Artykuły w czasopismach: „SiO2-tubes”

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Chen, Zhenzhong, Jia Li, Zheng Zhang, Jun-fa Liang, Qizhi Luo i Xuncai Chen. "Controllable Architecture of Mesoporous Double-Nanoshell SiO2/TiO2 Hollow Tube Based on Layer by Layer Method". Journal of Nanomaterials 2021 (29.01.2021): 1–9. http://dx.doi.org/10.1155/2021/6685355.

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Double-shell tubular on-dimensional structure can be fabricated through a layer by layer method, in which the core template was removed to create the tubular shape. In this paper, we report, for the first time, the double nanoshell SiO2/TiO2 hollow tubes prepared through a layer-by-layer deposition method involving the sol-gel process for the SiO2 and TiO2 generation. During TEOS and TEOT hydrolysis/condensation for the SiO2 and TiO2 shell layer formation, cetyltrimethylammonium bromide (CTAB) is adopted both as the structure-directing template and as the mesopore-channel template distributing around the shell. The obtained double-nanoshell hollow tubes illustrate a large surface area and high pore volume. Also, mesoporous double-nanoshell SiO2/TiO2 hollow tubes have the inner and outer shell thickness of about 80 nm and 120 nm, respectively. Plus, the shell thickness of SiO2 and TiO2 is controllable depending on the used concentration of TEOS and TEOT during their sol-gel process. Therefore, the technique for the preparation of SiO2/TiO2 mesoporous double-nanoshell hollow tubes could provide new insights into the construction of mesoporous double-shell and hollow structure for other multicomponent and hierarchical hybrid systems.

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Jeon, S. J., C. Sung i Chung Chao. "Characterization of Mo/SiO2 interfacial reactions in metal halide arc tube by analytical TEM". Proceedings, annual meeting, Electron Microscopy Society of America 54 (11.08.1996): 568–69. http://dx.doi.org/10.1017/s0424820100165306.

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The purpose of this study is to investigate the interfacial reactions between Mo foil and quartz in metal halide arc tubes. After welding to a tungsten cathode, the Mo foil was specially treated before Mo/SiO2 pinch seal operation. Mo foils in arc tubes show different performance in lamp depending on the type of the treatment. Mo/SiO2 interfacial reactions and amounts of Mo diffusion into the SiO2 were analyzed using TEM, SEM and EDS in order to understand the different properties of arc tubes.Arc tubes were treated with one of the following conditions : (A)untreated, (B)dry hydrogen fired, (C)process “B” plus humidity exposure. Cross-sectional TEM and SEM samples in the longitudinal direction of the arc tube through the center of Mo foil were prepared. Two Mo/SiO2 interfacial areas, one near the end of the W cathode and the other the longitudinal center of the foil were compared each other.

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Böttger-Hiller, Falko, Patrick Kempe, Gisela Baumann, Michael Hietschold, Philipp Schäfer, Dietrich R. T. Zahn, Albrecht Petzold, Thomas Thurn-Albrecht i Stefan Spange. "The Controlled Synthesis of Carbon Tubes and Rods by Template-Assisted Twin Polymerization". Advances in Materials Science and Engineering 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/872019.

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The application of porous carbon is versatile. It is used for high-performance catalyst support, electrode material in batteries, and gas storage. In each of these application fields nanostructuring improves the material properties. Supercapacitors store a high energy density. Exactly adapted carbon structures increase the life of lithium batteries and protect catalysts with increasing reaction rate and selectivity. Most of porous carbon materials have a spherical shape. To the best of our knowledge, there is no procedure to synthesize nanostructured cylindrical porous carbon systematically. Here, template glass fibres and SiO2-tubes were modified with nanostructured SiO2/phenolic resin and SiO2/poly(furfuryl alcohol) layers by surface twin polymerization (TP) of 2,2′-spirobi[4H-1,3,2-benzodioxasiline] and tetrafurfuryloxysilane. Afterwards the SiO2/polymer layer on the template is thermally transformed into a defect-free nanostructured SiO2/carbon layer. After completely removing the SiO2components microporous carbon tubes or rods are finally achieved. The diameters of the carbon rods and the inner as well as the outer diameter of the carbon tubes are adjustable according to the shape and size of the template. Thus, a huge variety of microporous carbon materials can be easily produced by template-assisted TP.

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Bica, Ioan. "Obtaining of SiO2 micro-tubes in plasma jet". Materials Science and Engineering: B 86, nr 3 (październik 2001): 265–68. http://dx.doi.org/10.1016/s0921-5107(01)00681-x.

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Guo, Lin Lin, Hong Min Wang, Wei Liu i Mei Xu. "Study on Film-Forming Technique of Aluminum Composite Membrane Prepared by Inorganic Precursor Sol-Gel Method". Advanced Materials Research 690-693 (maj 2013): 421–24. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.421.

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Al2O3-SiO2-ZrO2composite sol was prepared with inorganic precursors by sol-gel method. Using Al2O3ceramic tubes as supporter, well-surfaced Al2O3-SiO2-ZrO2composite microfiltration membrane was achieved by the film-forming technique of pretreatment of the ceramic tube supporter, 3 times recycled dipping-drying-sintering, being dried at 50°C thermostatic water bath and sintered at 900°C.

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Ma, Zongpeng, Ying Huang, Xiaoling Chen, Jiangnan Song, Xiang Zhang, Taike Li i Lunjun Chen. "Numerical investigation of effect of the flow field structure and cooling medium of tubes on the heat transfer performance of automotive radiator". Thermal Science, nr 00 (2023): 118. http://dx.doi.org/10.2298/tsci221229118m.

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The flow field structure and cooling medium of tubes have major influence on the heat transfer performance of automotive radiator. In this study, two novel types of radiator tube (wasp-waisted tube 2# and wasp-waisted tube 3#) are developed, six types radiator tubes with different flow field structures and equal flow cross-sectional area are numerically simulated. In addition, four nanofluids with different concentrations (Al2O3/water, SiO2/water, TiO2/water and CuO/water) were studied in Reynolds number 2500-7500. The results show that the heat transfer capacity of the wasp-waisted tube 2# and the wasp-waisted tube 3# is significantly better than that of the other radiator tubes, followed by the wasp-waisted tube. Compared with the wasp-waisted tube, the heat transfer coefficient of the wasp-waisted tube 2# and the wasp-waisted tube 3# increased by 10.6% and 3.5% respectively. On the other hand, nanoparticles improve the heat transfer efficiency of base fluid. When Re reaches 7500 and the volume concentration is 3%, the Nunf/Nubf of SiO2/water is 5.52%, 5.22% and 8.70% higher than that of Al2O3 /water, TiO2/water and CuO/water, respectively. The comprehensive heat transfer capacity of SiO2/water-3% in the wasp-waisted tube is the best.

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Anastasescu, C., M. Anastasescu, V. S. Teodorescu, M. Gartner i M. Zaharescu. "SiO2 nanospheres and tubes obtained by sol–gel method". Journal of Non-Crystalline Solids 356, nr 44-49 (październik 2010): 2634–40. http://dx.doi.org/10.1016/j.jnoncrysol.2010.03.038.

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Demirci, Mehmet Turan. "Low velocity impact and fracture characterization of SiO2 nanoparticles filled basalt fiber reinforced composite tubes". Journal of Composite Materials 54, nr 23 (2.04.2020): 3415–33. http://dx.doi.org/10.1177/0021998320915952.

