Transmission electron microscopic X-ray quantitative analysis of human dentin at 200 kV accelerating voltage

Qualitative and quantitative x-ray energy dispersive spectroscopy is now used successfully to analyze many features and processes in inorganic samples. When applied to inorganic samples, however, the results are often less satisfactory due to problems of preparation of organic samples, difficulty of measuring x-rays from organic samples, damage of the sample by the electron beam, and other practical problems. In the present study we used a high voltage transmission electron microscope equipped with an energy dispersive x-ray spectrometer to examine accurate quantitative standardless analysis of thin sections of an organic sample, human dentin. Based on our experiments we found the important parameters for quantitative analysis were sample thickness and appropriate choice of model sample. Further, we show that the method of Cliff and Lorimer can be used with biological samples at 200 kV, and we show that quantitative analysis of human dentin can be carried out at 200 kV. Finally, we show that areas of human dentin can be differentiated by their morphological characteristics and x-ray analyses obtained in the transmission electron microscope.     

Energy dispersive X-ray microanalysis of air dried casein micelles from bovine milk

Secretory proteins (casein micelles) were air dried prior to elemental analysis either without treatment, following glutaraldehyde fixation and dialysis, or following dialysis against distilled water. Samples were then examined by energy dispersive X-ray microanalysis in a scanning transmission electron microscope (STEM). Untreated samples and samples dialysed against distilled water retain colloidal (bound) elements as compared to glutaraldehyde treated samples. Contamination of air dried casein micelles by ionic constituents in the non-protein aqueous phase was observed in the untreated sample and in the glutaraldehyde treated sample. Dialysis of casein micelles against distilled water reduced contamination from the aqueous phase without diminishing the apparent concentrations of colloidal elements.     

Determination of conditions for optimum resolution of a high angle thin window energy dispersive spectrometer.

The energy resolution of an energy dispersive spectrometer (EDS) equipped with an ultrathin window (UTW) and mounted at a high take-off angle (72 degrees) on a transmission electron microscope has been studied under a variety of operating conditions. The spectrometer resolution is close to that specified by the manufacturer, up to count rates of 400 cps. Above 400 cps the resolution deteriorates rapidly, and the MCA dead time and zero width increase. Above 10 keV, the height of the background is much greater than expected for bremsstrahlung and shows the shape which has previously been attributed to backscattered electron flux into the detector. It is postulated that the deterioration in resolution with count rate is caused by backscattered electrons reaching the detector through the UTW.     

Sub-nanometre elemental analysis of Cu cluster in Fe-Cu-Ni alloy using aberration corrected STEM-EDS

In order to understand the mechanism of Cu clustering and Ni effects on Cu clusters, a sub-nano scale structural and elemental analysis of Cu-bearing steels was carried out through an aberration corrected scanning transmission electron microscope. Based on systematic observation condition adjustment by changing the electron scattered angle, we adopted an inner scattered semi angle of between 50 and 70 mrad for the scanning transmission electron microscope energy dispersive X-ray spectroscopy analysis. Under this condition, Cu precipitates such as 9R are clearly recognized through atomic scale scanning transmission electron microscope annular dark field images. Cu clusters, before transforming to 9R, are detected on the dislocation and have a periodical strain field. Ni enrichment is also observed in the vicinity of Cu clusters. Considering these enrichment phenomena of Cu and Ni, it is found that Cu diffuses rapidly through dislocation, while at the same time, Ni enrichment occurs by ejection from Cu clusters and forms a shell structure.     

Detection of ultra-soft X-rays with a variable geometry proportional counter fitted to a transmission electron microscope (TEM)

The ability of an end-window variable geometry flow proportional counter to detect the ultrasoft BeK and SiL X-ray lines induced by the electron beam of a transmission electron microscope (TEM) has been demonstrated. This counter has been used in the current work in the energy dispersive mode, and has been equipped with a Formvar window about 400 nm thick, aluminized on both sides with a layer of 65 nm total thickness. X-ray peaks generated by specimens of other light elements such as boron, carbon, oxygen, fluorine and aluminium, and detected with this technique, are also reported. In the case of the BK line, the counting rate obtained with this detector has been evaluated and compared with that of a crystal spectrometer equipped with a conventional side-window flow proportional counter. Finally, a linear relationship between X-ray energy and detected pulse height was found for the lines examined, i.e. from the SiL up to the SiK X-rays.     

Spatially resolved cathodoluminescence of luminescent materials using an EDX detector

Panchromatic cathodoluminescence (CL) maps were collected in a scanning electron microscope equipped with an EDX (energy dispersive x-ray analysis) detector. These CL maps can readily be correlated with elemental maps obtained by EDX. Although EDX detectors are designed to be insensitive to light and therefore not optimized for high sensitivity CL measurements, high-resolution images can be obtained from luminescent materials without the need for additional hard- or software. The method was tested on highly luminescent BaAl₂S₄ : Eu²⁺ thin films that have a potential use in flat panel displays. The spectral response and linearity of the overall system was determined by means of monochromatic light sources, illuminating the sample through an optical fibre. We studied the response of the EDX detector to the intensity of the incoming light as well as the influence of the detector settings. The observations were explained by numerical simulations.     

