ceramics technology

7/31/2019 Ceramics Technology

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RECOMMENDATIONS TO THE READER

The presentation of a systematic collection of information about technology

production of traditional ceramic materials, in particular pressed tiles,

presents many problems, since the very diverse cultural activity

work of possible users of the information gathered.It could be conceived as a user to access, descriptive of the operations

and machines, apart from a deeper understanding of the materials

and problems, or, conversely, as a text of a deepening of technological operations,

the result of which is taken for granted. The reader with a technical-scientific

would

led to search for specific news, innovative and original, or at least a collection of

difficult to find information in condensed form, the player with activities technical

productive

would, however, affected by a manual resolution of the problems that

daily beset the production line.

The young technician, recently screened in the bowels of a production process,

which little or nothing has been taught during the academic year of study or

academic

research, probably an overall picture that, with descriptions and required more

than enough, led him to understand what happens in the "Factory", from the arrival

of raw materials to packaging of finished products.To say that this volume is to be published soon, remember that the processes

production try to reconcile all these different needs is not guilty of

presumption: it would say that these books have to balance the demands described.

Here it is, instead, made a serious attempt to describe the best, albeit briefly,

a production line, ignoring the basics of descriptive and scientific matters,

giving substance to a first volume that is talked about what happens during the

individual

stages of production process, and, in particular the importance of defining the

propertynature of the raw materials used, their meaning in a body and the problems

they can generate, in addition to a general overview of the possible products,

according to their technological characteristics.

A brief introduction describes the main themes of the joints after

developed. The second volume, however, is intended to further clarify aspects

technology of each stage of the production process, through not so much a specific

description

machines, doomed to become obsolete in a short time,or through an explanation of the purpose and operation of each machine to

effects of the final product. In this sense, a lot of space is given to


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discussion of each stage of the casting defects in workmanship and a general

framework

Correlation between the defect in the final product and the production stage

in which the defect has been generated. The cutting of the information will be

available, as we said,

on the production of pressed tiles, but more information will be differentprovided on other technologies or products, if it leads to better

understanding of reaction mechanisms.

A large collection of tables and usability standards completes the work.

INTRODUCTIONo start talking ceramic technology is certainly useful to introduce

some key definitions to provide guidance in this area

primarily by defining what is meant by ceramide.In fact, what is actually a ceramic material?

Among dozens of possible definitions, a ceramic material can be described

effectively as "any product which has a shape composed of materials

inorganic non-metallic raw (both mineral and synthetic), which from a

dust inconsistent state is transformed by means of various operations on a

product

semi, which, by cooking, it becomes a solid object, which has a structure

partly crystalline and partly glassy. "After cooking, virtually all the transformations and / or combinations

are permanent. When we speak of inorganic materials is

necessary to consider the degree of abundance the most common

Earth's crust, as to make pottery, is obviously desirable

and advantageous to use the most common raw materials and economic.


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Figure 1 shows that we are talking mainly of

silicon and aluminum oxides, as well as with different contents of Fe, Ca, Mg,

Na and K, which are effectively the first 7 most abundant elements in nature

and the elements are always present in a ceramic paste.

By observing, then the Periodic Table of the Elements, Table 1,

PERIODIC TABLE OF THE ELEMENTS

We really appreciate the small number of items of interest related

with a ceramic body (Al, Si, Ca, Mg, Fe, Ti, Na and K), even whenconsider the main constituents of the enamel (eg. Pb, Zn, Sn, Zr,Cr, Ni, Cr, V, B, etc.), It is clear how narrow is the range of elements


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necessary to characterize a traditional ceramic material.Indeed, in the spirit of this generic introduction on these materials,we can define the field of study and that the products are mostly limitedbycomposed of natural oxides, ie- CERAMIC TILES.- HEALTH.- CROCKERY.- CONCRETE.- SOME TYPES OF REFRACTORIES.Another approach is necessary for the special ceramic material orADVANCED, which are usually composed of non-special-oxides oroxides:bioceramics, electrical and technical porcelain, ceramics for electronics,catalysts,special refractories, etc.Therefore, for a better understanding of the composition of a materialtraditional ceramic, we can generalize the composition of a ceramic paste,knowing that, with appropriate modifications, we can considerationssimilar to other traditional materials, the paste will be madeFrom

- Clay materials, which provide enough plasticity forto obtain a definite shape. These bring Al, Si and part of Ca, Fe, Ti.- Flux materials such as feldspar, nepheline etc., That theCooking generate glassy phases that act as binders between the particlesand promotesolid-solid reactions, are carriers of Na, K, Al, Si.- Other materials such as talc, silica, pyrophyllite, CaCO3, etc.. (Called"INERT"), which can obtain specific performance, contributing mostly

