Preparation of silicon boride SiBx (x = 3, 4, 5, 6) powders by chemical oven self-propagating combustion synthesis

2020 ◽  
Vol 111 (10) ◽  
pp. 792-798
Author(s):  
W. Liu ◽  
P. Feng ◽  
X. Ren ◽  
L. Zhu
Keyword(s):  
Combustion Synthesis ◽  
Combustion Temperature ◽  
Exothermic Reaction ◽  
Synthesis Process ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Quantitative Results ◽  
Adiabatic Combustion Temperature ◽  
Diffraction Peaks ◽  
Time And Energy

Abstract A new method was developed for quickly preparing a highemissivity silicon boride compound of SiBx (x = 3, 4, 5, 6) by highly exothermic Ti-TiO2-Si-Al chemical oven preheating. The SiBx combustion synthesis process and adiabatic combustion temperature were investigated. A large exothermic reaction occurred at the combustion temperature of 1 700 K. X-ray diffraction results indicate that an SiBx phase and a substantial amount of unreacted Si were identified in the products. By increasing the boron content until the Si-B ratio reached to 1 : 6, the diffraction peaks primarily indicated SiB6, SiB4, and Si11B33 in the final product. According to the spectra and quantitative results, the atomic chemical composition ratio of Si and B was close to the nominal composition. Thus, this method offers an efficient way to produce Si-B compounds with less time and energy consumption than current methods.

In Situ X-Ray Diffraction of an Arc Weld Showing the Phase Transformations of Ti and Fe as a Function of Position in the Weld Performed at a Synchrotron

1993 ◽  
Vol 37 ◽  
pp. 479-482 ◽  
Author(s):  
Joe Wong ◽  
J. W. Elmer ◽  
P. A. Waide ◽  
E. M. Larson
Keyword(s):  
Combustion Synthesis ◽  
Ferroelectric Material ◽  
Bragg Diffraction ◽  
Intermediate Species ◽  
X Ray Diffraction ◽  
Synchrotron Source ◽  
X Ray ◽  
Subsequent Phase ◽  
Diffraction Peaks

The synchrotron x-ray source provides a unique opportunity to observe many “in-situ” processes. The formation of the “short-lived” intermediate species, Ta2C, during the combustion synthesis of TaC, has been observed and reported by monitoring the Bragg diffraction peaks of the reactants and products, Similarly, the synthesis of the ferroelectric material, BaTiO3, and subsequent phase transfonnation from cubic to tetragonal have also been investigated. These experiments would not have been possible without the high incident x-ray flux available at a synchrotron source.

A time-resolved diffraction study of the Ta–C solid combustion system

1993 ◽  
Vol 8 (7) ◽  
pp. 1533-1541 ◽  
Author(s):  
E.M. Larson ◽  
Joe Wong ◽  
J.B. Holt ◽  
P.A. Waide ◽  
G. Nutt ◽  
...  
Keyword(s):  
Combustion Synthesis ◽  
Carbon Diffusion ◽  
Time Frame ◽  
Combustion System ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Reaction Proceeds ◽  
Diffraction Peaks ◽  
Product Powder

The formation of TaC and Ta2C by combustion synthesis from their elemental constituents has been studied by time-resolved x-ray diffraction (TRXRD) using synchrotron radiation. The reactions have been followed with a time resolution down to 50 ms. Since the adiabatic temperatures for both reactions are well below any liquidus temperature in the Ta—C phase diagram, no melting occurs and these combustion reactions occur purely in the solid state. The phase transformations associated with these reactions are followed by monitoring the disappearance of reactant and appearance of product powder diffraction peaks in real time as the reaction front propagates through the combusting specimen. In the synthesis of TaC, the results show the formation of the subcarbide (Ta2C phase as an intermediate. In the synthesis of Ta2C, the reaction proceeds directly to the product with no discernible intermediate Ta–C phase within a 50 ms time frame. The chemical dynamics associated with the combustion synthesis of TaC may be described by an initial phase transformation to hexagonal Ta2C arising from carbon diffusion into the Ta metal lattice. As more carbon is available this intermediate subcarbide phase, which has one-half of its octahedral interstices occupied by the carbon, further transforms to the cubic TaC final product, in which all octahedral sites are now occupied. The time-resolved data indicate that the rate of formation of Ta2C is a factor of two faster than that of TaC.

The combustion synthesis of the ferroelectric material, BaTiO3, studied by time-resolved X-ray diffraction

1999 ◽  
Vol 14 (2) ◽  
pp. 111-113 ◽  
Author(s):  
E. M. Larson ◽  
Joe Wong ◽  
J. B. Holt ◽  
P. A. Waide ◽  
B. Rupp
Keyword(s):  
Combustion Synthesis ◽  
Ferroelectric Material ◽  
Bragg Diffraction ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Tetragonal Form ◽  
Diffraction Peaks ◽  
The Common

The combustion synthesis of the common ferroelectric material, BaTiO3, was developed using the stoichiometry: BaO2+0.2 Ti+0.8 TiO2→BaTiO3+0.3 O2. An adiabatic temperature, Tad, of the reaction was calculated from known thermodynamic data to be 1917 °C. Real time chemical changes in the formation of BaTiO3 during the reaction have been monitored using time-resolved X-ray diffraction with synchrotron radiation as the X-ray source. A time resolution of 250 ms was achieved. The combustion synthesis of BaTiO3 was followed by observing the intensities of reactant and product Bragg diffraction peaks in order to qualitatively identify the phases present. Because BaTiO3 forms initially as a cubic phase, X-ray diffraction of the product was monitored for a period of 20 min after the reaction to observe the phase transformation to the tetragonal form. This transformation is evident in these post-reaction scans as the cubic 110 and 220 peaks are split to the tetragonal 101/110 and 202/220 ones, respectively.

