地质标准物质粒度测量与表征的现代方法

地质标准物质是地质材料分析的计量标准,在分析质量监控、仪器校准和分析方法评价中发挥着重要作用。地质标准物质大多为粉体材料,而粒度是粉体材料的一项重要特性指标。长期以来,地质标准物质的粒度一直采用过筛法检测;近年来在超细标准物质研制中引入了以激光粒度仪为代表的现代粒度分析方法,并以直观的粒度分布图和简洁的特征粒度来表达分析结果,大大提升了粉体地质标准物质粒度特性的测量及表征水平。在此工作基础上,测量了正在广泛使用的典型地质标准物质的粒度分布,获得了前所未知的粒度分布信息,为这些标准物质的正确使用和取样不确定度评价提供了有益的资料。简单地介绍了检测粉体材料颗粒特性的现代方法,讨论了地质分析与粒度分析在概念上的差异,并就今后地质标准物质乃至地质分析样品的粒度检测与表征方法提出了建议。     

富钴结壳超细标准物质的加工制备

用气流磨制备了2个具有超细粒度的海山富钴结壳标准物质MCPt-1和MCPt-2。原样先经球磨成74μm(-200目),再用气流磨进行超细加工。样品粒度采用激光粒度仪检测,用粒度分布图和特征粒度来表达测量结果。两个样品的平均粒度分别为1.8μm和1.5μm(约2 000目),是目前粒度最小的标准物质。文章介绍了用于超细加工的流化床式气流磨原理与方法,展示了样品加工后的粒度分析结果,对比了国内外超细标准物质的概况。最后讨论了当前关注样品加工的重要性、超细加工的问题及超细样品分析研究的意义。     

江苏潮滩沉积物激光粒度仪与移液管-筛析分析结果的对比

激光粒度仪的广泛应用带来了与历史数据的对比问题,因此需要建立激光粒度仪与早期分析结果之间的关系。根据江苏海岸潮滩沉积物样品的激光粒度仪和移液管-筛析法分析,对粒度参数、粒度组分等进行了对比,对两种方法的差异进行了分析。结果表明,对于江苏潮滩沉积物粒度参数中平均粒径的激光粒度仪与移液管-筛析分析结果之间有良好的线性关系;筛分法测得的粗颗粒物质较激光法偏少,而移液管法法测得的细颗粒物质较激光法偏多;将样品分类之后再进行两种方法所获粒度参数的回归分析,相关性得以提高,说明不同粒度组成的沉积物对分析结果的对比有不同的影响。两种方法之间的换算关系不仅与研究区域有关,而且与沉积物本身的粒度组成有关。     

江苏潮滩沉积物激光粒度仪与移液管-筛析分析结果的对比

激光粒度仪的广泛应用带来了与历史数据的对比问题,因此需要建立激光粒度仪与早期分析结果之间的关系。根据江苏海岸潮滩沉积物样品的激光粒度仪和移液管—筛析法分析,对粒度参数、粒度组分等进行了对比,对两种方法的差异进行了分析。结果表明,对于江苏潮滩沉积物粒度参数中平均粒径的激光粒度仪与移液管—筛析分析结果之间有良好的线性关系;筛分法测得的粗颗粒物质较激光法偏少,而移液管法法测得的细颗粒物质较激光法偏多;将样品分类之后再进行两种方法所获粒度参数的回归分析,相关性得以提高,说明不同粒度组成的沉积物对分析结果的对比有不同的影响。两种方法之间的换算关系不仅与研究区域有关,而且与沉积物本身的粒度组成有关。     

