Sol Content Research Articles

POLYSILICATE BINDER FOR SILICATE PAINTS

Information is given on the structure and properties of a polysilicate binder obtained by mixing a silicic acid sol with a liquid glass. It was found that the introduction of a silicic acid sol in a liquid glass promotes an increase in the fraction of high-polymer fractions of silicic anions. An increase in the sol content promotes an increase in the fraction of high-polymer fractions of silicic anions. The results of the kinetics of the change in the silica content in the monomeric form in the potassium and sodium polysilicate solution are given. It was found that the dependence of the silica content in the monomeric form in the early stages of the interaction of the silicic acid sol with liquid glass is extremely extreme. It has been shown that when the potassium liquid glass is mixed with silica sol, the formation of silica in the monomeric form proceeds more slowly at the initial stage than in the sodium liquid glass. The results of studying the structure of polysilicate solutions by the method of violation of total internal reflection are presented. IR-spectroscopy revealed a shift in the band corresponding to Si-O-Si vibrations to the region of higher frequencies compared to liquid glass, which indicates a higher degree of polymerization of silica. The presence of silica in the polysilicate binder polymeric species is established, which ensures an increase in the stability of silicate coatings. Information on the properties of silicate composition with the use of polysilicate film-forming and coatings based on it is given. The composition is intended for interior and exterior walls of buildings.

Effect of the addition of silica sol on layered extrusion forming of Al2O3-based cores

ABSTRACTLayered extrusion forming of ceramic cores with a nanoceramic suspension as a binder was conducted to explore a novel method to produce complex-shaped ceramic cores. Green bodies were prepared using Al2O3 particles as precursor materials and silica sol combined with aqueous polyvinyl alcohol solution as a binder. Increasing the silica sol content increased the viscosity of the slurry, enhanced the green bending strength, and decreased the green linear shrinkage. The green microstructure showed the nanosized silica particles were deposited on the surface of the Al2O3 particles and among the pores formed by Al2O3 particles irregular packing. In addition, increasing the silica sol content increased the bending strength, however, decreased linear shrinkage and open porosity of the sintered bodies. During sintering, the nanosized silica particles converted to the melting phase and reacted with Al2O3 and the microstructure of sintered bodies indicated the existence of sintering neck with silica sol addition.

Preparation of homogeneous mullite fibrous porous ceramics consolidated by propylene oxide

Silica sol, one of the most commonly used binders in the fabrication of fibrous porous ceramics, can diffuse as the solvent evaporates during the drying stage, leading to an uneven structure of ceramics. To prevent the diffusion of silica particles and prepare homogeneous mullite fibrous porous ceramics, propylene oxide (PO) was introduced into the fabricating procedures. The effects of solid content of silica sol and the molar ratio of PO /silica phase (PO/SiO2) on the microstructure and physical properties of mullite fibrous porous ceramics were also investigated. The results demonstrated that PO addition strongly consolidated the mullite fibrous skeleton and helped to obtain a homogenous property, because silica phase had been consolidated in situ around the fibers during the gelation stage. Furthermore, the mullite fibrous ceramics prepared with PO addition showed an even microstructure and a much better compressive strength (1.489 MPa), compared with the ones prepared without PO addition (0.868 MPa). Finally, the solid content of silica sol showed a very strong relevance to the properties of the ceramics: the compressive strength raised from 0.731 MPa to 1.715 MPa with the solid content of silica sols increasing from 9 wt% to 18 wt%; while the molar ratio of PO/SiO2 had little: the compressive strength was around 1.480 MPa, with the corresponding molar ratios of PO/SiO2 ranging from 0.43 to 1.72.

Fabrication and properties of lightweight SiOC fiber-based assembly aerogels with hierarchical pore structure

Here we report a novel aerogel material assembled by the electrospun SiOC fibers with a hierarchical pore structure. The fibrous aerogels were successfully fabricated by the gel-casting and freeze-drying method using the SiOC fibers as the matrix and the silica sols as the binders. The effect of the SiOC fiber content and the silica sol content on the properties of the samples were investigated. The SiOC fibrous aerogels after calcined at 1000 °C exhibited low densities of 46.87–128.48 mg/cm3, low thermal conductivities of 0.0302–0.0440 W/m K, high compressive strengths of 18–167 kPa and relatively high specific surface areas of 12.48–34.87 m2/g. Such unique fibrous aerogel materials are foreseen as the promising high-temperature insulators, absorbents and supports.

