Laser ablation method

Ablation Methods Laser Ablation Spark Ablaticm... 

The major methods used for vaporization (ablation) include lasers, electrically heated wires, or sample holders and electrical discharges (arcs, sparks). 

Laser-ablation method shown in Fig. 3 was used when Cgo was first discovered in 1985 [15]. This method has also been applied for the synthesis of CNT, but length of MWCNT is much shorter than that by arc-discharge method [17]. Therefore, this method does not seem adequate to the synthesis of MWCNT. However, in the synthesis of SWCNT described later (Sec. 3.1.2), marvelously high yield has been obtained by this method. Hence, laser-ablation method has become another important technology in this respect. 

Although laser-ablation method with pure carbon as the target only gives fullerenes, SWCNT can be obtained at high yield by mixing Co-Ni into the target carbon [16]. Isolation of thus synthesized SWCNT is rather of ease since the crude product is almost free of nanoparticle and amorphous carbon [39]. Such... 

The laser-ablation method can produce SWCNT under co-evaporation of metals like in the electric arc-discharge method. As metallic catalyst Fe, Co or Ni plays the important role and their combination or addition of the third element such as Y produces SWCNT in an efficient manner. But it is still difficult in the laser-ablation method to produce gram quantity of SWCNT. Nonetheless, remarkable progress in the research of physical properties has been achieved in thus synthesized SWCNT. 

All available methods (TG-MS, PyGC-MS and LDI-MS) suffer from difficult quantitation, although for different reasons. In TG-MS, selective volatilisation may not reflect the composition in the solid the quantitation problem of PyGC-MS requires assessment of the importance of matrix effects. Laser ablation methods cannot easily be calibrated. Quantitation is simplified in case of dual detection (MS for identification, FID for quantitation). A general drawback of many direct methods, which allow only small sampling volumes, is granule-to-granule variations. 

Morales, A. M. Lieber, C. M. 1998. A laser ablation method for the synthesis of crystalline semiconductor nanowires. Science 279 208-211. 

There are several sample introduction methods that are used in conjunction with ICP, including nebulization, electrothermal evaporation, gas chromatography, hydride generation, and laser ablation [30]. Laser ablation combined with ICP (LA-ICP) is useful for analysis of solids. In such a source the sample is positioned in a chamber prior to the ICP source, the ablation cell. Argon gas at atmosperic pressure flows through the cell towards the ICP source. The sample is irradiated by a laser beam and... 

Imanishi N, Matsumura T, Sumiya Y, Yoshimura K, Hirano A, Takeda Y et al. Impedance spectroscopy of perovskite air electrodes for SOFC preparated by laser ablation method. Solid State Ionics 2004 174 245-252. 

Smith II, R.D., Landis, G.P., Maroef, I., Olson, D.L., and Wildeman, T.R., The Determination of Hydrogen Distribution in High Strength Steel Weldments Part l Laser Ablation Methods , AWS, Welding Research Supplement, May, (2001), pp. 115-121. 

Rapid solidification and devitrification of amorphous metals and metallic glasses Combustion-flame chemical vapor condensation processes (Kear) Induction-heating chemical vapor condensation processes DC and RF magnetron sputtering, inclusive of the method of thermalization Laser ablation methods Supercritical fluid processing... 

The fabrication process of vanadium oxide (VO2) has also been studied using RBS/C. Since optieal and electrical properties of VO2 are dramatically changed at 68°C due to phase transition, VO2 is regarded as one of the candidates for thermally activated electronic or optical switching devices for optieal fibers or sensors. To obtain the desired properties, the development of the fabrication process for very thin films, without crystalline defects on various substrates, is required. Single-crystalline VO2 thin films on (0001) plane of a sapphire substrate have been synthesized by a laser ablation method. The quality of VO2 was examined by X-ray diffraction and RBS/C method. The eleetrieal resistanee and the optical transmittance of the VO2 film were measured under inereasing and deereasing temperatures. At a temperature of 68 °C, an abrupt transition of resistanee from metal to... 

A Co/Ni alloy is the next active catalyst among the binary combinations within the iron-group metals in the arc discharge method (51). Laser vaporization of metal/ carbon composite in argon atmosphere at high temperature (1200°C) can also produce SWNTs (41). Guo et al. (41) reported that the Co/Ni alloy was the most effectual, with a yield of 50-90% in the laser ablation method. 

The epitaxial YBa2Cu3C>7 x thin films were deposited by laser ablation method onto (100) surface of single crystal SrTi03. The sample showed a zero resistivity at 90 K in zero magnetic field. The film thickness and width were 400 nm and 7.53 pm, respectively. Electrodes of power measurement are in gold and deposited by in situ evaporation. The distance which... 

Although laser ablation methods have been used to fabricate large quantities of single-crystalline semiconducting nanowires with high aspect ratios, the wires obtained are randomly oriented with a variety of morphologies... 

But a wide application of such substances is hampered by their high costs of synthesis and purification. The most popular synthesis methods are the arc-discharge and laser-ablation method which have the disadvantage of either small fullerene yield or small quantity of the fullerene containing soot. Moreover it is necessary to use vacuum technique for maintaining of low pressure of helium for these methods. For the hydrocarbon combustion method it is necessary to use the additional expenses for fullerene purification [1-3], Thus, the search for improved methods of fullerene synthesis is of considerable importance. 

The sols are easy to prepare (see also Lee and Meisel, 1982) and the molecules whose SERS spectra are to be obtained are added to the sol in very small concentrations (10 ". ..10 mol/1). Recently a new method for preparing SERS active colloids has been pioneered by Neddersen et. al. (1993). By means of laser ablation of metals with a Nd YAG laser operating at 1064 nm, stable Ag, Au, Pt, Pd, and Cu colloids were directly prepared in water and organic solvents. An important advantage of this method over conventional chemical procedures is that the colloids are free of organic or ionic species. Consequently, the chemical and physical effects of ions or other adsorbates can be studied under carefully controlled conditions. The authors report that the SERS activity of colloidal metals prepared by this laser ablation method is comparable or even superior to that of chemically prepared colloids. 

In work not yet published the laser ablation method has also been applied to zeolites containing adsorbed species. It has been shown that the technique is able to generate molecular ions from strongly adsorbed species such as hexamethylbenzene in NaY, the tetrapropylammonium cation in as synthesized MFI zeolites, and polyethylene oligomers generated from ethylene in HZSM-5. 

In the application of atomic emission spectroscopy for quantitative analysis, samples must be prepared in liquid form of a suitable solvent unless it is already presented in that form. The exceptions are solids where samples can be analysed as received using rapid heating electro-thermal excitation sources, such as graphite furnace heating or laser ablation methods. Aqueous samples, e.g. domestic water, boiler water, natural spring, wines, beers and urines, can be analysed for toxic and non-toxic metals as received with... 

A block diagram of a typical ICP-MS instrument is shown in Figure 28-20. Ions formed in the plasma are introduced into the mass analyzer, where they are sorted according to mass-to-charge ratio and detected. Solution samples are introduced into the plasma through a nebulizer, as in ICP atomic emission. Solids are either dissolved in solution or introduced directly by laser ablation methods. Gases can be introduced directly. 

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