Ultra Lightweight Research Articles

Facile and Controllable Preparation of Poly(St-co-MMA)/FA Microspheres Used as Ultra-Lightweight Proppants.

Hydraulic fracturing is an important technology for the exploitation of unconventional oil or gas reservoirs. In order to increase the production of oil or gas, ultra-lightweight proppants with a high compressive strength are highly desirable in hydraulic fracture systems. In this work, a new type of ultra-lightweight proppant, poly(styrene-co-methyl methacrylate)/fly ash (poly(St-co-MMA)/FA) composites with a high compressive strength were prepared via in situ suspension polymerization. The Fourier transform infrared (IR) and X-ray powder diffraction (XRD) analyses confirmed that the poly(St-co-MMA)/FA composites were successfully prepared. The morphology analysis indicated that the composite microspheres show good sphericity, and FA powder was evenly dispersed in the matrix. The apparent density of the microspheres was between 1 and 1.3 g/cm3, which is suitable for hydraulic fracturing. Furthermore, the compressive strength and thermostability were dramatically improved with the incorporation of FA, which could withstand high pressures and temperatures underground. The obtained poly(St-co-MMA)/FA composite microspheres are promising for application as an ultra-lightweight (ULW) proppant in oil or gas exploitation, which provides a new approach for the design of high performance proppants.

Ultralight ethyl cellulose-based electret fiber membrane for low-resistance and high-efficient capture of PM2.5

Atmospheric particulate matter (PM) pollution is a serious threat to human health, so the preparation of electret films with high efficiency and low resistance capturing particulate has attracted wide attention. Herein, a strategy for the fabrication of all-polymer hybrid electret fiber membranes by electrospinning is reported based on the ethyl cellulose (EC) and polystyrene (PS). The preparation conditions of electret fiber membrane were optimized by focusing on the effect of the mass ratio of EC/PS and the spinning time on the structure, surface potential and purification performance of fiber membrane. The result showed that the fiber membrane has a low fiber diameter of 572 ± 113 nm and porosity of 82.4%, and a better potential stability when the EC/PS mass ratio was 2.5/1 and the spinning time was 10 min. As a result of the enhanced effect of electrostatic attraction on particle capture, the EC/PS composite electret membrane could make the purification efficiency of PM2.5 reach to100% within 11 min. Moreover, the EC/PS composite electret membrane has the properties of ultra-light base weight of 1.08 g·m −2 , low air resistance of 28 Pa and long service life. Therefore, the all-polymer EC/PS electret nanofiber membranes have broad application prospects in the field of air purification. • All-polymer electret EC/PS fibers without nanotoxicity are prepared. • Biomass-based electret based on ethyl cellulose as the main raw material increases the environmental friendliness of the material. • the fabricated electret fiber has an ultralight base weight. • the resultant electret fibers with high efficiency and low resistance can be compared with high efficiency air purification membrane.

Applications of Filled Single-Walled Carbon Nanotubes: Progress, Challenges, and Perspectives.

Single-walled carbon nanotubes (SWCNTs), which possess electrical and thermal conductivity, mechanical strength, and flexibility, and are ultra-light weight, are an outstanding material for applications in nanoelectronics, photovoltaics, thermoelectric power generation, light emission, electrochemical energy storage, catalysis, sensors, spintronics, magnetic recording, and biomedicine. Applications of SWCNTs require nanotube samples with precisely controlled and customized electronic properties. The filling of SWCNTs is a promising approach in the fine-tuning of their electronic properties because a large variety of substances with appropriate physical and chemical properties can be introduced inside SWCNTs. The encapsulation of electron donor or acceptor substances inside SWCNTs opens the way for the Fermi-level engineering of SWCNTs for specific applications. This paper reviews the recent progress in applications of filled SWCNTs and highlights challenges that exist in the field.

Ultra-low-density digitally architected carbon with a strutted tube-in-tube structure.

