Incorporation Of Aluminum Research Articles

Dynamics of biogenic silica dissolution in Jiaozhou Bay, western Yellow Sea

Dissolution of biogenic silica (BSi) in coastal environments is important for marine productivity. Understanding this process is central to assessing the global silicon cycle, which is closely linked to the global carbon cycle. BSi dissolution experiments were conducted to explore factors influencing this process, and to better understand the regeneration of silicic acid in Jiaozhou Bay sediments. The results showed that the BSi content in sediments varied from 0.44% to 2.73% (average, 1.90%). The horizontal distribution of BSi was slightly greater in the north of the bay than in the south, and was similar to the distributions of Chl-a and phytoplankton abundance. Experiments conducted under continuous flow conditions showed that the dissolution kinetics of BSi was non-linear; based on these data the mean solubility of BSi was calculated to be 277μM-Si for sediment samples, 297μM-Si for sediment trap samples and 559μM-Si for diatom–sediment mixture. The dissolution rate constant for BSi in surface sediments varied from 1.7 to 6.8yr−1. The highest rate was found for tidal flat sediments, and the lowest rate was found in the mouth of the bay; these values for sediment material are higher than those reported for sediments from the Arabian, Scotia and Norwegian seas. For the sediment trap samples the dissolution rate constant ranged from 1.5 to 3.0yr−1, and showed no obvious variation among the different sampling periods. Structural incorporation of trace aluminum to the BSi surface, and the specific surface area and the reactivity of BSi affected both the solubility and dissolution dynamics of BSi in Jiaozhou Bay sediment. BSi dissolution in the water column and sediment appears to be the key process that sustains diatoms as the dominant phytoplankton species in Jiaozhou Bay.

Crystallographic ordering of aluminium in laueite at Hagendorf-Süd

AbstractCrystals of laueite, Mn2+Fe23+(PO4)2(OH)2·8H2O, from the Cornelia mine open cut, Hagendorf Süd, Bavaria, are zoned due to aluminium incorporation at the iron sites, with analysed Al2O3contents varying up to 11 wt.%. Synchrotron X-ray data were collected on two crystals with different Al contents and the structures refined. The laueite structure contains two independent Fe3+-containing sites;M2 andM3, which alternate in 7 Å corner-connected octahedral chains. The coordination polyhedra are different for the two sites,M2O4(OH)2andM3O2(OH)2(H2O)2respectively. The structure refinements show that Al preferentially orders into siteM3. Refined site occupancies forM2 andM3 for the two crystals are: for crystal L-1,M2 = 0.70(1) Fe + 0.30(1) Al,M3 = 0.54(1) Fe + 0.46(1) Al and for crystal L-2,M2 = 0.67(1) Fe + 0.33(1) Al,M3 = 0.48(1) Fe + 0.52(1) Al. For crystal L-2, the octahedral chains have dominant Fe in M2, alternating with dominant Al inM3 along the chain, an ordering phenomenon not previously reported for laueite-related minerals.

Influence of the aluminum incorporation on the properties of electrodeposited ZnO thin films

Undoped and aluminum doped zinc oxide thin films were successfully deposited by electrodeposition technique from aqueous solution onto ITO substrates at optimized experimental conditions. The variations of the structural, electrical and optical properties with the doping concentration were investigated. X-ray diffraction analysis showed typical patterns of the hexagonal ZnO structure for both doped and undoped films. The films are single phase and polycrystalline with the (002) preferred orientation. The grain size, texture coefficient and optical band gap values were evaluated for different aluminum salt concentrations. The films, obtained from a 10−7M aluminum electrolyte, exhibit the highest crystallographic quality and lowest electrical resistivity of 2×10−4Ω·cm with an energy band gap of 3.35eV.

Investigation on room temperature photoluminescence of pure and aluminum doped zinc oxide nanoparticles

Abstract Pure and aluminum doped zinc oxide nanoparticles were prepared by soft chemical method. The prepared nanoparticles were characterized by XRD, SEM-EDAX, UV-Vis, PL and FT-IR studies. XRD patterns revealed that the nanoparticles were crystallized in hexagonal wurtzite structure with an average particle size of 19 nm to 26 nm. The surface morphology was explored using SEM micrographs. The incorporation of aluminum was confirmed by EDAX and FT-IR studies. The band gaps of the particles were found from 3.48 eV to 3.53 eV through UV-Vis spectral studies. The defect related mechanism was investigated using PL measurements. The chemical functional groups in FT-IR spectra proved the formation of pure and aluminum doped zinc oxide nanoparticles.

