Flake Diameter Research Articles

Biorefinery of peanut shell agroindustrial lignocellulosic waste for synthesis of a natural coagulant applied in the treatment of dairy wastewater

Agro-industrial lignocellulosic residue from peanut shell was used to obtain a natural coagulant, cationic hemicelluloses (CH), adding value to the residue through means of biorefinery. The hemicellulose was applied, after its cationization by etherification reaction in alkaline medium with ETA, as a natural coagulant in the treatment of synthetic dairy effluent (SDE). FTIR showed an increase of the methyl group band in 1480 cm-1, degree of substitution DS 0.38 ± 0.05 and the positive zeta potential of +13.1 ± 0.5 mV CH indicating the insertion of ETA in the structure hemicelluloses whose zeta potential was negative of ‐11.4 ± 0.6 mV. The evaluation of the CH was performed with jartest on turbidity, apparent color, and COD for a pHcoagulation range 5–11 and dosages from 50-500 ppm. Coagulation diagrams were determined using the data spatial interpolation method of the adapted Kringing regression model. The maximum performance of CH of SDE by sedimentation and DAF occurred at 50 ppm and pH 11 with turbidity removal efficiency, true color and chemical oxygen demand (COD) of 84.74%/87.48%, 98.75%/99.37% and 99.89%/93.38%, respectively. Flake morphology was analyzed through the application of an image capture non-intrusive method indicated low particle aggregation, with fractal dimension (Df) of the flakes stabilized in the range of 1.68–1.83 ± 0.020 in 15 min with a predominance of flakes with first-class flake diameters (0.022–1.20 mm) for all dosages. That explains the slower sedimentation and occurrence of smaller dispersed flakes which favored subsequent solid-liquid separation by DAF.

The effect of graphite flake diameter on the resistance to thermal shock, microstructure and mechanical properties of silicon carbide nanomaterials

The effect of graphite flake diameter on the resistance to thermal shock, microstructure and mechanical properties of silicon carbide nanomaterials

Effect of intercalated and exfoliated graphite particles on the mechanical properties of polymer composite: A micromechanics-computational approach

This study investigated the effects of intercalation and exfoliation of the graphite flake particles on the mechanical properties of elastomeric composites using analytical, computational, and experimental techniques. Relying on the modified Eshelby and incremental Mori–Tanaka approach, a new micromechanics model was proposed to estimate Young’s modulus and develop a constitutive model for expanded graphite (EG)-filled elastomer in finite strain deformation. It was found that when the initial graphite flakes expanded, the actual volume fraction and ultimate aspect ratio of the dispersed particles significantly affected the mechanical properties of the EG-reinforced composites. The present model and subsequent predictions reflect the initial flake diameter, actual volume fraction, ultimate aspect ratio of the particles, and other convenient physical properties of the composite constituents. In addition, molecular dynamics simulations were performed to evaluate the elastic properties of the EG-Matrix interphase region using the COMPASS force field function. The MD results showed that Young’s modulus of the interphase region increased significantly as the quantity of the graphene layer increased. The micromechanics-constitutive model results were validated using the experimentally determined stress–strain relation of the composites. EG- and CB-elastomer nanocomposite specimens were fabricated and tested in the experimental program. Field emission scanning electron microscopy (FESEM) analysis of the cryo-fractured surfaces of the elastomer compounds showed good interactions between the constituents. Numerical computations indicated that the proposed model incorporating the new parameters could accurately predict the experiment at a small particle concentration.

