La Content Research Articles

Bioaccumulation of Selenium, Heavy Metals and Rare Earth Elements with Different Rice Cultivars Grown on Seleniferous Soils in Lianchen County, Fujian Province, China

Seleniferous red soils cover a large area in the southern part of China. These agricultural soils are enriched in selenium (Se), heavy metals, and rare earth elements and have been cultivated for more than 1000 years for rice production without any consideration of the effects of selenium, heavy metals, and rare earth element bioaccumulation in the food plants produced. To address this knowledge gap, this study focuses on the investigation of Se, heavy metals, and rare earth elements within soils and plants in the region. The rice (Oryza spp.) plants studied were grown in the Gutian (GT), Gechuan (GC), and Pengkou (PK) villages in Lianchen (LC) County, Fujian Province. The surface soils and harvested rice tissues were collected to determine the Se, Cd, Zn, Pb, La, Ce, and Nd concentrations in the soils and plant tissues. Different rice cultivars possessed various potentials for elemental accumulation. Generally, rice plant tissues accumulated certain amounts of these elements; however, the elemental concentrations found in rice grain were within the acceptable ranges stipulated by the National Security Standard of Food. The Hongbaoshi (HBS) Indica red rice produced in the PK village accumulated more selenium, heavy metals, and rare earth elements than those in the plant tissues of the Xinyinzhan (XYZ) and Wushansimiao (WSSM) rice cultivars because HBS had more root hairs and finer root distribution. Thus, in the interest of food safety, increased attention needs to be given to the careful selection of the optimum crop species planted in these types of seleniferous red soils.

Reforming Methane with CO2 over Hierarchical Porous Silica-Supported Nickel Catalysts Modified with Lanthanum Oxide

Hierarchical porous silica-supported nickel catalysts modified with different amounts of lanthanum (La) were synthesized via “one-pot” method using cetyltrimethylammonium bromide as template, urea as precipitant, and tetraethyl orthosilicate as silica source. Their catalytic performances were evaluated in dry reforming with methane under different conditions (La loading, reaction temperature, and time on stream). The synthesized and spent catalysts were extensively characterized by ICP, physisorption, chemisorption, XRD, TPR, XPS, HAADF-TEM, TPH, Raman’s spectroscopy, and TG analysis. The impact of lanthanum amount on the catalytic performance, sintering, and carbon deposition was discussed. Compared to unmodified catalyst, La promoter induced the nickel nanoparticles with larger crystallite sizes and weakened the metal-support interaction as well as the formation of 1 : 1 nickel-phyllosilicate, leading to the metal sintering increasing in the order Ni1.5La/SiO2 < Ni3.0La/SiO2 < Ni4.5La/SiO2. The modified catalysts exhibited better carbon resistance, which was significantly enhanced with increasing La content. Despite this, the stability increased following the sequence of Ni3.0La/SiO2 < Ni4.5La/SiO2 < Ni1.5La/SiO2. Ni1.5La/SiO2 displayed the best stability at 750°C within 10 h stability test, with CH4 conversion dropping from 61.3 to 58.0%. The deactivation reason for Ni1.5La/SiO2 was mainly the carbon deposition, while that for Ni3.0La/SiO2 and Ni4.5La/SiO2 was the metal sintering. These results emphasized that the activity and stability in the NiLa/SiO2 catalysts for the dry reforming of methane depended on two important factors, the metal-support interaction and the particles size of nickel, providing the necessity and sufficiency to balance two attributes.

Study on Microstructural Evolution and Mechanical Properties of Mg-3Sn-1Mn-xLa Alloy by Backward Extrusion.

