Browsing by Author "Boumchedda, K."

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    Cu2O addition and sintering temperature dependence of structural, microstructural and dielectric properties of CaCu3Ti4O12 ceramics
    (Elsevier, 2020) Djafar, Rabah; Boumchedda, K.; Chaouchi, A.; Fasquelle, D.; Sedda, K.; Brahimi, S.; Khalfaoui, K.; Bououdina, M.
    This study is aimed in the replacement of commonly used (CuO) by Cu2O in the synthesis of perovskite CaCu3Ti4O12 (CCTO) phase by the solid-state reaction method. The XRD analysis of powder calcined at 1100 °C and ceramics sintered at different temperatures show that the CCTO phase was well crystallized with the presence of small quantities of additional phases. The SEM/EDS analysis of prepared pellets show that the formation of Cu2O/CuO phase occurs above 950 °C, resulting in enhanced densification at 1050 °C (>96%). However, it is found that the Cu2O-based CCTO begins to degrade around 1090 °C. The densification after sintering at 1050 °C reaches 96%, meanwhile dielectric constant and loss tangent values are optimum in the low frequency range (<103 Hz); i.e. 13378 and 0.177, respectively. This favors the use of Cu2O instead of CuO in CCTO ceramics for applications at low frequencies
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    Development and characterization of cellular ceramic bricks using Algerian kaolin
    (2020) Debbakh, S.; Boumchedda, K.
    Over recent years, a hot topic has been attracted much research attention is the development and/or optimization of porous materials with requirements for intended applications in catalyzing, filtration and isolation among others. This paper presents a method of elaboration of cellular ceramic bricks using three type of Algerian kaolin which were obtained from different regions at "Djebel Debbagh" in Eastern Algeria, Bechar "Tabelbala site" in Western Algeria and "Boudouaou site" in central region of Algeria. The elaboration of cellular ceramic bricks based on the creation of the cellular structure at room temperature, starting from barbotine (slurry), which was prepared by mixing argillaceous materials, foaming agent, and water. The solidification was carried out at room temperature by adding a mineral binder which allows the transformation of the foamed slurry into a rigid and stiff cellular body after being dried. The sintering treatments for 2 h at 1100, 1100 and 900 ℃, respectively, consolidate the so-called green cellular body and produced the interconnected cellular ceramic materials with a good pore size distribution. The volume of porosity and the cell sizes were exclusively controlled by the foam volume generated. The porosity was varied from 60 to 90% of the total volume of the material, where the cell sizes ranging from 0.01mm to 1mm. in this study, the followed approach of elaboration of cellular materials was clearly allowed us to envisage the volume of porosity with acceptable precisions
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    Dielectric properties of nanocrystalline CaCu3Ti4O12 (CCTO) ceramics fabricated from Algerian limestone raw material
    (Elsevier, 2023) Djafar, Rabah; Boumchedda, K.; Fasquelle, D.; Chaouchi, A.; Sedda, K.; Bououdina, M.; Bellucci, S.; Bánhegyi, G.
    Algerian natural limestone was used to fabricate the perovskite CaCu3Ti4O12 phase (CCTO) to replace commercial calcium carbonate (CaCO3) powder by a solid-state method. X-ray diffraction analysis of CCTO ceramics sintered at 1010 °C manifested the formation of well-crystallized pure (CCTO) phase with narrow crystallite size (43–99 nm) without any additional phases after sintering beyond 4 h. Thermal analysis by DSC indicated that CCTO phase is stable up to 1151 °C, afterwards it decomposes into CaTiO3 and TiO2 and accompanied by the segregation of the CuO/Cu2O phase. Scanning electron microscopy observations of the ceramics sintered at 1010 °C showed that most of the grains have an average particle size in the narrow range of 1–2 μm. The sintered pellet at 1010 C° for 14 h showed the optimum density (>94%). This study highlights the importance of using natural calcium carbonates (extracted from Guelma limestone in Algeria) as potential replacement to commercial counterpart for the fabrication of dense well-crystallized perovskite-type ceramics with controlled particle size distribution as promising candidates for electronic applications
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    Elaboration and characterization of a foam glass based on cullet with addition of soluble silicates
    (2010) Ayadi, A.; Stiti, N.; Benhaoua, F.; Boumchedda, K.; Lerari, Y.
