Wide Process Window Research Articles

Ionic Liquid Modified Poly(vinyl alcohol) with Improved Thermal Processability and Excellent Electrical Conductivity

The combination of polymer and ionic liquid (IL) is attracting increasing attention because of its versatile and tunable properties. In this paper, the IL 1-(2-hydroxyethyl)-3-methylimidazolium chloride ([HOEtMIM]Cl), which has a complementary structure with poly(vinyl alcohol) (PVA), was adopted to act as a novel plasticizer for PVA to improve its thermal processability. The results demonstrated that the hydroxyl group and Cl– in the IL formed strong hydrogen bonds with the hydroxyl groups of PVA, thus efficiently confining its crystallization, decreasing its melting point, and obtaining a wide thermal processing window, up to 110 °C. The resultant PVA/IL composites showed high ionic conductivity, up to 2.82 × 10–3 S/cm, and considerable flexible mechanical properties with an elongation at break of 317% when the IL content was 35 wt %, opening the potential applications of PVA in the field of flexible semisolid state electric double-layer supercapacitors (EDLC) and proton exchange membranes (PEM).

Kerfless epitaxial silicon wafers with 7 ms carrier lifetimes and a wide lift-off process window

Silicon wafers contribute significantly to the photovoltaic module cost. Kerfless silicon wafers that grow epitaxially on porous silicon (PSI) and are subsequently detached from the growth substrate are a promising lower cost drop-in replacement for standard Czochralski (Cz) wafers. However, a wide technological processing window appears to be a challenge for this process. This holds in particularly for the etching current density of the separation layer that leads to lift-off failures if it is too large or too low. Here we present kerfless PSI wafers of high electronic quality that we fabricate on weakly reorganized porous Si with etch current densities varying in a wide process window from 110 to 150 mA/cm2. We are able to detach all 17 out of 17 epitaxial wafers. All wafers exhibit charge carrier lifetimes in the range of 1.9 to 4.3 ms at an injection level of 1015 cm−3 without additional high-temperature treatment. We find even higher lifetimes in the range of 4.6 to 7.0 ms after applying phosphorous gettering. These results indicate that a weak reorganization of the porous layer can be beneficial for a large lift-off process window while still allowing for high carrier lifetimes.

Orientation Behavior and Mechanism of Ag-doped GdBa2Cu3O7-δ Superconducting thin Films Derived by Metal Organic Deposition

Ag-doped GdBa2Cu3O7−δ (GdBCO)-coated conductors are fabricated via a metal-organic process. The X-ray diffraction and scanning electron microscopy results show that the growth conditions of the GdBa2Cu3O7−δ matrix are modified, resulting in less a-axis growth and much smoother surface morphology and finally giving rise to much improvement of superconducting performance in a wide range of processing parameters. The orientation behavior and mechanism of Ag-doped GdBCO films are investigated. To reasonably explain the orientation behavior of Ag-doped GdBCO films, a simple nucleation model for Ag-doped GdBCO is established, suggesting quasi-liquid phases are perfected by Ag. As a consequence, a-axis nucleation is suppressed and strong c-axis nucleation is achieved in a wider processing window.

Self-curing triphenol A-based phthalonitrile resin precursor acts as a flexibilizer and curing agent for phthalonitrile resin.

Major problems currently limiting the widespread application of phthalonitrile resins are the high precursor melting point and volatility of the curing agent. Herein, a novel self-curing triphenol A-based phthalonitrile resin precursor (TPPA-Ph) was successfully synthesized by reacting α,α,α′-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene (TPPA) with 4-nitrophthalonitrile (NPh) via nucleophilic substitution. The presence of residual phenolic hydroxyl groups in the TPPA-Ph precursor promoted the curing reaction of phthalonitrile resin in the absence of an additional curing reagent. Self-cured TPPA-Ph resins exhibited relatively low melting points (less than 100 °C), high thermal stability, and a wide processing window (116 °C). Furthermore, the TPPA-Ph precursors contained phenolic hydroxyl and cyano groups that can be used as flexibilizers and curing agents to optimize other phthalonitrile resins. Resorcinol-based phthalonitrile resin (DPPH) cured with various amounts of TPPA-Ph possessed excellent thermal and thermo-oxidative stability with a 5% weight loss temperature exceeding 530 °C, Tgs above 380 °C, and a wide processing window and time. Therefore, as a novel precursor and curing agent for phthalonitrile resins, the triphenol A-based phthalonitrile resin is an ideal resin matrix for high-performance composites with broad application prospects in aerospace, shipping, machinery, and other high-tech fields.

