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To achieve high efficiency in the polishing process to obtain a high surface quality of black LT substrate (a kind of soft brittle material), shear thickening polishing (STP),which is a “gentle” finishing process developed in recent years, was employed in this study. The influence of three key parameters in the STP process including polishing speed, diamond abrasive size and diamond abrasive concentration were analyzed. To investigate the potential mechanical effect of the nanometre abrasive, nano-SiO2 abrasive particles were added in the slurry, and the concentration of SiO2 abrasive was also taken as a factor. Taguchi method was utilized to evaluate the influence of the four factors and optimize the polishing conditions. The surface roughness (Ra/Rz) was used as the evaluation index, and the optimized polishing conditions were verified through experiments. Diamond abrasive size has the most significant effect on Ra/Rz, followed by diamond abrasive concentration and then SiO2 concentration, as the polishing speed has been selected and limited in a small variation rang according to the previous study. Based on the S/N average response analysis, the surface quality is the best under the conditions with 8000# diamond abrasive, 5 wt% diamond abrasive concentration, 90 rpm polishing speed and 10 wt% SiO2 concentration. After 4 min polishing, the surface roughness Ra/Rz is reduced rapidly from 200.5/1374.6 to 4.2/22.1 nm without embedded abrasive particles on the surface of the black LT substrate. It also shows that the mechanical effect plays a dominant role in the material removal. A certain amount (10 wt% in this study) of nano-SiO2 can reduce friction between solid colloidal and workpiece, and helps to improve surface quality.

Recent technological advancement in flexographic printing has allowed flexography to catch up with other R2R processes such as gravure printing in the printed electronics field. However, there are many process parameters involved in flexography that can affect the print quality. This work attempted to achieve finer line printing compared to the current 45–100 µm printed line width range of flexography by manipulating and studying these process parameters. A design of experiments was conducted to investigate the influence and interaction of various process parameters such as anilox volume, anilox force and printing force on the printed line width. After identifying the key process parameter from the design of experiments, another in-depth study of the key process parameter was conducted to further investigate how printed line width was affected. The results showed that the printing plate was elastically deformed with a range of 50–400 N printing forces. Beyond the 400-N printing force, the printing plate experienced plastic deformation.

Shear thickening polishing (STP), an emerging polishing method, is used to polish the cemented carbide insert with complex shape in this study. The principle and performance of STP were introduced. Four parameters having significant influence on the STP process, including polishing speed, abrasive concentration, abrasive size, and inclination angle of fixture, were experimentally investigated. The influence of the four parameters on the surface quality of cemented carbide insert was analyzed by orthogonal experiment method, and the optimal processing parameter combination for the STP of cemented carbide insert was determined. Although the influence degree of the processing parameter on the left cutting edge PA, the top cutting edge PB, the root cutting edge PD, and the right cutting edge PK was different, the optimal processing parameter combination for each position was the same: polishing speed of 90 rpm, abrasive concentration of 9 wt%, abrasive size of #8000, and inclination angle of 4°. Under the optimal processing parameter combination, the surface roughness of cemented carbide insert at the left cutting edge PA was reduced from 121.8 to 7.1 nm after 15 min polishing. The scanning electron microscopy (SEM) and the white light interferometer confirmed the effectiveness of the STP process in the polishing of cemented carbide insert. The experimental results show that STP was a promising and feasible processing method in the polishing of cemented carbide insert with complex shape.

In this work, we investigated how elastomeric mold properties could affect the final replication accuracy in hot roller embossing. Amorphous polyethylene terephthalate was used as the polymer substrate. It was discovered that for dense features, the elastomeric mold provided better replication results compared to a metal mold. The experimental results revealed that embossing with larger pitch sizes such as 300 and 400 µm achieved better replication accuracy than that with smaller pitch sizes such as 100 and 200 µm. The side-wall surface areas of the features on the mold affected the embossing process, resulting in different degrees of replication accuracy.

This paper develops an axisymmetric flow model to predict the flow field inside a directcurrent plasma torch reactor, where the magneto-hydrodynamic equations, including the continuity, momentum, energy and current continuity equations as well as turbulence transport equations are solved with a finite volume discretization in a segregated manner. The thermodynamic and transport coefficients of thermal plasma are obtained from the condition of local thermal equilibrium, whereas a kinetics model is employed to consider the production and destruction of species due to the chemical reactions in a decomposition process. Species transport phenomena arising in the decomposition process are described by the transport equations for different species. The perfluorocarbons decomposition characteristics in a well-type, non-transferred nitrogen torch reactor are analyzed by the proposed numerical model to disclose the influence of working parameters on the decomposition efficiency.

The steel arches with weld H-shaped sections are frequently used in various engineering structures. The welding procedure will produce residual stress, which affects the stability of the arches. This paper presented a numerical model to explore the influence of welding residual stress on the stability behavior of the steel arch. Then, the buckling load and structural deformation of the steel arch under uniform load were obtained through the static analysis, and the stability performance of entire structure was discussed. Furthermore, in order to compare the mechanical properties of the arch simulated by different elements, the shell element and beam element were used respectively in the finite element modal to obtain ultimate bulking load of the structure with the same section. It is concluded that the existence of welding residual stress reduced the ultimate bearing capacity of steel arch under uniform load.

