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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.

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.

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.

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.

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.

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.

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

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.

Calcium phosphate glasses have a high potential for use as biomaterials because their composition is similar to that of the mineral phase of bone. Phosphate glasses can dissolve completely in aqueous solution and can contain various elements owing to their acidity. Thus, the glass can be a candidate for therapeutic ion carriers. Recently, we focused on the effect of strontium ions for bone formation, which exhibited dual effects of stimulating bone formation and inhibiting bone resorption. However, large amounts of strontium ions may induce a cytotoxic effect, and there is a need to control their releasing amount. This work reports fundamental data for designing quaternary CaO-SrO-P2O5-TiO2 glasses with pyro- and meta-phosphate compositions to control strontium ion-releasing behavior. The glasses were prepared by substituting CaO by SrO using the melt-quenching method. The SrO/CaO mixed composition exhibited a mixed cation effect on the glassification degree and ion-releasing behavior, which showed non-linear properties with mixed cation compositions of the glasses. Sr2+ ions have smaller field strength than Ca2+ ions, and the glass network structure may be weakened by the substitution of CaO by SrO. However, glassification degree and chemical durability of pyro- and meta-phosphate glasses increased with substituted all CaO by SrO. This is because titanium groups in the glasses are closely related to their glass network structure by SrO substitution. The P-O-Ti bonds in pyrophosphate glass series and TiO4 tetrahedra in metaphosphate glass series increased with substitution by SrO. The titanium groups in the glasses were crosslink and/or coordinate phosphate groups to improve glassification degree and chemical durability. Sr2+ ion releasing amount of pyrophosphate glasses with &gt, 83% SrO substitution was larger than 0.1 mM at day seven, an amount that reported enhanced bone formation by stimulation of osteogenic markers.

For disordered systems, a universal excitation called the boson peak appears in the terahertz range. In this study, we performed terahertz time-domain spectroscopy on an oxide glass with entropic elasticity—mixed alkali metal metaphosphate glass with the chemical composition Li 0.25 Na 0.25 K 0.25 Cs 0.25 PO 3 (LiNaKCsPO 3 )–to detect the boson peak. The obtained spectra were compared with results of low-frequency Raman scattering and low-temperature specific heat measurements.

Adhesion is becoming more and more important in many situations in dentistry. Effective adhesion retains restorative dental materials at proper positions of tooth structure, solves the problem of leakage around restorations, and, consequently, improves their performances. Treatment of ceramic surfaces with chemicals such as silane coupling agents or hydrogen fluoride has been proposed, but the adhesion has not been improved enough for practical applications. The most important but difficult requirement for dental adhesives is to maintain the performance in water for a long period of time, and we found that even methacrylate monomers 11–14 that showed high adhesion in air were not suitable in water. Some possible reasons of low adhesiveness of calcium metaphosphate ceramic (CMP) are as follows: CMP is not providing thorough wetting with adhesives; functional groups or atoms, probably associated with adhesion, are not readily accessible on the surface; and total surface area is insufficient.

Calcium phosphate coating is an attractive surface modification strategy for magnesium alloys, since it can increase their corrosion resistance and endow them with osteogenic function simultaneously. Herein, a calcium metaphosphate (CMP) coating was fabricated on magnesium alloy by using sol-gel approach assisted with micro-arc oxidation pre-treatment. Scanning electron microscopy showed that the micro-pores and cracks in micro-arc oxidation inner layer generated during the pre-treatment process were sealed by the grainy sol-gel outer layer. Energy dispersive spectrometry and X-ray diffraction results demonstrated the identity of the coating as CMP. The cross-cut test showed that the adhesion of CMP coating was strong. Applying bare magnesium alloy substrate as a control, the CMP coating surface was rougher and more hydrophilic. The potentiodynamic polarization test demonstrated that the corrosion resistance was significantly improved by using CMP coating. Hydrogen evolution in immersion test further confirmed that the degradation rate was decelerated within 14 days. Moreover, CMP coating facilitated the adhesion speed, spreading area, and focal adhesion formation of bone marrow stem cells. The number of cells in the active proliferating state and proliferated cells present on the CMP coating also increased. Additionally, CMP coating upregulated alkaline phosphatase activity and osteogenic gene expression in cells. In summary, the micro-arc oxidation assisted sol-gel CMP coatings increased the corrosion resistance and promoted the interfacial cell behavior for magnesium alloy implants, which might inform the further development of surface modifications on magnesium alloys for bone related applications.

