Showing papers in "Journal of Materials Science in 2019"

A review of the mechanical and thermal properties of graphene and its hybrid polymer nanocomposites for structural applications

Abstract: In the present review, the recent progress in describing the intricacies of mechanical and thermal properties of all types of graphene- and modified graphene-based polymer nanocomposites has been comprehensively examined. The effectiveness of microscopy bouquet for the intrinsic characterization of graphene family and their composites was clearly demonstrated in this research. Furthermore, the utility of the dynamic mechanical analysis and thermo-gravimetric analysis employed for thermal characterization that has been reported by various researchers was exhaustively analyzed in this paper. This research primarily focused on the analyses of several good articles concerned with hybrid graphene composites and the synergetic effect of graphene with other nanofiller to assess its effect on the mechanical properties of its corresponding composites. Such systematic analysis of previous literatures imparted a direction to the researchers about the solution of improved interfacial properties as well as the enhanced dispersion into the vicinity of the matrix. This current research has suggested that the presence of the graphene filler even at very low loadings has shown considerable improvement in the overall mechanical properties of graphene. Further studies to optimize the value of the filler need to be addressed in order to gain complete understanding of the properties of graphene. The potential applications, current challenges, and future perspectives pertaining to these nanocomposites were elaborately discussed in the current study with regard to the multi-scale capabilities and promising developments of the graphene-family-based nanocomposites materials.

Elastic, plastic, and creep mechanical properties of lithium metal

Abstract: With the potential to dramatically increase energy density compared to conventional lithium ion technology, lithium metal solid-state batteries (LMSSB) have attracted significant attention. However, little is known about the mechanical properties of Li. The purpose of this study was to characterize the elastic and plastic mechanical properties and creep behavior of Li. Elastic properties were measured using an acoustic technique (pulse-echo). The Young’s modulus, shear modulus, and Poisson’s ratio were determined to be 7.82 GPa, 2.83 GPa, and 0.381, respectively. To characterize the stress–strain behavior of Li in tension and compression, a unique load frame was used inside an inert atmosphere. The yield strength was determined to be between 0.73 and 0.81 MPa. The time-dependent deformation in tension was dramatically different compared to compression. In tension, power law creep was exhibited with a stress exponent of 6.56, suggesting that creep was controlled by dislocation climb. In compression, time-dependent deformation was characterized over a range of stress believed to be germane to LMSSB (0.8–2.4 MPa). At all compressive stresses, significant barreling and a decrease in strain rate with increasing time were observed. The implications of this observation on the charge/discharge behavior of LMSSB will be discussed. We believe the analysis and mechanical properties measured in this work will help in the design and development of LMSSB.

Thermal conductivity of carbon nanotube networks: a review

Abstract: Depending on their structure and order (individual, films, bundled, buckypapers, etc.), carbon nanotubes (CNTs) demonstrate different values of thermal conductivity, from the level of thermal insulation with the thermal conductivity of 0.1 W/mK to such high values as 6600 W/mK. This review article concentrates on analyzing the articles on thermal conductivity of CNT networks. It describes various measurement methods, such as the 3-ω method, bolometric, steady-state method and their variations, hot-disk method, laser flash analysis, thermoreflectance method and Raman spectroscopy, and summarizes the results obtained using those techniques. The article provides the main factors affecting the value of thermal conductivity, such as CNT density, number of defects in their structure, CNT ordering within arrays, direction of measurement in relation to their length, temperature of measurement and type of CNTs. The practical methods of using CNT networks and the potential directions of future research in that scope were also described.

A review of the electrical and mechanical properties of carbon nanofiller-reinforced polymer composites

Abstract: Within decades of development, carbon nanomaterials such as carbon black, fullerene, carbon nanotube, carbon nanofiber, graphene and their combined nanofillers have been tremendously applied in polymer material industries, generating a series of fascinating multifunctional composites in the fields from portable electronic devices, sports, entertainments to automobile, aerospace and military. Among the various material properties of the composites, electrical conductivity and mechanical performance are the two most important parameters for evaluating the effectiveness of nanofillers in the polymer matrices. In this review, we focus on the electrical and mechanical properties of diverse dimensional carbon nanofillers (e.g., zero-, one-, two-, three-dimensional nanofillers or their combinations)-reinforced polymer composites to seek the most efficient and effective approach to obtain high-performance polymeric nanocomposites.

