scholarly journals Multiphase composites obtained by sintering reaction of boehmite and zircon part I: Development and microstructural characterization

2014 ◽  
Vol 46 (3) ◽  
pp. 291-306
Author(s):  
H. Belhouchet ◽  
H. Makri ◽  
M. Hamidouche ◽  
N. Bouaouadja ◽  
V. Garnier ◽  
...  
Keyword(s):  
Sintering Temperature ◽  
Initial Conditions ◽  
Microstructural Characterization ◽  
X Rays ◽  
Reactive Sintering ◽  
Powder Mixtures ◽  
Heating And Cooling ◽  
Multiphase Composites ◽  
Cylindrical Form ◽  
Font Color

In this work, different composites (zircon-mullite, zirconia-mullite-zirconia, mullite-zirconia and alumina-zirconia-mullite) were developed by reactive sintering of a powder mixture of boehmite (AlOOH)) and zircon (ZrSiO)4. These powder mixtures were mixed and ground by ball milling and then pressed in cylindrical form. Finally, the green specimens were sintered in air during 2 hours between 1400?C and 1600?C, with a heating and cooling rate of 5?C/min. The dilatometric curves show that there are several microstructural transformations in these mixtures. X-rays diffraction spectra showed formation of several composites depending on the initial conditions (% of boehmite and zircon and sintering temperature). The micrographic observations of the samples confirmed the presence of various phases. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/SOS150330002E">10.2298/SOS150330002E</a><u></b></font>

Microstructure Formation of Al-Fe-Mn-Si Aluminides by Pressure-Assisted Reactive Sintering of Elemental Powder Mixtures

2009 ◽  
Vol 68 ◽  
pp. 21-33 ◽  
Author(s):  
Alfredo Flores ◽  
J.A. Toscano ◽  
S. Rodríguez ◽  
A. Salinas R. ◽  
Enrique Nava-Vázquez
Keyword(s):  
Microstructural Characterization ◽  
Rietveld Analysis ◽  
Reactive Sintering ◽  
X Ray Diffraction ◽  
Microstructure Formation ◽  
Powder Mixtures ◽  
X Ray ◽  
Intermediate Phases ◽  
Diffraction Patterns ◽  
Metallurgical Reactions

This paper presents the results of an investigation aimed at understanding microstructure formation of Al-Fe-Mn-Si intermetallics during pressure-assisted reactive sintering of elemental powders. The proportion of elements was selected such that the composition of the product was 55 wt % Al, 17 wt % Si, 14 wt % Mn, and 14 wt % Fe. Experiments were conducted at temperatures between 600 and 800°C, using compaction stresses of up to 20 MPa. Rietveld analysis of x-ray diffraction patterns of fully processed samples showed that the powders were transformed into a mixture of Al9FeMnSi and Al9FeMn2Si phases. However, as temperature and pressure were increased, the Al9FeMnSi phase was transformed into the Al9FeMn2Si phase. Differential Thermal Analysis, as well as microstructural characterization by scanning electron microscopy and x-ray diffraction, showed that these intermetallics do not form directly from the powder mixtures. Rather, they are the result of metallurgical reactions between a molten Al-Si solution and various intermediate phases formed during reactive sintering.

Numerical simulation of the disk dynamics around the black hole: Bondi–Hoyle accretion

2014 ◽  
Vol 29 (21) ◽  
pp. 1450115
Author(s):  
Fahrettin Koyuncu ◽  
Orhan Dönmez
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Mach Number ◽  
Initial Conditions ◽  
Outer Boundary ◽  
Compact Objects ◽  
Adiabatic Index ◽  
Computational Domain ◽  
X Rays ◽  
Flip Flop

