Zirconia Composites Research Articles

Zircon trace element geochemistry and Ti‐in‐zircon thermometry of the Linté Pan‐African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications

The Linté area belongs to the central part of the Adamawa‐Yadé Domain (AYD) within the Pan‐African Central African Fold Belt (CAFB) in Cameroon. This area is dominated by Neoproterozoic high‐K calc‐alkaline syenite and monzonite intruding Archean to Palaeoproterozoic gneisses. In this contribution, trace element compositions of zircon obtained using laser ablation inductively coupled plasma mass spectrometry are used to constrain the petrogenesis and tectonic setting of Linté area. The analysed zircon grains display restricted ranges of Hf contents with an average of 8,197 ppm in syenite, 8,220 ppm in alkali‐feldspar syenite, and 9,026 ppm in monzonite. They display high Th/U ratios (>0.5) typical of magmatic zircons. The monzonite zircons have a higher ∑REE content (483.42 ppm) than the syenite zircons (237.70 ppm). The chondrite‐normalized rare‐earth element (REE) diagram of Linté samples shows very similar patterns, characterized by a steeply rising slope due to important heavy rare‐earth element enrichment relative to light rare‐earth element, with distinctive positive Ce and negative Eu anomalies. The application of the Ti‐in‐zircon thermometer reveals a wide range of crystallization temperatures (574–1,137°C for syenites and 713–1,008°C for monzonite), implying a deep level of melting, likely within the lower continental crust of the CAFB. The integration of geochemical behaviours of some trace elements (U, Hf, Zr, Ce, Th, and Nb), together with discrimination diagrams, suggests the crystallization of a continental crust‐derived magma under variable oxidation states and emplacement in a magmatic‐arc setting. This finding represents and adds on to the N‐S geodynamic convergence model between the AYD and the northern border of the Congo Craton.

Synthesis and Characterizations of Barium Zirconate–Alkali Carbonate Composite Electrolytes for Intermediate Temperature Fuel Cells

Composite ionic conductors for intermediate temperature fuel cells (ITFC) were produced by a combination of yttrium-substituted barium zirconate (BaZr0.9Y0.1 O2.95, BZY) and eutectic compositions of alkali carbonates (Li2CO3, Na2CO3, and K2CO3, abbreviated L, N, K). These materials were characterized by X-ray diffraction, scanning electron microscopy, and impedance spectroscopy. The combination of BZY with alkali metal carbonate promotes the densification and enhances the ionic conductivity, which reaches 87 mS·cm−1 at 400 °C for the BZY–LNK40 composite. In addition, the increase of the conductivity as a function of hydrogen partial pressure suggests that protons are the main charge carriers. The results are interpreted in terms of the transfer of protons from the ceramic component to the carbonate phase in the interfacial region.

The largest plagiogranite on Earth formed by re-melting of juvenile proto-continental crust

The growth of continental crust through melt extraction from the mantle is a critical component of the chemical evolution of the Earth and the development of plate tectonics. However, the mechanisms involved remain debated. Here, we conduct petrological and geochemical analyses on a large (up to 5000 km2) granitoid body in the Arabian-Nubian shield near El-Shadli, Egypt. We identify these rocks as the largest known plagiogranitic complex on Earth, which shares characteristics such as low potassium, high sodium and flat rare earth element chondrite-normalized patterns with spatially associated gabbroic rocks. The hafnium isotopic compositions of zircon indicate a juvenile source for the magma. However, low zircon δ18O values suggest interaction with hydrothermal fluids. We propose that the El-Shadli plagiogranites were produced by extensive partial melting of juvenile, previously accreted oceanic crust and that this previously overlooked mechanism for the formation of plagiogranite is also responsible for the transformation of juvenile crust into a chemically stratified continental crust.

