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It07:Silicon Dioxide

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Silicon Dioxide

Silicon Dioxide
Chemical Family Metal Oxide
Molecular formula SiO2
SMILES O=[Si]=O
Physical State&Appearance White Solid with no odor
Molar mass 60.0848 g/mol
Properties
Relative Density 2.0-2.3 gm/cm3
Melting point 1710°C
Boiling Point 2230 °C
Electrical Conductivity varies widely
Breakdown Field >1E7 V/cm in thermal oxides;
can be as low as 1E6 V/cm in CVd oxides
Thermal Conductivity 0.01 W/cm K (bulk)
Thermal Diffusivity 0.009 cm2/sec (bulk)
Coefficient of Thermal Expansion 0.5 ppm/ K [note Si thermal exp 2.3 ppm/K]
Refractive Index 1.46 [thermal oxide]
Dielectric Constant 3.9 [thermal oxide];
CVD oxides vary widely depending on H
CAS RN 14808-60-7
ACX Number X1000239-2
Water Solubility Insoluble
Others Readily dissolves in hydrofluoric acid to form the gas silicon

tetrafluoride.

RTECS VV7330000
Hazards
Chemical Dangers Material may give toxic fumes if it is burned;
Prolonged exposure can cause fibrosis of the lung,silicosis;
Dermal/Eye Contact may cause irritation, inflammation.
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references


Introduction

Silicon dioxide (silica) is one of the most commonly and abundant oxide materials on the earth. It occurs as quartz, cristobalite, tridymite, silica sand, sandstone and quartzite in nature and exist in a variety of crystalline forms or as amorphous from. Silica has a great meaning to many minerals and gemstones as it is the important constituent both in pure and impure form (mixed with related oxides). On the surface of silicon compounds or silicon, SiO2 will often appears as a non-crystalline oxidation product.

Synonyms of Silicon Dioxide

Agate;Amethyst;Chalcedony;Cherts;Crystallized silicon dioxide;D & D;DQ12;Flint;Flintshot;Gold;bond R;Imsil;Min-U-Sil;ovaculite;nyx;uartz silica;Rock crystal;Rose quartz;SF 35;Sand;Sicron F 300;Siderite (SiO2);Fikron F 100;Sil-Co-Sil;Silica dust;Silica flour (powdered crystalline silica);Silicon oxide, di- (sand);Silver bond B;Snowit;TGL 16319;Tiger-eye;W 12;W 12 (Filler);alpha-Quartz


Pentahelicene


Atomic Charges and Dipole Moment
Si charge= 1.250
O charge=-0.625
O charge=-0.625
with a dipole moment of 0.00137 Debye

Bond Lengths
between Si and O: distance=1.538 Å
between Si and O (on the other side): distance=1.538 Å
between two O atoms: distance=3.076 Å

Bond Angles
for O-Si-O: angle=179.9o

Totally Electronic Energy
The electronic energy = all electric interactions + the kinetic energy of the electrons. (Translation, vibration, or rotation of the molecule are not include in this electric energy.)
Total electronic energy = -440.0400203969 Hartrees (1 Hartree = 2680.4 kJ/mol)

Uses of Silicon Dioxide

Silicon Dioxide has such a large application in a variety of fields.
The working of silicon dioxide into glass can be traced back to antiquity and nowadays is known as fused silica.
Silica gel is used as desiccants in new leather goods and clothes.
Owning to the unique properties of silicon dioxide (semiconductor which is stable at raised temperatures and in water) that makes it to be a mask to different, common diffusing species, an excellent electrical insulator as well as being capable of forming an almost perfect electric interface with its substrate.
It’s been applied through various ways in the IC fabrication due to its reliability, familiarity and versatility.
In the form of quartz, it has piezoelectric property which means it has the capability of converting mechanical energy into electrical energy and then turning electrical energy back into mechanical energy again. This property makes it a very valuable compound to modern electronics. One of its applications is to transmit, stabilize and receive signals for TV and radio stations. What is more, this property of silicon dioxide is also used to detect vibrations. Wrist watches use quartz to keep accurate time.
Silica’s application also involves in food industry as well as pharmacy world.


Chemistry of Silicon Dioxide

Interactions with Hydrogen and water are important in semiconductor applications of silica. Hydrides (such as silane (SiH4) and DCS (SiH2Cl2)) are often used as precursors for deposition of silicon dioxide. And water is everywhere in the ambient. Some important reactions are:
Si-O-Si + H2O ---> 2Si-OH
Si-H + H2O --->Si-OH + H2

Reference

1.http://ntp.niehs.nih.gov/index.cfm?objectid=E87DE98A-BDB5-82F8-F3EDD469386A683F
2.http://www.cise.columbia.edu/clean/msds/silicondioxide.pdf
3.http://www.crystran.co.uk/products.asp?productid=230
4.http://www.colby.edu/chemistry/webmo/SiO2.html
5.http://www.timedomaincvd.com/CVD_Fundamentals/films/SiO2_properties.html
6.http://web1.caryacademy.org/chemistry/rushin/StudentProjects/CompoundWebSites/2003/silicondioxide/Uses.htm