Specific Surface Measurements Research Articles

Physico-chemistry of coal combustion under blast furnace tuyere conditions

Replacement of metallurgical coke by pulverized coal injected in blast furnace tuyere is a major economical challenge, due to the high price of coke. Combustion conditions of the coal in this system are quite different compared to usual combustors: high temperature (1200°–2000°C), short residence time in presence of oxygen (less than 30 ms), followed by gasification in the presence of CO 2. Within the frame of a collaboration IRSID-CNRS, a series of experiments have been conducted to reproduce at laboratory scale industrial conditions. These experiments included: • — The study of devolatilization and initial combustion of coal at a high heating rate, using a drop tube furnace, with probes to quench and collect resulting chars, • — Char characterization by scanning electron microscopy and specific surface measurements, • — Char reactivity vs CO 2 in a thermobalance. Gasification rates during these processes were measured and related to char characteristics.

Experimental aspects of mercury intrusion porosimetry : Winslow, D N Trans Res RecN1089, 1986, P92–96

Several frequently ignored aspects of mercury intrusion porosimetry are discussed. The importance of knowing the correct contact angle between the mercury and the solid is emphasized. It is also suggested that mercury intrusion be considered in some instances when a specific surface measurement is desired. Also, a method for handling inhomogeneous samples is discussed. Finally, a possibly instructive use for the hysteresis found on depressurization is explored.

Physicochemical characterization of asbestos and attapulgite mineral fibers before and after treatment with phosphorus oxychloride

Among the hydrous silicates belonging to the serpentine, amphibole, and clay mineral families, chrysotile, crocidolite and attapulgite fibers reacted most strongly with phosphorus oxychloride. While the reactivity of crocidolite was linked mainly to the sodium cations of its structure, the reactivities of chrysotile and attapulgite correlated best with their high hydroxyl group content. The TG/DTG curves of chrysotile and attapulgite revealed significant modifications of their dehydroxylation profiles. IR spectra and specific surface measurements confirmed that, most probably, the phosphorylation process created: (a) a phosphorus coating at the surface of the chrysotile fibers, and (b) an obstruction of the pores by phosphorus compounds with the attapulgite fibers.

The Dynamic Behavior of the Electrical Conductivity of CAD-PbSe Films

PbSe films prepared by chemical “anorganic” deposition (CAD) are investigated. The electrical resistivity (R) and the thermoelectric power (tep) are measured in a thermal dynamic regime which disturbs the equilibrium of the PbSe-oxygen system. A comparison with the behavior of PbSe films prepared by the usual chemical “organic” deposition (COD) and vacuum evaporation (VE) procedures is made. Peaks in the electrical resistivity around 170 °C (for some COD and the CAD films) and around 225 °C (for some COD and the VE films) are found, due to the super-position of the oxygen desorption process on the normal R-T dependence. The change in the sign of tep occurs before the peak in resistivity appears. These effects are discussed in terms of the “double layer” model. Based on the results from thermogravimetric and specific surface measure-ments and on oxygen isotherms for the powdered COD and CAD materials, the influence of the surface and of the bulk diffusion on the electrical properties is analysed.

Influence of Citric and Tannic Acids on Hydroxy-Al Interlayering in Montmorillonite

AbstractThe formation of hydroxy-Al-interlayered montmorillonite was affected by complexing organic acids. Montmorillonite (<2.0 μm) was aged for three months at an initial pH of 5.0 or 6.0 in AlCl3 solutions containing citric or tannic acid at organic acid/Al molar ratios from 0 to 1.0. The Al/clay ratio in the system was 900 meq Al3+/100 g of montmorillonite. Ion-exchange experiments revealed that organically complexed Al ions have both positive and negative charges. Evidence from X-ray powder diffraction, electron microscopic examination, measurements of specific surface, cation-exchange capacity, organic carbon, and the nature of sorbed Al indicates that citric and tannic acids influence differently the hydroxy-Al interlayer formation in montmorillonite. Hydroxy-Al-citrate can be adsorbed as interlayers in montmorillonite, but hydroxy-Al-tannate exists principally as a separate phase binding the clay particles. The differences observed between the influence of citric and tannic acids on Al interlayering are probably due to their differences in molecular weight (size) and structure.

