High Dimensional Stability Research Articles

Sustainable polyamide elastomers from a bio-based dimer diamine for fabricating highly expanded and facilely recyclable microcellular foams via supercritical CO2 foaming

In this study, we developed a sustainable polyamide foam system. A new series of polyamide elastomers was synthesized using a bio-based dimer diamine monomer as a building block to copolymerize with aminocaproic acid and adipic acid through step-growth polymerization, followed by supercritical CO2 foaming for the fabrication of microcellular foams. The introduction of the branched-structured dimer diamine monomer effectively restricted the molecular packing and hydrogen bonding density of the polyamide system, leading to numerous small crystals acting as nucleation sites for heterogeneous cell nucleation. Simultaneously, the branched long chains of the dimer diamine formed chain entanglement networks, which increased the material melt strength against the elongational stresses of cell growth. The synergistic effect provided by dimer diamine led to the successful manufacture of foamed samples with a high expansion ratio and robust dimensional stability, effectively overcoming the foaming difficulties of high crystallinity and insufficient melt strength in traditional polyamide 6 (PA6). In addition, this polyamide elastomer foam system could be recycled and reprocessed due to the advantages of non-crosslinking and additive-free. Therefore, the study’s findings constitute a promising direction for the usage of renewable sources in the development of foamable polyamide materials for sustainable applications in the plastics industry.

Fabrication of Lightweight Polyphenylene Oxide/High‐Impact Polystyrene Composite Bead Foam Parts via In‐Mold Foaming and Molding Technology

Bead foam is one kind of important polymeric foam product, which has the advantages of complex product shape, a wide range of parts density, and a wide variety of available materials. Steam‐chest molding is usually used to prepare bead foams. However, it is challenging to prepare polymers with high melting point (T m) or glass transition temperature (T g). Herein, in‐mold foaming and molding technology (IMFM) is proposed to prepare bead foams from polyphenylene oxide/high‐impact polystyrene composite (PHC). PHC bead foam parts (PHCPs) with densities from 0.11 to 0.25 g cm−3 are successfully prepared by controlling the process parameters. Due to good interbead bonding, the bead foams have superior mechanical properties. The tensile and compression strength for PHCPs with a density of 0.25 g cm−3 are 2.84 and 2.93 MPa, respectively. The PHCPs also show high dimensional stability at 120 °C and good flame‐retardant properties, characterized by a high limiting oxygen index (LOI) value and HBF rating. In addition, the fabrication mechanism behind IMFM is proposed. This technology provides a new way to produce polymer bead foams, especially for engineering materials.

Durability of Biodegradable Polymer Nanocomposites.

Biodegradable polymers (BP) are often regarded as the materials of the future, which address the rising environmental concerns. The advancement of biorefineries and sustainable technologies has yielded various BP with excellent properties comparable to commodity plastics. Water resistance, high dimensional stability, processability and excellent physicochemical properties limit the reviewed materials to biodegradable polyesters and modified compositions of starch and cellulose, both known for their abundance and relatively low price. The addition of different nanofillers and preparation of polymer nanocomposites can effectively improve BP with controlled functional properties and change the rate of degradation. The lack of data on the durability of biodegradable polymer nanocomposites (BPN) has been the motivation for the current review that summarizes recent literature data on environmental ageing of BPN and the role of nanofillers, their basic engineering properties and potential applications. Various durability tests discussed thermal ageing, photo-oxidative ageing, water absorption, hygrothermal ageing and creep testing. It was discussed that incorporating nanofillers into BP could attenuate the loss of mechanical properties and improve durability. Although, in the case of poor dispersion, the addition of the nanofillers can lead to even faster degradation, depending on the structural integrity and the state of interfacial adhesion. Selected models that describe the durability performance of BPN were considered in the review. These can be applied as a practical tool to design BPN with tailored property degradationand durability.

