Lower Oxidation Rate Research Articles

Structural and Functional Insights into the Roles of Potential Metal-Binding Sites in Apostichopus japonicus Ferritin.

Ferritin is widely acknowledged as a conservative iron storage protein found in almost all living kingdoms. Apostichopus japonicus (Selenka) is among the oldest echinoderm fauna and has unique regenerative potential, but the catalytic mechanism of iron oxidation in A. japonicus ferritin (AjFER) remains elusive. We previously identified several potential metal-binding sites at the ferroxidase center, the three- and four-fold channels in AjFER. Herein, we prepared AjFER, AjFER-E25A/E60A/E105A, AjFER-D129A/E132A, and AjFER-E168A mutants, investigated their structures, and functionally characterized these ferritins with respect to Fe2+ uptake using X-ray techniques together with biochemical analytical methods. A crystallographic model of the AjFER-D129A/E132A mutant, which was solved to a resolution of 1.98 Å, suggested that the substitutions had a significant influence on the quaternary structure of the three-fold channel compared to that of AjFER. The structures of these ferritins in solution were determined based on the molecular envelopes of AjFER and its variants by small-angle X-ray scattering, and the structures were almost consistent with the characteristics of well-folded and globular-shaped proteins. Comparative biochemical analyses indicated that site-directed mutagenesis of metal-binding sites in AjFER presented relatively low rates of iron oxidation and thermostability, as well as weak iron-binding affinity, suggesting that these potential metal-binding sites play critical roles in the catalytic activity of ferritin. These findings provide profound insight into the structure-function relationships related to marine invertebrate ferritins.

Oxidation Behavior of Si-Modified Aluminide Coatings on K438 Superalloy Prepared Using a Hybrid Slurry/Pack Cementation Process

A Si-modified aluminide coating was prepared on nickel-based K438 superalloy using a hybrid slurry/pack cementation process. The microstructures indicated that the coatings exhibited a two-layer structure: the outer Al-rich Ni0.9Al1.1 layer with the dispersion of minor Ni2Al3 and Cr-rich phases of Al13Cr2 and Cr5Si3 and the inner interdiffusion layer. For comparison, simple aluminide coatings were also produced using normal pack cementation. Compared with the K438 superalloy and simple aluminide counterpart, the Si-modified aluminide coatings exhibited a lower oxidation rate and improved alumina scale adhesion in air at 1,100°C. Furthermore, the Si-modified aluminide coatings showed longer service life compared to the simple aluminide coatings because the addition of Si mitigated the degradation of coatings. Therefore, the simple aluminide lost protection while the Si-modified aluminide coatings were still protective after 300 h.

Effects of SCR catalyst breakage on mercury emission properties in coal-fired power plant: field testing and laboratory evaluation

Field testing toward mercury emission properties was conducted at a 300 MW coal-fired power station. Selective catalytic reduction (SCR) was found to reduce Hg content in flue gas significantly through catalyst breakage during the commercial testing in a 300 MW coal-fired power station. Field testing results indicate that the total mercury concentration in flue gas at electrostatic precipitator (ESP) inlet and ESP outlet increase due to SCR catalyst breakage. Correspondingly, mercury content in fly ash decrease and mercury content in gypsum increase. The evolution in laboratory confirmed the Hg0 oxidation capability of commercial SCR catalyst. Catalyst breakage leads to space velocity increasing, so that the lower Hg0 oxidation rates caused the mercury transformation change in flue gas and solid byproducts.

Signatures of Mitochondrial Dysfunction and Impaired Fatty Acid Metabolism in Plasma of Patients with Post-Acute Sequelae of COVID-19 (PASC).

