P2O5 System Research Articles

Theoretical Analysis of the Influence of Particle Size Distribution on the Kinetics of the Dissolution of Phosphorus-Containing Vitreous Fertilizers

The paper considers a complex physicochemical phenomenon: the destruction of granules of a vitreous phosphorus-containing fertilizer in a K2O−(Mg,Ca)O−P2O5 system in soil aqueous solutions. The factors influencing the release of nutrients into soil solutions are formulated. The theoretical study can be used to construct a mathematical model and develop computer programs.

Tribological behavior evaluation of dental fluorapatite glass ceramic

Fluorapatite glass ceramics have been widely used in dental restoration because of its excellent esthetics, biocompatibility, and mechanical performance. However, its tribological behavior has not been intensively studied. In this paper, SiO2–Al2O3–K2O–CaO–P2O5 system fluorapatite glass ceramic was prepared by a melt-quench route, and the tribological behavior of the material was investigated in the dry and saliva environments. Effect of saliva and initial surface topology on the friction and wear was evaluated. The results showed that glass ceramics containing a quantity of rod-like fluorapatite crystals with a mean length of 369 nm were obtained. The Vickers hardness of the material was 637 HV. The friction coefficient and wear volume in saliva environment were obviously larger than dry friction because of the increase of adhesion between the two contact surfaces and acid erosion induced by saliva. The wear mechanism in saliva environment is combination of adhesive wear and erosion wear. Friction coefficient and wear volume at the early stage became larger with the increase of initial surface roughness of glass ceramic under dry friction; therefore, smooth surface of the fluorapatite glass ceramic is beneficial to improve the friction and wear performance.

Optical and FTIR structural studies on CoO-doped strontium phosphate glasses

Glass samples in the system (60–x)P2O5–40SrO–xCoO ((0.0 ≤ x ≤ 0.6) mol%) were successfully prepared via melt-annealing route. X-ray diffraction (XRD) data reveal the amorphous nature of examined glasses. A strong absorption band is appeared in all glass samples (pure & doped) in the UV region. This band is considered due to the trace iron impurities that exist within the raw materials used to prepare these samples. Additional absorption bands were appeared in the optical absorption spectra and considered as a result of adding CoO with different concentrations (0.025, 0.05, 0.1, 0.2, 0.4, 0.6 mol%), indicating that the divalent cobalt ions (Co2+) exist in the two coordination states (octahedral and tetrahedral) in this glass system. Optical band gap energy, Eopt was calculated and found to be in the range of 3.94–3.5 eV. Eopt decreases as the amount of CoO increases. FT-IR experimental data reveal IR vibrational bands that are featured to the specific structural building units related to the phosphate matrix. The addition of cobalt oxide with small doping quantities together with the presence of cobalt ions in structural modifying sites causes slight variations in the IR spectra.

Ceramics Based on Powder Mixtures Containing Calcium Hydrogen Phosphates and Sodium Salts (Na2CO3, Na4P2O7, and NaPO3)

Ceramic materials in the Na2O–CaO–P2O5 system have been produced using powder mixtures containing calcium hydrogen phosphates (monetite/brushite: CaHPO4/CaHPO4 ∙ 2H2O) and sodium salts (Na2CO3 ∙ H2O, Na4P2O7 ∙ 10H,O, and NaPO3). These salts were used as precursors to the following high-temperature phases: Сa2P2O7, Na2O, Na4P2O7, and NaPO3. The amount of the salts in the powder mixtures was such that the oxide composition of the ceramics corresponded to 10 mol % sodium oxide for each mixture in the Na2O–CaO–P2O5 system. The powder mixtures were prepared using mechanical activation in acetone, which was accompanied by monetite rehydration to brushite. X-ray diffraction characterization showed that, after firing, the phase composition of the ceramics produced from the powder mixtures thus prepared lay in the Сa2P2O7–NaCaPO4–Na2СaP2O7–Са(РО3)2 phase field. The resultant ceramic materials contain biocompatible and bioresorbable phases and can be recommended for bone implant fabrication.

