Low-density Carbon Research Articles

Fabrication of Inkjet-Printed Carbon Nanotube for Enhanced Mechanical and Strain-Sensing Performance

This paper presents fabrication of inkjet-printed carbon nanotube film on flexible substrate for wearable electronics applications. The density of CNT films is optimized by droplet spacing (DS) and multiple passes to provide the best strain behavior. It is found that low-density carbon nanotubes have fewer conductive pathways resulting in less change and low GF under applied strain. Conversely, high-density carbon nanotubes have more conductive paths, and they are not easily broken under strain, resulting in poor strain-sensing ability. The inkjet printing process can adjust uniformity and density of CNT film through DS and multiple passes to optimize its strain characteristics. The highest GF of 3.36 was obtained under strain ranging from 71 to 3128 με when CNT printed by DS of 23 μm and 20 passes. The relative change in resistance under various strains, ranging from 71 to 3128 με, had a stable peak value for each 20 strain/release cycle which proved its repeatability and stability. Furthermore, inkjet-printed CNT sensors monitored human movement of various joints and distinguished bending angle demonstrating its potentially practical application in wearable electronics.

Polydopamine-treated hierarchical cellulosic fibers as versatile reinforcement of polybutylene succinate biocomposites for electromagnetic shielding

There is a need for scalable technologies to reduce electromagnetic pollution with materials of low density and low carbon footprint. Unfortunately, environmental adaptability, economic feasibility and lightweight are factors that are still far from optimal in most electromagnetic shielding materials. Herein, we address these challenges with polybutylene succinate (PBS) reinforced with bamboo fibers functionalized with Fe3O4 nanoparticles (Fe3O4-NPs) and polypyrrole (PPy). Such hybrid system was compatibilized via polydopamine (PDA) coupling, demonstrating magnetic, dielectric and interfacial polarization losses as well as distributed reflection, yielding a shielding effectiveness of ~36.9 dB. Simultaneously, the composite displayed gains in tensile strength and modulus (by 18 and 38%, respectively) combined with improved flexural strength and modulus (by 33% and 15%, respectively). Overall, this work demonstrates a new pathway toward low cost and lightweight bio-based materials for high-performance electromagnetic shielding.

In-Pile Performance of TRISO Particle Used Stainless Steel Foams as Buffer Layer

Thermal conductivity of TRISO particle deteriorated during in-pile operation due to the shrinkage of the low density carbon buffer layer and the gap appeared. In order to solve this problem, stainless steel foam was used to replace the low density carbon buffer layer as buffer layer in TRISO particle. The in-pile performance of the new type TRISO particle was simulated, and the result indicated that the stainless steel foam can avoid the gap between the buffer and the IPyC layer which can increase the thermal conductivity and decrease the kernel temperature during operation process; at the same time, regardless of stainless steel foam or low density carbon buffer layer used as buffer layer, the stress on IPyC and OPyC layers all exceeded the strength of the two layers. Hoop stress on SiC layer decreased with the elasticity modulus of metal foam, and the stress can be controlled by decreasing the elasticity modulus. To sum up, metal foam with high porosity and low elasticity modulus can be selected as the buffer layer to improve the thermal conductivity and assure the integrity of the coated layer and increase the life time. This study offered the optimization direction of TRISO particle for engineering application.

Graphitization of low-density amorphous carbon for electrocatalysis electrodes from ReaxFF reactive dynamics

We predict the three-dimensional structure of amorphous carbon generated by heating diamond superlattice at 6000 K with rapid quenching from the liquid phase for densities ranging from 2.0 to 3.5 g/cm3, in comparison with 2.26 and 3.54 g/cm3 for bulk graphite and bulk diamond, respectively. These predictions are based on reactive dynamics (RD) simulations using the ReaxFF reactive force field. Here, we simulate the graphitization of amorphous carbon at high temperature to calculate physical properties relevant to conductive carbon supports useful for electrocatalysts. The low-density graphitic materials mostly oriented in the (002) plane with a main X-ray diffraction (XRD) peak between 26 and 28°, as observed experimentally. For low density carbon (2.0–2.5 g/cm3), we find >90% sp2 character with ∼2-1% sp and <8% sp3. While for higher density carbon, the amount of sp2 fraction decreases with density and find 70.0% sp3 with 29.7% sp2 and 0.3% sp for 3.4 g/cm3 density, which can be compared to DLC of 3.24 g/cm3 density resulting good agreement with XPS experiments. Based on the simulated 3D structure, we create 2D surface slab consisting of various defective sites within the surface. The 2D surface dominates with hexagonal carbon ring along with few pentagon and heptagon rings in the graphitic structure that may be useful as electrocatalysts for different energy conversion reactions.

