Contact Properties Research Articles

Preparation and efficacy of antibacterial methacrylate monomer-based polymethyl methacrylate bone cement containing N-halamine compounds.

Our objective in this study was to prepare a novel type of polymethyl methacrylate (PMMA) bone cement, analyze its material properties, and evaluate its safety and antibacterial efficacy. A halamine compound methacrylate antibacterial PMMA bone cement containing an N-Cl bond structure was formulated, and its material characterization was determined with Fourier transform infrared spectroscopy (FT-IR) and 1H-NMR. The antibacterial properties of the material were studied using contact bacteriostasis and releasing-type bacteriostasis experiments. Finally, in vitro and in vivo biocompatibility experiments were performed to analyze the toxic effects of the material on mice and embryonic osteoblast precursor cells (MC3T3-E1). Incorporation of the antibacterial methacrylate monomer with the N-halamine compound in the new antibacterial PMMA bone cement significantly increased its contact and releasing-type bacteriostatic performance against Staphylococcus aureus. Notably, at 20% and 25% additions of N-halamine compound, the contact and releasing-type bacteriostasis rates of bone cement samples reached 100% (p < 0.001). Furthermore, the new antibacterial bone cement containing 5%, 10%, and 15% N-halamine compounds showed good biocompatibility in vitro and in vivo. In this study, we found that the novel antibacterial PMMA bone cement with N-halamine compound methacrylate demonstrated good contact and releasing-type bacteriostatic properties against S. aureus. In particular, bone cement containing a 15% N-halamine monomer exhibited strong antibacterial properties and good in vitro and in vivo biocompatibility.

Study on the mechanical and aging properties of an antibacterial composite resin loaded with fluoride-doped nano-zirconia fillers

Preventing the occurrence of secondary caries serves as one of the significant issues in dental clinic, thus make it indispensable to improving the properties of conventional composite resin (CR) by developing a novel CR. In present study, two groups of experimental CRs loaded with different contents of fluoride-doped nano-zirconia fillers (25 wt% and 50 wt%) were fabricated. The surface topography, mechanical performance, fluoride release, antibacterial effect, aging property and cytotoxicity of the experimental CRs were evaluated subsequently. A uniform distribution of the F-zirconia fillers over the whole surface of resin matrix could be observed. The experimental CRs showed continuous fluoride release within 28 days, which was positively correlated with the content of F-zirconia fillers. Moreover, the amount of fluoride release increased in the acidic buffer. Addition of F-zirconia fillers could improve the color stability, wear resistance and microhardness of the experimental CRs, without reducing the flexure strength. Furtherly, the fluoride ions released continuously from the experimental CRs resulted in effective contact and antibacterial properties, while they showed no cytotoxicity. As a consequence, considerations can be made to employ this new kind of composite resin loaded with fluoride-doped nano-zirconia fillers to meet clinical requirements when the antimicrobial benefits are desired.

First-Principles and Experimental Study of Ge, V, Ta-Doped AgNi Electrical Contact Materials

To explore the stability, electrical, and mechanical characteristics of undoped AgNi alongside AgNi doped with elemental Ge, V, and Ta, we performed calculations on their electronic structures using density functional theory from first-principles. We also prepared AgNi(17) and AgNi-x(Ge, V, Ta) electrical contact materials using the powder metallurgy technique, and they were subsequently assessed experimentally. The electrical properties of these materials were evaluated under a 24 V/15 A DC-resistive load using the JF04D contact material testing system. A three-dimensional morphology scanner was employed to examine the contact surface and investigate the erosion patterns of the materials. Our findings indicate that doping with metal elements significantly enhanced the mechanical properties of electrical contacts, including conductivity and hardness, and optimizes arc parameters while improving resistance to arc erosion. Notably, AgNi-Ge demonstrated superior conductivity and arc erosion resistance, showing significant improvements over the undoped AgNi contacts. This research provides a theoretical foundation for selecting doping elements aimed at enhancing the performance of AgNi electrical contact materials.

