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Highlights This study introduces an innovative technique for the fabrication of copper‐based polytetrafluoroethylene (PTFE)/graphite self‐lubricating composites. By harnessing the exceptional capabilities of selective laser sintering (SLS), we efficiently create three‐dimensional, continuous, and porous graphite preforms. Following this, the composite is formed through a combination of electroplating and vacuum extrusion methods. Subsequently, PTFE was vacuum impregnated into the microporous structure of the graphite preforms, and the composites were obtained through freeze‐drying, plasticizing, and machining processes. The resulting copper‐based PTFE/graphite self‐lubricating composites exhibit an exceptional blend of properties. Notably, there is a significant reduction in the average coefficient of friction, dropping from 0.14 to 0.02, and a marked decrease in the wear rate, from 1.358 × 10−5 to 1.109 × 10−5 mm3/N·m, as compared to graphite as a standalone lubricant. This represents a substantial improvement in performance, underscoring the effectiveness of the proposed fabrication method. The porous graphite with controllable shape distribution was prepared. Surface copper plating improves surface bonding. Controllable copper matrix composites with double lubricant were prepared. The average friction coefficient is as low as 0.02. [ABSTRACT FROM AUTHOR]

In this work, we used a 3D scanner for the volume measurement of foamed samples, a long-standing problem in the density evaluation of foams. The 3D scanning density measurement method can be selected as an alternative to or in combination with well-established, classical methods that involve the use of instruments like a caliper, a pycnometer, or other devices based on displacement or flotation principles. In particular, the classical methods show some limitations when the foamed sample geometry is irregular, when the polymer is highly hygroscopic, and when it has open porosities. We have tested numerous foamed samples of different sizes, shapes, densities, materials, and morphologies. We utilized different 3D scanner configurations for their volume measurement and compared the results with geometrical and displacement methods, when possible. Results showed that the proposed method is highly accurate, reproducible, and simple, although some specific precautions should be put in place to avoid misinterpretation by the shape-reconstructing software. [ABSTRACT FROM AUTHOR]

With the ability to manufacture complex functional structures, Additive Manufacturing (AM) enables new advanced applications which could not be realized before. An example of such structures is open porous structures. In the presented approach, the open porous structures are a result of the selected manufacturing parameters, instead of being defined in CAD models. Thereby, various porosities can be achieved flexibly without design adjustments. However, to comprehensively understand the correlation of manufacturing parameters and different properties, various tests are required. As an alternative, properties can be determined by means of simulation. This study presents 3D reconstructions of complex open porous structures, which are based on μ-CT imaging. The influence of the downsampling during voxelization on the 3D reconstructed geometry is studied. Further, different polyhedral mesh settings have been tested in order to find a mesh that minimizes the deviation between the CFD simulation results and the laboratory test results for flow resistance. A guideline for the creation of a calibrated CFD model based on μ-CT imaging is proposed. As it is acknowledged by the authors that the data availability to reconstruct shown cases is crucial, data for a reference case have been made freely available online. [ABSTRACT FROM AUTHOR]

In this research, the influence of the thermal treatment of geopolymer gels at 300 °C, 600 °C and 900 °C when incorporated with 5% rare earth elements (REEs) in the form of (GP-Sm) Sm2O3 and (GP-Nd) Nd2O3 was investigated. Changes in the chemical and structural properties of the geopolymer gels during thermal treatment for 1 h were monitored. Physico-chemical characterization was performed using the following methods: diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). Besides the characterization of the fundamental properties, some practical macroscopic properties were analyzed as well: sorptivity, open porosity, and Archimedean density. The stretching vibrations of Nd–O–Si and Sm–O–Si were confirmed at a value of around 680 cm−1and an Nd–O–Si absorption band at a higher value, together with the most dominant band of Si–O stretching vibration similar for all the samples. No significant chemical changes occurred. Structural analysis showed that for GP-Nd, the largest pore diameter was obtained at 900 °C, while for GP-Sm, the largest pore diameter was obtained at 600 °C. EDS confirmed the amount of dopant to be about 5%. X-ray photoelectron spectroscopy showed that for GP-Nd, the ratio of Si and Al changed the most, while for GP-Sm, the ratio of Si and Al decreased with increasing temperature. The contributions of both dopants in the GP-gel structure remained almost unchanged and stable at high temperatures. The atomic percentages obtained by XPS analysis were in accordance with the expected trend; the amount of Si increased with the temperature, while the amount of Al decreased with increasing temperature. The sorptivity and open porosity showed the highest values at 600 °C, while the density of both geopolymers decreased linearly with increasing temperature. [ABSTRACT FROM AUTHOR]

This paper proposes a method for determining the boundary values of open porosity (KPO_GR) and gas permeability (KPR_GR) of porous-type carbonate reservoir rocks using the example of Tournaisian deposits of one of the oil fields of the Republic of Tatarstan. When justifying the boundary values, two databases on core studies are used: 1) on standard core studies (used mainly to calculate hydrocarbon (HC) reserves); 2) on special core studies (used for technological development projects). In the proposed method, the residual oil saturation factor is not a constant, but is taken from flow studies or calculated from core dependencies. When determining the lower limits of porosity and permeability from both databases, approximately the same boundary values were obtained: KPO_GR = 0.11 fr. un., KPR_GR = 2·10–3 μm2 and KPR_GR = 1.7·10–3 μm2 , but they differ from the values, accepted by petrophysicists when calculating the reserves of considered deposit – KPO_GR = 0.09 fr. un., KPR_GR = 1·10–3 μm2 . Such a difference in determining the boundary porosity can significantly affect the calculation of hydrocarbon reserves, technological calculations and field development planning.

