The structure of hydroxyapatite (HA) plasma coatings obtained during changing of the power of a plasma torch (
P
) from 20 to 26 kW has been studied using X-ray diffraction analysis. All coatings ...contained the products of hydroxyapatite decomposition in the plasma flow, phases of tetracalcium phosphate (TTCP), and CaO. The increase in their contents with an increase in
P
and the plasma temperature (
T
p
) is due to the partial loss of phosphorus by the initial HA powder in plasma and due to the shift in the chemical composition of the coating to higher calcium contents. An increase in
P
and
T
p
is accompanied by an increase in the intensity of the HA base texture. In the range of 24 <
P
< 26 kW, the ratio of the intensity values of the HA X-ray reflections δ =
I
(200)/
I
(211) exceeds 3.0, while at
P
= 20 kW δ <1.5. The presence of the orientation relationships between the predominant crystallographic orientations of HA and TTCP crystals in coatings is associated with the similarity of their structures, the proximity of lattice periods, and the presence of identical fragments in their structures. The possibility of the formation of mixed-layered structures involving these compounds has been discussed. The following factors have been considered as those that most strongly affect the pattern of the obtained dependences: the substrate temperature, the particle size in the initial HA powder, and the composition of the plasma gases.
Layer-by-layer X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study a thick (~350 μm) plasma-sprayed hydroxyapatite (HA) coating deposited onto a titanium plate ...preheated to 300 °C. It was found that the main microstructure characteristics such as microdomain size (d) and microstrain (Δ) and the phase composition weakly change with depth. The absence of amorphous phase in the coating can be caused by the crystallization of the splats upon deposition. The HA crystal structure of the coating is substantially distorted relative to that of the parent powder. Changes in the HA crystal structure over the coating thickness relative to that of the parent HA powder are considered within a model representing the HA crystal structure as packing of Ca5(PO4)3 clusters.
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•The lattices of the crystals in the thick hydoxyapatite (HA) plasma-spray coatings are highly distorted.•The main microstructure characteristics of the coating are: microdomain sizes d≈1000 Å and a microstrains Δ≈1•10-3.•The change of crystal structure parameters have been analyzed by the model using the Ca5 (PO4)3 cluster.
The pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection involves dysregulations of iron metabolism, and although the mechanism of this pathology is not yet fully ...understood, correction of iron metabolism pathways seems a promising pharmacological target. The previously observed effect of inhibiting SARS-CoV-2 infection by ferristatin II, an inducer of transferrin receptor 1 (TfR1) degradation, prompted the study of competition between Spike protein and TfR1 ligands, especially lactoferrin (Lf) and transferrin (Tf). We hypothesized molecular mimicry of Spike protein as cross-reactivity of Spike-specific antibodies with Tf and Lf. Thus, strong positive correlations (R
2
> 0.95) were found between the level of Spike-specific IgG antibodies present in serum samples of COVID-19-recovered and Sputnik V-vaccinated individuals and their Tf-binding activity assayed with peroxidase-labeled anti-Tf. In addition, we observed cross-reactivity of Lf-specific murine monoclonal antibody (mAb) towards the SARS-CoV-2 Spike protein. On the other hand, the interaction of mAbs produced to the receptor-binding domain (RBD) of the Spike protein with recombinant RBD protein was disrupted by Tf, Lf, soluble TfR1, anti-TfR1 aptamer, as well as by peptides RGD and GHAIYPRH. Furthermore, direct interaction of RBD protein with Lf, but not Tf, was observed, with affinity of binding estimated by K
D
to be 23 nM and 16 nM for apo-Lf and holo-Lf, respectively. Treatment of Vero E6 cells with apo-Lf and holo-Lf (1–4 mg/mL) significantly inhibited SARS-CoV-2 replication of both Wuhan and Delta lineages. Protective effects of Lf on different arms of SARS-CoV-2-induced pathogenesis and possible consequences of cross-reactivity of Spike-specific antibodies are discussed.
The article describes the main advantages and disadvantages existing in the present time of calculation methods for plates on elastic Foundation. Consider automation of the calculation of rectangular ...plates on elastic basis by finite difference method, on the basis of which received automatic design algorithms. Conducted research of discretization on the accuracy of the calculations. The comparison of the results of strain and effort obtained by the finite element method and the proposed method.
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Electromechanical treatment (EMT) is a technology with great potential for post-processing of plasma sprayed coatings. In recent years it has been reported that the EMT can improve ...structure, mechanical and tribological properties of the coatings. In past studies the effect of process speed and current density during the EMT on the properties of the plasma sprayed coatings were investigated. But the influence of the load during the EMT process on microstructure and properties has not been investigated. It is obvious that detailed understanding of force acting on the rollers during the EMT process is necessary to advance this post-process technology. This work studies the influence of the load during the EMT process on the microstructure and the mechanical properties of the plasma sprayed Ni coating.
•Effect of novel capillary-porous coating on heat transfer and CHF at boiling is studied.•Maximum enhancement of heat transfer on the surfaces with coating observed at low heat fluxes.•Heat transfer ...coefficient and hysteresis phenomena significantly depend on thickness and morphology of the coatings.•Dynamics of transitional processes and crisis phenomena at stepwise heat release is studied.•The boiling crisis at transient heating degenerates on the coated heaters.
