Thermal characterization of coal using piezoelectric photoacoustic microscopy

1986 ◽  
Vol 64 (9) ◽  
pp. 1184-1189 ◽  
Author(s):  
A. Biswas ◽  
T. Ahmed ◽  
K. W. Johnson ◽  
K. L. Telschow ◽  
J. C. Crelling ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Characterization ◽  
Photoacoustic Signal ◽  
Photoacoustic Microscopy ◽  
Piezoelectric Detection ◽  
Theoretical Predictions ◽  
Coal Macerals

The organic constituents that make up the heterogeneous coal mass are called macerals. Vitrinite and pseudovitrinite are two of the most abundantly occurring macerals in North American coals. Photoacoustic microscopy using piezoelectric detection offers a useful technique for probing the thermal-elastic properties of these coal macerals. The experimental and theoretical conditions under which photoacoustic microscopy can be used to characterize the in situ thermal-elastic properties of macerals, as a function of the percentage of carbon or "rank" of coal, are investigated in this paper. Existing piezoelectric photoacoustic theory has been applied to our sample–transducer configuration to arrive at an expression for the voltage measured from the piezoelectric transducer. The theory indicates that the photoacoustic signal is related to the following sample properties: coefficient of thermal expansion a, bulk modulus B, density ρ, and specific heat c. These properties are coupled together into a dimensionless parameter given by aB/ρc, to which the measured voltage is proportional. Some experimental results used to test the validity of the theoretical predictions are presented. Photoacoustic data gathered on 10 Appalachian Basin coals are plotted as a function of the coal rank. These results are shown to compare favourably with a calculated curve, constructed using independently measured values of a, B, ρ, and c.

In Situ Characterization of the Mechanical Behavior of Gecko's Spatulae by Atomic Force Microscopy

2013 ◽  
Vol 22 ◽  
pp. 85-93
Author(s):  
Shuang Yi Liu ◽  
Min Min Tang ◽  
Ai Kah Soh ◽  
Liang Hong
Keyword(s):  
Mechanical Behavior ◽  
Hierarchical Level ◽  
Intrinsic Properties ◽  
In Situ Characterization ◽  
Force Microscopy ◽  
Atomic Force ◽  
Theoretical Predictions ◽  
Multi Mode

In-situ characterization of the mechanical behavior of geckos spatula has been carried out in detail using multi-mode AFM system. Combining successful application of a novel AFM mode, i.e. Harmonix microscopy, the more detail elastic properties of spatula is brought to light. The results obtained show the variation of the mechanical properties on the hierarchical level of a seta, even for the different locations, pad and stalk of the spatula. A model, which has been validated using the existing experimental data and phenomena as well as theoretical predictions for geckos adhesion, crawling and self-cleaning of spatulae, is proposed in this paper. Through contrast of adhesive and craw ability of the gecko on the surfaces with different surface roughness, and measurement of the surface adhesive behaviors of Teflon, the most effective adhesion of the gecko is more dependent on the intrinsic properties of the surface which is adhered.

scholarly journals On-Chip Thermal Insulation Using Porous GaN

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 776 ◽  
Author(s):  
Bogdan F. Spiridon ◽  
Peter H. Griffin ◽  
John C. Jarman ◽  
Yingjun Liu ◽  
Tongtong Zhu ◽  
...  
Keyword(s):  
Thermal Insulation ◽  
High Speed ◽  
Thermal Characterization ◽  
Semiconductor Materials ◽  
3Ω Method ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
On Chip ◽  
Fundamental Requirement

This study focuses on the thermal characterization of porous gallium nitride (GaN) usingan extended 3ω method. Porous semiconductor materials provide a solution to the need for on-chipthermal insulation, a fundamental requirement for low-power, high-speed and high-accuracythermal sensors. Thermal insulation is especially important in GaN devices, due to the intrinsicallyhigh thermal conductivity of the material. The results show one order of magnitude reduction inthermal conductivity, from 130 W/mK to 10 W/mK, in line with theoretical predictions for porousmaterials. This achievement is encouraging in the quest for integrating sensors with opto-, powerandRF-electronics on a single GaN chip.

scholarly journals In situ thermal characterization of existing buildings aiming at NZEB standard: A methodological approach

2020 ◽  
Vol 2 ◽  
pp. 100008
Author(s):  
Luca Evangelisti ◽  
Claudia Guattari ◽  
Francesco Asdrubali ◽  
Roberto de Lieto Vollaro
Keyword(s):  
Methodological Approach ◽  
Thermal Characterization ◽  
Existing Buildings

scholarly journals Processing and Characterization of Silicon Nitride Nanofiber Paper

