Two-stage Carbonization Research Articles

Permissible Extrapolation Justification of the Multiplicative Multifactorial Model and Its Application to the White Soot Production Technology

The solution to a specific technological problem is combined with the methodological development of a nonlinear multifactorial relationship to justify the boundaries of its extrapolation beyond the experimental range used. White soot was produced through two-stage carbonization of a silicate solution (composition, g/l: Na2O = 126.5, SiO2 = 107.7, Al2O3 = 3.1), obtained after processing waste tailings with carbon dioxide in a recirculation system. The influence of the deposition duration, temperature, and final pH value of the pulp on the formation of the specific surface area (Ssp, m2/g) of white soot was studied. The specific surface area was calculated from the average diameter of the white soot particles measured using an electron microscope. A multifactorial experiment was designed, and the experimental results were processed using a probabilistic deterministic method for experiment design (PDED) to obtain a nonlinear multiplicative combined model. A new interpretation of the subordination of the nonlinear multiple correlation coefficient R and the R2 value was given as relating to the structural and adaptive components of complex self-organizing systems. This determines their use for assessing the ratio of the basic R and extrapolated R2ranges of variation for each factor and any combinations thereof and multifactorial dependence in general. The results are presented in the form of multifactor tabular nomograms measured by the number of multifactor cells in localized areas of optimal sets that allow isolation by one or another combination of factors. The technological object of extrapolation of the ‘white soot’ production is linked to the solution of emerging methodological problems and illustrates the accessibility of the engineering application of the proposed method for combining nonlinear and linear approaches to mathematical experimental design. Doi: 10.28991/HIJ-2024-05-03-08 Full Text: PDF

STUDYING THE THERMOCHEMICAL CHARACTERISTICS OF SINTERING WITH ALKALI CONCENTRATE FROM WASTE COPPER TAILINGS

A long period of deposit development leads to a reduction in the volume of balance reserves of ores, while the volume of accumulation of waste (tailings) from mining and processing production increases. In connection with this, an urgent problem is the processing of waste tailings, which can serve as an additional source of commercial products of non-ferrous metals. The set objectives can be achieved by implementing comprehensive extraction of valuable components, reducing fuel, and energy costs at the stage of low-temperature sintering to produce white soot (grade BS-100). In order to determine the amount of heat of chemical reactions during sintering of rough copper concentrate with sodium hydroxide, thermochemical calculations were carried out. For the research, we used rough copper concentrate with a copper content of 4.40% and silver of 77.03 g/t. An equation has been obtained for calculating the heat of chemical reactions of rough concentrate sintering. According to this equation, the greatest contribution to the heat release is provided by the iron content (60%), three times less and equally (19%) - copper and silicon and about 0.2% is absorbed by aluminum. The thermal effect of sintering will be -920.45 kW·h/t of concentrate. From the heat balance of sintering it follows that with an alkali consumption of up to 200% of the mass of the concentrate. The heat of chemical reactions will be sufficient for the autogeneity of the process. Research has been carried out on sintering the concentrate with alkali in the temperature range of 250-500 °C and obtaining white soot from a productive leaching solution with the extraction of 60% silicon. White soot (mSiO2·nH2O) was isolated by two-stage carbonization of a silicate solution with carbon dioxide in a recirculation system with further washing of the precipitate with a solution of sulfuric acid. For citation: Karimova L.M., Kairalapov Ye.T., Makascheva G.K., Kharchenko Ye.M. Studying the thermochemical characteristics of sintering with alkali concentrate from waste copper tailings. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 72-79. DOI: 10.6060/ivkkt.20246707.7004.

