1.1 Background of Study
Natural Kalsilite (KAlSiO4) occur mainly in K-rich, silica-undersaturated ultrasonic volcanic rock with high potassium and low silica and sodium content but also can be found in metamorphic rock known as a very rare occurrence as a metamorphic mineral. Although it may be common than it supposed, it is rather difficult to identify with assurance in thin section. Kalsilite can be categorized as a feldspathoid which is a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. The structure of the KAlSiO4 is a framework structure of linked (Si, Al) O4 tetrahedral. KAlSiO4 exist in several polymeric forms (Cellai et al., 1997) that are low kalsilite (Perrotta and Smith 1965) and high kalsilite (Kawahara et al.,1986).

Variety techniques had been used previously to synthesized kalsilite including cation exchange from nepheline (Dollase and Freeborn 1977; Stebbins et al. 1986; Sobrados and Gregorkiewitz 1993), solid-state synthesis from oxides or zeolite (Smith and Tuttle 1957; Dimitrijevic and Dondur 1995; Heller-Kallai and Lapides 2003; Kosanovi? et al. 1997), sol-gel methods using TEOS or SiO2 as a Si source (Hamilton and Henderson 1968; Bogdanoviciene et al. 2007), crystallization from molten salts (Sobrados and Gregorkiewitz 1993); and
hydrothermal methods from muscovite (Kopp et al. 1961; Andou and Kawahara 1984). However, many of these methods give poorly ordered kalsilite or give rise to secondary product.
The hydrothermal method is economical and convenient to prepare pure materials with fine particle size at low temperature compared to the other synthesis method ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.2138/am.2009.3284”, “ISBN” : “0003-004X”, “ISSN” : “0003004X”, “abstract” : “Kalsilite (the low-temperature form, of KAlSiO4) is used as the precursor of leucite, an important component in porcelain-fused-to-metal, and ceramic-restoration systems, and it has also been proposed as a high-thermal expansion ceramic for bonding to metals. The present study reports the hydrothermal synthesis and characterization of pure kalsilite from kaolinite in subcritical conditions, as well as the characterization, of the intermediate products by means of XRD, 29Si and 27Al MAS NMR, IR, SEM, and TEM. Effects of time, temperature, and pH on the reaction, products are analyzed. The experimental data indicate that pure kalsilite is obtained after hydrothermal treatment of kaolinite at 300 u00b0C for 12 h in 0.5 M KOH solution. Longer reaction times increase the cry stallinity of the structure, whereas lower reaction times give rise to the metastable ABW-type KAlSiO 4 polymorph. Lower temperatures are not sufficient to produce kalsilite, but zeolite W is obtained instead as the unique reaction product. Finally, the pH of the aqueous solution in contact with kaolinite is an important parameter for the synthesis of kalsilite, which must be u2265 13.70.”, “author” : { “dropping-particle” : “”, “family” : “Becerro”, “given” : “Ana Isabel”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Escudero”, “given” : “Alberto”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Mantovani”, “given” : “Marco”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “American Mineralogist”, “id” : “ITEM-1”, “issue” : “11-12”, “issued” : { “date-parts” : “2009” }, “page” : “1672-1678”, “title” : “The hydrothermal conversion of kaolinite to kalsilite: Influence of time, temperature, and pH”, “type” : “article-journal”, “volume” : “94” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Becerro, Escudero, & Mantovani, 2009)”, “manualFormatting” : “(Becerro et al, 2009)”, “plainTextFormattedCitation” : “(Becerro, Escudero, & Mantovani, 2009)”, “previouslyFormattedCitation” : “(Becerro, Escudero, & Mantovani, 2009)” }, “properties” : { }, “schema” : “” }(Becerro et al, 2009). However, high pressure (1000 bars), relatively high temperature (up to 600?C), long reaction times (15 days) and with consequent increase in the production used to obtain kalsilite via hydrothermal method. According to Bacerro et al. (2009), the present study reports a very simple and economical method to synthesize single phase of kalsilite from kaolinite in mild hydrothermal conditions.

Kaolin can be categories as a clay mineral and it is one of the main group in clay mineral. Kaolin is a soft, lightweight, often chalk-like sedimentary that has an earthy door ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.14382/epitoanyag-jsbcm.2007.2”, “ISSN” : “0013970X”, “abstract” : “A kaolinit u00e9s a metakaolinit szerkezete A tanulmu00e1ny ru00f6viden ismerteti a kaolinit szerkeze-tu00e9t u00e9s a metakaolinit kialakulu00e1su00e1ra u00e9s szerkezetu00e9re vonatkozu00f3 fu0151bb elmu00e9leteket. A kaolinit szerkezete viszonylag ju00f3l ismert, de a kaolinitbu00f3l 400 u00baC fu00f6lu00f6tti hu0151mu00e9rsu00e9kleten kialakulu00f3 metakaolinitu00e9 mu00e9g nincs teljesen tisztu00e1zva.”, “author” : { “dropping-particle” : “”, “family” : “Varga”, “given” : “Gabriel”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Epitoanyag”, “id” : “ITEM-1”, “issue” : “59”, “issued” : { “date-parts” : “2007” }, “page” : “6-9”, “title” : “The structure of kaolinite and metakaolinite”, “type” : “article-journal”, “volume” : “1” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Varga, 2007)”, “plainTextFormattedCitation” : “(Varga, 2007)”, “previouslyFormattedCitation” : “(Varga, 2007)” }, “properties” : { }, “schema” : “” }(Varga, 2007). In industry kaolin clay has been used widely especially in the production of cement, ceramic, porcelain and bricks due to the good physical properties and has stable chemical structure for ceramic production. The main constituent of kaolin is kaolinite that formed by rock weathering. It contains 10-95% of mineral kaolinite in kaolin clay. Kaolinite minerals can be found easily around the world and it undergoes hydrothermal action to change kaolinite minerals to kalsilite. Kaolin clay will be used as a raw material.

1.2 Problem Statement
In industrial, the popularity of kalsilite is increasing in time. It has been studied as the precursor of leucite, an important component in porcelain-fused-to-metal (PFM) and ceramic dental-restoration systems (Zhang et al., 2007). Other than that, kalsilite has also been proposed as a high-thermal expansion ceramic for bonding to metals (Bogdanoviciene et al., 2008). Despite the fact that kalisilite shows many advantage and benefit, these uses require the production of single phase kalsilite. However, the past research shows the synthesis of kalsilite from different method produce either poorly kalsilite or give rise to secondary product. Compared to other synthesis methods, the hydrothermal method is economical and convenient to prepare pure materials with a fine particle size at a lower temperature.
Yet, the hydrothermal synthesis of kalsilite from kaolinite use a high temperature and it is relatively take long reaction time for industrial production. Apart from that, hydrothermal method used stainless steel hydrothermal reactor which have a high cost. Therefore, the more efficient method to synthesize kalsilite is needed. In this study, kalsilite is synthesized from a metakaolin instead of kaolin under the condition at 120°C, 150°C and 180°C temperature by hydrothermal method and using the Teflon line autoclave to reduce the cost.

