bluuebunny/crossref_metadata_2025 huggingface dataset:
Overview of Design of Modular Vaults for the Storage of Low Level Nuclear Waste in the UK
Authors: Gallagher Eugene M , Shaw Neil
Published: April 2011

Low level nuclear waste (LLW) will be stored in a series of modular vaults at the UK's principal LLW repository located near the village of Drigg in west Cumbria. The design of the new vaults is reviewed in the context of likely volume, composition and packaging of future waste streams; planning and regulatory considerations; and the site's geological and hydrogeological setting. Site construction work for the first of the new vaults (Vault 9) commenced in September 2008 and is anticipated to be substantially complete by the end of 2009 with future vaults constructed as required. The vaults are designed as a series of containment cells comprising a composite basal and sidewall lining system with an engineered capping system. Provision has been made for an extensive, deep cut-off wall as part of the longterm containment system for the whole repository site, which includes areas where LLW was historically tumble tipped into a series of trenches. Constraints on the design of the vaults include a complex hydrogeological setting controlled by two groundwater bodies influencing maximum excavation depth; geometrical limitations on the height, level and plan extents to which LLW could be stacked within the vaults; and strict limitations on the movement of construction materials by road.
Impact of Silicon Migration Through Buffer Material on the Lifetime of Vitrified Waste
Authors: Mitsui Seiichiro , Makino Hitoshi , Inagaki Manabu , Ebina Takanori
Published: April 2011

A sensitivity analysis was conducted to evaluate the impact of silicon migration through buffer material on the lifetime of vitrified waste. The results indicate that the lifetime depends on a combination of the dissolved glass fraction in the non-steady-state phase controlled by the silicon pore diffusion coefficient (Dp) and the silicon distribution coefficient (Kd) in the buffer material and the steady-state dissolution rate defined by Dp and the groundwater flow rate (Q) in the excavation disturbed zone. In the case where the glass dissolution rate reaches the steady-state dissolution rate, the sensitivity of the lifetime to Dp and Q varies according to the magnitude relationship between Dp and Q. We also discuss the impact on the lifetime of glass hydration, which proceeds simultaneously with glass matrix dissolution. The results show that glass hydration is less important for the lifetime than glass matrix dissolution in an open system and it can be concluded that silicon migration through the buffer material will be an important process for estimating the lifetime of the vitrified waste. A preliminary calculation of the long-term waste behavior with realistic assumptions indicates the importance of the silicon migration parameters Kd and Dp, which control the dissolution behavior of the vitrified waste in the non-steady-state phase, for evaluating radionuclide release.
Dynamic light scattering study of intrinsic colloids of tetravalent actinides
Authors: Kumar Sumit , Tomar B.S. , Manchanda V.K.
Published: April 2011

Kinetics of formation of intrinsic colloids by tetravelent metal ions, namely, Th(IV), Hf(IV) and Pu(IV) have been studied using the dynamic light scattering technique. The milli-molar solutions of Hf(IV) and Th(IV) were prepared at varying pH (2-4) and ionic strength (0-0.01 M) and the samples were subjected to dynamic light scattering measurements at regular intervals for few days. The results showed that the size of intrinsic colloids varies with pH and ionic strength. In the case of Pu(IV) the concentration of aqueous solutions was 4.5×10−5M.
Diffusion of Cesium and Iodine in Compacted Sodium Montmorillonite Under Different Saline Conditions
Authors: Tachi Yukio , Yotsuji Kenji , Seida Yoshimi , Yui Mikazu
Published: April 2011

Diffusion and sorption of cesium (Cs) and iodine (I) were investigated in a purified and moderately compacted sodium montmorillonite (dry density of 800 kg m-3) saturated with 0.01, 0.1 and 0.5M NaCl solutions. The effective diffusivity (De) and capacity factor (α) for Cs and I were measured by through-diffusion experiments, coupled with multiple curve analyses, including tracer depletion, breakthrough and depth concentration curves, which could be fitted with a conventional diffusion model using only one set of parameters. The De values obtained for Cs were of the order of 10-9-10-10 m2 s-1 and decreased as salinity increased, and those for I were of the order of 10-11-10-12 m2 s-1 and showed the opposite dependency. The distribution coefficient (Kd) of Cs decreased from the order of 100 to 10-2 m3 kg-1 as salinity increased. Diffusion and sorption parameters for Cs were also obtained by in-diffusion and batch sorption experiments and showed good agreement with those obtained by the through-diffusion experiments. The diffusion model, based on homogeneous pore structure and electrical double layer (EDL) theory, predicted the salinity dependence of De reasonably well, showing the effect of cation excess and anion exclusion as a function of salinity. The apparent diffusivity (Da), which includes sorption effects, was also interpreted by a coupled sorption model.
Radiation Damage in Materials – Effects of Disorder
Authors: Whittle Karl R. , Blackford Mark G. , Lumpkin Gregory R. , Smith Katherine L. , Zaluze Nestor J.
Published: April 2011

Radiation damage and the effect on physical and chemical properties is an important component in the prediction of the long-term stability of waste form materials. As part of the ongoing goal of increasing the accuracy of long-term predictions of radiation damage, two types of material, based on proposed materials with a waste form application have been irradiated. Results have shown that Y2TiO5 (Y2.67Ti1.33O6.67), and Yb2TiO5 (Yb2.67Ti1.33O6.67), both of which are non-stoichiometric, disordered pyrochlore-based compounds, behave significantly different to the stoichiometric, ordered pyrochlore equivalent. For example the critical temperature, the temperature above which materials remain crystalline during irradiation, is found to decrease from the ordered equivalents, e.g. Y2Ti2O7. ⁡ A second material based on La2TiO5 has been found to behave differently to both La2/3TiO3 and La2Ti2O7, with a change in Tc of ∼ 200 K.
Pressure Evolution of a Bituminized Washing Water Concentrate During Leaching
Authors: Waellisch Alexander H.
Published: April 2011

In this investigation the swelling pressure of confined samples of a real waste form, consisting of bitumen containing washing water concentrate, was measured. The theoretically reachable swelling pressure was estimated as high as ∼ 273 bar (27 MPa).

