scholarly journals Synthesis and characterization of (Ba, Yb) doped ceria nanopowders

2011 ◽  
Vol 5 (2) ◽  
pp. 69-72 ◽  
Author(s):  
Branko Matovic ◽  
Jelena Pantic ◽  
Jelena Lukovic ◽  
Svetlana Ilic ◽  
Nadezda Stankovic ◽  
...  
Keyword(s):  
Room Temperature ◽  
Average Diameter ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Doped Ceria ◽  
Fixed Amount ◽  
Fluorite Type ◽  
Powder Properties ◽  
The Mean

Nanometric size (Ba, Yb) doped ceria powders with fluorite-type structure were obtained by applying selfpropagating room temperature methods. Tailored composition was: Ce0.95-xBa0.05YbxO2-? with fixed amount of Ba - 0.05 and varying Yb content 'x' from 0.05 to 0.2. Powder properties such as crystallite and particle size and lattice parameters have been studied. R?ntgen diffraction analyses (XRD) were used to characterize the samples at room temperature. Also, high temperature treatment (up to 1550?C) was used to follow stability of solid solutions. The mean diameters of the nanocrystals are determined from the full width at half maxima (FWHM) of the XRD peaks. It was found that average diameter of crystallites is less than 3 nm. Williamson- Hall plots were used to separate the effect of the size and strain in the nanocrystals.

6H- AND 4H-SiC(0001) Si SURFACE RICHNESS DOSING BY HYDROGEN ETCHING: A WAY TO REDUCE THE FORMATION TEMPERATURE OF RECONSTRUCTIONS

2003 ◽  
Vol 10 (01) ◽  
pp. 55-63 ◽  
Author(s):  
M. DIANI ◽  
J. DIOURI ◽  
L. KUBLER ◽  
L. SIMON ◽  
D. AUBEL ◽  
...  
Keyword(s):  
High Temperature ◽  
Atomic Hydrogen ◽  
Room Temperature ◽  
Binary Systems ◽  
Temperature Treatment ◽  
Heating Time ◽  
High Temperature Treatment ◽  
Formation Temperature ◽  
Hydrogen Etching ◽  
Chemical Surface

In 6H- or 4H-SiC(0001) surface technology, a Si-rich 3 × 3 reconstruction is usually first prepared by heating at 800°C under Si flux, and two other most stable [Formula: see text] or [Formula: see text] reconstructions are obtained by further extensive annealing at higher temperatures ranging between 900 and 1250°C. The 3 × 3 Si excess is thus progressively depleted up to a graphitized C-rich surface. By crystallographic (LEED) and chemical surface characterizations (XPS and UPS), we show that all these reconstructions can be obtained at a unique, low formation temperature of 800°C if the Si richness is controlled before annealing. This control is achieved by exposing the 3 × 3 surface to atomic hydrogen at room temperature. This procedure allows one to etch or partially deplete the (3 × 3)-associated Si excess, and make it more comparable to the final Si coverages, required to form the less Si-rich [Formula: see text] or [Formula: see text] reconstructions. After annealing at 800°C, the latter reconstructions are no longer determined by the heating time or temperature but only by the initial Si coverage set by the H doses inducing the low temperature etching. The high temperature treatment, required to remove by sublimation a significant Si amount associated with the Si-rich 3 × 3 reconstruction, is thus avoided. Such a methodology could be applied to other binary systems in the formation of reconstructions that depends on surface richness.

Synthesis and characterization of mixed fluorides with PbF2 and ScF3

2005 ◽  
Vol 20 (3) ◽  
pp. 254-258 ◽  
Author(s):  
S. N. Achary ◽  
A. K. Tyagi
Keyword(s):  
Solid Solution ◽  
Phase Equilibria ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Solubility Limit ◽  
Synthesis And Characterization ◽  
Temperature Phase ◽  
Fluorite Type ◽  
Low Temperature Phase

A series of mixed fluoride compositions with PbF2 and ScF3 were prepared by heating the intimate mixtures of component fluorides at 600 °C for 10 h followed by slowly cooling to room temperature. The products obtained were analyzed by powder XRD to reveal the phases present in them and hence the low-temperature phase equilibria in the PbF2-ScF3 system. The phase equilibria show the fluorite-type solid solution up to the composition of about 15 mol% of ScF3 in the PbF2 lattice. The unit cell volume decreases with increasing ScF3 contents in the fluorite-type solid solutions. Beyond the solubility limit, the biphasic mixture of the cubic fluorite-type solid solution and leftover ScF3 is found to exist.

