AUSTRALIA PATENTS ACT 1990 REGULATION 12 Name of Applicant: SAINT-GOBAIN CERAMICS & PLASTICS, INC. Actual Inventor/s: Tihana Fuss; Laurie San-Miguel; Kevin R. Dickson; and Water T. Stephens. Address for Service: E. F. WELLINGTON & CO, Patent and Trade Mark Attomeys, 312 St. Kilda Road, Melboume, Southbank, Victoria, 3006. Invention Title: CERAMIC PARTICLE AND PROCESS FOR MAKING THE SAME The following statement is a full desciption of tis invention including the best method of perfibrming it known to us.
CROSREFERENCETO RELATED APPLICATION '[i application is a divisional application derived from Australian Patent Application No. 2012236861 (PCT/US20 I2/030539: WO 2012/13510 claiming priority S of S Application No 61/468773 the entire contents of whicb are incorporated by reference herein, BACKGROUND OF THE INVENTION to Ceramic particles are produced for use in a wide variety of industrial applications. Some of these applications include using a plurality of ceramic particles: as a proppant to facilitate the removal of liquids and/or gases from wells that have been drilled into geological fonarmions; as a media for scouring, grinding or polishing; as a bed support media in a chemical reactor; as a heat transfer media; as a filtration media; and as roofing 15 granules when applied to asphalt shingles, Examples of patents and patent applications that disclose ceramic particles and methods of manufacturing the same include US 4,632,876, US 7,036,591, CA 1,217,319 US 2010/0167056 and WO 2008/1 12260. 20 SUMMARY i one embodiment, the present invention is a sintered ceramic particle comprisig at leasttwo inicrostrctmralphases compising an amorphous phase, e se 30 volume percentmd 7 volume percent ofthe particle, and a first substantially' crystalline 25phase comnprising- a plur-ality of predomin ately crystalline regions distributed through the amorphous phase. h another embodiment the present invention is a process for producing a sintered ceramic el c proc mnay comprise the is. . a fA ceramic material hang a fluid conversiontemperature and a second ceramic material having a 0 fluid conversion temperature wherein the second ceamic matels flud conersion temperature is greater than the first ceramic material' fluid conversion temperature Mixing the materials to form a homogeneous mixture comprising between 30 weight percent and 70 weight percent of the first ceramic material. Forming the mixture into a particle precursor Heating the precursor to at leasthe first cerMic material's fluid conversion temperature wherein the first and secod ceramic materials cooperate to form an 5 amorphous phase that abuts arid embeds an array of predonmin ately crystalline regioIs Cooling the precursor to ambient temperature thereby forming a sintered ceramic particle. BRIEF DESCRIPTION OF THE DRAWINGS Fig, I is a process flow chart. DETAILED DESCRPTRN As used herein, the phrase "microstructural phase" refers to a sintered ceramic is particle's crystalline or amorphous phase(s) which are detectable using an X-ray diffracometer analytical device. A particle may have one or more microstructural phases, The uicrostmctural phase characterized by the physical armngement of atoms which orm repeating pattern in crystalline phases and do not form repeating patterns in an amorphous phase, 20 As used herein the phrase "thiid conversion temperature' refers to the temperature at which a solid ceramic material begins to soften and thereafter becomes flowable due to an increasein its temperature As used herein, the phrase "crush resistance" refers to the particle's ability to withstand crushing. Crush resistance is commonly used to denote the strength of a ceramic 25 particle, such as a proppa. and may be determined using ISO 13503-2:2006(E). A strong proppamt generates a lower weight percent crush resistance than a weak proppant at the same closure stress. For example, a proppant that has a 2 weight percem crush resistance is considered to be a strong proppant and is preferred to a weak proppant that has a 10 weight percent crush resistance, 30 The terms particlee", "particles" "proppatand "proppan ts" may he used interchangeably herein unless otherwise noted, Processes for manufaCturing Ceramc particles have been devised and used ot many years to manufacture large quantities of ceramic particles such as proppants. Because proppants are used in a wide variety of geological formations, at different depths and exposed to extremes in teniperature and pressure the physical characteristics of the S proppants may need to be customized in order to optimize the performance of the proppant in a particular environment. Some of the properties which may impact the performance of the proppant include: Specific gravy, porosity, crush strength and Conductivity Changing one physical property may inherently change one or more of the other properties in an undesirable manner. Consequently, significant effort has been made to develop processes 10 that alter the properties that are important in one application while simultaneously minimize uundesirable changes to the particle's other properties. Furthermore, proppant manufacturers have tried to reduce the cost of manufacturing proppants by eliminating materials andor- process epswithout compromisingthe performance of the proppant. With regard to producing a proppant having a low, and therefore desirable, crush ii resistance, certain technical teachings have heehn used for years to create a proppant this is resistant to crushing hile also trying to minimize the cost of the