共查询到20条相似文献,搜索用时 46 毫秒
1.
Effects of H2O/Na2O molar ratios (MRs) on the developed alkaline activated pozzolanic solid wastes (PMs)-ultrafine palm oil fuel ash (UPOFA) and ground blast furnace slag (GBFS)-were studied by using the constant mass of combined activators (10 M NaOHaq + Na2SiO3aq of silica-modulus (Ms = SiO2/Na2O) of 3.3).The free water content (FWC) expressed as FWC/(PMs) varied from 0.02 to 0.1 by mass while the total H2O/Na2O MRs ranged from 18.9 to 23.1 The findings revealed that increase in H2O/Na2O MRs negatively affects the strength but positively impact the mixture workability (consistency). The microstructural morphology examination using Scanning Electron Microscope coupled with Energy dispersive spectroscopy (SEM + EDS) reveals the contribution of H2O/Na2O MRs to the product nature, compactness, and the reactivity of Ca2+ and Al3+ while Fourier transform infra-red (FTIR) spectroscopy indicates that H2O/Na2O ratios contributed to the product amorphousity and carbonation process but sparingly affected its formed polymerized structural units (SiQn(mAl), n = 2 and 3). 相似文献
2.
The resistance of very high volume fly ash cement pastes and mortars activated by Na2SO4 has been monitored following immersion for up to 90 d in 0.1 M HCl, 4.4% Na2SO4 and ASTM-compliant sea water. Changes in the compressive strengths of mortars and in crystalline phases, bond environments, and the microstructure of pastes following immersion were monitored. Experiments were repeated with a commercially available sulfate resistant cement. Both cements were found to present adequate resistance to both sea water and the Na2SO4 solution. However, both were severely degraded by acid immersion. Differences in potential degradation mechanisms based on the chemistry of the fly ash binder and the reference cement are discussed. 相似文献
3.
An understanding of the rheological behaviour of OPC-based products has been widely studied, for it is essential to determining and predicting the fresh and hardened characteristics and properties of pastes, mortars and concretes. The rheology of alkali-activated material (AAM) systems has been much less intensely researched, however.The present study aimed to ascertain the effect of factors such as the nature and concentration of the alkaline activator on the rheological behaviour of alkali-activated slag (AAS) pastes, with a comparison between the rheological parameters and fluidity of these pastes to the same parameters in OPC. More specifically, the study explored how paste rheology was affected by the nature of the alkaline activator (NaOH, 50/50 wt% NaOH/Na2CO3 or waterglass – Wg), its concentration (3–5% Na2CO3 of slag weight) and, in the waterglass solution, the SiO2/Na2O ratio.The findings showed that AAS paste rheology is affected by the nature of the activator. The rheological behaviour in AAS pastes activated with NaOH alone or combined with Na2CO3 was similar to the rheology observed in OPC pastes, and fit the Bingham model. Conversely, the AAS pastes activated with waterglass fit the Herschel–Bulkley model and their rheology proved to depend on both the SiO2/Na2O ratio and the Na2O concentration. Moreover, regardless of the activator used (NaOH, Na2CO3 or waterglass), an increase in Na2O concentration implies a raise of shear stress.The formation of primary C–S–H gel in Wg–AAS and its effect on paste rheology were confirmed. Gel formation was likewise shown to be related to the SiO2/Na2O ratio and activator concentration. 相似文献
4.
《材料与设计》2015
This study investigates the effects of adding various concentrations, sources and compositions of ground red clay brick waste (RCBW) on the properties of fresh and hardened pastes and mortars of alkali-activated slag. The method used to grind the granulated blast furnace slag (GBFS) and RCBW (separate and conjoint) is also assessed, along with the fineness (300–900 m2/kg) of the blended alkali-activated GBFS-RCBW cement, the alkali activator (sodium carbonate or sodium silicate) and the curing conditions (normal conditions or steam curing). The water requirement and setting time for the fresh pastes are also considered; and in the case of the hardened paste and mortar, the water absorption, density and compressive/flexural strength are measured after 1, 3, 7 and 28 days of aging. From the results obtained, it is demonstrated that the addition of 40% RCBW improves the 7- and 28-day strength of blended alkali-activated slag pastes and mortars, and can replace up to 60% of the slag without losing strength. 相似文献
5.
