Archimedes Method Research Articles

Upcycling low-grade coal fly ash for the production of fly ash fibers and their applications in fiber-reinforced cement composites

Fly ash (FA) fibers were produced from low-grade coal FA, which exhibited high SO3 content, in combination with dolomite and basalt. To identify the optimal combination of these raw materials, glass samples were cast with varying ratios of these materials. Subsequently, an alkaline resistance test was conducted by immersing the ground glass samples in a 1 M Ca(OH)2 solution for a duration of 75 days. The results of the alkaline resistance test revealed that the formulation consisting of 70 wt% FA, 20 wt% dolomite, and 10 wt% basalt, exhibited the highest alkaline resistance with a weight loss of less than 2 wt%. Based on this formulation, FA fibers were then produced and utilized as a reinforcing phase in fiber-reinforced cement composite (FRCC) samples, ranging from 0.1 to 0.8 wt%. Mechanical testing showed that, after 28 days of air curing, the FRCC samples containing 0.8 wt% FA fibers exhibited the highest modulus of elasticity (MOE) at 16,890 ± 434 MPa, along with a modulus of rupture (MOR) of 13.86 ± 0.98 MPa and an impact strength of 1792 ± 134 J/m2. These results meet industry requirements, with a MOR and MOE exceeding 5 MPa and 7000 MPa, respectively, as well as an impact strength exceeding 1000 J/m2. Using the Archimedes method, the density of the FRCC samples containing 0.8 wt% FA fibers, is 1.71 ± 0.03 g/cm3, falling within the industry standard range of 1.5 to 2.2 g/cm3. Furthermore, according to the cost analysis, the production cost for FA fibers is $324.40 per ton, compared to $5000 and $1000 per ton for commercially available fibers. Consequently, utilizing FA fibers would result in significant savings for the raw material costs for FRCC production.

Composite Materials of Epoxy Resin–W System for Radiation Shielding Against Gamma Radiation

Сomposite materials based on the epoxy resin–W system with varying W content (0–80 %) were obtained using the method of chemical curing. Microstructural investigations of the samples showed that with increasing W content there is a more uniform distribution of grains in the epoxy resin matrix could be observed. Agglomeration of W grains is noted for samples with filler content up to 40 %. Statistical analysis of the grain size of the initial W powder revealed that the probable diameter of W grains is 475 nm. The values of effective and relative densities of the experimental samples were obtained using the Archimedes method. The effective density varied from 1.16 to 4.36 g/cm3 with W powder content rising. The relative density values received ranged from 91 to 94 %, indica ting that there were no significant defects in the samples. X-ray diffraction analysis showed the presence of vcc-W and WO2 phases, indicating the oxidation of W in the thin surface layer of the powder. Calculation in Phy-X/PSD software allowed to evaluate the gamma radiation shielding efficiency for the epoxy resin–W system composite materials in 0.8–2.5 MeV energy range. It was observed that samples with filler content of 60 and 80 % were the most suitable for radiation shielding. It was found that the addition of W powder to the epoxy matrix contributed to the reduction of half attenuation layer values by 3.5 times from 9.448 to 2.672 cm for samples with 0 and 80 % W content, respectively, for 1.25 MeV radiation energy. The obtained results demonstrate the high efficiency of the proposed composite materials for shielding gamma radiation, which makes them a perspective candidate for manufacturing radiation shields.

Parameter development for Laser Powder Bed Fusion of nickel-based Haynes 282 using diverse density determination methods

To manufacture functional components using laser powder bed fusion (PBF-LB/M), the execution of a parameter development with the specific material and machine is an indispensable step. Typically, in the search for the optimal parameter set, the volumetric energy density (VED) used to melt the material serves as an adjustment variable, while the resulting part density as the target parameter. Although this approach effectively reduces the process parameters search-space, additional criteria concerning part quality should be considered in the development. This paper introduces a systematic parameter selection approach, refining the characterization process for processing the nickel-based superalloy Haynes® 282®. The presented strategy not only incorporates the density as target condition but also considers the surface quality and dimensional accuracy of the manufactured samples, crucial for near-net-shape manufacturing. Additionally, three porosity measurement methods (Archimedes method, microscopy, gaspycnometry) for AM metal parts are compared, and their validity for this purpose is discussed.

