Laser melting deposition

Thin horizontal, vertical selective laser melting plates and rolled plates of 1.5-2.5 mm have been used as substrate materials for a laser melting deposition process to analyze the tensile properties, microhardness, microstructure, and internal defects. 

The results showed that the laser melting deposition process forms a hybrid with the aforementioned plates. The relative density of hybrid-forming area can reach 99.5%, because of the existence of the pores with diameter < 20 ym. The tensile strength and the elongation of the hybrid produced in this way can reach 918 MPa and 11%, respectively. Fractures are located in the laser melting deposition zone. An internal layer fracture of the laser melting... 

Onion-like graphitic clusters have also been generated by other methods (a) shock-wave treatment of carbon soot [16] (b) carbon deposits generated in a plasma torch[17], (c) laser melting of carbon within a high-pressure cell (50-300 kbar)[l8]. For these three cases, the reported graphitic particles display a spheroidal shape. 

Janai and Moser (1982) have used chemical-vapor-deposited amorphous silicon films that were deposited at 600°C on silica (fused quartz) substrates. Information was recorded in films with thickness d between 2500 and 5000 A by irradiation with a ruby laser pulse of 50 nsec duration and an energy density ranging from 0.4 to 1.5 J cm-2. The upper energy limit is known to be above the threshold for laser melting in a-Si (Baeri et al., 1980). To determine the optical transmission density difference... 

The selective laser sintering (SLS) process is also known as laser powder deposition (24). Laser deposition is a solid free-form fabrication method. There, a laser beam is used to melt an addition material to create a material track with approximately hemispherical cross section. 

The laser deposition process epitaxially generates coarse columnar crystals, and laser remelting reduces the microhardness of the selective laser melting substrate in the 2 mm to 3 mm thick grain increased heat affected zone (31). 

A laser pulse strikes the surface of a sample (a), depositing energy, which leads to melting and vaporization of neutral molecules and ions from a small, confined area (b). A few nanoseconds after the pulse, the vaporized material is either pumped away or, if it is ionic, it is drawn into the analyzer of a mass spectrometer (c). 

The most widely deposition technique is the ion assisted deposition (lAD). A material in a melting-pot is vaporized by heating either with an electron beam, or by Joule effect, or with a laser beam, or with microwaves, or whatever else. The vapor flow condensates on the substrate. In the same time, an ion... 

The last problem of this series concerns femtosecond laser ablation from gold nanoparticles [87]. In this process, solid material transforms into a volatile phase initiated by rapid deposition of energy. This ablation is nonthermal in nature. Material ejection is induced by the enhancement of the electric field close to the curved nanoparticle surface. This ablation is achievable for laser excitation powers far below the onset of general catastrophic material deterioration, such as plasma formation or laser-induced explosive boiling. Anisotropy in the ablation pattern was observed. It coincides with a reduction of the surface barrier from water vaporization and particle melting. This effect limits any high-power manipulation of nanostructured surfaces such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses. 

Disordering on surfaces Layers on materials Vapour deposition, laser surface melting, ion beam modification... 

On a metal surface, silicide layers can be formed by two methods. In the first, Si atoms are vapor deposited by heating either a well degassed silicon wafer or a silicon rod to near its melting point. In the second method the metal is heated in 10 to 50 mTorr of silane for a desired length of time, usually about 10 to 60 s at a desired temperature, usually about 300 to 700°C. The first method is better suited for studying very early stages of silicide formation, the second more convenient for growing thick layers of silicides. Chemical vapor deposition or laser enhanced chemical vapor deposition may probably be used also, but have not yet been explored. 

The simplest recording medium is a bilayer structure. It is constructed by first evaporating a highly reflective aluminum layer onto a suitable disk substrate. Next, a thin film (15-50 nm thick) of a metal, such as tellurium, is vacuum deposited on top of the aluminum layer. The laser power required to form the mark is dependent on the thermal characteristics of the metal film. Tellurium, for example, has a low thermal diffusivity and a melting point of 452 °C which make it an attractive recording material. The thermal diffusivity of the substrate material should also be as low as possible, since a significant fraction of the heat generated in the metal layer can be conducted to the substrate. For this reason, low cost polymer substrates such as poly (methylmethacrylate) or poly (vinyl chloride) are ideal. 

Pulsed laser deposition (PLD) [1-3] uses high-power laser pulses with an energy density of more than 108 W cm 2 to melt, evaporate, excite, and ionize material from a single target. This laser ablation produces a transient, highly luminous plasma plume that expands rapidly away from the target surface. The ablated material is collected on an appropriately placed substrate surface upon which it condenses and a thin film nucleates and grows. 

SFF encompasses many different approaches to additive fabrication, including Stereolithography (SLA), Selective Laser Sintering (SLS), Electron Beam Melting (EBM), Laminated Object Manufacturing (LOM), Fused Deposition Modeling (FDM), and 3D Printing. 

---