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At least 559 records · Page 31

Morphology and conductivity study of solid electrolyte Li{sub 3}PO{sub 4}

The comparison between two different methods of synthesize of solid electrolyte Li{sub 3}PO{sub 4} as precursor material for developing lithium ion battery, has been performed. The first method is to synthesize Li{sub 3}PO{sub 4} prepared by wet chemical reaction from LiOH and H{sub 3}PO{sub 4} which provide facile, abundant available resource, low cost, and low toxicity. The second method is solid state reaction prepared by Li{sub 2}CO{sub 3} and NH{sub 4}H{sub 2}PO{sub 4.} In addition, the possible morphology identification of comparison between two different methods will also be discussed. The composition, morphology, and additional identification phase and another compound of Li{sub 3}PO{sub 4} powder products from two different reaction are characterized by SEM, EDS, and EIS. The Li{sub 3}PO{sub 4} powder produced from wet reaction and solid state reaction have an average diameter of 0.834 – 7.81 µm and 2.15 – 17.3 µm, respectively. The density of Li{sub 3}PO{sub 4} prepared by wet chemical reaction is 2.238 gr/cm{sup 3}, little bit lower than the sample prepared by solid state reaction which density is 2.3560 gr/cm{sup 3}. The EIS measurement result shows that the conductivity of Li{sub 3}PO{sub 4} is 1.7 x 10{sup −9} S.cm{sup −1} for wet chemical reaction and 1.8 x 10{sup −10} S.cm{sup −1} for solid state reaction. The conductivity of Li{sub 3}PO{sub 4} is not quite different between those two samples even though they were prepared by different method of synthesize.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

OPC Paste Samples Exposed To Aggressive Solutions. Cementitious Barriers Partnership

The study presented in this report focused on a low-activity wasteform containing a high-pH pore solution with a significant level of sulfate. The purpose of the study was to improve understanding of the complex concrete/wasteform reactive transport problem, in particular, the role of pH in sulfate attack. Paste samples prepared at three different water-to-cement ratios were tested. The mixtures were prepared with ASTM Type I cement, without additional admixtures. The samples were exposed to two different sodium sulfate contact solutions. The first solution was prepared at 0.15M Na 2 SO 4 . The second solution also incorporated 0.5M NaOH, to mimic the high pH conditions found in Saltstone. The data collected indicated that, in Na 2 SO 4 solution, damage occurs to the pastes. In the case of the high-pH sulfate solution (Na 2 SO 4 + NaOH), no signs of damage were observed on any of the paste mixtures. These results indicate that the high sulfate content found in the wasteform pore solution will not necessarily lead to severe damage to concrete. Good-quality mixtures could thus prove durable over the long term, and act as an effective barrier to prevent radionuclides from reaching the environment.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

EBSD characterization of metallic nuclear fuel

Grain structure and texture are important in all materials as they influence most mechanical properties. In particular for nuclear materials texture can influence material properties important for reactor performance, such as swelling, yield stress, fracture toughness etc. Moreover such data are of primary importance to develop and validate physics-based models for nuclear fuels based on microstructure evolution during irradiation (e.g. MARMOT). Scanning Electron Microscopy (SEM) coupled with Electron Back Scatter Diffraction (EBSD) has been proven as an effective technique for evaluating grain size, shape, and orientation. However it has been seldom used for nuclear fuels. This has been mostly related to difficulties in handling and preparing such materials for EBSD analyses. Particularly challenging remains sample preparation for metallic irradiated fuels, as they are prone to rapid oxidation. Indeed EBSD analyses require the elimination of any surface defect or oxide layer as the signal arise from 50-100 nm depth in the material. At Idaho National Laboratory (INL) great effort has focused in developing techniques to obtain suitable surfaces for EBSD analyses. In this paper the first results from EBSD analyses obtained from a wide range of nuclear materials will be presented. Sample analyzed included fresh U, U-Zr, Pu-Zr , and U-Mo, including some irradiated fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Advanced Curation Activities at NASA: Preparation for Upcoming Missions

The responsibility for curating NASA's astromaterials collections falls to the NASA Curation Office at Johnson Space Center. Under the governing document, NASA Policy Directive (NPD) 7100.10F and derivative requirements documents, JSC is charged with curation of all extraterrestrial material under NASA control, including future NASA missions to include material returned in Mars Sample Return (MSR) efforts, OSIRIS-REx, NASA's subset of Hayabusa-2 samples, and any other sample return missions. The Directive defines Curation as activities including documentation, preservation, sample preparation, distribution, and tracking of samples for research, education, and public outreach. In this abstract we will describe Curation's research and development efforts to improve the care of existing collections and prepare for future NASA sample return missions. These efforts are collectively referred to as Advanced Curation, a term first coined in 2002.

