Improved Packing Density Research Articles

Enhanced Magnetic Permeability Through Improved Packing Density for Thin-Film Type Power Inductors for High-Frequency Applications

Enhanced Magnetic Permeability Through Improved Packing Density for Thin-Film Type Power Inductors for High-Frequency Applications

Concentration of Diynoic Acids in Bicellar Mixtures Derived from Those Phase Separation.

Bicellar mixtures containing diacetylene molecules, such as diynoic acids, can be used as parent materials for functional membranes. A bicellar mixture consisting of a diynoic acid-10,12-tricosadiynoic acid (TCDA)-, a phospholipid-1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-, and a detergent-3-[(3-cholamidopropyl) dimethylammonio]-2-hydroxypropanesulfonate (CHAPSO)-was evaluated for its morphology and packing of TCDA molecules in its bicellar mixture. A TCDA/DMPC vesicle was prepared at different molar ratios, TCDA/DMPC = 2/8, 5/5, and 8/2; a TCDA/DMPC/CHAPSO bicellar mixture was prepared by mixing a CHAPSO solution with a TCDA/DMPC vesicle solution as a detergent at different composition ratios, x TCDA/DMPC = [TCDA/DMPC]/([TCDA/DMPC]+[CHAPSO]), of 1.0, 0.70, 0.50, and 0.30. A DMPC molecule formed a bilayer membrane structure and was used to suppress its precipitation. The packing density of the TCDA/DMPC/CHAPSO bicellar mixtures was increased by mixing a CHAPSO molecule in x TCDA/DMPC = 1.0 to 0.70 or 0.50. A TEM image of a TCDA/DMPC/CHAPSO bicellar mixture showed many discoidal assemblies at x TCDA/DMPC = 0.5 of TCDA/DMPC = 5/5. Polymerization of the TCDA molecules in the bicellar mixture by UV light suggested an ordered arrangement of TCDA. Polymerization at x TCDA/DMPC = 0.70 and 0.50 correlated with improved packing density.

Bi-modal particle size distribution for high energy product hybrid Nd–Fe–B—Sm–Fe–N bonded magnets

In this work, we have demonstrated high energy product bonded magnet by leveraging the variation in sizes between Nd-Fe-B and Sm-Fe-N, as well as their hard magnetic properties. The hybrid anisotropic bonded magnets contain 70 vol% of magnet powder (Dy-free Nd-Fe-B and Sm-Fe-N) and 30 vol% of nylon. The objective of the work was to create bi-modal and bi-compositional bonded magnets in which the fine (3μm) particles of Sm-Fe-N would be used to fill the voids between the bigger Nd-Fe-B (105μm) particles, thus improve packing density. The magnetic hysteresis loop did not show significant signs of decoupled interactions between the magnetic phases. It was also found that the performance of the bonded magnet was most enhanced at 1:4 ratio of Nd-Fe-B and Sm-Fe-N. At that ratio, maximum density of 5 g/cm3 and the highest (BH)max value of 18.5 MGOe were obtained, although the intrinsic coercivity decreased, relative to the trend seen for other ratios. This work advances the opportunity to expand the use of Sm-Fe-N in bonded magnet applications.

Tailoring calcination products for enhanced densification of Li7La3Zr2O12 ceramics

The densification of Ga-doped Li7La3Zr2O12 (LLZO) ceramics was optimized by controlling the phase chemistry and morphology of green powders after calcination. A solution-based approach was used to synthesize the green powders which were calcined at temperatures between 600 °C and 950 °C and free-sintered into dense pellets. The ionic conductivity and relative density were optimized at a calcination temperature of 700 °C to be 1.28×10−3 S/cm and 96.2%, respectively. At this condition, the green powder consisted primarily of La2Zr2O7 pyrochlore nanoparticles (80–100 nm) and LLZO particles (0.5–1 µm), which promoted reaction-driven densification and enabled a favorable bimodal size distribution for improved packing density. Further increasing the calcination temperature was correlated with a reduction in density due to the detrimental effects of particle coarsening on sintering activity. These findings show that controlling the calcination conditions is an effective method for tailoring green body properties for improved densification of LLZO.

