Showing papers in "International Journal of Applied Ceramic Technology in 2015"
TL;DR: In this article, a new process for additive manufacturing (AM) of dense and strong ceramic objects is described, based on the selective curing of a photosensitive slurry by a dynamic mask exposure process, which is able to produce strong, dense and accurate alumina ceramics without virtually any geometrical limitations.
Abstract: In this study, a new process for additive manufacturing (AM) of dense and strong ceramic objects is described. The lithography-based ceramic manufacturing (LCM) technique is based on the selective curing of a photosensitive slurry by a dynamic mask exposure process. The LCM technique is able to produce strong, dense and accurate alumina ceramics without virtually any geometrical limitations. With over 99.3% of a theoretical alumina density, four-point bending strength of 427 MPa, and very smooth surfaces, the LCM process distinguishes itself from other AM techniques for ceramics and provides parts with very similar mechanical properties as conventionally formed alumina.
324 citations
TL;DR: In this article, a high-filled ceramic suspension based on thermoplastic binder systems is used to produce dense ceramic components by additive manufacturing, and the results showed a homogenous microstructure and a good bond between the single printed layers.
Abstract: In our new approach—thermoplastic 3D printing—a high-filled ceramic suspension based on thermoplastic binder systems is used to produce dense ceramic components by additive manufacturing. Alumina (67 vol%) and zirconia (45 vol%) suspensions were prepared by ball milling at a temperature of about 100°C to adjust a low viscosity. After the preparation the suspension solidified at cooling. For the sintered samples (alumina at 1600°C, zirconia at 1500°C), a density of about 99% and higher was obtained. FESEM studies of the samples' cross section showed a homogenous microstructure and a very good bond between the single printed layers.
114 citations
TL;DR: In this paper, the feasibility of using lunar regolith simulant to create objects with selective laser melting (SLM) process is investigated and the process parameters are optimized and multiple objects are fabricated.
Abstract: Selective Laser Melting (SLM) is a candidate for on-site manufacturing as its characteristics of energy source and powder-based fabrication process are suitable for use with in situ material. The feasibility of using lunar regolith simulant to create objects with SLM process is investigated in this study. The process parameters are optimized and multiple objects are fabricated. A qualitative chemical analysis is carried out with scanning electron microscopy using energy-dispersive X-ray emission. Lastly, properties such as particle size distribution, particle shape, and crystal structure of the lunar simulant powder as well as the crystallinity and hardness of the fabricated objects are investigated.
85 citations
TL;DR: In this paper, the microstructure of laser-sintered bodies is discussed and strategies for an improved micro-structure during sintering are introduced, based on the basis of existing additive manufacturing technologies.
Abstract: Most additive manufacturing (AM) techniques have in common that material is spread out as thin layers of a dried powder/granulate by a roller or a shaker system. These layers are mostly characterized by a low packing rate. On the other hand, appreciable densities can be reached by the use of ceramic slurries. In this context, the layer-wise slurry deposition (LSD) has been developed. Specific features of the LSD process are reflected on the basis of already existing additive manufacturing technologies. The microstructure of laser-sintered bodies will be discussed, and strategies for an improved microstructure during sintering will be introduced.
82 citations
TL;DR: In this article, a new production alternative for 45S5 bioactive glass structures resulting in parts with high density and strength was provided. But, clinical applications as bone substitute or scaffold material are highly limited because of the often poor mechanical behavior of bioactive glasses.
Abstract: Bioactive glasses and glass ceramics like the 45S5 formulation have been studied toward biocompatibility and biodegradability for years. Nevertheless, clinical applications as bone substitute or scaffold material are highly limited because of the often poor mechanical behavior of bioactive glasses. In this study, we are able to provide a new production alternative for 45S5 bioactive glass structures resulting in parts with high density and strength. Using the stereolithographic ceramic manufacturing (SLCM) process, it is possible to additively produce solid bulk glass ceramics as well as delicate scaffold structures. Recent developments in SLCM slurry preparation together with an appropriate selection of raw materials led to 3D parts with a very homogeneous microstructure and a density of about 2.7 g/cm³. Due to the low number and small size of defects, a high biaxial bending strength of 124 MPa was achieved. Weibull distribution also underlines good process control showing a Weibull modulus of 8.6 and a characteristic strength of 131 MPa for the samples tested here. By reaching bending strength values of natural cortical bone, bioactive glasses processed with SLCM could eventually advance to be an interesting bone substitute material even in load-bearing applications, valuing the huge efforts undertaken to understand their bioactive behavior.