Product characterization of a traditional sausage aiming at geographical indication certification and entrepreneurship prospects: an empirical study of Goan “choris”

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Solomon Rajkumar ◽  
Renuka Nayar ◽  
Kavitha Rajagopal ◽  
Namratha Valsalan ◽  
Sudharsan Chinnasamy ◽  
...  
Keyword(s):  
Room Temperature ◽  
Fatty Acid Content ◽  
Storage Period ◽  
Geographical Indication ◽  
Content Type ◽  
Pork Sausage ◽  
Product Characterization ◽  
Physico Chemical ◽  
The Mean

PurposeThe purpose of this paper is the physico-chemical, microbiological, colorimetric, sensorial characterization of choris, a traditional smoked pork sausage produced in the state of Goa (India), including its storage stability (0–180 days) at room temperature, aiming at the geographical indication certification and entrepreneurship prospects.Design/methodology/approachA total of 48 samples of “choris” were collected from 24 villages of Goa and were analyzed at different intervals (0–180 days) for physico-chemical, proximate, microbiological, colorimetric and sensory attributes during the storage at room temperature.FindingsThe mean pH of 4.45 and water activity (aw) of 0.78 were recorded. The pH, tyrosine value, fat percentage and free fatty acid content registered a significant increase, whereas moisture content, aw and moisture–protein ratio reduced as storage progresses. The colorimetric values lightness (L*), hue angle (H*) and redness index values reduced significantly during storage. The mean total viable count, yeast and mold, and lactic acid bacteria count were found to proliferate significantly as storage advanced. Nevertheless, the hedonic scores not reaching an unacceptable level (= 4) at the end of the storage period.Originality/valueIn accordance with the various parameters adopted during the study, choris could be characterized as “naturally fermented dry smoked” sausages, which were shelf-stable at room temperature for 180 days. The product characterization of choris is essential to guarantee the genuineness, safety and consumer's acceptability. This study will also rebound in an augmented uniformity of the product, which will favor the geographical indication certification and the entrepreneurship prospects of this traditional product.

Neutron diffraction studies of the actinide oxides II. Thermal motions of the atoms in uranium dioxide and thorium dioxide between room temperature and 1100 °C

1963 ◽  
Vol 274 (1356) ◽  
pp. 134-144 ◽  
Keyword(s):  
Room Temperature ◽  
Characteristic Temperature ◽  
Relaxation Effect ◽  
Thorium Dioxide ◽  
Metal Atoms ◽  
Fluorite Type ◽  
Thermal Displacements ◽  
Actinide Oxides ◽  
The Mean ◽  
Oxygen Atoms

The mean-square thermal displacements of the atoms in U 0 2 and T h 0 2 have been determined as a function of temperature from the analysis of two-dimensional diffraction data. In the range investigated, 20 to 1100°C, the oxygen atoms vibrate more strongly than the metal atoms and at each temperature the displacements of the metal and oxygen atoms are slightly less in T h 0 2 than in U 0 2. The interpretation of these results gives a Debye characteristic temperature which is independent of tem temperature above 400 °C and equal to 377 °K for U 0 2 and 393 °K for T h 0 2. As the temperature rises, the oxygen atoms tend to be displaced from the fluorite-type sites at 1/4 1/4 1/4. . . towards the large interstitial holes at 1/2 1/2 1/2.... At 1000°C the mean atomic co-ordinates of the oxygen atoms are 1/4+ 8 1/4+8 1/4 ...where, 8 — 0*016 for UO 2 and 8 = 0.014 for ThO 2 . This relaxation effect indicates either that the oxygens are disordered or that they vibrate anharmonically across the 1/4 1/4 1/4. . . positions.

Temperature Dependence of 4H-SiC JBS and Schottky Diodes after High Temperature Treatment of Contact Metal

2005 ◽  
Vol 483-485 ◽  
pp. 945-948 ◽  
Author(s):  
R. Pérez ◽  
Narcis Mestres ◽  
Dominique Tournier ◽  
Xavier Jordá ◽  
Phillippe Godignon ◽  
...  
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Schottky Diodes ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Schottky Junction ◽  
Temperature Dependent ◽  
Working Temperature ◽  
Sic Wafer ◽  
Contact Metal

In this work we demonstrate performant characteristics of 1.2KV Schottky, Junction Barrier Schottky (JBS) and implanted PN diodes processed on the same 4H-SiC wafer. A bi-layer Ni/Ti scheme for the contact metallisation submitted to high temperature rapid thermal anneals is proved to form good ohmic contact on p+ implanted areas while maintaining good Schottky characteristics on lightly doped n-type regions. I-V characteristics have been evaluated from room temperature up to 560K. At room temperature, Schottky diodes have slightly better specific onresistance, but when working temperature is increased, the JBS diode exhibits better characteristics due to the temperature dependent activation of bipolar current injection from the p+ grid. From reverse measurements, the JBS diodes showed lower leakage current and higher breakdown voltages in comparison to that of the Schottky diodes in the whole range of temperatures.

