Glassy Phosphates Research Articles

Foamed Glassy Phosphate Materials for Biosorbents

The paper considers the applications of foamed glassy phosphate materials as carriers of biologically active substances. One of the advantages of phosphate materials is their ability to effectively support the life of microorganisms. This feature of phosphate glassy materials opens up the prospects for the application of microorganism strains - destructors of oil products to their foamed samples, that is, the creation of biosorbents for purification of water and soil from hydrocarbon contamination. The advantages of a biosorbent are explained by the high biological activity of microorganisms on the surface of foamed glassy phosphates and the possibility of active development of microorganisms with the simultaneous destruction of petrochemical contaminants. The use of biosorbent eliminates the problem of its utilization and regeneration, thus it is suitable for repeated use. The formation of porous glassy phosphate materials on the surface by the method of molecular layering of monolayer coatings allows obtaining chemically modified composite materials, which improves their performance characteristics such as strengthening the material structure with a simultaneous increase in the catalytic activity of biochemical processes.

Influence of surface roughness and ZDDP additive on the friction and wear of reciprocating sliding surfaces at high contact pressures

PurposeSurface roughness has been proved to be influencing the running-in wear of machined components under dry and lubricated sliding conditions. Zinc dialkyl dithiophosphate (ZDDP) is widely used as an anti-wear additive, which reduces the wear by the formation of a tribofilm on the surface (Spikes, 2004). Factors such as temperature, sliding distance, etc. influence the formation of the film. A significant reduction in the power loss due to friction and wear is possible if a synergy is attained between surface roughness effects and the effectiveness of the tribofilm. The present work aims to study the influence of surface roughness and ZDDP addition on the formation and removal of the tribofilm under high contact pressures.Design/methodology/approachSamples were prepared by machining. Surface roughness was varied by varying the milling parameters. A reciprocating friction and wear test machine with a ball-on-flat geometry was used for the study. Tests were performed with mineral base oil and base oil added with 1 per cent by weight ZDDP under different operating parameters. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) with energy dispersive X-Ray spectroscopy (EDS) analysis were conducted to study the surface morphology of the tribofilm.FindingsA quasi-steady-state analysis conducted showed that the wear rate was much lower when tested with base oil containing ZDDP after about 65 min. AFM analysis confirmed the presence of chemically reacted films on the surface. SEM analysis revealed agglomeration of crystal like glassy phosphates. However, high contact pressures at the interface caused the removal of the films resulting in variations in the coefficient of friction. A comparison of the wear rates among the samples of different roughness values tested at 100°C showed that the anti-wear performance of ZDDP was not effective due to high contact pressures.Originality/valueThe findings in this study regarding the tribofilm formation with ZDDP additive and its failure due to high contact pressures will be beneficial for further investigation on wear resistant boundary films developed under such extreme conditions.

Preparation and characterization of phosphate glass system A2MnMP2O10(A = Li, Na, K) and (M = W, Mo)

New materials based glassy phosphates and transition elements A 2 MnMP 2 O 10 (A = Li, Na, K) and (M = Mo, W) were prepared by direct fusion of the mixture of the reactants followed by quenching in the air. Analysis by X-ray diffraction showed that the obtained materials are amorphous. Differential scanning calorimetry DSC was used to determine the glass transition (Tg) and crystallization (Tc) temperatures. The thermal stability of tungsten glasses is higher than that of molybdenum ones. Tungsten plays, certainly, a role of cross-linking polyphosphate groups by creating more covalent new bonds P-O-W and W-O-W. Moreover, it has been shown that lithium glasses are more stable than sodium and potassium, probably due to the potassium hygroscopy. Raman analysis confirms that the studied glasses have similar structures and the predominant structural units are PO 4 , P 2 O 7 and MO 6 polyhedra (M = W, Mo, Mn).

Nanominerals and nanoparticles in feed coal and bottom ash: implications for human health effects

Environmental and human health risk assessments of nanoparticle effects from coal and bottom ash require thorough characterisation of nanoparticles and their aggregates. In this manuscript, we expand the study of human exposure to nanosized particles from coal combustion sources (typically <100 nm in size), characterising the complex micromineralogy of these airborne combustion-derived nanomaterials. Our study focuses on bottom ash generated in the Santa Catarina power station (Brazil) which uses coal enriched in ashes, many potential elements (e.g. Cr and Ni) and pyrite. Transmission electron microscope data reveal nanoscale C deposits juxtaposed with and overgrown by slightly larger aluminosilicate (Al-Si) glassy spheres, oxides, silicates, carbonated, phosphates and sulphates. Iron oxides (mainly hematite and magnetite) are the main bottom ash products of the oxidation of pyrite, sometimes via intermediate pyrrhotite formation. The presence of iron oxide nanocrystals mixed with silicate glass particles emphasises the complexity of coal and bottom ash micromineralogy. Given the potentially bioreactive nature of such transition metal-bearing materials, there is likely to be an increased health risk associated with their inhalation.

