Role of Microstructure on the Potential of MAX and MAB Phases …
35
By using Rigaku Diffractometer (SmartLab, Rigaku, Japan), all the etched particulates were scanned by using a scan rate of 4°/min from 20° to 50°. JEOL JSM-7600F
scanning electron microscope (JEOL USA, Inc., Peabody, MA) was used to obtain
Field Emission Scanning Electron Microscope (FESEM) micrographs in Secondary
(SE) and Backscattered Electron (BSE) mode. A chemically uniform region, microregion, was analyzed by using an energy-dispersive spectroscopy (EDS) which
consisted of UltraDry silicon drift X-ray detector and NSS-212e NORAN System 7
X-ray Microanalysis System (Thermo Fisher Scientific, Madison, Wisconsin). For
each quantifying a micro-region, an average of three EDS readings were taken. The
results are summarized in Table 2.
Conclusions
i. By using MAX phases, different types of microstructure are designed for manufacturing composites. In this review, I have classified the microstructure of
composites by using the concepts of connectivity.
ii. In type-I composites, MAX phases can act as reinforcement in metal, ceramic,
or polymer matrix composites (Fig. 1a) to form composites with 3-0 connectivity where metal or ceramic or polymer forms the main matrix, and the
MAX phases are dispersed in the microstructure. These composites have shown
enhanced mechanical and triboactive performance.
iii. In type-II composites, metal is used to bond or cement the MAX phase particles.
These composites have also shown promise for tribological applications, for
example, foil bearings.
iv. Various research groups have developed MAX-metal composites with 3-3
connectivity (type-III composites). The composites have shown enhanced
strength and damping behavior due to synergistic behavior of metal and MAX
phase additives.
v. The MAX phase matrix can be also be reinforced with ceramic additives to
form composites with 0-3 connectivity (type-IV, Fig. 1d). These composites
showed higher hardness due to the inclusion of hard ceramic particles which
reinforce the MAX phase matrix.
vi. MAX phases can be oriented in different matrices to form 3-0 composites
(type-V, Fig. 1e).
vii. Composites with multiple layered can be also designed with 3-0 connectivity
(type-VI, Fig. 1f). These composites have shown anisotropic behavior.
viii. Finally, a case study has been presented to showcase that Ti 3 AlC 2 particles can
be etched to form engineered surfaces.
Acknowledgements Mr. Maharshi Dey is acknowledged for synthesizing the Ti 3 AlC 2 powders.
35
By using Rigaku Diffractometer (SmartLab, Rigaku, Japan), all the etched particulates were scanned by using a scan rate of 4°/min from 20° to 50°. JEOL JSM-7600F
scanning electron microscope (JEOL USA, Inc., Peabody, MA) was used to obtain
Field Emission Scanning Electron Microscope (FESEM) micrographs in Secondary
(SE) and Backscattered Electron (BSE) mode. A chemically uniform region, microregion, was analyzed by using an energy-dispersive spectroscopy (EDS) which
consisted of UltraDry silicon drift X-ray detector and NSS-212e NORAN System 7
X-ray Microanalysis System (Thermo Fisher Scientific, Madison, Wisconsin). For
each quantifying a micro-region, an average of three EDS readings were taken. The
results are summarized in Table 2.
Conclusions
i. By using MAX phases, different types of microstructure are designed for manufacturing composites. In this review, I have classified the microstructure of
composites by using the concepts of connectivity.
ii. In type-I composites, MAX phases can act as reinforcement in metal, ceramic,
or polymer matrix composites (Fig. 1a) to form composites with 3-0 connectivity where metal or ceramic or polymer forms the main matrix, and the
MAX phases are dispersed in the microstructure. These composites have shown
enhanced mechanical and triboactive performance.
iii. In type-II composites, metal is used to bond or cement the MAX phase particles.
These composites have also shown promise for tribological applications, for
example, foil bearings.
iv. Various research groups have developed MAX-metal composites with 3-3
connectivity (type-III composites). The composites have shown enhanced
strength and damping behavior due to synergistic behavior of metal and MAX
phase additives.
v. The MAX phase matrix can be also be reinforced with ceramic additives to
form composites with 0-3 connectivity (type-IV, Fig. 1d). These composites
showed higher hardness due to the inclusion of hard ceramic particles which
reinforce the MAX phase matrix.
vi. MAX phases can be oriented in different matrices to form 3-0 composites
(type-V, Fig. 1e).
vii. Composites with multiple layered can be also designed with 3-0 connectivity
(type-VI, Fig. 1f). These composites have shown anisotropic behavior.
viii. Finally, a case study has been presented to showcase that Ti 3 AlC 2 particles can
be etched to form engineered surfaces.
Acknowledgements Mr. Maharshi Dey is acknowledged for synthesizing the Ti 3 AlC 2 powders.