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Dense ceramic components of complex shapes are fabricated by combining the techniques of rapid prototyping and gelcasting (RPGC process). Free‐flowing slurries of ceramic powders are set into precision molds fabricated out of expanded polystyrene (EPS) from computer‐aided design files, employing subtractive manufacturing. The removal of the mold from gelled parts is often a serious problem when attempting to produce large and complex‐shaped products. The EPS molds have advantages over the commonly used acrylonitrile butadiene styrene (ABS) molds in this context. Process innovations led to easy demolding and near‐net shaping of components of large and complex geometries that required minimal machining. Fabrication of complex‐shaped products out of alumina with a density of 99%, flexural strength of 389 MPa, and fracture toughness of ∼3 MPa√m is demonstrated. The RPGC process is extended to fabricate composites of alumina and yttria‐stabilized zirconia (YSZ) with α‐alumina platelet inclusions, with enhanced fracture toughness. The components have exhibited uniform density across the body of large and complex‐shaped parts, uniform microstructures, and good mechanical properties. EPS molds are also cost effective for fabricating large parts. The process is generic, allows for easy design modifications to include corrections for shrinkage, and also enables uniform distribution of second phases. [ABSTRACT FROM AUTHOR]

In view of the lack of conformal, load‐bearing, light‐weight, and high temperature‐resistant integrated wave‐absorbing composites suitable for extremely complex conditions, the gel‐casting process was successfully applied to porous Si3N4 wave‐absorbing composites in this work. A universal low‐slurry for gel casting was prepared by using two dispersants acting together (tetramethylammonium hydroxide solution and sodium lauryl sulfate), which ensured the smooth completion of the gel casting process. Combining the thermogravimetric and differential thermal gravity curves of the composite green body, reasonable parameters of the rubber discharge process are given to avoid the problem of the green body swelling and cracking. The porous TiC/Si3N4 composites were successfully prepared by holding them at 1650°C for 3 h. The bending strength, density, minimum reflection loss, absorption bandwidth, and matched thickness in the P‐band of the composites with 30 wt.% TiC addition were 54.08 ± 3.02 MPa, 1.906 g/cm3, ‐37.75 dB, 1.9 GHz, and 4.1 mm, respectively. The electromagnetic wave loss mechanisms of the composites are a combination of conductivity loss, multiple reflections and scattering, interfacial polarization, and defect polarization. [ABSTRACT FROM AUTHOR]

Porous Si3N4 ceramics were prepared by gel casting combined with a reaction bonding route using monodispersed PMMA as the pore former, and Isobam was used as a gel agent. With the PMMA addition varying from 0 to 20 wt.%, the bending strength was degraded from 94.0 to 39.1 MPa owing to the increased porosity and decreased bulk density. The β‐Si3N4 prismatic grains and round pores introduced by the monodispersed PMMA micro balls would endow the samples with high strength, and the permeability of the resulting samples was increased obviously with the increase of PMMA addition. Flue gas filtration test exhibited that the filtration efficiency of the porous ceramics filter was not degraded with introducing of the PMMA pore former, even though the permeability was increased obviously. The block type of the sample with 20‐wt.% PMMA additions during filtration was cake filtration, which indicates that the sample has the characteristic of being reusable after back‐blowing in flue gas filtration applications. Porous Si3N4 with high strength and permeability fabricated via the reaction bonding route exhibits great potential for low‐cost high‐performance ceramics filters. [ABSTRACT FROM AUTHOR]

