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Sample records for chemical cement metals

  1. Content of heavy metals and chemical composition of the hydraulic cement marketed in Costa Rica

    International Nuclear Information System (INIS)

    Venegas Padilla, Jimmy; Calderon Jimenez, Bryan; Sibaja Brenes, Jose Pablo; Salazar Delgado, Jorge; Rodriguez Castro, Ellen

    2017-01-01

    The concentration of heavy metals, specifically lead (Pb), chromium (Cr), and mercury (Hg), and also the chemical composition (CaO, SiO 2 , Al 2 O 3 , Fe 2 O 3 among others) were quantified of the hydraulic cement marketed in Costa Rica. The physical parameters of density and fineness confirmed the homogeneity of the samples to determinate accurately the content of the major components and heavy metals in the cements. The mineralogical constitution was determined by X-ray Fluorescence (XRF). Specifically, the cements showed a mass fraction in the range of (61.22 - 63.12) % of CaO, (18.10 - 26.14) % of SiO 2 , (3.70 - 6.05) % of Al 2 O 3 , (2.57 - 3.36) % Fe 2 O 3 and (0.60 - 4.09) % de MgO. Other components such as MgO, TiO 2 , K 2 O, P 2 O 5 , Na 2 O and Mn 2 O 3 were found on an average mass fraction lower than 1%. Moreover, using the ignition test results and assuming a complete decomposition of the limestone, it was possible to estimate (indirectly) the content of CaCO 3 and CaO given by the raw materials. The metal content of the heavy metals was determined using Flame Atomic Absorption Spectroscopy (FAAS), Electrothermal Atomic Absorption Spectroscopy (ETAAS), and Cold Vapor Atomic Absorption Spectroscopy (CVAAS). The analysis demonstrated that the Pb in cements is present in different concentrations ranging the (2.45 ± 0.72) mg kg -1 to the (8.95 ± 1.34) mg kg -1 . Chromium (Cr) was presented in higher concentrations of (10.69 ± 0.92) mg kg-1. The Hg concentration was below 0.141 ± 0.021 mg kg -1 . In general terms, the hydraulic cements marketed and used in Costa Rica have a suitable chemical composition compared with some cements marketed in Germany. The results of the content of heavy metals presented in this study provide significant information for future studies in the area of toxicology, ecotoxicology, standardization and national regulation. (author) [es

  2. Chemical environment in cements

    International Nuclear Information System (INIS)

    Glasser, F.B.; Angus, M.J.; McCulloch, C.E.; Macphee, D.; Rahman, A.A.

    1984-01-01

    The alkalinity of Portland cements is responsible for precipitation and low solubility of many radwastes species. The sources of alkalinity are evaluated and two chemical models, based on experimental and theoretical data presented enabling the effect of blending agents (PFA, silica fume, etc.) to be evaluated and the alkalinity of the system at longer ages predicted. The data take the form of a solubility model which is applicable to non-heat generating wastes. 7 refs., 10 figs

  3. Chemical alteration of cement hydrates by dissolution

    International Nuclear Information System (INIS)

    Sugiyama, Daisuke; Fujita, Tomonari; Nakanishi, Kiyoshi

    2000-01-01

    Cementitious material is a potential waste packaging and backfilling material for the radioactive waste disposal, and is expected to provide both physical and chemical containment. In particular, the sorption of radionuclides onto cementitious material and the ability to provide a high pH condition are very important parameters when considering the release of radionuclides from radioactive wastes. For the long term, in the geological disposal environment, cement hydrates will be altered by, for example, dissolution, chemical reaction with ions in the groundwater, and hydrothermal reaction. Once the composition or crystallinity of the constituent minerals of a cement hydrate is changed by these processes, the pH of the repository buffered by cementitious material and its sorption ability might be affected. However, the mechanism of cement alteration is not yet fully understood. In this study, leaching experiments of some candidate cements for radioactive waste disposal were carried out. Hydrated Ordinary Portland Cement (OPC), Blast Furnace Slag blended cement (OPC/BFS) and Highly containing Flyash and Silicafume Cement (HFSC) samples were contacted with distilled water at liquid:solid ratios of 10:1, 100:1 and 1000:1 at room temperature for 200 days. In the case of OPC, Ca(OH) 2 dissolved at high liquid:solid ratios. The specific surface area of all cement samples increased by leaching process. This might be caused by further hydration and change of composition of constituent minerals. A model is presented which predicts the leaching of cement hydrates and the mineral composition in the hydrated cement solid phase, including the incongruent dissolution of CSH gel phases and congruent dissolution of Ca(OH) 2 , Ettringite and Hydrotalcite. Experimental results of dissolution of Ca-O-H and Ca-Si-O-H phases were well predicted by this model. (author)

  4. Radionuclide and metal sorption on cement and concrete

    CERN Document Server

    Ochs, Michael; Wang, Lian

    2016-01-01

    Cementitious materials are being widely used as solidification/stabilisation and barrier materials for a variety of chemical and radioactive wastes, primarily due to their favourable retention properties for metals, radionuclides and other contaminants. The retention properties result from various mineral phases in hydrated cement that possess a high density and diversity of reactive sites for the fixation of contaminants through a variety of sorption and incorporation reactions. This book presents a state of the art review and critical evaluation of the type and magnitude of the various sorption and incorporation processes in hydrated cement systems for twenty-five elements relevant for a broad range of radioactive and industrial wastes. Effects of cement evolution or ageing on sorption/incorporation processes are explicitly evaluated and quantified. While the immobilisation of contaminants by mixing-in during hydration is not explicitly addressed, the underlying chemical processes are similar. A quantitativ...

  5. Solidification of metallic aluminum on magnesium phosphate cements

    International Nuclear Information System (INIS)

    Lahalle, Hugo

    2016-01-01

    This work deals with the stabilization/solidification of radioactive waste using cement. More particularly, it aims at assessing the chemical compatibility between metallic aluminum and mortars based on magnesium phosphate cement. The physical and chemical processes leading to setting and hardening of the cement are first investigated. X-ray diffraction (XRD), thermogravimetry (TGA) and nuclear magnetic resonance spectroscopy ("3"1P and "1"1B MAS-NMR) are first used to characterize the solid phases formed during hydration, while inductively coupled plasma atomic emission spectroscopy analysis (ICP-AES), electrical conductometry and pH measurements provide information on the pore solution composition. Then, the corrosion of metallic aluminum in magnesium phosphate mortars is studied by monitoring the equilibrium potential and by electrochemical impedance spectroscopy (EIS). Magnesium phosphate cement is prepared from a mix of magnesium oxide (MgO) and potassium dihydrogen orthophosphate (KH_2PO_4). In the presence of water, hydration occurs according to a dissolution - precipitation process. The main hydrate is K-struvite (MgKPO_4.6H_2O). Its precipitation is preceded by that of two transient phases: phosphorrosslerite (MgHPO_4.7H_2O) and Mg_2KH(PO_4)_2.15H_2O. Boric acid retards cement hydration by delaying the formation of cement hydrates. Two processes may be involved in this retardation: the initial precipitation of amorphous or poorly crystallized minerals containing boron and phosphorus atoms, and/or the stabilization of cations (Mg"2"+, K"+) in solution. As compared with a Portland cement-based matrix, corrosion of aluminum is strongly limited in magnesium phosphate mortar. The pore solution pH is close to neutrality and falls within the passivation domain of aluminum. Corrosion depends on several parameters: it is promoted by a water-to-cement ratio (w/c) significantly higher than the chemical water demand of cement (w/c = 0.51), and by the addition of boric

  6. Immobilisation of heavy metal in cement-based solidification/stabilisation: A review

    International Nuclear Information System (INIS)

    Chen, Q.Y.; Tyrer, M.; Hills, C.D.; Yang, X.M.; Carey, P.

    2009-01-01

    Heavy metal-bearing waste usually needs solidification/stabilization (s/s) prior to landfill to lower the leaching rate. Cement is the most adaptable binder currently available for the immobilisation of heavy metals. The selection of cements and operating parameters depends upon an understanding of chemistry of the system. This paper discusses interactions of heavy metals and cement phases in the solidification/stabilisation process. It provides a clarification of heavy metal effects on cement hydration. According to the decomposition rate of minerals, heavy metals accelerate the hydration of tricalcium silicate (C 3 S) and Portland cement, although they retard the precipitation of portlandite due to the reduction of pH resulted from hydrolyses of heavy metal ions. The chemical mechanism relevant to the accelerating effect of heavy metals is considered to be H + attacks on cement phases and the precipitation of calcium heavy metal double hydroxides, which consumes calcium ions and then promotes the decomposition of C 3 S. In this work, molecular models of calcium silicate hydrate gel are presented based on the examination of 29 Si solid-state magic angle spinning/nuclear magnetic resonance (MAS/NMR). This paper also reviews immobilisation mechanisms of heavy metals in hydrated cement matrices, focusing on the sorption, precipitation and chemical incorporation of cement hydration products. It is concluded that further research on the phase development during cement hydration in the presence of heavy metals and thermodynamic modelling is needed to improve effectiveness of cement-based s/s and extend this waste management technique

  7. In vitro tensile strength of luting cements on metallic substrate.

    Science.gov (United States)

    Orsi, Iara A; Varoli, Fernando K; Pieroni, Carlos H P; Ferreira, Marly C C G; Borie, Eduardo

    2014-01-01

    The aim of this study was to determine the tensile strength of crowns cemented on metallic substrate with four different types of luting agents. Twenty human maxillary molars with similar diameters were selected and prepared to receive metallic core castings (Cu-Al). After cementation and preparation the cores were measured and the area of crown's portion was calculated. The teeth were divided into four groups based on the luting agent used to cement the crowns: zinc phosphate cement; glass ionomer cement; resin cement Rely X; and resin cement Panavia F. The teeth with the crowns cemented were subjected to thermocycling and later to the tensile strength test using universal testing machine with a load cell of 200 kgf and a crosshead speed of 0.5 mm/min. The load required to dislodge the crowns was recorded and converted to MPa/mm(2). Data were subjected to Kruskal-Wallis analysis with a significance level of 1%. Panavia F showed significantly higher retention in core casts (3.067 MPa/mm(2)), when compared with the other cements. Rely X showed a mean retention value of 1.877 MPa/mm(2) and the zinc phosphate cement with 1.155 MPa/mm(2). Glass ionomer cement (0.884 MPa/mm(2)) exhibited the lowest tensile strength value. Crowns cemented with Panavia F on cast metallic posts and cores presented higher tensile strength. The glass ionomer cement showed the lowest tensile strength among all the cements studied.

  8. 21 CFR 888.3550 - Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint patellofemorotibial polymer/metal/metal... § 888.3550 Knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis. (a) Identification. A knee joint patellofemorotibial polymer/metal/metal constrained cemented prosthesis is a device...

  9. Analysis of Chemical Composition of Portland Cement in Ghana: A Key to Understand the Behavior of Cement

    OpenAIRE

    Bediako, Mark; Amankwah, Eric Opoku

    2015-01-01

    The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC) and Portland limestone cement (PLC), CSIR-BRRI Pozzomix, Dangote OPC, a...

  10. Characteristics of Cement Solidification of Metal Hydroxide Waste

    Directory of Open Access Journals (Sweden)

    Dae-Seo Koo

    2017-02-01

    Full Text Available To perform the permanent disposal of metal hydroxide waste from electro-kinetic decontamination, it is necessary to secure the technology for its solidification. The integrity tests on the fabricated solidification should also meet the criteria of the Korea Radioactive Waste Agency. We carried out the solidification of metal hydroxide waste using cement solidification. The integrity tests such as the compressive strength, immersion, leach, and irradiation tests on the fabricated cement solidifications were performed. It was also confirmed that these requirements of the criteria of Korea Radioactive Waste Agency on these cement solidifications were met. The microstructures of all the cement solidifications were analyzed and discussed.

  11. Characteristics of cement solidification of metal hydroxide waste

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Dae Seo; Sung, Hyun Hee; Kim, Seung Soo; Kim, Gye Nam; Choi, Jong Won [Dept. of Decontemination Decommission Technology Development, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-02-15

    To perform the permanent disposal of metal hydroxide waste from electro-kinetic decontamination, it is necessary to secure the technology for its solidification. The integrity tests on the fabricated solidification should also meet the criteria of the Korea Radioactive Waste Agency. We carried out the solidification of metal hydroxide waste using cement solidification. The integrity tests such as the compressive strength, immersion, leach, and irradiation tests on the fabricated cement solidifications were performed. It was also confirmed that these requirements of the criteria of Korea Radioactive Waste Agency on these cement solidifications were met. The microstructures of all the cement solidifications were analyzed and discussed.

  12. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different......Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

  13. Retention of metal-ceramic crowns with contemporary dental cements.

    Science.gov (United States)

    Johnson, Glen H; Lepe, Xavier; Zhang, Hai; Wataha, John C

    2009-09-01

    New types of crown and bridge cement are in use by practitioners, and independent studies are needed to assess their effectiveness. The authors conducted a study in three parts (study A, study B, and study C) and to determine how well these new cements retain metal-ceramic crowns. The authors prepared teeth with a 20-degree taper and a 4-millimeter length. They cast high-noble metal-ceramic copings, then fitted and cemented them with a force of 196 newtons. The types of cements they used were zinc phosphate, resin-modified glass ionomer, conventional resin and self-adhesive modified resin. They thermally cycled the cemented copings, then removed them. They recorded the removal force and calculated the stress of dislodgment by using the surface area of each preparation. They used a single-factor analysis of variance to analyze the data (alpha = .05). The mean stresses necessary to remove crowns, in megapascals, were 8.0 for RelyX Luting (3M ESPE, St. Paul, Minn.), 7.3 for RelyX Unicem (3M ESPE), 5.7 for Panavia F (Kuraray America, New York) and 4.0 for Fuji Plus (GC America, Alsip, Ill.) in study A; 8.1 for RelyX Luting, 2.6 for RelyX Luting Plus (3M ESPE) and 2.8 for Fuji CEM (GC America) in study B; and 4.9 for Maxcem (Kerr, Orange, Calif.), 4.0 for BisCem (Bisco, Schaumburg, Ill.), 3.7 for RelyX Unicem Clicker (3M ESPE), 2.9 for iCEM (Heraeus Kulzer, Armonk, N.Y.) and 2.3 for Fleck's Zinc Cement (Keystone Industries, Cherry Hill, N.J.) in study C. Powder-liquid versions of new cements were significantly more retentive than were paste-paste versions of the same cements. The mean value of crown removal stress for the new self-adhesive modified-resin cements varied appreciably among the four cements tested. All cements retained castings as well as or better than did zinc phosphate cement. Powder-liquid versions of cements, although less convenient to mix, may be a better clinical choice when crown retention is an issue. All cements tested will retain castings

  14. Cement for oil well developed from ordinary cement: characterization physical, chemical and mineralogical

    International Nuclear Information System (INIS)

    Oliveira, D.N.S.; Neves, G. de A.; Chaves, A.C.; Mendonca, A.M.G.D.; Lima, M.S. de; Bezerra, U.T.

    2012-01-01

    This work aims to characterize a new type of cement produced from the mixture of ordinary Portland cement, which can be used as an option in the cementing of oil wells. To enable this work we used the method of lineal programming for the new cement composition, then conducted tests to characterize through particle size analysis by laser diffraction, chemical analysis by EDX, TGA, X-ray diffraction, time grip, resistance to compression. The overall result showed that the new cement had made low-C3A, takes more time to the CPP, thermal stability up to 500 ° C, the kinetics of hydration and low levels of major components consistent with the specifications of ABNT. (author)

  15. Characterization and chemical activity of Portland cement and two experimental cements with potential for use in dentistry.

    Science.gov (United States)

    Camilleri, J

    2008-09-01

    To evaluate the chemical activity of Portland cement and two other cement types with similar chemical composition to mineral trioxide aggregate with the aim of developing these cements for further applications in dentistry. The chemical composition of the three cement types namely Portland cement, calcium sulpho-aluminate cement and calcium fluoro-aluminate cement was evaluated by elemental analysis using energy dispersive analysis with X-ray under the scanning electron microscope and by X-ray diffraction analysis (XRD) to determine the phases. The constituents of the hydration reaction by-products were evaluated by XRD analysis of the set cements at 1, 7, 28 and 56 days and by analysis of the leachate by ion chromatography. The pH of both cements and leachate was determined at different time intervals. Cements admixed with micro-silica were also tested to determine the effect of micro-silica on the reaction by-products. All three cement types were composed of tricalcium silicate as the main constituent phase. The hydration reaction of Portland cement produced calcium hydroxide. However, this was not present in the other cements tested at all ages. Admixed micro-silica had little or no effect on the cements with regard to reaction by-products. The pH of all cements tested was alkaline. Both the experimental calcium sulpho-aluminate cement and calcium fluoro-aluminate cement had different hydration reactions to that of Portland cement even though calcium silicate was the major constituent element of both cement types. No calcium hydroxide was produced as a by-product to cement hydration. Micro-silica addition to the cement had no effect on the hydration reaction.

  16. Radiation effects on metals, alloys and cement

    International Nuclear Information System (INIS)

    Lucki, G.; Sciani, V.

    1988-12-01

    High - energy particle irradiation of materials brings as a consequence changes in their atomic structures that alter the electrical, magnetic and mechanical properties which are the most important characteristics for practical applications of metals and alloys. A review is made on experimental results of in-pile (IEA-RI reactor) and CV-28 cyclotron irradiated materials. Resistivity measurements on CuPd and FeNi alloys showed different behaviour during fast neutron irradiation. While CuPd had almost coincidental relaxation curves, FeNi presented a distinguishable short and long-range ordering with the critical order-disorder temperature at 515 0 C. Vacancy supersaturation curves of FeNiSi (49-49-2 at %), FeNiCr (49-95-49, 95-0,1 at. %), FeNiMo (50-50 at.% + 50 ppm) and pure FeNi (50-50 at.%), determined by means of the Magnetic After Effect are presented as an effective pre-selection method of nuclear materials before the destructive stage of void formation and swelling. A displacement of damage peak from 480 to 500 and 570 0 C was detected on pure AISI 321 stainless steel and with 0,05 wt.% and 0,10 wt.% of Nb additions by means of resistivity and micro-hardness. Ultrasound techniques applied to fast neutron irradiated portland cement paste (fluence 7,2 x 10 18 n/cm 2 ) showed a 24% decrease in its dynamic elasticity modulus. Helium diffusion on Au, Ag and Al foils irradiated in cyclotron was studied, suggesting a vacancy mechanism for single He atom diffusion. Embrittlement by Alpha particle implantation in cyclotron to simulate in-pile (n,α) reaction-was measured by high temperature creep on AISI 316 stainles steel. (author) [pt

  17. A Study of Metal-Cement Composites with Additives

    Directory of Open Access Journals (Sweden)

    Mironov Victor

    2014-12-01

    Full Text Available The application of small-sized metal fillers (SMF provides a combination of high bulk density, increased durability and ferromagnetic properties of composite materials on the cement basis. However, the total strength of the composite can be compromised by poor adhesion of metal particles with the cement matrix. The use of versatile additives like microsilica and metakaolin is able to improve the structural integrity and mechanical properties of heavy concretes. The paper considers the results of a study using specimens of heavy concretes with SMF aiming to estimate its strength, structural features and ultrasonic parameters. It was found that the contact of SMF particles with the cement was not perfect, since the voids appeared between them and the cement matrix during the cement hydration process (exothermal reaction. Due to the border porosity, the specimens with the metal fillers have lower compressive strength, lower ultrasound velocity and increased frequency slope of attenuation. Microsilica and metakaolin additives facilitate better contact zone between the cement matrix and metal fillers.

  18. Elution behavior of heavy metals from cement solidified products of incinerated ash waste - 59102

    International Nuclear Information System (INIS)

    Meguro, Yoshihiro; Kawato, Yoshimi; Nakayama, Takuya; Tomioka, Osamu; Mitsuda, Motoyuki

    2012-01-01

    A method, in which incinerated ash is solidified with a cement material, has been developed to dispose radioactive incinerated ash waste. In order to bury the solidified product, it is required that elution of hazardous heavy metals included in the ash from the solidified products is inhibited. In this study, the elution behavior of the heavy metals from the synthetic solidified products, which included Pb(II), Cd(II), and Cr(VI) and were prepared using ordinary portland cement (OPC), blast furnace slag cement (BFS), or a cement material that showed low alkalinity (LA-Cement), was investigated. Several chemicals and materials were added as additive agents to prevent the elution of the heavy metals. When OPC was used, Cd elution was inhibited, but Pb and Cr were not enough even using the additive agent examined. FeSO 4 and Na 2 S additive agents worked effective to inhibit elution of Cr. When BFS was used, the elution of Pb, Cd and Cr was inhibited for the all products prepared. In the case of LA-Cement, the elution of Pb and Cd was inhibited for the all products, but only the product that was added FeSO 4 showed good result of the elution of Cr. (authors)

  19. Properties of cemented carbides alloyed by metal melt treatment

    International Nuclear Information System (INIS)

    Lisovsky, A.F.

    2001-01-01

    The paper presents the results of investigations into the influence of alloying elements introduced by metal melt treatment (MMT-process) on properties of WC-Co and WC-Ni cemented carbides. Transition metals of the IV - VIll groups (Ti, Zr, Ta, Cr, Re, Ni) and silicon were used as alloying elements. It is shown that the MMT-process allows cemented carbides to be produced whose physico-mechanical properties (bending strength, fracture toughness, total deformation, total work of deformation and fatigue fracture toughness) are superior to those of cemented carbides produced following a traditional powder metallurgy (PM) process. The main mechanism and peculiarities of the influence of alloying elements added by the MMT-process on properties of cemented carbides have been first established. The effect of alloying elements on structure and substructure of phases has been analyzed. (author)

  20. 3.4. Chemical additives and granulometric composition influence on soils armed by cement

    International Nuclear Information System (INIS)

    Saidov, D.Kh.

    2011-01-01

    Purpose of this work was to evaluate an influence of various chemical additives on soils armed by portland cement. Experimental research of kinetics of soil cements structure formation after adding the chemicals was carried out. According to the investigations it was determined that structure formation process of soil cements depended on granulometric composition of armed soil, cement quantity, type and quantity of chemical additives.

  1. Chloride Ingress in Chemically Activated Calcined Clay-Based Cement

    Directory of Open Access Journals (Sweden)

    Joseph Mwiti Marangu

    2018-01-01

    Full Text Available Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800°C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na2SO4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC, and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients (Dapp were estimated from solutions to Fick’s second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of Dapp, compared to OPC, PPC, and nonactivated PCC35.

  2. Sustainable Blended Cements-Influences of Packing Density on Cement Paste Chemical Efficiency.

    Science.gov (United States)

    Knop, Yaniv; Peled, Alva

    2018-04-18

    This paper addresses the development of blended cements with reduced clinker amount by partial replacement of the clinker with more environmentally-friendly material (e.g., limestone powders). This development can lead to more sustainable cements with reduced greenhouse gas emission and energy consumption during their production. The reduced clicker content was based on improved particle packing density and surface area of the cement powder by using three different limestone particle diameters: smaller (7 µm, 3 µm) or larger (70 µm, 53 µm) than the clinker particles, or having a similar size (23 µm). The effects of the different limestone particle sizes on the chemical reactivity of the blended cement were studied by X-ray diffraction (XRD), thermogravimetry and differential thermogravimetry (TG/DTG), loss on ignition (LOI), isothermal calorimetry, and the water demand for reaching normal consistency. It was found that by blending the original cement with limestone, the hydration process and the reactivity of the limestone itself were increased by the increased surface area of the limestone particles. However, the carbonation reaction was decreased with the increased packing density of the blended cement with limestone, having various sizes.

