Al2O3 P2O5 Research Articles

Sol–gel synthesis and photoluminescence of AlP nanocrystals embedded in silica glasses

AlP nanocrystals embedded in silica glasses were prepared via an easy sol–gel process. The gels synthesized by the hydrolysis of a complex solution of Si(OC2H5)4, Al(NO3)3·9H2O and PO(OC2H5)3 were heated at 600°C for 10h in an air atmosphere to form an Al2O3–P2O5–SiO2 gel glass. The gel glasses were then heated in the presence of H2–N2 mixed gas, in which the P(V) are reduced by the H2 gas, and react with Al(III) to form fine cubic AlP crystallites embedded in silica glasses. The X-ray diffraction patterns showed (111), (220), and (311) diffraction lines from cubic AlP crystals. The AlP (220), (311), (422), and (440) diffraction lines were observed in the electron diffraction pattern. The size of AlP nanocrystals was found to be from 5 to 10nm in diameter by transmission electron microscopy. A strong room temperature photoluminescence (PL) with peaks at 533, 582, 649, and 688nm was observed from AlP/SiO2 nanocomposites. The PL is suggested to originate from the hydrogen-related species (PL band at 533nm), the small “peroxy radical” (PL band at 582nm), and the nonbridging oxygens (PL bands at 649 and 688nm), respectively.

Chemical characteristics of water-insoluble components in aeolian dust collected in China in spring 2002

Aeolian dust collected at three stations in China (Beijing, Qingdao, and Hefei) in spring 2002 has been analyzed and their chemical features have been thoroughly discussed. The mass concentrations of aeolian dust collected were high in coarse grains, and the distribution patterns against particle size were different among the sampling stations. When large-scale dust events were observed, the concentrations of suspended particle with a particle size over 2 μm especially increased. The chemical compositions (Al2O3 Na2O, P2O5, Total Fe2O3, Rb, Zr, and La) of all but one aeolian dust sample were almost constant in coarse grains and quickly decreased below 1.1-2.1 μm. This result suggests that the contribution of mineral aerosol to aeolian dust sharply decreased in fine grains. In the dust event of March at Beijing, however, these elemental concentrations were almost constant over the variations of particle size. This fact indicates that the large-scale dust event supplied a large amount of mineral aerosol even in fine grains. The elemental concentration ratios to Al2O3 were almost constant in coarse-medium grains, but suddenly increased below 1-2μm: the mineralogical composition was homogenous in coarse-middle grains, but changed in fine grains. The grain-size distribution pattern of the elemental concentration ratio has no systematic variations with or without a dust event or among three sampling stations. Therefore, chemical features of aeolian dust coming from inland China and suspended particle accumulated around sampling locations are very similar. On the contrary, some heavy elements (Cr, Ni, Cu, Zn, Mo, Cd, Sb, Sn, Pb, and Bi) had different features from elements that originated form mineral aerosol such as Al2O3. The concentrations and metal/Al2O3 ratios for these heavy metals increased with decreasing particle size. For example, the Cu/Al2O3 and Pb/Al2O3 ratios dramatically increased tenfold to hundredfold with decreasing particle size. These distribution patterns against the particle size suggest that anthropogenic materials were contaminated to finer grains.

Neodymium fluorescence quenching by hydroxyl groups in phosphate laser glasses

Non-radiative losses due to OH fluorescence quenching of the Nd3+4F3/2 state are quantified over a range of OH concentrations from 4×1018 to 4×1020cm−3 and Nd doping levels from 0.4 to 9×1020cm−3 in two K2O–MgO–Al2O3–P2O5 metaphosphate glasses having different K/Mg ratios (∼1/1 and 2/1). The quenching rate varies linearly with the Nd and OH concentrations as predicted by Forster–Dexter theory. However, in contrast to theory, the OH quenching rate extrapolates to a non-zero value at low Nd3+ doping levels. It is proposed that at low Nd3+ concentrations the OH is correlated with Nd sites in the glass. The quenching strength of OH on a per ion basis is weak compared to common transition metal impurities (V, Fe, Co, Ni, Cu and Cr). Nevertheless, OH dominates the Nd quenching in phosphate glass because under most processing conditions OH is present at concentrations 102–103 greater than transition metal ion impurities.

