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Radiation-induced graft polymerization is introduced to effectively fabricate proton exchange membrane based on 12.5 μm fluorinated ethylene propylene (FEP) film. The graft side chains penetrate FEP film and distribute inside the bulk matrix evenly. The membranes exhibit hydrophilic/hydrophobic microphase-separated morphology as well as good thermal stability. The influences of irradiation parameters on the membrane property are investigated and the resulting membranes (named FEP-g-PSSA) exhibit excellent physicochemical properties. Membrane with 27.48% degree of graft and 130.1 mS cm−1 proton conductivity is employed for fuel cell performance measurement. Under optimized operate conditions (80 °C, 75% relative humidity), the power density could reach up to 0.896 W cm−2, inspiring for fuel cell application. The mass-transport-controlled polarization of membrane electrode assembly (MEA) based on FEP-g-PSSA membrane is higher than Nafion® 211 within the whole current density range and the gap is widening with increasing current density. At 2.0 A cm−2, the mass transfer polarization of FEP-g-PSSA reaches up to 0.204 V, far higher than Nafion® 211 (0.084 V). By promoting the compatibility between the ionomer in the catalyst layer and FEP-g-PSSA membrane and optimizing the membrane/catalyst layer/gas diffusion layer interfaces, the fuel cell performance could be significantly enhanced, making the FEP-g-PSSA membranes promising in fuel cell application.

Organic semiconducting polymers exhibited promising photocatalytic behavior for hydrogen (H2) evolution, especially when prepared in the form of polymer dots (Pdots). However, the Pdot structures were formed using common nonconjugated amphiphilic polymers, which have a negative effect on charge transfer between photocatalysts and reactants and are unable to participate in the photocatalytic reaction. This study presents a new strategy for constructing binary Pdot photocatalysts by replacing the nonconjugated amphiphilic polymer typically employed in the preparation of polymer nanoparticles (Pdots) with a low-molecular-weight conjugated polyelectrolyte. The as-prepared polyelectrolyte/hydrophobic polymer-based binary Pdots truly enhance the electron transfer between the Pt cocatalyst and the polymer photocatalyst with good water dispersibility. Moreover, unlike the nonconjugated amphiphilic polymer, the photophysics and mechanism of this photocatalytic system through time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements confirmed the Forster resonance energy transfer (FRET) between the polyelectrolyte as a donor and the hydrophobic polymer as an acceptor. As a result, the designated binary Pdot photocatalysts significantly enhanced the hydrogen evolution rate (HER) of 43 900 μmol g-1 h-1 (63.5 μmol h-1, at 420 nm) for PTTPA/PFTBTA Pdots under visible-light irradiation.

Stacked nanosheet nFETs considering a six-stack four-finger transistor array are studied and optimized by validated TCAD simulation. Stacked Si nanosheet (NS) nFETs have lower parasitics than nFinFETs in the same six-fin/stack four-finger transistor array layout. With the same electron mobility, back-end-of-line (BEOL), equivalent oxide thickness (EOT) of 1.4 nm, and gate length of 30 nm, the stacked Si NSs have $1.1\times $ cut-off frequency (240 versus 215 GHz) and $1.15\times $ maximum oscillation frequency (290 versus 251 GHz) when compared to FinFETs due to larger transconductance increase than capacitance increase and output conductance decrease. With the optimized EOT of 0.8 nm and gate length of 18 nm, the stacked Si NSs can achieve cut-off frequency of 340 GHz and maximum oscillation frequency of 370 GHz. Furthermore, considering the higher electron mobility on {100} surfaces of NSs than {110} sidewalls of FinFETs as suggested by the ${I} _{D}$ – ${V}_{\text {GS}}$ fitting, the cut-off frequency and maximum oscillation frequency of stacked Si NSs can reach 380 and 390 GHz, respectively.

A 6T-SRAM bitcell with the footprint of only two transistors is demonstrated by stacking four n-type vertical gate-all-around transistors (VFET) on two pFinFETs. The local interconnects are all within the footprint of the two bottom pFinFETs. The bitcell area is $0.014~\mu \text{m}^{{2}}$ considering the experimentally achievable metal pitch of 52 nm and bottom pFinFETs of 5 nm node. It can be further reduced to $0.009~\mu \text{m}^{{2}}$ considering the metal pitch of 30 nm. The minimum operating voltage is analyzed considering the dominant work function variation. The fin height of pFETs and the gate length of nFETs are used to optimize the read/write static noise margin (RSNM/WSNM) for the same bitcell area. The cell ratio is insensitive to pFET fin height and nFET gate length, leading the read stability to be less affected by pFET fin height and nFET gate length as compared to the write stability. The minimum operating voltage is reduced to 0.59 V using pFET fin height of 15 nm and nFET gate length of 20 nm to balance the read/write SNM without assist circuit techniques. The minimum operating voltage can be further improved to 0.56 V by optimizing the threshold voltage of −0.27 and 0.27 V for pFETs and nFETs, respectively. Moreover, using the negative bitline (NBL) technique can provide an additional 320 mV reduction on the write minimum operating voltage.

