Varying Al Content Research Articles

Effect of Al content on mechanical properties and corrosion performance of novel Fe-Cr-Al alloy steels in a CO2-O2 coexistence environment

The present study involved preparing five novel Fe-Cr-Al alloy steels with varying Al content based on commercially available 3Cr steel. The effect of Al content on the mechanical properties and corrosion performance in a CO2-O2 coexistence environment was investigated in novel Fe-3Cr-(0–2.5)Al alloy steels, and the microhardness, impact, and tensile properties were measured and compared. The corrosion rate, corrosion product film, and corrosion mechanism were studied using a weight-loss method, microscopic characterization, and electrochemical tests. The results showed that the tensile and impact properties of Fe-Cr-Al alloy steels exhibited a decreasing trend with increasing Al content. No localized corrosion was observed at an Al content of 2 wt%, attributed to the formation of a dense amorphous corrosion product film on the material surface and pre-passivation. Among the alloy steels examined in this study, the 3Cr2Al alloy steel exhibited the most optimal balance between mechanical properties and corrosion resistance.

Optical absorption coefficient of a hydrogenic impurity in a surface quantum well

In this study, the first excited state binding energy and the linear, non-linear and total optical absorption coefficients (OAC) of a hydrogenic impurity in a surface quantum well (SQW) of the type vacuum/GaAs/AlxGa1-xAs are calculated as functions of the incident photon energy, the Al content and the well width using a variational method within the effective mass approximation. The results show that the first excited state energy and the linear, non-linear and total OAC are strongly influenced by variations in the well width, and only a slight, yet interesting, impact of the Al content is observed. A redshift in the extreme values of the linear, non-linear and total OAC is found for a SQW with fixed Al content and variable width, whereas no significant variation is observed in the reciprocal system of fixed width and variable Al content.

Effect of Al doping on structural and optical properties of atomic layer deposited ZnO thin films

In this work, zinc oxide (ZnO) and aluminum-doped ZnO (AZO) thin films with varying Al contents were grown via atomic layer deposition on Si and glass substrates. The structural and optical properties of ZnO and AZO thin films were investigated using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), photoluminescence (PL), and ultraviolet-visible spectroscopy. While undoped ZnO had a wurtzite crystal structure, Al2O3 layers altered the crystal structure depending on the Al content. With the increasing number of Al2O3 monolayers, the γ- Al2O3 structure became more prominent, and ZnO peaks were completely suppressed when the Zn ratio reached 10:1 and beyond. SEM images revealed that the thin films homogeneously covered the entire substrate surface. EDS mapping showed a uniform distribution of Zn, Al, and O in the structure. According to the XPS results, the thin films displayed significant peak intensities corresponding to the main components Zn, O, and Al. Zinc atoms were present only in their oxidized state, not as interstitial atoms. The O 1 s peak could be deconvoluted into three components: the oxygen-zinc bond, the oxygen-aluminum bond, and chemisorbed or OH species. In the AZO samples, a direct correlation was observed between the intensity of the Al 2p peak and the number of Al2O3 layers. Additionally, the calculated elemental ratio of Al increased from 2.582 to 23.955 at.% with more Al2O3 layers. Optical measurements revealed that ZnO and AZO thin films exhibit high transmittance in the visible region. Moreover, introducing Al2O3 layers into the supercycle led to an increasing trend in transmittance. Another improvement in the optical properties was observed as a blue shift in the absorption edge with Al doping, indicating band gap widening. The optical band gap of the ZnO thin films increased from 3.2 to 3.5 eV with Al doping. The origin and concentration of defects were evaluated by deconvoluting the PL spectra. A comparative investigation of the PL spectrum and XPS results revealed variations in defect concentration with deposition parameters and defect formation mechanism was discussed.

