玉皇庙山戎墓土遗址的盐分调查研究

玉皇庙山戎墓土遗址中可溶-微溶盐导致的遗址表面酥碱、起甲、泛白和块状脱落等病害较为严重。本文利用X射线荧光光谱(XRF)、离子色谱(IC)、X射线光电子能谱(XPS)、X射线衍射仪(XRD)以及透射电镜(TEM)等分析方法测定了玉皇庙山戎墓土遗址不同位置取样点及距遗址表面及不同深度处样品中可溶盐的成分及含量,并分析了盐分对遗址的破坏可能机制。结果表明,该遗址的样品中主要的可溶盐是Na_2Ca(SO_4)_2、Na_2SO_4、NaCl,微溶盐主要是CaSO_4和CaSO_4·2H_2O,此外还含有少量的CaCl_2·6H_2O、KNO_3、KCl、MgCl_2、K_2SO_4和MgSO_4等。随着取样深度增加,样品中各盐分的种类及含量有所减少,此种分布规律可能与可溶盐的赋存环境及水分运移有关。这些结果对于玉皇庙山戎墓土遗址的保护具有一定的参考价值。     

老山汉墓土遗址盐分调查与分布规律探索

老山汉墓土遗址中可溶-微溶盐导致遗址表面酥碱、起甲、泛白和块状脱落等病害较为严重.利用X射线荧光光谱(XRF)、X射线衍射仪(XRD)、X射线光电子能谱(XPS)以及离子色谱(IC)等方法测定了老山汉墓遗址不同取样位置及距遗址表面不同深度处可溶盐的成分及含量,并分析了盐分对遗址破坏的可能机制.结果表明,该遗址的主要有可溶盐有Na2SO4、Na2SO4·10H2O、Na Cl、Na12Mg7(SO4)13·15H2O,微溶盐有Ca SO4、Ca SO4·2H2O,此外还含有少量的Ca Cl2、KNO3、KCl、Mg Cl2、K2SO4、Mg SO4等盐分.随着取样深度增加,各盐分的种类及含量有所减少,此分布规律可能与可溶盐的赋存环境及水分运移有关.试验结果对于老山汉墓土遗址的保护措施具有一定的参考价值.     

利用康普顿散射分析碳化硅陶瓷在高温下使用氧化后组成的变化

用波长色散X射线荧光光谱仪,通过测量散射体(样品)对铑的康普顿散射线(RhKα-C)强度的变化,实现了碳化硅陶瓷在高温下使用时氧化情况的监控。用一套8只碳化硅校准样品建立了康普顿散射强度与样品平均原子序数之间关系的数学模型。利用此模型计算了碳化硅氧化后组成含量的变化。结果表明:用此方法测得的样品中碳、硅及氧的相对含量与X射线光电子能谱法所测结果相符,两者间的相对偏差均小于1%。据此认为,此方法所测得的数据是可以接受的。     

稀土三元催化剂对二氧化碳/环氧化合物共聚反应的催化机理研究

采用X射线光电子能谱(XPS)技术研究了二氧化碳与环氧丙烷共聚反应的稀土三元催化剂,探讨了中心金属的X射线光电子能谱与催化活性间的关系,指出稀土三元催化剂的活性中心在于配位活化后的锌氧键,稀土盐通过与烷氧基锌形成双金属桥键,改变了活性中心的电子云分布,从而提高了反应活性.     

提高能谱无标样定量分析准确度的参数选择

针对如何提高X射线能谱仪(EDS)无标样定量分析的准确度,进行了一系列实验研究和理论分析.讨论了样品制样的基本要求,能谱分析过程中加速电压、收集时间和分析区域等方面对能谱分析结果的影响及其最佳的选择参数,如对于轻元素分析应采用较低电压、分析时间过长可能导致样品在电子束轰击下引起更大碳沉积等,通过合理的参数选择均能得到较为满意的分析结果,提高了定量测试的准确度.     

X射线衍射法钾混盐无标样定量相分析

采用EVD、TOPAS应用软件和TOPAS结构数据库以及无机晶体结构数据库,对一些混合盐样品(如钾混盐、尾矿等)进行了X射线粉末衍射无标样定量相分析全谱拟合模拟研究。在用Rietveld分析法对上述样品中无机盐成分的X射线衍射谱进行模拟过程中,选择基本参数函数为峰形函数,并通过March-Dolase择优取向校正拟合,提高了拟合精度。测得钾混盐样品中钾盐镁矾相含量为72.44%,岩盐相含量为27.56%,误差值Rwp(17.45),Rp(12.21)和拟合度S(4.91)均有所降低。     

Ce0.8Gd0.2-xPrxO1.9固溶体的合成与表征

利用X射线衍射(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)和交流阻抗谱对溶胶-凝胶法制备的稀土双掺杂固溶体Ce0.8Cd0.2-xPrxO1.9(x=0,0.02,0.10)的结构和导电性进行了研究.XRD结果表明,经800℃焙烧所得样品都形成了单相立方萤石结构,平均晶粒尺寸在23～30 nm之间;X...     

