Precursor Composites Research Articles

Microstructure evolution of interface and matrix during the preparation of SiCf/Ti60 composites

In this paper, continuous SiC fiber-reinforced Ti60 (SiCf/Ti60) composites were fabricated by preparing SiCf/Ti60 precursor wires from matrix-coated fibers and hot isostatic pressing (HIP) consolidation. The microstructures of the precursor wires and composites were investigated using XRD, SEM, EPMA, EBSD, and TEM, which led to the microstructure evolution of the composites. The conclusions of this study are as follows. 1. A reaction layer (RL) with a thickness of approximately 0.1 μm already exists at the interface of the precursor wires during the preparation. The HIP process accelerates the diffusion of the carbon coating with the Ti60 matrix, resulting in an increase in the thickness of the RL to approximately 0.5 μm. This layer is primarily composed of fine-grained TiC layer || discontinuous silicides || coarse-grained TiC layer. 2. The matrix of SiCf/Ti60 precursor wires contains α-Ti (∼ 1.9 μm), S2 (∼ 50 nm), and β-Ti (∼ 50 nm), in the matrix, β-Ti is precipitated from α-Ti, and HIP makes α-Ti, S2, and β-Ti grow to ∼ 2.4 μm, ∼ 200 nm, and ∼ 300 nm, respectively. 3. There are 〈0001〉//axial direction (AD) and 〈10−10〉//AD fiber textures in the matrix of the precursor wires, and HIP makes the matrix undergo a plastic deformation dominated by dislocation slip, and the pole density of the two kinds of textures are both increased.

Air-Stable Prussian White Cathode Materials for Sodium-Ion Batteries Enabled by ZnO Surface Modification.

Iron-based Prussian white (PW) is one of the promising cathodes for sodium-ion batteries, owing to its high capacity and low cost. However, the practical application of PW is hindered by its poor air stability. The metal-oxide coating has been proven to be an effective way to improve the air stability of electrode materials. Whereas, the target electrode materials conventionally need to be dissolved in the aqueous solution to obtain precursor composites and subsequently calcined at a high temperature during the metal-oxide coating process, which could destroy the phase structure of PW as a result of the sodium leaching into the water and thermal decomposition at the high temperature. In this work, we propose a facile method to construct a ZnO surface layer on PW by utilizing ethanol as a solvent and a mild post-treatment temperature. The ZnO coating layer effectively enhances the air stability of PW and induces the formation of the stable interface on PW. The PW-5 wt % ZnO-E (exposed in 60% humidity air after 30 days) cathode demonstrates a much higher capacity retention (94.1%) at 1 C after 200 cycles than that of PW-E (54%). This work lays a solid foundation for further application of PW.

Low-temperature synthesis of porous high-entropy (CoCrFeMnNi)3O4 spheres and their application to the reverse water-gas shift reaction as catalysts.

A high-entropy porous spinel oxide [(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4] was synthesized via a solvothermal method and calcination. Solvothermal conditions yielding homogeneous precursor composites with five metals were optimized. Low-temperature calcination of the amorphous composites at 500 °C for 60 min yielded porous spheres formed by small primary particles, with crystal structures attributed to single-phase spinels. The homogeneity of the five elements in the spheres was verified via scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy analysis. The high-entropy (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4 spheres exhibited superior catalytic activity and long-term stability for the reverse water-gas shift reaction at 700 °C for at least 15 h. The importance of the Cr component in stabilizing the spinel structure was demonstrated. Mn, Fe, Co, and Ni served as active sites in the reaction. The advantage of solvothermal synthesis for porous high-entropy materials was discussed.

