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Ceramic Samples (ceramic + sample)
Selected AbstractsA SPECTROSCOPIC INVESTIGATION OF PIGMENT AND CERAMIC SAMPLES FROM COPÁN, HONDURAS,ARCHAEOMETRY, Issue 1 2009R. A. GOODALL A combination of micro-Raman spectroscopy, micro-infrared spectroscopy and SEM,EDX was employed to characterize decorative pigments on Classic Maya ceramics from Copán, Honduras. Variation in red paint mixtures was correlated with changing ceramic types and improvements in process and firing techniques. We have confirmed the use of specular hematite on Coner ceramics by the difference in intensities of Raman bands. Different compositions of brown paint were correlated with imported and local wares. The carbon-iron composition of the ceramic type, Surlo Brown, was confirmed. By combining micro-Raman analysis with micro-ATR infrared and SEM,EDX, we have achieved a more comprehensive characterization of the paint mixtures. These spectroscopic techniques can be used non-destructively on raw samples as a rapid confirmation of ceramic type. [source] Investigation of Islamic ceramics from Tell Tuneinir using X-ray diffractionGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 8 2001M.L. Eiland In this study, X-ray diffraction (XRD) is applied to select ceramics, particularly dating to the Ayyoubid (A.D. 1174,1250) period from Tell Tuneinir in Syria. Because XRD has not been commonly applied to archaeological ceramics, a thorough background of the technique is given, with emphasis on quantitative measurements of quartz and calcite tempers. Several compositional groups based on raw materials and firing conditions emerge. While most ceramic samples are of local manufacture, Islamic stonepaste wares, and the "grenade" sample emerge as likely imports. We conclude that XRD is a powerful tool in characterizing archaeological ceramics and may be used to semi-quantitatively gauge the amount of quartz, calcite, and feldspars in a sample. © 2001 John Wiley & Sons, Inc. [source] High-Temperature Instability of Li- and Ta-Modified (K,Na)NbO3 PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008Yongli Wang This paper addresses the high-temperature instability of Li- and Ta-modified (K,Na)NbO3 piezoceramics. The grains with abnormal size evolve out of the fine matrix grains during high-temperature annealing. They are found to be precipitates with a tetragonal tungsten bronze structure, which result from the volatilization and segregation of the alkali metal elements. With the growth of the abnormal grains the composition of the perovskite matrix phase also changes remarkably, as has been suggested by EDX analysis (for Na) and electric measurements (for Li). These variations lead to a large increase in the tetragonal/orthorhombic phase transition temperature and appreciable variations in the dielectric, ferroelectric, and piezoelectric properties of the ceramic samples. Control of the volatilization of the alkali metal elements can efficiently depress the abnormal grain growth and the compositional segregation. [source] Microwave Dielectric Properties of Sintered Alumina Using Nano-Scaled Powders of , Alumina and TiO2JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Cheng-Liang Huang The microstructure and the microwave dielectric properties of nano-scaled , alumina (,-Al2O3) ceramics with various added amounts of nano-scaled TiO2 have been investigated. The sintering temperature of nano-scaled , alumina can be effectively lowered by increasing the TiO2 content. The Q×f values of nano-scaled , alumina could be tremendously boosted by adding an appropriate amount of TiO2. However, introducing excessive TiO2 into the alumina ceramics would instead lead to a decrease in the Q×f values. The phases of TiO2 and Al2TiO5 co-existed at 1350°C, and the maximum Q×f value appeared right after the eradication of TiO2 phase at 1400°C. Consequently, increasing the TiO2 content to 0.5 wt% yielded a Q×f value of 680 000 GHz (measured at 14 GHz) for nano-scaled , alumina prepared at 1400°C for duration of 4 h. In addition, a very low loss tangent (tan ,) of 2 × 10,5 was also obtained at 14 GHz. The ,f value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, ,f could be adjusted to near zero by adding 8 wt% TiO2 to , alumina ceramics. A dielectric constant (,r) of 10.81, a high Q×f value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (,f) of 1.3 ppm/°C were obtained for nano-scaled , alumina with 8 wt% TiO2 sintered at 1350°C for 4 h. Sintered ceramic samples were also characterized by X-ray diffraction and scanning electron microscopy. [source] Preparation of Ceramic Well Plates for Combinatorial Methods Using the Morphogenic Effects of Droplet DryingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Yong Zhang When droplets of a ceramic suspension dry on a non-wetting substrate, powder migrates to the periphery and builds there a wall of powder. This