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The ZrB2-SiC-graphite composite is one of the most promising ceramics, which show significant potential in manufacturing parts served in ultra-high temperature. Micro-electrical discharge machining (micro-EDM) is an effective method in machining this conductive hard ceramic. However, the recast layer characterized by craters and micro-cracks is formed on the machined surface, resulting in poor surface quality. In this paper, micro-EDM and micro-ultrasonic machining (micro-USM) combined milling is proposed for manufacturing 3D micro-cavities in the ZrB2-SiC-graphite composite. The micro-cavity is firstly machined by micro-EDM milling, followed by micro-USM finish milling to remove the recast layer in the same system without changing the micro-tool. The machining performances are investigated with consideration of the surface topography and finishing depth. It is found that the more recast layer is removed when a higher ultrasonic amplitude, larger abrasive grain size, and lower tool feedrate are employed. Based on the preliminary experiments, the proper machining parameters are obtained and applied to the fabrication of micro-cavities. The machining results show that the surface quality is improved with the low surface roughness and absence of defect layer. Meanwhile, the high machining accuracy in the depth direction and processing efficiency are achieved. It is verified that the micro-EDM and micro-USM combined milling process is feasible for fabricating 3D micro-cavities in the ZrB2-SiC-graphite composite.

Wire electric discharge machining (WEDM) and electrical discharge machining (EDM) promise to be effective and economical methods for the machining of metal matrix composites and conducting ceramic blanks. However, the machining process of Ni–Al2O3 functionally graded materials (FGMs) is extremely difficult because the insulating ceramic layer cannot be machined directly by EDM. In this paper, the pure Al2O3 layer has been machined by self-induced EDM, using the conductive layers of Ni–Al2O3 FGMs to trigger the discharges in the insulating ceramic layer. Machining experiments have been performed to investigate the effects of discharge capacitance, pulse off-time, and charging resistance on the process performance of the pure Al2O3 layer using RC-type pulse generator. From the experimental results, the discharge waveform of pure Al2O3 layer includes long pulse discharge waveform, in addition to conventional normal discharge of conductive layers. The shape of long pulse discharge waveform can be changed by pulse off-time. The appropriate pulse off-time not only improves the stability of EDM but also increases the material removal rate (MRR). Moreover, it was observed that the MRR increases with increasing discharge capacitance and decreasing charging resistance. The surface roughness increases with increasing discharge capacitance. Finally, a small hole with a depth-diameter ratio of 5, little tapper is machined based on the experimental analysis.

The trade-off criterion is used to systemically investigate the performance features of two chemical engine models (the low-dissipation model and the endoreversible model). The optimal efficiencies, the dissipation ratios, and the corresponding ratios of the dissipation rates for two models are analytically determined. Furthermore, the performance properties of two kinds of chemical engines are precisely compared and analyzed, and some interesting physics is revealed. Our investigations show that the certain universal equivalence between two models is within the framework of the linear irreversible thermodynamics, and their differences are rooted in the different physical contexts. Our results can contribute to a precise understanding of the general features of chemical engines.

Ni–Al2O3 functionally graded materials (FGMs) have become important for high-temperature applications due to a continuous change in composition. However, the manufacturing of Ni–Al2O3 FGMs with conventional machining methods is a long and costly process because of the insulating ceramic composition. This paper presents a new method of machining Ni–Al2O3 FGMs by self-induced electrical discharge machining (EDM). Self-induced EDM uses the conductive compositions of Ni–Al2O3 FGMs to trigger the discharges in the insulating composition. Machining characteristics of a four-layered Ni–Al2O3 FGMs drilled by self-induced EDM have been investigated, which include the material removal mechanisms, discharge properties, surface characteristics, material removal rate, and electrode wear ratio. It has been found that graded layers, 70 % Ni-graded layer and 30 % Ni-graded layer, are removed by dislodgement of Al2O3 particles, in addition to conventional melting and evaporation. Pure Al2O3 layer is melted and evaporated by utilizing conductive layer-induced discharges. The discharge properties, surface characteristics, material removal rate, and electrode wear ratio are significantly influenced by the material removal mechanisms of graded compositions. These findings demonstrate that self-induced EDM is able to effectively machine Ni–Al2O3 FGMs.

Twenty-one N-phenyl heteroarylamine analogues of fluazinam 3a–3u were prepared via nucleophilic substitution reaction of 2,6-dichloro-3,5-dinitrotoluene with heteroarylamines using the intermediate derivatization method. 2,6-Dichloro-3,5-dinitrotoluene, the key intermediate, was synthesized by nitration of 2,6-dichlorotoluene. The synthesized compounds were identified by 1H NMR, 13C NMR, MS and elemental analyses. Preliminary bioassays indicated that most of the compounds showed good fungicidal activity against rice blast. The activity of 3p was equal to that of fluazinam. The relationship between molecular structure and biological activity suggested that introduction of electron-withdrawing groups in the pyridine ring was important for optimizing fungicidal activity against rice blast.