Forozan Gholamian Mohammad Ali Sheikh-Mohseni Hossein Naeimi 《Materials science & engineering. C, Materials for biological applications》2012,32(8):2344-2348
In the present paper, the use of a nanostructured electrochemical sensor was described for simultaneous determination of phenylhydrazine (PhH) and hydrazine (HZ). This electrochemical sensor was prepared by a simple and rapid method by modification of carbon paste electrode with a derivative of hydroquinone and TiO2 nanoparticles. The modified electrode showed an excellent character for electrocatalytic oxidation of PhH. Using differential pulse voltammetry, a highly selective and simultaneous determination of PhH and HZ has been explored at the modified electrode. Differential pulse voltammetry peak currents of PhH and HZ increased linearly with their concentration at the ranges of 2.0 × 10? 6 to 1.0 × 10? 3 M and 7.5 × 10? 5–1.0 × 10? 3 M, respectively and the detection limits for PhH and HZ were 7.5 × 10? 7 M and 9.0 × 10? 6 M, respectively. 相似文献
6.
The effects of sodium hydroxide (NaOH) concentration on setting time, compressive strength and electrical properties at the frequencies of 100 Hz–10 MHz of high calcium fly ash geopolymer pastes were investigated. Five NaOH concentrations (8, 10, 12, 15 and 18 molar) were studied. The liquid to ash ratio of 0.4, sodium silicate to sodium hydroxide ratio of 0.67 and low temperature curing at 40 °C were selected in making geopolymer pastes. The results showed that NaOH concentration had significant influence on the physical and electrical properties of geopolymer paste. The pastes with high NaOH concentrations showed increased setting time and compressive strength due to a high degree of geopolymerization as a result of the increased leaching of silica and alumina from fly ash. The dielectric constant and conductivity increased with NaOH concentration while tan δ decreased due to an increase in geopolymerization. At the frequency of 103 Hz, the dielectric constants of all pastes were approximately 104 S/cm and decreased with increased frequency. The relaxation peaks of tan δ reduced with an increase in NaOH concentration and ranged between 2.5 and 4.5. The AC conductivity behavior followed the universal power law and the values were in the range of 3.7 × 10−3–1.5 × 10−2 at 105–106 Hz. 相似文献
7.
Zhenning Yan Yuanchao Pei Jing Fan Shuangqiang Wang Jianji Wang 《Materials science & engineering. C, Materials for biological applications》2013,33(1):356-361
The feasibility of the newly synthesized ionic associates L1 and L2 formed by ionic liquid [C4mim][PF6] and cationic dyes (malachite green and methylene blue) has been tested as a novel ionophore for the preparation of anion-selective polymeric membrane electrodes. The electrode exhibits Nernstian response and enhanced potentiometric selectivity towards [PF6]? compared to many other anions. The influence of some experimental parameters such as membrane composition, nature of plasticizer and amount of additive on the potential response of the [PF6]? sensor are investigated. Under the optimized conditions, the response slopes of the membrane electrodes towards [PF6]? are 59.7 ± 0.5 and 58.1 ± 0.5 mV/decade based on ionophore L1 and L2, respectively, in 1.0 × 10? 5–1.0 × 10? 1 or 1.0 × 10? 6–1.0 × 10? 1 mol/L concentration range. Interestingly, the optimized electrodes based on ionophores L1 and L2 also exhibit Nernstian response characteristics (60.3 ± 0.5 and 56.0 ± 0.5 mV/decade) for tetrafluoroborate anion [BF4]? in a wide concentration range. Thus, the proposed sensor has been used for the determination of [PF6]? and [BF4]? in aqueous ionic liquids samples and the solubility of the [PF6]? and [BF4]? based ionic liquids in water. The satisfactory results are obtained. 相似文献
8.
