Catalytic Nanoparticle Additives in the Combustion of AP/HTPB Composite Solid Propellant

Presented in this thesis is a study of the effects of nano-sized particles used as a catalytic additive in composite solid propellant. This study was done with titanium oxide (titania)-based particles, but much of the findings and theory are applicable to any metal oxide produced by a similar method. The process required for efficiently producing larger batches of nanoparticle additives was seen to have a significant impact on the effectiveness of the additive to modify the burning rate of composite propellant consisting of ammonium perchlorate (AP) and hydroxyl terminated polybutadiene (HTPB). Specifically, titania was seen to be both an effective and ineffective burning rate modifier depending on how the nanoparticle additive was dried and subsequently heat treated. Nanoadditives were produced by various synthesis methods and tested in composite propellant consisting of 80 percent AP. Processability and scale-up effects are examined in selecting ideal synthesis methods of nanoscale titanium oxide for use as a burning rate modifier in composite propellant. Sintering of spray-dried additive agglomerates during the heat-treating process was shown to make the agglomerates difficult to break up during mixing and hinder the dispersion of the additive in the propellant. A link between additive processing, agglomerate dispersion mechanics and ultimately catalytic effect on the burning rate of AP/HTPB propellants has been developed by the theories presented in this thesis. This thesis studies the interaction between additive dispersion and the dispersion of reactions created by using fine AP in multimodal propellants. A limit in dispersion with powder additives was seen to cause the titania catalyst to be less effective in propellants containing fine AP. A new method for incorporating metal oxide nanoadditives into composite propellant with very high dispersion by suspending the additive material in the propellant binder is introduced. This new method has produced increases in burning rate of 50 to 60 percent over baseline propellants. This thesis reviews these studies with a particular focus on the application and scale-up of these nanoparticle additives to implement these additives in actual motor propellants and assesses many of the current problems and difficulties that hinder the nanoadditives’ true potential in composite propellant

Scale-Up Effects Of Nanoparticle Production On The Burning Rate Of Composite Propellant

Exfoliated graphite nanoplatelets (xGnPs) were used to improve the flame resistant performance of glass fiber-reinforced polyester composites. Along with xGnP, traditional intumescent fire retardant ammonium polyphosphate (APP) was introduced into the polymer matrix as the dominant additive to reduce the heat release rate (HRR) and total heat released (THR) of the composites. The cone calorimeter test results Indicate that the optimal weight ratios of xGnP and APP were 3% and 17% by weight, respectively. At such weight ratio, a synergistic effect between xGnP and APP was demonstrated. The flame resistant performance of the nanocomposites was further improved by applying xGnP-dominant carbon nanofiber (CNF)/xGnP hybrid nanopaper onto the surface of the samples. Compared with the control sample, the integration of the HRR (THR) from 0 to 100 s of the sample coated with the nanopaper of CNF/xGnP = 1/3 shows more than 30% decrease in THR. Based on the results of mass loss, the nanopaper coating is also shown to enhance the structural stability of the samples under fire conditions, which affects the mechanical properties of the composites. The results show that the thermal properties, permeability of composites, and char formation play important roles in determining the fire behavior of the composites. Copyright © 2011 John Wiley & Sons, Ltd

Development Of Highly Active Titania-Based Nanoparticles For Energetic Materials

Recent advances in nanostructured fuels and oxidizers may lead to high-performance energetic materials for propulsion, but these nanoparticulates present serious challenges due to their inherent instability and safety hazards and difficulty of manufacture. In this paper, we develop an alternate route, the use of nanoscale metal-oxides to catalyze reactions between micrometer-scale energetic constituents. Methods to synthesize TiO2-based nanoparticles that are highly active toward energetic reactions and effectively incorporate them into energetic composites are reported. Activity was maximized by tuning the physical and chemical properties of the nano-TiO2 dispersion in the composite. An 81% increase in combustion rate was achieved with a nanoparticle loading of 1 wt %, making energetically active nano-TiO 2 a viable material for advanced propulsion, without the hazards and difficulties of competing technologies. © 2011 American Chemical Society

Quo vadis multiscale modeling in reaction engineering? A perspective

This work reports the results of a perspective workshop held in summer 2021 discussing the current status and future needs for multiscale modeling in reaction engineering. This research topic is one of the most challenging and likewise most interdisciplinary in the chemical engineering community, today. Although it is progressing fast in terms of methods development, it is only slowly applied by most reaction engineers. Therefore, this perspective is aimed to promote this field and facilitate research and a common understanding. It involves the following areas: (1) reactors and cells with surface changes focusing on Density Functional Theory and Monte-Carlo simulations; (2) hierarchically-based microkinetic analysis of heterogeneous catalytic processes including structure sensitivity, microkinetic mechanism development, and parameter estimation; (3) coupling first-principles kinetic models and CFD simulations of catalytic reactors covering chemistry acceleration strategies and surrogate models; and finally (4) catalyst-reactor-plant systems with details on linking CFD with plant simulations, respectively. It therefore highlights recent achievements, challenges, and future needs for fueling this urgent research topic in reaction engineering