Component regulation and high-entropy engineering for enhanced antioxidant and high-temperature mechanical properties of protective films

Transition metal nitrides (TMNs) have gained widespread application in protecting structural components due to their high strength and hardness. However, TMNs still have the challenge of structural instability and mechanical deterioration caused by oxidation under harsh high temperature conditions. Herein, we present a strategy combining component regulation with high-entropy engineering to develop an advanced high-temperature Al-containing high-entropy nitrides (HENs) material. To prevent the phase decomposition of AlN within the (NbMoTaWAl)N, theoretical simulations were employed to determine a critical atomic percent of 25.0% Al for maintaining the stability of the high-entropy structure. Ensuing experimental synthesis creates three NbMoTaWAlN films with varying Al content: a high-entropy film with 0.0% Al (HEN), a high-entropy film with 21.2% Al (HEN-Al), and an amorphous transition metal nitride film with 30.2% Al (a-TMN-Al), validating key high-entropy engineering benchmarks. It is found that the unique HEN-Al film exhibits excellent oxidation resistance and high-temperature hardness, attributed to the uniform distribution of Al atoms in the robust high-entropy structure, which creates conditions for forming a dense and continuous Al2O3 barrier layer, effectively hindering the diffusion of oxygen into the film interior. This study provides new insights to develop a new generation of high-temperature protective materials.

High P-T phase relations of Al-bearing magnetite: Post-spinel phases as indicators for P-T conditions of formation of natural samples

Abstract The phase relations of Al-bearing magnetite were investigated between 6–22 GPa and 1000–1550 °C using a multi-anvil apparatus. This study demonstrates that the spinel-structured phase persists up to ~9–10 GPa at 1100–1400 °C irrespective of the amount of hercynite (FeAl2O4) component present (20, 40, or 60 mol%). At ~10 GPa, the assemblage Fe2(Al,Fe)2O5 + (Al,Fe)2O3 forms and remains stable up to 16–20 GPa and 1200–1550 °C. Fe2(Al,Fe)2O5 adopts the CaFe3O5-type structure with the Cmcm space group. At 18–22 GPa and T >1300 °C the assemblage Fe3(Fe,Al)4O9 + (Al,Fe)2O3 becomes stable. Fe3(Fe,Al)4O9 is isostructural with Fe7O9, having the monoclinic structure of the C2/m space group. At T <1300 °C, Fe3(Fe,Al)4O9 + (Al,Fe)2O3 gives way to the assemblage of a hp-Fe(Fe,Al)2O4 + (Al,Fe)2O3. This hp-Fe(Fe,Al)2O4 phase is unquenchable; a defect-bearing spinel-structured phase was recovered instead, and it contained numerous lamellae parallel to {100} or {113} planes and notably less Al than the initial starting composition. While low-pressure spinel can have a complete solid solution between Fe3+-Al, the post-spinel phases have only very limited Al solubility, with a maximum of ~0.1 cpfu Al in hp-Fe(Fe,Al)2O4, ~0.3 cpfu in Fe2(Fe,Al)2O5, and ~0.4 cpfu in Fe3(Fe,Al)4O9, respectively. As a result, the phase relations of Fe(Fe0.8Al0.2)2O4 can also be applied to bulk compositions richer in Al with the only difference being that larger amounts of an (Al,Fe)2O3 phase are present. Coexisting rhombohedral-structured phases demonstrate that the binary miscibility gap established at low pressure between hematite and corundum is still valid up to 20 GPa. Since iron oxides (e.g., magnetite) with variable Al contents are found in extraterrestrial rocks or as inclusions in diamond, constraints on their high-P-T-fO2 stability might help unravel their formation conditions.

Effect of lateral inhomogeneous AlGaN barrier layer on electronic properties of GaN HEMTs

In this study, an AlGaN/GaN high electron mobility transistor with lateral inhomogeneous AlGaN barrier layer (LI-AlGaN HEMT) is proposed and studied systematically. The LI-AlGaN HEMT comprises three AlGaN regions with varying Al content, connected to the source, gate, and drain, respectively. With the increase of Al content in each region, the saturation current of the LI-AlGaN HEMT increases gradually, while the on-resistance (Ron) and breakdown voltage (BV) decrease. The threshold voltage (Vth) of the LI-AlGaN HEMT depends only on the Al content of AlGaN beneath the gate. By introducing the source field plate (FP), the calculated output current of the conventional FP-HEMT is consistent with the experimental data. After optimizing Al content, the LI-AlGaN FP-HEMT has the same Vth compared with conventional FP-HEMT. However, the saturation current is increased by approximately 20 % and the Ron is decreased by approximately 30 %. Additionally, the BV is increased to 1008 V. So the optimized lateral inhomogeneous AlGaN HEMT has better DC characteristics and is suitable for high power GaN device applications.

