麦夸特算法在X射线衍射物相定量分析中的应用

常规的X射线衍射物相定量分析方法有各自的优点,但这些方法往往也存在一些不足.在实际应用中迫切需要一种简便、高效的普适性多物相无标样定量分析方法.选择麦夸特算法、粒子群算法、遗传算法、差分进化算法这4种迭代搜索领域的经典算法构建了基于非线性模型参数估计方法的4模冗余系统,以19个配制的4相样品中各相“前三强线”的积分强度之和作为计算的原始数据,通过Matlab软件进行了含量计算.理论分析及试验结果表明,运用麦夸特算法进行定量分析具有更小的计算复杂度、更快的收敛速度及更好的全局搜索能力,各相含量的计算值与配比值的绝对误差在5%以内的约占总计算量的83%.为了验证该算法,计算了昭苏黄土剖面82个混合样品及青海湖二郎剑钻孔359个混合样品中刚玉的含量,刚玉含量的配比值与计算值的相关性分别达到0.83和0.63,刚玉含量的误差超过5%的分别占总计算量的4.88%和9.75%.基于麦夸特算法的定量分析方法在批量化处理多物相定量中具有效率高、可操作性强、准确度高等优点.      

Quantitative analysis of calcite and Mg-calcite by X-ray diffraction: effect of grinding on peak height and peak area

Mineralogical analysis of calcite and Mg-calcite by X-ray diffraction requires that the samples be ground to a powder. Such grinding determines the particle size of the powder and the structural damage of the minerals. Both of these in turn affect the peak intensities recorded by the X-ray machine. Most carbonate sediments are inhomogeneous; they contain both calcite and Mg-calcite which are affected differently by grinding. Such differences cause quantitative analytical results to be inconsistent with the true mineralogical abundance. The two acceptable methods of analysis—(1) measurement of peak height from the base and (2) measurement of the area under the peak—were compared to determine if sample preparation affects the quantitative results. In samples with variable and relatively small amounts of calcite and Mg-calcite the measurement of peak height yields more reproducible results than does the measurement of peak areas. Different proportions of particle size of the mineralogical components in a sample powder, affect proportionally more the peak areas than the peak heights. Extensive grinding causes structural damage of the component minerals which affects much more the peak areas than the peak heights. Thus for quantitative analyses of calcite and Mg-calcite in inhomogeneous carbonate samples which require differing grinding times and have greatly variable amounts of calcite and Mg-calcite, the peak height measurement seems to be a better method than peak area measurement.     

Quantifying carbon fixation in trace minerals from processed kimberlite: A comparative study of quantitative methods using X-ray powder diffraction data with applications to the Diavik Diamond Mine,Northwest Territories,Canada

The capacity of mine waste to trap CO₂ is, in some cases, much larger than the greenhouse gas production of a mining operation. In mine tailings, the presence of secondary carbonate minerals that trap CO₂ can therefore represent substantial fixation of this greenhouse gas. The abilities of three methods of quantitative phase analysis to measure trace nesquehonite (MgCO₃·3H₂O) in samples of processed kimberlite have been assessed: the method of reference intensity ratios (RIR), the internal standard method, and the Rietveld method with X-ray powder diffraction data. Tests on synthetic mixtures made to resemble processed kimberlite indicate that both the RIR and Rietveld methods can be used accurately to quantify nesquehonite to a lower limit of approximately 0.5 wt.% for conditions used in the laboratory. Below this value, estimates can be made to a limit of approximately 0.1 wt.% using a calibration curve according to the internal standard method. The RIR method becomes increasingly unreliable with decreasing abundance of nesquehonite, primarily as a result of an unpredictable decline in preferred orientation of crystallites. For Rietveld refinements, structureless pattern fitting was used to account for planar disorder in lizardite by considering it as an amorphous phase. Rietveld refinement of data collected from specimens that were serrated to minimize preferred orientation of crystallites gives rise to systematic overestimates of refined abundances for lizardite and underestimates for other phases. The resulting pattern of misestimates may be mistaken for the effect of amorphous and/or nanocrystalline material in samples. This effect is mitigated by collecting data from non-serrated specimens, which typically give relative errors on refined abundances for major and minor phases in the range of 5–20%. However, relative error can increase rapidly for abundances less than 5 wt.%. Nonetheless, absolute errors are sufficiently small that estimates can be made for the amount of CO₂ stored in secondary nesquehonite using the RIR method or the Rietveld method for abundances ?0.5 wt.% and a calibration curve for abundances <0.5 wt.%. The extent to which C is being mineralized in an active mine setting at the Diavik Diamond Mine, Northwest Territories, Canada, has been investigated. Rietveld refinement results and calibrated abundances for trace nesquehonite are used to estimate the amount of CO₂ trapped in Diavik tailings. Results of quantitative phase analysis are also used to calculate neutralization potentials for the kimberlite mine tailings and to estimate the contribution made by secondary nesquehonite.     