A first simple experimental set-up was a sample of bituminized radwaste embedded in a cylinder of sintered bronze with a piezo-resistive pressure transducer. This was put into a leaching medium. A maximum pressure of 2 bar (0.2 MPa) was measured. The leaching rates of these confined samples were similar to those of unconfined ones.

The second set-up was a sample of bituminized radwaste embedded in a cylinder of stainless steel, also equipped with a pressure transducer. The open bottom of the cylinder was closed with a disc of porous cement with water/cement ratio of 1.3. In two similar experiments with this set-up the swelling pressure reached in one case a value of 9 bar = 0.9 MPa and in the second improved one about 15 bar = 1.5 MPa.
Ceramic formulation and processing design for plutonium disposition
Authors: Hyatt Neil C. , Stennett Martin , Jenni Andreas , Reid Daniel , Maddrell and Ewan R.
Published: April 2011

The focus of this research programme is to develop a single phase ceramic wasteform for waste PuO2 that is unsuitable for fuel manufacture. A suite of synthetic mineral systems have been considered including titanate, zirconate, phosphate and silicate based matrices. Although a wealth of information on plutonium disposition in some of the systems exists in the literature, the data is not always directly comparable which hinders comparison between different ceramic hosts. The crux of this research has been to compile a database of information on the proposed hosts to allow impartial comparison of the relative merits of each system.
Heavy ion implantation combined with grazing incidence X-ray absorption spectroscopy (GIXAS): A new methodology for the characterisation of radiation damage in nuclear ceramics
Authors: Stennett Martin C. , Hyatt Neil C. , Reid Daniel P. , Maddrell Ewan R. , Peng Nianhua , Jeynes Chris , Kirkby Karen J. , Woicik Joseph C. , Ravel Bruce
Published: April 2011

An understanding of the effect of cumulative radiation damage on the integrity of ceramic wasteforms for plutonium and minor actinide disposition is key to the scientific case for safe disposal. Alpha recoil due to the decay of actinide species leads to the amorphisation of the initially crystalline host matrix, with potentially deleterious consequences such as macroscopic volume swelling and reduced resistance to aqueous dissolution. For the purpose of laboratory studies the effect of radiation damage can be simulated by various accelerated methodologies. The incorporation of short-lived actinide isotopes accurately reproduces damage arising from both alpha-particle and the heavy recoil nucleus, but requires access to specialist facilities. In contrast, fast ion implantation of inactive model ceramics effectively simulates the heavy recoil nucleus, leading to amorphisation of the host crystal lattice over very short time-scales. Although the resulting materials are easily handled, quantitative analysis of the resulting damaged surface layer has proved challenging.

In this investigation, we have developed an experimental methodology for characterisation of radiation damaged structures in candidate ceramics for actinide disposition. Our approach involves implantation of bulk ceramic samples with 2 MeV Kr+ ions, to simulate heavy atom recoil; combined with grazing incidence X-ray absorption spectroscopy (GI-XAS) to characterise only the damaged surface layer. Here we present experimental GI-XAS data acquired at the Ti and Zr K-edges of ion implanted zirconolite, as a function of grazing angle, demonstrating that this technique can be successfully applied to characterise only the amorphised surface layer. Comparison of our findings with data from metamict natural analogues provide evidence that heavy ion implantation reproduces the amorphous structure arising from naturally accumulated radiation damage.
The Relative Merits of Oxides of Hafnium, Cerium and Thorium as Surrogates for Plutonium Oxide in Calcium Phosphate Ceramics
Authors: Metcalfe B. L. , Fong S. K. , Gerrard L. A. , Donald I. W. , Welch E. S. , Stennett M. C. , Hyatt N. C.
Published: April 2011

The choice of surrogate for plutonium oxide for use during the initial stages of research into the immobilization of intermediate level pyrochemical wastes containing plutonium andamericium oxides in a calcium phosphate host has been investigated by powder X-ray diffraction and X-ray absorption spectroscopy. Two non-radioactive surrogates, hafnium oxide and cerium oxide, together with radioactive thorium oxide were compared. Similarities in behaviour were observed for all three surrogates when calcined at the lowest temperature, 750°C but differences became more pronounced as the calcination temperature was increased to 950°C. Although some reaction occurred between all the surrogates and the host to form a substituted whitlockite phase, increasing the temperature led to a significant increase in the cerium reaction and the formation of an additional phase, monazite. Additionally it was observed that the cerium became increasingly trivalent at higher temperatures.
Irradiation effects of synthetic coffinite (USiO4) studied by in-situ TEM
Authors: Zhang J.M. , Lu F. Y. , Pointeau V. , Zhang F. X. , Lang M. , Poinssot C. , Lian J. , Ewing R. C.
Published: April 2011

