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A comprehensive understanding of material deformation behavior holds importance in enhancing the properties of materials, which can be achieved through modeling the relationship between microstructure and deformation behavior by an appropriate crystal plasticity (CP) model. However, before simulations, obtaining a high-fidelity representative microstructure (RM) to simultaneously meet the efficiency and accuracy requirements of the CP model is still a challenge. Thus, taking the Al–Al2Cu eutectics as an example, we successfully obtained a high-fidelity RM with two-point statistics and some fashionable image processing techniques. Then a high-resolution RMCP model was developed and the deformation behavior of Al–Al2Cu eutectics at room temperatures was uncovered. Due to multiple activated slip systems on {111}<110> inducing obvious cross-slip behavior, severe and heterogenous plastic deformation occurs in α-Al. And dislocations originate from the microstructure defects. In θ-Al2Cu, all possible slip systems are not activated, resulting in no plastic deformation. The predictions of the RMCP model are verified to be reliable by comparing with the results of in-situ tensile tests. Our proposed RMCP method is not only applicable to the two-phase eutectic systems, but also suitable for various multiphase and polycrystalline systems.

The traditional clustering algorithm is difficult to deal with the identification and division of uncertain objects distributed in the overlapping region, and aimed at solving this problem, the Evidential Clustering based on General Mixture Decomposition Algorithm (GMDA-EC) is proposed. First, the belief classification of target cluster is carried out, and the sample category of target distribution overlapping region is extended. Then, on the basis of General Mixture Decomposition Algorithm (GMDA) clustering, the fusion model of evidence credibility and evidence relative entropy is constructed to generate the basic probability assignment of the target and achieve the belief division of the target. Finally, the performance of the algorithm is verified by the synthetic dataset and the measured dataset. The experimental results show that the algorithm can reflect the uncertainty of target clustering results more comprehensively than the traditional probabilistic partition clustering algorithm.

As-cast and rapidly solidified Ti23V40Mn37alloy doped with Zr7Ni10was synthesized by arc melting and melt-spinning. The microstructure, activation property, hydrogen absorption kinetics, and hydrogen absorption/desorption thermodynamics were investigated to evaluate a comprehensive hydrogen storage property of the alloys. Both preparation methods had a negligible effect on the lattice parameter of BCC and C14 Laves phases in the alloys. The alloy prepared by melt-spinning showed an increased proportion of BCC phase, larger hydrogen absorption capacity, faster hydrogen absorption rate, and higher hydrogen absorption/desorption platform pressure. The dehydriding enthalpy and endothermic peak temperature of the rapidly solidified alloy were 33.55 ± 2.14 KJ/mol H2and 526.2 K, respectively, which are smaller than those of the as-cast alloy. It indicates the decreased hydride stability and improved hydrogen desorption property. By contrast with the as-cast alloy, the rapidly solidified alloy showed a preferable comprehensive hydrogen storage property.

• Hyperbranched seaweed could prevail in bulk sample of metallic alloy. • Quantitatively exploring the growth dynamics of seaweed in 2D-like and 3D samples. • Well understanding the effect of sample size on the seaweed growth. The seaweed-like microstructure in quasi-two-dimensional (2D) and three-dimensional (3D) samples is studied by controlling the orientation-dependent interface energy anisotropy during directional solidification of an Al-3 wt.% Mg alloy. Here, we produce asymmetrically shaped seaweed and degenerate seaweed patterns in 2D samples for the (0 1 ¯ 1)[111] and (2 ¯ 11)[111] orientations. During solidification in the 3D sample, a hyperbranched seaweed formation prevails for the [111] orientation. The comparison of these growth patterns shows that the morphologic features are qualitatively similar. In addition, the spacing (λ) and frequency (ƒ) of tip splitting in seaweed patterns follow a power law with respect to growth velocity. The 3D sample exhibits a lower tip spacing and higher frequency than the 2D sample. These quantitative relationships between growth dynamics and the role of sample size deserve attention. Our results clearly show that the seaweed pattern could survive and grow stably in 3D metallic alloys, and the exploration of this complex morphology for application is feasible in the future. [ABSTRACT FROM AUTHOR]

