scholarly journals Langasite as Piezoelectric Substrate for Sensors in Harsh Environments: Investigation of Surface Degradation under High-Temperature Air Atmosphere

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5978
Author(s):  
Thierry Aubert ◽  
Ninel Kokanyan ◽  
Omar Elmazria
Keyword(s):  
High Temperature ◽  
Measurement Errors ◽  
Elevated Temperatures ◽  
Prolonged Exposure ◽  
Acoustic Properties ◽  
Annealing Duration ◽  
Low Oxygen ◽  
Air Atmosphere ◽  
Before And After ◽  
The Stability

Langasite crystals (LGS) are known for their exceptional piezoelectric properties at high temperatures up to 1000 °C and more. In this respect, many studies have been conducted in order to achieve surface acoustic wave (SAW) sensors based on LGS crystals dedicated to high-temperature operations. Operating temperatures of more than 1000 °C and 600 °C for wired and wireless sensors, respectively, have been reached. These outstanding performances have been obtained under an air atmosphere since LGS crystals are not stable in high-temperature conditions under a low-oxygen atmosphere due to their oxide nature. However, if the stability of bulk LGS crystals under a high-temperature air atmosphere is well established, the surface deterioration under such conditions has been hardly investigated, as most of the papers dedicated to LGS-based SAW sensors are essentially focused on the development of thin film electrodes that are able to withstand very elevated temperatures to be combined with LGS crystals. Yet, any surface modification of the substrate can dramatically change the performance of SAW sensors. Consequently, the aim of this paper is to study the stability of the LGS surface under a high-temperature air environment. To do so, LGS substrates have been annealed in an air atmosphere at temperatures between 800 and 1200 °C and for durations between one week and one month. The morphology, microstructure, and chemical composition of the LGS surface was examined before and after annealing treatments by numerous and complementary methods, while the surface acoustic properties have been probed by SAW measurements. These investigations reveal that depending on both the temperature and the annealing duration, many defects with a corolla-like shape appear at the surface of LGS crystals in high-temperature prolonged exposure in an air atmosphere. These defects are related to the formation of a new phase, likely an oxiapatite ternary compound, the chemical formula of which is La14GaxSi9−xO39−x/2. These defects are located on the surface and penetrate into the depth of the sample by no more than 1–2 microns. However, SAW measurements show that the surface acoustic properties are modified by the high-temperature exposure at a larger deepness of at least several tens of microns. These perturbations of the LGS surface acoustic properties could induce, in the case of LGS-based SAW sensors operating in the 434 MHz ISM band, temperature measurement errors around 10 °C.

High-Temperature Properties of Langasite

1999 ◽  
Vol 604 ◽  
Author(s):  
H. Fritze ◽  
H. L. Tuller ◽  
G. Borchardt ◽  
T. Fukuda
Keyword(s):  
High Temperature ◽  
Oxygen Diffusion ◽  
Elevated Temperatures ◽  
Low Oxygen ◽  
Bulk Resistivity ◽  
Load Response ◽  
Oxidation Reduction ◽  
Mass Load ◽  
Potential Applications ◽  
Related Compounds

AbstractMaterials such as langasite (La3Ga5SiO14) and related compounds are promising candidates for piezoelectric applications at high temperatures. In particular, langasite does not exhibit phase transformations up to the melting point of 1470 °C. Langasite was investigated with respect to potential applications in high temperature resonator devices. In contrast to current resonator materials, we have observed bulk oscillations at temperatures of up to 750 °C in langasite devices. At 700 °C the mass load response for 0.78 mm thick resonators is approximately 0.10 µg/Hz.At elevated temperatures, the bulk resistivity of the resonator devices cannot be neglected due to attenuation of the resonance signal. Therefore, the temperature dependence of the electrical properties of langasite resonator devices, including bulk resistivity, capacity and resonance frequency were measured and are presented. The electrical conductivity is characterized by an activation energy of 105 kJ/mol. In order to confirm langasites stability with respect to oxidation-reduction reactions, we examined the oxygen diffusivity by measuring 18O tracer profiles by SIMS. The diffusivity along the Y-axis is given by D = 5-10−5 exp(-140 kJ/mol / RT) cm2/s in the temperature range from 500 to 800 °C. Langasite shows low oxygen diffusion coefficients with respect to other materials which might be investigated using a langasite microbalance. This would, for example, enable oxygen diffusion kinetics to be examined in YBa2Cu3O6 at 600 °C by means of 18O/16O exchange.

