Increasing Carbonization Temperature Research Articles

Structural and electronic characteristics induced by carbonization control of mesoporous carbon nanofibers

Abstract Mesoporous carbon nanofibers (MCNFs) are fabricated at various carbonization temperatures. The carbonization temperature plays a key role in determining the structural characteristics and the electronic properties of MCNFs. The band gap energies of MCNFs are estimated to be 0.080, 0.036, and 0.014 eV at the carbonization temperatures of 600, 900, and 1200 °C, respectively. The MCNF carbonized at 1200 °C has the highest stacking height of graphene planes ( L c ) and the largest number of graphene layers ( L c / d ). Raman data show the intensity ratio of D to G peaks, which is related to the graphene size ( L a ). L a increases with increasing the carbonization temperature. In addition, as the carbonization temperature increases, the conductivity of MCNF increases due to larges values of L c , L a , and L c / d .

To Produce Electromagnetic Shielding Material from Lignin of Black Liquor

Lignin was obtained from black liquor of papermaking by the acid to separation, and carbonized after loading various amounts of nickel and calcium or nickel alone. The influences of the temperature, amount of nickel and amount of calcium on the crystallized size (Lc) and the electromagnetic shielding (EMS) capacities in the range of 50~800 MHz for the chars from lignin were investigated. The results showed that Lc and EMS capacities in the entire of frequency of the chars with 6wt% calcium increased with increasing amount of the nickel loaded and also increased with increasing carbonization temperature from 700 to 900°C. Some amounts of calcium significantly enhanced the formation of crystallized carbon. Lc and EMS capacities of the chars with loaded 8wt% nickel increased with increasing amount of calcium and then decreased. It was founded that chars of lignin with co-loading of 8wt% nickel and 6wt% calcium were suitable as EMS materials with exceeding a practical standard of EMS capacity (30dB) in the range of 50~800 MHz.

Effect of carbonization treatment on the morphology and microstructure of mesoporous bioactive glass/nanocrystalline hydroxyapatite nanocomposite

Mesoporous bioactive glass/nanocrystalline hydroxyapatite (MBG–nHA) nanocomposite synthesis was prepared through evaporation-induced self-assembly method followed by in situ carbonization process, with non-ionic block copolymer as mesoporous template and carbon sphere as co-template. Conducting carbonization before calcination provided an effective and simple method of controlling the structural and morphological features of MBG–nHAs. The results show that the MBG–nHA350 nanocomposite with low carbonization temperature possessed a relatively ordered hexagonal structure, high specific surface area, and large pore volume. The increment of carbonization temperature induced the presence of micropores on the surface of the nanocomposite and increased the HA nanoparticles. These findings suggest that the surface area and pore volume of the nanocomposite decrease with increasing carbonization temperature. The structural changes in the nanocomposites were related to the inclusion of HA nanoparticles in the channels through carbonization. The in vitro bioactivity evaluation in the simulated body fluid (SBF) confirms that the MBG–nHA350 sample exhibits fast apatite formation ability, thereby denoting that the proposed method enhances the potential application of MBG–nHAs in bone tissue regeneration and drug delivery.

Characterization of Biochar from Switchgrass Carbonization

Switchgrass is a high yielding, low-input intensive, native perennial grass that has been promoted as a major second-generation bioenergy crop. Raw switchgrass is not a readily acceptable feedstock in existing power plants that were built to accommodate coal and peat. The objective of this research was to elucidate some of the characteristics of switchgrass biochar produced via carbonization and to explore its potential use as a solid fuel. Samples were carbonized in a batch reactor under reactor temperatures of 300, 350 and 400 °C for 1, 2 and 3 h residence times. Biochar mass yield and volatile solids decreased from 82.6% to 35.2% and from 72.1% to 43.9%, respectively, by increasing carbonization temperatures from 300 °C to 400 °C and residence times from 1 h to 3 h. Conversely, biochar heating value (HV) and fixed carbon content increased from 17.6 MJ kg−1 to 21.9 MJ kg−1 and from 22.5% to 44.9%, respectively, under the same conditions. A biomass discoloration index (BDI) was created to quantify changes in biochar colors as affected by the two tested parameters. The maximum BDI of 77% was achieved at a carbonization temperature of 400 °C and a residence time of 3 h. The use of this index could be expanded to quantify biochar characteristics as affected by thermochemical treatments. Carbonized biochar could be considered a high quality solid fuel based on its energy content.

