Papers by Keyword: Pumice

Abstract: Silica can be utilized as a DSSC anti-reflection layer material due to its wide storage, low refractive index, and harmlessness. Pumice is a volcanic shaft rock made of silica and alumina. Here, silica was extracted from pumice at 800°C and various aging times of 18 and 24 hours to be used as an anti-reflection in the fabricated DSSC. The extraction results were characterized by XRD and SEM-EDX, revealing that the highest silica content of 79.56% was obtained at the aging time of 24 hours. It was then deposited on the opposite of the FTO active area using the spin coating with varied layer numbers (1 and 2). A UV-Vis spectrophotometer was performed on the sample to observe the transmittance of the FTO without and with silica anti-reflective coatings. It showed that the 1 layer of silica had the highest transmittance. The DSSC performance was tested by an I-V meter to determine current, voltage, and efficiency. It demonstrated that, as it had the highest transmittance value, the fabricated DSSC with 1 layer of silica efficiency by 0.15% compared to the one without anti-reflection coating. Therefore, it could be concluded that the addition of anti-reflection could improve the efficiency of DSSC.Keywords: Pumice, Silica anti-reflection layer, DSSC

Abstract: Raw pumice samples were modified with nano carbon black, borax, and nano carbon-borax using the sol-gel method by applying surface modification processes, and the changes in the thermal behavior of the surface modification of the raw pumice were studied by characterizing them with FE-SEM, EDX, FT-IR, XRD, BET and TGA-DTA. In the analyses made with FE-SEM, it was observed that the surface and pore structure of the raw pumice changed after the modified process, and in the EDX analysis, it was determined that nano carbon black and borax adhered to the surface of the raw pumice. In the XRD results, no change in the crystal structure of the raw pumice was observed after the modified treatment. TGA-DTA analysis showed that the mass loss of raw pumice (P) was greater than pumice-nano carbon black (PC), pumice-borax (PB), and pumice-borax-nano carbon black (PBC). Accordingly, raw pumice showed a mass loss of approximately 25%, pumice-borax (PB) and pumice-nano carbon black (PC) 0.45%, and pumice-borax-nano carbon black (PBC) nearly 3%. According to the BET analysis results, it was determined that the raw pumice has a surface area of 28.126 m²/g. After the surface modification process, the surface area of the raw pumice was determined as 52.127 m²/g in the pumice-nano carbon black sample, 49.125 m²/g in the pumice-borax sample, and 32.523 m²/g in the pumice-borax-carbon black sample. Considering the data obtained, the best surface properties were showed in pumice-nano carbon black (PC). Research results showed that; the modification process with nano carbon black and borax changed the thermal behavior of raw pumice.

Abstract: In the last decade, a continuous increasing research activity is focused on the surface modification of natural porous materials for the efficient removal of oil contaminants from water. A continuous in-situ oil/water separation technique for oil spill cleanup had been designed using surface modified Irind mine pumice as a sorbent. Irind mine pumice is an aluminosilicate rock, with well-developed porosity, mechanical strength, high buoyancy, chemically inert and eco-friendly, therefore it must exhibit certain water-and oil absorption capacities. The modified pumice absorbs a broad variety of oils and organic solvents with high oil absorption capacity and negligible water take-up at both static and dynamic conditions. Irind mine pumice have been used with grain sizes ranging from 2.5 ... 5.0 mm. Oligomethylhydride siloxane is used as a modifier.

Abstract: Pumice is a volcanic rock that consists of a highly vesicular rough textured volcanic glass. It is very porous and shows a high absorption - it can contain a lot of water. Thanks to its low volume density, it is sometimes used as a light natural aggregate, especially for some small elements such as chimney blocks. The paper is focused on the development of concretes and mortars for these purposes. The optimum content of pumice was specified from the point of view of mechanical properties. Special attention was paid to absorbed water - it can be a source of self-curing of concrete.

Abstract: This research studies compositions of diatomite, leonardite and pumice for utilization appropriate to the properties of materials. Chemical compositions of these materials were characterized by X–ray fluorescence spectrometry (XRF) and energy dispersive X–ray spectrometry (EDXS). The silica was major component of these materials. The morphology was investigated by scanning electron microscopy (SEM). Diatomite was cylindrical in shape, leonardite was sheet or flake in shape and pumicewas prismatic in shape. The structure was studied by X–ray diffraction (XRD). It was found that the mineral composition of diatomite, leonardite and pumice showed cristobalite low, quartz and anorthite, respectively. The functional groups were identified by Fourier transform infraredspectrometry (FTIR). The functional group of siloxane was obtained and dominated vibration in these materials. And the vibration of carboxylic, alcoholic and carbonyl groups were obtained in leonardite.

