Coarse Agglomerates Research Articles

Experimental investigation and CFD study of direct reduction of iron ore in the conical fluidized bed

The reduction behavior of iron ore is the fundamental process in ferrous metallurgy. Considering the gas–solid interface-structure relationship, heterogeneous transfer-reaction behavior, and multiple reaction kinetics, this work provides an effective analytical tool to investigate the fluidized reduction of iron ore. The conical fluidized bed is numerically examined to be capable of preventing de-fluidization induced by the sticking behavior, due to the steady circulation of flow pattern and full fluidization of coarse agglomerates. Compared with the hydrogen concentration, the gas velocity shows a stronger influence on the agglomerate reduction rate for the more efficient gas–solid contact. For the simulated transitions of Fe2O3 → Fe3O4 → Fe(1-x)O → Fe are assumed to overlap each other, there exist discrepancies between computed and theoretical reduction degrees. The experimental and numerical findings can be used to develop a methodology for optimizing the operational complexity and economic benefits of the fluidized reduction of iron ore.

Epoxidized technical Kraft lignin as a particulate resin component for high-performance anticorrosive coatings

Deterioration of steel infrastructures is often caused by corrosive substances. In harsh conditions, the protection against corrosion is provided by high-performance coatings. The major challenge in this field is to find replacements for the fossil-based resins constituting anticorrosive coatings, due to increasing needs to synthesize new environmentally friendly materials. In this study, softwood Kraft lignin was epoxidized with the aim of obtaining a renewable resin for anticorrosive coatings. The reaction resulted in the formation of heterogeneous, solid, coarse agglomerates. Therefore, the synthetized lignin particles were mechanically ground and sieved to break up the agglomerates and obtain a fine powder. To reduce the use of fossil fuel-based epoxy novolac resins in commercial anticorrosive coatings, a series of formulations were prepared and cured on steel panels varying the content of epoxidized lignin resin. Epoxidized lignin-based coatings used in conjunction with conventional epoxy novolac resin demonstrated improved performance in terms of corrosion protection and adhesion properties, as measured by salt spray exposure and pull-off adhesion test, respectively. In addition, the importance of size fractionation for the homogeneity of the final coating formulations was highlighted. The findings from this study suggest a promising route to develop high-performing lignin-based anticorrosive coatings.

Particle aerosol generation and potential altering in airflow used for acute/repeated inhalation toxicity testing

Reproducible aerosol generation in combination with stable aerosol properties are essential prerequisites for compliant performance of acute or repeated inhalation toxicity tests of particulate materials according to OECD TG 403, 436, 412, or 413. A frequent problem of powder aerosol generation is the formation of coarse agglomerates with low shear resistance, which are beyond the tolerable size range but not detected by the prescribed aerodynamic measurement techniques by cascade impactor as the measurement conditions cause a disintegration into smaller fragments. But such agglomerates are observed during the transport to the inhalation chambers. These effects particularly apply to high mass concentrations and low-density powders, i.e., pyrogenic oxides. This study describes the transport influence in the airflow on the change of powder aerosols and on their respirability.A simplified short tube set-up was developed for the aerosol transport pre-tests, which allows the determination of the optimal aerosol formation conditions for the inhalation tests. The particles were measured with low shear using laser diffraction measurement or optical particle counters. The calculation of the aerodynamic particle sizes prescribed in the guidelines requires knowledge of the effective particle density of the porous aerosol particles. A practicable method for determining these is presented and described. In the outlook, first low concentration measurements show that clear agglomeration effects can also occur at particle concentrations around 20 mg/m³.

In-situ synthesis of TiB2 particulate reinforced copper matrix composites with ultrasonic vibration treatment

In this paper, ultrasonic vibration treatment (UVT) was directly introduced into Cu-Ti-B melt through a Sialon sonotrode. The effects of UVT on the microstructures and properties of TiB2/Cu composite thus fabricated were investigated. The results indicate that with the application of UVT, the average size of the particle agglomerates in the as-cast composite reduced from 24.84 μm to 19.69 μm. Besides, the 3D morphology of the agglomerates changed from irregular to near-spherical under the effect of ultrasound cavitation. The acoustic streaming promotes the flow of the melt to realize a more uniform distribution of particles in the bulk. Dispersion of TiB2 particles alleviates the stress concentration caused by coarse agglomerates, resulting in the concurrent improvements in both strength and ductility of the composite.

