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Query: UMLS:C0276640 (TEM)
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This paper introduces the composition of Castabe Glass-Ceramic (CGC), synthetic technique and physical and chemical properties. By means of TEM, SEM, XRD and EPMA techniques, the structure of CGC on K2O-MgO-Al2O-SiO2-F glass, type and size of crystallization are investigated. The results are as follows: the main crystal phase is tetrasilicic flourmica (K2Mg2.5Si4-O10F2), refractive index = 1.53, transparency = 48%, Density = 2.7 g/cm3, elastic modulus = 68.22 GPa, breaking strength = 141.1 MPa, breaking durability = 1.83 and V. H. = 505 kg/mm2. Base the above properties described, the function of CGC is similar to the Dicor (Dentsply. Int. U. S. A.) which is one of the well known material in western countries in now days.
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PMID:[Castable glass-ceramic-synthesizing and testing]. 181 64

Single crystal MgO specimens having low load Vickers indentations were thinned in an ion milling machine employing a single ion gun, and their characteristics were investigated with optical microscopy and high voltage electron microscopy (HVEM). It was found that the state of cleanliness of the specimen chamber of the ion milling machine had a very marked influence on the quality of the thinned specimens. If the specimen chamber was not well cleaned before ion milling a fresh specimen, the latter tended to show amorphisation due to the deposition on the specimen of the debris left in the chamber from the previously ion-milled specimens. Such observations were made from MgO specimens ion milled in several different types of commercial ion milling machine employing a single gun. It is proposed that to obtain good-quality ion milled TEM specimens, it is important to clean the specimen chamber thoroughly prior to milling.
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PMID:Amorphisation of MgO single crystal specimens prepared by ion milling for transmission electron microscopy studies. 239 63

Diopside ceramic pellets with a nominal composition of 55.5 wt % SiO(2)-25.9 wt % CaO-18.0 wt % MgO were soaked in human parotid saliva (HPS) over different time intervals, to investigate the behavior of the material in a natural medium of high protein content. The results showed the formation of a hydroxyapatite (HA)-like layer on the surface of the ceramic, and suggested that the mechanism of HA-like layer formation in saliva was similar to that showed in vitro test by other silica-based materials. The HA-like layer formed at the interface was found to be compact, continuous, and composed of many small crystallites with ultrastructure similar to that of natural cortical bone and dentine. The study concluded that the high pH conditions (9.8) existing right at the ceramic/human parotid saliva interface promoted HA-like phase precipitation. At this stage of the study, it is possible to suggest that the diopside ceramic could be of interest in specific periodontal applications for bone restorative purposes. Morphology, structure, and composition of the interfacial reaction product were examined by Scanning and Transmission Electron Microscopy techniques (SEM and TEM), combined with Energy Dispersive X-say Spectroscopy (EDS). Changes in ionic concentrations were measured using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), while the pH right at the interface of diopside/PHS were determined with an Ion Sensitive Field Effect Transistor (ISFET-Meter) instruments.
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PMID:Bioactivity of diopside ceramic in human parotid saliva. 1573 73

Magnesium oxide thin films have been deposited with use of single source chemical vapor deposition (SSCVD). The resultant films were examined by using transmission electron microscopy, X-ray texture analysis, and pole figure analysis. Due to the nature of the chemical reactions occurring at the surface during SSCVD growth, which result in a high growth rate/low flux environment, films of (111) orientation have been achieved without an amorphous underlayer, an unusual result for films of this orientation. Moreover the films have a strong degree of biaxial texturing in the x-y plane as found with X-ray texture analysis. These findings have important implications for buffer layers in perovskite thin film devices. The mechanism producing these structures has been revealed by using TEM and is discussed here.
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PMID:Growth mechanism of textured MgO thin films via SSCVD. 1667 39

The interaction of water and methanol with MgO samples with different distributions of oxide ions of low coordination has been investigated by physical techniques, particularly in situ photoluminescence. First, the three photoluminescence fingerprints of oxide ions vs their coordination number have been obtained for samples outgassed at 1273 K. By a pseudo quantitative approach, the relative distribution of the oxide ions of low coordination O(2-)LC (where LC = 3C, 4C, and 5C refer to tri-, tetra-, and pentacoordinated oxide ions, respectively) was determined and correlated with the shape and size of MgO particles determined by TEM and XRD. The photoluminescence of surfaces of MgO obtained after outgassing at increasing temperature or after interaction of water or methanol with a clean surface, i.e., obtained by outgassing at 1273 K, was then studied and evidenced three other photoluminescent species assigned to surface OH groups. The nature and mechanism of formation of the hydroxyls groups responsible for these new luminescent species are discussed in relation with their thermal stability and FTIR experiments.
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PMID:Physicochemical and in situ photoluminescence study of the reversible transformation of oxide ions of low coordination into hydroxyl groups upon interaction of water and methanol with MgO. 1685 Dec 35

