Al Peak Research Articles

STEPWISE DETERMINATION OF ALUMINUM AND CHROMIUM IN WATER AND BIOMEDICAL SAMPLES BY HPLC-UV, BASED ON THEIR DIFFERENT KINETICS WITH 8-HYDROXYQUINOLINE

ABSTRACT A reversed-phase high performance liquid chromatographic (RP-HPLC) method, with spectrophotometric detection for determination of trace amounts of aluminum (Al) and chromium (Cr) in water and biomedical samples, has been developed using 8-hydroxylquinoline (8-HQ) as a precolumn reagent based on the differential chelation kinetics of these two ions. The analysis is achieved with a Spherisorb ODS 2 column, with an eluent consisting of 4.0 mmol L−1 acetate buffer (pH 6.0) and 3.2 mmol L−1 8-HQ in 57% (v/v) methanol–water, at a flow rate of 1.0 mL min−1. On the basis of the fact that the peaks of Al and Cr chelates appear at the same retention time, the procedure is divided into two stages: 1. (1) determining Al concentration by peak area after precolumn chelation at ambient temperature; 2. (2) measuring total peak area of Al and Cr after reaction at 90°C for 30 min, and the concentration of Cr being determined by the difference between Al peak area and the total area. The response of both Al and Cr is linear from 0.002 to 0.6 µg mL−1 with a detection limit of 0.001 µg mL−1. The analysis is free from interference from common ions except 10-fold excess of cobalt. The values obtained by this method are in good agreement with those of ICP-AES or GF-AAS. The proposed method has been successfully applied to the direct determination of Al and indirect determination of Cr in natural water, serum, synthetic renal dialysate, parenteral solution, and pharmaceutical-grade organic acid with the recoveries of over 90%.

Characterization investigations of melt-spun ternary Al– xSi–3.3Fe ( x=10, 20 wt.%) alloys

Two ternary Al– xSi–3.3Fe alloys, one with the hypoeutectic ( x=10 wt.% Si) and the other with the hypereutectic ( x=20 wt.% Si) composition were rapidly quenched from the melt at cooling rates between 10 6 and 10 7 K/s using the melt-spinning technique. The resulting melt-spun ribbons were characterized using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) and microhardness techniques. On the basis of the Al peak shifts measured in the XRD scans, solid solubility extension values of 3.01 and 2.97 at.% Si in Al were determined for the hypoeutectic and hypereutectic alloy, respectively. Whereas SEM investigations showed the presence of dendrites rich in Al, TEM investigations revealed nanosized spherically-shaped Si crystals 5–10 nm in size in the hypoeutectic alloy and those equiaxed in shape having a size range between 50 and 70 nm. Both XRD and TEM investigations confirmed the absence of any intermetallic phase formation for both alloys. The microhardness values of the hypoeutectic and hypereutectic ternary Al–Si–Fe alloys were measured as 251 and 297 kg/mm 2, respectively.

Texture in Ti/Al and Nb/Al multilayer thin films: Role of Cu

Fiber texture in Ti/Al and Nb/Al polycrystalline multilayer thin films, with bilayer thicknesses (Λ) ranging from 20–333 nm and having a fixed stoichiometry of 1/3, has been investigated by using x-ray pole figures and transmission electron microscopy. Two sets of films were deposited; one set contained pure Al and the other Al–1.0 wt% Cu. The results indicated that texture was strengthened by the formation of a coherent superlattice for the Nb/pure-Al film with the smallest bilayer thickness. By contrast, the texture in Ti/pure-Al films with a similar period was not as strong. The texture also decreased with increasing Λ for both the Ti/pure-Al and Nb/pure-Al films. An increase in the width of the Al (111) peak and an offset of the fiber axis from the substrate normal of 5–8° was observed in the Λ = 333 nm films prepared by using Al–1.0 wt% Cu. The decrease in texture on addition of Cu to Al was attributed primarily to an increase in interlayer roughness as a consequence of reduction in the Al(Cu) grain size. These observations were interpreted in the context of structure zone and dynamic roughness models of film growth.

Investigation of the aluminium oxidation in an oxygen plasma excited by microwaves

Al-coatings of approximately 50 nm thickness were deposited by thermal evaporation on Si(100)-wafers. The changes of the Al-films during oxygen plasma treatment in a 2.45-GHz microwave discharge at a pressure of 0.1 Pa were investigated. To study the oxidation kinetics the formed aluminium oxide was investigated using grazing incidence X-ray reflectometry (GIXR), XPS and IR and the residual Al layers were studied using grazing incidence X-ray diffractometry (GIXRD). It was observed that oxygen plasma treatment lead to reactions at low temperatures (<300°C) where thermal treatment show no noticeable effect. The developed oxide is X-ray amorphous. To quantify the alumina formation the change of the film thickness and of the Al(111) peak integral intensity of the non-reacted part of aluminium were determined time-controlled. From these results it can be concluded that two processes, an oxidation and a sputtering process, influence the oxide film growth. The crystallization behaviour was investigated by means of in situ GIXRD during post-annealing in dependence on different plasma treatments.

