Improved X-ray Spectrum Simulation for Electron Microprobe Analysis.

The accurate calculation of characteristic peak intensity is essential for interpreting X-ray spectra in electron microprobe analysis. Conventionally, the measured intensity from a standard of known composition is used as a reference to simplify the calculation. However, if no such standard is available, then all factors influencing X-ray generation and X-ray detection efficiency must be included. If the intensity and energy distribution of the background radiation can also be calculated, the investigator can simulate an entire spectrum from an assumed composition, gaining powerful benefits in setting up an experiment and in confirming the results. The study presented here demonstrates a fast method of spectrum simulation, suitable for energydispersive spectroscopy (EDS), and assesses the accuracy using 309 spectra from samples of known composition. These include K, L, and M lines from elements of atomic number 6–92, excited by beam energies in the range of 5–30 keV. The RMS error between 360 measured and calculated peak intensities was found to be 7.1%. Central to the method is the use of the ratio of peak intensity/total background intensity, which allows spectra to be compared from instruments of differing collection efficiency, thereby easing the collection of data over a wide range of conditions.

ABSTRACTBulk samples of a novel cermet (ceramic/metal composite) hydrogen transport membrane (HTM) were subjected to thermal cycling in the temperature range between 25-850°C to study phase transformations and microstructural changes under thermal shock. Scanning electron microscopy (SEM) and electron probe micro analyzer (EPMA) with energy dispersive spectroscopy (EDS) were used to characterize the microstructural and chemical changes in the membrane upon thermal cycling. SEM & EPMA analyses indicated that the temperature gradient during thermal cycling produced more micro-cracks inside the HTM disc, whereas, the chemical reaction between Pd and oxygen to form PdO disturbed the continuity of the metal palladium (Pd) - Yttria Stabilized Zirconia (YSZ) dual phases interconnection system from surface down. The agglomerates of un-crystallized YSZ grains found to be the inherent in the cracks of the as-received HTM. A combination of trans-granular and inter-granular crack propagation results around the YSZ grains and the new precipitates. Based on the electron fractography analyses by both SEM and EPMA, the micro voids coalescence develops ahead of the crack tips in the cross-section of the HTM after 500 thermal cycles.

THE intensity of the diffuse cosmic background radiation for photon energies of 13.6 to ∼ 150eV cannot be measured directly because of absorption by the neutral component of the interstellar medium. In the range 150–300 eV, there is considerable galactic emission within a few hundred parsecs of the Sun which places severe limitations on attempts to measure the intensity and spectrum of the metagalactic background radiation at these energies. An indirect means of estimating the diffuse metagalactic flux of ionising radiation was proposed by Sunyaev1, who studied the interaction of this radiation with neutral hydrogen at the peripheries of galaxies. More locally, the intensity of this radiation within ∼ 1 kpc of the Sun can be probed by studying the ionisation of heavy elements in the interstellar medium2. Here we re-examine Sunyaev's proposal in the context of more detailed studies of the interaction of metagalactic ionising radiation with galactic gas. We give a firm upper limit on the intensity of metagalactic ionising background radiation to which the neutral interstellar medium is exposed, and discuss some important consequences of this result. Our principal conclusion is that further than ∼ 30 kpc from the centre of the Galaxy, self-shielding by H II3,4 is possible only if the flux of ionising radiation is below a certain critical value5–7.