Since the basic probability of an interval‐valued belief structure (IBS) is assigned as interval number, its combination becomes difficult. Especially, when dealing with highly conflicting IBSs, most of the existing combination methods may cause counter‐intuitive results, which can bring extra heavy computational burden due to nonlinear optimization model, and lose the good property of associativity and commutativity in Dempster‐Shafer theory (DST). To address these problems, a novel conflicting IBSs combination method named CSUI (conflict, similarity, uncertainty, intuitionistic fuzzy sets)‐DST method is proposed by introducing a similarity measurement to measure the degree of conflict among IBSs, and an uncertainty measurement to measure the degree of discord, non‐specificity and fuzziness of IBSs. Considering these two measures at the same time, the weight of each IBS is determined according to the modified reliability degree. From the perspective of intuitionistic fuzzy sets, we propose the weighted average IBSs combination rule by the addition and number multiplication operators. The effectiveness and rationality of this combination method are validated with two numerical examples and its application in target recognition.

MoVTeNbOxcatalysts were prepared through a high-pressure hydrothermal method, in which the crystalline structure and properties of the catalysts were tuned by varying the system pressure (0-12.0 MPa). Results showed that the system pressure had a significant influence on the structure and catalytic performance of MoVTeNbOx. Under 3.0 MPa, MoVTeNbOxprepared possessed the highest content of M1 phase (90.6%) and V5+content (60.7%), exhibiting a uniform short and thick needle-like morphology. Also, it showed excellent selectivity (79.1%) and yield (52.8%) to acrylic acid at the catalytic temperature of 380°C. However, under 4.4 and 11.6 MPa, the characteristic peaks of M1 shifted to a certain extent and the morphology changed from short and thick to slender. As a result, the V5+content of M1 (001) plane decreased, resulting in a remarkable decline of the selectivity to acrylic acid. Moreover, DFT simulation results showed that the anti-bond orbital energy of V-O bond is the highest under 3.0 MPa, while further increase of pressure leads to obvious extrusion between atoms in the internal structure of MoVTeNbOx. Moreover, it was clear that the lower the anti-bond orbital energy of V-O bond, the lower the selectivity to acrylic acid.

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Twin crystal structured Al-10 wt.% Mg alloys that were grown over a broad solidification velocity range were prepared and studied for the first time. The high thermal gradient (G) and growth velocity (V) of directional solidification resulted in the dominant solidification of twins: the twinned dendrite trunks at constant high V s curved in the G direction with large angles in 7 mm diameter crucibles and invaded regular columnar grains because of a distinct kinetics growth advantage. Transitive deceleration experiments were designed to produce twin crystals that evolved with lower values of V (100, 10, and 0.5 μm/s) and had a structural coarsening trend. Twin cell growth in the absence of arms occurred at a growth velocity of 10 μm/s. A coherency loss was observed at a growth velocity of 0.5 μm/s with straight coherent twin boundaries turning into curved incoherent boundaries. Linear theoretical analyses were performed to understand the structural evolution of the twins. These results demonstrate the possibility of producing dense and controlled twin crystals in the Al-Mg system under most industrial production conditions; thus, this approach can be a new structural choice for designing Al-Mg-based alloys that have widespread commercial applications. [ABSTRACT FROM AUTHOR]

As appealing alternatives to noble-metal-based electrocatalysts for catalyzing hydrogen evolution reaction (HER) in alkali electrolyzers, earth-abundant MoNi-based catalysts have attracted intensive attention. Unfortunately, the exploration of MoNi-based electrocatalysts with superior intrinsic activity and ultralong-term stability still remains a grand challenge. Here, ultralong high-index faceted Mo@MoNi core–shell nanowires were topochemically synthesized through the thermal reduction of Mo@NiMoO4core–shell nanowires, where single-crystalline Mo support facilitates the topological transformation of NiMoO4into high-index faceted MoNi. When the as-achieved Mo@MoNi core–shell nanowire film serve as a free-standing cathode in alkaline solutions, it exhibit a remarkably decreased HER overpotential of 18 mV at 10 mA cm–2and a Tafel slope of ∼33 mV dec–1, which are much lower than those for the state-of-the-art earth-abundant electrocatalysts and even commercial Pt/C. Experimental and theoretical investigations reveal that the exposed high-index (331) facets of MoNi can considerably reduce the energy barriers of initial water dissociation and subsequent hydrogen combination steps, which synergistically accelerates the sluggish alkaline HER kinetics. Significantly, after a 70-day HER operation, the overpotential of Mo@MoNi electrocatalysts at 10 mA cm–2decreases by only 4 mV. Therefore, this work sheds a bright light on the rational design of high-performance HER electrocatalysts and their practical utilization for alkaline electrolyzers.

