Sintering Behavior: Al–SiC Compacts in Different Atmospheres

2019 ◽  
Author(s):  
Tadeusz Pieczonka
Keyword(s):  
Fine Particles ◽  
Pure Aluminum ◽  
Sintering Behavior ◽  
Sintering Atmosphere ◽  
Dimensional Changes ◽  
Ceramic Bond ◽  
Large Particles ◽  
Solid Phases ◽  
Sic Reinforcement

The effect of sintering atmosphere on densification of Al–SiC compacts was investigated. Dimensional changes were monitored in situ in a dilatometer in flowing nitrogen, nitrogen/hydrogen mixture (95/5 by volume), and argon. Two grades of SiC powder were used—F240 characterized by large particles and FCN13 with very fine particles. Mixtures containing 10 and 30 vol.% of SiC reinforcement were prepared in a Turbula mixer. Green compacts of about 80% of theoretical density were made of each mixture. For comparison, compacts made of pure aluminum powder were also investigated. It was shown that nitrogen is the only sintering atmosphere producing shrinkage. This ceramic constituent lowers the sintering densification. Metallographic examinations of sintered composites revealed that sintering of compacts occurs in the presence of a liquid phase exclusively in nitrogen. The melt appearing in Al–SiC compacts is capable to wet the solid phases, which makes shrinkage possible and is beneficial for metal/ceramic bond formation.

scholarly journals Dilatometric investigations of Fe – Cr – Mo – C system

2018 ◽  
Vol 2 (2) ◽  
pp. 1-13
Author(s):  
Maciej Sulowski ◽  
Ewa Lichańska ◽  
Paweł Kulecki ◽  
Monika Tenerowicz-Żaba ◽  
Anna Staniek
Keyword(s):  
Carbon Content ◽  
Sintering Behavior ◽  
Density Level ◽  
Pressing Pressure ◽  
Pure Nitrogen ◽  
Sintering Atmosphere ◽  
Single Action ◽  
Dimensional Changes ◽  
Heating And Cooling ◽  
Final Density

Sintering behavior in high purity nitrogen and mixture of 5% H2-95% N2 of Fe-(Cr)-(Mo)-C system was investigated. The mixtures, differ from chromium, molybdenum and carbon content were prepared in Turbula mixer. Then, using single-action pressing in a rigid die at pressing pressure 400 MPa, green compacts with density level 5.9±0.17 g/cm3 were pressed. Sintering was carried out in a horizontal push rod dilatometer Netzsch 402E at 1120 and 1250°C for 60 min. Heating and cooling rates were 10 and 20°C/min., respectively. After heating, compacts were isothermal sintered at 1120 or 1250°C for 60 minutes an cooled up to 200°C, then isothermally hold for 60 minutes and definitely cooled to the room temperature. Pure nitrogen and mixture of 5% H2-95% N2 were employed as sintering atmospheres. During investigations the influence of isothermal sintering temperature, chemical composition of sintering atmosphere, chromium, molybdenum and carbon content was followed by dilatometry. The aim of investigations was to determine transformation temperatures. It was shown that the dimensional changes occurring during heating and isothermal sintering and the final density of sintered compacts are influenced by sintering parameters and the alloying elements concentration in powder mixture.

A Review on In Situ Synthesis of Al/TiC and Al/SiC-Composites

2016 ◽  
Vol 684 ◽  
pp. 287-292 ◽  
Author(s):  
Hrusikesh Nath
Keyword(s):  
Fine Particles ◽  
Matrix Composites ◽  
Homogeneous Microstructure ◽  
Large Particles ◽  
The Matrix ◽  
Matrix Reinforcement ◽  
Sic Composites ◽  
Al Matrix Composites ◽  
Al Matrix

The in-situ synthesis of ceramic particles in Al-matrix composites gives an uniform and homogeneous microstructure. The matrix reinforcement interface is compatible with the matrix, interface is clean and provides good interface bonding. The evenly distributed sub micron sized reinforcement particles in Al-matrix enhances the strength and toughness of the composite. The formation of particle clusters and agglomerations are minimized or eliminated by suitably choosing the in-situ process parameters. Large particles and agglomerate are easily fractured where as evenly distributed fine particles are resistant to crack propagation and improves the strength of the composites. The problem encountered with the formation of secondary intermetallic Al3Ti and Al4C3 phases are addressed.

In situ monitoring of the sintering behavior of microcomposite particles using a laser scanning micrometer

1998 ◽  
Vol 13 (8) ◽  
pp. 2202-2205 ◽  
Author(s):  
Z. Chen ◽  
S-F. Chen ◽  
R. A. Overfelt ◽  
M. F. Rose
Keyword(s):  
Laser Scanning ◽  
In Situ Monitoring ◽  
Sintering Behavior ◽  
Temperature Sensitive ◽  
Densification Behavior ◽  
Free Condition ◽  
Dimensional Changes ◽  
Alumina Particles ◽  
Higher Temperature

The densification behavior of silica-coated alumina particles was investigated during sintering using a laser scanning micrometer. Traditional dilatometric techniques require contact between a push-rod and the sample under study and thus place the sample under stress during the test. However, the utilization of a noncontact laser micrometer to measure dimensional changes during sintering enabled the densification behavior to be very accurately characterized under a stress-free condition. Thus higher temperature experiments, where densification rates are particularly temperature sensitive and the samples are especially soft, can be reliably investigated without the disturbing influence of an external force. The present paper describes an application of the technique to evaluate the densification behavior from 900–1300 °C of silica-coated alumina microcomposite particles used for the fabrication of mullite.