Coffinite (USiO4, I41/amd, Z=4) is the major alteration phase of uraninite, UO2+x, under reducing conditions in natural uranium deposits. Thus, it is important to understand the radiation response of coffinite because it is an expected alteration product of the UO2 in spent nuclear fuel. In the present study, we conducted in-situ transmission electron microscopy (TEM) investigation of synthetic coffinite under 1 MeV-Kr2+ ion beam irradiation. The radiation-induced crystalline-to-amorphous transformation was observed in the synthetic nanocrystalline USiO4, with a critical dose of ∼ 0.27 displacements per atoms (dpa) for which full amorphization occurred at room temperature. The critical dose increases as rising irradiation temperature, and above the critical temperature (Tc), ∼ 608 K, coffinite cannot be amorphized. These results are compared with previous studies on the isostructural zircon (ZrSiO4, Tc=1000K) and thorite (ThSiO4, Tc>1100K), which indicates that synthetic coffinite is more stable to ion beam irradiation at elevated temperature.
Heavy Doping of Li+-ion into NiO Epitaxial Thin Films via Unequilibrium Room-temperature Processing for New Functionalization
Authors: Shiraishi Naoki , Kato Yushi , Arai Hideki , Tsuchimine Nobuo , Kobayashi Susumu , Mitsuhashi Masahiko , Soga Masayasu , Yoshimoto Mamoru
Published: April 2011

NiO is a typical material for new p-type oxide semiconductors. Conductivity of NiO can be raised with Li+ doping. In case of Li-heavy doping, we can obtain LixNiO2(0.5< × <1.0). Recently the importance of LiNiO2 has been increased as an electrode material for rechargeable lithium cells.

In this work, we tried to fabricate a novel NiO material with Li+-heavily doped by applying the pulsed laser-induced room temperature (R.T.) film process. Previously, we have succeeded in the epitaxial growth of various oxide thin films at R.T. such as Sn-doped In2O3 transparent electrodes [1]. Although the many studies have been made on the deposition of NiO epitaxial thin film at low temperatures [2], there are few reports on fabrication and the conductive characteristic for Li-heavily doped NiO epitaxial films. The film deposition at R.T., which is the unequilibrium vapor phase process, is expected to result in different crystal structure and characteristics from the films grown at high-temperatures.

A composition-adjusted thin film of LixNi1-xO(0.10< × <0.40) was deposited on a sapphire (α-Al2O3)(0001) or MgO(100) substrates by pulsed laser deposition (PLD) technique in 10−6 Torr of oxygen at R.T. and the high temperatures of 350 and 515°C. Crystalline properties of thin films deposited at R.T. or high temperatures were examined using reflection high energy electron diffraction (RHEED) and X-ray diffraction. For the Li-heavily doped NiO films(x>0.30) grown at R.T., a clear streak RHEED pattern showing epitaxial growth was observed. But the Li-heavily doped NiO films grown at high temperatures, exhibited the ring RHEED pattern, which indicates the policrystal growth of films. Electric conductivity of various Li-doped NiO thin films deposited at R.T. or high temperatures on sapphire (0001) substrates were measured by two-probe method. The interesting results were obtained that conductivity of the film was increased remarkably with an increase of Li-doping for R.T. deposition, but was not changed so much regardless of Li-doping for high-temperature depositions.
Thermoelectric Generators Made with Novel Lead Telluride Based Materials
Authors: Wu Chun-I , Girard Steven N , Sootsman Joseph , Timm Edward , Ni Jennifer , Schmidt Robert , Kanatzidis Mercouri , Schock Harold , Case Eldon D. , Chung Duck Young , Hogan Timothy
Published: April 2011

For the material (Pb0.95Sn0.05Te)1-x(PbS)x nanostructuring from nucleation and growth and spinodal decomposition were reported to enhance the thermoelectric figure of merit over bulk PbTe, producing ZT of 1.1 - 1.4 at 650 K for x = 0.08[1]. Thermoelectric modules made from (Pb0.95Sn0.05Te)1-x(PbS)x materials with various hot-side metal electrodes were fabricated and tested. Short circuit current was measured on unicouples of Pb0.95Sn0.05Te – PbS 8% (n-type) legs and Ag0.9Pb9Sn9Sb0.6Te20 (p-type) legs over 10 (A) for a hot side temperature of 870K, and a cold side of 300K. Hot pressed (Pb0.95Sn0.05Te)1-x(PbS)x materials were also investigated for module fabrication. Investigations of the electrical properties of hot-pressed (Pb0.95Sn0.05Te)1-x(PbS)x materials are presented along with the latest advancements in the fabrication and characteristics of modules based on the processing of these materials.
Phase Stability and Thermoelectric Properties of Half-Heusler Compounds (Ti,M)NiSn (M = Zr, Hf)
Authors: Kenjo Takahiro , Kimura Yoshisato , Mishima Yoshinao
Published: April 2011

