Papers by Keyword: Zirconia

Abstract: There is a growing demand in the dental implant sector which aims to recreate the exact function and appearance of natural teeth, including strength, textures, and seamless blending with nearby teeth. Therefore, choosing the best crown material is a vital and challenging decision. To address this challenge, current study employs a comprehensive approach using Finite Element Analysis (FEA) on a 3-D CAD model. The stress analysis was carried out on three different crown materials - commercially pure Titanium (cp Ti), Zirconia (ZR), and Lithium Disilicate (LD) and compared their performance with that of human tooth material. The computational analysis results reveal that the pure Titanium (cp Ti) crown has shown the least deformation while the LD crown has showed the highest deformation under same loading conditions. When maximum stress is compared, Titanium showed the highest value, followed by Zirconia, whereas Lithium Disilicate (LD) demonstrated stress and deformation levels comparable to those of natural teeth.

Abstract: This study analyzes the wear mechanisms of a Kevlar-Zirconia-Epoxy composite casing coating under varying drillpipe joint speeds and side loads, using both dry and water-based mud lubrications. Employing Scanning Electron Microscopy, the research highlights the influence of ceramic microfillers on the wear characteristics. Findings indicate that abrasive wear dominates at low speeds, while higher speeds increase adhesive wear. Side load changes had minimal impact on wear mechanisms. Additionally, specimen temperature significantly affects composite behavior, underscoring the importance of lubrication for maintaining composite integrity. The results suggest this composite is well-suited for applications requiring high durability and wear resistance.

Abstract: Direct ink writing (DIW) is an extrusion additive manufacturing (AM) technique in which inks are extruded through a nozzle and then deposited layer-by-layer. This technology allows 3D printing many different materials such as ceramics, metals, food, etc. In this work, the performance of zirconia pastes is addressed. The pastes are composed of yttria stabilized zirconia (YSZ) powder and a polymeric binder. Ceramic content is a mix of two components: A and B. Both the total content of ceramic and the content of component A in the paste are varied, according to a 3² design of experiments. The paste was characterized regarding Densification (%) and Elastic modulus G’ (Pa). A new parameter w³/G’ is defined to evaluate the viscosity of the inks. In the tests, the ceramic percentage is limited by the pressing force of the plunger that will be used to extrude the pastes. On the other hand, the binder concentration is also limited, because it requires to be in a gel form in order to be properly extruded. The results showed that Densification depends mainly on ceramic content, while the w³/G’ parameter is related to percentage of component A. In this work, the properties of the pastes prior to 3D printing are assessed. However, in the future, the pastes will be used to extrude complex parts with medical applications. AM extrusion processes constitute a possible way to overcome the difficulties to obtain complex geometries with conventional methods such as machining, in which zirconia parts can break due to their brittleness. Thus, the results of this work will help to manufacture complex shapes with porous areas in zirconia, when the DIW technology is employed.

Abstract: This paper highlights the study on effect of sintering temperature on the morphologies and compressive strength of zirconia ceramics doped with calcium oxide (CaO) as stabiliser to enhance the zirconia structure undergo sudden phase transformation. CaO reportedly has good stability in cubic phase at all temperature, which open up a new possibility for new material to evolve for zirconia ceramic dental application. CaO synthesis from calcium nitrate tetrahydrate (Ca(NO₃)₂.4H₂O) is used as metal precursor to produce Calcia-Sabilized Zirconia (Ca-SZ). 8 wt. % of Ca(NO₃)₂.4H₂O and 92 wt. % of zirconium oxide (ZrO₂) mixed and stirred together with ethanol as solvent and sintered at temperatures 1200, 1300 and 1400°C. Surface morphologies are investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) element analysis, X-ray Diffraction (XRD) for composition studies, as well as compressive strength to figure out the mechanical properties of Ca-SZ sample. Increment in sintering temperature enhance the surface morphologies, the phase of Ca-SZ become intensified and transformed from monoclinic to tetragonal ZrO₂ also flexural strength increases as well. The compressive strength recorded the highest value of 4537 MPa for Ca-SZ at temperature of 1400°C. The optimal temperature of Ca-SZ suitable for dental application was 1400°C due to the good morphologies and mechanical properties suitable for teeth restoration. The development of Ca-SZ can establish a pathway as an alternative material for dental applications.

Abstract: The aim of this study was to upscale the production of calcium oxide (CaO) derived from cockle shells using an improved protocol and determine its purity, as well as to study the hardness of the new, improved calcia stabilized zirconia (Ca-SZ). A mixture of diluted cockle shells powder with hydrochloric acid solutions (HCl) was stirred to obtain calcium chloride (CaCl₂). The homogenous CaCO₃ solutions were obtained by mixing CaCl₂ solution with potassium carbonate (KCO₃) using upscaled mechanochemical synthesis process. Then, CaCO₃ powder underwent calcination process at a temperature in range of 300°C – 550°C to obtain CaO powders. CaO showed the result under FESEM analysis as a spherical shape with crystal-like structure as well dispersed with no visible agglomeration. The yield production of CaO obtained was approximately about 5.0g which was upgraded from a previous study. The morphologies of Ca-SZ were observed at three different sintering temperatures at 1200°C, 1300°C and 1400°C were selected in order to understand the morphological and mechanical properties of Ca-SZ after incorporating 8wt% of CaO powders derived from cockle shells. The Ca-SZ pellets were then characterized using Field Emission Scanning Electron Microscopy (FESEM) and Vickers Hardness Test to ensure the effectiveness of CaO powder in fabricating Calcia-Stabilized Zirconia (Ca-SZ). As a result, sintered Ca-SZ at 1400°C showed the most promising performance for nano-CaO act as a stabilizer as it has the highest hardness at 590.03MPa with significantly difference (p<0.05) among all sintered Ca-SZ specimens. Therefore, these findings revealed that by adjusting the previous protocol, upscaling of a pure CaO may be synthesized using natural Ca source from cockle shells. The fabricated Ca-SZ showed a significantly lower hardness when sintered at 1400°C, which may be easier for machining.

