Wollastonite Phases Research Articles

Zirconia-containing wollastonite ceramics derived from biowaste resources for bone tissue engineering

Zirconia-containing wollastonite (CaSiO3) ceramics with partial substitution of zirconia (1, 3 and 5 mol%) were prepared using eggshells and rice husk ash as source materials for calcium oxide and silica, respectively, through a sol–gel technique. The effect of incorporation of zirconia on in vitro bioactivity, mechanical properties, degradability and cytocompatibility of wollastonite was studied. Bioactivity was evaluated by in vitro assay using simulated body fluid while degradability was tested in Tris-HCl buffer solution for different time periods (1, 3, 7, 14 and 21 d) according to the ISO 10 993-14 standard. Human osteosarcoma (MG-63) cells were used to assess cytocompatibility with the MTT assay. X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy–energy dispersive spectroscopy were used to characterize the ceramics before and after in vitro studies. The results obtained showed that increasing the zirconia content in the wollastonite phase increases microhardness, compressive strength, bending strength and the elasticity modulus, while slightly decreasing the rate of formation of the hydroxyapatite layer. Moreover, the samples doped with zirconia had a lower degradation rate and it was noticed that cell viability is unaffected by the incorporation of zirconia.

Effect of sintering temperature on the crystal growth, microstructure and mechanical strength of foam glass-ceramic from waste materials

This study was conducted to synthesize foam glass-ceramic using SLS glass as a precursor; eggshell (ES) as a foaming agent and investigated the effect of sintering temperature on the crystal growth, microstructure and mechanical properties of the final product. The samples undergo the sintering process at different temperatures such as 700, 800 and 900°C for 60min with the heating rate of 10°C/min. The structural properties were studied by XRD, FTIR and FESEM measurement. The cristobalite (SiO2) and wollastonite (CaSiO3) phases were identified after the sintering process and their microstructure was recorded by the FESEM micrograph. The physical properties of the samples were measured by average density measurement, linear expansion and compressive strength. The lowest density measurement using the Archimedes principle was achieved by 0.421g/cm3 with the highest volumetric expansion at 92% after the sample sintered at 800°C. Good correlations between porosity, mechanical strength and crystal phase were observed. The invention of foam glass-ceramics from waste materials can be applied as a potential building insulation material that gives benefit to the environment and energy usage.

Effect of sintering temperatures and foaming agent content to the physical and structural properties of wollastonite based foam glass-ceramics

This study aims to fabricate low-cost foam glass-ceramic using soda-lime-silica (SLS) glass waste and clamshells (CS) as foaming agent in content between 1 and 12 wt.% by conventional powder processing method. The samples were undergoing sintering process between 700 and 1000?C with holding time of 30 minutes and characterized according to the physical and structural properties. Samples containing 3 wt.% CS treated at 800?C show the greatest size of porosity. As the sintering temperature increased, the samples tend to become less dense. However, for the samples sintered at 900 and 1000?C, the trend of the density changes because of the excess CO2 gases generated during the heat treatment process promotes an increase in internal pressure, which results in the rupture of the pore walls. For linear expansion, for samples with a sintering temperature of 800?C and higher, the increment of the temperature will lead to the decrement of linear expansion (%). As the sintering temperature increases from 700 to 800?C, the water absorption (%) increases. However, the percentage of water absorption decreases with the further increment of sintering temperature. The XRD characterization showed the formation of wollastonite phase (CaSiO3) and further revealed the formation of greater peaks of CaSiO3 at the higher sintering temperatures. The results of compressive mechanical strength between 0.15 and 1.50 MPa indicate that the obtained glass-ceramic foams have potential for building material applications.

Crystallization kinetics, structure and dielectric properties of CaO–B2O3–SiO2 glass–ceramics nucleated by composite nucleating agents

The crystallization kinetics, structure and dielectric properties of CaO-B2O3–SiO2 (CBS) glass–ceramics, nucleated by composite nucleating agents (TiO2, ZrO2), are systematically investigated. The results reveal that the addition of composite nucleating agent (TiO2/ZrO2) destroyed the continuity of the glass network structure formed by SiO2 and B2O3, promoted the precipitation of wollastonite phase and enhanced the dielectric properties of as-prepared CBS glass–ceramics. However, the composite nucleating agent increased the crystallization temperature of the glass and introduced some impurity phases, influencing the microscopic arrangement of the wollastonite phase, whereas the content of impurity phases decreased with the increase of TiO2 content in the composite nucleating agent. Furthermore, the crystallization kinetics study showed that the composite nucleating agent reduced the crystallization activation energy of glass, and the crystallization of glass is controlled by one-dimensional interfacial crystal growth.

