ANNEALING STABILITY OF CRISTOBALITE NANO CRYSTAL IN BRAVAIS CRYSTAL LATTICE AND BIOCHEMICAL HEALTH HAZARDS OF SILICA

Dr. Sampa Dhabal, Dr. Dhananjoy Saha and *Dr. Dhrubo Jyoti Sen

ABSTRACT

Nanocrystalline powder of SiO2 synthesized by gas phase condensation technique has been characterized by X-ray and electron diffractometric techniques. As received powder is composed of mostly amorphous and a minor number of α-cristobalite phases. On annealing at higher temperatures amorphous phase gradually transforms to small crystallites of α-cristobalite. The tiny crystallites subsequently form small domains in the structural form of β-cristobalite. Silicosis is a chronic lung disease caused by breathing in tiny bits of silica dust. Silica is the second most common mineral in the earth's crust. It is a major component of sand, rock and mineral ores like quartz. People who work in jobs where they can be breathing in these tiny silica bits—like sandblasting, mining, construction and many others—are at risk for silicosis. When people breathe silica dust, they inhale tiny particles of silica that has crystallized. This silica dust can cause fluid build-up and scar tissue in the lungs that cuts down your ability to breathe. There are three types of silicosis: Chronic silicosis, the most common type of silicosis, usually occurs after 10 or more years of exposure to crystalline silica at low levels, Accelerated silicosis occurs 5-10 years after exposure and is caused by exposure to higher levels of crystalline silica. Acute silicosis can occur after only weeks or months of exposure to very high levels of crystalline silica. Acute silicosis progresses rapidly and can be fatal within months. Anyone with silicosis may suffer from several complications: Increased risk for lung infections and tuberculosis. Progressive massive fibrosis—severe scarring and stiffening of the lung, which makes it difficult to breathe. Progressive massive fibrosis can occur in either simple or accelerated silicosis, but is more common in the accelerated form with respiratory failure.

Keywords: Nanocrystalline SiO2, phase transformation, X-ray diffraction, electron diffraction, grain growth, silicosis, chronic simple silicosis, accelerated silicosis, complicated silicosis, acute silicosis, coniosis, scleroderma, SLE, PMF, leukotriene B4, cytokin