Helium Pycnometer Research Articles

3D-printed MOF/MoS2 aerogel for dye adsorption and photocatalytic degradation

The escalating challenge of water resources contamination, attributed to toxic pollutants, requires urgent attention from both governments and society. Furthermore, the inefficacy of conventional water treatment methods emphasizes the critical necessity for exploring the development of affordable, renewable, and high-performance materials, which should, for instance, enable the mutual adsorption and photocatalytic degradation of organic pollutants. Here we employed the 3D printing technique to manufacture an aerogel based on alginate, gelatin, and carboxymethylcellulose incorporated with 5 and 7.5 wt % of MOF/MoS2. FTIR spectra and EDS analysis evidenced the presence of MOF/MoS2 in the structure of the aerogels, while Helium pycnometer analysis and SEM micrographs demonstrated that the aerogels presented low density and a porous structure with porosity above 80 %. The swelling test showed that the aerogels displayed a high water absorption capacity (1400 %) after 70 h of immersion. The rheology test demonstrated that elastic behavior prevails over viscous behavior (G' > G″) and the incorporation of 7.5 wt % MOF/MoS2 favored shear thinning and viscosity recovery in the hydrogel. Adsorption tests to methylene blue (employed as a model) showed that the aerogel (HD) without the presence of MOF/MoS2 and the aerogels HD/MOF/MoS2 5 % and MOF/MoS2 7.5 % showed removal efficiencies of 16.77 %, 28.66 %, and 95.86 %, respectively. Conversely, the photodegradation test showed that HD/MOF/MoS2 5 % and HD/MOF/MoS2 7.5 % had an efficiency of 89 % and HD of 80 %. Therefore, our results demonstrate that the developed aerogels are promising candidates for the adsorption and photodegradation of dye while being low-cost, environmentally friendly, and easy to manufacture.

Change in Microstructure, Mechanical Strength, Fire Resistance, and Radiation Attenuation Properties of Gypsum Plaster with Boric Acid

AbstractIn this study, the effect of boric acid addition on the microstructure of gypsum plaster was investigated to determine an environmentally friendly gypsum additive that may enhance mechanical strength, fire resistance, and X-ray radiation attenuation properties. The mechanical strengths of bare gypsum and boric acid-added (0–0.5% by weight with respect to gypsum amount) gypsum plasters were evaluated in terms of compressive and bending strengths. The effects of the different addition procedures of boric acid (0.1% by wt.) on the fire resistance of the gypsum plasterboard were also evaluated. X-ray radiation attenuation properties of boric acid-added (0.1% by wt.) gypsum plasterboard were investigated as well. XRD, ATR-FTIR, Helium pycnometer, N2 adsorption–desorption, and SEM analysis were performed to determine the microstructural properties of gypsum plaster. XRD and ATR-FTIR analysis revealed that boric acid did not change the calcium sulfate dihydrate structure of gypsum plaster. Whereas, Helium pycnometer, N2 adsorption–desorption, and SEM analysis showed that the physical properties of gypsum changed with an increase in pore volume, skeletal density, and particle size after boric acid addition. The increase in the pore volume and particle size decreased the mechanical strength of gypsum. However, boric acid addition on the gypsum plaster plate, especially using the spraying method, enhanced the fire resistance of gypsum. Additionally, boric acid slightly enhanced the X-ray radiation attenuation properties (0.7%) of the gypsum plasterboard.

Structure and physicochemical characteristics of the glasses in the system Na2O/BaO/ZrO2/TiO2/SiO2/B2O3/Al2O3 – Influence of the ZrO2 addition on the physico-chemical and mechanical properties

