Range Of Characterization Techniques Research Articles

Microstructural development and tensile behavior of a hot isostatically pressed nickel-based superalloy

A powder nickel-based superalloy, FGH4096, was hot isostatically pressed at a super-solvus temperature. The microstructure of the as-fabricated sample was investigated by using a range of characterisation techniques and the properties evaluated by tensile testing. Prior particle boundaries (PPBs) decorated by near-continuous precipitates were observed throughout the sample. The PPB precipitates were identified to be face centred cubic (FCC) TiC through transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analysis. In addition to γ, γ′ and TiC, a new phase formed and homogeneously distributed within prior powder particles after HIPing. TEM analysis reveals that it is tetragonal CrMo2B2 or Cr3Mo3B4 [a = b = 5.825 Å, c = 3.115 Å, α = β = γ = 90°, space group = P4/mbm], both of which have the same crystallographic structure and lattice parameter. A great number of fine γ grains were found to form around PPBs and a high density of annealing twins were present throughout the as-HIPed sample, indicating that full recrystallization has happened during HIPing. With the presence of PPBs, the as-HIPed sample failed in an inter-particle de-bonding fracture mode but in a highly dimpled way, giving rise to both high strengths and good ductility at both room temperature and high temperature. Deformation happened by dislocation slipping through grains. Dislocations, however, did not cut through PPB precipitates but instead accumulated around these precipitates, which may have caused stress concentration along PPBs and eventually led to inter-particle de-bonding.

Thin‐film transistors based on wide bandgap Ga 2 O 3 films grown by aqueous‐solution spin‐coating method

Ga2O3 is a wide bandgap oxide semiconductor material with the bandgap value only second in magnitude to diamond among known semiconductors. As a wide-bandgap semiconductor, Ga2O3 has emerged as a new competitor to silicon carbide and III-nitrides in various applications of ultraviolet optoelectronics and high power electronics. However, almost all the devices are based on the Ga2O3 grown by molecular-beam epitaxy or chemical vapour deposition, which is time-consuming and expensive. In this work, the authors report on thin-film transistors based on wide bandgap Ga2O3 films grown by aqueous-solution spin-coating method. The morphological, optical and electrical properties of the films and devices are investigated using a range of characterisation techniques, whilst the effects of post-deposition annealing are also investigated. Both as fabricated and post-annealed Ga2O3 films are found to be very smooth and exhibit wide energy bandgaps of around 4.8 and 4.9 eV, respectively. Thin-film transistors based on the grown Ga2O3 films show n-type conductivity with the maximum electron mobility of 0.1 cm2/Vs.

The synthesis of SmCo/Co nanoplates: reductant effect in the synthesis process

In search for improvement in synthesizing the nanoparticles, specifically for rare earth-transition metals (Re-Tm), Pechini method was employed followed by thermal oxidation process. The SmCo nanoplates were formed due to a reduction–diffusion phenomenon. A range of characterization techniques including XRD, FE-SEM, and VSM were used for further investigations. Hard phases of SmCo5 and Sm2Co17 were obtained by adjusting the ratios of the solutes. The presence of cobalt, as the soft phase along with SmCo, as well as the single-phase behavior of magnetic hysteresis loop together with the high remanence ratio of the synthesized nanoplates, confirmed the hard–soft exchange coupling interaction. The data also indicated that hydrogen was not sufficient to act as a reducing agent; significant amount of CaH2 was added to the mixture. The quantity of CaH2 and consequently its weight ratio to the oxide powder had an effect on the synthesis process and final products in different aspects, including the evolution, microstructure, morphology, and magnetic properties. Eventually, when the weight ratio CaH2/oxide powder was kept at 2:1 the SmCo5 was the dominant phase of the nanoplates; whereas, for the 3:1 mixture, Sm2Co17 was the prominent, containing distinguishable nanoplates of Sm2Co17/Co with the average thickness of 32 nm.

