What is the best and easiest method for thermally etching of UHTCs? I want to analyze the microstructure, calculate the grain size, and investigate the grain boundaries of a polished sample. Is there any standard method?
Anneal at 100 °C below the densification or sintering temperature for half an hour. This is the ceramic engineer's rule of thumb. Depending on the diffusivity of your material, it may take long, so keep annealing in increments of 1/2 hour.
Happy New Year!
Anneal at 100 °C below the densification or sintering temperature for half an hour. This is the ceramic engineer's rule of thumb. Depending on the diffusivity of your material, it may take long, so keep annealing in increments of 1/2 hour.
Happy New Year!
Because your ceramic is a ultra high form and you need to vacuum condition i suggest to you chemical etching.
We generally characterize our UHTCs (carbides nitrides and borides) at SEM (and FE-SEM) without any thermal etching. You should be able to observe clearly your sample after an accurate polishing until using belowmicron abrasives and a successive careful cleaning of surfaces...By the way, if phases in your composite are so hard to distinguish even by backscattered electrons (trimming eV, sensitivity and contrast of the detector), I would suggest a mild plasma etching in CF4/O2 mix atmosphere, modulating gas flow, dwell times and pasma current to optimize ablation of phases or grain boundaries.
Soak at 100 degree below the sintering temp for an hr. Depending upon the grain structure it may take longer. You need to optimize the thermal etching profile withe fewd set of samples. Good luck.
You can think of using a laser beam of high power. Be careful, because you can change the local densification and consequently promote regions of surface tension and change of crystalline phase.
In our research, we annealed the samples at 200C below the sintering temperature for 4 hrs. You may need to optimize the thermal etching conditions based on your samples.
hi! and happy new year
you can try the chemical etching by no strong acid (HCl solution or nitric acid solution) you can also use a diluted HF (5%) if ther is an amorphous or glass phases.
these acid attacks must be used after polishing with (0.03 to 0.5 µm) Al2O3 abrasives
You can also try to use ion etching on the polished sample or You can try ion cross section. Then by using chanelling contrast You can observe grain size and shape
Ceramic based materials can be observed using SEM (SE or BSE) after surface cleaning or polishing. Chemical etching by mineral acids may be helpful.
Dear Mehdi,
I agree with Waltraud, thermally etching is the simplest way for you. I just want to add one thing, sometimes thermally etching will also give you good results at annealing temperature as low as 300 degree C below the sintering temperature (for example, your sintering temperature is 1500 degree C, you can anneal your sample at 1200 degree C). In that case, you should increase the duration of annealing. Hope this information can help you, I know sometimes the maximum temperature of heating furnace is much lower than the sintering temperature.
Happy New Year!
Soak at 100 °C below the densification or sintering temperature for half an hour is the best way. Chemcal etching is very useful if glassy phases are presnt in grainboundary. In my openion if soaking time at 300oC below sintering become prolong, actual microstructure may change(e.g. grain growth due to larger diffusion time).
does it depend on the sample that you measure?
don't you think that you should first have a standard decomposition mode of your samples ?
Before thermal etching, how well-ground or polished does the surface need to be?
Hossein, to remove sample from cold mount, you can cut away most of the mounting material abrasively or with a saw. Then, I soak the remaining mounted sample+mounting material in acetone to soften the mount material and remove. You may need to repeat the immersion several times. This works for the epoxy I use as mounting material for grinding.
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