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Fracture mechanics analysis of shear band propagation requires knowledge of the material’s shear fracture energy and its related properties such as the characteristic slip displacement. Yet these properties of stiff clays and shales have not been investigated systematically. This work characterizes and analyzes the shear fracture energies and characteristic slip displacements of various stiff clays and shales based on their triaxial compression data from the literature. A methodology originally developed for hard rocks was adopted for this purpose. Results show that the shear fracture energies of stiff clays and shales generally increase with the effective normal stress on the slip plane, varying by orders of magnitude—approximately from $$4\times 10^{1}$$ to $$7\times 10^{3}$$ J/m $$^{2}$$ —in the range of effective normal stresses from $$10^{2}$$ to $$10^{5}$$ kPa. An empirical equation is presented for a first-order estimate of the shear fracture energy under a given effective normal stress. The characteristic slip displacements at the laboratory scale are calculated to be smaller than 6 mm, and they appear independent of the effective normal stress. Compared with their nominal values calculated without considering the change of normal stress in triaxial tests, the shear fracture energies are approximately 70% of the nominal values, whereas the characteristic slip displacements are nearly identical to the nominal ones.

This paper presents a new additive manufacturing process of ceramics, named hydrothermal-assisted transient jet fusion, pairing heat and pressure in attempts to create a highly dense green part. The process utilizes water as a transient binder to fuse particles eliminating the possible contamination caused by traditional organic binders. Inkjet printing was employed to selectively deposit water into a powder bed. Bentonite clay powder was used as a model material for the study, due to its excellent solubility in water. An analysis of the effects of pressure and heat on powder fusion was completed using the compression strength as a quantitative measure. A processing map was created to provide a preliminary understanding of the relationship between the combination of heat and pressure and selective fusion of powder. Test cases were printed to show the capabilities of the developed process. A prediction of the parts compressive strength was done based on previous data collected. Results proved that an increase in temperature culminates a higher compression strength. Results also showed that an increase in pressure contributes to a postponed evaporation of water in the part; once the evaporation has taken place, a denser part has a more dramatic increase in compressive strength.

Description, Electroresponsive and synergistic brain-targeting nanoparticles improve efficacy of pharmacotherapy for epilepsy., Long-term pharmacotherapy, serving as the main therapeutic approach for epilepsy prophylaxis, has suffered from limited efficacy and potential side effects because of the blood-brain barrier (BBB) and untimely medication. Here, we reported a nanoengineered drug delivery system for synergistic brain-targeting delivery and on-demand drug release of antiepileptic drugs (AEDs). The dopamine-pyrrole hybrid system can improve delivery efficiency through a combination of receptor-mediated transcytosis and BBB disruption–enabled transport induced by photothermal conversion of near-infrared light. Incorporation of polydopamine endowed the delivery system with enhanced conductivity and sensitivity, giving sustained (2 hours) and rapid (30 s) drug release in response to epileptiform discharges. Acute, continuous, and spontaneous seizure models validated that the delivery system could inhibit seizures upon epileptiform abnormalities, treated by one-fifth of the conventional dosage. Complemented with satisfactory biosafety results, this “smart” modality is promising to be an effective and safe strategy to improve the therapeutic index of AEDs for epilepsy.

Ceramic additive manufacturing (AM) provides a freeform fabrication method for creating complex ceramic structures that have been extremely difficult to build by traditional manufacturing processes. However, ceramic structures made by AM processes usually exhibit a relatively low density, which is largely due to the use of a large amount of organic binder in shaping green bodies. In this research, we present a new ceramic AM process, named hydrothermal-assisted transient binder jetting (HTBJ), which utilizes a water-based hydrothermal mechanism to fuse particles, eliminating the use of binders in forming green bodies. A prototype system for the proposed HTBJ process is introduced. The effects of process parameters (such as layer thickness, printing passes, prepressing and final pressing pressure, and temperature) on the properties of achieved green parts are investigated. Experimental results indicate that, with optimized process parameters, HTBJ can achieve three-dimensional ceramic green parts with a high density of up to 90%.

Poly(vinylamine) (PVAm) is an important polymer with the highest content of primary amine groups of any polymer. PVAm has a great potential in selective separation and smart materials. It is difficult to fabricate pure PVAm nanofibers by electrospinning and rotary jet spinning (RJS) without additional polymers. In this work, rotary jet wet spinning (RJWS) was applied to fabricate molecular imprinting nanofibers (MINFs) with polyelectrolyte for the first time. Initially, optimal parameters of spinning are investigated, including coagulation bath, solution viscosity, and rotation speed. The PVAm aqueous solution is sensitive to alcohol. To demonstrate RJWS application, PVAm-based MINFs for bisphenol A (one endocrine disruptor) recognition are prepared by adding dummy template, cross-linking, and template elution. The association constant (8.6 mg/L), equilibrium time (30 min), and binding sites utilization rate (80%) of MINFs are evaluated. Its adsorption amount and selectivity are little lower than those of MIPs prepared by bulk polymerization; however, its adsorption speed is faster than that of MIPs.