High-Li+-fraction ether-side-chain pyrrolidinium–asymmetric imide ionic liquid electrolyte for high-energy-density Si//Ni-rich layered oxide Li-ion batteries

In this study, Si nanoparticles with interweaving carbon nanotubes are wrapped by graphitic sheets to achieve high conductivity and high dimensional stability of a composite anode (denoted as Si/CNT/G) for Li-ion batteries. In addition, an ionic liquid (IL) electrolyte that consists of ether-side-chain pyrrolidinium, asymmetric imide, and a high Li+ fraction is prepared. This electrolyte is for the first time employed for Si-based Li-ion batteries. Decomposition of the ether groups creates organic components in the solid electrolyte interphase (SEI). The high Li+ concentration promotes decomposition of the (fluorosulfonyl)(trifluoromethanesulfonyl)imide (FTFSI−) anions, leading to a LiF- and Li3N-rich SEI. The organic-inorganic balanced SEI is responsible for the excellent charge-discharge properties of the Si/CNT/G anode. The FTFSI− anions exhibit low corrosivity toward the Al current collector and high compatibility with the LiNi0.8Co0.1Mn0.1O2 (NCM-811) cathode. With a charging voltage of 4.5 V, remarkable reversible capacities and cycling stability of NCM-811 in the high-Li+-fraction N-methoxyethyl-N-methylpyrrolidinium/FTFSI IL electrolyte are observed. Differential scanning calorimetry is used to examine the interfacial exothermic reactions between the delithiated NCM-811 and various electrolytes. After 300 charge-discharge cycles, the capacity retention of a Si/CNT/G||NCM-811 full cell with the proposed IL electrolyte is 80% with a Coulombic efficiency of ∼99.9%. These values are significantly higher than those of the conventional carbonate electrolyte cell.

Photo‐Curing Vis‐IR Hybrid Fresnel Lenses with High Refractive Index

AbstractConventional IR lenses, typically refractive lenses, composed of inorganic semiconductors or chalcogenide glasses, are usually bulky, heavy, and difficult processable. Here, a one‐step photo‐curing imprinting strategy is presented to fabricate lightweight, compact, and high refractive index (HRI) hybrid Fresnel lenses for optical devices based on thiol‐ene/‐yne reactions. The hybrid Fresnel lenses consist of two layers: the silicon/quartz as the support substrate and HRI polymer films as functional layer which are synthesized by thiol‐ene/‐yne reactions with high sulfur‐content comonomers 2,3‐bis((2‐mercaptoethyl)thio)‐1‐propanethiol (BMETP) and its derivatives. The as‐prepared photopolymer films exhibit excellent transparency properties and HRI above 1.62 both in the visible and infrared regions, resulting from the large ratio of sulfur element with high molar refraction. A series of images captured by vis‐IR hybrid Fresnel lenses are demonstrated to confirm the applicability in the area of the optical imaging technique. This strategy, based on the one‐step photo‐curing imprinting, integrating the advantages of the easy processability of organic polymers and high dimensional stability of the inorganic substrate materials, provides a facile, processable, and highly efficient process for fabricating lightweight optical lenses.

Energy-Dispersive X-Ray Spectrometry Analysis and Radiopacity of Five Different Root Canal Sealers.

