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Distribution of Mn2+ ions into lithium metaphosphate glass through modifier-site engineering is an effective approach to generate single-doped red phosphors for light emitting diodes (LED). This has been achieved through the systematic Li+-Mn2+ modifier mixing in xMnO‧(50-x)Li2O‧50P2O5 (0 ≤ x ≤ 50 mol%). In this regard, the mixed modifier effect on the structural and optical properties has been studied. While XRD demonstrates the amorphous structure of the prepared compositions, SAED reveals the formation of crystalline clusters in 50MnO‧50P2O5. XPS reveals that the ratio of BOs/NBOs (~0.5) is in agreement with that of theoretical stoichiometry. FTIR spectroscopy shows that the concentration of Q2 decreases, whereas Q1 increases. Also, it can be found that the density increases linearly with about 22% as the content of MnO increases. This is associated with a small decrease in molar volume (~3%). Overall, XPS, FTIR and density analyses indicate that Li+ and Mn2+ ions behave as network modifiers that resides in octahedral sites through the formation of LiO6 and MnO6, respectively. Indeed, there are strong absorption and excitation spectra due to the electronic transition in Mn2+. This results in an intensive orange-red emission around 608 nm (at x = 0.5) with a red-shift up to 684 nm (at x = 50) at excitation wavelength of 409 nm. This is ascribed to 4T1(G) → 6A1(S) electronic transition in the octahedrally coordinated Mn2+ ions with O2− anions. With increasing the MnO content, the emission is systematically intensified up to 10 mol% of MnO, and then quenched. This quenching is attributed to the increase in MnO6 groups, which cluster with each other. In these clusters, the electron transfer occurs between the neighboring Mn2+ ions. Furthermore, the independence of emission peak (shape and position) on the excitation wavelength demonstrates the presence of only high-dispersed Mn2+ activator center.

A series of (50 − x) P2O5–20B2O3–20CaO–10Na2O (x = 0–15 mol% MoO3) glass composition was prepared. Glass structure was analyzed using infrared absorption, UV–visible spectroscopy, electron spin resonance, density, and molar volume calculations. FTIR confirmed that Mo ions are contributed as MoO6 octahedral units in the glassy matrix, resulting in an increase in the pyrophosphate and BO3 groups at the expense of metaphosphate and BO4 units. UV–visible and ESR spectra detected Mo3+ and Mo5+ ions as species in the host glass due to the increase in MoO3 content. Broadband dielectric spectroscopy investigation on a broad range of frequencies and at different temperatures indicated that the enhancement of electrical conductivity of the prepared glasses due to molybdenum doping was prevented using confinement effect at the wells, causing demobilization of the charge carriers. Hence the dielectric spectra were caused by the mobility of charge carriers rather than the dynamics at the molecular scale. There is a clear correlation between the transport mechanism and dynamics at the interface of the charge carriers. Presently, the challenge is to understand if optimizing the accumulation of charges at the interfaces and electrodes is the origin of electrical storage energy.

A study of the high temperature (up to 1200 °C) degradation of aluminum metaphosphate Al(PO3)3 has been carried out to evaluate the stability of this compound used for many purposes. For the preparation of Al(PO3)3, an aluminum dihydrogen-phosphate Al(H2PO4)3 solution has been heated at 700 °C. Thermal degradation of Al(PO3)3 has been followed through the measurement of weight loss on isothermal mode at 1000 and 1200 °C and by thermogravimetric analysis coupled with mass spectroscopy (TGA-MS). Structural data have been obtained by 27Al, 31P and 1H MAS NMR spectroscopy. NMR analyses have shown that [A] and [B] allotropic forms of Al(PO3)3 are formed after the preparation procedure. In addition, NMR revealed that hydroxyls groups are also present in the sample, and they form P OH groups. TGA-MS showed that they are decomposed at a temperature of 875 °C, while the decomposition of Al(PO3)3 into AlPO4 and P2O5 begins at 1000 °C.

Bifunctional electrocatalysts are pre-eminent to achieve high capacity, cycling stability, and high Coulombic efficiency for rechargeable hybrid sodium-air batteries. The current work introduces metaphosphate (Na)KCo(PO3)3 nanostructures as noble metal-free bifunctional electrocatalysts suitable for the rechargeable aqueous sodium-air battery. Prepared by the scalable solution combustion method, the metaphosphate class of (Na)KCo(PO3)3 with spherical morphology exhibited robust oxygen reduction as well as evolution activity similar to the state-of-the-art catalysts. NaCo(PO3)3 metaphosphate, when employed as an air cathode in hybrid sodium-air batteries, delivered reasonably low overpotential along with excellent cycling stability with a round-trip energy efficiency of 78%. Cobalt metaphosphates thus form a new class of economical bifunctional catalysts to develop hybrid sodium-air batteries.

