60 research outputs found
Particle In Cell Simulation of Combustion Synthesis of TiC Nanoparticles
A coupled continuum-discrete numerical model is presented to study the
synthesis of TiC nanosized aggregates during a self-propagating combustion
synthesis (SHS) process. The overall model describes the transient of the basic
mechanisms governing the SHS process in a two-dimensional micrometer size
geometry system. At each time step, the continuum (micrometer scale) model
computes the current temperature field according to the prescribed boundary
conditions. The overall system domain is discretized with a desired number of
uniform computational cells. Each cell contains a convenient number of
computation particles which represent the actual particles mixture. The
particle-in-cell (discrete) model maps the temperature field from the
(continuum) cells to the respective internal particles. Depending on the
temperature reached by the cell, the titanium particles may undergo a
solid-liquid transformation. If the distance between the carbon particle and
the liquid titanium particles is within a certain tolerance they will react and
a TiC particle will be formed in the cell. Accordingly, the molecular dynamic
method will update the location of all particles in the cell and the amount of
transformation heat accounted by the cell will be entered into the source term
of the (continuum) heat conduction equation. The new temperature distribution
will progress depending on the cells which will time-by-time undergo the
chemical reaction. As a demonstration of the effectiveness of the overall model
some paradigmatic examples are shown.Comment: submitted to Computer Physics Communication
Structural and mechanical properties of TiB 2 and TiC prepared by self-propagating high-temperature synthesis/dynamic compaction
Titanium-diboride and titanium-carbide compacts with diameters of 100 mm and thicknesses of 25 mm were fabricated by self-propagating high-temperature synthesis/dynamic compaction (SHS/DC) of the elemental powders. Under the best conditions, the densities were greater than 99% and 96.8% of the theoretical densities for TiB 2 and TiC, respectively. The microhardness, compressive strength, and elastic modulus of the TiB 2 prepared by the SHS/DC method were comparable to reported values for hot-pressed TiB 2 . While the microhardness and elastic modulus of the TiC compacts were comparable to those for hotpressed TiC, the compressive strength was lower due to extensive cracks in the compacts. The TiB 2 prepared using a low-purity boron powder (1–5% carbon impurity) compacted to higher densities and had less cracking than that prepared using a high-purity boron powder (0.2% carbon). This result could have an impact on the cost of producing TiB 2 /TiC structural components by the SHS/DC process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44732/1/10853_2005_Article_BF01162518.pd
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