  3. Statistical study of chemical additives effects in the waste cementation

    International Nuclear Information System (INIS)

    Tello, Cledola C.O. de; Diniz, Paula S.; Haucz, Maria J.A.

    1997-01-01

    This paper presents the statistical study, that was carried out to analyse the chemical additives effect in the waste cementation process. Three different additives from two industries were tested: set accelerator, set retarder and super plasticizers, in cemented pates with and without bentonite. The experiments were planned in accordance with the 2 3 factorial design, so that the effect of each type of additive, its quantity and manufacturer in cemented paste and specimens could be evaluated. The results showed that the use of these can improve the cementation process and the product. The admixture quantity and the association with bentonite were the most important factors affecting the process and product characteristics. (author). 4 refs., 9 figs., 4 tabs

  4. 21 CFR 888.3320 - Hip joint metal/metal semi-constrained, with a cemented acetabular component, prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal/metal semi-constrained, with a... Devices § 888.3320 Hip joint metal/metal semi-constrained, with a cemented acetabular component, prosthesis. (a) Identification. A hip joint metal/metal semi-constrained, with a cemented acetabular...

  5. 21 CFR 888.3360 - Hip joint femoral (hemi-hip) metallic cemented or uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint femoral (hemi-hip) metallic cemented or... Hip joint femoral (hemi-hip) metallic cemented or uncemented prosthesis. (a) Identification. A hip joint femoral (hemi-hip) metallic cemented or uncemented prosthesis is a device intended to be implanted...

  6. Effects of complexing compounds on sorption of metal ions to cement

    Energy Technology Data Exchange (ETDEWEB)

    Loevgren, Lars [Umeaa Univ. (Sweden). Inorganic chemistry

    2005-12-15

    This present report is a literature review addressing the effects of complexing ligands on the sorption of radionuclides to solid materials of importance for repositories of radioactive waste. Focus is put on laboratory studies of metal ion adsorption to cement in presence of chelating agents under strongly alkaline conditions. As background information, metal sorption to different mineral and cement phases in ligand free systems is described. Furthermore, surface complexation model (SCM) theories are introduced. According to surface complexation theories these interactions occur at specific binding sites at the particle/water interface. Adsorption of cationic metals is stronger at high pH, and the adsorption of anions occurs preferentially at low pH. The adsorption of ions to mineral surfaces is a result of both chemical bonding and electrostatic attraction between the ions and charged mineral surfaces. By combining uptake data with spectroscopic information the sorption can be explained on a molecular level by structurally sound surface complexation models. Most of the metal sorption studies reviewed are dealing with minerals exhibiting oxygen atoms at their surfaces, mainly oxides of Fe(II,III) and Al(III), and aluminosilicates. Investigations of radionuclides are focused on clay minerals, above all montmorillonite and illite. Which mechanism that is governing the metal ion adsorption to a given mineral is to a large extent depending on the metal adsorbed. For instance, sorption of Ni to montmorillonite can occur by formation of inner-sphere mononuclear surface complexes located at the edges of montmorillonite platelets and by formation of a Ni phyllosilicate phase parallel to montmorillonite layers. Also metal uptake to cement materials can occur by different mechanisms. Cationic metals can both be attached to cement (calcium silicate hydrate, CSH) and hardened cement paste (HCP) by formation of inner-sphere complexes at specific surface sites and by

  7. Study of commercial chemical additives for cementation of radioactive waste

    International Nuclear Information System (INIS)

    Mota Vieira, V.; Oliveira, C.C. de

    2015-01-01

    In this research it has been studied the effects of chemical additives (admixtures) in the cementation process of radioactive wastes, which are used to improve the properties of waste cementation process, both of the paste and of the solidified product. However there are a large variety of these materials that are frequently changed or taken out of the market, then it is essential to know the commercially available materials and their effects. The tests were carried out with a solution simulating the evaporator concentrate waste coming from PWR nuclear reactors. It was cemented using two formulations, A and B, incorporating higher or lower amount of waste, respectively. It was added chemical admixtures from two manufacturers (S and H), which were: accelerators, set retarders and superplasticizers. The experiments were organized by a factorial design 23. The measured parameters were the viscosity, the setting time, the paste and product density and the compressive strength. In this study we performed comparative analyzes of the results of compressive strength at age of 28 and 90 days and between the densities of the samples at the same ages. The compressive strength test at age of 28 days is considered a parameter essential issues related to security handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented product, but presented lower values density products. (authors)

  8. Corrosion of metal containers containing cemented radioactive wastes

    International Nuclear Information System (INIS)

    Duffo, G.S.; Farina, S.B.; Schulz, F.M.; Marotta, F

    2010-01-01

    Nuclear activities generate different kinds of radioactive wastes. In the case of Argentina, wastes classified as low and medium level are conditioned in metal drums for final disposal in a repository whose design is based on the use of multiple and independent barriers. Nuclear energy plants generate a large volume of mid-level radioactive wastes, consisting mainly of ion-exchange resins contaminated by fission products. Other contaminated products such as gloves, papers, clothing, rubber and plastic tubing, can be incinerated and the ashes from the combustion also constitute wastes that must be disposed of. These wastes (resins and ashes) must be immobilized in order to avoid the release of radionuclides into the environment. The wastes usually undergo a process of cementing to immobilize them. This work aims to systematically study the process of degradation by corrosion of the steel drums in contact with the cemented resins and with the ashes cemented with the addition of different types and concentrations of aggressive compounds (chloride and sulfate). The specimens are configured so that the parameters of interest for the steel in contact with the cemented materials can be measured. The variables of corrosion potential, electric resistivity of the matrix and polarization resistance (PR) were monitored and show that the presence of chloride increases the susceptibility to corrosion of the drum steel that is in contact with the cement resin matrix

  9. Influence of Temporary Cements on the Bond Strength of Self-Adhesive Cement to the Metal Coronal Substrate.

    Science.gov (United States)

    Peixoto, Raniel Fernandes; De Aguiar, Caio Rocha; Jacob, Eduardo Santana; Macedo, Ana Paula; De Mattos, Maria da Gloria Chiarello; Antunes, Rossana Pereira de Almeida

    2015-01-01

    This research evaluated the influence of temporary cements (eugenol-containing [EC] or eugenol-free [EF]) on the tensile strength of Ni-Cr copings fixed with self-adhesive resin cement to the metal coronal substrate. Thirty-six temporary crowns were divided into 4 groups (n=9) according to the temporary cements: Provy, Dentsply (eugenol-containing), Temp Cem, Vigodent (eugenol-containing), RelyX Temp NE, 3M ESPE (eugenol-free) and Temp Bond NE, Kerr Corp (eugenol-free). After 24 h of temporary cementation, tensile strength tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min and 1 kN (100 kgf) load cell. Afterwards, the cast metal cores were cleaned by scraping with curettes and air jet. Thirty-six Ni-Cr copings were cemented to the cast metal cores with self-adhesive resin cement (RelyX U200, 3M ESPE). Tensile strength tests were performed again. In the temporary cementation, Temp Bond NE (12.91 ± 2.54) and Temp Cem (12.22 ± 2.96) presented the highest values of tensile strength and were statistically similar to each other (p>0.05). Statistically significant difference (pcementation of Ni-Cr copings with self-adhesive resin cement. In addition, Temp Cem (120.68 ± 48.27) and RelyX Temp NE (103.04 ± 26.09) showed intermediate tensile strength values. In conclusion, the Provy eugenol-containing temporary cement was associated with the highest bond strength among the resin cements when Ni-Cr copings were cemented to cast metal cores. However, the eugenol cannot be considered a determining factor in increased bond strength, since the other tested cements (1 eugenol-containing and 2 eugenol-free) were similar.

  10. Particulate metallic debris in cemented total hip arthroplasty.

    Science.gov (United States)

    Salvati, E A; Betts, F; Doty, S B

    1993-08-01

    Several studies conducted by the authors in the last six years demonstrate that the generation of metallic debris is more severe with titanium alloy than with cobalt-chrome alloy femoral components in cemented total hip arthroplasty (THA). The debris is generated from the articulating surface, particularly if entrapped acrylic debris produces three-body wear, and from the stem surface when the component loosens and abrades against fragmented cement. In selected cases in which the titanium metallic debris is copious, premature failure and severe progressive bone loss occurs. Electron microscopy demonstrates that the particles of metallic debris can be extremely small (a few hundredths of 1 micron). They are phagocytized by the macrophages and transported to the phagolysosomes. In this highly corrosive environment, the very high surface area of the particles may release toxic concentrations of the constituents of the alloy intracellularly, probably leading to progressive cell degeneration and death, with subsequent release of intracellular enzymes and ingested metallic debris. This cycle most likely repeats itself, leading to tissue necrosis. The results presented do not support the use of titanium alloy femoral components for cemented THA, particularly for the articulating surface.

  11. Longevity of metal-ceramic crowns cemented with self-adhesive resin cement: a prospective clinical study

    Directory of Open Access Journals (Sweden)

    Lucas Pradebon BRONDANI

    2017-04-01

    Full Text Available Abstract Resin cements are often used for single crown cementation due to their physical properties. Self-adhesive resin cements gained widespread due to their simplified technique compared to regular resin cement. However, there is lacking clinical evidence about the long-term behavior of this material. The aim of this prospective clinical trial was to assess the survival rates of metal-ceramic crowns cemented with self-adhesive resin cement up to six years. One hundred and twenty-nine subjects received 152 metal-ceramic crowns. The cementation procedures were standardized and performed by previously trained operators. The crowns were assessed as to primary outcome (debonding and FDI criteria. Statistical analysis was performed using Kaplan-Meier statistics and descriptive analysis. Three failures occurred (debonding, resulting in a 97.6% survival rate. FDI criteria assessment resulted in scores 1 and 2 (acceptable clinical evaluation for all surviving crowns. The use of self-adhesive resin cement is a feasible alternative for metal-ceramic crowns cementation, achieving high and adequate survival rates.

  12. Longevity of metal-ceramic crowns cemented with self-adhesive resin cement: a prospective clinical study

    Science.gov (United States)

    Brondani, Lucas Pradebon; Pereira-Cenci, Tatiana; Wandsher, Vinicius Felipe; Pereira, Gabriel Kalil; Valandro, Luis Felipe; Bergoli, César Dalmolin

    2017-04-10

    Resin cements are often used for single crown cementation due to their physical properties. Self-adhesive resin cements gained widespread due to their simplified technique compared to regular resin cement. However, there is lacking clinical evidence about the long-term behavior of this material. The aim of this prospective clinical trial was to assess the survival rates of metal-ceramic crowns cemented with self-adhesive resin cement up to six years. One hundred and twenty-nine subjects received 152 metal-ceramic crowns. The cementation procedures were standardized and performed by previously trained operators. The crowns were assessed as to primary outcome (debonding) and FDI criteria. Statistical analysis was performed using Kaplan-Meier statistics and descriptive analysis. Three failures occurred (debonding), resulting in a 97.6% survival rate. FDI criteria assessment resulted in scores 1 and 2 (acceptable clinical evaluation) for all surviving crowns. The use of self-adhesive resin cement is a feasible alternative for metal-ceramic crowns cementation, achieving high and adequate survival rates.

  13. 21 CFR 888.3350 - Hip joint metal/polymer semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal/polymer semi-constrained cemented... HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3350 Hip joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. A hip joint metal/polymer semi...

  14. 21 CFR 888.3300 - Hip joint metal constrained cemented or uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal constrained cemented or uncemented... HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3300 Hip joint metal constrained cemented or uncemented prosthesis. (a) Identification. A hip joint metal constrained...

  15. 21 CFR 888.3530 - Knee joint femorotibial metal/polymer semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/polymer semi... § 888.3530 Knee joint femorotibial metal/polymer semi-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer semi-constrained cemented prosthesis is a device intended...

  16. 21 CFR 888.3540 - Knee joint patellofemoral polymer/metal semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint patellofemoral polymer/metal semi... § 888.3540 Knee joint patellofemoral polymer/metal semi-constrained cemented prosthesis. (a) Identification. A knee joint patellofemoral polymer/metal semi-constrained cemented prosthesis is a two-part...

  17. 21 CFR 888.3500 - Knee joint femorotibial metal/composite semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/composite semi... § 888.3500 Knee joint femorotibial metal/composite semi-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite semi-constrained cemented prosthesis is a two-part...

  18. 21 CFR 888.3520 - Knee joint femorotibial metal/polymer non-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/polymer non... § 888.3520 Knee joint femorotibial metal/polymer non-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/polymer non-constrained cemented prosthesis is a device intended to...

  19. 21 CFR 888.3490 - Knee joint femorotibial metal/composite non-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/composite non... § 888.3490 Knee joint femorotibial metal/composite non-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite non-constrained cemented prosthesis is a device...

  20. 21 CFR 888.3110 - Ankle joint metal/polymer semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ankle joint metal/polymer semi-constrained... Ankle joint metal/polymer semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer semi-constrained cemented prosthesis is a device intended to be implanted to replace an ankle...

  1. 21 CFR 888.3120 - Ankle joint metal/polymer non-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ankle joint metal/polymer non-constrained cemented... HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3120 Ankle joint metal/polymer non-constrained cemented prosthesis. (a) Identification. An ankle joint metal/polymer non...

  2. A Review of Metal Injection Molding- Process, Optimization, Defects and Microwave Sintering on WC-Co Cemented Carbide

    Science.gov (United States)

    Shahbudin, S. N. A.; Othman, M. H.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

    2017-08-01

    This article is about a review of optimization of metal injection molding and microwave sintering process on tungsten cemented carbide produce by metal injection molding process. In this study, the process parameters for the metal injection molding were optimized using Taguchi method. Taguchi methods have been used widely in engineering analysis to optimize the performance characteristics through the setting of design parameters. Microwave sintering is a process generally being used in powder metallurgy over the conventional method. It has typical characteristics such as accelerated heating rate, shortened processing cycle, high energy efficiency, fine and homogeneous microstructure, and enhanced mechanical performance, which is beneficial to prepare nanostructured cemented carbides in metal injection molding. Besides that, with an advanced and promising technology, metal injection molding has proven that can produce cemented carbides. Cemented tungsten carbide hard metal has been used widely in various applications due to its desirable combination of mechanical, physical, and chemical properties. Moreover, areas of study include common defects in metal injection molding and application of microwave sintering itself has been discussed in this paper.

  3. Chemical decontamination of metals

    International Nuclear Information System (INIS)

    Partridge, J.A.; Lerch, R.E.

    1979-10-01

    A metal decontamination process based upon removal of contamination by treatment with a cerium (IV)-nitric acid solution (or other redox agent in nitric acid) is feasible and highly promising. The technique is effective in dissolving the surface layer of stainless steel. Dissolution rates of approximately 1.5 mils/h were demonstrated with cerium (IV)-nitric acid solutions. Removal of plutonium contamination from stainless steel was demonstrated in laboratory tests, in which activity levels were reduced from greater than 5 x 10 5 counts per minute to nondetectable levels in approximately one hour at 90 0 C. Removal of paint from stainless steel surfaces was also demonstrated. Advantages of this process over other chemical solutions include: (1) The solutions are not high salt systems; therefore, there is potentially less waste generated. (2) Cerium(IV) in nitric acid is a good dissolution agent for plutonium oxide. (3) Regeneration of Ce(IV) during the decontamination is accomplished by electrolysis. (4) The process should be effective for irregularly shaped equipment. (5) It could be effective as a spray or a flow-through system. 13 figures

  4. Sulfur polymer cement encapsulation of RCRA toxic metals and metal oxides

    International Nuclear Information System (INIS)

    Calhoun, C.L. Jr.; Nulf, L.E.; Gorin, A.H.

    1995-06-01

    A study was conducted to determine the suitability of Sulfur Polymer Cement (SPC) encapsulation technology for the stabilization of RCRA toxic metal and metal oxide wastes. In a series of bench-scale experiments, the effects of sodium sulfide additions to the waste mixture, residence time, and temperature profile were evaluated. In addition, an effort was made to ascertain the degree to which SPC affords chemical stabilization as opposed to physical encapsulation. Experimental results have demonstrated that at the 25 wt % loading level, SPC can effectively immobilize Cr, Cr 2 O 3 , Hg, Pb, and Se to levels below regulatory limits. SPC encapsulation also has been shown to significantly reduce the leachability of other toxic compounds including PbO, PbO 2 , As 2 O 3 , BaO, and CdO. In addition, data has confirmed sulfide conversion of Hg, Pb, PbO, PbO 2 , and BaO as the product of their reaction with SPC

  5. Synthesis and characterisation of pack cemented aluminide coatings on metals

    International Nuclear Information System (INIS)

    Houngninou, C.; Chevalier, S.; Larpin, J.P.

    2004-01-01

    The exposition of metallic materials to high temperature environments leads to their corrosion because of oxidation or sulphidation. One way to protect such materials is to produce an Al 2 O 3 layer which needs to be continuous enough to limit diffusion of oxygen or metallic elements, and withstand this corrosion. Since a few years, it has been proved that aluminide compounds are one of the most effective materials to achieve this goal. Indeed, they possess sufficient Al and many beneficial mechanical properties when exposed to high temperature conditions to make possible the formation of a protective Al 2 O 3 scale. This study is aimed at the elaboration of iron, nickel and molybdenum aluminides by modification of the surface of the base materials by a pack cementation process. The as-cemented alloys were analysed by means of SEM coupled with EDX and by XRD. Cross-section examinations showed, in each case, a progressive diffusion of aluminium through the substrates. The diffusion thickness layer was more or less important depending on the base material and on the coating conditions

  6. 21 CFR 888.3370 - Hip joint (hemi-hip) acetabular metal cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint (hemi-hip) acetabular metal cemented... HUMAN SERVICES (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Prosthetic Devices § 888.3370 Hip joint (hemi-hip) acetabular metal cemented prosthesis. (a) Identification. A hip joint (hemi-hip) acetabular...

  7. 21 CFR 888.3310 - Hip joint metal/polymer constrained cemented or uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal/polymer constrained cemented or... Hip joint metal/polymer constrained cemented or uncemented prosthesis. (a) Identification. A hip joint... replace a hip joint. The device prevents dislocation in more than one anatomic plane and has components...

  8. Marginal Fit of Metal-Ceramic Copings: Effect of Luting Cements and Tooth Preparation Design.

    Science.gov (United States)

    de Almeida, Juliana Gomes Dos Santos Paes; Guedes, Carlos Gramani; Abi-Rached, Filipe de Oliveira; Trindade, Flávia Zardo; Fonseca, Renata Garcia

    2017-12-22

    To evaluate the effect of the triad finish line design, axial wall convergence angle, and luting cement on the marginal fit of metal copings used in metal-ceramic crowns. Schematic dies and their respective copings were cast in NiCr alloy. The dies exhibited the following finish line/convergence angle combinations: sloping shoulder/6°, sloping shoulder/20°, shoulder/6°, shoulder/20°. Marginal fit was evaluated under a stereomicroscope, before and after cementation. Copings were air-abraded with 50 μm Al 2 O 3 particles and cemented with Cimento de Zinco, RelyX U100, or Panavia F cements (n = 10/group). Data were square-root transformed and analyzed by 3-way factorial random effect model and Tukey's post hoc test (α = 0.05). Statistical analysis showed significance for the interactions finish line and convergence angle (p marginal discrepancy when compared to the other finish line/convergence angle combinations, which were statistically similar among each other. For both convergence angles and for all luting cements, the marginal discrepancy was significantly higher after cementation. Before and after cementation, 6° provided better marginal fit than 20°. After cementation, Panavia F provided higher marginal discrepancy than Cimento de Zinco. Lower convergence angle combined with shoulder and a low-consistency luting cement is preferable to cement metal copings. © 2017 by the American College of Prosthodontists.

  9. Chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement.

    Science.gov (United States)

    Hwang, Yun-Chan; Kim, Do-Hee; Hwang, In-Nam; Song, Sun-Ju; Park, Yeong-Joon; Koh, Jeong-Tae; Son, Ho-Hyun; Oh, Won-Mann

    2011-01-01

    An experimental Portland cement was manufactured with pure raw materials under controlled laboratory conditions. The aim of this study was to compare the chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement with those of mineral trioxide aggregate (MTA) and Portland cement. The composition of the cements was determined by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDAX). The setting time and compressive strength were tested. The biocompatibility was evaluated by using SEM and XTT assay. SEM and EDAX revealed the experimental Portland cement to have a similar composition to Portland cement. The setting time of the experimental Portland cement was significantly shorter than that of MTA and Portland cement. The compressive strength of the experimental Portland cement was lower than that of MTA and Portland cement. The experimental Portland cement showed a similar biocompatibility to MTA. The experimental Portland cement might be considered as a possible substitute for MTA in clinical usage after further testing. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  10. The role of chemical admixtures in the formation of the structure of cement stone

    Directory of Open Access Journals (Sweden)

    Sopov Viktor

    2017-01-01

    Full Text Available The influence of sulfates and carbonates of potassium and sodium on the character of the formation of the microstructure of cement stone was studied. The role of cations in the structure formation of cement stone is shown. The efficiency of chemical additives, hardening accelerators, was estimated from the ratio of the volumes of gel and capillary micropores. The ratio of gel and capillary pores allows to determine the efficiency coefficient of the action of chemical additives. It is shown that the potassium carbonate for Portland cement is the most effective additive for hardening in terms of microstructure modification, and potassium sulfate for slag Portland cement.

  11. Wide-scale utilization of MSWI fly ashes in cement production and its impact on average heavy metal contents in cements: The case of Austria.

    Science.gov (United States)

    Lederer, Jakob; Trinkel, Verena; Fellner, Johann

    2017-02-01

    A number of studies present the utilization of fly ashes from municipal solid waste incineration (MSWI) in cement production as a recycling alternative to landfilling. While there is a lot of research on the impact of MSWI fly ashes utilization in cement production on the quality of concrete or the leaching of heavy metals, only a few studies have determined the resulting heavy metal content in cements caused by this MSWI fly ashes utilization. Making use of the case of Austria, this study (1) determines the total content of selected heavy metals in cements currently produced in the country, (2) designs a scenario and calculates the resulting heavy metal contents in cements assuming that all MSWI fly ashes from Austrian grate incinerators were used as secondary raw materials for Portland cement clinker production and (3) evaluates the legal recyclability of demolished concretes produced from MSWI fly ash amended cements based on their total heavy metal contents. To do so, data from literature and statistics are combined in a material flow analysis model to calculate the average total contents of heavy metals in cements and in the resulting concretes according to the above scenario. The resulting heavy metal contents are then compared (i) to their respective limit values for cements as defined in a new technical guideline in Austria (BMLFUW, 2016), and (ii) to their respective limit values for recycling materials from demolished concrete. Results show that MSWI fly ashes utilization increases the raw material input in cement production by only +0.9%, but the total contents of Cd by +310%, and Hg, Pb, and Zn by +70% to +170%. However these and other heavy metal contents are still below their respective limit values for Austrian cements. The same legal conformity counts for recycling material derived from concretes produced from the MSWI fly ash cements. However, if the MSWI fly ash ratio in all raw materials used for cement production were increased from 0.9% to 22

  12. The effect of chemically adjusting cement compositions on leachabilities of waste ions

    International Nuclear Information System (INIS)

    Barnes, M.W.; Scheetz, B.E.; Roy, D.M.