Enhancing sputtered GaN/Si film quality by adding AlGaN buffer layer in a continuous deposition process

In this work we demonstrate the achievement of significative improvements in the structural and morphological quality of wurtzite GaN films (approximately 250 nm thick) by introducing an initial growth step involving an AlGaN buffer layer on p-type Si (100) substrates through a continuous reactive sputtering process. We investigated the influence of using single and multiple AlxGa1-xN buffer layers with varying Al content (x ranging from 0.07 to 0.37) and different thicknesses (from 166 nm to 1 µm). The obtained samples underwent characterization through X-ray diffraction and scanning electron microscopy. The results reveal a slight increase in the c-axis preferred growth direction and grain sizes even with a single and thin (250 nm) Al0.07Ga0.93N buffer layer. Conversely, the use of a single Al0.37Ga0.63N buffer layer led to significant morphological changes and a remarkable improvement in the c-axis preferred orientation. The most favorable outcomes were observed with the implementation of a triple AlGaN buffer layer, featuring decreasing Al content from the substrate, indicating the attainment of a high-quality GaN top layer comparable to epitaxial GaN.

Effect of Al content on in-situ formation of Al2O3 protective layer on Ni-Al coatings in high-temperature chloride molten salt

The microstructure, strength, toughness, and resistance to chloride molten salt corrosion of Ni-Al coatings with varying Al content were investigated. Increasing the Al content from 9.9 to 61.1 at.% resulted in a decrease in adhesion strength and toughness, while an increase in corrosion rate. Contrary to previous reports, it is noteworthy that Ni-Al coatings with the lowest Al content exhibited superior resistance corrosion due to the formation of an oxidation layer which effectively blocked corrosion. This protective layer was primarily in-situ formed through the reaction between crystalline water present in the molten salt and an appropriate amount of Al. The balance between Al and O content is precisely regulated, resulting in the in-situ formation of Al2O3 protective.

Crystal chemistry and molar volume of potassic-chloro-hastingsite

Abstract. Several geological processes such as crustal and mantle metasomatism, high-grade metamorphism, and the formation of ore deposits involve the exchange of halogens, especially chlorine, between silicate minerals and fluids. It is well established that the presence of octahedral iron is vital to the process of Cl incorporation into amphiboles. However, other compositional controls on Cl incorporation, such as the effect of TAl, ANa, AK, and A-site occupancy are not as well constrained. This study reports on the compositional and structural relationships amongst a suite of 25 synthetic calcium amphiboles with a diverse range of Cl contents (0–1.68 atoms per formula unit (apfu)). Most amphiboles were synthesized along the potassic-hastingsite–potassic-chloro-hastingsite join (KCa2(Fe4Fe3+)(Al2Si6)O22(OH,Cl)2). Additional work involved substitution of Na for K, variable Al content, and substitution of Mg for Fe2+ in the bulk composition to explore these compositional effects on Cl incorporation. The relationship between pressure and the Cl content of amphiboles was also explored over the pressure range 0.3–2.0 GPa. Otherwise, synthesis conditions were 700 °C and 0.3 GPa with fO2 near Ni–NiO. Iron (II) chloride was used as the source of Cl. Some experiments used variably concentrated FeCl2 brines (0–100 molal), while others were nominally anhydrous, containing only the water absorbed by the hygroscopic FeCl2. All amphiboles were characterized by Rietveld refinements of powder X-ray diffraction patterns, electron microprobe analysis, and Mössbauer spectroscopy, the latter to determine Fe3+ fraction. This study finds a positive relationship between pressure and the Cl content of the amphibole. Both Fe2+ and Fe3+ are positively correlated with Cl among amphiboles with variable Fe#, but the correlation is poor to nonexistent for Mg-free amphiboles. Results indicate that the substitution of CFe2+,3+ for CMg and CFe2+,3+ for CAl facilitate Cl incorporation, with the former having a larger effect. The A-site occupancy is positively correlated with Cl in all amphiboles except those synthesized in dilute FeCl2 brines (≤ 6 m), which are negatively correlated. No correlation is observed between the Cl content of the amphibole and either the species of A cation (K vs. Na) or TAl. The composition vs. unit cell parameter data were analyzed using multivariate linear regression to better understand the process of Cl incorporation and to predict the molar volume of endmember chloro-amphiboles. The regression indicates an expansion of 0.181 Å (0.99 %) and 0.048 Å (0.90 %) along the b and c edges respectively, a reduction in β by 0.76° (0.72 %), and a contraction of 0.060 Å (0.59 %) along a when fully substituting Cl for OH in potassic-hastingsite. The multivariate linear regression equations allow the prediction of molar volumes for select endmember chloro-amphiboles, such as potassic-chloro-hastingsite = 964.63 ± 1.29 Å3 or 290.5 ± 0.4 cm3 mol−1.