Large surface area sucrose-based carbons via template-assisted routes: Preparation, microstructure, and hydrogen adsorption properties

We report the preparation of sucrose-based nanoporous carbons via template-assisted routes using zeolite USY as the hard-template. Sulfuric acid-pretreated sucrose solution is polymerized and carbonized via adjusting the mass ratios of zeolite over sucrose and temperatures. Large surface area carbons with wide micropore size, developed mesoporosity and moderate storage capacity were obtained. We find that preparation parameters have great effects on the pore structure of carbons. Total pore volume of carbons develops with an increase of carbonization temperature and the presence of zeolite in carbonization processes can effectively enlarge the surface area and pore volume. However, the morphology of carbons is not transferred from zeolites, and micropore in the carbons is almost wholly from the sucrose precursor itself. The hydrogen adsorption properties of carbons at 77K and 20bar are further investigated in this work. Carbon with a surface area of 1200m2/g exhibits a hydrogen storage capacity of up to 3.65wt% at 77K and 20bar, and the hydrogen capacities at higher pressures are found to be much more correlated with surface area and micropore volume of carbons.

Mechanical, Microstructure and Surface Characterizations of Carbon Fibers Prepared from Cellulose after Liquefying and Curing.

In this study, Cellulose-based carbon fibers (CBCFs) were prepared from cellulose after phenol liquefaction and curing. The characteristics and properties of CBCFs were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that, with increasing carbonization temperature, the La, Lc, and Lc/d(002) of CBCFs increased gradually, whereas the degree of disorder R decreased. The –OH, –CH2–, –O–C– and phenyl group characteristic absorption peaks of CBCFs reduced gradually. The cross-linked structure of CBCFs was converted into a graphite structure with a six-ring carbon network during carbonization. The surface of CBCFs were mainly comprised of C–C, C–O, and C=O. The tensile strength, carbonization yield and carbon content of CBCFs obtained at 1000 °C were 1015 MPa, 52%, and 95.04%, respectively.

Fire performance of carbonized medium density fiberboard manufactured at different temperatures

Authors established a new manufacturing technology for crack-free carbonized boards by pressing and carbonizing the medium-density fiberboard. Industrialization of new functional carbon materials was performed by investigating the fundamental properties of the carbonized boards. To be used as a construction material, the carbonized board needs to satisfy the fire performance regulation. In this study, the carbonized boards were manufactured from medium-density fiberboard (c-MDF) at different temperatures and then fire performance including flame retardancy and smoke toxicity was analyzed using a cone calorimeter and noxious gas analyzer. The results show that as the carbonization temperature increases, weight loss ratio decreases and flame retardancy increases. In the c-MDF at 800 and 1000 °C, no external damage was observed after combustion. These c-MDFs satisfy the total heat release (standard below 8 MJ/m2) and heat release rate (standard below 200 kW/m2) regulations according to the Building Standard Law of Korea and Japan. In addition, the c-MDFs showed the lower total smoke release (TSR, 0.213 m2/m2) than that of virgin MDF (94.281 m2/m2). The c-MDF at 800 and 1000 °C were, therefore, classified as a class III flame retardancy material and can be used as indoor finishing material.

Investigation on cotton stalk and bamboo sawdust carbonization for barbecue charcoal preparation

In the paper, biochar preparation from cotton stalk and bamboo sawdust by carbonization process was addressed. The physical and chemical properties and combustion characteristics of the biochar prepared using a tubular fixed bed were investigated. The combustion character index (S), the ignition temperature (Ti) and burnout temperature (Tf) were used to evaluate the combustion characteristics of the biochars. The results indicate that the yield and the volatile yield of the biochar decrease and the fixed carbon yield increases with the increase of the carbonization temperature. The ignition temperature and burnout temperature of the biochar increase and the value of S decreases when the carbonization temperature increases. The biochar produced from cotton stalk shows better combustion characteristics than the bamboo sawdust biochar does. Compared with commercial barbecue charcoal, the cotton stalk biochar produced under 600 °C can be utilized as barbecue charcoal.

