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WO2002030572A1 - Commande dynamique et traitement chimique ameliore de ceramiques aux dimensions de particules submicroniques - Google Patents

Commande dynamique et traitement chimique ameliore de ceramiques aux dimensions de particules submicroniques Download PDF

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Publication number
WO2002030572A1
WO2002030572A1 PCT/US2000/028592 US0028592W WO0230572A1 WO 2002030572 A1 WO2002030572 A1 WO 2002030572A1 US 0028592 W US0028592 W US 0028592W WO 0230572 A1 WO0230572 A1 WO 0230572A1
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Prior art keywords
milling
suspension
ceramic powder
ceramic
passivating agent
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PCT/US2000/028592
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English (en)
Inventor
James H. Adair
Thomas R. Shrout
Gary L. Messing
Tarah M. Pecora
Michael M. Mandanas
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The Penn State Research Foundation
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Priority to AU2001212072A priority Critical patent/AU2001212072A1/en
Publication of WO2002030572A1 publication Critical patent/WO2002030572A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
    • B02C17/16—Mills in which a fixed container houses stirring means tumbling the charge
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/06—Selection or use of additives to aid disintegrating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/60—Production of ceramic materials or ceramic elements, e.g. substitution of clay or shale by alternative raw materials, e.g. ashes

Definitions

  • the present invention pertains to milling of ceramic powders and an improved process for the same.
  • Ceramic powders are important in a variety of different fields. Examples include manganese zinc ferrites, aluminum nitride, zinc oxide, silicon dioxide, barium titanate, and iron oxide.
  • Manganese zinc ferrites are important ceramic materials for the manufacture of ferromagnetic devices including inductors and transformers.
  • MZF are prepared through calcination of mixtures of the single component precursor metal carbonates or oxides followed by milling to the desired particle size range. The milling operation usually involves suspension of the calcined, aggregated material in water to promote a higher milling efficiency than that encountered with dry milling.
  • Aluminum nitride (A1N 3 ) is commonly used in circuit substrates. Zinc oxide is used as a varistor material, and, of course, uses for silicon dioxide ceramics are ubiquitous. Barium titanate is often used in multi-layer capacitors and in piezoelectric devices such as transducers and ultrasonic vibrators.
  • manganese zinc iron ferrite is often made by mixing a precursor mix of magnesium carbonate, zinc carbonate, iron oxide, which is then calcined at about 1000°C. The chemicals "homogenize” during the calcination process at the high temperature, but this results in primary particles which have sintered.
  • Zinc oxide ceramic typically comes from calcining a mixture of zinc hydroxide and zinc carbonate or the single precursors, and the resultant product, too, needs milling to be useful.
  • Silicon dioxide as commercially provided, comes from chemical vapor deposition, but while it is very fine, it often aggregates in the process, and therefore also needs milling.
  • Barium titanate is prepared by calcining either BaCO 3 and TiO 2 or a precursor such as (BaTiO)(C 2 O 4 ) 2 -4H 2 O, which results in polycrystalline aggregates. All are in need of further treatment to make satisfactory submicron particles for their various ceramic material uses.
  • dielectric layers As an example, the importance of being able to produce thinner dielectric layers is becoming increasingly recognized by the producers of multilayer capacitors (MLC's) due to end user requirements of reduced size and cost. These capacitors are typically manufactured by co-firing, i.e., sintering alternating multilayers of the ceramic dielectric formulation and a conductive electrode material in a controlled atmosphere at a temperature in the range of about 1000° to 1400°C. Dielectric layers have traditionally been produced by preparing a suspension of ceramic powder in a liquid vehicle, usually containing a dispersant, and then adding an organic resin matrix which functions to bind the ceramic particles after tape formation and drying.
  • suspension and binder mixture hereafter defined as slip
  • Methods such as wet coating, tape-casting (casting), or doctor-blading are readily known to those skilled in the art.