Porous materials with engineered stretching-dominated lattice designs, which offer attractive mechanical properties with ultra-light weight and large surface area for wide-ranging applications, have recently achieved near-ideal linear scaling between stiffness and density. Here, rather than optimizing the microlattice topology, we explore a different approach to strengthen low-density structural materials by designing tube-in-tube beam structures. We develop a process to transform fully dense, three-dimensional printed polymeric beams into graphitic carbon hollow tube-in-tube sandwich morphologies, where, similar to grass stems, the inner and outer tubes are connected through a network of struts. Compression tests and computational modelling show that this change in beam morphology dramatically slows down the decrease in stiffness with decreasing density. In situ pillar compression experiments further demonstrate large deformation recovery after 30-50% compression and high specific damping merit index. Our strutted tube-in-tube design opens up the space and realizes highly desirable high modulus-low density and high modulus-high damping material structures.

Elastic aerogel thermoelectric generator with vertical temperature-difference architecture and compression-induced power enhancement

Despite the rapid development for thermoelectrics (TEs) and aerogels, elastic aerogel TE generators (TEGs) with vertical-type architectures have not been found to harvest heat utilizing vertical temperature difference. Herein, an elastic poly(3,4-ethylenedioxytiophene)-tosylate(PEDOT-Tos)/single-walled carbon nanotube (SWCNT) TE aerogel was fabricated via convenient chemical oxidative polymerization, physical mixing and subsequent freeze-drying process. Then, we report the first elastic TEGs consisting of vertical-type aerogel legs, which not only inherit the advantages of ultralight weight and compressibility of aerogels, but also display high TE performance. The output performance can be conveniently adjusted by the number of legs, the temperature difference and compressive strain. An optimum output power of 1967 nW (output power density of 30.73 mW m−2) is achieved for the TE generator using 10 unipolar aerogel legs at 50% strain and temperature difference of 50 K. Furthermore, the ultralight and compressible TEG displays excellent capability of harvesting heat under vertical temperature difference and mechanical deformation, such as on hot oil/plate or compression by human body. The results will greatly facilitate the development of TE aerogels and TEGs, and widen the versatile application scenarios.

Update on the Evidence: RESNA Ultralight Manual Wheelchair Position Paper

<h3>Research Objectives</h3> To identify optimal manual wheelchair configuration for people who self-propel for full-time wheeled mobility. To identify new evidence on how prescribing an ultralight weight manual wheelchair can minimize secondary complications in the body functions, promote functional independence with mobility related activities of daily living, and provide opportunities to participate in life roles <h3>Design</h3> This position paper was written following a scoping literature review process, open review period through RESNA and peer-review process. <h3>Setting</h3> This position paper is relevant to any prescribers or clinicians recommending manual wheelchairs. The results of the scoping review is applicable to treatment settings where people use a manual wheelchair for primary mobility, from pediatrics to long term care. <h3>Participants</h3> N/A. <h3>Interventions</h3> The RESNA Paper on the Application of Ultralight Manual Wheelchairs was published in 2012 and sought to provide evidence to support the application of fully customizable manual ultralight weight wheelchairs. Since that time, new developments in clinical research in our understanding of manual wheelchair considerations have prompted a revision of this foundational document. <h3>Main Outcome Measures</h3> The presentation will describe the intention of the revision and review new evidence based topics incorporated into the new position paper including: Manual wheelchair configuration, wheelchair training and wheelchair skills relating to function, rolling resistance and propulsion effort, various propulsion styles and considerations for overuse injuries in all extremities. <h3>Results</h3> The results of the scoping literature review and position paper will provide supportive evidence for the need for ultralight weight manual wheelchair configuration and the impact on body functions and structures, activities of daily living, and participation. <h3>Conclusions</h3> This scoping review and position paper will allow the clinician and practitioner to have supportive evidence for equipment recommendation for their patients who use a manual wheelchair full-time for mobility. <h3>Author(s) Disclosures</h3> Jennith Bernstein is a full-time employee of Permobil, Inc.; however, this work is presented on behalf of an entire work group of clinicians, engineers, and professors.