Synthesis, characterization & cytocompatibility of poly (diol-co-tricarballylate) based thermally crosslinked elastomers for drug delivery & tissue engineering applications

The aim of this study was to investigate the synthesis and in vitro characterization of thermoset biodegradable poly (diol-co-tricarballylate) (PDT) elastomeric polymers for the purpose of their use in implantable drug delivery and tissue engineering applications. The synthesis was based on thermal crosslinking technique via a polycondensation reaction of tricarballylic acid with aliphatic diols of varying chain lengths (C6-C12). PDT prepolymers were synthesized at 140 °C for 20 min. After purification, the prepolymers were molded and kept at 120 °C for 18 h under vacuum to complete the crosslinking process. PDT prepolymers were characterized by DSC, FT-IR, 1H NMR and GPC. The PDT elastomers were also subjected to thermal and structural analysis, as well as sol content, mechanical testing, in vitro degradation and cytocompatibility studies. The mechanical properties and sol content were found to be dependent on synthesis conditions and can be controlled by manipulating the crosslinking density and number of methylene groups in the chain of precursor aliphatic diol. The family of thermally crosslinked PDT biodegradable polyesters were successfully prepared and characterized; besides they have promising use in drug delivery and other biomedical tissue engineering applications.

Devulcanization of waste rubber powder using thiobisphenols as novel reclaiming agent

In this study, thiobisphenols, 4,4′-dithiobis(2,6-di-t-butylphenol), was synthesized and used as novel reclaiming agent for the chemo-thermomechanical devulcanization process of waste rubber powder (WRP). The devulcanization process was carried out in an internal mixer at 180 °C and 200 °C using different content of reclaiming agent such as thiobisphenols. The degree of devulcanization was estimated by measuring sol content, crosslink density, and Mooney viscosity of the reclaimed rubber (RR). Devulcanization conditions have been studied further with respect to the processability, and the mechanical properties of the revulcanized reclaimed rubber (REVR). Photomicrographs from scanning electron microscopy (SEM) indicate the improvement of the coherency in the REVR with increasing degree of devulcanization. Dynamic properties were also studied for REVR. Again, in order to establish the effect of thiobisphenols as reclaiming agent, the devulcanization of WRP and revulcanization of RR were also evaluated in this study.

The role of the polymer matrix in solvent-free hot melt extrusion continuous process for mechanochemical synthesis of pharmaceutical cocrystal

Solid-state synthesis of pharmaceutical cocrystals is of contemporary interest as it offers an efficient way to modify the physicochemical properties of Active Pharmaceutical Ingredient (API) including its melting point, solubility, compressibility or physical stability, without compromising its structural integrity and bioactivity. Therefore, research of novel and emerging techniques for solvent-free, continuous and scalable methods for cocrystal formation is of paramount importance for further industrial development. In this work we form a basis for knowledge-based synthesis and formulation of model pharmaceutical cocrystal (flufenamic acid, FFA: nicotinamide, NA; 1:1) via matrix-assisted cocrystallisation (MAC) using Hot Melt Extrusion (HME). Five different polymers frequently used in pharmaceutical drug delivery: Poloxamer P407 (PXM), PEG-PVA copolymer, Soluplus® (SOL), PVPVA64 and HPMCAS with different structural features and physicochemical properties were investigated as functional matrices for FFA:NA cocrystal synthesis via HME. Significant decrease of the torque value during MAC process was observed for all investigated polymers as compared to extrusion of neat FFA:NA cocrystal. The FFA:NA cocrystal encapsulated in the polymer matrix was successfully formed using semicrystalline PXM and PEG-PVA polymers at all investigated FFA:NA/polymer ratios. The use of amorphous polymers (SOL, PVPVA64, HPMCAS) as a cocrystallisation matrix resulted in formation of FFA:NA cocrystal embedded in an amorphous FFA:NA/polymer matrix (at polymer contents of 10 and 20 wt.%) or FFA:NA/polymer amorphous composites at SOL and PVPVA64 content of 30 wt.%. Furthermore, the significant increase of FFA dissolution was observed for FFA:NA cocrystal encapsulated in PXM and PEG-PVA matrices as compared to neat FFA form I. FFA form III and FFA:NA cocrystal. The presented work enables for the first time knowledge-based approach for simultaneous synthesis and formulation of pharmaceutical cocrystals via Hot Melt Extrusion a solvent-free, scalable and continuous process.