Mg-3Sn-1Mn-xLa alloy bars were prepared using backward extrusion, and the effects of the La content on the microstructures and mechanical properties of the alloy were systematically studied using an optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile tests. The results of this research show that the Mg2Sn phases were mainly formed at the α-Mg grain boundaries and within the grains in the Mg-3Sn-1Mn alloy. After adding a certain amount of La, the plate-shaped MgSnLa compounds consisting of Mg17La2, Mg2Sn, and La5Sn3 gradually disappeared in the α-Mg matrix and grain boundaries. With an increase in La content, the Mg2Sn phase in the crystal was gradually refined and spheroidized. When the content of La reached 1.5%, the tensile strength of the alloy reached 300 Mpa and the elongation reached 12.6%, i.e., 25% and 85% increases, respectively, compared to the Mg-3Sn-1Mn alloy. The plate-shaped compound of Mg-3Sn-1Mn-1.5La had an average length of 3000 ± 50 nm, while the width was 350 ± 10 nm. Meanwhile, the extruded alloy's grain size was significantly refined, and there were many small cleavage steps and dimples in the fracture surface of the alloy. When the La content reached 2%, the alloy performance showed a downward trend due to the coarsening of the grains. The formed plate-shaped MgSnLa compounds and Mg2Sn phases were consistent with the α-Mg matrix. They effectively pinned the dislocations and grain boundaries, which is the main reason for strengthening the mechanical properties of extrusion alloys.

La3+ substituted Ni0.5 Co0.5 Fe2 O4 nanoferrites: Magnetically separable catalysts for sunlight-driven photo-oxidative degradation of Methylene Blue

LaxNi0.5Co0.5Fe2−xO4 nanoparticles (x = 0.0, 0.03, 0.06, 0.09, 0.12) were investigated in the current work as Methylene Blue degradation catalysts. Using the citrate-aided sol-gel auto-combustion approach, the nanoferrites with homogenous size distribution were produced. Powder X-ray diffraction was used to analyse the structure of the material. The optical characteristics of ferrite nanoparticles were investigated using diffused UV–visible reflectance spectroscopy. It was noted that when the concentration of La3+ increased, the band gap of produced ferrites shrank. Morphological and compositional studies were performed by FE-SEM and EDX spectra. Surface area was depicted using BET analysis. Raman Spectroscopy was used to estimate the parameters of vibration. Testing has been done on synthesized nanoferrites to see whether they can remove Methylene Blue's concentration in water. In addition, it was examined how La3+ incorporation in Ni0.5Co0.5Fe2O4 nanocomposites resulted in aspects of doping ratio, reaction time and amount of catalyst. The most effective material, La0.06Ni0.5Co0.5Fe1.94O4, achieved a 98.69 per cent efficiency in 140 min. Due to three positive characteristics, including high recycling (up to five cycles), stability, and simplicity of separation using an external magnet, toxic dyes in actual wastewaters can be photodegraded in sunlight using La3+ substituted Ni0.5Co0.5Fe2O4 nanoferrites as an efficient and competitive catalyst.

Effect of La substitution on energy storage properties of (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)TiO3 lead‐free high‐entropy ceramics

AbstractIn this study, a novel lead‐free high‐entropy ceramic (HEC) system, (Bi0.2Na0.2Ca0.2Ba0.2Sr0.2)(1–3x/2)LaxTiO3 (0 ≤ x ≤ 0.15) (abbreviated as BNCBST‐xLa), was designed to enhance energy storage performance through La substitution and prepared via a hydrothermal method. Results indicate that La doping at A site in BNCBST induces lattice distortion and further improves dielectric relaxation. Moreover, grain growth is inhibited by the La content, which results in an increase in the insulation resistance and thus significant enhancement in the electric breakdown strength (Eb). Accordingly, the system with x = 0.03 exhibits an excellent recoverable energy density (Wrec) of 2.43 J/cm3 and a high energy storage efficiency (η) of 85.5% under a great Eb of 245 kV/cm, together with wide temperature stability (Wrec and η vary within ± 8.3% and ± 1.1% at 30–150°C). The findings of this study suggest that the obtained La‐modified BNBCST HECs are promising for energy storage applications.

