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1.
Archeological specimen were examined by the radioisotope-excited X-ray method to determine their chemical composition. Individual
K and L X-rays of Fe, Ni, Cu, Zn, Pb, Mo, Ag, In, Sn, Sb, and Ba were induced by using241Am−I and241Am−Tm source—target assemblies. A lithium drifted silicone diode coupled to a 400-channel analyzer was used for detection.
No sample preparation was required and all the elements were measured simultaneously in 40 min counting time. 相似文献
2.
质子交换膜燃料电池作为重要的电化学能源转换装置,在提高能量转换效率、减少环境污染等方面具有诱人的前景.然而,阴极氧还原过电位较大、活性较低、稳定性差,且铂基催化剂昂贵,使该燃料电池难以商业化.纳米结构电催化剂的发展有望解决此难题。对纳米合金电催化剂其组分和结构的设计是开发高活性、高稳定性和低成本的燃料电池电催化剂的重要因素.本文综述了近期由分子设计和热化学控制处理法制备的三元纳米合金电催化剂对燃料电池氧还原反应催化性能的最新进展.该方法可控制纳米合金的尺寸、组成以及二元和三元纳米催化剂的合金化程度.以高活性的三元纳米合金催化剂PtNiCo/C为例,综述了在设计燃料电池电催化剂时结构和组成的纳米级调优的重要性.PtNiCo/C电催化剂的质量比活性远高于其二元合金催化剂和Pt/C商业电催化剂.三元电催化剂的催化活性可通过控制其组成来调节.文章还讨论了三元纳米合金催化剂的结构及其协同效应对增强其电催化性能的影响. 相似文献
3.
New Polyurethane/Docosane Microcapsules as Phase‐Change Materials for Thermal Energy Storage
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Dr. Paula Felix De Castro Prof. Dmitry G. Shchukin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11174-11179
Polyurethane microcapsules were prepared by mini‐emulsion interfacial polymerization for encapsulation of phase‐change material (n‐docosane) for energy storage. Three steps were followed with the aim to optimize synthesis conditions of the microcapsules. First, polyurethane microcapsules based on silicone oil core as an inert template with different silicone oil/poly(ethylene glycol)/4,4′‐diphenylmethane diisocyanate wt % ratio were synthesized. The surface morphology of the capsules was analyzed by scanning electronic microscopy (SEM) and the chemical nature of the shell was monitored by Fourier transform infrared spectroscopy (FT‐IR). Capsules with the silicone oil/poly(ethylene glycol)/4,4′‐diphenylmethane diisocyanate 10/20/20 wt % ratio showed the best morphological features and shell stability with average particle size about 4 μm, and were selected for the microencapsulation of the n‐docosane. In the second stage, half of the composition of silicone oil was replaced with n‐docosane and, finally, the whole silicone oil content was replaced with docosane following the same synthetic procedure used for silicone oil containing capsules. Thermal and cycling stability of the capsules were investigated by thermal gravimetric analysis (TGA) and the phase‐change behavior was evaluated by differential scanning calorimetry (DSC). 相似文献
4.
Tomáš Křenek Nataliya Murafa Petr Bezdička Jan Šubrt Husain M. Masoudi Josef Pola 《应用有机金属化学》2012,26(3):135-139
Pulsed IR laser irradiation of metal (Au or Ag) target in gaseous tetramethyltin (TMT) results in metal ablation and adjacent dielectric breakdown (DB) in TMT and allows gas phase deposition of films containing metal (Au or Ag), Sn and C elements. Volatile products of DB of TMT were examined by FT‐IR spectroscopy and revealed as intermediates of gas phase carbonization reactions. The solid films were analyzed by FT‐IR and Raman spectroscopy, X‐ray diffraction and electron microscopy and shown as amorphous nanostructured Au–Sn/C and Ag–Sn/C phases containing β‐Sn nanograins. These Sn nanograins exhibit irreversible amorphization upon heating and melt below the melting point of bulk β‐Sn phase. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
A novel layered K(4)Ag(2)Sn(3)S(9) x 2KOH was synthesized solvothermally. A mixture of ethanol and HSCH(2)CH(SH)CH(2)OH was used for the synthesis. The HSCH(2)CH(SH)CH(2)OH plays an important role and appears to serve as a mineralizer for the solvothermal reaction. A layer comprises Sn(3)S(9)(6)(-) clusters linked by Ag(+) ions and possesses two types of 1D channels in which potassium ions are located. The compound crystallizes in the monoclinic P2(1)/m space group [a = 7.8071(2) A, b = 27.3508(1) A, c = 10.5008(2) A, alpha = 90 degrees, beta = 103.874(1) degrees, gamma = 90 degrees, Z = 4]. Its crystal structure, composition analysis, and IR are presented. 相似文献
6.