Copoly (arylene ether sulfone)s was employed for proton exchange membrane preparation via atom transfer radical polymerization followed by mild sulfonation, enhanced phase-separated morphology and favorable proton conductivity were achieved. The comprehensive ex-situ properties of a range of membranes with different ion exchange capacities were characterized alongside the fuel cell performances investigation. The membranes exhibit higher water uptake, which is beneficial to the proton conduction, compared to Nafion® 211 while maintaining similar swelling ratio. The prepared membranes exhibit reasonably high proton conductivity (0.16 S/cm at 85 °C) benefitting from the well-defined microstructure and high connectivity of the hydrophilic domains. Considering the comprehensive property, membrane with moderate ion exchange capacity (1.39 mmol/g) was employed to fabricate the membrane electrode assembly and peak power density of 0.65 W/cm2 at 80 °C, 60% relative humidity was achieved for a H2/O2 fuel cell, these hydrocarbon membranes can therefore be implemented in PEMFCs.

Marginal-restraint mandrel-free spinning is an advanced technology for manufacturing ellipsoidal heads with large diameter-thickness ratios. Nevertheless, the spinning-induced residual stress, which greatly influences the in-service performance of spun heads, should be removed. In this study, the effects of annealing on the residual-stress relaxation behavior of 5052H32 aluminum alloy spun heads were investigated. It is found that the residual stress first rapidly decreases and then remains steady with the increase in annealing time at the tested annealing temperatures. The relaxation of the residual stress becomes increasingly obvious with the increase in annealing temperature. When the annealing temperature is less than 220 °C, there are no obvious changes in grain size. Moreover, the spinning-induced dislocations are consumed by the static recovery behavior, which decreases the residual stress during annealing. When the annealing temperature is approximately 300 °C, the broken grains transform into equiaxed grains. In addition, static recrystallization and recovery behaviors occur simultaneously to promote the relaxation of the residual stress. Considering the different stress relaxation mechanisms, a model based on the Zener-Wert-Avrami equation was established to predict the residual-stress relaxation behavior. Finally, the optimized annealing temperature and time were approximately 300 °C and 30 min, respectively.

Two kinds of TiB2/Fe-15Cr-Mn-Al composites with low Mn and low Al as well as intermediate Mn and intermediate Al were prepared by using mechanical alloying (MA) with subsequent spark plasma sintering (SPS). The effects of Mn and Al contents on the microstructure as well as mechanical properties of the composites were investigated and compared with the composite with high Mn (20 wt.%) and high Al (8 wt.%) studied previously. The results indicated that during the sintering process, CrFeB-type boride formed in the two different composites which was similar to the high Mn and high Al composites but no Mn2B-type boride was observed. Furthermore, the matrix structure changed with the content of Mn and Al. Low contents of Mn (2 wt.%) and Al (1.5 wt.%) led to solid solution-strengthened α-Fe (Cr, Mn, Al) matrix, whereas intermediate contents of Mn (10 wt.%) and Al (5 wt.%) resulted in Fe2AlCr intermetallic matrix. The two composites showed high compressive strength and Vickers hardness, which increased as the Mn and Al contents in the matrix increased, which mainly resulted from the difference in hardness between α-Fe (Cr, Mn, Al), Fe2AlCr and CrFeB.

Conductivity of molten alkali metal chlorides is the foundation of molten-salt electrolysis process. In the study, equilibrium molecular dynamics was performed to investigate the ionic conductivities of the molten alkali metal chloride binary systems. The calculated values were in good agreement with the experimental results. Simple databases for conductivity have been built based on the verified algorithm. Mathematic expressions of conductivity vs. temperature & composition have also been obtained according to calculated data. Ionic conductivities of these melts exhibited positive dependences on temperature. Adding a smaller alkali metal cation into molten alkali chlorides could improve the conductive performance. With the gradual addition of LiCl, ionic conductivities of molten LiCl-NaCl, LiCl-KCl, LiCl-RbCl, and LiCl-CsCl all increased monotonously. The conductivities of molten NaCl-KCl, NaCl-RbCl, and NaCl-CsCl also increased with the continuous addition of NaCl. The improvement effects of LiCl on ionic conductivities of molten KCl, RbCl, and CsCl are more significant than those of NaCl.

In order to effectively improve the afterglow properties of CaAl2O4:Eu2+,Nd3+ phosphors, a series of Ca0.982–xAl2O4:0.012Eu2+,0.006Nd3+,xGd3+ (x = 0,0.012,0.024,0.036,0.048,0.060 mol) phosphors were prepared by a high-temperature solid-phase approach. Crystalline composition and microstructure were characterized by XRD, TEM, HRTEM, and XPS, luminescence properties were systematically analyzed by fluorescence spectra, afterglow decay curves and TL glow curve. Results show that all of Ca0.982–xAl2O4:0.012Eu2+,0.006Nd3+,xGd3+ phosphors belong to monoclinic CaAl2O4, without other cystalline phase. The blue emission at 442 nm is observed, which is assigned to the 4f65d →4f7 transition of Eu2+ ions. Doping with appropriate amount of Gd3+ ions (x = 0.036mol) significantly improves the afterglow properties of phosphors, but the excessive doping of Gd3+ induces the fluorescent quenching. The doping of moderate Gd3+ changes the traps states, the trap depth varies from 0.598 to 0.644 eV and the trap concentration is also greatly improved, thus significantly improving afterglow performance.