Melt-crystallization of syndiotactic polystyrene (sPS) is studied using simultaneous small/wide angle X-ray scattering (SAXS/WAXS). Emergence, intensification, and saturation of WAXS reflections within 120 s at isothermal crystallization temperature Tc = 250 °C after quenching from 300 °C illustrate crystallinity development through successive nucleation of instantaneously stabilized crystallites of lateral (hk0) coherence length Λ ≈ 75 nm. The corresponding SAXS profiles exhibit increased density heterogeneity due to formation of nanograins; fitting of time-resolved SAXS data with a model of arrayed disks reveals slightly thickened (lc = 7.4–8.4 nm) disks of radius R ≈ 9 nm and long period L ≈ 19 nm with polydisperse stacking number slowly enhanced from an average of 1.2 to 2.4. The moderate ratio of Λ/2R ≈ 4 indicates imperfect coalescence of nanograins in the lamellar assembly process. More importantly, with successively increased Tc from 250 to 260 °C the development of density heterogeneity of SAXS invariant Q inv is found to precede that of the WAXS-determined crystallinity Xc increasingly more, suggesting a precursor mesophase with non-crystalline nanograins. Avrami analysis for the developments of Xc and Q inv further reveals the same Avrami exponent n ≈ 3, consistent with heterogeneous nucleation of crystallites; the corresponding Avrami rate constant κ1/n(Tc) extracted from Xc is correlated to the crystal growth rates G(Tc) described by the Hoffman-Lauritzen theory with a common surface-nucleation rate constant Kg. A lateral surface energy σ ≈ 17 mJ m−2 can be deduced on the basis of Kg using previously determined fold surface energy σe ≈ 27 mJ m−2. Correspondingly, κ1/n(Tc) extracted from Qinv is described by a mesophase model proposed by Strobl with a zero-growth temperature of the nanograin mesophase ca. 30 K below the β-crystal melting point of sPS. Together, these results suggest that sPS melt-crystallization proceeds with nucleation of non-crystalline nanograins (SAXS-before-WAXS regime) at the crystal growth front, followed by crystallization of the nanograins with similar kinetics to sustain the growth front. Branching/twisting can occur at the lamellar growth front due to frustrated nanograin alignment, favoring the microscopically observed sheaf-like crystal morphology.

The interest in flexible stretchable printed electronics has increased because of the wide applications, especially for wearables devices. The conventional manufacturing processes were time consuming and expensive, which led to developing of stretchable interconnects using screen printing. In this research, meander patterns of varying meander angles were designed and screen-printed on thermoplastic polyurethane substrates. Silver inks and carbon inks were used to print the circuits, which were subjected to tensile tests while their changes in resistance were measured. The electrical characteristics were utilised to determine the elastic limits of the circuits and the conditions for cyclic tests of up to 10,000 cycles. It was found that the maximum strain at break of the silver ink was 47%. Carbon ink had a higher initial resistance value and the maximum strain at break was 125%. The best stretchability was obtained at the 0° meander angle, a curing time of 30 min and curing temperature of 130 °C with oven cooling.

In this research, we designed serpentine patterns of varying radii of curvature and the meander angle and screen printed the test coupons on thermoplastic polyurethane. The inks chosen were silver flake ink and carbon black ink. The test coupons are then subjected to destructive tensile testing while monitoring the change in resistance. The electrical characteristics are then used to determine the elastic limit of the test coupons and set the conditions for a cyclical test. The coupons were then tested to 1000 cycles. For the silver inks, it is found that the maximum strain at break is 42% and the best design for stretchability is at 22.5 degree meander angle. Detailed failure analysis shows the mechanical deformation is similar to bulk metal where dislocations propagate and crack through beyond the elastic limit in silver ink. Carbon ink, on the other hand, has a higher initial resistance but the maximum strain at break is 125.84%. It was found that for carbon ink the increase in resistance follows a consistent power law progression and the behavior is similar to diffusion based failure mechanisms We have thus provided an insight into the printing of stretchable circuits with conductive inks based on bulk mechanism and percolation mechanism and found that percolation brings about a big increase in the stretchability in the circuits.

The mixed metal oxalate bridged compounds NBu4MAIInFeII1–n[FeIII(ox)3](MA = Mn, Zn) were investigated by magnetic measurements. The temperature dependence of the compounds NBu4ZnIInFeII1–n[FeIII(OX)3] (n = 0. 04, 0·08, 0·10) shows two temperature compensation points in the temperature range of 32–41·5 K and multiple magnetic pole reversals are observed in the material. When n≧0·1 the temperature compensation point disappears, the value of M increases and exhibits weak irreversibility in the field cooled (FC) magnetisation curves. At the same time, spin glass state is founded below 35 K and the bifurcation of the zero field cooled and FC plots below the Neel temperature of 30 K indicates irreversibility. At the Neel temperature of 39·9 K, a compensation temperature and a spin canting are observed in the compound NBu4FeII0·97MnII0·03[FeIII(OX)3].

In order to improve the inclusion type and composition in tyre cord steel, ladle furnace refining has been simulated by laboratory experiments and thermodynamic calculation. It was found that slag metal reaction time and top slag composition have an important influence on the inclusion compositions in the final steel. To produce the desired low melting point ductile inclusions the optimum conditions were: reaction time 60 min, basicity (CaO/SiO2) of top slag in the range of 1·0–1·2 and Al2O3 content of slag in the range of 3–9 mass-%. These were then confirmed in industrial trials.