73 citations
TL;DR: In this paper, a synopsis of an experimental investigation study on SLM of soda-lime glass powder is presented, and the process parameters are analyzed using various test geometries, and a set of optimized process parameters is determined and used to build multiple objects.
Abstract: Although process parameters of Selective Laser Melting (SLM) method have been established for different materials, fabrication of parts using SLM of glass powder has remained a challenge so far. This study presents a synopsis of an experimental investigation study on SLM of soda-lime glass powder. The process parameters are analyzed using various test geometries, and a set of optimized process parameters is determined and used to build multiple objects. The morphology and mechanical properties of the fabricated parts are analyzed. The results demonstrate the feasibility of SLM process to successfully build objects from soda-lime glass powder for different applications.
62 citations
TL;DR: In this paper, the authors synthesize hydroxyapatite (HA) powders using calcium hydroxide Ca(OH)(2) and orthophosphoric acid H3PO4 via wet chemical precipitation method in aqueous medium.
Abstract: In this work, hydroxyapatite (HA) powders were synthesized using calcium hydroxide Ca(OH)(2) and orthophosphoric acid H3PO4 via wet chemical precipitation method in aqueous medium. Calcium-to-phosphorus (Ca/P) ratio was set to 1.57, 1.67, 1.87 that yield calcium-deficient HA, stoichiometric HA, and calcium-rich HA, respectively. These synthesized HA powders (having different Ca/P ratio) were characterized in terms of particle size and microstructural examination. Then, the densification and mechanical properties of the calcium-deficient HA, stoichiometric HA, and calcium-rich HA were evaluated from 1000 to 1350 degrees C. Experimental results have shown that no decomposition of hydroxyapatite phase was observed for stoichiometric HA (Ca/P = 1.67) and calcium-deficient HA (Ca/P = 1.57) despite sintered at high temperature of 1300 degrees C. However, calcium oxide (CaO) was detected for calcium-rich HA (Ca/P = 1.87) when samples sintered at the same temperature. The study revealed that the highest mechanical properties were found in stoichiometric HA samples sintered at 1100-1150 degrees C, having relative density of similar to 99.8, Young's modulus of similar to 120 GPa, Vickers hardness of similar to 7.23 GPa, and fracture toughness of similar to 1.22 MPam(1/2)
61 citations
TL;DR: A review of the development of ceramic radomes, manufacturing methods for variety of applications is presented in this paper, where the existing different near-net shape fabrication techniques for manufacturing of ceramics are discussed and compared.
Abstract: Radome is an aerodynamic structural part attached to the fore-end of a missile. It transmits electromagnetic signals with minimum attenuation and also protects radar communication system, and thus, the radomes are made of ceramics as they have desirable properties required by the radomes. The flexural strength, dielectric constant, and loss tangent values of various ceramic materials used in the development of radomes are important in the selection of radome materials. Different nose cone shapes of missile radomes are also important. Ceramic materials show variational properties with sintering time, temperature, and other additives. The existing different near-net shape fabrication techniques for manufacturing of ceramic radomes are discussed and compared. Gelcasting is one of the manufacturing techniques to produce radomes with homogeneous and high green strength. Gelcast parts of silicon nitride ceramics are hard, tough, brittle, and wear-resistant and are difficult to machine using conventional methods of machining. Therefore, laser-assisted machining is used for fine finish of ceramic radomes with excellent surface integrity and productivity. This paper deals with a review of development of ceramic radomes, manufacturing methods for variety of applications.
53 citations
TL;DR: In this paper, the energy harvesting capabilities of bulk lead-free ferroelectric materials using Olsen cycle was demonstrated, and the maximum harness-able energy density for KNTM and BZT-50BCT compositions were found to be 629 J/L (629 KJ/m3) and 87 J /L (87 KJ /m3), respectively.