  • the thin, dried layers generally termed as green layers, may then be coated with conductive electrodes and stacked together with similar layers to form a green body.
  • the stack is then trimmed and co-fired to produce a structure consisting of alternating layers of sintered electrode and dielectric which is finally leaded with end terminations to form the finished capacitor.
  • Suspensions used for dielectric compositions in the past have used both aqueous and organic liquids, but because of the environmental and safety concerns, the tendency of late has been to increase the use of aqueous suspensions, which are therefore preferred.
  • dielectric layers thinner to obtain more capacitance per unit volume. Therefore, the thickness of dielectric layers has been reduced, e.g., from 25 microns to 10 microns. It is now desirable to reduce the thickness even less to, for example, 5 microns or less.
  • These thinner layers necessitate the use of extremely small solid ceramic particles in the suspension to produce the required high density and fine grain size in the final fired layer.
  • ceramic powders are reduced to such small particle sizes, i.e., less than 0.5 microns, they tend to have a significant soluble portion that dissolves in an aqueous suspension, thus causing chemical reactions with the dispersants and binders in solution which may create process problems. Then too, ever smaller particles are also more difficult to handle, making automated systems unduly complex and expensive.
  • Barium titanate the base material of choice for capacitor formulations due to its dielectric characteristics, forms a soluble barium cation in aqueous conditions.
  • the organic additive typically used in the processing contains chemical groups that can react with the soluble cation or its companion hydroxyl ion. Agglomerates of polymer and phase separation or "salting out” or precipitation of the metal cation organic complex can take place. These complexes or agglomerates often create voids in the ceramic body during the binder burnout phase prior to sintering and can result in either elevated levels of electrical leakage or electrical shorting paths and/or a deletion effect on the strength of the ceramic. Void formation is particularly unforgiving in layers having a thickness of less than 10 microns and must be eliminated.
  • U.S. Patent No. 3,496,008 discloses the ball milling of a ferroelectric material such as barium titanate in a 60% by weight solids loading level of milled material to water. The mixed suspension is rediluted to a desirable consistency for spray application.
  • a dielectric composition is prepared with between 40 to 90 weight percent of a ceramic powder in water.
  • the ceramic powder is selected from a group including barium titanate, strontium titanate, calcium titanate, and lead titanate, and has a particle size of 0.5 to 3 micron.
  • the suspended ceramic material is combined with a binder such as polymethylene glycol or diethylene glycol, for example.
  • a binder such as polymethylene glycol or diethylene glycol, for example.
  • an aqueous emulsion of water soluble polymeric binder is combined with an aqueous suspension of ceramic material in a solids loading of at least 50 weight percent.
  • the polymeric binder is used in a range of 0.5 to 35 weight percent and optionally with up to 5 weight percent of a selected dispersing agent. Tapes prepared from the slip composition had a thickness of between 30 microns and 2.540mm. Particle sizes in the range of 0.5 to 12 micron are disclosed.
  • wet milling in water is the most desirable approach because of greater efficiency in wet milling and lower toxicity and cost of aqueous-based processing schemes. Since milling efficiency is better for low viscosity slurries, additives for wet mill slurries are usually present that act as dispersants and/or modifiers of the particle surface charge. For example, the solution pH is often controlled to avoid the isoelectric point of the powder where there is no net surface charge to provide an electrostatic barrier to agglomeration. Organic dispersants are also typically added to provide viscosity control. As fracture takes place during milling, the fresh surfaces created react with the solution phase.
  • Bi-modified ZnO is generally conducted in more toxic and expensive non-aqueous solvents such as acetone, methylethylketone, or toluene.
  • non-aqueous solvents such as acetone, methylethylketone, or toluene.
  • BaTiO 3 and similar A x B y O z compounds, the Ba 2+ leaches out of the particle surfaces to form the more thermodynamically stable, but less desirable BaCO 3 .