scholarly journals Improvement of mechanical properties of HfB2-based composites by incorporating in situ SiC reinforcement through pressureless sintering

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Ghadami ◽  
E. Taheri-Nassaj ◽  
H. R. Baharvandi ◽  
F. Ghadami
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Relative Density ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Vacuum Atmosphere ◽  
Sic Reinforcement ◽  
Microstructural Studies ◽  
Composite Samples

AbstractHfB2, Si, and activated carbon powders were selected to fabricate 0–30 vol% SiC reinforced HfB2-based composite. Pressureless sintering process was performed at 2050 °C for 4 h under a vacuum atmosphere. Microstructural studies revealed that in situ SiC reinforcement was formed and distributed in the composite according to the following reaction: Si + C = SiC. A maximum relative density of 98% was measured for the 20 vol% SiC containing HfB2 composite. Mechanical investigations showed that the hardness and the fracture toughness of these composites were increased and reached up to 21.2 GPa for HfB2-30 vol% SiC and 4.9 MPa.m1/2 for HfB2-20 vol% SiC, respectively. Results showed that alpha-SiC reinforcements were created jagged, irregular, and elongated in shape which were in situ formed between HfB2 grains and filled the porosities. Formation of alpha-SiC contributed to improving the relative density and mechanical properties of the composite samples. By increasing SiC content, an enhanced trend of thermal conductivity was observed as well as a reduced trend for electrical conductivity.

Structure of Microphase-Separated Silica/Siloxane Molecular Composites

1989 ◽  
Vol 171 ◽  
Author(s):  
Dale W. Schaefer ◽  
James E. Mark ◽  
David Mccarthy ◽  
Li Jian ◽  
C. -C. Sun ◽  
...  
Keyword(s):  
Phase Separation ◽  
Kinetic Studies ◽  
Organic Content ◽  
Small Particles ◽  
X Ray ◽  
Filled Elastomers ◽  
Polymeric Networks ◽  
Large Particles ◽  
Molecular Composites

ABSTRACTThe structure of several classes of silica/siloxane molecular composites is investigated using small-angle x-ray and neutron scattering. These filled elastomers can be prepared through different synthethic protocols leading to a range of fillers including particulates with both rough and smooth surfaces, particulates with dispersed interfaces, and polymeric networks. We also find examples of bicontinuous filler phases that we attribute to phase separation via spinodal decomposition. In-situ kinetic studies of particulate fillers show that the precipitate does not develop by conventional nucleation-and-growth. We see no evidence of growth by ripening whereby large particles grow by consumption of small particles. Rather, there appears to be a limiting size set by the elastomer network itself. Phase separation develops by continuous nucleation of particles and subsequent growth to the limiting size. We also briefly report studies of polymer-toughened glasses. In this case, we find no obvious correlation between organic content and structure.

Effect of sample preparation when evaluating feed degradability using dacron bags

1996 ◽  
Vol 1996 ◽  
pp. 229-229
Author(s):  
H.J. Kim ◽  
M.S. Dhanoa ◽  
W.J. Maeng ◽  
M.A. Neville ◽  
R.T. Evans ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Dry Matter ◽  
Fine Particles ◽  
Important Measurement

In dacron bag methodology an important measurement is the wash value component. This component is assumed to be wholly degrabable and forms a major proportion of effective degradability calculations (Cockburn et al., 1993). Grinding of feeds with a high content of solubles or fine particles may result in high initial wash-out values and may affect feed degradability adversely. An experiment, was conducted to assess the effect of grinding on dry matter (DM) degradation of maize and wheat, using the in situ dacron bag technique.

scholarly journals Conditions for Production of Composite Material Based on Aluminum and Carbon Nanofibers and Its Physic-Mechanical Properties

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 550 ◽  
Author(s):  
Oleg Tolochko ◽  
Tatiana Koltsova ◽  
Elizaveta Bobrynina ◽  
Andrei Rudskoy ◽  
Elena Zemtsova ◽  
...  
Keyword(s):  
Carbon Nanofibers ◽  
Carbon Nanostructures ◽  
Pure Aluminum ◽  
Metallic Matrix ◽  
Chemical Vapor ◽  
Matrix Composites ◽  
Mechanically Alloyed ◽  
Alumina Particles ◽  
Composite Microstructure

Aluminum-based metallic matrix composites reinforced by carbon nanofibers (CNFs) are important precursors for development of new light and ultralight materials with enhanced properties and high specific characteristics. In the present work, powder metallurgy technique was applied for production of composites based on reinforcement of aluminum matrices by CNFs of different concentrations (0~2.5 wt%). CNFs were produced by chemical vapor deposition (CVD) and mechanical activation. We determined that in situ synthesis of carbon nanostructures with subsequent mechanic activation provides satisfactory distribution of nanofibers and homogeneous composite microstructure. Introduction of 1 vol% of flux (0.25 NaCl + 0.25 KCl + 0.5 CaF2) during mechanic activation helps to reduce the strength of the contacts between the particles. Additionally, better reinforcement of alumina particles and strengthening the bond between CNFs and aluminum are observed due to alumina film removal. Introduction of pure aluminum into mechanically alloyed powder provides the possibility to control composite durability, plasticity and thermal conductivity.

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