The Effect of GaAlAs Laser, Sandblasting, and Primers on Bond Strength between Zirconia Ceramic and Direct Resin Composite after Thermocycling

Objective: This study was conducted to evaluate the shear bond strength (SBS) of resin composite on zirconia ceramic after different surface treatments and thermocycling. Material and Methods: Two hundred and seven zirconia specimens were divided into 9 groups and treated as follows: Group C-no treatment (served as the control); Group PC-Clearfil Ceramic primer (CP); Group PZ-Z-Prime Plus primer (ZP); Group A-sandblasted with 50 µm Al2O3 at 0.25 MPa for 20 s at a distance of 10 mm; Group AC-sandblasted and coated with CP; Group AZ-sandblasted and coated with ZP; Group L-GaAlAs diode laser with 808±5 mm wavelength, 3 watts power, and 10 Hz frequency; Group LC-GaAlAs diode laser coated with CP; and Group LZ-GaAlAs diode laser coated with ZP. All specimens were directly bonded with a resin composite cylinder using Adper Scotchbond Multi-purpose. Specimens were stored at 37ºC for 30 days and subjected to 2,500 thermocycles from 5ºC and 55ºC before the SBS was performed. One-way ANOVA and Tukey’s HSD test (=0.05) were performed. Surface topography changes were evaluated with a scanning electron microscope (SEM). Results: Sandblasting combined with CP or ZP (25.08±0.86 and 24.78±0.13 MPa, respectively) yielded the highest SBS and was significantly different from other methods (p<0.05). SEM showed various degrees of changes depending on different surface treatments. Conclusion: Surface treatment by sandblasting combined with a CP or ZP significantly provide the highest SBS between zirconia and resin composite. KEYWORDS Bond strength; Resin composite; Surface treatment; Zirconia ceramic.

U-Pb ages and Hf isotopic compositions of detrital zircons from the Seochangni Formation of the northeastern Okcheon Metamorphic Belt: Implications to the crustal evolution of the Sino-Korean craton since Paleoproterozoic

The age-unknown Seochangni Formation is distributed in the northeastern part of the Okcheon Metamorphic Belt in central South Korea. It unconformably overlies the Paleoproterozoic Busan gneiss complex exposed as a small dome and is in contact with the Cambrian-Ordovician Joseon Supergroup of the Taebaeksan Basin to the east. We separated detrital zircons from the quartzite units of the Seochangni Formation and used SHRIMP and LA-MC-ICPMS to determine their UPb ages and Hf isotopic compositions. The UPb age distribution of the detrital zircons is divided into two types. In the main type, the ages of Late Paleoproterozoic to Mesoproterozoic are dominant, whereas they have little or no older age components of about 1.87Ga and 2.5Ga, which are characteristic of the Korean peninsula basement rocks. However, the minor type has age components of 0.75 Ga and 1.87 Ga. Age patterns similar to the former type have recently been reported in the western region of the Gyeonggi Massif on the Korean peninsula, as well as in the Sangwon System in North Korea and the southern margin of North China Craton. It suggests a correlation between them and a common crustal evolution within a single craton linked since the Paleoproterozoic. The high positive εHf(t) values of detrital zircons in the Late Paleoproterozoic to Mesoproterozoic period indicate an enhanced input of juvenile materials from the depleted mantle, reflecting the igneous activity associated with the breakup of the supercontinent Columbia.

Studying the Damage Evolution and the Micro-Mechanical Response of X8CrMnNi16-6-6 TRIP Steel Matrix and 10% Zirconia Particle Composite Using a Calibrated Physics and Crystal-Plasticity-Based Numerical Simulation Model

The mechanical behavior of newly developed composite materials is dependent on several underlying microstructural phenomena. In this research, a periodic 2D geometry of cast X8CrMnNi16-6-6 steel and 10% zirconia composite is virtually constructed by adopting microstructural attributes from literature. A physics-based crystal plasticity model with ductile damage criterion is used for defining the austenitic steel matrix. The zirconia particles are assigned elastic material model with brittle damage criterion. Monotonic quasi-static tensile load is applied up to 17% of total strain. The simulation results are analyzed to extract the global and local deformation, transformation, and damage behavior of the material. The comprehensively constructed simulation model yields the interdependence of the underlaying microstructural deformation phenomena. The local results are further analyzed based on the interlocked and free regions to establish the influence of zirconia particles on micro-mechanical deformation and damage in the metastable austenite matrix. The trends and patterns of local strain and damage predicted by the simulation model results match the previously carried out in-situ tensile tests on similar materials.