raw materials used to make the proppant A frst well known teaching for improving the proppant's crush strength is to increase the percentage of AlAchemical content in the proppant. The O is calcined at a sufficnly high temperatre.,, such as 1 300'C,., to convert the transitional 20 crystalline phases to alpha alumina which is known to be strong and therefore highly resistant to mushig nforunately raw ateials thatconangh concentrations of ABtY chemical content are expensive and must he purchased in large quantities which can sigznicantlv increase the manufacturing cost of the proppant producer and is undesirable A second well known technical teaching is that some amorphous ceramic materials sich as 25 glass eads, tend to fracture at low stress and thereor has undesirably h$ji cush, resistance when used as an ingredient in a proppant f-However, amorphous materials are relai vely inexpensive and therefore desirable from a cost perspective. Furthermore armrphous materials are prob lenaic because they arc known t o have a; flid conversion temperature well below the mini mum temperature needed to convert transitional ahumina to 3 0 alpha auina When an aruorphous natea beins to soften, itay become tacky and mdividual proppant particles may adhere to adaceni particlesthereby forming large, loosely bound agglomerates made up of thousands of individual proppan particles. The proppants also tend to adhere to the inside surfaces ofkilns and other equipment used to calcine the proppants. During the time the proppants reside in the kiln, such as a rotary kiln, the proppants may build up an increasingly thick layer of proppants on the inside S surface of the kiln which uhimately results in the shut down of the kiln so that it can be cleaned and then restarted. Using the technical teachings described above, some proppant manufacturers have elected to produce proppants having high alumina content, to achieve the desired crush resistance, and low amorphous material, to avoid the problems associated With proppan agglomeration andlowy crush resistance. [0 in contrast to the technical teachings described above, the inventors of the invention claimed herein have discovered how to manufacture a proppant wherein regions of predominately crystalline phase ceramic material and a matrix of a predominately aiorphous phase ceramic rnaterial cooperate to form a proppant that has good resistance to crushing. More specifically, in a proppant of the present invention, predominately 5 crystalline regions are surrounded by and embedded within a matrix of an amorphous ceramic materiaL The matrix forms a continuous phase through the proppant. 'The predominatelyv crystalline regions collectively define a discontinuous phase. As described above, amorphous ceramic materials tend to fracture at low stress and therefore have undesirably high crush resistance when used as an ingredient in a proppant To improve the 20 crush resistance of the nomally weak amorphous material, the crystalline material and the amorphous material are selected so that a synergistic relationship is established between the materials which results in the creation of a beneficial stress, such as compressive stress, on the amorphous material. The compressive stress is believed to improve the particle's crush resistance by orphous material thereby hind crack origination and 25 propagation through the amorphous phase. H indering crack propagation effectively improves the crush resistance of the particle at a specified stress by reuring the exertion of a higher mechanical force to crush the particle. The compressive stress on the amorphous material may be created by selecting the crystalline and amorphous materials so that after forming, heating and cooling the proppam the crystalline material's coefficient of thermal 30 expansion is greater than the amorphous material's coefficient of thermal expansion. The difference in coeffi cients of thermal expansion may cause the discreet crystalline material to attempt to shrink more than the adjacent amorphous material to which it has been bonded during the cooling step, The difference in the coefficients of thernal expansion is believed to cause the amorphous material to experience compressive stress as it resists the greater relative movement of the crystalline material, A fer a ceramic particle has been exposed to a specinc thermal profile the coefficients of thermal expansion of the particle's ceramic materials nmay be detennined using the procedure described below. The exact value of a materials coeffcient of thermal expansion aner heating of the particle may not he critical to the use of that material to manufacture a ceramic particle of this invention. Instead. the size of the difference between i the coefficients of thermal expansion is the characteristic that may directly impact the creation of the compressive stress and the resulting resistance to crushing. A difference of at least 0,x 1 /' may be sufficient to exert a compressive stress. More preferably, the difference in coefficients of thermai expansion may be 0,2 or 0O3x 1 0taC For ceramic particles usefi as proppants, the coefficient of theral expansion of the crystalline material is n~ay be greater than r .0 more preferably, greater than 70 x 10/C The coeffcient of thermal expansion of the amorphous material may be less than 6.0 nore preferably, less than 5.0 x 10tY>C The quantity of the amorphous ceramic material in a porous ceramic particle of this invention may be between 30% and70%based on the volume of the particle after