Magnetic properties of SmMn1-xCoxO3 and Sm1-yRyMn0.6Co0.4O3

Polycrystalline SmMn1-xCoxO3 and Sm1-yRyMn0.6Co0.4O3, which have a single orthorhombic perovskite-type structure without any impurities, were prepared by complex polymerization to investigate the effects of A- and B-site element substitutions on the crystal structure and magnetic properties. The unit-cell volume of SmMn1-xCoxO3 decreased with increasing x and that of Sm1-yRyMn0.6Co0.4O3 increased with increasing average radius of A-site ions ⟨rR⟩, and the chemical pressure due to element substitution was observed in these two systems. At 0.0 ≤ x ≤ 0.4 in SmMn1-xCoxO3, a marked increase in the field-cooled magnetization MFC and an increase in the canted-antiferromagnetic transition temperature Tc were observed with increasing x, but they decreased for 0.5 ≤ x ≤ 1.0. However, no specific spin reversal phenomenon was observed, unlike in other RMnO3 compounds. The magnetic susceptibility of both compounds obeyed the Curie–Weiss law with constant susceptibility above 200 K, which was not common in other Sm compounds, and the effective magnetic moment Peff could be easily evaluated. By analyzing Peff of SmMn1-xCoxO3, we determined the electronic states of the ions constituting the sample as Mn3+(high spin, HS), Mn4+, and Co2+(HS) at 0 < x ≤ 0.5 and Mn4+, Co3+(low spin), and Co2+(HS) at 0.5 < x ≤ 0.9. The MFC of Sm1-yRyMn0.6Co0.4O3 decreased with increasing Y and Lu concentrations and increased with La concentration. The Tc and Weiss temperature of Sm1-yRyMn0.6Co0.4O3, both of which increased linearly with increasing ⟨rR⟩, could be attributed to the effects of chemical pressure. Although M − H measurements showed that Sm3+ in Sm1-yRyMn0.6Co0.4O3 was paramagnetic, the Peff analysis results suggested that the excited state of Sm3+ was affected.

Application of Onuma and lattice strain derived methods to calculate missing REE and Ce and Eu anomalies in magmatic zircons

The shape of chondrite normalized zircon rare earth element (REE) patterns, including the magnitude of the Cerium (Ce) and Europium (Eu) anomalies, provide valuable insights into the magmatic conditions under which a zircon formed. However, lanthanum (La) and praseodymium (Pr), which are essential for the calculation of Ce anomalies, are often present at concentrations close to or below the detection limit of most analytical methods. We propose two new methods to calculate missing REE, based on Onuma diagrams (Chondrite-Onuma) and the lattice strain theory (Chondrite-Lattice), but using chondrite normalized values instead of partition coefficients. We compiled a dataset of ~ 1500 zircons with known REE + Y concentrations and used it to test and calibrate these methods and demonstrate that they are more accurate than other previously published models, with the Chondrite-Onuma method performing better than the Chondrite-Lattice method. These methods require analyses of as few as five REEs to impute the missing REE data or to estimate La and Pr concentrations or Ce anomalies in magmatic zircons, which allows a reduction in the number of REE analysed, where desirable, or to impute missing REEs in legacy data. The imputeREE package for the R programming language was written with a set of tools to apply these methods. A companion app is available to calculate missing REE and Ce and Eu anomalies.

Effect of Rare Earth La on the Microstructure, Mechanical Properties, Electrical Conductivity, and Corrosion Behavior of an As-Cast Al-0.5 wt%Fe Aluminum Alloy

The effect of La content on the microstructure, mechanical properties, electrical conductivity and corrosion resistance of as-cast Al-0.5 wt%Fe alloys was evaluated. The results showed that the La addition can promote the refinement of the α-Al grains and modify the Fe-containing phases. The addition of La has limited effect on the strength of Al-0.5 wt%Fe alloy. The elongation and electrical conductivity increases first and then decreases with the increase of La content in Al-0.5 wt%Fe alloy. When the addition of La is 0.10 wt% in Al-0.5 wt%Fe alloy, the maximum elongation and electrical conductivity are about 46.56% and 59.59%IACS, respectively. Polarization curves indicated that the corrosion current density (Icorr) and corrosion rate decrease with the increase of La content. Electrochemical impedance spectroscopy (EIS) tests also presented that the impedance is increased with the increase of the La content. Therefore, the addition of La improved the corrosion resistance of the Al-0.5 wt%Fe alloy.

