The rapid increase of operation speed, transmission efficiency, and power density of miniaturized devices leads to a rising demand for electromagnetic interference (EMI) shielding and thermal ...management materials in the semiconductor industry. Therefore, it is essential to improve both the EMI shielding and thermal conductive properties of commonly used polyolefin components (such as polyethylene (PE)) in electronic systems. Currently, melt compounding is the most common method to fabricate polyolefin composites, but the difficulty of filler dispersion and high resistance at the filler/filler or filler/matrix interface limits their properties. Here, a fold fabrication strategy was proposed to prepare PE composites by incorporation of a well-aligned, seamless graphene framework premodified with MXene nanosheets into the matrix. We demonstrate that the physical properties of the composites can be further improved at the same filler loading by nanoscale interface engineering: the formation of hydrogen bonds at the graphene/MXene interface and the development of a seamlessly interconnected graphene framework. The obtained PE composites exhibit an EMI shielding property of ∼61.0 dB and a thermal conductivity of 9.26 W m
K
at a low filler content (∼3 wt %, including ∼0.4 wt % MXene). Moreover, other thermoplastic composites with the same results can also be produced based on our method. Our study provides an idea toward rational design of the filler interface to prepare high-performance polymer composites for use in microelectronics and microsystems.
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IJS, KILJ, NUK, PNG, UL, UM
The rapid increase of operation speed, transmission efficiency, and power density of miniaturized devices leads to a rising demand for electromagnetic interference (EMI) shielding and thermal ...management materials in the semiconductor industry. Therefore, it is essential to improve both the EMI shielding and thermal conductive properties of commonly used polyolefin components (such as polyethylene (PE)) in electronic systems. Currently, melt compounding is the most common method to fabricate polyolefin composites, but the difficulty of filler dispersion and high resistance at the filler/filler or filler/matrix interface limits their properties. Here, a fold fabrication strategy was proposed to prepare PE composites by incorporation of a well-aligned, seamless graphene framework premodified with MXene nanosheets into the matrix. We demonstrate that the physical properties of the composites can be further improved at the same filler loading by nanoscale interface engineering: the formation of hydrogen bonds at the graphene/MXene interface and the development of a seamlessly interconnected graphene framework. The obtained PE composites exhibit an EMI shielding property of ∼61.0 dB and a thermal conductivity of 9.26 W m–1 K–1 at a low filler content (∼3 wt %, including ∼0.4 wt % MXene). Moreover, other thermoplastic composites with the same results can also be produced based on our method. Our study provides an idea toward rational design of the filler interface to prepare high-performance polymer composites for use in microelectronics and microsystems.
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IJS, KILJ, NUK, PNG, UL, UM
Infrared windows such as sapphire, aluminum oxynitride (AlON) and zinc sulfide (ZnS) have excellent optical properties, but restricted for application due to low thermal conductivity (<30 W/m °C). ...Diamond could provide a solution for overcoming the problems due to ultrahigh thermal conductivity (∼2000 W/m °C). In this paper, a finite element simulation software (ANSYS) was used to simulate the thermal shock behavior of the infrared materials and their composite with diamond coatings (0–0.04 mm in thickness). The performance in an extremely hot environment was simulated by analyzing the thermal distribution, temperature uniformity, and central stagnation temperature. A constant heat flow of 0.5 MW/m2 was applied to investigate the influence of coating thickness on thermal transfer. The results showed that the central stagnation temperatures of the single sapphire and the corresponding composite windows were the lowest. Temperature difference of the windows was mainly determined by the intrinsic thermal parameters, which became narrow with the increase of diamond thickness. Thermal stress and deformation of diamond films and the substrates were calculated and the results indicated that the diamond film can significantly improve the structural stability of these windows. For single diamond windows (1–5 mm in thickness), ultralow central stagnation temperatures of ∼86–226 °C were obtained even at ultrahigh heat flux of 2.0 MW/m2. Diamond film could greatly help to decreasing central temperature and improving the thermal uniformity. Related research could provide theoretical reference for the design and application of the “heat free” infrared window.
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•Sapphire has the lowest temperature under high heat flux among common traditional infrared ceramic materials.•Temperature of composite windows decreases significantly after diamond film coating.•Selection of heating surface is essential while single-side coating.•Thermal stress of diamond films and substrates decreases as diamond films thickening and makes windows more stable.•Diamond freestanding window can maintain low temperature under extremely high heat flux.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Highly sensitive wearable strain sensors based on graphene and its derivatives have shown great potential to be applied in home monitoring and electronic skin. To date, it still remains a technical ...challenge to achieve a reliable performance with high responsiveness at a small elastic strain for graphene strain sensors. Here we demonstrate the fabrication of micro/nanocrack-based strain sensors by using a porous thin film composed of graphene nanowalls (GNWs), which showed ultrahigh sensitivity with a gauge factor up to 8.6 × 10
4
at 4% strain. The ultrahigh gauge factor at such a small deformation can be attributed to the synergistic effect of micro/nanocrack evolution of GNW building blocks derived from the substrate's Poisson's ratio effect. This working mechanism is distinct from the general case where the cracks were created in an initially continuous film. The wearable GNW strain sensors were functionally presented as audio analog-to-digital converters for acoustic signature recognition and electronic skin devices to monitor physiological signals from the human body at high resolution.
