Sodium alginate was successfully utilized to improve cohesion and limit particulate debris of a premixed calcium phosphate cement (pCPC) that following the exchange of water set to form monetite. Modified pastes using glycerol and 2wt% alginate exhibited initial and final setting times of 60 +/- 9 and 1355 +/- 105minutes, respectively. Despite these setting times being significantly longer than clinically recommended the improved washout resistance of this formulation would allow for wound closure during setting. Set monetite pastes exhibited a maximum compressive strength of 8.6 +/- 3.5MPa with a corresponding porosity of 59% compared to 15.6 +/- 5.8MPa and 25% for the unmodified aqueous brushite cement. Storage of the pCPC paste at 4 degrees C for 14days was shown to significantly (P<0.05) increase the compressive strength of the harden matrix (13.2 +/- 1.5MPa), however, subsequent deterioration was observed after 90days storage. Methylene blue was utilized to visualize perfusion into the matrix during setting, demonstrating that the use of glycerol altered mass transport and ultimately shifted the crystallization kinetics in favor of monetite. Samples >20mm did not reach full saturation after 10days of immersion, which for the first time suggests an upper volume limit that will form a homogeneous cement highlighting an important consideration for clinical translation of pCPCs.

For the first time solution enthalpies of Al, H3PO4, and AlH2P3O10 x 2H(2)O in 2 mol dm (3) NaOH have been measured as following: Delta H-sol(o) (1) = -404.75 +/- 4.36 kJ mol (1); Delta H-sol(o) (2) = -189.48 +/- 0.54 kJ mol (1); Delta H-sol(o) (3) = -238.95 +/- 3.32 kJ mol (1). On the basis of experimental data the standard molar enthalpy of formation and enthalpies of some reactions with participation of AlH2P3O10 x H2O were calculated. The enthalpy of interaction of Al with H3PO4 is Delta H-r(o) = -734.24 +/- 5.56 kJ mol (1). It was established that according to thermodynamic data Al2O3 can react with H3PO4 forming investigated compound at 513 K. Employed compound (AlH2P3O10 x H2O) can react with H2O with formation of AlPO4 and phosphorous acid. All the data were obtained for the first time. (C) 2017 Elsevier Ltd.

Sr-87, I-127 and Sn-119 wideline NMR spectroscopy was successfully applied to inorganic and hybrid materials: (i) Sr derivatives of medicinal interest (Sr-malonate, Sr-pyrophosphates, mixed Ca,Sr-fluoroapatites); (ii) apatitic structures acting as host matrices for iodine; and (iii) Sn-derived oxo-clusters which can be used as inorganic nanobuilding blocks. The BRAIN (BRoadband Adiabatic INversion) CP (Cross Polarization) approach (by Schurko et al.) was applied to a non integer quadrupolar nucleus (Sr-87, I = 9/2). The sequence was used in combination with WURST (Wideband Uniform-Rate Smooth-Truncation) QCPMG (Quadrupolar Carr-Purcell Meiboom-Gill) for optimal sensitivity. We showed that I-127 WURST QCPMG experiments were sufficiently sensitive to allow rapid characterization of the incorporation of iodide (I-) anions in lead vanadate/phosphate apatites, and that I-127 acted as a sensitive probe for the description of local disorder. H-1/F-19 -> Sn-119 BRAIN CP was successfully applied to the detailed characterization of tin oxo-clusters, using H-1 and F-19 as spin baths. We demonstrated that BRAIN CP can be effectively used as a tool of spectral editing leading to the estimation of spatial proximities between Sn-119 and H-1/F-19 nuclei.

87 Sr, 127 I and 119 Sn wideline NMR spectroscopy was successfully applied to inorganic and hybrid materials: (i) Sr derivatives of medicinal interest (Sr‐malonate, Sr‐pyrophosphates, mixed Ca,Sr‐fluoroapatites); (ii) apatitic structures acting as host matrices for iodine; and (iii) Sn‐derived oxo‐clusters which can be used as inorganic nanobuilding blocks. The BRAIN (BRoadband Adiabatic INversion) CP (Cross Polarization) approach (by Schurko et al .) was applied to a non integer quadrupolar nucleus ( 87 Sr, I=9/2). The sequence was used in combination with WURST (Wideband Uniform‐Rate Smooth‐Truncation) QCPMG (Quadrupolar Carr‐Purcell Meiboom‐Gill) for optimal sensitivity. We showed that 127 I WURST QCPMG experiments were sufficiently sensitive to allow rapid characterization of the incorporation of iodide (I − ) anions in lead vanadate/phosphate apatites, and that 127 I acted as a sensitive probe for the description of local disorder. 1 H/ 19 F → 119 Sn BRAIN CP was successfully applied to the detailed characterization of tin oxo‐clusters, using 1 H and 19 F as spin baths. We demonstrated that BRAIN CP can be effectively used as a tool of spectral editing leading to the estimation of spatial proximities between 119 Sn and 1 H/ 19 F nuclei.