Copper/graphene composites: a review

Abstract: Recent research upon the incorporation of graphene into copper matrix composites is reviewed in detail. An extensive account is given of the large number of processing methods that can be employed to prepare copper/graphene composites along with a description of the microstructures that may be produced. Processing routes that have been employed are described including powder methods, electrochemical processing, chemical vapour deposition, layer-by-layer processing, liquid metal infiltration among a number of others. The mechanical properties of the composites are described in detail along with an account of the structural factors that control mechanical behaviour. The mechanics and mechanisms of deformation are discussed, and the effect of factors such as the graphene content and the type of graphene used, along with processing conditions for the fabrication of the composites, is described. The functional properties of copper/graphene composites are also reviewed including their electrical and thermal properties, and tribological and corrosion behaviour. In each case, the effect of the graphene type and content, and processing conditions are also described. Finally, possible future applications of copper/graphene composites are discussed.

Energy absorption of a bio-inspired honeycomb sandwich panel

Abstract: In this study, a novel bio-inspired honeycomb sandwich panel (BHSP) based on the microstructure of a woodpecker’s beak is proposed. Unlike a conventional honeycomb, the walls of the bio-inspired honeycomb (BH), which is used as the core of a sandwich panel, are made wavy. Finite element simulation shows that under dynamic crushing the proposed BHSPs exhibit superior energy absorption capability compared with the conventional honeycomb sandwich panel (CHSP). In particular, the specific energy absorption (SEA) of the BHSP increases by 125% and 63.7%, respectively, compared with that of the honeycomb sandwich panel with the same thickness core or the same volume core. In addition, a parametric study of the BHSPs is carried out to investigate the influences of the wave amplitude, wave number and core thickness on the energy absorption performance of the BHSPs. It is found that the BH core with a larger wave number and amplitude shows higher SEA. Furthermore, an increase in core thickness can improve the SEA. These results provide guidelines in the design of a lightweight sandwich panel for high-energy absorption capability.

Review: recent progress in low-temperature proton-conducting ceramics

Abstract: Proton-conducting ceramics (PCCs) are of considerable interest for use in energy conversion and storage applications, electrochemical sensors, and separation membranes. PCCs that combine performance, efficiency, stability, and an ability to operate at low temperatures are particularly attractive. This review summarizes the recent progress made in the development of low-temperature proton-conducting ceramics (LT-PCCs), which are defined as operating in the temperature range of 25–400 °C. The structure of these ceramic materials, the characteristics of proton transport mechanisms, and the potential applications for LT-PCCs will be summarized with an emphasis on protonic conduction occurring at interfaces. Three temperature zones are defined in the LT-PCC operating regime based on the predominant proton transfer mechanism occurring in each zone. The variation in material properties, such as crystal structure, conductivity, microstructure, fabrication methods required to achieve the requisite grain size distribution, along with typical strategies pursued to enhance the proton conduction, is addressed. Finally, a perspective regarding applications of these materials to low-temperature solid oxide fuel cells, hydrogen separation membranes, and emerging areas in the nuclear industry including off-gas capture and isotopic separations is presented.

Interface reaction and intermetallic compound growth behavior of Sn-Ag-Cu lead-free solder joints on different substrates in electronic packaging

Abstract: During soldering and service, intermetallic compounds (IMCs) have an important impact on the performance and reliability of electronic products. A thin and continuous intermetallic layer facilitates the formation of reliable solder joints and improves the creep and fatigue resistance of solder joints. However, if the IMCs overgrow, the coarse IMC becomes brittle and tends to crack under stress, leading to a decrease in solder joint reliability. Based on the latest developments in the field of lead-free solders at home and abroad, this paper comprehensively reviews the interfacial reaction between SnAgCu Pb-free solders and different substrates and the growth behavior of IMCs and clarifies the growth mechanism of interfacial IMCs. The effects of the modification measures of lead-free solder on the IMCs and reliability of SnAgCu/substrate interface are analyzed, which provide a theoretical basis for the development and application of new lead-free solder.

