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In the current scenario, energy generation is relied on the portable gadgets with more efficiency paving a way for new versatile and smart techniques for device fabrication. 3D printing is one of the most adaptable fabrication techniques based on designed architecture. The fabrication of 3D printed energy storage devices minimizes the manual labor enhancing the perfection of fabrication and reducing the risk of hazards. The perfection in fabrication technique enhances the performance of the device. The idea has been built upon by industry as well as academic research to print a variety of battery components such as cathode, anode, separator, etc. The main attraction of 3D printing is its cost-efficiency. There are tremendous savings in not having to manufacture battery cells separately and then assemble them into modules. This review highlights recent and important advances made in 3D printing of energy storage devices. The present review explains the common 3D printing techniques that have been used for the printing of electrode materials, separators, battery casings, etc. Also highlights the challenges present in the technique during the energy storage device fabrication in order to overcome the same to develop the process of 3D printing of the batteries to have comparable performance to, or even better performance than, conventional batteries.

Liquid phase exfoliation of two-dimensional (2D) materials from their bulk counterparts has attracted a lot of attention due to its applications in the large-scale synthesis of these materials. Herein, detailed molecular dynamics simulations to understand the exfoliation process of graphene followed by an in-situ exfoliation experiment of graphite suspended in polyacrylonitrile (PAN) using a well-known electro-spinning technique were performed. Submicron-scale fibers reinforced with graphene exhibited multi-fold improvements in terms of mechanical (stiffness, elastic modulus), thermal (degradation temperature) and electrochemical (ionic conductivity) properties. This method is a unique way of synthesizing in-situ composites with large lengths and submicron-diameter fibers. The present technique and the key ideas can be readily extended to other 2D materials as well.

Silicon carbide nanotube/nanowires (SiCNT/NWs) exhibit excellent mechanical properties in extreme thermal and oxidative environments. Here, we demonstrate an easily scalable process to synthesize millimeter-sized three-dimensional architectures using SiCNT/NW building blocks to create materials with excellent mechanical strength, stiffness, and resiliency with ultra-low density. The structure of these macro-materials is initially synthesized using carbon nanotubes, then utilizing the shape memory synthesis (SMS) method are converted to nano-silicon carbide. It is proposed that using this technique, any micro-structure can initially be created with nano-carbon building blocks, optimized for the necessary morphological features of a specific application. Here, the synthesis and subsequent SiCNT/NW conversion of carbon nanotube spheres and graphene foam, demonstrates the ability to use a simple, cost-effective conversion method to create a material that can mechanically perform in extreme environments.

Additive manufacturing technologies are expected to disrupt the majority of the traditional way of manufacturing methods, particularly in the field of medical and healthcare. Bones and teeth are vital organs that are susceptible to various disorders due to environmental, traumatic, genetic factors and inherent malignant disorders. Most of the implants/prostheses normally used are cast and have a standard size and shape. Additive manufacturing has opened opportunities to replace these hard tissues with customized implants, prostheses or the whole additive manufactured organ itself while considering anatomical/structural parts and functional aspects of the body. It helps to visualize and mimic internal organs/models, pre-planning via simulation, anatomical demonstration, treatments and surgical teaching/training to technical staff by medical professionals. The current review covers additive manufacturing applications for the possible treatment of osteosarcoma, bone tumors, traumatic fracture, congenital anomalies, dental diseases, vertebral and cranial abnormalities, etc. from toe to head highlighting printing of long bones, short bones, cartilages, teeth and more based on the general classification of bones shape, that is, the external shape and size of different bones with some case studies. The article has also touched upon the additive manufacturing competitive edge over the conventional methods in terms of complexity, easiness, cost-effectiveness and reduced time. However, the internal structures have not been addressed so far in additive manufacturing which could be a new corner to enhance the properties of bones and teeth in the future.