Controlled synthesis of magnetic nanoparticles with a well-known size and composition is always a challenge. A soft chemical synthesis was developed to obtain magnetic alloy nanocrystals with a high ability to control composition, size, and polydispersity. Cobalt-platinum alloy nanocrystals were synthesized using a colloidal approach by the liquid-liquid phase transfer method. Structural characterization using HRTEM and XRD was carried out on nanocrystals in the range of 25-75% cobalt composition, which indicated the formation of nanoalloy bimetallic CoxPt100-x. Adjusting the alkylamine capping agent and the kinetics of the reduction process allowed tuning of the size in the range of 1.8-4 nm while keeping an equiatomic composition. The narrow size distribution led to the possibility of inducing nanoparticle self-organization over a long range. The magnetic properties of the Co50Pt50 nanoalloy in the disordered face-centered cubic phase A1 were studied for different nanoparticle sizes. 相似文献
7.
在模板剂溴化十六烷基三甲基胺(CTAB)作用下,采用溶胶-凝胶法再结合程序升温溶剂热法制备了纳米复合材料Ag/ZnO-SnO2(CTAB),其中Ag,Zn,Sn摩尔比为0.1∶2∶1.利用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、扫描电子显微镜配合X射线能量色散谱(SEM-EDS)和N2吸附-脱附测定等方法对复合材料的组成、结构及形貌等进行了表征.结果表明,该复合材料具有纤锌矿和金红石结构,Ag以单质形式存在.与未经CTAB作用的样品相比,Ag/ZnO-SnO2(CTAB)颗粒分布更均匀,且呈现规则的纳米棒状结构.复合材料在紫外光和可见光作用下对罗丹明B(RhB)的光催化降解结果显示,样品Ag/ZnO-SnO2(CTAB)的光催化活性明显高于Ag/ZnO-SnO2、ZnO-SnO2、ZnO和商用P-25. 相似文献
8.
在乙醇为溶剂和还原剂、碳粉为载体的体系中,采用水热法将Ag+或Ag+-Sn2+还原,形成纳米多孔网状结构的Ag或Ag-Sn双金属纳米颗粒,制备碳粉负载的Ag/C和Ag-Sn/C催化剂。 利用循环伏安和线性扫描技术,研究了碱性溶液中这些催化剂对氧还原反应(ORR)的电活性。 研究表明,Ag/C和Ag-Sn/C对ORR均表现出强的电催化活性,它们对ORR的起始电位约0.05 V(vs.Ag/AgCl)。 在Ag97Sn3/C催化剂上,ORR的电流密度为2.87×10-3 A/cm2(800 r/min),高于Ag/C。 Levich方程分析表明,在Ag-Sn/C催化剂上,ORR转移电子数明显大于Ag/C,说明在Ag-Sn/C催化剂上,氧气能够较为彻底被还原。 此外,在甲醇存在下,Ag/C和Ag-Sn/C对ORR的活性基本保持不变,表明它们对甲醇有较强的耐受力。 相似文献
9.
Riyadh Zendin Mawlud Sangar S. Ahmed Sobhan Mortazavi-Derazkola Omid Amiri Zahra Salehi Peshawa H. Mahmood 《应用有机金属化学》2020,34(8):e5652
In this study, dendrite-like Sn nanocomposites were achieved by engineering the synthesis parameters. The dendritic Sn nanostructures show higher photocatalytic activity compared to nanoplate Sn and hierarchical Sn nanostructures. Flower-like Sn–Cu and cactus-like Sn–Ag nanostructures were prepared to improve the photocatalytic activity of Sn nanostructures. Adding Cu and Ag improved the photocatalytic activity of Sn by 24% and 46%, respectively. The photodegradation results revealed that the cactus-like Sn–Ag has a high degradation rate (5.3 × 10−4 mmol L−1 min−1) compared to the Sn nanostructures (2.9 × 10−4 mmol L−1 min−1). This work provides new insight into the design of highly efficient photocatalysts by engineering the morphology. 相似文献
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11.