The results of experimental study of heat transfer and crisis phenomena at pool boiling of liquid nitrogen with different heating conditions on the surface with capillary-porous coating are presented. Porous coatings with different thicknesses (400 and 1390μm), morphology and high porosity (up to 80%) were obtained using the new plasma spraying technique. It was shown that at steady-state heat release the heat transfer at boiling essentially depends on the thickness and morphology of the coating. The maximum enhancement (∼300%) compared to the smooth heater was detected to coated heater with a thickness of 1390μm at low heat fluxes. The mechanism of heat transfer enhancement at pool boiling by using the capillary-porous coatings was proposed. Heat transfer hysteresis was detected for the heater with the coating of 400μm. For the smooth heaters and the heater with 1390μm coating, the heat transfer coefficients almost coincide with an increase in the heat flux and with its decrease. Data on the effect of coatings with different thicknesses on the critical heat flux (CHF) at boiling under steady-state heat release are presented. It is shown that for the smooth heaters the value of critical heat flux at rapid heating decreases in comparison with steady-state heat release. Capillary-porous coatings have a significant influence on development of the transition process and crisis phenomena at stepwise heat release. There is degeneration of boiling crisis development at rapid heating on the coated surfaces at the heat fluxes below the value of the CHF at steady state heat release. Fast transition to film boiling at stepwise heat release on the coated heaters with different thicknesses is observed at the heat fluxes 2 times higher than the critical heat fluxes, obtained at steady state heating.
Plasma spraying of composite coatings is developed and investigated. Three-dimensional capillary porous titanium (3DCP Ti) coatings with a thickness of 1 mm are sprayed using a wire. Hydroxyapatite ...(HA) coatings with a thickness of 0.08–0.35 mm are sprayed on 3DCP Ti coatings at a temperature of 300–550°C. The joint between the coating and plastic is analyzed at shear. The plastic simulates bone tissue that grows into the coating surface. The heating of the 3DCP Ti coating to 550°С when the HA coating is being sprayed increases the shear strength of the coating with respect to the plastic to 9.8 MPa. Modeling approximations are proposed for the shear of the joint between the coating and the plastic.
Adhesion of Hydroxyapatite Plasma Coatings Komlev, D. I.; Kalita, V. I.; Radiuk, A. A. ...
Inorganic materials : applied research,
03/2021, Letnik:
12, Številka:
2
Journal Article
Recenzirano
Hydroxyapatite (HA) coatings were sprayed by an arc plasma gun with argon-nitrogen plasma at the power of 25 kW from the powder with particle size of 25–63 μm at the distance of 95 mm. Before ...spraying of the coatings, the samples were preheated in a resistance furnace in air to the temperatures within the range from 20 to 600°C. Adhesion of the HA plasma coating to a titanium substrate was determined on pin samples. The maximum mean value of adhesion was observed when the titanium substrate was preheated to the temperature of 550°C. The results of the study were discussed by reference to the way of increase in activity of the titanium substrate at its preheating for increase in the HA coating adhesion and formation of an equilibrium phase state in the HA coating necessary for long-term usage of the implants. The obtained results will be used for formation of the optimal structure of the bioactive coating consisting of a three-dimensional capillary-porous titanium coating (3D CP Ti) in the form of crests and hollows with porosity of 50% and HA coating sprayed on its surface at the temperature of 550°C. Such mode of the spraying provides formation of a dense, strong, and stable HA coating on endosseous implants.
•Magnetic properties of the multiferroic elastomers were investigated by the FORC method.•At least two possible magnetization reversal processes in multiferroic magnetoactive elastomers were detected ...by FORCs.•The FE microparticles modulate the spatial distribution of FM particles and polymer properties.
Composites based on ferromagnetic (FM) microparticles or a mixture of FM and ferroelectric (FE) microparticles embedded into a soft polymer matrix were studied. This class of materials belongs to magnetoactive elastomers (MAE) which received renewed interest stimulated by breakthroughs in their applications, for example, in soft robots and biomedical technologies. Moreover, the MAE with a mixture of FM and FE particles exhibit multiferroic properties which open new ways for their application. Here, the magnetic properties of this type of material were studied using the First Order Reversal Curve (FORC) method in terms of local distributions of the switching fields and interaction fields. In particular, the influence of FE particles on the magnetization reversal processes was determined. The latter is related to the influence of FE particles on the structural properties of the polymer and the possibility of displacement of FM particles in the matrix.
Remagnetization processes of amorphous glass-coated microwires have been studied using First Order Reversal Curve (FORC) analysis. This method allows us to study the magnetostatic interactions in ...these samples. The number, shape, size, and location of the peaks in the FORC diagram can provide information about the different remagnetization processes of the microwires and their system. The sign of magnetostriction of the sample strongly influences the type of FORC diagram. The remagnetization process also depends on the mechanical stresses at the ends of the Fe-based microwire. This dependence tends to zero with increasing wire length. For Co-based samples, the effect of the demagnetization factor on the FORC diagram has been described. In addition, the magnetostatic interactions for a system of densely packed microwires with positive magnetostriction are visualized in this work.
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