Effects of a liquid metal co‐filler on the properties of epoxy/binary filler composites

AbstractLiquid metals (LMs) with high fluidity and high thermal conductivity (TC) are receiving considerable attention in the research on thermal management polymer composites as alternatives to conventional rigid solid fillers or as co‐fillers to overcome the trade‐off between TC and composite processability at high filler loads. While most previous studies have investigated the effects of LM fillers in soft elastomeric matrices, their effects on the composite properties with rigid matrices, such as epoxy‐based polymers, have not been discussed extensively. Herein, we investigated the effects of LM eutectic Ga‐In (EGaIn) as a co‐filler on the properties of rigid epoxy‐based composites with a binary filler (Al2O3/EGaIn) system. The increase in the volume fraction of LM fillers significantly improves the processability of uncured precursor composites but markedly decreases the mechanical strength of the cured composites at their high loads—the latter effects have rarely been examined in previous studies. However, with adequate LM loads, the composites exhibited superior mechanical properties compared with the all‐solid‐filler system, withstanding a surprisingly high compressive load (~100 kN) under which the all‐solid‐filler system fractured. Furthermore, the epoxy/binary filler composites exhibited reasonably high TC values (~1 W/mK) comparable to that of commercial epoxy molding compounds, suggesting their potential applicability for electronic packaging.

Surface modification of TiO2 nanoparticles with terephthalic acid in supercritical carbon dioxide

This paper presents a supercritical CO2 strategy for surface modification of TiO2 nanoparticles with carboxylic acids. The reaction between TiO2 nanoparticles and terephthalic acid molecules in sc-CO2 provides carboxylic acid-modified TiO2 nanoparticles with a modification efficiency much higher than the conventional solvent immersion method. From the statistical method of response surface methodology, modifier ratio 4.04 (mol/mol), temperature 401.5 K, and pressure 14.8 MPa resulted in an optimum modification rate of 25.34%. The modified TiO2 was characterized by FTIR, TG-DTA, FE-SEM, TEM-EDS, and zeta potential analysis. The results showed the surface modification of TiO2 in sc-CO2 is made of modifier molecules bonding chemically. Surface modification by terephthalic acid affects the surface electrical property of TiO2 nanoparticles in water, leading to a positive charge surface. Since this method is ecologically and environmentally friendly, it can be applied in precursor composites for the synthesis materials of biomedical application.

Solution blow spinning (SBS) and SBS-spun nanofibers: Materials, methods, and applications

Solution blow spinning (SBS) is a maturing nanofiber fabrication technology. Over the past decade, there has been a growing interest in employing and developing this facile method of fabricating nanofibers, sourced from different materials to suit varied applications. For the first time, this review will provide a comprehensive overview of solution blow spinning, including the principles, materials, methods, and applications. We start with the principles of the SBS method, followed by a detailed account of the different precursor polymers (i.e., synthetic, biocompatible, and bio-based materials) and composites that have been used in the SBS of nanofibers. The proceeding section presents the known applications of nanofibers obtained through SBS which are discussed primarily in the areas of energy and electronics, biomedical, environmental, membrane separation, and, textile and smart material applications. We highlight the most important and recent advances related to SBS over the last ten years. Lastly, we give perspectives, challenges, opportunities, and new directions of the SBS technology.

Boosting gravimetric and volumetric energy density of supercapacitors by 3D pomegranate-like porous carbon structure design

Recently, the heteroatom-enriched porous carbons have received considerable attention on the research of electrodes with high gravimetric capacitances for supercapacitors (SCs). However, their relatively low volumetric capacitances have limited their practical applications due to very low packing density and poor ion diffusion at high mass loadings. In this study, by means of a facile modified chemical activation route, a functionalized N and O co-doped three-dimensional (3D) hierarchical pomegranate-like porous carbon (PPC) was rationally synthesized. First, A core–shell structured precursor composite for PPC was constructed. The polypyrrole (PPy) with the desired functional group was adopted as the precursor of the pomegranate-like core, and the polyacrylamide (PAM) hydrogel as the precursor of the pomegranate-like shell (designated as PPy/PAM). Then, after calcination of the PPy/PAM hydrogel precursor composites, a novel 3D hierarchical PPC was achieved. The as-obtained PPC offers short diffusion paths of ions, increases packing density and provides abundant active sites for pseudocapacitance by increasing self-oxygen–nitrogen-doped content. The performance tests of SC with PPC manifest that at 156 W kg−1 (109.7 W L-1), boosted energy density of 11.5 Wh kg−1 (8.05 Wh L-1) can be achieved. The as-obtained PPC is the promising electrode material of high-performance SCs for practical applications.