Ultraviolet/visible reflection spectroscopy of molten and glassy silicates (MeOn–CaO–SiO2) and phosphates (MeOn–CaO–P2O5), Men+ = Fe3+, Mn2+

This work deals with the reflectivity of liquid oxides (silicates and phosphates) in the ultraviolet and visible spectral range using a reflection angle of 0°. For these considerations, we have developed a spectroscopic reflection method (impulse-flash-technique). By use of this method, we can also record kinetic processes, such as crystallization processes of a supercooled glassy matrix to a crystalline equilibrium phase at high temperatures (transition from specular reflection to diffuse reflection). We have investigated the systems CaO–MeOn–SiO2 and CaO–MeOn–P2O5 (Men+=Fe3+, Mn2+) with Fe2O3- and MnO-contents above 24% (mass-%) in the temperature range from 1400°C to 1550°C applying an oxygen partial pressure of pO2=0.21bar. The spectra are compared with a CaO–Fe2O3-flux with an Fe2O3-content of 60%. The increased reflectivity in the ultraviolet spectral range is based on the very intensive electron transfer (charge transfer bands, CT) from the oxide ion (bound to the respective matrix) to the Men+-ion. The increased reflectivity in the visible spectral range is due to d–d-transitions in the Men+-ion located in Men+–O2−-complexes. This can be proven in the following way. The reflection bands in the visible range are much less pronounced than the CT-bands in the UV range. In the fluxes, complexes with the coordination number 4, Men+(O2−)4 with Men+=Fe3+ or Mn2+, were found. In glassy silicates and phosphates, complexes with a coordination number of six dominate. During the quenching process of a silicate to a temperature in the solidus range (up to 900°C) the complexes with a coordination number of six are formed with low order in the glassy matrix. This takes place within a rapid reaction. Subsequently, the crystallization process of the silicates into equilibrium phases starts. The reflection spectra were analyzed quantitatively and related to the molecular structure of the liquid and glassy solidified systems. In the present work, we describe a quantitative correlation between the reflectivity in the UV range and the molar Men+-content. The basic investigations for recording the redox state of liquid silicates and phosphates during a running metallurgic process are part of this work. Liquid silicates and phosphates are the most important slag systems in this context.

Dipolar NMR Strategies for Multispin Systems Involving Quadrupolar Nuclei: 31P{23Na} Rotational Echo Double Resonance (REDOR) of Crystalline Sodium Phosphates and Phosphate Glasses

A new procedure for the site-selective measurement of heteronuclear magnetic dipole−dipole interactions involving quadrupolar nuclei has been developed. Particular attention is given to the case of S{I} rotational echo double resonance (REDOR) with S = 1/2 and I = 3/2, where the nuclear electric quadrupole splitting affects the efficiency of the π(I) pulses in recoupling the S−I dipolar interactions. Detailed two- and three-spin simulations using the SIMPSON code indicate that the REDOR response is sensitively affected by the quotient of the nutation frequency and the nuclear electric quadrupole frequency (ν1/νq). Multispin systems can be conveniently analyzed using a curvature determination of REDOR data in the limit of short dipolar evolution times (ΔS/S0 < 0.2), to yield dipolar second moment (M2) values. The apparent M2 values measured in this fashion include a scaling factor f1, the magnitude of which can be predicted if ν1/νq is known. Based on this finding, a robust method has been developed to analyze experimental REDOR data in multispin systems, in terms of average dipolar M2 values, which are shown to be affected by distributions of magnetic dipolar and nuclear electric quadrupolar coupling constants only to a minor extent. Validation experiments on suitable model compounds indicate that dipolar M2 values can be measured within 10% accuracy in this fashion for crystalline compounds. For glasses, the error may be higher, because of possible cumulative errors that may occur from unknown geometries and distribution effects. Experiments conducted on glassy sodium phosphates indicate that the 31P−23Na dipolar interaction strengths in these systems are differentiable for the various Q(n) sites and increase as the charge of the phosphate moiety increases.

High Microwave Susceptibility of NaH 2PO 4·2H 2O: Rapid Synthesis of Crystalline and Glassy Phosphates with NASICON-Type Chemistry

High microwave susceptibility of NaH 2PO 4·2H 2O has been discovered. This hydrated acid phosphate of sodium can be heated upto 1000 K or more when exposed to 2.45 GHz microwaves. Using this, a novel microwave-assisted preparation of a number of important crystalline and glassy materials with NASICON-type chemistry has been accomplished in less than 8 min which is only a fraction of the time required for conventional synthetic procedures. The present single-shot approach to the preparation of phosphates is attractive in terms of its simplicity, rapidity, and general applicability. A “step-ladder” heating mechanism has been proposed to account for the high microwave absorbing ability of NaH 2PO 4·2H 2O.

