Authors:F. Albuquerque, B. Parente, S. Lima, C. Paskocimas, E. Longo, A. Souza, I. Santos, and V. Fernandes
The use of clays for ceramic filter processing may reduce its cost, leading to different applications, as water treatment.
In this work, a low cost tile clay mixed with kaolin, for use in ceramic filters, were evaluated. Mineralogical and thermal
changes occurring during sintering were characterized by differential thermal analysis, thermogravimetry, thermomechanical
analysis and X-ray diffraction. An increase in the initial melting temperature of samples due to kaolin addition was observed.
Mullite formation in kaolin was observed by DTA and in other samples by XRD. TMA analysis permitted the observation of pre-sintering
step, around 850C. This step is difficult to observe in other types of analysis.
Differential thermal analysis (DTA) was the first thermal analysis technique used to qualitatively characterize natural clays
and respective curves has been used since more than 60 years as their ‘fingerprint’. With the development of microprocessed
equipments in the last decades, derivative thermogravimetric (DTG) curves also may be used for this purpose in some cases,
which also may allow a quantitative characterization of clay components. TG and DTG curves are more indicated than DTA or
DSC curves to identify and to better analyze the several decomposition steps of natural or synthetic organoclays. These questions
are discussed in applications developed to characterize Brazilian kaolinitic clays, bentonites and organophilic clays.
The formation at high temperatures of phases such as β′,X, and O′-sialon by carbothermal reduction of clays has been studied using simultaneous thermal analysis (STA) and thermomechanical
analysis (TMA). Two reducing agents, silicon carbide and carbon, were used, with either kaolinite or bentonite. The progress
of reaction was followed by interrupted and continuous thermal analysis procedures using STA and TMA and the changes correlated
with the phases observed by X-ray diffraction at different stages. The conversion of kaolinite to β′-sialon is characterised
by the dehydration and transformation of kaolinite independent of the nitriding atmosphere below 1400°C. At higher temperatures
nitriding commences. Similar behaviour is observed with bentonite transforming to lower substitution sialon phases. The weight
changes are correlated with oxidation/reduction reactions and mechanisms are suggested to explain the observed phenomena.
The data obtained will permit the optimization of thermal cycles for batch production of sialon powders from natural minerals.
Authors:Veridiana Reyes-Zamudio, Carlos Angeles-Chávez, and Jorge Cervantes
deterioration of this kind of stone has been reported [ 4 – 7 ]. One of the main weathering processes is the dissolution of feldspars and volcanic glass and the formation of secondary clay minerals such as halloysite, smectite, illite, allophane, and kaolinite
Authors:Laith Sh. Rasheed, Laith Mohammed Ridha Mahmmod, Sara Alaa Abed Alameer, and Abdulrasool Thamer Abdulrasool
to produce concrete with sustainable curing technique in which the potential cracking would be substantially reduced. Graded Clay Brick Waste (CBW) was employed as internal curing agent as alternative martial with 10% and 15% volumetric percentage