Synthesis and characterization of semiaromatic copolyamide 10T/1014 with high performance and flexibility

Poly (decamethylene terephthalamide) (PA10T) is a kind of engineering plastics with high strength and high modulus, but one of its disadvantages is its low elongation at break. In order to improve the flexibility of PA10T, one aliphatic comonomer with a long alkyl chain is introduced to the molecular chain of PA10T. Then long chain semiaromatic copolyamides 10T/1014 were synthesized with different contents of 1014 units by polycondensation reaction of 1,10-diaminodecane, terephthalic acid and 1,12-dodecanedicarboxylic acid in deionized water. The intrinsic viscosities of the resultant polyamides ranged from 0.90 to 1.03 dL/g were obtained. The chemical and crystal structures of the copolymers were characterized by FTIR, 1H-NMR and WAXD. These copolyamides exhibited outstanding thermal properties with melting points range of 306–295 °C and degradation temperatures range of 479–472 °C at maximum degradation rate, and also have a wider processing window than PA10T. The tensile strength of PA10T/1014 copolymers decreased gradually from 80.02 to 72.95 MPa as the content of 1014 units increasing from 5 to 20 mol %, while the elongation at break increased significantly from 57 to 150%. The moisture content of 10T/1014 copolyamides decreased with increasing the 1014 unit contents. It suggests that 10T/1014 copolyamides could be a kind of promising heat-resistant engineering thermoplastic in the future applications.

Experiences with inline feedback control and data acquisition in deep drawing

The increasing complexity of parts produced in deep drawing needs an enhanced process design, which results in different methods of the visualization of process windows. With these visualization methods, the process is usually designed to reach wide process window. Due to changing friction through rising temperatures in the tools, tool wear or batch to batch variations in the material, the process window is reduced again. Therefore new methods are needed to keep the process inside the process window.The paper deals with a possible approach of keeping the process inside these windows. The proposed approach tries to unite the measurement of possible influence factors like the batch to batch variation of material properties with a feedback control to eliminate the non-measurable influences. The measurement of the material properties is done by a measurement system based on eddy-currents, while the needed measurement for a feedback control is done with an optical system. Finally the paper will show the experiences with the proposed system, as well as it will show the prerequisites for such a system.

Specific cutting energy of Inconel 718 under dry, chilled-air and minimal quantity nanolubricants

Efficient and optimal consumption of energy in manufacturing industries appear as vital strategies towards minimisation of cost due to the uncertainties of energy prices apart from emphasising on the environmental sustainability of manufacturing processes. It has been reported that energy efficiency for material removal processes can be quite small compared to the total energy for the machine tool operation. Notwithstanding this, due to novel strategies alongside with a wide process window of machining operations being proposed from research work, the need to reevaluate the energy efficiency in metal machining is inevitable. Coolant strategy in machining processes is capable of reducing the energy consumption during the cutting process, due to the cooling and lubricating effects provided by the coolant system. Hence, in this work, the specific energy consumption during turning of Inconel 718 with different coolant approaches namely; dry, vortex-tube chilled air, and nanolubricants enhanced minimum quantity lubricant (MQL) were compared. A general purpose coated carbide tool was used with a constant depth of 0.25 mm. Four different feed rates in the range of 0.1 to 0.4 mm/rev with six different cutting speeds of 60 to 110 m/min were tested to evaluate the specific cutting energy. For each of the cutting speeds and coolant approaches, the specific cutting energies were determined from the gradient of power consumption against material removal rate. Apart from that, the power law relationships between the feed rate and specific cutting energy were also established for each of the coolant approaches. Experimental results suggest that the use of aluminium oxide nanolubricants enhanced with MQL system leads to a marginal reduction in specific cutting energy as to that of dry and vortex chilled air. The specific cutting energy was the highest for the vortex chilled air, although it was earlier anticipated that dry cutting should be poor in term of energy consumed upon this short-duration machining.

