比表面积简易测定法

简易干燥器乙醇法测定多孔物质比表面积。叙述了测定比表面积的原理，仪器装置，溶液的配制，乙醇分了截面积的推测和干燥器乙醇法测比表面积的实际操作。     

高比表面磁性有序介孔炭的合成及对亚甲基蓝的吸附性能

具有高比表面积、大孔容的铁磁性有序介孔炭(Fe/OMCs)对含染料废水的处理提供了一种简单有效的方法。采用苯酚树脂作炭源,三嵌段共聚物F127为模板剂,正硅酸乙酯为硅前驱体,硝酸铁为磁源,通过软模路线合成了Fe/OMCs。利用X射线衍射仪(XRD),氮气吸附仪,透射电镜(TEM)和综合物性测试仪研究了硝酸铁加入量对Fe/OMCs的相态、孔结构参数和磁性的影响;并以亚甲基蓝(MB)为染料探针分子,研究了Fe/OMCs对MB的吸附行为。结果表明材料有序性、比表面和孔容随着硝酸铁加入量的增加而降低,而饱和磁化强度明显增强。Fe/OMCs对MB有快速吸附能力,其行为符合Sips吸附方程。     

Capacitance limits of high surface area activated carbons for double layer capacitors

A large specific surface area (SSA) of carbon materials used for electrochemical double layer capacitors (EDLC) is the most important parameter leading to a large gravimetric capacitance (C_g). However, for a SSA determined with the differential functional theory (DFT) model above a value of 1200 m²/g the plot of C_g versus S_DFT exhibits a plateau. We suggest that this limitation of C_g can be ascribed to a space constriction for charge accommodation inside the pore walls. As a consequence, the use of extremely high surface area carbons for EDLCs may be unprofitable.     

Nitrogen BET surface area measurement as a fingerprint method for the estimation of pore volume in active carbons

A good correlation was found between apparent BET surface area and total pore volume determined for a number of active charcoals by measurement of the nitrogen adsorption isotherms at 77 K. A similar correlation is also illustrated in which apparent BET surface area is calculated from the uptake of nitrogen at relative pressure $\text{p}\text{p°}\text{= 0.1}$. This method is suggested as a rapid means of estimating pore volume in predominantly microporous carbons.     

Comparison of parameters calculated from the BET and Freundlich isotherms obtained by nitrogen adsorption on activated carbons: A new method for calculating the specific surface area

The empirical linear relationship between the BET surface area S_BET and the Freundlich constant K_F, calculated from nitrogen adsorption isotherms of activated carbons, S_BET = a₀K_F is mathematically demonstrated. This correlation exists in the relative pressure domain in which the BET equation is valid, whatever the value of c for the BET equation and for values of the Freundlich exponent, , between 0 and 0.2. This study allows to determine the correlation factor a₀ = 1/a with . From this result, a new expression, depending of and K_F, can be deduced for calculating the specific surface area.     

Rapid adsorption of alcohol biofuels by high surface area mesoporous carbons

Surfactant templated mesoporous carbons were evaluated as biofuel adsorbents through characterization of equilibrium and kinetic behavior for both ethanol and n-butanol. Variations in synthetic conditions enabled facile tuning of specific surface area (500-1300 m²/g) and pore morphology (hexagonally packed cylindrical or BCC spherical pores). n-Butanol was more effectively adsorbed than ethanol for all mesoporous carbons, suggesting a mechanism of hydrophobic adsorption. The adsorbed alcohol capacity increased with elevated specific surface area of the adsorbents, irrespective of pore morphology. While adsorption capacity of these mesoporous carbons is comparable to commercially-available, hydrophobic polymer adsorbents of similar surface area, the pore morphology and structure of mesoporous carbons greatly influenced adsorption rates, enhancing them by up to 1-2 orders of magnitude over commercial polymer adsorbents. Multiple cycles of adsorbent regeneration did not impact the adsorption equilibrium or kinetics. The high chemical and thermal stability of mesoporous carbons provide potential significant advantages over other commonly examined biofuel adsorbents, such as polymers and zeolites.     

A TEM-based method as an alternative to the BET method for measuring off-line the specific surface area of nanoaerosols

At the present time, no stabilised method exists allowing an estimation of the specific surface area for airborne nanostructured particles (nanoaerosols). Recent toxicological studies have, however, revealed biological effects linked to the surface area of these particles. Only the BET method, which can determine the specific mass surface area of a powder, constitutes a reference both in toxicology and in the materials domain. However, this technique is not applicable to nanostructured aerosols given the mass quantities of particles required (between approximately some mg to hundreds of mg taking into account the limit of quantification of existing BET instruments).To characterise the specific surface area of airborne nanostructured particles, a method based on analysing transmission electron microscopy (TEM) images is proposed. This has recourse in particular to previous work carried out in the area of nanoparticles originating from combustion (soot), and takes into account structural parameters of nanostructured particles including the number distribution of primary particles, their overlap coefficient and the fractal dimension of agglomerates and aggregates.The approach proposed in this work was applied to five commercially-available nanostructured powders of differing natures (SiO₂, ZrO₂, Al₂O₃, Fe₂O₃ and Fe₃O₄). This first involved their prior analysis by the BET method and then being placed in suspension in aerosol form using a vortex-type shaker system. The procedure to calculate the specific surface area using image analysis was then applied to the sampled aerosols and compared to the BET measurements. The experimental results obtained on the five nanostructured powders cover a range of specific surface areas from 20 to 200 m²/g, the primary particles having mean diameters varying from 7 to 47 nm. Close agreement was observed between the two approaches which, taking into account measurement uncertainties, are statistically equivalent at significance level α = 0.05.     

