Deposition of iron oxide nanoparticles on mesoporous alumina network by wet-combustion technology

Materials Chemistry and Physics 225 (2019) 340–346

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Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys

Deposition of iron oxide nanoparticles on mesoporous alumina network by wet-combustion technology

T

Nikhil Kamboja, Ali Saffar Shamshirgara, Elena V. Shirshneva-Vaschenkob, Irina Hussainovaa,b,∗ a b

Tallinn University of Technology, Department of Materials Engineering, Ehitajate 5, 19180, Tallinn, Estonia ITMO University, Kronverksky 49, St. Petersburg, 197101, Russian Federation

H I GH L IG H T S

G R A P H I C A L A B S T R A C T

of mesoporous alu• Functionalization mina network by iron oxide nanoparticles.

of wet-combustion • Development method for deposition of iron oxides nanoparticles.

of effect of fuel on com• Assessment bustion process. morphology of the final • Tailoring product. anisotropic magnetic proper• Slightly ties of the produced network.

A R T I C LE I N FO

A B S T R A C T

Keywords: Wet-combustion Mesoporous alumina Nanocomposite Iron oxide nanoparticles Functionalization

The physico-chemical functionality within mesoporous networks dictates their performance as magnets, catalysts, and electro-thermal conductive materials. In this work, a method of wet-combustion was developed for functionalization of a mesoporous network of alumina nanofibres by iron oxide nanoparticles. As the basic fuels, urea and glycine were used. Iron nitrate was applied as an oxidant and a precursor of iron. The fuel type and oxidizer-to-fuel ratio dominantly affects the formation of the final product. The yielded wet-combusted product varies from iron (II) oxides [FeAl2O4] with crystallite size of 12 nm when glycine is used to iron (III) oxides [AlFeO3] with crystallite size of 21 nm when urea is used as a fuel. The agglomerates of spherical nanoparticles of γ-Fe2O3 with an average crystallite size less than 15 nm were homogenously distributed throughout the mesoporous alumina network in both cases. The magnetization curves reveal saturation point is around 6.3 emu.g−1 alongside the Fe2O3 coated-mesoporous alumina nanofibers, and 6 emu.g−1 for a transversal field.

1. Introduction Mesoporous materials are expected to open new applications and novel technological solutions to many industrial problems including but not limiting by catalysis, gas sensors, water splitting, biomedical microdevices and environmental protection [1–3]. Due to unique physicalchemical properties and enhanced functionality, fabrication of

mesoporous networks of high complexity and wide and tailorable range of properties has recently attracted considerable efforts in the research community. Specific properties of porous substrate with highly aligned canals can be derived not only from the simple addition of properties of parent constituents but also from their morphology and interfacial characteristics. However, anisotropic multi-phased structures require deep knowledge and comprehensive efforts for their fabrication.

∗

Corresponding author. ITMO University, Kronverksky 49, St. Petersburg, 197101, Russian Federation. E-mail addresses: [email protected] (N. Kamboj), ali.saff[email protected] (A.S. Shamshirgar), [email protected], [email protected] (I. Hussainova). https://doi.org/10.1016/j.matchemphys.2018.12.095 Received 18 September 2018; Received in revised form 13 December 2018; Accepted 31 December 2018 Available online 02 January 2019 0254-0584/ © 2019 Elsevier B.V. All rights reserved.

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nanoparticles during exploitation. Herein, we report the successful application of recently developed wet-combustion method to the synthesis of iron (II,III) oxide nanoparticles for functionalization of mesoporous network of porous alumina nanofibers (MAN) for the production of one-dimensional fibrous magnetic nanostructures. Different fuels were added to the reactive solution for initiation of the wet-combustion synthesis. The effect of synthesis method on the end-product composition and morphological features caused by the fuel chosen for the initial solution is thoroughly studied. The effect of fuel nature and amount on the wet-combustion product is reported. The yielded wet-combusted product is evaluated for magnetic properties in both transversal and alongside magnetic field. The major number of iron oxide nanostructure synthesis approaches require a complex instrumentation and a long processing time. Therefore, scalable and cost-effective production of iron oxide nanostructures remains a challenge due to uncontrollable size, morphology and homogeneity of the nanostructures. Herein, we report a rapid synthesis of iron oxide (II, III) nanoparticles using a mesoporous highly aligned alumina network of nanofibers as a template to form hetero-nanostructures through a straightforward and scalable approach without additional procedures of calcination.