Abstract

Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ (100)[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting (λ) in the degenerate of the alloys followed a power law, λ ∝ V −0.5, and the frequency (f) of the splitting was related to the growth velocity (V) by ƒ∝ V 1.5. The dimensionless growth direction (θ / θ 0) increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction. [ABSTRACT FROM AUTHOR]

Abstract

Abstract

Deep shale gas reservoirs buried underground with depth being more than 3500 m are characterized by high in-situ stress, large horizontal stress difference, complex distribution of bedding and natural cracks, and strong rock plasticity. Thus, during hydraulic fracturing, these reservoirs often reveal difficult fracture extension, low fracture complexity, low stimulated reservoir volume (SRV), low conductivity and fast decline, which hinder greatly the economic and effective development of deep shale gas. In this paper, a specific and feasible technique of volume fracturing of deep shale gas horizontal wells is presented. In addition to planar perforation, multi-scale fracturing, full-scale fracture filling, and control over extension of high-angle natural fractures, some supporting techniques are proposed, including multi-stage alternate injection (of acid fluid, slick water and gel) and the mixed- and small-grained proppant to be injected with variable viscosity and displacement. These techniques help to increase the effective stimulated reservoir volume (ESRV) for deep gas production. Some of the techniques have been successfully used in the fracturing of deep shale gas horizontal wells in Yongchuan, Weiyuan and southern Jiaoshiba blocks in the Sichuan Basin. As a result, Wells YY1HF and WY1HF yielded initially 14.1 × 104 m3/d and 17.5 × 104 m3/d after fracturing. The volume fracturing of deep shale gas horizontal well is meaningful in achieving the productivity of 50 × 108 m3gas from the interval of 3500–4000 m in Phase II development of Fuling and also in commercial production of huge shale gas resources at a vertical depth of less than 6000 m.

The formation of degenerate seaweed in Al-4.5 wt % Cu, Al-3 wt % Mg, and commercial A356 alloys during quasi-two-dimensional directional solidification is studied. By designing (100)[011]-and (−211)[111]-oriented planar-front seeds, the surface tension profiles are symmetrically arranged with respect to the temperature gradient direction. The results show that growth toward the surface tension maxima is preferred, and the tips tend to grow outward in both directions, leading to degenerate seaweed formation. The comparison of the degenerate seaweeds in the three Al alloys shows that the morphologic features are qualitatively similar. However, the anisotropic surface tension has a significant effect on the growth dynamics of the degenerate seaweed. This quantitatively indicates that Al alloys with a larger anisotropy tend to exhibit growth with a smaller tip spacing (λ) and a higher splitting frequency (f).

Abstract

Post-fracturing evaluation by using limited data is of great significance to continuous improvement of the fracturing programs. In this paper, a fracturing curve was divided into two stages (i.e., prepad fluid injection and main fracturing) so as to further understand the parameters of reservoirs and artificial fractures. The brittleness and plasticity of formations were qualitatively identified by use of the statistics of formation fracture frequency, and average pressure dropping range and rate during the prepad fluid injection. The composite brittleness index was quantitatively calculated by using the energy zones in the process of fracturing. It is shown from the large-scale true triaxial physical simulation results that the complexity of fractures is reflected by the pressure fluctuation frequency and amplitude in the main fracturing curve, and combined with the brittleness and plasticity of formations, the fracture morphology far away from the well can be diagnosed. Well P, a shale gas well in SE Chongqing, was taken as an example for post-fracturing evaluation. It is shown that the shale beds are of stronger heterogeneity along the extension directions of horizontal wells, and with GR 260 API as the dividing line between brittleness and plasticity in this area, complex fracture systems tend to form in brittleness-prone formations. In Well P, half of the fractures are single fractures, so it is necessary to carry out fine subsection and turnaround fracturing so as to improve development effects. This paper provides a theoretical basis for improving the fracturing well design and increasing the effective stimulated volume in this area.

