Amorphous SiO2 Research Articles

Study of optical and cooperative parameters of fibrous quartz heat shielding on experimental data on its reflection spectra

The paper presents the results of a study of a number of key optical characteristics of some highly porous thermal protection materials based on amorphous SiO2 fibers in the near and mid IR ranges. In the optical part of the statistical simulation model of such materials, based on the rigorous Mie theory, its application requires the introduction of cooperative corrections to the results of interaction with electromagnetic radiation of individual fragments. These corrections are introduced into the model in the form of an additional multiplier (Cs) of the scattering and absorption Mie efficiencies, which was usually used as a model tuning parameter when interpreting the experimental results of thermophysical studies. In this work, using the example of TZM-23M materials (Russia), made of a relatively thick (~9 μm) silica fiber PS-23 (Belarus), for the first time, data were obtained that make it possible to study the Cs parameter as a spectral quantity. The study is based on the results of experimental determination of the spectral hemispherical reflectivity of layers of material of two or more optical thicknesses in the wavelength range 0.83-16.65 μm. These data and Zege's asymptotic formulas were used to estimate the values of the absorption and scattering coefficients. The spectral parameter Cs is determined from the value of the scattering coefficient in the process of solving the inverse optical problem. The data obtained are compared with the results calculated on the basis of classical approximations of the optical constants. The results of this work can be useful for specialists in the field of radiation heat transfer and the interaction of electromagnetic radiation with complex partially transparent media with high spectral albedo scattering values. Keywords: Silica fibrous thermal protection, reflectivity, experiment, absorption and scattering spectrum, optical model, Mie theory, cooperative corrections.

Full-field deformation measurements in the transmission electron microscope using digital image correlation and particle tracking

Determining displacement and/or strain fields at the nanoscale during material deformation can be instrumental in developing a multiscale understanding of material response. Full-field quantitative kinematic measurements based on transmission electron microscopy (TEM) are lagging behind other microscopy techniques. Here, we develop an experimental approach combining digital image correlation (DIC) and particle tracking (PT) for characterizing in situ microscale deformation of amorphous SiO2 in the TEM. Gold nanoparticles deposited on SiO2 provide both the speckle pattern required by DIC when averaged over a subset region and target particles for PT. To demonstrate and validate the feasibility of using DIC and PT in the TEM, micron sized SiO2 beam samples are machined using a focused ion beam (FIB) and loaded in the TEM via indentation. DIC and PT are then applied to measure in situ displacements from a sequence of TEM images taken during loading and creep of the beam. Results of the two measurement methods agree well with each other and with the applied displacement measurements, thus demonstrating their effectiveness in determining local displacements from TEM experiments. Sources of noise resulting from sample drift and image intensity variations are discussed.

Thickness dependence of spin–orbit torques in Pt/Co structures on epitaxial substrates

We investigate the Pt thickness dependence of spin–orbit torques (SOTs) in Co/Pt layers grown on single crystalline SrTiO3 and LaAlO3 and amorphous SiO2 substrates. We measure the SOT-induced effective damping-like fields and spin Hall magnetoresistances of the Co/Pt (tPt) samples, where tPt varies from 0.5 to 5.5 nm. We find that the Co/Pt layers grown on the single crystalline substrates show weaker thickness dependence of the SOT than the samples on the SiO2 substrate, which cannot be explained by the conventional bulk spin Hall effect in the Pt layer. This indicates that there is a non-negligible interfacial SOT originating from the Pt/substrate interface, which is more pronounced for thinner Pt. These results provide a way to design SOT material structures with enhanced SOT efficiency by incorporating interfacial SOT.

Combine XPS- and AFM Study of Silicon Oxide Film with Zinc Impurity for ReRAM Devices

The composition, structure and properties, as well as the current-voltage characteristics of a layered structure consisting of two 50 nm thick amorphous SiO2 films deposited by electron beam evaporation, between which a Zn film with a thickness that varied from 100 nm to 50 nm was deposited. Then these structures were annealed in air in the temperature range from 300 up to 400oC with a step of 50oC for 30 min. Planar electrodes with different configuration were used. They were made from gold, platinum and aluminum. It was found that after deposition on the sample surface, a granular structure with a grain size of 50-100 nm of SiO2 composition was formed. After annealing at 400oC, the sample roughness decreases from 25 nm after deposition to 10 nm, and the grain size in plan increases to 100-200 nm. For films annealed at 400oC the current-voltage characteristics with hysteresis were obtained. Keywords: silicon oxide film, zinc impurity, electron beam evaporation, annealing, nanoclusters, ZnO.