The organic matrix of a bone mainly composed of a collagen matrix serves as a crucial component for remarkable toughness and strength in bones. The porous collagen matrix can also serve as an efficient template for various applications such as nanoparticle synthesis, catalysis or catalysis supports, electrochemical separator, filtration membrane, and tissue engineering. However, fabricating collagen matrix from bones without degrading its morphological structure still remains a challenge. Here, we present evidence of how ceramic crystals from a bone can be removed to fabricate a complete ‘transparent bone’ structure with improved porosity and elasticity. We show that demineralization or selective etching using dilute acid (citric) can remove ceramic mineral nanoparticles without degrading the collagen matrix. The transparent bone collagen matrix is investigated as the separator in electrochemical supercapacitor with aqueous electrolyte where it shows better performance compared with conventional separators.

Low-dimensional atomic layered structures have gained much attention due to their fascinating properties such as surface area, mechanical properties, chemical inertness, conductivity, etc. However, to integrate these outstanding materials into the today’s technology, their structures need to be modified. One of the paths that can be used to integrate these structures into the novel technologies is building three-dimensional structures with inspiration from nature. Nature teaches us how to combine the intrinsic properties of these low-dimensional materials with the novel behavior that originates from the assembly of the macroscopic architecture. In this review, we summarize approaches to fabricate three-dimensional (3D) architectures using low-dimensional nanostructures, which include zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) nanostructures. Furthermore, we discuss interface interactions between these structures, which is the paramount element for creating robust and efficient 3D structures using these nanomaterial systems.

Since its isolation by Geim and coworkers, graphene has received a lot of attention from the research community as well as industry. Interesting and groundbreaking research has been published on graphene showing excellent properties and a wide range of applications. It was thought that graphene could replace well-established applications currently being controlled by graphite. In this perspective, we review large-scale applications of graphite that we think graphene can replace. We also discuss niche applications that we think graphene can make inroads for large-scale applications.

Three-dimensional (3D) architectures based on carbon nanotubes (CNTs) have been applied to fields ranging from aerospace to biomedicine. In this report, the fabrication of 3D CNT patterns having various orientations has been described. These 3D architectures acted both as efficient optical switching devices and barriers to protect against laser-induced damage. Such devices can switch from transparent to opaque upon application of a very small strain (

Conductive epoxy composites are of great interest due to their applications in electronics. They are usually made by mixing powdered conductive fillers with epoxy. However, the conductivity of the composite is limited by the low filler content because increasing filler content causes processing difficulties and reduces the mechanical properties of the epoxy host. We describe here the use of ultra-stiff graphene foams (uGFs) as three-dimensional (3D) continuous conductive fillers for epoxy resins. The powder metallurgy method was used to produce the dense uGFs monoliths that resulted in a very high filler content of 32 wt % in the uGF–epoxy composite, while the density of epoxy was only increased by 0.09 g/cm3. The composite had an electrical conductivity of 41.0 ± 6.3 S/cm, which is among the highest of all of the polymer-based composites with non-conductive polymer matrices and comparable with the conductive polymer matrices reported to date. The compressive modulus of the composite showed a remarkable i...

Natural building blocks like proteins and hydroxyapatite (HA) are found in abundance. However, their effective utilization to fabricate environment-friendly, strong, stiff, and tough materials remains a challenge. This work reports on the synthesis of a layered material from entirely natural building blocks. A simple process to extract HA from bones, while keeping collagen intact, is presented. These HA nanocrystals have a high aspect ratio as a result of the extraction method that largely retains the pristine nature of the HA. To fabricate the materials, polymerized egg white is used to induce toughness to the crystals where it acts like a load transfer entity between the crystals. As shown by atomic force microscope modulus mapping, the result is a layered material with a modulus that ranges from 3 to 180 GPa. Furthermore, the material exhibits self-stiffening behavior. Hydrogen and ionic bonds are likely to regulate the chemical interactions at the egg white/HA interface and are likely to be responsible for the observed high toughness and stiffness, respectively. The use of the HA/egg white composite as printed scaffolds is also demonstrated together with their biocompatibility.