Utilization of agricultural, industrial waste and nanosilica as replacement for cementitious material and natural aggregates – Mechanical, microstructural and durability characteristics assessment

This study examines the effect of rice husk ash (RHA) and nanosilica, and ground granular blast furnace slag (GGBS) on concrete mechanical and durability properties. The cement had been partially replaced with nanosilica and RHA having substitution percentages up to 6% and 10% respectively whereas the sand had been partially replaced by GGBS at 20% for all mixes. A water-to-cementitious materials ratio of 0.38 and a sand-to-cementitious materials ratio of 2.04 were used to cast eight different concrete mixes. The nanosilica used in the present research possessed some favorable effects such as rich fineness, higher surface area and greater reactivity which signified one of the best cement replacement materials. Both the durability and strength of concrete specimens possessing nanosilica, RHA and GGBS was evaluated using in-elastic neutron scattering, SEM image, piezoresistive test, split tensile strength, flexural strength and compressive strength test. Concrete specimens were also subjected to chloride penetration and water absorption to examine the impact of replacement materials on the concrete's durability attributes. Concrete performance was increased by the ternary blending of concrete because of the active participation of nanosilica in durability and strength at early ages, both RHA and GGBS played an important role in improving packing density. It was found that as the percentage of cement replaced with nanosilica increases, the durability of concrete also significantly increases. But the optimum strength parameter was found when 4% of cement was replaced by the nanosilica effectively. The proposed ternary mix may be eco-friendly by saving cement and enhancing strength and durability effectively.

Enhancing the Performance of Roller-Compacted Concrete Pavement by Synergetic Improvement of Packing Density, Lubrication, and Moisture State of Recycled Concrete Aggregate

Roller-compacted concrete pavement (RCCP) is considered superior to other pavement types with reference to cost, ease of construction, and performance. However, the aggregate demand is significantly higher in RCCP than in the conventional concrete pavement. It is predicted that natural minable limestone sources would be exhausted in India in the next 30 to 40 years. One way to reduce the natural aggregates (NA) requirements in RCCP is through the integration of recycled concrete aggregates (RCA). However, the physical property of RCA is significantly inferior to that of NA owing to the presence of adhered mortar (AM), which increases the water demand by 2.3 to 4.6 times and affects the compactness and hardened-state behavior of RCCP. This study has tried to enhance the compactness and improve the performance of RCCP containing RCA (coarse, fine, and total RCAs) through different synergetic approaches. This, in turn, enhances the interlocking capacity using the particle packing approach, followed by mitigating the negative effects of AM by altering the moisture states, then improving the compactability and lubricating the matrix with superplasticizers. The results depict that altering the moisture states alone could adversely affect the RCCP performance because of the moisture transfer mechanism from the hydraulic gradient. Moreover, the inclusion of superplasticizers in different moisture states could manifest better aggregate rearrangement and compactability. Further, it could improve the tensile behavior of the RCCP compared with the concrete containing NA. These findings favor the complete replacement of NA by RCA for low-volume rural road construction.

Use of steel slag and LAS-based modifying admixture in obtaining highly eco-efficient precast concrete products

This paper presents a study on improving the eco-efficiency of no-slump concrete for precast elements using Basic Oxygen Furnace Slag (BOFS). Recycled BOFS powders and aggregates have been produced to obtain mixtures with better particle size distribution and improved packing density based on a particle packing method. A comprehensive experimental investigation was carried out on mixtures with different cement contents (5%, 10%, and 15% vol.) and compaction energy levels (6, 10, and 20 blows in a sand rammer). A modifying admixture based on Linear Alkyl Benzene Sodium Sulfonate (LAS) has also been evaluated as a workability and cohesiveness enhancer for steel slag concretes. In addition, concrete eco-efficiency was evaluated by measuring the binder intensity (bi) and waste consumption. The highest compaction energy provided packing densities ranging from 0.78 to 0.80, and BOFS aggregates led to better mechanical performances. The BOFS concrete containing 15% cement obtained the best strength (52.1 MPa) and bi value (7.0 kg/m³/MPa), with a waste consumption of 2356.57 kg/m³. The mixture with the lowest cement consumption (5% - 121.56 kg/m³) and the highest consumption of waste (2637.82 kg/m³) reached 16 MPa, delivering a bi of 7.6 kg/m³/MPa.