沉积物粒度分析方法的比较

近年来激光粒度分析法在沉积物粒度分析方面的应用得到了进一步扩展。本文利用美国麦克奇公司生产的S3500型激光粒度分析仪开展沉积物粒度分析方法实验,研究表明:S3500型仪器较优的样品用量约为0.2 g;稀释过程会影响样品的粒度分布;样品分取方式会带来不同的随机误差。与薄片图像法和筛析法两种传统粒度分析方法获得的粒度分布参数比较表明:激光法测得的平均粒径较薄片图像法和筛析法偏细;激光法和筛析法的峰度相关性较好。采用Malvern 2000和Micro S3500两种激光粒度分析仪测量结果的比较表明:Malvern 2000测得的平均粒径较Micro S3500测得的平均粒径偏细,但二者的相关性很好(r=0.9574),研究认为这两种粒度仪的测试结果会给岩石粒度定名带来差异。由于各种粒度分析方法存在差异和局限性,在实际工作中粒度分析应尽可能建立在同一测量体系上,以便资料对比。     

激光粒度仪测试结果及其与沉降法、筛析法的比较

分析了Cilas 940L激光粒度仪的测试结果,并与沉降法、筛析法进行了比较。激光粒度仪测试结果的重复性较好,测量精度较高。对于玻璃珠样品,激光粒度仪和筛析法测试结果十分接近,对于天然沉积物,激光粒度仪测定的平均粒径偏粗,分选偏差。和沉降法相比,激光粒度仪测定的粘土组份 (<8%)的含量为沉降法的 46.7%～ 70.5 %,平均为 6 0 %,测定的平均粒径较沉降法偏粗,分选偏差。造成激光粒度仪与沉降法、筛析法之间差异的原因主要在于这些测试方法原理的不同和天然沉积物不规则的形状。     

测试超细煤粉粒度的实验研究

利用激光粒度仪测试超细煤粉的粒度。对测试超细煤粉试样粒度时的试样浓度、测试温度、分散时间、分散剂的种类及浓度等方面的影响进行了实验研究,给出了激光粒度仪测试超细煤粉粒度的最佳实验条件。     

HELOS/BF型激光粒度仪湿法测试条件的优化

激光粒度仪以测试速度快、操作方便、重复性好等优点得到越来越广泛的应用,但仪器技术参数和测试条件不同对样品粒度测试结果有着显著影响。本文通过实验得到了HELOS/BF型激光粒度仪的优化测试条件,结果表明:对于比重小或粒径小的样品,采用低搅拌速率、高超声强度和较长超声时间;对于粒径大或比重大的样品,应采用高搅拌速率、低超声强度和较短超声时间。分散剂能加快样品颗粒的分散,且对于粒径小的样品分散效果更好。测试时进样浓度(遮光度)过低,样品中的颗粒数过少,检测不到足够的信号,使样品不具有代表性,样品粒径测定结果偏高;进样浓度过高,出现多重散射而使粒度分布范围较宽,样品粒径测定结果偏低。研究认为,HELOS/BF型激光粒度仪的合适进样浓度为10%～25%。     

激光法粒度筛析校正研究

激光法和筛析法分析作为两种最常见的用于沉积地质粒度分析的方法,其间的数据转换校正是在数据对比、数据对接时经常遇到且无法回避的问题。为此设计了两个实验,实验一对比了窄粒度范围样品两种分析方法的分析结果,统计分析了筛析法比激光法偏大的幅度,并提出一个校正方法;实验二对不同磨圆程度的样品进行分析,研究了磨圆度与两种分析方法差异程度之间的相关关系,认为实验一提出的校正方法适合一般条件下的天然沉积物粒度分析校正。文章又以实例展示了所提出的校正方法的校正效果并讨论了激光粒度法存在的问题。激光粒度分析法用于天然沉积物粒度分析时,结果常见明显的光滑化、正态化、双峰合并现象,扭曲了真实的粒度分布。文章认为实际样品具体情况远远复杂于米氏理论的设定条件,样品条件参数并未全部带入计算过程,所以激光法粒度求解是不精确的。更好的数据校正方法有待于激光粒度仪的软件、硬件改进。激光法合理的用于天然沉积物粒度分析还有一些问题需要讨论。     