能量色散-X射线荧光光谱法测定光伏玻璃中铁含量

提出了X射线荧光能谱法测定光伏玻璃中铁含量。优化的仪器工作条件为:①PdMedium滤光片;②激发电压为20kV;③激发电流为1.08mA;④有效测量时间为100s;⑤总测量时间为200s。选用经火焰原子吸收光谱法对其含铁量定值的6个光伏玻璃样品作为校准样品。方法的线性范围为99.0～158mg.kg-1,检出限(3s)为11.5mg.kg-1。方法用于光伏玻璃实际样品分析,测定值与火焰原子吸收光谱法分析结果吻合,测定值的相对标准偏差(n=11)在4.5%～9.0%之间。     

用于X射线荧光光谱法测定聚丙烯材料中有害元素的标准样品的制备北大核心CSCD

制备了一套适用于X射线荧光光谱法测定聚丙烯(PP)材料中5种有害元素(铅、镉、铬、汞和溴)的标准样品。首先,制备聚丙烯材料目标元素高含量母粒,然后通过逐级稀释的方法制备目标元素含量梯度的样品原料,最后制得符合X射线荧光光谱分析使用要求的标准样品。采用电感耦合等离子体原子发射光谱法和离子色谱法测定所制得标准样品中各元素的含量。所制备的用于X射线荧光光谱分析的PP标准样品通过F检验和t检验,得到统计量F相似文献   

SDD探测X射线中BP网络全谱定量分析技术研究

针对能量色散X荧光分析技术中面临的能谱复杂、标样难于制备、基体效应难于校正等问题,建立了基于BP神经网络的特征X射线全谱分析模型,对SDD探测器测量获得的Ti-V-Fe伪三元系样品特征X射线荧光谱进行定量分析,对含量较高的Fe元素的分析误差范围在0.06%～2.5%内,含量较低的Ti和V元素分析误差范围在0.33%～8.4%内,基本克服了由于谱峰重叠和基体效应对解谱带来的复杂性。     

基于莫高窟成盐元素相关系探究壁画盐害作用机理

壁画盐害与壁画的成盐元素种类、盐分迁徙活动以及环境气象条件等密切相关.莫高窟壁画酥碱病变的可溶盐主要为NaCl和Na2SO4,盐的结晶是破坏力的重要来源.本文运用经典溶液化学的研究方法,界定了三元体系NaCl-Na2SO4-H2O于308K,298K,288K,278K,268K的相关系,以此为基础阐释了壁画盐害的发生和发展规律,计算得到了安全含盐量和环境条件的临界数值.研究表明:NaCl的饱和溶解度对温度敏感度不大,它的结晶析出更多的是伴随着水分的蒸发而发生;Na2SO4的饱和溶解度对温度表现较为敏感,它的结晶析出,除了因溶剂水分的蒸发而发生发展之外,还将因温度的降低而产生,他们各自在壁画盐害的发生发展过程中有一定的行为差异,其主导作用的交替点大致在wNa2SO4 /w NaCl=1:3～6左右,即当该体系中Na2SO4的质量比约达30%～15%时,Na2SO4将成为壁画盐害随洞窟温度变化而发生的主导诱因.三元体系NaCl-Na2SO4-H2O中NaCl和Na2SO4在5～35℃的介稳饱和溶解度的测定,取得了与相图相一致的结果.NaCl结晶物质地坚硬、粒度均匀,在壁画盐害表现形式上应以点状疱疹为主;Na2SO4结晶物主要以十水硫酸钠Na2SO4·10H2O的形式析出,质地疏松,易风化,易返潮,所导致的壁画酥碱病变有一定的反复性.Na2SO4的过饱和溶解度大,易富集,易浓缩,结晶区域较大,相应破坏面也较大,在壁画盐害的表现形式应以粉状酥碱为主,如壁画较大面积的空鼓、地仗层酥松等.     