The Effect of Lithium on Crystallization and Microstructure of Glass-Ceramics in Soda-Lime Silicate System

This study investigated the crystallization of soda-lime silicate (NCS) system by re-melting soda-lime silicate glass cullet with Al2O3 CaCO3 and Li2O. The Li2O was added as a nucleating agent. The effect of the nucleating agent on crystallization was investigated in order to study the possibility for use as a parent glass for glass-ceramics. Soda-lime silicate cullet was the main raw material and its chemical composition by weight was 68% SiO2 2% Al2O3 9% Na2O 9% K2O 3.5% CaO 2.5% MgO 1.2% TiO2 3% SrO and 2% ZnO. Glass batches with composition (%wt) of (65-x) Cullet:13Al2O3:22CaCO3:x(Li2O) (x = 0, 1, 2, 4, 6 and 8) were melted at 1500°C for 3 hours and annealed at 600°C. All glasses added with Li2O were clear except x = 8. The crystallization was investigated by Differential Scanning Colorimetry technique (DSC). The results exhibited the exothermic peak of crystallization (TpI and TpII). The glasses with added Li2O exhibited decreasing crystallization temperature with increasing Li content. The glasses were heated at temperatures around the crystallization temperature (700, 750 and 800°C). After heat treatment, the crystalline phase in the glasses was determined by X-ray diffraction technique (XRD). The microstructure was investigated by optical microscope and Scanning Electron Microscope (SEM). The phases of Nepheline (Na,K)AlSiO4 and Wollastonite (CaSiO3) were found. The crystallization depended on the heat treatment temperature. The thermal expansion of the glasses was determined by the dilatometric method to indicate the characteristics of the glass-ceramics. In conclusion, Li2O had a strong effect on the crystallization in soda-lime silicate system. The result could be applied for the production of glass-ceramics from soda-lime cullet.

A new route to sol-gel crystalline wollastonite bioceramic

ABSTRACTArtificial bone graft materials formed from wollastonite have been extensively used in bone repair because of their high degree of bioactivity and biocompatibility, thereby justifying the development of a protocol for large-scale production. This work reports a novel route for preparing wollastonite via the sol-gel process using bentonite clay as a cheap silica source. The obtained wollastonite was characterized for morphology, elemental composition, phase composition and bioactivity using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction and Fourier transform infrared spectroscopy. Results obtained revealed that wollastonite phase was successfully formed in the material and it showed ability to induce formation of apatite within 0.5 day in biological fluid, an indicator for bone-bonding capability. Overall, the wollastonite prepared from the bentonite clay exhibited properties comparable to that synthesized from commercially obtained sodium metasilicate. Hence, our synthetic route may be useful for commercial-scale preparation of wollastonite.

Evaluation of Bioactive Properties of <i>α</i> and <i>β</i> Wollastonite Bioceramics Soaked in a Simulated Body Fluid

Dense natural wollastonite bioceramics (CaSiO3) were prepared by a sintering method, varying the pressing load and sintering temperature, in order to obtain different phases of wollastonite, and different physical properties in the materials. The products were characterized by TGA-DTA, XRD, FT-IR, SEM-EDS, TEM and XPS techniques. The results indicate the presence of two polymorphic phases of wollastonite, the β-wollastonite and α-wollastonite with a transition temperature of the β phase to α phase at approximately 1250℃. These materials were soaked in a simulated body fluid (SBF) during 1, 2 and 3 weeks, to study their solubility and bioactivity. The effect of different wollastonite phases on the solubility of Ca and Si, as well as the capacity of producing layers of “newly formed apatite” on the surfaces of these materials in SBF solution were analyzed.

