Incorporation Of Aluminum Research Articles

Plasma-enhanced atomic layer deposition of barium titanate with aluminum incorporation

Plasma-enhanced atomic layer deposition (PEALD) of ultrathin (∼7 nm) slightly Ti-rich BaxTiyOz (BTO) films with different Al-doping concentration ([Al]/([Al] + [Ba] + [Ti]) = 0 to 22 at%) was studied. In particular, the effects of Al-doping in BTO on compositional, crystallographic and electrical properties were investigated. Previously, BTO films with a Ti cation composition, [Ti]/([Ba] + [Ti]) = ∼60 at% was reported to be advantageous for crystallization, resulting in superior dielectric properties. These Ti-rich BTO films, however, suffered from high leakage currents, necessitating the change in its crystalline structure as well as elemental composition. By incorporating Al2O3 into the BTO films, the leakage current can be controlled, where the BTO films with an Al-doping concentration of 12 at% showed a leakage current reduced by one order of magnitude compared to un-doped BTO (i.e., ∼10−7 to ∼10−6 A/cm2 at +1.6 V) without a significant drop of the dielectric constant (43,un-doped to 40, Al-doped).

Synthesis of aluminum-containing hierarchical mesoporous materials with columnar mesopore ordering by evaporation induced self-assembly

The incorporation of aluminum into the silica columns of hierarchical mesoporous materials (HMMs) was studied. The HMMs were synthesized by a combination of hard and soft templating methods, forming mesoporous SBA-15-type silica columns inside the pores of anodic aluminum oxide membranes via evaporation induced self-assembly (EISA). By adding Al-isopropoxide to the EISA-mixture a full tetrahedral incorporation of Al and thus the creation of acid sites was achieved, which was proved by nuclear magnetic resonance spectroscopy. Electron microscopy showed that the use of Al-isopropoxide as an Al source for the HMMs led to a change in the mesopore ordering of silica material from circular hexagonal (donut-like) to columnar hexagonal and a 37% increase in specific surface (BET surface). These results were confirmed by a combination of nitrogen physisorption and small-angle X-ray scattering experiments and can be attributed to a swelling of the P123 micelles with isopropanol. The columnar mesopore ordering of silica is advantageous towards the pore accessibility and therefore preferential for many possible applications including catalysis and adsorption on the acid tetrahedral Al-sites.

Rootlike Morphology of ZnO:Al Thin Film Deposited on Amorphous Glass Substrate by Sol-Gel Method

Zinc oxide (ZnO) and aluminum doped zinc oxide (ZnO:Al) thin films have been deposited onto a glass substrate by sol-gel spray coating method at atmospheric pressure. X-ray diffractometer (XRD), scanning electron microscopy (SEM), and UV-Vis spectrophotometer have been used to characterize the films. XRD spectra indicated that all prepared thin films presented the wurtzite hexagonal structure. SEM images exhibited rootlike morphology on the surface of thin films and the shortest root diameter was about 0.219 μm. The UV-Vis absorption spectra exhibited the absorption edges that were slightly shifted to the lower wavelength. From this result, the incorporation of aluminum into the ZnO involved a slight increase in the optical band-gap of films. The optical bands of films were 3.102 eV, 3.115 eV, 3.118 eV, 3.115 eV, 3.109 eV, and 3.109 eV for ZnO, ZnO:Al 2%, ZnO:Al 4%, ZnO:Al 6%, ZnO:Al 8%, and ZnO:Al 10%, respectively. Increase of Al doping concentration in ZnO films contributed to the increase of their optical band-gap which can be explained by the Burstein-Moss effect.

P-Type Doping of 4H- and 3C-SiC Epitaxial Layers with Aluminum

Exhaustive experimental study of aluminum incorporation in epitaxial 4H-SiC and 3C‑SiC films grown by chemical vapor deposition (CVD) was performed. The influence of polytype and substrate orientation was verified. Role of principal process conditions (growth temperature and pressure, deposition rate, chemical environment) was investigated in details. Finally, the evolution of optical properties of resulting SiC films with Al content was examined.