Artificial neural network for mechanism identification and process prediction of the nanoclusters deagglomeration in the in-line HSM

A multiple-input multiple-output artificial neural network (ANN) for the mechanism identification of nanoclusters deagglomeration and the prediction of particle size distribution (PSD) evolution of nanocluster in deagglomeration process of in-line high shear mixer (HSM) was successfully established. It can successfully realize the description of nanoclusters deagglomeration process within single or multiple processing batches. Besides, this ANN model also can realize the accurate prediction of the d32 of fine and coarse agglomerates, and the fines fraction, at different operating conditions and structural parameters, within the relative error of 10 % and 20 % respectively. Meanwhile, 3D profiles of PSD versus different operating conditions and structural parameters were output by the established ANN model, which were useful for parameter selection of in-line HSM to realize efficient production of nanoparticles suspension. The successful establishment of this ANN model provides an effective, flexible, and advanced intelligent method for guiding the parameter selection of in-line HSM, for realizing the controllable and efficient production of the high-end nanoparticle products with specific particle characteristics.

Worker’s Personal Exposure to PM0.1 and PM4 Titanium Dioxide Nanomaterials during Packaging

For the appropriate hygienic management of workplaces where workers handled nano-TiO2 products, the status of the personal exposure of workers to respirable dust (PM4) and nanoparticles (PM0.1) was investigated. Using a cyclone sampler for PM4 and a personal sampler for PM0.1, PM4 and PM0.1 exposure levels were evaluated to discuss them in relation to worker’s duties. The number of particles of 0.01–10 µm was also monitored online in order to examine the short-term fluctuation in the concentration and size distribution of particles. The 8h-time-weighted average (TWA) and 95% upper limit for respirable dust exposure were below the occupational exposure limit specified by the Japan Society for Occupational Health and the recommended exposure limits for TWA by NIOSH. The action level was exceeded during the filling of a flexible container bag. More than 70% of particles in the breathing zone was coarse agglomerates of > 1 µm, while it may be influenced by powder properties and the handling process as well as the management of local ventilation. The maximum PM0.1 concentration (31.3 µg m–3) occurred in a powder filling booth without air ventilation. The operation of a gasoline powered forklift temporarily increased the concentration of ultrafine particles. Most of TiO2 powder was suspended as micron-order agglomerates in the breathing zone. However, since PM0.1 exposure was much larger than those in outdoor environment particularly under insufficient cares to aerosolized powder and air ventilation, PM0.1 exposure should also be monitored.

Degree of dispersion assessments of highly filled stereolithography suspension using fineness of grind measurement

Agglomerates are a large cluster of primary particles, which may result in the flaws of the final ceramics. Stereolithography suspensions could pose challenges to identify their coarse agglomerates without modifications to their properties; the suspensions are mostly high turbid and viscous in some cases. Any modifications, such as dilution, can alter the actual degree of agglomeration. In this study, a means to characterize the degree of dispersion was developed using the automated fineness of grind gauge. The fineness of grind gauge was visualized to determine the nature of the trapped agglomerates and their distribution. The resulted agglomerate size distribution was treated mathematically as a power law distribution in a selected region. The power law function was found to describe the degree of dispersion of suspensions, which was associated with the coarse agglomerate distribution behavior.

Self-Propagating High-Temperature Synthesis of (Al–2% Mn)–10% TiC and (Al–5% Cu–2% Mn)–10% TiC Nanostructured Composite Alloys Doped with Manganese Powder

