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The fabrication of complex shaped Si3N4 parts by conventional methods is challenging due to its high hardness and mechanical strength. Additive manufacturing (AM) appeared as a competitive way to attain three-dimensional complexity at lower costs. However, most of AM technologies still present limitations in producing high dense ceramics, mainly due to several difficulties in developing proper feedstock. This work presents the fabrication of dense silicon nitride-based ceramics by using an extrusion based additive manufacturing technique (direct ink writing, also known as robocasting) and cold isostatic pressing (CIP) as a post processing step. Silicon-nitride aqueous based inks containing different amounts of solids loading (36, 38 and 39 vol%) and proper rheological characteristics for the printing process were studied. The use of CIP (200 MPa) is suggested to reduce or even eliminate defects and porosity and consequently, to improve mechanical performance of the final parts. Relative density, microhardness and flexural strength increased as solids loading in the inks increased and were further improved when CIP pressing was used. Parts produced by robocasting with an ink containing 39 vol% and cold isostatic pressed at 200 MPa exhibited an average relative density around 99%, 1475 HV2 microhardness value and 650 MPa flexural strength, values similar to those of silicon nitride ceramics fabricated by conventional processing. published

Translucent zirconias have been developed with better esthetics than high-strength zirconias by reducing opacity. However, studies on their translucency and strength are sparse.The purpose of this in vitro study was to compare the relationship between translucency and biaxial flexural strength of recently developed high-translucency zirconia, high-strength zirconia, and lithium disilicate ceramics.Disks (n=12) were fabricated for 5 ceramic materials: high-strength zirconia (BruxZir 16 shaded), translucent zirconia (BruxZir Anterior shaded, Katana UTML, Katana STML), and lithium disilicate (IPS e.max, Press HT, and LT). A standard tessellation language (STL) file was designed, and the specimen milled, finished, and glazed according to manufacturer's instructions for each material. The translucency parameter was calculated against black and white backgrounds and white and stump shade with ND4 background by using a spectrophotometer. Biaxial flexural strength was calculated by using the 3-ball test. The load was applied at a crosshead speed of 0.5 mm/min with a 49-N load cell until failure occurred. Translucency parameter and biaxial flexural strength data were analyzed with 1-way analysis of variance (ANOVA). A Tukey honest significant difference multiple comparison test was used to determine significant differences (α=.05).The IPS e.max HT was more translucent against both backgrounds (32.85 for black/white and 15.34 for white/stump), while BruxZir 16 was the least translucent (19.78 for B/W and 8.83 for W/S). All groups tested differed in translucency (P.001) except for BruxZir Anterior and Katana STML, which were not significantly different (P=.052). For biaxial flexural strength, BruxZir 16 had the highest strength (995.44 MPa) and e.max HT, the lowest (186.75 MPa). No significant differences were found between BruxZir anterior and Katana STML, Katana UTML and IPS e.max LT, or IPS e.max LT and IPS e.max HT (P.05). Translucency parameter values using both backgrounds were strongly correlated (r=0.99). However, biaxial flexural strength values were inversely related to translucency parameter values when using black/white and white/stump shade but with high correlation (r=-0.777 and -0.756 respectively).Lithium disilicate was the most translucent and yet the weakest material, whereas high-strength zirconia was the most opaque ceramic and the strongest. Katana UTML had the highest translucency but was weakest among translucent and high-strength zirconia materials. Overall, translucency was negatively correlated with biaxial flexural strength.

This paper describes a statistical and mathematical approach to optimize the mechanical properties of a wood plastic composite with Polyethylene Terephthalate (PET) as polymeric matrix. Wood plastic composite are materials that consist of a primary continuous polymer phase, where a secondary filler dispersed phase is embedded, the filler generally is wood fibers or sawdust. The slack variable approach in mixture experiments, consist in selecting a component of the mixture as slack variable, to subsequently design and analyze the experiment in terms of the remaining components. With the experimental design information three slack variable model were fit. Using response surface graphs, we show how different compositions modify the mechanical properties of wood plastic composite. Besides, by the desirability function, the optimal formulation of the compound that simultaneously maximizing the mechanical properties of wood plastic composite, was obtained. Finally, the components proportions that provides the best tensile, flexural and compression strength are presented.

The mechanical properties of two commercial epoxides have been investigated in both unfilled and filled with varying the weight fraction of Nano Aluminum powder and Nano Aluminum with Nano Titanium powder. The values of Young’s modulus, modulus of rigidity, yield stress, tensile strength, flexural strength have been studied at room temperature to identify the specific influence of Aluminum powder (the particle size for Aluminum powder is less than or equal to 50 nm (d ≤ 50). The weight fraction has different values (equals to 10%, 20% and 30%), and Nano Aluminum with Nano Titanium powder for Aluminum powder, the particle size (d) is less than or equal to 50 nm (d ≤ 50). The weight fraction has different values (equals to 10%, 20% and 30%). Also for Titanium powder, the particle size is less than or equal to 50 nm (d ≤ 50), and the weight fraction is 1% for each different weight fractions of Aluminum powder to epoxy resin. The experimental results obtained from laboratory have been analyzed in order to achieve the best result. It is concluded that Young’s modulus and modulus of rigidity increase when the weight fraction for Nano Aluminum powder and Nano Aluminum with Nano Titanium powder increase.

Nowadays, renewable source materials play a significant part in creating lightweight structural materials. In this work, Azadirachta indica (Neem Gum) was taken as natural filler material in epoxy matrix with different volume fraction. The hand lay-up method was used. The mechanical properties such as tensile, flexural and impact tests were found for five different specimens. The effect of natural filler on the mechanical properties was observed and found that 40% addition of neem powder produces better mechanical strength in tensile, flexural and impact strength.

A typical conversion process of a complete-arch immediate loading protocol entails preparing holes in a complete denture for connection to interim copings, which reduces the strength of the prosthesis. The excellent mechanical properties of milled polymethyl methacrylate (PMMA) disks may provide interim prostheses with improved strength.The purpose of this in vitro study was to measure the flexural strength and failure load of simulated acrylic resin immediate implant-supported interim prostheses fabricated by conventional processing and computer-aided manufacturing.A master patient model was created with an acrylic resin base and 2 BioHorizons Internal 4.5-mm-diameter implants placed with a 21.5-mm span and multiunit abutments (MUA) tightened to place. Two groups with different prosthodontic designs were used: one represented the standard fixed prosthesis with support at each end (noncantilever, NC), and the other group represented the cantilever portion of the prosthesis (cantilever, C). Two connection designs of prosthesis blocks to MUA abutments were evaluated: one with typical holes in the prosthesis for capturing interim copings and one with a low-profile coping. For the heat-processed PMMA groups (HP/NC and HP/C), wax patterns were milled, and heat-polymerized denture base PMMA prostheses were processed. The milled PMMA groups (M/NC and M/C) were milled from a tooth-shaded PMMA disk for the prosthesis blocks. The milled low-profile groups (Mlp/NC and Mlp/C) had identical dimensions except that connection to the low-profile coping was designed with a cement space and a narrow diameter screw access hole and was milled from a PMMA disk. The failure load (N) of the cantilever prostheses was recorded, and for NC groups, the 3-point flexural strength formula (MPa) was calculated. The Weibull modulus, characteristic strength, and summary statistics were computed, and the groups were statistically analyzed with ANOVA and the post hoc Tukey test (α=.05).The mean flexural strengths (MPa) were HP/NC=91.35 ±18.92; M/NC=143.94 ±36.79; Mlp/NC=117.06 ±13.86. Significant differences were found among groups (P.001). Mean failure loads (N) and Weibull modulus (WM) of cantilever prosthesis strengths were for HP/C=512.66, WM=5.597; M/C=695.06, WM=4.875; Mlp/C=254.97, WM=1.797 (P.001).Implant fixed interim structures milled from high-density PMMA blanks had a 35% higher flexural strength for both the standard prostheses and the cantilever prostheses than heat-processed denture base PMMA. The low-profile coping design was stronger than the heat-processed material, and the failure point was relocated from the lateral walls to the cervical margin area.

