Non-metallic Samples Research Articles

Modulate the laser phase to improve the ns-LIBS spectrum signal based on orbital angular momentum.

Aiming to enhance the ns-LIBS signal, in this work, we introduced orbital angular momentum to modulate the laser phase of the Gaussian beam into the vortex beam. Under similar incident laser energy, the vortex beam promoted more uniform ablation and more ablation mass compared to the Gaussian beam, leading to elevated temperature and electron density in the laser-induced plasma. Consequently, the intensity of the ns-LIBS signal was improved. The enhancement effects based on the laser phase modulation were investigated on both metallic and non-metallic samples. The results showed that laser phase modulation resulted in a maximum 1.26-times increase in the peak intensities and a maximum 1.25-times increase in the signal-to-background ratio (SBR) of the Cu spectral lines of pure copper for a laser energy of 10 mJ. The peak intensities of Si atomic spectral lines were enhanced by 1.58-1.94 times using the vortex beam. Throughout the plasma evolution process, the plasma induced by the vortex beam exhibited prolonged duration and a longer continuous background, accompanied by a noticeable reduction in the relative standard deviation (RSD). The experimental results demonstrated that modulation the laser phase based on orbital angular momentum is a promising approach to enhancing the ns-LIBS signal.

Tracking interface position of a high-speed imploding composite liner based on magnetic diffusion difference

A technique for tracking the interface position of non-metal–metal composite liners during high-speed implosion is proposed in this paper. Based on the magnetic diffusion difference between metal and non-metal, the interface position information is obtained by measuring magnetic fields in the cavity of the liner. An efficient magnetic flux estimation algorithm based on iterative magnetic diffusion simulation is also proposed to estimate the magnetic flux loss of the liner. Numerical experiments show that the estimation algorithm can reduce the relative error to less than 0.5%. The composite solid liner experimental results show that the maximum error is about 2% under imperfect experimental conditions. Detailed analysis suggests that this method can be widely applied to non-metallic sample materials (electrical conductivity is less than 103 ∼ 104 S/m). The technique provides a useful supplement to the existing interface diagnosis methods for high-speed implosion liners.

Lattice effects on the physical properties of half-doped perovskite ruthenates

We investigate the unusual phase transitions in SrRuO3 and Sr0.5Ca0.5RuCr x O3 (x = 0, 0.05 and 0.1) employing x-ray diffraction, resistivity, magnetic studies and x-ray photoemission spectroscopy. Our results show the compounds undergo a crossover from itinerant ferromagnetism to localized ferromagnetism. The combined studies suggest Ru and Cr be in the 4+ valence state. A Griffith phase and an enhancement in Curie temperature (T c ) from 38 K to 107 K are observed with Cr doping. A shift in the chemical potential towards the valence band is observed with Cr doping. In the metallic samples, interestingly, a direct link between the resistivity and orthorhombic strain is observed. We also observe a connection between orthorhombic strain and T c in all the samples. Detailed studies in this direction will be helpful to choose suitable substrate materials for thin-film/device fabrication and hence manoeuvre its properties. In the non-metallic samples, the resistivity is mainly governed due to disorder, electron-electron correlation effects and a reduction in the number of electrons at the Fermi level. The value of the resistivity for the 5% Cr doped sample suggests semi-metallic behaviour. Understanding its nature in detail using electron spectroscopic techniques could unravel the possibility of its utility in high-mobility transistors at room temperature and its combined property with ferromagnetism will be helpful in making spintronic devices.

Development of a sample cell for Radio Frequency µSR studies of metal nanoparticle systems with surface-adsorbed reactants in mesoporous hosts

We have recently begun an investigation of paramagnetic (free-radical) final states formed on metal nanoparticles by muonium (Mu) reactivity with surface-adsorbed molecules. The nanoparticles are incorporated into mesoporous silica, facilitating specific reaction steps in the silica host that involve H-atom transfer reactions important to studies in heterogeneous catalysis. Radio frequency (RF) methods are an essential tool for characterising final state species in these systems, and a non-metallic sample cell is essential for the RF field to penetrate the sample. Unfortunately, several significant problems were encountered during initial experiments using a cell made from PEEK polymer, the most serious being a temporal instability in the signals likely due to reactant molecules adsorbing on the PEEK. This paper discusses the problems encountered using the PEEK cell, and then considers the development of a ceramic cell designed to give better reproducibility in the measurements. The success of this new cell is demonstrated both through off-line tests and by muon measurements, including a series of TF 2G Mu spin precession measurements verifying the temporal stability of the experimental setup. Finally, an RF cavity was fashioned, and RF measurements made for muons stopped in bare silica, with signals from both diamagnetic and paramagnetic muon states clearly seen.

