Showing papers in "International Journal of Applied Ceramic Technology in 2008"
TL;DR: In this article, the authors used the laser-engineered net-shaping (LENS) process to fabricate dense, net-shaped structures of α-Al 2 O 3.
Abstract: Application of rapid prototyping (RP) in ceramics manufacturing is motivated by advances in engineering ceramics where attaining complex shapes using traditional processing is difficult. Laser Engineered Net Shaping (LENS™), a commercial RP process, is used to fabricate dense, net-shaped structures of α-Al 2 O 3 . Shapes such as cylinder, cube, and gear have been fabricated successfully with 10-25 mm section sizes. As-processed structures show anisotropy in mechanical properties with a high compressive strength normal to the build direction and columnar grains along the build direction. Heat treatment did not alter strength and anisotropy, but increased the grain size from 6 to 200 μm and hardness from 1550 to 1700 Hv.
158 citations
TL;DR: In this article, a method for engraving an image on a surface of an article selected from a group consisting of a group of bricks, ceramic tile, concrete pavers and natural stone articles was proposed.
Abstract: A method for engraving an image on a surface of an article selected from a group consisting of brick, ceramic tile, concrete pavers and natural stone articles, comprising providing a laser engraving apparatus comprising a steerable laser beam, steering the laser beam continuously over a first beam path on the surface to provide an engraved image and repeatedly traversing the laser beam over a path substantially parallel to the first beam path and incrementally spaced therefrom to define a perimeter of the engraved image. The method further comprises steering the laser beam within an infill area defined by the perimeter of the engraved image to provide a plurality of engraved segments extending within infill area.
109 citations
TL;DR: A review of research activities to improve fracture toughness of alumina matrix systems and the enhancements achieved can be found in this paper, where the authors present a review of the research activities pursuant to improving fracture toughness.
Abstract: Investigations have been carried out to determine ways of tailoring ceramic materials in order that one or more toughening mechanisms are activated in service. Microstructural manipulations, as well as composite formulations involving metallic, intermetallics, and ceramic phases have been used with ceramic matrices. Macrostructurally, laminated structures and functional gradient materials (FGMs) have also been formulated to enhance mechanical properties. Although significant improvements in material properties have been reported, ceramics are still below their projected positions on the materials map. This article presents a review of research activities pursuant to improving fracture toughness of alumina matrix systems and the enhancements achieved.
95 citations
TL;DR: In this article, the porosities of YSZ ceramics with PVA addition were higher than those of non-PVA addition, and the compressive strength of porous yttria-stabilized ziroconia (YSZ) was found to range from 23.57 to 63.86 MPa.
Abstract: Porous yttria-stabilized ziroconia (YSZ) ceramics were fabricated by freeze casting using aqueous ceramic slurries. Polyvinyl alcohol (PVA) was added to the slurry with the aim of controling the microstructures and properties of the porous YSZ ceramics. The experimental results indicated that the large and noninterconnected lamellar pores of YSZ ceramics without PVA transformed changed into small and interconnected lamellar pores with PVA addition. The porosities of YSZ ceramics with PVA addition were higher than those of YSZ ceramics without PVA addition. The compressive strength of porous YSZ ceramics is the range from 23.57 to 63.86 MPa. All specimens exhibit noncatastrophic failure behaviors.
88 citations
TL;DR: In this paper, a porosity-filled polytetrafluoroethylene (PTFE) composite was used as the matrix and the dispersion of CeO2 in the composite was varied up to 0.6 by volume fraction, and the dielectric properties were studied at 1 and microwave frequencies.
Abstract: Cerium oxide (CeO2) filled polytetrafluoroethylene (PTFE) composites prepared by powder processing technique for microwave substrate application is presented in this paper. The PTFE is used as the matrix and the dispersion of CeO2 in the composite is varied up to 0.6 by volume fraction, and the dielectric properties were studied at 1 MHz and microwave frequencies. The relative permittivity and dielectric loss increased with increase in CeO2 content. For 0.6 volume fraction loading of the ceramic, the composite has ɛr of 5 and tan δ of 0.0064 at 7 GHz. Different theoretical approaches have been employed to predict the effective permittivity of composite systems and the results were compared with that of experimental data. The serial mixing model shows good correlation with the experimental results.