The phase stability of the Laves phase Cr2Nb in a two-phase Cr-Cr2Nb alloy produced by arc-melting was investigated using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The experimental results indicated that the as-cast ingot was consisted of C15-Cr2Nb and Cr phases; the intermediate C36 and high-temperature C14 modifications of Cr2Nb, reported in literatures, were not detected in this study. These results, combined with a detailed analysis of the actual solidification conditions, revealed that the C14-Cr2Nb was a metastable rather than a stable high-temperature modification. Moreover, a kind of extremely fine lamellar structure was found to be randomly distributed in the eutectic cells, which may be formed by decomposition of the supersaturated C15-Cr2Nb viaa discontinuous precipitation reaction.

A new separation method, negative pressure cavitation (NPC) extraction followed by HPLC‐MS‐MS for the determination of paclitaxel and its analogues in the needles of Taxusspecies is described in this study. Compared with three conventional extraction methods, NPC is a more effective, economical, and facile method for the separation of nature compounds from herbal plants. In contrast to high‐temperature extraction, NPC at low temperature can minimize undesirable reactions such as thermal decomposition or degradation. In addition, the extraction mechanism of NPC was also illuminated. The effects of vacuum degree, extraction solvent, ratio of solid to liquid, time, and times extraction were studied and optimized. The optimum extraction conditions were as follows: vacuum degree –0.03 MPa, solvent 80% v/v alcohol, ratio of material to liquid 1:15 (g/mL), extraction time 60 min, extraction (×3). Using these conditions, the recoveries of 10‐deacetyl‐7‐xylosylpaclitaxel, 10‐deacetylpaclitaxel, cephalomannine, and paclitaxel were higher than 95.88, 95.82, 94.85, and 96.18%, respectively. The contents of paclitaxel, 10‐deacetyl‐7‐xylosylpaclitaxel, 10‐deacetylpaclitaxel, and cephalomannine for Taxus chinensiswere 0.0053, 0.0467, 0.0132, and 0.0076%, and 0.0067, 0.0153, 0.0047, and 0.0064% for Taxus cuspidata, respectively. Furthermore, a comparison of SEM images observed the morphological changes of microstructures and cellular damage in yew needles.

An environment‐friendly method was established for the preparative separation and enrichment of four taxoids, namely 10‐deacetylbaccatin III (10‐DAB III), 7‐xylosyl‐10‐deacetyltaxol (7‐xyl‐10‐DAT), cephalomannine and paclitaxel fromTaxus chinensis needles extracts. Characteristics of seven widely used macroporous resins for four taxoids were compared, AB‐8 resin offered better adsorption and desorption capacities than others. AB‐8 resin column chromatography was used to study the desorption process for four taxoids. The optimum parameters for desorption were 30% ethanol 5 RV for removing impurities, following 15 RV for 10‐DAB III, after the desorption of impurities with 35% ethanol 10 RV, 45% ethanol 30 RV for 7‐xyl‐10‐DAT, then 65% ethanol 10 RV for cephalomannine and paclitaxel, the flow rate was 6 RV/h. After separation on AB‐8 resin column chromatography, the contents of 10‐DAB III, 7‐xyl‐10‐DAT, cephalomannine and paclitaxel in the product reached 4.58, 13.17, 1.36 and 3.08%, respectively, which were 7.63‐, 3.68‐, 6.18‐ and 6.55‐fold to those inT. chinensisneedles extracts. The recovery yields were 94.96, 77.32, 88.09 and 95.25%. In general, the AB‐8 resin column chromatography has the advantages of lower cost, high efficiency and simple procedure. Therefore, it may provide scientific references for the preparative separation and enrichment of taxoids from otherT. species.

