Oxidation of carbon derived from phenolic resin

The oxidation of carbon derived from phenolic resin and heat-treated at temperatures ranging from 1000 to 2400°C for 1 hr was studied in a flowing oxygen atmosphere at temperatures between 424 and 692°C. The heat-treatment alters the crystallite size, L_c, from 10.7 to 21.4 Å; the interlayer spacing, d₀₀₂, from 3.74 to 3.52 Å and the surface area from 0.22 to 1.34 m²/g. $\text{L}{}_{\mathrm{a}}\text{L}{}_{\mathrm{c}}$ ratio ranges from 1.62 to 2.22 and appears to be independent of heat treatment temperature and oxidation level. The surface area of the carbon and its change with oxidation were found to be sensitive to the heat treatment process. Heat treatments at 1000 and 1400°C produce carbon with surface area which increases by nearly two orders of magnitude after 10% oxidation. The oxidation rate decreases with increasing heat treatment temperature with the largest change between 1000 and 1400°C. Samples heat-treated at different temperatures give slightly different activation energies with an average value of 41.5 kcal/mole.     

Preparation of phenolic resin derived 3-D ordered macroporous carbon

Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m²/g (1.32 cm³/g) ∼ 93.7 m²/g (0.12 cm³/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique, which has potential applications in the microreaction technology.     

Silicon carbide-based foams derived from foamed SiC-filled phenolic resin by reactive infiltration of silicon

Macro-cellular porous silicon carbide-based foams were fabricated by reactive infiltration of melt silicon into porous carbonaceous preforms pyrolyzed from foamed SiC-filled phenolic resins (PF). The SiC-filled PF foams were prepared at 80 °C with different heating rate. The effect of heating rate on the foaming behavior of the liquid SiC-filled PF mixture and the microstructure of the foams were investigated. The foamed SiC-filled PF was then pyrolyzed at 1000 °C and infiltrated by melt Si at 1600 °C, leading to the formation of open macro-cellular structure. At a heating rate of 6 °C min⁻¹, Si-infiltrated foams with a porosity of ~72% and a mean pore size of ~0.5 mm were obtained. The Si-infiltrated foams with dense struts mainly inherited the pore structure of pyrolyzed preforms. The main phases of SiC-based foams were α-SiC, β-SiC and the remnant Si, which contributed to high compressive strength of the SiC-based foams.     

以线性酚醛树脂为炭前驱体制备有序介孔炭及其表征

以三嵌段共聚物F127和P123为模板剂,线性酚醛树脂(PF)为炭前驱体,利用有机-有机自组装制备了具有二维六方结构和蠕虫结构的介孔炭.采用XRD、TEM、N2吸附/脱附等方法对介孔炭的结构进行了表征,研究了模板剂用量和模板剂类型对上述介孔炭结构的影响.结果表明:当模板剂F127与PF的质量比由1:2变为1:1时,所得介孔炭的孔壁厚度有所下降,但比表面积、孔容和孔径分别从576 m2·g-1、0.29 cm3·g-1和2.7 nm提高到670m2·g-1、0.40 cm3· g-1和3.2 nm;分别以F127和P123为模板剂制备的介孔炭F-1-500和P-1-500的孔径大小基本相同,但P-1-500的孔壁厚度相对于F-1-500降低了37.4％,且有序性下降,仅能得到蠕虫状结构.     

Hierarchically Fe-doped porous carbon derived from phenolic resin for high performance supercapacitor

Supercapacitors are promising for high power application in the recent years. In particular, the conversion of simple and available carbon materials into economic and high performance electrical devices receives excellent scientific and technological interest. This paper reports a one-step strategy for synthesizing hierarchical porous carbon derived from phenolic resin (PR), which is then used to configure electric double-layer capacitors (EDLCs). Here, a carbon material with a flexible porous structure, large specific surface area, and high graphitization degree is prepared using potassium ferrate (K₂FeO₄) to catalytically activate PR and to realize synchronous carbonization and graphitization. This method overcomes the disadvantage of time-consuming, high-cost, and environmentally unfriendly. In addition, the as-prepared carbon material has a high specific surface area (1086 m² g^?1) and a large pore size (3.07 nm), which can increase the transfer rate of electrolyte ions. The specific capacitance of the obtained electrode material is 315 F g^?1 at 1.0 A g^?1, and the optimized electrode material has an ultra-long cycle lifetime (capacitance retention rate is 96.3% after 10,000 cycles). Thus, the hierarchically Fe-doped porous carbon material derived from PR material is expected to realize high rate capacitance for supercapacitor applications.     