Specific contact resistivity reduction in amorphous IGZO thin-film transistors through a TiN/IGTO heterogeneous interlayer

Oxide semiconductors have gained significant attention in electronic device industry due to their high potential for emerging thin-film transistor (TFT) applications. However, electrical contact properties such as specific contact resistivity (ρC) and width-normalized contact resistance (RCW) are significantly inferior in oxide TFTs compared to conventional silicon metal oxide semiconductor field-effect transistors. In this study, a multi-stack interlayer (IL) consisting of titanium nitride (TiN) and indium-gallium-tin-oxide (IGTO) is inserted between source/drain electrodes and amorphous indium-gallium-zinc-oxide (IGZO). The TiN is introduced to increase conductivity of the underlying layer, while IGTO acts as an n+-layer. Our findings reveal IGTO thickness (tIGTO)-dependent electrical contact properties of IGZO TFT, where ρC and RCW decrease as tIGTO increases to 8 nm. However, at tIGTO > 8 nm, they increase mainly due to IGTO crystallization-induced contact interface aggravation. Consequently, the IGZO TFTs with a TiN/IGTO (3/8 nm) IL reveal the lowest ρC and RCW of 9.0 × 10−6 Ω·cm2 and 0.7 Ω·cm, significantly lower than 8.0 × 10−4 Ω·cm2 and 6.9 Ω·cm in the TFTs without the IL, respectively. This improved electrical contact properties increases field-effect mobility from 39.9 to 45.0 cm2/Vs. This study demonstrates the effectiveness of this multi-stack IL approach in oxide TFTs.

Structural optimization, interfacial contact, and transverse thermoelectric properties of Ag2Te/Bi0.5Sb1.5Te3 artificially tilted multilayer thermoelectric devices

Structural optimization, interfacial contact, and transverse thermoelectric properties of Ag2Te/Bi0.5Sb1.5Te3 artificially tilted multilayer thermoelectric devices

Finite element study on the micromechanics of cement-augmented proximal femoral nail anti-rotation (PFNA) for intertrochanteric fracture treatment

Blade cut-out is a common complication when using proximal femoral nail anti-rotation (PFNA) for the treatment of intertrochanteric fractures. Although cement augmentation has been introduced to overcome the cut-out effect, the micromechanics of this approach remain to be clarified. While previous studies have developed finite element (FE) models based on lab-prepared or cadaveric samples to study the cement-trabeculae interface, their demanding nature and inherent disadvantages limit their application. The aim of this study was to develop a novel 'one-step forming' method for creating a cement-trabeculae interface FE model to investigate its micromechanics in relation to PFNA with cement augmentation. A human femoral head was scanned using micro-computed tomography, and four volume of interest (VOI) trabeculae were segmented. The VOI trabeculae were enclosed within a box to represent the encapsulated region of bone cement using ANSYS software. Tetrahedral meshing was performed with Hypermesh software based on Boolean operation. Finally, four cement-trabeculae interface FE models comprising four interdigitated depths and five FE models comprising different volume fraction were established after element removal. The effects of friction contact, frictionless contact, and bond contact properties between the bone and cement were identified. The maximum micromotion and stress in the interdigitated and loading bones were quantified and compared between the pre- and post-augmentation situations. The differences in micromotion and stress with the three contact methods were minimal. Micromotion and stress decreased as the interdigitation depth increased. Stress in the proximal interdigitated bone showed a correlation with the bone volume fraction (R2 = 0.70); both micromotion (R2 = 0.61) and stress (R2 = 0.93) at the most proximal loading region exhibited a similar correlation tendency. When comparing the post- and pre-augmentation situations, micromotion reduction in the interdigitated bone was more effective than stress reduction, particularly near the cement border. The cementation resulted in a significant reduction in micromotion within the loading bone, while the decrease in stress was minimal. Noticeable gradients of displacement and stress reduction can be observed in models with lower bone volume fraction (BV/TV). In summary, cement augmentation is more effective at reducing micromotion rather than stress. Furthermore, the reinforcing impact of bone cement is particularly prominent in cases with a low BV/TV. The utilization of bone cement may contribute to the stabilization of trabecular bone and PFNA primarily by constraining micromotion and partially shielding stress.