Moreover, the fabrication methods to control the spatial distribution of the functional centers with designed phase and morphology are limited. Recently, the large portion of research efforts have been directed toward fabrication of iron oxide nanoparticles aimed at enhancement of their performance in currently existing applications. Nano-sized oxides of transition of metallic, such as iron oxide, exhibit unique electrical, optical and magnetic properties for numerous applications such as production of inorganic pigments, magnetic storage media, development of gas sensors, electronic and optical devices, color-imaging, magneto-caloric refrigeration, bioprocessing, ferrofluid technology and wastewater treatment adsorbents [3–10]. To date, a wide variety of well-defined nanostructures of iron oxides with different dimensionalities such as nanoparticles, nanorods, nanowires, nanotubes, nanorings, nanobelts, nanocubes have been successfully synthesized [4–7]. However, the synthesis of nanocrystalline iron-based mesoporous materials is an ultimate provocation to fill the necessary gap. Deposition of iron-based species on silica, alumina, and zeolite supports was carried out by hydrothermal processing [8], impregnating [9], liquid flame spray [10] and vapor deposition [11]. However, these methods require expensive precursors and can hardly be scaled-up and/ or precisely controlled over the reaction pathway; therefore, a final product morphology is highly dependent on the process variables. In Refs. [12,13], an advanced one-step combustion-impregnation synthesis technique for loading iron oxide on alumina, zirconia [12], or silica supports [13] is proposed. In this work, a method for deposition of a wide variety of metals and ceramics on mesoporous substrates, which is beneficial from a controlled interaction between a host and a functional material, is reported. Moreover, the morphology and chemical composition of the obtained mesoporous functional network is shown to be manipulated by changing the reaction conditions. Recently, one-stage wet-combustion method was successfully applied for fabrication of a Ni-based catalyst on a network of highly aligned alumina nanofibers (MAN) [14]. The method presents significant advantages over the others, among them there are precise control of the quantity of the deposited particles, an enhanced adhesion due to the energetic nature of the process, the possibility of controlling surface properties, and no need of specialized equipment, with allow industrial scale-up of the process. The wet-combustion approach is based on combination of dip coating and solution combustion techniques providing deposition of different materials on a support with a tunable microstructure and possibility to manipulate by interaction between a host and a functional material. The high temperature of flame, generated during the combustion process and lasting for few seconds, results in formation of nanoscale particles in a single-stage without requirement for further calcination. This method involves infiltration of a reactive combustible solution into the mesoporous network due to the capillary forces, and a subsequent heat-treatment for ignition of a self-sustaining combustion process. One of the technological challenges of synthesis is controlling the nanoparticles characteristics, including size and shape, polydispersity, morphology, etc. Structural characteristics are greatly affected by reaction parameters and may have a critical influence on electrical, mechanical, optical and magnetic properties, determining the behavior of iron oxide

2. Experimental The method of the wet-combustion synthesis involves infiltration of a reactive solution containing a metal precursor into the mesoporous network of well-aligned alumina nanofibers (MAN) and followed by a heat-treatment. In this work, the reactive aqueous solution contained iron nitrate (Fe(NO3)3.9H2O, ACS reagent, ≥98%, Sigma-Aldrich), as a precursor of iron; and glycine (C2H5NO2, ≥99%, Sigma) or urea (CH4N2O, ≥99%, Sigma) with different fuel-to-oxidizer ratios (φ) were used. The amount of precursors was calculated using the stoichiometry expressed by Equations (1) or (2), which demonstrated the combustion reactions between the iron nitrate and glycine or urea, respectively.

