Novel Heating-Induced Reversion during Crystallization of Al-based Glassy Alloys.

Thermal stability and crystallization of three multicomponent glassy alloys, Al86Y7Ni5Co1Fe0.5Pd0.5, Al85Y8Ni5Co1Fe0.5Pd0.5 and Al84Y9Ni4Co1.5Fe0.5Pd1, were examined to assess the ability to form the mixture of amorphous (am) and fcc-aluminum (α-Al) phases. On heating, the glass transition into the supercooled liquid is shown by the 85Al and 84Al glasses. The crystallization sequences are [am] → [am + α-Al] → [α-Al + compounds] for the 86Al and 85Al alloys, and [am] → [am + α-Al + cubic AlxMy (M = Y, Ni, Co, Fe, Pd)] → [am + α-Al] → [α-Al + Al3Y + Al9(Co, Ni)2 + unknown phase] for the 84Al alloy. The glass transition appears even for the 85Al alloy where the primary phase is α-Al. The heating-induced reversion from [am + α-Al + multicomponent AlxMy] to [am + α-Al] for the 84Al alloy is abnormal, not previously observed in crystallization of glassy alloys, and seems to originate from instability of the metastable AlxMy compound, in which significant inhomogeneous strain is caused by the mixture of solute elements. This novel reversion phenomenon is encouraging for obtaining the [am + α-Al] mixture over a wide range of high temperature effective for the formation of Al-based high-strength nanostructured bulk alloys by warm working

Novel deformation-induced polymorphic crystallization and softening of Al-based amorphous alloys

© 2018 Acta Materialia Inc. Melt-spun amorphous ribbons of Al 90 Y 10 (at.%) (90Al) and Al 84 Y 8.5 Ni 4 Co 2 Pd 1 Fe 0.5 (84Al) are cold-rolled at near to liquid-nitrogen temperature or at room temperature, inducing partial crystallization to nanoscale fcc-Al (α-Al). The crystallization is characterized and contrasted with the distinct sequences of reactions on annealing 90Al and 84Al amorphous alloys. Rolling-induced crystallization leads to softening, opposite to the effect of nanocrystallization induced by annealing. The origins of the hardness changes are analyzed. The rolling induces novel polymorphic crystallization to α-Al with extended solid solubility. This transformation, which occurs equally in 84Al and 90Al, despite the much greater thermal stability of the former, allows the ribbons to retain good bending ductility, and delays the onset of embrittlement on subsequent annealing. Partial crystallization induced by cold-rolling is useful in avoiding the formation of compound phases associated with brittleness, and is a promising process for high-solute Al-based amorphous alloys to be further developed as structural materials

Adsorption Sites of Hydrogen Atom on Pure and Mg-Doped Multi-Walled Carbon Nanotubes

Hydrogen adsorption sites on pure multiwalled carbon nanotube (MWCNT) and Mg-doped MWCNTs material system have been investigated using molecular dynamics (MD) simulations as well as quantum chemical calculations. Through combining MWCNTs with Mg, the hydrogen adsorption sites energy on this Mg-MWCNTs system is found to be larger than that of the pure MWCNTs. Additionally, it was found that, through Mg-doping, new adsorption sites for hydrogen molecules are created in comparison with undoped nanotubes. It is also found that H atom is preferably adsorbed at every place near magnesium atom

Methane Mitigation:Methods to Reduce Emissions, on the Path to the Paris Agreement

The atmospheric methane burden is increasing rapidly, contrary to pathways compatible with the goals of the 2015 United Nations Framework Convention on Climate Change Paris Agreement. Urgent action is required to bring methane back to a pathway more in line with the Paris goals. Emission reduction from “tractable” (easier to mitigate) anthropogenic sources such as the fossil fuel industries and landfills is being much facilitated by technical advances in the past decade, which have radically improved our ability to locate, identify, quantify, and reduce emissions. Measures to reduce emissions from “intractable” (harder to mitigate) anthropogenic sources such as agriculture and biomass burning have received less attention and are also becoming more feasible, including removal from elevated-methane ambient air near to sources. The wider effort to use microbiological and dietary intervention to reduce emissions from cattle (and humans) is not addressed in detail in this essentially geophysical review. Though they cannot replace the need to reach “net-zero” emissions of CO2, significant reductions in the methane burden will ease the timescales needed to reach required CO2 reduction targets for any particular future temperature limit. There is no single magic bullet, but implementation of a wide array of mitigation and emission reduction strategies could substantially cut the global methane burden, at a cost that is relatively low compared to the parallel and necessary measures to reduce CO2, and thereby reduce the atmospheric methane burden back toward pathways consistent with the goals of the Paris Agreement