Tm3+/Al3+ co-doped silica glass was prepared by sol–gel method combined with high temperature sintering. Glasses with compositions of xTm2O3–15xAl2O3–(100 − 16x) SiO2 (in mol%, x = 0.1, 0.3, 0.5, 0.8 and 1.0) were prepared. The high thulium doped silica glass was realized. Their spectroscopic parameters were calculated and analyzed by Judd–Ofelt theory. Large absorption cross section (4.65 × 10−21 cm2 at 1668 nm) and stimulated emission cross section (6.00 × 10−21 cm2 at 1812 nm), as well as low hydroxyl content (0.180 cm−1), long fluorescence lifetime (834 μs at 1800 nm), large σem × τrad (30.05 × 10−21 cm2 ms) and large relative intensity ratio of the 1.8 μm (3F4 → 3H6) to 1.46 (3H4 → 3F4) emissions (90.33) are achieved in this Tm3+/Al3+ co-doped silica glasses. According to emission characteristics, the optimum thulium doping concentration is around 0.8 mol%. The cross relaxation (CR) between ground and excited states of Tm3+ ions was used to explain the optimum thulium doping concentration. These results suggest that the sol–gel method is an effective way to prepare Tm3+ doped silica glass with high Tm3+ doping and prospective spectroscopic properties. 相似文献
9.
Zholt Kormosh Iryna Hunka Yaroslav Bazel Oksana Matviychuk 《Materials science & engineering. C, Materials for biological applications》2010,30(7):997-1002
The characteristics, performance and application of ion-selective electrodes for ketoprofen and piroxicam ions based on Rhodamine 6G as electrode-active substances are described. These electrodes respond with sensitivities of (58.0 ± 1.0) and (57.0 ± 2.0) mV/decade over the range 1.0 × 10? 4–1.0 × 10? 1 and 1.0 × 10? 4–5.0 × 10? 2 mol/l at pH 5–9 and 6–10 and a detection limit of 6.3 × 10? 5 and 3.2 × 10? 5 mol/l for ketoprofen and piroxicam, respectively. The electrodes are easily constructed at a relatively low cost, have a fast response time and can be used for a period of 5 months without any considerable divergence in potential. The proposed sensor displayed good selectivity for ketoprofen and piroxicam in the presence of several substances and inorganic anions. It was used for the direct assay of ketoprofen and piroxicam in commercial pharmaceutical preparations. 相似文献
10.
Tarushee Ahuja D. Kumar Nahar Singh A.M. Biradar 《Materials science & engineering. C, Materials for biological applications》2011,31(2):90-94
A novel potentiometric urea biosensor has been fabricated with urease (Urs) immobilized multi-walled carbon nanotubes (MWCNTs) embedded in silica matrix deposited on the surface of indium tin oxide (ITO) coated glass plate. The enzyme Urs was covalently linked with the exposed free –COOH groups of functionalized MWCNTs (F-MWCNTs), which are subsequently incorporated within the silica matrix by sol–gel method. The Urs/MWCNTs/SiO2/ITO composite modified electrode was characterized by Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) and UV–visible spectroscopy. The morphologies and electrochemical performance of the modified Urs/MWCNTs/SiO2/ITO electrode have been investigated by scanning electron microscopy (SEM) and potentiometric method, respectively. The synergistic effect of silica matrix, F-MWCNTs and biocompatibility of Urs/MWCNTs/SiO2 made the biosensor to have the excellent electro catalytic activity and high stability. The resulting biosensor exhibits a good response performance to urea detection with a wide linear range from 2.18 × 10? 5 to 1.07 × 10? 3 M urea. The biosensor shows a short response time of 10–25 s and a high sensitivity of 23 mV/decade/cm2. 相似文献
11.