Abstract: This article demonstrates the energy harvesting capabilities of bulk lead-free ferroelectric materials using Olsen cycle. Lead-free compositions K[(Nb0.90Ta0.10)0.99Mn0.01]O3 (KNTM) and 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-50BCT) have been explored for their energy harvesting capabilities. Further, we studied the variation in energy density over wide range of applied temperature and electric field. The maximum harness-able energy density for KNTM and BZT-50BCT compositions are found to be 629 J/L (629 kJ/m3) and 87 J/L (87 kJ/m3), respectively. This estimated energy density, obtained for the bulk samples, is comparable with the highest energy density reported to-date (888 J/L for lanthanum-doped lead zirconate titanate (8/65/35 PLZT) thick films).
45 citations
TL;DR: In this paper, a powder-bed additive manufacturing (AM) is incorporated into the manufacturing of graphene nanocomposite 3D structures, and the synthesized powder was utilized in a powderbed AM system to fabricate 3D porous structures of GHN powder.
Abstract: In this article, a powder-bed class of additive manufacturing (AM) is incorporated into the manufacturing of graphene nanocomposite 3D structures. For AM of graphene-based 3D structures, graphene oxide (GO)/hydroxyapatite (Hap) nanocomposite (GHN) was synthesized at different GO to Hap percentage (wt.%), including 0.2% and 0.4% to develop a printable powder. The synthesized powder was utilized in a powder-bed AM system to fabricate 3D porous structures of GHN powder. It was shown that at layer thickness of 125 μm and core binder saturation level of 400%, the compressive mechanical strength of the samples with higher content of graphene was improved significantly.
43 citations
TL;DR: In this paper, the Stober process was used for the fabrication of almost monodispersed silica (SiO2) nanoparticles with narrow particle size distributions of around 85 ± 5nm.
Abstract: This article presents a novel systematic approach to the fabrication of highly functionalized, silica (SiO2) nanoparticles used for the adsorption of heavy-metal ions (Hg2+, Pb2+, Cd2+, Zn2+). Almost monodispersed silica (SiO2) nanoparticles with narrow particle size distributions of around 85 ± 5 nm were formed using the Stober process. The prepared SiO2 nanoparticles were successfully surface-treated during a one-step procedure by the covalent attachment of mercaptopropyl groups onto the surfaces of the SiO2 nanoparticles. A FTIR spectra analysis confirmed that the binding of the mercaptosilane molecules onto the surface of the silica nanoparticles mediated the Si–O–Si and –SH vibrations. TEM/EDXS micrographs indicated the almost monodispersed and spherical morphology of the prepared product with strong signals of Si and S, thus implying that the coating procedure involving the mercapto groups onto the silica surface had been successfully accomplished. The final results for the heavy-metal (Hg2+, Pb2+, Cd2+, Zn2+) adsorption showed the strongest affinity within the following sequence Hg2+ (99.9%) > Pb2+ (55.9%) > Cd2+ (50.2%) > Zn2+ (4%). Adsorption equilibrium was achieved after 1 h for all the analyzed samples.
TL;DR: In this article, the electrocaloric effect in Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZO) using an indirect approach based on Maxwell's relations is presented.
Abstract: This article presents electrocaloric effect in Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZO) using an indirect approach based on Maxwell's relations. The peak electrocaloric performance is found to be an adiabatic temperature change of 0.41 K with electrocaloric strength of 19 mK cm/kV and a heat carrying capacity of ~0.17 J/g under an electric field of 0–21.5 kV/cm. The ferroelectric hysteresis scaling relations for coercive field (EC), remnant polarization (Pr), and hysteresis area ( ) as a function of temperature (T) are also systematically investigated. The power-law temperature exponents are obtained for all the hysteresis parameters. The scaling relations are established as Ec ∝ T−0.6584, Pr ∝ T−1.59, and ∝ T−1.01623. The presented scaling relations are compared with those reported in the literature for other ferroelectric materials.
TL;DR: In this paper, a continuous SiC fiber-reinforced HfB2-SiC composite laminates were developed using pressure and vibration-assisted pressure infiltration techniques.