The Study on the Decolorization and Properties of Bismuth Glass

PbO glass has an adverse effect on the environment; the bismuth glass has a high refractive index, low melting temperature, softening temperature, and glass transition temperature (Tg), so that it can be used as a lead-free glass, used in optoelectronics, electronics, optics, and other components, which bismuth glass has been proved to be an important replacement material. Due to the higher melting temperature, Bi3+ ions tend to partially reduce to the low valence state of Bi0, which in turn causes coloration of the glass. In this experiment, the absorption peaks of glass oxidized brown color were observed at about 470 nm at 1,100°C (Bi2O3 = 40, 45 mol%) and 1,000°C (Bi2O3 = 40 mol%) for these three curves. The bismuth glass produced by high-temperature melting is not suitable for optical applications; by adding an oxidant (Sb2O3), which inhibits the reduction reaction of bismuth ions and maintains the ions in the state of Bi3+, the glass becomes more transparent in appearance and the transmittance is also improved and raised to approximately 75%–80%, which proves that appropriate additives are sufficient to greatly improve the application of bismuth glass for optical components. In the research process, the density and molar volume were measured by Archimedes method, Raman analysis was used to explore the influence of its structural changes, UV/Vis spectroscopy was used to measure the transmittance and absorption spectra for analysis and discussion, and TMA was used to observe the thermal properties, in the hope of developing a good optical properties of the glass, and the present experiments have confirmed that the addition of a small amount of Sb2O3 changes the color of the glass from black to a light yellow, which can be better used in the optical glass.

Light-weighing traditional ceramics by porosity control and consequences on mechanical strength

This work evaluates the impacts of the addition of cellulose fibres (5 and 10 wt%) and pumice powder (5 wt%) as pore forming agents on the porosity, microstructure and mechanical strength of two traditional ceramic compositions: stoneware and terracotta. Open and closed porosities, pore size distribution and morphology were obtained from the combined use of the Archimedes method, mercury intrusion porosimetry and SEM image analyses.The results show an increase in the open porosity ratio in the case of cellulose fibre addition, whereas pumice powder addition promotes an increase in the closed porosity. The addition of cellulose also modifies the pore morphology of stoneware samples and induces a pore size increase. The decrease in mechanical strength caused by a lower firing temperature is greater than the decrease linked to the porosity generated by pore-forming agent addition. As the moduli of rupture of the produced porous tiles are higher than those needed by the standards, this work proposes new opportunities for lightning ceramic products.

Microstructure and electrical conductivity of La10Si6O27–La0.9Sr0.1Ga0.8Mg0.2O2.85 composite electrolytes for SOFCs

Composite ceramic electrolytes with heterostructure have attracted wide attention from the scientific community due to their enhanced conductivity and stability compared with single component electrolytes. Along these lines, in this work, to improve the conductivity of lanthanum silicate, a series of La10Si6O27 (LSO) - La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolytes were developed, which were composed of apatite/perovskite heterostructure. The phase composition, heterogeneous structure, and morphology of the samples were investigated by performing X-ray diffraction (XRD), transmission electron microscopy (TEM) measurements, as well as, field emission scanning electron microscopy (FE-SEM) for in-depth analysis. In addition, the Archimedes method was employed to test the relative density of the samples. X-ray photoelectron spectroscopy (XPS) was used to examine changes in oxygen vacancies at different LSGM contents. Compared with the pure LSO material, the content of oxygen vacancies increases significantly and the conductivity is highest when the LSGM content is 10 %, which indicates that the newly formed oxygen vacancies in the composite LSO-LSGM electrolyte play an important role in improving the ionic conductivity. At 400 °C, the conductivity of 90 wt%LSO:10 wt%LSGM was 3.4 times that of pure LSO, and at 600 °C, the conductivity of 90 wt%LSO:10 wt%LSGM was an order of magnitude higher than that of pure LSO. From the electrochemical impedance spectra (EIS) analysis, it was shown that the small resistance achieved by the grain boundary was the main reason for its excellent performance. Our results provide valuable insights for the design of more composite electrolytes for intermediate-temperature SOFCs.