  • the BaCO 3 and the resulting Ti- rich BaTiO 3 surfaces can lead to loss of grain size control critical in preparing capacitors with specific electronic properties.
  • the a-Al 2 O 3 undergoes surface hydrolysis reactions that also lead to loss of grain size control during subsequent sintering processes.
  • manganese zinc ferrites undergo dissolution of the manganese ion and the zinc ion, ultimately leading to loss of grain size control.
  • many water-sensitive materials can be chemically passivated with simple organic salts.
  • the passivation-dispersion approach has not been applied to materials during milling. It would be expected that as milling proceeds with fresh surface being generated continually requiring passivation that the passivating agent would become rapidly depleted. Thus, passivation would be ineffective in milling operations to produce submicron particles as commonly practiced today.
  • the pH of the suspension also changes with so much new surface continually being exposed.
  • An additional objective and result of the present invention is to provide a very thin metal organic salt coating on the ceramic particles which will produce passivation layer minimizing dissolution, and in concert with suitable dispersants, if required, producing a zeta potential which weakens the inherent interparticle attraction. This is effected by dynamic monitoring of the passivating agent during wet milling.
  • An improved wet milling process for ceramic powders that results in materially- enhanced surfaces on the ceramic powder particles and less energy consumption in the milling process. This is achieved by a process that provides dynamic monitoring solution constituent concentration, passivating agent concentration, and careful control of pH with adjustments as necessary, as the wet milling process is occurring. This dynamic or constant monitoring and real time adjustment during the milling process results in substantially improved ceramic powders.
  • Figure 1 is a schematic representation of how the dynamic monitoring of a wet milling process can occur.
  • Figures 2 and 3 compare the chemically aided milling of the invention with typical milling as explained in Example 1.
  • Figure 4 shows chemically aided milling of BaTiO 3 of Example 2.
  • ceramic or ceramic powder refers to a powder product made by the action of heat on earthy raw materials in which the elements form complex compounds during heating or sintering. They are usually polycrystalline originally formed in aggregates needing milling. The particular ceramic to be treated is non- limiting, and all come within the scope of this invention if, to be useful, they need milling.
  • ...term ceramic powders include metallic oxides such as zinc oxide, bismuth oxide, or aluminum oxide; metallic sulfides, metallic borides, metallic nitrides, metallic carbides, metallic tellurides, metallic arsenides, metallic suicides, metallic selenides, and metallic halides; and including mixed materials such as metallic titanates, metallic tantalates, metallic zirconates, metallic silicates, metallic germanates, and metallic niobates.
  • Dispersing agents are, of course, used to maintain the suspension during milling.
  • the passivating agent is to form a coating on the surface of the particle as new surfaces become exposed during the milling process. It results in less disrupted scarred surfaces and smoother surfaces which enhance usefulness of the resulting products made from the ceramic. It is an important feature of the resulting ceramic products of the milling process of this invention that the surfaces are definably different, i.e., less scarring and smoother. This makes the ceramic function better as a component part of, for example, a capacitor.
  • ceramic compositions for tape fabrication were prepared by uniformly suspending ceramic powder up to about 30 volume percent, and more particularly from 20 to 30 volume percent in an aqueous carrier fluid of deionized water to which the passivating agent had been previously added.
  • uniform is defined to mean pore sizes of 0.5 microns or less formed in green layers which were prepared from suspensions or slips of the present invention.
  • Prepared suspensions had consistencies of from fluid-like to paste-like, depending on the loading level, of ceramic powder.
  • the dispersant was subsequently added to the mixture to obtain a uniform suspension.
  • the powders that will benefit most from the passivation-dispersion technology and therefore dynamic milling are those powders that display phase instability in the presence of water or those powders with relatively high solubilities or leachability of at least one of the metal components of the ceramic powder between 10 "4 M to 10 "1 M in a pH range of 4 to about 11.
