Technical Ceramics Debinding and sintering processes are necessary to remove organic binder and to densify ceramic components

Technisch keramiek omvat een breed scala van geavanceerde keramische materialen, ontwikkeld voor hun uitstekende mechanische, elektrische en thermische eigenschappen. Ze zijn vaak zeer goed bestand tegen smelten, buigen, strekken, corrosie en slijtage. Het gebruik van geavanceerde keramiek in lucht-en ruimtevaart, automobiel-, defensie- en energiemarkten breidt zich steeds verder uit.

Carbolite ovens worden op grote schaal gebruikt in zowel onderzoek en productie voor de 'debinding' en sinteren van technische keramiek. Voor het 'debinding' proces (van de groene delen) zijn lagere temperatuur kamerovens met uitstekende temperatuur uniformiteit vereist. De bruine onderdelen worden vervolgens gesinterd tot 1800°C in een hoge temperatuur oven.

Furnaces for Debinding

The debinding and ashing processes both involve the removal of certain materials before further analysis. Hence, Carbolite Gero ashing furnaces can efficiently perform thermal debinding by removing the binder from the furnace chamber.
Targets:

• The binder must be removed uniformly without damaging the part
  • Temperature uniformity and heating rates determine if the binder is removed from the sample uniformly
  • Air exchanges determine if the binder is removed efficiently from the chamber
    
    
• The efficient removal of the binder improves the material properties and the final density of the ceramic
• Pre-sintering increases the strength of the brown body and makes handling it easier

Furnaces for sintering

Sintering results in the densification and the formation of a durable ceramic structure. Carbolite Gero offers furnaces ideal for this process.

Targets:

• Densification of parts
• Uniform shrinkage
• Temperature uniformity is key
• Control of heating and cooling rates is important to prevent cracking

Furnaces for Debinding & Sintering

A solution combining debinding and sintering processes. These Carbolite Gero furnaces are extremely functional for binder removal and densification of ceramic components.

Targets:

• Efficient debinding
• Densification of parts
• Uniform shrinkage

Achtergrond informatie

Technical ceramics, also known as engineering ceramics or advanced ceramics, are designed to possess exceptional mechanical, thermal, electrical, and chemical properties. Unlike traditional ceramics, which are primarily used for decorative purposes, the unique characteristics of technical ceramics make them indispensable in high-performance applications where other materials, such as metals or polymers, may fall short.

Applications for technical ceramics span across various industries, including aerospace, automotive, electronics, medical, energy, and defence. They are employed in a wide array of components, such as cutting tools, ball bearings, insulators, sensors, catalyst supports, and even in bio-ceramic implants for medical purposes.

Oxide ceramics

Oxide ceramics are inorganic compounds that consist of oxygen and one or more metallic elements. The prevalence of oxygen within the composition contributes to their unique properties. Oxide ceramics possess excellent thermal stability, high electrical insulation and are chemically inert. Additionally, oxide ceramics often exhibit good mechanical strength and hardness, making them suitable for various structural and functional applications.

Non-oxide ceramics

Non-oxide ceramics are inorganic compounds that are made up of a combination of metallic and non-metallic elements without the presence of oxygen. These compounds possess high thermal and electrical conductivity, high oxidation resistance and are chemically inert. In addition to having high strength and hardness non-oxide ceramics are resistant to wear and corrosion.

Composites

Composites are formed by combining two or more materials to merge and enhance performance. Ceramic-based composites undergo a complex manufacturing process that can result in superior properties in terms of strength and toughness.

Sintering of ceramics

Sintering is a crucial thermal process in the production of ceramics. It involves heating a compacted or shaped ceramic material to high temperatures below its melting point. During sintering, the ceramic particles bond together, resulting in densification and the formation of a solid, coherent, and durable ceramic structure. The sintering process involves three main stages: particle rearrangement, particle necking, and pore elimination. Initially, at lower temperatures, the ceramic particles begin to rearrange and move closer together due to interparticle diffusion. The diffusion process is driven by the reduction in surface energy of the particles. As the temperature increases, the particles start to form necks. This starts to create a bridge between them and facilitates the transfer of material and further consolidation of the structure. This stage is crucial for achieving increased strength and density in the ceramic material. In the final stage, the remaining pores are eliminated as the ceramic structure continues to densify, resulting in a nearly fully dense ceramic body.

The sintering temperature and duration are carefully controlled to achieve the desired properties of the final ceramic product. High temperatures and prolonged sintering times generally lead to better densification and improved mechanical properties, but excessive sintering may cause grain growth, which can adversely affect certain properties.

The sintering process is influenced by various factors, including the chemical composition of the ceramic, the size and distribution of the particles, the sintering atmosphere (oxidizing, reducing, or inert), and the presence of any sintering aids or additives. Sintering aids can promote densification and help to lower the sintering temperature, making the process more efficient.

Sintering is a fundamental step in the manufacturing of a wide range of ceramic products, including bricks, tiles, advanced technical ceramics, and more. The process transforms the initially porous and fragile green ceramic material into a dense, durable, and functional ceramic component. This component is then ready to meet the demands of its intended application in industries such as electronics, automotive, aerospace, and construction.

Microstructural Changes During Sintering

During sintering

During sintering, the particles of the ceramic part diffuse through the structure and fuse together, increasing the overall density of the part.

Microstructure after sintering

During sintering in a furnace, the microstructure of the ceramic part is significantly denser and has fewer gaps between the particles. The sintering process leads to some shrinkage, with some parts becoming smaller. This is a normal part of manufacturing process and should be considered in the original design of moulds.

Experiment 1

Thermal Debinding using AAF-BAL

During the thermal debinding process, the printed green part was heat treated in air for approximately 13 hours. The mass loss after the thermal debinding was in the order of 9.5%.

Experiment 2

Debinding & Sintering using HTF

During the heat treatment, the 3d printed components were heat treated in the same furnace. The weight loss for the X shaped sample was in the order of 6.5%. The weight loss for the Rectangular shaped sample was in the order of 11.1%.

Experiment 3

Sintering using TF1 16/100/450

During the sintering process, the weight loss of the component was in the order of 0.5%

Technical Ceramics - FAQ