Electron Probe Microanalysis Results Research Articles

Precipitation of bismuth nanoparticles and elements distribution in bismuth germanate glass induced by femtosecond laser

Bismuth nanoparticles are directly precipitated inside a bismuth germinate glass by irradiation with a 1030nm, 500kHz femtosecond laser, which are confirmed by means of X-ray diffraction, transmission electron microscope and Raman spectra. In addition, the results of electron probe microanalyzer indicate that the elements distribution around the focal point is induced simultaneously. We suggest that the precipitation of Bi nanoparticles and redistribution of ions with different diffusion coefficients should mainly be ascribed to the heat accumulation effect and thermal diffusion. The results provide a novel approach to produce Bi nanoparticles inside glass and have promising applications for the fabrication of photonic devices.

Isothermal solidification stage during transient liquid-phase bonding single-crystal superalloys

In this work, the isothermal solidification stage during transient liquid-phase bonding (TLP) single-crystal superalloys has been investigated. Experiments were performed to ascertain the bonding microstructures and the kinetics during the isothermal solidification. The results have shown that the isothermal solidification stage deviates from the standard parabolic TLP models. Lots of the borides with fine, short bar and acicular morphologies formed in the diffusion affected zone (DAZ) in the thick wall and thin wall substrate specimens at the isothermal solidification stage. Electron probe microanalysis results have shown that there exists B composition peak in the DAZ. Examination of the bonding kinetics presented that there are three stages in the isothermal solidification stage: initial stage, transient stage and final stage with different growth velocity of the isothermal solidification zone (ISZ). And the relationship of the width of the ISZ with the square root of the bonding time didn’t satisfy the parabolic relationship. Based on the microstructures and kinetics observed, a film ISZ mechanism is proposed, and a model is constructed to illustrate the isothermal solidification stage during bonding single-crystal superalloys.

Electrochemical Characteristics of a Diamond-Like-Carbon-Coated LiV3O8 Cathode When Used in a Li-Metal Battery with a Li-Powder Anode

A diamond-like-carbon (DLC)-coated LiV3O8 cathode was synthesized for use in a rechargeable 2032-coin-type cell with a Li-powder electrode (LPE) as the anode. The LPE anode was produced using the droplet emulsion technique and was compacted by pressing. The initial discharge capacity of the LPE/DLC-coated LiV3O8 (LVO) cell was 238 mAh g-1 at a C-rate of 0.5, while that of a LPE/bare-LVO cell was 236 mAh g-1. After 50 cycles, the capacity retention rate of the DLC-coated-electrode-containing cell (92%) was higher than that of the uncoated-electrode-containing cell (77%). Results of electron probe microanalysis and Raman spectroscopy confirmed that the electrode had been coated with DLC. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used to determine the sequence of formation of byproducts on the electrode after charging/discharging and to determine its surface composition. The voltage profile and impedance of the DLC-coated-electrode-containing cell were analyzed to determine the electrochemical characteristics of the DLC-coated cathode.

Corrosion Behavior of Rusted 550 MPa Grade Offshore Platform Steel

The corrosion behavior of a rusted 550 MPa grade offshore platform steel in Cl− containing environment was investigated. The results revealed that the corrosion process can be divided into initial stage in which corrosion rate increased with accumulation of corrosion products and later stage in which homogeneous and compact rust layer started to protect steel substrate out of corrosion mediums. On the contrary, structural analysis of rust layers by X-ray diffraction showed that A-FeOOH increased from 1. 3% to 3. 6% and the Fe3O4 increased from 1. 0% to 1. 5% while γ-FeOOH reduced slightly according to corrosion time increased from 30 cycles to 73 cycles. The results of electron probe microanalysis indicated that Cr concentrated mainly in the inner region of the rust, inner/outer interface especially., whereas Ni and Cu were uniformly distributed all over the rust after 73 corrosion cycles. According to electrochemical measurements, it was found that the corrosion rate of rusted steel reduced from 0. 61 mm/a after 45 cycles to 0. 34 mm/a after 85 cycles, 44. 3% reduction approximately, and Rrust values increased with increment of corrosion time. Therefore, formation of compact inner rust layer and enrichment of Cr are important to improve corrosion resistance of offshore platform steel.

