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Advances in Phosphate Materials: Structural, Technological and Biomedical Applications

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced and Functional Ceramics and Glasses".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 9799

Special Issue Editors

Department of Organic and Inorganic Chemistry, University of Oviedo—CINN (CSIC), Oviedo, Spain
Interests: phosphates; synthesis; structure; ion exchange; catalysis
Institute for Scientific and Technological Resources, University of Oviedo, Oviedo, Spain
Interests: HR-TEM; biomaterials; protein crystal growth; biophysics; biomedical
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Special Issue Information

Dear Colleagues,

Phosphates are a large group of materials that are present in nature as minerals and can also be synthesized. The impact of inorganic phosphorus in the form of phosphate PO43− is undeniable in our lives, since it is a basic constituent in the most vital biological macromolecules in living organisms, such as RNA, DNA, ADP, ATP, proteins, and lipids. The biological apatite that forms hard bones and teeth is carbonated hydroxyapatite, which is a phase of calcium phosphates. Nowadays, different phases of biocompatible calcium phosphates can be synthesized and further functionalized by incorporating different elements, such as strontium, zinc, magnesium, silver, etc., and used as filling cement or coating for metallic medical implants. Phosphate salts are also synthesized and used mainly in agricultural applications. Inducing the formation of metal phosphates has dramatically increased the possible applications of phosphate compounds to catalysis, separation, and ion exchange. For instance, titanium phosphates are efficient ion exchangers, acid oxidizers, photocatalysts, solid electrolytes, and, recently, have even been considered as a better variant than titanium oxide for cosmetics applications. Lithium metal phosphates are among the best materials used for realizing lithium-ion batteries. Manganese and strontium phosphates are used as anticorrosive and biocompatible coatings for metals. NASICON-type compounds are crystalline materials with high ionic conductivities. These compounds are therefore used as solid electrolytes in batteries and are conductive at elevated temperatures. NASICON materials are also used in catalysis, the immobilization of radioactive waste, and the removal of sodium from water. Some ceramic phosphate compounds bear the property of negative thermal expansion, and this makes their combination with other compounds that have positive thermal expansion the most adequate solution to synthesize composites with applications in high-precision technologies. Phosphate-based compounds containing actinides have been successfully synthesized and reported for their potential use in the nuclear waste industry. Recently, phosphate-containing or -doped metal–organic frameworks have been synthesized and used to decrease the flame retardancy and toxicity of epoxy resin, realize highly stable and efficient heterostructured photocatalysts, and have been used in supercapacitors and slow-release fertilizer.

We kindly invite you to submit manuscripts for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Dr. José R. García
Dr. Alaa Adawy
Guest Editors

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Keywords

  • phosphate salts
  • biomaterials
  • batteries
  • catalysis
  • ceramics
  • coating
  • ion exchange
  • ionic conductivity
  • negative thermal expansion
  • nuclear waste

Published Papers (4 papers)