Influence of Flash Graphene on the acoustic, thermal, and mechanical performance of flexible polyurethane foam

In this study, flexible polyurethane foam (PUF) composites were prepared using three types of Flash Graphene (FG) produced from different feedstock material. The acoustic, thermal, and mechanical properties of foam composites containing 0.025 wt% FG were characterized. It was shown that PUF-1 and PUF-3 had higher sound absorption in the frequency range of 500–2000 Hz compared to neat PUF (baseline). PUF-3 experienced a 47% reduction in thermal expansion coefficient relative to the baseline. The tensile strength and compressive modulus of all composites increased by 16–26% and 33–37% respectively. Compression force deflection and tear strength did not change relative to the baseline. This may be explained by the relatively low flake diameter and aspect ratio of each FG which led to agglomeration and impacted load transfer between the filler and matrix. Overall, the addition of 0.025 wt% FG1 and FG3 improved acoustic, thermal, and tensile properties of PUF without diminishing compression force deflection and tear resistance. PUF reinforced with FG had similar or enhanced properties compared to PUF containing commercially available, exfoliated graphene nanoplatelets (GNP). This supports the use of FG as a relatively sustainable, low-cost alternative to exfoliated GNP or chemical vapor deposition (CVD)-grown graphene in porous polymer composites.

Determination of Graphene Migration Single Defect Site and Its Electronic Structure with Various Sizes

The planar hexagon graphene nanoflakes can deform their shape to be distorted after the single vacancy site creation. In this work, density functional theory (DFT) calculations are performed massively on a series sizes of graphene flake with all possible single vacancy site to determine its energetic, structural and electronic properties. It is found that the planar original graphene nanoflakes deform after a single vacancy is generated, and the deformation of graphene nanoflakes decreases with the increase of flake diameter. The formation energy of graphene nanoflakes with single vacancy indicates the stability increases with the size graphene nanoflakes increases. The HOMO-LUMO (Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital) gap values are only highly related to the size of the system and much less related to different migration locations. The calculate the root mean squared deviation (RMSD) is also calculated to quantify the geometric distortion between original atomic structure and the structures after the creation of single vacancy. The results provide insights into better understanding of the relationship between the formation energy and the size, as well as the distortion change as a function of the graphene flake size, and sufficiently perspective into quantifying the uncertainties in these measurements.

Effect of Microwave Treatment in a High Pressure Microwave Reactor on Graphene Oxide Reduction Process-TEM, XRD, Raman, IR and Surface Electron Spectroscopic Studies.

Reduced graphene oxide (rGO) was prepared by chemical reduction of graphene oxide (GO) (with a modified Hummers method) in aqueous solutions of hydrazine (N2H4), formaldehyde (CH2O), formic acid (HCO2H) accompanied by a microwave treatment at 250 °C (MWT) by a high pressure microwave reactor (HPMWR) at 55 bar. The substrates and received products were investigated by TEM, XRD, Raman and IR spectroscopies, XPS, XAES and REELS. MWT assisted reduction using different agents resulted in rGOs of a large number of vacancy defects, smaller than at GO surface C sp3 defects, oxygen groups and interstitial water, interlayer distance and diameter of stacking nanostructures (flakes). The average number of flake layers obtained from XRD and REELS was consistent, being the smallest for CH2O and then increasing for HCO2H and N2H4. The number of layers in rGOs increases with decreasing content of vacancy, C sp3 defects, oxygen groups, water and flake diameter. MWT conditions facilitate formation of vacancies and additional hydroxyl, carbonyl and carboxyl groups at these vacancies, provide no remarkable modification of flake diameter, what results in more competitive penetration of reducing agent between the interstitial sites than via vacancies. MWT reduction of GO using a weak reducing agent (CH2O) provided rGO of 8 layers thickness.

Improvement of the Appearance of Injection Molded Products made of Polypropylene Containing Bright Flakes by Injection Mold Capable of Melt Flow Control and Induction Heating and Cooling

In polymer injection molding, to achieve surface appearance resembling metallic coating without painting the molded product, bright material such as aluminum flake is sometimes mixed into the resin. In such cases, the generation of weld lines which appear as lines with different gloss and coloring are formed at the flow front meeting area of molded products and the vicinity areas. In this study, we used an electromagnetically induced heating and cooling injection mold equipped with system to control the melt flow to mold polypropylene containing aluminum flakes. As a result, it was clarified that weld lines with inconsistent coloring can be reduced by controlling the melt flow while heating the mold, and that the preventive effect of the above weld lines improves by a rise of the heating temperature of the cavity wall, advance at the timing of melt flow control starting and increase of a bright flake diameter.