Hot Corrosion Resistance Properties of Al-Si Coatings Obtained by Slurry Method

2012 ◽  
Vol 326-328 ◽  
pp. 273-278 ◽  
Author(s):  
Agnieszka Kochmańska
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Hot Corrosion ◽  
Protective Coatings ◽  
Cast Steel ◽  
High Temperature Corrosion ◽  
Air Atmosphere ◽  
Before And After ◽  
Slurry Method ◽  
Thermal Shocks

This paper presents the results of research on aluminide protective coatings manufactured on hightemperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, at carburizing and oxidizing potential atmosphere. Coatings were obtained on cast steel type GXNiCrSi 3018 by slurry cementation in air atmosphere. The tests of carburizing and oxidizing were carried out. The structure of the coatings before and after carburizing and oxidizing is described in the present paper. The chemical composition, thickness and microstructure of coatings were determined. These coatings could protect equipment against hot corrosion at carburizing and oxidizing atmosphere and have thermal shocks resistance.

Stability of Nanometer-Thick Layers in Hard Coatings

MRS Bulletin ◽  
2003 ◽  
Vol 28 (3) ◽  
pp. 169-172 ◽  
Author(s):  
Scott A. Barnett ◽  
Anita Madan ◽  
Ilwon Kim ◽  
Keith Martin
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Temperature Stability ◽  
Hexagonal Wurtzite Structure ◽  
Thin Layers ◽  
Hard Coatings ◽  
High Temperature Stability ◽  
The Stability ◽  
Hardness Values ◽  
Thick Layers

AbstractThis article reviews two topics related to the stability of hard coatings composed of nanometer-thick layers: epitaxial stabilization and high-temperature stability. Early work on nanolayered hard coatings demonstrated large hardness increases as compared with monolithic coatings, but it was subsequently found that the layers interdiffused at elevated temperatures. More recently, it has been shown that nanolayers exhibit good stability at elevated temperatures if the layer materials are thermodynamically stable with respect to each other and are able to form low-energy coherent interfaces. This article discusses metal/nitride, nitride/nitride, and nitride/boride nanolayers that exhibit good high-temperature stability and hardness values that are maintained (or even increase) after high-temperature annealing. Epitaxial stabilization of nonequilibrium structuresin thin layers is a well-known phenomenon that has been applied to hard nitride materials. In particular, AlN, which crystallizes in the hexagonal wurtzite structure in bulk form, was stabilized in the rock-salt cubic structure in nitride/nitride nanolayers (e.g., AlN/TiN). These results and the current understanding of epitaxial stabilization in hard nanolayers are discussed.

Processing Methods for Ultra High Temperature Ceramics

2013 ◽  
pp. 180-202 ◽  
Author(s):  
J.K. Sonber ◽  
T.S.R. Ch. Murthy ◽  
C. Subramanian ◽  
R.C. Hubli ◽  
A.K. Suri
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Thermal Protection ◽  
Leading Edge ◽  
Powder Synthesis ◽  
Ultra High Temperature Ceramics ◽  
Sharp Edges ◽  
The Stability ◽  
Intense Heat ◽  
Ultra High Temperature

Ultra-high-temperature ceramics (UHTCs) are a group of materials that can withstand ultra high temperatures (1600-3000 oC) which will be encountered by future hypersonic re-entry vehicles. Future re-entry vehicles will have sharp edges to improve flight performance. The sharp leading edges result in higher surface temperature than that of the actual blunt edged vehicles that could not be withstood by the conventional thermal protection system materials. To withstand the intense heat generated when these vehicles dip in and out of the upper atmosphere, UHTC materials are needed. UHTC materials are composed of borides of early transition metals. From the larger list of borides, ZrB2 and HfB2 have received the most attention as potential candidates for leading edge materials because their oxidation resistance is superior to that of other borides due to the stability of the ZrO2 and HfO2 scales that form on these materials at elevated temperatures in oxidizing environments. Processing of these materials is very difficult as these materials are very refractory in nature. In this chapter, processes available for powder synthesis, fabrication of dense bodies, and coating processes is discussed.

Critical Load Analysis of Double-Hinged Circular Steel Arch In-Plane under High Temperature of Fire

2011 ◽  
Vol 243-249 ◽  
pp. 3-6 ◽  
Author(s):  
Yu Lai Han ◽  
Bai Tao Sun ◽  
Zhu Ju ◽  
Yong Gang Wang
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Critical Load ◽  
Thermal Loading ◽  
Elevated Temperatures ◽  
Structural Response ◽  
Steel Material ◽  
The Stability ◽  
Variation Trends ◽  
Significant Factors

This paper addresses the stability behaviour in-plane and the critical load of the double-hinged circular steel arch when subjected to elevated temperature caused by fire, the study is restricted to the thermoelastic structural response of the steel material and therefore the high-temperature effects of yielding are not considered. In order to model structural response of the steel arch under thermal loading, some significant factors such as the degradation of the stiffness of the steel arch prior to yielding at elevated temperatures is taken into account, the formulation of critical load is proposed and their variation trends with temperatures is analysed. The proposed method has significant potential for use in the analysis of steel arches subjected to uniformly distributed load at elevated temperature and can provide a foundation for codified procedures in design.

