Designing Advanced Ceramic Structures with Novel Environmental Microscopy and Related Methods

2001 ◽  
Vol 7 (S2) ◽  
pp. 386-387
Author(s):  
Pratibha L. Gai
Keyword(s):  
Phase Transformations ◽  
Room Temperature ◽  
Single Phase ◽  
Atomic Level ◽  
Chemical Processes ◽  
Atomic Resolution ◽  
Vast Array ◽  
Β Phase ◽  
Silica And Titania

Silica and titania based ceramics and their analogs are some of the most fundamental in crystal chemistry and ceramic science Our interests include applications of nanostructures and chemical composites of the ceramics in nanoelectronics, chemical processes and as scaffolds in biotechnologies. Finely divided titania is used in a vast array of products including paper, paint, food and clothing. Novel microscopy methods including dynamic environmental-high resolution transmission EM (EHREM) at the atomic level, FESEM and cathodoluminescence are leading to striking progress in the development of the ceramic nanotechnologies.Phase transformations in the cristobalite form of silica, from the tetragonal a phase (low or room temperature form) to the cubic β phase (high temperature, (270°C) form) result in discontinuous thermal expansion and are not conducive to nanotechnology. Here we report fundamental in situatomic resolution studies of the phase transformations using EHREM and have used the results to design a number of stable, single-phase structures at room temperature (RT).

An In Situ Observation of Slip Deformation in a Compressed Ti-Mo-Al Single Crystal

2018 ◽  
Vol 941 ◽  
pp. 1463-1467
Author(s):  
Ryotaro Hara ◽  
Masaki Tahara ◽  
Tomonari Inamura ◽  
Hideki Hosoda
Keyword(s):  
Martensitic Transformation ◽  
Slip System ◽  
Single Crystal ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Martensite Phase ◽  
Slip Direction ◽  
Β Phase ◽  
Slip Deformation

The stress-induced martensitic transformation and slip deformation behavior were investigated by the compression test with anin-situobservation in a Ti-6Mo-10Al (mol %) alloy single crystal. Owing to the stress-induced martensitic transformation from the parent β phase to the α′′ martensite phase, the single crystal of α′′ martensite without internal twinnings was successfully obtained at room temperature. By further compression, the slip deformation occurred in the single crystal of α′′ martensite. The operated slip system in the α′′ martensite was analyzed by the two face trace analyses, and the slip direction was determined to be []o.

scholarly journals Understanding controversies in the α-ω and ω-β phase transformations of zirconium from nonhydrostatic thermodynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lin Zhang ◽  
Ying-Hua Li ◽  
Yan-Qin Gu ◽  
Ling-Cang Cai
Keyword(s):  
Shear Stress ◽  
Phase Transformations ◽  
Room Temperature ◽  
Solid Medium ◽  
Thermodynamic Formalism ◽  
Initial Pressure ◽  
Theoretical Explanation ◽  
Β Phase ◽  
Key Factor ◽  
The Impact

AbstractSignificant debate has been noted in the α-ω and ω-β phase transformations of zirconium. The initial pressure of the α-to-ω transformation at room temperature has been reported to vary from 0.25 to 7.0 GPa, while the hydrostatic transformation is believed to occur at approximately 2.2 GPa. Shear stress is commonly considered as a key factor leading to the discrepancy. However, the principal mechanisms previously proposed concluded that the phase transformation pressure would be decreased in the presence of shear stress. The experimental results of the α-ω transformation in zirconium are contrary to this conclusion. In the ω-β phase diagram of zirconium, the dT/dP along the phase boundary near the α-ω-β triple-point was reported to be either positive or negative, but no theoretical explanation, especially a quantitative one, has been proposed. This article aimed to quantitatively investigate and explain the controversies reported in the α-ω and ω-β phase transformations of zirconium by applying a new nonhydrostatic thermodynamic formalism for solid medium, which has recently been proposed and is capable of quantitatively estimating the impact of shear stress on phase transformations in solids.

scholarly journals Electric Field-Induced Surface Melting of Gold Observed In Situ at Room Temperature and at Atomic Resolution Using TEM

