Lower Oxidation Rate Research Articles

Evaluation of the Heat Resistance of the Fe-Cr-Al System Coatings

The influence of the chemical composition of aluminide coatings of the Fe-Cr-Al system on their heat resistance at 1100 °C was investigated. It is shown that the lowest oxidation rate is possessed by the coating obtained by aluminizing the Cr15Al5 alloy in the silumin melt, for which the depth of corrosion penetration after 500 h at 1100 °C did not exceed 2.5 μm. The depth of corrosion penetration after 500 h at 1100 °C in coatings with a higher chromium content (23 at.%) reaches 8.9 μm. A decrease in the content of chromium (up to 5 at.%) or aluminum (up to 10 at.%) in the surface layer is accompanied by a critical increase in the corrosion rate. The longest time of retention of heat-resistant properties at 1100 °C is possessed by the coating obtained by aluminizing the Cr23Al5 alloy in an aluminum melt.

Ammonia Nitrogen Removal Performance with Parallel Operation of Conventional and Inverted A2/O Sewage Treatment Processes in Winter

Ammonia nitrogen (NH4+-N) removal capacities of the A2/O and inverted A2/O processes were analyzed with the same inlet and parallel operation during winter. When the operating water temperature was 14℃, the inverted A2/O process exhibited lower NH4+-N removal from the volumetric load[0.13 kg ·(m3 ·d)-1vs. 0.29 kg ·(m3 ·d)-1] and a lower ammonia oxidation rate (AOR)[0.07 kg ·(kg ·d)-1 vs. 0.11 kg ·(kg ·d)-1] than the A2/O process, whereas the two processes exhibited similar performance at 26℃.The quantitative results for the ammonia oxidizing bacteria (AOB) population were almost the same in the two parallel processes (3.2%±0.24% for the inverted A2/O process and 3.4%±0.31% for the A2/O process). Clone library analysis showed that at low temperatures, the inverted A2/O process had a lower capacity for ammonia nitrogen removal than A2/O process. This is because the particular AOB species[spirillum (Nitrosospira)] facilitated the slower AOR type (K-growth strategy) of nitrosation in the inverted A2/O process, whereas in the A2/O process, the faster AOR type (r-growth strategy) of nitrosation was facilitated by bacterium (Nitrosomonas). At 26℃, the dominant species in the two processes were Nitrosomonas. Through comprehensive analysis of the pollutants during the removal process, we found that although temperature is the leading cause of AOB advantage in species succession, the changes in the inverted A2/O process structure, caused by the aerobic unit, resulted in high COD load and high NH4+-N concentration, which were unfavorable for the growth of AOB. This shows that under conventional sewage conditions, the K-growth strategy is advantageous for the AOB species. Therefore, the structure of the inverted A2/O process for heterotrophic bacteria (phosphorus accumulating bacteria and denitrifying bacteria) indirectly affects the population distribution and succession of autotrophic ammonia-oxidizing bacteria, through COD load and other factors, thereby leading to weakened nitrification capacity at low temperatures.

Regulating the radial structure of polyacrylonitrile fibers during pre-oxidation and its effect on the mechanical properties of the resulting carbon fibers

The radial structure of polyacrylonitrile fibers oxidized before carbonization and its distribution directly affect the performance of the resulting carbon fibers. Optimizing the radial distribution of the oxidized structure and establishing a relationship between this structure and the mechanical properties of the final carbon fibers will help optimize the oxidation conditions for the preparation of high-performance carbon fibers. Solid-state nuclear magnetic resonance spectroscopy, optical microscopy, thermogravimetric analysis, and mechanical tests were used to investigate the effect of the oxidation reaction rate on the radial distribution of the structure of the oxidized fibers and the mechanical properties of the resulting carbon fibers. The oxidation reaction rates were controlled by regulating the oxidation temperature gradient. Results show that the degree of oxidation increases with both the average and initial oxidation rates. By increasing the average oxidation reaction rate, the oxidized structure penetrates deeper into the core region of the fibers, the content of oxygen-containing functional groups increases, the thermal stability of the fibers decreases, and the degree of graphitization of the final carbon fibers increases, but the density of the fibers is decreased and their mechanical properties are degraded. Compared with sample obtained with the lower initial oxidation rate, the number of oxygen-containing functional groups, thermal stability, degree of graphitization and density of the final carbon fibers of the sample with the higher initial oxidation rate are higher, and its tensile strength and modulus are respectively 4.2% and 2.2% higher. A new type of carbon fiber with high strength, medium modulus and a relatively large diameter is obtained under the optimized oxidation conditions.

