Larger Atomic Radius Research Articles

Fast and Durable Potassium Storage Enabled by Constructing Stress-Dispersed Co3Se4 Nanocrystallites Anchored on Graphene Sheets.

Transition metal dichalcogenides are regarded as promising anode materials for potassium-ion batteries (PIBs) because of their high theoretical capacities. However, due to the large atomic radius of K+, the structural damage caused by the huge volume expansion upon potassiation is much more severe than that of their lithium counterparts. In this research, a stress-dispersed structure with Co3Se4 nanocrystallites orderly anchored on graphene sheets is achieved through a two-step hydrothermal treatment to alleviate the structural deterioration. The ability to reduce the contact stress by the well-dispersed Co3Se4 nanocrystallites during K+ intercalation, together with the highly conductive graphene matrix, provides a more reliable and efficient anode architecture than its two agminated counterparts. Given these advantages, the optimized electrode delivers excellent cycling stability (301.8 mA h g-1 after 500 cycles at 1 A g-1), as well as an outstanding rate capacity (203.8 mA h g-1 at 5 A g-1). Further in situ and ex situ characterizations and density functional theory calculations elucidate the potassium storage mechanism of Co3Se4 during the conversion reaction and reveal the fast electrochemical kinetics of the rationally designed electrode. This work provides a practical approach for constructing stable metal-selenide anodes with long cycle life and high-rate performance for PIBs.

Microstructural evolution and mechanical properties of CoCrFeNiMnTix high‐entropy alloys

AbstractThis study was conducted to investigate the effect of titanium addition on the microstructure and properties of an equitaomic CoCrFeNiMn high‐entropy alloy. Homogenized microstructures of CoCrFeNiMnTix (x = 0.1 and 0.3) alloys consist of face‐centered cubic phase; however, addition of more titanium led to formation of a (chromium, titanium)‐rich σ phase in CoCrFeNiMnTi0.4 alloy. The average electron hole number calculations indicate the higher possibility of σ phase formation by adding more titanium. Furthermore, addition of an atom like titanium with a larger atomic radius in comparison with other elements can affect stability of face‐centered cubic structure. Chromium and manganese has a destabilizing influence on the single face‐centered cubic phase and manganese may reject chromium to facilitate the formation of a (chromium, titanium)‐rich phase in alloys containing more than 5.5 at.% titanium (x>0.3). The mechanical properties revealed an improvement in strength without losing the ductility drastically by adding titanium up to 5.5 at.% (x = 0.3). Nevertheless, the strength remarkably increased and ductility significantly decreased in CoCrFeNiMnTi0.4 alloy due to formation of brittle σ phase in the microstructure.

Enhanced peroxymonosulfate decomposition into [rad]OH and 1O2 for sulfamethoxazole degradation over Se doped g-C3N4 due to induced exfoliation and N vacancies formation

The development of low-cost and facile synthesized metal-free peroxymonosulfate (PMS) activation catalysts is paramount important for the practical remediation of organic pollution caused by antibiotics. Graphitic carbon nitride (g-C3N4) as a promising alternative, to improve its PMS activation performance, we proposed an efficient method to prepare exfoliated Se doped g-C3N4 (Se-g-C3N4) with 0.095 wt% Se and more exposed reactive N vacancies through the thermal polycondensation of melamine and Se powder at 550 ℃. The results proved that 93.0% of sulfamethoxazole (SMX) can be degraded over Se-g-C3N4 with PMS in 180 min, and the corresponding degradation rate constant of 0.0149 min−1 was even 4-fold higher than that of bulk g-C3N4 (0.0039 min−1). It was found that more 1O2 was generated and OH was further identified because of the enhanced PMS self-decomposition process, especially PMS reduction via electron transfer from Se-g-C3N4. The introduction of Se atom in g-C3N4 structure not only induced the formation of nitrogen vacancies to modulate the electron distribution of g-C3N4, but also favored the exfoliation of inter-facial stacking to increase the exposure of active sites due to the large atomic radius of Se. Hence, this work offered a new strategy for improving the PMS activation performance of g-C3N4 by regulating its electron deficiency and exposing more reactive N vacancies simultaneously.