激光粒度仪转速对河流砂质沉积物测量的影响

激光粒度仪是沉积物粒度测量中常用的仪器,通过对河流沉积物的粒度测量发现,激光粒度仪的转速会影响粒度测量结果。实验结果表明:被测样品的颗粒易受撞击而破碎,激光粒度仪转速对样品遮光度有影响;转速太大会使大颗粒的破碎严重,转速太小又会导致样品颗粒不能均匀分散于溶液中,综合分析得出河流砂质沉积物应用Mastersizer 2000激光粒度仪测量的较适宜转速为1 900~2 000 r/min左右,且不宜加超声波震荡。     

Preparation of Five China Sea and Continental Shelf Sediment Reference Materials (MSCS-1–5) with Ultra-Fine Particle Size Distributions

We report the preparation and characterisation of five sediment reference materials MSCS-1–5 from the China Sea and continental shelf. The raw samples were individually collected from the East China Sea and the South China Sea. They were first ground by ball mill to a homogenous powder of -200 mesh (< 74 μm). Then, half of each sample was further processed by an ultra-fine powder processing technique, a jet mill, to form a powder with an average particle size of < 4 μm (about 800 mesh). The homogeneity was tested by high-precision WD-XRF and the precision was found to be less than 1% RSD, which is compatible with the precision range for modern analytical techniques. An F-test showed that all five samples were homogeneous. Twelve laboratories participated in the cooperative study and sixty constituents were determined. Between fifty and fifty-two analytes were characterised as recommended values in MSCS-1–5 in compliance with Chinese national norms. The sum of the major and minor elements or components in the five reference materials MSCS-1–5 was 99.91%, 99.86%, 100.43%, 100.12% and 99.66%, respectively.     

Platinum‐Group Element Results for Two Cobalt‐Rich Seamount Crust Ultra‐Fine Reference Materials: MCPt‐1and MCPt‐2

Two Co‐rich seamount crust reference materials, MCPt‐1 and MCPt‐2, were prepared using ultra‐fine particle size milling technique and characterised for the platinum‐group elements (PGEs). The raw material for these two reference materials was collected separately from the Magellan seamounts of the western Pacific Ocean and the seamounts of the central Pacific Ocean by Russian and Chinese scientists. First, they were ground by ball mill to a ?200 mesh powder, then further processed by ultra‐fine jet mill and well‐mixed. The particle size distributions of the samples were tested by a laser particle analyser; the average particle size was 1.8 and 1.5 μm (equal to about 2000 mesh) respectively. The homogeneity of six major and minor elements in these two materials was tested at the milligram level of sampling mass by high‐precision wavelength dispersive X‐ray fluorescence (XRF) spectrometry and at the microgram level of sampling mass by electron probe microanalyser. The homogeneity of more than forty trace elements, including Pt, was tested at the microgram level of sampling mass by LA‐ICP‐MS. Except for Rh, all PGEs were determined by isotope dilution‐ICP‐MS. Platinum in MCPt‐1 and MCPt‐2 was characterised as certified values, whereas the other five PGEs in MCPt‐1 and MCPt‐2 were reported as reference values. In addition, the information values of sixty‐two major, minor and trace elements were obtained by XRF, ICP‐AES and ICP‐MS. The minimum sampling mass for the determination of PGEs was 1 g, while the minimum sampling mass for the determination of the other elements was 2–5 mg.     

汶川地震科钻WFSD-3孔金刚石钻进岩粉粒度分析研究

固相控制是维护钻井液性能的关键工作。通过对汶川地震断裂带科学钻探三号孔(WFSD-3)金刚石钻进产生的岩粉进行激光粒度测试,分析岩粉粒度分布规律,从而为科学设计地质岩心钻探固控设备和合理配置地质岩心钻探固控系统提供依据,最终达到有效控制固相含量,稳定钻井液性能的目的。     

Investigations into the Preparation of Ultra-Fine Particle Size Geochemical Reference Materials