Capillary electrophoresis of longer-chain polyphosphates

Capillary electrophoretic separations of sodium polyphosphates with anion chain lengths from 1 to >30 are presented. A buffer containing pyromellitic acid, triethanolamine and hexamethonium hydroxide gives a high resolution separation of linear and cyclic polyphosphate species. Distinct separation patterns can be obtained in 20 min for glassy sodium phosphates with number-average chain lengths from 5 to 44. The preliminary electrophoretic separations presented here should be useful for the rapid characterization of complex polyphosphate mixtures.

31P MAS NMR Investigations of Crystalline and Glassy NASICON-Type Phosphates

31P MAS NMR investigations of crystalline and glassy NASICON-type phosphates have been carried out. The origin for the two signals in the case of the crystalline compounds is discussed. The spectra show the presence of pyrophosphate units in all glasses studied along with various other phosphate species resulting from structural disproportionation.

Polyphosphate separations and chain length characterization using minibore ion chromatography with conductivity detection

The separation of linear and cyclic polyphosphates with chain lengths of 1 to ca. 30, using 2 mm I.D. polymeric ion-exchange columns and suppressed conductivity detection, is described. The separations are characterized by good resolution of phosphate species and analysis times < 30 min. To assess the accuracy of the chromatograms obtained, average chain lengths of sodium hexametaphosphate and glassy phosphates in the range 5–25 are determined and compared with results obtained by 31P NMR and potentiometric titration. General agreement among the three techniques is seen. An example is presented using ion chromatography to follow the hydrolysis of sodium hexametaphosphate.

Characterization of metamict and Glassy Lead Phosphates

ABSTRACTSingle crystals of Pb2P2O7 (beam stable under 200 kV TEM electrons to a fluence &gt; 1027 e/M2 and an ionizing dose &gt; 1014 Gy) were rendered Metamict (amorphized) with ion-implantation (100 kV P+ ions with several fluences between 5 × 1017/M2 - 2 × 1020/M2). Pb2P2O7 and PbO-P2O5 glasses were also ion implanted at identical fluences. Radial distribution functions for metamict and glassy phosphates generated using energy filtered electron diffraction (EFED) data collected on 100 kV field emission STEM (VG HB-5) indicate significant alterations in the medium range order.

Characterization of metamict and glassy phosphates using energy-filtered electron diffraction

Lead phosphate glasses have been investigated for decades with respect to fundamental glass properties such as glass transition, devitrification, electrical and optical properties. In these glasses, [PO4] tetrahedra, (like [SiO4] tetrahedra in silicates) can link up together by corner sharing oxygen atoms to form polymerized structures upto and including three dimensional glassy networks. Although, little electron diffraction data on amorphous phosphates is available, radial distribution functions have been generated for lime phosphate glasses and amorphous aluminum phosphates using x-ray diffraction techniques. More recently, Sales et al. have examined near surfaces of single crystals of lead pyrophosphate (Pb2P2O7), rendered aperiodic (metamict) by ion implantation, and lead pyrophosphate glass using high-performance liquid chromatography (HPLC), making use of the fact that condensed phosphates do not alter their state of polymerization when dissolved in aqueous solutions.In our studies, single crystals of Pb2P2O7 were found to be beam stable under 200 keV TEM electrons to an electron fluence &gt; 1027 e/m2 and an ionizing dose &gt; 1014 Gy. This negative radiolytic result leaves ballistic displacement by ions or neutrons as the only route to render the samples metamict.

Structure Characterization of Metamict and Glassy Lead Phosphates

ABSTRACTSingle crystals of Pb2P2O7 (beam stable under 200 kV TEM electrons to a fluence &gt; 1027 e/m2 and an ionizing dose &gt; 1014 Gy) were rendered metamict (amorphized) with ion-implantation (100 kV P+ ions with several fluences. Pb2P2O7 and PbO·P2O5 glasses were also ion implanted at identical fluences. Radial distribution functions of metamict and glassy phosphates are being generated using energy filtered electron diffraction (EFED) data collected on 100 kV field emission STEM (VG HB-5). Ion-implanted lead phosphate glasses exhibit a significant difference in their FSDP as compared to the non-irradiated ones. XTEM results also show that ion-beam damage layer was around 200 nm deep. XTEM-HREM structure images of ion-implanted single crystals, along with their optical diffraction analysis will be presented and briefly discussed.

