C. Richard Liu

Laser sintering of separated and uniformly distributed multiwall carbon nanotubes integrated iron nanocomposites

Uniform distribution of carbon nanotubes (CNTs) in metal matrix during additive manufacturing of nanocomposites is always a challenge since the CNTs tend to aggregate in the molten pool. In this study, Multiwall carbon nanotubes (MWNTs) were separated and distributed uniformly into iron matrix by laser sintering process. MWNTs and iron powders were mixed together by magnetic stir, coated on steel 4140 surface, followed by laser sintering. Due to the fast heating and cooling rate, the CNTs are evenly distributed in the metal matrix. The temperature field was calculated by multiphysics simulation considering size effects, including size dependent melting temperature, thermal conductivity, and heat capacity. The SEM, TEM, and XRD were used to understand the laser sintering of CNT integrated nanocomposites. The results proved the feasibility of this technique to synthesize MWNTS integrated metal matrix nanocomposites.

Mechanism of Fatigue Performance Enhancement in a Superhard Nanoparticles Integrated Nanocomposites by a Hybrid Manufacturing Technique

A hybrid manufacturing process, which contains Laser Sintering (LS) and Laser shock peening (LSP), is introduced to generate iron-TiN nanoparticle nanocomposites. It is a two-step process including LS followed with LSP. Before LS, TiN nanoparticles mixed with iron powders are coated on samples surface. After LS, TiN nanoparticles are embedded into iron matrix to strengthen materials. Then LSP is performed to introduce work hardening and compressive residual stress. The existed nanoparticles increase the dislocation density and also help to pin the dislocation movement. Better residual stress stability under thermal annealing can be obtained by better dislocation movement stabilization, which is beneficial for fatigue performance.© 2013 ASME

Nanoparticles embedding into metallic materials by laser direct irradiation

We report a method to half-embed nanoparticles into metallic materials. Transparent and opaque nanoparticle (laser wavelength 1064 nm) were both successfully half-embedded (partial part of nanoparticles embedded into matrix while other parts still stay above the matrix) into metallic materials. Nanoparticles were coated on sample surface by dip coating before laser irradiation. After laser irradiation of different pulses and laser fluencies, nanoparticles were embedded into metal. The mechanism and process of embedding were investigated.Copyright