Exploiting novel nanomaterials with fast and durable sodium/potassium ion storage capability is key to alleviate the application limitations of lithium-ion batteries. Herein, a novel energy storage material based on cobalt metaphosphate nanosheet arrays self-supported on carbon cloths [Co(PO3)2 NSs/CC] is fabricated by a two-step strategy. This rationally designed strategy avoids the preparation of the complex {Co[O2P(OtBu)2]2}n precursor, which significantly simplifies the synthesis process. The active CC acts not only as an electrically conductive substrate as usual but also as a functional basis to suppress PH3-involved reaction and to promote HPO3-involved reaction during the phosphating process, contributing to the formation of Co(PO3)2. The mutual cross-linked porous Co(PO3)2 nanosheets vertically grow on the surface of activated CC, ensuring sufficient electrolyte infiltration and fast electron transport among the electrodes. Sodium ion storage analysis for the Co(PO3)2 NSs/CC electrode reveals a multi-step reaction mechanism with high reversibility, as reflected by the high reversible capacity (667 mA h g-1 at 50 mA g-1) and excellent cyclability (with almost no capacity decay over 500 cycles). This novel electrode is also well capable of storing potassium ions, exhibiting high reversible capacity, which outperforms most reported anodes for potassium-ion batteries. The development of this novel high-performance nanomaterial would advance the performance of sodium/potassium-ion batteries toward practical applications.

Insertion of Al2O3 in the widely used zinc metaphosphate glasses is investigated in this contribution thanks to a 1D/2D NMR protocol. Glasses formulated in the (50–x/2)ZnO–xAl2O3-(50–x/2)P2O5 compo...

Li–Cs metaphosphate glasses show one of the strongest mixed ion effects (MIE) known in d.c. conductivity. Previous studies had shown that the ions in these glasses are randomly distributed relative...

Electrocatalytically hydrogen evolution reaction (HER) is most promising approach for the large-scale generation of hydrogen, but the prohibitive and scarce Pt-based electrocatalyst therein greatly restricts the advancement of hydrogen-related technology. Exploring low-cost electrocatalysts with superior activity and stability at different applicable conditions is being of great concern. Herein, we controllably synthesized highly dispersed ~3 nm cobalt metaphosphate (Co(PO3)2) nanoparticles embedded in N,P,S-tridoped carbon by a facile two-step mixing and pyrolysis method. The resultant nanocomposite with hierarchical microflower morphology assembled by the tridoped carbon nanosheets dotted with ultrafine Co(PO3)2 particles, showing superior all-pH activity, and particularly a better alkaline large-current-density activity than Pt/C. The ultrasmall Co(PO3)2 particles together with abundant phosphate groups and heteroatom dopants synergistically afford highly active catalytic centers for HER, as well as the all-pH robust stability of which endowed by the encapsulation of tridoped carbon. The mesoporous carbon composite nanosheets integrate into open and accessible microflower structures and thus facilitate the unhampered mass and charge transfer.

The atomic structure of a series of sodium iron phosphate glasses is studied using different experimental techniques: X‐ray and neutron diffraction (ND), infrared spectroscopy, extended X‐ray absorption fine structure (EXAFS), and X‐ray absorption near‐edge structure (XANES). Detailed information about the atomic pair correlations is obtained. The high resolution of ND in real space resolves two P–O distances at 1.48 Ǻ and 1.59 Ǻ as expected. All the glasses are found to consist of a phosphate tetrahedral network with metaphosphate chains and pyrophosphate units, and every phosphate unit is found to have two or three nonbridging oxygen (NBO) links available to coordinate with Na and Fe cations. The Fe–O coordination number in these glasses is found to decrease from 5.7 to 4.8 with increasing the Fe content, whereas the Na coordination number of approximately 5 is detected for all the samples.