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Kei-Peng Jen ◽  
Ronald Warzoha ◽  
Ji Guo ◽  
Michael Tang ◽  
Sridhar Santhanam
Keyword(s):  
Silicon Nitride ◽  
Thermal Insulation ◽  
Reduction Process ◽  
Thermal Characterization ◽  
Nitride Phase ◽  
Mechanical Stiffness ◽  
Precursor Material ◽  
Processing Step

Papers of silicon nitride nanofibers were synthesized by a carbothermal reduction process. These nanofiber papers were synthesized in situ and did not require a secondary processing step. The process utilized silica nanopowders and silica gel as the precursor material. Processing geometry played a crucial role in regulating the growth of the nanofiber papers. Characterization of the nanofiber papers indicated that the nanofibers were of the alpha silicon nitride phase. Both mechanical stiffness and strength of the nanofiber papers were measured. Thermal conductivity and specific heat of the papers were also measured and were found to be lower than many common thermal insulation materials at much smaller thicknesses and were comparable to those values that are typically reported for carbon-nanotube-based buckypaper. Results of the mechanical and thermal characterization indicate that these silicon nitride nanofiber papers can be utilized for specialized thermal insulation applications.

Thermal Characterization of Bi-Material Microcantilevers: Thermal Conductance and Microscale Convection

2009 ◽  
Author(s):  
Arvind Narayanaswamy ◽  
Ning Gu
Keyword(s):  
Heat Transfer ◽  
Thermal Environment ◽  
Coefficient Of Thermal Expansion ◽  
Ambient Pressure ◽  
Thermal Conductance ◽  
Thermal Characterization ◽  
Temperature Changes ◽  
Atomic Force ◽  
The Heat Transfer Coefficient

Bi–material atomic force microscope cantilevers have been used extensively over the last 15 years as physical, chemical, and biological sensors. As a thermal sensor, the static deflection of bi–material cantilevers due to the mismatch of the coefficient of thermal expansion between the two materials has been used to measure temperature changes as small as 10−5 K, heat transfer rate as small as 40 pW, and energy changes as small as 10 fJ. Bi–material cantilevers have also been use to measure “heat transfer - distance” curves a heat transfer analogy of the force–distance curves obtained using atomic force microscopes. In this work, we concentrate on characterization of heat transfer from the microcantilever. The two quantities that we focus on are the thermal conductance of the cantilever, Gcant (units WK−1), and the thermal conductance due to microscale convection from the cantilever to the ambient fluid, Gconv (units WK−1). The deflection of the cantilever to changes in its thermal environment is measured using the shift in position, on a position sensitive detector, of a laser beam focused at the tip of the cantilever. By determining the response of the microcantilever to (1) uniform temperature rise of the ambient, and (2) change in power absorbed at the tip, the thermal conductance of heat transfer from the cantilever can be determined. When the experiment is performed at low enough ambient pressure so that convection is unimportant (¡ 0.1 Pa), Gcant can be measured. When the experiment is performed at atmospheric pressure the heat transfer coefficient due to convection from the cantilever can be determined.

PHOTOEMISSION STUDY OF THE ELECTRONIC STRUCTURE OF SIZE-SELECTED Ptn — CLUSTERS DEPOSITED ON Ag(110)

1993 ◽  
Vol 07 (01n03) ◽  
pp. 556-559 ◽  
Author(s):  
H.-V. ROY ◽  
J. BOSCHUNG ◽  
P. FAYET ◽  
F. PATTHEY ◽  
W.-D. SCHNEIDER
Keyword(s):  
Electronic Structure ◽  
Cluster Size ◽  
Crystal Surface ◽  
Bound State ◽  
In Situ Characterization ◽  
Theoretical Predictions ◽  
Photoemission Study ◽  
Energy Dependent

We report on a photoemission study (XPS, UPS) of the evolution of the electronic structure with cluster size of Pt n ( n = 1-10) clusters deposited on a Ag(110) single crystal surface. The clusters are produced by Xe-ion bombardment of a Pt target. The ionized clusters are mass-selected by a quadrupole mass spectrometer and guided to the substrate by an RF-mode only quadrupole. The substrate is in the center of the analysis chamber allowing in-situ characterization of the supported clusters. Photoemission spectra taken on submonolayer quantities of mass-selected monodispersed Pt clusters indicate individual discrete electronic structure features of the Pt 5d emission. In the atomic-like limit virtual bound state formation with different 5d3/2 and 5d5/2 line broadening is observed which points to an energy dependent Vsd hopping matrix element in agreement with theoretical predictions. With increasing cluster size the splitting between the bonding-like and antibonding-like Pt 5d states reflects the Pt-Pt interaction. The shift of the center of gravity of the Pt 5d state towards the Fermi energy and their concomittant broadening indicate the trend to Pt-metal formation.

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