In this paper, we present calculations based on density functional theory using generalized gradient approximation (GGA) in double perovskite structure La2BB’O6 (B,B’ = 3d transition metal) out of combinational possibilities. Considering 4 types of magnetic states, namely, ferromagnetic (FM), ferrimagnetic (FiM), antiferromagnetics (AF), and nonmagnetic (NM) with full structure optimization, 13 possible surviving, stable FM/FiM-HM materials containing 6 FM-HM materials (La2ScNiO6, La2CrCoO6, La2CrNiO6, La2VScO6, La2VZnO6, and La2VNiO6) and 7 FiM-HM materials (La2VFeO6, La2ZnCoO6, La2TiCoO6, La2CrZnO6, La2CrMnO6, La2ScFeO6, and La2TiMnO6) are found. Considering the correlation effect (GGA+U), there are 6 possible half-metallic stable, surviving (HM) materials containing 3 FMHM materials (La2ScNiO6, La2CrCoO6, and La2CrNiO6) and 3 FiM-HM materials (La2VFeO6, La2ZnCoO6, and La2TiCoO6).

Owing to ingredient segregation, non-uniform microstructure and porosity defects in Cr–Cu alloys are frequently produced by melting process. Even subsequent heat treatment and hot working would not be able to completely resolve the problem. Therefore, this study investigated Cr60Cu40 alloy targets produced via vacuum sintering followed by hipping. Experimental results showed that the relative density of the sintered Cr60Cu40 alloy targets reached 99·69%, the apparent porosity decreased to 0·31% and transverse rupture strength increased to 553 MPa after hipping treatment at 1050°C at 175 MPa for 4 h. In addition, the closed pores were almost completely eliminated after the hipping treatment. The resistivity decreased to 643×10−8 Ω cm, and the International Annealed Copper Standard value was enhanced to 26·81% after optimal hipping treatment. This study shows that hipping treatment can effectively eliminate internal pores of sintered Cr60Cu40 alloy targets and also improve their electrical properties.

In roll-to-roll processing, the feeding speed of substrate ranging from several meters to several tens meters per minutes are required for some processes, such as roll-to-roll coating or gravure printing; reducing the speed will lead to other problems. On the other hand, some other processes need prolonged dwelling or holding time, such as thermal embossing. In the case of integrating different processes (for example, embossing and printing) into one roll-to-roll processing line, it is necessary to synchronize the feeding speeds of different processes. In this study, we will focus on thermal embossing process, discuss how the process speed, holding time will affect the fidelity of formed structures. Based on our investigation and comparison, we identified the problems of roll-to-roll thermal embossing, and developed a novel roll-to-roll embossing system. The developed system consists of two metallic belts — the top belt used for embossing template and the bottom belt for carrier. The developed system allows active driving from both sides of polymer films; it also provides an extended template-film contact time even with high speed roll-to-roll thermal embossing. This allows the roll-to-roll embossing to be integrated with other roll-to-roll manufacturing processes such as printing or coating.

R2R large area fabrication of functional panels gained popularity in recent years and micro 3D profiles for optical films and biomedical applications have gained momentum with improving replication accuracies in hot embossing systems. However, studies on the effect of heat flux on the replication accuracy have been lacking. In this study, a twin belt based roll-to-roll embossing system was designed and built to study the effects of various in-situ heat transfer at the hot embossing nip. Seamless embossing was then demonstrated on PVC film. The effects of different heat transfer schemes have been modeled using Solidworks simulation applying experimentally obtained mechanical properties of the polymer film. The simulation results are compared quantitatively to the experimental results to analyze the effect of heat transfer schemes on the replication accuracies. We achieved 92% replication accuracies on the PVC film replicated by application of heat on the side of the film not in contact with the mold. It is significantly higher than the features replicated using an isothermal condition at T g and also heat transfer from the mold. Thermal simulation shows a steep thermal gradient between the polymer under nip and the immediate surrounding for the isothermal conditions and a gentle thermal gradient for the other two schemes. Displacement of the polymer shows a highest flow of material from the surrounding of the feature for the underside heating method. This results in a more accurate replication onto the PVC film.

Structural evolution processes of solution-cast and melt-quenched poly(9,9-di-n-hexyl- 2,7-fluorene) (PFH) were quantitatively examined using small/wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry. SAXS/WAXS profiles of solution-cast PFH indicated presence of nanograins (radius of gyration Rg z 5 nm) of 2D-ordered b phase. Upon heating above Tg, perfected packing order and growth of b nanograins up to Rg z 10 nm result in suppressed formation of a crystallites up to 190 � C, beyond which extensive melting accompanied by significant (albeit partial) transformation of b nanograins into a nanocrystals of Rg z 13 nm can be observed in a narrow temperature range of 190 e200

The impacts of tensile stress on the non-linear electrodissolution behaviour of carbon steel were investigated in an aqueous solution of 5M phosphoric acid. The frequency of the current oscillations within the transpassive potential region increases slightly when the elastic deformation was introduced to the electrode by applying tensile stress, but the oscillatory mode is essentially unchanged. The elastic deformation could induce the current oscillations in the passive potential region that was not observed on stress free state. This fact suggests that the tensile stress can reduce the stability of passive film. Immediately after the tensile stress exceeds the yield strength, the oscillatory mode changes into a chaotic one with high frequency and recovers the original state gradually. This phenomenon resembles the consequence due to the injection chloride to the electrode/electrolyte interface and implies that the plastic deformation may result in the formation of more defective passive films.

The organic–inorganic nanocomposite films were fabricated by grafting polystyrene (PS) onto the vinyltriethoxysilane (VTEOS) modified titanium dioxide nanopowders using free radical polymerization. The composition of the surfaces and the structure for the PS grafted titania (PS-g-TiO2) were examined by infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis, and the rough surface was confirmed by the evaluation of the morphological characteristics of the coating using hybrid particles. The wetting properties of the VTEOS modified titania and PS-g-TiO2 films were investigated, which show the maximum static water contact angles of 160° and 154°, and minimum sliding angles of 3° and 4°, respectively.