Abstract: This paper discusses the development of continuous SiC fiber-reinforced HfB2-SiC composite laminates. A range of techniques, based on resin-based precursors and slurries, for infiltrating porous SiC preforms with HfB2 powder were developed. While resin-based precursors proved to be ineffective due to low HfB2 yield and poor adhesion, the slurry infiltration techniques were effective to varying degrees. The greatest pore filling and composite densities were achieved using pressure and vibration-assisted pressure infiltration techniques. SiCf/HfB2-SiC laminates were subsequently developed via lamination, cure and pyrolysis of fabrics using a HfB2-loaded polymeric SiC precursor, followed by HfB2 slurry infiltration and preceramic polymer infiltration and pyrolysis (PIP). Repeated PIP processing, for 6–10 cycles, resulted in density increases, from the 3.03–3.22 g/cm3 range after HfB2 slurry infiltration, to 3.97–4.03 g/cm3 after PIP processing. Correspondingly, there was a decrease in open porosity from approximately 52% to less than 11%. The matrix consisted of discreet, lightly sintered HfB2 particles dispersed in SiC. The PIP SiC matrix was primarily nanocrystalline after 1300°C pyrolysis, but experienced grain growth with further heat treatment at 1600°C.
TL;DR: In this article, LiAluminosilicate was fabricated by microwave and spark plasma sintering, from 1200 to 1300°C, and a considerable difference in densification, microstructure, coefficient of thermal expansion behavior and hardness and Young's modulus was observed.
Abstract: Lithium aluminosilicate was fabricated by conventional and nonconventional sintering: microwave and spark plasma sintering, from 1200 to 1300°C. A considerable difference in densification, microstructure, coefficient of thermal expansion behavior and hardness and Young's modulus was observed. Microwave technology made possible to obtain fully dense glass-free lithium aluminosilicate bulk material (>99%) with near-zero and controlled coefficient of thermal expansion and relatively high mechanical properties (7.1 GPa of hardness and 110 GPa of Young's modulus) compared with the other two processes. It is believed that the heating mode and effective particle packing by microwave sintering are responsible to improve these properties.
TL;DR: In this article, the authors firstly synthesized the fine SrAl2O4:Eu2+,Dy3+ phosphors and then produced the composite film as spectral shifters to understand the effects of the fine S2O 4: Eu2+Dy 3+/SiO 2 composite films on photoelectric conversion efficiency of a silicon photovoltaic module.
Abstract: SrAl2O4:Eu2+,Dy3+ phosphors can convert near ultraviolet light with lower sensitivity to the solar cell to yellow-green light at which the solar cell has higher sensitivity and exhibit the excellent luminescent property of long persistence. Therefore, in this study, the authors firstly synthesized the fine SrAl2O4:Eu2+,Dy3+ phosphors and then produced SrAl2O4:Eu2+,Dy3+/SiO2 composite films as spectral shifters to understand the effects of SrAl2O4:Eu2+,Dy3+ phosphor on photoelectric conversion efficiencies of a crystalline silicon photovoltaic module. Under one sun illumination, the composite film containing an appropriate amount of SrAl2O4:Eu2+,Dy3+ phosphor enhances the photoelectric conversion efficiency of the cell through spectral down-shifting as compared to the bare glass substrate, and the maximum achieves 11.12%. In contrast, the commercial SrAl2O4:Eu2+,Dy3+ phosphor composite film is not effective for improving the photoelectric conversion efficiency because of the relatively lower visible light transmittance of film caused by the large aggregates. After one sun illumination for 1 min, the light source was turned off, and the cell containing the synthesized SrAl2O4:Eu2+,Dy3+ phosphor still shows an efficiency of 1.16% in the dark due to the irradiation by the long persistent light from SrAl2O4:Eu2+,Dy3+, which provides a possibility to fulfill the operation of solar cells even in the dark.
TL;DR: In this article, an innovative low-temperature sonochemical synthesis pathway for synthesizing the carbonate-free SrTiO3 nanocrystals with tailored morphology was developed, which is simple, fast, cost-effective and useful for large-scale production purposes.
Abstract: This work aims to develop an innovative low-temperature sonochemical synthesis pathway for synthesizing the carbonate-free SrTiO3 nanocrystals with tailored morphology. Ultrasonication causes the formation of stoichiometric SrTiO3 nanocrystals and accelerates their formation. Moreover, SrTiO3 nanocrystals are synthesized at low temperature. The methodology described here is simple, fast, cost-effective, and useful for large-scale production purposes.
TL;DR: In this article, the effect of substrate roughness on photocatalytic performance before and after different aging tests was determined, and the results showed that the photodegradation process was clearly affected by the surface roughness of the substrate.
