Noncrystalline Aluminum Research Articles

Effects of soil physical and chemical properties on phosphorus adsorption-desorption in fluvo-aquic soil under conservation tillage

Conservation tillage has been widely used in the North China Plain to improve the aggregate structure and promote soil organic matter (SOM) retention, which is closely associated with phosphorus (P) turnover. However, a quantitative description of how conservation tillage alters P adsorption and desorption characteristics via affecting soil physical and chemical properties remains lacking. Thus, we conducted a batch experiment using pilot soils that had experienced two tillage regimes (conventional/reduced tillage) and two types of straw management (straw returning/removal) for 13 years. The results indicated that the maximum adsorption capacity (Qm) and adsorption binding energy (KL) of reduced tillage decreased by 36.2% and 21.5%, respectively, and the average desorption rate (Dr) increased by 14.4% compared with conventional tillage. In addition, the Qm and KL of straw returning decreased by 40.5% and 51.9%, respectively, and the Dr increased by 25.2% compared with straw removal. The adsorption capacity of aggregates with different particle sizes showed the order of silt + clay > macroaggregate > / (≈) microaggregate, while the desorption capacity exhibited the opposite trend. Moreover, the Qm and KL depicted negative correlations with SOM, total P (TP), Olsen-P, and the mass proportion of macroaggregate. However, they exhibited positive correlations with free aluminum oxides (Ald), non-crystalline aluminum oxides (Alo), pH, specific surface area (SSA), and the mass proportion of microaggregate and silt + clay. The Dr was just the opposite with Qm and KL. The random forest results indicated that SOM, pH, SSA, TP, Ald, Olsen-P, and the mass proportion of macroaggregate were the key factors affecting the P adsorption and desorption. The physical and chemical properties collectively explained 80.8% of the total variance, and their interaction made the largest contribution. This study provides insights into how conservation tillage reduced P adsorption potential and promoted P desorption capacity from a physical and chemical perspective and emphasizes the importance of aggregate in the environmental behavior of P, which is of great importance for sustainable agricultural development and protecting food security.

КОМПЬЮТЕРНОЕ МОДЕЛИРОВАНИЕ СТРУКТУРНЫХ ДЕФЕКТОВ В МОНОКРИСТАЛЛИЧЕСКОМ И АМОРФНОМ АЛЮМИНИИ

The paper covers the study of microscopic mechanisms of melting of metals and the structural relaxation of metallic glasses. Despite the extensive efforts and numerous important results obtained in this field, this task does not have a generally accepted final solution. One of the main issues is the microscopic nature of structural defects in metallic glasses – the nanosized regions, which are responsible for the evolution of their physical properties under the external influence. The interstitialcy theory (IT) proposed by Granato provides the advanced interpretation of nature of such defects. The interstitialcy theory is based on the unique hypothesis of the interstitialcy mechanism for melting of metals and associates heat effects in the glass with the shear elasticity of a maternal crystal. The experimental study and computer simulation of the diaelastic effect near the melting temperature T m of crystalline aluminum provided a strong evidence of the avalanche generation of interstitial dumbbells near T m . In this work, the authors carried out the computer simulation to check the presence of interstitial dumbbells (or similar atomic structures) in the solid glassy state produced in the result of melt- quench. The computer simulation shows that the amorphous aluminum produced by rapid melt quenching contains a significant number of “defects” similar in their properties to the interstitial dumbbells in the crystalline state. Although these “defects” do not have any well-defined uniform topological structure, unlike the defects of crystal, and they can be exactly identified by their basic properties – high sensitivity to shear stresses and typical low/high-frequency peculiarities of the spectrum of the vibrational density of states of the “defective” atoms. Using the methods of molecular dynamics and statics, it is shown that the solid non-crystalline aluminum contains the specific atomic configurations similar to the interstitial dumbbells in the crystalline state, which can be considered as the amorphous structure “defects”.

