نتایج جستجو برای: silicates
تعداد نتایج: 5604 فیلتر نتایج به سال:
A closer look into close packing: pentacoordinated silicon in a high-pressure polymorph of danburite
Due to their high technological and geological relevance, silicates are one of the most studied classes of inorganic compounds. Under ambient conditions, the silicon in silicates is almost exclusively coordinated by four oxygen atoms, while high-pressure treatment normally results in an increase in the coordination from four- to sixfold. Reported here is a high-pressure single-crystal X-ray dif...
Experimental results on the formation of molecular hydrogen on amorphous silicate surfaces are presented for the first time and analyzed using a rate equation model. The energy barriers for the relevant diffusion and desorption processes are obtained. They turn out to be significantly higher than those obtained earlier for polycrystalline silicates, demonstrating the importance of grain morphol...
The initial microscale mechanisms and materials interfacial process responsible for hydration of calcium silicates are poorly understood even in model systems. The lack of a measured microscale chemical signature has confounded understanding of growth mechanisms and kinetics for microreaction volumes. Here, we use Raman and optical spectroscopies to quantify hydration and environmental carbonat...
Cosmic dust analogue materials including amorphous and crystalline silicates, ferrous oxide, and iron sulfide have been studied by reflectance spectroscopy of bulk surfaces as well as by transmission spectroscopy of particulates at temperatures down to 10 K. From the reflectance measurements optical data have been derived. The spectra show a sharpening and strengthening of the vibrational bands...
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