With continued urbanization in China, the construction of urban gas pipelines is increasing, and the safety of gas pipelines are also increasingly affected by urban development and the increased scope of buildings and roads. Pipes with defects are more likely to fail under the surface loads. In this study, uniaxial tensile tests of high-density polyethylene (HDPE) pipes were carried out to obtain the real material parameters of pipe. A pipeline-soil interaction finite element model of HDPE pipeline with defects under surface load was established. The failure mechanism of the urban gas pipeline was studied and the influence of parameters such as internal pressure, defect position, defect depth on the mechanical behavior, and failure of pipelines were analyzed. A failure criterion for HDPE pipes with defects under surface load was proposed based on the limit-state curves obtained under different working conditions. Furthermore, an accurate and efficient fitness-for-service assessment procedure of pipes with defects under surface load was proposed. The results showed that maximum Mises stress of the pipeline gradually increased with increasing surface load and the position of maximum stress changed from the top and bottom of the pipe to the defect position and both sides of the pipe. Finally, when Mises stress of the HDPE pipe exceeds the yield limit, failure will occur. Internal pressure, defect location, and defect depth were found to influence the failure process and critical surface load of the pipeline. Safety evaluation curves of the gas pipeline with defects under surface load were obtained by calculating the critical failure load of the pipeline under various working conditions. Finally, a nonlinear fitting method was used to derive a formula for calculating the critical surface load under different defect parameters. The proposed method provides a useful reference for urban gas pipeline safety management.

The sulfur concrete samples were prepared by the optimized process, which were mixed with cement, fly ash and slag, respectively. The influence of the type and content of filler on the compressive strength of sulfur concrete was studied. The phase and micromorphology of filler and sulfur mixture were characterized by X-ray diffraction and scanning electron microscope, and the bonding mode was studied. The results show: the cement filler has the best effect on the compressive performance of sulfur concrete,and the compressive strength is 87.2 MPa by adding cement filler with the same quality as sulfur; there is no chemical reaction between filler and sulfur, and the filler is physically bonded to sulfur matrix.

Ceramic stereolithography (CSL) is an additive manufacturing method for creating ceramic three-dimensional (3D) objects via the layer-by-layer photopolymerization of a ceramic suspension. A key challenge in CSL is that support structures are required for building overhanging structures to prevent part damage or deformation caused by gravity or process-induced shears. Removing the support structures can result in issues such as poor surface quality, high risk of cracking, etc. To overcome this challenge, this article presents a new CSL-based ceramic fabrication method that uses an elasto-viscoplastic ceramic suspension as the feedstock material. The suspension's inherently strong interparticle resistive force can support overhangs without the need for building additional support structures; a temperature-controlled layer-coating module is designed to dynamically form a localized suspension bridge above the free surface of previously deposited materials, which allows for the application of fresh thin layers with a controlled shear force. The article presents material design and characterizations and discusses key process parameters and their effects on the geometry retention of fabricated overhangs. This new process provides the potential for fabricating ceramic 3D objects with complex overhangs, such as vascular networks, biomimetic heat exchangers, and microreactors.

In this work, novel Cu-Co bimetal/reduce graphene oxide nanostructures with excellent catalytic activity were prepared by embedding Cu-Co bimetallic nanospheres into the interlayer of graphene. The composite materials were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) etc. The characterisation results indicated that the diameters of the bimetallic nanospheres were controlled within ~60 nm, which embedded uniformly in graphene. A series of electrochemical tests were carried out and the composites were found to exhibit excellent oxygen evolution properties under alkaline conditions. The excellent catalytic activity and stability make the composite have great potential for wide application and provide a basis for its industrial application.

State-of-the-art metal alloy additive manufacturing (AM) techniques construct a three-dimensional structure through sintering or melting dry metal powders in a layer-by-layer fashion, which typically results in several AM-specific issues in the final structure, such as staircase effect, residual stress and highly-orientated microstructures. In this paper, we present a new extrusion-based metal AM process, named Immiscible-interface assisted Direct Metal Drawing (II-DMD), which fabricates metal alloy structures, in particular lattice structures, in a layerless manner. In the II-DMD process, metal lattice structures are fabricated by continuously extruding a metal colloidal suspension within a second immiscible matrix colloidal suspension. The shape of the metal colloidal suspension is stabilized due to the presence of an immiscible interface between the two colloidal suspension systems. Dense metal lattice structures can be achieved via post-consolidation of the self-stabilized metal-matrix systems, including liquid-phase drying and metal-phase sintering. The II-DMD process is presented and the immiscible-interface-assisted self-stabilization mechanism is studied. The post-consolidation processes are discussed. Several test cases were fabricated and characterized.

Effect of charge compensation codoping on electronic structure, magnetic and optical absorption of SrNbxTi1-2xFexO3 ((Nb, Fe)-STO) and SrNbxTi1-2xCrxO3 ((Nb, Cr)-STO) within doping concentration x ...

NIST is using atomically precise fabrication to develop electronic devices for use in quantum information processing and novel quantum materials. We are using hydrogen-based scanning probe lithography to enable deterministic placement of individual dopant atoms with atomically aligned contacts and gates to fabricate single atom transistors, devices for single electron spin manipulation, and arrayed devices for analog quantum simulation research. Atomic precision devices, where individual atoms or electrons fundamentally affect device performance, bring about a variety of new manufacturing and metrology challenges. Single atom defects and charge instability deeply change device performance, affecting reliable manipulation and sensing of individual electrons. Conventional metrology methods such as transmission electron and scanning electron microscopy often prove inadequate at this length scale and new, challenging electrical test methods are needed.

