Relative Bulk Density Research Articles

Preparation and characterization of nanotitania@fatty acid modified quartz sand proppant with super-hydrophobic and oleophilic properties

In this work, long-chain fatty acid (lauric acid (LA), myristate acid (MA) or stearic acid (SA))@nanotantia (TiO2) composites (LATC, MATC and SATC) are applied to modify the surface of the quartz sand proppant (LATC@sand, MATC@sand, and SATC@sand proppant) to achieve excellent hydrophobic and oleophilic properties. The water contact angle (WCA) increases with increasing long chain length of the fatty acid. The WCA of SATC@sand proppant even reaches 157.9°, indicating a super-hydrophobic behavior. Moreover, after putting in boiling water for 4 hours, the SATC@sand proppant still exhibits super-hydrophobic property with WCA of 156.2°. Compared with LATC@sand and MATC@sand proppant, the SATC@sand proppant displays better thermal stability, and the thermal decomposition temperature of SATC@sand proppant is at about 170°C. Meanwhile, the SATC@sand proppant demonstrates relative lower acid solubility, bulk density (13.1 g/cm3) and apparent density (2.24 g/cm3) than raw sand proppant, indicating SATC@sand proppant shows great potential for using in hydraulic fracturing to increase petroleum production.

Influence of additives and stoichiometry amounts in the manufacturing of [formula omitted] components by laser powder bed fusion process combined with pressureless sintering

Influence of additives (micro-alloying), niobium addition, and stoichiometry amounts on parts characteristics, in the manufacturing of Ti2AlC components by laser powder bed fusion process are investigated. The experiment is conducted with an optimal powder composition labeled Nb(O1) comprising a significant reduction of carbon amount to half of Ti2AlC stoichiometry set to fabricate high-density part with an improved wear-resistance and hardness, via processing conditions similar to those found optimal from previous work. A part with relative bulk and skeletal density as high as 80 % and 92 % respectively was achieved. Details of all obvious aspects of laser and powder interaction, such as absorptivity and wettability problems, on the resulting microstructure (porosity) and properties of parts are discussed.

The improvement mechanism of mechanical properties of B4C ceramics by constructing core–shell powders

AbstractB4C ceramics have been widely used in armor plate and cutting tools due to their high hardness. However, their poor sintering performance and low fracture toughness have limited their extended applications. In order to solve these problems, B4C@TiB2 composite powders with core–shell structure were prepared by a sol–gel method using B4C and TiCl4 as raw materials and then sintered by spark plasma sintering. The composite powders were characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The mechanical properties of B4C ceramics were tested by indentation and three‐point bending methods. The results showed that the B4C@TiB2 composite powders exhibited a tight core–shell structure, and the chemical bonds on the surface were mainly B–C and B–Ti bonds. When the molar ratio of B4C:TiCl4 was 2:1, the relative density and bulk density of B4C ceramics reached 96.2% and 2.92 g/cm3, respectively. Because of the good sintering performance of the B4C@TiB2 composite powders, the Vickers hardness and fracture toughness reached 26.6 GPa and 5.22 MPa m1/2, respectively. The bending strength reached a maximum of 570 MPa. The excellent fracture toughness can be attributed to crack deflection, crack branching, and the residual thermal stress of the core–shell structure.

Enhanced energy storage performance in reaction-sintered AgNbO3 antiferroelectric ceramics.

In this research, AgNbO3 ceramics were produced by two sintering methods: reaction sintering (RS) and conventional solid-state sintering (CSSS). The process was similar for both methods, except that in RS, Ag2O and Nb2O5 precursors were mixed, then formed into pellets, skipping the calcination step, and sintered at 1100 °C for 6 hours. Both prepared ceramics had the same perovskite crystal structure with an orthorhombic crystal system and Pbcm and Pmc21 space groups with similar lattice dynamic vibration modes at room temperature. The average grain size of the polycrystalline samples prepared by RS and CSSS was found to be ∼2.03 ± 0.77 and ∼1.85 ± 0.96 μm, respectively. The relative bulk densities of the ceramics produced by RS and CSSS were found to be ∼94.0 ± 1.8 and ∼96.5 ± 1.3%, respectively. Ceramics prepared by both methods showed antiferroelectric behavior, and reaction-sintered AgNbO3 ceramics exhibited lower energy loss density than CSSS samples. In addition, a recoverable energy storage density (Wrec) of 3.1 J cm-3 and higher energy storage efficiency (η) for RS samples were measured at 175 kV cm-1. Moreover, the η values of 74.2% and 57.7% were measured for samples sintered by RS and CSSS, respectively. This energy storage efficiency is the highest ever reported for pure AgNbO3 ceramics. Furthermore, reaction-sintered samples showed good temperature stability for Wrec and η in the 30-80 °C temperature range.