This present research and explores the properties of concrete's structural and durability High-density polyethylene granules (HDPE) are partly replaced by the coarse aggregate. Five separate concrete mixtures of grade M30 have been built to partially replace the coarse aggregate from 1% to 5%. The properties of strength and durability such as compressive strength, split tensile test, flexural test and durability test such as rapid chloride permeability test, acid test, alkaline test, sulphate test assault. In the acids, the samples will equate with control concrete after 190 days for durability test cubes. The experiment is conducted to evaluate how much the acid attacks on the concrete. The loads are determined by an average of 3 for the compressive strength, split tensile, flexural test.

Nowadays, environmental sustainability is the responsible of engineering community for which the usage of waste or recycling is essential towards ecological sustainability, for which green materials are considered widely in all sectors. Because of the significance of characteristic filler supported composites in the advancement of lightweight materials, this research exploration centers around utilizing biodegradable garbage such as used tea dust powder reduces the impact of environmental pollution. In this study, effect of organic residue, tea dust is effectively recycled/utilized for fabricating polymer composite to find its suitability in engineering applications. Epoxy polymer is considered as matrix material and different volume fractions of used tea dust powders (10, 20, 30, 40, 50, and 60 vol%) are used as reinforcement. Hand-layup approach is adopted for fabricating the polymer composite and the samples are tested for their mechanical properties viz., impact, flexural and tensile strength. Based on the mechanical strength the best combination is found to be 40% vol. in epoxy matrix; higher addition than 40% reduces the strength due to lower bonding between the powders and matrix.

Whether it's concrete technology, design approaches, or the creation of novel materials, there's always a time delay between laboratory innovations and their practical implementations in the construction sector. However, practical application of steel fibre reinforced concrete is much ahead in the field of research and development. The purpose of this research was to examine the flexural behaviour of high-performance fibre reinforced concrete (HPFRC) in particular. HPFRC mix has been designed to obtain a concrete grade of M60. The modified IS technique is used to create the mix design. Dosage of superplasticizer was adjusted for each mix with incremental fibre content. Steel fibre used in the study comprised of crimpled fibre having 0.4 mm diameter and aspect ratio of 69.09. The hooked end fibre bearing 0.62 mm and aspect ratio of 69.09 is also used. The volume of the fraction of steel fibre namely 0.25 %, 0.5 %, 0.75 %, 1 %, 1.25 % and 1.5 % used in this experimental investigation. Results indicate that introduction of steel fibre significantly improved not only the crack behaviour but also increased the flexural strength significantly. Addition of steel fibre to HPFRC imparted significant increase in Young’s Modulus. Strength studies were conducted by means of Young’s Modulus for 28 days respectively for M 60 concrete. The goal of this study is to determine the role of fibres in post-cracking and fracture behaviour of concrete, as well as the stress–strain behaviour of cracked concrete specimen.

This review reports the outcome of an research experimental on flexural behaviour of partially strengthened reinforced concrete beams along with Engineered Cementitious Composite (ECC). 6 beams were moulded and examined in total. Three beams were tested to determine the influence of plastic hinge length, whereas two beams were examined to determine the effect of large layers of ECC in the tension zone. The remaining beam acted as control beam. Along with beam specimens, cylinders and cubes were tested to evaluate the mechanical characteristics of both ECC and concrete. All the beams are strengthened using ECC plastic hinges and layers. And they could withstand maximum load than the regulate beams. Load capacities of reinforced concrete (RC) beams strengthened with ECC plastic hinges were 2.85 – 6.34 times more than those of the corresponding control beams. Similarly, RC beams having load capacities 5.71–8.45 times with ECC layers were even better. In general, ECC application increased the ductility of Reinforced concrete beams.

Concrete will be the very flexible material. Because of continuous and persistent demands made on concrete to assemble the several problematic necessities, extensive examination work is being carried out in region of concrete method. The engineers have frequently pushing restrictions to expand its presentation with support of supplementary cementitious materials and innovative chemical admixtures such as steel slag, fly ash, and silica fume and so on. Nanomaterial concrete is advanced one the composition of nanomaterial concrete it has following water, coarse aggregate, cement nano silica grain of the size of 10 nm-140 nm and fine aggregate. The nano materials like nano alumina, nano titanium oxide, nano silica, and carbon nano tubes, so on, which are currently utilized in concrete to change its strength assets. The “nano materials” have functions or properties diverse from same materials of bigger size. The “nano materials” have a bigger value of ratio among volume and surface region than other same particles in larger size, creating the “nano-materials” much reactive. The “nano silica” will react with C3S and C2S in cement &generate CSH-2 that will create a solid &strong connection of gel. In current survey, properties of strength like split tensile, compressive, and flexural strength of M50 and M40 grades of concrete with utilization of nano silica (1%, 1.5%, 2%, 2.5%) and micro silica (5%, 7.5%, 10%, 15%) as incomplete replacement of cement were deliberated. It was establish from evaluation survey that concrete composites with better properties could be generated utilizing nano silica, micro silica, and mixture of nanosilica and micro silica.

The purpose of this study was to determine the strength of hollow concrete block masonry walls, beams, and columns, and compare their values with brick masonry walls and ordinary reinforced concrete beams and columns. The specimens for the hollow concrete block and brick masonry walls were prepared and tested for compressive and flexural strengths as well as horizontal and diagonal shear strengths. Moreover, two hollow concrete blocks and two ordinary reinforced concrete beams were designed to experience flexural and shear failure and loaded under a two-point bending load. Meanwhile, a hollow concrete block and an ordinary reinforced concrete column were also constructed and subjected to centric axial loads until they collapsed. The results showed the hollow concrete block masonry walls have greater strength than those made with bricks while both flexural and shear capacity as well as the flexural ductility of reinforced hollow concrete block beams were higher than ordinary reinforced concrete beams. Meanwhile, the centric compressive axial strength of the reinforced hollow concrete block column was smaller due to the inefficient bond it has with the infilled concrete which leads to their separation under the compressive axial load.

The objectives of this study were to evaluate the mechanical properties of lithium disilicate components produced by additive manufacturing (AM) and to assess the effect of build orientation on the resistance to fracture.Oversized bars were printed with a glass-filled photoactive resin using a digital light processing technique. After sintering and post-processing, flexure and chevron notch fracture toughness bars were obtained in three principal orientations (0°, 45°, and 90°) with respect to the build direction. Mechanical properties were obtained according to the relevant ASTM standards. The hardness, indentation fracture resistance, and elastic modulus were measured for each orientation, and a Weibull analysis was conducted with the flexure responses. Fractography of the fracture surfaces was performed to identify the failure origins.The 0° orientation exhibited characteristic strength, Weibull modulus, and elastic modulus of 313 MPa, 4.42, and 168 ± 3 GPa, respectively, which are comparable to lithium disilicate materials from traditional processes. However, build orientation contributed significantly to the flexure strength, elastic modulus, and Weibull modulus; the characteristic strengths for the 45° and 90° build orientations were 86 MPa and 177 MPa, respectively. The primary contribution to the orientation dependence was the number of residual build layer-related flaws from incomplete union between printed layers. Of note, hardness and the fracture toughness were not dependent on build orientation.AM of lithium disilicate materials can achieve the mechanical properties of materials produced by traditionally processing. Thus, while further process development is warranted, the outlook for dentistry is promising.