구형 고분자수지로 활성탄제조 시 운전인자의 영향

Using a cation exchange resin of polystyrene-DVB copolymer as a carbon source for the production of activated carbon, the effects of operating parameters on the physical properties of activated carbon such as specific surface area and specific pore volume were experimentally studied. In carbonization process specific surface area and specific pore volume of carbonized pro- duct decreased with the increase of carbonization temperature and time. They were proportional to activation temperature and time up to the specific temperature and time in activation process. In carbonization process the increase of heating rate gave negative effect to the properties. The properties of activated product, on the contrary, increased with the heating rate in carbonization process. The properties of activated carbon manufactured with the resin exchanged with divalent cations were lower than those with raw resin.

Change of Heating Value, pH and FT-IR Spectra of Charcoal at Different Carbonization Temperatures

To understand transition characteristics from wood to charcoal, Quercus variabilis wood was carbonized at 200, 250, 300, 340, 540 and <TEX>$740^{\circ}C$</TEX>, respectively. Heating value, pH and surface property by FT-IR spectroscopy of the carbonized charcoal were investigated. Heating value and pH increased with increasing carbonization temperature from 4500 cal/g and 4.3 of the control wood to 8,000 cal/g and 9 of the charcoal carbonized at <TEX>$740^{\circ}C$</TEX>, respectively. From FT-IR spectroscopy, the peaks from O-H, C-H and C-O stretching disappeared during carbonization at 540 and <TEX>$740^{\circ}C$</TEX>. Aromatic skeletal vibration at near <TEX>$1,506{\sim}1,593cm^{-1}$</TEX> was repidly increased until <TEX>$540^{\circ}C$</TEX>. These results suggest that the chemical and physical characteristics of wood components in cell wall can be easily changed by increasing carbonization temperature and the carbonization seem to be incomplete at temperature below <TEX>$540^{\circ}C$</TEX>.

Structure-mediated transition in the behavior of elastic and inelastic properties of beach tree bio-carbon

Microstructural characteristics and amplitude dependences of the Young modulus E and of internal friction (logarithmic decrement δ) of bio-carbon matrices prepared from beech tree wood at different carbonization temperatures T carb ranging from 600 to 1600°C have been studied. The dependences E(T carb) and δ(T carb) thus obtained revealed two linear regions of increase of the Young modulus and of decrease of the decrement with increasing carbonization temperature, namely, ΔE ∼ AΔT carb and Δδ ∼ BΔT carb, with A ≈ 13.4 MPa/K and B ≈ −2.2 × 10−6 K−1 for T carb < 1000°C and A ≈ 2.5 MPa/K and B ≈ −3.0 × 10−7 K−1 for T carb > 1000°C. The transition observed in the behavior of E(T carb) and δ(T carb) at T carb = 900–1000°C can be assigned to a change of sample microstructure, more specifically, a change in the ratio of the fractions of the amorphous matrix and of the nanocrystalline phase. For T carb < 1000°C, the elastic properties are governed primarily by the amorphous matrix, whereas for T carb > 1000°C the nanocrystalline phase plays the dominant part. The structurally induced transition in the behavior of the elastic and microplastic characteristics at a temperature close to 1000°C correlates with the variation of the physical properties, such as electrical conductivity, thermal conductivity, and thermopower, reported in the literature.