Pycnometric methods of characterization of the pore structure of solids, based on density measurements, provide data on the pore size distribution. Here we report results of open porosity determination via weighing of a dry sample, followed by evacuation and saturation with distilled water at atmospheric pressure; via pressure infiltration with water using a manostat system; and by mercury intrusion porosimetry. We have studied porous nickel samples prepared by a powder metallurgy process involving sintering of green compacts consisting of mixtures of nickel nanopowder and ammonium bicarbonate (NH4HCO3) powder as a pore former, with volume fractions of 80 and 20%, respectively. The particle size ranges of the pore former were 63–125, 140–200, and 250–315 μm. For the three methods used to determine open porosity, we theoretically evaluated the size of pores accessible to infiltrating liquid. The results demonstrate that, in the case of saturation with water after evacuation, the liquid can penetrate only pores more than 3 μm in size. Moreover, in the case of porous structures with a large fraction of submicron pores, the open porosity determined via saturation with distilled water after evacuation is considerably underestimated. The larger the fraction of small pores in the material, the larger the underestimation. The difference between the open porosity values obtained via pressure infiltration with water and by mercury porosimetry is insignificant. We demonstrate that, of the three porosity determination methods, only saturation with distilled water after evacuation cannot be used to analyze structures with submicron pores. The results we obtained can be useful in designing porous functional materials and articles with a tailored pore structure. [ABSTRACT FROM AUTHOR]

One of the most feasible approaches to reduce the carbon footprint of concrete, a critical contributor to global CO2 emissions, is to consider the high-volume replacement of cement with supplementary cementitious materials (SCMs). However, this approach currently has two issues: 1) low early-age strength, 2) inconsistent carbon accounting. To address these issues, we investigate the micro- and macro-scale performance of a series of low-carbon concrete mixes and analyze their global warming potential (GWP) using 5 unique LCA tools. We report that the cumulative heat, when normalized to the total water content, exhibits correlations with key performance metrics such as open porosity (R2 = 0.83) and compressive strength (R2 = 0.92). In addition, all LCA tools suggest that high-SCM mixes (55–70% replacement), broadly, can reduce the GWP values for concrete by ∼50% (from ∼450 to ∼240 kg CO2-eq/m3). However, depending on the mix and the LCA tool used, for GWP values, the relative variation can be as high as 30% (∼50–80 kg CO2-eq/m3). Finally, we normalize the compressive strength to the GWP metric using an ‘Integrated Strength Eco-Efficiency’ (I-SEE) coefficient, which can be a potential parameter for simultaneously assessing concrete’s performance and environmental impact.

Porous Ti–Al intermetallic compounds were successfully fabricated through powder metallurgy process with Zn as space holders. The influence of Al content and cold compacting pressure on samples of microstructure, phase identification, expansion behavior, open porosity and density were investigated. The results show that Ti–3 wt% Al alloy possessed high open porosity (55.47%) and exhibited three-dimensional connected pore channels. Therefore, the research placed emphasis on the Ti–63 wt% Al with 20 vol.% Zn at different cold compacting pressure. It was found that in the presence of Zn, the morphology of products changed from irregular round spheres to laminated shape, but the phase composition always remained as a single Al3Ti phase. Furthermore, the volume expansion rate increased continuously with the increase in cold compacting pressure, and the axial, radial expansion rate also followed the same law. The open porosity of porous materials and the initial density of green billet also increased, reaching 76.74% and 3.52 g cm−3, respectively, but the density of samples after sintering showed a linear decreasing trend, with the lowest being only 0.89 g cm−3. [ABSTRACT FROM AUTHOR]

In this research, the influence of the thermal treatment of geopolymer gels at 300 °C, 600 °C and 900 °C when incorporated with 5% rare earth elements (REEs) in the form of (GP-Sm) Sm2O3 and (GP-Nd) Nd2O3 was investigated. Changes in the chemical and structural properties of the geopolymer gels during thermal treatment for 1 h were monitored. Physico-chemical characterization was performed using the following methods: diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). Besides the characterization of the fundamental properties, some practical macroscopic properties were analyzed as well: sorptivity, open porosity, and Archimedean density. The stretching vibrations of Nd–O–Si and Sm–O–Si were confirmed at a value of around 680 cm−1and an Nd–O–Si absorption band at a higher value, together with the most dominant band of Si–O stretching vibration similar for all the samples. No significant chemical changes occurred. Structural analysis showed that for GP-Nd, the largest pore diameter was obtained at 900 °C, while for GP-Sm, the largest pore diameter was obtained at 600 °C. EDS confirmed the amount of dopant to be about 5%. X-ray photoelectron spectroscopy showed that for GP-Nd, the ratio of Si and Al changed the most, while for GP-Sm, the ratio of Si and Al decreased with increasing temperature. The contributions of both dopants in the GP-gel structure remained almost unchanged and stable at high temperatures. The atomic percentages obtained by XPS analysis were in accordance with the expected trend; the amount of Si increased with the temperature, while the amount of Al decreased with increasing temperature. The sorptivity and open porosity showed the highest values at 600 °C, while the density of both geopolymers decreased linearly with increasing temperature.