Statement of problem Whether procedures performed before the cementation of computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramic restorations, including milling, fitting adjustment, and hydrofluoric acid etching introduce defects on the ceramic surface that affect the mechanical and surface properties is unclear. Purpose A systematic review and meta-analysis were conducted to assess the effect of milling, fitting adjustments, and hydrofluoric acid etching (HF) on the flexural strength and roughness (Ra) of CAD-CAM glass-ceramics. Material and methods Literature searches were performed up to June 2020 in the PubMed/MEDLINE, Web of Science, and Scopus databases, with no publication year or language limits. The focused question was “Do milling, fitting adjustments, and hydrofluoric acid etching affect the flexural strength and roughness of CAD-CAM glass-ceramics?” For the meta-analysis, flexural strength and Ra data on milling, fitting adjustment, and HF etching versus control (polishing) were analyzed globally. A subgroup analysis assessed the effect of etching parameters (HF concentration and time) on the flexural strength and roughness of CAD-CAM glass-ceramics with different microstructures. Comparisons were performed with random-effect models at 5% significance. Results Fourteen studies from 2764 potentially relevant records were included in the qualitative syntheses, and 12 in the meta-analysis. Milling and fitting adjustments increased roughness and reduced the flexural strength of CAD-CAM glass-ceramics. The effect of HF etching was dependent on the glass-ceramic microstructure, HF concentration, and etching time. For feldspathic- and leucite-reinforced ceramics, HF 5% applied for between 30 and 120 seconds increased roughness without affecting flexural strength. For lithium disilicate glass-ceramics, HF concentrations greater than 4.9% used for 20 seconds or more reduced the strength without affecting the surface roughness. Conclusions The flexural strength of CAD-CAM glass-ceramic is reduced by grinding procedures such as milling and fitting adjustment. Ceramic microstructure, HF concentration, and etching time determined the effect of hydrofluoric acid etching on the flexural strength and surface roughness of glass-ceramic materials.

Statement of problem The development of polymethyl methacrylate (PMMA) computer-aided design and computer-aided manufacturing (CAD-CAM) resin blocks with reported improved mechanical properties has simplified complete denture production. However, whether the objective of improved mechanical properties has been achieved compared with conventional heat-polymerized PMMA is not yet clear. Purpose The purpose of this systematic review and meta-analysis was to evaluate the mechanical properties of denture base resins manufactured by conventional heat-polymerization and by CAD-CAM in terms of flexural strength, flexural modulus, and surface roughness. Material and methods Electronic databases (PubMed/MEDLINE, Scopus, Web of Science) were independently searched by 2 researchers for relevant studies published up to November 2020. The population, intervention, comparison, and outcome (PICO) question was, “Does the conventionally manufactured, heat-polymerized PMMA resin, as a denture base, demonstrate the same mechanical properties as the CAD-CAM resin block?” In addition, a meta-analysis was based on the inverse variance method. Flexural strength, flexural modulus, and surface roughness were analyzed through the continuous outcome evaluated by mean difference and standard deviation, with 95% confidence intervals. To evaluated heterogeneity, the I2 value (≤25%=low, ≥50%=moderate and ≥75%=high) and the P value were considered. P Results Thirteen in vitro studies were included in the analysis. A total of 507 specimens were evaluated, 222 conventional and 285 CAD-CAM. In terms of flexural strength, the data showed no significant difference when conventional heat-polymerized PMMA was compared with CAD-CAM PMMA resins (P=.06; mean difference=18.28; 95% confidence interval:-0.42 to 36.97). In terms of flexural modulus, there was a significant difference for the CAD-CAM PMMA group (P=.01; mean difference=589.22; 95% confidence interval: 117.95 to 1060.48). In terms of surface roughness, a significant difference was observed between the groups (P=.02; mean difference=-0.53; 95% confidence interval: -0.97 to -0.09) with the conventional heat-polymerized PMMA resin having higher surface roughness values. Conclusions The mechanical properties of CAD-CAM PMMA resins were generally improved when compared with heat-polymerized polymethyl methacrylate resin.

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.

High-performance ballistic fibers, such as aramid fiber and ultra-high-molecular-weight polyethylene (UHMWPE), are commonly used in anti-ballistic structures due to their low density, high tensile strength and high specific modulus. However, their low modulus in the thickness direction and insufficient shear strength limits their application in certain ballistic structure. In contrast, carbon fiber reinforced epoxy resin matrix composites (CFRP) have the characteristics of high modulus in the thickness direction and high shear resistance. However, carbon fibers are rarely used and applied for protection purposes. A hybridization with aramid fiber reinforced epoxy resin matrix composites (AFRP) and CFRP has the potential to improve the stiffness and the ballistic property of the typical ballistic fiber composites. The hybrid effects on the flexural property and ballistic performance of the hybrid CFRP/AFRP laminates were investigated. Through conducting mechanical property tests and ballistic tests, two sets of reliable simulation parameters for AFRP and CFRP were established using LS-DYNA software, respectively. The experimental results suggested that by increasing the content of CFRP that the flexural properties of hybrid CFRP/AFRP laminates were enhanced. The ballistic tests’ results and the simulation illustrated that the specific energy absorption by the perforation method of CFRP achieved 77.7% of AFRP. When CFRP was on the striking face, the shear resistance of the laminates and the resistance force to the projectiles was promoted at the initial penetration stage. The proportion of fiber tensile failures in the AFRP layers was also enhanced with the addition of CFRP during the penetration process. These improvements resulted in the ballistic performance of hybrid CFRP/AFRP laminates was better than AFRP when the CFRP content was 20 wt% and 30 wt%.

Made available in DSpace on 2022-04-29T08:45:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Indiana University Delta Statement of problem: Whether a computer-aided design and computer-aided manufacture (CAD-CAM) fabricated high-translucency lithium disilicate veneer on a lithium disilicate substructure would increase the strength of the restoration compared with a traditional feldspathic porcelain veneer is unclear. Purpose: The purpose of this in vitro study was to evaluate the effect of different lithium disilicate veneer application methods on a lithium disilicate substructure on their biaxial flexural stress (BFS). Material and methods: Lithium disilicate disks were fabricated so that when combined with the veneering disks, they had a dimension of 12×1.2 mm. Experimental groups were as follows (n=15): resin-bonded lithium disilicate veneer, lithium disilicate veneer adhesively cemented to lithium disilicate; sintered lithium disilicate veneer, lithium disilicate veneer sintered to lithium disilicate; sintered feldspathic veneer, feldspathic porcelain applied to lithium disilicate; and monolithic lithium disilicate, the control group. Weibull distribution survival analysis was used to compare the differences in the resistance to fracture after fatigue. The total number of cycles was analyzed by using 1-way ANOVA (α=.05). A finite element analysis (FEA) was also performed. The maximum principal stress (MPS) was used as the failure criterion. Results: The sintered feldspathic veneer group had significantly lower fatigue resistance than sintered lithium disilicate veneer or resin-bonded lithium disilicate veneer (P