85 citations
TL;DR: In this paper, the microstructures and mechanical properties of Si 3 N 4 made by fused deposition of ceramics (FDC) were investigated using optical microscopy, scanning electron microscopy and X-ray diffraction.
Abstract: We present processing (green and sintered), part shrinkage and warping, microstructural characterization, and mechanical properties of Si 3 N 4 made by fused deposition of ceramics (FDC), using optical microscopy, scanning electron microscopy, and X-ray diffraction. The mechanical properties (fracture strength, fracture toughness, and Weibull modulus) are also reported. Proper FDC build parameters resulted in dense, homogeneous, near-net-shape Si 3 N 4 , with microstructures and mechanical properties similar to conventionally processed material. Mechanical properties are shown to be isotropic, while there is some degree of microstructural texturing (preferred β-Si 3 N 4 grain orientation) in sintered components.
60 citations
TL;DR: Sintered reaction-bonded silicon nitride (SRBSN) materials were prepared from a high-purity Si powder doped with Y2O3 and MgO as sintering additives by nitriding at 1400°C for 8h and subsequently postsintering at 1900°C with various times ranging from 3 to 24h as mentioned in this paper.
Abstract: Sintered reaction-bonded silicon nitride (SRBSN) materials were prepared from a high-purity Si powder doped with Y2O3 and MgO as sintering additives by nitriding at 1400°C for 8 h and subsequently postsintering at 1900°C for various times ranging from 3 to 24 h. Microstructures and phase compositions of the nitrided and the sintered compacts were characterized. The SRBSN materials sintered for 3, 6, 12, and 24 h had thermal conductivities of 100, 105, 117, and 133 W/m/K, and four-point bending strengths of 843, 736, 612, and 516 MPa, respectively. Simultaneously attaining thermal conductivity and bending strength at such a high level made the SRBSN materials superior over the high-thermal conductivity silicon nitride ceramics that were prepared by sintering of Si3N4 powder in our previous works. This study indicates that the SRBSN route is a promising way of fabricating silicon nitride materials with both high thermal conductivity and high strength.
48 citations
TL;DR: In this article, the same porous aggregates and different matrices by converter slag (C/S = 3) were conducted using the static crucible test through the counting pixels method, XRD, SEM, EDAX, and so on.
Abstract: Corrosion of five corundum-spinel castables containing the same porous aggregates and different matrices by converter slag (C/S = 3) was conducted using the static crucible test through the counting pixels method, XRD, SEM, EDAX, and so on. It was found that the corrosion and penetration resistance depend on the microsilica content. Microsilica content strongly affects liquid phase formation in the matrix, changes the porosity, pore size distribution of matrix, and viscosity of slag penetrated, and thus affects its corrosion and penetration resistance. Increasing microsilica, decreasing the porosity, or increasing the viscosity of the penetrating slag improves, whereas increasing the pore size or liquid content reduces the penetration and corrosion resistance. The penetration resistance increased abruptly with an increase of the microsilica content from 0.65 to 1.95 wt%, but changed slightly with increase of the microsilica content from 1.95 to 3.90wt%. The corrosion resistance increased with an increase of the microsilica content from 0 to 2.60 wt%, but slightly decreased with a further increase of the microsilica content to 3.90wt%. 1.95-2.60 wt% microsilica leads to a compromise between low corrosion and low penetration.
47 citations
TL;DR: In this article, ZnO nanorod arrays were synthesized on a seeded substrate using the aqueous solution method, and the growth rate, morphology, and crystallinity of the arrays were controlled by tailoring various process parameters and the [Zn(NO3)2]/[C6H12N4] ratio.
