Question

1. What is the difference between traditional ceramics and the new ceramics, as far as raw materials are concerned? 2. List the basic steps in the traditional ceramics sequence. 3. What is the technical difference between crushing and grinding in the preparation of traditional ceramic raw materials? 4. Describe the slip casting process in traditional ceramics processing. 5. List and briefly describe some of the plastic-forming methods used to shape traditional ceramics products. 6. What is the process of jiggering? 7. What is the difference between dry pressing and semi dry pressing of traditional ceramics parts? 8. What happens to a ceramic material when it is sintered? 9. What is the name given to the furnace used to fire ceramic ware? 10. What is glazing in traditional ceramic processing? 11. Why is the drying step important for processing of traditional ceramics, usually not required in processing of new ceramics? 12. Why is raw material preparation more important in the processing of new ceramics than for traditional ceramics? 13. What is the freeze drying process used to make certain new ceramic powders? 14. Describe the doctor-blade process. 15. Liquid phase sintering is used for WC-Co compacts, even though the sintering temperatures are below the melting points of either WC or Co. How is this possible? 16. What are some design recommendations for ceramic parts?

Answer 1

1.

Traditional Ceramics	Advanced Ceramics
These are only made of clay.	These are made of composite materials such as nitrides, carbides, etc.,
These can be classified according to the composition of the clay used.	These are man-made materials. Their quality depends on the material purity and process of production.
The gran size, Structure of the crystal and the chemical composition cannot be controlled.	The gran size, Crystal structure and the chemical composition can be maintained accurately.
Raw material preparation cannot be pre-determined.	Raw material preparation is strictly controlled.
Properties of the material cannot be determined.	Desired properties can be obtained because, the control on Raw materials and compositions.

2.
As we see in the daily life, the basic steps involved in the Processing of Traditional Ceramics are
(a) Preparation of Raw Materials: First, the Raw materials are to be prepared. i.e., the moist clay.
(b) Shaping: Next, the clay is to be placed on the pottery wheel and shaped while it is revolving.
(c) Drying: The shaped product is to be dried for a while to retain some strength.
(d) Firing: Finally, the product is to be fired to loss all the moisture and gain toughness.

3.
When the Raw material is brought out, it consists of rock like structures in it. Traditional potters use two methods namely Crushing and Grinding. When the Raw material is crushed, the rocks are reduced into small minerals. Then, grinding is followed in order, to make the material into a fine powder.

4.
Slip Casting is an easy shaping process used in Traditional Ceramic Processing. As we usually see it in Idol making, a Plaster of Paris (POP) Replica will be made firstly. The Clay slurry is poured into it. The POP absorbs the water from the clay and produces a hard layer of the clay, at its surface. The slurry is then, removed and the Clay shape is extracted carefully.

5.
The plastic forming methods used to shape Traditional Ceramic Materials are
(a) Throwing Pottery: The clay is placed on the pottery wheel and shaped while the wheel is revolving.
(b) Jiggering: Jiggering is a process, where, the hand modeling is replaced with metal jigs (for accurate shapes).
(c) Plastic Pressing: The clay is pressed into a mold.
(d) Extrusion: The Raw material is compressed and made to come out from an outlet which will have a desired shape.

6.
Jiggering:
The process of jiggering is defined as, forming the clay into the desired shape with the use of Jigs (Stepped metal plates). Dinner plates are usually made with jiggering.

7.
In Dry Pressing, the clay is pressed whose water content is below 5 percent. Whereas, In the Semi-Dry Pressing, the clay contains 10 percent to 15 percent of water. The Dry Pressing has limitations due to its low plasticity.

8.
Sintering increases the bond between the clay particles (i.e., Makes it denser) and reduces the pores in the product.

9.
The name of the Furnace which is used to fire the ceramic ware is Klin.

10.
Glazing is the Oxide ceramic coating made over the ceramic products in order to increase its shine and water proofing.

11.
The Traditional Ceramic material (i.e., Green sand or clay) consists of water. Whereas, water is not important in Advanced ceramic processes. So, the Traditional Ceramic process requires the Drying Stage.

12.
The New or Advanced ceramics are made in the view of attaining more strength and additional desired properties. So, the preparation of raw materials is crucial in Advanced Ceramics.

13.
Freeze Drying:
First, the chemical salts will be dissolved into the water and sprayed in the form of droplets. Then, they will be frozen immediately. Vacuum chamber is used to remove water from the droplets. This is called Freeze-Drying. Next, they will be heated to get decomposed and Ceramic powder will be formed.

14.
Doctor-Blade process is similar of a belt drive process. The Slurry is flown over a belt. The belt will have a wiping blade above a certain height. The slurry passed in between them, becomes a thin film, which then, will be used for further processing.

15.
When heated for sintering, WC dissolves into the Cobalt and that, reduces the melting point of the Cobalt (thus, keeps it from becoming into solid). Hence, the Sintering phase occurs in Liquid State.

16.
Design recommendations for ceramic parts are:

• Only Compressive stresses. No Tensile Stresses.
• No Impact loading
• No threading
• Simple Part geometries
• Shrinkage should be accounted