We synthesized a nanoparticle (NP) for ex-vivo cell labeling and MRI tracking by covalently coupling the C-terminus of a rhodamine-labeled protamine (ProRho) to Feraheme (FH) in order to yield the nanoparticle denoted ProRho-FH. Since protamine can adsorb to certain charged surfaces, we confirmed a covalent interaction between ProRho and FH by heparin affinity chromatography. ProRho-FH lacks a net charge (zeta potential approximately 0) due to the combination of negative FH and positive ProRho charges. ProRho-FH was readily internalized by U87 cells and mouse mesenchymal stem cells as determined by FACS and MR relaxometry. Finally, some 4,000 stem cells were implanted in a mouse brain and imaged by MRI. Due to its lack of net surface charge, ProRho-FH relies on the internalizing properties of the surface guanidinium groups present in the arginine-rich protamine to induce NP uptake. ProRho-FH is a unique cell-labeling agent due to its synthesis using two approved drugs, magnetofluorescence, site-specific covalent attachment chemistry, and lack of surface charge.

Inactivation of E scherichia coli and B acillus subtilis using the jet region of a parallel-plate air dielectric barrier discharge (DBD) driven by a distorted sinusoidal voltage power supply under atmospheric-pressure condition is reported. Various types of working gases, including pure N 2 , pure O 2 , and compressed air, were tested. Discharges were characterized electrically by measuring the discharge current, applied voltage and absorbed power, and optically by measuring the optical emission spectra in the UV–visible range and absorption spectra in the IR range. Results of survival rate show that both E. coli and B. subtilis cells (up to 10 7 CFU/mL) can be effectively inactivated using less than 18 passes (1.8 s of residence time in total) of exposure to the post-discharge jet region of compressed air and oxygen discharges at different treating distances in the range of 4–20 mm. Among these, the compressed-air discharge performs the best in inactivating both two types of the bacterial cells, because of the abundant ozone generation and probably through the assistance of nitrous oxide generated in the discharge. In summary, the post-discharge jet region of an oxygen-contained parallel-plate DBD driven by a distorted sinusoidal voltage power driven is very effective in inactivating both E. coli and B. subtilis cells under the present test conditions.

Structural evolution of syndiotactic polystyrene (sPS) in a cold crystallization process was quantitatively examined with in-situ small/wide-angle X-ray scattering and differential scanning calorimetry (SAXS/WAXS/DSC). After removal of background scattering from fractal-like matrix structure, SAXS profiles obtained during programmed heating of an amorphous sPS specimen from 30 to 240 at 10 °C/min can be interpreted with a similar sequence of events previously observed in cold crystallization of poly(9,9-di-n-octyl-2,7-fluorene) (PFO). Specifically, the nanograin evolution of sPS involves four stages: (1) the frozen-in stage below 90 °C, (2) the nucleation of oblate-like nanograins with a constant radius of gyration Rg ≈ 2.6 nm between 90 and 130 °C, (3) the growth of nanograin size to Rg ≈ 3.2 nm concomitant with the emergence and development of WAXS-determined crystallinity (Xc,WAXS) from 130 to 180 °C, and finally (4) the coalescence (and thickening) of the nanocrsytals into a greater size of Rg ≈ 4.6 n...

By means of in situ small/wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC), we examined evolutions of lamellar crystal thickness for R and β crystals, respectively, in bulk-crystallized syndiotactic polystyrene (sPS) during the partial melting-reorganization process upon progressive heating up to 290 � C. For the SAXS data analysis, the Kratky-Porod approxima- tionprovestobeparticularlyhelpfulinextractingthecrystalthicknesswhenapproachingfinalmeltingwhere crystalline lamellae (near equilibration with the melt) exist in low concentrations as dispersed entities instead of in arrays. On the basis of the crystal thicknesses at elevated temperatures under solid-melt equilibration, weconstructedmeltinglinesofthetwoseparateformsintheGibbs-Thomsonphaseplane.Theextrapolated (to infinite lamellar thickness) equilibrium melting temperature Tm,R* ≈ 294 � C of the R form is moderately lower than Tm,β* ≈ 306 � C of the β form. The two melting lines intercept at a crossover temperature TQ ≈ 284 � C and crystal thickness lQ ≈ 9.6 nm, where the relative thermal stability of the two phases inverses. For crystals thicker than lQ (practically hard to reach for bulk crystallization under ambient pressure), the β form is the stable phase; for crystals thinner than lQ (the commonly accessible case), the R form is circumstantially more stable. With crystallinity-corrected values of the heat of fusion ΔHf,R ≈ 82 MJ m -3 and ΔHf,β ≈ 146 MJ m -3 obtained from a combination of DSC and WAXS results, we determined from the slope (= 2σe/ΔHf) of the melting line that basal surface energy σe,R ≈ 8.2 mJ m -2 and σe,β ≈ 26.8 mJ m -2 , which are considerably lower than those expected for tight folds, indicative of nonadjacently re-entered or loosely looped folds. The combination of lower Tm*, ΔHf, ΔSf, and σe values renders the R phase highly competitive in the rate of nucleation at low temperatures but much less so at high temperatures as compared tothe βphase.Thehigher σe,βvalueisalsoconsistentwiththeobservationthatthe βphaseismoreresponsive to externally added heterogeneous nucleation agents.