Reclaiming of waste guayule natural rubber vulcanizate—reclaim rubber for green tire applications: An approach for sustainable development

This article illustrates the reclaiming of guayule natural rubber (GNR) vulcanizate by bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT), and as-grown reclaim rubber facilitates the silica dispersion in GNR product application without adding any coupling agent. This article deals with the performance evaluation of silica-filled revulcanizates with promising application in green tire. The extent of reclaiming was monitored through the measurement of sol content, cross-link density, Mooney viscosity, and degree of reclaiming. The differential scanning calorimetry study was carried out to evaluate the fraction of immobilized polymer chains and its dependence on cross-link density of the vulcanizates. The Fourier transform infrared study and also sulfur analysis independently indicate the attachment of the fragmented TESPT with the polymer chain and cross-link bonds. The study of mechanical properties clearly shows that in revulcanized GNR, the optimum property is achieved when reclaiming time is set for 40 min. The effect of reclaiming time on dynamic mechanical behavior such as storage modulus and loss tangent was studied. The scanning electron microscopy studies show the coherency and homogeneity of silica-filled revulcanize rubber with reclaiming time.

Properties of silica sol bonded corundum‐spinel castables for steel ladles

AbstractIn order to overcome the shortcoming of the calcium aluminate cement (CAC) bonded castables, we prepared corundum‐spinel castables using silica sol as binder and tabular corundum, sintered magnesia‐alumina spinel, and reactive alumina as raw materials in this study. The effect of spinel grain size and solid content of silica sol on the flow value, sintering, mechanical strength and microstructure of the specimens treated at varying temperature of 400, 1000, 1500, and 1650°C for 5 hours in an air atmosphere were studied by SEM and EDS analyses. The results indicate that silica sol is suitable as a binder for corundum‐spinel systems. And silica sol with solid content of 25% bonded samples containing ≤90 μm spinel perform quite better than the others. At the same time, silica sol bonded samples had high strength in medium temperature. This is because that the closer proximity of silica sol and alumina powder and the high activity of nanometer SiO2 in silica sol are beneficial for the reaction of SiO2 and Al2O3 to generate mullite needed for reinforcement of castables matrix.

Preparation of homogeneous mullite‐based fibrous ceramics by starch consolidation

AbstractSilica sol is one of the frequently used binders in high‐temperature resisting fibrous porous ceramics, but in the drying process, it can diffuse with water and influence the uniformity of ceramics. To solve this diffusion problem and fabricate homogeneous fibrous porous ceramics, cationic starch was firstly introduced in mullite fibrous system. The effects of starch content and high‐temperature binder content on microstructure, physical, and mechanical properties were also investigated. The results indicate that starch consolidated mullite fibrous ceramics owned a homogeneous 3D skeleton structure, since the introduced starch can absorb both water and silica particles by gelatinization and ensure the even distribution of binders. Compared with the mullite fibrous ceramics fabricated without starch addition, starch consolidated ceramics owned better microstructure and higher interior compression strength. Furthermore, both the starch and silica sol content had great impact on the microstructure, density, porosity, thermal conductivity, and compressive strength of the fibrous ceramic.

