A method for rough estimation of the catalyst surface area in a fuel cell

A method for a rough estimation of the catalyst surface area in a fuel cell is developed. It is based on the deconvolution of experimental CO oxidation data by use of a mathematical model. The kinetic parameters of the model are determined by fitting the experimental curves. The experimental data are collected at different sweep rates (2–100 mV s⁻¹) and at different temperatures (room −60.0 °C). The model can predict the sweep rate dependence of the CO oxidation onset potential, the peak current, the peak potential and the peak broadness. The model is further used for the prediction of the baseline in the presence of CO and for calculation of the CO charge consumed up to half peak potential. It is obtained that the latter value is constant at different sweep rates and that the baseline deviates from linearity already at low sweep rates (2 mV s⁻¹), but not very significantly (2.0% in comparison to 8.8% at 100 mV s⁻¹, based on calculated CO charge). It is suggested that lower sweep rates should be used for experimental surface area determination.     

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.     

Determination of surface area/monolayer capacity or limiting micropore volume of carbons from binary and ternary mixtures

It is shown that one can predict the adsorption of binary and ternary mixtures in any percentage ratio from the adsorption of individual component gases by means of John's isotherm equation. The surface area of mesoporous materials or the limiting micropore volume of microporous materials from binary and ternary mixture adsorption isotherms is given. The relation given by Lewis et al. may be used to prove the validity of the above method and determine the contribution of each component of the mixture.     

HZSM-5沸石分子筛孔容与孔径的分子探针测定

对于ZSM-5沸石晶胞结构参数,目前只有静态的借助X光衍射法获得,本文着重用二甲苯的异构物等作分子探针,动态地估算了ZSM-5沸石分子筛的孔径和孔容,在实际应用中,更加具有实际意义。     

A method for measuring the titania surface area on mixed oxides of titania and silica

We have used temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA) of 2-propanol to characterize several silica, titania, and silica-supported titania samples. Upon evacuation, most of the 2-propanol desorbed intact from the silica samples. This is in contrast to the results on titania and on silica-supported titania, where a significant amount remained on the surface following evacuation, with a fraction of this reacting to propene and water. The coverages of 2-propanol are approximately proportional to the titania surface area, corresponding to between 2.4 and 6.1×10¹⁸ molecules/m² of titania, depending on the form of the titania. The results suggest that selective adsorption of 2-propanol may be useful for determining the surface area of titania in titania-silicates.     

Effect of alumina content on surface area and micropore distribution of porous glass prepared from borosilicate glass

The surface area and micropore distribution of porous glass prepared from borosilicate glass were controlled by the addition of alumina up to 8 wt%. The surface area increased with increased alumina content in the range from 0 to 3 wt%, but it suddenly decreased when the percent alumina exceeded 4 wt%. The mean pore diameter and micropore volume also decreased with increased alumina content. When nickel ion was supported into the porous glass, the surface area decreased to about one-half that of the original glass. Since the amount of nickel supported on the porous glass increased directly with surface area, the silanol group was considered to be uniformly distributed on the glass.     

A study on the thermo-pressing sewing method for prevention of allergen penetration through micropore fabric

Micropore fabrics have been proposed to reduce exposure to house dust mite allergens in the field of environmental management methods. However, there is not an adequate method for verifying allergen impermeability of these micropore fabrics yet. In this study a particle penetration device was developed to test the allergen barrier performance of micropore fabrics against house dust mite allergens. The weight reduction rate of each micropore fabric was measured using the particle penetration device. At the given pressure and 90 seconds, the weight reduction ratio reached 35.6% for 6550 fabric, 13.6% 6560 fabric and 6.8% for 6563 fabric compared to 99.9% of 6060 fabric. In addition, a thermos-pressing sewing method, in which the bonding thread and the stitching portion were pressed using a thermos-pressing device, was proposed. The fabric made by the thermo-pressing sewing method effectively prevented particle penetration compared with the fabric made by the general sewing process.     

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.     

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。     

Use of n-nonane pre-adsorption for the determination of micropore volume of activated carbon aerogels

When the α_s or t methods and the DR (Dubinin-Radushkevich) or DA (Dubinin-Astakhov) Equations are used to analyse nitrogen adsorption isotherms determined at 77 K on activated carbon aerogels it is found that, in contrast to the behaviour generally found with other carbon materials, the α_s or t estimate of micropore volume is significantly less than the DR or DA estimate. In this paper the reasons for the overestimation of the DA micropore volume and underestimation of the α_s micropore volume are explained and it is shown how use of the n-nonane pre-adsorption method enables consistent values of micropore volume to be obtained.     

Ethylene glycol retention method for estimating specific surface area of adsorbent carbons

Ethylene glycol retention method, standardised by Dyal and Hendricks for clays and soils, has been used for determining specific surface areas of a large variety of adsorbent carbons differing widely in the extent as well as chemical nature of their surfaces. The proposed method yields values comparable with those obtained by the gaseous adsorption methods, irrespective of the oxygen contents of the carbons. A small amount of oxygen, probably within 0.2%, is essential to bring about proper wetting of the carbon by glycol.     