Root canal sealers should have optimum adhesion to the root dentin, low cytotoxicity, sufficient radiopacity and high dimensional stability, which depend mainly on their chemical composition. The aims of this study were to evaluate the chemical composition of Syntex (Cerkamed, Stalowa Wola, Poland), Adseal (Meta Biomed, Cheongju-si, Korea), Sealapex (SybronEndo, Scafati, Italy), MTA Fillapex (Angelus, Londrina, Brazil) and GuttaFlow Bioseal (Coltene/Whaledent, Altstätten, Switzerland) and to determine their radiopacity comparatively. Stainless steel molds with an inner diameter of 5 mm and a depth of 2 mm were constructed. Tested root-canal sealers were mixed and poured into the molds. Following setting, digital periapical radiographs of the specimens (n=12) were taken under standard exposure conditions and the mean gray-values of specimens were measured using a computer graphics program. Then the specimens were examined by scanning electron microscopy, and Energy-dispersive X-ray analysis was performed. The data were analyzed using One-way ANOVA followed by Holm-Sidak multi-comparison test (p = 0.05). Sealapex showed higher calcium peak than MTA Fillapex, GuttaFlow Bioseal, Adseal and Syntex sealers. MTA Fillapex contained a highest amount of tungstate. Sealapex presented the highest radiopacity value among the tested materials (p < 0.05), whereas MTA Fillapex was the least radiopaque material (p < 0.05). Each root canal sealer contains different compositions of radiopacifiers including bismuth oxide, calcium tungstate and zirconium oxide. The tested root canal sealers had radiopacity values above the ISO-specified limit. Sealapex was the most radiopaque root canal sealer followed by GuttaFlow Bioseal, Syntex, Adseal and MTA Fillapex.

Wood quality of Khaya senegalensis trees from a multi-stratified agroforestry system established in an open ombrophilous forest zone

ABSTRACT The African mahogany (Khaya senegalensis) in homogenous plantations and natural forests is widely studied, but there is a lack of information on wood from trees grown in agroforestry systems (AFSs). The objective of this work was to evaluate the wood quality of African mahogany produced in AFS. The wood was obtained from a multi-stratified AFS located in the State of Rondônia, Brazil. The contents of holocellulose (67.2%) and lignin (25.8%) of mahogany wood are comparable to those found in other tropical woods from the Amazon with high natural durability. The results found for the densities presented low variation, allowing to classify the African mahogany wood as of medium density (basic density around 520 kg m−3) and high dimensional stability (ie, anisotropy coefficient <1.3%). The results obtained for parallel-to-grain compression strength (26.5 MPa), static bending strength (56.0 MPa), shear strength (10.4 MPa), and Janka hardness parallel to the grain (3420.0 N), indicate that the mechanical performance was similar to wood from other African and South American mahogany species from monocultures and natural forests. Experimental results indicated that the wood produced in the AFS can be suitable for furniture, musical instruments, applications in external structures, residential floors, and vehicle bodies.

Development of Optimal Design and Circular Broach Modular Design of Disc Cutters with the Development of a Parametric Model

Cutting tool is one of the most important instruments in production. It is used for machining of different components on machine tools. A material is cut into a chip to incur the desired work piece surface currently used in engineering various cutting tools. The directions of development of structures of metal cutting tools are: higher precision of dimensional and geometrical parameters, the use of new tool materials, cost, and quick. The cutting tools are not only affected by the design of machine, technology of manufacturing of products, but also impact the constructive forms of machine parts. The emergence of mechanical spine, thanks to the pull method. Spine broach can provide high-performance processing spine bore with the required accuracy. The development of heavy machine tools required the creation of new designs of large instruments. The use of mechanical automatic lines also required design tools with high dimensional stability capable of handling the items within the specified tolerance for a certain time. Instruments were developed in the process of renewing the cutting edge of the cutting tools with automatic adjustment; setting up tools on the size of the machine is a device for automatic replacement of worn tool in the process line of the Computer-Aided Manufacturing CAM of the cutting tool special requirements. Equipment must operate with high level efficiency, so to reduce the loss of time resetting of the need to minimal. A cutting tool requires knowledge of the theoretical foundations of design and calculation tools using CAD.