Bio-derived materials could play an important role in future sustainable green and health technologies. This work reports the synthesis of a unique egg white-based bio-derived material showing excellent stiffness and ductility by polymerizing it with primary amine-based chemical compounds to form strong covalent bonds. As shown by both experiments and theoretical simulations, the amine-based molecules introduce strong bonds between amine ends and carboxylic ends of albumen amino acids resulting in an elastic modulus of ∼4 GPa, a fracture strength of ∼2 MPa and a high ductility of 40%. The distributed and interconnected network of interfaces between the hard albumen and the soft amine compounds gives the structure its unique combination of high stiffness and plasticity. A range of in-situ local and bulk mechanical tests as well as molecular dynamics (MD) simulations, reveal a significant interfacial stretching during deformation and a micro-crack diversion leading to an increased in ductility and toughness. The structure also shows a self-stiffening behavior under dynamic loading and a strength-induced aging suggesting adaptive mechanical behavior. This egg white-derived material could also be developed for bio-compatible and bio-medical applications., by Peter Samora Owuor, Thierry Tsafack, Himani Agrawal, Hye Yoon Hwang, Matthew Zeliskob, Tong Lic, Sruthi Radhakrishnan, Jun Hyoung Park, Yingchao Yang, Anthony S. Stender, Sehmus Ozden, Jarin Joyner, Robert Vajtai, Benny A. Kaipparettu, Bingqing Wei, Jun Lou, Pradeep Sharma, Chandra Sekhar Tiwarya and Pulickel M. Ajayan

Instantaneous adhesion between different materials is a requirement for several applications ranging from electronics to biomedicine. Approaches such as surface patterning, chemical cross-linking, surface modification, and chemical synthesis have been adopted to generate temporary adhesion between various materials and surfaces. Because of the lack of curing times, temporary adhesives are instantaneous, a useful property for specific applications that need quick bonding. However, to this day, temporary adhesives have been mainly demonstrated under dry conditions and do not work well in submerged or humid environments. Furthermore, most rely on chemical bonds resulting from strong interactions with the substrate such as acrylate based. This work demonstrates the synthesis of a universal amphibious adhesive solely by combining solid polytetrafluoroethylene (PTFE) and liquid polydimethylsiloxane (PDMS) polymers. While the dipole-dipole interactions are induced by a large electronegativity difference between fluorine atoms in PTFE and hydrogen atoms in PDMS, strong surface wetting allows the proposed adhesive to fully coat both substrates and PTFE particles, thereby maximizing the interfacial chemistry. The two-phase solid-liquid polymer system displays adhesive characteristics applicable both in air and water, and enables joining of a wide range of similar and dissimilar materials (glasses, metals, ceramics, papers, and biomaterials). The adhesive exhibits excellent mechanical properties for the joints between various surfaces as observed in lap shear testing, T-peel testing, and tensile testing. The proposed biocompatible adhesive can also be reused multiple times in different dry and wet environments. Additionally, we have developed a new reactive force field parameterization and used it in our molecular dynamics simulations to validate the adhesive nature of the mixed polymer system with different surfaces. This simple amphibious adhesive could meet the need for a universal glue that performs well with a number of materials for a wide range of conditions., by Chandra Sekhar Tiwary et al.

Hexagonal boron nitride (h-BN), graphene oxide (GO) and hybrid (GO/h-BN) nanosheets were employed as fillers in order to enhance the physical properties of the polymer matrix. Composites based in epoxy and these two-dimensional (2D) nanofillers were produced with different wt% and their microstructure, mechanical and thermal properties were investigated. Increases up to 140% in tensile strength, 177% in ultimate strain and 32% in elastic modulus were observed for the hybrid GO/h-BN composite with 0.5 wt% content. The hybrid nanofiller also contributed to the increase up to 142% on thermal conductivity with respect to the pure epoxy for GO/h-BN composite with 2.0 wt% content. Molecular dynamic simulation was used to predict the behavior of possible stacking arrangements between h-BN and GO nanosheets tensioned by normal and shear forces. The results showed that the hybrid GO/h-BN combination can prevent the re-stacking process of exfoliated layers, demonstrating the synergism between these nanostructures with the final effect of better dispersion in the composite material. The excellent thermal and mechanical performance of these hybrid composites engineered by the combination of different types of the 2D inorganic nanoparticles make them multifunctional candidates for advanced materials applications.

Low-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption applications, even under high compressive deformations. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. Recently, a new and scalable synthetic approach to produce low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) was proposed. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. In order to obtain further insights on mechanisms behind the enhanced mechanical pGO response we carried out fully atomistic molecular dynamics (MD) simulations. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.