Effects of Cr, Ni and Cu on the Corrosion Behavior of Low Carbon Microalloying Steel in a Cl− Containing Environment

The effects of Cr, Ni and Cu on the corrosion behavior of low carbon microalloying steel in a Cl − containing environment were investigated. The results revealed that the corrosion process could be divided into the initial stage in which the corrosion rate increased with accumulation of corrosion products and the later stage in which homogeneous and compact inner rust layers started to protect steel substrate out of corrosion mediums. The results of X-ray diffraction (XRD) indicated that the rust layers of the three-group steels (Cr, Cr–Ni and Cr–Ni–Cu steels) were composed of α-FeOOH, β-FeOOH, γ-FeOOH, Fe 3 O 4 and large amounts of amorphous compounds. The content of amorphous compounds of Cr–Ni–Cu steel was about 2%–3% more than that of Cr–Ni steel. The results of electron probe microanalysis (EPMA) showed that Cr concentrated mainly in the inner region of the rust of Cr–Ni–Cu steel, inner/outer interface especially, whereas Ni was uniformly distributed all over the rust and Cu was noticed rarely after 73 wet/dry cycles. The addition of Cr and Ni was beneficial to the formation of dense and compact inner rust layer, which was the most important reason for the improvement of corrosion resistance of experimental steel.

An experimental study of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the system CaO–FeO–Fe2O3–MgO–Al2O3–SiO2: implications for garnet–clinopyroxene geothermometry

Samples with eclogitic composition in the system CaO–FeO–Fe2O3–MgO–Al2O3–SiO2 were produced from various kinds of starting materials held in graphite-lined Pt capsules at a pressure of 2.5–3.0 GPa and temperatures of 800–1,300 °C using a piston-cylinder or Belt apparatus. Garnets and clinopyroxenes were characterized by analytical transmission electron microscopy and electron probe micro-analysis (EPMA). Fe3+/ΣFe ratios determined by electron energy-loss spectroscopy (EELS) decrease in clinopyroxene from 22.2 ± 3.4 % at 800 °C to 13.3 ± 5.4 % at 1,300 °C, while in garnet, they vary between 10.8 ± 1.5 and 15.4 ± 4.7 %, respectively. Temperature estimates according to Krogh (Contrib Mineral Petrol 99:44–48, 1988) reproduce the experimental temperature to ±60 °C without systematic deviations if total iron is used in the calculation. If only the Fe2+ content is used, which was obtained by combining EPMA and EELS results, the experimental temperature is underestimated by 33 °C on average at 800–1,200 °C and overestimated by 77 °C on average at 1,300 °C. These systematic deviations can be explained by the temperature-dependent ratio of Fe2+/ΣFe in garnet divided by that in clinopyroxene. Since the difference between the calculated and experimental temperature is relatively small, a Fe2+-based recalibration of the thermometer appears not to be necessary for the investigated system in the range of pressure, temperature and composition covered by the experiments of this study.

Solution Heat Treatment Optimization of Fourth-Generation Single-Crystal Nickel-Base Superalloys

The optimization of the solution heat treatment (SHT) of fourth-generation single-crystal nickel-base superalloys LDSX-6B and LDSX-6C is presented. The methodological approach to optimizing the SHT process is particularly highlighted. Differential scanning calorimetry (DSC) measurements and electron-probe microanalysis (EPMA) mapping were carried out to investigate material properties in the as-cast condition and after SHT. The DSC equipment was also adopted as a vacuum furnace to evaluate the suitability of the SHT ramp profile and to check the safety margins with regard to incipient melting during SHT. SHT trials were carried out in a laboratory-scale vacuum furnace, after which the heat-treated samples were subjected to DSC experiments, microstructural analysis, and EPMA mapping to assess the effects of SHT peak temperatures and soak periods. From the DSC and EPMA results, as-cast LDSX-6B shows a lower degree of elemental microsegregation; hence, this alloy is relatively easier to homogenize in the SHT trials. In contrast, as-cast LDSX-6C was found to have a higher degree of elemental microsegregation; therefore, it is much more difficult to homogenize and is highly prone to incipient melting. The results of this study indicate that an increase in the SHT peak temperature and/or soak period will lead to an improved compositional homogeneity in the material as expected. After SHT, both alloys retained some residual elemental microsegregation and the LDSX-6C alloy showed precipitation of topologically close-packed (TCP) phase at the dendrite cores. The most appropriate and economic SHT process may be determined based on the methodological approach presented in this study and the requirements of the materials during service.