Cross-Linked Chitosan as an Eco-Friendly Binder for High-Performance Wood-Based Fiberboard

High-performance wood-based fiberboards with high strength and dimensional stability were fabricated by hot-pressing method using 2,5-dimethoxy-2,5-dihydrofuran (DHF) cross-linked chitosan (CS) as an eco-friendly binder. The effects of cross-linked chitosan on the mechanical properties and dimensional stability of wood-based fiberboards were investigated. It is evident that cross-linked chitosan addition was effective in improving mechanical properties and dimensional stability of wood-based fiberboards. The prepared wood-based fiberboard bonded by DHF cross-linked CS displayed optimum modulus of rupture (MOR) of 42.1 MPa, modulus of elasticity (MOE) of 3986.0 MPa, internal bonding (IB) strength of 1.4 MPa, and thickness swelling (TS) value of 16.3%. The improvement of physical and mechanical properties of wood-based fiberboards could be attributed to the amide linkages and hydrogen bonds between wood fibers and cross-linked chitosan. The high-performance wood-based fiberboards fabricated in this study may be a promising candidate for eco-friendly wood-based composites.

An Investigation of corrosion of friction welded and post-weld heat-treated AA6061/SiC/graphite hybrid composites

The aluminium-based hybrid metal matrix composites have noteworthy applications in sub-sea installations, structures of deep-sea crawlers, submarine parts, engine cylinders, drum brakes etc., as they possess high strength, corrosion resistance, chemical, and dimensional stability. In this investigation, the pitting corrosion behaviour of friction welded and post-weld heat-treated AA6061/SiC/graphite hybrid composites were analysed. The corrosion rates of AW (as welded), ST (Solution treated), STA (Solution treated and Aged), and AA (Artificially Aged) weld joints were experimentally determined. The corrosion behaviour has been discussed in light of microstructure. The experimental results revealed that the STA joints exhibited better corrosion resistance characteristics as compared to AW, AA, and ST joints. The corrosion rate was high for AW joints, followed by AA and ST joints, respectively. Taking into account the corrosion rates of AW and STA joints, the STA joints have a corrosion rate 34.6% lesser than that of AW joints. A comparison of AA and ST with STA joints reveals that the rate of corrosion for STA joints was 31.1% lesser than that of AA joints and 28.8% lesser than that of ST joints. A lower corrosion rate was observed for STA joints as compared to AA, AW, and ST joints.

Quasi-solid-state sodium-ion hybrid capacitors enabled by UiO-66@PVDF-HFP multifunctional separators: Selective charge transfer and high fire safety

The practical application of sodium-ion hybrid capacitors is limited by their low energy densities resulted from the kinetics mismatch between cathodes and anodes, and the fire safety related to the flammable electrolyte-separator system. Hence, we report a rational design of metal–organic frameworks (MOFs, UiO-66) modified PVDF-HFP separator. High tensile strength and dimensional thermal stability of the separator reduce the risk of electrode short circuit caused by the separator deformation. MCC test demonstrates a reduction of 75% in peak heat release rate (pHRR), indicating an enhanced fire-resistant property of the separator. This is due to the transformation of UiO-66 into ZrO2 accompanied by the consumption of oxygen and the formation of the barrier char that suppresses further heat release. Quasi-solid-state electrolyte prepared based on this separator presents an enhanced ionic conductivity of 2.44 mS cm−1 and Na-ion transference number of 0.55, which are related to the high porosity (>70%) and electrolyte uptake (~320%) of the separator. Moreover, the open metal sites of UiO-66 can capture PF6–and consequently liberate the Na+ for faster migration, thus reducing the kinetics mismatch between cathodes and anodes. Such multifunctional separator enables the quasi-solid-state Na-ion hybrid capacitor to achieve high energy density (182 Wh kg−1 @31 W kg−1) and power density (5280 W kg−1 @22 Wh kg−1), as well as excellent cyclic stability (10,000 cycles @1000 mA g−1).