Preparation and characterization of bioceramic composites based on anorthite and β-TCP from dolomitic phosphate and kaolin rocks

The current study demonstrates the possibility of producing novel economic biomaterials with biocompatible and acceptable mechanical properties for bone tissue engineering applications from dolomitic phosphate and kaolin rocks. The solid-state reaction was adapted to produce various batch compositions, through the substitution of kaolin with dolomitic phosphate rocks in which 20–30 wt% dolomitic phosphate rock was combined with kaolin material (20 PK, 25 PK and 30 PK). The fabricated ceramics composites were sintered at different temperatures ranging from 1175 to 1325 ᴼC. The phase composition, bulk density and bending strength of the sintered bioceramics were evaluated through X-ray diffraction (XRD), applying the Archimedes method, and 3-point bending test, respectively. Moreover, the in-vitro tests were estimated by immersing the samples in stimulated body fluid solution (SBF). The results showed that anorthite, β-tricalcium phosphate, and calcium magnesium phosphate were produced as primary phases during the sintering process and that their content increased with the increase in the phosphate rock content. Notably, the sample containing 20 wt% dolomitic phosphates exhibited good densification of 1.99 g/cm3 and achieved a bending strength of 45.66 MPa at 1250 °C. After immersing in the SBF for four weeks, changes in the surfaces of all the studied materials were observed, owing to the deposition of apatite particles. The pH values were in a nearby region of the natural pH levels. Such behaviour may be related to the sample's high stability, which originated from its chemical composition and dense structure. Moreover, a cytotoxicity test was carried out using osteosarcoma cells (HOS). The results demonstrated that all the studied bioceramics composites are safe for use as potential biomaterials.

Effect of Na2CO3/Al2O3 ratio on the calcium fluoroaluminosilicate-based bioactive glass-ceramics derived from waste materials

The development and fabrication of bioactive glass (bioglass)-ceramics derived from waste materials enhance the mechanical properties of calcium fluoroaluminosilicate based bioglass-ceramics for biomedical applications. This study aims to examine the effect of the Na2CO3/Al2O3 ratio on the 44SLS-(20-x) Na2CO3-24ES-6P2O5-6CaF2-xAl2O3 system where x = (0,3,6, and 9 wt%) as well as its mechanical performance. Structural and microstructural properties were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). In the interim, the density of glass ceramic samples was measured using the method of Archimedes. Afterwards, the bioglass ceramics with the Na2CO3/Al2O3 ratio of 11/9 sintered at 950 °C exhibited excellent results in terms of density that is 2.734 g/cm3. XRD analysis also confirmed the increase in crystallisation of anorthite, fluorapatite and nacaphite. Moreover, SEM analysis revealed the morphology of round-shaped fluorapatite with a variation in the size of sintered glass ceramics. The optimal compressive strength of 136.58 MPa is in the range of human cortical bone.