Mineralogy and crystal chemistry of a low grade nickel laterite ore

To acquire understanding of Ni enrichment from laterite ore, the mineralogy and crystal chemistry of a low grade limonite type nickel laterite ore sample assaying 0.97% Ni from Indonesia were studied using optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). According to EPMA results, the mineral includes 80% goethite ((Fe, Ni, Al)O(OH)) with 0.87% Ni, 15% silicate minerals with lizardite ((Mg, Fe, Ni)3Si2O5(OH)) and olivine ((Mg, Fe, Ni)2SiO4), and 1.19% Ni, and other minor phases, such as hematite, maghemite, chromite and quartz, and no Ni was detected. The mineralogy of the laterite ore indicates that due to the complicated association of the various phases and the variable distribution of Ni, this refractory laterite ore can not be upgraded by traditional physical beneficiation processes.

The effect of 0.4 wt.% Mn addition on the localized corrosion behaviour of zinc in a long-term experiment

The corrosion performances of pure Zn and Zn–0.4Mn alloy exposed in marine environment (Qingdao, east of China) have been studied after exposure for three years. Pitting corrosion occurs on both pure Zn and Zn–0.4Mn with fewer and smaller pits on Zn–0.4Mn alloy as revealed by confocal scanning laser microscope (CSLM), which indicates that the addition of Mn can reduce the localized corrosion of Zn. Corrosion products formed on pure Zn and Zn–0.4Mn have been characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA). The main crystalline phases identified by XRD are Zn5(CO3)2(OH)6, Zn4SO4(OH)6 and NaZn4Cl(OH)6SO4·6H2O, respectively. Small amounts of ZnO and Zn(OH)2 are also found which mainly present on top surface of corrosion films as revealed by XPS. Combined results of XRD and EPMA disclose that Zn4SO4(OH)6 and NaZn4Cl(OH)6SO4·6H2O are the main compounds inside the pits with Zn4SO4(OH)6 locating at the pit bottom. The formation mechanism of corrosion products inside pits and the role of small Mn addition on localized corrosion of Zn have been discussed.

Electron probe microanalysis of HgCdTe heteroepitaxial structures with CdTe buffer layers

Some results of electron probe microanalysis of HgCdTe heteroepitaxial structures with wide-gap semiconductor CdTe buffer layers are described. It is shown that these structures may be used for manufacturing high-performance photodetectors for registration of infrared radiation in the ranges of 3–5 and 8–12 μm.

The Preparation and Characteristics of InxGa1−xN (0.06 ≤ x ≤ 0.58) Films Deposited by ECR-PEMOCVD

We investigate the structural property and surface morphology of InxGa1−xN films for In compositions ranging from 0.06 to 0.58, which are deposited by electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The results of x-ray diffraction (XRD) in InGaN films confirm that they have excellent c-axis orientation. The In content in the InGaN epilayers is checked by electron probe microanalysis (EPMA), which reveals that In fractions determined by XRD are in good agreement with the EPMA results. Atomic force microscopy measurements reveal that the grown films have a surface roughness that varies between 4.16 and 8.14nm. The results suggest that it is possible to deposit high-c-axis-orientation InGaN films with different In contents.

An Examination of Kernite (Na2B4O6(OH)2·3H2O) Using X-Ray and Electron Spectroscopies: Quantitative Microanalysis of a Hydrated Low-Z Mineral

Mineral borates, the primary industrial source of boron, are found in a large variety of compositions. One such source, kernite (Na2B4O6(OH)2·3H2O), offers an array of challenges for traditional electron-probe microanalysis (EPMA)-it is hygroscopic, an electrical insulator, composed entirely of light elements, and sensitive to both low pressures and the electron beam. However, the approximate stoichiometric composition of kernite can be analyzed with careful preparation, proper selection of reference materials, and attention to the details of quantification procedures, including correction for the time dependency of the sodium X-ray signal. Moreover, a reasonable estimation of the mineral's water content can also be made by comparing the measured oxygen to the calculated stoichiometric oxygen content. X-ray diffraction, variable-pressure electron imaging, and visual inspection elucidate the structural consequences of high vacuum treatment of kernite, while Auger electron spectroscopy and X-ray photoelectron spectroscopy confirm electron beam-driven migration of sodium and oxygen out of the near-surface region (sampling depth ≈ 2 nm). These surface effects are insufficiently large to significantly affect the EPMA results (sampling depth ≈ 400 nm at 5 keV).