1.3 Objectives
The objectives of this study are:
To synthesis Kalsilite from metakaolin via hydrothermal method.

To evaluate the reaction of temperature and concentration of alkaline activator towards the development of Kalsilite Crystallization.

To characterize Kalsilite by using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron microscopy (SEM).

1.4Scope of study
The throughout study of hydrothermally synthesis kalsilite from kaolin is done by using two basic steps. Firstly, the kaolin clay will be used as raw material and undergoes thermal treatment to obtain metastable phase of dehydrated kaolin called metakaolin. Then, metakaolin will react with an aqueous alkali medium that is Potassium hydroxide solution (KOH) to obtain Kalsilite via hydrothermal method. The effect of the reaction time, temperature and pH in the development of the kalsilite crystallization will be studied. Other than that, the characterization of the kalsilite product will be determine by using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron microscopy (SEM).

2.1 Clays and Clay mineral
Clays are a fine-grained mineral that naturally occur in rock or soil material that can be combine one or more clays mineral with traces of metal oxides and organic matter. Clays are very abundant on the earth surface, they form rocks known as shales and are a major component in nearly all sedimentary rocks (Guggenheim, 2001). Clays composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. It can be considered as a plastic due to the water content and will become hard and non-plastic when dried or fired.

The term “clay mineral” refers to phyllosilicate minerals and to minerals which impart plasticity to clay and which harden upon drying or firing (Al-Ani and Sarapää ,2008). It can be found in the soils, in fine-grained sedimentary rocks such as shale, mudstone, and siltstone and in fine-grained metamorphic slate and phyllite and clay mineral will be in the form in the presence of water. Clay mineral is in layer silicate that are formed usually as product of chemical weathering of other silicate minerals at the earth’s surface (Al-Ani and Sarapää ,2008).

Clay mineral have two different sheet that built of tetrahedral silicate sheet and octahedral silicate sheet also can be classified as 1:1 and 2:1. Whereas the 1:1 phyllosilicates consist of one tetrahedral silicate sheet and one octahedral silicate sheet while 2:1 phyllosilicate will be formed from an octahedral silicate sandwiches between two tetrahedral silicate sheets. Clay mineral can be divided into three main group that are kaolinite that can be classified as 1:1 phyllosilicate, illite can be classified as 2:1 phyllosilicate and lastly smectites or montmorillonite that classified as 2:1 phyllosilicate.

Figure 2.1 Structure of 1:1-layer silicate (kaolinite) illustrating the
connection between tetrahedral and octahedral sheets ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “ISBN” : “M19/3232/2008/41”, “abstract” : “PHYSICAL u2013 CHEMICAL PROPERTIES AND INDUSTRIAL USES foru0161u0101 somu gru0101mata”, “author” : { “dropping-particle” : “”, “family” : “Al-Ani”, “given” : “T.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Sarapaa”, “given” : “O.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “id” : “ITEM-1”, “issued” : { “date-parts” : “2008” }, “page” : “1-91”, “title” : “Clay and clay mineralogy”, “type” : “article-journal” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Al-Ani & Sarapaa, 2008)”, “plainTextFormattedCitation” : “(Al-Ani & Sarapaa, 2008)”, “previouslyFormattedCitation” : “(Al-Ani & Sarapaa, 2008)” }, “properties” : { }, “schema” : “” }(Al-Ani
; Sarapaa, 2008)
Figure 2.2 Structure of 1:2 layer silicate (illite) illustrating the connection
between tetrahedral and octahedral sheets (Al-Ani ; Sarapäa,
There are many uses of clay that give benefits to people nowadays. One of the uses of clay is that it being used as drilling mud. The bentonite and other clays in the drilling of oil and water wells. The clay will turn into mud which then will seal the wall of the boreholes, lubricates the drill head and removes drill cuttings. Next, due to high absorbing properties clay used as filtering and will filter and purify animal, minerals, vegetable oils and greases. Lastly, clay also being used as contaminant removal where the Clay slurry have effectively been used to remove a range of contaminant, including heavy metals, and overall water clarification.

2.2 Overview on Kaolinite
The decomposition of potassium feldspars mainly formed kaolin clay. Kaolin is a natural component of the soil and can occur widely in ambient air (Programme, 2005). The physical properties of kaolin are soft, lightweight, white or greyish white in colored and powdery appearance. The Chinese word Kiu-ling named given to a hill near Jau-Chau Fu China give the idea to derived the word of “kaolin” where it was first mined (Sepulveda et al, 1983). Kaolin that commonly called china clay contain 10 – 95% of kaolinite mineral and usually consists mainly of kaolinite (85–95%). Kaolin also contain other element such as quartz and mica besides kaolinite but content differ from kaolinite. These kaolin minerals are typically formed under three environments: chemical weathering, hydrothermal alteration and sedimentary rock (Zhang et al., 2010; Johnson ; Arshad, 2014).

Kaolinite is the main component of kaolin clay and known as hydrous aluminum silicate. Kaolinite has a very good physical structure and stable chemical structure. The chemical structure of kaolinite is Al2Si2O5(OH)4. It is made up of tiny sheets of triclinic crystals with pseudo hexagonal morphology (Programme, 2005). Kaolinite is forms at relatively low temperatures and pressure. It contains little or no surface adsorbed water in the structural units. Kaolinite can adsorb small molecular substance such as lecithin, quinoline and also protein, viruses and bacteria. The adsorbed material can be easily removed from the particles because adsorption is limited to the surface of the particles (Programme, 2005).
Kaolinite structure consist of tetrahedral silica sheet alternating with an octahedral alumina sheet which forming the 1:1 clay mineral layer. These sheets are arranged so that the tips of the silica tetrahedrons and the adjacent layers of the octahedral sheet form a common layer (Grim, 1968). In layer common, there will be two or three oxygen atoms shared by silicon and aluminium. The repeating 1:1 layer is attached to each other by hydrogen bonds (Johnson ; Sazmal, 2014). The structure of kaolinite is shown in the figure 2.3.