Optimal design of integrated main supporting structure with ultra-light weight and high stability for space camera

To ensure excellent performance of a micro reflective space camera, an integrated main supporting structure (IMSS) combined with a thin-walled tube and a supporting rod structure design is applied in this study. Firstly, this paper covers the design and comparison of the performance of three traditional types of main supporting structures (MSS), including thin-walled cylinder type, rod-supporting type and truss type. Then, an IMSS combined with a thin-walled tube and a supporting rod structure is described. In addition, a multi-objective integrated optimization method which allows automatic modeling, analysis, calculation and optimization is proposed. Further, the influence of the supporting rod angle on the structure performance is studied, the performance of stiffness, deformation and mass is better when the height ratio of the rod-structure and the thin-walled cylinder is 6:1. The IMSS mass is only 0.56 kilograms, that is 11.2 % of the total mass of the payload, and the maximum deformation on the supporting bar is no more than 4.5 nm. Finally, the IMSS performance is analyzed by the finite element method and experimental verification, and the first order frequency is up to 192.7 Hz. The degree of light weight is significantly better than that of the traditional structures. The results of the experiment further prove the stability of the IMSS.

Lightweight Low‐Frequency Sound‐Absorbing Composites of Graphene Network Reinforced by Honeycomb Structure

AbstractEfficient, facile, lightweight, and low‐frequency sound‐absorbing materials are in great demand for noise elimination and insulation. However, the applications of some candidate materials are limited by their large space, mass, or unsatisfactory sound‐absorption performance especially in low‐frequency sound‐wave region. Graphene network structure can be promising sound‐absorbing materials due to ultrahigh porosity, ultralight weight, and excellent intrinsic properties. Conventionally, allowing for poor mechanical strength, such graphene materials are needed to be reinforced by polymer, metal, or ceramic. Here, a novel strategy of graphene network reinforced by honeycomb structure is proposed, in which graphene is used as a sound absorber, and meanwhile flexible aramid honeycomb is introduced to enhance the graphene composite. In this work, the compressive strength of graphene network structure is improved 1000 times by the flexible aramid honeycomb, and meanwhile the density is only increased 2.5 times. Moreover, the sound‐absorption coefficient of graphene network is about 0.9 at 700 Hz for the thickness of 30 mm. Further, the sound‐absorption coefficient is above 0.9 in the frequency range of &gt;1000 Hz. Therefore, the graphene composite is expected to be saving space and weight for the engineering design of sound absorbers in low‐frequency regions.

Crashworthiness analysis and optimization design of TPMS-filled structure

TPMS (triply periodic minimal surface) sheet structure consists of a spatially continuous surface, which forms a periodic porous structure, and has outstanding mechanical performance and ultralight weight. However, there are few studies on the periodic structure as an internal reinforcement energy absorber. In this study, we mainly discuss the collision ability of TPMS -filled square tubes under axial compression. Based on the numerical simulation results, it can be found that the unit-cell length and thickness of TPMS filler have great sway with the SEA and PCF of the TPMS-filled structure. The crashworthiness performance of TPMS-filled structures is better than the sum of separate structures attributed to the interaction effect. In addition, incomplete cell of the TPMS filler has a negative influence on the mechanical property at the low relative density and the shape of the TPMS filler can also affect the mechanical properties. To obtain an optimal TPMS-filled tube, a metamodel-based multi-objective optimization (MOO) method was employed to attain the Pareto front, in which the SEA is maximized and the PCF is minimized. It can be found that IWP-filled tube has maximum PCF among the four structures and FRD-filled tube owns maximum SEA.