Glasses with the compositions 20.1Na2O∙(23.1-y)BaO∙yZrO2∙23TiO2∙9.8B2O3∙21SiO2∙3Al2O3 with y = 0, 0.5, 1, 2, 3 and 6 mol% were prepared using a traditional melt-quenching technique. The thermophysical properties, i.e. glass transition temperature, Tg and crystallization peak maximum temperature, Tc were determined for the obtained glasses by differential scanning calorimetry and showed that increasing zirconium oxide concentrations resulted in an increasing Tc and an initial decrease followed by an increase of Tg values. The difference Tc-Tg, used as glass stability criterium, increases for ZrO2 concentrations up to 2 mol% and then starts to decrease for the compositions with higher zirconium oxide concentration. The densities were measured by using a helium pycnometer and served to determine main physico-chemical characteristics of the prepared glasses such as molar volume, oxygen packing density and refractive index. The obtained results reveal that the values of the density and of all estimated physico-chemical characteristics increase with increasing ZrO2 concentrations. X-ray photoelectron spectroscopy showed that all elements from the glass composition are present in oxide states with Zr4+ ions being only in octahedral coordination while Ti4+ ions are of 6-, 5- and 4-fold coordination to oxygen. The structure of the glasses was studied by Fourier Transformed Infrared Spectroscopy on powdered samples and the existence of Si–O–Si/O–B–O bending, Si–O–Si rocking, B–O–B bending and B–O–B/B–O–Si stretching vibrations was observed. The presence of BO3, BO4 and SiO4 polyhedra as interconnected as well as isolated structural units and the occurrence of some TiO62− and a larger number of TiO4 and mainly of TiO5− units is suggested. At 570-580 cm−1, a peak typical for the compound BaTiO3 is also registered for all samples. The conducted depth-sensing indentation on the obtained glasses allowed to determine mechanical properties such as universal and indentation hardness, elastic modulus and elastic part of indentation work. Increasing the ZrO2 concentration resulted in increasing elastic moduli which together with the DSC data implies that the addition of ZrO2 leads to structural changes in the glass network and enhanced mechanical properties which results in increased hardness.

Biosorption of nickel and cadmium using Pachira aquatica Aubl. peel biochar

This study aimed to assess the value of Pachira aquatica Aubl. fruit peels by exploring their applicability in the biosorption process for the removal of Ni(II) and Cd(II) metal ions. The Pachira aquatica Aubl. fruit peel biochar (PAB) was extensively characterized through various techniques, including proximate analysis, helium pycnometer, XRD, SEM, point of zero charge determination, zeta potential measurement, and Boehm titration. Subsequently, kinetic, isotherm, and thermodynamic batch biosorption studies were conducted, followed by column biosorption tests. The characteristics of PAB, including low moisture content, a neutral point of zero charge, porosity, an irregular and heterogeneous structure, a negatively charged surface, and the presence of functional groups, indicate its remarkable capacity for efficiently binding with heavy metals. Biosorption equilibrium time was achieved at 300 min for both ions, fitting well with a pseudo second-order kinetic model and Langmuir isotherm model. These data suggest that the biosorption process occurred chemically in monolayer. The column C presented an exhaust volume of 1200 mL for Ni(II) and 1080 for Cd(II) and removal of 98% and 99% of removal for Ni(II) and Cd(II), respectively. In summary, PAB demonstrates substantial potential as a biosorbent for effectively removing heavy metals, making a valuable contribution to the valorization of this co-product and the mitigation of environmental pollution.

Textural evidence of fragmentation and densification processes in a fossilised shallow conduit on the flank of Nevados de Chillán Volcanic Complex

Eruptive style transitions are common in silicic volcanoes and an improved understanding of transitional controls is necessary for hazard forecasting. Examples of hybrid eruptions where both explosive and effusive eruptive behaviours occur simultaneously have led to a re-examination of models used to understand these complex and poorly understood processes. Exposed fossilised conduits record evidence of magmatic processes and provide the opportunity to examine structures and textures related to these transitions. Here we present a conceptual model of the evolution of a narrow (2.5 m wide) conduit located on the SW flank of the Nevados de Chillán Volcanic Complex, Chile. This conduit records evidence of fragmentation and densification processes through intercalated and juxtaposed banded, porous and dense domains. To understand how the products of each eruptive style relate and evolve during conduit formation, we combined qualitative textural analyses at different scales (outcrop, optical microscope and electron microscope), pore size and shape measurements using ImageJ, connected porosity measurements made using a helium pycnometer and total water content measurements using Fourier transform infrared spectroscopy. The results allow us to identify five principal phases of the conduit evolution: (I) an explosive phase where the conduit is filled with pyroclastic material, evidenced in the pyroclastic deposit preserved at the conduit wall, (II) a cyclic process of fragmentation and densification within the conduit that generates intercalation of the porous and dense domains, and leads to a hybrid explosive-effusive phase, (III) the formation of a dense magma plug that eventually seals the conduit and deforms vesicles and bands, (IV) the compaction of the pyroclastic domain due to the ascent of the plug, driving porosity reduction (to as little as 3% in the densest bands), with micro-folds and glassy fiamme, and (V) a final phase of post-sintering vesicle relaxation, yielding regular, mainly rounded, shapes. We compare our results with other exposed and examined conduits to propose a model of conduit evolution during small-volume, short-lived silicic eruptions.

