Trans. Nonferrous Met. Soc. China 28(2018) 1793-1800

Modified combustion synthesis of y-LiAlO₂ using metal oxides

Daniel CRUZ¹, H. B. ORTIZ-OLIVEROS², L. M. ¹, R. M. FLORES-ESPINOSA², G. ROSANO-ORTEGA³

1. Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, 14 Sur y San Claudio, Ciudad Universitaria, C.P. 72570, Cd. Puebla, Mexico;

2. Instituto Nacional de Investigaciones Nucleares, Direccion de Investigacion Tecnologica, Apartado Postal 18-1027, 11801 Mexico, DF, Mexico;

3. Universidad Popular Autonoma del Estado de Puebla, 21 Sur no. 1103, Colonia Santiago, C.P. 72410, Puebla, Mexico

Received 2 November 2017; accepted 10 May 2018

Abstract: An alternative solution for the direct formation of y-LiAlO₂ was presented by a modified combustion method, to apply it to rather simple systems, utilizing non-oxidizer compounds such as Al₂O₃ and LiOH, and urea as fuel. LiAlO₂ was prepared via non-stoichiometric 1:1, 1.5:1 and 2:1 of Li/Al molar ratios at 900 and 1000 ¡ãC for 5 min. Textural and structural characterization of ¦Ã-LiAlO₂ was performed. Also, the effect of different Li/Al molar ratios on material morphology and its stability before high gamma radiation gradients was evaluated. The results showed that the crystal structures of the obtained powders were ¦Ã-LiAlO₂ and ¦Á-LiAlO₂, depending on the Li/Al molar ratio. The results obtained demonstrate that y-LiAlO₂ microbricks, polyhedral and laminar shapes can be successfully synthesized with the proposed method and without any subsequent process. Additionally, gamma irradiation showed that the y-LiAlO₂ obtained does not decompose, forming only small amounts of Li₂CO₃. It can be established that the irradiation produces consolidation, which is not favourable for an efficient extraction of tritium. Finally, it could be demonstrated that nitrate precursors are not necessary in the combustion method to produce ¦Ã-LiAlO₂ with high purity.

Key words: urea; oxide; combustion; lithium aluminate; ceramic

1 Introduction

It is well documented that economic development and consumption of energy resources in the last 200 years have caused the deterioration of environment, as evidenced by phenomena such as the degradation of water resources, deforestation, loss of biodiversity and global warming due to the emission of greenhouse gases [1,2]. Global warming is an alarming symptom that shows the unsustainability of the form of energy production and consumption [3-5]. Total energy consumption at the end of 2014 was 12.928 million tons of oil equivalent barrels [6]. According to the International Energy Agency, in the same year around 32190 million tons of CO₂ were emitted [7].

In this context, nuclear energy has a fundamental role to meet the growing energy demand, as it is considered by many countries as an energy base of operation, contributing to the reduction of greenhouse gases [5,8].

Currently nuclear energy production was carried out by nuclear fission, having the disadvantage of generating a significant amount of radioactive waste. Projects with the International Thermonuclear Experimental Reactor, work on the development of nuclear fusion reactors, as well as large-scale and carbon-free source [9,10]. Fission reactors use lithium ceramics such as tritium breeders. A variety of breeding blanket concepts have been considered, ranging from more conservative concepts to higher-risk higher-payoff concepts for future fusion reactors. The major candidates for breeding materials consist of liquid breeders, mainly liquid metals although recently some attention has been given to FLiBe, and lithium ceramic breeders. Candidate breeder materials are mainly lithium oxide (Li₂O), lithium orthosilicate (Li₄SiO₄), lithium metatitanate (Li₂TiO₃), lithium metazirconate (Li₂ZrO₃) and lithium aluminate (LiAlO₂) [11-13]. LiAlO₂ is one of the most promising ceramics for excellent chemical, structural and mechanical stability against intense fields of thermal and gamma radiation, as well as mixed fields (gamma-neutron) [14].

Additionally, it is used in polymeric composites, matrix of molten carbonate fuel cells (MCFC), electrolyte tiles in MCFC, among other applications such as electrical pumped ultraviolet-blue, light emitting diodes, laser, biosensors and photon detectors, due to its thermal conductivity [15-18].

The lithium aluminate crystal structure exhibits four allotropic forms depending on thermodynamic states and chemical environmental conditions, namely, ¦Á-LiAlO₂ (hexagonal), b-LiAlO₂ (orthorhombic), y-LiAlO₂ (tetragonal) and d-LiAlO₂ (tetragonal) [11,19]. Among all polymorph modifications of LiAlO₂, y-LiAlO₂ is the most stable one, so that at elevated temperature (above 750 ¡ãC, and present lattice parameters a=(5.1687¡À 0.0005) and c=(6.2679¡À0.0006) [18].