Effect of SiO2 concentration in silica sol on interface reaction during titanium alloy investment casting

Using silica sol as a binder for titanium investment casting is very attractive due to its good stability and reasonable cost as compared with yttrium sol and zirconium sol. However, the mechanism of interface reaction in the related system remains unclear. In this investigation, the interface reaction between Y2O3-SiO2 (Y-Si) shell mold and titanium alloys was studied. A group of shell molds were prepared by using Y2O3 sand and silica sol with different contents of SiO2. Ti-6Al-4V alloy was cast under vacuum by gravity casting through cold crucible induction melting (CCIM) method. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) were employed to characterize the micromorphology and composition of the reaction area, respectively. X-ray photoelectron spectroscopy (XPS) was used to confirm the valence state of relevant elements. White light interferometer (WLI) was used to obtain the surface topography of Y-Si shells. The results show that the thickness of reaction layers is below 3 μm when the SiO2 content of silica sol is below 20wt.%. Whereas, when the SiO2 content increases to 25wt.%, the thickness of the reaction layer increases sharply to about 15 μm. There is a good balance between chemical inertness and mechanical performance when the SiO2 content is between 15 and 20wt.%. Moreover, it was found that the distribution of SiO2 and the roughness at the surface of the shell are the key factors that determine the level of reaction.

Photopolymerized maleilated chitosan/methacrylated silk fibroin micro/nanocomposite hydrogels as potential scaffolds for cartilage tissue engineering

Hydrogels composed of natural materials exhibit great application potential in artificial scaffolds for cartilage repair as they can resemble the extracellular matrices of cartilage tissues comprised of various glycosaminoglycan and collagen. Herein, the natural polymers with vinyl groups, i.e. maleilated chitosan (MCS) and methacrylated silk fibroin (MSF) micro/nanoparticles, were firstly synthesized. The chemical structures of MCS and MSF micro/nanoparticles were investigated using Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Then MCS/MSF micro/nanocomposite hydrogels were prepared by the photocrosslinking of MCS and MSF micro/nanoparticles in aqueous solutions in the presence of the photoinitiator Darocur 2959 under UV light irradiation. A series of properties of the MCS/MSF micro/nanocomposite hydrogels including rheological property, equilibrium swelling, sol content, compressive modulus, and morphology were examined. The results showed that these behaviors could be tunable via the control of MSF content. When the MSF content was 0.1%, the hydrogel had the compressive modulus of 0.32±0.07MPa, which was in the range of that of articular cartilage. The in vitro cytotoxic evaluation and cell culture of the micro/nanocomposite hydrogels in combination with mouse articular chondrocytes were also investigated. The results demonstrated that the micro/nanocomposite hydrogels with TGF-β1 was biocompatible to mouse articular chondrocytes and could support cells attachment well, indicating their potential as tissue engineering scaffolds for cartilage repair.

Antibacterial thermoplastic polyurethane electrospun fiber mats prepared by 3-aminopropyltriethoxysilane-assisted adsorption of Ag nanoparticles

Antibacterial thermoplastic polyurethane (TPU) electrospun fiber mats were prepared by adsorption of Ag nanoparticles (Ag NPs) onto TPU/3-aminopropyltriethoxysilane (APS) co-electrospun fiber mats from silver sol. The use of APS can functionalize TPU fibers with amino groups, facilitating the adsorption of Ag NPs. The effects of pH of silver sol and APS content on Ag NP adsorption and antibacterial activity were investigated. Ag NP adsorption was evidenced by TEM, XPS and TGA. Significant Ag NP adsorption occurred at pH = 3−5. The main driving force for Ag NP adsorption is electrostatic interaction between ―NH3 + of the fibers and ―COO− derived from the ―COOH group capped on the surfaces of Ag NPs. The antibacterial activity of the Ag NP-decorated TPU/APS fiber mats was investigated using both gram-negative Escherichia coli and gram-positive Bacillus subtilis. The antibacterial rate increases with increasing APS content up to 5% where the antibacterial rates against both types of bacteria are over 99.9%.

