CN1699639A

CN1699639A - Method for solvent thermal reaction preparation of a-Si3N4 monocrystal nano wire

Info

Publication number: CN1699639A
Application number: CN 200510038877
Authority: CN
Inventors: 钱逸泰; 邹贵付; 谷云乐
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2005-04-12
Filing date: 2005-04-12
Publication date: 2005-11-23
Anticipated expiration: 2025-04-12
Also published as: CN100392159C

Abstract

The present invention relates to a solvent hot reaction preparation method of alpha -Si3N4 single crystal nanometer wire. The procedure is: mixing SiCl4 and Mg3N2 at mol ratio of 1:1.5-15, sealing in a vessel at 500 -700 degree C, reacting for more than 5 hours, acid washing and water washing the product, followed by centrifugal separating and drying, and then alpha-Si3N4 nanometer wire powders are obtained. The nanometer wire prepared in accordance with the present invention is about 35 nanometers in diameter, several micrometers in length. The reaction temperature of the invention is comparatively low and product phase is single, suitable for mass production.

Description

α -Si3N4Solvothermal reaction preparation method of single crystal nanowire

The technical field is as follows:

the invention belongs to the technical field of preparation of silicon nitride nano materials, and particularly relates to α -Si₃N₄A method for preparing single crystal nano wire by solvothermal reaction.

Background art:

U.S. Pat. No. 4,512,2005 (JOURNAL OF THE AMERICAN CERAMIC SOCIETY 88 (3): 566 & 569 MAR2005) reports THE preparation OF silicon nitride nanowires by annealing amorphous silicon nitride nanoparticles at 1450 & 1550 ℃ in a nitrogen stream, Poland 'chemical ACADEMY OF SCIENCES' BULLETIN (BULLETIN OF THE POLISH ACADY OF SCIENCES-CHEMISTRY 50 (2): 165 & 174 JUN 2002) reports THE preparation OF α -nitrogen nanowires by reacting silicon gel with ammonia at 1360 ℃The Netherlands chemical physical Rapid report (CHEMICAL PHYSICS LETTERS 372 (1-2): 269 274 APR 222003) reports that silicon nitride nanowires are grown in a silicon substrate and a gas stream at 1200 ℃ by using a catalyst. the British Material chemistry (JOURNAL OF MATERIALS CHEMISTRY 12 (6): 1910. F19132002) also reports that catalytic methods are used to prepare silicon nitride nanowires, the methods are both at a higher temperature and use a catalyst to provide a complicated process for preparing a purified product.the British Material chemistry (JOURNAL OF MATERIALS CHEMISTRY 14 (4): 590. F.B 212004) reports that amorphous silicon nitride nanowires are prepared by using gallium as a solvent for silicon hydride and nitrogen under microwave radiation, the preparation OF amorphous silicon nitride nanowires by using gallium under microwave radiation, the preparation OF amorphous silicon nitride nanowires by using DEC-140 ℃ silicon nitride nanowires is difficult to obtain a single crystalline silicon nitride nanowire product, and the method is not reported that the silicon nitride nanowires are obtained by using a single crystalline silicon nitride nanowire (JOURNAL OF α) (JOURNAL OF 864): 590. the preparation OF amorphous silicon nanowires under microwave radiation₃N₄Besides many advantages of silicon nitride nano-particles, the single crystal nano-wire also has good elasticity and bending property. So Si₃N₄The single crystal nano wire is used as the base material of ceramic, and is favorable to raising the strength and toughness of silicon nitride ceramic material, so that it can prepare great amount of single phase α -Si at relatively low temperature₃N₄The nano-wire has important significance for improving the performance of the silicon nitride ceramic and expanding the application of the silicon nitride ceramic.

The invention content is as follows:

the invention provides a method for preparing single-phase α -Si by uniform reaction at relatively low temperature by utilizing solvothermal reaction₃N₄The method of nano wire powder is used to overcome the defects of high reaction temperature and impure obtained product in the prior art.

α -Si of the invention₃N₄The solvothermal reaction preparation method of the single crystal nano wire is characterized in that S is added according to the mol ratio of 1: 1.5-15iCl₄And Mg₃N₂Mixing, sealing and reacting at 550-700 deg.C for more than 5 hr, acid washing, water washing, centrifugal separation and drying to obtain α -Si₃N₄And (3) nanowire powder.

The reaction time is too long, the product hardly changes, and the reaction time is usually suitably 5 to 24 hours.

The chemical equation of the above reaction is:

compared with the prior art, α -Si prepared by the method₃N₄The method of the nano wire adopts the solvothermal reaction, so the reaction temperature is relatively lower than that of the prior art, and the reaction is simple and easy to control; the obtained product is simple in phase, the average diameter of the nano-wire is about 35 nanometers, and the length of the nano-wire is about several micrometers. The method is beneficial to realizing industrial production with larger yield.

Description of the drawings:

FIG. 1 is α -Si prepared by the method of the present invention₃N₄X-ray diffraction spectra (XRD) of the nanowire product.

FIG. 2 is α -Si₃N₄Photoelectron Spectroscopy (XPS) of Si2p of the nanowires.

FIG. 3 is α -Si₃N₄Photoelectron spectrum of N1s of the nanowire.

FIG. 4 is α -Si₃N₄Field emission electron microscopy of nanowires.

FIG. 5 is α -Si₃N₄Transmission electron microscope photograph of the nano powder.

FIG. 6 shows a single α -Si₃N₄Transmission Electron Micrograph (TEM) of nanowires and their selected area electron diffraction pattern (SAED) of transmission electron microscopy.

FIG. 7 is a single root α -Si in FIG. 6₃N₄High Resolution Transmission Electron Microscopy (HRTEM) of nanowires.