The ¦Ã-LiAlO₂ has been obtained by several conventional powder synthesis techniques, including solid-state synthesis, co-precipitation and sol-gel process [20-23]. Although these methods have advantages, elevated temperatures and long heat treatment time are required to ensure the formation of pure y-LiAlO₂. The situation is even more complicated due to many sophisticated techniques and time- consuming procedures that are required, which are not cost effective and represent obstacles to reproducibility and reliability of the final powder [15,24-26].

Combustion synthesis is an innovative and promising powder preparation method, it is a very rapid chemical process based on the principle of explosive decomposition of nitrate reagents and fuel mixtures, using the instantaneous heat generated by the chemical reaction between the desired metal nitrates (the oxidizing agent) and a reducing agent, which is called as the fuel [27-30]. The advantages of this method have been demonstrated as it needs little heating to start a rapid reaction and it permits considerable savings of time and energy compared with other techniques [31,32]. The fuel (glycine, urea, alanine, carbohidrazide) produces two different effects: first, it produces complexes with metal cations, which increases their solubility and prevents selective precipitation when water is evaporated; and second, it serves as fuel for the combustion reaction [33-36]. It was proved that combustion synthesis allowed the direct formation of the desired oxide compound with and without any subsequent calcination. For instance, starting from a stoichiometric mixture of lithium nitrate/aluminium as starting materials and urea/carbohidrazide as fuels, IANOS et al [29] and LI et al [33] reported the formation of pure y-LiAlO₂ by the combustion synthesis only after thermal treatment at 900 and at 450 ¡ãC, respectively.

In this work, the aim is to present an alternative solution for the direct formation of y-LiAlO₂ by a modified combustion method, to apply it to rather simple systems, utilizing non-oxidizers compounds such as aluminium oxide (Al₂O₃), lithium hydroxide (LiOH) and, urea as fuel.

2 Experimental

2.1 Synthesis of ¦Ã-LiAlO₂

¦Ã-LiAlO₂ powder was prepared, as starting materials, analytical grade reagents without further purification: aluminium oxide (Al₂O₃ powder, J. T. Baker, 99.0%), lithium hydroxide (LiOH powder, Merck, 98.0%) and urea (CH₄N₂O powder, Merck, 99.5%). The required mass of each reactant was calculated from the desired mass of the products, according to the chemical reactions. In this work, the main parameters studied were: lithium hydroxide molar ratio and calcination temperature (900-1000 ¡ãC). Different molar ratios of LiOH to Al₂O₃ (1:1, 1.5:1 and 2:1) were prepared and were placed in distilled water with urea at a molar ratio of 3:1 [37,38]. The mixture was dried at 60 ¡ãC until most of the water was evaporated resulting in a humid integrated solid; this mixture was transferred into 30 mL crucible which was introduced during 5 min into a High Temperature Muffle Furnace Barnstead Thermolyne Corporation at different heat treatment temperatures (900-1000 ¡ãC).

Samples were referred in this work as their LiOH:Al₂O₃:CH₄N₂O molar ratios. For example, sample (1:1:3) is the name given to the sample prepared with lithium hydroxide, aluminium oxide and urea with the corresponding LiOH:Al₂O₃:CH₄N₂O molar ratio of 1:1:3 at the study temperatures (900 ¡ãC or 1000 ¡ãC).

2.2 Textural and structural characterization of ¦Ã-LiAlO₂

Powder XRD patterns were recorded on a Siemens D-5000 diffractometer using Cu K_¦Á1 radiation. The relative percentages of the various compounds present in the pellets were estimated semi-quantitatively from the total area under the most intense diffraction peak for each phase identified, with the simplifying assumption this was proportional to the volume fraction of each compound. In this way, the amounts of the crystalline compounds present in the samples were obtained within an estimated experimental error of 5% [39,40].

Since no internal standard was introduced, the X-ray absorption for each compound was assumed to be the same. Standard deviations of the measured samples were around 3.0%. A Philips XL-30 scanning electron microscopy (SEM), equipped with an energy dispersive X-ray spectroscopy (EDS) detector was used to study morphology of the samples. Powders were covered with gold to prevent the lack of conductivity. The thermogravimetric analyses (TGA) were performed with a heating rate of 10 ¡ãC/min up to 800 ¡ãC, flowing N₂ (TGA 51, Thermogravimetric Analyzer, T.A. Instruments) to determine the mass loss at high temperatures.

