Search

The high energy density of Si makes it a preferred anode material for lithium-ion batteries. However, the low conductivity and large volume changes associated with the charging and discharging processes lead to a rapid decay in capacity during cycling, which hinders its commercialization. In this study, micron-scale PSi@PEDOT/GO composites were prepared by coating commercial Al–Si alloys with poly 3,4-ethylenedioxythiophene (PEDOT) and graphene oxide (GO) using in situ polymerization and freeze-drying methods. The core layer of the PSi@PEDOT/GO composite has abundant internal pores to provide sufficient space to adapt to the volume change of silicon, whereas the PEDOT and GO coating layers can accelerate the ion and electron transport and accommodate the volume change of silicon, which can effectively improve the cycling stability and rate performance of the silicon anode. The characterization results show that the PSi@PEDOT/GO-2 (mass ratio = 6:4:5) composite electrode material has a specific capacity of 1102.30 mAh/g after 100 cycles. When the current density is 0.3A/g, the specific capacity is still 1102.30 mAh/g after 100 cycles, and the capacity retention rate is 75.8%. In addition, it exhibits a specific capacity of 406.87 mAh/g at a current density of 4 A/g, indicating excellent cycling and rate performance and good application prospects.

The Au/Ni/Ni(OH)2/C bimetallic nanocatalysts with different Au loadings (Au/Ni/Ni(OH)2/C-1: 0.05 wt%Au; Au/Ni/Ni(OH)2/C-2: 0.46 wt%Au; Au/Ni/Ni(OH)2/C-3: 2.60 wt%Au) were prepared at room temperature. The characterization results proved the nanostructure of Au islands supported on the Ni/Ni(OH)2 nanoparticles (NPs) and synergy effect of Au-, Ni- and Ni(OH)2-related species in Au/Ni/Ni(OH)2/C. These are the main reasons why their catalytic performance and selectivity to m-nitroaniline in m-dinitrobenzene hydrogenation were much higher than those of monometallic catalysts (Au/C and Ni/Ni(OH)2/C). Because Au/Ni/Ni(OH)2/C-2 was with high dispersion of Au, Au(0)/Aun+ ratio≈1:1 on the surface, novel nanostructure, moderate capacity of activating and dissociating hydrogen, and synergistic effect, it had much better catalytic activity (conversion of m-dinitrobenzene-100%) and higher selectivity to m-nitroaniline (95.0%) in m-dinitrobenzene hydrogenation reaction compared to other two supported bimetallic catalysts (Au/Ni/Ni(OH)2/C-1 and Au/Ni/Ni(OH)2/C-3). Au/Ni/Ni(OH)2/C-2 also exhibited high stability.

The ruthenium-nickel bimetallic nanoparticles supported on carbon black (Ru-Ni/C) with various Ru and Ni loadings, while keeping a constant Ru/Ni atomic ratio (51/49), were synthesized at ambient temperature by liquid reduction with hydrazine hydrate as reducing agent and galvanic replacement reaction approaches. Different Ru-Ni interfaces (Ru-Ni-NiO with 1.250 wt% or 0.630 wt% Ru, and RuO2-NiO with 0.160 wt% Ru) were formed after being annealed in N2 at 380 °C for 3 h. Several techniques, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and synchrotron radiation X-ray absorption spectroscopy (XAS) and in-situ XAS (in hydrogen) have been employed for structural characterization. It was found that most Ru atoms and a small amount of Ni atoms at the Ru-Ni-NiO interface were reduced, leading to the occurrence of hydrogen spillover and hence synergy effect of Ru, Ni and NiO active sites. However, such a synergy was not observed at the RuO2-NiO interface. The catalytic properties of the Ru-Ni/C nanocatalysts in the hydrogenation of benzene reaction were significantly improved due to the presence of particular Ru-Ni-NiO interface.

Four types of sustainable sodium carboxylate-derived materials are investigated as novel electrodes with high performance for lithium-ion batteries. Benefiting from the porous morphology provided by their intermolecular interactions, increasing capacity, excellent cycle stability and superior rate performance are observed for the sodium carboxylate- derived materials. The sodium oxalate (SO) electrodes displayed an increasing discharging capacity at a current density of 50 mA g−1 with with maximum values of 242.9 mA h g−1 for SO-631 and 373.9 mA h g−1 for SO-541 during the 100th cycle. In addition, the SO-541, SC-541 (sodium citrate), ST- 541 (sodium tartrate) and SP-541 (sodium pyromellitate) electrode materials displayed high initial capacities of 619.6, 392.3, 403.7 and 278.1 mA h g−1, respectively, with capacity retentions of 179%, 148%, 173% and 108%, respectively, after 200 cycles at 50 mA g−1 with. Even at a high current density of 2,000 mA g−1 with, the capacities remain 157.6, 131.3, 146.6 and 137.0 mA h g−1, respectively. With these superior electrochemical properties, the sodium carboxylate-derived materials could be considered as promising organic electrode materials for large-scale sustainable lithium-ion batteries.