Multicomponent oxide composites for carriers in catalytic applications

AbstractBinary, ternary, and quaternary composite oxides of rare earths (La and Ce) with one or more of aluminum, magnesium, and zirconium, prepared by coprecipitation are studied. Potential use is carrier in steam or dry reforming of hydrocarbons and ethanol. Individual components influence specific surface area, porosity, acidity, hydrothermal stability, and oxygen storage capacity (OSC) differently. Interaction effects between components further influence these properties resulting in unexpected trends. Alumina and magnesia form solid solutions with zirconia until 650℃. Magnesia imparts better hydrothermal stability to zirconia. Aluminum and magnesium form MgAl2O4 spinel in ternary composites. Specific surface area varies linearly with alumina content. Alumina influences porosity, whereas magnesia influences pore diameter. The composites are mesoporous. Only binary composites present unimodal, pore size distribution. Composites containing alumina present type H2 isotherms while the remaining composites present H3 type isotherms. OSC increases over ZrO2/CeO2 5.7 to 15.3 molar. Magnesia and alumina affect microstructure and hydrothermal stability in contrasting ways. Thermogravimetry indicates that ternary composites of zirconia with alumina or magnesia form through oxolation. Surface hydroxyls with varying acidity are seen by FTIR in as synthesized samples. Magnesia and zirconia influence acidity in opposite ways, which impacts deactivation in the decomposition of 2‐methyl‐3‐butyn‐2‐ol.

Characterization of in-situ zirconia/mullite composites prepared by sol-gel technique

ABSTRACT The main objective of this study was to investigate the role of zirconia addition to mullite through an in-situ reaction aimed at improving both the mechanical properties and the sinterability behavior. In this work, mullite–zirconia composites were produced using a sol-gel technique. Different amounts of zirconia (0, 10, 15, and 20 wt.%) were added to the mullite, and the calcined gels were sintered at 1550–1700°C for 1 h. The apparent porosity and bulk density of the blank and zirconia/mullite composites were estimated in accordance with ASTM C-20. The phase composition and sample morphology were evaluated via X-ray diffraction (XRD) and scanning electron microscopy analysis (SEM), respectively. Furthermore, the mechanical properties and thermal expansion coefficient (TEC) were also evaluated. The results revealed that the apparent porosity decreased and the density of the zirconia/mullite composites increased when the sintering temperature was increased from 1550 to 1700°C. However, the mechanical properties improved with increasing zirconia content and MZ20 sintered at 1700°C exhibited the maximum bending strength. The TEC results reflected the influence of the composition on the sample TEC. Samples with higher ZrO2 content yielded higher TEC figures than those with lower content.

Zircon record of an Archaean crustal fragment and supercontinent amalgamation in quaternary back-arc volcanic rocks

Magmatism has profoundly influenced the evolution of the geosphere, hydrosphere, atmosphere, and biosphere in back-arc basins. However, the timing of the magmatism in the Okinawa Trough (OT) is not well constrained by the age spectra of zircons. Here, for the first time, we carry out an integrated study combining in situ analysis of zircon U–Th–Pb and Hf–O isotopes, and trace element compositions of zircons from the volcanic rocks from the southernmost part of the OT. We found that the young (< 100 ka) zircons in these volcanic rocks have old (108 Ma to 2.7 Ga) inherited cores, which were captured as the magma ascended through the rifting continental crust. In particular, the inherited Archean zircons strongly suggest that remnants of the old East Asian continental blocks underlie the embryonic crustal rifting zone. Moreover, the ages of most of the inherited zircons correspond to five supercontinent amalgamation events. Specifically, the Archaean inherited zircons, which have positive εHf(t) and low δ18O values, correspond to the formation of juvenile continental crust. In contrast, the negative εHf(t) and high δ18O values of the post-Archaean inherited zircons indicate that their parental magma contained recycled older crust due to the enhanced crust-mantle interactions during the evolution of the early continental crust. Therefore, the inherited zircons in the back-arc volcanic rocks not only reflect the evolution of the local magmatism, but they also contain a record of the Archaean crustal fragment and of several global continental amalgamation events.