2.3 Gamma irradiation of ¦Ã-LiAlO₂

The gamma irradiation of y-LiAlO₂ synthesized by the proposed method was performed in order to determine structural changes due to gamma radiation. Exposure to gamma radiation was performed in an industrial irradiator JS-6500 equipped with a ⁶⁰Co source of 28971.56 TBq (1 July 2016). The solid was placed in aluminium containers (in duplicate) and subjected to a dose of 12000 kGy, applying a calculated dose rate of 14.09 kGy/h (8 September 2016).

3 Results and discussion

3.1 Synthesis and structural characterization of ¦Ã-LiAlO₂

Synthesis of lithium aluminate ceramics by a modified combustion method was investigated using insoluble metal oxide. Most samples obtained utilizing different LiOH:Al₂O₃:CH₄N₂O molar ratios and different heating temperatures were white opaque powders.

Figure 1 compares the diffraction patterns of samples with n(LiOH):n(Al₂O₃):n(CH₄N₂O)=1:1:3, 1.5:1:3, 2:1:3 heat treated in a muffle furnace at 900 and 1000 ¡ãC. It was found in sample (1:1:3)₉₀₀ that y-LiAlO₂ is a main compound (72%), but ¦Á-LiAlO₂ and Al₂O₃ were also present (14% in both samples) showing that the reaction was not completed under these working conditions (Fig. 1(a) and Fig. 2(a)). Although LiAlO₂ exists in three forms, only ¦Á and g phases were observed, it can be explained due to that ¦Â phase form only exists at high pressures [41].

Fig. 1 XRD patterns of samples prepared by modified combustion method

Fig. 2 Percentage of products obtained by modified combustion method as function of temperature and lithium concentration according to XRD

In this work, the synthesis of LiAlO₂ was carried out to atmospheric pressure. The low-temperature ¦Á tetragonal structure transforms to the high-temperature  g structure irreversibly by sintering the ¦Á phase at 1350 ¡ãC [40,42]; however, in this work samples were heated in the presence of urea (fuel) at 900 ¡ãC. Although combustion temperature was not measured directly, we can predict that the combustion of the urea reached a temperature of at least 1200 ¡ãC, to carry out the transformation of ¦Á tetragonal structure to g structure of high-temperature. In the present work, the maximum combustion temperature during reaction was inferred due to the fact that:

1) The Li₂O-Al₂O₃ phase diagram reported by NAKAGAWA et al [43] allows us to predict that the combustion of the urea reached a temperature of at least 1200 ¡ãC, to carry out the transformation of ¦Á tetragonal structure to g structure of high-temperature.

2) CHICK et al [34] have reported that fuel combustion can be achieved at one peak flame temperature of about 1450 ¡ãC. Then, following reactions will occur:

LiOH+Al₂O₃+CH₄N₂O¦Á-LiAlO₂¦Ã-LiAlO₂+H₂O+CO₂+N₂                             (1)

Heat due to combustion urea:

¦Á-LiAlO₂+CO₂¡úLi₂CO₃+Al₂O₃                (2)

LiOH+CO₂¡úLi₂CO₃+H₂O                   (3)

3) Finally, ZU et al [44] have reported that the combustion process can be divided into three stages: a slowly heating zone (Stage I), a rapidly reaction zone (Stage II), and a cooling zone (Stage III). In Stage I, the oxidation reaction is essentially absent at the beginning due to the low temperature. As the sample is heated, the temperature continues to increase (about 1397 ¡ãC). The obtained high heating rate indicates that the combustion reaction is violent with a large amount of heat released.

The presence of Al₂O₃ can be attributed to incomplete reaction with LiOH, probably due to Li sublimation at 900 ¡ãC [40,41]. Although the XRD analyses did not show the presence of Li₂CO₃, the thermal analyses demonstrated that materials contained some minor impurities. Note that the lower limit detection by XRD technique depends on the scattering properties of the components of the materials.

