2016 Vol. 31, No. 2

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2016, 31(2): 1-1.
Abstract(46) PDF(13)
Abstract:
Top-down fabrication of two-dimensional nanomaterials:Controllable liquid phase exfoliation
SHAO Jiao-jing, ZHENG De-yi, LI Zheng-jie, YANG Quan-hong
2016, 31(2): 97-114.
Abstract(1122) PDF(2105)
Abstract:
Two-dimensional nanomaterials have unique structural characteristics and various extraordinary properties, which make them attractive for use in the preparation of advanced materials and new products. Large-scale fabrication of these nanomaterials in a controllable way is key for the realization of their applications. Liquid phase exfoliation has been given a great deal of attention in making two-dimensional nanomaterials owing to its high efficiency and excellent controllability. This review elaborates on the superior characteristics and potential applications of two-dimensional nanomaterials while focusing on liquid phase exfoliation methods, including ion-exchange, intercalation-exfoliation, oxidation-reduction, selective etching, direct sonication and shear exfoliation methods. The mechanisms and applicability of these methods are compared and the development prospects of two-dimensional nanomaterials are discussed.
Controlled preparation and electrochemical performance of a flaky Li4Ti5O12-graphene hybrid with a high crystallinity
DONG Hai-yong, HE Yan-bing, LI Bao-hua, KANG Fei-yu
2016, 31(2): 115-120.
Abstract(638) PDF(809)
Abstract:
A Li4Ti5O12(LTO)-graphene(G) hybrid with a flaky structure was fabricated by solvothermal treatment of a suspension of graphene oxide(GO), lithium hydroxide and tetrabutyltitanate in 1-methyl-2-pyrrolidinone, followed by calcination of the solid product at 700℃ for 1 h. GO as the precursor of graphene is amphiphilic and acts as an anionic surfactant and template for the growth of LTO under alkaline conditions to form the flaky LTO-G hybrid with a high crystallinity. Compared with the material without GO, the LTO-G has a typical flaky morphology and exhibits a much higher capacity and betterrate capability.
Preparation and properties of reduced graphene oxide/polyimide composites produced by in-situ polymerization and solution blending methods
MA Lang, WANG Guo-jian, DAI Jin-feng
2016, 31(2): 129-134.
Abstract(1333) PDF(1423)
Abstract:
Reduced graphene oxide/polyimide(rGO/PI) composites were prepared by the incorporation of the PI by in-situ polymerization and solution blending methods. The influence of these methods on the mechanical and electrical properties of the composites was investigated. Results indicate that the addition of the rGO to PI significantly changes its mechanical and electrical properties. The rGO is more homogeneously dispersed in the PI, its re-aggregation in the PI is significantly inhibited, and the tensile strength and electrical conductivity of the composites are higher for the in-situ polymerization method than the solution blending one. The tensile strength and electrical conductivity of the composite reach the highest values of 132.5 MPa and 6.87×10-4 S·m-1 with rGO additions of 1.0 and 3.0 wt%, respectively for the in-situ polymerization method, which are 68.8% and 8 orders of magnitude higher than the corresponding values for pure PI.
Synthesis of carbon nanoparticles from waste rice husk used for the optical sensing of metal ions
Peggy Zhen Zhen Ngu, Stephanie Pei Phing Chia, Jessica Fung Yee Fong, Sing Muk Ng
2016, 31(2): 135-143. doi: 10.1016/S1872-5805(16)60008-2
Abstract(751) PDF(559)
Abstract:
This work reports on a synthesis of carbon nanoparticles(CNPs) from waste rice husk by thermally-assisted carbonization in the presence of concentrated sulfuric acid. The fluorescent emmision characteristics of the CNPs, their quenching effects by metal ions and their use as a sensing material for Sn(Ⅱ) ions were investigated. Results indicated that the yield of CNPs was optimized at a sulphuric acid concentration of 12 mol/L, heating temperature of 1200℃ and heating time of 30 min. The sample showed a strong blue luminescence in water with a maximum emission at 439 nm. The fluorescence can be quenched by adding various metal ions by the formation of complexes between the metal ions and surface of the CNPs. Sn(Ⅱ) ions had the most significant quenching effect on the fluorescence of the CNPs, which is concentration-dependent. The concentration dependent quenching was linearized with the Stern-Volmer equation, and showed a linear response up to a Sn(Ⅱ) concentration of 6.13 mmol/L. The limit of detection for Sn(Ⅱ) ions is 18.7μmol/L with good repeatability.
Carbon microspheres formed by the carbonization of cotton fibers in subcritical water
SHI Sheng, DAI Jin-ming, HOU Wen-sheng, ZHANG Yong-fang, WANG Shu-hua, CHEN Xu-hong
2016, 31(2): 144-150.