Aiming to improve thermoelectric properties of half-Heusler compounds MNiSn (M = Ti, Zr, Hf), phase equilibria in the (Ti,M)NiSn systems have been investigated focusing on the half-Heusler phase separation between TiNiSn and ZrNiSn, TiNiSn and HfNiSn. Solubility limit of an element M in each half-Heusler phase was determined by XRD and EPMA. Nearly single phase alloys were fabricated by the directional solidification using optical floating zone melting method to evaluate intrinsic thermoelectric properties of the alloys. Lattice thermal conductivity can be reduced in (Ti,M)NiSn alloys by phonon scattering due to the solid solution effect of M site substitution. Moreover, electrical properties can be enhanced by the Ti addition in (Ti,Zr)NiSn alloys. Among present MNiSn alloys, (Ti0.15,Zr0.85)NiSn alloy has the highest power factor of 5.3 mWm-1K-2 at around 745 K.
Improvement of the Thermoelectric Properties of the Chimney–Ladder Compounds in the Ru-Mn-Si System
Authors: Okamoto Norihiko L. , Hashimoto Yutaka , Koyama Tatsuya , Adachi Hiroki , Kishida Kyosuke , Tanaka Katsushi , Inui Haruyuki
Published: April 2011

Directionally solidified alloys in the Ru-Mn-Si system exhibit a particular microstructure including columnar compositional variation due to the formation of many different chimney-ladder phases along the growth direction. Despite the existence of the compositional variation, the crystal orientations of the neighboring chimney-ladder phases are preserved. Over the compositional interfaces, the metal sublattice is considered to be continuous while the Si sublattice is not. Heat treatment of the directionally solidified alloy with the nominal composition of Ru0.10Mn0.90Si1.732 at 1100°C coarsens the compositional domains so as to reduce the density of the compositional interfaces. The values of the thermal conductivity increase with the decrease in the density of the compositional interfaces whereas those of the Seebeck coefficient and electrical resistivity are almost unchanged after the heat treatment. It is considered that the thermoelectric properties of the chimney-ladder compounds in the Ru-Mn-Si system can be enhanced by introducing a high density of the compositional interfaces.
Advanced Soldier-Based Thermoelectric Power Systems Using Battlefield Heat Sources
Authors: Hendricks Terry J. , Karri Naveen K. , Hogan Tim P. , D'Angelo Jonathan , Wu Chun-I , Case Eldon D. , Ren Fei , Morrison Andrew Q. , Cauchy Charles J.
Published: April 2011

The U.S. military uses large amounts of fuel during deployments and battlefield operations. Consequently, the U.S. military has a strong need to develop technologies that increase fuel efficiency and minimize fuel requirements all along the logistics trail and in all battlefield operations. There are additional requirements to reduce and minimize the environmental footprint of various military equipment and operations and reduce the need for batteries (non-rechargeable) in battlefield operations. The tri-agency SERDP (Strategic Environmental Research and Development Program) office is sponsoring a challenging, high-payoff project to develop a lightweight, small form-factor, soldier-portable advanced thermoelectric generator (TEG) system prototype to recover and convert waste heat from a variety of deployed equipment with the ultimate purpose of obtaining additional power for soldier battery charging, advanced capacitor charging, and other battlefield power applications. The project seeks to achieve power conversion efficiencies of 10% (double current commercial TE conversion efficiencies) in a system with ˜1.6-kW power output for a spectrum of battlefield power applications. In order to meet this objective, the project is taking on the multi-faceted challenges of tailoring LAST/LASTT-based thermoelectric (TE) materials for the proper temperature ranges (300 K – 700 K), fabricating these materials with cost-effective hot-pressed and sintered processes while maintaining their TE properties, measuring and characterizing their thermal fatigue and structural properties, developing the proper manufacturing processes for the TE materials and modules, designing and fabricating the necessary microtechnology heat exchangers, and fabricating and testing the final TEG system. The ultimate goal is to provide an opportunity to deploy these TEG systems in a wide variety of current military equipment. This would help the Army in achieving one of the Office of Secretary of Defense’s major strategic objectives to maintain and enhance operational effectiveness while reducing total force energy demands. The presentation will review the progress made on 1) the performance of LAST / LASTT TE materials and tailoring their temperature dependency; 2) evaluating the structural (Elastic modulus, Poisson’s ratio and mechanical strength) properties of these materials, 3) development of the necessary LAST/LASTT-based TE modules, 4) development of the required hot- and cold-side microtechnology heat exchangers, and 5) the overall system designs for 30 kW and 60 kW TQG applications and potential performance pathways/differences for these two TQG cases. This work leverages critical fundamental research performed by the Office of Naval Research in developing LAST/LASTT materials.
Thermoelectric Topping Cycle for Trough Solar Thermal Power Plant
Authors: Muto Andy , Chen Gang
Published: April 2011

Solar thermal power generation is fast becoming cost competitive for utility scale electricity. Parabolic trough concentrators have proven economical and reliable but their efficiency is limited by the maximum temperature of the heated fluid. This work will explore the possibility of adding a thermoelectric power generator (TEG) as a topping cycle at high temperature to increase the overall efficiency of the system. In this design the perimeter of the receiver tube is covered with thermoelectrics so that the absorber temperature is raised and the energy rejected from the TEG is used to heat the fluid at its originally specified temperature. A heat transfer analysis was carried out on the design to determine the overall system efficiency. Our findings show the state of the art solar thermal trough collector is not a good application for a ZT=1 thermoelectric material. To increase the overall power output of the system by approximately 10% would require a ZT=3 material.
Adsorption of Chromium (VI) from Aqueous Solutions Using Sol-Gel Anionic Clays with Mg/ Al=7
Authors: Esthela Ramos R. , Norma Gutiérrez O. , Cesar Contreras S. , Javier Álvarez R. , Rosalba Fuentes R.
Published: April 2011