Characteristics of Carbon from Oil Palm Shell Activated by Low Concentration of Zinc Chloride Activator

Currently, a large amount of oil palm shell has been dumped as waste from palm oil processing in Indonesia. Using a low concentration of zinc chloride (ZnCl2), thermal treatment during pre-carbonization was applied in the preparation of activated carbon from oil palm shells at various temperatures and reaction durations. This study, therefore, aims to investigate the physical and chemical characteristics of activated carbon prepared. Oil palm shells collected from a plantation in Palembang were carbonized by two methods, one-stage carbonization (at 300°C for 3 hours) and two-stage carbonization (at 300°C for 3 hours, then at 600°C for an hour) before chemical activation using ZnCl2, at a concentration of 10 and 15%wt. Activation of oil palm shell charcoal was conducted at 600, 700, and 800°C and reaction times of 60, 120, and 180 minutes. The results showed two-stage carbonization, high temperature, and prolonged reaction time is bound to increase burn-off as well as methylene blue adsorption, and decrease the yield and volatile matter content of the activated carbon prepared. Meanwhile, high ZnCl2 concentration increased the ash content and the methylene blue adsorption. In addition, the two-stage carbonization had higher iodine adsorption compared to the one-stage carbonization. The activated carbon with high iodine (769.3 mg/g) and methylene blue adsorption (133.7 mL/g) levels was obtained by two-stage carbonization using 15%wt ZnCl2 at a temperature and reaction time of 800°C and 180 minutes, respectively.

Carbonization characteristics of ethylene tar narrow fractions

In this study, the feasibility of using ethylene tar (ET) as raw material for needle coke production was investigated. The basic properties, structural compositions, and thermal stability of ethylene tar and its narrow fractions were studied by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), the coke induction period, and simulation of thermal stability of coking feed. The properties of the products were analyzed by a polarized light microscope, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the content of asphaltenes was up to 22.04% in ET, and the thermal stability was poor due to the high content of olefin and other thermally sensitive components. Thus, the coke induction period of ET was only 34 min. After distillation, narrow fractions had no asphaltenes and a low quantity of heat-sensitive components, resulting in improved fraction thermal stability with coke induction period of more than 55 min. Due to its narrow molecular distribution and low content of heat-sensitive components of narrow fractions, the semi-cokes formed from narrow fractions possessed better anisotropic and microcrystalline structures than those formed from the ET. Compared with one-stage carbonization, the two-stage carbonization was more conducive to the coalescence, development, and orientation of mesophase, leading to the formation of a fibrous wide-area streamline structure. The needle coke prepared from the fraction of ET-C had a lower thermal expansion coefficient (CTE), as low as 2.49×10−6 °C−1, meeting the CTE requirement of needle coke.

Facile heteroatom doping of biomass-derived carbon aerogels with hierarchically porous architecture and hybrid conductive network: Towards high electromagnetic interference shielding effectiveness and high absorption coefficient

In order to eliminate the secondary electromagnetic pollution, it is imperative to develop high-performance electromagnetic shielding materials with high-efficiency absorption coefficient. However, it remains a formidable challenge to simultaneously achieve high EMI shielding effectiveness (SE) and high absorption coefficient. Herein, a facile and environmentally strategy was proposed to fabricate heteroatom-doped carbon aerogels via graphene oxide nanosheet (GONS)/cellulose composite hydrogels as precursors for absorbing organic dyes, followed by freeze-drying and a specific two-stage carbonization process. The biomass-derived carbon aerogels possessed hierarchically porous architecture and heterogeneous conductive network with great conductivity difference. Consequently, the heteroatom-doped GNS-based carbon aerogels exhibited an outstanding EMI SE of 97.3 dB in the X band and high absorption coefficient of 0.69 at a density of as low as 68.9 mg/cm3. The highly efficient EMI shielding performance originated from the multiple shielding mechanisms involving multiple reflection, interfacial polarization, conduction loss and dipole polarization, which could effectively absorb and dissipate the incident EMWs as heat energy. The ingenious structural design puts forward a promising approach to conquering the contradiction between high EMI SE and high absorption coefficient, and the carbon aerogels have great potential or value in the applications of aircraft and spacecraft as lightweight shielding materials.

