In this study gamma and neutron attenuation properties of boron carbide-aluminium (B4C-Al) composites were investigated. B4C-Al composites were produced by spark plasma sintering method. Aluminum percentages in the B4C-Al composites were 0%, 10%, 15%, and 20% by volume. The composite materials were performed against gamma and neutron sources. Cs-137 and Co-60 gamma radioisotopes were used as gamma sources and Pu-Be neutron howitzer was used for neutron source. Theoretical mass attenuation coefficients were determined by using XCOM computer code and compared with the experimental results. It has been seen that the experimental results were close to the theoretical results. Total macroscopic cross-sections of the samples were determined for Pu-Be neutrons. It is concluded that increasing aluminum ratio in the B4C-Al composites causes higher gamma attenuation behavior for Cs-137 and Co-60 gamma sources and the total macroscopic cross-sections of the B4C-Al composites decrease by increasing Al concentration.

B4C ceramics were fabricated by spark plasma sintering technique at 1700• C1800• C for 5 min under applied pressure of 50 MPa under vacuum atmosphere. Two dierent grades of B4C powder from H.C. Starck Company namely HP grade and HS grade were used in all related experiments. Eect of sample geometry and dimensions as well as sample thickness on sintering parameters were analyzed. Samples having 5 mm thickness and 50 mm diameter, 8 mm thickness in circular geometries and 50 × 50 square cross-section, 8 mm thickness were fabricated. Using the powder, which provided the densest sample, yttrium oxide (Y2O3) was added, mixed and sintered. Optimization of SPS method production parameters for pure B4C samples and B4C samples with 5 wt% yttrium oxide additive were accomplished. The eect of geometry on density, Vickers hardness, fracture toughness, and microstructure were examined. The hardness and fracture toughness values of the samples were evaluated by the Vickers indentation technique.

Boron carbide (B4C) ceramics were produced by spark plasma sintering technique with 5, 10, 15, and 20 vol.% aluminum (Al) in order to improve sintering behaviours of B4C ceramics. B4C ceramics were produced, having square cross-section and 50×50×5 mm 3 dimensions. The sintering process was carried out at different temperatures by applying 40 MPa of pressure with 100 • C/min under vacuum. The effects of various amounts of Al additive and sintering temperature on density, vickers hardness, fracture toughness and microstructure were examined. The hardness and fracture toughness of the samples were evaluated by the Vickers indentation technique. Microstructures of the samples were characterized by scanning electron microscopy technique. Fast neutron attenuation properties of the ceramics having highest density were also investigated.

Square-shaped boron carbide ceramic composites have been produced by spark plasma sintering with the addition of 5 to 20 vol % titanium metal powder in the B 4 C matrix in order to initiate an in situ self-propagating high-temperature synthesis (SHS) of TiB 2 . The SHS reaction not only enhances many of the physical and mechanical properties of B 4 C, but also reduces the required sintering temperature and pressure because of the enthalpy of reaction between metallic Ti and B 4 C. Sintering has been carried out in the SPS-temperature range of 1450 to 1550 °C with a uniaxial pressure of 40 MPa and a dwell time of 4 min under a 1 atm argon atmosphere. The effects of various amounts of Ti additions and sintering temperature on the phase composition, density, hardness, fracture toughness, and microstructure are examined. X-ray diffraction and transmission electron microscopy evaluations have shown that added Ti completely transforms into TiB 2 , resulting in a core−shell microstructure with a carbon core, surrounded by a TiB 2 shell in the B 4 C matrix. Moreover, by carrying out a control experiment where TiB 2 was added instead of Ti, and performing a molecular dynamics simulation of the B 4 C-Ti interface, the significance of the in situ SHS process has been validated.

We studied the effect of geometry on single focusing of particles in the passive microfluidic channels. There is a quantitative analysis of focusing on non-axisymmetric straight channels with two different unique designs as well as curved channels having symmetrical and asymmetrical radius of curvatures in one turn. We found that there is a clear relationship in existence of single line focusing with the degree of non-symmetry in microchannels. One-degree of asymmetry in straight channels does not induce any formation of single focusing, but single line focusing is pronounced by two-degree of asymmetry in straight channels. On the other hand, single line focusing in the curved channels is enhanced with asymmetrical radius of curvatures in one turn. The single line focusing in curved channels is seen at Rep values higher than 1, which gives us better continuous and high-throughput performance. The position of single focused particles in the microchannels is found to be 50 m with respect to the channel wall in the asymmetrical curved microchannels.