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Nano-microscale fracture mechanisms, which affect fracture toughness, play an important role in improving the impact characterization of fiber reinforced polymer composites. Therefore, crack behaviors are tried to be controlled with fracture mechanisms by filling nanoparticles into polymer matrix for improving impact characteristics and fracture toughness in latest studies. In this study, it was aimed to investigate the effects of SiO2 nanoparticles addition into epoxy matrix on the low velocity impact characteristics and fracture toughness in basalt fiber reinforced filament wound composite tubes. SiO2 nanoparticle of 4% wt. filled and unfilled ± [55]6 filament wound basalt fiber reinforced/epoxy composite tubes were subjected to low velocity impact tests at 5 J, 10 J, and 15 J of energy levels. It was seen that while the addition of nanoparticles were increasing the maximum impact forces in the range of about 19%–32%, displacements and absorbed energies decreased because of the increase in the bending stiffness. Charpy impact tests were performed to three different notched arc shaped specimens for determining the impact fracture toughness. SiO2 nanoparticles increased the fracture toughness by 20%–23%. It was observed that SiO2 nanoparticles delayed the formation of failures such as debonding and delamination, and reduced the fiber breakage branching in low velocity impact tests. A liquid penetrant test was used to inspect the crack formations and progressions on the impacted surfaces of all composite tubes as practical inspection for industrial applications. It was seen that microscope and SEM analysis supported the liquid penetrant inspection, which is a non-destructive testing method.

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Schneider, Jörg J., i Meike Naumann. "Template-directed synthesis and characterization of microstructured ceramic Ce/ZrO2@SiO2 composite tubes". Beilstein Journal of Nanotechnology 5 (25.07.2014): 1152–59. http://dx.doi.org/10.3762/bjnano.5.126.

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An exo-templating synthesis process using polymeric fibers and inorganic sol particles deposited onto structured one-dimensional objects is presented. In particular, CeO2/ZrO2@SiO2 composite tubes were synthesized in a two-step procedure by using electrospun polystyrene fibers as fiber template. First, a sol–gel approach based on an exo-templating technique was employed to obtain polystyrene(PS)/SiO2 composite fibers. These composite fibers were subsequently covered by spray-coating with ceria and zirconia sol solutions. After drying and final calcination of the green body composites, the PS polymer template was removed, and composite tubes of the composition CeO2/ZrO2@SiO2 were obtained. The SiO2/ZrO2/CeO2 microtubes, which consist of interconnected silica particles, are held together by ceria and zirconia deposits formed during the thermal treatment process. These microtubes are mainly located in the pendentive connecting the individual spherical silica particles and glue them together. The composition and crystallinity of this material connecting the individual silica particles contains the elements Ce and Zr and O as mixed oxide solid solution identified by XRD, Raman and high-resolution TEM and EFTEM. High-resolution microscopy techniques allowed for an elemental mapping on the surface of the silica host structure and determination of the O, Zr and Ce elemental distribution with nm precision.

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Sobel, Nicolas, Christian Hess, Manuela Lukas, Anne Spende, Bernd Stühn, M. E. Toimil-Molares i Christina Trautmann. "Conformal SiO2 coating of sub-100 nm diameter channels of polycarbonate etched ion-track channels by atomic layer deposition". Beilstein Journal of Nanotechnology 6 (16.02.2015): 472–79. http://dx.doi.org/10.3762/bjnano.6.48.

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Polycarbonate etched ion-track membranes with about 30 µm long and 50 nm wide cylindrical channels were conformally coated with SiO2 by atomic layer deposition (ALD). The process was performed at 50 °C to avoid thermal damage to the polymer membrane. Analysis of the coated membranes by small angle X-ray scattering (SAXS) reveals a homogeneous, conformal layer of SiO2 in the channels at a deposition rate of 1.7–1.8 Å per ALD cycle. Characterization by infrared and X-ray photoelectron spectroscopy (XPS) confirms the stoichiometric composition of the SiO2 films. Detailed XPS analysis reveals that the mechanism of SiO2 formation is based on subsurface crystal growth. By dissolving the polymer, the silica nanotubes are released from the ion-track membrane. The thickness of the tube wall is well controlled by the ALD process. Because the track-etched channels exhibited diameters in the range of nanometres and lengths in the range of micrometres, cylindrical tubes with an aspect ratio as large as 3000 have been produced.

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Aresipathi, Catherine, Armin Feldhoff i Michael Wark. "Ultra-long SiO2 and SiO2/TiO2 tubes embedded with Pt nanoparticles using magnus green salt as templating structures". Journal of Materials Science 45, nr 5 (4.12.2009): 1179–88. http://dx.doi.org/10.1007/s10853-009-4062-y.

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Aguas, Yelitza, Margarita Hincapié, Camilo Sánchez, Liliana Botero i Pilar Fernández-Ibañez. "Photocatalytic Inactivation of Enterobacter cloacae and Escherichia coli Using Titanium Dioxide Supported on Two Substrates". Processes 6, nr 9 (23.08.2018): 137. http://dx.doi.org/10.3390/pr6090137.

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The antibacterial photocatalytic activity of TiO2 supported over two types of substrates, borosilicate glass tubes (TiO2/SiO2-borosilicate glass tubes (BGT)) and low-density polyethylene pellets (TiO2-LDPE pellets), which were placed in a compound parabolic collectors (CPC) reactor, was evaluated against Enterobacter cloacae and Escherichia coli under sunlight. Three solar photocatalytic systems were assessed, suspended TiO2, TiO2/SiO2-BGT and TiO2-LDPE pellets, at three initial bacterial concentrations, 1 × 105; 1 × 103; 1 × 101 CFU/mL of E. coli and total bacteria (E. cloacae and E. coli). The solar photo-inactivation of E. coli was achieved after two hours with 7.2 kJ/L of UV-A, while total bacteria required four hours and 16.5 kJ/L of UV-A. Inactivation order of E. coli was determined, as follows, suspended TiO2/sunlight (50 mg/L) > TiO2-LDPE pellets/sunlight (52 mg/L) > TiO2/SiO2-BGT/sunlight (59 mg/L), the best E. coli. inactivation rate was obtained with TiO2-LDPE pellets/sunlight, within 4.5 kJ/L and 90 min. The highest total bacteria inactivation rate was found for TiO2/sunlight (50 mg/L) and TiO2-LDPE pellets/sunlight (52 mg/L), within 11.2 kJ/L and 180 min. TiO2 deposited over LDPE pellets was the most effective material, which can be successfully used for water disinfection applications. Bacterial regrowth was assessed 24 h after all photocatalytic treatments, none of those microorganisms showed any recovery above the detection limit (2 CFU/mL).

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Lima, N. M. O., Crislene Rodrigues da Silva Morais, L. M. R. Lima i A. V. Albuquerque. "Electronic Waste: Characterization of the Glass of Cathode Ray Tube Computer for Making Decorative Pieces by Recycling". Materials Science Forum 727-728 (sierpień 2012): 1525–29. http://dx.doi.org/10.4028/www.scientific.net/msf.727-728.1525.

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The vigorous industrialization of the modern world and the incorporation of new consumption habits of society made appears electronic waste. This work had as objective to collect and characterize vitreous residues originating from Cathode Ray Tubes or, popularly, "image tubes", identified for the acronym CRT, which integrate computers monitors that will be recycled in the production of handicrafts. For its characterization were used techniques: X-Ray Fluorescence, Granulometric Analysis, X-Ray Diffraction. After analyses it was observed that glasses of the screen and of the funnel presented different chemical compositions, being silicium oxide (SiO2) the component of larger percentage in these glasses, 59.89% and 48.63%, for screen and funnel, respectively. Funnel presented 29.47% of lead oxide (PbO) while this oxide is absent in the screen. Screen presents significant amounts of barium oxide (10.75%) and strontium oxide (7.71%). Vitreous samples X-ray diffractions of residues of the funnel and the screen are to each other similar, presenting an amorphous band that indicates silica presence, with absence of crystalline phases. Through the presented results can be concluded that computer monitors CRTs has potential for be recycled, because present great amounts of SiO2, oxide that forms the vitreous net.

