Precision classified Minbloc[R] grades produced from microcrystalline silica,
cristobalite, or nepheline syenite are available for clarity and high-clarity blown and cast flexible packaging and agricultural film applications.
Department of the Interior 2003], of which quartz,
cristobalite, and tridymite are the most common.
This light-grey powder consists of several minerals including 75.4% of montmorillonite, 11.7% of quartz, 7.3% of
cristobalite, 4.3% of feldspar, 0.5% of calcite, and 0.8% kaolinite [38].
But also our own previous research results (without publishing) indicate that, in rice husk treated with NaOH and calcined at 700[degrees]C, silicon dioxides were organized into a crystalline structure known as
cristobalite. Due to the fact that the rice husk specific surface area increases when silica in the ash is amorphous [31,32], the presence of
cristobalite could explain the decrease in specific surface area in RHc700 sample.
Changes over 4% are seen as a result of either tridymite or
cristobalite transformations.
The DSC curves show endothermic and exothermic reactions during calcination, such as desorption of surface water (H2O), dehydroxy lation (structural OH-groups) and the transformation to mullite and
cristobalite, with resultant temperature effects of dehydroxylation and polymorphic transformation strongly dependent on kaolinite structural order (Ece et al., 2003; Ekosse, 2008).
Firing of bricks at high temperatures ([greater than or equal to] 900[degrees]C) caused deterioration at their amorphous structures and formation of such high temperature products like spinel, mullite, and
cristobalite. The fact that no such minerals as mullite and
cristobalite were detected in the X-ray diffraction patterns of 5 bricks and illite mineral was observed shows that the firing temperatures of these bricks did not exceed 900[degrees]C.
Associated minerals include dolomite, mordenite,
cristobalite and synchysite-(Ce).
This clay has a smectite content greater than 90% (93 [+ or -] 2%), with quartz (2 [+ or -] 1%), plagioclase (3 [+ or -] 1%),
cristobalite (2 [+ or -] 1%), potassic feldspar, calcite, and trydimite as accessory minerals.
Precision classified Minbloc grades produced from microcrystalline silica,
cristobalite, or nepheline syenite are available for clarity and high-clarity blown and cast flexible packaging and agricultural film applications.
The remaining portion is amorphous (glass) and contains minor amounts of
cristobalite (3%) and quartz (< 1%).