Abstract: In this study, ZnO nanorod arrays were synthesized on a seeded substrate using the aqueous solution method. The growth rate, morphology, and crystallinity of ZnO nanorods were controlled by tailoring various process parameters and the [Zn(NO3)2]/[C6H12N4] ratio. A high density of ZnO nanorods with well-defined hexagonal facets (002) were grown almost vertically over the entire substrate surface in all cases. The largest growth rate of length was observed in the ZnO nanorods grown in solution with a [Zn(NO3)2]/[C6H12N4] ratio in the vicinity of 1, which corresponds to an environment of small excess NH3, or OH− ions, while the change in diameter of the nanorods was insignificant with the [Zn(NO3)2]/[C6H12N4] ratio. In the solution of [Zn(NO3)2]/[C6H12N4]=5, ZnO nanorod arrays with a high concentration of oxygen vacancy were formed, due to the deficiency of C6H12N4 and thus OH− concentration. The average diameter and length of ZnO nanorods increased from 43 to 70 nm and from 65 to 320 nm, respectively, as the precursor concentration was increased from 0.008 to 0.04M. Mechanical stirring of the solution doubles the growth rate and enhances the crystallinity of ZnO nanorods, because stirring reduces the thickness of the Zn2+ depletion layer surrounding the fast-growing (002) surfaces of ZnO nanorods. Both the radial and the axial dimensions increased almost linearly with the reaction time up to 240 min. The growth rates of diameter and length are 0.21 and 2.16 nm/min, respectively.
46 citations
TL;DR: In this article, the authors investigated the effect of CMAS penetration on the thermal barrier coatings on the turbine blades and vanes of gas turbines and showed that silicate infiltration of an electron beam-deposited TBC can increase radiative transport through the coating.
Abstract: One of the adverse effects of sand ingestion in gas turbines is that the thermal barrier coatings on the blades and vanes can be infiltrated at high temperatures by molten calcium–magnesium–aluminum–silicate (CMAS) and cause premature failure of the coating. To investigate the effect of CMAS penetration, the optical properties of a synthetic glass representative of CMAS are reported from 500 nm to 2.5 μm. Results are then presented to show that silicate infiltration of an electron beam-deposited TBC can increase radiative transport through the coating. The results are qualitatively consistent with a simple optical scattering model for radiative transport through a porous coating.
46 citations
TL;DR: In this article, a laminar-structured YAG/YAG transparent ceramic was fabricated by a solid-state reaction method and vacuum sintering using high-purity α-Al 2 O 3, Y 2O 3, and Nd 2 O3 as raw materials with tetraethoxysilane as a sintered aid.
Abstract: A laminar-structured YAG/1.0 at.% Nd:YAG/YAG transparent ceramic was fabricated by a solid-state reaction method and vacuum sintering using high-purity α-Al 2 O 3 , Y 2 O 3 , and Nd 2 O 3 as raw materials with tetraethoxysilane as a sintering aid. The microstructure, the optical property, and the laser performance of the ceramic composite prepared were investigated in this paper. It is found that the sample exhibits a pore-free structure and the average grain size is about 15 μm. There is no secondary phase both at the grain boundary and at the grain matrix. The optical transmittance of the sample (5.0 mm thick) is 80.2% at 1064 nm. The lasing sample is Φ16.2 mm x 5.0 mm in size, mirror polished on both sides and without a coating. A laser diode (808 nm) was used as a pump source with a maximum output of about 1000 mW, and the end-pumped laser experiment was demonstrated. With 658 mW of maximum absorbed pump power, a laser output of 8 mW has been obtained with a slope efficiency of 4.0%.
TL;DR: In this paper, the sintering behavior of these nanoparticles have been investigated and compared with the commercially obtained mixed phase (86% anatase+14% rutile) nanopowders of TiO2.