Objectives: To evaluate the effect of in-lab simulation of CAD/CAM grinding and intaglio surface treatments on the surface characteristics (topography and roughness) and fatigue behavior of adhesively luted 4YSZ simplified restorations. Methods: Ceramic discs (Ø = 10 mm, thickness = 1 mm) were randomly allocated into 6 groups considering: “In-lab simulation of CAD/CAM grinding” (ground or polished) and “intaglio surface treatments”: Ctrl (without surface treatment), AlOx (aluminum oxide air abrasion) or GLZ (glaze spray application). The surface roughness of all samples was measured, the treated discs received a ceramic primer, were luted with resin cement onto a dentin analogue material (woven glass-reinforced epoxy resin) and tested under a cyclic fatigue test (step-stress approach, n = 15; 1.4 Hz, 10,000 cycles/step, step-size of 100N starting at 200N until failure). A complementary analysis was performed to corroborate the findings in the fatigue test that the glaze fill defects increase the mechanical properties of the ceramic. To do so, bars (n= 10; 1.0 × 1.0 × 12 mm; considering the groups: N-ID: non-indented; ID: indented; ID-GLZ: indented plus glaze spray application) were indented in a vickers hardness tester to produce a crack pattern, treated with glaze or not, and then submitted to flexural strength tests (FS). Fractographic and topographic analysis were performed. Results: In-lab simulation of CAD/CAM grinding decreased the fatigue failure load of the 4YSZ ceramic when comparing polished and ground groups, regardless of surface treatment. GLZ induced better fatigue performance compared to the air abrasion, regardless of the grinding condition (ground or polished surface). The results of the flexural strength test corroborated the findings in the fatigue test, as the ID-GLZ group presented superior FS than the ID group, however both had inferior FS than N-ID. There is an inverse association between roughness and fatigue failure load, as the higher the surface roughness, the lower the fatigue failure load. Failures in the fatigue and flexural strength tests started from the face subjected to tensile stresses. Conclusion: In-lab simulation of CAD/CAM grinding had a detrimental effect on the fatigue behavior of 4YSZ and glaze spray induced better 4YSZ performance compared to the air abrasion. The intaglio surface treatments differently influenced the 4YSZ fatigue performance, however, only glaze spray can reverse the damage caused by the grinding.

The as-solution-treated Sm2Co17-type magnets exhibiting a single 1:7H phase with different average grain sizes (D) are designed. Anisotropy of bending strength (Rbb) and compressive strength (Rmc) of the magnets was investigated. Moreover, the Rbb increases from 86 to 173 MPa with D decreasing from ∼52 to ∼18 μm for group c//h samples. The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets, giving deep understand the mechanical anisotropy characteristics. The relatively high Hall-Petch coefficient KRbb (0.79 MPa·m1/2) gives rise to the largest Rbb (173MPa) for group c//h samples. The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features (grain boundaries). Grain refinement is an effective way to enhance the mechanical properties of Sm2Co17-type sintered magnets.

This study aimed to develop and characterize an ion-releasing experimental fiber-reinforced flowable composite (Bio-SFRC) and dentin treatment solution made of poly(acrylic acid) (PAA) with a high molecular weight. In addition we also evaluated the interface structure and mineralization potential between the Bio-SFRC and dentin.Some mechanical properties (flexural properties and fracture toughness) of Bio-SFRC in comparison with commercial inert (G-aenial Flo X) and ion-releasing materials (ACTIVA-BioActive Base/Liner and Fuji II LC) were assessed (n = 8/group). Calcium-release at different time-points was measured during the first six weeks by using a calcium-ion selective electrode. Surface analysis of composites after being stored in simulated body fluid (SBF) was investigated by using SEM/EDS. Dentin disks (n = 50) were prepared from extracted sound teeth and demineralization was simulated by acid etching. SEM/EDS was used to evaluate the microstructure of dentin on the top surface and at interface with composites after being stored in SBF.Bio-SFRC showed higher fracture toughness (1.6 MPa mDeveloping such reinforced ion-releasing flowable composite and PAA solution might offer the potential for mineralization at the interface and inside the organic matrix of demineralized dentin.

Micro-cracks are inherently present in concrete, leads to debilitation of structures. Methods used for managing micro-cracks have a certain degree of toxicity and also possesses certain drawbacks that made them not completely efficient. Bacterial technique when used in fresh concretes results in calcite precipitation in voids and consequently improves the strength and lowers permeability of concrete. Bio- cement is the combination of Bacillus pasteurii 5% and nutrients Urea, Calcium Lactate 95%. In this study by adding 0.5, 1, 1.5 and 2% Bio- cement by weight of cement and observed compressive strength, flexural strength values after 7 and 28 days of curing for M25 grade of concrete.

In this paper, the manufacturing of macro-porous tubular ceramic supports for membranes is described. The novel supports are fabricated from natural diatomite and alumina raw materials using the extrusion method. The structure was analyzed by X-ray diffraction (XRD) and mercury porosimetry techniques; the presence of possible defects was investigated by scanning electron microscopy (SEM). The permeability has been measured from water flux in standard experiments. Experimental results show that the open porosity, the average pore size (APS), the pore size distribution, the strength, and the permeability of sintered supports, have been found to depend, mainly on the concentration of alumina (Al2O3) additive. Supports prepared with the addition of 10 wt.% of alumina and sintered at 1200 °C, can be considered as the most optimized; they have a porosity ratio of about 46%, an APS is around 7.7 μm, a flexural strength value of about 28 MPa, and water permeability of around 15 m3 h−1 m−2 bar−1. Such materials could be of great interest in the supports fabrication for membrane application, for instance, water filtration.

Shear and flexural failure are commonly known as the highest catastrophic failure mode as it never gives any earlier notice before the collapse. The most common shape in the structure of beams and girders is T-section. Therefore it will be more necessary to investigate the condition of these structures. In this research, the flexural behaviour of RC T-beams is investigated experimentally and analytically strengthened with Basalt Fiber Reinforced Polymer (BFRP). A symmetrical one-point static loading system is applied on RC T-beams superficially bonded with 45° degree, and 90° wrapping up to failure. The effects of both wrapping patterns of BFRP on RC T-beams were investigated for ultimate load carrying capacity, deflection, strain, and failure modes. The experimental results demonstrate that superficially bonded BFRP can enhance the flexural capacity and reduce the deflection of the beam significantly. Further, the results show that the most effective wrapping pattern was a 45° degree than 90°wrapping and without wrapping. Then the RC T- beam was modeled by using ABAQUS to validate the present experimental and analytical results. After a series of comparative studies, the analytical results fairly admit with the experimental results. In the end, this study surmised showing different cracking patterns and yield points of the beam with and without strengthening. It is hoped that the results of this study will be of considerable help for the strengthening of T- beams and structures.

La2Sn2O7/SnO2 powder was synthesized by chemical co-precipitation method, and Ag-La2Sn2O7/SnO2 composites were prepared by hot-pressing sintering. The electrical resistivity, density, Brinell hardness and flexural strength of Ag-La2Sn2O7/SnO2 composites were measured. Moreover, the effect of La2Sn2O7 content on the arc erosion behavior of Ag-La2Sn2O7/SnO2 composites at 7 kV voltage was studied. With the increase of La2Sn2O7 content, the arc duration and arc energy decrease, and the breakdown strength increases. The surface morphology of Ag-La2Sn2O7/SnO2 composites after arc erosion was investigated using scanning electron microscopy and three-dimensional laser confocal scanning microscopy. With the increase of La2Sn2O7 content, the smaller the erosion damage, the better the anti-arc erosion performance. However, too much La2Sn2O7 results in the decrease of Ag-La2Sn2O7/SnO2 properties and severe arc erosion. X-ray photoelectron spectroscopy was used to determine the composition of the erosion region. The effect of La2Sn2O7 on wettability between Ag and SnO2 was investigated, and the erosion mechanism of Ag-La2Sn2O7/SnO2 composites was discussed systematically. This study can provide a reference for the application of Ag matrix electrical contact materials in high-voltage electrical appliances.

