Magnesia Partially Stabilized Zirconia Research Articles

Local strain heterogeneity and damage mechanisms in zirconia particle-reinforced TRIP steel MMCs: in situ tensile testing with digital image processing

In this work, the microstructural deformation and damage mechanisms of TRIP steel metal matrix composites (MMCs) reinforced with Magnesia Partially Stabilized Zirconia (Mg-PSZ) particles are investigated by employing in situ tensile testing within a scanning electron microscope chamber, complemented by digital image correlation and advanced image processing techniques. The study is carried out on samples with varied volume fractions (0%, 10%, and 20%) of zirconia particles and damage mechanisms in different samples under specified loading conditions. Through both qualitative and quantitative assessments of deformation, damage, and clustering, the investigation provides a comprehensive understanding of the distribution and damage initiation. The study findings reveal that, generally, the steel matrix exhibits high toughness, with minimal occurrences of microcracking at high strains that cause significant damage. In samples with increasing particle content, delamination at the matrix–particle interface and cracking of Mg-PSZ particles were found to be critical contributors to material failure and were quantitatively analyzed using computational analyses conducted with MATLAB. The work highlights the initiation and evolution of each damage mechanism in zirconia particle-reinforced TRIP steel MMCs to facilitate scientists and engineers in improving manufacturing and application decisions in industries such as automotive, aerospace, and heavy machinery, which demand materials with exceptional toughness and durability.Graphical

Developing a deposited calcium-phosphate layer on zirconia surface by chemical grafting of L-Serine molecules

Due to the proper mechanical properties and desirable aesthetic properties of zirconia, it is considered as a good candidate for replacement of metallic implants. In this study, zirconia was functionalized by l-serine amino acid to provide surface COOH/OH groups for calcium-phosphate formation (CPF) of hydroxyapatite and chemical bonding to bone tissue following implantation. Magnesia-partially stabilized zirconia (Mg-PSZ) discs were prepared and hydroxylated using hydrothermal process at 120 °C for different times to provide reactive hydroxyl groups. Thereafter, the discs were immersed in 0.01 mg/mL aqueous l-Serine solution at temperatures between 40 °C and 80 °C for different times and pH to graft l-Serine molecules on the zirconia surface. Afterward, the specimens were incubated in simulated body fluid (SBF) for 7 and 21 days. The results indicated that the grafting of l-Serine on the zirconia surface, at 80 °C in neutral pH, created negative charges. The hydroxyl apatite, on the surfaces grafted with l-Serine, started to nucleate and grow almost simultaneously after 7 days of exposure to alkaline pH. The soaking was continued for 21 days to form more uniform mineral apatite with developed surface wettability (i.e., contact angle of 18.3° ± 1.3). Herein, the absorption of calcium and phosphate ions caused the formation of hydroxyapatite nucleation and growth in 21 days.

Evaluation of Structural Stability, Mechanical Properties, and Corrosion Resistance of Magnesia Partially Stabilized Zirconia (Mg-PSZ).

Nano Zirconia (ZrO2) has been used in dental implants due to having excellent mechanical properties and biocompatibility that match the requirements for the purpose. Zirconia undergoes phase transformation during heating: monoclinic (room temperature to 1170 °C), tetragonal (1170 °C to 2370 °C), and cubic (>2370 °C). Most useful mechanical properties can be obtained when zirconia is in a multiphase form or in partially stabilized zirconia (PSZ), which is achieved by adding small amounts of a metal oxide dopant, such as MgO (magnesia). This study aimed to synthesize nano Mg-PSZ from a local resource found in West Kalimantan, Indonesia, and examine its structural stability, biochemical stability, and mechanical properties. Nano Mg-PSZ was prepared from a zircon local to Indonesia, from West Kalimantan Province, MgSO4∙7H2O, and polyethylene glycol (PEG)-6000 was used as a template. The obtained t-ZrO2 after calcination at 800 °C was shown to be stable at room temperature. The highest percentage of the t-ZrO2 phase was obtained at Zr0.95Mg0.05O2 with a variation of 99.5%. The hardness of Mg-PSZ increased from 554 MPa for ZrO2 without MgO doping to 5266 MPa for ZrO2 with a doping of 10% MgO. An in vitro biodegradation test showed that the greater the concentration of MgO in doping the ZrO2, the greater the degradation resistance of Mg-PSZ in simulated body fluid (SBF) solution.