In order to obtain y-LiAlO₂, LiOH molar ratio was increased to 1.5, to compensate Li₂O sublimation (Fig. 1(b)). Under these conditions in sample (1.5:1:3)₉₀₀, it was observed that Al₂O₃ decreased from 14% to 4% probably because it was able to react with the LiOH in excess. The main product found was y-LiAlO₂ (76%); however, ¦Á-LiAlO₂ increased up to 20% (Fig. 2(a)). High concentration Li reacts with Al₂O₃ to produce ¦Á-LiAlO₂ first, and subsequently, due to the combustion of urea, it produces y-LiAlO₂ (Reaction 1). BECKERMAN et al [45] reported that y-LiAlO₂ is produced by ¦Á-LiAlO₂ at temperatures between 650 and 1350 ¡ãC. In order to obtain pure y-LiAlO₂, LiOH molar ratio was increased from 1.5 to 2. Figure 1(c) shows that y-LiAlO₂ increased considerably (88%) and ¦Á-LiAlO₂ decreased (8%); however, Al₂O₃ was still present (4%), probably due to decomposition of ¦Á-LiAlO₂ to Al₂O₃ according to reaction 2. It is well known that ¦Á and b phases of LiAlO₂ are unstable at high temperatures and are transformed into y-LiAlO₂ when heat treated at temperatures of 650-1350 ¡ãC for 4 h [45]. Therefore, in order to eliminate the ¦Á-phase, samples were heat treated at 1000 ¡ãC.

Increase of the muffle furnace temperature to 1000 ¡ãC caused a considerable change in the percentage of the powders. Figures 1(d), (e) and (f) compare the diffraction patterns of samples with mole ratios of 1:1:3, 1.5:1:3 and 2:1:3 heat treated at 1000 ¡ãC. y-LiAlO₂ (Fig. 1(d)) was found as main compound (80%) in sample (1:1:3)₁₀₀₀, but ¦Á-LiAlO₂ and Al₂O₃ were also present (7% and 13% respectively, Fig. 2(b)) showing that the reaction is not completed under these working conditions. As at 1000 ¡ãC Li₂O sublimates in high proportion, LiOH molar ratio was increased to 1.5 to compensate Li₂O sublimation. Under these conditions Al₂O₃ was present in 6% (Fig. 1(e) and Fig. 2(b)). The main product found was y-LiAlO₂ (86%), and ¦Á-LiAlO₂ was still present in the sample (8%). By increasing the LiOH molar ratio to 2 (Fig. 1(f)), the only product obtained was y-LiAlO₂ (100%) showing that molar ratio (2:1:3)₁₀₀₀ was the best condition to obtain pure y-LiAlO₂ (Fig. 2(b)). Although Li₂CO₃ was not observed in XRD, TG analysis showed a mass loss attributed to carbonates present in the sample. Comparing the products obtained by the modified combustion method and the conventional combustion method [33], it was found that the conventional combustion method produces nitrogen contaminants. While in this work, due to the use of metal oxide instead metal nitrate, it was not observed contamination due to nitrate compounds. LI et al [33] have reported that y-LiAlO₂ could be synthesized using lithium nitrate/aluminium nitrate as starting materials and urea as fuel by the combustion process. In this study, the pure y-LiAlO₂ could be easily synthesized using lithium oxide/aluminium oxide and urea as fuel by the similar combustion process.

Representative scanning electron microscope (SEM) images of the reaction products are shown in Fig. 3 (1:1:3, 1.5:1:3 and 2:1:3 samples heat-treated at 900 ¡ãC). As shown in Fig. 3(a), the product obtained by the modified combustion method with (1:1:3)₉₀₀ molar ratio clearly reveals a brick-like morphology with one cross-section rectangular; hence they could be called ¡®¡®microbricks¡¯¡¯. Length of microbricks was 2-3.5 ¦Ìm. In this case, growth of bricks is not template-directed, or surfactant assisted, because no additional template or surfactants were introduced into the reaction. X-ray diffraction patterns in Fig. 1(a) showed that microbricks are composed mainly of crystalline tetragonal ¦Ã-LiAlO₂ structures. Previous work reported the synthesis of Li₂TiO₃ by the modified combustion method, where reaction between LiOH and TiO₂ depends on the lithium incorporation, diffusion and reaction into the TiO₂ particles, in the present work, reaction between lithium and Al₂O₃ should be taking a similar mechanism as in the case of titanium [46]. Increasing LiOH concentration from 1 to 1.5 (Fig. 3(b)), polygonal particles were observed between 0.4 and 4.5 mm and agglomerates of about 5 mm. Finally, (2:1:3)₉₀₀ sample (Fig. 3(c)) showed smaller particles of about 0.5-2 mm with laminar shapes ranging between which form considerably bigger agglomerates than the previous ones, of about 25 mm. The formation of the different structures can be attributed to the lithium volatilization during the calcination process. Due to easy volatilization of Li element, the excess Li element existing in the powder easily migrates to the surface of particles and turns into liquid phase. The local existence of liquid phase is conducive to the formation of new LiAlO₂ particles at the site and also encourages the formation of networks between the particles [47,48].