Low‐cost and environment‐friendly MgO was used as a new gelling and consolidating agent to fabricate porous Al2O3‐based ceramics via a gel casting routine. Effects of 800°C calcined additions of MgO (.5, 1.0, 1.5, and 2.0 wt%, respectively) on open porosity (OP), pore size distribution, gas flux, and microstructure of the porous ceramics were investigated deliberately. The experimental results showed that 800°C calcined MgO exhibits excellent gelling and consolidating performance at 80°C, mainly owing to the hydration reaction between MgO and H2O and thus results in high‐quality porous Al2O3‐based ceramics without deformation and cracking. The Al2O3–water suspensions with different MgO additions have good flowability at room temperature. Moreover, water absorption, open porosity, and gas flux of the as‐prepared porous ceramics increase remarkably with rising of MgO addition. Furthermore, MgO addition significantly suppresses the abnormal growth of Al2O3 grains, and thus the microstructure of the porous Al2O3‐based ceramics becomes more uniform. This technique of gel casting using MgO as a new gelling and consolidating agent offers an alternative routine for a large‐scale production of porous ceramics. [ABSTRACT FROM AUTHOR]

Porous alumina, with monodispersed PMMA as pore former and Y2O3 as sintering additive, was prepared via a gel casting route with Isobam as a gelling agent. The effects of PMMA addition on its properties, including apparent porosity, bulk density, strength, permeability, and corrosion resistance to acid/alkali, were investigated. With PMMA addition increased, the apparent porosity and permeability were increased obviously, while strength and corrosion resistance to acid/alkali were deteriorated due to increased porosity. Higher firing temperature resulted in lower porosity, higher strength, lower permeability, and better corrosion resistance to acid/alkali. Coarser raw powders resulted in lower strength and higher permeability due to the coarser structure and larger pores of the fabricated samples. Because Y2O3 was used as a sintering additive, and no silica was introduced, the resulting samples possess better corrosion resistance to acid and alkali, especially much better corrosion resistance to alkali, than those reported with silica introduced. [ABSTRACT FROM AUTHOR]

Mullite‐bonded porous SiC ceramics sintered in air by gelcasting are still challenges due to the high porosity induced severe oxidation of SiC, which results in the formation of large amount of detrimental cristobalite phase. Here in this work, small amounts of Y2O3 and CaF2 were added in SiC and Al(OH)3 raw materials as sintering additives for the in situ growth of mullite reinforcement. This additive system promoted the reaction between oxidation‐derived SiO2 from SiC and Al2O3 decomposed from Al(OH)3 to mullite phase. Almost no cristobalite phase was detected when sintered at 1450℃/2 h with CaF2 addition of more than 2.0 wt%. Mullite whisker reinforcement was in situ formed due to the gas reaction mechanism caused by CaF2 addition. Thus obtained porous SiC ceramics exhibited a flexural strength of 67.6 MPa at porosity of 41.3%, which maintained exceeding 36 MPa after 8 h corrosion in 10 wt% NaOH 80℃ solution, being the best performance up to now. This high performance of porous SiC was attributed to the additive induces proper phase control and in situ formation of whisker‐like mullite reinforcement. [ABSTRACT FROM AUTHOR]

Thermal insulators were fabricated by freezing gelatin gels containing calcined kaolinite with alumina nanofibers, followed by sintering. The resultant porosity could be varied from 81.0% to 89.8% by solid loadings in the initial slurry. The relationship among porosity, microstructure, compressive strength, and thermal conductivity was examined. The compressive strength and thermal conductivities of the insulators prepared with initial solid loadings from 3 to 6 vol% ranged from 11.6 to 56.7 MPa and from.25 to.46 W/mK, respectively. Those properties were also estimated by simulation using modeling of overall pore morphology, resulting in good agreement. [ABSTRACT FROM AUTHOR]