Abstract: Nanopowders of phase pure TiO2 (rutile) have been synthesized by hydrothermal method using dilute nitric acid as a peptizer. The nanoparticles exhibited bimodal morphological features. The sintering behavior of these nanoparticles have been investigated and compared with the commercially obtained mixed phase (86% anatase+14% rutile) nanopowders of TiO2. The hydrothermally synthesized nanopowders were found to sinter to nearly 90% of the theoretical density at approximately 850°C and still maintain nanostructured grains. This is important for the application of these materials for gas sensors, disinfectants, and as photocatalysts. The nanopowders of TiO2 synthesized by hydrothermal method have superior physical and microstructural features compared with commercial nanopowders. It is possible to scale up the process with relative ease and at much lower capital cost.
TL;DR: In this paper, a multicomponent thermoplastic binder system for injection molding of yttria-stabilized zirconia (8-YSZ) bars based in polypropylene and paraffin wax (PW) is presented.
Abstract: The development of a new multicomponent thermoplastic binder system for injection molding of yttria-stabilized zirconia (8-YSZ) bars based in polypropylene and paraffin wax (PW) is presented in this paper. The surface coating of YSZ powder with stearic acid in a high-performance dispersing instrument reduced the viscosity of the feedstock by one order of magnitude with respect to a feedstock with the same composition and uncoated powder. This fact allowed us to obtain a feedstock with a viscosity curve more suitable for the injection process without requiring high proportions of PW in the binder composition. The density of the samples was >98% and the conductivity of sintered parts are comparable to those of samples uniaxially compacted, around 0.10 S/cm at 900°C.
TL;DR: In this article, a sol-gel route using calcium acetate and triethyl phosphate as precursors of hydroxyapatite and high-purity natural wollastonite added in ratios of 20, 50, and 80 Wt%.
Abstract: Composites of hydroxyapatite–wollastonite were synthesized by a sol–gel route using calcium acetate and triethyl phosphate as precursors of hydroxyapatite and high-purity natural wollastonite added in ratios of 20, 50, and 80 wt%. These composites were characterized by thermal analysis, X-ray diffraction, FT-IR and Raman spectroscopy, and scanning and transmission electron microscopic techniques. Formation of hydroxyapatite occurs at a relatively low temperature, about 420°C, accompanied by calcium carbonate; wollastonite remains unreacted. The composites were purified by heat treatment to a higher temperature and washed with hydrochloric acid and distilled water, to produce B-type carbonated hydroxyapatite–wollastonite composites as final products.
TL;DR: In this paper, MgO samples have been microstructured by laser treatment and surfaces with a controlled stripe design have been manufactured, and sessile drop wetting measurements were performed in a special heating microscope by determining horizontal contact angles as well as contact angle as a function of surface inclination angles.
Abstract: In this work, MgO samples have been microstructured by laser treatment and surfaces with a controlled stripe design have been manufactured. Sessile drop wetting measurements were performed in a special heating microscope by determining horizontal contact angles as well as contact angles as a function of surface inclination angles. In a further step, voltage was applied to ground MgO surfaces and the wetting behavior was registered as a function of the voltage level. Activation energy analysis was conducted for all the experiments.
TL;DR: In this paper, a nanosecond-pulsed Nd:YAG laser system was used to improve the finish of millisecond-machined yttria-stabilized tetragonal zirconia polycrystal surfaces.
Abstract: Millisecond-pulsed Nd:YAG laser systems can be used for high-speed cutting of ceramics, due to the high average power available. However, due to the relatively long pulse duration (0.3–5 ms), millisecond laser-machining is predominantly a thermal, melt-eject process. The quality of the finished surface is limited by a redeposited melt and a heat-affected zone, in particular surface cracking. Shorter pulse duration lasers can provide a better surface finish but with a significantly longer processing time. This paper presents a method of improving the finish of millisecond-machined yttria-stabilized tetragonal zirconia polycrystal surfaces by postprocessing with a nanosecond-pulsed laser. Nanosecond machining was carried out directly onto the as-cut surface produced after millisecond processing, yielding a dramatic improvement of the surface finish in a relatively short time.