intriguing phenomenon, which is a nuisance in some processes, can be used to make arrays of ceramic wells on a ceramic substrate. These wells can, after sintering, be used to hold ceramic samples made from powder by controlled mixing of ceramic inks or could be made from ceramics that act as heterogeneous catalysts and used to hold reactants. The well plates can even be made from electrically conducting ceramics so that electrical property measurements can be made with a ground electrode. [source] Effect of Porosity on the Electrical Properties of Polycrystalline Sodium Niobate: I, Electrical ConductivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2003Silvania Lanfredi The electrical behavior of NaNbO3 ceramic samples with different relative densities was investigated by ac impedance spectroscopy in a range of 13 MHz to 10,3 Hz between 400° and 800°C in dry air. Measurements were performed during heating and cooling cycles. The Nyquist impedance diagrams of dense sodium niobate exhibit only one semicircle representing the grain contribution with depression angles as small as 1°, indicating a high homogeneity of the specific electrical properties. In the case of porous samples, the data reveal an additional low-frequency semicircle related to microstructure. For all studied samples, the Arrhenius conductivity plots show a change in the activation energy around 640°C, attributed to the tetragonal-cubic phase transition. The electrical conductivity of porous samples appears to be higher than that of dense ones. [source] Nonlinear refractive index of ceramic laser media and perspectives of their usage in a high-power laser-driverLASER PHYSICS LETTERS, Issue 10 2004Yu. Senatsky Abstract At the recent years a technology of ceramic laser media on the base of crystals with a cubic symmetry has been developed. The perspective of the usage of ceramic materials in many different applications including high - power short pulse lasers stimulates the work on the systematic study of the properties of these new laser media. A nonlinear refractive index, n2 was studied for several garnet and sesquioxide laser ceramics using Z-scan method. n2 indices in the range of (2 , 6) × 10,13 were measured for YAG, Y2O3, Lu2O3, and Sc2O3 ceramic samples. These data together with the other laser and spectroscopic parameters of several Nd3+ and Yb3+ doped crystals of a cubic symmetry were used to estimate the properties of laser ceramics for the application in a high-power pulsed-repetitive laser - driver for inertial confinement fusion (ICF) program. A high heat conductivity of ceramic materials is a profitable characteristic for this application as compared to glasses, which are used now for experiments in ICF at single shots regime. Compared to single crystals, ceramic elements provide laser designers with a variety of new design options for the projects of laser-drivers. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] NiO-induced crystallization and optical characteristics of Li2O,CaF2,P2O5 glass systemPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2008G. Murali Krishna Abstract Li2O,CaF2,P2O5 glasses mixed with different concentrations of NiO (ranging from 0 mol% to 2.0 mol%) were crystallized. The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy and differential thermal analysis. Studies were extended to optical absorption and magnetic susceptibility of these glass ceramic samples. The XRD and SEM studies reveal the presence of lithium phosphate, calcium phosphate and nickel phosphate crystal phases. The optical absorption studies together with magnetic susceptibility measurements indicate a gradual transformation of nickel ions from tetrahedral sites to octahedral sites (lasing sites) as the concentration of NiO is increased beyond 0.8 mol%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] TIME-OF-FLIGHT NEUTRON DIFFRACTION CHARACTERIZATION OF CERAMIC FINDINGS FROM SOUTHERN AND WESTERN SICILY,ARCHAEOMETRY, Issue 4 2009L. BARTOLI We present the results of a study that is part of a wider research programme regarding knowledge of the initial living phases of Sicilian agricultural and pastoral society. Three sets of ceramic samples were analysed through time-of-flight neutron diffraction (TOF-ND) to derive information about the composition of the clay and the manufacturing techniques. The first two sets of sherds came from an excavation in Licata, close to Agrigento, and are composed of findings dated around the third century bc, while the third set was of samples from prehistoric sites located in the northwestern part of Sicily. Measurements were performed to obtain a quantitative identification of the mineralogical composition of the samples in a totally non-destructive way. Hints about manufacturing techniques and firing temperatures are derived to provide information on provenance and production processes of the objects. [source] | ||||||||||