Development of CaO-rich blast furnace slag containing fluorine mica-based glass ceramic coatings

In the present study, Blast Furnace Slag (BFS) waste was evaluated as a sustainable, cost-effective CaO, SiO₂, Al₂O₃ and MgO substitute for inorganic oxides for the production of frit, a raw material for glass ceramic production. Two different frits were prepared to compare a commercially available frit (F-STD) with frit produced using BFS waste (F-BFS). The samples were characterized by XRF, XRD, heating microscopy, dilatometry and TG-DTA to determine the chemical composition, phase formation and thermal properties. The frits were applied on steel using the electrostatic spray method and subsequently thermally treated at 830 °C for 4.5 min. The reference (GC-STD) and partially BFS-substituted glass ceramic (GC-BFS) coatings were examined by XRD, SEM-EDS and ICP-MS experiments. The main crystal phase for both samples was Ni-substituted fluorine mica (KLiNi₂Si₄O₁₀F₂). GC-BFS was slightly more amorphous (70%) than GC-STD (69.1%), which was correlated with the thermal properties of the BFS waste. Likewise, ICP-MS analysis after a boiling citric acid test (ISO 28706-1: 2008) revealed that the GC-BFS had relatively higher chemical resistance. The total release from the reference sample (GC-STD) was 23.556 mg/L, whereas the total release from the sustainably produced sample (GC-BFS) was 21.451 mg/L, which was consistent with the XRD results.     

Porosity of heat-resistant glass ceramic coatings based on a nonfritted glass matrix

The porous macrostructure of heat-resistant coatings is described as a function of the content of Al₂,O₃, Cr₂O₃, NiO, ZrO₂, and Fe₂O₃ additives. The relationship between the porosity of the coating and its refractoriness is established. The introduction of Cr₂O₃ and NiO provides the requisite melting characteristics in the coating and the optimum porous macrostructure.Translated from Steklo i Keramika, No. 9, pp. 23 – 25, September, 1996.     

The properties of hydroxyapatite ceramic coatings produced by plasma electrolytic oxidation

Calcium phosphate coatings produced on the surface of Ti6Al4V by plasma electrolytic oxidation (PEO) using different concentrations of hydroxyapatite (HA) in a 0.12 M Na₃PO₄ (NAP) electrolyte solution was investigated. It was found that the amount of calcium phosphate particles infiltrated into the coating layer as well as the thickness and the surface roughness of the coating increased with increasing HA concentration. The porosity of the ceramic coatings indicated an inverse relationship with the concentration of HA particles dispersed in the NAP solution. The result also demonstrates that higher scratch adhesive strength was achieved using 1.5 g/L HA solution, producing a critical load of 2099 mN, while 0 g/L HA only produced a critical load of 1247 mN. The adhesion becomes independent of thickness when the concentration of HA exceeds 1.5 g/L. The failure of the coating was characterized by large periodic hemispherical chipping, while intermittent delamination was noticed with the coating embedded with HA particles. This study demonstrate the viability of using PEO to produce a thin layer of HA ceramic coating on Ti6Al4V suitable for biomedical applications.     

Glass ceramic coatings based on a fritless glass binder

The conditions and significant factors for preparing heat-resistant glass ceramic coatings for alloyed steels without using frit are considered. It was established that in order to obtain a glassy coating the radius of a particle characterizing the average dispersion of the system should not exceed 2.3 pin and the degree of polydispersion (the ratio of the maximum radius to the minimum one) should be 22. The use of water-insoluble charge ingredients and their calcination after the first crushing ensures complete sealing of shrinkage cracks.     

Micro-arc oxidation of bioceramic coatings containing eggshell-derived hydroxyapatite on titanium substrate

In the present study eggshells-derived hydroxyapatite (EHA) coatings were successfully produced on Ti6Al4V substrates using micro-arc oxidation process (MAO) at various concentrations of EHA (i.e. 1, 1.5 and 2 g/L) in an electrolyte consisting of tri-sodium orthophosphate. The attributes of the coatings were determine by X-ray diffraction, attenuated total reflectance-fourier transform infrared spectroscopy, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The adhesion strength was evaluated using micro scratch tester, while the corrosion behavior of the MAO-coated substrates in phosphate buffer solution was determined by an electrochemical method. The results showed that as the EHA concentration increased, this was accompanied by a reduction in the porosity due to the formation of a dense and thick coating layer. This has also resulted in an increased in the surface roughness and degree of crsytallinity of the HA phase. The MAO-coated substrate prepared with 1.5 g/L EHA concentration exhibited a well-formed coating layer with improved adhesive strength and excellent corrosion resistance. The mechanism of EHA-coating formation as well as the enhanced corrosion resistance of the coated substrates were discussed. This research shows the viability of using calcium-rich waste eggshells to produce phase pure HA suitable for coating on Ti6Al4V substrate using MAO method.     