Hydrothermal-assisted transient jet fusion (HTJF) is a powder-based additive manufacturing (AM) method of ceramics, which utilizes a water-mediated hydrothermal mechanism to fuse particles together, eliminating the use of organic binders in forming green bodies and thereby contributing to high green-density parts (>90%) advantageous for fabricating functional materials with high performance. In the HTJF process, a transient solution such as water is selectively deposited into a powder bed in a layer-by-layer fashion followed by a hydrothermal fusion process. Upon the ejection and deposition of a droplet of the transient solution on the surface of the powder bed, the diffusion behavior of the liquid significantly influences the particle fusion and the fabrication accuracy of the HTJF process. Precise control of the liquid diffusion in the powder bed is critical for the fabrication of ceramic structures with both high density and accuracy. In this paper, the dependence of transient solution diffusion on different process parameters (i.e., powder packing density, droplet size, pressure, etc.) in the HTJF process were studied. Both numerical modeling and experimental methods were used to quantify the relationships between processing parameters and diffusion profiles of transient solution droplets (e.g., diffusion width/depth). Optimum processing conditions were identified to mitigate the undesired diffusion of transient solution droplets in the powder bed.

This work presents a general method for producing edge-modified graphene using electrophilic aromatic substitution. Five types of edge-modified graphene were created from graphene/graphite nanoplatelets sourced commercially and produced by ultrasonic exfoliation of graphite in N-methyl-2-pyrrolidone. In contrast to published methods based on Friedel–Crafts acylation, this method does not introduce a carbonyl group that may retard electron transfer between the graphene sheet and its pendant groups. Graphene sulphonate (G–SO3−) was prepared by chlorosulphonation and then reduced to form graphene thiol (G–SH). The modifications tuned the graphene nanoparticles’ solubility: G–SO3− was readily dispersible in water, and G–SH was dispersible in toluene. The synthetic utility of the directly attached reactive moieties was demonstrated by creating a “glycographene” through radical addition of allyl mannoside to G–SH. Chemical modifications were confirmed by FT-IR and XPS. Based on XPS analysis of edge-modified GNPs, G–SO3− and G–SH had a S:C atomic ratio of 0.3:100. XPS showed that a significant amount of carbon sp2 character remained after functionalisation, indicating little modification to the conductive basal plane. The edge specificity of the modifications was visualised on edge-modified samples of graphene produced by chemical vapour deposition (CVD): scanning electron microscopy of gold nanoparticles attached to G–SH samples, epifluorescence microscopy of a glycographene bioconjugate with a fluorescently tagged lectin, and quenched stochastic optical reconstruction microscopy (qSTORM) of thiol-reactive fluorophores on CVD G–SH samples. Microelectrochemistry of unmodified CVD graphene and dye-modified CVD G–SH showed no statistically significant difference in interfacial electron transfer rate (k0). This platform synthesis technology can allow pristine graphene, rather than graphene oxide or its derivatives, to be used in applications that require the superior mechanical or electronic properties of pristine graphene, including theranostics and tissue engineering. Graphical Abstract

Bone defects caused by osteoporosis, bone malignant tumors, and trauma are very common, but there are many limiting factors in the clinical treatment of them. Bone tissue engineering is the most promising treatment and is considered to be the main strategy for bone defect repair. We prepared polydopamine-coated poly-(lactic-co-glycolic acid)/&beta, tricalcium phosphate composite scaffolds via 3D printing, and a series of characterization and biocompatibility tests were carried out. The results show that the mechanical properties and pore-related parameters of the composite scaffolds are not affected by the coatings, and the hydrophilicities of the surface are obviously improved. Scanning electron microscopy and micro-computed tomography display the nanoscale microporous structure of the bio-materials. Biological tests demonstrate that this modified surface can promote cell adhesion and proliferation and improve osteogenesis through the increase of polydopamine (PDA) concentrations. Mouse cranial defect experiments are conducted to further verify the conclusion that scaffolds with a higher content of PDA coatings have a better effect on the formation of new bones. In the study, the objective of repairing critical-sized defects is achieved by simply adding PDA as coatings to obtain positive results, which can suggest that this modification method with PDA has great potential.

Mono-layer silica-based antireflective laser coating with modulated structure has been designed and fabricated, in which cross-linking network structure of polysiloxane was prepared as backbone and porous silica spheres (PSSs) were inserted to create interior porosity. Cured polysiloxane provided dense structure that could both prevent the invasion of volatile organic compounds (VOCs) and improve the mechanical property of this coating, while PSSs endowed this coating with proper porosity to adjust its refractive index and relax the high-power laser energy. With certain structure modulation, excellent transmission and laser-damage resistance of this coating at 355 nm (for the application in high-power laser system) and 1064 nm (for the application in laser-guided component) was both achieved. Meanwhile, the hardness of this coating increased significantly compared with that of the conventional porous silica coating. In addition, qualified VOCs endurance of this coating was also proved, which effectively extended the lifetime of such coating.

