Carbon nanotubes (CNTs) reinforced FeCo alloys were produced by high energy ball-milling and spark plasma sintering (SPS). CNTs distribution in the FeCo alloy was gradually improved as ball-milling time increased, with a uniform dispersion achieved after 6 h ballmilling. Tensile tests demonstrated that, as the ball-milling time increased, the yield strength increased in the composites; a maximum 50 % relative increase in tensile strength due to the addition of CNTs was achieved after 1 h ball-milling, which then decreased with further ballmilling. The elongation to fracture was significantly increased after 1 h ball-milling and then decreased with further ball-milling. SEM results show a patch of dimples in the fracture surface of the composite, indicating improved ductility due to CNTs. The coercivity was increased with increased ball-milling time, while the saturation induction showed a peak value after 1 h of ball-milling and then decreased with further ball-milling. Raman spectra of the composite indicated that no serious damage had been imparted to the CNTs during ballmilling.

Novel corona virus (COVID-19) pandemic in the last 4 months stimulates the international scientific community to search for vaccine of antiviral agents suitable for in activating the virus inside and outside the human body. More than 4 million people globally are infected by the virus and about 300,000 dead cases until this moment. The ventilation and airborne filters are also investigated aiming to develop an efficient antiviral filtration technology. Human secretion of the infected person as nasal or saliva droplets goes as airborne and distributes the virus everywhere around the person. N95 and N98 filters are the must use filters for capturing particles of sizes around 300 nm. The average size of the novel corona virus (COVID-19) is 100 nm and there is no standard or special filter suitable for this virus. The nanoparticle-coated airborne filter is a suitable technique in this regard. While the efficiency of this type of filters still needs to be enhanced, new developed nanofiber filters are proposed. Most recently, the charged nanofiber filters of sizes below 100 nm are developed and provide an efficient viral filtration and inactivation. The efficiency of filter must be kept at accepted level without increasing the pressure drop. The present review outlines the most efficient antiviral nanoparticles including the recent functional nanoparticles. The filtration theory, filtration modeling, filter testing, and different types of filter with special concentration on the charged nanofiber filter were discussed. The charged nanofiber filter able to capture novel corona virus (COVID-19) with 94% efficiency and a pressure drop less than 20 MPa.

Equiatomic FeCo alloys were densified using spark plasma sintering (SPS). Using a constant 50 MPa pressure, the sintering temperature and dwell times for the SPS process were optimised for different heating rates (50, 100, 300 ºC.min-1). All samples used in this optimisation process were analysed in terms of their mechanical and magnetic properties. Interestingly, for all heating rates, FeCo samples sintered at the highest temperatures (1100 ºC) without dwelling exhibited an increased tensile yield strength combined with an improvement in the elongation to fracture. This occurred despite the microstructural coarsening observed at this sintering temperature, which decreased the ultimate tensile strength. Improved grain boundary bonding in the samples sintered at the highest sintering temperature led to a suppression of intergranular fracture; something previously considered to be inherent to all equiatomic FeCo alloy structures. An optimum combination of mechanical (ultimate tensile strength = 400 MPa, yield strength = 340 MPa and strain to failure = 3.5 %) and magnetic (saturation induction (Bsat) of 2.39 T and coercivity (Hc) of 612 A.m-1) properties was achieved by sintering to 1100 ºC using a relatively slow heating rate of 50 ºC.min-1 with no dwell time.

The effect of the addition of graphene nanoplatelets (GNP) and graphene nanoplatelet/carbon nanotube (GNT) mixtures on the mechanical and magnetic properties of spark plasma sintered (SPS) soft magnetic FeCo alloys was studied. Three different volume fractions (0.5, 1& 2 vol.%) of GNPs and GNTs were investigated. Ball milling was used to disperse the GNPs in monolithic FeCo powder; while magnetic stirring and ultrasonic agitation were used to prepare hybrid GNT prior to ball milling. The highest saturation induction (Bsat) of 2.39 T was observed in the 1 vol. % GNP composite. An increase in the volume fraction of the ordered nano crystalline structure was found to reduce the coercivity (Hc) of the composites. The addition of CNTs to the GNP composite prevented grain growth, leading to grain refinement. An 18% increase in hardness was observed in the 1 vol. % GNP composite as compared to the as received FeCo alloy. A reduction in tensile strength was observed in all of the composite materials, except for the 0.5 vol. % GNT composite, for which a value of 643 MPa was observed. Raman spectroscopy indicated a reduction in the defect density of the GNPs after adding CNTs.