The housing problem in Tunisia has become more acute due to the high cost of construction materials, thus constituting a source of concern for the population. To resolve the crisis, upgrading abundant local materials has become a necessity. This paper aimed to assess the potential use of Jebel Menchar's geomaterial to develop compressed earth brick (CEB). Laboratory tests were performed to determine the physical, chemical and mineralogical properties. Series of destructive and non-destructive tests were carried out to characterize the properties of bricks based on their composition in terms of compressive strength, flexural strength, water absorption and ultrasonic testing. The results indicated that all of the bricks studied exhibited a compressive strength greater than 2.3 Mpa during the 28-day experiments, thus suggesting a high potential ability to reduce building material problems, while also providing the brick industry a useful and inexpensive new raw material with less CO2 emissions.

The present study evaluated the effect of different rinsing postprocessing solutions on surface characteristics, flexural strength, and cytotoxicity of an additive manufactured polymer for orthodontic appliances. These solutions have been deemed an alternative to the standard isopropanol which is a flammable liquid, known to have toxic effects.Tested specimens were manufactured using direct light processing of an orthodontic appliance polymer (FREEPRINT® splint 2.0, Detax) and post-processed with different post-rinsing solutions, including isopropanol (IPA), ethanol (EtOH), EASY 3D Cleaner (EYC), Yellow Magic7 (YM7), and RESINAWAY (RAY), respectively. All groups were post-cured following the manufacturer's instructions. Surface topography and roughness (Ra and Rv) were evaluated. In addition, flexural strength was measured by a three-point bending test. An extract test was performed to evaluate cytotoxicity. The data were analyzed by the Kruskal-Wallis test with Dunn's multiple comparisons test (p 0.05).Various post-rinsing solutions did not significantly affect the roughness values (Ra and Rv). Specimens post-processed with EtOH (98.1 ± 12.4 MPa) and EYC (101.1 ± 6.3 MPa) exhibited significantly lower flexural strength compared to the groups of IPA (110.7 ± 5.3 MPa), RAY (112.1 ± 5.6 MPa) and YM7 (117.3 ± 5.9 MPa), respectively. Finally, there were no cytotoxic effects of parts cleaned with different post-rinsing solutions.Considering the use of 3D-printed orthodontic appliance materials, different rinsing postprocessing procedures did not affect surface characteristics. However, the flexural strength was significantly influenced, which could be attributed to the chemical ingredients of the post-rinsing solutions. Various post-rinsing treatments had no alternation concerning cytocompatibility.

To evaluate the effect of post-curing times on the color change, flexural strength (FS), modulus (FM) and microhardness at different depths of four 3D printed resins.A characterization of the light emitted by 3D-resin post-curing unit (Wash and Cure 2.0, Anycubic) was performed. The tested 3D printed resins were Cosmos Temp3D (COS), SmartPrint BioTemp (SM) Resilab3D Temp (RES) and Prizma3D BioProv (PRI) were evaluated under five different post-curing conditions (no post-curing or 5-, 10-, 15, and 20 min of post-curing). For color change analysis, 10 mm diameter x 1 mm thick discs (n = 7) were printed, and the luminosity, color and translucency were measured before post-curing as control, and repeatedly after 5 min cycles of post-curing until a total of 20 min was reached for ΔEThe post-curing time significantly influenced the ΔEA fine adjustment of the post-curing time is crucial to produce adequate mechanical properties in 3D-printed restorative resins, while minimizing the color alterations on the restorations. For the evaluated resins, 5-10 min of post-curing will result in adequate mechanical properties, without affecting the acceptability in the color of the material. However, the results are material-dependent, and evaluation of each specific resin is advised.

Studies investigating the mechanical stability of lithium disilicate-strengthened aluminosilicate glass-ceramic that do not require sintering after milling compared with other computer-aided design and computer-aided manufacturing (CAD-CAM) materials are lacking.The purpose of this in vitro study was to investigate the flexural strength of CAD-CAM zirconia, lithium disilicate, and lithium disilicate-strengthened aluminosilicate glass-ceramics with and without fatigue conditions.Specimens (N=90, n=15) (12×4×3 mm) from the following CAD-CAM materials were prepared and polished: lithium disilicate glass-ceramic (IPS e.max CAD); lithium disilicate-strengthened aluminosilicate glass-ceramic (N!ce); and zirconium dioxide ceramic (IPS e.max ZirCAD). All specimens were divided into 2 subgroups: immediate testing without aging and simulation of aging by using a mastication simulator for 1 200 000 cycles (5 °C-55 °C). Thereafter, flexural strength testing was performed by using a universal testing machine (1 mm/min) on nonaged and aged specimens. The data were evaluated by using nonparametric 2-way ANOVA and Wilcoxon rank post hoc tests (α=.05).Both the material type and aging significantly affected the results (P.001). The interaction was not significant (P.05). Under nonaged conditions, zirconium dioxide ceramic (1136 ±162 MPa) showed significantly higher mean ±standard deviation flexural strength (P.001) than lithium disilicate (304 ±34 MPa) and lithium disilicate-strengthened aluminosilicate glass-ceramic (202 ±17 MPa). The glass-ceramic groups were also significantly different from each other (P.001). After aging, zirconium dioxide (1087.9 ±185.3 MPa) also presented significantly higher mean ±standard deviation flexural strength (P.001) than lithium disilicate (259 ±62 MPa) and lithium disilicate-strengthened aluminosilicate glass-ceramic (172 ±11 MPa) (P.001). Aging significantly decreased the flexural strength of lithium disilicate (14.6%) (P=.03) and lithium disilicate-strengthened aluminosilicate glass-ceramic (14.5%) (P=.01) but had minimal effect on the zirconium dioxide ceramic (4.3%) (P=.29).Among the tested CAD-CAM materials, the mechanical performance of lithium disilicate-strengthened aluminosilicate glass-ceramic was comparable with that of lithium disilicate and considerably lower than that of zirconia. Aging decreased the flexural strength of both lithium disilicate and lithium disilicate-strengthened aluminosilicate glass-ceramic.