Figure 2.3 Schematic view of the structure of kaolinite ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.14382/epitoanyag-jsbcm.2007.2”, “ISSN” : “0013970X”, “abstract” : “A kaolinit u00e9s a metakaolinit szerkezete A tanulmu00e1ny ru00f6viden ismerteti a kaolinit szerkeze-tu00e9t u00e9s a metakaolinit kialakulu00e1su00e1ra u00e9s szerkezetu00e9re vonatkozu00f3 fu0151bb elmu00e9leteket. A kaolinit szerkezete viszonylag ju00f3l ismert, de a kaolinitbu00f3l 400 u00baC fu00f6lu00f6tti hu0151mu00e9rsu00e9kleten kialakulu00f3 metakaolinitu00e9 mu00e9g nincs teljesen tisztu00e1zva.”, “author” : { “dropping-particle” : “”, “family” : “Varga”, “given” : “Gabriel”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Epitoanyag”, “id” : “ITEM-1”, “issue” : “59”, “issued” : { “date-parts” : “2007” }, “page” : “6-9”, “title” : “The structure of kaolinite and metakaolinite”, “type” : “article-journal”, “volume” : “1” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Varga, 2007)”, “plainTextFormattedCitation” : “(Varga, 2007)”, “previouslyFormattedCitation” : “(Varga, 2007)” }, “properties” : { }, “schema” : “” }(Varga, 2007)
The uses of kaolin as an aluminosilicate source in synthesis is widely known. Besides, kaolin has a variety of industrial application as large volume of kaolin clay used for the production of paper coating, cement, ceramics, bricks and porcelain. The largest market for kaolin is in paper coating because of its fine particle size, platy particles, good viscosity, white in color and good printing quality. Furthermore, kaolin also used in aqueous based paint and inks and as functional additive in polymers. Recently, a specially formulated spray contain kaolinite clay is used in fruit and vegetable production to repel the insects and prevent sun burn. The total world production is currently estimated to be 39 million tons per year as distributed in Table (2.1).

Table 2.1 The total world production of kaolin per year ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “ISBN” : “M19/3232/2008/41”, “abstract” : “PHYSICAL u2013 CHEMICAL PROPERTIES AND INDUSTRIAL USES foru0161u0101 somu gru0101mata”, “author” : { “dropping-particle” : “”, “family” : “Al-Ani”, “given” : “T.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Sarapaa”, “given” : “O.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “id” : “ITEM-1”, “issued” : { “date-parts” : “2008” }, “page” : “1-91”, “title” : “Clay and clay mineralogy”, “type” : “article-journal” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Al-Ani & Sarapaa, 2008)”, “plainTextFormattedCitation” : “(Al-Ani & Sarapaa, 2008)”, “previouslyFormattedCitation” : “(Al-Ani & Sarapaa, 2008)” }, “properties” : { }, “schema” : “” }(Al-Ani ; Sarapaa, 2008)
Paper Filling and Coating 45%
Refractories 16%
Ceramics 15%
Fiberglass 6%
Cement 6%
Rubber and Plastics 5%
Paint 3%
Catalyst 2%
Others 2%
*Roskill Information Services, Ltd. The Economics of [email protected] 10th Edition

2.3 Overview of Kalsilite
2.3.1 Introduction to Kalsilite
Kalsilite is a well-known ceramic material ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.1107/S2053229614002423”, “ISSN” : “20532296”, “PMID” : “24594712”, “abstract” : “The X-ray powder diffraction pattern that corresponds to the disordered state of kalsilite (potassium aluminium orthosilicate), KAlSiO4, is investigated. The directionality of (Al,Si)O4 tetrahedra within single six-membered tetrahedral ring building units (S6R) could not be defined. With equal probability for the directionality of each tetrahedra within one S6R free apex pointing up (U) or down (D), an undefined sequence of U and D directionalities is needed to describe the S6R building units. The extinction conditions of disordered kalsilite are also different compared to ordered kalsilite within the space group P63. In disordered kalsilite, h0l and hhl reflections with l = 2n + 1 are systematically absent.”, “author” : { “dropping-particle” : “”, “family” : “Kremenoviu0107”, “given” : “Aleksandar”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Vuliu0107”, “given” : “Predrag”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Acta Crystallographica Section C: Structural Chemistry”, “id” : “ITEM-1”, “issue” : “3”, “issued” : { “date-parts” : “2014” }, “page” : “256-259”, “title” : “Disordered kalsilite KAlSiO4”, “type” : “article-journal”, “volume” : “70” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Kremenoviu0107 & Vuliu0107, 2014)”, “plainTextFormattedCitation” : “(Kremenoviu0107 & Vuliu0107, 2014)”, “previouslyFormattedCitation” : “(Kremenoviu0107 & Vuliu0107, 2014)” }, “properties” : { }, “schema” : “” }(Kremenovi? ; Vuli?, 2014). It is relatively uncommon in natural rocks and occurs mainly undersaturated volcanic which usually accompanied by nepheline, leucite, olivine melilite, phlogopite and clinopyroxene. Kalsilite is microporous where it is having a framework structure of linked (Si, Al) O4 tetrahedra that based upon a tridymite type framework similar to nepheline ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.1007/BF00357849”, “ISSN” : “0022-2461”, “author” : { “dropping-particle” : “”, “family” : “Ota”, “given” : “T.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Takebayashi”, “given” : “T.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Takahashi”, “given” : “M.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Hikichi”, “given” : “Y.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Journal of Materials Science”, “id” : “ITEM-1”, “issued” : { “date-parts” : “1996” }, “page” : “1431-1433”, “title” : “High thermal expansion KAISiO4 ceramic”, “type” : “article-journal”, “volume” : “31” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Ota, Takebayashi, Takahashi, & Hikichi, 1996)”, “manualFormatting” : “(Ota et al, 1996)”, “plainTextFormattedCitation” : “(Ota, Takebayashi, Takahashi, & Hikichi, 1996)”, “previouslyFormattedCitation” : “(Ota, Takebayashi, Takahashi, & Hikichi, 1996)” }, “properties” : { }, “schema” : “” }(Ota et al, 1996). It contains strongly basic potassium active sites, low silica content and weakly soluble in methanol and oils.

Kalsilite that have chemical formula KAlSiO4 can exist in several polymorphic forms that are low kalsilite and high kalsilite due to its high temperature form. In low kalsilite, P63 kalsilite also known as simply as kalsilite is where there is a room temperature variant of stuffed tridymite derivative occurring mainly in K-rich silica undersaturated volcanic rocks. According to Perrotta and Smith (1965), the first structure refined was a volcanic kalsilite crystal with Na: K =0.02:0.98 and space group P63 (low kalsilite).

