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Abstract  

The thermal behaviour of the intercalation complex of a dickite from Tarifa, Spain, with dimethylsulfoxide was studied by high-temperature X-ray diffraction, differential thermal analysis and thermogravimetry, and attenuated total reflectance infrared spectroscopy. The ATR-FTIR study indicated that the heating between room temperature and 75C produced the elimination of adsorbed molecules. Above this temperature the elimination of intercalated molecules occurs through several stages. Loss of 6.5% of the intercalated DMSO first causes a slight contraction of the basal spacing at 90şC due to a rearrangement of the DMSO molecules in the interlayers positions. This contraction is followed by the formation of a single layer complex and the restoring of the dickite structure, at 300C, when the loss of intercalated species have been completed.

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Abstract  

The products of dickite heated in air at 1000 to 1300°C were studied using curve-fitting of transmission and photoacoustic infrared and micro-Raman spectra. The spectra were compared with those of mullite, Al-spinel, corundum, cristobalite, amorphous silica and meta-dickite. Bands that characterize crystalline phases appeared at 1100°C and became stronger with increasing temperature. Mullite, Al-spinel, corundum and amorphous silica were identified by their characteristic bands. The characteristic IR bands of cristobalite overlap those of mullite and amorphous silica, and its presence was therefore established from intensity ratios of the appropriate bands. The research clearly demonstrated the advantage of using curve-fitting for the identification of high temperature phases in the study of the thermal treatment of kaolin-like minerals by infrared and Raman spectroscopy. This technique seems to be a useful method for materials analysis in the ceramic industry.

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Abstract  

A dickite from Tarifa (Spain) was used to study the influence of the intercalation and the later deintercalation of hydrazine on the dehydroxylation process. The dehydroxylation of the untreated dickite occurs through three overlapping endothermic stages whose DTA peaks are centred at 586, 657 and 676C. These endothermic effects correspond, respectively, to the loss of the inner-surface, the inner hydroxyl groups, and the loss of the water molecules, product of dehydroxylation process, which has been trapped in the framework of the dehydroxylated dickite. The intercalation of hydrazine in the interlayer space of dickite and the later deintercalation affect the dehydroxylation process. It occurs through only two endothermic stages which DTA peaks are centred at 575 and 650C. The first corresponds to the simultaneous loss of both the inner and the inner-surface hydroxyl groups, whereas the second one is analogous to that at 676C observed in the DTA curve of untreated dickite. These effects appear shifted to lower temperatures compared to those observed in the untreated dickite.

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Abstract  

Thermal analysis has been employed in a study of the degradation of heritage Sydney sandstone used in St Mary’s Cathedral in Sydney, Australia. TG and DSC have been used to characterise the clay components removed from weathered and unweathered sandstone. Two types of kaolin clays — kaolinite and its polymorph, dickite — have been identified. A higher amount of dickite present in the clay of weathered sandstone indicates that a kaolinite-to-dickite transformation occurs upon weathering. XRD hot stage analysis was also used to demonstrate the presence of a more thermally stable polymorph of the kaolinite.

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Abstract  

In this study, radiocesium sorption on ceramic clay was investigated as a function of particle size and initial 137Cs concentration using a batch method. Ceramic clay samples taken from the Söğüt(İnisar) clay deposit were composed of kaolinite, dickite and quartz. The equilibrium time and the liquid–solid ratio were determined as 60 min and 250 mL g−1, respectively. The distribution coefficients (K d) for variable liquid–solid ratio and the percentage adsorption (P Ad) were calculated. The values of K d and P Ad ranged from 483 to 3165 mL g−1 and 34–93%, respectively. The K d and P Ad values increased with increasing particle size, but decreased with increasing initial concentration. The sorption data were interpreted in terms of a Langmuir isotherm. The results indicated that the Söğüt(İnhisar) ceramic clay has good sorption capacity for cesium.

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A number of natural kaolinite-group minerals, nacrite, dickite, kaolinite and halloysite, were heated up to 1400‡ and investigated by means of ESR at the X band. The results show systematic differences, some of which are related to the crystallinity of the kaolinites and to the mutual orientation of adjacent layers in polytype modifications. The most intense features of the spectra, centred atg values of 4.3 and 3.0, are attributed to Fe3+ ions occupying different sites in the structure. Studies of the changes caused in the ESR spectra by thermal treatment led to some general conclusions about structure modification.

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% – – <1% Dickite ∼30% ∼30% – ∼5%–10% Anatase

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. J Tongji Univ (Natural Science) 33 : 1646 – 1650 . 3. Franco , F , Cecila , JA , Pérez-Maqueda , LA , Pérez-Rodríguez , JL , Gomes , CSF 2007 Particle-size reduction of dickite

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from weathered and unweathered sandstone, and identified two types of kaolin clays, namely, kaolin and its polymorph, dickite. Cekerevac and Laloui [ 5 ] studied the thermal effects on the mechanical behavior of saturated clays such as kaolin

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, Michaelian , KH , Boudeulle , M , Panczer , G , Lapides , I , Yariv , S . Study of thermally treated dickite by infrared and micro-Raman spectroscopy using curve-fitting technique . J Therm Anal Cal 2002 69 : 205 – 225 10.1023/A:1019954227093

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