Al Solubility Research Articles

Predicting the formation enthalpy and phase stability of (Ti,Al,TM)N (TM = III-VIB group transition metals) by high-throughput ab initio calculations and machine learning

The development of transition-metal-alloyed (Ti,Al)N thin films has become a common strategy to achieve optimized mechanical and thermal properties. Selection of a suitable alloying element, however, should consider the effect on Al solubility, directly influencing phase stability during the deposition. Here we use high-throughput ab initio formation enthalpy calculations to assess stability of the cubic (c) vs. hexagonal wurtzite-type (w-) phase of TM-alloyed (Ti,Al,TM)N. This compositionally-limited ab initio dataset serves to fit several machine-learning (ML) models enabling phase stability predictions over the entire compositional range. Of all the models, the linear regression using Magpie feature descriptor pre-processed by a genetic algorithm has the highest accuracy. For Ta, Nb, Mo, and W addition below ∼10 at.%, our ML model predicts enhanced stability of c-(Ti,Al,TM)N due to increased solubility of Al. Other alloying elements, especially Sc and Y from IIIB group and Hf and Zr from IVB group, decrease the cubic metastable solubility limit. In agreement with available experimental data, all transition metals except for Cr and V increase the volume of c-(Ti,Al,TM)N and w-(Ti,Al,TM)N.

Exopolysaccharides from Rhizobium Tropici mitigate aluminum bioaccumulation and toxicity in earthworm Lumbricus Terrestris

Aluminum is one of the most abundant elements in earth’s crust and soils. Global soil acidification has occurred with industrialization and enhances Al solubility in acidic soils, resulting in Al phytoxicity and reducing crop production. Earthworms play an important role in nutrient recycling in soils and maintaining soil health. Rhizosphere microorganism excretes exopolysaccharides (EPS) into the rhizosphere. The objectives of this study is to examine effects of EPS from Rhizobium Tropici on aluminum uptake and ecotoxicity to earthworms in soils and litters. Overall this study provides the scientific understanding of the EPS in alleviation of Al toxicity to earthworms in soils. Results showed the clear mitigation of EPS in reducing earthworm mortality rate and increasing its reproductivity under Al stress. EPS significantly decreased Al uptake from soil and litters, and decreased Al in subcellular distribution (cell membrane, cytosol and organelle fractions) in earthworms from soils. Al in purges was found to be mainly present in the residual fraction, while EPS slightly increased Al in water soluble and exchangeable fractions in purges. Overall water soluble and organic matter bound Al in soils were correlated well with Al in earthworms, but Al in earthworms were controlled by total Al in purges. The current study concluded that earthworm Lumbricus Terrestre may be a potential bio-indicator of Al ecotoxicity in soils and EPS from Rhizobium Tropici effectively mitigated Al ecotoxicity in soils.

High P-T phase relations of Al-bearing magnetite: Post-spinel phases as indicators for P-T conditions of formation of natural samples

