Journal of Materials Research最新文献

With mushrooming of wireless wearable devices, demand of efficient electromagnetic interference (EMI) shielding material gained much interest to obstruct the unwanted radiations. This paper reports the fabrication of CaCu₃Ti₄O₁₂(CCTO)/CoFe₂O₄(CFO)/silicone composites and investigation of their dielectric and EMI shielding characteristics. The EMI shielding effectiveness and dielectric properties of prepared composites are evaluated for different compositions of CaCu₃Ti₄O₁₂ (50, 35, 25, 15 wt%) and CoFe₂O₄ (0, 15, 25, 35 wt%) in silicone matrix. The dielectric constant found maximum (~ 50) for CCS-3 composite. The CaCu₃Ti₄O₁₂/CoFe₂O₄/silicone composites (0 and 35% CoFe₂O₄) exhibited total shielding effectiveness (SE_T ~ 6 dB) corresponds to 75% shielding efficiency in X-band. By introducing magnetic filler with CaCu₃Ti₄O₁₂ in silicone matrix, better EMI attenuation is remarkably achieved. The shielding mechanism displays synergistic contribution of magnetic particles, colossal dielectric particles, and insulating elastomeric matrix. This work provides an avenue for developing better electromagnetic radiation shielding material for wearable electronics, and dielectric resonators.

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The progress of the automated industry produces undesired electromagnetic interference (EMI) that distresses the end-users and functionality of electronic devices. This article develops new composite based on a polyaniline matrix and lithium-substituted magnesium ferrite (Mg0.8Li0.2Fe2O4) nanofiller. The composite was designed to contain both electric and magnetic sources by including polarizable groups in the PANI structure and by loading this matrix with magnetic nanoparticles, respectively. Magnetic analyses indicated a saturation magnetization and coercivity of 32.5 emu gm⁻¹ and 32 Oe, respectively, for the ferrite nanoparticles which reduces to magnetization of 13.5 emu gm⁻¹ with the composite formation. These novel composites are investigated from the point of view of their EMI shielding properties, showing the high shielding effectiveness of 73 dB in X-band frequency region. The composite’s remarkable shielding qualities make it a very promising material for a variety of applications, including radar absorption and stealth technology.

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Si is the n-type dopant of choice for GaN and β-Ga₂O₃. However, in (Al,Ga)N and β-(Al,Ga)₂O₃ alloys, when the Al content is increased, the n-type conductivity produced by the added Si impurities is efficiently compensated. The experimentally determined critical Al fractions are about 70% for the (Al,Ga)N alloys and as low as 25% for the β-(Al,Ga)₂O₃ alloys. AlN and Al₂O₃ are well known to be poorly n-type dopable even with Si, but the detailed compensation mechanisms in the alloys are not necessarily the same as in the compounds. This short review discusses recent research in Si-doped (Al,Ga)N and β-(Al,Ga)₂O₃ alloys in the light of the compensation phenomena caused by Si DX center and cation vacancy formation.

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Total X-Ray Fluorescence (TXRF) is a non-destructive technique for the characterization of metallic contaminants on bare silicon wafers. TXRF is sensible to roughness leading to a diffraction phenomenon. In this study, the effects of roughness on TXRF analysis were evaluated with various rough silicon wafers produced by microelectronic processes of grinding, wet cleaning and chemical mechanical polishing. TXRF parameters rise as roughness increases, starting from 3 nm RMS (Root Mean Square) roughness. On spectra, characteristic Si (silicon wafer) and W (TXRF anode) peaks widen. Secondary peaks, sum/escape peaks appear, inducing interferences with Al, Cu, Zn and background noise increases as well. Through intentionally contaminated grinded wafers (RMS 12 nm) by spin-coating at selected concentrations, it was observed that most of the elements are quantified at 1 × 10¹² at/cm². At concentrations of 1 × 10¹⁰ at/cm² and 1 × 10¹¹ at/cm², only few elements are quantified due to the elevated background noise and interferences.

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This research article explores the comprehensive characterization of Mg₈Si₄ and Sr₂Mg₆Si₈ systems, delving into their structural, electrical, dynamical, optical, and thermoelectric properties. Employing GGA and HSE06 hybrid functional calculations alongside semiclassical Boltzmann technique calculations, the study reveals intriguing insights. Through examination of cohesive and formation energies, it is established that Sr₂Mg₆Si₈ exhibits the most stable condition. Phonon dispersion confirms the structural stability of both compounds. Mg8Si4 possesses an indirect band gap of 0.222 eV, whereas Sr₂Mg₆Si₈ showcases a direct band gap of 0.752 eV under HSE06 analysis. Notably, Sr2Mg6Si8 displays superior electrical conductivity and Seebeck coefficient despite low lattice thermal conductivity, resulting in a promising thermoelectric figure of merit (ZT) of 0.64 at 700 K. Moreover, the composition Sr2Mg6Si4 exhibits a notable Power Factor of 4 × 10¹² WK⁻² m⁻¹ s⁻¹ at 700 K, highlighting its potential for thermoelectric applications.