New insight on mechanisms of Si element improving the oxidation resistance of titanium matrix composites

Initial oxidation behaviors of (Ti5Si3 + TiC)/Ti6Al4V composites were investigated using the simultaneous thermal analyzer in air for 2 h at 700 °C, 750 °C and 800 °C, respectively. Composites had a higher effective activation energy of oxidizing and lower oxidation rate than Ti6Al4V alloy, revealing that the composites possessed the higher oxidation resistance. The improvement of oxidation resistance of composites derived from the dissolved Si element in matrix and was strengthened with the content of dissolved Si increasing. Ti5Si3 and TiC particles showed a minor influence on the oxidation behaviors of composites.

Influence of ultrasound on the microbiological and physicochemical stability of saramunete ( Pseudupeneus maculatus ) sausages

The objective of this study was to investigate the stability of saramunete sausages submitted to different post-packaging procedures [heat treatment—HT (80°C/10 min); ultrasound—US (37 kHz/10 min); the combination of heat treatment and ultrasound—HT+US (80°C & 37 kHz/10 min); and control—C (no treatment)]. The combination HT+US at day 1 provided lower water activity (0.974 ± 0.002), pH (6.79 ± 0.03), and non-protein nitrogen (NPN—440.14 ± 4.86 mg/100 g) compared to the other treatments. During storage at 6.0 ± 1.0°C, HT+US provided better stability with lower rates of lipid oxidation, a shorter time for NPN stabilization, and a longer time for the accumulation of TVB-N. On the 22nd storage day, counts of ~4 log CFU psychrotrophic microorganisms were found and kept up to end of storage. Therefore, shelf life of up to 22 days is recommended for vacuum-packed saramunete sausage submitted to HT+US during refrigerated storage. Practical applications Fish consumption in Brazil is low compared to the recommended by the Food and Agriculture Organization. To increase consumption, it is necessary to use species of commercial interest, such as saramunete, to produce high added value products such as sausages (easier to prepare at home and longer shelf life). The use of combined processing steps employing emerging conservation techniques such as ultrasound may warrant the quality and increase the stability of saramunete sausages. It was observed that the use of ultrasound combined with heat treatment, after vacuum packing, warranted quality and increased the shelf life of the sausages. Ultrasound is a cost-effective and easy-to-apply technique that can be implemented at pilot and industrial scales.

Y-Hf co-doped Al1.1CoCr0.8FeNi high-entropy alloy with excellent oxidation resistance and nanostructure stability at 1200°C

A new type of Y-Hf co-doped Al1.1CoCr0.8FeNi high-entropy alloy (HEA) with a coherent nanostructure and its oxidation behavior at 1200°C are reported in this work. The nanostructure is highly stable and almost no phase coarsening can be observed in the HEA substrate during the prolonged oxidation. The Y-Hf co-doped Al1.1CoCr0.8FeNi HEA exhibits a very low oxidation rate, which is even lower than that of the typical FeCrAlYHf alloy, while its resistance to scale spallation significantly outperforms the typical NiCoCrAlYHf alloy. The highly stable nanostructure is beneficial to increase the homogeneity of Y and Hf distribution and thus strengthens the reactive elements effect, which can lower the oxidation rate and the growth stress of Al2O3 scale. Generally, the structural stability, the low growth rate of scale and the low growth stress of scale contribute to the excellent oxidation performance of Y-Hf co-doped Al1.1CoCr0.8FeNi HEA at 1200°C.