Совместное XPS- и AFM-исследование пленок оксида кремния с примесью цинка для ReRAM устройств

The composition, structure and properties, as well as the current-voltage characteristics of a layered structure consisting of two 50 nm thick amorphous SiO2 films deposited by electron beam evaporation, between which a Zn film with a thickness that varied from 10 to 50 nm was deposited. Then these structures were annealed in air in the temperature range from 300 up to 450°C with a step of 50°C for 30 minutes. Planar electrodes with different configuration were used. They were made from gold, platinum and aluminum. It was found that after deposition on the sample surface, a granular structure with a grain size of 50-100 nm of SiO2 composition was formed. After annealing at 400°C, the sample roughness decreases from 25nm after deposition to 10 nm, and the grain size in plan increases to 100-200 nm. For films annealed at 400°C the current-voltage characteristics with hysteresis were obtained.

Исследование оптических и кооперативных параметров волокнистой кварцевой теплозащиты по экспериментальным данным о ее спектрах отражения

The paper presents the results of a study of a number of key optical characteristics of some highly porous thermal protection materials based on amorphous SiO2 fibers in the near and mid IR ranges. In the optical part of the statistical simulation model of such materials, based on the rigorous Mie theory, its application requires the introduction of cooperative corrections to the results of interaction with electromagnetic radiation of individual fragments. These corrections are introduced into the model in the form of an additional multiplier Cs of the scattering and absorption Mie efficiencies, which was usually used as a model tuning parameter when interpreting the experimental results of thermophysical studies. In this work, using the example of TZM-23M materials (Russia), made of a relatively thick (~ 9 μm) silica fiber PS-23 (Belarus), for the first time, data were obtained that make it possible to study the Cs parameter as a spectral quantity. The study is based on the results of experimental determination of the spectral hemispherical reflectivity of layers of material of two or more optical thicknesses in the wavelength range 0.83 - 16.65 μm. These data and Zege's asymptotic formulas were used to estimate the values of the absorption and scattering coefficients. The spectral parameter Cs is determined from the value of the scattering coefficient in the process of solving the inverse optical problem. The data obtained are compared with the results calculated on the basis of classical approximations of the optical constants. The results of this work can be useful for specialists in the field of radiation heat transfer and the interaction of electromagnetic radiation with complex partially transparent media with high spectral albedo scattering values.

МОЛЕКУЛЯРНО-ДИНАМИЧЕСКОЕ МОДЕЛИРОВАНИЕ СТРУКТУРЫ И СВОЙСТВ СТЕКЛООБРАЗНОЙ ПОДЛОЖКИ SiO2 В ШИРОКОМ ДИАПАЗОНЕ ТЕМПЕРАТУР

F.V. Grigoriev's paper “Force Fields for Molecular-Dynamic Modeling of Sputter Deposition Process on Silicon Dioxide Film”, proposes a simple DESIL inter-ion potential for modeling amorphous SiO2 substrates widely used for thin film sputter deposition. This potential provides an important advantage when compared with popular potential of BKS due to the absence of a non-physical attraction region at short distances between particles. This is important when simulating SiO2 substrate sputtering where collisions between particles result in short-range proximity. In this case an artifact of particle inter-capture may be observed which distorts the simulation results. The purpose of this work is to demonstrate the potential for predicting the structural and thermodynamic characteristics of amorphous silicate glasses over a broad temperature range.

Occurrence forms of major impurity elements in silicon carbide

In this study, the forms of occurrence of impurity elements in silicon carbide (SiC) with different particle sizes were systematically investigated using a combination of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that in SiC powders prepared using the Acheson process, the contents of O, free-Si, free-C, and Fe impurities are high, and those of other trace impurity elements follow the order: Ti > Al > Ni > V. Moreover, O impurities mainly cover the SiC particle surface in the form of amorphous SiO 2 . Fe impurities exist around SiC particles as Fe 2 O 3 , Fe x Si y , Fe x Si y Ti z , and Fe x Al y Si z phases. Impurity elements are often introduced during the smelting of SiC and/or during milling or subsequent storage.

