Apparent Bulk Density Research Articles

Performance Evaluation of Pebble Concrete for Pavement: A Study on the Sucre Highway Project

Bolivia has abundant pebbles, while the supply of crushed stone is limited and unstable. Thus, the resource utilization of local pebble as a coarse aggregate and the guarantee of concrete durability are the key scientific issues in the Sucre Highway Project. In this paper, a comparative analysis was conducted of the performance of crushed stone concrete and pebble concrete. Additionally, the impact of fly ash on the water permeability resistance of concrete was investigated. The results indicate that the apparent density, bulk density, and void ratio of pebbles are lower than those of crushed stone, and the aggregate gradation of pebbles is dispersed. The type of aggregate is the primary factor influencing the splitting tensile strength of concrete, with the main failure modes of pebble concrete being slurry cracking, aggregate crushing, and interface debonding. While aggregate and fly ash have a minor effect on compressive strength, they significantly impact flexural tensile strength; however, all concretes meet the requirements for extra-heavy, very heavy, and heavy traffic load levels. In terms of impermeability, fly ash effectively mitigates the negative impact of aggregate type on the impermeability of concrete. These findings support the application of pebble concrete in the highway project.

Turning waste concrete powder into high calcium alkali-activated cementitious materials and artificial aggregates

In order to handle the environmental pollution caused by waste concrete powder, recycled concrete powder (RCP) is utilized to prepare high calcium alkali-activated cementitious materials and artificial aggregates. This study first investigates the high calcium alkali-activated cementitious materials, exploring the effects of different mineral admixtures, liquid-to-solid ratios (L/S), RCP/slag, Na2SiO3 modulus, and Na2O content. The results illustrate that slag powder is the best mineral admixture and the most critical factor affecting cementitious materials. Increasing the slag dosage enhances the generation of C-(A)-S-H, improves the microstructure, and increases compressive strength, with a maximum compressive strength reaching 68.42 MPa. According to these test results, the impact of various factors on RCP aggregates is further explored. The results illustrate that the L/S and slag content are primary factors influencing particle size distribution and strength. Increasing these factors leads to larger aggregate particle sizes and higher strength. The compressive strength of the aggregates at 7d reaches 93.24–-99.5 % of that at 28d, with a maximum strength of 8.2 MPa. Additionally, slag content (10–30 %) and Na2O content significantly impact the physical properties of aggregates, improving apparent density and bulk density while reducing water absorption. To verify the applicability of RCP aggregates, they were used in concrete, and the effects of aggregate strength and replacement rate on concrete performance were explored. The results display that as aggregate strength rises, the mechanical properties of the concrete improve. When RCP aggregates are incorporated, the mechanical properties of the natural concrete decline only slightly (<16.70 %). The probability of aggregate damage increases with decreased RCP aggregate strength or increased RCP aggregate content under pressure. RCP aggregate concrete exhibits better shrinkage resistance compared to natural concrete. The process of utilizing RCP is low-energy, non-polluting, and results in high-performance products, making the large-scale effective utilization of RCP feasible.

Study of the Sintering Process Behavior on Some Structural and Physical Properties of (Ni-47Ti-3Cu) Alloy Prepared by Powder Metallurgy

This research aims to prepare the alloy (Ni-47Ti-3Cu) using powder metallurgy techniques and study the sintering behavior of this alloy at different temperatures. Powders of nickel, titanium, and copper, were mixed to ensure homogeneity, then compacted under a pressure of (5ton) for (2 min) to obtain cohesive samples. The sintering process was carried out at temperatures of (1050, 950, 850, 750, 650) °C for 1 hour. The structural properties were studied using X-ray diffraction (XRD), and the physical properties (apparent density, bulk density, porosity, and water absorption) were examined using Archimedes' principle-based tests. The XRD results indicated the emergence of a new phase with a different crystalline structure from the elements used in the preparation of the models, identified as (TiCuNi2) with a rhombohedral crystal system, while the constituent elements of the alloy exhibited face-centered cubic (F.C.C) structures for nickel and copper and a hexagonal close-packed (H.C.P) structure for titanium. The physical examination results showed that both apparent and bulk densities increased with increasing sintering temperature, while porosity and water absorption decreased with increasing sintering temperature.