Compositional effects on the optical and thermal properties of potassium aluminophosphate glasses

The K2O–Al2O3–P2O5 glass system has been examined and various compositions have been melted. Their optical and thermal properties have been measured to assess their potential for athermalisation. The addition of alumina (Al2O3) increases the refractive index (n) and glass transition temperature (Tg) and decreases the thermal expansion coefficient (α), consequently leading to positive thermo-optic coefficient (dn/dT). In addition to thermal expansion, polarisability of the glass also affects dn/dT. Generally, glasses must exhibit negative dn/dT to counter thermal expansion, in order to have potential application in athermalisation.

Preparation and characterization of sol–gel derived glasses in the ternary Na2O–Al2O3–P2O5system

A new sol–gel synthesis route to organic free Na2O–Al2O3–P2O5 xerogels was developed. These xerogels contain P2O5 up to 67.5 mole % and Al2O3 up to 20 mole % and could be melted to homogeneous glasses in air at significantly lower temperatures than those applied using the conventionally melting method. Aluminum isopropoxide dissolved in isopropanol, orthophosphoric acid dissolved in isopropanol and sodium nitrate were used as precursors for Al2O3, P2O5 and Na2O respectively. Clear stable alcoholic solutions were prepared in the presence of HNO3. Addition of HNO3 in the concentration used, enabled homogeneous mixing of the precursors, controlled over the gelation step and prevented the fast precipitation of the AlPO4 crystalline phase which breaks down the glass formation ability. The sol–gel route developed was investigated using different analytical tools. Differential thermal analysis (DTA) coupled with thermo-gravimetric (TG) analysis indicated that neither organic residues nor sodium nitrate residues were present in the dried gels after gelation. Fourier transform infrared spectroscopy (FTIR) showed the presence of all characteristic phosphate groups and bonds in the dried gels, especially the P=O and the P–O–P bonds. Solid state 31P Magic angle spinning nuclear magnetic resonance (MAS NMR) revealed the formation of Q2 chain-like polyphosphates of variable polymerization degrees in the dried gels. Solid state 27Al MAS NMR revealed that octahedrally coordinated Al is the preferred moiety in the dried gels. However, powder X-ray diffraction (XRD) investigation indicated the presence of crystalline Q1 oligomeric pyrophosphate species in the dried gels. Isotropic chemical shifts belonging to these pyrophosphate species were also recorded in the 31P MAS NMR spectra. Characterization of the prepared glasses showed that their properties are in very good agreement with those glasses prepared by the conventionally melting method.

Fluoroapatite glass-ceramic coatings on alumina: structural, mechanical and biological characterisation

The aim of this work was to realise bioactive coatings on full density α-alumina substrates.An SiO2–CaO-based glass (SC) and an SiO2–Al2O3–P2O5–K2O–CaO–F−-based glass-ceramic (SAF) were used for this purpose. Specifically, SAF is a fluoroapatite containing glass-ceramic and previous studies have shown that it is a highly bioactive biomaterial. Furthermore, these fluoroapatite crystals possess a needle-shaped morphology which mimics that of hydroxylapatite found in human hard tissues, particularly in teeth.SAF is a very viscous glass-ceramic and for this reason an intermediate, less viscous, SC layer was interposed in direct contact with alumina aiming to obtain a good coating adhesion.Moreover, this intermediate layer strongly lowers the Al3+ diffusion and thus minimises both compositional changes in the SAF outer layer and the risk of detrimental modifications of the nature of the crystalline phases.A complete characterisation of the coated samples was performed by means of X-ray diffraction, optical and scanning microscopy. Coating adhesion on alumina was tested by comparative shear tests while biocompatibility was investigated on alumina, bulk SAF and on the realised coatings. For this purpose, cytotoxicity, adhesion and proliferation of human osteoblast-like cells were cultured onto the three materials. Results showed that the interposition of the SC layer was successful in allowing a good softening and spreading of the SAF outer layer and in avoiding the crystallisation of undesired crystalline phases maintaining the good bioactive properties of the bulk one. In vitro results on the coatings showed osteoblast-like cell behaviour similar to bulk fluoroapatite glass-ceramic and better respect to alumina substrates, being a promising index of bone material integration and of its in vivo possible applications.