Fries, M. D.↗

Simultaneous Isotopic Analysis of U, Pu, and Am in Spent Nuclear Fuel by Resonance Ionization Mass Spectrometry

Solid samples of spent nuclear fuel were analyzed for actinide isotopic composition by resonance ionization mass spectrometry. Isotopes of U, Pu, and Am were simultaneously quantified using a new method that removes and/or resolves the isobaric interferences at 238 U/ 238 Pu and 241 Pu/ 241 Am without sample preparation other than cutting and mounting small (~10 μm) samples. Trends in burnup and neutron capture product distributions were correlated with the sampling positions inside the reactor. Overall, the results show the skin effect, in which the core and near-edge regions of a fuel pellet exhibit strong differences in actinide concentrations and isotope distributions due to differences in the neutron energy spectra between the pellet rim and the core. While no elemental concentration measurements were made, the ability to measure the 238 Pu/ 239 Pu ratio in the presence of a 7400× excess of 238 U enabled an estimate of the enhancement in Pu concentration due to the skin effect at the rim of the pellet.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB{sub 2} bulk samples

Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB{sub 2}) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ∼ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB{sub 2} phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (J{sub c}) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

36 MATERIALS SCIENCE↗

Analysis of the Tank 6F Final Characterization Samples-2012 (U)

The Savannah River National Laboratory (SRNL) was requested by Savannah River Remediation (SRR) to provide sample preparation and analysis of the Tank 6F final characterization samples to determine the residual tank inventory prior to grouting. Fourteen residual Tank 6F solid samples from three areas on the floor of the tank were collected and delivered to SRNL between May and August 2011. These Tank 6F samples were homogenized and combined into three composite samples based on a proportion compositing scheme and the resulting composite samples were analyzed for radiological, chemical and elemental components. Additional measurements performed on the Tank 6F composite samples include bulk density and water leaching of the solids to account for water soluble components. The composite Tank 6F samples were analyzed and the data reported in triplicate. Sufficient quality assurance standards and blanks were utilized to demonstrate adequate characterization of the Tank 6F samples. The main evaluation criteria were target detection limits specified in the technical task request document. While many of the target detection limits were met for the species characterized for Tank 6F some were not met. In a few cases, the relatively high levels of radioactive species of the same element or a chemically similar element precluded the ability to measure some isotopes to low levels. The isotopes whose detection limits were not met in all cases included Sn-126, Sb-126, Sb-126m, Eu-152, Cm-243 and Cf-249. SRNL, in conjunction with the customer, reviewed all of these cases and determined that the impacts of not meeting the target detection limits were acceptable. Based on the analyses of variance (ANOVA) for the inorganic constituents of Tank 6F, all the inorganic constituents displayed heterogeneity. The inorganic results demonstrated consistent differences across the composite samples: lowest concentrations for Composite Sample 1, intermediate-valued concentrations for Composite Sample 2, and highest concentrations for Composite Sample 3. The Hg and Mo results suggest possible measurement outliers. However, the magnitudes of the differences between the Hg 95% upper confidence limit (UCL95) results with and without the outlier and the magnitudes of the differences between the Mo UCL95 results with and without the outlier do not appear to have practical significance. It is recommended to remove the potential measurement outliers. Doing so is conservative in the sense of producing a higher UCL95 for Hg and Mo than if the potential outliers were included in the calculations. In contrast to the inorganic results, most of the radionuclides did not demonstrate heterogeneity among the three Tank 6F composite sample characterization results.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Analysis of the Tank 5F Final Characterization Samples-2011 (U)