Powder Mixtures Based on Calcium Hydroxyapatite and Sodium Salts

Powder mixtures based on calcium hydroxyapatite (HAP) and sodium salts in the amount corresponding to 25 mol % of Na2O in the Na2O–CaO–P2O5 system were studied by isothermal exposures in the range of 600—1200°C. According to XRD data, the phase composition of the samples of HAP/Na2CO3 after calcination included HAP, β-CaNaPO4, and CaO. The phase composition of the ceramic samples from the HAP/Na2HPO4 powder mixture after calcination contained the phases of β-CaNaPO4 and Na4P2O7. The phase composition of the ceramic samples from the powder mixture of HAP/NaH2PO4 after calcination contained Ca2P2O7, Ca10Na(PO4)7, β-CaNaPO4, CaNa2P2O7, and Na4P2O7. The presence of sodium salts in the amount corresponding to 25 mol % of Na2O in the Na2O–CaO–P2O5 system provided the occurrence of liquid- phase sintering in compact preforms from the studied powder mixtures. However, the presence of the water-soluble salt Na4P2O7 in ceramic samples of HAP/Na2HPO4 and HAP/NaH2PO4 after calcination imposes a restriction on the use of such materials in contact with an aqueous medium. And the presence of CaO in the HAP/Na2CO3 samples excludes the use of such materials as bone implants.

Observation of the metal-insulator transition of VO2 in glasses and nanomaterials of MV2O5–P2O5 system (M [dbnd] Li, Na, Mg)

In this research, special attention has been paid to an observation of a metal-insulator transition (MIT) in lithium/sodium/magnesium-vanadate-phosphate glasses and nanomaterials. Two series (A & B) of glassy 90MV2O5 ⋅10P2O5 (M Li, Na, Mg) samples were prepared by melt-quenching technique at 1300 °C using double-crucible technique. Series B was synthesized in more reducing conditions. DSC traces of the synthesized samples were typical for glassy materials. Glass transition and crystallization occurred in series A at significantly higher temperatures than in series B. In addition, an endothermic peak was observed at low temperature (67 °C). XRD patterns of the samples contained amorphous halo, but also some diffraction reflexes corresponding to monoclinic VO2. In series A, the reflexes had low intensity, whereas in series B the intensity of the peaks at the same positions was significantly higher. Dependences of electrical conductivity were typical for nanocrystallized glasses in case of series A, whereas in series B a reversible change of the conductivity was observed at 67 °C. Samples of series A exhibited positive and constant Seebeck coefficient S within wide temperature range, whereas in series B a change in thermoelectric power was observed above 67 °C. All these phenomena around 67 °C are due to metal-insulator transition in VO2 impurities in the samples.

EFFECTS OF Nd2O3 ON THE CRYSTALLIZATION AND PROPERTIES OF GLASS CERAMIC IN Li2O–K2O–Al2O3–SiO2–P2O5 SYSTEM

Glass ceramics (GCs), which often contain a small amount of rare earth oxides to improve their performance, are ideal for dental restorative applications. The aim of this study was to investigate the various effects of Nd2O3 content (0–1 wt%) on crystallization and properties of GC derived from Li2O–K2O–Al2O3–SiO2–P2O5 system. The glass blocks were formed from the molten at 1450 °C. Based on the DTA results, the glass samples were experienced by two–stage heat–treatment (600 °C/ 90 min + 720 °C/ 30 min) to change to ingots. After that, the ingot samples were fired in a hot pressing furnace EP3000 at 930 °C for 30 min. The results of powder X–ray diffraction (XRD) indicated that the final GCs contained crystals such as lithium disilicate (Li2Si2O5 or LS2), lithium metasilicate (Li2SiO3 or LS) and the traces of lithium phosphate (Li3PO4). With increasing Nd2O3 content, the relative amount of LS phase increased slightly while LS2 phase decreased. However, the final GC containing 0.75 wt% Nd2O3 had the highest bending strength at 293 MPa, the lowest chemical solubility and relative high Vicker hardness. These samples had a high degree of crystallization and the highest relative content of desired LS2 phase.