Thermal wet oxidation of GaP and Al0.4Ga0.6P

Thermal wet oxidations of GaP and Al0.4Ga0.6P at 650 °C for various times have been performed. Comparisons are made on oxidation rates and post oxidation morphology. Transmission electron microscopy shows that when oxidizing GaP, polycrystalline monoclinic GaPO4⋅2H2O forms without noticeable loss of phosphorus. Oxidation for 6 h or more leads to poor morphology resulting in cracks and detachment. A thickness expansion of about 2.5–3 times is noticed as a result of oxidation. In contrast, oxidized Al0.4Ga0.6P exhibits much better morphology without cracks or detachment from the substrate. The oxide has an almost amorphous-like microstructure. The oxidation process shows typical diffusion-limited reaction at long anneals. Preliminary work on the oxidation of AlP indicates that the reaction leads to formation of Al2O3 and possible volatile P2O5 diffusing out of the specimen. Thus, from the structural viewpoint, AlGaP forms a better oxide suitable for device needs.

Microstructural evolution in bone china

Abstract Phase and microstructural evolution in model bone china bodies was determined by XRD and electron microscopy of quenched samples fired for 3 h at 600–1500°C. Unfired but shaped bone china comprised bone ash and clay agglomerates (≤70 μm) in a matrix of smaller (from submicron to 10 μm) mixed clay, feldspar, and bone ash particles. The unfired microstructure and subsequent phase evolution is believed to be strongly dependent on the extent of prior mixing. On firing, the clay component dehydroxylated to metakaolin at ∼550°C. Metastable sanidine formed from decomposition of the feldspar component above 600°C and dissolved at 1100°C. The bone ash com ponent decomposed into β-TCP and lime (and/or Ca2+ and O2- ions) beginning at ∼800°C. CaO from the bone ash reacts with the clay decomposition products forming liquid and anorthite at ∼900°C. Liquid formation is due to reaction of CaO with feldspar and clay relict grains and is discussed in terms of the CaO–P2O5–Al2O3 ternary phase diagram. Above 1200°C ...

Preparation by microwave irradiation of nanometre-sized AlPO4-5 molecular sieve

The influence of the synthesis conditions on the crystallization and crystal size of AlPO 4 -5 molecular sieve is investigated in a (TEA) 2 O–Al 2 O 3 –P 2 O 5 –H 2 O system. The initial mixture composition and the crystallization method affect the crystallization and the crystal size of the product. Microwave heating of the synthesis mixture results in the formation of AlPO 4 -5 with nanometre-sized particles.

A rhythmically banded basaltic andesite intrusion in the Shiretoko Peninsula, Hokkaido, Japan.

The Oshinkoshin Intrusion is a mushroom-shaped, basaltic andesite intrusion of Pliocene age that occurs in the Shiretoko Peninsula, Hokkaido, Japan. The intrusion is 1000 m long and 400 m wide and consists of three concentric zones: inner massive zone, polyhedral jointed zone, and marginal banded zone. The inner massive zone occupies the central part of the intrusion, and is characterized by columnar joints 100 to 250 cm across. The polyhedral jointed zone encircles the inner massive zone, and is characterized by columnar joints 70 to 150 cm across and small polyhedral joints. The small joints outline 10 to 25 cm polyhedra on both longitudinal and transverse surfaces of the columns. The marginal banded zone encircles the polyhedral jointed zone, and shows rhythmic banding parallel to the margins and columnar joints perpendicular to the margins. The rhythmic banding is composed of alternating protruding, more weathering-resistant and recessive, less resistant bands, both of which are a few centimetres thick. Each protruding band characteristically encloses a central vein. Chemically, protruding bands have higher SiO2 and K2O and lower MgO and total Fe contents than recessive bands. Veins in the protruding band have much higher SiO2, TiO2, Na2O, K2O, P2O5, and lower Al2O3, MgO, CaO than the protruding band. The thicknesses of the protruding and recessive bands gradually decrease toward the margin of the intrusion. The concentric zonal structure in the Oshinkoshin Intrusion formed by cooling of a magma which was emplaced in a single intrusive phase into wet, poorly consolidated sediment. The rhythmic banding in the marginal banded zone formed by concentration of residual melt in numerous parallel cooling fractures along the margin of the intrusion, as the rheological behavior of magma changed from ductile to brittle.

Structure of gel materials in the system Ce2O3Al2O3P2O5

By using the sol-gel method, amorphous materials have been obtained in the Ce2O3Al2O3P2O5 system. Their phase formation and microstructural changes have been investigated as a function of thermal treatment in the temperature range of 300–1400°C by X-ray diffraction, infrared spectroscopy and transmission electron microscopy. It is established that gels containing Ce3+ possess high thermal stability. According to the X-ray data, they are amorphous up to 500°C. After crystallization, phases characteristic of the Ce3+ ions are present. The network of the gel materials is built up from PO4 phosphate complexes, by contrast with the gel products containing Ce4+.

