Fabrication of polyetheretherketone(PEEK)-based 3D electronics with fine resolution by a hydrophobic treatment assisted hybrid additive manufacturing method

Additive manufacturing(AM)is a free-form technology that shows great potential in the integrated creation of three-dimensional(3D)electronics.However,the fabrication of 3D conformal circuits that fulfill the requirements of high service temperature,high conductivity and high resolution remains a challenge.In this paper,a hybrid AM method combining the fused deposition modeling(FDM)and hydrophobic treatment assisted laser activation metallization(LAM)was proposed for manufacturing the polyetheretherketone(PEEK)-based 3D electronics,by which the conformal copper patterns were deposited on the 3D-printed PEEK parts,and the adhesion between them reached the 5B high level.Moreover,the 3D components could support the thermal cycling test from-55℃ to 125℃ for more than 100 cycles.Particularly,the application of a hydrophobic coating on the FDM-printed PEEK before LAM can promote an ideal catalytic selectivity on its surface,not affected by the inevitable printing borders and pores in the FDM-printed parts,then making the resolution of the electroless plated copper lines improved significantly.In consequence,Cu lines with width and spacing of only60μm and 100μm were obtained on both as-printed and after-polished PEEK substrates.Finally,the potential of this technique to fabricate 3D conformal electronics was demonstrated.

Quantitative analysis of steel and iron by laser-induced breakdown spectroscopy using GA-KELM

According to the multiple researches in the last couple of years, laser-induced breakdown spectroscopy(LIBS) has shown a great potential for rapid analysis in steel industry.Nevertheless, the accuracy and precision may be limited by complex matrix effect and selfabsorption effect of LIBS seriously. A novel multivariate calibration method based on genetic algorithm-kernel extreme learning machine(GA-KELM) is proposed for quantitative analysis of multiple elements(Si, Mn, Cr, Ni, V, Ti, Cu, Mo) in forty-seven certified steel and iron samples.First, the standardized peak intensities of selected spectra lines are used as the input of model.Then, the genetic algorithm is adopted to optimize the model parameters due to its obvious capability in finding the global optimum solution. Based on these two steps above, the kernel method is introduced to create kernel matrix which is used to replace the hidden layer's output matrix. Finally, the least square is applied to calculate the model's output weight. In order to verify the predictive capability of the GA-KELM model, the R-square factor(R^2), Root-meansquare Errors of Calibration(RMSEC), Root-mean-square Errors of Prediction(RMSEP) of GAKELM model are compared with the traditional PLS algorithm, respectively. The results confirm that GA-KELM can reduce the interference from matrix effect and self-absorption effect and is suitable for multi-elements calibration of LIBS.

A Jacobi Spectral Collocation Method for Solving Fractional Integro-Differential Equations

The aim of this paper is to obtain the numerical solutions of fractional Volterra integrodifferential equations by the Jacobi spectral collocation method using the Jacobi-Gauss collocation points.We convert the fractional order integro-differential equation into integral equation by fractional order integral,and transfer the integro equations into a system of linear equations by the Gausssian quadrature.We furthermore perform the convergence analysis and prove the spectral accuracy of the proposed method in L∞norm.Two numerical examples demonstrate the high accuracy and fast convergence of the method at last.

Jacobi Collocation Methods for Solving Generalized Space-Fractional Burgers Equations

The aim of this paper is to obtain the numerical solutions of generalized space-fractional Burgers' equations with initial-boundary conditions by the Jacobi spectral collocation method using the shifted Jacobi-Gauss-Lobatto collocation points. By means of the simplifed Jacobi operational matrix, we produce the diferentiation matrix and transfer the space-fractional Burgers' equation into a system of ordinary diferential equations that can be solved by the fourth-order Runge-Kutta method. The numerical simulations indicate that the Jacobi spectral collocation method is highly accurate and fast convergent for the generalized space-fractional Burgers' equation.

Effects of Different Vermicompost Rates on Growth,2-Acetyl-1-Pyrroline,Photosynthesis and Antioxidant Responses of Fragrant Rice(Oryza sativa L.)Seedling

Vermicompost is an organic fertilizer contains multiple nutrient elements.However,the application of vermicompost in fragrant rice production is rarely reported.In order to study the effects of vermicompost application on fragrant rice(Oryza sativa L.)seedling performances,present study was conducted with two fragrant rice cultivars and four vermicompost rate treatments(0(CK),2.5(Wo1),5.0(Wo2)and 10.0(Wo3)g kg−1).The results showed that vermicompost treatments significantly increased dry weight of fragrant rice seedling by 8.31–32.56%compared with CK.21.10–59.13%higher net photosynthetic rates and 10.66–59.16%higher chlorophyll contents(chlorophyll a,chlorophyll b and total chlorophyll)were recorded in vermicompost treatments than CK.Application of vermicompost also significantly increased 2-acetyl-1-pyrroline(2-AP,the key compound of fragrant rice aroma)content and reduced the transcript level of gene BADH2 which related to 2-AP biosynthesis in fragrant rice seedling.Moreover,compared with CK,vermicompost treatments enhanced activities of superoxide dismutase,peroxidase,catalase by 24.42–28.66%,24.98–25.73%and 22.45–23.57%,respectively.11.54–40.53%lower malonaldehyde contents were recorded in vermicompost treatments in related to CK.In conclusion,vermicompost improved growth,increased 2-AP content and might enhance stress resistant of fragrant rice seedling.