A simple way of modulating in vitro angiogenic response using Cu and Co-doped bioactive glasses

The copper and cobalt-doped bioactive glasses (BGs) from the basic SiO2–CaO–P2O5 system, differing in the CaO/SiO2 molar ratios, were produced using sol-gel method. The in vitro angiogenic response of human fibroblasts and umbilical vein endothelial cells (HUVECs) on Cu-BGs and Co-BGs was investigated. The incorporation of Cu and Co into BGs significantly enhanced vascular endothelial growth factor secretion from fibroblasts. Cu-BGs and Co-BGs extracts might facilitate the migration of HUVECs and the self-assembled network formation after 3 days of culture without basement membrane matrix, demonstrating strong angiogenic activity. The results show that cellular response was correlated with Cu and Co release rate which, in turn, was affected by the CaO/SiO2 molar ratios, indicating new opportunities for controlling the release rate of therapeutic ions from BGs.

New calcium‐free Na2O–Al2O3–P2O5 bioactive glasses with potential applications in bone tissue engineering

AbstractSodium aluminophosphate glasses were evaluated for their bone repair ability. The glasses belonging to the system 45Na2O–xAl2O3‐(55‐x)P2O5, with x = (3, 5, 7, 10 mol%) were prepared by a melt‐quenching method. We assessed the effect of Al2O3 content on the properties of Na2O–Al2O3–P2O5 (NAP) glasses, which were characterized by density measurements, DSC analyses, solubility, bioactivity in simulated body fluid and cytocompatibility with MG‐63 cells. To the best of our knowledge, this is the first investigation of calcium‐free Na2O–Al2O3–P2O5 system glasses as bioactive materials for bone tissue engineering.

Towards Novel High-Voltage Cathode Polyanionic Materials: Exploration of the Na2Ο–V2O3–P2O5 System

Polyanionic-type materials have a wider variety of crystal architectures compared to structurally simple transition metal oxides, thus leading to a huge diversity of possible structural features beneficial to some specific electrochemical properties of the batteries [1, 2]. In particular, the 4-, 5-, and 6-fold coordinations and various oxidation states (from +2 to +5) of vanadium in polyanionic compositions may result in the formation of various structural building units, each with its own structural role in the crystal structures. Electrochemically, vanadium also provides the opportunity of exchanging more than one electron per transition metal upon charge/discharge processes. At the same time, natural abundance of sodium and its low cost compared to lithium used in widespread electrode materials have recently attracted a significant attention of the research community to such Na-containing polyanion-based materials [3,4]. However, there are still only 5 reported compositions in the Na2O–V2O3–P2O5 system so far (Fig. 1). Among them, the only NASICON-type Na3V3+ 2(PO4)3 phase with a theoretical capacity of about 118 mAh/g at 3.4 V vs. Na/Na+ has been deeply investigated owing to its stable long-term cyclability and high mobility of sodium ions [5]. It was recently also demonstrated that the metal substitution in NASICON-type phases may lead to increasing of the theoretical gravimetric capacity and the average operating voltage due to the access to the V4+/V5+redox couple [6]. In order to continue further exploration of the Na2O–V2O3–P2O5 system, herein we present new compounds, which were structurally and electrochemically characterized. We also report the results of our investigation of the influence of a substitution of a part of vanadium by aluminum in the Na7V3+ 4(P2O7)4(PO4) and Na3V3+ 2(PO4)3 compositions on the electrochemical behavior of these materials. This work was carried out under the framework of the NAIADES project titled “Na-ion battery demonstration for electric storage” supported by the Regional Council of Picardie and the University of Picardie Jules Verne.

Proton Environments in Biomimetic Calcium Phosphates Formed from Mesoporous Bioactive CaO-SiO2-P2O5 Glasses in Vitro: Insights from Solid-State NMR.

