Search results for "MINERALOGY"

Kinetic Parameters for Thermal Degradation of Green Asparagus Texture by Unsteady-state Method

1998

An unsteady-state method was developed for estimating texture degradation during heating-cooling of green asparagus spears. The method used a mathematical model of heat transmission for time-temperature history estimation, and a nonlinear regression of texture measurements of asparagus spears to estimate kinetic parameters. The specific heat, conductivity and convective coefficient of green asparagus were determined experimentally and used In the mathematical model for temperature estimation. Values obtained were Ea = 76.19±0.13 kJ/mol and k 1158°C = 0.00528±0.00005 s -1 . Good agreement was found between predicted and observed texture values. The method was compared with the classical stea…

Charge transport properties in CdZnTe detectors grown by the vertical Bridgman technique

2011

Presently, a great amount of effort is being devoted to the development of CdTe and CdZnTe (CZT) detectors for a large variety of applications such as medical, industrial, and space research. We present the spectroscopic properties of some CZT crystals grown by the standard vertical Bridgman method and by the boron oxide encapsulated vertical Bridgman method, which has been recently implemented at IMEM-CNR (Parma, Italy). In this technique, the crystal is grown in an open quartz crucible fully encapsulated by a thin layer of liquid boron oxide. This method prevents contact between the crystal and the crucible, thereby allowing larger single grains with a lower dislocation density to be obta…

Structural characterization of relaxor ferroelectric PbMg 1/3 Nb 2/3 O 3 -PbTiO 3 thin film heterostructures deposited by pulsed laser ablation

2000

Highly oriented and epitaxial films of relaxor ferroelectric PbMg1/3Nb2/3O3-PbTiO3 (PMN-PT) with a composition (68/32) near the morphotropic phase boundary were deposited by pulsed laser ablation on La0.5Sr0.5CoO3 bottom electrodes, deposited on MgO (100) and LaAlO3 (100). The formation of crystalline phases, epitaxy, film–electrode–substrate orientation relationships and crystal perfection were studied by X-ray diffraction and scanning electron microscopy. The structural properties were found to depend on the deposition conditions and substrate. Correlation of both the dielectric and relaxor properties in the heterostructures and the structural properties of the PMN-PT films was observed.

Local Bonding Influence on the Band Edge and Band Gap Formation in Quaternary Chalcopyrites

2017

Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu2ZnGeS4-x Se x , the anion bond alteration parameter changes, showing larger bond lengths for metal-selenium than for metal-sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu-anion and Ge-anion interactions, respectively. The knowledge of the underlyi…

Aluminum and Gallium Substitution in Yttrium and Lutetium Aluminum–Gallium Garnets: Investigation by Single-Crystal NMR and TSL Methods

2016

The work reports the results on 71Ga and 27Al NMR investigation of the gallium and aluminum ions distribution over tetrahedral and octahedral positions in the Y3Al5−x GaxO12:Ce single crystals and Lu3Al5−xGaxO12:Ce single-crystalline epitaxial films. The gallium content x varies between 0 and 5 in crystals and between 0.3 and 2 in films.. We find that in both the Y- and Lu-based solid solutions the larger gallium ions are preferably located at the tetrahedral position while the smaller aluminum ions prefer the octahedral position of the garnet host. Based on NMR data, the dependence of fractional occupation parameters of the tetrahedral site of Ga and Al ions on the Ga content is determined…

ECS-3: A Crystalline Hybrid Organic-Inorganic Aluminosilicate with Open Porosity

2011

Outline and arrangement of enamel rods in human deciduous and permanent enamel. 3D-reconstructions obtained from CLSM and SEM images based on serial …

2001

Human enamel rods were made visible continuously from the dentino-enamel junction (DEJ) up to the enamel surface. From 12 teeth (1st and 2nd dentition) enamel blocks from the cervical third were prepared with perpendicular planes, embedded in resin, and ground down in steps of 15 microm parallel to the enamel surface. Enamel rods were made visible by acid etching (35% H3PO4, 45 s), sputtered and examined in the scanning electron microscope (SEM). Prior to this, the enamel blocks were viewed under the CLSM and optical sections at distances of 2 microm were obtained, starting in the same plane as the grinding surface. The outlines of the rods were digitized and reconstructed three dimensional…

Raman spectrum of the high pressure phase of polyethylene

1982

The Raman spectrum of the hexagonal high pressure phase of polyethylene was measured at 5.2 kbar and 240 °C, using a hydrostatic high pressure cell. The spectrum is largely identical to that obtained for the melt. This result indicates that the conformational short range order in the hexagonal phase remains melt —like and is not modified by the overall straightening of chains.

Microfocus X-ray computed tomography analysis of corroded glass objects

2009

Abstract Microfocus X-ray computed tomography (µCT) is a useful tool for non-destructive analysis of corroded archaeological glass objects and for monitoring restoration and conservation processes for these materials. This was demonstrated by µCT analysis of artificially corroded laboratory-produced glasses and corroded archaeological glasses retrieved from soil environments. Corrosion layers with a thickness of 20 µm or more can be detected as areas with lower X-ray attenuation values than the non-corroded glass. Features that are revealed by µCT analyses include the degree and patterns of corrosion and the presence of various internal structures in the corrosion layers. The study of resto…

Pore shape affects the determination of the pore size of ordered mesoporous silicas by mercury intrusion.

2008

MCM-41 and SBA-15 micelle-templated silicas are ideal reference materials to study the effect of surface roughness on pore size measurement by mercury intrusion, as the inner surface of the mesoporous channels is much rougher in the case of SBA-15 than MCM-41. In the case of MCM-41, the pressure of mercury intrusion is related to the pore size by the classical Washburn−Laplace law, while in the case of SBA-15, the pressure of intrusion is much higher than expected and classical models underevaluate the size of the channels. Defects on the pore surface of SBA-15 affect the mercury intrusion in a similar way as the deviation from cylindrical geometry does for the pores of spongelike silica gl…