Study on the Pressure Dependence of Boiling Point, Flashpoint, and Lower Flammability Limit at Low Ambient Pressure

The cubic Laves phase compound YMn2 exhibits a huge spontaneous volume magnetostriction at the Néel temperature (TN=100 K). The magnetic moment per Mn atom is 2.7 μB at 2 K. From polarized neutron diffraction in the paramagnetic state it has been shown that the effective moment persisting above TN is reduced (1.6 μB at 120 K). The anomalously large pressure dependence of TN (dTN/dp=–35 K/kbar) is an evidence for the sensitive role played by the Mn—Mn interatomic distances. In the paramagnetic state, the influence of spin fluctuations dominates the physical properties. We have studied the effect of pressure on the resistivity up to 16 kbar. From dρ/dT we have estimated the spinfluctuation temperature as a function of pressure. The value at ambient pressure is 15 K which is in agreement with that determined in the paramagnetic Y0.9Lu0.1Mn2 compound.

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Pressure dependence of the deuterium isotope effect in the photolysis of formaldehyde by ultraviolet light

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-3455-2010 ◽

2010 ◽

Vol 10 (7) ◽

pp. 3455-3462 ◽

Cited By ~ 17

Author(s):

E. J. K. Nilsson ◽

V. F. Andersen ◽

H. Skov ◽

M. S. Johnson

Keyword(s):

Isotope Effect ◽

Pressure Dependence ◽

Kinetic Isotope Effect ◽

Ambient Pressure ◽

Deuterium Isotope Effect ◽

Kinetic Isotope ◽

Molecular Channel ◽

The University ◽

First Time ◽

Gas Pressures

Abstract. The pressure dependence of the relative photolysis rate of HCHO vs. HCDO has been investigated for the first time, using a photochemical reactor at the University of Copenhagen. The dissociation of HCHO vs. HCDO using a UVA lamp was measured at total bath gas pressures of 50, 200, 400, 600 and 1030 mbar. The products of formaldehyde photodissociation are either H2 + CO (molecular channel) or HCO + H (radical channel), and a photolysis lamp was chosen to emit light at wavelengths that greatly favor the molecular channel. The isotope effect in the dissociation, kHCHO/kHCDO, was found to depend strongly on pressure, varying from 1.1 + 0.15/−0.1 at 50 mbar to 1.75±0.10 at 1030 mbar. The results can be corrected for radical channel contribution to yield the kinetic isotope effect for the molecular channel; i.e. the KIE in the production of molecular hydrogen. This is done and the results at 1030 mbar are discussed in relation to previous studies at ambient pressure. In the atmosphere the relative importance of the two product channels changes with altitude as a result of changes in pressure and actinic flux. The study demonstrates that the δD of photochemical hydrogen produced from formaldehyde will increase substantially as pressure decreases.

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Lower Flammability Limit of Difluoromethane and Percolation Theory

International Journal of Thermophysics ◽

10.1023/b:ijot.0000038502.85062.eb ◽

2004 ◽

Vol 25 (4) ◽

pp. 1085-1095 ◽

Cited By ~ 6

Author(s):

I. Kul ◽

D. L. Gnann ◽

A. L. Beyerlein ◽

D. D. DesMarteau

Keyword(s):

Percolation Theory ◽

Flammability Limit ◽

Lower Flammability Limit

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