Effects of dopants with various valences on densification behavior and phase composition of a ZrO2–SiO2 nanocrystalline glass-ceramic

Effects of dopants with different valences on the densification behavior and phase composition of a ZrO2–SiO2 nanocrystalline glass-ceramic (NCGC) during pressureless sintering were investigated in this study. The raw powder of Ca2+, La3+, Ce4+ and Ta5+ ions doped ZrO2–SiO2 (referred to as Ca-ZS, La-ZS, Ce-ZS, Ta-ZS, respectively) and pure ZrO2–SiO2 (PZS) sample were synthesized by sol-gel method, followed by pressureless sintering. Compared with the PZS sample, doping of Ca2+ and La3+ ions significantly promoted the densification of the NCGCs. The “densification promotion” effect was attributed to the formation of oxygen vacancies and the decrease of SiO2 viscosity due to doping of aliovalent cations. The dopants with various valences showed significant effects on the phase compositions of the NCGCs during sintering. Doping of Ca2+ ion accelerated the reaction kinetics between ZrO2 nanocrystallites and amorphous SiO2 to yield ZrSiO4. The La3+ ion acted as destabilizer of t-ZrO2, which resulted in a rapid tetragonal (t) to monoclinic (m) ZrO2 phase transformation during sintering, while in the Ta5+ and Ce4+ ions doped sample, the phase transformation occurred gradually. All the doping ions increased the lattice parameters and the volume of t-ZrO2 unit cell, while the effects of the doping ions on the lattice parameters of m-ZrO2 unit cell were more complex.

Sustainable process for enhanced CO2 mineralization of calcium silicates using a recyclable chelating agent under alkaline conditions

This study explored a key challenge of aqueous indirect CO2 mineralization: the consumption of chemicals for a large pH swing between acidic and alkaline conditions and the production of waste fluid. Herein, we proposed and experimentally examined the technical feasibility of a sustainable process for enhanced CO2 mineralization using a new potentially recyclable alkaline solution of chelating agent [N,N-dicarboxymethyl glutamic acid (GLDA)] at near-room temperatures. This process comprising the following: enhanced Ca extraction from silicates with suppressed formation of silica-rich passivation layer via the combined actions of proton and chelating agent attacks at weakly alkaline conditions; Ca carbonation using sodium carbonate at high pH and temperature; and regeneration of the extraction solution (i.e., a decrease in pH and silicon removal) via CO2 gas dissolution. Ca extraction experiments using representative calcium silicate (CaSiO3) at various GLDA concentrations and initial pHs under 50 °C demonstrated the possibility of enhanced Ca extraction with almost all GLDA molecules combining with Ca (Ca/GLDA≈1) at an optimum condition (0.1 M GLDA and pH 8 in this study). This type of extraction is desirable as it contributes to an efficient Ca carbonation in addition to a decreased stability of the Ca-GLDA complex; indeed, most of the extracted Ca were carbonated to aragonite at 80 °C. Moreover, such extraction with the relatively low pH of 8 was found to be desirable for solution regeneration that involves pH adjustment (reduction) because of low silica solubility at lower pH. It was demonstrated that room-temperature CO2 bubbling removed almost all Si as amorphous SiO2, during which CO2 captured as NaHCO3 was also occurring. The recyclability of extraction solution was also demonstrated in this paper. This study encourages further extensive studies to optimize reaction conditions, particularly for using alkaline solid wastes, to make the process both technically and economically feasible.

Vanadia nanoparticles encapsulated in mesoporous silica as a rattle-like structure for oxidation of dibenzothiophene: A kinetic study

A rattle-like structure of V2O5 encapsulated in mesoporous silica was successfully prepared through a surfactant-supported selective etching strategy. The structural analysis showed that V2O5 nanoparticles in the core of mesoporous hollow silica spheres with void diameter ∼290 nm, V2O5 core diameter ∼93 nm, amorphous SiO2 shell thickness ∼17 nm, surface area of ∼368.19 m2/g and average pore radius of 16 nm. The as-prepared material was employed in catalytic oxidation of dibenzothiophene (DBT) in the presence of H2O2 as an oxidizing agent at different conditions of temperature, contact time and initial concentration using a batch system under either stirring or ultrasonication. The ultrasonication was found to be more effective (∼100%) and faster in oxidation process than the stirring (∼68%, after 5 h). The analysis of the outputs significantly indicated the adsorption of the produced sulfone onto the catalyst surface. The catalytic system exhibited high removal efficiency, qe (∼493 mg/g), as detected experimentally at ambient condition. The thermodynamic analysis confirms the spontaneous physic-sorption nature of the adsorption process with adsorption energy ∼2.155 kJ/mol. The intra-particle diffusion model indicates that the process passes through three stages to attain the equilibrium state.

