Determination of227Ac in geological materials through neutron activation and alpha-spectrometric assay of induced228Th

A new route has been developed for the micro-determination of²²⁷Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of²²⁸Th, the β-decay product of the 6.1 hrs²²⁸Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10^?17 g²²⁷Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.     

Ag+/MPTMS/PMHS-mediated two-step acid–base synthesis of hybrid materials with embedded nanosilver

A newly designed two-step acid–base sol–gel method for the synthesis of Ag-doped hybrid materials with tailored physicochemical properties is presented. In the proposed protocol, Ag⁺ is in situ reduced by Si–H bonds of polymethylhydrosiloxane (PMHS) in the absence of an additional reductant. Hydrolysis of the alkyloxysilane groups of tetraethoxysilane and PMHS or 3-mercaptopropyltrimethoxysilane (MPTMS) can be promoted by the release of H⁺ due to complexation between Ag⁺/Ag⁰ and thiol groups. Newly formed nanosilver can be fully stabilized by a sol–gel reaction and embedded parallel to the skeletons. The MPTMS dosage used during synthesis has a significant impact on the textural characteristics of the final products. The properties of as-prepared materials are characterized by Brunauer-Emmett-Teller analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. This study presents a novel method for the synthesis of Ag-doped hybrid materials using the synergetic effects of common organosilane precursors.     

A new method for determining the radon emanation coefficients and radon production rates in different building materials using solid state nuclear track detectors

Radon α-activity concentrations have been measured inside and outside various building materials by combining a calculational method with the solid state nuclear track detector (SSNTD) technique. Radon emanation coefficients of the studied materials have been evaluated. A new calibration method for determining the radium (²²⁶Ra) and thorium (²³²Th) specific activities of the considered building materials has been developed. The radon production rates per unit volume of the studied materials have been evaluated. The influence of the material porosity on the radon emanation coefficient and radon production rate have been investigated.     

Optical and conductive properties of functional materials extracted from coal tar pitches treated by air oxidization method

The oligomers having the blue photoluminescence and conductivities of 5 × 10–7^–7.4 × 10^–4 S m^–1 after doping by iodine are extracted successfully from coal tar pitches which were dealt with by the air oxidization method at 350°C. Meanwhile, it is observed that extracted materials have the blue photoluminescence with the fluorescence quantum yield of 7–10.2%. In these cases, we used the solutions of toluene and pyridine to extract these functional materials from coal tar pitches. Consequently, we consider these extracted materials showing the advantages in the application of fabricating the electronic devices, because it can decrease the production cost remarkably than use of the materials obtained by general organic synthesis methods. Finally, this research also can provide the one of beneficial references for solving the serious problem of overproduction of coal tar pitches in China. The oligomers having the blue photoluminescence and conductivities of 5 × 10^–7–7.4 × 10^–4 S m^–1 after doping by iodine are extracted successfully from coal tar pitches which were dealt with by the air oxidization method at 350°C. Meanwhile, it is observed that extracted materials have the blue photoluminescence with the fluorescence quantum yield of 7–10.2%. In these cases, we used the solutions of toluene and pyridine to extract these functional materials from coal tar pitches. Consequently, we consider these extracted materials showing the advantages in the application of fabricating the electronic devices, because it can decrease the production cost remarkably than use of the materials obtained by general organic synthesis methods. Finally, this research also can provide the one of beneficial references for solving the serious problem of overproduction of coal tar pitches in China.     

Determination of cadmium using radiochemical neutron activation analysis

A method has been developed for the determination of cadmium in samples of food and biological materials using neutron activation analysis with radiochemical separation. The irradiated sample is digested in presence of cadmium carrier, with a nitric-perchloric mixture, evaporated to dryness, dissolved in 6M HCl and placed onto an ion exchange column loaded with Dowex 1-X8 resin in chloride form and conditioned with HCl 6M. The cadmium is retained in the resin. After a washing procedure with several portions of HCl of decreasing concentration, the cadmium is eluted with an ammonia-ammonium chloride buffer. The activity of ^115mIn which is in equilibrium with ¹¹⁵Cd, is measured using a NaI(Tl) well type detector. The method has been evaluated by analyzing certified reference materials with cadmium concentrations covering a range of 0.020 to 200 mg^.kg^-1. The agreement of the results with the certified values is within 95%, which gives an indication of the sensitivity and accuracy of the proposed method.     