Synthesis and Hydrogen Desorption Properties of Mg1.7Al0.15Ti0.15Ni-CNT Nanocomposite Powder

In this research, the effects of nanocrystallization and incorporation of aluminum, titanium, and carbon nanotubes (CNTs) on hydrogen desorption behavior of Mg2Ni alloy were investigated. Toward this purpose, nanocrystalline Mg2Ni intermetallic compound with average grain size of 20 nm was prepared by ball milling of elemental magnesium and nickel powders. Mg2Ni powder was then ball milled with aluminum and titanium powders for 20 h to dissolve these elements into the Mg2Ni structure, leading to the formation of Mg1.7Al0.15Ti0.15Ni compound. The elemental x-ray mapping analysis revealed the uniform dissolution of aluminum and titanium inside the Mg2Ni structure. Mg2Ni and Mg1.7Al0.15Ti0.15Ni compounds were further ball milled with 3 wt.% CNT for 5 h. The high-resolution field emission scanning electron microscopy and transmission electron microscopy revealed that CNTs have retained their tubular shape after ball-milling process. The hydrogen desorption properties of the samples were identified using a Sieverts-type apparatus at 473 K. The Mg2Ni, Mg2Ni-CNT, and Mg1.7Ti0.15Al0.15-CNT samples showed the desorbed hydrogen of 0.17, 0.25, and 0.28 wt.% after 1 h, respectively, indicating 47 and 65% increase in the hydrogen desorption capability of Mg2Ni via CNT addition and co-presence of aluminum-titanium-CNT. The direct hydrogen diffusion through CNTs and development of local atomic distortion due to substitution of magnesium atoms by aluminum and titanium appears to be responsible for enhancement of desorption behavior of Mg1.7Al0.15Ti0.15-3 wt.% CNT.

Synthesis of Zeolite Nanomolecular Sieves of Different Si/Al Ratios

Nanosized zeolite molecular sieves of different Si/Al ratios have been prepared using microwave hydrothermal reactor (MHR) for their greater application in separation and catalytic science. The as‐synthesized molecular sieves belong to four different type zeolite families: MFI (infinite and high silica), FAU (moderate silica), LTA (low silica and high alumina), and AFI (alumina rich and silica‐free). The phase purity of molecular sieves has been assessed by X‐ray diffraction (XRD) analysis and morphological evaluation done by electron microscopy. Broad XRD peaks reveal that each zeolite molecular sieve sample is composed of nanocrystallites. Scanning electron microscopic images feature the notion that the incorporation of aluminum to MFI zeolite synthesis results in morphological change. The crystals of pure silica MFI zeolite (silicalite‐1) have hexagon lump/disk‐like shape, whereas MFI zeolite particles with Si/Al molar ratios 250 and 100 have distorted hexagonal lump/disk and pseudo spherical shapes, respectively. Furthermore, phase pure zeolite nanocrystals of octahedron (FAU), cubic (LTA), and rod (AFI) shape have been synthesized. The average sizes of MFI, FAU, LTA, and AFI zeolite crystals are 250, 150, 50, and 3000 nm, respectively. Although the length of AFI zeolite rods is in micron scale, the thickness and width are of a few nanometers.

A Novel Type of Environmentally Friendly Slurry Coatings

A variety of commercial slurries are available to aluminize the surfaces of nickel-based superalloys; however, they have three main disadvantages. First, the phosphates and chromates or halides used as binders or to activate the diffusion species are environmentally harmful and toxic; second, the slurry coatings can only produce high-aluminum-activity coatings which form precipitate-rich coatings that are detrimental to adherence. Finally, these coatings are limited to the incorporation of aluminum and silicon, whereas the co-deposition of other elements such as chromium or cobalt has not been achieved so far. In this work, the limitations of slurry coatings have been overcome by carefully designing the powder composition and controlling the process to produce co-deposition coatings with chromium, cobalt, or nickel by using nontoxic water-based slurries. This also opens an effective way to control Al activity and to produce low-activity aluminized coatings for the first time when using the slurry technique. These results expand the application range of slurry coatings so they can also be applied under ambient atmosphere, making it possible to fully coat aero engine pieces or large-scale industrial components, providing all properties that are usually only achieved by using more complex and expensive methods such as chemical vapor deposition. Furthermore, these new coatings offer unique advantages that can be very favorable especially as a repairing technique.

