scholarly journals Mechanoactivation of chromium silicide formation in the SiC-Cr-Si system

2002 ◽  
Vol 34 (3) ◽  
pp. 231-240 ◽  
Author(s):  
M. Vlasova ◽  
M. Kakazey ◽  
J.G. Gonzales-Rodriguez ◽  
G. Dominguez ◽  
Momcilo Ristic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silicon Carbide ◽  
High Pressure ◽  
High Temperature ◽  
Ir Spectroscopy ◽  
Phase Analysis ◽  
Temperature Treatment ◽  
Silicide Formation ◽  
X Ray ◽  
Chromium Silicide

The processes of simultaneous grinding of the components of a SiC-Cr-Si mixture and further temperature treatment in the temperature range 1073-1793 K were studied by X-ray phase analysis, IR spectroscopy, electron microscopy, and X-ray microanalysis. It was established that, during grinding of the mixture, chromium silicides form. A temperature treatment completes the process. Silicide formation proceeds within the framework of the diffusion of silicon into chromium. In the presence of SiO2 in the mixture, silicide formation occurs also as a result of the reduction of silica by silicon and silicon carbide. The sintering of synthesized composite SiC-chromium silicides powders at a high temperature under a high pressure (T = 2073 K, P = 5 GPa) is accompanied by the destruction of cc-SiC particles, the cc/3 transition in silicon carbide and deformation distortions of the lattices of chromium silicides.

Changes in the defect structure of diamond due to high temperature+ high pressure treatment

1975 ◽  
Vol 344 (1636) ◽  
pp. 111-130 ◽  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
High Temperature ◽  
Optical Absorption ◽  
Defect Structure ◽  
Pressure Treatment ◽  
High Pressure Treatment ◽  
X Ray ◽  
High Temperature High Pressure ◽  
Absorption Measurements

Type la and type IIa diamonds have been heated to temperatures in the range 2000-2300 °C under a pressure of about 4.8 GPa. The changes in the defect structure of these diamonds as a result of the heat treatm ent have been examined by optical absorption measurements, integrated X-ray spike measurements and by electron microscopy. Type la diamonds changed colour from colourless to yellow after being heated for 1 min in the temperature range 2250-2300 °C and it has been shown that the yellowing was due to scattering. The scattering centres responsible were elliptically shaped cracks in the cube planes with their longest dimension in a <110> direction

Synthesis, Structure and Dielectric Properties of Na2SnTeO6

1998 ◽  
Vol 547 ◽  
Author(s):  
J.-H. Park ◽  
P.M. Woodward ◽  
J.B. Parise ◽  
I. Lubomirsky ◽  
O. Stafsudd
Keyword(s):  
Dielectric Constant ◽  
High Pressure ◽  
High Temperature ◽  
Dielectric Properties ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Powder Diffraction Data ◽  
Ambient Conditions ◽  
X Ray ◽  
High Pressure High Temperature

AbstractA new perovskite was recovered from the high pressure-high temperature treatment of the α-TlSbO3 form of Na2SnTeO6 at 7 GPa and 950 °C for 30 minutes. Synchrotron x-ray powder diffraction data show the space group is P21/n with a=5.40361 (5), b=5.46152(5), c=7.69288(7) Å and ß=90.034(3)°. Using disk samples of both polymorphs, the dielectric properties were measured as a function of temperature. At ambient conditions, the perovskite form has a more than 1.5 fold enhancement in dielectric constant compared to the α-TlSbO3 form while the molar volume and the molecular polarizability decrease.

scholarly journals Al5B12O25(OH) and Ga4InB12O25(OH) – two additional triel borates with the structure type M5B12O25(OH) (M = Ga, In)

2020 ◽  
Vol 75 (6-7) ◽  
pp. 605-613
Author(s):  
Daniela Vitzthum ◽  
Daniel S. Wimmer ◽  
Ingo Widmann ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Ir Spectroscopy ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Type ◽  
Hydroxyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure High Temperature

AbstractThe isotypic triel borates Al5B12O25(OH) and Ga4InB12O25(OH) were synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 12.0 GPa/1400 °C and 12.3 GPa/1200 °C, respectively. The crystal structures of both compounds, determined by single-crystal X-ray diffraction, constitute new representatives of the structure type M5B12O25(OH) (M = Ga, In) crystallizing in the space group I41/acd. The presence of the hydroxyl groups was confirmed via single-crystal IR spectroscopy.

