Percentage Of Aluminum Research Articles

Variability in velocity of detonation of commercial explosives as measured in field trials

The velocity of detonation (VOD) is one of the most important properties of explosives. It is essential that the explosive in the field condition detonates at its optimum rate and induces sufficient detonation pressure leading to good fragmentation. As the explosive pressure is directly proportional to the VOD of an explosive, VOD measurements indicate the performance of explosive in real time. Experiments were conducted to measure VOD in blastholes in order to understand the effect of primer quantity, contamination, hydrostatic pressure, aluminium percentage, water, sleep time, hole diameter and stemming length on VOD. The experiments were conducted in opencast coal mines and limestone quarries using resistance wire continuous VOD measurement systems.

Computational Thermodynamics Application on the Calcium Inclusion Treatment of SAE 8620 Steel

A thermodynamic study was carried out to evaluate the contents of Al, Ca, S and O at which liquid or partially liquid inclusions are formed to optimize the castability of SAE 8620 steel. Samples of steel secondary treatment (Ladle) and continuous‐casting billets (Tundish) were obtained from an electric steel mill. Entry data for this study were obtained in heats carried out in the steel plant. Furthermore, analyses were performed with a Scanning Electron Microscope (SEM) and an Energy‐Dispersive Spectrometer (EDS), as well as chemical analysis of both steel and total oxygen. In the Ladle sample, after calcium addition, inclusions had concentrations between 30 and 45% CaO and consisted mainly of calcium‐aluminates with MgO content of 10%. In the Tundish sample, inclusions contained a high percentage of alumina. Combining the characterization of inclusions with a computational thermodynamics model, the obtained results showed that the ideal range of calcium may vary between 10 and 14 ppm to form liquid inclusions with a minimum CaS content for the O, S and Al levels from SAE 8620 in this process stage. An analysis of Mg influence on the formation of calcium‐aluminates was also carried out. For contents of Mg found in aluminium‐killed steels treated with Ca, Mg does not significantly influence the formation of calcium‐aluminates inclusions. Higher calcium contents can be taken into account, depending on both the process type in steel production and the demanded product properties. The present study shows that the combined application of both inclusions characterization techniques and computational thermodynamics can drastically reduce the empiricism regarding the development of processes for the control of non‐metallic inclusions in steels. Thus, this research can contribute to increase the efficiency of manufacturing processes, improve the quality of existent products and make possible the economic development of new ones.

Fuzzy rule-based prediction of hardness for sintered HSS components

Abstract In this work, an approach for predicting the hardness of sintered high speed steel (HSS) components using fuzzy rule-based model has been discussed. Sintered HSS components have been produced using powder metallurgy (PM) process. Water-atomized and vacuum-annealed powders of T15 HSS along with other ingredients like Zn-stearate (2%) and alumina (Al2O3) were used to produce the components. The percentage of alumina, sintering temperature and sintering time were considered as the controllable process parameters while the hardness of the sintered components was considered as the response variable. A statistical design of experiments known as central composite design (CCD) has been used to collect the data for developing the fuzzy model. The performance of the fuzzy predicting model has been compared with the response surface (RS) model with respect to mean squared error (MSE), mean percentage error (MPE) and co-efficient of determination (R2). It has been observed that the fuzzy model has much better predicting capability than the RS model.

Electrical and optical properties of Al doped cadmium oxide thin films deposited by radio frequency magnetron sputtering

Cadmium oxide thin films with different percentages of aluminum doping have been synthesized via radio frequency magnetron sputtering technique. Thin films were deposited on glass and silicon substrates with different percentages of aluminum at a substrate temperature of 573 K and pressure of 0.1 mbar in Ar+O 2 atmosphere. The deposited films were characterized by studying their structural, electrical and optical properties. The X-ray diffraction pattern revealed good crystallinity with preferred (1 1 1) orientation in the films. Aluminum doping in CdO thin films were confirmed by X-ray photoelectron spectroscopic studies and actual doping percentages were also measured from it. The optical band gap was found to decrease first and then increase with increasing percentages of aluminum concentrations. The electrical conductivity was found to increase with increase of aluminum doping concentration up to 5% but for higher doping concentration (>5%) the conductivity was found to decrease.