Steric hindrance effect on adsorption of xanthate on sphalerite surface: A DFT study

The influence of steric hindrance effect on xanthate adsorption on sphalerite surface has been studied by adopting density functional theory (DFT). On the relaxed sphalerite (110) surface, one surface zinc atom coordinates with three sulfur atoms and is located in the center of a planar triangular structure. The sulfur atom with a large atomic radius could spatially hinder the zinc atom, which subsequently results in steric hindrance effect. Consequently, the interaction of xanthate S atoms with surface Zn has to overcome a potential barrier caused by steric hindrance effect. In addition, the DFT simulation and LST search confirmed that the replacement of surface Zn atom by Cu atom could decrease the energy barrier caused by steric hindrance effect, which is favorable for the adsorption of xanthate. The results could explain why ethyl xanthate with short chain length is hard to adsorb on the clean sphalerite surface, but can strongly adsorb on the Cu-activated sphalerite surface.

Influence of tungsten on microstructure evolution and mechanical properties of selected novel FeCoCrMnWx high entropy alloys

A novel equiatomic FeCoCrMnW-based High Entropy Alloy system has been designed with the help of well-established thermodynamic parameters as well as a unique learning strategy based on multi-criteria decision-making tool named ‘TOPSIS’. The present study describes the effect of W addition on as-cast FeCoCrMnWx HEAs on their phase identities and mechanical properties. The results showed that the as-cast FeCoCrMnWx (molar ratio x = 0.2, 0.4, 0.6, 0.8, 1) HEAs were composed of BCC, FCC and several minor Fe–Cr and Co–Cr type σ phases. Transmission Electron Microscopy (TEM) analysis confirms the formation of potentially-embrittling intermetallic phases in minor amounts. The designed HEAs exhibit desirable compressive fracture strength of 1771 MPa and compressive plasticity of 17.1% at room temperature. Hike in Vickers microhardness and compressive strength values could be attributed to a large atomic radius of ‘W’ which further plays a crucial role in grain refinement and solid solution strengthening. This work not only provides advancement in decision making studies of HEAs with new and essential perspectives but also reveals possibly concealed relationships amongst some critical belief in the field of material science.

Design, synthesis and characterization of advanced tritium breeder: Li4Si1-xTixO4 ceramics

Lithium orthosilicate (Li4SiO4) is an important tritium breeder for the fusion blanket concept. It was selected as the first candidate in China's test blanket model. In this study, in order to improve the thermal conductivity and mechanical properties of Li4SiO4, titanium was chosen to replace the silicon in it. This is because Ti has large atomic radius and the same charge as that of silicon. The fabrication and characterization of Li4Si1-xTixO4 solid solution was carried out. The Li4(Si,Ti)O4 powders were synthesised via a solid-state reaction, and the pebbles were fabricated using the freeze-drying method. The structure, morphology, thermal conductivity, and mechanical properties of the Li4(Si,Ti)O4 samples were analysed using X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, a laser thermal conductivity meter, and a universal testing machine. Moreover, the thermal conductivity of Li4SiO4 improved significantly after Ti doping, and the mechanical properties of the Li4(Si,Ti)O4 pebbles sintered at 1000 °C were significantly better than those of Li4SiO4.

Clariant preserves profitability in first nine months of 2020 despite difficult economic environment: 3Q 2020

Here, in this work, the structural, electronic, optical, and transport properties of Magnesium-based group II-VI materials are studied by employing the density functional theory calculations. The WC-GGA and EV-GGA generalized gradient approximations were employed to compute the structure parameters along with the electronic nature of the ternary-type materials. Our calculations confirmed the materials to be indirect band-type semiconductors with a bandgap value of 1.17 ​eV, and 0.51 ​eV, for the MgCdO2 and MgCdS2 materials respectively. Since Sulfur has a larger atomic radius than Oxygen, the bandgap value declines in going from MgCdO2 to MgCdS2 material. The computed total density of states for these materials displayed a sequential shift with increasing energy. The linear optical parameters like the real and imaginary parts of the dielectric function, the energy loss function, the absorption coefficient, the reflectivity, and the refractive index values are calculated and analyzed in detail. Moreover, the thermoelectric properties were also computed, and the results are presented in depth, suggesting all these materials to be efficient for thermoelectric device applications.

Crystallization behavior, soft magnetic properties and good bending ductility of high Fe content FeSiBCuPC alloys induced by composition design

Effects of the minor addition of similar ferromagnetic elements (Fe, Co, Ni, and Gd), metal element with strong non-metallic properties (Al), and transition metal elements with large atomic radius (V, Hf, Ti, and Cr) on crystallization behavior, magnetic properties and bending ductility of Fe85Si0·5B9P4Cu0·5C0.1M0.9 alloys were systematically investigated. The addition of Al, Ni, and Co improves the thermal stability and inhibits the growth of the α-Fe grains. Besides, Gd addition causes a large temperature interval, which suppresses the precipitation of secondary phase. Through the optimum heat treatments, the nanocrystalline alloys exhibit excellent soft magnetic properties, such as higher Ms of 191.7–208.7 emu/g and lower Hc of 6.7–12.1 A/m. Due to the nature of brittleness, the shear morphology induced by elemental microalloying is critical for understanding microscopic mechanism of plastic deformation and achieving high toughness amorphous alloys. We demonstrate that the formation of shear bands are related to the degree of amorphization, shear transformation zones and Poisson’s ratio.

