Ultrahigh Mechanical Strength Research Articles

Properties of Thermoresponsive N-maleyl gelatin-co-P(N-isopropylacrylamide) hydrogel with ultrahigh mechanical strength and self-recovery

Thermo-responsive polymer hydrogels with superior strength and toughness are potential candidate materials in biomedical field, such as drug delivery system and tissue engineering. By introducing maleylgelatin (MAGEL) into the conventional PNIPAAm hydrogel, a series of composite P(NIPAAm-co-MAGEL) hydrogels with combined features were fabricated. Thermo-responsive behaviors, equilibrium swelling ratio (ESR), compression strength, tensile strength (TS) and elongation at-break (E), cyclic compression tests, and thermal stability properties of hydrogels with different amount of MAGEL were investigated. Experimental data indicated that the amount of MAGEL could modulate the mechanical property of the composite hydrogel. With the increase of the MAGEL contents from 0 to 50%, the composite hydrogel with relatively high water content possessed good compressive strength, tensile strength and stretrability. Only when the weight ratio of MAGEL/NIPAAm was 30:70, did the P(NIPAAm-co-MAGEL) have a homogeneous distribution and stable 3D networks which played a significant role in the properties of the hydrogels. Cyclic compression tests results indicated that P(NIPAAm-co-MAGEL) hydrogel had an excellent thermo-reversible ability. This research would expand the scope of the PNIPAAm hydrogel applications.

Hybrid dual crosslinked polyacrylic acid hydrogels with ultrahigh mechanical strength, toughness and self-healing properties via soaking salt solution

Broader applications of polymer hydrogels are largely constrained by their poor mechanical performance. Here, we report our strategy of achieving ultrahigh mechanical strength, toughness, and self-healing properties simultaneously in a hybrid dual crosslinked polyacrylic acid (PAAc) hydrogel. The hybrid PAAc hydrogel was fabricated in a one-pot reaction with two types of crosslinking points, i.e. the primary chemical cross-linkers that create covalent cross-linking among PAA chains and the secondary physical cross-linkers Fe3+ that introduce ionic coordinates between Fe3+ and −COO− groups. The resulting hybrid PAA hydrogel was subsequently subject to a simple saline solution soaking to become highly mechanically robust as a result of chain entanglement within the network. Favorable mechanical properties possessed by such hybrid hydrogels included high tensile strength (ca. 1.794 MPa), large elongation at break (ca. 13.209 times), and excellent work of extension (ca. 11.475 MJ m−3). In addition, the hydrogels exhibited self-healing properties because of their inter-chain interactions at ambient conditions (tensile strength can recover approximately 30% of the initial after self-healing for 48 h from a cut-off state). This work demonstrates a simple and promising strategy of preparation of novel ductile and doughty hydrogels through dual crosslinking and saline solution soaking.

Functionalized chitosan biosorbents with ultra-high performance, mechanical strength and tunable selectivity for heavy metals in wastewater treatment

Water pollution is the most challenging issue facing mankind nowadays as a result of ever-increasing population and steadily improving life standards. More and more wastewater without effective treatments is arbitrarily discharged into the aquatic environment, which causes irreversible damage and incalculable loss. Especially, the industrial wastewater containing heavy metal ions, such as copper (Cu), cobalt (Co), and manganese (Mn), are toxic to human and living organisms even at low concentrations. A highly efficient and selective removal method has been long sought for heavy metal ions wastewater treatment. In this study, a highly monodispersed polyethylenimine-chitosan (PEI-CS) biosorbent, synthesized by an integrated process with facile microfluidic emulsion, chemical crosslinking, solvent extraction and chemical modification, was used as an efficient adsorbent to remove heavy metal ion from contaminated water. The as-prepared biosorbents demonstrated ultra-high adsorption capacity of 146mgg−1 towards Cu ions, almost triple the performance reported in literature. Besides, PEI-CS biosorbents were also endowed with good mechanical strength, excellent adsorption selectivity towards targeted ion in the presence of other metal ions with different valence states, and high reusability. Therefore, the newly developed PEI-CS biosorbents is a highly promising candidate for wastewater treatment with heavy metal ions.