The influence of alloying with powder manganese on the preparation of nanostructured (Al‒2% Mn)–10% TiC and (Al–5% Cu–2% Mn)–10% TiC composite alloys with the application of the self-propagating high-temperature synthesis (SHS) of titanium carbide TiC nanoparticles from the Ti + C charge in a melt of matrix alloys is investigated. Powder metallic manganese in an amount of 2 wt % is preliminarily introduced into Al and Al–5%Cu matrix bases of composite alloys. This makes it possible to increase the ultimate tensile strength of the aluminum base from 81 MPa (for initial aluminum of the A7 brand) to 136 MPa and that of the aluminum–copper base to 169 MPa. It is revealed that, when alloying aluminum only with manganese, the SHS reaction proceeds weakly and incompletely, while the carbide phase size in the (Al‒2% Mn)–10% TiC alloy varies from a nanolevel to several microns. When adding 10% of the Na2TiF6 haloid salt into the SHS charge, the SHS process is intensified, but the resulting alloy contains numerous pores, inclusions of the unreacted charge, and coarse agglomerates of ceramic nanodimensional TiC particles. When using Ti + C and Ti + C + 10% Na2TiF6 SHS charges with coalloying matrix aluminum by copper and manganese, similar results are acquired. The difference is in the larger distribution uniformity of the nanodispersed TiC phase. The best results are attained with a decrease in the Na2TiF6 additive to 5% of the charge weight, which promotes the smoother and complete synthesis of preferentially nanodimensional TiC particles and the formation of the poreless homogeneous microstructure of the (Al–5% Cu–2% Mn)–10% TiC composite alloy with an ultimate tensile strength of 213 MPa and relative elongation of 6.6%.

Application of coarse gibbsite agglomerates to formation of 2D and 3D boehmite particles by the dehydration of the hydrothermal treatment and atmospheric pressure

The coarse agglomerates of gibbsite (γ-Al(OH)3) are grateful starting materials for preparation aluminum oxides and hydroxides as boehmite and γ-Al2O3, which are extensively used as a catalysts and catalyst support for the petrochemical industry. By preparing the boehmite particles from the gibbsite and product of the heat gibbsite, we demonstrate the influence of different treatments to a morphology and particle size of the formed boehmite (γ-AlOOH). It is been established for the first time that the flaky-shaped 2D γ-AlOOH particles are formed within the coarse agglomerates producing a laminated packaging film lozenge-shaped crystals which results in a 0.1 cm3/g pore volume and 29 m2/g specific surface area. The obtained data have a high industrial importance in the area of producing materials based on the coarse boehmite agglomerates with different properties.

Formation of ethylene-vinyl acetate composites filled with Al–Cu–Fe and Al–Cu–Cr quasicrystallline particles

Icosahedral Al65Cu23Fe12 and decagonal Al73Cu11Cr16 quasicrystalline powders were synthesized by the mechanical alloying and subsequent annealing. Morphology evolution at mechanical alloying of Al-based powders was found to be determined by competition between cold welding and fracture mechanisms. Mechanical alloying results in formation of coarse agglomerates consisting of fine particles. The chemical binding between the polymer matrix and quasicrystals, destruction of agglomerated at extrusion, and the uniform distribution of quasicrystals over the polymer melt were provided by surface treatment of quasicrystalline particles with silanes. The highly filled (up to 60wt%) ethylene-vinyl acetate/quasicrystals composites were obtained, and their rheological characteristics were studied. It was shown that the fluidity of the melt is retained at a high level providing uniform distribution of quasicrystalline particles over the polymer.

Modified Two-Step Method to Prepare Long-Term Stable CNT Nanofluids for Heat Transfer Applications

CNT nanofluids are getting attention in heat transfer applications due to their very high thermal conductivity in comparison with conventional fluids. For commercial exploitation of CNT nanofluids as heat transfer media, they must have long-term stability. In this study, the two-step method was modified to prepare dynamically stable CNT nanofluids by utilizing commercial grade multiwalled carbon nanotubes and SDBS as a surfactant. The modified technique consists of separation of coarse agglomerates of CNT from the CNT nanofluids by applying centrifugal action after its preparation. The effect of relative centrifugal force was also studied for the very first time on the stable concentration of CNT nanofluids. The stability of CNT nanofluids was analyzed by measurement of their CNT concentration and Zeta potential. Results showed that CNT nanofluids possess good stability and remain stable for more than 15 months. In addition to stability, thermo-physical properties such as thermal conductivity, density, and viscosity of CNT nanofluids were also measured. The results of this study elucidated the effect of RCF on the stable concentration of CNT nanofluids. It is expected that the results obtained in this study may significantly contribute to the proper tailoring of CNT nanofluids, by providing long-term stable CNT nanofluids which are suitable for industrial heat transfer applications.

