An improved goniometer head for high-temperature single-crystal X-ray diffraction

1999 ◽  
Vol 32 (4) ◽  
pp. 824-826 ◽  
Author(s):  
Patrice Delarue ◽  
Michel Jannin
Keyword(s):  
High Temperature ◽  
Data Collection ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Charge Coupled Device ◽  
X Ray ◽  
Space Saving ◽  
The Stability ◽  
Ccd Detectors ◽  
Goniometer Head

A reliable and inexpensive goniometer head has been designed. Its stability, resulting from its compact construction, makes it very suitable for accurate measurements. Moreover, its space-saving design facilitates its application in X-ray data collection using charge-coupled device (CCD) detectors. This head has been improved for high-temperature measurements and has been tested by comparison of accurate K0.88Rb0.12TiOPO4data collected both at room temperature and at 973 K on the same crystal. The excellent structure results obtained at 973 K during the 360 h of measurements prove the stability of the goniometer head.

Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

1988 ◽  
Vol 133 ◽  
Author(s):  
K. S. Kumar ◽  
S. K. Mannan
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
Crystalline Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

scholarly journals Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1141
Author(s):  
Georgia Basina ◽  
Hafsa Khurshid ◽  
Nikolaos Tzitzios ◽  
George Hadjipanayis ◽  
Vasileios Tzitzios
Keyword(s):  
Room Temperature ◽  
Colloidal Particles ◽  
Iron Pentacarbonyl ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
Organometallic Synthesis ◽  
X Ray ◽  
Transmission Electron ◽  
Hot Injection ◽  
The Stability

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids’ surface functionalization in a nonpolar solvent.

Phase Diagram of the W-doped Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 System Around a Morphotropic Phase Boundary Composition

2002 ◽  
Vol 17 (5) ◽  
pp. 1085-1091 ◽  
Author(s):  
W. Z. Zhu ◽  
M. Yan ◽  
A. L. Kholkin ◽  
P. Q. Mantas ◽  
J. L. Baptista
Keyword(s):  
High Temperature ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical Neutrality ◽  
Phase Boundary Composition ◽  
A Site ◽  
Successive Phase

The morphotropic phase boundary (MPB) composition that is characterized by the coexistence of rhombohedral and tetragonal phases in the Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 system was modified by W-doping at the B site of a perovskite structural block. To maintain the electrical neutrality, creation of A-site vacancies was intentionally introduced in the formulation of the examined compositions. Incorporation of W ions was revealed to stabilize the tetragonal phase against the rhombohedral one, shifting the MPB toward the PZN-rich end at room temperature. High-temperature x-ray diffraction examination in combination with dielectric measurements discloses two successive phase transitions as a sample is cooled from high temperature, namely, paraelectric cubic to ferroelectric rhombohedral followed by ferroelectric rhombohedral to ferroelectric tetragonal. W addition appears to suppress the first transition while promoting the second one.

scholarly journals Crystal Chemistry and Luminescence Properties of Eu-Doped Polycrystalline Hydroxyapatite Synthesized by Chemical Precipitation at Room Temperature

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 250 ◽  
Author(s):  
Francesco Baldassarre ◽  
Angela Altomare ◽  
Nicola Corriero ◽  
Ernesto Mesto ◽  
Maria Lacalamita ◽  
...  
Keyword(s):  
Fourier Transform ◽  
High Temperature ◽  
Inductively Coupled Plasma ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Inductively Coupled

Europium-doped hydroxyapatite Ca10(PO4)6(OH)2 (3% mol) powders were synthesized by an optimized chemical precipitation method at 25 °C, followed by drying at 120 °C and calcination at 450 °C and 900 °C. The obtained nanosized crystallite samples were investigated by means of a combination of inductively coupled plasma (ICP) spectroscopy, powder X-ray diffraction (PXRD), Fourier Transform Infrared (FTIR), Raman and photoluminescence (PL) spectroscopies. The Rietveld refinement in the hexagonal P63/m space group showed europium ordered at the Ca2 site at high temperature (900 °C), and at the Ca1 site for lower temperatures (120 °C and 450 °C). FTIR and Raman spectra showed slight band shifts and minor modifications of the (PO4) bands with increasing annealing temperature. PL spectra and decay curves revealed significant luminescence emission for the phase obtained at 900 °C and highlighted the migration of Eu from the Ca1 to Ca2 site as a result of increasing calcinating temperature.

