GPa Strength Research Articles

Damage-Tolerant Wood Layers for Corrosion Protection of Metal Structures.

Mechanically strong and damage-tolerant corrosion protection layers are of great technological importance. However, corrosion protection layers with high modulus (>1.5 GPa) and tensile strength (>100 MPa) are rare. Here, we report that a 130 μm thick densified wood veneer with a Young's modulus of 34.49 GPa and tensile strength of 693 MPa exhibits both low diffusivity for metal ions and the ability of self-recovery from mechanical damage. Densified wood veneer is employed as an intermediate layer to render a mechanically strong corrosion protection structure, referred to as "wood corrosion protection structure", or WCPS. The corrosion rate of low-carbon steel protected by WCPS is reduced by 2 orders of magnitude than state-of-the-art corrosion protection layers during a salt spray test. The introduction of engineered wood veneer as a thin and mechanically strong material points to new directions of sustainable corrosion protection design.

Tailoring the amorphous-nanocrystalline structures of TiNbZrNx films towards improving the anti-corrosion and mechanical properties by controlling nitrogen flow ratio

Multi-principal element alloy (MPEA) films demonstrate superior corrosion resistance and tribological properties, which have substantial potential for applications in marine engineering equipment. In this study, the TiNbZrNx MPEA nitride films were successfully deposited on 316 L austenitic stainless steel by direct current (DC) magnetron sputtering at various nitrogen flow ratio (RN2). The phase, composition, microstructure, corrosion and mechanical behaviors were investigated in detail. The results showed that the phase transitioned from amorphous to amorphous/nanocrystalline as RN2 increased. The TiNbZrNx films deposited at RN2 = 0.15–0.4 exhibited better corrosion performance in the electrochemical and salt spray tests. The RN2 = 0.4 film presented the optimal corrosion resistance, with the lowest self-corrosion current density (0.249 μA/cm2) and the largest passivation zone (from OCP to >1.2 VSCE). The amorphous/nanocrystalline film deposited at RN2 = 0.2 showed a remarkable nanohardness of 7.03 GPa and adhesion strength of 18.86 N. The strengthening effect can be attributed to the interstitial dissolution of nitrogen atoms among the metal atoms. The formation of nitride nanocrystalline phases and the existence of interfaces can effectively improve the plastic deformation ability of amorphous alloy films. This work provides theoretical guidance for the development of MPEA nitride films with tunable properties for key moving parts in marine equipment.

Synthesis, microstructure and thermophysical properties of (La0.2Y0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 high-entropy oxide ceramic

In this study, a dense high-entropy oxide ceramic (La0.2Y0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 with a relative density of 93.7 %RD was synthesized by cold isostatic pressing, coupled with the pressureless sintering method. The microstructure and physical properties were characterized systematically, revealing an intrinsic hardness of 7.9 GPa and flexural strength of 187.9 MPa. Moreover, the elastic and shear moduli decreased from 148.05 to 56.68 GPa at 25 °C to 117.44 and 44.63 GPa at 1200 °C, respectively. The thermal diffusivity in the temperature range of 25–1200 °C decreased from 0.0053 to 0.0041 cm3/s, and the thermal expansion coefficient was 11.0 × 10−6 K−1. The excellent thermal insulation performance of the high-entropy oxide ceramic (La0.2Y0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 and its similar thermal expansion coefficient to those of Ni-based superalloys demonstrate that the material has broad application prospects in the field of thermal barrier coatings.