Synthesis and characterization of CAM-1, a novel aluminophosphate molecular sieve precursor

A new aluminophosphate molecular sieve precursor was synthesized hydrothermally in a non-aqueous system, Al2O3–P2O5–triethylamine–triethylene glycol, and characterized by powder X-ray diffraction, 27Al and 31P magic-angle-spinning NMR with cross-polarization, scanning electron microscopy, energy-dispersive X-ray analysis, IR spectroscopy, thermogravimetric analysis and elemental analysis. The material has molar composition 3.0 Al2O3:3.0 P2O5:2.0 N(C2H5)3:3 H2O. NMR reveals the presence of at least two crystallographic sites for phosphorus in a population ratio of 2:1 and three inequivalent sites for aluminium. The chemical shift anisotropy and hydrophilicity of the phosphorous resonating at –23.6 ppm are much greater than that of phosphorus at –30.3 ppm. IR spectroscopy monitors very strong interactions between the organic template and the aluminophosphate framework. Upon calcination at 200 °C the material transforms into the dense-phase AlPO4-tridymite, while the sample loses 21% of its weight as a result of the decomposition of the template.

X-ray powder diffraction of crystalline phases in phosphate bioglass ceramics

Abstract Pure phosphate bioglass ceramics of the system Na2O–CaO–Al2O3–P2O5–F− with the additives ZrO2, TiO2 and FeO/Fe2O3 were investigated by X-ray powder diffraction at temperatures up to 750°C. The glass system with ZrO2 and TiO2 exsolves eight crystalline phases in this temperature range. Three of them are new phosphate phases (U2, U3, U4) whereas NaZr2(PO4)3 and U1 (Na–Ca–(Zr, Ti)–Al-monophosphate), which is isostructural to NaTi2(PO4)3 with space group R[unk]c, belong to the Nasicon-structure-type. Lattice constants of these phases were determined by transmission electron microscopy. Energy dispersive X-ray analysis gave some indication of the chemical composition of the various phases.

Porous Glass‐Ceramics with a Skeleton of the Fast‐Lithium‐Conducting Crystal Li1+xTi2−xAlx(PO4)3

Porous glass‐ceramics with a skeleton of the fast‐lithium‐conducting crystal Li1+xTi2−xAlx(PO4)3 (where x= 0.3–0.5) were prepared by crystallization of glasses in the Li2O─CaO─TiO2─Al2O3–P2O5 system and subsequent acid leaching of the resulting dense glass‐ceramics composed of the interlocking of Li1+xTi2−xAlx(PO4)3 and β‐Ca3(PO4)2 phases. The median pore diameter and surface area of the resulting porous Li1+xTi2−xAlx(PO4)3 glass‐ceramics were approximately 0.2 μm and 50 m2/g, respectively. The electrical conductivity of the porous glass‐ceramics after heating in LiNO3 aqueous solution was 8 × 10−5 S/cm at 300 K or 2 × 10−2 S/cm at 600 K.

Synthesis of a new crystalline aluminophosphate

A crystalline aluminophosphate, AlPO4–NCL, has been synthesized from a 2DBA–Al2O3–P2O5–40H2O system (DBA =n-dibutylamine), and characterized by means of X-ray powder diffraction, scanning electron microscopy, 27Al MASNMR and thermal analysis. The presence of a large amount of occluded amine and high instability during air drying, even at ambient temperature, seem to suggest a layered structure for the material.

Orthophosphates in the Ternary System Al2O3P2O5H2O

AbstractOrthophosphates of aluminum have been the subject of numerous studies since the middle of the nineteenth century. They have acquired importance in such diverse fields as the earth sciences, chemical engineering, and medicine. The chemical problems associated with this Al2O3P2O5H2O system mainly arise from the marked tendency to form polymeric aluminum orthophosphate complexes in solution; equilibrium is reached only with difficulty, and crystallization of single phases is the exception rather than the rule. However, the crystal structures of several aluminum orthophosphates (including minerals) have been elucidated, and it is now possible to give a systematic description of this class of compounds and the conditions necessary for their formation.

