Showing papers in "Applied Clay Science in 1993"

TL;DR: In this article, a model for Ni/Al mixed oxides obtained from HT anionic clays is proposed involving the formation of NiO and Ni-doped alumina phases, which strongly interact with a spinel-type phase present at their interface.

TL;DR: In this article, the behavior of a typical composition of low porosity ceramic tiles during firing was characterized before studying the mechanisms involved in sintering, and the main physico-chemical transformations were studied by evaluating changes in porosity, microstructure and mineralogical composition in samples fired at different temperatures.

TL;DR: In this paper, the nature and formation of minute sanidine crystals which appear in the sine of the glaze of some Hispano-Moresque pottery from a 14th century A.D. workshop at the Testar del Moli, in Paterna (Valencia, Spain), were studied by scanning electron microscopy.

TL;DR: In this paper, the polytypic structure of a purified pyrophyllite sample from Zalamea (Badajoz, Spain) and the structural alteration induced after dry grinding and leaching were studied by means of infrared spectroscopy, nitrogen adsorption, thermal analysis and by X-ray diffraction methods (reflection and transmission).

TL;DR: In this article, the sintering mechanism of low porosity tiles has been studied from variations in their porosity during firing, and samples pressed at different pressures and moisture contents have been tested to quantify the effect of initial porosity; the influence of the firing cycle was studied by isothermal experiments performed at different temperatures and firing times.

TL;DR: In this paper, the authors compared three methods, involving both in-diffusion and through diffusion techniques, for measuring the apparent diffusion coefficient, D, of I− and Cs+ in dense saturated bentonite.

TL;DR: In this paper, a method of preparing spherical kaolinite was developed, using the most straight-forward procedure, reducing handling and preparation time to a minimum, using amorphous aluminosilicate gels, prepared by cohydrolysis of tetraethyl orthosilicates and aluminum tri-isopropoxide in water.

TL;DR: In this article, the porosity of extruded test objects has been studied by different methods in order to follow its evolution during firing, and two populations of pores are recognized, i.e., partially closed at intermediate temperatures, open again at temperatures above 1000°C.

TL;DR: The Rupelian boom clay has been investigated with respect to its bloating characteristics and it was found that too much organic matter has a negative impact on bloating and that iron compounds have to be added to facilitate the expansion process as discussed by the authors.

TL;DR: The main techniques of thermal analysis are listed in Table 1. as mentioned in this paper, where the sample is heated at a constant rate until the reaction rate exceeds a pre-set limit, at which point the temperature is reduced.

TL;DR: In this article, the maximum monomolecular capacity (Q 0 ) according to the Langmuir model is 153 mg/g for an initial organic matter concentration of 251.5 mg/l, at 30°C.

TL;DR: The conditions of alteration of the upper Eocene zeolite-bearing volcaniclastic sediments at Metaxades, Thrace, Greece, were examined using a variety of petrographic and mineralogical techniques as mentioned in this paper.

TL;DR: In this paper, three types of sedimentary materials are studied, referred to as green, brown and pink clays, and the structural formula of the smectite in Adsorption, external specific surface and swelling pressure are very similar in the saponitic clays with, respectively, average values of: 73-75 meq/100 g (CEC), : 160-170 m2/g (SBET) and 4.6-5.28 MPa (Ps) (precompacted at dry density 1.4 g).

TL;DR: In this paper, a controlled transformation rate evolved gas analysis (CR-EGA) was applied to the study of the thermolysis of kaolinite, which showed evidence of three steps between −30° and 1000°C: removal of adsorbed water, elimination of hydroxyls from octahedral layers, in a layer-by-layer sequence, by an intersheet diffusion D3 mechanism, and release of the remaining hydroxys located in the middle of the sheets as the kaolinite structure collapsed.

TL;DR: The diatomitic materials are of only fair quality, but, upon appropriate treatment, can be used as catalyst supports, filter aids and lightweight structural ceramics bodies as discussed by the authors.

TL;DR: The presence of smectite and illite in a pyroclastic flow deposit from the Mt. Vulture volcanic area (southern Italy) has been investigated by the XRD and the SEM-EDS methods.

TL;DR: In this article, a heterogeneous dehydroxylation mechanism involving magnesium and oxygen concentration in acceptor regions and micropores in donor regions is proposed, which leads to a structure where micropore and enriched oxide interlayers alternate along the z-axis of the mineral which generates long basal spacings.

TL;DR: In this paper, the kinetics of the anaerobic treatment of dairy wastewater has been studied and the apparent kinetic constant, K 0, was determined in each of the situations studied and its mean value was 1.32 day −1 (sepiolite), 1.00 day−1 (saponite), and 0.37 day − 1 (bentonite).

TL;DR: In this paper, the results of a study on organo-mineral soil clay fractions isolated from long-term fertilization experiments in eastern Germany were compiled, and the results showed that the cation exchange capacities of the clay fractions were closely correlated with the organic carbon concentrations, and therefore dependent on the management practice.

TL;DR: In this paper, a combination between the Bruker IFS 48 FTIR spectrometer and the TA Instruments TGA 951-2000 was used to monitor the gases evolving from heated Kortemark Clay.

TL;DR: In this paper, a clay mineral from Ecuador has been analyzed by X-ray, thermal and infrared analyses and shown to contain approximately 35% of disordered kaolin phase, followed by dilatometric analysis.

TL;DR: In this paper, a series of experiments were carried out to establish the influence of various parameters on β′-sialon formation and determined which by-products were formed from all clays.

TL;DR: The adsorption of N-methyl 8-hydroxy quinoline methyl sulphate by natural and acid-treated sepiolite has been investigated in this article, showing that the mixture of aqueous solutions and mechanical mixing of the components in the solid state served as good sunburn shields.

TL;DR: In this article, the characteristics of each layer were studied under indigenous conditions to understand sludge stability, and the three separated layers were found to be distinctly different in appearance, density and surface functionalities.

TL;DR: In this article, the authors examined the hydrothermal and weathering alteration products of the gabbroic rocks at Griva, Macedonia, Greece, using petrographic, mineralogical and chemical data.

TL;DR: In this paper, the authors studied the mineralogy and internal structure of the sandstone in order to explain how far it affects its use as a construction material and found that the differences in the quality of this material, displaying different kinds of technological behaviour, are reflected by the deterioration of the buildings.

TL;DR: Underground coal gasification (UCG), an unconventional technique of coal utilization, is associated with large-scale firing of rocks adjacent to the coal seam A significant fraction of these rocks are argillaceous and have a composition comparable to mixes of raw material utilized in brickmaking, and in the manufacturing of lightweight aggregates which employes a bloating and expansion fabrication mechanism as mentioned in this paper.

TL;DR: The influence of microbes on clays was studied on a kaolinitic clay from the Westerwald area, Germany, where the total loss in weight increased and the growth of microbes in clay slurries increased.

TL;DR: In this article, the ion exchange reaction of smectite clay with a cationic oligomer of hydroxy aluminum (COHA) in the presence of a preswelling agent resulted in better thermal stability of the resultant aluminapillared clay (APC).