Virtual voids method to generate low-density microporous carbon structures using quenched molecular dynamics simulation

The creation and properties of porous carbons are of extreme importance for optimizing the performance of battery and supercapacitor electrodes, as well as vehicular hydrogen storage. Atomistic simulation methods with reactive potentials have shown promise to create realistic porous carbon structures. However, such models have been unable to reproduce low-density microporous carbon structures due to clustering of atoms in high density regions, resulting in a small number of mesopores. Here we present a new method using virtual voids, generating excluded volume by a soft repulsive potential which is progressively decoupled from the carbon atoms. This allows us to prevent densification and to create disordered carbon models with porosities up to 90%. We vary the size and density of the virtual voids and show that the mean of the pore size distribution and the accessible surface area can be controlled. By choosing the desired porosity and virtual void size, we create amorphous carbon models with mean pore sizes ranging from 10 to 32 Å, which agree favorably with experimental pore sizes for low-density microporous carbons.

Fabrication of low density carbon foams by gel-casting method from sucrose/microcapsules

The carbon forms made from sucrose and microcapsules have successfully fabricated using gel-casting method. The structure, density, compressive strength and thermal conductivity were characterized. Carbon foams have porous structure of open cells and closed cells. The density of carbon foams is regulated in the range of 0.29–0.65 g/cm3, whereas the compressive strength is in the range of 1.03–20.25 MPa. The thermal conductivity at room temperature of carbon foams can be as low as 0.11 W/m·K . Therefore, these carbon foams have potential for use as the thermal insulator.

Possibilities of attrtribute analysis of seismic data to clarify the structural features of geological section

Seismic attributes are used for qualitative estimation of changes in the wave field performed within the analysis of seismic response characteristics. Related changes can be associated with sedimentation characteristics and structural features of the geological section. Subject of the study is Kovalivka field in the northern pre-flank zone of the western part of Dnieper-Donets basin. The aim of the study was to specify geological structure of the sub-salt Devonian sediments by means of attribute analysis of the wave field dynamic characteristics. It should be mentioned that Devonian sediments in Dnieper-Donets depression are very poorly studied by seismic and well drilling. New attempts to study Devonian formation here were caused by obtained inflows from similar Devonian reservoirs in Prypiat depression and by finding new prospects within the investigated area. The results of old seismic data re-processing have been analyzed as well as recent seismic and well data. Basing on the obtained data, the attribute analysis has been conducted and madden a prognosis of the geological section by wave field dynamic characteristics using Petrel software (Sсhlumberger). Due to performed interpretation procedures, we have specified location of faults, stratigraphic boundaries and distribution of sub-salt Devonian sediments. Also, we predicted a zone of development sub-salt carbonate sediments with possible a rifogenic origin. Significant increase of a total thickness of sub-salt formation and presence of quite thick relatively pure low-density organogenic carbonate sediments take place in Kovalivka field. It significantly increases the prospect potential of the area.

Characteristics of carbon-containing low-k dielectric SiCN thin films deposited via remote plasma atomic layer deposition

This study investigates amorphous SiCN thin films deposited by remote plasma atomic layer deposition. Bis[(diethylamino)dimethylsilyl](trimethylsilyl)amine (DTDN-2) and N2 plasma were used as the precursor and reactant, respectively. The deposition temperature ranged from 100 to 300 °C, and the plasma power was set to 100 and 300 W. It was determined that the SiCN film carbon content increased with decreasing plasma power and deposition temperature. Likewise, decreasing the plasma power and deposition temperature lowered the dielectric constant of the film owing to the low film density and high carbon content. It was found that the composition of the SiCN film deposited at 300 °C was similar to that of the SiN film. The wet etch rate of the film deposited at 200 °C had the lowest value owing to the carbon content and high film density. The chemical bonding states of Si, C, and N were measured by x-ray photoelectron spectroscopy.

Ultralight GO-Hybridized CNTs Aerogels with Enhanced Electronic and Mechanical Properties for Piezoresistive Sensors.