Context. Future observations of CMB anisotropies will be able to probe high multipole regions of the angular power spectrum, corresponding to a resolution of a few arcminutes. Dust emission from merging haloes is one of the foregrounds that will affect such very small scales. Aims. We estimate the contribution to CMB angular fluctuations fro m objects that are bright in the sub-millimeter band due to intense star formation bursts following merging episodes. Methods. We base our approach on the Lacey-Cole merger model and on the Kennicutt relation which connects the star formation rate in galaxies with their infrared luminosity. We set the free par ameters of the model in order to not exceed the SCUBA source counts, the Madau plot of star formation rate in the universe and COBE/FIRAS data on the intensity of the sub-millimeter cosmic background radiation. Results. We show that the angular power spectrum arising from the distribution of such star-forming haloes will be one of the most significant foregrounds in the high frequency channels of future CMB experiments, such as PLANCK, ACT and SPT. The correlation term, due to the clustering of multiple haloes at redshift z∼ 2− 6, is dominant in the broad range of angular scales 200< l< 3000. Poisson fluctuations due to bright sub-millimeter sources are more important at higher l, but since they are generated from the bright sources, such contribution could be strongly reduced if bright sources are excised from the sky maps. The contribution of the correlation term to the angular power spectrum depends strongly on the redshift evolution of the escape fraction of UV photons and the resulting temperature of the dust. The measurement of this signal will therefore give important information about the sub-millimeter emission and the escape fraction of UV photons from galaxies, in the early stage of their evolution.

Dual codoping for the fabrication of low resistive p-ZnO

We focused on the surface reinforcement of ligth weight casting alloys with Ni3Al intermetallic compounds by in-situ combustion reaction to improve the surface properties of nonferrous casting components. In the present work, by setting the mixture of elemental Ni and Al powders in a casting mold, the powder mixture reacted to form Ni3Al intermetallic compound by SHS reaction ignited by the heat of molten AZ91D Mg alloy and simultaneously bonded with the Mg casting alloy. The AZ91D Mg alloy bonded with the Ni3Al intermetallic compound was sectioned and observed by optical microscopy and scanning electron microscopy(SEM). The chemical composition of intermetallic compounds and diffusion layer formed around bonding interface were identified by energy dispersive spectroscopy(EDS), X-ray diffraction analysis(XRD) and electron probe micro analyzer(EPMA). The main intermetallic compound was Ni3Al phase and a little Ni2Al3 intermetallic compound was formed from the Ni and Al powder mixtures. Residual pores were observed in the synthesized intermetallic compound. The AZ91D Mg alloy and Ni3Al intermetallic compound were bonded very soundly by the interdiffusion of Mg, Ni and Al elements, but some cracks were observed around the bonded interface on the interdiffusion layer. The diffusion length formed between AZ91D Mg alloy and Ni3Al was different depending on the diffusivity of Ni and Al elements into the molten Mg alloy. Ni was more deeply diffused into the Mg alloy than Al. The diffusion layer was about 200m thickness and various phases were formed by the interdiffusion of Mg, Ni and Al. From this challenge we have successfully produced a coating layer based on nickel aluminide on ligth weight Mg alloy using molten metal heat without any additional process. On the basis of the results obtained, it is concluded that near-net shaped nickel aluminide coating layer can be formed using this unique process.

Wide-range continuous spatial variation of the film composition in lateral compositionally graded epitaxial films requires the development of high throughput measurement techniques for their local and non-destructive characterization with the highest possible spatial resolution. Here we report on the first application of the picosecond laser ultrasonics (PLU) technique for the evaluation of acoustical and optical parameters of lateral compositionally graded film, the Ba1−xSrxTiO3 (0 ≤ x ≤ 1) material library. The film was not dedicatedly prepared for its opto-acousto-optic evaluation by PLU, exhibiting significant lateral variations in thickness and surface roughness. Therefore, the achieved measurements of the sound velocity and of the optical refractive index, and characterization of the surface roughness confirm the robustness of the PLU technique for thin film evaluation. We hope that the first measurements of the acoustical and optical properties of epitaxial grown Ba1−xSrxTiO3 (0 ≤ x ≤ 1) by PLU technique accomplished here provide the parameters required for more extended predictive design of the phononic, photonic and phoxonic mirrors and cavities with superior properties/functionalities for novel multifunctional nanodevices.