Abstract The phase relations of Al-bearing magnetite were investigated between 6–22 GPa and 1000–1550 °C using a multi-anvil apparatus. This study demonstrates that the spinel-structured phase persists up to ~9–10 GPa at 1100–1400 °C irrespective of the amount of hercynite (FeAl2O4) component present (20, 40, or 60 mol%). At ~10 GPa, the assemblage Fe2(Al,Fe)2O5 + (Al,Fe)2O3 forms and remains stable up to 16–20 GPa and 1200–1550 °C. Fe2(Al,Fe)2O5 adopts the CaFe3O5-type structure with the Cmcm space group. At 18–22 GPa and T >1300 °C the assemblage Fe3(Fe,Al)4O9 + (Al,Fe)2O3 becomes stable. Fe3(Fe,Al)4O9 is isostructural with Fe7O9, having the monoclinic structure of the C2/m space group. At T <1300 °C, Fe3(Fe,Al)4O9 + (Al,Fe)2O3 gives way to the assemblage of a hp-Fe(Fe,Al)2O4 + (Al,Fe)2O3. This hp-Fe(Fe,Al)2O4 phase is unquenchable; a defect-bearing spinel-structured phase was recovered instead, and it contained numerous lamellae parallel to {100} or {113} planes and notably less Al than the initial starting composition. While low-pressure spinel can have a complete solid solution between Fe3+-Al, the post-spinel phases have only very limited Al solubility, with a maximum of ~0.1 cpfu Al in hp-Fe(Fe,Al)2O4, ~0.3 cpfu in Fe2(Fe,Al)2O5, and ~0.4 cpfu in Fe3(Fe,Al)4O9, respectively. As a result, the phase relations of Fe(Fe0.8Al0.2)2O4 can also be applied to bulk compositions richer in Al with the only difference being that larger amounts of an (Al,Fe)2O3 phase are present. Coexisting rhombohedral-structured phases demonstrate that the binary miscibility gap established at low pressure between hematite and corundum is still valid up to 20 GPa. Since iron oxides (e.g., magnetite) with variable Al contents are found in extraterrestrial rocks or as inclusions in diamond, constraints on their high-P-T-fO2 stability might help unravel their formation conditions.

Increasing the amorphous content in river sediments intended for supplementary cementitious materials using flame synthesis

Dredged river sediments are currently a waste material which is mainly landfilled or reintegrated into rivers. They can also be used as a renewable resource for the construction sector. Pre-treatments at high temperatures allow their use for more advanced applications such as supplementary cementitious materials (SCMs) or as a precursor for alkali activated materials (AAMs). The work presented here shows that flame synthesis can be used to almost completely vitrify such sediments and increase their leachability for Al and Si beyond the levels achieved by conventional calcination at 750–950 °C for 1h.The reactivity of the prepared samples was analyzed via the Si and Al solubility in 10 M NaOH and was generally increased by the applied treatments but maximized by flame synthesis. Their microstructure was analyzed using scanning electron microscopy and their phase composition was monitored using X-ray diffraction. The results show an almost complete amorphization of the sediments by flame synthesis, however their reactivity does not increase at the same rate.

Pengaruh Pemberian Beberapa Jenis Pupuk Kandang dan Pupuk Hijau Terhadap Ketersediaan dan Serapan Nitrogen pada Jagung di Tanah Podsolik

The study aimed to determine the effect of application fertilizer derived from animals (manure) or plants (green manure) on the supply and absorption of plant N, changes in pH, CEC, and suppressing Al solubility and to determine the best type of organic matter in supplying and absorbing plant N, change in pH, CEC, and suppress Al solubility. This study was carried out in the field and arranged using a single factor completely randomized design (CRD). The treatments applied in study were K0 = control, K1 = cow manure (50 g pot-1), K2 = goat manure (50 g pot-1), K3 = chicken manure (50 g pot-1), K4 = green manure for weed hair buns (50 g pot-1), K5 = rice straw green manure (50 g pot-1), K6 = gamal green fertilizer (50 g pot-1). The application of various organic materials can increase pH, CEC, available N, plant dry weight, N uptake of corn plants, and reduce Al solubility.

Spodosol formation on sandy ruins in a semi-arid climate in the Catimbau National Park, Northeast Brazil

