Granulometric Distribution Research Articles

Preparation and characterization of cordierite powders

The current paper presents different preparation methods for cordierite ceramic powders: solid state reactions and wet preparation. In the solid state method, γ-Al 2O 3, SiO 2 and Mg(CO 3) 2 were used as raw materials. For wet preparation, the following compounds were used as precursors: silica gel, AlCl 3·6H 2O and Mg(NO 3) 2·6H 2O. The powders obtained by the different methods employed were characterized in what concerns mineralogical composition and granulometric distribution. It was determined that the results are influenced by the nature of raw materials used and the processing conditions.

Selecting the structuring element for morphological texture classification

This paper deals with a concrete aspect of texture classification: the choice of a good structuring element (SE) when the texture features used for classification are obtained from morphological granulometries. First, a granulometry is defined from the morphological opening of the texture using a convex and compact subset containing the origin as SE. Then, some usual distributional descriptors (mean, variance, skewness and kurtosis) of the granulometric size distribution are used as texture features. The main point of the paper is the choice of a good SE from the point of view of texture classification. A methodology is explained and software has been developed that helps in such a choice, for any given criterion for the quality of the classification.

Siloxane surfactants in polymer nanoparticles formulation

AbstractCarbohydrate‐modified cyclosiloxanes were synthesized by hydrosilylation reactions of protected allyl‐monosaccharides and subsequent deprotection with a gel‐type ion exchanger. They were characterized by 1H and 13C‐NMR, FT‐IR, GPC and surface tension measurements. These compounds, as well as other water soluble, carboxylate‐based siloxanes were tested as stabilizers in nanoparticle formulations, with polydimethylsiloxane (PDMS), poly(ε‐caprolactone) (PCL) and UDEL polysulfone (PSF) as polymer cores. Owing to their low critical micelle concentrations (cmc), small amounts of surfactants were required. The particle size and granulometric distribution were measured by dynamic light scattering (DLS). Electron microscopy confirmed the DLS results and revealed aggregation phenomena in dry state, depending on the polymer core. In the tested conditions, the glass transition temperature of the polymer seems to be the driving force for the stability of dry nanoparticles. Copyright © 2006 John Wiley & Sons, Ltd.

Modelling of comminution processes in Spex Mixer/Mill

It is well known that mathematical models which simulate comminution processes represent a useful tool in several fields of academic and industrial research, with particular emphasis on nano-material and pharmaceutical production. In the present work a mathematical model which is able to quantitatively describe comminution processes in a ball milling system (i.e., Spex-Mixer/Mill) has been developed. The proposed approach takes into account three different contributions: dynamics of the vial, dynamics of spheres motion and simulation of the comminution process. The vial dynamics has been modelled by taking advantage of an appropriate roto-translation matrix. Model results have been successfully compared with literature experimental data. The spheres motion within the Spex Mixer/Mill has been simulated using a 3D dynamic model based on classical mechanics as well as the so-called discrete element method, which is widely adopted to quantitatively describe multi-body collision behaviour. In particular, existing models of impact with dissipation as well as the classical Hertz impact theory have been taken into account. This part of the global model allows one to obtain, for different operating conditions, the impact specific energy and impact velocity as a function of time. The latter ones represent input parameters for the simulation of comminution processes that is performed through suitable population balances, where different breakage functions as well as appropriate breakage probabilities have been considered. Model results are reported in terms of granulometric distribution of powders within the mixer-mill as a function of time, minimal grain size obtainable and time needed to complete the comminution process for various operating conditions (i.e., mill frequency and charge ratio).

The structure of the chromium coatings modified by the dispersed particles

The microhardness and structure of composite chromium coatings modified by dispersed CeO2 and ultradispersed diamond (UDD), as well as the granulometric UDD distribution (both in the coatings and the bath) were investigated. The presence of the particles in the coatings reduced the number of microcracks and enhanced the microhardness. Passing from the chromium to the composite coatings makes the microhardness measured on the microsections and the specimen surface converge. Despite the uniform distribution of the particles in the coatings, nonuniform distribution of their sizes is satisfactorily described by a lognormal distribution function. A selective deposition of nano-size particles (with the most probable radius of UDD particles of 204 nm) was found out, although dynamic aggregates found in the solution have the most probable radius of 4530 nm. This is possibly associated with their disaggregation near the electrode and the inclusion of the finer particles into the coating.