Fabrication of Y2O3-doped MgO refractory raw materials based on magnesium hydroxide from salt-lake brine

High-purity magnesia refractories were fabricated by brine magnesium hydroxide from the salt-lake brine (Qinghai Salt Lake) and Y2O3 as an additive at 1780 °C. It avoided the substantial CO2 emissions and ultra high temperature sintering process (＞1900 °C) when compared with the conventional magnesite-calcination technical approach. The results confirmed that Y2O3 was dispersed on the MgO grains boundaries in the fabricated MgO aggregates, resulting in a decrease in apparent porosity and enhancing the grains' boundaries. With 3 wt% addition of Y2O3, the apparent porosity and bulk density of the sample reached to 15.9 % and 3.10 g/cm3 from 37.9 % to 2.30 g/cm3 of blank control group, respectively. Compared to the blank control without Y2O3-adding, the sample with 5 wt% Y2O3 exhibited a 54.17 % increase in the resistance to molten slag. SEM results indicated that the incorporation of Y2O3 in samples increased the porosity of small pores and enhanced grains boundaries, thereby suppressing slag's penetration. Furthermore, the Y2O3-adding was employed to disperse the MgO grains boundaries and existed as separate phases for grains boundaries enhancement. The slag attack of the fabricated MgO–Y2O3 refractory raw materials were controlled by an inter-crystalline corrosion process.

Optimization of All-Desert Sand Concrete Aggregate Based on Dinger–Funk Equation

In recent years, with the development of the construction industry and the wide application of concrete materials, the demand for natural resources such as sand and gravel in China has continued to grow. The Xinjiang region is rich in natural desert sand resources due to its large desert area, which are inexpensive and easy to obtain, providing new possibilities for the production of concrete materials. The use of natural desert sand as concrete aggregate not only reduces the cost of construction but also contributes to the protection of the environment and the rational development and utilization of natural resources. However, poor particle gradation in natural desert sand leads to poor concrete properties. In this study, the Dinger–Funk equation was used to optimize the aggregate gradation of natural desert sand from Toksun, Xinjiang, and concrete specimens were prepared for mechanical properties and sulfate erosion resistance tests. The test results show that the four groups of aggregates optimized by the Dinger–Funk equation are better than the single gradation and natural gradation in terms of apparent density, bulk density, void ratio, mechanical properties, and durability of concrete. Where the distribution modulus n = 0.3 was the best, the compressive strength, splitting strength, and flexural strength were increased by 13.14%, 15.71%, and 11.08%, respectively, as compared to the natural gradation. After 90 sulfate erosion and dry–wet cycles, the mass change rate and relative dynamic elastic modulus of concrete specimens first increased and then decreased, and at the distribution modulus n = 0.3, the aggregate particles of 0.3–0.6 mm, 0.6–1.18 mm, and 1.18–2.36 mm accounted for 26.98%, 32.33%, and 40.69%, respectively, and the smallest of the mass change rates of durability was the best.

Oxygen transport mechanism and the effect of microstructure on the oxygen response behavior of an oxygen-sensitive composite Ce0.9Gd0.1O2-ẟ – La0.6Sr0.4FeO3-ẟ at high temperature

Compositions like gadolinium doped cerium oxide Ce0.9Gd0.1O2-ẟ and strontium doped lanthanum ferrite La0.6Sr0.4FeO3-ẟ, or their composites are well known in the field of fuel cell electrolyte, oxygen transporting membrane and catalytic reactor applications. This work offers insight into composite material's oxygen response characteristics, taking Ce0.9Gd0.1O2-ẟ and La0.6Sr0.4FeO3-ẟ in 70: 30 wt percent. One pot sol-gel method was employed for the powder synthesis. The powder was characterized by TG-DSC, XRD, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). FESEM-EDX and EDX-line profiling techniques were used to check the compositional homogeneity of sintered bodies. Oxygen response tests were conducted from ambient (20 % O2) to 100 % O2 concentration, using bulk samples sintered at three different temperatures, i.e., 1000, 1150, and 1250 °C at a fixed soaking time of 4 hours. The sintered specimens' apparent porosity, bulk density, surface morphology, and electrical conductivity were also examined. The sintering temperature significantly impacts response behavior as the porosity and grain size of the sintered body plays a vital role in sensing performance. The mechanism of response towards oxygen is also discussed. Sample 73–100 displayed the best performance among others. We achieved the lowest response and recovery time of 15 – 48 sec and 45 – 80 sec from a 0.60 mm thick bulk material at 950 °C. Harsh environments were intentionally created to check the reliability and reproducibility of the response data. This material could be a good candidate as an oxygen gas sensor at high temperatures owing to its good sensitivity, reliability, reversibility, and stability.