TL;DR: In this paper, a hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared by a chemical method by varying the HAp content by 10-60% (w/w).
Abstract: A hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared by a chemical method by varying the HAp content by 10-60% (w/w). The bonding between HAp and PVAP has been investigated through Fourier transform infrared absorption spectra, X-ray diffraction, and thermogravimetric analyses. Transmission electron microscopy study shows a homogeneous dispersion of nanoparticles in the polymer matrix. Scanning electron microscopy study shows enhancement of the surface roughness of the composite with an increase in the nanoparticle content. The mechanical properties of the composites improve significantly with an increase in the HAp content. The HAp/PVAP nanocomposite prepared may have bone-implant applications.
TL;DR: In this article, a glass frit with a high B{sub 2}O{sub 3} concentration has been designed which, when combined with high alumina concentration nuclear waste streams, will form glasses with durabilities that are acceptable for repository disposal and predictable using a free energy of hydration model.
Abstract: Glass frits with a high B{sub 2}O{sub 3} concentration have been designed which, when combined with high-alumina concentration nuclear waste streams, will form glasses with durabilities that are acceptable for repository disposal and predictable using a free energy of hydration model. Two glasses with nepheline discriminator values closest to 0.62 showed significant differences in normalized boron release between the quenched and heat treated versions of each glass. X-ray diffraction confirmed that nepheline crystallized in the glass with the lowest nepheline discriminator value, and nepheline may also exist in the second glass as small nanocrystals. The high-B{sub 2}O{sub 3} frit was successful in producing simulated waste glasses with no detectable nepheline crystallization at waste loadings of up to 45 wt%. The melt rate of this frit was also considerably better than other frits with increased concentrations of Na{sub 2}O.
TL;DR: In this paper, the authors describe the machining of a zirconia ceramic with millisecond pulses at 1064nm (Nd:YAG) and present techniques that allow this material to be processed effectively.
Abstract: We describe the machining of a zirconia ceramic with millisecond pulses at 1064nm (Nd:YAG) and present techniques that allow this material to be processed effectively. We show experimentally that due to the thermal expansion rate and absorption of the material, laser machining processes such as drilling and milling can critically fail in the millisecond regime. Results are also presented indicating that the phase structure of the bulk material postmillisecond-processing remains largely unmodified. Furthermore, we show that the addition of a nanosecond system to the process confers not only flexibility but the capability of precision machining at 1064nm.
TL;DR: In this paper, carbonated amorphous calcium phosphate (CACP) precursors were precipitated by the wet chemical method at 5°C in the presence of poly(ethylene glycol) and carbonates.
Abstract: Carbonated amorphous calcium phosphate (CACP) precursors were precipitated by the wet chemical method at 5°C in the presence of poly(ethylene glycol) and carbonates. The nano carbonate-substituted hydroxyapatite (HAp) was obtained after heat treat CACP precursors at a low temperature (800°C) for 3 h. The calcium phosphates were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma, thermal gravimetric and differential thermal analysis, transmission electron microscopy, and scanning electron microscopy. The results show that calcium phosphate particles with a Ca/P molar ratio of 1.73 are AB-type carbonate-substituted HAp with about 50 nm in diameter.
TL;DR: In this article, a method is proposed for the precise fabrication of 3D ceramic microstructures that utilize shrinkage guiders to lead to isotropic shrinkage, which can be applied to various microscale devices that are used in harsh conditions that demand high strength, high temperature endurance, and good chemical corrosion properties.
Abstract: The two-photon cross-linking (TPC) process using ceramic precursors is recognized as a unique fabrication means of real three-dimensional (3D) ceramic microstructures. These structures can be applied to various microscale devices that are used in harsh conditions that demand high strength, high temperature endurance, and good chemical corrosion properties. However, the large shrinkage amount of 3D structures during pyrolysis is a serious limitation to the practical application of these structures; during pyrolysis, asymmetric distortion and shrinkage occur intrinsically. In an attempt to address this, a method is proposed for the precise fabrication of 3D ceramic microstructures that utilize shrinkage guiders to lead to isotropic shrinkage. SiCN ceramic woodpile structures were fabricated to show the efficiency and usefulness of the proposed method. In the results, the woodpiles showed no distortion after pyrolysis.