Systematic development of predictive molecular models of high surface area activated carbons for adsorption applications

Adsorption in porous materials is a promising technology for CO₂ capture and storage. Particularly important applications are adsorption separation of streams associated with the coal power plant operation, as well as natural gas sweetening. High surface area activated carbons are a promising family of materials for these applications, especially in the high pressure regimes. As the streams under consideration are generally multi-component mixtures, development and optimization of adsorption processes for their separation would substantially benefit from predictive simulation models. Here, we develop a molecular model of a high surface area carbon material based on a random packing of small fragments of a carbon sheet. In the construction of the model, we introduce a number of constraints, such as the value of the accessible surface area, concentration of the surface groups, and pore volume to bring the properties the model structure close to the reference porous material (Maxsorb carbon with the surface area in excess of 3000 m²/g). We use experimental data for CO₂ and methane adsorption to tune and validate the model. We demonstrate the accuracy and robustness of the model by predicting single component adsorption of CO₂, methane and other relevant components under a range of conditions.     

高比表面积介孔碳材料的混合模板法制备

以纳米氧化锌和氧化镁为混合模板剂,以氢氧化钾为活化剂,中温煤沥青为碳源,经热处理、酸洗、干燥制备出介孔碳材料。通过X射线衍射分析介孔碳材料制备过程中组分的变化情况,通过扫描电子显微镜观察介孔碳材料的表面形貌,通过氮气吸脱附等温线对所得的介孔碳材料进行表征。结果表明,随着温度的升高,由于体系内反应越来越剧烈,体系内呈现碎片状,因而所得的介孔碳材料比表面积逐渐增大;随着模板剂含量的增加,酸洗后的介孔碳材料由于孔的联结而使所得介孔碳材料的比表面积逐渐减小,平均孔径逐渐增大。所得介孔碳材料比表面积最大为2 509.76 m²/g。     

氮吸附法测定炭黑比表面积的方法研究

研究炭黑比表面积的测定方法。测定方法为:低温氮吸附法及统计厚度法。该方法样品用量小、速度快,结果准确。     

颗粒肥料比表面积快速测定法在控释肥料研制中的应用

推荐一种快速测定颗粒肥料比表面积的方法。首先用排体积法测定一定量的颗粒肥料所排开液体质量,再根据这种液体的密度计算其体积,然后假设肥料颗粒为球体,根据肥料体积及其百粒质量可以计算出单粒肥料的平均半径。最后按照球体表面积公式计算肥料的比表面积。这一比表面积的测定方法可以方便地应用于控释肥料研制过程计算包膜的厚度和膜材的用量。     

Correlation of methane uptake with microporosity and surface area of chemically activated carbons

Two series of activated carbon discs have been prepared by chemical activation of olive stones with ZnCl₂ and H₃PO₄. Some of the carbons have been post-treated in order to modify their porous texture and/or surface chemical composition. All carbons have been characterized by adsorption of N₂ (−196 °C) and CO₂ (0 °C) and immersion calorimetry into dichloromethane. The volume of methane adsorbed at 25 °C and 3.5 MPa is proportional to the surface area deduced from immersion calorimetry into dichloromethane. Consequently, it is possible to estimate, using a single experiment, the possibility of using activated carbons for the storage of natural gas. On the other hand, the methane uptake can be also correlated to the volume of micropores, provided by the adsorption of N₂ at −196 °C and CO₂ at 0 °C, although the correlations is not as good. Only carbons slightly activated, with low surface area and microporosity below around 0.6 nm, do not adjust the above correlations because they adsorb more methane than the expected, the effect of chemical nature of the carbon surface being almost negligible.     

Co-gelation synthesis of porous graphitic carbons with high surface area and their applications

An easy co-gelation route has been developed to synthesize porous graphitic carbons with high surface areas by using teraethylorthosilicate (TEOS), furfuryl alcohol (FA), and metal nitrates as precursors. Using a one-pot co-gelation process, a polyfurfuryl alcohol–silica interpenetrating framework with metal ions uniformly dispersed was formed during the polymerization of FA and the hydrolysis of TEOS within an ethanol solution of the three precursors. This synthesis process is simple and time-saving in comparison with the conventional preparation methods. During the heat treatment, Fe₇Co₃ alloy nanoparticles were produced by carbothermal reduction and they then catalyzed the graphitization of the amorphous carbon. The graphitic carbons obtained have a high crystallinity as shown by X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy analysis. The degree of graphitization can be controlled by the varying the loading amount of catalyst. The porous texture of the carbons combines miropores and bimodal mesopores, mainly originating from the silica template formed with different sizes and the loose packing of the graphite sheets. The carbons have large surface areas (up to 909 m²/g) and exhibit excellent electrochemical performance.     