Two-dimensional (2D) nanomaterials as molybdenum disulfide (MoS2), hexagonal boron nitride (h-BN), and their hybrid (MoS2/h-BN) were employed as fillers to improve the physical properties of epoxy composites. Nanocomposites were produced in different concentrations and studied in their microstructure, mechanical and thermal properties. The hybrid 2D mixture imparted efficient reinforcement to the epoxy leading to increases of up to 95% in tensile strength, 60% in ultimate strain, and 58% in Young’s modulus. Moreover, an enhancement of 203% in thermal conductivity was achieved for the hybrid composite as compared to the pure polymer. The incorporation of MoS2/h-BN mixture nanofillers in epoxy resulted in nanocomposites with multifunctional characteristics for applications that require high mechanical and thermal performance.

Weak van der Waals forces between inert hexagonal boron nitride (h-BN) nanosheets make it easy for them to slide over each other, resulting in an unstable structure in macroscopic dimensions. Creating interconnections between these inert nanosheets can remarkably enhance their mechanical properties. However, controlled design of such interconnections remains a fundamental problem for many applications of h-BN foams. In this work, a scalable in situ freeze-drying synthesis of low-density, lightweight 3D macroscopic structures made of h-BN nanosheets chemically connected by poly(vinyl alcohol) (PVA) molecules via chemical cross-link is demonstrated. Unlike pristine h-BN foam which disintegrates upon handling after freeze-drying, h-BN/PVA foams exhibit stable mechanical integrity in addition to high porosity and large surface area. Fully atomistic simulations are used to understand the interactions between h-BN nanosheets and PVA molecules. In addition, the h-BN/PVA foam is investigated as a possible CO2 abs...

It is one of the most important needs to develop renewable, scalable and multifunctional methods for the fabrication of 3D carbon architectures. Even though a lot of methods have been developed to create porous and mechanically stable 3D scaffolds, the fabrication and control over the synthesis of such architectures still remain a challenge. Here, we used Magnetospirillum magneticum (AMB-1) bacteria as a bio-template to fabricate light-weight 3D solid structure of carbon nanotubes (CNTs) with interconnected porosity. The resulting porous scaffold showed good mechanical stability and large surface area because of the excellent pore interconnection and high porosity. Steered molecular dynamics simulations were used to quantify the interactions between nanotubes and AMB-1 via the cell surface protein MSP-1 and flagellin. The 3D CNTs-AMB1 nanocomposite scaffold is further demonstrated as a potential substrate for electrodes in supercapacitor applications.

Owing to the weak physical interactions such as van der Waals and π-π interactions, which hold nanotubes together in carbon nanotube (CNT) bulk structures, the tubes can easily slide on each other. Creating covalent interconnection between individual carbon nanotube (CNT) structures could remarkably improve the properties of their three-dimensional (3D) bulk structures. The creation of such nanoengineered 3D solid structures with improved properties and low-density remains one of the fundamental challenges in real-world applications. Here, we report the scalable synthesis of low-density 3D macroscopic structure made of covalently interconnected nanotubes using free-radical polymerization method after functionalized CNTs with allylamine monomers. The resulted interconnected highly porous solid structure exhibits higher mechanical properties, larger surface area and greater porosity than non-crosslinked nanotube structures. To gain further insights into the deformation mechanisms of nanotubes, fully atomistic reactive molecular dynamics simulations are used. Here we demonstrate one such utility in CO2 uptake, whose interconnected solid structure performed better than non-interconnected structures.

Advanced composite materials are characterized by lightweight and unusually high stiffness, strength, modulus, etc. [ 1 , 2 ]. Their application field keeps on expanding as cheaper methods for synthesizing raw materials are found. Composite materials are now found in virtually all facets of applied materials [3] . Unlike a few decades ago when their application was limited to small parts; for example spoilers, failings, bonnets, etc., currently a new generation of airplane fuselage and wings are completely made of high-performance fiber reinforced composites [ 4 – 6 ]. The inherent high specific strength, low density, chemical and corrosion resistance [7] make them ideal for future applications. Typically, composite materials consist of a combination of two or more materials that are mixed with an aim of achieving a specific structural properties [8] . An effective composite should be able to optimize the properties of the individual components as one.