The oxidation behavior of multi-layered SiC coated graphite in water vapor containing environment

In this study, an investigation was conducted on the oxidation behavior of multi-layered SiC coated graphite spheres at 1673 K in H2O/Helium gas mixtures with water vapor at a concentration of 5–100 g/m3 under atmospheric pressure. In the 3D X-ray nondestructive test, carbon agglomeration was identified on the as-prepared multi-layered SiC coating. The multi-layered porous SiC coating lower than 0.16% was found to ensure that the graphite spheres would not fail for at least 10 h when oxidized under water-gas mixing conditions of 1673 K. After oxidation for 10 h, a layer of amorphous SiO2 was formed. In the subsequent oxidation, no amorphous SiO2 was transformed to the cristobalite phase. Excessive moisture was found to inhibit SiO2 from being crystallized. Furthermore, water vapor concentration was found to be critical to the oxidation morphology of the coating.

Toward understanding the activation and hydration mechanisms of composite activated coal gangue geopolymer

The feasibility of coal gangue as primary cementitious material was experimentally investigated in this paper. An Orthogonal method was employed to investigate the optimum activation strategy for coal gangue-based geopolymer. Experiment parameters included the modulus of sodium silicate (M), alkali content (A), calcination temperature (T), holding time (H), and water-to-binder ratio (W/B). Meanwhile, the phase transitions, chemical compositions, and microstructure evolution were investigated by supplementary techniques, such as ESEM, XRD, and FTIR. Experimental results indicated that the hydration reactivity of coal gangue was markedly enhanced. And the formations of high contents of amorphous SiO2 and Al2O3 phases are the critical factors for the high reactivity, which highly depends on the proper calcination temperature and holding time. The hydration productions of alkali-activated coal gangue, mainly N-A-S-H gels, can rapidly precipitate around the unreacted particles and fill the existing cavities. Meanwhile, the average surface area, diameter, and porosity considerably declined with the hydration degree of geopolymer. In summary, coal gangue can be viewed as a new eco-friendly cementitious material via the proposed composite activation strategy.

Physicochemical properties and operational stability of Taguchi design-optimized Candida rugosa lipase supported on biogenic silica/magnetite/graphene oxide for ethyl valerate synthesis

Biobased ternary nanocomposites can stabilize enzymes for greater stability, catalytic activity and easy recovery. This study aimed to optimize biogenic silica/magnetite/graphene oxide nanocomposite supported Candida rugosa lipase (CRL/SiO2/Fe3O4/GO) for ethyl valerate (EV) synthesis and characterize the biocatalysts’ physicochemical properties and operational stability. CRL conjugated-oil palm leaves-derived biogenic SiO2/Fe3O4/GO nanocomposite showed a maximum immobilized protein of 44.13 ± 2.1 mg/g with a specific activity (534.87 ± 9.5 U/mg), than free CRL (≥700 U/mg). GL-A-SiO2/Fe3O4/GO exhibited the highest surface area (260.87 m2/g) alongside superior thermal stability in TGA/DTG. XRD revealed an amorphous SiO2 (crystallinity = 26.7%), while Fe3O4 existed as cubic spinel crystal (crystallinity = 90.2%). Taguchi Design-optimization found that CRL/SiO2/Fe3O4/GO best catalyzed the EV synthesis (90.4% in 3 h) at 40 ℃ using 3 mg/mL of biocatalyst, valeric acid/ethanol molar ratio of 1:2, in 10% (m/v) molecular sieves with stirring in heptane at 200 rpm. EV production was confirmed by FTIR- (C=O: 1738 cm−1 and C–O–C: 1174 cm−1) and GC–MS ([M]+m/z = 130, C7H14O2). CRL/SiO2/Fe3O4/GO’s reusability for 11 successive esterification cycles demonstrated the SiO2/Fe3O4/GO’s exceptional hyperactivation and stabilization properties on immobilized CRL. These findings conveyed the SiO2/Fe3O4/GO’s efficacy to alter CRL's physicochemical properties and operational stability for catalyzing higher yields EV.

