Organic/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 abstractThe properties of nanoparticle–polymer composites strongly depend on the network structure of the polymer matrix. By introducing nanoparticles into a monomer (solution) and subsequently polymerizing it, the formation of the polymer phase influences the mechanical and physicochemical properties of the composite. In this study, semi-conducting indium tin oxide (ITO) nanoparticles were prepared to form a rigid nanoparticle scaffold in which 1,6-hexanediol diacrylate (HDDA), together with an initiator for photo-polymerization, was infiltrated and subsequently polymerized by UV light. During this process, the polymerization reaction was characterized using rapid scan Kubelka–Munk FT-IR spectroscopy and compared to bulk HDDA. The conductivity change of the ITO nanoparticles was monitored and correlated with the polymerization process. It was revealed that the reaction rates of the radical initiation and chain propagation are reduced when cured inside the voids of the nanoparticle scaffold. The degree of conversion is lower for HDDA infiltrated into the mesoporous ITO nanoparticle scaffold compared to purely bulk-polymerized HDDA.
Graphical abstractThe 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 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 abstractHere, we report a multiferroic relaxor material 0.41Bi(Ni1/2Zr1/2)O3–0.59PbTiO3, which exhibits a large piezoelectric coefficient (d33, 391 pC/N), high remnant polarization (Pr, 52.3 μC/cm2) and a high electrical freezing temperature (Tf, 498 K). The electric-field-induced transition from a cubic-like phase to a tetragonal phase was confirmed by the XRD patterns and first-cycle bipolar electrostrain loop. The magnetization and magnetic field relationship changes from nonlinear to linear when cooled from 300 to 2 K. The unusual trend in magnetic behavior could be interpreted as the transitions between the super short-range orderings. Furthermore, the maximum value of magnetization shows a 14% decrease at 300 K after electrical poling.
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 AbstractSilica aerogel composites reinforced with different aramid fibres have been synthesized and compared considering their potential use in thermal protection systems of Space devices. These composites were prepared from tetraethoxysilane and vinyltrimethoxysilane and the network was strengthened with aramid fibres. The results showed that the physical and chemical properties of the fibres were relevant, leading to composites with different properties/performance. In general, the obtained values for bulk density were low, down to 150 kg m?3. Very good thermal properties were achieved, reaching thermal conductivities bellow 30 mW m?1 K?1, and thermal stability up to 550 °C in all cases. Short length fibres produce stiffer composites with lower thermal conductivities, while among longer fibres, meta-aramid-containing fibres lead to nanocomposites with best insulation performance. Standard tests for Space materials qualification, as thermal cycling and outgassing, were conducted to assess the compliance with Space conditions, confirming the suitability of these aerogel composites for this application.
Graphical abstractCold welding technique at room temperature is the preferred option in nano-assembly and nano-jointing. In this study, the cold welding behavior and mechanical strength of Cu50Zr50 metallic glass nanowires (MGNWs) in head-to-head contact are investigated by molecular dynamics simulation based on the embedded atom method potential. Effects of welding velocity, operating temperature, and size of nanowires are discussed with the consideration of stress, shear strain, atomic deformation processes, and weld quality. Our simulation results demonstrate that a desirable weld quality can be obtained at room temperature. With an increase in welding velocity, the shear deformation zones of the welded MGNWs increase, leading to a decrease in mechanical strength. However, the effect of temperature on the weld quality is not pronounced. Besides, the elongation ability of the welded MGNWs increases with increasing diameters of nanowires. Smaller diameter results in better weld quality due to the size effect of metallic glass. For a pair of MGNWs with different diameters, the necking and fracture of the welded MGNWs occur in the regions of the nanowire with a relatively smaller diameter. This study carries major implications for the fabrication and structural assembly of metallic glass-based nanomaterials.
Graphical AbstractWell-dispersed Ni-based nanocrystals with Ni/NiO hybrid nanostructure are built on cellulose-derived carbon (Ni-C-500), which exhibits outstanding photocatalytic performance in the hydrogen evolution from water. Control experiments confirm that the optimal nickel content in Ni-C-500 is 16 wt% and the optimum calcination temperature is 500 °C. The hydrogen evolution rate on Ni-C-500 in the presence of Eosin Y and triethanolamine (TEOA) reaches 13.5 mmol/gcat/h in the first hour, which is even higher than that on commercial Pt/C catalyst (11.4 mmol/gcat/h). The carbon support facilitates the transfer of photogenerated electrons from photosensitizer to Ni-based nanocrystals, efficiently preventing the recombination of photogenerated electrons and holes during the photocatalytic procedure. Density functional theory (DFT) calculations further demonstrate that the NiO islands on Ni(111) surface facilitate the adsorption of water molecules because of the interaction between the oxygen atom of NiO island and the hydrogen atom of water. Furthermore, produced Had around NiO island of Ni(111) surface is more easily to form hydrogen on Ni/NiO hybrid nanostructure than on clean Ni(111) surface.
Graphical abstractNi/NiO hybrid nanostructure supported on biomass carbon for visible-light photocatalytic hydrogen evolution
Macrophages play a vital role in rejection of the implant materials by producing pro-inflammatory TNF and IL6 cytokines. They are also important for the normal function of the immune system to fight against infections. Therefore, characterizing the immunotoxicity on this cell type will be informative for the medical use of the biocompatible materials. Chitosan-based materials have been widely considered as biocompatible and safe. They have been suggested for the bone implants. Studies suggest that depending on the setup and chitosan functionalization, the immune system may react differentially to the chitosan-based materials. In this study, we characterized the immunocompatibility of injectable chitosan cryogel microspheres on mammalian macrophages by measuring their effect on cell viability and these cells’ ability to produce pro-inflammatory cytokines in the absence and presence of LPS, as a stimulant. Different sizes of microspheres were used to examine the effect of the size on their plausible effects. Our results suggest that independent of their size, chitosan cryogel microspheres were immunocompatible. They did not influence the cell viability and pro-inflammatory cytokine production by LPS-induced macrophages. Moreover, these materials lacked immunostimulatory activity as well, which means they would not activate the macrophages in the absence of any stimulant after their direct interaction with these cells. These properties are advantageous for their possible utilization in the medical fields as minimally invasive materials due to their injectable properties.
Graphical abstractThe kinetics of electrochemical corrosion of aluminum alloy (AlMg6) surfaces with different wettability was analyzed. The surfaces were processed by three different methods, in particular, polishing, laser texturing, the combination of laser texturing and low-temperature heating. After laser processing, the dimple-like texture was formed on the surface, and the wettability significantly enhanced. Low-temperature heating of laser-textured AlMg6 alloy surfaces led to the wettability inversion from strongly hydrophilicity to superhydrophobicity. Microscopic and profilometric methods were used to estimate the surface degradation due to corrosion when aggressive solution droplets (a mixture of NaCl and hydrogen peroxide aqueous solutions) evaporated. The potentiodynamic polarization measurements of AlMg6 alloy surfaces were conducted. The typical modes of corrosion and evaporation of aggressive solution droplets were detected. The kinetics of corrosion was estimated by the behavior of the corrosion area evolution. In addition, when immersing laser-textured sample with strongly hydrophilic properties into aggressive solution, the higher corrosion rate was found in the liquid meniscus region (aggressive mixture / alloy / air interface) compared to the textured site immersed in the mixture. This was explained by convection increasing the rate of reaction products removal and promoting a stronger deviation from the equilibrium state in the aggressive mixture. Experimental results of the potentiodynamic polarization measurements revealed that laser-textured samples exhibit enhanced corrosion protective properties compared to polished samples.
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 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 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 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 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 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 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 abstract