In-situ synthesis of coral reef-like synergistic zinc cobalt oxide and zinc manganese oxide composite as a battery-type electrode material for supercapacitors

Recently, in-situ preparation of metal oxide composite structures has gained much importance in fabricating electrode materials for energy storage and conversion devices because of its advantageous properties of beneficial interfacial contact, high conductivity, good synergism, short ion diffusion distance, better electrochemical performance, etc. Binary transition metal oxides (BTMOs) are given great attention for their significant electrochemical performances over primary MOs because of the two metal ions with different valent states for the redox reactions. In this study, we synthesize zinc cobalt oxide (ZnCo2O4) and zinc manganese oxide (ZnMn2O4) composite via a solvothermal synthetic method. The existence of both phases is identified using an X-ray diffraction analysis (XRD). The unique coral reef-like structures of the composite electrode are analysed via field emission scanning electron microscopy, and the nanostructure was identified using transmission electron microscopy. The X-ray photoelectron spectroscopy confirms the surface oxidation states of the composite and supports the XRD analysis. The synergetic composite electrode provides a large surface area of 50.86 m2 g−1 with many pores. The composite electrode has a specific capacity of 250 C g−1 at 1 A g−1. The ZCO/ZMO composite demonstrated impressive stability, retaining a specific capacity of 180 C g−1 at 6 A g−1 over 5000 cycles.

Arc erosion resistance of Al2O3–Cu/35Mo composites reinforced by trace graphene oxide

In this study, Al2O3–Cu/35Mo composites were prepared by rapid hot-press sintering-internal oxidation method, and the materials were modified by adding trace amounts of graphene oxide (GO). The results show that the relative densities of the composites are above 99%, the γ-Al2O3 generated by internal oxidation is diffusely distributed on the copper matrix. The incorporation of GO produced a small number of hard MoC particles at the interface, which facilitated the interfacial bonding of the composites. In the 30 V DC, 10–30 A electrical contact test, the anode mass of the composites increases, while the cathode mass decreases. And GO reduces the total mass loss of the electric contact by 63.6%, 38.9%, 51.3% and 20.9%, respectively. A comparison of the electrical contact properties of the two materials showed that the addition of GO dispersed the concentrated erosion of the arc. At 10 A and 30 A, the arc energy is reduced by 75.5% and 12.5%, respectively. With the gradual increase in electric current, GO makes the Al2O3–Cu/35Mo composites more stable during the electric contact process, improves the anti-welding ability of the contact and reduces contact resistance.

Study on the encapsulation effect and mechanism of hollow ceramsite to phase change materials (PCMs)

In order to promote the development of phase change materials (PCMs) and make them better applied, more in-depth research on the PCMs encapsulation is needed. The hollow ceramsite prepared in this study is a new type of PCMs carrier. Due to its unique structure, the encapsulation of PCMs by hollow ceramsite differs from that of ordinary porous ceramsite. In this paper, the adsorption and sealing effect of hollow ceramsite on PCMs was studied, the key factors affecting the adsorption and sealing effect were determined, and the encapsulation mechanism was revealed. The results show that the driving force of PCMs into the cavity of hollow ceramsite is mainly from the external pressure; the pore size and PCMs properties are the key factors determining the adsorption effect of hollow ceramsite. The pressure on the pore is proportional to the square of the pore diameter; increasing pore size enhances the possibility of the PCMs entering the cavity of ceramsite. The contact angle between PCMs and pores is smaller, and the surface tension of the PCMs in the pores is greater, making it difficult for PCMs to enter the cavity of ceramsite. The sealing mechanism of the coating on infiltrating PCMs is achieved by reducing the pore diameter of the sealing coating and increasing the resistance of PCMs to break through the pore. The sealing mechanism of the coating on non-infiltrating PCMs is achieved by changing the contact property between the PCMs and pore, increasing the energy barrier. After coating, the mass loss rate of infiltrating paraffin was controlled within 5 %, and the leakage rate of non-infiltrating hydrated salt was controlled within 1 %.