Then, high temperature polymorph KAlSiO4-01 with orthorhombic symmetry has different framework topology than tridymite and transform into KAlSiO4-02 at higher temperature (Bacerro and Mantovani, 2009). Figure 2.6 shows the average structure of kalsilite showing splitting of one atoms into three partially occupied sites, each with a site occupancy of 1/3. (Modified from Perrotta and Smith 1965 and Merlino 1984.)

Figure 2.4 The average structure of kalsilite showing splitting of 1 atoms
into three partially occupied sites, each with a site occupancy
of 1/3, ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “author” : { “dropping-particle” : “”, “family” : “Xu”, “given” : “Nc”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “id” : “ITEM-1”, “issued” : { “date-parts” : “1996” }, “page” : “1360-1370”, “title” : “Superstructures and domain structures kalsilite in natural and synthetic”, “type” : “article-journal”, “volume” : “81” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Xu, 1996)”, “plainTextFormattedCitation” : “(Xu, 1996)”, “previouslyFormattedCitation” : “(Xu, 1996)” }, “properties” : { }, “schema” : “” }(Xu, 1996)
The thermal expansions of ceramic materials are generally lower than that of metals but leucite and kalsilite with high thermal expansion coefficients were prepared by appropriate procedures in order to achieve thermal compatibility when bonding to substructures and as reinforcing agent in all ceramic restorations (Kosanovi? et al., 2008). The high thermal expansions are interpreted as being due to the effect of the rotation of the frame work (Si, Al) O4 tetrahedra from partially collapsed state towards fully expanded state and the untwisting of the collapsed frame work.

Kalsilite contain a random network of tetrahedral silica and alumina units with charge balancing alkali metals ions, which conventionally produces at high pH by condensing a source of alumina and silica with alkali silicate solution ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.1007/s11705-010-0574-x”, “ISSN” : “16737369”, “abstract” : “The transesterification reaction of soybean oil with methanol over kalsilite-based heterogeneous catalysts was investigated. The kalsilite was synthesized from potassium silicate, potassium hydroxide, and aluminum nitrate aqueous solutions by controlling the pH value at 13. After calcination in air at 1200u00b0C, a very porous kalsilite (KAlSiO4) was obtained with surface pores ranging from 0.2 to 1.0 u03bcm. However, this kalsilite had relatively low catalytic activity for the transesterification reaction. A biodiesel yield of 54.4% and a kinematic viscosity of 7.06 cSt were obtained at a high reaction temperature of 180u00b0C in a batch reactor. The catalytic activity of kalsilite was significantly enhanced by introducing a small amount of lithium nitrate in the impregnation method. A biodiesel yield of 100% and a kinematic viscosity of 3.84 cSt were achieved at a temperature of only 120u00b0C over this lithium modified catalyst (2.3 wt-% Li). The test of this lithium modified catalyst in pellet form in a laboratory-scale fixed-bed reactor showed that it maintained a stable catalytic performance with a biodiesel yield of 100% over the first 90 min. u00a9 2011 Higher Education Press and Springer-Verlag Berlin Heidelberg.”, “author” : { “dropping-particle” : “”, “family” : “Wen”, “given” : “Guang”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Yan”, “given” : “Zifeng”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Frontiers of Chemical Engineering in China”, “id” : “ITEM-1”, “issue” : “3”, “issued” : { “date-parts” : “2011” }, “page” : “325-329”, “title” : “Transesterification of soybean oil to biodiesel over kalsilite catalyst”, “type” : “article-journal”, “volume” : “5” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Wen & Yan, 2011)”, “plainTextFormattedCitation” : “(Wen & Yan, 2011)”, “previouslyFormattedCitation” : “(Wen & Yan, 2011)” }, “properties” : { }, “schema” : “” }(Wen ; Yan, 2011). The presence of the alkali metal ion in the crystal structure of kalsilite prevent leaching of the ions from kalsilite even at relatively high temperature.

2.3.2 Previous Study of Kalsilite
There are a few of researchers have been reported studying the synthesis of kalsilite. One of them is Kopp et al (1961), hydrothermally converted shred muscovite that produce kalsilite and iron-rich mica at 1200 bars. Runs were made lasting for twenty-one days’ fourteen days, and twenty-nine days. A leak developed at some undetermined time during the first run of twenty-one days duration, where in the second run of fourteen days larger crystals of kalsilite were obtained. The final run of twenty-nine days duration was made to learn whether larger crystals of kalsilite could be grown’. The result shows the run produced more kalsilite crystal they were no larger than those produced in the preceding run. The x-ray and optical data indicates that the kalsilite obtained corresponds closely to the natural kalsilite described by bannister and Hey (1942). However, the use of muscovite as a starting material in the hydrothermal method needs a higher pressure (100 MPa), a higher temperature (nearly 600?), and longer reaction time.

Thus, Bacerro et al. (2009), hydrothermally synthesis of kalsilite using kaolinite instead of muscovite at 300°C for 12 hours in 0.5 M potassium hydroxide (KOH) solution. When the hydrothermal reaction goes on for 12 hours, metastable ABW-type KAlSiO4 transforms completely into kalsilite. The result shows that longer reaction time increase the crystallinity of the structure, whereas lower reaction time give rise to a metastable ABW-type KAlSiO4 polymorph. The lower temperatures cannot form kalsilite, instead zeolite W will form as the unique reaction product.

Figure 2.5 Experimental (crosses) and fitted (solid line) X-ray diffraction
patterns of the product obtained after hydrothermal reaction of
kaolinite in a 0.5M KOH solution for 12 h (Bacerro et al., 2009).

Su et al. (2011), synthesized microline powder which prepared from syenite rich in potassium, aluminum and silicon via hydrothermal reaction at 240-280? for 2-8 hours in the hydrothermal reactor. The result showed the product had a single phase kalsilite without non-crystalline precursors or other polymorphic forms of KAlSiO4. In 2014, Su et al. study the synthesis of kalsilite from the microcline powder by an alkali-hydrothermal process to examine the influence of temperature time and the alkali concentration. The product obtained from the hydrothermal reaction that carried out within two hours are mixture of both kalsilite and metastable KAlSiO4 polymorph, but after two hours kalsilite is the predominant product. The diffraction peak of metastable KAlSiO4 weakens with increasing temperature, and when the reaction temperature is 280?, the metastable peak completely disappears.

2.3.3 Synthesis of Kalsilite
(a) Raw Material of Kalsilite
The preparation of the synthesis kalsilite need the chemical source of silica and alumina, but it is expensive. In order to reduce the cost, material such as clay minerals, muscovite, syenite are used as the starting materials. When the cheap raw materials used to synthesis kalsilite, its offer economic advantage over standard synthetic chemical. Kaolinite is one of the important industrial raw materials and has variety application in industry is used as the starting material for the synthesis of kalsilite as the main alumina and silica sources.