A novel PES-TiO2 hollow fiber hybrid membrane prepared via sol-gel process assisted reverse thermally induced phase separation (RTIPS) method

A new attempt to prepare polyethersulfone (PES)-Titania (TiO2) organic-inorganic hollow fiber hybrid membranes were investigated by sol-gel process assisted reverse thermally induced phase separation (RTIPS) method. The membrane formation mechanism underwent NIPS (coagulation temperature lower than cloud point) or RTIPS (coagulation temperature higher than cloud point) process. Properties of hollow fiber hybrid membranes, which varied with TiO2 sol addition and coagulation temperature, were investigated by SEM, EDX, AFM, TGA, XPS and contact angle. SEM results showed that the dense skin layer was produced in the hybrid membranes via NIPS process, while porous skin layer and sponge-like structures emerged in the hybrid membranes via RTIPS process. As a result, pure water flux, BSA rejection, mechanical properties of hybrid membranes by RTIPS were higher than that via NIPS. EDX mapping spectra proved that the dispersion uniformity of TiO2 particles through sol-gel process on the top surface of 1wt% TiO2 embedded PES membrane, which prepared in 60°C coagulation bath. XPS data revealed the element distribution in the hybrid membranes. AFM and TGA revealed increased surface roughness and thermal stability of the hybrid membranes by the addition of TiO2 sol, respectively. The organic-inorganic hybrid membranes prepared with 1wt% TiO2 sol content by RTIPS method exhibited decent performance, which reached maximum pure water flux of 1046L/(m2h) and BSA rejection of 75%.

Mexico: JSR/Elastomix – carbon black masterbatch

A stepwise separation of reclaimed silanized silica (r-SS) from waste green tire rubbers was achieved using a thermo-oxidative reclamation process, and the interfacial interaction between silanized silica and rubber was quantified. The exfoliation of the residual and bound rubber from the r-SS surfaces under different temperatures ranging from 150 to 230 ℃ was investigated, with or without the addition of vegetable oil. The particle size of r-SS decreased from hundreds of micron-meters to nanometers with the increase of reclamation degree, i.e., the degree of devulcanization of vulcanized rubber, as quantified by the sol content, and the thickness of the bound rubber layer decreased to 4–6 nm at 230 ℃. This work provides a feasible solution for recycling of waste green tires, and also promote the understanding of the interfacial interactions between silanized silica and rubber by thermo-oxidative reclamation.

Biodegradable star-shaped polycyclic ester elastomers: Preparation, degradability, protein release, and biocompatibility in vitro

Effective local delivery methods for sustained and stable release of protein drugs are urgently needed. Biodegradable elastomers based on star-shaped polycyclic esters have received attention for their drug-loading and drug-release kinetics. However, the long degradation periods resulting from their strong lipophilicity greatly hinder their application. In this study, we synthesized new cross-linked elastomers based on methyl-acrylic-star-poly(ϵ-caprolactone- co-d,l-lactide) cyclic ester and methyl-bi-acrylic-poly(ϵ-caprolactone-b-poly(ethylene glycol)-b-ϵ-caprolactone) with different molecular weights; determined their physical, thermal, and morphological characteristics; and studied their in vitro degradation and release of bovine serum albumin and recombinant human interleukin 2. Elastomer hydrophilicity improved with the introduction of methyl-bi-acrylic-poly(ϵ-caprolactone-b-poly(ethylene glycol)-b-ϵ-caprolactone), and a shorter degradation period (~25 weeks) was achieved. Additionally, the degradation rate could be adjusted by varying the composition of methyl-bi-acrylic-poly(ϵ-caprolactone-b-poly(ethylene glycol)-b-ϵ-caprolactone) to directly influence the degree of swelling, cross-linking density, and sol content of the elastomer. The controlled rate of bovine serum albumin and recombinant human interleukin 2 release increased with a larger degree of swelling, higher sol content, and lower cross-link density of the elastomers. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis showed good biocompatibility. These results suggest that these new elastomers are potential candidates for carrier materials in controlled, implantable delivery systems for protein drugs and other biomedical applications.