Metal foams, which are similar to other types of foam materials, are composed of solid material with a significant proportion of the volume consisting of pores. Although metal foams retain some of the properties of the original material, they also possess several advantageous characteristics such as low density and thermal conductivity, high specific stiffness, and porosity. As a result, metal foams are becoming increasingly popular for applications such as heat exchangers, soundproofing devices, and gas–liquid filters. Additive manufacturing has the potential to expand the production capabilities of foams by reducing materials consumption and the creation of complex geometry. This work demonstrates the possibility of direct 3D printing of metal foams made of titanium, aluminum, and aluminum-bronze using direct energy deposition and special parameters of the printing process. This method is superior to traditional methods in terms of cost and the absence of additional stages of preparation and post-processing. The open porosity of the foam can be easily changed by varying the laser power. The laser power in the range of 10 to 180 W along with rapid prototyping makes it possible to obtain metal foams of complex geometry with a high degree of open porosity (up to 50% for titanium and up to 30% for aluminum alloys), not inferior in quality to foams obtained by conventional methods. Moreover, by changing the printing modes, it is possible to adjust the structure of foam from uniform to columnar, increasing the thermal conductivity and insulating properties of the samples. [ABSTRACT FROM AUTHOR]

This paper addresses the study of renders and plasters' physical and mechanical characteristics from selected buildings awarded during the 20th century with a renowned architectural prize in Lisbon, Portugal. The characterisation was done to understand mortars' physical and mechanical properties and their evolution during the 20th century. These characteristics will also help determine compatibility requirements for future conservation and restoration interventions. Since these buildings have a heritage great interest status, the need to preserve them is a paramount issue. Fifty-three samples from nine case studies were studied via capillary water absorption, drying rates, open porosity, dynamic modulus of elasticity, and compressive strength. There were limitations in sample collection due to the buildings being in service and technical constraints regarding sample quantity for testing and separating layers of the multi-layer mortar system. Nevertheless, the results showed different ranges of quantitative values for these tests, whether the mortars were lime, gypsum, cement-based or had lime–cement blended formulations. [ABSTRACT FROM AUTHOR]

Regression mathematical models of the second full order were obtained for six quality indicators (objective parameters) for driving masses type “Fosuk”. The adequacy of the obtained regression equations for the quality indicators was approved. The optimal values of amount of clay substance Al2O3, %, and temperature of heat treatment, °C, were determined. The lines of constant values for each of the quality indicators in the range of variation in amount of clay substance Al2O3 and heat treatment temperature are presented. A multi-criteria optimization based on arithmetic mean, geometric mean and harmonic mean functions of usefulness was performed. An analysis of strategies for multi-criteria decision-making using a fractional-rational generalized function of usefulness is carried out. [ABSTRACT FROM AUTHOR]

The application of an integrated research approach to the reconstruction of ceramic production technology on the territory of the Kyrgyz Republic is considered based on the results obtained by modern methods. For the first time, the results of studying physicomechanical and physicochemical properties are summarized and an attempt is made to open up methods of technical analysis of ceramic artifacts. A unified scientific approach has been developed to the ceramics of various periods ranging from the 2nd millennium BC to our era up to the 10th – 12th centuries, and excavated in Kyrgyzstan, so as to determine the relationship between their microstructure and physical and mechanical properties. Ceramic technology, like no other industry, requires this kind of research because of the specificity of technical information associated with both natural and social factors. The lack of solid knowledge in the field of ceramics technology prevents the acquisition of important information about the history, culture, and economy of Kyrgyzstan as a nation-building entity. However, a comprehensive study of production techniques, types, compositions, and quality of ceramics would open up completely new prospects for confirming the antiquity of Kyrgyzstan. [ABSTRACT FROM AUTHOR]

Natural building stones, used as floor cladding stones in outdoor applications in cold regions, are negatively affected by freezing and thawing processes, and this reduces the service life of the stone. The aim of this study is to reveal the change of abrasion resistance of natural stones determined by the wide wheel abrasion test (WA) with laboratory freeze–thaw (FT) tests. For this purpose, FT tests were applied up to 84 cycles on 23 groups of samples, mainly consisted of carbonate rocks. According to the results, no significant decrease was determined in the dry unit weight (γd) value, but significant decreases were obtained in open porosity (n) and P-wave velocity (VP) values. It has been revealed that WA values are also significantly affected by increasing FT cycles and increased up to about 14%. It was concluded that the increase was evident up to 35 FT cycles, and after this level, the increase continued with a decrease. [ABSTRACT FROM AUTHOR]