An experimental refinement of solid–solution relationship in Ca-α-Sialon ceramics by analytical electron microscopy

Local dopant compositions within individual α-Sialon grains were measured by analytical electron microscopy (AEM) in hot-pressed CaxSi12−3xAl3xOxN16−x (x = 0.3–1.4) ceramics. The reduction of local x values from the nominal dopant compositions is about 40% in general, and it reaches 60% for the end member (x = 1.4) which contains inclusions of AlN-based 21R phase. This results exhibit stronger departures from x than the previous report of 30% dopants missing in α-Sialon phase by electron probe micro-analysis (EPMA) [J Eur Ceram Soc 19:1637, 1999]. Amorphous films of ~1 nm thick were commonly found at grain boundaries (GBs), which could only take a small fraction of undetected dopants while the film composition exhibits a quite different behavior. The general presence of GB films can rationalize the discrepancy between AEM and EPMA results by their differences in probe size and detection geometry, while the much larger gap in the end member suggests the existence of Ca-rich glasses in the intergranular regions. By excluding this end member, a linear relation between dopant solution and lattice expansion is restored in α-Sialon structure, which leads to 20 and 80% increases of the expansion coefficients from those given in the previous and original reports, respectively. This study not only demonstrated the necessity of solubility study in ceramics by AEM refinement, but also opens a new front to correlate the solution behavior with the intergranular glass/amorphous structures, both were regarded so far as largely independent.

Effect of aluminum content on the mechanochemical synthesis of in-situ TiN in the Al–Ti–AlN system and subsequent shock consolidation

To determine the effect of aluminum content on the formation of in-situ TiN in the Al–Ti–AlN system, a mixture of aluminum, titanium and aluminum nitride powders was subjected to high energy milling. Al content of the mixture was changed according to the following stoichiometric reaction: Ti+AlN+ XAl→TiN+(1+ X)Al. The value of X was varied from 5.35 to 19.65 based on the stoichiometric calculation of the molar mass of each component expected to result in aluminum matrix composite with TiN weights of 30%, 20% and 10%, respectively, in addition to reaction corresponding to X=0(Ti+AlN→TiN+Al). Thermodynamic factors determine that the amount of Al in the mixture plays a key role in the formation of in-situ TiN. XRD and EPMA results showed that at lower Al content ( X=0, 5.35), reaction proceed through a gradual mode. By increasing Al content ( X=19.65), no mechanochemical reaction occurred between Ti and AlN. Continuation of the milling process allowed acquisition of in-situ TiN in the designed compositions of AlN–TiN, Al–Ti–AlN–30%TiN, and to some extent, of Al–Ti–AlN–20%TiN. A nanocrystalline solid solution evolved by mechanical alloying (MA) was sustained for prolonged milling time. The mean TiN crystallite size obtained was 10 nm for the AlN–TiN composition. The end product milled powder after 40 h of milling time, equating to the Al–Ti–AlN–30%TiN composition was consolidated into bulk compact using the underwater shock compaction method. The milled specimens were characterized by XRD, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and microhardness testing. The sample had a uniform and fine-grained composite structure with 99% theoretical density and average microhardness of 434 HV0.1. The results confirmed the possibility of fabricating reliable bulk nanostructured materials by imposing shock compaction on submicron sized powders.

Geochemical characterization of placic horizons in subtropical montane forest soils, northeastern Taiwan

