Chemical Properties
Heavy, white, amorphous powder. Mohs hardness 6.5, refr index 2.2. Insoluble in water and most acids or alkalies at room temperature; soluble in nitric acid and hot concentrated hydrochloric, hydrofluoric, and sulfuric acids. Most heat resistant of commercial refractories; dielectric.
Chemical Properties
Zirconium dioxide is a white, amorphous powder, insoluble
in water but slightly soluble in acid.
Physical properties
White, heavy, amorphous powder or monoclinic crystals; refractive index 2.13; density 5.68 g/cm3; Mohs hardness 6.5; transforms to tetragonal structure above 1,100°C and cubic form above 1,900°C; melts at 2,710°C and vaporizes at about 4,300°C; insoluble in water; soluble in hydrofluoric acid and hot sulfuric, nitric and hydrochloric acids.
General Description
Zirconium(IV) oxide (ZrO2) which is also known as zirconia is a ceramic nanoparticle that can be used as a nano-filler. It can be incorporated in a variety of polymer and metal composites to improve the thermo-mechanical properties of the base material.
Flammability and Explosibility
Nonflammable
Industrial uses
There are several types of zirconia: a pure(monoclinic) oxide and a stabilized (cubic)form, and a number of variations such asyttria- and magnesia-stabilized zirconia andnuclear grades. Stabilized zirconia has a highmelting point, about 2760°C, low thermal conductivity,and is generally unaffected by oxidizingand reducing atmospheres and mostchemicals. Yttria- and magnesia-stabilized zirconiasare widely used for equipment and vesselsin contact with liquid metals. Monoclinicnuclear zirconia is used for nuclear fuel elements,reactor hardware, and related applicationswhere high purity (99.7%) is needed.Zirconia has the distinction of being an electricalinsulator at low temperatures, graduallybecoming a conductor as temperaturesincrease.
Carcinogenicity
To simulate the chronic alpha radiation of Thorotrast, the
liver of female Wistar rats was exposed to fractionated
neutron irradiation at 14-day intervals (0.2Gy per fraction)
over 2 years to a total dose of 10.0Gy. Before the start of
irradiation, half of the animals received 120 mL of nonradioactive
Zirconotrast (ZrO2), which is comparable to
Thorotrast in all other physical and chemical properties.
The first liver tumor was detected 1 year after the beginning
of irradiation. At the end of the life span study, the
incidence of irradiated animals with liver tumors was about
40%. In the animals treated additionally with ZrO2, the
incidence, time of onset, and overall number of liver
tumors were nearly equal, indicating that the fractionated
neutron irradiation was the exclusive cause of tumor
development. The lifelong-deposited ZrO2 colloid had
no influence on tumor induction or development. Histological
types of benign and malignant liver tumors seen in
this study were the same as those seen in animals treated
with Thorotrast.