The Catimbau National Park (CNP) is found in the Caatinga biome under a semi-arid climate. The soils of certain humid areas have horizons with morphology typical of Spodosols, and their occurrence in the CNP seems to be in discord with their formation model. This study aimed to investigate the genesis of Spodosols in the semi-arid climate of the CNP, testing the hypothesis that these soils are the result of local tectonic conditions associated with a past climate. As such, a sandy soils toposequence over sandstone of the Tacaratu Formation, under Caatinga vegetation and a semi-arid climate in northeast Brazil was studied. Sampling was based on the structural model of the pedological coverage, whereby physical and chemical analyses, Fourier transform infrared spectroscopy, X-ray diffraction, and soil micromorphological analysis were carried out. The results indicate that paludization of the soils occurred in two more humid phases, being compounded by the occurrence of distended faults/fractures related to the geology of the CNP. Microbiological decomposition under hydromorphic conditions led to humification of the organic constituents, which acidified the environment and increased Al solubility, forming organometallic complexes with fulvic and humic acids. The FTIR spectra and the presence of charcoal confirm the condensed aromatic nature and the abundance of carboxylic groups in the soils, these being related to the pyrolysis of biotransformed plant residues. Podzolization occurred in pulses promoted by intense rains under a dry climate and Fe-poor parent material, which favored the translocation of organometallic compounds of Al. The dense packing of fine organomineral material in the Bh horizons and the open matrix in the adjacent horizons indicate that the narrowing of the porous environment may be an important factor for the immobilization of translocated material. With the return of the current drier conditions in Brazil’s semi-arid, the podzolization process remains incipient.

Phase Equilibria in the Ti-Rich Part of the Ti-Al-Nb System—Part II: High-Temperature Phase Equilibria Between 1000 and 1300 °C

The knowledge of phase equilibria in the Ti-Al-Nb system above 1000 °C is of importance for the manufacturing of TiAl-based parts for high-temperature structural applications. Especially the extended homogeneity range of the cubic (βTi,Nb) phase, which is determined by its Al solubility, and the position and extension of the high-temperature (αTi) phase is of crucial importance for the hot-workability and microstructure control of these alloys. However, the phase diagrams reported in the literature are very contradicting especially regarding these aspects. For this reason, a systematic reinvestigation of the phase equilibria in this part of the system was carried out. A total of 17 ternary alloys were synthesized, heat-treated at 1000-1300 °C, and analyzed by electron probe microanalysis (EPMA), x-ray diffraction (XRD), high-energy XRD (HEXRD), and differential thermal analysis (DTA) to determine composition and type of equilibrium phases as well as transition temperatures. With this information, isothermal sections of the Ti-rich part of the Ti-Al-Nb system at 1000, 1100, 1200, and 1300 °C were established. An isolated (βTi,Nb)o phase field is found to be stable at 1000 and 1100 °C. Furthermore, the formation and homogeneity range of (αTi) at high temperatures as well as the presence of Ti3Al at 1200 °C is experimentally investigated and discussed. Based on the observed phase equilibria and transition temperatures, an improved reaction scheme for the entire Ti-Al-Nb system is proposed.

The Effect of Dosage and Biochar Types On the Availability Of Phosphorus Nutrients In Acid Soil In Sebatik, Indonesia

The low availability of P nutrients is one of the problems in managing acid land in Sebatik. The low availability of P in acidic soils is due to the low soil pH and the high Al-exch solubility. One of the efforts to increase the availability of P is by increasing the soil pH and reducing the solubility of Exchangeable Al through the addition of a soil amendment agent, namely biochar. This study aims to determine: 1) the effect of the type of biochar on P availability; 2) the effect of biochar dose on P nutrient availability; and 3) the effect of the combination of types and dosage of biochar on the availability of P in acid soils in Sebatik. The study was conducted using a completely randomized design (CRD) 2 factors, namely the type of biochar (coconut shell and palm shell) and the dosage of biochar (0, 0.5, 1.0 and 1.5 g), resulting in 8 treatment combinations, repeated 3 times. produced 24 experimental units, which were incubated at 0, 21 and 42 days. The parameters observed were soil pH, C-organik content, Exchangeable Al solubility, and available P-soil. The results of this study indicate that the type and dose of biochar can increase the availability of P from very low to medium. The highest availability of P nutrients was obtained in the provision of palm shell biochar (6.36 ppm), a biochar dose of 1.5 g (8.64-8.80 ppm), and in a combination of coconut shell biochar with a dose of 1.5 g (8. 80 ppm).