The Effect of Reduction Process Parameters on Magnetic and Structural Properties of SmCo/Co Nanocomposites

SmCo nanoplates were synthesized by a combination of Pechini type sol-gel method and reduction-diffusion process. The synthesis process started with (i) preparation of Sm-Co citrate gel, (ii) followed by annealing to obtain Sm-Co oxide powder and (iii) reduction of the powder by CaH2 at different temperatures of 870, 890, 910, 930, 950, and 970 °C for 3 h under hydrogen flow and (iv) separation of the magnetic nanoparticles through a multi-step washing process. A range of characterization techniques including XRD, TG-DTA, FE-SEM, and VSM were employed to investigate the effect of reduction temperature in terms of phase, morphology, microstructure, and magnetic properties of products. The results showed that the SmCo/Co nanocomposites were synthesized at all reduction temperatures of 870–970 °C, but by temperature increase from 930 to 950 °C, the dominant phase turned into SmCo5; the superior phase was Sm2Co17 before this step. The TG/DTA analysis indicated that at reduction temperature of 950 °C and higher, the Sm2Co17 phase is formed at the beginning, then releasing more Sm atoms results in the phase transformation to SmCo5. Meanwhile, after the temperature of 930 °C, the particle’s morphology was also changed from the nanoplates and turned into lumps. Reduced particles at 910 °C, had a maximum coercivity of 881 Oe, and the highest amount of remanence ratio (78%). However, in this sample, in spite of the presence of cobalt, as the soft phase along with SmCo, the magnetic hysteresis loop behaved like a single-phase and it proposed the hard-soft exchange coupling interaction. SmCo/Co nanocomposites were synthesized via Pechini type sol-gel method followed by reduction-diffusion process. By increasing the temperature, the dominant phase changes to SmCo5 due to the formation of excessive amount of Sm atoms. By raising reduction temperature from 930 to 950 °C, the morphology of particles changed from nanoplates to lumps. Magnetic single phase behavior as well as high remanence ratio of samples proposed the existence of exchange coupling interaction between hard and soft phases of SmCo/Co nanocomposites.

Development of a Refractory Hexagonal Closed Packed High Entropy Alloy Based on Thin Film Screening

In order to identify candidate high entropy alloys (HEAs) that have the hexagonal closed packed crystal structure, gradient thin films in the OsRuWMoRe system were deposited by sputtering from multiple elemental targets onto Si substrates. In addition to having compositional gradients, the films exhibited regions with different phases, some of which were single-phase and non-equiatomic. Such alloys have the potential to exhibit properties superior to the primarily equiatomic HEAs that have been the focus of most work in this area. To screen the phases that exist across the thin film gradient samples, a range of characterization techniques were employed, including focused ion beam and scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray diffraction and electron backscattered diffraction analysis. The combinatorial method described in this study enabled the identification of a candidate single-phase HEA that was subsequently fabricated as a bulk alloy.

On the solidification behaviour and cracking origin of a nickel-based superalloy during selective laser melting

Inconel 738LC samples were fabricated by selective laser melting (SLM) using different laser powers and scanning speeds and investigated using a range of characterisation techniques. High melting point Al-, Si- and W-based oxide particles and γ cellular structure were observed in the as-fabricated samples, implying that the solidification of the alloy melt during SLM may have started with preferential nucleation of oxide particles, followed by the widespread nucleation and growth of γ cellular structure. Cracks in the as-fabricated samples are associated with pores, or Al-, Si- and W-based oxide particles and small grains along some large grain boundaries (GBs). Those pores with sharp corners or rugged inner surfaces are particularly prone to cracking development during SLM. Most of the cracks were developed at γ grain-oxide interfaces or along the central line of oxide clusters, which is attributed to solidification contraction and thermal shrinkage of the grains that are associated with oxides. Nano-indentation tests show that Si/W/O-rich GB regions demonstrate a significantly higher hardness as compared with γ matrix, indicating that the segregation of Si, W and O has caused embrittlement to the GBs. Large misorientation was observed between grains (large or small) that are either associated with cracks or not, suggesting that large grain misorientation does not inevitably lead to cracking development in the current material. Small grains present along large grain boundaries were found to act as crack initiation sites or affect crack propagation path.

Lipid-based siRNA Nanodelivery Systems: A Learning Process for Improving Transfer from Concepts to Clinical Applications.

The molecular mechanism of silencing genes using small interference RNA is as particular and innovative phenomenon as the proposed delivery systems to release them. Recent advances in RNAi have resulted in the development of multiple siRNA candidates that are currently being evaluated in preclinical / clinical instances. SNALP®, Atuplex® and Rondel® technologies stand out; they are mainly based on polymers, cyclodextrins or lipids. The objective of this work is to review the main features that Gene Therapy Medicinal Product under current clinical evaluation present from a pharmaceutical technology point of view; it tries to bring up theoretical concepts that give scientific support to the interpretation of data obtained during pharmaceutical development process. It is basically focused on improving the translation from bench/theoretical concepts to bedside of non viral vectors carrying siRNA. The extensive presence of lipid-based nanoparticle non-viral systems in clinical stages is due to the advantages of their formulations. These include: safety, low immunogenicity, high degree of material properties control, function tuning and ability to impact pharmacokinetics and in vivo biodistribution. This work presents a pharmaceutical approach so as to improve the potential of success in siRNA delivery using liposomal systems. Formulation design should be increasingly addressed with industrial criteria; it should be based on quality by design and on the estimation of critical attributes that affect product performance, and supported by a range of characterization techniques and appropriate analytical methods.