A review of recent applications of porous metals and metal oxide in energy storage, sensing and catalysis

Abstract: Nanoporous metals and nanoporous metal oxide-based materials are representative type of porous and nanosized structure materials. They have many excellent performances (e.g., unique pore structure, large clear surface area and high electrical conductivity) to be prodigiously promising potentials, for a variety of significant applications (e.g., energy storage, sensing and catalysis). Therefore, this review summarized the recent advances in the development of nanoporous metals/metal oxide-based materials, with special emphasis on superior electrochemical applications: supercapacitors, lithium ion batteries, sensing, electrocatalysis and photocatalysis. The significant and representative studies in each area are comprehensively reviewed and discussed as a reference for researchers working in related areas. We also outline the key challenges and future opportunities in this exciting field.

Recent advances in electrochemical nonenzymatic hydrogen peroxide sensors based on nanomaterials: a review

Abstract: The development of efficient electrochemical hydrogen peroxide (H2O2) sensors has received great attention due to the significance of H2O2 in biological systems and its practical applications in various fields. With the new class of H2O2 sensors, the nonenzymatic detection of the target can provide many attractive characteristics, such as simple fabrication, ultrahigh sensitivity, and excellent stability. Considering the rapid expansion of nonenzymatic H2O2 detection using advanced nanomaterials, an overview of the current state of methods for electrochemical nonenzymatic H2O2 sensors is presented (with 399 refs.). The first part of the review covers the sensors based on the use of nanoparticles consisting of metals, metal oxides/sulfides, and bimetallic nanoparticles/alloys. The next major section discusses sensors that make use of carbon nanomaterials, such as carbon nanotubes, graphene, graphene oxide, carbon dots, and of other carbonaceous materials. Advantages and the intrinsic drawbacks of employing various nanomaterials to detect H2O2 are emphasized.

Gold nanoparticles supported by amino groups on the surface of magnetite microspheres for the catalytic reduction of 4-nitrophenol

Abstract: Fe3O4/P(GMA-DVB)/PAMAM/Au microspheres are fabricated to research the catalytic performances to 4-nitrophenol. In the preparation process, Fe3O4 microspheres act as magnetic cores, PAMAM dendrimers growing up on the surface of P(GMA-DVB) polymer work as carriers, and Au nanoparticles serve as catalytic materials. The stability of the prepared microspheres is evaluated by successively catalytic experiments to measure the conversion of 4-nitrophenol, and catalytic efficiency can still maintain up to 78.7% after ten cycles. Moreover, the effects of major factors including the concentration of the prepared microspheres and the temperature of reaction system on the conversion of 4-nitrophenol are also investigated in detail. The manuscript reveals that 4-nitrophenol can be almost converted to 4-aminophenol within 7 min at 45 °C in the case of using 1.0 g/L Fe3O4/P(GMA-DVB)/PAMAM/Au microspheres. Such excellent catalytic properties are ascribed to the optimum structure of the prepared microspheres, which favors the sufficient contact between Au nanoparticles and 4-nitrophenol. The results and strategies exhibited here provide insight into the preparation of sophisticated structures of catalysts to treat wastewater.

Nanoedible films for food packaging: a review

Abstract: Edible packaging is a thin layer formed on food surface, which can be eaten as an integral part of the food product. While an edible coating is formed as thin layer directly on the food surface for improving shelf life of fruits and vegetables, the edible film is formed as thin layer separately and wrapped on food surface later. The edible films have attracted much interest as it has potential to overcome the problems associated with plastic packaging. However, their film properties are not as good as the conventional packaging materials, such as plastics. The food and beverage industry is showing much interest to incorporate the benefits of nanotechnology. The nanomaterials have unique characteristics (such as, large surface area-to-volume ratio, distinct optical behaviour and high mechanical strength), which, when incorporated with the edible films, could improve the film properties of the edible films. Therefore, the right selection and incorporation of nanomaterials can improve the film properties. Most of the previous review articles on food packaging summarized the research findings of synthetic and/or biodegradable films and coatings. Only few review articles were devoted for edible films and coatings. Among them, very few review articles had discussion about the use of nanotechnology for all kinds of food packaging applications. However, there is no comprehensive review on nanoedible films. The objective of this review article is to cover the recent works on nanoedible films prepared incorporating the nanofillers (such as, nanostarch, nanocellulose, nanochitosan/nanochitin, nanoproteins and nanolipids), the film properties (such as, the mechanical properties, WVP and film colour of some of the recent nanoedible films), and the challenges and opportunities for future research.