Quantitative mineralogical analysis of carbonate sediments by X-ray diffraction: a new, automatic method for sediments with low carbonate content

A new X-ray diffraction method has been developed whereby the weight percentages of aragonite and low and high-magnesium calcite are determined from the integrated peak areas of samples. Peak areas are measured by a step scanning method. The weight percentages of MgCO₃ in calcite are determined from the angular position of the calcite peak. This technique uses a direct calculation method which simplifies the preparation of the samples and the calibration processes and increases the quality of the results. The fully automatic method uses a desk-top computer to guide the diffractometer and to carry out the necessary calculations. Tests on precision and accuracy of the method indicate that results with less than ± 4% error (mineral %) and ± 0.6% error (MgCO₃%) are obtainable for all samples even those with a low (10%) carbonate content.     

基于麦夸特算法的X射线衍射物相定量分析的影响因素研究

X射线衍射物相定量分析方法很多,新近提出的麦夸特算法(Levenberg-Marquardt)在XRD物相定量分析中具有明显的优势,但在实际应用过程中,哪些因素会对该方法计算结果的准确度产生影响仍不清楚。为了指导实际操作过程并提高麦夸特算法在X射线衍射物相定量分析中的准确度和处理效率,本研究通过Matlab软件,将已知配比含量的刚玉、石英、方解石和钠长石与其计算值进行比较,探讨衍射峰强度、衍射峰背底、样品数量等因素对麦夸特算法应用于X射线衍射物相定量分析中计算结果的影响。结果表明:通过前三强峰法的计算结果比通过最强峰法的计算结果具有更高的准确度;由于物相晶体结构及衍射特性的差异,衍射峰背底对不同物相定量结果的影响程度各异,扣除背底后各物相计算结果的准确度整体上都有不同程度的提高;在利用麦夸特算法进行批量分析过程中,当样品数低于一定阈值时,样品数越多,计算结果的准确度提高越明显,但当计算的样品超过一定阈值时准确度不会有明显的提高。     

Climatic signals in the Holocene carbonate sedimentary record of Namshi-Nur lake,West Baikal region

A new high-resolution Holocene climate record of the Western Baikal region from the evaporite sediments of one of the small saline lakes with the carbonate type of sedimentation are obtained on the basis of detailed mineralogical and crystallochemical studies of chemogenic carbonates. All carbonate phases occurring in the sediment are identified by decomposition of complex XRD-profiles of carbonates into individual peaks using the Pearson VII function, and the quantitative relationships between them are determined. Mg-calcites provide the major paleoclimatic information. The carbonate record contains data on the stratigraphic distribution of Mg-calcites, in which the number and ratio between the phases of different magnesium contents are determined by the past values of the Mg/Ca ratio, salinity, and total alkalinity of lake water that vary according to climatic cycles and fluctuations of the lake level. The high potential of the approach proposed for paleoclimatic reconstructions is demonstrated.     

