La Addition Research Articles

Effects of trace La additions on the microstructures and properties of nanoprecipitates strengthened Cu–Zr alloys

Abstract

Novel compounds that enhance Agrobacterium-mediated plant transformation by mitigating oxidative stress.

Agrobacterium tumefaciens caused tissue browning leading to subsequent cell death in plant transformation and novel anti-oxidative compounds enhanced Agrobacterium -mediated plant transformation by mitigating oxidative stress. Browning and death of cells transformed with Agrobacterium tumefaciens is a long-standing and high impact problem in plant transformation and the agricultural biotechnology industry, severely limiting the production of transgenic plants. Using our tomato cv. MicroTom transformation system, we demonstrated that Agrobacterium caused tissue browning (TB) leading to subsequent cell death by our correlation study. Without an antioxidant (lipoic acid, LA) TB was severe and associated with high levels of GUS transient expression and low stable transformation frequency (STF). LA addition shifted the curve in that most TB was intermediate and associated with the highest levels of GUS transient expression and STF. We evaluated 18 novel anti-oxidative compounds for their potential to enhance Agrobacterium-mediated transformation, by screening for TB reduction and monitoring GUS transient expression. Promising compounds were further evaluated for their effect on MicroTom and soybean STF. Among twelve non-antioxidant compounds, seven and five significantly (P < 0.05) reduced TB and increased STF, respectively. Among six antioxidants four of them significantly reduced TB and five of them significantly increased STF. The most efficient compound found to increase STF was melatonin (MEL, an antioxidant). Optimal concentrations and stages to use MEL in transformation were determined, and Southern blot analysis showed that T-DNA integration was not affected by MEL. The ability of diverse compounds with different anti-oxidative mechanisms can reduce Agrobacterium-mediated TB and increase STF, strongly supporting that oxidative stress is an important limiting factor in Agrobacterium-mediated transformation and the limiting factor can be controlled by these compounds at different levels.

Effects of dietary α-lipoic acid, acetyl-l-carnitine, and sex on antioxidative ability, energy, and lipid metabolism in broilers

An experiment was conducted to evaluate the effects of dietary α-lipoic acid (LA), acetyl-l-carnitine (ALC), and sex on antioxidative ability, energy, and lipid metabolism in broilers. A total of 972 one-day-old broilers with equal sex were randomly assigned in a 3 × 3 × 2 factorial design using 3 LA, 3 ALC levels, and 2 sexes (6 replications, 9 birds/replication). The LA and ALC levels were 0, 50, and 100 mg/kg, respectively. Results showed that increased LA or ALC resulted in increased total antioxidant capacity and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and decreased levels of malondialdehyde in serum and liver of birds (P < 0.05). In addition, with increasing addition of LA or ALC, an increased (P < 0.01) level of insulin (Ins), as well as decreased (P < 0.05) levels of glucose and glucagon (Glu), were observed in serum of broilers. Total cholesterol and triglyceride (TG) levels decreased (P < 0.05) and nonesterified fatty acid, lipoprotein lipase, and lipase levels increased (P < 0.05) in serum with increased administration of LA or ALC. Moreover, a significant (P < 0.05) interaction of LA × ALC was observed for serum and liver SOD, serum GSH-Px, glucose, and TG levels. Birds fed diets containing 50 mg/kg of LA and 50 mg/kg of ALC had higher serum and liver SOD activities and lower serum glucose and TG levels than those fed diets containing 100 mg/kg of LA or ALC alone. The main effect of sex and all interactions among main effects (except LA × ALC) were not significant (P > 0.05) for all of the above parameters. Overall, the present data indicate that LA or ALC supplementation, or both, at low levels (50 or 100 mg/kg) improved antioxidative ability, energy metabolism, and lipid metabolism in broilers, and synergistic effects by the combined supplementation of LA and ALC were indicated by serum and liver SOD activities and serum glucose and TG levels.