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    Elaboration and characterization of porous granules based on waste glass
    (2011) Ayadi, A.; Stit, N.; Boumchedda, K.; Rennai, H.; Lerari, Y.
    The evolutions of the world today and the population increase have resulted in pollution and human wastes, which contaminate the environment and adversely affect the human's quality of life. All forms of food and drink packages, made of paper, plastic foam, aluminum and glass, are designed for the consumers' convenience. After being used, these packages are discarded as garbage and have today become a social problem. It is in this context that our work for obtaining a building material (foam glass granules) that is much lighter is registered with the properties of heat insulation and acoustic improved based on cullet in order to recycle it and for improving the present laws about the waste products in closed circuit (finished products → waste products → finished products). Investigations have shown that grinding waste glass to particle size less than 0.1mm and adding 1% of Ca CO3 content provide the production of material with the following properties: particle density of 0.5 g/cm3, strength of 17.50 MPa and water adsorption of 95%, with the temperature for foaming ranges determined at 850 °C. The microstructures are homogenous, with pore sizes of up to 2 mm. The foamglass is counted among the newglass products meeting certain requirements on comfort, in particular in the building industry (thermal and acoustic insulation). The product obtained presents excellent thermal (λ=0,031 W/m°C) and acoustic (R=15 dB) properties
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    Elaboration of cordierite ceramic starting from Algerian clays
    (2012) Boumchedda, K.; Kerfal, H.; Ayadi, A.
    Cordierite ceramic are elaborated by mixing a Algerian kaolin which is located in “Djebel Debbagh” region in the Algerian east, and hydroxide of magnesium. This kaolin named “DD3”, contains a large tenor of manganese oxide (MnO>1.34 %) what gives a blackish colouring to this clay, which limit its utilization in luxury porcelain and sanitary ware where brightness and whiteness are required. However DD3 is composed mainly by kaolinite and gibbsite which is also bearer of alumina. Fusible compound such iron and alkalis are less than 1 %. Elaboration of cordierite is carried out by mixing magnesium hydroxide to DD3. Fumed Silica powder is added to respect the stoichiometric composition of cordierite. Magnesium hydroxide is prepared by precipitation from MgCl2 and NH4OH. The mixtures with various compositions of DD3 kaolin and magnesium hydroxide are pressed to give samples in form of pastilles, and sintered at temperatures ranging from 1200 °C to 1350 °C to determine the ceramics properties such apparent and specific density, linear shrinkage, water absorption. Formation of Cordierite phase and structural changes are investigated by Xray diffraction (XRD), simultaneous thermal analysis (DTA-TG), and thermal dilatometry
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    Impedance spectroscopy studies on steatite with B 2 O ceramics materials from Algerian palygorskite
    (International Institute for the Science of Sintering (IISS), 2021) Khalfaoui, K.; Boumchedda, K.; Chaouchi, A.; Saidi, M.; Lamrani, N.