Oxidation of Al–Cu–Fe and Al–Pd–Mn quasicrystals

Oxidation of Al–Cu–Fe and Al–Pd–Mn quasicrystals as compared to related crystalline phases was studied in air at high temperatures. Parabolic rate constants at 840°C were about 6×10−12g2cm−4s−1 for icosahedral Al–Cu–Fe, but only 3×10−13g2cm−4s−1 for cubic AlFe. The oxide layer formed on the icosahedral alloy was inhomogeneous with respect to the oxide growth morphology. Oxide compositions were studied by Auger electron spectroscopy (AES) and X-ray induced photo electron spectroscopy (XPS). The θ-Al2O3 layer on Al–Cu–Fe did not contain any quantities of Cu or Fe that were significant according to the analyses by AES and XPS. In an advanced oxidation stage the θ-Al2O3 layer was penetrated by α-Al2O3 nodules, which contained about 5% Cu.Oxidation of Al–Pd–Mn quasicrystals was found to be strongly influenced by evaporation of Mn. Whereas the formation of δ-Al2O3 was observed at 800°C on Al–Pd–Mn quasicrystals followed by growth of needle-like θ-Al2O3, oxidation of hot isostatically pressed (HIPed) specimens at 850°C led to the formation of a θ-Al2O3 layer containing also extremely thin areas. The metallic Al(LMM) Auger peak observed in these areas was four times the oxidic Al(LMM) peak. Neither in the thick nor the thin oxide areas were Pd or Mn observed.

Dopant - Extended Defects Interactions: The Case of Aluminum

AbstractWe studied the Al redistribution in the vicinity of a well-defined EOR band formed by Ge pre-amorphization. Aluminum was implanted in Si at 3 MeV to a low dose before the preamorphization step in order to localize the as-implanted Al peak away from the EOR band. Rapid thermal annealings were performed in the temperature range [900-1000°C] for times varying from 20 s up to 200 s. The results of this study evidence a clear accumulation of the dopant on the extended defects, indicating a direct trapping mechanism of the dopant by the EOR.

Thermal redistribution of Al implanted in Si: evidences for interactions with extended defects

Al was implanted at 180 keV to a dose of 4.5 × 10 14 cm −2. Various anneals were performed in the temperature range (900–1100°C), for times varying from 15 min up to several hours. The SIMS measurements reveal anomalous redistribution of the aluminium profiles. The bulk side of the profiles diffuses normally at a rate in agreement of the Al intrinsic diffusivity, but two peaks of apparently immobile atoms are formed near the surface. Cross observations by Transmission Electronic Microscopy (TEM) prove that there is no Al precipitation, and reveal the existence of two extended defects bands, the position of which is perfectly correlated with Al peaks. This strongly suggests that these peaks are due to Al trapping on the extended defects. First simulations also support this assumption.

Texture and surface morphology improvement of Al by two-stage chemical vapor deposition and its integration in an Al plug-interconnect scheme for sub 0.25 μm metallization

A two-stage deposition with successive seed and bulk deposition steps was developed to improve the morphology and texture of chemical vapor deposited (CVD) aluminum on titanium. Dimethylaluminumhydride (DMAH) was used as the precursor. Typically, CVD Al deposited using a single deposition stage showed highly granular structure with surface “defects” resulting in films that become rough with increase in thickness creating integration problems with photolithography and etch. Here, a two-stage deposition process for CVD Al is described that significantly improves the morphology and texture of Al on titanium. In this process, the wafer surface is preconditioned with a short burst of DMAH before stabilizing gas flows or pressure. Such a treatment in the very first step results in a seed layer upon which proceeds the bulk film deposition in a subsequent step after stabilizing pressure, gas flows and equilibrating temperature. The two-stage deposition resulted in reflectivity improvement of CVD Al on Ti from ⩽ 160% to &amp;gt;210% (%Si, 480 nm) for a 3.5 kÅ thick film with complete elimination of surface defects. X-ray rocking curves show a decrease in the full width at half maximum of the Al(111) peak from 5.1° to 2.6°, indicating significantly improved texture. Secondary ion mass spectroscopy analysis of the CVD Al shows a decrease in carbon content using the two-stage deposition. The two-stage deposition for CVD Al was integrated with AlCu sputter process at temperatures below 380 °C, without a vacuum break between the CVD Al and PVD AlCu, to develop sub-0.25 μm technology via fill capability.