The macroscopic piezoelectric properties of piezoelectric materials can be regulated via localized control of microstructures to introduce site-specific electric displacement vectors, but much of the current research is centered around design and manipulation of meso-scale architectural units that are inherently limited in achieving high functionality. In this study, we propose a stereolithography-based additive manufacturing (AM) strategy to spatially tune the properties of piezoelectric ceramics at a grain-microstructural scale through selectively incorporating dopants into the ceramic materials for tailoring the grain development. The effects of different doping parameters (including ceramic solid loading, dopant type, and dopant concentration) on the microstructures and properties of printed piezoelectric ceramics are investigated. The thermodynamics and kinetics of different doping additives in the dopant-ceramic interaction are experimentally and numerically studied to enable location-specific inhibition of microstructures. Our results indicate that a doping concentration of 2 wt% promoted the homogeneity of local grain growth, resulted in a higher compressive strength and lower porosity, and improved dielectric permittivity and piezoelectric voltage constant in printed piezoelectric ceramics. Moreover, our results suggest that thermochemically stable particles (e.g., ZrO2) with a high melting point and a low vapor pressure exhibited micro-scale diffusion behaviors, in contrast to millimeter-scale diffusion behaviors of common doping additives (e.g., ZnO), which are more suitable as a locally incorporated dopant for achieving location-specific property tuning. Test cases of selectively doped piezoelectric components in predefined patterns highlight the potential of the proposed approach in creating novel piezoelectric materials with programmable location-specific properties.

We introduce a phase-field method for continuous modeling of cracks with frictional contacts. Compared with standard discrete methods for frictional contacts, the phase-field method has two attractive features: (1) it can represent arbitrary crack geometry without an explicit function or basis enrichment, and (2) it does not require an algorithm for imposing contact constraints. The first feature, which is common in phase-field models of fracture, is attained by regularizing a sharp interface geometry using a surface density functional. The second feature, which is a unique advantage for contact problems, is achieved by a new approach that calculates the stress tensor in the regularized interface region depending on the contact condition of the interface. Particularly, under a slip condition, this approach updates stress components in the slip direction using a standard contact constitutive law, while making other stress components compatible with stress in the bulk region to ensure non-penetrating deformation in other directions. We verify the proposed phase-field method using stationary interface problems simulated by discrete methods in the literature. Subsequently, by allowing the phase field to evolve according to brittle fracture theory, we demonstrate the proposed method's capability for modeling crack growth with frictional contact.

Robust, ion-stabilized membranes from polybenzimidazole (PBI) and its blends with polymer of intrinsic microporosity (PIM-1) were fabricated for organic solvent nanofiltration in polar aprotic solvents (PAS). Flat sheet membranes comprising of polybenzimidazole and 4–12 wt% PIM-1 were fabricated via conventional phase inversion followed by the reduction of nitrile PIM-1 to amine PIM-1. Stabilization of the membranes were achieved via ion formation (chloride salt) under acidic condition. Such simple ion-stabilization methodology could replace cumbersome crosslinking. The aging of the membranes and the their performance at room and elevated temperatures, in a wide range of pH, in the presence of organic bases, in 6 conventional and 2 green PAS, were investigated. The PIM-1 content enabled fine-tuning of the molecular weight cut-off (MWCO) of the membranes between 190 and 650 g mol-1.

This study reports a systematic investigation of fine-tuning the filtration performance of nanofiltration membranes with biophenol coatings to produce solvent-resistant membranes with 390–1550 g mol–1 molecular weight cutoff (MWCO) and 0.5–40 L m–2 h–1 bar–1 permeance. Six kinds of inexpensive, commercial biophenols (dopamine, tannic acid, vanillyl alcohol, eugenol, morin, and quercetin) were subjected to identical oxidant-promoted polymerization to coat six kinds of loose asymmetric membrane supports: polyimide (PI), polyacrylonitrile (PAN), polysulfone (PSf), polyvinylidene difluoride (PVDF), polybenzimidazole (PBI), and polydimethylsiloxane (PDMS). The coatings were characterized by Fourier-transform infrared spectroscopy (FTIR), and the morphologies were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The long-term stability of 42 membranes were tested in 12 organic solvents, including emerging green solvents MeTHF and Cyrene. The biophenol coatings led to tighter membranes with a decrease in MWCO of 12–79% at a penalty of a 22–92% permeance decrease in acetone.

Cracking of rocks and rock-like materials exhibits a rich variety of patterns where tensile (mode I) and shear (mode II) fractures are often interwoven. These mixed-mode fractures are usually cohesive (quasi-brittle) and frictional. Although phase-field modeling is increasingly used for rock fracture simulation, no phase-field formulation is available for cohesive and frictional mixed-mode fracture. To address this shortfall, here we develop a double-phase-field formulation that employs two different phase fields to describe cohesive tensile fracture and frictional shear fracture individually. The formulation rigorously combines the two phase fields through three approaches: (i) crack-direction-based decomposition of the strain energy into the tensile, shear, and pure compression parts, (ii) contact-dependent calculation of the potential energy, and (iii) energy-based determination of the dominant fracturing mode in each contact condition. We validate the proposed model, both qualitatively and quantitatively, with experimental data on mixed-mode fracture in rocks. The validation results demonstrate that the double-phase-field model – a combination of two quasi-brittle phase-field models – allows one to directly use material strengths measured from experiments, unlike brittle phase-field models for mixed-mode fracture in rocks. Another standout feature of the double-phase-field model is that it can simulate, and naturally distinguish between, tensile and shear fractures without complex algorithms.

