Development of undersized (12.5 mm diameter) low‐dilution glass beads for X‐ray fluorescence determination of 34 components in 200 mg of igneous rock for applications with geochemical and archeological silicic samples

A low‐dilution, undersized (12.5 mm diameter) glass–bead technique was developed for X‐ray fluorescence determination of 34 components (Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, MnO, Fe₂O₃, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Hf, W, and Pb) in precious silicic samples for geochemistry and archeology. This preparation was consolidated based on the properties of the specimen, including disk formability and detachability from a small crucible, through variation of the amounts of the two samples (basaltic and granitic rocks) and releasing reagent. The specimen was prepared by fusing a mixture of 200 mg of powdered sample, 200 mg of lithium tetraborate as a flux, and 60 µl of 18.42 mass% lithium chloride solution as a releasing agent in a small platinum crucible. Calibration curves were drawn using synthetic calibration standards, which were prepared by compounding chemical reagents, such as oxides, carbonates, and diphosphates containing analytes. The calibration curves showed good linearity with correlation coefficient values greater than 0.990. Using the proposed method, we determined 34 components in five igneous rock reference samples. The results were in agreement with the recommended values, accounting for uncertainties. With this method, preparation requires only small amounts of the powdered sample and alkali flux; however, still allowing for determination of many analytes, which is advantageous when dealing with limited quantities of precious samples. The present method has potential applications in the chemical characterization of various geological and archeological samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrical properties of Na<Subscript>2</Subscript>SO<Subscript>4</Subscript>-based composite systems

Composite electrolytes are well-known multiphase systems and exhibit maxima in the conductivity at certain second-phase concentration. An attempt has been made to investigate a number of sodium sulfate (Na₂SO₄)-based composite systems. The dispersoids that have been used are MgO, Al₂O₃, and SiO₂. The samples have been characterized using impedance spectroscopy, X-ray diffraction, and differential scanning calorimetry. The maximum conductivity has been observed for MgO dispersed system, and the percolation threshold has been observed at 30-mol% dispersoid, MgO concentration. Interestingly, two maxima have been observed in case of the Na₂SO₄–SiO₂ and Na₂SO₄–Al₂O₃ composite systems. In the Na₂SO₄–SiO₂ system, the first maximum occurs at lower concentration, i.e., in the range between 10 and 20 mol%, whereas the second occurs at the 40-mol% dispersoid concentration. For the Na₂SO₄–Al₂O₃ system, although slightly indistinguishable, two peaks in the conductivity vs composition plot have been observed around 12- and 30-mol% Al₂O₃ concentrations.     

Loose‐powder technique for X‐ray fluorescence analysis of ancient pottery using a small (100 mg) powdered sample

A molded‐loose‐powder technique using a small powdered sample (100 mg) was developed for the X‐ray fluorescence analysis of 22 components (Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, MnO, Fe₂O₃, V, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, and Pb) in ancient pottery. This loose powder specimen was prepared by pressing the small powdered sample into a sample holder, formed from a stainless steel disk (48‐mm diameter × 0.8‐mm height) with a hole (11‐mm diameter), by hand. Calibration standards were prepared by homogenizing chemical reagents containing these 22 analytes using the concentration ranges of 166 ancient potteries and three clay materials from Japan. The calibration curves of these benchmark mixtures exhibited a good linearity (correlation coefficient, r = 0.990–1.000), accuracy, and reproducibility compared with those of other synthesized specimens and three reference standards. The lower limits of detection were less than tens of mg kg^?1 (e.g., 94 mg kg^?1 for Na₂O, 11 mg kg^?1 for P₂O₅, 1.1 mg kg^?1 for Rb, and 0.9 mg kg^?1 for Y). Using the present method, we determined 22 components in two prehistoric potteries from Japan. The advantage of this method is that only a small amount of sample is required, which can be prepared easily and rapidly and reused for other analyses. Copyright © 2012 John Wiley & Sons, Ltd.     