The Savannah River National Laboratory (SRNL) was requested by SRR to provide sample preparation and analysis of the Tank 5F final characterization samples to determine the residual tank inventory prior to grouting. Two types of samples were collected and delivered to SRNL: floor samples across the tank and subsurface samples from mounds near risers 1 and 5 of Tank 5F. These samples were taken from Tank 5F between January and March 2011. These samples from individual locations in the tank (nine floor samples and six mound Tank 5F samples) were each homogenized and combined in a given proportion into 3 distinct composite samples to mimic the average composition in the entire tank. These Tank 5F composite samples were analyzed for radiological, chemical and elemental components. Additional measurements performed on the Tank 5F composite samples include bulk density and water leaching of the solids to account for water soluble species. With analyses for certain challenging radionuclides as the exception, all composite Tank 5F samples were analyzed and reported in triplicate. The target detection limits for isotopes analyzed were based on customer desired detection limits as specified in the technical task request documents. SRNL developed new methodologies to meet these target detection limits and provide data for the extensive suite of components. While many of the target detection limits were met for the species characterized for Tank 5F, as specified in the technical task request, some were not met. In a few cases, the relatively high levels of radioactive species of the same element or a chemically similar element precluded the ability to measure some isotopes to low levels. The Technical Task Request allows that while the analyses of these isotopes is needed, meeting the detection limits for these isotopes is a lower priority than meeting detection limits for the other specified isotopes. The isotopes whose detection limits were not met in all cases included the following: Al-26, Sn-126, Sb-126, Sb-126m, Eu-152 and Cf-249. SRNL, in conjunction with the plant customer, reviewed all these cases and determined that the impacts were negligible.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Analysis of the Tank 6F Final Characterization Samples-2012

The Savannah River National Laboratory (SRNL) was requested by Savannah River Remediation (SRR) to provide sample preparation and analysis of the Tank 6F final characterization samples to determine the residual tank inventory prior to grouting. Fourteen residual Tank 6F solid samples from three areas on the floor of the tank were collected and delivered to SRNL between May and August 2011. These Tank 6F samples were homogenized and combined into three composite samples based on a proportion compositing scheme and the resulting composite samples were analyzed for radiological, chemical and elemental components. Additional measurements performed on the Tank 6F composite samples include bulk density and water leaching of the solids to account for water soluble components. The composite Tank 6F samples were analyzed and the data reported in triplicate. Sufficient quality assurance standards and blanks were utilized to demonstrate adequate characterization of the Tank 6F samples. The main evaluation criteria were target detection limits specified in the technical task request document. While many of the target detection limits were met for the species characterized for Tank 6F some were not met. In a few cases, the relatively high levels of radioactive species of the same element or a chemically similar element precluded the ability to measure some isotopes to low levels. The isotopes whose detection limits were not met in all cases included Sn-126, Sb-126, Sb-126m, Eu-152, Cm- 243 and Cf-249. SRNL, in conjunction with the customer, reviewed all of these cases and determined that the impacts of not meeting the target detection limits were acceptable. Based on the analyses of variance (ANOVA) for the inorganic constituents of Tank 6F, all the inorganic constituents displayed heterogeneity. The inorganic results demonstrated consistent differences across the composite samples: lowest concentrations for Composite Sample 1, intermediate-valued concentrations for Composite Sample 2, and highest concentrations for Composite Sample 3. The Hg and Mo results suggest possible measurement outliers. However, the magnitudes of the differences between the Hg 95% upper confidence limit (UCL95) results with and without the outlier and the magnitudes of the differences between the Mo UCL95 results with and without the outlier do not appear to have practical significance. It is recommended to remove the potential measurement outliers. Doing so is conservative in the sense of producing a higher UCL95 for Hg and Mo than if the potential outliers were included in the calculations. In contrast to the inorganic results, most of the radionuclides did not demonstrate heterogeneity among the three Tank 6F composite sample characterization results.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Experimental Findings on Minor Actinide and Lanthanide Separations using Ion Exchange

