Interfacial microstructure and strength of brazed copper/porous copper foam towards the effect of porous copper foam pore density and brazing holding time

The porous copper foam was sandwiched between two coppers plate and then brazed using copper-tin (9.7 %)-nickel (5.7 %)-phosphorus (7 %) filler foil. Brazing process was conducted to joint copper/porous copper foam by evaluating the effect of porous copper foam pore densities [pore per inch (PPI)] and brazing holding times. The brazed joint interface of copper and porous copper foam was characterised using Field emission scanning electron microscopy and Energy-dispersive x-ray spectroscopy for the microstructure and elemental composition analysis, respectively. X-ray diffraction analysis was carried out on the shear fractured surfaces of brazed copper and porous copper foam for phase determination. The results exhibited distinct phases of copper (Cu), copper phosphide (Cu₃P), nickel phosphide (Ni₃P), and copper compound with tin (6 : 5) (Cu₆Sn₅). The filler layer was formed as an island-shaped that consists of copper phosphide and nickel phosphide. Prolong brazing holding time causes a thinner filler layer in brazing seam. While the non-uniform thickness of the filler layer was observed at different pore densities of porous copper foam. The shear strength of brazed copper/porous copper foam 15 PPI with a 10 min brazing holding time yield a maximum shear strength of 2.9 MPa.     

Numerical simulation of stochastic replicator models in catalyzed RNA-like polymers

A stochastic model for replicators in catalyzed RNA-like polymers is presented and numerically solved. The model consists of a system of reaction–diffusion equations describing the evolution of a population formed by RNA-like molecules with catalytic capabilities in a prebiotic process. The diffusion effects and the catalytic reactions are deterministic. A stochastic excitation with additive noise is introduced as a force term. To numerically solve the governing equations we apply the stochastic method of lines. A finite-difference reaction–diffusion system is constructed by discretizing the space and the associated stochastic differential system is numerically solved using a class of stochastic Runge–Kutta methods. Numerical experiments are carried out on a prototype of four catalyzed selfreplicator species along with an activated and an inactivated residues. Results are given in two space dimensions.     

Open-cell copper foam joining: joint strength and interfacial behaviour

A copper (Cu) foam was brazed with Cu-4.0Sn-9.9Ni-7.8P filler foil for joint strength and interface analysis. Brazed 50 pores per inch (PPI) Cu foam yielded a maximum compressive strength of 14.4?MPa with a 127% increment compared to nonbrazed Cu foam. 15 PPI Cu foam produced a maximum shear strength of 2.7?MPa. Scanning electron microscopy showed that the thickness of the brazed seam decreased with increasing the Cu foam’s PPI. The formation of the Cu, Cu₃P (P: phosphorus) and Ni₃P (Ni: nickel) at the Cu/Cu foam interface was validated using energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction. EDX line scanning analysis revealed the diffusion of P and Ni into Cu foam, which took place via capillary force action.     

Barycentric interpolation of interface solution for solving stochastic partial differential equations on non-overlapping subdomains with additive multi-noises

The purpose of this paper is to develop a new numerical method for solving a class of stochastic partial differential equations with additive multi-noise. Based on the domain decomposition method, we combine the deterministic method of lines and the stochastic Itô-Taylor method to construct high-order stochastic numerical method. For numerical approximation of the interface solutions, we introduce the Barycentric interpolation method. The solution is then carried out by collecting the interior solutions on the subdomains and the updated interface solutions. Finally, we computationally analyse on meaningful subdomains with linear and nonlinear interfaces, the case of a stochastic advection–diffusion with additive multi-noise and Dirichlet boundary conditions.     

Effect of Porous Copper Pore Density on Joint Interface: Microstructure and Mechanical Analysis

The effect of the pore density of porous copper (Cu) on brazed Cu/porous Cu was investigated. A filler with a composition of Cu-9.0Sn-7.0Ni-6.0P (Sn: Tin; Ni: Nickel; P: Phosphorus) and porous Cu with pore densities of 15 pores per inch (PPI), 25 PPI, and 50 PPI were employed. The joint strength of Cu/porous Cu was evaluated with shear tests at different brazing temperatures. Characterizations of the joint interface and fractured surface were achieved with scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The micro-hardness test of Cu/porous Cu joint interface showed a high hardness value (HV) for 50 PPI porous Cu. This result was in line with its low shear strength. It was proved that the joint strength of Cu/porous Cu is dependent on the pore density of the porous Cu structure and brittle phases of Cu₃P and Ni₃P in the brazed interface.