    1986-01-01

    The chemical composition of both portland and aluminate cements was adjusted by adding amorphous silica. In the case of portland cement, the object was to react with excess portlandite and obtain an overall composition compatible with C-S-H gel or C-S-H gel + silica at low temperatures, and to obtain the tobermorite composition in order to be in equilibrium with this phase at temperatures above normal ambient. In the case of aluminate cement, the object was to be in equilibrium with more silica-rich phases. These silica-adjusted cements were used to make composites with nuclear waste forms. Leach tests showed that the silica-adjusted composites were chemically more stable than those made with as-received cement. Leach rates were lower in the case of the adjusted cements for Rb, Cs, Ca, Sr, Ba, La, Ce, Nd, Gd, Al, and Si. Only Na in the case of both portland and aluminate cements, and Mg and U in the case of aluminate cements, had greater leach rates in adjusted cements. Adjusting the composition of cements with silica is concluded to be beneficial when making composites to encapsulate nuclear waste forms

  13. Evaluation of physical stability and leachability of Portland Pozzolona Cement (PPC) solidified chemical sludge generated from textile wastewater treatment plants

    International Nuclear Information System (INIS)

    Patel, Hema; Pandey, Suneel

    2012-01-01

    Highlights: ► Stabilization/solidification of chemical sludge from textile wastewater treatment plants using Portland Pozzolona Cement (PPC) containing fly ash. ► Physical engineering (compressive strength and block density) indicates that sludge has potential to be reused for construction purpose after stabilization/solidification. ► Leaching of heavy metals from stabilized/solidified materials were within stipulated limits. ► There is a modification of microstructural properties of PPC with sludge addition as indicated by XRD and SEM patterns. - Abstract: The chemical sludge generated from the treatment of textile dyeing wastewater is a hazardous waste as per Indian Hazardous Waste Management rules. In this paper, stabilization/solidification of chemical sludge was carried out to explore its reuse potential in the construction materials. Portland Pozzolona Cement (PPC) was selected as the binder system which is commercially available cement with 10–25% fly ash interground in it. The stabilized/solidified blocks were evaluated in terms of unconfined compressive strength, block density and leaching of heavy metals. The compressive strength (3.62–33.62 MPa) and block density (1222.17–1688.72 kg/m 3 ) values as well as the negligible leaching of heavy metals from the stabilized/solidified blocks indicate that there is a potential of its use for structural and non-structural applications.

  14. The effect of portland cement for solidification of soils contaminated by mine tailings containing heavy metals

    Science.gov (United States)

    Jian-Jun, Chen; Zheng-Miao, Xie

    2010-05-01

    Portland cement(PC) was used to solidify the lead-zinc mine tailings contaminated soils(CS) in this work. The soils were heavily polluted by heavy metals with lead(up to 19592 mg/kg), zinc(up to 647mg/kg), Cd(up to 14.65mg.kg) and Cu(up to 287mg/kg). Solidified/stabilized(s/s)forms with a range of cement contents, 40-90 wt%, were evaluated to determine the optimal binder content. Unconfined compression strength test(UCS), Chinese solid waste-extraction procedure for leaching toxicity - Horizontal vibration method, toxicity characteristic leaching procedures(TCLP) were used for physical and chemical characterization of the s/s forms. The procedure of Tessier et al.(1979) was used to separate S/S forms Pb, Zn, Cd, Cu into different fractions. The results show that addition of 50% cement was enough for the s/s forms to satisfy the MU10 requirements (0.10 MPa). Under the 50% addition, the content of the water-exchangeable fraction of Pb reduced from 2.25% to 0.2%, the carbonate-bound fraction and organic-bound fraction reduced by about half, while the Fe-Mn oxide-bound fraction was more than doubled. The residual fraction decreased 8% on the contrary. For Zn, except for the carbonate-bound fraction increased slightly, the features of other items were same as that of Pb. For Cd, the water-exchangeable fraction was reduced largely, the residual fraction and Fe-Mn oxide-bound fraction increased 2-3%. For Cu, A distinct feature is the organic-bound fraction reduced with the reduction in consumption of cement, at the same time, the residual fraction increased corresponding. Leaching test results indicate that the leaching contents of Pb2+ of the six specimens are quite different at low pH value(

  15. Chemical and physical properties of bone cement for vertebroplasty

    Directory of Open Access Journals (Sweden)

    Po-Liang Lai

    2013-08-01

    Full Text Available Vertebral compression fracture is the most common complication of osteoporosis. It may result in persistent severe pain and limited mobility, and significantly impacts the quality of life. Vertebroplasty involves a percutaneous injection of bone cement into the collapsed vertebrae by fluorescent guide. The most commonly used bone cement in percutaneous vertebroplasty is based on the polymerization of methylmethacrylate monomers to polymethylmethacrylate (PMMA polymers. However, information on the properties of bone cement is mostly published in the biomaterial sciences literature, a source with which the clinical community is generally unfamiliar. This review focuses on the chemistry of bone cement polymerization and the physical properties of PMMA. The effects of altering the portions and contents of monomer liquid and polymer powders on the setting time, polymerization temperature, and compressive strength of the cement are also discussed. This information will allow spine surgeons to manipulate bone cement characteristics for specific clinical applications and improve safety.

  16. Assessing Metal Exposures in a Community near a Cement Plant in the Northeast U.S.

    OpenAIRE

    Zhao Dong; Michael S. Bank; John D. Spengler

    2015-01-01

    Cement production is a major source of metals and metalloids in the environment, while exposures to metals and metalloids may impact human health in the surrounding communities. We recruited 185 participants living in the vicinity of a cement plant in the northeast U.S., and measured the levels of aluminum (Al), arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and selenium (Se) in blood and Hg in hair samples from them. A questionnaire was used to assess potential sources of Hg exposure...

  17. 21 CFR 888.3340 - Hip joint metal/composite semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal/composite semi-constrained... Hip joint metal/composite semi-constrained cemented prosthesis. (a) Identification. A hip joint metal... hip joint. The device limits translation and rotation in one or more planes via the geometry of its...

  18. Analyses of heavy metals in mineral trioxide aggregate and Portland cement.

    Science.gov (United States)

    Schembri, Matthew; Peplow, George; Camilleri, Josette

    2010-07-01

    Portland cement is used in the construction industry as a binder in concrete. It is manufactured from chalk, limestone, and clay, which are clinkered at very high temperatures and ground with gypsum to form Portland cement. The raw materials and the manufacturing process can result in the inclusion of heavy metals in Portland cement. Portland cement with a four to one addition of bismuth oxide is marketed as mineral trioxide aggregate (MTA), which is used mainly as a dental material. Heavy metal inclusion can be of concern because MTA is in contact with hard and soft tissues. Measurements of arsenic, lead, and chromium in hydrated gray and white Portland cement, ProRoot MTA, and MTA Angelus were conducted with graphite furnace atomic absorption spectrophotometry after acid digestion on the hydrated material. The leaching of the metal ions from the solid material in water and simulated body fluid (SBF) was also determined. All cement types showed high relative values of leached chromium compared with arsenic and lead in both the total metal content and leached species. The gray Portland cement showed the highest total amount of metal. The white Portland and both MTAs had lower values for all the leached metal ions. Both MTAs released more arsenic than the amount specified in ISO 9917-1 (2007). Portland cements and MTAs showed evidence of heavy metals in the acid-soluble form as well as leaching in deionized water and SBF. MTA contained levels of arsenic higher than the safe limit specified by the ISO 9917-1 (2007). Copyright 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  19. Nickel speciation in cement-stabilized/solidified metal treatment filtercakes

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Amitava, E-mail: reroy@lsu.edu [J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, LA 70806, USA (United States); Stegemann, Julia A., E-mail: j.stegemann@ucl.ac.uk [Centre for Resource Efficiency & the Environment, Department of Civil, Environmental & Geomatic Engineering, University College London, Chadwick Building, Gower Street, London WC1E 6BT, UK (United Kingdom)

    2017-01-05

    Highlights: • XAS shows the same Ni speciation in untreated and stabilized/solidified filtercake. • Ni solubility is the same for untreated and stabilized/solidified filtercake. • Leaching is controlled by pH and physical encapsulation for all binders. - Abstract: Cement-based stabilization/solidification (S/S) is used to decrease environmental leaching of contaminants from industrial wastes. In this study, two industrial metal treatment filtercakes were characterized by X-ray diffractometry (XRD), thermogravimetric and differential thermogravimetric analysis (TG/DTG) and Fourier transform infrared (FTIR); speciation of nickel was examined by X-ray absorption (XAS) spectroscopy. Although the degree of carbonation and crystallinity of the two untreated filtercakes differed, α-nickel hydroxide was identified as the primary nickel-containing phase by XRD and nickel K edge XAS. XAS showed that the speciation of nickel in the filtercake was unaltered by treatment with any of five different S/S binder systems. Nickel leaching from the untreated filtercakes and all their stabilized/solidified products, as a function of pH in the acid neutralization capacity test, was essentially complete below pH ∼5, but was 3–4 orders of magnitude lower at pH 8–12. S/S does not respeciate nickel from metal treatment filtercakes and any reduction of nickel leaching by S/S is attributable to pH control and physical mechanisms only. pH-dependent leaching of Cr, Cu and Ni is similar for the wastes and s/s products, except that availability of Cr, Cu and Zn at decreased pH is reduced in matrices containing ground granulated blast furnace slag.

  20. Cermet cements.

    Science.gov (United States)

    McLean, J W

    1990-01-01

    Cermet ionomer cements are sintered metal/glass powders, which can be made to react with poly(acids). These new cements are significantly more resistant to abrasion than regular glass ionomer cements and are widely accepted as core build-up materials and lining cements. They can strengthen teeth and provide the clinician with an opportunity to treat early dental caries.

  1. 21 CFR 888.3390 - Hip joint femoral (hemi-hip) metal/polymer cemented or uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint femoral (hemi-hip) metal/polymer... § 888.3390 Hip joint femoral (hemi-hip) metal/polymer cemented or uncemented prosthesis. (a) Identification. A hip joint femoral (hemi-hip) metal/polymer cemented or uncemented prosthesis is a two-part...

  2. 21 CFR 888.3510 - Knee joint femorotibial metal/polymer constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/polymer constrained... Knee joint femorotibial metal/polymer constrained cemented prosthesis. (a) Identification. A knee joint... of a knee joint. The device limits translation or rotation in one or more planes and has components...

  3. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ankle joint metal/composite semi-constrained... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint... ankle joint. The device limits translation and rotation: in one or more planes via the geometry of its...

  4. Physical and chemical durability of cement impregnated epoxy resin

    International Nuclear Information System (INIS)

    Suryantoro

    1997-01-01

    Immobilization of simulation radioactive waste contains Cs and Sr with cement impregnated epoxy resin has been done. Low level liquid waste in 30% weight mixed cement homogeneously and then set in its curing time about 28 days. Waste from was impregnated with epoxy resin (Bisphenol-A-diglycidylether) and use Triethylenteramin as catalyst. the sample of cement impregnated epoxy resin 2.5 cm x 2.5 cm in diameter and length was tested by Paul Weber. The compressive strength was obtained of 4.08 kN.cm - 2. The sochxlet apparatus was run on flow rate of 300 ml/hour at 100 o C and during 24 hours. The leaching rate of Cs was round on 5.5 x 10 - 4 g.cm - 2.d - 1 and Sr was 6.1 x 10 - 4 g.cm - 2.d - 1 (author)

  5. Chemical composition, radiopacity, and biocompatibility of Portland cement with bismuth oxide.

    Science.gov (United States)

    Hwang, Yun-Chan; Lee, Song-Hee; Hwang, In-Nam; Kang, In-Chol; Kim, Min-Seok; Kim, Sun-Hun; Son, Ho-Hyun; Oh, Won-Mann

    2009-03-01

    This study compared the chemical constitution, radiopacity, and biocompatibility of Portland cement containing bismuth oxide (experimental cement) with those of Portland cement and mineral trioxide aggregate (MTA). The chemical constitution of materials was determined by scanning electron microscopy and energy-dispersive X-ray analysis. The radiopacity of the materials was determined using the ISO/6876 method. The biocompatibility of the materials was tested by MTT assay and tissue reaction. The constitution of all materials was similar. However, the Portland cement and experimental cement were more irregular and had a larger particle size than MTA. The radiopacity of the experimental cement was similar to MTA. The MTT assay revealed MTA to have slightly higher cell viability than the other materials. However, there were no statistically significant differences between the materials, with the exception of MTA at 24 h. There was no significant difference in the tissue reaction between the experimental groups. These results suggest that the experimental cement may be used as a substitute for MTA.

  6. Study of chemical additives in the cementation of radioactive waste of PWR reactors

    International Nuclear Information System (INIS)

    Vieira, Vanessa Mota; Tello, Cledola Cassia Oliveira de

    2011-01-01

    Cementation is a very useful process to solidify radioactive wastes. Depending on the waste it can be necessary to use of chemical additives (admixtures) to improve the cementation process and its product. Admixtures are materials, other than cement, aggregate and water, that are added either before or during the mixing to alter some properties, such as workability, curing temperature range, and setting time. However there are a large variety of these materials that are frequently changed or taken out of the market. In this changeable scenario it is essential to know the commercially available materials and their characteristics. In this research the effects of chemical admixtures in the solidification process has been studied. For the tests it was prepared a solution simulating the evaporator concentrate waste, cemented by two different formulations, and three chemical admixtures from two manufacturers. The tested admixtures were accelerators, set retarders and super plasticizers. The experiments were organized by a planning factorial 23 to quantify the effects of formulations, of the admixtures, its quantity and manufacturer in properties of the paste and products. The measured parameters were the density, the viscosity and the setting time of the paste, and the product compressive strength. The parameter evaluated in this study was the compressive strength at age of 28 days, is considered essential security issues relating to the handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented products. (author)

  7. Assessing Metal Exposures in a Community near a Cement Plant in the Northeast U.S.

    Directory of Open Access Journals (Sweden)

    Zhao Dong

    2015-01-01

    Full Text Available Cement production is a major source of metals and metalloids in the environment, while exposures to metals and metalloids may impact human health in the surrounding communities. We recruited 185 participants living in the vicinity of a cement plant in the northeast U.S., and measured the levels of aluminum (Al, arsenic (As, cadmium (Cd, lead (Pb, mercury (Hg, and selenium (Se in blood and Hg in hair samples from them. A questionnaire was used to assess potential sources of Hg exposure. Multivariate regressions and spatial analyses were performed to evaluate the relative importance of different routes of exposures. The metal concentrations in blood or hair samples of our study participants were comparable to the U.S. general or regional population. Smoking contributed significantly to Cd and Pb exposures, and seafood consumption contributed significantly to Hg and As exposures, while variables related to the cement plant were not significantly associated with metal concentrations. Our results suggest that our study population was not at elevated health risk due to metal exposures, and that the contribution of the cement plant to metal exposures in the surrounding community was minimal.

  8. Leaching of heavy metals from cementitious composites made of new ternary cements

    Science.gov (United States)

    Kuterasińska-Warwas, Justyna; Król, Anna

    2017-10-01

    The paper presents a comparison of research methods concerning the leaching of harmful substances (selected heavy metal cations ie. Pb, Cu, Zn and Cr) and their degree of immobilization in cement matrices. The new types of ternary cements were used in the study, where a large proportion of cement clinker was replaced by other non-clinker components - industrial wastes, ie. siliceous fly ash from power industry and granulated blast furnace slag from the iron and steel industry. In studied cementitious binders also ground limestone was used, which is a widely available raw material. The aim of research is determining the suitability of new cements for neutralizing harmful substances in the obtained matrices. The application of two research methods in accordance with EN 12457-4 and NEN 7275 intends to reflection of changing environmental conditions whom composite materials may actually undergo during their exploitation or storing on landfills. The results show that cements with high addition of non-clinker components are suitable for stabilization of toxic substances and the obtained cement matrices retain a high degree of immobilization of heavy metals at the level of 99%.

  9. Development of a Zero-Cement Binder Using Slag, Fly Ash, and Rice Husk Ash with Chemical Activator

    Directory of Open Access Journals (Sweden)

    M. R. Karim

    2015-01-01

    Full Text Available The increasing demand and consumption of cement have necessitated the use of slag, fly ash, rice husk ash (RHA, and so forth as a supplement of cement in concrete construction. The aim of the study is to develop a zero-cement binder (Z-Cem using slag, fly ash, and RHA combined with chemical activator. NaOH, Ca(OH2, and KOH were used in varying weights and molar concentrations. Z-Cem was tested for its consistency, setting time, flow, compressive strength, XRD, SEM, and FTIR. The consistency and setting time of the Z-Cem paste increase with increasing RHA content. The Z-Cem mortar requires more superplasticizer to maintain a constant flow of 110±5% compared with OPC. The compressive strength of the Z-Cem mortar is significantly influenced by the amounts, types, and molar concentration of the activators. The Z-Cem mortar achieves a compressive strength of 42–44 MPa at 28 days with 5% NaOH or at 2.5 molar concentrations. The FTIR results reveal that molecules in the Z-Cem mortar have a silica-hydrate (Si-H bond with sodium or other inorganic metals (i.e., sodium/calcium-silica-hydrate-alumina gel. Therefore, Z-Cem could be developed using the aforementioned materials with the chemical activator.

  10. 21 CFR 888.3380 - Hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint femoral (hemi-hip) trunnion-bearing... Devices § 888.3380 Hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis. (a) Identification. A hip joint femoral (hemi-hip) trunnion-bearing metal/polyacetal cemented prosthesis is a two...

  11. Influence of chemical composition of civil construction waste in the cement paste

    International Nuclear Information System (INIS)

    Cunha, G.A.; Andrade, A.C.D.; Souza, J.M.M.; Evangelista, A.C.J.; Almeida, V.C.

    2009-01-01

    The construction and demolition waste when disposed inappropriately might cause serious public health problems. Its reutilization focusing on the development of new products using simple production techniques, assuring a new product life cycle and not damaging the environment is inserted in sustainable concept. The aim of this work was identifying the characteristics of types of waste generated in a residential reform (glassy ceramic and fill dirt leftovers) verifying separately its influence on cement pastes mechanical behavior. Cement pastes + wastes were prepared in 25% and 50% proportions with an approximately 0,35 water/cement relation and, glue time determination, water absorption, resistance to compression and X-ray fluorescence assays were taken. The results indicate that the chemical composition of the waste causes changes in the behavior of cement pastes, reflecting on their resistance to compression. (author)

  12. A simulator study of adverse wear with metal and cement debris contamination in metal-on-metal hip bearings.

    Science.gov (United States)

    Halim, T; Clarke, I C; Burgett-Moreno, M D; Donaldson, T K; Savisaar, C; Bowsher, J G

    2014-03-01

    Third-body wear is believed to be one trigger for adverse results with metal-on-metal (MOM) bearings. Impingement and subluxation may release metal particles from MOM replacements. We therefore challenged MOM bearings with relevant debris types of cobalt-chrome alloy (CoCr), titanium alloy (Ti6Al4V) and polymethylmethacrylate bone cement (PMMA). Cement flakes (PMMA), CoCr and Ti6Al4V particles (size range 5 µm to 400 µm) were run in a MOM wear simulation. Debris allotments (5 mg) were inserted at ten intervals during the five million cycle (5 Mc) test. In a clean test phase (0 Mc to 0.8 Mc), lubricants retained their yellow colour. Addition of metal particles at 0.8 Mc turned lubricants black within the first hour of the test and remained so for the duration, while PMMA particles did not change the colour of the lubricant. Rates of wear with PMMA, CoCr and Ti6Al4V debris averaged 0.3 mm(3)/Mc, 4.1 mm(3)/Mc and 6.4 mm(3)/Mc, respectively. Metal particles turned simulator lubricants black with rates of wear of MOM bearings an order of magnitude higher than with control PMMA particles. This appeared to model the findings of black, periarticular joint tissues and high CoCr wear in failed MOM replacements. The amount of wear debris produced during a 500 000-cycle interval of gait was 30 to 50 times greater than the weight of triggering particle allotment, indicating that MOM bearings were extremely sensitive to third-body wear. Cite this article: Bone Joint Res 2015;4:29-37. ©2015 The British Editorial Society of Bone & Joint Surgery.

  13. Modelling of chemical evolution of low pH cements at long term

    International Nuclear Information System (INIS)

    El Bitouri, Y.; Buffo-Lacarriere, L.; Sellier, A.; Bourbon, X.