Exercise intolerance is a major manifestation of post-acute sequelae of severe acute respiratory syndrome coronavirus infection (PASC, or "long-COVID"). Exercise intolerance in PASC is associated with higher arterial blood lactate accumulation and lower fatty acid oxidation rates during graded exercise tests to volitional exertion, suggesting altered metabolism and mitochondrial dysfunction. It remains unclear whether the profound disturbances in metabolism that have been identified in plasma from patients suffering from acute coronavirus disease 2019 (COVID-19) are also present in PASC. To bridge this gap, individuals with a history of previous acute COVID-19 infection that did not require hospitalization were enrolled at National Jewish Health (Denver, CO, USA) and were grouped into those that developed PASC (n = 29) and those that fully recovered (n = 16). Plasma samples from the two groups were analyzed via mass spectrometry-based untargeted metabolomics and compared against plasma metabolic profiles of healthy control individuals (n = 30). Observational demographic and clinical data were retrospectively abstracted from the medical record. Compared to plasma of healthy controls or individuals who recovered from COVID-19, PASC plasma exhibited significantly higher free- and carnitine-conjugated mono-, poly-, and highly unsaturated fatty acids, accompanied by markedly lower levels of mono-, di- and tricarboxylates (pyruvate, lactate, citrate, succinate, and malate), polyamines (spermine) and taurine. Plasma from individuals who fully recovered from COVID-19 exhibited an intermediary metabolic phenotype, with milder disturbances in fatty acid metabolism and higher levels of spermine and taurine. Of note, depletion of tryptophan-a hallmark of disease severity in COVID-19-is not normalized in PASC patients, despite normalization of kynurenine levels-a tryptophan metabolite that predicts mortality in hospitalized COVID-19 patients. In conclusion, PASC plasma metabolites are indicative of altered fatty acid metabolism and dysfunctional mitochondria-dependent lipid catabolism. These metabolic profiles obtained at rest are consistent with previously reported mitochondrial dysfunction during exercise, and may pave the way for therapeutic intervention focused on restoring mitochondrial fat-burning capacity.

Role of Al and Cr on cyclic oxidation behavior of AlCoCrFeNi2 high entropy alloy

In this work, cyclic oxidation behavior of AlCoCrFeNi 2 , Al 1.5 CoCrFeNi 2 , AlCoCr 1.5 FeNi 2 , and Al 1.5 CoCr 1.5 FeNi 2 High Entropy Alloys (HEAs) has been studied at 1050 °C for 10 cycles to understand the effect of Al and Cr in AlCoCrFeNi 2 based HEAs. X-ray photoelectron spectroscopy, X-ray diffraction, electron backscattered diffraction, scanning electron microscopy with energy dispersive spectroscopy were used to study the base metals and oxidized samples. It was found that in all the samples, face centered cubic, and body centered cubic phases were present in different phase fractions. Al 1.5 CoCrFeNi 2 alloy shows lower oxidation rate with oxidation rate constant (K p ) in the order of 10 −13 g 2 cm −4 s −1 . The lowest oxidation rate of Al 1.5 CoCrFeNi 2 alloy is attributed to the presence of higher Al content as it forms protective continuous thin Al 2 O 3 oxide layer which suppress further oxidation by preventing ingress of oxygen into the substrate. Presence of higher Cr content results in forming protective Cr 2 O 3 oxide layer but eventually it spalls off leading to the exposure of substrate for further oxidation. • Cyclic oxidation behavior of AlCoCrFeNi 2 , Al 1.5 CoCrFeNi 2 , AlCoCr 1.5 FeNi 2 , and Al 1.5 CoCr 1.5 FeNi 2 alloys was studied at 1050 °C for 10 cycles. • Al 1.5 CoCrFeNi 2 alloy shows lower oxidation rate with oxidation rate constant (K p ) in the order of 10 −13 g 2 cm −4 s −1 . • Formation of continuous Al 2 O 3 oxide layer is observed in Al 1.5 CoCrFeNi 2 alloy. • Presence of higher Cr content results in forming protective Cr 2 O 3 oxide layer but eventually it spalls off.