Comparison of tribological behaviours of AlCrN and TiAlN coatings—Deposited by physical vapor deposition

TiAlN has been one of the most extensively investigated hard coatings in laboratory as well as in real life applications. However, a new ternary nitride AlCrN with high percentage of aluminum and superior properties has become the subject of ever-increasing interest. Therefore, it is worthwhile to investigate the tribological behaviours of AlCrN versus TiAlN coatings with focus on their wear mechanism. AlCrN and TiAlN coatings were deposited on cemented carbide by the arc-physical vapor deposition. Microhardness as well as nanoindentation tests have been performed to characterize the mechanical properties of the coatings. Reciprocating sliding and ball-on-disc wear tests against 4 mm diameter Si 3N 4 balls have been performed on the CETR UMT-2 test system. The coating surfaces and wear scars were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDX), X-ray diffraction (XRD) and laser confocal scanning microscope (LCSM). The results showed that the AlCrN coating exhibited lower friction coefficient and wear rate than those of the TiAlN coating under same testing condition. Combination of abrasive and oxidative wear was the main wear mechanism for the AlCrN and TiAlN coatings in both types of the sliding wear tests, in which the tribo-oxidation played an important role. However, for the ball-on-disc testing, an extra thin transferring film was formed in the center area of the wear track probably due to the different wear debris behaviours as a consequence of the different relative sliding modes. The AlCrN coating presented better performance of anti-oxidation and anti-spalling as compared with the TiAlN coating.

Prediction of hardness for sintered HSS components using response surface method

Abstract Sintered high speed steel (HSS) components have been formed using powder metallurgy (PM) process. Water-atomized and vacuum—annealed powders of T-15 grade HSS along with other ingredients like Zn-stearate (2%) and alumina (Al 2 O 3 ) were used to produce the components. The percentage of alumina, sintering temperature and sintering time were considered as the controllable process parameters while the hardness of the sintered components was considered as the response variable. A 2 3 full factorial design of experiments (DOE) was used to collect experimental data to statistically analyze the effect of process parameters on the hardness of sintered HSS components. It has been observed that the percentage of alumina, sintering temperature and also their interaction affects the hardness very significantly while duration of sintering temperature does not affects the hardness significantly. A second order response surface model (RSM) has been used to develop a predicting equation of hardness based on the data collected by a statistical design of experiments known as central composite design (CCD). The analysis of variance (ANOVA) shows that the observed data fits well into the assumed second order RSM model.

Lime, sewage sludge and mineral fertilization in a silvopastoral system developed in very acid soils

In recent years, in the European Union, sewage sludge production has been increased as a result of EU policy (European directive 91/271/EEC). Organic matter and nutrient sewage sludge contents, principally nitrogen, indicate it can be used as fertilizer. The objective of the experiment was to compare the effect of no fertilization, three doses of sewage sludge, with or without liming, and the fertilization usually used in the region applied over a period of 3 years on pasture production and tree growth in a silvopastoral system. The experiment was conducted in the northwest of Spain. The soil was very acid (soil pH = 4.5) and had very low nutrient levels, especially P, that is related to site index. It was sown with a grass mixture (25 kg ha−1 of Lolium perenne L. 10 kg ha−1 of Dactylis glomerata L. and 4 kg ha−1 of Trifolium repens L.) in Autumn 1997 under a plantation of 5-year-old Pinus radiata D. Don at a density of 1,667 trees ha−1. Liming and sewage sludge fertilization increased soil pH and reduced saturated aluminium percentage in the interchange complex (Al/IC) in the soil, coming up the effect before with liming. Medium and high sewage sludge doses increased pasture production in the two first years. In a silvopastoral system, positive tree growth response to different fertilization treatments depended on tree age, initial soil fertility, soil pH, the relationship of competition with pasture production and previous liming application.