Performance assessment of aluminum chips in reduced-scale friction for developing copper-free elastomer-modified friction composites

This research paper investigates the frictional and thermomechanical properties of a copper (Cu) free non-asbestos organic (NAO) composite for developing brake friction material for automotive/railway applications. Reduced-scale brake composites were manufactured and tested in a pin on disc tribometer. The effect of aluminum (Al) chips on the dry sliding wear behavior of acrylonitrile-butadiene rubber (NBR) modified phenolic resin-based reduced-scale friction composites was investigated. Other common ingredients of friction materials like fiber, filler, and friction modifiers were not included to get the specific effect of Al on the various properties of the composites. Four composites were prepared with varying Al content, for example, 25, 50, 75, and 100 phr (parts per hundred resins). The average COF increases by ∼70% for 75 phr Al loaded composite (optimum composition) compared to the base composite (devoid of Al). However, mechanical properties, such as hardness and flexure strength, decrease with increasing phr of Al, although compressive strength does not change significantly. The optimum composite exhibits the lowest specific wear rate among Al chips loaded composites. The optimum composite also shows nearly three times improvement in thermal conductivity compared to the base composite. The wear behavior of the composites has been analyzed from the scanning electron microscopy (SEM) images.

Room temperature two-dimensional electron gas scattering time, effective mass, and mobility parameters in AlxGa1−xN/GaN heterostructures (0.07 ≤ x ≤ 0.42)

AlxGa1−xN/GaN high-electron-mobility transistor (HEMT) structures are key components in electronic devices operating at gigahertz or higher frequencies. In order to optimize such HEMT structures, understanding their electronic response at high frequencies and room temperature is required. Here, we present a study of the room temperature free charge carrier properties of the two-dimensional electron gas (2DEG) in HEMT structures with varying Al content in the AlxGa1−xN barrier layers between x=0.07 and x=0.42. We discuss and compare 2DEG sheet density, mobility, effective mass, sheet resistance, and scattering times, which are determined by theoretical calculations, contactless Hall effect, capacitance-voltage, Eddy current, and cavity-enhanced terahertz optical Hall effect (THz-OHE) measurements using a low-field permanent magnet (0.6 T). From our THz-OHE results, we observe that the measured mobility reduction from x=0.13 to x=0.42 is driven by the decrease in 2DEG scattering time, and not the change in effective mass. For x<0.42, the 2DEG effective mass is found to be larger than for electrons in bulk GaN, which in turn, contributes to a decrease in the principally achievable mobility. From our theoretical calculations, we find that values close to 0.3m0 can be explained by the combined effects of conduction band nonparabolicity, polarons, and hybridization of the electron wavefunction through penetration into the barrier layer.

In-situ X-ray diffraction study of the oxidation behavior of arc-evaporated TiAlSiN coatings with low Al contents

TiAlSiN hard coatings are commonly known to exhibit a high oxidation resistance, however, the influence of a varying Al content on the oxidation mechanism has not yet been examined in detail. Thus, in this work, the temperature dependent phase composition of two powdered TiAlSiN coatings with low Al contents (Ti37Al2Si7N54 and Ti33Al6Si7N54) was evaluated by in-situ X-ray diffraction (XRD) in ambient air up to 1200 °C and subsequent Rietveld refinement complemented by differential scanning calorimetry measurements. The in-situ XRD experiments revealed the formation of metastable anatase TiO2 during oxidation for both TiAlSiN coatings, however, the maximum wt% of this phase was found to be doubled for the coating with higher Al content from 9 to 21 wt% at ~1025 °C. Furthermore, the microstructure of the compact Ti33Al6Si7N54 coating oxidized at 950 and 1100 °C was investigated comprehensively by means of XRD, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. These microstructural investigations revealed the formation of a thin protective Al2O3 layer, which was broken by the growth of TiO2 grains after oxidizing at 950 °C, leading to fully enclosed Al2O3 grains within coarsened TiO2 grains at 1100 °C. The present work allows to close the literature gap concerning the changes in oxidation mechanism of TiAlSiN coatings when exclusively varying the Al content and further illuminates the microstructure of an oxidized TiAlSiN with low Al content in detail.