Surface Diels–Alder Reactions as an Effective Method to Synthesize Functional Carbon Materials

The post‐synthesis chemical modification of various porous carbon materials with unsaturated organic compounds is reported. By this method, amine, alcohol, carboxylate, and sulfonic acid functional groups can be easily incorporated into the materials. Different carbonaceous materials with surface areas ranging from 240 to 1500 m² g^?1 and pore sizes between 3.0 and 7.0 nm have been studied. The resulting materials were analyzed by elemental analysis, nitrogen sorption, FTIR spectroscopy, zeta‐potential measurements, thermogravimetric analysis, photoelectron spectroscopy, and small‐angle X‐ray scattering. These analyses indicated that the degree of functionalization is dependent on the nature of the dienophile (reactivity, steric hindrance) and the porosity of the carbon material. As possible applications, the functionalized carbonaceous materials were studied as catalysts in the Knoevenagel reaction and as adsorbents for Pb²⁺ from aqueous solution.     

具有多级孔MCM-41/Y复合分子筛的合成及表征

采用晶种法和纳米组装法合成了MCM-41/Y复合分子筛,通过粉末XRD、SEM、TEM和BET等手段对其物性进行表征,结果显示:采用晶种法合成的形貌以包埋型为主,采用纳米组装法合成的材料为附晶生长和自组装型.二者均具有微、介孔多级孔道结构,比表面积达到665.1和849.3 m2·g-1,总孔容分别为0.6438和0.6529 cm3·g-1,相对于单一Y分子筛明显增大.纳米组装法合成样品的比表面积增大更为显著,这是由于两种合成体系粒子表面电荷和集聚方式不同.     

Preparation and properties of ZnMoO4 anode materials with polymer network gel method

Polymer network gel method combines the advantages of solid-phase method and liquid phase method, triggering acrylamide (AM) radical polymerization in aqueous solution and N, N′- methylene bis acrylamide (MBAM) active double bond cross-linking reaction, forming polymer chains to form a three-dimensional network. The polymer network space formed by the gel is bound and evenly distributed to the ions in the solution, thereby reducing the contact and aggregation of molecules and achieving the purpose of uniform particle size and small particle size. The principle diagram of network gel is shown in Figure. Using cubic zinc acetate and ammonium molybdate tetrahydrate as raw materials, cubic ZnMoO₄ negative electrode materials were prepared with polymer network gel method. The polymer network gel method has various effects on the structure, morphology and electrochemical properties of materials. Besides, the calcination temperature and calcination time were also the key factors to the electrochemical properties of the materials. In this paper, the effects of the ratio of monomer and crosslinker, calcination temperature and calcination time on ZnMoO₄ materials were studied by single variable method, the preparation process was optimized, and its characterization and electrochemical tests were carried out. After 100 cycles, the optimized ZnMoO₄ electrode has a discharge capacity of 374.0 mAh· g^?1, 332.5, 263.5 and 177.1 mAh · g^?1 at current densities of 0.1, 0.5, 1.0 and 2.0 A g^?1, respectively. The electrochemical results show that the optimized ZnMoO₄ has high capacity, large rate capability and excellent cycle stability.     