Extremely low density carbon nanotubes/graphene hybrid aerogels (CNG) are highly potential active materials for fabricating flexible devices, owing to synergistic effects with one (nanotubes) and two (graphene) dimensional characters in a single structure. However, conquering the long-standing dilemma among low electronic conductivity and inferior mechanical properties for CNG remains a challenging task. Here, an ultralight CNG aerogel (1.52 mg cm-3) with prominent electronic conductivity and mechanical resilience is facilely fabricated through a triple roles design of the sodium dodecyl sulfate (SDS), namely anchoring metal ions, dispersing carbon nanotubes, and inducing self-assembly. It is demonstrated that the Ba2+ can be effectively anchored into the GO interlayers by coupling it with the SDS to reinforce the intersheet interactions, thereby achieving remarkable improvement in mechanical properties (Young's moduli up to 18.3 kPa). Density functional theory calculations reveal that the anchored Ba2+ acting as molecular bridges can availably reduce the tunneling barrier between the GO sheets and facilitate the multidirectional and fast transport of electronics, inducing the high electrical conductivity of CNG (12.55 S cm-1). Taking advantage of these features, potential applications in flexible sensing devices have been demonstrated utilizing the remarkable CNG as an active material, giving extraordinary sensing performance including high sensitivity (48.6 kPa-1), ultralow detection limit (10 Pa), and ultrafast response (18 ms).

ReaxFF reactive molecular dynamics study on oxidation behavior of 3C-SiC in H2O and O2

Simulations of the initial oxidation process of 3C-SiC involving different polar surfaces C (1-00), C(1-1-1-),Si (100), and Si (111) exposed to H2O were studied by ReaxFF. The results show that SiC is gradually converted into silicon oxide and forms low-density carbon chains. The activation energy of the C face is lower than that of the Si face, which reflects lower oxidative stability. In addition, an oxidation reaction was carried out on a C (100) surface with different concentration ratios of H2O and O2. The results indicate the reaction rate of O2 is much higher than that of H2O, while the oxidation capacity of O2 is effectively improved with the addition of water. It is clearly observable that the addition of water leads to the porosity of the oxide layer and the separation of Si atoms.

An assessment of urban horticultural soil quality in the United Kingdom and its contribution to carbon storage.

As participation in urban horticulture grows, understanding the quality of urban horticultural soils is of increasing importance. Until now, case studies of individual cities or gardens have limited the potential of such studies to draw generalised conclusions. Here, we present the first national scale assessment of soil quality in allotments, a dominant form of urban horticulture in the United Kingdom. We sampled soils in 200 allotments in 10 urban areas across Great Britain. We assessed a range of soil quality indicators (carbon and nitrogen concentration, C:N ratio, bulk density, carbon density, pH) comparing them to the quality of soils in rural arable and horticultural land. We present the first estimate of nationwide carbon storage on allotments. We found that allotment gardeners consistently employ management practices conducive to high soil quality. Allotment soil quality differed significantly between soil types but in general soils were of a high quality: low bulk density (0.92gcm-3) and high soil organic carbon concentration and density (58.2mgg-1 and 58.1mgcm-3 respectively). Allotment soil organic carbon concentration was 250% higher than in the surrounding arable and horticultural land. Covering only 0.0006% of Great Britain, allotments contribute a disproportionate 0.05-0.14% of nationwide total organic carbon stocks. This national-scale study provides compelling evidence that small-scale urban horticultural production, unlike conventional horticulture, does not degrade soil quality. Indeed, allotments hold a small but previously unaccounted for carbon stock nationally. Urban horticultural land is a vital part of the urban landscape with effectively functioning soils that should be protected. As public demand for urban horticultural land rises and policy-makers from local to trans-national levels of governance advocate for urban food production, our findings demonstrate that urban horticulture can protect or enhance the ecosystem services provided by soils in cities and towns where the majority of people live.

Design, Development, and Characterization of a Low Frequency CMUT-Based Anemometer

The design fabrication and development of a 67.5 kHz capacitive micromachined ultrasonic transducer (CMUT) suited for Martian anemometry is presented in this paper. To have low signal attenuation under Martian conditions, the device operating frequency is limited to 100 kHz. This is due to the low-density carbon dioxide (CO2) atmosphere and acoustic impedance mismatch transduction losses. CMUTs capable of generating frequencies less than 100 kHz need either large Silicon area or higher operating voltages. This is a problem for the battery operation and portability of devices. The devices presented in this paper are designed and fabricated using low cost commercially available surface micromachining technique. COMSOL Multiphysics and MATLAB simulations were used to analyze the device critical design parameters and investigate the operability of devices. Simulation results show that the designed single cell 170- $\mu \text{m}$ radius membrane has a resonant frequency ~65 kHz. The device exhibits a static displacement of 105nm under 20 V DC bias. Using the developed single cell model, a $3\times 10$ array CMUT anemometer was fabricated and evaluated that generates a ~65 kHz acoustic signal in lab environment. This proposed CMUT anemometer can operate for a supply < 38 V. The device performance was evaluated using a commercial air-coupled capacitive microphone named CAP1. Successful transmit-receive of ultrasound from the developed 2D array to CAP1 for separation in the range of 1–15 cm was performed. The experiment results performed in lab environment show the speed of sound and the atmospheric attenuation can be accurately measured using this developed technology with a ±5% accuracy.