Behavior of carbon nanotubes under high pressure and high temperature

2000 ◽  
Vol 15 (2) ◽  
pp. 560-563 ◽  
Author(s):  
D. S. Tang ◽  
L. C. Chen ◽  
L. J. Wang ◽  
L. F. Sun ◽  
Z. Q. Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
High Pressure ◽  
High Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diamond Crystallization ◽  
Graphite Sheets

The structural changes of carbon nanotubes induced by high pressure and high temperature were investigated by means of x-ray diffraction, Raman scattering, scanning electron microscopy, and transmission electron microscopy. It is shown that, with increasing pressure and temperature, the lattice constant d002 of tubes shortens, and then tubes collapse into tapelike ones; at the same time the C–C bonds at high curvature break, which lead the tapelike tubes to break into graphite sheets as diamond crystallization centers. Compared with graphite, the diamond particles from carbon nanotubes have many defects as the trace of tubes.

scholarly journals Synthesis and Physicochemical Study of Xanthan Butyl Ether

2021 ◽  
pp. 137-146
Author(s):  
Aleksandr S. Kazachenko ◽  
Olga Yu. Fetisova ◽  
Aleksandr V. Antonov ◽  
Galina N. Bondarenko ◽  
Valentine V. Sychev
Keyword(s):  
Electron Microscopy ◽  
Thermal Analysis ◽  
Scanning Electron Microscopy ◽  
Ir Spectroscopy ◽  
Phase Analysis ◽  
Elemental Analysis ◽  
Butyl Ester ◽  
Butyl Ether ◽  
X Ray ◽  
Scanning Electron

Xanthan is an important polysaccharide widely used in many industrial fields. It is produced by the bacteria Xanthomonascampestris. Chemical modification of xanthan can open up new horizons for its use. In this work, xanthan butyl ester was obtained for the first time by the interaction of xanthan and bromobutane using sodium hydroxide as a catalyst. The composition and structure of the obtained new xanthan derivative was studied by elemental analysis, IR spectroscopy, X-ray phase analysis, scanning electron microscopy and thermal analysis. The introduction of a butyl group into the xanthan molecule was proved by elemental analysis and IR spectroscopy by the appearance of corresponding bands. It was shown by X-ray phase analysis that xanthan butyl ether has a more X-ray amorphous structure in comparison with the original xanthan. It was shown by scanning electron microscopy that xanthan butyl ether powder consists of particles of a larger size and a layered structure in comparison with the original xanthan. It has been shown by thermal analysis that xanthan butyl ether is less thermostable than the starting xanthan

Effect of high pressure-temperature on silicon layered structures as determined by X-ray diffraction and electron microscopy

2004 ◽  
Vol 27 (1-3) ◽  
pp. 415-418
Author(s):  
J. Bak-Misiuk ◽  
A. Misiuk ◽  
J. Ratajczak ◽  
A. Shalimov ◽  
I. Antonova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Layered Structures ◽  
X Ray Diffraction ◽  
X Ray

Hydrolytic products of Fe(III) after oxidation of Fe(II) by chlorate

1982 ◽  
Vol 47 (4) ◽  
pp. 1069-1077 ◽  
Author(s):  
Karel Mádlo ◽  
František Hanousek ◽  
Antonín Petřina ◽  
Jaroslav Tláskal
Keyword(s):  
Electron Microscopy ◽  
Ir Spectroscopy ◽  
Chemical Analysis ◽  
Ferrous Sulphate ◽  
Reaction Medium ◽  
Potassium Chlorate ◽  
X Ray Diffraction ◽  
X Ray

Ferrous sulphate was oxidized by potassium chlorate in the pH region 2-7 and at temperatures ranging from 298.1 to 323.1 K and various hydrolytic products of Fe(III) were separated and indentified. The separated solid ferric products were analyzed using a combination of the chemical analysis, IR spectroscopy, X-ray diffraction, and electron microscopy. The following substances were found as major components of the products: Fe2O3.n H2O ("ferric gel"), Fe2O3.n H2O with bound SO2-4 ions ("sulphogel"), α-FeO(OH), γ-FeO(OH) and Fe3O4. Their amount depends particularly on the pH temperature of the reaction medium.

scholarly journals High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

2019 ◽  
Vol 74 (4) ◽  
pp. 357-363
Author(s):  
Daniela Vitzthum ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
X Ray ◽  
Mixed Cation ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe mixed cation triel borate Ga4In4B15O33(OH)3 was synthesized in a Walker-type multianvil apparatus at high-pressure/high-temperature conditions of 12.5 GPa and 1300°C. Although the product could not be reproduced in further experiments, its crystal structure could be reliably determined via single-crystal X-ray diffraction data. Ga4In4B15O33(OH)3 crystallizes in the tetragonal space group I41/a (origin choice 2) with the lattice parameters a = 11.382(2), c = 15.244(2) Å, and V = 1974.9(4) Å3. The structure of the quaternary triel borate consists of a complex network of BO4 tetrahedra, edge-sharing InO6 octahedra in dinuclear units, and very dense edge-sharing GaO6 octahedra in tetranuclear units.

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