The specific implementation mode is as follows:

EXAMPLE 1 preparation of α -Si by reaction of magnesium nitride with silicon tetrachloride₃N₄Nanowire and method of manufacturing the same

Taking 2 millimoles of magnesium nitride and 5 millimoles of silicon tetrachloride, filling the magnesium nitride and the silicon tetrachloride into a stainless steel reaction kettle with a hafnium alloy lining, removing air in the kettle by using nitrogen, sealing the kettle, placing the kettle in a resistance crucible furnace, and reacting for 5 to 24 hours at 550 ℃, 600 ℃ and 700 ℃ (the furnace temperature is controlled to be +/-5 ℃); after stopping heating, naturally cooling the reaction kettle to room temperature; opening the kettle and removing unreacted SiCl₄Washing the obtained product with acid and water, centrifuging and drying to obtain α -Si₃N₄And (5) producing the product. Drying under vacuum at 50 deg.C for 6 hr to obtain off-white powder.

The product was subjected to X-ray diffraction analysis using a japanese Rikagu Dmax γ AX powder diffractometer using Cu K α radiation (wavelength λ 1.54178 Å) as a diffraction light source.

FIG. 1 is an X-ray diffraction spectrum of a product prepared by reacting magnesium nitride with silicon tetrachloride, and as can be seen from FIG. 1, 20 diffraction peaks are formed at 10-60 degrees 2 theta in the X-ray diffraction spectrum, and the positions and intensities are α -Si₃N₄All diffraction peaks can be indexed to α -Si in a simple hexagonal lattice₃N₄Lattice parameters a-7.770 and c-5.627 Å, with α -Si₃N₄The results a-7.765 and c-5.627 Å for a standard powder diffraction card (JCPDS #83-0700) agree with each other if the reaction temperature is below 550 ℃, then a mixed phase product is obtained₃N₄Nanoparticles. On the other hand, if the reaction time is less than 5 hours, the product obtained in the experiment is not pure or the reaction is incomplete.If the reaction time exceeds 24 hours, the product is hardly changed, so that the reaction time is usually preferably 5 to 24 hours, and as can be seen from FIG. 1, the product obtained by the experiment is α -Si which is phase-pure and well-crystallized₃N₄The product does not contain β -Si according to XRD pattern₃N₄And cubic Si₃N₄And no by-products and other impurities. In addition, if SiCl₄And Mg₃N₂A molar ratio of less than 1.5: 1 is detrimental to the production of phase-pure α -Si₃N₄If the molar ratio is more than 15: 1, a large amount of nanoparticles are produced. Therefore, it is generally preferred to select a molar ratio of 1.5 to 15: 1.

The product composition was analyzed using a VGESCALAB MKII type photoelectron spectroscopy (XPS) analyzer using a non-monochromatized magnesium K α line (energy 1253.6eV) as an excitation light source, FIGS. 2 and 3 show the photoelectron spectra of Si2p and N1s of the product, respectively, and the combined energy positions of the Si2p peak in FIG. 2 and the N1s peak in FIG. 3 are 101.55 and 397.75eV, respectively, in comparison with Si reported in J.Mater.Sci.1988, 7, 548 of the Netherlands of journal of materials science and technology (J.Vac.Sci.Tehnol.1989, A7, 3048) and U.S.Chem.Phys.1978, 68, 1776₃N₄The Si2p peak and the N1s peak of the film were consistent in value, with Si in these reports₃N₄The Si2p peak and the N1s peak are around 101.60eV and 397.70eV, respectively, indicating that the silicon and the nitride in the product are silicon nitride. The atomic ratio of silicon to nitrogen, calculated from the Si2p peak in FIG. 2 and the N1s peak in FIG. 3, was 3.1: 4, also with Si₃N₄Due to Si₃N₄The atomic ratio of silicon to nitrogen of (a) was 0.75, indicating that the product was silicon nitride and had Si₃N₄Silicon to nitrogen atomic ratio.

The morphology and particle size of the product were observed using a JSM-6300F Field Emission Scanning Electron Microscope (FESEM) and a 2010 Transmission Electron Microscope (TEM) from JEOL corporation, and the product was subjected to selective electron diffraction (SAED) analysis:

from the FESEM photographs given in fig. 4, the product consisted of a large number of nanowires about 35 in diameter (some nanowires were only about 20 nm in diameter) and several microns in length. In addition to the nanowires, some nanoparticles are also present.

From the TEM photograph of the product, fig. 5, it can be seen that the photomicrographs of the nanowires of different contrasts show that the nanowires are very thin and have non-uniform diameters.

FIGS. 6 and 7 are single α -Si₃N₄Transmission electron microscopy of nanowires with their SAED pattern (fig. 6 top right) and their High Resolution Transmission Electron Microscopy (HRTEM). From the analysis of SAED, it can be indicated that the band axis of the nanowire is [010 ]]And the electron diffraction pattern of the index is consistent with the result of XRD, which also indicates that the obtained sample is a single-crystal nanowire.

In HRTEM image 7 of the nanowires, α -Si₃N₄The (002) and (200) crystallographic planes of the nanowires are clearly visible, with their interplanar spacings of 0.336 and 0.281 nm, respectively. In combination with SAED and HRTEM, nanowires were confirmed to be along [001 ]]And (4) directionally growing.

The above analysis confirmed that the product obtained by the experiment was α -Si which crystallized well₃N₄A single crystal nanowire.

Claims

1.α -Si₃N₄The solvothermal reaction preparation method of the single crystal nano wire is characterized in that SiCl is added according to the mol ratio of 1: 1.5-15₄And Mg₃N₂Mixing, sealing and reacting at 550-700 deg.C for more than 5 hr, acid washing, water washing, centrifugal separation and drying to obtain α -Si₃N₄And (3) nanowire powder.