Pozzolanic Metakaolin Reactions: Stoichiometric and Kinetic Modeling

In the pursue of environmentally-friendly binders for the construction industry, metakaolin (MK) has emerged as promising material, with its hardening performance primarily driven by pozzolanic reactions. However, in systems containing MK and calcium hydroxide (CH), transformation reactions from metastable to stable phases, particularly in excessive CH conditions, can adversely affect material properties. To anticipate these processes, this study introduces a stoichiometry-based reaction modeling approach for pozzolanic MK reactions, encompassing both short-term kinetics and long-term transformation processes. The primary pozzolanic reactions of MK are briefly outlined, highlighting two sequential, partially overlapping reactions forming C4AH13 and C2ASH8. Short-term reaction kinetics are modeled using isothermal calorimetry measurements and deconvoluting the two reaction peaks. The model is in good agreement with experimental quantitative X–ray diffraction (qXRD), thermogravimetric analysis (TGA) and helium pycnometer (density, i.e. solid volume) results. Model limitations are discussed based on qualitative scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) analysis. Leveraging the proposed model, the temperature dependency of pozzolanic MK reactions is analyzed, revealing an activation energy for the primary reaction of 84 kJ/mol. The model is intended to lay a foundation for designing innovative binder systems based on metakaolin, while paving the way for sustainable construction in the future.

Investigating the mechanisms of hydraulicity regeneration in pure C3S paste

The study introduces a technique to regenerate hydraulicity in C3S by thermally treating powders from crushed hydrated alite cubes at various temperatures (ranging from 400 °C to 800 °C). Several characterization techniques, including XRD, FTIR, 29Si-NMR, SEM, and helium pycnometer were used to comprehend the mechanisms behind hydraulicity regeneration. XRD analysis showed anhydrous binder powders with β-C2S, Calcite, and calcium oxide phases after heat treatment, with β-C2S appearing at 600 °C. Hydration of regenerated binders resulted in Portlandite and Calcite phases, and the amorphous phase increased with curing due to the C-S-H formation confirmed by FTIR peaks. NMR analysis revealed distinct characteristics in TP800's C-S-H compared to the original C3S paste, primarily due to shorter chain lengths.

Multimodule imaging of the hierarchical equine hoof wall porosity and structure

The equine hoof wall has a complex, hierarchical structure that can inspire designs of impact-resistant materials. In this study, we utilized micro-computed tomography (μ-CT) and serial block-face scanning electron microscopy (SBF-SEM) to image the microstructure and nanostructure of the hoof wall. We quantified the morphology of tubular medullary cavities by measuring equivalent diameter, surface area, volume, and sphericity. High-resolution μ-CT revealed that tubules are partially or fully filled with tissue near the exterior surface and become progressively empty towards the inner part of the hoof wall. Thin bridges were detected within the medullary cavity, starting in the middle section of the hoof wall and increasing in density and thickness towards the inner part. Porosity was measured using three-dimensional (3D) μ-CT, two-dimensional (2D) μ-CT, and a helium pycnometer. The highest porosity was obtained using the helium pycnometer (8.07%), followed by 3D (3.47%) and 2D (2.98%) μ-CT. SBF-SEM captured the 3D structure of the hoof wall at the nanoscale, showing that the tubule wall is not solid, but has nano-sized pores, which explains the higher porosity obtained using the helium pycnometer. The results of this investigation provide morphological information on the hoof wall for the future development of hoof-inspired materials and offer a novel perspective on how various measurement methods can influence the quantification of porosity.

