These materials exhibit unique characteristics that make them ideal nanocarriers to host, protect and transport drugs to the target site. Highly porous silica xerogels are suitable for a variety of applications in the drug delivery systems. The process involves conversion of monomers into a colloidal solution (sol) that acts as a precursor for an integrated network (or gel) of either discrete particles or network polymers. The method is used for the fabrication of metal oxides, especially oxides of silicon (Si) and titanium (Ti). The sol–gel process is a method for producing solid materials from small molecules. These materials cause no adverse tissue reactions and degrade in the body to silicic acid, i.e., Si(OH) 4, which is eliminated through the kidneys.
Sol-gel derived silica xerogels are nontoxic and biocompatible in vivo. Silica xerogels are used as matrix materials for the extended and controlled release of different kinds of biologically active agents administered by various routes, as are therefore of interest to the pharmaceutical industry. In the latter case, the material is properly called Silica xerogel. The voids may contain water or some other liquids or may be filled by gas or vacuum.
Silica gel is an amorphous and porous form of silicon dioxide, consisting of an irregular tri-dimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The Greek root of the word, morphē means “form,” and a- means “lacking or without.” Called quartz glass or fused quartz, it is beneficial to a number of applications. What is amorphous quartz?Īmorphous quartz, by its definition, is non-crystalline form of silica. The addition of trace elements in the quartz crystals give them distinctive colors.
FORMULA OF SILICA SERIES
Quartz is typically found in crystalline form, and as such is made up of a series of regularly repeating arrangement of atoms and external plane faces that make the material transparent. It is the most abundant mineral found at Earth’s surface, and its unique properties make it one of the most useful natural substances. In the respirable size fraction the concentration is below 0.1%.Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO 2, commonly found in nature as quartz. The concentration of quartz in silica fume is usually below the limit of quantification (LOQ) (see arrow in the figure) and it has been shown to be concentrated in the coarse fraction of silica fume. Silicon carbide in silica fume is in its non-fibrous form, as demonstrated by Scanning Electron Microscopic (SEM) investigations on pre-treated (HF digested) silica fume samples. Respirable crystalline silica (RCS) < 0.1 % The main impurities include carbon, silicon carbide and oxides of alkaline (earth) metals.Īs silica fume is generated from raw materials which inevitably vary in composition depending on the source, the impurities will also individually vary up to a maximum of 5 %, but the total amount of impurities will not exceed 15 %:ĬaO, MgO, Na2O, K2O, Al2O3, Fe2O3, SO3, SiC, Si, C, Cl-< 5 % The primary component of silica fume is amorphous silicon dioxide SiO2 in a range of 85 % - 98 %.
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