Statement of problem The use of reduced platform sets (implants and abutments) can help to control crestal bone loss around implants, which is essential for optimizing esthetics and biomechanical behavior. However, the information available on the fracture resistance of implants with a reduced platform is sparse. Purpose The purpose of this in vitro study was to analyze the maximum fracture strength value of implants with different platform designs during quasistatic fatigue, followed by a simulation of different bone levels of cervical insertion. Material and methods One hundred and twenty sets of dental implants and abutments with different diameters and platform designs were tested. All implants had an internal hexagon connection and conical macrogeometry. Four groups (n=30) were studied: O4.0-mm implants with a regular matched platform (rMatch group), O4.0-mm implants with a regular switched platform (PSwitch group), O5.0-mm implants with a wide matched platform (wMatch group), and O5.0-mm implants with a wide switched platform (wSwitch group). Three conditions simulating different levels of bone position around the cervical portion of the implants were proposed: insertion at the implant shoulder level=0 mm (L0), level=3 mm of insertion loss (L3), and level=5 mm of insertion loss (L5). All sets of all groups and proposed insertion level were subjected to a fracture strength test at 30 degrees in relation to the axis of the sets in a universal testing machine. Results Regardless of the insertion levels tested, the switched platform implants (rSwitch and wSwitch groups) showed similar mean fracture strength values (P>.05), while the implants of matched platforms (rMatch and wMatch groups) showed different fracture strength values for all insertion levels tested (P Conclusions The fracture strength values of the switched platform implants were lower at all insertion levels tested. However, for all insertion levels tested, the implants with a switched platform presented less deformation, whereas, in the matched platform implants, there was significant deformation of the implant structure.

The aim of this study was to compare the mechanical properties of three-dimensionally (3D)-printed and conventional surgical plates used for the repair of maxillary or mandibular defects under the same experimental conditions, and to provide experimental evidence for the future application and clinical trial of 3D-printed individualized surgical plates. For the experimental group, two groups of surgical plates with thicknesses of 2.0 mm and 2.5 mm were designed and 3D-printed by electron beam melting, using Ti-6Al-4V as raw material. Conventional commercially available surgical plates with the same thickness were adopted as the control group. A Vickers hardness tester and universal testing machine were used to measure the mechanical properties of the plates (hardness, bending strength, tensile strength, and yield strength). The mechanical properties of 3D-printed surgical plates were significantly better than those of conventional surgical plates of the same thickness (P 0.001). Comparing the surgical plates of different thickness, the 2.5 mm-thick plates had the highest bending strength in the experimental group (P 0.001) and the best hardness (P 0.001), bending strength (P = 0.001), tensile strength (P = 0.001), and yield strength (P = 0.001) in the control group. No statistical difference was found between the two kinds of plates in the experimental group in terms of hardness (P = 0.060), tensile strength (P = 0.096), and yield strength (P = 0.496). The 3D-printed surgical plates have better mechanical properties than the conventional ones.

Improvement in individual mechanical properties of carbon steels, such as strength or ductility, can no longer keep up with the increasingly demanding service environment. Therefore, it is of practical significance to improve two or more mechanical properties accurately and efficiently. In this work, five machine learning algorithms are first employed to establish prediction models for different mechanical properties (tensile strength, fracture strength, Charpy absorbed energy, hardness, fatigue strength, and elongation) based on the collected carbon steels data. Then, a set of mutually exclusive properties (tensile strength and elongation) and the key descriptors of the corresponding properties are identified by feature engineering, and the importance of the key materials descriptors is analyzed. The prediction models based on key descriptors for tensile strength and elongation also demonstrate good accuracy. All the key descriptors are considered as input features for the comprehensive performance (CP) calculated from the product of tensile strength and elongation. Finally, we develop a machine learning prediction model for CP and successfully apply the efficient global optimization algorithm to optimize two mutually exclusive mechanical properties. This work provides a new multi-objective optimization strategy that is expected to be used for the development of new steels with excellent comprehensive performance.

Although dielectric ceramic capacitors possess attractive properties for high-power energy storage, their pronounced electrostriction effect and high brittleness are conducive to easy initiation and propagation of cracks that significantly deteriorate electrical reliability and lifetime of capacitors in practical applications. Herein, a new strategy for designing relaxor ferroelectric ceramics with K0.5Na0.5NbO3-core/SiO2-shell structured grains was proposed to simultaneously reduce the electric-field-induced strain and enhance the mechanical strength of the ceramics.The simulatation and experiment declared that the bending strength and compression strength of the core-shell structured ceramic were shown to increase by more than 50% over those of the uncoated sample. Meanwhile, the electric-field-induced strain was reduced by almost half after adding the SiO2 coating. The suppressed electrical deformation and enhanced mechanical strength could alleviate the probability of generation of cracks and prevent their propagation, thus remarkably improving breakdown strength and fatigue endurance of the ceramics. As a result, an ultra-high breakdown strength of 425 kV cm−1 and excellent recoverable energy storage density (Wrec ∼ 4.64 J cm-3) were achieved in the core-shell structured sample. More importantly, the unique structure could enhance the cycling stability of the ceramic (Wrec variation

In this study, the variation of microstructural properties in porcelain stoneware tiles was determined by changing the holding time at peak temperature during sintering, and effects of these microstructural changes on impact resistance of porcelain stoneware tiles were examined. Only the F4 samples passed the impact resistance test according to CSTB-NF-UPEC test. This sample has 12.3 wt.% quartz, 1.5 wt.% corundum, 5.8 wt.% anorthite, 13.5 wt.% mullite, and 66.9 wt.% glassy phase. When the relationship between mechanical properties and impact resistance was evaluated, it should be emphasized that only F4 sample with a breaking strength higher than 75 MPa passed the impact test. It can be said that there is a critical threshold in terms of impact resistance, especially for samples which have bending strength greater than 75 MPa. When evaluating the microstructural details, this study shows that a single crystalline phase is not effective for impact resistance behavior of the porcelain stoneware tiles and many factors should be evaluated together.

Electromagnetic wave absorption (EWA) materials for use in extreme environments are of great interest. Herein, SiC nanowires / SiC whiskers (SiCnw/SiCw) foam with unique “wire-on-sphere” hierarchical structure was developed for efficient high-temperature EWA. SiCw were assembled to porous SiCw spheres via spray drying and then SiCw spheres were 3D printed to SiCw foam. The catalyst-free precursor infiltration pyrolysis process was first developed to ensure that SiCnw can intentionally grow in situ on the surface of SiCw spheres, thereby achieving “wire-on-sphere” hierarchical structure foam. At room-temperature, the maximum electromagnetic wave effective absorption bandwidth (EABmax) and minimum electromagnetic wave reflection coefficient (RCmin) of SiCnw/SiCw foam can reach 4 GHz and -57 dB, respectively. At 600 °C, the EABmax and RCmin were 3 GHz and -15 dB, respectively. Furthermore, even oxidized at 1000–1500 °C, SiCnw/SiCw foam can still retain EABmax ranging from 2.7 to 3.9 GHz and RCmin ranging from -16 dB to -64 dB, because the formation of SiO2 layer with appropriate thickness can boost interfacial polarization and regulate impedance matching. The SiCnw/SiCw foam also shows the flexural strength as high as 17.05 MPa. All results demonstrate that the SiCnw/SiCw foam is a promising EWA material for applications of harsh environments. And the material-independent “wire-on-sphere” hierarchical structure and its novel preparation process should find the widespread use in the design and fabrication of high-efficiency EWA micro-nano materials.