Luminous Glass: A Study on the Optics Governing Luminescent Solar Concentrators and Optimization of Luminescent Materials through Combinatorial Gradient Sputter Deposition

Dolomite [CaMg(CO3)2] is an important carbonate mineral mainly composed of calcium magnesium carbonate. The correct determination of magnesium content in carbonate rocks is important for accessing its suitability for different applications; however, presence of different phases with varying magnesium contents makes their analysis difficult. In the present work, a natural carbonate mineral dolomite is analyzed qualitatively and quantitatively using laser-induced breakdown spectroscopy along with X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and electron-probe microanalysis. The optical emission spectra recorded in 200–720 nm wavelength region revealed presence of emission lines for Ca, Mg, Al, Sr, and Na with varying intensities. We used two different techniques, that is, Boltzmann plot and Saha–Boltzmann plot methods to calculate the plasma temperature, and an average value of 4500 ± 450 K was deduced.The Stark broadening line profile method was exploited to calculate the electron number density using calcium and magnesium lines which resulted in 2.39 × 1017 cm–3. The quantitative compositional analysis was carried out using calibration-free laser-induced breakdown spectroscopy method for which the local thermodynamic equilibrium and optically thin plasma conditions were satisfied.The composition for dolomite major constituents calcium and magnesium were estimated as 68.58 and 31.41%, respectively.The results demonstrated the LIBS, EDS, and EPMA ability as an effective, powerful and complementary analytical techniques for the elemental composition analysis of carbonate minerals.

We consider the non-resonant mixing between photons and scalar ALPs with masses much less than the plasma frequency along the path, with specific reference to the chameleon scalar field model. The mixing would alter the intensity and polarization state of the cosmic microwave background (CMB) radiation. We find that the average modification to the CMB polarization modes is negligible. However the average modification to the CMB intensity spectrum is more significant and we compare this to high precision measurements of the CMB monopole made by the far infrared absolute spectrophotometer (FIRAS) on board the COBE satellite. The resulting 95\% confidence limit on the scalar-photon conversion probability in the primordial field (at 100 GHz) is P < 2.6x10^{-2}. This corresponds to a degenerate constraint on the photon-scalar coupling strength, g, and the magnitude of the primordial magnetic field. Taking the upper bound on the strength of the primordial magnetic field derived from the CMB power spectra, B < 5.0x10^{-9}G, this would imply an upper bound on the photon-scalar coupling strength in the range g < 7.14x10^{-13}GeV^{-1} to g < 9.20x10^{-14}GeV^{-1}, depending on the power spectrum of the primordial magnetic field.

ناحیه مطالعاتی در شمال استان خراسان رضوی و 45 کیلومتری جنوب نیشابور قرار دارد. رگه های طلادار درون سنگهای گرانیت، گرانودیوریت، گرانودیوریت پورفیری، آندزیت، برش و توف نفوذ کرده اند. رگه ها از جنس کوارتز و کلسیت هستند. مناطق اصلی دگرسانی شامل منطقه سرسیتیک، سیلیسی، پروپلیتیک و منطقه کربنات است. کانی زایی به‌طور نزدیکی با دگرسانیهای سیلیسی و سرسیتیک به شکل رگه‌چه و با منطقه پروپلیتیک به شکل افشان همراه است. کانی شناسی کانیهای باطله کوارتز، کلسدونی، سرسیت، آدولاریا، کلسیت، دولومیت، ایلیت، دیکیت، آلبیت، کائولینیت و کلریت است. کانی زایی رگه ای عمدتا با رگه‌چه ها، برش، افشان و استوک ورک همراه هستند. رگه‌چه ها از پیریت، مارکازیت، آرسنوپیریت و کمتر کالکوپیریت، اسفالریت، گالن، مگنتیت و هماتیت تشکیل شده اند. بیشترین عیار طلا در رگه های سیلیسی دیده می شود. پیریت کانی سولفیدی اصلی در کانی سازی اولیه است. سه نوع پیریت بر اساس ترکیب شیمیایی شناسایی شده است: پیریت خالص، پیریت غنی از آرسنیک و پیریت تیتانیوم- وانادیوم دار. تجزیه های ریزکاوشگر الکترونی بیشترین غلظت آرسنیک، تیتانیوم و وانادیوم را به ترتیب 62/3، 91/3 و 53/0 درصد وزنی در پیریتهای رگه های طلادار نشان می دهند. طلا معمولا همراه با پیریت آرسنیک دار و پیریت تیتانیوم- وانادیوم دار است. براساس مطالعه بافت و ترکیب پیریتها، رگه‌چه‌های پیریت آرسنیک دار همراه با کانیهای سولفیدی آرسنوپیریت، کالکوپیریت، گالن، اسفالریت در دمای بالا و با کاهش دما و فشار، پیریتهای فرامبوئیدال با حاشیه حاوی آرسنیک و طلا شکل گرفته اند و در ادامه پیریتهای درشت تیتان دار به‌وجود آمده اند. پیریتهای خالص و تأخیری درشت بلور آخرین فاز کانی ساز در منطقه هستند.

