Wide Process Window Research Articles

Fabrication of Silicone Rubber-Based Biochip for Disinfection Under Deep-UV Light by ArF Excimer Laser-Induced Photodissociation

A silicone rubber-based biochip for disinfection under deep-UV light exposure was successfully fabricated by an ArF excimer laser. To fabricate the biochip, periodic micro-swelling structure of silicone rubber was photochemically formed by the ArF excimer laser-induced photodissociation of Si–O bonds of silicone rubber. It was found that the growth rate of the micro-swelling structure could be controlled by varying the laser pulse repetition rate; a slow growth of roughly 100 ms and longer per laser pulse was recognized. In addition, no change of each the micro-swelling height formed at various laser pulse repetition rates was also found in the range of 300–18,000 of laser pulse number. Using such the wide processing window, moreover, the periodic micro-swelling structure could be modified into photoluminescent property by long irradiation of ArF excimer laser, while maintaining the micro-swelling height. Blue photoluminescence from the modified micro-swelling structure was observed under a deep-UV light exposure. Thus, each the periodic micro-swelling structure with various desired heights could be bonded to a flat plate of fused silica glass to have equal gaps. A small amount of solution could be confined in the equal gap to disinfect virus/bacteria in the solution under deep-UV light for analytical application.

Synthesis and properties of phthalonitrile-based resins containing spirocycle acetal

Designing novel low-melting, high-rigidity phthalonitrile resin is of great significance in the current context of development. In this study, rigid spirocycle acetal structure was introduced into phthalonitrile to reduce the melting point and maintain their thermal stability. The chemical structure of resins was confirmed by nuclear magnetic resonance (NMR) spectrometry, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry and Fourier-transform infrared (FTIR) spectroscopy. The curing behaviors were studied by differential scanning calorimetry (DSC). Thermal stability and mechanical properties of the cured resins were investigated by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The processability was studied by rheological analysis. The results indicated the three monomers had a low melting temperature, wide processing windows and low viscosities. These polymers did not exhibit Tg from room temperature to 400°C, exhibited superb dynamic mechanical property and thermal stability.

A comparative study on the rheological, thermal, and mechanical performance of epoxy resin modified with thermoplastics

Thermoplastics and functional polymers are commonly used modifiers for epoxy (EP) resin. In this study, an EP system was fabricated and modified with methyl methacrylate block copolymer (BMG), polyphenylene oxide (PPO) and polysulfone (PSF). This was carried out to study the influence of thermoplastic polymers and functional polymers on the properties of EP resins, and the performance of the different modified EP systems was studied and compared. The curing reaction, rheological performances, heat resistance, and mechanical properties of the EP blends were investigated. Curing process of EP resin was determined as 110 °C for 1 h and 150 °C for 3 h by using non-isothermal differential scanning calorimetry (DSC) method. The rheological test revealed that the EP/BMG and EP/PPO blends exhibited low viscosity and wide processing window compared to the EP/PSF blend, thereby indicating good processing performance. The thermal stability of the modified EP blends was evaluated by using dynamic mechanical analysis methods. The results showed that the glass transition temperature (Tg ) of EP/BMG, EP/PPO and EP/PSF blends were 123 °C, 129 °C, and 131 °C, respectively. BMG showed an excellent toughening effect on EP resin compared to PPO and PSF. In addition, the flexural strength and impact strength of EP/BMG were 114 MPa and 21.2 kJ/m2, respectively. The influence of polymers on the properties of EP resin stems from their molecular structures.

Influence of Hot Consolidation Conditions and Cr-Alloying on Microstructure and Creep in New-Generation ODS Alloy at 1100 °C.

The coarse-grained new-generation Fe-Al-Y2O3-based oxide dispersion strengthened (ODS) alloys contain 5 vol.% homogeneously dispersed yttria nano-precipitates and exhibit very promising creep and oxidation resistance above 1000 °C. The alloy is prepared by the consolidation of mechanically alloyed powders via hot rolling followed by secondary recrystallization. The paper presents a systematic study of influence of rolling temperature on final microstructure and creep at 1100 °C for two grades (Fe-10Al-4Y2O3 and Fe-9Al-14Cr-4Y2O3 in wt%) of new-generation ODS alloys. The hot rolling temperatures exhibit a rather wide processing window and the influence of Cr-alloying on creep properties is evaluated as only slightly positive.

High-Pressure Nitrogen-Extraction and Effective Passivation to Attain Highest Large-Area Perovskite Solar Module Efficiency.