The Si‐rich pressureless sintering was used to fabricate the Ti3SiC2 bulk ceramic. The results show that the optimized Ti3SiC2 suspension could be prepared at the absolute value of zeta potential, pH level, PAA‐NH4 dosage, and solid loading of 62.1 mV, 11, 2.0 wt%, and 50 vol%, respectively. The channels existing in the Si‐free sintered body facilitated the reactants and products to diffuse to the interior and out of the Ti3SiC2 matrix, thereby forming the porous reaction layer of TiC‐Ti3SiC2. The co‐effects of the channels and the reaction layer of TiC‐Ti3SiC2 severely lowered mechanical properties of the Si‐free sintered Ti3SiC2 ceramic. On the contrary, the Si‐rich sintering method isolated the volatile carbon and established a closed Si‐rich atmosphere to sinter the green Ti3SiC2 cylinder. The porosity, density, fracture toughness, hardness, and flexural strength of the Si‐rich sintered Ti3SiC2 ceramic reached 0.74 vol%, 4.36 g/cm3, 5.49 MPa·m1/2, 4.03 GPa, and 383 MPa, respectively. [ABSTRACT FROM AUTHOR]

The aim of this paper was to establish the general suitability of the centrifugal slip casting technique for fabrication of graded material from the Al2O3–Cu–Ni system. The present investigation is a preliminary one and the obtained results may be regarded as a point for acquiring the new knowledge in the ternary ceramic metal system fabricated using centrifugal slip casting. The rheological study provided the evidence that the suspension used to fabricate composites is a non‐Newtonian slurry. Moreover, the results demonstrated that the prepared slurry is stable over time. The obtained composites has a hollow cylindrical shape with relative density of > 95%. The XRD study results revealed three phases: Al2O3, Ni, and CuNi. The microscopic investigations revealed a nonhomogeneous distribution of the metallic phase in the composite. It has been shown that the content of the metallic phase decreased with the increased distance from the outside to the inner edge of the ceramic‐metal composite. The study results allow to conclude that the interface between the phases is more continuous when sintering was carried out in a solid phase. However, it was found that when sintering was carried out in a liquid phase separated metal particles with spherical phase are formed. [ABSTRACT FROM AUTHOR]

A potentially near‐net‐shape manufacturing procedure for macroporous alumina monoliths with 20%‐75% porosity was presented by gel casting of nano γ‐Al2O3. Although monolith obtained by nano alumina had a high surface area and low sintering temperature, an optimum fraction of micron alumina needed to be added to achieve the proper rheological and mechanical properties of slurries. The preparation parameters including alumina loading, sintering temperature, monomer concentration, and the fraction of nano alumina were investigated. The green densities ranging from 0.66 to 0.86 g cm−3 were obtained by raising alumina loading from 10 to 20 vol%. Depending on the monomer concentration and sintering temperature, the mean pore size ranging from 45 to 412 nm, total porosity (20%–75%), and open porosity varying from 12% to 89% were obtained. The sintered density (from 0.95 to 3.15 g cm−3) and compressive strength (CS) (from 4.2 to 31.46 MPa) were suitable for use in different fields. [ABSTRACT FROM AUTHOR]

Impeller is the key part of centrifugal pump to convey liquid. And combined with the engineering practice, we fabricated two types of open and semi‐open SiC ceramic impellers with diameter of 100 mm and 160 mm via gelcasting and pressureless sintering. B4C and C were used as the sintering additives and sprayed drying granulation method was adopted for the starting SiC powder processing. Given the size and shape complexity of impeller, the optimized pH value, dispersant content, and solid‐loading content for the fabrication of the SiC impellers were determined to be 10‐11, 0.8 wt%, and 40 vol%, respectively. For the open impeller, blade height, cover board thickness, drying shrinkage, and sintering shrinkage are 10.5 mm, 4 mm, 10.3%, and 21.3%, respectively. For the semi‐open ones, the corresponding parameters are 41 mm, 10 mm, 10.3%, and 21.3%, respectively. The average density of the two types of impellers is 3.15 g/cm3, and the mechanical properties of both impellers, including average hardness, flexural strength, compressive strength, and fracture toughness are 2478 HV, 436 MPa, 2093 MPa, and 3.17 MPa·m1/2, respectively. All variation coefficient values are smaller than 5%, which indicates a good uniformity in densities and mechanical properties of both the impellers. [ABSTRACT FROM AUTHOR]