Leveraging detrital zircon geochemistry to study deep arc processes: REE-rich magmas mobilized by Jurassic rifting of the Sierra Nevada arc

Anomalous trace element compositions of Middle to Late Jurassic detrital zircon separated from Sierra Nevada forearc and intra-arc strata reveal processes of differentiation occurring within the deep arc lithosphere. REE-Sc-Nb-Ti-Hf-U-Th covariations define three populations of atypically REE-rich grains that we interpret as crystallizing from (1) differentiates produced by olivine+clinopyroxene+plagioclase+garnet±ilmenite fractionation; (2) mixing between mafic arc magmas and partial melts of Proterozoic Mojave province crust; and (3) compositionally transient, low Gd/Yb magmas generated by hornblende resorption during decompression. We interpret a fourth population of Middle Jurassic to Early Cretaceous zircons having REE contents similar to “typical” arc zircon but with atypically high Gd/Yb ratios as having crystallized from partial melts of recycled arc crust and from deep-arc differentiates that evolved down-temperature through hornblende saturation. We hypothesize that latest Jurassic extension ripped open the arc, facilitating upward migration and eruption of geochemically anomalous zircon-bearing magmas. The anomalous compositions relative to “typical” arc zircon imply that these zircons and their host magmas rarely reach the upper arc crust, where eruption and/or erosion would release their zircon cargo to the clastic system. Focusing on the trace element compositions of zircons of syn-extensional age represents a productive new strategy for learning about deep magmatic reservoirs and early differentiation pathways within the thick lithosphere of continental margin arcs.

Force-displacement analysis of PMMA/zircon composites using dynamic mechanical analyzer (DMA)

In the study, poly(methyl methacrylate) (PMMA)/zircon (ZrSiO4) composites were successfully prepared using the liquid method at different compositions of 1, 2.5, and 5 wt% of zircon. The zircon filler was processed from a natural, local zircon sand and was processed via a top-down method using wet ball-milling for 5 and 15 h as well as annealing at temperature of 200 °C for 1 h. The force-displacement curves of the composites have been acquired using a DMA (dynamic mechanical analyzer) technique in tensile mode. XRD (x-ray diffraction) data of the composites were collected and analyzed in order to examine the present phases and used as the evidence of the formation of the composites. Furthermore, MAUD software was used to estimate the crystallite size of the filler. Results indicated that zircon crystallite size for 15 h wet ball-milling was smaller than that of 5 h. Furthermore, the maximum DMA force (also representing stress) for the composite with smaller filler was generally higher than that of 5 h, ca. by 2.5 times. In addition, in general, the composites exhibited an increasing slope of force-displacement curve with increasing amount of filler.

Effect of Adding Silver Element and Zirconia Ceramic on Corrosion Behavior and Mechanical Properties of Pure Titanium