Effect of surface acidity of activated carbons on their characteristics of adsorption from the vapour phase—comparison of retention time for carbons used as adsorbents for gas chromatography

Seventeen kinds of activated carbons of different surface acidity and of known pore-structure were used as adsorbents for gas chromatography. The retention time of various kinds of substrates was determined for each carbon at different temperatures. It was found that surface acidity of carbons has a marked effect on increasing the retention time for polar substances while showing no effect for non-polar substances. Retention times varied with temperature which suggested, when the effect of surface acidity is taken into account, that the pores which were effective for the Chromatographic adsorption have been determined by the temperature. The heat of adsorption calculated on the basis of the retention times observed at different temperatures showed an inverse correlation with dielectric constant of the adsorbates.     

Reliable specific surface area measurements on anhydrous cements

The specific surface area (SSA) of anhydrous cement has a direct impact on its reactivity and on the properties of fresh and hardened concrete. However, measuring this physical parameter is non-trivial.The choice of the degassing conditions (temperature, pressure and time) is essential for reliable SSA measurements by nitrogen adsorption because of the dehydration of the gypsum it contains. Such dehydration involves a significant increase of the SSA_BET, whereas Blaine test is poorly sensitive to the hydration state and structural modification of the calcium sulfate carrier. Because of this, SSA_BET values may be more variable than Blaine fineness. More consistent SSA_BET results could be obtained by degassing anhydrous cement samples at 40 °C under N₂ flow for 16 h, as at these conditions the cement composition is preserved.     

A fryer design with constant specific surface area

The specific surface area (surface area/volume) of a traditional frying vessel with a rectangular profile increases as the oil level decreases. In order to maintain a constant specific surface area of frying oil regardless of oil consumption, a special fryer was designed and constructed. The specific surface area of a frying vessel having a linear-inclined profile (Valentine batch fryer) deviated from a constant value by a maximum of 7.5%. The specific surface area of a frying vessel with an exponentially curved profile maintained a constant specific surface area even though the oil level varied.     

高比表面积羟基氧化铁的脱砷性能

利用羟基氧化铁的吸附特性可以有效脱除水体中的重金属,考察在不同条件下的脱砷效果。采用浆态床脱除法进行评价实验,主要考察废液砷含量、p H、温度、羟基氧化铁浓度和震荡时间等对脱砷率的影响。结果表明,废液砷含量和p H对脱砷率影响较小,时间、温度及羟基氧化铁浓度对脱砷率影响较大,羟基氧化铁浓度为影响脱砷效果的主要因素,整体来看,脱除率较高。在羟基氧化铁浓度为150 mg·m L-1、震荡时间1 h和温度50℃条件下,可将初始砷含量176.00 mg·L-1的废水降至砷含量为5.46 mg·L-1。     

Porosity and specific surface area of Roman cement pastes

Mercury porosimetry, water vapour and nitrogen adsorption were used to follow the hydration of Roman cements — belite cements calcined at low temperature. Generally, unimodal distribution of pore sizes was observed, with the threshold pore width decreasing considerably with increasing curing time. An open porous structure with the threshold pore diameter between 0.2 and 0.8 μm and the specific surface area not exceeding 20 m²/g was produced at early ages when quick growth of the C–A–H phases is observed. The surface area reached up to 120 m²/g and the threshold pore width shifted to around 0.02 μm when the subsequent formation of C–S–H gel filled the larger pores. Both mercury porosimetry and water vapour adsorption were found to be capable of following the progress of hydration of the Roman cements with high reliability at least for a comparative evaluation of historic Roman cement mortars and repair materials used in restoration projects.     

Correlation of the irreversible lithium capacity with the active surface area of modified carbons

Negative electrodes of lithium-ion batteries are generally based on graphite. Higher storage capacities can be obtained with disordered carbons, however they demonstrate a noticeable hysteresis and irreversibility, which can preclude a practical application. In this paper, the main parameters which may affect the irreversible capacity are analyzed and we show that the irreversible lithium consumption which occurs at the negative carbon electrode during the first charge (C_irr) is proportional to the active surface area (ASA). Composites with a reduced ASA have been obtained after coating a hard carbon or milled graphite samples with a thin film of pyrolytic carbon. Deactivating the surface by pyrolytic carbon deposition allows the irreversible capacity to be noticeably reduced, being lower than in graphite, while the reversible capacity is 50% higher than in graphite. The electrochemical properties of this new C/C composite are investigated by galvanostatic cycling at various current densities and by impedance spectroscopy. The main effect of the dense carbon coating is to hinder the diffusion of solvated lithium ions to the active sites of the carbon host during the first discharge, giving rise to a moderate development of the Solid Electrolyte Interphase (SEI).