Micromechanical properties and microstructure evolution of magnesia partially stabilized zirconia prepared by spark plasma sintering

Magnesia partially stabilized zirconia (Mg-PSZ) is a widely used engineering ceramic owing to its high hardness and exceptional toughness. It is usually processed by conventional firing followed by subeutectoid aging. In this work, Mg-PSZ was prepared by spark plasma sintering (SPS) followed by sequential subeutectoid aging to fine-tune its mechanical properties. Mg-PSZ prepared by SPS with the rapid heating capability presents much smaller grains than conventionally prepared counterparts. After aging, a significant fraction of the matrix cubic phase transforms into tetragonal, orthorhombic, and monoclinic zirconia. Microindentation and in-situ microcompression tests reveal that aging Mg-PSZ for 4 h leads to maximum fracture toughness and fracture strain due to the tetragonal-to-monoclinic transformation toughening. Post compression TEM analyses show dominant monoclinic ZrO2 decorated by a high density of twin boundaries and stacking faults formed to accommodate the shear deformation. Preparation of Mg-PSZ by SPS offers rapid and effective approaches in finetuning the phases and mechanical properties.

Preparation of Magnesia Partially Stabilized Zirconia Nanomaterials from Zirconium Hydroxide and Magnesium Carbonate Precursors Using PEG as a Template

Stabilized zirconia is a promising material due to its great physical and chemical properties, and thermal stability. In this work, MgO was used as a stabilizer in ZrO2 to obtain Magnesia Partially Stabilized Zirconia (MSZ) nanomaterials assisted with PEG as a template through conventional mixing process. Zirconium hydroxides prepared from local zircon and MgCO3 were used as MSZ precursors. Meanwhile, the stabilizer concentration was varied from 1 to 4 wt% of ZrO2. The effect of the stabilizer concentration and the calcination temperature to the crystallinity and the morphological properties of the MSZ nanoparticles were studied using X-ray diffraction and scanning and transmission electron microscopy. The ZrO2 content in the zirconium hydroxides precursors is accounting 89.52 wt% of the total and exhibits the dominant m-phase at 1000 °C. Meanwhile, the tetragonal and the monoclinic phases were formed in all MSZ samples at a temperature of 800–1000 °C. The as-synthesized MSZ samples show typical FT-IR spectra, consisting of the metal–oxygen bonds at below 500 cm−1 and the organic functional groups ranging at 1000–3000 cm−1. The ZrO2 morphologies exhibit spherical-like shapes with elongated agglomeration at 800 °C. In addition, the average particle sizes of the final product ranges from 20 to 50 nm. At a sintering temperature of 1500 °C, MSZ samples show the monoclinic phase of ZrO2 and densities in the range of 3.95–4.14 g/cm3.

Low-calcination temperatures of magnesia partially stabilized zirconia (Mg-PSZ) nanoparticles derived from local zirconium silicates