Capillary Evaporation‐Induced Fabrication of Compact Flake Graphite Anode with High Volumetric Performance for Potassium Ion Batteries

AbstractImprovement in volumetric performance is growing requirements for rechargeable batteries of lightweight and compact size. Flake graphite (FG) with thin lamellar structure realizes a satisfactory K‐ion storage performance, but its low packing density leads to poor volumetric capacity. Herein, this work fabricates an FG anode with improved packing density by hydrothermal treatment of the FG with graphene oxide and subsequent capillary evaporation‐induced drying process. A three‐dimensional flake graphite/reduced graphene oxide (FG/rGO) hydrogel is formed after hydrothermal treatment, which can be compressed during drying process via the capillary force generated by water evaporation, resulting in a compact structure with enhanced packing density. Compared to the pristine FG electrode (106.0 mAh cm−3), the FG/rGO‐82 anode realizes an ultrahigh volumetric capacity of 218.9 mAh cm−3 and good rate performance with a retained capacity of 152.3 mAh cm−3 at 2 C. Moreover, the FG/rGO‐82 exhibits excellent cycle stability with a capacity retention of 90.1% after 300 cycles. Even under a high mass loading of 7.4 mg cm−2, it still remains a volumetric capacity of 145.4 mAh cm−3 after 300 cycles at 1 C. The results prove that the capillary evaporation induced drying of hydrogel is an effective way to prepare electrode material with high volumetric capacity.

Exploring novel carton footprints for improved refrigerated containers usage and a more efficient supply chain

Large quantities of fresh produce are exported every year to international markets across the world using refrigerated freight containers (RFCs). However, many packaging systems are legacy designs for older shipping technologies. For fruit, more than 10% of the RFC floor area is unused by current packaging systems, and designs often do not facilitate adequate cooling conditions. This study showed that novel packaging designs could improve packing density by up to 19%. Two new packaging systems were investigated using CFD to emulate conditions similar to forced-air cooling (FAC) and a RFC, respectively. The proposed packaging increased floor area utilisation to about 98%. The FAC energy efficiency was improved by 29%. An analysis of the results indicates considerable cooling improvements are possible by modifying vent hole designs and using taller cartons. The study thus demonstrated substantial merits to implementing new fruit packaging systems.

Scalable fabrication of highly selective SSZ-13 membranes on 19-channel monolithic supports for efficient CO2 capture

Zeolite CHA (SSZ-13) membranes with record-high CO2/N2 selectivities are reproducibly prepared on 19-channel monolithic supports by one-step secondary growth approach using the concentrated gel and vacuum seeding. Packing density and mechanical strength for the monolithic membranes are much higher than those for normal tubular and disc membranes. The membrane thickness in each channel of the monolithic support is quite uniform after synthesis modification. The best 19-channel monolith supported SSZ-13 membrane with an effective area of 85 cm2 shows high CO2/CH4 selectivity of 132 with CO2 permeance of 464 × 10−9 mol/(m2 s Pa) at 298 K and pressure drop of 0.2 MPa for an equimolar CO2/CH4 mixture. The membrane also has the highest CO2/N2 selectivity of 46 among zeolite membranes to date. Large-area monolithic SSZ-13 membrane elements with an effective area of 270 cm2 are fabricated in the same way. It is larger than the surface area of industrial tubular supports. The large-area membrane still displays high CO2/CH4 and CO2/N2 selectivities of 120 and 44 under the same test conditions, respectively, indicating that the current synthesis procedure is scalable. The effects of temperature and pressure drop on the separation performance of the monolithic membranes are investigated. The 19-channel monolithic SSZ-13 membrane with improved packing density is a good candidate for CO2 capture from natural gas and flue gas.