Anionic clays has been used in the adsorption of anionic species of toxic heavy metals, such as chromium (VI), which is considered to be a dangerous pollutant, due to its deleterious effects on human health such as epithelial irritation and cancer. In this work the removal of chromium in aqueous solutions using anionic clays with Mg/Al=7 was determined. The anionic clays were synthesized by the sol-gel method at pH 10 and 11.5, and were characterized by X-ray diffraction, thermal analysis, infrared spectroscopy and N2 adsorption Brunauer-Emmett-Teller (BET). By this method, anionic clay containing brucite was obtained. The solids exhibited meso-porosity, high surface areas and thermal stability until 500°C. The data obtained from the adsorption experiments of chromium fitted to the Langmuir adsorption isotherm model and the adsorbent capacity was determined using the Langmuir adsorption equation. The maximum chromium uptake was 45 mg of Cr/g sorbent and 43 mg Cr/g sorbent for anionic clays prepared to pH 10 and 11.5, respectively. The Cr saturation point was attained after eight minutes stirring time. According to chromium adsorption values, the solution pH does not have a significant affect on the adsorption capacity of the anionic clays.
Macro and Microstructural Effects of the Application of an Induced Axial Magnetic Field During the Deposition of Aluminum Weld Beads
Authors: García M. A. , López M. V. H. , García H. R. , Curiel L. F. F. , Ambríz R. R. R.
Published: April 2011

In this work, aluminum weld beads were deposited on aluminum plates of commercial purity (12.7 mm thick), using an ER-5356 filler wire. The aim of the experiments was to assess the effects that yield the induction of an axial magnetic field (AMF) during the application of the weld beads using the direct current gas metal arc welding process (DC-GMAW). An external power source was use to induce magnetic fields between 0 to 28 mT. The effects of the magnetic fields were assessed in terms of the macrostructural features of the deposits, morphology of the grain structure, grain size and grain size distribution in the weld metal. Macrostructural characteristics of the weld beads revealed that increasing the intensity of the magnetic induction to produce a magnetic field above 14 mT, leads to a significant loss of feeding material and there is a tendency of the deposits to increase their width and reduce penetration. Perturbation of the weld pool induced by the application of the AMF noticeably modified the grain structure in the weld metal. In particular, for the intensities of 5 and 14 mT, columnar growth was essentially non-existent. Grain size distribution plots showed, generally speaking, that the use of magnetic fields is an efficient method to produce homogeneous grain structures within the weld metal. Finite element analysis was used to explain the weld bead geometry with the intensity of the magnetic field.
Secondary Phases Precipitation in the 2510 Duplex Stainless Steel
Authors: Reyes Arturo , Calliari Irene , Ramous Emilio , Zanellato Michela , Merlin Mattia
Published: April 2011

A lot of duplex and super duplex stainless steels are prone to secondary phases but with different sequence and kinetic which depend on the chemical composition and thermo-mechanical history of the steel. In this paper the results of secondary phase's determination in a welding grade 2510 duplex steel, heat treated at 850–1050°C for 3–30 min are presented. The precipitation stars at grain boundaries with a consistent ferrite transformation for short times. The noses of the TTP curves are at 1000°C (sigma phase) and at 900°C (chi phase) with a partial transformation of chi to sigma, as evidenced in 2205 and 2507 grades.
Growth and Characterization of Organic Polymeric Thin Films From Isopropanol by PECVD.
Authors: Martínez-Gutiérrez J. O. , Romero-Paredes G. , Peña-Sierra R. , Ávila-García A. , Juárez-Díaz G.
Published: April 2011

Polymerized organic thin films were synthesized on a variety of substrates by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique using isopropanol as precursor. Hydrogen peroxide, ammonium hydroxide, and iodine dissolved in isopropanol were used as dopants and chlorobenzene as copolymerization precursor. The structural, optical and electrical properties of the films were studied as functions of the dopant type and concentration.

The polymeric films were characterized by variable angle ellipsometry (VAE), atomic force microscopy (AFM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible transmission spectroscopy and photoluminescence. The electrical film behavior was explored by the four points probe method.

The growth rate, refractive index, optical bandgap, chemical structure and resistivity of the films strongly depend on the concentration and type of dopant added. The AFM microphotographs showed smooth surfaces with RMS roughness less than 10 nm. The optical bandgap values of the films were in the range of 2.6 to 3.26 eV, the resistivity was in the order of 103 – 104 ohm-cm. The photoluminescence response of the polymerized films was obtained in the visible region, by exciting with a UV laser.
Rietveld Structure Refinement of Hydrothermally Grown Zinc Peroxide Nanoparticles
Authors: García-Ruiz A. , Aguilar M. , Aguilar A. , Escobedo-Morales A. , Esparza R. , Pérez R.
Published: April 2011

Nanocrystals of zinc oxides have demonstrated to be very important materials for several applications in many fields, particularly in catalysis. Nanocrystalline zinc peroxide (ZnO2), which is a precursor of zinc oxide (ZnO), has been prepared by means of a hydrothermal process from zinc acetate dehydrates. On the other hand, it is of great interest to have a detailed structural characterization, in order to correlate it with the catalytic properties of the synthesized material. In this work, some results are presented about the nanostructure of the prepared zinc peroxide. By using X-ray diffraction followed of a pattern refinement by the Rietveld techniques, refined average cell parameters and crystallite size were calculated and, from these refined values, crystallite morphology was simulated in an averaged manner. With the aim to get a more complete characterization, besides these results, some micrographs of the crystalline structure of ZnO2, observed by TEM, were also included in this work.
Evaluation of Modulus of Elasticity, Mineral Composition and Bone Mineral Density of Trabecular Bone L3- Vertebrae Samples Extracted From Mexican Men
Authors: Valdés R. , Solis A. L. , Godínez F. A. , Martínez E. , Villegas C.H. , Navarrete M.
Published: April 2011

Extracted samples of L3 vertebrae, the healthy, osteopenic and osteoporotic from Mexican men, were fixed to carry out measurements of the modulus of elasticity (ME) and the minerals content, on the trabecular zone to study their behavior as a function of age.

