Investigation of MgF2 optical thin films with ultralow refractive indices prepared from autoclaved sols.
We have successfully developed a process to form high quality MgF(2) thin films with ultralow refractive indices from autoclaved sols prepared from magnesium acetate and hydrofluoric acid. And we have confirmed that our porous MgF(2) coatings have not only high transmittance in the UV region but also high uniformity of film thickness. They can be uniformly formed on phiv 300 mm substrates as a single coating and as a hybrid coating with sublayers formed by physical vapor deposition. They are expected to be applied to various optics that need high transmittance in the UV region.
Preparation of magnesium carbonate nanoparticles encapsulated by nanocomposite material derived from fluoroalkyl end-capped vinyltrimethoxysilane oligomer – Application to the surface modification of glass and poly(methyl methacrylate)
Abstract Sol–gel reactions of fluoroalkyl end-capped vinyltrimethoxysilane oligomer in the presence of magnesium carbonate fine particles were found to proceed smoothly under alkaline conditions at room temperature to give the corresponding fluorinated oligomeric silica nanocomposites-encapsulated magnesium carbonate nanoparticles [R F -(VM-SiO 2 ) n -R F /MgCO 3 ]. The obtained composites have good dispersibility in traditional organic media, and these composites are nanoparticles without agglomeration or coagulation before and even after calcination at 800 °C. Parent magnesium carbonate undergoes the decarboxylation at around 400 °C to afford magnesium oxide; however, the more smooth pyrolysis of the R F -(VM-SiO 2 ) n -R F /MgCO 3 nanocomposites can be observed at around 300 °C to cause the selective formation of not magnesium oxide but magnesium fluoride. The modified glass surfaces treated with the R F -(VM-SiO 2 ) n -R F /MgCO 3 nanocomposites after calcination from 200 to 460 °C were found to exhibit the same superhydrophobic (water contact angle value: 180°) characteristic with good oleophobicity as that of the corresponding nanocomposites before calcination. The transparent colorless modified poly(methyl methacrylate) (PMMA) film was prepared by the treatment of the R F -(VM-SiO 2 ) n -R F /MgCO 3 nanocomposites to give the good oleophobicity imparted by fluorine in the composites on the modified surface. R F -(VM-SiO 2 ) n -R F /MgCO 3 nanocomposites after calcination at 200–800 °C were also applied to the surface modification of PMMA films, and refractive indices of the obtained transparent colorless PMMA films were found to decrease with increasing the calcination temperatures of the nanocomposites, indicating that magnesium fluoride is likely to form in the composites by increasing the calcination temperatures.
Variations common to the interplanetary magnetic field, the zonal atmospheric circulation and the earth's rotation
A study of the cyclic fluctuations in the earth's rotation, the geomagnetic field, the global atmospheric circulation and solar activity reveals the existence of 50-day and 120-day oscillations common to all. Our results, as well as the results obtained by radiometric measurements from the satellites Nimbus-7 and the Solar Maximum Mission (Wilson 1982; Pap 1985), suggest that their origin lies in the physical processes in the sun. The mechanism remains unexplained but from this work it follows that the role of the interplanetary magnetic field could very well be important.