Effect of raw materials on emissions of polychlorinated dibenzo- p-dioxins and dibenzofurans from the stack flue gases of secondary aluminum smelters

The present study was undertaken to investigate the effect of raw materials on PCDD/F emission from secondary aluminum smelters (ALS). Four plants each of aluminum ingot smelters (over 50% ingot) and secondary ALS (over 70% waste or recycled aluminum) were selected and the results compared. The secondary ALS yield much higher PCDD/Fs than the aluminum ingot smelters, or 7.94–22.76 ng/Nm 3 versus 0.57–2.67 ng/Nm 3, due to the large percentage of waste or recycled aluminum used. As for air pollution control devices (APCDs), the wet scrubber system in one of the aluminum ingot smelters exhibits an adverse effect on PCDD/F removal, due to the continuous recycle of the contaminated water through the scrubber system. Another ingot plant equipped with cartridge filter, there is a significant reduction in PCDD/F TEQ (52%). The powdered activated carbon injection at 2 kg/h (110 mg/Nm 3) in one ALS reduces 70% of the total PCDD/Fs. The average emission factor of four secondary ALS is much higher than that of aluminum ingot smelters, or 20-fold higher based on either raw materials or product. Consequently, more attention should be paid to the emission reduction of PCDD/Fs from the secondary ALS, including installation of a secondary burner, additional APCDs and the pre-cleaning of raw materials.

Effect of surface modification of Ti–6Al–4V by laser and duplex treatment on selective dissolution of aluminium

The corrosion properties of laser surface melted (LSM) Ti–6Al–4V and duplex treated Ti–6Al–4V samples were investigated in 0·05M H2SO4/0·05M NaCl solution. Duplex treatment was found to increase the corrosion potential and the corrosion current of the alloy. Semipassive regions were evident in the polarisation curves for both types of treated surface. The current in the semipassive region increased at a more rapid rate in the case of the duplex treated surface. The potential current diagrams were found to be generally noisy for both types of surface, indicating an unstable surface which undergoes continuing active dissolution and repassivation. Inductively coupled plasma (ICP) analysis of metal ions in solution was carried out following electrolysis at controlled potentials. Generally, the percentage of aluminium ions in solution was found to be high in comparison with titanium and vanadium, reaching ∼94% after polarisation in the active region at 0·4 V (cf. Ag/AgCl) for 2 h. Duplex treatment, which involved physical vapour deposition coating with TiN after laser surface melting, lowered the percentage of aluminium leached into solution to 55% after polarisation at 1·0 and 2·7 V. SEM showed that some local, shallow pitting had occurred on both the LSM and duplex treated surfaces. Energy dispersive spectroscopy showed that the aluminium content in the surface region of the LSM material after polarisation at 0·4–2·7 V (cf. Ag/AgCl) for 2 h was lower than that for the original material, having decreased from 6% in the original alloy to 0·18–0·21%. The percentage of aluminium in the surface of the duplex treated material following polarisation at the same potentials for 2 h was also low, in all cases being in the range 0·2–0.3%.

Environmental, economic and social analysis of materials for doors and windows in Sri Lanka

This paper compares the environmental, economic and social impacts of two types of doors and windows (elements), namely timber and aluminum taking into consideration the life cycle perspective. These elements are widely used for the buildings in Sri Lanka. Thus, it will help in the decision-making process when selecting materials for these elements. Major materials used for these elements are timber, brass, glass, paint, aluminum, rubber, steel and PVC boards. Environmental burdens associated with these materials are analyzed in terms of embodied energy, and environmental impacts that are relevant to Sri Lanka, such as global warming (GWP), acidification (ACP) and nutrient enrichment (NEP). Economic analysis is done using market prices of materials and affordability for those materials. Social concerns such as thermal comfort, good interior (aesthetics), ability to construct fast, and durability are analyzed based on the data collected through the questionnaires and also, interviews with the stakeholders of the buildings such as engineers, architects, building contractors and building users. It was found that timber elements are superior to aluminum elements in environmental scores (GWP, ACP and NEP). On economic score, also, timber elements are better. But on social score, aluminum elements are better than timber. It was also found that the higher the recycling percentage of aluminum, the higher the environmental favorability of the aluminum.

