Rev Sci Instrum
Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS-Cachan, Université Paris-Saclay, 91405 Orsay, France.
Published: March 2019
Vibrations in cryocoolers are a recurrent concern to the end user. They appear in different parts of the acoustic spectrum depending on the refrigerator type, Gifford McMahon or pulse-tube, and with a variable coupling strength to the physical system under interest. Here, we use the piezospectroscopic effect in rare-earth doped crystals at a low temperature as a high resolution, contact-less probe for the vibrations. With this optical spectroscopic technique, we obtain and analyze the vibration spectrum up to 700 kHz of a 2 kW pulse-tube cooler. We attempt an absolute calibration based on known experimental parameters to make our method partially quantitative and to provide a possible comparison with other well-established techniques.
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Rev Sci Instrum
March 2019
Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS-Cachan, Université Paris-Saclay, 91405 Orsay, France.
Vibrations in cryocoolers are a recurrent concern to the end user. They appear in different parts of the acoustic spectrum depending on the refrigerator type, Gifford McMahon or pulse-tube, and with a variable coupling strength to the physical system under interest. Here, we use the piezospectroscopic effect in rare-earth doped crystals at a low temperature as a high resolution, contact-less probe for the vibrations.
View Article and Find Full Text PDFPhys Chem Chem Phys
June 2018
Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan.
The phase stability and Raman spectra of Yb2O3, Yb2SiO5 and Yb2Si2O7 under hydrostatic pressure are investigated using density functional theory calculations. The calculated energies of polymorphs of each compound show that the stable phases at zero pressure, viz., C-type Yb2O3, X2-Yb2SiO5 and β-Yb2Si2O7, exhibit a pressure-induced phase transition as compressive pressure increases, which is consistent with available experimental data.
View Article and Find Full Text PDFJ Res Natl Inst Stand Technol
December 2017
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
The numerical coefficients linearly relating the effects of stress (including pressure), temperature, and composition to shifts in the energies of the Cr-related fluorescence in alumina (AlO) are reviewed. The primary focus is the shift of the R and R "ruby" fluorescence lines under conditions typical for stress determination in polycrystalline AlO. No significant experimental difference in the R and R responses is observed for hydrostatic stress (or pressure) conditions (average shift coefficient of about 7.
View Article and Find Full Text PDFJ Mech Behav Biomed Mater
January 2018
Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna "Alma Mater Studiorum" Piazza di Porta San Donato 1, 40126 Bologna, Italy; Centro di Ricerche Interdisciplinari di Biomineralogia, Cristallografia e Biomateriali, Università di Bologna "Alma Mater Studiorum" Piazza di Porta San Donato 1, 40126 Bologna, Italy. Electronic address:
The calcium apatite minerals are among the most studied in the biomaterial field because of their similarity with the mineral phase of bone tissues, which is mainly the hexagonal polymorph of hydroxylapatite. Given the growing interest both in the microscopic processes governing the behaviour of these natural biomaterials and in recent experimental methods to investigate the Raman response of hydroxylapatite upon mechanical loading, we report in the present work a detailed quantum mechanical analysis by DFT/B3LYP-D* approach on the Raman and infrared responses of hydroxylapatite upon deformation of its unit cell. From the vibrational results, the piezo-spectroscopic components Δν = Πσ were calculated.
View Article and Find Full Text PDFACS Appl Mater Interfaces
February 2014
Mechanical and Aerospace Engineering Department, ¶CREOL, The College of Optics and Photonics, §Advanced Materials Processing Analysis Center (AMPAC) and Nanoscience Technology Center, ∥Materials Science and Engineering and College of Medicine , University of Central Florida, Orlando, Florida, United States.
Plasma-spray coatings have a unique microstructure composed of various types of microcracks and weakly bonded interfaces which dictate their nonlinear mechanical properties. The intrinsic photo-luminescence (PL) characteristics of alpha-alumina (α-Al2O3) within these coatings offer a diagnostic functionality, enabling these properties to be probed experimentally at the microscale, under substrate loading. The piezospectroscopic (PS) measurements from the coatings are capable of revealing microstructural stress at high spatial resolution.
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