Synthesis of Hydraulically Active Calcium Silicates Produced by Combustion Methods

2015 ◽  
Vol 1768 ◽  
Author(s):  
Juan C. Restrepo ◽  
Andrés Chavarriaga ◽  
Oscar J. Restrepo ◽  
Jorge I. Tobón
Keyword(s):  
High Temperature ◽  
Portland Cement ◽  
Combustion Synthesis ◽  
Exothermic Reaction ◽  
Cement Industry ◽  
Synthesis Process ◽  
Synthesis Methods ◽  
Processing Plant ◽  
Dry Process ◽  
Calcium Silicates

ABSTRACTPortland cement is synthesized from a mixture of limestone and clay at high temperature (1450 °C) via a conventional process (solid-phase synthesis), in which partial fusion of raw materials and the formation of clinker nodules are produced. The clinker is mixed with a small percentage of gypsum and ground together to make the cement. This synthesis process holds the cement industry accountable for 5–8% of global anthropogenic CO2 emissions. The production of a ton of cement emits between 0.62 and 0.97 tons of CO2 into the atmosphere, depending on the processing plant. Furthermore, the use of fossil fuels in cement production is another important factor in the environmental impact of this industry. The production of 1 ton of clinker consumes approximately 5.86 GJ per tons of clinker produced in wet processes and 3.35 GJ per tons of clinker produced by dry process. Some researches have reported the possibility to obtain silicate and aluminate cements by alternative synthesis methods, which optimize both time and temperature, such as Pechini method, sol-gel method and microwave assisted method. The combustion methods, another alternative, are chemical redox processes in which the use of chemical precursors and organic fuels at high temperature generate a self-sustaining fastwave. The said wave is characterized by the fact that once the initial exothermic reaction starts, it generates a reaction wave (0.1–10 cm/s) at high temperature (1000–3000 °C) that propagates, in a self-sustaining way, through the heterogeneous mixture which leads to the formation of the solid material. For this reason, and the irreplaceable role of cement in the construction industry, this paper shows the advances in the production of silicates, similar to those found in the Portland cement, by combustion synthesis method.This paper shows the production of calcium silicates similar to the silicates of Portland cement, by combustion synthesis. Thermal analysis and XRD techniques were used to compare the syhthetized silicates with alite and belite of Portland cement.

scholarly journals Optical, Structural, Morphological Properties of Chromium (III) Oxide Nanostructure Synthesized Using Spray Pyrolysis Technique

2021 ◽  
Vol 19 (51) ◽  
pp. 79-86
Author(s):  
Fatin Hameed Mohammed ◽  
Haitham M. Mikhlif
Keyword(s):  
Spray Pyrolysis ◽  
Chromium Oxide ◽  
Spray Pyrolysis Technique ◽  
Morphological Properties ◽  
Synthesis Process ◽  
Rhombohedral Structure ◽  
X Ray Diffraction ◽  
Glass Substrates ◽  
Cr2o3 Nanoparticles ◽  
Diffraction Peaks

Nanostructure of chromium oxide (Cr2O3-NPs) with rhombohedral structure were successfully prepared by spray pyrolysis technique using Aqueous solution of Chromium (III) chloride CrCl3 as solution. The films were deposited on glass substrates heated to 450°C using X-ray diffraction (XRD) shows the nature of polycrystalline samples. The calculated lattice constant value for the grown Cr2O3 nanostructures is a = b = 4.959 Å & c = 13.594 Å and the average crystallize size (46.3-55.6) nm calculated from diffraction peaks, Spectral analysis revealed FTIR peak characteristic vibrations of Cr-O Extended and Two sharp peaks present at 630 and 578 cm-1 attributed to Cr-O “stretching modes”, are clear evidence of the presence of crystalline Cr2O3. The energy band gap (3.4 eV) for the chromium oxide nanostructures was measured using the UV-VIS-NIR Optical Spectrophotometer. It was found that by scanning electron microscopy (SEM) and image results, there is a large amount of nanostructure with an average crystal size of 46.3-55.6 nm, which indicates that our synthesis process is a successful method for preparing Cr2O3 nanoparticles.

