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Beryllium copper alloys are the ideal materials to fabricate the supporting parts owing to their excellent physical and chemical properties. Many high aspect ratio micro-holes are often required to realize the special missions. However, they were not easily fabricated by the traditional machining methods owing to the materials' mechanical strength. Here, we presented a high efficiency method for drilling high aspect ratio micro-holes on C17200 beryllium copper alloy by combining deionized water based micro-EDM and in situ PMEDM with boron carbide additives. The machining parameters were systematically investigated and optimized to realize the ever high aspect ratio of 23.26 at the holes' diameter of 215 μm. The surface quality of the micro-hole was improved further by in-situ PMEDM, which was demonstrated by the decreasing of surface roughness (Ra) from 2.65 μm to 0.92 μm. Our method will open an avenue to fabricate high aspect ratio micro-holes on C17200 with high efficiency. [ABSTRACT FROM AUTHOR]

Catalysts with amorphous structures have shown excellent performance in electrocatalytic water oxidation, but it remains a challenge to prepare efficient catalysts using simple methods while maintaining high yields. Herein, amorphous Fe x Co y W z oxides nanoparticles were prepared by a one-step co-precipitation method, and the Fe content was optimized to ensure efficient water oxidation. The prepared Fe 0.05 Co 0.09 W 0.61 O 0.25 had the best OER performance with a yield of 95.6% when the Co and Fe feeding ratio was 2:1. The Fe 0.05 Co 0.09 W 0.61 O 0.25 possessed an overpotential of 267 mV at 10 mA cm−2 with a small Tafel slope of 39.4 mV dec−1. The activation energy at 1.5 V is only 49.4 kJ mol−1, and Faraday efficiency is close to 100%. The water oxidation performance of the two-electrode test shows that the voltages at 10 mA cm−2 are only 1.50 V. In addition, it still maintained high activity after 72 h of chronoamperometry test, which exhibits excellent water oxidation performance among similar non-precious transition metal catalysts. Therefore, the present work provides a simple and easy way to prepare high-activity and high-yield transition metal amorphous electrocatalysts. [Display omitted] • The simple method successfully prepared high performance amorphous Fe 0.05 Co 0.09 W 0.61 O 0.25. • Fe modulates the electronic configuration and morphology of CoWO 4. • The optimal ratio of Fe doping into CoWO 4 is regulated. • Co acts as the main catalytic site in the OER process instead of Fe. [ABSTRACT FROM AUTHOR]

Organic fuels are the main factors affecting the morphology, pore structure and catalytic active sites of metal oxides in solution combustion synthesis (SCS). However, due to the diversity of organic fuel structures, the specific role of organic fuel types on SCS is questionable. In this work, we compared the effects of five organic fuels on the thermocatalytic active sites of graded porous MgCo 2 O 4 nanomaterials. MgCo 2 O 4 (CA-MCO) prepared with citric acid as fuel has the largest specific surface area and the richest pore structure with the largest number of active sites. And the porous CA-MCO exhibited the best catalytic properties that the T HTD of AP decreased by 206.06 °C, the activation energy (E a) decreased by 104.58 kJ·mol−1, and the reaction rate (k) increased by 2.49 s−1. A possible catalytic mechanism for the thermal decomposition of AP was also proposed based on TG-MS and Hall effect tests. Finally, CA-MCO was applied to AP/HTPB-based composite solid propellants (CSPs), and the results showed that the introduction of CA-MCO significantly shortened the ignition delay time of the CSPs (From 29 ms to 8 ms), indicating its potential application in the CSPs. [Display omitted] [ABSTRACT FROM AUTHOR]

Co 3 O 4 is an excellent catalyst for the thermal decomposition of ammonium perchlorate (AP) due to its spinel structure and more Co3+ as catalytically active sites. In this work, MCo 2 O 4 (M=Fe, Cu, Ni and Zn) with different Co species substituted with transition metal ion were prepared using triblock copolymer F127 as soft template by simple solvothermal and subsequent heat treatment. The porous MCo 2 O 4 samples have higher Co3+ / Co2+ ratio than Co 3 O 4 , and exhibits better catalytic performance for thermal decomposition of AP. Especially with the addition of FeCo 2 O 4 , the high decomposition temperature (HDT) of AP decreases by an amazing 196.25 °C, showing the most excellent catalytic performance. The activation energy (E a) decreases from 290.19 kJ·mol−1 for pure AP to 203.05 kJ·mol−1, while the reaction rate (k) increases from 0.499 s−1 to 1.699 s−1. Based on the electron transfer theory, the catalytic mechanism and active site of porous MCo 2 O 4 series cobaltate materials are discussed. The results show that the porous FeCo 2 O 4 not only has highest specific surface, but also has the highest Co3+/ Co2+ ratio, which suggest that the Co3+ on octahedral coordination sites is known as the catalytic active site for AP thermal decomposition. [Display omitted] • Ordered nanoporous MCo 2 O 4 (M=Fe, Cu, Ni and Zn) were successfully syntesized and substituted for the Co in Co 3 O 4. • The high Co3+ / Co2+ ratio and specific surface area of FeCo 2 O 4 provide higher catalytic activity and sites. • The kinetic parameters of AP thermal decomposition have been better optimized after adding porous FeCo 2 O 4. • The catalytic mechanism of porous FeCo 2 O 4 for thermal decomposition of AP is proposed. [ABSTRACT FROM AUTHOR]