  • powders with an average particle size of 0.5 micron or less and preferably between 0.05 micron and 0.5 micron will benefit most from the passivation- dispersion technology and dynamic control of these and pH.
  • the passivating agent can be any acid, base, salt addition organic or metal organic which (1) bums out cleanly from the suspension or slip at a temperature of about 1050°C or less, (2) provides a relatively uniform surface charge on the ceramic particles as a function of the carrier fluid pH, (3) has reasonably flat solubility over a pH range of 4 to about 11, (4) forms relatively insoluble precipitates with at least 1 metallic species of the ceramic powder, (5) promotes adsorption of desired anionic or cationic dispersants, and (6) after adsorption of the dispersant, has "improved settling characteristics".
  • passivating agents While a number of passivating agents will be known to those skilled in the art, particularly desirable agents may include compounds or mixtures of succinates, benzoates, formates, cupferons, and 8-hydroxyquinoline.
  • oxalic acid is the preferred passivating agent.
  • the oxalic acid is dissolved in deionized water at 0.1% to 5% by weight of ceramic powder.
  • an optimum passivating agent loading level of 1 to 3 weight percent exists for a quantity of dispersing agent of greater than or equal to 1 weight percent.
  • the ceramic powder begins to form agglomerates.
  • the excess passivating agent in the carrier fluid forms precipitates with dilute metals and dispersants, and apparent viscosity increases to unacceptably high levels, i.e., to greater than 3000 centipoise as determined at 50 to 100/s.
  • Dispersing agents preferably include the characteristics of being polymers which are (1) compatible with a ceramic powder particle passivated in the manner discussed above and which uniformly coat the particle; (2) which have trains which stretch in a generally parallel manner across the particle surface rather than extending radially therefrom; (3) which minimize crosslinking or "salting out" in the bulk suspension solution; and (4) which have a zeta potential in excess of +10 millivolts and preferably either in the range of +10 millivolts to about +40 millivolts or of -10 millivolts to about -40 millivolts for the loading levels discussed above.
  • a zeta potential magnitude which is less than ⁇ 10 millivolts results in a suspension where there is insufficient electrostatic repulsion to prevent particle agglomeration.
  • anionic and cationic surfactants having molecular weight in the range from less than 1000 to greater than 30,000 are contemplated as dispersants. Included are sodium, potassium, or preferably ammonia salts of stearate, lauryl sulfate, alkyl polyphosphate, dodecyl benzene sulfonate, disopropylnaphthalene sulfonate, dioctylsulfosuccinate, ethoxylated and sulfated lauryl alcohol, and ethoxylated and sulfated alkyl phenol.
  • Various cationic surfactants include polyethyleneimine, ethoxylated fatty amine and stearylbenzyldimethylammonium chloride or nitrate.
  • Alternate dispersants contemplated in the present invention include: polyethylene glycols, lecithin, polyvinyl pyrrolidone, polyoxyethylene, isoctylphenyl ether, polyoxyethylene nonylphenyl ether, amine salts of alkylaryl sulfonates, polyacrylate and related salts, polymethacrylate and related salts, and fish oil. Additional anionic and cationic dispersants having the characteristics described above may be found in the reference entitled McCutcheon's, Volumes 1 and 2, McCutcheon Division, published by The Manufacturing Confectioner Publishing Co.
  • Dynamic control refers to monitoring, and, if necessary, adjusting conditions and ingredient concentrations as milling is occurring. For example, to control solution constituents or pH by dynamic monitoring and adjusting during milling. pH control can be via injection of alkaline or acidic solutions (depending on the direction of pH change). This permits one to obtain constant pH during the milling process. The same can be done for passivating agent as concentration levels change with new exposed milled particle surfaces.
  • Figure 1 presents a scheme for dynamic control using an automatic titration system in conjunction with an attrition (or mixed media) mill.
  • optical sensors based upon UV-visible spectroscopy can be used that monitor the level of dispersant and other milling additives so they too can be dynamically controlled.
