Research on the Rotary Ultrasonic Facing Milling of Ceramic Matrix Composites

AbstractCeramic matrix composites (CMC) has got increasing importance in many fields of industry, especially in the aerospace. However, due to the special properties, the conventional machining methods are generally very challenging for CMC. The rotary ultrasonic machining (RUM) is a high efficiency processing technology for these advanced materials. This paper carried out research on the rotary ultrasonic facing milling of C/SiC and developed the cutting force simulation software to optimize the cutting parameters. Verification experiments were conducted showing that the efficiency improved by RUM is 5.8 times while the surface quality is improved by 54.4% compared with the conventional milling

A novel semi-active suspension design based on decoupling skyhook control

A semi-active suspension design based on the traditional method of skyhook control is not capable of effectively controlling the attitude of the vehicle. However, an innovative approach called decoupling skyhook control allows the attitude of the vehicle body and its vibration characteristics to be effectively controlled. In this paper, a new decoupling skyhook controller for semi-active suspension is presented. Vehicle body motions in the three directions of vertical, pitch, and roll have been adopted to develop three skyhook controllers and directly control the vehicle body attitude. Furthermore, three orientation skyhook control forces are converted into actual damping forces of four adjustable dampers through the input decoupling transformation. The simulation results show that the developed controller is more effective than the traditional skyhook control in improving ride comfort

Oxygen reduction reaction for generating H2O2 through a piezo-catalytic process over bismuth oxychloride

Oxygen reduction reaction (ORR) for generating H2O2 through green pathways have gained much attention in recent years. Herein, we introduce a piezo‐catalytic approach to obtain H2O2 over bismuth oxychloride (BiOCl) through an ORR pathway. The piezoelectric response of BiOCl was directly characterized by piezoresponse force microscopy (PFM). The BiOCl exhibits efficient catalytic performance for generating H2O2 (28 μmol h−1) only from O2 and H2O, which is above the average level of H2O2 produced by solar‐to‐chemical processes. A piezo‐catalytic mechanism was proposed: with ultrasonic waves, an alternating electric field will be generated over BiOCl, which can drive charge carriers (electrons) to interact with O2 and H2O, then to form H2O2

A novel semi-active suspension design based on decoupling skyhook control

A semi-active suspension design based on the traditional method of skyhook control is not capable of effectively controlling the attitude of the vehicle. However, an innovative approach called decoupling skyhook control allows the attitude of the vehicle body and its vibration characteristics to be effectively controlled. In this paper, a new decoupling skyhook controller for semi-active suspension is presented. Vehicle body motions in the three directions of vertical, pitch, and roll have been adopted to develop three skyhook controllers and directly control the vehicle body attitude. Furthermore, three orientation skyhook control forces are converted into actual damping forces of four adjustable dampers through the input decoupling transformation. The simulation results show that the developed controller is more effective than the traditional skyhook control in improving ride comfort

A novel semi-active suspension design based on decoupling skyhook control

A semi-active suspension design based on the traditional method of skyhook control is not capable of effectively controlling the attitude of the vehicle. However, an innovative approach called decoupling skyhook control allows the attitude of the vehicle body and its vibration characteristics to be effectively controlled. In this paper, a new decoupling skyhook controller for semi-active suspension is presented. Vehicle body motions in the three directions of vertical, pitch, and roll have been adopted to develop three skyhook controllers and directly control the vehicle body attitude. Furthermore, three orientation skyhook control forces are converted into actual damping forces of four adjustable dampers through the input decoupling transformation. The simulation results show that the developed controller is more effective than the traditional skyhook control in improving ride comfort

Efficient photocatalytic fixation of N2 by KOH-treated g-C3N4

Development of N2 photofixation under mild conditions is challenging; one reason for low efficiency is the poor reactivity between water and photocatalysts. Herein, C3N4 after KOH etching was used as an efficient photocatalyst, and CH3OH was first introduced as a proton source. The photocatalyst presented a high ammonia evolution rate of 3.632 mmol g−1 h−1 and achieved an apparent quantum yield of 21.5% at ∼420 nm. In addition to the role of reacting with holes to accelerate the production and transfer of electrons, CH3OH also promoted the solubility of N2 and provided a proton to the activated N2. The CH3OH system should be instructive for a better understanding of proton-enhanced photocatalysis