Tetra-β-nitro-substituted nickel phthalocyanine (TN-NiPc) and hollow phthalocyanine (TN-H2Pc) were synthesized and investigated as novel organic electrode materials for rechargeable lithium batteries. After the two H atoms in the center of TN-H2Pc were replaced with Ni atoms, the interactive force between the phthalocyanine rings was reduced, which resulted in a fluffy morphology for the TN-NiPc that was beneficial to the transition of Li+. As a result, better electrochemical properties and reversibility were observed in the TN-NiPc electrodes compared to the TN-H2Pc electrode. The capacity of TN-NiPc electrode was stable at about 280 mAh g−1 at 0.2 C after 250 cycles at several different current rates of 0.1, 0.2, 0.5, and 1 C. The TN-NiPc based cathode materials may provide new opportunities for organic, flexible, and stable secondary lithium batteries.

The space environment is a complex environment full of microgravity, high vacuum, high and low temperature, strong radiation and plasma. Polymers used in the space environment will inevitably experience aging and degradation which result in changes of the material mechanics, physics and chemical properties, until they lose usefulness. To make a material that can be used for a long time and whose performance is not changed in the space environment, its ability to resist environmental factors must be excellent. Therefore, this paper provides an introduction to the harmful conditions in the space environment and their effects on the polymers, also it reviews the aging mechanisms of the adhesives used in the space environment and the effect of thermal cycling, stress, electromagnetic radiation and ionizing particles on the properties of polymers and optical devices, to provide the reference basis for selection, modification and reliability analysis of materials used in the space environment.

This is great interest in tuning diameter of carbonaceous materials for applications in energy storage, templates and separation etc. In this study, different texture and size distribution of carbon spheres were obtained in only one step by hydrothermal carbonization of glucose using metal chlorides, such as NaCl, MgCl2, CaCl2 and FeCl3. Then, structure and chemical composition of the products were characterized by means of SEM, TEM, FTIR and Zetasizer. The combination of these results had allowed us to infer that adding metal ions was more efficient than prolonging hydrothermal treatment in promoting the formation of carbon microspheres. In addition, metal ions strength is proportional to the size of the particles. At last, through investigating the morphology transformation process of the products, a possible growth mechanism was proposed.

A novel anode materials composed of pomegranate structured carbon @ porous silicon/reduced graphene oxide composite (C@pSi/rGO) was prepared by a facile high temperature pyrolysis and freeze drying technology. In this pomegranate-like composite, porous silicon is equivalent to pomegranate seeds providing sufficient specific capacity, the coated carbon layer is equivalent to pulp which can inhibit the volume expansion and improve electrical conductivity of silicon, and the outermost graphene is equivalent to the inner diaphragm and the outer fruit shell, which can accelerate the ion and electron transport and buffer the volume change of the inner silicon again, so that the cycling stability and rate performance of the material can be effectively improved. As a result, the initial discharge capacity of the C@pSi/rGO composite electrode is 825.7 mAh g−1, after 100 cycles, the reversible capacity of the C@pSi/rGO composite electrode can be maintained at 746 mAh g−1 at a current density of 0.4 A/g with a capacity retention up to 90.4%. However, for the pure porous silicon pSi electrode without carbon coating and graphene recombination, the initial discharge capacity is 769.4 mAh g−1 with almost 0% capacity retention after 30 cycles. Under the dual action of carbon coating and graphene composite, the performance of porous silicon electrode has been significantly improved, which will provide a new idea for the development of high performance silicon carbon anode materials.

The current collectors play a key role in the stability, safety and performance of the lithium-ion batteries, so it is of significance to provide a strategy to modify conventional current collectors. Here we develop a graphite-like carbon (GLC) film to modify the copper/aluminum current collectors so as to improve the physical contact and interface characteristics between the current collector and the active materials. The effects of GLC modified current collectors on the performances of LTO and LCO half-cells as well as LTO/LCO full cell were investigated, respectively. The results showed that the discharge capacity was increased and the cycle stability was improved for the LTO and LCO half-cells. Also, the GLC modified current collector was effective to enhance the LTO/LCO full cell. EIS tests presented that GLC modified current collectors could reduce the resistance of LTO half-cell, LCO half-cell, and LTO/LCO full cell. Particularly, GLC modified current collectors caused a great impact on the cycle performances of lithium-ion batteries. After 100 cycles of testing, the capacity retention rate of the P-Cu-LTO battery was only 89.14%, while the capacity retention rate of the GLC-Cu-LTO battery could maintain 93.47%. The capacity retention rate of the P-Al-LCO battery was 64.50%, and the capacity retention rate of the GLC-Al-LCO battery could maintain 92.91%. Moreover, the capacity retention rate of the LTO/LCO battery after 100 cycles of testing was 61.63%, while the GLC film modified LTO/LCO battery capacity retention rate could maintain 88.90%. These indicated that GLC film could provide a feasible approach of modification of current collector to improve the overall performances of lithium-ion batteries.