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In this study, In718/LaB₆ composite coatings with LaB₆ content of 0–8 wt% were prepared on In718 substrate by laser cladding method, and the mechanism of LaB₆ strengthening of In718 nickel-based high-temperature alloy was investigated by studying the phase composition, microstructure, microhardness, and wear resistance of the coatings. The results show that the addition of LaB₆ reduces the G/R ratio and promotes the formation of equiaxed grains. The best wear resistance was achieved at 6 wt% of LaB₆, with a wear rate of 4.59 × 10⁻⁴ mm³/N m. The maximum microhardness of the coating was achieved at 8 wt%, with an increase of 52.7% in the average microhardness as compared to that of the substrate. However, the excessive addition of LaB₆ promotes a non-uniform tissue distribution, which negatively affects the wear resistance of the coatings.

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Nanocomposite Al–Si–N thin films were deposited on SS 304, silicon and quartz substrates through magnetron sputtering. Silicon addition in AlN has transformed the coating structure from a single-phase coating into a nanocomposite structured film. It affected the phase formation and interband electronic transition in the Al–Si–N thin film. XPS study suggests the formation of Al–N, Si–N and composite Al–Si–N phases in the Al–Si–N film. The Urbach energy increases from 535 to 763 meV with addition of Si, for nanocomposite Al–Si–N film. No significant change in hardness and microstructure were observed up to 400 °C. The Al–Si–N film showed good hydrophobicity on both SS 304 and quartz substrates along with high hardness values. Low wettability and high strength make them a potential candidate for protective optical coatings as they are optically transparent too.

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A thermally induced phase separation method was successfully developed to prepare spherical composite nylon 12 (PA12)/Nano-silica (Nano-SiO₂) powder. By comparing the performance of pure PA12 and composite PA12 powders, it was found that the introduction of Nano-SiO₂ can improve the sphericity of the composite PA12 powder, with a median particle size of 54–70 μm. Moreover, the presence of Nano-SiO₂ can induce the formation of more α-phase during the crystallization of PA12, and most of Nano-SiO₂ was coated by PA12 molecular chains during the solidification crystallization process, which improved the crystallization temperature and crystallinity of the composite PA12 powder. When the amount of Nano-SiO₂ was 0.3 wt%, the composite PA12 powder had the highest crystallinity, and the powder spreading performance was the best.

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Mechanism diagram of the reaction between PA12 and Nano-SiO₂. In this figure, it was found that Nano-SiO₂ was treated with silane coupling agent can form siloxane, so that amino groups were grafted to the surface of Nano-SiO₂. The amino groups can react with carboxyl groups in PA12 to form amide bonds, thereby improving the interfacial adhesion between nano silica and PA12 matrix and enhancing their compatibility. Meanwhile, by comparing the microstructure before and after addition, it was found that the addition of Nano-SiO₂ increased the sphericity of the powder, and the powder particle size increased from 55.2 to 68.71 μm.

Bioactive glass 58S (BG58S) is widely recognised for its bioactivity and antibacterial properties, making it a promising material for orthopaedic implant applications. This study investigates the effects of incorporating silver (BG58S-2.5Ag) and cerium oxide (BG58S-5C) into BG58S on early-stage bacterial adhesion and subsequent bacterial growth inhibition. Using a high-intensity ball milling approach, BG58S was modified with 5% cerium oxide (CeO₂) and 2.5% silver (Ag) nanoparticles to create homogeneous BG58S-2.5Ag and BG58S-5C nanocomposites. Custom-made biomineral probes were employed to measure the bacterial adhesion within one second of contact with Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, using Atomic Force Microscopy (AFM). The results demonstrated that BG58S-2.5Ag showed significantly stronger transient adhesion to bacteria compared to BG58S, leading to a more effective long-term antibacterial response. Additionally, it was observed that the antibacterial effect of Ag commenced within one second of contact. These findings indicate a potential correlation between the rate of bond strengthening and cell wall penetration. This study highlights the potential for enhancing the effectiveness of antibacterial implant surfaces for various biomaterial applications.

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Due to their excellent mechanical properties and biodegradability, biodegradable magnesium alloy vascular stents have become a hot topic in current research on vascular stent material. However, the further application of magnesium alloy is limited by its rapid degradation rate and insufficient ability to promote surface endothelialization. This study proposed a strategy of co-depositing a PDA-LYS coating on the surface of magnesium alloy treated with an alkaline pre-heating process. Experimental results demonstrated that the PDA-LYS composite coating significantly improved the corrosion resistance of the magnesium alloy. Furthermore, with the increase in LYS content in the samples, the coating facilitated the adhesion and proliferation of endothelial cells and effectively inhibited the excessive proliferation of pathological smooth muscle cells. In summary, the PDA-LYS composite coating had a positive impact on the biocompatibility of magnesium alloy, which has offered a new approach for surface modification of magnesium alloy vascular materials.

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