The panel-level redistribution-layer (RDL)-first fan-out packaging for hybrid substrate is studied. Emphasis is placed on the process, materials, design, and fabrication of: 1) heterogeneous integration of one large chip and one small chip with 50- $\mu \text{m}$ pitch (minimum); 2) fine metal linewidth and spacing RDL-first substrate on a temporary panel carrier; 3) ordinary build-up package substrate on a panel; 4) hybrid substrate which is by soldering the RDL-first substrate on the build-up substrate; and 5) chips to hybrid substrate bonding and underfilling. Reliability assessment by thermomechanical simulation includes thermal cycling of the heterogeneous integration of the two-chip package on the hybrid substrate that is performed by a nonlinear temperature- and time-dependent finite-element analysis.

To promote substantially the performances of red phosphorous (P) anode for lithium and sodium-ion batteries, a simple plasma assisted milling (P-milling) method was used to in-situ synthesize SeP2/C composite. The results showed that the amorphous SeP2/C composite exhibits the excellent lithium and sodium storage performances duo to the small nano-granules size and complete combination of selenium (Se) and phosphorous (P) to generate Se–P alloy phase. It was observed that inside the granules of SeP2/C composite the nanometer size of the SeP2 particles ensured the fast kinetics for Li+ and Na+ ​transfer, and the amorphous carbon wrapping the SeP2 particles relieved volume expansion during lithium/sodium storage processes and enhances electric conductivity. Therefore, the SeP2/C electrode retained reversible capacities of 700 ​mA ​h ​g−1 at 2 ​A ​g−1 after 500 cycles and 400 ​mA ​h ​g−1 at 0.5 ​A ​g−1 after 400 cycles as anode for LIBs and SIBs, respectively. The result proves that the amorphous SeP2/C composite can be a new type of anode material with great potential for lithium and sodium-ion batteries.

A facile solvothermal method coupled with an annealing strategy is developed to synthesize Fe3O4/carbon (Fe3O4@C) magnetic composite microstructures with different morphologies, including flower-like, hollow spheres and egg-like. The unique multiporous and hollow structure of the as-prepared hierarchical Fe3O4@C hollow microsphere results in an appealing performance as an absorber of Cr(VI) ions in aqueous solution, delivering a high capacity of ~ 197.2 mg/g. Meanwhile, the magnetic Fe3O4 ‘‘core’’ in the hierarchical microstructures can be easily separated from aqueous systems by magnetic separation. Furthermore, the carbon layers effectively prevent the aggregation of magnetic Fe3O4 nanoparticles. The excellent absorbing ability of Cr(VI) ions and easy separation process strongly suggest that the Fe3O4@C magnetic microstructures would have a great potential as adsorbing materials in the large-scale application in environmental purification.

Ti-6Al, Ti-6Al-2Mo and Ti-6Al-3Nb alloys were prepared to investigate the toughening effects of β stabilizers Mo and Nb on impact toughness and crack resistance of titanium alloys. Instrumented Charpy impact tests showed that the total impact absorbed energy of Ti-6Al-2Mo and Ti-6Al-3Nb (∼64 J) were two times higher than that of Ti-6Al (∼30 J), indicating the higher impact toughness of Ti-6Al-2Mo and Ti-6Al-3Nb alloys. Analysis of load-displacement curves revealed the similar crack initiation energy of Ti-6Al, Ti-6Al-2Mo and Ti-6Al-3Nb (15.4 J, 16.1 J and 15.0 J, respectively). However, the higher crack propagation energy of Ti-6Al-2Mo and Ti-6Al-3Nb (46.7 J and 48.3 J, respectively) were about three times higher than that of Ti-6Al (14.4 J), indicating the stronger resistance to crack propagation in Ti-6Al-2Mo and Ti-6Al-3Nb. Post-mortem analysis of impact samples demonstrated that the increased dislocation density and deformation twinning were mainly responsible for the stronger resistance to crack propagation in Ti-6Al-2Mo and Ti-6Al-3Nb. Due to the invisibility of dislocation activation and deformation twinning during the Charpy impact process, a mathematical model has been proposed to evaluate the effects of Al, Mo and Nb elements on dislocation mobility based on the Yu Rui-huang electron theory. Addition of Mo and Nb elements significantly improved the dislocation mobility in Ti-6Al-2Mo and Ti-6Al-3Nb compared to that in Ti-6Al alloy. Therefore, more dislocations were activated in Ti-6Al-2Mo and Ti-6Al-3Nb which supplied the larger plastic deformation under impact loading. A dislocation-based model also has been proposed to interpret the nucleation and propagation of deformation twinning under the impact loading. Dislocation pileup at α/β interfaces provided potential sites for nucleation of deformation twinning in Ti-6Al-2Mo and Ti-6Al-3Nb. Furthermore, deformation twinning facilitated the dislocation motion in α grains with hard orientations. The increased dislocation mobility and deformation twinning were responsible for the stronger crack resistance as well as the higher impact toughness of Ti-6Al-2Mo and Ti-6Al-3Nb alloys.

Increasing static recrystallization (SRX) nucleation rate and decreasing grain growth rate are the main ways to obtain uniform and fine grain microstructure by annealing treatment. However, it is contradictory to raise the SRX nucleation rate and reduce grain growth rate during isothermal annealing treatment. This is because the increase of the SRX nucleation rate needs to raise annealing temperature, while the decline of grain growth rate needs to reduce the annealing temperature. To solve the contradiction, a novel method named cooling recrystallization annealing treatment (CRT) is designed and verified. For the CRT, the relatively high annealing temperature in the primary stage can promote SRX nucleation, and the gradually decreased annealing temperature can reduce the growth rate of SRX grains. Besides, an aged treatment is first carried out to precipitate high content of the δ phase before the CRT. Enough δ phases not only provide large numbers of sites for SRX nucleation but also limit the grain growth due to the pinning effect, especially in the primary high-temperature stage. The results show that the novel method can refine deformed mixed grain microstructure well when the suitable cooling rate, start and final recrystallization annealing temperatures are employed. The deformed mixed grain can be uniformly refined to an average size of 8.26 μm with the route of 900°C×12 h+1020°C→970°C×20 min.