Sorption of Phenolic Acids on Powdered Carbon Prepared by Complex Processing of Spent Coffee Grounds

Activated carbons are prepared by conventional two-stage carbonization–activation processing and complex processing of spent coffee grounds. The latter method includes preliminary solvent extraction of organic compounds. The samples prepared by conventional and complex processing methods have a high BET (Brunauer–Emmett–Teller) surface area (SBET = 864 and 1089 m2/g, respectively), specific surface area of mesopores (400 and 464 m2/g), and total pore volume VΣ (0.68 and 0.87 mL/g). It is shown that the complex processing produces activated carbons with a specific surface area 27% higher, compared to the conventional method. We propose that this sorption material can be used in purification of pharmaceutical production effluents. The capacity of the carbons to adsorb phenolic acids, in particular, salicylic and sulfosalicylic acids, which represent pharmaceutical microimpurities, is studied. The equilibrium concentrations of salicylic and sulfosalicylic acids are determined spectrophotometrically at λ = 296 and 294 nm, respectively, using a UV-2450 instrument (Shimadzu, Japan). The carbon produced by complex processing exhibits the most effective sorption properties (18 mg/g). The carbon prepared by conventional method displays intermediate characteristics (13.3 mg/g), and a reference Natural Brand adsorbent derived from lignocellulose material has the lowest characteristics (11.4 mg/g). The same pattern is observed for adsorption of sulfosalicylic acid, with the saturation adsorption being lower for sulfosalicylic than salicylic acid. We can state that substances with good solubility in water exhibit poorer physical adsorption than those with limited solubility. Processing the experimental data within the Langmuir and Freundlich adsorption models suggests that adsorption of the phenolic acids on the highly porous sorbents follows the Langmuir model, i.e., adsorption occurs at active sites where a dynamic equilibrium is established between adsorption and desorption processes.

Preparation of Lignocellulose-Based Activated Carbon Paper as a Manganese Dioxide Carrier for Adsorption and in-situ Catalytic Degradation of Formaldehyde.

Formaldehyde is a colorless, highly toxic, and flammable gas that is harmful to human health. Recently, many efforts have been devoted to the application of activated carbon to absorb formaldehyde. In this work, lignocellulose-based activated carbon fiber paper (LACFP) loaded with manganese dioxide (MnO2) was fabricated for the adsorption and in-situ catalytic degradation of formaldehyde. LACFP was prepared by two-stage carbonization and activation of sisal hemp pulp-formed paper and was then impregnated with manganese sulfate (MnSO4) and potassium permanganate (KMnO4) solutions; MnO2 then formed by in situ growth on the LACFP base by calcination. The catalytic performance of MnO2-loaded LACFP for formaldehyde was then investigated. It was found that the suitable carbonization conditions were elevating the temperature first by raising it at 10°C/min from room temperature to 280°C, then at 2°C/min from 280 to 400°C, maintaining the temperature at 400°C for 1 h, and then increasing it quickly from 400 to 700°C at 15°C/min. The conditions used for activation were similar to those for carbonization, with the temperature additionally being held at 700°C for 2 h. The conditions mentioned above were optimized to maintain the fiber structure and shape integrity of the paper, being conducive to loading with catalytically active substances. Regarding the catalytic activity of MnO2-loaded LACFP, the concentration of formaldehyde decreased by 59 ± 6 ppm and the concentration of ΔCO2 increased by 75 ± 3 ppm when the reaction proceeded at room temperature for 10 h. The results indicated that MnO2-loaded LACFP could catalyze formaldehyde into non-toxic substances.

ADSORPTION OF Cd(II) BY CARBON PREPARED FROM PEELS AND STEMS OF KEPOK BANANA (MUSA PARADISIACA FORMATYPICA)

Carbon was produced from peels and stems of kepok banana and was characterized. Also, its Cd(II) adsorption ability was determined. The carbon material was prepared through two-stage carbonization. First, carbonization was carried out at 400 °C for 30 minutes, and then it was continued at 450 °C and 500 °C for 10 minutes. The results showed that the carbon content obtained after carbonization of banana peels at temperatures of 400 °C, 450 °C and 500 °C was 60.92%, 55.16% and 50.11%, respectively, while that achieved from banana stems was 65.37%, 56.97% and 45.80%, respectively. The moisture content of the carbon prepared from banana peels was 7.01%, 5.37% and 5.28%, respectively, for each temperature level, while that of the carbon material made from banana stems was 4.93%, 4.17% and 3.44%, respectively. The ash content of the banana peel carbon prepared at different temperature levels was 4.56%, 7.23% and 11.04%, respectively, and that of the banana stem carbon was 7.73%, 9.65% and 13.85%, respectively. The highest iodine number of banana peel carbon (450 °C) was 1006.74 mg/g, while that of banana stem carbon (450 °C) was 1019.43 mg/g. Surface analyses were conducted using scanning electron microscopy – energy dispersive spectroscopy (SEM-EDS). The Cd(II) adsorbed by the carbon materials was measured using atomic absorption spectrometry (AAS). The results showed that increasing the weight of the adsorbent leads to an increased amount of adsorbed Cd(II).