High-P–T impedance measurements using a laser-heated diamond anvil cell

The electrical conductivity (EC) of minerals found on Earth and throughout the solar system is a fundamental transport property that is used to understand various dynamical phenomena in planetary interiors. High-pressure and high-temperature (P-T) EC measurements are also an important tool for observing phase transitions. Impedance measurements can accurately measure the EC of a nonmetallic sample. In previous measurements under static conditions using a laser-heated diamond-anvil cell (LHDAC), only direct current resistance is measured, but this method overestimates the bulk sample resistance. Moreover, the previous methodology could only be applied to nontransparent samples in an LHDAC using infrared lasers, limiting the range of measurable composition. To the best of our knowledge, no in situ high-P-T EC measurements of transparent materials have been reported using LHDAC techniques. We developed a novel impedance measurement technique under high-P-T conditions in an LHDAC that applies to transparent samples. As a validation, we measured the EC of Mg0.9Fe0.1SiO3 bridgmanite up to 51GPa and 2000K and found that the results are consistent with those of previous studies. We also measured the EC values of sodium chloride to compare with those of previous studies, as well as those of cubic boron nitride and zirconia cement to quantify how well they insulate under high P-T conditions. This is the first report of the impedance and EC measurements of transparent minerals in an LHDAC, which allows the measurement of Fe-poor/-free materials, including the major constituents of the interiors of gas giants and icy planets, under extreme conditions.

Nonmetallic power-law behavior of conductance in Ni-doped NbSe3 nanowires

We report on diverse transport properties observed in NbSe3 nanowires of dilute Ni concentrations, where the resistance of some nanowires retains metallic behavior with regions of negative absolute resistance and switching transition showing up in current-voltage curve at sufficiently low temperatures, while others demonstrate metal-insulator transitions below the first charge density wave (CDW) transition. The temperature and voltage dependence of the resistance for the nonmetallic samples are governed by power laws; however, the anomalous features of the CDW transitions still retain. The observed transport behaviors are apparently due to the variation of potential along the conducting channel caused by different kinds of nonuniformities. A phenomenological model with one-dimensional phase slippage occurring in the certain segment of the nanowire, where Friedel oscillations-enhanced local CDW domains cluster altogether over the whole cross section, is presented as the possible mechanism for the nonmetallic power-law behavior. Our work sheds new light on the possible origin of nonmetallic power-law behavior in NbSe3, which has been under debate for a long time.

Molecular emission dynamics from a femtosecond filament induced plasma plume

In this study, we investigated the filament-induced plasma properties and the associated molecular emission features from three different non-metallic samples. Graphite, polymethyl methacrylate, and Teflon samples have been ablated using a tightly focused filament, and their emission spectra were analyzed using a time-integrated optical emission spectroscopy technique. The temporal responses and evolution dynamics of molecular species such as CN and C2 from these samples in ambient conditions are compared. The tightly focused filament was generated by focusing the Ti:Sapphire femtosecond pulses having a pulse duration of 29 fs using a short focal length external focusing system. The time-integrated intensified charge-coupled device images of air filament show that the filament survives up to a few nanosecond time duration after the onset of air plasma. The influence of physical and chemical properties of the samples during filament ablation has also been studied by characterizing the optical emission spectra. We find that the molecular signal intensity strongly depends on the sample properties and the position of the sample in the filament. The increase in molecular emission intensity from a graphite sample as a function of incident laser intensity suggests that the tightly focused filament surpasses the intensity clamping value.