Fabrication of scalable, aligned and low density carbon nanotube/silicon carbide hybrid foams by polysilazane infiltration and pyrolysis

Polymer-derived ceramic (PDC) process is an attractive technique that has high ceramic yield. This versatile method allows for fabrication of porous carbon nanotube (CNT)/ silicon carbide (SiC) hybrid materials that is important high temperature structural applications. Although several forms of CNT assemblies have been used with the PDC approach, the fabricated CNT/ceramic nanocomposites were either one or two dimensional. Herein, we report, for the first time, the fabrication of a low density, three-dimensional (3D) and scalable CNT/SiC structure using PDC technique. It was synthesized by impregnating preceramic polysilazane (PSZ) into ultralow density, anisotropic, and highly aligned CNT foams, followed by thermosetting and pyrolysis processes. The ceramic phase conformally coated the CNTs. The X-ray diffraction (XRD) diffractogram confirmed the presence of β-SiC crystalline phase. The resulting hybrid foam inherited the morphology and form factor of the original CNT foam, and possessed mechanical robustness, improved electrical properties, and extraordinary thermal stability.

Design and analysis of a corona motor with a novel multi-stage structure

A corona motor at the centimeter scale is presented to improve the output performance, which features a novel multi-stage structure of staged stators and rotors that produces more charges for generating larger electrostatic force. The analytical model derived from the distributions of the electric field and current density predicts well the performance characteristics of the proposed motor. A simple and cheap fabrication process using the laser-micromachining technology and low-density carbon fibers enables the design to achieve high torque-to-weight ratios and power-to-weight ratios. The experimental results show that the output performance is greatly improved by the multi-stage structure compared to the traditional single-stage motor.

Resolving Potential-Dependent Degradation of Electrodeposited Ni(OH)2 Catalysts in Alkaline Oxygen Evolution Reaction (OER): In Situ XANES Studies

The activation and degradation mechanism of Ni-LDH catalysts electrodeposited on low and high-density carbon papers for the oxygen evolution reaction (OER) in alkaline media was investigated using in situ X-ray absorption near-edge structure (XANES) spectroscopy coupled with CV cycles in a potential range of 0–0.9 V (vs Hg/HgO), which allowed proposing two-stage degradation mechanisms with respect to cyclic voltammetry (CV) cycles. The electrodeposited α-Ni(OH)2 is firstly transformed to γ-NiOOH as an active phase in OER. In the reducible potential region, however, γ-NiOOH was partially reduced to β-Ni(OH)2, isolating the rest, which is the first stage of degradation. In the following anodic potential region, β-Ni(OH)2 is readily converted to β-NiOOH, which is mostly reversible, but only a small portion of β-NiOOH is overcharged to unstable γ-NiOOH, being responsible for the second stage degradation. It was noted that Ni(OH)2 catalysts electrodeposited on a low-density carbon paper (Ni-LC) underwent a severe degradation in the first stage, losing at least 56.9 % current density at 0.65 V (vs Hg/HgO), followed by a steady degradation in the second stage, while the use of a high-density carbon substrate (Ni−HC) effectively improved redox stability, maintaining a minimal loss of overpotential less than 5%, particularly with the second stage degradation being negligible even under potential changes, providing an important insight into designing durable and active Ni-LDH catalysts for the OER.

Nanographitic coating enables hydrophobicity in lightweight and strong microarchitected carbon

Metamaterials that are lightweight, stiff, strong, scalable and hydrophobic have been achieved separately through different materials and approaches, but achieving them in one material is an outstanding challenge. Here, stereolithography and pyrolysis are employed to create carbon microlattices with cubic topology and a strut width of 60–70 µm, with specific strength and stiffness of up to 468.62 MPa cm3 g−1 and 14.39 GPa cm3 g−1 at a density of 0.55 g cm−3, higher than existing microarchitected materials and approaching those of the strongest truss nanolattices. Subsequent fast Joule-heating then introduces a hierarchical nanographitic skin that enables hydrophobicity, with a water contact angle of 135 ± 2°, improving the hydrophilic response of pyrolytic carbon. As the Joule heating induced sp2-hybridization and nano-texturing predominantly affect the strut sheath, the effect on mechanical response is limited to a reduction in the distribution of compressive strength of as-pyrolyzed architectures by ~80% and the increase of the mean effective stiffness by ~15%. These findings demonstrate a technique to fabricate high strength, low density, and hydrophobic nanographite-coated carbon microlattices.

