U.S. natural gas futures rose about 5 percent to a near nine-week high as global energy prices surged on concerns over a pricing plan for energy exports, keeping U.S. LNG export demand near record highs. U.S. natural gas prices have risen despite forecasts of mild weather and lower-than-expected demand, which will allow utilities to fill up storage facilities next week. On Wednesday, Germany launched an emergency plan to manage gas supplies in Europe's largest economy. If natural gas supplies are interrupted or stopped, the German government could take unprecedented steps to limit electricity supply.
Affected by the increase in the price of natural gas, the price of the silicon nitride powder will also increase.
Silicon nitride powder is the main raw material of silicon nitride ceramics and related products. At present, the main preparation methods include silicon powder direct nitridation, carbothermal reduction, thermal decomposition, sol-gel method, chemical vapor deposition, and self-propagating method.
Direct nitridation of silicon powder
Direct nitridation of silicon powder is the earliest method to prepare silicon nitride powder. The method is relatively simple and low cost. the metal silicon powder is heated in the atmosphere of nitrogen or ammonia, and the metal silicon powder reacts directly with the nitrogen source to form silicon nitride powder. The reaction equation is as follows:
3Si+2N2 (g) = Si3N4.
3Si+4NH3 (g) = Si3N4+6H2 (g).
This method has the advantages of low cost and low equipment requirements. However, the nitriding reaction of metal silicon powder is an exothermic reaction. If the heat is not released in time in the nitriding process, it will make the nearby metal silicon powder melt and seriously affect the nitriding reaction. Therefore, this process must strictly control the nitriding temperature, nitriding speed, particle size of raw materials and the concentration of diluent and so on. The synthesized silicon nitride is non-uniform block, so it is necessary to prepare silicon nitride powder by ball milling or other methods, which is inefficient and easy to introduce impurities in the process.
Carbothermal reduction method
In the carbothermal reduction method, silica powder is reduced by carbon in high temperature nitrogen environment. SiO2 is first reduced to gas phase SiO, and gas phase SiO reacts with nitrogen in atmosphere to form silicon nitride. The total reaction equation is as follows:
3SiO2 (s) + 6C (s) + 2N2 (g) = Si3N4 (s) + 6CO (g).
The carbothermal reduction method has the advantages of low raw material cost, small particle size, fast reaction speed and high α-Si3N4 content, so it is suitable for large-scale production. However, the silicon nitride powder prepared by this method often contains residual carbon or silicon carbide, so the purity of the powder is not high, which affects the quality and application of the product.
Thermal decomposition method
In this method, SiCl4 reacts with ammonia at low temperature to obtain solid imino silicon Si(NH2) or amino silicon Si(NH2)4, which can be decomposed at high temperature to obtain silicon nitride powder. This method has high reaction efficiency and can prepare a large number of silicon nitride powders with high purity in a short time. The silicon nitride powder prepared by this method has uniform particle size and high purity, which is the process used to prepare high quality silicon nitride powder. At present, this method has become the most important method used in the commercial production of high purity and high-quality silicon nitride powder.
Sol-gel method is a method to prepare uniform and high-quality silicon nitride powders, which usually uses highly active silicon sources as precursors and uniformly mixes the raw materials in the presence of liquid phase to form stable sol. After aging, the gel is slowly polymerized, and then the nano-sized silicon nitride powder can be prepared by drying-sintering. This method overcomes the shortcomings of other methods, such as uneven mixing and large gap in particle size distribution.
Chemical vapor deposition
High temperature Chemical Vapor deposition (CVD) is a method to prepare high purity and ultra-fine silicon nitride powder by reacting gaseous silicon sources such as SiCl4 and SiH4 with gaseous nitrogen sources such as NH3. The reaction equation is as follows:
3SiCl4 (g) + 16NH3 (g) = Si3N4 (s) + 12NH4Cl (g).
3SiH4 (g) + 4NH3 (g) = Si3N4 (S) + 12H2 (g).
Because the reaction process is a gas phase reaction process, the mixture is uniform, and the reaction process is very fast, it is easy to control the progress of the reaction by controlling the flow of the gas phase.
Self-propagating high temperature synthesis
Self-propagating high temperature synthesis (SHS) is a synthesis technology which uses the heat released by the chemical reaction as the heat source to heat the adjacent reactants so that the reaction can be sustained and conducted. Once the reaction begins, it does not need external energy, and the reaction continues on its own exothermic until the reaction is completely over.
Because the nitriding of silicon powder is a large amount of exothermic reaction, silicon nitride can be prepared by self-propagating synthesis. The production equipment and process are relatively simple, and the reaction speed is fast. The silicon nitride powder prepared in this way has high purity and good sintering activity. However, this process needs to control the diffusion of heat, such as poor diffusion, it is prone to the phenomenon of molten silicon and prevent nitriding reaction.
Silicon Nitride Si3N4 Powder Price
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With Russia taking the lead on Poland and Bulgaria at the end of last month, there appears to be a growing sense of compromise within the EU over whether to accept Moscow's proposed rouble settlement order.
Italy's prime minister said recently that European companies would be able to buy gas in roubles without violating sanctions. This apparently ignores the guidance of hardliners in the EU to "fight to the end".
For weeks, European companies have been trying to find ways to meet Russia's payment demands for the rouble while maintaining vital gas supplies without violating sanctions against Moscow.
Late last month, European Commission President Von der Leyen said operating under the mechanism would violate sanctions and asked European companies not to bow to Russian demands. However, the EU has yet to issue more rigorous written guidelines on how companies should pay Gazprom.
The Italian prime minister said recently, "There is no official announcement from the European Union about what ruble settlement means for sanctions violations, and no one has said whether ruble payments violate sanctions or not. It's a grey area."
"In fact, most gas importers are already opening rouble accounts for deals with Gazprom,"
He also used German companies as a shield. He said Germany's largest gas importer had already paid in rubles. "In fact, we saw evidence yesterday that the largest gas importer in Germany has already paid in rubles."
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