Atomic layer deposition of Al-incorporated Zn(O,S) thin films with tunable electrical properties

Zinc oxysulfide, Zn(O,S), films grown by atomic layer deposition were incorporated with aluminum to adjust the carrier concentration. The electron carrier concentration increased up to one order of magnitude from 1019 to 1020 cm−3 with aluminum incorporation and sulfur content in the range of 0 ≤ S/(Zn+Al) ≤ 0.16. However, the carrier concentration decreased by five orders of magnitude from 1019 to 1014 cm−3 for S/(Zn+Al) = 0.34 and decreased even further when S/(Zn+Al) > 0.34. Such tunable electrical properties are potentially useful for graded buffer layers in thin-film photovoltaic applications.

Investigation of Aluminum Incorporation in 4H-SiC Epitaxial Layers

In the present contribution, the trends in voluntary incorporation of aluminum in 4H-SiC homoepitaxial films are investigated. The films were grown on Si-and C-face 4H-SiC 8°off substrates by chemical vapor deposition (CVD) in a horizontal, hot wall CVD reactor. Secondary Ion Mass Spectrometry (SIMS) and capacitance-voltage (C-V) measurements were used to determine the Al incorporation in the samples. The influence of Trimethylaluminum (TMA) flow rate, growth temperature, growth pressure and C/Si ratio on the dopant incorporation was studied.

SBA-15 intercalated Mg–Al hydrotalcite: An environmental friendly catalyst for hydroisomerization of olefin

SBA-15 Molecular sieve-intercalated Mg–Al hydrotalcite (MASBA-HT) was synthesized for the first time by a simple straightforward method. The intercalation of SBA-15 molecular sieve between the interlayer of HT was evident from powder XRD, TEM and FT-IR studies. The presence of SBA-15 facilitates retention of the layered structure for first time, even after calcination at high temperature of 550°C. The resultant material possesses moderate acidity which comes from incorporation of aluminum into the framework of SBA-15 and also contained soluble basicity similar to HT materials. The material shows promising activity for hydroisomerization of 1-octene resulting in good substrate conversion (80%) and branched isomers selectivity (45%). The catalytic activity remains constant over longer duration and repeated runs.

The role of the alumina content of slag, plus the presence of additional sulfate on the hydration and microstructure of Portland cement-slag blends

The effects on composite cements of the aluminium content of slag, plus that of additional sulfate, have been investigated. Samples containing cement or composites with 40% replacement by one of 2 different slags, differing in aluminium contents, were prepared. A further blended sample was prepared with additional anhydrite replacing 3% w/w of binder. Slag blended mortars showed comparable strengths to the neat cement system at later ages. Adding slag changed the hydration kinetics of the clinker phases. The addition of sulfate had no effect on slag reactivity but increased that of alite. Slags richer in aluminium resulted in greater incorporation of aluminium into C-S-H and encouraged the presence of hemicarboaluminate over monocarboaluminate. The Ca/Si ratios of the C-S-H formed were comparable between the two blends, being marginally lower than that of the neat system. The addition of anhydrite resulted in the adsorption of sulfate onto the C-S-H, plus stabilisation of ettringite.

Polymorphism and electronic transformations of deep Earth minerals

While powder X-ray diffraction studies stepped over a megabar in pressure already in the 1970s, single crystal experiments remained much rarer and covered until recently a very limited pressure range barely reaching 15 GPa. Recent technological advances resulted in a revolutionary breakthrough in the high-pressure crystallography. The structure solution and the full refinement are now possible at pressures over 100 GPa. A comprehensive understanding of the iron- and aluminum-bearing magnesium silicate perovskite (Pv) and post-perovskite (PPv, CaIrO3-type) crystal structures and their evolution under pressure and temperature is vital for evaluating seismic data of the Earth's lower mantle. We investigated materials with different compositions and iron oxidation states by means of single-crystal X-ray diffraction at pressures over 150 GPa and temperatures over 2500 K, and by Mössbauer spectroscopy. By structural studies of Pv at extreme conditions, we found (a) no spin state crossover in ferric iron occupying the bicapped trigonal prism ("A" crystallographic site), and (b) no crystal-chemically significant amount of ferric iron in the octahedral "B-site at any conditions of our experiments. We synthesized single crystals of PPv, refined their structure and distribution of iron between the structural sites. We demonstrated that incorporation of ferric iron and aluminum significantly increases the compressibility of magnesium silicate Pv and PPv. Based on experimental data we constrained the thermal equation of state for Pv and PPv with a variable content of iron (ferrous and ferric) and aluminum. We concluded that variation of Fe3+/ΣFe can lead to significant changes of Pv bulk sound velocity (over 1%) demonstrating that the oxidation state of iron is a critical parameter for interpretation of seismic tomography data.