Isobutanol synthesis from syngas over K–Cu/ZrO2–La2O3(x) catalysts: Effect of La-loading

A series of K–Cu/ZrO2 catalysts with different La loadings for isobutanol synthesis from CO hydrogenation were prepared by a co-precipitation method. The catalysts were characterized by XRD, reactive N2O adsorption, XPS, H2-TPR, in situ IR and Raman techniques, and then tested for isobutanol synthesis from CO hydrogenation at the conditions of 360°C, 10.0MPa, GHSV=3000h−1 and H2/CO=2.5. These characterization results showed that incorporation of La into the K/Cu–Zr catalyst resulted in increase of BET surface area and dispersion of catalyst particles. Especially, medium La addition facilitated the synergistic effect between Cu–Zr interactions, improved the reducibility of catalyst and increased the amounts of dispersed copper. An enrichment of C1 intermediates on catalyst surface related to high dispersed CuO is better for chain growth. In the isobutanol synthesis reaction, the conversion of CO and selectivity of isobutanol increased first and then decreased as the increase of La concentration. Among these La-promoted K/Cu–Zr catalysts, the 3% La/Cu/Zr catalyst exhibited the highest alcohol selectivity of 32.8wt%, which can be radically attributed to the highest Cu surface area.

Ab initio calculation of relative permittivity of La-doped HfO2

First principles calculations of HfO2 and La-doped HfO2 structures were carried out to investigate the effect of La doping on the relative permittivity of HfO2 films. In this study 6.25% of La was incorporated into HfO2. Upon examination, we found out that La addition increased the value of the relative permittivity from 19 to 26 and this was because the La-induced distortion increased the range of frequencies that contribute to the IR-active modes.

Mechanical Properties Comparison of Different La Content in AZ91

In order to improve the comprehensive mechanics performance of AZ91 magnesium alloy which is used as car's material, the La element was added in AZ91 magnesium alloy and specimens was prepared by powder metallurgy method. The influence of La on microstructure, hardness and compression performance of AZ91 a magnesium alloy specimen was studied using metallographic electronic microscope, hardness tester, universal tension and compression testing machine. The experimental results show that when amount of La's addition is 1.2%, its mechanical performance is best, hardness is 67.1 HV, compressive strength is 115.8 MPa, increased respectively by 20.0% and 29.5% compared the AZ91 magnesium alloy substrate, and the grain refinement effect of AZ91 magnesium alloy is the best at this time.

Structural, optical, and electrical properties of strained La-doped SrTiO3 films

The structural, optical, and room-temperature electrical properties of strained La-doped SrTiO3 epitaxial thin films are investigated. Conductive La-doped SrTiO3 thin films with concentration varying from 5 to 25% are grown by molecular beam epitaxy on four different substrates: LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, SrTiO3, and DyScO3, which result in lattice mismatch strain ranging from −2.9% to +1.1%. We compare the effect of La concentration and strain on the structural and optical properties, and measure their effect on the electrical resistivity and mobility at room temperature. Room temperature resistivities ranging from ∼10−2 to 10−5 Ω cm are obtained depending on strain and La concentration. The room temperature mobility decreases with increasing strain regardless of the sign of the strain. The observed Drude peak and Burstein-Moss shift from spectroscopic ellipsometry clearly confirm that the La addition creates a high density of free carriers in SrTiO3. First principles calculations were performed to help understand the effect of La-doping on the density of states effective mass as well as the conductivity and DC relaxation time.

Effects of microalloying with La on microstructure and properties of cold rolled pure copper

The microstructure and mechanical properties of pure copper with microalloying lanthanum (La) addition after cold rolling and subsequent aging were investigated. Tensile tests of the aged specimens were performed to examine the effect of aging temperature and microstructure on mechanical properties. Optical microscope, scanning electronic microscope and hardness tests were used to characterise the deformation and recrystallisation behaviour, as well as microstructure evolution in the alloys. The results show that the tensile strength increases gradually with increasing La concentration, but elongation increases at first and then decreases when the addition level of La is more than 0·089 wt-%. The improvement of properties of rolled copper with proper La addition is attributed to the effect of second particle strengthening and purifying. However, overaddition of La leads to the decrease of elongation of rolled copper owing to the excessive La rich second phase. In addition, an important finding was that when the content of La is less than 0·1 wt-%, recrystallisation was inhibited, while the content of La is more than 0·1 wt-%, recrystallisation was promoted.