Unveiling the Link between the Third Law of Comminution and the Grinding Kinetics Behaviour of Several Ores

As a continuation of a previous research work carried out to estimate the Bond work index (wi) by using a simulator based on the cumulative kinetic model (CKM), a deeper analysis was carried out to determine the link between the kinetic and energy parameters in the case of metalliferous and non-metallic ore samples. The results evidenced a relationship between the CKM kinetic parameter k and the grindability index gbp; and also with the wi, obtained following the standard procedure. An excellent correlation was obtained in both cases, posing the definition of alternative work index estimation tests with the advantages of more straightforward and quicker laboratory procedures.

Internal resistive heating of non-metallic samples to 3000K and >60GPa in the diamond anvil cell.

High pressure-temperature experiments provide information on the phase diagrams and physical characteristics of matter at extreme conditions and offer a synthesis pathway for novel materials with useful properties. Experiments recreating the conditions of planetary interiors provide important constraints on the physical properties of constituent phases and are key to developing models of planetary processes and interpreting geophysical observations. The laser-heated diamond anvil cell (DAC) is currently the only technique capable of routinely accessing the Earth's lower-mantle geotherm for experiments on non-metallic samples, but large temperature uncertainties and poor temperature stability limit the accuracy of measured data and prohibits analyses requiring long acquisition times. We have developed a novel internal resistive heating (IRH) technique for the DAC and demonstrate stable heating of non-metallic samples up to 3000K and 64GPa, as confirmed by in situ synchrotron x-ray diffraction and simultaneous spectroradiometric temperature measurement. The temperature generated in our IRH-DAC can be precisely controlled and is extremely stable, with less than 20K variation over several hours without any user intervention, resulting in temperature uncertainties an order of magnitude smaller than those in typical laser-heating experiments. Our IRH-DAC design, with its simple geometry, provides a new and highly accessible tool for investigating materials at extreme conditions. It is well suited for the rapid collection of high-resolution P-V-T data, precise demarcation of phase boundaries, and experiments requiring long acquisition times at high temperature. Our IRH technique is ideally placed to exploit the move toward coherent nano-focused x-ray beams at next-generation synchrotron sources.

Improving sample preheating capabilities for dynamic loading on high-pulsed power drivers.

The CEA operates several High-Pulsed Power (HPP) drivers for dynamic loading experiments. The aim of these experiments is to provide quantitative information about the response of various materials of interest, mainly under quasi-isentropic compression. In order to improve our ability to explore these materials' behavior over a wide range of thermodynamic paths and starting from various non-ambient conditions, we developed a device capable of pre-heating both metallic and nonmetallic samples up to several hundred degrees prior to loading. This device is based on conductive heating and on a configuration that allows homogeneous heating with unprecedented temperature stability on our HPP platforms. Moreover, it is designed to allow efficient sample heating, within extremely severe electromagnetic environments associated with such platforms. The main features of this preheating device, whose design was guided by extensive thermal simulations, are presented, along with various technical solutions that enabled its insertion in a reliable experimental configuration on our HPP drivers. The results obtained from preliminary experiments on a composite material (carbon fibers embedded in epoxy resin) and on a high purity copper sample preheated to 323 K and 573 K, respectively, are presented. The performance and robustness of this heating device are potentially valuable for extending the range of studies in dynamic loading experiments for various materials under ramp compression using HPP drivers.

Testing the influence of temperature on mass at high temperatures

Special relativity predicts a very small influence of temperature on mass of around Δmm≈10-14. More than 100 years ago, experiments were performed that revealed a limit of <10−8 for changes of a few degree at room temperature. A similar limit was obtained with a magnetic suspension balance at cryogenic temperatures. Recently, some measurements claim to have seen a negative dependence at the 10−6 level for a variety of metal samples at room temperature, which would be of interest e.g. to explain variations in the measurement of the gravitational constant. We have performed measurements with an analytical balance in vacuum and with a commercial thermogravimetric balance in argon and obtained a 3σ limit of <1.8×10-8 for both metallic (Cu, Pt) and non-metallic (Al2O3) samples ranging from room temperature to above 1000 °C. This extends previous measurements to the high-temperature regime and rules out all claimed anomalies by more than two orders of magnitude.