Arnaud Demortière Rémi Losno Christophe Petit Jean-Paul Quisefit 《Analytical and bioanalytical chemistry》2010,397(4):1485-1491
The synthesis of bimetallic alloy nanocrystals with a well-controlled relative composition is a real challenge and requires
chemical analysis techniques with high accuracy. A new chemical route has been used to synthesize cobalt–platinum nanocrystals
of 2-nm diameter in a wide range of relative stoichiometry. A study of the elemental composition of the nanoalloy was carried
out by X-ray fluorescence (XRF) spectroscopy and energy-dispersive X-ray analysis. We have developed a set-up for XRF analysis
using a silicon wafer as a support to determine the elemental composition with only a small amount of sample. The calibration
step and the measurement capabilities are described. In a composition range of 25–75% cobalt, the results of both analytical
methods are discussed and compared in detail. 相似文献
12.
A new way to prepare hydrophobic membranes is reported. Polydimethylsiloxane oil (and any other silicone oil molecules) was grafted onto a porous alumina membrane (or any hydroxylated ceramic or glass) by heating, to 180°C, producing a covalently grafted monolayer of silicone oil, chemically and thermally stable, unaffected by organic solvents but susceptible to alkali attack (as is the silicone oil itself). The membrane is totally impermeable to pure water, and organic solvents may be extracted from water mixtures by pervaporation. Very high permeation fluxes were obtained, suggesting possible use of these silicone/ceramic membranes in extraction of volatile organic compounds (VOCs). This simple modification can be applied to macroporous membranes increasing hydrophobicity without pore blocking. 相似文献
13.
A series of AuPd@C nanoalloy catalysts with tunable compositions were successfully prepared by a co-reduction method. The use of borane-tert-butylamine complex as reductant and oleylamine as both solvent and reductant was very effective for the preparation of the monodispersed nanoalloy. We evaluated the catalytic activity of these AuPd@C nanoalloys for oxidative dehydrogenative coupling of aniline, which showed better catalytic activity than equal amounts of sole Au@C or Pd@C catalyst. The Au1Pd3@C catalyst exhibited the best performance, indicating that the conversion and selectivity were improved along with the increase of Pd composition. However if the Pd composition was too high in the AuPd alloy, Au1Pd7@C achieved only 81% conversion in this reaction. 相似文献
14.
A novel hexagonal phase discovered near the Ca(15)Au(60)Sn(25) quasicrystal and its cubic approximants (ACs) was synthesized by means of high-temperature solid-state reactions. Single-crystal structural analyses show that this is a Gd(14)Ag(51) isotype with composition within the range Ca(14)Au(45.56(4)-46.67(4))Sn(5.14(3)-4.14(3)), space group P6/m (No. 175), and lattice parameters a = 12.763(3)-12.879(3) ? and c = 9.326(3)-9.3815(4) ?. In this phase, Sn mixes with Au in two of seven anionic sites to give a strong coloring that generates a narrow honeycomb-like Au/Sn template, in which sizable columns of hexagonal Au stars are confined. This phase transforms into the cubic 2/1 AC phase through a peritectic reaction at ~678 °C. The valence electron count per atom (e/a) of the present phase is in the range 1.41-1.45. However, it does not appear to follow a Hume-Rothery mechanism. 相似文献
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16.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(8):938-946
Complicated cases of retinal detachment can be treated with silicone oil tamponades. There is the potential for silicone oil tamponades to have adjunctive drug releasing behaviour within the eye, however the lipophilic nature of silicone oil limits the number of drugs that are suitable, and drug release from the hydrophobic reservoir is uncontrolled. Here, a radiometric technique was developed to accurately measure drug solubility in silicone oil and measure release into culture media. All‐trans retinoic acid (atRA), a lipophilic drug known to act as an anti‐proliferative within the eye, was used throughout this work. Chain‐end modification of polydimethylsiloxane with atRA produced a polydimethylsiloxane retinoate (PDMS‐atRA), which was used as an additive to silicone oil to modify the solvent environment within the silicone oil and the distribution coefficient. Blends of PDMS‐atRA and silicone oil containing different concentrations of free atRA were produced. The presence of PDMS‐atRA in silicone oil had a positive effect on atRA solubility and the longevity of release in vitro. The drug release period was independent of atRA starting concentration and dependent on the PDMS‐atRA concentration in the blend. A clinically relevant release period of atRA over 7 weeks from a silicone oil blend with PDMS‐atRA was observed. © 2018 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 938–946 相似文献
17.
