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

A műszaki kerámiák közé sokféle olyan anyag tartozik, melyeket kiváló mechanikai, elektromos vagy termikus tulajdonságaik érdekében fejlesztettek ki. Gyakran nagyon ellenállóak a megolvadásal, hajlítássl, nyújtással, korrózióval vagy kopással szemben. Műszaki kerámiák használata egyre elterjedtebbé válik a repülőgép- és járműgyártásban, a hadi- és energiaiparban.

Carbolite kemencéket a műszaki kerámiák kutatásában és gyártásában kiégetés és szinterelés művelete során alkalmaznak. A kötőanyagnak a nyers formából (green part) történő eltávolításához alacsonyabb hőmérsékletű, ám kiváló hőmérséklethomogenitású kemence szükséges. Az eredményül kapott formát (brown part) azután még magas hőmérsékletű kemencében 1800°C-on szinterelni kell.

Solutions from Carbolite Gero

Debinding and sintering are two important processes for manufacturing technical ceramics. Carbolite Gero offers ovens and furnaces, optimised for laboratory and industrial settings. Depending on customer requirements, a two-furnace solution (separate furnaces for debinding and sintering) or a single-furnace solution (combined debinding and sintering furnace) can be offered.

Two-furnace solution

The debinding and sintering process can be carried out in two separate furnaces. This provides the advantage of having an optimized furnace for each process step, keeping any contaminants from the binder removal restricted to the debinding furnace. In addition, biscuit firing also takes place in the debinding furnace to ensure the stability of the ceramic component. This approach is suitable for batches being treated in a laboratory and industrial environment.

Single-furnace solution

A combined debinding and sintering system is a suitable solution for higher batch loads. This saves time and eliminates the need for handling parts between the two steps, reducing risks of breakage that could occur for parts that become unstable during the debinding.

Carbolite Gero offers furnaces that include options for debinding, afterburner safety system and a high temperature heating system for both two-furnace and single-furnace solutions.

Advantages of investing in a Carbolite Gero furnace:

  • Efficient removal of binder due to a high airflow
  • Great temperature uniformity at low temperatures due to the air pre-heater
  • Safe handling of binder by using the thermal afterburner
  • Unique uniformity at high temperatures due to an optimized heating element arrangement
  • Air blowers can be used for fast cooling to minimize run times

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

Safety options for Technical Ceramics

The process produces volatiles that can prove to be harmful. Precautions should be taken to reduce any risks. Carbolite Gero considers options to optimise the production process.

Afterburner

An afterburner (left) is used to oxidize volatiles from the removal process into NOx, CO2, and H2O. This ensures all volatiles are transformed into safer molecules and released into the environment. Burns all volatiles, including those with a boiling point below 20 °C, such as hydrogen, ammonia, and ethane.

Condensate trap

A condensate trap (right) is used to condensate all compounds over 20 °C. All volatiles with the boiling point lower than 20 °C are let through.

If required due to the process or recommended by the customer, the afterburner and condensate trap can be combined. Similarly, the igniter and condensate trap can also be combined due to reason. We are experts and have multiple solutions in our portfolio to guide you to the right product and safety equipment. Please contact us for any enquires on a suitable solution for your application needs.

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Háttérinformáció

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.

Debinding of ceramics

Debinding plays a vital role in the production of high-quality and functional ceramic components by effectively removing organic binders or additives from a green ceramic body before the final sintering stage. Green ceramics are made by shaping ceramic powders that are mixed with organic binders. These binders provide the material with cohesiveness and moldability during shaping or forming processes such as injection moulding, tape casting, or extrusion.

The debinding process involves subjecting the green ceramic to controlled heating in an atmosphere or under conditions that allow the organic components to vaporize or decompose. This can be achieved through various techniques, including thermal debinding, solvent extraction, or a combination of both. The choice of debinding method depends on the specific composition of the green ceramic and the desired final properties of the finished product.