Synthesis and Thermoelectric Properties of La-doped n-type Mg3SbBi Materials

Mg3Sb2-based materials are very promising for thermoelectric applications at low temperatures, and are strong candidates to replace n-type Bi2Te3 for cooling and power generation. Substituting Sb atoms with chalcogen elements (S, Se, Te) is a typical method of n-type doping, while doping the Mg site with Group 3 elements (Y, Sc) and Lanthanides has also been studied. Unique advantages have been recently reported. In this study, a La-containing compound, LaSb, was used to fabricate n-type Mg3SbBi. The thermoelectric properties of polycrystalline Mg3LaxSbBi (0 ≤ &lt;i&gt;x&lt;/i&gt; ≤ 0.02) were investigated after synthesis by sequential processes of arc melting, ball milling, and spark plasma sintering. Undoped Mg3SbBi is p-type with poor thermoelectric performance, and switched to n-type with La doping. The electron concentration of Mg3LaxSbBi increased linearly with La content &lt;i&gt;x&lt;/i&gt;, reaching up to 9.4 × 10&lt;sup&gt;19&lt;/sup&gt; cm&lt;sup&gt;-3&lt;/sup&gt; at &lt;i&gt;x&lt;/i&gt; = 0.02. The power factor and the figure of merit were also maximized in Mg3La0.02SbBi, reaching 1.8 mW m&lt;sup&gt;-1&lt;/sup&gt;K&lt;sup&gt;-2&lt;/sup&gt; (573 K) and 0.89 (623 K), respectively. The lattice thermal conductivity decreased with increasing La content above ~500 K, and the minimum value of 0.73 W m&lt;sup&gt;-1&lt;/sup&gt;K&lt;sup&gt;-1&lt;/sup&gt; was obtained in Mg3La0.02SbBi. This study shows that La doping using LaSb provides a reliable method for n-type doping of Mg3Sb2-based materials.

Effects of La Addition on Microstructure Evolution and Thermal Stability of Cu-2.35Ni-0.59Si Sheet.

A Cu-2.35Ni-0.69Si alloy with low La content was designed in order to study the role of La addition on microstructure evolution and comprehensive properties. The results indicate that the La element demonstrates a superior ability to combine with Ni and Si elements, via the formation of La-rich primary phases. Owing to existing La-rich primary phases, restricted grain growth was observed, due to the pinning effect during solid solution treatment. It was found that the activation energy of the Ni2Si phase precipitation decreased with the addition of La. Interestingly, the aggregation and distribution of the Ni2Si phase, around the La-rich phase, was observed during the aging process, owing to the attraction of Ni and Si atoms by the La-rich phase during the solid solution. Moreover, the mechanical and conductivity properties of aged alloy sheets suggest that the addition of the La element showed a slight reducing effect on the hardness and electrical conductivity. The decrease in hardness was due to the weakened dispersion and strengthening effect of the Ni2Si phase, while the decrease in electrical conductivity was due to the enhanced scattering of electrons by grain boundaries, caused by grain refinement. More notably, excellent thermal stabilities, including better softening resistance ability and microstructural stability, were detected for the low-La-alloyed Cu-Ni-Si sheet, owing to the delayed recrystallization and restricted grain growth caused by the La-rich phases.

Investigations on structural, Mossbauer, dielectric, and ferroelectric properties of La doped barium hexaferrite

La substituted Barium hexaferrite, Ba(1-x)La(x)Fe12O19, (x = 0, 0.1, 0.15, 0.20) was synthesized using ball milling followed by heat treatment. Rietveld analysis of X-Ray diffraction patterns reveals the formation of a single-phase magnetoplumbite structure of barium hexaferrite for all prepared samples. Morphological studies using FESEM shows the formation of hexagonal plate-like grains with different grain size, and the average grain size decreases with La doping. Elemental analysis using EDS confirms that the observed elemental composition for all the samples is within the expected range within the experimental error. Density measurements observed that porosity decreases up to La content x = 0.15 and then slightly increases for x = 0.20. Mössbauer spectroscopy studies reveal no formation of Fe2+ ions but delocalization of electrons after La doping. There is not much variation in the hyperfine structure with La doping. It is observed from the dielectric spectroscopy that the highest dielectric constant and low loss are observed for La content x = 0.20. The P-E loop of the pristine sample shows small polarisation but leaky behavior, whereas La substitution shows both leaky and resistor circuit-type behavior but large polarization.

