A Novel Composite Material Designed from FeSi Powder and Mn 0.8

A design of the novel microcomposite material composed of spherical FeSi particles and Mn0.8Zn0.2Fe2O4 ferrite is reported together with a characterization of basic mechanical and electrical properties. The sol-gel autocombustion method was used for a preparation of Mn0.8Zn0.2Fe2O4 ferrite, which has a spinel-type crystal structure as verified by XRD and TEM analysis. The final microcomposite samples were prepared by a combination of the traditional PM compaction technique supplemented with unconventional microwave sintering process of the prepared green compacts. The composition and distribution of the secondary phase formed by the spinel ferrite were examined by SEM. It is demonstrated that the prepared composite material has a tight arrangement without any significant porosity, which manifests itself through superior mechanical properties (high mechanical hardness, Young modulus, and transverse rupture strength) and specific electric resistivity compared to the related composite materials including resin as the organic binder

The effect of humidity on friction behavior of hydrogenated HIPIMS W-C:H coatings

The study of the effect of humidity on friction behavior in HiPIMS (High Power Impulse Magnetron Sputtering) W-C:H coating/steel ball system confirmed the formation of transfer layer adhered to the ball and consisting of hydrogenated carbon, ferritungstate and small amounts of tungsten (sub)oxides and iron oxides. The corresponding mechano(tribo)chemical reactions driven by flash temperature in the sliding asperities involved oxidation, water vapor dissociation and carbon hydrogenation. Such composition agreed with the results of modelling based on the minimization of free Gibbs energy in the mutually interacting thermochemical reactions. The applicability of modelling to friction was attributed to fast reactions among microscopic asperities eliminating kinetical factors. In inert atmospheres, oxidation and hydrogenation were suppressed and friction seemed to be controlled by the amount of additional carbon

Characterization of Tetracalcium Phosphate/Monetite Biocement Modified by Magnesium Pyrophosphate

Magnesium pyrophosphate modified tetracalcium phosphate/monetite cement mixtures (MgTTCPM) were prepared by simple mechanical homogenization of compounds in a ball mill. The MgP2O7 was chosen due to the suitable setting properties of the final cements, in contrast to cements with the addition of amorphous (Ca, Mg) CO3 or newberite, which significantly extended the setting time even in small amounts (corresponding ~to 1 wt% of Mg in final cements). The results showed the gradual dissolution of the same amount of Mg2P2O7 phase, regardless of its content in the cement mixtures, and the refinement of formed HAP nanoparticles, which were joined into weakly and mutually bound spherical agglomerates. The compressive strength of composite cements was reduced to 14 MPa and the setting time was 5–10 min depending on the composition. Cytotoxicity of cements or their extracts was not detected and increased proliferative activity of mesenchymal stem cells with upregulation of osteopontin and osteonectin genes was verified in cells cultured for 7 and 15 days in cement extracts. The above facts, including insignificant changes in the pH of simulated body fluid solution and mechanical strength close to cancellous bone, indicate that MgTTCPM cement mixtures could be suitable biomaterials for use in the treatment of bone defects

Formation of Effective Non-ferromagnetic Barrier in Fe/MgO Soft Magnetic Composite

Soft magnetic ferromagnetic/insulator composites are complex objects in terms of structure and magnetic properties. They depend on many different parameters, among which one of the main ones is the amount of insulator. In this work, the effect of MgO content on magnetization processes in Fe/MgO composites is studied in detail by using a wide combination of properties and structure analysis methods. Several series of samples with content steps up to 0.1 wt % were prepared using standard powder metallurgy operations such as dry mixing, cold pressing, and sintering. The study demonstrates that the evolution of Barkhausen noise with increasing MgO content is not systematic. The second phase acts as an effective barrier to magnetic interaction between neighboring Fe particles only after reaching a certain point, which was found to be about 0.9% wt. Some other properties (coercivity, permeability, elastic properties) also demonstrate nontrivial composition dependence. To reveal the causes of the observed phenomena, the structure of the composites was studied in detail, and it was shown that with an increase in the MgO content in the range of 0.8–1%, a change in the mechanisms of structure formation occurs, which, in turn, affects the properties. The presented results provide insights into developing advanced soft magnetic composites with an optimal combination of a ferromagnetic powder and an insulator