1,721,201 research outputs found
A CELL OF VARIABLE THICKNESS FOR OPTICAL STUDIES OF HIGHLY ABSORBING LIQUIDS
No full textA new design of a simple and inexpensive optical cell of variable thickness for absorption coefficient measurements in highly absorbing liquids is presented. The cell, which can be also used with highly corrosive samples and up to temperatures of 300 degrees C, is suitable for measurements from the near infrared up to near ultraviolet. As an example, the absorption spectrum of liquid iodine measured over six decades is reported
Chemistry at high pressure: tuning functional materials properties
No full textHigh pressure is a fascinating tool to promote and enhance the properties of materials as well as to induce new and exotic phenomena. This is especially of interest for functional materials, which are very sensitive to external pressure (P) and whose features can be tuned and controlled in a rigorous fashion. Through specific examples of the role of applied P on two families of functional compounds based on the perovskite lattice, manganites, and organic–inorganic hybrid perovskites, it is shown that the particular properties of interest can be manipulated by means of pressure. Examples highlight the effects at both the microscopic and macroscopic level, and show how the understanding of P-induced phenomena is essential for the development of materials chemistry design
FAR-INFRARED SPECTRA OF N2-AR ALLOYS
No full textThe far-infrared spectra of (N2)1-xArx solid mixtures have been studied at 18 K and p=0 for 0<x<0.25. At x=0, in addition to the phonon peaks Tu(1) and Tu(2), the combination bands recently observed at high pressure have been detected. In the alloy, the width of Tu(1) increases with x while its central frequency slowly decreases. In the phase (x=0.25) a translational mode still exists, which can be derived from the Tu(1) mode of the phase. Tu(2) is nearly insensitive to the concentration of impurities, but it disappears at the - transition. A concentration x=0.05 of Kr atoms is found to enhance the intensity of absorption in solid N2 by a factor of 5. © 1989 The American Physical Society
Phase Transitions of PYR14-TFSI as a Function of Pressure and Temperature: The Competition between Smaller Volume and Lower Energy Conformer
No full textdetailed Raman study has been carried out on the ionic liquid 1-
butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14-TFSI)
over a wide pressure (0−8 GPa) and temperature (100−300 K) range. The
explored thermodynamic region allowed us to study the evolution of the system
across different solid and liquid phases. Calculated Raman spectra remarkably
helped in the spectral data analysis. In particular, the pressure behavior of the
most intense Raman peak and the shape analysis of the ruby fluorescence (used
as a local pressure gauge) allowed us to identify a liquid−solid transition around
2.2 GPa at T = 300 K. The low-frequency Raman signal as well as the absence of
remarkable spectral shape modifications on crossing the above threshold and the
comparison with the spectra of the crystalline phase suggest a glassy nature of the
high-pressure phase. A detailed analysis of the pressure dependence of the
relative concentration of two conformers of TFSI allowed us to obtain an
estimate of the volume variation between trans-TFSI and the smaller cis-TFSI,
which is the favored configuration on applying the pressure. Finally, the combined use of both visual inspection and Raman
spectroscopy confirmed the peculiar sequence of phase transitions observed as a function of temperature at ambient pressure and
the different spectral/morphological characteristics of the two crystalline phases
- …