Quantum mechanical studies on dioxin‐imprinted polymer precursor composites: Fundamental insights to enhance the binding strength and selectivity of biomarkers

We present a benchmark study of binding energies for dioxin-imprinted polymer complexes. A density functional theory approach was used for screening the polymerization precursors in the rational design of molecularly imprinted polymers (MIPs). Tetrachlorodibenzo-p-dioxin (TCDD) was taken as an imprinted molecule. The geometry optimization, natural bond orbital charge, and molecular electrostatic potential of TCDD and acrylamide (AM) were studied at the M062X level and 6-31G(d,p) belonging to one of the hybrid density functional theories. The results of molecular electrostatic potential and natural bond orbital charge analysis were comparable. Among the studied functional monomers-AM, methacrylic acid (MAA), itaconic acid, and vinyl pyridine-AM was confirmed as the best functional monomer, because the strongest interaction (the maximum number of hydrogen bonds and the lowest binding energy) occurs between TCDD and AM. The stability property was excellent when the ratio of TCDD and AM was 1:4. The polarizable continuum model was used for solvent calculations. Computational results showed that acetonitrile plays an important role in the MIP formation, as it seems to control the size and the shape of the cavity. The atoms in molecule and Becke surface method have also been applied to understand the nature and strength of the hydrogen bonding interactions in complexes. TCDD-AM complexes were found involving C-O···Cl and N-H···Cl hydrogen bonds. Good correlations have been established between hydrogen bond lengths versus atoms in molecule topological parameter like electron density ρ(r) and its Laplacian ▽2 ρ(r) at the bond critical points. On ground of theoretical results, a series of MIPs were synthesized. The MIP prepared using TCDD as the template, the functional monomer (AM), and the cross-linker (TRIM) in acetonitrile solvent exhibited the highest adsorption capacity for TCDD. The maximum binding capacity of TCDD on the MIP was 3.7μg/mg. This research work can provide a theoretical reference for the fabrication and characterization of novel TCDD-MIPs for environmental applications.

Durometer test and impedance measurement of metal precursor reinforced polymer composites

Polymer composites were preferred for the domestic and industrial applications due to unique high performance properties. In the present work we demonstrated the preparation of polyvinyl alcohol (PVA)/Copper bismuth sulphide (CuBi2S3) metal precursor composites by solution blending. The decreased softness by 45% was confirmed as a function of metal precursor loading tested by shore – A durometer. It may be due to the presence of metal precursor in polymer system distinguished by Scanning Electron Microscope (SEM) techniques. We observed the influence of metal precursor on bulk resistance and impedance as function of temperature across the broadband frequency and wide temperature range. The dc conductivity obeys the Arrhenius relationship and confirmed the decrease in activation energy. This investigation may be feasible for the electrical and electronic domains.

Twin-nanoplate assembled hierarchical Ni/MnO porous microspheres as advanced anode materials for lithium-ion batteries

Transition metal oxides have been extensively studied as anode materials for lithium ion batteries due to their high capacity. However, the intrinsically low electronic conductivity and large volume changes upon repeated cycles are the obstacles for obtaining their high electrochemical properties. In this work, we report the novel construction of uniform Ni/MnO porous microspheres by an in situ conversion from their solvothermally synthesized precursor composites (xNiCO3·yMnCO3). The structures of the precursor composites can be controlled by the solvothermal duration and solution compositions. During the high-temperature annealing process, the precursor composites were transferred into Ni and MnO composite and porous structure was created by the decomposition of the carbonate materials. As an anode material for lithium-ion battery, the porous Ni/MnO electrode demonstrates high reversible capacity of 700.6 mA h g−1 after 250 cycles. Moreover, the Ni/MnO microspheres exhibit excellent rate capacity. The exceptional electrochemical performances are attributed to the homogeneous distribution of nickel nanoparticles within the MnO microspheres and porous structures throughout the whole microspheres, which can improve the electronic conductivity of the electrode materials and keep the structural integrity upon repeated cycles.