X‐ray fluorescence analysis of sludge ash from sewage disposal plant

Glass bead/x‐ray fluorescence spectrometry of the sludge incineration ashes generated in sewage processing was developed for the determination of ten major components (Na₂O, MgO, Al₂O₃, SiO₂, P₂O₅, K₂O, CaO, TiO₂, MnO, Fe₂O₃) and five minor elements (Zn, Cu, Cr, As, Pb). Sewage sludge ashes consisted of rock‐forming minerals and phosphate crystals that had been used for phosphorus removal. Ash samples were melted and molded with lithium tetraborate to 35 mm diameter glass disks in a Pt–Au crucible. Analytical results of ten major components and five minor elements agreed well with the recommended values of a phosphate rock standard reference material (NIST SRM 694). Elemental compositions of sewage sludge ash from seven sewage‐processing plants in Japan were determined using this method. Concentrations of Fe₂O₃, SiO₂, and CaO, along with loss of ignition in sewage sludge ash mutually differed among the sewage‐processing plant products. Seasonal variations in concentrations of ten major components and five minor components of ash samples produced from October 2001 to September 2002 were determined using the proposed method. Concentrations of SiO₂increased with the inflow of gravel by rainfall, thereby decreasing concentrations of P₂O₅ originating from excreta and microorganisms. Copyright © 2008 John Wiley & Sons, Ltd.     

A study on the solubility and distribution of carbon in oxides

Measurements of radiocarbon in oxides were conducted after annealing single crystalline und polycrystalline FeO, Fe₃O₄, MnO, MgO, Cr₂O₃ and Al₂O₃ in radioactive CO₂-CO mixtures at 1000°C for different times. Concentrations of ≥ 0.01 wt. ppm C could be detected by anticoincidence counting and the distribution was observed by autoradiography. The measurements showed no carbon (< 0.01 ppm) in the lattice or the grain boundaries of pore- and crack-free oxides, carbon was detected only in cracks, pores or in grain boundaries which had cracked open. Thus, there is no measurable solubility of carbon in the bulk oxides for all the different chemical compositions investigated. Permeation of carbon through oxide layers on metals and alloys can only occur by transport of carbon-bearing molecules through cracks and pores of the oxide.     

UV-protection properties of electrospun polyacrylonitrile nanofibrous mats embedded with MgO and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles

This article describes the ultraviolet (UV) protection of MgO and Al₂O₃ nanoparticles embedded electrospun polyacrylonitrile (PAN) nanofibrous mats. UV radiation is a harmful part of sunlight and prolonged exposure to it can cause serious skin damages. In this research, nanofibrous mats consisting of nanofibers with different diameters containing different amounts of MgO, Al₂O₃, MgO Plus, and Al₂O₃ Plus nanoparticles were produced, and their UV-protection was measured. The specific surface area of MgO, MgO Plus, Al₂O₃, and Al₂O₃ Plus nanoparticles was 230, 600, 275, and 550 m²/g, respectively. The mean diameter of electrospun PAN nanofibers embedded with metal oxide nanoparticles was in the range of 665–337 nm. The results showed that the UV-protection (shielding) capability of the mats strongly depends on fiber diameter; in fact a thin mat of nanofibers has a much stronger UV-protection in comparison to a thicker mat composed of regular fibers. UV transmission is reduced as a result of embedding MgO and Al₂O₃ nanoparticles in the electrospun PAN nanofibrous mats. MgO Plus and Al₂O₃ Plus show higher UV-protection than MgO and Al₂O₃.     

Metal oxide additives for the sintering of silicon carbide: Reactivity and densification

The effectiveness of sintering additives for β-SiC was examined based on thermodynamic calculations and experimental observations under hot pressing conditions of 1700–1800 °C. Various types of oxides, such as Al₂O₃, Fe₂O₃, MgO, TiO₂, WO₃ and Y₂O₃, were examined theoretically by considering the Gibbs formation free energy and vapor pressure. According to experimental observations expanded to their binary and ternary systems after hot pressing at 1750 °C and 20 MPa, Al₂O₃, MgO, Y₂O₃ and their mixed systems were found to be the only effective sintering additives that do not react with β-SiC at high temperatures. On the other hand, Fe₂O₃, TiO₂, WO₃ and their combinations with other oxides were not effective because of the reaction with β-SiC by forming the corresponding metal carbides and/or silicides, as predicted by thermodynamic simulations. Moreover, the experimental results for the additional possible components were also included.     

