Energy Transfer Medium Research Articles

MICROWAVE INDUCED SYNTHESIS OF 2-SUBSTITUTEDPHENYL-3-(3-ALKYL/ARYL-5,6-DIHYDRO-S-TRIAZOLO) [2,4-B] [1,3,4] THIADIAZO 6-YL INDOLES AND 2-PHENYL-3 [2, SUBSTITUTED BENZOTHIAZOLE] DERIVATIVES AND THEIR FUNGICIDAL ACTIVITY

The title compounds were synthesised by condensation of 3-alykl/aryl-4-amino-5-mercaptotriazole (II) and 5-substituted 2-aminothiophenols (IV) with appropriate 2-phenyl-1H-indole-3-carboxaldehyde (I) under microwave irradiation in the presence of piperidine/p-toluenesulphonic acid using ethanol/DMF as energy transfer media. The considerable increase in reaction rate with improved yield has been observed, using microwave as compared to classical method.

Laser assisted particle removal ‘dry’ cleaning of critical surfaces

Laser assisted particle removal (LAPR) is a technique for removing minute particles from surfaces using an energy transfer medium condensed under and around the particles. The laser energy is absorbed in the energy transfer medium, either directly or via conduction from the substrate, explosively evaporating the condensed medium and propelling the particles off the substrate. The effect of the amount of energy transfer medium, water in this case, has been studied and a technique developed for monitoring the condensation and amount of water condensed on the substrate.

Graphite/Liquid Mixed Matrices for Laser Desorption/Ionization Mass Spectrometry

A combination of liquid matrix and graphite particulates (2 μm) has been proposed as a method suitable for the laser desorption/ionization mass spectrometry of peptides and proteins (Sunner, J.; et al. Anal. Chem. 1995, 67, 4335). Here we demonstrate the potential of this approach as a straightforward, and very general, method of achieving the ultraviolet laser desorption/ionization of a broad range of intermediate weight analytes. The desorption/ionization mechanism, the influence of preparative procedures, and the breadth of application of this methodology have been investigated. A simple and robust preparative procedure is presented for the analysis of proteins, oligosaccharides, and synthetic polymers. Detection sensitivities are in the femtomole region for lower molecular weight peptides and oligosaccharides. The graphite acts as an energy transfer medium by absorbing the UV radiation, leading to thermal desorption of the liquid matrix and analyte. The liquid matrix was observed to fulfill several important roles. In the case of peptides and proteins, which preferentially form protonated molecular ions, it acts as a protonating agent. It also enhances the signal intensities of cationized species (e.g., polysaccharides and polar polymers) by assisting their desorption. An excess of liquid matrix serves to cool the analyte during the desorption step and minimize decomposition. The presence of liquid matrices increases the sample lifetime at a particular desorption spot, minimizing the time-consuming search for "hot spots". The addition of cationizing salts has been shown to improve the quality of mass spectra obtained for polar polymers and extend the range of materials that can be investigated to include apolar synthetic polymers.

Shock wave analysis of laser assisted particle removal

Laser assisted particle removal (LAPR) is an innovative laser cleaning technique which can remove various particles from solid surfaces via laser induced explosive evaporation of a chosen energy transfer medium, e.g., water. An Ar+ ion continuous-wave laser (488 nm) was used to study the CO2 laser pumped explosive evaporation of water adsorbed on a Si substrate. The probe laser beam was parallel to the sample surface at different displacements and interacted with the ejected material upon pulsed CO2 laser irradiation in analogy with the time resolved laser beam deflection experiments on laser induced vaporization of copper by Guo et al. [Opt. Commun. 77, 381 (1990)]. Using CO2 laser energies which are much greater than the LAPR thresholds, we observed the generation and propagation of a shock wave at supersonic speeds followed by a water vapor/aerosol/particle cloud at a much slower speed. From the evolution of the shock wave, the total conversion efficiency of the incident laser beam into the shock wave has been determined using a self-similar approximation.