Enhanced visible light photocatalytic activity of the mechanochemically prepared nanosized ZnxCd1-xS/Zn-Al layered double hydroxide precursor heterojunctions

ZnxCd1-xS/Zn–Al layered double hydroxide (LDH) precursor heterostructured composites were synthesized by a one-step mechanochemical method. X-ray diffraction, Fourier transform-infrared spectroscopy, SEM-EDS and thermogravimetric analysis confirmed the formation of the ZnxCd1-xS/Zn–Al LDH precursor composites. X-ray photoelectron spectroscopy indicated the formation of a heterojunction structure. The photocatalytic degradation activity for methyl orange of the heterostructured composites was observed even under visible light irradiation and exhibited a large enhancement with the increase in the molar ratio of sulfide solid solution to LDH as well as the increase in the ratio of Cd to Zn. A detailed investigation on the mechanism for the enhanced photocatalytic activity was performed, particularly regarding to the efficient separation of photogenerated electrons and holes with the heterostructure. This work provides a very simple and environment-friendly way to fabricate a series of heterostructured photocatalysts based on LDH precursor with transition metal sulfide well dispersed inside.

钌负载二氧化铈改性蒙脱土和凹凸棒黏土催化剂上甲苯完全氧化的性能

商用蒙脱土(MMT)和凹凸棒黏土(ATP)分步负载CeO2分别合成CeO2-MMT和CeO2-ATP复合材料，再等体积浸渍法制备Ru/CeO2-MMT和Ru/CeO2-ATP催化剂，研究其催化空气完全氧化甲苯的性能，使用XRD、BET、SEM和SEDX等技术对催化剂的结构、物理性能进行表征。结果表明：Ru/CeO2-MMT和Ru/CeO2-ATP催化剂中CeO2 的含量对甲苯催化完全氧化性能有不同的影响。分4次负载CeO2制备的催化剂，催化甲苯氧化的性能最好；CeO2改性蒙脱土比CeO2改性凹凸棒黏土负载Ru催化剂上甲苯连续氧化的性能更好。 Ru/CeO2-ATP and Ru/CeO2-MMT catalysts were prepared by incipient-wetness impregnation method using ruthenium salt as precursor, and CeO2-MMT and CeO2-ATP composites were synthesized with montmorillonite (MMT) and attapulgite (ATP) repeatedly supported by CeO2 as carrier, and the performance of catalysts was studied for complete combustion oxidation of toluene. The catalysts were characterized by XRD, BET, SEM and SEDX technique. The results showed that the activity of the catalyst repeatedly four times supported by CeO2 was the best, and Ru/CeO2-MMT catalyst was better than Ru/CeO2-ATP catalyst for the complete oxidation of toluene. So the activity of catalysts for toluene catalytic oxidation was influenced by carrier.

Electrochemical In Situ Synthesis: A New Synthesis Route for Redox Active Manganese Oxides for Rechargeable Sodium Ion Battery through Initial Charge Process

Positive electrode active materials for the rechargeable sodium ion battery are in-situ synthesized during initial charge process in an electrochemical cell from precursor composites of Na2O2 and Mn3O4. Unlike the synthesis of metal oxides, e.g., α-NaFeO2, etc., the present materials are subjected to no heat-treatment. When beginning with a precursor composite of which the Na/Mn ratio is 1.0, the electrode delivers 194 mA h g− 1during the subsequent discharge process. The electrode retains 84% of the initial discharge capacity after 30 cycles. X-ray diffractometry (XRD) and transmission electron microscopy identifies three phases in the precursor composite; i.e., crystalline Mn3O4 and Na2O2 as well as an amorphous phase. Ex-situ XRD reveals that Mn3O4 in the precursor transforms to λ-MnO2 after the initial charge process as a result of the in-situ synthesis. Moreover, we also found the composite functions when the Na/Mn ratio of the composite is more than 1.0. An extra amount of Na can be provided to cancel the irreversible capacity of the negative electrode when we start from a composite of which the Na/Mn ratio is greater than 1.0, whereby we demonstrate the feasibility of a full-cell.