Aging of Elastomers. Comparison of Creep with Some Conventional Aging Methods

1949 ◽  
Vol 22 (3) ◽  
pp. 699-711 ◽  
Author(s):  
M. C. Throdahl
Keyword(s):  
High Temperature ◽  
Temperature Region ◽  
Chain Scission ◽  
High Temperature Region ◽  
Secondary Bonds ◽  
Air Atmosphere ◽  
The Stability ◽  
Usual Laboratory ◽  
Primary Valence ◽  
Valence Bonds

Abstract Subjection of elastomers to mechanical stresses results in unusually complicated behavior. Recent theoretical researches have shown that this behavior cannot be described satisfactorily by either of the classical theories of elasticity or viscosity. The general molecular theories which describe the behavior of elastomers have experimental verification manifested by three regions of temperature-stress relationship: (1) a low temperature region in which stiffening is observed, due to the stability of secondary bonds between network chains, (2) an intermediate temperature region in which the secondary bonds are so unstable that complete relaxation occurs before measurements can be obtained; the scission of primary valence bonds is occurring at such a slow rate that no measurable effects are obtained during the course of the usual laboratory experiment; and (3) a high temperature region in which the relaxation of stress with time is associated with a chemical reaction which, through breaking of primary-valence bonds in the network, severs the chains rapidly enough to be measured during the course of usual laboratory experiments. The high temperature region is that in which elastomers soften and (or) harden and finally lose their rubbery characteristics. Oxygen has been shown to be necessary for the chain-scission reaction. Several papers have described this fundamental experimental technique for the stress-relaxation and creep of different elastomers. Well known laboratory methods for artificially aging elastomers in oxygen and air bombs and in circulating air atmosphere have selected conditions somewhat arbitrarily. In exploratory searches for promising compounds to be used as antioxidants in elastomers and in the evaluation of well known antioxidants, it has often been found that the conventional methods of aging do not differentiate among several antioxidants. It is the purpose of this paper to describe an application of the previously described creep technique as a convenient and precise means of studying the relative performance of antioxidants and accelerators in Hevea and GR-S rubbers.

In-situ analysis of chemical expansion and stability of SOFC cathodes

2014 ◽  
Vol 1655 ◽  
Author(s):  
Mirela Dragan ◽  
Scott Misture
Keyword(s):  
High Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Lattice Parameter ◽  
Low Oxygen ◽  
X Ray Diffraction ◽  
Chemical Expansion ◽  
X Ray ◽  
Reducing Conditions ◽  
The Stability

ABSTRACTIn this work high-temperature X-ray diffraction has been used to investigate thermal and chemical expansion as well as overall phase stability for various cathode materials: Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF), La0.3Sr0.7CoO3 (LSC37), La0.6Sr0.4CoO3 (LSC64) and La0.6Sr0.4Fe0.8Co0.2O3 (LSCF), as a function of temperature in reducing conditions. When perovskites materials are under a low oxygen partial-pressure condition, the lattice parameter and overall dimension increase. Their chemical expansion has comparable values. From the viewpoint of the stability of these phases, the high-temperature X-ray diffraction results indicate no phase decomposition can be one of the reasons for material failure at the current experimental oxygen partial pressure. LSF is most stable, while LSC and LSCF form oxygen vacancy-ordered phases and then decompose when heated to 1000°C under atmospheres with pO2 as low as 10-5 atm.

Mechanical properties of a 20 vol % SiC whisker-reinforced, yttria-stabilized, tetragonal zirconia composite at elevated temperatures

1995 ◽  
Vol 10 (1) ◽  
pp. 113-118 ◽  
Author(s):  
S.E. Dougherty ◽  
T.G. Nieh ◽  
J. Wadsworth ◽  
Y. Akimune
Keyword(s):  
Grain Size ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Tetragonal Zirconia ◽  
Tensile Tests ◽  
Engineering Properties ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Deformation Properties ◽  
Before And After

The high-temperature deformation behavior of a SiC whisker-reinforced, yttria-stabilized, tetragonal zirconia polycrystalline composite containing 20 vol % SiC whiskers (SiC/Y-TZP) has been investigated. Tensile tests were performed in vacuum at temperatures from 1450 °C to 1650 °C and at strain rates from 10−3 to 10−5 s−1. The material exhibits useful high-temperature engineering properties (e.g., ∼100 MPa and 16% elongation at T = 1550 °C and at a strain rate of ∼10−4 s−1). The stress exponent was determined to be n ≍ 2. Scanning electron microscopy was used to characterize the grain size and morphology of the composites, both before and after deformation. The grain size in the composite was initially fine, but coarsened at the test temperatures; both dynamic and static grain growth were observed. The morphology of ceramic reinforcements appears to affect strongly the plastic deformation properties of Y-TZP. A comparison is made between the properties of monolithic Y-TZP, 20 wt. % Al2O3 particulate-reinforced Y-TZP (Al2O3/Y-TZP), and SiC/Y-TZP composites.

