Material In Substrate Research Articles

Emergency control of dinoflagellate bloom in freshwater with chlorine enhanced by solar radiation: Efficiency and mechanism

Dinoflagellate requires a lower temperature and blooms frequently in the spring and autumn compared to regular cyanobacteria. The outbreak of dinoflagellate bloom will also lead to the death of some aquatic organisms. However, research on freshwater dinoflagellates is still lacking due to the challenges posed by classification and culture in laboratory. The removal effect and mechanism of Peridinium umbonatum (P. umbonatum, a typical dinoflagellate) were investigated using solar/chlorine in this study. The effect of simulated solar alone on the removal of algae was negligible, and chlorine alone had only a slight effect in removing algae. However, solar/chlorine showed a better removal efficiency with shoulder length reduction factor and kmax enhancement factor of 2.80 and 3.8, respectively, indicating a shorter latency period and faster inactivation rate for solar/chlorine compared to solar and chlorine alone. The removal efficiency of algae gradually increased with the chlorine dosage, but it dropped as the cell density grew. When the experimental temperature was raised to 30 °C, algal removal efficiency significantly increased, as the temperature was unsuitable for the survival of P. umbonatum. Attacks on cell membranes by chlorine and hydroxyl radicals (•OH) produced by solar/chlorine led to a decrease in cell membrane integrity, leading to a rise in intracellular reactive oxygen species and an inhibition of photosynthetic and antioxidant systems. Cell regeneration was not observed in either the chlorine or solar/chlorine systems due to severe cell damage or cysts formation. In addition, natural solar radiation was demonstrated to have the same enhancing effect as simulated solar radiation. However, the algal removal efficiency of solar/chlorine in real water was reduced compared to 119 medium, mainly due to background material in the real water substrate that consumed the oxidant or acted as shading agents.

The theory of continuous distributions of composite defects

This work undertakes the analysis of continuous media that carry simultaneously two different material or geometric structures in the same material substrate. Even when these two structures are individually perfectly uniform and homogeneous, their combination may result in a non-uniform assembly. Thus, in contradistinction to the classical interpretation of material defectivity as a manifestation of material inhomogeneity, the lack of uniformity of a composite is physically interpreted as the presence of a different kind of continuously distributed material defects. Various quantitative measures of misalignment and lack of uniformity are proposed associated with solid constituents of different symmetry types. Finally, from a more formal point of view, the use of double groupoids and their associated double Lie algebroids is suggested as the natural setting for further developments of the theory.

Deciphering the role of moringa leaf powder as a supplement in the cotton waste substrate for the growth and nutrition of king oyster mushroom

The addition of supplementing material in the substrate is an efficient way to increase mushroom yield and nutrition. The addition of moringa leaf powder (MLP) could boost the yield and nutrition of mushrooms. To improve the nutritional properties and yield of king oyster mushroom, moringa leaf powder as supplementing material in the cotton waste substrate was added with different ratios to standardize the supplementing material in the substrate. In the present research, the impact of moringa leaf powder at various concentrations (2%,4%,6%,8% and 10%) in cotton waste were used to check the suitability of king oyster mushroom production and quality. Results showed that addition of MLP substantially increased production and nutritional value of mushroom. The MLP at 6% on dry weight basis in cotton waste showed markedly higher total yield, biological efficiency as compared to control or cotton waste alone. The addition of 6% MLP in cotton waste also enhanced the Vitamin C, Folic acid, protein, carbohydrate, fats, fibers, ash and minerals (N, Na, K, Ca, Zn, Mg, Mn, Fe and P) of king oyster mushroom, Moreover, total phenolic contents and antioxidant activity were improved in King oyster mushroom fruit bodies. Vitamin D was quantified by HPLC-UV chromatograph in P. eryngii. Vitamin-D content was also varied with MLP addition in the substrate.. In conclusion, MLP addition in substrate could be an effective approach for the increase in production and nutritional quality of mushrooms.

Migration of adhesive material in electrostatically actuated MEMS switch

Microelectromechanical systems (MEMS) switches are attractive for many applications including radio frequency and microwave systems, logic devices, acceleration sensing and electric protection. However, low reliability limits the introduction of these devices into the commercial use. For two decades of research, many reliability issues have been successfully overcome, but some aspects have received little attention. The paper describes a failure mechanism of electrostatically actuated MEMS switch related to the migration of adhesive material in a dielectric substrate. The phenomenon is demonstrated for the device with Au and Pt electrodes deposited on Cr adhesion layer. After 102–105 working cycles, nanoscale structures consisting of Cr and C appear at the gate. The structures grow and coalesce into micron-sized formations that touch the beam during actuation and cause stiction or short circuiting. The material transfer takes place not only in the gap between the electrodes, but also around the gate and its connecting line, where Cr and C agglomerate into spots and droplets. In addition, the adhesive material migrates under the Au and Pt films, causing the delamination of electrodes from the substrate. A possible explanation of the described effect is the drift of Cr at the SiO2 surface under electric field. Chromium is widely used in microtechnology, but the field-induced migration was not reported previously. To all appearance, it became possible due to the features of the fabrication process. The conditions for the migration must be clarified in order to avoid this reliability issue for MEMS switches of various types and other microfabricated devices.