heating 20 and cooling of the same If the amorphous materialrepresents less than30% of the particle's olume, the amorphous material may not form a continuous phase throughout the particle The amorphous phase material may represent at least 40% 45% or even 50% of the particle's volume. Examples of amorphous ceramic materials suitable for use in a porous ceramic particle of this invention include feldspar and nepheline syenite 25 To identi a proppant of' this invention, the proppants's nicrostructural phases, the chemical composition of those phases and the coefficient of thermal expansion of those phases should be determined. The notification of these physical characteristic may be determined using the folkoing amdyical procedures Wihregad to the microstructural phases, an X-ray diffractometer, such as an PAN alyticalW XRD is used to detect the 30 existence of one or iore crysal line phases, The height of the lines on the X-ray diffraction patter may be used to determne the relative quantis of each crystaline phase The location of the lines on the X-ray diffraction patten horintanuil axis is indicative of a ostructua phase. furthermore, the use of an internal standard may faCilitate the analysis of the X-ray diffraction pattem. The amount of amorphous phase material may be calculated as the amount of proppani that is not crystalline. With regard to the proppant's 5 chemical composition the compositions chemical elements may be determined using X ray fluoresCence (XRF), After determining the proppant's microstructural phases and chemical composition, the coefficient of thermal expansion of each microstructural phase may be determined using an analytical technique known as dilatometry. A dilatometer. such as a Ilnitherm 1161 from I Anter Corporation, is an instrument capable of measuring the coefficient of thermal expansion ((-.) of a material. The dilatometer may be used to measure the change in length of a rectangular bar test sample as a function of temperature The bar may be 40 mm o2 n25 tmn wide and 2 mm high. The CTE is obtained through recording the change in relative length of the rectangular bar upon cooling from below the fluid convention 15 temperature to 25 0 C. Commonly the TE is reported as units of 10 such as 5 x 10?C. which represents a change of 000O1% of the rectam gulr bar's length per every C1 change in temperature. Test samples of each microstructure amorphous phase can be prepared using reagent grade raw materials, in a formulation equal to (he determined chemical compoSition which 20 are then melted at high temperatures greater than the fluid conversion temperature. These melted, samples of the amorphous. phase arc ground to a tine powder and fbrmcd in the shape such as a rectangular bar which is suitable to dilatometry asurements, and sintered to high temperature. The same XRD and XRF techniques descrbed above can be used to confirmn the phase and chemical content of each crystalline and amorphous phase test 25 sample. The quantity of crystalline alumina material in a porous ceramic particle of this invention may be between 30% and 70% of the particle's volume. Preferably the quantity of crystalline alunina material may be greater thani 30% 35% or even 40% of the particle's volume. lithe quantity of crystaline alumina material is less then30volnie percent there 10 may not be enough crystalline alumina to create a sufficient amount of compressive stress on the amorphous material to provide acceptable resistance to crushing the qantiyo crystalline alumina material is greater than 70 volume percent, there may not be suffcient improvement in the crush resistance to justify the cost associated with using alumina containing ceramic material instead of a less expensive amorphous material In a porous ceramic partie of this invention, the crystalline material may be a single crystalline phase, 5 such as alpha alumina. Alternatively, the crystalline alumina may be a mixture of transitional phases or a combination of alpha alumina and one or more transitional phases. Shown in Fig I is a flow chart of a process that includes the following steps. Step 20 includes providing a first ceramic material and a second ceramic material, The first ceramic material has a fuid conversion temperature. The second ceramic material has a i0 fluid conversion temperature that is less than the fluid conversion temperature of the first ceramic material. Step 22 includes mixing the first and second Materials to frim a mixture wherein the mixture comprises between 30 and 70 weight percent of the first ceramic material Step 24 is directed to forming the mixture into a particle precursor. Step 26 includes heating the precursor to a naximum temperature that is no less than the first 15 ceramic materials fluid conversion temperature and no greater than the second ceramic material's fluid conversion temperature wherein the first and second ceramic materials cooperate to form an amorphous phase that abuts and embeds predominately crystalline regions. During the hting step, the temperature of the precursor must at least equal and perhaps slightly exceed the first materials fluid conversion temperature. in step 28 the 2o heated precursor is cooled to ambient temperature thereby creating a sintered ceramic particle, With regard to step 22, the mixture may optionally include other materials such as binders and solvents. Suitable solvents include water and some alcohols. A binder may be one or more materials selected from organic starches, such as drilling starch, as well as 25 gums or resins that are sold commercially for such purposes. A binder may also be an inorganic material such as clay or an acid. Binders are usually added in an amount less than 10 weight percent of the mixture and nay he added dry or as a solution. While a binder may be responsible for some level of porosity in a ceramic particle, binders are not considered pore forners herein. The composition of the mixture may be limited to less 3) than 0. 