12003-63-3Relevant articles and documents
Cristobalite-Related Phases in the KAlO2-KAlSiO4 System
Husheer, Shamus L. G.,Thompson, John G.,Melnitchenko, Alexandra
, p. 624 - 630 (1999)
A study of the K-rich end of the potassium aluminate-silica system (K1-xAl1-xSixO2; 0≤x≤0.25) at temperatures up to 1500°C has confirmed the existence of a cubic cristobalite-type solid solution extending to x≈0.235 at 1500°C. The end member, KAlO2, transforms on cooling to an orthorhombic KGaO2-type structure at 531°C (orthorhombic Pbca: a=5.4327(8), b=10.924(2), c=15.469(2) A, Z=16). The room temperature structure has been modeled using chemically restrained refinement of Guinier-Haegg X-ray powder diffraction (XRD) data by the Rietveld method (reduced χ2=0.074, wRp=0.065, Rp=0.049). With progressive substitution of SiO2 into KAlO2 the cubic-to-orthorhombic phase transition temperature is lowered. A new cristobalite-related phase field has been identified as existing close to room temperature between x≈0.10 and 0.125. The XRD data for this phase can be indexed to a tetragonal superstructure with ar=2√2ap and cr=2cp (r=resultant, p=parent). Analysis of K-rich specimens by XRD and differential scanning calorimetry required extreme care to avoid rapid degradation by atmospheric moisture.
Refractory selection for high-temperature black liquor gasification
Rezaie, Alireza,Headrick, William L.,Fahrenholtz, William G.
, p. 309 - 315 (2006)
A methodology has been established for the selection of materials for refractory linings in black liquor gasifiers that are to be employed by the pulp and paper industry. As a first step, a thermodynamic software package was used to determine that black liquor smelt was composed of a liquid solution of primarily Na2CO3 and Na2S under the operating conditions of the gasifier (950°C, 1 atm). Next, the software was used to predict the interaction of the black liquor smelt with various ceramics such as aluminosilicates, single component oxides, and binary oxides that are candidates for the application. Finally, experiments were performed to verify or disprove the predictions. Using sessile drop testing, contact angles were determined for molten Na2CO3 on candidate refractory compounds. All of the candidate ceramics were wet by molten Na2CO3. Among the candidates, MgAl2O4 was found to have the highest contact angle (～13°). Post-mortem analysis was performed on sessile drop specimens using X-ray diffraction analysis and scanning electron microscopy with energy dispersive spectroscopy to determine if molten Na2CO 3 had penetrated into or reacted with the ceramics. From the candidates, MgO and CeO2 were found to have the best resistance to attack, while MgAl2O4 was also found to be a promising candidate.
Electron beam stimulated chemical reaction in solids
Lyakhov,Boldyrev,Voronin,Gribkov,Bochkarev,Rusakov,Auslender
, p. 21 - 31 (1995)
Use of electron beams allows to obtain new effects in high temperature chemistry of solid state. A stimulated influence of irradiation at comparable temperature conditions may be a subject of technological interest taking into account that increase of reaction rate can reach significant values.
Synthesis and thermal behaviour of gallium-substituted aluminosilicate inorganic polymers
Durant, Andrew T.,MacKenzie, Kenneth J.D.,Maekawa, Hideki
, p. 4865 - 4870 (2011)
A combined sol-gel and solid-state method reported for the synthesis of gallium silicate analogues of aluminosilicate inorganic polymers has also been extended to the formation of related compounds with a range of Al-for Ga substitutions. Homogeneous, robust products were obtained at an optimum composition of SiO2:(Ga2O3 + Al 2O3) = 7. After curing at 40 °C, all the products were typically X-ray amorphous, and the Al and Ga was shown by 27Al and 71Ga MAS NMR spectroscopy to be in solely tetrahedral coordination. The 29Si MAS NMR spectra were as expected for silicate inorganic polymers, but also indicated the presence of some unreacted silica. Electron microscopy in conjunction with EDS elemental mapping showed that the Ga, Al and Si was homogeneously distributed in the products. Thermal treatment of these compounds results in endothermic water loss at about 75-160 °C followed by an exothermic event at about 950 °C corresponding to crystallization of KGaSi2O6 in the gallium end-member. By contrast, the Al-substituted compounds never fully crystallised, but melted at 1200 °C to an X-ray amorphous product.