5 15 1 10 Fe(NO3)3⋅+⋅ ⋅ϕ⋅C2H5NO2⋅+⋅ ⋅(ϕ − 1)⋅O2 = ⋅ ⋅Fe2O3⋅+⋅ ⋅ϕ⋅CO2 3 4 2 3 5ϕ + 9 25 ⋅+⋅ ⋅ϕ⋅H2O⋅+⋅ ⋅N2 (1) 6 6

5 15 1 5 Fe(NO3)3⋅+⋅ ⋅ϕ⋅CO(NH2)2⋅+⋅ ⋅(ϕ − 1)⋅O2 = ⋅ ⋅Fe2O3⋅+⋅ ⋅ϕ⋅CO2 2 2 2 2 5ϕ + 3 ⋅+⋅5ϕ⋅H2O⋅+⋅ ⋅N2 (2) 2 Where ϕ is fuel-to-oxidizer ratio (ϕ = 1 implies to the fact that all oxygen required for complete combustion of a fuel derives from the oxidizer; while ϕ > 1 or ϕ < 1 implies to fuel-rich or fuel-lean conditions, respectively). The MAN network and the amount of fuels used are demonstrated in Fig. 1. The mesoporous network of alumina was used as a substrate. The specific surface area, measured by BET for nanofibers of 10 ± 2 nm in diameter, was 155 m2 g−1. The X-ray diffraction pattern of the mesoporous alumina network (MAN) functionalized with iron oxide

Fig. 1. (a) Macroscopic and microscopic side view of alumina nanofibers substrate, and (b) compositions of the initial solution with fuel to oxidizer ratio. 341

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NO3−, eliminated from the iron nitrate, can react with glycine triggering the combustion reaction at a lower temperature. At the end of the process, the final product may lose up to 80% of its initial mass. Fast raise in the temperature followed by the ignition of the combustion results in immediate decomposition of iron nitrate and formation of γ-Fe2O3 or Fe3O4. The reduced iron oxide (Fe3O4) reacts with mesoporous alumina substrate leading to the formation of FeAl2O4 as illustrated in Fig. 3. The possibility of formation of Fe3O4 during combustion was proved by thermodynamic calculations referred in Ref. [19]. In Ref. [20], the reaction between Fe3O4 and Al2O3 over 600 °C under reducing atmosphere is reported. It should be noted that in the fuel – rich system (ϕgly > 1.0), the ratio of the obtained FeAl2O4/Fe2O3 decreases with increasing the glycine amount as the oxidant fuel ratio is changed from 1 to 1.5. This is caused by a decrease in the combustion temperature with an increase in the amount of fuel [19]. The low temperature drastically influences the interaction of Fe3O4 with alumina. Thus, glycine appears to be not only a source of energy, but also a reducing agent, enabling to produce nanocomposites in a single step. Fig. 2(c–f) represent the SEM micrographs of the wet-combustion products. Agglomeration of the well-aligned fibers homogeneously covered by fine particles (< 5 nm) of γ-Fe2O3 is demonstrated in Fig. 2(c) for the case of ϕgly = 0.5. However, at ϕgly = 1.0, γ-Fe2O3 particles of less than 15 nm in size are recognized in SEM image in Fig. 2(d). The increase of particle size can be explained by the increase of the maximum combustion temperature using the stoichiometric amount of the fuel. Further increase of fuel amount (ϕgly = 2) results in the formation of less homogenously distributed particles attributed to FeAl2O4 with size of around 12 nm in diameter, Fig. 2(f).

nanoparticles was done using a D8 diffractometer (Bruker) with CuKα radiation at 40 kV in a scanning range from 20° to 70° with a step of 0.04°. The detailed characterization of the substrate is provided at the co-authors works [15,16]. PANalytical X'pert Highscore Plus software was used to analyze the XRD data in the combusted glycine and urea samples with different oxidizer to fuel ratio. The following card number were used: rhombohedral AlFeO3 (JCPD, 00-030-0024), γ-Fe2O3 (JCPD, 04-007-2479), α-Al2O3 (JCPD, 04-010-6477) and FeAl2O4 (JCPD, 00034-0192) to identify the phases. To prepare the reactive solutions, the precursors were dissolved in 5 ml deionized water, thoroughly stirred, dropped onto the MAN substrate, and left for 60 min at room temperature for homogenization. Then, the wetted substrates were placed in a furnace preheated to 400 °C for 30 min. The substrates producing by infiltration of the reactive solution in stoichiometric amount of urea (ϕur = 1) and glycine (ϕgly = 1) were analysed with simultaneous differential thermal (DTA) and thermogravimetric analysis (TGA) (Setsys Evolution Setaram, France). Experiments were performed in air at a temperature interval from 50 up to 300 °C with a heating rate of 10 °C/min. Scanning electron microscopy (SEM Zeiss EVO MA 15, Germany) was used to characterize the microstructure of the final products. The particle size and morphology of the nanoparticles were evaluated using a JEOL 2100F transmission electron microscope (TEM/ HRTEM) operating at 200 KV and equipped with a field emission electron gun providing a point resolution of 0.19 nm. The glycine-MAN sample with oxidizer to fuel ratio (ϕgly= 1) was selected for TEM since the dominant phase was γ-Fe2O3. For TEM sample preparation, the particles were carefully suspended in ethanol. The suspension was dropped on a copper TEM grid with carbon film support. The particles were kept at the grid after evaporation of ethanol. The microscope coupled with an INCA x-sight energy dispersive X-ray spectrometer (EDXS), from Oxford Instruments, was used for chemical elemental analysis. Room temperature magnetization test was done up to 1.2 T on a fibrous sample with 0.02 g of mass with parallel and transversal fields. Susceptibility measurement was done at temperatures from 150 K up to 400 K on the fibers to study the temperature influence on the properties. The sample was first heated to 400 K and then cooled using liquid nitrogen vapor at the rate of 10 °C/min.