Effect of ball milling process on the mechanical and thermal properties of the nanodiamond/2024Al composites

In this study, 5 wt.% nanodiamond (ND) reinforced 2024Al matrix composites (ND/2024Al) were fabricated with various ball milling processes. The microstructure, compressive yield strength (σyc) and coefficient of thermal expansion (CTE) of ND/2024Al composites were investigated. It is found that the addition of 5 wt.% NDs significantly increases the σyc and decreases the CTE of 2024Al. High energy ball milling further increases σyc and decreases CTEs of ND/2024Al composite due to it enhances the fine grain strengthening of α-Al matrix and the dispersion strengthening of NDs, decreases the thermal mismatch stress at the ND/α-Al matrix interface, and increases the constraint of NDs on α-Al. The composites fabricated by the combinations of ball milling speeds and times of (5−7) h×(200−250)rpm and 9 h×300 rpm have the highest σyc and the lowest CTE respectively. Considering the different influence of ball milling parameters on σyc and CTEs, a evaluation coefficient α=σycC⋅εkcCσycM⋅εkcM⋅CTEMCTEC is proposed to evaluate the synergistic influence of mechanical properties and CTEs on the dimensional stability of ND/2024Al composites. Large value of α may lead to high dimensional stability of material, hence the α can be used to determine the ball milling parameters.The ball milling process of 250−300 rpm ball milling speeds and 5−7 h ball milling times are recommended based on α, which causes a 95–100 % increase in σyc and a 30–35 % decrease in CTE compared with 2024Al alloy, respectively.

Physico-mechanical properties of the wood of freijó, Cordia goeldiana (Boraginacea), produced in a multi-stratified agroforestry system in the southwestern Amazon

ABSTRACT Agroforestry systems (AFSs) integrate, through sustainable practices, agricultural and forest crops for the production of wood and food, providing environmental services, and conserving biodiversity. The freijó (Cordia goeldiana) has potential for cultivation in the Amazon for timber purposes, but data on the characteristics of its wood produced in AFSs are scarce. Our objective was to determine the physical-mechanical properties and suggest technological applications of freijó wood produced in a multi-stratified AFS established in the state of Rondônia, Brazil in 1996. Agricultural and forest species were established in the AFS in double rows with 5.0-m x 2.5-m spacing. Three 19-year-old freijó trees were harvested for chemical, physical (density and dimensional stability), and mechanical (compression, static bending, Janka hardness, and shear strength) characterization of the wood. The wood presented a chemical composition similar to tropical hardwoods, was moderately heavy (582.63 kg m-3), and had high dimensional stability in comparison with other consecrated woods on the market (longitudinal, radial, and tangential retraction = 0.25, 4.27, and 6.83%, respectively). The values determined for parallel (32.32 MPa) and perpendicular compression (8.02 MPa), specific strength (55.32 MPa kg-1 m-3), parallel (2373.33 N) and perpendicular Janka hardness (2326.67 N), strength to static bending (63.5 MPa), and shear (5.94 MPa) were similar to the values observed in other high-density tropical woods grown in either monoculture plantations or natural forests. The wood under study is suitable for manufacture of high-value-added products, such as fine furniture, residential floors, musical instruments and structural pieces.

Dimensionally accurate parts made of high-strength steels - compressive stress superposition instead of tool compensation

As a result of the increasing use of high-strength and ultra-high-strength steels as part of the automobile lightweight construction strategies, the issue of dimensional accuracy of component structures is increasingly becoming the focus of toolmakers, pressed part suppliers and automobile manufacturers. In particular, the modern dual-phase steels with strengths of over 800 MPa possess-depending on the respective component geometry and the forming process employed-a pronounced springback behaviour. The compensation measures commonly used so far are more and more reaching their limits, which in turn impairs the process ability of these grades in the cold forming process. The smartform® process developed by thyssenkrupp Steel Europe AG allows the cold forming of high-strength steels with high repeatable accuracy, which significantly expands their areas of application. In this process, the tensile stresses from the forming operation causing the springback of the part are eliminated by compressive stress-superposition, which leads to high dimensional stability. There is almost no need to adapt the tool surfaces to achieve a dimensionally accurate part. How close the formed component comes to the dimensional tolerances specified by the end user is usually determined within the framework of numerical method development. In this context, the result of a springback simulation depends on various parameters. The description of the material behaviour is of major importance. Moreover, the use of extended material models can have an influence on the predictive accuracy and reduce the deviations between simulation and real material behaviour. It remains to be identified to what extent the increase in accuracy is proportional to the modelling effort.