    B2O3 was used to reduce the sintering temperature of steatite (named MSB) dielectric ceramics. Electrical properties of this composition have been studied using impedance spectroscopic method to get better understanding of the electrical conduction, dielectric relaxation mechanism, and microstructure –electrical properties relationship of the materials as a function of temperature and frequency. These samples were prepared by a solid-state reaction technique and their single phase formation was confirmed by the X-ray diffraction technique. Dielectric and complex impedance spectroscopic studies were carried out in a wide frequency (102-106 Hz) and temperature (30-500oC) range. The dielectric constants decrease with increasing frequency for each sample, and then stabilize at frequencies lower than 100 kHz. The dielectric constant increases with the addition of B2O3. The nature of frequency dependence of ac conductivity of MSB follows the Jonscher power law and calculated DC conductivity follows Arrhinius behavior. The Nyquist plot (Z″ vs Zʹ) revealed the presence only of the grain boundary effect from 350oC onwards. The occurrence of single arc in the complex modulus spectrum of MSB compositions confirms the single-phase characteristics, and also confirms the presence of non-Debye type of multiple relaxations in the material
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    Properties of a hydrophone produced with porous PZT ceramic
    (2007) Boumchedda, K.; Hamadi, M.; Fantozzi, G.
    Interconnected piezoelectric porous ceramics PZT have been tested for possible use in hydrophone applications. These materials consisted of: (1) ceramics with fine porosity having pores from 50 to 100 μm and (2) cellular ceramics having cavities of the order of the millimeters. Porous ceramics are coated with flexible polymer standard polyurethane for the hydrostatics tests. The effect of the size of the pores and porous volume on the sensitivity of the sensor is studied and the performances of the hydrophones devices are presented
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    Recycling dam sediments for the elaboration of stabilized blocks
    (Scientific.net, 2020) Gueffaf, N.; Rabehi, B.; Boumchedda, K.
    Through this work we propose one of the solutions that allow us to recycle dam sediments as a potential raw material for the development of stabilized soil blocks. For the stabilization of the prepared samples, different percentages of cement and lime were chosen respectively (0, 6, 8, 10 and 15%), (0, 5, 8 and 10%). Different compaction pressures 2, 5 and 7MPa are used. The tests carried out showed very interesting results on the mechanical strength for specimens stabilized with cement up to 8.32MPa for 15% and 5.67MPa for 10% of lime at 7MPa compaction. The obtained water absorption coefficient is about 2.6 for 15% cement and 4.04% for 10% lime; however a thermal conductivity of specimens with cement and lime is about 1.06 and 0.731W/m.k, respectively
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    Strength and compressive behaviour of ultra high-performance fibre-reinforced concrete (UHPFRC) incorporating algerian calcined clays as pozzolanic materials and silica fume
    (Taylor & Francis, 2013) Rabehi, B.; Ghernouti, Y.; Boumchedda, K.
    This paper presents results of an experimental study which investigates the effect of four pozzolan additions made from various by-product materials on physical and mechanical properties of ultra-high performance fibre-reinforced concrete (UHPFRC) compared with the silica fume (SF): waste bricks (WB) and three types of metakaolin (MK) as calcined clays at 750 °C: calcined clay of Djbel Debbagh quality 3 (DD), calcined sludge incineration at the manufacture of paper (PS) and calcined silt of dams (SD) having median particle sizes less than 45 μm are used as addition. For each addition, five percentages of steel fibres (1, 1.5, 2, 2.5 and 3%) were used to improve the performance of concrete. The results suggest that the use of WB, PS and SD has no significant effect on the compressive strength as compared with SF concretes. Calcined clay DD can be used as pozzolanic materials in making UHPFRC. This MK competes with the SF, after 28 days of curing, the concrete containing 25% of DD and 2.5% steel fibre presents a compressive strength of 179 MPa compared with the concrete containing 25% of SF and 2.5% steel fibre, which presents strength of 183 MPa
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    Study of calcined halloysite clay as pozzolanic material and its potential use in mortars
    (2012) Rabehi, B.; Boumchedda, K.; Ghernouti, Y.