Demonstration of non-negligible oxygen exchange in the thermal oxidation of silicon carbide

Oxygen incorporation mechanism with various temperatures during the thermal oxidation of 4H–SiC in dry O2 has been investigated by the isotopic tracing technique. The results suggest that the oxygen exchange is the main incorporation mechanisms of oxygen for SiC oxidation. The temperature and locations of oxygen exchange are different from those in Si oxidation. In SiC thermal oxidation, oxygen exchange occurs even for extremely low oxidation rate at low temperature, and it is not confined to the surface region but throughout the oxide layer. The rate of oxygen exchange increases as temperature increases. This is the direct evidence that oxygen exchange in SiC oxidation cannot be negligible. By analysing the results of X-ray photoelectron spectroscopy and capacitance-voltage measurements, it is found that such significant oxygen exchange is not caused by a large number of defects. Moreover, based on the fitting of refractive index and extinction coefficient, the number of defects in the oxide layer decreases with the increase of temperature, which indicates that oxygen exchange contributes to reducing defects in the oxide layer during high-temperature oxidation and low-temperature post-oxidation annealing.

Combined effect of ultrasound and basic electrolyzed water on the microbiological and oxidative profile of low-sodium mortadellas

Ultrasound (US) and basic electrolyzed water (BEW) are considered emerging technologies; however, few studies have addressed the combination of both technologies in emulsified meat products. This study aimed to evaluate the individual and combined effect of US (25 kHz; 175 W; 20 min) and BEW (pH 10.99; −92.33 mV) on the microbiological and oxidative profile of low-sodium mortadellas (30% of NaCl reduction) stored for 90 days at 5 °C. The use of BEW alone increased the pH and reduced the redox potential of mortadellas, while the US did not affect these parameters. The combined application of US and BEW reduced the lactic acid bacteria counts by up to 0.36 log CFU/g. In addition, BEW stimulated the growth of lipolytic bacteria. The treatments subjected to US application alone showed a lower growth rate of lipolytic bacteria, lower lipid and protein oxidation, and higher ΔE* values. Therefore, the application of US and BEW may be a promising strategy to improve the microbiological and oxidative quality of mortadella during storage.

Copper Binding in Sweet Worts Made from Specialty Malts.

Trace levels of copper can impact the flavor stability of beer. The main source of copper is malt, and the wort copper levels are established during mashing and lautering. This study focuses on sweet worts made from experimental roasted and caramel malts. Potentiometric titrations using ion-selective electrodes combined with electron paramagnetic resonance spectroscopy have been used to investigate Cu(II) binding in worts as well as the impact of Cu(II) ions on the wort oxidative stability. High-temperature treatment during malting decreased Cu(II) binding affinities in the worts, with roasted malt worts having lower affinities than caramel malt worts of similar color and pH. Electron paramagnetic resonance spectra indicated dipeptides as the main Cu(II) chelators. A positive correlation between Cu and free amino nitrogen levels in worts is demonstrated. In dark worts with high rates of radical formation, Cu(II) had pronounced antioxidative effects. In contrast, moderate prooxidative effects were observed when adding Cu(II) to pale worts with inherently low rates of oxidation.

MoO3/TiO2 catalyst with atomically dispersed O-Mo-O structures toward improving NH4HSO4 poisoning resistance for selective catalytic reduction of nitrogen oxides