Castaing’s first electron probe microanalyzer(l) was a modified electrostatic transmission electron microscope equipped with a curved-crystal x-ray spectrometer. This combination was perfected in later years by the introduction of Langmuir-Blodgett devices(2) and of diffractors consisting of evaporated metal layers, (3) so that the elements of atomic number above 3 could also be observed and analyzed.

The accuracy of quantitative analysis was evaluated extensively for a commercial SEM with energy dispersive X-ray spectrometer.For acquiring reliable X-ray spectra for quantitative analysis, several improvements of electron and X-ray collimation systems were required to eliminate extraneous X-rays excited due to scattered electrons and fluorescing X-rays. In the spectrum processing procedure, theoretical model for prediction of the background distribution was modified to fit the observed spectrum even at low energy regions and the deconvolution routine for the overlapping X-ray peaks and the low energy tailing were also improved.After these improvements, the absolute accuracy of analyses of 21 standard reference silicates (supplied from Smithsonian Museum) is found to be within ± 0.3%, which is comparable to the best measurements with conventional wavelength dispersive EPMA.Applications of this energy dispersive EPMA to some mineralogical problems in the iron and steelmaking process are reported.

Electrochemical chloride extraction (ECE) from laboratory prepared mortar samples has been applied considering two experimental configurations; using different external anodes and studying the influence of aggregate size.ECE experimental conditions together with analytical procedures were carefully addressed. Combination of two analytical methods has been employed to monitor the efficiency of chloride extraction process; chloride ion selective electrode (ISE) to obtain free chloride cumulative amount in the external anolyte solution upon applying ECE, and electron probe micro analysis (EPMA)to gain depth profile information of chloride in the mortar samples before and after ECE process. A comparison between three X-ray detection based analytical techniques has been briefly reviewed. ECE performance was discussed and recommendations were introduced.

• Metal concentrations within reproductive tissues of metallophytes are rarely reported. Here, the spatial distribution of nickel (Ni) within the fruits (seeds) of the Ni hyperaccumulator Stackhousia tryonii was investigated. • Two microanalytical techniques, energy dispersive x-ray spectrometry (EDXS) and nuclear microprobe (micro-proton-induced x-ray emission spectrometry; micro-PIXE) were employed for qualitative and quantitative assessment, respectively, of localized Ni, within the fruits of S. tryonii. The results were compared with quantitative analysis made using inductively coupled plasma-optical emission spectrometry (ICP-OES). • Nickel analysis made using micro-PIXE was consistent with bulk (ICP-OES) analysis (at 1800µgg-1 d. wt), however, a beam resolution of approx. 2×2µm2 allowed tissue localization. Nickel was partitioned to the fruit wall (pericarp) (4433µgg-1 ), while endospermic and cotyledonary tissues possessed little Ni (309 and 182µgg-1 d. wt, respectively). • This distribution is consistent with the interpretation that principal pathway of Ni movement within the fruit is symplastic rather than apoplastic (as the filial generation lacks symplastic connection with the parent).