The Interaction of Social, Physical and Nutritive Factors in Triggering Early Developmental Language Delay in a Sample of Egyptian Children

BACKGROUND: Language acquisition and child development during the early years of life depend on multiple interacting factors. AIM: To explore potential factors that can impact language development in 2 groups of Egyptian children, one with normal language development and the second with delayed development. Also, to explore to what extent can the involvement of impaired motor development potentiate the risk of developmental language delay. METHODS: This cross-sectional case-control study involved Egyptian children belonging to the middle socioeconomic class between 18 and 36 months of age. Children were classified according to their performance on language domain of Bayley Scales of Infant and Toddler Development (Bayley-III) into two groups, infants with the average or above score (control group) and those having below-average scores (cases). Motor development was assessed on the same scale. Factors affecting language development were tested, including socio-demographic, obstetric, and maternal medical factors in addition to Infant Feeding Practices. RESULTS: The independent factors lowering the language scores were early introduction of complementary food, low family income, history of delivery problems, pregnancy-related diseases of the mother, and maternal education. Impaired motor development appears as a further highly significant risk factor to the previously mentioned factors CONCLUSION: In Egyptian children, delayed language development is severely affected by the interaction of medical, social and nutritional factors. Providing adequate maternal health care during pregnancy and childbirth, regular developmental monitoring at each child visit, and screening for such risk factors, can reduce size of the problem and promote child’s social and psychological development

Softening and good ductility for nanocrystal-dispersed amorphous Fe-Co-B alloys with high saturation magnetization above 1.7 T

Fe80-xCo20Bx (x = 12-15 at%) alloy ribbons consisting of single bcc phase (12%B), amorphous plus bcc-Fe(Co) mixed phases (13%B) and amorphous single phase (14%B and 15%B) were synthesized by the melt-spinning technique. It is noticed that all the alloy ribbons containing amorphous phase exhibit good bending ductility in the as-spun state and even after annealing which leads to the precipitation of nanoscale bcc-Fe(Co) phase. The amorphous plus bcc-Fe(Co) phase alloys with lower hardness exhibited a number of microcracks in the region near the hardness indentation trace, in addition to distinct slip step markings. The decrease in hardness and the maintenance of ductility in the nanocrystalline state are interpreted to originate from microcrack-induced softening phenomenon. The nanocrystalline alloys also exhibit good soft magnetic properties with high saturation magnetization above 1.7 T in combination with low coercivity of about 20 A/m. The good bending ductility as well as the microcrack-induced softening for the amorphous alloys including nanoscale bcc-Fe(Co) phase is believed to be the first evidence in the long development history of Fe-based nanocrystalline soft magnetic alloys. The finding of the ductile Fe-based nanocrystalline alloys with high saturation magnetization is encouraging for further extension of nanocrystalline magnetic materials. (C) 2015 Elsevier B.V. All rights reserved

Formation, stability and ultrahigh strength of novel nanostructured alloys by partial crystallization of high-entropy (Fe <inf>0.25</inf> Co <inf>0.25</inf> Ni <inf>0.25</inf> Cr <inf>0.125</inf> Mo <inf>0.125</inf> ) <inf>86‒89</inf> B <inf>11‒14</inf> amorphous phase