High-temperature multi-nuclear NMR investigation of analcime

Two analcimes of hydrothermal and diagenetic origin were investigated by in situ 29 Si, 27 Al, and 23 Na NMR from room temperature to 550 degrees C, and by TGA and DSC. The two samples dehydrate at different temperatures, and the high-temperature NMR behavior is closely related to the dehydration. The diagenetic analcime (CR-6) has higher surface area, and thus its dehydration starts and is completed at lower temperatures than the hydrothermal analcime (Hilaire). The 29 Si chemical shifts and 27 Al peak maxima become first more shielded and then less shielded with increasing temperature and are related to changes in the Si-O-Si and Si-O-Al bond angles caused by thermal expansion, distortion of framework due to H 2 O loss at high temperature, and the decreased bond length caused by rigid unit modes (RUMs). Changes in the 27 Al NMR peak widths are also correlated to H 2 O loss at high temperature and are due to the increased mobilities of H 2 O and Na. Paramagnetic impurities and motion of H 2 O and Na play important roles in the T 1 relaxation of 27 Al. The 23 Na NMR peak maxima become first more negative and then less negative with increasing temperature, with the most negative values occurring near the temperature of maximum H 2 O loss. The 23 Na peak width decreases, increases, and then again decreases with increasing temperature. These results are best interpreted as due to Na undergoing exchange between the 24(c) Na sites and other sites, possibly the 16(b) H 2 O sites, combined with collapse of the cages. The less negative 23 Na peak and increasing and then decreasing 23 Na peak widths at high temperature are due to the effects of motional averaging of the intensity due to the (+ or -1/2, 3/2) satellite transitions.

Gastrointestinal absorption of aluminium and citrate in man

Aluminium (Al) is an abundant terrestrial element, but toxic to tissues, including brain. The body is largely protected because systemic Al absorption is very low and in normal individuals almost all absorbed Al is excreted from the body. However gastrointestinal (Gl) absorption is enhanced by organic acids, including citrate. Aluminium and citrate Gl absorption was measured in three healthy males, aged 40–46. After overnight fast, subjects drank a 100 ml fruit drink containing 280 mg Al and 3.2 g citrate (104 and 167 mM, respectively). Al was measured in timed blood and urine samples by GFAAS and serum citrate by enzymatic assay. Blood Al peaked by an increase of 13 ± 2.1 μg/l after 87 ± 19 min then fell slowly over 24 h. Plasma citrate peaked after 32 min, returning to baseline by 90 min. Al was excreted at a constant rate for the first 24 h, 0.4% of the dose being excreted in urine by this time. It is unlikely that Al is absorbed as Al citrate because the blood citrate peak preceded the Al peak by 45–60 min.

パルス通電加圧焼結法による２Ｎｂ／Ａｌ組成ＭＡ粉末の初期焼結過程

The mechanically alloyed powder of 2Nb/Al composition was sintered in the temperature ranges from 973K to 1173K using either the pulse current pressure sintering (PCPS) apparatus or a conventional electric furnace. X-ray diffraction patterns for the compacts sintered by PCPS showed the weak Al peaks in halo, although the diffraction patterns for the compacts sintered by conventional electric heating did not show the Al peaks. A set of 2Nb/Al powder compact and balls of SUS304 stainless steel were sintered at 973K by PCPS in order to make clear the reason why the Al peaks were detected. Using EDX, Nb were not, but Al were detected in the circumference area in contact with 2Nb/Al compact on the surface of SUS ball. This fact indicates that evaporation and deposition of Al occured during PCPS. It can be estimated that the contact area in the earlier stages of PCPS was heated up to the order of 2000 to 4000K.

Effect of Ar Sputtering Pretreatment on the Electromigration Resistance in Al-Cu/TiN/Ti Interconnects

AbstractThe 1 µm-wide Al-0.5wt%Cu/TiN/Ti interconnect, on the oxidized Si(100) wafer without Al sputtering pretreatment on the SiO2 surface prior to Ti deposition, failed after stressing with a current density of 1 × 106 A/cm2 for 190 hr at 175°C. In contrast, the interconnect with Ar sputtering pretreatment did not fail after stressing under the same condition for 550 hr. X-ray diffraction spectra indicated that the Ar sputtering pretreatment lowered Al(111) peak intensity down to 1/46 of its magnitude. This result suggests that the improvement of electromigration resistance by Ar sputtering pretreatment is not due to Al(111) texture, which is opposite to the result of Shibata et al. (Jpn. J. Appl. 32, 4479 (1993)). The elemental concentration distribution in depth was characterized on Al-Cu/TiN/Ti multilayers with and without Ar sputtering pretreatment by using secondary ion mass spectroscopy and Auger electron microscopy. A fairly large amount of oxygen and nitrogen was found to segregate near the Al-Cu/TiN interface. The phenomenon associated with the large amount of segregated oxygen and nitrogen is attributed to the enhancement of electromigration resistance.