Efficient strain modulation of 2D materials via polymer encapsulation

Strain engineering is a promising method to manipulate the electronic and optical properties of two-dimensional (2D) materials. However, with weak van der Waals interaction, severe slippage between 2D material and substrate could dominate the bending or stretching processes, leading to inefficiency strain transfer. To overcome this limitation, we report a simple strain engineering method by encapsulating the monolayer 2D material in the flexible PVA substrate through spin-coating approach. The strong interaction force between spin-coated PVA and 2D material ensures the mechanical strain can be effectively transferred with negligible slippage or decoupling. By applying uniaxial strain to monolayer MoS2, we observe a higher bandgap modulation up to ~300 meV and a highest modulation rate of ~136 meV/%, which is approximate two times improvement compared to previous results achieved. Moreover, this simple strategy could be well extended to other 2D materials such as WS2 or WSe2, leading to enhanced bandgap modulation.

A 3D-printed stretchable strain sensor for wind sensing

Stretchable strain sensors with large strain range, high sensitivity, and excellent reliability are of great interest to applications in soft robotics, wearable devices, and structure-monitoring systems. Unlike conventional template lithography-based approaches, 3D-printing can be used to fabricate complex devices in a simple and cost-effective manner. In this paper, we report 3D-printed stretchable strain sensors that embed a flexible conductive composite material in a hyper-elastic substrate. Three commercially available conductive filaments are explored, among which the ETPU from Rubber3D Printing, Sweden, shows the highest sensitivity (gauge factor of 20), with a working strain range of 0%–12.5%. The ETPU strain sensor exhibits an interesting behavior where the conductivity increases with the strain. In addition, the resistance change of the ETPU sensor in a doubly-clamped configuration in response to a wind stimulus is characterized, and the sensor shows sensitivity to wind velocity beyond 3.5 m s−1. The experimentally identified material parameters are used in finite-element modeling and simulation to investigate the behavior of the 3D-printed stretchable strain sensor when subjected to wind loading. In particular, the model-predicted sensor output at different wind speeds, obtained with the computed sensor strain and the experimentally characterized strain-resistance relationship, achieves good match with the experimental data.

Ultrathin Broadband Absorber Using Frequency-Selective Surface and Frequency-Dispersive Magnetic Materials

The bandwidth of frequency-selective surface (FSS)-based absorber decreases when high permittivity material is used to reduce the thickness of the absorber. A solution of this thickness-bandwidth dilemma was presented by using resistive FSS layer and frequency-dispersive magnetic material (FDMM) in substrate. The FDMM was designed for a certain profile of complex permeability, and the FDMM substrate has both high permeability and permittivity for thickness reduction and near frequency-nondispersive input susceptance for bandwidth expanding at low frequencies. A 2.3 mm thick FSS-based FDMM absorber was designed and fabricated, which achieved a broad absorption band of 4–15 GHz (3.75:1) with −10 dB reflectivity. In terms of the same bandwidth ratio, the thickness of FSS-based FDMM absorber is only $0.031\lambda _{L}$ against the thickness of $0.114\lambda _{L}$ of conventional FSS-based absorber.

Mechanical Reliability of Embedded Array Capacitors in Ultrahigh-Performance Microprocessors

Increasing power delivery and performance requirements for next-generation Intel microprocessors has led to the need for a high-capacitance low-inductance decoupling option very close to the die. An embedded array capacitor (EAC) is a large array capacitor embedded in the high-density interconnect (HDI) substrate core and provides a low-inductance path to the die. This paper describes technology development challenges encountered while enabling EACs on Intel's advanced microprocessors. Various package interfaces resulting from the EAC embedding showed very high stress and propensity to delaminate. These defects were addressed by tailoring suitable materials and process modifications during the manufacturing process. Expansion of the embedding material in the HDI substrate resulted in high C4 area warpage. This led to issues such as solder bump bridging, underfill voids, and reliability fails. The technology development challenges and the solution paths described in this paper are very useful to industry in understanding the integration of advanced decoupling options in ultrahigh-performance microprocessor packages.