Visible light‐active pure and lanthanum‐doped copper oxide nanostructures for photocatalytic degradation of methylene blue dye and hydrogen production

AbstractClean water and renewable energy sources are becoming increasingly important in the current era, as well as a future challenge, and one of the potential solutions is photocatalysis. In the current study, a simple one‐step hydrothermal technique is employed to fabricate the pure and La‐doped CuO (0%, 1%, 3%, 5%, and 7%) photocatalysts. The influence of varying La concentration on structure, morphology, and optical properties is determined by scanning electron microscope (SEM), X‐ray diffraction (XRD), ultraviolet (UV)–visible spectroscopy, and photoluminescence. SEM showed that synthesized nanostructures are irregularly spherical and transform into needle‐like nanostructures on increasing La concentration. XRD revealed the monoclinic phase with a crystallite size of 15–23 nm. The UV–visible spectrum exhibited a decrease in the band gap of La‐doped CuO needle‐like nanostructures from UV to visible light. The composition and purity of synthesized nanostructures are evaluated via the energy‐dispersive X‐ray spectrum which revealed that needle‐like nanostructures are pure without any impurity traces. The synthesized nanostructures were used as a photocatalyst against methylene blue dye to examine their photocatalytic activity. The synthesized CuO‐3La photocatalyst exhibited excellent photocatalytic performance of dye degradation and hydrogen production 95.3 μmol h−1 g−1 with more than 97% cyclic stability. Therefore, the synthesized La‐doped CuO nanostructures are potential candidates for photocatalytic water splitting and hydrogen evolution.

Effect of Compound Additives on Nutritional Composition, Fermentation Quality, and Bacterial Community of High-Moisture Alfalfa Silage

The wilting process is required for the preparation of traditional low-moisture silage, which is not only subject to the interference of rainfall during the harvest season in many areas, but also increases labor, economic, and time costs. Therefore, in this experiment, newly harvested alfalfa was supplemented with a complex additive consisting of lactic acid bacteria (LAB), sucrose, and corn flour, and then ensiled directly in order to explore a suitable high-moisture silage processing method. There were four groups: control (CK), 0.01 g/kg LAB plus 2% sugar (S), 0.01 g/kg LAB plus 5% corn flour (C5), and 0.01 g/kg LAB plus 5% corn flour (C10). The results show that all four types of silage had significantly reduced acid detergent fiber, acetic acid content, and ammonia/total nitrogen (p &lt; 0.05). The relative abundance of Lactobacillus spp. was significantly higher (p &lt; 0.05), and that of Weissella, Clostridium sensu stricto 12, and Pantoea genera was significantly lower (p &lt; 0.05) in all four treatments. Group S had significantly increased crude protein content, and groups C5 and C10 had significantly reduced neutral detergent fiber. Overall, group C10 had the highest LA concentration, the highest relative abundance of Lactobacillus spp., and the lowest pH, ammonia/total nitrogen, neutral detergent fiber, and acid detergent fiber. Silage with a complex additive consisting of LAB + 10% corn flour is recommended to achieve good fermentation with high nutritional quality.

An investigation of the correlation between the photovoltaic, magnetic and optical properties of CoCr2O4 due to the doping effect of rare-earth La3+ions

In the new approach, undoped and (0.1,0.3, and 0.5) La3+doped CoCr2O4 samples were prepared using microwave combustion methods. The Transmission Electron Microscope (TEM) and X-ray diffraction (XRD) are used to characterize the material's surface morphology and for phase identification and crystallinity. The samples were also studied with a UV–visible, diffuse reflectance spectrum (DRS) and a (VSM) Vibrating Sample Magnetometer. Spherical particles in agglomeration are visible in the TEM images. The average crystal size is about 15 - 43 nm was observed from the X-ray diffraction pattern results, and it was also confirmed that a cubic spinel structure existed. In addition to providing insight into the divalent and trivalent metal cation distributions at the A and B sites of the chromite lattice, XRD data also revealed divalent and trivalent metal cations distributions. Increased La content results in a decrease in estimated band gap energy. An increasing trend with increasing in La concentration resulting from cation rearrangement. Because La3+replaces some Cr ions in octahedral sites of cobalt chromite, there is a variation in its magnetic parameters.