Reducing Lattice Thermal Conductivity of the Thermoelectric Compound AgSbTe2 (P4/mmm) by Lanthanum Substitution: Computational and Experimental Approaches

In this study we performed lattice dynamics first-principles calculations for the promising thermoelectric (TE) compound AgSbTe2, and estimated the stability of its three polymorphs over a wide temperature range from 0 to 600 K. We calculated the vibrational density of states of the AgSbTe2 (P4/mmm) phase. The results suggested that formation of substitutional defects at Ag-sublattice sites impedes lattice vibrations, thereby reducing lattice thermal conductivity. We focused on calculations based on the Debye approximation for the compound La0.125Ag0.875SbTe2, and predicted reduction of the average sound velocity from 1684 to 1563 m s−1 as a result of La doping. This is manifested as a ca. 14% reduction in thermal conductivity. To confirm the results from computation we produced two Ag–Sb–Te-based alloys, a ternary alloy without La addition and a quaternary alloy containing La. We measured the thermal conductivity of both alloys by use of the laser flash analysis method, and, as a result of La alloying, observed a reduction in thermal conductivity from 0.92 to 0.71 W m−1 K−1 at 573 K, as calculated from first principles.

Large Electromechanical Response in Lead‐Free La‐Doped BNKT–BST Piezoelectric Ceramics

Piezoceramics 0.99[(Bi0.5Na0.4K0.1)1−xLaxTiO3]−0.01[Ba0.7Sr0.3TiO3] (BNKT–BST–Lax, x = 0–0.030) were synthesized using a conventional solid‐state reaction method. X‐ray diffraction revealed a phase transition from a tetragonal to cubic phase at x ≥ 0.005. The maximum dielectric constant as well as the depolarization temperature (Td) decreased with increasing La content. La addition interrupted the polarization and strain hysteresis loops and demonstrates that the ferroelectric order of the BNKT–BST ceramics lead to a reduction in the remnant polarization and coercive field. However, the destabilization of the ferroelectric order is accompanied by a significant increase in the unipolar strain which is highest at x = 0.020 with a value of ~0.39% and corresponding normalized strain, d*33 (= Smax/Emax) of 650 pm/V. It was observed that the unipolar strain of x = 0.020 is very temperature insensitive up to 125°C, even at 125°C the d*33 is as high as ~431 pm/V. Moreover, an electric‐field‐dependent XRD was conducted to identify the main source of the high strain and a recoverable transformation from cubic to a rhombohedral–tetragonal mixed phase was observed. The recoverable field‐induced phase transformation is suggested to be the main cause for the obtained large strain at x = 0.020 in the BNKT–BST–Lax ceramics.

Microstructure and hydrogen storage properties of (Ti0.32Cr0.43V0.25) + x wt% La (x = 0–10) alloys

The composite alloy of Ti0.32Cr0.43V0.25 with x wt% La (where x = 0–10) was prepared by arc melting technique. The effect on hydrogen storage capacity, flatness of the plateau pressure, and residual hydrogen was investigated in La added Ti0.32Cr0.43V0.25. Crystalline phase and microstructure of the prepared composite alloy were investigated and characterized by XRD, SEM and TEM. The crystal structure was refinement using Rietveld analysis. The effective hydrogen storage capacity of the composite alloy was found comparable to the parent alloy, when 5 wt% La was added. The effective hydrogen capacity (∼2.31 wt%) was close to that of the parent alloy (2.35 wt%) and the plateau slope was significantly improved from 30.5 of the parent alloy to 14.6. Appropriate mechanisms associated with the improved flatness by the La addition has been discussed in terms of the refined crystalline structure. Using TG/DTA method we have shown the differences in the interaction of residual hydrogen with the BCC phase of both parent alloy and 5 wt % La mixed alloy.

First-principles study of the effect of lanthanum on the Cu diffusion mechanism in bcc-Fe

The influence of La on the Cu precipitation in bcc-Fe is determined by first-principles density functional calculations. The binding energies of La-vacancy, Cu-vacancy pairs, and La-Cu pair are calculated, and the effects of La atoms on the diffusion activation energy of Cu atoms in bcc-Fe are considered. It is found that there exist strong attractive interactions between La atom and vacancy and between La atom and adjacent Cu atom. In addition, the formation energy of the vacancy adjacent to Cu atom increases significantly with the La addition, suggesting that vacancy is difficult to form in the La and Cu segregation zone. Meantime, we find that the migration energy of Cu atom is enhanced due to the attractions of La atom to adjacent vacancy and Cu atom. The calculated results of the vacancy formation energy and migration energy indicate that Cu atom possesses a higher diffusion activation energy after the La addition, and in turn, delays the segregation and precipitation process of the Cu rich phase in bcc-Fe.