Laser sintering devices have been increasingly used to fabricate the metal frameworks of metal-ceramic restorations. In the fabrication process, the sintering layer thickness is an important parameter; however, information on how it may affect the flexural strength of metal frameworks remains limited.The purpose of this in vitro study was to evaluate the flexural strength of 3-unit and 4-unit cobalt-chromium (Co-Cr) metal frameworks laser sintered with 20-μm, 30-μm, and 40-μm layer thicknesses.Three-unit and 4-unit master metal die models with premolar and molar abutments were prepared through direct metal laser sintering (DMLS). A total of 40 metal frameworks (n=10 for each metal die model) were fabricated by the lost-wax technique (group C, served as the control group) and through DMLS with 20-μm, 30-μm, and 40-μm layer thickness (experimental groups LS20, LS30, and LS40, respectively). Each metal framework was cemented to a master die with a polyvinyl siloxane impression material and then subjected to a 3-point bend test at a crosshead speed of 1 mm/min. The yield force of each metal framework was used to calculate the flexural strength. Data were statistically analyzed by using 1-way ANOVA followed by a Tukey honestly significant difference (HSD) test and an independent-samples t test (α=.05) The microstructure of the fracture surface was evaluated by scanning electron microscopy.Group C reported the lowest mean flexural strength (P.05), whereas group LS20 reported the highest mean flexural strength, although no significant difference (P.05) in flexural strength was observed among the DMLS groups. The 3-unit metal frameworks exhibited a statistically significant higher mean flexural strength than the 4-unit metal frameworks (P.05).The sintering layer thickness did not significantly affect the flexural strength of the laser-sintered metal frameworks. However, the DMLS groups reported a higher mean flexural strength than the cast group.

In this study, B4C–SiC–rGO composites with different SiC contents were prepared by spark plasma sintering at 1800 °C for 5 min under a uniaxial pressure of 50 MPa. The effects of SiC on the microstructures and mechanical properties of the B4C–SiC–rGO composites were investigated. The optimal values for flexural strength (545.25 ± 23 MPa) and fracture toughness (5.72 ± 0.13 MPa·m1/2) were obtained simultaneously when 15 wt.% SiC was added to 5 wt.%–GO reinforced B4C composites (BS15G5). It was found that SiC and rGO inhibited the grain growth of B4C and improved the mechanical properties of the B4C–SiC–rGO composites. The clear and narrow grain boundaries of rGO–B4C and rGO–SiC, as well as the semi-coherent B4C–SiC interface, indicated strong interface compatibility. The twin structures of SiC and B4C observed in the composites improved their fracture toughness. Crack deflection and crack bridging caused by the SiC grains as well as rGO bridging and rGO pull-out were observed on the crack propagation path.

The development of efficient and quick method to prepare structure-function integrative C/SiC composites is always a major challenge in this field. Herein, the thermal conductivity and bending strength of C/SiC composites were enhanced simultaneously via continuous high heat conductive channels constructed by continuous wave laser machining and pitch-based high thermal conductivity carbon fiber in thickness direction. Results revealed that the thermal conductivity of the modified C/SiC composites is three times higher than that of referential C/SiC composites due to its highly ordered heat conducive channel in the thickness direction. Importantly, the bending strength of modified C/SiC composites increased to 457 MPa. To better understand the enhance mechanism, the micro-structure for both the composites and heat conductive channel was systematically analyzed. The results demonstrated that the rivet effect of heat conductive channel and the formed two phases structure on the fibers dispersed partial of load and finally enhanced the property of the composites. In a word, this method holds a nice applicable future in constructing structure-function integrative C/SiC composites.

Ti2AlN powders were synthesized through molten salt method and re-calcination process using TiH2, Al and TiN powders as raw materials at 1100 ℃. The composition of final composite was directly influenced by the initial Al and TiH2 content in the starting mixture. The purity of the synthesized Ti2AlN powder could reach 97.1 wt% when the Al molar ratio was 1.05. Then high strength Ti2AlN ceramics were successfully prepared in different modes, including two forms of pulse electric current sintering (PECS/SPS) and hot-pressing sintering (HP). A record-high flexural strength of 719 MPa was obtained for the PECS/SPS with an electrical insulating die (PECS/SPS II) sintered sample, based on the synthesized powder in which the initial molar ratio of Al was 1.1. The sintering behaviors in various modes were analyzed, confirming the shrinkage of particles starting at lower temperature in PECS/SPS II. The density, microstructure, Vickers hardness and elastic modulus of sintered ceramics were also investigated. Therefore, the present work provided the new methods about powder preparation and ceramic sintering of Ti2AlN, making it possible to be used as high strength structural ceramics.

The effect of water contact on the propagation of microscale surface cracks is investigated in two types of glass: annealed and tempered glass. Initial flaw is artificially created on the glass surface using a Vickers indenter, and is covered with a water droplet for 20 min. Micrographs of the flaw taken before and after water contact confirms the increase in crack length from around 61 to 103 µm for thermally tempered glass. After water dipping, the maximum length to which the crack growth is approximately 57% smaller in the thermally tempered glass than in the annealed glass. Despite the severe effect of water contact on crack propagation, it is found that the fracture strength is not substantially altered by water dipping; even though the crack length is enlarged, the fracture strength of glass is similar, and in the case of tempered glass, its fracture strength is slightly changed within 7% due to the blunting of the crack tip by water or others.

Titanium silicon carbide (Ti3SiC2) film was synthesized by molten salt synthesis route of titanium and silicon powder based on polymer-derived SiC fibre substrate. The pre-deposited pyrolytic carbon (PyC) coating on the fibre was utilized as the template and a reactant for Ti3SiC2 film. The morphology, microstructure and composition of the film product were characterized. Two Ti3SiC2 layers form the whole film, where the Ti3SiC2 grains have different features. The synthesis mechanism has been discussed from the thickness of PyC and the batching ratio of mixed powder respectively. Finally, the obtained Ti3SiC2 film was utilized as interphase to prepare the SiC fibre reinforced SiC matrix composites (SiCf/Ti3SiC2/SiC composites). The flexural strength (σF) and fracture toughness (KIC) of the SiCf/Ti3SiC2/SiC composite is 460 ± 20 MPa and 16.8 ± 2.4 MPa∙m1/2 respectively.

The additive composition of an AlN ceramic substrate material was optimized to achieve high strength and thermal conductivity. MgO-CaO-Al2O3-SiO2 (MCAS) glass and Y2O3 were used as basic additives for improved sintering properties and thermal conductivity, thereby allowing for AlN to be sintered at a relatively low temperature of 1600 °C without pressurization. Yttria-stabilized zirconia (YSZ) was added (0–3 wt%) to further improve the strength of the AlN ceramic. YSZ and Y2O3 reacted with AlN to produce ZrN, Y4Al2O9, and Y3Al5O12 secondary phases. The formation of these yttrium aluminate phases improved the thermal conductivity by removing oxygen impurities, while ZrN formed at the AlN grain boundaries provided resistance to grain boundary fractures for improved strength. Overall, the AlN ceramic with 1 wt% MCAS, 3 wt% Y2O3, and 1 wt% YSZ exhibited excellent thermal and mechanical properties, including a thermal conductivity of 109 W/mK and flexural strength of 608 MPa.

Zirconia ceramic is a significant structural material, but its use under some extreme circumstances is limited by its mechanical properties. In this work, SiC particles (SiCp) were added into alumina toughened zirconia ceramics to prepare ZrO2–Al2O3-SiCp ceramics with high performance by using oscillatory pressure sintering (OPS). Results showed that the best OPS temperature of 1600 °C was obtained, and the optimal SiCp particle size and content were 200 nm and 10 vol% respectively. Under these conditions, the specimen exhibited higher mechanical properties including Vickers hardness of 15.43 GPa, bending strength of 1162 MPa and fracture toughness of 6.36 MPa m1/2. Moreover, it was found that the atomic matching between ZrO2/SiCp, Al2O3/SiCp, and ZrO2/Al2O3 was much higher, showing the coherent interface relationship. Therefore, it was favorable for enhanced mechanical properties of as-prepared ZrO2–Al2O3-SiCp ceramics.