Optimization of the pore structure stands out as an effective approach for bolstering the tritium release performance of lithium-based tritium breeding ceramics, particularly when employing a high open porosity configuration. In this study, Li 2 TiO 3 fibers were synthesized via the hydrothermal method, with the assistance of TiO 2 -B nanowires acting as templates. Subsequently, porous Li 2 TiO 3 pebbles with varying microstructures were fabricated through a combination of the wet method and a sintering process. Sintering process plays a crucial role in determining the microscopic morphology. An increase in temperature resulted in a suppression of the growth of fibrous grains and the transformation of fibrous grains into quasi-spherical grains. Moreover, a two-step sintering process was proposed as a means of improving the crush load (15.9 N vs. 22.0 N) of Li 2 TiO 3 pebbles while simultaneously preserving their high porosity (24.91%). The Li 2 TiO 3 pebbles, produced by the two-step sintering process, exhibited a distinctive micromorphology characterized by interconnected particles forming short rod-shaped microstructures. This distinctive micromorphology contributes to the maintenance of a high degree of open porosity (10.52%). [ABSTRACT FROM AUTHOR]

The problem of hydraulic parameters estimation lies in the depth: the deeper the rock formation, the more expensive and difficult the field tests and samples acquisition, and the more challenging the technical issues. The article assesses the Triassic sandstone's drainage potential at the stage of shaft sinking. It focuses on parameter analysis in varied scales, from drill-core sample laboratory testing, through a single well drawing test, to long-term pumping and recovery tests in the well with observation piezometers. The obtained results are compared to the values estimated in the past using different methods. Finally, the paper states whether it is reliable to forecast pore-fissure sandstone drainage potential based only on core samples' laboratory tests. This research proved that lab tests underestimate pore-fissure rocks' hydraulic parameters (mean hydraulic conductivity k = 9.79 × 10 − 8 m/s) tenfold more than long-term pumping tests (mean k = 4.45 × 10 − 7 m/s). However, it can be concluded that the group of so-called "witness samples", 10% of all core samples with a top value of the hydraulic conductivity tested in the laboratory, can be representative of the aquifer and comparable to the values obtained in pumping tests. With this in mind, we recommend using the highest values of hydrogeological parameters from laboratory tests based on the worst-case scenario. Therefore, it is possible to forecast inflows to the shafts reliably. This methodology is recommended only for rocks of porous and pore-fissure character. [ABSTRACT FROM AUTHOR]

This work presents an energy-efficient, cheap, and rapid production method of a metal–ceramic preform with open porosity suitable for liquid metal infiltration and filtration applications. It is based on cold isostatic pressing of a mixture of relatively hard Ni and Al2O3 powders with the addition of small amount of Al powders, acting as a binding agent. Open porosity is primarily controlled by Al2O3 particles partially separating Ni particles from mutual contacts. Cold isostatic pressed green compacts were subjected to thermal oxidation by heating in air to 600 °C, 700 °C, and 800 °C. The weight gain and open porosity of oxidized compacts were examined. The chemical composition and microstructure were analyzed by SEM-EDS and XRD techniques. The stability of preforms and the effect of thermal cycling on the open porosity were tested by thermal cycling in an inert Ar atmosphere in the temperature range up to 800 °C. It appeared that, in addition to NiO being an expected product of oxidation, Ni aluminides and spinel particles also played an important role in inter-particle bonding formation. Ni-NiO porous composites resist chemical corrosion and exhibit structural and chemical stability at higher temperatures and admixed Al2O3 particles do not deteriorate them. After subsequent infiltration with Al, it can offer a lower density than other materials, which could result in lower energy consumption, which is highly needed in industries such as the automotive industry. [ABSTRACT FROM AUTHOR]

It has become vital to look for alternatives to the non-renewable natural resources utilized in the building industry due to the vast and quick expansion in that sector in order to safeguard such resources from waste. Recycling varied concrete debris from demolished concrete buildings to substitute natural gravel in the production of various concrete mix types is one way to do this. In this study, the physico-mechanical characteristics of steel fiber-reinforced self-compacting concrete made of quartz gravel were examined. The percentages of recycled gravel used to replace the quartz gravel were 25, 50, and 75%, respectively. According to the findings, up to 75% of the quartz gravel may be replaced with recycled gravel. The correlation between the concrete's ultrasonic speed and mechanical strength was strong and promising. [ABSTRACT FROM AUTHOR]

The ceramic properties of "Fosuk" type driving masses, used for the monolithic construction of the walls of the steel foundry ladles, strongly depend on the content of the clay substance and the temperatures of heat treatment. The subject of the present study is to determine the influence of two independent variables (process control parameters) on the quality indicators of the driving masses, used in the refractory lining of steel foundry ladles in metallurgy. In the present study, statistical evaluation of the driving masses indicators with three different Al2O3 contents was performed. The linear correlation between the quality indicators of driving masses in different combinations of two main independent variables has been studied. Multicriteria optimization of the generalized functions for three different quality indicators was performed in order to determine the optimal amount of Al2O3 (clay substance) and the temperature of the heat treatment of the inner lining of the steel foundry ladles. [ABSTRACT FROM AUTHOR]