The effects of aluminum on structural development of a carbon derived from phenolic resin

The catalytic graphitization of a phenolic resin carbon by aluminum powder was carried out under an N₂ atmosphere. The following catalytic mechanism is proposed: In the heating process up to 2000°C, AlN is formed at first by the reaction of the aluminum with the N₂ gas. At approximately 2000°C, the AlN begins to react with the carbon matrix to form an intermediate, A₁₄C₃. The Al₄C₃ penetrates into the surrounding carbon matrix through an Al₄C₃ formation-decomposition sequence, leaving a graphite crystal behind. As the penetration proceeds, smaller graphite crystals are formed because of the division of the Al₄C₃ particles. When a most finely divided Al₄C₃ is produced by the further penetration, instead of the graphite, only turbostratic carbon is formed by this catalytic process.     

Pore structure control of mesoporous carbon monoliths derived from mixtures of phenolic resin and ethylene glycol

Mesoporous carbon monoliths derived from phenolic resin mixtures have been prepared in the process based on polymerization-induced phase separation. The effect of the composition of resin mixtures and the resin curing temperature on the pore structure of carbon monoliths has been systematically investigated, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions have been introduced to evaluate the morphologies of the carbon monoliths. The results showed that mesoporous carbon monoliths with narrow pore size distribution were obtained. The pore structure of carbon monoliths could be controlled by changing the resin curing temperature and the content of ethylene glycol, curing catalyst and water in the resin mixtures. The apparent porosity of carbon monoliths varied from 54.27% to 26.83%. Carbon monoliths had narrower pore size distribution when more ethylene glycol and higher resin curing temperature were employed. The pore structure of carbon monoliths would be changed radically when the initial resin samples were prepared with excess water (9.8 wt%), i.e. porous carbon foams with sponge structure were obtained. Carbon monoliths inherit their porosity from precursing cured resins where it was formed as a result of phase separation of resin-rich and glycol-rich phases. Volume contraction had certain effect on the pore structure of carbon monoliths.     

Preparation and characterization of highly thermostable polyisocyanurate foams modified with epoxy resin

A series of epoxy resin–modified polyisocyanurate (EP‐PIR) foams with oxazolidone (OX) rings and isocyanurate (IS) rings have been successfully prepared by the reaction of polymethylene polyphenyl isocyanate (PAPI) and diglycidyl ether of bisphenol‐A (DGEBA). Fourier transform infrared spectroscopy and differential scanning calorimetry are performed to investigate the influence of curing temperature on the chemical structure of EP‐PIR foams. The results indicate that low temperature is beneficial to the formation of the IS ring, and high temperature is in favor of the OX ring. The influence of the mole ratio of [PAPI]/[DGEBA] on the mechanical properties and thermal stability has also been studied. With the increase of [PAPI]/[DGEBA], the specific compressive strength shows a maximum of 0.0135 ± 0.0003 MPa m³/kg. The optimized mole ratio of [PAPI]/[DGEBA] is around 2.5 to reach the better mechanical and thermal properties, and the glass‐transition temperature is as high as 323.5°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43085.     

Preparation of activated carbon from phenolic resin by KOH chemical activation under microwave heating

Microwave irradiation was used as a heat source in the preparation of activated carbon (AC) from phenolic resin by potassium hydroxide chemical activation. The input microwave power was varied from 0.26 to 0.52 kW, while weight ratios of KOH to phenolic resin, R, were changed from 2 to 6. For a comparison, phenolic resin was also activated at R = 4 using electric furnace heating. During microwave irradiation of KOH and KOH/phenolic resin mixtures, the sample temperatures increased rapidly, which proved that activated carbon was prepared from the mixture under microwave irradiation. The most developed porosity of AC was obtained at R = 4 with a microwave power of 0.39 kW, and the activated carbon was characterized by high mesopore ratio. The development of mesopores under microwave heating was attributed to the rapid heating of the sample in contrast to slow electric furnace heating. The possibility of using the AC as a desiccant humidity conditioner was confirmed in terms of its effective water adsorptivity.     