GA-coupled ANN model for predicting porosity in alginate gel scaffolds

Alginate gel scaffolds are biocompatible and biodegradable materials that have been used in a variety of tissue engineering applications. The porosity of alginate gel scaffolds is an important property that affects their performance. However, it is difficult to predict the porosity of alginate gel scaffolds accurately. In this study, a GA-coupled ANN model was developed to predict the porosity of alginate gel scaffolds. The model was trained on a dataset of 107 scaffolds with known porosities. The model was able to achieve a mean absolute error of 0.13, which suggests that it is able to accurately predict the porosity of alginate gel scaffolds.The alginate scaffold was fabricated by a microfluidic technique using a syringe pump and a flow device. The crosslinker solution was poured into the Petri dish to crosslink the polymer to the gel structure. The Archimedes method was used to determine the scaffold's apparent porosity. The artificial neural network has been used to model the porosity of the gel scaffold using the input parameters such as alginate-pluronic viscosity, surface tension, and contact angle etc. The maximum porosity was modelled to be 96.4 % using GA whereas the experimental value for the same was measured to be 92.8 ± 2 %. A 3.7% variation in the porosity was found from modelled value. To the best of our knowledge, this study is the first to develop an integrated ANN-coupled GA model to predict the maximum porosity of the gel scaffold. The result indicates that artificial intelligence has great potential for optimizing the parameters to fabricate the gel scaffold that can be used for tissue engineering applications.

Development of hydrogels based on xylan and poly (acrylic acid) for melamine adsorption in batch and continuous mode: experimental design, kinetics, isotherms, recyclability, and fixed-bed column.

Two hydrogels were synthesized, characterized, and applied as alternative materials to remove melamine (MEL) from aqueous media by adsorption. For the first time, a complete study of MEL adsorption is presented, including optimization, kinetics, isotherm, reuse, and column studies with these new materials. One hydrogel is based on xylan and poly (acrylic acid) and was named HXy, and the other is based on the same components functionalized with activated carbon and was named HXy-AC. The materials were synthesized by free radical polymerization and characterized by FTIR, XRD, TGA, DSC, SEM, zeta potential, point of zero charge, N2 adsorption isotherms (BET), helium gas pycnometry, Archimedes method, swelling analysis, and stability tests. The characterization results confirmed the intended synthesis and showed the thermal, morphological, textural, structural, and compositional profile, as well as the adsorption characteristics of the materials. The adsorption studies in batch process included experimental design, kinetics, isotherms, and recyclability, and in continuous mode, the studies included fixed-bed column experiments. The full factorial design showed that adsorbent dosage, pH, and ionic strength are significant for adsorption capacity and removal percentage responses. Doehlert design enabled the definition of the values of adsorbent dosage and pH that were most suitable for MEL adsorption into the materials, indicating the optimal adsorption conditions. The kinetics were well described by the pseudo-first-order model, with R2 above 0.9920 for both materials at all concentrations tested. The isotherm obeyed the Langmuir model, with R2 above 0.9939 for both materials at all temperatures tested. Equilibrium was attained at 180 min, and the maximum experimental adsorption capacity was up to 132.46 and 118.96 mg g-1 at pH 7, with adsorbent dosage of 0.5 g L-1, and 298 K for HXy and HXy-AC, respectively. Furthermore, HXy and HXy-AC materials maintained about 58 and 70% of their initial adsorption capacity at the end of five adsorption/desorption cycles, respectively. Breakthrough curves were described by the Yan model and presented a maximum adsorption capacity of 30.2 and 30.4 mg g-1, treating 3.4 and 6.1 L of influent until the breakthrough point of 0.5 mg L-1 with HXy-AC using 2.0 and 4.0 g of material, respectively. These findings show that the hydrogels produced present the potential to be applied in the adsorption of basic molecules, such as MEL.

Processing of membranes and 3D scaffolds based on n-TiO2 colloidally dispersed on a thermoplastic matrix for photocatalytic pollutant removal