Spectroscopic Characterisation and Elemental Composition of Biochars Obtained from Different Agricultural Wastes

The use of biochar (BC) has an environmental importance in terms of climate change, soil fertility, waste management and energy generation. The purpose of this study was to reveal some of the structural characteristics of BC produced from agricultural wastes by employing spectroscopic techniques within a short time frame. The BCs were produced via slow pyrolysis at 300 °C from four feedstocks: tea waste (TW), hazelnut husk (HH), rice husk (RH) and poultry litter (PL). The pH of plant-derived BC was alkaline (pH: 7-9), and the pH of manure-derived BC was strongly alkaline (pH: 10.1). PLBC has the highest (4.67 dS m-1) electrical conductivity (EC) when compared to other BC materials. According to the X-ray fluorescence (XRF) analysis method, organic compound contents of TWBC and HSBC were found to be higher than the other two BCs, while the other two BCs (RHBC and PLBC) were richer in mineral content. TWBC and HHBC were composed of more mineral elements when compared to RHBC and PLBC, but the latter two were still rich in minerals. The surface area of RHBC was found higher (12.9 m2 g-1) than other BC materials. According to the X-ray fluorescence (XRF) analysis method, the total element content of PLBC was found higher than the other BCs. In addition, the silicon (Si) content of RHBC was considerably higher (16.4%). In PLBC’s XRD diagram: quartz (SiO2) at 3.41 (Å); calcite (CaCO3) at 3.96, 2.94 and 1.91 (Å); sylvine (KCl) at 3.06 and 1.85 (Å); and whitlockite ([Ca, Mg]3 [PO4]2) at 2.78 and 2.17 (Å) were found. In HHBC and RHBC diagrams, partially crystallized carbon (CryC) peaks were mainly observed between 1.20 and 2.34 (Å), and cristobalite peaks (i.e., amorphous SiO2) were observed at 3.91 and 3.40 (Å).

Insight into low-temperature sintering of samarium-doped ceria mixed with scavenging lithium

The refractory nature of oxide-ion conducting Sm-doped CeO2 (SDC) has hindered the development of SDC devices. Lithium has been found to be an excellent sintering aid that enables sintering at temperatures as low as 900 °C and also increases grain boundary conductivity. Even though Li–Si oxides melt only above the sintering temperature in reality, it is generally believed that these benefits are given by virtue of a formation of liquid phases with silicon contaminants. In this study, the key element for low-temperature sintering was revealed to be aluminum, which is spontaneously introduced into SDC by a covert but intense chemical reaction between the mixed lithium and the alumina crucible. The results show that 1 wt% lithium addition is responsible for the unintended introduction of 32 mol% aluminum. Computational thermodynamic calculations for a Li–Si–Al oxide system clarified that aluminum introduction is essential to reduce the melting point below the sintering temperature. A nano-scale analysis clearly indicates the segregation of aluminum at SDC grain-boundary triple junctions, like LiAlO2, while silicon appears to migrate towards the SDC-SDC grain boundaries as amorphous SiO2. This suggests that the decomposition of the Li–Si–Al liquid oxide filling the grain boundaries is associated with the reflow of silicon and the loss of lithium as sintering proceeds. It was shown that zirconium is also introduced into SDC due to ball-mill processing, and that it potentially forms Li–Si–Zr oxides which remain in their solid state during sintering. The results of this study highlight the importance of taking the impact of unintended aluminum introduction into consideration for a variety of ceramics mixed with even minute quantities of lithium.

BaGdF5 Nanophosphors Doped with Different Concentrations of Eu3+ for Application in X-ray Photodynamic Therapy.