Synthesis, structural stability and phase diagram of BiFeO3–CaSnO3 ceramics

BiFeO 3 -based materials have received extensive attention in electronic device applications due to their high Curie temperature and large electromechanical response. In this study, new solid solutions of (1- x )BiFeO 3 - x CaSnO 3 (BF-CS) ceramics were successfully synthesized via conventional solid-state reaction method. With increasing CS content, the ceramics exhibit a single-phase perovskite and the structure changes from a main rhombohedral phase with a small amount of impurity phase to a stable rhombohedral phase and then to MPB region separating the rhombohedral and orthorhombic phases in the composition of 0 ≤ x ≤ 0.15, indicating that introducing CS can stabilize the perovskite structure formed in the sintering process. Unfortunately, the solid solubility limit of CS into BF perovskite structure is reached when x > 0.15. The dielectric peak associated with oxygen vacancies become weaker and finally disappear at x = 0.15. Moreover, the ceramics with x = 0.12–0.15 feature saturated and square-shaped P - E hysteresis loops with increased polarization can be attributed to effectively promote domain switching process at MPB, in which the highest piezoelectric coefficient d 33 = 259 pC/N can be ascribed to the combined effect of coexistence phases, high relative bulk density and low leakage current. In particular, a partial phase diagram is constructed in terms of temperature and composition, which helps to understand the structure-property relations. The distinct structures and phase transition behavior on each side of the vertical MPB line offer the guidelines and strategy to design other BF-based binary or ternary solid solutions with enhanced piezoelectric property in high temperature application.

Sintering Property and Hydration Resistance of CaO-Y2O3 Composite Materials

A preparation method of CaO-Y2O3 composite materials and its sintering property and hydration resistance were investigated in this paper. The CaO-Y2O3 core-shell structure powders were obtained by precipitation, after calcination, pressing and sintering the CaO-Y2O3 composite materials were prepared. The obtained powders and composite materials were characterized by crystalline phase formation, thermodynamic property, density, hydration resistance and microstructural analysis. The results showed that the prepared CaO-Y2O3 core-shell structure powders had good coating property, the sintering property and hydration resistance of composite materials were excellent. As the molar ratio Ca to Y was 1:1, the relative bulk density was 95.68%, the apparent porosity was 1.28%, and the hydration weight gain rate of the sample after 21 days in the atmospheric environment was 0.45%.

Laser powder bed fusion (L-PBF) 3D printing thin overhang walls of permalloy for a modified honeycomb magnetic-shield structure

Modified honeycomb parts of Ni-15Fe-5Mo permalloy for magnetic shielding applications were designed and fabricated via laser powder bed fusion (L-PBF) 3D printing. We focused on the L-PBF process and performances of the thin-walled samples with different overhangs. After temperature-field numerical simulations and mechanism analyses on the L-BPF molten pools, the process optimizations were conducted to achieve a high bulk relative density. The thin walls with different wall thicknesses (0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 mm) and overhanging angles (10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, and 90°) were printed without any supporting struts. The structures, mechanical properties, and formation mechanisms of the thin-walled overhangs were studied. We roughly gained some such trends or inferences about the tensile properties of the thin-walled overhangs. The microstructural anisotropies and surface “step effects” were the primary factors affecting the tensile properties. The numerical simulation and experiment of compression on the modified honeycomb parts with several sidewall inclination angles were performed. The modified honeycomb structures transferred stress and premature failure to other local structures far away from the compression face. The preferential plastic deformation of the modified honeycomb structures occurred at the inclined corners, exhibiting good plastic deformation buffering effect and thus avoiding instantaneous cracking. This work presented some reference significance for high-quality formation and performance evaluation of thin-walled overhanging structures via L-PBF.

Molecular simulation of poly(ethylene-ran-propylene) nanoparticles with different comonomer composition

Poly(ethylene-ran-propylene), PErP, nanoparticles at various comonomer compositions were studied by Monte Carlo simulation of coarse-grained copolymer models for their structural and surface properties. At higher ethylene fraction (fE) in PErP chains, the relative bulk densities in the interior portion of nanoparticles were increased and the nanoparticles became more condensed structures with sharper surfaces. In addition, chain ends were more preferably segregated at the surface while the co-monomers at the middle position were homogeneously distributed in the interior of nanoparticles. Chain dimensions and chain shape were changed mostly in the surface region and significantly decreased with fE. Bond orientation was mostly random arrangement irrespective of fE. For orientation at the molecular level, the longest principal axis of copolymer chains tended to align parallel to the surface but preferably changed toward isotropic random arrangement for copolymers with smaller fE.