The objective of this work is to prepare porous Ni-Sn alloys by low temperature activation reaction sintering method. The phase composition, volume expansion ratio, pore structures and pore morphology of the sintered samples were studied by x-ray diffraction (XRD), vernier caliper measurement, aperture tester, and scanning electron microscopy (SEM). The results indicate that the phase composition is related to Sn content, pore size and porosity. The volume expansion rate of porous Ni-Sn alloys decreases first and then increases with the Sn amount. For Ni-Sn alloy with 50 wt.% of Sn content, the main phases are found to be Ni3Sn and Ni3Sn2. The average pore size is measured to be 2.78μm, which leads to an open porosity of 45.01% and a total porosity of 47.51%. Meanwhile, the volume expansion rate and permeability are determined to be – 0.99% and 105.1 m3 m–2 kpa–1 h–1, respectively. The high porosity of Ni-Sn alloy is attributed to the interconnected pores in the green compacts and the Kirkendall effect due to the difference in diffusion rates of Ni and Sn atoms. [ABSTRACT FROM AUTHOR]

The problems of microporous condensed materials obtained from the vapour phase are discussed in this article. The influence of the secondaryphase amount on the pore sizes and the pore-sizes’ dependence on the deposition temperature as well as on conditions, under which they are regulated, are shown. As established, the creation of materials with adjustable open porosity is possible with a content of refractory nanoparticles of not less than 4 wt.% and a deposition temperature of not less than 600°C. The concentration of the refractory phase has a significant effect on the volume and size of the pores; so, increasing the concentration of the refractory phase at a constant substrate temperature increases the probability of interaction of condensed atoms of the refractory compound. An increase of the annealing temperature leads to an intensification of pore fusion processes. With increasing annealing time in vacuum, a significant part of the porosity turns into open porosity in condensates containing 20–30 wt.% Al2O3. As shown, the coalescence processes of the pores are completed after 25 hours of annealing in vacuum at a temperature of 1200°C. As a secondary phase, it can be used such inclusions as oxides, fluorides, sulphides. The salt content in the titanium matrix of more than 45 wt.% is undesirable, because it violates significantly the continuity of the material. Therefore, the average pore size depends significantly on the deposition temperature and the annealing time of the condensates in vacuum. Open porosity can be adjusted in the range 0–50% of the total porosity with average pore sizes from 0.1 to 8 μm. As proved, the open porosity prevails at higher substrate temperatures in the relative balance of open–closed porosities. In addition, the physical and mechanical properties of condensate after exposure in water and after vacuum annealing are presented. Concentrations of refractory particles over 10 wt.% in the porous composite leads to significant deterioration of plasticity and strength. Vacuum annealing increases significantly the strength. Compacted microporous materials can be applied as coatings on the surface of any shape or in the form of precursors up to 6 mm in thick and up to 1 m in diameter. [ABSTRACT FROM AUTHOR]

Modern construction has a growing interest in geosourced materials for their low carbon footprint. This study aims to investigate the hygrothermal properties of two clay materials reinforced with wheat fibres using the traditional heavy cob technique for modern wood frame construction. The water absorption coefficients (α mat), water vapor permeability (δ), water vapor diffusion resistance (µ), moisture diffusivity (D W), moisture effusivity (b m), equivalent moisture penetration depth (dp 1 %), specific moisture capacity (ζ), theoretical and experimental moisture buffer value (MBV exp and MBV theo), porosity (η) and sorption isotherms were studied as a function of the fibre content in the samples of fibre percentages of 0 %wt, 3 %wt, and 6 %wt. The thermal conductivity (λ), heat capacity (C p), thermal diffusivity (D), and thermal effusivity (E) were evaluated as a function of the moisture content. The results indicate that the moisture buffering capacity of the clay samples, with and without fibre reinforcement, is greater than 2 g/(m2. %RH). The open porosities of the samples varied from 20 % to 45 %, with specific moisture capacities from 0.014 to 0.031 kg/kg. The equivalent moisture penetration depth of the samples ranged from 2.17 cm to 2.68 cm. After the exposure of the cob wall containing 3 %wt fibre to temperatures of −5 ℃, 20 ℃, 35 ℃, and 45 ℃, the experimental results of the interior temperature of the wall varied between 19.5 ℃ and 23 ℃. It is therefore recommended to use cob containing at least 3 % or more fibre for wall construction in a real environment. [Display omitted] • Samples made using the cob technique contained 3 % and 6 % bulk fibres. • Thermal and hydric properties, thermal and hydric inertia assessed for the samples. • Humidity buffer capacity of samples exceeded 2 g/(m². %RH). • A wall study kept the inside 19.5–23°C when exposed to −5°C to 45°C for a week. • Materials obtained are reproducible and can fill wooden structures. [ABSTRACT FROM AUTHOR]

Alkali-activated cement (AAC) produced with metakaolin and black rice husk ash was investigated. The characteristics, physical properties, and thermal properties were investigated. Porosity assessments were carried out using synchrotron radiation X-ray tomographic microscopy (XTM). The results revealed that the concentration of NaOH solution and Na2SiO3 solution was the key parameter which affected the morphology and properties of AAC. Particle-structures and prolonged structures were formed when using NaOH as an activator. However, stacked plate-like structures were observed when using Na2SiO3 together with NaOH. The amorphous phases of N-A-S-H gel and geopolymer were formed. XTM profiles showed that the pore volume decreased with increasing NaOH solution concentration and Na2SiO3 contents. The 3D images illustrated that the pore structures were occupied by pores less than 50 µm in size. Pore connections within the range of 0–50 µm were the main parameter which controlled the thermal and physical properties. [ABSTRACT FROM AUTHOR]