X射线衍射全谱拟合法分析蓝晶石的矿物含量

蓝晶石矿物定量分析通常采用的化学物相法分析流程繁琐,易受同质异象矿物和难熔矿物的干扰;采用X射线衍射内标法需要提纯矿物绘制标准曲线,但矿物包体的存在使得获取纯净单矿物成为难题;由于不同矿区蓝晶石矿物成分之间存在着差异性,以上两种方法都仅仅适用于同一矿区样品的矿物定量分析。为简化分析流程,提高测试效率,本文采用X射线衍射(XRD)全谱拟合法对蓝晶石国家二级标准物质和野外样品进行分析,并与RIR法、绝热法和K值法等衍射定量方法及化学分析结果进行了比较验证方法的可靠性。结果表明:全谱拟合法无需采用标准物质,也不用引入内标物,一次扫谱分析能获得样品中所有成分的信息,操作简单,能有效降低择优取向对衍射定量结果的影响;对于含量大于5%的矿物,组分分析结果的绝对误差小于1%,显著低于绝对误差允许限;采用Highscore和Jade两种衍射数据处理软件获得的定量结果吻合度高,目标矿物蓝晶石分析结果的双差均小于0.8%,相对偏差小于2.5%;蓝晶石的加标回收率在95.3%～101.0%之间,能实现不同矿区蓝晶石矿的快速定量分析。     

Comparison of neutron and X-ray diffraction in texture analysis of deformed carbonate rocks

The paper compares pole figure determinations with neutron diffraction and X-ray diffraction on experimentally deformed carbonate rocks, a coarse grained marble and fine grained limestone. Neutron diffraction enables determination of complete pole figures on a single spherical specimen and is advantageous for coarse grained materials. Results obtained with both diffraction techniques agree satisfactorily, although uncertainties introduced by counting statistics are more serious for neutrons than for X-rays. Continuous detectors add new possibilities which are still little explored.     

A powder diffraction quantification method (ALJOR) for atmospheric particulate matter

The percentage calculation of crystalline phases in atmospheric particulate matter samples by means of an adiabatic approach of the matrix-flushing method with preferred preparations that avoids preferential orientations, should never be interpreted as absolute values. On the contrary, it should be seen as an indicator of the significant differences between each and every analyzed sample. Factors such as the application of constants, which are only useful for preparations of polycrystalline samples free of preferential orientation, and/or like the deficient resolution shown by the diffraction diagrams for certain phyllosilicate phases, bring a high degree of uncertainty to these percentage calculations. An alternative method of crystalline and amorphous phase quantification is presented below. Once the majority phases in the samples were identified, appropriate pure phases corresponding to each of them were selected. Then, the corresponding calibration curves were built using corundum (number 676 NIST) as a reference pattern phase. After validating the obtained calibration curves, the constants corresponding to each phase and selected spacing were calculated. The ALJOR method has been used for the quantification of five samples.     

多组分混合物X射线衍射直接定量相分析方法

研究了物质粉末衍射强度与样品堆积密度的关系,将粉末样品紧密度导入衍射强度公式。在此基础上推导出直接法测定多组分混合物质量吸收系数及各相浓度的数学公式,并通过实验证明了方法的实用性。还研究了缺乏纯样品以及样品中存在非晶质相、结晶度变化大的柑、择优取向严重的相等特殊情况的实验方法。 该方法不需要向待测样品中加入任何参考物质,不称样,不混样,不损耗纯样品,制样简便,特别适合大批量样品的定量相分析。     

X射线衍射增量法在三水铝石定量分析中的应用--以桂西堆积型铝土矿中的红土为例

简述了X射线衍射增量法进行定量分析的原理、实验过程和实验条件,并用该方法对桂西堆积型铝土矿中的红土三水铝石进行了定量分析.实验表明,在红土样品中加入一定量的标准样品后,利用X射线衍射增量法测定红土样品中三水铝石的含量,与原有的利用化学物相分析方法相比,具有不受红土样品中物相数量和矿物组合限制的优点;同时,X射线射线衍射增量法具有简便、快速、准确、经济的特点,是测定桂西堆积型铝土矿中的红土中三水铝石最为理想的定量分析方法.     