Solvent extraction involves immersing the green ceramic in a suitable solvent that selectively dissolves the organic binders. This process can be facilitated by agitation, ultrasonic energy, or by other means to enhance the removal of the organic components. After the solvent extraction, the ceramic is dried to remove any remaining solvent before sintering.

Debinding is a crucial step in the manufacturing of ceramics. It impacts the properties of the ceramic by eliminating organic materials that can hinder densification during sintering. The success of the debinding process significantly influences the final product's density, strength, and dimensional accuracy.

Microstructural Changes During Debinding

Microstructure of the green part

The starting material is formed by moulding, extruding or 3D printing into the desired shape. The binder is highlighted in blue and green. At this point, the part is called the "green part".

After solvent binding

In solvent debinding, the main binder (blue) is removed, leaving only the backbone binder (green), which must be thermally removed.

After thermal (residual) debinding

During residual debinding, the backbone binder (green) is removed, and the part is now called the "brown part". To increase the density and strength of the part, it must be sintered. At this stage, the particles begin to diffuse and stick to each other.

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.

About 3DCeram MAT

3dceram’s MAT machine is the one-stop solution for extrusion technologies. The Machine has now 3 different extrusion heads for printing and complemented by a CNC tool for green machining of printed parts.

MAT Machine Specifications

  • Footprint: 60 (W) x 60 (D) x 115 (H) cm
  • Print volume: 20 (W) x 20 (D) x 20 (H) cm
  • Machine weight: ca. 90 kg
  • Supply: 230V, 16A, 50Hz
  • Closed Loop Stepper Motors
  • Heated Print Chamber (<60°C)
  • Heated Filament Chamber (<50°C)

3DCeram Heads:

  • FFF head for working with ceramic and metal filaments
  • Pellet Head for working with ceramic and metal pellets
  • Robocasting (one-component or two-component) for ceramics, metal and silicone
  • 3-axis CNC tool for green machining

A comparison of different shaping technologies with the MAT have been done below:

Shaping technology Material cost Surface roughness Printing resolution Material recycling
FFF ★★★ ★★★
Pellet printing ★★★ ★★ ★★ ★★★
Robocasting ★★ ★★

To know more about 3DCeram Sinto Tiwari, please contact 3dceram-tiwari

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%

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Whether it is a standard product or a fully customised solution, Carbolite Gero has manufactured thousands of drying solutions over the years and realised projects around the globe.

Contact us for a free consultation and talk to a product specialist to find the most suitable solution for your application needs!
 

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Technical Ceramics - Gyakori kérdések

What type of ceramics can be processed in the ovens and furnaces?

Carbolite gero offers solutions for oxide and non-oxide ceramics. Oxide ceramics include inorganic compounds that consist of oxygen and one or more metallic elements while non-oxide ceramics include inorganic compounds that are made up of a combination of metallic and non-metallic elements without the presence of oxygen.

What is the difference between debinding and sintering?

The debinding process involves effectively removing the organic binder or additives from a green ceramic body through various techniques including thermal debinding, solvent extraction, or a combination of both. Sintering involves heating a material to a high temperature below its melting point. The sintering process encompasses 3 main stages particle rearrangement, particle necking, and pore elimination. These stages facilitate the bonding of particles together, resulting in the overall densification of the ceramic structure.

What solutions do we offer for the debinding and sintering of technical ceramics?

Carbolite gero provides a variety of solutions for debinding and sintering. We offer a two-furnace solution, where separate furnaces are used for debinding and sintering. This approach has the advantage of confining any contaminants from the binder removal process to the debinding furnace. An alternative single-furnace solution is offered where one furnace is utilized for both debinding and sintering. This option is ideal for larger, high batch loads as it reduces transfer between stages and breakage risk during debinding.

What type of sintering atmosphere can the furnaces support?

Carbolite Gero furnaces can support oxidising, reducing and an inert atmosphere during the sintering process. Please contact Carbolite Gero to obtain further information on gas equipment and processing atmosphere for your application.