Ca, Mg, Si.- ADDITIVES primarily to improve the rheology of aqueous suspensions;can be inorganic or organic, and introduced into the paste in quantitiesvery small (


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SiO2 structure, skeleton, and newly formed phasesFe2O3 and TiO2 smell and sometimes melting propertiesMgO CaO and control of contraction through the formation ofcalcium and magnesium silicatesK2O and Na2O fluxes, which form glassy phasesAl2O3 refractory and plasticity (when associated with the presenceof clay materials)SiO2 structure, skeleton, and newly formed phasesFe2O3 and TiO2 smell and, Although this description of the featuresceramic compositionchemistry brings to the pasta, is a proven fact that the same chemicalanalysisa ceramic substrate or raw material is not the most important datafor the characterization of the product: it can be shown products easilytechnically very different, for its use and technical characteristicspavers as low water absorption compared to the tiles,health, bricks, etc., have very similar chemical analysis.Any major effect may be the proportion of Ca and Mg, which leadsto a differential contraction done: in fact, the higher the contentof these elements, the smaller is this effect, as it silicates arecalcium and magnesium to increase its volume with temperature, in

contrast tocontraction due to the collapse of the silicate phases. Figure 2b shows aexample of state diagrams, which serve to establish a balance betweenthe various components.Figures 3 through 8 below, you can see a good example of this


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Table 2a. Composition and characteristics of different types of pasta.

ehavior where, in the form of ternary diagrams, represent the areascompositional types of product such as the tiles (covering


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low shrinkage), pieces of red paste type cottoforte "or fired tile strong(Intermediate behavior, the high water absorption) and stoneware (highshrinkageand low water absorption).[It is recalled that permits the identification of ternary diagrams in asystem in equilibrium,For example, the composition of systems of three components,represented in percentagesvariables, according to the schema below (Figure 2b): the composition ofaany point in the resulting triangular diagram is given by the intersectionin parallel with the sides of the triangle that cut through and which siderepresentsA percentage value on the left side, on the basis of B and C onright side. For example, in the figure, the point P represents acomposition of 30%A (E) + 20% of B (F) + 50% C (G)].

Figure 2b. Reading the percentage composition of the axes of a triangulardiagram.


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Figure 4. Ternary diagram K2O/MgO Fe2O3/Na2O + + CaO withcompositional fields

pastes majolica, stoneware cooking cottoforte and red (Vincenzini andFiori, 1977 / 2).


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Figure 5. Ternary diagram SiO2/Al2O3/TiO2 + Fe2O3 + MgO + CaO +Na2O + K2O with

compositional fields of red stoneware pasta and white stonewarepotassium and sodium(Fabbri and Fiori, 1983 / 1).


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Figure 6. Ternary diagram Al2O3/Na2O / K2O with compositional fieldspastesred sandstone and white sandstone potassium and sodium


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Figure 7. Ternary diagram K2O/TiO2 Al2O3/Na2O + + Fe2O3 + MgO +CaO with fieldscompositional pastes of red sandstone and white sandstone potassium andsodium

Figure 8. Ternary diagram TiO2/Fe2O3 SiO2/Al2O3 + + MgO + CaO +Na2O + K2O withcompositional fields of clay majolica, stoneware and red cottoforte

In order to effectively describe a raw material or a paste for ceramics,with relevant information on technological behavior, itthen much rather use the mineralogical analysis (crystallographic)and sieve analysis.To better understand the utility of these techniques is necessary toconsiderhow does a raw clay into a paste, as labor inputplastic. In terms of a simple representation of the structure of aclay, we can consider that this is composed of a combination of unitsrepetition SiO4, tetrahedral (T), associated with octahedral basic units Al(OH) 6,designated (O), 9 and 10;


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Figure 9. Repeating units of the phyllosilicates Figure 10. Projection of thestructural units

SiO4 tetrahedral base on the octahedral plane.+ And octahedralbase (Al (OH) +6 3 -.

These are two-dimensional particles, the distance between two unitsrepeating identical structural variable, depending on the type of material, such asexample shown in Figure 11.Through this provision based on the repeating units, the space betweentwo particles, micelles, or between two particles tapes etc., may vary fromminimum of 2.7 (in the kaolinite) to a maximum of 8 or more Angstrom [1A = 10-8cm], particularly chlorite, giving the possibility or not to incorporate moleculesor foreign ions in the structure.


