Wood's Metal Research Articles

Non-Linear Dynamic Analysis of Timber Frame Structure with Bolted-Fastener Connections

Understanding the dynamics of timber structures is essential for the timber structural engineering field, where it is necessary to build predictive numerical models and digital twins. Three similar-sized representative post-beam bracing frames with wood–metal assemblies were tested. Experimental modal analysis gave some indication of the non-linear behaviour of the structure. Then, the frame was submitted to a logarithmic sine sweep, which highlighted some specificities of the non-linear modes: dependence on the sweep direction and amplitude, jump, etc. These phenomena can be explained by friction and shocks in the assemblies. An accurate model of these non-linearities could lead to resilient and more earthquake-resistant timber structures, as the equivalent damping of a non-linear structure is way lower than for a linear one.

Synthesis of Ag@SiO2 core-shell nanoparticles for antibacterial application in water-based acrylic polymer coatings

In this study, Ag@SiO2 core-shell nanoparticles were synthesized using the Stöber method and then physically mixing with MPS functionalized poly (styrene-co-acrylate) (PSA) emulsion to obtain a novel antibacterial composite material (PSA/Ag@SiO2). The dispersion of composite latexes was improved by the formation of Si-O-Si covalent bonds, and the migration of AgNPs on the surface of composite films enhanced their antimicrobial activity. Analysis of UV-Vis absorption spectra, TEM images, XPS and XRD data confirmed the core-shell structure of Ag@SiO2 and the successful coating of AgNPs by SiO2. TEM micrographs showed that Ag@SiO2 core-shell nanoparticles were uniformly dispersed in the composite latexes, with an average particle size of 198 nm for PSA/Ag@SiO2 composite latexes, larger than that of PSA latexes (162 nm). FTIR spectra also indicated the presence of Si-O-Si covalent bonds resulting from the sol-gel reaction between MPS functionalized PSA with Ag@SiO2. XPS and WCA characterization revealed the disruption of the core-shell structure of Ag@SiO2, leading to the migration of AgNPs to the air-film interface. The results of antibacterial activity demonstrated that PSA/Ag@SiO2 composite films displayed antibacterial activity against both E. coli and S. aureus, and the former displayer a slightly better antibacterial activity than the latter. The water-based acrylic polymer coatings with antibacterial properties explored in current work have various applications in wood paints, varnishes, metal protection, decorative systems and other related fields.

Characterizing microstructural evolutions in low-mature lacustrine shale: A comparative experimental study of conventional heat, microwave, and water-saturated microwave stimulations

Most of the shale oil reservoirs in China are of medium to low maturity. The effective exploitation of hydrocarbon resources in such formations is technically challenging. This study explores the impact of various thermal stimulation methods on low-maturity shale oil reservoirs, focusing on conventional heating, microwave heating, and water-saturated microwave heating methods. A suite of techniques, including small angle neutron scattering (SANS), mercury injection capillary pressure (MICP), and field emission-scanning electron microscopy (FE-SEM) after wood's metal injection were used to investigate the evolution of microstructures under different thermal stimulation. This integrated approach allows for a comprehensive characterization of reservoir connectivity and permeability across multiple scales, from visually observable centimetre and millimetre scales down to the nanoscale. The response of shale to thermal stimulation is significantly influenced by its mineral composition, with shales rich in absorbent minerals like pyrite undergoing selective heating when exposed to microwaves, leading to new pores and fracture formations. The use of CM-SANS has revealed substantial untapped hydrocarbon potential within the reservoir, emphasizing the importance of thermal stimulation in enhancing production. Furthermore, integrating microwave irradiation with hydraulic fracturing effectively increases the number of pores, micro-fractures, and natural fracture openings, mitigates the hydration effects of hydraulic fracturing, and increases permeability by three orders of magnitude. The results indicated that microwave combined with hydraulic fracturing positively impacts the production from low-maturity reservoirs and provides the theoretical basis for in-situ thermal recovery of shale oil.