In this paper, one single leg T-type converter with full silicon carbide (SiC) half-bridge power modules and hybrid power modules combined silicon carbide (SiC) with silicon (Si) power module, are designed and investigated. Firstly, the switching characteristics of Cree SiC device CAS300M12BM2 and Semikron SiC device SKM350MB120SCH17 single-leg T-Type converters are compared with double pulse testing (DPT). Then, to further investigate the performance, the hybrid power modules of the single leg T-type converter with Cree SiC device CAS300M12BM2 and Semikron Si device SKM300GM12T4 are built, which can increases the power density, compared to the full SiC devices T-type converter. To suppress the ringing of the middle leg switching device, the resistor-capacitor (RC) snubber are designed and demonstrated with DPT. Finally, the function testing of the hybrid single leg T-type converter are experimentally verified. Nanyang Technological University National Research Foundation (NRF) Accepted version This research work was conducted in the Rolls-Royce@NTU Corporate Lab with funding support from the National Research Foundation (NRF), Rolls-Royce and Nanyang Technological University; under the Corp Lab@University Scheme.

This paper sets out in vitro protocols for studying the relative effectiveness of chelators used in the dissolution-based treatment of hard calcinosis. Pulverized hard calcinosis samples from human donors or synthetic hydroxyapatite nanoparticles were deposited by electrophoretic deposition on the surface of a quartz crystal microbalance sensor. Over 150 deposits of

One kind of quaternary thin films of SiAlON were deposited by ion beam sputtering method at ambient temperature, through a sintered SiAlON ceramic target. Ultraviolet, visible and near infrared (UV–VIS–NIR) Spectrophotometer, Fourier transformed infrared spectroscopy (FTIR), glancing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the optical, crystalline and chemical composition properties. The optical properties of the deposited amorphous films could be tailored by changing the relative content of O or N in the films, through introducing different working gas and gas flux adjusting (oxygen, nitrogen or their mixtures). By this way, the refractive index at 850 nm can be tailored from 1.53 to 1.83, and the chemical composition data from XPS analysis supplied strong evidences. Reasonably, the SiAlON films were thought to be one kind of candidate films either as a buffer layer benefit from their high temperature stability, or a mid infrared antireflective layer for silicon and other infrared window materials.

Orthorhombic (α) SSPbF2 microcrystal was synthesized by a normal hydrothermal method. The influence of F/Pb ratio and hydrothermal reaction time on the crystal phase of the acquired PbF2 samples were discussed, and a β to α phase transition was found according to the XRD results. The undoped α-PbF2 powder showed a broad but weak emission band around 450–570 nm, which was due to (Pb2)3+ nearest neighbor pair centers. Dy3+ ion doped α-PbF2 samples showed main emission bands at 480 nm and 574 nm, which were assigned to the transitions from 4F9/2 to 6H15/2 and 6H13/2 of Dy3+, respectively. Furthermore, the morphology and crystalline properties of the undoped and Dy3+ doped α-PbF2 microcrystal powder were also discussed carefully. The decay time results combined with the X-ray excitation results suggested that Dy3+ ion doped α-PbF2 is a useful scintillating material for high energy physics applications, such as X-ray scintillating panel, etc.

Previous work about the oblique fin channels shows an abnormal variation on the static pressure drop. Thus numerical work was performed to investigate the influence of the lengthwise distance and the parallelogrammic fin section shape separately using two groups of fin mesh. The results showed that the influence of the parallelogrammic fin section shape was similar to the three-dimensional oblique fin channels. Besides, when air flow is askew to the fin, there is a vortex near the leeward side. The pressure had a rapid change in the entrance and vortex region and then decreased linearly along the flow length. The static pressure drop in the vortex region is determined by both the fin slope angle and the inlet angle. Thus the variation law of oblique fin channels is different from the straight fin channels.Copyright © 2016 by ASME

Single spinel phase nanocrystalline ferrite (Ni0.5Zn0.5)1-XCoxFe2O4was prepared using the spraying co-precipitation method. The coercivity of prepared (Ni0.5Zn0.5)1-XCoxFe2O4 increases with an increasing content of cobalt. The enhancement of the saturation magnetization was observed up to the maximum value of 102.1emu/g as x was 0.5. This can be attributed to the substitution of the Ni2+ and Zn2+ ions with Co2+ ions. This changed the net magnetic moment between the sublattices of structure.

Nanocrystalline CoFe2O4 ferrite have been synthesized by a spraying-coprecipitation method. X-ray diffraction (XRD) and Transmission electron microscope (TEM) confirmed the formation of single-phase CoFe2O4 ferrite nanoparticles in the range 10 nm ~ 100 nm depending on the calcining temperature. The magnetic measurements show that specific saturation magnetization of nanocrystalline CoFe2O4 ferrite increases from 36.1 A•m2•kg-1 to 88.6 A•m2•kg-1 as grain size increases from 12 nm to 98 nm. The coercivity shows a peak with grain size, peaking at around 43 nm. The magnetic behaviour of nanocrystalline CoFe2O4 ferrite might be attributed to the effects of surface and random anisotropy.

