Evaporation Of Material Research Articles

Anomalous behavior of optical density of iron nanoparticles heated behind shock waves

Nonmonotonous variation of the optical properties of iron nanoparticles with a temperature increase during heating behind reflected shock waves is discovered. Iron nanoparticles, within 12 nm in size, were formed at 0.5–1% Fe(CO)5 pyrolysis in argon behind the incident shock waves. Using a laser extinction method, a variation of the volume fraction of the condensed phase was registered at the main wavelength of 633 nm and, in several experiments, at the additional wavelengths of 405, 520, and 850 nm. At the second heating of the produced nanoparticles behind the reflected shock waves within the temperature range 800–1500 K, the function of the complex refractive index, E(m), decreased at all the wavelengths. Within the temperature range of 1500–2250 K, it increased with the temperature increase behind the reflected shock wave almost up to the values that we observed behind the incident shock wave. At the temperatures above 2250 K, due to the essential evaporation of the iron nanoparticle material, the optical properties were not measured. The iron nanoparticle E(m) variations within the temperature range 800–2250 K are possibly related to their structure variations.

Thermal and chemical evolution in the early Solar System as recorded by FUN CAIs: Part II – Laboratory evaporation of potential CMS-1 precursor material

We present the results of laboratory experiments in which a forsterite-rich melt estimated to be a potential precursor of Allende CMS-1 FUN CAI was evaporated into vacuum for different lengths of time at 1900°C. The evaporation of this melt resulted in residues that define trajectories in chemical as well as magnesium, silicon and oxygen isotopic composition space and come very close to the measured properties of CMS-1. The isotopic composition of the evaporation residues was also used to determine the kinetic isotopic fractionation factors [α2,1 (vapor-melt) defined as the ratio of isotopes 2 and 1 of a given element in the evaporating gas divided by their ratio in the evaporating source] for evaporation of magnesium (α25,24 for 25Mg/24Mg), silicon (α29,28 for 29Si/28Si) and oxygen (α18,16 for 18O/16O) from the forsterite-rich melt at 1900°C. The values of α25,24=0.98383±0.00033 and α29,28=0.99010±0.00038 are essentially independent of change in the melt composition as evaporation proceeds. In contrast, α18,16 changes from 0.9815±0.0016 to ∼0.9911 when the residual melt composition changes from forsteritic to melilitic. Using the determined values of α25,24 and α29,28 and present-day bulk chemical composition of the CMS-1, the composition of the precursor of the inclusion was estimated to be close to the clinopyroxene+spinel+forsterite assemblage condensed from a solar composition gas. The correspondence between the chemical composition and isotopic fractionation of experimental evaporation residues and the present-day bulk chemical and isotopic compositions of CMS-1 is evidence that evaporation played a major role in the chemical evolution of CMS-1.

Near-Atomic Three-Dimensional Mapping for Site-Specific Chemistry of 'Superbugs'.

Emergence of multidrug resistant Gram-negative bacteria has caused a global health crisis and last-line class of antibiotics such as polymyxins are increasingly used. The chemical composition at the cell surface plays a key role in antibiotic resistance. Unlike imaging the cellular ultrastructure with well-developed electron microscopy, the acquisition of a high-resolution chemical map of the bacterial surface still remains a technological challenge. In this study, we developed an atom probe tomography (APT) analysis approach to acquire mass spectra in the pulsed-voltage mode and reconstructed the 3D chemical distribution of atoms and molecules in the subcellular domain at the near-atomic scale. Using focused ion beam (FIB) milling together with micromanipulation, site-specific samples were retrieved from a single cell of Acinetobacter baumannii prepared as needle-shaped tips with end radii less than 60 nm, followed by a nanoscale coating of silver in the order of 10 nm. The significantly elevated conductivity provided by the metallic coating enabled successful and routine field evaporation of the biological material, with all the benefits of pulsed-voltage APT. In parallel with conventional cryo-TEM imaging, our novel approach was applied to investigate polymyxin-susceptible and -resistant strains of A. baumannii after treatment of polymyxin B. Acquired atom probe mass spectra from the cell envelope revealed characteristic fragments of phosphocholine from the polymyxin-susceptible strain, but limited signals from this molecule were detected in the polymyxin-resistant strain. This study promises unprecedented capacity for 3D nanoscale imaging and chemical mapping of bacterial cells at the ultimate 3D spatial resolution using APT.