(Invited) Tuning Physicochemical Properties of MoS2 By Mechanical Strain

Monolayers of 2D materials have ultrahigh mechanical strength, which enables application of very large elastic strains (e.g., ~11% for MoS2 and 25% for graphene). The ability of sustaining such large elastic strain offers unprecedented opportunities to engineer the physicochemical properties by applying mechanical strain. In this talk, I will present two examples on the effect of strain on the properties of MoS2 layer. The first example shows that elastic tensile strain reduces the bandgap of MoS2. When a gradient strain field is applied to MoS2 monolayer, the created bandgap gradient acts as an efficient funnel of photogenerated excitons that leads to enhanced photoluminescence. The second example shows that when elastic strain is applied to the sulfur vacancy on the basal planes of monolayer 2H-MoS2, the strain modifies the local electronic structure and catalytic activity. The proper combination of S-vacancy and strain allows us to achieve higher intrinsic activity for hydrogen evolution reaction than the edge site of MoS2.

Investigating interfacial contact configuration and behavior of single-walled carbon nanotube-based nanodevice with atomistic simulations

Carbon nanotubes (CNTs), including single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), are considered to be the promising candidates for next-generation interconnects with excellent physical and chemical properties ranging from ultrahigh mechanical strength, to electrical properties, to thermal conductivity, to optical properties, etc. To further study the interfacial contact configurations of SWNT-based nanodevice with a 13.56-A diameter, the corresponding simulations are carried out with the molecular dynamic method. The nanotube collapses dramatically into the surface with the complete collapse on the Au/Ag/graphite electrode surface and slight distortion on the Si/SiO2 substrate surface, respectively. The related dominant mechanism is studied and explained. Meanwhile, the interfacial contact configuration and behavior, depended on other factors, are also analyzed in this article.

Electrodeposition of Nanotwin Cu by Pulse Current for Through-Si-Via (TSV) Process.

Recently, the through-Si-via (TSV) had been focused as an optimal solution for interconnecting the 3-dimensionaly stacked semiconductor devices. One of core processes in the TSV technology is the Cu filling process which electrochemically forms the Cu in the via with high aspect ratio. The nanotwin Cu is effective candidate for replacing the conventional electrodeposited Cu due to its ultrahigh mechanical strength and good electrical conductivity. In this work, the formation of the nanotwin Cu in the TSV by applying pulse current was systematically studied. Also, TSV filling behavior by electrodeposition with pulse current was compared with direct current. The variation of mechanical properties as well as the electrical resistivity of electrodeposited Cu by the pulse current also investigated.

A thermo-responsive dual-crosslinked hydrogel with ultrahigh mechanical strength

A thermal-responsive hydrogel with ultrahigh mechanical strength was engineered by a covalently cross-linked and an ionic coordinated network.

Molecularly Engineered Dual‐Crosslinked Hydrogel with Ultrahigh Mechanical Strength, Toughness, and Good Self‐Recovery

A molecularly engineered dual-crosslinked hydrogel with extraordinary mechanical properties is reported. The hydrogel network is formed with both chemical crosslinking and acrylic-Fe(III) coordination; these, respectively, impart the elasticity and enhance the mechanical properties by effectively dissipating energy. The optimal hydrogel achieves a tensile stress of ca. 6 MPa at a large elongation ratio (>7 times), a toughness of 27 MJ m(-3) , and a stiffness of ca. 2 MPa, and has good self-recovery properties.

Facile ion-exchange synthesis of silver films as flexible current collectors for micro-supercapacitors

Flexible MSCs were created using the SMIE technique in the open air, and it did not involve any complicated clean-room processes. The MSCs developed in this study offer high power density, high flexibility, and long endurance, especially ultrahigh mechanical strength.

Consolidation of nanometer-sized aluminum single crystals: Microstructure and defects evolutions

Deriving bulk materials with ultra-high mechanical strength from nanometer-sized single metalic crystals depends on the consolidation procedure. We present an accurate molecular dynamics study to quantify microstructure responses to consolidation. Aluminum single crystals with an average size up to 10.7nm were hydrostatically compressed at temperatures up to 900K and pressures up to 5GPa. The consolidated material developed an average grain size that grew exponentially with the consolidation temperature, with a growth rate dependent on the starting average grain size and the consolidation pressure. The evolution of the microstructure was accompanied by a significant reduction in the concentration of defects. The ratio of vacancies to dislocation cores decreased with the average grain size and then increased after reaching a critical average grain size. The deformation mechanisms of poly-crystalline metals can be better understood in the light of the current findings.

