scholarly journals Quantification of High Temperature Transition Al2O3 and Their Phase Transformations

2020 ◽  
Author(s):  
Libor Kovarik ◽  
Mark Bowden ◽  
Amity Andersen ◽  
Nicholas R. Jaegers ◽  
Nancy Washton ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Disorder ◽  
Study Phase ◽  
Temperature Transition ◽  
Polymorphic Transformations ◽  
Transition Alumina ◽  
Formidable Challenge ◽  
Temperature Exposure ◽  
Xrd Patterns ◽  
High Degree

<p>High temperature exposure of gamma-Al<sub>2</sub>O<sub>3</sub> can lead to a series of polymorphic transformations, including the formation of delta-Al<sub>2</sub>O<sub>3</sub> and theta-Al<sub>2</sub>O<sub>3</sub>. Quantification of the microstructure in the delta/theta-Al<sub>2</sub>O<sub>3</sub> formation range represents a formidable challenge as both phases accommodate a high degree of structural disorder. In this work, we explore the use of XRD recursive stacking formalism for quantification of high temperature transition aluminas. We formulate the recursive stacking methodology for modelling of disorder in delta-Al<sub>2</sub>O<sub>3 </sub>and twinning in theta-Al<sub>2</sub>O<sub>3</sub> and show that explicitly accounting for the disorder is necessary to reliably model the XRD patterns of high temperature transition alumina. In the second part, we use the recursive stacking approach to study phase transformation during high temperature (1050 ºC) treatment. We show that the two different intergrowth modes of delta-Al<sub>2</sub>O<sub>3</sub> have different transformation characteristics, and that a significant portion of delta-Al<sub>2</sub>O<sub>3</sub> is stabilized with theta-Al<sub>2</sub>O<sub>3 </sub>even after prolonged high-temperature exposures. In discussions, we outline the limitation of the current XRD approach and discuss a possible multimodal XRD and NMR approach which can improve analysis of complex transition aluminas.</p>

scholarly journals Quantification of High Temperature Transition Al2O3 and Their Phase Transformations

2020 ◽  
Author(s):  
Libor Kovarik ◽  
Mark Bowden ◽  
Amity Andersen ◽  
Nicholas R. Jaegers ◽  
Nancy Washton ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Disorder ◽  
Study Phase ◽  
Temperature Transition ◽  
Polymorphic Transformations ◽  
Transition Alumina ◽  
Formidable Challenge ◽  
Temperature Exposure ◽  
Xrd Patterns ◽  
High Degree

<p>High temperature exposure of gamma-Al<sub>2</sub>O<sub>3</sub> can lead to a series of polymorphic transformations, including the formation of delta-Al<sub>2</sub>O<sub>3</sub> and theta-Al<sub>2</sub>O<sub>3</sub>. Quantification of the microstructure in the delta/theta-Al<sub>2</sub>O<sub>3</sub> formation range represents a formidable challenge as both phases accommodate a high degree of structural disorder. In this work, we explore the use of XRD recursive stacking formalism for quantification of high temperature transition aluminas. We formulate the recursive stacking methodology for modelling of disorder in delta-Al<sub>2</sub>O<sub>3 </sub>and twinning in theta-Al<sub>2</sub>O<sub>3</sub> and show that explicitly accounting for the disorder is necessary to reliably model the XRD patterns of high temperature transition alumina. In the second part, we use the recursive stacking approach to study phase transformation during high temperature (1050 ºC) treatment. We show that the two different intergrowth modes of delta-Al<sub>2</sub>O<sub>3</sub> have different transformation characteristics, and that a significant portion of delta-Al<sub>2</sub>O<sub>3</sub> is stabilized with theta-Al<sub>2</sub>O<sub>3 </sub>even after prolonged high-temperature exposures. In discussions, we outline the limitation of the current XRD approach and discuss a possible multimodal XRD and NMR approach which can improve analysis of complex transition aluminas.</p>

Unraveling the Origin of Structural Disorder in High Temperature Transition Al2O3: Structure of θ-Al2O3

2015 ◽  
Vol 27 (20) ◽  
pp. 7042-7049 ◽  
Author(s):  
Libor Kovarik ◽  
Mark Bowden ◽  
Dachuan Shi ◽  
Nancy M. Washton ◽  
Amity Andersen ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Disorder ◽  
Temperature Transition

REMANIT 4509

Alloy Digest ◽  
1995 ◽  
Vol 44 (9) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Exhaust System ◽  
Heat Treating ◽  
Exhaust Gas ◽  
Gas Purification ◽  
Temperature Performance ◽  
Scale Resistance ◽  
High Degree

Abstract REMANIT 4509 was developed specially for silencers and exhaust gas purification plants. Due to its composition, this steel exhibits scale resistance up to 950 C and a high degree of corrosion resistance to the gases occurring in the exhaust system. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-613. Producer or source: Thyssen Stahl AG.