Slot-die coating holds advantages over other large-scale technologies thanks to its potential for well-controlled, high-throughput, continuous roll-to-roll fabrication. Unfortunately, it is challenging to control thin.film uniformity over a large area while maintaining crystallization quality. Herein, by using a high-pressure nitrogen-extraction (HPNE) strategy to assist crystallization, a wide processing window in the well-controlled printing process for preparing high-quality perovskites is achieved. The yellow-phase perovskite generated by the HPNE acts as a crucial intermediate phase to produce large-area high-quality perovskite film. Furthermore, an ionic liquid is developed to passivate the perovskite surface to reduce surface defect density and to suppress carrier recombination, resulting in significantly increased efficiency to 22.7%, the highest for large-area fabrication. The strategies are successfully extended to large-area device fabrication, making it possible to produce a 40×40 mm2 module with stabilized PCE as high as 19.4%, the highest-efficiency for a large-area module to date.

Roll-to-roll gravure-printed flexible perovskite solar cells using eco-friendly antisolvent bathing with wide processing window

Driven by recent improvements in efficiency and stability of perovskite solar cells (PSCs), upscaling of PSCs has come to be regarded as the next step. Specifically, a high-throughput, low-cost roll-to-roll (R2R) processes would be a breakthrough to realize the commercialization of PSCs, with uniform formation of precursor wet film and complete conversion to perovskite phase via R2R-compatible processes necessary to accomplish this goal. Herein, we demonstrate the pilot-scale, fully R2R manufacturing of all the layers except for electrodes in PSCs. Tert-butyl alcohol (tBuOH) is introduced as an eco-friendly antisolvent with a wide processing window. Highly crystalline, uniform formamidinium (FA)-based perovskite formation via tBuOH:EA bathing was confirmed by achieving high power conversion efficiencies (PCEs) of 23.5% for glass-based spin-coated PSCs, and 19.1% for gravure-printed flexible PSCs. As an extended work, R2R gravure-printing and tBuOH:EA bathing resulted in the highest PCE reported for R2R-processed PSCs, 16.7% for PSCs with R2R-processed SnO2/FA-perovskite, and 13.8% for fully R2R-produced PSCs.

Influence of global and local process gas shielding on surface topography in laser micro polishing (LμP) of stainless steel 410

Laser micro polishing (LμP) is a new laser-based material processing method that has a high potential to overcome common disadvantages of traditional polishing techniques. A special challenge in LμP is the processing of large areas since processing in a process gas atmosphere is deemed necessary to avoid undesired oxidation and minimize surface roughness. Therefore, a new process strategy for LμP on stainless steel AISI 410 was investigated in which a gas nozzle was used to create a local process gas shielding and therefore to significantly increase the field of maximal processing. Using a Nd:YAG high power Q-switch laser, we demonstrated that local process gas shielding is feasible for LμP in terms of avoidance of surface defects and achieved micro-roughness. In addition, a wide process window in terms of nozzle distances and gas flow exists for LμP. The resulting surfaces are highly reproducible in terms of surface roughness. Besides Argon, Nitrogen is another process gas that is highly suitable for LμP of AISI 410. The use of Nitrogen might therefore significantly lower future production costs in LμP. Finally, spatially resolved LμP was explicitly demonstrated on a textured press plate.

Fabrication of stretchable and conductive polymer nanocomposites based on interconnected graphene aerogel

The construction of advanced nanocomposite structures is a principal strategy to realize the electrical and mechanical functionalities of graphene for flexible electronic applications. Herein, two types of conductive and stretchable networks were fabricated by incorporation of polyurethane and silicone elastomers into highly porous and interconnected graphene gels. The layer-by-layer assembly of the graphene aerogel was solution-processable at room temperature, which offers a wide processing window for the solvent engineering and infiltration of polymers to improve wettability. Effects of graphene-polymer interfacial properties were investigated by their cross-sectional morphologies and viscoelastic analyses to elucidate the packing density, dispersion state, surface chemistry, polymer distribution and chain mobility. The polymer-infiltrated graphene network exhibited a high conductivity of ~100 S/m at a low filler content of 0.8 wt%. Given the excellent structural integrity, the graphene composites demonstrated unique electrical properties under stretching and bending conditions. Particularly, a maximum conductivity of 47 S/m was achieved under 50% tensile strain and the resistance deviation was less than 5% upon 500 bending cycles. The proposed design of graphene architecture and polymer infiltration techniques serve to pave the way for the next-level development of graphene electronics.