Critical behavior and room temperature magnetocaloric effect of La-doped Pr0.7Sr0.3MnO3 compounds

In this work, we present the critical and the magnetocaloric properties of Pr0.7-xLaxSr0.3MnO3 compounds around room temperature. The samples exhibit a single phase with an orthorhombic structure. However, the lattice parameters increase with an increase in La content (x). The Curie temperature (TC) of the ferromagnetic (FM)-paramagnetic (PM) phase transition of compounds increases from 256 K for x = 0–319 K for x = 0.3. We observed a large magnetocaloric effect with high maximum magnetic entropy change (|ΔSmax|) values occurring around room temperature, corresponding to |ΔSmax| = 6.65 and 5.21 J/kgK under a magnetic field change (ΔH) of 50 kOe for x = 0.2 and 0.3, respectively. We also pointed out that the change in |ΔSmax| obeys an exponential function of ΔH (|ΔSmax| ∼ ΔHn), where the value of field exponent (n) is approximately 0.52. Furthermore, the critical behavior around TC for compounds with x = 0.2 and 0.3 has been investigated. The results indicate that these compounds undergo a second-order phase transition with the critical parameters (β = 0.311, γ = 1.137, and δ = 4.656 at TC = 298.4 K for x = 0.2; and β = 0.319, γ = 1.098, and δ = 4.442 at TC = 318.7 K for x = 0.3) that are quite close to those expected for the 3D-Ising model. This suggests the existence of the short-range magnetic interactions in these compounds.

Structural, morphological, optical, photoluminescent and electrochemical performance of ZnS quantum dots: Influence of Mn2+ and La3+ ions

The Mn, La dual doped ZnS QDs synthesized using co-precipitation method and the XRD analysis confirmed the cubic phase and HR-TEM estimates the average crystallite size ∼ 2 nm. FT-IR spectroscopy and EDAX ensure the purity of the prepared samples. The surface morphological examination discovered the surface structure and particle aggregation of the sample. From the UV-visible optical spectroscopy, It is observed that La 2% doped Mn:ZnS tuned large band gap (3.98 eV).The size dependence of the Zn0.98-xMn0.02LaxS QDs appears to be confirmed by the apparent shift of the absorption and emission peaks of the QDs. The optical absorbance was increased as the increase of La concentration. Defect-induced red emission was obtained through PL study. The Cyclic Voltagram (CV) findings demonstrate that the electrical properties of ZnS electrolytes can be further enhanced by co-doping with an ideal ratio of La3+ and Mn2+ ions.

Kirlenmiş Bir Alanda Olgun ve Olgunlaşmamış Domateslerdeki Kritik Hammadde Grubundan Toksik Elementler: Birikim ve Potansiyel Sağlık Riski Değerlendirmesi

Accumulation and health risk assessment of cobalt (Co), antimony (Sb), vanadium (V), and lanthanum (La) in tomatoes growing in an area contaminated with municipal wastewater were investigated. For this aim, tomatoe samples were taken and sepertaed into root, stem and leaf parts. Co, Sb, V and La concentrations were detected in plant organs. The arrangement of the elements in the root, stem, and leaf of ripe and unripe tomatoes was V&gt;Co&gt;La&gt;Sb. According to total element values in the ripe and unripe tomatoes; the highest values were 23±1.1 mg/kg and 35±1.7 mg/kg for V, respectively. Co, Sb, V, and La values accumulated by ripe and unripe tomatoes were determined as 24.65 and 25.6 times for Co, 1.8 and 2.7 times for Sb, 46 and 70 times for V and 4.4 and 6.15 times for La, respectively when compared with control. Total Co, Sb, V, and La were male