Materials exhibiting mixed electronic and proton conductivity are of great interest for applications ranging from electrodes for proton conducting ceramic fuel cells to hydrogen separation membranes.

Hydrated calcium pyrophosphates (CPP, Ca2P2O7 center dot nH(2)O) are a fundamental family of materials among osteoarticular pathologic calcifications. In this contribution, a comprehensive multinuclear NMR (Nuclear Magnetic Resonance) study of four crystalline and two amorphous phases of this family is presented. H-1, P-31 and Ca-43 MAS (Magic Angle Spinning) NMR spectra were recorded, leading to informative fingerprints characterizing each compound. In particular, different H-1 and Ca-43 solid state NMR signatures were observed for the amorphous phases, depending on the synthetic procedure used. The NMR parameters of the crystalline phases were determined using the GIPAW (Gauge Including Projected Augmented Wave) DFT approach, based on first-principles calculations. In some cases, relaxed structures were found to improve the agreement between experimental and calculated values, demonstrating the importance of proton positions and pyrophosphate local geometry in this particular NMR crystallography approach. Such calculations serve as a basis for the future ab initio modeling of the amorphous CPP phases.Statement of significanceThe general concept of NMR crystallography is applied to the detailed study of calcium pyrophosphates (CPP), whether hydrated or not, and whether crystalline or amorphous. CPP are a fundamental family of materials among osteoarticular pathologic calcifications. Their prevalence increases with age, impacting on 17.5% of the population after the age of 80. They are frequently involved or associated with acute articular arthritis such as pseudogout. Current treatments are mainly directed at relieving the symptoms of joint inflammation but not at inhibiting CPP formation nor at dissolving these crystals. The combination of advanced NMR techniques, modeling and DFT based calculation of NMR parameters allows new original insights in the detailed structural description of this important class of biomaterials. (C) 2016 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

In this article we comment on the results published by Thompson et al. (, J. Solid State Chem. 219 (2014) 173–178) on the crystal structure of SrFeO2F, who claim the compound to crystallize in the cubic space group Pm-3m. We give a more detailed explanation of the determination of our previously reported structural model with Imma symmetry (Clemens et al., J. Solid State Chem. 206 (2013) 158–169), with addition of variable temperature XRD measurements with high counting time to provide unambiguous evidence for the Imma model being correct for our sample.

This article reports on the synthesis and crystallographic and magnetic structure of barium-doped BiFeO3 compounds with approximate composition Bi(1-x)Ba(x)FeO(3-x/2), as well as those of the fluorinated compounds Bi(1-x)Ba(x)FeO(3-x)F(x) (both with x = 0.2, 0.3), prepared by low-temperature fluorination of the oxide precursors using polyvinylidenedifluoride. Whereas the oxide compounds were obtained as cubic (x = 0.2) and slightly tetragonal (x = 0.3, c/a ≈ 1.003) distorted perovskite compounds, a large tetragonal polar distortion was observed for the oxyfluoride compounds (c/a ≈ 1.08 for x = 0.2 and ∼1.05 for x = 0.3), being isostructural to tetragonal PbTiO3. Although described differently in previous reports on Ba-doped BiFeO3, the observed remanent magnetization is found to agree well with the amount of BaFe12O19 only detectable by neutron diffraction and the well-known magnetic properties of BaFe12O19. The oxyfluoride compounds show G-type antiferromagnetic ordering with magnetic moments lying in the a/b plane.

We report here on the characterization of the vacancy-ordered perovskite-type structure of BaFeO2.5 by means of combined Rietveld analysis of powder X-ray and neutron diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c [a = 6.9753(1) Å, b = 11.7281(2) Å, c = 23.4507(4) Å, β = 98.813(1)°, and Z = 28] containing seven crystallographically different iron atoms. The coordination scheme is determined to be Ba7(FeO4/2)1(FeO3/2O1/1)3(FeO5/2)2(FeO6/2)1 = Ba7Fe([6])1Fe([5])2Fe([4])4O17.5 and is in agreement with the (57)Fe Mössbauer spectra and density functional theory based calculations. To our knowledge, the structure of BaFeO2.5 is the most complicated perovskite-type superstructure reported so far (largest primitive cell, number of ABX2.5 units per unit cell, and number of different crystallographic sites). The magnetic structure was determined from the powder neutron diffraction data and can be understood in terms of "G-type" antiferromagnetic ordering between connected iron-containing polyhedra, in agreement with field-sweep and zero-field-cooled/field-cooled measurements.

