B. Kasalica

The galvanoluminescence spectra of porous oxide layers formed by aluminum anodization in oxalic acid

This paper presents the result of the most recent investigations of the galvanoluminescence (GL) spectra of porous oxide layers formed by aluminum anodization in oxalic acid. A new experimental procedure for GL spectra recording was established. This method can be easily applied to GL spectral measurements on porous anodic films. The spectra were recorded for different values of temperature and anodization current density. Two spectral peaks at 446 and 485 nm, respectively, were observed, indicating the probable existence of two kinds of luminescence centers incorporated in the oxide. In addition, it was discovered that the intensity ratio for the two peaks changes with the current density. Those GL measurements, with further photoluminescent (PL) measurements should lead to a definitive explanation of the GL phenomena, as well as of the nature and distribution of luminescent centers in both porous and barrier oxide films on aluminum.

Light-Emitting-Diode-Based Light Source for Calibration of an Intensified Charge-Coupled Device Detection System Intended for Galvanoluminescence Measurements

A spectrally tunable light source utilizing three light-emitting diodes (LEDs) for calibration of a highly sensitive intensified charge-coupled device (ICCD) optical detection system intended for time-resolved galvanoluminescence (GL) measurements is described. The source has been conceived as a low-cost substitute for standard tungsten lamps usually used for relative and absolute calibration of optical detection systems. Three LEDs with different spectral characteristics in conjunction with a system of two integrating spheres as light mixers and light reducers are used. This construction provides control over the source spectrum by changing individual LED contributions. The use of integration spheres eliminated angular distribution of light intensities of LEDs as well as angular dependence of their spectral contributions. Moreover, by using the source we have avoided the problem of stray and diffuse light of higher wavelengths, as well as different light intensities for different wavelengths (up to three orders of magnitude in the range from 400 nm to 750 nm), which we have with standard tungsten lamps. A complete calibration procedure for the LED source and ICCD detection system is described. Finally, for the first time, we have performed time-resolved spectral GL measurements during aluminum anodization in porous film-forming electrolyte phosphoric acid in a transient regime. Two peaks at 425 nm and 595 nm are recognized, confirming the same mechanism of GL in both transient and steady-state regimes of anodization.

Identification of the C2∏–X2Σ+ band system of AlO in the ultraviolet galvanoluminescence obtained during aluminum anodization

The first galvanoluminescence spectrum in the ultraviolet region obtained during anodization of high purity aluminum samples annealed at temperature above 525°C is presented. An intense broad peak with the maximum at about 31,900 cm(-1) is assigned to the transitions (some of them heretofore unobserved) between vibrational levels of the C(2)∏→X(2)Σ(+) spectral system of AlO, partly overlapped with the A(2)Σ(+)→X(2)∏ system of OH.

The anomalous sodium doublet D2/D1 spectral line intensity ratio – a manifestation of CCD's presaturation effect

In this paper we present the results of intensity measurements of D1 (589.5224 nm) and D2 (588.9950 nm) sodium doublet spectral lines emitted from a short-lifetime plasma randomly appearing across the aluminum anode surface during its electrolytic oxidation from the water solution of boric acid with sodium tetraborate. We found that the D2 to D1 intensity ratios were not constant, varying from 2 to 1.2. Assuming that the plasma is in local thermal equilibrium it is expected that the intensity ratio of sodium doublet components equals the ratio of the statistical weights of the atomic sublevels corresponding to the electronic transitions (D1: 32P1/2–32S1/2, D2: 32P3/2–32S1/2) i.e. 2. After detailed analyses of a series of spectra obtained by applying different detection parameters, like exposure time, slit width, detection mode, and number of accumulations, we attributed the anomalous D2/D1 intensity ratio to the effect of approaching a saturation condition of the charge coupled device detector and thus to an early indication of saturation occurrence.

Continuous wave laser for tailoring the photoluminescence of silicon nanoparticles produced by laser ablation in liquid

Silicon nanoparticles (SiNPs) are attracting attention for applications in various fields, from energy storage to bio-imaging. One of their main advantages is good photoluminescence (PL) properties combined with the relatively high bio-compatibility. Here, we fabricated SiNPs by the laser ablation of silicon single crystal in de-ionized water, employing simultaneously the picosecond pulse laser (150 ps, 1064 nm, 7 mJ/pulse) and a continuous wave (CW) laser (532 nm, 270 mW). TEM analysis (bright field TEM, HRTEM, HAADF, EDS) clearly shows that the introduction of the CW laser significantly increases the crystallinity of the produced nanoparticles, which may be crucial for many optical and electronic applications. The obtained SiNPs exhibit good blue photoluminescence properties, and the introduction of the CW laser into the fabrication process leads to the considerable increases in the photoluminescence. Additionally, we conducted a detailed analysis on the aging-time dependence and the excitation waveleng...

Luminescence During the Electrochemical Oxidation of Aluminum

Electrochemical oxidation of aluminum has attracted considerable attention because of the widespread use of aluminum oxide layers in different areas of technology and industry. Traditionally, the anodization of aluminum is used to protect metals from corrosion and to increase the abrasive and adsorption properties, hardness, etc. The oxide layers on aluminum are widely used in electronics due to its excellent dielectric properties, perfect planarity, and good reproducibility during production. In recent years, scientists have focused on the formation of self-ordered oxide structures on aluminum in various electrolytes. This is a result of the application of porous oxide layers arranged pores with dimensions ranging from micrometers to nanometers, as the mold in nanotechnologies for the synthesis of nanotubes, nanowires, solar cells, micro-optical elements, photonic crystals, etc.

Two-color pyrometer-based method for measuring temperature profiles and attenuation coefficients in a coal power plant

ABSTRACT A novel method and the appropriate instrumentation for the measuring of temperature profiles and attenuation coefficients in a combustion chamber of a coal-fired power plant are described. The instrument is based on a two-color pyrometer. Results were verified by the pneumatic Venturi pyrometer measurements, as well as by sampling unburnt particles using a cooled extraction probe.

Metrological Assurance of Biodevices: The New Method of Calibration of Biochemical Analyzers

Abstract Medical diagnostics and therapy use an extensive amount of electronics, optoelectronics, and laser devices. For their reliable functioning, calibration is unavoidable. Biochemical analyzers, which work on principles of absorptional spectrophotometry, became most widely present in medical biochemical laboratories. Construction of these devices is such, that in most cases, it does not allow calibration by usual methods, using neutral density (ND) filters as standards. For this reason, it was necessary to create a solution that could be used as a mean of comparison or even as a standard solution for methods of calibration of biochemical analyzers. In this article, the metrological characterization of solutions that are developed is presented, and the measuring uncertainty (ISO 1993) of methods used for calibration is estimated. The method that is developed provides metrological traceability to the primary spectrophotometric standard. With this method, metrological assurance in the field of the spectrophotometry in medical laboratories is completed.