Fly ash particles reinforced aluminum matrix composites were fabricated by powder metallurgy method. The influence of different fly ash content on hardness, the friction and wear behavior of the composites were investigated at a constant sliding velocity of 400r/min. The worn surfaces of composites were observed by scanning electron microscope, and worn mechanism of composites was discussed. The results showed that the hardness of composites increased first and then decreased with fly ash content increasing. Under the lower loads and at the lower fly ash content, the friction co-efficient is steadily lower than that of Al alloy matrix. The wear resistance of composites increased with the volume fraction of fly ash particles and the wear mechanism was characterized as abrasive wear and adhesive wear.On the other hand, the wear mechanisms in the composites have been transformed with increasing load and fly ash volume; it mainly was delamination wear and abrasive wear.

A new quaternary Gd 4 Ni 2 Sb 1.07(1) Si 1.93(1) phase was synthesized by arc-melting and its structure was determined through single crystal X-ray diffraction techniques. It crystallizes in an orthorhombic unit cell (the Pnma space group) with a = 11.1735(9), b = 4.2054(2) and c = 16.711(1) A and represents a new structure type. The isostructural Gd 4 Ni 2 BiSi 2 phase was obtained and characterized using the powder X-ray diffraction techniques: Pnma space group, a = 11.2715(2), b = 4.2046(1) and c = 16.7421(3) A. By the means of electron microprobe analysis, Sb/Si and Bi/Si solid solutions were proven to exist for corresponding phases, and their general formulas can be given as Gd 4 Ni 2 Sb 1± x Si 2± x and Gd 4 Ni 2 Bi 1± x Si 2± x . Gd 4 Ni 2 Sb 1.07 Si 1.93 and Gd 4 Ni 2 BiSi 2 order ferromagnetically at 93 K and 46 K, respectively.

Nickel was successfully introduced into the Gd 5 Sb 3 and Gd 5 Bi 3 binaries to yield the Gd 5 Ni 0.96(1) Sb 2.04(1) and Gd 5 Ni 0.71(1) Bi 2.29(1) phases. Both Ni-substituted compounds adopt the orthorhombic Yb 5 Sb 3 -type structure. While the Gd 5 Ni 0.71 Bi 2.29 phase is thermodynamically stable at 800 °C and decomposes at lower temperatures upon annealing, it can be easily quenched to room temperature by rapid cooling from 800 °C. The Gd 5 Ni 0.96 Sb 2.04 phase is found to be thermodynamically stable till room temperature. Through annealing at different temperatures, Gd 5 Bi 3 was proven to undergo the Mn 5 Si 3 -type (LT)↔Yb 5 Sb 3 -type (HT) transformation reversibly, whereas Gd 5 Sb 3 was found to adopt only the hexagonal Mn 5 Si 3 -type structure. Orthorhombic Gd 5 Ni 0.96 Sb 2.04 and Gd 5 Ni 0.71 Bi 2.29 and low-temperature hexagonal Gd 5 Bi 3 order ferromagnetically at 115, 162 and 112 K, respectively. In Gd 5 Bi 3 , the ferromagnetic ordering is followed by spin reorientation below 64 K. Magnetocaloric effect in terms of Δ S was evaluated from the magnetization data and found to reach the maximum values of −7.7 J/kgK for Gd 5 Ni 0.96 Sb 2.04 and −5.6 J/kgK for Gd 5 Ni 0.71 Bi 2.29 around their Curie temperatures.

SiAlON films with antireflective and protective functionality for zinc sulfide were prepared by an ion beam sputtering method. A great transmittance improvement (at 3.8 μm) of 25.1% has been realized for zinc sulfide substrate. At the same time, the in situ high temperature transmittance was also recorded and it was proven that the SiAlON films on zinc sulfide window materials can keep thermal stability well at temperature as high as 250 °C in the region of 3–5 μm. The micro hardness of the zinc sulfide was improved by 75% in average after being coated with SiAlON films, and the SiAlON films possess good behaviors in harsh environmental tests including adhesion, abrasion, moisture, and thermal shock circle.

A nonamer metamaterial composed of nine split ring resonators with different orientations was experimentally and numerically researched in terahertz band. The nine split rings were arranged spirally. From the first split ring, the subsequent split rings were rotated anti-clockwise by 40. Generally, the split ring resonator was polarization-dependent. It was found that split rings oligomer, which can produce multiple resonance modes, was polarization-independent owing to the near-field energy coupling. The split rings oligomer composed of polarization-dependent resonators exhibited a polarization-independent effect, which enriched the design idea of traditionally uncoupled metamaterial composed of disperse resonators, and induced a new path for terahertz functional devices, like optical switch, modulator, filter and so on.

A metamaterial device was designed and fabricated for microfluidic sensing in the terahertz regime, its transmission, resonance and sensing properties were numerically simulated in terms of the Finite Difference Time Domain(FDTD). The influence of polarization direction on the sensitivity of sensor was experimentally investigated by terahertz time-domain spectroscopy system. The experimental result shows that when the resonant metamaterial ring opening direction is parallel and perpendicular with the direction of polarization of the incident THz wave, the refractive index sensing sensitivity can reach 39.29 GHz/RIU and 74.43 GHz/RIU, respectively. The transmission and resonance characteristics of the metamaterials are analyzed by the equivalent circuit model to further clarify the sensing mechanism. This THz metamaterial device has the potential applications in sensing chemical and biological component because it is capable of realizing the refractive index sensing of microliquid (5 l/mm2) with a high sensitivity.