The synthesis of high-K flexible dielectric material is presented using two commonly used inorganic materials S and Se., Upcoming advancements in flexible technology require mechanically compliant dielectric materials. Current dielectrics have either high dielectric constant, K (e.g., metal oxides) or good flexibility (e.g., polymers). Here, we achieve a golden mean of these properties and obtain a lightweight, viscoelastic, high-K dielectric material by combining two nonpolar, brittle constituents, namely, sulfur (S) and selenium (Se). This S-Se alloy retains polymer-like mechanical flexibility along with a dielectric strength (40 kV/mm) and a high dielectric constant (K = 74 at 1 MHz) similar to those of established metal oxides. Our theoretical model suggests that the principal reason is the strong dipole moment generated due to the unique structural orientation between S and Se atoms. The S-Se alloys can bridge the chasm between mechanically soft and high-K dielectric materials toward several flexible device applications.

Here we report a combined study of experiments and simulations to understand how chemical functional groups can mechanically stabilize aggregates of carbon nanotubes (CNTs). Ultralow density aggregates of chemically functionalized CNTs, in the form of macro-scale spheres made by freeze-drying method, show mechanical stabilization and near complete elastic recovery during deformation. Simulations of interacting functionalized carbon nanotube aggregates show better structural retention compared to non-functionalized CNTs under compression, suggesting that the atomic-level interactions between functional groups on adjoining CNTs help maintain structural rigidity and elastic response during loading. Aggregates of non-functionalized CNTs collapses under similar loading conditions. The dynamic mechanical responses of CNT macrostructures and mechano-chemical stabilization are directly observed using in-situ deformation inside a scanning electron microscope.

This study suggests the simple and effective synthesis method of chemically interconnected hexagonal boron nitride (h-BN)–carbon nanotubes (CNTs) hybrid materials (BN–Fe-CNT) with aminosilane functionalized iron oxide nanoparticles (NH2–Fe) via amide bond formations. Synthesized BN-Fe-CNT was acting as an effective filler that enhanced the mechanical, thermal, and electrical properties of polyimide (PI) nanocomposites and accelerated polycondensation reaction of poly(amic acid) (PAA) due to its high thermal conductivity and heat diffusivity. At a 2 wt% filler reinforcement, the in-plane thermal conductivity of the BN-Fe-CNT/PI reached 15 W m−1 K−1 at 200 °C, which represents an enhancement of approximately 11430% compared to that of pure PI. Moreover, thermal stability was enhanced from 400 °C to 570 °C. Furthermore, the connected CNTs between the individual h-BN produced electron pathways through the PI matrix, with the BN-Fe-CNT/PI exhibiting 106 times higher electrical conductivity than that of pure PI. The results in this study clearly suggested that the BN-Fe-CNT could be applicable as an effective multi-functional reinforcement in the fabrication of lightweight polymer nanocomposites with superior mechanical properties, high thermal properties, and high electrical conductivities.

Biological materials are multifunctional performing more than one function in a perfect synergy. These materials are built from fairly simple and limited components at ambient conditions. Such judicious designs have proven elusive for synthetic materials. Here, we demonstrate a multifunctional phase change (pc) composite from simple building blocks, which exhibits high stiffness and optical transmittance control. We show an increase of more than one order of magnitude in stiffness when we embed paraffin wax spheres into an elastomer matrix, polydimethylsiloxane (PDMS) in a dynamic compression test. High stiffness is mainly influenced by presence of microcrystals within the wax. We further show fast temperature-controlled optical switching of the composite for an unlimited number of cycles without any noticeable mechanical degradation. Through experimental and finite element method, we show high energy absorption capability of pc-composite. Based on these properties, the pc-composite could be used as an effective coating on glasses for cars and windows. This simple approach to multi-functionality is exciting and could pave way for designs of other multifunctional materials at the macro-scale., by Peter Samora Owuor, Varun Chaudhary, Cristiano F. Woellner, V Sharma, R.V. Ramanujan, Anthony S. Stender, Matias Soto, Sehmus Ozden, Enrique V. Barrera, Robert Vajtai and Douglas S. Galvao