Effect of Al content on chemical corrosion resistance of Al/SiC composites

Al/SiC composites with different Al contents were prepared by high-energy ball milling with Al powder and SiC powder as raw materials at a temperature of 1800 °C, a pressure of 50 MPa, and heat preservation for 5 min. The microstructures and phase compositions of the Al/SiC composites were observed using scanning electron microscopy and X-ray diffraction. The results showed that the Al/SiC composites prepared by adding 10 vol% aluminum had the best properties: the strength was 310 MPa, the apparent porosity was 6.50%, and the density was 2.9192 g/cm3. Furthermore, the corrosion rate of the Al/SiC composites gradually decreased with increasing corrosion time when the Al/SiC composites were placed in a 3.5 wt% NaCl solution at room temperature. However, the corrosion rate differed for varying Al contents. The experimental results showed that the Al/SiC composites with 10 vol% Al have the best properties, including the smallest porosity, the largest density, and the highest corrosion resistance.

Metal-semiconductor-metal solar-blind ultraviolet photodetector based on Al0.55Ga0.45N/Al0.4Ga0.6N/Al0.65Ga0.35N heterostructures.

We have designed a metal-semiconductor-metal (MSM) solar-blind ultraviolet (UV) photodetector (PD) by utilizing Al0.55Ga0.45N/Al0.4Ga0.6N/Al0.65Ga0.35N heterostructures. The interdigital Ni/Au metal stack is deposited on the Al0.55Ga0.45N layer to form Schottky contacts. The AlGaN hetero-epilayers with varying Al content contribute to the formation of a two-dimensional electron gas (2DEG) conduction channel and the enhancement of the built-in electric field in the Al0.4Ga0.6N absorption layer. This strong electric field facilitates the efficient separation of photogenerated electron-hole pairs. Consequently, the fabricated PD exhibits an ultra-low dark current of 1.6 × 10-11 A and a broad spectral response ranging from 220 to 280 nm, with a peak responsivity of 14.08 A/W at -20 V. Besides, the PD demonstrates an ultrahigh detectivity of 2.28 × 1013 Jones at -5 V. Furthermore, to investigate the underlying physical mechanism of the designed solar-blind UV PD, we have conducted comprehensive two-dimensional device simulations.

Study of oxidation mechanisms of Ni-Al alloys with different phase structures at 1200 °C

In this study, Ni-Al alloys with different phase structures were prepared by varying Al content using vacuum arc melting technique, and suitable doping of reactive elements (Hf, Y) was carried out to improve the oxidation resistance at 1200 °C. It was found that the isothermal oxidation performance of β-NiAlHf alloy was much better than that of γ'-NiAlY alloy. The growth mechanism of TGO on Ni-Al alloys with different phase structures is significantly different. On the surface of β-phase alloys, TGO was transformed from unstable θ-Al2O3 to stable α-Al2O3 at the early stage and maintained for long-term. By contrast, on the surface of γ' phase alloys, NiO and NiAl2O4 were firstly generated, then Al2O3 was generated at the bottom layer accompanied by the disappearance of NiO, and finally the constitute of the TGO was consisted of NiAl2O4 and Al2O3. The growth mechanism of the TGO and the regulatory role of reactive elements are discussed for alloys with different phase structures.