Carborane-containing bismaleimide resins with excellent heat resistance and dimensional stability

Novel carborane-containing bismaleimides with excellent heat resistance and dimensional stability for advanced composites are presented. First, a new kind of carborane-containing mono-maleimido-terminated monomer 1-(4-tolyl)-2-(4-maleimido phenyl)- o-carborane (CB-MI) was synthesized and characterized by FT-IR and 1H-NMR. Then, it was used as a modifier for bismaleimide resin 4,4’-bismaleimidodiphenylmethane (BDM) with different weight fraction of CB-MI. The curing behavior and thermal property of the CB-MI/BDM resin systems were studied and presented here. Results displayed that a wide processing window and low curing temperature provided a good processability for the CB-MI/BDM resin system. Due to the effect of carborane groups, the char yield at 600°C of the cured resin systems tended to be increased with the addition of CB-MI. Moreover, the coefficient of thermal expansion of the resin was found to be reduced with the increase of CB-MI, indicative of a remarkable dimensional stability. This study might open up great opportunities for the preparation and design of various novel bismaleimides in a simple and feasible way and the resins with good thermal property and processability at the same time.

Impact of Si and Al on Microstructural Evolution and Mechanical Properties of Lean Medium Manganese Quenching and Partitioning Steels

Herein, the investigation of the tensile behavior of lean medium Mn Quenching and Partitioning (Q&P) steels containing 0.2 wt% C, 4.5 wt% Mn, and additions of 1.5 wt% Si or 1.3 wt% Al is concentrated upon. By the variation of the quenching temperature (TQ), different volume fractions of primary martensite (α′prim) are adjusted, influencing the subsequent microstructural evolution during Q&P processing. Using scanning electron microscopy (SEM), the final microstructure consisting of tempered martensite (α″), retained austenite (RA), partially bainitic ferrite (αB), and final martensite (α′final) is characterized. Furthermore, interrupted tensile tests at gradually increased strains are conducted to investigate the stability of RA against strain‐induced martensite transformation (SIMT) and overall tensile behavior of lean medium Mn Q&P steels. The investigations manifest the formation of larger amounts of αB and consequently lower RA contents, when Si is substituted by Al. As an aftermath, the tendency to form α′final is significantly lower, compared with the Si‐alloyed composition, reflected in the overall stress–strain behavior. Especially in case of the Si‐alloyed samples containing RA fractions exceeding 15 vol%, an over‐accelerated SIMT is observed, inducing failures occurring prior to necking, whereas for the Al‐alloyed samples, a wider process window is obtained.

Nanotwin formation in Ni–Mo–W alloys deposited by dc magnetron sputtering

Nanotwinned metals and alloys have an attractive suite of properties, but the formation of the underlying nanostructure is generally dependent on the alloy chemistry and processing conditions. This study was undertaken to investigate the effect of deposition rate on nanotwin formation in sputter deposited Ni84Mo11W5 that possess ultrahigh strength and stability. Deposition rates of 0.5–2.3 nm/s were examined and the grain size, texture, twin spacing and hardness were characterized. Minimal variations in the underlying nanostructure and attendant hardness were observed, elucidating a wide processing window and the importance of chemistry on the formation of nanotwins in this alloy.

Influence of Segregation on Microstructure and Hot Workability of Grade 250 Maraging Steel

The optimal process parameters of grade 250 maraging steel for hot forging were investigated with a process map and microstructure analysis. To generate the process map, hot compression tests were performed at 800–1200 °C and strain rates of 0.01–5 s−1. The flow stress–strain curves were calibrated by Bayesian artificial neural network (ANN) modeling to compensate the heat generated by dynamic deformation. The Ni and Mo segregation during the solidification of the ingot caused alternating layers of Ni- and Mo-rich and -lean bands, which affected the recrystallization behavior during hot compression. According to the calculated process map, 1100–1200 °C × 0.01–0.7 s−1 and 1000–1200 °C × 0.01–0.2 s−1 are favorable process conditions that ensure wide process windows in terms of strain rate and temperature, respectively. The common features of the microstructure deformed under both conditions were relatively coarse martensite blocks and low values in the electron backscattered diffraction (EBSD) kernel average misorientation (KAM) results (i.e., low residual stresses), which were attributed to a low fraction of fine martensite block region.