Structural composite batteries made from carbon fibre reinforced electrodes / polymer gel electrolyte prepregs

Full cells of structural composite batteries comprising carbon fibre reinforced anodes and cathodes decorated with lithium titanate and LiNi0.3Mn0.3Co0.3O2 (NMC111), respectively, embedded in a polymer gel electrolyte were produced. Spread carbon fibres were coated with cathode and anode active materials followed by impregnation with a polymer gel electrolyte consisting of PVDF particles dispersed in an ionic liquid containing a lithium salt. The resulting carbon fibre reinforced electrodes/polymer gel electrolyte prepregs could be easily stored, handled or, if needed, transported. Cathode and anode prepregs were laminated and fused by compression moulding, resulting within a time frame of couple of minutes in full cell structural composite batteries. The batteries were charged and discharged at current densities of 0.1C, resulting in a specific capacity of 35 mAh/gNMC111 and energy density of 5.6 Wh/(kg battery). The composite batteries had a Young's modulus of 4.6 GPa and tensile strength of 32 MPa. A facile layup process enabled proof-of-concept demonstration of ‘all’ carbon fibre full cell multifunctional structural composite batteries.

Phase composition, microstructure, and mechanical properties of PcBN composites with Ti and Ti[sbnd]Al binders: Effects of holding time and synthesis pressure

This paper prepared cBN-Ti and cBN-Ti-Al system composites by high-temperature and high-pressure method using cubic boron nitride powder, titanium powder, and aluminum powder as raw materials. The phase composition, microstructure, and mechanical properties of the two systems based on varying holding time and synthesis pressure were studied and analyzed. The results showed that when the holding time was <480 s, the mechanical properties of the composites worsened for the intermediate products remained. The composites of the cBN-Ti and cBN-Ti-Al systems exhibited their highest bending strengths of 779 MPa and 957 MPa, respectively, after being held for 480 s. Both composites' hardness and bending strength increased as the synthesis pressure increased. At a synthesis pressure of 6 GPa, the hardness and bending strength of the cBN-Ti system composite were 33.3 GPa and 804 MPa, respectively. Similarly, the cBN-Ti-Al system composite showed a hardness of 33.3 GPa and a bending strength of 994 MPa at the same pressure.

On the role of alkali content on one-part alkali activated slag pastes produced with tri- blend solid activators

The paper investigates the effect of tri-blend solid alkaline activators, based on sodium metasilicate pentahydrate, potassium hydroxide and sodium carbonate, on the physico-chemical features, the fresh and hardened performances of activated slag pastes prepared with the one-part methodology. Specifically, the alkali to slag ratio (Ac) and the total amount of the selected activators were varied at a fixed water/binder ratio, molar silica modulus (Ms) and relative mass activators ratio. Microstructures and reaction products were analyzed by means of X-ray diffraction, thermogravimetry, scanning electron microscopy and FT-IR. Fresh and elasto-mechanical properties of pastes were also evaluated. Amorphous calcium carbonate (ACC) as well as metastable vaterite were found in low reacted systems, produced by the preferential early-age reaction between dissolved carbonate ions present in the pore solution and the calcium ions released by the partial dissolution of the slag and stabilized by a sufficient high concentration of magnesium in the pore solution, not consumed to the form hydrotalcite. Sodium carbonate failed in extending the pot life of the investigated systems. The optimal alkali content was found to be close to 0.075 as it determines the development of compact and dense microstructure (2025 kg/m3), the maximum elasto-mechanical properties (elastic modulus of 26.1 GPa and compressive strength of 102.8 MPa at 28 days) and it allows to produce flowable mixtures (200 mm).

Optimization of Laser Powder Bed Fusion Process for Forming Porous Ta Scaffold

To improve the performance of porous tantalum (Ta) manufactured by laser powder bed fusion (L-PBF) and meet its application requirements in medicine, the authors of this paper studied the influence of L-PBF process parameters on the strut surface morphology and mechanical performance. It was found that the powder layer thickness had a significant influence on the microstructure and mechanical properties based on statistical analysis. We proposed optimal process parameters of laser power of 150 W, scanning speed of 270 mm/s, thickness of 0.05 mm, and scanning spacing of 0.07 mm. After parameter optimization, we successfully obtained Ta samples with an elastic modulus of 1.352 ± 0.007 GPa and yield strength of 53.217 ± 0.114 MPa. The results show that the elastic modulus and yield strength of porous Ta samples with a porosity of 80% under the optimal process parameters are significantly superior to previous studies. The porous Ta scaffolds with higher mechanical properties fabricated with the optimized process parameters of L-PBF have significant value for applications in medicine.