In the present work, we studied Er-doped KPO3-Ca(PO3)2 metaphosphate glass and its devitrification behavior. It is shown that two concurrent crystallization processes (surface and bulk crystallization) are observed in this glass with the precipitation of two different phases of KCa(PO3)3: the hexagonal phase is mostly formed at the surface, whereas the orthorhombic isomorph is found in the bulk. The possibility of synthetizing a transparent glass-ceramic is demonstrated. From the changes in the spectroscopic properties of the obtained glass-ceramic materials, Er3+ ions are suspected to enter into the lattice of the KCa(PO3)3 crystal. acceptedVersion

Modulus formalism and dielectric relaxation in metaphosphate glass with MgO modifier using imaginary and real impedance measurements and dielectric relaxation spectroscopy are investigated. In the range of temperatures 721 – 822 K and over the range of frequency from 10 Hz to 2 MHz the electrical conductivity measurements were performed. Arrhenius conductivity activation energy calculated from DC measurements and the activation energies estimated from electric modulus and impedance AC measurements are in good agreement.

We report a novel negative conversion electrode material, manganese (II) metaphosphate Mn(PO3)2. This compound can be synthesized by a facile solid-state method, and after carbon-coating delivers an attractively high reversible capacity of 477 mAh/g at 0.1C and 385 mAh/g at 1C. We investigated the reaction mechanism with a combination of ex situ X-ray absorption spectroscopy, in situ X-ray diffraction, and high-resolution transmission electron microscopy. We observed a direct conversion process by monitoring the first discharge in operando, in which Mn(PO3)2 reacts with Li to give fusiform Mn nanograins a few Ångstroms in width, embedded in a matrix of lithium conducting LiPO3 glass. Due to the fine nanostructures of the conversion products, this conversion reaction is completely reversible.

The development of efficient, inexpensive, and stable hydrogen evolution reaction (HER) electrocatalysts is the key to large-scale water electrolysis technologies for hydrogen production. Constructing heterojunction electrocatalysts has become one of the effective strategies for designing high-performance HER electrocatalysts due to their unique heterogeneous interfaces. Herein, a new strategy of PH3 assisted synthesis of metaphosphate is reported, which is used to construct Co(PO3)2@NPC/MoS2 heterostructures (where NPC is N-doped porous carbon). The results show that the formation of Co(PO3)2@NPC/MoS2 heterogeneous interfaces can optimize the electronic structure of the electrocatalyst and greatly improve its HER performance. As a result, a lower overpotential of 119 mV at 10 mA cm-2 is obtained in alkaline electrolyte. This work provides a new perspective for the design of high-performance electrocatalysts for electrocatalytic water splitting.

The calcination of phosphogypsum (PG) was employed to produce gypsum plaster to achieve its recovery and utilization. Although previous studies have indicated the possibility of producing hemihydrate and anhydrous gypsum, the influence mechanism of the impurities in calcined PG (CPG) on the properties of plaster is unclear. Herein, the paper aims to investigate the effect of the impurities on the properties of gypsum plaster at elevating calcination temperatures. The phase transformation of PG and impurities were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), and the hydration properties of gypsum plaster were investigated, including water requirement for normal consistency (WR), setting time, compressive and flexural strength, hydration products and degree, and microstructure. The results show that the increase in calcination temperature resulted in higher anhydrite content, and CPG showed similar chemical and mineral compositions at high temperatures (500°C–800 °C). Additionally, harmful impurities barely changed at low calcination temperatures (150°C–400 °C), resulting in the reduced mechanical properties despite its higher hydration degree; however, the calcination at high temperatures converted harmful impurities into inert insoluble calcium pyrophosphate (Ca 2P2O7), calcium metaphosphate (Ca(PO3)2 ), calcium fluoride (CaF 2 ) and sodium sulfate (Na 2SO4). With the best calcination temperature of 800 °C, gypsum plaster showed a relatively quick setting and maximum strength with a compact microstructure and low hydration degree due to the large formation of Na2SO4 and nucleation sites . Recycling PG to prepare anhydrite is recommended because of its excellent performance and lower energy consumption than traditional building materials.