Formation mechanism of carbon foams derived from mesophase pitch

Carbon foams were prepared from mesophase pitch using foaming, carbonization and graphitization processes. The physical and chemical properties of the mesophase pitch during thermal treatment were studied by Fourier transform infrared spectroscopy, thermogravimetry, mass spectroscopy, rheometry and scanning electron microscopy. The results suggest that gases released from the pitch dissolve, saturate, nucleate and grow in the molten pitch during foaming. Then the resultant bubbles coalesced with the neighboring bubbles driven by the surface tension of the molten pitch. This coalescence generates a shear stress to force aromatic planes of the pitch to arrange regularly and paralleled to the axis of a ligament. The growth of bubbles stopped when the pitch became semi-coke at a temperature above 733 K. The viscosity and surface tension of the molten pitch are major factors that influence the growth of bubbles. After carbonization at 1073 K and graphitization at 2873 K, the well aligned aromatic planes in the foams evolve into highly aligned graphitic structures.     

由酚醛树脂基板C02活化法制备高性能活性炭

采用CO2活化法以阻燃的FR-1型酚醛树脂基板为原料制备出性能优良的活性炭。研究了活化温度、活化时间和气体流量对产品性能的影响。所得产品BET比表面积达到1198m^2／g,总孔体积达到0．703cm^3／g。在最佳条件,即活化温度910℃,活化时间140rain和CO2流量350cm。／min时,亚甲基蓝值和碘值分别达到292．0mg／g和1113．05mg／g,均达到国家一级品标准。     

由酚醛树脂基板CO2活化法制备高性能活性炭

采用CO2活化法以阻燃的FR-1型酚醛树脂基板为原料制备出性能优良的活性炭。研究了活化温度、活化时间和气体流量对产品性能的影响。所得产品BET比表面积达到1 198 m2/g,总孔体积达到0.703 cm3/g。在最佳条件,即活化温度910℃,活化时间140 min和CO2流量350 cm3/min时,亚甲基蓝值和碘值分别达到292.0 mg/g和1 113.05 mg/g,均达到国家一级品标准。     

异氰酸酯/可发性酚醛树脂泡沫体的制备

采用端异氰酸酯聚醚预聚物与可发性酚醛树脂制备了新型泡沫体。通过ESI-MS光谱分析和泡沫物理力学性能测试研究了异氰酸酯基团与可发性酚醛树脂比例、异氰酸酯基团和三聚体相对含量、可发性酚醛树脂分子质量对泡沫体制备及性能的影响。结果表明:异氰酸酯基团与酚醛树脂质量比为40/100、三聚体质量分数17.33%、酚醛树脂聚合时间45min时,泡沫体的体积稳定性好,收缩率低;可发性酚醛树脂分子质量增加时,泡沫体的密度从60.16kg/m3增加到63.96kg/m3,基本保持稳定;其弯曲强度为0.2MPa,弯曲应变达到15%以上,远高于纯酚醛泡沫(6%)。在150℃下烘烤2h,泡沫体的质量损失为6%左右,体积变化为-5%左右。泡沫体的热稳定性优于聚氨酯泡沫,同时又有良好的韧性。     

Reaction forming of silicon carbide ceramic using phenolic resin derived porous carbon preform

SiC ceramics were prepared with porous carbon preforms derived from phenolic resin by a reaction-forming method. The effects of the structure of the preform pores and the infiltration process on the properties of SiC ceramics were investigated, and components with complex shapes were fabricated by combining this process with stereolithography (SLA). Dense SiC ceramics were obtained from carbon preforms with high apparent porosities, but SiC ceramics with many macrodefects resulted from a carbon preform with an apparent porosity of 39%. The infiltration of molten silicon into the preform pore channel was accelerated under vacuum pressure, resulting in an increase in the depth of the Si infiltration. The growth of SiC was predominantly controlled by carbon diffusion at the last stage of the reaction. The extended grain growth caused the SiC grains to coalesce and some free Si was enveloped in the SiC grains. SiC components with complex geometries were fabricated by combining reaction forming with SLA. The geometry was controlled by SLA.     