Gel‐casting method was used to fabricate mullite ceramics because this method has not been applied to fabricate dense mullite in literature. Gel‐casting parameters such as monomer types (acrylamide and metyhlenebisacrylamide), effect of initiator (ammonium persulfate), and catalyst (tetramethylenediamine) were studied. All samples reached to relative densities of 97% to 98.2% after sintering at 1540°C for 2 hours. Backscattered SEM images revealed anisotropically grown mullite grains, glassy phase located at triple junctions, hexagonally‐shaped and faceted Al2O3 grains, and white‐color grains consisting of ZrO2 and undissolved TiO2. A Weibull modulus of 12.33 (ie, indicating tough ceramics) and characteristic strength of 186 MPa were calculated, below which no failure was expected. A critical quenching temperature was found as about 400°C (ΔT ~ 380°C) by indentation‐quench method. In addition, a thermal shock resistance parameter (eg, R in °C) of 142.4°C was calculated, which was higher than commonly used Al2O3 ceramics. Lower dielectric constant and loss are desired for wide frequency band application and shorter signal transmission delay time in radomes. The dielectric constant was found as nearly 7.5 up to 10 GHz and loss tangent was 0.0031 at 5 MHz. Dielectric and thermomechanical results suggest that mullite is a suitable candidate ceramic for radome applications. [ABSTRACT FROM AUTHOR]

Porous Al2O3 ceramics with different contents of alumina fibers were prepared by gel‐casting process. The effects of Al2O3 fiber content on pore size distribution, porosity, compressive strength, and load‐displacement behavior of the ceramic materials were investigated. Initial results showed that with the increase of Al2O3 fiber content, the pore size and porosity of the material is increased, and the compressive strength is decreased. However, upon increasing the fiber content from 50 wt% to 67 wt%, the performance of the samples changed greatly. The compressive strength of the material increased, while the porosity remained unchanged, the pore size increased greatly, and the shape of the load displacement curve changed. It showed that when the fiber content increased from 50 wt% to 67 wt%, the loading body in the fiber‐reinforced porous ceramics changed from particles to fibers. [ABSTRACT FROM AUTHOR]

Abstract: The freeze‐cast ceramics process involves the use of an aqueous slurry in which ice acts as a fugitive template, providing control of the morphology of the resultant green body, which is then sintered. Here, we report a variety of applications of ice‐templated ceramics, showcasing the versatility of the process. Applications include: as a suitable scaffold for silver loading and release at concentrations that could show antibacterial properties; as a component of a robust composite material with negative thermal expansion but reduced material cost; as thin porous structures for dye‐sensitized solar cells. [ABSTRACT FROM AUTHOR]

Abstract: A novel kind of 3D interconnected porous carbon‐bonded B4C preform with flexural strength of about 20MPa is fabricated by gel‐casting method. As the control, the B4C/C preforms via molding‐produced method are fabricated. The B4C/C preforms own the same carbon content and almost the same porosity with different molding method. Compared with the conventional compression molding‐produced B4C/C preform, the 3D‐interconnected porous carbon‐bonded boron carbide preforms afford three‐fold advantages in the fabrication of reaction‐bonded boron carbide (RBBC) composite via the liquid silicon infiltration (LSI) process, including induced formation of continuous SiC‐bonded boron carbide skeleton structure, a reduction in the size of residual silicon, and prevented the coarsening of ceramic grains as well. As a result, the RBBC composite fabricated by gel‐casting appears as a more refined structure resulting in enhanced mechanical properties: the Vickers hardness, flexural strength, and fracture toughness of I‐GC composites fabricated from 3D‐interconnected porous carbon/B4C preforms are 19.4 ± 1.3 GPa, 389 ± 17 MPa, and 4.37 ± 0.1 MPa·m1/2, respectively, which are statistically higher than those of RBBC fabricated by the conventional compression molding‐produced B4C/C preform. [ABSTRACT FROM AUTHOR]