Sustainable Conversion of Lignocellulose to High-Purity, Highly Crystalline Flake Potato Graphite

The carbon net negative conversion of biochar, the byproduct of pyrolysis bio-oil production from biomass, to very high-purity (99.95%), highly crystalline flake graphite that is essentially indistinguishable from high-grade commercial Li-ion grade graphite, is reported. The flake size of the graphite is determined by the physical dimensions of the metal particles imbedded in the biochar, demonstrated in the range of micrometers to millimeters. “Potato”-shaped agglomerates of graphite flakes result when the flake diameter is in the 1–5 μm range. The process is shown to work with a variety of biomass, including raw lignocellulose (sawdust, wood flour, and corn cob) and biomass components (cellulose and lignin), as well as lignite. The synthesis is extremely rapid and energy efficient (0.25 kg/kWh); the graphite is produced with a very high yield (95.7%), and the energy content of its coproduct, bio-oil, exceeds that needed to power the process. The demonstrated process is a tremendous advance in the sustai...

Controlling Coffee Ring Formation during Drying of Inkjet Printed 2D Inks

AbstractThe morphology of drops of graphene oxide (GO) inks produced by inkjet printing shows a distinctive coffee ring after drying when the mean diameter of the GO is below a critical size. Inks with larger diameter flakes do not show a coffee ring and the transition mean flake diameter decreases as the substrate temperature increases and when the printed drop size decreases. This behavior can be predicted with a model that compares the characteristic time for the agglomeration of high aspect ratio particles in suspension with the time scale for an evaporating liquid drop to begin receding during the drying process. The model is shown to accurately describe the transition from a coffee ring to a uniform dried deposit using a range of GO inks with mean flake size in the range 0.68–35.9 µm, drying temperatures of 20–60 °C, and drop sizes with contact diameter ranging from 30 to 800 µm.

Inkjet printing ultra-large graphene oxide flakes

Graphene oxide 2D materials inks with mean flake diameter 36 µm can be inkjet printed, with no significant blockage of the printer or apparent damage to the flakes, despite the mean flake size being >50% of the printer nozzle diameter and the ink containing individual flakes considerably larger than the nozzle. Printed flakes show a similar level of wrinkle and fold defects as observed in flakes deposited by drop casting. Polarised light imaging of the ink in the printhead prior to printing shows alignment of the flakes in the shear flow and this is believed to allow passage without agglomeration or blocking of the nozzle. The bulk electrical conductivity of these ultra-large flake printed films is 2.48 × 104 Sm−1 after reduction, which is comparable to that reported with printed pristine graphene. The conductivity of the printed films increases slightly with increasing flake size indicating that there is no increase in damage to electrical properties as the flakes approach and exceed the nozzle diameter.

The effect of flake diameter on the reinforcement of few-layer graphene–PMMA composites

The effect of the lateral dimensions of the graphene reinforcement on the physical properties of poly(methyl methacrylate) (PMMA) nanocomposites was studied. Electrochemically-exfoliated, few-layer graphene with average diameters of 5 μm (5-FLG) and 20 μm (20-FLG) were incorporated into a PMMA matrix at loadings from 0.5 to 20 wt.% by melt mixing using a twin screw compounder. The smaller graphene flakes were found to have only a slight effect on the rheological properties of the PMMA, whereas the larger flakes significantly increased the viscosity and dynamic moduli of the PMMA melt. Mechanical testing showed that the 5 μm flakes behaved in a similar way to short fibers and reinforced the PMMA matrix poorly compared to the 20 μm flakes, in line with previous predictions on the critical length of graphene. Significantly, these larger flakes gave a linear increase in the modulus with loading even at high loadings, without any of the detrimental aggregation effects seen in most other graphene systems.