The synthesis and characterization of polymeric and monomeric Zinc phosphinates are reported. Bis(hydroxymethyl)phosphinic acid is used as a ligand for the synthesis of both polymeric and monomeric phosphinates. A polymeric zinc phosphinate is synthesized by the reaction of bis(hydroxymethyl)phosphinic acid with zinc acetate dihydrate at room temperature. Each phosphinate ligand coordinates with two different zinc centers to generate polymeric zinc phosphinate. The above reaction is carried out with the addition of 1,10-phenanthroline to form monomeric zinc phosphinate compound. When the N-donor chelating ligand (1,10-phenanthroline) is introduced, the construction of polymeric zinc phosphinate is blocked by 1,10-phenanthroline which facilitates the formation of discrete monomeric zinc phosphinate. The synthesized zinc phosphinate compounds are characterized by FT-IR, 1H, 13C and 31P NMR, and also noticed thermal stability by thermogravimetric analysis (TGA). Both the polymeric and monomeric zinc phosphinate compounds are subjected for calcinations at 800 °C to produce zinc metaphosphate materials. Finally the crystalline phase of zinc metaphosphate materials is characterized by powder x-ray diffraction technique (PXRD).

The technology of synthesis of inorganic binder material based on sodium tripolyphosphate Na5P3O10 and orthophosphoric acid has been developed. The sequence of physicochemical transformations in this system, as well as the optimal mass ratio of orthophosphoric acid and sodium tripolyphosphate are established. The research uses methods of quantitative and qualitative X-ray phase analysis, differential thermal analysis, standard methods of testing samples for compressive strength. The ratios of the atomic radii of the cation (Na) and the anion (P2O7), as well as the presence of hydrogen bonds, provide a significant increase in the binding potential compared to other sodium phosphates. It was found that the strengthening of mixtures with 2…8 mass parts including sodium pyrophosphate, the filler of which is quartz-based sand, occurs as intensely as possible when heated to 150°C. A further increase in temperature above 250 °C leads to the conversion of sodium pyrophosphate to ordinary (non-polymeric) metaphosphate NaPO3, which exists without changes in chemical structure up to 1000°C. The developed binder material, given the global trends of decarbonization and resource conservation, is a competitive alternative to widely used synthetic resins and other organic materials. It does not contain harmful substances and does not emit dangerous products when heated.

Thermally and hydrolytically unstable di-tert-butyl phosphate (dtbp-H) has been used as synthon to prepare discrete and polymeric calcium phosphates that are convenient single-source precursors for a range of calcium phosphate ceramic biomaterials. The reactivity of dtbp-H toward two different calcium sources has been found to vary significantly, e.g., the reaction of Ca(OMe)2 with dtbp-H in a 1:6 molar ratio in petroleum ether forms a mononuclear calcium hexa-phosphate complex [Ca(dtbp)2(dtbp-H)4] (1), whereas the change of calcium source to CaH2, in a 1:2 molar ratio under otherwise similar reaction conditions, yields the calcium phosphate polymer, [Ca(μ-dtbp)2(H2O)2·H2O]n(2). Compounds 1 and 2 have been extensively characterized by various spectroscopic and analytical techniques. The solid-state structures of both 1 and 2 have been determined by single-crystal X-ray diffraction studies. In discrete molecule 1, the central calcium ion is surrounded by two anionic dtbp and four neutral dtbp-H ligands in an octahedral coordination environment. Compound 2 is a one-dimensional polymer in which adjacent calcium ions are connected through double dtbp bridges. Solid-state thermolysis of bulk 1 in air leads to the exclusive formation of calcium metaphosphate β-Ca(PO3)2 in the entire temperature range of 400-800 °C. Thermal decomposition of polymer 2, however, can be fine-tuned to produce either α-Ca(PO3)2 or β-Ca(PO3)2 depending on the thermolysis conditions employed. Although the sample sintered at 600 °C produces exclusively α-form of Ca(PO3)2, the sample annealed at 800 °C or above produces β-form. Both α- and β-forms can also be successively formed one after other by a slow heating of a freshly prepared 2 on the powder diffractometer sample holder. Additional forms of ceramic phosphates have been prepared by solvothermal conditions because of the highly labile nature of the tert-butoxy groups of dtbp in 1 and 2. Solution decomposition of either 1 or 2 in boiling toluene at 140 °C in a sealed tube produces calcium dihydrogen phosphate [Ca(H2PO4)2·H2O] as the only product in the form of single crystals. Solution thermolysis of 2 in protic solvents such as water and methanol can be biased to produce other calcium phosphate biomaterials such as hydroxyapatite [Ca10(PO4)6(OH)2]and calcium monohydrogen phosphate [Ca(HPO4)] in the presence of additional calcium precursors such as CaO and Ca(OMe)2, respectively.