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Vasilieva, O. V., T. S. Vinogradova, A. V. Parchukov i B. V. Farmakovsky. "Specific features of glass applied for high-speed micrometallurgical casting of microwires". Voprosy Materialovedeniya, nr 3(95) (10.01.2019): 76–81. http://dx.doi.org/10.22349/1994-6716-2018-95-3-76-81.

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The present paper provides a justification for the selection of the basic composition of the system SiO2–B2O3–MgO–BaO–Na2O–K2O; its additional alloying with such elements as oxides PbO, Na2O + K2O, ZrO2 and TiO2 alters the main characteristics of glass tubes for casting microwires. The proposed glass compositions vary significantly the range of metals and alloys used to produce cast microwires in glass insulation.

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Wang, Zhi Qian, Jin Hai Gao, Ning Yao i Bing Lin Zhang. "Preparation of Chain-Like Carbon Nano-Tubes Film and its Field Emission Properties". Materials Science Forum 561-565 (październik 2007): 1153–56. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.1153.

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Chain-like Carbon Nano-tubes films have been synthesized by microwave plasma enhanced chemical vapor deposition (MWPECVD). The titanium-coated ceramic substrate was placed in a stainless steel reaction chamber of MPCVD system. Prior to deposition, The substrates were grinded with SiO2 powder with Fe dopant . The mixture gas of methane (CH4) and hydrogen (H2) was introduced into the chamber. The flow rates of CH4/H2 were controlled at 14/100 sccm by mass flower, respectively. The total pressure in the chamber was kept at 6.2kPa during the deposition. The microwave power of 1700w, worked at a frequency of 2450Mhz, was applied during deposition. The deposition time was only 1minute. The nano-structure of the deposited films was analyzed by SEM, TEM and Raman spectroscopy. The chain-like nano-tubes randomly distributed on the substrates. The nano-tubes are multi-wall with diameter of about 60 nm. The field electron emission characteristics of the Chain-like Carbon Nano-tubes films were measured under the vacuum of 10-5Pa. The low turn-on field of 0.74V/μm and emission current density of 8.5mA/cm2 at electric field 2.9V//μm were obtained. The mechanism of its field emission properties was also discussed.

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Thi, My Hanh Nguyen, Thuc Minh Bui i Nguyen Doan Quoc Anh. "Aiming to the superior of phosphor pattern: Influence of SiO₂ nanoparticles on photoluminescence intensification of YAG:Ce". International Journal of Electrical and Computer Engineering (IJECE) 11, nr 6 (1.12.2021): 4833. http://dx.doi.org/10.11591/ijece.v11i6.pp4833-4839.

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<span lang="EN-US">Yttrium aluminum garnet (YAG: RE) rare-earth-doped phosphors have great photoluminescence (PL) characteristics and are commonly used in light-emitting rectifying tubes. The RE elements used in these phosphors, however, are precious and in shortage. The production of phosphorus containing a limited amount of RE content is therefore essential. One solution is to manufacture Nano composite phosphors that use an inexpensive and more easily available content as a matrix for RE oxide. In this research, we developed a YAG: Ce/SiO2 Nano composite using a sol-gel procedure; in order to impulse micelle formation and agglomeration, poly (ethylene glycol) and urea have been added, respectively. X-ray diffraction, scanning and transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy were used to characterize the Nano composites. In proposing an explanation for this enhancement, we defined the concentration of SiO2 that produced optimum PL enhancement and used geometric models as well as the characterization consequences. Our results demonstrated that a 10% SiO2 concentration produced a 120% PL intensity of pure YAG:Ce. TEM analysis revealed that SiO2 nanoparticles filled the voids between the YAG:Ce crystals' single grain borders, hence inhibiting light scattering, resulting in increased PL. This procedure would be beneficial for the synthesis of low-RE and high-PL phosphors on a wide scale.</span>

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Jan, Jeng Shiung, Po Jui Chen i Yu Han Ho. "Synthesis of Gold Nanoparticle/Silica Nanostructures". Materials Science Forum 688 (czerwiec 2011): 321–25. http://dx.doi.org/10.4028/www.scientific.net/msf.688.321.

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A novel approach is proposed to prepare organic-inorganic composite tubular structure by mineralizing silica and/or gold nanoparticle in the LbL assembled polypeptide multilayers films. Mesoporous silica (m-SiO2) and gold nanoparticle/mesoporous silica (Au NP/m-SiO2) tubes were prepared by subsequent calcination. The LbL assembled poly-L-lysine (PLL)/poly-L-tyrosine (PLT) multilayer film within the inner pores of polycarbonate templates acts as both a mineralizing agent and template for the formation of these materials. The as-prepared mesoporous SiO2and Au NP/m-SiO2tubes have well-defined structures. Gold nanoparticles with size smaller than 8 nm were immobilized in the silica network and the as-prepared Au NP/m-SiO2tubes exhibit good catalytic activity towards the reduction of p-nitrophenol. This approach may provide a facile and general method to synthesize organic-inorganic and metal-oxide nanocomposites with different composition and structures.

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Levy, R. A., E. S. Ramos, L. N. Krasnoperov, A. Datta i J. M. Grow. "Microporous SiO2/Vycor membranes for gas separation". Journal of Materials Research 11, nr 12 (grudzień 1996): 3164–73. http://dx.doi.org/10.1557/jmr.1996.0402.

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In this study, porous Vycor tubes with 40 Å initial pore diameter were modified using low pressure chemical vapor deposition (LPCVD) of SiO2. Diethylsilane (DES) in conjunction with O2 or N2O were used as precursors to synthesize the SiO2 films. Both “single side” (reactants flowing on the same side of porous membrane) and “counterflow” (reactants flowing on both sides of porous membrane) reactant geometries have been investigated. The flow of H2, He, N2, Ar, and toluene (C7H8) was monitored in situ after each deposition period. Membranes modified by the “single side” reactants geometry exhibited good selectivities between small and large molecules. However, cracking in these membranes after prolonged deposition limited the maximum achievable selectivity values. Higher selectivities and better mechanical stability were achieved with membranes produced using the “counterflow” reactants geometry. Pore narrowing rate was observed to increase with oxidant flow (O2 or N2O). For membranes prepared using both oxidants, selectivities on the order of 1000: 1 were readily attained for H2 and He over N2, Ar, and C7H8. As compared to O2, the use of N2O caused improvements in both the pore narrowing rate and N2: C7H8 selectivity. Membranes prepared using the “counterflow” geometry showed no signs of degradation or cracking after thermal cycling.

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Arun, M., Debabrata Barik, K. P. Sridhar i Milon Selvam Dennison. "Thermal Performance of a Dimpled Tube Parabolic Trough Solar Collector (PTSC) with SiO2 Nanofluid". International Journal of Photoenergy 2022 (28.08.2022): 1–14. http://dx.doi.org/10.1155/2022/8595591.