Effect of carbon nanofibers fabricated from electrospun PAN precursors on the characteristics and densification of MgO–CaO ceramic systems

MgO–CaO composites are basic materials with high melting points, high chemical resistance to alkaline environments, clean steel production, environmental friendliness, and abundant sources. In the current work, carbon nanofibers (CNFs) with diameters between 150 and 270 nm were prepared at different temperatures (up to 1200 °C) by carbonization of electrospun polyacrylonitrile (PAN) precursors. Then, the MgO–CaO composites were prepared in two steps. First, 3 wt% CNFs carbonized at different temperatures were added to the composite to determine the optimal carbonization temperature. Subsequently, the physical properties (apparent porosity and bulk density) and mechanical properties (flexural strength (FS) and cold crushing strength (CCS)) of the MgO–CaO-CNF composites were investigated. X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) were used to analyze the composition, morphology, and structure of the CNFs powders and composite samples. Based on the results obtained, such as the percentage graphitization, length, average diameter, and morphology of the CNFs, 1000 °C was determined as the appropriate carbonization temperature for the next steps of this study. In a second step, the CNFs synthesized at 1000 °C were added to the MgO–CaO with different wt% (0, 0.5, 1, 1.5, 2, 2.5, and 3 wt%). It was found that by adding CNFs (up to 1.5 wt%) into the MgO-CaO composites, the physical properties increased due to the improvement of densification, and mechanical properties improved due to the activation of reinforcing mechanisms, the reduction of surface defects and the creation of a dense body. However, these properties decreased from 1.5 to 3 wt% due to the agglomeration and poor dispersion of the CNFs. Finally, the results illustrated that adding CNFs, even in small amounts, significantly improved the features of MgO-CaO compounds; the ideal content was 1.5 wt% CNFs.

Preparation and properties of mullite ceramic-based porous aggregates with high closed porosity utilizing low-voltage electroceramics waste

Mullite ceramic-based porous aggregates, known for their high strength and closed porosity, are widely utilized in engineering. This study successfully prepared mullite-ceramic-based porous aggregates from low-voltage electroceramics waste, investigating the impact of pore-forming agents, bauxite chamotte, and sintering temperature on the physical properties and cold compressive strength. Finally, a mechanism of closed and open pores formation was proposed. The results show that when 10 wt% activated carbon was added, enhanced particle dispersion and stability in apparent porosity, bulk density, and diameter shrinkage ratio were observed, with an optimal range of activated carbon addition identified at around 10.0 wt%. Furthermore, increasing bauxite chamotte addition from 5.0 wt% to 15.0 wt% at 1000°C promoted mullite nucleation, facilitating mullite crystal formation and reducing the relative content and viscosity of the liquid phase. This led to increased apparent porosity, reduced closed porosity, and a decrease in average pore size. However, stress concentration around surface pores resulted in reduced cold compressive properties. The sintering temperature was then increased from 900°C to 1200°C using 10.0 wt% activated carbon and 15 wt% bauxite chamotte, leading to changes in crystallinity and porosity. At 1100°C, isolated islands of the liquid phase between grain boundaries resulted in the highest cold compressive strength and bulk density, while further heating to 1200°C led to a reduction in these properties due to excess liquid phase filling grain boundaries. The formation of closed and open pores is primarily influenced by changes in sintering temperature, which affect the quantity, viscosity, and flowability of the aluminum-silicon liquid phase.

