Determination of the specific surface by measurement of permeability

The determination of the specific surface of porous solids and packed powders from measurements of gas and liquid permeability is described. The theoretical background is outlined, and suitable experimental techniques are discussed, involving both constant and variable gas pressures.

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Résumé On décrit la détermination de la surface spécifique des poudres comprimées d’après des mesures de perméabilité des gaz et des liquides. On examine l’équation de Kozeny-Carman et ses applications. On décrit les techniques expérimentales appropriées, comprenant les méthodes à pression constante (Lea et Nurse, Rigden) et les méthodes à pression variable (Blaine). On souligne l’importance de ces mesures pour les essais de matériaux et l’on cite les normes nationales correspondantes.

     

Determination of the specific surface by adsorption from solution

The determination of the specific surface from measurement of adsorption of dyes and of phenol from aqueous solution, and of fatty acids from non-aqueous solution, is described. Experimental methods are outlined, and results obtained for a wide range of solids which are compared with values determined by electron microscopy and by nitrogen adsorption.

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Résumé On décrit la détermination de la surface spécifique par mesure de l’adsorption de colorants et de phénol en solution aqueuse et d’acides gras en solution dans des solvants. L’adsorption des colorants et des acides gras est généralement monomoléculaire. L’analyse des isothermes se fait par la méthode de Langmuir. On constate néanmoins une adsorption multimoléculaire du phénol, et les isothermes sont alors étudiés conformément à l’équation de Brunauer-Emmett-Teller. On présente brièvement les méthodes expérimentales et les résultats obtenus pour une large gamme de solides, lesquels sont comparés aux valeurs déterminées par microscopie électronique et par adsorption d’azote.

     

BET法间接测定石粉颗粒的圆度

为了定量描述石粉颗粒的圆度,本文中提出一种采用BET法间接测定石粉颗粒圆度的新方法,介绍了其原理和测定方法。实例表明,石粉颗粒表面的分维数间接地刻画了其圆度,此法可以定量描述磷渣、水泥、硅粉等粉末颗粒的圆度。     

多孔金属比表面积的计算方法

提出了一种根据泡沫金属的孔率和孔径这两个基本参量计算其比表面积的方法.利用泡沫金属比表面积与孔率和孔径的对应数理关系,结合有关实验数据,成功地计算出了电沉积法和高压渗流铸造法制备的泡沫金属的比表面积.     

Determination of surface deviations of plane workpieces by the “moving over” method

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 16–17, December, 1990.     

Determination of nonstationary surface distortions of an axisymmetrically heated half-space by the Green's function method

The nonstationary normal displacements and the surface temperature of an elastic half-space heated in a circular region by a constant-power heat flux are evaluated.L'vov State University, the Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 5, pp. 627–633, May, 1994.     

A discrete-geometrical method of measuring the specific surface of powders of superhard materials

A new method of measuring the external specific surface of powers of superhard materials, based on 3D-modeling methodology using the mathematical apparatus of affine space mapping, is described. The results of a test of the method on DSTU 3292-95 standard ground and micropowders of synthetic diamond are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 59–64, January, 2008.     

物理吸附分析仪单点BET方法误差分析

BET理论为测量材料比表面积提供了极其有用的方法。在实际操作中，为减轻实验工作量，减少测量成本以及快速得到测量结果，多采用单点BET方法。单点BET方法与多点BET方法相比较，其相对误差大小不仅取决于被测材料本身的特性（c值），而且与单点法所选择的相对压力值大小有关。研究发现，采用单点BET方法测量比表面积时，在0．05〈p/p^0〈0．35范围内单点法与多点法相对误差有一极小值，而这一极小值所对应的相对压力值大小随材料而异。无孔材料在0．25左右，中孔分子筛为0．20，普通活性炭及中微孔分子筛0．3，微孔活性炭为0．35。按照这一原则选择单点法的相对压力值，可使单点法与多点法的相对误差小于1％。     

石墨纤维的比表面积与孔隙结构的测定与分析

为了定量地描述和分析石墨纤维的比表面积和孔隙结构,采用低温氮吸附法测定石墨纤维在液氮温度和不同压力条件下的氮气吸附-脱附等温曲线.研究表明石墨纤维属于微孔材料,含有大量的微孔和极少量的介孔;石墨纤维的BET比表面积、总孔体积和平均孔径分别为541.00m2/g、0.2436cm3/g、1.8010nm,其微孔的比表面积...     