Dependence of microwave dielectric properties on ceramics filler in wollastonite glass-ceramics

The effect of various ceramics fillers (TiO2, CaTiO3, SrTiO3, Sr0.8Ca0.2TiO3) on the microwave dielectric properties of wollastonite glass-ceramics was investigated as a function of the content and particle size of the ceramics filler. The temperature coefficient of resonant frequency (TCF) of the specimen increased as the amount of ceramics filler was increased. In addition, the TCF value of the specimens could be tailored to be nearly zero when 10 wt.% ceramics fillers were added except in the case of TiO2. As the amount of ceramics filler was increased, the quality factor (Qf) of the specimens decreased because of the formation of mixture phases of wollastonite and ceramics filler, while the dielectric constant (K) of the specimens increased owing to the fact that the ceramics fillers have higher K values than wollastonite glass-ceramics. When the particle size of the ceramics fillers was increased, the Qf and K value decreased because the specimens with a small particle size of ceramics filler showed larger crystallite size than the others; however, the TCF value did not change significantly with the particle size of the ceramics filler. The optimum dielectric properties of K = 8.66, Qf = 33,800 GHz and TCF = -2.1 ppm/°C were obtained for the specimens with 10 wt.% CaTiO3, heat-treated at 725°C for 7 h and crystallised at 900°C for 3 h.

Effects of heating rates and SBE loading on sintered properties of spent bleach earth/recycled glass composite

The purpose of this study is to investigate the influence of different heating rates on the properties of glass ceramic composite (GCC) at different spent bleach earth (SBE) loadings. GCC was prepared using SBE and recycled soda lime silicate (SLS) glass. The particle size of SLS glass was approximately <45μm. The GCC was formed by uniaxial dry pressing at weight fractions of SBE loading of 40 wt. %, 45 wt. %, and 55 wt. %. The GCC was then sintered at different heating rates of 2 oC/min, 4 ˚C/min, 6 oC/min and 8 ˚C/min at 700 oC of sintering temperature. The GCC specimens were analysed in terms of their physical properties, while crystalline phase and microstructure were characterized using X-Ray diffraction and scanning electron microscope (SEM), respectively. The results from X-Ray diffraction pattern showed that quartz and wollastonite phases were formed with no major changes on the phases as the heating rate increased. The results indicate that the variation of heating with 2 oC/min interval does not give a remarkable result of physical properties on GCC. High loading of SBE sintered at 2 oC/min of heating rate produced low water absorption, density and porosity. SEM analysis showed that the physical properties and crystalline phases were correlated to the SBE loading and changes in the heating rate. The study concluded with the prospect of continuing the work of optimisation on schedule heat treatment at sintering temperature regimes.

¬¬Chromium fluoride-containing bioactive glasses: Structure and properties

Bioglasses in the system 24.5Na2O.24.5CaO.6P2O5.xCrF2.(45-x)SiO2 have been studied in the composition region of x= 0-10 mol%. CrF2. Glass of molar ratio (Ca+Na)/SiO2 ~1.1 is the base material for the glasses containing different CrF2 concentrations. X-ray diffraction (XRD), differential scanning calorimetriy (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Vicher hardness (Hv) measurements have been carried out. Crystalline feature of the glasses is followed up by XRD spectroscopy. It is found that crystallinity was enhanced via CrF2 addition. More enhancement was confirmed via thermal heat treatment process. Increasing CrF2 and sintering temperature will induce new ordered phases which will be distributed in the main glassy phase. Well formed flouroapatite (Ca5(PO4)3F and wollastonite Ca3Cr2(SiO4)3 phases containing fluorine and chromium ions are evidenced in CrF2 containing glasses. Increasing glass transition temperature Tg and hardness number Hv upon increasing CrF2 concentration was discussed on bases of formation of additional bonds by the effect of CrF2 molecules. The measured temperature window between Tc and Tg was found to have a great influence in material structure. Wide window is a feature of amorphous glass which free from CrF2. The window scale is found to quickly decrease with increasing CrF2, since crystalline phases are already formed in glasses containing CrF2. Formation of crystalline intermediate phases with more shielded silicate and phosphate structural is considered as the main reason for increasing Tg and (Hv) of the glasses. EDS as well as XRD analyzed spectra confirm that crystalline wollastonite of calcium inosilicate mineral (CaSiO3) phase is well formed. The wollastonite species is evidenced to contain small amounts of chromium and fluorine ions which are substituting for calcium cations. Wollastonite phases with Cr/Si=1 is the most dominant type. This ratio is a characteristic feature of crystalline CaSiO3 species. Small concentration from fluorine ions are involved in apatite phases. Presence of both crystalline apatite and wollastonite in the sample matrix promotes its biocompatibility, particularly orthopedic bioactivity. As a consequence, some of investigated glasses are recommended to be applicable in dental field of applications. This depends on its own crystallinity, hardness, its apatite and wollastonite concentration as biocompatible phases in the crystallized glass