Control of Carbon Content in Steel by Introducing Proeutectoid Ferrite Transformation into Hot-Rolled Q&P Process

A processing strategy involving primary and secondary carbon partitioning is proposed for the hot-rolled quenching and partitioning process through the introduction of proeutectoid ferrite transformation after rolling. The microstructures of the steels were characterized using scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, and x-ray diffraction, and the mechanical properties were evaluated using a universal tensile machine. The blocky retained austenite that distributed along the ferrite grain boundaries was promoted based on the coupling action of the primary and secondary carbon partitioning, which enhanced the transformation-induced plasticity effect during deformation despite the high carbon concentration. A ferrite formation temperature range of ~ 760 to 800 °C was proposed. In addition, from the perspective of industrialization, the observed ‘plateau trends’ for the retained austenite fraction and product of strength and elongation suggest the availability of a wide processing window of 215-362 °C for controlling the coiling temperature.

Low‐viscosity and soluble phthalonitrile resin with improved thermostability for organic wave‐transparent composites

ABSTRACTHigh processing viscosity and poor solubility limit the application of heterocyclic polymers for fabricating organic wave‐transparent composites for aerospace applications. In this paper, a novel resin, poly(phthalazinone ether bisphenol fluorene) encapped with phthalonitrile (PPEBF‐Ph), was synthesized and used as the matrix. Biphenol‐based phthalonitrile monomer BP‐Ph was also synthesized and blended with PPEBF‐Ph to further lower the processing viscosity. Solubility tests showed that the resin was soluble in dimethylformamide, N,N‐dimethyl acetamide, N‐methylpyrrolidone, dimethyl sulfoxide, chloroform, and other solvents. Differential scanning calorimetry and rheological studies revealed that the mixed resins exhibited low processing viscosity and a wide processing window below the gel temperature. Thermogravimetric analysis indicated that the cured resins were stable below 510–530 °C under nitrogen atmosphere after 6 h of curing (decreased by 40–60% compared with previous reports on phthalonitrile resin). In air, the char yields of the resins reached 20–30% when heated at 800 °C. The composites were reinforced by a quartz fiber cloth and exhibited a dielectric constant of 2.94–3.27 in an electromagnetic field with frequency ranging from 8 to 18 GHz. Retention of the bending modulus exceeded 70% at 400 °C according to dynamic mechanical analysis, indicating excellent mechanical stability was obtained. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45976.

Synthesis and properties of a novel naphthyl-containing self-promoted phthalonitrile polymer

A novel naphthyl-based self-promoted phthalonitrile monomer, 4-(8-amino-2-naphthyloxy)phthalonitrile (8-ANP), was successfully synthesized via nucleophilic substitution reaction through a one-pot reaction, and it exhibited desirable processing feature with a wide process window (temperature between the melting point and the cure temperature) and low complex viscosity. The activation energy ( Ea) value of the self-promoted curing reaction was ascertained using integral isoconversional Starink method. Even without post cure at high temperature for a long time, the properties of 8-ANP polymers were still outstanding, which exhibited high glass transition temperatures, high storage modulus, low average coefficient of thermal expansion, and excellent thermal and thermo-oxidative stabilities.