TL;DR: In this article, a segmented-in-series solid oxide fuel cells (SOFCs) were presented, where small cone-shaped anode tubes were fabricated by slip casting and the yttria-stabilized zirconia (YSZ) electrolyte membranes were deposited onto the anode tube by dip coating.
Abstract: A new design of segmented-in-series solid oxide fuel cells (SOFCs) is presented in this paper. The small cone-shaped anode tubes were fabricated by slip casting and the yttria-stabilized zirconia (YSZ) electrolyte membranes were deposited onto the anode tubes by dip coating. After sintering at 1400°C for 4 h, a dense and crack-free YSZ membrane with a thickness of 20 μm was successfully obtained. The single cell, using moist hydrogen as a fuel and ambient air as an oxidant, provides maximum power densities of 1.15, 0.8, 0.47, 0.26, 0.14, and 0.07 W/cm2 at 850°C, 800°C, 750°C, 700°C, 650°C, and 600°C, respectively.
TL;DR: In this paper, low-pressure injection molding was used to produce helical ceramic springs using two different kinds of molds: submicrometer-sized alumina and partially stabilized zirconia.
Abstract: Injection molding has important advantages over other methods for the production of advanced ceramic parts with complex shapes In this work, low-pressure injection molding was used to produce helical ceramic springs using two different kinds of molds The ceramic powders used were submicrometer-sized alumina and partially stabilized zirconia Sintered alumina and zirconia springs were obtained free of defects, with densities from 96% to 99% of the theoretical value In preliminary mechanical tests, these ceramic springs supported axial deformations up to 10% before failure
TL;DR: In this paper, the rheological characterization of agar and foaming surfactant-containing suspensions for obtaining stoichiometric cordierite samples with tailored open macroporosity and their characterization through density and microstructural studies is discussed.
Abstract: This paper deals with the rheological characterization of agar and foaming surfactant-containing suspensions for obtaining stoichiometric cordierite samples with tailored open macroporosity and their characterization through density and microstructural studies. The influence of the processing parameters solid loading (20, 30, and 45 vol%), slip temperature (65°C, 45°C, and 40°C), and agar/surfactant ratio (10.2, 8.0, and 5.6) on the obtained bodies is discussed. Open Porosity (up to 76 vol%) and average cell size were found to be strongly dependent on solids loading.
TL;DR: In this article, the effect of addition of ZrO2 on the microstructure and mechanical properties of a ZrB2-based ceramic composites by means of hot-pressed sintering was reported.
Abstract: The present work reported the effect of addition of ZrO2 on the microstructure and mechanical properties of ZrB2-based ceramic composites by means of hot-pressed sintering. Observation of microstructure and systematic testing results of mechanical properties were carried out. Through X-ray diffraction analysis and calculation of the volume fraction of ZrO2 phase transformability, the toughening mechanism of the present composites was explored. The phase transformation toughening by ZrO2 additive played an important role in improving the fracture toughness of ZrB2-based composites.
TL;DR: A water-based method for producing aluminum oxynitride (AlON) green bodies with a relatively high density is described in this paper, which utilizes water to form a rigid network of aluminum hydroxide in Al2O3-AlN preforms.
Abstract: A water-based method for producing aluminum oxynitride (AlON) green bodies with a relatively high density is described. While alcohol is usually the medium for ball milling, this approach utilizes water to form a rigid network of aluminum hydroxide in Al2O3–AlN preforms. Al2O3–AlN preforms were prepared by four different routes based either on alcohol or water-based slips, and underwent identical sintering procedures. Samples prepared using the water-based method and pressure filtration reached a green density of 67%, compared with 52% and 47% for samples prepared from alcohol-based slips and formed using pressure filtration and dry pressing, respectively.