Electron probe determination of trace elements in olivine

Evaluation of the error of computations using analysis results requires knowing the error of determining the analyte. The necessity of limiting the error of computations conditions the value of the permissible error of determining the concentration: it should not exceed a certain predetermined limit. In particular, such a requirement is made for determining a component by the content of which the temperature of rock formation is calculated in a mineral. This study demonstrates derivation of a formula for quantitation limit C_lim of an analyte. Relations have been obtained connecting C_lim, the detection limit C_min, and the relative standard deviation V of the element quantitation. The equations connecting metrological characteristics allowed identifying the required analysis conditions and their practicability. The characteristics of the methodology for quantitation of Na₂O, Al₂O₃, CaO, Cr₂O₃ и MnO in the olivines of depleted peridotites have been identified using microanalyzer JXA‐8100, with the accelerating voltage of 20 kV and the probe current of 400 nA. The count rate per measurement was 10 s in the line and background positions. The number of measurements per quantitation was 25. Under these conditions, C_min of the aforementioned oxides does not exceed 9 ppmw for 1σ‐criterion. For V = 0.1, C_lim is within the range of 45–100 ppmw. The example of an ‘aluminum’ geothermometer serves to demonstrate that electron probe micro analysis may ensure the error required for calculating the temperature by the content of trace elements. Copyright © 2014 John Wiley & Sons, Ltd.     

Evolution of MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> crystals in Al-Mg-SiO<Subscript>2</Subscript> composites

The present study analyzes the morphological transformations of reaction products i.e., MgO, MgAl₂O₄ occurring during the reaction between SiO₂ and Al-Mg alloy in Al-Mg-SiO₂ composite processed by the liquid metallurgy technique. Different phases of platelet and hexagonal morphologies are detected and their composition analysis by EDS has confirmed them as being transition phases existing between MgO, MgAl₂O₄ and Al₂O₃. This study has also revealed the gradual transformation of (i) MgO needles to octahedral MgAl₂O₄ through Mg-Al-Si-O and Mg-Al-O transition phases having platelet morphologies and (ii) MgAl₂O₄ to Al₂O₃ through hexagonal transition phases on holding of Al-5Mg-SiO₂ and Al-1Mg-SiO₂ composites respectively at 1023K. Fully developed α-Al₂O₃ crystals are not observed under the present experimental conditions, wherein the Mg content is well above the equilibrium Mg content required for the formation of stable Al₂O₃ (<0.05 wt. %). PACS 05.70.Np     

Relaxation, self-trapping, and decay of electron excitations in wide-gap oxides

Emission spectra ofMgO, Al ₂O₃, Y₂O₃, andSc ₂O₃ crystals, excited at 8 K by photons with energies 5–40 eV, are measured. The luminescence of free excitons andGe ²⁺ centers forMgO, the self-trapped exciton emission (STEE) forAl ₂O₃ andY ₂O₃, and the tunnel self-luminescence forScO ₃ are studied. A distinction between hole polarons in oxides and self-trapped holes in halides leads to a sharp difference in the mechanisms of STEE creation on electronhole recombination for these two classes of solids. The electron-hole, hole-electron, and exciton mechanisms of excitation multiplication are identified. The high radioresistance of wide-gap oxides and the behavior of oxygen interstitials inMgO crystals are discussed. Institute of Physics of Estonia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 5–16, March, 2000.     

X‐ray fluorescence analysis of Co,Ni, Pd,Ag, and Au in the scrapped printed‐circuit‐board ash

A method for the quantitative analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed‐circuit‐board ash by X‐ray fluorescence (XRF) spectrometry using loose powder was developed. The printed‐circuit‐board samples were converted to ash pyrolytically in porcelain crucibles by sequential heating using a gas burner and electric furnace, and then were ground with a ball mill. The calibrating standards were prepared by adding the appropriate amounts of NiO powder and aqueous standard solutions containing Co, Pd, Ag, and Au to the base mixtures of Al₂O₃ (5.0 mass%), SiO₂ (49 mass%), CaCO₃ (11 mass%), Fe₂O₃ (3.3 mass%), and CuO (30 mass%) as a matrix. Then, 10 g of the resulting mixtures were dried and homogenized for 90 min with a V‐type mixing machine. Specimens for XRF analysis were prepared from the so‐called loose‐powder method in which powder samples were compacted into a hole (12.0‐mm diameter and 5.0‐mm height) in an acrylic plate and covered with a 6‐µm thickness of polypropylene film. Matrix effects were corrected using the intensity value of Compton scattering for PdKα, AgKα, and AuLβ₂, and that of background scattering at 35.8° (2θ) for CoKα and NiKα. The detection limits corresponding to three times the standard deviation of the blank intensity were 2.5–45 µg g^?1. The proposed method was validated against the pressed‐powder‐pellet method by comparing the calibration curves. Moreover, the concentrations of Co, Ni, Pd, and Ag determined using the proposed XRF method were approximately the same as those resulting from an atomic‐absorption‐spectrometric analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Element analysis of complex materials by calibration-free laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a promising method for fast and quantitative element analysis of complex materials. We report on LIBS measurements of multi-component oxide materials and the compositional analysis of materials by a calibration-free (CF) method. This CF-LIBS method relies on modeling of the optical emission of laser-induced plasma assuming local thermodynamic equilibrium. Various materials are investigated and the calculated concentration values (C _CF) of oxides CaO, Al₂O₃, MgO, SiO₂, FeO, and MnO are in agreement with nominal concentration values (C _N) from reference analysis. The relative error in oxide concentration e _r=|C _CF?C _N|/C _N decreases with increasing concentration. The quantification is limited to major oxides (C _N≥1 wt%). Slag samples from industrial steel production are analyzed on site by means of a mobile measurement system. LIBS measurements are performed at different sample temperatures. The results obtained show that CF-LIBS is applicable to fast compositional analysis of complex materials in harsh environments.     