Slow progress in discovering new catalysts to circumvent the problem of ammonium bisulfate (NH4HSO4, ABS) poisoning has hindered further development of selective catalytic reduction (SCR) technology of NOx with ammonia (from numerous industrial processes) in afterburning systems at temperatures below dew point of ABS (typically between 280 °C and 320 °C). Recently, we have explored the use of atomically dispersed Mo species on TiO2 particles (hereafter denoted as MoO3/TiO2) as highly efficient catalyst for NH3-SCR reaction. In the present study, it will be shown that this type of catalyst is highly resistant to ABS poisoning for NH3-SCR reaction, overcoming a major issue afflicting the application of commercial V2O5-WO3/TiO2 catalyst at temperatures below the dew point of ABS. Aberration-corrected scanning transmission electron microscopy (STEM) suggests that most of the Mo species are present in atomically dispersed form in the MoO3/TiO2 catalyst. SO2 oxidation measurements show that the MoO3/TiO2 catalyst exhibits a substantially lower SO2 oxidation rate compared to the commercial V2O5-WO3/TiO2, mitigating ABS formation. Furthermore, decomposition of ABS on MoO3/TiO2 surface is found to be extremely facile. Temperature-programmed surface reaction (TPSR) with NO shows that the decomposition temperature of ABS over MoO3/TiO2 is 70 °C lower than that found on the commercial V2O5-WO3/TiO2 catalyst. Our investigations provide valuable information for the development of NH3-SCR catalysts with exceptional resistance to ABS poisoning for NOx emission control.

THE INFLUENCE OF THE FE-CR-AL SYSTEM COATINGS CHEMICAL COMPOSITION ON THEIR HEAT RESISTANCE

The influence of the chemical composition of the Fe-Cr-Al system coatings on their heat resistance at 1100 °C was investigated. It is shown that the lowest oxidation rate is possessed by the coating obtained by aluminizing the Cr15Al5 alloy in the silumin melt, for which the depth of corrosion penetration after 500 h at 1100 °C was 2.5 μm. The depth of corrosion penetration in coating with a higher chromium content (23 at.%) reaches 8.9 μm. A decrease in the chromium content (up to 5 at.%) or aluminum (up to 10 at.%) in the surface layer is accompanied by a critical increase in the corrosion rate. Based on the kinetics of changes in the aluminum content in the surface layer, it was established that the coating obtained on the Cr23Al5 alloy has the highest heat resistance.

Modeling of Thermal-Hydrological-Chemical (THC) Processes During Waste Rock Weathering Under Permafrost Conditions

The oxidation of sulfide minerals such as pyrite present in waste rock results in elevated sulfate, enhanced metal loadings and in many cases low pH conditions. Recently, many mines have opened in remote areas, including regions subject to permafrost conditions. In these regions, freeze-thaw cycles and the possible development of permafrost in mine waste add to the complexity of weathering processes, drainage volumes and mass loadings. To assess weathering in these waste rock piles, the reactive transport code MIN3P-HPC has been enhanced by implementing constitutive relationships related to freeze-thaw cycles that control flow patterns, solute transport, generation and transport of heat, as well as geochemical reactions and their rates. Simulations of a hypothetical pyrite-rich waste rock pile placed onto natural permafrost were conducted under reference climate conditions. Additionally, the effect of a warming climate was also studied through a sensitivity analysis. The simulation results indicate a potentially strong coupled effect of sulfide mineral weathering rates and a warming climate on the evolution and persistence of permafrost within waste rock piles and the release of acidic drainage. For relatively low sulfide mineral oxidation rates, the simulations indicate that permafrost can develop within waste rock piles, even under warming climate conditions. However, the results for low reactivity also show that mass loadings can increase by >50% in response to a slight warming of climate (3°C), relative to reference climate conditions. For the chosen reference reaction rates, permafrost develops under reference climate conditions in the simulated waste rock pile; however, permafrost cannot be maintained for a marginally warmer climate, leading to internal heating of the pile and substantially increased production of acidic drainage (>550%). For high reaction rates, the simulations suggest that internal heating takes place irrespective of climate conditions. Evaluation of thermal covers indicates that significant reductions of mass loadings can be achieved for piles with low and reference reactivity (91–99% in comparison to uncovered piles), but also suggest that thermal covers can be ineffective for piles with high sulfide content and reactivity. Together, these simulations provide insights into the complex interactions controlling waste rock weathering in cold-region climates.