Rational design and facile synthesis of highly active electrocatalysts with low cost for oxygen reduction reaction (ORR) are always of great challenge. Specifically, development of a new type of energy-saving materials with convenient method is regarded as the current bottleneck. Herein, an innovative strategy based on amino trimethylene phosphonic acid (ATMP) as chelating agent for cobalt-metaphosphate coordination polymer is reported to one-pot synthesis of a novel precursor in methanol for ORR electrocatalyst. Carbonization of the precursor at 900 °C at N2 atmosphere results in the feasible formation of cobalt metaphosphate based composite (Co(PO3)2/NC). A further step in the thermal cleavage at 650 °C at air for 4 h, Co(PO3)2/NC can be finally transformed into inorganic Co(PO3)2. Advanced spectroscopic techniques and density function theory (DFT) calculations are applied to confirm the main catalytically active center and the physical properties of Co(PO3)2/NC. This obtained Co(PO3)2/NC nanocomposite exhibits superior electrocatalysis to Co(PO3)2 with an enhanced onset potential (0.906 V vs. RHE) and diffusion limiting current (5.062 mA cm−2), which are roughly close to those of commercial 20% Pt/C (0.916 V, 5.200 mA cm−2).

Aluminum phosphates are known as inorganic hardening agents for the setting of alkali silicate solutions, but only few studies have been published on the setting mechanism of potassium water glass. The solution behavior of two aluminum metaphosphates in alkaline environments were investigated photometrically determining the dissolved aluminum content. The crystalline phase composition of the hardened potassium silicate systems was determined by X‐ray diffraction. New insights into the setting mechanism were obtained concerning the structure of the aluminum metaphosphate and the SiO2/K2O ratio of three different potassium silicate solutions. With increasing pH value aluminum tetrametaphosphate reacts rapidly and forms crystalline potassium tetrametaphosphate dihydrate by an ion‐exchange‐reaction. In parallel, a depolymerization of the cyclic metaphosphate structure occurs leading to potassium dihydrogen phosphate as final fragmentation product. With aluminum hexametaphosphate no ion‐exchange reaction product was observed. Only potassium dihydrogen phosphate could be found in higher quantities compared to the reaction with aluminum tetrametaphosphate., Insights on potassium silicates: Mechanism of the chemically initiated hardening of potassium silicate solutions with aluminum metaphosphates. Ion‐exchange reaction, depolymerization of the cyclic metaphosphate structures, and polycondensation of the amorphous alumosilicate binder matrix. Investigation of the dissolution behavior of aluminum metaphosphates in alkaline environment. Description of the crystalline phase composition.

Phosphate glasses of composition 48P2O5-30CaO-(22−x)Na2O-xTiO2 (with 0 °C ± 20°C. The chemical durability of these glasses shows an improvement when the TiO2 content varies from 0 to 2 mol%. The measurements of differential thermal analysis and density, both, indicate the increase of the glass transition temperature and the density. The increase of Tg leads to an improvement of glass rigidity. X-ray diffraction analysis of the glasses annealed at 650°C for 48 h, indicates the appearance of a mixture of metaphosphate and pyrophosphate phases when the TiO2 content varies from 0 to 2 mol%, the last become majority when the TiO2 content rich 2 mol%. Nevertheless, when the TiO2 content exceeds 2 mol%, the analysis, both, by infrared spectroscopy and X-ray diffraction, reveals a radical change of structure with the formation of majorities isolated orthophosphate groups. SEM micrographs illustrated that the number of crystallites increased in the glass network when the TiO2 content increased at the expense of the Na2O content. An increase in the TiO2 content beyond 2 mol% led to the formation of a larger number of crystallites of different sizes, dominated by small crystallite sizes assigned to majority isolated short orthophosphate groups. This phenomenon led to a decrease in chemical durability and seems to be the main cause promoting the bioactivity of glasses. The results of the bioactivity, after a test in an SBF physiological solution within 15 days, shows, both, the formation of hydroxyapatite and tricalcium phosphate layers, in addition to the layer Ca2P2O7, known by its bioactivity, in some samples. The results obtained on the glasses studied make them potential candidates for an application in tissue engineering.

