High-Temperature Electromechanical Properties of CTGS

2014 ◽  
Vol 1655 ◽  
Author(s):  
Michal Schulz ◽  
Holger Fritze ◽  
Ward L. Johnson
Keyword(s):  
Resonance Frequency ◽  
Elevated Temperatures ◽  
Bulk Acoustic Wave ◽  
Linear Temperature Dependence ◽  
Temperature Dependent ◽  
Electromechanical Properties ◽  
Linear Temperature ◽  
Sensing Applications ◽  
Lower Temperature Range ◽  
Lower Temperature

ABSTRACTCTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting temperature of 1350 °C. In order to determine the loss at elevated temperatures, two different resonance techniques are used. A contactless transduction method is employed up to about 600 °C, whereas transduction involving standard keyhole-shaped film electrodes is employed up to 1285 °C. Comparison of the temperature-dependent inverse Q factor shows that contactless measurements are best suited for the lower temperature range, where sample clamping and losses caused by the electrodes contribute significantly to the total loss. However, at higher temperatures, measurement of the electrical impedance of samples with film electrodes in the vicinity of the resonance frequency proves to be suitable. Even at 1100 °C, 5 MHz CTGS resonators are found to have a Q factor of about 1200, which is great enough to enable numerous bulk-acoustic-wave applications. Further, a nearly linear temperature dependence of the resonance frequency with a temperature coefficient of 210 Hz/K makes Y-cut CTGS well suited for temperature-sensing applications.

Thermal degradation of EDTA chelates in aqueous solution

1982 ◽  
Vol 60 (10) ◽  
pp. 1207-1213 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
X. B. Cox III ◽  
Patrick Taylor ◽  
Arthur E. Martell ◽  
Brad Miles ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Thermal Degradation ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Iminodiacetic Acid ◽  
Reaction Products ◽  
Degradation Rates ◽  
Lower Temperature Range ◽  
Higher Temperature ◽  
Lower Temperature

The thermal degradation of Ca(II), Mg(II), Zn(II), Fe(II), and Ni(II) chelates of EDTA was investigated in alkaline aqueous solution at elevated temperatures (230–310 °C). The kinetics of decomposition were followed by nmr, titrimetry, and spectrophotometry. Reaction products were identified through nmr and by gas chromatography. The relative order of degradation rates, as measured by the loss of EDTA, was found to be Mg(II) > Ca(II) > Zn(II) > Fe(II) > Ni(II). The main degradation products formed in the lower temperature range (~250 °C) are iminodiacetic acid, hydroxyethyliminodiacetic acid, and ethylene glycol. Higher temperature products are primarily dimethylamine and carbon dioxide. The rates of degradation of Ca(II), Mg(II), and Zn(II) EDTA chelates are considerably enhanced when either phosphate is present or a glass-lined autoclave is employed.

Temperature and annealing dependence of the longitudinal ultrasonic velocity in aluminum alloys

1993 ◽  
Vol 8 (7) ◽  
pp. 1558-1566 ◽  
Author(s):  
Ward Johnson ◽  
F. Mauer ◽  
D. Pitchure ◽  
S.J. Norton ◽  
Y. Grinberg ◽  
...  
Keyword(s):  
Aluminum Alloys ◽  
Temperature Dependence ◽  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Low Frequency ◽  
Additional Contribution ◽  
Linear Temperature Dependence ◽  
Linear Temperature ◽  
Nonlinear Temperature Dependence ◽  
Velocity Changes

The longitudinal ultrasonic velocities of four commercial aluminum alloys and Al(1.8 wt.% Si) were measured between room temperature and the solidus temperatures. In all of the samples, the velocity deviated significantly from a linear temperature dependence at the highest temperatures. In commercially pure (1100) aluminum, this effect is found to be consistent with reported low-frequency damping and elastic modulus changes that are associated with dislocations or grain boundaries. In the four heat-treatable alloys studied, an additional contribution to the nonlinear temperature dependence arises from the dissolution of precipitates at elevated temperatures. Irreversible velocity changes occur during the first heating, as a result of the recovery from work-hardening and heat treatments which were performed during the production of the material. Small hysteretic changes above ∼ 250 °C are correlated with the precipitation and dissolution of alloying elements. The activation energy for the hysteretic changes in Al(1.8% Si) is found to be 0.82 eV, which is consistent with precipitation limited by silicon diffusion along grain boundaries.

