Carbon-Coated Nanopowder as Sintering Aid for Water-Atomized Iron Powder

The influence of carbon coating on the nanopowder when used as a sintering aid for water-atomized iron powder is explored. Iron nanopowder without such a coating was used as a reference sintering aid to isolate and depict the influence of the carbon coating. Both nanopowder variants were characterized using XPS and HRTEM, and the results showed a core-shell structure for both nanopowder variants. Iron nanopowder is covered by a 3-4 nm thick iron oxide layer, while the carbon-coated nanopowder is encapsulated with a number of nanometric carbon layers. Thermogravimetry carried out in a pure hydrogen environment shows a multipeak behaviour for carbon-coated nanopowder, while a single peak behaviour is observed for the iron nanopowder. This difference was correlated with chemical analysis. Two types of micro/nanobimodal powders were obtained by mixing the nanopowder with water-atomized iron powder. An improved linear shrinkage was observed when carbon-coated iron nanopowder was added. This can be explained by the reduced surface diffusion in the nanopowder due to the carbon coating, which allows the nanopowder to sinter at higher temperatures and improves densification.

Topological properties of Sb(111) surface: A first-principles study

First-principles calculations based on density functional theory were performed to systematically study the electronic properties of the thin film of antimony in (111) orientation. Considering the spinorbit interaction, for stoichiometric surface, the topological states keep robust for six-bilayer case, and can be recovered in the three-bilayer film, which are guaranteed by time-reversal symmetry and inverse symmetry. For reduced surface doped by non-magnetic Bi or magnetic Mn atom, localized three-fold symmetric features can be identified. Moreover, band structures show that the non-trivial topological states stand for non-magnetic substitutional Bi atom, while can be eliminated by adsorbed or substitutional magnetic Mn atom.

Inhibiting wood-water interactions by hydrothermal hemicellulose extraction combined with furfurylation

Wood-water interactions affect durability and performance of wood products, such as dimensional stability and biodegradation. To upgrade wood, a combined modification via hemicellulose extraction and furfurylation was proposed to inhibit wood-water interactions. More intense hemicellulose extraction caused larger voids and led to higher pore volume. The increment of porosity resulted in more uniform distribution of polymerized furfural resin in cells, as indicated by scanning electron microscopic and confocal laser scanning microscopic observations. The combined modification greatly reduced surface wettability with an increase of water contact angle (CA) of over 134% at 100 s. With hemicellulose extraction, polymerized furfural resin partially occupied the accommodation initially for water molecules and reduced accessible sorption sites, causing water absorption (WA) of wood to decrease by over 30% after soaking in water for 768 h. Dynamic moisture sorption was weakened after combined modification, and the moderate hemicellulose extraction combined with furfurylation reduced the moisture content by over 50% due to incorporative changes of chemical sorption sites and physical porosity. The results confirmed the efficiency of the combined modification in inhibiting wood-water interactions and indicated the importance to accurately control hemicellulose content during modification. This study could provide useful information for sustainably enhancing wood performance and upgrading low-quality wood.

Influence of Semi-Random and Regular Shot Peening on Selected Surface Layer Properties of Aluminum Alloy

This paper attempts to compare regular shot peening (RSP) and semi-random shot peening (SRSP). A characteristic of the first method is that the peening elements hit the treated surface in sequence, with a regular distance maintained between the dimples. The other method (SRSP) is a controlled modification of the shot-peening process, which is random by nature. The shot-peening method used in this study differs from conventional shot peening (shot blasting and vibratory shot peening) in that it allows controlled and repeatable determination of the configuration and distribution of impacts exerted by the peening element on the workpiece surface, which makes the process more repeatable and easier to model. Specimens of EN-AW 7075 aluminum alloy were used for testing. The following variables were used in the experiments: ball diameter, impact energy, and distance between the dimples. Microhardness distribution in the surface layer, 2D surface roughness, and surface topography were analyzed. FEM simulations of the residual stress distribution in the surface layer were performed. It has been found that regular shot peening results in reduced surface roughness, while semi-random shot peening leads to higher surface layer hardening.

Future summer warming pattern under climate change is affected by lapse-rate changes

Greenhouse-gas-driven global temperature change projections exhibit spatial variations, meaning that certain land areas will experience substantially enhanced or reduced surface warming. It is vital to understand enhanced regional warming anomalies as they locally increase heat-related risks to human health and ecosystems. We argue that tropospheric lapse-rate changes play a key role in shaping the future summer warming pattern around the globe in mid-latitudes and the tropics. We present multiple lines of evidence supporting this finding based on idealized simulations over Europe, as well as regional and global climate model ensembles. All simulations consistently show that the vertical distribution of tropospheric summer warming is different in regions characterized by enhanced or reduced surface warming. Enhanced warming is projected where lapse-rate changes are small, implying that the surface and the upper troposphere experience similar warming. On the other hand, strong lapse-rate changes cause a concentration of warming in the upper troposphere and reduced warming near the surface. The varying magnitude of lapse-rate changes is governed by the temperature dependence of the moist-adiabatic lapse rate and the available tropospheric humidity. We conclude that tropospheric temperature changes should be considered along with surface processes when assessing the causes of surface warming patterns.

