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Three-dimensional graphene materials have been studied as typical supercapacitors electrode materials by virtue of their ultra-high specific surface area and good ion transport capacity. However, improvement of the poor volumetric electrochemical performance of these graphene materials has been required although they have high gravimetric energy density. In this work, nanocellulose/nitrogen and fluorine co-doped graphene composite hydrogels (NC-NFGHs) were prepared through a convenient hydrothermal approach utilizing ammonium fluoride as the heteroatom source. Nanocellulose (NC) and high concentration of graphene oxide (GO) were utilized to adjust the structure of NC-NFGHs and increase their packing density. Subsequently, the aqueous symmetric supercapacitor based on NC-NFGH-80 exhibits remarkable gravimetric (286.6 F·g −1 ) and volumetric (421.3 F·cm −3 ) specific capacitance at 0.3 A·g −1 , good rate performance, and remarkable cycle stability up to 10,000 cycles. Besides, the all-solid-state flexible symmetric supercapacitors (ASSC) fabricated by NC-NFGH-80 also delivered a large specific capacitance of 117.1 F·g −1 at 0.3 A·g −1 and long service life over 10,000 cycles at 10 A·g −1 . This compact porous structure and heteroatom co-doped graphene material supply a favorable strategy for high-performance supercapacitors.

Laser powder bed fusion (LPBF) additive manufacturing (AM) has been adopted by various industries as a novel manufacturing technology. Powder spreading is a crucial part of the LPBF AM process that defines the quality of the fabricated objects. In this study, the impacts of various input parameters on the spread of powder density and particle distribution during the powder spreading process are investigated using the DEM (discrete element method) simulation tool. The DEM simulations extend over several powder layers and are used to analyze the powder particle packing density variation in different layers and at different points along the longitudinal spreading direction. Additionally, this research covers experimental measurements of the density of the powder packing and the powder particle size distribution on the construction plate.

Concrete mixture design is the foundation of cement and concrete research. Innovations in concrete materials could, should, and would inevitably be incorporated into new mixture designs. Thus, a rigorous method for concrete mixture design can better bridge the research community and the construction industry with high reliability and high fidelity. However, current methods for concrete mixture design vary a lot in the literature, thus compromising the accuracy and consistency in interpreting the properties of concrete subject to changes in its raw ingredients. Moreover, the extraneous variables in controlled experiments are not always controlled well. To solve this old but critical problem, this paper summarizes the prevalent concrete mixture design methods in the literature and in practice. By contrast, the volume-based mixture design method is superior to the mass ratio-based mixture design method in terms of simplicity, accuracy, and consistency. Further discussion on packing density measurement and water or slurry film thickness (SFT) as a basis of volume-based mixture design is elaborated. Mathematically, the hardened properties were linked to the particle packing behavior and fresh properties of concrete. This research contributes to a unified volume-based design method to bridge the research community and the construction industry. In the end, it is conducive to upgrading from concrete technology to science. Keywords: slurry film thickness; strength; volume-based design; wet packing density.

Poisson’s ratio (ν) defines a material’s propensity to laterally expand upon compression, or laterally shrink upon tension for non-auxetic materials. This fundamental metric has traditionally, in some fields, been assumed to be a material-independent constant, but it is clear that it varies with composition across glasses, ceramics, metals, and polymers. The intrinsically elastic metric has also been suggested to control a range of properties, even beyond the linear-elastic regime. Notably, metallic glasses show a striking brittle-to-ductile (BTD) transition for ν-values above ~0.32. The BTD transition has also been suggested to be valid for oxide glasses, but, unfortunately, direct prediction of Poisson’s ratio from chemical composition remains challenging. With the long-term goal to discover such high-ν oxide glasses, we here revisit whether previously proposed relationships between Poisson’s ratio and liquid fragility (m) and atomic packing density (Cg) hold for oxide glasses, since this would enable m and Cg to be used as surrogates for ν. To do so, we have performed an extensive literature review and synthesized new oxide glasses within the zinc borate and aluminoborate families that are found to exhibit high Poisson’s ratio values up to ~0.34. We are not able to unequivocally confirm the universality of the Novikov-Sokolov correlation between ν and m and that between ν and Cg for oxide glass-formers, nor for the organic, ionic, chalcogenide, halogenide, or metallic glasses. Despite significant scatter, we do, however, observe an overall increase in ν with increasing m and Cg, but it is clear that additional structural details besides m or Cg are needed to predict and understand the composition dependence of Poisson’s ratio. Finally, we also infer from literature data that, in addition to high ν, high Young’s modulus is also needed to obtain glasses with high fracture toughness.