High energy ball milling of titania and titania–ceria powder mixtures

Titania alone and several titania–ceria blends of powders were milled by high energy ball milling for different periods of time. Phases, crystal size, particle size and morphology were evaluated. The research has demonstrated that milling reduces the mean crystallite size to less than 30nm for any time whereas powder particles coalesce into coarse agglomerates. At the same time anatase titania transforms to rutile after 3hour milling, but a thermal treatment at 700°C for 1h partially recovers the original crystal structure. The behaviour of ceria–titania blends is similar to that of titania alone, but the reversibility of the anatase–rutile transformation does not occur when the quantity of ceria is greater than a critical level which we have set between the composition with Ce/Ce+Ti ratios of 5 and 10wt.%.

Gold Recovery from Gold Bearing Materials Using Bio-Diesel, Vegetable Oils and Coal

The present work is focused on the performance of three types of coal-oil agglomerates on recovery of liberated gold from gold bearing materials. Pre-formed agglomerates developed using bio-diesel, castor oil and mineral diesel as liquid hydrophobic phases were used in the study. The influence of the type of liquid hydrophobic phase on the degree of gold recovery and the effect of factors such as gold particle concentration, viscosity, agglomerate size, agglomerate/ore ratios and particle penetration into agglomerates have been studied as a function of time. It is shown that gold recovery rate can be increased by an increase in agglomerate loading, surface area and the viscosity of the hydrophobic phase and high recoveries are attained up to 98.5%. Increase in concentration of gold particles per unit volume of slurry increased attachment rate but did not change the final recoveries attained. It is shown that gold particle penetration occurs mainly in the coarse agglomerates if contact is prolonged beyond 60 minutes. Examination of sections of gold-loaded agglomerates under reflected light microscope showed gold and some silicate particles penetrated in few cracked agglomerates and only gold particles were observed inside the uncracked agglomerates suggesting the possibility of gold selectivity during particles penetration. It was shown that the increase in gold recovery attained at prolonged contact time is due to both gold penetration and oleophilic attachment.

Effects of external energetic factors on tritium release from the EXOTIC 8-3/13 neutron-irradiated beryllium pebbles

Tritium release from samples of 9–13 mg of the EXOTIC 8-3/13 neutron-irradiated beryllium pebbles under the separate and simultaneous action of temperature 490–770 K, 5 MeV fast-electron radiation 14 MGy h −1 for 3 h and magnetic field (MF) of 1.7 T was investigated. The pebbles were found to be very dissimilar with respect to their total tritium content—2.5–9 MBq g −1. The batch contained also some coarse agglomerates of the pebbles containing 10–19 MBq g −1 of tritium having also a high tritium release. For the pebbles having the total tritium 2.5–5.3 MBq g −1, the electron radiation for 3 h caused the fractional tritium release 17–26% ( B = 0) and 21–29% ( B = 1.7 T), the temperature of the pebbles being <550 K. The annealing of the pebbles at the temperature ramp at 5 K/min to 553 K and at 553 K for 3 h caused the fractional tritium release 10–19% ( B = 0) and 14% ( B = 1.7 T). For the pebbles having the total tritium 3.6–5.8 MBq g −1, the annealing of the pebbles at the temperature ramp at 5 K/min to 770 K and at 770 K for 1 h caused the fractional tritium release 17–24% ( B = 0) and 25% ( B = 1.7 T), but with the simultaneous additional action of the electron radiation for 3 h the fractional tritium release was 24–42% ( B = 0) and 32–37% ( B = 1.7 T).

Optimized dispersion of nanoparticles for biological in vitro and in vivo studies

BackgroundThe aim of this study was to establish and validate a practical method to disperse nanoparticles in physiological solutions for biological in vitro and in vivo studies.ResultsTiO2 (rutile) dispersions were prepared in distilled water, PBS, or RPMI 1640 cell culture medium. Different ultrasound energies, various dispersion stabilizers (human, bovine, and mouse serum albumin, Tween 80, and mouse serum), various concentrations of stabilizers, and different sequences of preparation steps were applied. The size distribution of dispersed nanoparticles was analyzed by dynamic light scattering and zeta potential was measured using phase analysis light scattering. Nanoparticle size was also verified by transmission electron microscopy. A specific ultrasound energy of 4.2 × 105 kJ/m3 was sufficient to disaggregate TiO2 (rutile) nanoparticles, whereas higher energy input did not further improve size reduction. The optimal sequence was first to sonicate the nanoparticles in water, then to add dispersion stabilizers, and finally to add buffered salt solution to the dispersion. The formation of coarse TiO2 (rutile) agglomerates in PBS or RPMI was prevented by addition of 1.5 mg/ml of human, bovine or mouse serum albumin, or mouse serum. The required concentration of albumin to stabilize the nanoparticle dispersion depended on the concentration of the nanoparticles in the dispersion. TiO2 (rutile) particle dispersions at a concentration lower than 0.2 mg/ml could be stabilized by the addition of 1.5 mg/ml albumin. TiO2 (rutile) particle dispersions prepared by this method were stable for up to at least 1 week. This method was suitable for preparing dispersions without coarse agglomerates (average diameter < 290 nm) from nanosized TiO2 (rutile), ZnO, Ag, SiOx, SWNT, MWNT, and diesel SRM2975 particulate matter.ConclusionThe optimized dispersion method presented here appears to be effective and practicable for preparing dispersions of nanoparticles in physiological solutions without creating coarse agglomerates.