Synthesis of Cu nanoparticles by condensation from the gas phase

ABSTRACTA series of computer experiments was conducted by the raw material evaporation and subsequent condensation to determine the most efficient regimes of copper nanoparticles synthesis. By variation of the cooling rate of the metal vapor the formation of Cu clusters were studied. The computer experiments showed the influence of different final temperatures on the shape of the resultant particles. This allowed to determine the conditions for a predominant formation of worm-like clusters of a spherical shape in the gas phase synthesis.

Revealing the Location of the Mixing Layer in a Hot Bubble

AbstractThe fast stellar winds can blow bubbles in the circumstellar material ejected from previous phases of stellar evolution. These are found at different scales, from planetary nebulae (PNe) around stars evolving to the white dwarf stage, to Wolf-Rayet (WR) bubbles and up to large-scale bubbles around massive star clusters. In all cases, the fast stellar wind is shock-heated and a hot bubble is produced. Processes of mass evaporation and mixing of nebular material and heat conduction occurring at the mixing layer between the hot bubble and the optical nebula are key to determine the thermal structure of these bubbles and their evolution. In this contribution we review our current understanding of the X-ray observations of hot bubbles in PNe and present the first spatially-resolved study of a mixing layer in a PN.

Nanoscale photoconductive switching effect applied to atom probe tomography

By combining a laser pulse and a high-voltage (HV) pulse on the same sample, field evaporation of materials with poor electrical conductivity using ultra-short HV pulses is reported. Using a pump-probe setup, the shape of HV pulses experienced by surface atoms of the sample apex is experimentally observed. These results are in good agreement with classical models considering the temperature and free carriers produced by a laser pulse giving rise to local photoconduction.

Nanoparticle growth by collection of ions: orbital motion limited theory and collision-enhanced collection

The growth of nanoparticles in plasma is modeled for situations where the growth is mainly due to the collection of ions of the growth material. The model is based on the classical orbit motion limited (OML) theory with the addition of a collision-enhanced collection (CEC) of ions. The limits for this type of model are assessed with respect to three processes that are not included: evaporation of the growth material, electron field emission, and thermionic emission of electrons. It is found that both evaporation and thermionic emission can be disregarded below a temperature that depends on the nanoparticle material and on the plasma parameters; for copper in our high-density plasma this limit is about K. Electron field emission can be disregarded above a critical nanoparticle radius, in our case around nm. The model is benchmarked, with good agreement, to the growth of copper nanoparticles from a radius of nm– nm in a pulsed power hollow cathode discharge. Ion collection by collisions contributes with approximately 10% of the total current to particle growth, in spite of the fact that the collision mean free path is four orders of magnitude longer than the nanoparticle radius.

Real-Time Monitoring of DNA Amplification By Nanogap Ipedimetric Sensor

As our global society has been more complex and connected closely, infectious diseases could be easily and fast propagated to everywhere. And it makes early diagnostic detection be necessary with various ways based on optical, electrical and electrochemical methods. Real-time PCR (Polymerase Chain Reaction) has been powerful detection technology to recognize the amplified target DNA fragments that would be essential to diagnostic assays, but it needs optical labels and apparatus to detect the amplification of DNA. A variety of electric/electrochemical methods have been applied for label-free detection. Impedance assay is attractive tool for biomolecule real-time sensing, however, most of impedance studies are based on the immobilization of biomolecules on the electrode surface. That ascribes to additional steps and makes impossible to reuse electrode chip and biological samples. In this study, we aimed to develop the electrical impedance detection not optical method measuring the bulk impedance of PCR product solution by nanogap electrode. Electrical impedimetric nanogap devices could be very useful for detecting slight changes of amplifying DNA fragments in PCR cycling due to double layer capacitance and charge transfer resistance between two opposing nanogap electrodes. The electrode chip was fabricated using gold thin film by easy photolithography designed the nanogapped Si/SiO2 substrate by evaporation of oxide materials. Applying electric impedance measuring in nanogap chip avoiding the use of optical labels and immobilization on the electrode surface would be very impact detection system on DNA real-time screening.