    2015-01-01

    In the context of the underground radioactive waste repository, low-pH cements were developed to reduce interactions between concrete and clay barrier. These cements contain high proportions of mineral additions like silica fume, fly ash or blast furnace slag for example. The high ratio of cement replacement by pozzolanic additions allows to reduce the pH by a global reduction of Ca/Si ratio of the hydrates (according to the one observed on CEM I pastes). In order to predict the short term development of the hydration for each component of this cement, a multiphasic hydration model, previously developed, is used. The model predicts the evolution of hydration degree of each anhydrous phase and consequently the quantity of each hydrate in paste (CH, aluminates, CSH with different Ca/Si ratios). However, this model is not suitable to determine the long term mineralogical and chemical evolution of the material, due to the internal change induced by chemical imbalance between initial hydrates. In order to evaluate the chemical characteristics of low pH cement based materials, and thus assess its chemical stability in the context of radioactive waste storage, a complementary model of chemical evolution at long term is proposed. This original model is based on 'solid-solution' principles. It assumes that the microdiffusion of calcium plays a major role to explain how the different Ca/Si ratio of initial C-S-H tends together toward a medium stabilized value. The main mechanisms and full development of the model equations are presented first. Next, a comparison of the model with experimental data issue from EDS (Energy Dispersive X-ray Spectroscopy) analysis on low pH cement allows to test the model. (authors)

  14. Study of chemical additives in the cementation of radioactive waste of PWR reactors

    International Nuclear Information System (INIS)

    Vieira, Vanessa Mota; Tello, Cledola Cassia Oliveira de

    2012-01-01

    In this research it has been studied the effects of chemical admixtures in the cementation process of radioactive wastes. These additives are used to improve the properties of waste cementation process, both of the paste and of the solidified product. However there are a large variety of these materials that are frequently changed or taken out of the market. Then it is essential to know the commercially available materials and their effects. The tests were carried out with a solution simulating the evaporator concentrate waste coming from PWR nuclear reactors. It was cemented using two formulations, A and B, incorporating higher or lower amount of waste, respectively. It was added chemical admixtures from two manufacturers (S and H), which were: accelerators, set retarders and superplasticizers. The experiments were organized by a factorial design 23. The measured parameters were: the viscosity, the setting time, the paste and product density and the compressive strength. The parameter evaluated in this study was the compressive strength at age of 28 days, is considered essential security issues relating to the handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented products. (author)

  15. Chemical composition influence of cement based mortars on algal biofouling

    Science.gov (United States)

    Estelle, Dalod; Alexandre, Govin; Philippe, Grosseau; Christine, Lors; René, Guyonnet; Denis, Damidot

    2013-04-01

    The main cause of building-facade biodegradation is the growth of microorganisms. This phenomenon depends on several parameters such as the geographical situation, the environmental conditions and the surface state of the substrate. Several researches have been devoted to the study of the effect of porosity and roughness on the biofouling of stones and mortars. However, none of them have addressed the influence of the mortar chemistry on the microorganism growth kinetic. The main objective of this study is to highlight the influence of the mortar chemistry in relationship with its physical properties on biological weathering. Earlier work showed a good resistance of Calcium Aluminate Cements to biodeterioration by acidogenic bacteria (Thiobacillus) and fungi (Alternaria alternata, Aspergillus Niger and Coniosporium uncinatum). In order to characterize the influence of the mortar chemistry on biofouling, two Portland cements and two alumina cements are used. Among micro-organisms able to grow, green algae are most involved in the aesthetic deterioration of facades. Indeed, they can colonize any type of media and can be a source of nutrients for other micro-organisms such as fungi. The green algae Klebsormidium flaccidum is chosen because of its representativeness. It is indeed the species the most frequently identified and isolated from samples taken on sites. The biofouling kinetic is followed on samples exposed outdoor and on samples tested in a laboratory bench which consists in spraying an algae culture on mortar specimens. The results obtained by in situ trials are compared with the results obtained on the laboratory bench. The microorganism growth kinetic is measured by image analysis. To improve the detection of algae on the surface of the cementitious samples, the raw image is converted in the YIQ color space. Y, I and Q correspond respectively to luminance, in-phase, and quadrature. On the Q channel, the areas covered by algae and the areas of clean mortar

  16. Analysis of metal contents in Portland Type V and MTA-based cements.

    Science.gov (United States)

    Dorileo, Maura Cristiane Gonçales Orçati; Bandeca, Matheus Coelho; Pedro, Fábio Luis Miranda; Volpato, Luiz Evaristo Ricci; Guedes, Orlando Aguirre; Dalla Villa, Ricardo; Tonetto, Mateus Rodrigues; Borges, Alvaro Henrique

    2014-01-01

    The aim of this study was to determine, by Atomic Absorption Spectrometry (AAS), the concentration levels of 11 metals in Type V gray and structural white PC, ProRoot MTA, and MTA Bio. Samples, containing one gram of each tested cement, were prepared and transferred to a 100 mL Teflon tube with a mixture of 7.0 mL of nitric acid and 21 mL of hydrochloric acid. After the reaction, the mixture was filtered and then volumed to 50 mL of distilled water. For each metal, specific patterns were determined from universal standards. Arsenic quantification was performed by hydride generator. The analysis was performed five times and the data were statistically analyzed at 5% level of significance. Only the cadmium presented concentration levels of values lower than the quantification limit of the device. The AAS analysis showed increased levels of calcium, nickel, and zinc in structural white PC. Type V PC presented the greatest concentration levels of arsenic, chromium, copper, iron, lead, and manganese (P cements, and the lowest concentration levels were observed in Portland cements, while the highest were observed in ProRoot MTA. Both PC and MTA-based cements showed evidence of metals inclusion.

  17. Radiation chemical treatment of cement mortar - polymer composites

    International Nuclear Information System (INIS)

    Younes, M.M.

    1994-01-01

    The development of the hardened cement pastes,mortars and concretes which contain polymers has progressed rapidly in years. Developmental work has identified a number of applications where the high strength and excellent durability of the composite materials will provide definite advantages over conventional mortars and concretes. The first investigations of polymer - impregnated concrete tried mainly to increase the quantity of absorbed and polymerised monomer because this gave a greater decrease in the original of concrete and a subsequent improvement in physico - mechanical properties. However, the production costs which is due mainly to the organic polymer, becomes the most important item. In this respect recent research showed the possibility of obtaining with a very compact concrete, of relative low porosity, a compound material with high performances after impregnation 26 tabs.,28 figs.,109 refs

  18. Physical and chemical characterization of pastes of bone cements with ZrO2

    International Nuclear Information System (INIS)

    Quinto H, A.; Pina B, M.C.

    2003-01-01

    Setting times and temperature of sixteen calcium phosphate cements added with ZrO 2 were evaluated. Their behaviors were analysed to be used like injectable formulations in surgery of bone. Two cements of calcium phosphates enriched with ZrO 2 with the best characteristics in setting times and temperature, were mechanically tested after 1 and 7 days of prepared. Density was determined using a pycnometer, chemical composition was determined by X-ray diffraction and the molecular structure was determined by infrared spectroscopy. (Author)

  19. Assessment of Pollution Potentialities of some Portland Cement ...

    African Journals Online (AJOL)

    Chemical analysis of some Portland cement commonly used in Nigeria was carried out. All the cement studies were found to be good for concrete work especially where no special property is required. The concentration levels of heavy metals in all the cement samples were above the tolerance limit and therefore need to ...

  20. Coupling between cracking and chemical degradation in cement based materials: characterisation and modelling

    International Nuclear Information System (INIS)

    Tognazzi, C.

    1998-01-01

    The aim of this work is to study the durability of concretes used for radioactive waste storage. It has already been shown that the concrete degradation during a storage phenomenon is due to the attack of the cement barrier by the water of the host rock, at ambient temperature. The modelling of this chemical degradation is now validated for un-cracked materials. However, a concrete preexisting crack can exist. In this work, has then been particularly studied the influence of a crack on the long term chemical degradation. The studies have been carried out on a mortar cracked mechanically (in compression or traction) and chemically degraded by leaching (reference degradation) and by accelerated degradations (with ammonium nitrate or under electric field). The diffusion properties have been measured at each step of the experiment. They have been confronted with transfer models. Results have revealed the existence of a coupling between the preexisting crack and the chemical degradation. At last, a modelling of the chemical degradation for cement materials has been proposed and validated both for pure cement and for mortars, in the cases of simple leaching and of leaching with ammonium nitrate. Its application to cracked materials by a microscopic approach (crack described in the lattice) has allowed to specify the interpretation of the experimental results. (O.M.)

  1. Structural-chemical characteristics of implanted metals

    International Nuclear Information System (INIS)

    Kozejkin, B.V.; Pavlov, P.V.; Pitirimova, E.A.; Frolov, A.I.

    1988-01-01

    Corrosion and structural characteristics of metallic layers implanted by ions of chemically active impurities and noble gases are studied. Dependence of experimental results on parameters of initial materials and technological conditions of implantation is established. In studying corrosion characteristics of implanted metals a strong dependence of chemical passivation effect on technological conditions of ion-implantation and structure of initial material is stated. On the basis of developed mathematical model of chemical passivation effect it is shown that increase of corrosion characteristics of implanted metals is defined by superposition of surface and volumetric mechanisms

  2. Waiting Time for Coronal Preparation and the Influence of Different Cements on Tensile Strength of Metal Posts

    Directory of Open Access Journals (Sweden)

    Ilione Kruschewsky Costa Sousa Oliveira

    2012-01-01

    Full Text Available This study aimed to assess the effect of post-cementation waiting time for core preparation of cemented cast posts and cores had on retention in the root canal, using two different luting materials. Sixty extracted human canines were sectioned 16 mm from the root apex. After cast nickel-chromium metal posts and cores were fabricated and luted with zinc phosphate (ZP cement or resin cement (RC, the specimens were divided into 3 groups (n = 10 according to the waiting time for core preparation: no preparation (control, 15 minutes, or 1 week after the core cementation. At the appropriate time, the specimens were subjected to a tensile load test (0.5 mm/min until failure. Two-way ANOVA (time versus cement and the Tukey tests (P < 0.05 showed significantly higher (P < 0.05 tensile strength values for the ZP cement groups than for the RC groups. Core preparation and post-cementation waiting time for core recontouring did not influence the retention strength. ZP was the best material for intraradicular metal post cementation.

  3. Chemical processes causing cementation in heat-affected smectite - the Kinnekulle bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Pusch, R. [Geodevelopment AB, Lund (Sweden); Takase, Hiroyasu; Benbow, S. [Quantisci Ltd., Oxfordshire (United Kingdom)

    1998-12-01

    Numerical calculation of silica migration and precipitation that can cause cementation of smectite buffer clay has been made using the Grindrod/Takase chemical model. It is used here to investigate whether the silicification of the bentonite and surrounding sediments at Kinnekulle, southwestern Sweden, can be explained by the heat pulse caused by the diabase intrusion that took place in Permian time. Compilation of data concerning silica cementation and associated microstructural and rheological changes showed that significant silica precipitation should have occurred in the Kinnekulle case and this is also documented. Thus, precipitation of quartz has taken place to an extent that can be explained by the chemical model, which also showed conversion of smectite to illite by neoformation of the latter mineral but only for the 3000 years long heating period. Introduction of a criterion for non-reversible illitization is hence a necessary improvement of the model for explaining the actual presence of neoformed illite, which may in fact be wholly or partly responsible for the cementation. (The report is made up of two articles: `Cementation processes in smectite clay associated with conversion of smectite to illite as exemplified by the Kinnekulle bentonites` and `Nonisothermal modelling of geochemical evolution in the Kinnekulle bentonite layer. Mathematical modelling and simulation`) 33 refs, 40 figs.

  4. Chemical processes causing cementation in heat-affected smectite - the Kinnekulle bentonite

    International Nuclear Information System (INIS)

    Pusch, R.; Takase, Hiroyasu; Benbow, S.

    1998-12-01

    Numerical calculation of silica migration and precipitation that can cause cementation of smectite buffer clay has been made using the Grindrod/Takase chemical model. It is used here to investigate whether the silicification of the bentonite and surrounding sediments at Kinnekulle, southwestern Sweden, can be explained by the heat pulse caused by the diabase intrusion that took place in Permian time. Compilation of data concerning silica cementation and associated microstructural and rheological changes showed that significant silica precipitation should have occurred in the Kinnekulle case and this is also documented. Thus, precipitation of quartz has taken place to an extent that can be explained by the chemical model, which also showed conversion of smectite to illite by neoformation of the latter mineral but only for the 3000 years long heating period. Introduction of a criterion for non-reversible illitization is hence a necessary improvement of the model for explaining the actual presence of neoformed illite, which may in fact be wholly or partly responsible for the cementation. (The report is made up of two articles: 'Cementation processes in smectite clay associated with conversion of smectite to illite as exemplified by the Kinnekulle bentonites' and 'Nonisothermal modelling of geochemical evolution in the Kinnekulle bentonite layer. Mathematical modelling and simulation')

  5. Pore size distribution, strength, and microstructure of portland cement paste containing metal hydroxide waste

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Z.A.; Mahmud, H.; Shaaban, M.G.

    1996-12-31

    Stabilization/solidification of hazardous wastes is used to convert hazardous metal hydroxide waste sludge into a solid mass with better handling properties. This study investigated the pore size development of ordinary portland cement pastes containing metal hydroxide waste sludge and rice husk ash using mercury intrusion porosimetry. The effects of acre and the addition of rice husk ash on pore size development and strength were studied. It was found that the pore structures of mixes changed significantly with curing acre. The pore size shifted from 1,204 to 324 {angstrom} for 3-day old cement paste, and from 956 to 263 {angstrom} for a 7-day old sample. A reduction in pore size distribution for different curing ages was also observed in the other mixtures. From this limited study, no conclusion could be made as to any correlation between strength development and porosity. 10 refs., 6 figs., 3 tabs.

  6. Fracture resistance of metal-free composite crowns-effects of fiber reinforcement, thermal cycling, and cementation technique.

    Science.gov (United States)

    Lehmann, Franziska; Eickemeyer, Grit; Rammelsberg, Peter

    2004-09-01

    The improved mechanical properties of contemporary composites have resulted in their extensive use for the restoration of posterior teeth. However, the influence of fiber reinforcement, cementation technique, and physical stress on the fracture resistance of metal-free crowns is unknown. This in vitro study evaluated the effect of fiber reinforcement, physical stress, and cementation methods on the fracture resistance of posterior metal-free Sinfony crowns. Ninety-six extracted human third molars received a standardized tooth preparation: 0.5-mm chamfer preparation and occlusal reduction of 1.3 to 1.5 mm. Sinfony (nonreinforced crowns, n=48) and Sinfony-Vectris (reinforced crowns, n=48) crowns restoring original tooth contour were prepared. Twenty-four specimens of each crown type were cemented, using either glass ionomer cement (GIC) or resin cement. Thirty-two crowns (one third) were stored in humidity for 48 hours. Another third was exposed to 10,000 thermal cycles (TC) between 5 degrees C and 55 degrees C. The remaining third was treated with thermal cycling and mechanical loading (TCML), consisting of 1.2 million axial loads of 50 N. The artificial crowns were then vertically loaded with a steel sphere until failure occurred. Significant differences in fracture resistance (N) between experimental groups were assessed by nonparametric Mann-Whitney U-test (alpha=.05). Fifty percent of the Sinfony and Sinfony-Vectris crowns cemented with glass ionomer cement loosened after thermal cycling. Thermal cycling resulted in a significant reduction in the mean fracture resistance for Sinfony crowns cemented with GIC, from 2037 N to 1282 N (P=.004). Additional fatigue produced no further effects. Fiber reinforcement significantly increased fracture resistance, from 1555 N to 2326 N (P=.001). The minimal fracture resistance was above 600 N for all combinations of material, cement and loading. Fracture resistance of metal-free Sinfony crowns was significantly increased by

  7. Additional chemical polymerization of dual resin cements: reality or a goal to be achieved?

    Directory of Open Access Journals (Sweden)

    Luzia Sakaguti UMETSUBO

    Full Text Available Abstract Introduction This study serves as a warning to dentists and researchers that dual-cured resin cements may not polymerize completely under some prosthetic crowns. Objective The aim of this study was to analyse the polymerization degree of dual-cured resin cements under prosthetic barrier, by microhardness test. Material and method Three cements (Bistite II, RelyX ARC and Variolink II were light-cured through different barriers, placed between the cement and the light source: G1: without barrier; G2: composite resin (Cesead; G3: Inceram alumina; G4: IPS Empress; G5: Inceram zirconia; G6: tooth fragment. Photopolymerization was carried out using a halogen light unit (650 mW/cm2; microhardness was evaluated using the Microhardness Tester FM 700, under a load of 50gf with a dwell time of 15s, at two evaluation times (30min and 24h. Result The results were submitted to ANOVA and Tukey tests (5%. Both Inceram alumina and Inceram zirconia ceramic barriers hindered polymerization. Bistite, followed by RelyX and Variolink, exhibited the highest microhardness values (p<0.05. As the highest values were obtained without a barrier, it was determined that the barrier, followed by the tooth, influenced microhardness. Both Empress and Cesead had the smallest microhardness values but with no statistically significant difference between them. Conclusion The barrier negatively affected the microhardness of dual-cured resin cements; evaluation time did not affect microhardness values for most of the conditions tested. There is a limited effect of the chemical activator on the polymerization of some dual-cured cements, and their performance is product specific.

  8. 21 CFR 888.3410 - Hip joint metal/polymer or ceramic/polymer semiconstrained resurfacing cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hip joint metal/polymer or ceramic/polymer... Devices § 888.3410 Hip joint metal/polymer or ceramic/polymer semiconstrained resurfacing cemented prosthesis. (a) Identification. A hip joint metal/polymer or ceramic/polymer semi-constrained resurfacing...

  9. 21 CFR 888.3560 - Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint patellofemorotibial polymer/metal... Devices § 888.3560 Knee joint patellofemorotibial polymer/metal/polymer semi-constrained cemented prosthesis. (a) Identification. A knee joint patellofemorotibial polymer/metal/polymer semi-constrained...

  10. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties

    Directory of Open Access Journals (Sweden)

    Hongfang Sun

    2015-02-01

    Full Text Available Calcium carbide residue (CCR is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP. The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement pastes was also examined through SEM (scanning electron microscope. Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

  11. Evaluation of physico-chemical properties of Portland cements and MTA

    Directory of Open Access Journals (Sweden)

    Jorge Luis Gonçalves

    2010-09-01

    Full Text Available The purpose of this study was to evaluate the hydrogenionic potential and electrical conductivity of Portland cements and MTA, as well as the amount of arsenic and calcium released from these materials. In Teflon molds, samples of each material were agitated and added to plastic flasks containing distilled water for 3, 24, 72 and 168 h. The results were analyzed with a Kruskal-Wallis non-parametric test for global comparisons and a Dunn-Tukey test for pairwise comparisons. The results revealed no significant differences in the pH of the materials (p > 0.05. The electrical conductivity of the cements were not statistically different (p > 0.05. White non-structural cement and MTA BIO released the largest amount of calcium ions into solution (p 0.05. The results indicated that the physico-chemical properties of Portland cements and MTA were similar. Furthermore, all materials produced an alkaline environment and can be considered safe for clinical use because arsenic was not released. The electrical conductivity and the amount of calcium ions released into solution increased over time.

  12. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties.

    Science.gov (United States)

    Sun, Hongfang; Li, Zishanshan; Bai, Jing; Memon, Shazim Ali; Dong, Biqin; Fang, Yuan; Xu, Weiting; Xing, Feng

    2015-02-13

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)₂, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

  13. Evaluation of physico-chemical properties of Portland cements and MTA.

    Science.gov (United States)

    Gonçalves, Jorge Luis; Viapiana, Raqueli; Miranda, Carlos Eduardo Saraiva; Borges, Alvaro Henrique; Cruz Filho, Antônio Miranda da

    2010-01-01

    The purpose of this study was to evaluate the hydrogenionic potential and electrical conductivity of Portland cements and MTA, as well as the amount of arsenic and calcium released from these materials. In Teflon molds, samples of each material were agitated and added to plastic flasks containing distilled water for 3, 24, 72 and 168 h. The results were analyzed with a Kruskal-Wallis non-parametric test for global comparisons and a Dunn-Tukey test for pairwise comparisons. The results revealed no significant differences in the pH of the materials (p > 0.05). The electrical conductivity of the cements were not statistically different (p > 0.05). White non-structural cement and MTA BIO released the largest amount of calcium ions into solution (p 0.05). The results indicated that the physico-chemical properties of Portland cements and MTA were similar. Furthermore, all materials produced an alkaline environment and can be considered safe for clinical use because arsenic was not released. The electrical conductivity and the amount of calcium ions released into solution increased over time.

  14. Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

    Science.gov (United States)

    Kirgiz, Mehmet Serkan

    2014-01-01

    Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement. PMID:24587737

  15. Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

    Directory of Open Access Journals (Sweden)

    Mehmet Serkan Kirgiz

    2014-01-01

    Full Text Available Effects of chemical compositions changes of blended-cement pastes (BCPCCC on some strength gains of blended cement mortars (BCMSG were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP or 6%, 20%, 21%, and 35% brick powder (BP for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min. Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS and flexural strengths (FS of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2, sodium oxide (Na2O, and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2 at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM in comparison with reference mortars (RM at whole cure days as MP up to 6% or BP up to 35% was blended for cement.

  16. Influence of the mineralogical composition of cement in the diffusion of chemical species

    International Nuclear Information System (INIS)

    Galicia A, E.

    2015-01-01

    , color and others. Portland cements commonly used in the construction industry, they are based primarily on the mineral phases of limestone and silica. In conventional cement admixtures the chemical reactivity depends on the ratio of tricalcium and dicalcium silicate (C 3 S/C 2 S), the tricalcium aluminate (C 3 A) influences in the setting time and tetra calcium ferro aluminate (C 4 AF) gives a different color to the cement. In this research the mineralogical composition of two commercial cements is studied and its influence on the phenomenon of radionuclides retention. For this particular concrete discs were manufactured with water, sand and two commercial cements: Tolteca Extra CPC 30-RRS and Cruz Azul CPC Type II 30-R. The solid observation techniques used for analysis of the cement paste and concrete they are: X-ray Diffraction and Scanning Electron Microscopy, as well as the nuclear analytic techniques of Moessbauer and X-ray Fluorescence. (Author)

  17. Release kinetics and mechanisms of trace heavy metals from cement based material; Cinetiques et mecanismes de relargage des metaux lourds presents en traces dans les matrices cimentaires

    Energy Technology Data Exchange (ETDEWEB)

    Moudilou, E.

    2002-12-15

    Chemical species contained in a solid matrix may be transferred to the environment through water leaching. Previous studies of trace metals released from building materials (particularly cement-based ones) highlight an important analytical difficulty. The aim of this study is to determine the kinetics and the mechanisms involved in the release of trace heavy metals (Cr, Cu, Ni, Pb, V and Zn) from industrial cement pastes (usually ranging from 20 to 300 ppm). The development of a dynamic leaching system, named CTG-LEACHCRETE, (used at pH=5, 20 C) which permits the evaluation of the kinetics of trace heavy metals is presented in the first part. Also, innovative solid analysis techniques (ICP-MS-Laser Ablation, local and Grazing Incidence X-rays Diffraction (GIXD) technique) were used to characterise the cement-degraded layers formed during leaching experiments. These techniques enable to monitor the mineralogical evolution and the distribution of trace metals in these areas. The confrontation of these two approaches, kinetic and solid analysis, coupled with a thorough investigation of previously developed models, lead to proposals concerning the mechanisms of release of the trace heavy metals studied. In all the cement pastes studied (CPA-CEM I, CPJ-CEM II/A and CLC-CEM V/A), chromium is trapped in ettringite by substitution SO{sub 4}{sup 2-}(U)CrO{sub 4}{sup 2-} and its release is then controlled by the dissolution of this hydrate. The behaviour of copper, nickel and zinc in degraded areas and in leachates, are correlated to the silicon of the hydrated calcium silicate (CSH), which imply that they are localised there. Lead, was never detected in the leachates. But it is also correlated to the silicon in the degraded layers. (author)

  18. Mechano-Chemical Interactions at Cement-Geomaterial Interfaces in Repository and Borehole Scenarios

    Science.gov (United States)

    Mohagheghi, J. R.; Dewers, T. A.; Matteo, E. N.; Heath, J. E.; Jove Colon, C. F.; Fuller, T.

    2017-12-01

    A number of factors negatively affect wellbore integrity including interactions at boundaries between cement and surrounding geomaterial. These include mechanical and chemical mechanisms that can lead to wellbore failure. To examine these interactions, potential coupling, and pathways to failure, we discuss progress on an experimental and modeling study involving cement-clay and cement-salt interfaces. A sample shotcrete-bentonite interface from the FEBEX heater test at the Grimsel Test Site in Switzerland is examined using multi-beam scanning electron microscopy (mSEM) at 4 nm resolution over an area 10's of square millimeters. We examine changes in alteration as manifested by pore structural changes as a function of distance from the interface. A parallel effort examines time-dependent changes in interface structure in cement cores in a triaxial coreholder. Cores are exposed to conditions of 70oC, 14 MPa pressure, and small differential loads, with degradation being monitored by effluent pH, pulse-echo ultrasonics, and piston displacement (measuring sample shortening). We will measure the mechanical consequences of interface alteration using nano-indentation. Experimental results are being incorporated as a validation effort in a coupled reactive-transport mechanics model linking the Sandia ALBANY finite element code, the KAYENTA elasto-plastic constitutive model, with the reactive transport code PFLOTRAN. Plans call to apply the model to understanding the evolution of the FEBEX sample, as well as a cement-salt sample from the Waste Isolation Pilot Plant in Carlsbad, New Mexico. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. SAND 2017-8277 A

  19. Behaviour of a cement stone with chemical additions under short high temperature effects

    International Nuclear Information System (INIS)

    Falikman, V.R.; Veselova, V.I.; Ershov, V.Yu.; Muzalevskij, L.P.