Additive Manufacturing has proven to be a valuable complement to conventional means of manufacturing. As it is a data-driven process, its flexible customization of part shapes and manufacturing parameters plays a crucial role for this development. This study investigates the novel possibilities enabled by laser-based powder bed fusion for the development of functionality driven design. As an example, open porosities are manufactured, structures known to be advantageous to flow and heat transfer applications. Samples are investigated by laboratory tests and 3D imaging to gain knowledge about application-related properties. The results contribute to correlating manufacturing parameters to resulting properties and thus to design future applications. [ABSTRACT FROM AUTHOR]

We have analyzed the surface of a plasma three-dimensional capillary-porous (TDCP) Ti coating with an additional bioactive hydroxyapatite coating formed by microplasma oxidation (MPO). Scanning electron microscopy (SEM) was used to analyze the open porosity of these composite coatings. The surface of the TDCP Ti coating consists of ridges and valleys. The main porosity of the TDCP Ti coating is concentrated within the volume of valleys and reaches 43%. The presence of macro- and micropores 0.08–600 μm in size makes TDCP Ti coatings promising for using in a variety of fields, including as the surface coatings of intraosseous implants. [ABSTRACT FROM AUTHOR]

An analytical model is developed to obtain qualitatively and semiquantitatively estimate the changes in the integral pore size during the oxidation of heterophase materials. The model is tested on studying the oxidation of CCCM with a pyrocarbon matrix at 600°C up to a mass loss of 75 wt %. The change in the pore size is analyzed to quantify the structural degradation of the composite. [ABSTRACT FROM AUTHOR]

The object of the research is the firing temperature of ceramic materials based on barium titanate. In laboratory conditions, barium titanate was synthesized from raw materials of barium carbonate and titanium dioxide using ceramic technology, taking into account the stoichiometric composition of the compound. In order to study the effect of the firing temperature on the properties of the ceramic material, three temperatures were selected: 1270, 1300, and 1350 °C. The physical properties of the samples (imaginary density, water absorption, open porosity) were determined by the method of hydrostatic weighing in water. The samples were saturated with water after their preliminary evacuation. The dielectric characteristics of the obtained materials were measured on an E7-8CLR automated device (Ukraine) at a frequency of 1 kHz. The structural and morphological features of ceramics based on synthesized barium titanate were investigated by direct scanning electron microscopy and X-ray phase analysis. On the basis of the complex of studies carried out, the technological parameters of the production of ceramics were selected. Thus, the duration of grinding at the first and second stages is 10 and 30 minutes; moisture content of the press powder – 8 %; pressing pressure – 20 MPa; temperature of the first firing – 1000 °С; temperature of the second firing – 1350 °C. The regularity of the change in the dielectric constant on the firing temperature of ceramics based on barium titanate was established. The investigated samples, obtained according to the given technological regime, are characterized by the following indicators: dielectric constant – 259.9; open porosity – 0.02 %; water absorption – 0.01 %; imaginary density – 5.45 g/cm³. The resulting material can be used to create composite ceramic materials that protect biological and technical objects from the effects of electromagnetic radiation, and can also be used to create new functional materials for space, aerospace, electronic engineering and medicine. [ABSTRACT FROM AUTHOR]

In the last several decades, the growth of Construction and Demolition Waste (CDW) production and the increased consumption of natural resources have led to promoting the use of secondary raw materials for a more sustainable construction. Specifically, the use of Recycled Concrete Aggregate (RCA), derived from waste concrete, for the production of Recycled Aggregate Concrete (RAC) has attracted a significant interest both in industry and in academia. However, the use of RAC in field applications still finds some barriers. In this context, the present study investigates experimentally the effects of freeze-thaw and wet-dry cycles on the stress transfer mechanisms of reinforced RAC elements through tension stiffening tests. First of all, the paper presents a detailed analysis of the degradation due to the aging process of RAC with RCAs obtained from different sources. Particularly, the results of tension stiffening tests are analyzed in terms of crack formation and propagation, matrix tensile strength contribution and steel-to-concrete bond. The results highlight that the pre-cracking elastic modulus, the first crack strength as well as the maximum concrete strength are strongly influenced by the presence of the Attached Mortar (AM) in RCA, as the former affects the concrete's open porosity. Therefore, the amount of AM is identified as the key parameter for the evaluation of durability of reinforced RAC members: a degradation-law is also proposed which correlates the initial concrete open porosity with the damage observed in reinforced RAC elements. [ABSTRACT FROM AUTHOR]