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Figure 11. Examples of different spaced interreticulares that characterize raw materialsclay.


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The presence of water, in particular, between the particles means having the possibilityof moving a particle over another, ie in practice to have plasticity.The presence of water, in particular, between the particles means having the possibilityof moving a particle over another, ie in practice to have plasticity.Moreover, in these spaces, you can enter as ion flux

Na + and K +, which will change the technological properties of raw materials.The presence of water, in particular, between the particles means having the possibilityof moving a particle over another, ie in practice to have plasticity.It is therefore very important to know the mineralogy ofclay content of a paste, in order to anticipate problems and advantagesuse: all this information can be obtained from diffraction techniquesX-ray (XRD).The presence of water, in particular, between the particles means having the possibilityof moving a particle over another, ie in practice to have plasticity.Considering now the flux materials, and mainly of feldspar,

is, again, important to know the mineralogy, asformation temperature of the glass phase and the viscosity of glass are formedclosely correlated with the type of feldspar, the feldspars (mineralogicallydefined as albite) have a higher melting temperaturelow, but also a low melt viscosity, while feldsparspotassium (microcline, orthoclase, sanidine, etc.) have a higher viscosity,that can help in the case of dimensional sizes and bonding probleg problems duringcooking. On the other hand, knowledge of the mineralogical natureindividual raw materials of a paste helps the design characteristicsspecific, such as the formation of "eutectic", ie compositionsindividuals with lower melting points.The presence of water, in particular, between the particles means having the possibilityof moving a particle over another, ie in practice to have plasticity.If we now turn to the particle size distribution, it is obvious that the objective ofthe formation and firing of a blank tile is to obtain aproduct that have been activated and completed the greatest number of reactionssolid-solid, and this depends largely on the contact surfaceparticles as the larger, more favors the development with temperaturefrom sintering, through the reaction to the merger, asshown in Figure 12.

Figure 12. Schematic representation of a process sinterizacin.in.

The clay particles themselves are small, but need to be mixedeach other and with particles of other materials of suitable dimensions, taking


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the city to obtain the maximum filling of space and, therefore,maximum density: this isachieved with an appropriate mix of different grain sizes.Therefore, to have good control of the fineness of apasta is a simple enough residue on screen, but it would be advisablecontrol with proper instrumentation, which is based on the principles of interactionof individual particles (diffraction, scattering, etc..) X-ray or laser.

THE PRODUCTION PROCESSRegardless of the way to make the selection of raw materialsto mix into a dough, to get the right mix, the production phases willinvariably the following:- Selection, use and control of quarries.- Preparation of raw materials for mixing.- Preparation of pasta, by appropriate grinding.- Formation of the semi.- DRYING.- Several operations to add aesthetic value to the product.

- COOKING.- CLASSIFICATION, PACKAGING AND STORAGE.Each of these phases requires attention and must be planned and executed withappropriate controls.The following outline describes the most common production process, phase byphase of the manufacture of ceramic tiles:

PREPARATION OF PASTA dry Hammer MillPendulum millAlsing wet mill (ball)Continuous MillDesleidoresDry Pressed CONFORMATIONExtrusionCastAny decorations chargesmultiple, pressingConvection drying, slow or fast,radiationCosmetic surgery usually glazed or applicationsspecialCOOKING traditional (slow) or fast: for bothtechniquesSingle firing (support + enamel)Double-fired (baked enamel and media)Third, fourth fire etc. (Decorations,stickers)

In the following tables (Tables 3-4) summarizes the production processescommon.


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Tables 3-4. Different production processes for the manufacture of ceramic tiles.

If all phases of production have been well planned, canget the output of ceramic tiles plant. However: How and why


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distinguish these tiles that can be used in various situations,from one airport to the bath house, from an operating room to a floorindustrial, etc..?It is therefore necessary to introduce briefly the concept of classificationceramic tiles:Usually classified according to:

- INTERNATIONAL STANDARDSbased mainly on the typeproduction process, or the absorption water of the cookedand still, referring to

- USAGE OF TRADEusing old classifications as Gres, Majolica, Clinker, etc.

The correct approach, obviously, would be to take into account acomplete set of technological characteristics of the fired pieces,main ones being:

- Type of use (floor or wall covering - interior or exterior).- Absorption of water, but also resistance to freeze / thaw.- Contraction.- Resistance to bending.- Resistance to abrasion and stains.- Color of the paste.