In this research, all the samples are prepared using the powder metallurgy technique by adding silver element and Zirconia ceramic material to the commercially pure titanium at a different weight percent of (10, 20 and 30) to investigate the effect of adding these materials to the CP-Ti on corrosion behavior and mechanical properties. There are two sets of each type of alloys Ti-Ag and Ti ZrO2. The Preparation process was by Weighing, Mixing and Homogenizing Powders by Ball Mill, compacting at 4 tons for 1 min. and Sintering at 700 and 900 °C for 2 hrs. under a controlled atmosphere. The corrosion results showed a good corrosion resistance increases with increasing the silver content as the corrosion rate would be the best in (30% Ag) content with(0.091 mpy) at sintering temperature of 700 °C. And with a sintering temperature of 900 °C, the best result was with (30% Ag) with (0.059) mpy. In the Ti-ZrO2 alloys, the best result was with the zirconia content of (30%ZrO2) when cooled in the air with (1.347) mpy at sintering temperature of 700 °C, this results obtained in Ringer’s solution. And microstructures analysis stated that at the silver and the Zirconia content of (10-20 wt%) single phase of (α- Ti alloy), as the silver and Zirconia content increased to (30% wt), in addition to (α-phase), (Ti2Ag) intermetallic compound developed in the silver alloy microstructure and (TiZr)3O intermetallic compound developed in the microstructure of Ti- Zirconia composites and the hardness test result best hardness of...

On the petrogenesis of Paleoarchean continental crust: U-Pb-Hf isotope and major-trace element constraints from the Bastar Craton, India

Combined geochronological and (isotope) geochemical investigations of tonalite-trondhjemite-granodiorite (TTG) suites, which dominate Archean cratons, provide constraints on the sources and petrogenetic processes that gave rise to the Earth's early continental crust. In situ U-Pb and bulk Lu-Hf analyses of single zircon grains from TTGs of the Paleoarchean Bastar Craton in central India date the emplacement of the igneous rock suite and trace the chemical evolution of its source rocks. Complementary whole rock Lu-Hf and major and trace element data constrain the petrogenesis of the TTGs. The rocks are variably enriched in fluid mobile elements, particularly K and Pb, and are characteristically depleted in heavy rare earth elements. Calculated initial Hf isotopic compositions of zircon and whole rocks cluster around the chondritic value at ca. 3.55 to 3.45 Ga. The high precision Hf-isotope data reveal a trend of increasing radiogenic 176Hf/177Hf with age, the slope of which implies a 176Lu/177Hf = 0.02, and thus derivation from a mafic protolith. Geochemical modeling indicates that the granitoids can be directly produced by melting of a hydrous basalt in the garnet stability field, followed by minor fractional crystallization. Variations in the modal abundance of garnet suggest the source rocks melted at different depths. Rocks with moderately to strongly depleted HREE patterns require >10% garnet in the residue, consistent with derivation from a garnet-amphibolite or garnet-pyroxenite source. Modeling of the Lu-Hf systematics further highlights the important role of melting as opposed to fractional crystallization for reproducing the primary chemical characteristics of TTGs.The global Hf-isotope record of Archean mantle-derived rocks is considerably more radiogenic than that of the bulk silicate Earth, providing unambiguous evidence that parts of the mantle were significantly depleted in incompatible elements since at least the early Archean. The differences between Hf isotopic compositions of the mafic (greenstone belts) and felsic (gneissic terranes) rocks can be accounted for by crustal residence times of several 100 million years for the protoliths of the felsic magmatic suites. Consequently, TTGs integrate the geologic history of their precursor(s), complicating their isotopic record. Therefore, the near-chondritic Hf isotopic composition of TTGs is not direct evidence for their derivation from a primitive mantle, but rather a consequence of their specific petrogenesis involving an aged, mafic precursor. This relationship introduces uncertainties into models of crustal growth and geodynamics that are based on the felsic record, especially where the whole rock context is absent. In contrast, high-precision Hf-isotope analyses of single zircon grains, combined with whole rock isotope and elemental constraints, can be used to reliably identify the sources and processes involved in the generation of Earth's oldest continental crust.

