FREQUENCY SPECTRA OF FREE LATTICES AND PARTICLE SIZE EFFECTS ON THE HEAT CAPACITY OF SOLIDS

1955 ◽  
Vol 33 (6) ◽  
pp. 1079-1087 ◽  
Author(s):  
D. Patterson
Keyword(s):  
Particle Size ◽  
Heat Capacity ◽  
Low Temperature ◽  
Temperature Effect ◽  
Size Effects ◽  
Continuum Model ◽  
Free Boundaries ◽  
Frequency Spectra ◽  
Optical Modes ◽  
Effect Of Particle Size

The effect of particle size on the heat capacity of solids has been investigated using lattices with free boundaries as models. A monatomic lattice shows a low temperature effect associated with the acoustic modes. This can be compared with results obtained from a continuum model. With a diatomic lattice, however, an effect is also associated with the optical modes and is apparent at higher temperatures. The possibility that this latter effect can explain some recent experimental results is examined.

The effect of particle size on the heat capacity of titanium dioxide

1954 ◽  
Vol 224 (1157) ◽  
pp. 228-235 ◽  
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Heat Capacity ◽  
Titanium Dioxide ◽  
Theoretical Calculations ◽  
Particle Size Effect ◽  
The Other ◽  
Optical Modes ◽  
Modes Of Vibration ◽  
Effect Of Particle Size

The heat capacities of four samples of titanium dioxide, differing in particle size, have been measured in the temperature range 12 to 270° K in order to determine the effect of particle size on the specific heat. Contrary to the prediction of existing theories, no effect attributable to a change in particle size has been found in the low-temperature region. On the other hand, above 50° K a pronounced particle-size effect is evident which may be accounted for qualitatively as an effect on the optical modes of vibration of the solid. The complexity of the titanium dioxide crystal structure precludes any quantitative theoretical calculations.

A LOW TEMPERATURE PARTICLE SIZE EFFECT ON THE HEAT CAPACITY OF SODIUM CHLORIDE

1955 ◽  
Vol 33 (2) ◽  
pp. 240-244 ◽  
Author(s):  
D. Patterson ◽  
J. A. Morrison ◽  
F. W. Thompson
Keyword(s):  
Particle Size ◽  
Heat Capacity ◽  
Sodium Chloride ◽  
Low Temperature ◽  
Size Effect ◽  
Specific Heat ◽  
Significant Contribution ◽  
Particle Size Effect ◽  
Extensive Property ◽  
Effect Of Particle Size

An effect of particle size upon the heat capacity of sodium chloride has been found in the temperature range 9° to 21°K. The experiments were done with three NaCl samples of specific surfaces between 38 and 59 sq. meters per gm. The observed effect has the temperature dependence predicted by theory but its magnitude is three to four times larger than expected. It is unlikely that adsorbed gases have made any significant contribution in the experiments. The accuracy with which the specific heat and surface area differences have been determined is not high enough to show definitely whether or not the surface specific heat is an extensive property of the surface.

scholarly journals Heat capacity anomalies of the molecular crystal 1-fluoro-adamantane at low temperatures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daria Szewczyk ◽  
Jonathan F. Gebbia ◽  
Andrzej Jeżowski ◽  
Alexander I. Krivchikov ◽  
Tatiana Guidi ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Low Temperature ◽  
Density Of States ◽  
Molecular Crystal ◽  
Molecular Crystals ◽  
Disordered Materials ◽  
Vibrational Density Of States ◽  
Disorder Phase Transition ◽  
Optical Modes ◽  
Vibrational Density

AbstractDisorder–disorder phase transitions are rare in nature. Here, we present a comprehensive low-temperature experimental and theoretical study of the heat capacity and vibrational density of states of 1-fluoro-adamantane (C10H15F), an intriguing molecular crystal that presents a continuous disorder–disorder phase transition at T = 180 K and a low-temperature tetragonal phase that exhibits fractional fluorine occupancy. It is shown that fluorine occupancy disorder in the low-T phase of 1-fluoro-adamantane gives rise to the appearance of low-temperature glassy features in the corresponding specific heat (i.e., “boson peak” -BP-) and vibrational density of states. We identify the inflation of low-energy optical modes as the main responsible for the appearance of such glassy heat-capacity features and propose a straightforward correlation between the first localized optical mode and maximum BP temperature for disordered molecular crystals (either occupational or orientational). Thus, the present study provides new physical insights into the possible origins of the BP appearing in disordered materials and expands the set of molecular crystals in which “glassy-like” heat-capacity features have been observed.

Effect of Particle Size on Low-Temperature Pyrolysis of Woody Biomass

2014 ◽  
Vol 28 (12) ◽  
pp. 7527-7537 ◽  
Author(s):  
Hayat Bennadji ◽  
Krystle Smith ◽  
Michelle J. Serapiglia ◽  
Elizabeth M. Fisher
Keyword(s):  
Particle Size ◽  
Low Temperature ◽  
Woody Biomass ◽  
Effect Of Particle Size ◽  
Low Temperature Pyrolysis
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