Ceramic powders are granular form of fine Ceramic Oxides or nitrides that are used to make Ceramic components. The type and nature of powdered ceramic depends upon the end use of the ceramic. Some of the most common global manufacturing methods of ceramic powder is covered in the article below.

What is Ceramic powder?

A powdered ceramic is known to be a culmination of fine particles. As described above, ceramic powders are made of components such as Aluminum, Silicon or Zirconium oxide. It can also be made of carbides and nitrides of ceramic media.

While making ceramic powder, one key point to check is to make the powder easily handleable.  For that reason, the ceramic powder constitutes certain additives in addition to agglomerates. They also use binding agent and a releasing agent. The binding agent keeps the powder intact during moulding and the releasing agent releases the ceramic from the die.

Regarding the nature of ceramic powder, powdered ceramic efficiency depends upon several entities. The particle size and distribution play a significant role when it comes to the properties of Ceramic powder.  The amount of binding and releasing agent in the powder impacts the powder nature.  Any available defects and the presence of lumps are the other influencings factors.

What is ceramic powder made of?

On a very detailed structural note, Ceramic powders are made up of particles called as agglomerates. The primary particles are crystallites which are made up of single unit cells that are either systematically or randomly arranged. The secondary particle is formed by clubbing primary particle and are known as agglomerates. The properties of the agglomerates are generally controlled during synthesis or during granulation.

Unless there is an effort to control particle size, the average agglomerate size remains equal to the average particle size in ceramic powders. Particle size determine the nature of the powdered ceramic whether it is easily formable or not. An illustration of the constitution of ceramic powder is given above for reference.

What is Ceramic powder used for?

The temperature range of ceramic powders lies in between ceramic components and alloys. Ceramic powders have high toughness, Higher melting point, better plasticity, corrosion resistance and wear and tear resistance. Ceramic powders remain intact even at a temperature greater than 1000 degC. They will sustain without any degradation up to 1900 degC.

Ceramic powders are also better electrical insulators. Some of the prominent applications of Ceramic powders are given here for reference.

Application in the field of Advanced ceramics

• The dielectric properties of ceramic powder make them suitable for the manufacture of electrical components. Ceramic powders are used to make Substrates for integrated electrical circuits, Insulators and Capacitors.

• They are used in sensor materials, actuator components and others that converts mechanical energy into electrical signals. In short, Ceramic powders are used for manufacturing piezoelectric devices.

• Ceramic powders can also be used as protective coatings in industries of automobiles and aerospace to deal with higher temperature. Once function as an integral engine part , ceramic powder controls the heat effect on accessories .

• Ceramic powder is biocompatible. They are used as bio ceramic materials as medical implants and dental crowns. Ceramic powders are popular in dentistry due t the smooth finish and structural strength they offer.

Application of ceramic powder in the field of traditional ceramic and Industries

• Ceramic powders are used as building material for conventional pottery and is used in traditional ceramic paste arts.

• They are used as refractory linings for their better thermal stability.

• Ceramic powders are also used as integral components of cutting and grinding tools. They are abrasion resistant and is known for their mechanical strength.

• Powdered ceramic can also cater coating industry.  Powdered ceramic coatings ensure corrosion resistance, provide thermal stability and increases durability.

• Ceramic powders are used in 3D printing to obtain complex ceramic parts and offers high precision.

Futuristic application of Ceramic Powders

• Ceramic powders are being considered as a research material in the field of solid-state batteries
• Nano ceramic powders are being developed as advanced ceramic materials which is expected to grow further by 2031.

How to make ceramic powder

There are variety of global manufacturing methods to produce ceramic powders. Let us cover the different aspects of some of the most popular processing methods.

Milling or grinding

Milling or grinding stands for the conventional manufacture of powders.  In the process, the raw material is milled until the particle size are reduced and ceramic powder is formed. Milling can be either through ball milling or through  attrition milling.

In ball milling, hard balls are used to mill the raw materials. Ball billing produces fine powders where shear and impact force plays major roles. The milling ball is designed to operate above the critical speed to obtain better milling results. Attrition milling uses frictional force to reduce particle size for producing ceramic powders.

Freeze Drying to prepare ceramic powders

Freeze drying or dehydration is used to produce formable ceramic powders.  From a sprayed ceramic mist, the powder is manufactured through freeze drying. In freeze drying the mist is cooled below the eutectic point initially, followed by 95% of moisture removal by drying.

The primary drying removes maximum moisture   followed by secondary drying. Once the process is done vacuum sealing through an inert gas is done. Freeze drying process of ceramic powder preparation are generally considered expensive.

Spray Drying

Spray drying is a proven technology when it comes to producing ceramic powders of granular nature. Spray drying to form ceramic powders would obtain homogenized powder with moisture range of 5-7% offering better plasticity. This is attributed to the wet milling of clay or the constituent materials. The major concern of spray drying and the use of wetting agents are high energy and water consumption in the process.

The granulated particles produced from spray drying are almost spherical with smooth surfaces. They have the particle size in the range of 125 to 1000 microns. The particles are hollow inside due to the physical phenomenon of the formation of granules.

High Shear mixing granulation

High shear mixing granulation method of ceramic powder production is a dry production technology. The major advantages cited for this process are less energy and water consumption. In high shear mixing granulation technique the ceramic powder agglomerates are made to form in a pendulum mill with the help of water.

High shear mixing technology offers grain size of around 300 – 500 micrometres. The minimum expected from the process is around 125 micrometres almost similar to spray drying granule size.

Rolling Compaction technology

Rolling compaction methodology of powdered ceramic production uses the dry powder from the pendulum mill further in a pelletizer. The pelletizer compacts the powder and further grinds it into fine powder form.

The shear compaction technology   is not efficient when it comes to homogeneous grain size, however ceramic behaviour of the powders will be in the useful range.

How to make ceramic

This section is crucial to shed light on why would we require ceramic powders. A general simple understanding, ceramic powders serve as the raw material for making ceramic. The different process of ceramic making using ceramic powder are compaction, extrusion, injection moulding, tape slip and gel casting.

• Compacting is the process of converting ceramic powder from granular to denser form by increasing the cohesive force. The method includes hot and cold pressing. Once pressed the material is later sintered to obtain ceramic.

• Injection moulding is done for high precision entities or to obtain complex geometries. It is a process used to manufacture oxide and non-oxide ceramics and is often favoured in industries.

• Tape casting is common for synthesising substrates for PCB’s. A powder with a polymer binder is casted over a non-sticky material such as Teflon. The slurry is further pressed to her the desired thickness and a smooth finish.

• Slip casting is employed where the traditional pottery methodology cannot be used. The method ensures high precision. When the powder is mixed with a suspension, the material forms a slip that which further is redirected into a porous mould.  Later, the mould is dried and solid layer of ceramic is obtained for use.

• Gel casting uses a free radical, a monomer and a cross-linking agent which is used to make a suspension. The gel mixture hence formed is poured into a mould to solidify and   form the required ceramic material. Once the ceramic is formed, the green material is sintered and the left out are removed.

• Extrusion is a relatively simple process where the powder passes through a die and get to the form of the required component. The extrusion process can be dry cold or hot depending upon the mechanical strength that is required for the body.

Closing Comments

Ceramic powders play a significant role in curating the functional properties of different grades of ceramic. Different ceramic powder making techniques cater to different property requirements. A better knowledge on the making process is hence necessary. This helps the engineer decide the making process for the desirable property expected.