Enhancing selectivity of novel outer-selective hollow fiber forward osmosis membrane by polymer nanostructures

An ideal forward osmosis (FO) membrane module for osmotic membrane bioreactor (OMBR) application would have high packing density, low reverse solute flux and low fouling propensity. Recently, an outer-selective hollow fiber forward osmosis (HFFO) membrane has been developed to simultaneously improve packing density and reduce fouling propensity. However, a high reverse solute flux of the HFFO membrane still generates a salinity build-up in the reactor and remains the main challenge of this technology. To tackle this problem, we successfully improved the selectivity of an outer-selective HFFO membrane by incorporating a prior developed formulation based on Pluronic® nanostructures containing water selective proteins into the active layer of the membrane. The assimilation of these nanostructures in the membrane resulted in a significant decrease of the specific reverse solute flux from 0.36 ± 0.01 gL-1 to 0.12 ± 0.02 gL-1 with no significant decrease in water flux. Also, urea was selected as a challenging solute to investigate the selectivity of the developed membranes. In comparison with the pristine membranes, membranes containing nanostructures presented a superior rejection of urea from 87.7 ± 2.0 % to 95.2 ± 0.9 %. The developed membranes are able to be used for future OMBR application tests to prove feasibility of the process. Thus, this study can lead to the development of new membranes suitable for efficient and long-term operation in OMBR configurations. Additionally, the nanostructures investigated here can be used for different thin-film composite membranes as an additive to improve membrane selectivity.

Carbonaceous admixtures in cementitious building materials: Effect of particle size blending on rheology, packing, early age properties and processing energy demand

Application of biochar, produced from locally generated wastes, as admixture in cement is a strategy to upcycle biomass waste and produce durable building materials. This research explores the influence of particle size and porosity of biochar, prepared from coconut shell and wood waste, added at 2 wt% of cement, on rheology, setting time, hydration and early age strength of cement mortar. For each biochar type, three particle size gradations are explored – coarser biochar (d50 = 45–50 μm) (obtained by sieving), finer biochar (d50 = 10–18 μm) (obtained by ball milling) and combination of coarser and finer biochar (d50 = 15–25 μm). Experimental findings suggest that combination of coarser and finer biochar improves workability and rheological properties of binder pastes compared to that with (only) coarser biochar. Depending on biochar type, hydration and rate of setting are accelerated compared to control. Inclusion of finer biochar and combination of finer and coarser biochar improve packing density and degree of hydration of pastes compared to coarser biochar and control, leading to 12–19% enhancement in compressive strength at 7-day age. Micro-structural investigations show that the macro-pores of coarser biochar can be filled with dense hydration products, although some macro-pores may remain unfilled. This offsets improvement in strength that can be achieved through enhancement in packing density. The approach of blending coarser and finer biochar reduces the energy demand and cost associated with ball-milling by 23–37% and SGD 2.30–4.80 per ton respectively compared to only finer (ball-milled) biochar per cubic meter of concrete. Overall, the findings from this research demonstrate that blending of biochar of different particle size distributions can enhance physical properties of cement-based materials, while reducing associated energy consumption.

Influence of Particle Packing Theories on Strength and Microstructure Properties of Composite Cement–Based Mortars

Supplementary cementitious materials (SCMs) have become a part of cementitious composites in the manufacturing of cement for improved performance and sustainability. Composite cement is one such type of cement in which ordinary Portland cement (OPC) is partially replaced with fly ash and granulated blast furnace slag (GBFS). In this study, the replacement levels of fly ash and GBFS are optimized to 20% and 30%, respectively, with a 50% OPC content. Apart from the superior properties of these binding materials, a better packing of aggregate comes in handy for improved properties. In this study, the modified Taufer model (MTM) and J. D. Dewar (JDD) model of proportioning the fine aggregates are adopted for improved packing density to obtain better mixes, and a comparison is made with proportions recommended by Indian standard (IS) 383 and IS 650. The packing density obtained in proportioning fine aggregates using the MTM, JDD, IS 650:2008, and IS 383:2016 methods are 0.6814, 0.6737, 0.6238, and 0.6008, respectively. The aggregate sizes recommended based on particle packing models (PPM) particularly, the MTM method tends to improve the packing by reducing the voids content. A direct influence of such effective packing can be observed from the microstructure studies conducted on different samples. MTM samples evidenced better packing compared to other methods of proportioning the mixes. The compound phase changes and development of microstructure were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), a back scattered electron (BSE), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Also, the quantification of portlandite and calcium carbonate available in the samples was determined using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) for different proportions. At 28 days, the specimens cast using MTM showed 11.11% and 15.5% higher compressive strength than the specimens prepared using IS 650:2008 and IS 383:2016, respectively. At every stage of curing, MTM mixes exhibited superior compressive strength.