Detailed microwave loss mechanisms for nanocomposites of La-doped BaFe12O19 and polyaniline

To mitigate the undesirable effects of electromagnetic pollution on the precise instrument, biological health, and human life, high-efficiency microwave-absorbing materials (MAMs) have been pursued by the scientific community. MAMs also have important potential for information security, 5G, energy harvesting, reduced radar cross-section, and military stealth technology. In this work, magnetic/dielectric composites of La-doped BaFe12O19 (La-BaM) and polyaniline (PANI) were developed to be MAMs. Composites with no and 30% of La concentration (named M0-C and M3-C, respectively) showed poor microwave absorption performance with reflection loss (RL) values of about −20 dB, meaning 99% of the incident microwave was absorbed. The effective absorption bandwidths (EABs) were narrow, with values of 0.70 and 1.55 GHz, respectively. In contrast, the microwave absorption performance of composites with 10% and 50% of La concentration (named M1-C and M5-C, respectively), reached excellent values in both RL and EAB of −47.83 and −43.53 dB and 3.98 and 3.43 GHz, respectively. These RL values implied that 99.99% of the incident microwave could be absorbed. The superior microwave absorption properties of M1-C and M5-C composites could be attributed to their excellent impedance matching, better natural ferromagnetic resonance, exchange resonance, and better attenuation constant. The loss mechanism of microwave energy in La-BaM/PANI composites could be attributed to interfacial polarization at the interfaces of two phases, dipole polarization and micro-current and conductive loss (from PANI), eddy current (from La-BaM), multiple reflection and scattering (from the dispersion of PANI into La-BaM), as well as thermal energy dissipation (from embedding La-BaM/PANI into the epoxy matrix).

Thermal, structural and optical properties of Pb1−x La x TiO3 prepared using modified sol–gel route

Abstract La doped lead titanate ceramic compositions Pb1−x La x TiO3 (PLT) for x = 0.0, 0.05, 0.1, 0.2 and 0.3 were synthesized by an acrylic acid modified sol-gel route. The microstructure, surface morphology, and optical properties of the resulting compositions were studied by using TGA, X-ray diffraction, Raman Spectroscopy, and UV–Vis spectroscopy. It was found that the acrylic acid acts as a strong gelling agent and the organic residue gets removed completely below 450 °C. Very smooth ceramic powders characterized by single perovskite phase were obtained. A reduction in the tetragonality ratio from 1.0698 to 1.0033 was observed with increasing La content from x = 0.0 to x = 0.3. The effect of reduced tetragonality was corroborated by the peak shift of soft modes in Raman spectra and approximately 2 cm−1 downshift of E(TO1) mode was observed for each atomic weight percent La addition in lead titanate. The average grain size was found decreasing marginally with the increasing La content in PLT. Using the UV–vis data, a slight but systematic increase in the direct absorption edge (band gap) from 3.155 eV to 3.234 eV was observed with increasing La content in the PLT compositions.

X-ray Diffraction and Trace Element Analyses of K/Pg Boundary Samples Collected from Agost and Caravaca, Spain

The boundary between Cretaceous and Paleogene (K/Pg) plays an important role in deciphering the Earth’s history and biological evolution from Mesozoic to Cenozoic. As such, the delineation and characterization of the boundary layer has attracted significant attention. In this study, X-ray diffraction (XRD) and elemental analyses were conducted to characterize the samples of boundary layer and the layers around Agost and Caravaca, Spain. The XRD results showed that the layers immediately above and below the boundary layer are made of limestone, while in the boundary layer, a significant increase in the clay minerals smectite, kaolinite, and illite was observed. The major element analyses revealed an increase in Si and Al contents, confirming the presence of clay minerals. The trace element analyses showed elevated concentrations of V, Cr, Ni, Zn, Pb, and Th, but not for Rb, Cu, and U. The rare Earth element (REE) analyses showed elevated La, Ce, and Nd concentrations in the boundary layer. Correlation analyses between selected trace elements and REE showed good agreements, with R2 values of about 0.9. The results agreed well with the finding in the area, except the lower contents of Rb, Cu, and U; thus, they may promote further studies to make detailed comparisons.