PEERLESS LCT2

Alloy Digest ◽  
1963 ◽  
Vol 12 (11) ◽  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
High Heat ◽  
High Heat Resistance ◽  
Steel Company ◽  
Temperature Performance ◽  
Crucible Steel ◽  
High Degree

Abstract PEERLESS LCT2 is a hot work steel which possesses high heat resistance and a high degree of working hardness at elevated temperatures. This steel is best applied where hardness and resistance to abrasion are of more importance than toughness. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on high temperature performance as well as forming, heat treating, and machining. Filing Code: TS-140. Producer or source: Crucible Steel Company of America.

scholarly journals Novel Multilayer SAW Temperature Sensor for Ultra-High Temperature Environments

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 643
Author(s):  
Xuhang Zhou ◽  
Qiulin Tan ◽  
Xiaorui Liang ◽  
Baimao Lin ◽  
Tao Guo ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Sensor ◽  
X Ray Diffraction ◽  
Aero Engine ◽  
Before And After ◽  
Application Potential ◽  
Passive Sensors ◽  
Temperature Exposure ◽  
Engine Systems

Performing high-temperature measurements on the rotating parts of aero-engine systems requires wireless passive sensors. Surface acoustic wave (SAW) sensors can measure high temperatures wirelessly, making them ideal for extreme situations where wired sensors are not applicable. This study reports a new SAW temperature sensor based on a langasite (LGS) substrate that can perform measurements in environments with temperatures as high as 1300 °C. The Pt electrode and LGS substrate were protected by an AlN passivation layer deposited via a pulsed laser, thereby improving the crystallization quality of the Pt film, with the function and stability of the SAW device guaranteed at 1100 °C. The linear relationship between the resonant frequency and temperature is verified by various high-temperature radio-frequency (RF) tests. Changes in sample microstructure before and after high-temperature exposure are analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The analysis confirms that the proposed AlN/Pt/Cr thin-film electrode has great application potential in high-temperature SAW sensors.

Viscoelastic Behavior of Segmented Elastomers

1967 ◽  
Vol 40 (4) ◽  
pp. 1105-1110 ◽  
Author(s):  
Stuart L. Cooper ◽  
Arthur V. Tobolsky
Keyword(s):  
Hydrogen Bonding ◽  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Viscoelastic Behavior ◽  
Temperature Transition ◽  
Hydrogen Bonding Interactions ◽  
Structural Nature ◽  
Hard Segments

Abstract Viscoelastic behavior of linear segmented elastomers was examined. The unusual properties found in spandex systems are also observable in hydrocarbon block co-polymers, indicating that hydrogen bonding interactions are perhaps not essential. Low temperature properties of segmented systems are governed by the structural nature of the associated flexible segments, which determines the value of the major glass transition temperature (Tg). It appears that an association of the hard segments provides a broad temperature range of enhanced rubbery modulus. This occurs between the major Tg and a secondary high temperature transition.

Photoluminescence Properties of Ca3Si2O7: Pr3+ Orange-Red Phosphors Prepared by High-Temperature Solid-State Method

2018 ◽  
Vol 73 (6) ◽  
pp. 555-558 ◽  
Author(s):  
Zhi-Qing Peng ◽  
Rong Chen ◽  
Wen-Lin Feng
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Solid State ◽  
Solid State Method ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Red Phosphors ◽  
Typical Sample ◽  
State Method ◽  
Xrd Patterns

AbstractNovel luminescent materials Ca3-xSi2O7: xPr3+ were successfully prepared by the high-temperature solid-state method. The crystal structure, morphology, and optical spectrum were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopy, respectively. The XRD patterns of the samples indicate that the crystal structure is monoclinic symmetry. The SEM shows that the selected sample has good crystallinity although its appearance is irregular and scalelike. The peak of the excitation spectrum of the sample is located at around 449 nm, corresponding to 3H4→3P2 transition of Pr3+. The peak of the emission spectrum of the sample is situated at around 612 nm which is attributed to 3P0→3H6 transition of Pr3+, and the colour is orange-red. The optimum concentration for Pr3+ replaced Ca2+ sites in Ca3Si2O7: Pr3+ is 0.75 mol%. The lifetime (8.48 μs) of a typical sample (Ca2.9925Pr0.0075)Si2O7 is obtained. It reveals that orange-red phosphors Ca3-xSi2O7: xPr3+ possess remarkable optical properties and can be used in white light emitting devices.

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