Microstructure and mechanical properties of nucleant-free Li2O-CaO-SiO2 glass-ceramics

An attractive characteristic of the Li2O-CaO-SiO2 glass-forming system is the possibility of obtaining internally nucleated crystal phases – CaSiO3 and Li2SiO3 – having elongated morphologies that can potentially lead to tough glass-ceramics. Another great advantage of this system is that it does not need a nucleating agent to crystallize internally. In this research work, three glasses with systematic compositional variations within the range of 30–50 mol% CaSiO3/70-50 mol% Li2SiO3 were prepared, heat-treated and their microstructures and mechanical properties evaluated. Heating cycles were applied in two-stage treatments. The temperatures were selected based on previous DSC analyses. The crystallized samples were characterized by XRD and SEM to examine the nature, size and morphology of their crystals. The effect of microstructure on the Vickers hardness (Hv) and indentation fracture toughness (Kc) of the glass-ceramics was determined. Elastic modulus (E), biaxial strength (σm) and fracture toughness (KDTIC) were determined from nanoindentation, ball-on-three-balls and double torsion tests, respectively. The level of internal residual stresses was evaluated by X-rays diffraction. The best mechanical properties were exhibited by a composition containing 44 mol% CaSiO3 heat-treated at 498 °C for 24 h for nucleation and at 700 °C for 2 h for crystal growth. This composition resulted in a glass-ceramic with the following microstructural features and properties: average Li2SiO3 (LS) crystal size of 8.5 μm, wollastonite (CS) phase surrounding the LS crystals with approximately 50% LS crystallized volume fraction, KDTIC = 2.3 ± 0.5 MPa m1/2, σm = 270 ± 20 MPa, HV = 8.4 ± 0.7 GPa and E = 146 ± 8 GPa. These are exciting mechanical properties for glass-ceramics intended for load bearing applications.

Comparative investigations of structure and properties of micro-arc wollastonite-calcium phosphate coatings on titanium and zirconium-niobium alloy

Investigation results of micro-arc wollastonite–calcium phosphate (W–CaP) biocoatings on the pure titanium (Ti) and Zr–1wt.%Nb (Zr–1Nb) alloy were presented. The voltages of 150–300 V generate the micro-arc oxidation (MAO) process with the initial amplitude current of 150–550 A and 100–350 A for Ti and Zr–1Nb substrates, respectively. The identical dependencies of changes of the coating thickness, surface roughness and adhesion strength on the process voltage were revealed for the both substrates. The W–CaP coatings with the thickness of 10–11 μm were formed on Ti and Zr–1Nb under the low process voltage of 130–150 V. Elongated wollastonite particles with the size in the range of 40–100 μm were observed in such coatings. The structure of the coatings on Ti was presented by the X–ray amorphous and crystalline phases. The X–ray reflexes relating to the crystalline phases of Ti and wollastonite were observed only in XRD patterns of the coatings deposited under 130–200 V on Ti. While, the crystalline structure with phases of CaZr4(PO4)6, β–ZrP2O7, ZrO2, and Zr was detected in the coatings on Zr–1Nb. FT–IRS, XRD, SEM, and TEM data confirmed that the increase of the process voltage to 300 V leads to the dissociation of the wollastonite. No toxic effect of specimens on a viability, morphology and motility of human adipose–derived multipotent mesenchymal stem cells was revealed in vitro.