酚醛树脂基板真空热解炭制备高性能活性炭

以一种全新的物质--阻燃的FR-1型酚醛树脂电路板基板的真空热解炭渣为原料,采用CO₂和KOH活化法制备高性能的活性炭。分别研究了CO₂活化法中的活化温度和KOH活化法中的碱炭比对活性炭产品性能的影响。用氮气吸附表征了活性炭的孔结构性质,并检测了产品的亚甲基蓝值和碘值。结果表明,KOH活化所得活性炭有更高的亚甲基蓝值(928.3 mg·g^-1 vs 231.5 mg·g^-1)、碘值(2442.2 mg·g^-1 vs 946.6 mg·g^-1)、比表面积(2289 m²·g^-1 vs 1198 m²·g^-1)和孔体积(1.317 cm³·g^-1 vs 0.703 cm³·g^-1)。所得产品均达到国家一级品标准。用这种原料制备高性能活性炭不仅解决了废弃物资源化的问题,还开发出一种新的、廉价的制备高性能活性炭的原料和方法工艺。     

Preparation and characterization of polystyrene foams from limonene solutions

The foaming process has been traditionally performed at high temperature because the CO₂ and the polymer should behave as a homogeneous solution. The addition of a solvent could avoid the high working temperature while the homogeneity is ensured. Among the terpene oils, limonene outlines as a good candidate to carry out the dissolution of polystyrene because it respects the green chemistry principle, it is highly soluble in CO₂ and very compatible with the polymer.The sorption of CO₂ is the first step of the foaming process. The presence of the terpene oil enhances the solubility of the gas which is solubilized in the Polystyrene as well as in the limonene. During the foaming process, many parameters can be tuned to customize the foams. In this work, a fractional factorial design of experiment was proposed to determine the effect of pressure, temperature, concentration of the solution, contact time and vent time over the diameter of cells, its standard deviation and the cells density. The proposed foaming process can be simply performed at mild pressure and temperature thanks to the presence of the solvent. The results showed that the most suitable conditions to foam polystyrene from limonene solutions are 90 bar, 30 °C, 0.1 gPS/ml Lim, 240 min contacting and 30 min venting. Finally, the samples were characterized to determine the amount of residual solvent, their glass transition and degradation temperature checking that the foams presented around 5% of solvent traces but did not show any evidence of degradation.     

Preparation of carbon foams by thermo-foaming of activated carbon powder dispersions in an aqueous sucrose resin

Thermo-foaming of activated carbon (AC) powder dispersions in an aqueous sucrose resin followed by carbonization has been studied to prepare carbon foams. The dispersions were characterized by viscosity measurements and sedimentation studies. The OH to OH condensation reactions, leading to the cross-linking of the sucrose polymer, were retarded by the AC powder. The AC particles adsorbed on the gas–liquid interface stabilized the gas bubbles that resulted in foaming of the poorly cross-linked sucrose polymer resin having low viscosity. The carbon produced by the carbonization of the sucrose polymer binds the AC particles as in reaction bonding. The carbon foams have an interconnected cellular structure. Density (0.138–0.22 g/cc), cell size (0.62–3 mm) and compressive strength (0.42–3.4 MPa) of the carbon foams depends on the AC powder to sucrose weight ratio. Incorporation of the AC powder in the sucrose resin decreases the carbonization shrinkage that enables the preparation of large carbon foam bodies without warping. The carbon foam prepared at an AC powder to sucrose weight ratio of 0.1 shows the highest density and compressive strength and the lowest cell size.     

Synthesis and characterization of a nanofiltration carbon membrane derived from phenol–formaldehyde resin

We have synthesized carbon membranes by carbonizing a phenol–formaldehyde (PF) resin in the absence of air, and evaluated their physical properties and separation performance. Carbonization of the PF resin at 500 °C for 30 min resulted in around 20% mass reduction and produced a membrane material which exhibited a moderate BET surface area of 29.6 m²/g, with the majority of its porous structure confined to pores <15 nm. As observed by visible Raman spectroscopy, the carbon membrane seems to consist of a crystalline structure imbedded in an amorphous carbon matrix. The average grain size was found to be around 9.18 nm, which matches closely the results of Raman studies. The crystal structure is based on a hexagonal structure with a=7.8072 Å and c=7.066 Å with the latter length matching that of graphite. The difference in the former parameter was attributed to a motif consisting of a seven-membered plane benzene ring (one ring surrounded by six others) due to internal strain which was determined to be 3.22% by an XRD technique. The molecular weight cut-off (MWCO) of this membrane was found to be about 7500 Daltons. The performance of the membrane was studied by separating hexavalent chromium ions from an aqueous chromic acid solution. The apparent and intrinsic rejection of Cr⁶⁺ ions was of the order of 70 and 90%, respectively, and was found to increase with an increase in applied pressure.