Layered BiOBr/Ti3C2 MXene composite with improved visible-light photocatalytic activity

Abstract: Layered BiOBr/Ti3C2 (BTC) composites were synthesized by first preparing Ti3C2 nanosheets through the liquid etching of Ti3AlC2 powder and then hybridizing with BiOBr via a facile reflux process. The morphology, crystal structure, light-harvesting capacity, chemical nature of atoms and visible-light photocatalytic degradation activity were systematically studied and discussed. It was found that the introduction of Ti3C2 nanosheets improved UV–Vis light absorption region of BiOBr. A contact interface was formed between BiOBr nanoplate and Ti3C2 nanosheet due to the similar layered structures, which could accelerate the efficient separation and transfer of photoinduced electrons and holes. Thus, the obtained BTC composites showed the higher visible-light photocatalytic activity for the degradation of RhB than pure BiOBr. The generated active species were determined by the active species capture experiment and ESR spectra, showing that ·O2− and ·OH played a crucial role in the photocatalytic degradation of RhB. The corresponding photocatalytic mechanism was proposed. This work may provide a new insight into the construction of earth-abundant MXene-based photocatalysts with high performance and low cost.

Investigation on the optimization, design and microwave absorption properties of BaTb0.2Eu0.2Fe11.6O19/PANI decorated on reduced graphene oxide nanocomposites

Abstract: A novel hybrid material with excellent microwave absorption property has been designed by decorating reduced graphene oxide with Ba Tb0.2Eu0.2Fe11.6O19/PANI composite, and the effect of graphene content on microwave absorption property has been investigated. The microstructure of the composite is characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscope, transmission electron microscope and Raman spectroscopy. The mechanism of microwave absorption is discussed minutely. The result shows that the ternary nanocomposites demonstrate unexceptionable microwave absorption property due to its special nanostructures and synergistic effect among BaTb0.2Eu0.2Fe11.6O19, PANI and RGO. The minimum reflection loss can reach − 60.9 dB at 16.4 GHz with a thickness of only 1.95 mm, and the corresponding effective absorption bandwidth (below − 10 dB) is 4.2 GHz. BaTb0.2Eu0.2Fe11.6O19/PANI/RGO composite can be one of the most promising microwave absorption materials.

Recent advancements in Fe-based biodegradable materials for bone repair

Abstract: Degradable metallic biomaterials represent a new concept of bioactive biomaterials used for implants with temporary function. They should support the tissue healing process for a certain period and should progressively degrade thereafter. Degradable metallic materials could potentially replace the corrosion-resistant metals currently used for orthopaedic, cardiovascular, and paediatric implants. The interest in the study of degradable metallic biomaterials has dramatically increased in the last decade. This article reviews the current achievements in the design of biodegradable iron-based materials for orthopaedic load-bearing applications. It introduces a broad overview of the different alloying elements, coating materials, and processing methods used to improve the corrosion behaviour, mechanical properties, and biocompatibility of iron implant materials for temporary hard tissue scaffolds. An emphasis is set on Mn and Zn as the most promising alloying elements for Fe as well as on innovative calcium phosphate-based ceramic and polymeric coatings. In addition, the novel iron–ceramic composite biomaterials for orthopaedic implants are mentioned. Finally, recent challenges and future development direction for iron-based materials are proposed.

High-capacity lithium sulfur battery and beyond: a review of metal anode protection layers and perspective of solid-state electrolytes

Abstract: Li metal has the highest specific capacity (3860 mA h g−1) and the lowest electrochemical potential (− 3.04 V vs. SHE) of available metal anodes. Together with the high specific capacity of sulfur cathodes (1670 mA h g−1), Li metal–S batteries are a promising candidate to achieve high energy density batteries for electric vehicles and future industry. However, Li metal anodes suffer from corrosive reactions with electrolytes, a theoretically infinite volume change, and the growth of dendrites during electrochemical cycling. To realize the practical application of Li metal–S batteries, protective layers or artificial solid-electrolyte interphase (ASEI) layers have been applied to the surface of Li metal. These ASEI layers demonstrate capabilities to suppress the growth of dendrites and mitigate side reactions, which enhance the performance and safety of Li metal anodes in liquid-electrolyte systems, though there are still limitations and challenges. The development of solid-state electrolytes as artificial SEIs provides a promising route to suppress the issues of dendrite formation and the polysulfide “shuttle effect” in Li–S chemistry; however, the improvement in the interfacial compatibility and stability between the Li metal and the solid-state electrolyte is crucially needed. In this review, we summarize different types of ASEI layers used to protect Li metal, especially in Li–S batteries, with both liquid- and solid-electrolyte systems. We also briefly introduce the concept of anode protection of Mg metal and its application in Mg–S batteries. Perspectives regarding the further development and improvement of ASEI layers for Li metal and Mg metal are discussed.