Fast microwave synthesis of high-silica natural soil based porous geopolymer

This study describes a simple microwave process for fabricating porous geopolymer-polymer based Shirasu soil. The porous geopolymer samples were synthesized using sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution as alkaline solution in range of 0.5 M to 9 M. After mixing process, the geopolymer slurry was heated and stimulated geopolymerization reaction by different microwave powers at 200 W, 500 W and 700 W for 30 s, 60 s, 90 s and 120 s. The influence of NaOH concentration, microwave powers and heating times on the apparent bulk density, the water adsorption was focused. Results showed that the microwave powers and heating time affected the apparent bulk density, the water adsorption, and the densification of geopolymer matrix. Higher microwave power can promote higher water adsorption related to lower apparent bulk density. Moreover, the results revealed that the porosity and the nitrogen adsorption of geopolymers at 120 s of heating time increased with an increment of the NaOH from 1 M to 4 M. On the other hand, geopolymers activated by 200 W at 30 s could not be hardened. This work provides the feasibility of porous geopolymer synthesis based natural soil.

Low-temperature preparation of lightweight ceramic proppants using high-proportioned coal-based solid wastes

Lightweight ceramic proppants are prepared using coal gangue, fly ash, and bauxite as raw materials, and a mixture of manganese dioxide and magnesium oxide is used as composite additives. The total content of the coal gangue and fly ash in the raw materials reaches up to 70 wt%. The effects of coal gangue and fly ash precalcination, sintering temperature, and composite additive content on the phase compositions, microstructures, and performances of the resulting ceramic proppants are studied in detail. The ceramic proppant prepared at 1285 °C using 1 wt% of the composite additive is composed of quartz, corundum, and mullite. It also presents the desired sphericity, roundness, and microstructure. The apparent density, bulk density, and breakage ratio of the ceramic proppant described above are 2.55 ± 0.06 g/cm3, 1.03 ± 0.02 g/cm3, and 8.30 ± 0.68% at 35 MPa, respectively. This ceramic proppant belongs to lightweight ceramic proppants and meets the requirement of the 5K grade in the standards of SY/T 5108-2014 and API STD 19C-2018.

Utilization of all components of waste concrete: Recycled aggregate strengthening, recycled fine powder activity, composite recycled concrete and life cycle assessment

Waste concrete can be crushed to produce a large amount of recycled aggregate(RA) and recycled fine powder(RFP). Different recycled components have different characteristics. RA should focus on its pretreatment method, while RFP should focus on its morphology and volcanic ash activity. This study investigated the effects of two single and composite strengthening methods in RA, mechanical vibration and acid solution immersion. The results showed that the composite strengthening method was more effective in improving the properties of RA, which resulted in an increase in apparent density and bulk density by 5.59 % and 12.55 %, respectively, and a decrease in crush value and water absorption by 26.05 % and 15.52 %, respectively. Three methods were used to analyze the volcanic ash activity of RFP with different particle sizes, and the RFP with a particle size of 23.08 μm has a high volcanic ash activity, which can effectively play its role of filling and volcanic ash activity in recycled concrete. Based on the preferred pre-treated RA and RFP, the effect of RA and RFP on the macroscopic and microscopic properties of recycled concrete under different mixing amounts was studied, and the results showed that the compressive strength of 20 % RA single mixing could reach 40.17 MPa, and that the compressive strength of 20 % RFP single mixing could reach 38.6 MPa, and both of them had no significant effect on the frost resistance. Further, 20 % RA and 20 % RFP were compounded to prepare recycled concrete, and the results showed that the compressive strength of RA-RFP was slightly improved to 40.12 MPa, and the mechanism of its action was explained by microscopic analysis. Finally, the environmental impact and carbon emission reduction of the life cycle of RA and RFP were evaluated, and the results showed that the utilization of recycled materials can play an effective environmental benefit.