Clarifying the mitigation effect of proton irradiation on the intergranular oxidation of 316L stainless steel in high temperature water

The role of proton irradiation in the intergranular oxidation of 316L stainless steel after long-term immersion in simulated PWR primary water was clarified by comparing the microstructural and microchemical features of oxide between the irradiated grain boundary (GB) and its un-irradiated counterpart. As such, the interference from difference in GB structure can be ruled out. Surprisingly, the results reveal that the intergranular oxide penetration in the irradiated region is shallower than that in the un-irradiated region. It is found that Si segregated at the irradiated GB diffuses outwards preferentially and gets oxidized due to its high diffusivity and affinity to oxygen. The Si-enriched oxide in the intergranular oxide tip of irradiated GB can act as a temporary diffusion barrier for oxygen, although it tends to dissolve near the sample surface. Meanwhile, the efficiency of elements (especially Cr) transport along irradiated GB to the oxidation front is promoted mainly due to the vacancies created by preferential diffusion of Si, resulting in higher Cr content at the intergranular oxide tip. The combination of Si and Cr enrichments in the intergranular oxide tip can enhance the resistance to oxidation and eventually leads to a lower oxidation rate for the irradiated GB. For the first time, our study determines that irradiation can enhance the intergranular oxidation resistance of stainless steel after long-term immersion in simulated PWR primary water when the sample is not stressed.

Improvement in oxidation resistance of TiAl alloys by in-situ precipitation of Ti2AlC at the interface of α2 and γ lamellae

Herein, in-situ sintered micro-nano Ti2AlC/TiAl composite with fully lamellar structures were designed by spark plasma sintering to improve the high-temperature oxidation resistance of TiAl alloys. The Ti2AlC/TiAl composite exhibited lower oxidation rate and thinner oxide scale enriched Al2O3 compared to TiAl alloy after 750 ℃ and 850 ℃ oxidation, suggesting that oxidation resistance of the Ti2AlC/TiAl composite was improved. The superior oxidation resistance of the Ti2AlC/TiAl composite was mainly attributed to Ti2AlC particles hindered the diffusion of O atoms and stabilized the Al-rich oxide layer by the formation of more Ti-Al-N layers due to the nitridation susceptibility of Ti2AlC.

EFFECTS OF STATINS ON SUBSTRATE UTILIZATION DURING EXERCISE

PURPOSE: Statin is the most prescribed medicine worldwide to lower cardiovascular risk. Its blood triglyceride lowering effect, may limit fat mobilization/oxidation during exercise. METHODS: Nine individuals with metabolic syndrome, chronically treated with statins to correct their dyslipidemia exercised at three increasing intensities (40, 70, and 85% VO2 MAX) while taking statins or placebo using a randomized double-blind crossover design. Indirect calorimetry and stable isotope tracer techniques were combined to assess plasma substrate kinetic and oxidation. RESULTS: As expected, statin use lowered resting plasma triglyceride concentration (i.e., PLAC 1.4±0.7 vs STAT 1.1±0.5 mmol·L-1, p = 0.003), and also plasma triglyceride concentration during exercise (i.e., PLAC 1.7±0.8 vs STAT 1.2±0.5 mmol·L-1; p < 0.001). Ra glycerol (i.e., index of whole-body lipolysis) increased along with exercise intensity but the increase was attenuated by statins (p < 0.014) at the 85% VO2 MAX exercise intensity (i.e., PLAC 7.4±1.9 vs STAT 5.8±2.2 mM·kg·min-1; p = 0.046). This 21% lower lipolysis during STAT did not limit fat oxidation that was similarly low in PLAC and STAT (i.e., PLAC 0.7±2.1 vs STAT 0.8±2.2 mM·kg·min-1; p = 0.459). STAT increased resting plasma glucose concentration (i.e., PLAC 6.6±1.6 vs STAT 6.8±1.6 mmol·L-1, p = 0.036) but did not affect exercise glucose or insulin plasma. Rates of glucose appearance (i.e., Ra glucose, index of liver glucose output) were similar during PLAC and STAT at rest and during exercise. Glucose disappearance rates increased during the first two exercise intensities (i.e., 40 and 70% VO2 MAX), but decreased in both groups at 85% VO2 explaining the ensuing hyperglycaemia at this intensity. CONCLUSIONS: Statin reduces exercise lipolysis during high intensity exercise, without affecting the already low rates of fat oxidation at that intensity. However, statin use does not affect plasma glucose kinetics or carbohydrate oxidation during exercise in a wide range of intensities in individuals chronically medicated with this drug.