The importance of pore-fracture connectivity in overmature marine shale for methane occurrence and transportation

Pore-fracture connectivity is a critical factor in gas occurrence and transportation in shale plays. To investigate the limiting factors of multiscale pore-fracture connectivity, which might control methane occurrence and transportation in shale reservoirs, small-angle neutron scattering (SANS) under vacuum and high-pressure conditions incorporated with repeated mercury intrusion capillary pressure (MICP), and field emission-scanning electron microscopy (FE-SEM) imaging after Wood's metal (WM) impregnation were performed on overmature marine shale samples of the Wufeng-Longmaxi and Niutitang Formations from south China. Based on the electron micrographs of the WM-injected samples, it was found that the sealing of the pore system by brittle minerals is the root cause for a reduction in overall pore connectivity within the shale matrix. Aside from being favorable to the preservation of organic and clay mineral pores, brittle minerals however, resulted in the closure of pore network, thus, forming an isolated pore system. The novel approach of integrating repeated MICP measurement and FE-SEM imaging after WM impregnation provides a new evaluation method for pore-fracture connectivity of shale. The minimum fraction of pores within the overmature shales accessible to methane was at 38% and 78% within 100 nm. Moreover, because of confinement effects, the density of methane in a pore space less than 20 nm under high pressure was greater than that of an ideal gas under the same pressure conditions which even increased with decreasing of pore size to several times of its inert state and formed nanoscale methane clusters. The combination of contrast-matching SANS (CM-SANS) and repeated MICP measurements can effectively reveal the connectivity of pores within the matrix and the connectivity between such pores and microfractures, which helps to evaluate the distribution of closed pores and dominant transport spaces of gas in shale reservoirs. Overall, the pore-fracture connectivity in overmature marine shale controls the amount of gas that is supplied from matrix pores into fracture systems and also affects the density of the gas in pore spaces within the matrix.

POLYMERIC MATERIALS IN GLUING TECHNIQUES

Polymeric materials have an important role in gluing technology due to their broad application in the wood industry, metal industry, glass, and ceramics industry as well as medicine. This article discusses the basic physicochemical aspects of bonding with adhesives and also, the mechanisms of action of the adhesive materials during bonding based on polymerization processes and different types of polymerization. It was emphasized that depending on the material used in gluing, various adhesives with different physicochemical characteristics facilitate and contribute to the quality of the bonded joints. In this way, it is an insured procedure that is suitable for materials that are sensitive to the effects of heat, because welding and soldering would deform the base material and often the total degradation of its mechanical properties.

Experimental and numerical analysis of impingement temperature effect on the sacrificial plate's hole formation during nuclear severe accident

Liquid metal breaching onto a metal plate is an important aspect that needs to be considered in the nuclear severe accident analysis. This relates to the downward relocation of molten material to the supporting system such as sacrificial grid plate and lower head while accident happened. The molten core material impinged the sacrificial grid plate which was quenched before interacted with reactor pressure vessel. The present study aims to investigate the dynamic behaviors of holes formation due to liquid metal jet impingement onto a metal plate at initial temperatures 423 K, 473 K, and 523 K. The experiments and numerical simulation were performed with molten Wood's Metal and 5 mm thickness of Lead Bismuth Eutectic plates. The modified Moving Particle Semi-Implicit method was used to perform the numerical calculation based on the particle movement. The results showed that the plate was locally melted by the heat supplied from the liquid metal jet and induced the penetration. A larger amount of liquid metal stayed, then liquid metal pool was formed when the liquid temperature jet was lower. The temperature variation resulted unsignificant change of hole size diameter on both surfaces. The formed hole sizes in the plate's top and bottom surfaces were around 5.7–14 mm and 3.7−5 mm, respectively. The required time for the liquid metal penetration was shorter when the liquid metal temperature was higher. The increase of conduction heat transfer during the solidification of liquid metal could decrease the Nusselt number at the stagnation zone. The findings show that the experiment and numerical results can predict the sacrificial grid plate's hole formation and dynamic mechanism within critical time of molten core material impingement.