Laser-induced graphene (LIG), a graphene structure synthesized by a one-step process through laser treatment of commercial polyimide (PI) film in an ambient atmosphere, has been shown to be a versatile material in applications ranging from energy storage to water treatment. However, the process as developed produces only a 2D product on the PI substrate. Here, a 3D LIG foam printing process is developed on the basis of laminated object manufacturing, a widely used additive-manufacturing technique. A subtractive laser-milling process to yield further refinements to the 3D structures is also developed and shown here. By combining both techniques, various 3D graphene objects are printed. The LIG foams show good electrical conductivity and mechanical strength, as well as viability in various energy storage and flexible electronic sensor applications.

Weak van der Waals forces between inert hexagonal boron nitride (h-BN) nanosheets make it easy for them to slide over each other, resulting in an unstable structure in macroscopic dimensions. Creating interconnections between these inert nanosheets can remarkably enhance their mechanical properties. However, controlled design of such interconnections remains a fundamental problem for many applications of h-BN foams. In this work, a scalable in situ freeze-drying synthesis of low-density, lightweight 3D macroscopic structures made of h-BN nanosheets chemically connected by poly(vinyl alcohol) (PVA) molecules via chemical cross-link is demonstrated. Unlike pristine h-BN foam which disintegrates upon handling after freeze-drying, h-BN/PVA foams exhibit stable mechanical integrity in addition to high porosity and large surface area. Fully atomistic simulations are used to understand the interactions between h-BN nanosheets and PVA molecules. In addition, the h-BN/PVA foam is investigated as a possible CO

The most recent and innovative silicon carbide (SiC) fiber ceramic matrix composites, used for lightweight high-heat engine parts in aerospace applications, are woven, layered, and then surrounded by a SiC ceramic matrix composite (CMC). To further improve both the mechanical properties and thermal and oxidative resistance abilities of this material, SiC nanotubes and nanowires (SiCNT/NWs) are grown on the surface of the SiC fiber via carbon nanotube conversion. This conversion utilizes the shape memory synthesis (SMS) method, starting with carbon nanotube (CNT) growth on the SiC fiber surface, to capitalize on the ease of dense surface morphology optimization and the ability to effectively engineer the CNT-SiC fiber interface to create a secure nanotube-fiber attachment. Then, by converting the CNTs to SiCNT/NWs, the relative morphology, advantageous mechanical properties, and secure connection of the initial CNT-SiC fiber architecture are retained, with the addition of high temperature and oxidation resistance. The resultant SiCNT/NW-SiC fiber can be used inside the SiC ceramic matrix composite for a high-heat turbo engine part with longer fatigue life and higher temperature resistance. The differing sides of the woven SiCNT/NWs act as the "hook and loop" mechanism of Velcro but in much smaller scale.

Effects of UV radiation and associated elevated temperature on properties of polymeric composites have been well documented, limiting the scope of their usage in outdoor applications. In order to improve on this limitation, current study focused on incorporating nanoparticles into epoxy polymer composites and delay onset of deleterious effects of UV radiation by partially curing these samples. Samples were fabricated and cured to 80% conversion (partially cured) based on isothermal cure kinetic studies. Influence of 1, 2 and 3 wt. % loading of montmorillonite nanoclay on the cure behavior and development of physical properties of these composites were evaluated. Results of the study revealed that for optimization of modified epoxy composite properties a different curing cycle was necessary due to interaction of different amounts of nanoclay and epoxy molecules. Fabricated samples infused with 1, 2 and 3 wt. % montmorillonite nanoclay were exposed to 2500 h of continuous UV radiation, where effects of UV radiation on viscoelastic and thermal properties were evaluated and compared with identical set of fabricated samples using manufacturers' recommended cycle (fully cured). Addition of nanoclay increased the viscoelastic properties, and at the end of the study, storage modulus and activation energy of decomposition of partially cured samples evolved over exposure time, while fully cured samples degraded over the same period. Samples cured to 80% showed delayed UV radiation degradation effects.

