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Aging-induced enhancement of corrosion resistance in Al-4Ni-1Mn alloys through Al3(Sc, Zr) precipitates
(2025-05-05)
Masthong, Anuchit
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Eskin, Dmitry
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Limmaneevichitr, Chaowalit
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Pandee, Phromphong
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Diewwanit, Onnjira
Al-Ni-Mn alloys are attractive for high-temperature, corrosive environment due to the formation of stable intermetallic compounds that can reduce corrosion susceptibility. This study showed that the additions of Mn, Sc, and Zr in Al-4 % Ni alloys significantly enhanced hardness and thermal stability through the simultaneous effect of transformation of the Al + Al<inf>3</inf>Ni to Al + Al<inf>9</inf>(Ni, Mn)<inf>2</inf> eutectic and precipitation of Al<inf>3</inf>(Sc, Zr). The thermal stability of an Al-4 % Ni-1 % Mn alloy was very good when exposed to 350 °C for 60 h. Additionally, the hardness substantially increased in an Al-4 % Ni-1 % Mn alloy with the addition of Sc and Zr, showing an approximate increase of 30 %. The highest hardness achieved was approximately 50 % higher with the optimal Sc and Zr content as compared to the Al-4Ni-1Mn alloy. Addition of 1 % Mn to an Al-4 % Ni alloy decreased the current density (I<inf>corr</inf>) and increased the corrosion potential (E<inf>corr</inf>), indicating better corrosion resistance. The effects of Sc and Zr additions on corrosion were also investigated, revealing that the increased Sc and Zr content led to more aggressive corrosion in the as-cast condition due to the eutectic coarsening and a high solid solution concentration of Sc and Zr that led to microstructural instability and electrochemical effects. However, after aging at 350 °C, the corrosion resistance significantly improved due to the Al<inf>3</inf>(Sc, Zr) precipitates that interrupted the corrosion path.
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Non-monotonic evolution of the responses of ZnO-nanoparticle UV-sensitive devices under ambient aging
(2023-08-01)
Sratongkham, Pittayathorn
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Chuenchom, Rattana
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Tuantranont, Adisorn
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Lomas, Tanom
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Wasapinyokul, Kamol
Ultraviolet (UV) sensitive devices based on spin-coated zinc-oxide nanoparticles (ZnO) were fabricated and characterised. They were subsequently stored in the ambient and dark conditions with low humidity for 56 days, during which time they were intermittently recharacterised to determine the aging effect on their sensing properties, including responsivity, sensitivity, and response and recovery times. Over the 56-day period, both the dark and illumination currents increased, causing the non-monotonic evolution of the performances of the devices – the responsivity improved by 9–18 folds, the sensitivity remained stable, and the response and recovery times deteriorated as they were 46 and 33 times longer, respectively. These changes were associated with an increase in the number of adsorbed oxygen molecules on the ZnO surface with time. This resulted in more photodesorbed oxygen molecules and thus more remaining charge carriers under illumination, which increased the photo-generated current and consequently responsivity. However, it also caused the current to rise and decay more slowly when the illumination appeared and disappeared, respectively, leading to the prolonged response and recovery times. The longer recovery times led in an increase in dark current, which, when combined with an increase in illumination current, resulted in a stable sensitivity. The trends of these sensing parameters were similar, but to varying degrees, regardless of the change in the radiation levels and ZnO layer thicknesses.
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The Possible Sarcopenia Associated with Independent Walking Older Adults
(2023-05-01)
Raksadawan, Natte
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Sermswan, Anawat
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Jansri, Ukkrit
The amount of skeletal muscle mass and mobility function increase during the childhood, peak at young adult, and then decline after middle age. Older adults with low skeletal mass and mobility function are associated with reduced physical performance. The older adult with a low level of mobility function, regardless of the amount of muscle mass, is defined as "possible sarcopenia". This study aims 1) to characterize the current state of the physical and mobility function at the peak levels of these parameters among young adults 2) to characterize their deterioration rates during middle-age and older-age years and older adults; and 3) to study the prevalence of possible sarcopenia among older adults. The cross-sectional study of anthropometric parameters, body compositions, and mobility assessments was conducted from independent walking young, middle, and older age adults in the community. Young adult male had higher levels of physical and mobility function than female. The changes in physical and mobility function during middle age were subtle. Older age male (female) lost skeletal muscle mass at-0.125 (-0.0190) kg/year, grip strength at-0.495 (-0.307) kg per year, and gait speed at-0.007 (-0.013) m/sec per year, respectively. The prevalence of possible sarcopenia in older age independent walking adults, determined by low grip strength, was 19.4%. The prevalence increased with advancing age.
