Ceramic TilesHow it’s made?

Farooq Ahmad ShahA presentation by:

The Basics• Ceramic means “fired clay” and tile

means “covering.” • Common raw materials are sand, clay,

talc, feldspar.• A typical example of

ceramic powder metallurgy.• A ceramic tile is just clay that's formed,

glazed and baked.

Figure 1: Wall & floor tiles.

Preparation of Powder• Rock lumps reduction to powder through

crushing and grinding.• Crushing – reduction of large lumps to

smaller. Jaw breaker, gyratory crushers, roller crushes, hammer mills. Picture

• Grinding - further reduction to fine powder. Ball mill.. Picture

• Wet milling - Water, alumina, silica, binders and lubricants mixed in ball mill with powder to form a slurry.

• Spray drying – Slurry is dried using a rising column of hot air.

• The raw materials are mixed in specific proportions according to weight. The specified mixture is achieved by varying the speed of conveyors that feed the master conveyor belt

Video

Shaping Process• Dry Pressing – Powder is deposited into

a tray and hydraulically pressed (). Binders and lubricants added keep the shape intact and prevent sticking to the mold.

Video

Figure 5: Dry pressing

Glazing Process

Glaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.

Without glazing, ceramics would remain porous and would remain unsuitable for holding liquids. Special glazing processes are used to make dinnerware, porcelain and stoneware beautiful.

Glazing ProcessComposition:

Ceramic glazes generally contain silica to form glass, in combination with a mixture of metal oxides such as sodium, potassium and calcium which act as a flux and allow the glaze to melt at a particular temperature, alumina (usually from added clay) to stiffen the glaze and prevent it from running off the piece.

glazing Process

To prepare glaze the raw materials are weighed, then mixed and dry or wet milled. The milled glazes are then applied by following methods.

1. In centrifugal glazing or discing, the glaze is fed through a rotating disc that throws the glaze onto the tile.

2. In the waterfall method, a stream of glaze falls onto the tile as it passes on a conveyor underneath.

3. Sometimes, the glaze is simply sprayed on.4. For multiple glaze applications, screen printing

method is used.

glazing Process

Water fall glazing:

Spray glazing:

glazing Process

Video

Firing (sintering) Process

Before firing the ceramic piece is said to be GREEN.Means not fully processed or treated. This GREEN piece lacks hardness and strength, so it is heated to fix is shape and to achieve hardness and strength.

Firing is the heat treatment process that sinters the ceramic material it is performed in a furnace called a kiln. In sintering , bonds are developed between the ceramic grains, and this is accompanied by reduction of porosity.

Firing Process

•  Typical firing temperatures for alumina, mullite, and zirconia reach 2850 °F - 3100 °F.

• Typical firing cycles can range from 12 - 120 hours depending upon the kiln type and product.

• Ceramics shrink approximately 20% during the sintering process.

• Unglazed ceramic ware is fired only once but glazed product s are fired twice. Fire the ware once before glazing to harden the body of the piece, apply the glaze, fire the piece a second time to harden the glaze.

Firing (sintering) Process

Finishing Process

Parts made of ceramics sometimes require finishing. In general, these operations have of the following purposes, to

(1) increase dimensional accuracy,

(2) Improve surface finish, and

(3) make minor changes in part geometry. Finishing operations usually involve grinding and other abrasive processes.

Glazing and Firing

THANK YOU.

“We hear only those questions for which we are in a position to find answers.”Friedrich Nietzsche

Ceramic Processing

Figure 2: A typical work part during the sequence, and the condition of the powders.

Crushing Operations

Figure 3: Crushing operations: (a) jaw crusher, (b) gyratory crusher, (c) roll crusher, and (d) hammer mill.

Grinding Operation

Figure 4: Hard spheres mixed with the stock are tumbled inside a rotating cylindrical container.