The Structure and Properties of MoSi2-Mo5Si3 Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
H. Kung ◽  
D. P. Mason ◽  
A. Basu ◽  
H. Chang ◽  
D. C. Van Aken ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Second Phase ◽  
Structure And Properties ◽  
Transmission Electron ◽  
Interfacial Structures ◽  
Two Phases ◽  
Hardness Values

ABSTRACTThe addition of Mo5Si3 as a reinforcing second phase in a MoSi2 matrix has been investigated for possible high temperature strengthening effects. MoSi2 with up to 45 vol % Mo5Si3 was fabricated using powder metallurgy (PM) and arc-casting (AC) techniques. Effects of processing routes, which result in different microstructures, on their mechanical properties are given. PM composites, which have an equiaxed microstructure, exhibit a limited increase in hardness. Higher hardnesses are observed in script-structured AC eutectics and Er-modifiedeutectics throughout the temperatures studied (25–1300°C). Crack propagation paths induced by indentation show long transphase cracks in the AC materials vs short intergranular and interphase cracks in the PM composites at high temperatures.Transmission electron microscopy discloses that the interface in the AC composites has a low-index orientation relationship between the two phases and shows regularly faceted interfacial structures, while planar interfaces are found in the PM composites. These observations suggest the interface is stronger and lower in energy in the AC composites, which is consistent with the higher hardness values and long transphase cracks observed.Dislocation analysis shows the presence of ordinary dislocations (<100>, <110> and 1/2<111>) in MoSi2 in the as-fabricated composites. These types of dislocation are also responsible for the high temperature plastic deformation in compression in both the monolithic MoSi2 and the composites. <331> types of dislocation are only found in MoSi2 either near the interface of the AC composites or in materials deformed below 1000°C.

Effect of Coupled Conditions of Thermal Cycle and Dump Environment on Conductivity of 5mol% Yttria Stabilized Zirconia

2013 ◽  
Vol 591 ◽  
pp. 245-248 ◽  
Author(s):  
Jin Feng Xia ◽  
Hong Qiang Nian ◽  
Tao Feng ◽  
Hai Fang Xu ◽  
Dan Yu Jiang
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Thermal Cycle ◽  
Oxygen Sensor ◽  
Yttria Stabilized Zirconia ◽  
Cyclic Change ◽  
Stabilized Zirconia ◽  
Transmission Electron

In some applications such as automotive oxygen sensor, 5mol% Y2O3stabilized zirconia (5YSZ) is generally used because it has both excellent ionic conductivity and mechanical properties. The automotive oxygen sensor would experience a cyclic change from high temperature (engine running) environment to the low temperature damp environment (in the tail pipe when vehicle stops). The conductivity change with coupled conditions of thermal cycle and dump environment in the 5mol%Y2O3ZrO2(5YSZ) system was examined by XRD,Impedance spectroscopy and transmission electron microscopy (SEM) in this paper.

Interfacial Structures of MoSi2-Mo5Si3 Eutectic Alloys

1991 ◽  
Vol 238 ◽  
Author(s):  
H. Kung ◽  
H. Chang ◽  
R. Gíbala
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Orientation Relationship ◽  
Antiphase Boundary ◽  
Eutectic Alloys ◽  
Lamellar Phases ◽  
Transmission Electron ◽  
Interfacial Structures ◽  
Interfacial Dislocations ◽  
Two Phases

ABSTRACTScript lamellar microstructures which occur in certain intermetallic eutectic alloys, such as in the Mo-Si system, may provide desirable mechanical properties. Arc-melted specimens of MoSi2-Mo5Si3 eutectic alloys which exhibit the interlocking lamellar phases were examined in this study. We have observed, by conventional transmission electron microscopy (TEM), an orientation relationship between the MoSi2 and the Mo5Si3 phases, (110)[001]1-2 ‖ (330)[110]5-3, which is consistent with the crystallographic coordinate transformation matrix. High resolution transmission electron microscopy (HRTEM) discloses the interfacial dislocations to be of <100> and 1/2<111> types and the interfaces are regularly faceted. A shear fault which may be consisting of antiphase boundary (APB)-coupled 1/6<331> superpartial dislocations was observed in MoSi2 grain near the interface. Crack propagation paths suggest that the eutectic has a strong, low energy interface which is consistent with the observations of a low index orientation relationship between the two phases and the faceted interfacial structures.

The Structure and Properties of EPDM/PP/OMMT Nanocomposites by Melt Extrusion

2014 ◽  
Vol 909 ◽  
pp. 63-66
Author(s):  
Ping Han ◽  
Zheng Gu ◽  
Yang Yu ◽  
Pei Yao Li ◽  
Guo Jun Song
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Structure And Properties ◽  
Melt Extrusion ◽  
Microstructure And Mechanical Properties ◽  
Transmission Electron ◽  
Different Types ◽  
Extrusion Method

The EPDM/PP/OMMT nanocomposites were prepared with three different types of OMMT by melt extrusion method. The microstructure and mechanical properties of the nanocomposites were investigated. The intercalated structures of the nanocomposites were confirmed by transmission electron microscopy (TEM). The mechanical results showed that the OMMT (FMR242#) has the best reinforcement. When the content of OMMT was lower than 4wt. %, the mechanical properties of the nanocomposites improved greatly with the increase of the OMMT content.

Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

1974 ◽  
Vol 32 ◽  
pp. 514-515
Author(s):  
S. Fujishiro
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Mechanical Processing ◽  
Ray Method ◽  
X Ray ◽  
Transmission Electron ◽  
Water Quench ◽  
Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

In Situ High-Temperature Transmission Electron Microscopy Observations of the Formation of Nanocrystalline TiC from Nanocrystalline Anatase (TiO2)

1998 ◽  
Vol 4 (3) ◽  
pp. 269-277 ◽  
Author(s):  
A. Agrawal ◽  
J. Cizeron ◽  
V.L. Colvin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Solid Phase ◽  
Anatase Phase ◽  
High Resolution Electron Microscopy ◽  
Rutile Phase ◽  
Transmission Electron ◽  
New Phase

In this work, the high-temperature behavior of nanocrystalline TiO2 is studied using in situ transmission electron microscopy (TEM). These nanoparticles are made using wet chemical techniques that generate the anatase phase of TiO2 with average grain sizes of 6 nm. X-ray diffraction studies of nanophase TiO2 indicate the material undergoes a solid-solid phase transformation to the stable rutile phase between 600° and 900°C. This phase transition is not observed in the TEM samples, which remain anatase up to temperatures as high as 1000°C. Above 1000°C, nanoparticles become mobile on the amorphous carbon grid and by 1300°C, all anatase diffraction is lost and larger (50 nm) single crystals of a new phase are present. This new phase is identified as TiC both from high-resolution electron microscopy after heat treatment and electron diffraction collected during in situ heating experiments. Video images of the particle motion in situ show the nanoparticles diffusing and interacting with the underlying grid material as the reaction from TiO2 to TiC proceeds.

Application and Study of Reactive Polyacrylate Microgel in Pigment Paint of Printed Fabric

2011 ◽  
Vol 311-313 ◽  
pp. 1044-1048
Author(s):  
Hong Long Xing ◽  
Shui Lin Chen
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Sodium Dodecyl ◽  
Ammonium Persulfate ◽  
Color Fastness ◽  
Adhesive Film ◽  
Transmission Electron ◽  
Divinyl Benzene

Polyacrylate microgel emulsion was prepared by emulsion polymerization using styrene, α-n-butyl acrylate and methyl methacrylate as monomer, polyoxyethylene octylphenol ether (TX-30) and sodium dodecyl sulfate(SDS) as combine emulsifier, divinyl benzene and ammonium persulfate (APS) as initiator，respectively. The prepared microgel was analyzed by a variety of measurment methods, such as Fourier transform infrared spectroscopy and transmission electron microscopy. The effect of microgel on the rheological properties of adhesives, leveling, mechanical properties and pigment printing performance was studied. The rhelogy and the color fastness of the pigment printing binder of printed fabrics were measured by rheometer and friction color fastness test instruments, respectively. At the same time, the mechanical properties of the adhesive film was measured by strength tester. The results show that the thixotropy, leveling and mechanical properties of adhesive printing binder and pringting quality of coating fabrics were improved when the microgel was added.

Mechanical Properties and Microstructure Evolution of Typical Over-Aging State Al-Zn-Mg-Cu Alloy during Thermal Exposure

2021 ◽  
Vol 1026 ◽  
pp. 84-92
Author(s):  
Tao Qian Cheng ◽  
Zhi Hui Li
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Mechanical Property ◽  
Electrical Conductivity ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Thermal Exposure ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Thermal Stability Of

Al-Zn-Mg-Cu alloy have been widely used in aerospace industry. However, there is still a lack of research on thermal stability of Al-Zn-Mg-Cu alloy products. In the present work, an Al-Zn-Mg-Cu alloy with T79 and T74 states was placed in the corresponding environment for thermal exposure experiments. Performance was measured by tensile strength, hardness and electrical conductivity. In this paper, precipitation observation was analyzed by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). The precipitations of T79 state alloy were GPⅡ zone, η' phase and η phase while the ultimate tensile strength, hardness and electrical conductivity were 571MPa, 188.2HV and 22.2MS×m-1, respectively. The mechanical property of T79 state alloy decreased to 530MPa and 168.5HV after thermal exposure. The diameter of precipitate increased and the precipitations become η' and η phase at the same time. During the entire thermal exposure, T74 state alloy had the same mechanical property trend as T79 state alloy. The precipitate diameter also increased while the types of precipitate did not change under thermal exposure. The size of precipitates affected the choice of dislocation passing through the particles to affect the mechanical properties.

Motion of Crystal/Crystal and Crystal/Amorphous Interfaces

1990 ◽  
Vol 183 ◽  
Author(s):  
J. L. Batstone
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Grain Boundary ◽  
Boundary Motion ◽  
High Temperature Annealing ◽  
Thermally Activated ◽  
Transmission Electron ◽  
Grain Boundary Motion

AbstractMotion of ordered twin/matrix interfaces in films of silicon on sapphire occurs during high temperature annealing. This process is shown to be thermally activated and is analogous to grain boundary motion. Motion of amorphous/crystalline interfaces occurs during recrystallization of CoSi2 and NiSi2 from the amorphous phase. In-situ transmission electron microscopy has revealed details of the growth kinetics and interfacial roughness.

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