Bulk glasses of the compositional series (A) xNb2O5–(50-x)ZnO–50P2O5 and (B) xNb2O5–50ZnO-(50-x)P2O5 were prepared to investigate possible substitution of cation (Zn2+), series A, and anion (PO3−), series B, with niobium and the effect of this substitution on the structure, density, molar volume, glass transition temperature and coefficient of thermal expansion. The structure was studied by Raman and 31P MAS NMR spectroscopies. The chemical model, based on the idea of chemical compounds as components with the lowest Gibbs energy and therefore the most stable, and on the results of 31P MAS NMR spectroscopy, was proposed for series B. It was found that niobium acts in glasses of series B only as a cation NbO3+, unlike the original idea of forming an anion of NbO−, that is, similarly to series A, where it replaces the cation. This leads to a change in the metaphosphate network of series B to the network that is similar to series A glass. The validity of this idea was verified by experimentally obtained compositional dependencies of molar volume, glass transition temperature and thermal expansion coefficient. Changes observed in thermal measurements indicate the evolution of a more rigid structure and more intensive cross-linking of the phosphate chains with increasing content of niobium.

Phosphate glasses are of great interest for basic research and for special applications in various fields as technical and optical glasses. Metaphosphate compositions with PO4-chain structure are mostly used. The cations have a significant effect on the properties of the glasses and melts. This was studied in more details. High purity metaphosphate glasses, Mn(PO3)n with M = Na+, K+, Zn2+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+ and Fe3+, were prepared and the optical and thermal properties were measured with different methods. The electrical conductivity of glasses and melts is the property of great practical importance. It was determined by impedance spectroscopy in a wide temperature range from 300 to 1250 °C in frequency range of 0.1 Hz to 6 MHz. The electrical conductivity of alkaline earth phosphate glasses and melts increases with increasing ion radius of the cation. NaPO3 and KPO3 glasses and melts have much higher conductivity. Viscosity measurements were carried out from transformation temperature, Tg, to the melt. The measured data were fitted and the activation energies of the conductivity and viscosity were calculated. Simple exponential behavior was found at temperatures below Tg, but above Tg only in very narrow temperature range. The relation between conductivity and viscosity was considered.

Microbial fuel cells (MFCs) as renewable electricity-generation devices are often confronted with the poor long-term durability and high cost of cathodic catalysts. In this study, iron (III) metaphosphate/iron phosphide/partly-graphitized carbon ((Fe(PO3)3)/FeP/PGC) catalysts obtained at 750–950 °C are used as air–cathode catalysts for oxygen reduction reaction (ORR) in single-chamber MFCs. As temperature increases, graphitization degree of carbon skeleton in (Fe(PO3)3)/FeP/PGCs gradually increases to obtain a higher electrical conductivity. At 900 and 950 °C, monoclinic structured Fe(PO3)3 is formed in PGC structure to constitute the Fe(PO3)3/FeP heterojunctions, which should originate from the partial oxidation of FeP. The maximum power density (1.162 ± 0.022 W m−2) of MFCs is obtained by Fe(PO3)3/FeP/PGC (900 °C) cathode, which is higher than that of commercial Pt/C (1.052 ± 0.015 W m−2) and only has a decline of 4.56% after 1900 h operation (excellent durability). Well-dispersed Fe(PO3)3/FeP heterojunctions and abundant oxygen-containing groups (C–O–C, C–O–H and C–OH) play the important roles in achieving the high charge transfer efficiency (8.7 ± 0.2 Ω) and long-term durability in bio-electricity generation. Fe(PO3)3/FeP/PGC (900 °C) primarily proceeds the efficient four-electron ORR pathway by exploiting the synergistic effects between the active components (Fe(PO3)3/FeP) and porous structure (533.77 m2 g–1). This study provides the promising non-precious-metal ORR electro-catalysts for replacing Pt/C in renewable energy-generation systems.

