Structural phase transition, equation of state and phase diagram of functional rare earth sesquioxide ceramics (Eu1-xLax)2O3.

The intriguing functional nature of ceramics containing rare earth sesquioxide (RES) is associated with the type of polymorphic structure they crystallize into. They prefer to be in the cubic, monoclinic or hexagonal structure in the increasing order of cation size, RRE. Since the functional properties of these ceramics varies with RRE, temperature and pressure, a systematic investigation delineating the cation size effect is indispensable. In the present work we report the structural stability and compressibility behaviour of the RES ceramics, (Eu1-xLax)2O3, of RESs with dissimilar structure and significant difference in cationic radii. The selected compositions of (Eu1-xLax)2O3 have been studied using the in-situ high pressure synchrotron X-ray diffraction and the structural parameters obtained through Rietveld refinement. The cubic structure, which is stable for 0.95 Å [Formula: see text] RRE [Formula: see text] Å at ambient temperature and pressure (ATP), prefers a cubic to hexagonal transition at high pressures. The biphasic region of cubic and monoclinic structure, which is stable for 0.98 Å [Formula: see text] RRE [Formula: see text] Å at ATP, prefers a cubic/monoclinic to hexagonal transition at high pressures. Further, in the biphasic region of monoclinic and hexagonal structure, observed for 1.025 Å [Formula: see text]RRE [Formula: see text] Å, the monoclinic phase is found to be progressing towards the hexagonal phase with increasing pressure. The pure hexagonal phase obtained for 1.055 Å [Formula: see text] RRE [Formula: see text] 1.10 Å is found to be structurally stable at high pressures. The bulk moduli are obtained from the Birch-Murnaghan equation of state fit to the compressibility data and its dependance on the cation size is discussed. The microstrain induced by the difference in cation size causes an internal pressure in the crystal structure leading to a reduction in the bulk modulus of [Formula: see text] and 0.6. A pressure-concentration (P-x) phase diagram upto a pressure of 25 GPa is constructed for (Eu1-xLax)2O3. This would provide an insight to the fundamental and technological aspects of these materials and the RESs in general.

An innovative modified feeding appliance for an infant with cleft lip and cleft palate: A case report.

Cleft lip and palate is one of the most common craniofacial anomalies of humans. A child born with cleft lip and palate may experience difficulties while feeding due to lack of seal of the oral cavity due to incomplete facial and palatal structures. Difficulty in feeding leads to inadequate nutrition and affects the health of the infant. Feeding difficulties should be assessed and intervened as early as possible, as they are an important aspect of the multidisciplinary team approach in the management of cleft lip and palate. Feeding appliance is a favorable feeding option in these infants as it creates a separation between oral and nasal cavities and thus helps in creating a negative intraoral pressure during suckling. This case report represents a fabrication of feeding appliance for a 2-day-old neonate born with cleft lip and palate, using copper wire as a retainer for the appliance.

Physicochemical properties of nanocomposite: Hydroxyapatite in reduced graphene oxide.

Graphene oxide (GO) based nanocomposites have gained considerable attention in the field of material science due to their excellent physicochemical and biological properties. Incorporation of nanomaterials into GO sheets prevents the formation of π-π stacking bond thereby giving rise to composites that show the improved properties compared to their individual counterparts. In this work, reduced graphene oxide (rGO) - hydroxyapatite (HAP) nanocomposites were synthesized by ultrasonic method. Increasing the c/a ratio of HAP in the diffraction pattern of rGO/HAP nanocomposites indicates the c-axis oriented grown HAP nanorods interacting with rGO layers. Shift in wavenumber (15cm-1) and increase of full width at half maximum (45cm-1) of G band in Raman spectra of the rGO/HAP nanocomposites are observed and attributed to the tensile strain induced due to the intercalated HAP nanorods between the rGO layers. Atomic force microscopy (AFM) and phase imaging studies revealed the intercalation of HAP nanorod with diameter 30nm and length 110-120nm in rGO sheets was clearly perceived along with improved elasticity compared to pristine HAP. 13C-NMR results proved the synergistic interaction between both components in rGO/HAP nanocomposite. The novel properties observed and the microscopic mechanism responsible for this are a result of the structural modification in rGO layers brought about by the intercalation of HAP nanorods.

Temporomandibular pain.

Temporomandibular joint pain has various medical and dental etiological factors. The etiology of the temporomandibular joint pain is enigmatic, no single etiological factor is regarded as the cause. Its distribution is also not confined to a single area. This article presents the basic etiologic factors, its epidemiology, distribution of pain, classification of patients and the psychosocial behavior of patients suffering with temporomandibular pain. As overwhelming majority of medical and dental conditions/issues related to etiology of temporomandibular pain in patients have traditionally been presented and interpreted from the clinician's point of view.

Valence state, hybridization and electronic band structure in the charge ordered AlV2O4.

The valence state, hybridization and electronic band structure of charge ordered AlV2O4 are investigated by measuring the electron energy loss spectra (EELS) and performing band structure calculations using the WIEN2k code. White line ratio and O K edges of V2O5, VO2, V2O3 and AlV2O4, obtained using electron energy loss spectroscopy, are analysed specifically to probe systematically the VO6 octahedra in all of them. The systematic decrease of the L2 intensity and the O K edge intensity from V(5+) in V2O5 to AlV2O4 indicates a progressive increase in the occupancy of the hybridized states, which is corroborated by the absence of a transition from O 1s to hybridized 2t(2g). Band structure calculations on the parent charge frustrated cubic phase and the charge ordered rhombohedral phase clearly document a band gap in the charge ordered state. From the structural information obtained after convergence and the spectroscopic information from EELS, it appears that partial orbital occupancy may lead to a deviation from an integral valence state on all the vanadium in this exotic charge ordered spinel system.