Genesis and mineralization potential of the Late Cretaceous Chemen granodioritic intrusion in the southern Gangdese magmatic belt, Tibet

• The ~91 Ma Chemen intrusion represents a magmatic product of the Late Cretaceous Gangdese magmatic ‘flare-up’ event. • The Chemen intrusion was derived from partial melting of Neo-Tethys oceanic crust during ridge subduction . • Compositions of zircon and apatite indicate that the Chemen intrusion has a high mineralization potential. • The mineralization potentials of some other Late Cretaceous intrusions may be limited due to low magma oxygen fugacities. Large-scale Late Cretaceous magmatic intrusions have been recognized in the southern Gangdese magmatic belt, although their genesis and mineralization potential remain controversial. In this paper, we present new zircon U-Pb ages, whole-rock compositions, and major- and trace element compositions of zircon and apatite from the Chemen granodioritic intrusion. When integrated with compiled literature data for other Late Cretaceous igneous rocks in the southern Gangdese belt, our new dataset provides new insight into their genesis and mineralization potential. The Chemen intrusion obtains a zircon U–Pb age of ~91 Ma, similar to the age of Late Cretaceous magmatic intrusions across the entire southern Gangdese belt. Both the Chemen and other Late Cretaceous intrusions have geochemical characteristics that resemble those of adakites. When considered alongside the coeval formation of mafic intrusive rocks, high-temperature adakitic charnockites, and thickening of continental crust in the region, ridge subduction is considered most likely to be responsible for this ‘flare-up’ event. The Ce 4+ /Ce 3+ ratios in zircon and SO 3 contents of apatite from the Chemen granodiorites both indicate a high oxygen fugacity during crystallization. Further, trace elements in Chemen apatite indicate that the Chemen intrusion has a great mineralization potential; however, no mineralization has been found in some of the Late Cretaceous intrusions in the southern Gangdese belt. Compiled data show that these barren Late Cretaceous intrusions generally formed from magmas with a low oxygen fugacity. Thus, we speculate that the low oxygen fugacity of some Late Cretaceous intrusions may limit the extent to which mineralization may occur.

Metasomatism of the Kaapvaal Craton during Cretaceous intraplate magmatism revealed by combined zircon U-Pb isotope and trace element analysis

The origins of the mica-amphibole(K-richterite)-rutile-ilmenite-diopside (MARID) and the, presumably related, phlogopite-K-richterite-peridotite (PKP) mantle xenolith suites remain enigmatic. For instance, it is unclear if MARID rocks represent pervasively metasomatised peridotite or veins of magmatic material. In the Kaapvaal Craton, previous studies employing zircon U-Pb dating in MARID and PKP xenoliths demonstrated that ages of zircon are broadly coincident with nearby expressions of Cretaceous kimberlite and orangeite magmatism, implying a genetic link. However, the use of typically small sample sizes (i.e. few analysed grains) in previous studies may mask complexities in the growth history of zircon in mantle lithologies, as key populations may remain undetected. In this paper, we analyse the isotopic (U-Pb) and trace element composition of zircon (n > 40) from three MARID/PKP rocks from the Kimberley region of the Kaapvaal Craton, in order to reveal not just the timing, but the tempo of metasomatism. This protocol takes its inspiration from studies of detrital zircon in clastic sedimentary rocks, in which large numbers of grains are typically dated, so that no important parts of the zircon U-Pb record are missed.Our data show that zircon growth is broadly coincident with nearby expressions of Cretaceous kimberlite magmatism and orangeite magmatism. While the range of zircon U-Pb ages we detect mirrors the range detected by previous workers, the addition of larger sample sizes means we can detect that zircon growth was episodic. By integrating trace element data with zircon ages, we demonstrate that older zircon, generally has greater geochemical affinity to lamproitic zircon. By contrast, most zircons with ages coincident with peak kimberlite magmatism have trace-element compositions similar to megacrystic zircon - a suite of zircon crystals thought to be connected to early high-pressure proto kimberlitic liquids/fluids.These data strongly indicate that MARID and PKP rocks form during localized and recurrent melting of enriched lithosphere. The metasomatizing effects of the passage of varying magmas at shallow depth in the lithosphere may also contribute to their complex age and geochemical signatures. The presence of zircon with U-Pb ages that span the entire range of Cretaceous intra-cratonic magmatism nearby to Kimberley, and trace element compositions that derive from both major phases of intracratonic magmatism in a single MARID xenolith, necessitates a more complex origin for the MARID suite than that of a simple magmatic cumulate. This observation argues for a complex origin for zircon in MARID and presumably PKP rocks.