Partially stabilized zirconia (PSZ) exhibits excellent physical, mechanical, electrical, chemical, thermal, and bioactive properties. Therefore, it is frequently used as a material for thermal barrier coatings, refractories, oxygen-permeating membranes, dental and bone implants. In this study, magnesia-partially stabilized zirconia nanoparticles were successfully prepared from zirconium silicates and MgSO4 assisted with PEG-6000 via a facile templating method. The MgO concentration was varied from 1%–10% in wt% of ZrO2. Zirconium silicates were initially converted to Zr-precursor solution, exhibiting pH 3. Then, the appropriate amount of the Mg-precursor was mixed with the proper amount of the Zr-precursor solution. A 10%(w/v) PEG-6000 solution was added into the PSZ precursor solution at a ratio of the precursor-to-PEG volumes of about 15:1 under stirring and heating, resulting in a very fine white gel. The gel was filtered, dried, and then calcined at elevated temperatures of 600, 800, and 1000 °C. The characteristics of the final product were then evaluated. According to the experimental results, the MgO concentration influences the ZrO2 phase transformation at elevated calcination temperatures. In this study, the lower the MgO dopant concentration added into ZrO2, the more stable the t- ZrO2 phase in PSZ samples at high temperatures. However, the MgO presence is detected as periclase in all samples with a very low peak intensity at elevated calcination temperatures. The obtained PSZ samples consist of nanoparticles and high agglomeration, some of particles exhibit elongated and rod-like shapes. The PEG existence during the PSZ preparation has restrained particle interaction and aggregation of the as-synthesized PSZ samples, leading to PSZ nanoparticles evolution.

The use of Knoop indentation for the assessment of the plastic properties of mortars and natural stones

The present work investigates the Knoop hardness of rocks and other pressure sensitive materials. We tested ten different types of rocks, a cement paste, and PMMA. We also analyzed existing experimental results for Mg-PSZ (magnesia-partially stabilized zirconia) and Pb40Ni40P20 metal glass. We performed finite element indentation analysis for three types of material models: Mohr-Coulomb (associative), Drucker Prager (associative and non-associative), and foam-type. The material models assumed isotropic elasticity (with low elastic strains) and no strain-hardening effects. We compared our analytical results with our experimental results using material data from the literature. We found that different materials can be best described by either the Mohr-Coulomb or Drucker-Prager models. Highly porous materials showed unreasonably high Knoop hardness, raising questions on how their surface can be prepared for indentation tests. Materials with known model types such as cement, PMMA, Mg-PSZ and metal glass, verified our analytical results.

Investigations on the sintering response of steel-ceramic composites

Purpose of this article is the evaluation of the influence of sintering parameters on the microstructure evolution and mechanical properties of pressureless sintered metal matrix composites consisting of metastable 16Cr7Mn7Ni-steel with 0 or 5 vol.% magnesia partially stabilized zirconia (Mg-PSZ) particles. The materials were prepared from powder raw materials via extrusion at ambient temperature. Three different temperatures between 1280 °C and 1380 °C and two varying dwell times of 40 min and 120 min at maximum temperature were applied. Both, tensile and compression tests are conducted at quasi-static strain rates for comparison of strength level, deformability and energy absorption capability. The results are discussed with regard to the porosity of the specimens, the interface between steel and ceramic, the TRansformation Induced Plasticity (TRIP)-effect occurrence and the failure behavior.

Effect of sintering temperature on mechanical properties of magnesia partially stabilized zirconia refractory

The optimized sintering conditions for a 3.5wt% magnesia partially stabilized zirconia (Mg-PSZ) refractory were proposed in our recent research. The influence of the sintering temperature on the development of phase composition, microstructure, densification, thermal expansion and mechanical strength was studied in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), He-pycnometer, high temperature dilatometry and three-point bending test. The samples sintered at 1670°C had the highest bend strength, the maximum densification, the lowest thermal expansion coefficient (CTE), a homogeneous microstructure and a linear change in thermal expansion.

Comparative study of TRIP/TWIP assisted high density composite honeycomb structures under compressive load

The mechanical behavior of a high density square celled composite honeycomb structure is examined with respect to the influence of different matrix materials and ceramic particle additions. For this purpose two high alloyed metastable austenitic CrMnNi-steels with varying Ni contents and reinforcements of 0, 5 and 10vol.% magnesia partially stabilized zirconia (Mg-PSZ) were chosen as cell wall material to evaluate the contribution of the TRansformation Induced Plasticity (TRIP)- and TWinning Induced Plasticity (TWIP)-effect on the strength, deformation and damage characteristics of the honeycombs. Out-of-plane compression tests were conducted in the strain rate range of 0.001–180s−1 and at temperatures of −60°C and 20°C having a great effect on the driving force and extent of both material effects. The results reveal a considerably higher strength level for the TRIP-assisted structures which can be improved by the addition of Mg-PSZ at certain deformation degrees whereas the TWIP-matrices are more damage-tolerant.