  • dynamic monitoring schemes can be used to monitor and control additives such as dispersant concentrations through a feedback loop to maintain additive levels at constant solution values.
  • Dynamic monitoring combined with continual injection of the passivating agent and/or pH regulator via acid and base addition, is required to prevent undesirable reactions of water-sensitive materials during milling.
  • essentially the same scheme shown in Figure 1 can be used to control passivation at milled material surfaces.
  • the oxalate passivation of Ba 2+ ions that dissolve from the surfaces of barium titanate particles is controlled by the chemical reaction.
  • the preparation involves the following steps: addition of the passivating agent(s), addition of the dispersing agent(s), addition of the powder of interest, pH control and 5 milling.
  • agent(s) additives are calculated with respect to the weight of the dry powder and are referred to as w/w from now on to designate weight percent with respect to the dry powder.
  • This example contains 2.0 w/w passivating agent and 3.0 w/w dispersing agent.
  • the passivating agent in this example is oxalic acid and is added in the form of oxalic acid dihydrate (H 2 C 2 O 4 • 2H 2 O), source: Aldrich Chemicals.
  • Oxalic acid dihydrate is composed of oxalic acid and water (71.4% oxalic acid and 28.6% water).
  • the calculation should only account for the passivating agent, oxalic acid, and the water from the dihydrate should be subtracted from the total deionized water.
  • the dispersing agent in this example is polyethyleneimine, MW 25,000 and is added from a 33.3 wt.% aqueous stock solution. Polyethyleneimine is stirred with deionized water to produce a 33.3 wt% stock solution.
  • 350.0g (Mn,Zn,Fe)Fe 2 O 4 , the amount of oxalic acid added, is 7.0g (9.8g in the dihydrate form), and the amount of polyethyleneimine is 10.5g (31.5g in the stock solution form).
  • the amount of deionized water added is 110.7g, and the total amount of deionized water, accounting for the additions from the passivating agent and dispersing agent, is 134.5g.
  • polyethyleneimine is added to deionized water to prepare the dispersing agent stock solution (50.0g polyethyleneimine and lOO.Og deionized water).
  • a magnetic stir bar is used to stir the solution. This solution is prepared a minimum of 24 hours in advance to ensure a homogeneous solution.
  • deionized water 111.5g is weighed into a Nalgene® beaker, and oxalic acid dihydrate (9.8g) is added in.
  • a magnetic stir bar and stir plate is used to dissolve the passivating agent, oxalic acid. Once dissolved, the dispersing agent in the stock solution form is added (31.5g polyethyleneimine stock solution).
  • the tank was filled with ⁇ 2100g of -3/16" ( ⁇ 5mm) stainless steel milling media.
  • the milling run started.
  • the mill was operated at 250 rpm, and the slurry prepared was poured into the mill vessel.
  • the other half of the powder (175.0g) was slowly added to the mill vessel. Once all of the powder was in the vessel, the mill was operated at 490 rpm. The suspension was milled for 4 hours and the pH was measured at different time intervals.
  • the average agglomeration number is used.
  • the AAN is the average number of primary particles contained within an agglomerate. It was calculated from the ratio of the volume of the median particle size determined by a light scattering technique to the average equivalent spherical volume given by the BET gas adsorption method. This is shown in equation (1).
  • the AAN decreases approximately 3 orders of magnitude, i.e.
  • An alternative milling approach typically used in industry is to use -0.5 - 2 w/w of a dispersant.
  • An example of a typical dispersant used for ferrite materials is LOMAR, which is based on a naphthalene sulfonated condensate.
  • LOMAR a 75.2 wt% (33.4 vol%) (Mn,Zn,Fe)Fe 2 O 4 suspension (350.0 g (Mn,Zn,Fe)Fe 2 O powder, 115.1 g total deionized water) was prepared in a similar fashion as example 1. In this case, 1 w/w of LOMAR was used.