Analyzing coarsening versus densification phenomenon present in partial sintering of Al2O3/TiO2 composites

Alumina–titania (Al2O3/TiO2) composites are well-known for their physical and microstructural properties, which allow several engineering applications. However, these properties change when different sintering temperatures are used, due to the existence of two antagonistic phenomena (grain coarsening versus densification) that occurs during sintering process. The aim of this study was to evaluate the microstructural and physical properties of the alumina–titania composites and to understand these two antagonistic phenomena when different partial sintering temperatures are used. The composites were prepared from alumina and titania powders by uniaxial pressing and sintered at different temperatures (1100–1400 °C). The structural analysis showed that in addition to expected phases (α-Al2O3 and rutile), the alumina–titania composite sintered at 1100 °C presents anatase phase, while those obtained at 1300 and 1400 °C present tialite phase. The morphology analysis revealed a random distribution of grains with irregularly shaped pores. According to the Archimedes-based immersion test, all composites have a relative bulk density ranging 60.43–73.59%, showing that none of them reached the final sintering stage. Statistical analysis revealed that the average grain size of the matrix ranges from 3.62 to 5.24 μm. Moreover, the statistical analysis also showed that the grain coarsening predominates over densification for the composites sintered from 1100 to 1150 °C. The densification predominates over grain coarsening for the composites sintered from 1150 to 1200 °C, and from 1250 to 1400 °C. The two phenomena coexist only for the composites sintered from 1200 to 1250 °C.

Feasibility Study of an Iron-Based Composite Added with Al2O3/ZrO2 as an Oxygen Carrier in the Chemical Looping Applications

The chemical looping process is a promising approach for carbon capture. Oxygen carriers play the crucial role of carrying oxygen between oxidation and reduction reactors. In this study, iron-based composites, added with alumina and zirconia, were used as the oxygen carriers. The feasibility study of these composites for chemical looping applications was then evaluated by measuring their properties, including mechanical properties, relative density, microstructures, crystal structure, and their capacity of oxygen. The results suggest that the addition of zirconia led the decrease of the bulk relative density and thus had a negative effect to both crush strength and attrition. Crush strength declined from 57 kgf to 26 kgf when using zirconia, replacing alumina, in an iron-based composite as the inner material. In addition, the phases in oxidizing and reducing reaction were also revealed. The formation of the spinel phase (FeAl2O4) was the major factor that altered the capacity of oxygen. It inhibited Fe2O3’s ability to be completely reduced to Fe and thus decrease the capacity of oxygen. The value was therefore decreased from 9.7% to 6.2% after 50 redox cycles in alumina addition composite. On the other hand, for the zirconia addition, all of the Fe2O3 could transform to Fe, which provided 8.5% of oxygen capacity after 50 redox cycles. A dense layer which was identified as the Fe2O3 in the bulk surface was observed in the samples reacted with 50 redox cycles. The proposed mechanism of the formation of Fe2O3 layer and its corresponding kinetic analysis was also revealed in this study.

Electrical conductivity of porous binary powder mixtures

Simultaneous data of the quasi-static compaction and electrical conductivity of porous, binary powder mixtures have been collected as a function of bulk density. The powder mixtures consist of a metal conductor, either titanium or iron, an insulator, and pores filled with ambient air. The data show a dependency of the conductivity in terms of relative bulk density and metal volume fraction on conductor type and conductor particle characteristics of size and shape. Finite element models using particle domains generated by discrete element method are used to simulate the bulk conductivity near its threshold while the general effective media equation is used to model the conductivity across the compression regime.

Binder Jetting of Silicon Steel, Part I: Process Map of Green Density

Abstract This study focuses on developing and demonstrating a straightforward workflow for identifying pathways to increase green part density in binder jetting additive manufacturing (BJAM) using statistically driven process maps. The workflow was applied to investigate the effects of process parameters toward improving green part density, with a direct application in manufacturing of Fe-Si components. Specifically, a half-factorial experimental design was used to study the effects of four key parameters—layer thickness, powder spreading speed, roller rotational speed, and binder saturation—on Fe-Si spherical powder with D50 of 32.40 µm. Relative bulk density was estimated via three methods: geometrical and mass measurements, the Archimedes test, and CT imaging. The study discusses relative bulk density as well as localized density variation in the printed parts, which is attributed to both parameter selection and inherent process variability. A regression analysis was used to reveal the significance of main effects and second-order interactions. The regression model (R2 = 0.915) was used to derive an expression for green density as a function of the parameters and had a prediction error of 0.96%. Based on the regression model, an optimized set of parameters was obtained that would maximize green density up to 57.96% for the machine and material system.