Ionic self-diffusion of Al cations and O anions in the vitreous Al2O3 with molecular dynamics simulations

Ionic self-diffusion in the non-crystalline aluminum oxide is not well understood for the scarcity of experimental and simulation investigation. In this paper, the molecular dynamics (MD) simulation is employed to investigate the diffusion mechanism of Al cations and O anions in the vitreous Al2O3. According to the trajectories of ions, three moving modes are defined, including local vibration, fast jumping and slow collective moving. The collective motion is very important for the ionic diffusion in the vitreous configurations. The diffusion of O anions in vitreous Al2O3 is greatly enhanced attributed to the collective moving between Al cations and O anions. If the Al cations are pinned, the oxygen diffusivity drops more than three orders. The collective motion also reduces the energy barrier of diffusion, thus resulting in the non-Arrhenius effect of temperature on diffusivity.

Effect of organic matter removal treatments and addition of aluminum-containing substances on incidence of Fusarium wilt of lettuce

In order to determine the mechanism of lettuce root rot suppression in topsoil of andosols we investigated the effect of removing humus from a topsoil of andosol and adding aluminum substances to a disease-conducive subsoil of andosol on the incidence of lettuce root rot. Both topsoil of andosols heated at 250°C and treatment with hydrogen peroxide sustained disease suppressive effect, and exhibited similar levels of disease suppression as the untreated topsoil of andosol. The disease suppressive effect was lost by heating topsoil of andosol at 400°C. Next, both subsoil of andosol amendment with aluminum-containing humic acid (Al-humic acid) and aluminum hydroxide gel (Al(OH)3) added the disease suppressive effect, but not with humic acid or crystalline structure aluminum hydroxide [crystalline Al(OH)3]. The addition of Al-humic acid and Al(OH)3 to potato dextrose agar medium significantly inhibited growth of the causal agent of lettuce root rot, Fusarium oxysporum f. sp. lactucae, compared with the control. Based on the above results, we speculate that noncrystalline aluminum hydroxide, which forms complexes with humus, inhibits growth of pathogenic fungus and thereby suppresses incidence of lettuce root rot.

Effect of vegetation on soil C, N, P and other minerals in Oxisols at the forest-savanna transition zone of central Africa

The forest-savanna transition zone, which evolves as a result of past climate change, is widely distributed in central Africa. Because nutrient-poor soils (Oxisols) are widely distributed in this area, it is necessary to understand the characteristics of soil nutrients in relation to the vegetation. We collected 52 soil samples from five pits each for two different vegetation types (forest and savanna) in this area and evaluated the effect of vegetation type on soil physicochemical properties [pH, soil texture, cation-exchange capacity, bulk density, crystalline and non-crystalline aluminum (Al) and iron (Fe)] and nutrient status [carbon (C), nitrogen (N), phosphorus (P) and other soil minerals]. We also evaluated the fractionated P. Whereas most physicochemical properties were similar between the two vegetation types throughout the soil profile (0–80 cm depth), clay content, bulk density and soil pH clearly differed between the vegetations at the surface layer (0–10 cm). At 80 cm soil depth, soil C, N and P were 87.9, 7.7 and 3.7 Mg ha−1, respectively, in forest, and 98.6, 7.1 and 3.1 Mg ha−1, respectively, in savanna. Although there was no clear difference between the amounts of soil C, N and P, the upper-soil (0–40 cm) C:N ratio was clearly lower in forest (11.0–12.0) compared with savanna (13.0–15.7), because the main plant species in the forest can fix N effectively. We also found a smaller ratio of sodium hydroxide (NaOH)-extractable inorganic P to total soil P in forest compared with savanna. Because the content of crystalline and non-crystalline Al and Fe in forest soil was similar to that of savanna, the different soil C:N ratio would cause different availability of P between the vegetation types, although the mechanism is unclear. These results indicate that savanna vegetation is N-limited and forest vegetation is N-saturated (and possibly P-limited) in this zone. We also found that, at 20 cm soil depth, total soil potassium (K) in forest was 1590 kg ha−1, which was 930 kg ha−1 less than that in savanna (2520 kg ha−1; P < 0.05), although a similar difference was not measured for Na, Ca, and magnesium (Mg). Because we observed lower soil pH in forest, not only plant K uptake but also K leaching loss would contribute to lower soil K in forest.