Understanding solute effect on grain boundary strength based on atomic size and electronic interaction

Solute segregating to grain boundary can stabilize the microstructure of nanocrystalline materials, but a lot of solutes also cause embrittlement effect on interfacial strength. Therefore, uncovering the solute effect on grain boundary strength is very important for nanocrystalline alloys design. In this work, we have systematically studied the effects of various solutes on the strength of a Σ5 (310) grain boundary in Cu by first-principle calculations. The solute effects are closely related to the atomic radius of solutes and electronic interactions between solutes and Cu. The solute with a larger atomic radius is easier to segregate the grain boundary but causes more significant grain boundary embrittlement. The weak electronic interactions between the s- and p-block solutes and Cu play a very limited role in enhancing grain boundary strength. While the strong d-states electronic interactions between transition metallic solutes and Cu can counteract embrittlement caused by size mismatch and significantly improve the grain boundary strength. This work deepens our understanding of solute effects on grain boundary strength based on atomic size and electronic interactions.

Gene Expression of 4'-Thioguanine DNA via 4'-Thiocytosine RNA.

DNA and RNA nucleotides are ubiquitous molecules that store and transmit genetic information. The emergence of synthetic elements that fulfill the function of DNA and RNA provides an alternative gene expression system. Herein, we demonstrate the gene expression of 4'-thioguanine DNA (dSG DNA) via 4'-thiocytosine RNA (dSC RNA) to give green fluorescent protein (GFPuv) in a single test tube. In replication, transcription, and translation, DNA/RNA polymerases and Escherichia coli (E. coli) ribosome can tolerate the replacement of O4' with S4' in the nucleotide, despite the fact that sulfur has a larger atomic radius than oxygen. Additionally, dSG DNA and dSC RNA acted as alternative genetic polymers to natural DNA and RNA for protein synthesis in artificial cells comprising a reconstituted E. coli gene expression machinery. This work involved simple experiments that are widely used in molecular biology, but which underscore the feasibility of life control by substances other than DNA/RNA nucleotides.

First-principles study of de-twinning in a FCC alloy

First-principles calculations were used to study the effects of several alloying elements X (i.e., Al, Sc, Zn, and Ce) on the de-twinning of Cu alloys. The results show that the nanotwin (Nt) formation energy of Cu-X alloy gradually decreases with the de-twinning, but Ce improve the Nt formation energy and segregation energy of Cu alloys in T4. Furthermore, charge transfer and redistribution were investigated to explore the physical mechanisms of twinning and de-twinning. When the alloying atom is introduced, a “local effect” is formed in its neighboring regions. The anisotropic distribution of the density charges around Ce improves its bonding strength with Cu atoms, while the Sc atom and Ce atom have a smaller electronegativity and a larger atomic radius, forming strong bonds and high mechanical energy.

Strengthening mechanism in two-phase FeCoCrNiMnAl high entropy alloy coating

The two-phase FeCoCrNiMnAl high entropy alloy cladding layer was produced by laser cladding method, and its strengthening mechanism was studied. Using XRD, EDS, TEM and EBSD analyses, the phase and microstructural evolutions, dislocation density and distribution, and degree of lattice distortion were investigated. Nano-indentation and tensile tests were employed to study the hardness and tensile properties of the cladding layer, respectively. The results show that Al element, due to its large atomic radius, promoted the formation of BCC solid solution in the cladding layer and significantly refined the grains. Diffraction peak shift, change lattice constant change, interplanar spacing and crystal plane included angle calculations indicate that all the phases in the FeCoCrNiMn and FeCoCrNiMnAl cladding layers experienced serious lattice distortions. Dislocations in the FeCoCrNiMnAl coating mainly accumulated and moved in the softer FCC phase, increasing the material's resistance to plastic deformation. The combined effects of grain size, lattice distortion, dislocation density and dual-phase interaction significantly increased the plastic deformation resistance (i.e., tensile strength, yield strength and microhardness) of the FeCoCrNiMnAl coating compared to the FeCoCrNiMn coating, but also reduced the elastoplasticity.

Lithium Bonds in Lithium Batteries.