Facile fabrication of ultrastrong polyethylene nanocomposite films with low filler content via flow-driven graphene re-dispersion assisted crystallization

Fabrication of polymer films with superb mechanical properties is far from mature compared to that of fibers, hampering the further engineering applications of lightweight polymer materials. Herein, high density polyethylene (HDPE) films reinforced with re-dispersed or refined reduced graphene oxide (rGO) are prepared via a facile melt-stretching strategy. The incorporation of only 0.2 wt% rGO is demonstrated to endow the melt-stretched film (80× stretch ratio) with ultrahigh Young's modulus of 2.9 GPa and tensile strength of 162.2 MPa, which are comparable to many engineering plastics and also significantly superior to the existing HDPE/graphene composites. More importantly, these modulus and strength values are increased by 71 and 65% compared to the neat PE (80×), respectively, far more than the theoretical prediction with the mixing rule. Experimental characterizations indicate that the high-efficient mechanical enhancement is attributed to the strong synergy of melt stretching-driven crystallization and rGO re-dispersion or refinement in constructing the compact and robust shish-kebabs crystal network. Such microstructural characteristics greatly promote the load transfer along the covalently bonded molecular chains, and also from polymer to rigid fillers under loading. Furthermore, the excellent puncture resistance and thermo-mechanical properties of PE/rGO films have been demonstrated. This work provides a feasible way towards scalable manufacturing of high-performance polymer nanocomposite films from general plastics and carbonaceous nanomaterials.

Diamond-structured nanonetwork gold as mechanical metamaterials from bottom-up approach

Herein, this work aims to develop a facile method for the fabrication of metallic mechanical metamaterial with a well-ordered diamond structure from a bottom-up approach using a self-assembled block copolymer for templated electrochemical deposition. By controlling the effective volume fraction of PDMS in PS-b-PDMS via solvent annealing followed by HF etching of PDMS, it is feasible to obtain nanoporous PS with diamond-structured nanochannels and used it as a template for templated electrochemical deposition. Subsequently, well-ordered nanonetwork gold (Au) can be fabricated. As evidenced by nanoindentation and micro-compression tests, the mechanical properties of the diamond-structured Au after removal of PS give the combination of lightweight and mechanically robust characteristics with an exceptionally high reduced elastic modulus of 11.9 ± 0.6 GPa and yield strength of 193 ± 11 MPa above the Hashin-Shtrikman upper bound of 72 MPa with a bending-dominated structure at equivalent density. The corresponding deformation mechanism can be elucidated by morphological observations experimentally and finite element analysis (FEA) numerically. This work demonstrates the bottom-up approach to fabricating metallic monolith with diamond structure in the nanoscale, giving a superior performance as mechanical metamaterials.

Mechanical and Microstructural Properties of Autogenous Arc Welds of 2 GPa Strength Hot-Press-Forming Steel

Mechanical and Microstructural Properties of Autogenous Arc Welds of 2 GPa Strength Hot-Press-Forming Steel

From amyloid fibrils to microfiber condensates: Tuning microfluidic coextrusion of food-grade β-lactoglobulin-pectin core-shell fibers by changes of protein structure

Protein-based microfibers have potential applications in bioengineering and food but preserving and utilizing the unique nanomechanical properties of their protein building blocks at the micrometer scale remains a challenge. This study investigates the bottom-up fabrication of core-shell fibers by coaxial microfluidic spinning of pectin and β-lactoglobulin in different conformational states (monomeric, amyloid fibrils, shortened amyloid fibrils in their isotropic/nematic phases), gelled in CaCl2 solution. Fiber diameters ranged between 478 and 855 μm (wet state) and 107–135 μm (dry state). They showed clear core-shell cross-sections, except pectin-β-lactoglobulin monomer fibers where the compact protein is presumably understood to diffuse through the pectin matrix. The molecular orientation of the fiber building blocks was expressed as order parameters representing the alignment of pectin chains and amyloid fibrils parallel to the fiber axis calculated from synchrotron wide-angle X-ray scattering (WAXS) with a spatial resolution of 20 μm. Introduction of amyloid fibrils as the protein core increased the Young's modulus from 3.3 to 6.4 GPa and tensile strength from 117 to 182 MPa compared to pure pectin fibers. Increasing the protein core flow rate from 1 to 2 mL/h, however, caused helical bending of the core jet, a decrease in order, and ultimately worsened mechanical performance. Overall, full length amyloid fibrils proved to be more beneficial to the mechanical properties than shortened amyloid fibrils. By providing insight into the relationship between protein conformation, spinning flow rate, and resulting mechanical properties of core-shell microfibers, these results may contribute to the field of novel fibrous protein-based materials.