Synthesis of silver nanoparticles in mesoporous high-aluminum aluminosilicate matrices

A new method for the synthesis of Ag/AlxSi1−xO2−0.5x nanocomposite materials was proposed. The method is based on the use of charged mesoporous aluminosilicate matrices as nanoreactors. The porous structure of the matrices was characterized by 27Al NMR spectroscopy and nitrogen capillary sorption at 77 K. An increase in the aluminum loading destroys the matrix structure and decreases the specific surface area. The resulting aluminosilicates were used as matrices for the synthesis of silver nanoparticles. The nanocomposites were examined by transmission electron microscopy and chemical analysis to estimate the silver percentage in specimens. Silver nanowires (∼20% Ag) are formed in the low-aluminum (<10 mol.%) matrices, whereas an increase in the aluminum percentage affords both nanowires and spherical particles 3–10 nm in size and decreases the total amount of silver in the nanocomposite.

Influence of Aluminium on Performance of HTPB-based Aluminised PBXs

The paper describes the development of aluminised plastic-bonded explosives (PBXs) based on aluminium and nitramine explosives using hydroxy-terminated polybutadiene as polymer matrix. The PBXs were processed as per standard procedures. Compositions with different formulations were prepared by varying the percentages of aluminium and RDX and their explosive properties, including velocity of detonation (VOD), peak overpressure, duration, impulse and sensitivity to different types of stimuli, were studied. The experimental and theoretical values of the VOD have been compared. It is observed that about 15 per cent aluminium content in the aluminised PBXs shows the optimum VOD.

Mixture and pore volume fraction estimation in Al2O3/SiC ceramic cake using artificial neural networks

In this study, the percentage of alumina in produced Al2O3/SiC ceramic cakes and the pore volume fraction in the ceramic cake are obtained by designing a back propagation neural network that uses a gradient descent learning algorithm. Artificial neural network (ANN) is an intelligent technique that can solve non-linear problems by learning from the samples. Therefore, some experimental samples have been firstly prepared to train the ANN to get it to give (to estimate) pore volume fraction (%) and Al2O3 wt% in Al2O3/SiC ceramic cake for any given SiC (g) amount. The most important point in this paper is that after ANN is trained using some experimental samples, it has given approximately correct outputs for some of experimental inputs that have not been used in the training. Firstly, to prepare a training set some results are experimentally obtained. In these experiments, we have obtained Al2O3/SiC ceramic cakes; SiC is obtained commercially, particles dimensions are obtained by a chemical process method. In order to prepare ceramic preforms, a chemical process was used rather than one using a mixing of ceramic powders to obtain porous Al2O3/SiC ceramic foams. These products were heated in a ceramic crucible in a furnace. It foamed and an Al2O3/SiC cake was obtained. Resulting Al2O3 grains had a 3D honeycomb structure and SiC particles were in the alumina grains. Consequently, a homogeneous powder mix and porosity were obtained within the cake. The morphology of the powder connections was a networking with flaky particles. These flaky alumina particles provided a large amount of porosity, which was desired for ceramic preforms to allow liquid metal flow during infiltration. A resulting high porous ceramic cake (preform) was obtained. In the preparation of ANN training module, the amount of SiC (g) is used as the input and the percentage of alumina in produced Al2O3/SiC ceramic cake and high porous ceramic cake (preform) are used as outputs. Then, the ANN is trained using the samples obtained in the experimental processes. In this paper, the alumina and pore volume fraction in the produced cake have been estimated for different amounts of SiC using neural network efficiently instead of time consuming experimental processes.