A green and low-cost synthetic approach based on deep eutectic choline-urea solvent toward synthesis of CZTS thin films

In this paper, a new, simple, and sustainable method of the Cu2ZnSnS4 (CZTS) thin-film synthesis is presented. The CZTS films have been electrochemically deposited by a single-step electrodeposition from deep eutectic (choline-urea) electrolyte, without sulfurization step, onto fluorine-doped tin oxide (FTO)-coated glass substrates. − 1.3 V/SCE has been selected as the optimum deposition potentials to grow the CZTS thin films. As-deposited CZTS films were characterized using a range of characterization techniques to study the structural, morphological, and compositional properties and confirmed the presence of the Cu2ZnSnS4 phases. The direct band gap energy for the CZTS thin films is found to be about 1.48 eV.

Mechanistic aspects for the removal of Congo red dye from aqueous media through adsorption over N-doped graphene oxide nanoadsorbents prepared from graphite flakes and powders

This work reports the mechanistic models responsible for the adsorptive removal of Congo red (CR) dye molecules by nitrogen-doped graphene oxide nanosheets (NGO) prepared via a one-pot modified Hummer's method using either graphite powder (to form NGOp) or graphite flakes (to form NGOf) as starting materials. The microstructural properties, surface chemistry and thermal stability of the produced NGO adsorbents were ascertained using a range of characterization techniques. The effects of adsorbent dosage, CR dye initial concentration, contact time and solution pH on the removal of CR dye were studied. The NGO adsorption process was highly dependent on initial dye concentration, contact time, adsorbent dosage, pH, NGO surface area and nanosheet size. The NGOp nanoadsorbents exhibited excellent selectivity towards the removal of CR dye molecules than NGOf. NGOp adsorbents achieved maximum removal efficiency of 98–99% at a pH of 2 compared to NGOf that achieved 96–98%. The adsorption kinetics and isotherms for CR dye on the NGO adsorbents were well fitted to the pseudo second-order kinetic model. The Langmuir isotherm model indicated that the adsorption behavior occurred via chemisorption and in a homogeneous monolayer on the surface of NGO. Our findings suggest that the adsorption mechanism involved was due to electrostatic interactions between the negatively charged (oxygen-containing) and positively charged (nitrogen-containing) groups on the NGO adsorbents and the positively charged (amino and cationic azo-linkages) and negatively charged (sulfonic (SO3−)) groups on the anionic CR dye molecules. The electrostatic interactions between oxygen and nitrogen containing functional groups present on the NGO surface and functional moieties of CR molecules are necessary for the enhancement of CR adsorption over NGO surface (based on the existing pH dependence). NGOp nanosheets have shown to have higher removal potential and adsorption capacity toward CR dye compared to undoped GO and NGOf adsorbents. In particular, this work indicates that NGOp can serve as good adsorbents in the removal of anionic dyes in wastewater treatment processes.

Preparation of polymers of intrinsic microporosity composite membranes incorporated with modified nano‐fumed silica for butanol separation

AbstractIn this work, the modified nano‐fumed silica particles (MNFS) as fillers were incorporated into the polymer of intrinsic microporosity (PIM‐1) matrix to fabricate composite membranes for removing butanol from water. A range of characterization techniques was employed to analyze the properties and pervaporation (PV) performances of the composite membranes. It was found that the addition of MNFS into the PIM‐1 matrix dramatically decreased the swelling degree as compared to pure PIM‐1, implying an increment of the stability of separation performances. Moreover, the PV performances of the composite membranes were significantly enhanced, and the superior PV performances were on account of the following reasons: there was a good compatibility between PIM‐1 and MNFS; and the incorporation of MNFS improved the hydrophobicity of the membranes and disrupted the packing of polymer chains, therefore providing special channels for rapid transport of butanol molecules.