Thermolysis of potassium tetraperoxochromate(V). I. Isothermal conditions

The thermolysis of K 3CrO 8 is characterized by autocatalytic-kinetics and the mean values of effective Arrhenius parameters are E = 69 ± 12 kJ mol −1, log A = 7 ± 2 s −1. Mass spectrometer, microscopic, X-ray diffraction and particularly ESR-sprectroscopic studies, as well as specific surface measurements, have led to the conclusion that K 3CrO 8 thermolysis is characterized by nuclei multiplication through the entire crystal bulk. Defects in the crystal volume appearing in the induction period of thermolysis or in γ-irradiated K 3CrO 8 make the most important contribution to nucleation. K 3CrO 8 is found to be promising as a model object in topochemistry.

Effect of granulation of soil samples and minerals on measurements of specific surface by nitrogen adsorption

Measurements were made of nitrogen adsorption by a few soil samples and minerals to compare the effects of having specimens in loose or in granular form. Specific surface remains the same whether samples were loose or had been compacted at pressures up to 1 ton cm −2 and then broken into small lumps or granules. The compacted specimens were found to be less subject to disturbance by outward spurts of materials as gases were being removed (outgassing) prior to nitrogen adsorption. Moreover, the standard deviation for measurements on the compacted specimens was smaller than that on loose specimens.

Choice of adsorbate pressure in a gas mixture for specific surface measurements

Choice of adsorbate pressure in a gas mixture for specific surface measurements

Is there a "citrate-apatite" in biological calcified systems?

An apatite containing citrate ions has been synthesized. Measurements of specific surface, as well as Ca/P ratio, infrared, X-ray, and calcination data are all consistent with the idea that citrate ion substitutes for PO4(3-) ion on the apatitic surface.

製紙用麻類の構造 ＩＩＩ こう解による非木材繊維の繊維形態およびシートの変化

Fibres of flax waste and kenaf bark were studied on their morphological changes during pulping and beating by means of scanning electron microscopy and specific surface measurement. Following results were obtained.1) Flax fibres were frozen smashed in liquid nitrogen and gently delignified with chloriteacetic acid solutions. Thus middle lamellae and the primary walls were removed and disappeared, then the secondary walls with fibrils of about 10° inclined S helics were exposed. These fibrils were split into fibril bundles of one to several μm width parallel to the fibrilar angle. Moreover, the secondary walls were delaminated easily to separate.2) Kenaf fibres, which were treated as flax fibres, exposed the secondary walls with fibrils of Z helics of about 10°. However, no fibril bundle was observed. This can be considered that a cohesion force between fibrils of kenaf fibres is stronger than that of flax fibres.3) At the same freeness level, specific surface area of handsheet from flax fibres was larger than that of kenaf. This is because flax fibre is more subjected to the external fibrillation, so fibril bundles and fibrils are easily separated from a parent fibre to form a closed sheet structure.On the other hand, kenaf fibres are least changed macroscopically during pulping and beating, so fibres are the main geometrical component of the sheet strcture.

A chromatographic method for specific surface measurements on powders

1. An apparatus and a procedure based on thermal nitrogen desorption have been developed for the determination of the specific surfaces of powders, enabling the lime of a single measurement to be reduced to 30 min. 2. The apparatus and procedure can be recommended for adoption in routine specific surface measurements on metal powders in industrial powder metallurgy processes.

Estimation of Components of Soil Cation Exchange Capacity from Measurements of Specific Surface and Organic Matter

AbstractCation exchange capacities of Irish soils developed from a wide range of parent materials were found to be highly correlated with organic matter content and specific surface but not with clay content. Multiple regression analysis showed that organic matter in combination with specific surface accounted for 97% of the variation in CEC whereas organic matter and clay content only accounted for 58% of the variation. The better correlation between CEC and specific surface than between CEC and clay content, is attributed to the ability of surface area measurements to reflect the presence of phyllosilicates in silt and sand fractions of soils and to the fact that these minerals have less variable surface charge densities than cation exchange capacities. It is proposed that specific surface provides a better estimate than clay content, of the mineral component of CEC for soils of varying mineralogy.

Determination of clay contents in soils containing allophane

Abstract The clay contents of soils containing allophane were derived by separating clay fractions at the appropriately value and correcting the amount of clay so indicated by means of specific surface measurements ts on the clay and residual silt plus sand fractions, as: described in a previous indication. Where the soil appeared to be derived from fairly homogeneous parent material, clay contents of topsoils and subsoils as given by this procedure were very similar, but coarse-iextured soils low in clay and high in organic matter showed somewhat more clay in the topsoils. Measurement of specific surface by absorption of acetic acid from toluene solution led to values of clay content that were similar to those obtained when specific surfaces were measured by adsorption of nitrogen if the topsoils were d medium to high clay content. For these topsoils the relationship of clay fraction constituents to pH for optimum dispersion was the same as for subsoils, but topsoils low in clay and high in organic matte...