The effect of phosphorus poisoning on the catalytic behavior of diesel oxidation catalysts was investigated over model and supplier monolith catalysts, i.e., Pd–Pt/Al2O3. The results of ICP and XPS from the vapor-phase poisoning over model catalysts suggested that the temperature of phosphorus poisoning affects both the overall content of phosphorus and the dispersion of phosphorus (i.e., inlet/outlet and surface/bulk). Phosphorus oxide (P2O5), metaphosphate (PO3−), and phosphate (PO43−) were identified in the poisoned model and supplier catalysts. The distribution of these species on poisoned model catalysts was highly dependent on the poisoning temperature, i.e., a higher temperature resulted in a higher concentration of PO43−. The outlets of the monoliths contained more PO43− and less P2O5 than the inlets. Both active sites and surface OH groups on model and supplier catalysts were contaminated upon phosphorus poisoning. It is found that PO43− had a stronger influence on the active sites than P2O5. One significant finding in this study is that the vapor-phase phosphorus poisoning could be a practical and cost efficient approach to simulate an accelerated aging/poisoning process.

Phosphate glasses are of large interest for a variety of technological applications due to their several unique properties. In this work we investigate structural, optical and electrical properties of some alkali metaphosphate glasses doped with manganese oxide inside the system (50-x/2) K2O-xMnO2-(50-x/2) P2O5 with (0 ≤ x ≤ 30%mol). The glassy samples have been prepared using a melt-quench process. The obtained glasses are colored and the valence of manganese is composition dependence. The local structure of Mn2+ in the glasses is evaluated by EPR spectroscopy. The optical absorption spectra have been used to evaluate the values of the optical band gap (Eg) and Urbach energy (ΔE). The variation of these optical parameters as a function of composition is investigated. The presence of Mn3+ in the glasses is established by the optical absorption and this ion is associated with the absorption band at 520–530 nm. dc conductivity of the glasses is studied and it is found that it is thermally activated and followed an Arrhenius behavior.

Ab initio calculations have been performed to investigate the competition and conversion between the pnicogen bonds and hydrogen bonds in complexes containing prototype organophosphorus compounds RPO2 (R = CH3 and CH3O). The competition between the pnicogen bonds and hydrogen bonds is controlled by the magnitude of Vs,min and Vs,max in the prototype organophosphorus compounds. Monomeric methyl metaphosphate (CH3OPO2), with more positive π-holes, is more likely to form pnicogen bonds with different electron donors, such as NH3, H2O, HNC and HCCH. Methoxyphosphinidene oxide (trans- and cis-CH3OPO) is inclined to form hydrogen bonds with H2O, HNC and HCCH. Most of the pnicogen bonds have covalent or partially covalent character, while most of the hydrogen bonds exhibit the noncovalent characteristics of weak interactions. The mechanisms of three typical conversions between the pnicogen bond and the hydrogen bond have been investigated and the breakage and formation of the bonds along the reaction pathways have been analyzed using topological analysis of electron density. For the three studied conversion processes, the transformation between the hydrogen-bonded complex and pnicogen-bonded complex is achieved readily through several T-shape structure transition states.

Sodium-calcium-lead phosphate glasses having a mol.% composition (25-z/2)Na2O-(25-z/2)CaO-zPbO-50P2O5 (0 ≤ z ≤ 50) were prepared by using the melt-quench technique. Some physical properties have been measured and their structure has been studied by IR and Raman spectroscopies. Density of the glass increases linearly with the substitution of Na2O and CaO by PbO. Glass molar volume vary slightly with the substitution, and a non-linear increase of PbO molar volume and a non-linear decrease of P2O5, Na2O and CaO ones is observed. Glass transition temperature increases non-linearly with PbO substitution. FTIR and Raman spectra reveal the formation of P–O–Pb bonds, which replace P–O–Na and P–O–Ca bonds, and no modification of the network polymerization is observed with substitution by PbO. However, Raman spectra exhibit shoulder's peak due to (PO3)2- terminal groups, which seemingly results from disproportionation of species in the glass melts. PbO is assumed to play a network modifier role like Na2O and CaO, but it reticulates the phosphate network, which causes an increase of Tg and a slight effect on molar volume.

In order to provide a short-term oxidation protection system for graphite at high temperature, an aluminum metaphosphate coating was prepared on the surface of graphite by cathodic electrochemical treatment, and its oxidation protective ability was investigated using an isothermal oxidation test. The microstructure, chemical composition, and phase components of the aluminum metaphosphate coating were respectively analyzed through scanning electron microscope, dispersive X-ray analysis, and X-ray diffraction. The results showed that aluminum metaphosphate coating with a thickness of about 24 μm provides good oxidation resistance for graphite at 1250 °C, and it reduces the oxidation rate of graphite in a 5-h period by a factor of two. The good oxidation protective ability of the as-prepared coating at 1250 °C is related to the formation of a layer consisting of aluminum metaphosphate and aluminum orthophosphate phases.