By means of in situ small-angle X-ray scattering/wide-angle X-ray scattering/differential scanning calorimetry (SAXS/WAXS/DSC), structural evolution of poly(9,9-di-n-octyl-2,7-fluorene) (PFO) in a cold crystallization process was quantitatively examined. After removal of background scattering from the fractal-like structure, SAXS profiles obtained during programmed heating of an amorphous PFO specimen unveil a sequence of stages of structural evolution. These include (1) a frozen-in stage below the glass transition temperature (Tg ≈ 62 °C), (2) the nucleation of prolate nanograins with radius of gyration Rg ≈ 3.3 nm from 65 to 85 °C, (3) growth of the prolate ellipsoids up to Rg ≈ 5.0 nm between 95 and 105 °C, and (4) coalescence (and thickening) of the nanocrsytals into oblates (of Rg ≈ 10 nm) upon further heating to 145 °C. There were no further changes in morphological features in the subsequent isothermal annealing at 145 °C for up to 1 h, as the size of the coalesced nanograins quickly reached a threshold value where the orientation and attachment of neighboring nanograins via thermally activated Brownian rotation became seriously hindered. Developments in the DSC- determined crystallinity (Xc,DSC) and the degree of heterogeneity (Qinv from SAXS) coincided with the nucleation and growth stages, respectively; in contrast, buildup of the WAXS-determined crystallinity (Xc,WAXS) proceeded mainly in the subsequent coalescence stage where large nanocrystallites were developed.

Highly orientated polycrystalline ZnO films were deposited on sapphire, silicon and quartz substrates at room temperature by r.f. magnetron sputtering. Different photoluminescence (PL) spectra were observed when excited with different wavelength light. A UV emission peak (356 nm) and a blue peak (446 nm) were generated for the films on sapphire, silicon and quartz substrates, and only the 446 nm blue emission appeared for the films on glass substrates when the wavelength of the excitation light was 270 nm. With increasing the wavelength of the excitation light up to 300 and 320 nm, the UV emission disappeared for films on various substrates and the wavelength of the PL peaks increased up to 488 and 516 nm, respectively. When the wavelength of the excitation light increased to 398 nm, the PL spectrum becomes a wide band that is consistent with three emission peaks.

Blue InGaN/GaN multiple-quantum-well light-emitting diodes were grown on sapphire substrates by using a metal-organic vapor phase epitaxy system. A Mg-doped AlGaN electron-blocking barrier was introduced under various Cp2Mg ow conditions at a high temperature of 1050 C. The characterization included current-voltage, capacitance-voltage and electroluminescence analyses. The luminescence e ciency showed an improvement of more than 90 % when the Cp2Mg ow rate was increased from 50 to 200 sccm. The forward voltage was reduced to 3.18 V at 20 mA. The series resistance was also estimated to be 10.81 . Secondary-ion mass spectrometry revealed the Mg doping pro les close to the quantum-well active region. The increased Mg concentration resulted in improved hole injection and carrier concentration. This is in agreement with the increased electroluminescence e ciency and luminous intensity and with the lower turn-on voltage. The Xray di raction study showed a full width at half maximum of 290.1 arcsec from the GaN (0002) di raction and 325.9 arcsec from the GaN (10 12) di raction.

In this paper, we demonstrate the use of photonic crystal (PC) directional couplers to separate light of wavelengths at 1.31 and 1.55 m. The PC structure consists of InAlGaAs nanorods arranged in hexagonal lattice. The simulation of our device is implemented by the finite-difference time-domain method. The devices are fabricated by e-beam lithography and conventional photolithography. We use the strong inverse method (SIM) of e-beam lithography to make the pattern smoother. The measurement results confirm that 1.31/1.55-m wavelength splitter can be realized in PC structures formed by nanorods.

A compact circular stacked planar inverted-F antenna implantable for biotelemetry communication in the 402–405 MHz medical-implant-communication-service (MICS) frequency band is presented. By properly embedding a circular hook-shaped slot to each radiating patch of the proposed PIFA structure, antenna size and impedance bandwidth can be significantly improved. The constructed antenna presents a broad 10 dB impedance bandwidth of 84 MHz from measurement by inserting it inside the skin-simulating fluid. Also, the proposed antenna has characteristics of a compact size with a radius of only 5 mm, a radiation efficiency of 1.3%, and a monopole-like radiation pattern suitable for implantable device use.

The correlation between morphology and charge-carrier mobility in the vertical direction in thin films of poly(2-methoxy-5-(2′ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) is investigated by a combination of X-ray reflectivity (XRR), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), fluorescence optical microscopy (FOM), photoluminescence spectroscopy (PL), photoluminescence excitation spectroscopy (PLE), as well as time-of-flight (TOF) and transient electroluminescence (TrEL) techniques. The mobility is about two orders of magnitude greater for drop-cast films than for their spin-cast counterparts. Drop-casting in the presence of a vertical static electric field (E-casting) results in films with an additional increase in mobility of about one order of magnitude. While PL and PLE spectra vary with the method of film preparation, there is no correlation between emission spectra and charge-carrier mobility. Our XRR measurements on spin-cast films indicate layering along the film depth while no such structure is found in drop-cast or E-cast films, whereas FESEM examination indicates that nanodomains within drop-cast films are eliminated in the E-cast case. These observations indicate that carrier transport is influenced by structure on two different length scales. The low mobility observed in spin-cast films is a direct result of a global layered structure with characteristic thickness of ca. 4 nm: in the absence of this layered structure, drop-cast films with inherent nanoscale heterogeneities (ca. 20 nm in size) exhibit much better hole mobility. Elimination of nanodomains via electric-field alignment results in further improved charge mobility.