Pure anorthite porous ceramics have been fabricated using γ-Al2O3, CaCO3, and SiO2 as raw materials through foam-gelcasting method. XRD, thermal analysis, SEM, and TEM were used to study the synthesis and grain growth of anorthite during the in situ process. The results indicated that the initiator (ammonium presulfate) took part in the chemical reaction to form CaSO4, which played an effective role during synthesis of anorthite. Besides, CaO and CaSiO2 were the other intermediate phase during synthesis. Anorthite first occurred at 1050°C, and it was the only phase after it sintered over 1260°C. With sintering temperature increasing from 1300°C to 1450°C, the large sphere pore wall got denser and the anorthite grains obviously showed platelike. It was deduced that the preferential growth of anorthite crystals was parallel to the (004) plane. [ABSTRACT FROM AUTHOR]

Fused silica ceramics was prepared by using conventional organic binder, mathacrylamide- N, N′-methylenebisacrylamide ( MAM- MBAM) system by gelcasting process. Mechanical properties of green bodies were studied as a function of solid loading varying from 60 to 72 vol%. After evaluating the green body mechanical properties, the samples were densified at different sintering temperature from 1200 to 1450°C with definite intervals of 50°C and subjected to flexural strength analysis. Variation in flexural strength with sintering temperature was observed and correlated with the quantity of devitrification of fused silica during sintering. Quantification of devitrified cristobalite was carried out by using 20 wt% rutile (TiO2) as an internal standard by X-ray diffraction. It was found that, as the cristobalite content increased, flexural strength decreased. Reliability studies were carried out for the samples having maximum flexural strength with and without crystalline content. Reliability studies have shown that for this organic binder system the sample sintered at 1300°C is crystalline free and most reliable product. The mechanical properties and reliability of this product processed with organic binder are compared with inorganic binder system. Results indicate that the sample fabricated using inorganic binder system is exhibiting high Weibull modulus and thus better reliability. [ABSTRACT FROM AUTHOR]

Ethylene glycol diglycidyl ether ( EGDGE), a water-soluble epoxy resin, was used as a complementary gelling agent to improve the strength of alumina green bodies gelcast using PIBM (a copolymer of isobutylene and maleic anhydride acting as both dispersant and gelling agent) gelling system. The effects of EGDGE on the gelling behavior of PIBM- EGDGE aqueous solutions and alumina slurries, mechanical properties of the resultant alumina gels, green bodies, and sintered ceramics were evaluated. Gelation of both the solutions and the slurries was accelerated with the addition of EGDGE. The changes in storage modulus (G′) of the slurries during gelation were quite different from those of the solutions. With the addition of 0.6 wt% EGDGE, G′ of the gel from a slurry with 50 wt% solid loading and 0.3 wt% PIBM increased 63% (100 min of testing), and flexural strength of the resultant green body increased 167%. Such gels and green bodies are strong enough for subsequent processing. They resulted in presintered bodies with low porosity and sintered ceramics with high relative density and flexural strength. [ABSTRACT FROM AUTHOR]

Recently, we developed an efficient method for rapid drying and improving relative density of the gelcast green body. In this work, polymerization and rheological behavior of the thermoresponsive gelcasting system based on N-isopropylacrylamide were investigated. To initiate reaction of the system with 4 mL/L of catalyst, 0.25-0.5 mg/mL of initiator is considered optimal in the optimized temperature range 15-20°C. Suspensions with 40-55 vol.% solid loading still show shear-thinning behavior, which is favorable for mixing, degassing, and casting. The final storage moduli of consolidated suspensions are approximately 104 Pa, which is sufficiently high for gelcast green bodies. [ABSTRACT FROM AUTHOR]