Recent progress on fluorescent probes for viruses

Viruses are ubiquitous in human life. Some viruses can be used as vectors of genetic engineering and specific pesticides. Other viruses trigger a variety of diseases in humans, animals and plants, resulting in high infection rates and mortality. Therefore, convenient, accurate and rapid detection of viruses is of great significance for the diagnosis and treatment of subsequent diseases. In contrast to traditional methods of detection, which rely on time-consuming and complex techniques such as polymerase chain reaction (PCR), fluorescent probes and imaging methods generate real-time results, with high specificity, and have been widely used in viral detection. In this review, the application of viral fluorescent probes in analyzing the molecular structure, detection and biological imaging is discussed. In particular, we categorized the probes based on their specificity for human and plant viruses, reviewing the latest findings and analyzing their limitations. The potential of fluorescent molecular probes in the treatment of viral disease and environmental analysis, and their possible combinations with protein and immune technology are discussed.

Heptamethine cyanines in bioorthogonal chemistry

Due to their excellent fluorescence properties and biological function,cyanine dyes have been widely applied in biological imaging.Heptamethine cyanine(Cy7)dyes,as a type of classic near-infrared(NIR)fluorescent dyes,are considered as one of the effective fluorescent tools in the living organisms due to their good biocompatibility and very low background interference.Bioorthogonal reactions performed in living cells and tissues have developed by leaps and bounds in recent years.The NIR fluorescent labeling technique involving cyanine has attracted widespread attention.This review summarizes their recent application in the field of bioorthogonal imaging,mainly concluding Cy7-type dyes,labeling strategy,bioimaging application,etc.We expect this work can provide some helps for the studies of NIR bioorthogonal reaction in vivo.

Influence of tungsten particle size on microstructure and mechanical properties of high strength and tough tungsten particle-reinforced nickel-based composites by laser-direct energy deposition

Tungsten(W)particle-reinforced nickel(Ni)-based composites were fabricated via laser-direct energy de-position(L-DED).The influence of the W particle size on the microstructure and mechanical properties of the deposited samples was systematically studied.The results indicate that refining the W particle size could refine theγ-Ni grains and subgrains,thin the(Ni,Cr)_(4)W interface layer,and increase the disloca-tion density of the intergranular matrix,thus improving the tensile strength and elongation of the L-DED samples.As W particle size decreased from 75 to 150μm to 6.5-12μm,the tensile strength and elonga-tion of the deposited samples increased by 150 MPa and 2.9 times to 1347.6±15.7 MPa and 17.5±0.4%,respectively.Based on the properties of the interface(Ni,Cr)_(4)W,a load-transfer efficiency factor suitable for this composite was proposed and the load-transfer strengthening formula was optimized.A quanti-tative analysis of the strengthening mechanisms was established considering load-transfer strengthening,Hall-Petch strengthening,thermal-mismatch strengthening,and solid-solution strengthening.The calcu-lated contribution of each strengthening mechanism to the yield strength and theoretical calculations were in good agreement with the experimental data.The article breaks the bottleneck of poor plasticity of W particle-reinforced Ni-based composites prepared by L-DED and provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites with excellent mechanical properties.

Effect of rotation angle on surface morphology, microstructure, and mechanical properties of Inconel 718 alloy fabricated by high power laser powder bed fusion

Rotation angle of the laser scan direction between two adjacent layers is a key controlling parameter during the high-power (≥ 1 kW) laser powder bed fusion (HP-LPBF) process. This study investigates the influences of rotation angles (θ = 0°, 45°, 90°, 105°) on the surface morphology, microstructure, and mechanical properties of Inconel 718 (IN718) alloy produced by HP-LPBF. Results show that adopting low rotation angles (e.g., 0° and 45°) is prone to relatively poor surface finish and lack-of-fusion defects, whereas adopting high rotation angles (e.g., 90° and 105°) induces smaller surface roughness and better relative density. Each case reveals a noticeable edge effect but the maximal heights witness a downward trend with the increase of rotation angle. There are some minor differences in the primary dendrite arm spacing and grain morphology by varying the rotation angles. Moreover, the tensile property is slightly enhanced as the rotation angle increases. The present work suggests that high rotation angles like 90° and 105° would probably be more favorable for the 1 kW HP-LPBF process than rotation angles with relatively low values.