Measurement of specific surface of colorants in cellulose

AbstractA new method is described whereby the specific surface of colorants, i.e. pigments or insoluble or water‐soluble dyes, in cellulose can be measured. The principle of the method is the selective adsorption of p‐nitrophenol (PNP) from water by the colorant particles but not by the cellulose, thus permitting determination of the surface of the particles and the effect thereon of various treatments.Results with organic pigments in spun‐dyed viscose rayon agree with calculations of specific surface from particle‐size analysis of the pigments before incorporation. This shows that the whole surface of the colorants in the cellulose is accessible to PNP and thus measurements can be made with a variety of dyes.Azoic dyes and vat dyes give results that correspond to average particle diameters of ∼ 0.1–0.6 μm and the method detects the increase in their particle size on soaping.A direct cotton dye of low light fastness and a reactive dye give specific surface values much too low for a monolayer and they appear to exist as multilayers in cellulose. A direct cotton dye of high light fastness appears to be present as three‐dimensional aggregates of diameter ∼ 0.08 μm, in agreement with published electron micrograph values for similar dyes.

Critical concentrations of polymers in solutions according to measurements of the viscosity and specific surface area of aerogels resulting after sublimation of the solvent

Critical concentrations of polystyrene and cyclolinear polyphenylsiloxane solutions corresponding to rising of structural networks have been determined by viscosity measurements and by measurements of specific surface of aerogels obtained by solvent sublimation. Theoretical and experimental values of critical concentrations coincide. Conditions for preparation of aerogels with developed surface by sublimation drying have been determined. Dependence of aerogel specific surface on polymer concentration in solutions shows distinct maximum at critical concentration found by viscosimetric method.

411. Measurement of specific surface and pore size distribution using a microbalance

411. Measurement of specific surface and pore size distribution using a microbalance

Emanation method for estimating reactivity of ferric oxides prepared from different sources

AbstractA method for estimating the reactivity of ferric oxide in solid state reaction processes is proposed. The temperature of the emanation curve maximum is taken as a characteristic parameter for the testing of the reactivity.The reactivity of ferric oxides prepared from ferrous sulphate, Mohr's salt (ferrous ammonium sulphate), ferrous oxalate and basic carbonate of iron by decomposition at 700°, 900° and 1100° has been studied. The results of the proposed method are compared with those of specific surface and catalytic activity measurements. The method is more objective and representative of the compound's ability to react with other solids.

Use of p‐nitrophenol for specific surface measurement of granular solids and fibres

AbstractEarlier work describing the use of p‐nitrophenol (PNP) in measuring specific surface of finely divided solids is supplemented here by a description of recent investigations which enable the usefulness of the method to be more clearly defined. Normally PNP is used in aqueous solution, but for some materials liable to dissolve in, swell in, or react chemically with, water, e.g. sugar, certain inorganic oxides and textile fibres, an organic solvent is used. The method is suitable for a wide variety of solids, both non‐porous and porous, provided they either form a hydrogen bond with PNP or have aromatic nuclei. Thus, with appropriate solvents, oxides, textile fibres with polar molecules and carbons can be used, but not, for example barium sulphate. With porous solids the results may or may not reveal a lower accessible surface than the area measured by nitrogen, depending on the pore size distribution. With porous solids the method enables a rapid estimate of the relative proportion of small and large pores to be made. Also, it can be used to measure the external specific surface only, as distinct from the total surface of some porous granular solids and fibres. Normally PNP appears to be adsorbed flatwise from water or organic solvents with an effective molecular area of 52.5 Å2. (An earlier value for this area given for special cases of adsorption from non‐aqueous solutions is now shown to be invalid). In some cases on polar inorganic solids it is adsorbed end‐on with an effective area of 25 Å2. The mode of adsorption is indicated by the type of isotherm.

Gas permeability apparatus for teaching purposes

The advantages of using an apparatus of the basic Lea and Nurse type to develop an appreciation of fundamentals of specific surface measurement are discussed. Some limitations of permeability measurements are easily demonstrated with the apparatus.

On the Specific Surface Measurement of Various Powders by the Blaine Air Permeability Apparatus

On the Specific Surface Measurement of Various Powders by the Blaine Air Permeability Apparatus