In-situ Formation of TiC from Titanium/Stearic Acid Powders by Mechanical Alloying Structural and Microstructural Point of View.

Titanium carbide (TiC) is an attractive material to be used as reinforcement in polymers, ceramics, aluminum, and their alloys [1]. It is possible to obtain reinforced materials with high hardness and low weight parameters, which are highly demanded in the aerospace and automotive industries [2]. Previous reports suggest that the in-situ TiC preparation which uses a carbon source in combination with mechanical grinding has the main purpose to reduce agglomeration and decrease the size of particles. This approach is an efficient and economical technique to obtain this type of reinforcement [3]. To the best of our knowledge, few reports suggest the use of a process control agent known as steric acid to prepare in-situ TiC. This control agent has the dual function of preventing particle agglomeration and being the carbon source to generate carbides [4]. The motivation of this work is to evaluate the steric acid effects on the structure and microstructure of in-situ TiC. 4g of titanium (Ti, 99.5%) and 2g of steric acid (C18H36O2, 99.5%) powders were mixed in a high-energy ball spex8000 mill to obtain the in-situ TiC. The grinding was carried out with a 5:1 ball ratio and a time of 4 h in an Ar atmosphere. The powders obtained inside a quartz ampoule were heat treated at 1300 oC for 2 h. The structural characterization was carried out in a Panalytical X´pert PRO diffractometer operated at 40 kV and 30 mA using CuKαϕ radiation (λ = 0.15406 nm). The microstructures of the TiC were characterized using bright-field mode in the transmission electron microscope using a Hitachi 770 model TEM. The in-situ TiC nanoparticles were successfully produced using steric acid and the ball mill on a high-energy miller. Fig.1(a-b) presents a representative bright-field TEM image that displays black agglomerated zones formed from TiC particles with sizes ranging from 30 to 80 nm. The selected area electron diffraction (SAED) pattern displays well-defined rings associated with the polycrystalline character of TiC particles. The SAED analysis using the CrystTbox RingGUI software in combination with the CIF file confirms the cubic phase with Fm-3m space group. This result is in good agreement with the x-ray diffraction pattern indexing using the reference PDF card 00-032-1383. Fig. 2(a-b) exhibits the scanning electron microscopy (SEM) image of milled composite powder along with the energy dispersion spectroscopy (EDS) image. This micrograph corroborates that the small particles also contain Ti and C demonstrating TiC agglomerations with the presence of porosity. EDS elemental mapping from the corresponding SEM image Fig.2 (c) confirms that the agglomerations are constituted by Ti and C. This result indicates that TiC has been obtained and the distribution of Ti and C is in accordance with the expected ratio of C/Ti [5]. (a) Bright-field TEM image for TiC. (b) SAED ring pattern analysis for in-situ TiC. (a) SEM image for in-situ TiC. (b) EDS analysis and (c) EDS mapping for the elements Ti and C.