    1987-01-01

    The purpose of the paper is to investigate the influence of different chemical additions used in NPP construction on thermal stability of a cement stone under short- and high-temperature effects. S-3 and dihydroxyphenyl utilized as peptizing agents for increase of placeability of concrete mixtures as well as sodium nitrite utilized as an antifreezing addition at conccreting at low temperatures are used as additions. The investigations were conducted in the 0-900 deg C temperature range divided into 4 ranges. Shrinkage and mass losses of specimens were determined. The obtained data show that specimens with additions are subjected to smaller shrinkage and mass losses as compared with specimens without additions. The highest positive effect is attained in portland cements with active mineral additions

  20. Graphene composites containing chemically bonded metal oxides

    Indian Academy of Sciences (India)

    the oxide layers are chemically bonded to graphene (Zhang ... sists of three glass chambers, one to contain the metal halide. (TiCl4, SiCl4 ... In this step, the metal halide reacts with the oxygen function- ... 1·0 g of FeCl3 were vigorously stirred in 30 ml of ethylene ... Reaction with water vapour results in hydrolysis of the un-.

  1. Early age volume changes in concrete due to chemical shrinkage of cement paste

    Directory of Open Access Journals (Sweden)

    Ebensperger, L.

    1991-12-01

    Full Text Available Unrestrained early age volume changes due to chemical shrinkage in cement pastes, mortars and concretes have been determined. The measurements were performed on sealed and unsealed samples which were stored under water. The chemical shrinkage of unsealed specimens represents the amount of absorbed water due to the chemical reaction of the cement It depends only on the cement content of the sample and does not lead to changes of the external dimensions. However the chemical shrinkage of sealed specimens is connected with a real volume change due to self-desiccation and the effect of internal pressures. The shrinkage depends in this case on the restraining effect of coarse aggregates as well as the cement content. The chemical shrinkage measured on sealed concretes was much higher than the one expected to ocurr on concretes, because normally an equalization of pressure takes place to some extent in the interior of the concrete. The use of expansive additives showed that they may compensate the chemical shrinkage, but its dosage is very sensitive and should be defined exactly for each case particularly.

    Se han determinado los cambios volumétricos que ocurren en pastas de cemento, morteros y hormigones a edad temprana debido al efecto de la retracción química. Las mediciones se realizaron en probetas selladas y no selladas sumergidas bajo agua. La retracción química en probetas no selladas representa la cantidad de agua absorbida debido a la reacción química del cemento. Depende solamente del contenido de cemento de la probeta y no produce ningún cambio en las dimensiones de la probeta. Por el contrario, la retracción química en probetas selladas está relacionada con un cambio volumétrico real debido al efecto de la autodesecación y presiones internas. La retracción en este caso depende tanto de la restricción que imponen los áridos, como del contenido de cemento. La retracción química medida en hormigones sellados

  2. Leaching Behavior of Heavy Metals from Cement Pastes Using a Modified Toxicity Characteristic Leaching Procedure (TCLP).

    Science.gov (United States)

    Huang, Minrui; Feng, Huajun; Shen, Dongsheng; Li, Na; Chen, Yingqiang; Shentu, Jiali

    2016-03-01

    As the standard toxicity characteristic leaching procedure (TCLP) can not exhaust the acid neutralizing capacity of the cement rotary kiln co-processing solid wastes products which is particularly important for the assessment of the leaching concentrations of heavy metals. A modified TCLP was proposed. The extent of leaching of heavy metals is low using the TCLP and the leaching performance of the different metals can not be differentiated. Using the modified TCLP, however, Zn leaching was negligible during the first 180 h and then sharply increased (2.86 ± 0.18 to 3.54 ± 0.26 mg/L) as the acidity increased (pH leaching is enhanced using the modified TCLP. While Pb leached readily during the first 126 h and then leachate concentrations decreased to below the analytical detection limit. To conclude, this modified TCLP is a more suitable method for these cement rotary kiln co-processing products.

  3. Physico-Chemical Studies Involving Incorporation of Radioactive and Industrial Waste In Cement-Epoxy Resin Matrix

    International Nuclear Information System (INIS)

    Sayed, M.S.; Hafez, N.

    1999-01-01

    Cement and epoxy resin as chemical additives are proposed to incorporate different types of wastes. The study was extended to prepare different mixtures of cement and epoxy resin in presence of some toxic ions. The studied ions were Cd II, Ni II, Cu II, Fe III, Ce IV, 154+152 Eu, phenol and toluene. The physical, mechanical and leaching properties of the mixtures were studied. The thermal analysis and infrared spectra were also investigated. It was observed that all the studied properties of the epoxy modified cement as a disposal matrix was improved

  4. Physico-chemical studies of gamma-irradiated polyester. Impregnated cement mortar composite

    International Nuclear Information System (INIS)

    Ismail, M.R.; Afifi, M.S.

    1998-01-01

    The effect of impregnation time on the physico-chemical and mechanical properties of polyester-cement mortar composite has been investigated. The samples were soaked in unsaturated polyester resin containing 40% styrene monomer at impregnation times ranging from 1-15 hours and then exposed to 50 kGy of γ-irradiation. The effects on polymer loading, compressive strength, apparent porosity, and water absorption in addition to IR spectra and TGA of the samples were studied. It was found that, the polymer loading and compressive strength increase with the increased of soaking time up to 4 hours and there is no significant improvement of the polymer loading and strength. Whereas, the apparent porosity and water absorption behave in an opposite direction. These are attributed to the presence of polymer in the pores of the samples. IR spectra showed that, new bands appeared as result of the reaction between polyester and set cement. TGA showed that, the polyester cement composite has higher thermal stability as a compared to irradiated polyester. (author)

  5. Chemically reducing decontamination method for radioactive metal

    International Nuclear Information System (INIS)

    Tanaka, Akio; Onuma, Tsutomu; Sato, Hitoshi.

    1994-01-01

    The present invention concerns a decontamination method of electrolytically reducing radioactive metal wastes, then chemically dissolving the surface thereof with a strong acid decontaminating solution. This method utilizes dissolving characteristics of stainless steels in the strong acid solution. That is, in the electrolytic reduction operation, a portion of the metal wastes is brought into contact with a strong acid decontaminating solution, and voltage and current are applied to the portion and keep it for a long period of time so as to make the potential of the immersed portion of the metal wastes to an active soluble region. Then, the electrolytic reduction operation is stopped, and the metal wastes are entirely immersed in the decontaminating solution to decontaminate by chemical dissolution. As the decontaminating solution, strong acid such as sulfuric acid, nitric acid is used. Since DC current power source capacity required for causing reaction in the active soluble region can be decreased, the decontamination facility can be minimized and simplified, and necessary electric power can be saved even upon decontamination of radioactive metal wastes made of stainless steels and having a great area. Further, chemical dissolution can be conducted without adding an expensive oxidizing agent. (N.H.)

  6. On chemical activity of heavy metal oxides

    International Nuclear Information System (INIS)

    Mechev, V.V.

    1994-01-01

    Interaction of solid oxides of heavy nonferrous metals with sulfur and carbon is investigated. The results are discussed. Direct dependence of chemical activity of oxides on disordering of their crystal lattice at heating is established. Beginning of interaction in the systems studied is accompanied by change of oxide conductivity type

  7. Chemical decontamination method for radioactive metal waste

    International Nuclear Information System (INIS)

    Tanaka, Akio; Onuma, Tsutomu; Yamazaki, Sei; Miura, Haruki.

    1993-01-01

    The present invention provides a chemical decontamination method for radioactive metal wastes, which are generated from radioactive material handling facilities and the surfaces of which are contaminated by radioactive materials. That is, it has a feature of applying acid dissolution simultaneously with mechanical grinding. The radioactive metal wastes are contained in a vessel such as a barrel together with abrasives in a sulfuric acid solution and rotated at several tens rotation per minute. By such procedures for the radioactive metal wastes, (1) cruds and passive membranes are mechanically removed, (2) exposed mother metal materials are uniformly brought into contact with sulfuric acid and further (3) the mother metal materials dissolve the cruds and the passive membranes also chemically by a reducing dissolution (so-called local cell effect). According to the method of the present invention, stainless steel metal wastes having cruds and passive membranes can rapidly and efficiently be decontaminated to a radiation level equal with that of ordinary wastes. (I.S.)

  8. Effect of uniaxially pressing ordinary Portland cement pastes containing metal hydroxides on porosity, density, and leaching

    International Nuclear Information System (INIS)

    Cheeseman, C.R.; Asavapisit, S.; Knight, J.

    1998-01-01

    Synthetic metal hydroxide wastes containing Zn and Pb have been mixed with partially hydrated cement and uniaxially pressed. The effect on porosity, pore size distribution, and bulk and skeletal densities has been characterized using mercury intrusion porosimetry. Ca(OH) 2 formation has been determined using differential thermal analysis and metal leaching has been assessed in a series of static leach tests completed on monolithic samples. Pressed solidified materials have increased density, reduced porosity, and reduced Ca(OH) 2 . They exhibit increased resistance to acid attack in terms of sample weight loss during leaching due to reduced release of alkalis. Leaching of Zn and Pb is primarily determined by pH. A peak observed in Zn leaching from pressed samples is due to the effect of changing leachate pH on the dominant Zn species present

  9. Analysis of heavy metal contents in gray and white MTA and 2 kinds of Portland cement: a preliminary study.

    Science.gov (United States)

    Chang, Seok Woo; Shon, Won Jun; Lee, WooCheol; Kum, Kee Yeon; Baek, Seung Ho; Bae, Kwang Shik

    2010-04-01

    The levels of 10 heavy metals (arsenic, bismuth, cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc) in gray Portland cement (GPC), white Portland cement (WPC), gray MTA (GMTA), and white MTA (WMTA) were analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). One gram of each material was digested with 80 degrees C "aqua-regia" (7 mL of 60% HNO3 and 21 mL of 35% HCl), filtered, and analyzed by ICP-AES. The analysis was performed 6 times and the data were analyzed statistically. Arsenic and lead concentrations were the highest in GPC (P cements (P Portland cement versus MTA, the differences in purity may be considered. Copyright 2010 Mosby, Inc. All rights reserved.

  10. Anomalous dissolution of metals and chemical corrosion

    Directory of Open Access Journals (Sweden)

    DRAGUTIN M. DRAZIC

    2005-03-01

    Full Text Available An overview is given of the anomalous behavior of some metals, in particular Fe and Cr, in acidic aqueous solutions during anodic dissolution. The anomaly is recognizable by the fact that during anodic dissolutionmore material dissolves than would be expected from the Faraday law with the use of the expected valence of the formed ions. Mechanical disintegration, gas bubble blocking, hydrogen embrittlement, passive layer cracking and other possible reasons for such behavior have been discussed. It was shown, as suggested by Kolotyrkin and coworkers, that the reason can be, also, the chemical reaction in which H2O molecules with the metal form metal ions and gaseous H2 in a potential independent process. It occurs simultaneously with the electrochemical corrosion process, but the electrochemical process controls the corrosion potential. On the example of Cr in acid solution itwas shown that the reason for the anomalous behavior is dominantly chemical dissolution, which is considerably faster than the electrochemical corrosion, and that the increasing temperature favors chemical reaction, while the other possible reasons for the anomalous behavior are of negligible effect. This effect is much smaller in the case of Fe, but exists. The possible role of the chemical dissolution reacton and hydrogen evolution during pitting of steels and Al and stress corrosion cracking or corrosion fatigue are discussed.

  11. Mechanical and chemical properties of polyvinyl alcohol modified cement mortar with silica fume used as matrix including radioactive waste

    International Nuclear Information System (INIS)

    Dakroury, A. M.

    2007-01-01

    This paper discussed the mechanical and chemical properties of polyvinyl alcohol - modified cement mortar with silica fume to assess the safety for disposal of radioactive waste. The modified cement mortars containing polyvinyl alcohol (PVA) in the presence of 10 % silica fume (SF) .The chemical reaction between polymer and cement - hydrated product were investigated by the Infrared Spectral Technology, Differential Thermal Analysis and X-ray diffraction. The leaching of 137Cs from a waste composite into a surrounding fluid has been studied .The results shown that PVA increases the strength and decreases the porosity. The increase in strength duo to the interaction of PVA with cement , may be forming some new compound that fill the pores or improve the bond between the cement . The pozzolanic reaction of the SF increases the calcium silicate hydrates in the hardening matrix composites. There is distinct change in the refinement of the pore structure in cement composites giving fewer capillary pores and more of the finer gel pores

  12. Chemical and morphological characteristics of mineral trioxide aggregate and Portland cements.

    Science.gov (United States)

    Khan, Shahbaz; Kaleem, Muhammad; Fareed, Muhammad Amber; Habib, Amir; Iqbal, Kefi; Aslam, Ayesha; Ud Din, Shahab

    2016-01-01

    The purpose of this study was to investigate the chemical composition and particle morphology of white mineral trioxide aggregate (WMTA) and two white Portland cements (CEM 1 and CEM 2). Compositional analysis was performed by energy dispersive X-ray spectroscopy, X-ray fluorescence spectrometry and X-ray diffraction whereas, morphological characteristics were analyzed by scanning electron microscope and Laser scattering particle size distribution analyzer. The elemental composition of WMTA, CEM 1 and CEM 2 were similar except for the presence of higher amounts of bismuth in WMTA. Calcium oxide and silicon oxide constitute the major portion of the three materials whereas, tricalcium silicate was detected as the major mineral phase. The particle size distribution and morphology of WMTA was finer compared to CEM 1 and CEM 2. The three tested materials had relatively similar chemical composition and irregular particle morphologies.

  13. Preparation, physical-chemical characterisation and cytocompatibility of calcium carbonate cements.

    Science.gov (United States)

    Combes, C; Miao, Baoji; Bareille, Reine; Rey, Christian

    2006-03-01

    The feasibility of calcium carbonate cements involving the recrystallisation of metastable calcium carbonate varieties has been demonstrated. Calcium carbonate cement compositions presented in this paper can be prepared straightforwardly by simply mixing water (liquid phase) with two calcium carbonate phases (solid phase) which can be easily obtained by precipitation. An original cement composition was obtained by mixing amorphous calcium carbonate and vaterite with an aqueous medium. The cement set and hardened within 2h at 37 degrees C in an atmosphere saturated with water and the final composition of the cement consisted mostly of aragonite. The hardened cement was microporous and showed poor mechanical properties. Cytotoxicity tests revealed excellent cytocompatibility of calcium carbonate cement compositions. Calcium carbonates with a higher solubility than the apatite formed for most of the marketed calcium phosphate cements might be of interest to increase biomedical cement resorption rates and to favour its replacement by bone tissue.

  14. Effects of Co-Processing Sewage Sludge in the Cement Kiln on PAHs, Heavy Metals Emissions and the Surrounding Environment.

    Science.gov (United States)

    Lv, Dong; Zhu, Tianle; Liu, Runwei; Li, Xinghua; Zhao, Yuan; Sun, Ye; Wang, Hongmei; Zhang, Fan; Zhao, Qinglin

    2018-04-08

    To understand the effects of co-processing sewage sludge in the cement kiln on non-criterion pollutants emissions and its surrounding environment, the flue gas from a cement kiln stack, ambient air and soil from the background/downwind sites were collected in the cement plant. Polycyclic aromatic hydrocarbons (PAHs) and heavy metals of the samples were analyzed. The results show that PAHs in flue gas mainly exist in the gas phase and the low molecular weight PAHs are the predominant congener. The co-processing sewage sludge results in the increase in PAHs and heavy metals emissions, especially high molecular weight PAHs and low-volatile heavy metals such as Cd and Pb in the particle phase, while it does not change their compositions and distribution patterns significantly. The concentrations and their distributions of the PAHs and heavy metals between the emissions and ambient air have a positive correlation and the co-processing sewage sludge results in the increase of PAHs and heavy metals concentrations in the ambient air. The PAHs concentration level and their distribution in soil are proportional to those in the particle phase of flue gas, and the co-processing sewage sludge can accelerate the accumulation of the PAHs and heavy metals in the surrounding soil, especially high/middle molecular weight PAHs and low-volatile heavy metals.

  15. Influence of porcelain firing and cementation on the marginal adaptation of metal-ceramic restorations prepared by different methods.

    Science.gov (United States)

    Kaleli, Necati; Saraç, Duygu

    2017-05-01

    Marginal adaptation plays an important role in the survival of metal-ceramic restorations. Porcelain firings and cementation may affect the adaptation of restorations. Moreover, conventional casting procedures and casting imperfections may cause deteriorations in the marginal adaptation of metal-ceramic restorations. The purpose of this in vitro study was to compare the marginal adaptation after fabrication of the framework, porcelain application, and cementation of metal-ceramic restorations prepared by using the conventional lost-wax technique, milling, direct metal laser sintering (DMLS), and LaserCUSING, a direct process powder-bed system. Alterations in the marginal adaptation of the metal frameworks during the fabrication stages and the precision of fabrication methods were evaluated. Forty-eight metal dies simulating prepared premolar and molar abutment teeth were fabricated to investigate marginal adaptation. They were divided into 4 groups (n=12) according to the fabrication method used (group C serving as the control group: lost-wax method; group M: milling method; group LS: DMLS method; group DP: direct process powder-bed method). Sixty marginal discrepancy measurements were recorded separately on each abutment tooth after fabrication of the framework, porcelain application, and cementation by using a stereomicroscope. Thereafter, each group was divided into 3 subgroups according to the measurements recorded in each fabrication stage: subgroup F (framework), subgroup P (porcelain application), and subgroup C (cementation). Data were statistically analyzed with univariate analysis of variance (followed by 1-way ANOVA and Tamhane T2 test (α=.05). The lowest marginal discrepancy values were observed in restorations prepared by using the direct process powder-bed method, and this was significantly different (Pdirect process powder-bed method is quite successful in terms of marginal adaptation. The marginal discrepancy increased after porcelain application

  16. Effects of abutment diameter, luting agent type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments.

    Science.gov (United States)

    Safari, Sina; Hosseini Ghavam, Fereshteh; Amini, Parviz; Yaghmaei, Kaveh

    2018-02-01

    The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly ( P =.006). The difference in retention between the cemented and recemented copings was not statistically significant ( P =.40). Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement.

  17. Effects of abutment diameter, luting agent type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments

    Science.gov (United States)

    Safari, Sina; Amini, Parviz; Yaghmaei, Kaveh

    2018-01-01

    PURPOSE The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. MATERIALS AND METHODS Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). RESULTS The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly (P=.006). The difference in retention between the cemented and recemented copings was not statistically significant (P=.40). CONCLUSION Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement. PMID:29503708

  18. 21 CFR 888.3353 - Hip joint metal/ceramic/polymer semi-constrained cemented or nonporous uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... linkage across-the-joint. The two-part femoral component consists of a femoral stem made of alloys to be... ceramic (aluminium oxide, A1203) head of the femoral component. The acetabular component is made of ultra... nonporous metal alloys, and used with or without bone cement. (b) Classification. Class II. [54 FR 48239...

  19. Chemical decontamination method for radioactive metal waste

    International Nuclear Information System (INIS)

    Onuma, Tsutomu; Akimoto, Hidetoshi

    1991-01-01

    The invention relates to a decontamination method for radioactive metal waste products derived from equipment that handles radioactive materials whose surfaces have been contaminated; in particular it concerns a decontamination method that reduces the amount of radioactive waste by decontaminating radioactive waste substances to a level of radioactivity in line with normal waste products. In order to apply chemical decontamination to metal waste products whose surfaces are divided into carbon steel waste and stainless steel waste; the carbon steel waste is treated using only a primary process in which the waste is immersed in a sulfuric acid solution, while the stainless steel waste must be treated with both the primary process and then electrolytically reduces it for a specific length of time and a secondary process that uses a solution of sulfuric acid mixed with oxidizing metal salts. The method used to categorize metal waste into carbon steel waste and stainless steel waste involves determining the presence, or absence, of magnetism. Voltage is applied for a fixed duration; once that has stopped, electrolytic reduction repeats the operative cycle of applying, then stopping voltage until the potential of the radioactive metal waste is retained in the active region. 1 fig. 2 tabs

  20. Effects of chemical and mineral additives and the water/cement ratio on the thermal resistance of Portland cement concrete

    International Nuclear Information System (INIS)

    Cesar, Leandro Cesar Dias; Morelli, Arnaldo C.; Baldo, Joao Baptista

    1998-01-01

    The exposure of Portland concrete to high temperatures (>250 deg C) can damage drastically the microstructural integrity of the material. Since the water/cement ratio as well as the inclusion of superplasticizers and mineral additives (silica fume) can alter constitutively and micro structurally the material, in this work it was investigated per effect of these additions on the damage resistance of portland concrete after exposure to high temperatures. (author)

  1. Chemical stability of seven years aged cement-PET composite waste form containing radioactive borate waste simulates

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, H.M., E-mail: hosamsaleh70@yahoo.com [Radioisotope Department, Atomic Energy Authority, Dokki (Egypt); Tawfik, M.E. [Department of Polymers and Pigments, National Research Center, Dokki (Egypt); Bayoumi, T.A. [Radioisotope Department, Atomic Energy Authority, Dokki (Egypt)

    2011-04-15

    Different samples of radioactive borate waste simulate [originating from pressurized water reactors (PWR)] have been prepared and solidified after mixing with cement-water extended polyester composite (CPC). The polymer-cement composite samples were prepared from recycled poly (ethylene terephthalate) (PET) waste and cement paste (water/cement ratio of 40%). The prepared samples were left to set at room temperature (25 deg. C {+-} 5) under humid conditions. After 28 days curing time the obtained specimens were kept in their molds to age for 7 years under ambient conditions. Cement-polymer composite waste form specimens (CPCW) have been subjected to leach tests for both {sup 137}Cs and {sup 60}Co radionuclides according to the method proposed by the International Atomic Energy Agency (IAEA). Leaching tests were justified under various factors that may exist within the disposal site (e.g. type of leachant, surrounding temperature, leachant behavior, the leachant volume to CPCW surface area...). The obtained data after 260 days of leaching revealed that after 7 years of aging the candidate cement-polymer composite (CPC) containing radioactive borate waste samples are characterized by adequate chemical stability required for the long-term disposal process.