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In this research work, dimple texture tubes and silicon dioxide (SiO2) nanofluid were used to analyze the performance parameters of a solar water heater. For this purpose, SiO2 was mixed with deionized (DI) water using an ultrasonic dispersion device to prepare the nanofluids (SiO2/DI-H2O). The size of the nanoparticle was in the range of 10-15 nm. Different volume concentrations of the nanoparticles in the range of 0.1% to 0.5%, in steps of 0.1%, were chosen to prepare the nanofluids to carry out the experiments. Apart from this, computational fluid dynamics (CFD) tool was used to numerically analyze the parameters affecting the performance of the solar water heater, as well as the fluid flow pattern in the dimple texture tube. During the experiment, the mass flow rate of the base fluid (water) varied in the range of 0.5 kg/min to 3.0 kg/min in steps of 0.5 kg/min. The added advantage of the dimple texture tube design led to an increase in turbulence in the flow pattern, resulting 34.2% increase in the convective heat transfer efficiency compared with the plain tube. Among all experimental modules, SiO2/DI-H2O with a mass flow rate of 2.5 kg/min and 0.3% volume concentration gives overall optimized results in absolute energy absorption, gradient temperature, and efficiency of the solar water heater. The efficiency metrics of the experimental results were compared with the simulation results, and it was in the acceptable range with an overall deviation of ±7.42%.

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Darzi, A. A. Rabienataj, Mousa Farhadi, Kurosh Sedighi, Rouzbeh Shafaghat i Kaveh Zabihi. "Experimental investigation of turbulent heat transfer and flow characteristics of SiO2/water nanofluid within helically corrugated tubes". International Communications in Heat and Mass Transfer 39, nr 9 (listopad 2012): 1425–34. http://dx.doi.org/10.1016/j.icheatmasstransfer.2012.07.027.

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Thanheiser, Stefan, Markus Haider i Paul Schwarzmayr. "Experimental Investigation of the Heat Transfer between Finned Tubes and a Bubbling Fluidized Bed with Horizontal Sand Mass Flow". Energies 15, nr 4 (11.02.2022): 1316. http://dx.doi.org/10.3390/en15041316.

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The sandTES technology utilizes a fluidized bed counter current heat exchanger for thermal energy storage applications. Its main feature is an imposed horizontal flow of sand (SiO2) particles fluidized by a vertical air flow across a heat exchanger consisting of several horizontal rows of tubes. Past international research on heat transfer in dense fluidized beds has focused on stationary (stirred tank) systems, and there is little to no information available on the impact of longitudinal or helical fins. Previous pilot plant scale experiments at TU Wien led to the conclusion that the currently available correlations for predicting the heat transfer coefficient between the tube surface and the surrounding fluidized bed are insufficient for the horizontal sand flow imposed by the sandTES technology. Therefore, several smaller test rigs were designed in this study to investigate the influence of different tube arrangements and flow conditions on the external convective heat transfer coefficient and possible improvements by using finned tubes. It could be shown that helically finned tubes in a transversal arrangement, where the horizontal sand flow is perpendicular to the tube axes, allows an increase in the heat transfer coefficient per tube length (i.e., the virtual heat transfer coefficient) by a factor of 3.5 to about 1250 W/m2K at ambient temperature. Based on the literature, this heat transfer coefficient is expected to increase at higher temperatures. The new design criteria allow the design of compact, low-cost heat exchangers for thermal energy storage applications, in particular electro-thermal energy storage.

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Rasoolizadeh Shooroki, Abolfazl, Asghar Dashti Rahmatabadi i Mahdi Zare Mehrjardi. "Effect of using hybrid nano lubricant on the thermo-hydrodynamic performance of two lobe journal bearings". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 236, nr 6 (19.11.2021): 1167–85. http://dx.doi.org/10.1177/13506501211053089.

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Due to the wide range of journal bearings applications in the industrial machine, significant efforts have been made by tribology researchers to improve their performance in recent years. Designing new bearings geometry and using lubricants with new chemical compounds including additives are the most common solutions proposed to enhance the performance of journal bearing supports. New advancements in nanotechnology and producing the various types of nano particles have provided the chance of upgrading the properties of commercial lubricants. According to the different effect of nano fluids on the performance of mechanical systems corresponding to their composition, today they are used to achieve different goals in lubrication systems. Upgrading the steady state performance parameters including load carrying capacity, attitude angle, surface cooling and effective viscosity are among the expected results of applying nano lubricant in journal bearings. So, in this study the performance of hydrodynamic two lobe journal bearings lubricated with SiO2-multiwall carbon nano tubes /SAE40 hybrid nano fluid is presented considering the thermal effects. For this purpose, the governing Reynolds and energy equations as well as the equation of heat transfer in bearing shell are modified based on the properties of assumed rotor-bearing system. Then the effects of solid volume fraction of nano particles on the performance of two lobe bearings are studied for different amount of bearing noncircularity. The results indicate that upgrading the solid volume fraction of added nano particle to the SAE40 base oil, enhances the lubricant pressure distribution, load carrying capacity, and lubricant effective viscosity. Further, by increasing the solid volume fraction, the attitude angle and temperature of lubricant and rotor-bearing surfaces experience a decreasing trend. Generally, it's obvious from the results that choosing the appropriate solid volume fraction of SiO2-multiwall carbon nano tubes in hybrid nano oil composition, especially for high value of preload factor, can improve the performance of two lobe bearings.

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Bai, Li, i Tan Liu. "Research on Different Heat Transfer Characteristics of the Dirt on the Pipe". Applied Mechanics and Materials 644-650 (wrzesień 2014): 5179–82. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.5179.

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In this study, the dirt adhered on the tubes of different materials (copper alloy tube, stainless steel pipe, polyethylene-aluminum composite pipe) were studied by the scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, PCR amplification, DGGE electrophoresis analyzers. Experimental results show that the microorganism in dirt on the copper alloy tube is mainly shuttle-type bacteria, and the distribution is dense. Stainless steel pipe’s dirt colony is assembling with long bacilli and cocci, polyethylene-aluminum composite pipe’s dirt is the large bacilli and density cocci. Three kinds of dirt in the pipe contains inorganic crystals with SiO2 and CaCO3, and the same type of element, but the content is differences, polyethylene-aluminum composite pipe have greater richness of microbial species, a copper alloy tube’s dirt is of little microorganisms.

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Ye, Zhupeng, Zhihao Zhou, Yuan Zhang, Longfei Zhao i Yanwei Zeng. "Fe3+-assistantly carbon-impregnated porous SiO2 mesoscale tubes as Li-ion battery anode materials with highly enhanced performances". International Journal of Hydrogen Energy 47, nr 27 (marzec 2022): 13442–59. http://dx.doi.org/10.1016/j.ijhydene.2022.02.085.

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Ferrouillat, Sébastien, André Bontemps, João-Paulo Ribeiro, Jean-Antoine Gruss i Olivier Soriano. "Hydraulic and heat transfer study of SiO2/water nanofluids in horizontal tubes with imposed wall temperature boundary conditions". International Journal of Heat and Fluid Flow 32, nr 2 (kwiecień 2011): 424–39. http://dx.doi.org/10.1016/j.ijheatfluidflow.2011.01.003.

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Kahlenberg, Volker, i Tanja Manninger. "Rb2Lu[Si4O10]F, a tubular chain silicate". Acta Crystallographica Section E Structure Reports Online 70, nr 3 (19.02.2014): i14. http://dx.doi.org/10.1107/s1600536814003043.

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Single crystals of Rb2Lu[Si4O10]F (dirubidium lutetium tetrasilicate fluoride) were obtained in flux-synthesis experiments in the system SiO2–Lu2O3–RbF. The compound belongs to the group of tubular chain silicates,i.e.it is based on multiple chains of condensed [SiO4] tetrahedra forming closed columns. The periodicity of the unbranched multiple chains is four and corresponds to the length of thebaxis. Adjacent columns are connected by Lu3+cations, which are coordinated by four oxide and two fluoride anions in the form of slightly distorted octahedra. By sharing common fluoride corners, the single octahedra are linked into chains running parallel to the silicate tubes. Electroneutrality is achieved by the incorporation of additional Rb+cations. All four symmetrically independent rubidium ions, four out of twelve oxide as well as the two fluoride anions are located on mirror planes. The remaining atoms reside on general positions.

