Bao Rima

Consistency-dependent optical properties of lubricating grease studied by terahertz spectroscopy

The optical properties of four kinds of lubricating greases (urea, lithium, extreme pressure lithium, molybdenum disulflde lithium greases) with difierent NLGL (National Lubricant Grease Institute of America) numbers were investigated using terahertz time-domain spectroscopy. Greases with difierent NLGL grades have unique spectral features in the terahertz range. Comparison of the experimental data with predictions based on Lorentz{Lorenz theory exhibited that the refractive indices of each kind of lubricating grease were dependent on the their consistency. In addition, molybdenum disulflde (MoS2) as a libricant additive shows strong absorption from 0.2 to 1.4 THz, leading to higher absorption of MoS2-lithium grease than that of lithium grease.

Terahertz time-domain spectroscopy of a simulated pore structure to probe particle size and porosity of porous rock

The particle sizes and porosities of simulated pore structures are probed by terahertz time-domain spectroscopy. A double-peak time-domain spectrum phenomenon is observed when the terahertz (THz) pulses illuminated a pore and a particle. The amplitudes of the two peaks depend strongly and monotonically on the particle size and porosity. A model is used to study the phenomenon, and the computational results agreed with the experimental measurements. These measurements indicate the terahertz spectroscopic behaviors of pores and particles, suggesting that terahertz spectroscopy can be used as a noncontact probe of porosity.