Study on Fractal Characteristics and Performance of Ultrafine Slag Grains

Ultrafine slag, which is ground with the process of vertical mill, is tested with the laser granulometric distribution apparatus quickly. The characteristics of granulometric distribution of ultrafine slag are analyzed using fractal theory. The fractal dimension of different fineness powders is tested and counted. The result shows that ultrafine slag powders have self-similar characteristics. With the laser granulometric distribution apparatus, the fractal dimension of its powders might be tested and counted with the fractal theory and its characteristics might be fast evaluated. The inherent law between powders fineness and activity is studied, and the mathematical model is built with the results. The fractal characteristics of powders might be used to meticulously evaluate fineness of ultrafine powders and be used to describe complexity of powders. The test of activation indicates that the slag fineness appraised by fractal dimension has fine linear relevant characteristic with its 7 d, 28 d activity.

Quantification and speciation of mercury in soils from the Tripuí Ecological Station, Minas Gerais, Brazil

Contents of total mercury, organic carbon, total sulfur, iron, aluminum and grain size and clay mineralogy were used along with Pearson's correlation and Hg thermal desorption technique to investigate the presence, distribution and binding behavior of Hg in soils from three depths from the Tripuí Ecological Station, located near Ouro Preto, Minas Gerais State, Brazil. The soils studied had predominantly medium and fine sand texture (0.59–0.062 mm), acid character and Hg contents ranging from 0.09 to 1.23 μg/g. The granulometric distribution revealed that Hg is associated with coarse sand (2–0.59 mm) and silt and clay (< 0.062 mm) and presents similar Hg concentrations in both fractions. Mercury distribution in soil profiles showed that Hg was homogeneously distributed throughout the depths at most sites. Hg thermal desorption curves show that mercury occurs not only as Hg 2+ predominantly bound to organic components in most of the samples, but also in the form of cinnabar in some. Pearson's correlation confirmed that mercury is associated with organic matter and sulfur and possibly with sulfur-bearing organic matter in most samples.

A method for the characterization of emulsions, thermogranulometry: Application to water-in-crude oil emulsion

Emulsions are used in a wide range of applications and industries. Their size distribution is an important parameter because it influences most of the emulsion properties of emulsions. Several techniques of characterization are used to determine the granulometric distribution of emulsions, but they are generally limited to dilute samples and are based on complex algorithms. We describe a method that allows characterization of the droplet size distribution of emulsions using thermal analysis (thermogranulometry). This method permits the use of very concentrated samples without any dilution or perturbation of the system. We first define our method by a thermodynamic and kinetic approach. We studied a real system, i.e., crude oil emulsions, which form very concentrated, viscous, and opaque emulsions with water. We present a correlation between the size of droplets and their freezing temperature, corresponding to our system. Then we compare the size distributions obtained by our method with those derived by direct microscopy observations. The results obtained show that thermogranulometry may be an interesting method of characterization of emulsions, even for concentrated systems.

Effect of biofiltration on particle characteristics and flocculation behavior

AbstractBiodegradable dissolved organic material and ammonia present problems for conventional water treatment processes and may contribute to biological instability in the treated water. One solution may be to use a biological process upstream of the regular water treatment process. Biofiltration may be cost‐effective in removing ammonia and the precursors of trihalomethanes but the characteristics of the biotreated effluent may affect to the subsequent coagulation process. A continuous flow biological filter packed with reticulated polyurethane foam markedly altered the particle size distribution and the charge density of the mixed liquor, shifting the granulometric distribution toward larger sizes. The mean and median diameter of the particles increased from 9.7 and 5.9 µm to 97.6 and 37.1 µm, respectively. The average charge density of the biofilter effluent (7.6 meq dm−3) was much lower than that of the raw water (12.7 meq dm−3). The optimum coagulant dosage for the subsequent coagulation was reduced substantially from 10 mg dm−3 to 1 mg dm−3 as Al due to the lowered charge density of the mixed liquor and the enhanced cation bridging of the extracellular polymers on the bioparticle surface. Copyright © 2005 Society of Chemical Industry

Clayey materials from the Sierra de la Demanda Range (Spain): their potential as raw materials for the building ceramics industry

AbstractThis work describes the possible use of thick Early Cretaceous clay deposits, which occur in the southern sector of the Sierra de la Demanda range, as raw materials in the manufacture of ceramic articles. The global mineralogical composition is characterized by high proportions of phyllosilicates and quartz with variable quantities of feldspars, carbonates and hematite. The clay mineralogy differentiates two types of raw materials: illitic clay and kaolinitic-illitic clay. A granulometric distribution in the 2–60 µm fraction, good behaviour during the drying stage and acceptable results in firing tests confirmed that most samples can be utilized as raw material in the building ceramics industry. The range of suitable firing temperatures for these materials is 950–1000°C, a temperature which needs to be raised for samples with a high percentage of kaolinite and quartz. Moreover, other materials with abundant calcite (20–30%) are suitable for use as modifiers of some properties or colour.

