Search results for "MINERALOGY"
showing 10 items of 1516 documents
A comparative thermogravimetric study of waterlogged archaeological and sound woods
2010
Waterlogged archaeological woods Pinus pinaster and Fagus sylvatica L. were analyzed by using TG technique. Degradation processes ascribable to the holocellulose decay were evidenced at nearly the same temperature for sound and archaeological samples. The residual matters at 600 and 900 °C of the sound woods are much lower than those of archaeological waterlogged woods in agreement with the presence of inorganic materials encapsulated during the burial into the marine environment. It was proposed a new protocol to rapidly calculate the maximum water content parameter, which is related to the wood degradation state. TG experiments at variable heating rates were performed to obtain kinetic pa…
Dependence of thermal conductivity on structural parameters in porous samples
2012
The in-plane thermal conductivity of porous sintered bronze plates was studied both experimentally and numerically. We developed and validated an experimental setup, where the sample was placed in vacuum and heated while its time-dependent temperature field was measured with an infrared camera. The porosity and detailed three-dimensional structure of the samples were determined by X-ray microtomography. Lattice-Boltzmann simulations of thermal conductivity in the tomographic reconstructions of the samples were used to correct the contact area between bronze particles as determined by image analysis from the tomographic reconstructions. Small openings in the apparent contacts could not be de…
Study of the ZnO crystal growth by vapour transport methods
2004
Abstract The crystal growth of ZnO by vapour transport is classically made with the assistance of additional species that produce a gaseous mixture, the role of which remains often uncertain in the transport and growth process. Initially, in order to study the mass transport process, a numerical simulation is made to analyse which are the requirements to have an effective transport. As the pressure of each gaseous species is generally unknown, the numerical study has been performed for different total pressures. It is found that, if congruent and equilibrium conditions are assumed at the sublimation and crystallisation interfaces, effective growth conditions can only be attained for a narro…
Influence of titanium-vanadium alloys on cell morphology: electron microscopy and ESCA studies
2000
Titanium and its alloys provide optimum metallurgical properties for implants. The formation of an oxide layer favours compatibility with the adjacent hard and soft tissues. Research focuses on further optimizing the passive layer, particularly with respect to minimizing metal ion migration into the tissues. The present study concentrates on two alloys (Ti6A14V and Til.5A125V) coated with oxide layers generated by different techniques: thermal oxidation, anodic oxidation and sol-gel treatment. Only thermal oxidation fails to reduce surface and subsurface concentrations of vanadium, whereas other treatments avoid the element in the outermost surface areas of the alloys. Additionally, the the…
Low-pressure-MOCVD LaMnO3±δ very thin films on YSZ (100) optimized for studies of the triple phase boundary
2000
Abstract This paper deals with the preparation of LaMnO 3± δ (LM) layers by low pressure-metal organic chemical vapor deposition (LP-MOCVD) using La(tmhd) 3 and Mn(acac) 3 as organometallic precursors. By thermogravimetric analysis, these precursors were found to be suitable for LP-MOCVD in a well-defined range of total pressure and temperature of sublimation. The activation energies of the sublimation process were found to be independent of the pressure within the appropriate range (0.06–3 kPa) and their values were 177 and 100.5 kJ mol −1 for La(tmhd) 3 and Mn(acac) 3 , respectively. LM layers of various thickness ranging between a few and a few hundred nanometers with a controlled La/Mn …
A multi-analytical approach for the characterization of black crusts on the facade of an historical cathedral
2020
Abstract This study focuses on the characterization of black crusts collected from the Monza cathedral located in the homonymous city (N Italy), a hot spot from the point of view of the atmospheric pollution. Black crusts and substrate marble specimens were analyzed by a multi-analytical approach including X-ray Diffraction (XRD), Fourier Transform-Infrared spectroscopy (FT-IR), Stereomicroscopy (SM), Polarized Light Microscopy (PLM), High Resolution Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (HRSEM-EDX) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP/MS). The characterization of the carbon fraction (organic carbon, OC, and element…
Some comments on the history of thermogravimetry
1990
Abstract In a review of the authors about the history of vacuum microbalance techniques (including a chronology in table form), also published in Thermochimica Acta, (ref. 1) it uas pointed out, that also some corrections are to be made on the history of therinogravimetry. The first findings of balances are dated to about 3000 B.C. A gravimetric hygrometer is mentioned by Nicolaus Cusanus in 1450. In the 19th century chemical reactions at variable temperatures uere investigated using balances. The very beginning of the thermogravinietry is antedated to the work of Talabot who in 1833 at Lyon equipped a laboratory with thermobalances for quality control of Chinese silk.
DIFFERENT APPROACHES TO DATE BRICKS FROM HISTORICAL BUILDINGS
2014
Abstract The application of Thermally (TL) and Optically (OSL) Stimulated Luminescence on bricks used as building material has allowed solving an chronological issue in the field of historical building dating. The possibility to use one or more methodologies of dating is closely related to the luminescent and granulometric characteristics of the sample. Using some brick samples collected in the church of Sain Seurin in Bordeaux (France), this paper discusses the implications and the possibility to use different approaches and techniques for dating. With this aim luminescence measurements were performed on both polymineral fine grain and quartz inclusion phases extracted from each brick. For…
Reconsidering the accuracy of X-ray fluorescence and ion beam based methods when used to measure the thickness of ancient gildings
2017
Since at least 5000 years ago, gilding techniques have been used for decoration purposes or to make artefacts appear as made of solid gold. Investigation of ancient gildings inevitably requires measuring their thickness, which is usually done either through the observation of cross-sections or by methods such as Rutherford backscattering spectroscopy, particle-induced X-ray emission and X-ray fluorescence. Whereas the former method requires sampling, the latter ones are non-invasive and therefore preferable. These non-invasive methods, however, measure the number of atoms per unit area, which can be converted into thickness only if the density is known. So far this has not been considered a…
Flow and thixotropy of non-contaminating oil drilling fluids formulated with bentonite and sodium carboxymethyl cellulose
2007
Abstract A study has been made of low-contaminating oil drilling mud in water base, composed of bentonite, at concentrations in the range of 6–12% (w/w), and sodium carboxymethyl cellulose at two different concentrations. Flow analysis yielded an empirical formula indicating shear stress as a function of the formulation concentrations of bentonite and sodium carboxymethyl cellulose, stirring time and shear rate. To study the thixotropy of the different formulations the cycles' method has been used. Calculations were made of the thixotropic areas, obtaining a semi-empirical equation for these areas. The results are analyzed on the base of relative thixotropic area and total relative thixotro…