《材料与设计》2015
The plasma electrolytic oxidation (PEO) of aluminum and magnesium alloys is carried out in electrolytes which contain the same reactants, but in fundamentally different concentrations. In this research the possibility of the PEO of aluminum and magnesium alloys in a universal electrolyte is studied. The two most commonly encountered alloys, namely, aluminum alloy 5052 and magnesium alloy AZ91D, are chosen. The oxide layers obtained are studied using SEM, EDX, XRD, and a microhardness tester. The corrosion properties are determined using a potentiostat. The effect of variation of the silicate concentration in the electrolyte on the growth kinetics of the coating and its qualitative characteristics is discussed. It is shown that at Na2SiO3·5H2O concentrations in the electrolyte ranging from 3.2 to 32 g l− 1, the rate of growth of the oxide layer increases from 15 to 55 μm h− 1 with significant variation of the phase composition of the coating. The greatest hardness of an oxide ceramic layer was obtained in the outer sublayer on the magnesium alloys (874.7 HV10) and in the inner sublayer on the aluminum alloys (1123 HV10). The most favorable combination of physical and chemical properties for both alloys is obtained in an electrolyte containing 12.72 g l− 1 Na2SiO3·5H2O. 相似文献
12.
Wei Sun Jun Liu Xiuzhen Wang Tongtong Li Guangjiu Li Jie Wu Liqi Zhang 《Materials science & engineering. C, Materials for biological applications》2012,32(7):2129-2134
In this paper a new electrochemical method was proposed for the determination of adenosine-5′-triphosphate (ATP) based on a chitosan (CTS) and graphene (GR) composite film modified carbon ionic liquid electrode (CTS–GR/CILE). CILE was fabricated by using ionic liquid 1-butyl-3-methylimidazolium dihydrogen phosphate ([BMIM]H2PO4) as the binder, which was further modified by GR and CTS composite. The modified electrode exhibited an excellent electrocatalytic activity toward the oxidation of ATP with the increase of the oxidation peak current and the decrease of the oxidation peak potential. The electrochemical parameters of ATP on CTS–GR/CILE were calculated with the electron transfer coefficient (α) as 0.329, the electron transfer number (n) as 2.15, the apparent heterogeneous electron transfer rate constant (ks) as 3.705 × 10? 5 s? 1 and the surface coverage (ΓT) as 9.33 × 10? 10 mol cm? 2. Under the optimal conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10? 6 to 1.0 × 10? 3 M with the detection limit of 0.311 μM (S/N = 3). The proposed electrode showed excellent reproducibility, stability, anti-interference ability and further successfully applied to the ATP injection sample detection. 相似文献
13.
Lin Chu Guizheng Zou Xiaoli Zhang 《Materials science & engineering. C, Materials for biological applications》2012,32(8):2169-2174
A novel and sensitive electrogenerated chemiluminescence (ECL) sensor for formaldehyde was developed with the amine-functionalized Ru(bpy)32+-doped silica nanoparticles (Ru-DSNPs) as ECL emitter. Ru(bpy)32+ doped on the silica nanoparticle can maintain its electrochemical activities, which made silica nano-beads a excellent carrier of Ru(bpy)32+ species. The uniform Ru-DSNPs (about 75 nm) were conjugated with Au electrode using mercaptoacetic acid as the intermediate to fabricate an ECL sensor for formaldehyde. The ECL analytical performances of this ECL sensor for formaldehyde based on its enhancement ECL emission of Ru(bpy)32+ were investigated in details. Under the optimum condition, the ECL intensity was linear with the formaldehyde concentration in the range of 1.0 × 10? 8 mol/L to 1.0 × 10? 6 mol/L. The detection limit was 6.0 × 10? 9 mol/L (S/N = 3). This approach offered obvious advantages of being simpler, faster, and more stable compared with other sensors, and possessed great potential for formaldehyde detection which could be applied to determine directly the formaldehyde in real samples without pre-separation. 相似文献
14.