(100 − x)NaPO3–xZnO (0 ≤ x ≤ 33 mol%) phosphate glasses have been prepared using the conventional melt quenching technique. Amorphous state was checked up by X-ray diffraction. Glasses have been investigated in detail by mean of differential scanning calorimetry, inductively coupled plasma. Incorporation of ZnO oxide increases the Tg value and the thermal stability of samples. For this glass series, 31P solid state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy revealed the decrease of Q2 tetrahedral sites and the increase of phosphate dimers (Q1), when ZnO oxide is progressively introduced, suggesting the shortening of metaphosphate chains. Dissolution of glasses has been followed calorimetrically and showed a change in thermal signs resulting from the depolymerization of metaphosphate groups when ZnO oxide is added. A thermochemical cycle involving a number of dissolution and mixing processes have been carried out in order to get the standard enthalpy of formation of these glasses. Calculation of these quantities needs the standard enthalpy of formation of sodium trimetaphosphate. Formation enthalpy of glasses increases with the incorporation of ZnO oxide.

Phosphate glasses are special class of optical glasses composed with metaphosphate of different metals. When rare earth elements are added to glass matrix as dopant, it improves glass melting and also enhances some unique glass properties. Lanthanum oxide doped Phosphate glass system were prepared with melt quenching method. The effect of different concentration (0.5% & 1.5%) of La2O3 on electrical, structural and optical properties of phosphate glasses have been studied. The FTIR studies shows, in 0.5% of La2O3 doped phosphate glass, sharp peaks were observed with high intensity values. The absence of crystalline structure in the prepared phosphate glasses were confined by both Raman and XRD studies. With the addition of La2O3 to P2O5, the phosphate glasses alters its structure from cross-linked network to chain network. The absence of crystalline structure in the prepared phosphate glasses were confined by both Raman and XRD studies. According to the Raman spectra, there is a corresponding decrease in the number of Q2 units with increasing lanthanum oxide content with the addition of La2O3 to P2O5, the phosphate glasses alters its structure from cross-linked network to chain network.

In a rotary kiln process for phosphoric acid production, the reaction between gaseous phosphorus pentoxide (P 2 O 5 ) and phosphate ore and silica contained in feed balls (the so-called P 2 O 5 “absorption”) not only reduces phosphorous recovery but also generates a large amount of low melting-point side products. The products may give rise to formation of kiln ring, which interferes with kiln operation performance. In this study, the reactions of gaseous P 2 O 5 with solid calcium phosphate (Ca 3 (PO 4 ) 2 ), silica (SiO 2 ) and their mixture, respectively, were investigated via combined chemical analysis and various characterizations comprised of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis and differential scanning calorimeter (TG&DSC), and scanning electron microscopy and energy dispersive spectrometer (SEM&EDS). Attentions were focused on apparent morphology, phase transformation and thermal stability of the products of the P 2 O 5 “absorption” at different temperatures. The results show that the temperature significantly affected the “absorption”. The reaction between pure Ca 3 (PO 4 ) 2 and P 2 O 5 occurred at 500 °C. Calcium metaphosphate (Ca(PO 3 ) 2 ) was the primary product at the temperatures ≤ 900 °C with its melting point ≤ 900 °C while calcium pyrophosphate (Ca 2 P 2 O 7 ) was obtained over 1000 °C, which has a melting point ≤ 1200 °C. The “absorption” by pure SiO 2 started at 800 °C and the most significant reaction occurred at 1000 °C with formation of silicon pyrophosphate (SiP 2 O 7 ) product of melting point ≤ 1000 °C. Using mixed Ca 3 (PO 4 ) 2 and SiO 2 as raw material , the “absorption” by Ca 3 (PO 4 ) 2 was enhanced due to existence of silica. At 600–700 °C, silica was inert to P 2 O 5 and thus formed a porous structure in the raw material, which accelerated diffusion of gaseous P 2 O 5 inside the mixture. At higher temperatures, the combined “absorption” by calcium phosphate and reaction between silicon dioxide and the “absorption” product calcium pyrophosphate, reinforced the “absorption” by the mixture. Besides, it was found that both Ca(PO 3 ) 2 and SiP 2 O 7 were unstable at high temperatures and would decompose to Ca 2 P 2 O 7 and SiO 2 , respectively, at over 1000 °C and 1100 °C with the release of gaseous P 2 O 5 at the same time.

