S.X. Li

Unprecedented metal-free 3D porous carbonaceous electrodes for full water splitting

Earth-abundant, active and stable water splitting electrocatalysts operating in the same electrolyte at all pH values is important for many renewable energy conversion processes. We report here the first carbon nanomaterials-based metal-free water splitting electrocatalyst. The nitrogen, phosphorus and oxygen tri-doped porous graphite carbon@oxidized carbon cloth (ONPPGC/OCC) electrocatalyst can be prepared by a simple cost-effective method using aniline, phytic acid and OCC as precursors. Being a robust integrated three-dimensional porous bifunctional electrode, ONPPGC/OCC enables a high-performance basic water electrolyzer with 10 mA cm−2 at a cell voltage of 1.66 V. Additionally, this electrode offers excellent catalytic performance and durability under both neutral and acidic conditions.

Influence of Grain Size and Texture on the Yield Asymmetry of Mg-3Al-1Zn Alloy

The yield asymmetry between compression and tension of magnesium alloy Mg-3Al-1Zn (AZ31) with different grain sizes and textures has been studied by tensile and compressive testing of as-cast, as-extruded and equal channel angular pressed (ECAPed) specimens. The significant yield asymmetry (the ratio of yield strength between compression and tension sigma(yc)/sigma(yt) is similar to 0.44) was found in as-extruded specimens and the corresponding microstructure evolution during deformation revealed that {1012} tensile twinning is the underlying reason for the large yield asymmetry. Strong texture and grain size are influential factors for large yield asymmetry. The separate contributions of grain size and texture on yield asymmetry were investigated.

Formation mechanism of nanostructures in austenitic stainless steel during equal channel angular pressing

An ultra-low carbon austenitic stainless steel was successfully pressed from one to eight passes by equal channel angular pressing (ECAP) at room temperature. By using X-ray diffraction, optical microscopy and transmission electron microscopy, the microstructural evolution during ECAP was investigated to reveal the formation mechanism of strain-induced nanostructures. The refinement mechanism involved the formation of shear bands and deformation twins, followed by the fragmentation of twin lamellae, as well as successive martensite transformation from parent austenitic grains with sizes ranging from microns to nanometres through the processes γ(fcc)u2009→u2009ε(hcp)u2009→u2009α′(bcc). After pressing for eight passes, two types of nanocrystalline grains were achieved: (a) nanocrystalline austenite with a mean grain size of ∼31u2009nm and (b) strain-induced nanocrystalline α′-martensite with a size of ∼74u2009nm. The formation mechanisms are discussed in terms of microstructural subdivision via deformation twinning and martensite transformation.

Designed multimetallic Pd nanosponges with enhanced electrocatalytic activity for ethylene glycol and glycerol oxidation

We report an effective synthesis of surfactant-free multimetallic Pd nanosponges with tunable compositions using EDTA as the structure-directing reagent and NaBH4 as the reducing reagent. Among the mono-metallic Pd, binary PdNi and PdAu, ternary PdAuNi nanosponges and commercial Pt/C catalysts studied, Pd62Au21Ni17 nanosponges exhibit excellent activities and are the most efficient nanoparticle catalysts ever reported for both ethylene glycol and glycerol oxidation reactions.

Survey of plateau behaviour in the cyclic stress-strain curve of copper single crystals

Experimental results relating to the plateau behaviour in the cyclic stress-strain (CSS) curve of copper single crystals located on different sides of the stereographic triangle are summarized. Unlike the situation for single-slip-oriented crystals, the crystallographic orientation has a strong effect on the plateau behaviour in the CSS curves of double- and multiple-slip-oriented crystals. The existence or non-existence of a plateau in the CSS curves, as well as the corresponding plateau stress amplitude, depend not only on the modes and intensities of dislocation interactions among slip systems operating in the crystals but also on the slip deformation characteristics associated with crystal orientations. The plateau region in CSS curve disappears only when multiple slip plays a determining role during cyclic deformation.

Cyclic deformation and fatigue cracking behaviour of polycrystalline Cu, Cu–10 wt% Zn and Cu–32 wt% Zn

The cyclic deformation behaviour of polycrystalline Cu, Cu–10 wt% Zn and Cu–32 wt% Zn was systematically investigated in the plastic strain amplitude range of 1 × 10−4–4 × 10−3. The differences in the cyclic stress–strain (CSS) responses and fatigue cracking behaviour between Cu, Cu–10 wt% Zn and Cu–32 wt% Zn were compared. It was found that the occurrence of a cyclic saturation for Cu–10 wt% Zn and Cu–32 wt% Zn strongly depends on the applied strain amplitude, whereas polycrystalline Cu always displays cyclic saturation. Surface deformation morphologies were analyzed by scanning electron microscopy (SEM). One of the major features observed is that the slip bands become increasingly homogenous with Zn addition. The fatigue cracks were found to frequently nucleate along the annealing twin boundaries (TBs) in Cu–10 wt% Zn and Cu–32 wt% Zn, but not in polycrystalline Cu. Based on these experimental results, the cyclic deformation response and fatigue cracking behaviour are discussed, and a developed TB cracking mechanism is proposed to explain the difference in fatigue cracking mechanisms in Cu, Cu–10 wt% Zn and Cu–32 wt% Zn.

The characteristics of granular-bright facet in hydrogen pre-charged and uncharged high strength steels in the very high cycle fatigue regime

In this study, the effect of hydrogen on fatigue strength of high strength steels in the very high cycle fatigue regime was further discussed. It is found that the calculated results of fatigue strength by modified Murakami’s expression are in good accordance with the experimental results in ±15% error band. The relationship between fatigue life (Nf) and the ratio of granular-bright facet (GBF) to inclusion size

Influence of crystallographic orientation on cyclic strain-hardening behaviour of copper single crystals

left({frac{{sqrt {A_{text{GBF}} } }}{{sqrt {A_{text{inc}} } }}}right)