Comparison of the Properties of Activated Carbons Produced in One-Stage and Two-Stage Processes

Activated carbons (ACs) can be produced from biomass in a thermal process either in a direct carbonization-activation process or by first carbonizing the biomass and later activating the bio-chars into activated carbons. The properties of the ACs are dependent on the type of process used for production. In this study, the properties of activated carbons produced in one-stage and two-stage processes are considered. Activated carbons were produced by physical activation of two types of starting materials: bio chars produced from spruce and birch chips in a commercial carbonization plant and from the corresponding raw chips. The activated carbons produced were characterized regarding specific surfaces, pore volumes, and pore size distributions. The un-activated bio chars had varying surface areas, 190 and 140 m2 g−1 for birch and spruce, respectively, and pore volumes of 0.092 and 0.067 cm3 g−1, respectively. On the other hand, 530–617 and 647–679 m2 g−1 for activated bio chars from birch and spruce, respectively, and pore volumes 0.366–0.509 and 0.545–0.555 cm3 g−1, respectively, were obtained. According to the results obtained, two slightly different types of activated carbons are produced depending on whether a one-stage or a two-stage carbonization and activation process is used. The ACs produced in the one-stage process had higher specific surface areas (SSA), according to the BET-model (Brunauer–Emmett–Teller), compared to the ones produced in a two-stage process (761–940 m2 g−1 vs. 540–650 m2 g−1, respectively). In addition, total pore volumes were higher in ACs from the one-stage process, but development of micro-pores was greater compared to those of the two-stage process. This indicates that the process can have an influence on the ACs’ porosity. There was no significant difference in total carbon content in general between the one-stage and two-stage processes for spruce and birch samples, but some differences were seen between the starting materials. Especially in the one-stage procedure with 2 and 4 h steam activation, there was nearly a 10% difference in carbon content between the spruce and birch samples.

An investigation into the rapid removal of tetracycline using multilayered graphene-phase biochar derived from waste chicken feather

This study investigated the removal of tetracycline (TC) using multilayered graphene-phase biochar (MGB) derived from waste chicken feather. MGB was produced through a two-stage carbonization and KOH-activation method. MGB was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared (FT-IR), Raman spectra, Zeta potential and elemental analysis. Various chemical functional groups were demonstrated on the surface of MGB. MGB was featured by a very large BET surface area of 1838m2/g. A rapid equilibrium (within 30s) and an ultrahigh removal efficiency (up to 99.65%) were obtained when MGB was used in the adsorption of TCs. The adsorption processes were temperature-dependent and the maximum adsorption capacity of MGB was 388.33mg/g at 30°C. The data of adsorption isotherms and kinetics were represented well by the Langmuir and Elovich models, respectively. The chemical monolayer adsorption could play an important role in this process. Furthermore, the adsorption of MGB was tolerant with wide pH, high ionic strength and even co-existing anions. Regeneration experiments indicated the removal efficiency was still satisfied (96.61%) even after four cycles. These results have important implications for the future application of animal waste-derived adsorbents in the treatment of wastewater containing antibiotic residues.

Effect of high temperature treatment on electrochemical properties of carbon nanofiber membrane

In this study, polyacrylonitrile was used as the nanofiber membrane material. Through A two-stage continuous process, namely, oxidation process and carbonization and activation process, an activated nanofiber membrane material was fabricated. Subsequently, the membrane underwent high-temperature heat treatment (1100-1500 °C) to explore the effect of temperature on its properties. Charge/discharge rate was employed to determine the capacitance retention ratio to evaluate the applicability of the fabricated membrane in high-power super capacitor electrodes. The results revealed that in the treated membrane, the lattice size increased from 1.24 nm to between 3.20 and 4.72 nm. In addition, the volume resistivity was reduced from 6 Ω-cm to between 9.70E-2 and 3.85E-2 Ω-cm, substantially improving the electric conductivity. The activated carbon nanofiber membrane treated with high temperature at 1100 °C exhibited the highest capacitance of 704 F/g at a scan rate of 5 mV/s.