While the seaweed pattern is one the most important classes of interfacial morphologies, their mechanical properties are not well understood. Here we produce axial seaweed (AS), tilted seaweed (TS) and degenerate seaweed (DS) by controlling the orientation-dependent interfacial energy anisotropy during the directional solidification of an Al-4.5 wt.% Cu alloy. Characterization of the disordered morphology by electron backscattered diffraction (EBSD) showed that the seaweed growth was oriented in the <110> direction, which was significantly different from that of a <100> regular dendrite. The mechanical properties of seaweed morphology specimens were evaluated using a tensile-testing machine at room temperature. The ultimate tensile strength (σb), elongation (δf) and toughness of the seaweed morphology specimens reach 186.1 MPa, 45.5% and 72.9 MJ m−3, respectively, for AS; 151.6 MPa, 50.9% and 67.9 MJ m−3, respectively, for TS; and 164.3 MPa, 62.2% and 89.4 MJ m−3, respectively, for DS. With respect to specimens with regular dendrite, the DS specimen exhibited a significant improvement in the elongation and toughness of 109% and 96%, respectively. Additionally, the seaweed morphology specimens show a stronger work hardening effect (n = 0.33, 0.30 and 0.38 for AS, TS and DS specimens, respectively) than the dendrite specimen (n = 0.22). Continuous tip-splitting of the seaweed morphology specimen produced refined and uniformly distributed second-phase particles that contributed to the aforementioned enhancement. Our results provide the underlying insight of the mechanical properties of seaweed morphology specimens, a topic crucial to the design of aluminum alloys.

A method is described for the simultaneous determination of paclitaxel and three related taxoids, 10‐deacetylbaccatin III (10‐DAB III), baccatin III, and cephalomannine, in the extracts from the needles of three Chinese yew species,Taxus cuspidata, T. chinensis, andT. media. SPE was applied as the sample preparation technique and RP‐HPLC with a photodiode array detector (PAD) was used for the analysis of extract samples. The crude extracts were treated with an improved SPE cartridge packed with a combination of 1‐vinyl‐pyrrolidin‐2‐one and divinyl‐benzene. The eluent was 75% methanol. The following separation was achieved with a gradient program on an HIQ SIL C18W column in a system of ACN/water within 60 min. The samples were detected by PAD at wavelengths of 232.1 nm for 10‐DAB III, 229.8 nm for baccatin III and paclitaxel, and 223.9 nm for cephalomannine. The content of 10‐DAB III, baccatin III, cephalomannine, and paclitaxel varied from 0.0277 to 0.0875, 0.0254 to 0.0405, 0.0715 to 0.2486, and 0.0996 to 0.1301 mg/g in fresh needles of the above yew species, respectively. The assay achieved good resolution in the separation between the four compounds, and it can be used for quality control or purity determination for those in bulk and pharmceutical dosage forms.

AbstractElectromagnetic confinement and shaping is a kind of newly developing solidification technology. With the electromagnetic field imposed, the metal is melted to some superheating degree by Joule heating and is confined and shaped to the desired form by the electromagnetic force at the same time. The frequency effect of the electromagnetic field on the electromagnetic confinement and shaping is investigated. The relationship between the Joule heat, the electromagnetic force and the frequency is revealed from the viewpoint of the magnetohydrodynamics theory. The results show that, given the condition of the same magnetic field strength, the time-averaged volume electromagnetic force at the melt surface is approximately proportional to the field frequency, whilst at the same time the volume Joule heating rate is approximately proportional to the square of the field frequency. However, as the frequency increases, the shaping stability and the surface quality decrease due to the violent surface electromagnetic stir. The frequency effect is also correlative to the sample's size and electric conductivity. The bigger is the sample, the lower ought to be the frequency and vice versa. The bigger is the electric conductivity, the lower can be the frequency and vice versa. Thus there is an optimum frequency range for each different sample, which is tens to hundreds of kilohertz for the small-size or medium-size steel sample. The experimental research is carried out with aluminium, copper and stainless steel samples, and the results show good agreement with the theoretical predictions.