In this study, a conductive polymer, poly(3,4-ethylenedioxythiophene) or PEDOT, was used as binder in the sulfur electrode to study electrochemical performance of lithium–sulfur (Li–S) batteries. PEDOT-based sulfur electrode was compared with that of polyvinylidene difluoride binder based sulfur electrode. Different particle size sulfur materials including commercial micrometric sulfur particles and synthesized colloidal nanometric sulfur powders were chosen as active materials to study the impact of particle size on the cell performance. Different electrolytes including lithium bis(trifluoromethanesulfonyl)imide in polyethylene glycol dimethyl ether (PEGDME) or 1,3-dioxolane-dimethoxy ethane were used in the Li–S batteries to investigate the impact of electrolyte on cell performance. The PEDOT and micrometric sulfur based electrode with PEGDME electrolyte had the best cycle performance, which showed a capacity retention of 68% and specific capacity of 578 mAh/g after 100 cycles. The increased conductivity by conductive polymer and the high viscosity of PEGDME play important roles in the improvement of cycle performance.

This work presents experimental data on the surface and grain boundary energies of tin dioxide nanoparticles at room temperature and high temperature conditions (quenched from 1300 °C), and a discussion of impacts on the fundamental understanding of the nondensification mechanism of SnO2 during sintering. The results were obtained using a combination of water adsorption microcalorimetry, high-temperature oxide melt drop solution calorimetry, and scanning electron transmission microscopy. At room temperature, the average surface and grain boundary energies of anhydrous SnO2 were 1.20 ± 0.02 and 0.71 ± 0.08 J m−2, respectively. At high temperature, SnO2 showed a surface energy of 0.94 ± 0.03 J m−2. This remarkable decrease was attributed to the lower oxygen pressure and was associated with a decrease in contact angle during sintering. This observation indicates a moderate but significant thermodynamic reason behind nondensification behavior of SnO2 in addition to common kinetic descriptions: high sintering temperatures and atmospheres cause smaller dihedral angles that decrease sintering stresses.

P-type Cu1.8+xSe (x = 0, 0.16, 0.20) compounds were synthesized by mechanical alloying and spark plasma sintering technique. A 100% enhancement of the Seebeck coefficient was achieved in the whole temperature interval for x = 0.16 and x = 0.20 bulks compared with that of the x = 0 bulk. The thermal conductivity was all below 1.6 W m−1 K−1 in the whole temperature interval for x = 0.16 and x = 0.20 bulks, showing a pronounced reduction compared with that of the x = 0 bulk. The lowest thermal conductivity 0.69 W m−1 K−1 was achieved in the x = 0.16 sample at 773 K, whereby a maximum ZT value of 1.23 was obtained, revealing that optimizing Cu content in Cu1.8+xSe system is an effective method to improve the thermoelectric (TE) merit and indicating a great potential for TE application along with their nontoxicity and low cost.

The structure and phase transition behavior of monoclinic phase of the morphotropic phase boundary composition Pb(Sc1/2Nb1/2)O3]0.58 –[PbTiO3]0.42 (PSN–42PT) in lead scandium niobate–lead titanate (PSN–PT) system have been investigated by in situ high-temperature polarized light microscopy (PLM) and x-ray diffraction (XRD) studies. Temperature-dependent powder XRD studies of PSN–42PT indicated monoclinic structure at 25 °C and cubic structure at 400 °C. It is observed that the room temperature monoclinic structure transforms to cubic structure through an intermediate tetragonal structure. The temperature-induced domain changes at the phase transition are investigated on (001) face of unpoled PSN–42PT crystal while heating as well as cooling the crystal on hot stage of the PLM. Under crossed polar condition, the striplike polar domains observed at lower temperature vanish gradually with increasing temperature. In the vicinity of ferroelectric transition temperature, the mesosize domains that appeared in the variable temperature PLM images are in accordance with the monoclinic–tetragonal–cubic transition sequence concluded by in situ high-temperature XRD studies. The domain rotation corresponding to the structural transformation sequence is concluded for the first time in the PSN–42PT.

The present study describes magnetic interactions in (Zn1–xCox)Ga2O4 (x = 0.05, 0.10, and 0.20) particles dependant on Co atoms in both tetrahedral and octahedral sites. The effects of substituted Co atoms to magnetic character are analyzed using Curie–Weiss law. The ferromagnetic character is found dominant in (Zn1–xCox)Ga2O4 semiconductors for x values lower than 0.10; in addition, a specific hysteresis with 139 ± 50 Oe coercivity is observed for 5% Co-doped ZnGa2O4. The high Co amount in tetrahedral site increased the number of antiferromagnetic couplings and the hysteresis at 300 K disappeared for (Zn0.80Co0.20)Ga2O4 particles. Furthermore, the Co+3 ions in the octahedral site decreased µeff values, per Co amounts, in the range of 4.89 ± 0.01 µB/Co to 4.44 ± 0.02 µB/Co, because of enhancing paramagnetic behaviors.