The ironmaking process in blast furnaces using iron lumps is an energy-efficient and low-carbon initiative that helps lower the cost of the ironmaking process. The physical and chemical properties of raw materials, process mineralogy, and metallurgical properties of three Malaysian iron ore lumps were researched in this paper, with the goal of showing the relationship between metallurgical qualities and mineralogy. The results show that lump ore A has a better decrepitation index, with a DI−6.3mm of only 0.2%; lump ore J has better reducibility and low-temperature reduction disintegration index, with RI and RDI+6.3mm values of 88.39% and 87.55%, respectively; and the three lump ores have excellent softening and melting properties and a high permeability index. The metallurgical properties of lump ore and mineralogical characterizations are generally correlated, the decrepitation performance of lump ore is mostly determined by the presence of goethite, and the original porosity is unrelated. The higher the content, the worse the decrepitation performance; lump ore’s reducibility is mostly determined by the open porosity and the content of newly generating hematite at high temperatures, which has no relationship to its original porosity. The higher the open porosity, the higher the goethite content, the higher the newly generated porous hematite content, and the better the lump ore’s reducibility; the higher the original hematite content in the lump ores, the lower the open porosity at high temperatures and the worse the reduction degradation characteristics.

Characterizing the morphology of polymeric foams is crucial for determining their practical applicability. The internal cellular structure of polymeric foams is typically analyzed by 2 D imaging techniques, such as Scanning Electron Microscopy (SEM) and optical microscopy. The problem with these techniques is that their tests are tedious, destructive, and the accuracy of the obtained results is questionable. The objective of this paper is to establish and experimentally verify an efficient 3- dimensional (3 D) Microcomputed-tomography based methodology for reliably estimating and characterizing each of the phases commonly present in multiple types of polymeric foam samples, such as the open, the closed, and the solid phase. A comparative study was carried out between morphology data obtained from 2-dimensional (2 D) analysis and those obtained from 3 D analysis to investigate the reliability of the 2 D analysis results. In this context, the experimental results revealed that by using a 2 D method the open porosity was underestimated at the expense of closed porosity, which in turn was overestimated, while the total porosity was not impacted. Also, visualization of the internal structure of polymer foams by using Micro-CT provides details about the 3 D space which cannot be obtained from SEM images. The analysis of foamed specimen demonstrated that the polymeric foam phases extracted from Micro-CT images were in agreement with the experimentally measured values of total porosity of the samples. In an effort to reduce computational requirements, the effects of reducing data size on the accuracy of results has also been studied by averaging image pixels in 3 D space and the results were compared for multiple types of foam structures. This method reduced the processing time considerably, and yielded comparable porosity values. However, the number of detected pores were lowered due to the inability of this method to detect very small cells after 3 D averaging of image pixels. [ABSTRACT FROM AUTHOR]

A new method for the electrodeposition of copper on oxidized aluminum alloys to form electrolytic coatings exhibiting high performance properties has been discussed. The effect of an azo compound—methyl red (MR)—additive on the structure and physicomechanical properties of the copper coatings formed on oxidized aluminum has been studied. Samples of aluminum alloys AD1M and AMg6BM have been subjected to an anodic treatment under identical conditions in two oxidation electrolytes of different compositions. Copper has been electrodeposited on oxidized aluminum alloy samples using a standard copper plating electrolyte. Comparison with a copper plating electrolyte of an identical composition with an MR azo dye additive has been conducted. The microstructure and adhesive properties of the copper coating formed on oxidized aluminum alloys have been studied. The relationship between the physicomechanical properties of the copper coating (microhardness, open porosity, adhesion) and the action of an azo dye additive in the copper plating electrolyte has been studied. The use of this technology will make it possible not only to increase the reliability and durability of machine parts and mechanisms but also to restore old parts and mechanisms. [ABSTRACT FROM AUTHOR]

We developed a set of certified reference samples of solid substances with open porosity (imitators) (OPGP SO UNIIM set) GSO 11116-2018/GSO 11119-2018 in the form of ceramic cylinders based on aluminum oxide. The certified values of open porosity are determined by the method of gas pycnometry. The reference specimens are intended for the certification of the procedures of measurements and checking of the accuracy of the data of measurements of open porosity in the course of petrophysical investigations of cores and slime under the laboratory conditions. The reference materials can be used for the calibration and verification of the tools used for measuring the open porosity of rocks, as well as for the purposes of testing of measuring instruments. The complete budget of uncertainties is presented for the certified values obtained for reference materials with regard for the variations of ambient temperature in the case of their use in testing and calibration laboratories. [ABSTRACT FROM AUTHOR]

Porous ceramics with complex structure were prepared by selective laser sintering (SLS) method using coal-series kaolin as raw materials. The effect of SLS process parameters and sintering temperature on properties of porous coal-series kaolin ceramics was investigated. The phase composition and microstructure of porous coal-series kaolin ceramics were characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results indicate that the coal-series kaolin/E12 composite powders can be formed well through SLS method. The green bodies show the superior quality. Z direction error is 10.43%, relative density is 37.89% and bending strength is 0.984MPa under laser power of 5W, scanning speed of 2000mm/s, scanning space of 0.13mm and layer thickness of 0.15mm. With the increase of sintering temperature, the linear shrinkage and bending strength of the porous coal-series kaolin ceramics increase gradually, while the open porosity decreases. The porous coal-series kaolin ceramics possess a high open porosity of 44.55% and a good bending strength of 6.1MPa when the sintering temperature is 1450℃. The main phase in the prepared porous ceramics is mullite phase, and they have a typical three-dimensional skeleton structure.