Fig. 3 SEM images of LiAlO₂ synthesized at 900 ¡ãC with different molar ratios

Figure 4 shows micrographs of 1:1:3, 1.5:1:3 and 2:1:3 samples heat-treated at 1000 ¡ãC. The morphology is denser than that discussed previously, mainly due to the sinterization effect produced by the high temperature. The particle size in sample (1:1:3)₁₀₀₀, ranges between 0.4 and 2 mm (Fig. 4(a)), with agglomerates of about 5 mm. (1.5:1:3)₁₀₀₀ sample (Fig. 4(b)) shows particles between 0.4 and 4.1 mm. Finally, (2:1:3)₁₀₀₀ sample (Fig. 4(c)) shows particles between 1 and 2 mm with a laminar shape and agglomerates considerably bigger ones (about 20 mm). Therefore, the morphology of the resulting y-LiAlO₂ crystals also seems to depend upon the lithium concentration and temperature. It is well known that one of the major parameters that determine the phase formation of the ceramics is the Li/metal molar ratio and temperature [25,46]. In this study, the effects of Li/metal molar ratio and temperature on the characteristics of the synthesized powder were investigated in a precursor solution consisting of urea as a fuel and a mixed oxide of lithium and aluminium. Finally, morphology has been reported which affected product parameters such as surface reaction on the grain, diffusion through pores of sintered particles and diffusion through the boundary layer formed on the particle surface must be considered, and therefore tritium production can be altered [49].

Fig. 4 SEM images of LiAlO₂ synthesized at 1000 ¡ãC with different molar ratios

Figure 5 shows the thermogravimetric curves of samples with molar ratios (1:1:3)₉₀₀ and (1.5:1:3) ₉₀₀ (Figs. 5(a) and (b)), no significant mass loss was observed (<1%). The mass loss observed throughout the analysis can be attributed to the evaporation of Li element due to its low melting temperature [48].

Samples (2:1:3)₉₀₀ and (2:1:3)₁₀₀₀, presented total mass loss of about 10% (Fig. 5(c)). The first mass loss of about 3%, in both samples, occurs at 25-250 ¡ãC. This process is associated to the dehydration of the samples, which were hydrated after the combustion during the cooling by two processes [14]; one at T<573 K (physic- sorption) and second one at T>573 K (chemisorption). At temperatures between 580 and 650 ¡ãC, a mass increase of ~1% could be observed, probably due to one of the following two processes: 1) chemical reactions with the components of the purge gas, N₂, in the present case, forming non-volatile or less volatile compounds, and 2) physical transformations, as adsorption of gaseous products in the sample. Finally, the second mass loss of about 5%, between 600 and 800 ¡ãC, is attributed to decarbonation process. The presence of carbonates in samples can be attributed to capturing process of CO₂ over lithium aluminate [50].

Fig. 5 TGA analyses of samples with different molar ratios prepared by modified combustion method at 900 (a, c, e) and 1000 ¡ãC (b, d, f)

3.2 Gamma irradiation of ¦Ã-LiAlO₂

The results obtained from the gamma irradiation of y-LiAlO₂ showed that the material synthesized changed from white to grey colour as a consequence of gamma dose received. The XRD spectra obtained (not shown) of the y-LiAlO₂ allowed to observe that the y-LiAlO₂ decreases from 97% to 89% with the formation of Al₂O₃ and Li₂CO₃. Li₂CO₃ formation could be explained by the reaction of excess carbon and lithium present in the sample. Figure 6 shows the micrograph of y-LiAlO₂ irradiated. It is observed that the gamma radiation causes changes in the morphology and particle size of the material. The radiation caused the formation of agglomerates of polyhedral particles of a size of approximately 170 mm.

Fig. 6 SEM image of y-LiAlO₂ irradiated at 12000 kGy

However, y-LiAlO₂ does not decompose, forming only small amounts of Li₂CO₃. It can be established that the irradiation produces consolidation, which is not favourable for an efficient extraction of tritium. The extraction efficiency is increased by decreasing the particle size.

4 Conclusions

1) The present study demonstrates that y-LiAlO₂ microbricks, polyhedral and laminar shapes can be successfully synthesized from Al₂O₃ and LiOH by simple modified combustion method in 5 min without any subsequent process. A critical effect of Li/Al molar ratio and synthesis temperature was clearly demonstrated on the morphology of the products, at 900 ¡ãC, n(Li)/n(Al)= 1:1 ratio gives microbricks, whereas n(Li)/n(Al)=2:1 ratio gives laminar shapes. However, at 1000 ¡ãC microbricks structures were not observed, instead polyhedral structures were observed in (1:1:3)₁₀₀₀ and (1.5:1:3)₁₀₀₀ samples. Sample (2:1:3)₁₀₀₀ presented laminar shapes. ¦Ã-LiAlO₂ was obtained with a yield of 100%.