Abstract: The aim of this investigation was the evaluation of the durability of photocatalytic sol–gel coating deposited on industrial ceramic tiles. In particular, the effect of substrate roughness on photocatalytic performance before and after different aging tests was determined. The results showed that the photodegradation process was clearly affected by the surface roughness of the substrate. In particular, the smoother surface had a higher photocatalytic activity, faster hydrophilicity but a lower durability to abrasion with respect to the matt surface.
TL;DR: In this paper, a novel method was developed to synthesize reduced graphene oxide/alumina nanocomposite (RGO/Al2O3) by in situ depositing Al 2O3 nanoparticles on graphene oxide flakes by a dry sol-gel process.
Abstract: A novel method was developed to synthesize reduced graphene oxide/alumina nanocomposite (RGO/Al2O3) by in situ depositing Al2O3 nanoparticles on graphene oxide flakes by a dry sol–gel process. The scanning electron microscopy and energy dispersive X-ray spectroscopy investigations results showed that Al2O3 nanoparticles (19 ± 5 nm) were homogeneously distributed onto the surface of curly-shaped RGO flakes acting as a spacer between individual flakes. The high BET-specific surface area of the analyzed composite (242.4 m2/g) together with very low open porosity indicates that RGO/Al2O3 nanocomposites have a very friable structure and show low tendency to agglomeration.
TL;DR: In this article, the authors investigated the effect of Bi2O3 addition on NiCuZn ferrite densification, magnetic properties, and DC superposition behavior, and found that a suitable compromise between the initial permeability and DC-bias superposition characteristic can be obtained by adding a proper amount of Bi 2O3 to adjust the nonmagnetic copper and bismuth-rich precipitate thickness at the grain boundaries.
Abstract: The Bi2O3 addition effects on the densification mechanism, magnetic properties, and DC superposition behavior of NiCuZn ferrites are investigated in this study. Bi2O3 addition can effectively promote NiCuZn ferrite densification. The densification controlling mechanism is dominated by the liquid formation resulting from the Bi2O3 and Bi2CuO4 eutectic reaction as Bi2O3 addition is increased above 2wt%. A suitable compromise between the initial permeability and DC-bias superposition characteristic can be obtained by adding a proper amount of Bi2O3 to adjust the nonmagnetic copper and bismuth-rich precipitate thickness at the grain boundaries.
TL;DR: In this paper, the effect of submicrometer-sized B4C (5,10 and 15 wt%) on microstructure, phase composition, hardness, fracture toughness, scratch resistance, wear resistance, and thermal behavior of hot-pressed ZrB2-B4C composites is reported.
Abstract: The effect of addition of submicrometer-sized B4C (5,10 and 15 wt%) on microstructure, phase composition, hardness, fracture toughness, scratch resistance, wear resistance, and thermal behavior of hot-pressed ZrB2-B4C composites is reported. ZrB2-B4C (10 wt%) composite has VH1 of 20.81 GPa and fracture toughness of 3.93 at 1 kgf, scratch resistance coefficient of 0.40, wear resistance coefficient of 0.01, and ware rate of 0.49 × 10−3 mm3/Nm at 10N. Crack deflection by homogeneously dispersed submicrometer-sized B4C in ZrB2 matrix can improve the mechanical and tribological properties. Thermal conductivity of ZrB2-B4C composites varied from 70.13 to 45.30 W/m K between 100°C and 1000°C which is encouraging for making ultra-high temperature ceramics (UHTC) component.
TL;DR: In this article, the relationship between zeta potential, morphology, surface area, porosity, chemical composition, and ecotoxicity of nanocomposite powders was observed.
Abstract: The aim of this research was to observe the relationship between zeta potential, morphology, surface area, porosity, chemical composition, and ecotoxicity of nanocomposite powders such as Au/TiO2, Ag2O/TiO2, PdO/TiO2, Ag/TiO2/SiO2, Ag/N(C)TiO2, and SiO2/TiO2 from which Ag2O/TiO2, Ag/N(C)/TiO2, and Ag/TiO2/SiO2 were exhibiting good antimicrobial properties. It was observed, that nanomaterials characterized by similar morphology and zeta potential revealed the similar toxic behavior. The samples of higher agglomeration and higher zeta potential, especially Ag/TiO2/SiO2 xerogel and TiO2/SiO2 aerogel were generally less ecotoxic to water organisms and plants. They were also not genotoxic in concentrations up to 500 and 250 mg/L, respectively.