Determination of uranium and thorium in solar salts by neutron activation analysis

Uranium and thorium contents of solar salts were measured by neutron activation analysis. In advance of neutron irradiation, U and Th were concentrated and separated from some interfering elements by neutralization in which they were precipitated with aluminium hydroxide from solutions obtained by dissolving the salts in water or dilute nitric acid solution. The uranium and thorium concentrations determined were from several hundred ppt to 10 ppb. It was strongly indicated that uranium tends to remain in the solution (brine from seawater) phase in the process of solar salt production while thorium tends to transfer to the solid (solar salt) phase.     

Soluble polymer-supported catalysts containing pendant quaternary onium salts for the addition reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 15a-d ) with carbon dioxide (CO₂) was carried out using 1 mol % of soluble polymer-supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a-d with CO₂ proceeded very smoothly to give the corresponding five-membered cyclic carbonates ( 16a-d ) in high yields at 90-100°C. The catalytic activity of the soluble polymer-supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer-supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.     

The Significance of Interfacial Water Structure in Soluble Salt Flotation Systems

Flotation of soluble salts with dodecyl amine hydrochloride (DAH) and sodium dodecyl sulfate (SDS) collectors has demonstrated that the interfacial water structure and hydration states of soluble salt surfaces together with the precipitation tendency of the corresponding collector salts are of considerable importance in explaining their flotation behavior. In particular, the high concentration of ions in these soluble salt brines and their hydration appear to modify the bulk and interfacial structure of water as revealed by contact angle measurements and this effect is shown to be an important feature in the flotation chemistry of soluble salt minerals including alkali halide and alkali oxyanion salts. Depending on characteristic chemical features (salt type), the salt can serve either as a structure maker, in which intermolecular hydrogen bonding between water molecules is facilitated, or as a structure breaker, in which intermolecular hydrogen bonding between water molecules is disrupted. For structure making salts the brine completely wets the salt surface and no contact angle can be measured. For structure breaking salts the brine does not completely wet the salt surface and a finite contact angle is measured. In this regard it has been found that soluble salt flotation either with the cationic DAH or anionic SDS collector is possible only if the salt is a structure breaker. Copyright 2001 Academic Press.     

Enantiopure O-substituted phenylphosphonothioic acids: chiral recognition ability during salt crystallization and chiral recognition mechanism

[structure: see text] The chiral recognition ability of enantiopure O-methyl, O-ethyl, O-propyl, and O-phenyl phenylphosphonothioic acids (1a-d) for various kinds of racemic amines during salt crystallization and the chiral recognition mechanism were thoroughly investigated. The chiral recognition abilities of enantiopure 1a-d for a wide variety of racemic amines varied in a range of 6 to >99% enantiomeric selectivity. Deposited less-soluble diastereomeric salts were classified into two categories, prism- and needle-type crystals; the prism-type crystals were composed of a globular molecular cluster, while there existed a 2(1) column in the needle-type crystals. In contrast to a general observation of a similar 2(1) column in the less-soluble diastereomeric salt crystals of chiral primary amines with chiral carboxylic acids, the globular molecular cluster is a very unique hydrogen-bonding motif that has never been constructed in diastereomeric salt crystals. Excellent chiral recognition was always achieved when the less-soluble diastereomeric salts were prism-type crystals. Significant correlations were found between the degree of the chiral recognition with 1a-d, the crystal shape of the less-soluble diastereomeric salts, and the hydrogen-bonding motif (molecular cluster/2(1) column). The chiral recognition mechanisms via the molecular cluster and the 2(1) column formations are discussed in detail on the basis of X-ray crystallographic analyses.     

Phosphinoselenothioic acids and their salts: synthesis, characterization, and reaction with electrophiles

[reaction: see text] Phosphinoselenothioic acid ammonium salts were synthesized in good yields by reacting phosphinoselenothioic acid S-[2-(trimethylsilyl)ethyl] esters with ammonium fluorides. Phosphinoselenothioic acid alkali metal salts were obtained as 18-crown-6 ether complexes with high efficiency by treating the esters with alkali metal fluorides and 18-crown-6 ether. The salts were stable under air and soluble in water. The structures of the phosphinoselenothioic acid tetramethylammonium salt and P-methylseleno-P-methylthiophosphonium triflate were determined by X-ray molecular structure analyses. These salts exhibited monomeric structures, and the central phosphorus atoms adopted tetrahedral structures. Alkylation of the ammonium salts selectively gave phosphinoselenothioic acid Se-alkyl esters, whereas acylation of the salts preferentially gave S-acyl products. Protonation of the salts selectively gave the phosphinoselenothioic S-acid. The S-acid generated in situ was reacted with alpha,beta-unsaturated carbonyl compounds and cyclohexene oxide to give the adducts. Molecular orbital calculations were carried out for the model compound H2P(Se)S- to elucidate the electronic structure.     