An investigation into the optimal granular sludge size for simultaneous nitrogen and phosphate removal

An aerobic granular sludge (AGS) pilot plant fed with a mixture of acetate amended centrate and secondary effluent was used to investigate the optimal granule size range for simultaneous nitrification and denitrification (SND) and ortho-phosphate removal. The anaerobic phase was mixed to understand how AGS will perform if integrated with a continuous flow activated sludge system that cannot feed the influent through the settled sludge bed. Five different granule size fractions were taken from the pilot (operated at DO setpoint of 2mgO2/L) and each size was subjected to activity tests in a well-controlled lab-scale AGS reactor at four dissolved oxygen (DO) concentrations of 1, 2, 3, and 4 mgO2/L. The size fractions were: 212 – 600 µm, 600 – 1000 µm, 1000 – 1400 µm, 1400 – 2000 µm, and >2000 µm. The smallest size range (212 – 600 µm) had the highest nitrification and phosphate removal rates at DO setpoints from 1 – 3 mgO2/L, which was attributed to the higher aerobic volume fraction in small granules and hence a higher abundance of phosphorus accumulating organisms (PAO) and ammonia oxidizing bacteria (AOB). In comparison, large granules (>1000 µm) had 1.4 – 4.7 times lower ammonia oxidation rates than the smallest size range, which aligned with their lower AOB abundance relative to granule biomass. The granules with the highest anoxic volume fraction had the highest abundance of nitrite reductase genes (nir gene) but did not show the highest specific nitrogen removal rate. Instead, smaller granules (212 – 600 and 600 – 1000 µm), which had a lower nir gene abundance, had the highest specific nitrogen removal rates (1.2 – 3.1 times higher than larger granules) across all DO values except at 4 mgO2/L. At a DO setpoint of 4 mgO2/L, nitrite production by ammonia oxidation (ammonia monooxygenase) exceeded nitrite reduction by nitrite reductase in granules smaller than 1000 µm, in addition, some denitrifying heterotrophs switched to oxygen utilization in deeper layers hence suppressing denitrification activity. At the DO range of 2 – 4 mg/L, granular size had a greater effect on nutrient removal than DO. Therefore, for AGS developed at an average DO setpoint of 2 mgO2/L, selecting for size fractions in the range of 212 – 1000 µm and avoiding DO values higher than 3 mgO2/L can achieve both a higher nitrogen removal capacity and energy savings. This study is the first to investigate the influence of different DO values on SND and biological phosphorus removal performance of different aerobic granular sludge sizes.

Bimodal α-Mo grain structure inducing excellent oxidation resistance in Mo-12Si-8.5B alloy at 1100 °C

Bimodal Mo-12Si-8.5B-1.0wt%ZrB2 alloys were fabricated via hot pressing sintering of a mixture of mechanical alloying Mo-Si-B-ZrB2 powders and unmechanical alloying Mo-Si-B-ZrB2 powders in selected proportion. The bimodal Mo-12Si-8.5B-1.0wt%ZrB2 alloys consisted of fine and coarse α-Mo grains, showing mainly bimodal structure with a part of submicron-scaled α-Mo grains and partial micron-scaled α-Mo grains, where the intermetallics showed weak bimodal distribution but with fine grain structure. Oxidation behavior of the alloys was studied at 1100 °C in air. When average grain sizes of the fine and coarse α-Mo grains in the bimodal alloy were 0.45 μm and 2.15 μm, respectively, and their volume fraction ratio was approximately 1.7:1, a superior oxidation resistant property was achieved. Its mass loss in the transient stage was decreased, showing a 62% decrease compared to that of the ultrafine-grained alloy, and the oxidation recession rate of the alloy substrate was decreased significantly. Additionally, a thinner borosilicate glass scale was formed after oxidation for 30 h which exhibited excellent protective capability. The improved oxidation resistance at 1100 °C was mainly because of the combination of lower oxidation rate of the coarser α-Mo grains and the higher lateral flow rate of the borosilicate glass due to the presence of partial fine α-Mo grains and intermetallics.