3D printed cartridge for high-speed capillary electrophoresis with sheath liquid thermostatting and contactless conductivity detection

The high-speed capillary electrophoresis (HSCE) method is a technique that utilizes a high electric field strength applied through a short capillary to reduce the time required for sample separation. However, the increased electric field strength may result in pronounced Joule heating effects. To address this, we describe a 3D-printed cartridge with integrated contactless conductivity detection (C4D) head and a sheath liquid channel. The C4D electrodes and Faraday shield layers are fabricated by casting Wood's metal in chambers inside the cartridge. Effective thermostatting of the short capillary is achieved by flowing Fluorinert liquid, which provides better heat dissipation compared to airflow. A HSCE device is created by using the cartridge and a modified slotted-vial array sample-introduction approach. Analytes are introduced through electrokinetic injection. With the help of sheath liquid thermostatting, background electrolyte concentration can be increased to several hundred mM, resulting in improved sample stacking and peak resolutions. Additionally, the baseline signal is flattened. Typical cations such as NH4+, K+, Na+, Mg2+, Li+, and Ca2+ can be separated within 22 s with an applied field strength of 1200 V/cm. The limit of detection ranges from 2.5 to 4.6 μM with a relative standard deviation of migration times of 1.1–1.2% (n = 17). The method has been applied to detect cations in drinking water and black tea leaching for drink safety testing, and to identify explosive anions in paper swabs. Samples can be directly injected without the need for dilution.

A COMPREHENSIVE STUDY OF LIMITATIONS ASSOCIATED WITH SIX DEGREES OF FREEDOM SPINE TESTING

Lower back pain (LBP) is a worldwide clinical problem and a prominent area for research. Numerous in vitro biomechanical studies on spine specimens have been undertaken, attempting to understand spinal response to loading and possible factors contributing to LBP. However, despite employing similar testing protocols, there are challenges in replicating in vivo conditions and significant variations in published results. The aim of this study was to use the University of Bath (UoB) spine simulator to perform tests to highlight the major limitations associated with six degree of freedom (DOF) dynamic spine testing.A steel helical spring was used as a validation model and was potted in Wood's metal. Six porcine lumbar spinal motion segments were harvested and dissected to produce isolated spinal disc specimens. These were potted in Wood's metal, ensuring the midplane of the disc remained horizontal and then sprayed with 0.9% saline and wrapped in saline-soaked tissue and plastic wrap to prevent dehydration. A 400N axial preload was used for spinal specimens. Specimens were tested under the stiffness and flexibility protocols.Tests were performed using the UoB custom 6-axis spine simulator with coordinate axes. Tests comprised five cycles with data acquired at 100Hz. Stiffness and flexibility matrices were evaluated from the last three motion cycles using the linear least squares method.According to theory, inverted flexibility matrices should equal stiffness matrices. In the case of the spring, the matrices matched analytical solutions and inverted flexibility matrices were equivalent to stiffness matrices. Matrices from the spinal tests demonstrated some symmetry, with similarities between inverted flexibility- and stiffness matrices, though these were unequal overall. Matrix element values were significantly affected by displacements assumed to occur at disc centre.Spring tests proved that for linear, elastic specimens, the spine simulator functioned as expected. However, multiple factors limit the confidence in spine test results. Centre of rotation, displacement assumptions and rigid body transformations are known to impact the results from spinal testing, and these should be addressed going forward to improve the replication of in vivo conditions.

FULLY CHARACTERIZING SPINAL LOAD DISPLACEMENT BEHAVIOUR USING VISCOELASTIC MODELS

Lower back pain (LBP) is a global problem. Countless in vitro studies have attempted to understand LBP and inform treatment protocols such as disc replacement devices (DRDs). A common method of reporting results is applying a linear fit to load-displacement behaviour, reporting the gradient as the specimen stiffness in that axis. This is favoured for speed, simplicity and repeatability but neglects key aspects including stiffening and hysteresis. Other fits such as polynomials and double sigmoids better address these characteristics, but solution parameters lack physical representation. The aim of this study was to implement an automated method to fit spinal load-displacement behaviour using viscoelastic models.Six porcine lumbar spinal motion segments were dissected to produce isolated disc specimens. These were potted in Wood's metal, ensuring the disc midplane remained horizontal, sprayed with 0.9% saline and wrapped in saline-soaked tissue and plastic wrap to prevent dehydration. Specimens were tested using the University of Bath spine simulator operating under position control with a 400N axial preload.Specimens were approximated using representative viscoelastic elements. These models were constructed in MATLAB Simulink R2020b using the SimScape library. Solution coefficients were determined by minimizing the sum of squared errors cost function using a non-linear least squares optimization method.The models matched experimental data well with a mean % difference in model and specimen enclosed area below 6% across all axes. This indicates the ability of the model to accurately represent energy dissipated. The final models demonstrated reduced RMSEs factors of 3.6, 1.1 and 9.5 smaller than the linear fits for anterior-posterior shear, mediolateral shear and axial rotation respectively.These nonlinear viscoelastic models exhibit significantly increased qualities of fit to spinal load-displacement behaviour when compared to linear approximations. Furthermore, they have the advantage of solution parameters which are directly linked to physical elements: springs and dampers. The results from this study could be instrumental in improving the design of DRDs as a mechanism for treating LBP.