Effect of Iron Substitution on the High-temperature Properties of Sm(Co,Cu,Ti)z Permanent Magnets

2001 ◽  
Vol 674 ◽  
Author(s):  
Jian Zhou ◽  
Ralph Skomski ◽  
David J. Sellmyer ◽  
Wei Tang ◽  
George C. Hadjipanayis
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Permanent Magnets ◽  
Site Occupancy ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Iron Substitution

ABSTRACTRecently, Ti-substituted Sm-Co permanent magnets have attracted renewed attention due to their interesting high-temperature coercivity. Our presentation deals with the effect of iron substitutions on the magnetic properties of the materials. X-ray diffraction shows that the investigated Sm(Co,Fe,Cu,Ti)z materials (z = 7.0 - 7.6) are two-phase magnets, consisting of 1:5 and 2:17 regions. The iron content affects both the coercivity and the magnetization. Depending on composition and heat treatment, some samples show a positive temperature coefficient of the coercivity in the temperature range from 22 °C to 550 °C. Moderate amounts of iron enhance the room-temperature coercivity. For example, the room-temperature coercivity of Sm(Co6.0Fe0.4Cu0.6Ti0.3) is 9.6 kOe, as compared to 7.6 kOe for Sm(Co6.4Cu0.6Ti0.3). At high temperatures, the addition of Fe has a deteriorating effect on the coercivity, which is as high as 10.0 kOe at 500 °C for Sm(Co6.4Cu0.6Ti0.3). The room-temperature magnetization increases on iron substitution, from 73 emu/g for Sm(Co6.4Cu0.6Ti0.3) to 78 emu/g for Sm(Co6.0Fe0.4Cu0.6Ti0.3). The observed temperature dependence is ascribed to the preferential dumbbell-site occupancy of the Fe atoms.

Thermal and Chemical Stability of Micron Aluminum Powders Subjected to Gaseous Water

2016 ◽  
Vol 712 ◽  
pp. 241-245
Author(s):  
Sergey V. Zmanovskiy ◽  
Alexander M. Gromov ◽  
Valentina V. Smirnova ◽  
Vadim F. Petrunin ◽  
Jin Chun Kim
Keyword(s):  
Room Temperature ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Aluminum Powders ◽  
X Ray ◽  
The Stability ◽  
Heating Up ◽  
The Impact ◽  
Thermal And Chemical Stability ◽  
Composition Of Products

The paper studies the impact of gaseous water on the stability of micron aluminum powders in time at room temperature using the method of gravimetric analysis. The stability was studied using methods of thermal analysis during heating up to 1200 °С in air. The composition of products was analyzed using X-ray diffraction analysis. It was found out that the stability of micron aluminum powders depends on partial pressure of water vapor: the increase of pressure results in decreased stability of powders. The work gives recommendations for storing micron aluminum powders.

High-pressure syntheses and crystal structures of orthorhombic DyGaO3 and trigonal GaBO3

2015 ◽  
Vol 70 (4) ◽  
pp. 207-214 ◽  
Author(s):  
Daniela Vitzthum ◽  
Stefanie A. Hering ◽  
Lukas Perfler ◽  
Hubert Huppertz
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
High Pressure High Temperature

AbstractOrthorhombic dysprosium orthogallate DyGaO3 and trigonal gallium orthoborate GaBO3 were synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 8.5 GPa/1350 °C and 8 GPa/700 °C, respectively. Both crystal structures could be determined by single-crystal X-ray diffraction data collected at room temperature. The orthorhombic dysprosium orthogallate crystallizes in the space group Pnma (Z = 4) with the parameters a = 552.6(2), b = 754.5(2), c = 527.7(2) pm, V = 0.22002(8) nm3, R1 = 0.0309, and wR2 = 0.0662 (all data) and the trigonal compound GaBO3 in the space group R3̅c (Z = 6) with the parameters a = 457.10(6), c = 1419.2(3) pm, V = 0.25681(7) nm3, R1 = 0.0147, and wR2 = 0.0356 (all data).

