In the oxidizing atmosphere nickel is oxidized to nickel oxide, therefore are reducing (H2) or inert (Ar) atmosphere absolutely necessary for sintering.

Large amount of gases are produced during combustion process . There are CO2, N2, and water steam (reducing atmosphere). If you will make an insulated vessel, or better vessel with pump you can try to synthesised Ni in metal form at the expense of protection of combustion process gases.

This question is not so easily answered, because the specifications of what product you need is unclear. The following questions need to be answered before you can choose a manufacturing process for your needs:

- Do you want to get rid of the sintering process and search for an alternative way of production?

- Do you want to get rid of the reducing atmosphere but sintering is ok for you in general?

- What is the form of product that you need? Do you need blocks (if so what size) or is a coating of 1-2mm sufficient for your needs?

There's a lot of alternative ways of producing cermets apart from traditional sintering, like laser cladding, thermal spraying, spark sintering, electric discharge sintering. All of them have their special applications and advantages (and disadvantages as well). To choose a promising process is always a matter of your product specifications.

I believe you are trying to produce a lightweight hard metal with low thermal conductivity, is that right?

@Vadim Verlotski, Thank you for your answer. 

@Aleksandr Khort, also thank you for your anwser. 

@Birger Hussong, thank you for your explanations. I did learned alot from reading that. In fact, my objective is to produce a cermet Ni-BCZY by mixing a NiO with synthesized BCZY powder. However, I don't have a special oven in which i could sinter the pellet in a controlled atmosphere (in this case, a reducing atmosphere like H2 or ArH2). That's why I was seeking an alternative way to sinter it in such a way that reducing atmosphere is not needed. However, I could not find any solutions in my lab with regards to the facility that i have at my disposal. So, I was obligated to sinter in atmospheric air. But then, I figured out that I had a test brench where I can reduce my cermet. Now, the problem is solved. Anyways, thank you for your suggested solutions. 

However, I encounter another problem. 

i am using a chemical product called Zironium(IV) oxynitrate hydrate whose chemical formula is ZrO(NO3)2 xH2O. My collegue told me that the x = 5. However, I found several papers in which one author mentioned for their products, the x = 2.3 and another said x = 6.

So, i wonder what is the exact value of x for this specific product.

Thank you for anwsers.