Stress evaluation of Through-Silicon Vias using micro-infrared photoelasticity and finite element analysis

The Through-SiliconVias (TSV) is a key component of three dimensional electronic packaging. Obtaining its stresses is very important for evaluating its reliability. A micro-infrared photoelasticity system with a thermal loading function was built and applied to characterize the stresses of the TSV structure. Through testing it was found that the stress of each TSV is different even if their fabrication technology is exactly the same, that different TSVs obtain their stress free states at different elevated temperatures, and that their stress free states are maintained even when the temperature is further elevated. A finite element model was used to quantitatively determine the stresses of a TSV under different stress-free temperatures. Different virtual photoelasticity fringe patterns were then created based on the principle of photoelasticity and the simulated stresses. Comparing the virtual fringe patterns with the experimental pattern, an appropriate virtual photoelasticity fringe pattern and the corresponding stresses of TSV were determined     

Effect of Oil Palm and Jute Fiber Treatment on Mechanical Performance of Epoxy Hybrid Composites

In this work, oil palm empty fruit bunch (EFB) and jute fibers were treated with 2-hydroxy ethyl acrylate (2-HEA) to improve interfacial bonding of oil palm EFB and jute fibers with epoxy matrix. Hybrid composites were fabricated by incorporation of modified oil palm EFB and jute fibers into an epoxy matrix by the hand lay-up technique. Mechanical (flexural and impact) and morphological properties of modified hybrid composites were measured. Results indicated that flexural and impact properties of modified fiber–reinforced hybrid composites improved as compared to untreated hybrid composites due to better fiber/matrix interfacial bonding, which was confirmed by scanning electron microscopy. We confirmed that treated oil palm/jute hybrid composite may be fabricated by advanced techniques such as resin transfer molding, extrusion, and injection molding for industrial applications in the automotive sector.     

Fabrication of core/shell hybrid organic–inorganic polymer microspheres via Pickering emulsion polymerization using laponite nanoparticles

Oil-in-water (o/w) emulsions of styrene, as monomer oil in water, were achieved successfully via Pickering emulsification with laponite nanoparticles as the sole inorganic stabilizers. The formed emulsions showed excellent stability not only against droplets coalescence (before polymerization) but also against microparticles coagulation (after polymerization). Generally, the number of composite polystyrene microparticles (PS) increased and their sizes decreased with the content of solid nanoparticles used in stabilizing the precursor o/w emulsions. This is consistent with the formation of rigid layer(s) of the inorganic nanoparticles around the PS microparticles thus a better stability was achieved. The composite microparticles were characterized using various techniques such as surface charge, stability, transmission electron microscope (TEM), scanning electron microscope (SEM) and Fourier transform infra-red (FT-IR). Coating films of the prepared latexes were applied to flat glass surfaces and showed reasonable adhesion compared to PS latex particles prepared with conventional surfactants. The effect of employed conditions on the features of the resulting emulsions in terms of stability and particle size has been discussed.     

Colloidal hybrid heterostructures based on II–VI semiconductor nanocrystals for photocatalytic hydrogen generation

Hydrogen generated through the photochemical cleavage of water using renewable solar energy is considered to be an environmentally friendly chemical fuel of the future, which neither results in air pollution nor leads to the emission of greenhouse gases. The photocatalytic materials for water cleavage are required to perform at least two fundamental functions: light harvesting of the maximal possible part of the solar energy spectrum and a catalytic function for efficient water decomposition into oxygen and hydrogen. Photocatalytic systems based on colloidal semiconductor nanocrystals offer a number of advantages in comparison with photoelectrochemical cells based on bulk electrodes: (i) a broad range of material types are available; (ii) higher efficiencies are expected due to short distance charge transport; (iii) large surface areas are beneficial for the catalytic processes; (iv) flexibility in fabrication and design which also allows for tuning of the electronic and optical properties by employing quantum confinement effects. The presence of co-catalysts on colloidal semiconductors is an important part of the overall design of the photocatalytic colloidal systems necessary to maximize the water splitting efficiency. This review article discusses the rational choice of colloidal nanoheterostructured materials based on light-harvesting II–VI semiconductor nanocrystals combined with a variety of metal and/or non-metal co-catalysts, with optimized light harvesting, charge separation, and photocatalytic functions.     