Towards an ultra lightweight block ciphers for Internet of Things

Conventional cryptographic methods are not appropriate for IoT environments due to the specific IoT devices constraints, such as memory usage, time and computational costs. This leads to the emergence of the lightweight cryptography field. This paper investigates the different lightweight cryptographic design methods and proposes an IoT-based cryptographic method, called Ultra-Lightweight method (ULM), to enhance the performance, memory usage and security of IoT devises. The proposed method is based on three methods (i.e, bitslice, WTS and involutive), and thus accumulating their various advantages such as, memory use, efficiency and security. To validate our proposal, a cryptosystem is designed using ULM method. The designed cryptosystem is benchmarked based on the following metrics: performance (by measuring its execution time and the number of clock cycles needed to run it), the quantity of used memory (by measuring ROM and RAM consumption), and security level (by measuring its diffusion and confusion levels along with its resistance to linear and differential attacks). The results show that the cryptosystem designed using the proposed method outperforms existing methods in terms of memory use, security and performance.

Multi-functional 2D hybrid aerogels for gas absorption applications

Aerogels have attracted significant attention recently due to their ultra-light weight porous structure, mechanical robustness, high electrical conductivity, facile scalability and their use as gas and oil absorbers. Herein, we examine the multi-functional properties of hybrid aerogels consisting of reduced graphene oxide (rGO) integrated with hexagonal boron nitride (hBN) platelets. Using a freeze-drying approach, hybrid aerogels are fabricated by simple mixing with various volume fractions of hBN and rGO up to 0.5/0.5 ratio. The fabrication method is simple, cost effective, scalable and can be extended to other 2D materials combinations. The hybrid rGO/hBN aerogels (HAs) are mechanically robust and highly compressible with mechanical properties similar to those of the pure rGO aerogel. We show that the presence of hBN in the HAs enhances the gas absorption capacities of formaldehyde and water vapour up to ~ 7 and > 8 times, respectively, as compared to pure rGO aerogel. Moreover, the samples show good recoverability, making them highly efficient materials for gas absorption applications and for the protection of artefacts such as paintings in storage facilities. Finally, even in the presence of large quantity of insulating hBN, the HAs are electrically conductive, extending the potential application spectrum of the proposed hybrids to the field of electro-thermal actuators. The work proposed here paves the way for the design and production of novel 2D materials combinations with tailored multi-functionalities suited for a large variety of modern applications.

Altitude Performance and Fuel Consumption Modelling of Aircraft Piston Engine Rotax 912 S/ULS

Rotax 912 spark-ignition (SI) naturally aspirated aircraft piston engine is one of the most popular prime movers for the ultra-light weight aircrafts used for short and moderate range flights. SI engines operate at stoichiometric combustion and at high altitude conditions atmospheric pressure is lower than sea level reducing mass of air intake to the engine. At these conditions engine power degrades significantly from sea level, affecting flight parameters such as range and endurance. In order to optimize these parameters, engine power modelling is of vital importance. Within the scope of this study, a thermodynamic SI engine model with performance parameters (break torque and power) and fuel consumption estimation developed in MATLAB/Simulink software. Model tuning is realised using data extracted from Rotax engine operating manual at sea level and high altitude conditions. Model inputs are set as altitude, throttle lever and engine speed. Pressure drop at the intake port is modelled as a function of mass air flow using engine operating manual pressure data at various engine speed points. Mass air flow is determined via employing a volumetric efficiency map based on intake port pressure and engine speed inputs, calibrated using engine operating manual fuel data considering stoichiometric combustion. Compression and expansion strokes area modelled as isentropic events and combustion is modelled as constant volume heat input at top dead centre (TDC). However a combustion efficiency map based on engine speed and fuel flow is employed for the heat input in order to tune the work output of the engine and heat loss to the coolant and exhaust. Pumping loss is calculated based on friction mean effective pressure data. Introduced approach provides high accuracy performance and fuel consumption modelling based on engine operating manual data and can be used for flight parameters optimization studies.