Polyoxometalate Modified Biomass Carbon Composites for Supercapacitor Electrodes

Polyoxometalates (POMs), nanoscale transition metal-oxide clusters, have emerged as promising building blocks for the fabrication of pseudocapacitive electrodes.[i] These POM clusters undergo fast reversible electron transfer reactions and have multiple stable redox states, ideal characteristics for energy storage applications.[ii] In order to leverage these properties for use in electrochemical capacitor (EC) electrodes, these POM clusters must be immobilized on a stable carbon substrate to create a composite electrode. There is synergy in this combination as the POMs contribute faradaic redox processes, while the carbon provides stability, high conductivity, and electrochemical double layer capacitive (EDLC) contributions. Porous carbon derived from biomass is an excellent potential substrate for these POM-carbon composites owing to its low cost, simple synthesis procedure, and high specific surface area. Here, we will report on our synthesis of porous carbon substrates derived from pine cone biomass via a two-stage carbonization and chemical activation procedure. These pine cone carbon samples are highly porous with specific surface areas over 2500 m2 g-1. In a sulfuric acid electrolyte, the high surface area of these samples results in a double layer capacitance of 265 F g-1. In order to further enhance this already large capacitance, the biomass carbons were modified with Keggin POM clusters, PMo12O40 3- and PW12O40 3- via a single step chemisorption. We have discovered that the intrinsic porosity and surface conditions of the pine cone biomass carbon are particularly well suited to the immobilization of Keggin POMs. Additionally, by adjusting the activation conditions, the carbon porosity can be tuned to further enhance POM chemisorption. The result is biomass carbon hybrids with exceptionally high loading of POM clusters. The redox activity of these immobilized POMs leads to significantly enhanced area and volume specific capacitance compared to the bare carbon substrate (Figure 1). In this talk, we will present the full characterization of the POM-biomass carbon hybrids as well as discuss the activation conditions and resulting substrate porosity necessary for superior POM adsorption. The POM chemistry that results in the optimal pseudocapacitive performance will also be presented and discussed. [i] M. Genovese, K. Lian. Current Opinion in Solid State and Materials Science. 19 (2015) 126-127 [ii] B.B Xu, L. Xu, G.G. Gao, W.H. Guo, S.P. Liu. J. Colloid Interface Sci. 330 (2009) 408 Figure 1

Coal based magnetic activated carbon as a high performance adsorbent for methylene blue

Coal based magnetic activated carbons (MACs) were prepared by using the two-stage carbonization and activation of coal in the presence of Fe2O3 as the magnetic source. Compared with the single-stage carbonization and activation, the two-stage temperature method was found to be efficient for the preparation of MACs with the high specific surface area and good magnetic properties in a lower alkali/carbon ratio. The as-synthesized MACs at optimized conditions exhibited specific surface areas of up to 2075 m2/g and optimal saturation magnetization of as high as 15.02 emu/g. Moreover, as an adsorbent, the efficiency of removing methylene blue (MB) from aqueous solutions is excellent. Based on MB adsorption behaviors at various conditions, including initial dye concentration, contact time and temperature, MACs prepared at optimized conditions exhibited a maximum equilibrium MB adsorption capacity of 871 mg/g. The data of adsorption kinetics and isotherms could be well fitted by using the pseudo-second-order equation and the Freundlich model. Importantly, MACs can be separated and recovered easily by applying a magnetic field. Therefore, the coal-based magnetic activated carbons might be a promising candidate of high efficiency, low cost for removal of organic dyes.