Phase behavior and morphological features of regioregular, n-type semiconducting poly(4-alkyl-2,6-quinoline)s were examined in detail via a combination of thermal, microscopic, and diffraction methods. Two members (P4OQ and P4DQ, with n-octyl and n-decyl substitutions, respectively) in this series were selected as representatives. Results indicate the dominance of lamellar mesophase throughout the experimentally accessed temperature range (from ambient to above 300 degrees C), with lamellar spacing well-correlated with side-chain length and temperature. Optical textures observed via polarized light microscopy reveal clear domain-wall features in P4OQ but more solid-like characteristics for P4DQ; improved lamellar order was also observed for P4DQ as compared to P4OQ. These signify stronger tendency toward supramolecular self-assembly with increasing side-chain length. A model of molecular arrangement in the lamellar mesophase in which the free volume is identified as the gap between tips of extended (and interdigitated) side chains and the backbone of the neighboring chain is proposed to account for the observed variation of layer spacing with side-chain length and temperature. The presence of nanodomains (similar to those previously reported for p-type conjugated polymers) is also identified in the present n-type series, implying general existence of this inherent morphological heterogeneity in semiconducting hairy-rod polymers. This means that molecular aggregation is determined solely by ground-state intermolecular forces; differences in carrier transport characteristics are irrelevant during morphological development. Origins of these nanodomains are discussed in terms of backbone folding (via inherent chemical defects or elastic bending) as well as fringed-micelle aggregates.

We have previously demonstrated that solution-cast films of conjugated polymers with grafted alkyl side chains comprise clearly identifiable domains ca. 10 nm in size upon solvent evaporation. Here we show that these nanodomains indeed serve as basic units for morphological development in poly(9,9-di-n-octyl-2,7-fluorene) (PFO) films during cold crystallization. Results of our microscopic and diffraction observations indicate that the cold crystallization process involves intradomain nucleation and growth, followed by nanodomain alignment and coalescence into fibrils in the sub-micrometer length scale via thermally activated adjustment of nanodomain orientation. An analogy with oriented aggregation (or oriented attachment−coalescence) behavior of nanocrystals of metal oxides is drawn; the relevance to recently proposed models of polymer crystallization via primary nucleation induced at the growth front is addressed.

Due to the unique characteristics of laser energy in the broad applications for nanotechnologies, there are many important developments in laser processing methods for modern industries, especially for the urgent needs of nanoscale metallic particles and the related laser processes. In this chapter, the formation of copper particles by laser-enhanced electroplating with continuous and pulsed laser output modes is introduced. According to the electrochemical dynamics theory, the mechanism of the proposed technique for particles formation is mainly due to the thermal effects from the laser interaction in electroplating. In the experiments, the laser energy absorbed by the electrolyte jet and the temperature rise of the electrode during the laser radiation were measured. In the numerical simulation, the temperature fields of the impinging jet of the laser nozzle were calculated. It shows that the growth of the particle corresponds significantly to the laser power and pulse mode of the laser interaction.

Based on results of small-angle X-ray scattering and differential scanning calorimetric measurements, the equilibrium melting temperature and basal surface energy (σe) of crystalline poly(9,9-di-n-octyl-2,7-fluorene) (PFO) were preliminarily estimated as ca 451.6 K and 0.084 J m−2, respectively, via Gibbs–Thomson analysis. This σe value leads to a value of 76 kJ mol−1 for the work of fold that greatly exceeds the values for typical polymers, reflecting the semi-rigid nature of the PFO backbone and consistent with the large-loop folds proposed earlier for this particular conjugated-backbone polymer. This is in strong contrast to the commonly held belief that conjugated polymers are generally too rigid to form folded-chain lamellar crystals.

Morphological features of melt crystallized poly(9,9-di-n-octyl-2,7-fluorene) (PFO) were examined by means of polarized light microscopy, scanning electron microscopy, and transmission electron mic...

In this work, a simplified model for on-chip spiral inductors was developed to accurately predict key parameters in the giga hertz range, i.e., peak quality factor Qpeak, frequency at peak quality factor fpeak, and self-resonance frequency fSR. To save area on the test-key layout, inductors were laid out with a ground-signal-ground-signal-ground (GSGSG) pad structure. In addition, we used two conventional ground-signal-ground (GSG) probes to measure the inductors with the GSGSG pad structures to save the cost of GSGSG probes. Very good fits between the predicted and the measured data indicate the suitability of the model and the new pad structure.

At ambient pressure, bulk liquid water shows an anomalous increase of thermodynamic quantities and apparent divergences of dynamic properties on approaching a temperature Ts of 228 K. At normal pressure, supercooled water spontaneously freezes below the homogeneous nucleation temperature, TH = 235 K. Upon heating, the two forms of Amorphous Solid Water (ASW), LDA (Low Density Amorphous Ice) and HDA (High Density Amorphous Ice), crystallise above TX = 150 K. As a consequence, up to now no experiment has been able to explore the properties of liquid water in this very interesting temperature range between 150 and 235 K. We present nanosecond-time-scale measurements of local rotational and translational dynamics of interfacial, non-crystalline, water from 77 to 280 K. These experimental dynamic results are combined with calorimetric and diffraction data to show that after exhibiting a glass transition at 165 K, interfacial water experiences a first-order liquid-liquid transition at 240 K from a low-density to a high-density liquid. This is the first direct evidence of the existence of a liquid-liquid transition involving water.