Tungsten Infused Grain Boundaries Enabling Universal Performance Enhancement of Co-Free Ni-Rich Cathode Materials

Ni-rich cathode materials suffer from poor capacity retention due to micro-cracking and interfacial reactivity with electrolyte. Addition of tungsten (W) to some Ni-rich materials can improve capacity retention. Here, a WO3 surface coating is applied on Ni-rich hydroxide precursors before heating with lithium hydroxide. After heating in oxygen, Ni-rich materials with any of the commonly used dopants (magnesium, aluminum, manganese, etc.) show a “universal” improvement in capacity retention. Experimental characterization and theoretical modelling showed W was concentrated in the grain boundaries between the primary particles of secondary particles of the layered oxides, and W is incorporated in amorphous LixWyOz phases rather than as a substituent in the LiNiO2 lattice. This self-infusion of W in the grain boundaries during synthesis also significantly restricts primary crystallite grain growth. Along with smaller primary grain size, the LixWyOz phases in the grain boundaries lead to improved resistance to microcracking and reduced surface or interfacial reactivity. Improving the intrinsic properties of primary grains through doping of Mg, Al or Mn and reinforcing the secondary particle structure mechanically and chemically using W or a similar element, M, that forms LixMOy phases and does not substitute into LiNiO2 is a universal strategy to improve polycrystalline Ni-rich materials.

A LysR-Type Transcriptional Regulator Controls Multiple Phenotypes in Acinetobacter baumannii

Acinetobacter baumannii is a multidrug-resistant, Gram-negative nosocomial pathogen that exhibits phenotypic heterogeneity resulting in virulent opaque (VIR-O) and avirulent translucent (AV-T) colony variants. Each variant has a distinct gene expression profile resulting in multiple phenotypic differences. Cells interconvert between the VIR-O and AV-T variants at high frequency under laboratory conditions, suggesting that the genetic mechanism underlying the phenotypic switch could be manipulated to attenuate virulence. Therefore, our group has focused on identifying and characterizing genes that regulate this switch, which led to the investigation of ABUW_1132 (1132), a highly conserved gene predicted to encode a LysR-type transcriptional regulator. ABUW_1132 was shown to be a global regulator as the expression of 74 genes was altered ≥ 2-fold in an 1132 deletion mutant. The 1132 deletion also resulted in a 16-fold decrease in VIR-O to AV-T switching, loss of 3-OH-C12-HSL secretion, and reduced surface-associated motility. Further, the deletion of 1132 in the AV-T background caused elevated capsule production, which increased colony opacity and altered the typical avirulent phenotype of translucent cells. These findings distinguish 1132 as a global regulatory gene and advance our understanding of A. baumannii’s opacity-virulence switch.

Highly Stable Photocatalytic Removal of Paraquat Dichloride using ZnO/TiO2 supported on PVC

This study presents on ZnO/TiO2 supported on PVC (ZnO/TiO2@PVC) in the photocatalytic removal of paraquat dichloride. The ZnO/TiO2@PVC was characterized using XRD, FESEM-EDX, FTIR, and AFM. Findings indicated that ZnO/TiO2@PVC allowed degradation of paraquat dichloride under UV irradiation by the rate of up to 73%. XRD pattern indicated the presence of both TiO2(anatase) and ZnO (zincite) crystalline as well as PVC amorphous structures. FESEM and AFM results revealed the observed shape and surface of TiO2 interconnected nanowires with ZnO nanorods uniformly distributed according to EDX mapping. The reduced surface roughness was also shown in the supported photocatalyst. FTIR analysis clearly demonstrate the combined spectra of immobilised ZnO/TiO2 powder catalyst onto the PVC in the composite. Kinetic study of the degradation process was performed according to pseudo-first-order and the influence of ZnO/TiO2 coating onto PVC polymer and initial paraquat concentration were investigated on the treatment performance. Under optimized condition (pH = 7, PQ =20 mg/L and catalyst coating =15%), the stability and reusability of the supported catalyst was also evaluated over ten sequential treatment runs, and the catalyst maintain high reactivity. High recyclability of the ZnO/TiO2@PVC composites as catalyst in photodegradation processes are also reported in this study.

Preparation and characterization of lanolin-based condensate and its utilization as a nonionic softener for wool fabric surface

Two forms of pollutants are usually discharged from scouring of wool fleece; namely the effluent liquid phase and the solid phase. These phases comprise a significant quantity of wool wax which would be a suitable candidate for valuable products and applications. This work is devoted to extraction, recovery, and characterization of lanolin from wool fleece from different sheep breeds to assign possible ways for its utilization in the textile field. The results show that the amount of wool wax extracted from coarse wool fleece as well as its chemical composition and physical properties are almost similar to those extracted from other finer wool fleece. The aim of this work is further devoted to separation and characterization of fatty acids (FAs) from the extracted wool wax. The separated wool FAs were esterified with poly ethylene glycol (PEG) to obtain a condensate which was utilized as a nonionic softener for wool. The alteration in morphology of the coated wool fabric was assessed using scanning electron microscopy. The results revealed that the WFA/PEG-coated fabrics exhibit reduced surface roughness and improved resistance to felting shrinkage during mechanical agitation.