An eco-friendly gelcasting system has been developed for the fabrication of alumina ceramics using alumina sol as a binder. 0.5 wt% of ammonium polymethacrylate dispersant was used based on total alumina solid loading to obtain completely dispersed slurry with high solid loading. Ceramic slurries having different volume percentage of alumina loading from 46 to 52 vol% in alumina sol were made, and the rheological properties were evaluated. 51 vol% of alumina slurry having viscosity 0.73 Pa.s with 2 wt% of alumina sol binder content per weight of alumina was optimized. The gelling behavior of concentrated slurry was evaluated by measuring storage modulus, and the consolidated green sample is homogeneous and exhibiting the bending strength of 4 MPa and 55% theoretical density. On sintering the sample at 1550°C for 2 h, the flexural strength was found to be 317 ± 30 MPa, and the corresponding theoretical density was 98%. [ABSTRACT FROM AUTHOR]

In this study, aluminum nitride ( AlN) ceramics were first prepared by aqueous gelcasting. The effect of various parameters such as concentration of N, N-dimethylacrylamide ( DMAA, as monomers), N, N′-methylenbisacrylamide ( MBAM, as cross-linking agent), ammonium persulfate amount ( APS, as initiator), solid content and polymerization temperature on AlN ceramics was discussed for aqueous gelcasting system. Finally, drying methods of aqueous gelcasting AlN green bodies were investigated. Aqueous gelcasting AlN ceramics, sintered at 1850°C for 4 h, had homogeneous grain size and little grain boundary phase, and the relative density, flexural strength and thermal conductivity of aqueous gelcasting AlN ceramics were 99.9%, 333(±10) MPa, 136(±9) W/(m·K), respectively. [ABSTRACT FROM AUTHOR]

Dense (97.3%) zirconium diboride (ZrB2) ceramics were obtained via gelcasting and pressureless sintering. Four wt% B4C was used as sintering aid. ZrB2, SiC, and B4C can codisperse well in the alkaline region, using a polyacrylate dispersant. Compared with monolithic ZrB2 (Z), the mechanical properties of ZrB2-SiC ( ZS) were enhanced. The Vickers hardness and fracture toughness of ZS were (13.1 ± 0.6) GPa and (2.5 ± 0.4) MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

Porous YSZ ceramics reinforced by different fibers were prepared by gel-casting with 15% solid content and pressureless sintering. The four kinds of fibers (mullite, aluminosilicate, Al2O3, and YSZ fibers) were added into the YSZ ceramics with the same 10% vol content. After sintered at 1500°C for 2 h, aluminosilicate and mullite fibers could not be found in the samples of porous YSZ ceramics, which showed they reacted with YSZ ceramics at high temperature, while YSZ and Al2O3 fibers still kept perfect after sintering. Furthermore, the influences of fiber content, sintering temperature, porosity of matrix materials on compressive strength and porosity of the porous YSZ ceramics were studied. The results showed that Al2O3 fiber showed more obvious reinforcing effect than YSZ fiber on porous YSZ ceramics. The fiber-reinforcing effects depend on fiber content, sintering temperature, and porosity of matrix materials. The fiber addition can improve the shrinkage behavior of porous ceramics during sintering and strengthen the skeleton of porous ceramics. [ABSTRACT FROM AUTHOR]

Porous mullite ceramics were fabricated from an industrial grade mullite powder by gelcasting process using fly ash cenospheres ( FAC) as a pore-forming agent. The influence of content of FAC and sintering temperature on the density and strength was evaluated. The microstructure showed that FAC can act as a sintering aid and a pore-forming agent. When the sintering temperature at 1200°C, porous mullite ceramics with a relatively high porosity (48.1-72.2%), low density (0.84-1.64 g/cm3), low thermal conductivity (0.16-0.22 W/m · K), and high compressive strength (6.21-14.70 MPa) have been obtained. [ABSTRACT FROM AUTHOR]

