Thermoanalytical study on surface reactivity and characterization of oxide powders at elevated temperatures

ABSTRACTThe growth and chemical intermixing of submonolayer and a few monolayer thick Fe films on a Au(001) surface was studied by High Resolution Low Energy Electron Diffraction (HRLEED) technique. Through the analysis of the energy dependent angular profiles as a function of time, we obtained the distribution of islands and distribution of spacings during submonolayer growth. The interference of electron waves from different chemical elements in terraces at different heights in the surface contributes to the background intensity and broadening in the angular profiles of diffraction beams. A subsurface Fe capped by Au islands as a result of atomic place exchange was observed at the initial stage of monolayer growth. From the energy dependent angular profiles as a function of temperature, we determine the quantitative change of inhomogeneity length (∼20 Å) at the interface of ultrathin films at elevated temperatures due to intermixing.

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The High Temperature Deformation Behavior of A Cr2Nb Ordered Intermetallic System

MRS Proceedings ◽

10.1557/proc-213-739 ◽

1990 ◽

Vol 213 ◽

Cited By ~ 3

Author(s):

G. E. Vignoul ◽

J.M. Sanchez ◽

J. K. Tien

Keyword(s):

Deformation Behavior ◽

Elevated Temperatures ◽

High Temperature Deformation ◽

Temperature Deformation ◽

Deformation Law ◽

Ordered Intermetallic ◽

Intermetallic System ◽

Increasing Temperature ◽

Stress Term

ABSTRACTA basic characterization of the deformation behavior of Cr2Nb by microindention at ambient and elevated temperatures (up to 1400 °C) was undertaken. The microhardness of this system was seen to decrease with increasing temperature, from 1040 MPa at 25°C to 322 MPa at 1400 °C. Further, the microindention creep behavior of this system was studied by varying time on load at T = 1000 and 1200°C. Analysis of the data showed that m = 24 and Qapp = 477.61 kJ/mole. These unusually high values are indicative of the existence of an effective resisting stress against creep. When the data was fit against a microindention creep deformation law which was modified to incorporate an effective resisting stress term, it was determined that m = 4.5, Qcreep = 357 kJ/mole and the resisting stress term σr = 300 MPa.

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Characterization of Wafer-Level Au-In-Bonded Samples at Elevated Temperatures

Metallurgical and Materials Transactions A ◽

10.1007/s11661-015-2865-9 ◽

2015 ◽

Vol 46 (6) ◽

pp. 2637-2645 ◽

Cited By ~ 12

Author(s):

Thi-Thuy Luu ◽

Nils Hoivik ◽

Kaiying Wang ◽

Knut E. Aasmundtveit ◽

Astrid-Sofie B. Vardøy

Keyword(s):

Elevated Temperatures ◽

Wafer Level

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Measurement of the Material State Including the Effects of Recovery and Recrystallization

10.1115/imece2000-1865 ◽

2000 ◽

Author(s):

M. E. Bange ◽

A. J. Beaudoin ◽

M. G. Stout ◽

S. R. MacEwen

Keyword(s):

Elevated Temperatures ◽

High Strain ◽

Quantitative Measure ◽

Experimental Program ◽

Strain Rates ◽

Compression Tests ◽

State Variable ◽

Mechanical Threshold ◽

Material State

Abstract Deformation at elevated temperatures in combination with high strain rates leads to recovery and recrystallization in aluminum alloys. Previous work in recrystallization has emphasized the detailing of microstructural trend in progression from the deformed to the annealed state. In the following, we examine the effect of rate dependence on deformation on AA 5182 and AA 6061. It is demonstrated that identification of underlying microstructural mechanisms is critical. An experimental program is then outlined for characterization of recovery and recrystallization of AA 5182. Instantaneous hardening rate and flow stress are developed from interrupted compression tests. These data are used to establish a quantitative measure of recovery through evaluation of a state variable for work hardening, the mechanical threshold. It is intended that the results serve as a foundation for development of relations for evolution of a mechanical state variable in the presence of recrystallization. Such a framework is necessary for the practical prediction of interstand recrystallization in hot rolling operations.