The undesirable properties of conventional recycled fine aggregate (RFA) often limit its application in the construction industry. To overcome this challenge, a method for preparing completely recycled fine aggregate (CRFA), which crushes all concrete waste only into fine aggregate, was proposed. The obtained CRFA had high apparent density, and its water absorption was lower than that of the conventional RFA. To take advantage of the CRFA, this paper introduced the modified packing density method for the CRFA concrete mix design. The modified packing density method took account of the powder with a particle size of smaller than 75 μm in the CRFA and balanced both the void ratio and the specific surface area of the aggregate system. Concrete (grade C55) was prepared using the CRFA to validate the feasibility of the proposed method. The unit price of the prepared CRFA concrete was around 12.7% lower than that of the natural aggregate concrete. Additionally, the proposed procedure for the concrete mixture design could recycle all concrete waste into the new concrete and replace all the natural fine aggregate in the concrete mixture.

An exploration was undertaken to examine the physical and optical traits of a quaternary glass system utilizing tellurium dioxide as its primary component. The glasses were prepared with 60TeO 2 -15B 2 O 3 -(25− x )Bi 2 O 3 -xSrCl 2 molar composition, where x = 5 mol.%, 10 mol.%, 15 mol.%, and 20 mol.%. The utilization of x-ray diffraction interpretation verified the amorphous nature of the glasses. Several physical properties were measured, including density ( ρ ), molar volume ( V m ), and oxygen packing density (OPD). It was observed that the density decreased (from 5.301 g/cm 3 to 3.542 g/cm 3 ) as the heavier molar mass of bismuth(III) oxide was replaced with the lighter molar mass of strontium chloride. Consequently, the glass matrix became less dense. The molar volume increased (from 40.129 cm 3 /mol to 51.612 cm 3 /mol) with higher strontium chloride content. Adding strontium chloride decreased the OPD (from 56.069 to 34.875), reducing the number of oxygen atoms in the glass sample. The optical properties were analyzed via the ultraviolet absorption spectrum. The cutoff wavelength ( λ c ) decreased (from 442 nm to 359 nm) as the strontium chloride content increased. With increased strontium chloride content, the prepared glasses showed indirect transitions in their energy band gaps. Additionally, the values of the indirect band gap energy ( E opt ) increased from 2.02 eV to 2.95 eV. The Urbach energy (Δ E ), which characterizes the disorder in the glass structure, decreased (from 0.288 eV to 0.270 eV) with increasing strontium chloride concentration, indicating a lower defect concentration. The molar refractivity values ranged from 26.82 to 31.79, reflecting the polarizability of the constituent ions. The glasses demonstrated a metallization criterion within the range of 0.332 to 0.384, indicating their promise for applications in the area of nonlinear optical devices. Graphical Abstract Spectra of optical absorption for the TBSr glasses.