Fabrication of Freestanding Metallic Ni-Mo-W Microcantilever Beams With High Dimensional Stability

Recent studies have elucidated a promising balance of physical and mechanical properties of sputter deposited nickel-molybdenum-tungsten (Ni-Mo-W) films that have a unique nanotwinned microstructure and promising potential for use in high temperature microelectromechanical systems (MEMS). The current study was undertaken to establish the feasibility of making nanotwinned Ni-Mo-W microcantilevers with standard microfabrication processing, to assess their dimensional stability, and to demonstrate the possibility of using nanotwinned Ni-Mo-W in metal MEMS devices. Deposition of Ni-Mo-W films in commercial sputtering chambers revealed a wide processing window for the formation of the requisite nanotwinned microstructure. Conventional photolithography and etchants were employed to shape blanket Ni-Mo-W films into freestanding microcantilever beams. Monitoring microcantilever deflections via interferometry provided a direct measure of residual stresses and overall dimensional stability. Heat treatments of 200°C and 400°C were used to mimic wafer bonding temperatures. At 400°C, microcantilevers exhibited modest stress relaxation, yielding beam deflection profiles on the nanometer scale and portending dimensional stability and control for future metal MEMS devices.

Mastering Yield Stress Evolution and Formwork Friction for Smart Dynamic Casting.

The construction industry is a slow adopter of new technologies and materials. However, interdisciplinary research efforts in digital fabrication methods with concrete aim to make a real impact on the way we build by showing faster production, higher quality and enlarged freedom of design. In this paper, the potential and constraints of a specific digital slip-forming process, smart dynamic casting (SDC), are investigated with a material-focused approach in the complex task of producing thin folded structures. Firstly, the workability and the strength evolution of different material compositions are studied to achieve the constant processing rate for SDC. Secondly, friction between the formwork walls and the concrete, a key aspect in slip-casting, is studied with a simplified experimental setup to identify if any of these mixes would provide an advantage for processing. Finally, a theoretical framework is constructed to link the material properties, the process conditions and the designed geometry. This framework introduces the ‘SDC number’ as a simplified approach to formulate the process window, the suitable conditions for slip-forming. The experimental results prove the assumption of the model that friction is proportional to yield stress for all base compositions and acceleration methods regardless of the filling history. The results are evaluated in the context of the narrow process window of thin folded structures as well as the wider process window of columns. The necessity of consistent strength evolution is underlined for narrow windows. Further, friction is shown to be the highest initially, thus with both narrow and wide process windows, after a successful start-up the continuation of slipping is less prone to failure. The proposed theoretical model could provide material and geometry-specific slipping strategy for start time and slipping rate during production.

Zinc Oxide Films with High Transparency and Crystallinity Prepared by a Low Temperature Spatial Atomic Layer Deposition Process.

Zinc oxide (ZnO) attracts much attention owing to its remarkable electrical and optical properties for applications in optoelectronics. In this study, ZnO thin films were prepared by spatial atomic layer deposition with diethylzinc and water as precursors. The substrate temperature was varied from 55 to 135 °C to investigate the effects on the optical, electrical, and structural properties of the films. All ZnO samples exhibit an average transmittance in visible and near-infrared light range exceeding 80% and a resistivity in the range of (3.2–9.0) × 10−3 Ω·cm when deposited on a borosilicate glass with a refractive index of ≈1.52. The transmittance, band gap, refractive index, and extinction coefficient are rarely affected, while the resistivity only slightly decreases with increasing temperature. This technique provides a wide process window for depositing ZnO thin films. The results revealed that the films deposited at a substrate of 55 °C were highly crystalline with a preferential (1 0 0) orientation. In addition, the grains grow larger as the substrate temperature increases. The electrical properties and reliability of ZnO/PET samples are also studied in this paper.

Effect of Blending Modifications for Phenylethynyl-terminated Polyimides

A reactive diluent (ODA-PEPA) and a flexible phenylethynyl-terminated imide oligomer (PEI-PEPA) were designed and synthesized based on the 2,3,3’,4’-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA), 3,4’-oxydianiline (3,4’-ODA), and 4-phenylethynylphthalic anhydride (PEPA). Solution blended systems with the addition of 5, 10, and 15 wt% ODA-PEPA to PEI-PEPA oligomer and their cured resin systems were prepared. Results showed that ODA-PEPA is semi-crystalline in nature. The Tg values of cured resins were improved from 273 °C to 280 °C by the addition of ODA-PEPA, due to the higher crosslink densities. In addition, rheological properties of blends showed lower melt viscosity and wider processing window, revealing improved melt processabilities for potential application in making advanced composites. The isothermal viscosity in 280 °C of PEI-PEPA containing 15 wt% ODA-PEPA reactive diluent decreased by two thirds, due to the low molecular weight of ODA-PEPA. The cured blends demonstrated high thermal stability and heat resistance. 5 wt% thermal decomposition temperatures (Td5) of the cured blends were above 549 °C and 547 °C in N2 and air atmosphere, respectively. The char yield reported at 800 °C in N2 atmosphere increased from 58.8% to 63.7 % with the addition of ODAPEPA. Meanwhile, the cured polyimides blends possessed good bond strength (> 9.3 MPa).