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Enhancing the Thermal and Mechanical Characteristics of Polyvinyl Alcohol (PVA)-Hemp Protein Particles (HPP) Composites

International Polymer Processing ◽

10.1515/ipp-2020-3974 ◽

2021 ◽

Vol 36 (2) ◽

pp. 137-143

Author(s):

S. A. Awad

Keyword(s):

Mechanical Properties ◽

Elevated Temperatures ◽

Composite Films ◽

Tensile Tests ◽

Mechanical Analysis ◽

Decomposition Temperature ◽

Scanning Calorimetry ◽

Solution Casting Method ◽

Protein Particles

Abstract This paper aims to describe the thermal, mechanical, and surface properties of a PVA/HPP blend whereby the film was prepared using a solution casting method. The improvements in thermal and mechanical properties of HPP-based PVA composites were investigated. The characterization of pure PVA and PVA composite films included tensile tests, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results of TGA and DSC indicated that the addition of HPP increased the thermal decomposition temperature of the composites. Mechanical properties are significantly improved in PVA/HPP composites. The thermal stability of the PVA composite increased with the increase of HPP filler content. The tensile strength increased from 15.74 ± 0.72 MPa to 27.54 ± 0.45 MPa and the Young’s modulus increased from 282.51 ± 20.56 MPa to 988.69 ± 42.64 MPa for the 12 wt% HPP doped sample. Dynamic mechanical analysis (DMA) revealed that at elevated temperatures, enhanced mechanical properties because of the presence of HPP was even more noticeable. Morphological observations displayed no signs of agglomeration of HPP fillers even in composites with high HPP loading.

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Characterization of Hot-Pressed Silicon Nitride Ceramics with Alkoxide-Derived Oxide Mixtures As the Sintering Aid

MRS Proceedings ◽

10.1557/proc-287-429 ◽

1992 ◽

Vol 287 ◽

Author(s):

Y. Sato ◽

C. Sakurai ◽

M. Ueki ◽

K. Sugita

Keyword(s):

Mechanical Properties ◽

Room Temperature ◽

Weight Ratio ◽

Sintering Aids ◽

Sintering Aid ◽

Oxide Powders ◽

Nitride Ceramics ◽

Final Weight ◽

Alkoxide Method

ABSTRACTA homogeneous mixture of Y2O3, CeO2 and MgO with a final weight ratio of 3:1: 2 was prepared by the alkoxide method. The powder mixture was then added into Si3N4 powder in amounts ranging from 4 to 12 wt%, andconsolidated by hot-pressing. Microstructure and mechanical properties of the sintered bodies were determined and compared to those of materials prepared by the conventional route of mixing the oxide powders as sintering aids individually in essentially same composition. The β-fraction (modification ratio) in same composition was higher in thesintered bodies made through the alkoxide method than those made through the conventional one. The room temperature flexural strength was maximized with 6wt% addition of the alkoxide derived oxide, whereas, 12wt% addition of the total oxide was required to maximize the strength by conventional processing.

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Mechanical Property and Oxidation Behavior of LPS-SiC Materials

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.321-323.913 ◽

2006 ◽

Vol 321-323 ◽

pp. 913-916

Author(s):

Sang Ll Lee ◽

Yun Seok Shin ◽

Jin Kyung Lee ◽

Jong Baek Lee ◽

Jun Young Park

Keyword(s):

Mechanical Property ◽

Fracture Toughness ◽

Oxidation Behavior ◽

Elevated Temperatures ◽

Indentation Test ◽

Bending Test ◽

Secondary Phases ◽

Three Point Bending ◽

Different Temperatures

The microstructure and the mechanical property of liquid phase sintered (LPS) SiC materials with oxide secondary phases have been investigated. The strength variation of LPS-SiC materials exposed at the elevated temperatures has been also examined. LPS-SiC materials were sintered at the different temperatures using two types of Al2O3/Y2O3 compositional ratio. The characterization of LPS-SiC materials was investigated by means of SEM with EDS, three point bending test and indentation test. The LPS-SiC material with a density of about 3.2 Mg/m3 represented a flexural strength of about 800 MPa and a fracture toughness of about 9.0 MPa⋅√m.

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