Thrust characteristics of nano-carbon/Al/oxygenated salt nanothermites for micro-energetic applications

Combustion within small motors is key in the application-specific development of nanothermite-based micro-energetic systems. This study evaluates the performance of nanothermite mixtures in a converging-diverging nozzle and an open tube. Mixtures were prepared using nano-aluminum(n-Al),potassium perchlorate(KClO_(4)), and different carbon nanomaterials(CNMs) including graphene-oxide(GO), reduced GO, carbon nanotubes(CNTs) and nanofibers(CNFs). The mixtures were packed at different densities and ignited by laser beam. Performance was measured using thrust measurement,high-speed imaging, and computational fluid dynamics modeling, respectively. Thrust, specific impulse(ISP), volumetric impulse(ISV), as well as normalized energy were found to increase notably with CNM content. Two distinctive reaction regimes(fast and slow) were observed in combustion of low and high packing densities(20% and 55%TMD), respectively. Total impulse(IFT) and ISPwere maximized in the 5%GO/Al/KClO_4 mixture, producing 7.95 m N·s and 135.20 s respectively at 20%TMD, an improvement of 57%compared to a GO-free sample(5.05 m N·s and 85.88 s). CFD analysis of the motors over predicts the thrust generated but trends in nozzle layout and packing density agree with those observed experimentally;peak force was maximized by reducing packing density and using an open tube. The numerical force profiles fit better for the nozzle cases than the open tube scenarios due to the rapid nature of combustion. This study reveals the potential of GO in improving oxygenated salt-based nanothermites,and further demonstrates their applicability for micro-propulsion and micro-energetic applications.

Carbon dioxide catalytic conversion to nano carbon material on the iron–nickel catalysts using CVD-IP method

The over-consumption of fossil fuels resulted in the large quantity emission of carbon dioxide （CO2）, which was the main reason for the climate change and more extreme weathers. Hence, it is extremely pressing to ex- plore efficient and sustainable approaches for the carbon-neutral pathway of CO2 utilization and recycling. In our recent works with this context, we developed successfully a novel ＂chemical vapor deposition integrated process （CVD-IP）＂ technology to converting robustly CO2 into the value-added solid-form carbon materials, The monometallic FeNi0-Al2O3 （FNi0） and bimetallic FeNix-Al2O3 （FNi2, FNi4, FNi8 and FNi20） samples were synthesized and effective for this new approach. The catalyst labeled FNi8 gave the better performance, exhibited the single pass solid carbon yield of 30%. These results illustrated alternative promising cases for the CO2 capture utilization storage （CCUS）, by means of the CO2 catalytic conversion into the solid-form nano carbon materials.

Tribological behavior of nanocarbon materials with different dimensions in aqueous systems

Due to the widespread use of nanocarbon materials(NCMs),more researchers are studying their tribological performances.In this work,the tribological behaviors of the following five types of NCMs with different geometric shapes were evaluated in a novel oil‐in‐water system:spherical fullerenes(C60,0D),tubular multi‐walled carbon nanotubes(MWCNT,1D),sheet graphene oxide(GO,2D),sheet graphene oxide derivative(Oct‐O‐GO,2D),and lamellar graphite(G,3D).Among these,GO with two types of oxidation degrees,i.e.,GO(1),GO(2),and Oct‐O‐GO(1)were synthesized and characterized using Fourier‐transform infrared spectroscopy,Raman spectroscopy,x‐ray diffraction,thermogravimetric analysis,scanning electron microscopy,and contact angle measurements.The load‐carrying capacity of the NCM emulsions were evaluated using a four‐ball test machine,and the lubrication performances were investigated using a high‐frequency reciprocating friction and wear tester with a sliding distance of 1,800 mm under different loads(50 N and 100 N)at 0.5 Hz.The results revealed that the Oct‐O‐GO(1)emulsion exhibited the best load‐carrying capacity,and the best friction‐reducing and anti‐wear properties compared to other emulsions.Moreover,the anti‐wear advantage was more prominent under high load conditions,whereas the other emulsions exhibited a certain degree of abrasive or adhesive wear.The lubrication mechanism was determined through the analysis of worn surfaces using scanning electron microscopy/energy‐dispersive x‐ray spectroscopy,micro‐Raman spectroscopy,and x‐ray photoelectron spectroscopy.The results revealed that during frictional sliding,the ingredients in the emulsion can absorb and react with the freshly exposed metal surface to form surface‐active films to protect the surfaces from abrasion.Moreover,it was found that the higher the amount of ingredients that contain alkyl and O‐H/C=O,the better was the lubrication performance in addition to an increase in the carbon residue in the tribofilm generated on the meal surface.