The geology and mineralogy of a range of kaolins from the Santa Cruz and Chubut Provinces, Patagonia (Argentina)

In the Santa Cruz and Chubut provinces, Patagonia, Argentina, kaolin deposits were formed by "in situ" alteration of volcaniclastic rocks, such as the Bajo Grande, Chon Aike or Marifil Formations, or by erosion, transportation, and deposition of residual clays in small basins. This paper describes the genesis; geology; mineralogy; major, minor, and trace element geochemistry; grain size distribution; and specific surface area of natural and washed kaolins in an attempt to understand their behavior in the ceramic process. The sedimentary clays of the Baquer? Fm Lower Member, related to the Bajo Grande basement, are kaolinitic?-smectitic, very fine?grained, and with a very high specific surface area. The clays related to the Chon Aike or Marifil Fms are kaolinitic, showing intermediate values of specific surface area and a coarser particle size distribution, associated with quite a fine?-grained texture. The Baquer? Fm Upper Member received a considerable pyroclastic supply, fostering the development of a fine?-grained clay in which kaolinite (? halloysite) with higher values of kaolinite crystal order prevailed. Primary kaolins - derived from weathering of pyroclastic sequences of Chon Aike and Marifil Fms - are coarse-?grained, composed of kaolinite+ quartz? halloysite and exhibit a very low specific surface area. Alteration of mostly crystalline pyroclastics yielded ordered kaolinite and illite (? halloysite) with a fine particle size distribution and intermediate values of specific surface area. Alteration of mainly vitreous pyroclastics produced halloysite (+kaolinite) with a fine?grained texture and moderately high values of specific surface area. A supergene origin of primary kaolins is inferred on the basis of palaeoclimatic and geochemical evidence that corroborates stable isotopic data. The mineralogy, grain size, and textural characteristics of clays are controlled by parent rock composition (primary kaolins) or by provenance and proximity to source areas (sedimentary kaolins)

High-performance yellow ceramic pigments Zr(Ti1-x-ySnx-yVyMy)O4 (M = Al, In, Y): crystal structure, colouring mechanism and technological properties

Zirconium titanate-stannate doped with V with co-dopants Al, In or Y was synthesised by solid state reaction and its structural (XRD, SEM), optical (DRS) and technological properties were determined to assess its potential use as ceramic pigment. These compounds have a srilankite-type, disordered orthorhombic structure, implying a random distribution of Zr, Ti, Sn and dopants in a single, strongly distorted octahedral site. Doping caused an increase of unit-cell dimensions, metal-oxygen distances and octahedron distortion. Optical spectra show crystal field electronic transitions of V4+ as well as intense bands in the blue-UV range due to V4+-V5+ intervalence charge transfer and/or to V-O charge transfer. The formation of oxygen vacancies is supposed to compensate the occurrence of V4+ ensuring the lattice charge neutrality. These srilankite-type oxides develop a deep and brilliant yellow shade with colourimetric parameters close to those of industrial ceramic pigments. Technological tests in several ceramic applications proved that zirconium titanate-stannate is very stable at high temperature, exhibiting an excellent performance in the 1200-1250?C range, even better than praseodymium-doped zircon

Recycling PC-TV waste glass in clay bricks and roof tiles

Disposal of PC and TV sets is a growing problem, involving for over 40 wt. % waste glasses with high Pb (funnel) or Ba-Sr concentration (panel) which cannot be recycled in the glass manufacture. A possible way to re-use these glasses is in the manufacturing of clay bricks and roof tiles, that was appraised by laboratory simulation of the brickmaking processing and technological characterization of unfired and fired products. The recycling of both funnel and panel glasses into clay bodies is technologically feasible, resulting in a behaviour substantially plasticity-reducing during shaping-drying (implying a reduction of mechanical strength) and promoting sintering during firing. No significant release of Pb, Ba and Sr was found during firing and leaching test for the carbonate-poor body; in contrast, some Pb volatilization during firing and Sr leaching were observed for the carbonate-rich body. Additions of 2 wt. % appear to be practicable, while 5 wt. % glass induces unacceptable modifications of technological properties. The recommended amount is within 2 and 4 wt. %, depending on the characteristics of clay bodies. The main constraint is that glass must have a particle size below the limit of pan mills used in brickmaking (<1 mm)