Influence of Ti on Oxide Formation During Isothermal Oxidation of 800H Ni-Based Alloys

In this research, a 800H Ni-based alloy was experienced a solution treatment procedure at two different temperatures. The solution-treated alloys were undergo a high-temperature oxidation under isothermal conditions at 500°C for 500 hours in laboratory air. The alloy was characterized using OES, XRD, SEM and FESEM equipped with an EDX spectrometer. It was found that the solution-treated alloy at 950°C produced a small grain size, and alloy treated at 1100°C produced a large grain size. The XRD results show that various oxides phases were detected. The oxidation kinetics followed the parabolic rate law indicating the oxide was formed based on diffusion-controlled oxide growth rate. The alloys with small grain sizes exhibited a lower oxidation rate, hence have excellent oxidation resistance. This is due to the accessibility of the high ion diffusion route through the grain boundaries of small-grained alloy and thus permits the speedy establishment of the initial oxide layer. Uniform oxide scale formed on a small-grained oxidized sample with visible overgrow discrete oxide particle comprised of Ti-rich oxide. The large-grained oxidized sample indicates evidence of oxide exfoliation indicating poor oxidation protection.

Catalyzed degradation of polycyclic aromatic hydrocarbons by recoverable magnetic chitosan immobilized laccase from Trametes versicolor.

The capability of laccase to oxidate a broad range of polyphenols and aromatic substrates in vitro offers a new technological option for the remediation of polycyclic aromatic hydrocarbon (PAH) pollution with high cytotoxicity. However, laccase application in the remediation of PAH-contaminated sites mainly suffers from a low oxidation rate and high cost because of the difficulty in its recovery. In this study, laccases were immobilized on magnetic Fe3O4 particles coated with chitosan (Fe3O4@SiO2-chitosan) to improve the operational stability and reusability in the treatment of PAH pollution. The enzyme fixation capacity reached 158mg g-1, and 79.1% of free laccase activities were reserved under the optimum immobilized condition of 4% glutaraldehyde, 1.0mg mL-1 laccase, 2 h covalent bonding time, and 6 h fixation time. The degradation efficiencies of anthracene (ANT) and benzo[a]pyrene (B(a)P) by Fe3O4@SiO2-chitosan immobilized laccase in 48h were 81.9% and 69.2%, respectively. Furthermore, it is very easy to magnetically recover the immobilized laccase from reaction systems and reuse it in a new batch. The relative activities of immobilized laccase were over 50% for the degradation of ANT and B(a)P in three catalytic runs, reaching the goal of substantially reducing cost in practice. According to the results from quantum calculations and mass spectrum analyses, the degradation products of ANT and B(a)P by laccase were anthraquinone and B(a)P-dione, respectively. The findings from this study provide valuable insight in promoting the application of immobilized laccase technology in the remediation of PAH contamination.

Oxidation behavior of Ti-Nb-Mo-Al-Six refractory high entropy alloy at 1000℃

The oxidation behavior of TiNbMo0.5Al0.225Six (x = 0.1, 0.25, 0.4, 0.55) refractory high entropy alloys in air at 1000 ℃ was investigated. These novel alloys have a BCCss / (Nb, Ti)5Si3 eutectic structure in the as-cast state. Oxidation resistance results reveal that the mass gain shifts from a mass loss (Si0.1) to a parabolic law (Si0.25, Si0.4, Si0.55). An appropriate increase in Si content favors a lower oxidation rate. The β-(Nb, Ti)5Si3 was studied to have excellent oxidation resistance, while the region where γ-(Nb, Ti)5Si3 existed is the main site of porosity generation. The suitable Si content promotes the appearance of a Mo-rich layer, thus preventing the oxide evaporation. Data availabilityThe data that support the findings of this study are available from the corresponding author, specifically Professor Liang Wang of the Harbin Institute of Technology (email: wliang1227@hit.edu.cn) upon reasonable request.