FCCSP용 기판의 warpage에 미치는 설계인자와 두께편차 영향에 대한 수치적 해석

본 논문에서는 FCCSP용 기판의 휨에 미치는 설계인자와 두께편차의 영향도를 분석하고 최적설계조건을 도출하기 위해 유한요소법에 의한 수치해석을 사용하였고 다구찌법에 의한 파라메타설계와 분산분석을 수행하였다. 해석 결과에 의하면 휨에 미치는 영향은 코어재료가 가장 크고 층별 두께(솔더레지스트, 프리프레그, 회로층)의 영향도는 낮은 것으로 분석되었다. 이때 솔더 레지스트와 프리프레그의 두께는 감소할수록 기판 휨은 감소하지만 회로층의 두께는 증가할수록 기판 휨이 감소하였다. 또한, 기판 휨에 대한 두께편차의 영향도 분석결과에 의하면 두께편차의 조합에 따라 기판휨은 최대 40%까지 증가하였다. 이것은 비록 개별 층의 두께편차가 기판품질 수준에 부합하더라도 두께편차 조합조건에 따라 기판 휨이 크게 달라질 수 있다는 것을 의미한다. 따라서, 제조공정에서 기판 휨을 줄이기 위해서 기판두께편차는 최적화되고 정밀하게 제어되어야 한다. In this paper, numerical analysis by finite element method, parameter design by the Taguchi method and ANOVA method were used to analyze about effect of design deviations and thickness variations on warpage of FCCSP substrate. Based on the computed results, it was known that core material in substrate was the most determining deviation for reducing warpage. Solder resist, prepreg and circuit layer were insignificant effect on warpage relatively. But these results meant not thickness effect was little importance but mechanical properties of core material were very effective. Warpage decreased as Solder resist and circuit layer thickness decreased but effect of prepreg thickness was conversely. Also, these results showed substrate warpage would be increased to maximum 40% as thickness deviation combination. It meant warpage was affected by thickness tolerance under manufacturing process even if it were met quality requirements. Threfore, it was strongly recommended that substrate thickness deviation should be optimized and controlled precisely to reduce warpage in manufacturing process.

Optimization of Rotational Speed in the Growing of the Thin Film Using Sol Gel Method which is Prepared with Spin Coating

We investigated the effects of the rotational speed in the spin coating process for growing the BZT thin film. In this process, the rotational speed is taken to be 2000 rpm, 3000 rpm and 4000 rpm while the number of layer is kept constant in five layers. We also discuss the effect of the layers number in the growing of the BZT thin films. For this purpose, we take the layers number to 5, 10 and 15 layers and take the constant rotational speed of 4000rpm. In order to characterize the formed BZT thin film, the composition, crystal structure and morphological tests are performed. We found that the increasing of the rotational speed then the deposited material in the Si substrate is decreased. As a result, the X-ray intensity in certain orientation is also decreased which is indicates that the probability to form the crystal in a certain orientation is influenced by deposited material in the Si substrate. The measured grains size of the BZT thin film almost similar for the three rotational speeds. However, in the variation of layer numbers, the grain size is increasing as the increasing of layers number.

Numerical Study on Heat Transfer and Lubricant Depletion in a Heat Assisted Magnetic Recording System with Multilayer Disk Structure

Heat transfer and lubricant depletion in a HAMR system with multilayer disk substrate are numerically simulated in this study. Cases under two types of multilayer disk substrates with different materials on the top layer as well as different laser powers are examined. The results show the significant effects of the material property and the laser power. Compared with pure glass disk substrate, larger thermal conductivity of top-layer material in the multilayer disk substrate causes faster heat conduction and thus substantial reductions in the temperature increase and lubricant depletion on the top surface. Hence it is necessary and important to incorporate the real multilayer structure in modeling heat transfer and lubricant depletion in practical HAMR systems.