2) The complexion effect of the fuel with Al₂O₃ was not possible; however, it was demonstrated that insoluble metal oxides can substitute the metal nitrates to produce LiAlO₂ by a modified combustion method with high purity.

3) It can be established that the irradiation produces consolidation, which is not favourable for an efficient extraction of tritium. Finally, the modified combustion process described for the synthesis of y-LiAlO₂ seems to have a great potential in the preparation of ceramic materials.

Acknowledgments

This work was supported by National Institute of Nuclear Research (ININ), Autonomous University of Puebla (BUAP) and co-financed by National Council of Science and Technology (CONACYT, Mexico). Furthermore, the authors thank to M. Espinosa, L. Banos, C. Rodr¨ªguez an L. Carapia for the analysis.

References

[1] HOUGHTON R A, SKOLE D L. 1 Carbon [C]//The earth as transformed by human action. Global and regional changes in the biosphere over the past 300 years. New York, United States of America: University Press, 1995: 393-421.

[2] SALVATI L, SATERIANO A, ZITTI M. Long-term land cover changes and climate variations¡ªA country-scale approach for a new policy target [J]. Land Use Policy, 2013, 30: 401-407.

[3] KHANDEKAR M L, MURTY T S, CHITTIBABU P. The global warming debate: A review of the state of science [J]. Pure and Applied Geophysics, 2005, 162: 1557-1586.

[4] LIOR N. Sustainable energy development: The present (2009) situation and possible paths to the future [J]. Energy, 2010, 35: 3976-3994.

[5] SAITO S. Role of nuclear energy to a future society of shortage of energy resources and global warming [J]. Journal of Nuclear Materials, 2010, 398: 1-9.

[6] BRITISH PETROLEUM. BP Statistical review of world energy 2015 [M]. London: BP, 2016.

[7] International Energy Agency. World energy outlook [M]. Paris, France: IEA, 2015.

[8] LOVERING J, YIP A, NORDHAUS T. Historical construction costs of global nuclear power reactors [J]. Energy Policy, 2016, 91: 371-382.

[9] CHARPIN J, BOTTER F, BRIEC M, RASNEUR B, ROTH E, ROUX N. Investigation of y lithium aluminate as tritium breeding material for a fusion reactor blanket [J]. Fusion Engineering and Design, 1989, 8: 407-413.

[10] JOHNSON C E. Tritium behavior in lithium ceramics [J]. Journal of Nuclear Materials, 1999, 270: 212-220.

[11] MA Sheng-gui, GAO Tao, LI Shi-chang, MA Xi-jun, SHEN Yan-hong. Theoretical investigations on the ¦Á-LiAlO₂ properties via first-principles calculation [J]. Fusion Engineering and Design, 2016, 113: 324-330.

[12] COLLING B R, MONK S D. Development of fusion blanket technology for the DEMO reactor [J]. Applied Radiation and Isotopes, 2012, 70: 1370-1372.

[13] KHORRAMIE S A, BAGHCHESARA M A, GOHARI D P. Fabrication of aluminum matrix reinforced with Al₂ZrO₃ nano particulates synthesized by sol-gel auto-combustion method [J]. Transactions of Nonferrous Metals Society of China, 2013, 23: 1556-1562.

[14] KAWAMURA Y, NISHIKAWA M, TANAKA K, MATSUMOTO H. Adsorption characteristics of water vapor on gamma-lithium aluminate [J]. Journal of Nuclear Science and Technology, 1992, 29: 436-444.

[15] KIM S D, HYUN S H, LIM T H, HONG S A. Effective fabrication method of rod-shaped ¦Ã-LiAlO₂ particles for molten carbonate fuel cell matrices [J]. Journal of Power Sources, 2004, 137: 24-29.

[16] ANTOLINI E. The stability of LiAlO₂ powders and electrolyte matrices in molten carbonate fuel cell environment [J]. Ceramics International, 2013, 39: 3463-3478.

[17] MA Sheng-gui, SHEN Yan-hong, GAO Tao, CHEN Pi-heng. First-principles calculation of the structural, electronic, dynamical and thermodynamic properties of ¦Ã-LiAlO₂ [J]. International Journal of Hydrogen Energy, 2015, 40: 3762-3770.