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Effect of Zr and Sc on Intermetallic Morphology and Hardening of an Al–Fe Alloy
(2023-01-01)
Chankitmunkong, Suwaree
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Eskin, Dmitry G.
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Limmaneevichitr, Chaowalit
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Pandee, Phromphong
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Diewwanit, Onnjira
We studied the effect of zirconium and scandium on an Al-7 wt% Fe cast alloy with potential heat- and wear-resistant applications. An addition of 0.2% Zr resulted in thinning of primary Al<inf>3</inf>Fe particles, while an addition of 0.15% Zr and 0.15% Sc changed the morphology of primary intermetallics from needles to flower-like shape. While the addition of Zr did not affect the properties, the Zr + Sc joint additions increased the hardness of the as-cast Al–Fe alloy. The hardness of the base alloy increased upon annealing from 40 to 80 HV (450 °C, 2 h) and to 110 HV (350 °C, 20 h). The wear resistance of the Al–Fe alloy was also improved by Zr and Sc addition, especially after annealing. The observed effects are likely to be linked to the supersaturation of Zr and Sc in the aluminum solid solution during solidification and precipitation of dispersoids during annealing.
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Ambient- and elevated temperature properties of Sc- and Zr-modified Al–6Ni alloys strengthened by Al3Ni microfibers and Al3(Sc,Zr) nanoprecipitates
(2022-04-28)
Suwanpreecha, C.
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Rakhmonov, J. U.
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Chankitmunkong, S.
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Pandee, P.
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Dunand, D. C.
The eutectic Al–6Ni (wt.%) alloy exhibits excellent strength at ambient and elevated temperature, provided by a high volume fraction of Al<inf>3</inf>Ni microfibers formed during solidification. Here, Al–6Ni is micro-alloyed with Sc and Zr (with 0.1Sc+0.2Zr, 0.2Sc+0.4Zr and 0.3Sc+0.2Zr, wt.%), creating two additional populations of primary and secondary Al<inf>3</inf>(Sc,Zr) precipitates. The fully eutectic microstructure (α-Al + Al<inf>3</inf>Ni) observed in Al–6Ni alloy changes, with Sc and Zr addition to hypoeutectic microstructure with primary α-Al grains nucleated on solidification by primary Al<inf>3</inf>(Sc,Zr) precipitates. Upon subsequent aging, fully-coherent Al<inf>3</inf>(Sc,Zr) nanoprecipitates form in the α-Al matrix between Al<inf>3</inf>Ni microfibers, providing substantial precipitation strengthening, which is maintained for up to 1 month at 350 °C. Alloy strength - both at ambient temperature and during creep at 300 °C - can be quantitatively described through a superposition of precipitation strengthening by Al<inf>3</inf>(Sc,Zr) nanoprecipitates and load-transfer strengthening by Al<inf>3</inf>Ni microfibers.
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The aging of the insulation system of large rotating machines in frequency domains
(2019-07-01)
Phloymuk, Natthawut
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Pattanadech, Norasage
The insulation of stator winding in a rotating machine consisted of mica and epoxy resin materials. The structure was also composed of junctions, so, a diagnostic monitoring condition of this insulation was taken into consideration. First, the results of the polarisation and depolarisation current measurement (PDC) of the test sample (stator winding rate of 13.8 kV) were investigated, as an experiment in the laboratory. The conditions of the experiment were conducted under different thermal stresses of 25°C and 100°C. The test sample was full stator bar. As found, the trend of the temperature of the winding rise if the current of the polarisation and depolarisation was increased. Second, the results of the PDC were calculated from the time domain to the frequency domain. The aim found that the aging point of the insulation system should take into consideration the results of the calculation of the frequency domain. The aging of the insulation system was a variant by the thermal stress, which was an effect from the complex capacitance and polarisation losses in the insulation winding system. Finally, this identified the phenomenon of the aging of the machine insulation system.