Weldability, microstructure and mechanical properties of laser-welded selective laser melted 304 stainless steel joints

Laser welding is a promising process for joining small components produced by selective laser melting (SLM) to fabricate the large-scale and complex-shaped parts. In the work, the morphology, microstructure, microhardness, tensile properties and corrosion resistance of the laser welded stress-relieved SLMed 304 stainless steel joints are investigated, as the different sections of stress-relieved SLMed 304 stainless steel are joined. Results show that the SLMed 304 stainless steel plates have a good laser weldability. The microstructure of laser-welded joints consists of the cellular dendrites in austenite matrix within columnar grains, exhibiting a coarser dendrite structure, lower microhardness (~220HV) and tensile properties (tensile strength of ~750 MPa, and area reduction of ~27.6%), but superior corrosion resistance to those of SLMed plates. The dendrite arm spacing of the joints varies from ~3.7μm in center zone, to ~5.0 (xm in fusion zone, to ~2.5 in epitaxial zone. The SLMed anisotropy shows a negligible effect on the microstructure and performance of the laser-welded joints. The laser welding along the building directions of the SLMed base plates can induce a slightly finer dendritic structure and higher tensile properties.

Cracking behavior and control of β-solidifying Ti-40Al-9V-0.5Y alloy produced by selective laser melting

Aβ-solidifying Ti-40 Al-9 V-0.5 Y(at.%)alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting(SLM)in this study.The influence factors for cracking sensitivity,cracking behavior and crack inhibition mechanism were investigated.The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes.The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode.Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility ofβ-solidifyingγ-Ti Al alloys during SLM.On this basis,the formation and inhibition mechanism of solidification and cold cracking are proposed.Finally,the crackfree Ti-40 Al-9 V-0.5 Y sample with fine equiaxed microstructures and favorable mechanical properties(microhardness of 542±19 HV,yield strength of 1871±12 MPa,ultimate strength of 2106±13 MPa and ultimate compressive strain of 10.89±0.57%)can be produced by SLM.The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.

Recent progress and future perspectives of flexible metal‐air batteries

With the rapid development of wearable and intelligent flexible electronic devices(FEDs),the demand for flexible energy storage/conversion devices(ESCDs)has also increased.Rechargeable flexible metal‐air batteries(MABs)are expected to be one of the most ideal ESCDs due to their high theoretical energy density,cost advantage,and strong deformation adaptability.With the improvement of the device design,material assemblies,and manufacturing technology,the research on the electrochemical performance of flexible MABs has made significant progress.However,achieving the high mechanical flexibility,high safety,and wearable comfortability required by FEDs while maintaining the high performance of flexible MABs are still a daunting challenge.In this review,flexible Zn‐air and Li‐air batteries are mainly exemplified to describe the most recent progress and challenges of flexible MABs.We start with an overview of the structure and configuration of the flexible MABs and discuss their impact on battery performance and function.Then it focuses on the research progress of flexible metal anodes,gel polymer electrolytes,and air cathodes.Finally,the main challenges and future research perspectives involving flexible MABs for FEDs are proposed.

南海东海岛近海固氮细菌多样性及对菜心的促生作用

海洋固氮细菌在自然界氮循环中发挥着重要作用,筛选和开发海洋固氮促生的菌种资源,对于生物菌肥的开发应用和农业生产具有重要意义。[目的]研究海洋固氮细菌的生物多样性及对陆地作物的促生作用,筛选优良的植物根际促生菌株。[方法]通过形态特征、生理生化试验和16S rRNA基因序列比对进行菌属鉴定;将解磷、解钾、产蛋白酶和纤维素酶等性能优良的菌株作为菜心盆栽试验的组合菌液,探究对菜心能否起促生作用。[结果]本研究从南海东海岛的海岛沉积物中筛选出18株固氮菌,分布在6个属9种,不动杆菌属4株,假交替单胞菌属1株,芽孢杆菌属8株,嗜冷杆菌属1株,海单胞菌属1株,交替单胞菌属3株。菜心幼苗经过组合菌剂的浇灌,在茎高、茎粗、最大叶宽和最大叶长4个指标均表明对菜心有显著的促生作用。其中,以芽孢杆菌属和不动杆菌属的菌株在菜心的生长过程中起关键的促进作用,对菜心的促生性能最佳。[结论]南海近海具有种类丰富多样的固氮细菌,以芽孢杆菌属和不动杆菌属的菌株促生作用最为显著,具有开发成微生物菌肥的潜力,为优良的海洋促生微生物菌种资源的定向利用及蔬菜的无公害生产提供重要依据。

Controllable in-situ aging during selective laser melting: Stepwise precipitation of multiple strengthening phases in Inconel 718 alloy

A controllable in-situ aging treatment of Inconel 718 alloy was successfully developed by governing the types and times of the thermal cycles during selective laser melting(SLM).The sequential precipitation of γ’,composite phase of primary/secondary γ’ coated by a γ " shell,and γ" occurs as the times of vertical thermal cycles increase when laser peak temperature(Tp)is between the precipitation temperature of strengthening phase(Tpre)and liquid temperature(T_L),which causes an increase in microhardness by 40 HV.Also,short-term aging mechanisms on three types of strengthening phases are proposed based on a great number of vacancies in the matrix.