研究目的
To investigate the use of green additives (water and alcohol) in the combustion synthesis of α-Si3N4 to control reaction kinetics, improve α-phase formation, and provide a safer alternative to toxic and corrosive ammonium halides for industrial applications.
研究成果
The combustion synthesis of α-Si3N4 using green additives (water and alcohol) effectively controls reaction kinetics and enhances α-phase formation through vapor reactions. Water addition increases α-phase content but raises oxygen levels and forms Si2N2O, while alcohol reduces oxygen but yields slightly lower α-phase and introduces SiC. These additives are nontoxic and noncorrosive, making them superior to ammonium halides for industrial applications, though further optimization is needed to minimize impurities and scale up the process.
研究不足
The addition of water increased oxygen content and led to the formation of Si2N2O phase. Alcohol addition reduced oxygen content but resulted in lower α-phase content and the appearance of SiC at higher concentrations. The reaction did not occur with additive contents above 20 wt% due to paste formation. The study is limited to laboratory-scale synthesis and may require optimization for industrial scalability.
1：Experimental Design and Method Selection:
The study employed combustion synthesis (CS) to produce α-Si3N4 powders, focusing on the effects of green additives (water and alcohol) on reaction kinetics and phase formation. The rationale was to replace harmful additives with environmentally friendly ones while maintaining or enhancing product quality.
2：Sample Selection and Data Sources:
Raw materials included Si powder (99.99%, particle size < 10 μm), Si3N4 powder (particle size < 5 μm), deionized water, and alcohol. Eleven samples were prepared with varying additive contents (0% to 15% weight of water or alcohol) and analyzed.
3：99%, particle size < 10 μm), Si3N4 powder (particle size < 5 μm), deionized water, and alcohol. Eleven samples were prepared with varying additive contents (0% to 15% weight of water or alcohol) and analyzed.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a planetary mill for mixing, a porous graphite crucible, a stainless-steel CS reactor, W-Re3/W-Re25 thermocouples for temperature recording, a tungsten filament ignition agent, X-ray diffraction (XRD; D8 Advance, Bruker Co.), field-emission scanning electron microscopy (FESEM; JSM-7001F, JEOL), and X-ray fluorescence spectrometry (XRF; XRF-1800, Shimadzu). Materials were Si powder, Si3N4 powder, water, and alcohol.
4：Experimental Procedures and Operational Workflow:
Si and Si3N4 powders were mixed by planetary milling for 4 hours, then mixed with water or alcohol. The mixture was packed into a graphite crucible with 40% porosity, placed in the CS reactor under 4.5 MPa high-purity nitrogen. Ignition was achieved using a tungsten filament in titanium powder with a 20 A current for 5-10 s. Temperature was monitored, and products were analyzed by XRD, FESEM, and XRF.
5：5 MPa high-purity nitrogen. Ignition was achieved using a tungsten filament in titanium powder with a 20 A current for 5-10 s. Temperature was monitored, and products were analyzed by XRD, FESEM, and XRF.
Data Analysis Methods:
5. Data Analysis Methods: Phase content was calculated using quantitative XRD analysis based on Gazzara's method. Microstructure was observed via FESEM, and oxygen content was measured by XRF. Data were compared across samples to assess the effects of additives.
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