We have solved the General Relativistic Hydrodynamic (GRH) equations using the high resolution shock capturing scheme (HRSCS) to find out the dependency of the disk dynamics to the Mach number, adiabatic index, the black hole rotation parameter and the outer boundary of the computational domain around the non-rotating and rotating black holes. We inject the gas to computational domain at upstream and downstream regions at the same time with different initial conditions. It is found that variety of the mass accretion rates and shock cone structures strongly depend on Mach number and adiabatic index of the gas. The shock cones on the accretion disk are important physical mechanisms to trap existing oscillation modes, thereupon these trapped modes may generate strong X-rays observed by different X-ray satellites. Besides, our numerical approach also show that the shock cones produces the flip–flop oscillation around the black holes. The flip–flop instabilities which are monitored in our simulations may explain the erratic spin behavior of the compact objects (the black holes and neutron stars) seen from observed data.

scholarly journals Microstructure and Mechanical Behavior of Al-Mg Composites Synthesized by Reactive Sintering

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 762 ◽  
Author(s):  
Rub Nawaz Shahid ◽  
Sergio Scudino
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Yield Strength ◽  
Mechanical Behavior ◽  
Intermetallic Compounds ◽  
Metal Matrix ◽  
Stress Model ◽  
Matrix Composites ◽  
Reactive Sintering ◽  
Powder Mixtures

Lightweight metal matrix composites are synthesized from elemental powder mixtures of aluminum and magnesium using pressure-assisted reactive sintering. The effect of the reaction between aluminum and magnesium on the microstructure and mechanical properties of the composites due to the formation of β-Al3Mg2 and γ-Al12Mg17 intermetallics is investigated. The formation of the intermetallic compounds progressively consumes aluminum and magnesium and induces strengthening of the composites: the yield and compressive strengths increase with the increase of the content of intermetallic reinforcement at the expense of the plastic deformation. The yield strength of the composites follows the iso-stress model when the data are plotted as a function of the intermetallic content.

scholarly journals Influence of Various Process Parameters on the Density of Sintered Aluminium Alloys

10.14311/1604 ◽  
2012 ◽  
Vol 52 (4) ◽  
Author(s):  
Mateusz Laska ◽  
Jan Kazior
Keyword(s):  
Sintered Density ◽  
Sintering Temperature ◽  
Compaction Pressure ◽  
Nitrogen Atmosphere ◽  
Chemical Compositions ◽  
Green Density ◽  
Heating And Cooling ◽  
Wide Range ◽  
Different Temperatures ◽  
Metallurgy Industry

This paper presents the results of density measurements carried out on Alumix sintered parts. ECKA Alumix aluminium powders were used because of their wide application in the powder metallurgy industry. The compacts were produced using a wide range of compaction pressures for three different chemical compositions. The compacts were then sintered under a pure dry nitrogen atmosphere at three different temperatures. The heating and cooling rates were the same throughout the entire test. The results showed that the green density increases with compaction pressure, but that sintered density is independent of green density (compaction pressure) for each sintering temperature.

scholarly journals Dielectric and electrical properties of a mullite/glass composite from a kaolinite clay/mica-rich kaolin waste mixture

Cerâmica ◽  
2019 ◽  
Vol 65 (373) ◽  
pp. 117-121 ◽  
Author(s):  
J. P. F. Grilo ◽  
H. P. A. Alves ◽  
A. J. M. Araújo ◽  
R. M. Andrade ◽  
R. P. S. Dutra ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Glassy Phase ◽  
Low Cost ◽  
Microstructural Characterization ◽  
Reactive Sintering ◽  
X Ray Diffraction ◽  
Glass Composite ◽  
Kaolinite Clay ◽  
X Ray ◽  
Waste Mixture

Abstract A mullite/glass composite has been prepared by reactive sintering of a kaolinite clay/mica-rich kaolin waste mixture with 25 wt% waste. Phase composition, microstructure, dielectric and electrical properties of the composite fired at 1400 °C were evaluated by X-ray diffraction, scanning electron microscopy and impedance spectroscopy (between 25 and 600 °C in air). The microstructural characterization showed the attainment of dense samples composed of acicular (orthorhombic) mullite (47.6 wt%), glassy phase (50.1 wt%), and residual quartz (2.3 wt%). Electrical conductivity (1.9x10-8 S/cm at 300 °C), dielectric constant (6.7 at 1 MHz, 25 °C) and dielectric loss (0.024 at 1 MHz, 25 °C) results gave evidence that the mullite/glass composite is a promising low-cost material for commercial use in electronics-related applications.