Stability and Detectability of Exomoons Orbiting HIP 41378 f, a Temperate Jovian Planet with an Anomalously Low Apparent Density

Moons orbiting exoplanets (“exomoons”) may hold clues about planet formation, migration, and habitability. In this work, we investigate the plausibility of exomoons orbiting the temperate (T eq = 294 K) giant (R = 9.2 R ⊕) planet HIP 41378 f, which has been shown to have a low apparent bulk density of 0.09 g cm−3 and a flat near-infrared transmission spectrum, hinting that it may possess circumplanetary rings. Given this planet’s long orbital period (P ≈ 1.5 yr), it has been suggested that it may also host a large exomoon. Here, we analyze the orbital stability of a hypothetical exomoon with a satellite-to-planet mass ratio of 0.0123 orbiting HIP 41378 f. Combining a new software package, astroQTpy, with REBOUND and EqTide, we conduct a series of N-body and tidal migration simulations, demonstrating that satellites up to this size are largely stable against dynamical escape and collisions. We simulate the expected transit signal from this hypothetical exomoon and show that current transit observations likely cannot constrain the presence of exomoons orbiting HIP 41378 f, though future observations may be capable of detecting exomoons in other systems. Finally, we model the combined transmission spectrum of HIP 41378 f and a hypothetical moon with a low-metallicity atmosphere and show that the total effective spectrum would be contaminated at the ∼10 ppm level. Our work not only demonstrates the feasibility of exomoons orbiting HIP 41378 f but also shows that large exomoons may be a source of uncertainty in future high-precision measurements of exoplanet systems.

Effect of popping and milling on physical, chemical, structural, thermal properties and angle of repose of amaranth seed (Amaranthus cruentus L.) and finger millet (Eleusine coracana L. Gaertn) from Udhagamandalam

The study was conducted to examine the effect of popping and milling on selected properties of amaranth and finger millet from Udhagamandalam. The amaranth and finger millet are cleaned, popped at high temperature for short time in an open pan method, and pulverised using a mixer at the laboratory. Water activity had decreased as the heat processing had reduced the bound water content 0.53 to 0.23. Alcoholic acidity had elevated levels in popped and pulverised grains in comparison to native grains. Grains showed a major change in surface area and porosity in the range of 0.12 to 1.20 m2/g and 3.20 to 4.54 Å. The intensity of the colour had shown higher in amaranth samples and lower on finger millet upon processing in the range of 44-74 L*, 4-7 a* and 2.8-11.6 b*. Crystallinity had shifted from A-shaped curves to a single V curve during processing. The native material underwent various treatments and decreased apparent and compact bulk density in comparison to native grains significantly from 0.82 to 0.14 and 0.69 to 0.35 in amaranth and finger millet respectively. The processing has improved overall physio-chemical properties.

Effect of heating rate, temperature, and residence time during graphitization on the mechanical and electrical properties of isotropic graphite blocks

The present study aimed to determine the correlation between graphitization parameters during the manufacturing of isotropic graphite blocks, including temperature, residence time, and heating rate, and the physical properties of the obtained graphite blocks. It was found that during graphitization, nitrogen- and sulfur-containing gases were generated, and the isotropic graphite blocks exhibited volume shrinkage, and their apparent density and bulk density increased, regardless of any changes in the process parameters, due to the intrinsic microstructure of the isotropic coke. Graphite blocks with varying graphitization temperatures and residence time exhibited increased bulk density and open porosity but decreased flexural strength and electrical resistivity compared to carbonized blocks. It was also confirmed that the heating rate process parameter was related to gas release rates and crystallization. In addition, it was observed that micron-sized pores were created around the developed graphite layered structure with increasing graphitization degree.

Direct Tableting on a Continuous Manufacturing Line—Impact of Mixing Parameters, Material Densities, and Drug Load on Subsequent Process Parameters and Tablet Quality