Laser-assisted particle removal from silicon surfaces

Abstract Laser-assisted particle removal (LAPR) is a new technique capable of removing micron and submicron scale particles from solid surfaces. In LAPR, the contaminated substrates are dosed with water vapor or other condensible gases as an energy transfer medium which preferentially adsorbs in the capillary spaces under and around the particles. The dosed substrate is then irradiated with a pulsed laser causing explosive evaporation of the energy transfer medium and propelling the particles off the substrate surface. In our experiments, LAPR was used to remove 9.5 μm Al 2 O 3 , 5 μm Al 2 O 3 , 1 μm Al 2 O 3 , and 1 μm polystyrene (PS) particles from Si substrates. Removal threshold measurements were obtained using a TEA CO 2 laser (TEM 00 mode) at wavelengths of 9.6 μm and 10.6 μm. The temperature rise in the energy transfer medium, water, was estimated at the LAPR threshold. The results suggest that superheating of the water droplet is a reasonable mechanism for LAPR. Reflection and scattering for a cw Ar + laser parallel to the substrate surface at various displacements indicated the presence of a shock wave, water vapor and ejected particles. These results are similar to time-resolved measurements of polymer ablation in which shock wave generation, propagation away from the surface at supersonic speeds and ablated particulate materials travelling at slower speeds were observed. To determine the conversion efficiency and the threshold of the shock wave, we used a self-similar approximation. The results show that we can remove particles from the surface at laser fluences significantly below the shock wave threshold.

CO2 laser assisted particle removal threshold measurements

Laser removal of particulates from solid surfaces was achieved using an energy transfer medium which preferentially adsorbs in the capillary spaces under and around the particulates on the contaminated surface. Subsequent laser irradiation causes explosive evaporation of the energy transfer medium and propels the particles off the substrate much like a small rocket engine. In our experiments, a TEA CO2 (10.6 and 9.6 μm) laser was used to remove 9.5 μm Al2O3, 5 μm Al2O3, and 1 μm polystyrene particles from Si surfaces using water as the energy transfer medium. At these wavelengths the laser energy is absorbed predominantly in the water not in the substrate. The threshold fluence for particle removal was found to follow a degenerate threshold model with measured thresholds significantly below the substrate damage threshold. The temperature rise in the energy transfer medium was estimated using energy conservation, suggesting that superheating of the adsorbed water is a reasonable mechanism for water assisted laser particle removal.

Energy requirements for the dissociative adsorption of hydrogen on Cu(110)

The activation energy for the dissociative adsorption of H2 on Cu(110) is determined to be 14.3±1.4 kcal/mol (95% confidence limit). This value represents a true Arrhenius activation energy from Boltzmann distributions of impinging H2 gas at ∼623 K. The results were obtained by titrating atomic oxygen from a Cu(110) surface under conditions where the rate of titration was equal to the rate of dissociative hydrogen adsorption and where the oxygen coverage did not affect the rate. The hot copper surface was exposed to ∼10−4 Torr H2 in a microreactor whose walls were at 300 K. The degree to which the H2 translational, rotational, and vibrational populations approach the surface temperature was controlled by adding N2 as an energy transfer medium. The dissociative adsorption probability at 623 K increased from ∼5×10−7 to ∼10−5 when the N2 pressure was increased from 0 to ∼80 Torr. About 70% of this increase occurred below 2 Torr. Known gas‐phase energy transfer rates suggest that the translational temperature of H2 hitting the Cu surface was already at the surface temperature after addition of only 2 Torr N2, but that the v=1 vibrational population was still unchanged. It approached the population of the surface temperature only at 80–300 Torr N2. These results together with beam experiments suggest either translational or vibrational energy can dominate in overcoming the activation barrier to dissociation of an H2 molecule.

Molten Salt Electric Experiment at CRTF

A joint effort between the Department of Energy and private industry through the Electric Power Research Institute combined various subsystems at the Central Receiver Test Facility (CRTF) in Albuquerque, NM, with a steam generator and a turbine/generator to produce electric power. This effort demonstrates the feasibility of using molten salt as the primary medium for energy transfer from a central tower solar receiver through thermal storage to a steam generator. A conventional steam turbine converts the energy by means of the electric generator for delivery of electrical power to the utility grid. The Molten Salt Electric Experiment (MSEE) uses a 5 megawatt thermal (5MWt) solar receiver, which was successfully tested in 1980, to produce 566 °C (1,050 °F) liquid sodium nitrate‐potassium nitrate (60/40) from a 310 °C (590 °F) feed supply at the rate of 43,900 kg/h (97,000 lbs/hr). (MWt=electrical equivalent of Btu/hr of thermal energy absorbed by a soiar receiver.) The hot molten salt then flows into a sto...