Superior Textured Film and Process Tolerance Enabled by Intermediate-State Engineering for High-Efficiency Perovskite Solar Cells.

As the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is increased to as high over 25%, it becomes pre‐eminent to study a scalable process with wide processing window to fabricate large‐area uniform perovskite films with good light‐trapping performance. A stable and uniform intermediate‐state complex film is obtained by using tetramethylene sulfoxide (TMSO), which extends the annealing window to as long as 20 min, promotes the formation of a high‐quality perovskite film with larger grains (over 400 nm) and spontaneously forms the surface texture to result in an improved fill factor and open‐circuit voltage (V oc). Moreover, the superior surface texture significantly increases the long‐wavelength response, leading to an improved short‐circuit current density (J sc). As a result, the maximum PCE of 21.14% is achieved based on a simple planar cell structure without any interface passivation. Moreover, a large area module with active area of 6.75 cm2 is assembled using the optimized TMSO process, showing efficiency as high as 16.57%. The study paves the way to the rational design of highly efficient PSCs for potential scaled‐up production.

Synthesis and Properties of a Silicon‐Containing Arylacetylene Resin with 2,6‐Diphenoxypyridine Unit

AbstractA novel silicon‐containing arylacetylene resin called poly(dimethylsilylene‐ethylene‐phenoxypyridyloxy‐phenylene‐ethylene) (PSPPY) was made from 2,6‐bis(4‐ethynyl‐phenoxy) pyridine and dimethyldichlorosilane by Grignard reactions. The structure and properties of the resin were characterized by 1H‐NMR, FT‐IR, GPC, XRD, DSC, TGA and universal testing machine. The resin has a wide processing window ranged from 35 °C to 155 °C. The cured resin shows excellent mechanical property, low dielectric property and high thermal stability. The flexural strength of the cured resin at room temperature reaches 58.7 MPa. The cured resin has dielectric constant 3.0–3.5, dielectric loss 0.008‐0.040 in the frequency of 10−1‐106 Hz, and low water uptake (0.8 %). The degradation temperature at 5 % weight loss and the residue at 800 °C of the cured resin arrive at 500 °C and 77.1 % in nitrogen atmosphere, respectively.

Deep penetration laser welding of austenitic stainless steel thick-plates using a 20 kW fiber laser

The deep penetration laser welding of a thick section of austenitic stainless steel by a 20 kW laser is systematically evaluated. The welding phenomena of bead-on-plate and butt-welding of 20 and 30 mm thick steel plates are examined. The results show that the penetration depth of bead-on-plate welding can reach 32 mm and that wide processing windows exist to obtain defect-free butt-welding of 20 mm thick plates, but not for 30 mm thick plates. When the welding position is changed from a flat welding position (1G) to a horizontal welding position (2G), butt-welding of 30 mm thick plates can be penetrated successfully to obtain defect-free welds. The weld joint maintains the full austenite microstructure, which is composed of mostly directional columnar and cellular grains, while there are some equiaxed grains at the weld center.

Synthesis and characterization of thermosetting polyacetylene‐terminated silicone resins

ABSTRACTA novel polyacetylene‐terminated silicone (PTS) resins possessing low curing temperature and high heat resistance has been prepared by Grignard reaction using m‐diacetylenylbenzene (DEB), 1,3,5‐triacetylenylbenzene(TEB), and dichlorosilane as original materials. The reaction of the functional groups was characterized by in situ Fourier transform infrared spectrometer. The experimental results indicated that Si─H and C≡CH bonds are almost exclusively involved in the crosslinking reaction, while ─C≡C─ bonds only partially react. Further, Si─H and C≡CH bonds can participate in the curing reaction at relatively low temperatures, but ─C≡C─ bonds require higher temperature, indicating the higher activity of Si─H and C≡CH bonds than ─C≡C─ bonds. As determined by differential scanning calorimetry, PTS resins have low peak exothermic temperature at 184.5 °C, which is lower than MSP resin (~ 210 °C); in addition, rheological test showed that PTS resins have a very wide processing window from 40 to 163.3 °C, indicating that the PTS resins have excellent processability with a low curing temperature and wide processing window. What is more, TGA results of thermal‐cured PTS resins revealed that Td5 (5% weight loss temperature) of PTS‐H10 reached the highest of 684.4 °C. Compared with PTS‐H0 resin, there is an increase of 124.2 °C and the remarkably increased heat resistance correlated with a higher m‐DEB input ratio. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48783.