Tetra-carboxylic acid lithium phthalocyanine (t-CAL-Pc) and tetra-(di-acyl) substituted phthalocyanine (t-DA-Pc) were prepared to construct a new type of organic electrode material. The electrochemical properties were investigated and the effects of group substitution on the electrochemical properties were analyzed for the first time. The results indicated that after the hydrogen in the carboxyl group was substituted by lithium and a di-acyl group respectively, the cyclic stability performance of phthalocyanines (t-CAL-Pc and t-DA-Pc) was improved and the irreversible capacities were reduced. The capacities can still remain at 169 mA h g−1 after 100 cycles for t-CAL-Pc and 241 mA h g−1 after 200 cycles for t-DA-Pc, and the initial columbic efficiencies were 94% and 97% respectively, which were much higher than that of 70% for tetra-carboxyl phthalocyanine (t-C-Pc).

A new monomer, N,N '-bis(4-phenoxybenzoyl)-4,4'-diaminodiphenyl sulfone (BPBDAS), was prepared by the condensation of 4,4'-diaminodiphenyl sulfone with 4-phenoxybenzoyl chloride in N,N-dimethylacetamide. Novel soluble aromatic poly(ether amide sulfone amide ether ketone ketone)s (PEASAEKKs) were synthesized by electrophilic solution copolycondensation of BPBDAS with a mixture of terephthaloyl chloride and isophthaloyl chloride in the presence of anhydrous aluminum chloride and N-methylpyrrolidone in 1,2-dichloroethane. The influences of reaction conditions on the preparation of polymers were examined. All these polymers are amorphous and soluble in aprotic polar solvents due to the incorporation of 4,4'-dibenzoylaminodiphenyl sulfone moieties in the main chain. Thermal analyses showed that the polymers had high Tg values of 236—259 °C and exhibited high thermal stability. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 97.6—103.7 MPa, Young’s moduli of 2.12—2.45 GPa, and elongations at break of 10.6—13.8%.

A new monomer, 4,4′-bis(4-phenoxybenzoyl)diphenyl(BPOBDP), was synthesized via a two-step synthetic procedure. A series of novel poly(ether sulfone ether ketone ketone)/poly(ether ketone diphenyl ketone ether ketone ketone) copolymers were prepared by electrophilic Friedel–Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of 4,4′-diphenoxydiphenylsulfone (DPODPS) and 4,4′-bis(4-phenoxybenzoyl)diphenyl (BPOBDP), in the presence of anhydrous aluminum chloride and N-methylpyrrolidone (NMP) in 1,2-dichloroethane (DCE). The copolymers with 10–50 mol% DPODPS are semicrystalline and have remarkably increased Tgs over commercially available PEEK and PEKK. The copolymers with 40–50 mol% DPODPS had not only high Tgs of 170–172°C, but also moderate Tms of 326–333°C, which are extremely suitable for melt processing. These copolymers have tensile strengths of 96.5–108.1 MPa, Young's moduli of 1.98–3.05 GPa, and elongations at break of 13–26% and exhibit excellent thermal stability and good resistance to acidity, alkali, and common organic solvents. Copyright © 2009 John Wiley & Sons, Ltd.

Poly(aryl ether ketone)s (PAEKs) are a class of high-performance engineering thermoplastics known for their excellent combination of chemical, physical and mechanical properties, and the synthesis of semicrystalline PAEKs with increased glass transition temperatures (Tg) is of much interest. In the work reported, a series of novel copolymers of poly(ether ketone ketone) (PEKK) and poly(ether amide ether amide ether ketone ketone) were synthesized by electrophilic solution polycondensation of terephthaloyl chloride with a mixture of diphenyl ether and N,N′-bis(4-phenoxybenzoyl)-4,4′-diaminodiphenyl ether (BPBDAE) under mild conditions. The copolymers obtained were characterized using various physicochemical techniques. The copolymers with 10–35 mol% BPBDAE are semicrystalline and have markedly increased Tg over commercially available poly(ether ether ketone) and PEKK due to the incorporation of amide linkages in the main chain. The copolymers with 30–35 mol% BPBDAE not only have high Tg of 178–186 °C, but also moderate melting temperatures of 335–339 °C, having good potential for melt processing. The copolymers with 30–35 mol% BPBDAE have tensile strengths of 102.4–103.8 MPa, Young's moduli of 2.33–2.45 GPa and elongations at break of 11.7–13.2%, and exhibit high thermal stability and good resistance to organic solvents. Copyright © 2010 Society of Chemical Industry