Synthesis and characterization of amorphous aluminum oxide thin films prepared by spray pyrolysis: Effects of substrate temperature

Amorphous and non-crystalline aluminum oxide thin films have been deposited on glass substrate by spray pyrolysis method. The structural, morphological and optical properties were investigated using X-Ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-visible spectrophotometry. For two specific molarities (0.15M and 0.25M), substrate temperature was varied between 250°C, 350°C, 500°C, and 550°C. The XRD results exhibited dominant amorphous nature for all samples as expected, whereas SEM and AFM showed the presence of substrate temperature effects on alumina thin film properties. Enhancement of optical transmittance with temperature increase was observed. Using the transmittance data other optical quantities namely absorption coefficient, optical band gap, refractive index and extinction coefficient, dielectric constants, volume and surface energy loss functions and optical conductivity were determined. It was also observed that the volume energy loss (VELF) increases more than the surface energy loss (SELF).

Preparation and Characterization of Alumina Nanofibers by Gas-Solid Reaction Method

Using gas-solid reaction method, the non-crystalline alumina nanofibers with different morphology and aspect ratios could exuberantly grow by feeding air into one closed box or bubbling air into several organic liquids which contained the thin aluminum amalgam sheet at room temperature. Their diameters were about 2-10nm, whereas the length-diameter ratios were distributed widely. The diameters and length could be controlled by adjusting the kinds of the organic reagent. The as-grown nanofibers were then heat-treated at temperatures range from 300 to 1000°C. The results of X-ray diffraction and thermo-gravimetric analysis indicated the γ-Al2O3 nanofibers would be produced at 500°C and the α-Al2O3 particles could be obtained at about 1000°C. The electron micrographs suggested the nanofibers growth direction was randomly in the air or organic solutions, except for growing regular naonofibers in polyoxyalklene-400. The growth mechanics of alumina nanofibers were briefly discussed.

Spectroscopic and macroscopic studies of the adsorption of arsenate and phosphate on polynuclear aluminum organomineral precipitates

Aluminum organic coprecipitates play important roles in the transport of oxyanions in soil environment. A new polynuclear aluminum organomineral precipitate (Al13-oxalate precipitate) was prepared to investigate the adsorption behavior of arsenate and phosphate on noncrystalline aluminum precipitates. Important thermodynamic parameters for adsorption reaction were evaluated using macroscopic adsorption data and equations. The result showed that, the adsorption reaction basically is a diffusion process. FTIR spectroscopic studies have provided evidence for the formation of two different types of complexes in substrate, protonated bidentate and deprotonated bidentate complexes at pH 4 and pH≥6, respectively. The classic competitive adsorption and XPS studies both indicated that phosphate has stronger chemical interaction with substrate than arsenate. The findings of XPS studies revealed that the precipitate substrate can act as Lewis acid when adsorbing oxyanions.

Structure and Properties of Noncrystalline Aluminum Oxide-Hydroxide Fluorides

The thermal treatment of sol−gel derived aluminum hydroxide fluorides leads to new, X-ray amorphous, macroporous aluminum oxide-hydroxide fluorides. Followed by EA, DTA-TG, XPS, FT-IR, NH3-TPD, BET, XRD, and MAS NMR, it can be shown that the simplified composition of these compounds is “AlFO” and “AlF2O1/2”, respectively. These aluminum oxide-hydroxide fluorides exhibit a large number of acid centers. The local structure consists of AlFxOcn-x units (cn, coordination numbers 6, 5, 4), and all sites are partially fluorinated. It can be shown that bridged and terminal F-sites are related to 5- and 6-fold coordinated Al sites.

Crystallization of nordstrandite in ethylene glycol / water solutions: electron microscopic studies

Abstract The present work shows the growth of nordstrandite microcrystals observed by transmission and scanning electron microscopy. Nordstrandite was synthesised from non-crystalline aluminium hydroxide reacted in 20% ethylene glycol/water solution, at room temperature. This material was characterized by TEM, SEM, SAED, XRD and EDS/TEM, during six month and revealed the formation and growth of nordstrandite. Fibrillar pseudoboehmite is the only aluminium hydroxide which could be identified during the first two weeks. The nuclei grow, from complete dissolution/recrystallization of pseudoboehmite fibrils, into platy rectangular microscrystals of nordstrandite. Some tabular microcrystals recrystallise, forming after six months only the multi-point nordstrandite stars. This electron-optical study suggest that the star shape results from the overlapping of rectangular plates, and pseudoboehmite fibrils act as the precursor of nordstrandite crystallisation in ethylene glycol/water solution.