High-entropy transition metal nitride thin films alloyed with Al: Microstructure, phase composition and mechanical properties

Deviation from equimolar composition in high-entropy multielement ceramics offers a possibility of fine-tuning the materials’ properties for targeted application. Here, we present a systematic experimental and theoretical study on the effects of alloying equimolar pentanary (TiHfNbVZr)N and hexanary (TiHfNbVZrTa)N high-entropy nitrides with Al. Although being predicted to be metastable by ab initio density-functional theory calculations, single-phase fcc NaCl-structured solid solution thin films with Al solubility limits as high as x ∼ 0.51–0.61 in (TiHfNbVZr)1-xAlxN and x ∼ 0.45–0.64 in (TiHfNbVZrTa)1-xAlxN are synthesised utilizing a hybrid deposition technique that offers dynamic mixing of film atoms from Al+ subplantation and non-equilibrium growth conditions leading to quenching of the desired film structure. In experimental studies supplemented with density-functional theory calculations, it is demonstrated that Al concentration in alloys with the multielement compositions of high-entropy nitride thin films determine hardness, yield strength, toughness, and ability to deform plastically up to fracture due to different deformation mechanisms arising from the electronic structure and phase compositions.

The Potential Swamp Land Development to Support Food Estates Programmes in Central Kalimantan, Indonesia

The objective of this study is to analyse the potentials, obstacles and socio-economic condition of swamp land development for food estate programmes in Central Kalimantan, Indonesia. The results for qualitative descriptive and quantitative analysis showed there were approximately 33.4 million hectares of swamp land area, 9.5 million of which have the potential for agricultural land, particularly for rice. The rationale of food estate location are a wide area of land availability, with abundant water resources. The main obstacles of land use of swamp land are: (a) low soil pH (acid); (b) low NPK content in the soil; (c) high Al and Fe solubility (toxic); and (d) tidal influence such that during the wet season the land is flooded and during the dry season the land is dry. This research recommends that swamp land development for food estates requires: water management infrastructure rehabilitation, land management, adaptive and potential commodity selection and farmer institution strengthening and facilitation.

Influence of Si content on phase stability and mechanical properties of TiAlSiN films grown by AlSi-HiPIMS/Ti-DCMS co-sputtering

Ti 1−x (Al y Si 1−y ) x N coatings covering a wide compositional range, 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00, are deposited to investigate the influence of Al + /Si + ion irradiation on microstructural and mechanical properties. The samples are grown in Ar/N 2 atmosphere by the hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) method with substrate bias synchronized to the Al + /Si + -rich portion of the HiPIMS pulses. Two Ti targets are operated in DCMS mode, while one AlSi target is operated in HiPIMS mode. Four different AlSi target compositions are used: Al 1.0 Si 0.0 , Al 0.9 Si 0.1 , Al 0.8 Si 0.2 , and Al 0.6 Si 0.4 . X-ray diffractometry reveals that films without Si (i.e., y = 1.0) have high Al solubility in NaCl-structure, c-TiAlN, up to x ≤ 0.67 no w-AlN is detected. Once Si (y < 1.0) is introduced the Al solubility limit decreases, but remains higher than other PVD techniques, along with grain refinement and the formation of a SiN z rich tissues phase, as shown by transmission electron microscopy. The nanoindentation hardness is high (~30 GPa) for all films that do not contain the w-AlN phase. All the coatings have compressive stresses lower than −3 GPa. Interestingly, a range of films with different compositions displayed both high hardness (~30 GPa) and low residual stress ( σ < 0.5 GPa). Such a unique combination of properties highlights the benefits of using HiPIMS/DCMS configuration with metal-ion-synchronized substrate bias, which utilizes the Al + /Si + supplantation effect and minimizes the Ar + incorporation. • TiAlSiN films are grown by AlSi-HiPIMS/Ti-DCMS with wide compositional range. • Substrate bias is synchronized to the Al + /Si + -rich portion of the HiPIMS pulses. • The Al + /Si + irradiation effects on film properties are studied. • High Al and Si solubilities in c-TiAl(Si)N are achieved without w-AlN formation. • Specific films yield the combination of low residual stress and high hardness.