Polymerization of pyrrole with 4-hydroxybenzaldehyde over Al-MCM-41 mesoporous aluminosilicate materials

Mesoporous MCM-41 materials containing aluminum with different Si/Al ratios (20, 40, and 80) were synthesized under hydrothermal condition. The materials were characterized using X-ray diffraction (XRD), nitrogen adsorption, Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), transmission electron microscopy (TEM), and NH3 temperature programmed desorption (TPD) techniques. Incorporation of aluminum into MCM-41-type silica leads to creation of active and selective catalysts for condensation of pyrrole with 4-hydroxybenzaldehyde. The reaction was carried out at room temperature whilst stirring at 500 rpm. The catalyst Al-MCM-41 with Si/Al ratio of 20 produced a very high yield of [(pyrrole-2,5-diyl)-co-(benzylidene)]. The catalyst could be easily separated from the polymer product and regenerated by calcination.

Enhanced heterogeneous asymmetric catalysis via the acid–base cooperation between achiral silanols of mesoporous supports and immobilized chiral amines

The heterogeneous acid–base cooperation between achiral silanols of mesoporous silica and immobilized chiral amines in asymmetric catalysis has been investigated in this work using direct asymmetric aldol condensation as model reaction. To accomplish the acid–base cooperative asymmetric catalysis as expected, not only the quantity and the acidity of surface hydroxyls have been controlled by the silyation of silica surface and the incorporation of framework aluminum, but also the structure of chiral pyrrolidine amines has been tuned. With appropriate acidity and sufficient quantity of surface silanols, impressive activity acceleration has been achieved for each pyrrolidine amine. For immobilized (2S)-N-(quinine-9-yl)pyrrolidine-2-carboxamid, in which the chiral pyrrolidine amine is modified with neighboring carboxamine moiety, the enantioselectivity has been well preserved, even though the achiral acidic sites compromise the asymmetric induction. The mechanism for the acid–base cooperative asymmetric catalysis between achiral silanols and immobilized chiral amines has been discussed.

Impact of Aluminum Incorporation into In-Zn-O Active Channel for Highly-Stable Thin-Film Transistor Using Solution Process

Top-gate Al-In-Zn-O (AIZO) thin-film transistors (TFTs) were fabricated using solution process and their device characteristics were demonstrated. The μsat, SS, and on/off ratio of the AIZO TFT post-annealed at 250°C were approximately 0.66 cm2 V−1 s−1, 0.24 V/dec, and 2.1 × 107. Slight negative shifts in turn on voltage were observed as small as 0.2 and 0.5 V under positive and negative-bias stress tests, respectively. Al incorporation into the IZO channel had important impacts on the annealing process optimization at lower temperature and highly-stable TFT performances.

Effect of Current at Aluminum Target on the AZO Thin Films by DC Magnetron Sputtering

Deposition of aluminum and zinc targets was carried out by DC magnetron sputtering to produce aluminum doped zinc oxide (AZO) thin films. These films were deposited on quartz, glass and silicon substrates under 5.5x10-3 mbar pressure. At a ratio of argon gas to oxygen gas (Ar:O2) of 5:10 and a voltage at zinc target of260 V, AZO thin films were deposited at different currents at aluminum target such as 900, 1,000, 1,100 and 1,200 mA. Effect of current at aluminum target on the structural, optical and electrical properties of resulting films was studied. Structural characterization by X-ray diffraction (XRD) technique and Energy Dispersive X-Ray Spectroscopy (EDS) confirmed incorporation of aluminum in ZnO lattice. The thickness measurement by Scanning Electron Microscope (SEM) showed that the thickness of AZO thin films is in the range of 270–350 nm. An average transmittance of above 80% in the visible wavelength region was obtained for aluminum doped zinc oxide. The optical direct bandgap and the resistivity of AZO thin films were found in the range 3.3-3.5eV and 6.0x10-1-9.0x10-1 Ωcm; respectively.