Absent Exercise-Induced Improvements in Fat Oxidation in Women With Polycystic Ovary Syndrome After High-Intensity Interval Training.

Background: Polycystic ovary syndrome (PCOS) and metabolic inflexibility are linked to insulin resistance, and women with PCOS appear to be metabolic inflexible in the rested, insulin-stimulated state. Exercise training is a primary lifestyle intervention in PCOS. Exercise training improves whole-body fat oxidation during submaximal exercise in healthy women, yet little is known about the effect on this outcome in women with PCOS.Methods: We measured whole-body fat oxidation rates during sub maximal exercise before and after 16 weeks of high-intensity interval training (HIT) in women with PCOS randomly allocated to either: low- or high-volume HIT (n = 41; low-volume HIT, 10 × 1 min work bouts at maximal, sustainable intensity and high-volume HIT, 4 × 4 min work bouts at 90–95% of maximal heart rate) or non-exercise control (n = 23), and in women without PCOS (Non-PCOS) allocated to low- or high volume HIT (n = 15). HIT was undertaken three times weekly. In a subset of women with and without PCOS, we measured mitochondrial respiration in abdominal and gluteal subcutaneous adipose tissue using high-resolution respirometry, as well as fat cell sizes in these tissues.Results: At baseline, women with PCOS had lower whole-body fat oxidation and mitochondrial respiration rates in abdominal adipose tissue compared to Non-PCOS. Peak oxygen uptake (mL/min/kg) increased in women with PCOS (~4%, p = 0.006) and Non-PCOS (~6%, p = 0.003) after 16 weeks of HIT. Whole-body fat oxidation only improved in Non-PCOS after HIT. No changes were observed in mitochondrial respiration and cell size in abdominal and gluteal adipose tissue after HIT in either group of women.Conclusion: We observed exercise-induced improvements in whole-body fat oxidation during submaximal exercise in Non-PCOS, but not in women with PCOS, after 16 weeks of HIT, suggesting metabolic inflexibility in women with PCOS.Clinical Trial Registration: www.clinicaltrials.gov, identifier NCT02419482 and NCT02943291.

High-temperature oxidation behavior of monolithic Zr3[Al(Si)]4C6 and its composite incorporating 30vol% ZrB2-SiC: Providing a basis for broadening the service temperature

To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics.

High temperature oxidation of higher manganese silicides

The oxidation kinetics and mechanisms of higher manganese silicides (HMS) MnSi1.75, MnSi (1.75-x)Gex, MnSi(1.75-x)Alx (with x = 0.005 and 0.01)were studied and the effects of densification methods and dopant concentration discussed. Oxidation experiments were conducted using thermogravimetry (TGA), while post characterization with X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope (SEM) showed that spark plasma sintering (SPS) is a better densification method than hot pressing (HP). Except for undoped HMS, HMS doped with 0.5at% Ge had the lowest oxidation rate. Stable formation of a SiO2 protective layer was the main reason for improved oxidation resistance in air in the temperature range 200 °C–500 °C.

Experimental and computational contribution to chip geometry evaluation when micromilling Inconel 718

The spheroidal chip, or specifically dendritic spherical chip, was recently reported during Inconel 718 micromilling. It is believed that this kind of chip is obtained when oxidation is induced due to the high specific energy in a small volume of chip. If a high rate oxidation is possible, the exothermic reaction will allow the chip to obtain enough heat and therefore, change its shape to a spherical geometry. It has been reported that Inconel 718 favor the occurrence of this chip once it has low thermal conductivity and high oxidation rates. However, it is a new kind of chip and still needs literature consolidation. In this sense, this work aims to contribute in the comprehension of the different chip geometries obtained in the micromilling process. To evaluate chip formation, micro slots were machined in Inconel 718 workpiece, with a 400 μm diameter WC micromill tool. The chips were collected and analyzed into the scanning electron microscope. Considering the small chip dimensions and the inability of accessing the cutting zone, computer simulation analyses were performed to complement the discussion. Three main types of chips could be identified: helicoidal, ribbon and spheroidal. Helicoidal chip is formed by the cutting properly occurring in the main cutting edge and the ribbon (or arc) chips are attributed to the minor cutting edge. Despite unexpected, both chip types are formed in the same amount which indicates that the cut in the minor cutting edge is higher than expected, leading to higher wear in this region of the micromill. This action could be caused by an insufficient end cutting edge angle in the micromill and could also be associated with a higher friction, and therefore generating the higher energy that contribute to the sphere's formation. Thus, the presence of spheroidal chip could indicate that the process needs improvement.

