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.