In this paper, we investigate the effect of silica additive on the structural and luminescence properties of Eu3+ and Eu3+/Tb3+co-doped sodium-calcium phosphate glasses. Eu3+ doped phosphate glasses have been prepared using melt-quenching technique and characterized through X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier Transform Infrared (FTIR), Raman spectroscopy, ultraviolet–visible (UV–Vis) and luminescence measurements at room temperature. The incorporation of SiO2 led to an increase of glass transition temperature (Tg), indicating an improvement of glass network rigidity. This result was correlated with FTIR and Raman investigations which revealed the occurrence of more hydration-resistant P O Si bonds. An intense red luminescence has been observed due to 5D0 → 7F2 transition of Eu3+ ions in these glasses. The luminescence spectra for Eu3+/Tb3+ co-doped phosphate glasses were then recorded with various Eu3+:Tb3+ molar ratio. Dependence of luminescence lifetimes on the increase of Eu3+: Tb3+ molar ratio was investigated. It was observed that the energy transfer process occurs from Tb3+ to Eu3+ in the studied glasses. Our results show that a tuneable color is achieved when Eu3+: Tb3+ molar ratio changed. The variation of the excitation wavelength can also tune the luminescence spectra of the new phosphate glasses.

Proton concentration of simple binary metaphosphate glasses under a pseudo fuel cell anode reaction was investigated at 350 °C by utilizing an in-situ Fourier transform infrared (FTIR) spectroscopy. Proton concentrations of both MO·P2O5 (M = Ca, Sr) glasses increase under humidified hydrogen atmosphere and applying a direct current voltage between platinum electrodes, suggesting that a proton infiltration occurs into these glasses. Compared with CaO·P2O5 glass, SrO·P2O5 glass shows higher proton concentration at the same period of time. Structure of glass network was investigated using synchrotron radiation X-ray diffraction, 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) and FTIR (KBr method) spectroscopies. Strength of the cross-linking between phosphate chains via M2+ metal cations is correlated for the proton infiltration into phosphate glasses.

Phosphate glasses containing different concentrations of zinc oxide inside the (1 − x)(NaPO3–KPO3)–xZnO system (0 ≤ x ≤ 50 mol%) have been prepared using the conventional melt quenching technique. The prepared glasses were transparent, bubble-free and colourless. Their density, molar volume, glass transition temperature, and structural properties using infrared and Raman spectroscopies are investigated. As the content of ZnO increases, the density increases while the molar volume decreases. The composition dependence of Tg shows a minimum for the glass (x = 20 mol%). Structural approach realized by IR and Raman spectroscopies reveals that zinc ions occupy different sites in the glassy-network, mainly modifier sites and middle phosphate network in low-zinc and high-zinc glasses, respectively. The introduction of ZnO in the network induces some structural rearrangements through the conversion of metaphosphate structural units to pyrophosphate ones. It is also highlighted that the presence of ZnO in the glassy matrix allows the transformation of some P–O–P and P=O bonds to P–O–Zn linkages. From the UV–Visible absorption studies, the values of the optical band gap, Eg, and Urbach energy, ΔE, were evaluated. The optical band gap is found to depend on the glasses composition. Eg and ΔE show a minimum and a maximum respectively, for the glass (x = 20 mol%).

Separate and combined effects of sodium hex metaphosphate (SHMP) and polycarboxylate superplasticizer (PCS) of different dosages (0.5%, 1%, 1.5%, and 2%) on the dispersion stability of nanoSiO2 (NS) were studied. The effect of the dispersant was characterized by the change of absorbance. When SHMP and PCS were used separately and in combination, the stability of nanoSiO2 dispersions was compared and the optimal amount of dispersant for different dosage of nanoSiO2 dispersions were summarized. Finally, the mechanism of dispersant compounding was discussed. The results show that with the increase of the concentration, the optimal amount of SHMP increases significantly while the optimal amount of PCS dispersant is lower and better than SHMP. A clear linear relationship between the optimal dosage of SHMP and the concentration of NS could be found. If SHMP is used combined with PCS, the stability of the dispersed NS will increase and the dosages of both dispersants will be reduced.