Abstract(612) PDF(599)
Abstract:
Carbon microspheres(CMs) were prepared by the carbonization of waste cotton fibers in subcritical water, and were characterized by SEM, XPS, XRD, FTIR and elemental analysis. The amount of fibers as a function of volume of water, carbonization temperature and time was optimized based on the morphology, elemental composition and size of the CMs. Results indicate that the best CMs have the highest fraction of spheres with sizes from 0.8 to 3μm and a carbon content of 74.99 wt% and are obtained under subcritical water at 280℃ for 10 h when the amount of cotton fibers is 20 g per liter of water. The CMs have an amorphous structure and their surface C/O ratio is higher than the global C/O ratio. The cotton fibersare converted into CMs by hydrolysis, cracking, polymerization, condensation, aromatization and finally spheroidizing to decrease surface energy.
A sizing agent modified with carbon nanotubes used for the production of carbon fiber/bisphenol A epoxy composites
CAO Li-juan, YANG Yu, LU Chun-xiang
2016, 31(2): 151-158.
Abstract(614) PDF(631)
Abstract:
An emulsion made by mixing carbon nanotubes(CNTs), epoxy, Tween-80 and Span-60 was used as a sizing agent of carbon fibers(CFs) used to prepare CF/bisphenol A epoxy composites. The effects of the CNT modification on the stability of the emulsion, surface morphology and composition of the CFs, the contact angle of bisphenolA epoxy on the CFs and the interfacial shear strength of the composites were investigated by SEM, XPS, AFM and mechanical tests. Results indicate that the stability of the CNT-modified emulsion against sedimentationis better than the unmodified one. The surface roughness of the CFs is increased by 73.1%, the contact angle is reduced by 11.9%, and the number of surface oxygen functional groups on the CFs is increased by 45.96% compared with those without CNT modification. The interfacial shear strength of the composite with an optimized CNT content of 0.75 wt% is 14.7% higher than that without CNTs.
Influence of the microstructure of the carbon matrices on the internal friction behavior of carbon/carbon composites
YANG Wei, LUO Rui-ying, HOU Zhen-hua, ZHANG You, SHAGN Hai-dong, HAO Ming-yang
2016, 31(2): 159-166. doi: 10.1016/S1872-5805(16)60009-4
Abstract(495) PDF(529)
Abstract:
Three carbon/carbon composites with rough laminar, smooth laminar and dual matrix carbon were prepared by chemical vapor infiltration(CVI) using hydrogen-diluted methane, CVI using nitrogen-diluted propane, and two-step CVI using first methane/hydrogen and carbon dioxideand then furan resin impregnation and carbonization. The influence of the microstructure of the carbon matrix on the internal friction behavior of the composites was investigated. Results indicate that the microstructure of the carbon matrix plays an important role in the internal friction. The overall internal friction is related to the motion of dislocations, the sliding of the fiber/matrix interface and the sliding of the carbon planes. The internal friction of the composite is very sensitive to temperature and amplitude, but less sensitive to frequency. Among these composites, the dual matrix carbon has the highest density of crystal-defects and the highest internal friction while the rough laminar carbon has perfect carbon planes and the lowest internal friction.
Simulation of the kinetics of pyrolytic carbon deposition in C/C composites
HUANG Qing-bo, ZHANG Dan, BAI Rui-cheng, LI Ai-jun, SUN Jin-liang
2016, 31(2): 167-175.
Abstract(581) PDF(493)
Abstract:
A multistep heterogeneous reaction kinetic model for pyrocarbon deposition is proposed to investigate the sharp and clear transition between the high-texture(HT) and medium-texture(MT) pyrocarbons in C/C composites synthesized by chemical vapor infiltration(CVI). The model is based on the Langmuir-Hinshelwood mechanism and a particle-filler conceptual model, which models both the pyrocarbon deposition and the texture formation. The model assumes that adsorption, desorption and dehydrogenation reactions are involved. Unimolecular dehydrogenation reactions of either light linear hydrocarbons as the source of fillers(F) or light aromatic species as the source of particles(P) result in the formation of MT pyrocarbon, while a bimolecular dehydrogenation reaction between P and F species leads to the formation of HT pyrocarbon. The relationship between the types of pyrocarbons and gas-phase compositions is simulated under steady state. It is found that MT and HT pyrocarbon formation are two dominant stable processes with a hysteresis interzone that is affected by gas composition, initial linear hydrocarbon concentration and deposition temperature. Simulated results account for the sharp and clear transition between MT and HT pyrocarbon, and agree well with most pyrocarbon evolution studies under various conditions during CVI with only a few exceptions that may be caused by simplification in constructing the model.
Effects of three types of T700 carbon fiber on the mechanical properties of their composites with bismaleimide resin
PENG Gong-qiu, SHI Feng-hui, WANG Ying-fen, LI Guo-li, ZHENG Hong-liang, ZHANG Bao-yan, XIE Fu-yuan
2016, 31(2): 176-181.