A thorough knowledge of all these parameters can actually definewhich belongs to a class ceramic tile, allowing its proper use.After rinsing, now in this kind of "summary" of introducing theargument in question, we go deeper into the subject to be treated, indicatingresearch methodologies that could and would be suitable to use forthen move to the systematic analysis of ceramic raw materials and their behaviorin different phases of production.

IDENTIFICATION AND CHARACTERIZATIONCERAMIC RAW MATERIALS

Many properties of clays and other ceramic raw materials dependthe type and proportion of various minerals that make them up, so thatIdentification of these minerals is of fundamental importance. The solutionThis problem is complicated by the fact that rarely ceramic raw materialsconsist of pure and well crystallized minerals: generally, wewith lots of minerals present in significant amounts and manyother constituents in smaller quantities. In this case, can be very difficultidentifying the main phases, especially if they are similar.Sometimes, it is often the case with clay, a mineral can not be identifiedif not carried out preventive cleansing and separation. On the other hand,same clay can contain different minerals and almost always is associated with importantamounts of quartz, limestone materials, mica and other materials.Moreover, the clay minerals have particle sizes toosmall (the dimensions are common to 100 , ie 10-6 cm), whichcertainly not conducive to the identification, in addition, raw materials are clayoften characterized by isomorphic substitutions, due to conditionsgenesis, as described in another chapter.


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Therefore, in general, the analytical methods used to studyof these materials premiums must be able to recognize the minerals thatpresent a composition is not constant, which are often mixedeach other, sometimes with tiny grains of dimensions. Since the identificationof a mineral depends on its fundamental characteristics that must benecessarily always the same, regardless of the position and environment

surrounding it, should employ analytical methods using propertiesthe univocal individual classes of minerals.These can be summarized as follows:- The properties depend on the chemical nature of the mineral.- The aspect dependent mineral crystal.- The management dependent atomic or ionic crystal structure.- Those that rely on chemical or physical changes due to mineralthe controlled alteration of the external parameters, ie p., the enthalpy changesby heating or cooling.Likewise, other known practical methods to identif identify or estimate in a

about the presence of some minerals in raw materialceramics: for example, high values of the rheological properties as plasticity,thixotropy etc., may suggest the presence of certain mineralsclay, like the magnetic properties can indicate the presence offerromagnetic minerals, etc. These methods usually provide a picturefeatures of the predominant mineral in the mixture, but are unableto solve the identification of individual components.The detailed description of the analytical methodologies that can be usedfor the recognition of the minerals in a ceramic material beyondof the objectives of this work, but it is certainly useful to indicate aspectsmost important of the main techniques and criteria that are based, as inthe description of individual species, often also refer to dataanalytical features.

SamplingA good analysis, in whatever form, running on a composite samplea mixture of base components, especially if it is homogeneous, requiresFirst, a good sampling, which allows a small aliquot of material,necessary for analysis, representing all of the shows, sometimes consistingby several tons of material taken from the stockpile for the preparation of pastaa ceramic company: the analytical sample must therefore be representativeof the total, and not a part of it.Based on the more general case, ie the ie the sampling in the quarry (for whichand standardized procedures are in place), the sample must be takenfrom different parts of the extraction front, and at various depths, whenthe material seems to really even be able to select and retain, afterquadripartition mixed and samples taken, a sample equivalent to about1% of total but in the case of heterogeneous basic material, you must chooseup to 5% of the sample, to obtain a reasonable samplefor analysis.The same reasoning applies for samples taken from shipsor articulated trucks loaded with bulk material.The preliminary sample selected in this way is homogenized then


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possible presence of sulfide minerals (pyrite, for example).Therefore, before starting a chemical analysis is necessary to select the sampleaccurately, using the methods described above, whose consistency variestypically from a few hundred milligrams to 1-2 grams afterhave carried out a careful drying at a temperature that does not alter the contentvolatile substances, and then passed to the mill to be conducted

grinding media to ensure maximum performance without contaminating the sample.These methods vary depending on the hardness of the sample, moving frommanual methods corundum mortar, or preferably natural agate upmicromolinos with bodies grinding hard alloy appropriate.After weighing the sample (and this is the phase error that may result in morethroughout the analysis), identify the method of attack itself, which allowsthe most complete homogenization, normally operated by dissolvingsample in the appropriate chemical reagents, and obtaining a solutionhomogeneous liquid, or by the dissolution, in the molten state in a glassconvenient to conduct a further analysis of this solid solution.