Structural properties of different sphere packings with arbitrary porosities for planetary-science applications

Granular solids in planetary science are found in the regolith that covers planetary surfaces as well as in the bulk of rubble-pile asteroids, comets and planetesimals. To help understand the physics of these planetary bodies, we aim at deriving the structural properties of granular packings over a large range of porosities. Relevant to fluid flow and gas diffusion are the void spaces inside the granular packings so that we analyze the mean free path of point-like particles, their diffusion constant and their total traveled path lengths. For mechanical and heat-transport properties, the coordination number and the absolute chain length of the inter-connected particles are important. Generally, we also derive the homogeneity and isotropy of the granular solids. We compare granular packings generated by four algorithms for porosities in the range between 85 and 42%, which are the upper and lower limits for natural packings of equal-sized spheres. All produced sphere packings arrive at very similar quantities for the mean free path, the free path probability distribution function, the diffusion constant and the total traveled path length for the entire range of porosities. Hence, transport processes governed by the void-space properties are independent of the specific generation algorithm for the granular packing. In contrast, heat conduction or mechanical stresses almost exclusively depend on the existence and properties of particle contacts and particle chains in the network of spheres. In this case, the four algorithms deliver very different results.Graphic abstract

Isobutyramide Additive to Improve the Performance of CsPbBr3 Perovskite Solar Cells Prepared by Green Solvent

The inorganic cesium lead bromide (CsPbBr3) perovskite solar cell (PSC) is considered as an attractive option for new solar cells due to its outstanding stability. Preparing CsPbBr3 PSCs with H2O can effectively save costs and reduce the harm of toxic solvents to the environment. However, the poor contact property of the PbBr2 layer to the CsBr/H2O solution and the ability of water to dissolve the CsPbBr3 phase has a significant impact on the performance of the CsPbBr3 devices. In this article, isobutyramide is introduced into the PbBr2 film in the first step to improve the wettability of the PbBr2 film to CsBr/H2O solution, followed by spin‐coating of the 150 mg mL−1 CsBr/H2O solution on the PbBr2 film. Using this strategy, the fabricated PSCs with the architecture of FTO/compact‐TiO2/mesoporous‐TiO2/CsPbBr3 film/carbon demonstrate outstanding performance with a maximum efficiency of 9.59%. Furthermore, after 45 days of storage at ambient temperatures, the unencapsulated device retains more than 96% of its original efficiency. Therefore, this work provides a good demonstration for the preparation of high‐efficiency and eco‐friendly CsPbBr3 PSCs.

Particle size dependence of nanoclustered ceria abrasives on surface activity and chemical mechanical planarization performance

The particle size of cerium oxide (ceria) abrasives plays a crucial role in the design and development of advanced self-stopping slurries for the chemical mechanical planarization (CMP) process in semiconductor device manufacturing. However, a lack of ceria nanoparticles (NPs) with a narrow size distribution and uniform shape poses challenges in investigating the fundamental principles of the relationship between abrasive size and CMP performance. In this study, we thoroughly investigated the effect of ceria NP size on the removal rate (RR) of silicon oxide using uniform-sized nanoclustered (NC) ceria NPs with three diameters: 51.4 nm (NC51), 68.6 nm (NC69), and 108.0 nm (NC108). While all three types of ceria NPs shared a crystallinity of ∼ 70.6 %, they exhibited distinct physicochemical characteristics. As the particle size decreased, the specific surface area and chemical activity (i.e., Ce3+/Ce4+) increased by 155 % and 69 %, respectively. In the CMP process, where direct contact between the abrasives and wafer occurs, the abrasive size influences CMP performance. Experimentally, NC51 achieved the highest RR among the three slurries, along with complex size-dependent contact properties and chemical activities. These experimental results offer significant insights into precise semiconductor manufacturing in a practical manner.

