Morphological,mechanical, and biological evolution of pure hydroxyapatite and its composites with titanium carbide for biomedical applications

Pure hydroxyapatite (HAp) was synthesized successfully via a wet chemical precipitation method. To study the influence of TiC (weight % of 5, 10, 15) substitution on the mechanical behavior of pure HAp, its composites with TiC were synthesized using a solid-state reaction method. Herein, detailed investigations of pure HAp and its composites using X-ray powder diffraction (XRD), FTIR spectroscopy, Raman spectroscopy, UV-VIS spectroscopy, SEM followed by EDAX and particle size analysis were carried out. XRD study reveals the phase stability of the prepared HAp and composite samples. However, FTIR and Raman spectroscopic studies revealed the bond formation among the various constituents. Mechanical behavior of HAp, and its composites with TiC were studied using numerous parameters like density, Young's modulus, fracture toughness, and load absorption capability. Based on these studies, it was revealed that the addition of 5 wt % substitution of TiC sintered at 1200 °C significantly enhanced the mechanical properties of pure HAp. Hence, 5 wt % of TiC composite 95HAp-5TiC showed the best mechanical characteristics such as density (2.3060 g/cm³), Young's modulus (14.53 MPa), fracture toughness (19.82 MPa m^1/2), maximum compressive strength (186 MPa) respectively. Cytotoxicity and osteogenic activities of the synthesized pure HAp and its composite, 95HAp-5TiC were performed using osteoblast cells (mouse calvarial) at different concentrations of the samples (0.01 μg, - 100 μg). From the above studies, the cell viability and ALP activities of the composite, 95HAp-5TiC found to be excellent than that of pure HAp. Hence, this composite sample may be utilized for bone implant applications.     

Synthesis,structural, mechanical,and biological properties of HAp-ZrO2-hBN biocomposites for bone regeneration applications

Nowadays researchers are much interested in bioceramics for their use as biological implants. Researchers have succeeded to derive few bioceramic materials which show good biological response with living tissues. Few of the bioceramics are zirconia, hexagonal boron nitride and hydroxyapatite. Herein, the effects of zirconia nanoparticles and hexagonal boron nitride nanosheets in hydroxyapatite powder on the structural, mechanical, and biological properties were investigated. In this study, the formation of a potential composite with desired mechanical and biological properties is strongly anticipated. The present study is also proposed to provide further faces to improve osteogenic properties of the scaffolding material without altering the established mechanical and biological properties. Three different compositions in the system [(95-x)HAp-x(ZrO₂)-5hBN] (x = 10, 20, 30) were prepared using a simple solid-state reaction technique. In the samples, significant phase was identified for HAp [Calcium Phosphate Hydroxide: Ca₅(PO₄)₃(OH)]. SEM analysis of the composites revealed well-connected and uniform distribution of ZrO₂ and HAp nanoparticles on h-BN sheets. The composite samples 65H30Z5B9h (65HAp-30ZrO₂-5hBN sintered at 900 °C) and 65H30Z5B1T (65HAp-30ZrO₂-5hBN sintered at 1000 °C) showed improved mechanical and tribological behaviors. These samples exhibited excellent mechanical properties like compressive strength, Young's modulus, toughness and density. The obtained values were 2.154 MPa, 0.0182 MPa, 553.82 MJ/m³, 2.29 g/cm³ for 65H30Z5B9h and 3.798 MPa, 0.0832 MPa, 231.59 MJ/m³, 2.31 g/cm³ for 65H30Z5B1T respectively. Cytotoxicity of the composites was studied on Drosophila fly and Mice calvarial osteoblasts cells at five different concentrations. Toxic effect of the composite 65H30Z5B1T on the fly was confirmed by phenotypic observations, trypan blue staining, pupal count, and larval crawling speed. Composite 65H30Z5B1T was found to be toxic in this study, but the composite 65H30Z5B9h was not. Further, cell viability, alkaline phosphates, and mineralization tests confirmed non-toxic property and enhanced osteogenic activities for the composite sample 65H30Z5B9h.     