Facile synthesis of exfoliated graphitic carbon nitride for photocatalytic degradation of ciprofloxacin under solar irradiation

Abstract: Exfoliated g-C3N4 nanoparticles prepared by a green route (an aqueous bi-thermal method) were characterized by techniques such as XRD, UV-VDRS, FESEM, PL, TEM. Degradation of an aqueous solution of ciprofloxacin (CPN), when exposed to solar irradiation in the presence of g-C3N4 nanoparticles, was studied to evaluate the photocatalytic activities of semiconductor photocatalyst. The photocatalytic activities of g-C3N4 have enhanced after its exfoliation. The exfoliated g-C3N4 obtained with the aqueous bi-thermal method provided about three times the large surface area and about two and half times effective photocatalyst as bulk g-C3N4. The results of electrochemical tests like linear sweep voltammetry, MS graphs of exfoliated g-C3N4 nanoparticles together with electrochemical impendence (EIS) corroborated the results of photocatalytic activities of g-C3N4 after exfoliation. The enhanced photocatalytic behavior of exfoliated g-C3N4 is the result of its efficient separation, low recombination of photogenerated charge carriers and high surface area. The effects of exfoliated g-C3N4 catalyst concentration, irradiation time and initial CPN concentration on the degradation of CPN were carefully studied. We found that 1 g/L nano-exfoliated g-C3N4 can degrade up to 78% a 20 ppm CPN solution exposed to solar light for 1 h. The studies also incorporated scavenger tests to possibly identify reactive species and mechanism for CPN degradation. This work provided a new method for scalable exfoliation of g-C3N4.

2D visible-light-driven TiO 2 @Ti 3 C 2 /g-C 3 N 4 ternary heterostructure for high photocatalytic activity

Abstract: A novel 2D visible-light-driven TiO2@Ti3C2/g-C3N4 ternary heterojunction photocatalyst with modified interfacial microstructure and electronic properties was synthesized by ultrasonic-assisted calcination method. The remarkably active g-C3N4 could provide high productivity of photogenerated electrons and holes. Meanwhile, the O/OH-terminated Ti3C2 and by-product TiO2 could act as excellent supporters by migrating electrons in TiO2@Ti3C2/g-C3N4 hybrids. As a result, the highest photocatalytic activities in the degradation of aniline and RhB were increased to 5 and 1.33 times higher than that of pristine g-C3N4 under visible-light irradiation, respectively. Furthermore, we proposed that n–n heterojunction and n-type Schottky heterojunction were built up across their interfaces, which efficiently improve the transition of electrons and further promote the photocatalytic activity of TiO2@Ti3C2/g-C3N4 hybrids. More appealingly, all the results highlight that the environment-friendly TiO2@Ti3C2/g-C3N4 heterojunction hybrids would be desirable candidates for pollutants degradation.

CaO impregnated highly porous honeycomb activated carbon from agriculture waste: symmetrical supercapacitor study

Abstract: This study presents the electrochemical studies of activated carbon prepared from palm kernel shell (ACPKS), with CaO impregnation. The CaO is obtained from chicken eggshell waste to produce CaO/ACPKS, which shows highly porous honeycomb structure with homogeneous distribution of CaO nanoparticles (30–50 nm in size). The prepared materials are evaluated as supercapacitor electrodes by testing their electrochemical characteristics. A high specific capacitance value of 222 F g−1 at 0.025 A g−1 is obtained for CaO/ACPKS, which is around three times higher than that for ACPKS (76 F g−1). In addition, electrochemical impedance data show lower impedance for CaO/ACPKS. Lastly, a practical symmetrical supercapacitor is fabricated by CaO/ACPKS and its performance is discussed.