隔膜对双电层电容器和混合型电池-超级电容器的电化学性能的影响

隔膜是双电层电容器和混合型电池-超级电容器等电化学储能器件的重要组成元件.本文采用1 mol?L-1四乙基四氟硼酸铵的丙烯碳酸酯电解液制备了基于活性炭的扣式双电层电容器,并采用1 mol?L-1六氟磷酸锂锂离子电解液制备了(LiNi0.5Co0.2Mn0.3O2+活性炭)/石墨体系的混合型电池-超级电容器.研究了不同类型隔膜的物理化学性能,以及其对双电层电容器和混合型电池-超级电容器的电化学性能的影响.四种隔膜分别是无纺布聚丙烯毡、多孔聚丙烯薄膜、Al2O3涂层的聚丙烯薄膜和纤维素纸隔膜.进行了表面形貌、差示扫描量热、电解液吸液量和表观接触角测试表征.电化学测试表明,采用纤维素隔膜的双电层电容器具有最高的比电容和更优的倍率性能,电容器的自放电性能差别不大.而对于混合型电池-超级电容器,采用聚丙烯薄膜和无纺布聚丙烯毡隔膜器件的比容量比其它器件约高20%,且采用纤维素隔膜的器件自放电率最高.     

Rheological and antimicrobial properties of epoxy-based hybrid nanocoatings

The modification of nanocomposite coatings with fillers having unique characteristics in the polymeric matrix is a promising strategy to enhance the durability as well as to prevent the growth of microorganisms that decrease the stability of the materials. This study was conducted to evaluate the rheological and antimicrobial behavior of epoxy-based nanocomposite coatings filled with nanosilica, titanium oxide (TiO₂) and zinc oxide (ZnO) against Staphylococcus aureus and Escherichia coli. A rheometer was used for characterizing the rheological properties of the various fillers embedded epoxy nanocomposite coatings. All of the composites inhibited the growth of Staphylococcus aureus and Escherichia coli on modified Kirby Bauer antimicrobial testing, only when they are in contact with samples. Upon quantitative analysis, bioactive constituent dependent antimicrobial activity was observed which increased with the exposure of contact times. The epoxy/silica/TiO₂/ZnO (ESTZ) coating showed the highest bacterial reduction of more than 95% for 4 h of treatment. The bioactivity was decreased for the case of epoxy/silica/ZnO (ESZ) or epoxy/silica/TiO₂ (EST). The combined effect of the nanosilica, TiO₂, and ZnO shows the highest performance in terms of stress, viscosity and torque compared to the individual effect of these three fillers onto the epoxy. Results showed that the shear stress of ESZ, EST, epoxy/silica (ES), and ESTZ coating was increased by 4.4%, 7.7%, 32.2%, and 42%, respectively, compared to the neat epoxy (NE) coating. The torque versus strain curve also showed that the torque of ESTZ composites was the highest (0.52 mN m) compare to NE (0.36 mN m), ESZ (0.38 mN m), EST (0.40 mN m), and ES (0.45 mN m). The studies indicate that the epoxy-based thermoset nanocomposite coatings can be utilized as bactericidal surfaces for the industrial and medical purpose to reduce microbial growth.     

Low velocity impact response of flax/polypropylene hybrid roving based woven fabric composites: Where does it stand with respect to GRPC?

Flax-PP based thermally bonded roving (TBR) has a unique structure where the flax fibres remain twist-free and fully aligned along the roving axis. The present study describes an experimental investigation on the low velocity impact (LVI) behaviour of the TBR based woven fabric composites and compares the same with plain woven glass fabric reinforced PP composites (GRPC). Two different fabric architectures namely plain woven (PW) and unidirectional (UD) are fabricated using flax/PP based TBR. These TBR based woven fabrics and the glass fabric/PP sheets are consolidated in a compression moulding machine and the resultant composite-laminates are tested for their LVI behaviour. The impact test results revealed that the glass/PP composites absorb more energy and exhibit a higher peak load than both TBR based PW and UD fabric composites. However, the specific load and energy of all flax/PP composites are higher than the glass/PP composite. The damage tolerance of all composite laminates are evaluated by comparing their flexural strength before and after the impact. It is observed that the proportionate loss in flexural strength due to impact thrust is larger in case of glass/PP composites than all flax-PP composites.     