(b) Alkaline Activator
Alkaline activator is a chemical process where a powder aluminosilicate is mixed with an alkaline activator to produce a paste capable of setting and hardening within a reasonably short period time. A synthetic alkaline aluminosilicate material produces when a solid aluminosilicate reacts with a highly concentrated aqueous alkali hydroxide or silicate solution. According to Palomo and Fernàndez-Jiménez (2011), depending on the raw materials and processing conditions used, alkali activated binders may feature high compressive strength, low shrinkage, fast or slowing setting, acid resistance, fire resistance and low thermal conductivity. Figure 2.6 indicated the process occurs in alkaline activation.

Figure 2.6 Conceptual model for Alkaline Activation Process ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “abstract” : “Alkaline activation is a chemical process in which a powdery aluminosilicate such as a fly ash is mixed with an alkaline activator to produce a paste capable of setting and hardening within a reasonably short period of time. The strength, shrinkage, acid and fire resistance of the resulting materials depend on the nature of the aluminosilicate used and the activation process variables. The alkaline activation of fly ash is consequently of great interest in the context of new and environmentally friendly binders with properties similar to or that improve on the characteristics of conventional materials.”, “author” : { “dropping-particle” : “”, “family” : “Palomo”, “given” : “Angel”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Fernu00e1ndez-Jimu00e9nez”, “given” : “Ana”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Proceedings of World of Coal Ash ( u2026”, “id” : “ITEM-1”, “issued” : { “date-parts” : “2011” }, “page” : “1-14”, “title” : “Alkaline Activation, Procedure for Transforming Fly Ash into New Materials. Part 1: Applications”, “type” : “article-journal” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Palomo & Fernu00e1ndez-Jimu00e9nez, 2011)”, “manualFormatting” : “(Palomo & Fernu00e1ndez-
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Fernández-Jiménez, 2011)
(c) Metakaolinization of Kaolinite
Metakaolinization of kaolinite is a process to transform the kaolinite into an amorphous, highly reactive metastable phase by the loss of hydroxyl group in kaolinite also known as calcination process (Johnson ; Sazmal, 2014; Kovo ; Holmes, 2009). The temperature used for the calcination process is between 700?C and 1000?C where the reaction involved in the transformation of kaolinite to metakaolinite as follow (Johnson ; Sazmal, 2014).

150876093980 Si2Al2O3(OH)4 Al2O3. 2SiO2 + 2H2O
In this reaction, four hydroxyl group transforms into water molecules, leaving two oxygen anions in the material. The dihydroxylation occurs based on two elementary processes: diffusion and first order. The diffusion process is where the transportation of water occurs, while the formation of water from two adjacent hydroxyl groups occurs in the first order process. After this process, the metakaolin will undergo hydrothermal synthesis in potassium hydroxide solution to produce kalsilite.

(d) Hydrothermal Synthesis
Hydrothermal synthesis of aluminosilicate kalsilite involves in a few steps. The mixture of metakaolin as a supplementary of aluminosilicate source is converted into microporous crystalline aluminosilicate, via an alkaline supersaturates solution that is potassium hydroxide solution. The solution is heated at 120°C, 150°C and 180°C in the Teflon bottle for 24 hours.

2.3.4 Industrial Applications of Kalsilite
Leucite Precursor
In industrial, the popularity of kalsilite is increasing in time. The demand of kalsilite is high due to the important uses of Kalsilite. One of the application of Kalsilite is as the precursor of leucite. It is the major component in the porcelain-fused-to-metal and ceramic dental restoration system. The fact is that the kalsilite has a high thermal expansion ceramic for bonding to metals and in application in diesel engines.

b) Catalyst
Kalsilite has been used as a catalyst additive in ammonia synthesis and hydrogen production from steam reforming and as a heterogeneous catalyst for transesterification of soybean oil with methanol to biodiesel. However, kalsilite showed relatively low catalytic for the transesterification reaction (Wen ; Yan, 2011). So, it is enhanced by introducing a small amount of lithium nitrate by impregnation method.

c) Kalsilite Glass Ceramic
The production of Kalsilite glass ceramic composite used kalsilite as their starting material. Bioactive kalsilite composite material is produce for the application in tissue attachment and sealing of the marginal gap between fixed prosthesis and tooth. The preparation of micro fine kalsilite glass ceramic is by using traditional melt quenching method and mechanochemical synthesis. The material is expected to have good thermal, bioactive and mechanical properties (Kumar et al., 2015).

2.4 Hydrothermal Synthesis
2.4.1 History
A self-explanatory word, “hydro” meaning water and “thermal” meaning heat. The term Hydrothermal was first used in the mid-19th Century by Sir Roderick Murchison ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.1016/C2009-0-20354-0”, “ISBN” : “9780123750907”, “ISSN” : “0884-2914”, “PMID” : “324438958”, “abstract” : “Thoroughly updated, this handbook remains the single source for understanding how aqueous solvents or mineralizers work under temperature and pressure to dissolve and recrystallize normally insoluble materials and decompose or recycle waste material. u00a9 2013 Elsevier Inc. All rights reserved.”, “author” : { “dropping-particle” : “”, “family” : “Byrappa”, “given” : “K.”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Yoshimura”, “given” : “Masahiro”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Handbook of Hydrothermal Technology”, “id” : “ITEM-1”, “issued” : { “date-parts” : “2013” }, “title” : “Handbook of Hydrothermal Technology”, “type” : “book” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Byrappa & Yoshimura, 2013)”, “manualFormatting” : “(Byrappa & Yoshimura, 2001)”, “plainTextFormattedCitation” : “(Byrappa & Yoshimura, 2013)”, “previouslyFormattedCitation” : “(Byrappa & Yoshimura, 2013)” }, “properties” : { }, “schema” : “” }(Byrappa ; Yoshimura, 2001).
The term hydrothermal usually refers to any heterogeneous reaction in the presence of aqueous solvents or mineralizers under high pressure and temperature conditions to crystallize ceramic materials directly from solution. It will be quite impossible to simulate the natural conditions or processes responsible for the formation of rocks and minerals except under the hydrothermal conditions because in nature, minerals and mineral assemblages were formed at elevated temperature and pressure conditions in the presence of volatiles like water.
The first publication on hydrothermal research appeared in 1845 which reports the successful synthesis of tiny quartz crystal upon transformation freshly precipitated silicic acid in pain digester by Schafthaul.

Today, the hydrothermal technique is used in several branches of science and technology. There are different kinds of hydrothermal techniques such as hydrothermal synthesis, hydrothermal growth, hydrothermal alteration, hydrothermal treatment, hydrothermal dehydration, hydrothermal decomposition, hydrothermal extraction, hydrothermal sintering, and so on (Byrappa and Yoshimura 2001).