Uranium isotope dilution mass spectrometry using NBL certified reference materials as spikes

The isotope dilution mass spectrometry method of analysis is used to determine the elemental uranium contents in a wide variety of uranium bearing materials. The method is based on the mass spectrometric analysis of a mixture prepared by diluting the sample to be analyzed with a spike of distinctly different isotopic composition to that of the sample. In this work, a beginning is made to identify suitable candidates among the multitude of certified reference materials (CRMs) available at the New Brunswick Laboratory to supplant the use of ²³³U which remains now as the preferred spike nuclide. The results of the study presented here identify CRM 112-A (of normal isotopic composition) and CRM 115 (depleted uranium composition) as suitable candidates to replace ²³³U as spike material for determining uranium in high enriched uranium materials, and CRM 116 (²³⁵U mass fraction of >90 %) for determining uranium in materials of low enrichment.     

锡基复合氧化物的高能球磨法制备及其电化学性能

随着锂离子电池的发展,人们越来越多地要求可充锂离子电池电极材料具有更高的容量.许多研究小组正致力于寻找和开发能够取代现有碳材料(理论最大比容量为372 mAh·g-1)的新型负极材料[1].锡氧化物基材料由于其高的储锂容量和低的锂离子脱嵌平台电压倍受人们关注,有望作为新一代锂离子电池负极材料[2～5].通过在线X-射线研究,Courtney等[4,5]提出了这类材料作为锂离子电池负极材料的两步反应机理:在首次放电过程中,锡氧化物被不可逆地还原成金属锡,同时生成氧化锂;随后,金属锡与锂发生可逆的合金化与去合金化反应,用反应式表示如下:     

Morphology and Texture of Silica Prepared by Sol–Gel Synthesis on the Surface of Fibrous Carbon Materials

Silica materials are synthesized by the sol–gel method including the deposition of tetraethoxysilane on various micro- and nanocarbon fibers. The use of nanofibrous carbon as a template makes it possible to prepare thermally stable mesoporous SiO₂ samples with unusually high surface areas (up to 1255 m²/g) and high porosity (up to 5.6 cm³/g). These silica materials and aerogels prepared by supercritical drying have comparable pore volumes. It is found by high-resolution electron microscopy that a thin-wall matrix permeated by channels is a prevailing structure of silica materials. When some catalytic fibrous carbons are used as templates, silica nanotubes can be prepared.     

Determination of total tin in geological materials by electrothermal atomic absorption spectrometry

A graphite-furnace atomic-absorption spectrometric method is described for the determination of total tin in geological materials. Samples are decomposed by fusion with lithium metaborate and the melt is dissolved in diluted (1 + 9) nitric acid. Spectral and non-spectral interferences are minimized by a combination of platform volatilization, “normal” heating rate, addition of ammonia as chemical modifier, use of integrated absorbance values and Zeeman background correction. Results are reported for six reference materials showing good accuracy and a precision of 12% at the 3 μg g^?1 level. The detection limit for tin in the original materials in 0.7 μg g^?1.     

Radiochemical proton activation analysis for the determination of cadmium and lead in sediment reference materials

Proton activation analysis was used for the determination of cadmium and lead in three sediment reference materials. The method is based on the^111,112Cd(p, xn)¹¹¹ In and the^206,207,208Pb(p, xn)²⁰⁶Bi reactions.¹¹¹In and²⁰⁶Bi were chemically separated by anion exchange. The results obtained were taken into account for the certification of the materials and are in the excellent agreement with the certified values.     

Preparation and characterization of hybrid cationic hydroxyethyl cellulose/sodium alginate polyelectrolyte antimicrobial films

This study aimed to develop polyelectrolyte‐structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic hydroxyethyl cellulose was synthesized and characterized by Fourier‐transform infrared, ¹H NMR, and ¹³C NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte‐structured antimicrobial food packaging materials were prepared using hydroxyethyl cellulose, cationic hydroxyethyl cellulose, and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by thermal gravimetric analysis and differential scanning calorimetry. Surface morphology of samples was investigated by SEM. The obtained results prove that produced food packaging materials have good thermal and antimicrobial properties, and they can be used as food packaging material in many industries.     