TL;DR: In this article, the authors presented a ferroelectric-ferromagnetic composite based on a doped PZT-type and ferrite powders, and the results indicated the influence of the magnetic subsystem on the electrical properties.
Abstract: The study presents a ferroelectric–ferromagnetic composite based on a doped PZT-type and ferrite powders. Ferroelectric powder (in amount of 90 wt-%) was based on multicomponent PZT-type materials, while nickel–zinc ferrite Ni1–xZnxFe2O4 (in amount of 10 wt-%) served as the magnetic component of the composite. The syntheses of the ferroelectric–ferromagnetic composite's components were performed using solid-phase sintering, while final densification of the synthesized powder was achieved using free sintering. X-ray analysis of the composite confirmed the presence of strong maxima originating from particular PZT-type material phases, as well as weak peaks from the Ni0.64Zn0.36Fe2O4 ferrite, without foreign phases. The microstructure of the fracture of the ferroelectric–ferromagnetic composites shows that the ferrite grains on the surface of the ferroelectric component are distributed heterogeneously. Magnetic studies have characterized composite as a soft ferromagnetic material. The study indicated the influence of the magnetic subsystem on the electrical properties. In the two-phase PBZTMC–NZF ceramic composite, the magnetic component causes the decrease in electric permittivity and increased value of the dielectric losses.
TL;DR: In this paper, a novel aqueous gelcasting technique was employed to prepare porous silicon nitride ceramics using water-soluble copolymer of isobutylene and maleic anhydride (Isobam) as both dispersant and gelling agent.
Abstract: A novel aqueous gelcasting technique was employed to prepare porous silicon nitride ceramics using water-soluble copolymer of isobutylene and maleic anhydride (Isobam) as both dispersant and gelling agent The effects of fabrication parameters, including sintering additives, the second phase (BN), and pore-forming agent (corn starch), on the microstructure and mechanical properties were separately investigated The sample with Yb2O3 as sintering additive, having a porosity of ~486%, showed a high flexural strength of 233MPa and a high fracture toughness of 272 MPa·m1/2 With addition of 25wt% BN, the sample exhibited a high flexural strength of 211 MPa due to the uniform microstructure with β-Si3N4 grains A high porosity of ~60% and a flexural strength of 110 MPa were obtained by adding 20wt% starch into the sample
TL;DR: In this paper, the liquid binder amount was investigated in calcium polyphosphate bone substitutes and two part categories were produced with 150 and 190mm layer thickness and 70, 80, 90, 100, and 90/70% gray scale.
Abstract: An additive manufacturing platform was developed for fabricating constructs with heterogeneous properties. The liquid binder amount was investigated in calcium polyphosphate bone substitutes. Two part categories were produced with 150 and 190 μm layer thickness and 70, 80, 90, 100, and 90/70% gray scale. It was shown that the gray scale level had an effect on samples with 150 μm layer thickness where porosity ranged between 43 ± 1% and 49 ± 2% and the compressive strength varied between 4.8 ± 1.3 MPa and 15.5 ± 1.9 MPa. The results suggest that the binder gray scale level can be used to locally predict porous properties.
TL;DR: In this paper, a single-phase β-Yb2Si2O7 was synthesized by solid-state reaction using Yb2O3 and SiO2 gel, which significantly decreased the synthesis temperature and shortened the holding time.
Abstract: Single-phase β-Yb2Si2O7 was synthesized by solid-state reaction using Yb2O3 and SiO2 gel. SiO2 gel significantly decreased the synthesis temperature and shortened the holding time. Bulk Yb2Si2O7 was obtained by pressureless sintering. Grain size, relative density (92.9%), and flexural strength [(182.3 ± 2.0) MPa] were enhanced as the sintering temperature increased and equiaxed grains were obtained with an average grain size of approximately 3 μm. Bulk Yb2Si2O7 possessed a suitable thermal expansion coefficient [(4.64 ± 0.01) × 10−6/K] between 473 and 1573 K, and the thermal conductivities at 300 and 1400 K were 4.31 and 2.27 W/m·K, respectively.
TL;DR: In this paper, the crystal structure and luminescence properties of the Sr2P2O7:Sm3+ phosphor were investigated and the results indicated that a potential suitable reddish orange emitting phosphor candidate for W-LEDs with excitation of a ~400nm n-UV LED chip was proposed.