The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated. The two-stage heat treatment experiments include an aging annealing treatment (AT) and a subsequent recrystallization annealing treatment (RT). The object of AT is to precipitate some δ phases and consume part of storage energy to inhibit the grain growth during RT, while the RT is to refine mixed and coarse grains by recrystallization. It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high, while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low. In addition, the mixed microstructure composed of some abnormal coarse recrystallization grains (ACRGs) and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT temperature is 980 ℃. The phenomenon attributes to the uneven distribution of δ phase resulted from the heterogeneous deformation energy when the AT time is too short. In the regions with a large number of δ phases, the recrystallization nucleation rate is promoted and the growth of grains is limited, which results in fine grains. However, in the regions with few δ phases, the recrystallization grains around grain boundaries can easily grow up, and the new recrystallization nucleus is difficult to form inside grain, which leads to ACRGs. Thus, in order to obtain uniform and fine annealed microstructure, it is a prerequisite to precipitate even-distributed δ phase by choosing a suitable AT time, such as 12 h. Moreover, a relative high RT temperature is also needed to promote the recrystallization nucleation around δ phase. The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as: 900 ℃×12 h + 990 ℃×(40−60 min) and 900 ℃×12 h + 1000 ℃×(10−15 min).

ispartof: JOURNAL OF PHYSICAL CHEMISTRY C vol:126 issue:25 pages:10494-10505 status: published

We study a metal organic chemical vapor deposition regrowth process for electrically driven photonic-crystal surface-emitting lasers (PCSELs). The photonic-crystal (PC) structure consisting of air ...

Ion-mediated effective interactions are important for the structure and stability of charged particles such as colloids and nucleic acids. It has been known that the intrinsic electrostatic repulsion between like-charged particles can be modulated into effective attraction by multivalent ions. In this work, we examined the dependence of multivalent ion-mediated attraction between like-charged colloidal particles on the particle charge in a wide range by extensive Monte Carlo simulations. Our calculations show that for both divalent and trivalent salts, the effective attraction between like-charged colloidal particles becomes stronger with the increase of the particle charge, whereas it gradually becomes weakened when the particle charge exceeds a “critical” value. Correspondingly, as the particle charge is increased, the driving force for such effective attraction transits from an attractive electrostatic force to an attractive depletion force, and the attraction weakening by high particle charges is attributed to the transition of electrostatic force from attraction to repulsion. Our analyses suggest that the attractive depletion force and the repulsive electrostatic force at high particle charges result from the Coulomb depletion which suppresses the counterion condensation in the limited region between two like-charged colloidal particles. Moreover, our extensive calculations indicate that the “critical” particle charge decreases apparently for larger ions and smaller colloidal particles due to stronger Coulomb depletion and decreases slightly at higher salt concentrations due to the slightly enhanced Coulomb depletion in the intervening space between colloidal particles. Encouragingly, we derived an analytical formula for the “critical” particle charge based on the Lindemann melting law.

AlGaAs/InGaAs high-electron mobility transistors (HEMTs) are grown by molecular beam epitaxy (MBE). The studied HEMTs use two AlAs layers as etch-stop layers in the selective-etch recessed-gate fabrication of the HEMTs. The influence of passivation using silicon nitride on HEMTs is examined. Passivation improves the dc, high-frequency, and power characteristics of AlGaAs/InGaAs HEMTs. The passivated HEMT has a maximum extrinsic transconductance of 207 mS/mm, a unity-current-gain frequency (fT) of 13 GHz, and a maximum oscillation frequency (fmax) of 26 GHz. Furthermore, the variation of dc characteristics of the passivated HEMT with temperature is reduced.

Commercially pure titanium (CP-Ti) has seen major applications in biomedical equipment. The use of selective laser melting (SLM) has become more common concerning the fabrication of CP-Ti components with a complicated shape in biomedical implants, where high strength and ductility are required. However, SLM manufactured CP-Ti often exhibits high strength and low ductility, as well as mechanical anisotropy because SLM process typically results in the formation of long columnar grains comprising of fine acicular α′ martensite. Heat treatment must be preceded to transform the acicular α′ to equiaxed α grain. This study demonstrated that annealing at 650 °C of SLM CP-Ti can create an equiaxed structure, resulting in a weakened texture. The formation of equiaxed grains occurred at two types of microstructural features, acicular α′ and irregular massive (α′m) martensite, which exhibited different sizes, morphologies, and contained different types of substructures under SLM as-fabricated condition. The formation mechanism of equiaxed grains in the α′ region is dominated by the coalescence of acicular α′ of the same variant and the dissolution of α′ into the matrix, whereas the formation mechanism in the α′m region is primarily dominated by the growth of the preexisting subgrains. A small number of equiaxed grains with new orientations were formed in the α′m region. The majority of equiaxed grains were formed in the acicular α′ region and inherited the grain orientations of the preexisting α′ or matrix. Therefore, a similar but weakened texture was inherited from the microstructure of the SLM CP-Ti after annealing.