INVESTIGATING THE EFFECT OF LABORATORY-INDUCED DISC INJURIES ON THE BIOMECHANICAL BEHAVIOUR OF ISOLATED SPINAL DISC SPECIMENS SUBJECT TO CYCLIC LOADING

Injury of the intervertebral disc (IVD) can occur for many reasons including structural weakness due to disc degeneration. A common disc injury is herniation. A herniated nucleus can compress spinal nerves, causing pain, and nucleus depressurisation changes mechanical behaviour. Many studies have investigated in vitro IVD injuries including endplate fracture, incisions, and nucleotomy. There is, however, a lack of consensus on how the biomechanical behaviour of spinal motion segments is affected. The aim of this study was to induce defined changes to IVDs of spine specimens in vitro and apply 6 degree of freedom testing to evaluate the effect of these changes.Six porcine lumbar spinal motion segments were harvested from organically farmed pigs. Posterior structures were removed to produce isolated spinal disc specimens. Specimens were potted in Wood's metal, ensuring the midplane of the IVD remained horizontal. After potting, specimens were sprayed with 0.9% saline, wrapped in saline-soaked tissue and plastic wrap to prevent dehydration. A 400N axial preload was equilibrated for 30 minutes before testing. Specimens were tested intact and after a partial nucleotomy removing ~0.34g of nuclear material with a curette through an annular incision.Stiffness tests were performed using the University of Bath's custom 6-axis spine simulator with coordinate axes and displacement amplitudes. Tests comprised five cycles with data acquired at 100Hz. Stiffness matrices were evaluated from the last three motion cycles using the linear least squares method.Stiffness matrices for intact and nucleotomy tests were compared. No significant differences in shear, axial or torsional stiffnesses were noted. Nucleotomy caused significantly higher stiffness in lateral bending and flexion-extension with increased linearity and the load-displacement behaviour in these axes displayed no neutral zone (NZ).Induced changes were designed to replicate posterolaterally herniated discs. Unaffected shear, axial and torsional stiffnesses suggest the annulus is crucial in these axes. However, reduced ROM and NZ after nucleotomy suggests bending is most affected by herniation. Increased linearity and lack of defined NZ in these axes demonstrates herniation causes major changes to the viscoelastic behaviour of spine specimens in response to loading.

A scoping study on remelting process of a debris bed in the lower head of reactor pressure vessel

Coolability and retention of core melt (corium) in the lower head of reactor pressure vessel (RPV) has been accepted as a severe accident management strategy to maintain the reactor pressure vessel (RPV) integrity of a light water reactor. To qualify the in-vessel melt retention strategy, lots of studies have been performed to investigate the natural convection heat transfer of a melt pool in the lower head. However, little work has been attributed to the precursory phase of the melt pool, i.e., the remelting process of a debris bed which is formed in the lower head at the very beginning of corium relocation from the core the lower head. The present study is motivated to conduct an experimental study on the debris remelting process. For this purpose, a dedicated test facility named COREM (COrium REMelting) is conceived and constructed, which features internal heating of electromagnetic induction and visualization of debris remelting dynamics. The test section is a semicircular vessel representing a slice of scaled-down RPV lower head, whose front and back walls are made of transparent tempered glass which facilitate visualization and induction heating of the debris bed. Fiber probes with multiple optical temperature sensors are mounted in the semicircular wall of the test section to measure its temperature distribution. In the scoping test, n-octanol and Wood's metal are selected as the simulant materials of metallic and oxidic components of corium, respectively, and their particles ware loaded in the test section to form a debris bed. This paper presents the first two scoping tests which have been performed with the COREM facility so far, under different mixing ratios of two debris materials. The measured data include the photography of debris remelting processes and the temperatures in the debris bed and the semicircular wall. Based on the temperature distributions, heat flux profile along the semicircular vessel wall is also estimated. The scoping tests well reproduce the dynamic process of debris remelting, with two distinct stages of fusion of n-octanol and Wood’s metal, i.e., melting successively from low to high melting-point debris particles. During the remelting process, the vessel wall temperatures increase with the polar angle firstly and then decrease gradually, leading to the highest temperature appearing in the middle of the lower layer of the stratified molten pool which is finally formed.