Enhanced physical and mechanical properties of resin added with aluminum oxyhydroxide for dental applications

Resin has limited applications however, its composites with metal oxides exhibited improved characteristics for numerous applications such as dental restoration, dentures etc. Herein, various compositions were fabricated by substituted aluminum oxyhydroxide (AlOOH) into resin via a scalable heat cure process. For phase identification and structural study, XRD and FT-IR techniques were employed. As increasing the content of AlOOH into the PZ {Poly (methyl-methacrylate)-zirconia, (PMMA-ZrO₂)} matrix, the percentage of crystallinity and the crystallite size were also estimated and varied from 14.8 to 18.4 and 1.48 nm–1.82 nm respectively. Moreover, to reveal the surface morphology, optical and mechanical behaviour of fabricated nano-composites, the SEM, UV–Vis and Universal testing machine (UTM) were also performed. The direct, indirect band gap, urbach energy of the fabricated composites were noticed within the range of 5.14 ± 0.005–5.19 ± 0.005 eV, 5.31 ± 0.005–5.35 ± 0.005 eV, and 189 ± 3.78–69.6 ± 1.39 eV respectively. The skin depth of the nanocomposites were also studied, the cut-off energy and cutoff-wavelength are 5.66 eV and 220 nm. However, the compressive strength, flexural strength, and the lowest friction coefficient value at 1 m/s sliding speed of the best composite sample (PZA15) are 85.2 MPa, 56.7 MPa and 0.311. The highest flexural modulus (846 MPa) of the PZA15 were determined using the 3-point bending test. Further, to check the biocompatibility of these resin-based composites the MTT assay was carried out. The synthesized composite (PZA15) was found to be highly biocompatible with enhanced mechanical and tribological performances.     

Influence of ZrO2 oxide on the properties and crystallization of calcium fluoro-alumino-silicate glasses

The impact of ZrO₂ content of the glass on the formation, properties and crystallization of glass ionomer cements (GICs) was investigated. Glass series based on SiO₂–Al₂O₃–ZrO₂–P₂O₅–CaO–CaF₂ system was synthesized and studied. The cements were characterized using a setting time, flexural strength, fracture toughness and in vitro biocompatibility test. The setting time of the ionomer cement increased with increasing the ZrO₂ content of the glass. The cements showed a slight decrease of cell biocompatibility with increase the ZrO₂ oxide content in the glasses. The results also showed that the flexural strength and the fracture toughness of the cements increased with immersion time and ZrO₂ oxide content. The crystallization characteristics of the glasses were investigated by differential scanning calorimeter (DSC) and X-ray diffraction analysis (XRD). The addition of ZrO₂ oxide in the glasses led to increase both the glass transition and crystallization temperatures. Fluorapatite [Ca₅(PO₄)₃F], mullite [Al₆Si₂O₁₃], cristobalite [SiO₂] and zircon [ZrSiO₄] phases were crystallized from the investigated glasses. The role played by the glass oxide constituents in determining the setting time, mechanical properties and crystallization characteristics of the prepared glass ionomer was discussed.     

Structures,mechanical properties and applications of silk fibroin materials

For centuries, Bombyx mori silkworm silk fibroin has been used as a high-end textile fiber. Beyond textiles, silk fibroin has also been used as a surgical suture material for decades, and is being further developed for various emerging biomedical applications. The facile and versatile processability of silk fibroin in native and regenerated forms makes it appealing in a range of applications that require a mechanically superior, biocompatible, biodegradable, and functionalizable material. In this review, we describe the current understandings of the constituents, structures, and mechanical properties of silk fibroin. Following that, we summarize the strategies to bring its mechanical performance closer to that of spider dragline silk. Next, we discuss how functionalization endows silk fibroin with desired functionalities and also the effects of functionalization on its mechanical properties. Finally, from the mechanical point of view, we discuss various matrices/morphologies of silk fibroin, and their respective applications in term of functionalities, mechanical properties and performance.     