3.2. Wet-combustion synthesis using urea as a fuel Fig. 4(a) shows the XRD patterns the iron nitrate-urea-MAN system with different fuel-to-oxidizer ratio. Using small amount of urea with oxidizer-to- fuel ratio, φ = 0.5, an amorphous mass was formed. Suppression of crystallization can be explained by the formation of a stable [Fe(CON2H4)6](NO3)3 complex, which isolates and disperses iron ions [21]. However, after decomposition of the complexes during heating, the amorphous iron oxide was developed. [Fe(CON2H4)6] (NO3)3 complex is intentionally used to fabricate the nanosized iron oxide [22]. Using the stoichiometric amount of urea (ϕur = 1.0), the decomposition of [Fe(CON2H4)6](NO3)3 favors the formation of dominant AlFeO3 phase with crystallite size of 21 nm as explained in Fig. 5. Further increase in the fuel amount to ϕur = 1.5 leads to smoldering of the process with the yield of γ-Fe2O3 phase and an additional phase of α-Al2O3. In ϕur = 2, the phase of γ-Fe2O3 is found, and the peaks related to α-Al2O3 increase because of the fact that urea provides the crystallization of α-alumina, which can be explained due to the increase of the crystallinity of α-Al2O3 [23]. XRD data revealed that the dominant phase, which accounts for 95% is the γ-Fe2O3 (maghemite) while the residual phase consists of α-Fe2O3 (hematite) and AlFeO3. This can be attributed to the fact that nanoparticles of maghemite phase are thermodynamically more stable than hematite. Henceforth, it was concluded in the study that in the case of crystallite sizes below 30 nm only maghemite phase was obtained and above 30 nm size only hametite was obtained [25]. The results were also confirmed by TEM studies with average crystallite size less than 15 nm of maghemite nanoparticles. Henceforth, it was concluded in the studies that crystallite size below 30 nm only maghemite was obtained and above 30 nm size only hametite was obtained [24]. The results were also confirmed by TEM studies with average crystallite size less than 15 nm of maghemite nanoparticles. Fig. 4(b) shows the DTA-TGA curves for the iron nitrate-urea-MAN system (ϕur = 1.0). The process started with the decomposition of urea

3. Results and discussion 3.1. Wet-combustion synthesis using glycine as a fuel The XRD patterns of the as-synthesized products obtained by wetcombustion synthesis of iron nitrate-glycine-MAN with different glycine-to-oxidizer ratio (ϕgly) are presented in Fig. 2(a). At the low oxidizer to fuel ratio (ϕgly = 0.5), an amorphous mass forms with a small peak related to γ-Fe2O3. Increasing the glycine-to-oxidizer ratio (ϕgly = 1.0) leads to the formation of γ-Fe2O3 and FeAl2O4 phases with crystallite size of 12 nm. The intensity of peaks related to γ-Fe2O3 phase decreases with increasing the glycine amount (ϕgly = 1.5) and totally disappear at (ϕgly = 2.0). The mechanism of the combustion process of the iron nitrate-glycine-MAN system was studied with the help of DTA-TGA for the batch with ϕgly = 1.0. DTA-TGA records an intensive mass loss started from the temperature of 120 °C and was accompanied by an endothermic effect, Fig. 2(b), caused by dehydration of iron nitrate hydrate described by Equation (3) [17]. Fe(NO3)3.3H2O→Fe(OH)2NO3→Fe(OH)3→Fe2O3

