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The present investigation uses a blend of Nigella sativa biodiesel, diesel, n-butanol, and graphene oxide nanoparticles to enhance the performance, combustion and symmetric characteristics and to reduce the emissions from the diesel engine of a modified common rail direct injection (CRDI). A symmetric toroidal-type combustion chamber and a six-hole solenoid fuel injector were used in the current investigation. The research aimed to study the effect of two fuel additives, n-butanol and synthesized asymmetric graphene oxide nanoparticles, in improving the fuel properties of Nigella sativa biodiesel (NSME25). The concentration of n-butanol (10%) was kept constant, and asymmetric graphene oxide nano-additive and sodium dodecyl benzene sulphonate (SDBS) surfactant were added to n-butanol and NSME25 in the form of nanofluid in varying proportions. The nanofluids were prepared using a probe sonication process to prevent nanoparticles from agglomerating in the base fluid. The process was repeated for biodiesel, n-butanol and nanofluid, and four different stable and symmetric nanofuel mixtures were prepared by varying the graphene oxide (30, 60, 90 and 120 ppm). The nanofuel blend NSME25B10GO90 displayed an enhancement in the brake thermal efficiency (BTE) and a reduction in brake-specific fuel consumption (BSFC) at maximum load due to high catalytic activity and the enhanced microexplosion phenomenon developed by graphene oxide nanoparticles. The heat release rate (HRR), in-cylinder temperature increased, while exhaust gas temperature (EGT) decreased. Smoke, hydrocarbon (HC), carbon monoxide (CO2) and carbon monoxide (CO) emissions also fell, in a trade-off with marginally increased NOx, for all nanofuel blends, compared with Nigella sativa biodiesel. The results obtained indicates that 90 ppm of graphene oxide nanoparticles and 10% n-butanol in Nigella sativa biodiesel are comparable with diesel fuel.

Composites have revolutionized the field of aeronautics with its intriguing properties including high strength to weight ratio, low weight, chemical and weather resistance, flexible design and low cost of installation. Also, composites are used as radar absorbing materials (RAMs) in the manufacturing of stealth aircraft. Stealth technology (ST) uses a combination of RAMs and geometry to minimize the reflection of electromagnetic waves back to a radar system. In this review article, working principle and basic constituents of ST are examined along with RAMs types in the light of composites. Moreover, recently developed carbonaceous‐based polymer composites are critically discussed in terms of RAMs for stealth applications. A carbonaceous‐based composite provides a high flexibility for the design and properties control. Carbon black particles, carbon fibers, carbon nanotubes (CNTs), and graphene are used in composites to tailor the wave's absorption properties of a composite. Multilayered structures are also recommended by researchers to extend the absorption band for better stealth application. Optimized absorption properties were achieved from composites containing carbon fiber as filler. Also, CNTs are preferred due to its smaller loading (0.35%) to get conductivity equal to higher concentration of carbon black (20%), which consequently improves the ST. Enhanced electromagnetic absorption properties can be achieved form the graphene‐based RAMs along with incorporating the magnetic particles of different microstructures, particle size, and electromagnetic characteristics. This review will intensively cover the methodology of ST and different composites including carbon‐based composites as RAMs for the use in stealth technology.