Quantitative analysis of electrolytes in frozen dried sections

During recent years our group has employed the technique of electron microprobe analysis to determine the electrolyte concentrations in various epithelial tissues. The specimen preparation is characterized by shock-freezing of small tissue pieces in liquid propane/isopentane mixtures at 77 K, cryosectioning of 1 μm thick serial sections at 170 K and subsequent freeze-drying at 190 K and 10^?4 Pa. The analysis of the frozen dried cryosections is performed in a scanning electron microscope which is equipped with an energy dispersive X-ray detector. The measuring conditions selected are 17–20 kV acceleration voltage and 0·1–0·5 nA probe current. For quantification, the cellular X-ray spectra are compared with those of an internal albumin standard layer. The evaluation of the characteristic X-ray intensities is performed using a computer program. Some critical points of this technique will be discussed.     

Segmentation of elemental EDS maps by means of multiple clustering combined with phase identification

An imaging concept is proposed for the phase identification and segmentation of elemental map images from energy dispersive spectroscopy. The procedure starts with presegmentation using common clustering algorithms, continues with automated identification of the chemical compositions, followed by their screening by professional expertise. The ultimate phases are finally clustered by applying a minimum Euclidean distance classifier. The potential, performance and limitations of the approach are presented on energy dispersive spectroscopy maps acquired by a scanning electron microscope and conducted on samples produced from cement clinker, natural rock and hydrated cement mortar. Nevertheless, the technique is suitable for arbitrary types of materials and general devices for energy dispersive spectroscopy acquisition. It is an approach for extending common energy dispersive spectroscopy analysis by means of visual examination and ratio plots towards quantitative rating.     

Determination of Cliff-Lorimer k factors by analysis of crystallized microdroplets

The Cliff-Lorimer ratio technique for thin foils was used to determine a set of k factors at 120 kV for calibration of the energy dispersive X-ray analyser on a Philips EM400 analytical electron microscope. The standards used were the crystallized forms of microdroplets of solutions of inorganic salts. These experimental data were compared with other experimental work and found to agree within the experimental error with theoretical k factors.     

硅烷偶联剂修饰纳米ZrO2润滑油添加剂的摩擦学性能研究

以氧氯化锆为原料制备纳米ZrO2并对其结构进行了表征;用硅烷偶联剂对其表面进行表面改性处理,使其具有良好的亲油性;用摩擦磨损试验机测定了所制备的纳米ZrO2作为20#机械油添加剂的摩擦磨损性能。结果表明所制备的ZrO2为粒径为10nm左右的球形颗粒,具有无定形晶体结构;纳米ZrO2作为添加剂可以显著提高20#机械油的抗磨减摩性能,当纳米ZrO2的添加量为0.1%(质量分数)时相应的磨斑直径最小、摩擦因数最低、磨损量最少。     

Characterization of Tribofilms Generated from Serpentine and Commercial Oil Using X-ray Absorption Spectroscopy

The chemical and tribological properties of serpentine particles suspended in lubricating oil were investigated using a pin-on-disk high frequency friction machine at 100 °C. The wear scar width of the upper steel pins was measured by an optical microscope. The tribofilm was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) elemental mapping, and X-ray absorption near-edge structure (XANES) spectroscopy. It was found that the addition of serpentine to commercial engine oil improves its tribological properties. The SEM and EDX elemental mapping shows that a tribofilm formed by the commercial oil with serpentine contains silicon, magnesium, oxygen, phosphorus, sulfur, zinc, calcium, and carbon on the worn surface, which is different from the tribofilm formed by the commercial oil without serpentine. The results of the XANES analysis show that the addition of serpentine to the commercial oil changes the chemical compositions of the tribofilms. This change may account for the better tribological properties of the lubricating oil containing serpentine. The formation mechanism of the tribofilm is discussed.     

Effect of Ag nanoparticles additive on the tribological behavior of multialkylated cyclopentanes (MACs)

Monodisperse Ag nanoparticles with a particle size of about 6–7 nm and low volatile multialkylated cyclopentanes (MACs) lubricant were prepared. The effect of Ag nanoparticles as additive in MACs base oil on the friction and wear behavior of MACs was investigated. The friction and wear test of a steel disc sliding against the same steel counterpart ball was carried out on an Optimal SRV oscillating friction and wear tester. The morphology and elemental distribution of the worn surface of both the steel ball and steel disc and the chemical feature of typical element thereof were examined using a JEM-1200EX scanning electron microscope (SEM) equipped with a Kevex energy dispersive X-ray analyzer attachment (EDS) and X-ray photoelectron spectroscope (XPS), respectively. Friction and wear test indicates that the wear resistance and load-carrying capacity of MACs base oil were markedly raised and its friction coefficient changed little when 2% Ag nanoparticles were added in it. Results of SEM/EDS and XPS show that Ag nanoparticles were deposited on the friction pair surfaces to form low shearing stress metal Ag protective film in rubbing process.     