The correlation of local deformation and stress-assisted local phase transformations in MMC foams

Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation.

Second Phase‐Induced Degradation of Fused MgO Partially Stabilized Zirconia Aggregates

Magnesia‐partially stabilized zirconia (Mg‐PSZ) fired refractory crucibles used under vacuum induction melting (VIM) furnaces, are routinely cycled above 1500°C in service, sometimes experiencing failure in under a dozen cycles. This has negative financial implications, given the high value Ni–Co superalloys melted in them. To evaluate aggregate response to cycling, the microstructural evolution of two commercial varieties of fused Mg‐PSZ aggregate has been studied within their host refractories, over eight cycles to 1700°C. The aggregates contain 0.1–0.2 wt% alumina and silica impurities and at 1700°C, these generate a liquid phase which on cooling, crystallizes segregated secondary phases of spinel, forsterite, and cordierite. These minerals have thermal expansion coefficients that are markedly different to zirconia and the mismatch in volume change rates between adjacent phases leads to aggregate breakdown. Micro‐Raman mapping reveals internal boundaries within the aggregates which are attributed to retention of original surface concentrations of alumina and silica on zircon sand particles at the time of conversion into zirconia and which act as the main location for secondary phase development. Crucibles made with aggregates containing higher concentrations of stabilizer (>2 wt% MgO) and MgO fines in their matrix phase, show significantly greater aggregate breakdown.

Effect of alumina addition on the microstructure and grain boundary resistance of magnesia partially-stabilized zirconia

The electrical properties of 9 mol% MgO–ZrO2 (Mg-PSZ) with 1 mol% Al2O3 and the mechanisms for electrical degradation were investigated using structural, morphological, and electrochemical analyses. The addition of Al2O3 caused an increase in both the monoclinic and the Mg-rich phases at the grain boundaries in the Mg-PSZ. Coarse grains larger than 20 μm and an intergranular layer composed of the Mg-rich phase were identified in a specimen sintered at 1600 °C. This specimen exhibited a minimum of ionic conductivity (4.98 × 10−4 S cm−1 at 700 °C) due to the grain boundary resistance (245 Ω cm2), which dominated the overall resistance. A similar trend was observed over the entire temperature range (600–1500 °C). An intergranular siliceous impurity (SiO2) was present in conjunction with the Mg-rich phase. This impurity and the Mg-rich phase acted as a barrier layer for oxygen ion diffusion. The presence of the intergranular phases (i.e. the monoclinic and Mg-rich phases) contributed to the degradation of the ionic conductivity in Mg-PSZ with an Al2O3 addition.

Application of response surface methodology (RSM) for optimization of sintering process for the preparation of magnesia partially stabilized zirconia (Mg-PSZ) using natural baddeleyite as starting material

In this work, instead of chemical pure zirconia, natural baddeleyite was used as starting material to prepare partially stabilized zirconia (PSZ) with magnesia as stabilizer. Response surface methodology (RSM) involving central composite design (CCD) was employed to optimize the sintering process for the preparation of magnesia partially stabilized zirconia (MgO-PSZ) with the aim of improving the relative density and bending strength of the materials. The interaction between three variables i.e. sintering temperature, holding time and heating rate was studied and modeled. The statistical analysis of the results showed that in the range studied, sintering temperature had a significant effect on relative density and bending strength. The optimum combination predicted by RSM was experimentally confirmed, whereby almost complete densification with the relative density 99.44% was obtained at a 3°C/min cooling rate.