Well‐developed placic horizons have been found in subalpine forest soils with large clay contents in Taiwan. We investigated their formation processes in five profiles in a subalpine ecosystem of northeastern Taiwan, using scanning electron microscopy (SEM), energy‐dispersive spectrometry (EDS), electron probe microanalysis (EPMA), differential X‐ray diffraction (DXRD) and chemical extractions. The placic horizons, ranging from 3‐ to 17‐mm thick, always occurred above argillic horizons with abrupt changes in pH and texture between the two horizons. When fully developed, the placic horizons were clearly differentiated between upper and lower sub‐horizons. EDS and chemical extractions revealed that the cementing materials in both were predominantly inorganic Fe oxides. However, contents of aluminosilicates and organically complexed Fe and Al were greater in the lower than in the upper placic sub‐horizon. Results of EPMA indicated that interstitial fine materials in the upper placic sub‐horizon were composed mainly of Fe oxides, whereas Fe oxides were codominant with illuvial clay in the lower sub‐horizon. These analyses identified the migration of Fe and clay as major formation processes in both sub‐horizons. We hypothesize that there is a pedogenic sequence that starts with clay illuviation, followed by podzolization. The resultant textural and permeability differentiation reinforces the tendency to profile episaturation that is already inherent from the heavy rainfall and clayey surface soils. Topsoil Fe is therefore reduced and mobilized, and then illuviated with clay and organically complexed Fe/Al to initiate the lower placic sub‐horizon. The poor permeability of this layer reinforces the moisture conditions in the surface soils, and the further reduction, illuviation and deposition of inorganic Fe to form the upper placic sub‐horizon.

Zinc Oxysulfide Thin Films Grown by Pulsed Laser Deposition

Pulsed laser deposition was used to produce thin films of zinc oxysulfide (ZnOxS1� x) on quartz substrates. The target was a sintered pellet (ZnO0.39S0.61) made of a solution precipitate. The film composition obtained by electron probe microanalysis (EPMA) was ZnO0.41S0.59, ZnO0.44S0.56, and ZnO0.37S0.63 for substrate temperatures of 450� C, 540� C, and 630� C, respectively. X-ray diffraction (XRD) showed that samples deposited at 450� C and at 540� C had a prominent cubic sphalerite phase, whereas samples deposited at 630� C consisted of three phases, viz. hexagonal wurtzite and cubic sphalerite (ZnS), and hexagonal zincite (ZnO). With respect to the tabulated lattice spacings for sphalerite (cell constant 0.5406 nm), distinct shifts were observed for the low temperature samples, yielding cell constants around 0.533 nm. Transmission electron microscopy (TEM)–selected area electron diffraction studies support the XRD data. Patterns of films deposited at 540� C could be indexed as sphalerite, with similar lattice shifts as in XRD, resulting in a cell constant of 0.53. Locally highly resolved chemical analysis by TEM–energy dispersive x-ray analysis revealed a stoichiometry that was consistent with the EPMA results. Ultraviolet (UV)–visible transmission measurements of the films led to bandgap energies around 3.3 eV, which is well below the reported bandgap energies of ZnS.

An investigation of formation of second phases in microalloyed, AZ31 Mg alloys with Ca, Sr and Ce

The present work studied the formation of new phases by adding alloying additions (Ca, Sr, and Ce) in AZ31 alloy at micro-levels (approximately 0.2 wt.% per element). Quantitative electron probe micro-analysis (EPMA) was used to identify the compositions of these phases; a comparison in the morphology and distribution of an identical phase in different alloy systems was made; and the thermodynamic software of FactSage™ was utilized to calculate the possible intermetallic phases during solidification. The results of EPMA showed the existence of phases other than Mg17(Al, Zn)12 and Al8Mn5 in AZ31 alloy, namely: Al2Ca, Al2Sr, Al11Ce3, Al8CeMn4, and Al2(Ca Sr); and these new phases were thermally stable at 450 °C for 10 h. The morphology and distribution of second phases in different alloy systems were self-consistent. These phases were well predicted by FactSage™ with recent light alloy database.