The effect of expanded natural graphite added at different ratios of metal hydride on hydrogen storage amount and reaction kinetics

In this study, metal hydride pellets were formed to accelerate the hydrogen charge/discharge processes. The heat transfer in hydrogen storage material was improved by employing Expanded natural graphite (ENG). The ideal grinding time for LaNi5 material was determined to be 5 h. In the study, LaNi5 alloy was mixed with ENG in 1%, 5%, 10%, and 20% proportions by weight. The amount of hydrogen stored in the reactor by each mixture at 10 bar pressure was measured depending on time. Within the scope of experimental studies, the thermal conductivity coefficient of LaNi5 materials containing 20% ENG by weight was increased by 1380%. Thus, hydrogen charge/discharge processes were accelerated. Storage materials were characterized by XRD and SEM. The thermal conductivity coefficients were measured with the Hot Disk Thermal Constants Analyzer device, and the densities were measured with the Helium Pycnometer device. LaNi5 was chosen as the storage material in the study. It was found that 1–5 wt% ENG addition increased the reaction kinetics without significantly reducing the hydrogen storage capacity in storage alloys. However, in alloys with higher ENG concentrations, the hydrogen storage capacity decreased. The reaction kinetics were increased in the range of 135–260%.

Production and Characterization of Calcium Silica Aerogel Powder as a Food Additive.

In this study, mesoporous calcium silica aerogels were produced for use as an anticaking food additive in powdered foods. A low-cost precursor (sodium silicate) was used, and calcium silica aerogels with superior properties were obtained with different pH values (pH 7.0 and pH 9.0) by modeling and optimizing the production process. The Si/Ca molar ratio, reaction time, and aging temperature were determined as independent variables, and their effects and interactions to maximize the surface area and water vapor adsorption capacity (WVAC) were evaluated by response surface methodology and analysis of variance. Responses were fitted with a quadratic regression model to find optimal production conditions. Model results showed that the maximum surface area and WVAC of the calcium silica aerogel that was produced with pH 7.0 were achieved at a Si/Ca molar ratio of 2.42, a reaction time of 5 min, and an aging temperature of 25 °C. The surface area and WVAC of calcium silica aerogel powder produced with these parameters were found to be 198 m2/g and 17.56%, respectively. According to the results of surface area and elemental analysis, calcium silica aerogel powder produced at pH 7.0 (CSA7) had the best results compared to that produced at pH 9.0 (CSA9). Therefore, detailed characterization methods were examined for this aerogel. The morphological review of the particles was performed with scanning electron microscopy. Elemental analysis was performed via inductively coupled plasma atomic emission spectroscopy. True density was measured in a helium pycnometer, and tapped density was calculated by the tapped method. Porosity was calculated using an equation using these two density values. The rock salt was powdered with a grinder and used as a model food for this study, and CSA7 was added at a rate of 1% by weight. The results showed that adding CSA7 powder to the rock salt powder at a rate of 1% (w/w) improved the flow behavior from the cohesive region to the easy-flow region. Consequently, calcium silica aerogel powder with a high surface area and high WVAC might be considered as an anticaking agent to use in powdered foods.

Probing the Pore Structure of the Berea Sandstone by Using X-ray Micro-CT in Combination with ImageJ Software

During diagenesis, the transformation of unconsolidated sediments into a sandstone is usually accompanied by compaction, water expulsion, cementation and dissolution, which fundamentally control the extent, connectivity and complexity of the pore structure in sandstone. As the pore structure is intimately related to fluid flow in porous media, it is of great importance to characterize the pore structure of a hydrocarbon-bearing sandstone in a comprehensive way. Although conventional petrophysical methods such as mercury injection porosimetry, low-pressure nitrogen or carbon dioxide adsorption are widely used to characterize the pore structure of rocks, these evaluations are based on idealized pore geometry assumptions, and the results lack direct information on the pore geometry, connectivity and tortuosity of pore channels. In view of the problems, X-ray micro-CT was combined with ImageJ software (version 1.8.0) to quantitatively characterize the pore structure of Berea Sandstone. Based on its powerful image processing function, a series of treatments such as contrast enhancement, noise reduction and threshold segmentation, were first carried out on the micro-CT images of the sandstone via ImageJ. Pores with sizes down to 2.25 μm were accurately identified. Geometric parameters such as pore area, perimeter and circularity could thus be extracted from the segmented pores. According to our evaluations, pores identified in this study are mostly in the range of 30–180 μm and can be classified into irregular, high-circularity and slit-shaped pores. An irregular pore is the most abundant type, with an area fraction of 72.74%. The average porosity obtained in the image analysis was 19.10%, which is fairly close to the experimental result determined by a helium pycnometer on the same sample. According to the functional relationship between tortuosity and permeability, the tortuosity values of the pore network were estimated to be in the range of 4–6 to match the laboratory permeability data.