Optimizing Hydrogen Storage in MOFs through Engineering of Crystal Morphology and Control of Crystal Size.

Metal-organic frameworks (MOFs) are promising materials for hydrogen storage that fail to achieve expected theoretical values of volumetric storage density due to poor powder packing. A strategy that improves packing efficiency and volumetric hydrogen gas storage density dramatically through engineered morphologies and controlled-crystal size distributions is presented that holds promise for maximizing storage capacity for a given MOF. The packing density improvement, demonstrated for the benchmark sorbent MOF-5, leads to a significant enhancement of volumetric hydrogen storage performance relative to commercial MOF-5. System model projections demonstrate that engineering of crystal morphology/size or use of a bimodal distribution of cubic crystal sizes in tandem with system optimization can surpass the 25 g/L volumetric capacity of a typical 700 bar compressed storage system and exceed the DOE targets 2020 volumetric capacity (30 g/L). Finally, a critical link between improved powder packing density and reduced damage upon compaction is revealed leading to sorbents with both high surface area and high density.

High-Density Lignin-Derived Carbon Nanofiber Supercapacitors with Enhanced Volumetric Energy Density.

Supercapacitors are increasingly used in short‐distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g−1). To improve their market penetration, while minimizing onboard weight and maximizing space‐efficiency, materials costs must be reduced (<10 $ kg−1) and the volumetric energy‐density increased (>8 Wh L−1). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05–0.1 g cm−3). Here, the authors increase the packing density of low‐cost, free‐standing carbon nanofiber mats (from 0.1 to 0.6 g cm−3) through uniaxial compression. X‐ray computed tomography reveals that densification occurs by reducing the inter‐fiber pore size (from 1–5 µm to 0.2–0.5 µm), which are not involved in double‐layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm−3 and energy density of 6 Wh L−1 at 0.1 A g−1 using a loading of 3 mg cm−2. The results outperform most commercial and lab‐scale porous carbons synthesized from bioresources (50–100 F cm−3, 1–3 Wh L−1 using 10 mg cm−2) and contribute to the scalable design of sustainable electrodes with minimal ‘dead volume’ for efficient supercapacitors.

Value added usage of granular steel slag and milled glass in concrete production

Industrial development has generated enormous conveniences for humans at the cost of environmental pollution. Cement production is a major cause of carbon dioxide emission in the construction industry, and utilization of a large number of aggregates in concrete is causing scarcity of natural resources and irreversible depletion. The practice of utilizing industrial wastes in the production of concrete can be a useful solution. In this research, green concrete of enhanced properties is produced by incorporation of milled glass as partial replacement of cement, and fine aggregates are replaced by granular steel slag with different dosages. Ten types of concrete mixes substituting 10%, 20%, and 30% of cement by glass powder (GP) and 40%, 60%, and 80% of sand by granular steel slag (SS) were assessed in terms of rheological, mechanical, and microstructural properties. Results indicated that concrete having 80% granular steel slag and 20% glass powder shows a maximum increase of 42%, 16%, 16%, and 14% in splitting tensile strength, flexural strength, modulus of elasticity, and compressive strength, respectively. Scanning electron microscopy depicts the formation of secondary calcium silicate hydrate (CSH) and improved packing density in concrete mixes having granular steel slag and glass powder. Thus, granular steel slag and glass powder can effectively be used as cement and sand replacement in the production of value-added green economical concrete, reducing environmental pollution.

Improving Environmental Efficiency of Reverse Filling Cementitious Materials through Packing Optimization and Fiber Incorporation.