A plasticidade dos amorfos: fazendo pigmentos brancos com fosfato de alumínio

A new white pigment made out of nano-structured non-crystalline aluminum phosphate was recently launched as an industrial product. Pigment opacifying properties are not intrinsic to aluminum phosphate but they arise as the result of a rare hollow particle nano-structure. This is in turn derived from the core-and-shell structure of amorphous aluminum phosphate precipitated under well-defined conditions. The new pigment is a product of the often neglected chemistry of non-crystalline ionic solids that can probably be a rich source of new successful products. The text describes a short account of the R&D activities, from the initial ideas to the present.

Effect of Reaction Time on Pb Removal from Allophanic Volcanic Ash Soil by Acid-washing

To investigate the effects of reaction time on removal of heavy metals in acid-washing, we conducted acid-washing using hydrochloric acid on allophanic and smectitic soils contaminated with lead (Pb). The Pb removal percentage in the smectitic soil increased with reaction time. On the other hand, in the allophanic soil, it reached to a maximum at around 10 min, and then decreased monotonically. This suggests that effective removal of heavy metals from allophanic volcanic ash soils can be achieved by separating the washing solution from the soil as quickly as possible. The pH of the washing solutions of the two soils were similar just after the acid addition but it rose much more quickly in the allophanic soil than in the smectitic soil. Under comparable conditions, the pH of the washing solution and Al concentration were always far higher for the allophanic soil than for the smectitic soil, probably due to the higher solubility of allophane and related non-crystalline aluminum silicate in the former soil. These experimental results indicate that the Pb that was once released from allophane was re-adsorbed via surface complexation as a result of pH increase.

Importance of Noncrystalline Hydroxide Phases in Sequential Extractions to Fractionate Antimony in Acid Soils

Sequential extraction techniques have been used to make inferences about speciation of phosphorus (P) and to a lesser extent arsenic (As) in soils. However, sequential extraction studies on the less‐abundant group V element, antimony (Sb), are limited. In this work, a widely used P sequential extraction scheme was modified and used to extract P, As, and Sb from two acidic soils from the Macleay River floodplain, NSW, that were enriched with Sb (26.9 and 23.0 mg kg−1). An ammonium oxalate–oxalic acid step was included in the extraction sequence to dissolve the noncrystalline iron (Fe) and aluminium (Al) hydroxide phase. It extracted 30 to 47% of Sb, indicating the importance of this fraction, which may be mobilized in the floodplain by acid sulfate soil processes and periodic waterlogging. The original method overestimated P, As, and Sb in the residual fraction (30–71%). Relative efficiency values of extracts for P, As, and Sb were compared, and inferences about phase distributions were made. The results suggest some potential in using extractions to assess bioavailability of Sb in soil.

Estimation of Phosphorus Status of Soil Fe‐Enriched Concretions with the Acid Ammonium Oxalate Method

Iron (Fe)‐enriched concretions, a complex natural matrix with high chemical heterogeneity and phosphate‐sorption capacity, is widespread in soils with restrictive drainage in Greece. However, the phosphorus (P) status and related characteristics of Fe‐enriched concretions in agricultural soils in areas where P fertilization is mainly inorganic are relatively unknown. Active noncrystalline Fe and aluminum (Al) oxides (Feox, Alox), oxalate extractable P (Pox), P sorption capacity (PSC), and the degree of P saturation (DPS) of Fe‐enriched concretions from agricultural imperfectly drained soils in central Greece were determined using the acid ammonium oxalate method. The concretions contain 13 times as much Feox, twice as much Alox, and almost 15 times as much Pox than the surrounding soil matrix. Pox accounted for 50–80% of total P of the soil concretions, indicating strong accumulation of noncrystalline P components (Al‐ and Fe‐P). The PSC, expressed as a 0.5 (Alox+Feox), ranged from 184.7 to 314 mmol kg−1, demonstrating the strong affinity of the Fe‐enriched concretions for P. The DPS, which represents the fraction of concretion sorbent surface coverage by P, was computed as 100 (Pox/PSC) with values ranging from 6 to 13% (mean=8%). The results of this study indicate that the Fe‐enriched concretions, due to their high noncrystalline Fe and Al oxides content, act as major sink of phosphate, controlling the location, mobility, and dynamics of P in agricultural soils with restrictive drainage.

