Papers by Keyword: CaCO₃

Abstract: CaCO₃ is one of abundant minerals in nature, which is a promising material in thermochemical energy storage (TCES). In this work, we have succeeded in synthesizing CaCO₃/ZrO₂ composites by physical mixing with a magnetic stirrer using CaCO₃ from natural limestone. The mixing was carried out by mechanical stirring with various molar percentages of CaCO₃:ZrO₂ of 100:0, 85:15, 70:30 and 50:50. The phase and structure of the CaCO₃/ZrO₂ composites were characterized by x-ray diffraction (XRD). Thermal properties were characterized by thermogravimetri analyzer. Morphology of the composites was observed by scanning Electron microscopy (SEM) with energy dispersive x-ray (EDX). Based on the XRD results, the peak intensity of CaCO₃ at the crystalline plane of (104) decreased with increasing percentage of ZrO₂. The lattice volume of CaCO₃ also relatively decreases with increasing percentage of ZrO₂. The increase in the percentage of ZrO₂ in the CaCO₃/ZrO₂ composites makes the decomposition temperature also decreases. This is probably due to heat and mass transfer of ZrO₂.

Abstract: This study aims to fabricate and characterize the hybrid composites of duck eggshell (DE) and abaca fiber reinforced epoxy. The composites were fabricated with 20 vol.% fillers consisting of DE/abaca fiber with ratios of 0/20, 5/15, 10/10, and 20/0. We then characterized their mechanical (tensile and flexural) and water absorption properties. At the same time, the characteristics of eggshell particles were examined by SEM/EDS and XRD. We observed that the DE contains higher CaCO₃ than chicken eggshells, making it appropriate to be chosen as a filler. The alkali-treated (AT) abaca improves the flexural and tensile strengths of abaca/epoxy composite but slightly decreases those of DE/AT abaca/epoxy composites. The composite with a 5/15 DE/AT abaca fiber ratio shows the maximum flexural strength. However, the flexural strength of the composites made of the epoxy matrix is almost the same as that of polyester and is 21% lower than that of PMMA. The use of polyester and PMMA matrixes significantly reduces the water absorption rate to around 3.50%.

Abstract: Polypropylene filled calcium carbonate (CaCO₃) nanocomposites were fabricated by employing melt blending/compounding method using masterbatch. To investigate the efffect of reprocessing on the melting properties of PP/CaCO₃ nanocomposites, the melt compounding process was conducted twice (two cycles). The effect of nano-CaCO₃ loadings (i.e. 5, 10 and 15 wt%) on the melting properties of PP/CaCO₃ nanocomposites were also studied. The meling properties of the nanocomposites were analyzed by using a DSC (Differential Scanning Calorimetry). Additionally, the nanocomposites samples were also analyzed by an SEM (Scanning Electron Microscopy). The SEM analysis results revealed that at higher nano-CaCO₃ loading (i.e. 15 wt%), the nano-CaCO₃ particles in the 2^nd cycle were more well distributed/dispersed in the polypropylene matrix as compared to the 1^st cycle. Whereas, the DSC test results showed that the crystallinity of the nanocomposites samples were similar to that of neat PP for the 1st cycle of melt blending process, which was about 41%. In the other hand, for the 2^nd cycle, the crystallinity of the samples slightly increased wtih increasing nano-CaCO₃ loadings, which were about 39.6; 43; 44% for nano-CaCO₃ loadings of 0, 5, 10 wt%, respectively. Nevertheless, at the highest nano-CaCO₃ loadings (i.e. 15 wt%), the crystallinity of the nanocomposites (i.e. NCC-15-II) decreased again and lower than that of neat PP, which was about 37.7%.

Abstract: Reinforcement of both fibrous and particulate materials can improve composite properties for various applications, such as biomedical applications. The alkali-treated kenaf fibers and (SiO2, bentonite, and CaCO3) microparticles 400 mesh in size reinforce the epoxy matrix for hybrid composites. The bending and impact properties of hybrid composites, as well as their water absorption, are compared. The hybrid composites were prepared in a compression mold using a hand lay-up technique at 100°C for 20 – 50 minutes consisting of 28 vol.% of short kenaf fibers ~5 mm in length, 2 vol.% of each type of microparticle, and 70 vol.% the epoxy resin. The flexural and impact properties of kenaf/silica/epoxy composite indicated the highest flexural strength (58.37±3.9 MPa), flexural modulus (4.68 ± 0.17 MPa), and impact strength (7.49 kJ/m²⁾. The addition of the microparticles reduced water absorption in the composites. The water absorption of kenaf/silica/epoxy composite appeared to be stable for immersion time near 216 hours. Other microparticle-filled composites did not show this pattern. The incorporation of silica microparticles to the kenaf/epoxy composite potentially enhanced the mechanical properties of the composite, with the expectation of using it to be developed for biomedical composite material.