2019 ◽  
Vol 25 (S2) ◽  
pp. 1830-1831 ◽  
Author(s):  
Ludvig de Knoop ◽  
Mikael Juhani Kuisma ◽  
Joakim Löfgren ◽  
Kristof Lodewijks ◽  
Mattias Thuvander ◽  
...  
Keyword(s):  
Electric Field ◽  
Room Temperature ◽  
Surface Melting ◽  
Atomic Resolution

scholarly journals Attaining atomic resolution from in situ data collection at room temperature using counter-diffusion-based low-cost microchips

2020 ◽  
Vol 76 (8) ◽  
pp. 751-758
Author(s):  
Jose A. Gavira ◽  
Isaac Rodriguez-Ruiz ◽  
Sergio Martinez-Rodriguez ◽  
Shibom Basu ◽  
Sébastien Teychené ◽  
...  
Keyword(s):  
Data Collection ◽  
Diffraction Data ◽  
Room Temperature ◽  
Low Cost ◽  
Atomic Resolution ◽  
Microfluidic Channels ◽  
High Symmetry ◽  
X Ray ◽  
Counter Diffusion

Sample handling and manipulation for cryoprotection currently remain critical factors in X-ray structural determination. While several microchips for macromolecular crystallization have been proposed during the last two decades to partially overcome crystal-manipulation issues, increased background noise originating from the scattering of chip-fabrication materials has so far limited the attainable resolution of diffraction data. Here, the conception and use of low-cost, X-ray-transparent microchips for in situ crystallization and direct data collection, and structure determination at atomic resolution close to 1.0 Å, is presented. The chips are fabricated by a combination of either OSTEMER and Kapton or OSTEMER and Mylar materials for the implementation of counter-diffusion crystallization experiments. Both materials produce a sufficiently low scattering background to permit atomic resolution diffraction data collection at room temperature and the generation of 3D structural models of the tested model proteins lysozyme, thaumatin and glucose isomerase. Although the high symmetry of the three model protein crystals produced almost complete data sets at high resolution, the potential of in-line data merging and scaling of the multiple crystals grown along the microfluidic channels is also presented and discussed.

Microstructure Design for Enhancement of Room-temperature Ductility in Multi-component TiAl Alloys

MRS Advances ◽  
2019 ◽  
Vol 4 (25-26) ◽  
pp. 1523-1529 ◽  
Author(s):  
Ryosuke Yamagata ◽  
Yotaro Okada ◽  
Hideki Wakabayashi ◽  
Hirotoyo Nakashima ◽  
Masao Takeyama
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Significant Contribution ◽  
Volume Fraction ◽  
Microstructure Design ◽  
Tial Alloys ◽  
Volume Fractions ◽  
Β Phase ◽  
Room Temperature Ductility

AbstractEffects of microstructure constituents of α2-Ti3Al/γ-TiAl lamellae, β-Ti grains and γ grains, with various volume fractions on room-temperature ductility of γ-TiAl based alloys have been studied. The ductility of the alloys containing β phase of about 20% in volume increases to more than 1% as the volume fraction of γ phase increases to 80%. However, γ single phase alloys show very limited ductility of less than 0.2%. The present results, thus, confirmed the significant contribution of β phase to enhancement of the room-temperature ductility in multi-component TiAl alloys.

Stranski-Krastanov Growth of Ni on Si(111) at Room Temperature

1989 ◽  
Vol 159 ◽  
Author(s):  
J. R. Butler ◽  
P. A. Bennett
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Pure Nickel ◽  
Temperature Reaction ◽  
Compound Formation ◽  
Lineshape Analysis ◽  
Coexisting Phases ◽  
Reaction Proceeds ◽  
Three Stages

ABSTRACTWe introduce quantitative Auger lineshape analysis methods to study the room temperature reaction of nickel on Si(111). We show that coexisting phases may be separated by numerically fitting the composite lineshapes using a linear combination of single phase “fingerprint” spectra, obtained by scraping bulk compounds in situ. The reaction proceeds in three stages. For nickel coverage below 1 Å, the growth is layerwise, forming NiSi2. For nickel coverage from 3 to 12 Å, islands of Ni2Si are formed. For nickel coverage above 12 Å, islands of pure nickel are formed. The overlayer reactions appear to be a kinetically limited form of Stranski-Krastanov growth, with multiple compound formation.

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