    In this research, we will try to understand the mechanisms involved in the introduction of calcined clays in substitution for a portion of cement in the manufacture of mortars. This experimental work focuses on the recovery of a clay type haloysite quality three, from eastern Algeria. This clay comes from a region called Djbel Debbagh hence its name (DD3). The main objective of this study is to see the influence of the activated clay by calcination with different percentages of 5, 10, 15 and 20% in substitution of cement, on the physical-mechanical properties and behaviour of mortars towards chemical attacks. The study of pozzolanic activity allows to optimize a calcinations temperature of about 750°C, the study of its mechanical performance has shown an improvement of strength. Finaly the results of the durability test showed a good performance in different environments
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    Study of vibratory behavior of interconnected porous PZT by impulse method
    (2010) Boumchedda, K.; Ayadi, A.; Aouaroun, T.; Fantozzi, G.
    Performances in ultrasonic active transducers of interconnected porous lead zirconate titanate (PZT) piezoelectric disks with a porosity ranging from 30 to 70%, and polarized along their axial axis, are investigated. The characterization method used is based on the measurement of the voltage, which appears between the two faces of the piezoelectric element when it is excited by a current impulse. The device used, allows the acquisition of axial and radial vibrations of the transducer, and from these data, electromechanical and acoustic parameters are deduced. One observes that interconnected porosity causes the disappearance of the radial vibrations, and for large porosities the disk vibrates exclusively according to the axial mode. kt is increased, the acoustic impedance is reduced, and the axial propagation velocity reaches ∼2500 m s−1 for 30% of porosity. These results show that interconnected porous PZT are suitable for making ultrasonic active transducer, such as biomedical imaging devices
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    Synthesis Cordierite Materials Starting from Algerian Kaolin
    (2018) Kheloui, Meriem; Boumchedda, K.; Boumchedda, S.; Rabehi, Bahia
    The objective of this work is to study the synthesis of the cordieritephase from Algerian kaolin known as DD kaolin. To do this, the kaolin iswashed and sieved to prepare a particle size fraction <20l, rich in clay particles,and precipitated magnesium hydroxide is prepared to give magnesium andfinally silica fume is added to the mixtures experimental, tofill the silica deficit.The weighing of the materials is carried out in such a way as to producemixtures close to the ideal phase of the cordierite (2MgO.2Al2O3.5SiO2). Themixing is carried out in a large quantity of water with a metal stirrer at highspeed. The mixture is heated during stirring until the sludge is obtained. Thefinal drying is continued in an oven, the coarse powder obtained isfinely groundin a porcelain mortar.The results of investigations carried out by simultaneous thermal analysis(ATD-TG) show afirst exothermic peak at 945 °C. which is attributed tol-cordierite, a second exothermic peak at 1200 °C. which indicates the crystal-lization ofl-cordierite in Indialite, andfinally an endothermic peak above1400 °C which indicates the fusion of the indialite.The results of investigations of the X-ray diffraction analysis on the calcinedpowders at high temperature, shows that only the Indialite phase is present from1300 °C.
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    Tuning the dielectric properties of CaCu3Ti4O12 ceramic by Cu2O addition and microstructural modifications
    (Elsevier, 2023) Djafar, Rabah; Boumchedda, K.; Fasquelle, D.; Chaouchi, A.; Sedda, K.; Bououdina, M.; Bellucci, S.
    Cuprous (I) oxide (Cu2O) was used instead of Cupric (II) oxide (CuO) for the synthesis of CCTO ceramic by solid-state reaction. The impact of sintering time on the structure stability, grain size, and dielectric performance of Cu2O-based CCTO ceramics was discussed. XRD analysis indicates that the CaCu3Ti4O12 cubic phase was successfully synthetized. The studied samples manifested high permittivity and quite low dielectric loss values in the frequency range (20–106 Hz); with optimum values of 15,423 and 0.083 respectively achieved after sintering at 1050 °C for 14 h while for longer sintering times of 19 h and 24 h resulted in higher values of permittivity of 19,943 and 21,392 respectively were obtained and associated with an improved loss tangent of ∼0.114 and 0.127, respectively. It was found that a longer sintering time of Cu2O-based CCTO ceramics resulted in an important improvement of the dielectric properties