A Novel Method of Si and Si3N4 Powder Resources Recycling: Cold Bonding Briquettes

Abstract

Silicon nitride (Si3N4) and silicon powder (Si) are two kinds of harmful solid waste in industrial production. As an environmental and low-consumption method, the cold-bonding technique is a novel method to utilize the problem of powder resource cycling. In this experiment, mechanical and high-temperature properties of Si and Si3N4 briquettes were studied after cold bonding. The results are as follows: (1) The compressive strength of the Si and Si3N4 briquettes increased with the improvement of molding pressure. With the same binder (1 wt.%) and water (10 wt.%) addition, the compressive strength of the Si3N4 briquette arrived at 12,023.53 N under 40 Mpa molding pressure, which is much higher than that of the Si briquette (942.40 N). The Si particles are uneven and irregular, which leads to an intense arch bridge effect in the Si briquette and the compressive strength decrease. Compared with Si powder, the particle size and shape of Si3N4 is small, uniform, and regular. The influence of the arch bridge effect is smaller than that in the Si briquette. (2) After being treated at 1473 K for 1 h, the compressive strength of the Si briquette increased to 5049.83 N, and the compressive strength of the Si3N4 briquette had a slight change. The surface of the briquettes was contacted with oxygen and reacted to form an outer shell which mainly contains SiO2 in the high-temperature treatment. FT-IR results have shown there were no extra impurities in cold-bonded briquettes when using the organic binder. (3) The microstructure of the cross section of the Si and Si3N4 briquettes after high-temperature treatment presented that oxygen entered the briquette through the pores and continued to react with the Si and Si3N4. The outer shell of the Si briquette grew and thickened continuously with the oxygen spreading in the Si briquette. However, because of the smaller particle size and regular shape, little oxygen diffused in the Si3N4 briquette. The outer shell of the Si3N4 briquette is fairly thin, so the compressive strength did not change too much.

Special Issue “Research and Development of Building Materials Based on Industrial Waste”

“…This Special Issue presents original research results in the following areas: the use of solar panels after the end of their life cycles in the production of cement composites [1]; the radioactivity of building materials in historical buildings [2]; the use of silicon nitride (Si 3 N 4 ) and silicon powder (Si) in the production of briquettes with defined properties [3]; the utilization of by-products of solid waste incineration in concrete production [4]; the comparison of the thermal conductivity of aerated concrete based on fly ash [5]; the utilization of by-products of the incineration of solid municipal waste in the production of foam concrete [6]; the mechanical properties of micropowder cement mortar and engineered cementitious composites (ECC), involving investigations of the use of different methods of processing for municipal solid waste incineration (MSWI) as a mineral admixture [7]; the use of marble dust and blast furnace slag in the production of self-compacting concrete [8]; a new method for the synthesis of insulating aerogel via recycling solid waste coal gangue, which has the potential to reduce the industrial production costs of silica aerogels and realize the high-value-added utilization of solid waste [9]; strength tests and numerical simulations of the Loess modified by desulfurization ash and fly ash [10]; research on the rheological properties of cement paste prepared using silica fume [11]; and, finally, research on the properties of cement paste prepared from superfine basalt powder [12].…”