Lithium bonds are analogous to hydrogen bonds and are therefore expected to exhibit similar characteristics and functions. Additionally, the metallic nature and large atomic radius of Li bestow the Li bond with special features. As one of the most important applications of the element, Li batteries afford emerging opportunities for the exploration of Li bond chemistry. Herein, the historical development and concept of the Li bond are reviewed, in addition to the application of Li bonds in Li batteries. In this way, a comprehensive understanding of the Li bond in Li batteries and an outlook on its future developments is presented.

Lithium Bonds in Lithium Batteries

AbstractLithium bonds are analogous to hydrogen bonds and are therefore expected to exhibit similar characteristics and functions. Additionally, the metallic nature and large atomic radius of Li bestow the Li bond with special features. As one of the most important applications of the element, Li batteries afford emerging opportunities for the exploration of Li bond chemistry. Herein, the historical development and concept of the Li bond are reviewed, in addition to the application of Li bonds in Li batteries. In this way, a comprehensive understanding of the Li bond in Li batteries and an outlook on its future developments is presented.

Determination of regularities of the influence of the elemental composition of niobium­based alloys on their structure and properties

The method of x-ray diffractometry was used to study the effect of the composition of two, three, four and five elemental niobium-based alloys on their phase-structural state, average crystallite size, and thermal expansion coefficient in the temperature range of +20 °С...–170 °С. As elements of filling, vanadium, tantalum, hafnium, molybdenum, zirconium, tungsten and titanium were used. These elements either in equilibrium – at room temperature (RT=+20 °С), or in high-temperature states have a bcc crystal lattice similar to Nb.It is found that in alloys based on two, three, four and five elements, for the compositions used in the work, the formation of a single-phase state with a bcc crystal lattice of a solid solution occurs. At the structural level, the alloy composition affects the ratio of the intensity of the diffraction peak from different planes. For two diffraction orders from the most closely packed {110} plane in the bcc lattice, a change in the intensity value for the second diffraction order is revealed. The greatest decrease in relative intensity occurs in binary alloys with a large discrepancy in the size of the atomic radii of the components. In multi-element alloys, a smaller drop in intensity is observed. This may be associated with a reduction in the distortion of the crystal lattice due to the ordering of the elements that make up the alloys.At the substructural level, the alloy composition affects the average crystallite size. For binary alloy compositions, the greatest effect is associated with Zr and Hf filling elements having a significantly larger atomic radius. This leads to a decrease in the average crystallite size of the alloy solid solution to the smallest value of 11 nm (NbZr alloy) and the release of the second phase (NbHf alloy).It is found that the coefficient of linear thermal expansion determined by the X-ray diffraction method at 2 temperatures (RT=+20 °С and Т=–170 °С) in multi-element alloys exceeds the values for the starting elements. The largest increase in CTE is observed in alloys containing 17–26 at. % V and W, which have the smallest atomic radius

Laser Cladding of Al0.5CoCrCuFeNiSi High Entropy Alloy Coating without and with Yttria Addition on H13 Steel

Al0.5CoCrCuFeNiSi high entropy alloy coating without and with a 1 wt.% Y2O3 addition was fabricated by laser cladding technique on H13 substrate. The results showed that the laser cladding coatings without and with Y2O3 addition consist of a mixture of body centered cubic (BCC) dendrites and face centered cubic (FCC) interdendrites. With the addition of Y2O3, the peaks of BCC dendrites in the coating shifted to leftwards, which is caused by the distortion of lattice due to the dissolution of Y with larger atomic radius. There exist cracks and porosities in the coating without Y2O3 addition. With Y2O3 addition, the cracks and porosities in the laser cladding coating were inhibited greatly. In addition, the microstructure of the coating with Y2O3 addition was refined due to the improving of the ratio of nucleation. The enhancement of properties, such as hardness, wear resistance and corrosion resistance, of the coating with Y2O3 addition came from the inhibition of cracks and porosities and the refinement of microstructure.

Samarium influence on current induced atomic displacement in Aluminium and Copper combinatorial thin film alloys