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Pal, Sunil K., Youngsuk Son, Theodorian Borca-Tasciuc, Diana-Andra Borca-Tasciuc, Swastik Kar, Robert Vajtai i Pulickel M. Ajayan. "Thermal and electrical transport along MWCNT arrays grown on Inconel substrates". Journal of Materials Research 23, nr 8 (sierpień 2008): 2099–105. http://dx.doi.org/10.1557/jmr.2008.0256.

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This work reports on thermal and electrical conductivities and interface resistances for transport along aligned multiwalled carbon nanotubes (CNT) films grown on a nickel superalloy (Inconel) substrate. The measured specific thermal resistance of the combined Inconel–CNT and indium–CNT interfaces is of the same order as reported for CNT and silicon or SiO2 interfaces but much higher than theoretical predictions considering perfect contact between the tubes and substrate. Imperfect mechanical contact with the substrate and a large contribution caused by indium–CNT interface are thought to be mainly responsible for the high interface resistances and the low effective values of thermal and electrical conductivities. However, reported results represent an incentive for further research on CNT synthesis on metallic substrates for thermal management applications and pave the way for much easier integration of carbon nanotubes in electronic applications.

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Kawase, Makoto, Akifumi Ido i Masahiko Morinaga. "Effectiveness of SiO2/TiO2/Al2O3-Based/TiO2 Coating for Suppressing Circumferential Cracking in Boiler Tubes at Thermal Power Plants". Oxidation of Metals 96, nr 3-4 (27.07.2021): 361–72. http://dx.doi.org/10.1007/s11085-021-10065-4.

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Kawahara, Yuuzou, Kouji Sasaki i Yuuji Nakagawa. "Development and Application of High Cr-High Si-Fe-Ni Alloys to High Efficiency Waste-To-Energy Boilers". Materials Science Forum 522-523 (sierpień 2006): 513–22. http://dx.doi.org/10.4028/www.scientific.net/msf.522-523.513.

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In order to improve the durability of high efficiency waste-to-energy boilers, it is essential to develop and apply high temperature corrosion-resistant materials having a long life time according to the intensity of the corrosion conditions. Two types of high Cr-high Si-Fe-Ni base and high Cr-high Si-Ni-Fe base alloy seamless tubes; MAC-N (26Cr-3.5Si-11Fe-Ni base) alloy and MAC-F (23Cr-3.8Si-38Ni-Fe base) alloy respectively which contain no expensive Mo and have better corrosion resistance than the existing alloys under severe corrosive environments of waste combustion gas, have developed. The optimum alloy composition range were defermined by confirming the effect of the alloying elements on the corrosion resistance in the laboratory corrosion tests. Furthermore, the seamless tubes were mounted on the actual superheater of the 500oC/9.8MPa high efficiency waste-to-energy boiler to examine the durability over a period of four years. As a result, it was confirmed that the MAC-N and MAC-F alloys have better corrosion resistance than the Alloy625 and 310HCbN. In addition, it has become clear that corrosion resistance of both alloys is displayed through the formation of SiO2 rich protective scale due to the combined addition of the principal elements, Si, Cr, Fe and Ni. Under conditions of high Cl content molten deposits and severe thermal cycle, the corrosion rate increases as the results of deterioration of protective oxidation scale.

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Hejl, Ewald, i Friedrich Finger. "Chiral Proportions of Nepheline Originating from Low-Viscosity Alkaline Melts. A Pilot Study". Symmetry 10, nr 9 (18.09.2018): 410. http://dx.doi.org/10.3390/sym10090410.

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Chromatographic interaction between infiltrating solutions of racemic mixtures of enantiomers and enantiomorphic minerals with chiral excess has been proposed as a scenario for the emergence of biomolecular homochirality. Enantiomer separation is supposed to be produced by different partition coefficients of both enantiomers with regard to crystal faces or walls of capillary tubes in the enantiomorphic mineral. Besides quartz, nepheline is the only common magmatic mineral with enantiomorphic symmetry. It crystallizes from SiO2-undersaturated melts with low viscosity and is a promising candidate for chiral enrichment by autocatalytic secondary nucleation. Under liquidus conditions, the dynamic viscosity of silicate melts is mainly a function of polymerization. Melts with low concentrations of SiO2 (<55 wt%) and rather high concentrations of Na2O (>7 wt%) are only slightly polymerized and hence are characterized by low viscosities. Such melts can ascend, intrude or extrude by turbulent flow. Fourteen volcanic and subvolcanic samples from alkaline provinces in Africa and Sweden were chemically analyzed. Polished thin sections containing fresh nepheline phenocrysts were etched with 1% hydrofluoric acid at 20 °C for 15 to 25 min. Nepheline crystals suitable for a statistical evaluation of their etch figures were found in four samples. Crystals with chiral etch figures are mainly not twinned. Their chiral proportions in grain percentages of single crystals are close to parity in three samples. Only one sample shows a slight chiral excess (41.67% L-type vs. 58.33% D-type) but at a low level of significance (15 vs. 21 crystals, respectively).

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Vidyasagar Shetty et al.,, Vidyasagar Shetty et al ,. "An Effect of SiO2 and Carbon Nano Tubes on Mechanical Properties of LM-12 Aluminium Alloy Hybrid Metal Matrix Composite". International Journal of Mechanical and Production Engineering Research and Development 9, nr 2 (2019): 537–44. http://dx.doi.org/10.24247/ijmperdapr201952.

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Ardekani, A. Mokhtari, V. Kalantar i M. M. Heyhat. "Experimental study on the flow and heat transfer characteristics of Ag/water and SiO2/water nanofluids flows in helically coiled tubes". Journal of Thermal Analysis and Calorimetry 137, nr 3 (16.01.2019): 779–90. http://dx.doi.org/10.1007/s10973-018-08001-x.

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Jin, Tetsuro, Koji Kuraoka, Yasuyuki Matsumura, Takaaki Onishi i Tetsuo Yazawa. "Formation of Silicalite-1 in Channels of Novel SiO2-ZrO2 Porous Glass Tubes Used as Both a Silica Source and a Substrate". Journal of the American Ceramic Society 85, nr 10 (październik 2002): 2569–71. http://dx.doi.org/10.1111/j.1151-2916.2002.tb00497.x.

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Weikart, Christopher M., Adam P. Breeland, Matt S. Wills i Martin E. Baltazar-Lopez. "Hybrid Blood Collection Tubes: Combining the Best Attributes of Glass and Plastic for Safety and Shelf life". SLAS TECHNOLOGY: Translating Life Sciences Innovation 25, nr 5 (19.05.2020): 484–93. http://dx.doi.org/10.1177/2472630320915842.

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SiO2 Medical Products, Inc. developed hybrid blood collection tubes (BCTs) that combine the breakage resistance of plastic and a shelf life approaching that of glass. These blended attributes provide improved BCT safety and reliability for patients and clinical workers. A shelf life of at least 2 y with less than 10% draw volume variation was demonstrated on evacuated hybrid BCTs, which is approximately 7 times longer than standard polyethylene terephthalate (PET) BCTs. This translates into more consistent and reliable blood draw volumes over a longer shelf life. The moisture vapor barrier of hybrid BCTs is 5 times lower than that of PET BCTs, which significantly reduces preservative evaporation over their shelf life. As a result, the risk of preservative gelation and alteration to the blood-to-preservative ratio mix is practically eliminated. Cyclic olefin polymer (COP) exhibits superior impact resistance to breakage because of its high ductility and impact strength and is not influenced by defects and flaws as is glass. Although COP has a mechanical toughness comparable with that of PET, it maintains this over a wider range of temperatures (–70 to 121 °C). As a result, COP can tolerate steam sterilization and cold storage temperatures without mechanical fatigue, deformation, or breakage. Lastly, extreme centrifugation of water-filled BCTs did not impose breakage of any kind.