(3)

The mass loss became even more intensive in the temperature range of 170 °C - 205 °C and was accompanied by a sharp exothermic reaction due to the combustion reaction. In Ref. [18], it was reported that glycine decomposition began in the temperature range of 210–242 °C. 342

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Fig. 2. (a) XRD patterns of the combustion products obtained in the iron nitrate-glycine-MAN system at different fuel-to-oxidizer ratios (ϕ) ϕgly = 0.5, 1, 1.5, 2; (b) DTA-TGA curve of iron nitrate-glycine-MAN system; (c), (d), (e) and (f) SEM images of the samples at ϕgly = 0.5, 1, 1.5, 2 respectively.

Fig. 3. Mechanism of interaction of iron nitrate-glycine-MAN system.

3.3. TEM study on the common phase γ-Fe2O3 present in both fuels

at 152 °C, [25]. Below 155 °C, a weight loss of 11% was caused by evaporation of water. In the range of the temperatures of 155 °C–164 °C, a weight loss was measured to be 4%, which announced the start of urea decomposition. The decomposition of urea resulted in biuret and NH3 release. In the range of 155°C–168 °C, a weight loss of 55% together with an exothermic peak at 166 °C is attributed to the combustion process. It should be noted that the combustion takes place at relatively lower temperature as compared with the iron nitrate-glycineMAN system. Fig. 4(c–f) represents the SEM micrographs of the as-synthesized product. At the fuel-lean conditions, the agglomeration of fibrous network of alumina adhered with fine particles (< 5 nm) of γ-Fe2O3, as can be seen in Fig. 4(c). With increasing in the fuel-to-oxidizer ratio, the fine well-recognized particles of Fe2O3 nanoparticles onto MAN network can be observed in Fig. 4(e and f).

In order to elucidate the morphology and the composition of the system, the transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis have been performed in the hetero-nanostructure (Fig. 6) prepared by the impregnation method and thermally treated at 400 °C. Fig. 6(a) shows a low-magnification image of the Fe2O3 nanoparticles deposited onto the mesoporous alumina nanofibers (MAN), and Fig. 6(b-e) is magnified images taken from the marked squares and indicated as 1 and 2 in Fig. 6(a). Morphologically, two types of particle agglomerates can be identified on mesoporous alumina network, i.e., spherical dark aggregates, and large bright aggregates (marked in Fig. 6(a) as SDA, and LBA, respectively). Small dark particles (Fig. 6(e)) with an average sizes of ∼15 nm are seen to coexist within the large spherical aggregates (Fig. 6(c)) in a close contact with a bundle of the mesoporous alumina network with an 343

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Fig. 4. (a) XRD patterns of the combustion products obtained in the iron nitrate-urea-MAN system at different fuel-to-oxidizer ratios ϕur = 0.5, 1, 1.5, 2; (b) DTATGA curve of iron nitrate-urea-MAN system; (c), (d), (e) and (f) SEM images of the samples at (ϕ) ϕur = 0.5, 1, 1.5, 2 respectively.

average single fibre diameter of about ∼7 nm (Fig. 6b–d). The contrast observed for the larger spherical agglomerates can be ascribed to the presence of a larger electron density typical for Fe species, while the brightness of the nanofibers is likely a consequence of the low electron density of metal oxides (i.e., Al2O3). Indeed, EDX analysis (Fig. 6(f)) has revealed that the large bright bundle has a composition rich in aluminum oxide (region marked on the black box and indicted as 6 in panel a), while the darker spherical aggregates present a composition which is rich with the iron oxide (regions marked as 2 in panel a). Summarizing, when the iron precursor compound, Fe(NO3)3•9H2O, is thermally treated with glycine fuel at 400 °C, it decomposes into fine nearly spherical nanoparticles with an average particle size of < 15 nm.