Sol-gel synthesis of mesoporous aluminosilicates with a narrow pore size distribution and catalytic activity thereof in the oligomerization of dec-1-ene

Porous aluminosilicates with Si/Al ratio of 80 have been prepared by the sol-gel synthesis using tetraethyl orthosilicate (TEOS) and aluminum nitrate (Al(NO3)3*9H2O). It has been shown that the precipitation pH value and the gelation conditions strongly affected characteristics of the porous structure, the incorporation of aluminum into the silicate framework, and the surface acidity. It has been found that the implementation of the sol-gel synthesis initially in the acidic medium followed by the alkaline one allowed producing the mesoporous aluminosilicate with the specific surface area SBET of 660 m2 g−1, the mesopore volume V of 0.74 cm3 g−1, and the pore size distribution within the range of 2–5 nm. The high activity and selectivity of synthesized aluminosilicates in the oligomerization of dec-1-ene have been revealed.The conversion of dec-1-ene reached 92%. The formation selectivity of dec-1-ene oligomers with the oligomerization degree n = 2–3 amounted 87%.

Influence of calcium to silica ratio on aluminium uptake in calcium silicate hydrate

Aluminium uptake in calcium silicate hydrate (C–S–H) was studied at different Ca/Si ratios from 0.6 to 1.6 at 20°C.Aluminium incorporation in C–S–H depends on the total amount of aluminium present in the sample. At low Al/Si ratio (≤0.05), the major part of the aluminium is taken up in C–S–H while at higher Al/Si ratio, the precipitation of stratlingite and/or katoite limits the Al/Si ratio in C–S–H to ≈0.15, regardless of the Ca/Si ratio.A strong correlation between the aqueous aluminium concentration and the aluminium uptake in the solid phase is observed. At high Ca/Si ratios, aluminium in C–S–H is observed mainly as octahedrally coordinated Al(VI) in TAH and the aluminium uptake increases with the aqueous aluminium concentration. At low Ca/Si ratio (≤0.8), aluminium is observed mainly as tetrahedrally coordinated Al(IV) and low aqueous aluminium concentrations (below detection limit) indicate a high affinity of aluminium towards C–S–H.

Post-stishovite transition in hydrous aluminous SiO2

Lakshtanov et al. (2007) showed that incorporation of aluminum and some water into SiO2 significantly reduces the post-stishovite transition pressure in SiO2. This discovery suggested that the ferroelastic post-stishovite transition in subducted MORB crust could be the source of reflectors/scatterers with low shear velocities observed in the mid to upper lower mantle. A few years later, a similar effect was observed in anhydrous Al-bearing silica. In this paper, we show by first principles static calculations and by molecular dynamics using inter-atomic potentials that hydrogen bonds and hydrogen mobility play a crucial role in lowering the post-stishovite transition pressure. A cooperative redistribution of hydrogen atoms is the main mechanism responsible for the transition pressure reduction in hydrous aluminous stishovite. The effect is enhanced by increasing hydrogen concentration. This perspective suggests a potential relationship between the depth of seismic scatterers and the water content in stishovite.

Aluminum incorporation efficiencies in A- and C-plane AlGaN grown by MOVPE**Project supported by the National Natural Science Foundation of China (Grant Nos. 61504128, 61504129, 61274041, and 11275228), the National Basic Research Program of China (Grant No. 2012CB619305), the National High Technology Research and Development Program of China (Grant Nos. 2014AA032603, 2014AA032609, and 2015AA010801), and the Guangdong Provincial Scientific and Technologic

The aluminum incorporation efficiencies in nonpolar A-plane and polar C-plane AlGaN films grown by metalorganic vapour phase epitaxy (MOVPE) are investigated. It is found that the aluminum content in A-plane AlGaN film is obviously higher than that in the C-plane sample when the growth temperature is above 1070 °C. The high aluminum incorporation efficiency is beneficial to fabricating deep ultraviolet optoelectronic devices. Moreover, the influences of the gas inlet ratio, the V/III ratio, and the chamber pressure on the aluminum content are studied. The results are important for growing the AlGaN films, especially nonpolar AlGaN epilayers.

Revealing the effects of nitrogen on threshold current density in GaNxAsyP1−x−y/GaP/AlzGa1−zP type I QW laser structures by hydrostatic pressure

We present a comprehensive theoretical analysis of threshold current in dilute nitride direct bandgap Ga(NAsP)/GaP/AlGaP quantum wells (QW) on silicon substrates using model calculations. The pressure dependence of band structure, radiative and non-radiative recombination rates, optical confinement factor, transparency- and threshold-carrier densities are calculated in a range of 0–1GPa at room temperature. The effect of aluminium incorporation into cladding-layer Gallium Phosphide (GaP) with the employed five-layer slab waveguide model is considered and we have shown that incorporation of Aluminium (Al) into cladding-layer GaP increases the photon confinement in well layer. It is found that incorporation of Nitrogen (N) into GaAsP reduces the non-radiative Auger recombination rates which brings an improvement in threshold current. The comparison of our calculated results with that of the experimental data indicates that the Auger effect involving CHCC process can be considered as the dominant non-radiative loss mechanism at 300K.