Building three-dimensional (3D) structures from their constituent zero-, one-, and two-dimensional nanoscale building blocks in a bottom-up assembly is considered the holey grail of nanotechnology. However, fabricating such 3D nanostructures at ambient conditions still remains a challenge. Here, we demonstrate an easily scalable facile method to fabricate 3D nanostructures made up of entirely zero-dimensional silicon dioxide (SiO2) nanoparticles. By combining functional groups and vacuum filtration, we fabricate lightweight and highly structural stable 3D SiO2 materials. Further synergistic effect of material is shown by addition of a 2D material, graphene oxide (GO) as reinforcement which results in 15-fold increase in stiffness. Molecular dynamics (MD) simulations are used to understand the interaction between silane functional groups (3-aminopropyl triethoxysilane) and SiO2 nanoparticles thus confirming the reinforcement capability of GO. In addition, the material is stable under high temperature and o...

Mimicking the remarkable properties of natural materials such as toughness, self?stiffening, self?healing, etc., is useful for several structural, functional, and biomedical applications. The judicious combination of natural and synthetic building blocks to design hybrid materials could offer an alternative route to achieving the aforementioned properties of natural materials. This study reports easily scalable process to synthesize graphene oxide (GO)/egg white hybrid material (polyalbumene) by cross?linking GO nanosheet with the amine?based cross?linker diethylenetriamine (DETA) and egg white. The result is a layered material like nacre, exhibiting high strength and toughness. Abundant functional groups on the GO allow covalent interactions between DETA and egg white protein amino acids. The atomistic simulations reveal that the insertion of GO into the composite has a sizeable impact on the composite's stiffness. As shown by experiments, the hybrid material has an elastic modulus of ?41 MPa and a ductility of more than 25%. The hybrid material also exhibits a fracture repair property under laser exposure as well as CO2 absorption and stiffening over time, suggesting an adaptable behavior. This work explores the possibility that the combination of synthetic and natural approaches offers a better route to designing advanced, tough, strong, adaptable, and fracture recovering materials., by Chandra Sekhar Tiwary et al.

This chapter aims at exploring the revolutionary field of nanotechnology and some of its promising aspects in polymer nanocomposites in view of preparation, characterization, materials properties, and processing of polymer layered silicate nanocomposites. These materials are attracting considerable interest in polymer science research. Polymer layered silicate nanocomposites are an important class of hybrid, organic/inorganic materials with substantially improved mechanical, thermal, and thermomechanical properties in comparison to pristine polymers. In addition, they also show superior ultraviolet (UV) as well as chemical resistance and are widely being investigated for improving gas barrier and flame retardant properties. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of polymer–clay nanocomposites. Smectites are a valuable mineral class for industrial applications due to their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity and transparency in solution. A wide range of polymer matrices are explored for the preparation of polymer–clay nanocomposites, however, this chapter deals with special emphasis on biodegradable polymers––cellulose and natural rubber. Also, the chapter describes the common synthetic techniques in producing polymeric layered silicate nanocomposites, its properties, and applications.

Schwartzites are 3D porous solids with periodic minimal surfaces having negative Gaussian curvatures and can possess unusual mechanical and electronic properties. The mechanical behavior of primitive and gyroid schwartzite structures across different length scales is investigated after these geometries are 3D printed at centimeter length scales based on molecular models. Molecular dynamics and finite elements simulations are used to gain further understanding on responses of these complex solids under compressive loads and kinetic impact experiments. The results show that these structures hold great promise as high load bearing and impact-resistant materials due to a unique layered deformation mechanism that emerges in these architectures during loading. Easily scalable techniques such as 3D printing can be used for exploring mechanical behavior of various predicted complex geometrical shapes to build innovative engineered materials with tunable properties.

Solid-solid interface mechanism understanding of composite inclusions, when extended to solid-liquid interface design of composite using Eshelby theory, indicates a possibility of decreasing effective stiffness with increasing liquid inclusion in a solid matrix. In contrast, experimental evidence in the current paper suggests high stiffness and enhanced dynamic energy absorption in a soft polymer (polydimethylsiloxane) with high bulk modulus liquid inclusions (gallium). The basic deformation mechanism is governed by hydrostatic stress causing shape change of the liquid inclusion in large deformation regime and strain hardening of a soft polymer matrix. In addition, dynamic viscoelasticity and fluid motion also play a significant role. These understandings are developed here based on analytical modeling and a detailed finite element with smooth particle hydrodynamic simulations. The large deformation with viscoelasticity of gallium composite shows higher energy absorption and dissipation. Similar strategies of liquid reinforcement to compliant solid matrices are abundant in nature, for example, the intervertebral discs in the spinal cord and deep sea animal skin and lungs.