Combustion synthesis of ultrafine tungsten carbide powder

2008 ◽  
Vol 23 (9) ◽  
pp. 2393-2397 ◽  
Author(s):  
H.I. Won ◽  
H.H. Nersisyan ◽  
C.W. Won
Keyword(s):  
Tungsten Carbide ◽  
Combustion Synthesis ◽  
Solid Phase ◽  
Synthesis Process ◽  
Carbide Powder ◽  
X Ray Diffraction ◽  
Phase Pure ◽  
Tungsten Carbide Powder ◽  
Conversion Efficiencies ◽  
Phase Transport

The synthesis of ultrafine tungsten carbide (WC) powder has been investigated from a WO3 + Mg + C mixture via combustion technique. The values of combustion parameters were estimated over the Mg concentration range 3 to 16 mol. Fast increasing tendency of the WC/W2C phase ratio from Mg concentration has been found in the final products. Phase pure WC was prepared with more than 10 mol Mg, and a small amount of ammonium carbonate (or urea) was blended with the WO3+ C mixture. The effects of the combustion conditions on product morphology and composition were evaluated using scanning electron microscopy and x-ray diffraction analysis. The results of the investigation indicate that carbon-containing compounds significantly enhance the combustion synthesis process; leading to higher conversion efficiencies and phase pure WC formation at 1500–1550 °C. The crystalline particles of WC showed a narrow distribution in particle size, with a mean diameter around 200 nm. The results are discussed in the context of gas-phase and solid-phase transport models.

Combustion Synthesis of Ti(C,N) Powder

2007 ◽  
Vol 280-283 ◽  
pp. 1421-1424 ◽  
Author(s):  
Yan An Wang ◽  
Ke Xin Chen ◽  
He Ping Zhou
Keyword(s):  
Reaction Mechanism ◽  
Combustion Synthesis ◽  
Phase Formation ◽  
Combustion Temperature ◽  
Nitrogen Pressure ◽  
Nitrogen Atmosphere ◽  
Titanium Carbonitride ◽  
Synthesis Process ◽  
Reaction Parameters ◽  
N Powder

Titanium carbonitride powders were synthesized directly by a combustion synthesis process between titanium and carbon in a nitrogen atmosphere. The relationships between properties of the final product and the combustion reaction parameters were systematically investigated. Especially, the effects of nitrogen pressure on the phase formation and microstructure of the as-synthesized products were experimentally investigated. The reaction mechanism of Ti(C,N) was proposed through quench experiment, the variation of combustion temperature on time and thermodynamics analysis.

Electron Microscopy/Diffraction Study of the Ternary Mn-Er-S System

1990 ◽  
Vol 48 (1) ◽  
pp. 76-77
Author(s):  
A. R. Landa Canovas ◽  
L.C. Otero Diaz ◽  
T. White ◽  
B.G. Hyde
Keyword(s):  
Electron Microscopy ◽  
Gas Flow ◽  
Graphite Crucible ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Alumina Crucible ◽  
X Ray ◽  
Intermediate Phases ◽  
Twin Band ◽  
Ar Gas

X-Ray diffraction revealed two intermediate phases in the system MnS+Er2S3,:MnEr2S4= MnS.Er2S3, and MnEr4S7= MnS.2Er2S3. Their structures may be described as NaCl type, chemically twinned at the unit cell level, and isostructural with CaTi2O4, and Y5S7 respectively; i.e. {l13} NaCl twin band widths are (4,4) and (4,3).The present study was to search for structurally-related (twinned B.) structures and or possible disorder, using the more sensitive and appropiate technigue of electron microscopy/diffraction.A sample with nominal composition MnEr2S4 was made by heating Mn3O4 and Er2O3 in a graphite crucible and a 5% H2S in Ar gas flow at 1500°C for 4 hours. A small amount of this material was thenannealed, in an alumina crucible, contained in sealed evacuated silica tube, for 24 days at 1100°C. Both samples were studied by X-ray powder diffraction, and in JEOL 2000 FX and 4000 EX microscopes.

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

Comparative Studies of Ultra Low-κ Porous Silica Films with 2-D Hexagonal and Disordered Pore Structures

2004 ◽  
Vol 812 ◽  
Author(s):  
Nobutoshi Fujii ◽  
Kazuhiro Yamada ◽  
Yoshiaki Oku ◽  
Nobuhiro Hata ◽  
Yutaka Seino ◽  
...  
Keyword(s):  
Pore Structure ◽  
Nonionic Surfactants ◽  
Porous Silica ◽  
Silica Film ◽  
X Ray Diffraction ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Porous Silica Film ◽  
Diffraction Peaks

AbstractPeriodic 2-dimensional (2-D) hexagonal and the disordered pore structure silica films have been developed using nonionic surfactants as the templates. The pore structure was controlled by the static electrical interaction between the micelle of the surfactant and the silica oligomer. No X-ray diffraction peaks were observed for the disordered mesoporous silica films, while the pore diameters of 2.0-4.0 nm could be measured by small angle X-ray scattering spectroscopy. By comparing the properties of the 2-D hexagonal and the disordered porous silica films which have the same porosity, it is found that the disordered porous silica film has advantages in terms of the dielectric constant and Young's modulus as well as the hardness. The disordered porous silica film is more suitable for the interlayer dielectrics for ULSI.

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