A lightweight Fe–Mn–Al–C austenitic steel with ultra-high strength and ductility fabricated via laser powder bed fusion

Lightweight Fe–Mn–Al–C steels have become a topic of significant interest for the defense and automotive industries. These alloys can maintain high strength and ductility while also reducing weight in structural applications. Conventionally processed Fe–Mn–Al–C austenitic steels with high Al content (∼9 wt%) demonstrate greater than 1.5 GPa strength with 35% elongation. Several recent studies have demonstrated success in fabricating steel parts using laser powder bed fusion (L-PBF) additive manufacturing (AM), which can generate near-net-shape components with complex geometries and is capable of local microstructural control. However, studies on L-PBF processing of Fe–Mn–Al–C alloys have focused on low Al content (<5 wt%) compositional regimes representing alloys that undergo transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP). Here, we present the effects of L-PBF processing on the microstructure and mechanical properties of an Fe–30Mn–9Al–1Si-0.5Mo-0.9C austenitic steel. A process optimization framework is employed to determine an ideal L-PBF processing space that will result in >99% density parts. Implementing this framework resulted in near-fully dense specimens fabricated over a broad range of process parameters. Additionally, two bi-directional scan rotation strategies (90° and 67°) were applied to understand their effects on texture and anisotropy in this material. As-printed specimens displayed considerable work-hardening characteristics with average strengths of up to 1.3 GPa and 36% elongation in the build direction. However, solidification microcracks oriented in the build direction resulted in anisotropy in tensile strength and ductility resulting in average strengths of 1.1 GPa and 20% elongation perpendicular to the build direction. The successful L-PBF fabrication of Fe–30Mn–9Al–1Si-0.5Mo-0.9C presented here is expected to open new avenues for weight reduction in structural applications with a high degree of control over part topology.

Open-loop recycling of post-consumer PET to closed-loop chemically recyclable high-performance polyimines

Intriguing high-performance polyimines (PI) were designed from diamines recovered by open-loop recycling of postconsumer PET bottles by microwave-assisted aminolysis. These new PIs had excellent thermal properties (Tm = 226–286 °C, Tg = 88–148 °C, heat resistance up to 327 °C) and super-high toughness and strength with Young's modulus of 4.02–4.93 GPa and tensile strength of 237–467 MPa, both significantly higher compared with common engineering plastics. The synthesized PIs also demonstrated recyclability “on demand” to original building blocks via mild and ultrafast acetic acid catalysed hydrolysis (70 °C for 10 min). Furthermore, the recovered monomer mixture was directly repolymerizable providing attractive closed-loop polymer-to-polymer recyclability under extremely mild conditions. These high performance thermoplastics, with easily tunable properties by selection of diamine used for aminolysis, in combination with closed-loop chemical recyclability have great promise as next-generation circular materials, designed from recycled plastics waste, for a wide property and application range.