Gallium and vanadium extraction from red mud of Turkish alumina refinery plant: Hydrogarnet process

In this paper the treatment of red mud by autoclave leaching for its conversion into ferrous hydrogarnet product and extraction of valuable components (i.e. Na2O, Al2O3, Ga and V2O5) was investigated. Leaching of red mud using high modulus alkaline solution (Na2O 240g/L; αк=30) in the presence of lime at 240–260°C was found to allow the recovery of the contained values (98.5% Na2O, 65.3% AI2O3, 55.5% Ga and 65.8% V2O5) and the fixing silica in the form of hydrogarnet mud (3СаО·Fe2O3·2SiO2·2Н2О) with a low alkali content (0.35% Na2O). An effective treatment scheme for the leach solution based on precipitation and two-stage carbonization processes was developed and demonstrated. This allowed the generation of alkaline solutions suitable for recycling back to leaching stage and recovery of a concentrate (30% AI2O3) that is rich in Ga (0.32%) and V2O5 (3.7%). The chemical and phase composition of the solid products obtained from each stage of processing were determined by XRF and XRD analyses. This study has demonstrated that Bayer–hydrogarnet process can be suitably exploited for processing of red mud.

Nanoemulsion drug delivery by ketene based polyester synthesized using electron rich carbon/silica composite surface

A new carrier matrix for nanoemulsion drug delivery was synthesized from glycine as the raw material, using mesoporous/microporous electron rich carbon–silica composite surface (MAC 800). MAC 800 was prepared from rice husk in two-stage carbonization. The surface area, pore volume, and pore size distribution of MAC 800 were measured, using nitrogen adsorption isotherms at 77 K. The unpaired electron density of MAC 800 was measured in electron spin resonance spectroscopy (ESR), using TEMPOL (4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl) as the reference spin probe. Glycine was converted into ketene at the surface of MAC 800, which further underwent radical polymerization to form a low molecular weight ketene polymer (LMKP) of ester structure. The structure and the properties of LMKP were confirmed through 13C, 1H and DEPT nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and size exclusion chromatography (SEC). The two hydrophilic drugs namely ciprofloxacin hydrochloride (CPH) and gentamicin sulphate (GS) were chosen for the nanoemulsion preparation and characterization. They were characterized for morphology, interaction of drugs with the polymer and their crystallinity, using HR-TEM, DSC and XRD, respectively. The encapsulation efficiency of the LMKP towards the drugs ciprofloxacin hydrochloride and gentamicin sulphate were 26% and 12%, respectively. The dissolution studies of the nanoemulsion were carried out for the pH 6.5, 7.4 and 8.0. The cytocompatibility studies were done for LMKP as well as nanoemulsion using Hep2 epithelial cells.

Utilization of Buckwheat Husks through a Two-stage Cooking and Carbonization Treatment

廃棄物として処理されているソバ殻を有効に活用するために, 蒸煮―炭化の2段処理法を提案した。蒸煮はソバ殻から有用成分を熱水抽出するために行うもので, ルチンが約600mg/kgの収量で得られた。蒸煮処理後の湿潤ソバ殻は乾燥することなくそのまま炭化を行うことが可能であり, 良質なソバ殻炭とソバ殻酢液を得ることができた。ソバ殻炭は家屋調湿材や農地の土壌改良用として利用が可能であり, 酢液は農業資材として木酢液と同等の性質を示した。この2段処理により, 付加価値の高いルチンを得るとともに, 2次廃棄物を産出することなく, 残渣をすべて炭・酢液に変えることができることが示された。

Relationship between two-stage carbonization speeds for polyacrylonitrile based carbon fibre