Using nanocapsules as building blocks to fabricate organic polymer nanofoam with ultra low thermal conductivity and high mechanical strength

A new strategy using the performed nanocapsules with well-defined highly crosslinked polymer shell as building blocks was proposed to fabricate the organic polymeric nanofoam. This new strategy allowed us to fabricate the high performance organic polymeric nanofoam, for the first time, under normal drying conditions. The thermal conductivities of the nanofoams in the forms of powder and monolith were far lower than that of the stagnant air and half those of the standard commercial polymer foams. The nanofoam monoliths showed the crush strength up to 8.55 ± 2.10 MPa and compressive strain at break up to 45% ± 6%.

First-principles study of the binary Ni60Ta40 metallic glass: The atomic structure and elastic properties

Ni–Ta bulk metallic glass (BMG) with compositions around Ni60Ta40 is a newly found binary BMG with high glass forming ability and extraordinary mechanical strength. Using ab initio molecular dynamics, the local atomic structure, elastic properties and electronic structures of Ni60Ta40 glass have been explored. The pair-correlation functions, coordination numbers, and chemical compositions of the most abundant local clusters have been analyzed. We demonstrated the existence of icosahedral Ni7Ta6 clusters as the major Ni-centered clusters, while the most popular Ta-centered cluster is Ta7Ni8. These findings agree with our previous cluster model of Ni–Ta binary BMG. The elastic moduli of Ni60Ta40 glass were also computed and the experimental Young's modulus is well reproduced. Analysis of electronic structures further revealed that the interaction between d electrons of Ni and Ta atoms is responsible for the experimentally observed ultrahigh mechanical strength for the Ni–Ta BMGs.

Laser beam welding tempered 300M ultrahigh mechanical strength steel

AISI 300M ultrahigh strength steel has been used in a number of high demanding applications, such as the VLS Brazilian rocket project. This work intends to propose laser beam welding, with subsequent tempering, as a possible route for the fabrication of engineering pieces of this steel. A 2 kW fiber laser was used to produce welded coupons for metallographic, hardness and tensile strength tests. It has been shown that convenient laser parameters for a 3 mm thick plate are 50 mm/s welding speed and 1200 W laser power. However, both welded materials and heat-affected zones presented high hardness and negligible plastic deformation. In order to produce useful engineering parts, it was suggested a tempering treatment for 2 hours at temperatures of 200 or 400oC. Tensile mechanical testing has shown that welded and tempered coupons presented both yield and maximum strengths comparable to the unwelded material. On the other hand, a maximum elongation of about 4% was obtained, in comparison with 12% from the bulk sample.

Enhancement of the soft magnetic properties of FeCoZrMoWB bulk metallic glass bymicroalloying

The Fe61Co7Zr9.5Mo5W2B15.5 bulk metallic glass (BMG) has the best glass forming-ability (GFA), highthermal stability, and the highest strength (the compressive strengthσ = 3800 MPa) among known Fe-based alloys. Unfortunately, this BMG does not have the samegood soft magnetic properties as other Fe-based BMGs do. We report here that a smallamount of Ni addition (microalloying) can significantly enhance the soft magneticproperties of the alloy without deteriorating its high GFA. The saturation magnetization isincreased threefold, while the coercivity is decreased about 40-fold, with only 3 at.% Niaddition. The improvement is interpreted to result from the enhancement of the magneticexchange interaction as the Ni content increases. The results indicate that it is possible toadjust the magnetic properties of Fe-based BMGs by a minor change in the content ofsome component. BMGs with good soft magnetic property, ultrahigh mechanicalstrength, good GFA and high thermal stability show some promise for futureapplications.

Magnetic and magnetoelastic properties of 18% nickel maraging steels

The variation of the magnetic properties of two commercial 18% Ni maraging steels with processing conditions is studied. These steels, notable for their ultra-high mechanical strength properties, do not exhibit the conventional correlation between mechanical and magnetic hardness. Stress is found to have large softening effects on the magnetic properties regardless of metallurgical conditions. This apparently stems from the substantial magnetostriction and relatively low crystal anisotropy of the predominantly Ni-Fe martensitic matrix. In view of this unusual combination of high strength and stress sensitivity, applications in transducers and as cores of specialized apparatus are foreseen. >