Ceramic suitability of a Moroccan triassic clays

The drying behaviour, plasticity and firing properties (water absorption, shrinkage and bending strength) of two clays, RA and RO from the East and West of the high atlas (Morocco) respectively, were evaluated and discussed in view of the granulometric distribution and mineralogical compositions. It is found that the almost identical drying shrinkages is linked to the similar granulometry, and the higher Atterberg limits for RA are associated to the presence of chlorite (11 wt.%). In addition, it is established that, in spite of their different mineralogical compositions, the sintering process for both clays is controlled by melt flow and consequently the bending strengths at the maximum firing temperatures (1000 and 1075 °C for RA and RO respectively) are similar (∼ 58 MPa). On the other hand, it is observed that RA sherds shrink more and absorb less water, likely because of the presence of chlorite which is considered as a highly fluxing compound. In all cases, the use of both clays for structural products manufacturing should be improved by the addition of fillers.

Speciation and quantification of mercury in Oxisol, Ultisol, and Spodosol from Amazon (Manaus, Brazil)

In order to investigate the content and distribution of Hg in soils from Amazon areas not impacted by gold mining activities, the concentration and granulometric distribution of Hg were determined in three different types of soils. Hg speciation data were obtained by a thermodesorption atomic spectrometry system and the role of physico-chemical and mineralogical characteristics on Hg content were also studied. Hg concentrations found in the soil fraction <2000 μm were similar to values found in other Amazon areas without anthropogenic sources. The fine fraction (<53 μm) of podzolized soils had a higher Hg content than clayey soils. Multivariate analysis shows that there are marking differences between Spodosols of two distinct areas (fine fraction Hg contents up to 10-fold as high) indicating the importance of pedogenic processes. All statistical data analysis indicated that organic matter plays an important role in Hg accumulation in the types of soils studied. Thermodesorption analysis revealed the presence of only Hg 2+, and the predominance of organically bound Hg in the majority of the studied samples.

Dissolved pollutant transport in tailings ponds

Water and dissolved ion transport in mineral tailings was studied at laboratory scale with three different tailings samples. Percolation rate, determined in column experiments, depends mainly on the granulometric distribution of the solid and varies between 3.0×10−4 cm/s for a tailings sample with coarser particles (d90>700 μm) to 4.0×10−5 cm/s for the tailings sample with higher content of fine particles (d90<200 μm). In stationary conditions, the ascending rate of water by capillarity through the solid bed is controlled by the evaporation rate at the top surface of the tailings. Rates between 2.6×10−5 cm/s (2.2 mm/day) and 8.1×10−5 cm/s (7.0 mm/day) have been obtained under forced evaporation at 40 °C. Ion transport in the percolation process is mainly controlled by the hydraulic diffusion of the solution through pores in the solid bed. In the capillarity process, ion transport is controlled by chemical diffusion of the dissolved ion in the ascending solution.

Polyvinyl Alcohol Particles versus Tris-acryl Gelatin Microspheres for Uterine Artery Embolization for Leiomyomas

THE method of uterine artery embolization (UAE) has been extensively described in the literature (1–5). In essence, it involves the placement of a catheter into the uterine arteries and injection of embolization particles into the uterine arteries to obtain infarction and shrinkage of leiomyomata. There are some differences in technique among operators, with some catheterizing the uterine arteries directly with 4-F or 5-F catheters (1–3) and other using microcatheters (4,5). When considering the choice of an embolization agent, the physical properties (eg, granulometric distribution, compressibility) and the method of delivery should be considered.

Conversion of rapid prototyping models into metallic tools by ceramic moulding - an indirect rapid tooling process

INEGI developed a process to convert models made by rapid prototyping or conventional techniques into metallic moulds. The main purpose is to rapidly obtain prototype tools by casting a metal into a ceramic mould produced by mixing in variable proportions, ceramic particles, a liquid binder and a catalyst added to start a sol-gel reaction. This liquid slurry is poured into the box containing the mould to be reproduced. After a short period of time the ceramic mixture acquires a rubber consistency. The pattern is removed from the ceramic mould, which is fired and sintered in order to generate an inert mould with the desired strength in which most alloys can be cast. The effect of ceramic materials (shape, granulometric distribution, chemical composition), sintering conditions (time and temperature) and casting conditions (mould preheating temperature and pouring temperature) were studied in order to obtain ceramic moulds and, subsequently, metallic moulds with tailored properties (accuracy reproduction of details, low roughness and high mechanical strength).