Aluminum matrix composites (AMCs) reinforced with graphene nanoplatelets (GNPs) were fabricated by using an accumulative roll-compositing (ARC) process. Microstructure, mechanical and electrical properties of the nanostructured AMCs were characterized. The results showed that small addition (0.2 vol% and 0.5 vol%) of GNPs can lead to a simultaneous increase in the tensile strength and ductility of the GNPs/Al nanocomposites, as compared with the same processed pure Al. With increasing GNPs content, the tensile strength of the GNPs/Al nanocomposites can be enhanced to 387 MPa with retained elongation of 15%. Meanwhile, the GNPs/Al nanocomposites exhibited a good electrical conductivity of 77.8%–86.1% that of annealed pure Al. The excellent properties (high strength, high ductility and high conductivity) of the GNPs/Al are associated with the particular ARC process, which facilitates the uniform dispersion of GNPs in the matrix and formation of ultrafine-grained Al matrix. The strengthening and toughening of the GNPs/Al nanocomposites were discussed considering different mechanisms and the unique effect of GNPs.

In this study, a novel gradient grating period guided-mode resonance (GGP-GMR) biosensor is proposed, and albumin was successfully detected as a test model. The GGP-GMR sensor exhibits a gradient resonant wavelength along the device. At a fixed incident wavelength, light resonates at a specific period such that the light is reflected at this period (or resonant period) and transmitted to other periods. Thus, for a charge-coupled device under the GGP-GMR sensor, a dip-like intensity distribution was measured with a specific pixel of minimum intensity corresponding to the resonant period. The variation in sample concentrations caused changes in the refractive index (RI) on the sensor surface, which induced a shift in the resonant period and in the pixel corresponding to the minimum intensity. A GGP-GMR sensor can achieve a limit of detection of $8.58\times 10^{{-4}}$ RIU within a detection range of sucrose solutions of 0%–60% concentrations that corresponds to the RI from 1.333 to 1.442. In a buffer solution, albumin was successfully detected to measure the clinically relevant concentration. The simple design and easy fabrication of the GGP-GMR sensor combined with its simple readout and optical path design facilitates system miniaturization for handheld devices and its integration with smartphones, which could be beneficial for future point-of-care applications.

Biobased polymers have received extensive research attention in flexible and renewable electronics to meet the concept of environmental sustainability. In this study, we develop a series of new polyimides (PIs) from biosources to serve as the substrate and dielectrics for a flexible organic field-effect transistor (OFET). The bioderived diamine, (3R,6S)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-aminobenzoate) (ISBA), synthesized from isosorbide (ISB), was reacted with three dianhydrides of pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride (BPDA), and cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) to obtain PIs and copolyimides (Co-PIs) with a high biomass content up to 53%. These bioderived PIs possessed high Td’s over 400 °C and Tg’s over 250 °C. Furthermore, the CBDA-based and PMDA-based PIs exhibited CTE values below 50 ppm K–¹ due to the rigid heterocyclic ISB unit and the structural linearity of the CBDA and PMDA moieties in the polymer backbone. High transparency and low coloration were also observed in the biobased PIs. Finally, highly thermal-resistant PI(ISBA-C95B5) consisting of the CBDA/BPDA mole ratio of 95/5 was applied as the substrate and dielectrics in flexible OFET, demonstrating the compatible and stable performance even after being baked at 200 °C for 2 h or 1000 bending cycles. The present study reveals the potential application of biobased PIs in electronic devices for a sustainable economy.

In Taiwan, due to intensive religious ceremonial activities, the flying and pyrotechnic fireworks of firecrackers are commonly used. In the course of the activities, the use of water as a cooling measure has been pointed out in the past literature that it may cause pyrotechnic materials to deteriorate and reduce their thermal stability. To determine the possible influence of water addition on pyrotechnic deterioration, this study estimates the degree of thermal hazard of pyrotechnic based on the analysis of heat release, reaction kinetics, and the heat exchange model of pyrotechnic deterioration. The explosion sound (ES) firecracker was used to analyze the thermal hazard and mixed water (ES + W) to simulate the dampness condition using differential scanning calorimetry. Thermodynamic equations simulating thermal hazard safety parameters, combined with thermokinetic and thermal runaway data results, were used to discuss the safety and potential thermal hazard characteristics of ES, as the safety of fireworks in storage, transportation, process conditions, and operation assessment to curtail the probability of accidents. The results showed that if the initial exothermic temperature of ES + W is higher than ES, a thermal decomposition reaction will occur at a lower temperature, and the exothermic heat rises and the apparent activation energy decreases, indicating that the ES will increase its instability after being damp. The presence of water degenerated the ES and resulted in a violent reaction during the release process to explode the ES, which increased the chance of accidents among the onlookers.