Crystallization and high-temperature structural stability of titanium oxide nanotube arrays

2003 ◽  
Vol 18 (1) ◽  
pp. 156-165 ◽  
Author(s):  
Oomman K. Varghese ◽  
Dawei Gong ◽  
Maggie Paulose ◽  
Craig A. Grimes ◽  
Elizabeth C. Dickey
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Titanium Oxide ◽  
Elevated Temperatures ◽  
Anatase Phase ◽  
Argon Atmosphere ◽  
Nanotube Arrays ◽  
Nanotube Array ◽  
Inner Diameter ◽  
The Stability

The stability of titanium oxide nanotube arrays at elevated temperatures was studied in dry oxygen as well as dry and humid argon environments. The tubes crystallized in the anatase phase at a temperature of about 280 °C irrespective of the ambient. Anatase crystallites formed inside the tube walls and transformed completely to rutile at about 620 °C in dry environments and 570 °C in humid argon. No discernible changes in the dimensions of the tubes were found when the heat treatment was performed in oxygen. However, variations of 10% and 20% in average inner diameter and wall thickness, respectively, were observed when annealing in a dry argon atmosphere at 580 °C for 3 h. Pore shrinkage was even more pronounced in humid argon environments. In all cases the nanotube architecture was found to be stable up to approximately 580 °C, above which oxidation and grain growth in the titanium support disrupted the overlying nanotube array.

scholarly journals Evaluation of Welded Joints in P91 Steel under Different Heat-Treatment Conditions

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 99 ◽  
Author(s):  
Francisco José Gomes Silva ◽  
António Pedro Pinho ◽  
António Bastos Pereira ◽  
Olga Coutinho Paiva
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Welding Parameters ◽  
Hardness Profile ◽  
P91 Steel ◽  
Treatment Conditions ◽  
Before And After

P91 steel has been of interest to many researchers over the past two decades. This interest is because this steel has very interesting characteristics for application in power plants, where it is common to have pipes that need to support steam at temperatures between 570 and 600 °C, and at pressures in the range of 170 to 230 bar. These working conditions are quite severe for most common steels, requiring increased high-temperature mechanical strength as well as high creep resistance. The manufacture of these pipes normally includes welding operations, which must preserve the main characteristics of this type of steel. This justifies the concern of the researchers to ensure the best welding conditions so that the preservation of the properties of these steels becomes possible. The present work intends to depict the best results obtained varying the heat-treatment conditions applied to weldments made on heat-resistant steel P91. This steel usually takes the designation SA 213 T91 (seamless tube) or SA 335 P91 (seamless pipe), according to ASME II, as well as the designation X10CrMOVNb9-1 according to EN 10216-2. The purpose of this study is to compare the behavior of pipe welding under different post-welding heat-treatment (PWHT) conditions. One of them is performed with thermal cycles (preheating, post-heating, and the post-weld heat treatment) in agreement with most construction codes and standard rules. The second one is performed without any thermal cycle before and after welding. Both welds were made by the same process, TIG (Tungsten Inert Gas, or GTAW—Gas Tungsten Arc Welding) in the horizontal position (2G according to ASME IX) and the same welding parameters. In order to evaluate the results obtained in the welds, microstructure analyses, hardness measurements, bending tests, and tensile tests at room and high temperature (600 °C) have been performed. Other tests were also carried out according to the quality procedures, such as visual, penetrant dye, and X-ray tests. Regarding the different strategies used in the heat treatments, the best results have been obtained using a strategy similar to the one currently in use and recommended by construction codes and steel manufacturers but excluding the phases’ transformation time, and it was possible to observe that the tensile strength is impaired by about 2% to 9% at room and elevated temperatures, respectively; the elongation is reduced by 39% at room temperature but keeps a good performance at elevated temperature; the hardness profile is very similar at both temperatures; the microstructure presented is compatible with the requirements; and no cracking trend has been reported. Thus, a new strategy for the welding heat treatment of grade 91 steels was drawn, saving energy and processing time.

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