Evaluation of mechanical and biocompatibility properties of hydroxyapatite/manganese dioxide nanocomposite scaffolds for bone tissue engineering application

The aim of this research was to evaluate the mechanical properties, biocompatibility, and degradation behavior of scaffolds made of pure hydroxyapatite (HA) and HA-modified by MnO₂ for bone tissue engineering applications. HA and MnO₂ were developed using sol-gel and precipitation methods, respectively. The scaffolds properties were characterized using X-ray diffraction (XRD), Fourier transform spectroscopy (FTIR), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The interaction of scaffold with cells was assessed using in vitro cell proliferation and alkaline phosphatase (ALP) assays. The obtained results indicate that the HA/MnO₂ scaffolds possess higher compressive strength, toughness, hardness, and density when compared to the pure HA scaffolds. After immersing the scaffold in the SBF solution, more deposited apatite appeared on the HA/MnO₂, which results in the rougher surface on this scaffold compared to the pure HA scaffold. Finally, the in vitro biological analysis using human osteoblast cells reveals that scaffolds are biocompatible with adequate ALP activity.     

In vitro evaluation and mechanical studies of MgO added borophosphate glasses for biomedical applications

The objective of current research is to evaluate the bioactive and tribological properties of the MgO doped borophosphate glass system. The glass system constituted of 40% B₂O₃ - (20-x) % CaO – 25% Li₂O – 15% P₂O₅ – x % MgO (mol%), x = 0, 0.5, 01, 02, 03 and synthesized using the melt quench technique. In-vitro bioactivity was determined using simulated body fluid (SBF) at 37 °C with time intervals of 7, 14 and 21 days. Hydroxyapatite (HA) layer formation was assessed using characterization techniques like XRD, FTIR and FESEM-EDS for structural, functional and morphological analysis respectively. The effect of MgO content on microhardness and tribological properties was studied by making cylindrical shaped glass samples. MTT assay was performed for various doses (62.5–1000 μg/ml) of glass dilutions using MG-63 cell line. In-vitro bioactivity showed higher Ca/P ratio with increase in MgO content after 21 days of immersion. MgO content seemed to promote degradation of glass due to formation of open structure in glass network. Borophosphate glass having 3% MgO exhibited the highest hardness value of 5.79(±0.08) GPa with minimum specific wear rate of 1.86 × 10^?11 and 1.38 × 10^?11 m³/Nm at a load of 15 N and 20 N respectively. MTT assay demonstrated the non-toxic behaviour of glass samples even at a higher dose level of 1000 μg/ml which confirmed its biocompatible behaviour. The study suggests that produced MgO doped borophosphate glass exhibits essential characteristics of bioactive materials and hence could be effective in bone filling and wound healing applications.     

Effect of boron nitride nanosheets addition on the mechanical and dielectric properties of magnesium oxide ceramics

Boron nitride nanosheets (BNNSs)/magnesium oxide (MgO) composites were prepared via hot pressing. Mechanical properties of MgO ceramics were improved obviously in virtue of adding BNNSs. The bending strength of the 1 wt% BNNSs/MgO composite increased by about 85% than that of the monolithic MgO. The fracture toughness increased by 34% with the addition of 1.5 wt% BNNSs. Microstructural analyzes have shown that the toughening mechanisms are combinations of the pull-out and bridging of BNNSs, crack deflection, and crack bypassing mechanisms. The addition of a small amount of BNNSs don't destroy the excellent dielectric properties of composites. The dielectric constant of the sample doped with 1 wt% BNNSs was about 9.5 in the whole X-band and the vast majority of P-band, and the loss tangent was less than 5 × 10⁻³ in 10–15.8 GHz.     