High strength and ductility combination in nano-/ultrafine-grained medium-Mn steel by tuning the stability of reverted austenite involving intercritical annealing

Abstract: The structure–property relationship in 0.06C–5.5Mn steel subjected to different annealing temperatures and time was studied. Mn played a stronger effect on stabilizing austenite in comparison with Ni, and low-C medium-Mn steel possessed excellent hardenability. The reverse transformation of martensite to austenite occurred during intercritical annealing, and the volume fraction was first increased and then decreased on increasing annealing temperature or prolonging annealing time, indicative of change in thermal stability by element partitioning and coarsening of grain size. Correspondingly, the elongation was first increased and then decreased, consistent with the variation in the stability of reverted austenite. The yield strength was gradually decreased because of several factors, including recrystallization of α′ martensite, decreased stability of reverted austenite, and coarse grain size. The maximum product of strength and ductility was obtained on annealing at 650 °C for 10 min, which was attributed to the optimal stability of reverted austenite rather than the highest volume fraction, and tensile strength and elongation were 1120 MPa and 23.3%. The strain partitioning behavior of two phases was elucidated by analyzing Luders straining and continuous work hardening after yield point elongation, and the deformation mechanism was strongly related to the stability of reverted austenite.

Dielectric relaxations and transport properties parameter analysis of novel blended solid polymer electrolyte for sodium-ion rechargeable batteries

Abstract: A novel blended solid polymer electrolyte comprising polyethylene oxide and polyvinylpyrrolidone polymers for blending and sodium nitrate (NaNO3) as ion conducting species has been optimized via standard solution-cast technique. XRD, FESEM, and FTIR were performed to obtain the information about the structural changes, morphology, and microstructural changes (polymer–ion and ion–ion interactions) of the solid polymer electrolyte films. The electrochemical impedance spectroscopy, linear sweep voltammetry, and i–t characteristics were performed to evaluate the ionic conductivity, voltage stability window, and ion transference number. The impedance study was done in a broad temperature range (40–100 °C). The DSC and TGA were used to obtain information about the thermal transitions and thermal stability of prepared films. The ion dynamics is further investigated by analyzing the complex permittivity, loss tangent, and complex conductivity. All the plots were fitted through established theoretical model/expressions in whole frequency window to obtain dielectric strength, ion conduction path behavior, and relaxation time. Transport parameters such as number density (n), mobility (μ), and diffusion coefficient (D) of mobile ions were obtained by three methods and compared satisfactorily. Lastly, a coherent mechanism for the migration of charge transport carriers within the solid polymer composites has been proposed based on the performed experimental outcome.

Photocatalytic disinfection efficiency of 2D structure graphitic carbon nitride-based nanocomposites: a review

Abstract: Nanostructured carbon-based photocatalysts have gained attention in photocatalytic disinfection of microbial species. With distinctive features of possessing appropriate electronic band gap structure and high chemical and thermal stability, metal-free polymeric 2D stacked structure graphitic carbon nitride (g-C3N4) is an important photocatalytic material for environmental and energy applications. Besides, it has the potential for inactivation of harmful pathogens. Disinfection of microbial species is mainly ascribed to the formation of reactive oxidative species. Further, surface modification of g-C3N4 can remarkably improves photocatalytic disinfection efficiency. In this review, we have discussed the recent advances in photocatalytic disinfection using g-C3N4-based nanocomposites. An overview of metal-free nanostructure g-C3N4, metal (anions) and nonmetal (cations)-doped g-C3N4 and g-C3N4 hybridized with low band gap semiconductor is also presented. Moreover, we have emphasized on the photocatalytic disinfection mechanism associated with g-C3N4-modified composites. Nitrogen-rich g-C3N4 polymeric material can serve as an alternative to metal oxide (TiO2 and ZnO) photocatalysts for photocatalytic disinfection technology. Other applications such as CO2 photoreduction, H2 generation, organic pollutant degradation, and sensing using g-C3N4-based nanocomposites are also summarized.