A thermogravimetric and infrared emission spectroscopic study of alunite
Frost,Wain, Daria
, p. 267 - 274 (2008)
Thermogravimetric and differential thermogravimetric analysis has been used to characterize alunite of formula [K2(Al3+) 6(SO4)4(OH)12]. Thermal decomposition occurs in a series of steps (a) dehydration up to 225°C, (b) well defined dehydroxylation at 520°C and desulphation which takes place as a series of steps at 649, 685 and 744°C. The alunite minerals were further characterized by infrared emission spectroscopy (IES). Well defined hydroxyl stretching bands at around 3463 and 3449 cm-1 are observed. At 550°C all intensity in these bands is lost in harmony with the thermal analysis results. OH stretching bands give calculated hydrogen bond distances of 2.90 and 2.84-7 A. These hydrogen bond distances increase with increasing temperature. Characteristic (SO4)2- stretching modes are observed at 1029.5, 1086 and 1170 cm-1. These bands shift to lower wavenumbers on thermal treatment. The intensity in these bands is lost by 550°C.
(Oxo)(Fluoro)-Aluminates in KF-Al2O3 System: Thermal Stability and Structural Correlation
?imko, Franti?ek,Rakhmatullin, Aydar,Florian, Pierre,Kontrík, Martin,Korenko, Michal,Netriová, Zuzana,Danielik, Vladimír,Bessada, Catherine
, p. 13349 - 13359 (2017)
Precise investigation of part of the phase diagram of KF-Al2O3 system was performed in an experiment combining different techniques. Solidified mixtures of KF-Al2O3 were studied by X-ray powder diffraction and high-field solid-state NMR spectroscopy over a wide range of compositions. To help with the interpretation of the NMR spectra of the solidified samples found as complex admixtures, we synthesized the following pure compounds: KAlO2, K2Al22O34, α-K3AlF6, KAlF4, and K2Al2O3F2. These compounds were then characterized using various solid-state NMR techniques, including MQ-MAS and D-HMQC. NMR parameters of the pure compounds were finally determined using first-principles density functional theory calculations. The phase diagram of KF-Al2O3 with the alumina content up to 30 mol % was determined by means of thermal analysis. Thermal analysis was also used for the description of the thermal stability of one synthesized compound, K2Al2O3F2.
Thermodynamic properties of KAlO2
Beyer, R. P.,Ferrante, M. J.,Brown, R. R.
, p. 985 - 992 (1980)
The heat capacity of KAlO2 has been measured from 5 to 303 K by adiabatic calorimetry.High-temperature enthalpies were determined up to 1197.8 K by copper-block drop calorimetry.A reversible transition was found at 810 K with an enthalpy of transition of 1295 J mol-1.The values at 298.15 K of C0p, 0(T) - S0(0)>, and -0(T) - H0(0)>/T are calculated as 76.12, 85.55, and 40.76 J K-1 mol-1, respectively.These thermodynamic functions are also calculated from 5 to 1400 K.
Reaction of aluminum oxide with potassium hydroxide
Dmitruk,Yashchenko,Zarubitskii
, p. 1 - 3 (2008/10/08)
A derivatographic study of interactions in mixtures of α-Al2O3 with potassium hydroxide was carried out in component mole ratios of 1:2 and 1:3. The reaction products were determined by X-ray-phase analysis. It was established that production of potassium meta-aluminate is preceded by the formation of an intermediate product.