Potential of Mechanochemically Activated Sulfidic Mining Waste Rock for Alkali Activation

Sulfidic mining waste rock is a side stream from the mining industry with a potential environmental burden. Alkali activation is a promising method for transforming mining waste into construction materials. However, the low reactivity of minerals can be a sizeable challenge in alkali activation. In the present study, the reactivity of waste rock was enhanced by mechanochemical treatment with a LiCl-containing grinding aid. X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) analysis were utilized to display the structural alteration of individual minerals. A schematic implication of the grinding mechanism of mica was provided according to the results of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The alkaline solubility displayed the enhanced chemical reactivity of the waste rock, in which Si and Al solubility increased by roughly 10 times and 40 times, respectively. The amorphization of aluminosilicate is achieved through chemical assisted mechanochemical activation. Sulfidic waste rock, as the sole precursor in alkali activation, achieved a 28-day compressive strength exceeding 10 MPa under ambient curing conditions. The simulation of the upscaled grinding process was conducted via the HSC Chemistry® software with a life-cycle assessment. The results showed that mining waste rock can be a promising candidate for geopolymer production with a lower carbon footprint, compared to traditional Portland cement.Graphical

Ocean Dust Deposition Rates Constrained in a Data‐Assimilation Model of the Marine Aluminum Cycle

AbstractAluminum (Al) is delivered to surface ocean waters by aeolian dust, making it a promising tracer to constrain dust deposition rates and the atmospheric supply of trace metal micronutrients. Over recent years, dissolved Al has been mapped along the GEOTRACES transects, providing unparalleled coverage of the world ocean. However, inferring atmospheric input rates from these observations is complicated by a suite of additional processes that influence the Al distribution, including reversible particle scavenging, biological uptake by diatoms, hydrothermal sources, sediment resuspension. Here we employ a data‐assimilation model of the oceanic Al cycle that explicitly accounts for these processes, allowing the atmospheric signal to be extracted. We conduct an ensemble of model optimizations that test different dust deposition distributions and consider spatial variations in Al solubility, thereby inferring the atmospheric Al supply that is most consistent with GEOTRACES observations. We find that 37.2 ± 11.0 Gmol/yr of soluble Al is added to the global ocean, dominated in the Atlantic Ocean, and that Al fractional solubility varies strongly as a function of atmospheric dust concentration. Our model also suggests that 6.1 ± 2.4 Gmol Al/yr is injected from hydrothermal vents, and that vertical Al redistribution through the water column is dominated by abiotic reversible scavenging rather than uptake by diatoms. Our results have important implications for the oceanic iron (Fe) budget: based on the soluble Fe:Al ratio of dust, we infer that aeolian Fe inputs lie between 3.82 and 9.25 Gmol/yr globally, and fall short of the biological Fe demand in most ocean regions.

Investigation of the phase occurrence and H sorption properties in the Y33.33Ni66.67-xAlx (0 ≤ x ≤ 33.33) system

The Y33.33Ni66.67-xAlx system has been investigated in the region 0 ≤ x ≤ 33.3. The alloys were synthesized by induction melting. Phase occurrence and structural properties were studied by X-Ray powder Diffraction (XRD). The Al solubility in each phase has been investigated by XRD and Electron Probe Micro-Analysis (EPMA). The hydrogenation properties were characterized by pressure-composition isotherm measurements and kinetic curves at 473 K. For x = 0, the binary Y33.33Ni66.67 alloy crystallizes in the cubic superstructure with F4̅3m space group and ordered Y vacancies. For 1.67 ≤ x ≤ 8.33, the alloys contain mainly Y(Ni, Al)2 and Y(Ni, Al)3 pseudobinary phases; while for 16.67 ≤ x ≤ 33.33 they are mainly formed by ternary line compounds Y3Ni6Al2, Y2Ni2Al and YNiAl. Contrary to the binary Y33.33Ni66.67, Y(Ni, Al)2 pseudo-binary compounds crystalize in C15 phase (space group Fd3¯m) with disordered Y vacancies. The solubility limit of Al in the C15 YNi2-yAly phase is y = 0.11 (i.e., x = 3.67). The Y(Ni, Al)3 phase changes from rhombohedral (PuNi3-type, R3¯m) to hexagonal (CeNi3-type, P63/mmc) structure for x increasing from 5.00 to 6.67. Upon hydrogenation, the disproportion of C15 Y(Ni, Al)2 and losses of crystallinity of YNi and Y2Ni2Al are the main reasons causing capacity decay of Y33.33Ni66.67-xAlx (0 ≤ x ≤ 33.33) alloys upon cycling.