In order to evaluate the extent of silicone oil contamination in a drug substance derived from processing equipment, a novel extraction method was developed which uses a mixture of polar and non-polar solvents (toluene/acetonitrile). Unlike the majority of silicone oil extraction methods in the literature that yield very low recoveries, this procedure proved able to completely recover the silicone oil from this compound. The recovered silicone oil was rediluted in isopropanol alcohol (IPA)/toluene mixture and subsequently analyzed by an inductively coupled plasma atomic emission spectrometer (ICP-AES) coupled to an ultrasonic nebulizer (USN). 相似文献
18.
Lupu C Downie C Guloy AM Albright TA Mao JG 《Journal of the American Chemical Society》2004,126(13):4386-4397
A new lithium silver stannide, Li17Ag3Sn6, was synthesized from high-temperature reactions of the pure elements in tantalum containers. Its crystal structure, in the space group, P31m, with a = 8.063(3) A, c = 8.509(4) A, Z = 1, features two distinct AgSn-based anionic layers. Defect graphitic layers of Ag2Sn3, with ordered vacancies at one-third of the Ag sites, are alternately stacked with Kagome-like nets of isolated trigonal planar AgSn3 units. Double layers of Li ions are sandwiched between the stacked AgSn-based layers. Theoretical calculations show unusual pi-interactions within both anionic layers, with the trigonal planar [AgSn3]11- units being isoelectronic with CO(3)2-. In addition, the chemical bonding of the layered [Ag2Sn3]6- pi-network features incompletely filled lone-pair Sn states involved in in-plane trefoil aromatic interactions. Transport and magnetic susceptibility measurements on Li17Ag3Sn6 indicate excellent metallic behavior and temperature-independent paramagnetism consistent with results from band structure calculations. The "trefoil" aromaticity, previously postulated for aromatic molecular systems, is finally observed, albeit in a polar intermetallic solid-state structure that lies at the border between metals and nonmetals. 相似文献
19.
J. Runt B. D. Hanrahan I. R. Harrison 《Journal of Polymer Science.Polymer Physics》1982,20(9):1687-1693
The fold periods and longitudinal acoustic modes [LAMs] for isothermally crystallized polyethylene (PE) single crystals were determined in the dried state and in the presence of decalin and silicone oil. Upon swelling with decalin, the fold period increased by 7% while the LAM peak frequency decreased by approximately 1 cm?1. Several possible explanations for the change in LAM frequency are discussed but the exact interpretation is open to question. No change in fold period was observed upon soaking a dried crystal mat in silicone oil. This fold period invariance along with the fact that silicone oil has no effect on the melting point of PE crystals indicates that there is no significant interaction between the oil and the methylene groups on the crystal surface. The effect of suspending crystals (which have never been dried down) in silicone oil should only be to increase the average interlamellar distance and, therefore, to reduce any interlamellar forces. It is shown that the LAM peak frequency for crystals suspended in silicone oil is the same as that for the dried crystals, indicating that interlamellar forces do not exert a significant perturbing influence on the LAM of polyethylene crystals. 相似文献
20.
谭龙奇 《中国无机分析化学》2020,10(2):39-41
以氟化铵为液体缓冲剂,采用直接固体进样,使用CCD-I型交流电弧直读发射光谱法同时测定土壤中的Ag、Sn,其检出限为Ag 0.035μg/g,Sn 0.52μg/g。免去称样及与粉末缓冲剂混合磨匀的过程,缩短流程,快速简便。滴加氟化铵作缓冲剂,使Sn难挥发元素快速蒸发,增强检测信号强度,增加灵敏度。 相似文献