A novel anion exchange membrane based on poly (2,6-dimethyl-1,4-phenylene oxide) with excellent alkaline stability for AEMFC

We report a novel comb-shaped anion exchange membrane based on poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and 4-(dimethylamino)butyraldehyde diethyl acetal (DABDA). The Menshutkin reaction successfully introduced DABDA into the brominated PPO backbone, which was proved through FT-IR and 1H NMR. The distinct hydrophilic/hydrophobic microphase separation structure observed by transmission electron microscope (TEM). As the increase of grafting degree, so does the water uptake, swelling ratio, hydroxide conductivity and alkaline stability. The membranes also possess good mechanical property with tensile strength from 14.2 to 38.11 MPa. This is due to the increasing number of hydroxide and unique steric hindrance effect caused the higher water uptake and higher dimensional stability. Simultaneously, especially PPO/DABDA-60 in comb-shaped membranes demonstrate an excellent long-term alkali resistance stability. In a 576-h alkali resistance stability test, the retained ionic conductivity of the PPO/DABDA-60 membrane is 96% of the initial value. The PPO/DABDA-60 is a potential candidate material for AEM.

Side-Chain-Type Anion Exchange Membranes Based on Poly(arylene ether sulfone)s Containing High-Density Quaternary Ammonium Groups.

To obtain anion exchange membranes with both high ionic conductivity and good dimensional stability, a series of side-chain-type poly(arylene ether sulfone)s (PAES-QDTPM-x) were designed and synthesized. Quaternary ammonium (QA) groups were densely aggregated and grafted onto the main chain via flexible hydrophobic spacers. Well-defined microphase separation was confirmed by small-angle X-ray scattering. PAES-QDTPM-0.30 exhibited reasonably high conductivity (39.4 mS cm-1 at 20 °C and 76.1 mS cm-1 at 80 °C) and excellent dimensional stability at 80 °C (11.9% in length, 11.2% in thickness) due to the concentration of ion clusters and the side-chain-type structure. All membranes maintained over 82% of the conductivity after alkali treatment for 14 days. In the H2/O2 fuel cell performance test, the maximum power density of PAES-QDTPM-0.30 at 60 °C was 225.8 mW cm-2.

Double-network cross-linked aerogel with rigid and super-elastic conversion: simple formation, unique properties, and strong sorption of organic contaminants.

Novel adsorbents with high adsorption capacity, broad-spectrum adsorption performance, and good reusability are needed for the treatment of diverse and complex contaminants in water. In this work, we used in situ hydrothermal reaction to fabricate graphene oxide (GO) and poly(vinyl alcohol) (PVA) based aerogels (GPXA, X represented the volume of PVA) through the cross-linking network that meets the above requirement. After adding Ca2+, GP16A (with 16 mL PVA) had surprisingly rigid and super-elastic conversion that is dependent on water stimulus. The strong adsorption of methylene blue (MB) on GP16A illustrated that it had excellent dye removal ability. The adsorption capacity of GP16A to MB was 698.38 mg g-1 and it remained 85.62% after repeated adsorption-desorption cycles. The adsorption was controlled by multiple mechanisms including electrostatic interaction, π-π interaction, and hydrogen bond. In addition, hydrophobically modified GP16A (GP16A-MTMS) effectively absorbed common oils and organic solvents. Repeated absorption of GP16A-MTMS was re-activated by squeezing operation. This study provides an alternative technique for preparing aerogel materials with high recyclability, dimensional stability, and solvent resistance, and for dealing organic contaminants in water.

Vegetable Fillers and Rapeseed Oil-Based Polyol as Natural Raw Materials for the Production of Rigid Polyurethane Foams.