When exposed to body fluids, mesoporous bioactive glasses (MBGs) of the CaO–SiO2–P2O5 system develop a bone-bonding surface layer that initially consists of amorphous calcium phosphate (ACP), which transforms into hydroxy-carbonate apatite (HCA) with a very similar composition as bone/dentin mineral. Information from various 1H-based solid-state nuclear magnetic resonance (NMR) experiments was combined to elucidate the evolution of the proton speciations both at the MBG surface and within each ACP/HCA constituent of the biomimetic phosphate layer formed when each of three MBGs with distinct Ca, Si, and P contents was immersed in a simulated body fluid (SBF) for variable periods between 15 min and 30 days. Directly excited magic-angle-spinning (MAS) 1H NMR spectra mainly reflect the MBG component, whose surface is rich in water and silanol (SiOH) moieties. Double-quantum–single-quantum correlation 1H NMR experimentation at fast MAS revealed their interatomic proximities. The comparatively minor H species of each ACP and HCA component were probed selectively by heteronuclear 1H–31P NMR experimentation. The initially prevailing ACP phase comprises H2O and “nonapatitic” HPO42–/PO43– groups, whereas for prolonged MBG soaking over days, a well-progressed ACP → HCA transformation was evidenced by a dominating O1H resonance from HCA. We show that 1H-detected 1H → 31P cross-polarization NMR is markedly more sensitive than utilizing powder X-ray diffraction or 31P NMR for detecting the onset of HCA formation, notably so for P-bearing (M)BGs. In relation to the long-standing controversy as to whether bone mineral comprises ACP and/or forms via an ACP precursor, we discuss a recently accepted structural core–shell picture of both synthetic and biological HCA, highlighting the close relationship between the disordered surface layer and ACP.

Preparation of orthophosphate glasses in the MgO-CaO-SiO2-Nb2O5-P2O5 system.

Niobia/magnesia-containing orthophosphate invert glasses were successfully prepared in our earlier work. Orthophosphate groups in the glasses were cross-linked by tetrahedral niobia (NbO4) and magnesia. The aim of this work is to prepare calcium orthophosphate invert glasses containing magnesia and niobia, incorporating silica, and to evaluate their structures and releasing behaviors. The glasses were prepared by melt-quenching, and their structures and ion-releasing behaviors were evaluated. 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies showed the glasses consist of orthophosphate (PO4), orthosilicate (SiO4), and NbO4 tetrahedra. NbO4 and MgO in the glasses act as network formers. By incorporating SiO2 into the glasses, the chemical durability of the glasses was slightly improved. The glasses reheated at 800°C formed the orthophosphate crystalline phases, such as β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4 in the glasses. The chemical durability of the crystallized glasses was slightly improved. Orthosilicate groups and NbO4 in the glasses coordinated with each other to form Si-O-Nb bonds. The chemical durability of the glasses was slightly improved by addition of SiO2, since the field strength of Si is larger than that of Ca or Mg.

Nature of electronic conductivity in olivine-like glasses and nanomaterials of Li2O–FeO–V2O5–P2O5 system

In previous research, we have investigated glasses and highly-conducting nanomaterials of Li2O–FeO–V2O5–P2O5 system. However, it was unclear which hopping centers (iron or vanadium ions) dominated in charge carrier transport. Therefore, this phenomenon was investigated by combination of Mössbauer spectroscopy and thermoelectric power measurements. The Seebeck coefficient in glasses was close to zero, but negative. After nanocrystallization, |S| increased significantly and remained negative in all the samples. Thermal treatment of the samples at elevated temperature (up to ca. 500°C) in air resulted only in insignificant oxidation of iron ions. Considering both Mössbauer and thermoelectric power measurements, one can conclude that Fe2+/Fe3+ ratio does not have major influence on electronic conductivity of studied samples. It is rather V4+/V5+ hopping centers situated on highly disordered nanocrystallites shells that play major role in high electronic conductivity of nanocrystallized samples (up to 7 ⋅ 10−3S/cm).