Influence of mineralogy and particle size on the technological properties of ball clays for porcelainized stoneware tiles

The influence of the mineralogical and granulometric characteristics of ball clays on the technological properties of ceramic tiles was investigated with special reference to porcelainized stoneware production. The raw materials currently used by the tilemaking industry are fine-grained clays consisting mainly of kaolinite, quartz, illite and randomly interstratified illite/smectite, with occasional smectite. The particle size distribution affects in particular the plasticity and the size changes of tiles during processing, the finest fraction (<0.2 ?m) being the most effective. The mineralogical composition has a relevant effect on the mechanical properties and pressing behaviour: smectite and interstratified I/S play a prevalent role, together with the structural order of kaolinite and illite. Sintering is to a large extent conditioned by the amount of fluxing components (i.e. feldspars, illite, iron oxyhydroxides, etc.) while the firing shrinkage is also related to the powder compressibilit

Predicting the initial rate of water absorption in clay bricks

The effect of product characteristics and processing conditions on the initial rate of water absorption of fifteen clay bricks was investigated and the influence of porosimetric parameters (amount, size and tortuosity of pores) as well as of phase composition (amount of calcium-silicates and amorphous phase) was established. The suction behaviour of bricks, which may be brought back to the models of Gummerson et al. (1981) and Hoffman and Niesel (1988), was also evaluated on the basis of both the product microstructure and the liquid physical properties. According to the model of Beltran et al. (1988), which reveled to be sufficiently reliable, the values of the capillary coefficient Ks were calculated and their correlation with the experimental ones has been provided. For a given liquid and in the same experimental conditions, the results indicate that varying in a controlled way the product microstructure (i.e. decreasing the pore size, increasing the pore tortuosity and/or controlling the amorphous/new formed phases ratio) should allow to design materials having a most suitable behaviour

Titania slag as a ceramic pigment

The phase transformations and colouring mechanisms that occur during the ceramic processing of titania slag were investigated using XRF-EDS, XRD, DRS and laboratory-scale application in glazed and unglazed tiles. The slag transforms to pseudobrookite, undergoing a drastic colour change during firing as a consequence of thermal oxidation with Fe2+ to Fe3+ and Ti3+ to Ti4+ reactions. The intense brown colour imparted by titania slag is stable at both low (up to 1050 degrees C) and high (around 1200?C) temperatures and is suitable for porcelain stoneware tiles. In through-body application, titania slag enables \u27spotting\u27 effects to be achieved

Genesis of the La Espingarda kaolin deposit. Implications for epithermal deposit exploration in Patagonia

The La Espingarda kaolin deposit was formed by ?in situ? alteration of sub-alkaline rhyolites belonging to the Jurassic Mari&#64257;l Formation. Three altered volcanic lithofacies were identi&#64257;ed: a porphyric biotitic ignimbrite (RPB), a coarse lithic ignimbrite (ILG), and a &#64258;uidal intrusive rhyolite (RFI). The kaolinization covers an ellipsoidal surface area of &#8764;20,000 m2, with the alteration intensity decreasing downwards and disappearing at 8?12 m from the surface. In two mine sectors small stockworks of &#64257;ne quartz veins appears (b3 m2). The deepest alteration is related to two fault zones where the three volcanic units are in contact. There is no lateral clay zoning at the faults. The mineralogical composition is kaolinite? halloysite ?illite quartz+feldspars +Fe-hydr(oxides). At least three kaolinite generations were identi&#64257;ed. The &#64257;rst is pervasive; the second appears as a &#64257;lling of vugs in the quartz veinlets that crosscut the pervasively altered rocks; and the third occurs as pure kaolin veins without quartz vein cross cuts. During the alteration processes almost total alkali cations were leached. The argillized lithofacies showed Ni enrichment and Cu, Sr, and Ba depletions. The main weathering genesis for La Espingarda is supported by the deposit morphology, its location in topographic lows, the paleoclimatic record, its simple mineralogical composition; vertical zonation, the kaolinite veins isotopes (&#948;18O ? 18.3; &#948;D ? &#8722;59.0), and the trace element distribution. A steam heated water activity produced some kaolinite overprint according to one isotopic value and the S and P contents slightly higher in the kaolinized rocks. Neither Au, Ag, As, Sb, Hg, or Ba epithermal path&#64257;nders\u27 anomalies nor drill data support the existence of any metallic mineralization at the kaolin blanket bottom. In Patagonia hydrothermal kaolinite manifestations are located around and beneath silici&#64257;ed, erosion-resistant hills and include some of the following minerals: dickite, alunite, pyrophyllite, or pyrite and have As, S, Ba, and Ag trace elements within the range of weak geochemical anomalie