The continuous manufacturing (CM) of solid oral dosage forms has received increased attention in recent years and has become a leading technology in the pharmaceutical industry. A model has been developed based on process data from two design of experiments (DoEs), where the impact of the mixer process parameters, throughput (THR), hold up mass (HUM), impeller speed (IMP), and the input raw material bulk density (BDi), on the continuous process and the resulting drug product has been investigated. These statistical models revealed equations, describing process parameter interactions for optimization purposes. For the exit valve opening width (EV) at the bottom of the continuous mixer (CMT), the combination of high throughput (30 kg/h) and low impeller speed (300 rpm) resulted in optimal process conditions. Apparent bulk density of the blend (BD) within the process, fill depth (FD), and tensile strength (TS) were mainly impacted by input bulk density (BDi) of the tableting mixture, emphasizing the role of material attributes on the continuous manufacturing process. The apparent bulk density itself was, other than from the input bulk density, equally dependent from THR and IMP in opposite deflections. However, process parameters (THR and IMP) revealed a minor impact on the apparent BD compared to the input bulk density. FD was impacted mainly by THR ahead of IMP and the TS by IMP and THR to a similar extend, in opposite deflections. A simplified linear model to estimate the input bulk density revealed satisfactory prediction quality when included in the derived statistical model equations.

Enhanced optical and thermal conductivity properties of barium titanate ceramic via strontium doping for thermo-optical applications

In this study, we prepared a homogeneous fine powder of barium titanate (BaTiO3, BT) doped with different concentrations of strontium (x = 0, 0.05, 0.125, 0.15, 0.20, and 0.3) and having the composition Ba1-xSrxTiO3 (barium strontium titanate, BSrxT). XRD patterns and Rietveld refinement revealed the existence of a single tetragonal phase structure for BSrxT, x = 0–20%, and a single cubic structure for BSr30%T. The physical properties of the pure and doped mixtures were studied. The results showed that the addition of strontium to the physical properties of BaTiO3, including the apparent porosity, bulk density, linear shrinkage, and water absorption have been changed when increasing the Sr content. Moreover, the inclusion of 15% Sr in BaTiO3 increases the apparent porosity and water absorption of the sample to 6.2 and 28.5%, respectively. The optical properties were investigated by Ultraviolet–visible spectroscopy and it was found that the optical band gap decreases significantly with increasing Sr concentration, from 3.10 for pure BaTiO3 to 2.46 eV for the BSr30%T compound. The thermal conductivity measurements showed that the doping mechanism and the increased temperature have a significant effect on the thermal conductivity results of the fabricated ceramic materials. Therefore, it was found that the value of thermal conductivity increases with increasing Sr doping and at higher temperatures. A correlated behavior of optimum values is observed in band gap energy, absorption, and thermal conductivity which can be exploited for thermo-optical applications.

Hardened and fired geopolymer mortars fabricated from Cyclone’s waste clay and submicron sand: A comparative study

This work focuses on recycling of Cyclone’s waste clay in the existence of various percentages of submicron sand (400–800 nm), i.e. 2.50, 5.00 and 7.50 wt-%, for production of hardened and fired geopolymer mortars. After drying the hardened geopolymer mortars, they were subjected to low rate firing at different temperatures, i.e. 800, 1000, and 1200 °C. The physico-mechanical properties of dried and sintered geopolymer mortars were investigated by various tools. The apparent porosity and bulk density were tested by water-displacement method. The mineralogical composition and reaction products were identified by X-ray diffraction technique and Fourier transform infrared spectroscopy, respectively. The microstructure was investigated by scanning electron microscopy. The compression strength was also evaluated. The results revealed that the addition of submicron sand to geopolymer mortars enhances the physico-mechanical properties of geopolymer mortars. The mortar that contained 7.5 wt-% submicron sand exhibited lower porosity (25%) and the highest compressive strength (27 MPa) as compared to the other mortars. After firing, the mortars fired at 1000 °C exhibited improved properties than that fired at 800 °C, while that fired at 1200 °C was deformed and fused. On the other hand, the mortar that contains 2.50 wt-% submicron sand showed the best physico-mechanical properties as compared to the other ones. It exhibited the lower porosity (2.50 wt-%) and the highest compressive strength (85 MPa) after firing at 1000 °C.