Comparative investigation on physicochemical and photocatalytic properties of CuS and Al3+ doped CuS thin films

By using the chemical bath approach, CuS, and Al-doped CuS thin films were formed onto glass substrates. To enhance the photocatalytic capabilities of the traditional CdS thin film, Al3+ ions were used as doping element. Investigations were done into how the amount of Al doping affected the physical characteristics of CuS films by varying Al content as 2 wt%, 4 wt%, 6 wt%, and 8 wt%). The bandgap energy, thickness, morphology, and crystalline structure of CuS and Al-doped CuS thin films were examined. By using FTIR and FT-Raman studies, the functional groups contained in the CuS and Al-doped CuS thin films were observed. EDS was used to estimate the elemental components that are present in the prepared thin films. Degradation of the textile dyes rhodamine B (RhB) and methylene blue (MB) was used to examine the photocatalytic characteristics of the produced films. Among the produced films 8 wt% Al-doped CuS thin film showed high efficiency in degradation of both MB (98 %) and RhB (98 %) dyes.

Tuning the Bandgaps of (AlxGa1−x)2O3 Alloyed Thin Films for High‐Performance Solar‐Blind Ultraviolet Fully Covered Photodetectors

AbstractGa2O3 is a promising semiconductor for deep ultraviolet optoelectronics, because of its ultrawide bandgap of 4.85 eV. Here, the bandgap modulation of (AlxGa1−x)2O3 thin films through varying Al contents is reported –and the achievement of high‐performance photodetectors sensitive to the entire solar‐blind UV bands. It is shown that the bandgaps of (AlxGa1‐x)2O3 can be widely tuned from 4.85 eV to 5.9 eV. Solar‐blind ultraviolet photodetectors based on the (AlxGa1–x)2O3 films show detection cut‐off wavelengths varying from 263 to 236 nm, and response peaks varying from 238 to 209 nm. The photodetectors exhibit high performance with a high specific detectivity (up to 1015 Jones), low dark current (<0.35 nA), large photodark current ratio (≈107), UV–vis rejection ratio (>105), and long‐term device stability. Furthermore, a combination of high‐resolution X‐ray photoemission spectroscopy and density functional theory calculations is used to reveal insights into the evolution of electronic structures of (AlxGa1–x)2O3. The wide variations of the bandgap of (AlxGa1−x)2O3 mainly result from the upshift of the conduction band edges induced by the high energy Al 3s state hybridizing with the Ga 4s‐derived conduction band, while the valence band edge keeps almost the same for different Al content.

Correlation between local lattice distortions and up-/down-conversion luminescence of (Y,Al)NbO4:Yb3+/Er3+

The changes in the crystallographic parameters of Y 0.79- z Al z Yb 0.18 Er 0.03 NbO 4 powders prepared with varying Al content were determined by Rietveld refinement, and their effects on the up- (UC) and down-conversion (DC) spectra were studied. The findings confirmed that the Al 3+ , Yb 3+ , and Er 3+ ions were completely incorporated at the Y 3+ sites. The substitution of the small Al 3+ ions led to the modification of the interatomic distance. As a result, the highest polyhedral distortion index of the YO8 dodecahedron ( D YO ) could be achieved at z = 0.2. Under infrared radiation, UC spectra demonstrated that a two-photon energy transfer (ET) UC process from Yb 3+ to Er 3+ was responsible for the green and red emissions, whose intensities increased dramatically by 160 and 166% at z = 0.2, respectively. This enhancement was a consequence of a large crystal-field asymmetry surrounding the Yb 3+ and Er 3+ ions, which resulted from the highest D YO at z = 0.2. In addition to D , the Yb‒Er interatomic distance was responsible for the enhanced UC emission, affecting the ET probability from Yb 3+ to Er 3+ . Under 379 nm excitation, the DC green emission of Er 3+ also showed the maximal intensity at z = 0.2 owing to the largest D YO . However, a correlation between the crystallographic variations and the DC emissions activated by [NbO 4 ] 3- niobates could not be fully elucidated owing to the complexity of the emission mechanism.