Non-volatile aluminum oxide resistive memory devices on a wrapping paper substrate

We fabricated non-volatile resistive memory devices on a commercially available flexible paper substrate using physical vapor deposition methods in all of the fabrication steps. By using only evaporable component materials including aluminum oxide (Al2O3) and metal electrodes, it has become possible to constitute the vertical stacking Al2O3 active layer structure with metal electrodes in the memory devices without wet or crumpled damage on the paper substrate. The memory devices showed the typical unipolar switching characteristic with excellent electrical performances of low operating threshold voltage (∼3.2 V), high ON/OFF ratio (∼104), good reproducibility (∼500 endurance cycles), and stability (∼104 s of retention times). The outstanding flexibility of the paper substrate has made it possible to stably maintain the electrical properties of the memory devices both in flat and bent configurations (radius of 5 and 1 mm) without any serious degradation.

Lifetime experimental study of graphite cathode for relativistic backward wave oscillator

Graphite cathodes are widely used due to their good emission properties, especially their long lifetime. Some previous papers have researched their lifetime under certain conditions and uncovered some important phenomena. This paper is dedicated to research the lifetime of the graphite cathode under higher power. In the lifetime test, the voltage and current amplitudes are about 970 kV and 9.7 kA, respectively. The repetition rate is 20 Hz. An X-band relativistic backward wave oscillator is used to generate high power microwave by utilizing the electron beam energy. The experimental results demonstrate that the emission property of the graphite cathode remains quite stable during 105 pulses, despite some slight deteriorations regarding the beam and microwave parameters. The macroscopic morphology change of the cathode blade due to material evaporation is observed by a laser microscope. The mass loss of the graphite cathode is about 60 μg/C. Meanwhile, the observation by a scanning electron microscope unco...

Calculation of output power and X-ray spectrum of Z-pinches based on multiwire arrays

We present mathematical models and methods of the computational experiment using a three-dimensional RMHD model simulating the implosion of Z-pinches formed by an imploding cylindrical array of thin tungsten wires. The calculations take into account the discrete structure of the array and the extended plasma formation at the evaporation of the wire material and they yield the estimated values of the output power and X-ray spectrum. The data are presented on the spatio-temporal distribution in the parameters of the Z-pinch plasma, including the velocity, electron and ion temperatures, ionization degree, and the power output integrated over space. We have also calculated the characteristics of the Z- pinch X-ray spectrum depending on the photon energy at different times after the discharge current starts. It has been found that the trailing mass of tungsten on the periphery affects the emission intensity of the central part of the pinch in the radial direction, which can be explained by the emission absorption in the peripheral plasma layers of the trailing tungsten mass. A detailed model has been constructed of the central pinch formed by the electric current implosion of the material of multiwire tungsten arrays. This model enables one to calculate the intensity of the soft X-ray emission with a temporal, spatial, angular, and spectral resolution for specific experiments on the Angara-5-1 experimental complex intended to study the implosion of cylindrical multiwire arrays, for which there is sufficient information about the time profile of the absolute emission intensity in the low-energy range of the X-ray emission. The obtained numerical results can be directly compared with the experimental values. The RMHD model simulating the implosion of Z-pinches has been verified by comparing its results with the experimental implosion indicators.