Simple synthesis of magnetic mesoporous carbons with high surface areas by soft-template method

Magnetic Fe-containing ordered mesoporous carbons (Fe/OMCs) with high surface areas and pore volume were synthesized through a simple soft-template route, wherein phenolic resin was used as a carbon precursor, triblock copolymer F127 as a template agent, tetraethyl orthosilicate (TEOS) as a silica precursor and hydrated iron nitrate as an iron source. The effects of carbonization temperature, loading degree of TEOS on the structural parameters of these Fe/OMCs were evaluated by X-ray diffraction (XRD) and N2 sorption analysis. The ordering, the specific surface area and the total pore volumes increased with the increase of carbonization temperature from 600 to 850 °C. And the specific surface area and the total pore volumes increased with the increase of TEOS loading.

Phenolic resin infiltration and carbonization of cellulose-based bamboo fibers

Cellulose-based bamboo fibers were infiltrated with phenolic resin with assistance of vacuum and carbonized at 700, 900, and 1200°C. The effects of resin infiltration on the chemical composition, thermal shrinkage, weight loss, and the thermal stability of carbonized bamboo fibers were explored. It was noted that phenolic resin infiltration contributed not only to the decrease of thermal shrinkage and weight loss occurring in the furnace during carbonization but also to the increase of carbon contents and thermal stability of carbonized bamboo fibers, with increasing carbonization temperature. The fiber morphology revealed that the cellular structure of bamboo fiber with resin infiltration was retained after carbonization.

Gas separation performance of carbon materials produced from phenolic resin: Effects of carbonization temperature and ozone post treatment

The effect of carbonization temperature and treatment with ozone on the porosity and gas separation behavior of carbons produced from phenolic resin was investigated. Results showed that with increasing carbonization temperature from 500 to 800 °C, the average pore diameter decreased, while the pore volume and the adsorption capacity of the carbons first increased and then decreased. A molecular sieve separation mechanism was also observed for the sample carbonized at 800 °C. The pore size increased and the adsorption capacity and the kinetic adsorption selectivity for oxygen/nitrogen were decreased by the ozone treatment. [New Carbon Materials 2013, 28(1): 39–46]

Relation of micropores/mesopore ratio on high electrochemical performance of nano-porous carbons

Fluorine-doped microporous carbons (F-MCs) are prepared only by carbonization of poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF–HFP) without further heteroatom doping process and activation. The effects of the porous features and surface characteristics of F-MCs are investigated as a function of carbonization temperature. Without additional activation, the F-MCs, which have an irregular particle shape, have a high specific surface area (856 m2 g−1) due to micropore formation caused by the release of fluorine groups during carbonization. From the charge/discharge results, the specific capacitance of the F-MCs increase with increasing carbonization temperature, and the specific capacitance (268 F g−1) of F-MCs prepared with high carbonization (800 °C) is higher than F-MCs (221 F g−1) obtained at 600 °C. This suggests that the well-developed carbon structure, microporous features (<1 nm), and functional groups (F and O) of F-MCs allow the easy transfer and excellent accessibility of electrolyte ions, resulting in the maximizing of electrochemical performance of PVDF–HFP-based carbons for supercapacitors.

Gas separation performance of carbon materials produced from phenolic resin: Effects of carbonization temperature and ozone post treatment

The effect of carbonization temperature and treatment with ozone on the porosity and gas separation behavior of carbons produced from phenolic resin was investigated. Results showed that with increasing carbonization temperature from 500 to 800 °C, the average pore diameter decreased, while the pore volume and the adsorption capacity of the carbons first increased and then decreased A molecular sieve separation mechanism was also observed for the sample carbonized at 800°C. The pore size increased and the adsorption capacity and the kinetic adsorption selectivity for oxygen/nitrogen were decreased by the ozone treatment.

Comparison of Kinetic Models for CO2 Gasification of Coconut-Shell Chars: Carbonization Temperature Effects on Char Reactivity and Porous Properties of Produced Activated Carbons