An Overview Study on Laser Technology and Conventional Technology’s Effect on Wood and Sheet Metal Manufacturing for The Furniture Industry

The laser was one of the most important inventions of the twentieth century, improving many aspects of daily life. Because of its clean cutting-edge capabilities, delicate welding lines, potent etching strokes, high power operation, and precise distance measurement capabilities, laser technology has gradually taken over and dominated the mechanical market, particularly in the field of material handling and metal parts for the furniture industry. By creating intricate and continuous features, lines, shapes, and patterns in metal using lasers, the wood, and sheet metal furniture industries are given new opportunities. However, it is still confusing for designers and manufacturers which is the best method to produce their designs. Hence, there is a need to compare the conventional technology of traded furniture production with laser technology. In order to support the industry in a way that serves to save time and effort and enhances sustainability. We demonstrate that using laser cutting and engraving devices in intricate and sophisticated processing is an amazing technology on flat sheet materials. In conclusion, the laser is more flexible in conjugation with a high degree of accuracy, and the quality of the cutting kerf all add up to make the use of this tool particularly interesting for machining. The focused beam of a modern CO2 laser cuts wood and metal sheets quickly, and accurately and requires no contact or clamping. There is no tool wear and the laser is more or less maintenance-free. Otherwise, using a CNC router is preferred when cutting, or engraving in case of thick wood or metals sheet.

Three-in-One Detector by 3D Printing: Simultaneous Contactless Conductivity, Ultraviolet Absorbance, and Laser-Induced Fluorescence Measurements for Capillary Electrophoresis.

We describe a 3-in-1 detector for simultaneous contactless conductivity (C4D), ultraviolet absorbance (UV-AD), and laser-induced fluorescence (LIF) measurements on a single detection point for capillary electrophoresis (CE). A key component of the detector was a rectangular detector head that was assembled with four 3D-printed parts. Two parts covering the detector head to function as a Faraday cage were fused deposition modeling printed using an electrically conductive material. The other two parts in between the conductive parts were stereolithography (SLA) printed with high-resolution (50 μm) constructions on the surface. After assembling the two SLA printed parts, several cavities were built with the surface constructions. Two electrodes and a Faraday shield for C4D were cast by injecting molten Wood's metal into the cavities. For UV-AD, a slit (100 μm width) was created by putting together two grooves (50 μm depth) on the surface of the SLA printed parts. A 255 nm UV-LED was used as the light source. The effective path length and stray light for a 50 μm id capillary were 39 μm and 13%, which were superior to those of other reported 3D-printed AD detectors. Confocal LIF detection was conducted by using an objective lens to focus the laser on the capillary via a through-hole. The detector was used to detect model analytes, including inorganic and organic ions, and fluorescein isothiocyanate labeled amino acids in a signal-run CE separation. In detecting fluorescein, LODs were 1.3 μM (C4D), 2.0 μM (UV-AD), and 1 nM (LIF). The calibration ranges covered from 0.01 μM to 500 μM.

The "Ware Joint" Container: An Exploration of Chinese Cultural Meaning in Tableware Design

The way to eat and the way to serve food is one of the most explicit cultural styles. Chinese food utensils and eating furniture contain the Chinese view of nature and material use. In order to reflect Chinese cultural meaning in the design of Chinese food utensils, the iconic symbols and material design should not be left to the curiosity of formal innovation, but ignore the transmission of cultural meaning in the works, so that the existing works of Chinese meaning tableware design often present Therefore, the existing Chinese tableware design works often show unsatisfactory results. The author believes that if Chinese tableware design products are to go global, they must reflect the demands of Chinese cultural experience in terms of shape, material and combination, and meet the aesthetic needs and practical functions of contemporary design. In this paper, we take the Chinese cultural symbolic element "bamboo" as the theme, and combine wood and traditional metal hammering and forging techniques to create "ware joint", which has been exhibited in many countries. As an example, an exploration is conducted on the creation of Chinese cultural meaning in tableware design by combining wood and traditional metal hammering and forging techniques.

