Search Results
Abstract
Using neutron activation the nitrogen and fluorine contents in fossile bones could be measured relative to main constituents of the inorganic bone material (phosphorus and calcium). By determining the ratio of N and F a relative and absolute age determination was possible. The method is relatively simple, quick, cheap and nondestructive.
-cure can be measured and quantified using DSC. However, glass transition, relaxations and thermal ageing [ 2 ] give a low response with DSC, particularly when the polymer is highly crosslinked and mobility restricted by the fibrous filler phase
Endrodi, A. & Gyulai, F. , 1999. Soroksár-Várhegy. A fortified Bronze Age settlement in the outskirts of Budapest. Plant cultivation of Middle Bronze Age fortified settlements. Communicationes Archaeologicae Hungariae. 1999. 5
Abstract
Two aged cement pastes (7 years) were studied for H2O and CO2 evolution, the combined amounts of which were measured by TG and identified by thermo-IR analysis. This indicated the presence of three forms of carbonates, which decomposed at different temperatures. The displacement with time of the evaporation of sorbed water to higher temperatures (500–700C, TG, MS) shows the possibility of its incorporation into carbonate hydrates and/or hydroxy hydrates, postulated previously. The decomposition of all the hydration products needed a thermal energy increasing with ageing (increased temperature measured by TG). The carbonation process proceeded for 7 years in the weaker paste, whereas it terminated before 5 years in the stronger one. The CSH water content did not change with ageing, whereas that of portlandite was lowered, which though did not account for the increase in carbonate content (TG). Possibly some Ca2+ from the CSH gel was involved in this process. In the stronger paste the growth with time of organic matter was found (IR, TG/DTG).
Abstract
It is well known, from ancient Egypt, that some pigments and colourants can change with time for light effect or chemical attack. Cennino Cennini in the fifteenth century in his book “Il libro dell'arte o trattato della pittura” describes the use of many pigments and their degradation. He was aware of the problems and was able to suggest the answers in the use of pigments on several supports, but he could not understand the physical–chemical reason of the alteration processes. In this study, we point out the aging effects in seven paintings, practically of the same period (1650–1655). We considered in particular green, white and blue pigments of the palette of Valerio Castello. About 150 spots were selected on works painted on four different supports, canvas, wood panel, copper and slate. For each point, several determinations were carried on the pigments and decomposition products, aiming to determine the state of conservation of the paintings, the nature of the pigments, their alteration and if the support can affect the kinetics of degradation.
Abstract
An accurate means of determining bone age is a goal for forensic scientists. In this study, thermogravimetric analysis (TGA) has been used to examine pig bone specimens of different post-mortem age. Analysis of bone in both air and nitrogen atmospheres reveals a decrease in total mass loss as the bones age. Two mass loss steps due to the decomposition of the organic bone components were observed and show decreasing trends with age for decomposition in an air atmosphere. In a nitrogen atmosphere the decomposition was observed to be more complex and age dependence of the mass loss for each step was not identified. The TGA data, however, demonstrates the potential of the technique as a means of estimating post-mortem age of forensic bone specimens.
Árkai, P. & Balogh, K. , 1989. The age of metamorphism of East Alpine type basement, Little Plain, W-Hungary: K-Ar dating of K-white micas from very lowand low-grade metamorphic rocks. Acta Geol
Abstract
The chemical stability of a propellant and its influence on the ballistic properties during aging is a subject of interest. The effect of aging on ballistic properties, viz., ignition delay, burning rate, and heat of combustion for an aluminised ammonium perchlorate–hydroxyl-terminated polybutadiene (AP/HTPB) composite propellant during accelerated aging were investigated. Samples of composite propellants were aged at 60 and 70 °C at relative humidity of 50% in a climatic chamber. The propellant samples were tested with pressurized nitrogen gas environment for ignition delay measurement. Test results indicate that aging does not have any appreciable effect on ignition delay. The change in ignition delay time is less than 3% within the scatter of the data. Experiment results indicate that burn rate do affect with pressure but aging does not have much effect on burn rate. It was also observed that the burning rate at low pressures did not undergo significant changes during the aging period. The most significant of all the ballistic properties of this propellant is the burning rate exponent which increased by about 10% during the aging period.
Abstract
The physical aging characteristics of maltose glasses aged at two temperatures below the glass transition temperature, Tg, (Tg-10C and Tg-20C) from 5 to 10 000 min were measured by standard differential scanning calorimetry (SDSC) and modulated differential scanning calorimetry (MDSC). The experimentally measured instrumental Tg, the calculated Tg, and the excess enthalpy values were obtained for aged glasses using both DSC methods. The development of excess enthalpy as a function of aging time, as measured by both SDSC and MDSC, was fit using the Cowie and Ferguson and Tool-Narayanswamy-Moynihan models. The change in the Tg values and the development of the excess enthalpy resulting from physical aging measured by the two DSC methods are discussed.
Abstract
The carbonate cements of conglomeritic deposits of late Pleistocene age have been leached with 0.2N hydrochloric acid and analyzed radiochemically. The leachate and the residue fractions were separately measured for238U,234U and230Th, using isotope-dilution and alpha-spectrometric techniques. The data are used to estimate the isotopic activities of uranium and thorium in the carbonate phase. These activities give age information for the carbonate cementation. Ages in the range of 185–320·103 years were obtained for the samples studied.