Au/Pd/g-C3N4 nanocomposites for photocatalytic degradation of tetracycline hydrochloride

Abstract: The arbitrary discharge of antibiotic residuals has seriously influenced the ecosystem and human health. Photocatalytic degradation of antibiotic residuals with semiconductor photocatalyst is considered to be more effective method due to its unique superiority. Herein, Au/Pd/g-C3N4 nanocomposites were synthesized by loading Au and Pd nanoparticles on the surface of g-C3N4 sheets for photocatalytic degradation of tetracycline hydrochloride. The modification of g-C3N4 with Au and Pd nanoparticles efficiently enhanced the visible-light absorption, improved the separation and transfer of photogenerated electrons and decreased the recombination of electron–hole pairs. As-prepared Au/Pd/g-C3N4 nanocomposites exhibited improved photocatalytic performance with more than 90% degradation rate. Furthermore, the good stability and reusability of Au/Pd/g-C3N4 nanocomposites would be beneficial to further photocatalytic degradation application.

High-performance polyamide-imide films and electrospun aligned nanofibers from an amide-containing diamine

Abstract: Polyamide-imides (PAIs) are highly desired in many applications because of their superior thermal and mechanical properties. In this work, PAI was prepared from an amide-containing diamine and dianhydride by polycondensation and thermal treatment. Both PAI films and aligned electrospun nanofibers (ANFs) were fabricated. FT-IR was used to determine the structure formation of PAI at different annealing temperatures. DSC and TGA were used to evaluate the thermal properties of PAI, while tensile test was applied to evaluate the mechanical properties of PAI films and ANFs. The results indicated that the PAI possessed both outstanding thermal stability and mechanical properties, which provide opportunities for applications in gas separation, high temperature filtration, reinforcement, etc.

Structural, mechanical and thermal features of Bi and Sr co-substituted hydroxyapatite

Abstract: Bismuth and strontium ions were successfully substituted into hydroxyapatite (HAP) lattice upon the chemical formula $$ {\text{Bi}}_{x} {\text{Sr}}_{y} {\text{Ca}}_{10 - x - y} ({\text{PO}}_{4} )_{6} \left( {\text{OH}} \right)_{2} $$ via co-precipitation microwave-assisted route. The samples with different concentrations were investigated via X-ray diffraction, Fourier transform infrared, field emission scanning electron microscopy, thermogravimetric analysis and microhardness. In addition, lattice parameters, lattice distortion and crystallite size upon different models were computed. The two ions competed to replace both Ca2+ sites, and it was found that Bi3+ preferred Ca(2), while Sr2+ selected Ca(1). The hardness was enhanced via substitution where the highest value reached 3.1 GPa at the highest concentration of Bi3+ ions. This study has displayed that co-substituted ions into HAP can cause a great influence on its physico-chemical properties. The thorough study of the co-substitution effects is needed to deepen the understanding of synthetic HAP which may contribute in growth its applications particularly in bone tissue engineering.

Fabrication of superhydrophobic green surfaces with good self-cleaning, chemical stability and anti-corrosion properties

Abstract: Superhydrophobic surfaces with a high contact angle and a low sliding angle are promising candidates for corrosion resistance. In general, an excellent chemical and mechanical stability is the most critical property for superhydrophobic surfaces. In this paper, we proposed a facile, effective and environment friendly method using a simple solution immersion method to fabricate a superhydrophobic surface on copper mesh. The as-fabricated superhydrophobic surface possessing dendritic rough structure and low surface energy displayed a high contact angle of 155.5°. The excellent anti-fouling and self-cleaning properties were demonstrated. The mechanical stability was also exhibited when it was subjected to an impact by a continuous stream of water. In addition, the excellent chemical stability both in acidic and alkaline solutions and the outstanding anti-corrosion effect were showed in electrochemical test due to the air pockets formed between the superhydrophobic surface and water which can well block corrosive medium. This method is facile, timing-saving and environment friendly, which can play a crucial role in practical industries application of superhydrophobic surface.