A General Method for Aluminum Incorporation into High-Silica Zeolites Prepared in Fluoride Media

The fluoride method of zeolite synthesis yields materials with unique characteristics such as high Si/Al ratio, large crystal size, and hydrophobic properties, and it has been advantageous for the synthesis of new pure-silica or high-silica zeolites. It is often difficult, however, to incorporate aluminum—and thus bring about useful catalytic properties—in materials prepared through the fluorite method. In this report, we show that FAU-type zeolites are an effective source of aluminum to the growing crystals in the high-silica LTA-type zeolite synthesis (ITQ-29). A key advantage of using aluminosilicate zeolite crystals as aluminum source in fluoride media was the high reproducibility and easy control of the Si/Al ratio of the product. The broad applicability of this methodology was demonstrated in the synthesis of several high-silica zeolites in fluoride media: we report the synthesis of aluminosilicate ITQ-12 (ITW-type zeolite). Other more conventional aluminosilicate zeolites (CHA-, *BEA-, and STT-type...

Synthesis of NbFAPO-5 and NbFAPSO-5 Molecular Sieve by Hydrothermal Method and Comparison of Their XRD Patterns and Their Acidic Properties Evaluation by Infrared Spectroscopy

Mesoporous molecular sieves, NbFAPO-5 and NbFAPSO-5 were hydrothermally synthesized with AlPO-5 type structure. Characterization of these molecular sieves was performed by X-ray diffraction to determine their structure, ICP-EAS for their elemental composition and infrared spectrometry to access their acidic properties. X-ray diffraction patterns confirmed well AlPO-5 type structure. ICP-EAS analysis confirmed the incorporation of silicon (12.9%), aluminium (15.4%), phosphorous (21.9%), iron (5.62%) and niobium (0.39%) into AlPO-5 framework. Infrared spectrometry analysis showed that both Bronsted and Lewis sites were found in the synthesized samples. The presence of both Bronsted and Lewis acid site led to bifunctional function of NbFAPO-5 and NbFAPSO-5 molecular sieve in promoting both oxidation and esterification reactions. NbFAPSO-5 Bronsted acidity was higher than that of NbFAPO-5 and for Lewis acidity, NbFAPO-5 was higher than that of NbFAPO-5.

Effects of crystal size, acidity, and synthesis procedure on the catalytic performance of gallium and aluminum MFI zeolites in glycerol dehydration

The influence on gas-phase catalytic glycerol dehydration of crystal size (S: small, or L: large crystals), acidity, and synthesis procedure for isomorphous incorporation of gallium (Ga-S; Ga-L) or aluminum (Al-S; Al-L) in MFI zeolites was studied. The main product observed was acrolein, with the undesirable parallel formation of deactivating coke molecules such as polyglycols and polyaromatics. The Ga-S zeolite showed the best performance in this reaction, as it provided a combination of adequate accessibility to the microporous system and weak Brønsted acid sites. The chemical and structural properties of the fresh MFI zeolites were studied by X-ray diffraction, nitrogen sorption measurements, scanning electron microscopy, temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, and 27Al and 29Si MAS-NMR. Solid-state 13C MAS-NMR and thermogravimetric analyses of the spent MFI zeolites confirmed the differences in the nature and amounts of the carbonaceous deposits formed. The polyglycols were preferentially formed on the external surface of the zeolite crystals, as expected due to the greater exposed area. On the other hand, the polyaromatic compounds formed were more abundant inside the micropores of the MFI zeolites, especially those composed of larger crystals and with a greater number of strong Brønsted acid sites.