Biocompatible glass ceramic coatings for titanium alloys (Review)

Coatings from hydroxylapatite and bioglass for titanium are considered. A review of patents and scientific publications shows that there are prerequisites for creating coatings on titanium alloys that would ensure the biological compatibility of titanium on the basis of known technologies.Translated from Steklo i Keramika, No. 4, pp. 22–24, April, 1995.     

Multifunctional ceramic-metal biocomposites with Zinc containing antimicrobial glass coatings

A biocompatible glassy coating with a high antimicrobial activity (>3 log of reduction) versus the gram-bacterium Escherichia coli has been obtained. The substrates are based on new zirconia ceramic matrix composites reinforced with biological tolerant metals (3Y-TZP/Ta and 3Y-TZP/Nb biocermets). Biocompatibility was studied using NIH-3T3-cells (mouse embryonic fibroblast) and >70% viability was found. These results open up the possibility of using these materials in large panoply in orthopaedics, dentistry and other hard tissue replacement applications where biofunctional, structural and antimicrobial properties are required.     

Protection of epoxy coatings containing polyaniline modified ultra-short glass fibers

Polyaniline (PANI) was covered on the surface of ultra-short glass fibers uniformly by in situ polymerization of aniline. Epoxy coatings with different contents of PANI ultra-short glass fibers and ultra-short glass fibers were formulated and their protection abilities were evaluated by means of open-circuit potential, electrochemical impedance spectroscopy and salt spray test. The results showed that the PANI ultra-short glass fibers had a significant inhibitive effect and its best volume fraction was10% in epoxy coating. XPS results indicated that a dense, stable passive oxide film of Fe₂O₃/Fe₃O₄ was formed on the steel surface beneath the coating.     

Feasibility of using low pressure cold gas spray for the spraying of thick ceramic hydroxyapatite coatings

This article deals with the production of thick ceramic hydroxyapatite coatings obtained by Low Pressure Cold Gas Spray (LPCGS) system. Several factors such as powder microstructure, surface roughness and cold gas spray system are here discussed in the build-up process. The use of nanocrystalline powder composed by fine agglomerates and needle-like shape microstructure allows the realignment and compaction of individual crystallites to form thick deposits. In addition, the activation of the substrate surface results convenient for the first impinging particles anchored properly. Then, layer by layer, particles can remain attached leading to coating build-up. Additionally, the use of low shock pressure as well as constant feeding system provided by LPCGS system lead to homogeneous coatings in comparison with High Pressure Cold Gas Spray (HPCGS) system. The successful coating build-up has been achieved not only by the use of an agglomerated feedstock powder, but also by previous surface treatment and the use of the low pressure system. The obtaining of HA components by LPCGS is promising within biomedical field. An improvement of component strength is also suggested by means of thermomechanical analysis of the powder. The performance of a post heat-treatment leads to an increase in HA strength, as well as crystal size.     

Synthesis and characterization of ceramic - polymer composites containing bioactive synthetic hydroxyapatite for biomedical applications