Investigation of the structural and thermal properties of Y, Ag and Ce-assisted SiO2–Na2O–CaO–P2O5-based glasses derived by sol–gel method

A glass with the composition of the SiO2–Na2O–CaO–P2O5 was synthesized by sol–gel method at temperature of 900 °C, and then yttrium-, silver- and cerium-containing glasses were prepared at the same conditions using this base system. The structural and thermal properties of the glass samples were investigated by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDX) spectroscopy and differential thermal analysis techniques. The Ca5(PO4)2(SiO4)6 phase having the orthorhombic crystal system is detected for each sample without any secondary phase, and this phase is confirmed by the FTIR spectra. With the addition of Y, Ag and Ce to the SiO2–Na2O–CaO–P2O5 system, the variations in the average crystallite size, crystallinity percent, lattice parameters and unit cell volume are observed. A decrease in the crystallization peak temperature and the changes in the glass transition temperature are seen with the addition of Y, Ag and Ce to the base system. The addition of Y, Ag and Ce to the base glass increases significantly its density. The EDX spectra of the as-prepared samples verify the introduction of the as-mentioned elements.

Controlled Parallel Crystallization of Lithium Disilicate and Diopside Using a Combination of Internal and Surface Nucleation

In the mid-19th century, Dr. Donald Stookey identified the importance and usability of nucleating agents and mechanisms for the development of glass-ceramic materials. Today, a number of various internal and surface mechanisms as well as combinations thereof have been established in the production of glass-ceramic materials. In order to create new innovative material properties the present study focuses on the precipitation of CaMgSiO6 as a minor phase in Li2Si2O5 based glass-ceramics. In the base glass of the SiO2-Li2O-P2O5-Al2O3-K2O-MgO-CaO system P2O5 serves as nucleating agent for the internal precipitation of Li2Si2O5 crystals while a mechanical activation of the glass surface by means of ball milling is necessary to nucleate the minor CaMgSi2O6 crystal phase. For a successful precipitation of CaMgSi2O6 a minimum ratio of MgO and CaO in the range between 1.4 mol% and 2.9 mol% in the base glasses was determined. The nucleation and crystallization of both crystal phases takes place during sintering a powder compact. Dependent on the quality of the sintering process the dense Li2Si2O5-CaMgSi2O6 glass-ceramics show a mean biaxial strength of up to 392 ± 98 MPa. The microstructure of the glass-ceramics is formed by large (5-10 µm) bar like CaMgSi2O6 crystals randomly embedded in a matrix of small (≤ 0.5 µm) plate like Li2Si2O5 crystals arranged in an interlocking manner. While there is no significant influence of the minor CaMgSi2O6 phase on the strength of the material, the translucency of the material decreases upon precipitation of the minor phase.

Evaluation of amorphous magnesium phosphate (AMP) based non-exothermic orthopedic cements

This paper reports for the first time the development of a biodegradable, non-exothermic, self-setting orthopedic cement composition based on amorphous magnesium phosphate (AMP). The occurrence of undesirable exothermic reactions was avoided through using AMP as the solid precursor. The phenomenon of self-setting with optimum rheology is achieved by incorporating a water soluble biocompatible/biodegradable polymer, polyvinyl alcohol (PVA). Additionally, PVA enables a controlled growth of the final phase via a biomimetic process. The AMP powder was synthesized using a precipitation method. The powder, when in contact with the aqueous PVA solution, forms a putty resulting in a nanocrystalline magnesium phosphate phase of cattiite. The as-prepared cement compositions were evaluated for setting times, exothermicity, compressive strength, biodegradation, and microstructural features before and after soaking in SBF, and in vitro cytocompatibility. Since cattiite is relatively unexplored in the literature, a first time evaluation reveals that it is cytocompatible, just like the other phases in the MgO–P2O5 (Mg–P) system. The cement composition prepared with 15% PVA in an aqueous medium achieved clinically relevant setting times, mechanical properties, and biodegradation. Simulated body fluid (SBF) soaking resulted in coating of bobierrite onto the cement particle surfaces.