Synthesis and Characterization of Nanocapsules with Shells Made up of Al13 Tridecamers

The synthesis of samples by the sol-gel method with aluminum tri-sec-butoxide as cation precursor, 2-propanol as solvent, and sulfuric acid as hydrolysis catalyst gave rise to nanocapsules with an average diameter of 20 nm and a shell thickness of 3.5 nm. The analysis of the X-ray diffraction patterns and the 27Al MAS NMR spectra showed that the shell of the nanocapsules was made up of Al13 tridecamers ordered in a noncrystalline symmetry. The interaction between the capsule's shells opened the capsule structure, producing curved fibers, but maintaining the atomic local order. This opening of the capsules favored the reordering of the atomic local order of Al13 tridecamers into the one of crystalline boehmite, when the sample was aged at room temperature for several days; it also increased the pore volume and the specific surface area of the sample. The crystallization transformed the curved fibers into rods made of small crystalline boehmite bars. The capsule morphology was preserved after calcining the nonaged sample at 700 degrees C, indicating that the transformation of the phase made up of ordered Al13 tridecamers into a noncrystalline alumina was pseudomorphic. We describe and partially explain one of the possible atomic ordering evolutions from the one of an isolated Al13 tridecamer, to the phase forming the nanocapsules shell, until eventually coming to the ordering corresponding to boehmite crystalline rods.

Availability of soil boron fractions to M.26 apple rootstock

The availability of various boron (B) fractions in soil to M.26 apple (Malus spp.) rootstock was examined. The study was carried out in a greenhouse on soils with diverse chemical and physical properties. The following B fractions were determined: (i) B in soil solution, (ii) B non‐specifically adsorbed on soil surface, (iii) B specifically adsorbed on soil colloid surfaces, (iv) B occluded in Mn oxyhydroxides, (v) B occluded in noncrystalline aluminum (Al) and iron (Fe) oxides, (vi) B occluded in crystalline Al and Fe oxides, (vii) B fixed with soil silicates, and (viii) total soil B. In the studied soils there were: 0.07–0.17 mg kg‐1 B in soil solution, 0.01–0.03 mg kg‐1 B non‐specifically adsorbed on soil surface, 0.04–0.08 mg kg‐1 B specifically adsorbed on soil colloid surfaces, 0.28–0.67 mg kg‐1 B occluded in manganese (Mn) oxides, 4.03–17.22 mg kg‐1 B occluded in noncrystalline Al and Fe oxides, 8.93–50.62 mg kg‐1 B occluded in crystalline Al and Fe oxides, 12.2–42.5 mg kg‐1 B fixed with soil silicate, and 52.9–82.2 mg kg‐1 total B. Simple correlation analysis showed positive correlation between B contents in M.26 apple rootstocks and amounts of B in soil solution (r=0.77), B non‐specifically adsorbed on soil colloid surfaces (r=0.65), B specifically adsorbed on soil surface (r=0.76) and B occluded in Mn oxyhydroxides (r=0.77). No relation was found between plant B contents and amounts of B occluded in non‐crystalline and crystalline Al and Fe oxides, B fixed with soil silicates and total B. The results indicated that extraction of B by 0.1 M NH2OH HCl solution adequately represented amounts of B in soil solution, B non‐specifically and specifically adsorbed on soil compound surfaces and B occluded in Mn oxyhydroxides to assess availability of B to apple trees.