Development of highly selective PdZn/CeO2 and Ca-doped PdZn/CeO2 catalysts for methanol synthesis from CO2 hydrogenation

Effect of Pd, Zn, PdZn alloy and Ca-doped PdZn on CeO2 for CO2 hydrogenation to methanol was investigated. CeO2-supported PdZn and Ca-doped PdZn nanoparticles (NPs) proved to be highly selective, fairly active and quite stable for CH3OH synthesis at reasonably low temperature conditions. In the case of Ca-doped PdZn/ CeO2, methanol selectivity of ∼100% was achieved at low temperature (T = 220 °C, P = 30 bar and GHSV = 2400 mL g−1h−1) with reasonable CO2 conversion (7.7%). CeO2-supported PdZn nanoparticles (NPs) (3–6 nm, measured from HR-TEM) were successfully prepared by the chelating method using citric acid as a chelating agent. The developed catalysts were investigated using a range of characterization techniques (BET, CO-Chemisorption, CO2-TPD, H2-TPR, XRD, XPS, STEM-EDS and HR-TEM). XPS results revealed the presence of Ce+3 ions implying the generation of oxygen-vacant sites over the surface of CeO2-supported catalysts which aided in increased CO2 dissociation resulting in higher methanol rates. An in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) study was also carried out for the best performing catalyst at actual reaction conditions to determine the intermediate species and a probable reaction mechanism. Characterization results revealed the significance of CeO2 interaction with PdZn nanoparticles for selective CH3OH formation over ceria-supported PdZn nanoparticles. Addition of Ca, to the CeO2-supported PdZn catalysts, as a promoter, slightly improved the selective conversion of CO2 to methanol by raising the amount of oxygen-vacant sites as revealed by XPS results. DRIFT studies revealed the emergence of monodentate, bidentate formates, CH2O and methoxy species and their subsequent conversion to methanol and CO, steering the reaction mechanism towards formate route for selective formation of methanol.

A comprehensive investigation of refinery preheaters foulant samples originated by heavy crude oil fractions as heating fluids

A deep understanding of the mechanisms responsible for fouling from both crude oils and their fractions is paramount to ensure efficient energy recovery in heat exchangers of crude preheat trains. In this work, seven samples of fouling deposits, carefully collected from a number of refinery heat exchangers processing vacuum gas oil (VGO) and vacuum bottom (VB) streams in an atmospheric crude preheat train were investigated using a range of characterization techniques with the aim of identifying the underlying mechanisms that led to deposition. Characterization of the deposits included morphological and physical examination, fractionating solubility test, Scanning Electron Microscopy-Energy Dispersive X-ray, Combustion Analysis and X-ray Diffraction. In all samples examined, more than 75 wt% of the deposits were identified as inorganic, with about 50 wt% being FeS. At 270–300 °C, FeO(OH) was also identified to be deposited on the tube surfaces made in Cr steel alloy, where more fouling and less corrosion were evident compared to carbon steel (CS). These observations were found in agreement with recent laboratory studies aimed at identifying the role of temperature and tube material in petroleum corrosion. Furthermore, sulphur crystals were found in several VGO fouling samples. Based on the experimental results obtained, a mechanism was proposed to explain the corrosion fouling phenomenon, considered to be the underlying mechanism affecting the refinery. The mechanism involves naphthenic acid attack to the tubes’ metal surface, decomposition of iron naphthenate, disproportion of iron oxide and sulphidation reactions. The results highlighted the importance of studying deposits formed under industrial conditions, timescales and variation of the deposition process, evidenced by the deposit characteristics, along extensive heat exchanger networks.

Facile synthesis of porous dendritic Pt68Ag32 nanodandelions for greatly boosting electrocatalytic activity towards oxygen reduction and hydrogen evolution

Contrary to single counterparts, Pt-based bimetallic nanocrystals are attractive and feasible to decrease the cost, improve the catalytic activity and enhance the stability via morphology-, structure- and composition-engineering. Herein, porous dendritic alloyed Pt68Ag32 nanodandelions (NDs) were synthesized by a one-pot successive co-reduction method, using amrinone as the new stabilizer and structure director, without any template, seed or complicated instrument. The correlative shapes, composition, and crystalline structure were examined by a range of characterization techniques. It is found that the molar ratio of the precursors (AgNO3 and H2PtCl6), the dosage of amrinone, and different reductants play the essential roles during the synthesis process. The Pt68Ag32 NDs exhibited dramatically enlarged electrochemically active surface area, enhanced catalytic activity and stability for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) as compared to commercial Pt/C, Pt black, home-made Pt75Ag25 nanocrystals (NCs) and Pt56Ag44 NCs catalysts.