New magneto-optical vitreous materials were obtained by melting-quenching technique comprising wet route raw materials preparation. The glass has the following composition in oxide mol. %: 10 Li 2 O, 9 Al 2 O 3 , 5 ZnO, (35; 20; 50) B 2 O 3 , (35; 50; 20) P 2 O 5 , 3 Bi 2 O 3 , 3 PbO, phosphorus and boron oxide being the vitreous network formers. It was also prepared a similar reference glass composition but without Bi 2 O 3 and PbO. Optical and structural characterization by ultraviolet-visible (UV–Vis), Fourier Transform Infrared (FTIR) and Raman Spectroscopy of the bulk glasses showed a transmission over 90%, metaphosphate structure of glass together with Q 2 boron oxide units and P–O‒B bonds. The mechanical parameters, hardness ( H ), Young's modulus ( E ) and fracture toughness ( K IC ) of boron phosphate glasses, evaluated by micro- and nanoindentation techniques, demonstrated mostly higher values in comparison with those for alumino-phosphate glasses due to mixed boro-phosphate network. Thermal behavior was investigated by Differential Scanning Calorimetry (DSC) putting in evidence the vitreous transition temperature which decreases with about 45 °C when Bi and Pb oxides were added and two crystallization effects. The diamagnetic character of a highly transparent Bi and Pb oxide co-doped boron phosphate glass was confirmed by ellipsometry, and the glass presented high magneto-optical properties at the top of the commercial bulk products.

Iron impurity in raw material remains a major challenge in producing colourless glass. In this investigation, we report microwave (MW) heating capable of altering Fe-redox ratio (Fe2+/∑Fe) enabling preparation of colourless phosphate glass. The effect of Sn concentration in retention of Fe[II] in glass melted in MW was compared with conventional glasses. Colourimetric study developing Fe2+-ferrozine colour complex reveals Fe-redox ratio ≥0.49 required to obtain colourless phosphate glass. In microwave heating, addition of 1 wt.% Sn metal powder can impart the desired effect whereas addition of 1.9 wt.% Sn metal powder is required in conventional heating. The correlation equation of Fe-redox ratio with concentration of Sn metal is found to be different in microwave and conventional heating. Thus, exploiting this different redox changes in MW heating optical properties can be tailored. Preservation of higher Fe[II] in MW melted glass is also confirmed by XPS and TGA. 31P MAS NMR spectra suggest that transition from cross linked ultra phosphate to linear polymer metaphosphate network in incorporation of Sn is found different in glass prepared adopting microwave irradiation. 27A1 MAS NMR spectra suggest higher relative content of Al6+ in glass obtained from MW heating. Energy consumption analysis revels 3.4 kWh in MW heating while 14 kWh in conventional glass melting using resistance heating. Further, glass melting in MW can be completed within 2 h unlike ~5 h needed in conventional. MW heating plays a significant role in improving properties to make colourless phosphate glass in addition to significant energy and time saving.