Cosmogenic noble gas nuclides in zircons from the Estherville mesosiderite

AbstractZirconium produces cosmogenic Kr through spallation reactions with cosmic rays. Meteoritic zircons (ZrSiO4) therefore possibly contain a significant amount of cosmogenic Kr in addition to other cosmogenic nuclides. Detection of cosmogenic nuclides from meteoritic zircons would make it possible to determine precise cosmic ray exposure (CRE) ages without knowing the whole rock chemistry because of the robust nature of zircons and limited target elements that produce cosmogenic nuclides in a zircon crystal. Herein, we report the noble gas compositions of zircons separated from the Estherville mesosiderite in addition to those of the silicate and metal parts. The zircons contain cosmogenic noble gas nuclides, and more importantly, cosmogenic 81Kr (t1/2 = 2.29 × 105 years) was successfully detected in the zircons. The 81Kr‐Kr exposure age of the zircons was calculated to be 76 ± 5 million years (Ma). This age corresponds to the CRE ages obtained from cosmogenic 3He and 21Ne (82 ± 8 and 88 ± 9 Ma, respectively) of the silicate part and the previously reported 36Cl‐36Ar age of the metal part (77 ± 9 Ma). The consistent CRE ages using different dating methods demonstrate that the 81Kr‐Kr dating using meteoritic zircons is a new promising tool for determining the CRE age of meteorites. Moreover, based on the 81Kr‐Kr age of the zircons, the production rates of cosmogenic 3He and 21Ne in a meteoritic zircon were estimated to be (15 ± 2) × 10−9 and (0.69 ± 0.04) × 10−9 cm3 STP g−1 Ma−1, respectively.

Effect of Sintering Temperature to the Mechanical Properties of Different Filler Loading of Zirconia Powder in Hydroxyapatite Composites

Hydroxyapatite (HA)-Zirconia (ZrO2) composite with varying zirconia composition ranging from 1 to 10 wt% was investigated for biomedical applications in order to produce high compressive strength. Precipitation method was used to prepare both hydroxyapatite and zirconia powders. To find the ideal composition, mixture-containing 1, 3, 5 and 10 wt% ZrO2 powder was added. Each mixture was sintered for 4 hours at 750oC, 1050oC and 1250oC. Hardness and compressive strength test were used for evaluation. It was found that with 1 wt% of ZrO2 sintered at 1250oC showed the greatest structural strength as its volume fraction porosity is the lowest. The hardness and compressive strength of this sample were found to be 2.75 GPa and 72.0 MPa respectively. This can be useful for biomedical applications especially in promoting osteo-integration.

Tensile Strength of PMMA/n-ZrSiO&lt;sub&gt;4&lt;/sub&gt; Composites Using Dynamic Mechanical Analyzer (DMA)

This study aimed to determine the tensile strength and strain properties of poly(methyl methacrylate) (PMMA)/nano-zircon (n-ZrSiO4) composites with various nano-zircon sizes. Wet milling method for 5 and 15 h without annealing treatment was used to obtain the nano-zircon powders. Results showed that milling for 15 hours can reduce zircon size up to 93 nm. Meanwhile, the composites were synthesized with zircon compositions of 1, 2.5, and 5 wt.%. Dynamic Mechanical Analyzer (DMA) measurement were carried out to characterize the tensile-strain dependence on filler compositions of the PMMA/n-ZrSiO4 composites. The PMMA/n-ZrSiO4 composite with 5 wt.% and 15h milling zircon exhibited the highest tensile strength, ca. 10.02 MPa or 2 times of the pure PMMA. The tensile strength of the composites can be explained from the mean size and size distribution of the filler.