Rapid Thermal Processed CuInSe2 Layers Prepared by Electrochemical Route for Photovoltaic Applications

Impact of rapid thermal (RT) annealing and normal selenization process on the properties of CuInSe2 (CIS) layers prepared by electrochemical route is reported. Cyclic voltammetric measurement was carried out to optimize the co-deposition potentials. A range of characterization techniques were employed to study the properties. Three prominent reflections(112),(204/220) and (312/116) of tetragonal CIS were exhibited in as-deposited CIS layers. Upon selenization, the crystallinity was found to be improved. Uniform, compact, densely packed surface morphology was observed in as-prepared sample. Large grains are developed upon RT annealing due to recrystallization. Elemental composition obtained by EDAX confirms the growth of stoichiometric layers. Photo-electrochemical study demonstrates the p-type conductivity. Current-voltage, capacitance-voltage, electrochemical impedance spectroscopy were conducted to investigate the influence of the grain size and crystallinity on electrical properties. Energy band-gap estimated from absorption spectra were 1.18, 1.04 and 0.98 eV for as-deposited, selenized, RT annealed samples, respectively. X-ray Photoelectron spectroscopy confirms the presence of Cu+, In3+ and Se2− oxidation states in all CIS layers. Power conversion efficiency of 3.05% and 5.94% were achieved for selenized and RT annealed samples, respectively. The improved efficiency measured for RT annealed sample is proposed due to the growth of highly crystalline, large grain and compact surface morphology.

Characterization of a low-grade copper-sulphide ore to assess its suitability for in situ recovery

CSIRO Minerals is developing new technologies and approaches for the in situ recovery (ISR) of valuable metals. ISR provides opportunities to process small and/or deep deposits and could create additional revenue for conventional uneconomic mines. Unlike for conventional processing, no standard methodology exists for characterizing sample suitability for ISR. The authors are developing a workflow to understand sample and deposit amenability to ISR processing. A South Australian low-grade iron-oxide-copper-gold sulphide ore was studied. A total of 37 drill cores samples were obtained from the ore sample for detailed mineralogical and leaching characterization. A range of characterization techniques including chemical analysis, X-ray fluorescence mapping, quantitative evaluation of minerals by scanning electron microscopy, computed tomography scanning, and bulk- and micro-X-ray diffraction analyses were applied to understand the ore mineralogy. Leaching tests at 50 °C were performed on selected samples to understanding their leaching behaviour. Mineralogical characterization found that copper was present mostly as discrete secondary copper sulphides distributed in various areas and at various specimen depths, which, in theory should be readily available for leaching, provided sufficient solution access exists. Leaching results showed steady copper recovery under the conditions tested. This study provides insight into understanding the suitability of an ore for ISR processing.

Thermal conductivity, morphology and mechanical properties for thermally reduced graphite oxide-filled ethylene vinylacetate copolymers

Systematic variation of copolymers (Poly (ethylene-covinylacetate)) composition provide an opportunity to change matrix polarities and thus explore their effects on the polymer/filler interactions and composite properties. The main objective of this work is to study the effect of vinyl acetate (VA) content on the extent of exfoliation and dispersion of thermally reduced graphite oxide (TrGO), as well as its impact on the thermal conductivity and mechanical properties of the resultant composites. The use of ethylene vinyl-acetate (EVA) copolymers of different (0–40 wt%) vinyl acetate content with similar melt viscosities allowed us to keep the processing conditions constant and quantitatively compare the thermal conductivity and mechanical properties of composites with different matrix polarities. Composites with conductive graphite (GT) and multiwalled carbon nanotubes (MWCNT) were also prepared and examined for comparison. Melt dispersion of TrGO in EVA copolymers was quantified using a range of characterization techniques: transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray scattering measurements. Electron microscopy and X-ray diffraction revealed highly exfoliated morphology of TrGO throughout the entire matrix, while GT remained multi-layer even after melt processing. Nanocomposites reinforced with TrGO showed significantly improved thermal conductivities and mechanical properties combined with low rheological percolation thresholds comparable to those achieved using MWCNT and GT. We propose a formalism to assess the thermal conductivity and mechanical properties of graphene nanocomposites based upon the interfacial excess energies of EVA copolymers.