Oxidation kinetics of overstoichiometric TiB2 thin films grown by DC magnetron sputtering

We systematically study the oxidation properties of sputter-deposited TiB2.5 coatings up to 700 °C. Oxide-scale thickness dox increases linearly with time ta for 300, 400, 500, and 700 °C, while an oxidation-protective behavior occurs with dox=250∙ta0.2 at 600 °C. Oxide-layer’s structure changes from amorphous to rutile/anatase-TiO2 at temperatures ≥ 500 °C. Abnormally low oxidation rate at 600 °C is attributed to a highly dense columnar TiO2-sublayer growing near oxide/film interface with a top-amorphous thin layer, suppressing oxygen diffusion. A model is proposed to explain the oxide-scale evolution at 600 °C. Decreasing heating rate to 1.0 °C/min plays a noticeable role in the TiB2.5 oxidation.

Preparation and enhanced oxidation behavior of microalloyed Mo5SiB2 alloy at 1300 °C

Microalloyed Mo5SiB2 alloys were fabricated by spark plasma sintering (SPS). The effects of different sintering temperatures and yttrium additions on the microstructure and high-temperature oxidation behavior of the alloys were systematically investigated. For the optimum Mo-13Si-25B-0.2Y alloy sintered at 1750 °C, adding small amounts of rare-earth yttrium refined the grains to an average size of ~400 nm without reducing the Mo5SiB2 content. During oxidation at 1300 °C, the “fishlike” Y2Si2O7 and Y2O3 phases were formed and anchored on the surface of the oxide layers, promoting the oxidation of silicon and accelerating the formation and coverage of the oxide protective film. Moreover, yttrium promoted the in situ deformation of a self-generated protective borosilicate glass film under high-temperature oxidation by accelerating Si oxidation. With prolonged oxidation time, viscous flow occurred to repair the internal cracks and tiny defects caused by the volatilization of MoO3 and prevented the inward diffusion of oxygen, as evidenced by a low oxidation rate constant of 0.95 mg2 cm−4 h−1 at 1300 °C for 50 h in the Mo-13Si-25B-0.2Y alloy.

Food insecurity is associated with higher respiratory quotient and lower glucagon-like peptide 1.

Food insecurity is known to be associated with obesity, but its association with physiological measures is unclear. Therefore, it was hypothesized that, compared with food-secure individuals, those with food insecurity would have higher 24-hour energy expenditure (EE [kilocalories per day]) and 24-hour respiratory quotient (RQ [ratio]). Subsequently, hormones involved in appetite regulation, substrate oxidation, and EE were explored. A total of 113 healthy participants without diabetes (75 men; mean [SD], age 40 [12] years; BMI 30 [8] kg/m2 ) were included in this analysis. Participants completed the Food Security Short Form, underwent a dual-energy x-ray absorptiometry scan, and spent 24 hours in a human respiratory chamber following a weight-maintaining diet. Compared with individuals with food security, participants with food insecurity had no difference in 24-hour EE. However, they had higher carbohydrate oxidation rates (p = 0.03) and lower lipid oxidation rates (p = 0.02), resulting in higher 24-hour RQ (p < 0.01). They also had lower fasting glucagon-like peptide 1 (p = 0.03) concentrations. Food insecurity is associated with higher 24-hour RQ and lower fasting glucagon-like peptide 1 concentrations, metabolic and hormonal differences previously shown to drive greater calorie intake in the setting of unrestricted food availability. These findings therefore provide new insight into the paradoxical link between restricted food access and increased adiposity.

