An important step in establishing any new metrological method is a prenormative interlaboratory study, designed to verify and validate the method against its stated aims. Here, the 57 Fe Mössbauer spectrometric ‘centre of gravity’ (COG) method was tested as a means of quantifying the magnetite/maghemite (Fe 3 O 4 /γ-Fe 2 O 3 ) composition ratio in biphasic magnetic nanoparticles. The study involved seven laboratories across Europe and North and South America, and six samples—a verification set of three microcrystalline mixtures of known composition, and a validation set of three nanoparticle samples of unknown composition. The spectra were analysed by each participant using in-house fitting packages, and ex post facto by a single operator using an independent package. Repeatability analysis was performed using Mandel’s h statistic and modified Youden plots. It is shown that almost all (83/84) of the Mandel h statistic values fall within the 0.5% significance level, with the one exception being borderline. Youden-based pairwise analysis indicates the dominance of random uncertainties; and in almost all cases the data analysis phase is only a minor contributor to the overall measurement uncertainty. It is concluded that the COG method is a robust and promising candidate for its intended purpose.

CaTiO3 is a promising candidate as a pseudo-piezoelectric scaffold material for bone implantation. In this study, pure and magnesium/iron doped CaTiO3 are synthesized by sol-gel method and spark plasma sintering. Energy dispersive X-ray mapping confirm the homogenous distribution of doping elements in sintered samples. High-energy X-ray diffraction investigations reveal that doping of nanostructured CaTiO3 increased the strain and defects in the structure of CaTiO3 compared to the pure one. This led to a stronger pseudo-piezoelectric effect in the doped samples. The charge produced in magnesium doped CaTiO3 due to the direct piezoelectric effect is (2.9 ± 0.1) pC which was larger than the one produced in pure CaTiO3 (2.1 ± 0.3) pC, whereas the maximum charge was generated by iron doped CaTiO3 with (3.6 ± 0.2) pC. Therefore, the pseudo-piezoelectric behavior can be tuned by doping. This tuning of pseudo-piezoelectric response provides the possibility to systematically study the bone response using different piezoelectric strengths and possibly adjust for bone tissue engineering.

The polycrystalline perovskite calcium titanate has an orthorhombic crystal structure at room temperature, which belongs to a centro-symmetric point group. Due to this fact, it does not show piezoelectric behaviour. However, such behaviour is observed in nanostructured calcium titanate prepared by sol-gel synthesis and field assisted sintering. Whereas, the conventionally sintered sample does not show this behaviour. Presumably, the instability of regular TiO6 octahedra results in the off-centering of titanium positions of the field assisted sintered calcium titanate. This phenomenon leads to the generation of electric dipoles due to the lattice distortions produced by the formation of highly localized defects, i.e. oxygen vacancies, during densification by the field assisted sintering. As a result, pseudo-piezoelectric behaviour is observed, which confirms that the field assisted sintering triggers the piezoelectric effect but not the conventional sintering. The charge (Q) produced in the field assisted sintered sample and the piezoelectric constant (d(33)*) values have been determined to be Q = (2.1 +/- 0.3) pC and d(33+)* similar to(7.13 +/- 0.4) pm/V or d(33-)* similar to (-5.95 +/- 0.3) pm/V, respectively. This particular response of nanostructured calcium titanate is of great interest in biomedicine because it can improve the osseointegration of an implant.

The attractive electronic and magnetic properties together with their biocompatibility make iron-oxide nanoparticles appear as functional materials. In Fe-oxide nanoparticle (IONP) ensembles, it is crucial to enhance their performance thanks to controlled size, shape, and stoichiometry ensembles. In light of this, we conduct a comprehensive investigation in an ensemble of ca. 28 nm cuboid-shaped IONPs in which all the analyses concur with the coexistence of magnetite/maghemite phases in their cores. Here, we are disclosing the Verwey transition by temperature dependent (4-210 K) Raman spectroscopy.

Calcium titanate has an orthorhombic crystal structure and should not exhibit piezoelectric behavior. However, in the present study such behavior is observed in nanostructured calcium titanate prepared by sol–gel synthesis and field assisted sintering. This behavior is referred to as pseudo-piezoelectricity since it is generated by distorted structure. In-situ high-energy X-ray diffraction studies have been performed to investigate this behavior. Strain and defects in the nanostructured bulk material led to its piezoelectric response with non-180° domains reorientation and domains switching under external electric field. The piezoelectric constant is comparable with the piezoelectric constants of natural bone.

Investigating the polyol-assisted synthesis of maghemite nanoflowers, a strong impact of the iron precursor stoichiometry on physical properties is found.

