This article and video shows, how you can design your sintering process to the best with KINETICS NEO and the data from Thermal Analysis. Simulate before firing and speed up your sintering process up to 60%
Design your Sintering Process to the Best – with KINETICS NEO and the Data of Thermal Analysis.
See and read how it works:
NETZSCH customers in the ceramics industry were able to accelerate their sintering process by up to 60% with KINETICS NEO without compromising material quality.
Whether technical ceramics, sanitary ware or tableware – the manufacturing process of every ceramic component basically undergoes similar basic manufacturing steps. The tedious step in which the fragile, shaped green body becomes a robust, dense ceramic body at high temperature is called sintering. In this step, the goal is to achieve the theoretically highest density with low energy consumption in a short time. During the sintering process, various processes take place simultaneously:
Grain boundary diffusion.
Depending on the local temperature, particle size and atmosphere, the process with the the highest conversion rate dominates. The kinetics (speed and time sequence) of the corresponding processes is difficult to predict in advance. What happens at what time and at what temperature in a sintering component can be reconstructed with thermoanalytical and thermophysical measuring methods:
Dilatometry – shows temperature dependent length and volumechanges and gives information about phase transformations which are accompanied by a change of the expansion coefficient. It tells us, where sintering-steps accur.
Thermogravimetry – TGA gives information about debindering and dehydration my detection of temperature-depending mass-loss.
Laser- or Light-Flash-Method – LFA shows the thermal diffusivity and by knowing the density and the specific heat capacity is gives the thermal conductivity. This helps transfer sintering behaviour to bigger parts.
All these methods show us in time sequence and in relation to the temperature how a sintering body of a certain size and shape behaves.
Design and Optimization of Firing Programs for your Sintering Process.
The process-engineer can use “trial & error” to find suitable firing programs. He tries to do justice to each individual process during the sintering process. This leads to long firing programs that do not optimally match the real course of the sintering process. What can I do to find the optimum for my process? At first, it makes sense to look at the dehydration and debindering by Thermogravimetry. With this Method you get worthwile data about the temperatures, where the specimen lose weight – which tells us: “Something comes out of the material”. If you no longer see mass losses, you can assume, that debindering is completed. In a second step, you characterize your material with the help of dilatometry. With dilatometry you see, where sintering starts and at which temperatures sintering steps accur. Finally, if you no longer see shrinkage, sintering is completed. Running both tests under different heating rates, it tells you, how the processes are dependent on speed. Now “Thermo-Kinetics” come into Play! If you load those data, which were developed under different heating rates into the simulation software KINETICS NEO, the reaction kinetics can be mathematically modeled. What you get is a simulation model that reliably describes the temperature-dependent and time-dependent processes in your material. The picture shows the dilatometer-curves and the fit calculation from the model. With this model you can now simulate ANY burning program and the effect on your sintering process by simple tabular input.
Example 1: Modelled sintering curve based on a simple temperature programm with one isothermal segment (100 Minutes).
With respect to the conversion rates in every sintering step, you can optimize you firing programm directly in the software and see, how the change of programm will affect the sintering process and the conversion rates for every step. Too big conversion rates can cause cracks or deformation on your parts. The model for the conversion rates can be seen in the picture based on different heating rates. The challenge is to find out, what the maximum conversion rate will be without compromising the quality. Next to more complex sintering programs, the easiest first step is to simulate with a constant conversion rate – what you get as a result is the temperature curve:
Example 2: Modelled temperture curve based on a conversion rate of 0.5%/min.
With optimizing your debindering and sintering process with the respect to maximum conversion rates and the ability of your furnace in terms of heating- and cooling rates, you will get close to the optimum with modelling your firing programm in the software. With Thermo-Kinetic Simulation you’ll get faster to the optimum!
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Our customers in the ceramics industry were able to accelerate their sintering processes by up to 60% with KINETICS NEO without compromising material quality.