  • LOMAR contains -45% "active ingredient" and was accounted for in the calculation, i.e.
  • FIG. 1 illustrates a schematic of how chemically aided milling using constant real time monitoring of pH, followed by as necessary addition of acid or base, can be used to enhance the milling.
  • the suspension 10 is being milled. It is connected via a sampling tube 12 and pump 14 and a return sampling tube 16 and pump 18 to a pH selective electrode 20. Material is removed from the suspension 10 and pumped to electrode monitor 20, which continuously reads pH.
  • the pH or given ion sends a signal to the automatic titrator 22 which is connected to a buret 24 that provides the appropriate reagent (e.g., H + or OH " ) so that pH is maintained constant during milling.
  • the appropriate reagent e.g., H + or OH "
  • buret 24 is used for pH or ion adjustment.
  • monitoring of hydrogen ion concentration or other specific ions is constantly being determined.
  • Any changes sensed as necessary by the electrode arrangement sends a signal to the automatic titrator 22 coupled to buret 24 that provides an appropriate reagent (e.g. H+ or OH) so that the pH or selected ion is maintained at a constant value during milling.
  • the illustration of Figure 1 shows only one electrode, but multiple electrodes and burets could easily be accommodated and often would be used.
  • Surfactant electrodes and/or optical fiber sensors could also be used to monitor and control dispersant levels during the milling process.
  • Example 2 BaTiO 3 This is an example of the preparation and milling of a -71.3 wt% (-30.0 vol%) calcined BaTiO 3 suspension (504.5g BaTiO 3 powder, 189.4g total deionized water) for the invention.
  • the preparation involves the following steps: addition of the passivating agent(s), addition of the dispersing agent(s), addition of the powder of interest, pH control and milling.
  • agent(s) additives are calculated with respect to the weight of the dry powder and are referred to as w/w from now on to designate weight percent with respect to the dry powder.
  • This example contains 2.1 w/w passivating agent and 1.0 w/w dispersing agent.
  • the passivating agent in this example is oxalic acid and is added in the form of oxalic acid dihydrate (H 2 C 2 O 4 • 2H 2 O), source: Aldrich Chemicals.
  • Oxalic acid dihydrate is composed of oxalic acid and water (71.4% oxalic acid and 28.6% water). The calculation should only account for the passivating agent, oxalic acid, and the water from the dihydrate should be subtracted from the total deionized water.
  • the dispersing agent in this example is polyethyleneimine, MW avg 50-60,000 and is added in the form of the as-received 50 wt% aqueous solution.
  • the amount of oxalic acid added is 10.8g (15.2g in the dihydrate form), and the amount of polyethyleneimine is 5.07g (10.14g in the solution form).
  • the amount of deionized water added is 180.0g, and the total amount of deionized water, accounting for the additions from the passivating agent and dispersing agent, is 189.4g.
  • the suspension was milled by attrition milling.
  • a plastic shaft with plastic arms was used, and the mill tank was 750 ml and made of stainless steel (source: Union Process). Once the shaft and tank was attached to the mill (source: Union Process), the tank was filled with ⁇ 1500g of -3/16" ( ⁇ 5mm) yttria stabilized zirconia milling media. At this point, the milling run started.
  • the mill was operated at 250 rpm, and the slurry prepared was poured into the mill vessel. The other two-thirds of the powder (334.5g) was slowly added to the mill vessel. Once all of the powder was in the vessel, the mill was operated at 490 rpm. The suspension was milled for 2 hours, and the pH was measured at the different time intervals.
  • the AAN decreases approximately 3 orders of magnitude, i.e. -22000 to -13 in 120 minutes (2 hrs.). This indicates that milling efficiency is enhanced by the dynamic passivation/dispersion during the chemically aided milling approach.