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

ABSTRACTThe theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

Facile fabrication of superhydrophobic coatings based on two silica sols

Superhydrophobic coatings were successfully fabricated by using two silica sols and fluorinated acrylate copolymers through the organic-inorganic hybrid method. The two silica sols contained different nanoparticles, namely, silica nanoparticles with many hydroxyl groups on their surfaces and silica nanoparticles with many long-chain alkyls on their surfaces. The integration of these two silica sols and fluorinated acrylate copolymers satisfied two necessary conditions of multi-scale nano/microstructures and low surface energy for fabricating superhydrophobic coatings. The superhydrophobic surfaces were constructed by using appropriate weight ratios of silica/copolymers and silica sol (methanol) contents. The superhydrophobic coatings displayed a water contact angle as high as 156.2° and contact angle hysteresis of 2.4°, which indicated their good self-cleaning capability. In particular, these coatings showed good mechanical properties and excellent thermal stabilities. The method is not only a facile and inexpensive way to achieve the lotus effect but could also create coatings with high values in practical application.

Mechanochemical devulcanization of natural rubber vulcanizate by dual function disulfide chemicals

Devulcanized natural rubber (DeVulcNR) was produced from NR vulcanizate in an open roll mixing mill by using bis(3-triethoxysilyl propyl) tetrasulfide (TESPT), a novel devulcanizing agent. The versatility of the proposed devulcanizing agent TESPT is that it acts as a devulcanizing agent during devulcanization and as a coupling agent during dispersion of silica filler in devulcanize rubber compound. The extent of devulcanization was monitored through the measurements of sol content, gel content, crosslink density, molecular weight between crosslinks, Mooney viscosity of devulcanized rubber and degree of devulcanization as a function of devulcanization time and the concentration of TESPT. The study of extent of devulcanization by monitoring the above mentioned parameters clearly indicate that the optimum concentration of TESPT is 6 mL. Therefore, for further study DeVulcNR is prepared using 6 mL TESPT and designated as DeVulcNR-6 to optimize the devulcanization time. Determination of the fraction of immobilized polymer chains of DeVulcNR-6 by differential scanning calorimetry (DSC) study indicates that with sol content the fraction of immobilized polymer chains decreases due to increasing molecular weight between crosslinks. To get an idea about the application of DeVulcNR in product formulation revulcanization characteristics in the presence of silica filler were studied. The optimum cure time decreases whereas cure rate increases with devulcanization time. The mechanical properties e.g., modulus at 50% and 100% elongation, tensile strength and elongation at break increases with devulcanization time upto 40 min. To see the reinforcement of silica filler, the mechanical properties of ReVulcNR-6 with silica is compared to that of the ReVulcNR-6 without silica. The mechanical property and thermal behavior data clearly indicates that the optimum time for devulcanization is 40 min. Scanning electron microscopy (SEM) studies further show the coherency and homogeneity of DeVulcNR-6 in the revulcanizate when devulcanization is carried out by optimum TESPT concentration 6 mL and devulcanization time 40 min.

Effect of silica sol content on the structure and properties of MoSi2-BaO-Al2O3-SiO2 coating

ABSTRACTThe MoSi2-BaO-Al2O3-SiO2 (BAS) coating with BAS glass as binder, MoSi2 as high emissive agent and silica sol as annexing agent have been prepared on porous fibrous insulation. The addition of silica sol affects the structure and properties of the coating by promoting the fusion of it during sintering. The MoSi2-BAS coatings gradually change from a porous structure (with 0 wt%–5 wt% silica sol) into a dense structure (with 5 wt%–10 wt% silica sol) with obviously decreasing porosity when the silica sol content increases. In addition, the porous coatings show better thermal insulation property (0.18 ± 0.01 W·mK−1 thermal conductivity) and interface bonding strength (0.58 ± 0.01 MPa) than the dense coatings (0.27 ± 0.01 W·mK−1 thermal conductivity, 0.42 ± 0.02 MPa). However, the flexural strength of substrates with dense coatings (6.12 ± 0.12 MPa) is higher than that of substrates with porous coatings (4.97 ±0.17 MPa).