Taguchi design for optimization of structural and mechanical properties of hydroxyapatite-alumina-titanium nanocomposite

The Taguchi methodology was utilized to determine the influence of three factors, namely nanostructured alumina (A) and micro-structured titanium (B) weight percents and sintering temperature (C) on the phase stability, mechanical and structural properties of hydroxyapatite (HA) composites. HA nanosized powder was synthesized via wet precipitation method. According to L9 orthogonal array, different combinations of powder mixtures were cold isostatically pressed and pressure-less sintered in a reducing atmosphere. XRD analysis confirmed the presence of HA phase and metallic Ti after sintering. Analyze of Variance (ANOVA) method was used to specify the percentage contributions of three factors. Addition of 5–10?wt% titanium contributed to increasing the decomposition of HA and the amount of open porosity by 43.07% and 55.40%, respectively and caused a decrease in the strength by 44.67%. Alumina nanoparticles consistently inhibited the grain growth but showed a negligible effect on the decomposition of HA. It also caused enhancements in the strength and toughness by 14.61 and 23.70% contributions. According to ANOVA, sintering temperature illustrated considerable effects on the properties of HA composites. It exhibited more than 56% contribution to the grain growth and decomposition of HA. Structural investigations led to a total optimum condition with a combination of 7?wt % alumina/3?wt % titanium/1150?°C.     

Influence of the addition of carbonated hydroxyapatite and selenium dioxide on mechanical properties and in vitro bioactivity of borosilicate inert glass

Five nanocomposite samples containing different percentages of carbonated hydroxyapatite (CHA), selenium dioxide (SeO₂) and inert glass (IG) have been prepared using high-energy ball milling method with the aim of improving the in vitro bioactivity of these nanocomposites. Fourier transform infrared (FTIR) spectroscopy along with X-ray diffraction (XRD) technique was applied on both nanopowders and the sintered nanocomposites to record the structural changes and examine the resultant sintered phases. Mechanical properties were measured by ultrasonic non-destructive technique. In order to assess the bioactivity of the sintered specimens, they were soaked in simulated body fluid for 14 days and then, they were investigated by FTIR and scanning electron microscopy (SEM). Both FTIR and XRD spectra showed that the glasses encouraged the partial HA decomposition to tricalcium phosphate (TCP) and calcium silicate (CaSiO₃) phases. The formation of the latter phase along with the remainder HA contents was responsible for good bioactivity and appropriate mechanical properties of the investigated nanocomposites. The successive addition of selenium dioxide to these nanocomposites led to further improvement of their bioactivity without any recorded changes in the mechanical properties. Based on the abovementioned results, the prepared nanocomposites can be used in various tissue-engineering applications.     

Enhanced mechanical properties and self-healing behavior of PNIPAM nanocomposite hydrogel by using POSS as a physical crosslinker

In this study, water-soluble octa(3-chloroammoniumpropyl) silsesquioxane (OCAPS) was found to aggregate into nanoparticles with a positive charge in solution, which can attract persulfate anion radical to initiate N-isopropylacrylamide monomers. Due to the electrostatic and hydrogen bond interaction between OCAPS and poly(N-isopropylacrylamide) (PNIPAM) chain, OCAPS can act as an effective physical crosslinker to result in a nanocomposite hydrogel (OCAPS-PNIPAM) with very small loading N, N′-methylene-bisacrylamide (50–100 ppm). The incorporation of OCAPS increases the crosslinking degree of the PNIPAM hydrogel and decreases the swelling ratio in deionized water. The mechanical properties of OCAPS-PNIPAM hydrogel were enhanced greatly by the presence of OCAPS and can be adjusted by the feed ratio. The compression and elasticity moduli vary from 3.52 to 7.59 kPa and 7.67 to 33.91 kPa, respectively. The tensile strength ranges from 6.82 to 243.41 kPa with fracture energy between 503.5 and 4781.7 J·m⁻². Rheological measurements suggest that OCAPS-PNIPAM hydrogels have stable networks and the loss factor decreases as increasing OCAPS content. OCAPS-PNIPAM hydrogels also can self-heal under certain conditions with low crosslinker loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48486.     