2.4.2Definition and Concept
Various scientist had proposed different definitions for hydrothermal method in literature. Morey and Niggli (1913) defined that in the hydrothermal method the reactants are subjected to the action of water, at temperatures generally above the critical temperature of water (~370°C) in closed bombs, and therefore, under the corresponding high pressures developed by such conditions (Byrappa and Yoshimura 2001). In 1985, Rebenau defined hydrothermal synthesis as the heterogeneous reactions in aqueous media above 100°C and one bar. Roy (1994) declares that hydrothermal synthesis involves water as a catalyst and occasionally as a component of solid phases in the synthesis at elevated temperature (;100°C) and pressure (greater than a few atmospheres). Byrappa (1992) in the other hand, defined hydrothermal synthesis as any heterogeneous reaction in an aqueous media carried out above room temperature and at pressure greater than one atm. According to Yoshimura (1994), reactions occurring under the conditions of high-temperature–high-pressure (;100°C, ;1 atm) in aqueous solutions in a closed system. In 2001, K. Byrappa purposed to defined hydrothermal reaction as “any heterogeneous chemical reaction in the presence of a solvent (whether aqueous or non-aqueous) above room temperature and at pressure greater than one Atm in a closed system”.

The majority of scientists think of hydrothermal synthesis as taking place above 100°C temperature and above 1 Atm, however there is no definite lower limit for temperature and pressure conditions. Upper limits of hydrothermal synthesis extend to over 1000ºC and 500 MPa pressure yet, mild conditions are preferred for commercial processes where temperatures are less than 350ºC and pressures less than approximately 50 MPa. The transition from mild to severe conditions is determined mostly by corrosion and strength limits of the materials of construction that comprise the hydrothermal reaction vessels (Suchanek and Riman, 2006).

Hydrothermal synthesis is used as one of the methods in synthesizing kalsilite as this method is economical, effective and convenient to prepare pure materials with fine particle size at low temperature. Hydrothermal synthesis can be classified into two groups: subcritical and supercritical synthetic reaction which is based on their reaction temperature. Subcritical synthetic reaction involves a range temperature of 100-240? while the temperature for the supercritical synthetic reaction could reach up to 1000?C (Johnson et al., 2014). This technique is successfully closes the gap between materials processing at low ambient pressure and high to ultrahigh pressure in a temperature range between 100°C and about 1600°C (Byrappa and Yoshimura 2001).

2.4.3 Advantages and disadvantages of Hydrothermal Synthesis
Hydrothermal synthesis offers many advantages over conventional and non-conventional synthesis methods. The respective cost for instrumentation, energy and precursors are far less for hydrothermal method compared to the advanced method that can prepare large variety of forms and chemical compounds. Based on the environmental perspective, hydrothermal methods are more environmentally friendly than other synthesis methods, which can be attributed in part to energy conserving low processing temperatures, absence of milling, ability to recycle waste, and safe and convenient disposal of waste that cannot be recycled ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “DOI” : “10.4028/”, “ISBN” : “978-3-908158-01-1”, “ISSN” : “00027812”, “abstract” : “This paper briefly reviews hydrothermal synthesis of ceramic powders and shows how understanding the underlying physico-chemical processes occurring in the aqueous solution can be used for engineering hydrothermal crystallization processes. Our overview covers the current status of hydrothermal technology for inorganic powders with respect to types of materials prepared, ability to control the process, and use in commercial manufacturing. General discussion is supported with specific examples derived from our own research (hydroxyapatite, PZT, 2 O 3 , ZnO, carbon nanotubes). Hydrothermal crystallization processes afford excellent control of morphology (e.g., spherical, cubic, fibrous, and plate-like) size (from a couple of nanometers to tens of microns), and degree of agglomeration. These characteristics can be controlled in wide ranges using thermodynamic variables, such as reaction temperature, types and concentrations of the reactants, in addition to non-thermodynamic (kinetic) variables, such as stirring speed. Moreover, the chemical composition of the powders can be easily controlled from the perspective of stoichiometry and formation of solid solutions. Finally, hydrothermal technology affords the ability to achieve cost effective scale-up and commercial production.”, “author” : { “dropping-particle” : “”, “family” : “Suchanek”, “given” : “Wojciech L”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Riman”, “given” : “Richard E”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Advances in Science and Technology”, “id” : “ITEM-1”, “issued” : { “date-parts” : “2006” }, “page” : “184-193”, “title” : “Hydrothermal Synthesis of Advanced Ceramic Powders”, “type” : “article-journal”, “volume” : “45” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Suchanek & Riman, 2006)”, “plainTextFormattedCitation” : “(Suchanek & Riman, 2006)”, “previouslyFormattedCitation” : “(Suchanek & Riman, 2006)” }, “properties” : { }, “schema” : “” }(Suchanek ; Riman, 2006). This is where the different chemical can be recovered and recycled because the synthesis run in a closed system. The low reaction temperatures also avoid other problems encountered with high temperature processes, for example poor stoichiometry control due to volatilization of components like Pb volatilization in Pb-based ceramics.

Hydrothermal processing can take place in a wide variety of combinations of aqueous and solvent mixture-based systems. Hydrothermal processing with liquids allows for automation of a wide range of unit operations such as charging, transportation, mixing and product separation. Besides, liquids give a possibility for acceleration of diffusion, adsorption, reaction rate and crystallization which relative to solid state processes, especially under hydrothermal condition.

All forms of ceramics can be prepared by hydrothermal synthesis, which are powders, fibers, and single crystals, monolithic ceramic bodies, and coatings on metals, polymers, and ceramics (Suchanek and Riman, 2006). In the production of ceramic powder, the time reduced and the energy consumed take place via hydrothermal synthesis since high temperature calcination, mixing, and milling steps are either not necessary or minimized. Moreover, the ability to precipitate already crystallized powders directly from solution regulates the rate and uniformity of nucleation, growth and aging. This shows the improved control of size and morphology of crystallites and significantly reduced aggregation levels, that is not possible with many other synthesis processes.

The purity of hydrothermally synthesized powders significantly exceeds the purity of the starting materials as the hydrothermal crystallization is a self-purifying process. The growing crystals or crystallites tend to reject impurities present in the growth environment during the self-purifying process. The impurities are subsequently removed from the system together with the crystallizing solution, which does not take place during other synthesis routes, such as high temperature calcination (Suchanek and Riman, 2006).