Aluminum Incorporation in the C–S–H Phase of White Portland Cement–Metakaolin Blends Studied by 27Al and 29Si MAS NMR Spectroscopy

The composition and structure of the calcium‐silicate‐hydrate (C–S–H) phases formed by hydration of white portland cement–metakaolin (MK) blends have been investigated using 27Al and 29Si MAS NMR. This includes blends with 0, 5, 10, 15, 20, 25, 30 wt% MK, following their hydration from 1 d to 1 yr. 29Si MAS NMR reveals that the average Al/Si ratio for the C–S–H phases, formed by hydration of the portland cement–MK blends, increases almost linearly with the MK content but is invariant with the hydration time for a given MK content. Correspondingly, the average aluminosilicate chain lengths of the C–S–H increase with increasing MK content, reflecting the formation of a C–S–H with a lower Ca/Si ratio. The increase in Al/Si ratio with increasing MK content is supported by 27Al MAS NMR which also allows detection of strätlingite and fivefold coordinated aluminum, assigned to AlO5 sites in the interlayer of the C–S–H structure. Strätlingite is observed after prolonged hydration for MK substitution levels above 10 wt% MK. This is at a somewhat lower replacement level than expected from thermodynamic considerations which predict the formation of strätlingite for MK contents above 15 wt% after prolonged hydration for the actual portland cement–MK blends. The increase in fivefold coordinated Al with increasing MK content suggests that these sites may contribute to the charge balance of the charge deficit associated with the incorporation of Al3+ ions in the silicate chains of the C–S–H structure.

Thermal Activation of a Pure Montmorillonite Clay and Its Reactivity in Cementitious Systems

Clay minerals are potential candidates as raw materials for new supplementary cementitious materials (SCMs) that can partly replace Portland cement and thereby significantly reduce CO2 emissions associated with cement production. We present the characterization of the complex, disordered structure of a pure montmorillonite clay heated at various temperatures (110–1100 °C), by solid-state 27Al and 29Si MAS NMR methods. The SiO4 tetrahedra and AlO6 octahedral sites become progressively more distorted, exhibit a significant degree of disorder upon dehydroxylation (600–800 °C), and do not lead to the formation of any metastable phase. At high temperatures (1000–1100 °C), the layer structure of the clay breaks down, forming stable crystalline phases. The chemical reactivity, measured as the degree of dissolution/precipitation in an alkaline solution, is found to be proportional to the degree of disorder/dehydroxylation. The maximum reactivity as a function of the heating temperature is achieved at 800 °C prior to the formation of inert, condensed Q4-type phases in the material. At maximum reactivity the calcium silicate hydrate (C-S-H) phase contains silicate chains with the highest aluminum incorporation, leading to blended cements containing a C-S-H phase with longer chain lengths. Most importantly, by exploiting the differential spin–lattice relaxation behavior of the 29Si spins, evidence of multiple sites and components in both the naturally occurring and heated montmorillonite is being reported for the first time.

Aluminum manganese oxides with mixed crystal structure: high-energy-density cathodes for rechargeable sodium batteries.

We report a new discovery for enhancing the energy density of manganese oxide (Nax MnO2 ) cathode materials for sodium rechargeable batteries by incorporation of aluminum. The Al incorporation results in NaAl(0.1) Mn(0.9) O2 with a mixture of tunnel and layered crystal structures. NaAl(0.1) Mn(0.9) O2 shows a much higher initial discharge capacity and superior cycling performance compared to pristine Na(0.65) MnO2 . We ascribe this enhancement in performance to the formation of a new orthorhombic layered NaMnO2 phase merged with a small amount of tunnel Na(0.44) MnO2 phase in NaAl(0.1) Mn(0.9) O2 , and to improvements in the surface stability of the NaAl(0.1) Mn(0.9) O2 particles caused by the formation of Al-O bonds on their surfaces. Our findings regarding the phase transformation and structure stabilization induced by incorporation of aluminum, closely related to the structural analogy between orthorhombic Na(0.44) MnO2 and NaAl(0.1) Mn(0.9) O2 , suggest a strategy for achieving sodium rechargeable batteries with high energy density and stability.

One-pot hydrothermal synthesis of Al-containing SBA-3 mesoporous materials

AlSBA-3 mesostructured materials with different Si/Al ratios were directly synthesized for the first time. The influence of the synthesis medium (different pH of synthesis mixture) and aluminium source on the efficiency of aluminium incorporation was studied. The increase in pH of reacting mixture allows to introduce much higher number of Al atoms, but on the other hand it causes worse ordering of the structure. The aluminium isopropoxide used as Al source leads to relatively high Al content in the final materials. The presence of Al in the framework positions is proved by 27Al MAS NMR. The obtained materials show considerable catalytic activity for the acid-catalyzed reactions (dehydration of 2-propanol, cumene cracking).