Middle Eocene clay from Goset Abu Khashier: Geological assessment and utilization with drinking water treatment sludge in brick manufacture

This investigation aims to study the physico-ceramic properties of bricks that were made from the Goset Abu Khashier clay (Qarara Formation, Middle Eocene deposits, El-Minia, Egypt) replaced with 15–60wt% drinking water treatment sludge (DWTS). The Qarara Formation deposits located in the east bank of the Nile River between Beni Suef and El-Minia Governorates, belong to the Middle Eocene deposits. The Qarara Formation deposits in the Goset Abu Khashier area contain several million tons of clay deposits. The Qarara Formation is composed of a grey to green shale (silty clay) grading upward to marl and limestone. The clay contains kaolinite (29wt%), montmorillonite (20wt%), albite (27wt%) and quartz (23wt%). The clay contains a high content of silica (49.41wt%) and a low content of alumina (19.77wt%) with considerable amounts of Fe2O3 (11.37wt%) and fluxing oxides (3.7wt%). Clay bricks containing 15–60wt% DWTS were fired at a temperature of 700–1000°C. The ceramic properties of bricks were determined according to the ASTM specifications. The phase composition of bricks was determined by XRD, FTIR and SEM techniques. It was investigated that the incorporation of DWTS in the body of clay bricks moderates the ceramic properties of fired bricks to be in agreement with the limiting values that were recommended for traditional bricks. XRD results illustrated that dehydration of kaolinite and the formation of metakaolinite facilitates vitrification and contributes to brick densification. FTIR results showed the formation of a wollastonite phase and indicated that increasing DWTS content facilitates the persistence of a vitrified phase. SEM micrographs illustrated that the porosity and densification of brick matrix was affected by the formation of amorphous vitreous phases and decreased with DWTS contents. It is recommended that the replacement of examined clay by 15–30wt% of DWTS is considered as the appropriate percentage for building bricks production and minimizes environmental impacts due to DWTS disposal into water bodies.

Crystallisation behaviour of the iron oxide-devoid BOF slag with adding SiO2

The current research attempted to investigate the crystallisation mechanism of iron oxide-devoid basic oxygen furnace (BOF) slag with adding SiO2. First, the glass sample was prepared by adding 29 wt-% of SiO2 to BOF slag, followed by eliminating iron oxide by reduction process. Non-isothermal DSC analysis together with confocal laser microscopy, XRD and EPMA mappings were carried out to observe the crystallisation process. The glass sample showed that the crystallisation process started from the surface where the main phases were identified to be akermanite, merwinite and wollastonite. In addition, the crystallisation process was affected by the nucleation temperature which was decided by the heating rate because of the difference in the nucleation rate between wollastonite and Mg-rich phases. The current results could be used to propose the feasibility of utilising BOF slag as glass-ceramics by chemical modification with heat treatment, which controls the crystallisation behaviour.

Síntesis de silicatos de calcio por el método Pechini e intercambio iónico de alginato de sodio-cloruro de calcio

Calcium silicates samples were synthesized using tetraethyl orthosilicate (TEOS) and by Pechini methodology assisted with ion-exchange of sodium alginate, followed by a heat treatment of 800°C by two hours. A, B and C samples were obtained using 1.7×10−3M, 3.4×10−3M and 5.1×10−3M of TEOS, respectively, and without heat treatment; these samples were characterized by thermogravimetric analysis (TGA) and infrared spectroscopy with attenuated total reflectance (FTIR-ATR). Furthermore, samples A800, B800 and C800 obtained using a heat treatment of 800° by two hours were characterized by FTIR-ATR, absorption technique (BET), X-ray diffraction (XRD) and by scanning electron microscopy. The XRD patterns indicate that sample A800 contains olivine (Ca2SiO4) in orthorhombic phase and wollastonite-2M (CaSiO3); sample B800 showed the earlier phases and quartz (SiO2), whereas sample C800 contains wollastonite phases and larnite-2M (Ca2SiO4).

Glass-ceramic coated Mg-Ca alloys for biomedical implant applications

Biodegradable metals and alloys are promising candidates for biomedical bone implant applications. However, due to the high rate of their biodegradation in human body environment, they should be coated with less reactive materials, such, for example, as bioactive glasses or glass-ceramics. Fort this scope, RKKP composition glass-ceramic coatings have been deposited on Mg-Ca(1.4wt%) alloy substrates by Pulsed Laser Deposition method, and their properties have been characterized by a number of techniques. The prepared coatings consist of hydroxyapatite and wollastonite phases, having composition close to that of the bulk target material used for depositions. The 100μm thick films are characterized by dense, compact and rough morphology. They are composed of a glassy matrix with various size (from micro- to nano-) granular inclusions. The average surface roughness is about 295±30nm due to the contribution of micrometric aggregates, while the roughness of the fine-texture particulates is approximately 47±4nm. The results of the electrochemical corrosion evaluation tests evidence that the RKKP coating improves the corrosion resistance of the Mg-Ca (1.4wt%) alloy in Simulated Body Fluid.