Bioceramic composites for orthopaedic applications: A comprehensive review of mechanical,biological, and microstructural properties

Bioceramics have been widely utilized for orthopaedic applications in which the biocompatibility and mechanical properties of the materials are vital characteristics to be considered for their clinical use. Till date, extensive studies have been devoted to developing a range of scientific ways for tailoring the microstructure of bioceramics in order to attain the trade-off of mechanical properties and biocompatibility of the final product. Owing to low reactivity, earlier stabilization and longer functional life of bioceramic, the developed implants are capable of replicating the mechanical behaviour of original bone. As the safety of the patient and its ultimate functionality are the ultimate goal of the selected implant material hence, the present literature survey investigates and brings forth the important aspects associated to the mechanical, biological and microstructural characteristics of bioceramics employed in orthopaedic applications. The review paper majorly focuses on effective utilization of various materials as an additive in bioceramics and processing techniques used for enhancement of properties, enabling the use of material in orthopaedic applications. The influence of various additives on the microstructure, mechanical properties and biological performance of developed bioceramics orthopaedic implants has been elaborately discussed. Furthermore, future prospects are proposed to promote further innovations in bioceramics research.     

UV-cured clay/based nanocomposite topcoats for wood furniture. Part II: Dynamic viscoelastic behavior and effect of relative humidity on the mechanical properties

Topcoat constituting multi-layer coatings for wood furniture used in high humidity environments, like bathrooms, must have not only good barrier properties, but also good mechanical properties. Three different types of commercial organoclays, namely Cloisite 10A (C10A), Cloisite 15A (C15A) and Cloisite 30B (C30B), were chosen in this study as reinforcing agents. These nanoparticles were dispersed (1 and 3 wt% into the formulation) into a commercial epoxy acrylate oligomer by means of a three roll mill. Samples obtained from free standing UV-cured coatings were used for mechanical assessments. Mechanical tests were performed in both dynamic and static mode in order to investigate the viscoelastic behavior and tensile properties of coatings. Results from dynamic mechanical analysis have shown that all nanocomposite coatings have higher (72–75 °C) glass transition temperature compared to that observed (71 °C) in unreinforced coatings. The restriction of polymer chains mobility, due to the presence of layered silicate nanoparticles, has been used to explain the increase of glass transition temperature related to the decrease of the free volume. The storage modulus for nanocomposites containing 3 wt% of C10A, C15A and C30B was found to be slightly higher than that observed in pure coatings. The analysis of tensile stress–strain curves has revealed that tensile properties are affected by relative humidity (RH) due to the plasticization effect of humidity. In fact, results have shown that regardless of the organoclay type, the increase of RH decreases both Young's modulus and tensile strength while increasing maximum strain. We believe that low interfaces between photocrosslinked polymer chains and organoclays explain the lack of any effect of organoclays on both storage and Young's moduli. Among samples from each type of UV-cured coating tested at 0, 20 and 80% of RH, regardless of the organoclay type and content, only samples tested (tensile tests in static mode) at RH = 80% were broken. SEM images obtained from the fractured surface of these samples have shown that unreinforced UV-cured coatings and nanocomposite coatings are respectively characterized by smooth and rough fracture surface.     