Flexural Resistance Factors for Structural Ultra Lightweight Engineered Cementitious Composite Slabs

Many problems associated with the use of normal weight concrete have been solved with the development of structural ultra-lightweight engineered cementitious composite (SULWECC) that has the capability to exhibit strain-hardening behavior prior to failure. However, the feasibility and standards that address the design of such engineered cementitious composites (ECC) in flexural slab systems are not available. In this study, reliability analysis and calibration process are carried out on three different SULWECC slab systems with the intention of estimating the potential flexural resistance factors. Although the high volume of randomly dispersed synthetic short fiber is considered the main reinforcement, SULWECC slab systems internally reinforced with carbon FRP mesh are also considered. The reinforcement ratio is selected so that the section is under-reinforced. Relevant load and resistance random variables are used, and appropriate statistical parameters are selected. The target reliability indices are chosen to be consistent with those used to develop current design code specifications. The nominal moment capacity is calculated based on a new model that consists of: elastic linear stress distribution in the compression zone and elastic-perfectly-plastic uniform stress distribution in the tension zone. The determined flexural resistance factors ranged from 0.59 to 0.69, although higher values are justifiable in special circumstances. The average slab thickness needed to satisfy the strength requirements ranged from 1/37 to 1/22 times the slab length. Flexural toughness to measure ductility is evaluated using load-deflection curves of experimentally tested SULWECC specimens.

In Situ X‐Ray Observations and Microstructural Characterizations for Understanding Combustion Foaming and Reaction Processes to Synthesize Porous Al3Ti Composites From Al–Ti–B4C Powders

Combustion foaming process enables the effective fabrication of ultralight weight porous Al3Ti composites that have closed-cellular structure. However, it is difficult to understand and control the rapid and irreversible process. The multi-scale dynamics are clarified by in-situ X-ray observations and microstructural characterizations in the article, number 2001284, by Asuka Suzuki and co-workers.

A Low-Cost and High-Efficiency Electrothermal Composite Film Composed of Hybrid Conductivity Fillers and Polymer Blends Matrix for High-Performance Plate Heater

Owing to easy processability, ultralight weight, and low cost, carbon- and polymer-based composite materials are among emerging and promising electrothermal materials for high-performance flexible electric heaters. In this work, a sandwich-like structured electrothermal film composed of hybrid conductive fillers [Super-P (SP) and graphite], polymer blends matrix [thermoplastic polyurethane (TPU) and polyethersulfone (PES)], and alumina oxide (Al2O3) as a non-conductive filler has been fabricated by a facile slurry coating method. Hybrid conductive fillers of graphite and SP particles have a uniform spatial distribution in a TPU/PES polymer matrix, which construct a highly stable and continuous conductive network with a low percolation threshold of conductive filler content (14.8 wt.%) that allows electrothermal films to operate at a low applied dc voltage. As for the electrothermal film with 15 wt.% hybrid conductive fillers (SP/G-15 sample), it exhibits a superior response feature, high electrothermal conversion efficiency, stable structural stability and remarkable electrothermal reproducibility. More impressively, SP/G-15 composite electrothermal film as an integrated electric heater for heating water demonstrates a high potential in practical application scenarios.

High-strength and long-term durable hydrophobic polystyrene microsphere: a promising ultra-lightweight proppant for fracturing technology

With the increasing difficulty in exploitation of low-permeability, high water content and other unconventional reservoirs, a new kind of proppants that possess not only ultra-light weight and high strength and but also hydrophobic performances have attracted more and more interests. Here, this kind of proppants were designed and prepared successfully in the form of polymer microspheres. What's more is that the polymer microspheres (named O-MSDBs) showing high strength and stable hydrophobicity were prepared by a one-step suspension polymerization between styrene, divinyl benzene and γ-methacryloxypropyl-trimethoxy silane accompanying with the formation of silica through sol–gel process. When compared with reported ultra-lightweight proppants (ULWPs), the O-MSDBs not only perform better in ultra-lightweight (0.9917 g·cm−3) and are comparable in high strength (low crushing ratio of 0.89–2.53% at 55–69 MPa), but also show new hydrophobic function. The water contact angle on the surface of O-MSDBs is 140.7° that keeps about more than 80% after mechanical abrasion or acid dissolution. The one-step facile preparation method and brilliant performances make O-MSDBs very promising to large-scale preparation and widely applied in fracturing technology as proppants.