Presented research involved preparation of hydroxyapatite and synthesis of composites based on gelatin, albumin and polyvinylpyrrolidone (PVP) modified with the obtained compound. Hydroxyapatite was attained as a product of two-stage processing of pig bones. Applied procedure involved hydrolysis of the raw material in acidic environment and double calcination. Molar ratio Ca/P of hydroxyapatite has been determined and its chemical structure has been characterized using X-ray diffraction and FT-IR spectroscopy. Ratio Ca/P calculated on the basis of conducted research was 1.50?±?0.05. Thus prepared material met the ISO requirements, which assume that the Ca/P ratio should be in the range 1.5–2.0, which qualifies the material for further studies. Next, series of polymer matrix on the basis of gelatin, albumin and polyvinylpyrrolidone (PVP) has been synthesized and subjected to some analyzes. On the basis of the conducted studies, matrixes with the most favorable features such as desirable strength, flexibility and crosslinking degree were modified with previously prepared hydroxyapatite. Surface morphology and elemental composition of the composites have been analyzed using SEM-EDS method. Additionally, sorption capacity of modified composites and their behavior in simulated body fluids have been determined. Based on the conducted research it can be concluded that pig bones represent a good material for preparation of hydroxyapatite. Furthermore, composites based on proteins of natural origin modified with attained hydroxyapatite constitute a promising material that can be used for biomedical purposes.     

Development of ceramic fiber reinforced glass ceramic sealants for microtubular solid oxide fuel cells

Ceramic fibers in various forms with different fiber sizes are tested to improve the sealing performance of glass ceramic seals for microtubular solid oxide fuel cell applications. In this regard, several sealing pastes are prepared by mixing each ceramic fibers type with glass ceramics at 1.25 wt %. Five layered microtubular anode supported cells are also fabricated by extrusion and dip coating methods to evaluate the sealing performance of the composite sealants. The pastes are applied between the cells and gas manifolds made of Crofer22 APU. The electrochemical and sealing performances at an operating temperature of 800 °C under hydrogen are investigated after the glass forming process. Microstructures of the sealants are also examined by a scanning electron microscope. Experimental investigations reveal that the cells sealed by the pastes with ceramic bulk fiber and ceramic fiber rope gasket show acceptable open circuit potentials close to the theoretical one. These cells can be also pressurized up to around 150 kPa back pressure in the sealing performance tests. On the other hand, the pastes without any filler, with ceramic rope and with ceramic blanket exhibit poor sealing performance due to gas leakage originated from flowing of the main glass ceramic matrix from the joints. Therefore, ceramic bulk fiber and ceramic fiber rope gasket are found to behave as a stopper and can be used to prevent glass ceramics from flowing for microtubular solid oxide fuel cells or similar applications.     

Development of composite tissue scaffolds containing naturally sourced mircoporous hydroxyapatite

The aims of this work were to investigate the conversion of a marine alga into hydroxyapatite (HA), and furthermore to design a composite bone tissue engineering scaffold comprising the synthesised HA within a porous bioresorbable polymer. The marine alga, Phymatolithon calcareum, which exhibits a calcium carbonate honeycomb structure, with a natural architecture of interconnecting permeable pores (microporosity 4–11 μm), provided the initial raw material for this study. The objective was to convert the alga into hydroxyapatite while maintaining its porous morphology using a sequential pyrolysis and chemical synthesis processes. Semi-quantitative XRD analysis of the post-hydrothermal material (pyrolised at 700–750 °C), indicated that the calcium phosphate (CaP) ceramic most likely consisted of a calcium carbonate macroporous lattice, with hydroxyapatite crystals on the surface of the macropores. Cell visibility (cytotoxicity) investigations of osteogenic cells were conducted on the CaP ceramic (i.e., the material post-hydrothermal analysis) which was found to be non-cytotoxic and displayed good biocompatibility when seeded with MG63 cells. Furthermore, a hot press scaffold fabrication technique was developed to produce a composite scaffold of CaP (derived from the marine alga) in a polycaprolactone (PCL) matrix. A salt leaching technique was further explored to introduce macroporosity to the structure (50–200 μm). Analysis indicated that the scaffold contained both micro/macroporosity and mechanical strength, considered necessary for bone tissue engineering applications.     

Development of ceramic coatings on titanium alloy substrate by laser cladding with pre-placed natural derived-slurry: Influence of hydroxyapatite ratio and beam power