Phase relation and transition in the Ti-Al-Mn system

Seeking and optimizing beta solidified gamma (BSG) TiAl alloys have been recognized as hot research topics in recent few decades. Knowledge on phase equilibrium information including solubility limit and stability range can contribute to a necessary basis for tuning the performance of BSG alloys. In this work, we investigated phase relation and transformation in the Ti-Al-Mn system from 973 to 1373 K. With the increase of temperature, the β(Ti) phase region extends continuously accompanied by the change of Al solubility from 9.0 at% at 973 K to 34.7 at% at 1373 K. TiAl shows a wide composition range with the solubility of Mn increasing slightly along the temperature. A ternary Heusler phase β1 (Ti2AlMn) is confirmed to be stable below 1110.5 ± 12.5 K. And B2 phase with an island-like region exists in the temperature range of 1098–1123 K and can connect with Al-rich β(Ti) to form a whole as the temperature increases. According to the evolution of phase relations, two peritectoid reactions B2 + TiAl → Ti3Al + TiMn2 (1160.5 ± 12.5 K) and TiMn1−x + TiMn2 → Ti3Al + TiMn1+x (973–1023 K) can be defined. In addition, it was found that TiMn1−x can be stable up to 1373 K.

Weathering features of a remineralizer in soil under different land uses

Abstract The objective of this work was to analyze the mineralogical, morphological, and compositional modifications resulting from the weathering of diabase grains buried into soil under different land uses for up to 378 days. Samples of comminuted diabase were put into polyester bags and buried into soil under corn crop, elephant grass, and woods, being unburied and evaluated after four time periods. The samples of the remineralizer (RM) were analyzed by X-ray diffractometry, total chemical analysis, scanning electron microscopy, and Al (Ald and Alo) and Fe (Fed and Feo) contents extracted by sodium dithionite-citrate-bicarbonate (DCB) and ammonium oxalate (AAO) solutions. Plagioclases and pyroxenes were the most weathered minerals in all three land uses and showed the same pattern of elemental gains and losses. The characterization of Fe and Al solubility in DCB and AAO showed that the greatest change in these elements was from the lithogenic and crystalline to the pedogenic and amorphous phase, when compared with their total content. Plagioclases and pyroxenes were the most weathered minerals, and Fe and Al show a great transfer from the crystalline to the amorphous phase, with values up to 26 and 175, respectively, for the ratios between bags with RM/Feo and RM-control and bags with RM/Alo and RM-control.

Atomic layer deposition supercycle approach applied to the Al-doping of nearly saturated ZnO surfaces

Current research on transparent conductive oxides deals with the development of environmentally friendly materials having competitive electrical and optical properties. Also, the synthesis methods need to be compatible with the state-of-the-art microelectronics and miniaturization. ZnO films doped with Al (AZO) via Atomic Layer Deposition (ALD) have been subjected to thorough investigation for the latter. However, the conventional doping schemes in ALD seem to have reached their limit and alternative approaches are currently being explored. This work contributes to the improvement of the Al-doping efficiency of ZnO by the ALD supercycle approach, applying the doping-cycle on nearly saturated ZnO surfaces. The electrical (ρ = 1.3 × 10−3 Ωcm, n = 3.79 × 1020 cm−3, and μ = 12.3 cm2/Vs) and optical (%T > 75) properties demonstrated typical values obtained by others applying the supercycle methodology. However, the main finding of this work is the trend observed in the electrical and optical properties, which suggests that the Al solubility limit was not reached as a result of the interaction between the dopant agent and the nearly saturated ZnO surfaces. This is also evidence that the dopant atoms do not become inactive once the compensation effect between substitutional doping and structural defects, has been established. These results open the possibility of exploring the incorporation of more Al into the ZnO structure following and optimizing the doping scheme used here, which at the same time, promises materials that could substitute indium-tin-oxide in many optoelectronic applications, attending the well-known environmental and economic issues.