Enhanced nitrogen photofixation over LaFeO3 via acid treatment

The N2 photofixation presents a green and eco-friendly ammonia synthesis approach. However, present strategies for light-induced N2 activation suffer from low efficiency and instability, largely hindering the development of this technology. Herein, we report the LaFeO3 co-optimization of N2 activation as well as subsequent photoinduced protonation with the further phosphate acid treatment. Efficient ammonia evolution rate reached 250 μmol g–1 h–1 over LaFeO3 under simulated sunlight with appropriate acid treatment. The enhancement of phosphate modified samples was mainly attributed to the “pull and push” effect. The hydrogen bonding centers and transition metals (Fe) served as two separation active sites, which improves the adsorption and activation of dinitrogen. In addition, the facilitation of H2O dissociation was also achieved after phosphate modification. These results suggested an alternative N2 photofixation strategy of traditional organic and precious metallic additives for efficient ammonia synthesis

Photocatalytic robust solar energy reduction of dinitrogen to ammonia on ultrathin MoS 2

The crux for solar N2 reduction to ammonia is activating N2 into its high-energy intermediate. Applying a simultaneous multi-electron reduction process could avoid intermediate generation and decrease the thermodynamic barrier. However, this process is extremely difficult from a kinetic view and experiments so far have not shown it is accessible. Here we show the first direct evidence of trion induced multi-electron N2 reduction on ultrathin MoS2. By applying light induced trions, N2 molecular was activated and transformed into ammonia by a simultaneous six-electron reduction process, with a high ammonia synthesis rate of 325 μmol/g h without the assistant of any organic scavengers or co-catalyst. Bulk MoS2 without trions did not exhibit any activity. This demonstrates multi-electron reduction may be realized in electron-rich semiconductors with high concentration of localized electrons such as trions. The methodology of simultaneous multi-electron reduction has wide implications for reactions beyond N2 reduction and for materials beyond MoS2

Investigation of red substances applied to chank shell beads from prehistoric site of Qulong in Ngari Prefecture, Tibet, China

“Applying red” is a common phenomenon observed in Chinese archaeological sites, with the red pigments having been identified as red ochre or cinnabar if ever been scientifically analyzed. However, this is not the case for Tibet. Although a relatively large number of red-painted artifacts have been recovered in Tibet dating from the Neolithic Period to the Tubo Dynasty, little effort has been made on the pigment composition. Recently, nearly one hundred red substances covered shell beads made of the scared chank (Turbinella pyrum), a large conch from the Indian Ocean, were unearthed from the Qulong site (c. 800–500 BC) in the Ngari plateau, western Tibet. This shell beads assemblage represents the largest and most concentrated group of chank shell beads recovered in the Tibetan Plateau and its surrounding regions. It provides a crucial clue for exploring the local “applying red” tradition. In this study, eight shell beads excavated from the Qulong site were examined by the Portable Energy-dispersive X-ray Fluorescence Spectrometer (pXRF), X-ray diffraction (XRD), Fourier Transform infra-red spectroscopy (FTIR), and Laser Raman spectroscopy. The results are as follows: 1) the coloring agent of all red pigments on the shell bead is iron oxide, i.e., red ocher; 2) bone powder that has not been heated to high temperatures (above 600°C) and proteinaceous binders were added to the paint on the outer surface of sample QSM1-11a, but the thin layer on its interior surface was without bone powder; 3) bone powder was not added to the red residues on samples other than QSM1-11a, QSM1-13b, and QSM2-12. This research may reveal the complexity and diversity of the red substances applied to shell beads from Qulong, and shed light on our understanding of human practices and local customs in the Tibetan plateau and the surrounding areas in prehistoric times

Efficient solar-driven nitrogen fixation over carbon-tungstic-acid hybrids

Ammonia synthesis under mild conditions is of supreme interest. Photocatalytic nitrogen fixation with water at room temperature and atmospheric pressure is an intriguing strategy. However, the efficiency of this method has been far from satisfied for industrialization, mainly due to the sluggish cleavage of the N≡N bond. Herein, we report a carbon–tungstic‐acid (WO3⋅H2O) hybrid for the co‐optimization of N2 activation as well as subsequent photoinduced protonation. Efficient ammonia evolution reached 205 μmol g−1 h−1 over this hybrid under simulated sunlight. Nitrogen temperature‐programmed desorption revealed the decisive role of carbon in N2 adsorption. Photoactive WO3⋅H2O guaranteed the supply of electrons and protons for subsequent protonation. The universality of carbon modification for enhancing the N2 reduction was further verified over various photocatalysts, shedding light on future materials design for ideal solar energy utilization