Dy5Ni0.66Bi2.34 and Lu5Ni0.56Sb2.44 were synthesized by arc-melting and were found to adopt an orthorhombic Yb5Sb3-type structure. Cell parameters are a = 12.075(2), b = 9.165(2), c = 8.072(1) A for Dy5Ni0.66Bi2.34 and a = 11.6187(9), b = 8.933(1) and c = 7.8377(6) A for Lu5Ni0.56Sb2.44. Dy5Ni0.66Bi2.34 undergoes a step-like ferromagnetic transition around 66 K. Magnetocaloric effect in terms of the magnetic entropy change, ΔS, reaches −3.73 J/kg K at 75 K for Dy5Ni0.66Bi2.34.

Applied to voltage, a dielectric elastomer membrane may deform into a mixture of two states under certain conditions. One of which is the flat state and the other is the wrinkled state. In the flat state, the membrane is relatively thick with a small area, while on the contrary, in the wrinkled state, the membrane is relatively thin with a large area. The coexistence of these two states may cause the electromechanical phase transition of dielectric elastomer. The phase diagram of idea dielectric elastomer membrane under unidirectional stress and voltage inspired us to think about the liquid-to-vapor phase transition of pure substance. The practical working cycle of a steam engine includes the thermodynamical process of liquid-to-vapor phase transition, the fact is that the steam engine will do the maximum work if undergoing the phase transition process. In this paper, in order to consider the influence of coexistent state of dielectric elastomer, we investigate the homogeneous deformation of the dielectric elastomer tube. The theoretical model is built and the relationship between external loads and stretch are got, we can see that the elastomer tube experiences the coexistent state before reaching the stretching limit from the diagram. We think these results can guide the design and manufacture of energy harvesting equipments.

Smart materials and structures is an international frontier field in current development of engineering and science. Representative of soft smart materials include Electroactive polymers (EAPs) and Shape Memory Polymers (SMPs), etc..As a new kind of smart deformation material, SMPs have a wide range of applications in the field of smart material and structures due to their controllable shape memory effects. Deformation mechanism of SMP material is the basis of its applications. This paper proposed an useful thermoviscoelastic constitutive model by considering thermal expansion, structure relaxation and viscoelastic properties of Epoxy-SMP material. To verify the applicability of the model, various experiments such as isothermal uniaxial tensile tests were carried out and then be simulated. The results showed that the constitutive model could nicely predict mechanical behavior of Epoxy-SMP, the proposed constitutive model is useful for the design of SMPs structures.

Polarization is one of the basic properties of electromagnetic wave conveying valuable information about signal transmission and sensitive measurements. Manipulations of polarization state and amplitude have aroused a lot of research interest in many different fields, especially in the terahertz (THz) regime. Although many researches on THz polarization controller have been carried out, their transmission losses are still difficult to lower in a broad bandwidth. And there are few reports on THz polarization controller which can rotate the polarization state and split beams at the same time. Multifunctional THz devices are required to meet the needs of the progress of THz technology and its applications. In order to overcome this constraint, semiconductor silicon is integrated into the proposed structure to manipulate the polarization state and the amplitude, because of its optical properties with the external pump light. Here, according to the electromagnetic resonance between split rings and silicon rings in Fabry-Prot-like cavity, we propose a metasurfaces-based terahertz polarization controller. The unite cell structure is composed of metal grids-split ring/Si ring-metal grids spaced by silica layers. By using the finite element method in CST Microwave Studio, we simulate the transport and polarization properties under different conditions. The results show that a linear polarization state can be nearly perfectly converted into its orthogonal one from 0.39 to 1.11 THz with a transmission loss of 1 dB, which fits well to the one of multiple-beam interference theory. Then we study the properties of the proposed metasurface structure for oblique incidence. The property of rotating polarization basically keeps stable even at an incident angle of 60 from 0.52 to 1.05 THz. At the end of the paper, the polarization splitting feature of the device is discussed in the THz regime. The results demonstrate that the transmitted and reflected beam power of the device can be tuned by changing the pump light power. The modulation depths of two beams reach more than 90% at 0.5 THz. It is worth noting that the proposed structure can not only rotate the polarization state of transmitted light in a broad bandwidth of 0.72 THz, but also modulate the transmitted and reflected beam power with a wide modulation depth. It can be used as a broad-band, low-loss and tunable terahertz polarization controller which is also insensitive to the incident angle. So it meets the requirements in THz communication, spectrum detection and imaging systems.