One of the most promising technologies for water treatment today is photocatalytic membrane reactors (PMRs). Manufacturing efficient membranes is still challenging as many factors are involved, like the porosity, specific surface area, nature and size of particles. In this work, a colloidal method to self-support commercial nanoparticles (n-TiO2) in a polymeric matrix of polylactic acid (PLA) is proposed allowing the fabrication of 2D and 3D structures with high inorganic content that can be adapted to the PMR configurations. Using a commercial filament of PLA loaded with up to 15 vol% of n-TiO2 as starting point, photocatalytic membranes have been manufactured by FFF. In addition, following a similar process, tapes with n-TiO2 particles up to 15 vol% have been processed by tape casting. Thermal characterisation (DTA) and dynamic rheometry evaluated the commercial filament for printing to determine the conditions used during the thermal extrusion and printing processes. FTIR and XRD technologies were used to determine the chemical interactions of PLA matrices with TiO2 nanoparticles. Porosity was measured by Archimedes's method for the filaments, by mercury intrusion for the membranes and by optical microscopy for the scaffolds. Finally, the microstructure of the 2D and 3D pieces was evaluated by scanning microscopy. 2D tape cast membranes were compared with individual filaments and 3D printed scaffolds in linear and gyroidal geometries. The catalytic activity results indicate that tape cast membranes show much higher kinetic constants than the individual filaments and the linear and gyroidal scaffolds. Regarding the two different printed scaffolds, in contrast to the kinetic values, gyroidal geometries achieve an average degradation time (t50) of 6.1 h, which is a lower value than those observed for linear scaffold geometries. Methyl orange degradation tests after 24 h exposure under UV light showed degradation rates of 98% for membranes, 90% for commercial filaments, 80% for gyroidal scaffolds and 60% for linear patterns. Therefore, these results are promising as a solution for fabricating easily extractable self-supported membranes for water treatment in PMRs.

Effect of TaC and graphene nanoplatelets on the microstructure and mechanical properties of ZrB2

In this experiment, in order to investigate the effect of TaC addition on the microstructure, densification and mechanical properties of ZrB2 composites reinforced with graphene nanoplatelets (GNP), three composites were fabricated via spark plasma sintering (SPS) at 1900 °C. Relative density was determined by Archimedes method. The XRD and EDS analyses were used to explore the phase composition and elemental distribution. Also, Field emission scanning electron microscopy (FE-SEM) was employed to characterize the microstructure (grain size and porosity). Flexural strength, fracture toughness and hardness were determined by three-point bending test, single-edge notched beam (SENB) and macro and micro Vickers methods, respectively. The results showed that the presence of the GNP, alone and combined with TaC, increases the relative density sharply to 99.6 %. In addition, full densification occurred by the addition of 10 and 20 vol% TaC compared to the monolithic ZrB2 ceramic with 83 % relative density. Maximum flexural strength and fracture toughness of 580 MPa and 4.5 MPa.m0.5 were obtained, respectively, for ZrB2- GNP and ZrB2- GNP doped with 10 vol% TaC.

Optical properties and radiation shielding performance of tellurite glassy composites: Role of rare earth oxides

In this research, the synthesis, optical parameters, and radiation absorption quantities of 50TeO2–15Na2O—(20-x)PbO—15ZnO—xEu2O3 glasses were reported. The glasses were prepared by the well-known melting and quenching method using high purity chemicals. The glasses were coded as TPEu-0, TPEu-1, TPEu-2, and TPEu-3 for glasses containing 0, 1, 2, and 3 mol% of Eu2O3, respectively. The density of the glasses was determined by the Archimedes method. The optical parameters of the glasses, such as the refractive index n, molar refractivity Rm, molar polarizability αm, reflection loss RL, optical transmission T, metallization criterion M, static dielectric constant εstatic, and optical dielectric constant εoptical were estimated by theoretical methods. The stopping powers and range of electrons, protons, α-particles, and carbon ions in the TPEu-X glasses for particle kinetic energies between 15 keV and 15 MeV were computed using the ESTAR, PSTAR, ASTAR, and STRIM software. In addition, the fast neutron (FN) removal cross section (FNRCS), thermal neutron (TN), and total cross-section (σtot) for the prepared glasses were evaluated theoretically using established models. The estimated optical parameters showed strong relationship with the chemical content of the glasses. Glass density and molar volume increased as Eu2O3 content increased. The Rm, αm, RL, εstatic, and εoptical vary from 16.24 to 17.20 cm3/mol, 6.44 × 10−24 cm3‒17.20 × 10−24 cm3, 0.17–0.19, 5.71–6.55, and 4.71–5.55 respectively, with TPEu-0 and TPEu-1 having the maximum and minimum values, respectively. Generally, the increase in Eu2O3 concentration increased the charged radiation shielding ability of the glasses. The increment in the Eu2O3 content of the glasses brought about an improvement in the thermal and fast neutron absorption probabilities of the glasses.