A major advantage of hydrothermal synthesis is that other processes like microwave, electrochemistry, ultrasound, mechano-chemistry, optical radiation and hot-pressing can be hybridized with hydrothermal synthesis to gain advantages such as enhancement of reaction kinetics and increase ability to make new materials. A great amount of studies has been done to enhance hydrothermal synthesis by hybridizing this method with many other processes. This facile method does not need any seed, catalyst, harmful and expansive surfactant or template thus it is promising for large-scale and low-cost production with high-quality crystals (Byrappa and Yoshimura 2001).

It is no doubt that hydrothermal synthesis gives many benefits since it was developed last few decades. Despite that, there must be some disadvantage of this synthesis. Firstly, the cost to set up the equipment used for the hydrothermal synthesis like autoclave, liners, valves, pressure tubing, control equipment is relatively high. Then, the fact that high pressure is applied along the hydrothermal process, there are safety issues that are emerge during the reaction process. For this case, there is requirement for a stringent safety regime to be applied during the reaction process such as appropriate shielding and utilization of buster disks.

However, the main disadvantage of this hydrothermal synthesis is the black box nature of the apparatus, since the closed autoclaves do not normally allow one to observe directly the crystallization process (Byrappa and Yoshimura 2001). The application for the transparent windows of corrosion-resistant materials such as alumina is possible yet the cost will be high as it has to be frequently replaced. Moreover, the inert metal or autoclave liners for the inner wall is needed as the presence of the alkaline or acidic mineralizers are potentially caused temperature corrosion problems.

2.5 Factors Effect the Synthesis of Kalsilite
2.5.1 Crystallization time and temperature
Crystallization temperature strongly affect the nucleation and crystal growth as rising the temperature will increase both of nucleation rate and the linear growth rate (Feijin et al., 1994). Normally, longer crystallization time will increase the crystallinity of the structure. Bacerro et al (2009) state that lower crystallization temperature is not sufficient to produce kalsilite. He also said that longer reaction time will increase the crystallinity of the structure whereas shorter reaction times give rise to the metastable KAlSiO4 polymorph with ABW zeolite-type unit cell. When the kaolinite submitted to hydrothermal reaction in 0.5 M KOH at 200? for 24, 48 and 120 hours, the result indicate that kalsilite crystallized in the first stage a very likely as a metastable phase. However longer reaction times give rise to the crystallization if zeolite W. While, the hydrothermal treatment of kaolinite in KOH solution at 300? produces pure kalsilite with full Si–Al ordering after only 12 hours of reaction.

2.5.2 Alkalinity
The important key for kalsilite formation is the pH of the alkaline synthesis solution as the OH anions play role as mobilizing agent. The role of the mobilizing agent is to bring the Si and Al oxides or hydroxides into the solution at an adequate rate. Bacerro et al. (2009) stated that the synthesis of kalsilite was reached using large excess of KOH that is 10 times more KOH than amount required based on the stoichiometry of the reaction which must be pH more than 13.70. On the report of Bacerro et al. (2009), zeolite W is formed when the concentration of KOH solution decreased to 0.33 M and 0.15 M but formed kalsilite at 0.5 M. The formation of different product very likely by the effect of the pH which increase from pH = 13.18 (0.15 M KOH), to pH=13.52 (0.33 M KOH) and to pH=13.70 (0.5 M KOH). Generally, increasing the alkalinity leads to an increase in kalsilite content of the reaction product.

2.6 Characterization Technique
characterization of kalsilite are done by using X-Ray Diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and scanning Electron Microscope (SEM).

2.6.1 X-ray Diffraction
X-ray diffraction is a rapid analytical technique used for phase identification of a crystalline material and can provide on unit cell dimension. The scattering of X-rays from atoms produce a diffraction pattern that contains information about the atomic arrangement in crystal. Amorphous materials like glass do not have periodic array with long-range order so they do not produce any significant peak in diffraction pattern.

The basic concept for XRD is the property of electromagnetic radiation. The x-ray of a fixed wavelength will bombard to a crystal at certain incident angle. When the wavelength of scattered x-ray interface constructively, an intense reflected x-ray produced. The general relationship between wavelength of incident x-rays, angle of incident and spacing between crystal lattice planes of atom known as Bragg’s Law. Constructive interference occurs when the differences in the travel path of the incident X-rays is equal to an integer multiple of the wavelength.
n? = 2dsin?
?: is the wavelength of the x-ray,
d: is the spacing of the crystal layers (path difference),
?: is the incident angle (the angle between incident ray and the scatter plane), and
n: is an integer.

2.6.2 Scanning Electron Microscope (SEM)
Scanning Electron Microscope (SEM) represent the high-performance method used to examine and analyses the microstructure morphology and chemical composition characterization of the materials. Although it only capable of determining only morphology of a specimen and not internal structure but it also important tool in structural assessment. It is defined by: easiness to prepare samples to be tested, large diversity of information reached good resolution associated with high field depth, large and continuous range of magnifying, etc. ADDIN CSL_CITATION { “citationItems” : { “id” : “ITEM-1”, “itemData” : { “abstract” : “This paper presents a study performed on type I Portland cement with respect to the cement hydration processes performed at various time intervals. The methods used concern X-ray diffraction and electronic microscopy applied to define materials and to understand the changes occurring in mineral compounds (alite, belite, celite and brownmillerite) during their modification into hydrated mineral compounds (tobermorite, portlandite and etringite).”, “author” : { “dropping-particle” : “”, “family” : “Elena”, “given” : “Jumate”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” }, { “dropping-particle” : “”, “family” : “Lucia”, “given” : “Manea Daniela”, “non-dropping-particle” : “”, “parse-names” : false, “suffix” : “” } , “container-title” : “Journal of Applied Engineering Sciences”, “id” : “ITEM-1”, “issued” : { “date-parts” : “2012” }, “page” : “35-42”, “title” : “Application of X-Ray Diffraction ( XRD ) and Scanning Electron Microscopy ( SEM ) Methods to the Portland Cement Hydration Processes”, “type” : “article-journal”, “volume” : “2(15)” }, “uris” : “” } , “mendeley” : { “formattedCitation” : “(Elena & Lucia, 2012)”, “plainTextFormattedCitation” : “(Elena & Lucia, 2012)”, “previouslyFormattedCitation” : “(Elena & Lucia, 2012)” }, “properties” : { }, “schema” : “” }(Elena & Lucia, 2012).

The main SEM component include the source of electron, column down, electron detector, sample chamber, computer and display to view the image. Figure 2.7 shows the example of field-emission SEM image of kalsilite, taken at low accelerating voltage. The scanning electron microscopy works by scanning the focused electron beam over a surface to create an image. The focused electron beam form when the electron produced at the top of microscope’s column accelerated down and passed through combination of lenses. Various of signal that can be used to obtain information about the surface topography and compositional produce when the electron in the beam interact with the sample. SEM uses an electron beam instead of beam of photons to image sample for higher magnification.