  2. Lithological and land-use based assessment of heavy metal pollution in soils surrounding a cement plant in SW Europe.

    Science.gov (United States)

    Cutillas-Barreiro, Laura; Pérez-Rodríguez, Paula; Gómez-Armesto, Antía; Fernández-Sanjurjo, María José; Álvarez-Rodríguez, Esperanza; Núñez-Delgado, Avelino; Arias-Estévez, Manuel; Nóvoa-Muñoz, Juan Carlos

    2016-08-15

    We study the influence of phasing out a cement plant on the heavy metal (Hg, Pb and Cr) content in the surrounding soils, taking into account factors often neglected, such as contributions due to local lithology or land use. The range of total Hg was 10-144µg kg(-1), reaching up to 41 and 145mgkg(-1) for total contents of Pb and Cr, respectively. Forest soils showed higher concentration of Hg than prairie soils, indicating the importance of land use on the accumulation of volatile heavy metals in soils. In forest soils, total Hg showed a trend to decrease with soil depth, whereas in prairie soils the vertical pattern of heavy metal concentrations was quite homogeneous. In most cases, the distance to the cement plant was not a factor of influence in the soils content of the analyzed heavy metals. Total Pb and Cr contents in soils nearby the cement plant were quite similar to those found in the local lithology, resulting in enrichment factor values (EF's) below 2. This suggests that soil parent material is the main source of these heavy metals in the studied soils, while the contribution of the cement plant to Pb and Cr soil pollution was almost negligible. On the contrary, the soils surrounding the cement plant accumulate a significant amount of Hg, compared to the underlying lithology. This was especially noticeable in forest soils, where Hg EF achieved values up to 36. These results are of relevance, bearing in mind that Hg accumulation in soils may be an issue of environmental concern, particularly in prairie soils, where temporal flooding can favor Hg transformation to highly toxic methyl-Hg. In addition, the concurrence of acid soils and total-Cr concentrations in the range of those considered phytotoxic should be also stressed. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Selenium recovery from kiln powder of cement manufacturing by chemical leaching and bioreduction.

    Science.gov (United States)

    Soda, S; Hasegawa, A; Kuroda, M; Hanada, A; Yamashita, M; Ike, M

    2015-01-01

    A novel process by using chemical leaching followed by bacterial reductive precipitation was proposed for selenium recovery from kiln powder as a byproduct of cement manufacturing. The kiln powder at a slurry concentration of 10 w/v% with 0.25 M Na2CO3 at 28°C produced wastewater containing about 30 mg-Se/L selenium. The wastewater was diluted four-fold and adjusted to pH 8.0 as preconditioning for bioreduction. A bacterial strain Pseudomonas stutzeri NT-I, capable of reducing selenate and selenite into insoluble elemental selenium, could recover about 90% selenium from the preconditioned wastewater containing selenium of 5 mg-Se/L when supplemented with lactate or glycerol. The selenium concentrations in the treated wastewater were low around the regulated effluent concentration of 0.1 mg-Se/L in Japan.

  4. The emission of particulate matters and heavy metals from cement kilns – case study: co-incineration of tires in Serbia

    Directory of Open Access Journals (Sweden)

    Dušan Todorović

    2010-09-01

    Full Text Available Co-incineration of wastes started more than 20 years ago. In the last 10 years, the use of alternative fuels in the cement industry is continuously increasing. The use of solid wastes in cement kilns is one of the best technologies for a complete and safe destruction of these wastes, due to the fact that there is a simultaneous benefit of destroying wastes and getting the energy. However, particulate matters (PM and gaseous chemicals emitted from a source into the environment could be directly transmitted to humans through air inhalation. Therefore, for accurate health risk estimation, the emission of pollutants must be determined. In this work, the analysis of the emission of different pollutants when replacing partially the fuel type used in a cement kiln is done. PM, PM10, heavy metals and inorganic pollutants are analyzed. The methods used for sampling and analysis are the standard methods suggested by the EU regulations for stack analysis. Experimental results have shown the encouraging results: in particular clinker characteristics were unmodified, and stack emissions (NOx, SO2 and CO mainly were in the case of tires, slightly incremented but remaining almost always below the law imposed limits, and in some cases were even decreased.

  5. Mechanism of alkalinity lowering and chemical equilibrium model of high fly ash silica fume cement

    International Nuclear Information System (INIS)

    Hoshino, Seiichi; Honda, Akira; Negishi, Kumi

    2014-01-01

    The mechanism of alkalinity lowering of a High Fly ash Silica fume Cement (HFSC) under liquid/solid ratio conditions where the pH is largely controlled by the soluble alkali components (Region I) has been studied. This mechanism was incorporated in the chemical equilibrium model of HFSC. As a result, it is suggested that the dissolution and precipitation behavior of SO 4 2- partially contributes to alkalinity lowering of HFSC in Region I. A chemical equilibrium model of HFSC incorporating alkali (Na, K) adsorption, which was presumed as another contributing factor of the alkalinity lowering effect, was also developed, and an HFSC immersion experiment was analyzed using the model. The results of the developed model showed good agreement with the experiment results. From the above results, it was concluded that the alkalinity lowering of HFSC in Region I was attributed to both the dissolution and precipitation behavior of SO 4 2- and alkali adsorption, in addition to the absence of Ca(OH) 2 . A chemical equilibrium model of HFSC incorporating alkali and SO 4 2- adsorption was also proposed. (author)

  6. Contact damage failure analyses of fretting wear behavior of the metal stem titanium alloy-bone cement interface.

    Science.gov (United States)

    Zhang, Lanfeng; Ge, Shirong; Liu, Hongtao; Wang, Qingliang; Wang, Liping; Xian, Cory J

    2015-11-01

    Although cemented titanium alloy is not favored currently in the Western world for its poor clinical and radiography outcomes, its lower modulus of elasticity and good biocompatibility are instrumental for its ability supporting and transforming physical load, and it is more suitable for usage in Chinese and Japanese populations due to their lower body weights and unique femoral characteristics. Through various friction tests of different cycles, loads and conditions and by examining fretting hysteresis loops, fatigue process curves and wear surfaces, the current study investigated fretting wear characteristics and wear mechanism of titanium alloy stem-bone cement interface. It was found that the combination of loads and displacement affected the wear quantity. Friction coefficient, which was in an inverse relationship to load under the same amplitude, was proportional to amplitudes under the same load. Additionally, calf serum was found to both lubricate and erode the wear interface. Moreover, cement fatigue contact areas appeared black/oxidative in dry and gruel in 25% calf serum. Fatigue scratches were detected within contact areas, and wear scars were found on cement and titanium surfaces, which were concave-shaped and ring concave/ convex-shaped, respectively. The coupling of thermoplastic effect and minimal torque damage has been proposed to be the major reason of contact damage. These data will be important for further studies analyzing metal-cement interface failure performance and solving interface friction and wear debris production issues. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Determination of Heavy Metal in Agricultural Soils near and Far From the Cement Factory in Tehran, Iran

    Directory of Open Access Journals (Sweden)

    Mohammad Rezaeian

    2016-08-01

    Full Text Available Background: Heavy metals (HMs are one of the most important polluting substances emitted to the environment during cement production. Tehran Cement Factory located in the southeastern of Tehran, Iran, closer to agricultural lands cultivates alfalfa, barley, and maize as feed. The objective of the study was to determine the concentration of HMs in agricultural soils. Methods: Thirty six soil samples were collected from two regions of Aminabad (close to the cement factory and Varamin (far from cement factory in 2015. The samples were taken from a depth of 0-15 cm and analyzed to determine their HM (zinc, lead, cadmium and chromium by atomic absorption spectrophotometry. Other relevant parameters of soil were evaluated, such as; pH, EC, TOM. Results: The concentration of HMs in both regions was as follows: Pb> Zn > Cr > Cd. Generally, the soil alfalfa, barley and maize, there was no significant difference. Conclusion: These data provide information on HM accumulations in agricultural soils and allow us to identify sources of pollution. In the industrial area due to the proximity to cement factory, concentration of zinc, lead, chromium, pH and EC were more than non-contaminated areas.

  8. Bitumen coating as a tool for improving the porosity and chemical stability of simulated cement-waste forms

    International Nuclear Information System (INIS)

    Saleh, H.M.

    2010-01-01

    Coating process of simulated cement-based waste form with bitumen was evaluated by performing physical and chemical experimental tests. X-ray diffraction (X-RD), Fourier transform infrared spectroscopy (FT-IR) and electron microscope investigations were applied on coated and non-coated simulated waste forms. Experimental results indicated that coating process improved the applicable properties of cement-based waste form such as porosity and leachability. Diffusion coefficients and leach indecies of coated specimens were calculated and show acceptable records. It could be stated that coating cemented waste form by bitumen emulsion, isolate the radioactive contaminants, thus reduces their back release to surrounding and in consequently save the environment proper and safe

  9. The rim zone of cement based materials - barrier or fast lane for chemical degradation?

    International Nuclear Information System (INIS)

    Schwotzer, M.; Kaltenbach, J.; Heck, P.F.; Konno, K.; Gerdes, A.

    2015-01-01

    This contribution focuses exemplarily on the chemical and mineralogical changes in the rim zone of cement paste samples exposed to different chloride solutions (NaCl, KCl, MgCl 2 and CaCl 2 ), to hard tap water and to demineralized water. The determination of the Ca(OH) 2 and Mg(OH) 2 content of the solid phases was performed by means of thermogravimetry with pulverized samples (TGA/SDTA 851, Mettler-Toledo). A potential relation between temperature and the time dependant development of the material due to reactive transport processes will also be addressed. The experiments with tap water showed that the contact between the cement paste samples and hard tap water did not lead to significant changes in the composition of the solid samples or of the reaction solution. This can be attributed to a rapid formation of a protective calcium carbonate layer on the surface of the cement paste. The slight decrease of the Ca 2+ content in the solution indicates that the growth of this layer occurs within the first few hours. In contrast to the tap water exposure, the results of the experiments with the MgCl 2 solutions show features of an intense attack despite the presence of crystalline covering layers. The quick formation of a thick and dense Mg(OH) 2 layer does not provide any protection against reactive transport processes. In this experiment, the degradation rate of Ca(OH) 2 as well as the Ca 2+ release was higher than in all other experiments. In addition the rapid formation of a Mg(OH) 2 layer starting already during the first hour of the experiment did not prevent the chloride ingress compared to the other experiments with chloride solutions. The pH value of the reaction solution remains stable and relatively low which indicates a crystallisation process. In the other experiments, performed with demineralized water, alkali chloride solutions, and the CaCl 2 solution, no significant formation of potentially protective covering layers and no development of transport

  10. Cement for oil well developed from ordinary cement: characterization physical, chemical and mineralogical; Cimento para poco de petroleo desenvolvido a partir de cimento comum: caracterizacao fisica, quimica e mineralogica

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, D.N.S.; Neves, G. de A.; Chaves, A.C.; Mendonca, A.M.G.D.; Lima, M.S. de [Universidade Federal de Campina Grande (UFCG), PB (Brazil); Bezerra, U.T., E-mail: daninascimento.eng@gmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia da Paraiba (IFPB), Campina Grande, PB (Brazil)

    2012-07-01

    This work aims to characterize a new type of cement produced from the mixture of ordinary Portland cement, which can be used as an option in the cementing of oil wells. To enable this work we used the method of lineal programming for the new cement composition, then conducted tests to characterize through particle size analysis by laser diffraction, chemical analysis by EDX, TGA, X-ray diffraction, time grip, resistance to compression. The overall result showed that the new cement had made low-C3A, takes more time to the CPP, thermal stability up to 500 ° C, the kinetics of hydration and low levels of major components consistent with the specifications of ABNT. (author)

  11. Preparation, physical-chemical characterisation and cytocompatibility of calcium carbonate cements

    OpenAIRE

    Combes, Christèle; Miao, Baoji; Bareille, Reine; Rey, Christian

    2006-01-01

    The feasibility of calcium carbonate cements involving the recrystallisation of metastable calcium carbonate varieties has been demonstrated. Calcium carbonate cement compositions presented in this paper can be prepared straightforwardly by simply mixing water (liquid phase) with two calcium carbonate phases (solid phase) which can be easily obtained by precipitation. An original cement composition was obtained by mixing amorphous calcium carbonate and vaterite with an aqueous medium. The cem...

  12. Utilisation of fly ash for the management of heavy metal containing primary chemical sludge generated in a leather manufacturing industry

    Energy Technology Data Exchange (ETDEWEB)

    Sekaran, G.; Rao, B.P.; Ghanamani, A.; Rajamani, S. [Central Leather Research Institute, Chennai (India). Dept. of Environmental Technology

    2003-07-01

    The present study aims at disposal of primary chemical sludge generated in the tanning industry by solidification and stabilization process using flyash generated from thermal power plant along with binders and also on evaluating the leachability of heavy metal from the solidified product. The primary chemical sludge containing heavy metals iron and chromium were obtained from a garment leather manufacturing company at Chennai in India. The sludge was dried in open environment and it was powdered to fine size in a grinder. Binding increases stabilization of heavy metal in calcined sludge with refractory binders such as clay, fly ash, lime and ordinary Portland cement. Fly ash can be considered as the additional binder for producing stronger bricks, with high metal fixation efficiency, and minimum rate of removal of heavy metal and minimum diffusion co-efficient. 15 refs., 5 figs., 5 tabs.

  13. physico-chemical studies on polymer impregnated blending cement mortar composite

    International Nuclear Information System (INIS)

    Abdel-Rahman, H.A.

    2001-01-01

    as the increasing of the demand on a specific performance characteristics in concrete such as improved strength, low heat, sulfate resistance, improved impermeability and certain other applications. some of the industrial waste materials such as the blast-furnace slag, silica fume and fly ash were mixed with the cement clinker to produce blended cement . the use of these materials modifies the strength, pore structure and permeability of hardened cement mortar or concrete. the incorporation of blast furnace slag and silica fume in the hardened blended cement mortar or concrete is a common practice recently due to technological, economical and environmental benefits

  14. Sulfur polymer cement concrete

    International Nuclear Information System (INIS)

    Weber, H.H.; McBee, W.C.

    1990-01-01

    Sulfur-based composite materials formulated using sulfur polymer cement (SPC) and mineral aggregates are described and compared with conventional portland cement based materials. Materials characteristics presented include mechanical strength, chemical resistance, impact resistance, moisture permeation, and linear shrinkage during placement and curing. Examples of preparation and placement of sulfur polymer cement concrete (SC) are described using commercial scale equipment. SC applications presented are focused into hostile chemical environments where severe portland cement concrete (PCC) failure has occurred

  15. Chemical Sensors Based on Metal Oxide Nanostructures

    Science.gov (United States)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  16. Chemical decontamination method for radioactive metal waste

    International Nuclear Information System (INIS)

    Onuma, Tsutomu; Tanaka, Akio; Shibuya, Sadao.

    1991-01-01

    When contaminants mainly composed of copper remained on the surface of stainless steel wastes sent from an electrolytic reduction as a first step are chemically decontaminated, metal wastes are discriminated to carbon steel wastes and stainless steel wastes. Then, the carbon steel wastes are applied only with the first step of immersing in a sulfuric acid solution, and stainless steel wastes are applied with a first step of immersing into a sulfuric acid solution for electrolytic reduction for a predetermined period of time and a second step of immersing into a liquid in which an oxidative metal salt is added to sulfuric acid. The decontamination liquid which is used for immersing the stainless steel wastes in the second step and the oxidation force of which is lowered is used as the sulfuric acid solution in the first step for the carbon steel wastes. In view of the above, the decontamination liquid of the second step can be utilized most effectively, enabling to greatly decrease the secondary wastes and to improve decontamination efficiency. (T.M.)

  17. Effects of the addition of oil shale ash and coal ash on physic-chemical properties of CPJ45 cement

    Directory of Open Access Journals (Sweden)

    Nabih K.

    2014-04-01

    Full Text Available We focused our research on recycling industrial wastes, fly ash (F.A, bottom ash (B.A and oil shale ash (S.A in cement production. The study concerns physico-chemical characterization of these products and the influence of their addition on the mechanical proprieties of the CPJ45 cement. XRF allowed us to rank the three additives used according to their contents on major oxides. Coal ashes belong to the class F, and thus possess poozzolanic properties and oil shale ash belongs to the class C and possesses hydraulic and poozolanic properties. The crystalline phases constituting each ash were analysed by XRD. We observe in bottom ash the presence of quartz and mullite. The same crystals are found in fly ash with hematite and magnetite. Oil shale ash is composed of quartz, anhydrite, gehlenite, wollastonite and periclase. The microstructures of fly ash and bottom ash were studied using SEM. The bottom ash was composed respectively of fine particles that are generally irregularly shaped, their dimensions are between 5 and 28μm and of big particles(300 μm. The EDX analysis coupled with an electronic microscope provided some information about the major elements that constitute our samples. The dehydrations of anhydrous and three days hydrated cement were examined by DSC. For hydrated cements we noticed endothermic peaks related to the dehydration of CSH, CH and decomposition of carbonates. The study of the mechanical properties of CPJ45 cement by adding different proportions of fly ash, bottom ash and oil shale ash helped clarifying the percentage of ash that leaded to improve the 28 days mechanical strength. The results show that the cements studied have their maximum mechanical resistance with the addition at 7% of fly ash or 10% of oil shale ash.

  18. The suitability of a supersulfated cement for nuclear waste immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Collier, N.C., E-mail: nick.collier@sheffield.ac.uk [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Milestone, N.B. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Callaghan Innovation, 69 Gracefield Road, PO Box 31310, Lower Hutt 5040 (New Zealand); Gordon, L.E. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Geopolymer and Minerals Processing Group, Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, Victoria 3010 (Australia); Ko, S.-C. [Holcim Technology Ltd, Hagenholzstrasse 85, CH-8050 Zurich (Switzerland)

    2014-09-15

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste.

  19. The suitability of a supersulfated cement for nuclear waste immobilisation

    International Nuclear Information System (INIS)

    Collier, N.C.; Milestone, N.B.; Gordon, L.E.; Ko, S.-C.

    2014-01-01

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste

  20. The hardness and chemical changes in demineralized primary dentin treated by fluoride and glass ionomer cement

    Directory of Open Access Journals (Sweden)

    Gisele Fernandes DIAS

    Full Text Available Abstract Background Fluoride plays an important role in the control of dental caries. Aim To evaluate the chemical exchange between restoration of glass ionomer cement of high viscosity (GIC and primary dentin with application of sodium fluoride (NaF 2% through changes in hardness from uptake of calcium, phosphate and fluoride. Material and method Class I cavities were prepared in 40 sound primary molars, and the sample was divided into two groups (n=20 according to dentin condition: sound (1 and demineralized (2. Sub-groups (n=10 were formed to investigate the isolated action of the GIC or the association with NaF (F. This in vitro study examined the chemical exchange under two conditions, sound and demineralized dentin (pH cycling, to simulate the occurrence of mineral loss for the caries lesion. G1 and G2 received GIC restoration only; groups G1F and G2F received NaF before GIC restoration. The specimens were prepared for Knoop hardness test and micro-Raman spectroscopy. A two-way ANOVA test (α = 0.05 was used for statistical analysis. Micro-Raman data were qualitatively described. Result Increased hardness was observed in all the sites of direct contact with GIC in sound and demineralized dentin for all groups (p0.05. In the evaluation of micro-Raman, direct contact between GIC and dentin for sound and demineralized dentin resulted in increased peaks of phosphate. Conclusion The exchange between GIC and demineralized dentin may induce changes of mechanical properties of the substrate, and uptake of mineral ions (phosphate occurs without the influence of NaF.

  1. The Long-Term Study of Some mechanical and Chemical Properties of Polymer Modified Cement Waste Forms

    International Nuclear Information System (INIS)

    Shatta, H.A.; Eskander, S.B.

    2002-01-01

    The present work is a new experimental trend to study the long-term durability of polymer/cement/borate waste forms in storage and disposal sites during the long period of time. The data obtained indicate that all the samples of polymer modified cement waste forms immersed in both distilled and ground water (for more than 2700 days) show a slight increase in the compressive strength values. The chemical stability of the immobilized borate waste forms in distilled and ground water was studied. The cumulative leach fraction in percentage, of Cs-137 isotope from the final solidified waste forms in case of using ground water was lower than that in distilled water for all samples used and the presence of polymer lowered the percent release of radioactive Cs-137 isotope in all samples studied . The leach coefficients (Lc) and the leach indices (Li) of radioactive cesium-137 isotope for cement borate and polymer modified cement waste forms were also calculated. It was found that the leach indices values greater than 6

  2. Physico-chemical characteristics and Heavy metal levels in Drinking ...

    African Journals Online (AJOL)

    Physico-chemical characteristics and Heavy metal levels in Drinking Water ... composition was analysed using X-ray Fluorescence spectroscopy. Majority of the water samples had neutral pH (6.80 – 7.20) few were slightly alkaline and one was acidic. ... Heavy metals (copper and lead), rare earth metals (gallium, rubidium, ...

  3. Durability of cement-based materials: modeling of the influence of physical and chemical equilibria on the microstructure and the residual mechanical properties

    International Nuclear Information System (INIS)

    Guillon, E.

    2004-09-01

    A large part of mechanical and durability characteristics of cement-based materials comes from the performances of the hydrated cement, cohesive matrix surrounding the granular skeleton. Experimental studies, in situ or in laboratory, associated to models, have notably enhanced knowledge on the cement material and led to adapted formulations to specific applications or particularly aggressive environments. Nevertheless, these models, developed for precise cases, do not permit to specifically conclude for other experimental conclusions. To extend its applicability domain, we propose a new evolutive approach, based on reactive transport expressed at the microstructure scale of the cement. In a general point of view, the evolution of the solid compounds of the cement matrix, by dissolutions or precipitations, during chemical aggressions can be related to the pore solution evolution, and this one relied to the ionic exchanges with the external environment. By the utilization of a geochemical code associated to a thermodynamical database and coupled to a 3D transport model, this approach authorizes the study of all aggressive solution. The approach has been validated by the comparison of experimental observations to simulated degradations for three different environments (pure water, mineralized water, seawater) and on three different materials (CEM I Portland cement with 0.25, 0.4 and 0.5 water-to cement ratio). The microstructural approach permits also to have access to mechanical properties evolutions. During chemical aggressions, the cement matrix evolution is traduced in a microstructure evolution. This one is represented from 3D images similarly to the models developed at NIST (National Institute of Standards and Technology). A new finite-element model, validated on previous tests or models, evaluates the stiffness of the cement paste, using as a mesh these microstructures. Our approach identifies and quantifies the major influence of porosity and its spatial

  4. TSCA Chemical Data Reporting Fact Sheet: Reporting Manufactured Chemical Substances from Metal Mining and Related Activities

    Science.gov (United States)

    This fact sheet provides guidance on the Chemical Data Reporting (CDR) rule requirements related to the reporting of mined metals, intermediates, and byproducts manufactured during metal mining and related activities.

  5. Swelling behavior of ion exchange resins incorporated in tri-calcium silicate cement matrix: I. Chemical analysis

    International Nuclear Information System (INIS)

    Neji, M.; Bary, B.; Le Bescop, P.; Burlion, N.

    2015-01-01

    This paper presents the first part of a theoretical and experimental work aiming at modeling the chemo-mechanical behavior of composites made up of ion exchange resins (IER) solidified in a tri-calcium silicate cement paste (C_3S). Because of ion exchange processes, the volume change of the IER may cause internal pressures leading to the degradation of the material. In this study, a predictive modeling is developed for describing the chemical behavior of such material. It is based on thermodynamic equilibria to determine the evolution of the ion exchange processes, and the potential precipitation of portlandite in the composite. In parallel, a phenomenological study has been set up to understand chemical phenomena related to the swelling mechanisms. The model created has been finally implemented in a finite elements software; the simulation of a laboratory test has been performed and the results compared to experimental data. - Highlights: • Ion exchange theory to model the swelling behavior of Ion exchange resin. • Experimental phenomenon analysis about Chemo-mechanical interaction between IER and cement paste matrix. • Chemo-Transport modeling on a composite material made with IER embedded into cement paste matrix.

  6. Physical, chemical and mineralogical characterization of water treatment plant waste for use in soil-cement brick

    International Nuclear Information System (INIS)

    Pessin, L.R.; Destefani, A.Z.; Holanda, J.N.F.