scholarly journals Synthesis of biomorphaus SiC-ceramics

2007 ◽  
Vol 61 (2) ◽  
pp. 75-78
Author(s):  
Adela Egelja ◽  
Jelena Gulicovski ◽  
Aleksandar Devecerski ◽  
Snezana Boskovic ◽  
Branko Matovic
Keyword(s):  
Photoelectron Spectroscopy ◽  
Abies Alba ◽  
Microstructural Characterization ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Sic Ceramics ◽  
Silica Source ◽  
Porous Sic ◽  
Highly Porous

The carbothermal reduction processing of partially mineralized fir (Abies alba) samples was used to obtain highly-porous SiC ceramics with cellular structure. The infiltration of TEOS (tetraetilortosilikat, Si(OC2H5)4) as a silica source, was conducted in order to carry out the mineralization process. Synthesis of the SiC was achieved with a C/SiO2 replica annealing at 1723 K in Ar atmosphere. The obtained samples were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The experimental results revealed that the hierarchical bimorphous wood structure was preserved even after high-temperature treatment. Microstructural characterization of the ceramics revealed the presence of the P-SiC phase and traces of the a-SiC phase.

scholarly journals Electrical and thermal properties of 10 mol% Gd3+ doped ceria electrolytes synthesized through citrate combustion technique

2009 ◽  
Vol 3 (3) ◽  
pp. 137-143 ◽  
Author(s):  
Viswanathan Mangalaraja ◽  
Solaiappan Ananthakumar ◽  
Manidurai Paulraj ◽  
Kasimayan Uma ◽  
Marta López ◽  
...  
Keyword(s):  
Citric Acid ◽  
Room Temperature ◽  
Doped Ceria ◽  
Nanocrystalline Ceria ◽  
Structure Surface ◽  
Particle Size And Morphology ◽  
Powder Properties ◽  
Size And Morphology ◽  
Combustion Technique ◽  
Ceria Electrolyte

Nanocrystalline ceria electrolyte doped with 10 mol% gadolinia [Ce0.9Gd0.1O1.95] was synthesized by citric acid combustion technique involving mixtures of cerium nitrate oxidizer (O) and citric acid fuel (F) taken in the ratio of O/F=1. The as combusted precursors produced crystalline ceria particles upon calcination performed at 700?C for 2h. Ceria pellets were made and sintered at temperatures 1200, 1400 and 1500?C with a dwell time of 2, 4 and 6 h. The sintered microstructures, electrical and thermal conductivities and thermal diffusivity properties were evaluated in addition to the powder properties such as crystalline structure, surface area, particle size and morphology. Sintered ceria samples had 99% theoretical density at 1500?C/6h. The sintered microstructures exhibit dense ceria grains with sizes 500 nm to one micron. The electrical conductivity versus temperature showed conductivity in the order of 10-2 and 10-1 S?cm-1 at 500 and 700?C, respectively. The ceria sintered at 1500?C has the maximum thermal conductivity of ~2.79 W?m-1K-1 at room temperature. .

scholarly journals Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC2N Ceramic

Materials ◽  
2011 ◽  
Vol 4 (12) ◽  
pp. 2061-2072 ◽  
Author(s):  
Wallace R. Matizamhuka ◽  
Iakovos Sigalas ◽  
Mathias Herrmann ◽  
Leonid Dubronvinsky ◽  
Natalia Dubrovinskaia ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
High Pressure High Temperature

scholarly journals Room temperature optical thermometry based on the luminescence of the SiV defects in diamond

2018 ◽  
Vol 190 ◽  
pp. 04024
Author(s):  
Caius Miller ◽  
Laurits Puust ◽  
Valter Kiisk ◽  
Evgeny Ekimov ◽  
Igor Vlasov ◽  
...  
Keyword(s):  
Room Temperature ◽  
Near Infrared ◽  
Temperature Treatment ◽  
Temperature Sensing ◽  
High Temperature Treatment ◽  
Temperature Dependent ◽  
Zero Phonon Line ◽  
High Pressure High Temperature ◽  
Optical Thermometry ◽  
Inorganic Precursors

SiV-containing microcrystals of diamond are synthesised by using high-pressure high-temperature treatment of a mixture of pertinent organic-inorganic precursors. Photoluminescence of SiV defects were investigated with the aim to use the microcrystals for optical temperature sensing in near infrared at room temperature based on temperature-dependent shift of the 740 nm zero-phonon line of SiV photoemission.

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