© 2019 Acta Materialia Inc. Heating-induced crystallization of high-entropy (HE) (Fe 0.25 Co 0.25 Ni 0.25 Cr 0.125 Mo 0.125 ) 86‒89 B 11‒14 amorphous (am) alloys is examined to develop new structural materials with low B contents. The crystallization of 11B alloy occurs in three stages: first nanoscale bcc precipitates form in the amorphous matrix, second nanoscale fcc precipitates form, and the residual amorphous phase disappears in the third stage which yields borides in addition to the bcc and fcc phases. Crystallization of 14B alloy is the same, except that the order of appearance of bcc and fcc is reversed. The bcc and fcc particle diameters are 5–15 nm and remain almost unchanged up to ∼960 K. On annealing, ultrahigh hardness of 1500–1550 (unprecedented for boride-free structures) is attained just before the third crystallization stage. This hardening and the thermal stability of the novel [am + bcc + fcc] structures are remarkable at such low boron content and encouraging for development as ultrahigh-strength alloys. The results are interpreted in terms of the nature and extent of partitioning of elemental components between the bcc/fcc phases and the amorphous matrix, and the size and defect structures of the bcc and fcc precipitates. The magnetic flux density at room temperature increases by precipitation of bcc and decreases by appearance of fcc. Slower quenching of the 11B alloy shows a pseudo-polymorphic crystallization that may be characteristic of multicomponent HE systems

Biotin-responsive basal ganglia disease should be renamed biotin-thiamine-responsive basal ganglia disease: a retrospective review of the clinical, radiological and molecular findings of 18 new cases

BACKGROUND: Biotin-responsive basal ganglia disease (BBGD) is an autosomal recessive neurometabolic disorder. It is characterized by sub acute encephalopathy with confusion, seizure, dysarthria and dystonia following a history of febrile illness. If left untreated with biotin, the disease can progress to severe quadriparesis and even death. METHOD: A retrospective chart review of 18 patients with BBGD from two tertiary institutions describing their clinical, magnetic resonance imaging and molecular findings was conducted. RESULT: Eighteen children from 13 families seen over a period of nine years (2003–2012) were included. (Age range: 14month to 23 years, M: F: 1:1). The clinical features included sub acute encephalopathy, ataxia (n= 18), seizures (n= 13) dystonia (n=12) ,dysarthria (n= 9), quadriparesis and hyperreflexia (n=9). Magnetic resonance imaging demonstrated abnormal signal intensity with swelling in the basal ganglia during acute crises (n= 13/13) and atrophy of the basal ganglia and necrosis during follow up (n= 13/13). One-third of the present patients showed the recurrence of acute crises while on biotin therapy alone, but after the addition of thiamine, crises did not recur. All of the patients have a homozygous missense mutation in exon 5 of the SLC19A3 gene. The frequency of acute crises, delay in diagnosis and initiation of treatment significantly influenced the outcome. On follow up, four patients died, two had spastic quadriplegia, six had normal outcome and the rest had speech and motor dysfunctions. CONCLUSION: Clinicians should suspect BBGD in any child presenting with sub acute encephalopathy, abnormal movement and MRI findings as described above. Both biotin and thiamine are essential for disease management. Since biotin alone could not prevent the recurrence of crises in some patients, a more appropriate term to describe the disease would be biotin-thiamine-responsive basal ganglia disease (BTBGD)

Influence of ejection temperature on structure and glass transition behavior for Zr-based rapidly quenched disordered alloys

We examined the influence of ejection liquid temperature (Tel) on the structure, thermal stability and crystallization of Zrsingle bondAlsingle bondNisingle bondCu ribbons prepared by the melt-spinning technique. The increase in Tel was found to cause the formation of an oxide phase on the ribbon surface, more loose atomic configurations, the absence of glass transition (GT) and supercooled liquid (SL) region, and the rise of crystallization temperature. The changes in the GT and SL region occur reversibly by controlling the Tel. Neither the change in alloy composition except oxygen nor the difference in crystallized phases is seen. Their hardness increases significantly by the disappearance of GT and SL region. The reversible changes in the appearance and disappearance of GT and SL region was found for different Zr-based glassy ribbons, being independent of alloy compositions. The disappearance is presumably due to the change in atomic configurations from high-coordinated to less-coordinated atomic packing in the melt-spun ribbons by freezing high-temperature liquid. The observed phenomenon of the reversible changes provides a novel opportunity for deep understanding of mutual correlations among liquid structure, GT, stability of SL and bulk glass-forming ability for metallic alloys