Structural characteristics of optical quality poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phen- ylenevinylene) (MEH-PPV) films drop-cast from toluene solutions have been examined by use of wide- angle (WAXS) and small-angle X-ray scattering (SAXS) as well as field-emission scanning electron microscopy. For the as-cast film SAXS and WAXS patterns clearly suggest existence of nanodomains of mesomorphic order. Under grazing incidence, both SAXS and WAXS patterns of the as-cast film exhibit impressive uniaxial symmetry with strong scattering along the film normal; however, the corresponding normal-incidence patterns are circularly isotropic, implying in-plane random orientation. A structural model consisting of preferentially uniaxial-oriented nanodomains and disordered matrix is therefore proposed for the as-cast film. Annealing at 210 °C results in disorientation of nanodomains: this decrease in structural asymmetry upon heat treatment correlates well with concomitant changes in charge transport behavior determined from time-of-flight measurements, manifesting dramatically decreased charge mobility as well as transition from nondispersive to dispersive modes.

Selective formation of amorphous, nematic (N), and beta phases in poly(9,9-di-n-octyl-2,7-fluorene) (PFO) films was achieved via judicious choice of process parameters. Phase structure and film morphology were carefully examined by means of X-ray diffraction as well as electron microscopy. "Amorphous" thin films were obtained by quick evaporation of solvent. Slow solvent removal during film formation or extended treatment of the amorphous film with solvent vapor resulted in predominantly the beta phase, which corresponds to a frozen (due to decreased segmental mobility upon solvent removal) and intrinsically metastable state of transformation midway between a solvent-induced clathrate phase and the equilibrium crystalline order in the undiluted state. The frozen transformation process is reactivated upon an increase in temperature beyond 100 degrees C. Compared to the amorphous film, extended backbone conjugation in the beta phase is evidenced from the emergence of a characteristic absorption peak around 430 nm near the absorption edge. For films of frozen nematic order (obtained by quenching from the nematic state), the conjugation length is also greater than the amorphous films as revealed by an absorption shoulder around 420 nm. Well-behaved single-chromophore emission with single-mode phonon coupling was observed for the beta phase; in the case of nematic films, dual-mode phonon coupling must exist if single-chromophore emission is assumed. In comparison, the emission spectrum of the amorphous film of generally shorter conjugation lengths exhibited mixed characteristics of nematic and beta phases, implying the presence of minor populations of extended conjugation similar to those in nematic and beta phases, which are of biased weightings in the emission spectra. All these films consist of nanograins (ca. 10 nm in size) of collapsed chains; the films are therefore inherently inhomogeneous in this length scale. In combination with previous observations on the crystalline (alpha and alpha') forms, the phase behavior of PFO is then generally summarized in terms of relative thermodynamic stability.

We synthesized dialkoxy-substituted poly[phenylene vinylene]s (dROPPV-1/1, 0.2/1, and 0/1) consisting of two repeating units with different side-chain lengths (methoxy and 3,7-dimethyloctyloxy). These polymers can serve as a model system to clarify roles of aggregates (the sites with ground-state interchain interactions) and the independent chain segments in the well-packed chains (the chain segments that are compactly packed without interaction) in the emission mechanism of conjugated polymers. Due to the packing of polymer chains, films of all of these polymers are accessible to interchain excitations, after which excitons can re-form to result in delayed luminescence. Besides, some chains form aggregates so that the delayed luminescence is no more the ordinary single-chain emission but red-shifted and less structured. Not only the re-formation of these indirect excitons but also the aggregation of chains are facilitated in the polymers with short methoxy side groups, revealing that both packing and aggregation of chain segments require a short spacing between polymer chains. However, the incorporation of other side chains such as the 3,7-dimethyloctyloxy group to dROPPVs is necessary for the formation of aggregates because these long branched side chains can reduce the intrachain order imposed by the short methoxy groups, which accounts for the absence of aggregate emission in the well-studied poly[2,5-dimethoxy-1,4-phenylene vinylene]. This study reveals that the well-packed chains do not necessarily form aggregates. We also show that the photophysical properties and the film morphology of conjugated polymers can be deliberately controlled by fine-tuning of the copolymer compositions, without altering the optical properties of single polymer chains (e.g., as in dilute solutions).

Direct and non-intrusive observations of crystallization and melting behavior of α and β polymorphs in bulk syndiotactic polystyrene were made by means of temperature-programmed x-ray diffraction. Results indicated that the highest sustainable temperature identifiable via wide-angle x-ray diffraction using stepwise annealing at increasingly higher temperatures (T a) for the perfected (with the initial crystallization temperature T c = 245 °C, followed by annealing at stepwise increased T a above 250 °C) α″ phase may be at least 286 °C. In a similar manner, the highest sustainable temperature of the perfected (with T c = 265 °C, followed by annealing at stepwise increased T a above 275 °C) β′ phase may be at least 280 °C. These observations suggest complete melting should occur only above the respective sustainable temperatures. It thus follows that equilibrium melting of the α and the β phases should occur at temperatures higher than 286 and 280 °C, respectively. Perfection of the less ordered α′ form into the better ordered α″ form within the α family is observed to occur in the vicinity of 270 °C; no evidence of transformation between α and β phases is identified.

By means of transmission electron microscopy (TEM) and X-ray diffraction (XRD) we demonstrate the presence of a previously unspecified modification (α‘) of the crystalline (α) phase in poly(9,9-di-...

Elevated temperature true stress – strain curves have been determined for the isothermal deformation of a TC6 titanium alloy using hot compression testing in the deformation temperature range 800 – 1040°C, strain rate range 0.001 – 50 s-1 and reduction in height of 30 – 50%. The experimental results show that the flow stress of TC6 titanium alloy is strongly dependent on process parameters, especially on the deformation temperature and strain rate. The peak stress and steady stress of such an alloy have the same characterisation, which increases with higher strain rate and lower deformation temperature. During isothermal forging, microstructural characterisation, including volume fraction, grain size, and grain pattern of prior α phase, varies with different temperatures, height reductions, and strain rates.