Facile Synthesis of Graphene via Direct Water-Sodium Dodecylbenzenesulfonate Exfoliation

Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science,University of Malaya, 50603 Kuala Lumpur, MalaysiaIn this study, a mild, one-step electrochemical exfoliation was demonstrated for the synthesis ofgraphene with the assistance of water and a surfactant, particularly sodium dodecylbenzenesul-fonate and sodium dodecyl sulphate. Different types of water-surfactant solutions in different con-centrations could influence the exfoliation of graphite rods. From one to several layers of grapheneflakes (with a thickness of approximately 1 nm) could be produced directly after sonication. AFMimages showed that the flake diameters from this source were typically small. Raman and IRspectroscopic analyses of the dispersed phase suggested that the exfoliation of graphene sheetswas accomplished. The flakes were also characterized using field emission scanning electronmicroscopy, X-ray diffraction, and cyclic voltammetry techniques. Further improvements in thismethodology may pave the way to develop green, cost-effective, and large-scale production meth-ods for graphene sheets.

Few layer graphene-polypropylene nanocomposites: the role of flake diameter.

Graphene shows excellent potential as a structural reinforcement in polymer nanocomposites due to its exceptional mechanical properties. We have shown previously that graphene composites can be analysed using conventional composite theory with the graphene flakes acting as short fillers which have a critical length of ∼3 μm which is required for good reinforcement. Herein, polypropylene (PP) nanocomposites were prepared using electrochemically-exfoliated few layer graphene (FLG) with two different flake diameters (5 μm and 20 μm). The crystallization temperature and degree of crystallinity of the PP were found to increase with the loading of FLG, which suggests that the flakes acted as crystallisation nucleation sites. Mechanical testing showed that the 5 μm flakes behaved as short fillers and reinforced the PP matrix poorly. The modulus of the 20 μm flake composites, however, increased linearly with loading up to 20 wt%, without any of the detrimental aggregation effects seen in other graphene systems. The mechanical data were compared with our previous work on other graphene composite systems and the apparent need to balance the degree of functionalization to improve matrix compatibility whilst not encouraging aggregation is discussed.

Single stage electrochemical exfoliation method for the production of few-layer graphene via intercalation of tetraalkylammonium cations

We present a non-oxidative production route to few layer graphene via the electrochemical intercalation of tetraalkylammonium cations into pristine graphite. Two forms of graphite have been studied as the source material with each yielding a slightly different result. Highly orientated pyrolytic graphite (HOPG) offers greater advantages in terms of the exfoliate size but the source electrode set up introduces difficulties to the procedure and requires the use of sonication. Using a graphite rod electrode, few layer graphene flakes (2nm thickness) are formed directly although the flake diameters from this source are typically small (ca. 100–200nm). Significantly, for a solvent based route, the graphite rod does not require ultrasonication or any secondary physical processing of the resulting dispersion. Flakes have been characterized using Raman spectroscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS).

Effects of graphite flake diameter on mechanical properties and thermal shock behavior of ZrB2–nanoSiC–graphite ceramics

ZrB2–20vol.% nanoSiC–20vol.% graphite (ZSnpG) ceramics that contained graphite flakes with different diameters were investigated to determine the effects of graphite flake diameter on the microstructure and mechanical properties, as well as thermal shock resistance. The results showed that the flexural strength and relative density of ZSnpG ceramics firstly increased and then decreased with increasing the diameter of graphite, whereas the fracture toughness did not change significantly. The improvement in the flexural strength of ZSnpG ceramics was strongly dependent on the controlling of graphite distribution, the reduction of the length of the microcrack that resulted from thermal residual stress and the presence of intragranular nano-sized SiC particles. The calculated thermal shock parameters revealed that the graphite with finer starting diameter had a beneficial effect on the blocking of the crack initiation and the graphite with larger diameter restrained the crack propagation of ZSnpG ceramics.

