Preparation And Property Comparison Study Of Molybdenum Based Thermite

As an important source of energy in micro n scale devices,metastable intermolecular composite?MIC?has been a hot spot in the field of energetic materials.It has high combustion rate,high energy density and micron critical diameter.The reaction rate of MIC depends on the amount of gaseous phase in the ignition products.The combustion reaction may even not be triggered without the formation of vapor phase products;hence the metal oxides with low melting point and reacting with Al to produce high mass heat become the first choice of excellent MIC.MoO₃ owes the above two advantages,so it becomes a promising metal oxide component for MIC in recent years.This work aims to find out the effect of the morphology of MoO₃ and preparation methods of MIC on the properties of MIC.First,different synthesis methods were employed to prepare MoO₃ with different morphologies and thereafter the performances of them were compared.On this basis,MoO₃ with good performance was chosen to be MIC metal oxide.Then MIC was prepared in different ways,and properties of the products were analyzed.Finally,the performances of different products were tested under the same standard,and the influence of preparation methods on the performance of MIC was comprehensively understood.Conclusions are listed below:First of all,hydrothermal method was employed to prepare molybdenum trioxide nanobelt.Influences of the reaction time,temperature,acidity coefficient,precursor type and concentrations of precursors on the morphology of the nanometer molybdenum trioxide were studied.MoO₃ nanobelt with good morphology and narrow size distribution can be acquired when ammonium molybdate is of 0.06⁰.08mol·L^-1,reaction time is less than 48 h,temperature is above 150°C,and acidity coefficient is more than 64.In comparison,the oil-assistant method was used to produce six-prismy molybdenum trioxide.The effects of calcination temperature,calcination time and mixing methods on the morphology of the product were studied.Six-prismy MoO₃ can be obtained only in the presence of oil phase.Hexagonal MoO₃will transfer into orthorhombic phase with the calcination temperature above 400°C.Crystal type changes gradually with the time increase under calcination temperature350°C.Sonic oscillation is conducive to preparation of six-prismy molybdenum trioxide,while stirring can only get irregular prisms.Then,electrospray?ES?method and physical mixing method were both used to prepare MoO₃ nanobelts based MIC.Pre-agglomerated MIC particles prepared by ES were acquired with the voltage ranges from 20 kV to 22.5 kV.Flow rate within 5mL·h^-1 can get smaller and uniformer distribution of MIC aggregates.When the amount of collodion is 4/10,better prepared products can be gotten.Compared with the physical mixing method,the products obtained by ES method are compact,uniform and stable.Thermal decomposition temperature of MIC prepared by ES method increased with collodion content increasing and thermal decomposition exothermic and weight loss also showed an upward trend.Finally,experiments on sensitivity,combustion heat and ignition of Al/MoO₃prepared by micron scale,nano scale and electrospray were carried out.Micron Al/MoO₃ is very insensitive to impact and flame.Nano Al/MoO₃ flame sensitivity is the highest of three samples,and sample prepared by electrospray method is most sensitive to impact.However,the combustion heat of micron Al/MoO₃ is the highest of all samples,4659 J·g^-1.Al/MoO₃ prepared by electrospray method showed superior combustion and P-t performance of al.