Properties of photocurrent and metal contacts of highly resistive ultrawide bandgap semiconductors

Properties of photocurrent and metal contacts of highly resistive ultrawide bandgap semiconductors

The discrete and continuum behaviour of railway ballast

The mechanics of coarse-grained geomaterials have traditionally been examined from a continuum mechanics standpoint, but this has led to ever more complex constitutive models as an increasing number of novel aspects of behaviour are investigated. For this reason, there is a tendency to move towards discrete approaches. Such approaches require accurate definition and modelling of the particle shapes, for which considerable progress has been made, and also the contact mechanics between particles, about which little is known. For very coarse materials such as railway ballast, our understanding at the continuum scale has been hampered further by the technical difficulties in the laboratory testing so that the very small strain behaviour has been difficult to define with accuracy. New apparatus and techniques will be described to test ballast at both the continuum and particulate scales. These allow the small strain stiffness to be defined with accuracy in triaxial tests and to carry out precise particle-to-particle contact tests. At the particle contact scale, the behaviour is dominated by the roughness of the particles and their relatively sharp contacts, so that plasticity and particle wear predominate, which both change the contact properties significantly. It is the contact plasticity that then controls the decay in continuum stiffness with strain. The work emphasises the inadequacy of using simple linear and/or elastic DEM models calibrated from macro-scale tests rather than deriving the correct contact behaviour directly.

Low-temperature fabrication of boron-doped amorphous silicon passivating contact as a local selective emitter for high-efficiency n-type TOPCon solar cells

Tunnel oxide passivating contact (TOPCon) solar cells (SCs) currently dominate the photovoltaic industry but grapple with efficiency challenges. A primary concern is the direct contact between front-sided metal electrodes and boron emitters, resulting in substantial carrier recombination losses and limiting further efficiency improvements. Here, we introduce a low-temperature approach to deposit a local boron-doped amorphous silicon [a-Si:H(p)] between front-sided metal electrodes and boron emitters. This method, avoiding issues associated with high-temperature processes, demonstrates excellent passivation and contact properties, featuring the lowest contact resistivity (< 1 mΩ·cm2) and a low saturation current density (< 400 fA/cm2). The outstanding passivation and contact properties remain robust even with variations in diborane flow rates during a-Si:H(p) fabrication, annealing temperatures, and sheet resistances of boron emitters. We elucidate the factors contributing to the enhanced passivation observed in boron emitters with a-Si:H(p) through a combination of simulations and experiments. The a-Si:H(p) layer between boron emitters and metal electrodes acts as a protective barrier, preventing the diffusion of metal atoms and suppressing carrier recombination. A heterojunction is formed between a-Si:H(p) and the boron emitter, facilitating electric-field passivation. Consequently, the TOPCon SCs incorporating a-Si:H(p) achieve an efficiency of 24.50%, surpassing their counterparts without a-Si:H(p) (23.11%). This work utilizes low-temperature technology to achieve fully passivated contact, providing insights for the development of high-efficiency TOPCon SCs.

Dual Strategy Based on Quantum Dot Doping and Phenylethylamine Iodide Surface Modification for High-Performance and Stable Perovskite Solar Cells

High-quality perovskite films (PFs) are crucial for achieving high-performance perovskite solar cells (PSCs). Herein, we report a dual-modification strategy via incorporating CsPbBr3 QDs into MAPbI3 perovskite bulk and capping the interface of the perovskite/hole transport layer (HTL) with phenylethylamine iodide (PEAI) to improve perovskite crystallinity and interface contact properties to acquire high-quality PFs with fewer defects. CsPbBr3 QDs promoted perovskite grain growth and reduced bulk defects, while PEAI surface modification passivated interfaces, improved hydrophobic properties, and prevented carrier recombination at the perovskite/HTL interface. Benefiting from growth control and the effective suppression of both bulk and interface carrier recombination, the resulting devices show a greatly improved photoelectric conversion efficiency (PCE) from 17.21% of the reference cells to 21.04% with a champion Voc of 1.15 V, Jsc of 23.30 mA/cm2, and fill factor (FF) of 78.6%. Furthermore, the dual-modification strategy endows PFs with promoted moisture tolerance, and the nonencapsulated PSCs retain 75% of their initial efficiency after aging for 30 days at 40% relative humidity and room temperature, which is significantly higher than the 59% value of the original PSCs. Good operational stability and the maintained efficiency of the target device over time suggest the potential for future commercialization.