During FY14, experimental work focused in the following areas: (1) synthesis, characterization and testing of ion-exchange materials and (2) investigating methods to oxidize americium(III) in dilute nitric acid using peroxydisulfate. Ion-exchange materials tested at SRNL included antimony silicates. Inorganic and hybrid ion-exchange materials tested previously in this project are limited to a pH of about 2. In more concentrated acid solutions, the ion-exchange material is chemically unstable or exhibits poor ion-exchange performance for metal ions. FY14 research focused on testing antimony silicates, which had been reported to exhibit good ion-exchange in 0.2 – 1.0 M nitric acid and some ion-exchange capacity in as high as 3 M nitric acid. Performance testing of archived antimony silicate samples from Prof. R. Harjula (U. Helsinki) and freshly prepared samples showed very low affinity for lanthanide ions in 0.1, 1.0 and 3.0 M nitric acid. Tests carried out in FY14 continued work initiated the previous year to understand the effects that Pu(IV) and nitrite have on the oxidation of Am(III) by peroxydisulfate. Findings indicate that both Pu(IV) and nitrite are oxidized by peroxydisulfate. Consequently, an excess of peroxydisulfate is needed to maximize the conversion of Am(III) to Am(V).

Hobbs, D. T.↗

Mercury Phase II Study - Mercury Behavior in Salt Processing Flowsheet

Mercury (Hg) in the Savannah River Site Liquid Waste System (LWS) originated from decades of canyon processing where it was used as a catalyst for dissolving the aluminum cladding of reactor fuel. Approximately 60 metric tons of mercury is currently present throughout the LWS. Mercury has long been a consideration in the LWS, from both hazard and processing perspectives. In February 2015, a Mercury Program Team was established at the request of the Department of Energy to develop a comprehensive action plan for long-term management and removal of mercury. Evaluation was focused in two Phases. Phase I activities assessed the Liquid Waste inventory and chemical processing behavior using a system-by-system review methodology, and determined the speciation of the different mercury forms (Hg+, Hg++, elemental Hg, organomercury, and soluble versus insoluble mercury) within the LWS. Phase II activities are building on the Phase I activities, and results of the LWS flowsheet evaluations will be summarized in three reports: Mercury Behavior in the Salt Processing Flowsheet (i.e. this report); Mercury Behavior in the Defense Waste Processing Facility (DWPF) Flowsheet; and Mercury behavior in the Tank Farm Flowsheet (Evaporator Operations). The evaluation of the mercury behavior in the salt processing flowsheet indicates, inter alia, the following: (1) In the assembled Salt Batches 7, 8 and 9 in Tank 21, the total mercury is mostly soluble with methylmercury (MHg) contributing over 50% of the total mercury. Based on the analyses of samples from 2H Evaporator feed and drop tanks (Tanks 38/43), the source of MHg in Salt Batches 7, 8 and 9 can be attributed to the 2H evaporator concentrate used in assembling the salt batches. The 2H Evaporator is used to evaporate DWPF recycle water. (2) Comparison of data between Tank 21/49, Salt Solution Feed Tank (SSFT), Decontaminated Salt Solution Hold Tank (DSSHT), and Tank 50 samples suggests that the total mercury as well as speciated forms in the assembled salt batches in Tanks 21/49 pass through the Actinide Removal Process (ARP) / Modular Caustic Side Solvent Extraction Unit (MCU) process to Tank 50 with no significant change in the mercury chemistry. (3) In Tank 50, Decontaminated Salt Solution (DSS) from ARP/MCU is the major contributor to the total mercury including MHg. (4) Speciation analyses of TCLP leached solutions of the grout samples prepared from Tank 21, as well as Tank 50 samples, show the majority of the mercury released in the solution is MHg.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

High-Resolution Frequency-Domain Spectroscopic and Modeling Studies of Photosystem I (PSI), PSI Mutants and PSI Supercomplexes