Al Incorporation at All Growth Stages of Al x Ga1−x N Epilayers Using SiN Treatment

Al compositional distribution of Al x Ga1−x N epilayers grown on SiN-treated sapphire substrate by atmospheric pressure metalorganic vapor phase epitaxy is investigated. The growth process was interrupted at various stages allowing a systematic study of Al x Ga1−x N epilayers during the smoothing process. A transition from three-dimensional (3D) to two-dimensional (2D) growth mode is revealed by in situ laser reflectometry (λ = 632.8 nm) as well as by atomic force microscopic images. Then, ion mass spectrometry analysis was performed to obtain the solid Al composition (x) profile as well as by photoluminescence measurements. Moreover, the in situ reflectivity signal is simulated; thereby Al x Ga1−x N growth rate is derived and compared with that of GaN layer in order to study the effect of the aluminum incorporation on the growth mechanism. It is worth emphasising that the growth mode of Al x Ga1−x N layers is dictated by SiN treatment, which influences the Al compositional distribution. Electron mobility and refractive index against the thickness of Al x Ga1−x N layers have similar trends, which confirm a competitive mechanism between growth mode and Al incorporation. Therefore, the correlation between the Al composition and morphological, optical, and electrical properties of Al x Ga1−x N layers is established.

Hydrogenolysis of glycerol to propanediols on Cu–Ca–Al hydrotalcites derived catalysts

A series of Cu–Ca–Al hydrotalcite derived catalysts were prepared by the co-precipitation method. Their catalytic activities were evaluated in the hydrogenolysis of glycerol. The catalysts were characterized by XRD, SEM, TEM, ICP, NH3-TPD, CO2-TPD and H2-TPR. It was observed that the incorporation of calcium and aluminum in the Cu–Ca–Al catalyst improved the conversion of glycerol and promoted the generation of 1,3-PDO. This is due to the appropriate acidity and basicity of the catalyst, which is confirmed by NH3-TPD and CO2-TPD. The conversion of glycerol over the catalyst with a Cu–Ca–Al mole ratio of 1:3:5 was up to 73.2 % with 42.6 % selectivity to 1,2-PDO and 9.1 % selectivity to 1,3-PDO. Effects of the reaction time, reaction temperature and initial hydrogen pressure on the conversion and selectivity were systematically investigated.

Effects of temperature on the atomic structure of synthetic calcium–silicate–deuterate gels: A neutron pair distribution function investigation

Due to the nanocrystallinity of the calcium–silicate–hydrate (C–S–H) gel in ordinary Portland cement-based paste combined with the presence of nanoscale heterogeneities such as varying calcium-to-silicon ratios and incorporation of aluminum in the structure, standard characterization techniques fail to fully capture the complex atomic structure and nanoscale morphology of this important binder phase. Here, neutron pair distribution function (PDF) analysis is applied to a range of deuterated C–S–H gels with varying Ca/Si ratios (denoted C–S–D). In situ temperature measurements reveal that the local atomic bonding environments in C–S–D gel undergo large structural rearrangements due to exposure to elevated temperature (above~200°C), including the collapse of the C–S–D gel interlayer spacing to 9.6Å and the emergence of a disordered dicalcium silicate phase (similar to larnite). At lower elevated temperatures, the atom–atom correlations are dominated by scattering from deuterium atoms and therefore can be used to quantify the dehydration kinetics.

Possible mechanism of structural incorporation of Al into diatomite during the deposition process I. Via a condensation reaction of hydroxyl groups

The structural incorporation of aluminium (Al) into diatomite is investigated by preparing several Al–diatomite composites by loading an Al precursor, hydroxyl aluminum polymer (Al13), onto the surface of diatomite and heating at various temperatures. The results indicate that Al was incorporated and implanted into the structure of diatomite by the condensation reaction of the hydroxyl groups of Al13 and diatomite, and the Si–O–Al(OH) groups were formed during the condensation reaction. Al incorporation by the condensation reaction of hydroxyl groups of Al13 with single silanols of diatomite occurred more readily than that with geminal silanols. The Al incorporation increased solid acidity of diatomite after Al incorporation. The acidity improvement was various for different types of acid sites, depending on the preparation temperature of the Al-incorporated diatomite. Both Brønsted and Lewis acid sites increased greatly after heating at 250 and 350°C, but only L acid sites significantly improved after heating at 500°C. These results demonstrate that the structural incorporation of Al3+ ions into diatomite can occur by the condensation reaction of the hydroxyl groups of the Al precursors and diatomite. Moreover, the rich solid acid sites of Al-incorporated diatomite show its promising application as a solid acid catalyst.

Effect of Heat-Treatment and Composition on Structure and Luminescence Properties of Spinel-Type Solid Solution Nanocrystals.