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Sieke, Corinna, Ingo Hartenbach i Thomas Schleid. "Sulfidisch derivatisierte Oxodisilicate der schweren Lanthanide vom Formeltyp M4S3[Si2O7] (M = Gd - Tm) / Sulfide Derivatized Oxodisilicates of the Heavy Lanthanides with the Formula M4S3[Si2O7] (M = Gd - Tm)". Zeitschrift für Naturforschung B 57, nr 12 (1.12.2002): 1427–32. http://dx.doi.org/10.1515/znb-2002-1214.

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The sulfide derivatized oxodisilicates M4S3[Si2O7] of the heavy lanthanides (M = Gd - Tm) have been synthesized by reaction of M, M2O3, S, and SiO2 using MCl3 as flux in evacuated silica tubes at 850 °C for 7 d. The title compounds crystallize tetragonally in the space group I41/amd with 8 formula units per unit cell. Their crystal structure contains isolated [Si2O7]6− pyroanions of two vertex-sharing [SiO4] tetrahedra in eclipsed conformation with Si-O-Si bridging angles of about 130°. The two crystallographically independent lanthanide cations (M3+) both reside in tricapped trigonal prismatic environments of chalcogen ligands. In the case of M1 five S2− and three plus one O2− anions (CN = 8+1), for M2 three S2− and six O2− anions (CN = 9) fill the coordination spheres. Two of the three different sulfide anions are surrounded by four M3+ cations forming a seesaw (S2) and a square (S3), respectively. The third one (S1) is coordinated by six lanthanide cations in the form of a distorted octahedron. The whole structure is basically built up of cationic lanthanide silicate layers which are threaded by sulfide anions.

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Shah, Tayyab Raza, Hafiz Muhammad Ali i Muhammad Mansoor Janjua. "On Aqua-Based Silica (SiO2–Water) Nanocoolant: Convective Thermal Potential and Experimental Precision Evaluation in Aluminum Tube Radiator". Nanomaterials 10, nr 9 (1.09.2020): 1736. http://dx.doi.org/10.3390/nano10091736.

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Although the research on potential use of nanofluids in automotive vehicles is in its embryonic stage, a number of studies have suggested the strong prospect of nanofluids for the efficient thermal management of automotive vehicles. Nevertheless, the pinnacle of nanofluid-based systems awaits stable nanoparticle suspension. The present work studies the heat transfer performance of an aluminum tube automotive radiator with 31 flattened tubes and louvered fins using water and different concentrations (0.04, 0.08, and 0.12 vol.%)-based SiO2/water nanofluids as the engine coolant. Inlet temperature and flowrate of the fluid were varied from 60 to 70 °C and 12 to 18 LPM, respectively. The topmost increment in heat transfer rate of 36.92% and Nusselt number of 45.53% were observed in the upper range of tested operational parameters, however, the relative heat transfer increment percentage dropped from 5% (between 0.04 and 0.08 vol.%) to 3.5% (between 0.08 and 0.12 vol.%) due to agglomeration and cluster formation caused by the presence of a greater number of nanoparticles. Precise evaluation of the experimental results was also carried out by reperforming the tests after three days of initial experimentations. A mere deviation of less than 1% was observed between the initial and repeated tests, however, the decline was caused due to the synergistic effects of clustering and fouling.

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Wan, Ye, Xiaolin Wang, I.-Ming Chou, Wenxuan Hu, Yang Zhang i Xiaoyu Wang. "An Experimental Study of the Formation of Talc through CaMg(CO3)2–SiO2–H2O Interaction at 100–200°C and Vapor-Saturation Pressures". Geofluids 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/3942826.

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The metamorphic interaction between carbonate and silica-rich fluid is common in geological environments. The formation of talc from dolomite and silica-rich fluid occurs at low temperatures in the metamorphism of the CaO–MgO–SiO2–CO2–H2O system and plays important roles in the formation of economically viable talc deposits, the modification of dolomite reservoirs, and other geological processes. However, disagreement remains over the conditions of talc formation at low temperatures. In this study, in situ Raman spectroscopy, quenched scanning electron microscopy, micro-X-ray diffraction, and thermodynamic calculations were used to explore the interplay between dolomite and silica-rich fluids at relatively low temperatures in fused silica tubes. Results showed that talc formed at ≤200°C and low CO2partial pressures (PCO2). The reaction rate increased with increasing temperature and decreased with increasingPCO2. The major contributions of this study are as follows:(1)we confirmed the formation mechanism of Mg-carbonate-hosted talc deposits and proved that talc can form at ≤200°C;(2)the presence of talc in carbonate reservoirs can indicate the activity of silica-rich hydrothermal fluids; and (3) the reactivity and solubility of silica require further consideration, when a fused silica tube is used as the reactor in highP–Texperiments.

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Abdul Jalil, Wijdan Deyaa, i Husaein Ali Hasan Kahachi. "The Impact of Nano-Concrete in Contemporary Architecture". Wasit Journal of Engineering Sciences 6, nr 2 (30.08.2018): 38–45. http://dx.doi.org/10.31185/ejuow.vol6.iss2.90.

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The rapid development in technology of building materials and systems could be easily observed these days in the huge building advances such as achieving building sizes, shapes, forms and speed of building which could never be achieved by using ordinary building materials. One of the interested break overs in building materials technologies is Nano-Concrete. Nano-Concrete is the substance of adding nanomaterial to concrete. Nano-concrete has special specifications and properties when compared with the ordinary concrete mixes such as adding Nano SiO2, Nano TiO2 and Carbon Nano tubes to improve performance and structural resistance. This extended the limits of building technologies thus enabling architects to achiev more complex forms with higher performance, or giving the concrete special properties such as light pass-through concrete or self-compacting concrete. The research deals with impact Nano-concrete on contemporary architecture by following a set of objectives: What is Nano-concrete in brief? How does Nano-concrete mixes differ from the ordinary mixes of concrete? The application of Nano-concrete in buildings and its effects on contemporary architecture. The research extracted a set of main findings and recommendations from the analyzing of the effects of Nano-Concrete on Architecture.

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Wolterbeek, Timotheus K. T., i Suzanne J. T. Hangx. "Remediation of Annular Gas Migration along Cemented Wellbores Using Reactive Mineral Fluids: Experimental Assessment of Sodium Bicarbonate and Sodium Silicate-Based Solutions". Energies 14, nr 22 (10.11.2021): 7507. http://dx.doi.org/10.3390/en14227507.

