Combustion Catalyst: Nano‐Fe2O3 and Nano‐Thermite Al/ Fe2O3 with Different Shapes

In order to enable the energetic materials to possess a more powerful performance, adding combustion catalysts is a quite effective method. Granular, oval, and polyhedral Fe2O3 particles have been prepared by the hydrothermal method and used to fabricate Al/Fe2O3 thermites. All the Fe2O3 and Al/Fe2O3 thermite samples were characterized using a combination of experimental techniques including scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and high‐resolution TEM (HRTEM). The non‐isothermal decomposition kinetics of the composites and nitrocellulose (NC) can be modeled by the Avrami‐Erofeev equation f(α)=3(1–α)[–ln(1–α)]1/3/2 in differential form. Through the thermogravimetric analysis infrared (TG‐IR) analysis of decomposition processes and products, it is speculated that Fe2O3 and Al/Fe2O3 can effectively accelerate the thermal decomposition reaction rate of NC by promoting the O‐NO2 bond cleavage. Adding oxides or thermites can distinctly increase the burning rate, decrease the burning rate pressure exponent, increase the flame temperature, and improve the combustion wave structures of the ammonium perchlorate/hydroxyl‐terminated polybutadiene (AP/HTPB) propellants. Among the three studied, different shapes of Fe2O3, the granular Fe2O3, and its corresponding thermites (Al/Fe2O3(H)) exhibit the highest burning rate due to larger surface area associated with smaller particle size. Moreover, Al/Fe2O3(H) thermites have more effective combustion‐supporting ability for AP/HTPB propellants than Fe2O3 structures and the other two as‐prepared Al/Fe2O3 thermites

Automatic 2.5D cartoon modelling

Non-photorealistic arts have been an invaluable form of media for over tens of thousands of years, and are widely used in animation and games today, motivating research into this field. Recently, the novel 2.5D Model has emerged, targetting the limitations of both 2D and 3D forms of cartoons. The most recent development is the 2.5D Cartoon Model. The manual building process of such models is labour intensive, and no automatic building method for 2.5D models exists currently. This dissertation proposes a novel approach to the problem of automatic creation of 2.5D Cartoon Models, termed Auto-2CM in this thesis, which is the first attempt of a solution to the problem. The proposed approach aims to build 2.5D models from real world objects. Auto-2CM collects 3D information on the candidate object using 3D reconstruction methods from Computer Vision, then partitions it into meaningful parts using segmentation methods from Computer Graphics. A novel 3D-2.5D conversion method is introduced to create the final 2.5D model, which is the first method for 3D-2.5D conversion. The Auto-2CM framework does not mandate specific algorithms of reconstruction or segmentation, therefore different algorithms may be used for different kinds of objects. The effect of different algorithms on the final 2.5D model is currently unknown. A perceptual evaluation of Auto-2CM is performed, which shows that by using different combinations of algorithms within Auto-2CM for specific kinds of objects, the performance of the system maybe increased significantly. The approach can produce acceptable models for both manual sketches and direct use. It is also the first experimental study of the problem

Reactive Molecular Dynamic Simulation of Thermal Decomposition for Nano-Aluminized Explosives

Aluminized explosives have important applications in civil construction and military armaments, but their thermal decomposition mechanisms are not well characterized. Here, the thermal decomposition of TNT, RDX, HMX and CL-20 on Al nanoparticles is examined by reactive dynamics simulations using a newly parameterized reactive force field with low gradient correction (ReaxFF-lg). Partially passivated Al nanoparticles were constructed and mixed with TNT, RDX, HMX and CL-20 crystals and then the mixed systems are heated to a high temperature in which the explosives are fully decomposed. The simulation results show that the aluminized explosives undergo three main steps of thermal decomposition, which were denoted "adsorption period" (0-20 ps), "diffusion period" (20-80 ps) and "formation period" (80-210 ps). These stages in sequence are the chemical adsorption between Al and surrounding explosive molecules (R-NO2-Al bonding), the decomposition of the explosives and the diffusion of O atoms into the Al nanoparticles, and the formation of final products. In the first stage, the Al nanoparticles decrease the decomposition reaction barriers of RDX (1.90 kJ g-1), HMX (1.95 kJ g-1) and CL-20 (1.18 kJ g-1), respectively, and decrease the decomposition reaction barrier of TNT from 2.99 to 0.29 kJ g-1. Comparing with the crystalline RDX, HMX and CL-20, the energy releases are increased by 4.73-4.96 kJ g-1 in the second stage. The number of produced H2O molecules increased by 25.27-27.81% and the number of CO2 molecules decreased by 47.73-68.01% in the third stage. These three stages are further confirmed by the evolutive diagram of the structure and temperature distribution for the CL-20/Al system. The onset temperatures (To) of generating H2O for all the aluminized explosives decrease, while those of generating CO2 for aluminized HMX and CL-20 increase, which are in accord with the experiment of aluminized RDX