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Research

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10 pages, 1648 KiB  
Article
Effect of the P/Al Molar Ratio and Heating Rate on the Composi-Tion of Alumino-Phosphate Binders
Materials 2022, 15(6), 2337; https://doi.org/10.3390/ma15062337 - 21 Mar 2022
Cited by 2 | Viewed by 1536
Abstract
New insights into the chemistry of alumino-phosphate solutions are provided in this contribution. In a first part, a solution with a P/Al molar ratio of 3.2 was prepared for the first time. The binders obtained at 500 and 700 °C were compared to [...] Read more.
New insights into the chemistry of alumino-phosphate solutions are provided in this contribution. In a first part, a solution with a P/Al molar ratio of 3.2 was prepared for the first time. The binders obtained at 500 and 700 °C were compared to those obtained with the 3 and 3.5 P/Al molar ratio solutions in order to determine the impact of moderate P2O5 excess on the final phosphate ceramic nature. In a second part, the widely used P/Al = 3 solution was heat-treated at 500 °C using different heating rates (0.2, 1, and 10 °C/min) to determine how this parameter modifies the final phosphate ceramic composition. Our data show that moderate P2O5 excess is sufficient to obtain binders with a high amount of stable cubic aluminium metaphosphate compound at 700 °C but not at 500 °C, where significant P2O5 excess is mandatory. We also show that slow heating favors the formation of cubic aluminium metaphosphate compound at 500 °C. Full article
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14 pages, 3026 KiB  
Article
Cobalt Minimisation in Violet Co3P2O8 Pigment
Materials 2022, 15(3), 1111; https://doi.org/10.3390/ma15031111 - 31 Jan 2022
Cited by 4 | Viewed by 1933
Abstract
This study considers the limitations of cobalt violet orthophosphate, Co3P2O8, in the ceramic industry due to its large amount of cobalt. MgxCo3−xP2O8 (0 ≤ x ≤ 3) solid solutions with [...] Read more.
This study considers the limitations of cobalt violet orthophosphate, Co3P2O8, in the ceramic industry due to its large amount of cobalt. MgxCo3−xP2O8 (0 ≤ x ≤ 3) solid solutions with the stable Co3P2O8 structure were synthesised via the chemical coprecipitation method. The formation of solid solutions between the isostructural Co3P2O8 and Mg3P2O8 compounds decreased the toxically large amount of cobalt in this inorganic pigment and increased the melting point to a temperature higher than 1200 °C when x ≥ 1.5. Co3P2O8 melted at 1160 °C, and compositions with x ≥ 1.5 were stable between 800 and 1200 °C. The substitution of Co(II) with Mg(II) decreased the toxicity of these materials and decreased their price; hence, the interest of these materials for the ceramic industry is greater. An interesting purple colour with a* = 31.6 and b* = −24.2 was obtained from a powdered Mg2.5Co0.5P2O8 composition fired at 1200 °C. It considerably reduced the amount of cobalt, thus improving the colour of the Co3P2O8 pigment (a* = 16.2 and b* = −20.1 at 1000 °C). Co3P2O8 is classified as an inorganic pigment (DCMA-8-11-1), and the solid solutions prepared were also inorganic pigments when unglazed. When introducing 3% of the sample (pigment) together with enamel, spreading the mixture on a ceramic support and calcining the whole in an electric oven, a colour change from violet to blue was observed due to the change in the local environment of Co(II), which could be seen in the UVV spectra of the glazed samples with the displacement of the bands towards higher wavelengths and with the appearance of a new band assigned to tetrahedral Co(II). This blue colour was also obtained with Co2SiO4, MgCoSiO4 or Co3P2O8 pigments containing a greater amount of cobalt. Full article
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12 pages, 3409 KiB  
Article
Nanolayered Metal Phosphates as Biocompatible Reservoirs for Antimicrobial Silver Nanoparticles
Materials 2021, 14(6), 1481; https://doi.org/10.3390/ma14061481 - 18 Mar 2021
Cited by 6 | Viewed by 2053
Abstract
There is an increasing demand on synthesizing pharmaceuticals and biomaterials that possess antimicrobial and/or antiviral activities. In this respective silver nanoparticles are known for their excellent antimicrobial activity. Nevertheless, their uncontrolled release in a biological medium can induce a cytotoxic effect. For this, [...] Read more.
There is an increasing demand on synthesizing pharmaceuticals and biomaterials that possess antimicrobial and/or antiviral activities. In this respective silver nanoparticles are known for their excellent antimicrobial activity. Nevertheless, their uncontrolled release in a biological medium can induce a cytotoxic effect. For this, we explored the use of nanolayered metal phosphates based on titanium and zirconium as materials that can be enriched with silver nanoparticles. Employing the hydrothermal route, crystalline α-phases of zirconium and titanium phosphates (α-ZrP, α-TiP) were synthesized and there after surface-enriched with silver nanoparticles. The structural assessment confirmed the stability of the structures and their sizes are in the nanoscale at least in one dimension. The cytocompatibility assays confirmed the biocompatibility of the pristine phases and the antimicrobial assay confirmed that both silver-enriched nanolayered structures maintain an antibacterial effect at reasonably low concentrations. Full article
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Review

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25 pages, 4300 KiB  
Review
Properties and Applications of Metal Phosphates and Pyrophosphates as Proton Conductors
Materials 2022, 15(4), 1292; https://doi.org/10.3390/ma15041292 - 09 Feb 2022
Cited by 19 | Viewed by 3078
Abstract
We review the progress in metal phosphate structural chemistry focused on proton conductivity properties and applications. Attention is paid to structure–property relationships, which ultimately determine the potential use of metal phosphates and derivatives in devices relying on proton conduction. The origin of their [...] Read more.
We review the progress in metal phosphate structural chemistry focused on proton conductivity properties and applications. Attention is paid to structure–property relationships, which ultimately determine the potential use of metal phosphates and derivatives in devices relying on proton conduction. The origin of their conducting properties, including both intrinsic and extrinsic conductivity, is rationalized in terms of distinctive structural features and the presence of specific proton carriers or the factors involved in the formation of extended hydrogen-bond networks. To make the exposition of this large class of proton conductor materials more comprehensive, we group/combine metal phosphates by their metal oxidation state, starting with metal (IV) phosphates and pyrophosphates, considering historical rationales and taking into account the accumulated body of knowledge of these compounds. We highlight the main characteristics of super protonic CsH2PO4, its applicability, as well as the affordance of its composite derivatives. We finish by discussing relevant structure–conducting property correlations for divalent and trivalent metal phosphates. Overall, emphasis is placed on materials exhibiting outstanding properties for applications as electrolyte components or single electrolytes in Polymer Electrolyte Membrane Fuel Cells and Intermediate Temperature Fuel Cells. Full article
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