Evaluation of mechanical behavior,bioactivity, and cytotoxicity of chitosan/akermanite-TiO2 3D-printed scaffolds for bone tissue applications

This report aimed to evaluate the mechanical behavior, bioactivity, and cytotoxicity of novel chitosan/akermanite-TiO₂ (CS/AK/Ti) composite scaffolds fabricated using the 3D-printing method. The morphological and structural properties of these scaffolds were characterized by Fourier transform spectroscopy (FTIR) and scanning electron microscopy (SEM). The mechanical behavior was examined by measuring the compressive strength, while the bioactivity was estimated in the simulated body fluid (SBF), and also the cytotoxicity of the scaffolds was assessed by conducting cell culturing experiments in vitro. It was found that the mechanical properties were considerably affected by the amount of TiO_2. The scaffolds had the possessed bone-like apatite forming ability, which indicated high bioactivity. Furthermore, L929 cells spread well on the surface, proliferated, and had good viability regarding the cell behaviors. The outcomes confirmed that the morphological, biological, and mechanical properties of developed 3D-composite scaffolds nearly mimicked the features of natural bone tissue. In summary, these findings showed that the 3D-printed scaffolds with an interconnected pore structure and improved mechanical properties were a potential candidate for bone tissue applications.     

Biocompatibility,physico-chemical and mechanical properties of hydroxyapatite-based silicon dioxide nanocomposites for biomedical applications

High-energy ball milling was employed to prepare carbonated hydroxyapatite/silicon dioxide (CHA/SiO₂) nanocomposites. Then, these nanocomposite powders were sintered at 900 and 1300 °C. XRD technique, FTIR spectroscopy and SEM were employed to examine the structure, molecular structure and microstructure of the sintered nanocomposites samples, respectively. Moreover, their mechanical properties were also measured. Furthermore, in vitro bioactivity and cytotoxicity of these nanocomposites were evaluated. The results indicated that the successive increases in SiO₂ contents led to remarkable enhancement for densification behavior, mechanical properties and in vitro bioactivity of nanocomposites sintered at 900 °C. However, further increase in the sintering temperature to 1300 °C caused dramatic decreases in density and mechanical properties of nanocomposites. On the contrary, better bioactivity behavior was achieved. Amazingly, the obtained results revealed that the sample having the highest content of SiO₂ and sintered at 900 °C had no toxic effects on bone-like cells while, that sintered at 1300 °C exhibited mild cytotoxicity. Based on the variations in the abovementioned properties, these nanocomposites can be used in different biomedical applications.     

Film‐forming behavior and mechanical properties of colloidal silica/polymer latex blends with high silica load

In this article, silica sol (diameter: 8–100 nm) and polymer latex (T_g < 25°C) were mixed and dried at room temperature to prepare nanocomposite films with high silica load (≥50 wt %). Effects of silica size, silica load, and the T_g of the polymer on the film‐forming behavior of the silica/polymer latex blend were investigated. The transparency, morphology, and mechanical properties of the nanocomposite films were examined by UV–Vis spectroscopy, SEM, and nanoindentation tests, respectively. Transparent and crack‐free films were produced with silica loads as high as 70 wt %. Thirty nanometers was found to be the critical silica size for the evolution of film‐forming behavior, surface morphology, and mechanical properties. Colloidal silica particles smaller than this critical size act as binders to form strong silica skeleton. This gives the final silica/polymer nanocomposite film its porous surface and high mechanical strength. However, silica particles with sizes of 30 nm or larger tend to work as nanofillers rather than binders, causing poor mechanical strength. We also determined the critical silica load appeared for the mechanical strength of silica/polymer film at high silica load. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The role of titania on the microstructure,biocorrosion and mechanical properties of Mg/HA-based nanocomposites for potential application in bone repair