Abstract: This study is aimed to discuss structural behavior of steel reinforced sandwich concrete beams (SWB) consisted of skins and a core. The skins were made of ordinary concrete and a core was of pumice lightweight concrete. The SWB skin compressive strengths of 30 MPa and the core compressive strength of 15 MPa were considered. Twelve SWB specimen of 150x250x2500 mm with 50 mm skin thickness and 150 mm core thickness were cast and tested after curing process under flexural points loading as simply supported beams. All the beams considered were reinforced with 3D12 mm deformed bar and 8 mm stirrups with 3 spacing variations. Shear span depth ratio (a/d) of 1.8, 2.3, 2.8, and 5.4 were also considered to reflect the behavior between short and slender beams. Results showed that the flexural behavior of sandwich beams were identical with normal or lightweight concrete beams behavior. Ultimate moment of beam section slightly increased with increasing the shear span to depth ratio, which were varies between 1.26 and 2.31 of the calculated moment. The yield moment to the ultimate moment ratio vary between 0.83 and 0.99. The ductility was increased with the decreased shear reinforcement spacing. The shear strength increased as the spacing of shear reinforcement decreases in almost all a/d variations. Shear strength was also increased with the increase of a/d ratio for short beam and the other hand shear strength decreased with the increasing a/d.

Abstract: In order to prepare energy saving and environmental protection building materials, a new kind of concrete was made by the combination of corn stalks which is the main crop in northern China, natural pumice resources and cement. Corn stalks and pumice are all lightweight material with open pores and large water absorption; therefore they must be pretreated before preparing concrete by blocking holes to reduce the amount of grout. The raw materials used in the experiments are lightweight materials; it is advisable to adopt the pressure vibration molding process to reduce aggregate stratification.

Abstract: Pumice is a kind of natural lightweight aggregate with well-developed porosity and moderate-intensity. Amorphous Si-Al oxide is its main mineral composition. This paper focused on the performance and features of the pumice pozzolan and aggregate firstly. Then a kind of pumice concretes was prepared with the ordinary Portland cement, ordinary sand and strengthened coarse pumice aggregates. And its mechanical properties, durability, insulation and absorbing performance were investigated. The result showed that the compressive strength of pumice concrete was 20MPa, anti-freezing durability was more than 100 freeze-thaw cycles, electric flux within 6 hours was 1749C, thermal conductivity coefficient was 0.318W/ mK, and the electromagnetic wave absorption was-5dB ranging from 8 to 18GHz. The results indicated that the pumice concrete could be developed as the green and multi-functional concrete materials in the future.

Abstract: Different amount of pumice were used to replace gravel to make mixed aggregate concrete, the fast freeze-thaw cycle test were conducted and the influence of pumice rate substitution to the frost resistance properties of concrete were studied.The mass loss rate, strength loss and relative dynamic elastic modulus were regarded as the evaluation index of frost resistance properties of concrete. Results showed that the mass loss rate and strength loss rate gradually decreased and the relative dynamic elastic modulus gradually increased with the increase of pumice rate, the mass loss rate, strength loss rate and the relative dynamic elastic modulus gradually decreased with the increase of freeze-thaw cycles. Polypropylene fibers could reduce the strength loss rate, improved the relative dynamic elastic modulus, but had little effect to improve the mass loss. Through the frost resistance, the frost resistance of concrete improved with the increase of pumice content, at the same time, polypropylene fiber also could improve the frost resistance of concrete.

Abstract: Rough surfaces of denture prosthesis promote adhesion of microorganisms and plaque formation. In dentistry ferric oxide, tin oxide, chrome oxide and pumice are the most commonly used materials for polishing of resins and other materials. Clinoptilolite that is in zeolitic structure resembles to pumice due to alumina silicate formations in its constitution. Surface roughness was evaluated by means of a surface roughness analyzing instrument, Perthometer There were 10 specimens for each acrylic resin and bis-acryl composite resin material and polishing method combination. Conventional lathe polishing with polishing paste served as surface roughness was determined with a profilometer and SEM microscope. ANOVA was applied to the all measurements and was statistically significant (p<0.001). The p-values were calculated using paired t-tests. The materials in order that are most successful at polishing PMMA surface are; clinoptilolite Ra 0,5 > Fe₂O₃ Ra 0,6 > Cr₂O₃ Ra 0,8> pumice Ra 1,2 > SnO₂ Ra 1,6. the surface roughness values for Bis-acryl Composite are as follows: clinoptilolite Ra 0,6 > Fe₂O₃ 0,8 Ra > Cr₂O₃ Ra 0,9 > pumice Ra 1,4 > SnO₂ Ra 1,9. The most successful material for PMMA and Composite resin were clinoptilolite followed by; clinoptilolite, Fe₂O₃, Cr₂O₃, pumice, and SnO₂ in order. The same results were confirmed with the scanning electron microscopic images. Within the light of the present study Clinoptilolite can be an alternative to pumice for polishing of PMMA.