    2011-01-01

    The water treatment plants (WTP) for human consumption generate huge amounts of waste in the form of sludge (sludge) that have been over the years mostly inadequately prepared in water resources and the environment. Moreover, traditional methods of disposal of waste water treatment plants commonly used are generally costly activities. An alternative method for disposal of this waste abundant is its incorporation in ceramic products. This work is focused on the physical-chemical and mineralogical composition of a sample of waste water treatment plants from the region of Campos dos Goytacazes-RJ to their use in the manufacture of soil-cement brick. Several characterization techniques were used including X-ray diffraction, X-ray fluorescence, scanning electron microscopy, picnometry, particle size analysis and plasticity. The experimental results indicate that the waste water treatment plants have the potential to be used in the manufacture of ecologic soil-cement bricks. (author)

  7. Evolution of cement based materials in a repository for radioactive waste and their chemical barrier function

    International Nuclear Information System (INIS)

    Kienzler, Bernhard; Metz, Volker; Schlieker, Martina; Bohnert, Elke

    2015-01-01

    The use of cementitious materials in nuclear waste management is quite widespread. It covers the solidification of low/intermediate-level liquid as well as solid wastes (e.g. laboratory wastes) and serves as shielding. For both high-level and intermediate-low level activity repositories, cement/concrete likewise plays an important role. It is used as construction material for underground and surface disposals, but more importantly it serves as barrier or sealing material. For the requirements of waste conditioning, special cement mixtures have been developed. These include special mixtures for the solidification of evaporator concentrates, borate binding additives and for spilling solid wastes. In recent years, low-pH cements were strongly discussed especially for repository applications, e.g. (Celine CAU DIT COUMES 2008; Garcia-Sineriz, et al. 2008). Examples for relevant systems are Calcium Silicate Cements (ordinary Portland cement (OPC) based) or Calcium Aluminates Cements (CAC). Low-pH pore solutions are achieved by reduction of the portlandite content by partial substitution of OPC by mineral admixtures with high silica content. The blends follow the pozzolanic reaction consuming Ca(OH) 2 . Potential admixtures are silica fume (SF) and fly ashes (FA). In these mixtures, super plasticizers are required, consisting of polycarboxilate or naphthalene formaldehyde as well as various accelerating admixtures (Garcia-Sineriz, et al. 2008). The pH regime of concrete/cement materials may stabilize radionuclides in solution. Newly formed alteration products retain or release radionuclides. An important degradation product of celluloses in cement is iso-saccharin acid. According to Glaus 2004 (Glaus and van Loon 2004), it reacts with radionuclides forming dissolved complexes. Apart from potentially impacting radionuclide solubility limitations, concrete additives, radionuclides or other strong complexants compete for surface sites for sorbing onto cement phases. In

  8. Assessment of metal loads in watersheds affected by acid mine drainage by using tracer injection and synoptic sampling: Cement Creek, Colorado, USA

    Science.gov (United States)

    Kimball, B.A.; Runkel, R.L.; Walton-Day, K.; Bencala, K.E.

    2002-01-01

    Watersheds in mineralized zones may contain many mines, each of which can contribute to acidity and the metal load of a stream. In this study the authors delineate hydrogeologic characteristics determining the transport of metals from the watershed to the stream in the watershed of Cement Creek, Colorado. Combining the injection of a chemical tracer, to determine a discharge, with synoptic sampling, to obtain chemistry of major ions and metals, spatially detailed load profiles are quantified. Using the discharge and load profiles, the authors (1) identified sampled inflow sources which emanate from undisturbed as well as previously mined areas; (2) demonstrate, based on simple hydrologic balance, that unsampled, likely dispersed subsurface, inflows are significant; and (3) estimate attenuation. For example, along the 12-km study reach, 108 kg per day of Zn were added to Cement Creek. Almost half of this load came from 10 well-defined areas that included both mined and non-mined parts of the watershed. However, the combined effect of many smaller inflows also contributed a substantial load that could limit the effectiveness of remediation. Of the total Zn load, 58.3 kg/day came from stream segments with no visible inflow, indicating the importance of contributions from dispersed subsurface inflow. The subsurface inflow mostly occurred in areas with substantial fracturing of the bedrock or in areas downstream from tributaries with large alluvial fans. Despite a pH generally less than 4.5, there was 58.4 kg/day of Zn attenuation that occurred in mixing zones downstream from inflows with high pH. Mixing zones can have local areas of pH that are high enough for sorption and precipitation reactions to have an effect. Principal component analysis classified inflows into 7 groups with distinct chemical signatures that represent water-rock interaction with different mineral-alteration suites in the watershed. The present approach provides a detailed snapshot of metal load

  9. A comparison of the marginal vertical discrepancies of zirconium and metal ceramic posterior fixed dental prostheses before and after cementation.

    Science.gov (United States)

    Gonzalo, Esther; Suárez, Maria J; Serrano, Benjamin; Lozano, Jose F L

    2009-12-01

    Marginal discrepancies of zirconia posterior fixed dental prostheses (FDPs) fabricated using various systems have been assessed to determine the quality of the restorations and facilitate clinical use; however, studies are limited and results are ambiguous because of the sample sizes and measurement methods. The purpose of this in vitro study was to compare changes in marginal fit of posterior fixed dental prostheses of 3 zirconia systems manufactured using CAD/CAM technology and metal ceramic posterior fixed dental protheses fabricated with the conventional lost-wax technique, before and after cementation. Forty standardized master steel dies with 2 abutments simulating first mandibular premolars were fabricated to receive a posterior 3-unit FDP (from first molar to first premolar) and divided into 4 groups (n=10): Lava All-Ceramic System, Procera Bridge Zirconia, VITA In-Ceram 2000 YZ, and metal ceramic (control group). All FDPs were prepared for an internal space of 50 microm. The external marginal gap of the restorations was investigated by measuring 30 points in the middle of the buccal and lingual surfaces; therefore, 60 measurements per abutment were recorded. Measurements were made with an image analysis program on the master steel model before and after conventional cementation with a glass ionomer agent (Ketac Cem Easymix). The data obtained were statistically analyzed using 1-way ANOVA, Duncan's multiple range post hoc test, and Student's paired t test (alpha=.05). No significant differences in the vertical marginal fit before and after cementation were recorded for the analyzed groups. The marginal discrepancy of Procera abutments before and after cementation (9 +/-10 microm and 12 +/-9 microm, respectively) was less than that of the other groups. Significant differences (P=.001) were observed in marginal adaptation between Procera Bridge Zirconia and the other groups. The results of this study showed that cementation did not cause a significant

  10. Cements in Radioactive Waste Disposal

    International Nuclear Information System (INIS)

    Glasser, F.P.

    2013-01-01

    nature of Portland cement is explained. Portland cement is the most widely used cement type and benefits from technology transfer from civil engineering research; also of the more than 150 years of experience of its durability and performance in a range of service environments. The origin of the chemical binding potential of cement arises from a combination of mechanisms: chemisorption on cement solids, incorporation by solid solution in cement solids and, at higher concentrations, precipitation of a solubility-limiting phase or phases in a calcium rich, high pH environment. These favourable potentials, especially pH conditioning, are, as noted, essentially sacrificial: cement must dissolve or react to maintain these conditions in the course of its service life. However the immobilisation potential will also change with time, even in isolation, because cement minerals undergo internal aging and slow reaction with other materials in the near field. Much research has been conducted, often on an empirical basis, leading to the characterisation of these potentials and of their time dependence. Yet the picture which emerges is incomplete and of variable quality. New research is described which, it is expected, will lead to a more scientific basis for the extrapolation of present-day cement performance into the future. The high pH of Portland cement matrices has advantages but also, disadvantages. For example, Portland cement gives excellent protection against corrosion to embedded steel but, on the other hand, it corrodes electropositive metals with evolution of hydrogen. Formation of a high pH 'plume' may also spread from the concrete to the near field, degrading other barriers such as bentonite and affecting the sorptive potential of the near field for radionuclides. These considerations have led to the search for alternative lower pH cements which are less alkaline than Portland cement. A description of some common types is given. However alternative choices present a

  11. Cements in Radioactive Waste Disposal

    Energy Technology Data Exchange (ETDEWEB)

    Glasser, F. P. [University of Aberdeen, Scotland (United Kingdom)

    2013-09-15

    nature of Portland cement is explained. Portland cement is the most widely used cement type and benefits from technology transfer from civil engineering research; also of the more than 150 years of experience of its durability and performance in a range of service environments. The origin of the chemical binding potential of cement arises from a combination of mechanisms: chemisorption on cement solids, incorporation by solid solution in cement solids and, at higher concentrations, precipitation of a solubility-limiting phase or phases in a calcium rich, high pH environment. These favourable potentials, especially pH conditioning, are, as noted, essentially sacrificial: cement must dissolve or react to maintain these conditions in the course of its service life. However the immobilisation potential will also change with time, even in isolation, because cement minerals undergo internal aging and slow reaction with other materials in the near field. Much research has been conducted, often on an empirical basis, leading to the characterisation of these potentials and of their time dependence. Yet the picture which emerges is incomplete and of variable quality. New research is described which, it is expected, will lead to a more scientific basis for the extrapolation of present-day cement performance into the future. The high pH of Portland cement matrices has advantages but also, disadvantages. For example, Portland cement gives excellent protection against corrosion to embedded steel but, on the other hand, it corrodes electropositive metals with evolution of hydrogen. Formation of a high pH 'plume' may also spread from the concrete to the near field, degrading other barriers such as bentonite and affecting the sorptive potential of the near field for radionuclides. These considerations have led to the search for alternative lower pH cements which are less alkaline than Portland cement. A description of some common types is given. However alternative choices present a

  12. Metallic taste from electrical and chemical stimulation.

    Science.gov (United States)

    Lawless, Harry T; Stevens, David A; Chapman, Kathryn W; Kurtz, Anne

    2005-03-01

    A series of three experiments investigated the nature of metallic taste reports after stimulation with solutions of metal salts and after stimulation with metals and electric currents. To stimulate with electricity, a device was fabricated consisting of a small battery affixed to a plastic handle with the anode side exposed for placement on the tongue or oral tissues. Intensity of taste from metals and batteries was dependent upon the voltage and was more robust in areas dense in fungiform papillae. Metallic taste was reported from stimulation with ferrous sulfate solutions, from metals and from electric stimuli. However, reports of metallic taste were more frequent when the word 'metallic' was presented embedded in a list of choices, as opposed to simple free-choice labeling. Intensity decreased for ferrous sulfate when the nose was occluded, consistent with a decrease in retronasal smell, as previously reported. Intensity of taste evoked by copper metal, bimetallic stimuli (zinc/copper) or small batteries (1.5-3 V) was not affected by nasal occlusion. This difference suggests two distinct mechanisms for evocation of metallic taste reports, one dependent upon retronasal smell and a second mediated by oral chemoreceptors.

  13. Comparative study of physico-chemical properties of MTA-based and Portland cements.

    Science.gov (United States)

    Borges, Alvaro H; Pedro, Fábio L M; Miranda, Carlos E S; Semenoff-Segundo, Alex; Pécora, Jesus D; Filho, Antônio M Cruz

    2010-01-01

    The purpose of this investigation was to evaluate the physicochemical properties of gray and white structural and nonstructural Portland cement, gray and white ProRoot MTA and MTA BIO. The water/powder ratio, setting time, solubility and pH (hydrogen-ion potential) changes of the materials were evaluated. Tests followed specification #57 from the American National Standard Institute/American Dental Association (2000) for endodontic sealing materials and pH was determined by a digital pH meter. The test results were statistically analyzed by variance analyses for global comparison and by the complementary Tukey's test for pairwise comparisons (5%). Considering the water/powder ratio, no significant difference (p > 0.05) was observed among the cements. MTA BIO (33.10 +/- 2.30) had the lowest setting time (p Portland cement (2.55 +/- 0.08) had the highest solubility (p 0.05) was observed among materials when considering pH evaluation. The pH levels were highly alkaline immediately after immersion in solution, remaining stable throughout the test period. The authors conclude that the cements had similar water/powder proportions. MTA BIO had the shortest setting time and gray ProRoot MTA had the lowest solubility. All cements had similar behavior in the pH analysis.

  14. Encapsulation, solid-phases identification and leaching of toxic metals in cement systems modified by natural biodegradable polymers

    International Nuclear Information System (INIS)

    Lasheras-Zubiate, M.; Navarro-Blasco, I.; Fernández, J.M.; Álvarez, J.I.

    2012-01-01

    Highlights: ► Speciation of Zn, Pb and Cr has been studied in chitosan-modified cement mortars. ► Metal retention mechanisms have been clarified by newly identified crystalline forms. ► Native chitosan induced and stabilized newly characterized Pb (IV) species. ► Dietrichite is responsible for the Zn immobilization in the polymer-modified mortar. ► Leaching of Zn decreased by 24% in the presence of low molecular weight chitosan. - Abstract: Cement mortars loaded with Cr, Pb and Zn were modified by polymeric admixtures [chitosans with low (LMWCH), medium (MMWCH) and high (HMWCH) molecular weight and hydroxypropylchitosan (HPCH)]. The influence of the simultaneous presence of the heavy metal and the polymeric additive on the fresh properties (consistency, water retention and setting time) and on the compressive strength of the mortars was assessed. Leaching patterns as well as properties of the cement mortars were related to the heavy metals-bearing solid phases. Chitosan admixtures lessened the effect of the addition of Cr and Pb on the setting time. In all instances, chitosans improved the compressive strength of the Zn-bearing mortars yielding values as high as 15 N mm −2 . A newly reported Zn phase, dietrichite (ZnAl 2 (SO 4 ) 4 ·22H 2 O) was identified under the presence of LMWCH: it was responsible for an improvement by 24% in Zn retention. Lead-bearing silicates, such as plumalsite (Pb 4 Al 2 (SiO 3 ) 7 ), were also identified by XRD confirming that Pb was mainly retained as a part of the silicate network after Ca ion exchange. Also, the presence of polymer induced the appearance and stabilization of some Pb(IV) species. Finally, diverse chromate species were identified and related to the larger leaching values of Cr(VI).

  15. Chemical and mineralogical characterization of two commercial cements and its evolution in function of time

    International Nuclear Information System (INIS)

    Gutierrez B, O.

    2014-01-01

    Mineralogical evolution of Portland cement is studied during hydration process using materials characterization techniques as X-ray diffraction (XRD) and scanning electron microscopy (Sem) in order to analyze the changes in the various cement minerals as alite, belite, celite, during processing to the hydrated phases of tobermorite gel, portlandite and ettringite, respectively, in the cement paste setting at different ages (3, 7 and 28 days). It was found that the hydration process occurs differently in each mineral because of their reaction rates or changes they experience in their crystals during processing of anhydrous to hydrated phase. You may notice changes in the appearance of the dough as you go hydration and the formation of tobermorite gel, portlandite and ettringite. (Author)

  16. Metals and dioxins on the air in a cement plant; Niveles ambientales de metales y dioxinas en las proximidades de una planta cementera

    Energy Technology Data Exchange (ETDEWEB)

    Domingo, J. L.

    2001-07-01

    In May 2000, the levels of a number of metals (As, Cd, Pb, Hg, Zn, Co, Cu, Mn, Sn, Tl, Cr, Ni, and V) were determined in soil and herbage samples taken from 16 sites in the vicinity of a cement plant (Sta. Margarita i els Monjos, Barcelona). During 2000, metal concentrations were also analyzed quarterly in filters from three stations placed near the facility. In soil and herbage samples, Mn and Zn showed the highest levels. However, most metal concentrations were similar or even lower than previously reported values for other areas in Catalonia. On the other hand, the levels of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) were also determined in 4 soil and 16 herbage samples. In comparison with the concentrations found in other places, the present levels are rather low. The current results show that the cement plant has a low impact on the metal and PCDD/PCDF levels in the environment under influence of the facility. (Author) 19 refs.

  17. Fracture prevention by prophylactic femoroplasty of the proximal femur--metallic compared with cemented augmentation.

    Science.gov (United States)

    Springorum, Hans-Robert; Gebauer, Matthias; Mehrl, Alexander; Stark, Olaf; Craiovan, Benjamin; Püschel, Klaus; Amling, Michael; Grifka, Joachim; Beckmann, Johannes

    2014-07-01

    To compare 2 different femoral neck augmentation techniques at improving the mechanical strength of the femoral neck. Twenty pairs of human cadaveric femora were randomly divided into 2 groups. In 1 group, the femora were augmented with a steel spiral; the other group with the cemented technique. The untreated contralateral side served as an intraindividual control. Fracture strength was evaluated using an established biomechanical testing scenario mimicking a fall on the greater trochanter (Hayes fall). The peak load to failure was significantly higher in the steel spiral group (P = 0.0024) and in the cemented group (P = 0.001) compared with the intraindividual controls. The peak load to failure showed a median of 3167 N (1825-5230 N) in the spiral group and 2485 N (1066-4395 N) in the spiral control group. The peak load to failure in the cemented group was 3698 N (SD ± 1249 N) compared with 2763 N (SD ± 1335 N) in the cement control group. Furthermore, fracture displacement was clearly reduced in the steel spiral group. Femoral augmentations using steel spirals or cement-based femoroplasty are technically feasible procedures. Our results demonstrate that a prophylactic reinforced proximal femur has higher strength when compared with the untreated contralateral limb. Prophylactic augmentation has potential to become an auxiliary treatment option to protect the osteoporotic proximal femur against fracture.

  18. Physical and chemical characterization of 50 pulverized coal ashes with respect to partial cement replacement in concrete

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sloot, H A; Weijers, E G

    1986-04-01

    Physical and chemical characterization of 50 pulverized coal ashes from Dutch, Belgian and German installations has been carried out to identify the parameters that have to be kept under control, when pulverized coal ashes are to be used as partial cement replacement in concrete. For a good workability of fly ash/cement mortars the particle size and the carbon content are important. By performing a mortar flow test (Heagermann) upon delivery exterme ashes can be easily eliminated. The compressive strength is largely determined by the fineness of the ash (weight fraction below 20 micron). A direct effect of carbon content on strength development is not observed, but a reduction in mortar slow due to carbon leads to loss in strength, while the workability has to be adjusted. Size distribution measurement by optical methods is recommended as the relevant part of the ash size distribution cannot be properly assessed by sieve methods. The net contribution of fly ash to the compressive strength of a fly ash/cement (20/80) mortar exhibits a minimum at 14 days curing, which is common to all 50 ashes studied. Improvements in ash quality as obtained from pulverized-coal fired installations can be achieved by improvements in coal milling and optimizing ash collection. 6 figs., 4 tabs., 19 refs.

  19. The influence of chemical composition and fineness on the performance of alkali activated cements obtained from blast furnace slags

    International Nuclear Information System (INIS)

    Langaro, Eloise Aparecida; Matoski, Adalberto; Luz, Caroline Angulski da; Buth, Islas Stein; Moraes, Maryah Costa de; Pereira Filho, Jose Ilo

    2017-01-01

    New binders are being developed for concrete in order to reduce the environmental impact mainly related to CO_2 emissions. Alkali -activated cements (CATs) are obtained from lime-aluminosilicate materials and an alkali activator and can reduce by 80% the emission of CO_2 compared to Portland Cement (PC). Papers have also shown physical and mechanical properties similar or higher than those presented by the PC, however, the activation of raw material is complex. Recent papers have also have showed a strong influence of the characteristics of raw material on the performance of CAT, however, little mentioned in the literature.. Therefore, this paper aimed to analyze the influence of characteristics of blast furnace slag (fineness and chemical composition) on the behavior of activated alkali cements. For this purpose, two slags were used, A and B, which were submitted to different milling times; and activated using 5% of NaOH. Mortars and pastes were prepared for compressive strength testing (7 and 28 days), measurements of heat of hydration and investigation of microstructure (XRD and DSC) were made. The results showed that the mortar made with slag A reached a very good mechanical performance, close to 48MPa at 28 days, and higher formation of CSH, in opposite of slag B. The probable hypothesis of this study is that the system formed in CAT made with slag A (containing more Al_2O_3) could provide CSH with a greater incorporation of Al and a lower crystallinity, increasing the mechanical strength. (author)

  20. The influence of organic cement additives on radionuclide mobility. A literature survey

    International Nuclear Information System (INIS)

    Hakanen, M.; Ervanne, H.

    2006-02-01

    This review evaluates the influence of organic cement additives on radionuclide mobility. The work outlines evaluations under cement conditions where report drafts were available, and an evaluation under groundwater conditions (non-cement conditions) based on the chemical structures of the main components in polyelectrolyte additives and on recent results of metal-humic bounding. Literature of effects of plasticizers on copper and bentonite are reviewed. (orig.)

  1. BiOBr@SiO2 flower-like nanospheres chemically-bonded on cement-based materials for photocatalysis

    Science.gov (United States)

    Wang, Dan; Hou, Pengkun; Yang, Ping; Cheng, Xin

    2018-02-01

    Endowment of photocatalytic property on the surface of concrete structure can contribute to the self-cleaning of the structure and purification of the polluted environment. We developed a nano-structured BiOBr@SiO2 photocatalyst and innovatively used for surface-treatment of cement-based materials with the hope of attaining the photocatalytic property in visible-light region and surface modification/densification performances. The SiO2 layer on the flower-like BiOBr@SiO2 helps to maintain a stable distribution of the photocatalyst, as well as achieving a chemical bonding between the coating and the cement matrix. Results showed that the color fading rate of during the degradation of Rhodamine B dye of the BiOBr-cem sample is 2 times higher compared with the commonly studied C, N-TiO2-cem sample. The photo-degradation rates of samples BiOBr-cem and BiOBr@SiO2-cem are 93 and 81% within 150 min, respectively, while sample BiOBr@SiO2-cem reveals a denser and smoother surface after curing for 28 days and pore-filling effect at size within 0.01-0.2 μm when compared with untreated samples. Moreover, additional C-S-H gel can be formed due to the pozzolanic reaction between BiOBr@SiO2 and the hardened cement matrix. Both advantages of the BiOBr@SiO2 favor its application for surface-treatment of hardened cement-based material to acquire an improved surface quality, as well as durable photocatalytic functionality.

  2. Optimization and validation of a chemical process for uranium, mercury and cesium leaching from cemented radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Reynier, N.; Lastra, R.; Laviolette, C.; Bouzoubaa, N., E-mail: nicolas.reynier@canada.ca [Natural Resources Canada, CanmetMINING, Ottawa, Ontario (Canada); Chapman, M. [Canadian Nuclear Laboratories, Chalk River, Ontario (Canada)

    2015-12-15

    Canadian Nuclear Laboratories (CNL) is developing a treatment and long-term management strategy for a legacy cemented radioactive waste that contains uranium, mercury, and fission products. Extracting the uranium would be advantageous for decreasing the waste classification and reducing the cost of long-term management. The chemical leachability of 3 key elements (U, Hg, and Cs) from a surrogate cemented waste (SCW) was studied with several lixiviants. The results showed that the most promising approach to leach and recover U, Hg, and Cs is the direct leaching of the SCW with H{sub 2}SO{sub 4} in strong saline media. Operating parameters such as particle size, temperature, pulp density, leaching time, acid and salt concentrations, number of leaching/washing steps, etc. were optimized to improve key elements solubilization. Sulfuric leaching in saline media of a SCW (U5) containing 1182 ppm of U, 1598 ppm of Hg, and 7.9 ppm of Cs in the optimized conditions allows key elements solubilisation of 98.5 ± 0.4%, 96.6 ± 0.1%, and 93.8 ± 1.1% of U, Hg, and Cs, respectively. This solubilization process was then applied in triplicate to 7 other SCWs prepared with different cements, liquid ratios, and at different aging times and temperatures. Concentrated sulfuric acid is added to the slurry until the pH is about 2, which causes the complete degradation of cement and the formation of CaSO{sub 4}. Sulfuric acid is particularly useful because it produces a leachate that is amenable to conventional ion exchange technology for the separation and recovery of uranium. (author)

  3. Preparation, Physical-Chemical Characterization, and Cytocompatibility of Polymeric Calcium Phosphate Cements

    Directory of Open Access Journals (Sweden)

    Rania M. Khashaba

    2011-01-01

    Full Text Available Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control. Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5–12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications.