The compositional dependence of the structure and properties of spinel-type solid solutions, Zn(A,Ga)2O4 was investigated by comparison with samples hydrothermally prepared and those after heat treatment at 1000 °C in air. Nanocrystalline spinel-type solid solutions in the whole composition range in the ZnAl2O4-ZnGa2O4 system were directly formed from the aqueous precursor solutions of ZnSO4, Al(NO3)3 and Ga(NO3)3 under hydrothermal conditions at 180 °C for 5 h in the presence of tetramethylammonium hydroxide. The incorporation of aluminum into the lattice, Zn(AlxGa1-x)2O4, resulted in lower crystallinity of the spinel. The relationship between the lattice parameter of as-prepared samples and the Al atomic ratio in the spinel composition was slightly apart from the ideal linear relationship that was obtained in the samples after heat treatment at 1000 °C. The optical band gap of both as-prepared solid solutions and those heat treated linearly increased from 4.1~4.2 to 5.25 eV by the incorporation of aluminum ion into the lattice, Zn(AlxGa1-x)2O4. Two main broad-band emission spectra centered at around 360 and 430 nm in the range of 300-600 nm were observed in the spinel solid solutions under excitation at 270 nm, thought their broad-band emission spectra and their peak wavelengths subtly changed depending on the composition and heat treatment.

Influence of Site Competition Effects on Dopant Incorporation during Chemical Vapor Deposition of 4H-SiC Epitaxial Layers

An exhaustive experimental study of the influence of C/Si ratio on voluntary incorporation of nitrogen (N) and aluminum (Al) in 4H-SiC thin films is presented. The films were grown by chemical vapor deposition (CVD) in a horizontal, hot wall CVD reactor on Si- and C-face substrates, under Si-rich and C-rich conditions. Under some conditions the observed variation of dopant incorporation with C/Si ratio could be clearly attributed to the site competition effects, while in several cases other mechanisms have to be taken into account.

Nanocomposite TiAlBN Coatings as a Corrosion Protection Layer for AZ91 Mg Alloy Substrate in NaCl

Magnesium alloys create increasing interest in structural application where weight reduction is vast concern. However, one of magnesium drawback in various applications is low corrosion resistance. In general, a hard coating can be applied on metal to combat such a problem. AlN and TiN coatings are most widely utilized in manufacturing area i.e for structural application due to its high hardness, high chemical stability, and excellent adhesion to substrates. Most recent, TiAlBN coating catch many attentions due to its superior properties than other most studied hard coating. The incorporation of aluminium in the cubic face centered TiN structure on Ti sites leads to deformation and strengthening of the crystal structure of the coating together. Moreover, incorporation of BN in this coating should improve and enhanced the corrosion resistance of Mg alloy. Therefore, in this study, TiAlBN coating have been chosen to be deposited on Mg alloy using reactive magnetron sputtering together with AlN and TiN coatings for comparison study. During depositions, target power, working pressure and bias voltage are optimized for each coating. Analysis on the effect of AlN, TiN and TiAlBN coatings on Mg alloy substrate include thickness measurement and microstructure by scanning electron microscope (SEM). Coatings phase were analysed using glancing angle X-ray diffraction analysis (GAXRD) and corrosion properties were evaluated using potentiodynamic polarization in NaCl solution. TiAlBN shows better performance of corrosion protection with the least corrosion rate (penetration rate = 0.20 mm/yr; mass loss rate=0.97g/m2d) in sodium chloride (NaCl) solution although having the lowest coating thickness (412 nm).

Simultaneous removal of cations and anions from waste water by bifunctional mesoporous silica

A novel, bifunctional mesoporous silica (Al-SBA-15-G) capable of the simultaneous removal of cations and anions from wastewater was synthesized by the incorporation of aluminum into the framework of SBA-15 followed by the immobilization of melamine-based dendrimer groups onto the surface of the Al-substituted SBA-15. This material was characterized by XRD, SEM, TEM, NH3-TPD, FTIR, and N2 adsorption/desorption. The bifunctional Al-SBA-15-G contains a large amount of aluminum hydroxyl groups and amine groups, which were considered to be responsible for the formation of cation and anion complexes, respectively. Due to the steric effects of the melamine-based dendrimer groups, the aluminum hydroxyl and amine groups on Al-SBA-15-G keep an appropriate distance with a cooperative manner and avoid spontaneous neutralization reactions. The maximum adsorption capacities toward Cu2+ and SO42− of Al-SBA-15-G were 0.763mmol/g and 0.511mmol/g, respectively. A mechanism for the simultaneous adsorption of cations and anions by Al-SBA-15-G is proposed. As a bifunctional adsorbent, Al-SBA-15-G can potentially be used for the simultaneous removal of cations and anions from wastewater.