Analysis of archaeological samples and local clays using ICP-AES, TG-DTG and FTIR techniques.
The spectrochemical and thermal analysis of different archaeological samples as bricks, terra-cotta and local clays were carried out. The concentration of major and minor elements of samples was determined by sequential inductively coupled plasma atomic emission spectrometry. The method was tested by determining Si, Al, Fe, Ca, Mg, Mn, Pb, Cu, Zn, Ti, Na and K in the standard solutions and reference material GXR-4. The precision of the determination (relative standard deviation) ranged from 0.4 to 1.54%. The clay minerals are the main materials for the production of bricks and terra-cotta figures. Thermogravimetric (TG) and differential (TG-DTG) analysis and Fourier transform infrared spectrometry (FTIR) methods can be used for the study of characteristic reactions, associated with the course of the heating. The TG-DTG curves were obtained in the temperature range 25-900 degrees C, and the dynamic experiment was carried out in the air and nitrogen atmosphere. The infrared evolved gas analysis was performed using FTIR in the dynamic nitrogen atmosphere.
Thermal behaviour of limestone and monocrystalline calcite tempers during firing and their use in ancient vessels
Limestone and monocrystalline calcite tempers (grains) are abundant in ancient pottery. In pottery from the Canaan area the former is common in Iron Age storage and table-ware vessels and the latter is present in cooking pots. Limestone is much more widespread than monocrystalline calcite and the potters used it often as tempers when manufacturing pottery vessels, but usually not for cooking pots. While defects appear frequently around limestone tempers, they do not appear around monocrystalline calcite ones. This study examines the reason for using the latter tempers rather than the former ones.Raw materials of carbonate tempers in a clay matrix were fired and the decarbonation process was followed by quantitative IR thermospectrometry. The results indicate that the monocrystalline calcite tempers prevent formation of defects in the cooking pots during firing or during use. The reasons for this are higher thermostability at elevated temperatures, lower intensity of decarbonation, and retention of grain shape, as compared to limestone tempers.ZusammenfassungIn alten Töpferwaren werden reichlich Kalkstein und monokristalline Kalzitmischungen gefunden. Bei Töpferwaren aus dem Gebiet Canaan ist ersteres bei Vorrats- und Tischgeschirrgefäßen, letzteres bei Kochtöpfen üblich. Kalkstein ist weitverbreiteter als monokristallines Kalzit und es wurde von den Töpfern bei der Fertigung von Töpfereigefäßen oft als Mischung eingesetzt, jedoch nicht für Kochgeschirr. Während Defekte oft an Kalkstein-mischungen auftreten, kommen sie an monokristallinen Kalzitmischungen nicht vor. In dieser Arbeit wird der Grund dafür gesucht, daß die letzteren Mischungen den ersteren vorgezogen wurden.Rohmaterialien aus Karbonatmischungen wurden in einer Tonmatrix gebrannt und der Dekarbonierungsprozeß mittels IR Thermospektrometrie verfolgt. Die Resultate zeigen, daß monokristalline Kalzitmischungen beim Brennen oder bei der Benutzung die Bildung von Defekten bei Kochgeschirr verhindern. Die Gründe dafür liegen—verglichen mit Kalksteinmischungen—in der höherem Thermostabilität bei erhöhten Temperaturen, in der weniger intensiven Dekarbonierung und in der Beibehaltung der Gefügestruktur.
Isocontour maps of electron temperature, electron number density and gas kinetic temperature in the Ar inductively coupled plasma obtained by laser-light Thomson and Rayleigh scattering
Abstract Isocontour maps of electron temperature (Tc), electron number density (nc, and gas-kinetic temperture (Tg) in an argon inductively-coupled plasma (ICP), have been constructed for five rf power settings and in the presence and absence of an aqueous aerosol, based on the simultaneous measurement of spatially resolved Thomson and Rayleigh scattering. Each map was assembled from 21 observation heights and 31 radial positions, the location of each point being controlled by a computer-driven three-axis translation stage. The maps demonstrate how Te,ne and Tg all increase throughout the plasma as rf power is raised, with the electron number density increasing most rapidly. At greater rf power levels (1.75 kW), the introduction of an aqueous aerosol into the central channel was found to increase ne over the entire plasma. In contrast, at lower applied power (0.75 kW), nc is depressed throughout the discharge upon the introduction of water aerosol. At intermediate rf powers (1.0, 1.25 and 1.5 kW), aerosol introduction raises nc only in the regions near the hot torus, while reducing nc at all other spatial positions, particularly lower in the central channel. Aerosol introduction was found also to thermalize the plasma at all rf power settings by increasing Tg in the higher regions and decreasing Te lower in the central channel. In general, Te is substantially higher than Tg in the lower regions of the discharge, but the two approach each other in the upper zones.