The viscosity and the shear relaxation behavior of supercooled Ag- and Sn- metaphosphate liquids are measured using parallel plate techniques. The fragility index m of these liquids, when taken together with that of other metaphosphate liquids, shows variation over a rather large range spanning from ~30 to 90 and is found to be a sensitive function of the strength and extent of connectivity or coupling between the phosphate chains provided by the modifier-oxygen coordination polyhedra. The high fragility of the Ag-metaphosphate liquid (m ≈ 90) is a result of the weak inter-chain coupling which is manifested in a polymer-like rheological behavior that is in contrast with the network-liquid like behavior of the metaphosphate liquids with lower fragility.

When used separately, biochar and orthophosphate are good materials to remove Pb from water, but few studies have been done on Pb removal by biochar-orthophosphate composite. Here biochar-orthophosphate composites were prepared by co-pyrolyzing rape straw with orthophosphate (Ca(H2PO4)2·H2O / KH2PO4) at ratio of 5:1 (W:W), noted as WBC-Ca and WBC-K, respectively, so as to explore the Pb removal capacities and mechanisms of co-pyrolysis biochars. The sorption isotherms of Pb were well fitted with Langmuir model and the maximum sorption capacities of Pb by original biochar, WBC-Ca, and WBC-K were 184.1, 566.3 and 1559 mmol kg−1, respectively. The results of FTIR, XRD, and XPS analyses showed that phosphorus in biochar played an important role to remove Pb by forming lead-precipitates. However, the species of lead-precipitates in three types of Pb-loaded biochars were Pb5(PO4)3Cl, Pb2P2O7, and Pbn/2(PO3)n, individually, and that was because speciation of phosphorus had undergone significant thermochemical transformation during pyrolysis process. Orthophosphate in WBC-Ca was mainly transformed to pyrophosphate, while orthophosphate in WBC-K was transformed to both metaphosphate and pyrophosphate. The present results warrant the promising application of co-pyrolysis biochar derived from rape straw and orthophosphate in removal of Pb from wastewater.

In the present work, phosphate-bonded porous silicon carbide (SiC) ceramics were prepared by using aluminum dihydrogen phosphate as binder. The morphologies, phase composition, microstructures, mechanical strength, porosity and bulk density of the porous ceramics were investigated. It was found that the aluminum dihygrogen phosphate binder bonding method was a novel and low cost process to prepare near net-shape and high strength porous SiC ceramics at low temperature. The bonding mechanism was A type and B type aluminum metaphosphate which formed from aluminum dihygrogen phosphate during heat treatment bonded the SiC particles together to form porous ceramics. With temperature increasing, the phase of B type gradually transformed into A type aluminum metaphosphate, and the transformation was completed at 900 °C. The A type aluminum metaphosphate began to decompose into AlPO4 and P2O5 when the sintered temperature higher than 908 °C. The flexural strength of the porous SiC ceramics reached the maximum at 900 °C and decreased sharply with temperature increasing. The decomposition of A type aluminum metaphosphate made the strength reduce. The bulk density increased with aluminum dihydrogen phosphate content and decreased with temperature, in contrast, the porosity decreased with increasing binder content and temperature.

Phosphate-based glass-ceramics were prepared by a traditional glass melt-quenching method in a high-temperature furnace. The effects of the ZrO2 substituted for Na2O on the crystal phase, thermal behavior, structure, and chemical stability of the prepared glass-ceramics were investigated in detail. X-ray diffraction (XRD) analysis showed that NaZr2(PO4)3 is the main crystalline phase of all the studied samples. ZrP2O7 and FePO4 respectively appeared when the ZrO2 substituted for Na2O reached or exceeded 8 mol% and 12 mol%. FTIR and Raman spectra showed that the network structure of the studied glass-ceramics consisted mainly of orthophosphate units, pyrophosphate units, and a small amount of metaphosphate units and [BO4] units. For the samples containing 10 mol% ZrO2 or less, the normalized leaching rates of Zr (LRZr), Fe (LRFe), Na (LRNa), and P (LRP) remained low (2.5 × 10−6 g m−2 d−1, 3.3 × 10−6 g m−2 d−1, 2.5 × 10−3 g m−2 d−1, and 6.2 × 10−4 g m−2 d−1, respectively) after immersion in deionized water at 90 °C for 28 days. The obtained results suggest that the traditional glass making process may potentially be applicable to the synthesis of some phosphate-based glass-ceramics for immobilizing nuclear waste.