First-principles characterization of lanthanum occupying tendency in -Fe and effect on grain boundaries

The -Fe 3[110] (112) symmetrical tilt grain boundary model is established by the coincidence site lattice theory. First-principles plane wave ultrasoft pseudopotential method based on the density functional theory is used to calculate the La occupying tendency in -Fe. The results show that La elements tend to be located at grain boundary in the -Fe since the impurity formation energy keeps lowest. On this basis, the electronic structure of La doped in -Fe grain boundary is also calculated. The results indicate that the charges in the system are redistributed to provide more electrons for the grain boundary bonding when the La occupies -Fe grain boundary. Meanwhile, Fe atoms obtain more electrons, and the La doped region combination has the ion-tendency toward strengthening the interaction between La atom and Fe atoms in the adjacent boundary region, and the Fe atom bonds in the grain boundaries and on both sides of the grain boundary also strengthen, which is the reason why the mechanical properties change from the energy point of view. Moreover, La addition also makes the atomic density of states on the grain boundary move to the left, reduce the total energy of the system, and make the grain boundary more stable.

Effects of Microalloying with Lanthanum on Recrystallization of Cold Rolled Pure Copper

The pure copper ingots with different microalloying lanthanum (La) addition were cold rolled to a cumulative area reduction of 80% at room temperature and then subjected to various annealing treatments. The results show that the recrystallization of alloys was retarded at first and then promoted with increasing La concentration. It is noted that the recrystallization of alloys with a small amount of La was retarded. But, the recrystallization of alloys with a large amount of La was accelerated. In addition, the models of recrytallization kinetics of alloys were established to predict the recrystallisation degree of the deformed pure copper with different lanthanum addition during an isothermal annealing.

Effect of dose methods of a synthetic organic polymer and PFC on floc properties in dyeing wastewater coagulation process

Papermaking sludge and spent pickling liquor were recycled to synthetize an organic polymer flocculant (LA) and polyferric chloride (PFC), respectively. They were used in synthetic dyeing wastewater treatment – disperse yellow (DY) and reactive blue (RB). Effect of PFC, dual-coagulant (PFC+LA) and second dose of LA after breakage period (PFC − LA) on color removal, floc regrowth and floc structure were comparatively investigated. The result showed that PFC could achieve excellent color removal, around 90% for the two dyes at optimal dosages. LA addition after PFC gave a little higher color removal efficiency but much larger flocs. Specifically, ratio values of PFC–flocs for DY and RB were approximately 1.43 and 0.59 respectively, compared with 1.75 and 0.72 for flocs formed by PFC+LA. Floc recoverability was also much higher at the usage of LA when there was a breakage period, and they were in the order of PFC − LA>PFC+LA>PFC. Additionally, comparing with those of PFC, roughly opener flocs were reformed by PFC − LA and PFC+LA after breakage because of LA bridging. For instance, TWV values (%) were 10.24, 13.24 and 16.16 respectively for PFC, PFC+LA and PFC − LA in RB treatment. LA favored charge neutralization, adsorption and bridging in the coagulation process.

Effect of Elements Cerium and Lanthanum on Eutectic Solidification of Al-Si-Cu near Eutectic Cast Alloy

The properties of Al-Si-Cu cast alloys are strongly affected by eutectic Al-Si and Al-Cu phases. The characteristic parameters of these two phases with additions cerium 1wt % (Ce) and lanthanum1 wt % (La) were investigated in Al-11Si-2Cu near eutectic alloy using computer-aided cooling curve thermal analysis. As a result, the La additive showed the highest (TNAl-Si) while the Ce additive showed very little effect. In addition, the growth temperature (TGAl-Si) is decreased by adding Ce compared to the base alloy and La addition. Additives showed an increase of recalescence magnitude (TRAl-Si). Addition La and Ce increased the nucleation and growth temperature of Al-Cu phase. The microstructure analysis on the silicon morphology showed that 1 wt % La and 1 wt % Ce additions play refiner role in Al-Si-Cu near eutectic alloys. Findings are also confirmed by aspect ratio of eutectic silicon phase.