Porous diatomite ceramics with hierarchical pores and high apparent porosity (50.29–56%) were successfully fabricated via direct stereolithography. The pre-ball-milling time, dispersant type and dispersant concentration were systematically investigated to prepare diatomite pastes with high solid loading, low viscosity and a self-supporting effect. The results showed that a pre-ball-milling time of 24 h was more suitable to prepare diatomite pastes with high solid loading, and Span80 at 2 wt% was the optimal dispersant to obtain 40 vol% diatomite paste with a low viscosity and a self-supporting effect. To restrain the formation of defects, a heating rate as low as 0.2 °C/min was allowed to control the pyrolysis rate in the multistage debinding process. At sintering temperatures ranging from 900 °C to 1000 °C, porous diatomite ceramics exhibited a typical bimodal porosity, high apparent porosity and great flexural strength.

Monolithic B4C, B4C–TiB2, and B4C–TiB2–graphene nanoplatelets (GNPs) were fabricated by hot pressing (HP) at 1900 °C for 1 h under an axial pressure of 30 MPa. The microstructures and mechanical and electrical properties of the B4C composites were investigated. The results show that the GNPs are distributed homogeneously in B4C-based ceramic composites. Compared with monolithic B4C, the TiB2–GNPs-containing B4C composite exhibits an approximately 68 % increase in flexural strength and a 169 % increase in fracture toughness due to the synergistic effects of TiB2 particles and GNPs. The toughening mechanisms mainly include TiB2 crack deflection, crack branching, transgranular fracture and GNPs crack deflection, crack bridging, and GNPs pull-out. Additionally, the electrical conductivity of the B4C composite reinforced with dual fillers is three orders of magnitude higher than that of monolithic B4C due to the establishment of a conductive network. The addition of GNPs can efficiently connect the isolated conductive TiB2 particles in the B4C matrix and provides an additional channel for electron migration.

Made available in DSpace on 2022-04-28T19:48:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The objective of this study was to assess the wear behavior and its effects on the flexural strength of silica-infiltrated zirconia compared to glaze and polishing finishing treatments. To do so, disc-shaped samples of a second-generation zirconia were prepared and divided into three groups: silica infiltration, glazing, or polishing. Half of the samples of each finishing were subjected to sliding wear testing using a steatite antagonist. The discs and antagonists had their volume loss measured. The wear-tested and the other half of samples were subjected to biaxial flexural strength testing and the following characterization analyses were also performed: roughness, hardness, X-ray diffraction, profilometry, and scanning electron microscopy (SEM). Data were evaluated with ANOVA and Weibull analyses. Glazing caused greater antagonist volume loss, followed by silica infiltration, and polishing. Silica-infiltrated zirconia surface was similarly worn to polished, which was lower than that for glazed zirconia. Polished zirconia presented the highest flexural strength. However,the strength decreased and became similar in all worn groups. Silica infiltration showed slightly lower characteristic strength after sliding wear. The highest roughness and hardness values were observed on glazed zirconia. These values decreased after wear testing and became similar to the other groups. SEM evidenced an irregular surface for glazing. No phase transformation occurred after sliding wear. Despite producing some volume loss on zirconia and antagonist surfaces, silica infiltration is a promising alternative for finishing monolithic restorations. Moreover, the damage caused by sliding wear leads to decreasing the strength of zirconia regardless of the surface finishing. Department of Dental Materials and Prosthodontics São Paulo State University (Unesp) Institute of Science and Technology, Av. Eng. Francisco José Longo, 777, Jardim São Dimas, SP Department of Physics Aeronautics Technological Institute (ITA), Praça Marechal Eduardo Gomes, 50, SP Department of Dental Materials and Prosthodontics São Paulo State University (Unesp) Institute of Science and Technology, Av. Eng. Francisco José Longo, 777, Jardim São Dimas, SP FAPESP: 2015/11405-7 FAPESP: 2016/07920-6 FAPESP: 2017/20633-9 FAPESP: 2018/22627-9 CNPq: 408932/2016-3

As main components of magnesia-based refractories, magnesia exhibits excellent properties such as high refractoriness and good basic slag corrosion resistance. However, magnesia produced from CaO containing cryptocrystalline magnesite has limited application owing to the low hydration resistance and poor thermal shock resistance (TSR). This work aimed to investigate the reinforcing effects of microscale monoclinic ZrO2 on free CaO containing magnesia for optimizing mechanical properties, TSR and hydration resistance. The results showed that adding ZrO2 could promote the removal of the open pores, strengthen the interface bonding between various grains and produce crack deflection, which improved flexural strength and fracture toughness. As a result, the TSR of the specimens was enhanced effectively due to increased strength and toughness and reduction in the thermal expansion coefficient. Besides, as the ZrO2 was introduced, hydration resistance of the specimens improved significantly, mainly attributing to the decrease in apparent porosity and elimination of the free CaO by forming CaZrO3 and cubic ZrO2 phases.

Carbon fibers reinforced SiCN ceramic matrix composites (C/SiCN) were prepared by PIP with homemade polysilazanes (PSN-T03). The PSN-T03 had a viscosity of less than 500 mPa·s and favorable good chemical stability at 80 ℃, which made it quite applicable for PIP process. PSN-T03’ curing reactions happened at temperatures ranging from 149℃ to 205℃, and conversion to amorphous SiCN ceramics could be finished at temperatures above 700℃ with a 70+ wt% ceramic yield. Tensile strength of C/SiCN composites were 230 MPa and 350 MPa respectively at room and high temperature (1400℃), and bending strength reached 380 MPa and 530 MPa. SiCN ceramics began to lose weight at 1400℃ due to the carbothermic reduction of the silicon nitride phase under inert atmosphere, which results in collapse of the mechanical properties of C/SiCN composites above 1400℃.

The abruptly increased dielectric loss in graphene oxide (GO) induced by high-temperature sintering has prevented GO from being used as an absorbent in ceramic-matrix microwave absorbing composites (MACs). Here, we show the first example that the pristine structure of GO can be largely preserved in ceramic composite by using cold sintering technology. Compared with the composites densified by ordinary spark plasma sintering, cold sintered samples possess lower complex permittivity and superior impedance matching. Therefore, the cold sintered ZnO composite with 0.50 wt% GO loading shows the minimum reflection loss of -47.5 dB at thickness of 3.2 mm, and the effective absorption bandwidth of 4.4 GHz at thickness of 1.7 mm. Moreover, both flexural strength and hardness of the cold sintered composite are improved considerably compared to the monolithic cold sintered ZnO. These findings imply that cold sintering enables the thermally unstable materials to be applied in highly effective MACs with robust mechanical performance.

High porosity and high strength are usually mutually exclusive in the preparation of ceramic materials. However, high porosity and flexural strength are required for the preparation of complex ceramic cores for hollow turbine blades. In this study, Al2O3 cores with high porosity and high flexural strength were successfully prepared using digital light processing (DLP) 3D printing technology. The influence of sintering temperature on the microstructure, pore evolution, and flexural strength of the cores were investigated. With an increase in the sintering temperature, the porosity of the ceramic cores first increased and then decreased, reaching a maximum value of 35% at 1400 °C. The flexural strength increased with the increase in sintering temperature, but at 1400°C the incremental enhancement of flexural strength was greatest. Combined with the core service requirements and core performance, this study selected 1400 °C (open porosity of 35.1% and flexural strength of 20.3 MPa) as the optimal sintering temperature for the DLP-3D printed Al2O3 core.