Photosystem I (PSI) is one of the two main pigment–protein complexes where the primary steps of oxygenic photosynthesis take place. This review describes low-temperature frequency-domain experiments (absorption, emission, circular dichroism, resonant and non-resonant hole-burned spectra) and modeling efforts reported for PSI in recent years. In particular, we focus on the spectral hole-burning studies, which are not as common in photosynthesis research as the time-domain spectroscopies. Experimental and modeling data obtained for trimeric cyanobacterial Photosystem I (PSI 3 ), PSI 3 mutants, and PSI 3 –IsiA 18 supercomplexes are analyzed to provide a more comprehensive understanding of their excitonic structure and excitation energy transfer (EET) processes. Detailed information on the excitonic structure of photosynthetic complexes is essential to determine the structure–function relationship. We will focus on the so-called “red antenna states” of cyanobacterial PSI, as these states play an important role in photochemical processes and EET pathways. The high-resolution data and modeling studies presented here provide additional information on the energetics of the lowest energy states and their chlorophyll (Chl) compositions, as well as the EET pathways and how they are altered by mutations. We present evidence that the low-energy traps observed in PSI are excitonically coupled states with significant charge-transfer (CT) character. The analysis presented for various optical spectra of PSI 3 and PSI 3 -IsiA 18 supercomplexes allowed us to make inferences about EET from the IsiA 18 ring to the PSI 3 core and demonstrate that the number of entry points varies between sample preparations studied by different groups. In our most recent samples, there most likely are three entry points for EET from the IsiA 18 ring per the PSI core monomer, with two of these entry points likely being located next to each other. Therefore, there are nine entry points from the IsiA 18 ring to the PSI 3 trimer. We anticipate that the data discussed below will stimulate further research in this area, providing even more insight into the structure-based models of these important cyanobacterial photosystems.

59 BASIC BIOLOGICAL SCIENCES↗

Effects of multifunctional crosslinking agents on the thermomechanical properties of polyimide films

The potential of high temperature resistant polymers such as polyimides (PI) and polyphenylquinoxalines (PPQ) as matrix resins in fiber-reinforced composites has not been fully realized to date. One of the problems associated with these resins is that they exhibit creep, or thermoplastic yielding under load at temperatures approaching 316 C (600 F). The purpose of this investigation was to further reduce thermoplastic behavior of polyimide resins by substituting a controlled amount of the diamine monomer with crosslinking agents having a higher amine functionality. The knowledge gained from a study of the thermomechanical properties of the crosslinked resins would then be used in the fabrication of fiber-reinforced polyimide composites. This report describes the synthesis and characterization of three new polyfunctional amines. Polyimide films containing varying amounts of the cross-linking agents were prepared, and their properties compared with those of control samples prepared with difunctional amines. The effect of crosslink density on isothermal weight loss, polymer softening, and glass transition temperatures is discussed.

Delvigs, P.↗

Determination of oxygen in silicon and carbide by activation with 27.2 meV alpha particles

The Si sample was polished on one side, and on the other side Ni was applied chemically and soldered with Pb to a water cooled Cu substrate. Optical quartz standard was fixed from the other side. Si carbide samples were soldered to a substrated with In. The prepared samples were irradiated in a cyclotron with a 27.2 MeV alpha particle beam. The layers were removed from the Si and Si carbide samples by grinding and the positron activity of F-18(t sub 1/2 110 min) was measured by using a gamma, gamma coincidence spectrometer with two NaI(TI) crystals. For analysis of Si carbide, the activity decay curve of the samples was recorded to find the contribution of the positron activity of Cu-65(t sub 1/2 12.9 hr) which formed from Ni impurity on irradiation.

Dolgolenko, A. P.↗

Luminescence properties in relation to controllable morphologies of the InBO{sub 3}:Eu{sup 3+} phosphor

Graphical abstract: Four kinds of morphologies of Eu{sup 3+} doped indium borate of InBO{sub 3} phosphors have been prepared via a facile flux method only by adjusting the kinds of reaction boron source materials[(a)B{sub 2}O{sub 3}, (b)NH{sub 4}B{sub 5}O{sub 8}·4H{sub 2}O, (c)Li{sub 2}B{sub 4}O{sub 7}, (d)K{sub 2}B{sub 4}O{sub 7}·4H{sub 2}O], in which the monodisperse octahedral sample prepared with K{sub 2}B{sub 4}O{sub 7}·4H{sub 2}O as the boron source and Eu{sup 3+} doping concentration being 5% possesses the higher PL intensity and color purity, which can be used as a potential orange luminescent material. - Highlights: • InBO{sub 3}:Eu{sup 3+} phosphor with four morphologies were prepared by adjusting the boron source. • The doping concentration also has a great influence on the morphology. • The fluorescence performance is strongly correlated with morphology. • The smooth octahedral sample possesses the higher PL intensity and color purity. • InBO{sub 3}:Eu{sup 3+} smooth octahedra can be used as a potential orange luminescent material. - Abstract: Four kinds of morphologies of Eu{sup 3+} doped indium borate of the InBO{sub 3} phosphors have been prepared via a facile flux method only by adjusting the kinds of reaction boron source materials, which have been characterized by XRD, EDS and SEM. In addition, the doping concentration also has a great influence on the morphology of samples. Furthermore, the luminescence properties of the prepared InBO{sub 3}:Eu{sup 3+} samples have been investigated by photoluminescence (PL) spectra. The results show that the fluorescence performance is strongly correlated with morphologies. The prepared InBO{sub 3}:Eu{sup 3+} phosphors show strong orange emissions under ultraviolet excitation at 237 nm, in which the monodisperse octahedra sample prepared with K{sub 2}B{sub 4}O{sub 7}·4H{sub 2}O as the boron source and Eu{sup 3+} doping concentration being 5% possesses the higher PL intensity and color purity, which can be used as a potential orange luminescent material.