Hassan Ali Zamani Abbas Zanganeh-Asadabadi Mitra Rohani Mohammad Saleh Zabihi Javad Fadaee Mohammad Reza Ganjali Farnoush Faridbod Soraia Meghdadi 《Materials science & engineering. C, Materials for biological applications》2013,33(2):984-988
In this research, we report a new Ho3 +-PVC membrane electrode based on N-(4,5-dimethyl-2-(picolinamido)phenyl)picolinamide (H2Me2bpb) as a suitable ion carrier. Poly vinylchloride (PVC)-based membrane composed of H2Me2bpb with oleic acid (OA) as anionic additives, and o-nitrophenyloctyl ether (NPOE) as plasticized solvent mediator. The sensor exhibits a Nernstian slope of 20.1 ± 0.2 mV decade? 1 over the concentration range of 1.0 × 10? 6 to 1.0 × 1? 2 mol L? 1, and a detection limit of 5.0 × 10? 7 mol L? 1 of Ho3 + ions. The potentiometric response of the sensor is independent of the solution pH in the range of 3.5–9.4. It has a very short response time, in the whole concentration range (< 10 s), and can be used for at least eight weeks. The proposed electrode shows a good selectivity towards Ho3 + ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. To assess its analytical applicability the proposed Ho3 + sensor was successfully applied as an indicator electrode in the titration of Ho3 + ion solutions in certified reference materials, alloy samples and for the determination of the fluoride ion in two mouthwash preparations. 相似文献
15.
Using the coal fly ash (FA), pure-form Na-A and -X zeolites were synthesized by two-step process. The FA was pretreated in aqueous NaOH solution under stirring condition at 85 °C for 18 h. The amorphous aluminosilicate of FA was dissolved during pretreatment. Increasing the stirring speed accelerated the dissolution of FA and increased Si4+ and Al3+ concentrations in the solution. This fact indicated that the stirring during pretreatment significantly affected on the dissolution of FA. After pretreatment, remaining FA was removed and aqueous NaAlO2 solution was added to the residual solution to control the molar ratio SiO2/Al2O3 of 0.5–4.5. After aging the resultant at 85 °C for 24 h, white precipitates were generated over the whole SiO2/Al2O3 range. Increment of Si4+ concentration by stirring during pretreatment increases the yield of the product. At SiO2/Al2O3 = 0.5, the material was identified as Na-A zeolite with a trace amount of hydroxysodalite. A single phase Na-A zeolite was obtained at SiO2/Al2O3 = 1.0. The Na-X zeolite was emerged at SiO2/Al2O3 ? 2.0. At SiO2/Al2O3 = 4.5, a single phase Na-X zeolite was formed. The cation exchange capacity of synthetic single phase Na-A and -X zeolites was respectively 4.78 and 3.88 meq./g. 相似文献
16.
Forozan Gholamian Mohammad Ali Sheikh-Mohseni Masoud Salavati-Niasari 《Materials science & engineering. C, Materials for biological applications》2011,31(8):1688-1691
In this paper, a highly selective poly (vinyl chloride) (PVC) membrane electrode based on (1, 9-dibenzyl-1, 3, 7, 9, 11, 15-hexaaza cyclohexa decane) copper(II) perchlorate; [Cu((benzyl)2[16]aneN6)](ClO4)2; as a synthesized ionophore, for perchlorate-selective electrode is reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The sensor responds to perchlorate ion in linear range from 1.0 × 10? 6 to 1.0 × 10? 1 M with a slope ? 59.4 ± 0.3 mV per decade. The limit of detection of the electrode was 4.0 × 10? 7 M ClO4–. Selectivity coefficients indicate a good discriminating ability towards ClO4– ion in comparison to other anions. The proposed sensor has a fast response time of about 7 s and can be used for at least 2 months without any considerable divergence in potential. Due to importance of analysis of perchlorate in water samples, this selective electrode was applied as potentiometric sensor in determination of perchlorate ion in real samples. 相似文献
17.
