Akmaral Kalybaeva

The conversion of renewable biomass waste into porous carbon materials is a promising approach for both efficient waste valorization and the development of environmentally sustainable electrode materials for modern electrochemical energystorage systems. Food waste, particularly orange peel, is of considerable interest as an abundant, renewable, and carbon-rich precursor. This study aimed to synthesize porous carbon materials from orange peel waste and to determine the effects of carbonization and chemical activation temperatures on their structural, elemental, and electrochemical properties. Porous carbon materials were prepared using a two-step process consisting of pre-carbonization followed by chemical activation. Carbonization was performed at 500, 600, and 700 °C, while activation was conducted at 700, 800, and 900 °C. The morphology and elemental composition of the resulting materials were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively, while their carbon structure was investigated by Raman spectroscopy. The electrochemical characteristics and specific capacitance of the prepared electrode materials were also evaluated. SEM analysis revealed that increasing the activation temperature promoted the development of a heterogeneous and well-developed porous structure. EDX analysis confirmed carbon as the predominant element (83–90 wt%), with an oxygen content of 10–14 wt% and a small amount of residual potassium. Raman spectroscopy demonstrated that the carbon structure varied depending on the synthesis conditions. Among the investigated materials, OPA500/700 exhibited the best electrochemical performance, delivering a specific capacitance of 367.5 F g-1 at 0.1 A g-1 and 259.6 F g-1 at 2 A g-1, corresponding to retention of more than 70% of the initial value. The results demonstrate that orange peel waste is a promising, readily available, and renewable precursor for producing high-capacitance porous carbon electrodes for supercapacitor applications.

The article presents the results of a study of the resonance oscillations of a gyroscopic vertical rotor supported at its lower end by a hinged joint, at its upper end, closer to the rotor disk by a viscoelastic support and above the disk connected to the fixed part using a shear magnetic bearing. Assuming that the radii of the turns are significantly smaller than the distance between them, the attractive force of the fixed current turn of the movable current turn is determined, the equations of motion of the gyroscopic rotor system are formulated. The amplitude characteristic shows that the use of the proposed magnetic bearing reduces the vibration amplitude of the rotor in the region to a critical speed, shifts the critical speed towards its increase. Involving the nonlinear stiffness of the support material when interacting with linear and cubical nonlinear damping transfers the vibration insulation properties of the magnetic bearing attractive forces from the region of less than the critical value of the shaft rotation speeds to the region near the resonant speed.