Finite element based fuel performance investigation of U3Si2–FeCrAl design under normal and RIA conditions

U3Si2–FeCrAl system has been a promising Accident Tolerant Fuels (ATFs) candidate for its higher thermal conductivity, higher uranium density and lower oxidation rate. As a part of wide efforts to analyze the thermo-mechanical behaviors of the proposed ATFs, a finite element-based fuel performance code called BEEs, developed based on MOOSE (Multiphysics Object-Oriented Simulation Environment) framework, has been extended to analyze the behaviors of U3Si2–FeCrAl under reactivity insertion accidents (RIA). In this work, CABRI-REP tests were simulated to validate the modeling capacity of BEEs for RIA firstly. Then, with the fuel behavior models applicable to U3Si2 and FeCrAl implemented in BEEs, the thermo-mechanical response of U3Si2–FeCrAl to postulated RIA conditions were evaluated and compared with UO2-Zircaloy, UO2–FeCrAl and U3Si2-Zircaloy systems. The results show that U3Si2–FeCrAl system can reduce the fuel temperature (about 400–600 K) and delay gap closure during normal operation. The performance of cladding in U3Si2–FeCrAl system is comparable with UO2-Zircaloy and UO2–FeCrAl systems. However, the fuel central temperature of U3Si2–FeCrAl system is found to increase (about 110–180 K when RIA occurs at zero burnup, and about 170–190 K when RIA occurs after normal operation) compared to systems with UO2 fuel due to the lower volumetric heat capacity of U3Si2, which can lead to a threat to fuel security in RIA conditions, especially taking the lower melting point of U3Si2 (U3Si2 is ∼1938 K and UO2 is ∼3138 K) into account.

Defect engineering over anisotropic brookite toward substrate-specific photo-oxidation of alcohols

Generally adopted design strategies for enhancing the photocatalytic activity are aimed at tuning properties such as the visible light response, the exposed crystal facets, and the nanocrystal shape. Here, we present a different approach for designing efficient photocatalysts displaying a substrate-specific reactivity upon defect engineering. The defective anisotropic brookite TiO2 photocatalyst functionalized with Pt nanocrystals are tested for alcohol photoreforming showing up to an 11-fold increase in methanol oxidation rate, compared to the unreduced one, whilst presenting much lower ethanol or isopropanol specific oxidation rates. We demonstrate that the alcohol oxidation and hydrogen evolution reactions are tightly related, and when the substrate-specific alcohol oxidation ability is increased, the hydrogen evolution is significantly boosted. The reduced anisotropic brookite shows up to twenty-six-fold higher specific photoactivity with respect to anatase and brookite with isotropic nanocrystals, reflecting the different type of defective catalytic sites formed depending on the TiO2 polymorph and its crystal shape. Advanced in-situ characterizations and theoretical investigations reveal that controlled engineering over oxygen vacancies and lattice strain produces large electron polarons hosting the substrate-specific active sites for alcohol photo-oxidation.

Assessment of CrFeCoNi and AlCrFeCoNi High-Entropy Alloys as Bond Coats for Thermal Barrier Coatings

High-entropy alloys (HEAs) represent a relatively new group of multicomponent alloys that have shown great potential for applications requiring tribological and oxidation resistant properties. Consequently, thermally sprayed coatings of different HEA chemistries have received increasing research attention. In this paper, atomized equimolar CrFeCoNi and AlCrFeCoNi feedstocks were used for high velocity air-fuel spraying (HVAF) to produce overlay coatings using two different nozzle configurations. The microstructure, phase constitution and hardness of the coatings were analyzed along with the primary aim of testing the coatings for their oxidation behavior. The performance of the two HEA chemistries was compared with two commercial MCrAlY coatings that are well-established bond coat materials for thermal barrier coatings (TBCs). An investigation was conducted to test the coatings’ performance as bond coats by applying suspension plasma sprayed yttria-stabilized zirconia top coats and evaluating the thermal cycling behavior of the TBCs. The AlCrFeCoNi-coating was found to demonstrate a lower oxidation rate than the CrFeCoNi-coating. However, the AlCrFeCoNi-coating was found to form more rapid oxide scales compared with the commercial bond coat material that also contained reactive elements.