Temperature-Dependent ESR Studies of Radical Pairs in Single Crystals of Barbituric Acid

1989 ◽  
Vol 44 (9-10) ◽  
pp. 849-856
Author(s):  
Robert Schupfner ◽  
Adolf Müller
Keyword(s):  
Single Crystals ◽  
Barbituric Acid ◽  
Singlet State ◽  
Linear Temperature Dependence ◽  
X Rays ◽  
Structure Parameter ◽  
Temperature Dependent ◽  
Radical Pairs ◽  
Linear Temperature ◽  
Different Types

Abstract After irradiation of single crystals of barbituric acid with X-rays at 77 K different types of radical pairs are found, which are com posed of only one type of monoradical. The properties of radical pairs of the unpaired electrons are studied using frequency-variable ESR methods at various temperatures. In addition to the radical pairs AD and BC two further pairs A′D′ and XY were identified. Measurements of the fine structure parameter D showed a linear temperature dependence in some regions between 77 K and 290 K. At 240 K the radical pairs AD and A′D′ changed reversibly into A*D* and this pair remained stable up to 290 K. A level anticrossing effect was observed with the pair AD. The exchange energy J between the singlet state and the triplet state was determined as -(15.1 ± 0.6) GHz at 77 K and its temperature coefficient as -(3.8 ± 0.8) × 10-3K-1.

PHONON DRAG, CARRIER DIFFUSIVE THERMOELECTRIC POWER AND SEMICONDUCTING RESISTIVITY BEHAVIOR OF Zn NANOWIRES

2010 ◽  
Vol 09 (05) ◽  
pp. 453-459
Author(s):  
K. K. CHOUDHARY ◽  
D. PRASAD ◽  
K. JAYAKUMAR ◽  
DINESH VARSHNEY
Keyword(s):  
Grain Boundaries ◽  
Thermoelectric Power ◽  
Charge Carriers ◽  
Fourth Power ◽  
Linear Temperature Dependence ◽  
Phonon Drag ◽  
Acoustic Phonons ◽  
Temperature Dependent ◽  
Linear Temperature ◽  
Model Hamiltonian

In this paper, we undertake a quantitative analysis of observed temperature-dependent thermoelectric power (S) of 4 nm Zn /Vycor composite nanowires by developing a model Hamiltonian that incorporates scattering of acoustic phonons with impurities, grain boundaries, charge carriers and phonons. Mott expression is used to determine the carrier diffusive thermoelectric power [Formula: see text]. The [Formula: see text] shows linear temperature dependence and the computed [Formula: see text] when subtracted from the experimental data is interpreted as phonon drag thermoelectric power [Formula: see text]. The model Hamiltonian within the relaxation time approximation sets the limitations of the scattering of acoustic phonons with impurities, grain boundaries, charge carriers and phonons for thermoelectric power in the nanowires. It is shown that for acoustic phonons the scattering and transport cross sections are proportional to fourth power of the phonon in the Rayleigh regime. The resultant thermoelectric powers is an artefact of various operating scattering mechanisms and are computed for the first time to our knowledge for Zn nanowires consistent with the experimentally reported behavior. The semiconducting nature of resistivity is discussed with small polaron conduction (SPC) model which consistently retraces the temperature-dependent resistivity behavior of Zn /Vycor composite.

scholarly journals Mixing properties of Ni-Al liquid alloy at different temperatures

BIBECHANA ◽  
2018 ◽  
Vol 16 ◽  
pp. 106-121 ◽  
Author(s):  
S K Yadav ◽  
P Sharma ◽  
R P Koirala ◽  
A Dhungana ◽  
D Adhikari
Keyword(s):  
Surface Tension ◽  
Statistical Model ◽  
Elevated Temperatures ◽  
Energy Parameter ◽  
Linear Temperature Dependence ◽  
Linear Temperature ◽  
Mixing Properties ◽  
Theoretical Investigations ◽  
Different Temperatures ◽  
Experimental Values

The validity of simple statistical model or simple theory of mixing has been first established by explaining the experimental values of the thermodynamic and structural properties of Ni-Al melt at 1873 K. Secondly, the linear temperature dependence of ordering energy parameter has been assumed to extend the model for predicting the mixing behaviours of the melt at different temperatures in correlation with R-K polynomials. The surface tension of the system has been explained and predicted with the help of Renovated Butler model. Theoretical investigations correspond that alloy is found to be strongly interacting or hetero-coordinating at its melting temperature. This tendency, however, gradually decreases at higher temperatures. Being more specific, the system shows ideal behaviours with respect to mixing properties at elevated temperatures. BIBECHANA 16 (2018) 106-121