Influence of Photochromic Microcapsules on Properties of Waterborne Coating on Wood and Metal Substrates

With the development of the economy and science and technology, consumers have put forward higher requirements for the functionality of surface coatings on wood products and metal products, which requires us to endow traditional coatings with new functions. Innovative research of coatings has been a research hotspot in recent years, and the combination of microencapsulation technology with coatings is a research direction attracting much attention. In this paper, a kind of spirooxazine color-changing microcapsules containing photochromic purple dye was selected to explore the effect of different loadings of the photochromic microcapsules on the properties of the coatings. The photochromic microcapsules were added to the waterborne coating with loadings of 5.0%, 10.0%, 15.0%, 20.0% and 25.0%. The coatings were coated on Tilia europaea boards and aluminum alloy plates to explore the optical properties, mechanical properties, cold liquid resistance and aging resistance of the coatings. The results showed that the coating had good photochromic property on wood substrate and metal substrate. When the loading was 15.0% and 10.0%, the comprehensive performance of the coating was good. The color difference of the coating before and after photochromism was 51.0 and 62.0, the glossiness was 7.1% and 15.9%, the hardness was 3H, the adhesion grade was 1, the impact resistance was 4 kg·cm, the roughness was 1.2 μm and 0.9 μm and the liquid resistance grade was 1. The research results show that the photochromic microcapsule can endow the paint with a reversible color change function and improve some mechanical properties of the coating, which indicates that the composite prepared in this study can be used in the surface finishing of wood and metal and has certain research value and application potential.

Metal-organic frameworks decorated wood aerogels for efficient particulate matter removal

The severe indoor/outdoor air contamination caused by hazardous particulate matters (PMs) has a devastating impact on the environment and human health. Herein, air filters fabricated from delignified wood aerogels and metal–organic frameworks (MOFs) were used for PM removal. Two specially designed MOFs (i.e. Zn-based ZIF-L and Zr-based UiO-66-NH2) were deposited into a highly porous wood matrix through in situ growth approach. The MOF crystals are attached tightly to the highly available cellulose surface groups and distributed uniformly. The integration of MOFs can regulate the aerogel morphology and surface property, leading to enhanced PM removal performance. Bare wood aerogels beard removal efficiencies of 70.7% and 75.0% for PM2.5 and PM10, with a low-pressure drop of 15 Pa. By contrast, ZIF-L decorated wood aerogels exhibited PM2.5 and PM10 removal efficiencies of 97.6% and 99.5%, respectively, which are ascribed to the increased interception/impaction of PMs with the positively charged ZIF-L layer. While UiO-66-NH2 functionalized wood aerogels demonstrated PM2.5 and PM10 removal efficiencies of 96.4% and 98.9% because of the hierarchical filter matrix and the presence of polar –NH2 groups. Moreover, MOF modified wood aerogels can be easily regenerated and superior reusability can be achieved. This work provides an effective and economic strategy for the preparation of air filters from renewable materials.

Mode I crack growth in paper exhibits three stages of strain evolution in reaching steady-state

The mechanical properties of wood fiber-based, commercial papers and metal foils are qualitatively similar, and their plane stress, Mode I crack growth resistances have not been reliably correlated with single-valued fracture mechanics parameters for centimeter-scale specimens. Experimentally-measured crack tip strain fields of Mode I cracks growing in commercial paper were used to define a three-stage, steady-state crack growth mechanism. Immediately upon loading, the net sections ahead of the cracks yielded. As the cracks began to grow, well-defined zones of (incremental) active plasticity (ZAPs) formed within the yielded ligaments. Cracks transitioned to steady-state growth with an average characteristic stress, σc, of 20.9MPa. In contrast to metallic foils, the characteristic stress in steady-state cracks in paper was offset by 8.3MPa due to a 1.9mm fiber bridging zone that scaled with the average fiber agglomerate (floc) size. The fiber network structure also induced a large, reversed steady-state zone in the crack wakes. While reversed ZAPS were previously predicted by numerical models of plane strain Mode I and III cracks under small-scale yielding conditions, they were never observed experimentally and were neglected. The types and evolution of the cumulative and incremental plastic zones in paper defined appropriate paths for steady-state J-integral calculations.