Reactivity in the chromium oxide-calcium fluoride system: An empirical approach

1999 ◽  
Vol 14 (6) ◽  
pp. 2518-2523
Author(s):  
Frans Vos ◽  
Luc Delaey ◽  
Marc De Bonte ◽  
Ludo Froyen
Keyword(s):  
Electron Microscopy ◽  
Thermal Analysis ◽  
Calcium Fluoride ◽  
Reaction Mechanisms ◽  
Sintering Temperature ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
Reaction Behavior ◽  
X Ray ◽  
Scanning Electron

The reaction mechanisms observed when sintering loose Cr2O3–CaF2 powder mixtures were analyzed, and the influence of the sintering parameters on the reaction behavior is presented. Using x-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and differential thermal analysis (DTA) measurements, CaCrO4 was shown to be the reaction product when sintering in air. The reaction occurs in two steps: CaF2 transforms to CaO at the Cr2O3–CaF2 interface, followed by a CaO–Cr2O3 interaction, which creates the reaction product. Scanning electron microscopy (SEM) and x-ray fluorescence (XRF) analysis showed an increasing loss of CaF2 with increasing sintering temperature and heating rate, while an opposite evolution of the amount of reaction product was observed.

The Dimensional Change in the Sintering of a Plain Iron Powder and High-Alloyed Iron Powder Mixtures

2006 ◽  
Vol 530-531 ◽  
pp. 747-752
Author(s):  
Maurício David Martins das Neves ◽  
Nelson Karsokas Filho ◽  
Daniel Rodrigues ◽  
Lucio Salgado ◽  
Francisco Ambrozio Filho
Keyword(s):  
Iron Powder ◽  
Composite Powder ◽  
Dimensional Change ◽  
Atomic Motion ◽  
Sintering Process ◽  
Powder Mixtures ◽  
Dilatometric Analysis ◽  
Heating And Cooling ◽  
Wide Range ◽  
High Alloyed Steel

In plain iron powder or powder mixtures sintering process, it is very important to control the dimensional change. In the sintering associated events, such as lubricant removal, atomic motion and phase transformation could change dimensions over a wide range. Dilatometric analysis has shown that most contributions in the dimensional change in the sintering of iron powder mixtures were due to the combination of several effects occurring in all stages of the processing, including the heating and cooling stages. The present paper has the objective of studying the dimensional behavior and to determine the transformation temperature of a composite powder mixture of a plain iron powder with various additions of high-alloyed steel, carbon, nickel and lubricant powders, during sintering by dilatometric analysis.

Effect of Sintering Temperature in Physical-Mechanical Behaviour and in Titanium-Hydroxyapatite Composite Sinterability

2006 ◽  
Vol 530-531 ◽  
pp. 249-254 ◽  
Author(s):  
W.R. Weinand ◽  
F.F.R. Gonçalves ◽  
W.M. Lima
Keyword(s):  
Room Temperature ◽  
Milling Time ◽  
Sintering Temperature ◽  
Microstructural Characterization ◽  
Thermal Treatments ◽  
X Ray ◽  
Hydroxyapatite Composite ◽  
Atmosphere Control ◽  
Ti Powder ◽  
Electronic Microscope

Mechanical alloying (MA) has been successfully used to produce alloys and composites with a high homogeneity degree. In current research, titanium (Ti) powder was mixed with 40, 50% volume of hydroxyapatite (HAp). MA was performed without atmosphere control, at room temperature, for 4.5 hours of milling time, at rotation speed of 300 rpm. Samples of material were compacted in cylindrical form at 350 MPa and sintered in 2.0 flux air (l/min) at 1000, 1100 and 1200oC during 1 hr. The material’s morphological and microstructural characterization, in powder form and in sintered material, was performed by scanning electronic microscope and X-ray diffractometry. Thermal treatments revealed that sintering temperature affects the microstructure, microhardness and the composition of the composites evaluated by EDS.

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