Nondestructive investigation of interface states in high‐k oxide films on Ge substrate using X‐ray absorption spectroscopy

The unoccupied electronic structures of 5 nm thick high permittivity (k) oxides (HfO₂, ZrO₂, and Al₂O₃) and SiO₂ films on Ge substrates were examined using O K‐edge X‐ray absorption spectroscopy. Comparative studies with those on Si substrates showed contrasts in the conduction bands, which should be due to the formation of interface states. In the Al₂O₃ and SiO₂ films, GeO₂ layers are formed at the interface and they suppress in part the formation of detrimental germanate phases. In contrast, in the HfO₂ and ZrO₂ films, no signature of the Ge‐oxide phase is observed but some germanate phases are expected to prevail, suggesting a degradation of the gate oxide characteristics. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sodium-rich beta-alumina

Sodium-rich beta-alumina, with a composition close to (Na₂O)_2.011Al₂O₃, has been prepared by exposure of single crystals of (Na₂O)_1.2511Al₂O₃ to oxygen-saturated sodium at 750°C. The hexagonal c axis of the sodium-rich crystals is shorter than that of the non-stoichiometric beta-alumina precursor. The ionic conductivity at 500°C is an order of magnitude lower and its activation energy higher than for (Na₂O)_1.2511Al₂O₃.     

Chemical analysis of phosphate rock using different methods—advantages and disadvantages

Many analytical methods are considered for chemical analysis of phosphate rock because the accuracy of analysis is very important. In the present investigations, spectrophotometric and x‐ray spectrometric methods were used to determine P₂O₅ whereas SiO₂, CaO, MgO, Al₂O₃ and Fe₂O₃ were determined by gravimetric and x‐ray spectrometric methods. Volumetric and x‐ray spectrometry methods are necessary for fluorine determination. The investigations revealed that x‐ray spectrometry is a precise and accurate technique, which is cost effective and so better than other methods. Spectrophotometric, volumetric and gravimetric methods are expensive, time consuming and laborious. X‐ray spectrometry is suggested for commercial companies using regular analyses to save chemicals, time and labour and to maintain quality. Copyright © 2006 John Wiley & Sons, Ltd.     

Non-stoichiometry in MgAl2O4 spinel

Stoichiometric magnesium aluminate spinel, MgAl₂O₄, contains equimolar proportions of Al₂O₃ and MgO. Spinel can, however, exhibit significant deviations from this stoichiometric composition. There is considerable disagreement concerning which species compensate for either excess Al₂O₃ or MgO non-stoichiometry. Here, we use empirical and quantum mechanical (density functional theory) atomistic simulation techniques to investigate the defect chemistry accommodating non-stoichiometry. The incorporation of excess Al₂O₃ was found to be a lower energy process than the solution of excess MgO. Elevated magnesium and aluminium cation vacancy defect concentrations are predicted in Al₂O₃ rich spinels, whilst MgO excess is facilitated by a combination of oxygen vacancy and magnesium interstitial defects.     