Atomic insights into combustion mechanism of nano‐aluminum hydride

As an important hydrogen storage material, aluminum hydride is widely used in the combustion field. However, the oxidation behavior and potential mechanism of aluminum hydride nanoparticle (AHNP) in the combustion process are not clear. Molecular reactive dynamics was used to explore the oxidation behavior and mechanism of pure and core-shell AHNP with different oxide layer thickness, particle size and oxygen concentration. The simulation results show that uneven oxidation of AHNP surface presents branched distribution, and the oxidation process is carried out by the interdiffusion of O and Al. The core Al diffusion coefficient of 40 ps (1.42 × 10−4 cm2/s) is much larger than that of shell O atoms (4.90 × 10−5 cm2/s), indicating that oxidation of core-shell AHNP is dominated by the uneven diffusion of core Al into the oxide layer driven by an electrostatic force. This leads to the formation of hydrogen gas chamber of different sizes. Mean square displacement shows that core Al tends to diffuse into a thinner oxide layer. The oxide layer inhibits the diffusion of core Al and H, resulting in a slower oxidation rate. The smaller AHNP exhibits a micro-explosion oxidation accompanied by the formation of small Al clusters, and the reaction process is dominated by aluminum diffusion. The initial reaction of the larger AHNP is mainly concentrated on the surface, the subsequent oxidation processes rely on heterogeneous reactions between the oxidation phase and AlH3. Under lower oxygen concentration, AHNP shows a lower oxidation rate and heat release, where core Al and environment O atoms diffuse toward each other to form a homogeneous OAl phase. Under higher oxygen concentration, the active Al atoms diffuse outward to form a hollow spherical structure. This work provides fundamental insight into the storage and application of AHNP that serve as a high energy density fuel.

Effect of Cr nanoparticle dispersions with various contents on the oxidation and phase transformation of alumina scale formation on Ni2Al3 coating

In this work, the NiCr nanocomposite films were fabricated with various contents of Cr nanoparticle dispersions and then subsequently aluminized to obtain the Cr nanoparticle-dispersed Ni2Al3 coating at temperature 620 °C. For comparison, the samples without Cr nanoparticle dispersions were prepared under the same experimental condition. The results showed that the Ni2Al3 coating with Cr nanoparticle dispersions has a lower oxidation rate than the Cr-free Ni2Al3 coating after oxidation. The result also indicates that Cr nanoparticle dispersions in the Ni2Al3 coating promoted the transformation of θ-into-α alumina phase and surface microstructure evolution based on the investigations of photo-stimulated luminescence spectroscopy (PSLS) and scanning electron microscopy (SEM), respectively. Furthermore, with increasing the content of Cr nanoparticle dispersions from 2.5 wt% to 5 wt% in the Ni2Al3 coatings can significantly reduce the oxidation rate through accelerated phase transformation of metastable to stable alumina. In addition, the Cr nanoparticles in Ni2Al3 not only mitigate the cavities formation at the interface, but also grow an adherent alumina scale on aluminide.

Elemental sulfur recommendation for pH reduction in soils from Southern Brazil

ABSTRACT The elemental sulfur (S0) application may reduce soil pH, benefiting plants adapted to acid conditions and lessening problems of overliming. Nevertheless, there is no official recommendation for its application. The objective of the study was to quantify the S0 doses required to reduce the pH of soils from Southern Brazil. The experiment was carried out in the laboratory in a factorial scheme (5 × 5), with a completely randomized design and three replicates. The treatments consisted of five soils, and five doses of S0, corresponding to 0, 50, 100, 150, and 200% of the estimated dose need to reach pH 4.0. The applied doses of S0 resulted in reduction of pH and base saturation (V%) and increase of potential acidity (H + Al). These effects, however, were reduced due to the low rate of oxidation of the S0 applied (0.76-3.36%). The soil variables correlated with S0 oxidation were Mg2+ (0.86***), Al3+ (-0.82***), H + Al (-0.89***), V% (0.68***) and aluminum saturation (m%) (-0.87***). In the evaluated soils the oxidation of 50 kg ha-1 of S0 was required to reduce one unit of pH in H2O.