An empirical model for estimating soil penetrometer resistance from relative bulk density, matric potential, and depth

Soil penetrometer resistance (PR), an indicator of soil strength, is often used to denote the force that roots need to exert to penetrate the soil. In this study, we propose an empirical model, which has a simplified form and fewer parameters than the previous ones, to estimate PR from relative bulk density, matric potential of soil water, and soil depth. The model was established by using field measurements of PR, bulk density, water content, and laboratory water retention data at various soil depths in a long-term tillage experiment during maize growing season in 2017. Relative bulk density was determined from soil texture, bulk density, and organic matter content. Model performance was evaluated by comparing the predictions from the new model against those obtained from four earlier models using independent field data collected from four soils of different textures in 2015, 2018 and 2019. The root mean square error of the new model ranged from 0.358 to 0.879 MPa, significantly lower than that of the other four models (0.404–2.689 MPa), indicating that the new model could be applied to estimate PR for a wide range of soil textures with improved accuracy.

Selective laser melting of tungsten: Effects of hatch distance and point distance on pore formation

An experimental study was conducted on the effects of point distance and hatch distance on pore formation in selective laser melting of tungsten. The Archimedes’ method was used to measure the apparent and closed porosities. Apparent (open) porosity and closed porosity were found to follow different trends: the apparent porosity increased but the closed porosity decreased as hatch distance or point distance increased. The open pores are attributed to the lack of fusion at the large hatch distance or point distance while the closed pores are attributed to the possible spattering and keyhole formation at the smaller hatch distance or point distance. The results led to understanding the effects of hatch distance and point distance on the formation of open and closed pores and provided insight on the optimization of process parameters to further increase the relative bulk density.

Specifics of Specifics of Obtaining Powdered Die Steel Alloys for Cold Forming and Higher Mouldability

Issues of obtaining chrome die steels for cold deformation from sprayed powders have been considered. The blanks are obtained in a gasostatic capsule covered with powder at a pressing temperature of 1100-1150C at a pressure of 1400 MPa with isothermic exposure of 1-2 hours. It has been discovered that powdered vanadium-doped (˜ 8%) and chromium-doped (˜ 4%) die steels do better in high loads. Mouldability of powdered die steel types KH12M and KH12MPH1. It has been found that mouldability of powders greatly depends on their relative poured bulk density (PBD). To increase mouldability, it is advisable to deformation-process and finally annealoriginal powder.

Use of water retention data and soil physical quality index S to quantify hard-setting and degree of soil compactness indices of gypsiferous soils

Hard-setting gypsiferous soils become hard and compact during drying without the impact of soil compaction caused by agricultural field traffic. Thus, these soils are difficult or impossible to cultivate unless they are re-wetted. Moreover, it has previously been shown that Dexter soil physical quality index (S-index) negatively affected by compaction. This study was done to quantify the hard-setting as well as the soil compactness (expressed in terms of the degree of compactness, DC, which is relative density expressed as the ratio of bulk density to a reference density) using water retention data and soil physical quality index of fifteen soils with a wide range of gypsum content (30−301 g kg−1). Repacked soil cores were prepared with less disturbance of soil aggregates ≤ 4 mm). Water retention curves of the soils were measured in the matric suction range 10−15000 hPa. A single-porosity van Genuchten-Mualem model was fitted to water retention data. S-index and Dexter hard-setting (HDexter) were calculated using the van Genuchten-Mualem parameters. The relationships between S-index and both DC and HDexter were investigated for the 15 gypsiferous soils. A strong positive polynomial and power correlation were found between DC and HDexter and S (i.e. 1/S) respectively, and that are valid across different soil gypsum content. Significant negative relationships between HDexter and soil gypsum content were observed. Positive polynomial relations were derived between S and bulk density and polynomial relation was obtained between HDexter and bulk density. Positive relationships were observed between HDexter, DC, and relative bulk density. These findings confirmed that the new proposed HDexter index enables the prediction of soil hard-setting behavior to quantify the gypsiferous soil physical quality using only water retention data with no need to measure soil mechanical strength.