Li-ion transport studies of NASICON-type LiZr2(PO4)3 solid electrolyte crystallizing in rhombohedral structure at room temperature

Li-ion conducting solid electrolytes exhibiting NASICON structure have received promising research interest for their potential applications in safer all-solid-state Li-ion batteries. LiZr2(PO4)3 (LZP) belongs to the NASICON-type of materials exhibiting Li-ion conduction and furthermore offers lower interfacial resistance and good electrochemical stability against the Li-metal. LZP is known to crystallize in four polymorphs, namely monoclinic, orthorhombic, triclinic, and rhombohedral, and further, LZP crystallizing in rhombohedral structure is known to exhibit the highest ionic conductivity. The present work demonstrates the synthesis of LZP exhibiting rhombohedral structure at room temperature using the modified sol-gel method at a lower sintering temperature (900 °C). The effect of sintering temperature on the structural and transport behavior of LZP is studied by XRD, SEM, and impedance spectroscopy techniques. The complex impedance plots show the presence of two depressed semicircles associated with different capacitance values, indicating both bulk and grain boundary conductions. The bulk, grain boundary and total conductivity of LZP sintered at different temperatures are calculated. The bulk conductivity of LZP is found to increase with increase in the sintering temperature from 800 °C to 1100 °C, whereas LZP sintered at 900 °C exhibits the highest total conductivity value at room temperature, indicating the significant role of the grain boundary conductions in the total conductivity of LZP material. The transport results of LZP sintered at different temperatures are discussed with their unit cell volume (XRD), relative density (Archimedes method), and microstructure (SEM). Furthermore, the ionic transport number measurement by dc polarization shows that the major charge carriers are the ions and the electrochemical stability measurements by both cyclic voltammetry and linear sweep voltammetry show its stability with Li-metal is up to 5.1 V.

Al2O3/GdAlO3 reaction sintered composites produced from milled powders: Microstructure, neutron-capture cross section, and mechanical properties

The incorporation of high thermal neutron capture elements in ceramic materials is relevant for the design of traceable proppants for obtaining information in petrology, such as the location and height of fractures in unconventional gas and oil wells. Among these, GdAlO3 has attracted interest because of its good thermo-mechanical properties. In this work, four Al2O3/GdAlO3 reaction sintered composites were prepared using Gd2O3 and Al2O3 powders as raw materials and high-energy ball milling followed by sintering at 1600 °C. This combination of ball milling and reaction sintering is considered as a mechanism to produce large bulk ceramics with different Al2O3/GdAlO3 compositions. The composite formulations range from pure alumina to eutectic ceramic. The obtained materials were characterized using X-ray diffraction for identifying the crystalline phases, Archimedes method for the textural properties, scanning electron microscopy for the microstructure, and Vickers indenter and three-point bending tests for the mechanical properties. In addition, the macroscopic capture cross-section Σ for thermal neutrons was estimated considering each composite formulation. It was found that the processing route is very suitable for producing low-porosity Al2O3/GdAlO3 composites, which present similar mechanical properties to those of alumina. Both the material density and Σ increase with increasing the starting amount of Gd2O3, in a way that for the eutectic composite the density is 50% higher than that of pure alumina, and Σ is about 550000 c.u. The effect of the material porosity on Σ was also considered. The obtained results indicate that the proposed processing route is very attractive for producing these ceramic composites for technological applications.