Microwave treatment of electric arc furnace dust with Tetrabromobisphenol A: Dielectric characterization and pyrolysis-leaching

In the present work microwave treatment of electric arc furnace dust (EAFD) mixed with tetrabromobisphenol A (TBBPA) was investigated. A range of characterization techniques were used to understand the thermal behavior of TBBPA-EAFD mixtures under microwave pyrolysis conditions. Dielectric and thermal properties of EAFD, TBBPA and their mixtures were determined. Both the dielectric constant and loss factor of the mixture were found to vary considerably with temperature and subsequently it was found that the mixtures of these materials absorbed microwaves effectively, especially at temperatures above 170°C. The high loss tangent of EAFD-TBBPA mixture above 170°C resulted in fast heating and high temperatures (above 700°C) resulting in reduction of Fe, Pb and Zn to their metallic form. This resulted in low recoveries of both Zn and Pb when the residue was leached in water. The recovery of Zn varied between 14 and 52wt,%, while Pb recovery varied between 3 and 31wt.% depending on microwave treatment efficiency. The low recovery of Zn and Pb could be ascribed by the reduction of metal oxides into their metallic form. More importantly this work has shown great selectivity in the leachability of both zinc and iron; with iron being left in the solid residue.

Hardystonite-diopside nanocomposite scaffolds for bone tissue engineering applications

A bioactive hardystonite (HT) - diopside (Dio) Nano-composite scaffold was fabricated by the space holder method. The structure, morphology and bioactivity potential of the Nano-composite scaffolds were examined using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The scaffold with optimized mechanical properties was HT-15 wt%Dio that had a total, interconnected porosity, micro and macro pore size of 77 ± 1%, 71 ± 1%, 40–80 μm and 400–500 μm, respectively, and a compressive modulus and strength and crystallite size of 45.45 MPa, 1.655 MPa and 41 nm, respectively. The feasibility of the produced scaffold for bone tissue engineering application was evaluated using simulated body fluid (SBF). A range of characterization techniques was applied to confirm the deposition of Hydroxyl carbonated apatite (HCA) deposition on the surface of HT-15%Dio scaffold following 7 days in SBF. Overall, results suggest that HT-15 wt%Dio Nano-composite scaffold with improved mechanical properties, pore size, porosity content and apatite formation ability can be a promising candidate for bone tissue engineering applications.

Particle Characterisation and Depletion of Li2CO3 Inhibitor in a Polyurethane Coating

The distribution and chemical composition of inorganic components of a corrosion-inhibiting primer based on polyurethane is determined using a range of characterisation techniques. The primer consists of a Li2CO3 inhibitor phase, along with other inorganic phases including TiO2, BaSO4 and Mg-(hydr)oxide. The characterisation techniques included particle induced X-ray and γ-ray emission spectroscopies (PIXE and PIGE, respectively) on a nuclear microprobe, as well as SEM/EDS hyperspectral mapping. Of the techniques used, only PIGE was able to directly map the Li distribution, although the distribution of Li2CO3 particles could be inferred from SEM through using backscatter contrast and EDS. Characterisation was also performed on a primer coating that had undergone leaching in a neutral salt spray test for 500 h. Overall, it was found that Li2CO3 leaching resulted in a uniform depletion zone near the surface, but also much deeper local depletion, which is thought to be due to the dissolution of clusters of Li2CO3 particles that were connected to the external surface/electrolyte interface.

Transfer Dehydrogenation of 1-Phenylethanol Over Pd/C Under Mild Conditions: Effect of Reaction Conditions and Optimization of Catalytic Performance

The catalytic activity of 5 wt% Pd/C has been evaluated using the liquid phase transfer dehydrogenation of 1-phenylethanol as a model reaction. The reaction parameters such as catalyst loading and stirring rate have been optimized to determine the required conditions to carry out the reaction under kinetic regime control. By performing the reaction under different temperatures, the value of apparent activation energy has been determined as being 61 kJ/mol. Furthermore, the influence of thermal treatment of 5 wt% Pd/C catalyst on its catalytic performance for the liquid phase transfer dehydrogenation of 1-phenylethanol has been investigated in a temperature range of 110–200 °C. The results reveal that the catalyst activity is strongly dependent on the ratio between Pd/PdO species. The fresh and used catalysts were characterized using a range of characterization techniques (XRPD, XPS, TEM, SEM-EDX, and BET) in order to investigate structure–activity relationships. The 5 wt% Pd/C exhibit high conversion (90%) and selectivity (91%) toward acetophenone under mild conditions. Moreover, the reusability tests have been carried out, and the results show that the catalyst preserves 80% of its initial catalytic activity after five cycles indicating the high stability of the 5 wt% Pd/C catalyst in the liquid phase transfer dehydrogenation of 1-phenylethanol. The influence of reaction conditions on the catalytic activity is also discussed.