With the continuous development of terahertz (THz) technology in recent years, many kinds of THz functional devices including switchers, filters, modulators, isolator and polarizers have been demonstrated. However, researches of the focusing devices in the terahertz frequency range are rarely reported. In this paper, we propose a subwavelength metal-air-InSb-metal periodic array structure to perform terahertz wave focusing. The dependence of permittivity of InSb in the THz regime on external magnetic field and temperature is calculated theoretically. Based on the magneto-optical effect of the semiconductor material InSb and asymmetrical waveguide structure, the influences of external magnetic field and temperature on the focusing and transmittance characteristics of the device are studied in detail. Numerically simulated results show that the structure proposed above can not only improve the transmittance greatly but also perform focusing perfectly. Calculations on the transmission properties show that in a certain range of temperature, the power flow transmittance at the focus point increases with the increase of temperature. In the meantime, for a certain temperature, with increasing the external magnetic field, the power flow continuously increases as well and reaches a maximum value at a certain magnetic field. For example, for a temperature of 172 K and a magnetic field of 0.6 T, the maximum power flow transmitted at the focus point is 10200 W/m2 at 0.8 THz, which is about 28 times larger than that without magnetic field at the same temperature. In addition, the simulation results also show that when the temperature and external magnetic field are fixed at 172 K and 0.5 T, respectively, the power flow transmittances for the incident waves at different frequencies are different. There is a peak value of the transmittance appearing at a specific frequency of 0.8 THz. Moreover, when the incident wave frequency is far from 0.8 THz, the transmittance decreases dramatically. It is worth noting that by choosing different temperatures and external magnetic fields, the structure proposed can not only enhance the transmittance over 20 times at the focus point, but also manipulate effectively the THz wave in a broad operating bandwidth of 400 GHz from 0.4 THz to 0.8 THz. These properties indicate that the proposed structure can act as an ideal tunable, broadband, and high transmittance focusing device in the terahertz regime.

The components and yield of the oil obtained by co-pyrolysis of a mixture of tobacco stem and waste rubber tire powder were investigated. The results shows that 450°C is an optimal temperature in terms of liquid product yield when the reactants are mixtures of tobacco stem and waste rubber tire powder with a mass ratio of 1∶1. It is found that the liquid product from co-pyrolysis contains less water and oxygen element, and meanwhile, hydrocarbon content increases to some degree compared with that from pyrolysis of solo pyrolysis of tobacco stem, which means the oil from co-pyrolysis is improved. However, how to improve the liquid product quality further and how to control the hazardous element emissions via co-pyrolysis needs still further studies.

Utilizing insulator-metal phase transition of vanadium dioxide thin film, we propose a thermally controlled terahertz modulator based on metamaterial, and research the transmission characteristics and temperature tunable characteristics of phase transition in metamaterials in THz wave band. While the incident THz wave is of horizontal polarization or vertical polarization, two independent pass bands are generated near 1 THz. The center frequencies of the two pass bands are 1.3 THz and 1.7 THz, the bandwidths of them are 0.2 THz and 0.35 THz. In addition, when temperature rises from 40℃ to 80℃, the transmissions of the two pass bands drop apparently, especially at phase transition temperature of 68℃. For the two polarization states, the modulation depths achieve 60% or more, which is the great function of a modulator.

A low-loss and broadband terahertz twin-core photonic band-gap fiber directional coupler is proposed, which consists of a cladding with a triangular lattice array of sub-wavelength air rods and two cores formed respectively by omitting seven nearby air rods. The group velocity dispersion, the coupling and the loss of the fibers are investigated by using a full-vector finite element method. The numerical simulations show that the loss coefficient of the coupler is less than 0.021 cm-1, and the coupling broadband of 0.14 THz can be realized. The directional coupler has potential applications in terahertz communication systems, such as filtering, wavelength-division multiplexing, polarization isolation, switching and so on.

A multifunctional terahertz polarization controller is designed based on the two-dimensional photonic crystal structure and the ferrite material. The different working devices including a controllable polarizer, a polarization beam splitter and a tunable phase retarder with continuous phase retardations of - at 1 THz are controlled by the shift of photonic band gap with different external magnetic fields. By using the plane wave expansion method and the rigorous coupled wave analysis, we calculate the band gap positions and transmittances of device with the variation of magnetic field. The field distribution and phase are simulated by the finite difference time domain method.

An A1-doped ZnO/p-Si heterojunction is fabricated by a laser molecular beam epitaxy technique. The abnormally high ideality factors (n ≫ 2) of the prepared heterojunction are observed in the interim bias voltage range. A theoretical model is proposed to understand the much higher ideality factor of the special heterojunction diode. The ZnO:A1 film shows metal-like conductivity with the electrical resistivity about 6.56 × 10−4 Ω·cm at room temperature. The temperature dependence of the photovoltage indicates that the photovoltaic effect of the A1-doped ZnO based heterojunction can be changed by the intrinsic metal-semiconductor transition at 120 K.

The phase-field crystal (PFC) model is used to simulate crystal growth from undercooled liquid by the finite difference method. The effects of phase region and undercooling on crystal growth process are analyzed. The simulation results show that crystal growth is inhibited in the region of liquid-crystal coexistence where liquid-crystal boundary becomes thicker gradually. In the single crystal phase region, crystallization is enhanced with undercooling increasing,while liquid-crystal boundary becomes thinner. It is found that there is a linear relationship between crystal growth velocity and undercooling.

The resistivity-temperature curve of 7050 aluminium alloy prepared by different casting methods (DC and LFEC) has been measured with D.C. four-probe method. By analysing the curve, it was found that a change occurred to the slope at 250℃ when the samples were heated, and the resistivity of LFEC sample changed with temperature more quickly than that of DC. Both the solidus and liquidus temperatures of LFEC samples were higher than those of DC samples during the process of temperature rise from room temperature to 900℃. However, the resistivity of DC samples increased remarkably when the temperature was kept at 900℃ and before it was decreased to 600℃. With the help of microstructure observation, the characteristics and phenomenon of the resistivity evolution with temperature were studied.