A simple estimation method for effective adaptation coefficient

A method was proposed in a previous article (CRA, 22, 240–258, 1997) to estimate the state of incomplete adaptation by using the effective chromatic adaptation coefficient α_min. The method could be applied to any experiment on chromatic adaptation using object-color or luminous-color stimuli, but its computational procedure was rather tedious. For this reason, the two simple methods, Methods I and II, are proposed to give the approximate estimates of α_min. Method I uses the corresponding reference color under reference illuminant to a test achromatic color under test illuminant. Method II uses the two kinds of relation equations between test adapting luminance and α_min. The estimates of α_min by each of the two methods agree fairly well with those given in the previous article to the three experiments studied. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 259–268, 1997     

A convenient method for the rapid estimation of carotene in butterfat

Summary A simple method is described for determining the carotene content of butterfat under conditions where extreme accuracy is not required. A direct comparison is made of the color of the melted fat with that of known concentrations of potassium dichromate solution. Since there is no loss of fat from dilution or in transferring from one container to another, the method is adaptable to small samples that later can be used for the determination of the usual fat-constants. The dichromate solutions are prepared by dilution of measured amounts of a 0.2 per cent stock solution to a volume of 25 ml. These dilute solutions and the fat samples are contained in cylindrical sample bottles of uniform diameters and their color matched with the aid of a comparator block placed before a “day-light” lamp.     

A new colorimetric method for estimation of argemone oil

Argemone oil is toxic even in low concentrations for human consumption. The author suggests a new colorimetric method in which an orange color is developed when antimony trichloride solution is added to the extracted alkaloid. The developed color is measured in a colorimeter and compared against known standards of the alkaloid. The alkaloid content of argemone oil has been found to be about 1.0%. This method determines an admixture of argemone oil as low as 0.005% in other edible oils.     

Preparation of ultrafine calcium carbonate particles with micropore dispersion method

Ultrafine particles of CaCO₃ were synthesized by dispersing the mixture of CO₂ and N₂ into the Ca(OH)₂/H₂O slurry with a micropore-plate. Because the micropore is micrometers scale, process of momentum transfer, mass transfer and reaction was significantly enhanced. The carbonation process of Ca(OH)₂/H₂O system was monitored with pH and conductivity. Operation conditions were investigated on the specific surface area of particles, such as initial slurry concentration and volume, gas flowrate and concentration, and temperature. The crystal structure of particles was characterized with BET, IR, TEM, SEM, etc. Results showed ultrafine particles were calcite with general shape of cube, whose size was about 40 nm and specific surface area was more than 25 m²/g. This preparation method is easy to operate.     

A new estimation method for the degree of graphitization for random layer lattices

The so-called P₁ structural parameter is well-known as an index for estimating the degree of graphitization, which was proposed by Houska and Warren. The parameter denotes the probability of finding a graphitic stacking relation between the adjacent carbon layer planes and was generally estimated by an inverse Fourier transform based on their theory. However, in their method, the Fourier integration range is too narrow to evaluate the Fourier coefficients precisely and to discuss in detail the P₁ values obtained from them. In the present study, a newly developed estimation method for the degree of graphitization with higher accuracy using the least square refinement method was presented and the obtained results were compared with those obtained using the conventional inverse Fourier method. The developed program for the analysis will be released in near future.     

Influence of the surface area/volume ratio on the chemistry of carbon deposition from methane

The chemistry of carbon deposition from methane as a function of methane pressure was studied at a temperature of 1100 °C and surface area/volume ratios of 0.8 and 3.2 mm⁻¹ by analysis of both gaseous and condensing, i.e. aromatic reaction products. Conversion of methane as well as the yields of the hydrocarbons formed increase with increasing pressure. The surface area/volume ratio has a significant influence on the formation of aromatic hydrocarbons showing much higher yields at the lower ratio. This result, expected from preceding studies of deposition rates, confirms that a change of this ratio leads to a change of the deposition chemistry of carbon.     

Preparation of carbon adsorbents with high surface area and a model for calculating surface area

Carbon adsorbents (CAs) were made by heat treatment of a mixture of coal char and KOH under the protection of an inert argon flow and the influence of operating conditions on the properties of adsorbents was investigated. Changes in the characteristics of graphitic crystallites during manufacture by X-ray diffraction (XRD) analysis indicated that disappearance of the peak corresponding to 002 faces correlated to high specific surface area. Based on the experimental results, a new model of graphitic crystallites containing hydrogen atoms is proposed to calculate idealized surface area of CAs. With this model, the idealized surface areas of CA can be precisely calculated with the aid of X-ray diffraction. In this way, some experimental problems can be overcome, such as the difficulty to measure specific surface area with N₂ adsorption when pore diameters are too small and overestimation when surface areas are too large.