θ扫描在粘土X射线定量分析中的应用

根据Ｘ射线衍射中θ扫描的基本原理，在理论分析的基础上认为θ曲线峰的形状能较精确地反映粘土矿物的定向水平和分层现象，而峰的积分面积比常规２θ曲线峰的积分面积更能客观地反映粘土矿物的含量。提出在粘土矿物Ｘ射线定量计算中用θ峰积分面积代替常规的２θ峰积分面积，并通过分析各粘土矿物的θ峰形了解样品中粘土矿物的分层情况     

A method for quantitative pyrite abundance in mine rock piles by powder X-ray diffraction and Rietveld refinement

The abundance of pyrite and other sulfide minerals in mine rock piles is a potentially significant if not a determinative factor in terms of the geochemical and geomechanical evolution of the dumps as oxidation produces acid solutions that drive hydrolysis reactions. A technique is presented here that supports the quantitative determination of pyrite abundance in mine rock dumps by heavy liquid mineral separation to concentrate pyrite for powder X-ray diffraction and then Rietveld method refinement of the diffraction data on a large number of samples using commonly available laboratory equipment. In order to improve and constrain the accuracy of XRD results, binary (pyrite-quartz) and 6-part mineral mixtures (pyrite and rock-forming andesite minerals) spanning a wide range of pyrite concentrations were prepared gravimetrically and run as standards. These standards were then used to minimize errors in pyrite abundance data by constraining key input parameters in the Rietveld refinement. A new polynomial relationship was derived between diffracting crystallite size and the Brindley microabsorption correction input size. This method provides a means to determine uncertainties in pyrite abundance, whereas conventional Rietveld refinement techniques done without the use of standards yield only statistical measures of the least-squares fit, rather than absolute uncertainties in mineral constituent weight percentages. The technique was applied to a number of mine rock pile samples and the uncertainty in the results determined by applying the relationship derived from the 6-part gravimetric standards to the results of the Brindley corrected Rietveld refinements. Uncertainties determined by this method are found to be on the order of ±10% for samples with pyrite content greater than 10 wt% and ±30% for samples with pyrite content less than 10 wt%. In order to evaluate the technique’s improvement upon traditional visual mineral abundance estimation the quantitative results are compared to manual volumetric estimates.     

西沙群岛琛航岛碳酸盐沉积物X射线定量分析方法研究

利用X射线衍射分析技术测定碳酸盐沉积物中的矿物成分及其含量是目前研究碳酸盐最有效的方法。本文根据西沙琛航岛碳酸盐矿物组成的具体情况采用了“自清洗法”,用峰值强度测定方解石、白云石、文石和石英的含量,用方解石特征峰所在位置确定其MgCO_3含量,对西沙琛航岛碳酸盐沉积物进行了比较全面的定量分析测定,取得了较好的效果,从而对西沙群岛第四纪礁相沉积作用、白云岩化作用、地球化学、年代学、地层学等问题的解决提供了有价值的资料。     

太平洋富钴结壳中稀土元素的赋存状态

采用化学提取方法对采自太平洋国际海域的板状和结核状富钴结壳的稀土元素进行了分级提取 ,并利用等离子质谱仪 (ICP MS)测定了稀土元素的质量分数。结果表明 ,结壳中稀土元素在不同结合态中的富集顺序为 :残渣态 >有机结合态 >锰氧化物结合态 >碳酸盐结合态 >吸附态。稀土总质量分数的 5 6 %以上集中在残渣态中 ,并主要赋存于非晶态FeOOH物相中 ,说明FeOOH的形成对稀土元素的富集具有重要作用。水羟锰矿占结壳中X衍射结晶矿物的 95 %以上 ,但其稀土质量分数仅占稀土总质量分数的 1 6 %左右。呈有机结合态的稀土元素含量约占结壳稀土总质量分数的 2 0 % ,表明有机质对于结壳的形成及稀土元素的富集具有显著影响     