Fluorinated aromatic polyimide films were treated by pulse electrical discharges formed in water or isopropanol. The relative permittivity, measured in large domains of frequencies and temperatures by broadband dielectric spectroscopy, slightly decreased after plasma discharge in both types of liquids. The dipolar relaxation calculated by Arrhenius equation showed that the liquid plasma treatment decreases the rotational potential energy barrier for non-cooperative motions of dipoles, as a consequence of an increased free volume of plasma exposed films. Higher values of hardness, Young's modulus, and an improved elongation were also measured for the plasma treated samples, indicating molecular rearrangements that occur after plasma treatment.

We investigated, in depth, the interrelations among structure, magnetic properties, relaxation dynamics and magnetic hyperthermia performance of magnetic nanoflowers. The nanoflowers are about 39 nm in size, and consist of densely packed iron oxide cores. They display a remanent magnetization, which we explain by the exchange coupling between the cores, but we observe indications for internal spin disorder. By polarized small-angle neutron scattering, we unambiguously confirm that, on average, the nano flowers are preferentially magnetized along one direction. The extracted discrete relaxation time distribution of the colloidally dispersed particles indicates the presence of three distinct relaxation contributions. We can explain the two slower processes by Brownian and classical Neel relaxation, respectively. The additionally observed very fast relaxation contributions are attributed by us to the relaxation of disordered spins within the nanoflowers. Finally, we show that the intrinsic loss power (ILP, magnetic hyperthermia performance) of the nanoflowers measured in colloidal dispersion at high frequency is comparatively large and independent of the viscosity of the surrounding medium. This concurs with our assumption that the observed relaxation in the high frequency range is primarily a result of internal spin relaxation, and possibly connected to the disordered spins within the individual nanoflowers.

Small magnetic nanoparticles with a narrow size distribution are of great interest for several biomedical applications. When the size of the particles decreases, the magnetic moment of the particles decreases. This leads to a significant increase in the separation time by several orders of magnitude. Therefore, in the present study the separation processes of bionized nanoferrites (BNF) with different sizes and concentrations were investigated with the commercial Sepmag Q system. It was found that an increasing initial particle concentration leads to a reduction of the separation time for large nanoparticles due to the higher probability of building chains. Small nanoparticles showed exactly the opposite behavior with rising particle concentration up to 0.1 mg(Fe)/ml. For higher iron concentrations the separation time remains constant and the measured Z-average decreases in the supernatant at same time intervals. At half separation time a high yield with decreasing hydrodynamic diameter of particles can be obtained using higher initial particle concentrations.

Since the mechanism of the synthesis of magnetite from a stoichiometric mixture of hematite and iron is still under debate, systematic studies of the phase transformations in such powder mixture processed under field assisted sintering conditions, are presented. Phase contributions, grain sizes and stoichiometries of the sintered composites were determined using scanning electron microscopy, high energy X-ray diffraction and Mößbauer spectroscopy. It was shown that with an increasing sintering temperature an accelerated growth of magnetite can be observed, while the amount of hematite decreases. Additionally, intermediate wustite phase was observed with a maximum intensity where iron vanished from the samples. Therefore, it was concluded that the transition from hematite - iron mixture to magnetite actually takes place in two steps. In the first step, iron reduces hematite to magnetite and oxidizes itself to wustite. In the second step, wustite enables the nucleation of magnetite and with the help of hematite it transforms into nearly pure stoichiometric magnetite at higher sintering temperatures. In composites sintered from pure hematite under the same conditions only a minor transition to highly nonstoichiometric magnetite was observed emphasizing the above mentioned route of transformation.

In this work spinel series with the general formula Fe1-xMnxAl2O4 (where x = 0, 0.3, 0.5 and 0.7) were synthesized and characterized with respect to their structure and microstructure. X-ray diffractometry (XRD) was used to identify the phase composition that revealed a single phase spinel material. Rietveld refinements of the XRD patterns were carried out in order to determine the lattice and oxygen positional parameters of the spinel compounds. Mössbauer effect measurements were performed at room temperature to determine the local chemical environment of the Fe ions, their valences, and degrees of spinels inversion. It was shown that an increase in the Mn content led to a decrease in the ratio of Fe2+ to Fe3+. The results obtained from Mössbauer spectroscopy (MS) were used to establish the chemical formulas of the synthesized spinels. Finally, the microstructure that was observed using scanning electron microscopy (SEM) showed a compact microstructure with an octahedral crystal habit.

Human body implants can be classified in general into two groups i.e. artificial bones for medical use and dental implants as artificial teeth for dental application. The implants in orthopedics are mostly used as structurally enforced artificial bone which is inserted inside the corpus. Dental implants are usually much smaller than medical implants and they are mostly applied to reconstruct the masticatory function if the tooth root is completely lost or extracted. Such dental implant is set in the jaw-bone from the outside and it has to replace bone tissue as well as the tooth itself [1]. Therefore, the function of a dental implant is quite different at different positions inside, outside or at the boundary of the bone. Current dental implants composed of only one material, sometimes covered with a coating layer, are essentially uniform in composition and structure. Thus, the concept of a functionally graded material (FGM) may be suitable for obtaining new dental implants.