Electronic shell and supershell structure in graphene flakes

We use a simple tight-binding (TB) model to study electronic properties of free graphene flakes. Valence electrons of triangular graphene flakes show a shell and supershell structure which follows an analytical expression derived from the solution of the wave equation for triangular cavity. However, the solution has different selection rules for triangles with armchair and zigzag edges, and roughly 40 000 atoms are needed to see clearly the first supershell oscillation. In the case of spherical flakes, the edge states of the zigzag regions dominate the shell structure which is thus sensitive to the flake diameter and center. A potential well that is made with external gates cannot have true bound states in graphene due to the zero energy band gap. However, it can cause strong resonances in the conduction band.

Effect of microstructural evolution on the mechanical properties of lepidolite based glass-ceramics

Abstract In this paper, effect of microstructural evolution on mechanical property of lepidolite based glass-ceramics of MgO–Al 2 O 3 –SiO 2 –Li 2 O–R 2 O–F(R=Na, K) system during the crystallization process has been studied. The results show that two distinct regions of strength dependence on grain size are found. The critical values of the flake diameter and aspect ratio of lepidolite are 1.8 and 4.6μm, respectively. The crystallization temperature ( T C ) of critical point locates at 1060 °C. When T C ⩽1060 °C, the bending strength increases with heat-treatment temperature ascribing to the randomly oriented and interlocked lepidolite crystallites, which cause crack divert or blunt to limit the further development of the flaw size and increase the surface energy of fracture. While T C > 1060 °C, the increased boundary shear stress arising from the mismatch of thermal coefficient between the lepidolite crystallite and the residual glass phase results in the decrease of strength.

Steam Flaking Characteristics of Sorghum Hybrids and Lines with Differing Endosperm Characteristics

ABSTRACTCommercial and food‐type sorghum hybrids with differing kernel and endosperm characteristics were grown under comparable conditions and steam flaked in each of three years. The raw‐grain kernel characteristics and proximate analyses were homogenous over the three‐year period. The waxy hybrid produced large, translucent, durable flakes that had significantly higher enzyme‐susceptible starch values for all years compared to the other varieties. Flakes with lower amylose contents (waxy endosperm) were positively correlated with percent whole flakes (r2 = 0.509), flake diameter (r2 = 0.846), and enzyme‐susceptible starches (r2 = 0.564) and negatively correlated with higher flake fragility (r2 = ‐0.647), test weight (r2 = ‐0.626), and flake breakage (r2 = ‐0.560). The heterowaxy flakes had a good appearance and were generally comparable in quality to the nonwaxy commercial and experimental hybrids. Heterowaxy sorghum hybrids with good grain yields can provide improved quality grain and flakes without sacrificing agronomic performance and yields. No difference in flaking performance was detectable among the kernels with different pericarp colors; flakes from the white food‐type sorghums had excellent appearance. Nontempered control samples were inferior in quality to all conditioned treatments.

Flake Metal Powders for Revealing Latent Fingerprints

Abstract Fine flake powders, having flake diameters ranging from 50 to 1 μm and stearic acid/powder ratios varying from 0 to 50 weight percent, were produced by laboratory-scale milling of aluminum, zinc, copper, and iron powders. The effectiveness of these flakes for detection of latent fingerprints was then assessed by comparing the print qualities obtained when using these flake powders with those achieved using commercial aluminum, commercial black, and commercial dark magnetic dusting powders. While the commercial aluminum powder was found to have an average flake diameter and stearic acid level close to the optimum values required to obtain bright fingerprints, several potential avenues of development were identified which could lead to the commercial availability of superior black powders.

Production and Characterisation of Flake Metal Powders for Fingerprint Detection

An investigation has been made of the effectiveness of currently available commercial fingerprint powders and the opportunities for development of new product ranges for fingerprint detection. Using laboratory scale milling procedures, aluminium, brass, copper, zinc, and iron flake powders were produced with a wide range of flake diameters and stearic acid contents. These laboratory manufactured flake products did not surpass the commercial aluminium and commercial brass dusting powders now commonly used by scene of crime officers for bright fingerprint development on dark backgrounds. However, print qualities considerably superior to those obtained with commercial black fingerprint powders could be achieved by using a magnetic wand to apply 10–25 μm dia. iron flake powders to latent fingerprints deposited on light backgrounds. PM/0540