Room temperature growth of thin Pd films on Al(110) surfaces

High-energy ion backscattering spectroscopy (HEIS) and X-ray photoemission spectroscopy (XPS) have been used to study the growth of thin Pd layers on Al(110) surfaces at room temperature. The results are not consistent with the layered growth model presented previously for this system, but suggest instead that an AlPd alloy forms at the interface. Measured Al and Pd surface peak areas for MeV He + ions incident normal to the surface show that the Pd atoms intermix with and displace Al substrate atoms. The interface mixing was observed to continue up to about 10 ML of Pd coverage, at which point the intermixing stops. XPS measurements of the Pd 3d photopeaks show a chemical shift that is consistent with the formation of an AlPd-like compound at the interface and the growth of Pd metal thereafter.

TEM studies of solid-state reactions in sputter-deposited Nb/Al multilayer thin films

Solid state reactions in sputter-deposited Nb/Al multilayer thin films have been studied by transmission and analytical electron microscopy (TEM/AEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The Nb/Al multilayer thin films for TEM studies were sputter-deposited on (1102)sapphire substrates. The periodicity of the films is in the range 10-500 nm. The overall composition of the films are 1/3, 2/1, and 3/1 Nb/Al, corresponding to the stoichiometric composition of the three intermetallic phases in this system.Figure 1 is a TEM micrograph of an as-deposited film with periodicity A = dA1 + dNb = 72 nm, where d's are layer thicknesses. The polycrystalline nature of the Al and Nb layers with their columnar grain structure is evident in the figure. Both Nb and Al layers exhibit crystallographic texture, with the electron diffraction pattern for this film showing stronger diffraction spots in the direction normal to the multilayer. The X-ray diffraction patterns of all films are dominated by the Al(l 11) and Nb(l 10) peaks and show a merging of these two peaks with decreasing periodicity.

Elemental composition of phytoplankton in a subtropical lake: X-ray microanalytical studies on the dominant algaeSpirulina platensis(Cyanophyta) andCyclotella meneghiniana(Bacillariophyceae)

Studies were carried out on the phytoplankton of a subtropical polluted lake (Lake Maryut, Egypt) over a 1 year sampling period. The elemental composition of two major algal constituents-Spirulina platensis (Cyanophyta) and Cyclotella meneghiniana (Bacillariophyceae)—was determined from mixed plankton samples using electron-probe X-ray microanalysis. X-ray emission spectra obtained from S. platensis revealed a wide range of detectable elements. Clear positive (e.g. K-P, Na-Cl) and negative (e.g. Na-S, P-Cl) statistical correlations were interpreted in terms of elemental associations and compartmentation within the cell. C. meneghiniana had a broadly similar range of elements, but differed in the additional presence of Al and frequent peaks of Fe and Cu. The high concentration of Si reduced the detectability of other elements, causing a general reduction in mass fraction levels. Comparison of correlation coefficients derived from four sets of data revealed a clear pattern of elemental occurrence in the cel...

Growth of ultrathin Pd films on Al(001) surfaces

High-energy ion backscattering spectroscopy (HEIS) and X-ray photoelectron spectroscopy (XPS) were used to determine the growth mode and the interface structure of ultrathin Pd films deposited on Al(001) surfaces at room temperature. Measured Al and Pd surface peak areas for MeV He + ions incident normal to the surface show that Pd atoms intermix with and displace Al substrate atoms. The mixing continues for Pd coverages from 0–5 monolayers, at which point a Pd metal film begins to grow on the alloy surface. XPS measurements of the Pd 3d photopeaks show a chemical shift that is consistent with the formation of an AlPd-like compound during the mixing phase, and Pd metal thereafter. HEIS results further reveal that the alloyed overlayer as well as the Pd metal film have some degree of axial alignment with respect to the Al substrate. The XPS intensity measurements are consistent with this two-stage growth model.