Expandable Graphite as a Fire Retardant for Cellulosic Materials—A Review

A diversity of chemicals is used to produce fire retardants (FRs); some of the main group of chemicals are hazardous to the environment as well as to human life; however, expandable graphite (EG) can be a gateway to a more environmentally friendly FRs or intumescent fire retardants (IFRs). Researchers define intumescent as the swelling of a particular substance placed between a heat source and an underlying substrate when they are heated. EG is a material with extraordinary thermophysical and mechanical properties. The referred EG properties are unparalleled. EG is a low-density carbon material having a series of unique properties: developed specific surface, binder-free pressing capacity, stability to aggressive media, and low thermal conductivity. Therefore, EG is a promising material both for research work and for industrial applications. The primary goal of this literature review was to report current knowledge on the use of EG as a fire retardant for cellulose and cellulose-modified materials. EG is produced, among other methods, by thermal shock of graphite oxide under forming gas. When exposed to heat, EG will expand. The expansion mechanism was presented in this review. Equally important to this review is the knowledge related to cellulose thermal degradation and cellulose impact on the development of science and technology.

Wettability Control of Nano-Columnar Dlc Thin Films Via Eb-Irradiation

Amorphous carbon (a-C:H/a-C) or Diamond-like carbon, have a very high potential diverse engineering application especially in protective coating which made it an ideal method to be manipulated in process parameters so to achieve the desired mechanical and functional properties; this correlates to the smoothness, atomic density, and the sp3 content. The nano-structure of this amorphous carbon is characterized by its disordered state of sp2 and sp3. The mechanical property would response to the sp2/sp3 matrix with the small hydrogen content which leads to the significant increases in hardness, tribological and also the wettability properties. This vague columnar structure of DLC is strictly modified to fine and self-organized structure, where high-density, graphitic inter-columnar structure is embedded into the low-density amorphous carbon phase as being confirmed through characterization, mechanical properties and response. This unique hybrid system in the a-C:H films would control the functionality of the final coating in customized way to suit multi-disciplinary engineering applications. This Nano-columnar a-C:H system. However, this hybrid system is still bound to the triangular diagram of sp2-sp3-H in the formation of a-C or a-C:H. This formed nano-columanar a-C:H films shows a unique nano-structure and its graphatized inter-columnar network with amorphous columns responsible the desired properties manipulation. In this paper, correlation between the degree of graphitization and wettability is established.

Analysis of LCV Chassis for Optimizing Weight by Using FEM

Chassis is the component of an automobile that acts as the frame to support the vehicle body. This study main objective of the study reduce the overall weight of the chassis with help of FEA method. Increase the overall strength of the chassis. Calculated the stress and deformations at different loading conditions. Proposed the best suitable material for chassis design. This results are the total weight of the chassis reduce up to 37 kg. And total deformation and equivalent stress was 26.285mm and10.441mpa. The FEA Analysis Of Tata Ace Chassis design is built with low density carbon fiber (1298Kg/m3) since it is a less weight and has an excellent strength weight ratio and shows good bending and torsion stiffness comparing with other material hence FEA Analysis Of Tata Ace Chassis with carbon fiber material is a best alternative design for the light weight chassis design.

Zeolite-templated Carbon Network: A Beta Zeolite Case Study

ABSTRACTIn this work, we report a preliminary study, based on molecular dynamics simulations, about 3D carbon nanotube networks that could be formed inside the beta zeolites. We investigated their structural stability and mechanical properties. Our results show that from all possible carbon nanotubes that can be embedded inside the channels of the beta zeolite, the one with chirality (6,0) is the most stable. Using the carbon nanotube (6,0), it is possible to build 3D structures with both all (higher density) and only partially (lower density) filled zeolite channels. Under tensile uniaxial force, the 3D low-density carbon nanotube networks are anisotropic and can be stretched along the direction in which all nanotubes are perpendicular up to 130% of strain without fracture. Also, the porosity and network stiffness can be tuned depending on the amount of carbon nanotubes filling the channels of the zeolites.