알칼리-실리카 반응에 의한 모르타르 봉의 SEM과 EPMA 분석을 통한 미세구조 연구

이 연구에서는 알칼리-실리카 반응성을 평가하는데 적용되는 ASTM C 227과 ASTM C 1260 모르타르 봉 시험법으로 쇄석골재의 반응성을 평가하고, 제작된 모르타르를 3년간 일반 환경에 노출시킨 뒤, 알칼리-실리카 반응으로 인해 생성될 수 있는 반응생성물 확인과 화학분석을 위해 SEM과 EPMA 분석을 실시하였다. 이 연구에서는 SEM의 secondary electron image(SEI)와 EPMA의 backscattered electron image(BSEI)를 이용하였다. 이 연구에 사용된 쇄석골재는 ASTM C 227에 의해서는 2년간 뚜렷한 팽창을 나타내지 않았지만, KOH 용액을 이용한 반응촉진법에 의해서는 유해 가능성이 있는 것으로 나타났다. 모르타르 봉 시험 시행 후, SEM SEI 분석 결과, ASTM C 227에 의해 제작된 모르타르 봉에서는 골재 입자와 시멘트페이스트 사이에 알칼리-실리카 반응에 의한 흔적이나 pore 내에서 반응생성물이 확인되지 않았다. 하지만 ASTM C 1260에 의한 모르타르 봉에서는 알칼리-실리카 반응의 전형적인 반응생성물로 알려진 꽃잎형(rosette morphology)의 알칼리-실리카 겔(gel)이 확인되었다. EPMA 분석 결과, ASTM C 227에 의한 모르타르 봉에서도 골재 입자 표면에 부분적으로 미세하게 Al-ASR gel이 확인됨에 따라 ASTM C 227에 의해 2년간 무해한 팽창을 나타내었던 모르타르 봉에서도 알칼리-실리카 반응이 발생하고 있음을 알 수 있었다. 반응성 촉진 시험 후의 모르타르의 EPMA 분석 결과에서는 골재 입자에 발생된 균열 내부뿐만 아니라 pore 내부에 알칼리-실리카 겔이 축적되어 있는 것으로 나타났으며, 또한 pore 내에서 확인된 겔이 골재 입자 내부에 생성된 겔에 비해 Ca 함량이 더 풍부한 것으로 나타났다. 국내에서 생산되는 쇄석골재 사용으로 인하여 구조물 내부에 발생한 변화를 미세구조를 통해 확인한 결과, 알칼리-실리카 반응에 의한 구조물 열화를 알 수 있었다. 따라서, 국내 쇄석골재 사용량 증가에 따라 새로운 건설에 있어서 알칼리-실리카 반응 방지를 위한 고려가 있어야 할 것으로 판단된다.

Paleoclimatic approach to the origin of the coloring of Turonian pelagic limestones from the Vispi Quarry section (Cretaceous, central Italy)

Samples of Turonian white to light gray and red limestones from the Vispi Quarry section in central Italy have been examined by X-ray Diffractometry (XRD), Electron Probe Micro-analysis (EPMA), Electron Spin Resonance (ESR), and Ultra violet-visible-near infrared (UV-VIS-NIR) Diffuse Reflectance Spectroscopy (DRS). The ESR, EPMA and XRD results suggest that Mn 2+ was well-incorporated into the structure of calcite during the precipitation of the limestones. Amorphous ferric oxide (most probably hematite) and the Mn 2+-bearing calcite endowed the limestone with a red color as the major pigmentation, and the Mn 2+-bearing calcite gave it a pink tinge. The mineral assemblage is composed mainly of detrital boehmite and quartz, which are interpreted as having been imported from the Eurasian paleo-continent into the ocean by seasonal northeasterly winds. The boehmite formed by dehydration of gibbsite as an end-product of intensive chemical weathering of Fe, Mg, and Al-bearing aluminosilicates exposed in a subtropical environment. XRD results for the residues of Cretaceous Oceanic Red Beds (CORBs) dissolved in dilute acetum differed from those from Cretaceous Oceanic White Beds (COWBs) in that they contain hematite. This suggests that no hematite was imported into the ocean during the precipitation of the white limestone, and may explain why the same detrital origin for red and white limestones resulted in different colors by suggesting that climatic variations occurred on the paleo-continent during the precipitation of these two types of limestone. The presence of boehmite and hematite suggests that, during the Late Cretaceous, central Italy lay within a subtropical climatic zone with a seasonal alternation of warm rainy winters and hot, dry summers during the formation of the CORBs, and a continuously warm climate during the formation of the COWBs. The Mn/Fe(mol) ratios in the shells of spherical carbonate assemblages (probable microfossils) suggested that the ocean was much richer in iron during the precipitation of COWBs.

ELECTRON PROBE MICROANALYSIS OF THE PASTE FROM CERAMICS OF THE FAR EAST

Results of electron probe microanalysis (EPMA) of ceramics from various sites in the Russian Far East, Sakhalin, and Japan are discussed. The proportions of the principal chemical elements (Ca–K–SiO2, K–Ca–Na, Mg–Fe–Ti) in the clay paste are shown by means of 3-D plots. New techniques for the computer-aided evaluation of sand grains and for processing images are proposed. Advantages and drawbacks of EPMA are assessed, and methodological guidelines are suggested for using this method for the study of feldspars in the clay paste of prehistoric pottery.