Jikuan Cheng

Bio: Jikuan Cheng is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Single crystal & Seed crystal. The author has an hindex of 4, co-authored 6 publications receiving 44 citations.

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.

Effects of source materials and container on growth process of SiC crystal

Abstract: Nucleation of SiC polycrystals was investigated using TaC and graphite lids. TaC and graphite containers were also used to compare the growth rates of SiC crystal in four systems (TaC + SiC, C + SiC, TaC + Si + SiC, and C + Si + SiC systems). The experimental results indicated that graphite lids provide growth conditions for SiC polycrystals that restrict the radial direction growth of seed. The TaC lid can restrain nucleation of SiC polycrystals, which creates better growth conditions for seed along the radial direction. The growth rates of SiC crystal for the TaC + Si + SiC and C + Si + SiC systems are higher than those of the TaC + SiC and C + SiC systems.

Effects of Grain Size of Source Material on Growing 6H-SiC Bulk Crystal by Physical Vapor Transport

Abstract: In this article, effects of grain size of source material on growing 6H-SiC bulk single crystal by physical vapor transport (PVT) have been studied by observing the experimental results using source materials of different grain sizes through optical microscope and calculative analysis and discussions. The results indicate that source materials with different grain sizes affect the growth process of SiC bulk single crystal by PVT mainly from three perspectives, i.e., the effective heat-transfer coefficient of the source material, the supersaturation, and the ratio of Si/C in the growth crucible on the basis of other parameters. Furthermore, a proposed way to improve the quality of 6H-SiC bulk single crystal is optimizing the grain size of the source material, and the optimum grain size for sublimation growth of 6H-SiC bulk crystal in our lab is 120 µm.

Comparison of the characteristic properties of reduced graphene oxides synthesized from natural graphites with different graphitization degrees

Abstract: In this study, an investigation on the characterization of reduced graphene oxides (rGOs) prepared from natural graphites with different graphitization degrees using Hummers method was conducted. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy and electrochemical performance were performed to characterize the as-prepared graphene oxides (GOs) and rGOs. The results demonstrate that graphites with a lower graphitization degree are more easily oxidized due to the active carbon atoms exposed on their edges and the effective diffusion of oxidants that intercalate into the graphitic layers. In addition, graphites with a low graphitization degree were more suitable for the synthesis of thin layer graphene with a high defect degree and small size in the in-plane sp2 domains as well as a relatively high specific capacitance.

Ultra-fine β-SiC quantum dots fabricated by laser ablation in reactive liquid at room temperature and their violet emission

Abstract: A simple and flexible route is presented for the fabrication of ultrafine β-SiC quantum dots (QDs) based on laser ablation of silicon wafers immersed in ethanol and subsequent etching. The obtained β-SiC QDs are nearly monodispersed and about 3.5 nm in size. The relative content of β-SiC after laser ablation depends on the liquid phase's ability to supply carbon atoms at a certain laser fluence. Proper liquid media with appropriate carbon atoms supply capacity can lead to nearly pure β-SiC in the as-prepared sample. The obtained β-SiC QDs exhibit strong and stable emission in the violet region, significantly blue-shifting relative to that of bulk SiC. This big blue shift of emission is attributed to the significant quantum confinement effect induced by their ultrafine size. This method can be extended to produce some other ultrafine Si compounds which are usually formed at high temperature and/or high pressure. This study could present the building blocks of nanostructured devices as violet light sources and new materials in biological molecular labels.

Influence of Solution Flow on Step Bunching in Solution Growth of SiC Crystals

Abstract: The control of step bunching by solution flow in 4H-SiC solution growth is proposed. We achieved the solution flow control with the specially designed top-seeded solution growth method as follows: by deviating a seed crystal from the center of a crucible and rotating the crucible in one direction, the solution flow direction was controlled to be parallel or antiparallel to the step-flow direction. After the growth, the widely spaced, accumulated macrosteps were observed and the surface of the grown crystal became rough under the parallel flow. On the other hand, the development of the macrosteps was suppressed under the antiparallel flow. As the growth proceeds, the surface roughness of the growth surface increases under the parallel flow, while the surface roughness decreases under the antiparallel flow. This fact suggests the solution flow control can be an effective method to suppress the step bunching during the solution growth of SiC single crystals.