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Achieving zonal isolation along wellbores is essential for upholding the containment integrity of subsurface reservoirs and preventing fluid seepage to the environment. The sealing performance of Portland cements conventionally used to create barriers can be severely compromised by defects like fractures or micro-annuli along casing–cement–rock interfaces. A possible remediation method would be to circulate reactive fluids through compromised cement sections and induce defect clogging via mineral precipitation. We assess the sealing potential of two prospective fluids: sodium bicarbonate and sodium silicate solutions. Reactive flow-through experiments were conducted on 6-m-long cemented steel tubes, bearing ~20-μm-wide micro-annuli, at 50 °C and 0.3–6 MPa fluid pressure. For the sodium bicarbonate solution (90 g/kg-H2O), reactive flow yielded only a minor reduction in permeability, with values remaining within one order. Injection of sodium silicate solution (37.1 wt.%, SiO2:Na2O molar ratio M= 2.57) resulted in a large decrease in flow rate, effectively reaching the setup’s lower measurement limit in hours. However, this strong sealing effect can almost certainly be attributed to gelation of the fluid through polymerisation, rather than defect clogging via mineral precipitation. For both fluids investigated, the extent of solids precipitation resulting from single-phase injection was less than anticipated. This shortfall is attributed to ineffective/insufficient liberation of Ca-ions from the alkaline phases in the cement.

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Kumar, Rajesh, i Ambesh Dixit. "All oxide sol-gel assisted SiO2/(ZnO/Sn-In2O3)n/SS dielectric/conducting multilayer based spectrally selective coating on Stainless Steel tubes for potential solar thermal application". Solar Energy 236 (kwiecień 2022): 561–68. http://dx.doi.org/10.1016/j.solener.2022.03.032.

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Kia, Seyedmahmood, Shoaib Khanmohammadi i Ali Jahangiri. "Experimental and numerical investigation on heat transfer and pressure drop of SiO2 and Al2O3 oil-based nanofluid characteristics through the different helical tubes under constant heat fluxes". International Journal of Thermal Sciences 185 (marzec 2023): 108082. http://dx.doi.org/10.1016/j.ijthermalsci.2022.108082.

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AL-Assadi, Zainab I., Fawzia Asadi i Ban M. Alameri. "Eliminate obstacles of use the solar systems as buildings facades using multilayers optical interference filters". Technium Romanian Journal of Applied Sciences and Technology 3, nr 8 (2.10.2021): 83–91. http://dx.doi.org/10.47577/technium.v3i8.4829.

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The Building design in a correct way and totalitarian requires integration of using solar energy technologies in the architectural design stage of the roofs and facades as the most appropriate places to obtain solar energy because it greatly affects the architectural aesthetic. This integration has to be taken into account at the design stage, which leads to effective and attractive solutions. Architecture needs the energy to complete its functions to increases human effectiveness and ability to do its tasks better, solar energy is the main factor of providing the necessary energy due to its abundance as well as being clean energy and does not cause polluting emissions to the environment. To provide a comfortable indoor environment for the occupants, Solar Thermal Collectors (STC) and Photovoltaics Cells (PV) used, which convert solar energy into thermal energy and electrical energy, respectively. The main problem of this study is concerning with the problems of the black color, visible tubes, metallic strip gradients (absorption strip), and welding points of the solar systems which gives the facades of the buildings an undesirable view and weakens the aesthetic aspect of the buildings and limits the abilities of architects to use because of their black color and undesirable aspect. The aim of this study is a design of optical interference filter (multilayer coatings) prepared by RF magnetron sputtering as a solution to the problem of black color, visible tubes, metallic strip gradients (absorption strip), and welding points in solar thermal collectors and photovoltaic cells, which are the main reasons for not using solar systems as building facades, this technique works to increase the efficiency of the solar systems and increase the amount of clean energy generated, also enhancing the expressive and aesthetic aspect of facades of buildings. In the NIR region this filter works as an anti-reflective coating. Also the coating includes a high color reflection at a certain wavelength in the VIS region to give the solar system an aesthetic feature, which is used as building facades by using appropriate dielectric substances with high and low reflective indexes likes SiO2 and MgF2 respectively. The results of the study showed that the increase in the number of layers will lead to an increase in the visible reflectivity peak, while near of infrared region remains an anti-reflective with a high Transmission of solar rays, thus increasing solar systems efficiency.

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Gunnasegaran, P., N. H. Shuaib, M. F. Abdul Jalal i E. Sandhita. "Numerical Study of Fluid Dynamic and Heat Transfer in a Compact Heat Exchanger Using Nanofluids". ISRN Mechanical Engineering 2012 (4.04.2012): 1–11. http://dx.doi.org/10.5402/2012/585496.

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Compact heat exchangers (CHEs) are characterized by a high surface area per unit volume, which can result in a higher efficiency than conventional heat exchangers. They are widely used in various applications in thermal fluid systems including automotive thermal fluid systems such as radiators for engine cooling systems. Recent development of nanotechnology brings out a new heat transfer coolant called “nanofluids,” which exhibit larger thermal properties than conventional coolants due to the presence of suspended nanosized composite particles in a base fluid. In this study, a numerical investigation using different types of nanoparticles in ethylene glycol-base fluid namely copper (Cu), diamond (DM), and silicon dioxide (SiO2) on automobile flat tube plate-fin cross-flow CHE is explored. The nanoparticles volume fraction of 2% is considered for all types of nanofluids examined in this study. The three-dimensional (3D) governing equations for both liquid flow and heat transfer are solved using a standard finite volume method (FVM) for the range of Reynolds number between 4000 and 7000. The standard κ-ε turbulence model with wall function is employed. The computational model is used to study the variations of shear stress, skin friction, and convective heat transfer coefficient. All parameters are found to yield higher magnitudes in the developing and developed regions along the flat tubes with the nanofluid flow than base fluid. The pressure drop is slightly larger for nanofluids but insignificant at outlet region of the tube. Hence, the usage of nanofluids in CHEs transfers more energy in a cost-effective manner than using conventional coolants.

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Baioumy, H. M., i M. S. Hassan. "Authigenic halloysite from El-Gideda iron ore, Bahria Oasis, Egypt: characterization and origin". Clay Minerals 39, nr 2 (czerwiec 2004): 207–17. http://dx.doi.org/10.1180/0009855043920131.

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AbstractHalloysite in El-Gideda iron mine occurs as very soft, light and white-to-pinkish white pockets and lenses ranging in diameter from 50 cm to 1 m within the iron ore. Highly hydrated halloysite is the main constituent of these pockets beside some kaolinite and alunite. The diffraction pattern of the clay fraction (<2 mm) shows a rather broad and diffuse 001 reflection spread between 10.3 and 13.6°2θ. Upon treatment, the 001 reflection of halloysite expands up to 10.94 Å and 11.9 Å corresponding to ethylene glycol and dimethyl formamide treatment, respectively. After these treatments, kaolinite appeared with its characteristic basal spacing (~7 Å). The percentage of halloysite in halloysite-intercalated kaolinite ranged between 80 and 90%. Heating to 350°C, produces a kaolinite-like structure (~7.1 Å) that developed to a metakaolinite-structure when heated to 550°C. Morphologically, halloysite appears as well developed tubes composed entirely of SiO2 and Al2O3, while kaolinite is characterized by very fine platelets arranged in book-like or rosette-like shapes. A differential thermal analysis curve of the studied halloysite showed an endothermic peak at ~138°C due to the dehydration of interlayer water of halloysite. The small shoulder at ~540°C and the endothermic peak at ~593°C is attributed to the dehydroxylation of halloysite, kaolinite and alunite. On the other hand the exothermic peak that appeared at 995°C is due to the formation of new phases such as mullite and/or spinel. The infrared vibrational spectrum is typical of highly disordered halloysite and kaolinite.Halloysite was formed as a result of alteration of the overlying glauconite suggesting intensive chemical alteration during a humid wet period that prevailed in the Bahria Oasis during the late Eocene. Glauconite alteration releases K, Fe, silica and alumina. Iron forms at least part of the iron ore in the El-Gideda mine while alumina forms halloysite as well as alunite when interacted with silica in an acidic environment.