4,4'-Bis(4-phenoxybenzoyl)diphenyl was prepared by the Friedel-Crafts reaction of 4-bromobenzoyl chloride and diphenyl followed by condensation with potassium phenoxide. Novel aromatic poly(ether ketone diphenyl ketone ether ketone ketone)s were obtained by the electrophilic Friedel-Crafts solution copolycondensation of 4,4'-bis(4-phenoxybenzoyl)diphenyl with a mixture of isophthaloyl chloride and terephthaloyl chloride over a wide range of isophthaloyl chloride/terephthaloyl chloride molar ratios in the presence of anhydrous aluminum chloride and N-methylpyrrolidone in 1,2-dichloroethane. The influence of the reaction conditions on the preparation of the copolymers was examined. The copolymers were characterized with different physicochemical techniques. Because of the incorporation of diphenyl, the resulting copolymers exhibited outstanding thermal stability. The glass-transition temperatures were above 174°C, the melting temperatures were above 342°C, and the 5% weight loss temperatures were above 544°C in nitrogen. All these copolymers were semicrystalline and insoluble in organic solvents.

A new monomer containing naphthalene, 2,6-bis( β -naphthoxy)benzonitrile (BNOBN) was synthesized by reaction of β -naphthol with 2,6-difluorobenzonitrile in N-methyl-2-pyrrolidone (NMP) in the presence of KOH and K 2CO3. Novel copolymers of poly(ether ketone ketone) and poly(ether ether ketone ketone) containing naphthalene moieties and pendant cyano groups were prepared by electrophilic Friedel—Crafts solution copolycondensation of terephthaloyl chloride (TPC) with varying mole proportions of diphenyl ether and 2,6-bis( β -naphthoxy)benzonitrile (BNOBN) using 1,2-dichloroethane as solvent and NMP as Lewis base in the presence of anhydrous AlCl3. The crystallinity and melting temperatures of the polymers were found to decrease as the concentration of BNOBN in the polymer increased, whereas the glass transition temperatures of the polymers increased as the concentration of BNOBN in the polymer increased. The copolymers with 20—25 mol% BNOBN had high Tg values of 182—184 ° C; moderate Tm values of 324—335 °C; tensile strengths of 101.8—103.2 MPa, Young’s moduli of 3.14—3.23 GPa, and elongations at break of 15—18%. The copolymers exhibited outstanding thermal stability and good resistance to organic solvents, acidity and alkali.

A new monomer, 4,4′-bis(4-phenoxybenzoyl)diphenyl (BPOBDP), was prepared by Friedel–Crafts reaction of 4-bromobenzoyl chloride and diphenyl, followed by condensation with potassium phenoxide. Novel poly(ether ketone ketone) (PEKK)/poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) copolymers were synthesized by electrophilic Friedel–Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of diphenyl ether (DPE) and BPOBDP, in the presence of anhydrous aluminum chloride and N-methyl-pyrrolidone (NMP) in 1,2-dichloroethane (DCE). The copolymers obtained were characterized by various analytical techniques such as FT-IR, DSC, TGA, and wide-angle X-ray diffraction (WAXD). The results showed that the resulting copolymers exhibited excellent thermal stability due to the existence of diphenyl moieties in the main chain. The glass transition temperatures are above 152°C, the melting temperatures are above 276°C, and the temperatures at a 5% weight loss are above 548°C in nitrogen. The copolymers with 50–70 mol% BPOBDP had tensile strengths of 101.5–102.7 MPa, Young's moduli of 3.23–3.41 GPa, and elongations at break of 12–17%. All these copolymers were semicrystalline and insoluble in organic solvents. Copyright © 2008 John Wiley & Sons, Ltd.

An adhesive potting technology for fiber coils of a fiber optic gyroscope (FOG) is proposed. The fiber coil is immersed in liquid adhesive with superior mechanical properties. The internal air is first removed completely by vacuum pumping, and the adhesive is then evenly pressed into the fiber coil under pressure. The potted fiber core is prepared by ladder-type temperature curing and a stress-release process. With this potting technology, the vibration performance of an FOG is greatly improved and, at the same time, will not lead to degradation of its temperature performance. Using this potting technique of adhesive impregnation, the adaptability of FOGs will be enhanced.