Synthesis and characterization of zirconium carbide-reinforced iron-based composite

The ZrC-reinforced iron-based composites (Fe–ZrC) were synthesized by a simple, cost-effective process involving aluminothermic reduction of blue dust (Fe2O3) and zircon sand (ZrSiO4) in the presence of carbon. The aluminothermic reduction of blue dust and zircon sand, being highly exothermic in nature, essentially leads to a self-propagating high-temperature synthesis (SHS) of the Fe–ZrC composite. The composites were synthesized with varying percentages of aluminum and carbon in the charge mixture. Both aluminum and carbon play important role in the reduction of zirconia. The composites have been subsequently characterized by techniques of optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). It has been found that along with ZrC, other phases (Fe3Al, FeZr4) also formed depending upon the charge composition. The charge composition has been optimized to get reasonable recovery of Zr in the form of ZrC. The mechanical properties, such as hardness and wear resistance of the composite, corresponding to the optimum charge composition have also been evaluated. The composite has been found to possess promising abrasive wear resistance property along with good high-temperature stability.

Phalaris persistence under rotational grazing on a highly acidic soil on the south-west slopes of New South Wales

Phalaris (Phalaris aquatica L.)-based pastures were established with and without lime in 1992 as a part of a long-term pasture–crop rotation experiment (Managing Acid Soils Through Efficient Rotations). Pre- and post-grazing pasture dry matter, phalaris basal cover and proportion of phalaris in sward were measured since 1992. In general, phalaris persisted well and its productivity was high on the highly acidic soil studied in the current experiment, and this was improved on the limed treatment. After establishment in 1992, the average proportion of phalaris in spring 2001 was 32.1% in the limed treatment and 15.6% in the unlimed treatment. Basal cover at the end of summer 2002 was 4.5% and 2.0% for the limed and unlimed treatments, respectively. The results from the current experiment showed that subsurface acidity (low pHCa and high exchangeable aluminium percentage in the 10–30 cm soil depth) had significant impacts on phalaris persistence. It is concluded that subsurface pH was one of the major constraints for the persistence of phalaris. The long-term management of soil acidity should aim to eliminate the exchangeable aluminium from the soil profile by maintaining a high pHCa (5.5 or above) in the 0–10 cm soil depth. Rainfall during growing season had no direct effect on phalaris persistence. Nevertheless, feed scarcity in dry years due to moisture stress often exacerbated grazing pressure on phalaris, which may affect the phalaris persistence indirectly. It is the grazing management in autumn and summer that had significant effects on phalaris persistence. It is suggested that rotational grazing plus strategic rest if possible in autumn could prolong the life of phalaris-based pastures. Repeated heavy grazing should be avoided during summer, particularly after light to moderate summer rainfall events have stimulated sprouting.

Investigation of the aluminium biokinetics in humans: a 26Al tracer study

Despite the well-known toxicity of aluminium in chronic renal failure, a solid database on its biokinetics has been difficult to establish. A highly sensitive method using 26Al as tracer and accelerator mass spectrometry (AMS) for detection was used. No perturbing background and saturation effects were taken into account using a delta function input of aluminium in time. Aluminium absorption, distribution, speciation and excretion in six healthy volunteers and in two patients with chronic renal failure were investigated following administration of a single oral or i.v. dose of 26Al. Serial samples of blood and urine were taken. In a speciation study, the time dependence of the binding of 26Al to low-molecular weight molecules in serum was investigated. The measured data were compared and interpreted with simulations in an open compartmental model. Fractional absorption, distribution, excretion and time constants for the aluminium transport were determined. Typical intestinal absorption rates for AlCl3 were found to be in the range of 10−3. The ultrafiltrable percentage of aluminium in serum of one volunteer was estimated to be 5.6±0.8%. Differences between healthy volunteers and patients with chronic renal failure were deduced. The employed method using 26Al and ams has proven to be highly sensitive for investigations of aluminium biokinetics at the ultra-trace element level. With the model, the measured values of 26Al in serum and urine were used to precisely determine absorption, speciation, distribution, retention and excretion of aluminium in humans.