The spin transport properties of Ni(111)/SnSe/Ni(111) lateral tunnel junction

Spin-resolved transport properties of the armchair-edged SnSe lateral contact with two magnetic Ni(111) leads are investigated by density functional theory combined with nonequilibrium Green's function method. The spin-polarized currents, magnetoresistances and k-resolved transmission spectrums are simulated in spin parallel and antiparallel configurations. It is found that the heterostructure exhibits a stable spin injection efficiency which can reach up to 80% at low bias range in spin parallel configuration, suggesting the large spin-diffusion length of SnSe. The magnetoresistance can be maintained stably at about 40% at a wide bias range. These results make SnSe material possible to be used in spintronic devices.

Waterproof, stretchable and wearable corrugated conductive carbon fiber strain sensors for underwater respiration monitoring and swimming instruction

Respiration is one of crucial vital signs, which can be used for health assessment and sports management. Flexible resistive strain sensors provide an opportunity to monitor personal respiratory behaviors in real time due to high sensitivity, good linearity and fast response. However, there are some critical issues with the resistive strain sensor, such as strain mismatch, poor contact properties and moisture sensitivity, which easily cause unexpected electrical response, limiting its application scenarios. Here, a novel stretchable carbon fiber strain sensor is developed by a simple structural design, which endow the device with a remarkable linearity (R2=0.99601 in 0–40 % tensile strain), excellent anti-jamming performance, long-term durability, and waterproofness. Moreover, a sophisticated wearable respiratory monitoring system is further developed, which can not only precisely distinguish diverse respiratory patterns to enhance the accuracy in early illness diagnosis but also remotely capture real-time breathing information during swimming for guiding swimming training. It demonstrates that our stretchable resistive strain sensor has an enormous application potential in wearable electronics and smart clothing for health monitoring and training guide.

Investigation on Contact Properties of 2D van der Waals Semimetallic 1T-TiS2/MoS2 Heterojunctions.

Two-dimensional transition metal dichalcogenides (2D TMDCs) are considered promising alternatives to Si as channel materials because of the possibility of retaining their superior electronic transport properties even at atomic body thicknesses. However, the realization of high-performance 2D TMDC field-effect transistors remains a challenge owing to Fermi-level pinning (FLP) caused by gap states and the inherent high Schottky barrier height (SBH) within the metal contact and channel layer. This study demonstrates that high-quality van der Waals (vdW) heterojunction-based contacts can be formed by depositing semimetallic TiS2 onto monolayer (ML) MoS2. After confirming the successful formation of a TiS2/ML MoS2 heterojunction, the contact properties of vdW semimetal TiS2 were thoroughly investigated. With clean interfaces of the TiS2/ML MoS2 heterojunctions, atomic-layer-deposited TiS2 can induce gap-state saturation and suppress FLP. Consequently, compared with conventional evaporated metal electrodes, the TiS2/ML MoS2 heterojunctions exhibit a lower SBH of 8.54 meV and better contact properties. This, in turn, substantially improves the overall performance of the device, including its on-current, subthreshold swing, and threshold voltage. Furthermore, we believe that our proposed strategy for vdW-based contact formation will contribute to the development of 2D materials used in next-generation electronics.

Mesoscopic simulation of the mechanical behaviour of foam concrete subjected to large compressive deformation

As an energy-absorbing material, foam concrete has gained recent application in tunnel support systems. Despite its capacity for substantial compressive deformation, including stress plateau and densification, limited research has delved into this aspect. This study investigates the stress-strain characteristics, fracture behaviour and energy absorption capacity of foam concrete, with a focus on the contact behaviour between its pore structures during large compressive deformation. Through experimental and numerical research, it was found that foam concrete retains compressive strength after reaching the peak stress, with stress levels showing recovery and increase during compression. X-ray computed tomography (X-CT) was utilised to acquire the mesostructured and perform mesoscopic simulations of foam concrete. The experimentally obtained stress-strain curves were used to validate the numerical model. The study discusses and compares mechanical properties and energy absorption capacity of foam concrete with different porosity conditions subjected to large compressive deformation, highlighting the effects of the pore structure and contact property on the densification behaviour of foam concrete. Overall, this research contributes to a deeper understanding of the mechanical behaviour of foam concrete subjected to large compressive deformation.