Presented are transmission electron microscopic observations of micron-sized single crystals of poly(9,9-di-n-octyl-2,7-fluorene) (PFO) prepared from thin films in the melt state. A preliminary determination of unit cell dimensions and molecular packing (orthorhombic, a = 2.56 nm, b = 2.34 nm, c = 3.32 nm, 8 chains, with space group P212121 and density 1.041 g mL-1) was made via combined considerations of the selected-area electron diffraction (SAED) pattern obtained along the [00l] zone of the single crystals, the SAED “fiber” pattern obtained from shear-oriented films, and the “powder” pattern from X-ray diffraction of melt-crystallized thick films in the absence of preferred orientation. In this model, PFO backbones are generally separated by transversely extended alkyl side chains, consistent with the dominance of single-chromophore emissions and the general lack of interbackbone delocalization of PFO chains in this ordered state as indicated by earlier photophysical studies. In addition, microscopic ...

Recent mode coupling theory (MCT) calculations show that in attractive colloids one may observe a new type of glass originating from clustering effects, as a result of the attractive interaction. This happens in addition to the known glass-forming mechanism due to cage effects in the hard sphere system. MCT also indicates that, within a certain volume fraction range, varying the external control parameter, the effective temperature, makes the glass-to-liquid-to-glass re-entrance and the glass-to-glass transitions possible. Here we present experimental evidence and details on this complex phase behavior in a three-block copolymer micellar system.

Structural evolution and its effect on the optical absorption/emission behavior of poly(2,5,2',5'-tetrahexyloxy-8,7'-dicyano-di-p-phenylenevinylene) (DH-CNPPV) upon short-term isothermal heat treatment at elevated temperatures were studied by means of a combination of X-ray diffraction, transmission electron microscopy, UV-vis spectroscopy, and photoluminescence spectroscopy. Results indicated kinetic preference for mesomorphic order in bulk DH-CNPPV, with the isotropization temperature (T i ) located in the vicinity of 210 °C. Upon heat treatment at elevated temperatures (T a ) below T i , supramolecular self-assembly of DH-CNPPV chains results in lamellar structure ca. 2.0 nm in layer spacing. This lamellar phase exists in the form of nanodomains (ca. 10-20 nm in diameter) that agglomerate into wormlike features with DH-CNPPV backbones and the mesomorphic lamellae lying transverse to the worm's long axis. Details in the selected-area electron diffraction pattern of shear-oriented specimens prescribe a short intraboard spacing of 0.38 nm and longitudinal displacement by one-third of the repeating unit between neighboring backbones, such that adequate interaction between the cyano group and the phenylene ring is allowed for. Accompanying the thermally induced morphological changes, UV-vis light absorption behavior varies consistently with improvement or disruption of the lamellar order whereas the major emission in the photoexcited spectrum shifts from 590 to 640 nm upon emergence of mesomorphic order, which is directly excitable and hence attributable to either extended backbone conjugation or enhanced interchain delocalization in the mesomorphic state. This is in dramatic contrast to the closely related case of poly(2,5-di-n-octyl-oxy-1,4-phenylenevinylene) (DO-PPV) without cyano substitutions in the backbone (for which excimer emission is the preferred mode upon morphological aggregation), signifying the role of specific cyano-phenylene interaction in the ground state of aggregated chains in the mesomorphic phase.

Flip chip package is the most important technology in IC package in terms of scale, velocity and cost in the development of semiconductor technology and the innovation of computer product. It has the advantage of low cost, low interface and small volume in IC package. This paper describes the analysis package of the solder ball and microchip for mold flow simulation (3D, midplane) and experiment. The numerical simulation of mold filling process is based on the concept of control volume finite element method. The injection point uses the corner, 1/4 side and central injection location. The injection process uses different parameters (mold temperature, injection temperature, injection pressure and injection time). For processing situation, the best result is from central injection, then 1/4 side injection and then corner injection. The results also show that the filling situation for 3D numerical simulation is closer to experiment.

Structural development in cast films of poly(2,5-di-n-octyloxy-1,4-phenylenevinylene) (DO-PPV) upon heat treatment was studied by means of polarized light microscopy, X-ray diffraction, ultraviolet−visible spectroscopy, and photoluminescence spectroscopy as well as scanning and transmission electron microscopy. Results indicated the dominance of a lamellar phase of biaxially refringent nematic-like texture upon short-term heat treatments at elevated temperatures (Ta) between 160 and 240 °C. A further increase in Ta results in dissipation of the mesomorphic order near the isotropization temperature Ti = ca. 300 °C. This lamellar phase, 1.8 nm in layer spacing at room temperature, typically consists of beads or grains approximately 10−20 nm in diameter that agglomerate into wormlike features in the absence of external stress. Mechanical shear right after high-temperature annealing results in disintegration of worms formed in the tranquil state; the constituent beads nevertheless reagglomerate into new worml...

We report a set of viscoelastic measurements in aqueous solutions of a copolymer micellar system with attractive interactions, a system characterized by a percolation line (PT), and a structural arrest (SA) in the particle diffusion motions of a kinetic glass transition (KGT). We observe, in both transitions, dramatic variations in both the elastic (or storage G ′( ω )) and loss components ( G ″( ω )) of the shear moduli. At the PT, rheological data are characterized by a scaling behavior, whereas at the SA G ′ and G ″ develop a plateau and a marked minimum, respectively. These behaviors are described in the frame of percolation models and mode coupling theory (MCT).