TRANSITION REGION ABUNDANCE MEASUREMENTS DURING IMPULSIVE HEATING EVENTS

ABSTRACT It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona, low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper we report on measurements of plasma composition made during impulsive heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O iv, v, and vi emission lines are enhanced relative to emission lines from Mg v, vi, and vii and Si vi and vii, and indicate a composition close to that of the photosphere. Long-lived coronal fan structures, in contrast, show an enrichment of low-FIP elements. We conjecture that the plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from the lower layers of the solar atmosphere and higher-frequency heating leading to long-lived structures and the accumulation of low-FIP elements in the corona.

Core-Shell Composite Hydrogels for Controlled Nanocrystal Formation and Release of Hydrophobic Active Pharmaceutical Ingredients.

Although roughly 40% of pharmaceuticals being developed are poorly water soluble, this class of drugs lacks a formulation strategy capable of producing high loads, fast dissolution kinetics, and low energy input. In this work, a novel bottom-up approach is developed for producing and formulating nanocrystals of poorly water-soluble active pharmaceutical ingredients (APIs) using core-shell composite hydrogel beads. Organic phase nanoemulsion droplets stabilized by polyvinyl alcohol (PVA) and containing a model hydrophobic API (fenofibrate) are embedded in the alginate hydrogel matrix and subsequently act as crystallization reactors. Controlled evaporation of this composite material produces core-shell structured alginate-PVA hydrogels with drug nanocrystals (500-650 nm) embedded within the core. Adjustable loading of API nanocrystals up to 83% by weight is achieved with dissolution (of 80% of the drug) occurring in as little as 30 min. A quantitative model is also developed and experimentally validated that the drug release patterns of the fenofibrate nanocrystals can be modulated by controlling the thickness of the PVA shell and drug loading. Thus, these composite materials offer a "designer" drug delivery system. Overall, our approach enables a novel means of simultaneous controlled crystallization and formulation of hydrophobic drugs that circumvents energy intensive top-down processes in traditional manufacturing.

Modelagem matemática dos perfis de temperatura do gás, do sólido e da parede do forno e dos perfis de concentração das principais espécies químicas presentes no interior do forno rotativo empregado na produção de clínquer

Resumo O cimento é um dos materiais de construção mais utilizados no mundo, sendo o tipo mais comum conhecido como cimento Portland. O processo de fabricação do cimento envolve numerosas e complexas reações endotérmicas e exotérmicas que ocorrem a diferentes temperaturas, o que o torna não trivial. Dessa forma, há um grande interesse na otimização do processo de produção de cimento. A clinquerização é uma das principais etapas da fabricação de cimento e ocorre dentro de forno rotativo. Neste estudo, o processo de produção de clínquer é analisado em um forno rotativo de via seca que atua em contracorrente. Os principais fenômenos envolvidos na obtenção do clínquer são: evaporação da água livre residual da matéria-prima; decomposição do carbonato de magnésio; descarbonatação; formação da fase líquida composta por C3A e C4AF; formação do silicato dicálcico e silicato tricálcico. O principal objetivo deste estudo é a proposta de um modelo matemático que descreve de forma realística o perfil de temperatura e de concentração dos componentes do clínquer ao longo do forno rotativo, desenvolvido a partir de mudanças propostas a um trabalho da literatura. O modelo, composto por equações diferenciais parciais, foi adaptado e implementado em linguagem computacional no programa Mathcad. O modelo proposto foi satisfatório para a descrição do perfil de temperatura e concentração dos componentes do clínquer ao longo de um forno rotativo.

Evaluation of Radiation Consequences of Releases in Accidents with Spills of Liquid Radioactive Materials in Areas with Forced Ventilation

This report focuses on assessment of radiation consequences of releases in accidents with spills of liquid radioactive materials in areas with forced ventilation. During the study, characteristic dependences between parameters of liquid radioactive materials and air exchange in areas with forced ventilation and associated radiation consequences were determined. The proposed approach is based on the theory of non-stationary heat and mass transfer in surface evaporation of liquid heated below the boiling temperature. The physical model includes: liquid radioactive material, steam-aerosol radioactive mixture, air of forced ventilation, airborne filters, and floor of the emergency area. The key aspects of the model are evaporation of liquid material, its removal with exhaust ventilation and partial trapping on airborne filters. It is considered that the steam-aerosol radioactive mixture is released to the environment after filters. The advantage of this model is the possibility to determine integral release of radionuclides to the environment and activity concentration of air in the emergency area at any moment after beginning of the accident, effective dose received by an adult during 14 days for a wide range of input thermodynamic and geometrical parameters, different operating modes of the ventilation system and different productivities of the filtering system. Results from assessment of radiation consequences for the selected accident are presented and the associated effect of filtering systems is analyzed.