500℃ high-temperature reliability of Ni/Nb Ohmic contact on n-type 4H-SiC

2021 ◽  
Author(s):  
Vuong Van Cuong ◽  
Tadashi Sato ◽  
Takamichi Miyazaki ◽  
Tetsuya Meguro ◽  
Seiji Ishikawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Ohmic Contact ◽  
Chemical Compounds ◽  
Etching Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Current Voltage ◽  
The Stability

Abstract The reliability of Ni/Nb ohmic contact on n-type 4H-SiC at 500℃ was investigated. The current-voltage characteristics showed that, while the Ni(50)/Nb(50)/4H-SiC sample without applying the CF4:O2 etching process degraded just after 25-hour and lost ohmic behavior after 50-hour aging, the Ni(75)/Nb(25)/4H-SiC contact undergone CF4:O2 surface treatment still showed excellent stability after aging for 100 hours at 500℃. Though X-ray diffraction results indicated that the chemical compounds remained stable during the aging process, transmission electron microscopy showed that there was a redistribution of the chemical compounds at the interface of the contact after 500℃ aging. The depth distribution of the elements and energy dispersive X-ray analyses revealed that the contribution of carbon agglomeration at the interface accounted for the degradation of the sample without applying the etching process. Whereas the well-controlled excess carbon atoms of the contact undergone CF4:O2 treatment ensured the stability of this contact when operating at high-temperature ambient.

Behaviors of the Zr–1.0Sn–0.39Nb–0.31Fe–0.05Cr Alloy at High Temperature

2011 ◽  
Vol 399-401 ◽  
pp. 80-84
Author(s):  
Yi Yuan Tang ◽  
Jie Li Meng ◽  
Kai Lian Huang ◽  
Jian Lie Liang
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
High Temperature ◽  
Oxide Film ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thin Oxide Film ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Phase transformation of the Zr-1.0Sn-0.39Nb-0.31Fe-0.05Cr alloy was investigated by high temperature X-ray diffraction (XRD). The XRD results revealed that the alloy contained two precipitates at room temperature, namely β-Nb and hexagonal Zr(Nb,Fe,Cr,)2. β-Nb was suggested to dissolve into the α-Zr matrix at the 580oC. Thin oxide film formed at the alloy’s surface was identified as mixture of the monoclinic Zr0.93O2and tetragonal ZrO2, when the temperature reached to 750oC and 850 oC. The thermal expansion coefficients of αZr in this alloy was of αa = 8.39×10-6/°C, αc = 2.48×10-6/°C.

Sintering and Mechanical Properties of Chromium Boride - Chromium Carbide Composites

2007 ◽  
Vol 534-536 ◽  
pp. 1077-1080 ◽  
Author(s):  
Junichi Matsushita ◽  
Kenji Shimao ◽  
Yoshiyuki Machida ◽  
Takumi Takao ◽  
Kiyokata Iizumi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Chromium Carbide ◽  
Vickers Hardness ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Measurement Temperature ◽  
Advanced Material ◽  
X Ray ◽  
Chromium Boride

Several boride sintered bodies such as TiB2, ZrB2, and SiB6 were previously reported. In the present study, the sinterability and physical properties of chromium boride (CrB2) containing chromium carbide (Cr3C2) sintered bodies were investigated in order to determine its new advanced material. The samples were sintered at desired temperature for 1 hour in vacuum under a pressure by hot pressing. The relative density of sintered bodies was measured by Archimedes’ method. The relative densities of CrB2 addition of 0, 5, 10, 15 and 20 mass % Cr3C2 composites were 92 to 95 %. The Vickers hardness of the CrB2 with 10 and 15 mass % Cr3C2 composites were about 14 and 15 GPa at room temperature, respectively. The Vickers hardness at high temperature of the CrB2 addition of 10 mass % Cr3C2 composite decreased with increasing measurement temperature. The Vickers hardness at 1273 K of the sample was 6 GPa. The Vickers hardness of CrB2 addition of Cr3C2 composites was higher than monolithic CrB2 sintered body. The powder X-ray diffraction analysis detected CrB and B4C phases in CrB2 containing Cr3C2 composites.

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