Unfortunately however, ceramic materials, being based on silicates,aluminates and oxides, is quite difficult to solubilize, and in this respectThere is an extensive bibliography that provides specific, as agents of attackhot liquid mixtures of hydrofluoric acid, HF, and other mineral acids,as nitric acid, HNO3, hydrochloric acid, HCl, or sulfuric acid, H2SO4, operating incontainersappropriate.Chemical analysis "classic" by expected wet and complex treatmentsystematic samples, by separating the individual componentsbefore the actual analysis, carried out mainly by means of gravity (longand complex), colorimetric or complexometric (need to make everyPreliminary calibrations precise time). These methodologies, but still todaymore than valid, have been clearly overcome by the development of techniquesincreasingly instrumental more sophisticated, which, on the sample promptlysolubilized or even, as they allow the immediate collectionanalytical results.Obviously, all the determination is influenced primarily instrumentalby the initial measurement of the mass of the sample and the correct preparation,which, whatever, should provide more standardized conditions andcomprehensive as possible to homogeneity.The main methods of attack and acid stabilization of raw materialsceramic interest are:- Hot acid attack in open containers, using mixturesacid-oxidizing, based on HCl, HNO3 and HClO4: the need to decouplesilicate matrix is almost always necessary as the use of HF, and attherefore unable to use normal glassware borosilicate glass. Theuse of ouse of open containers, together with a solubilizing acid high temperaturemay contribute to loss of volatile components.- Hot Acid attack in closed containers, and therefore also higherpressures. These systems are increasingly stretched by the speed of attackand the solution, usually make use of Teflon containers and systemsprogrammable heating with microwaves.- Fusion alkaline and acid solubilization then usually HCl.


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There is a wide range of alkaline fluxes, used in a function of temperaturedesired fusion and the efficiency of the process: in all cases, of course,There is the addition, through the flux of at least one cation, which is no longer trueeffectively quantify the unknown. More alkaline fluxesused are NaKCO3, NaOH, and Li2B4O7 LiBO2, with the addition of different saltsthat act as disintegrants (mainly lithium halide or alkaline

general) complexes, etc., see table below.

Melting temperature of the compounds used in the decomposition of material by melting.

(1) After the decomposition and transformation of bisulfate in pyrosulfate (K2S2O7)(2) Introduced bihidratada usually in the form;(3) As PbO after decomposition and release of carbon dioxide at 315 C;(4) As PbO after decomposition at about 500 C.

The fusion can be performed manually or automatically, with the assurancestandard operating conditions in any case in plat in platinum containersor the like, and glass can be obtained directly under the instrumental readingor be solubilized with precision, the solution for reading, thenby appropriate dilutions.

Whatever the instrumental technique used, it is obviously necessarypreventive construction of different calibration curves, usingstandard solutions or solid in the range of reading courseunknown samples.

The main instrumental analytical methods used for chemical analysisquantitative analysis of ceramic materials based on feedback, emitter typefluorescence, absorption or emission of the sample with electromagnetic radiation;These are, therefore:


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X-ray fluorescence (XRFnce (XRF) technique in which the minerals as such or,more finely dispersed in an alkaline glass is bombarded with radiation

High frequency, low wavelength, which contains enough energy toinduce a fluorescent emission due to excitation of internal electrons

the orbits of the elements present, these electrons emitted by the samplecollected by an appropriate detector, and the signal generated is associated with thepositionsample or the detector itself, establishing a relative intensity of signalcontrasts with the pattern. With these methods are easily quantifiableelements of medium-high atomic weight to the lower limit of Na - F, and moreRecently, considerable efforts have been made to obtain a determinationalso repeatable enough elements to boron (Figure 13).

Atomic Absorption Spectroscopy (AAS-GFAAS), which uses

energy absorption due to the presence of chemical species in atomic form,introduced in the path of one or more monochromatic radiation generatedby appropriate lighting: in practice the test solution injected intoa flame whose temperature, geometry and composition can ensure the presenceelements in atomic form, and nonionic, and maximum interaction withincident radiation. For a better resolution is possible with some elementsuse as an energy source spray instead of a flame, heatingrapid induction, within a tube made of graphite or other materialappropriate, in a stream of inert gas. Under certain conditions, through thisoperating technique, you can also analyze a solid sample ofeasy volatilization. With these techniques it is possible to obtain optimal analytical resultsfor all metal, to very low resolutions of the order, dependingelement of fractions of parts per million (Figure 14).

Atomic Emismic Emission Spectroscopy (ICP-AES), a technique similar toabove, however, where you use a subtractive rather than additive interaction ofatomized element incident radiation. In this case, the sample solutionis atomized by the combined action of high temperature of a standard torchapplying a radio frequency source. The advantage over the systemsabsorption, is the possibility of sequential analysis of each sample withoutmodify the source, the limit for registration of individual items is often worse,although some elements have better performance. In any case, it is possibledown to a detection of p.p.m. or p.p.b. without major problems (Figure 15).