36 MATERIALS SCIENCE↗

Optical and Chemical Characterization of Uranium Dioxide (UO 2 ) and Uraninite Mineral: Calculation of the Fundamental Optical Constants

Quantitative infrared single-angle reflectance spectroscopic measurements using a calibrated Fourier transform infrared spectrometer were performed on synthetic uranium dioxide (UO2), high-purity crystalline uraninite, and massive uraninite mineral. The massive uraninite mineral was found to contain not only UO2 but also large amounts of calcite and silicates. From the experimentally measured reflectance spectra across two spectral domains (the far- and mid-infrared) the fundamental optical constants n and k were calculated using the Kramers-Kronig transformation for each species. We discuss both the derived n and k results for these species as well as the careful sample preparation needed in order to mount, polish, and measure such samples through a wide spectral range using modern instrumentation and data processing techniques. Our results for the optical constants n and k of synthetic UO2 differ significantly from previously published literature values. This is attributed to both improved spectroscopic resolution but also to a better understanding of potential surface oxidation effects on the measured reflectance values, and hence the calculated optical constants.

DeVetter, Brent M.↗

A versatile elevated-pressure reactor combined with an ultrahigh vacuum surface setup for efficient testing of model and powder catalysts under clean gas-phase conditions

A small-volume reaction cell for catalytic or photocatalytic testing of solid materials at pressures up to 1000 Torr has been coupled to a surface-science setup used for standard sample preparation and characterization under ultrahigh vacuum (UHV). The reactor and sample holder designs allow easy sample transfer from/to the UHV chamber, and investigation of both planar and small amounts of powder catalysts under the same conditions. The sample is heated with an infrared laser beam and its temperature is measured with a compact pyrometer. Combined in a regulation loop, this system ensures fast and accurate temperature control as well as clean heating. The reaction products are automatically sampled and analyzed by mass spectrometry and/or gas chromatography (GC). Unlike previous systems, our GC apparatus does not use a recirculation loop and allows working in clean conditions at pressures as low as 1 Torr while detecting partial pressures smaller than 10{sup −4} Torr. The efficiency and versatility of the reactor are demonstrated in the study of two catalytic systems: butadiene hydrogenation on Pd(100) and CO oxidation over an AuRh/TiO{sub 2} powder catalyst.

36 MATERIALS SCIENCE↗

XRD analysis of undoped and Fe doped TiO{sub 2} nanoparticles by Williamson Hall method

Undoped and Fe doped titanium dioxide (TiO{sub 2}) nanoparticles were synthesized by sol-gel method at room temperature. The synthesized samples were annealed at 500°C. For structural analysis, the prepared samples were characterized by X-ray diffraction (XRD). The crystallite size of TiO{sub 2} and Fe doped TiO{sub 2} nanoparticles were calculated by Scherer’s formula, and was found to be 15 nm and 11 nm, respectively. Reduction in crystallite size of TiO{sub 2} with Fe doping was observed. The anatase phase of Fe-doped TiO{sub 2} nanoparticles was also confirmed by X-ray diffraction. By using Williamson-Hall method, lattice strain and crystallite size were also calculated. Williamson–Hall plot indicates the presence of compressive strain for TiO{sub 2} and tensile strain for Fe-TiO{sub 2} nanoparticles annealed at 500°C.

36 MATERIALS SCIENCE↗