Figure 2.7 Hexagonal particles of kalsilite obtained after 12 h treatment of
kaolinite in 0.5 M KOH solution at 300°C (Bacerro et al., 2009).

2.6.3 Fourier Transform Infrared Spectroscopy (FTIR)
Fourier Transform Infrared Spectroscopy (FTIR) is the most modern infrared spectrometers that operates on a different principle. It is a non-destructive technique that can provides a precise measurement method in determining the absorption spectrum for a compound. FTIR can provide information such as it can identify unknown materials, determine the quality or consistency of a sample and can determine the number of components in a mixture. In FTIR, the IR radiation will pass through the sample. Some of the infrared radiation is absorbed by the sample and some will be transmitted. The resulting spectrum show the absorption peaks which correspond to the frequencies of vibrations between the bonds of the atom making up the material (Lampman et al., 2010).
The process of the FTIR is firstly, Infrared energy is emitted from a glowing black-body source. The beam passes through an aperture which controls the amount of energy presented to the sample and to the detector. Then, the beam enters the interferometer where the “spectral encoding” takes place. The resulting interferogram signal then exits the interferometer. The beam enters the sample compartment where it is transmitted through or reflected off of the surface of the sample, depending on the type of analysis being accomplished. This is where specific frequencies of energy, which are uniquely characteristic of the sample, are absorbed. Next, beam finally passes to the detector for final measurement. The detectors used are specially designed to measure the special interferogram signal. Lastly, the measured signal is digitized and sent to the computer where the Fourier transformation takes place. Figure 2.8 below shows the schematic diagram of FTIR.

Figure 2.8 Schematic diagram of Fourier Transform Infrared
spectrophotometer (Lampman et al., 2010).
3.1 Chemicals and Materials
In this experiment, several materials are used for the synthesis of Kalsilite, the raw material that being used are the commercial kaolin clay. The kaolin clay is provided by Sibelco Malaysia Sdn Bhd. The other material used are potassium hydroxide pallet (KOH) and distilled water.
3.2 Metakaolinization
Metakaolinization is dihydroxylation process where it is based on a novel metakaolinization technique used by Johnson et al. (2014). This process transforms the kaolin clay into an amorphous but highly reactive metakaolin. To produce metakaolin, 500 g of kaolin was heated in the furnace at 800°C for four hours. Firstly, the furnace heated to 800°. Next, the crucible with refined kaolin loaded into the furnace after the temperature reached 800°C. The crucible is taken out after four hours of the thermal treatment. The sample cooled to room temperature inside the desiccator. The product obtained then characterized by using Fourier-Transform Infrared (FTIR) Spectroscopy for the structural and chemical composition.

3.3 Alkaline Activator Preparation
Alkaline activator used are potassium hydroxide (KOH). The volume of KOH is fixed to 150 mL with concentration of 0.5 M. To produce 0.5 M of KOH solution, 4.21 gram of KOH powder mixed with 150 mL of distilled water in 250 mL beaker. To study the effect of pH on the synthesis of kalsilite, different concentration of KOH solution was prepared according to 0.25 M, and 0.75 M with the same volume fixed to 150 mL by adding different amount of KOH powder.
3.4 Hydrothermal Synthesis
The metakaolin obtain by calcination of kaolinite was used as a combine source of alumina and silica and as a starting material. In the hydrothermal synthesis, KOH solution prepared earlier, 1.0 g of metakaolin and stirred for five minutes. Then, the solution transferred to Teflon bottle. The solution was heated at 120°C, 150°C and 180°C for 24 hours. After 24 hours, the teflon bottle taken out, product obtain clean by using distilled water and dried at 60°C in air (Becerro et al, 2009). The dried product was weighed and keep in plastic bag for characterization with SEM, XRD and FTIR.

3.5 Characterization Technique
3.5.1 Chemical Characterization of Kalsilite by using FTIR spectroscopy
The characteristic of kalsilite can be observed by using Perlin Elmer 1000 FTIR spectrometer. Firstly, the sample was grinded gently to avoid the large particle from disturbing the analysis before the sample placed in the FTIR spectrometer. The wavenumber that being used is from 1400-400 cm-1 range with resolution of 2 cm-1 in transmission rate by average four scan. The grinder sample was pressed on the disk, which already being dried in the oven at 60°C.

Photo 3.1 FTIR instrument located in laboratory of the Faculty of Science
and Natural Resources.

3.5.2 Chemical Characterization of Kalsilite by using XRD
X-ray Diffraction can be used in order to have pattern of metakaolinite sample and synthetic kalsilite that form. The percentage crystallinity can be calculated by the sum of the peak of height of unknown material divided by the sum of height if the standard solution.

% crystallinity = sum of the peak of height of the unknown material x 100(sum of height of the standard solution)
3.5.3 Chemical Characterization of Kalsilite by using SEM
Scanning Electron Microscopy (SEM) are used to examine the morphology of the product. Photo 3.2 is the SEM instrument located in laboratory of the Faculty of Science and Natural Resources.

Photo 3.2 SEM instrument located in laboratory of the Faculty of Science
And Natural Resources.

3.6 Flow chart of the metakaolin and hydrothermal Synthesis for
23977602813050002413635142494000 Kalsilite
24472905251450002427605405765000-201737centerThe teflon line autoclave heated in the furnace at 120°C, 150°C and 180°C for 24 hours for hydrothermal process
0The teflon line autoclave heated in the furnace at 120°C, 150°C and 180°C for 24 hours for hydrothermal process
2427936647857400center6385478Then, the product is filtered and clean by using distilled water.

0Then, the product is filtered and clean by using distilled water.

center3525079For hydrothermal synthesis, 150 ml KOH solution and 1.0 g of metakaolin was mixed together and stirred for five minutes.

0For hydrothermal synthesis, 150 ml KOH solution and 1.0 g of metakaolin was mixed together and stirred for five minutes.

-2044707452995The product is dry and store in desiccator.

The product is dry and store in desiccator.

-1854207524750Cool the sample to room temperature inside desiccator. The weighed obtained and the sample was characterized using FTIR and XRD
Cool the sample to room temperature inside desiccator. The weighed obtained and the sample was characterized using FTIR and XRD
center2128520500 g of kaolin treated in the furnace (800°C, four hours) for metakaolinization
by Johnson et al. (2014)
500 g of kaolin treated in the furnace (800°C, four hours) for metakaolinization
by Johnson et al. (2014)