We report what we believe is the first cw quasi-phase-matched intracavity frequency doubling of a diode-pumped 946-nm Nd:YAG laser by use of bulk periodically poled MgO-LiNbO(3). A maximum second-harmonic power of 5.9 mW was obtained at a laser diode power of 500 mW. The blue beam profile showed a TEM(00) single spatial mode of low ellipticity (1:1) because there was no walk-off problem. Bulk periodic domain inversion was accomplished by a corona discharge method with a first-order modulation period of 4.75 microm for a wavelength of 946 nm over a 2-mm interaction length in Z-cut 0.4-mm-thick MgO-LiNbO(3).
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PMID:Intracavity frequency doubling of a diode-pumped 946-nm Nd:YAG laser with bulk periodically poled MgO LiNbO(3). 1818 68

Cobalt oxide-modified mesoporous CeO(2), ZrO(2), and MgO oxides and their SBA-15 silica analogues were prepared and characterized by XRD, TEM, N(2) physisorption, FTIR, and TPR-TG analysis. Their catalytic activity in methanol decomposition to CO and hydrogen was tested. The support effect on the state and catalytic behavior of the loaded cobalt oxide nanoparticles is discussed. The best catalytic activity and selectivity of methanol decomposition to CO and hydrogen are registered for Co/CeO(2).
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PMID:Cobalt-modified mesoporous MgO, ZrO2, and CeO2 oxides as catalysts for methanol decomposition. 1921 34

We present a stable, high-power, cw, single-frequency green source in a compact and practical design based on a simple single-pass second-harmonic generation of a cw ytterbium fiber laser at 1064 nm in MgO-doped periodically poled stoichiometric LiTaO(3). Using a 30-mm-long crystal containing a single grating, we have generated 9.64 W of cw radiation at 532 nm with a fundamental power of 29.5 W at a single-pass conversion efficiency of 32.7%. The output power is naturally stable with a peak-to-peak fluctuation of 7.6% over the first 8 h and 9% over 13 h. Over the entire range of fundamental powers, the generated green output is single frequency with an instantaneous linewidth of 6.5 MHz and frequency stability of <32 MHz over 30 min and has a TEM(00) spatial profile with M(2)<1.33.
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PMID:Stable, 9.6 W, continuous-wave, single-frequency, fiber-based green source at 532 nm. 1944 21

We report a high-power, cw, singly resonant optical parametric oscillator (SRO) using a simple, compact fiber pump laser architecture in the green. The SRO, based on MgO:sPPLT, is pumped by 9.6 W of single-frequency cw radiation at 532 nm obtained by single-pass second-harmonic generation (SHG) of a 30 W Yb fiber laser, also in MgO:sPPLT. Using two identical crystals of 30 mm length for SHG and SRO, we generate cw idler powers of up to 2 W over 855-1408 nm, with a peak-to-peak power stability <11.7% over 40 min, in a TEM(00) spatial mode with M(2)<1.26. Using finite output coupling of the resonant wave, we extract 800 mW of signal power with peak-to-peak power stability <10.7% over 40 min, and a frequency stability <75 MHz over 15 min. The signal and idler output have TEM(00) beam profile with M(2)<1.52 across the tuning range.
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PMID:Continuous-wave optical parametric oscillator pumped by a fiber laser green source at 532 nm. 1964 62

The processing conditions to prepare nano-sized Cu and Mo dispersed Al2O3 (Al2O3/Cu and Al2O3/Mo) composites by pressureless sintering were explored. The composite powders of Al2O3/Cu and Al2O3/Mo were obtained by the hydrogen reduction of Al2O3/CuO and Al2O3/MoO3 powder mixtures and consolidated by pressureless sintering using infrared heating furnace with a heating rate of 200 degrees C/min. SEM and TEM analyses for the composite showed that the nano-sized metal particles were well distributed and situated on the grain boundaries of the Al2O3 matrix. The nanocomposites, sintered at 1300 to 1500 degrees C for 4 min, showed the relative density of above 90%. Maximum hardness of 16.1 GPa was obtained in Al2O3/Cu nanocomposites with sintering additive of 1 wt% MgO. The sintered nanocomposites exhibited the enhanced fracture toughness of above 4.5 MPa x m(1/2), compared with monolithic Al2O3. The mechanical properties were discussed in terms of observed microstructural characteristics.
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PMID:Fabrication of alumina-based metal nanocomposites by pressureless sintering and their mechanical properties. 2035 63


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