Mechanical and physical properties of synthetic sustainable geopolymer binders manufactured using rockwool, granulated slag, and silica fume

The substantial target of this work is to manufacture sustainable geopolymers by recycling low cost industrial wastes (granulated slag, GS; rockwool, RW; and silica fume, SF). To reveal the mineral and chemical compositions of these industrial solid wastes, they were investigated using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). The granulated slag, rockwool and silica fume were blended with the convenient quantity of alkaline reactor to formulate a hydrated pattern of geopolymers. The phase configuration, physico-mechanical effects [compressive strength (CS), porosity and bulk density] and the microstructural form of the geopolymers were studied via the X-ray diffraction, hydraulic mechanical testing device, helium pycnometer, and Field emission Scanning electron microscope (FE-SEM), respectively. The results declared that the partial substitution of RW by various ratios of SF in presence of GS affect successfully on the physico-mechanical properties of hardened geopolymers. Implication of 2 % SF boosts the physico-mechanical features of the 50GS-48RW hardened geopolymers at all curing ages especially at the age of 28 days. Therefore, the geopolymer 50GS-48RW-2SF displayed the best physico-mechanical characteristics especially the CS at 28-days (39.12 MPa) owing to the formation of diverse hydration products like CSHS, CAHS and NASHs. These results were confirmed via FE-SEM/EDX images that exhibited compact and dense microstructure rod-like crystals of CSHs and three dimensional framework structures of NASHs.

Assessment of physical, mechanical, and chemical properties of Dendrocalamus asper bamboo after application of wetting and drying cycles

Given the hygroscopic nature of bamboo and its reduction in strength with increasing moisture content, we evaluated the effects of hornification – generated through the application of drying and rewetting cycles – on the physical, mechanical, and chemical properties of the culms of Dendrocalamus asper. Our objective was to assess if the treatment would cause a reduction in water uptake, an increase in the dimensional stability of bamboo, and a stiffening of the material, increasing its mechanical strength. Specimens were submitted to a maximum of 15 cycles, being immersed at room temperature (22 ± 3 °C) and dried at 50 ± 5 °C. Absorption capacity, dimensional stability, density as measured with a helium pycnometer, tensile tests, scanning electron microscopy (SEM) analysis, X-ray diffractometer (XRD) and Fourier-transform infrared spectroscopy (FT-IR) were undertaken. Hornification increased the dimensional stability of bamboo proportionally to the number of cycles applied, and a 5.8 % increase in cross section was seen after 264 h for 15 cycles. The control samples increased by 17.8 %. Reduction in the water absorption was not verified for treated bamboo. The elastic modulus was maintained and the tensile strength after treatment was reduced (258.6 MPa for control and 207.5 MPa after 15 cycles). Chemical analysis and microscopy did not show any significant changes in the composition of the bamboo after the application of wetting and drying cycles.

Microstructure of zirconium carbide ceramics synthesized by spark plasma sintering

Zirconium carbide (ZrC) samples were prepared by spark plasma sintering (SPS), at temperatures of 1700 °C, 1900 °C and 2100 °C, all at pressure of 50 megapascal (MPa). The density of ZrC ceramic pellets was measured using a Micromeritics AccuPyc II 1340 Helium Pycnometer. The density of ZrC ceramic pellets was found to increase from (6.51 ± 0.032) g/cm3 to (6.66 ± 0.039) g/cm3 and (6.70 ± 0.017) g/cm3 when the temperature of the SPS was increased from 1700 oC to 1900 oC and 2100 oC respectively. Moreover, the hardness of ZrC ceramic pellets were measured using Rockwell hardness test. The hardness of ZrC ceramic pellets increased from (7.4 ± 0.83) to (17.0 ± 0.073) and (18.4± 0.05) gigapascals (GPa) at temperatures of 1700 oC, 1900 oC and 2100 oC respectively. X-ray diffraction shows the absence of spurious phases or impurity. XRD results showed that, all prepared ZrC samples has the same preferred orientation of the planes (i.e., 200). Furthermore, the average grain size of ZrC was calculated using Sherrers’s equation. The average grain size of the pure ZrC powder increased from 67.46 nm to 72 nm, 79 nm and 83 nm when the ZrC powder was sinteried at temperatures of 1700 oC, 1900 oC and 2100 oC respectively. The differences in the average grain size between the prepared samples leads to show different surface morphologies that monitored by scanning electron microscopy (SEM).