Abstract(1622) PDF(670)
Abstract:
Three types of T700 carbon fibers, A-3K, A-12K and T700SC-12K, were used as reinforcements of carbon fiber/bismaleimide resin composites. The surface roughness and fuzziness of the three fibers, their damage in the preparation of the prepreg and the mechanical properties of the final composites were compared. Results indicate that the surface roughness and fuzziness of A-3K and A-12K produced using a wet-spinning method are larger than that of T700SC-12K from a dry-jet wet-spinning method. The tensile strength retention ratio in the direction parallel to the fiber axis from fibers to composites of T700SC-12K is higher than those of A-3K and A-12K, owing to the smooth surface, best wear resistance and the minimum damage produced during the preparation of the prepreg for the former. The decreasing order of tensile strength in the direction parallel to the fiber axis of the composites is T700SC-12K, A-3K and A-12K. The interfacial bonding for the composites from A-3K and A-12K is much better compared with T700SC-12K because the former two have stronger mechanical anchoring between fibers and resin matrix than the third.
The oxidation behavior of A3-3 matrix graphite
ZHOU Xiang-wen, LU Zhen-ming, LI Xin-nan, ZHANG Jie, LIU Bing, TANG Ya-ping
2016, 31(2): 182-187. doi: 10.1016/S1872-5805(16)60010-0
Abstract(549) PDF(563)
Abstract:
The effects of temperature on the oxidation behavior of the A3-3 matrix graphite(MG) in the temperature range 798-973 K in air with a flow rate of 100 mL/min to burn-offs of 10-15 wt%, were investigated by a home-made thermo-gravimetric experimental setup. The oxidation rate(OR) increases significantly with the temperature. The OR at 973 K is over 70 times faster than at 798 K. The oxidation kinetics of A3-3 MG in air at temperatures up to 973 K is in the reaction control regime, where the activation energy is 176 kJ/mol and the Arrhenius equation could be described as:OR=2.9673×108·exp(21124.8/T) wt%/min. The relatively lower activation energy of MG than that of structural nuclear graphite indicates that MG is more easily oxidized.
Preparation and characterization of a TiB2/ZrB2-C eutectic coating
YANG Jin-hua, LIU Zhan-jun, WANG Li-yong, GUO Quan-gui, SONG Jin-ren, LIU Lang
2016, 31(2): 188-198.
Abstract(539) PDF(295)
Abstract:
74μm TiB2, and 74μm and 1μm ZrB2 powders were heated with isostatically pressed carbon blocks at 2550℃, which is above the eutectic temperature of TiB2-C and ZrB2-C, to form eutectic coatings, which are named TIB, ZRB-1 and ZRB-2, respectively. Results showed that the surface and the inner part of the coatings were different. The surface of the coatings was composed of B-doped highly ordered graphite, and the inner part was composed of TiB2-C or ZrB2-C alloy. The d002 values of graphite in samples TIB, ZRB-1 and ZRB-2 were 0.3359, 0.3360 and 0.3354 nm, respectively, which are almost the same as that of single crystal graphite(0.3354 nm), indicating the formation of highly ordered graphite. The features of the Raman spectra of these three coatings such as the appearance of D and D' bands, low intensity 2D bands and the shift of G bands to higher wave numbers are ascribed to B-doping in the graphene layers of the graphite. The small particle size of the ZrB2 powder favored the relaxation of the stress formed inside the surface of the coatings.
Microwave assisted preparation of expanded graphite/sulfur composites as cathodes for Li-S batteries
ZHU Fu-liang, YANG Zhi, ZHAO Jin-ping, ZHAO Xin
2016, 31(2): 199-204. doi: 10.1016/S1872-5805(16)60011-2
Abstract(700) PDF(928)
Abstract:
Expanded graphite/sulfur(EG/S) composites were prepared by microwave irradiation of mixtures of sulfur and expanded graphite with S/EG ratios from 4:1 to 12:1. Sulfur was sublimed and entered the EG pores when the mixtures were heated and was condensed to form particles within the pores during cooling. The pores of the EG acted as microcontainers to host the sulfur, and the material, with its interconnected and conductive pore walls, acted as a current collector for the cathode of the Li-S battery. The size of sulfur particles in the EG pores could be controlled by the S/EG mass ratio. When the ratio is 10:1, relatively uniform size sulfur particles could be obtained. Both the S/EG ratio and the sulfur particle size have an important effect on the capacity increase of the Li-S battery. Using a composite with a S/EG ratio of 10:1 as the cathode gives the highest capacity of 1020 mAhg-1 at a rate of 0.1 C.
Performance of different fillers in the reinforcement of rubber
SONG Yi-lan, CHEN Jian, FU Qing-shan, ZHANG Hua-zhi, XIE Chun
2016, 31(2): 205-212.
Abstract(481) PDF(503)
Abstract:
White silica powder, low-structure and high-structure carbon blacks were used as fillers for rubber and were incorporated into them by dry or solvent-aided mixing methods. The bonding strength between filler and rubber was investigated by AFM, mechanical tests and a bonding test using solvent extraction with xylene. Results indicate that the silica has an excellent reinforcing performance at normal temperature, but the bond energy is weakened at high temperatures. High-structure carbon blacks exhibit excellent reinforcement and bonding stability at low to high temperatures, and vulcanized rubbers have the highest tensile strength and can withstand the highest tensile stress, and are considered the best fillers. Low-structure carbon blacks show an intermediate reinforcing performance between the silica and the high-structure carbon blacks, but their reinforcement is best at ultra high temperatures.

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