DEVELOPMENT OF HIGH ENERGY AND FUEL ECONOMY CERAMIC INSULATED BIOMASS MULTI COOKING SYSTEM

The analysis of Inyi clay and its utilization in the production of an improved cook-stove is significant to the existence of mankind and his community. This study was carried out to analyse the mixture of clay, cassava peel and grog and its utilization in the production of an improved cook-stove. The clay deposits were collected from Inyi Local Government, Enugu State. Different ratios of the mixture was used in the following percentage proportions by weight of clay to cassava peel to grog: A (40:40:20), B (40:30:30), C (40:20:40), D (40:10:50) at firing temperatures 900oC and 1000oC. The physical analysis (apparent porosity, linear shrinkage, dry-fired shrinkage, total shrinkage, bulk density, water absorption and percentage making moisture) was carried out using rectangular shape test piece to ascertain the feasibility in the lightweight stove production, the strength and the durability of products. The chemical analysis (xrd and xrf) was carried out using x-ray diffractometer and x-ray fluorescence in order to determine their crystallographic parameters and elemental composition respectively. The morphological analysis (SEM) was carried out using the scanning electrode microscope to obtain the resolutions and magnifications. The addition of cassava peel and grog was found to have great effect on the insulating properties (shrinkage, bulk density, apparent porosity and water absorption) of the clay. Chemical analysis revealed SiO2 (45.26%) and Al2O3 (35.19%) as major constituent. The result of this study showed that cassava peel was suitable in enhancing the insulating properties of Inyi clay and can be utilized to induce insulation in clay minerals when desired.

Influence of Thermal Treatment of Moroccan Red Clay on its Physicochemical and Mechanical Behavior

AbstractRed clay is considered to be of significant value to the economy in Morocco, particularly in the Safi region, because of its abundance. This raw material has long been known for its quality in the manufacture of clay materials, but its use was limited to traditional ceramics. The red clay raw material was the subject of the current study with the objective of opening new industrial applications that will give added value to the Safi red clay. The physicochemical, mineralogical, and thermal properties of the Moroccan red clay were determined by X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis, X-ray diffraction (XRD), oriented aggregate, and particle-size analyses, powder density by helium pycnometry, carbonate content using the Bernard method, differential thermal analysis (TG–DTA), and the BET surface area. The compacted dry powder particles were calcined at three sintering temperatures: 900, 1000, and 1100°C for 2 h. The effect of sintering temperature on ceramic properties, such as apparent porosity, water adsorption, bulk density, and mechanical strength, was examined. Dense ceramics with lower porosity and greater mechanical resistance (~300%) were produced by increasing the sintering temperature from 900 to 1100°C. The conclusion was that the evolution of physicochemical and thermal properties is related to mineralogical changes, which show that anorthite is the major phase at higher temperatures.

Physical and chemical properties of Ag–Cu composite electrical contacts prepared by cold-press and sintering of silver-coated copper powder

Effects of silver content (5–35 wt %), sintering temperature (150–850 °C), sintering time (30–180 min), and compaction pressure (200, 300, and 400 MPa) were studied on characteristics of prepared contacts. XRD (X-Ray Diffraction), OM (Optical Microscope), SEM (Scanning Electron Microscope), and electrical resistance analyses were used to study the properties of the contacts. The Results showed that increasing the percentage of silver in the contacts as well as increasing the time and temperature of the sintering process increase the oxidation of copper. It was found that galvanic corrosion and the Kirkendall effect between Cu and Ag (especially in high silver content) resulted in the formation of microvoids around the copper particles facilitating the copper oxidation. Apparent bulk density remained almost constant as the sintering temperature increased from 150 to 700 °C, while it dropped sharply in a sintering temperature of 750 and 800 °C. It was determined that increasing the sintering time from 30 to 60 min increases the apparent bulk density, while increasing the sintering time to more than 60 min reduces it. Moreover, increasing the amount of compaction pressure in 200–400 MPa did not affect the apparent bulk density. The electrical resistance is almost independent of sintering temperature in 25 °C–700 °C. Further change in sintering temperature from 700 to 750 °C raised the electrical resistance from 0.2 Ω to 15 kΩ. A Study of the electrical resistance of the samples indicated that increasing the Ag content up to 25 wt% reduces the electrical resistance. The electrical resistance of the sample containing 35 wt% Ag was 14 kΩ that which was higher than that of the sample containing 25 wt% Ag (0.11 Ω).