To realize high-performance and intrinsically stretchable materials for field-effect transistor (FET) devices, a plethora of approaches about structure design have been explored. Herein, we report a new approach to control the carrier mobility–stretchability properties of the polymers by tuning the hydrophilicity and asymmetric side-chain combination. A series of isoindigo–bithiophene (II2T)-based semiconducting polymers with three kinds of side chains including carbosilane side chain, semifluorinated side chain, and oligoether side chain were synthesized for investigating the structure–mobility and structure–stretchability relationships. The experimental results showed that the molecular stacking pattern and orientation of the derived polymers could be controlled by altering the hydrophilicity and asymmetric side-chain combination. The side chains of carbosilane and oligoether and a semifluorinated side chain could provide an order edge-on stacking, conformability and backbone aggregation, and an irregular solid-state aggregation, respectively. Among them, P(Si–O) with oligoether and a carbosilane side chain exhibited an enhanced μₕ of 0.56 cm² V–¹ s–¹, edge-on stacking, and aggregation behavior owing to the favorable intermolecular interaction between the oligoether side chain and the asymmetric side chain to mitigate the steric hindrance. Also, P(Si–O) possessed a remarkable stretchability of (92%,⊥, 82%,∥) orthogonal μₕ retention under 100% strain and almost unchanged μₕ was observed after 1000 stretching–releasing cycles at 60% strain. The experimental results suggested that the combination and hydrophilicity of side chain played a pivotal role in developing semiconducting polymers with a high performance and an intrinsic stretchability.

The present work investigates the thermal stability and mechanical properties of a Co–20Cr–15W–10Ni (wt%) alloy with a bimodal grain (BG) structure. The BG structure consisting of fine grains (FGs) and coarse grains (CGs) is thermally stable under high-temperature exposure treatments of 760 °C for 100 h and 870 °C for 100–1000 h. The size of both FGs and CGs remains no significant changes after thermal exposure treatments. The microstructural stability is associated with the slow kinetics of grain growth and the pinning of carbides. The thermal stability enables to maintain the BG structures, leading to the same mechanical properties as the sample without thermal exposure treatment. In particular, the BG alloy samples after thermal exposure treatment exhibit superior mechanical properties of both high strength and high ductility compared to the unimodal grain (UG) structured ones. The BG structure of the alloy samples after thermal exposure is capable of avoiding severe loss of ductility and retaining high strength. More specifically, the ductility of the BG alloy samples after thermal exposure treatments of 870 °C for 500–1000 h is ten times higher (44.6% vs. 3.5% and 52.6% vs. 5.0%) than that of the UG ones. The finding in the present work may give new insights into high-temperature applications of the Co–20Cr–15W–10Ni alloy and other metallic materials with a BG structure.

The mechanical properties and structural design flexibility of charge-trapping polymer electrets have led to their widespread use in organic field-effect transistor (OFET) memories. For example, in the electrets of polyfluorene-based conjugated/insulating block copolymers (BCPs), the confined fiberlike polyfluorene nanostructures in the insulating polymer matrix act as effective hole-trapping sites, leading to controllable memory performance through the design of BCPs. However, few studies have reported intrinsically stretchable charge-trapping materials and their memory device applications, and a practical method to correlate the thin-film morphology of BCP electrets with their charge-trapping ability has not yet been developed. In this study, a series of new conjugated/insulating BCPs, poly(9,9-di-n-hexyl-2,7-fluorene)-block-poly(δ-decanolactone)s (PF-b-PDLx, x = 1-3), as stretchable hole-trapping materials are reported. The linear and branched PDL blocks with comparable molecular weights were used to investigate the effect of polymer architecture on morphology and device performance. Moreover, the coverage area of the polyfluorene nanofibers on the BCP films was extracted from atomic force microscopy images, which can be correlated with the trapping density of the polymer electrets. The branched PDL segments not only improve stretchability but also tailor crystallinity and phase separation of the BCPs, thus increasing their charge-trapping ability. The OFET memory device with PF-b-PDL3 as the electret layer exhibited the largest memory window (102 V) and could retain its performance at up to 100% strain. This research highlights the importance of the BCP design for developing stretchable charge-trapping materials.

Despite demonstrating higher photoluminescence quantum yield and better ambient and operational stability than organic–inorganic hybrid perovskites, all-inorganic perovskites encounter the problem of inferior film quality and interfacial electrical properties, which limits the resultant device performance. In this study, three polymers, P4a–c, bearing distinct pendant groups based on a similar conjugated group are synthesized and employed as an interlayer to modify the PEDOT:PSS/CsPbBr3 interface. Due to the pendant design, P4a–c possess deep-lying HOMO levels and high transparency across the visible range. The different structures of the pendant groups in P4a–c are shown to result in their different propensity in energy-level modulation and solid-state aggregation, which plays a non-trivial role in affecting the resulting device performance. Due to the more appropriate energy levels and better regulation of CsPbBr3 crystals, P4c with a polar bridge moiety is shown to better mediate the performance of the derived device. The P4c-mediated PeLED delivers six times enhanced luminance (Lmax, ∼36 000 cd m−2) and 3.6 times enhanced external quantum efficiency (EQE, 2.16%) as compared to the control device (∼6000 cd m−2, 0.60%). Notably, all the devices using P4a–c interlayers deliver a lower turn-on voltage than the control device, clearly revealing the positive role of P4a–c interlayers on diminishing the barrier across the associated interface to improve charge injection efficiency.

