The molecular SiO2 has a linear structure like CO2. It has been produced by combining silicon monoxide (SiO) with oxygen in an argon matrix. The dimeric silicon dioxide (SiO2)2 has been obtained by reacting O2 with matrix-isolated dimeric silicon monoxide (Si2O2). In dimeric silicon dioxide, two oxygen atoms are bridging between the silicon atoms with a Si–O–Si angle of 94° and bond length of 164.6 pm, and the terminal Si–O bond length is 150.2 pm. The Si–O bond length is 148.3 pm, which compares with the length of 161 pm in α-quartz. The bond energy is estimated at 621.7 kJ/mol. Geology: SiO2 is most commonly found in nature as quartz, which comprises more than 10% of the mass of the Earth's crust. Quartz is the only polymorph of silica stable at the Earth's surface. Metastable occurrences of the high-pressure forms of coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism. The high-temperature conditions of tridymite and cristobalite are known from silica-rich volcanic rocks. In many parts of the world, silica is the principal constituent of sand. Biology: Even though it is poorly soluble, silica occurs in many plants, such as rice. Plant materials with high silica phytolith content appear important to grazing animals, from chewing insects to ungulates. Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by herbivores may have developed as a defense mechanism against predation. Silica is also the primary component of rice husk ash, which is used, for example, in filtration and as supplementary cementitious material (SCM) in cement and concrete manufacturing. If you are looking for high quality, high purity, and cost-effective Silicon dioxide, or if you require the latest price of Silicon dioxide, please feel free to email contact mis-asia.