Pyrophosphate ions are both inhibitors of HA formation and substrates for phosphatase enzymes. Unlike polyphosphates their hydrolysis results simultaneously in the complete loss of mineral formation inhibition and a localised elevation in orthophosphate ion concentration. Despite recent advances in our knowledge of the role of the pyrophosphate ion, very little is known about the effects of pyrophosphate on bone formation and even less is known about its local delivery. In this work we first developed a self setting pyrophosphate based calcium cement system with appropriate handling properties and then compared its in vivo degradation properties with those of a non-pyrophosphate containing control. Contrary to expectation, the presence of the pyrophosphate phase in the cement matrix did not inhibit mineralisation of the healing bone around the implant, but actually appeared to stimulate it. In vitro evidence suggested that enzymatic action accelerated dissolution of the inorganic pyrophosphate ions, causing a simultaneous loss of their mineralisation inhibition and a localised rise in supersaturation with respect to HA. This is thought to be a rare example of a biologically responsive inorganic material and these materials seem to be worthy of further investigation. Bioceramics to date have mainly been limited to orthophosphate, silicate and carbonate salts of calcium, here we report the successful application of a pyrophosphate material as a degradable osteoconductive bone repair cement.

The compounds 15R-BaFeO2F and 15R-BaFeO2.27F0.5 have been synthesised by the low temperature fluorination of 15R-BaFeO3−dF0.2 using polyvinylidenedifluoride (PVDF) as a fluorination agent. The materials have been structurally characterised by Rietveld analysis of the X-ray- and HRPD-powder neutron diffraction data. A detailed analysis of bond valence sums suggests that the oxide and fluoride ions order on the different anion sites. A reinvestigation of our recently published structure (Clemens et al., 2013) [34] of 6H-BaFeO2F is also reported and incorporation of fluoride in h-type layers is also confirmed in this compound. The magnetic moments for 15R-BaFeO2F and 15R-BaFeO2.25F0.5 align in the a/b-plane with antiferromagnetic alignment of the moments between adjacent layers, and are flipped by 90° as compared to the precursor compound. 15R-BaFeO2F exhibits very robust antiferromagnetism with a Néel temperature between 300 and 400 °C.

The high temperature phase of manganese vanadate h.t.-Mn-3(VO4)(2) and the solid solution with NaMn4(VO4)(3) (NaxMn4.5-x/2(VO4)(3)) were shown to order ferrimagnetically below 55 K for x < 1, whereas NaMn4(VO4)(3) is an antiferromagnet. The materials show very soft magnetic properties with low coercitive fields required for demagnetisation (H-c < 0.001 T). The magnetic structure of h.t.-Mn-3(VO4)(2) was determined by Rietveld analysis of low temperature powder neutron diffraction data, and shows antiferromagnetic alignment of the magnetic moments of the Mn2+ ions on the 8c and 8d sites. The ferrimagnetic moments were shown to result from the magnetic moments of the Mn2+ cations located on the 4b site in unusual dodecahedral coordination (Hoard dodecahedron). This coordination can be understood as two penetrating oxygen coordination tetrahedra, one showing shorter and one showing longer Mn-O distances. The magnetic moments of the Mn2+ ions on the 4b site are aligned parallel to the ones on 8d and antiparallel to the ones on 8c, being in good agreement with the GKA rules. The local exchange interactions between the Mn2+ ions on the 4b to those on the 8c/8d sites are likely to be similar in strength and competitive and therefore probably contribute to the soft magnetic properties.