TL;DR: In this article, the FTIR, DSC/TG, XRD, and TEM properties of hydroxyapatite (HA)-YTZP (2, 5, 7.5, and 10-wt% ZrO2) composite powders were characterized by FTIR.
Abstract: Hydroxyapatite (HA)–YTZP (2, 5, 7.5, and 10 wt% ZrO2) composite powders prepared from inorganic precursors were characterized by FTIR, DSC/TG, XRD, and TEM. The calcined powders had HA and t/c-ZrO2, which undergo structural changes between 650°C and 1050°C. TEM of calcined powder showed larger HA particles (100 nm) and smaller ZrO2 particles (≤50 nm). HA and HA–2 wt% ZrO2-sintered samples had 98% density and it was (90–95%) for HA–5, 7.5, and 10 wt% ZrO2. The bending strength of HA–2wt% ZrO2 composites was 72 MPa. The grain sizes of HA showed a refinement with ZrO2 addition.
TL;DR: In this paper, a coextrusion approach was used to obtain filaments with inner conductive lines after proper doping, and the results on L929 and MG63 cell line models indicated good biological performance of Si-O-C ceramics and confirmed citocompatibility.
Abstract: A novel process, based on microextrusion of preceramic polymers, was developed for manufacturing ceramic microelectrodes, mainly for biomedical applications. A coextrusion approach was used to obtain filaments with inner conductive lines after proper doping. Chemical reticulation and high-temperature pyrolysis were applied to convert the meltable preceramic, polymeric resins into SiOC ceramic materials. Different cross-sectional geometries were produced. The flexural strength of filaments depended on the outer diameter size; doping produced filaments with an average conductivity of ∼0.4 1/Ω cm for a 50 wt% carbon black load. The results on L929 and MG63 cell line models indicated good biological performance of Si–O–C ceramics and confirmed citocompatibility.
TL;DR: In this article, the authors report on shear strength measurements of BK7-to-BK7 hydroxide bonds as well as present new results for BK 7-tosilicon carbide and BK-7to-Super Invar bonds.
Abstract: Optical contacting has long been used in interferometric experiments both on the ground and in space-based missions. Its optical clarity makes it an ideal method to joint materials of comparable coefficients of thermal expansion. Once the two pieces are bonded, they are commonly broken through thermal or vibrational cycling. Unfortunately, larger bond areas are needed for the bond to form appreciable strength, which often excludes it from being used in complex optical bench designs in space-based missions. Another method, known colloquially as hydroxide bonding, has shown to have superior strength to optical contacting using smaller bonding areas. In addition, the hydroxide bonding process will work on several materials that do not need to meet the stringent polishing requirements of optical contacting. These properties make hydroxide bonding suitable for complex optical bench designs that can withstand the large accelerations encountered during launch conditions for use in space-based missions. In this paper, we report on shear strength measurements of BK7-to-BK7 hydroxide bonds as well as present new results for BK7-to-silicon carbide and BK7-to-Super Invar bonds.
TL;DR: In this article, the complex perovskite Ba(Yb1/2Ta 1/2)O3 has been prepared by the two-stage solid-state reaction method and the dielectric constant is measured to be 29.1, the product of quality factor and resonant frequency (Q×f) is found to be 32,000 GHz and the temperature coefficient of resonant frequencies is 135 (ppm/°C).
Abstract: The complex perovskite Ba(Yb1/2Ta1/2)O3 has been prepared by the two-stage solid-state reaction method. Rietveld' refinement analysis indicates cubic perovskite phase with space group . The 1:1 cation ordering at the B-site is revealed by the presence of (111) superlattice reflection in the X-ray diffraction pattern and further evidenced by the presence of A1g and F2g vibrational modes in the Raman spectra. The dielectric constant is measured to be 29.1, the product of quality factor and resonant frequency (Q×f) is found to be 32,000 GHz and the temperature coefficient of resonant frequency (τf) is 135 (ppm/°C) in the temperature range 30–70°C.