O uso de microondas para determinação de umidade de bauxita

Nesse trabalho, é apresentado um estudo de secagem de bauxitas por microondas, visando a determinar a influência da umidade inicial das amostras, a massa a ser secada e a granulometria das mesmas no processo de secagem. Para a determinação da influência da umidade inicial, foram utilizadas amostras com teor de umidade igual a 12,2 e 6,9%. A influência da massa e a granulometria foram determinadas com uma amostra, cujo teor inicial de umidade era igual a 13%. Através desses estudos, observou-se que os tempos ótimos de secagem por microondas das amostras de bauxita estudadas têm uma relação direta com a umidade inicial das mesmas. Observou-se que as variáveis, massa da amostra a ser secada e o tempo de secagem, são diretamente proporcionais, apresentando elevada correlação. Dessa forma, pode-se obter os tempos de secagem para cada amostra a ser secada, de acordo com a sua massa. Não foi observada relação entre o tempo de secagem e a granulometria da amostra.

Granulometric Characterization and Alteration during Composting of Industrial Cork Residue for Use as a Growing Medium

This work describes the granulometry of industrial cork residue (bark of Quercus suber L.) and its possible alteration during composting to eliminate the high content of phytotoxic substances. Because of the differences in density of the different-sized cork particles, expression of the granulometric distribution in relation to volume reflected the size distribution more accurately than its expression in relation to weight. As a consequence, predictions of the physical and hydrological behavior of the substrate, deduced from its granulometry, were more accurate when this was calculated in relation to volume. Objective parameters used for textural comparison, such as the geometric mean (dg) and standard deviation of particle size (σg), which were previously used in soils, were tested. These permit the estimation of small differences in the particle size of different lots or the granulometric alteration occurring during composting. With the same purpose, a new diagram of textures for the classification of granular substrates was also studied.

Trace metals in the aerosol of the Logoon of Venice

Measurements of metal concentrations in the aerosols were carried out to highlight the importance of this contribution to contamination of the lagoon of Venice. Aerosol samples were collected by high-volume impactors fitted with PM 10 size selective inlets. Particles with aerodynamic diameters<10 μm were classified into six size intervals with cutoff aerodynamic diameters of 72.3. 1.5, 0.95, 0.49 and <0.49 μm. Samples were collected at four stations selecting the wind speed and the direction to characterise aerosols derived from the principal contaminant sources of the Venice Lagoon. Aerosol samples were analysed by ICP-SF-MS to determine the concentration of Li, Pb, U, Cd, Al, V, Mn, Fe, Cu, Zn and Co. The preliminary results obtained show that the elements with clear anthropogenic origin (in particular V and Pb) had a higher concentration in the fine fraction of aerosol, while other elements such as Mn and Fe showed higher concentrations at all sites with a bimodal distribution due to the crustal origin of these elements. On the basis of granulometric distribution of metals for the four sampling sites we can hypothesize that long range transport of contaminants can significantly contribute to the pollution of the Lagoon of Venice.

Lead exposure in day care centres in the Caracas Valley - Venezuela

Lead has been used as an additive to improve the anti-knock quality of gasoline. However, the combustion of lead gasoline produces particles rich in this element. These kinds of particles impact the alveoli and move into the bloodstream, causing serious health problems. The objective of this study is to determine the granulometric distribution, mineralogy, and lead levels in samples such as settled dust and soil, as well as lead concentration in drinking water, in different day care centers located in the metropolitan area of Caracas, which have been previously studied and classified, according to the Total Suspended Particles (TSP) levels by the national environmental office, as high (80 μg m−3) and low (50 μg m−3) polluted areas. The chemical analysis was performed by atomic absorption spectroscopy and atomic emission spectroscopy-inductively coupled plasma. The mineralogy was determined using X-ray differentiation. Results show that all samples are enriched by small particles (<44 μm). Lead concentrations in day care centres located in areas of high vehicular density were higher than those in areas of low vehicular traffic. Lead concentration for drinking water samples was below the standard value reported by the Environmental Protection Agency (EPA) (15 μg Pb/l).

Influence of Fluid Distribution on the Ultrafiltration Performance of a Ceramic Flat Sheet Membrane

The limiting permeation flux and the cake resistance are determined during ultrafiltration experiments of a low concentrated suspension of glass microparticles at a plane ceramic membrane surface for three inlet and outlet configurations with different forms and cross sections. The limiting permeation flux values are analyzed in view of wall shear rates local values obtained in previous work.[1] The ratio of the inlet velocity to the mean tangential one appears to be a key parameter for understanding the performance of the ultrafiltration process. Indeed, a ratio value different from 1 leads to an increace of the limiting permeation flux and a decrease of the specific energy consumption. Furthermore, it seems that the limiting permeation flux value depends not only on the wall shear stress values, but also on the granulometric distribution of the deposit.