Influence of Carbon Precursors on the Structure, Composition, and Oxygen Reduction Reaction Performance of Nitrogen-Doped Carbon Materials

Graphene oxide (GO), oxidized unzipped carbon nanotube (O-UCNT), and GO/O-UCNT composites were used as the carbon precursors to synthesize nitrogen-doped graphene (NG), nitrogen-doped unzipped carbon nanotube (NUCNT), and nitrogen-doped graphene/unzipped carbon nanotube (NG-NUCNT) composites. The influence of these carbon precursors on the synthesis of their corresponding nitrogen-doped carbon materials was systematically investigated. The results show that the synthesis of nitrogen-doped carbon materials not only depends upon the structure and composition of their corresponding carbon precursors, but also the morphology and surface property. As for single carbon precursor, the carbon precursor with higher oxygen content tends to make the nitrogen-doped carbon material with higher nitrogen content. Besides, we find that carbon precursor composites with 3D morphology and large specific surface areas contribute to fabricating nitrogen-doped carbon material with sufficient catalytic sites and high nitrogen c...

Macroporous alumina with cellular interconnected morphology from emulsion templated polymer composite precursors

Macroporous polymer composites with included alumina particles were prepared via an emulsion templating procedure by photopolymerising the monomer containing continuous phase. Methyl methacrylate and multifunctional acrylate monomer Sartomer SR 492 were used for the polymer matrix. Composites with open porous cellular morphology with cavities around 15μm were obtained and further processed by a calcination and sintering process to form alumina ceramic material with the same morphology as the polymer composite precursors. Emulsion composition was optimised in order to obtain monolithic type of the final material with macropores on a micrometer scale connected by a number of interconnecting channels. Mechanical and thermal properties both of precursor composites and ceramic materials were evaluated.

Graphene reinforced regenerated cellulose nanocomposite fibers prepared by lyocell process

Nanocomposites of regenerated cellulose containing different amounts of graphene nanoplatelets (GNPs) (0.5, 1, and 2 wt%) have been prepared by wet spinning using Lyocell process. The thermal stability, mechanical, and electrical properties of the nanocomposite fibers were studied. The nanocomposite fibers were characterized by Fourier transform infrared (FTIR), Transmission electron microscopy, X‐ray diffraction, and Scanning electron microscopy (SEM). The tenacity and initial modulus of the nanocomposite fibers improved by 66% and 61%, respectively with the addition of 2 wt% GNPs. The T20 decomposition temperature of regenerated cellulose fibers improved with the addition of GNPs up to 2 wt%. The morphology by SEM revealed exfoliated dispersion of GNPs into the regenerated cellulose matrix which subsequently resulted in good interaction between the nanofillers and the matrix. The addition of exfoliated GNPs generated electrical conductivity. The nanocomposite fibers containing 2 wt% GNPs has a conductivity of 2.3 × 10−4 S/cm. The FTIR spectra showed that the addition of GNPs in regenerated cellulose did not result in any noticeable change in its chemical structure. The resulting nanocomposite may find potential applications in the areas of carbon fiber precursor, conductive fibers, electrical tools, and biodegradable composites. POLYM. COMPOS., 38:E81–E88, 2017. © 2015 Society of Plastics Engineers

In situ reduction for synthesis of nano-sized Cu2O particles on MgCuAl-LDH layers for degradation of orange II under visible light

Cu2O-MgAl-LDH composites were synthesized from MgCuAl-layered double hydroxides (LDHs) as precursors using ascorbic acid for reduction of Cu2+. The synthesized precursor materials and composites were characterized by XRD, TEM, XRF, XPS and UV–vis diffuse reflectance spectroscopy. The results showed that the Cu2O nanoparticles were evenly distributed on the LDH nano-sheets, which greatly improved the catalytic property of Cu2O. For example, the Cu2O-Mg7Al5-LDH composite removed about 90% of Orange II while pure Cu2O removed only about 70% of the dye through photocatalytic degradation. The Cu2O-LDH composites showed very high efficiency in degrading Orange II dye because of uniform distribution of Cu2O nanoparticles on the surfaces of LDH with less amount of copper than in pure Cu2O. The Cu2O-LDH composites developed here are potential photocatalysts for dye degradation in water purification.