Naturally, other methods of chemical analysis that can be selectedparticularly in relation to the pursuit of certain elements (one for all:the flame photometry to search for alkali elements), butfor specific description we refer the reader to specialized texts.On the other hand, is undoubtedly important to note the option of selecting trialsspecific chemicals to verify the presence of certain elements (carbon,sulfur, fluorine, etc..) or anions (carbonate CO3 2 -, SO4 sulfate 2 -, etc.) Techniquesusually simple and effective analytical, allowing assessments veryimportant for the purposes of the applicability of a raw material for a process


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Figure 15. Operating principle of instrumentationfor atomic emission spectroscopy (ICP).

Mineralogical analysis (or crystallographic)

This type of research allows for the presence of single crystalline phasesin a sample, tracing and, in its mineral composition, whose valuationis of fundamental importance for defining the technical characteristicsraw material itself or its contribution to a paste.A preliminary form of the mineralogical data obtained by observation,First, the eye and then by microscopy, reflected light, polarizedand transmitted (in a sample reduced to a thin a thin film after being stuffedresin): combining other optical properties like refractive index with

those observations, it is possible, with the necessary scientific training rather simplespecified, get a good discrimination and recognition. All scienceapplication of optical microscopy mineralogical investigations in materialsceramics is a branch of application singular, supported by numerousand technical publications, which have been broadcast between 1940 especially1960. The technique may now be the main resolutionmineralogical analysis is, without doubt, the X-ray diffraction (XRD), realizableon individual crystals or, more commonly, on the powders (Fig. 16).

X radiation incident on a sample, appropriately filtered so as to

obtain monochromaticity, interacts with the crystal lattice of the same,resulting diffraction configurations are correlated by the equationN = 2dsen Bragg, with distance d interreticular glass, depending on the anglediffraction. By selecting a wide range of X-ray sources, although the mostspread is clearly one that can be obtained by anticathodes Cu, filteredNi to issue only the Cu Ka = 1541 , it is appropriate to list eachset of interactions of a given crystal lattice with the ratio of distancesactive grid, expressed in Angstrom ().For all crystalline substances are available indexes or databasesdata (PDF, see the examples in Tables 5 and 6), to be maintained and updated

charge an international organization for recognizing the crystalline speciesin natural and synthetic samples and recently are beingrefining computer programs that allow modal data management


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diffractometers, coming to provide quantitative assessments of the presenceof individual minerals.Of course, operating on the powder, it is essential that the sample is very representativethe whole, and not present at all orientations preferentialcrystals easily developed due to a two-way and for this reason,the preparation and processing of the sample assumes paramount importance.

The grind should be as efficient as possible, avoiding the modification of the characteristicsstructural sample, especially if clay, to promote betterstandardization of all phases present and the random direction of all facespresent clear, in fact, not wanting to proceed to the analysis by rotating sample holder,usually not available, we need to be reasonably surehave prepared a sample heavily disoriented, also the concomitant presence of phases ofdifferent density and crystallographic habit inopportunesuch as clays and mica materials, which have shaped micelleshighly developed in two directions.

Figure 16. Photo left: Team X-ray diffractometer analysis, upper panel: working principle.

The X-ray diffractometer analysis can be considered without more routine, withrelatively simple and quick, and simple enough matrices allowsinterpretation of the data easily obtained, also allowing forCombining the proven presence of some crystalline phases, the allocation ofits chemical formula "type" and, in combination with the quantitative chemical analysis,makingthe so-called rational analysis of a subject or a paste, ie make aapproximation of the typical mineral composition expressed. In this way,

example, a ceramic paste will be possible to assess not only their chemical compositionoxides, but also its mineral composition, expressed in quartz, kaolinite,illite, calcite, dolomite, albite (sodium feldspar), microcline (potassium feldspar), ETC.see example in Figure 17.

Thermal analysis

As noted by the name in plural, the analysis can beout to verify the variation of the parameters in terms of an increase (or decreasedecrease)temperature is more than one. In fact, it is possible to record, depending

a particular temperature gradient, changes in weight, temperature, heatdeveloped or absorbed, dimensions, gaseous substances emitted, and so on., to each ofThese techniques shall be a type of analysis, which takes its name from the initialscorresponding English words:


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TGA (ThermoGravimetricAnalysis) [TGA (thermogravimetric analysis)] DTA (DifferentialThermalAnalysis) [ATD (thermodifferential analysis)]

Table 5. PDF tab crystallographic data of quartz (SiO2).