一个各向异性磁稀释杂化钙钛矿系列[CH3NH3][CoxZn1-x(HCOO)3]

Inorganic-organic or hybrid perovskite materials, which are the complementary counterparts of pure inorganic perovskites, can provide many new opportunities in the researches of phase transitions, critical phenomena, and relevant properties, as they combine the characteristics of inorganic and organic components. Therefore, the hybrid perovskites of ammonium metal formate framework are very promising, and their properties have been found to be strongly dependent on the characteristics of the constituent metal ions and/or ammonium ions. Herein, we used solid solution strategies, borrowed from solid state chemistry, to investigate the anisotropic diluted magnetic hybrid perovskite system of [CH₃NH₃][Co_xZn_1-x(HCOO)₃], wherein the B-sites are occupied by the mixed metal ions of Co²⁺ and Zn²⁺. The solid solution compounds of this series in the range x = 0–1 (or the molar percent Co% = 0–100%) were successfully prepared using conventional solution chemistry methods. The resulting compounds were demonstrated to be iso-structural by using both single-crystal and powder X-ray diffraction analyses. The solid solution crystals belong to the orthorhombic space group Pnma, with the cell parameters being a = 8.3015(2)–8.3207(3) Å, b = 11.6574(4)–11.6811(5) Å, c = 8.1315(3)–8.1427(4) Å, and V = 787.89(5)–790.98(7) ų. The perovskite structure consists of a simple cubic anionic metal-formate framework and CH₃NH₃⁺ cations which are located in the framework cavities, with N―H···O hydrogen bonds formed between the framework and the cation. The members of this series showed negligible changes (< 0.4%) in their respective lattice and structural parameters. Thus, the prepared solid solution compounds constitute good molecule-based examples for the study of magnetic dilution under almost the same structural parameters and molecular geometries. Upon dilution, the magnetization per mole of Co at low temperatures and low fields was suppressed by the magnetic anisotropy of Co²⁺ and gradual destruction of the large spin canting between coupled Co²⁺ ions, in contrast to the magnetization enhancement observed in the isotropic diluted system of [CH₃NH₃][Mn_xZn_1-x(HCOO)₃] with the same perovskite structure. The percolation limit was estimated as (Co%)_P = 27(1)% (or x_P = 0.27(1)) from the magnetic data, which was slightly lower than that predicted by the percolation theory for a simple cubic lattice (31%); this trend was due to the strong magnetic anisotropy of the present system. In addition, rare incommensurate phase transitions were primarily detected below ~120 K for the pure Co and Zn members, which may also affect the magnetic properties of the materials.     

Hybrid Copolymerization via the Combination of Proton Transfer and Ring-opening Polymerization

Phosphazene base,t-BuP2,was employed to catalyze the proton transfer polymerization(PTP)of 2-hydroxyethyl acrylate(HEA),and PTP was further combined with ring-opening polymerization(ROP)to exploit a new type of hybrid copolymerization.The studies on homopolymerization showed that t-BuP2 was a particularly efficient catalyst for the polymerization of HEA at room temperature,giving an excellent monomer conversion.Throughout the polymerization,transesterification reactions were unavoidable,which increased the randomness in the structures of the resulting polymers.The studies on copolymerization showed that t-BuP2 could simultaneously catalyze the hybrid copolymerization via the combination of PTP and ROP at 25°C.During copolymerization,HEA not only provided hydroxyl groups to initiate the ROP ofε-caprolactone(CL)but also participated in the polymerization as a monomer for PTP.The copolymer composition was approximately equal to the feed ratio,demonstrating the possibility to adjust the polymeric structure by simply changing the monomer feed ratio.This copolymerization reaction provides a simple method for synthesizing degradable functional copolymers from commercially available materials.Hence,it is important not only in polymer chemistry but also in environmental and biomedical engineering.     

ZIF-67 derived hollow Ni-Co-Se nano-polyhedrons for flexible hybrid supercapacitors with remarkable electrochemical performances

Nano-polyhedral NiSe₂/CoSe₂ (Ni-Co-Se) with hollow architectures are synthesized by selenizing the precursors of Ni-Co bimetallic hydroxides that are directly derived from ZIF-67. The as-fabricated Ni-Co-Se electrodes exhibit high specific capacitance of 1668 F/g at 1 A/g accompanying with outstanding rate capability (about 82.8% retention of the initial capacity at 20 A/g). The corresponding Ni-Co-Se//AC all-solid-state hybrid supercapacitors are assembled by directly using the Ni-Co-Se on carbon fabric as the positive electrode, which deliver high energy density and power density (38.5 Wh/kg at 802.1 W/kg, 32.0 Wh/kg at 8008.8 W/kg), excellent cyclic stability (82.3% retention after 5000 cycle) and robust mechanical flexibility (no obvious attenuation at bending to different angles). This work will provide a new and smart route for constructing transition metal selenides for supercapacitor devices.