Temperature Dependent Phononic Response of Few Layered MoS2 Nanosheets

2018 ◽  
Vol 4 (5) ◽  
pp. 546-548
Author(s):  
Sneha Sinha ◽  
Vasant Sathe ◽  
Sunil K. Arora
Keyword(s):  
Temperature Dependence ◽  
Phonon Scattering ◽  
Linear Temperature Dependence ◽  
Mos2 Nanosheets ◽  
Temperature Dependent ◽  
Linear Temperature ◽  
First Order ◽  
Non Linear ◽  
Out Of Plane ◽  
Raman Modes

From the temperature dependent phononic studies of few layered liquid phase exfoliated MoS2 nanosheets we find that the E12g (in-plane) and A1g (out-of-plane) Raman modes follow red shift with increase in temperature and exhibits non-linear temperature dependence in the entire temperature range (80 to 600 K). The first-order temperature coefficients for E12g and A1g modes are found to be -0.0133 cm-1K-1 and -0.0092 cm-1K-1, respectively. The physical origin of the non-linear temperature dependence is analyzed using an analytical model that includes contribution of the thermal expansion and an-harmonic effects to the lattice potential. Our analysis suggests that the non-linear temperature dependence of E12g and A1g modes mainly originates from the an-harmonic contributions from three-phonon and four-phonon scattering.

scholarly journals The effect of air temperature on hospital admission of adults with community acquired pneumonia in Baotou, China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenfang Guo ◽  
Letai Yi ◽  
Peng Wang ◽  
Baojun Wang ◽  
Minhui Li
Keyword(s):  
Hospital Admission ◽  
Air Temperature ◽  
Meteorological Data ◽  
Community Acquired Pneumonia ◽  
Adult Patients ◽  
Distributed Lag ◽  
Specific Effects ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
Inner Mongolia Autonomous Region

AbstractThe relationship between air temperature and the hospital admission of adult patients with community-acquired pneumonia (CAP) was analyzed. The hospitalization data pertaining to adult CAP patients (age ≥ 18 years) in two tertiary comprehensive hospitals in Baotou, Inner Mongolia Autonomous Region, China from 2014 to 2018 and meteorological data there in the corresponding period were collected. The exposure–response relationship between the daily average temperature and the hospital admission of adult CAP patients was quantified by using a distributed lag non-linear model. A total of 4466 cases of adult patients with CAP were admitted. After eliminating some confounding factors such as relative humidity, wind speed, air pressure, long-term trend, and seasonal trend, a lower temperature was found to be associated with a higher risk of adult CAP. Compared to 21 °C, lower temperature range of 4 to –12 °C was associated with a greater number of CAP hospitalizations among those aged ≥ 65 years, and the highest relative risk (RR) was 2.80 (95% CI 1.15–6.80) at a temperature of − 10 °C. For those < 65 years, lower temperature was not related to CAP hospitalizations. Cumulative lag RRs of low temperature with CAP hospitalizations indicate that the risk associated with colder temperatures appeared at a lag of 0–7 days. For those ≥ 65 years, the cumulative RR of CAP hospitalizations over lagging days 0–5 was 1.89 (95% CI 1.01–3. 56). In brief, the lower temperature had age-specific effects on CAP hospitalizations in Baotou, China, especially among those aged ≥ 65 years.

scholarly journals Physical networks from entropy-driven non-covalent interactions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anthony C. Yu ◽  
Huada Lian ◽  
Xian Kong ◽  
Hector Lopez Hernandez ◽  
Jian Qin ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Dissociation Rate ◽  
Mathematical Framework ◽  
Temperature Dependent ◽  
Nanoparticle Interactions ◽  
Temperature Superposition ◽  
Non Covalent Interactions ◽  
Time Temperature Superposition ◽  
Covalent Interactions ◽  
Physical Crosslinking

AbstractPhysical networks typically employ enthalpy-dominated crosslinking interactions that become more dynamic at elevated temperatures, leading to network softening. Moreover, standard mathematical frameworks such as time-temperature superposition assume network softening and faster dynamics at elevated temperatures. Yet, deriving a mathematical framework connecting the crosslinking thermodynamics to the temperature-dependent viscoelasticity of physical networks suggests the possibility for entropy-driven crosslinking interactions to provide alternative temperature dependencies. This framework illustrates that temperature negligibly affects crosslink density in reported systems, but drastically influences crosslink dynamics. While the dissociation rate of enthalpy-driven crosslinks is accelerated at elevated temperatures, the dissociation rate of entropy-driven crosslinks is negligibly affected or even slowed under these conditions. Here we report an entropy-driven physical network based on polymer-nanoparticle interactions that exhibits mechanical properties that are invariant with temperature. These studies provide a foundation for designing and characterizing entropy-driven physical crosslinking motifs and demonstrate how these physical networks access thermal properties that are not observed in current physical networks.

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