To determine the ME the immersion ultrasonic method (IUM) was used, X-ray dispersion was applied to know the chemical element concentration (Ca++, Na++, P, and Mg++) and computerized axial tomography (CAT) to obtain bone mineral density (BMD).The samples were organized in four groups by decade. The samples in the range of 30-39 years revealed: a normal BMD and a concentration [% w/w] between pairs of Ca++/P, Ca++/Mg++, P/Mg++ and Mg++/ Na ++ with correlation positive due to the strong dependence between them.

The average ME results were: 2.79±0.326, 2.68±0.45, 2.66±0.43 and 2.70±0.397 [GPa] for each decade respectively. The ME profiles show a nonlinear behavior as a function of age, indicating a minimum value in the third decade, similar behavior is observed in the Ca++. An exponential behavior between ME and T-score was obtained. The plotted Ca++ and ME as a function of area showed a homogeneous distribution for the first and a non homogeneous for the second.
Biocompatibility and bio-corrosion resistance of amorphous oxide thin films
Authors: Rojas P. N. , Rodil S. E. , Muhl S. , Ramírez G. G. , Arzate H
Published: April 2011

The corrosion resistance of biocompatible materials in body fluids is one of the essential factors in the determination of the lifetime of medical implants. Therefore, it is of great relevance to understand the interface processes that occur when a surface is exposed to body fluids. To this end, amorphous titanium and niobium oxide films were deposited on medical grade stainless steel using a magnetron sputtering system. The biocompatibility of the films was evaluated by adhesion and viability/proliferation assays using human cells, showing non-toxic response. The electrochemical response of the films was evaluated by poteontiodynamic polarization and electrochemical impedance spectroscopy (EIS) as a function of time, up to 500 hrs, using three different simulated body fluids; the NaCl solution and Hartman (Ringer's + Lactate) and Gey's (Ringer's + Phosphates + Glucose) solution. The results indicated that the chemical composition of the solution was very important since different electrochemical behavior was observed for each case. For example, NbOxshowed a better resistance than the TiOxfilms in the Hartman's solution but it failed when Gey's solution was used. Meanwhile TiOxshowed a well passivated response for both NaCl and Gey's solution.
In VitroEffects of Cementum Protein 1 (CEMP1) on Calcium Phosphate Crystal Formation and its Role During the Mineralization Process
Authors: Romo-Arévalo Enrique , Villarreal-Ramírez Eduardo , Chávez-Pacheco Juan L. , Piña-Barba Cristina , Aguilar-Franco M. , Arzate Higinio
Published: April 2011

Cementum contains specific molecules that could serve to identify, isolate and characterize the cementoblast lineage and to determine the cellular and molecular mechanisms that regulate the cementogenesis process, since it plays a key role during the periodontal regeneration process. One of these molecules is the human cementum protein 1 (CEMP1); which has a molecular weight of 25,9 kDa.In vitroexperiments have shown that CEMP1 promotes cellular adhesion and differentiation. In addition, this protein has been implied in regulating the degree of deposition, composition and morphology of hydroxyapatite crystals formed by putative cementoblastin vitro. Therefore, it is possible that CEMP1 promotes the formation, growth and regulates the morphology of hydroxyapatite crystalsin vitro.We have produced a human recombinant CEMP1 (hrCEMP1) in a prokaryotic system. ThehrCEMP1 purification was realized using the column NiTA HisPrep FF/16. Assays of calcium phosphate crystal growth were realized by means of capillary counterdiffusion system. Our results demonstrated thathrCEMP1 promotes octacalcium phosphate crystal nucleation and possesses high affinity for hydroxyapatite. We infer thathrCEMP1 plays a key role during the regeneration of mineralized tissues.
Deposition of PEDOT/SWCNT Composites by Inkjet Printing
Authors: Angelo Peter David , Farnood Ramin R.
Published: April 2011

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), or PEDOT:PSS, a conductive polymer suspension, as well as carbon nanotubes (CNTs), were incorporated into a conductive ink suitable for use in a piezoelectric inkjet printer. Viscosity, surface tension, and particle size of the ink were controlled to achieve stable, high-resolution printing. Passage of the CNTs through the filtration and jetting steps involved in printing was evaluated using scanning transmission electron microscopy (STEM), UV-visible spectroscopy, and zeta-potential measurements of the filtered and printed inks. Only single-walled nanotubes (SWCNTs) passed through the jetting stage in significant amounts. Printed PEDOT/SWCNT sheet resistance was effectively minimized at ˜1 kΩ/on cellulose acetate, in ink containing 6 w/w% of an aqueous SWCNT solution (approximately 0.04 w/w% SWCNTs).
Magnetic Phase Diagram of Transition Metal Doped ZnO from Density Functional Theory Calculations and Monte Carlo Simulations
Authors: Nayak Sanjeev K. , Herper Heike C. , Entel Peter
Published: April 2011

Transition metals doped ZnO are possible candidates for multiferroics. Here, we have investigated the evolution of ferromagnetism due to Co dopants. The magnetic properties have been studied for Co concentrations from 0 to 100% by using ab-initio methods, i.e., KKR Green's function techniques. In order to estimate the Curie temperature we have performed Monte Carlo simulations with ab-initio calculated exchange parameters.