Power system harmonic analysis of a pulse DC sintering system

Pulse DC Sintering System (PDCS) produces metallic and nonmetallic samples in a cheap and efficient way in a short time. Some PDCS systems possess thyristor-based rectifiers to control their output power. This results in PDCS systems creating power system harmonics. The harmonic content of an PDCS system varies during sample manufacturing process since the PDCS container resistance is temperature dependent. In this study, power system harmonics of a PDCS system is examined for the first time in literature. A power analyzer device is used to measure and record the supply side current, voltage and power of the PDCS system as a function of time. Besides, an infrared temperature meter module is a used to measure PDCS container temperature and record it with respect to time during sample production. Total harmonic distortion is found to be decreasing with container temperature increasing.

Effects of repetition rate on the identification of elements in gemstone using the LIBS method

In material science, there are several methods for detecting elemental content in a material (sample) such as X-Ray Fluorescence (XRF), (X-Ray Diffraction) XRD, (Scanning Electron Microscope) SEM, (Transmission Electron Microscope) TEM), etc. Non-metallic samples such as gemstone can be detected by XRF and XRD methods. But in this method, the sample must get special treatment such as being crushed and converted into powder form. In this study, LIBS was used to identify elements in a gemstone. The laser-induced breakdown spectroscopy (LIBS) method is an alternative method for solving deficiencies in the previous study. The results show the same elements contained in the gemstone can clearly be detected. The elements are also confirmed by using the standard technique of X-ray fluorescence and the result revealed that the elements are consistent as in the case of the LIBS technique.

Modeling ballistic phonon transport from a cylindrical electron beam heat source

Recent electron microscopy experiments have used focused electron beams as nanoscale heat sources or thermometers to enable high spatial resolution studies of heat transfer in nanostructures. When the electron beam radius is smaller than the heat carrier mean free path, Fourier’s law will underpredict the temperature rise due to electron beam-induced heating, motivating the development of subcontinuum models to interpret thermal electron microscopy measurements. Here, electron beam-induced heating of nonmetallic samples is modeled by applying a recently developed general solution of the governing Boltzmann transport equation (BTE) under the relaxation time approximation. The analytical BTE solution describes thermal phonon transport from a time-periodically heated cylindrical region in a homogeneous infinite medium. The BTE results show that ballistic phonon effects in this radial heat spreading scenario are more conveniently represented using a ballistic thermal resistance rather than an effective thermal conductivity. Calculations of this ballistic resistance for three semiconductors (Si, GaAs, and 3C-SiC) show that ballistic effects dominate the total thermal resistance to radial heat flow for typical STEM or SEM beam radii (&amp;lt;10 nm), indicating that the ballistic resistance could potentially be measured using thin-film electron beam heating experiments. However, combining the BTE solution with recent calorimetric measurements shows that the magnitude of the temperature rise remains negligibly small (&amp;lt;1 K) under typical electron microscopy conditions, even when considering these ballistic effects. These BTE modeling results can be used to quantify electron beam-induced heating or to design experiments probing ballistic phonon transport using electron beam heat sources.

Probing disorder in high-pressure cubic tin (IV) oxide: a combined X-ray diffraction and absorption study.

The transparent conducting oxide, SnO2, is a promising optoelectronic material with predicted tailorable properties via pressure-mediated band gap opening. While such electronic properties are typically modeled assuming perfect crystallinity, disordering of the O sublattice under pressure is qualitatively known. Here a quantitative approach is thus employed, combining extended X-ray absorption fine-structure (EXAFS) spectroscopy with X-ray diffraction, to probe the extent of Sn-O bond anharmonicities in the high-pressure cubic (Pa\bar{3}) SnO2 - formed as a single phase and annealed by CO2 laser heating to 2648 ± 41 K at 44.5 GPa. This combinational study reveals and quantifies a large degree of disordering in the O sublattice, while the Sn lattice remains ordered. Moreover, this study describes implementation of direct laser heating of non-metallic samples by CO2 laser alongside EXAFS, and the high quality of data which may be achieved at high pressures in a diamond anvil cell when appropriate thermal annealing is applied.