Generation of Cretaceous high-silica granite by complementary crystal accumulation and silicic melt extraction in the coastal region of southeastern China

Abstract It is generally hypothesized that high-silica (SiO2 &amp;gt; 75 wt%) granite (HSG) originates from crystal fractionation in the shallow crust. Yet, identifying the complementary cumulate residue of HSG within plutons remains difficult. In this work, we examine the genetic links between the porphyritic monzogranite and HSG (including porphyritic granite, monzogranite, and alkali feldspar granite) from the coastal area of southeastern China using detailed zircon U-Pb ages, trace elements, Hf-O isotopes, and whole-rock geochemistry and Nd-Hf isotopic compositions. Zircon U-Pb ages indicate that the porphyritic monzogranite and HSG are coeval (ca. 96–99 Ma). The HSG and porphyritic monzogranite have similar formation ages within analytic error, identical mineral assemblages, similar Nd-Hf isotopic compositions, and consistent variations in their zircon compositions (i.e., Eu/Eu*, Zr/Hf, and Sm/Yb), which suggests that their parental magma came from a common silicic magma reservoir and that the lithological differences are the result of melt extraction processes. The porphyritic monzogranite has relatively high SiO2 (70.0–73.4 wt%), Ba (718–1070 ppm), and Sr (493–657 ppm) contents, low K2O and Rb concentrations and low Rb/Sr ratios (0.1–0.2), and it displays weak Eu anomalies (Eu/Eu* = 0.57–0.90). Together with the petrographic features of the porphyritic monzogranite, these geochemical variations indicate that the porphyritic monzongranite is the residual silicic cumulate of the crystal mush column. The HSG (SiO2 = 75.0–78.4) has variable Rb/Sr ratios (2–490) and very low Sr (1–109 ppm) and Ba (9–323 ppm) contents. Zircon from the HSG and porphyritic monzogranite overlap in Eu/Eu*, Zr/Hf, and Sm/Yb ratios and Hf contents; however, some zircon from the HSG show very low Eu/Eu* (&amp;lt;0.1) and Zr/Hf ratios. These features suggest that the HSG represents the high-silica melt that was extracted from a crystal-rich mush. The injection of mantle-derived hotter mafic magma into the mush column and the exsolution of F/Cl−-enriched volatiles (or fluids) from the interstitial melt rejuvenated the pre-existing highly crystalline mush. Subsequent extraction and upward migration of silicic melt resulting from compaction of the mush column formed the HSG at shallow crustal levels, which left the complementary crystal residue solidified as porphyritic monzogranite at the bottom.

Effect of water on δ18O in zircon

The mineral zircon is stable across a wide range of temperature and pressure conditions, and the most widely used geochronometer in felsic rocks. The oxygen isotope ratio recorded by zircon crystals is a sensitive tracer for crustal recycling in magmatic rocks and is a commonly used tool to address zircon petrogenetic questions (e.g. in studies on the evolution of geodynamics and continents). However, secondary processes (i.e. water uptake facilitated by radiation damage) can alter the oxygen isotopic composition of zircon. We present in-situ oxygen isotopic and 16O1H/16O data of natural zircon samples in combination with zircon trace element concentrations, and parameters that quantify crystal damage (i.e. Raman spectral parameters and alpha dose). In agreement with previous studies, our results demonstrate that the uptake of water into the zircon crystal structure strongly influences its recorded oxygen isotope ratio. Two distinct secondary processes are recorded which shift zircon δ18O values towards isotopically heavier and lighter values, respectively. Lower δ18O values associated with broadening of the zircon Raman bands and increasing 16O1H/16O are the result of a local charge-balance process during the interaction of radiation-damaged zircon with meteoric water. In contrast, an equilibrium fractionation process between zircon and percolating water leads to higher δ18O values with increasing 16O1H/16O. The disturbance of the oxygen isotopic system in zircon can be assessed through monitoring zircon 16O1H/16O; a parameter that is highly sensitive to the influx of water into radiation-damaged areas of the zircon grain, providing a powerful tool to access the validity of primary δ18O signatures.