Determination of aluminium in natural waters by single-column ion chromatography with indirect UV detection

The selective, sensitive and rapid determination of Al was achieved using ion-exchange separation and indirect UV detection. A solution of Ce salt was used as the eluent. The parameters influencing the shape of the Al peak, the selectivity of Al separation and sensitivity of its determination were studied. The separation of Al on chemically modified and on silica gel-based dynamically coated sorbents was achieved. With direction injection the detection limit under the optimum conditions was 50 ng/ml. The time of analysis was about 6 min. The use of a simple preconcentration procedure permitted the detection limit to be decreased. Preconcentration of Al was performed on a complexing sorbent with iminodiacetate functional groups. The technique presented was applied to the determination of Al in natural and tap waters. The technique also provides the determination of alkaline earth metals along with Al.

Effect of different exposure compounds on urinary kinetics of aluminium and fluoride in industrially exposed workers.

To conduct a field study to obtain information on the urinary concentrations of aluminium (Al) and fluoride (F-) depending on the different compounds exposed to in the aluminum industry. 16 workers from one plant that produced aluminium fluoride (AlF3), and from two plants that produced aluminium electrolytically by two different processes participated in the study for one working week. Pollutants were monitored by eight hour personal sampling every day, and urine samples were collected during the week. Al and F- were analysed in both atmospheric and urine samples by atomic absorption spectrometry and an ion selective electrode. The principal results show different characteristics of kinetic curves of Al and F- excretion in workers with different exposures. Some characteristics of excretory peaks were linked to specific exposures--for instance, after exposure to AlF3 there was one delayed Al peak associated with one delayed F- peak about eight hours after the end of the daily shift, and after mixed exposure to HF and AlF3, two F- peaks were noted, one fast peak at the end of the shift and another delayed peak at 10 hours synchronised with an Al peak. In one of the electrolysis plants, the exposure to Al and F- compounds led to the simultaneous excretion of Al and F- peaks, either as a single peak or two individual ones depending on the type of technology used on site (open or enclosed potlines). The average estimated half life of Al was 7.5 hours, and of F- about nine hours. Quantitative relations between excretion and exposure showed an association between the F- atmospheric limit value of 2.5 mg/m3 with a urinary F- concentration of 6.4 mg/g creatinine at the end of the shift, a peak of 7.4 mg/g creatinine, and 7.4 mg excreted a day. For Al, the exposure to 1.36 mg/m3 during the shift corresponded to a urinary concentration at the end of the shift of 200 microgram/g creatinine. Daily excretion of 200 micrograms corresponded to an exposure to 0.28 mg/m3. Particular differences in the behaviour of Al and F- in urine depended upon the original molecular form in the pollutant. These results reinforce the principle that, in biological monitoring, the sampling strategy and the choice of limit value should be dependent on kinetic data that take the exposure compound of the element in question into account.

Auger spectra of some Al-Cu alloys and several other alloys — a quantitative analysis

The Auger spectra of several carefully prepared Al-Cu alloys have been analysed in the light of recent models regarding the back-scattering factor and the escape depth. A detailed analysis of other bimetallic alloys taken from the literature is also presented. The analysis indicates that the choice of back-scattering factor model does not have much influence on the matrix factor and composition calculation. The calculated values of the compositional dependence of the matrix factor using different models of the back-scattering factor and escape depth do not agree with the experimental values throughout the whole concentration range. However, such a discrepancy in the matrix factor is dwarfed by the determination of the alloy composition, and it is seen that for lower concentrations of the component having a smaller atomic number in the alloy, the calculated value using Seah and Dench's (SD) model of the escape depth and that using only the density correction are better. For higher concentrations, the Tokutaka, Nishimori and Hayashi (TNH) model fits the experimental value well. For an Al-Cu alloy the three Cu peaks, very near to each other, have been combined with an Al peak to probe the compositional change with depth. A change of 0.1 nm in depth does not produce a significant change in the composition.

Effect of alumina strengthening particles on brazed joints of GlidCop Al-15 copper alloy

Brazed joints of the alumina dispersion-strengthened copper alloy were developed using resistance heating brazing with BCuP-3 braze alloy. Experimental results show that tensile strength and fatigue properties are a function of the brazing process temperature cycle. Maximum tensile and fatigue properties can be obtained by choice of an optimal braze time and temperature. However, in both tensile and fatigue tests the brazed joints exhibited low ductility. Metallography of the fractured tensile and fatigue samples showed that cracks always initiated in and propagated along the interface between the transition layer and the braze metal. EDS analysis across the joint showed that P diffused very quickly into base metal along grain boundaries. A strong Al peak (associated with the detection of Al 2O 3) was found that corresponded with the transition layer. Fractography showed an intergranular fracture pattern across this transition zone indicating that the observed segregation of alumina particles reduces the ductility of this region.