The dispersion of highly concentrated Zirconium diboride ( ZrB2) suspension in aqueous media was investigated in terms of zeta potential and rheological measurements, with a salt of polyacrylate polymer ( SD-07) as dispersant. The adsorption behavior of SD-07 on ZrB2 particle surface was also studied. Results showed that acid cleaning improved the fluidity of aqueous ZrB2 slurry. Concentrated (up to 50 vol%) and well-stabilized suspension was obtained in the alkaline pH region, with 0.60 mg/m2 SD-07. On this basis, 50 vol% ZrB2 gelcasting slurry was prepared. The linear shrinkage and flexural strength of as-casted green body were (3.42 ± 0.13)% and (9.4 ± 0.3) MPa, respectively. [ABSTRACT FROM AUTHOR]

A suspension with good rheology and high stability is crucial for slip casting and gelcasting technology. However, a mixed suspension from two or more different powders usually has bad rheology because of the easy agglomeration of mixed powders caused by the attractive force between the powders with heterocharges. We studied the surface modification of the each single-component powders ( SiC, Al2O3, ZrO2(3 Y) powders) and the SiC- Al2O3- ZrO2(3 Y) mixed powders to increase the repulsive force by adjusting the pH value and adding polyacrylic acid ( PAA) as dispersant. The PAA addition effects on the SiC- Al2O3- ZrO2(3 Y) mixture were investigated in terms of zeta potential, pH range for heterocharge region, dispersion of the mixed powders and rheology of the mixed slurry based on the study of each unary suspensions. The results show that before surface modification the SiC- Al2O3- ZrO2(3 Y) mixed powders were agglomerated severely because they were in the heterocharge region with a broad pH range from 3.5 to 8.25, while after surface modification ( pH = 10.5, PAA = 0.8wt%) the heterocharge region was narrowed with a relatively narrower pH range from 2.6 to 3.7. The mixed powders with homocharges were dispersed well because of the great electrostatic repulsive force and steric hindrance offered by PAA and the mixed suspensions had favorable rheology. [ABSTRACT FROM AUTHOR]

Localized mode is an important property of defect electromagnetic band gap ( EBG) structure, which plays a key role in the application of EBG structure. The purpose of this article was to study the impact on localized properties by introducing cavities of different shapes into diamond EBG structure. Alumina-based ceramic diamond EBG structures were fabricated using stereolithography ( SL), gel-casting and vacuum freeze-drying. When the microwave transmission properties of samples with cavities of different shapes were tested, the resonant peaks appeared within the band gap. By varying the cavity shape, the quality of the localized mode could be adjusted. The results have shown that localized mode with a high quality factor ( Q factor) corresponded to the optimal cavity shape in EBG structure. The experimental results agreed well with simulation results. These excellent microwave properties of 3D EBG structure could be directly applied in microwave devices, such as microwave antenna and filter devices. [ABSTRACT FROM AUTHOR]

Agar was used for gel casting barium titanate (BaTiO) ceramics. Aqueous suspensions of bimodal BaTiO powders, with 500 and 100 nm nominal particle sizes, were prepared with a 85:15 coarse:fine ratio. BaTiO suspensions were mixed with agar solutions from 2 to 8 wt%, with 0.5 or 1.0 wt% agar (as a function of BaTiO solids content) in the final gel-casting suspension. BaTiO green densities up to ∼53.2% of theoretical were obtained. Gel casting of high aspect ratio features (up to 7:1) could be routinely performed. Cast bodies were also amenable to computer-numerical-controlled based green machining. [ABSTRACT FROM AUTHOR]

Laminated ceramic composites are appealing for many applications due to their unique and customizable thermal and mechanical properties. Gelcasting is a relatively new, yet commercially proven, near-net-shape processing technique suitable for laminate production. A review of gelcasting techniques and a discussion of their application to laminate processing are provided, along with an overview of laminate design and processing concerns. Specific examples of single-phase laminates produced via gelcasting are provided, including porous/dense alumina and magnetically aligned iron titanate and barium hexaferrite structures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]