Of all the precursor materials available for preparing good-quality carbon fibres, polyacrylonitrile (PAN) is the most usefu] raw material at present [1,2]. The quality of PAN based carbon fibres depends strongly on the composition and quality of the precursor fibres [3-8] and on the oxidation conditions [9-11], as weh as on the carbonization conditions [12-14]. The stability of the PAN structure is achieved through the conversion of an open structure into a closed chain structure (aromatized structure). The aromaticity or aromatization index so developed can be determined by X-ray diffraction (XRD) or differential scanning calorimetry (DSC). As the aromatization index (AI) value for oxidized fibre is lower than 50%, the carbon fibre for a one-stage carbonizing furnace shows lower properties, but the properties can be improved by using a two-stage carbonizing furnace [9, l 0]. If the oxidized fibre has an AI value of 60%, the carbon fibre carbonized at 800 °C for the first-stage furnace and at 1200 °C for the second-stage furnace exhibits better mechanical properties [12]. From previous studies, we know that the most important variables affecting the modulus of carbon fibre are the oxidation time, carbonization speed and carbonization tension [15]. Generally, the same carbonization speed is used for the two stages, but we do not know what reaction time is required at the first-stage and second-stage carbonization individually. Hence, in this letter, we discuss the effect of different speeds of the first-stage and second-stage carbonization on the properties of carbon fibres. PAN copolymer was polymerized with acrylonitrile, methyl acrylate and itaconic acid in a mixed solvent of acetone and dimethyl sulphoxide (DMSO) at 60°C with a-a'-azo-bis(isobutyronitrile) as an initiator under an inert nitrogen atmosphere. The resultant polymerization solution was directly spun to form PAN fibre using a spinneret (12000 holes, 0.06mm hole -1, length:diameter= 1) through a 25% DMSO coagulation bath at 30 °C then stretched in boiling water and dried. The properties of the PAN fibre were 1.2 denier per filament, 0.9 GPa tensile strength, 13.2GPa modulus and 13.4% elongation. PAN fibres were stabilized at 220 °C for 7 h in a continuous oxidizing furnace in air, then carbonized in two continuous carbonizing furnaces (effective length of 150 cm, individually) in nitrogen. In order to control the different carbonization speeds at the first and second stages, a winder was laid out between the first and second furnaces. The properties of a single filament of carbon fibre were determined

The characterization of high-performance PAN-based carbon fibers developed by continuous carbonization and air oxidation

The properties of four kinds of Type II carbon fibers, which had been precarbonized at 300 °C, 400 °C, 500 °C, and 600 °C, respectively, during two-stage continuous carbonization, were measured after being air oxidized for periods of 1 to 6 min at 550 °C. The effects of precarbonization temperature on mechanical properties, density, morphology, elemental composition, and microstructure of the carbon fibers during the air oxidation are discussed in this article. The precarbonization process strongly affected the surface properties and mechanical properties of the final oxidized carbon fibers. The carbon fibers developed from the different precarbonization temperatures all had different structures. The carbon fibers that had been precarbonized at 300 °C had a more ordered structure than other fibers after air oxidation. These carbon fibers also had a higher performance than the other fibers. Carbon fibers also showed different oxidation behaviors caused by differences in surface morphology resulting from each different precarbonization temperature. Optimum conditions not only improved the tensile strength and modulus, but also increased the density and oxygen content. Experimental results showed that the tensile strength of the carbon fibers precarbonized at 300 °C increased from 2.4 GPa to 4.3 GPa (80%) after 6 min oxidation at 550 °C.

The characterization of PAN-based carbon fibers developed by two-stage continuous carbonization

A continuous stabilization and two-stage carbonization process was used to prepare polyacrylonitrile (PAN)-based carbon fibers. The effect of precarbonization on the final properties of carbon fibers was measured. The results of this study showed that a suitable precarbonization was very conducive to improvement in tensile strength or in Young's modulus of the final carbon fibers. When the final carbon fiber was precarbonized at 550°C, this fiber had a higher tensile strength than carbon fibers which were precarbonized at other conditions. On the other hand, the final carbon fibers developed at precarbonization temperatures of 650°C and 700°C, had better Young's modulus. Experimental results using a X-ray diffractometer indicated the presence of a less ordered phase at 2 Θ = 17° in the precarbonized fibers and the final carbon fibers. The formation of this less ordered structure is also discussed.

Two-stage carbonization of coal into blast furnace coke with controlled production of tar

Two-stage carbonization of coal was studied to obtain tars at high yield and solid coke of high strength. The coal was depolymerized sufficiently under pressure with an additive in the first stage and the residue after extraction of tar from the product from the first stage was carbonized after the moulding. The depolymerization of coal macro-molecules under pressure with a hydrogen donating additive is discussed in terms of tar production and fusibility of extracted residue. Influences of carbonization conditions of the first stage are also discussed.