Sol-gel preparation and structural investigations of silico-phosphate glasses doped with Fe ions

Different aspects related to the sol-gel preparation and structural investigation of silico-phosphate glasses (SiO2–P2O5 system) doped with Fe ions are reported. During the preparation process, tetraethoxysilane was used as a precursor for SiO2 and phosphoric acid (H3PO4-HP) for P2O5. Ferric chloride was used as precursor for Fe ions, water as reagent for hydrolysis reaction and ethylic alcohol as solvent. The pH of the sols was modified by adding hydrochloric acid and ammonia. It was observed that a slight increase of the solution temperature (up to 40 °C) allows a drastic decrease of the gelation time (from days to hours). The structure of the obtained powders dried in air at room temperature and at 100 °C for 10 h and subsequently thermally treated at different temperatures was investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy. Vibration modes specific to Si–O–Et, Si–OH, P–O–P, P–O–Si, hydrogen bonds and H2O, as well as combined modes have been observed. The local structure and electron configurations of the doping Fe ions have been investigated by 57Fe Mossbauer spectroscopy. Mossbauer spectra of the sample with molar composition 0.85SiO2 0.08P2O5 0.07Fe2O3 (Fe15) annealed at 300 °C collected at 5.7/6 K, 30 K, 60 K and at room temperature The magnetic pattern is assigned (by its hyperfine parameters) to α-Fe2O3 (36 % from total Fe, the rest being dispersed in the matrix as paramagnetic Fe with octahedral oxygen configuration).

The role of solvent type, size and chemical composition of bioactive glass particles in modulating material properties of poly(ε-caprolactone) based composites

The role of solvent type (dichloromethane, 1,4-dioxane, tetrahydrofuran), size (<45, <3μm) and chemical composition (silica-rich, calcium-rich) of bioactive glass (BG) particles in modulating surface properties, crystallinity, mechanical properties and in vitro bioactivity of poly(ε-caprolactone) based composite films was investigated. Films were prepared by solvent casting method. Bioactive glasses from the SiO2–CaO–P2O5 system were obtained by sol-gel method. The particle size and solvent type played an important role in nucleation and crystallisation kinetics of PCL, affecting morphology, topography and wettability of films. In contrast to BG particles of <45μm size, the smaller ones (<3μm) were exposed on the surfaces of films and consequently have improved hydrophilicity and have provided crystallisation of carbonated hydroxyapatite after incubation in SBF. Type of the solvent, by affecting surface properties, influenced hydroxyapatite crystallisation process. The addition of BG particles of both sizes resulted in enhanced modulus and drastic decrease in elongation at break.

Highly conductive cathode materials for Li-ion batteries prepared by thermal nanocrystallization of selected oxide glasses

Glassy analogs of two important cathode materials for Li-ion cells: V2O5 and phosphoolivine LiFePO4 were heat-treated in order to prepare nanocrystallized materials with high electronic conductivity of up to 7×10−2Scm−1 and ca 7×10−3Scm−1 at 25°C, respectively. There is a clear correlation between the crystallization phenomena and the increase in the electrical conductivity for both groups of glasses. Electrochemical tests of heat-treated glasses of the V2O5–P2O5 system, used as cathodes in lithium cells confirm their good gravimetric capacity and reversibility. Heat-treatment of glasses of the Li2O–FeO–V2O5–P2O5 system also leads to a high increase in the conductivity and to formation of nanocrystalline grains in the glassy matrix, evidenced by HR-TEM images. The temperature dependence of the conductivity of these materials follows the Arrhenius formula. The presented results indicate that the overall increase in conductivity in nanocrystallized materials is due to good charge transport properties of their interfacial regions.

Sol–gel synthesis and in vitro bioactivity of glass–ceramics in SiO2–CaO–Na2O–P2O5 system

Bioactive glass–ceramic powder in SiO2–CaO–Na2O–P2O5 system was successfully synthesised through a modified sol–gel route. The gel was prepared using tetraethyl orthosilicate, calcium nitrate, sodium nitrate and triethyl phosphate raw materials. The gel was calcined in the temperature range 700–1050 °C to get the glass–ceramic powder. Dissolution of the glass–ceramic powder was studied by in vitro immersion in Tris buffer solution for various period of time. The biodegraded powder was analyzed using XRD. The sintered glass–ceramic was characterized for in vitro bioactivity in simulated body fluid, and the incubated pellet was then analyzed for phase identification by XRD, surface morphology using SEM and elemental analysis using energy-dispersive X-ray analysis. The biocompatibility of the glass–ceramics was evaluated through MTT assay using MG-63 cells.