Experimental study on incipient shear stress of consolidated cohesive sediment

This paper analyzes the incipient motion mechanism of consolidated cohesive sediment. An experimental device based on previous studies was designed to investigate the influencing factors of the incipient shear stress, including the consolidation time, the density of dry bulk, cohesive particles content, and the composition of sediment mixtures. The experimental results indicated that the incipient shear stress of cohesive sediment increased with the increase of consolidation time, dry bulk density, and content of cohesive particles. The incipient motion mechanism of cohesive particles was further investigated using experimental data and theoretical analysis. A formula of the incipient shear stress for cohesive sediment was proposed herein, which is related to both the content of cohesive particles and the relative dry bulk density. The proposed formula was validated by the experimental data, and the calculated values of incipient shear stress using the formula were in good agreement with the experimental results.

Experimental investigation on performance deterioration of asphalt mixture under freeze–thaw cycles

Abstract Freeze-thaw cycling is a widely used experiment for characterizing the moisture susceptibility of asphalt mixture. Moreover, it can also be used as a simulation for pavement moisture damage in northern latitudes. To investigate the effect of freeze–thaw cycles on the performance deterioration of asphalt mixtures, three types of dense graded asphalt mixture specimens with different asphalt contents were prepared. These specimens were performed freeze–thaw cycles with the maximum cycles being ten times. Volumetric parameter measurements and Indirect Tensile Strength (IDT) test were carried out after one, three, five, and ten cycles. Based on the phenomenological method and macro damage mechanics, the damage variable composed of Strain Energy Density (SED) was presented to characterize the performance deterioration of asphalt mixture. Three types of models were chosen to perform regression analysis between the damage variable and freeze–thaw cycles. The results indicate that with the increase of freeze–thaw cycles, IDT strength and the Tensile Strength Ratio (TSR) decrease while Bulk Relative Density (BRD) increases first afterward decreases. It is suggested that the internal air-voids in specimens turn into open air-voids between five cycles and ten cycles. Compared to the other two models, S-typed Sigmoidal Logistic function is more suitable to describe the damage growth due to freeze–thaw cycles. Another finding is that an appropriate increase of asphalt content has a positive effect on slowing the damage growth in asphalt mixture.

Critical Values of Soil Physical Quality Indicators Based on Vegetative Growth Characteristics of Spring Wheat (Triticum aestivum L.)

This study was conducted to determine critical values of soil physical quality indicators according to vegetative growth of spring wheat in a range of degrees of soil compactness. A non-saline loam soil was used to produce a range of degrees of soil compactness in 10 mini-lysimeters. The mini-lysimeters were put outdoors and received similar amounts of water after sowing of spring wheat (Triticum aestivum L., cv. Pishtaz). Shoot dry weight (SDW) was measured, and relative SDW (RSDW) values of 0.9 and 0.8 were assumed to be the starting and end points of soil physical quality indicator limitation for wheat growth, respectively. Critical integral water capacity (IWC) values of 0.136 and 0.104 cm3 cm−3 were obtained for the start- and end-point limitations, respectively. This means that in the studied soil, the IWC values greater than 0.136 cm3 cm−3 represent good soil physical conditions for wheat growth. In the IWC range of 0.136–0.104 cm3 cm−3, there were slight physical limitations for wheat growth. In the IWC values smaller than 0.104 cm3 cm−3, unsuitable soil physical conditions (i.e., poor aeration and high mechanical impedance) strongly restricted the wheat growth. Start- and end-point limitations for Dexter’s index of soil physical quality (S) were found to be 0.051 and 0.038, respectively. Corresponding values for relative bulk density (RBD) were 0.805 and 0.846, respectively.

Experimental investigation of modified bentonite clay-crumb rubber concrete

This study was carried out to investigate the effects of jointly replacing cement and sand with bentonite clay and crumb rubber on the engineering properties of 25 MPa concrete. The materials used for the study were cement, bentonite clay, sand, crumb rubber, stone and water. Microstructural formation, elemental compositions and crystalline phases of cement, bentonite clay, sand, crumb rubber and stone were determined by using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) experiments respectively. Geotechnical properties of fine aggregates (sand and crumb rubber) and coarse aggregate (stone) were determined from sieve analysis, fineness modulus, moisture content, apparent relative density and bulk density experiments. Water samples were evaluated with pH and conductivity tests. Mechanical properties of the modified bentonite clay-crumb rubber concrete were evaluated with slump, bulk density, compressive strength and tensile splitting strength tests. The microstructural formation and elemental composition of the concrete were also evaluated with the aid of SEM and EDS respectively. The results revealed that the constituent materials possessed adequate engineering requirements for the production of concrete. The modified bentonite clay-crumb rubber concrete showed comparable mechanical and microstructural properties to that of plain concrete and can be suitable for the construction of driveways, floors and walkways.