Laser vaporization-condensation technique

Synthesis of Nanostructured Materials Using a Laser Vaporization—Condensation Technique... 

Figure 6.39. Schematic of nanoparticle growth via pulsed-laser vaporization with controlled condensation (LVCC), coupled to a differential mobility analyzer (DMA). A DMA is used to control the size of gas-phase synthesized nanoparticles by exploiting differences in the electrical mobility of nanoparticles under a flow of an inert gas. Reproduced with permission from Glaspell, G. Abdelsayed, V. Saoud, K. M. El-Shall, M. S. Pur. Appl. Chem. 2006, 75, 1667. Copyright 2006 lUPAC. The bottom image shows how gas-phase techniques may be used to synthesize Au/Ga core/shell nanoparticles with the assistance of multiple DMAs. Reproduced with permission from Karlsson, et al. Aerosol Sci. Technol. 2004, 38, 948.

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... 

Another thin film technology based nanoparticle preparation route is gas condensation, in which metal vapor is cooled to high levels of supersaturation in an inert gas ambient [126-128]. In these experiments particles necessarily nucleate in the gas phase. In a promising extension of this technique a pulsed laser beam replaces the conventionally used thermal metal vapor source [120,121,129-134]. 

Ullrafine particles (UFPs) of metal and semiconductor nitrides have been synthesized by two major techniques one is the reactive gas condensation method, and the other is the chemical vapor condensation method. The former is modified from the so-called gas condensation method (or gas-evaporation method) (13), and a surrounding gas such as N2 or NII2 is used in the evaporation chamber instead of inert gases. Plasma generation has been widely adopted in order to enhance the nitridation in the particle formation process. The latter is based on the decomposition and the subsequent chemical reaction of metal chloride, carbonate, hydride, and organics used as raw materials in an appropriate reactive gas under an energetic environment formed mainly by thermal healing, radiofrequency (RF) plasma, and laser beam. Synthesis techniques are listed for every heal source for the reactive gas condensation method and for the chemical vapor condensation method in Tables 8.1.1 and 8.1.2, respectively. 

Mixed Gas Plasmas. Water loading can be reduced by a desolvation system (condenser or membrane separator) only if the vast majority of the water can be removed. One way to eliminate the introduction of water into the plasma during measurement of the analyte signals is with electrothermal vaporization, laser ablation, or other direct solid sampling techniques. Mixed gas plasmas,... 

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