we suggest that this can be attributed to the influence of their porous architectures on the infusion of resin. We show also that the superior toughening performance of microfibre interleaves is only weakly influenced by the choice of fibre. We find also that the inclusion of carbon nanotubes within interleaves to deliver multifunctional composites can be optimised by using a hybrid system with microfibres.
Graphical abstractFumed silica nanoparticles (FSN) are one of the most common synthetic forms of silica, but prolonged exposure leads to cell toxicity and apoptosis due to reactive oxygen species (ROS) generation and cell membrane perturbation resulting from hydrogen bonding and electrostatic interactions. Increasing attention is being put on synthesizing FSN material that is safer both for workers involved in large-scale industrial production, and consumers coming in contact with FSN additives. In the present work, we explore the molecular structural differences and efficacy of Al- and Ti-metal-doped FSN which has previously been shown to reduce toxicity effects of FSN. We use a combination of 29Si and 27Al solid-state magic angle spinning (MAS) NMR, Raman spectroscopy, and thermogravimetric analysis (TGA) to probe the surface and bulk structure and quantify the adsorption capacity and reactivity of the metal-doped FSN with respect to amino acid thermal condensation. Alanine was selected as the amino acid of choice for its simplicity and ubiquity in biochemical reactions. The results indicate that metal doping has a modest impact on the fumed silica molecular structure with a small decrease in amino acid adsorption capacity and thermal condensation reactivity as a function of increased metal doping.
Graphical AbstractNon-dendritic microstructures are generally obtained in metals after semi-solid deformation (deformation during solidification); however, dendritic growth is preferred without deformation. The fragmentation of dendrites is recognized as an essential contributing factor to non-dendritic microstructures. However, the underlying mechanism of fragmentation needs to be clarified in depth. It is infamously hard for researchers to carry out a direct observation of this process. Moreover, a comprehensive numerical survey of this process is not trivial. The present research reported a new method to model dendritic growth during semi-solid deformation. The motion and deformation of the solid coupled with liquid flow in the melt were treated as the two-phase flow because plastic materials could be formulated as non-Newtonian fluids. The vector-valued phase-field formulation and the self-constructed Navier–Stokes solver made it possible to simulate the growth, motion, deformation, fragmentation and agglomeration of two dendrites coupled with liquid flow in the melt. Computational results suggest that fragmentation can occur when the grain boundary is wet and penetrated by the melt, giving new supporting evidence to a previously proposed mechanism for the fragmentation of dendrites.
Graphical abstractThe development of eco-friendly connection material instead of steel is a challenging problem in timber structures. Following densification, the mechanical properties of low-density species can be significantly improved. Densified wood may be a potential connection material in timber structures. This paper reviewed the different processing for densified wood, and obtained favorable mechanical properties and dimensional stability based on small specimen sizes, which are much less than the applicable sizes in practice. A densification processing with alkali pretreatment was adopted for poplar widely cultivated in the world to produce the densified poplar, which has been rarely reported as connection material. Various specimens of densified poplar were tested to obtain their main mechanical properties such as strength and deformability. The set recovery of densified poplar was also measured to observe their dimensional stability. In addition, the hygroscopic swelling strains for the diameter of densified poplar dowel were measured to present their moisture-dependent behavior. The improved mechanical properties and dimensional stability confirmed the fact that densified poplar with alkali pretreatment can be an optimal connection material.
Graphical abstractNanotechnologies known as a developing applied science have significant global socioeconomic values and many advantages obtained from nanoscale materials. Its applications can have significant effects on the performance of organizations. The advance of two-dimensional (2D) MXene-derived QDs (MQDs) is currently in the initial stages. Scholars have shown distinguished optical, electronic, thermal and mechanical attributes by surface chemistry and versatile transition metal. In this field of study, many applications are introduced like energy electromagnetic interference shielding, storage, sensors, transparent electrodes, photothermal therapy, catalysis and so on. The vast range of optical absorption attributes of MQDs along with high electronic conductivity has been detected to be key attributes because of their achievement in the mentioned usages. Currently, relatively little materials are highly known because of their basic electronic and optical properties, which can limit their full potentials. From a theoretical and experimental point of view, in this work, electronic and optical properties of MQDs along with applications corresponding to those properties were evaluated.