Role of dispersion conditions on grindability of yttria stabilized zirconia (YSZ) powders

A precursor for zirconia - 8 mole% yttria (YSZ-ZrO2-8 m% Y2O3) powder was prepared by coprecipitation and the calcination temperature was fixed as 900°C from TG-DTA and XRD studies. The calcined powder could be dry ground only to a mean particle size (D50) of 6 Μm containing substantial amount of coarse agglomerates in the size range 10–100 Μm. The dispersion conditions for its wet grinding were evaluated through zeta-potential and viscosity studies. The zeta-potential variation with pH of the aqueous suspensions of the powder exhibited maximum numerical values at 3 and 11 pH, exhibiting the ideal pHs for dispersion stability through electrostatic columbic repulsion mechanism. Slurries of dry ground powders with solid concentration in the range 15–30 vol.% exhibited pseudo-plastic flow characteristics, indicating presence of flocculates. With progress of grinding, the increase in viscosity of the slurries became less significant with decreasing solid concentration. Even though the particle size of the ground slurries decreased with decreasing solid content, there was little change in it for slurries with solid content < 20 vol.%. Grinding conditions for formation of sinter-active powders of YSZ with sub-micron size (D 50 ∼ 0.7 Μm free of agglomerates of size > 5 Μm) were established. Compacts from this powder could be sintered at 1400°C to translucent bodies with 99% theoretical density.

Synthesis of YAG powder by aluminum nitrate–yttrium nitrate–glycine reaction

Yttrium aluminum garnet (YAG) powders of controlled size distribution find application in the synthesis of optically transparent solid state laser components, advanced engineering materials and composites, etc. [1, 2]. Solution combustion is one of the simple methods for synthesizing the powder. In this technique, from a very concentrated solution of the metal nitrates a very porous sponge-like oxide compound is formed due to the evolution of a large amount of gaseous products formed in combustion reaction between an oxidizer (nitrate) and a fuel (urea, glycine etc.) present in the reactant system. The salient feature of combustion reaction is that it is exothermic and self sustaining. In this study the fuel, glycine, is chosen for formation of YAG since the amount of heat evolved and kinetics of the reaction are such that the combustion proceeds smoothly without bursting or spilling out of the product, a desirable aspect from the point of view of scaling up. The oxide formed is weakly agglomerated and needs to be ground into a fine powder before forming into shape. Formation of amorphous precursors for yttria–alumina compound phases by the nitrate–glycine reaction (with lean amount of fuel) and evolution of crystalline phases upon heat treatment has been studied by XRD [3]. However a study of the thermal evolution behavior by TG–DTA of the precursors formed by combustion to obtain temperature regimes of weight loss and heat effects (evolution/absorption) before and during crystallization of YAG is essential in obtaining conditions for formation of chemically pure YAG (Y3Al5O12 oxide compound). A study of the grinding behavior of the agglomerated mass formed is important from the point of view of its dispersion behavior, as the presence of coarse agglomerates reduces sinterability and homogeneity of microstructure of the product formed. As no study on these aspects has been reported yet for the precursors formed by the nitrates–glycine reaction (with stoichiometric amount of fuel), a detailed investigation of the same has been carried out. The stock solutions of aluminum nitrate (1.54 M) and yttrium nitrate (1.17 M) in the required molar ratio (5 : 3) for a batch size of 20 g. of YAG were placed in a pyrex beaker and the required amount of glycine was added. The ideal molar ratio of fuel (glycine) to oxidizer (nitrate ion) to be used was calculated using the following reaction and is 5/9 or 0.556 (i.e., 5 moles of glycine requires 9 moles of nitrate ions) [4]