Fe–Mn–Pd alloys are promising candidates as biodegradable material for use in temporary implant applications. In this study, the hardening phase of Fe-rich martensitic alloys containing 1, 3, and 6 wt.% Pd and a fixed Mn content of 10 wt.% was investigated. All of these alloys show considerable age-hardening upon isothermal aging at 500 °C, exhibiting a behavior characteristic of maraging steels. Atom probe tomography (APT) and x-ray diffraction (XRD) measurements were performed to characterize the composition and crystallography of nanometer-sized precipitates forming in the overaged region of the Fe–Mn–Pd alloys. The precipitates consist mainly of Mn and Pd and the peaks of the intermetallic particles observed in the XRD spectra can be ascribed to the face-centered tetragonal β1-MnPd phase. The precipitation sequence for Fe–Mn–Pd is revealed to be similar to that reported for Fe–Mn–Ni and Fe–Mn–Pt maraging steels.

Amorphous polymers are among the most common materials used in adhesives, and a clear understanding of the effects of molecular scale features on macroscopic responses is necessary to design new, better performing adhesives. While many features have been investigated, including effects of molecular weight, inclusion of filler materials, and some effects of crosslinking, much of the understanding of the adhesive response remains empirical. Specifically, choosing the appropriate combination of polymer properties that optimize the work required to debond is still a challenge and the interplay between mechanical and chemical properties of polymers at interfaces is largely unknown. Here, we perform molecular dynamics simulations on a simple coarse-grained polymer model to directly investigate the role of crosslinking in determining the adhesive response of amorphous polymers at the molecular level. We find that crosslinking has a dramatic effect on the mechanical properties even at relatively low crosslink densities, and that crosslinking alone can be effective for optimizing the adhesive response of amorphous polymer adhesives. We observe a clear transition from cohesive to adhesive failure as the crosslink density is increased which coincides with the optimal toughening in the films. Furthermore, we find that our model captures the key molecular scale deformation mechanisms that control the adhesive response. For low crosslink densities, increased crosslinking improves the adhesive response by inhibiting chain sliding and allowing the structures to achieve large deformations, but as the crosslink density is increased further, the adhesive response is diminished due to reduced overall deformability. Our results provide simple but important insights into how crosslinking in amorphous polymer adhesives can be used to tune the mechanical response and ultimately to optimize adhesive performance for various applications.

A new physical model of plastic deformation in nanocrystalline (NC) materials with finest grains (whose grain size is 2–4 nm) is suggested and theoretically described. The model represents the effect of the finest grains located at triple junctions on the fracture toughness of NC materials in the case that there are multiple dislocations pile-up at grain boundaries (GBs). The maximum number n of the pile-up dislocations is determined by both the capacity of dislocations emitting associated with the crack propagation and the capacity of dislocations pile-up due to the existence of the finest grains. The calculation indicates that the parameter n increases with increment of the grain size and decreases with the finest grain size increasing. The results theoretically reveal that the triple junctions with finest grains can significantly improve the fracture toughness of NC materials compared with the normal triple junctions in wide ranges of their structural parameters.

This paper aims to develop an integrated method to extract elastic–plastic parameters from a single instrumented spherical indentation curve. The expression of unloading work is chosen to be combined with the previous work [P. Jiang, T.H. Zhang et al, J. Mater. Res.24(3), 1045 (2009)]. An extensive numerical study was performed to examine the effectiveness of the method. Refitting Jiang's similarity solution based on the numerical study was also performed to simplify the form of the expression and improve the accuracy of the elastic–plastic parameters extracted. The results show that the error of our solution was less than ±5%. We also examined its sensitivity by assessing levels of artificial error introduced into the testing parameters used in the method. These results show that this method can provide reasonable estimates of the elastic–plastic parameters for most common metals.

We describe an improved experimental approach for characterizing the elastic modulus and hardness of single microfibers through instrumented indentation. A sample mounting technique on a curved surface is presented that ensures contact between an unmodified fiber and substrate. The indentation analysis considers three separate corrections to the well-known Oliver and Pharr method: (i) overestimation of the projected contact area due to sample curvature, (ii) overestimation of projected contact area due to substrate curvature, and (iii) underestimation of fiber stiffness due to the structural compliance of the sample. The method is applied to four types of high performance ballistic fibers: KM2 Plus, Twaron, AuTx, and Dyneema; the results are presented according to both the modified analyses as well as the standard Oliver and Pharr analysis. The modified analyses resulted in an increase in the elastic modulus and hardness of up to 35 and 60%, respectively, compared to the Oliver–Pharr method. The technique has the potential to be applied to single microfilaments under various environmental conditions that may otherwise be compromised by traditional fiber mounting methods.

Titanium carbide (TiC) twins are believed to be extremely unstable because of their high twin boundary energy. Here, we report that TiC twins are always presented in platelets with dimensions of 2–3 μm in length and less than 300 nm in width. In-depth microstructural characterizations by high-resolution transmission electron microscopy demonstrate that Al atoms at the twin boundary play a decisive role in stabilizing TiC twins. With different amounts of Al, perfect and defective TiC twins are formed. For perfect twins, three types of twin boundaries can be formed depending on the amount of remaining Al at the twin boundary. With inadequate Al, the TiC twins become defective with certain degrees of deviation from the perfect twin orientation. Based on a detailed analysis of the microstructure of the twin boundaries, a mechanism for the formation and stabilization of TiC twins is proposed.