The quantitative analysis of thin specimens

Results are reported concerning the use of an energy dispersive X-ray detector to carry out the analysis of thin foils in the electron microscope. The combination of a thin specimen and the extreme stability of the energy dispersive X-ray detector enables the experimental determination of a calibration curve of X-ray production—detection efficiency vs characteristic X-ray energy. Quantitative analysis can be carried out using the calibration curve without reference to standards at the time of analysis.     

Determination of UTW kXSi factors for seven elements from oxygen to iron

This study reports k factors for an ultra-thin window (UTW) Si(Li) energy dispersive (ED) X-ray detector which extends the limit for X-ray microanalysis in the analytical electron microscope (AEM) to elements below Na in the periodic table. The oxygen k factors reported for the UTW ED detector suggest that quantitative thin specimen X-ray analysis can be extended to oxygen.     

Application of the dual-beam FIB/SEM to metals research

The dual‐beam microscope is a combination of a focused ion beam with an electron beam. The instrument used in this work is also equipped with an energy‐dispersive X‐ray system for local elemental analysis. This powerful tool gives access to specific features inside a material. Two different applications are presented in this paper: (1) cross‐sections and transmission electron microscope specimens cut in order to investigate the interface between an aluminium substrate and its epoxy coating; and (2) a grain boundary in a Cu₃Au alloy. In both cases, the dual beam succeeded where other methods failed.     

Secondary electron imaging as an aid to STEM microanalysis

Secondary electron (SEM mode) imaging in a scanning transmission electron microscope (STEM) has been utilized as an aid to the STEM microanalysis of second phase particles in an Alloy 800 foil by identifying particles at the foil surface facing the incident beam and energy dispersive X-ray detector. Such particles were optimally situated for microanalysis because possible deleterious effects from beam spreading and matrix absorption were eliminated. This was demonstrated by orienting the sample to analyze the particles on the surface of the foil facing away from the beam and X-ray detector, and subsequently, for comparison, reorienting the sample to reanalyze the particles with the foil surface facing beam and detector. Theoretical calculations of the magnitude of the relative change in particle X-ray signal between the two orientations were in good agreement with the experimental observations. SEM imaging also provided surface reference points for parallax-effect measurements of local foil thickness and particle depth within the foil.     

油润滑条件下有机物修饰纳米铜颗粒改善铁基摩擦副摩擦磨损的研究

在球盘式摩擦磨损试验机上考察了有机物修饰的纳米铜颗粒作为50CC润滑油添加剂的摩擦学性能;采用SEM和EDS分析了磨损表面形貌和表面膜元素组成。探讨了纳米铜颗粒的摩擦学作用机制：结果表明：有机物修饰的纳米铜颗粒作为添加剂能显著改善50CC润滑油的抗磨减摩性能,含0．05％纳米铜油样润滑下的摩擦因数与磨损量同基础油润滑下相比分别降低了27．6％与60％。分析后认为,纳米铜颗粒通过对摩擦表面进行修复及在摩擦表面成膜两种作用有效地改善了摩擦磨损性能。     

Author index

Binder–oxidizer interactions in rocket composite propellants can be improved using adequate bonding agents. In the present work, the effectiveness of different 1,3,5‐trisubstituted isocyanurates was determined by stereo and metallographic microscopy and using the software package Image‐Pro Plus. The chemical analysis of samples was performed by a scanning electron microscope equipped for energy dispersive spectrometry.     

X-ray microanalysis of organic thin sections in TEM using an UTW Si(Li) detector: comparison of quantification methods

We compared Hall's peak to continuum ratio method with a peak ratio method in order to quantify light elements (C, N, and O) in organic specimens as a model for biological thin sections. X-ray spectra were recorded by an energy dispersive X-ray spectrometer equipped with an ultra thin window detector. Spectra were processed by means of a top-hat filter adapted to peak full-width half maximum. The peak intensities were measured by multiple least square fitting to reference spectra. For most elements of biological interest, theoretical and experimental k-factors were determined. Absorption correction was found to be important for quantitation of carbon, nitrogen, and oxygen. Boron was efficiently detected; however, quantitative analysis was not possible. We conclude from our experiments that the peak ratio method is more suitable for quantitation of elemental concentrations in biological thin sections than the peak to continuum method.     

X-ray microanalysis of plants containing the platinum group metals

It has been demonstrated that Water hyacinths, grown hydroponically in a solution containing the platinum group metals, accumulate and concentrate some of these metals in their roots. Root samples were examined in a scanning electron microscope, equipped with an energy dispersive spectrometer (SEM-EDS), and platinum was detected on the surface. Further examination in an electron microprobe analyser (EMPA), using both wavelength dispersive spectrometry (WDS) and EDS, show platinum localized in the epidermal region of the root. Ruthenium was detected in root material taken from plants that had accumulated the complexed metal ion from solution.