1 weight percent of one or more pore forners selected from the list consisting of a transint pore forne, an i-stu pore former, and combinations thereof Transient pore fornners may be limited to less than 0.05 welhit percent of the mixture. Isitt pore frners may be limited to less than 0:01 wei.gt percent of the mixture. In one embodiment, the mixture will not include any pore former, With regard to step 24, a particle precursor is defined herein as a particle wherein 5 the first and second ceramic materials are distributed therethrough and solvents, such as waterhave been removed so that the precursor's loss on drying (LOD) after heading to between 110*C and I 30*C for two hours is less than one percent of the precursofs starting weight The precursor may or mag not contain optional ingredients such as a hinder The precusor may include a least 30 weight percent of the first ceramic material and at least 30 M weight percent of the second ceramic material. in some embodimentsthe precursor may include between 60 weight percent and 70 weight percent of the first ceramic material and between 30 weight percent and 40 weight percent of the second ceramicmaterial. Forming a particle precursor may he achieved by processing the mixture through a machine such as an Fiich R02 mixer. which is available from American Process Systems. 5 inch Machines Inc. of Goumey. I USA. The action ofthe mixer causes the formation of a lage number of small generally spherical hails of mix which may be referred to as particle precursors or greenware. if the greenware contains optional ingredients,such as solvents and binders, the optional ingredients may be removed byrying thegreenware in an oven to a sufficiently high temperature, such as 200*C or higher, to drive the optioml 20 ingredients from the greenyare desireddhe pardcle precursors may be processedI through a screening apparais that inctdes a No.AST sieve degnation, which has 2.36 rum aperturs, anld a No, 70 ASTM1 sive designati, which has 212 gimv apertures. The precursors selected for heating in step 26 may flow through the No S sieve and not flow through the No. 70 siee. 25 In step 26, the precursor is heated to a maxunum temperature which is below the fluid conversion temperature of the second ceramic material and above the fluid conversion temperature of the first ceranic materia in some emhodtments the precursor may he heated to a ximnuni temrperatre which is above themelting teniperatre of the first ceramic material which is beloW the sintering temperature of the second Ceramic materl :0 When the. temperature to which the precursor is heated exceeds the fluid conversion 9 temperature of the first ceramic material, the first ceramic niaterial may convert from a solid material to a flowable material and then flow over the second ceramic material With regard to step 20, both the first and second ceramic materials may be provided as powvders which include a. plurality of granules. In particular embodiments, granules may 5 range from I to 1 1 microns, more specifically from 6 to microns The first and second ceramic materials may be selected so that the first ceramic material scoefficient of thermal expansion afer heating and cooling as described above is at least 10% higher than the second ceramic material's coefficient of thermal expansion after experiencing the same heating and cooling regime After heating and cooling, e coeffiient of thermal expansion of the first ceramic material may be 20% or even 30% higher than the coefficient o thennaI expansion of the second ceramic materiaL While the cxact difference between the fluid conversion tempenture of the first ceramic material and the fluid conversion temperature of the second ceramic material may not be critical, a difference of 50*YC may be workable in particular embodiments. is A suitable first ceramic material may be selected frM the group consisting of bauxite, alumina, kaolin clays, alunino-silicates, and magnesium silicates: A suitable second ceramic material may be selected from the grop consisting of feldspar and nepheline syenite The above description is considered that of particdar embodiments only 20 Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore it is understood that the embodiments shown in the sand described above are merely for illustrative purposes and are not intended to limit the scope of the invention which is defined by the toliowing clains as interpreted according to the principles of patent law. 25A reference herein to a patent document or othAr matter which is iven as prior ar is not taken as an adMission that that momentt or prior art was part of common general knowledge at the prority dateofam' of the claims. With reference to the use of then word(s)"corrprise or cmpries" or comprising" in the foregoing description and/or in the fllowng cairns n the context requires 0 otherwise. those words are used on the basic and clear understandingthat they are to be interpreted inclusiely, rather than exclusively and tat each of those words is to be so interpreted in corisirig the f description arid/or tJe bowing caimis. 10