scholarly journals Photoconductivity of activated carbon fibers

1991 ◽  
Vol 6 (5) ◽  
pp. 1040-1047 ◽  
Author(s):  
K. Kuriyama ◽  
M.S. Dresselhaus
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Carbon Fibers ◽  
Low Temperatures ◽  
Room Temperature ◽  
High Surface ◽  
Localized States ◽  
Activated Carbon Fibers ◽  
Disordered Carbon ◽  
Increasing Temperature

The conductivity and photoconductivity are measured on a high-surface-area disordered carbon material, i.e., activated carbon fibers, to investigate their electronic properties. This material is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000–2000 m2/g. Our preliminary thermopower measurements show that the dominant carriers are holes at room temperature. The x-ray diffraction pattern reveals that the microstructure is amorphous-like with Lc ≃ 10 Å. The intrinsic electrical conductivity, on the order of 20 S/cm at room temperature, increases by a factor of several with increasing temperature in the range 30–290 K. In contrast, the photoconductivity in vacuum decreases with increasing temperature. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The recombination kinetics changes from a monomolecular process at room temperature to a bimolecular process at low temperatures, indicative of an increase in the photocarrier density at low temperatures. The high density of localized states, which limits the motion of carriers and results in a slow recombination process, is responsible for the observed photoconductivity.

Photoconductivity of Highly Disordered Carbon Fibers

1990 ◽  
Vol 209 ◽  
Author(s):  
Kazuyoshii Kuriyama ◽  
Mildred.S. Dresselhauss
Keyword(s):  
Relaxation Time ◽  
Activated Carbon ◽  
Carbon Fibers ◽  
Localized States ◽  
Activated Carbon Fibers ◽  
Bulk Conductivity ◽  
Defect States ◽  
Disordered Carbon ◽  
Density Of Defect States ◽  
Increasing Temperature

ABSTRACTA highly disordered carbon material, activated carbon fibers, is investigated through bulk conductivity and photoconductivity measurements. This material has a high density of defect states introduced by an aqtivation process that leads to a huge specific surface area of up to 2000m2/g. The conductivity increases by a factor of 4–10 with increasing temperaturefrom 30K to 290K. In contrast, the photoconductivity decreases by a factor of three with increasing temperature. The relaxation time of the photoconductivity is rather long(on the order 10−1 sec), indicating that the recombination process proceeds through localized states. flopping processes are used to interpret the transport properties of this material.

Preparation and Characterization of Fibrous Cerium Oxide Templated from Activated Carbon Fibers

2005 ◽  
Vol 876 ◽  
Author(s):  
Mark Crocker ◽  
Uschi M. Graham ◽  
Rolando Gonzalez ◽  
Erin Morris ◽  
Gary Jacobs ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Cerium Oxide ◽  
Carbon Fibers ◽  
High Surface ◽  
Nitrate Solution ◽  
High Surface Area ◽  
Cerium Nitrate ◽  
Activated Carbon Fibers ◽  
Templating Method

AbstractHigh surface area cerium oxide has been prepared using a carbon templating method. Impregnation of a highly mesoporous activated carbon (Darco KB-B) with an aqueous solution of cerium nitrate, followed by carbon burn off, afforded ceria with surface area of up to 148 m2/g. According to thermogravimetric studies, ceria formation proceeds via decomposition of cerium nitrate at ca. 410 K; oxidation of the carbon template commences at the same temperature, being facilitated by the release of NO2 from the Ce compound. Use of activated carbon fibers (ACFs) as template was found to provide a simple route to fibrous cerium oxide. The lower surface areas (3 - 59 m2/g) of the resulting ceria fibers reflect the largely microporous nature of the ACFs; evidently the Ce nitrate solution is unable to penetrate their micropores. Consequently, the surface area of the ceria product is found to increase with increasing mesoporosity of the ACF template. Electron microscopy reveals that the ceria fibers are composed of highly crystalline primary particles of 5-10 nm diameter; further, the fibers display a number of interesting morphological features at the macro- and nano-scales.

scholarly journals Developing Lignosulfonate-Based Activated Carbon Fibers

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1877 ◽  
Author(s):  
Feng-Cheng Chang ◽  
Shih-Hsuan Yen ◽  
Szu-Han Wang
Keyword(s):  
Weight Loss ◽  
Activated Carbon ◽  
Surface Area ◽  
Carbon Fibers ◽  
Loss Rate ◽  
High Surface ◽  
High Surface Area ◽  
Physical Activation ◽  
Activated Carbon Fibers ◽  
Weight Loss Rate

In this study, electrospinning technology, physical activation, and carbonization processing were applied to produce lignosulfonate-based activated carbon fibers. The porous structure of the produced lignosulfonate-based activated carbon fibers primarily contained mesopores and a relatively small amount of micropores. Moreover, insufficient carbonization caused fiber damage during CO2 activation. The weight loss rate and specific surface area increased with increase in carbonization time, and products with carbonization temperatures of 700 °C were of higher quality than those with other temperatures. Moreover, the two-step carbonization process provided fibers with improved quality because of a low weight loss rate, improved processing, and high surface area. Lignosulfonate-based activated carbon fibers can be used as a highly efficient adsorption and filtration material, and further development of its applications would be valuable.

Modified polyacrylonitrile-based activated carbon fibers applied in supercapacitor

2016 ◽  
Vol 45 (3) ◽  
pp. 164-171 ◽  
Author(s):  
Linjie Su ◽  
Bohong Li ◽  
Dongyu Zhao ◽  
Chuanli Qin ◽  
Zheng Jin
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Specific Capacitance ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Fibers ◽  
Electrode Material ◽  
High Specific Capacitance ◽  
Activated Carbon Fibers ◽  
Content Type

Purpose The purpose of this paper is to prepare a new modified activated carbon fibers (ACFs) of high specific capacitance used for electrode material of supercapacitor. Design/methodology/approach In this study, the specific capacitance of ACF was significantly increased by using the phenolic resin microspheres and melamine as modifiers to prepare modified PAN-based activated carbon fibers (MACFs) via electrospinning, pre-oxidation and carbonization. The symmetrical supercapacitor (using MACF as electrode) and hybrid supercapacitor (using MACF and activated carbon as electrodes) were tested in term of electrochemical properties by cyclic voltammetry, AC impedance and cycle stability test. Findings It was found that the specific capacitance value of the modified fibers were increased to 167 Fg-1 by adding modifiers (i.e. 20 wt.% microspheres and 15 wt.% melamine) compared to that of unmodified fibers (86.17 Fg-1). Specific capacitance of modified electrode material had little degradation over 10,000 cycles. This result can be attributed to that the modifiers embedded into the fibers changed the original morphology and enhanced the specific surface area of the fibers. Originality/value The modified ACFs in our study had high specific surface area and significantly high specific capacitance, which can be applied as efficient and environmental absorbent, and advanced electrode material of supercapacitor.

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