Carbonate sedimentation in shallow saline lakes of Western Transbaikalia: The response to Holocene climate changes

New research results are presented on the processes of carbonate sedimentation in shallow saline lakes of Western Transbaikalia by the example of the Holocene bottom sediments of Sul’fatnoe Lake (the Selenga Dauria). The techniques of X-ray diffractometry (XRD), IR spectroscopy, laser granulometry, and isotope and elemental analyses were used. By means of decomposition the XRD profiles using the Pearson VII function, the carbonate phases were identified and their quantitative ratios were determined. The evolution of the lake basin caused by climate changes in the Holocene was reconstructed by comparing the carbonate record to the concentrations determined for the ¹⁸O and ¹³C stable isotopes and to lithological, geochemical, and palynological data in the dated sedimentary section.     

Chemical Fractionation of Aluminium in the Sediments of El-Burullus Lagoon of Nile Delta,Egypt

A five step sequential extraction technique, following Tessier’s protocol has been applied to determine the chemical association of aluminium with major sedimentary phases (exchangeable, carbonate, manganese and iron oxides, organic and residual fraction) in four short sediment cores collected from El-Burullus lagoon of the Nile delta, Egypt. This study is a first approach of chemical fractionation of aluminium in one of the protective areas of the Mediterranean Sea of Egypt. The total metal content was also determined. The results of the fractionation study indicated that aluminium was mainly associated with the residual fraction (>95%). The organic and Fe–Mn oxide fractions were the next important phases. The exchangeable and carbonate fractions were less than 1%, limiting its potential toxicity as a pollutant. The geochemical analysis of aluminium forms reflected the lithogenic origin of this metal in the study area.     

实验条件对X射线衍射物相定量分析结果的影响

通过实验验证了多物相试样X射线衍射定量分析的基体效应,着重研究了参比强度K值、衍射强度、混合物各物相粒度、X射线管功率等实验条件对物相定量分析结果的影响。结果表明,物相定性分析是定量分析的前提,采用积分强度、使各物相颗粒尽可能细而且均匀、采用较高的X射线管功率以及适合的扫描速率均有利于提高物相X射线衍射定量分析的准确度。     

傅里叶变换红外光谱鉴定粘土矿物复合组分的研究

应用傅里叶变换红外光谱可以达到最大信噪比的特性,有效地获得了粘土矿物复合体中的单体差示红外谱图。避免了X衍射光谱中的矿物间衍射线的覆盖和色散型红外光谱中谱带重叠等不利因素,为粘土矿物复合体的鉴定提供了新的途径。研究表明,对痕量和近似的矿物组分都可以得到谱峰不受任何影响的纯正的红外谱图。差示定量结果也十分满意。     

关于《凹凸棒粘土中坡缕石的内标法X衍射定量分析研究》一文的修正

熊飞（2005）探讨了用内标曲线定量分析凹凸棒粘土中坡缕石含量的方法。但是原文中获得内标曲线的方法还有改进的余地。为确立内标曲线的数据点,原来的积分强度（峰面积）是按照半峰宽乘以峰高获得。这种方法求得的峰面积误差相对较大,导致了原文所提出的内标曲线在用于计算粘土纯度时有时会出现较大的误差,尤其是高纯样品往往出现坡缕石含量大于100％的情况。采用积分方法计算衍射峰的面积,对熊飞（2005）提出的曲线做出了必要的修正。本文所涉及的峰面积都是扣除背景后进行讨论。改进后的方法效果较好