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Study of Viscoelastic Properties of Petroleum Products Using Impulsive Stimulated Brillouin Scattering (CAT#: STEM-ST-0146-YJL)

Introduction

Viscoelasticity refers to the comprehensive properties of fluid viscosity and elasticity. During processing, polymers usually change from solid to liquid (melting and flowing), and then from liquid to solid (cooling and hardening), so the polymer will exhibit the properties of solid and liquid under different conditions during processing, That is, it exhibits elasticity and viscosity. However, due to the long-chain structure of polymer macromolecules and the stepwise nature of macromolecular motion, the deformation and flow of polymers cannot be purely elastic and purely viscous. The response of plastic to stress has the dual characteristics of elastic solid and viscous fluid, which is called viscoelasticity. <br />Petroleum products such as gasoline or oils tend to age over time with iterative thermocycles, leading to a degradation in quality. To investigate this aging process, spectroscopy techniques involving nonlinear four-wave mixing have been recently used to shed light on the viscoelastic properties of these materials.




Principle

From a quantum point of view, Brillouin scattering is an interaction of light photons with acoustic or vibrational quanta (phonons), with magnetic spin waves (magnons), or with other low frequency quasiparticles interacting with light. The interaction consists of an inelastic scattering process in which a phonon or magnon is either created (Stokes process) or annihilated (anti-Stokes process). The energy of the scattered light is slightly changed, that is decreased for a Stokes process and increased for an anti-Stokes process. This shift, known as the Brillouin shift, is equal to the energy of the interacting phonon and magnon and thus Brillouin scattering can be used to measure phonon and magnon energies.

Applications

Brillouin scattering is used to determine acoustic velocities and elastic properties of a number of crystalline solids, glasses, and liquids.

Procedure

1. Sample preparation
2. Measurement by scattering detection instrument
3. Data analysis

Materials

Brillouin scattering measurement system (Brillouin spectrometer)