Fabrication of Wollastonite Coatings on Zirconia by Room Temperature Spray Process.

Wollastonite-based bioceramic powders were synthesized by solid-state reaction between calcite and silica powder. To control the phase and bioactivity of wollastonite, we also prepared four kinds of wollastonite-based bioceramics by adding an enstatite (MgSiO3) powder. After solid state reaction at 1000-1300 degrees C, micron-sized powders were obtained by milling and screening. By using these powders, wollastonite coatings were fabricated on zirconia substrates by a room temperature spray process, and their microstructure and composition under different coating condition were investigated. Wollastonite coatings on zirconia substrates were formed with the homogeneous microstructure and nanoscaled grain size. The phase composition of the resultant wollastonite coatings was similar to that of the starting powders, however, the grain size of the wollastonite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. The wollastonite coating layer exhibited bioactivity in a stimulated body fluid and forming ability of 25 nm sized-hydroxyapatite precipitates of during in vitro test in SBF solution.

Processing of High-Quartz Porcelain Tile with Large Yellow Sand

In this study, the yellow sand waste with enormous reserves in the Inner Mongolia Tengger desert was taken as the main raw material mixed with the same regional clays for the infrared functional low-temperature porcelained tile. The mineral composition and granule feature of Tengri yellow sand as well as the micro-structure and infrared property of the fired body were discussed by the means of various testing such as the grain fineness distribution analysis, the XRD diffraction analysis, the SEM scanning electron microscope analysis, the coefficient of thermal expansion measure and the infrared performance detection. The results revealed that the natural mineral could be replaced by the yellow sand waste in large for preparing the environmental protection functional porcelained ceramics with favorable properties. The flexural strength of porcelained tiles sintered at 1140°C~1160°Ckeeps from 40 to 55Mpa when the high addition of yellow sand varies 75wt% to 90wt%. And the body is composed of high quartz as the main phase and little wollastonite phase which meets with the thermal shock resistant standard of the present architectural material .

Synthesis and Characterization of Sol-Gel Derived SiO&lt;sub&gt;2&lt;/sub&gt;-CaO Glass

A phosphate-free glass based on SiO2-CaO was synthesized by a low temperature acid catalysed sol-gel route. The obtained material was evaluated by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The XRD analysis showed the sol-gel derived glass was amorphous in nature and crystallized when sintered at temperature above 900oC. The crystalline state was consisted of quartz and wollastonite phases. Meanwhile the infrared analysis showed typical transmission bands of monolith silica in the binary glass pattern. The bioactivity of the amorphous glass was investigated in vitro in simulated body fluid (SBF). The amorphous glasses were soaked in SBF for 1, 3 and 7 days. It is notable that the obtained results from FTIR, SEM and EDS analyses showed the deposition of spherical-shaped crystalline hydroxyl-carbonate-apatite (HCA) on the surface of the glass within 3 days of immersion in SBF solution. The HCA deposition was covered most of the surface after 7 days of immersion.

Comparison of mesh grinding and chemical washing techniques for the beneficiation of kaolins used in the white cement industry.

&#x0D; &#x0D; &#x0D; Kaolins are hydro aluminum silicates which are either monoclinic or triclinic in structure in accordance to their origin. Some common applications of kaolins are paper products, paints, catalyzers, white cement, etc. In the present research four different kaolins which were extracted from Villa de Reyes, S.L.P.; Mexico, were beneficiated using two different techniques: mesh grinding and chemical washing, in order to meet the requirements for the white cement industry, i.e. the mass content of Fe2O3 should be less than two percent of the total kaolin mass. XRD, Optical Microscopy, Colorimetry analysis were performed on the four studied kaolins. Mesh grinding and chemical washing techniques showed a similar degree ofbeneficiation. XRD analysis showed six different phases that make up the four different kaolins and are: saponite, kaolinite, wollastonite, stellerite, crystoballite and quartz. Most of Fe2O3 was located in the kaolinite, wollastonite and crystoballite phases, as could be corroborated by the combination of XRD, Optical Microscopy and Colorimetry analysis.&#x0D; &#x0D; &#x0D;