Methods and means of measurement of the characteristics of the porosity and permeability of solid substances and fabricated materials that are incorporated into GET 210-2019, the State Primary Standard of the units of specific adsorption of gases, specific surface area, specific volume, and dimension of pores, open porosity, and coefficient of gas permeability of solid substances and fabricated materials, are described. A comparison between the metrological characteristics of GET 210-2014 and GET 210-2019 is carried out. The basic means of transmission of the units of quantities that characterize the porosity and permeability of solid substances, such as calibration specimens of approved types based on the micro, meso-, and macroporosity of solid substances, are considered. The results of international comparisons are presented, measurement and calibration capacities are confirmed, and a comparison of the metrological characteristics of GET 210-2019 with the standards of other countries is performed. [ABSTRACT FROM AUTHOR]

A new laser irradiation fracturing method is employed to crack the Hot Dry Rock (HDR) and variations of rock temperature, specific energy (SE) and modified specific energy (MSE), thermal damages and open porosity of granite samples caused by moving laser beams with various irradiating conditions including laser power, diameter and moving speed of laser beam were investigated. Results indicate that rock temperature and the corresponding temperature gradients near the laser beam spots are strongly dependent on the laser power, beam diameter and irradiation time. The high temperature generated by the laser irradiation melts and cracks the HDR samples. The removed mass, cracked mass and size of grooving kerf induced by laser irradiation are also related to various irradiation conditions. SE and MSE are found nonlinearly reduced with the increased laser power density. Laser irradiation has a greater enhancement to thermal fracturing of granite than it does to thermal drilling. The open porosity (OP) of irradiated HDR samples increases with increasing laser power, decreasing diameter and moving speed of laser beam. The results can provide some guidance to those seeking a new economical and reasonable fracturing method for the HDR geothermal exploitation. Image 1 • A new graphite fracturing method by using laser irradiation is introduced. • Effect of laser power, beam diameter and moving speed on cracking is studied. • Graphite samples are melted and cracked by moving laser beam. • Modified specific energy decreases with increased laser power density. • Open porosity, removed and cracked mass depend on irradiation conditions. [ABSTRACT FROM AUTHOR]

A technology for producing nanoporous ceramics based on mullite (3Al2O3 ⋅ 2SiO2) is developed. The mechanochemical activation of oxides involved in the synthesis of mullite (γ-Al2O3 and amorphous SiO2) makes it possible to obtain single-phase 3Al2O3 ⋅ 2SiO2 and to reduce its sintering temperature to 1300°С. The effect of the pressing pressure and the amount of pore-forming additive (ammonium carbonate) on the value of open porosity, pore volume, and pore size distribution in sintered ceramics 3Al2O3 ⋅ 2SiO2 is established. Mullite nanoceramics with open porosity of 42–47%, pore size <200 nm, and compressive strength 50–65 MPa is obtained. [ABSTRACT FROM AUTHOR]

Processes for preparing ceramic microporous diaphragms based on aluminum and zirconium oxides are studied. Diaphragm test results for long-term corrosion resistance are presented. It is shown that ceramic material based on zirconium and aluminum oxides prepared at 1350°C with linear shrinkage of 75% has open porosity of 49% and ultimate strength in bending of 48 MPa. Diaphragms prepared from this material can withstand pressure up to 1.0 MPa and operate under aqueous chloride solution electrolysis conditions for at least 40,000 hours. [ABSTRACT FROM AUTHOR]

Specific features of the porous structure of irradiated and virgin reactor graphite of Russian brands have been analyzed. The porosity parameters affecting the leaching of radionuclides from graphite radioactive waste (RAW) were determined: fraction of open porosity, distribution of pore throat cross-sections, surface of open pores. The volume of open pores accessible for leaching aqueous media in the irradiated graphite was estimated. A model describing the leaching of radionuclides from irradiated graphite accounting for the porosity contribution is proposed. The parameters that numerically characterize the resistance of graphite RAW against leaching and are independent of the geometric shapes of separate fragments (samples) were determined. [ABSTRACT FROM AUTHOR]

The performance of attractive Ni-based composites can be affected by changing their microstructures, e.g., introducing pores. Here, we report a novel, relatively low-cost process to fabricate Ni/Al2O3 composites with open porosity modified by the size of Al2O3 particles. The mixture of powders was subjected to thermal oxidation twice in air after a maximal temperature of 800 °C was reached in a stepwise manner and maintained for 120 min. The oxidation kinetics were determined thermogravimetrically. The open porosity was evaluated by an Archimedes’ principle-based method. Localization and quantification of NiO, newly formed on the Ni particle surface and acting as a mechanical bonding agent, were explored by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. Larger ceramic particles prevented merging of NiO layers on adjacent Ni particles more efficiently; therefore, the open porosity increased from 21% to 24.2% when the Al2O3 particle diameter was increased from 5–20 µm to 32–45 µm. Because both Ni/Al2O3 composites exhibited similar flexural strength, the composite with larger Al2O3 particles and the higher open porosity could be a better candidate for infiltration by molten metal, or it can be directly used in a variety of filtration applications.