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  • Chemical & Material Sciences (AREA)
  • Food Science & Technology (AREA)
  • Manufacturing & Machinery (AREA)
  • Ceramic Engineering (AREA)
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  • Structural Engineering (AREA)
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Abstract

L'invention concerne un traitement chimiquement facilité de poudres céramiques. On peut ajouter à la suspension de support, aqueuse d'ordinaire, de la poudre céramique un agent dispersant et un passivant. On traite ensuite ladite suspension tout en surveillant continuellement le pH et, au besoin, en ajoutant de l'acide ou une base pour maintenir le pH dans une fourchette voulue durant le traitement. La surveillance en temps réel permet un traitement à faible consommation d'énergie et améliore les surfaces particulaires voulues de la poudre céramique. On peut également surveiller en temps réel le passivant et l'ajuster au besoin.
PCT/US2000/028592 2000-10-12 2000-10-16 Commande dynamique et traitement chimique ameliore de ceramiques aux dimensions de particules submicroniques WO2002030572A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1539903A4 (fr) * 2002-07-11 2007-08-08 Huw Treers Additif de sol
CN109970433A (zh) * 2019-04-02 2019-07-05 淄博山鼎陶瓷技术有限公司 建筑陶瓷砖烧成前废料的回收新工艺
CN113560582A (zh) * 2021-07-26 2021-10-29 河源帝诺新材料有限公司 一种碳化钨硬质合金研磨微珠及其滴定成型制备方法
EP3932560A4 (fr) * 2019-03-01 2023-01-25 Shionogi & Co., Ltd Composition de nanoparticule appauvrie en contaminants et son procédé de production

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5032555A (en) * 1988-05-16 1991-07-16 Allied-Signal Inc. Process for making zirconia-alumina
US5065946A (en) * 1988-07-21 1991-11-19 Matsushita Electric Industrial Co., Ltd. Media agitating mill and method for milling ceramic powder
US5213702A (en) * 1988-07-21 1993-05-25 Matsushita Electric Industrial Co., Ltd. Media agitating mill and method for milling ceramic powder
US5368795A (en) * 1993-10-01 1994-11-29 Ferro Corporation Use of ethylene/vinyl acetate polymer binders as drying pressing aids for ceramic powders
US5401697A (en) * 1992-09-08 1995-03-28 Hoechst Aktiengesellschaft Process for converting water-sensitive ceramic powders into a free-flowing granulated powder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5032555A (en) * 1988-05-16 1991-07-16 Allied-Signal Inc. Process for making zirconia-alumina
US5065946A (en) * 1988-07-21 1991-11-19 Matsushita Electric Industrial Co., Ltd. Media agitating mill and method for milling ceramic powder
US5213702A (en) * 1988-07-21 1993-05-25 Matsushita Electric Industrial Co., Ltd. Media agitating mill and method for milling ceramic powder
US5401697A (en) * 1992-09-08 1995-03-28 Hoechst Aktiengesellschaft Process for converting water-sensitive ceramic powders into a free-flowing granulated powder
US5368795A (en) * 1993-10-01 1994-11-29 Ferro Corporation Use of ethylene/vinyl acetate polymer binders as drying pressing aids for ceramic powders

Cited By (5)

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EP1539903A4 (fr) * 2002-07-11 2007-08-08 Huw Treers Additif de sol
EP3932560A4 (fr) * 2019-03-01 2023-01-25 Shionogi & Co., Ltd Composition de nanoparticule appauvrie en contaminants et son procédé de production
US12285526B2 (en) 2019-03-01 2025-04-29 Shionogi & Co., Ltd. Nanoparticle composition with reduced contaminant and production method thereof
CN109970433A (zh) * 2019-04-02 2019-07-05 淄博山鼎陶瓷技术有限公司 建筑陶瓷砖烧成前废料的回收新工艺
CN113560582A (zh) * 2021-07-26 2021-10-29 河源帝诺新材料有限公司 一种碳化钨硬质合金研磨微珠及其滴定成型制备方法

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