Pressure-induced frustration in charge ordered spinel AlV2O4.

AlV2O4 is the only spinel compound so far known that exists in the charge ordered state at room temperature. It is known to transform to a charge frustrated cubic spinel structure above 427 ° C. The presence of multivalent V ions in the pyrochlore lattice of the cubic spinel phase brings about the charge frustration that is relieved in the room temperature rhombohedral phase by the clustering of vanadium into a heptamer molecular unit along with a lone V atom. The present work is the first demonstration of pressure-induced frustration in the charge ordered state of AlV2O4. Synchrotron powder x-ray diffraction studies carried out at room temperature on AlV2O4 subjected to high pressure in a diamond anvil cell show that the charge ordered rhombohedral phase becomes unstable under the application of pressure and transforms to the frustrated cubic spinel structure. The frustration is found to be present even after pressure recovery. The possible role of pressure on vanadium t2g orbitals in understanding these observations is discussed.

Stability of embedded indium nanoclusters in silica under thermal treatment and ion irradiation.

The stability of embedded Indium (In) nanoclusters (NCs) in silica under thermal annealing and ion irradiation was investigated. The In NCs were prepared by implantation of 890 keV indium ions in silica matrix at room temperature. Post implantation annealing resulted in the shifting of the size distribution to higher side. On the other hand 140 keV Nitrogen ion irradiation at elevated temperature resulted in the reduction of NCs size, with significant narrowing of the size distribution. The paper discusses the results of the study in the light of the models pertaining to the stability of NCs under ion irradiation conditions.

Structure and photoluminescence properties of ion beam synthesized SiC nanoparticles in Si.

Silicon carbide nanoparticles were synthesized in Si(100) wafers by 300 keV C+ ion implantation at elevated substrate temperatures of 550, 650 and 700 degrees C. The implantation has been carried out upto a fluence of 2 x 10(17) ions/cm2 with a constant current density 1.2 microA/cm2. GIXRD analysis on the implanted sample confirms the formation of 3C-SiC. XTEM studies of sample implanted at 650 degrees C show that size of SiC nanoparticles is 6 nm at a depth 0.6 microm from the sample surface. PL spectrum of sample implanted at different temperatures showed a peak at 2.45 eV and 2.3 eV and the intensity of PL peak increases with implantation temperature. The peak at 2.45 eV corresponds to blue shifted emission from SiC nanoparticles having size 6 nm. The peak at 2.3 eV is assigned to the SiC nanoparticles with enhanced d-value.

Antibacterial copper-nickel bilayers and multilayer coatings by pulsed laser deposition on titanium.

Biofouling, especially microfouling, is a major concern with the use of titanium (Ti) in the marine environment as a condenser material in cooling water systems. Earlier, copper-nickel (Cu/Ni) alloys were extensively used in marine environments due to their high corrosion and biofouling resistance. However, the choice of condenser material for the new fast breeder reactor in Kalpakkam is Ti to avoid steam side corrosion problems, which may pose a threat to steam generator parts having sodium as the secondary coolant. This study evaluates the surface modification of Ti using nano films of copper (Cu) and nickel (Ni) to utilize the antibacterial property of copper ions in reducing microfouling. The surface modification of Ti was carried out by the deposition of a Cu/Ni bilayer and (Cu/Ni)(10) multilayer films using a pulsed laser deposition technique. Various surface characterization studies revealed that the deposited Cu/Ni films were thin and nanocrystalline in nature. The antibacterial properties were evaluated using total viable count and epifluorescence microscopic techniques. The results showed an apparent decrease in bacterial attachment on multilayered and bilayered Cu/Ni thin films on Ti surfaces. Comparative studies between the two types of films showed a bigger reduction in numbers of microorganisms on the multilayers.

Blue luminescence of Au nanoclusters embedded in silica matrix.

Photoluminescence study using the 325 nm He-Cd excitation is reported for the Au nanoclusters embedded in SiO(2) matrix. Au clusters are grown by ion beam mixing with 100 KeV Ar(+) irradiation on Au [40 nm]/SiO(2) at various fluences and subsequent annealing at high temperature. The blue bands above approximately 3 eV match closely with reported values for colloidal Au nanoclusters and supported Au nanoislands. Radiative recombination of sp electrons above Fermi level to occupied d-band holes are assigned for observed luminescence peaks. Peaks at 3.1 and 3.4 eV are correlated to energy gaps at the X- and L-symmetry points, respectively, with possible involvement of relaxation mechanism. The blueshift of peak positions at 3.4 eV with decreasing cluster size is reported to be due to the compressive strain in small clusters. A first principle calculation based on density functional theory using the full potential linear augmented plane wave plus local orbitals formalism with generalized gradient approximation for the exchange correlation energy is used to estimate the band gaps at the X- and L-symmetry points by calculating the band structures and joint density of states for different strain values in order to explain the blueshift of approximately 0.1 eV with decreasing cluster size around L-symmetry point.