Mechanical and electrical properties of aligned carbon nanotube/carbon matrix composites

To synthesize carbon nanotube/carbon matrix (CNT/C) composites rivaling or exceeding the mechanical and electrical properties of current carbon fiber/carbon matrix composites, it is essential to align carbon nanotubes in the composite. In this work, we fabricated CNT/polyacrylonitrile (PAN) precursor composites with high degree of CNT alignment, and carbonized and graphitized them at high temperatures. Carbonizing the precursor composites significantly improved their elastic modulus, strength, and electrical conductivity. The matrix was uniformly carbonized and highly graphitized. The excellent mechanical and electrical properties make the CNT/C composites promising for many high temperature aerospace applications.

Gelation and biocompatibility of injectable alginate–calcium phosphate gels for bone regeneration

An emerging approach toward development of injectable, self-setting, and fully biodegradable bone substitutes involves the combination of injectable hydrogel matrices with a dispersed phase consisting of nanosized calcium phosphate particles. Here, novel injectable composites for bone regeneration have been developed based on the combination of ultrapure alginate as the matrix phase, crystalline CaP [monetite and poorly crystalline hydroxyapatite (HA)] powders as both a dispersed mineral phase and a source of calcium for cross-linking alginate, glucono-delta-lactone (GDL) as acidifier and glycerol as both plasticizer and temporary sequestrant. The composites were maximized with respect to CaP content to obtain the highest amount of osteoconductive filler. The viscoelastic and physicochemical properties of the precursor compounds and composites were analyzed using rheometry, elemental analysis (for calcium release and uptake), acidity [by measuring pH in simulated body fluid (SBF)], general biocompatibility (subcutaneous implantation in rabbits), and osteocompatibility (implantation in femoral condyle bone defect of rabbits). The gelation of the resulting composites could be controlled from seconds to tens of minutes by varying the solubility of the CaP phase (HA vs. monetite) or amount of GDL. All composites mineralized extensively in SBF for up to 11 days. In vivo, the composites also disintegrated upon implantation in subcutaneous or bone tissue, leaving behind less degradable but osteoconductive CaP particles. Although the composites need to be optimized with respect to the available amount of calcium for cross-linking of alginate, the beneficial bone response as observed in the in vivo studies render these gels promising for minimally invasive applications as bone-filling material.

Biocatalytically Induced Growth of Gold Nanoshells: Using Enzyme Reaction for the Controllable Fabrication of Nanomaterials

In the present work, the enzymatically controlled growth process of gold nanoshells (GNSs) in the presence of O2/glucose/glucose oxidase (GOx) and its chloroaurate ion electron acceptor is described. The biocatalytically stimulated growth process is one of the bio-inspired synthetic procedures directed by biological molecules which occur under ambient conditions. It is found that hydrogen peroxide (H2O2) could enlarge the gold nanoparticles (GNPs) on the surface of GNSs precursor composites, of which the preadsorbed GNPs serve as nucleation sites for further gold deposition. Here, GOx is harnessed for its unparalled level of catalytic activity and substrate specificity while H2O2 is produced as a by-product during the oxidation of D-glucose to gluconic acid by GOx. Then the bio-generated H2O2 is used as the reducing agent in the catalytic deposition process of GNSs formation. During the procedure, the localized surface plasmon resonance peaks range across hundreds of nanometers from visible to near infrared region accompanying by the resultant formation of uniform and continuous core-shell nanostructures. The corresponding optical, morphological and enzyme kinetic properties are all well investigated. The novel protocol offers a new perspective for the bio-directed synthesis method in nanotechnology.