In this work, the impact of the atomic packing density/fractional glass compactness of Ca–Si–O–N glasses on glass transition and crystallization temperatures, glass density, microhardness, molar volume, and refractive index were examined. It was found that the atomic packing density increased with increasing the nitrogen content and decreased with increasing the Ca content in the glass network. Furthermore, density, glass transition and crystallization temperatures, and refractive index, increased with an increasing atomic packing density of the glass, while molar volume increased with decreasing atomic packing density values. The change in hardness with atomic packing density is less clear and suggests that the atomic packing density does not solely control the underlying deformation mechanism. There is indeed competition between densification (favored at low packing density values) and isochoric shear (at larger packing density). Despite that, the effects of nitrogen as a network former and Ca as a modifier are significantly independent. The obtained results indicate that the atomic packing density of the prepared samples linearly depends on many mechanical and optical properties, suggesting that the glass network and cross-linking are proportional to the ionic radius of the Ca and the nitrogen content, respectively.

Packing density is a key factor in governing the properties of materials such as concrete, asphalt, ceramic etc. Therefore, determination of packing density of a particulate mixture accurately, is of great importance. However, involvement of many external and internal factors such as surface texture, shape, method of packing etc. has made it very complicated and tedious to determine the packing density. The study investigated the combined effect of particle surface texture, size ratio and large particle volume fraction on packing density and developed a descriptive model to predict the packing density. Further, design graphs were also developed for the convenience. The study revealed that the British pendulum number value of the surface texture linearly varies with the packing density. The rougher the surface, the lower the packing density. The interparticle friction hinders the particle rearrangement. Hence, the ability to achieve a higher packing state is reduced. Further, irregularities in the surface boundary create void spaces, increasing the total voids in the mix. Thus, the packing density reduces. The increase of the size ratio decreases the packing density linearly. The packing density variation with a large particle volume fraction follows a 3rd order polynomial curve. The trend analysis was conducted to develop the descriptive model and design graphs to predict the packing density of binary mixtures.

Yellow phosphorus slag has been considered as a potential cement substitute for mine filling material due to its cementing activity; however, its slow setting and low early strength have limited broader use. This study investigates the grading, compactness, and strength of yellow phosphorus slag combined with tailing sand. Using yellow phosphorus slag as an aggregate, cement as a binder, and mixing tailing sand in different ratios, this study evaluates its feasibility as a coarse aggregate in mine backfill. The key findings are as follows. (1) The grading index of tailing sand was 0.5, aligning with Fuller grading, but it required mixing with coarse aggregates to enhance strength and reduce cement consumption. Yellow phosphorus slag, with a grading index of 0.97, does not match Fuller’s curve and thus benefits from mixing with tailing sand. (2) For mixtures of waste rock and tailings, the 5:5 ratio aligned closely with Fuller’s theory, showing optimal packing density and strength. Mixtures of yellow phosphorus slag and tailings at ratios of 3:7, 4:6, and 5:5 had R2 values of 0.73, 0.80, and 0.85, respectively, confirming reliable fit. The 5:5 mixture provided the best packing density and strength. (3) A new strength prediction model, accounting for aggregate, cement, and water effects, suggests that a 5:5 ratio with a 71% mass concentration and 1/7 ash–sand ratio meets industrial strength requirements. FLAC3D simulations indicated that cemented backfill reduces stress concentrations caused by excavation and supports stability during mining while also absorbing energy through compaction, creating favorable conditions for safe mining operations.

Protein sequences evolve under selection pressures imposed by functional and biophysical requirements, resulting in site-dependent rates of amino acid substitution. Relative solvent accessibility (RSA) and local packing density (LPD) have emerged as the best candidates to quantify structural constraint. Recent research assumes that RSA is the main determinant of sequence divergence. However, it is not yet clear which is the best predictor of substitution rates. To address this issue, we compared RSA and LPD with site-specific rates of evolution for a diverse data set of enzymes. In contrast with recent studies, we found that LPD measures correlate better than RSA with evolutionary rate. Moreover, the independent contribution of RSA is minor. Taking into account that LPD is related to backbone flexibility, we put forward the possibility that the rate of evolution of a site is determined by the ease with which the backbone deforms to accommodate mutations.