Role of Al in engineering the optical band gap and PL emission intensity properties of CdO thin films grown by SILAR method

Herein, we report on synthesizing pure and aluminum (Al) doped cadmium oxide (CdO) thin films onto glass slides by successive ionic layer adsorption and reaction (SILAR) method. The optical, electrical, structural, and morphological evaluations were conducted for the produced samples after the grown thin films heat treated in a convection ashing furnace at 200 °C. X-ray diffraction (XRD) results disclosed that the prepared samples posses the polycrystalline cubic phase of CdO material and the (1 1 1) plane was the preferred growth orientation. Besides, the XRD analysis strongly suggested that the integration of aluminum into the CdO lattices completed as no other phases, such as Cd, Al, or related oxides, were present in the diffraction patterns. From the field emission scanning electron microscope (FE-SEM) images, it was noticed that Al doping concentration changed the surface morphologies. Energy dispersive X-ray analysis (EDAX) confidently proves the presence of Al as a result of the SILAR process. The optical properties were assessed by performing Ultraviolet–visible spectroscopy (Uv–vis), and it was observed that the optical bandgap increased from 2.5 eV to 3 eV due to the increased percentages of Al content in the Al:CdO nanostructures. The Photoluminescence (PL) spectrum evidently showed that the PL emission intensity of prepared samples was directly influenced over varying Al content in the CdO nanostructures. The electrical features of the SILAR derived CdO thin films uncovered that the resistivity of samples showed increment with the Al doping, thus the electrical conductivity of the grown samples decreased in return.

Melting and metasomatism in West Eifel and Siebengebirge Sub-Continental Lithospheric Mantle: Evidence from concentrations of volatiles in fluid inclusions and petrology of ultramafic xenoliths

The possibility of constraining the composition and evolution of specific portions of the Sub-Continental Lithospheric Mantle (SCLM) by means of an integrated study of petrography, mineral chemistry, and concentrations of volatiles in fluid inclusions (FI) is a novel approach that can provide clues on the recycling of volatiles within the lithosphere. This approach is even more important in active or dormant volcanic areas, where the signature of the gaseous emissions at the surface can be that of the underlying lithospheric mantle domains. In this respect, the ultramafic xenoliths brought to the surface in West Eifel (~0.5–0.01 Ma) and Siebengebirge (~30–6 Ma) volcanic fields (Germany) are ideal targets, as they provide direct information on one of the most intriguing portions of SCLM beneath the Central European Volcanic Province (CEVP). Five distinct populations from these localities were investigated using petrographic observations, mineral phase analyses and determination of He, Ne, Ar and CO2 contents in olivine-, orthopyroxene-, and clinopyroxene-hosted FI. The most refractory Siebengebirge rocks have highly forsteritic olivine, high-Mg#, low-Al pyroxene, and spinel with high Cr#, reflecting high extents (up to 30%) of melt extraction. In contrast, xenoliths from West Eifel are modally and compositionally heterogeneous, as indicated by the large forsterite range of olivine (Fo83–92), the Cr# range of spinel (0.1–0.6), and the variable Al and Ti contents of pyroxene. Equilibration temperatures vary from 870 °C to 1070 °C in Siebengebirge, and from ⁓900 °C to ⁓1190 °C in West Eifel xenoliths, at oxygen fugacity values generally between −0.5 and + 1.3 ΔlogƒO2 [FMQ]. In both areas, the FI composition was dominated by CO2, with clinopyroxene, and most of the orthopyroxene had the highest concentrations of volatiles, while olivine was gas-poor. The noble gas and CO2 distributions suggest that olivine is representative of a residual mantle that experienced one or more melt extraction episodes. The 3He/4He ratio corrected for air contamination (Rc/Ra values) varied from 6.8 Ra in harzburgitic lithotypes to 5.5 Ra in lherzolites and cumulate rocks, indicating that the original MORB-like mantle signature was progressively modified by interaction with crustal-related components and melts having 3He/4He and 4He/40Ar* values consistent with those published for magmatic gaseous emissions. The Ne and Ar isotope systematics indicated that most of the data were consistent with mixing between a recycled atmospheric component and a MORB-like mantle, which does not necessarily require the involvement of a lower mantle plume beneath this portion of the CEVP. The major element distribution in mineral phases from West Eifel and Siebengebirge, together with the systematic variations in FI composition, the positive correlation between Al enrichment in pyroxene and equilibration temperatures, and the concomitant Rc/Ra decrease with increasing temperature, suggest that the SCLM beneath Siebengebirge represented the Variscan lithosphere in CEVP prior to the massive infiltration of melts/fluids belonging to the Quaternary Eifel volcanism. In contrast, West Eifel xenoliths reflect multiple heterogeneous metasomatism/refertilisation events that took place in the regional SCLM between ~6 and ~ 0.5 Ma.