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2014, 29(5)

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Research progress in graphene use in photonic and optoelectronic devices

LI Shao-juan, GAN Sheng, MU Hao-ran, XU Qing-yang, QIAO Hong, LI Peng-fei

2014, 29(5): 329-356.

Abstract(1558)

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Graphene has very significant optical and electronic properties, which attract enormous attention. As a unique two-dimensional crystal with one atom thickness, it has high electron and thermal conductivities in addition to exibility, robustness and impermeability to gases. Its ultra-broad band optical response and excellent non-linear optical properties make it a wonderful material for developing next generation photonic and optoelectronic devices. The fabrication of graphene-based devices is compatible with the existing semiconductor process, which has stimulated lots of graphene-based hybrid silicon-CMOS (Complementary metal-oxide- semiconductor transistor) applications. Here we review the latest progress in graphene-based photonic and optoelectronic devices, ranging from pulsed lasers, modulators and photodetectors to optical sensors. Other exciting topics such as graphene surface plasmons and their terahertz applications are also discussed.

Effect of high temperature treatment on the structure and thermal conductivity of 2D carbon / carbon composites with a high thermal conductivity

FENG Zhi-hai, FAN Zhen, KONG Qing, XIONG Xiang, HUANG Bo-yun

2014, 29(5): 357-362. doi: 10.1016/ S1872-5805(14)60142-6

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High thermal conductivity carbon / carbon composites (HTC-C / Cs) have a high specific modulus and a low thermal expansion in addition to all the excellent properties of traditional C / C composites, which have been a research focus in recent years. 2D HTC-C / Cs were prepared by hot pressure molding, densification by precursor impregnation and pyrolysis, and then heat treatment at high temperatures, using pitch-based carbon fiber fabric with a high thermal conductivity as reinforcement and mesophase pitch as the binder precursor. The structure and morphology of pitch-based carbon fibers and 2D HTC-C / Cs were investigated by XRD, SEM and TEM. The thermal conductivity was measured by laser-flash diffusivity. Results show that with increasing heat treatment temperature the crystallite size increases, the degree of order is improved, the thickness of laminar graphite around the carbon fibers increases, and the number of interfacial cracks between the fiber and matrix decrease and cracks between matrix layers are expanded. A linear relationship between thermal conductivity and heat treatment temperature was observed and the highest thermal conductivity was 443 W / m·K after heat treatment at 3 000°C.

Recovery of carbon fibers from carbon fiber / epoxy composites by epoxy degradation with concentrated zinc chloride in ethanol

2014, 29(5): 363-368.

Abstract(911)

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Concentrated zinc chloride in ethanol was used to decompose the epoxy in carbon fiber / epoxy (CF / EP) composites to recover carbon fibers. Factors affecting the degradation rate such as reaction temperature and zinc chloride concentration were investigated. The properties of the products decomposed by epoxy and the recovered carbon fibers were characterized. Results indicated that the molecular weight of the decomposed epoxy decreased and its solubility in ethanol increased with the reaction time. A significant fraction of the C—O bonds in epoxy is broken down by the degradation. The strength of the recovered fibers is 97. 1% of the original ones and their microstructure was only slightly changed, but the amount of the oxygen-containing functional groups on the surface of the recovered fibers decreased.

Effect of heat treatment on the microstructure of C / C composites with different high textured pyrolytic carbon contents

LI Wei, LI He-jun, WEI Jian-feng, ZHANG Shou-yang, FU Yang-xi, WANG Pei

2014, 29(5): 369-373.

Abstract(882)

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C / C composites reinforced using carbon felt and 3 K carbon cloth laminated preforms were prepared by chemical vapor infiltration and samples taken from them were subsequently subjected to heat treatment at 2500°C. The microstructures of the C / C composites were characterized by X-ray diffraction, polarized light microscopy and Raman spectroscopy. Results showed that the matrix of composites reinforced with carbon felt contained only high textured (HT) pyrolytic carbon, while those reinforced with the 3 K carbon cloth had a banded texture composed of isotropic, HT and medium textured (MT) pyrolytic carbon when moving from fibers to matrix, and the content of HT pyrolytic carbon was less than 50% . Regardless of the preform, both the asprepared and heat treated composites had a similar degree of graphitization. The Lc value of the carbon felt reinforced composites was higher than their counterparts both for the asprepared and heat treated samples. The La values of the carbon fibers, MT and HT pyrolytic carbon increased after the heat treatment, and the La value of the HT pyrolytic carbon had a much larger increase than that of the others.

Synthesis and microstructure analysis of aligned carbon nanotube/ pyrocarbon composites

Harshad Patel, L M Manocha| S Manocha

2014, 29(5): 374-379. doi: 10.1016/ S1872-5805(14)60143-8

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A two-step preparation of aligned CNT (ACNT) / pyrolytic carbon composites was carried out with chemical vapor deposition and chemical vapor infiltration by filling the space within the ACNT film with pyrolytic carbon, using methane as carbon precursor. The structure of the composites was investigated by scanning electron microscopy and Raman spectroscopy. Results showed that the CNTs were coated unevenly with densely-packed carbon spheres at 95℃. At 1 050℃, the CNTs were uniformly coated which increased their diameters from 20-60 nm to 400-500 nm and closed pores were formed as a result of the fast formation and a slow diffusion of carbonaceous nuclei during the latter stages of deposition. At both temperatures, the density of the film increased more than four fold when the pyrolytic carbon was graphitized.