Solid chars were prepared from coconut shell at different carbonization temperatures in the range from 250-750°C and gasified in a thermogravimetric analyzer under the atmosphere of carbon dioxide at 850 o C. The kinetic analysis showed an accelerating increasing of char conversion with reaction time, indicating an increase in the instantaneous gasification rate as the reaction proceeded. Four kinetic models for gas-solid reactions including, the volume- reaction model (VRM), the shrinking-core model (SCM), the random-pore model (RPM) and the modified volume-reaction model (MVRM) were tested against the measured kinetic data and the MVRM was found to predict the gasification kinetics most accurately. The char reactivity index was computed from the apparent rate constant of the MVRM and used to assess the reactivity of char towards carbon dioxide gasification. It was found that the char reactivity index decreased with increasing carbonization temperature, with the char produced at the lowest temperature of 250°C giving the highest reactivity. Surface area of activated carbon, produced from the gasification of various chars at 850°C for 60 and 120 min, correlated well with the char reactivity index, showing a proportional increasing of surface area with increasing reactivity index and passing through a maximum near the reactivity index of 0.02 min -1 .

탄화 온도에 의한 목탄의 특성

Characteristics of charcoals manufactured in each temperature as 400, 600 800, 1,000 and <TEX>$1,200^{\circ}C$</TEX> were examined. Sapwood and heartwood of Quercus variabilis that one of major species in charcoal materials were used for this experiment. Charcoal density was decreased highly 38-60% compared with wood density and density of sapwood was slightly decreased but heartwood was not changed with increasing carbonization temperature increase. Weight loss of sapwood and heartwood charcoal increased as carbonization temperature increases, and there is no difference between sapwood and heartwood charcoal. Refining degree of sapwood and heartwood charcoal was zero in charring over <TEX>$800^{\circ}C$</TEX>. Moisture and ash of sapwood and heartwood charcoal in each carbonization temperature were not differed between sapwood and heartwood. Volatile of sapwood charcoal was slightly higher than that of heartwood, and decreased as carbonization temperature increases. As the carbonization temperature increased, fixed carbon of sapwood and heartwood charcoal increased. Calorific values of charcoal prepared at <TEX>$600^{\circ}C$</TEX> were 7,200-7,300 cal/g and then decreased slightly as carbonization temperature increased.

Effect of nitrogen on the electrochemical performance of core–shell structured Si/C nanocomposites as anode materials for Li-ion batteries

Core–shell structured Si/C nanocomposites with different nitrogen contents are prepared by in situ polymerization of aniline in the suspension of silicon nanoparticles followed by carbonization of Si/polyaniline (PANI) nanocomposites at different temperatures. The nitrogen contents of Si/C nanocomposites decrease gradually with increasing carbonization temperatures. The effect of nitrogen contents on the electrochemical performance of Si/C nanocomposites as anode materials for lithium ion batteries is investigated. It is found that the Si/C nanocomposites with 4.75wt.% nitrogen exhibit the high specific capacity of 795mAhg−1 after 50 cycles at a current density of 100mAg−1 and excellent cycling stability. The appropriate nitrogen in Si/C nanocomposites plays a beneficial role in the improvement of electrochemical performance. The nitrogen in Si/C nanocomposites increases the reversible capacity, which may be due to the formation of vacancies and dangling bonds around the nitrogen sites.

Thermal properties of nanoporous carbons prepared by a template method using different polymeric and organic precursors

Six nanoporous carbons were prepared by a hard-template method using furfuryl alcohol (FA), 4,4′-bismaleimidediphenyl methane (BM), its copolymer with divinylbenzene (BM-DVB), and sucrose as carbon precursors, and two silica gels as templates. The influence of the templates and precursors on the properties of the synthesized porous carbons was studied. Other factors affecting the porous structure of the final products, such as surface activators and the final carbonization temperature, were also investigated. Results indicated that the specific surface areas and total pore volumes of the samples with micropores were in the range of 836–1785 m 2 g −1 and 0.9–2.0 cm 3 g −1 , respectively. The highest surface area was obtained for the systems when sulphosalicylic or/and phosphoric acids were used as surface activators. The porous carbons were mesoporous when benzene vapor was present during carbonization under argon atmosphere. An increase in final carbonization temperature resulted in an increase in total pore volume. The influence of carbon precursors on the properties of nanoporous carbons was not that obvious. The presence of nitrogen atoms in the precursors (BM and BM-DVB) improved the thermal stability of the product. [ New Carbon Materials 2012;27(5):337–43]