Although over recent years, sensitivity and precision of modern analytical techniques have continuously improved, traditional analytical specification for the particle size of samples has remained at 74 μm (-200 mesh). For this reason, the uncertainty caused by inhomogeneity in test portions of the sample itself has become a more and more significant contribution to the total analytical uncertainty. Therefore, to reduce this total uncertainty, the first step is to improve the homogeneity by reducing the particle size of a sample. For this purpose, we have investigated a method for the preparation of ultra-fine reference materials. Using the modern ultra-fine crushing technique (jet mill), six marine sediment samples MSAn and MSCS-1 to 5 were prepared and the particle distributions of these samples were measured using a laser particle-analyser. The average particle size of these samples was 4–5 (im and the largest particle size was less than 30 (im. MSAn will be used as the sample for a future GeoPT(tm) proficiency testing round and MSCS-1 to 5 will be prepared as reference materials. All geochemical laboratories are welcome to participate in this co-operative research programme. The processing and use of ultra-fine samples (< 30 μm) will have a significant influence on the future development of geoanalytical techniques as a consequence of the potential reduction in the mass of test portion and the development of new geoanalytical systems.     

Particle size distribution analysis of sand-sized particles by laser diffraction: an experimental investigation of instrument sensitivity and the effects of particle shape

Laser diffraction is now widely used for particle size distribution analysis of sediments and soils. The technique can be very precise, and offers advantages of speed and cost over many other methods when used to analyse mixtures of sand, silt and clay. This study presents the results of an experimental investigation that examined the sensitivity of the Beckman-Coulter LS230 instrument to mixtures of different grain populations and differences in particle shape. The instrument was found to have high sensitivity to coarse particles in a finer matrix (detection threshold 1–2%), but much lower sensitivity to finer particles in a coarser mixture (detection threshold 12–17%). Experiments using near-spherical ballotini showed that laser analysis provides very similar values to dry sieving for the mean, median and mode, but for a range of natural sand samples values for the mean, median and mode were offset by 8–21%, with an average of ca 15%, compared with sieving. Analysis using a Beckman-Coulter RapidVUE instrument, which provides both size and shape information, provided support for the hypothesis that the differences between laser analysis and sieving are partly attributable to the effects of particle shape. However, an additional factor is the way in which the laser software interprets the optical diffraction data. The software predicts a high degree of log-normality in the size distribution, such that highly skewed, truncated or bimodal samples are poorly represented. Experiments using sieved fractions of ballotini indicated that, even with near-perfectly spherical particles, the particle size distribution predicted by the laser software includes a relatively large percentage of particles outside the sieve class limits.     

中国地质标准物质制备技术与方法研究进展

评介了中国地质标准物质研制中技术方法方面的研究进展,包括样品加工技术,粒度检测与表征方法,均匀性检验与评价,最小取样量的确定,稳定性检验及其结果表述,定值方式,分析方法、数据处理及定值条件,不确定度评价与量值溯源保证等。对照国家相关的技术规范、国际标准化组织(ISO)的相关指南和国际地质分析者协会(IAG)关于地质标准物质研制的协议,讨论了目前中国地质标准物质制备技术的现状及未来的发展。     

考虑级配多样性的颗分试验取样质量理论研究

颗粒分析试验被广泛应用于土木、水利水电和采矿等诸多工程中,以确定材料的颗粒级配。但对于工程中常见的超大粒径填料合理取样质量问题,尚缺少可依据的文献资料。将试样选取视为一种分层抽样过程,结合抽样分析理论,建立了能够确定样本容量的理论公式;考虑到颗粒材料平均粒径与其级配分布的关系,提出了一种为确定材料整体级配所需试样质量的通用方法。对不同级配分布情况开展了针对性试验,验证了所提出方法的适用性。并将该方法应用于确定重庆江北机场和贵州龙洞堡机场填料的颗粒级配,取得了良好效果。所得结果可为相关工程实践及规范的发展和完善提供参考。