Very accurate,simultaneous determination of trace amounts of Co and Ni in biological materials by radiochemical neutron activation analysis

A very accurate and sensitive method for the simultaneous determination of trace amounts of Co and Ni in biological materials has been elaborated. The method is based on radiochemical neutron activation. Irradiation of samples in Cd-shielded channel of a nuclear reactor assures balanced activity ratio of⁵⁸Co and⁶⁰Co isotopes and favourable detection limits for both nickel and cobalt. Column chromatography (ion exchange and extraction) has been used for the quantitative and selective isolation of the determined radionuclides. High accuracy of the method has been demonstrated by the analysis of several certified reference materials.     

球形V-MCM-48的简单合成方法

活性金属掺杂的具有三维立方孔道结构的MCM-48在芳烃的氧化反应具有潜在应用价值。使用乙醇做助溶剂,在低的模板剂浓度下,经过一步水热法首次合成了球形的V-MCM-48。通过XRD,场发射扫描电镜,氮气吸附-脱附,红外,拉曼,核磁,X射线光电子能谱和ICP等技术对样品进行了表征。结果表明这些样品具有大的比表面积(1 005 m2.g),有序的孔道结构。当V/Si的物质的量比高达2.91%时,仍没有出现V2O5晶体。大部分的钒进入了硅的骨架。所合成材料在低温过氧化氢直接氧化苯乙烯的反应中表现出良好的催化性能。     

Charged particle activation analysis of light elements at sub-ppb level

We have developed charged particle activation analysis to determine light elements at a sub-ppb level. This analytical method is characterized by sample bombardment with charged particles at a few tens of mA and substoichiometric separation for¹³N,¹¹C and¹⁸F within two half-life times and with decontamination factors of more than 10⁸. Nuclear reactor interference is also estimated with this method. This analytical method is confirmed to be useful for characterizing highly purified materials from analytical results for boron, carbon, nitrogen and oxygen in Nb refined by the floating zone melting method.     

Rapid determination of uranium at the nanogram level in geological and biological materials

A rapid method for the determination of uranium at nanogram levels in geological and biological materials is described. The method is based on the separation of 23.5 min²³⁹U, produced on neutron activation, by solvent extraction with TBP from nitric acid medium in the presence of HF, which prevents interference from Th; a number of other possibly interfering elements were shown to be negligibly extracted. The method is selective and sensitive enough for the determination of nanogram levels of uranium in soils, ores and biological samples. Results for some standard reference materials were in good agreement with certified values. Presented at the International Conference on Analytical Chemistry, Interan '76, Prague, August 1976.     

The search for internal isotopic tracers in metallurgical materials

In a search for internal isotopic tracers in metallurgical materials a group of elements has been chosen which can be determined by the neutron activation method with the higher sensitivity. A method has been developed for the determination of W, As, Au, La, In, Sc, Re and Ir in metallurgical materials. The separation of the elements was carried out using extraction and precipitation. The determination of the elements was carried out in samples of chamotte brick and washed ores. The limits of the determination of the elements are of the order of 10⁻¹¹ g for Au, 10⁻¹⁰ g for In and La and 10⁻⁹ g for As, W, Sc, Re and Ir. The large scatter of the results indicates the inhomogeneity of the materials analyzed.     

Determination of trace quantities of tin by neutron activation analysis

A neutron activation method of general applicability has been developed for determining traces of tin in a variety of samples. The samples and comparative standards, sealed into ampoules, are irradiated intermittently for 3 days at a neutron flux of ca, 3 · 10¹¹ n/cm²/sec, followed by carrier radiochemical separations mainly consisting of solvent extraction steps. As little as 0.1 μg Sn can be easily determined by comparing the induced β-activity of ¹²¹Sn (27.5 h) with that of a standard, The method is rapid and has a reasonably high chemical yield of about 50%. Results are quoted for the tin contents of a number of materials including silicate rocks, sea waters, biological materials and steels.