Metasurfaces: Continuous-Gradient Plasmonic Nanostructures Fabricated by Evaporation on a Partially Exposed Rotating Substrate (Adv. Mater. 23/2016).

A continuous-gradient approach of material evaporation is employed by L. Shao, M. Käll, and co-workers to fabricate nanostructures with varying geometric parameters such as thickness, lateral positioning, and orientation on a single substrate. This method for mask lithography, described on page 4658, allows continuous tuning of the physical properties of a sample. The technique is highly valuable in simplifying the overall optimization process for constructing metasurfaces.

Laser Welding of Glass Replaces Glueing Procedure

AbstractGlass welding with femtosecond lasers is now ready for industrial practice. Clever heat management prevents tension and cracks occurring in the material. Laser welding supersedes earlier joining methods such as glueing as well as offering a number of advantages: no additional materials are necessary, no evaporation and embrittlement of materials, and greater durability. Laser welded glass protective caps for laser light cables are one demonstration of it. Furthermore, glass welding by laser opens up new design options.

Experimental investigation of heat transfer in a rivulet on the inclined foil

Heat transfer at rivulet water flow over the constantan foil with the length of 80 mm, width of 35 mm, and thickness of 25 mm was studied experimentally. The foil surface temperature was measured by an IR-scanner. Distributions of heat flux density on the surface of the foil, where the liquid flowed, were obtained. To determine the heat flux density from the foil to liquid near the contact line, the Cauchy problem was solved for the stationary heat equation using the thermographic data. Calculation results showed that the maximal heat flux occurs in the area of the contact line and exceeds the average heat flux from the entire foil surface by several times. This is explained by the influx of heat from the periphery of foil to the rivulet due to the relatively high value of heat conductivity coefficient of the foil material and high evaporation rate in the region of the contact line.

Schottky Diode Applications of the Fast Green FCF Organic Material and the Analyze of Solar Cell Characteristics

In this study, a device applications of organic material Fast Green FCF (C37H34N2Na2O10S3Na2) has been investigated. After chemical cleaning process of boron doped H-Si crystals, Al metal was coated on the one surface of crystals by thermal evaporation and fast green organic materials were coated on other surface of crystals with spin coating method (coating parameters; 800 rpm for 60 s). Finally, Ni metal was coated on Fast Green by sputtering and we obtained the Ni/Fast Green FCF/n-Si/Al Schottky type diode. And then we calculated the basic diode parameters of device with current-voltage (I-V) and capacitance- voltage (C-V) measurements at the room temperature. We calculated the ideality factory (n), barrier height (Φb) of rectifing contact from I-V measurements using thermionic emission methods. Furthermore, we calculated ideality factory (n), barrier height (Φb) and series resistance (Rs) of device using Cheung and Norde functions too. The diffusion potential, barrier height, Fermi energy level and donor concentration have been determined from the linear 1/C2-V curves at reverse bias, at room temperature and various frequencies. Besides we measured the current-voltage (I-V) at under light and analyzed the characteristics of the solar cell device.

Continuous-Gradient Plasmonic Nanostructures Fabricated by Evaporation on a Partially Exposed Rotating Substrate.

A continuous-gradient approach of material evaporation is employed to fabricate nanostructures with varying geometric parameters, such as thickness, lateral positioning, and orientation on a single substrate. The method developed for mask lithography allows continuous tuning of the physical properties of a sample. The technique is highly valuable in simplifying the overall optimization process for constructing metasurfaces.