The attraction towards Ti and its alloys reside in their superior mechanical and tribological features, as compared to CaPs, which are renowned for their compositional and structural features similar to those of natural bones. However, Ti-based materials suffer from limited biocompatibility and inertness when implanted for extended periods. As such, surface modification with ceramic coatings is required in order to achieve proper biomedical features and enhance their overall behavior in the human body. Hence, this study outlined for the first time the prospect of coating several Ti6Al4V substrates (disks) with bovine-bone derived hydroxyapatite (HA) by laser cladding technique with pre-placed slurry. During laser processing the input materials merge depending on the heating rate/temperature and clad materials. The proposed sample preparation set-up, followed for the first time in this study, involved the concomitant modulation of two parameters: the natural HA ratio (100 wt%, and 50 wt% HA + 50 wt% Ti blends) and laser beam power (500–1000 W range). The laser beam was applied after the ceramic slurries (prepared HA/HA-based blends mixed with polyvinyl alcohol) were placed inside the priorly machined channels on the metallic Ti disks. Partially overlapped cladding tracks (～30% overlapping ratio) resulted and the investigations were further performed in cross-section view. The structural analyses confirmed the formation of calcium titanate as main phase for all samples and the arrest of HA only for those prepared with 100% HA ratio at low to medium laser powers. In addition, the morpho-compositional evaluation revealed the formation of a fully ceramic coating only for the latter sample sets. Further, the surface wettability (contact angle and surface free energy) and Vickers micro-hardness results led to the selection of the optimal technological parameters for the development of ceramic cladded layers with prospect compatibility with regenerative medicine applications.     

Transparent and durable SiO2‐containing superhydrophobic coatings on glass

We fabricated novel superhydrophobic coatings based on SiO₂ nanoparticles combined with NH₂‐terminated silicone (SN₂) or SN₂‐modified polyurethane (SN₂‐prePU) by alternately spin‐coating them onto glass slides. The final fabricated surface contained SN₂/SiO₂ or SN₂‐prePU/SiO₂ bilayers. The conditions of spin‐coating method were also explored. SN₂‐prePU with different SN₂/prePU molar ratios were synthesized to study the influence of SN₂ ratio on the water contact angles of ultimate spin‐coated surfaces. The surface was found to be tunable from hydrophobic to superhydrophobic by choosing SN₂‐prePU with different SN₂/prePU molar ratios or SN₂ content. Water droplets easily rolled off on these superhydrophobic surfaces. Surfaces coated with SN₂/SiO₂ bilayers showed better transparency, whereas surfaces coated with SN₂‐prePU(2 : 1)/SiO₂ bilayers exhibited better durability. Droplets of varied pH were prepared to test the anti‐wettability of the coatings. Results showed that the as‐coated surfaces had stable superhydrophobicity to droplets with pH values ranging from 1 to 14. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41500.     

Development of multicomponent suspensions for catalytic coatings for block ceramic supports

The compositions of multicomponent boehmite suspensions in the pH range of the dispersion medium from 1.5 to 5.4 and methods of stabilizing cerium-and platinum-containing suspensions and application on a block cordierite support were investigated. The optimum conditions of preparing the suspensions and single-stage production of highly porous, strong, and uniform coatings of the Pt-CeO₂-γ-Al₂O₃ system with a high yield and specific surface area of 150–170 m²/g were established.     

Development of a glass matrix composition for light-colored heat-resistant glass ceramic coating for nichrome alloys

The specifics of glass formation in the R₂O ? Al₂O₃ ? SiO₃ ? TiO₂ multicomponent system (R=Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺) are considered. Regions of glass ceramic compositions are identified and the specifics of structure and phase formation of glass ceramic matrices are investigated. An optimum composition is determined, which can be used as a glass matrix for light-colored heat-resistant glass ceramic coating.     

Electrophoretic deposition of ceramic coatings on ceramic composite substrates

Abstract

The applicability of electrophoretic deposition (EPD) for the fabrication of single layer and multilayer ceramic coatings on dense ceramic composite materials has been examined. Al₂O₃/Y-tetragonal zirconia polycrystal (TZP) functionally graded composites of tubular shape were successfully coated with a two layer coating comprising porous alumina and dense reaction bonded mullite layers. The dual layer coating structure was designed to eliminate the numerous cracks caused by volume shrinkage during sintering of the individual EPD formed layers. In another example, mullite fibre reinforced mullite matrix composites were coated with a thin layer of nanosized silica particles using EPD. The aim was to achieve a compressive residual stress field in the silica layer on cooling from sintering temperature, in order to increase composite fracture strength and toughness. The EPD technique proved to be a reliable method for rapid preparation of single layer and multilayer ceramic coatings with reproducible thickness and microstructure on ceramic composite substrates.