THz spectroscopy for inspection and evaluation of internal structure of sandwich samples

Purpose The purpose of this paper is to discuss the application of THz spectroscopy for the inspection and evaluation of the internal structure of complex samples with honeycomb fillers. Design/methodology/approach Three complex samples with honeycomb fillers are investigated using THz spectrometer in order to determine the applicability of chosen non-destructive method for the analysis of internal structure of structural components. The first analysed sample has aluminium honeycomb filler with some cells filled with water. The aim of the analysis is to distinguish empty and full cells. The other two sandwich samples are made of different non-metallic components and for them the possibility of THz spectroscopy application is analysed. Findings The empty and full cells in metal honeycomb filler were easily distinguished due to different absorption coefficients of electromagnetic waves in THz range for air and water. It was especially visible for frequency domain. The THz spectroscopy was able to inspect the non-metallic samples internal structures and distinguish skins (with layers), honeycomb fillers and adhesive layers between them. It was also possible to detect, localise and determine the size of a local damage of honeycomb walls due to impact influence. Originality/value The present study is an original research work. There are very limited literature papers which present analyses of internal structures of sandwich elements using THz spectroscopy and investigate utility of the method for mechanical damage and contamination (water) detection and localisation.

Determining Curie temperature of (Ga,Mn)As samples based on electrical transport measurements: Low Curie temperature case

In this paper, we show that the widely accepted method of the determination of Curie temperature (TC) in (Ga,Mn)As samples, based on the position of the peak in the temperature derivative of the resistivity, completely fails in the case of non-metallic and low-TC unannealed samples. In this case, we propose an alternative method, also based on electric transport measurements, which exploits temperature dependence of the second derivative of the resistivity upon magnetic field.

Possibility of Using Nonmetallic Check Samples to Assess the Sensitivity of Penetrant Testing

Versions of check sample manufacturing for penetrant inspection are considered. A statistical analysis of crack width measuring for nonmetallic samples is performed to determine the possibility of their application to assess the penetrant testing sensitivity.

Applicability of post-ionization theory to laser-assisted field evaporation of magnetite

Analysis of the detected Fe ion charge states from laser-assisted field evaporation of magnetite (Fe3O4) reveals unexpected trends as a function of laser pulse energy that break from conventional post-ionization theory for metals. For Fe ions evaporated from magnetite, the effects of post-ionization are partially offset by the increased prevalence of direct evaporation into higher charge states with increasing laser pulse energy. Therefore, the final charge state is related to both the field strength and the laser pulse energy, despite those variables themselves being intertwined when analyzing at a constant detection rate. Comparison of data collected at different base temperatures also shows that the increased prevalence of Fe2+ at higher laser energies is possibly not a direct thermal effect. Conversely, the ratio of 16O+:(16O2+ + 16O+) is well correlated with field strength and unaffected by laser pulse energy on its own, making it a better overall indicator of the field evaporation conditions. Plotting the normalized field strength versus laser pulse energy also elucidates a non-linear dependence, in agreement with the previous observations on semiconductors, which suggests field-dependent laser absorption efficiency. Together these observations demonstrate that the field evaporation process for laser-pulsed oxides exhibits fundamental differences from metallic specimens that cannot be completely explained by post-ionization theory. Further theoretical studies, combined with detailed analytical observations, are required to understand fully the field evaporation process of non-metallic samples.

Effects of Different Mordants on Silk Fabric Dyed with Onion Outer Skin Extracts

At present, a higher demand is put towards the use of natural dyes due to increased awareness of the environmental and health hazards associated with the synthesis and use of synthetic dyes. This research was conducted using onion outer skins as a potential source of natural plant dyes. In this study, extraction of dye was carried out in aqueous boiling method. Premordanting technique was followed using different mordants, namely alum, ferrous sulphate, tin, tannic acid, tartaric acid, and their combinations on silk fabric. Fabric samples dyed without using any mordant were then compared with the dyed samples pretreated with the mordants. The range of colors developed on dyed materials was evaluated by measuring the color values with respect to K/S values and color coordinates. It was concluded that the color values were found to be influenced by the addition of mordants, and thus different fashion hues were obtained from the same amount of dye extract using different mordants. Ferrous sulphate was found as the most influential mordant. ΔEcmc values between unmordanted (Reference dyed) and metallic mordanted fabric samples were found higher than those between unmordanted and nonmetallic mordanted fabric samples. The dyed samples were evaluated for color fastness to washing, light, drycleaning, rubbing, and perspiration. The color fastness properties were found to be satisfactory and improved in many cases. From the fastness results, it was obvious that these dyes can also be applied on silk fabric without using any mordant if required.