Aldol reaction is a green approach that is exclusively suitable for developing conjugated polymers (CPs) with ladder-type structures. Herein, electron-deficient non-fused and fused bis-isoindigo (bis-IID) are copolymerized with axisymmetric thiophene (T) or centrosymmetric thieno[3,2-b]thiophene (TT) electron-rich spacers through Aldol polycondensation to prepare four donor–acceptor (D–A) CPs with ladder-type structures. The non-fused (P1 and P2) and fused (P3 and P4) bis-IIDs on the backbone lead to varied conformational flexibility that dominates aggregation, energy levels, and packing of the polymers. P3 and P4 with a planar backbone exhibit a stronger aggregation and lower bandgap (1.38 eV) than P1 and P2 (∼1.8 eV), while their intense non-crystalline aggregation also results in an amorphous structure. Meanwhile, the configurational differences arising from axisymmetric T unit (P1 and P3) and centrosymmetric TT unit (P2 and P4) spacers is shown to deeply affect the surface morphology and film ductility. The non-planar backbone endows P1 and P3 with low surface roughness and high brittleness. The combined low conformation and configuration regularity account for the inferior mobility of P1. On the contrary, P2–P4 exhibit comparable hole mobility ranging from 10−2–10−3 cm2 V−1 s−1 and up to 0.011 cm2 V−1 s−1 (P2), due to their better regularity in both conformation and configuration. Collectively, our results provide a new perspective for designing new D–A CPs through Aldol polycondensation.

A new donor–acceptor-type all-conjugated block copolymer (BCP), P(NDI-DBDT)-block-P(NDI-2T), is synthesized through the coupling of a naphthalene diimide (NDI)-bithiophene (2T) segment-based polymer (P1) and an NDI-dithienylbenzodithiophene (DBDT) segment-based polymer (P2). P1 has a prevailing backbone for NDI-based polymer acceptors, while P2 is modified to contain a p-type DBDT moiety to facilitate miscibility with the DBDT-based polymer donors. When adding 1 wt% BCP (the optimized blending amount) into the PBDB-T:N2200 blend that possesses similar constituent units to the BCP, the derived device can deliver an enhanced power conversion efficiency (PCE) of 7.07%, outperforming the control device (with a PCE of 5.71%). This improvement is found to arise from the more optimized bulk-heterojunction (BHJ) morphology as a result of facilitated intermixing between the photoactive components. This leads to reduced charge recombination and potential loss for the device. Moreover, the more optimized BHJ morphology endows the device with improved thermal robustness. It demonstrates longer T80 lifetimes when stored under constant thermal conditions at high temperatures. Consequently, the device lifetime can be extended to ∼2 years when stored under inert conditions at 50 °C. These results demonstrate that the rationally designed all-conjugated BCP can effectively modulate the BHJ morphology of an all-polymer blend to simultaneously enhance its photovoltaic performance and stability.

The development of conjugated polymers through the statistical terpolymerization of conjugation break spacers (CBSs) has received great attention because of their synergistic potential in enhancing fracture strain and tensile strength. In this study, a series of bulky and branched CBSs with ester functional groups and dimethyl (P1), methyl/propyl (P2), ethyl/butyl (P3), and dibutyl (P4) alkyl groups were incorporated into naphthalenediimide–bithiophene-based conjugated polymers through statistical terpolymerization. Morphological studies, including atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD) studies, were applied to pristine and stretched polymer films to decipher the structure–stretchability relationship; further, their mobility–stretchability relationship was investigated by studying their field-effect transistor (FET) characteristics. We found that polymers with bulky and branched CBSs exhibit reduced backbone rigidity, allowing polymer chains to entangle more easily than those of stiffer polymers with similar molecular weights. Therefore, the polymer film exhibits a more uniform load distribution throughout the channel layer, and the branched CBSs serve as lubricants that deter crack propagation during deformation. Consequently, P4 with symmetrically extended alkyl groups shows good ductility and mobility–stretchability properties, with orthogonal μe,‖/μe,⊥ retention of approximately 20–30% with 60% strain and 30–40% after 400 stretching–releasing cycles with 60% strain. Our results indicated that statistical terpolymerization with branched CBSs is a versatile and effective methodology for controlling orientational and stacking patterns to achieve good mobility–stretchability properties in conjugated polymers.

We report the synthesis, morphology and photo-memory device applications of a block copolymer (BCP) consisting of poly(9,9-dioctylfluorene) (PFO) and polystyrene (PS). Three BCPs were designed with various PS contents to manipulate the structure–performance relationship of the polymer electrets in a photonic field-effect transistor-type (FET) memory device. The memory device using the BCP electret exhibited a dynamic switching behaviour with photo-writing and electrical-erasing processes. We found that the BCPs with a high PS content provided improved device performance, which could be explained by two aspects: (1) the enhanced β-conformation of the PFO strengthened the electron-trapping capability, (2) the well-dispersed and microphase-separated morphology stabilized the trapped electrons on the interface of PFO and PS domains. Consequently, PFO5k-b-PS22k outperformed in terms of the photo-responding current along with having a high current on/off ratio of 104 and exhibited a retention time of more than 10 000 s. Our experimental results revealed the effectiveness of using the design based on a BCP for application in photonic FET memory devices.

To explore the mechanisms of squeak generation in automotive interior, the stick-slip experiments of polypropylene verse leather were conducted under various conditions. The friction properties wer...

The relationships between the structure and the dielectric properties of polyimides (PIs) were extensively studied to construct universal correlations of dielectric constant (Dk) and dissipation fa...

This study proposes a single-axis registration system based on monocular vision and CAD modelling without employing three-dimensional scanning or reconstruction techniques. The developed system use...