High-temperature-tolerable superconducting Nb-alloy and its application to Pb- and Cd-free superconducting joints between NbTi and Nb3Sn wires

For more than 30 years, Pb–Bi alloy and Wood's metal (50% Bi, 26.7% Pb, 13.3% Sn, and 10% Cd) have been used as representative superconducting solder intermedia to establish superconducting joints between NbTi and Nb3Sn wires in high-field nuclear magnetic resonance magnet systems. However, the use of Pb and Cd has been severely restricted by environmental regulations, such as the Restriction of Hazardous Substances Directive. Herein, a novel method of forming a superconducting joint between NbTi and Nb3Sn wires without Pb and Cd has been proposed. This approach is based on metallurgical bonding processes using a superconducting Nb-alloy intermedium, whose fine microstructure is maintained even after exposure to temperatures higher than 650 °C. Further, fine crystal defects become sources of magnetic flux pinning centers. Among transition elements close to Nb, Hf is considered the most suitable additive for realizing high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia. Utilizing the HTT characteristic of Nb–Hf, a superconducting joint between Nb3Sn filaments and one end of the Nb–Hf alloy core was created by forming a superconducting Nb3Sn layer at the interface through a chemical reaction. The other end of the Nb–Hf alloy core was cold-pressed with NbTi filaments, to connect their active new surfaces to each other in order to create a superconducting joint. Ultimately, a superconducting joint between NbTi and Nb3Sn wires was realized with a high critical magnetic field (Bc2) of more than 1 T. The formation of the superconducting joint was confirmed by current decay measurements. This method of forming a superconducting joint is promising for application in environmentally friendly nuclear magnetic resonance magnet systems.Graphical abstract

Pore structure and connectivity of tight sandstone reservoirs in petroleum basins: A review and application of new methodologies to the Late Triassic Ordos Basin, China

Pore structure and connectivity are key factors that determine the quality of tight sandstone reservoirs, which are a frontier field for exploration worldwide in the 21st century but are quite challenging to characterize. Here we explored novel methodologies based on a case study of the well-known Chang-7 reservoir in the Upper Triassic Yanchang Formation, Ordos Basin, China. Pore size distribution (PSD) can be quantitatively characterized by nuclear magnetic resonance cryoporometry (NMRC), and the connectivity of the reservoir can be described by using a combination of Wood's metal (WM) impregnation, environmental scanning electron microscopy (ESEM), and nano-computed tomography (CT). The PSD of tight sandstones with different oil-bearing levels exhibit obvious differences. The complexity of pore boundaries and orientations are key factors that affect reservoir physical properties and oiliness. The pore fracturing in tight sandstones can be divided into three types: poor, medium, and good connectivity. The ball-and-stick model is suitable for the study of reservoir connectivity, and the effect of tight sandstone heterogeneity on connectivity analysis can be reduced significantly. Our data suggest that multi-scale characterization is reliable for describing the pore structure and connectivity of tight reservoirs. It is found for the first time that the quality and oiliness of tight sandstone reservoirs are not determined solely by physical properties, but are also controlled by PSD and pore morphology and connectivity. This may lead to underestimation of the effective reservoir and potential resources as previously thought.

Study on melt jet breakup behavior with nonorthogonal central-moment MRT color-gradient lattice Boltzmann method

In this paper, the melt jet breakup behavior are numerically studied in 3D with nonorthogonal central-moment MRT color-gradient lattice Boltzmann method, which could significantly enhance the numerical stability and accuracy when applied to flows with very high Reynolds number. Firstly, the methodology to simulate immiscible two-phase flow is validated by conducting droplet oscillation tests. Then the ability of this model to accurately predict melt jet breakup in water is validated by simulating molten Wood's metal jet breakup experiments. Meanwhile, the breakup mechanisms are clarified. For the leading edge, the breakup of the side part is due to large eddies, the main part of the leading edge starts breakup owning to Rayleigh-Taylor instability. For the jet column, small droplets and filaments are stripping due to Kelvin-Helmholtz instability, segment breakup of the jet column is owning to Rayleigh-Taylor instability. Finally, the model is employed to simulate molten corium jet breakup in water. The hydrodynamic characteristics such as jet penetration depth, jet breakup length and fragment size are analyzed in detail. It is found that the simulation results are basically consistent with the dimensionless jet breakup length predicted by Epstein et al.‘s correlation when E0=0.1, but relatively shorter. RTI theory significantly overestimates mass median diameter while critical Weber number and KHI theories underestimate it.