Low Honing Requirement Ceramic Shaving Knife Of High Capacity Cigarette Making Machine For Tipping Paper Fluffing

Ceramic Fluffing Knife

Ceramic Fluffing Knife is a component consisted in high-speed cigarette machines for fluffing tipping paper so that they can be glued better and thus connected better to the cigarette rod.

Material

A ceramic knife is a knife designed with a ceramic blade typically made from zirconium dioxide (ZrO2; also known as zirconia). These knife blades are usually produced through the dry-pressing and firing of powdered zirconia using solid-state sintering. It is 8.5 on the Mohs scale of mineral hardness, compared to 4.5 for normal steel and 7.5 to 8 for hardened steel and 10 for diamond. The resultant blade has a hard edge that stays sharper for longer when compared to conventional steel knives. Whilst the edge is harder than a steel knife, it is less tough and thus more brittle. The ceramic blade is sharpened by grinding the edges with a diamond-dust-coated grinding wheel.

Zirconium oxide

Zirconium oxide is used due to its polymorphism. It exists in three phases: monoclinic, tetragonal and cubic. Cooling to the monoclinic phase after sintering causes a large volume change, which often causes stress fractures in pure zirconia. Additives such as magnesia, calcia and yttria are used in the manufacture of the knife material to stabilize the high-temperature phases and minimize this volume change. The highest strength and toughness is produced by the addition of 3 mol% yttrium oxide yielding partially stabilized zirconia. This material consists of a mixture of tetragonal and cubic phases with a bending strength of nearly 1,200 MPa. Small cracks allow phase transformations to occur, which essentially close the cracks and prevent catastrophic failure, resulting in a relatively tough ceramic material, sometimes known as TTZ (transformation-toughened zirconia).

Properties

Ceramic knives are substantially harder than steel knives, will not corrode in harsh environments, are non-magnetic, and do not conduct electricity at room temperature. Because of their resistance to strong acid and caustic substances, and their ability to retain a cutting edge longer than forged metal knives,[citation needed] ceramic knives are better suited for slicing boneless meat, vegetables, fruit and bread. Since ceramics are brittle, blades may break if dropped on a hard surface although improved manufacturing processes have reduced this risk. They are also unsuitable for chopping through bones, or frozen foods, or in other applications which require prying, which may result in chipping. Several brands now offer either a black-coloured or a designed blade made through an additional hot isostatic pressing step, which increases the toughness.

Material Structure

Three phases are known: monoclinic below 1170 °C, tetragonal between 1170 °C and 2370 °C, and cubic above 2370 °C. The trend is for higher symmetry at higher temperatures, as is usually the case. A small percentage of the oxides of calcium or yttrium stabilize in the cubic phase. The very rare mineral tazheranite (Zr,Ti,Ca)O2 is cubic. Unlike TiO2, which features six-coordinate Ti in all phases, monoclinic zirconia consists of seven-coordinate zirconium centres. This difference is attributed to the larger size of Zr atom relative to the Ti atom.