Reforming of a model sulfur-free biogas on Ni catalysts supported on Mg(Al)O derived from hydrotalcite precursors: Effect of La and Rh addition

Ni catalysts supported on calcined Mg–Al hydrotalcite, Mg(Al)O, were prepared and the effect of the addition of La and/or Rh was tested in the performance of the catalysts in the dry reforming of methane with excess of methane in the feed, simulating a model sulfur-free biogas. The effect of adding synthetic air was assessed. The catalysts were characterized by surface area (BET), XRD, TPR and XPD. The results showed the reconstruction of the hydrotalcite structure during the Ni(NO3) impregnation, with the segregation of the lanthanum. In the catalyst without Rh and La, Ni showed a strong interaction with the support Mg(Al)O, showing high reduction temperatures in TPR test. The addition of Rh and La increased the amount of reducible Ni species and facilitated the reduction of the species interacting strongly with the support which resulted in high rates of carbon deposition. The NiMgAl catalyst presented the strong Ni-support interactions and the best performance with low carbon deposition at both conditions of reaction. The NiMgAl catalyst did not present deactivation during 24 h of stability testing in the oxidative reforming of a model biogas.

Effect of cerium and lanthanum additives on plasma electrolytic oxidation of AZ31 magnesium alloy

Plasma electrolytic oxidation (PEO) coatings on AZ31 magnesium (Mg) alloy were developed using the aqueous solution with alkaline silicate and sodium hydroxide as a base electrolyte system. The effects of cerium (Ce) nitrate and lanthanum (La) nitrate additives on the voltage response, microstructure, compositions and corrosion resistance of PEO coatings were investigated by scanning electron microscopy (SEM), energy-dispersive spectrum (EDS), X-ray diffraction (XRD) and potentiodynamic polarization tests, etc. The results showed that Ce and La additives increased the stable voltage and compactness of the PEO coatings, while, those did not change the compositions of the PEO coatings. The corrosion resistance of the PEO coating obtained in solutions with La nitrate of 0.1 g/L was the best, followed by that with Ce nitrate of 0.1 g/L and that without additives.

Advanced lignin-acrylamide water treatment agent by pulp and paper industrial sludge: Synthesis, properties and application

A novel flocculant LA (lignin-acrylamide polymer), which was used as aid for aluminum sulfate and polyaluminum chloride in this study, was prepared by grafting acrylamide onto lignin that deriving from pulp and papermaking sludge. Physicochemical properties of LA were measured by X-ray photoelectron spectroscopy and scanning electron microscopy. The experimental outcome indicated acrylamide was grafted onto the lignin backbone successfully. The effects of LA addition were evaluated on coagulation performance and floc characteristics as a function of aluminum (Al) dosage, such as floc size, growth rate, strength and recoverability. Effects of different dosing sequences, Al dosed first and LA dosed first, were also investigated. LA used as coagulant aid markedly enhanced the removal efficiency of turbidity and dissolved organic carbon, especially at low Al dosages. The dissolved organic carbon removal efficiencies of aluminum sulfate and polyaluminum chloride at the Al dosage range selected in this study were improved more than 30% and 5% by LA, respectively. LA dramatically enlarged floc size and it was in the order: Al dosed first > LA dosed first > Al. Floc strength and recoverability were also improved by LA. LA played a significant role in charge neutralization, adsorption and bridging in floc formation.

Effect of La Promotion on Co/ZrO&lt;sub&gt;2&lt;/sub&gt; Catalysts in Fischer-Tropsch Synthesis

The effects of lanthanum promotion on cobalt based catalysts in Fischer-Tropsch synthesis were investigated. The Co/ZrO2 catalysts promoted by lanthanum had higher activity and selectivity in Fischer-Tropsch synthesis. The catalyst with the La content 1% had the highest activity and selectivity attributed to the promotion effect of La. However, excessive La addition could depress the activity of the catalyst due to the Co-La interaction and the lower reduction degree.