Table 6. PDF tab crystallographic data of kaolinite.

"Single firing porous, colored pasta" dry milling, pressing.


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Figure 17. Example of tab-pasta, with rational analysis obtained from techniquesXRF & XRD.

DSC (DifferentialScanningCalorimetry) [CBD (differential scanning calorimetry)]

TMA (ThermoMechanicalAnalysis) or DIL (Dilatometry) [ATM (analysis thermometerchanical) or DIL (dilatometry)] EGA (EvolvedGasAnalysis) [AGD (analysis of gases released)]

These types of analysis, and represents an obvious way to observe andpredict the behavior of a single material or a paste fordrying, cooking or cooling, represent an aid for determining optimalmineralogical composition of a mixture, observing the differenttypes of effects in close correlation with the crystal structure and transformationsphase of the different minerals, and also represent a possible aid

in determining the chemical, for example by allowingto recognize the presence of minerals and salts such as dolomite, carbonate,sulfates, sulfides, fluorides, etc. (Figures 18-22).

The instruments used for thermal analysis consist mainlyAs one head, suitable for hosting the test sample in the right wayand physical changes that transform electrical signals shown in zoomablemanageable, and a heating system, usually based on resistance


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Figure 18. Comparison of DTA curves more significant, conveniently schematized,clay minerals: A = kaolinite; metahalloysita B = C = montmorillonite-Na, D =montmorillonite-Ca, E = vermiculite, sepiolite F = G = palygorskite.

Figure 19: Differential Thermal Analysis (source: G. Peco 1952).


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C = kaolinite, Cr = cristobalite; H = halloysite, Q = quartz, I = illite, Ca = limestone; M =montmorillonite.TG analysis, PDD, ATD, ATE Hirschau on kaolin (source: E. Kaisersberg and C. Urso).

Figure 20. Examples of dilatometric curves of a crude sample, which undergoestransformationsirreversible (curve a), and a sample already cooked, which, on cooling, runs substantiallycurve obtained on heating.

power, which is due strong characteristics of stability, uniformity andprogrammability, thus ensuring perfect reproducibility of the measurements.It is often possible to combine some of these tests on a single computer,ATG + ATD example, or ATG + CBD, and ATD + AGE or ATG + ATD + AGE


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so that, in a single step, to obtain a large amount of information.In order to describe briefly the working principle of somethese teams, we can consider the most common applied to the ceramics sectornamely the simultaneous analysis dilatometer and ATG + ATD.Dilatometric analysis to measure the expansion and contraction of a sample


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but also all other materials, undergo expansion and contraction dependingwhat happens inside, in particular the loss of the componentsvolatiles, mostly water, induces a "collapse" of the crystal structureclays, which may manifest as a sharp contraction at temperaturescharacteristics. Thus, it may be possible to identify pointsCritics of a material and, depending on the temperature characteristic of values

maximum contraction and intensity will be possible to identify and distinguishpresence of zeolitic water, related to the presence of spaces interreticularesbetween the clay micelles sufficiently large chemical water isthat hydroxyl formation of the primary lattice, transformationsStructural yet (such as the important transition from -quartz - -quartz), thedisappearance of reactive phases, etc.

The curves obtained dilatometric some materials, presentin figures 20, 21 and 22 are significantly representative of thepossibility.There is also another important use of dilatometric curves obtained

pastes and ceramic raw materials: the measure of the tendency of a materialdilate or contract in a given temperature range, ie, its coefficientlinear thermal expansion.This is expressed by the following relationship:

being the linear thermal exprmal expansion coefficient between T1 and T2, L0 is thelengthinitial sample, L is the difference between LT1 and LT2, whereas in practice

production is a consolidated approach using the coefficient of expansioncube obtained by multiplying by 3 the linear coefficient obtained from thedilatometric measurements, according to the arbitrary assumption that the trenddimensional variation is the same in all directions.This information is extremely important for assessing the desirability of couplingof different materials during heating and, especially, during cooling,which leads to permanently retain any tensionsaccumulated due to a lack of agreement dilatometric, this is a classic case ofglazes applied over a fired ceramic bisque and then or at the sametime with the support (figure 23).