Deformation Mechanisms and Martensitic Phase Transformation in TRIP‐Steel/Zirconia Honeycombs

AbstractThe mechanical and structural response of powder metallurgical square‐celled honeycomb structures to quasi‐static and dynamic impact loads are described. By constructing the cellular lattice with a novel metal matrix composite material based on a metastable high‐alloyed austenitic TRIP‐steel particle‐reinforced by magnesia partially stabilized zirconia (Mg‐PSZ), high specific yield and ultimate collapse strengths as well as a high ductility and an enhanced specific energy absorption were gained. In order to prove the temperature sensitivity of the honeycomb structures, a selected low‐reinforced composite condition was investigated in a pre‐series of quasi‐static compression tests at temperatures in the range between −190 and 150°C. The present study shows that the deformation mechanisms of the TRIP‐matrix composite honeycomb structures can be classified with respect to strain rate and deformation temperature, including the failure characteristics and the strain‐induced α′‐martensite transformation in the austenitic steel matrices ensuring the TRIP effect. The evolution of the α′‐martensite phase content in the central crush zone of the TRIP steel and TRIP‐Matrix Composite honeycombs is demonstrated based on the results of magnetic balance measurements.

Strain Rate Effect on Material Behavior of TRIP‐Steel/Zirconia Honeycomb Structures

AbstractA pure TRIP‐steel alloy and a novel zirconia reinforced TRIP‐steel matrix composite were implemented in a 2D square‐celled honeycomb structure fabricated by a paste extrusion method, respectively. In terms of a series of compression tests in out‐of‐plane loading direction the buckling and the pronounced strain hardening behavior of the honeycomb structures are described with regard to different material compositions and varied nominal strain rates. Both the compressive flow behavior and the microstructure evolution in the crushed zones are controlled by the rate of formation of strain‐induced martensite and the ceramic particle/steel matrix interactions. The insertion of magnesia partially‐stabilized zirconia (Mg‐PSZ) particles in the austenitic steel matrix cause an increased yield strength and higher compression stresses up to certain deformations degrees. The limited ductility of the composite materials is a consequence of the rearrangement and fracture of zirconia particles initiating cracks and shear bands during deformation. Consistently, the visible strain rate effects on the mechanical responses of the honeycomb structures are similar to AISI 304L austenitic stainless steel specimens in the form of compact rods. However, at high local strain rates generated in drop weight impact tests a micro‐inertia factor support the failure behavior of the cellular structures.

용존산소활량 측정용 지르코니아 갈바니 센서

Magnesia partially stabilized zirconia(Mg-PSZ) solid electrolytes for an improvement of thermal shock resistance, which is suitable for the measurement of oxygen activity in a molten steel, were prepared by post-thermal aging treatment. The steelmaking oxygen sensor elements were formed by an injection molding method, sintered at <TEX>$1650^{\circ}C$</TEX>, and then thermal aged ranged from 1250 to <TEX>$1400^{\circ}C$</TEX>. Sintered density and porosity were decreased as increasing the magnesia content in a zirconia-magnesia solid solution. Fractions of cubic phase to the synthesized Mg-PSZ solid electrolytes were ranged from 13.13 to 79.54.% after post-thermal aging treatment. Very dense microstructure without voids in the grains was obtained by the post-thermal aging process. Fine tetragonal phase crystallites precipitated on the cubic surface during post-thermal aging up to <TEX>$1300^{\circ}C$</TEX> improve a thermal shock resistance and reappearance of electro motive force(EMF) curve.

