High-Pressure, High-Temperature Synthesis of Superhard Boron Suboxide

1995 ◽  
Vol 410 ◽  
Author(s):  
H. Hubert ◽  
L. A. J. Garvie ◽  
K. Leinenweber ◽  
P. R. Buseck ◽  
W. T. Petuskeyt ◽  
...  
Keyword(s):  
Pressure Range ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
X Ray ◽  
High Temperature Synthesis ◽  
Transmission Electron ◽  
High Pressure High Temperature ◽  
Boron Suboxide ◽  
Electron Energy Loss ◽  
Rhombohedral Boron

ABSTRACTA multianvil device was used to investigate the formation of BxO phases produced in the 2 to 10 GPa pressure range with temperatures between 1000 and 1800 °C.Amorphous and crystalline B and BP were oxidized using B2O3 and CrO3. Using powder X-ray diffraction and parallel electron energy-loss spectroscopy (PEELS), we were unable to detect graphitic or diamondstructured B2O, reported in previous studies. The refractory boride B6O, which has the α-rhombohedral boron structure, is the dominant suboxide in the P and T range of our investigation. PEELS with a transmission electron microscope was used to characterize the boron oxides.

Effect of NaCl on Synthesis of Si-SiC Nanocomposites by Self Propagating High Temperature Synthesis

2013 ◽  
Vol 664 ◽  
pp. 449-453 ◽  
Author(s):  
Sutham Niyomwas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Nano Composite ◽  
Argon Gas ◽  
X Ray ◽  
High Temperature Synthesis ◽  
Transmission Electron ◽  
Scanning Electron

The Si-SiC nanocomposites have been synthesized by self-propagating high temperature synthesis (SHS) from natural precursors. The effects of difference amount of added NaCl from 0 to 0.75 moles to the reactants on the Si-SiC conversion and particle size were investigated. The reaction were carried out in a SHS reactor under static argon gas at the pressure of 0.5 MPa. The nanocomposite results have been characterized by scanning electron microscope, Transmission Electron Microscopy and X-ray diffraction. The results showed that the production of nano-composite materials using SHS process is feasible and agree well with the thermodynamics calculations.

High-Pressure, High-Temperature Syntheses of Super-Hard α-Rhombohedral Boron-rich Solids in the B-C-N-O

1997 ◽  
Vol 499 ◽  
Author(s):  
Hervé Hubert ◽  
Laurence A.J. Garvie ◽  
Bertrand Devouard ◽  
Paul F. McMillan
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
High Pressures ◽  
X Ray Diffraction ◽  
Intermediate Phases ◽  
Transmission Electron ◽  
High Pressure High Temperature ◽  
Boron Suboxide ◽  
Quantitative Analyses ◽  
Electron Energy Loss

ABSTRACTWe prepared α-rhombohedral (α-rh.) B-rich materials in the B-C-N-O system at high-pressures and temperatures. Samples were synthesized using a multianvil device and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and parallel electron energy-loss spectroscopy (PEELS). The B-C-O compounds were obtained by reducing B2O3 with B, or mixtures of B and C between 1 to 10 GPa and 1200° and 1800° C In the B-O system we synthesized boron suboxide (nominally B6O) of high purity, crystallinity, and close to stoichiometric. Quantitative analyses give B6O0.95 and B6O0.77 for high-pressure and room-pressure samples, respectively. Between 4 to 5.5 GPa, B6O formed as macroscopic near-perfect regular icosahedra (to 30 μm in diameter). In the B-C-O system, intermediate phases were prepared showing evidence of solid solution between B4C and B6O. Boron carbide crystals, to 20 μm, containing a significant amount of O, typically B6C1.1O0.33 and B6C1.28O0.31, were grown for mixtures in which B and C were reacted with excess B2O3 at 7.5 GPa and 1700 °C. We also report the first conclusive bulk synthesis of a new boron nitride, B6N1-x. This subnitride was synthesized from B and hexagonal BN at 7.5 GPa and 1700 °C. XRD and PEELS shows that the boron subnitride has the α-rh. B structure and average composition B6N0.92

scholarly journals High-pressure synthesis of SmGe3

2020 ◽  
Vol 235 (8-9) ◽  
pp. 333-339
Author(s):  
Julia-Maria Hübner ◽  
Wilder Carrillo-Cabrera ◽  
Raul Cardoso-Gil ◽  
Primož Koželj ◽  
Ulrich Burkhardt ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Temperature Synthesis ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Unknown Phase ◽  
High Temperature Synthesis ◽  
Transmission Electron ◽  
High Pressure High Temperature ◽  
Pressure Synthesis

AbstractThe new samarium germanide SmGe3 is obtained by high-pressure high-temperature synthesis of pre-reacted mixtures of samarium and germanium at a pressure of 9.5 GPa and temperatures between 1073 and 1273 K. SmGe3 decomposes at 470(5) K into SmGe2, α-Sm3Ge5 and a hitherto unknown phase. SmGe3 exhibits a superstructure of the cubic Cu3Au-type. Transmission electron microscopy measurements of crystalline particles and prepared lamellae indicate a high density of defects on the nanoscale. Selected area electron diffraction and elaborate X-ray powder diffraction measurements consistently indicate a 2a0 × 2a0 × 2a0 superstructure adopting space group $Fm\overline{3}m$ with a = 8.6719(2) Å.