In light of the brief summary above, it is clear that there is a possibility orrather, the need to make a number of analytical tests "fine" onraw materials used in the ceramic process, the necessary instrumentationis not normally available to productive enterprises, so that the controlsis normally provided by outside laboratories or entities capable of performing theseaccurate investigations. This does not mean that, within firms, notof great importance to organize a series of production controls, whichallow work with continuity and consistency.The more frequent and accurate are these controls, the greater the control


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Figure 23. Opposite effect because of the lack of coupling between the enamel anddilatometric supportceramic set by cooling: A case Enamel> cake - enamel case B


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production process, with the possibility to quickly correct errors ordeviationsadjustment, the more precise and tidy are the collection, interpretation

and documentation of monitoring results, the easier it will resumeaftera particular product line, optimizing production in a short time.For these reasons, the following is a brief outline ofkey controls to be made.

Plastic Raw Materials, Semi plastic and nonplastic

Determination of the characteristics of the starting material. On

materialsbase are determined:Humidity

AspectResidueCarbonatesReducing substances

Expressed as% moistureWeigh a sample of wet material (Ph), dried to constant weight in alaboratory oven at 110 C for about 24 h and the sample is weigheddry (Ps). The difference between the 2 weighings divided by theweight of wet samplemultiplied by 100 gives directly the moisture of the sample:

Appearance of the starting materialRecorded the shape and dimensions (size) of the starting materialandcolor and all other known characteristics.Residue on different screensIt weighs 100 g of dry sample and treated in a laboratory shaker for30 minutes with 300 ml of deionized water, added 1 g of

tripolyphosphatesodium or sodium polyacrylate, until the particles are completelydisrupted


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and dispersed.Sieved sieves the slip in 1000, 2500 and 10,000 mallas/cm2 (180,125 and60 microns). Obtained are dried in several screens until constantweight andmust be weighed. These values give directly the percentage ofresidue ondifferent sieves.For non-plastic materials may be interesting to make a determinationDry, analyzing approximately 200 g of dried material on

Figure 25. Equipment for determination of different size fractions.

a column of sieves with appropriate clearances of [p. eg. 11 (2000) -35 (1000) -140 (500) - 590 (250) - 1600 (150) - 4700 (90) and 9500 (63)

mallas/cm2 (microns)].


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Carbonate content in% of CaCO3The determination was performed with a calcmetro (eg. Pizzarelli andDietrichFrhling). A sample of one gram of dried material at 110 C, whichshouldbe introduced into a suitable container.In the container, a tap is inserted dilute hydrochloric acid (1:1).In the event that the material contains carbonates of any kind, itfollowsCO2, which, exerting a pressure proportional to the amount ofcarbonates,cause the decrease of the water column on the graduated cylinderwhich is read directly, or calculated, the percentage value ofcarbonates,CaCO3 as contained in the raw material. Knowing the volume of CO2

developed and the absolute temperature, the calculation is applied:% CO2 = 52146.2 VCO2 (L) / K

Assuming that CO2 has been developed solely from CaCO3:% ofCaCO3 =% CO2 2273.

Determination of total reducing substances

Figure 26. Equipment for determination of carbonate minerals (calciteand dolomite).


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Is effected by a lowering retrovaloracin oxide.It weighs about 2 grams of powder less than 200 microns, istransferred to a beakerof 400-500 ml, and adding 10 ml of a solution of K2Cr2O7 1 N (49 gone liter of distilled water) and 10 ml of concentrated H2SO4, shakingthe containerhand for approximately one minute, then letting it slowly digested withmagnetic stirring for 30 minutes (the color should be a toneamarillonaranja:if green is added again 10 ml of dichromate).Then add 10 ml of 85% phosphoric acid, Complexediron present, and diluted with distilled water to 200 - 250 ml, is addedapproximately 2 ml of indicator solution (0.16 g of bariumdifenilaminosolfonato in 100 ml of distilled water) and titrated with 0.5N FeSO 4 (140 g in 200 ml of water + 40 ml distilled conc H2SO4.,led to a liter, stored in a dark glass) with slow agitation, increasingcolor blue to green equivalent point clear.The value obtained must be corrected by the actual ratio of oxidereducer reagents (white), obtained performing the same test withoutthe sample.Calculation:

reduced K2Cr2O7 ml x 0.69 (factor estequiomtrico) / sample weight(g) = total% reducing substances

Example:Test "white" additive K2Cr2O7 10.0 ml, FeSO4 needed for thesteering withoutclay 21.5 ml: correction factor = 0.465 (10/21.5).Test Measurement: 2,125 g sample + 10 ml K2Cr2O7, FeSO4

necessary for19.25 ml shift: 10 - (1925 x 0465) x 0.69 / 2125 = 0.34% reducingsubstancestotal.

This measure provides mainly organic substances in thesample, but is influenced obviously also by the simultaneouspresence of

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