Fracture resistance of all‐ceramic crowns placed on a preparation with a slice‐formed finishing line

The purpose of this study was to determine the fracture resistance of all-ceramic crowns with a core of a zirconia ceramic, using various stabilizing oxides and luted on a preparation with a slice-formed finishing line. Ten cores made of HIPed yttrium-oxide partially stabilized zirconia (HIPed Y-TZP) and five cores of densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) were made. The Mg-PSZ cores and five of the HIPed Y-TZP cores were made with a thickness of 0.2 mm. A further five cores 0.1-mm thick were made of HIPed Y-TZP. All 15 cores were then veneered with a feldspar ceramic and luted onto a stylized steel master die model with a slice-formed finishing line. The specimens were then loaded until fracture occurred. The HIPed Y-TZP specimens with the 0.2 mm core exhibited significantly higher fracture resistance than the Mg-PSZ specimens (P = 0.004) and the HIPed Y-TZP specimens with the 0.1 mm core (P = 0.001). The fracture resistance of the Mg-PSZ specimens was significantly (P = 0.015) higher than that of the HIPed Y-TZP specimens with the 0.1 mm core. The fracture resistance determined was equal or superior to reported values for bite forces and all-ceramic crowns. Thus, it seems likely that the type of restorations evaluated have the potential for successful use on a slice-formed preparation. However, long-term studies are essential in order to assess the performance of this ceramic system in a clinical context.

Functionally graded bioactive glass coating on magnesia partially stabilized zirconia (Mg-PSZ) for enhanced biocompatibility

The coating of magnesia partially stabilized zirconia (Mg-PSZ) with a bioactive glass was investigated for enhancing the bioactivity and bone-bonding ability of Mg-PSZ orthopedic implants. Individual coatings of three different bioactive glasses were prepared by depositing a concentrated suspension of the glass particles on Mg-PSZ substrates, followed by sintering at temperatures between 750 degrees C and 850 degrees C. Two silicate-based glass compositions (designated 13-93 and 6P68), and a borosilicate glass composition (H12) were investigated. The microstructure and adhesive strength of the coatings were characterized, and the in vitro bioactivity of the glasses was compared by measuring their conversion kinetics to hydroxyapatite in an aqueous phosphate solution at 37 degrees C. The 6P68 glass provided the highest adhesive strength (40 +/- 2 MPa) but showed very limited bioactivity, whereas the H12 glass had lower adhesive strength (18 +/- 2 MPa) but the highest bioactivity. A functionally graded coating, consisting of a 6P68 interfacial layer and an H12 surface layer, was developed to provide a coating with high adhesive strength coupled with rapid in vitro bioactivity.

A study of the bending resistance of implant-supported reinforced alumina and machined zirconia abutments and copies

Objectives The purpose of the present study was to evaluate the bending resistance of implant-supported CAD/CAM-processed restorations made out of zirconia or manually shaped made out of reinforced alumina. Methods Units of abutments and copies made of (i) a prefabricated hot isostatic pressed (HIPed) yttrium oxide partially-stabilized zirconia (Y-TZP) (Denzir), (ii) a prefabricated densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) (Denzir-M) or, copies made of (iii) a prefabricated partially-sintered, porous reinforced alumina ceramic (RN synOcta-In-Ceram) were subjected to static loading perpendicularly at the long axis. The abutments were attached to either stainless steel analogs or titanium implant fixtures. The Y-TZP and Mg-PSZ copies were bonded onto the ceramic abutments with a dual-cured resin composite (Rely-X Unicem). Units of titanium abutment attached to a titanium implant fixtures were used as reference. Results The units comprising Denzir abutments as delivered ( p < 0.05) and heat-treated Denzir copies bonded to the Denzir abutments as delivered ( p < 0.01) and attached to stainless steel analogs exhibited significantly higher bending resistance than the control. The heat-treated Denzir copies bonded to the heat-treated Denzir M abutments attached to titanium implant fixtures and the In-Ceram specimens attached to stainless steel analogs showed significantly ( p < 0.05) lower bending resistance than the heat-treated Denzir copies bonded to the Denzir abutments as delivered and attached to stainless steel analogs. No statistically significant ( p > 0.05) differences were seen among the other groups studied. Significance All the ceramic abutments and copies exhibited values that were equal or superior to that of the control and exceeded the reported value, up to 300 N, for maximum incisal bite forces. To assess the clinical behavior long-term clinical studies should be conducted.