From our calculations the onset of ferromagnetism occurs between 5 to 20% of Co depending on the numerical details of KKR method used. For Co concentrations larger than 50% the system is dominated by antiferromagnetic coupling and no Curie temperature can be obtained.
Oxidation Products in Inconel Alloys 600 and 690 Under Hydrogenated Steam Environments and Their Role in Stress Corrosion Cracking
Authors: Lopez Hugo F.
Published: April 2011

Thermodynamic considerations for the stability of Ni and Cr compounds developed under PWR environments (PH2O and PH2) are experimentally tested. In particular, the experimental outcome indicates that Ni(OH)2 and CrOOH are thermodynamically stable products under actual PWR conditions (T < 360°C and Pressures of up to 20 MPa). Accordingly, a mechanism is proposed to explain crack initiation and growth in inconel alloy 600 along the gbs. The mechanism is based on the existing thermodynamic potential for the transformation of a protective NiO surface layer into an amorphous non-protective Ni(OH)2 gel. This gel is also expected to form along the gbs by exposing the gb Ni-rich regions to H2 supersaturated water steam. Crack initiation is then favored by tensile stressing of the gb regions which can easily rupture the brittle gel film. Repeating the sequence of reactions as fresh Ni is exposed to the environment is expected to also account for crack growth in Inconel alloy 600. The proposed crack initiation mechanism is not expected to occur in alloy 690 where a protective Cr2O3 film covers the metal surface. Yet, if a pre-existing crack is present in alloy 690, crack propagation would occur in the same manner as in alloy 600.
Micromechanical Models of Structural Behavior of Concrete
Authors: Avdeev Ilya , Sobolev Konstantin , Amirjanov Adil , Hastert Andrew
Published: April 2011

A three-dimensional numerical model capable of predicting structural behavior of concrete under various loading conditions is developed. Concrete, as a composite material, is represented by the mechanically strong aggregates of various shapes and sizes incorporated into a cement matrix. The most important aspect of concrete modeling involves an accurate representation of the spatial distribution of the aggregate particles.

A micromechanical heterogeneous model based on prescribed spatial distribution of aggregates is developed. This model allows to compute the effective material properties of concrete using a representative cell homogenization approach. The results of numerical analysis of this model are compared to the models of particulate composite material.
Preparation and Mechanical Characterization of Composite Material of Polymer–Matrix with Starch Reinforced with Coconut Fibers
Authors: Torres-Hernández- Yaret G. , Altamirano-Torres Alejandro , Sandoval-Pérez Francisco , Rangel Enrique Rocha
Published: April 2011

In this work the synthesis and mechanical characterization of a polymer matrix composite is reported. An epoxy resin is used as matrix with addition of starch and coconut fibers as reinforcement. Vickers hardness and impact tests are used for mechanical characterization. Starch is used to promote degradability of the polymer matrix with clear benefits for the environment. Natural fibers have been used for reinforcing the composite materials. Natural fibers have several advantages such as price, low density and relatively high mechanical properties, they are also biodegradable and non abrasive In this investigation, the composite material samples are fabricated with epoxy resin, 5, 10, 15 wt % of starch and 5, 10 wt % of coconut fibers with the help of silicon molds which have the dimensions and geometry according to ASTM Standards for make Impact and Vickers hardness tests. The obtained results show that increases in the amount of coconut fibers cause an enhancement of the mechanical properties of the material, due to a good adhesion between the polymeric matrix and the natural fibers.
Synthesis of La4Ni3O10 Cathode Material (SOFC) by SOL-GEL Process
Authors: Cienfuegos Rene Fabian , Carranza Sugeheidy , Chávez Leonardo , Jouanin Laurie , Marie Guillaume , Hinojosa Moisés
Published: April 2011

The goal in this study is to synthesize a Ruddleden-Poper La-Ni phase (La4Ni3O10) using a polymeric route. This material exhibits mixed ionic and electronic conduction (MIEC) properties and can be used as cathode material in the manufacture of Solid Oxide Fuel Cells (SOFC). In addition, an easy and inexpensive synthesis method is presented The polymeric precursors are prepared following the Castillo method using optimized the complexation ratios (HMTA/metallic salts) from 1 to 6. The obtained powders are characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) in order to determine the processing conditions for formation of the crystalline phase. Experiments performed using complexation ratios of 5 and 6 do not show coagulation. However, the solution prepared using a complexation ratio of 5, is transformed into a gel after few days. Gels produced from solutions prepared with complexation ratios from 2 to 5 were heated at 800, 900 and 1000°C to obtain solid materials. These powders are characterized by TGS, DSC and XRD and it is found that the temperature needed to obtain crystalline La4Ni3O10 was 1000°C.
Antibacterial Effect of Biodegradable Magnesium Alloys Modified By Biocompatible Transitions Metals
Authors: García-Pérez V.I. , Almaguer-Flores A. , Ramírez-Brizuela C. , Rodil S.E.
Published: April 2011