Preparation and properties of acetylene-terminated benzoxazine/epoxy copolymers

Acetylene-terminated benzoxazines (A-BOZs) were copolymerized with bisphenol A diglycidyl ether (DGEBA) epoxy resin to improve their processibility and adhesive properties without sacrificing much thermal performance. The three possible polymerization reactions for A-BOZs/DGEBA blends were monitored by differential scanning calorimetry (DSC) analysis and Fourier transform infrared (FTIR) spectroscopy. The rheological characterization showed that a much wider processing window could be obtained for A-BOZs/DGEBA because of the dilution effect of the epoxy. The lap shear strength of A-BOZs improved significantly with the incorporation of DGEBA. Furthermore, the cured blends also showed good heat and water resistance properties and high glass transition temperature (Tg).

Microstructure and mechanical properties of medium Mn steel containing 3%Al processed by warm rolling

The present study was attempted to evaluate the microstructural evolution and mechanical properties of a 3wt%Al containing medium Mn steel which was warm rolled with different thickness reductions directly after intercritical annealing at 750°C by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction and tensile tests. The results show that the laths of ferrite and retained austenite (RA) not only gradually rotated their longitudinal axis to the rolling direction but also were refined with increasing rolling thickness reduction, and thus a well developed lamellar structure of bimodal size distributed lathy ferrite and RA was obtained after heavy rolling reduction. Though the strength increases while the ductility decreases with increasing rolling thickness reduction, an excellent combination of strength and ductility expressed by the product of ultimate tensile strength (UTS) to total elongation (TEL) of ~ 50GPa% was obtained through a wide process window of warm rolling. It is thus proposed that warm rolling is a promising way to simplify the traditional multi-stage rolling and annealing processes of Al-containing medium Mn steels, especially to overcome the cold rolling difficulty of medium Mn steels with high carbon content.

Micro friction stir welding of ultra-thin Al-6061 sheets

The plunging depth of 0.05mm was optimum for joint formation of 0.5mm thick Al-6061 sheet by micro friction stir welding. Increasing rotational velocity from 1500rpm to 2000rpm was beneficial to sound surface formation, while the taper pin with three flats owned wider process window than the single taper pin. The minimum ratio of thickness reduction of 2% was attained, which enhanced the area of load bearing. The taper pin with three flats owing to the severe stirring actions resulted in the finer grain size, improving tensile property. The maximum tensile strength by the taper pin with three flats reached 217MPa, equivalent to 90% of base material.

Preparation and properties of phthalonitrile resins promoted by melamine

Melamine, which has a unique structure and is known as an important raw material, was first employed as a curing agent to promote the curing reaction of phthalonitrile monomer 1,3-bis(3,4-dicyanophenoxy)benzene. Rheometric measurements and differential scanning calorimetry showed that the blends exhibited wide processing windows (∼80°C). The thermal properties of the final cured polymers were monitored by thermogravimetric analysis, and the results revealed that the polymers had outstanding thermal stabilities. Dynamic mechanical analysis indicated that the glass transition temperature of the final cured polymers exceeded 480°C.

Hydrophobic and Mechanical Characteristics of Hydrogenated Amorphous Carbon Films Synthesized by Linear Ar/CH4 Microwave Plasma

A 2.45 GHz microwave plasma with linear antenna has been prepared for hydrophobic and wear-resistible surface coating of carbon steel. Wear-resistible properties are required for the surface protection of cutting tools and achieved by depositing a hydrogenated amorphous carbon film on steel surface through linear microwave plasma source that has TE 10- TEM waveguide. Compared to the existing RF plasma source driven by 13.56MHz, linear microwave plasma source can easily generate high density plasma and provide faster deposition rate and wider process windows. In this study, Ar/CH₄ gas mixtures are used for hydrogenated amorphous carbon film deposition. When microwave power of 1000W is applied, 40 cm long uniform Ar/CH₄ plasma could be obtained in gas pressure of 200~400 mTorr. The Vickers hardness measurement of hydrogenated amorphous carbon film on steel surface was evaluated. It was found the optimized deposition condition at Ar : CH₄=25:25 sccm, 300 mTorr with microwave power of 1000W and RF bias power of 100W. By deposition of hydrogenated amorphous carbon film, contact angle on steel surfaces increases from 43.9° to 93.2°.