Influence of aluminum additions on phase formation in boron nitride films deposited by magnetron sputtering

Boron nitride (BN) thin films have been deposited by magnetron sputtering of an hexagonal BN (h-BN) target with an additional flux of aluminum provided by a special Al sputtering target. Up to an aluminum percentage of about 1.0 at. % the formation of the cubic BN (c-BN) phase was not influenced by the aluminum addition. An Al content of 1.3 at. % was connected with a remarkable delay in the transition from h-BN to c-BN growth as well as a certain deterioration in the crystal quality. An aluminum flux causing a concentration of 1.5 at. % did prevent the growth of the cubic BN phase completely. The dynamics of impurity incorporation were investigated using secondary ion mass spectrometry measurements. We found that the aluminum electrode plays an important role in the incorporation of hydrogen in the films. In connection with other results it can be concluded that for both h-BN and c-BN strong evidence for substitutional incorporation of aluminum on boron sites exists. Cross-section transmission electron microscopy revealed that the formation of the c-BN phase starts at particular sites (c-BN nuclei) which broaden via a wedge shaped growth up to the point where the c-BN nucleation is completed and a nanocrystalline, pure c-BN layer grows. Hence, the interface between h-BN and c-BN has a jagged shape. This structure of the films h-BN/c-BN was found to be essentially independent of the Al incorporation.

Surface composition analysis of failed cementless CoCr- and Ti-base-alloy total hip implants.

The surfaces of retrieved failed cementless total hip implants made of cobalt-chromium-molybdenum casting alloy and of wrought titanium 6-aluminum 4-vanadium alloy were studied with the use of scanning-electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). New implants of the same make served as controls. The XPS scans revealed a dense carbon layer on the entire analyzed specimen. The relative composition of the titanium alloy implants showed an overall agreement with the international standards for implants for surgery, and the overall surface composition did not change over the period of the implantation. However, an inhomogeneous distribution of the constituents could be demonstrated in the retrieved as well as in the new MEC-screw rings made of TiAl6V4 alloy, an implant that has been linked to a high early failure rate. In the CoCr-alloy components (Lord-screw rings) a high percentage of aluminum, mainly organized in aluminum inclusions, was found in the retrieved as well as in the new implants.

Potential dependent selective dissolution of Ti–6Al–4V and laser treated Ti–6Al–4V in acid/chloride media

The corrosion properties of Ti–6Al–4V and laser surface melted (LSM) Ti–6Al–4V samples were investigated in 0.05 M H2SO4/0.05 M NaCl solution. Laser surface treatment was found to increase the corrosion potential and decrease the corrosion rates of the alloy. The current–potential profile of the LSM was found to be generally noisy below 0.5 V, indicating an unstable surface, which undergoes continuous dissolution and repassivation. However, above 0.5 V the LSM specimen exhibited higher corrosion current compared to the untreated alloy. Inductively coupled plasma (ICP) analysis of metals in solution was carried out after controlled potential electrolysis. Generally, the aluminium percentage was found to be the highest in solution compared to titanium and vanadium. The aluminium percentage in solution reached 94% compared to titanium and vanadium upon polarization in the passive region at 1.01 V. SEM showed that some local and shallow pitting to occur in both the untreated and LSM alloy. EDS results showed that aluminium composition of the electrolysed alloy surface is lower than the original material composition, and decreased from 6% in the original alloy to 0.18% after two hours of electrolysis of the LSM specimen.

Speciation of aluminum in soil extracts using cation and anion exchangers followed by a flow-injection system with fluorescence detection using lumogallion.

Flow-injection analysis (FIA) with fluorescence detection of aluminum using lumogallion was applied to the chemical speciation of aluminum in soil extracts after the separation of aluminum species with ionic exchangers. Aluminum complexes with organic substances (anion species) can be specified from other species by using a strongly acidic cation exchanger in the pH range of 3 to 5. Furthermore, aluminum can be separated into three categories, namely, (i) the Al3+ and Al-OH complex, (ii) aluminum organic complexes (cation species), and (iii) its anion species by using a strongly acidic and a weakly acidic cation exchanger at around pH 5. A considerable percentage of water-soluble aluminum in soils was found to be complexes with humic substances.