Fluid Circulation Effects on Torque and Drag Results, Modeling, and Validation

Summary The hydraulic effects on torque and drag modeling have been thoroughly studied in the past, yet their interpretation still causes a lot of misunderstandings and confusion. Historical models disregard the circulation effects and focus on the fluid mass by employing buoyancy forces based on the Archimedes principle. On the other hand, the reference model including the fluid circulation effects, introduced by R. F. Mitchell in the 1990s, consists in computing the forces due to internal and external fluids along the drillstring. The first type of model (called the Archimedes method) directly produces an effective tension, while the second one (generally called the pressure area method) produces a true tension that must be further transformed to obtain the effective tension. These different forms of tensions add even more confusion. By returning to the basic equations of the fluid effects on the drillstring, an equivalency between Archimedes and pressure area models has been found for the case with no circulation. Furthermore, with the same principle, an Archimedes-like model is deduced for the case of fluid circulation, where the effects of fluid pressures, frictions, and flows could be more easily interpreted. These two hydraulic models, after implementation in a true stiff-string 3D model, enable them to fairly compare the two approaches in terms of forces applied on the structure. The comparison of this Archimedes formulation with pressure area model gave sensibly the same results for various scenarios, proving the equivalency of the two approaches even with the case of circulating fluid. In addition to the model-to-model comparisons, torque and drag results are compared to field experiments at different depths. The flow rate was varied while reciprocating the drillstring up and down, and the hookload was recorded for each flow rate and each tripping direction. The model-to-data comparisons showed a good agreement between the theoretical results and experimental data. An advanced Archimedes method with all fluid circulation effects has been developed. By tackling the problem of circulating fluid in the drillstring using two different approaches and proving their equivalency, a better understanding of the hydraulic effects can be achieved, which in terms can help settle the possible debates and confusion that might arise by drilling engineers.

The effects of pressure and pressure routes on the microstructural evolution and mechanical properties of sintered copper via SPS

Spark Plasma Sintering (SPS) is a pressure-assisted sintering process in which high density and mechanical properties are usually reached. This study applied the SPS to consolidate copper powder using different sintering pressures and pressure routes during holding time or heating. In the first route, the pressure was maintained (around 15 MPa) during the heating up to the sintering temperature (650 ºC), and the pressure was increased during the holding time. In the second route, the pressure was raised during the heating and kept constant during holding time at 650 ºC. Three different pressure levels were applied on each route: 110, 65, and 50 MPa. Microstructural evolution was investigated using densification (Archimedes method), scanning electron microscopy (SEM), hardness, and X-ray diffraction (XRD). The increase in pressure improves the microstructural features. In addition, in the first route, in which higher pressure rates were found, grain growth inhibition was observed, and densification was also improved significantly. The smallest crystallite size and highest microstrain were also observed at higher pressures. The increase in pressure also led to a rise in microhardness (17%), a decrease in pore volume fraction (10.5%), and an increase in pore circularity, causing substantial variations between the microstructures of samples. A finite element method (FEM) analysis was conducted using a thermo-mechanical approach to evaluate the stress distribution in the two different sintering routes. The results agree with the experimental results, and more pronounced effects were found in the first route because of higher compressive stresses, corroborating the results of microstrain and hardness.

Role of TiO2 addition on recycling of TV screen waste glasses: Experimental and theoretical studies on structure and radiation attenuation properties