Perovskite ink with wide processing window for scalable high-efficiency solar cells

Perovskite solar cells have made tremendous progress using laboratory-scale spin-coating methods in the past few years owing to advances in controls of perovskite film deposition. However, devices made via scalable methods are still lagging behind state-of-the-art spin-coated devices because of the complicated nature of perovskite crystallization from a precursor state. Here we demonstrate a chlorine-containing methylammonium lead iodide precursor formulation along with solvent tuning to enable a wide precursor-processing window (up to ∼8 min) and a rapid grain growth rate (as short as ∼1 min). Coupled with antisolvent extraction, this precursor ink delivers high-quality perovskite films with large-scale uniformity. The ink can be used by both spin-coating and blade-coating methods with indistinguishable film morphology and device performance. Using a blade-coated absorber, devices with 0.12-cm2 and 1.2-cm2 areas yield average efficiencies of 18.55% and 17.33%, respectively. We further demonstrate a 12.6-cm2 four-cell module (88% geometric fill factor) with 13.3% stabilized active-area efficiency output. Perovskite-based solar cells are often fabricated by methods that are not industrially scalable. Here, Yang et al. develop an ink formulation which gives similar devices by spin coating, the lab-scale standard, and blade coating, which is a more scalable, industry-relevant deposition method.

Modifying the Chemical Structure of a Porphyrin Small Molecule with Benzothiophene Groups for the Reproducible Fabrication of High Performance Solar Cells.

A porphyrin-based molecule DPPEZnP-BzTBO with bulky benzothiophene groups was designed and synthesized as an electron donor material for bulk heterojunction (BHJ) solar cells. The optimized devices under thermal annealing (TA) and then chloroform solvent vapor anneanling (SVA) for 80 s exhibited an outstanding power conversion efficiencie (PCE) of 9.08%. Contrasted with the smaller thienyl substituted analogues we reported previously, DPPEZnP-BzTBO-based BHJ solar cells exhibited a higher open circuit voltage due to the lower highest occupied molecular orbital energy level. The TA post-treatment of the active layers induced the formation of more crystallized components, and the subsequent SVA provided a driving force for the domain growth, resulting in more obvious phase segregation between the donor and the acceptor in nanoscale. Furthermore, the PCEs kept above 95% upon the further SVA treatment within the time range of 60 to 95 s probably because the bulky benzothiophene groups retard the too quick change of crystallinity, providing a wide processing window for the reproducible device fabrication.

Processable cyanate ester resin from Cis resveratrol

ABSTRACTTrans resveratrol isomerizes to cis resveratrol (cRes) with ultra‐violet light and undergoes cyanation to the new compound cRes tricyanate (2). Monomer 2 polymerizes to a polycyanurate that is remarkably stable to heat with a glass transition temperature > 350 °C and char yield of 73% in air up to 600 °C. The monomer 2 melts at <80 °C with a wide processing window before polymerization. The new thermosetting resin made from a natural product is a useful matrix material for polymer matrix composites requiring high‐performance characteristics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 971–980

A difluorobenzothiadiazole-based conjugated polymer with alkylthiophene as the side chains for efficient, additive-free and thick-film polymer solar cells

A difluorobenzothiadiazole-based polymer P-TT with alkylthiophene side chains diplays a desirable blend film morphology and high PCE with wide processing windows.

EUVL: Challenges to Manufacturing Insertion

Extreme ultraviolet (EUV) lithography with reflective photomasks continues to be a potential patterning technology for high volume manufacturing at the seven nm technology node and beyond. The advantages of EUV lithography are its superior pattern fidelity, wider process windows, and potential for extendibility to future nodes. The disadvantages of EUV lithography are its higher costs and complexity (than ArFi lithography) and the relative immaturity of its supporting infrastructure.