Protective coatings for alloys in contact with molten drawsalt (NaNO3-KNO3)

Molten drawsalt (NaNO 3-KNO3) is being considered as the energy transfer and storage medium for many solar central receiver applications. In an effort to reduce the cost of the containment material while maintaining corrosion resistance, alloys with aluminide coatings have been examined while in contact with molten drawsalt for more than 6000 hours at 600 °C. The alloys examined were 2.25 Cr-1 Mo, 5 Cr-0.5 Mo, and 9 Cr-1 Mo low-alloy steels, and 316 stainless steel. The results show a steady, albeit slow, net weight loss over the course of the experiment. The weight loss has been attributed to spoiling of Al2O3 from the surface (the occurrence of Al 2O3 is a result of the aluminizing process) and dissolution of corrosion products NaAlO2 and/or NaFeO2 during post-immersion handling. Scanning electron micrographs of exposed surfaces revealed little or no corrosion of the base metal. It has been concluded that aluminide coated alloys could provide significant cost savings (~50 pct) relative to INCOLOY Alloy 800, and provide at least equivalent corrosion resistance.

Kinetics of physical processes in an oxygen-iodine medium

An investigation is made of the kinetics of physical processes in an oxygen-iodine medium used as the active medium for fast near-resonant energy transfer from the α1Δg oxygen metastable state to the I(52P1/2) metastable state of atomic iodine. A gasdynamic method of cooling is proposed to reduce the harmful influence of heating of the mixture as a result of exothermic reactions. Existing experimental data on the reaction constants are used to determine the main parameters of the mixture and it is shown that high gains and high stored energies can be achieved. Methods of improving the efficiency are discussed.

An all-purpose fluid for filling sonar transducers

A fluid suitable for use in all liquid-filled transducers has long been needed. Historically, castor oil has been the most satisfactory; however, it will no longer meet all requirements. Substitute fluids have been used in special cases, but these have serious limitations even under the best of conditions. Studies have been made on silicone fluids and polyglycols as well as castor oil to determine their eligibility as a sound energy transfer medium in sonar transducers. Acceptability criteria covering acoustical, chemical, physical, and environmental properties are discussed. A modified polyalkylene glycol has been found to possess compatible features with transducer materials and to meet the criteria for a fluid to use in all sonar transducers.

Radiolysls In the adsorbed state. III. Methyl iodide adsorbed on silica gel

The 60Co γ-radiolysis of methyl iodide adsorbed on silica gel has been studied by examining the hydrocarbon products, which are mainly methane and ethane. These products are formed in large yields, indicating that a large fraction of the energy absorbed in the silica gel is able to cause decomposition of the methyl iodide. The “energy transfer” is thought to occur by electron or excitation transfer to the methyl iodide, leading to the production of methyl radicals.Evidence has been obtained that the silica gel takes part in the system as a chemical reactant as well as being an energy transfer medium, and that changing the nature of the surface changes the course of the reaction. This is most clearly shown in two ways. The ratio of methane to ethane decreases as the surface hydroxyl concentration decreases, and it is concluded that excited methyl radicals form methane by abstraction of hydrogen from surface hydroxyls. Experiments using methyl iodide-d3 adsorbed on protiated silica gel confirm the participation of hydrogen from the silica gel, as the methane is over 85% CD3H, while the ethane is over 95% C2D6.The effect of additives such as N2O and SF6, which are known to be electron scavengers, was also studied. It was shown that methyl iodide is a much better electron scavenger than N2O and is as good an electron scavenger as SF6 in this system.

Microwave-Assisted Solvent Free Synthesis of Spiro-Indole Derivative

A solid supported synthetic procedure has been developed for the synthesis of novel spiro indole derivatives using solid support as energy transfer medium under microwave irradiation (MWI). The results were compared with those obtained by the classical as well as solution phase method in MWI. This solvent-free technique coupled with the high yields and short reaction time makes this procedure eco-friendly for synthesis. Keywords: Spiro indoles; Microwave irradiation; 1HNMR; IRDOI: 10.3126/jncs.v24i0.2391 Journal of Nepal Chemical Society Vol. 24, 2009 Page: 49-52