Multi-wall carbon nanotubes and nano titanium dioxide coated on cotton fabric for superior self-cleaning and UV blocking

Loghman Karimi, Salar Zohoori, Atefeh Amini

2014, 29(5): 380-385. doi: 10.1016/ S1872-5805(14)60144-X

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Cotton fabrics were treated with nano titanium dioxide and multi-wall carbon nanotubes (MWCNTs) using succinic acid as a crosslinking agent. The photocatalytic self-cleaning properties of the samples were assessed by analyzing the degradation of Direct Green 6 under UV and sunlight. The UV absorption, abrasion resistance and tensile strength of the treated fabric were measured. It was found that coating the cotton fabrics with both MWCNTs and nano titanium dioxide effectively improves the photodeg radation efficiency of Direct Green 6 under both UV and sunlight. The abrasion resistance and UV blocking capability are improved, and tensile strength decreases a little after the coating. The increased photodegradation of Direct Green 6 can be ascribed to enhanced adsorption, a reduced electronhole pair recombination rate and an extended light absorption wavelength as a result of the joint action of nano titanium dioxide and MWCNTs.

Dispersion of carbon nanotubes in a polymer by the rapid expansion of a supercritical suspension

ZHAO Jian, LIU Zhen-sheng, HU Wen-bin

2014, 29(5): 386-391.

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We report a scalable and volatile organic compound-free process for the production of well-dispersed carbon nanotubes (CNTs) in a polymer by the rapid expansion of a supercritical suspension (RESS), in which CNTs had been suspended in supercritical carbon dioxide, and CO2 and CNTs released from the suspension were rapidly vented through a nozzle. Reagglomeration of the CNTs after RESS can be prevented by premixing them with dimethyl isophthalate or poly(methyl methacrylate), which can be dissolved in supercritical carbon dioxide, or by embedding the nozzle in molten poly(methyl methacrylate.

Diamagnetism of carbon onions probed by NMR of adsorbed water

A M Panich, V Yu Osipov, K Takai

2014, 29(5): 392-397. doi: 10.1016/ S1872-5805(14)60145-1

Abstract(643)

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We measured the 1 H chemical shift of water molecules adsorbed on defect sites of carbon onions and compared it with the shifts of bulk water and water adsorbed by chemically-derived graphene, graphene oxide and nanodiamond. The positions of 1H resonances for insulator nanodiamond and graphene oxide are close to that of bulk water, while water molecules adsorbed by graphene, and particularly by carbon onions, reveal a significant deviation in chemical shift from that of bulk water, which can be attributed to the diamagnetic screening effect of the conducting graphene layers. This conclusion is supported by a pronounced correlation established in our experiments between the proton chemical shifts and diamagnetic contribution to the magnetic susceptibility.

Fabrication and purification of carbon nano onions

ZHANG Wei-ke, FU Jun-jie, CHANG Jie, ZHANG Min, YANG Yan-qing, GAO Li-zhen

2014, 29(5): 398-403.

Abstract(917)

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Carbon nano onions (CNOs) with diameters of 70-100 nm were fabricated by chemical vapor deposition at 800
℃, using methane as carbon source and high-temperature steam treated 316 stainless steel mesh as catalyst. The CNOs were isolated from the substrate by HNO3 refluxing, calcination in air at 500℃ and magnetic separation. The morphology, microstructures and magnetic properties of the CNOs were characterized by SEM, TEM, XRD, Raman spectroscopy, FTIR spectroscopy and vibration sample magnetometer tests. Results showed that the surface attached catalyst particles and amorphous carbon can be effectively removed from raw CNOs through HNO₃ refluxing and calcination. Magnetic separation can selectively remove the CNOs encapsulating a [Ni,Fe] magnetic catalyst from the CNOs that are hollow.

Preparation and characterization of yellow-green fluorescence emitting SiC-encapsulated graphite

WANG Yun-wei, JIN Guo-qiang| WANG Ying-yong| GUO Xiang-yun

2014, 29(5): 404-408.

Abstract(764)

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SiC-encapsulated graphite was prepared by carbonization of a mixture of expanded graphite and silica sol at 1 300℃ for 6 h, heat treatment in air at 700 ℃ for 4 h to remove unreacted surface carbon and HCl-HF etching to remove silica. XRD, TGA, TEM and SEM were used to characterize the samples. Results indicated that the fluorescence emission of the SiC-encapsulated graphite shifts from blue to yellow-green light compared to pure SiC. This might be caused by a built-in potential near the junction between graphite and SiC, which makes the energy of the photogenerated electron released while returning to ground state lower than that of pure SiC.

The development and prospects of carbon science ———A report on the annual world conference on carbon, Carbon 2014

SONG Yan

2014, 29(5): 4040-4080.

Abstract(794)

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The 2014 Annual World Conference on Carbon (Carbon 2014), hosted by the Korean Carbon Society, was held in Jeju, Korea, June 29 July 4, 2014. 859 attendees from 35 countries / regions participated in the conference, and 729 papers were accepted for presentation, including 5 plenary lectures, 10 keynote talks, 46 invited lectures, 273 oral presentations and 395 posters, covering 7 topics: graphene; carbon nanotubes and related carbon nanomaterials; carbon precursors, carbon fibers and composites; industrial graphites, carbon industry news, and carbon blacks; porous carbons, carbon for health and environmental protection; carbons for sustainable energy conversion and storage, carbons for energy saving; analysis, characterization, computation and modeling of carbons. Research on and development of nanocarbons are quite active and in particular, graphene received tremendous interest. Rapid progress has also been made on the electrochemical properties, energy conversion and energy storage applications of carbon materials.

2014 Vol. 29, No. 5

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