Gas metal arc welding with undermatched filler wire for hot-press-formed steel of 2.0 GPa strength: Influence of filler wire strength and bead geometry

Gas metal arc welding with undermatched filler wire for hot-press-formed steel of 2.0 GPa strength: Influence of filler wire strength and bead geometry

High-Strength, Degradable and Recyclable Epoxy Resin Based on Imine Bonds for Its Carbon-Fiber-Reinforced Composites

Carbon fiber (CF) is widely used in the preparation of carbon-fiber-reinforced polymer composites (CFRP) in which it is combined with epoxy resin due to its good mechanical properties. Thermosetting bisphenol A epoxy resin, as one of the most common polymer materials, is a non-renewable resource, leading to a heavy environmental burden and resource waste. To solve the above problems and achieve high mechanical and thermal properties comparable to those of bisphenol A, herein, a high-performance, degradable and recyclable bio-based epoxy resin was developed by reacting the lignin derivative vanillin with 4-amino cyclohexanol via Schiff base. This bio-based epoxy resin showed a Young's modulus of 2.68 GPa and tensile strength of 44 MPa, 36.8% and 15.8% higher than those of bisphenol A epoxy, respectively. Based on the reversible exchange reaction of the imine bond, the resin exhibited good degradation in an acidic environment and was recoverable by heat treatment. Moreover, the prepared epoxy resin could be used to prepare carbon fiber (CF)-reinforced composites. By washing off the epoxy resin, the carbon fiber could be completely recycled. The recovered carbon fiber was well preserved and could be used again for the preparation of composite materials to realize the complete recovery and utilization of carbon fiber. This study opens a way for the preparation of high-performance epoxy resin and the effective recycling of carbon fiber.

Microstructure formation and mechanical performance of micro-nanoscale ceramic reinforced aluminum matrix composites manufactured by laser powder bed fusion

The constituent ratio merged into as-fabricated composites can directly influence the content of in-situ formed reinforcing phases, which is closely related to the mechanical performance of these composites. In this work, aluminum matrix composites reinforced with 10, 15, and 20 wt% (ZrC+TiC) ceramic fractions have been manufactured by laser powder bed fusion (LPBF) additive manufacturing. The effect of hybrid ceramic reinforcement content on laser absorption behavior, fabrication and fraction of micro-nanoscale reinforcing phases, mechanical performance of the as-fabricated aluminum matrix composites is studied. In the laser processing, TiC reacts with ZrC to synthesize interfacial layer on the unmolten ceramic particals and precipitate nano-particles. With the hybrid ceramic content raising from 10 to 20 wt%, the laser absorption behavior is enhanced, and the nano-particle fraction increases. The micro/nano hardness of the composites with 20 wt% ceramic content, reaches 120 HV0.2 and 1.33 GPa, respectively. An elastic modulus of ∼94.4 GPa and tensile strength of ∼280 MPa are obtained for the 15 wt% (ZrC+TiC)/Al composites, much higher than those of the unreinforced Al matrix. This is attributed to the combination of formation of nano-precipitates and coherent bonding at the reinforcement/matrix interfaces in these composites.

Finite element analysis based design of biomimetic functionally graded Ti-6Al-4V alloy scaffolds for human cortical bone applications

Bone defects may impede the functionality of a bone as an organ. The bone defects can be repaired using osteogenic cells, growth factors, and bone scaffolds. Functionally graded scaffolds ideally meet the purpose of repair of these damaged bones as they have mechanical and biological properties similar to the surrounding tissues. The properties of these biomaterial structures can be mimicked to that of the human bone for improved osseointegration and bone regeneration without causing any stress shielding effect. Triply Periodic Minimal Surface (TPMS) lattices have geometric properties similar to human bones, making them suitable for orthopaedic implant applications. In this study, the implicit modelling approach was adopted to create a TPMS gyroid unit cell using nTopology software. Thereafter, the gyroid TPMS lattice was used to parametrically design a functionally graded scaffold with radial grading, mimicking the topology of human bone. Here, the scaffold porosity and pore size were varied from 62 to 82% and 236–320 µm, respectively, from the outer to the inner layer. The mechanical responses and compression behaviour of the Ti-6Al-4V alloy scaffold were studied by employing Abaqus the commercial Finite Element Analysis (FEA) software. Capitalizing on the cyclic symmetry, only 1/24th of the geometric model was considered for Dynamic Explicit FEA, yielding a computationally efficient solution. The obtained Young's modulus of 22.1 GPa and compressive strength of 205 MPa of the designed scaffold closely matches with those of human cortical bone, confirming their ability to meet its structural requirements. The objective of this work is to develop a robust numerical framework to parametrically design functionally graded metallic bone scaffolds.