Abstract: Zirconia restorations are usually coated with glazing to provide an aesthetic and reduce wear on opposing teeth. Occlusal adjustments such as grinding and polishing to eliminate occlusal or internal interferences can affect the mechanical properties of zirconia. The purpose of this study was to evaluate the effect of glazing, reglazing, and polishing procedures on the biaxial flexural strength of zirconia ceramic. This experimental study used 20 samples of zirconia discs (12x1,2 mm), which were divided into fourth groups (n=5). The first group was zirconia discs without treatment as control, the second group with glazing treatment, the third group with reglazing treatment, and the fourth group with polishing treatment. Biaxial flexural strength was determined using a piston on three balls technique. The data were analyzed using 1-way ANOVA and t-test. The results of this study showed no statistically significant difference between the group with glazing, reglazing, polishing and the control group (p>0.05). The highest zirconia biaxial flexural strength was found in the polished group but not significant statistically (1913.64 ± 594.28 MPa). The reglazing group with the lowest average biaxial flexural strength was (1413.01 ± 365.66 MPa). It can be concluded that there were no differences in biaxial flexural strength between the polishing, glazing, and reglazing group. The use of polishing can be an alternative technique to improve aesthetics besides glazing and reglazing because it does not impair the biaxial flexural strength of zirconia.

Abstract: Zirconia is one of the materials used in prosthetic restoration because of its better physical, mechanical, chemical, and biological properties. The surface treatment for zirconia can be mechanical, with grinding, sandblasting, and laser or chemically, with silane and etching. The combination of chemical and mechanical surface treatment can increase the surface roughness so that the bonding with the resin cement also increases. The study aims to examine the zirconia surface roughness after different surface treatments. This study used 25 zirconia samples in 10x10x2 mm square-shaped, divided into five groups. Group 1 treats sandblasting as a control. Group 2 sandblasting then etching with 9.5% hydrofluoric acid at 25°C for 60 minutes. Group 3 sandblasting then etching with 9.5% hydrofluoric acid at 100°C for 1 minute. Group 4 etching with 9.5% hydrofluoric acid at 25°C for 60 minutes. Group 5 etching with 9.5% hydrofluoric acid at 1000C for 1 minute. The samples were cleaned with an ultrasonic cleaner and tested using a profilometer. The data test by using the ANOVA test and T-test. The highest surface roughness was the combination of sandblasting with 9.5% hydrofluoric acid etching at 25°C for 60 minutes. The lowest was 9.5% hydrofluoric acid etching at 100°C for 1 minute. ANOVA statistical analysis with a p-value <0.05 ((8.4051 x 10-12) indicates that the test was significant. The result of this study was the combination of surface treatments resulted in higher surface roughness. Duration of the etching time affected the increase of zirconia surface roughness.

Abstract: Functionally graded materials (FGMs) are multi-phase composites to be engineered with gradual spatial variations of constituents. Centrifugal techniques enable to have a continuous gradient manner in FGMs. In this study, zirconia (ZrO₂)/ 304 stainless steel (SUS304) FGMs were fabricated using centrifugal slurry methods with powders of ZrO₂ and SUS304 mixed with a dispersant, ammonium polycarboxylic acid (PCA). The green body samples produced by centrifugal techniques were consolidated using spark plasma sintering (SPS). The fabricated samples were investigated on their microstructures and contents using scanning electron microscope (SEM) with EDX and micro Vickers and nanoindentation hardness. The results demonstrated that controlling of the continuous gradient were possibly achieved using the combination of the current techniques.

Abstract: Ceramics/ metal functionally graded materials (FGMs) have been attracting much attention as composite materials that are intended for application to high-temperature structures. This study fucuses on toughening of ceramics and their matrix composites, which are building blocks of the FGMs. Partially stabilized zirconia (PSZ) with toughening additives such as Ni particles, Inconel fibers, SiC particles, SiC whiskers and a-alumina (Al₂O₃) particles were fabricated by spark plasma sintering (SPS). Toughening mechanisms were investigated based on their micro and macro-scale mechanical properties and microstructures. Disk bending tests, producing balanced biaxial loading conditions, were conducted probing bending strength at macro scales, while Vickers hardness tests were carried out to estimate fracture toughness and examine toughening mechanisms at micro scales. The results demonstrated that toughness of ZrO2 increased by adding Ni particles, Inconel fibers and Al₂O₃ particles. Addition of Al₂O₃ particles highly enhanced disk bending strength and deformability.

Abstract: Materials based on partially stabilized zirconia (ceramics and crystals) are distinguished by high values of mechanical strength, crack resistance, hardness, corrosion resistance, low coefficient of friction when operating in tandem with most metals, which makes them promising materials for a wide tribotechnical application in highly loaded friction units. An example of such a unit is the die mechanism, which is an integral part of the drawing die tool in the cable industry. These hard precision tools (drawing dies or wire dies) actually determine the ultimate success in the wire drawing process.