Preparation And Stabilization Of The Porous Silicon/Gadolinium Nitrate Energetic Materials

Porous silicon based energetic materials as a novel energetic materials has attractedextensive attention for its high explosive properties, less pollution to environment andcompatibility with manufacturing technics of whole silicon substrate. Fresh poroussilicon has poor stability for it is easily oxidized by oxygen, which limits its application.Based on the foundation of laboratory’s research, porous silicon/gadolinium nitrateenergetic materials with certain explosive capability was prepared by electrochemicalanodic oxidation technique on phosphorus-doped n-type Si substrate, and thestabilization methods were researched. The specific topics of this thesis are as follows:(1) This paper summarized the development status of energetic materials andporous silicon-based energetic materials, the preparation methods, formationmechanisms and stabilization methods of porous silicon.(2) The physicochemical properties and morphology of porous silicon werecharacterized, including porosity, thickness, mass loss and surface morphology. Theporosity of porous silicon increases with the extension of anodizing time, decreases withthe increasing hydrofluoric acid concentration, the porosity increases firstly and thendecrease with the increase of current density and the porosity to the minimum whencurrent density is15mA/cm2. The thickness increases with the increasing hydrofluoricacid concentration and anodizing time, and the thickness is linearly related to anodizingtime, the thickness increases when the current density increases and to be stable atcurrent density20mA/cm2. With the anodizing time and current density adding, massloss of silicon increases, but when the hydrofluoric acid concentration increases, massloss reduces.(3) The effects of anodization conditions on explosive properties of poroussilicon/gadolinium nitrate energetic materials were studied. The experiment resultsshow that the optimal explosive property of the energetic material can be obtained whenHF:DMF(v:v)=3:1, current density is20mA/cm2and anodizing time is25min.Explosion spectrum and color temperature were measured, and the color temperature ofthe optimal energetic material up to3612.74K.(4) Five surface treatment methods were adopted to post-treat porous silicon,including anodic oxidation, thermal annealing, photochemical oxidation, cathodicreduction and high-pressure water vapor annealing. The effect of stabilizing treatments on porous silicon surface oxidation degree: high-pressure water vapor annealing>anodic oxidation>thermal annealing>photochemical oxidation> cathodic reduction. Theexperiment result expresses that porous silicon/gadolinium nitrate energetic materialswas stabilized to some extent after different stabilization treatment, however theexplosive properties still decreases with longer storing time. The stabilizing effect ofdifferent methods: photochemical oxidation>thermal annealing>anodic oxidation>cathodic reduction>high-pressure water vapor annealing. The optimum surfacetreatment methods is photochemical oxidation, after photochemical oxidation treatment,porous silicon-based composite energetic materials can explode slightly after60days’storage in a vacuum.(5) The thermal stability of porous silicon/gadolinium nitrate energetic materialswas investigated, and the effects of ambient temperature were studied.