Structural composite based on 3D printing polylactic acid/carbon fiber laminates (PLA/CFRC) as an alternative material for femoral stem prosthesis

In recent years, surgical procedures for hip prostheses have increased. These implants are manufactured with materials with high stiffness compared to the bone, causing bone loss or aseptic loosening. This research proposes an alternative structural composite consisting of 3D-printing polylactic acid layers and carbon fiber laminates (PLA/CFRC) with potential application in prosthetic implants. Fourier-transform infrared spectroscopy (FTIR) achieved to characterize starting materials and structural composites revealed secondary chemical interactions between the carbonyl group of PLA with the hydroxyl group of epoxy resin from CFRC. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results show both components (PLA and CFRC) influence the structural composite's thermal behavior, observed in the temperatures of degradation, glass transition, and melting. Furthermore, the composite reached cell viability above 80%, a tensile modulus of 19.29 ± 0.48 GPa and tensile strength of 238.91 ± 25.95 MPa, with mechanical properties very similar to the bone. The results of this study demonstrated that the proposed PLA/CFRC composite can be used as candidate base material for the manufacturing of a hip femoral stem prostheses.

Effect of a multi-phase structure on the damping response of a novel high entropy alloy

• Dynamic behavior of a multi-phase high entropy alloy is investigated in a wide temperature range. • Effects of processing and the resulting phase constitution on the damping response is underlined. • The storage modulus and the internal friction values of the annealed alloys are improved. In this study, dynamic behavior of a novel multi-phase high entropy alloy (HEA) was investigated. Thermo-mechanical processes containing an 80% reduction in room temperature rolling followed by annealing at 750°C and 850°C were applied to modify the microstructure and the resulting damping properties of the HEA. Annealing at 750°C introduced the BCC phase, while at 850°C, the sigma phase was precluded in the microstructure, leading to over 1 GPa strength with decent ductility in the latter condition. The storage modulus and the internal friction values of the annealed alloys are noticeably improved, indicating that proper heat treatments could enhance both the mechanical response and the damping performance of this HEA.

Smart electromagnetic interference shields based on flexible PEDOT:PSS/Bi2Te3 films

Nowadays, the electromagnetic interference (EMI) shielding materials with an excellent electrical features, favorable flexibility and low density are the admirable desires that represent great challenges. Therefore, n-type bismuth telluride nanorods with diameter of 41.3 ± 5 nm (n-Bi2Te3) were incorporated into a p-type poly(3,4-ethylene-dioxythiophene):poly (styrenesulphonate) (p-PEDOT:PSS) to fabricate a (p-PEDOT:PSS/n-Bi2Te3) films for the electromagnetic interference shielding applications for the first time. Besides, the impact of n-Bi2Te3 nanorods on the electrical conductivity and the electromagnetic interference (EMI) shielding functions of p-PEDOT:PSS/n-Bi2Te3 films has been explored. The electrical conductivity (σ) has gradually increased with the n-Bi2Te3 nanorods in the shield films to obtain the highest value of 106.73 ± 6 S/cm at 16 wt%. Moreover, the total shielding effectiveness (SET) has also dramatically increased with the n-Bi2Te3 nanorods to obtain the highest value of 42.02 dB at 12 GHz for 16 wt%. The reflection mode is the dominance contribution in the shielding effectiveness process, presenting a good reflector of EM waves. Furthermore, the shield films have displayed a high mechanical performance with young modulus of 1.9 ± 0.3 GPa and tensile strength of 42.5 ± 5 MPa at 16 wt%. It can be suggested that these p-PEDOT:PSS/n-Bi2Te3 shields can be functionalized in many fields like electromagnetic shielding interference technology, military, electronic, smart fabric, wearable and biological apparatuses.