Thin film strain sensors composed of GNWs grown by MPCVD, showing ultrahigh sensitivity which can be applied for acoustic signature recognition, as well as electronic skin devices to detect both subtle and large motions of the human body.
Sintering aid was very crucial to influence the microstructure and thus the optical property of the sintered optical ceramics. The purpose of this work was to explain the difference between the ...sintering aids of Li
and Y
on Al
O
N
(AlON) ceramic via reaction sintering method. The effects of LiAl
O
(LA) and Y
O
on the sintering of Al
O
-AlN system were carefully compared, in terms of X-ray diffraction (XRD), microstructure, density, X-ray photoelectron spectroscopy (XPS) and optical transmittance. According to the XPS and XRD lattice analysis, the chemical structure of the materials was not obviously affected by different dopants. We firstly reported that, there was obvious volume expansion in the Y
dopped AlON ceramics, which was responsible for the low transparency of the ceramics. Obvious enhancements were achieved using Li
aids from the results that Li: AlONs showing a higher transparency and less optical defects. A higher LA content (20 wt%) was effective to remove pores and thus obtain a higher transmittance (~86.8% at ~3.5 μm). Thus, pores were the main contributions to the property difference between the dopant samples. The importance of sintering aids should be carefully realized for the reaction sintering fabrication of AlON based ceramics towards high transparency.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Sintering aid was very crucial to influence the microstructure and thus the optical property of the sintered optical ceramics. The purpose of this work was to explain the difference between the ...sintering aids of Lisup.+ and Ysup.3+ on Alsub.23Osub.27Nsub.5 (AlON) ceramic via reaction sintering method. The effects of LiAlsub.5Osub.8 (LA) and Ysub.2Osub.3 on the sintering of Alsub.2Osub.3-AlN system were carefully compared, in terms of X-ray diffraction (XRD), microstructure, density, X-ray photoelectron spectroscopy (XPS) and optical transmittance. According to the XPS and XRD lattice analysis, the chemical structure of the materials was not obviously affected by different dopants. We firstly reported that, there was obvious volume expansion in the Ysup.3+ dopped AlON ceramics, which was responsible for the low transparency of the ceramics. Obvious enhancements were achieved using Lisup.+ aids from the results that Li: AlONs showing a higher transparency and less optical defects. A higher LA content (20 wt%) was effective to remove pores and thus obtain a higher transmittance (~86.8% at ~3.5 μm). Thus, pores were the main contributions to the property difference between the dopant samples. The importance of sintering aids should be carefully realized for the reaction sintering fabrication of AlON based ceramics towards high transparency.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Vicatia thibetica de Boiss is a Tibetan medicinal her!) and mainly contains chemical components such as flavonoids, ß-sitosterol and ferulic acid. It has good pharmacological effects such as ...anti-inflammatory, analgesic, anti-fatigue, anti-oxidation, anti-aging and enhancing immunity. Based on relevant domestic and foreign literature, this paper comprehensively reviews the main component, pharmacological activity and clinical prescription application of V thibetica de Boiss, to provide a reference for the in-depth research and comprehensive development and utilization of V thibetica de Boiss.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Comprehensive Summary
As the power density of electronic devices increases, there has been an urgent demand to develop highly conductive polymer composites to address the accompanying thermal ...management issues. Due to the ultra‐high intrinsic thermal conductivity, graphene is considered a very promising filler to improve the thermal conductivity of polymers. However, graphene‐based polymer composites prepared by the conventional mixing method generally have limited thermal conductivity, even under high graphene loading, due to the failure to construct efficient heat transfer pathways in the polymer matrix. Here, a spiral graphene framework (SGF) containing continuous and highly ordered graphene microtubes was developed based on a modified CVD method. After embedding into the epoxy (EP) matrix, the graphene microtubes can act as efficient heat pathways, endowing the SGF/EP composites with a high through‐plane thermal conductivity of 1.35 W·m−1·K−1 at an ultralow graphene loading of 0.86 wt%. This result gives a thermal conductivity enhancement per 1 wt% filler loading of 710%, significantly outperforming various graphene structures as fillers. In addition, we demonstrated the practical application of the SGF/EP composite as a thermal interface material for efficient thermal management of the light‐emitting diode (LED).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A 63-year-old man developed scrotal swelling that became bilateral over 2 months. His symptoms persisted after treatment for epididymitis, and he developed a scrotal fistula with drainage. ...Mycobacterium tuberculosis grew from the urine and fistula. His symptoms resolved and fistula closed with medical therapy. His case highlights the importance of early recognition, diagnosis and treatment of this form of extrapulmonary tuberculosis.
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