Combinatorial thin film deposition from vapor phase combined with photolithography was involved in preparation of bidimensional wires for electromigration testing along Al-Cu, Al-Sm and Cu-Sm thin film libraries. Samarium was chosen as alloying element due to its larger atomic radius, directly impacting the crystallographic properties of the conducting alloy and decreasing the total grain boundary surface through amorphisation. As reference, pure Al and Cu wires were additionally deposited and studied. Empirical estimation of the experimental errors obtained during electromigration testing was performed by high throughput measurements and a value around 2% was found for pure Al and Cu metals. The resistance against electromigration of test wires was increased by electrochemical passivation (leading to void pinning), while the empirically evaluated experimental errors increased to 30%. Electrical screening of Al and Cu-based thin film combinatorial libraries was performed at extremely high current densities (MA cm−2). In the Al-Cu system, Al–14 at.% Cu was identified as the alloy able to withstand the highest power density of 2.10 MW cm−2 before failure. The Al-Sm and Cu-Sm thin film libraries showed compositional regions of total or partial amorphization likely impacting the electromigration resistance of the alloys. Electrical screening indicated that Al-6 at.% Sm is the alloy withstanding the highest power density before failure with a value of 2.48 MW cm−2. The highest current densities before electrical failure in conducting lines were measured on pure Al at 1.39 MA cm−2, with a value of maximum power density below 2.62 MW cm−2. Careful discrimination between these two variables is necessary before choosing one of the studied materials as ideal for specific applications.

Hierarchical Eutectoid Nano-lamellar Decomposition in an Al0.3CoFeNi Complex Concentrated Alloy

This paper reports a novel eutectoid nano-lamellar (FCC + L12)/(BCC + B2) microstructure that has been discovered in a relatively simple Al0.3CoFeNi high entropy alloy (HEA) or complex concentrated alloy (CCA). This novel eutectoid nano-lamellar microstructure presumably results from the complex interplay between Al-mediated lattice distortion (due to its larger atomic radius) in a face-centered cubic (FCC) CoFeNi solid solution, and a chemical ordering tendency leading to precipitation of ordered phases such as L12 and B2. This eutectoid microstructure is a result of solid-state decomposition of the FCC matrix and therefore distinct from the commonly reported eutectic microstructure in HEAs which results from solidification. This novel nano-lamellar microstructure exhibits a tensile yield strength of 1074 MPa with a reasonable ductility of 8%. The same alloy can be tuned to form a more damage-tolerant FCC + B2 microstructure, retaining high tensile yield stress (~900 MPa) with appreciable tensile ductility (>20%), via annealing at 700 °C. Such tunability of microstructures with dramatically different mechanical properties can be effectively engineered in the same CCA, by exploiting the complex interplay between ordering tendencies and lattice distortion.

A Versatile Sn‐Substituted Argyrodite Sulfide Electrolyte for All‐Solid‐State Li Metal Batteries

AbstractSulfide‐based solid‐state electrolytes (SSEs) for all‐solid‐state Li metal batteries (ASSLMBs) are attracting significant attention due to their high ionic conductivity, inherently soft properties, and decent mechanical strength. However, the poor incompatibility with Li metal and air sensitivity have hindered their application. Herein, the Sn (IV) substitution for P (V) in argyrodite sulfide Li6PS5I (LPSI) SSEs is reported, in the preparation of novel LPSI‐xSn SSEs (where x is the Sn substitution percentage). Appropriate aliovalent element substitutions with larger atomic radius (R<Sn> > R<P>) provides the optimized LPSI‐20Sn electrolyte with a 125 times higher ionic conductivity compared to that of the LPSI electrolyte. The high ionic conductivity of LPSI‐20Sn enables the rich I‐containing electrolyte to serve as a stabilized interlayer against Li metal in sulfide‐based ASSLMBs with outstanding cycling stability and rate capability. Most importantly, benefiting from the strong Sn–S bonding in Sn‐substituted electrolytes, the LPSI‐20Sn electrolyte shows excellent structural stability and improved air stability after exposure to O2 and moisture. The versatile Sn substitution in argyrodite LPSI electrolytes is believed to provide a new and effective strategy to achieve Li metal‐compatible and air‐stable sulfide‐based SSEs for large‐scale applications.

Mechanical properties and crystallization kinetics of Er-containing Cu–Zr–Al bulk metallic glasses with excellent glass forming ability

Investigations were carried out to explore the consequences of Er adding on the glass forming ability (GFA), mechanical properties, and crystallization kinetics of Cu50Zr43Al7 bulk metallic glass (BMG). It is found that the (Cu50Zr43Al7)100-xErx (x = 0, 2, 4, 6 at %) BMGs reflects its best GFA at x = 2 and correlate well with GFA indicator (γ and K) and thermal stability parameter (ΔTx). The Er-containing BMGs showed high compressive strength and Young module in the range of 1816–1890 Mpa and 116–120 GPa, respectively, but no plastic deformation observed in them. The crystallization kinetics lagged with 2 at % Er addition. The large atomic radius of Er and large negative mixing enthalpy of Er with the other constituent elements causes the significant atomic size mismatch and the formation of short-range order in the melt which restrict the long-range diffusion and ordering of atoms that lead to improving GFA and lagging the crystallization kinetics of (Cu50Zr43Al7)98Er2.