The bondability and reliability of Ag–5Pd–3.5Au alloy wire was verified previously for application in light-emitting diode (LED) packages. This Ag-alloy bonding wire has an electrical resistivity of 4.6 $\mu \Omega \cdot $ cm, lower than those of the ternary Ag–3Pd–20Au (8.6 $\mu \Omega \cdot $ cm) and Ag–3Pd–8Au wires (5.0 $\mu \Omega \cdot $ cm). Further evaluation of the resistance of ion migration in Ag-alloy bonding wires using water drop tests indicated that a declining tendency of ion migration rates existed for various binary Ag–Pd and ternary Ag–Pd–Au alloy wires with increases in Pd and Au contents. Among the all Ag-alloy bonding wires in this study, the Ag–5Pd–3.5Au wire exhibited the lowest ion migration rate of 4.87 $\mu \text{m}$ /s. The measurements of anodic dissolution rates were consistent with the tendency of ion migration rates, which were dependent on Pd and Au contents, resulting in the low value of Ag–5Pd–3.5Au alloy wire (0.017 $\mu \text{m}$ /s).

The organic semiconducting polymer dots (Pdot) or nanoparticles exhibited a promising efficiency as photocatalyst for hydrogen production. This study reported a new Pdot-based photocatalyst constructed in the form of Donor-Acceptor-Metal cocatalyst (D-A-Mcat). These D-A-Mcat Pdots systems consisting of fluorene (F) as the donor, thienyl-benzo-dithiophene-dione (TBDD) as the acceptor and [Ir (TPy)2 (acac)] as the metal complex, and their structural, thermal, electrochemical and photophysical properties were systematically demonstrated for the first time. Introducing the cyclometalated iridium (III) complex comonomer into the polymer chain resulting in PFTBDD-IrTPy Pdots showed enhancement of the hydrogen evolution rates, which is over 20-times higher than those of pure polymer (PFTBDD Pdots) under otherwise identical conditions. In addition, the optical and electrical measurements indicated that the cyclometalated iridium (III) part have an important function for inhibiting the charge recombination of the PFTBDD-IrTPy Pdots during the photocatalytic reaction. The result strongly implies that inserted catalytic amount of Ir(III)-complex into the D-A polymers is beneficial for the enhancement of photocatalytic hydrogen evolution, which can inspire further optimization and greater molecular design strategies at a low-cost are highly desirable for the development of high-performance in photocatalysis.

The influence of pre-strain on the formation of bimodal grain structures and tensile properties of a Co–20Cr–15W–10Ni alloy was investigated. The bimodal grain structures consist of fine grains (FGs; 2–3 μm in diameter) and coarse grains (CGs; 8–16 μm in diameter), which can be manipulated by changing the pre-strain (ɛ = 0.3–0.7) and annealing temperatures (1000–1100 °C). High pre-strain applied in the samples can intensify the plasticity heterogeneity through increasing the total dislocation density and the local volumes of high-density dislocations. This can essentially result in finer FGs, a higher FG volume fraction, and overall grain refinement in the samples after annealing. High-temperature essentially increases both the size and volume fraction of CGs, leading to an increase in the average grain size. The tensile test suggests that the bimodal grain structured samples exhibited both high strength and ductility, yield strengths of 621–877 MPa and ultimate tensile strengths of 1187–1367 MPa with uniform elongations of 55.0%–71.4%. The superior strength-ductility combination of the samples arises from the specific deformation mechanisms of the bimodal grain structures. The tensile properties strongly depend on the size ratio and volume fraction of FGs/CGs in addition to the average grain size in the bimodal grain structures. The grain structures can be modified via changing the pre-strain and annealing temperature.

This study determines the relationship between retention and endurance reliability for a HfOx-based resistive random access memory (ReRAM). A TiN (15 nm) / HfOx (6 nm) / Ti (10 nm) / TiN (40 nm) stacked structure is fabricated and tested to verify its basic characteristics and reliability. The high resistance states (HRS) retention behavior is characterized and is found to degrade over 100x on the endured bits because there is a sequential high temperature procedure. The degradation is reduced slightly to a ~30x drop for the endured devices with one single refresh cycle. During the endurance and retention test procedures, the HRS resistance decreases because neutral oxygen vacancy filaments grow and this cannot be reversed. The I-V characteristics for endured devices are also determined. The results show that isothermal treatment causes a gradual SET and RESET process with multiple feasible states. The thermally induced filament degradation model (isolated filament vs. continuous filament) is verified by the relationship between retention and endurance reliability. Design guidance is recommended for an improvement in ReRAM reliability.

Marginal-restraint mandrel-free spinning is an advanced technology for manufacturing ellipsoidal heads with large diameter-thickness ratios. The effects of spinning parameters on the forming accuracy of ellipsoidal heads have been studied, and optimized spinning parameters have been obtained. The microstructure evolution of a workpiece is usually very complicated in the spinning process. In this work, the influence of spinning parameters on the microstructures of two-pass spun ellipsoidal heads is studied. It is found that the forming angle and feed rate of the first pass, angle between passes, and feed rate of the second pass significantly affect the microstructures. Meanwhile, the evolution rule of the microstructures near the inner and outer surfaces of the spun parts is almost consistent. A large forming angle, large angle between passes, or large feed rate of the second pass are beneficial to obtain uniform microstructures. A small or large feed rate of the first pass reduces the microstructure uniformity. To improve the microstructure uniformity between the inner and outer surfaces, the optimized spinning parameters are determined.