Microagglomeration of pulverized pharmaceutical powders using the Wurster process I.: Preparation of highly drug-incorporated, subsieve-sized core particles for subsequent microencapsulation by film-coating

A novel agglomeration process of pulverized pharmaceutical powders into subsieve-sized agglomerates (microagglomeration) was designed for manufacturing highly drug-incorporated core particles for subsequent microencapsulation by film-coating. The microagglomeration of pulverized phenacetin powder, whose mass median diameter was 9 μm, was performed by spraying an aqueous colloidal dispersion of acrylic polymer, Eudragit® RS30D, as a binding/coating agent using a spouted bed assisted with a draft tube (the Wurster process), and the effect of process variables was examined. An appropriate spray liquid flow rate made it possible to produce microagglomerates of 20–50 μm with 60% yield. However, 10% of the product still survived as particles smaller than 10 μm even at the elevated liquid flow rate. In contrast, the survived particles smaller than 10 μm tended to be predominantly reduced to 2%, while coarse agglomerates larger than 53 μm were not excessively produced, by additionally setting a fixed bed of glass beads in the spouted bed apparatus. The length of the draft tube influenced compaction of the agglomerates as well as their surface-smoothening. Equipping the fixed bed of the glass beads and the long draft tube in the spouted bed allowed us to prepare microagglomerates of 20–50 μm at yield of 55% applicable as highly drug-incorporated, free-flowing, surface-smoothed, narrowly size-distributed core particles for subsequent microencapsulation by film-coating.

Microstructural observation of ZnAl2O4 formation affected by the physical nature of Al2O3 in the presence of LiF

Microstructures of ZnA2O4 formation in the presence of LiF were observed for specimens including both coarse and dense alumina and agglomerates of fine alumina, and their morphological changes were compared with each other. LiF formed an intermediate liquid phase with ZnO and Al2O3. In the specimen with agglomerated Al2O3, the porous ZnAl2O4 layer was developed from the Al2O3 agglomerates. However, on firing at 700° C, zeta-lithium aluminate developed just inside the ZnAl2O4 layer and interfered with the spreading of the liquid including Al2O3 to the ZnO phase. However, on firing above 800° C, the formation of ZnAl2O4 was promoted by the rapid spreading of the fluoride liquid including Al2O3 to the ZnO phase through the porous ZnAl2O4 layer before LiAl5O8 formation. In the specimen with coarse and dense Al2O3, the dense ZnAl2O4 layer grew around the coarse and dense Al2O3 and the fluoride liquid phase was confined between the ZnAl2O4 layer and the Al2O3 particles. The dense ZnAl2O4 layer interrupted the spread of the liquid phase to the ZnO phase and interfered with further formation of ZnAl2O4. The confined liquid phase gradually reacted with Al2O3 to form LiAl5O8. It is necessary for the fluoride liquid including Al2O3 to spread out to the ZnO phase through the porous ZnAl2O4 layer to form ZnAl2O4, before the dense ZnAl2O4 or LiAl5O8 layer grew around Al2O3. The use of fine Al2O3 powder and a high firing temperature were effective in the promotion of ZnAl2O4 formation in the presence of LiF.

遠心力成形法による部分安定化ジルコニア (PSZ) 焼結体の作製

Commercial ZrO2 powders containing 2 and 2.5 mol%Y2O3 (PSZ) (grain size ∼20 nm) were dispersed in nitric acid aqueous solution at pH 3 with the aid of high power (1 kW) ultrasonic agitation. Centrifugal force (accerelation>20000 G) was applied not only for sedimentation but for effective compaction of the powder. Semi-transparent sintered body was obtained after sintering of the powder at 1573 K for 14.4 ks, which turned out to have very low porosity (less than 0.5%).Three-point bending tests with the span length of 15 mm were carried out for the specimens of 1.5 mm×2 mm×20 mm fabricated by the above method. The highest strength was 1.9 GPa in the case of a specimen containing 2 mol%Y2O3.From observations of the microstructure it was evident that coarse agglomerates were condensed at the bottom of the consolidated body, and that no segregation of Y2O3 took place along the centrifugal direction. Application of high centrifugal force (accerelation>200000 G) was found to be effective for further compaction.