Compression Modulus and Apparent Density of Polymeric Excipients during Compression-Impact on Tabletability.

The present study focuses on the compaction behavior of polymeric excipients during compression in comparison to nonpolymeric excipients and its consequences on commonly used Heckel analysis. Compression analysis at compaction pressures (CPs) from 50 to 500 MPa was performed using a compaction simulator. This study demonstrates that the particle density, measured via helium pycnometer (ρpar), of polymeric excipients (Kollidon®VA64, Soluplus®, AQOAT®AS-MMP, Starch1500®, Avicel®PH101) was already exceeded at low CPs (<200 MPa), whereas the ρpar was either never reached for brittle fillers such as DI-CAFOS®A60 and tricalcium citrate or exceeded at CPs above 350 MPa (FlowLac®100, Pearlitol®100SD). We hypothesized that the threshold for exceeding ρpar is linked with predominantly elastic deformation. This was confirmed by the start of linear increase in elastic recovery in-die (ERin-die) with exceeding particle density, and in addition, by the applicability in calculating the elastic modulus via the equation of the linear increase in ERin-die. Last, the evaluation of “density under pressure” as an alternative to the ρpar for Heckel analysis showed comparable conclusions for compression behavior based on the calculated yield pressures. However, the applicability of Heckel analysis for polymeric excipients was questioned in principle. In conclusion, the knowledge of the threshold provides guidance for the selection of suitable excipients in the formulation development to mitigate the risk of tablet defects related to stored elastic energy, such as capping and lamination.

Modelling textural and mass transfer properties for gamma‐alumina catalysts using randomly generated pore networks

AbstractA Monte Carlo approach is used to generate 2D and 3D networks of randomly connected cylindrical pores with a variety of configurations. These networks are created to represent the gamma‐alumina supports of hydrotreating catalysts. Textural properties from generated pore networks are compared with experimental values of porosity, specific surface area, and specific pore volume. The experimental properties were estimated using a helium pycnometer and nitrogen sorption isotherms for five gamma‐alumina samples. Simulated and experimental textural properties concur. Internal diffusion is simulated by 1D Fick diffusion within each pore of the network. A macroscopic diffusion parameter for vacuum distillate type molecules, previously obtained by inverse liquid chromatography and by pulsed‐field gradient nuclear magnetic resonance experiments on alumina samples, is predicted and confronted with experimental values. Diffusional properties are in good agreement when considering two hierarchically organized porous domains.

Density of water adsorbed on bentonites: Determination and effect on microstructural void ratio modelling

The ability of helium gas displacement pycnometry to characterise the reduction of adsorbed water density with increasing bentonite water content was tested. For this purpose, after obtaining the grain density (which was assumed to be constant), an intensive campaign of 45 experiments was carried out with two bentonites for a total of 90 determinations, obtaining very consistent water density results. Furthermore, the water retention curve of one of the two bentonites was fully characterised by 95 tests with a chilled-mirror dew-point psychrometer. The water content results were used to determine the microstructural void ratio, both assuming a constant water density and considering the variation of the adsorbed water density obtained with the helium pycnometer. It was verified that with the constant value, by assuming a lower water density (1 g/cm3) than the experimental (values of 1.20 g/cm3 were obtained under hygroscopic conditions), higher values of microstructural void ratios are predicted, up to 15% greater for a relative humidity of 70% (0.46 instead of 0.40). For higher relative humidities the comparison loses its consistency, since the presence of capillary water cannot be disregarded, and the calculation of the microstructural void ratio is based on the assumption that the water present in bentonite is mainly in the form of adsorbed water. However, this does not compromise the analysis performed, as the results obtained for lower relative humidity values provide enough information to demonstrate the relevance of the errors that can occur when deriving models of the microstructural void ratio without taking into account the variation of the density of adsorbed water.