Analytical diagnosis methodology to evaluate nitrate impact on historical building materials

Nitrate salts have become of greater importance in the decay of materials from historical buildings due to changes in the environment. This work presents an analytical diagnosis methodology to evaluate the impact of nitrate salts in mortars and bricks, combining noninvasive and microdestructive analytical techniques together with chemometric and thermodynamic data analyses. The impact of nitrate salts cannot be well ascertained if other soluble salts are not taken into account. Therefore, the principal results from this work relate to nitrate salts but some results for other kinds of salts are included. Data from Raman microprobe spectroscopy and micro X-ray fluorescence (μ-XRF) are used to characterise the original composition and a first approximation of the nature of the decay compounds, mainly nitrates. The soluble salts are extracted and the anions and cations are quantified by means of ion chromatography with conductimetric detection for anions/cations and inductively coupled plasma mass spectrometry (ICP/MS) for cations. The values obtained allow two different data treatments to be applied. First, chemometric analysis is carried out to search for correlations among anions and cations. Second, thermodynamic modelling with the RUNSALT program is performed to search for environmental conditions of soluble salt formation. All the results are finally used to diagnose the impact of nitrates.     

Phase behavior of polyion-surfactant ion complex salts: effects of surfactant chain length and polyion length

The aqueous phase behavior of a series of complex salts, containing cationic surfactants with polymeric counterions, has been investigated by visual inspection and small-angle X-ray scattering (SAXS). The salts were alkyltrimethylammonium polyacrylates, CxTAPAy, based on all combinations of five surfactant chain lengths (C6, C8, C10, C12, and C16) and two lengths of the polyacrylate chain (30 and 6 000 repeating units). At low water contents, all complex salts except C6TAPA6000 formed hexagonal and/or cubic Pm3n phases, with the hexagonal phase being favored by lower water contents. The aggregate dimensions in the liquid crystalline phases changed with the surfactant chain length. The determined micellar aggregation numbers of the cubic phases indicated that the micelles were only slightly aspherical. At high water contents, the C6TAPAy salts were miscible with water, whereas the other complex salts featured wide miscibility gaps with a concentrated phase in equilibrium with a (sometimes very) dilute aqueous solution. Thus, the attraction between oppositely charged surfactant aggregates and polyions decreases with decreasing surfactant chain length, and with decreasing polyion length, resulting in an increased miscibility with water. The complex salt with the longest surfactant chains and polyions gave the widest miscibility gap, with a concentrated hexagonal phase in equilibrium with almost pure water. A decrease in the attraction led to cubic-micellar and micellar-micellar coexistence in the miscibility gap and to an increasing concentration of the complex salt in the dilute phase. For each polyion length, the mixtures for the various surfactant chain lengths were found to conform to a global phase diagram, where the surfactant chain length played the role of an interaction parameter.     

Infrared spectroscopy of aqueous ionic salt solutions at low concentrations

The analysis by infrared spectroscopy of aqueous solutions of the binary inorganic salts NaI and NaCl and the ternary salts CaCl2 and BaCl2 at concentrations from 1000 to 2 mM was carried out to complement a previous study done at higher concentrations on nine binary salts (alkali halides) and one ternary salt (MgCl2) [J.-J. Max and C. Chapados, J. Chem. Phys. 115, 2664 (2001)]. These salts are completely ionized in aqueous solutions, forming monoatomic species that do not absorb IR but that perturb the surrounding water, modifying its spectrum. The factor analysis of the spectra revealed that all these salt solutions were composed of two water types: pure water and salt solvated water. The authors obtained pure salt solvated water spectra for all the salts using an extrapolation technique. The water types obtained are constant for the binary and ternary salts down to 2 mM. For the binary salts, we determine that 5.0 and 4.0 water molecules are solvated to the Na+-Cl- and Na+-I- ion pairs, respectively. These numbers are the same as that obtained at higher concentrations. For the new ternary salts, we find that 6.0 and 8.0 water molecules are solvated to Ca++-(Cl-)2 and Ba++-(Cl-)2 ion pairs, respectively. These numbers are higher than the four water molecules solvated to Mg++-(Cl-)2 ion pairs determined previously, but show a progression that follows their atomic numbers. These results constitute new experimental results on "simple" systems whose molecular organization is still a matter of debate. The IR method that probes the system at the molecular level is a method different than the macroscopic ones that give the activity coefficients. The IR gives direct observation at the molecular level of the strong ion-water interactions that are often neglected and its water structure not considered in macroscopic methods. The present results and their analysis together with those obtained by other methods will facilitate the determination of the organization of these aqueous systems.