Graphical abstractSilver nanowires find use in a myriad of applications, including communication systems, sensors, medical devices and electrical equipment. Temperature-dependent electrical and thermal properties of chemically derived silver nanowires are rarely explored. In the present work, seed-mediated synthesis of silver nanowires has been carried out, and their electrical and thermal conductivity at 300 K is found to be 1.848?×?107 S/m and 64.8 W/mK, respectively. A screen-printable ink of silver nanowires is formulated and printed on low-cost and widely used substrates like paper and cotton fabrics. Flexible printed electrodes could be made possible with uniform printed structures obtained in cotton fabric and paper substrate. The printed pattern exhibited sheet resistance of 0.7 Ω/sq. Screen-printed silver nanowires on paper show shielding efficiency of 99.9% in X band, which promotes them as excellent candidates in fabricating lightweight electronic devices by a one-step printing process.
Graphical abstractApplication of phase change materials (PCMs)-based thermal management technology in flexible electronic devices has been inhibited due to the leakage and strong rigidity of PCMs. A novel flexible composite PCMs with ultrahigh extensibility was developed in this paper. Concretely, a kind of paraffin@copper (PA@Cu) microcapsule with paraffin as core and nano-Cu particle as “flexible” metal shell was prepared by a simple Pickering emulsion method in an aqueous medium. The encapsulation ratio of paraffin reached 98wt%. Then the PA@Cu microcapsules were introduced into uncured liquid silicone to fabricate flexible composite PCMs (PA@Cu/SE). SEM results demonstrated that the microcapsules were tightly and uniformly wrapped in the three-dimensional network structure of silicone elastomer matrix. Owing to the good compatibility of PA@Cu with the polymer elastomer and a barrier for the melted PA provided by the “flexible” nano-Cu shell, the resulting composite PCMs present superior flexibility and thermal reliability. Tensile tests showed that the flexible composites with a relative higher loading of PA@Cu (40wt%) exhibit outstandingly larger extensibility (>?730%) than many reported literatures. In addition, the composites presenting superior thermal protection for biological tissue make them well-suited for thermal management in wearable electronics.
Graphical abstractWO3, a visible light reaction catalyst, absorbs light at a wavelength of 470 nm and has many advantages, such as strong stability, long life, non-toxicity, low cost, and suitable band edges. In this review, the photocatalytic mechanism of WO3 in water pollution treatment is introduced, as well as a systematic summary, and some main strategies for improving the photocatalytic activity of WO3 in water pollution treatment are introduced, for example surface and morphology control, synthetic heterojunctions, and doping element. Finally, the main conclusions and prospects of WO3-based photocatalysts are pointed out. It can be expected that this review can provide guidance for designing low-cost, high-efficiency new WO3-based photocatalysts in the process of water pollution treatment and can meet the application prospects of efficient utilization of solar degradation in the field of environmental purification.
Graphical abstractProton conductivity, morphology, phase composition and mechanical properties of (1-x)CsH2PO4-xp(VDF/HFP) (x?=?0.05–0.25, weight ratio) polymer electrolytes were investigated for the first time. The chemical interaction of the organic matrix and acid salt was not observed and crystal structure of CsH2PO4 was preserved. A method for the synthesis of thin membranes with uniform distribution of the components was proposed. Thin flexible membranes with uniform distribution of sub-micrometer CsH2PO4 particles in the polymer membranes and improved hydrolytic stability were obtained firstly by using a bead mill. The mechanical strength of the hybrid polymer compounds was determined using the Vickers microhardness measurements. Proton conductivity in the (1-x)CsH2PO4-xp(VDF/HFP) electrolytes decreases monotonically with x increase due to the «conductor–insulator» percolation. Nevertheless, the values of proton conductivity remain sufficiently high, and along with small thickness, flexibility, improved mechanical and hydrophobic properties, it makes polymer electrolytes based on CsH2PO4 promising for membranes of medium-temperature fuel cells.
Graphical abstractPolyimide aerogels are promising for diverse applications owing to their nanoporous structure and superior performance in thermal insulation, dielectric protection, etc. However, the severe shrinkage they usually suffer has long been a threat, and can pose great challenges to their shape-stable preparation and reliable applications. It is very important to clarify the effects of various factors on the shrinkage of PI aerogels and the effective strategies available for shrinkage reduction. These are also the focuses of the present review, to provide guidance for preparing PI aerogels with greatly reduced shrinkage, and thereby improved shape stability and use reliability. Since the shrinkage of PI aerogels is quite a complex issue, further studies on PI aerogels against shrinkage deserve continuous attention.
Graphical abstract