Microstructural Evolution in Compositionally Tailored MoSi2/SiC Composites

1993 ◽  
Vol 322 ◽  
Author(s):  
S.E. Riddle ◽  
S. Jayashankar ◽  
M.J. Kaufman
Keyword(s):  
Mechanical Alloying ◽  
Microstructural Evolution ◽  
Processing Parameters ◽  
Processing Temperature ◽  
Processing Scheme ◽  
Powder Composition ◽  
Important Processing ◽  
Novel Processing ◽  
Sic Composites ◽  
Carbide Content

AbstractCompositionally tailored MoSi2/SiC composites with silicon carbide content ranging from 0 to 60 volume percent were synthesized through a novel processing scheme involving the mechanical alloying of elemental molybdenum, silicon, and carbon. The effects of important processing parameters such as the nominal powder composition and the processing temperature on the microstructural evolution during mechanical alloying and subsequent heating are described based on the results obtained from DTA and XRD.

Synthesis and Properties of In-Situ MoSi2/SiC Composites

1993 ◽  
Vol 322 ◽  
Author(s):  
S. Jayashankar ◽  
S.E. Riddle ◽  
M. J. Kaufman
Keyword(s):  
Fracture Toughness ◽  
Mechanical Alloying ◽  
Room Temperature ◽  
Indentation Fracture ◽  
Processing Scheme ◽  
Indentation Fracture Toughness ◽  
Novel Processing ◽  
Sic Composites

AbstractCompositionally-tailored, silica-free, MoSi2/SiC composites with SiC content ranging from 0 to 40 percent were synthesized through a novel processing scheme involving mechanical alloying and in-situ reactions for the formation of the reinforcement. Room temperature indentation fracture toughness and hardness measurements were obtained from these silica-free composites and were compared with values obtained from silica-containing, conventionally-processed MoSi2/SiC composites.

Tailored MoSi2/SiC composites by mechanical alloying

1993 ◽  
Vol 8 (6) ◽  
pp. 1428-1441 ◽  
Author(s):  
S. Jayashankar ◽  
M.J. Kaufman
Keyword(s):  
Mechanical Alloying ◽  
Carbothermal Reduction ◽  
Reduction Reaction ◽  
Partial Pressures ◽  
Micron Size ◽  
Important Processing ◽  
Sic Composites ◽  
Carbon Additions ◽  
Carbothermal Reduction Reaction

MoSi2-based composites have been synthesized through the mechanical alloying (MA) of elemental molybdenum and silicon powders with and without carbon additions. The interplay between the phase formation sequence in the powders and the microstructural evolution in the consolidated samples is described. It is shown that the glassy SiO2 phase characteristic of conventional powder processed MoSi2 can be effectively eliminated by combining mechanical alloying, carbon additions, and an in situ carbothermal reduction reaction. Using this approach, composites consisting of uniformly distributed micron-size SiC in an MoSi2 matrix can be formed. The effect of important processing variables such as the extent of carbon additions, extraneous iron pickup during MA, partial pressures of oxygen, consolidation temperatures, and consolidation atmospheres is discussed based on the evidence obtained from DTA, TGA, TEM, and XRD.

Synthesis of Si3N4 from Na2SiF6 as a Solid Precursor: Microstructural Evolution

2007 ◽  
Vol 560 ◽  
pp. 109-114
Author(s):  
Ana Lilia Leal-Cruz ◽  
Martin I. Pech-Canul
Keyword(s):  
Weight Loss ◽  
Substrate Temperature ◽  
Microstructural Evolution ◽  
Microstructure Evolution ◽  
Processing Time ◽  
Processing Parameters ◽  
Processing Temperature ◽  
Morphology Changes ◽  
Porous Substrates

The effect of processing parameters on the weight loss of the silicon solid precursor (Na2SiF6) and the deposition characteristics and morphology of Si3N4 formed onto SiCp/Si porous substrates by CVD has been investigated. The results show that the weight loss of Na2SiF6 is most significantly affected by the processing temperature, followed by the processing time and the type of nitrogen precursor. Formation of Si3N4 is mostly influenced by the substrate temperature, followed by the type of nitrogen precursor and processing time. An increase in processing time and temperature from 60 to 120 min and from 900 to 1300 oC, respectively, favors dissociation of Na2SiF6 and formation of Si3N4. Moreover, N2 enhances Na2SiF6 dissociation and hampers Si3N4 formation, while the N2-NH3 mixture hinders the solid precursor dissociation and favors Si3N4 formation. With regard to microstructure evolution, it is found that in N2 the amount of Si3N4 increases with temperature and the morphology changes from wool-like and light fibers to thicker and compact fibers. When N2-NH3 is used and the processing temperature is increased, the morphology of Si3N4 is modified from deposits with wool-like and compact appearance to whiskers and spheres and finally to thick and compact fibers.

Evaluation of matrix and interface properties in SiC/SiC composites

1993 ◽  
Vol 51 ◽  
pp. 922-923
Author(s):  
A.D. Surrett ◽  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Composite System ◽  
Chemical Vapor ◽  
Processing Parameters ◽  
Chemical Vapor Infiltration ◽  
Effect Of Temperature ◽  
Processing Temperature ◽  
Interface Properties ◽  
Composite Matrix ◽  
The Matrix ◽  
Sic Composites

It has become increasingly important to characterize composite matrix materials in terms of processing-microstructure-property relationships. The characteristics of composite matrices can differ significantly from monolithic materials processed using more conventional techniques such as hot-pressing or sintering. Knowledge of the mechanical and thermophysical properties of the matrix as a function of processing parameters is necessary for the modeling and design of composite materials. In this study, the microstucture and mechanical properties of the matrix in the Nicalon/SiC composite system have been characterized as a function of processing temperature.The composites were fabricated by stacking multiple layers of plain-weave Nicalon fabric rotated in a 30°-60°-90° sequence within the cavity of a graphite holder. The preforms were then coated with carbon at 1375 K and 3 kPa. The coated preforms were densified using a forced chemical vapor infiltration (FCVI) technique developed at ORNL. The SiC matrix was produced by the decomposition of methyltrichlorosilane carried in hydrogen at temperatures of 1000, 1100, 1200, 1300, and 1400°C in order to reveal the effect of temperature on the properties of the composite and matrix.