Characterization of Al2O3 Samples and NiAl-Al2O3 Composite Consolidated by Pulse Plasma Sintering.

The paper describes an investigation of Al2O3 samples and NiAl–Al2O3 composites consolidated by pulse plasma sintering (PPS). In the experiment, several methods were used to determine the properties and microstructure of the raw Al2O3 powder, NiAl–Al2O3 powder after mechanical alloying, and samples obtained via the PPS. The microstructural investigation of the alumina and composite properties involves scanning electron microscopy (SEM) analysis and X-ray diffraction (XRD). The relative densities were investigated with helium pycnometer and Archimedes method measurements. Microhardness analysis with fracture toughness (KIC) measures was applied to estimate the mechanical properties of the investigated materials. Using the PPS technique allows the production of bulk Al2O3 samples and intermetallic ceramic composites from the NiAl–Al2O3 system. To produce by PPS method the NiAl–Al2O3 bulk materials initially, the composite powder NiAl–Al2O3 was obtained by mechanical alloying. As initial powders, Ni, Al, and Al2O3 were used. After the PPS process, the final composite materials consist of two phases: Al2O3 located within the NiAl matrix. The intermetallic ceramic composites have relative densities: for composites with 10 wt.% Al2O3 97.9% and samples containing 20 wt.% Al2O3 close to 100%. The hardness of both composites is equal to 5.8 GPa. Moreover, after PPS consolidation, NiAl–Al2O3 composites were characterized by high plasticity. The presented results are promising for the subsequent study of consolidation composite NiAl–Al2O3 powder with various initial contributions of ceramics (Al2O3) and a mixture of intermetallic–ceramic composite powders with the addition of ceramics to fabricate composites with complex microstructures and properties. In composites with complex microstructures that belong to the new class of composites, in particular, the synergistic effect of various mechanisms of improving the fracture toughness will be operated.

The Influence of Sewage Sludge Content and Sintering Temperature on Selected Properties of Lightweight Expanded Clay Aggregate.

Wastewater treatment processes produce sewage sludge (SS), which, in line with environmental sustainability principles, can be a valuable source of matter in the production of lightweight expanded clay aggregate (LECA). The literature on the influence of SS content and sintering temperature on the properties of LECA is scarce. This paper aims to statistically evaluate the effects of SS content and sintering temperature on LECA physical properties. Total porosity, pore volume, and apparent density were determined with the use of a density analyzer. A helium pycnometer was utilized to determine the specific density. Closed porosity was calculated. The test results demonstrated a statistically significant influence of the SS content on the specific density and water absorption of LECA. The sintering temperature had a significant effect on the specific density, apparent density, total porosity, closed porosity, total volume of pores, and water absorption. It was proved that a broad range of the SS content is admissible in the raw material mass for the production of LECA.

Utilizing mining dam bottom sludge as a novel adsorbent for AuO removal from wastewaters: Batch and column studies

In this study, the adsorption of Auramine O (AuO) dye using bottom sludge (BS) was investigated in batch and continuous systems. The BS was characterized by EDX, BET, XRD, DLS, ζ-potential, SEM, FTIR, helium pycnometer, and mercury porosimetry. The kinetic and isotherm data were fitted to pseudo-second-order and Langmuir models. The maximum amount of adsorption calculated from the Langmuir isotherm model was 5.09 mg/g. Thermodynamic studies showed that adsorption was endothermic and occurred spontaneously. Thomas, Clark, and Yoon-Nelson models were suitable (R2 > 0.95 for all these models) to explain the dynamic behavior of AuO-BS in the column system. Increased bed depth increased breakthrough time, while the breakthrough time declined with increased initial AuO concentration and flow rate. Optimum conditions were determined for the batch system as 4 g of BS dose, 100 rpm agitation speed, and 90 min reaction time; optimum conditions for the column system were 3 cm bed depth, 0.14 mL/min flow rate, reaction time of 181 h; and optimum conditions for both systems were 100 mg/L AuO concentration, 20 °C reaction temperature and pH 6.18 (natural). Under these conditions, the amounts of AuO adsorbed in batch and column systems were calculated as 2.06 mg/g (89.75%) and 2.63 mg/g (47.13%), respectively. The studies showed that efficient remediation of AuO from aquatic environments is possible with BS.