confinement [24]. This properties change, which is different from conventional bulk material, can be employed in composite structures where the particle-covered nanofibers can function as reinforcement. Arguably, a more simplified dispersion can be expected while mixing these fibers with the matrix material. Furthermore, the fibrous base structure can enhance the sinter ability of the implemented composite. Magnetization test was performed on a fibrous structure with transversal and parallel fields. Since, the nanofibers used in the study are self-aligned, two fields provided us with two separate curves depicted in Fig. 7. Susceptibility measurement was performed separately. However, no transition was observed in the selected temperature 150K–400 K. The point of saturation is located at around 6.3 emu.g−1 (at 11 kG) alongside the fibers and 6 emu.g−1 (at 10 kG) for the transversal field. This parameter for the maghemite nanoparticles is 66 emu.g−1 [24]. Tan et al. [26] reported that an increase in particle size results in an increase in magnetic saturation. Subsequently, considering the average crystallite size of < 15 nm of the as-synthesized maghemite is slightly higher than the reported 5.6 emu.g−1 value for a sample with 22.1 nm particle size [26]. It is apparent that the saturation point is less pronounced in the case

4. Magnetic properties The magnetic properties of the nanoparticles of iron oxides has shown to differ by the particle size. One of the interesting phenomenon that occurs at small particles size is the superparamagnetic behavior of these particles due to the fluctuation in the direction of the magnetic moments, which is a consequence of the thermal agitation and quantum

Fig. 5. Mechanism of interaction of iron nitrate-urea-MAN system. 344

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Fig. 6. HRTEM images of iron nitrate-glycine-MAN ϕgly = 1 system thermally treated at 400 °C. Magnification increases from panel a to panel f so that scale bars in (a) correspond to 200 nm, in (b–c) to 20 nm, in (d) to 10 nm and in (e) to 5 nm. On the right, panel f, EDX spectra of the sample, corresponding to the regions marked as 1 and 2 in panel a.

of the field alongside the fibers. This can be explained by the inability of the magnetic moments to full spin alignment due to anisotropic linear density of the bulk fibers [21]. A very narrow hysteresis loop (Fig. 7, insets) was observed with small coercivity and retentivity of 72 G and 1.4 emu.g−1, respectively, which agrees with the reported values [27]. The narrow hysteresis loop with almost no coercivity indicates superparamagnetic behavior of the major particle populations which is in agreement with other studies [26,28]. Meanwhile, it has been already demonstrated that the magnetic anisotropy and the particle size are in a close connection in the case of maghemite nanoparticles. It has been shown that fine particles (< 4 nm) act as a subsystem with a paramagnetic and partially spin-glass behavior [25]. Fig. 8 shows susceptibilities for the samples in the temperature region from 150 K to 400 K. The susceptibility increases with an increase in temperature, which can be a result of superparamagnetic behavior of the compound [29]. 5. Conclusions Fig. 8. Susceptibility curves of Fe2O3 nanoparticles-covered mesoporous alumina network (MAN).

The template-assisted wet-combustion synthesis is a flexible and cost-effective technique to produce composite fibrous porous structures of tailored morphology. The fuel type and oxidizer-to- fuel ratio dominantly affects the formation of the final product. Addition of glycine and/or urea prevents incorporation of the iron ions into the amorphous alumina through a diffusion mode leading to the formation of iron oxide despite the high temperature generated during the combustion process. Mostly FeAl2O4 was formed when glycine was used as a fuel. On the contrary, AlFeO3 (Fe in +3 oxidation state) phase was observed when urea was used as a fuel. The common phase γ-Fe2O3 was detected in both of fuels. As a result, mesoporous network of highly oriented iron oxide (II,III) alumina composite nanofibers was obtained. The magnetization curves reveals saturation point to be around 6.3 emu.g−1

alongside the Fe2O3 coated mesoporous alumina network and 6 emu.g−1 for transversal field. Acknowledgements This work was supported by the Estonian Research Council under PUT1063 (I. Hussainova), and the Estonian Ministry of Higher Education and Research under Projects IUT19-29. The authors would like to acknowledge the help of Dr. Olga Volobujeva from Department of Materials and Environmental Technologies, TUT (project IUT-T4) for

Fig. 7. Room temperature magnetization curves for the fibrous alumina with deposited Fe2O3 nano particles in (a) perpendicular, and (b) parallel fields. 345

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SEM imaging; and PhD Mart Viljus and Mr. Rainer Traksmaa from Department of Mechanical and Industrial Engineering, TUT, for SEM and XRD analysis.

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