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Aging impairs protective host defenses against Clostridioides (Clostridium) difficile infection in mice by suppressing neutrophil and IL-22 mediated immunity
(2018-12-01)
Peniche, Alex G.
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Spinler, Jennifer K.
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Boonma, Prapaporn
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Savidge, Tor C.
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Dann, Sara M.
Background: Morbidity and mortality associated with Clostridioides (formerly Clostridium) difficile infection (CDI) rises progressively with advanced age (≥65 years) due in part to perturbations of the gut microbiota and immune dysfunction. Epidemiological data of community-acquired CDI suggests increased susceptibility may begin earlier during middle-age (45–64 years) but the causation remains unknown. Methods: Middle-aged (12–14 months) and young (2–4 months) adult mice were infected with C. difficile, and disease severity, gut microbiome and innate immune response were compared. Cytokine reconstitution studies were performed in infected middle-aged mice. Results: Infection of middle-aged mice with C. difficile led to greater disease compared to young controls, which was associated with increases in C. difficile burden and toxin titers, and elevated bacterial translocation. With the exception of an expansion of C. difficile in middle-aged mice, microbiome analysis revealed no age-related differences. In contrast, middle-aged mice displayed a significant defect in neutrophil recruitment to the colon, with diminished levels of innate immune cytokines IL-6, IL-23 and IL-22. Importantly, recombinant IL-22 administration during CDI reduced morbidity and prevented death in middle-aged mice. Conclusion: Increased susceptibility to C. difficile occurs in middle-aged mice modeling the community-acquired CDI demographics and is driven by an impaired innate immune response.
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Enthalpy relaxation in sucrose-maltodextrin-sodium citrate bioglass
(2017-10-01)
Sritham, Eakasit
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Gunasekaran, Sundaram
Glass transition characteristics of sucrose (SC)-maltodextrin (MD)-sodium citrate (NaCit) bioglass system were investigated using differential scanning calorimetry. Samples were formulated with different SC:MD (7:3, 5:5 and 3:7 by mass) and NaCit/SC (0, 0.1 and 0.2 by mole) ratios, and were equilibrated to residual moisture contents of 0.27–0.35 %wb. Isothermal aging experiments were conducted with the degree of undercooling from 12 to 57 °C and aging times of 8, 20, 47 and 71 h. In general, the Kohlrausch-Williams-Watts (KWW) decay function fit well with the experimental enthalpy relaxation data. The enthalpy relaxation time (τKWW) and the time required for 50% completion of theoretical possible maximum enthalpy relaxation at constant temperature (t<inf>ϕ(t)=0.5</inf>) increased with increasing MD content; lowering the aging temperature had similar effects on τKWW and t<inf>ϕ(t)=0.5</inf>. In the system with high SC and NaCit concentrations (SC:MD = 7:3 and NaCit/SC = 0.2), a substantial increase in τKWW and t<inf>ϕ(t)=0.5</inf> were observed when aging temperature <inf>decreased slightly;</inf> these systems also exhibited the greatest apparent activation energy. The findings reveal that NaCit can enhance the stability of low-moisture bioglass by primarily interacting with SC and form large less-mobile clusters, which helps to improve glass transition temperature and restrict the matrix mobility.
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The development of Artificial Neural Networks (ANN) for falls detection
(2017-06-07)
Yodpijit, Nantakrit
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Sittiwanchai, Teppakorn
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Jongprasithporn, Manutchanok
This paper presents the new design and development of a wearable-based fall detection system using an Accelerometer and Gyroscope as motion sensors for detecting body orientation and movement. The Threshold Based and Artificial Neural Networks (ANN) algorithm were developed to differentiate between Activities of Daily Living (ADL). Results indicated the possibility of using the new threshold-based method with ANN algorithm to reduce the number of false positive (false alarm) outcomes and improve the accuracy of fall detection system.

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