Phosphorus and/or nitrogen doping is an effective method of improving the physical and chemical properties of reduced graphene oxide (rGO). In this work, phosphorus and nitrogen co-doped rGO (PN-rGO), synthesized using a scalable hydrothermal and microwave process, was used as an additive to improve the flame retardancy of epoxy resin (EP) for the first time. Chemical structure and morphology characterization confirmed that the nitrogen and phosphorus atoms were doped into the graphite lattice adopting pyrrolic-N, pyridinic-N, quaternary-N and pyrophosphate and metaphosphate forms. Doping increased the oxidization resistance of rGO and the thermal-oxidative stability of its composites’ char, while also improving the catalytic charring ability of polymer. Both effects resulted in the formation of a stable char protective layer during burning and to a significant improvement in flame retardation and smoke suppression in the final composites. The peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) for the EP-based composite (containing 5 wt% PN-rGO) decreased by 30.9%, 29.3% and 51.3%, respectively, compared to neat EP. Our work has produced a promising graphene-based flame retardant additive for the mass production of high-performance composites, also expended the application of heteroatom-doped graphene.

A new melt derived glass system consisting of Co2O3 added to 40P2O5·25B2O3·25CaO·10Na2O matrix was investigated in order to evaluate the influence of cobalt ions on the network structure. Multiple techniques, i.e. X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the local structure, the nature of the chemical bonding and the surface composition of these samples. The XRD measurements proved the vitreous character of samples with 0 and 3 mol% Co2O3. At higher cobalt oxide content (5, 7 and 10 mol%) the occurrence of a crystalline phase characteristic to Co2P4O12 has been observed. The complementary spectroscopic studies (FTIR and Raman) revealed that the incorporation of Co2O3 enhances the network connectivity and thereby the short range order in samples. Depending on their amount, the cobalt ions differently influence the borophosphate network via the tetraborate/triborate and metaphosphate/pyrophosphate ratios. For the sample containing 10 mol% Co2O3 the FTIR analysis indicates absorptions assigned to vibrations in CoO6 tetrahedra and suggests the presence of six-coordinated cobalt ions in Co3 + valence state. This study has proven that borophosphate based glasses are able to entrap cobalt ions, are sensitive from structural point of view to the amount of Co2O3 and possess interesting structural peculiarities.

Modifier-mixing provides a useful tool for tailoring the structural dynamics of oxide glasses. Its physical basis, however, remains subject to intense discussion. Here, we extend our previous consideration of Ca-Mg mixing in alkaline earth metaphosphate glasses [J. Non-Cryst. Solids 468, 74–81 (2017)] across the broader range of alkaline earth species. We report on the effects of divalent modifier mixing for pairs selected from the group of Mg, Ca, Sr and Ba. For this, short-range structural features as obtained from nuclear magnetic resonance, Raman and far-infrared spectroscopy are related to various physical properties, including ionic mobility. Depending primarily on the difference in ion size and bond localization among the modifier cation species, we find different extents of the mixed-modifier effect. This agrees with the dynamic structure model in which the mismatch of cation sites governs non-linear mixing effects.

The structure and properties of xCeO2-(100-x)(40Fe2O3-60P2O5), where x = 0, 2, 4, 6 and 8 mol%, glass-ceramics prepared by melting and slow cooling method have been investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA) and the Product Consistency Test (PCT). The results show that the 40Fe2O3-60P2O5 sample is homogeneously amorphous and the sample containing 2 mol% CeO2 has a small amount of FePO4 phase embedded. For the sample containing up to 4 mol% CeO2, monazite CePO4 and a small amount of FePO4 appear. Spectra analysis show that the structure networks of the glass-ceramics mainly consist of orthophosphate, along with pyrophosphate and a small amount of metaphosphate units. Moreover, the leaching rates of Fe and Ce are about 3.5 × 10−5 g m−2 d−1 and 5.0 × 10−5 g m−2 d−1 respectively after immersion in deionized water at 90 °C for 56 days, indicating their good chemical durability. The conclusions imply that the prepared method may be a promising process to immobilize nuclear waste into glass-ceramic matrix.