Laser-induced breakdown spectroscopy (LIBS) has become a very popular analytical method in the last decade in view of some of its unique features such as applicability to any type of sample, practically no sample preparation, remote sensing capability, and speed of analysis The technique has a remarkably wide applicability in many fields, and the number of applications is still growing From an analytical point of view, the quantitative aspects of LIBS may be considered its Achilles' heel, first due to the complex nature of the laser–sample interaction processes, which depend upon both the laser characteristics and the sample material properties, and second due to the plasma–particle interaction processes, which are space and time dependent Together, these may cause undesirable matrix effects Ways of alleviating these problems rely upon the description of the plasma excitation-ionization processes through the use of classical equilibrium relations and therefore on the assumption that the laser-induced 

Laser-Induced Breakdown Spectroscopy (LIBS), Part I: Review of Basic Diagnostics and Plasma–Particle Interactions: Still-Challenging Issues Within the Analytical Plasma Community

This paper provides an overview of a workshop focused on fundamental experimental and theoretical aspects of soot measurements by laser-induced incandescence (LII). This workshop was held in Duisburg, Germany in September 2005. The goal of the workshop was to review the current understanding of the technique and identify gaps in this understanding associated with experimental implementation, model descriptions, and signal interpretation. The results of this workshop suggest that uncertainties in the understanding of this technique are sufficient to lead to large variability among model predictions from different LII models, among measurements using different experimental approaches, and between modeled and measured signals, even under well-defined conditions. This article summarizes the content and conclusions of the workshop, discusses controversial topics and areas of disagreement identified during the workshop, and highlights recent important references related to these topics. It clearly demonstrates that despite the widespread application of LII for soot-concentration and particle-size measurements there is still a significant lack in fundamental understanding for many of the underlying physical processes.

Laser-induced incandescence : recent trends and current questions

Recent advances in coherent anti-Stokes Raman scattering spectroscopy: Fundamental developments and applications in reacting flows

Lubricants perform as anti-friction media. They facilitate smooth operations, maintain reliable machine functions, and reduce the risks of frequent failures. At present, the increasing prices of crude oil, the depletion of crude oil reserves in the world, and global concern in protecting the environment from pollution have renewed interest in developing and using environment-friendly lubricants derived from alternative sources. A biolubricant is renewable lubricants that is biodegradable, non-toxic, and emits net zero greenhouse gas. This study presents the potential of a biolubricant based on vegetable oil as an alternative lubricant according to studies published in highly rated journals in scientific indices. In the first part of this paper, the source, properties, as well as advantages and disadvantages of the biolubricant are discussed. The second part describes the potential of vegetable oil-based biolubricants as alternative lubricants for automobile applications. The final part describes the world biolubricant market and its future prospects. Biolubricants are potential alternative lubricants because of their low toxicity, good lubricating properties, high viscosity index, high ignition temperature, increased equipment service life, high load-carrying abilities, good anti-wear characteristic, excellent coefficient of friction, natural multi-grade properties, low evaporation rates, and low emissions into the atmosphere.

The prospects of biolubricants as alternatives in automotive applications

Laser-induced incandescence: Particulate diagnostics for combustion, atmospheric, and industrial applications

Recent studies suggest that trace metals emitted by internal combustion engines are derived mainly from combustion of lubrication oil. This hypothesis was examined by investigation of the formation of particulate matter emitted from an internal combustion engine in the absence of fuel-derived soot. Emissions from a modified CAT 3304 diesel engine fueled with hydrogen gas were characterized. The role of organic carbon and metals from lubrication oil on particle formation was investigated under selected engine conditions. The engine produced exhaust aerosol with log normal-size distributions and particle concentrations between 105 and 107 cm-3 with geometric mean diameters from 18 to 31 nm. The particles contained organic carbon, little or no elemental carbon, and a much larger percentage of metals than particles from diesel engines. The maximum total carbon emission rate was estimated at 1.08 g h-1, which is much lower than the emission rate of the original diesel engine. There was also evidence that less ...

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Role of lubrication oil in particulate emissions from a hydrogen-powered internal combustion engine.

We developed an inverted, co-flow, methane/air/nitrogen burner that generates a wide range of soot particles sizes and concentrations. By adjusting the flow rates of air, methane, and nitrogen in the fuel, the mean electric mobility diameter and number concentration are varied. Additional dilution downstream of the flame allows us to generate particle concentrations spanning those produced by spark-ignited and diesel engines: particles with mean diameters between 50 and 250 nm and number concentrations from 4.7 {center_dot} 10{sup 4} to 10{sup 7} cm{sup -3}. The range of achievable number concentrations, and therefore volume concentrations, can be increased by a factor of 30 by reducing the dilution ratio. These operating conditions make this burner valuable for developing and calibrating diagnostics as well as for other studies involving soot particles.

/pdf/inverted-co-flow-diffusion-flame-for-producing-soot-1fepqy5pm8.pdf

Inverted co-flow diffusion flame for producing soot

Laser-induced breakdown spectroscopy (LIBS) was carried out on twenty-three low to high alloy steel samples to quantify their concentrations of chromium, nickel, and manganese. LIBS spectral data were correlated to known concentrations of the samples and three calibration methods were compared. A standard LIBS calibration technique using peak area integration normalized by an internal standard was compared to peak area integration normalized by total light and the multivariate statistical technique of partial least squares. For the partial least squares analysis, the PLS-1 algorithm was used, where a predictive model is generated for each element separately. Partial least squares regression coefficients show that the algorithm correctly identifies the atomic emission peaks of interest for each of the elements. Predictive capabilities of each calibration approach were quantified by calculating the standard and relative errors of prediction. The performance of partial least squares is on par with using iron as an internal standard but has the key advantage that it can be applied to samples where the concentrations of all elements are unknown.

Laser-induced breakdown spectroscopy of steel: a comparison of univariate and multivariate calibration methods.

Superaggregates (SAs) are formed due to late stage aggregation occurring near the gelling point of an aggregating system (Dhaubhadel et al. 2006). Percolation theory best describes their formation mechanism (Sorensen and Chakrabarti 2011). SAs have a long-range overall structure described by a fractal dimension Df ≈ 2.6 and a short-range local structure described by Df ≈ 1.8 (Sorensen et al. 1998; Sorensen and Chakrabarti 2011). Recently, based on the mechanism of SA formation in an aggregating system, Dhaubhadel and co-workers (Dhaubhadel et al. 2007) carried out enclosed-chamber aerosol aggregation to create “aerosol gels”—a novel material similar in properties to aerogels (Akimov 2003; Lerner 2004). Flame synthesis—which has been shown to be a cost-effective, scalable, and versatile route for large-scale production of nanoscale materials (Ulrich 1984)—is yet to be established as a viable method for production of aerosol gels. An upward-pointing flame system cannot facilitate steady and consistent formation of SAs in its product outflow upstream because of the aggregate fragmentation effects associated with buoyancy-driven flickering and shear stress of the flame’s “tipping” front (Shaddix and Smyth 1996). Here, we report our observations of steady outflow of SAs from a nontipping, reversed gravity (-g, up-side-down configuration) laminar methane–air diffusion flame. Figure 1 shows a

Christopher B. Stipe

Papers

Role of lubrication oil in particulate emissions from a hydrogen-powered internal combustion engine.

Inverted co-flow diffusion flame for producing soot

Laser-induced breakdown spectroscopy of steel: a comparison of univariate and multivariate calibration methods.

Observation of Superaggregates from a Reversed Gravity Low-Sooting Flame

Quantitative laser-induced breakdown spectroscopy of potassium for in-situ geochronology on Mars