[18] TSAI S C, CHEN H C, HUANG J C, CHANG C M, CHOU M C. Size and orientation effect on the mechanical properties of LiAlO₂ single crystal [J]. Materials Science and Engineering: A, 2016, 677: 302-306.

[19] LI X, KOBAYASHI T, ZHANG F, KIMOTO K, SEKINE T. A new high-pressure phase of LiAlO₂ [J]. Journal of Solid State Chemistry, 2004, 177: 1939-1943.

[20] OKSUZOMER F, SKOC S N, BOZ I, GURKAYNAK M A. Effect of solvents on the preparation of lithium aluminate by sol¨Cgel method [J]. Materials Research Bulletin, 2004, 39: 715-724.

[21] KHOMANE R B, AGRAWAL A, KULKARNI B D. Synthesis and characterization of lithium aluminate nanoparticles [J]. Materials Letters, 2007, 61: 4540-4544.

[22] KHARLAMOVA O A, MITROFANOVA R P, ISUPOV V P. Mechanochemical synthesis of fine-particle ¦Ã-LiAlO₂ [J]. Inorganic Materials, 2007, 43: 645-650.

[23] NASCIMENTO A C, QUEIROZ M E, MOHALLEM D S. Synthesis of high purity ¦Ã-lithium aluminate by freeze drying [J]. Advanced Materials Letters, 2016, 7: 267-270.

[24] NAYAK M, KUTTY T R N, JAYARAMANB V, PERIASWAMY G. Preparation of the layered double hydroxide (LDH) LiAl₂(OH)₇¡¤2H₂O, by gel to crystallite conversion and a hydrothermal method, and its conversion to lithium aluminates [J]. Journal of Materials Chemistry, 1997, 7: 2131-2137.

[25] RIBEIRO R A, SILVA G, MOHALLEM N D S. The influences of heat treatment on the structural properties of lithium aluminates [J]. Journal of Physics and Chemistry of Solids, 2001, 62: 857-864.

[26] KWON S W, PARK S B. Effect of precursors on the morphology of lithium aluminate prepared by hydrothermal treatment [J]. Journal of Materials Science, 2000, 35: 1973-1978.

[27] RAMANATHAN S, KAKADE M B, ROY S K, KUTTY K K. Processing and characterization of combustion synthesized YAG powders [J]. Ceramics International, 2003, 29: 477-484.

[28] IANOS R, LAZAU I, PACURARIU C, BARVINSCHI P. Peculiarities of CaO¡¤6Al₂O₃ formation by using low-temperature combustion synthesis [J]. European Journal of Inorganic Chemistry, 2008: 925-931.

[29] IANOS R, LAZAU I, PACURARIU C. Metal nitrate/fuel mixture reactivity and its influence on the solution combustion synthesis of c-LiAlO₂ [J]. Journal of Thermal Analysis and Calorimetry, 2009, 97: 209-214.

[30] CHENG J, ZOU Xiao-ping, LI F, ZHANG Hong-dan, REN Peng-fei. Synthesis of bamboo-like carbon nanotubes by ethanol catalytic combustion technique [J]. Transactions of Nonferrous Metals Society of China, 2006, 16: 435-437.

[31] CRUZ D, BULBULIAN S. Synthesis of Li₄SiO₄ by a modified combustion method [J]. Journal of the American Ceramic Society, 2005, 88: 1720-1724.

[32] INGLE J T, GAWANDE A B, SONEKAR R P, OMANWAR S K, WANG Y, ZHAO L. Combustion synthesis and optical properties of Oxy-borate phosphors YCa₄O(BO₃)₃:RE³+ (RE=Eu³⁺, Tb³⁺) under UV, VUV excitation [J]. Journal of Alloys and Compounds, 2014, 585: 633-636.

[33] LI F, HU K, LI J, ZHANG D, CHEN G. Combustion synthesis of ¦Ã-lithium aluminate by using various fuels [J]. Journal of Nuclear Materials, 2000, 300: 82-88.

[34] CHICK L A, PEDERSON L R, MAUPIN G D, BATES J L, THOMAS L E, EXARHOS G J. Glycine-nitrate combustion synthesis of oxide ceramic powders [J]. Materials Letters, 1990, 10: 6-12.

[35] STELLA K C, NESARAJ A S. Effect of fuels on the combustion synthesis of NiAl₂O₄ spinel particles [J]. Iranian Journal of Materials Science and Engineering, 2010, 7: 36-44.