Oxidation-resistant coating of FeCrAl on Zr-alloy tubes using 3D printing direct energy deposition

Zr-alloys are used as nuclear fuel cladding tubes in nuclear reactors. Recently, surface coating of conventional Zr-alloy tubes has been performed to enhance their resistance to corrosion and high-temperature oxidation. FeCrAl is a candidate coating material because of its extremely low oxidation rates and desirable mechanical properties. In this study, FeCrAl was deposited directly on a Zr-alloy using 3D printing technology. The processing conditions, such as laser beam power, scanning speed, and powder/gas feed rates, were optimized to attain a dense and adhesive FeCrAl layer. The minimum beam power required to melt the FeCrAl source powder was found to be 160 W. The FeCrAl layer coagulated when the scanning speed was low and the powder feed rate was high, and it became sparse and porous when the scanning speed was high and feed rate was low. The FeCrAl-coated Zr samples were tested for oxidation at 1200 °C. A thin Al2O3 (2–3 μm) formed on the FeCrAl surface, and a diffusion layer developed between the FeCrAl/Zr interfaces. By comparison, a thick ZrO2 (approximately 120 μm) layer formed in the Zr-alloy without coating. The oxidation resistance of the Zr-alloys increased by approximately 50 times by the formation of FeCrAl layer on their surfaces. This 3D printing method is expected to improve the safety of Zr fuel cladding tubes.

Influence of Alloying Elements on Cyclic Oxidation Behavior of (Cu/Al) Alloys

This study is conducted to extend the effective life of Cu/Al alloy. The used samples were (Cu/9.5%Al),(Cu/9.5%Al/5%Ni),(Cu/9.5%Al/5%Ni/0.9%Mn),(Cu/%9.5Al/5%Ni/4.5%Fe), (Cu/9.5%Al/5%Ni/0.9%Mn/4.5%Fe),(Cu/9.5%Al/5%Ni/0.9%Mn/4.5%Fe/0,1%Y),(Cu/9.5%Al/5% Ni/0.9%Mn/4.5%Fe/0.2%Ge) by using powder metallurgy these samples were prepared, the cyclic oxidation test was conducted in the presence of air in a programmable furnace (typeVBF-1200X-H8-USA) at 250°C and 800°C for 50 hours at 5-hours cycle. It was represented by the weight-gain of all examined samples that the oxidation rate increased as the temperature increased. It appears that cracking or spalling of oxides was at high temperatures such it found the weight gain of the base alloy (Cu/9.5%Al) was (12.09*10−3g/cm2)at 250°C otherwise, it was (5.98*10−2 g/cm2) at 800°C for the same alloy. This is attributable to the expected behavior of oxides when stressed. The addition of Ni, Mn, & Fe to (Cu/9.5%Al) caused a relative increase in resistance to cyclic oxidation, while the addition 0.1% Y to (Cu/9.5%Al/5%Ni/0.9Mn/4.5%Fe) caused the lowest oxidation rate as compared with other alloys, it showed that the reduction in weight gain (165.13%) relative to(Cu/9.5%Al) the highest weight gain at 250°C, and it was (285.22%) relative to (Cu/9.5%Al/5%Ni) which has highest weight gain at 800 °C. Both alloying elements Y and Ge represented a major change in cyclic oxidation resistance.