A voltage multiplier rectenna is a combination of a voltage multiplier rectifier and an antenna used for the conversion of AC to DC. It is an essential part of the system of RF energy harvesting. Conventional rectennas are characterized by low conversion efficiency. This study presents an analytical novel mode designed for RF energy harvesting systems to study the voltage and current output of rectifier stages for efficiency optimization. The design contains a voltage multiplier rectification circuit with seven stages. The Schottky diode HSMS 285-C was selected for the circuit modeling voltage multiplier circuit. Advanced Design System (ADS) simulation was used to validate the equations of the theoretical model solved with MATLAB code. The fabricated system was tested for an input power range of 10 μW to 100 mW; the maximum output power is 0.2577 mW with maximum efficiency of 29.85%.

Hematite nanocatalysts with different magnetic properties were synthesized by heating pure iron wires at temperatures (600 °C and 700 °C) with the presence of water vapor. The physical and chemical characteristics of the nanocatalysts were studied using analytical methods. From Field Emission Scanning Electron Microscopy (FESEM) results it was found that the morphology of the nanocatalyst was changed by changing the synthesis temperature. The nanowires were formed when the synthesis temperature was 600 °C while at 700 °C the shape changed to clusters. By using the Vibrating Sample Magnetometer (VSM) the results show that the magnetic properties of the nanocatalysts were changed by changing the synthesis temperature, the highest saturation magnetization value (168.8 emu/g) was obtained for the sample prepared at 600 °C. The iron oxide nanocatalysts were used to synthesize ammonia at 0.5T external magnetic field. The highest yield of ammonia (18.23 mmol h−1gcat−1) was achieved by using α−Fe2O3 nanowires which have the highest saturation magnetization.

Using adsorption locator for the most stable adsorption site searches, the authors investigated adsorption of mixture of gases with different carbon dioxide mole ratio at a single-walled carbon nanotube (SWCNT). A total of six mixtures were investigated, two mixtures consist of hydrogen, nitrogen and carbon dioxide with compositions 3:1:1 and 3:1:2. Whereas the remaining four mixtures consist of ammonia and carbon dioxide with compositions 5:1, 4:1, 3:1 and 3:2. Results demonstrated that gas interactions with carbon nanotubes increased as the mole ratio of carbon dioxide increased in H₂, N₂ and CO₂ mixture, conversely decreased for NH₃ and CO₂ mixture. After increasing CO₂ mole fraction from 1/5 to 1/3 for hydrogen, nitrogen and carbon dioxide mixture, adsorption energy and rate on carbon nanotube atoms increased by 45 and 33%, respectively, due to a 59% increase in Van der Waal interactions. The preferred molar ratio of H₂, N₂ and CO₂ mixture for adsorption is 3:1:2. The maximum adsorption energy and rate for NH₃ and CO₂ mixture is obtained using the 5:1 sample. Adsorption energy for the NH₃ and CO₂ mixtures increased by 18% when the ratio changed from 3:1 to 3:2 while the adsorption rate decreased considerably.