Brushite‐forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. Cell‐attached culture beads formed from this material could be of great use for cell therapy. Despite a significant amount of work on optimizing the physicochemical properties of these materials, there are very few studies that have evaluated the capacity of the materials to facilitate cell adhesion. In this study, we have formed resorbable calcium phosphate (brushite) culture beads and for the first time we showed that cell attachment to the surface of the brushite cement (BC) could be inhibited by the presence of an intermediate dicalcium phosphate–citrate complex, formed in the cement as a result of using citric acid, a retardant and viscosity modifier used in many cement formulations. The BC beads formed from the mixture of β‐TCP/orthophosphoric acid using citric acid did not allow cell attachment without further treatment. Ageing of BC beads in serum‐free Dulbecco's Modified Eagle's Medium (DMEM) solution at 37°C for 1 week greatly enhanced the cell adhesion capacity of the material. Scanning electron microscopy, X‐ray diffraction (XRD), and confocal Raman microspectrometry indicated the increased capacity for cell adhesion was due to the changes in phase composition of BC. XRD patterns collected before and after ageing in aqueous solution and a high initial mass loss, suggest the formation of a dicalcium phosphate–citrate complex within the matrix. Since compacts formed from brushite powder supported cell attachment, it was hypothesized that the dicalcium phosphate–citrate complex prevented attachment to the cement surface. Biotechnol. Bioeng. 2013; 110: 1487–1494. © 2012 Wiley Periodicals, Inc.

We report here a detailed study of the system La1−xSrxFeO3−xFx, by neutron powder diffraction- and magnetic-measurements. All the compounds are robust antiferromagnetics with ordering temperatures well above room temperature. Magnetic moments are shown to align parallel to the c-axis. FC-ZFC measurements indicate a small canting of the magnetic moments, resulting in a ferromagnetic component with a maximum for La0.5Sr0.5FeO2.5F0.5. We show that the system exhibits a composition-driven transition from a phase, for low fluorination levels (x≤0.5), with Pnma symmetry and the usual system of octahedral tiltings, to a phase with space group Imma for higher fluorine contents, where a correlated distortion of the oxygen octahedra plays a significant role. The consistency of the structural models, with respect to the expected continuity of the amplitudes of the different distortion modes and the invariance of their internal form, was monitored through the symmetry mode decomposition of the structures.

AbstractLa1‐xSrxFeO3‐xFx (x = 1, 0.8, 0.5, 0.2, 0) phases are prepared by solid state reaction of stoichiometric mixtures of La2O3, SrCO3, and Fe2O3 (1250 °C, 30 h) followed by fluorination with poly(vinylidenefluoride) at 400 °C for 24 h.

The compound 6H-BaFeO2F (P63/mmc) was synthesised by the low temperature fluorination of 6H-BaFeO3–d using polyvinylidenedifluoride (PVDF) as a fluorination agent. Structural characterisation by XRD and NPD suggests that the local positions of the oxygen and fluorine atoms vary with no evidence for ordering on the anion sites. This compound shows antiferromagnetic ordering at room temperature with antiparallel alignment of the magnetic moments along the c-axis. The use of PVDF also allows the possibility of tuning the fluorine content in materials of composition 6H-BaFeO3–dFy to any value of 0<y≤1. In addition, the oxygen content, and therefore the iron oxidation state, can be tuned by applying different partial pressures of oxygen during the reaction.

'Manganese violet' pigments have been known for over 150 years, but are receiving renewed interest due to their non-toxicity and earth-abundant components. For the first time we report here a detailed study into the structural aspects that define the sought-after pigment properties of these materials. This work identified two polymorphs, designated as alpha- and beta-NH4MnP2O7 that provide the strong colouration and compared them to a commercially available sample. Rietveld analysis of neutron powder diffraction data indicated that the a-polymorph crystallised in space group P2(1)/c (a = 7.4252(3) angstrom, b = 9.6990(4) angstrom, c = 8.6552(4) angstrom and beta = 105.627(3)degrees) and exhibited a highly distorted MnO6 coordination sphere. The apparent [2 + 2 + 2] distortion gives rise to the optical properties and appears to be driven, in part, by a "plasticity effect" in the Mn coordination induced by the pyrophosphate ligand. A second polymorph beta-NH4MnP2O7 was found to crystallise in space group P (1) over bar (a = 8.4034(6) angstrom, b = 6.1498(4) angstrom, c = 6.1071(4) angstrom, alpha = 104.618(5)degrees, beta = 100.748(5)degrees and gamma = 96.802(6)degrees) and possessed similarly distorted MnO6 octahedra, but was found to differ from alpha-NH4MnP2O7 in the relative dimensions of the intersecting framework tunnels that contained the ammonium cations. UV-visible spectroscopy was used to characterise optical behaviour and a combination of TGA-MS and in situ high temperature X-ray powder diffraction were used to determine thermal decomposition pathways.

Coprecipitation of ferric and ferrous iron salts in the presence of Bovine Serum Albumin (BSA) demonstrates an unusual impact on crystal growth mechanisms and eventual nanoparticle morphology. For BSA 200-800 mu Mol/ml, polycrystalline acicular and haloed spheroid particles were observed and these samples demonstrated surprising magnetic properties, including high coercivity.