Use of Sol-Gel or Coacervate Process to Formulate Glassy or Ceramic Phosphates for Coating

Abstract One of the objectives of present research on glassy and ceramic phosphates for coating materials is the synthesis of new precursors and the formulation of their mixtures. The properties of these materials depend mainly on the relative proportions of their constituents. Being able to varie at will the formulation of the materials the importance of the sol gel to glass or ceramics is dearly shown. This soft process is in a number of cases, preferable to the conventional high-temperature process.

Use of Sol-gel or Coacervate Process to Formulate Glassy or Ceramic Phosphates for Coating

Abstract One of the objectives of present research on glassy and ceramic phosphates for coating materials is the synthesis of new precursors and the formulation of their mixtures. The properties of these materials depend mainly on the relative proportions of their constituents. Being able to varie at will the formulation of the materials the importance of the sol gel to glass or ceramics is dearly shown. This soft process is in a number of cases, preferable to the conventional high-temperature process.

A magic-angle spinning 31P NMR investigation of crystalline and glassy inorganic phosphates

31NMR spectra of several inorganic phosphates have been examined both in the crystalline and the glassy states. The parameter (Z eff/ r) q clearly demarcates ortho-, pyro- and meta-phosphates in terms of the 31P chemical shifts. Based on such a diagram, inorganic phosphate glasses are found to consist essentially of metaphosphate units. NMR resonance of the glasses are generally much broader than those of crystalline phosphates.

Heats of Solution of Sodium Phosphate Glasses

Heats of formation for some glassy and crystalline sodium phosphates were investigated by measuring their heats of solution in distilled water and in 3N-HNO3 aq. using a microcalorimeter.The glass samples used in this study were prepared from reagent grade NaOH and H3PO4 through dehydrating condensation, that is, these reagents were mixed in such proportions that the resulting glasses possessed given chemical compositions and heated in a platinum crucible at 700° to 800°C for 2 hours to drive off water. The samples thus obtained were chemically analyzed for a constituent P2O5 and “residual water” which reached a maximum content of 2.5wt%.In this study the solution calorimetry was made with a twin type differential microcalorimeter in which the quantity of heat is measured as difference of the electromotive force produced with the thermomodules. The detecting sensitivity is 6.5mV/°C, and the thermostat is regulated within ±1μV. Both the time and the temperture difference were successively plotted in a recorder and the quantity of heat was measured as an area enclosed between the temperature curve and the time-axis, which was later compared with a standard heater for correction.It was confirmed by paper chromatography that both the glassy and crystalline samples were decomposed into orthophosphate molecules with 3N-HNO3 aq.. The heats of solution for water and 3N-HNO3 aq. at 25°C were found to be exothermic and the dependence of the chemical composition is shown in Figs. 9 and 10 where a minimum is seen near the meta composition on the curve of the phosphate glasses.At the stoichiometric meta composition the enthalpy difference between the glassy and crystalline samples was estimated to be about 21cal/g and the heat of formation of NaPO3 glass from Na(s), P(s) and O2(g) states was of about 277kcal/mole. The increase of ΔH in the ultra phosphate region may be attributed to hydrolysis of branching points in chain structure but the increase in the polyphosphate region can be explained by increase of P-ONa→P-OH ion-exchange reaction because the long chain structure is more easily cut by Na+ ions with increasing Na2O content in the glass. The enthalpy change associated with annealing of the glass was thought to be negligible small.

Use of Bimetallic Glassy Phosphates for Corrosion Control

This article discusses the development of a sodium‐zinc glassy phosphate containing 8‐9 per cent zinc. This complex bimetallic phosphate glass proved to be three to five times as effective (depending on conditions) as straight sodium phosphate glass in overcoming corrosion in water systems. Properly used and controlled, the bimetallic glassy phosphates can be very effective in inhibiting corrosion in municipal and industrial water systems.

Molecular Distributions at Equilibrium. I. Theory of Equilibria in Scrambling Reactions and Interpretation of NMR Spectra

Stochastic graph theory has been developed and applied to the interpretation of chemical equilibria resulting from scrambling reactions which lead to size distributions of molecules. By this means, deviations from random scrambling are treated in terms of the effect on any given site in a molecule of the environment of neighboring atoms within the molecule. This treatment is applied to molecular-distribution data on the glassy phosphates and to thermodynamic data on the aliphatic hydrocarbons. It is also shown to be the basis for interpretation of nuclear magnetic resonance data obtained on families of equilibrated compounds. A formal treatment of ring—chain equilibria is presented, and equilibrium constants for interactions between parts of molecules are related to the usual constants involving whole molecules. The concept of crowding of chain segments is employed in estimating the number of ring closures in infinite-network macromolecules (i.e., structures having as many branches as or more branches than correspond to the ``gel point'').

Heats of formation of some crystalline and glassy phosphates

Heats of formation of some crystalline and glassy phosphates