Bone defects are very challenging in orthopedic practice. The ideal bone grafts should provide mechanical support and enhance the bone healing. Biodegradable magnesium (Mg)–based alloys demonstrate good biocompatibility and osteoconductive properties, which are promising biomaterials for bone substitutes. However, the high rate of their biodegradation in human body environment is still challenging. For this scope, synthesis Mg-based composites with bioceramic additives such as HA and titania (TiO₂) is a routine to solve this problem. The aim of this study was to evaluate the effect of addition TiO₂ nanopowders on the corrosion behavior and mechanical properties of Mg/HA-based nanocomposites fabricated using a milling-pressing-sintering technique for medical applications. The microstructure of Mg/HA/TiO₂ nanocomposites, in vitro degradation and biological properties including in vitro cytocompatibility were investigated. The corrosion resistance of Mg/HA-based nanocomposites was significantly improved by addition 15 wt% of TiO₂ and decrease HA amount to 5 wt% this was inferred from the lower corrosion current; 4.8 µA/cm² versus 285.3 µA/cm² for the Mg/27.5 wt%HA, the higher corrosion potential; −1255.7 versus −1487.3 mV_SCE, the larger polarization resistance; 11.86 versus 0.25 kΩ cm² and the significantly lower corrosion rate; 0.1 versus 4.28 mm/yr. Compressive failure strain significantly increased from 1.7% in Mg/27.5HA to 8.1% in Mg/5HA/15TiO₂ (wt%). The Mg/5HA/15TiO₂ (wt%) nanocomposite possessed high corrosion resistance, cytocompatibility and mechanical properties and can be considered as a promising material for implant applications.     

A new nanocomposite based on polylactic acid/butadiene rubber/clay: Morphology development and mechanical properties

In this work, several samples based on poly(lactic) acid (PLA)/butadiene rubber (BR) blend with and without nanoclay (Cloisite 30B) were prepared using an internal mixer. Various methods were used to characterize the samples, including scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), rheometric mechanical spectrometer, stress–strain, and impact strength tests. The SEM results showed the droplet-matrix morphology for all prepared samples. With the incorporation of nanoclay, the mean diameter of the BR droplets generated within the PLA matrix decreased. AFM test revealed the placement of nanoparticles in the PLA phase, which was consistent with the thermodynamic prediction of their location. The XRD test showed that the interlayer space of nanoclay expanded by 86% due to the diffusion of polymer chains between them. In the rheology test, this resulted in an increment in modulus and viscosity at low frequencies for the nanocomposites compared to the simple blend. The highest elongation at break was observed for the PLA/BR blend containing 10 wt% BR with approximately 40 times its value for the neat PLA, while the impact resistance increased up to three times.     

Lanthanum-titanium-aluminum oxide: A novel thermal barrier coating material for applications at 1300 °C

Considerable efforts are being invested to explore new thermal barrier coating (TBC) materials with higher temperature capability to meet the demand of advanced turbine engines. In this work, LaTi₂Al₉O₁₉ (LTA) is proposed and investigated as a novel TBC material for application at 1300 °C. LTA showed excellent phase stability up to 1600 °C. The thermal conductivities for LTA coating are in a range of 1.0-1.3 W m⁻¹ K⁻¹ (300-1500 °C) and the values of thermal expansion coefficients increase from 8.0 to 11.2 × 10⁻⁶ K⁻¹ (200-1400 °C), which are comparable to those of yttria stabilized zirconia (YSZ). The microhardness of LTA and YSZ coatings were in the similar level of ∼7 GPa, however, the fracture toughness value was relatively lower than that of YSZ. The lower fracture toughness was compensated by the double-ceramic LTA/YSZ layer design, and the LTA/YSZ TBC exhibited desirable thermal cycling life of nearly 700 h at 1300 °C.     

Microstructure,mechanical behavior and flow resistance of freeze-cast porous 3YSZ substrates for membrane applications

Freeze-cast porous 3YSZ with different porosities were characterized as mechanical load carrying supports for oxygen transport membrane applications. Porosity influence on mechanical properties, i.e. elastic modulus and fracture stresses was assessed with biaxial ring-on-ring bending tests. The flow resistance was characterized in terms of the pressure drop using different gases to reveal the effect of the porous support on the accessing of the inlet gas flow to the functional dense membrane layer. Both properties were discussed in terms of the influence of porosity and pore structure, and compared with the properties of porous 3YSZ produced via pressing and sintering.