[EN] The glass forming ability of inorganic substances has traditionally been evaluated in kinetic terms related to the rate of spontaneous crystallization of their melts, which is related to viscosity from the macroscopic point of view. However, differences or similarities between the local structures of glasses and crystals of the same composition could have an additional influence on the kinetic ability to form a stable glass or a crystal from a melt. In this work, the local structure of alkali metaphosphate glasses and crystals has been analyzed by means of P MAS-NMR to demonstrate that the ability to form a glass is directly related to the differences between the atomic organization in the glassy states and the structure of the stable crystals at lower temperatures. This implies that chemical compositions having a similar atomic order in their glass and crystal structures will not easily develop the disordered long-range structure of glass., Agencia Estatal de Investigación/FEDER) MAT2017-87035-C2-1-P. The authors are thankful to G. Tricot from the University of Lille (France) for the acquisition of part of the NMR spectra.

The purpose of this work was to study a range of phosphate-based glasses of two groups of glasses with compositions (35-y)Li2O–yPbO–15ZnO–50P2O5 (0≤y≤35 mol% of PbO) and (35-z)Li2O–zZnO–15PbO–50P2O5 (0≤z≤35 mol% of ZnO) containing a fixed amount of (50 mol%) of P2O5, modified by the addition of PbO and ZnO respectively. Their thermal analysis, density, molar volume and infrared spectroscopy studies were conducted to compare the data obtained from both series glasses. Thermal analyses revealed a slight difference in the glass transition temperatures obtained between the two groups. The density values increased linearly with increasing PbO and ZnO contents for two series, whilst the molar volume decreases non-linearly with ΔVm = 2,39 cm3/mol for the addition of PbO and ΔVm = 5,94 cm3/mol for the addition of ZnO. FT-IR spectra reveal the formation of P–O–Pb and P–O–Zn bonds in these glasses and show that metaphosphate network is not affected when PbO and ZnO contents increase in both groups. Thus, PbO and ZnO are assumed to play an intermediate role in a way that Pb2+ and Zn2+ cations tend to break P–O–P bonds forming PbO4 and ZnO4 units with covalent Pb–O and Zn–O bonds. The predominant structural units in both series glasses are metaphosphate (P2O6)2- groups

Phosphofructokinases (Pfks) catalyze the ATP-dependent phosphorylation of fructose-6-phosphate (F6P) and they are regulated in a wide variety of organisms. Although numerous aspects of the kinetics and regulation have been characterized for Pfks, the knowledge about the mechanism of the phosphoryl transfer reaction and the transition state lags behind. In this work, we describe the X-ray crystal structure of the homodimeric Pfk-2 from E. coli, which contains products in one site and reactants in the other, as well as an additional ATP molecule in the inhibitory allosteric site adjacent to the reactants. This complex was previously predicted when studying the kinetic mechanism of ATP inhibition. After removing the allosteric ATP, molecular dynamic (MD) simulations revealed conformational changes related to domain packing, as well as stable interactions of Lys27 and Asp256 with donor (ATP) and acceptor (fructose-6-) groups, and of Asp166 with Mg2+. The phosphoryl transfer reaction mechanism catalyzed by Pfk-2 was investigated through Quantum Mechanics/Molecular Mechanics (QM/MM) simulations using a combination of the string method and a path-collective variable for the exploration of its free energy surface. The calculated activation free energies showed that a dissociative mechanism, occurring with a metaphosphate intermediate formation followed by a proton transfer to Asp256, is more favorable than an associative one. The structural analysis reveals the role of Asp256 acting as a catalytic base and Lys27 stabilizing the transition state of the dissociative mechanism.

Optical materials doped with manganese ions have attracted interest as a red phosphor for warm white light LEDs. Lead-phosphate glasses are chosen for doping with manganese ions due to high refractive index of such material. In this study, new 50 PbO – 50 P2O5 – xMnO2 (x = 0.1, 1, 3, 5, 7, 10, 13 mol%) glasses are synthesized. To determine the optimal manganese ion concentration (to be used as the red phosphor) in those glasses, their spectral and luminescent properties are investigated. Mn2+ ions in lead-phosphate glasses have intense red luminescence in the wavelength range 620–690 nm. The Mn3+ ion to the total Mn ions ratio is found less than 0.1% based on the visible absorption spectroscopy data. Manganese ions in that glass are disposed at non-equivalent positions that results in nonexponential lifetime decay. The maximum absolute quantum yield value of Mn2+ ions is 49% in glass with 2.91 mol% MnO2.