Stress-dependent prediction of metastable phase formation for magnetron-sputtered V1−xAlxN and Ti1−xAlxN thin films

Metastable transition metal aluminum nitride (TMAlN, TM = Ti, V) thin films are today deposited utilizing ionized vapor phase condensation techniques where variations in ion flux and ion energy cause compressive film stress, in turn affecting Al solubility. While the metastable phase formation of TiAlN has been modeled, the influence of film stresses on phase formation has so far been overlooked. Using combinatorial deposition via magnetron sputtering, thermodynamic modeling and density functional theory calculations, we investigated the phase formation of V1−xAlxN and Ti1−xAlxN thin films at various substrate temperatures and deposition rates. Ab initio calculations indicate that the maximum solid solubility of Al in face-centered cubic (fcc) V1−xAlxN or fcc-Ti1−xAlxN shows a linear trend as a function of the magnitude of compressive stress. Here, we consider the influence of film stresses on the metastable phase formation of fcc-V1−xAlxN and fcc-Ti1−xAlxN for the first time. Specifically, experimental data from a single combinatorial deposition is utilized to predict the stress-dependent formation of metastable phases based on thermodynamic and ab initio data. Explicit consideration of stress extends the Al solubility limit to higher values for both Ti1-xAlxN and V1-xAlxN thin films, previously unobtainable by energetics, but accessible experimentally. These predictions are experimentally verified and thus provide guidance for experimental efforts with the goal of increasing the Al concentration in fcc-TMAlN thin films.

Li conductivity in Li1+xTi2-xAlx(PO4)3 (0.3≤ x≤ 0.7) ceramics prepared from sol-gel precursors

Li1+xTi2-xAlx (PO4)3 (LTAP) x = 0.3, 0.4, 0.5 and 0.7) compounds, prepared at 800 °C by sol-gel, have been studied by X-ray diffraction, Nuclear Magnetic Resonance, Scanning Electron Microscopy and Impedance Spectroscopy. The increment of lithium enhances Li–Li repulsions, favoring the creation of vacancies at the conduction paths intersection (M1 sites), increasing Li mobility along (… M1-M2-M1 …) channels in NASICON phases. The partial elimination of segregated AlPO4, LiAlP2O7 and LiTiPO5 phases increased Ti, Al solubility in NASICON, improving overall conductivity in ceramics prepared at 950 °C. The maximum of “bulk” conductivity was produced in x = 0.4 sample, as a consequence of the creation of M1 vacancies and allocation of Li in M2 cavities with optimal Li/vacancy distribution. The presence of secondary phases increased grain boundary impedance, shifting maximum of overall conductivity to x = 0.3 compound. Obtained results are compared with those reported previously in LTPA samples prepared by the ceramic route.

The diversity of volcanic soils: focusing on the function of aluminum–humus complexes

ABSTRACT Andosols (or Andisols) are the typical soils developed from volcanoclastic materials. They possess several distinctive properties that are rarely found in other groups of soils. These properties are largely due to the dominance of short-range ordered minerals (allophane, imogolite, and ferrihydrite) and/or mineral–humus complexes (Al/Fe–humus complexes). In this review, I survey the diversity of volcanic soils mainly from the viewpoint of the function of Al–humus complexes. Specific topics include the role of Al–humus complexes in organic carbon accumulation, Al solubility and kinetics, Al phytotoxicity to plants, and the suppression of soil-borne diseases. It is shown that Al–humus complexes are heavily involved in the diversity of these properties of volcanic soils.