Peiyun Dai

Bio: Peiyun Dai is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Silicon carbide & Ceramic. The author has an hindex of 5, co-authored 8 publications receiving 84 citations.

Fabrication of pure SiC ceramic foams using SiO2 as a foaming agent via high-temperature recrystallization

Abstract: A novel method was developed to produce the pure silicon carbide foams via the high-temperature recrystallization with the presence of a novel foaming agent-SiO 2 . In this method, SiO 2 reacts with SiC to produce the gases in the silica liquid at high temperature, which leads to the formation of foams. The foams consist of the directional and interconnecting SiC crystals, and numerous intercommunicating pores that are located between them. The phase of foams was identified as 6H–SiC without the presence of SiO 2 since SiO 2 particles could react completely with SiC particles and vaporize from the sample at high temperature. The total porosity, weight loss and volume expansion rate can be increased with increasing SiO 2 contents while the three-point bending strength decreasing. The porosity of SiC foam with 25 wt.% SiO 2 as a foaming agent exhibits the maximum value while the three-point bending strength shows minimum value correspondingly. The sintered samples presented the porosities of 61–81%, the bending strength from 1.5 MPa to 4.8 MPa, and the volume expansion rate from 17.4% to 65%. This research can develop the theory for the preparation of SiC ceramics foams with controlled structure.

Fabrication of wood-like porous silicon carbide ceramics without templates

Abstract: The porous silicon carbide ceramics with wood-like structure have been fabricated via high temperature recrystallization process by mimicking the formation mechanism of the cellular structure of woods. Silicon carbide decomposes to produce the gas mixture of Si, Si 2 C and SiC 2 at high temperature, and silicon gas plays a role of a transport medium for carbon and silicon carbide. The directional flow of gas mixture in the porous green body induces the surface ablation, rearrangement and recrystallization of silicon carbide grains, which leads to the formation of the aligned columnar fibrous silicon carbide crystals and tubular pores in the axial direction. The orientation degree of silicon carbide crystals and pores in the axial direction strongly depends on the temperature and furnace pressure such as it increases with increasing temperature while it decreases with increasing furnace pressure.

Preparation method of compact silicon carbide ceramic

Abstract: The invention discloses a preparation method of compact silicon carbide ceramic, which is characterized in that the compact accumulation among silicon carbide crystalline particles is realized so as to obtain a polycrystalline block ceramic with high compactness by using decomposition and chemical combination reactions generated by pure silicon carbide or a material source of silicon carbide at the temperature of 2,250-2,500DEG C, wherein the material source of silicon carbide is generated by a chemical combination reaction, adopting a high-temperature physical gaseous phase transmission technology and controlling the gaseous phase recrystallizing and arraying accumulation process. For the compact silicon carbide ceramic prepared by the method, crystals are directly bonded by pure silicon carbide interfaces, silicon carbide crystalline particles are directionally arrayed and compactly accumulated according to the preferred orientation of crystals and the volume density of the ceramic can approach to the theoretical density.

Preparation of oriented hole silicon carbide porous ceramic

Abstract: The invention discloses a preparation method of a porous silicon-carbide ceramic provided with oriented pores. Firstly, according to weight percentage, 0 to 30 percent of carbon powder, 0 to 50 percent of silicon powder and 0 to 60 percent of silica are added into the 10 to 100 percent of the basic material of silicon-carbide; wherein, the granularity of the silicon-carbide is W3.5 to P220, and one granularity or two granularities are adopted for graduation; then the equally mixed materials are processed through powder accumulation or normal ceramic forming process to obtain a green compact which is put into a graphite crucible or a saggar; the graphite crucible or saggar is placed into a vacuum sintering furnace provided with a temperature field with a temperature grade from 15 to 30 DEG C/cm, and then the temperature is raised to 1900 to 2500 DEG C in an argon environment and with pressure of 0.2 to 1 multipliedby 10 Pa, and the insulation work for the graphite crucible or saggar is preserved for 0.5 to 3 hours; finally the temperature naturally falls down under air protection and the sintered body is taken out, namely, the recrystallization porous silicon-carbide ceramic provided with oriented pores is obtained.

Self-supported multidimensional Ni–Fe phosphide networks with holey nanosheets for high-performance all-solid-state supercapacitors

Abstract: Designing excellent electrode materials by establishing superb architectures provides a feasible way to boost the electrochemical properties of supercapacitors (SCs). Herein, a self-supported bimetallic Ni–Fe phosphide (Ni–Fe–P) electrode with a newfangled and multidimensional construction was synthesized by a two-step process. This electrode consists of connective nanosheets which combined numerous interlinked nanoparticles with well-distributed mesopores. By investigating the effects of phosphating temperatures, an optimal phosphide electrode with well-distributed pores throughout the interlaced nanosheets has been obtained. Due to this sophisticated porous structure and the mechanical stability enhanced by the direct growth on binderless Ni foam, the Ni–Fe–P electrode exhibits outstanding electrochemical performance. Density functional theory (DFT) calculations are also performed to demonstrate the increased electrical conductivity and reactivity after the introduction of Fe atoms and phosphorization. Impressively, the fabricated Ni–Fe–P//reduced graphene oxide solid-state SC device delivers an outstanding energy density of 50.2 W h kg−1 at a power density of 800 W kg−1, and remarkable cycle performance (91.5% retention rate after 10 000 cycles). This comprehensive work not only displays a new perspective of the phosphating mechanism at different temperatures but also suggests a versatile approach for engineering promising electrode materials for advanced SCs.