Magnesium (Mg) alloys can be use as biodegradable medical devices, eliminating the need for a second operation for implant removal. An important feature on biomedical devices is to avoid the bacterial adhesion and subsequent biofilm formation that cause most of the implant-failures. The aim of this study was to analyze the differences on bacterial adhesion and biofilm development on Magnesium alloys (Mg-Al-Zn) modified by different transition metals; Tantalum, Niobium and Titanium. Nine oral bacterial strains (Aggregatibacter actinomycetemcomitans serotipe b, Actinomyces israelii, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum, Parvimonas micra, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis) were incubated on the different alloys and commercial medical grade stainless steel (AISI 316L) was used as a control. The initial bacterial adhesion was determined after 24 hours using a counting plate technique and the subsequent biofilm development at 1, 3, 7 days was studied using the Scanning Electron Microscopy. Significant differences were determined using t-test. The results showed that on the magnesium-alloys, the number of bacteria attached after 24 hours was two orders of magnitude lower than the stainless steel. On the other hand, bacterial colonies were not observed by electron microscopy in any of the days of incubation, even though in the control surface clear colonies and biofilm development were observed. This study showed that magnesium alloys inhibits the bacterial adhesion and the subsequent biofilm development.
Protein Adsorption on Amorphous Metal Oxide Thin Films: An FTIR/ATR and Ellipsometry study
Authors: Silva-Bermudez Phaedra , Rodil Sandra E.
Published: April 2011

The adsorption of bovine serum albumin (BSA) and fibrinogen proteins dissolved on Phosphate buffer solution onto Ta, Nb and Ti oxide thin films was studied. The metal oxide thin films were deposited by magnetron sputtering on Si(100) wafers and characterized by contact angle measurements and profilometry. Spectroscopic ellipsometry was employed to characterize the kinetics of the protein adsorption process in-situ at the solid-liquid interface and the optical properties of the adsorbed protein layer formed after 45 minutes of immersion of the thin film in the protein solution. Infrared spectroscopy was used to study the proteins within the adsorbed layer. A trend indicating that the surface mass density of the adsorbed protein layer increases as the Rt (peak-to-valley height) surface roughness parameter increases was observed for fibrinogen and BSA. An increment in the surface mass density of the adsorbed protein layer was also observed onto surfaces with higher polar components of the surface energy. BSA and fibrinogen seemed to more readily adsorbed onto tantalum oxide than onto titanium oxide.
Cadmium(II) and Lead(II) removal by Chlorella sp. Immobilized and E. coli genetically engineered with mice Metallothionein I
Authors: Almaguer-Cantú V. , Morales-Ramos L. , Arevalo-Niño K. , Garza-González M.T. , Balderas-Rentería I.
Published: April 2011

The pollution caused by heavy metals is one of the major environmental problems that is imperative to be solved. New technologies, easy to implement and to adapt to any system, deserve special attention and are a focus of this work the ability of Chlorella sp. and E. coli genetically engineered with mice metallothionein I, both immobilized in alginate of calcium to remove Cd(II) and Pb(II) from aqueous solutions was investigated in batch assays for the treatment of diluted aqueous solutions. The kinetics, sorption capacities and sorption percentage were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solution containing 300 mg/L of metal, the observed uptake capacities were 94.941±1.094 mgCd/gChlorella., 24.076±2.292 mgCd/gE.coli and 239.17±2.478 mgPb/gChlorella, 37.952±4.245 mgPb/gE.coli. The Langmuir constants to Chlorella sp. were qmax=285.72(mgPb/g), b=0.0276(l/mgPb), qmax=103.65(mgCd/g) and b=0.0005(l/mgCd) while to E. coli were qmax=28.141(mgPb/g), b=0.113(l/mgPb), qmax=24.272(mgCd/g) and b =0.019(l/mgCd). The biomass of the algae showed to have better capacity of metallic sorption that the biomass of the bacteria genetically engineering. The study proved that microorganisms biomass is a suitable material for the removal of the studied heavy metals ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II) and Pb(II) ions.
A Practical Approach for Prioritizing The Replacement of Water Pipes in Mexico City
Authors: Tzatchkov V. , Hansen M. P. , Ramírez H.
Published: April 2011

In Mexico City, one of the largest cities in the world, large losses occur in the drinking water distribution system, mainly due to the age of the pipes and the type of materials used in water delivery to the end user. In the past, most of the water distribution networks in the city were built with asbestos-cement pipes. Currently, policies dictate that they be replaced by polyethylene pipes. While the size of the city leads to limited financial resources, it is important to prioritize pipe replacement; therefore, a practical approach based on Deterioration Point Allocation (DPA) is proposed to define the priority level. In the next set of factors, each is represented by appropriate indicators:

1. Failures in pipes and service connections

a. Number of failures (leaks) in pipes repaired in one year for every 100 km of pipeline.

b. Number of failures (leaks) repaired in one year per 1000 service connections.

c. Spatial concentration of failures (leaks) in a pipe

2. Annual pipe and service connections rehabilitation or replacement level per year.

3. Operating parameters of the network: intermittent water supply, water pressure, and water losses

4. Deterioration status of pipes and service connections

5. Land subsidence

A score and a weight are assigned to each factor. The score depends on the values of the indicator, and the weight on the relative importance of the factor. The final score is used to prioritize the replacement and it is calculated by adding up the scores of each factor.

Considering that available information is incomplete and unstructured, two levels of use are proposed: basic (with available data, using MS Excel) and advanced (using a GIS).