Search Results (4)

A study of the role of diamond nanoparticles on 5CB liquid crystal composites with Fe₃O₄ nanoparticles is presented. Composite ferronematic systems based on the nematic liquid crystal 5CB doped with Fe₃O₄ magnetic nanoparticles and additionally bound to diamond nanoparticles (DNPs), of a volume concentration of 3.2 mg/mL, 1.6 mg/mL and 0.32 mg/mL, were investigated using both magneto-optical effect and surface acoustic waves (SAWs) to study the role of diamond nanoparticles on the structural properties of ferronematic liquid crystals. The responses of light transmission and SAW attenuation to an external magnetic field were investigated experimentally under a linearly increasing and decreasing magnetic field, respectively. Investigations of the phase transition temperature shift of individual composites were also performed. The experimental results highlighted a decrease in the threshold field in the ferronematic LC composites compared to the pure 5CB as well as its further decrease after mixing Fe₃O₄ with diamond powder. Concerning the transition temperature, its increase with an increase in the volume fraction of both kinds of nanoparticles was registered. The role of diamond nanoparticles in the structural changes and the large residual light transition and/or attenuation (memory effect) were also observed. The presented results confirmed the potential of diamond nanoparticles in nematic composites to modify their properties which could lead to final applications. Full article

A study on 5CB liquid crystal composites with SiO₂ nanoparticles and an additional commixture with Fe₃O₄ nanoparticles using light transmission and SAW measurements is presented. The prepared liquid crystal composites exhibited an interesting memory effect characterized by the hysteresis of both light transmission and SAW attenuation responses investigated in the nematic phase. While in the case of SiO₂ nanoparticles as dopants, the liquid crystal composite showed an improvement in the memory effect, the addition of Fe₃O₄ magnetic nanoparticles resulted in the memory effect decreasing. Additional studies showed a significant shift in both the threshold voltage and nematic–isotropic transition temperature. Measurements in the magnetic field confirmed the increasing memory effect according to that of pure 5CB. The properties of these composites could lead to a potential application for the fabrication of memory devices suitable for information storage. Full article

A composite ferronematic system based on the nematic liquid crystal E7, doped with lath-like goethite magnetic nanoparticles of volume concentrations 10⁻³, 5 × 10⁻⁴, and 10⁻⁵, was investigated. Both surface acoustic waves (SAWs) and the magneto-optical effect were used to study the influence of magnetic nanoparticles on ferronematic liquid crystals’ structural changes, focused above all on structural transitions. The responses of SAW attenuation and light transmission to external magnetic fields were investigated experimentally under linearly increasing/decreasing or jumped (time influence) magnetic fields, respectively. An investigation of temperature on structural changes was performed, as well. The experimental results validated the decrease in the threshold field of the ferronematic composites in comparison with the pure E7, as well as an increase in the transition temperature with the increasing volume fraction of nanoparticles. The effect of the nanoparticles’ concentration on both total structural changes and residual attenuations at the vanishing magnetic field was also registered. The light transmission measurements confirmed the effect of the concentration of goethite nanoparticles on the resultant magneto-optical behavior, concerning both its stability and switching time. Full article

The effect of the liquid crystalline host on structural changes in magnetosomes based on ferronematics is studied using the surface acoustic wave (SAW) technique supported by some capacitance and light transmission measurements. The measurement of the attenuation response of SAW propagating along the interface between LC and the piezoelectric substrate is used to study processes of structural changes under magnetic field. The magnetosome nanoparticles of the same volume concentration were added to three different nematic LCs, 5CB, 6CB, and E7. Unlike to undoped LCs, the different responses of SAW attenuation under the influence of magnetic and electric fields in LCs doped with magnetosomes were observed due to characteristic structural changes. The decrease of the threshold field for doped LCs as compared with pure LCs and slight effects on structural changes were registered. The threshold magnetic fields of LCs and composites were determined from capacitance measurements, and the slight shift to lower values was registered for doped LCs. The shift of nematic-isotropic transition was registered from dependencies of SAW attenuation on temperature. The acoustic anisotropy measurement approved the previous supposition about the role of bulk viscosity in used SAW measurements. In addition, capacitance and light transmition investigations supported SAW results and pointed out conclusions about their magnetic field behavior. Obtained results are discussed and confronted with previous ones and coincide well with those observed using acoustic, optical, or dielectric techniques. Full article