[36] LI Y, LIU M. Gas sensing properties of Y-doped ZnO nanosheets synthesized via combustion method [J]. Transactions of Nonferrous Metals Society of China, 2015, 25: 2247-2252.

[37] CRUZ D, BULBULIAN S. Synthesis of lithium silicate tritium breeder powders by a modified combustion method [J]. Journal of Nuclear Materials, 2003, 312: 262-265.

[38] CRUZ D, BULBULIAN S, LIMA E, PFEIFFER H. Kinetic analysis of the thermal stability of lithium silicates (Li₄SiO₄ and Li₂SiO₃) [J]. Journal of Solid State Chemistry, 2006, 179: 909-916.

[39] JIMENEZ-BECERRIL J, BOSCH P, BULBULIAN S. Synthesis and characterization of ¦Ã-LiAlO₂ [J]. Journal of Nuclear Materials, 1991, 185: 304-307.

[40] PFEIFFER H, KNOWLES K M. Reaction mechanisms and kinetics of the synthesis and decomposition of lithium metazirconate through solid-state reaction [J]. Journal of the European Ceramic Society, 2004, 24: 2433-2443.

[41] COOK L P, PLANTE E R. Phase diagram of the system Li₂O-Al₂O₃ [J]. Ceramic Transactions, 1992, 27: 193-222.

[42] LU C H, WEI-CHENG L. Reaction mechanism and kinetics analysis of lithium nickel oxide during solid-state reaction [J]. Journal of Materials Chemistry, 2000, 10: 1403-1407.

[43] NAKAGAWA K, OHZU H, AKASAKA Y, TOMIMATSU N. Allotropic phase transformation of lithium aluminate in MCFC electrolyte plates [J]. Denki Kagaku, 1997, 65: 231-235.

[44] ZU B, LI F, SUN Y, WANG Q, WU Y, ZHU Z. The effects of additives on the combustion characteristics of aluminum powder in steam [J]. RSC Advances, 2017, 7: 5725-5732.

[45] BECKERMAN S J, FORD R B, NEMETH M T. Conversion of gamma lithium aluminate to lithium aluminium carbonate hydroxide hydrate [J]. Powder Diffraction, 1996, 11: 312-317.

[46] CRUZ D, PFEIFFER H, BULBULIAN S. Synthesis of Li₂MO₃ (M=Ti or Zr) by the combustion method [J]. Solid State Sciences, 2006, 8: 470-475.

[47] ZHAU H, LIU H, LI H, ZHENG L, HU C, ZHANG X, LI Q, YANG J. Hydrothermal-assisted sintering strategy towards Porous- and hollow-structured LiNb₃O₈ anode material [J]. Nanoscale Research Letters, 2017, 12: 463.

[48] ZHAU H, LIU H, LI H, ZHENG L, HU C, ZHANG X, LI Q, YANG J. The effects of Li/Nb ratio on the preparation and photocatalytic performance of Li-Nb-O compounds [J]. Nanoscale Research Letters, 2017, 12: 496.

[49] CARRERA L M,  J, BASURTO R, ARENAS J, LOPEZ B E, BULBULIAN S, BOSCH P. Tritium recovery from nanostructured LiAlO₂ [J]. Journal of Nuclear Materials, 2001, 299: 242-249.

[50] KORAKE P V, GAIKWAD A G. Capture of carbon dioxide over porous solid adsorbents lithium silicate, lithium aluminate and magnesium aluminate at pre-combustion temperatures [J]. Frontiers of Chemical Science and Engineering, 2011, 5: 215-226.

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Daniel CRUZ¹, H. B. ORTIZ-OLIVEROS², L. M. ¹, R. M. FLORES-ESPINOSA², G. ROSANO-ORTEGA³

1. Facultad de Ingenieria Quimica, Benemerita Universidad Autonoma de Puebla, 14 Sur y San Claudio, Ciudad Universitaria, C.P. 72570, Cd. Puebla, Mexico;

2. Instituto Nacional de Investigaciones Nucleares, Direccion de Investigacion Tecnologica, Apartado Postal 18-1027, 11801 Mexico, DF, Mexico;

3. Universidad Popular Autonoma del Estado de Puebla, 21 Sur no. 1103, Colonia Santiago, C.P. 72410, Puebla, Mexico

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(Edited by Xiang-qun LI)

Corresponding author: H. B. ORTIZ-OLIVEROS; Tel: +52-5553297200-13460; E-mail: huemantzin.ortiz@inin.gob.mx

DOI: 10.1016/S1003-6326(18)64823-X