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Mechanical alloying technique, such high energy ball milling process, is suitable for producing composite metal powders with a fine controlled microstructure. This method is crucial for obtaining homogeneous distribution of nano-sized dispersoids in a more ductile matrix (e.g. aluminium-or copper based alloys). The reinforcing particles Al4C3 have become an interesting reinforcing material because their high level of physical and mechanical properties, e.g. high temperature strength, thermal cyclic resistance, wear resistance and low linear expansion coefficient. Therefore, the reinforcement of the aluminum using Al 4 C 3 has recently become the subject of many studies and widely used for products and structures [1,2].The Al-based composites were produced by mixing Al powder (99.5 % purity) with 1 and 2 wt. % of Al 4 C 3 nanoparticle powder (previously synthetized by mechanical milling and subsequent heat treatment), each Al-Al 4 C 3 mixtures powder were mechanically milled in a high energy Simoloyer mill during 8 h. Argon was used as the milling atmosphere and ~4 ml methanol as a process-control agent. The device and milling media used were made from hardened steel. The milling ball to powder weight ratio was set to 50:1. Consolidated samples were obtained by pressing the powder mixtures during 20 s at 350 MPa in uniaxial load. The consolidate sample was sintered during 2h at 650°C. The Al4C3 reinforcing phase dispersed into the aluminum matrix also was observed by using electron microscopy analyses. Fig. 1a shows a STEM bright-field image of Al-20 sample (2 wt. % of Al 4 C 3 and not sintered), the image shows a graphite nanoparticle of about 10 nm long which is close to an Al4C3 nanoparticle that shows an irregular shape present in the aluminum matrix. Fig. 1b shows the simulated image that shows the interplanar distance of the A selected area of a Al 4 C 3 nanoparticle and the interplanar distance of the B selected area of a graphite nanoparticle. The Fig. 2a shows a STEM bright-field representative image of a rod-shaped aluminum carbide nanoparticle of about 100 nm long and 10 nm wide in the Al matrix of Al-22 sample (2 wt. % of Al 4 C 3 and sintered during 2 h). The HRTEM image of Figure 2b shows the interplanar distances of a rod shaped particle which correspond to Al 4 C 3 compound. At seems the Al 4 C 3 irregular shape nanoparticles dispersed into the Al matrix during the mechanical milling change to a regular rod-shaped after the sintering process.

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The effects of heat treatment (HT) at different temperatures from 25 to 600 ° C were studied in their morphology and crystal structure for particles of MoO3 with orthorhombic (OW sample) and hexagonal (HW sample) phases. Employing high energy mechanical milling technique was possible to get nanoparticles with size below 40 nm at 30 min milling time from HW sample with previous calcination process (HWCM sample) [1]. The milling nanoparticles showed greater removal of Methylene blue (MB) compared to the microparticles [2].The morphology and microstructure were determined using electron microscopy techniques and X-ray diffraction. Figures 1a and 1b show the X-ray diffraction patterns evolution during HT of the OW and HW samples, respectively. In general, at all temperatures the diffraction patterns correspond to the orthorhombic phase (see Fig. 1a) and practically remains stable as temperature increase, however there is a slight decrease in width at 600 ºC, indicating that exist an increase in crystallite size due to atomic diffusion during HT. Figure 1b, shows the X-ray diffraction patterns evolution during HT of the HW sample, above 440°C, hexagonal phase changes into orthorhombic phase, and an apparent broadening of the diffraction peaks is observed, this phenomenon corresponds to a delamination of the hexagonal phase [3]. The secondary electrons SEM image on OW sample before HT shows elongated, thin and smooth surface ribbon-like structures (see fig. 2a). For the 440 ° C temperature some particles were maintained with tape-shaped morphology but with larger dimensions (see fig, 2b). Figure 2c shows the SEM image of secondary electrons obtained before the HT of the HW sample, the particles show hexagonal prism shape morphology. Fig. 2d shows different agglomerates particles showing a micro-lamella type morphology corresponding to the orthorhombic phase of the HWC (before the MM process) sample submitted at 440 ° C. On the other hand an irregular morphology of agglomerated nanoparticles was observed when the particles were subjected to mechanical milling (samples named HWCM) as is shown in the TEM image (see Fig.3a). These particles were also analyzed through SAED diffraction patterns annexed. The nanometric particles produced allowed an increase in surface area, improving noticeable the adsorption activity of MB in a time of 50 min for the calcined milled HWCM sample. The nanometric particles powder increased the speed discoloration, without using photonic irradiation.

In the present work, nanocomposites-based 3XXX series Al alloy with three different types of hard nanoparticles, including TiO2, C, and CeO2, were produced employing two techniques such as mechanical milling and stir-casting method in order to evaluate the viability of integration of the reinforcement in the Al matrix. The integration and dispersion capability of the reinforcement into the Al alloy (3xxx Series) matrix was evaluated, using a phase angle difference and surface roughness analyses by atomic force microscopy operated in both the contact mode (CM-AFM) and tapping mode (TM-AFM), respectively. The distribution profile of both rugosity and the phase angle shift was used to statically quantify the integration and dispersion of the reinforcement into the extruded samples, by using the root mean square (RMS) parameter and phase shift coupled with the events number (EN) parameter. Results from Atomic Force Microscopy (AFM) analyses were corroborated by X-ray diffractometry and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness tests were conducted to identify the mechanical properties of the composites in the extruded condition and their correlation with the microstructure. A close relationship was found between the microstructure obtained from the AFM and X-ray diffractometry (XRD) analyses and mechanical properties. Among all, the C reinforcement produced the major changes in the microstructure as well as the best integration and dispersion into the Al-alloy coupled with the best mechanical properties.