Using the powder metallurgy, TiO2-doped TV screen glass ceramic samples were prepared with TiO2 concentrations of 0 (S-TV), 10 (S-TV/Ti10), and 20 (S-TV/Ti20) wt%. The TV screen glass was collected from a damaged TV's CRT. The fabricated materials were investigated for their physical, structural, and radiation-shielding attributes. The chemical composition of the prepared glasses was analysed with the aid of the X-ray fluorescence (XRF) method. The crystalline phase and microstructure of the glass ceramics were studied through the X-ray diffraction (XRD) method and scanning electron microscope (SEM), respectively. The density and Vickers hardness of the sample were determined by the Archimedes method and a micro hardness tester, respectively. The absorption parameters of electrons, protons, alpha particles, carbon ions, fast neutrons, and thermal neutron were calculated from various software and analytic expressions. The XRD spectra of the samples showed the presence of distinct crystalline peaks associated with TiO2, SiO2, and Ba2SiO4. The SEM images revealed that crystalline structures nucleated and increased with coarser crystalline grains when the amount of TiO2 was increased. The densities of the glass ceramics were 2.525, 2.546, and 2.285 g/cm3 for the S-TV, S-TV/Ti10, and S-TV/Ti20 samples, respectively while the corresponding Vickers hardness values were 495, 540, and 578 HV. The projected range of electrons, protons, alpha particles, and heavy carbon ions were within the limits 2.78–32182.18 μm, 0.215–1400 μm, 0.154–130.54 μm, and 0.053–14.10 μm in S-TV, 2.76–31991.36 μm, 0.205–1320 μm, 0.147–122.05 μm, and 0.049–13.11 μm in S-TV/Ti10, and 2.84–32824.95 μm, 0.212–1360 μm, 0.151–125.55 μm, and 0.051–13.45 μm in S-TV/Ti20, respectively. Among the three samples, S-TV was the best thermal neutron absorber, while S-TV/Ti10 is most effective in slowing down fast neutrons. The optimum TiO2 doping content for enhancing the charged particle and fast neutron moderating abilities of TV screens is 10 wt%.

SPS preparation of La10Si6O27 and the effect of sintering temperature on electrical conductivity

La10Si6O27 powder was synthesized by a high-energy ball milling method and its sintered body was prepared by spark plasma sintering (SPS) technology. Phase structure, microscopic morphology, density, porosity and oxide ion conductivity of La10Si6O27 were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Archimedes method and alternating current (AC) impedance spectrum, respectively. XRD results showed the ball-milled powder could form apatite-type La10Si6O27 at 1400 ℃. The crystal structure of La10Si6O27 sintered body remained stable. SEM results showed that La10Si6O27 sintered body using SPS sintering method had better sintering between grains and a large reduction in open pores compared to conventional sintering. Grains of the sintered body were clearly visible and the grain size was uniform, about 1 µm. Archimedes method analysis showed relative density of La10Si6O27 sintered body is 100%, and open porosity is 0. Electrical conductivity of La10Si6O27 sintered body has an Arrhenius relationship with temperature.

Characterization of Argentine dolostones with potential application in the manufacture of refractory materials

The chemical, mineralogical, mechanical, thermal and textural characterization of two samples of dolostones of Argentine origin has been carried out. In this work the samples were: rock fragments approximately 10 cm on a side, rock fragments approximately 1 cm on a side, powder <7200 μm (obtained from rock 1 cm by trituration) and powder <100 μm (obtained from powder <7200 μm by ball mill grinding). For the characterization of the rocks, analytical techniques were used. Particle size distributions were performed by sieving (for the samples <7200 μm) and laser granulometry (for the samples <100 μm) and the specific surface was determined by BET method. The chemical composition was determined by XRF technique. The mineralogical analysis was performed by XRD technique and complemented with Rietveld analysis for the quantification of the mineralogical phases. In addition, the FTIR technique was used to complement the previous spectroscopic technique. The pycnometric density was measured using kerosene as immersion liquid. The bulk density and porosity (open, close and total porosity) of the rocks were carried out on rock fragments 3 cm on a side, using Archimedes method employing kerosene as immersion liquid and complemented with the mercury porosimetry technique. The ceramic texture analysis was carried out by SEM. The mechanical strength to diametrical compression of the rocks was determined on cylindrical specimens, taking into account the ASTM D-3967-16 standard. Finally, the thermal behaviour of the rocks was carried out by thermogravimetric and differential thermal analysis (TGA/DTA); the setting was: 1300 °C in the air atmosphere. The loss on ignition (LOI) was calculated with four thermal techniques: ISO 10058:1992 standard, TGA technique, muffle test (ad hoc method), and a designed method. The results have shown that the rocks studied fall into the classification of “dolostones” with the majority constituent mineral being “dolomite”. The chemical profiles analysed and the content of impurities are within potential range for refractory application.