Abstract

We studied the possibility of producing powder catalysts Al–Fe/SiO₂ and Al–Co/SiO₂ by mixing precursor powders of Al, Fe, Co, and SiO₂ in a planetary mill in gross weight ratios corresponding to the domain of existence of intermetallic compounds Al₃Fe and Al₃Co and annealing in vacuum at 900°C for 30 min. Annealing in air at lower temperatures (580–600°С) leads to the formation of corundum Al₂O₃, mullite Al₆Si₂O₁₃, and silicides CoSi₂, CoSi, Co₂Si, FeSi₂, and Fe₃Si in the composite structure. The synthesized composite powders 13Al/4Co/6.5SiO₂ and 13Al/4Fe/6.5SiO₂ contain nonequilibrium phases. Powders without sintered masses with good flow and a fractional composition of less than 100 μm are obtained after synthesis in vacuum at 900°C for 30 min. The fractional composition of powder Fe–Al/SiO₂ is characterized by a distribution of less than 50 μm (27.1%), 50–63 μm (15.3%), and 63–100 μm (57.4%); the fractional composition of powder Co-Al/SiO₂ is 37.5%, 16.2%, and 46.3%, respectively. According to X-ray phase analysis, the powders synthesized at 900°С contain the phases of Fe₃Al, Fe_0.5Al_0.5, Fe₁₄Al₈₆, Co₂Al₅, and Co₂₇Al₇₃; they do not contain silicides and mullites of the type Al₆Si₂O₁₃. It is experimentally established that the mass fractions of the precursors Al, Fe, and Co are (Al + Fe) : SiO₂ = 31 : 69 and (Al + Co) : SiO₂ = 58 : 42 as a result of cladding of powder SiO₂. It is concluded that the vacuum annealing mode of 900°C for 30 min does not provide the formation of intermetallic structures of the type Al₁₃Fe₄/Al₃Fe and Al₁₃Co₄/Al₃Co during the synthesis. We suggest optimizing the synthesis mode by using precursors of finer fractions and increasing the time of their grinding, mixing, and annealing.

中文翻译：

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固相法生产Al–Fe / SiO 2和Al–Co / SiO 2粉末催化剂的特点

摘要

我们研究了通过在行星式磨机中按总重比（对应于存在的铁氧体的存在）混合Al，Fe，Co和SiO _2的前体粉末来生产粉末催化剂Al–Fe / SiO ₂和Al–Co / SiO ₂的可能性。金属间化合物Al ₃ Fe和Al ₃ Co并在900°C的真空中退火30分钟。在较低温度（580–600°С）下在空气中退火会导致形成刚玉Al ₂ O ₃，莫来石Al ₆ Si ₂ O ₁₃以及硅化物CoSi ₂，CoSi，Co ₂ Si，FeSi ₂和Fe ₃Si在复合结构中。合成的复合粉末13Al / 4Co / 6.5SiO ₂和13Al / 4Fe / 6.5SiO ₂包含非平衡相。在真空中于900°C合成30分钟后，获得无烧结块且流动性好且分数组成小于100μm的粉末。Fe–Al / SiO ₂粉末的分数组成的特征在于分布小于50μm（27.1％），50–63μm（15.3％）和63–100μm（57.4％）。粉末Co-Al / SiO ₂的分数组成_分别为37.5％，16.2％和46.3％。根据X射线相分析，在900℃下合成的粉末包含Fe ₃ Al，Fe _0.5 Al _0.5，Fe _14相。Al ₈₆，Co ₂ Al ₅和Co ₂₇ Al ₇₃ ; 它们不含Al ₆ Si ₂ O ₁₃类型的硅化物和莫来石。通过实验确定，通过粉末包覆，前体Al，Fe和Co的质量分数为（Al + Fe）：SiO ₂ = 31：69和（Al + Co）：SiO ₂ = 58:42 SiO ₂。结论是900℃30分钟的真空退火模式不能形成Al ₁₃ Fe ₄ / Al ₃ Fe和Al ₁₃ Co型金属间结构。₄ / Al的₃的合成过程中钴。我们建议通过使用更细小馏分的前体并增加其研磨，混合和退火的时间来优化合成模式。