ChemInform Abstract: PROPERTIES AND STRUCTURE OF ALKALI ALUMINOPHOSPHATE GLASS

AbstractFür eine Reihe von A2O‐Al2O3‐P2O5 (A: Na, K)‐Gläsern mit P2O5 Gehalten zwischen 32 und 63 mol‐% werden Dichten, Brechungsindices, IR‐Spektren, Molvolumina, Volumina pro Mol Sauerstoff und Molrefraktionen bestimmt.

Properties and Structure of Alkali Aluminophosphate Glass

Abstract Several series of alkali (sodium and potassium) aluminophosphate glasses were prepared with compositions of 32–63 mol % of P2O5 and the properties of these glasses were determined. In the glasses with a higher P2O5 content (P2O5\gtrsim42.5 mol % in the Na2O–Al2O3–P2O5 glass and P2O5\gtrsim45 mol % in the K2O–A12O3–P2O5 glass), the density, refractive index, and chemical resistivity increased with increasing amounts of Al2O3. In the glasses with a lower P2O5 content (P2O5\gtrsim37.5 mol % in the Na2O glass and P2O5≈40 mol % in the K2O glass), however, almost no increase of the density was found by an increase of Al2O3; the increases in the refractive index and chemical resistivity were also smaller than those in the glasses with a higher P2O5 content. The infrared absorption spectra of the glasses varied also with the P2O5 content. These changes in the properties are due to a marked structural difference between the glasses with a higher P2O5 content and those with a lower P2O5 content, and are also associated closely with the structural role of Al3+ ions in the glass.

Glass Formation and Crystallization in Ternary Phosphate Systems Containing Al2O3

Abstract Glass formation and crystallization were investigated in two types of three-component systems, M2O–Al2O3–P2O5 (M=Li, Na, and K) and MO–Al2O3–P2O5 (M=Mg, Ca, and Ba). In the Li2O–Al2O3–P2O5 and MO–Al2O3–P2O5 systems, wide regions of glass formation were found in compositions containing more than 50 mol% of P2O5. In the Na2O–Al2O3–P2O5 and K2O–Al2O3–P2O5 systems, the two peaks in Al2O3 content were found in the regions of glass formation corresponding to about 35 and 65 mol% of P2O5. In the devitrified products of the glasses with 60 and 70 mol% of P2O5, AlPO4, Al(PO3)3, and alkaline earth metaphosphate (in the MO–Al2O3–P2O5 system) were found by X-ray powder diffractometry. The crystalline phases in the samples obtained as mixtures of glass and crystal consisted of AlPO4 in the composition containing 60 mol% of P2O5, while those with a P2O5 composition of 70 mol% consisted of Al(PO3)3. By heating those samples at 700–900 °C, the X-ray diffractions of AlPO4 and Al(PO3)3 were intensified. On the other hand, in the samples with 37.5, 40, and 50 mol% of P2O5, all the crystalline phases consisted of AlPO4, and the intensities of these X-ray diffractions decreased after the samples were heated at 600–700 °C. Thus, there is a marked structural difference between the two peak-regions in the Na2O–Al2O3–P2O5 and K2O–Al2O3–P2O5 systems.

Diversity and origin of abyssal tholeiite from the Mid-Atlantic Ridge near 24� and 30� North latitude

On cursory examination of hand specimens and thin sections, the abyssal tholeiite in a dredge haul may appear to be uniform in composition. Chemical analyses of a considerable number of fragments, however, have always revealed the existence of regular compositional variation in them. The MgO content decreases with increasing SiO2. In abyssal tholeiites with relatively low Al2O3 contents, the SiO2, total iron, Na2O and P2O5 contents tend to increase and the MgO content tends to decrease with increasing iron/magnesia ratio, probably owing to crystallization differentiation. In a certain dredge haul, high-alumina abyssal tholeiites (with Al2O3 contents near or over 17%) occur in association with low-alumina abyssal tholeiites. The magma of high-alumina abyssal tholeiites would be generated from that of low-alumina abyssal tholeiites by differentiation at a depth around 30 km. In pillow lavas of abyssal tholeiite free from weathering and metamorphism, the chilled rim of the pillow usually has virtually the same chemical composition as the more crystalline core except for a decrease of K2O content toward the rim. On the other hand, the weathered rim of pillow lavas shows marked compositional change. The Fe2O3/FeO ratio of unweathered abyssal tholeiite is in the range of 0.1 to 0.3. This ratio and the H2O− and H2O+ contents increase with advancing weathering.