The clay deposit of Vila Nova da Rainha (VNR) is included in the lithostratigraphic formation named "Argilas de Tomar", and is located at the lower section of the Tertiary Tagus’ river basin. Clay from one quarry is being extracted for the production of construction ceramics. In this work the firing transformations undergone by VNR clays containing quartz, alkaline feldspar, iron oxy-hydroxides, and clay minerals have been studied. Carbonates have not been identified in these raw materials. The clay layers can be subdivided in three groups based upon composition and ceramic properties. The first group, VNR0, is represented by smectite-kaolinite sandy-silty clay, the second group (VNR1 and VNR2) corresponds to illite-kaolinite bearing clay and the third group (VNR3 and VNR4) is represented by illite-smectite silty clay. The firing process involves the formation of hematite and mullite both influencing the technical properties of the fired products. With regards to the ceramic properties assessed at 1100 ºC the first group showed the lowest total shrinkage value (7.35 %) the highest water absorption value (12.2 %) and the lowest mechanical bending strength value (12.0 MPa); the same properties assessed in the second group provided the highest firing shrinkage values (7.0-5.0 %), the lowest values of water absorption (0.1-0.2 %) and relatively high mechanical bending strength values (47.8-48.0 MPa); the third group showed firing shrinkage values within the range 3.5-4.2 %, water absorption values within the range 1.4-4.5 %, and the highest mechanical bending strength values (49.2-52.0 MPa). The results of the ceramic properties being appraised indicate that the raw materials being studied are suitable for the production of high-quality construction ceramics, such as brick, roof tile and rustic floor tile., João F. Coroado, Eduardo Ferraz, Celso F. Gomes and Fernando Rocha., and Obsahuje bibliografii
The prehistory of clay mineralogy is highlighted from the beginnings in ancient Greece to the mineralogical works of Agricola, in particular his famous handbook of mineralogy, entitled De natura fossilium (1546). Starting with a few scattered hints in the works of Archaic and Classic Greek authors, including Aristotle, the first treatment of clays as a part of mineralogy is by Theophrastus. This basic tradition was further supplemented by Roman agricultural writers (Cato, Columella), Hellenistic authors (the ge ographer Strabo and the physicians Diosco rides and Galen), the Roman engineer-architect Vitruvius, and finally summarized in Pliny’s encyclopedia Naturalis historia, which has become the main source for later authors, including Agricola. It is shown to what extent Agricola’s work is just a great summary of this traditional knowledge and to what extent Agricola’s work must be considered as original. In pa rticular, Agricola’s attempt to a rational, combinatorical classification of "earths" is recalled, and aplausible explanation is given for his effort to include additional information on Central European clay depos its and argillaceous raw material occurre nces. However, it is shown that - in contrast to common belief - Agricola was not the first to include "earths" in a mineralogical system. This had been done almost one thousand years earlier by Isidore of Seville., Willi Pabst and Renata Kořánová., and Obsahuje bibliografické odkazy
Polyaniline/montmorillonite (PANI/MMT) intercalate pressed into pellets using the pressure 28 MPa has been prepared in order to achieve two-dimensional conductivity which is close to pure PANI, however with improved mechanical and thermal stability (due to the presence of silicate). Structure-conductivity relationship has been investigated using X-ray diffraction analysis and diffraction patterns obtained from two perpendicular planes revealed the strong texture. The structural anisotropy led to the anisotropy in conductivity, which is much stronger for PANI/MMT than for pure PANI pellets. Anyway, the inplane conductivity is of the same order for both PANI/MMT and pure PANI pellets. The anisotropy factor, that means the ratio of in-plane conductivity and conductivity in the direction perpendicular to the pellet plane, was 328 (PANI/MMT pellet) and 6.7 (pure PANI pellet), respectively., Jonáš Tokarský, Kateřina Mamulová-Kutláková, Lucie Neuwirthová, Lenka Kulhánková, Vítězslav Stýskala, Vlastimil Matějka and Pavla Čapková., and Obsahuje bibliografii