Abstract: The paper presents the effect of CaCO₃ content on the tensile, flexural and water absorption properties of bamboo fiber/polystyrene-modified unsaturated polyester composites. Two volume fractions of bamboo fibers had been used with the CaCO₃ content varied from 2.5 to 10 (wt%). The tensile and flexural properties were used to characterize the composites. In addition, the water absorption and its effect of the flexural properties had also been conducted. The results showed that at the bamboo content of 30%, adding CaCO₃ up to 10wt% tended to decrease the tensile strength and elastic modulus of bamboo fiber/modified unsaturated polyester composites up to 27% and 4%, respectively; however, at the bamboo content of 20%, its effect was not significant for both the tensile strength and the elastic modulus. Adding CaCO₃ seemed not to have a significant effect for both the flexural strength and modulus. Having exposed in distilled water, CaCO₃ did not significantly affect the water uptakes and the flexural properties of bamboo fiber/modified unsaturated polyester composites; however, the flexural strength and modulus significantly decreased in the ranges of 24 - 45% and 36 - 43%, respectively, compared to those in dry condition.

Abstract: White Mineral Trioxide Aggregate (WMTA) using precipitated CaCO₃ (PCC) from limestone has been synthesized. PCC in calcite structure was extracted from limestone by calcination at 900 °C for 3 h, dissolved in 0.8 M nitric acid solution and followed with carbonation for 60 minutes. PCC was used for the synthesis of WMTA by mixing with tetraethoxyorthosilicate, bismuth oxide, aluminum oxide, catalyst of with HNO₃ and NH₃ solution and thermally treated at 1100 °C for 3 h. The products were characterized with Thermal Gravimetric Analysis-Differential Thermal Analysis (TGA-DTG), X-ray Diffraction (XRD), Frontier-Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray Fluorescence (XRF). The results showed that the PCC dominated calcite structure was obtained with 75.25% in yield and 99.42% in purity. The WMTA has been successfully synthesized by low thermal treatment at 1100 °C using catalysts of HNO₃ and NH₃ solution, proven by the presence of tricalcium silicate (C₃S), dicalcium silicate (C₂S), tricalcium aluminate (C₃A), and Bi₂O₃ in WMTA.

Abstract: PES is used as raw material for the preparation of membrane in this paper. Through gas-assisted-phase separation and synergetic pore-forming technology, the influence of the content of CaCO₃ in foaming pore-forming agent and the content of N,N-DMAc in coagulation bath on membrane property is studied. The results indicate that this method prepares PES hollow fiber membrane with uniform macroporous structure in which the cross section is wedge-shaped and running through internal and external surface. The addition of CaCO₃ can improve membrane property and the increase in the content of DMAc also has a great positive influence on membrane property.

Abstract: In this study, microwave irradiation technology was used for the calcification roasting followed by sulfuric acid leaching process. The effect of roasting temperature, m (CaO)/m (V₂O₅), and roasting time on the leaching ratio of vanadium were investigated and the roasted samples were characterized by TG-DSC, XRD, and SEM. The leaching ratio of vanadium can be significantly enhanced with the increasing in roasting temperature, m (CaO)/m (V₂O₅), and roasting time. The leaching ratio of chromium decreased with roasting temperature and increased with m (CaO)/m (V₂O₅), and roasting time. The optimal roasting parameters were roasting temperature of 850 °C, the m (CaO)/m (V₂O₅) of 0.85, and roasting time of 90 min. Under the optimal roasting parameters, the leaching ratio of vanadium reached 88.81%. While the leaching ratio of chromium is 3.98%. During roasting process, vanadium is oxidized to acid-soluble CaV₂O₅, Ca₂V₂O₇, and CaMgV₂O₇. After leaching, chromium mainly exists in form of chromohercynite (FeCr₂O₄) and chrome-manganese spinel (Mn_1.5Cr_1.5O₄) in leaching residues.

Abstract: The main objective of this study is to investigate the effect of cementitious capillary crystalline waterproofing (CCCW) material on the water impermeability and microstructure of concrete. The water impermeability of concrete covered with or without CCCW material was tested according to the Chinese standard GB 18445-2012. The results indicate that concretes coated with CCCW material showed much higher water impermeability than blank ones, and the ratio of water impermeability pressure between them reached 275. The samples obtained in various depths of hardened cement paste specimens with or without CCCW coating were analyzed through scanning electron microscopy (SEM) and thermogravimetry-differential scanning calorimetry (TG-DSC), to study the differences in microstructure and hydration products. The results present that after a 28-day standard curing, there were lots of ettringite crystals and CaCO₃ formed in the paste in 1 cm from the coating, but the action depth of the CCCW coating could not reach 3 cm. The ettringite and CaCO₃ is precipitated in the pore structure of cement matrix and filling the voids, which leads to the significant enhancement in water impermeability.

Abstract: This paper studies how the addition and various content of Carbon nanotube (CNT) affecting the properties, especially the color difference of ethylene propylene diene rubber (EPDM)/ CaCO₃ composites. The results show that the increased content of CNT can turn EPDM/CaCO₃ composites from lighter, greener, and bluer to darker, redder and yellower, respectively. The total color change (ΔE) of EPDM/CaCO₃ composites is acceptable, when the content of CNT is less than 2wt%. The optimum tensile strength of EPDM composites can be gained, when the content of CNT is 3%.