To improve the environmental efficiency of the reverse filling system, three strategies aim to optimize the packing density, and the mechanical property were adopted in this study. Based on the compressive packing model (CPM), the relationship between the D50 ratio and maximum theoretical packing density for a reverse filling system with 25% and 30% superfine Portland cement was established. For comparison, silica fume and steel fiber were also added to the reverse filling system, respectively. The improvement of packing density by adjusting the D50 ratio was verified through the minimum water demand method, CPM, and modified Andreasen and Andersen (MAA) model. Compared to the reverse filling system added with 3 wt % silica fume, which possesses a comparable mechanical property with the optimized group (adjusted D50 ratio), the incorporation of steel fiber shows a more significant increase. The environmental efficiency of all the samples was quantified into five aspects through the calculation based on the mix proportion, compressive strength, and hydration degree. The comprehensive evaluation demonstrated that the optimized reverse filling system exerts a lower environmental impact and possesses a much higher cement use efficiency compared to the majority of ultra-high performance concrete (UHPC)/ ultra-high performance fiber-reinforced concrete (UHPFRC) reported in published papers.

Hotspot development and shading response of shingled PV modules

The shingled architecture has gained attention in recent years for its improved packing density and reduced ohmic losses that have led to greater module efficiencies. In the photovoltaics industry where land and auxiliary costs scale with area utilization, shingling is a promising emergent technology. However, because current designs use smaller cell areas and upwards of 34 cell strips in series per string, shingled modules are vulnerable to hotspots, particularly due to smaller shading elements. In this work, we experimentally characterize the hotspot and power response of shingled modules. Two operating scenarios are considered, simulating both utility scale systems and standardized testing conditions. We report maximum hotspot temperatures of 145 °C at partial shading and show how non-uniformities in the cell properties lead to variations in module shading response and hotspot temperature. Furthermore, we observe that shingled modules develop higher hotspot temperatures than conventional half-cell modules. Finally, we demonstrate how unshaded parallel strings in a shingled module can concurrently develop minor hotspots at the onset of bypass diode activation.

Value-added waste latex paints in masonry cement for plastering applications

Polymeric latexes are commonly used in cement-based plastering and rendering works. This paper assesses the effect of recycled polymers obtained from waste latex paints (WLPs) on flowability and mechanical properties of masonry cement (MC) mortars, including whether such performance would be similar to that induced by virgin polymers. Three MC classes prepared with different cement-to-limestone ratios are produced in compliance to relevant EN 413-1 and ASTM C91 specifications. The WLPs were not obtained from waste collection sites, rather produced to monitor constituents and properties prior to use. Test results showed that water retention and rheological properties of mortars containing virgin or recycled polymers are remarkably higher than unmodified mixtures. The mechanical properties of WLP-modified mortars including compression, flexure, and pull-off adhesion strength were pretty similar, or even higher than equivalent mixtures containing virgin polymers. This was attributed the presence of ultrafine pigment and extender particles that improve packing density and infer nucleation benefits for the growth of additional hydrates. The dry curing regime applied for virgin and recycled polymer-modified mortars is particularly advantageous in construction sites, as this reduces the hassle of moist curing normally required for unmodified plasters while securing higher resistance against sorptivity and shrinkage cracks.

A New Route to Enhance the Packing Density of Buckypaper for Superior Piezoresistive Sensor Characteristics.

Transforming individual carbon nanotubes (CNTs) into bulk form is necessary for the utilization of the extraordinary properties of CNTs in sensor applications. Individual CNTs are randomly arranged when transformed into the bulk structure in the form of buckypaper. The random arrangement has many pores among individual CNTs, which can be treated as gaps or defects contributing to the degradation of CNT properties in the bulk form. A novel technique of filling these gaps is successfully developed in this study and termed as a gap-filling technique (GFT). The GFT is implemented on SWCNT-based buckypaper in which the pores are filled through small-size MWCNTs, resulting in a ~45.9% improvement in packing density. The GFT is validated through the analysis of packing density along with characterization and surface morphological study of buckypaper using Raman spectrum, particle size analysis, scanning electron microscopy, atomic force microscopy and optical microscopy. The sensor characteristics parameters of buckypaper are investigated using a dynamic mechanical analyzer attached with a digital multimeter. The percentage improvement in the electrical conductivity, tensile gauge factor, tensile strength and failure strain of a GFT-implemented buckypaper sensor are calculated as 4.11 ± 0.61, 44.81 ± 1.72, 49.82 ± 8.21 and 113.36 ± 28.74, respectively.