Sustainable polyethylene fabrics with engineered moisture transport for passive cooling

Polyethylene (PE) has emerged recently as a promising polymer for incorporation in wearable textiles owing to its high infrared transparency and tuneable visible opacity, which allows the human body to cool via thermal radiation, potentially saving energy on building refrigeration. Here, we show that single-material PE fabrics may offer a sustainable, high-performance alternative to conventional textiles, extending beyond radiative cooling. PE fabrics exhibit ultra-light weight, low material cost and recyclability. Industrial materials sustainability (Higg) index calculations predict a low environmental footprint for PE fabrics in the production phase. We engineered PE fibres, yarns and fabrics to achieve efficient water wicking and fast-drying performance which, combined with their excellent stain resistance, offer promise in reducing energy and water consumption as well as the environmental footprint of PE textiles in their use phase. Unlike previously explored nanoporous PE materials, the high-performance PE fabrics in this study are made from fibres melt spun and woven on standard equipment used by the textile industry worldwide and do not require any chemical coatings. We further demonstrate that these PE fibres can be dry coloured during fabrication, resulting in dramatic water savings without masking the PE molecular fingerprints scanned during the automated recycling process. The textile industry is one of the largest polluters. Here the authors show that polyethylene is a sustainable alternative textile with water wicking and fast-drying performance. The fabrication of polyethylene fabrics is compatible with standard equipment and could be dry-coloured, further reducing water consumption.

Design and mechanical failure analysis of Ti6Al4V alloy thin-walled parts by selective laser melting(SLM) manufacture

There is a growing interest in using additive manufacturing to produce smart structures, which have the capability to respond to thermal and mechanical stimulation. In this report, Selective Laser Melting (SLM) is used to build a thin-walled titanium alloy structure. The part creating a ultra lightweight is 2.15g, while its strenght achieve at 132.4MPa. The stages of compression process was analyzed in detail, meanwhile the deformation and failure mechanism of the thin-walled part was described.

An ultra-light, superhydrophobic and thermal insulation ultra-high molecular weight polyethylene foam

Multifunctional polymer foam becomes the tendency due to the single-functional foam is difficult to adapt the various complicated environments. However, preparing multifunctional porous ultra-high molecular weight polyethylene (UHMWPE) material with high porosity is still challenge. Thus, it is desirable to develop a simple and effective method that could integrate multiple functions into polymer foam. Herein, a multifunctional UHMWPE foam was fabricated via a facile thermally induced phase separation method. The foam displays a low density of 8.23 mg cm−3, high porosity of 99.2% and robust superhydrophobicity (water contact angle of 152°), thus exhibiting excellent adsorption capacity in oil-water separation under different extreme environments. Moreover, the thermal conductivity of the foam goes down to 11.6 mWm−1K−1, which endows the foam with great thermal insulation performance under various temperature conditions. Thus, this foam can meet the demands of various practical applications.

Multilayered Graphene-Assisted Broadband Scattering Suppression through an Ultrathin and Ultralight Metasurface

Here, we present an ultralight multilayered graphene-based metasurface for suppressing specular reflection. With the help of a joint optimization method, dual low-reflection mechanisms including absorption and random diffusion are realized within the same structure, resulting in a remarkable decrease in the backward reflected energy in an ultrabroadband range of 7.5 to 43 GHz (a relative bandwidth of 140.6%). Experiments demonstrate that our design with a thickness of approximately 3.27 mm can maintain excellent antireflection performance over a wide angle range of 0 to 45° for both TE and TM waves. Additionally, as a result of adopting low-density substrates (polyethylene terephthalate and polymethylacrylimide foam) and multilayered graphene films, the proposed metasurface shows the advantage of ultralight weight, thus opening an avenue for a number of engineering applications such as electromagnetic shielding, information security, and electromagnetic compatibility technology. In addition, owing to the natural characteristics (corrosion resistance, bending resistance, etc.) of multilayered graphene films, the proposed metasurface shows enormous potential in some particular application scenarios with harsh conditions.