Abstract: A reddish orange emission Sr2P2O7:Sm3+ phosphor is prepared by the solid-state reaction method in air, and the crystal structure and luminescence properties of phosphors are investigated. Sr2P2O7:Sm3+ phosphor shows Commission International de I'Eclairage (CIE) chromaticity coordinates (x = 0.5753, y = 0.4147). White light-emitting diodes (W-LEDs) fabricated using Sr2P2O7:Sm3+ phosphor etc. show CIE chromaticity coordinates (x = 0.3471, y = 0.3124). These results indicate that Sr2P2O7:Sm3+ phosphor could be a potential suitable reddish orange emitting phosphor candidate for W-LEDs with excitation of a ~400 nm n-UV LED chip.
TL;DR: In this article, the influence of BaTiO3 concentration on cure characteristics, mechanical (static and dynamic), dielectric, and morphological properties of the composites was investigated.
Abstract: Flexible composites with a high electrical permittivity are pursued in materials research, due to their potential applications in electrical devices. We synthesized such ceramic-polymer composites from BaTiO3 and epoxidized natural rubber. The influence of BaTiO3 concentration on cure characteristics, mechanical (static & dynamic), dielectric, and morphological properties of the composites was investigated. The tensile strength and elongation at break decreased with BaTiO3 loading, while the storage modulus and permittivity of composites increased. As for dynamic electrical properties, the dielectric loss factor and tan δ of the composites showed a maximum peak within the frequency range extending up to 105 Hz, reflecting the relaxation process of the polymer matrix. All of the composites showed two peaks in the frequency dependence of electric modulus, due to conductivity and molecular relaxation. Scanning electron microscopy micrographs confirmed the 0–3 structure of composites, with isolated BaTiO3 particles.
TL;DR: In this article, a composite system Ba0.6Sr0.4TiO3-ZnO-B2O3 for thick film preparation has been modified via copper-fluorine codoping of BST to make it suitable for the fabrication of co-fired metal-insulator-metal (MIM) components.
Abstract: The composite system Ba0.6Sr0.4TiO3–ZnO–B2O3 for thick film preparation has been modified via copper–fluorine codoping of BST to make it suitable for the fabrication of co-fired metal-insulator-metal (MIM) components. Based on the resulting improvement of the thick films, MIM varactors and phase shifters were produced by subsequent screen-printing of silver and BST pastes as well as co-firing. Microstructural investigations showed the compatibility of silver and BST with neither chemical reaction nor cracking of the layers. The microwave characterization revealed good results regarding tunability and quality factor of the varactors and high figure of merit of 70°/dB at 1.72 GHz for the phase shifter.
TL;DR: In this paper, the Rietveld refinement of the XRD pattern was used to quantify the crystalline phases of a sol-gel-based calcined sample of a Boehmite at temperatures between 500 and 1500°C.
Abstract: Boehmite synthesized through a sol-gel route from a nonconventional raw material, as an aluminum waste, was calcined at temperatures between 500 and 1500°C. Quantification of crystalline phases was performed by the Rietveld refinement of the XRD patterns. γ-Al2O3 is formed at 500°C, and up to 1000°C, is the dominant phase. At temperatures ranging from 1000 to 1400°C, it was observed the appearance of a four-phase region. The complete transformation into α-Al2O3 lasts until 12 h at 1400°C or at higher temperatures. The presence of an amorphous phase in calcined samples was confined by direct comparison with a standard of pure α-Al2O3.
TL;DR: A comprehensive review on synthesis, characterization and applications of solgel-derived mullite coating can be found in this paper, where the authors conduct a detailed analysis of the solgel derived mullite film on a ceramic substrate.
Abstract: Mullite is one of the popular ceramic materials for different engineering applications due to some of its important properties which include good thermal and chemical stability, high creep resistance, etc. Mullite synthesized by solgel process generally requires lower temperature for processing and generate product with better homogeneity and more purity compared with other conventional processes. Coating of solgel-derived mullite film on surface of a ceramic substrate can improve its thermomechanical properties, making it suitable for applications in different aggravated conditions. This study embarks a comprehensive review on synthesis, characterization and applications of solgel-derived mullite coating.