The role of sulphonated polymer and macrovoid-free structure in the support layer for thin-film composite (TFC) forward osmosis (FO) membranes

A new approach to fabricate thin film composite (TFC) membranes via interfacial polymerization for forward osmosis (FO) applications has revealed that it is possible to design TFC-FO membranes with fully sponge-like structure and likely anti-fouling characteristics while maintaining a high water flux. Not only does the sulphonated material in the substrate of TFC-FO membranes play the key role to create macrovoid-free structure but also induces hydrophilic properties with enhanced water fluxes. It is found that the TFC-FO membranes containing a 50 wt% sulphonated material in the membrane substrate exhibit a fully sponge-like structure, while those with lower or without sulphonated content show finger-like structures. In terms of FO performance, the TFC-FO membranes with 50 wt% sulphonated material content can achieve the highest water flux of 33.0 LMH against DI water and 15 LMH against the 3.5 wt% NaCl model solution using 2 M NaCl as the draw solution tested under the pressure retarded osmosis (PRO) mode. The value of 15 LMH for seawater desalination is the highest reported so far. Despite the debates on whether TFC-FO membranes should possess a finger-like or sponge-like structure, it is proven that the degree of hydrophilicity of membrane substrates is a much stronger factor enhancing the water flux in FO tests. Meanwhile, a fully sponge-like structure with expected anti-fouling property is preferred for long-term membrane stability. Furthermore, the structural parameter indicating the internal concentration polarization (ICP) can be remarkably decreased with an increase in sulphonated material content in membrane substrates.

Characterization of water transport in gas diffusion media

An in-depth insight in the role of gas diffusion layers (GDLs) and its impact on the water management is a key issue for the optimization of fuel cells. A new ex situ test method is developed to investigate the water transport in gas diffusion media for polymer electrolyte membrane fuel cells (PEMFCs). This research is focused on properties of GDLs, which influence the water removal and water retention in the cell. Gas diffusion media are evaluated ex situ in terms of liquid water and water vapor transport employing a conventional PEMFC setup. The amount of water transported through a GDL and out of the cell is determined by the properties of the gas diffusion medium. GDL properties such as the GDL thickness have a significant impact on water transport behavior. Furthermore, high impregnation weight or an additional micro-porous layer (MPL) reduces water removal due to enhanced mass transport resistances. The composition and distribution of the impregnation material in the GDL substrate also play a crucial role. Water transport rates depend not only on the GDL properties but increase exponentially with cell temperature. Finally, a two-phase water transport model is proposed taking into account both diffusive gas phase and liquid water transport in diffusion media. Based on this model, ex situ data set in correlation with in situ performance in PEMFCs on dry operating conditions and guidelines towards new design concepts for gas diffusion media are deduced.

Ball-milling processing of nanocrystalline nickel hydroxide and its effects in pasted nickel electrodes for rechargeable nickel batteries

Nanocrystalline Ni(OH)2 powder synthesized by a chemical precipitation method was processed using the planetary ball milling (PBM), and the physical properties of both the ball-milled and unmilled Ni(OH)2 were characterized by scanning electron microscopy (SEM), specific surface area, particle size distribution, and X-ray diffraction. It was found that the PBM processing could significantly break up the agglomeration, uniformize the particle size distribution, increase the surface area, decrease the crystallite size, and reduce the crystallinity of nanocrystalline β-Ni(OH)2, which were advantageous to the improvement of the electrochemical activity of Ni(OH)2. The ball-milled nanocrystalline (BMN) Ni(OH)2 was then used to alter the microstructure of pasted nickel electrodes and improve the distribution of the active material in the porous electrode substrate. Electrochemical performances of pasted nickel electrodes with a mixture of BMN and spherical Ni(OH)2 as the active material were investigated, and were compared with those of pure spherical Ni(OH)2 electrodes. Charge/discharge tests showed that BMN Ni(OH)2 addition could enhance the charging efficiency, specific discharge capacity, discharge voltage, and high-rate capability of pasted nickel electrodes. This performance improvement could be attributed to a more compact electrode microstructure, better reaction reversibility, and lower electrochemical impedance, as indicated by SEM, cyclic voltammetry, and electrochemical impedance spectroscopy. Thus, it was an effective method to modify the microstructure and improve the electrochemical properties of pasted nickel electrodes by adding an appropriate amount of BMN Ni(OH)2 to spherical Ni(OH)2 as the active material.

The transformation of LiAlO 2 crystal structure in molten Li/K carbonate

LiAlO 2 powder is used as a matrix material in the electrolyte substrate of molten carbonate fuel cells (MCFCs), and LiAlO 2 are known to undergo phase transformations between the α-phase and γ-phase in molten Li/K carbonate. In order to understand the phenomena involved in this phase transformation of LiAlO 2, it is clear that it will be necessary to consider the fact that the solubility and mass transfer rate in molten Li/K carbonate differ between these two phases. Also, the solubility differs due to differences in the particle sizes of the LiAlO 2 powder, namely, the fine particles dissolve more easily than the large particles. The other factors conventionally considered are the partial pressure of CO 2 and the temperature of the surrounding gas. In the present paper, it has become possible that the seemingly complex phenomena of LiAlO 2 phase transformation within molten carbonate can be understood without any contradiction.