Microstructural evolution and corrosion behavior of nanocrystalline FeAl synthesized by mechanical alloying

2016 ◽  
Vol 657 ◽  
pp. 330-335 ◽  
Author(s):  
M. Masmoudi ◽  
M. Mhadhbi ◽  
L. Escoda ◽  
J.J. Suñol ◽  
M. Khitouni
Keyword(s):  
Mechanical Alloying ◽  
Corrosion Behavior ◽  
Microstructural Evolution

PREDICTION OF PEEK RESIN PROPERTIES FOR PROCESSING MODELING USING MOLECULAR DYNAMICS

2021 ◽  
Author(s):  
KHATEREH KASHMARI ◽  
PRATHAMESH DESHPANDE ◽  
SAGAR PATIL ◽  
SAGAR SHAH ◽  
MARIANNA MAIARU ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Residual Stresses ◽  
Crystallization Kinetics ◽  
Material Properties ◽  
Elevated Temperatures ◽  
Processing Parameters ◽  
Thermomechanical Properties ◽  
Volumetric Shrinkage ◽  
Processing Temperature ◽  
Wide Range

Polymer Matrix Composites (PMCs) have been the subject of many recent studies due to their outstanding characteristics. For the processing of PMCs, a wide range of elevated temperatures is typically applied to the material, leading to the development of internal residual stresses during the final cool-down step. These residual stresses may lead to net shape deformations or internal damage. Also, volumetric shrinkage, and thus additional residual stresses, could be created during crystallization of the semi-crystalline thermoplastic matrix. Furthermore, the thermomechanical properties of semi-crystalline polymers are susceptible to the crystallinity content, which is tightly controlled by the processing parameters (processing temperature, temperature holding time) and material properties (melting and crystallization temperatures). Hence, it is vital to have a precise understanding of crystallization kinetics and its impact on the final component's performance to accurately predict induced residual stresses during the processing of these materials. To enable multi-scale process modeling of thermoplastic composites, molecular-level material properties must be determined for a wide range of crystallinity levels. In this study, the thermomechanical properties and volumetric shrinkage of the thermoplastic Poly Ether Ether Ketone (PEEK) resin are predicted as a function of crystallinity content and temperature using molecular dynamics (MD) modeling. Using crystallization-kinetics models, the thermo-mechanical properties are directly related to processing time and temperature. This research can ultimately predict the residual stress evolution in PEEK composites as a function of processing parameters.

Corrosion behavior and microstructural evolution of BN-ZrO2 -SiC composites in molten steel

2017 ◽  
Vol 14 (4) ◽  
pp. 665-674 ◽  
Author(s):  
Lei Chen ◽  
Li Zhen ◽  
Yujin Wang ◽  
Xiaoming Duan ◽  
Jia-Hu Ouyang ◽  
...  
Keyword(s):  
Corrosion Behavior ◽  
Microstructural Evolution ◽  
Molten Steel ◽  
Sic Composites

Microstructural Evolution and Thermal Stability Characterization of a High Temperature Die Attach Lead-Free System

2012 ◽  
Vol 2012 (HITEC) ◽  
pp. 1-11 ◽  
Author(s):  
Rogie I. Rodriguez ◽  
Dimeji Ibitayo ◽  
Pedro Quintero
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Microstructural Evolution ◽  
Diffusion Mechanism ◽  
Processing Temperature ◽  
Mechanical And Thermal Properties ◽  
Promising Alternative ◽  
Free System ◽  
Die Attach

There is a need for electromechanical devices capable of operating in high temperature environments (>200°C) for a wide variety of applications. Today's wide-bandgap (WBG) semiconductor based power electronics have demonstrated a potential of operating above 400°C, however they are still limited by packaging. Among the most promising alternative is the Au-Sn eutectic solder, which have been widely used due to its excellent mechanical and thermal properties. However, the operating temperature of this metallurgical system is still limited to ∼250°C owing to its melting temperature of 280°C. Therefore, a higher temperature resistant system is much needed, but without affecting the current processing temperature of ∼325°C typically exhibited in most high temperature Pb-Free solders. This paper presents the development and characterization of a fluxless die attach soldering process based on gold enriched solid liquid inter-diffusion (SLID). A low melting point material (eutectic Au-Sn) was deposited in the face of a substrate, whereas a high melting point material, gold in this instance, was deposited in its mating substrate. Deposition of all materials was performed using a jet vapor deposition (JVD) equipment where thicknesses were controlled to achieve specific compositions in the mixture. Sandwiched coupons where isothermally processed in a vacuum reflow furnace. SEM and EDS were employed to reveal the microstructural evolution of the samples in order to study the interfacial reactions of this fluxless bonding process. Mechanical characterization of the each individual intermetallic phase was achieved by nanoindentation. Differential scanning calorimetry demonstrated the progression of the SLID process by quantifying the remaining low melting point constituent as a function of time and temperature. Post-processed samples confirmed the inter-diffusion mechanism as evidenced by the formation of sound joints that proved to be thermally stable up to ∼490°C after the completion of the SLID process.

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