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Sunkara Venkata Satyanarayana Rahul, Busireddy Dinesh Reddy, Vegu Himasurya Teja i Harish Rajan. "Melting Characteristics of Hybrid Nano Enhanced Phase Change Material in a Finned Circular Tube". Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 102, nr 1 (3.02.2023): 37–50. http://dx.doi.org/10.37934/arfmts.102.1.3750.

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In this study, the melting characteristics of hybrid nano-enhanced phase change material in a finned circular tube were studied by using the Finite volume method. This setup of circular tubes with a phase change material is used as cooling systems in automotive industries, air-conditioning, refrigerators, and other applications of cooling systems. There is a need for enhancing the specific heat capacity of this system to ensure that the system works even at high temperatures. As the current problem includes many design parameters and boundary constraints, the finite volume method has been performed to obtain a detailed report and data to examine the deformation of the hybrid nanoparticles and heat transfer rate on the corresponding surface. The current paper reviews and focuses mainly on the high-temperature PCM. And the suitable PCM has been selected based on its limitations and properties. To ensure the increased specific heat capacity, a salt-based phase change material, i.e., a mixture of NaNO3-KNO3 (60:40 ratio) binary salt. This PCM could hold a temperature up to 334◦C before melting to change its phase. In addition to spherical-shaped nanoparticles of silica (SiO2) in this binary salt, it tends to have a significant potential for enhancing the thermal storage characteristics of the NaNO3-KNO3 binary salt. On an extended surface, Finns are used on the peripheral of the circular tube to increase the surface area, which leads to an increase in frictional resistance resulting in a reduced airflow rate in the vicinity of the finned surface. From case studies, it has been found that the optimum fork-shaped fin array with two branches gives higher heat dissipation than the optimum rectangular fin. In the majority of the cases, the optimum fork-shaped fin array gives a 59.9% higher heat transfer rate compared to the rectangular fin array. Thus, the melting characteristics of the hybrid of NaNO3- KNO3 with nanoparticles of silica are studied when placed in a circular tube containing fork-shaped fins.

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Wang, Shanlin, Jing Zhang, Xinquan Yu i Youfa Zhang. "Condensed dewdrops self-ejecting on sprayable superhydrophobic CNT/SiO2 composite coating". RSC Advances 7, nr 44 (2017): 27574–77. http://dx.doi.org/10.1039/c7ra04102k.

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We report a type of novel condensed dewdrops self-ejecting coating from sprayable paint, which was prepared by a self-assembly process of SiO₂ nano-particles on hydroxylated carbon nano-tubes with subsequent chemical modification.

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Awungacha Lekelefac, Colin, Peter Czermak i Michael Herrenbauer. "Evaluation of Photocatalytic Active Coatings on Sintered Glass Tubes by Methylene Blue". International Journal of Photoenergy 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/614567.

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A comparative study between ten different photocatalytic active coatings was done. The effectiveness and photocatalytic activity of the coatings were studied by degradation experiments of methylene blue (MB) dye under UV light illumination. The reactor design consisting of sintered glass packed in a borosilicate tube placed between two planar dielectric barrier discharge lamps (Osram Planon) is reported for the first time. The coatings consisted of either titania, silica, or zinc on sintered borosilicate glass. The advantage of sol-gel in catalyst preparation was exploited to combine catalyst to act as cocatalyst. TiO2-P25 widely applied in suspension systems was effectively immobilized on sintered glass support with the aid of tetraethylorthosilicate (TEOS) solution which acted as support material. Results indicated that TiO2-P25+SiO2, TiO2-P25+SiO2+Pt, and TiOSO4_30,6wt% films showed highest degradation rates close to 100% after 90 min illumination with degradation rates exceeding 50% after 30 minutes. TTIP+Pt showed lowest degradation rate.

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Nikitin, Vadim, Paulius Bogdevičius i Marijonas Bogdevičius. "OVERVIEW OF NUMERICAL METHODS FOR SIMULATING RANQUE-HILSCH EFFECT WITHIN VORTEX TUBES / LIETUVOS KARJERŲ UŽPILDŲ POVEIKIO BETONO ŠARMINEI KOROZIJAI TYRIMAI". Mokslas – Lietuvos ateitis 7, nr 5 (3.02.2016): 571–76. http://dx.doi.org/10.3846/mla.2015.830.

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The main goal of this paper is to present a summarized overview of the methods used for Ranque–Hilsch vortex tube numerical analysis using computational fluid dynamics (CFD). The overview is mainly focused on the most recently conducted studies that are both backed by experimental data and is evaluated by the authors as being in good agreement with experimental results. Generalized tendencies in computational vortex tube analysis are presented while focusing on researchers’ approach towards the geometric model used for the study and the governing equations. A brief introduction to the subject matter is presented followed by a short retrospective of the previous studies and related challenges. The conclusions are formed based on the most recent, as well as previously analysed, published research results. Užpildų šarminė korozija betone vyksta reaguojant cemente esantiems natrio ir kalio hidroksidams (šarmams) su aktyviu SiO2, esančiu kai kuriuose užpilduose. Vykstant šiai reakcijai betone susidaro didelių vidinių įtempių, kurie sukelia betono deformacijas, pleišėjimą ir suirimą. Reakcija vyksta lėtai, betono irimo požymių atsiranda tik po kelių mėnesių ar metų. Tyrimams buvo naudojami dviejų skirtingų karjerų užpildai. Atlikus tyrimus nustatyta, kad Lietuvos žvyro karjerai užteršti reaktyviomis dalelėmis, turinčiomis amorfinio silicio dioksido, reaguojančio su cemente esančiais natrio ir kalio šarmais, ir sukeliančiomis betono šarminę koroziją. Nustatyta, kad pagal AAR 2 stambieji užpildai priskiriami II grupei – galimai reaktyviems užpildams, nes jų plėtra po 14 parų viršija 0,1 %.

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Dolgih, Igor I., Dmitry A. Zhukalin i Larisa A. Bityutskaya. "КОЛЛЕКТИВНАЯ ДИНАМИКА И РАЗМЕРНЫЕ ЭФФЕКТЫ ФАЗООБРАЗОВАНИЯ В СИСТЕМЕ АЭРОСИЛ – ПОЛИСТИРОЛЬНЫЙ ЛАТЕКС". Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 21, nr 3 (26.09.2019): 366–73. http://dx.doi.org/10.17308/kcmf.2019.21/1150.

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В стандартных условиях проведен модельный эксперимент по влиянию сил обеднения на процесс высыхания капли взвесей невзаимодействующих частиц аэросил – полистирольный латекс. Впервые обнаружен быстропротекающий процесс фазового превращения аэросила в кристаллический SiO2 в течение десятков секунд, сопровождающийся резким изменением цвета раствора от светло-голубого до синего. Обнаружена дифракционная картина, свидетельствующая о нанокристаллической природе зародышеобразования новой фазы. Фазообразование интерпретировано как результат действия неравновесной силы обеднения в условиях гидродинамической неустойчивости высыхающей капли. REFERENCES Tret’yakov Yu. D. Self-organisation processes in the chemistry of materials. Uspekhi khimii [Russian Chemical Reviews], 2003, v. 72(8), pp. 651–679. https://doi.org/10.1070/RC2003v072n08ABEH000836 Kushnir S. E., Kazin P. E., Trusov L. A., Tret’yakov Yu. D. Self-organization of micro- and nanoparticles in ferrofl uids. 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Trukhina, I. G., Yu N. Mansurov, V. P. Reva i V. A. Pimenov. "Structure of TiO2 – ZrO2 – SiO2 tubes". Tsvetnye Metally, 25.01.2016, 61–65. http://dx.doi.org/10.17580/tsm.2016.01.10.

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