X-ray photodynamic therapy (XPDT) has been recently considered as an efficient alternative to conventional radiotherapy of malignant tissues. Nanocomposites for XPDT typically consist of two components—a nanophosphor which re-emits X-rays into visible light that in turn is absorbed by the second component, a photosensitizer, for further generation of reactive oxygen species. In this study, BaGdF5 nanophosphors doped with different Eu:Gd ratios in the range from 0.01 to 0.50 were synthesized by the microwave route. According to transmission electron microscopy (TEM), the average size of nanophosphors was ~12 nm. Furthermore, different coatings with amorphous SiO2 and citrates were systematically studied. Micro-CT imaging demonstrated superior X-ray attenuation and sufficient contrast in the liver and the spleen after intravenous injection of citric acid-coated nanoparticles. In case of the SiO2 surface, post-treatment core–shell morphology was verified via TEM and the possibility of tunable shell size was reported. Nitrogen adsorption/desorption analysis revealed mesoporous SiO2 formation characterized by the slit-shaped type of pores that should be accessible for methylene blue photosensitizer molecules. It was shown that SiO2 coating subsequently facilitates methylene blue conjugation and results in the formation of the BaGdF5: 10% Eu3+@SiO2@MB nanocomposite as a promising candidate for application in XPDT.

Capacitor-type thin-film heat flow switching device

We developed a capacitor-type heat flow switching device, in which electron thermal conductivity of the electrodes is actively controlled through the carrier concentration varied by an applied bias voltage. The device consisted of an amorphous p-type Si–Ge–Au alloy layer, an amorphous SiO2 as the dielectric layer, and an n-type Si substrate. Both amorphous materials are characterized by very low lattice thermal conductivity, ≤1 W m–1 K–1. The Si–Ge–Au amorphous layer with 40 nm in thickness was deposited by means of molecular beam deposition technique on the 100 nm thick SiO2 layer formed at the top surface of Si substrate. Bias voltage-dependent heat flow density through the fabricated device was evaluated by a time-domain thermoreflectance method at room temperature. Consequently, we observed a 55% increase in the heat flow density at the maximum.

Preparation of Ceria-Coated Silica Nanoparticles and Their Chemical Mechanical Planarization Performance on Si-Face 6H-SiC Substrates

Ceria-coated silica (SiO2/CeO2) composite abrasives were prepared through a novel homogeneous precipitation method using commercial silica (SiO2) sol as the silicon resource and cerium nitrate (Ce(NO3)3) and hexamethylenetetramine (HMT) aqueous mixtures as coating precursors. The phase composition, nano-topography, size distribution, and chemical structure of as-prepared particles were characterized by X-ray diffraction, transmission electron microscopy, Zetasizer Nano ZS90 and Fourier infrared spectra. In addition, the possible coating mechanism was discussed. Then, chemical mechanical planarization behaviors of SiO2 sol, ceria (CeO2) sol, and the novel abrasives and on Si-face (0001) 6H-SiC were investigated by atomic force microscopy. The results indicated that the composite particles were mono-dispersed nano-spheres composed of amorphous SiO2 core and cubic fluorite CeO2 shell, possessing complete core–shell structure and particle size of about 110 nm. CeO2 shell (10 nm) grew on the surface of SiO2 core by formation of Ce–O–Si chemical bonds, forming stable core–shell structure. SiO2/CeO2 composite abrasives provided an exponentially high material remove rate (MRR) of 1207 nm h−1 and an impressive surface finish with roughness average (Ra) 0.216 nm due to its active chemical property and unique structure.

Activity Trends in the Propane Dehydrogenation Reaction Catalyzed by MIII Sites on an Amorphous SiO2 Model: A Theoretical Perspective

One class of particularly active catalysts for the Propane Dehydrogenation (PDH) reaction are well-defined M(III) sites on amorphous SiO2. In the present work, we focus on evaluating the catalytic trends of the PDH for four M(III) single-sites (Cr, Mo, Ga and In) on a realistic amorphous model of SiO2 using density functional theory-based calculations and the energetic span model. We considered a catalytic pathway spanned by three reaction steps taking place on selected MIII–O pair of the SiO2 model: σ-bond metathesis of propane on a MIII–O bond to form M-propyl and O–H group, a β-H transfer step forming M–H and propene, and the H–H coupling step producing H2 and regenerating the initial M–O bond. With the application of the energetic span model, we found that the calculated catalytic activity for Ga and Cr is comparable to the ones reported at the experimental level, enabling us to benchmark the model and the methodology used. Furthermore, results suggest that both In(III) and Mo(III) on SiO2 are potential active catalysts for PDH, provided they can be synthesized and are stable under PDH reaction conditions.