Aging of coprecipitated Cu in alumina: changes in structural location, chemical form, and solubility

The longterm fate of metals in mineral solid phases is not well established, as aging effects can alter metal forms and solubility. We use a model system (Cu coprecipitation with alumina) to examine copper solubility, chemical form, and structural location during longterm aging (up to 2 y), and as a function of Cu concentration, suspension pH, and rate of coprecipitate formation. Electron spin resonance (ESR) spectroscopy and extractability with EDTA were used to determine the chemical form and structural location of Cu in coprecipitates with alumina. Soluble Cu was measured by differential pulse anodic stripping voltammetry (dpasv) and alumina transformation monitored by XRD. Decreased Cu solubility resulted after prolonged aging of the coprecipitates formed at pH 6 and pH 7.5. Longterm aging (up to 2 y at 23°C) induced the transformation of an initially noncrystalline alumina to more ordered products including gibbsite. Results obtained by ESR and EDTA extraction indicate Cu movement towards the surface of the coprecipitate at increased aging time. Copper was initially evenly distributed within the alumina, but segregated at or near the alumina surface forming CuO and/or clusters after longterm reaction (2 y) with alumina.

Effect of organic acids on ferric iron removal from iron-stained kaolinite

The effect of various organic acids viz. acetic, formic, citric, ascorbic, succinic, tartaric and oxalic acids, on the iron removal and the resulting brightness improvement of an iron-stained kaolinitic clay from Kalliyur, Thiruvananthapuram, South India, has been investigated. Oxalic acid was found to give the best results both at room temperature as well as at high temperatures because of its high acid strength, good complexing capacity and reducing power. The reaction parameters such as time, temperature and reagent concentration were optimised. The optimum conditions required for achieving brightness ≥80% were: temperature — 100°C, oxalic acid concentration — 0.1 M and reaction time — 90 min. The leaching tests at room temperature for 30 days improved the brightness from 66.3 to 83.5% ISO. The corresponding iron oxide removal was of the order of ∼80%. The addition of ferrous ions and protons improved the reaction kinetics. The leaching tests carried out on previously beneficiated samples using magnetic separation showed only a slight improvement in brightness indicating that brightness depended more on the surface coated iron oxides rather than on the discrete particles. The effect of acid leaching on the physical properties of the clay such as brightness, plasticity, viscosity, specific surface area and pore volume were compared. The slight increase in the specific surface area and the pore volume are suggestive of removal of the cementing non-crystalline alumina, silica and iron oxides from the clay surface and also due to the resulting delamination to a limited extent. No marked change was observed in the viscous as well as the plastic properties due to the deferration treatments.

Evaluation of Mehlich 3 reagent as a multielement extractant in mine soils

The usefulness of Mehlich 3 (M3) reagent was evaluated as a method to extract numerous elements from coalmine soils in As Pontes (Spain) showing a wide range of physicochemical properties. Critical levels (deficiency and/or toxicity) were established for plant available elements extracted by this reagent. The M3 method was compared to 1M NH4Cl, Olsen, acid oxalate, and DTPA methods as extractants for exchangeable Ca, Mg and K, available P, non-crystalline aluminium, and available heavy metals, respectively. The M3 method correlated significantly to NH4Cl for Ca, Mg and K (r=0·76, 0·84 and 0·87, respectively), to Olsen P (r=0·77) and to oxalate Al (r=0·77). Significant correlations were found between Fe, Cu, Zn and Cd extracted by M3 and DTPA; for Mn, Ni, Co and Pb different relationship between methods were obtained for acid and alkaline samples, so that critical levels were established for M3 metals as a function of soil pH. Copyright © 1999 John Wiley & Sons, Ltd.

Improved latex film-glass adhesion under wet environments by using an aluminum polyphosphate filler

—Non-crystalline aluminum polyphosphate (A1PP) was added as a filler to poly(vinyl acetate) latex and the resulting dispersion was used both as a glass coating and as a glass-to-glass adhesive. Latex-coated glass samples were subjected to a grid adhesion test following the ASTM D 3359 standard, in which the samples are immersed in water. A1PP improves the latex polymer film adhesion to glass, as evidenced by coating film and adhesive joint stabilities. This is explained in terms of the formation of Al3+ ion bridges between the polymer-polyphosphate bicontinuous composite film and the glass surface.