Synthesis, characterization and catalytic properties of sol-gel derived mixed oxides

Alumina and 1:1 mixed oxides of Al₂O₃-ZrO₂, Al₂O₃-TiO₂, SiO₂-TiO₂ and ZrO₂-TiO₂ were synthesized via a sol-gel process by the so-called neutral amine route, followed by calcination at 600 °C. The mixed oxides were characterized before calcination by X-ray diffraction, revealing ordered hexagonal (Al₂O₃, Al₂O₃-ZrO₂, ZrO₂-TiO₂) and lamellar (SiO₂-TiO₂, Al₂O₃-TiO₂) structures. After calcination, all samples exhibited amorphous structures. Surface areas and pore characteristics of all materials were determined by nitrogen adsorption isotherms. The calcined oxides are active catalysts in the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant. Epoxide yields from 14 to 45% were found for reaction times of 24 h. The titanium oxide containing catalysts are the most active and selective ones. On the other hand, the poisoning of acidic centers yields a decreasing activity while increasing selectivity.     

Utilization of blast furnace slag nano-fluids in two-phase closed thermos-syphon heat pipes for enhancing heat transfer

This article deals with utilization of blast furnace slag nano-fluids in two-phase closed thermo-syphon heat pipes for enhancing heat transfer at various states of operation. The utilization of nano-fluids obtained from X₂O₃-, XO-, XO₂-, and X₂O-type oxides, such as Al₂O₃, Fe₂O₃, CaO, SiO₂, MgO, MnO, K₂O, and Na₂O, on the improvement of heat pipe performance has been separately reported in a number of studies in the literature. The present study experimentally demonstrated the effect of using a nano-fluid obtained from blast furnace slag comprised of various types of metal oxides in varying ratios on improving the performance of a heat pipe. The slag was obtained from the iron blast furnace of Karabük Iron Steel Workings (Turkey). Triton X-100 (Dow Chemical Company) dispersant was used in the study to produce the blast furnace slag/water nano-fluid via direct-synthesis. The 2 wt% concentration of blast furnace slag/water nano-fluid was used as the working fluid in heat pipes. A straight copper tube with an inner diameter of 13 mm, outer diameter of 15 mm, and length of 1 m was used as the heat pipe in the present experimental study. The nano-fluid filled 33.3% (44.2 ml) of the volume of the two-phase closed thermo-syphon. Three heating power levels (200, 300, and 400 W) were used in the experiments with three different flow rates of cooling water (5, 7.5, and 10 g/s) used in the condenser for cooling the system. An increase of 22% was achieved in thermal performance of the two-phase closed thermo-syphon when 2 wt% blast furnace slag containing nano-fluid was used to replace pure water at a heat load of 200 W with a cooling water flow rate of 5 g/s.     

The influence of Fe,Cu, SiO<Subscript>2</Subscript>, TiO<Subscript>2</Subscript>, and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles in aqueous solution on proton relaxation times

Measurements of proton nuclear spin-spin and spin-lattice relaxation times are applied for determining the concentration of solid-phase nanoparticles in nanofluids. This approach is tested for metal oxides SiO₂, TiO₂, Al₂O₃ and metal-carbon nanoparticles of 3d-metals Fe and Cu. It is shown that the sensitivity of the method for determining concentrations of 3d-metals is much higher than for oxides (by 2–4 orders of magnitude). It is revealed that measurement of the proton spin-spin relaxation time allows one to determine the concentration of Cu nanoparticles to 0.0001 mg/ml and that of Fe nanoparticles to 0.00001 mg/ml.     

Surface passivation of phosphorus‐diffused n+‐type emitters by plasma‐assisted atomic‐layer deposited Al2O3

In recent years Al₂O₃ has received tremendous interest in the photovoltaic community for the application as surface passivation layer for crystalline silicon. Especially p‐type c‐Si surfaces are very effectively passivated by Al₂O₃, including p‐type emitters, due to the high fixed negative charge in the Al₂O₃ film. In this Letter we show that Al₂O₃ prepared by plasma‐assisted atomic layer deposition (ALD) can actually provide a good level of surface passivation for highly doped n‐type emitters in the range of 10–100 Ω/sq with implied‐V_oc values up to 680 mV. For n‐type emitters in the range of 100–200 Ω/sq the implied‐V_oc drops to a value of 600 mV for a 200 Ω/sq emitter, indicating a decreased level of surface passivation. For even lighter doped n‐type surfaces the passivation quality increases again to implied‐V_oc values well above 700 mV. Hence, the results presented here indicate that within a certain doping range, highly doped n‐ and p‐type surfaces can be passivated simultaneously by Al₂O₃. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)