Extrapolation-analytical method for determination of outer specific surface of powders of superhard materials

A new method is put forward for calculating the outer specific surface of powders of superhard materials. It is based on 3D modeling and involves a mathematical apparatus of affine space mapping. Input data include the grain height as well as the surface area, perimeter, maximum and minimum diameters of the grain projection. The paper provides the results of testing the proposed method on standard synthetic diamond grits and micron powders (as per Ukrainian Standard DSTU 3292-95). The authors offer some recommendations as to practical application of this method.     

Determination of stresses by the Barkhausen effect method

Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Leningrad. Translated from Problemy Prochnosti, No. 2, pp. 17–20, February, 1989.     

Determination of principal stresses by the Barkhausen-effect method

The results of measurement of the root-mean-square voltage of Barkhausen noise (BN) and the amplitudes of the first three harmonics of the BN-voltage envelopes of flat cross-shape steel St. 3 and steel 20 specimens in biaxial tension are presented. The possibilities of determining the principal stresses by the magnetic-noise method using curves of constant BN parameters in the plane of the principal stresses are demonstrated.Translated from Problemy Prochnosti, No. 11, pp. 87–90, November, 1990.     

Determination of the thermophysical characteristics by the self-oscillation method

A method is proposed for measuring the thermophysical characteristics by means of the self-oscillation frequency and the gain coefficient of the automatic regulation system containing the specimen under investigation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 2, pp. 255–260, February, 1987.     

Micro structuration of gaas surface by wet etching: towards a specific surface behavior

Resonant microelectromechanical systems are promising devices for real time and highly sensitive measurements. The sensitivity of such sensors to additional mass loadings which can be increased thanks to the miniaturisation of devices is of prime importance for biological applications. The miniaturisation of structures passes through a photolithographic process and wet chemical etching. So, this paper presents new results on the anisotropic chemical etching of the gallium arsenide (GaAs) crystal used for this application, in several solutions. This paper focuses on the micro/nanostructuration of the sensing surface to increase the sensor sensitivity. Indeed, this active surface will be biofunctionalized to operate in biological liquid media in view of biomolecules detection. Several experimental conditions of etching bath composition, concentration and temperature were examined to obtain a large variety of geometrical surfaces topographies and roughness. According to the orientation dependence of the chemical etching process, the experiments were also performed on various GaAs crystal plates. The bath 1 H3PO4:9 H2O2:1 H2O appeared to be particularly adapted to the fabrication of the GaAs microstructured membrane: indeed, the bath is highly stable, anisotropic, and, as a function of temperature, it allows the production of a large variety of GaAs surface topographies.     

pH摆动-共沸蒸馏法制备高比表面大孔容介孔纳米氧化铝

以硫酸铝为铝源,氨水为沉淀剂,采用pH摆动法辅以共沸蒸馏处理制备γ-Al2O3前驱体,经550℃焙烧得到了γ-Al2O3.采用XRD、BET法、SEM、TEM等手段对γ-A12O3进行表征.pH摆动法在反应温度80℃,pH摆动3次,不需额外老化条件制备的γ-A12O3比表面积、平均孔径、孔容最大,样品无规则形貌;辅以共...     

Synthesis of nanocrystalline TiO2 with high photoactivity and large specific surface area by sol-gel method

Nano-TiO₂ powder was prepared by sol-gel method with modified precursor, tetrabutyl titanate (TBT), and photocatalytic oxidation was applied in removal of organics in the powder. The microstructure of as-prepared nano-TiO₂ was determined using UV-vis, TEM, XRD and BET. The results indicated that the nano-TiO₂, with grain size of 3.8 nm and specific surface area of 359.1 m²/g, was composed of anatase alone, and that it exhibited significant blue-shift in its UV-vis spectrum. The decomposition of organics in the sample was systematically investigated using FT-IR and TG-DTA. According to the testing results, we could conclude that organics in the samples were completely eliminated by means of photocatalytic oxidation. With photocatalytic decoloration of active brilliant red X-3B in aqueous solution as model reaction, the photocatalytic activity of as-prepared nano-TiO₂ was investigated and was compared with that of the samples experiencing heat treatment and Degussa P-25 as well. The experimental results indicated that the photoactivity of as-prepared nano-TiO₂ is much higher than that of the samples experiencing heat treatment.