Waste recycling in ceramic tiles: a technological outlook

The ceramic industry is going to be deeply involved in the transition to a circular economy. However, the main obstacle to a widespread recourse to waste recycling is the lack of knowledge about its effect in ceramic tile manufacturing. The rationale behind this work is to look at recycling from the industrialist's point of view. The goal is overviewing the effects of different kinds of waste on technological behavior, technical performance, and environmental impact of ceramic tiles in the prospect of an industrial transfer. Technical constraints that waste recycling must comply to be transferable to ceramic tile manufacturing were examined in detail. Available information on the behavior of ceramic tile bodies containing wastes from various sources was critically reviewed for every manufacturing stage. The main outcome is an outlook about feasibility (expressed in terms of Technology Readiness Level) and recommended recyclable amount. In addition, hindrances to scale up and matters of concern (e.g., hazardous components and gaseous emissions) are pointed out and discussed. Examples and reasons of success/unsuccess are briefly illustrated, and prospect of waste recycling in ceramic tiles production from a circular economy perspective was appraised

The Effect of kaolin properties on their behaviour in ceramic processing as illustrated by a range of kaolins from the Santa Cruz and Chubut Provinces, Patagonia (Argentina)

The Patagonian kaolins offer a wide set of origin of deposits, composition, mineral processing and ceramic properties, giving a rare opportunity for investigating the interdependence of mineralogy, chemical composition, particle size distribution, texture, and surface activity with their technological behaviour in sanitaryware and porcelain stoneware production. Plasticity is strictly dependent on surface activity, <2 micron fraction and expandable clay minerals; slip rheology is affected by soluble salts and expandable clay minerals, but also by high specific surface or tubular halloysite. Kaolinite/halloysite play an opposite role versus smectite/interstratified I/S in slip casting and tile pressing: the former allow faster casting rates, while the latter improve powder flowability and mechanical strength. Kaolinite and quartz are beneficial for drying behaviour while high surface activity or expandable clay minerals increase significantly drying sensitivity. Firing behaviour is mainly affected by minor components supplying "fluxing" (i.e. iron, alkali and alkaline-earth) oxides. A great deal of technological parameters seem to be reasonably predicted by the surface activity of clays and especially the Methylene Blue index, which is the most reliable, simple and economic method to predict and control the ceramic response of kaolins and ball clays

M-doped Al2TiO5 (M= Cr, Mn, Co) solid solutions and their use as ceramic pigments

New ceramic pigments based on the tialite (Al2TiO5) structure, doped with Co (pink), Cr (green) or Mn (brown), were prepared through pyrolysis of aerosols followed by calcination of the obtained powders at 1400?C. The expected decomposition of Al2TiO5 into a mixture of Al2O3 and TiO2 on re-firing was inhibited by Cr-doping and also by co-doping with Mg the Mn or Co doped samples. Microstructure and phase evolution during pigment preparation were monitored by SEM and XRPD. Unit cell parameters of tialite were determined by Rietveld refinement of XRD patterns revealing in all cases the formation of solid solutions where the solubility of dopants in the Al2TiO5 lattice followed the trend: Co < Mn < Cr. Valence state and possible location of dopants in the tialite lattice were investigated by XPS and DRS spectroscopies, which suggested the presence of Cr3+ ions in a large interstitial site of the tialite lattice with distorted octahedral geometry, and of Mn3+ and Co2+ ions at the Al3+ octahedral sites of the tialite lattice in the former case, and in both Al3+ and Ti4+ octahedral sites, in the latter. Technological behaviour of pigments was assessed by testing in ceramic glazes finding that the color stability was reasonably good for the Mn-doped tialite and the Cr-doped pigment although the latter suffered a small loss of green hue, while the Co-doped pigment was not stable in glazes, undergoing a cobalt-leaching effect