Low-Temperature Synthesis of Nano-Crystalline ZnTiO3 Powders by Aqueous Sol-Gel Process

2014 ◽  
Vol 543-547 ◽  
pp. 3741-3744
Author(s):  
Quan Jing Mei ◽  
Cong Ying Li ◽  
Jing Dong Guo ◽  
Gui Wang ◽  
Hai Tao Wu
Keyword(s):  
Sol Gel ◽  
Zinc Nitrate ◽  
X Ray Diffraction ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Calcination Process ◽  
X Ray ◽  
Nano Crystalline ◽  
Transmission Electron ◽  
Sol Gel Process

The ecandrewsite-type ZnTiO3was successfully synthesized by the aqueous sol-gel method using TiO2dioxide and zinc nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized ZnTiO3powders were successfully obtained at 850 °C with particle size ~50 nm. By comparison, the aqueous sol-gel process was the most effective and least expensive technique used for the preparation of ZnTiO3nanopowders.

scholarly journals Intermetallic/Ceramic Composites Synthesized from Al–Ni–Ti Combustion with B4C Addition

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 873
Author(s):  
Chun-Liang Yeh ◽  
Chih-Yao Ke
Keyword(s):  
Combustion Velocity ◽  
Ceramic Composites ◽  
The Other ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Reaction Systems ◽  
X Ray ◽  
High Temperature Synthesis ◽  
In Situ Formation

The fabrication of intermetallic/ceramic composites by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) was investigated in the Al–Ni–Ti system with the addition of B4C. Two reaction systems were employed: one was used to produce the composites of xNiAl–2TiB2–TiC with x = 2–7, and the other was used to synthesize yNi3Al–2TiB2–TiC with y = 2–7. The reaction mechanism of the Al–Ni–Ti system was strongly influenced by the presence of B4C. The reaction of B4C with Ti was highly exothermic, so the reaction temperature and combustion velocity decreased due to increasing levels of Ni and Al in the reactant mixture. The activation energies of Ea = 110.6 and 172.1 kJ/mol were obtained for the fabrication of NiAl- and Ni3Al-based composites, respectively, by the SHS reaction. The XRD (X-ray diffraction) analysis showed an in situ formation of intermetallic (NiAl and Ni3Al) and ceramic phases (TiB2 and TiC) and confirmed no reactions taking place between Ti and Al or Ni. The microstructure of the product revealed large NiAl and Ni3Al grains and small TiB2 and TiC particles. With the addition of TiB2 and TiC, the hardness of NiAl and Ni3Al was considerably increased and the toughness was also improved.

A Study of Fe-Based Composite Coating Fabricated by the Self-Propagating High Temperature Synthesis

2012 ◽  
Vol 626 ◽  
pp. 138-142
Author(s):  
Saowanee Singsarothai ◽  
Vishnu Rachpech ◽  
Sutham Niyomwas
Keyword(s):  
High Temperature ◽  
Composite Coating ◽  
Steel Substrate ◽  
The Self ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
X Ray ◽  
High Temperature Synthesis ◽  
Precursor Powders ◽  
Scanning Electron

The steel substrate was coated by Fe-based composite using self-propagating high-temperature synthesis (SHS) reaction of reactant coating paste. The green paste was prepared by mixing precursor powders of Al, Fe2O3and Al2O3. It was coated on the steel substrate before igniting by oxy-acetylene flame. The effect of coating paste thickness and the additives on the resulted Fe-based composite coating was studied. The composite coating was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) couple with dispersive X-ray (EDS).

Effect of CaF2 in Precursors on Steel Pipe Lined Fe-Al Intermetallic-TiB2-Al2O3 Composite Coating by Centrifugal-SHS Process

2012 ◽  
Vol 488-489 ◽  
pp. 468-472 ◽  
Author(s):  
Pajaree Kerdkool ◽  
Sutham Niyomwas
Keyword(s):  
Energy Minimization ◽  
Standard Gibbs Energy ◽  
Raw Materials ◽  
Steel Pipe ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Minimization Method ◽  
X Ray ◽  
High Temperature Synthesis ◽  
Centrifugal Shs

Steel pipe lined Fe-Al intermetallic-TiB2-Al2O3composite were prepared by centrifugal-self-propagating high temperature synthesis (centrifugal-SHS) process from FeTiO3, B2O3, Fe2O3, Al and CaF2as raw materials. The standard Gibbs energy minimization method was used to calculate the equilibrium compositions of the reacting species. The effect of adding CaF2to the precursors on the result product were investigated. The phase separation between less porosity Fe-Al intermetallics-TiB2with Al2O3layer were affected greatly by adding CaF2. The phase compositions and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) couple with energy dispersive X-ray (EDX), respectively.

Fabrication of boron carbonitride (BCN) nanotubes and giant fullerene cages

2010 ◽  
Vol 88 (12) ◽  
pp. 1256-1261 ◽  
Author(s):  
Guifang Sun ◽  
Faming Gao ◽  
Li Hou
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
The Novel ◽  
X Ray Diffraction ◽  
Boron Carbonitride ◽  
X Ray ◽  
Transmission Electron ◽  
New Form ◽  
First Time ◽  
Electron Energy Loss

Boron carbonitride (BCN) nanotubes have been successfully prepared using NH4Cl, KBH4, and ZnBr2 as the reactants at 480 °C for 12 h by a new benzene-thermal approach in a N2 atmosphere. As its by-product, a new form of carbon regular hexagonal nanocages are observed. The samples are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), transmission electron diffraction (TED), electron energy loss spectroscopy (EELS), and high-resolution transmission electron microscopy (HRTEM). The prepared nanotubes have uniform outer diameters in the range of 150 to 500 nm and a length of up to several micrometerss. The novel carbon hexagonal nanocages have a typical size ranging from 100 nm to 1.5 µm, which could be the giant fullerene cages of [Formula: see text] (N = 17∼148). So, high fullerenes are observed for the first time. The influences of reaction temperature and ZnBr2 on products and the formation mechanism of BCN nanotubes are discussed.

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