The reported study concerns the introduction of renewable raw materials into the formulation of rigid polyurethane foams in the quest for the sustainable development of polymer composites. In this study, rigid polyurethane foam composites were prepared using 75 wt.% of rapeseed oil-based polyol and 15 parts per hundred parts of polyol (php) of natural fillers such as chokeberry pomace, raspberry seeds, as well as hazelnut and walnut shells. The influence of the used raw materials on the foaming process, structure, and properties of foams was investigated using a FOAMAT analyzer and a wide selection of characterization techniques. The introduction of renewable raw materials limited reactivity of the system, which reduced maximum temperature of the foaming process. Moreover, foams prepared using renewable raw materials were characterized by a more regular cell structure, a higher share of closed cells, lower apparent density, lower compressive strength and glass transition temperature, low friability (<2%), low water absorption (<1%), high dimensional stability (<±0.5%) and increased thermal stability. The proper selection and preparation of the renewable raw materials and the rational development of the polyurethane recipe composition allow for the preparation of environmentally-friendly foam products with beneficial application properties considering the demands of the circular economy in the synthesis of rigid foams.

Carbon Nanotubes Doped Poly (arylene) Ether Copolymerised Multiblock Based Proton Exchange Composite Membranes for Fuel Cell Application

The article reports the synthesis of nanophase-separated multiblock poly(arylene ether ketone sulfone) copolymers. A series of hydrophobic oligomers end-capped with decafluorobiphenyl (DFBP) group was reacted with disulphonated poly(arylene ether ketone) copolymer containing 4, 4′-bis (4-hydroxyphenyl) valeric acid moieties to synthesize multiblock copolymer. The copolymers were characterized using 1H-NMR, 13C-NMR, 19F-NMR spectroscopy and Gel Permeation Chromatography. The membranes with high dimensional and thermal stability were obtained through solution casting method. The multiblock copolymers were crosslinked with 6F-bisphenol-A (6F-BPA) based novolac epoxy resin. The functionalized multi-walled carbon nanotubes (f-MWCNTs), in 0.5, 0.7, and 0.9 wt.%, were also incorporated into the polymer matrix in order to prepare nanocomposite membranes. Polymer nanocomposite membranes showed high oxidative stability, and proton conductivity. The surface morphology and composition of polymer nanocomposite membranes were studied using field emission-scanning electron microscopic (FE-SEM), and high-resolution transmission electron microscopic (HR-TEM) techniques. The fuel cell related parameters such as water uptake, proton conductivity, ion exchange capacity, oxidative stability, and methanol permeability were also evaluated. The thermal performance and mechanical behavior of the synthesized polymer nanocomposite membranes were also studied. The nanocomposite membranes showed better fuel cell performance as compared to the pristine membranes.

Improvement of ceramic core strength by combining 3D printing technology and an organic-inorganic conversion process using dual polymers

Ceramic cores are essential for manufacturing hollow mechanical parts, such as impellers and blades, in the casting process. High temperature heat treatment, which causes dimensional deformation and breakage, is required to reveal the effective strength of ceramic cores. Therefore, in this study, a new 3D printing-based process, combined with an organic-inorganic binder conversion process, is proposed to fabricate a ceramic core with high dimensional stability using dual polymers with different chemical properties. The ceramic core was prepared using an extrusion-type 3D printer with a slurry prepared by mixing a starting powder with hydrophilic and hydrophobic polymers. The extruded samples molded from the heterogeneous polymers were immersed in water at 60 °C for 3 min to remove the hydrophilic polymer to create space for impregnating an inorganic binder. The core samples were then dipped in an inorganic binder solution composed of tetraethyl orthosilicate and sodium methoxide and then dried at 80 °C for 1h, followed by a heat treatment at 1000 °C for 1h. Using dual polymers, the amount of inorganic binder coating converted into the glass phase during heat treatment was increased, which resulted in improved core strength. These results confirm that the dual polymer can be used to manufacture ceramic cores with excellent dimensional stability and firing strength through 3D printing combined with the organic-inorganic binder conversion process.