Synthesis of graphene oxide/polyacrylamide composite membranes for organic dyes/water separation in water purification

Abstract: To obtain nanofiltration membranes with high-performance in desalination and water purification, membranes of graphene oxide (GO), reduced graphene oxide (rGO) and GO/polyacrylamide (PAM) are prepared by a vacuum filtration method. This method is conducted in aqueous solution without any organic solvents. The graphene-based membranes (GBMs) are characterized by UV–visible spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy. The hydrophilicity of GBMs is also evaluated by contact angle measurement. The interlayer spacing of GO membrane (0.85 nm), GO/PAM membrane (0.68 nm) and rGO membrane (0.36 nm) are measured by X-ray diffraction. The performance of the GBMs is evaluated on a dead-end filtration device. The water flux and retention of rhodamine B of the membranes are 399.04 L m−2 h−1 bar−1 and 85.03% (GO), 188.89 L m−2 h−1 bar−1 and 95.43% (GO/PAM), 85.85 L m−2 h−1 bar−1 and 97.06% (rGO), respectively. The GO/PAM membrane has the best comprehensive separation performance because of its proper interlayer spacing. GO/PAM membranes provide potential advantages in the design of high-performance membranes for molecular separation and water purification.

Polyaniline-based conducting hydrogels

Abstract: Conducting polymer hydrogels (CPHs) have been identified as a promising class of polymeric material for a wide range of applications such as biomedical, energy, environmental, health and agricultural domains. CPHs have received immense consideration because of their biocompatibility, hydrophilic properties, biodegradable nature, electroconductivity, ample resources and ease of preparation. Flexible nature of CPHs is considered as a potential candidate for some innovative technologies like flexible electronics especially flexible supercapacitors and solar cells, and their biocompatibility nature plays a key role in biomedical applications such as bioconductors, biosensors, implantable medical devices, electro-stimulated drug delivery systems, artificial muscle, and tissue engineering. When it comes to the matter of conductivity, among conducting polymers, polyaniline has been studied extensively for its stability, variable electrical conductivity, inexpensive raw material and better compatibility with other biopolymers. This review focuses on recent developments in polyaniline-based conducting hydrogels and their applications in biomedical and energy applications. Different strategies of synthesis, thermal, structural, electrochemical behavior of CPHs and their further opportunities and challenges are also discussed here.

Metal-free N, S co-doped graphene for efficient and durable nitrogen reduction reaction

Abstract: Electrochemical conversion of N2–NH3 provides a green and sustainable alternative for artificial NH3 synthesis but requires effective electrocatalysts to promote N2 reduction reaction (NRR). This work reported the first application of N, S co-doped graphene (NSG) as an efficient metal-free NRR catalyst. It was found that the NSG exhibited a high NH3 yield of 7.7 μg h−1 mg−1 and Faradaic efficiency of 5.8% at − 0.6 V versus reversible hydrogen electrode under ambient conditions, which largely outperformed undoped and single-doped counterparts, and compared favorably to most reported metal-based NRR catalysts. The combination of density functional theory calculations and experiments revealed that the N, S co-doping could effectively improve the NRR of graphene by promoting the N2 adsorption and N≡N bond elongation, boosting the electron transfer and creating more defective/active sites. Furthermore, the NSG showed an excellent selectivity and stability, suggesting its great potential for efficient electrochemical synthesis of NH3.

Nanocellulose-based magnetic hybrid aerogel for adsorption of heavy metal ions from water

Abstract: Heavy metal pollution is one of the most serious environmental problems, posing threats to human health. Here, we developed a magnetic hybrid aerogel by integrating nanocellulose and ferroferric oxide (Fe3O4) nanoparticles for effectively adsorbing heavy metal ions from water and realizing controllable recovery under magnetic condition. The magnetic behavior and adsorbing capacity of the hybrid aerogel on removal of heavy metal chromium (Cr)(VI) ion were examined. Results show that the ferroferric oxide nanoparticles physically adsorb the nanocellulose, each of which retains the original composition and structural characteristics. The magnetic hybrid aerogel possesses good ferromagnetic property with saturation magnetization value of 53.69 emu/g, enabling effective and controllable recovery of the aerogel under magnetic condition The adsorption efficiency of the hybrid aerogel on the Cr(VI) ion reaches the highest value of 2.2 mg/g when the mass ratio of the nanocellulose to ferroferric oxide nanoparticle is 1:1. Additionally, the hybrid aerogel presents similar adsorption behavior on plumbum (Pb)(II) and copper (Cu)(II) ions, suggesting extended applications of the hybrid aerogel on removal of heavy metal ions. Such strategy could provide new applications for the abundant nanocellulose resources and could be extended to integrate nanocellulose with other functional nanomaterials into novel hybrid aerogel for water purification.