Zupei Yang Hongmei Ren Xiaolian Chao Pengfei Liang 《Materials Research Bulletin》2012,47(5):1273-1277
The phase structure, microstructure and dielectric properties of Na0.5Bi0.5?xLaxCu3Ti4O12 (NBLCTO) ceramics were investigated. La3+ substitution had a great influence on the phase structure and dielectric properties. The results showed that the pure phase could be more easily obtained when substituting La3+ for Bi3+. Under the same processing condition (970 °C for 7.5 h) and measuring condition (10 kHz around room temperature), NBLCTO ceramics with x = 0.10 possessed the highest permittivity (1.02 × 104) and lowest dielectric loss (0.022). The obtained NBLCTO ceramics with x = 0.10 also had good frequency stability and good temperature stability (?1.87% to +3.27%) from ?60 °C to 120 °C at both 1 and 10 kHz. Complex impedance results revealed that the grain resistance Rg was 7.18 Ω cm and the grain boundary resistance Rgb was 1.19 × 106 Ω cm. 相似文献
18.
M.R. Ganjali M. Hosseini A. Ghafarloo M. Khoobi F. Faridbod A. Shafiee P. Norouzi 《Materials science & engineering. C, Materials for biological applications》2013,33(7):4140-4143
(E)-2-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide (L) has been used to detect trace amounts of praseodymium ion in acetonitrile–water solution (MeCN/H2O) by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to Pr3 + ions in MeCN/H2O (9/1:v/v) solution. The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and Pr3 +, which has been utilized as the basis for selective detection of Pr3 +. The sensor can be applied to the quantification of praseodymium ion with a linear range of 1.6 × 10? 7 to 1.0 × 10? 5 M. The limit of detection was 8.3 × 10? 8 M. The sensor exhibits high selectivity toward praseodymium ions in comparison with common metal ions. The proposed fluorescent sensor was successfully used for determination of Pr3 + in water samples. 相似文献
19.
《Cement and Concrete Composites》2006,28(1):39-46
This paper presents a laboratory study on the sulfate resistance of blended cement combination of reference Portland cement with high volume ground granulated blast-furnace slag (GGBS) and natural pozzolan (NP). The exposure solutions were tap water containing 5% magnesium sulfate solution and 5% sodium sulfate solution. Two types of grinding method (separately grinding and intergrinding, two finenesses (250 m2/kg and 500 m2/kg) and three different proportions (10%, 20%, and 30% by weight of mixture)) of each of two different additives (GGBS and NP) in equal amounts were employed. In addition to these blends, plain Portland cements without additives were prepared as references specimens. Standard Rilem sample size (40 mm × 40 mm × 160 mm) was used for the experimental study.It was observed that the sulfate resistances of blended cements were significantly higher both against sodium sulfate and magnesium sulfate attacks than references cement. Final strength reductions for finer mixes attacked by magnesium sulfate were marginally lower than those attacked by sodium sulfate. On the other hand, no particular relation was found between the sulfate resistance of the mortars and the grinding methods. 相似文献
20.
Tungsten based phosphate glasses are interesting non-crystalline materials, commonly known for photochromic and electrochromic effects, but also promising hosts for luminescent trivalent rare earth ions. Despite very few reports in the literature, association of the host́s functionalities with the efficient emissions of the dopant ions in the visible and near-infrared spectra could lead to novel applications. This work reports the preparation and characterization of glasses with the new composition 4(Sb2O3)96−x(50WO3 50NaPO3)xEu2O3 where x = 0, 0.1, 0.25, 0.5 and 1.0 mol%, obtained by the melt quenching technique. The glasses present large density (∼4.6 g cm−3), high glass transition temperature (∼480 °C) and high thermal stability against crystallization. Upon excitation at 464 nm, the characteristic emissions of Eu3+ ions in the red spectral region are observed with high intensity. The Judd–Ofelt intensity parameters Ω2 = 6.86 × 10−20, Ω4 = 3.22 × 10−20 and Ω6 = 8.2 × 10−20 cm2 were calculated from the emission spectra and found to be higher than those reported for other phosphate glass compositions. An average excited state lifetime value of 1.2 ms, was determined by fitting the luminescence decay curves with single exponential functions and it is comparable or higher than those of other oxide glasses. 相似文献