Strong van der Waals forces between individual carbon nanotubes pose a major hurdle for effective use of nanotubes as reinforcement in nanocomposite due to agglomeration. In this paper, the authors show that van der Waals forces in combination with functionalization of carbon nanotubes, can be utilized to design nanocomposites mimicking stiffening behavior normally observed in biological materials such as fibrin gels, health bones, actin filaments in cytoskeletons etc. Carbon nanotube spheres are used as reinforcement in an elastomer matrix and when subjected to dynamic loads exhibit significant self-stiffening. Increased stiffness is also observed in dynamic loading after every relaxation cycle. The authors further show high energy absorption of the nanocomposite in impact tests. Authors study shows that the rational design of macroscale materials from nano-scale constituents can be achieved utilizing simple methodology to produce multifunctional materials with broad applications.

Here, the scalable synthesis of low-density 3D macroscopic structure of graphene oxide (GO) interconnected with polydimethylsiloxane (PDMS) is reported. A controlled amount of PDMS is infused into the freeze-dried foam to result into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like glue between the 2D sheets. Molecular dynamics simulations are used to further elucidate the mechanisms of the interactions of graphene oxide layers with PDMS. The ability of using the interconnecting graphene oxide foam as an effective oil–water separator and stable insulating behavior to elevated temperatures are further demonstrated. The structural rigidity of the sample is also tested using laser impact and compared with GO foam.

Objective An experimental study was carried out to investigate the solvent uptake in E-glass/Carbon Fiber composites with two types of epoxy systems: SC-15 and 635 epoxy resins in water, saltwater and antifreeze. These resins were infused into carbon, E glass and a hybrid of carbon and E-glass fabrics. Unconditioned samples with 635 epoxy resin system showed better flexural properties in case of both carbon fiber and hybrid composites but poor response when used as a matrix for E-glass fibers compared to SC-15 epoxy resin. Flexural properties for conditioned samples were determined after an immersion period of 8 weeks at room temperature and results showed that the 635 epoxy resin has a poor retention of flexural properties compared to SC-15 epoxy resin with highest degradation recorded for samples fabricated using E-glass fabrics. Moisture absorption curves did not follow the Fick’s law of diffusion except for first week of immersion. Lowest solvent uptake was recorded in antifreeze while highest was recorded in saltwater. Low operation temperature was exhibited by 635 epoxy resin with lower values of glass transition temperature compared to SC-15 epoxy resin. Storage modulus and glass transition temperatures determined from dynamic mechanical analysis (DMA) showed that composites with 635 epoxy resin system had better storage modulus while those with SC-15 had higher glass transition temperatures. Highest degradation in storage modulus was seen in E-glass-635 epoxy samples when conditioned with salt water while the maximum reduction in the glass transition temperature was seen for E-glass-635 epoxy samples conditioned with water.Copyright © 2014 by ASME

Common dispersion methods such as ultrasonic sonication, planetary centrifugal mixing and magnetic dispersion have been used extensively to achieve moderate exfoliation of nanoparticles in polymer matrix. In this study, the effect of adding three roll milling to these three dispersion methods for nanoclay dispersion into epoxy matrix was investigated. A combination of each of these mixing methods with three roll milling showed varying results relative to the unmodified polymer laminate. A significant exfoliation of the nanoparticles in the polymer structure was obtained by dispersing the nanoclay combining three roll milling to magnetic and planetary centrifugal mixing methods. This exfoliation promoted a stronger interfacial bond between the matrix and the fiber, which increased the final properties of the E-glass/epoxy nanocomposite. However, a combination of ultrasound sonication and three roll milling on the other hand, resulted in poor clay exfoliation; the sonication process degraded the polymer network, which adversely affected the nanocomposite final properties relative to the unmodified E-glass/epoxy polymer.