  4. Local Chemical Reactivity of a Metal Alloy Surface

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Scheffler, Matthias

    1995-01-01

    The chemical reactivity of a metal alloy surface is studied by density functional theory investigating the interaction of H2 with NiAl(110). The energy barrier for H2 dissociation is largely different over the Al and Ni sites without, however, reflecting the barriers over the single component metal...

  5. Optimization and validation of a chemical process for uranium, mercury and cesium leaching from cemented radioactive wastes

    International Nuclear Information System (INIS)

    Reynier, N.; Riveros, P.; Lastra, R.; Laviolette, C.; Bouzoubaa, N.; Chapman, M.

    2015-01-01

    Atomic Energy of Canada Limited (AECL) is developing a treatment and long-term management strategy for a legacy cemented radioactive waste that contains uranium, mercury and fission products. Extracting the uranium would be advantageous for decreasing the waste classification and reducing the cost of long-term management. Consequently, there are safety and economic and environmental incentives for the extraction of uranium, mercury and cesium before subjecting the cemented waste to a stabilization process. The mineralogical analysis of the surrogate cemented waste (SCW) indicated that uranium forms calcium uranate, CaUO 4 , occurring as layers of several millimeters or as grains of 20 μm. Hg is found mostly as large (∼50 μm) and small grains (5-8 μm) of HgO. The chemical leachability of three key elements (U, Hg, and Cs) from a SCW was studied with several leaching materials. The results showed that the most promising approach to leach and recover U, Hg, and Cs is the direct leaching of the SCW with H 2 SO 4 in strong saline media. Operating parameters such as particle size, temperature, pulp density, leaching time, acid and salt concentrations, number of leaching/rinsing step, etc. were optimized to improve key elements solubilization. Sulfuric leaching in saline media of a SCW (U5) containing 1182 ppm of U, 1598 ppm of Hg, and 7.9 ppm of Cs in the optimized conditions allows key elements recovery of 98.5 ± 0.4%, 96.6 ± 0.1%, and 93.8 ± 1.1% of U, Hg, and Cs respectively. This solubilization process was then applied in triplicate to seven other SCW prepared with different cement, liquid ratio and at different aging time and temperature. Concentrated sulfuric acid is added to the slurry until the pH is about 2, which causes the complete degradation of cement and the formation of CaSO 4 . At this pH, the acid consumption is moderate and the formation of amorphous silica gel is avoided. Sulfuric acid is particularly useful because it produces a leachate that

  6. Influence of chemical bonding of chlorides with aluminates in cement hidratation process on corrosion steel bars in concrete

    Directory of Open Access Journals (Sweden)

    Bikić Farzet H.

    2010-01-01

    Full Text Available The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper, the influence of chemical bonding of chlorides with aluminates during the process of cement hydration on corrosion of steel bars in concrete was investigated. The process of chlorides bonding with aluminates yielding monochloride aluminate is monitored by XRD analyses. It was found that the amount of chlorides bonding with aluminates increases with an increase of temperature, and as a result, reduces the amount of 'free' chlorides in concrete. Potentiodynamic measurements have shown that increase in temperature of the heat treatment of working electrodes by chlorides leads to a reduction of steel bars corrosion as a result of either the increase of the monochloride-aluminate content or the decrease of free chlorides amount. Chlorides bound in chloroaluminate hydrates do not cause activation of steel bars corrosion in concrete. It was also proven that the increase of free chlorides concentration in the concrete leads to intensification of steel bars corrosion. This additionally approves that free chlorides are only the activators of process of steel bars corrosion in the concrete.

  7. Cement for Oil Well Cementing Operations in Ghana

    African Journals Online (AJOL)

    Michael

    For Portland cement to qualify as oil well cement, the chemical and physical properties must meet ..... Reservoir Engineering, Stanford University,. Stanford, California, pp. ... Construction”, PhD Thesis, Kwame Nkrumah. University of Science ...

  8. Influence of chemical composition of civil construction waste in the cement paste; Influencia da composicao quimica dos residuos da construcao civil a pasta de cimento

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, G.A.; Andrade, A.C.D.; Souza, J.M.M.; Evangelista, A.C.J.; Almeida, V.C., E-mail: valeria@eq.ufrj.b [Universidade Federal do Rio de Janeiro (EQ/UFRJ), RJ (Brazil). Escola de Quimica

    2009-07-01

    The construction and demolition waste when disposed inappropriately might cause serious public health problems. Its reutilization focusing on the development of new products using simple production techniques, assuring a new product life cycle and not damaging the environment is inserted in sustainable concept. The aim of this work was identifying the characteristics of types of waste generated in a residential reform (glassy ceramic and fill dirt leftovers) verifying separately its influence on cement pastes mechanical behavior. Cement pastes + wastes were prepared in 25% and 50% proportions with an approximately 0,35 water/cement relation and, glue time determination, water absorption, resistance to compression and X-ray fluorescence assays were taken. The results indicate that the chemical composition of the waste causes changes in the behavior of cement pastes, reflecting on their resistance to compression. (author)

  9. Crown and bridge cements: clinical applications.

    Science.gov (United States)

    Bunek, Sabiha S; Powers, John M

    2012-12-01

    Cement selection can be confusing because factors such as substrate, the type of restoration, and patient needs must be considered. Some substrates require additional treatment before cementation. This article describes the most commonly used traditional crown and bridge cements (GI and RMGI) used for metal and metal-ceramic restorations, and resin cements used for all-ceramic restorations. Advantages, disadvantages, indications, and contraindications of cements have been reviewed. Recommended uses of cements for metal, ceramic, and laboratory composite restorations have been presented. General guidelines for surface treatment ot silica- and zirconia-based restorations when using resin cements have been discussed.

  10. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives

    International Nuclear Information System (INIS)

    Voglar, Grega E.; Lestan, Domen

    2011-01-01

    Highlights: → We assess the feasibility of using soil S/S for industrial land reclamation. → Retarders, accelerators, plasticizers were used in S/S cementitious formulation. → We proposed novel S/S efficiency model for multi-metal contaminated soils. - Abstract: In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085 mg kg -1 of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12 N mm -2 achieved after S/S with CAC + PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC + Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively.

  11. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives

    Energy Technology Data Exchange (ETDEWEB)

    Voglar, Grega E. [RDA - Regional Development Agency Celje, Kidriceva ulica 25, 3000 Celje (Slovenia); Lestan, Domen, E-mail: domen.lestan@bf.uni-lj.si [Agronomy Department, Centre for Soil and Environmental Science, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana (Slovenia)

    2011-08-30

    Highlights: {yields} We assess the feasibility of using soil S/S for industrial land reclamation. {yields} Retarders, accelerators, plasticizers were used in S/S cementitious formulation. {yields} We proposed novel S/S efficiency model for multi-metal contaminated soils. - Abstract: In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085 mg kg{sup -1} of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12 N mm{sup -2} achieved after S/S with CAC + PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC + Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively.

  12. Physico-Chemical studies on irradiated polymer-reinforcement cement mortar composites

    International Nuclear Information System (INIS)

    Younes, M.M.

    2001-01-01

    The reinforced concrete suffers from corrosion by several salts, acids or alkalies and physico-mechanical properties are greatly affected. This leads to reduce the life of reinforced concrete structure. The present investigation deals with a comparison of corrosion presentation efficiency and passivity retention of reinforcement steel coated with methylethyl and propyl inhibitors which are prepared by using γ radiation and non-coated steel embedded in γ -induced polyester cement mortar composites. From the results of these studies several conclusions could be derived and these are summarized as follows: 1- The time required to reach passivation for coated steel embedded in the mortar after soaking in tap water for 28 days lies within the range 5-15 minutes; whereas, the time required to reach passivation for steel embedded in the polyester cement mortar composites is very short (1 minute). This result is related to the presence of copolymerized polyester in the pore system of the specimens. 2- The time required to reach passivation for steel coated by inhibitors in the mortar specimens after curing in tap water for 6 months is lower than that of non -coated steel embedded in the mortar specimens cured at the same conditions. 3- A relatively high degree of corrosion inhibition was obtained for the steel embedded in polyester-cement mortar composites after curing in sea water for 28 days, the time required to reach passivation is considered as moderate in the case of methyl and ethyl inhibitors the time to passivation (T.T.P.) = 9 minutes and the degree of inhibition of steel coated with the propyl inhibitor is comparatively low (T.T.P.=21 minutes)

  13. Evaluation method of radiation stability of hardened cement paste with chemical additives

    Energy Technology Data Exchange (ETDEWEB)

    Medvedev, Vyacheslav; Pustovgar, Andrey [National Research Univ. ' Moscow State Univ. of Civil Engineering' (MSUCE), Moscow (Russian Federation); National Research Univ. ' Moscow State Univ. of Civil Engineering' (MSUCE), Moscow (Russian Federation). Scientific Research Inst. of Constructional Materials and Technologies; Denisov, Alexander; Soloviev, Vitaly [National Research Univ. ' Moscow State Univ. of Civil Engineering' (MSUCE), Moscow (Russian Federation)

    2013-07-01

    The influence of additives on the radiation resistance of the concrete will occur through the influence of radiation changes of hardened cement paste on radiation changes of concrete and can be quite significant. The test sequence was produced according to the modified method. The samples were prepared in the form of prisms with the following dimensions: 10 mm x 10 mm, 30 mm long. Measurement series were produced after each heating and cooling sequence. Then the difference between the values before and after heating was calculated. (orig.)

  14. Tri-metallic ferrite oxygen carriers for chemical looping combustion

    Science.gov (United States)

    Siriwardane, Ranjani V.; Fan, Yueying

    2017-10-25

    The disclosure provides a tri-metallic ferrite oxygen carrier for the chemical looping combustion of carbonaceous fuels. The tri-metallic ferrite oxygen carrier comprises Cu.sub.xFe.sub.yMn.sub.zO.sub.4-.delta., where Cu.sub.xFe.sub.yMn.sub.zO.sub.4-.delta. is a chemical composition. Generally, 0.5.ltoreq.x.ltoreq.2.0, 0.2.ltoreq.y.ltoreq.2.5, and 0.2.ltoreq.z.ltoreq.2.5, and in some embodiments, 0.8.ltoreq.x.ltoreq.1.2, y.ltoreq.1.2, and z.gtoreq.0.8. The tri-metallic ferrite oxygen carrier may be used in various applications for the combustion of carbonaceous fuels, including as an oxygen carrier for chemical looping combustion.

  15. 21 CFR 888.3650 - Shoulder joint metal/polymer non-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ...) “Guidance Document for Testing Orthopedic Implants with Modified Metallic Surfaces Apposing Bone or Bone... “Implants for Surgery—Metallic Materials—Part 3: Wrought Titanium 6-Aluminum 4-Vandium Alloy,” (ii) ISO 5832-4:1996 “Implants for Surgery—Metallic Materials—Part 4: Cobalt-Chromium-Molybdenum Casting Alloy...

  16. 21 CFR 888.3660 - Shoulder joint metal/polymer semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ...),” (iii) “Guidance Document for Testing Orthopedic Implants with Modified Metallic Surfaces Apposing Bone... 5832-3:1996 “Implants for Surgery—Metallic Materials—Part 3: Wrought Titanium 6-aluminum 4-vandium Alloy,” (ii) ISO 5832-4:1996 “Implants for Surgery—Metallic Materials—Part 4: Cobalt-chromium-molybdenum...

  17. Chemical and topological short-range order in metallic glasses

    International Nuclear Information System (INIS)

    Vincze, I.; Schaafsma, A.S.; Van der Woude, F.; Kemeny, T.; Lovas, A.

    1980-10-01

    Moessbauer spectroscopy is applied to the study of chemical short-range order in (Fe,Ni)B metallic glasses. It is found that the atomic arrangement in melt-quenched glasses closely resembles that of the crystalline counterparts (Fe 3 B is tetragonal, Ni 3 B is orthorombic). The distribution of transition metal atoms is not random at high Ni concentrations: Ni atoms prefer a neighbourhood with a higher boron coordination. (P.L.)

  18. Evaluation of Heat Transfer to the Implant-Bone Interface During Removal of Metal Copings Cemented onto Titanium Abutments.

    Science.gov (United States)

    Cakan, Umut; Cakan, Murat; Delilbasi, Cagri

    2016-01-01

    The aim of this investigation was to measure the temperature increase due to heat transferred to the implant-bone interface when the abutment screw channel is accessed or a metal-ceramic crown is sectioned buccally with diamond or tungsten carbide bur using an air rotor, with or without irrigation. Cobalt-chromium copings were cemented onto straight titanium abutments. The temperature changes during removal of the copings were recorded over a period of 1 minute. The sectioning of coping with diamond bur and without water irrigation generated the highest temperature change at the cervical part of the implant. Both crown removal methods resulted in an increase in temperature at the implant-bone interface. However, this temperature change did not exceed 47°C, the potentially damaging threshold for bone reported in the literature.

  19. Physical, chemical and antimicrobial evaluation of a composite material containing quaternary ammonium salt for braces cementation

    Energy Technology Data Exchange (ETDEWEB)

    Sugii, Mari Miura [Departamento de Odontologia Restaurativa, Faculdade de Odontologia de Piracicaba – Universidade de Campinas, Piracicaba, SP 13414-903 (Brazil); Ferreira, Fábio Augusto de Souza, E-mail: ferreira.fabio.a.s@gmail.com [Grupo de Química de Materiais Híbridos e Inorgânicos, Instituto de Química de São Carlos – Universidade de São Paulo, São Carlos, SP 13563-120 (Brazil); Müller, Karina Cogo [Departamento de Ciências Fisiológicas, Área de Farmacologia, Anestesiologia e Terapeutica, Faculdade de Odontologia de Piracicaba – Universidade de Campinas, Piracicaba, SP 13414-903 (Brazil); Lima, Debora Alves Nunes Leite [Departamento de Odontologia Restaurativa, Faculdade de Odontologia de Piracicaba – Universidade de Campinas, Piracicaba, SP 13414-903 (Brazil); Groppo, Francisco Carlos [Departamento de Ciências Fisiológicas, Área de Farmacologia, Anestesiologia e Terapeutica, Faculdade de Odontologia de Piracicaba – Universidade de Campinas, Piracicaba, SP 13414-903 (Brazil); Imasato, Hidetake; Rodrigues-Filho, Ubirajara Pereira [Grupo de Química de Materiais Híbridos e Inorgânicos, Instituto de Química de São Carlos – Universidade de São Paulo, São Carlos, SP 13563-120 (Brazil); and others

    2017-04-01

    The antibiofilm effect of iodide quaternary ammonium methacryloxy silicate (IQAMS) in Transbond XT Light Cure Adhesive resin used for braces cementation was evaluated. Fourier Transform Infrared (FTIR) spectroscopy confirmed IQAMS formation and Scanning Electron Microscopy coupled to Energy-Dispersive X-ray Spectroscopy (SEM-EDS) revealed that as coating, the quaternary ammonium groups from IQAMS were homogeneously dispersed throughout the surface. When incorporated, the composite material presented homogeneous dispersion throughout the resin. Assays with Streptococcus mutans demonstrated enhanced antibiofilm effect for the IQAMS coated resin, with much lower colony-forming units (CFU), in comparison to incorporated IQAMS. Such a difference was assigned to low availability of quaternary ammonium groups at the surface of resin when IQAMS was incorporated, hindering its antibiofilm effect. Additionally, the incorporation of IQAMS led to slight decrease in ultimate bond strength (UBS) and shear bond strength (SBS), in comparison to the neat commercial resin. Thus, the synthesized IQAMS displays great potential as antibiofilm coating or sealant to prevent oral infections in brackets during orthodontic treatment. - Highlights: • Synthesis of ORMOSIL-based material with antibiofilm activity is performed. • Antibiofilm activity of the ORMOSIL-based material on commercial available resin for braces cementation is evaluated. • Antibiofilm ORMOSIL-based coating with potential application as varnish or sealant in orthodontic appliances is presented.

  20. Physical, chemical and antimicrobial evaluation of a composite material containing quaternary ammonium salt for braces cementation

    International Nuclear Information System (INIS)

    Sugii, Mari Miura; Ferreira, Fábio Augusto de Souza; Müller, Karina Cogo; Lima, Debora Alves Nunes Leite; Groppo, Francisco Carlos; Imasato, Hidetake; Rodrigues-Filho, Ubirajara Pereira

    2017-01-01

    The antibiofilm effect of iodide quaternary ammonium methacryloxy silicate (IQAMS) in Transbond XT Light Cure Adhesive resin used for braces cementation was evaluated. Fourier Transform Infrared (FTIR) spectroscopy confirmed IQAMS formation and Scanning Electron Microscopy coupled to Energy-Dispersive X-ray Spectroscopy (SEM-EDS) revealed that as coating, the quaternary ammonium groups from IQAMS were homogeneously dispersed throughout the surface. When incorporated, the composite material presented homogeneous dispersion throughout the resin. Assays with Streptococcus mutans demonstrated enhanced antibiofilm effect for the IQAMS coated resin, with much lower colony-forming units (CFU), in comparison to incorporated IQAMS. Such a difference was assigned to low availability of quaternary ammonium groups at the surface of resin when IQAMS was incorporated, hindering its antibiofilm effect. Additionally, the incorporation of IQAMS led to slight decrease in ultimate bond strength (UBS) and shear bond strength (SBS), in comparison to the neat commercial resin. Thus, the synthesized IQAMS displays great potential as antibiofilm coating or sealant to prevent oral infections in brackets during orthodontic treatment. - Highlights: • Synthesis of ORMOSIL-based material with antibiofilm activity is performed. • Antibiofilm activity of the ORMOSIL-based material on commercial available resin for braces cementation is evaluated. • Antibiofilm ORMOSIL-based coating with potential application as varnish or sealant in orthodontic appliances is presented.

  1. Front line of cement technolgy and control. Part 5. ; Baking process and chemical reactions. Cement saisentan sono gijutsu to kanri 5. ; Shosei katei to kagaku hanno

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, M. (Ube Industries, Ltd., Yamaguchi (Japan))

    1990-06-01

    The baking process in cement production means the process that the raw materials which were mixed and pulverized in the raw material preparation process are charged into a reaction furnace which is called kiln, and clinders (intermediate product of cement) are generated. It is the process which affects quality as well as production cost of cement more significantly than anything else. In this article, an outline of the above baking facilities, how the raw materials change and clinkers are generated therein, and how they are controlled are introduced. Clinkers are composed of such products as alite, belite, aluminate and ferrite, etc. which were generated after decomposition reactions of such raw materials as lime stone, clay, silica rock and iron oxide in the above kiln. The essential ponts of the process control which makes the generation reactions of clinker compounds efficiently are such two points as well balanced raw materials to be charged into the baking facilities and stable operation of such facilities. The quality of cement which is required as finished goods is achieved by the quality control at each intermediate process and the quality tests of cement. 5 refs., 10 figs., 2 tabs.

  2. Effects of toxic metals and chemicals on biofilm and biocorrosion.

    Science.gov (United States)

    Fang, Herbert H P; Xu, Li-Chong; Chan, Kwong-Yu

    2002-11-01

    Microbes in marine biofilms aggregated into clusters and increased the production of extracellular polymeric substances (EPS), by over 100% in some cases, when the seawater media containing toxic metals and chemicals, such as Cd(II), Cu(II), Pb(II), Zn(II), AI(III), Cr(III), glutaraldehyde, and phenol. The formation of microbial cluster and the increased production of EPS, which contained 84-92% proteins and 8-16% polysaccharides, accelerated the corrosion of the mild steel. However, there was no quantitative relationship between the degree of increased corrosion and the toxicity of metals/chemicals towards sulfate-reducing bacteria, or the increased EPS production.

  3. STUDY OF CHEMICAL INTERACTION OF MAGNESIA CEMENT WITH HIGH CONCENTRATION MAGNESIUM CHLORIDE SOLUTIONS

    Directory of Open Access Journals (Sweden)

    DEREVIANKO V. N.

    2015-10-01

    Full Text Available Problem statement. In activating MgO by electrolyte salts, as a result of formation of non water-resist magnesium silicate hydrate are obtained the durable cement stone having the low water-resist. I. P. Vyrodov considers [9; 5], that magnesia cement curing in mixing with sufficiently concentrated (C > 20 % solutions MgCl2 is caused with the crystallization of oxyhydrochloride composition: 3MgO∙MgCl2∙11Н2О, 5MgO∙MgCl2∙13Н2О and 7MgO∙MgCl2∙15Н2О. In the lower concentration parts of MgCl2 solution is formed a transitional compound of Mg[(OHnCl2-n] with isomorphous Mg(OH2 structure. At very low Cl concentration only Mg(OH2 is practically formed. Purpose. The Formation of water-resist magnesium silicate hydrates for obtaining of fast curing and solid structure of the magnesia stone. Conclusion. The dependence of the formation of the magnesia stone from the ratio (MgO/MgCl2 of the magnesia cement (MgO and the magnesium chloride solution (MgCl2 of different density has been identified in order to obtain the best content for oxyhydrochloride 3MgO•MgCl2•11Н2О, 5MgO•MgCl2•13Н2О and magnesium hydroxide (Mg(OH2. In putting into the system MgO∙–∙H2О of the silicic acid or fine ground quartz grains with size of less than 20 – 30 microns, over 1 month for the magnesium silicate hydrates formation is needed, where from 2 to 5 % of the total number of newgrowths are created. The study is proved by the expert opinion, that magnesium silicate hydrates do not have binding properties, unlike calcium silicate hydrates, and the main role in the system curing is played with the Mg(OH2 gel recrystallization, which provides the acceptable stone strength (R ≈ 30MPa in a few years. It has been also established, that in mixing of cement with low concentration MgO solutions of less than 1,5 mol/l (or 13% 1,1g/sm3, the final product in the stone structure is Mg(OH2. With increasing the sealer (MgCl2 solution there is formed by turn in

  4. Chemical compatibility of structural materials in alkali metals

    International Nuclear Information System (INIS)

    Natesan, K.; Rink, D.L.; Haglund, R.

    1995-01-01

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures in the range that are of interest for International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal-environments

  5. Comparative analysis of compressive strength tests at age of 28 and 90 days and density of products using chemical additives in cementing radioactive waste

    International Nuclear Information System (INIS)

    Vieira, Vanessa Mota; Tello, Cledola Cassia Oliveira de

    2013-01-01

    In this research it has been studied the effects of chemical additives (admixtures) in the cementation process of radioactive wastes, which are used to improve the properties of waste cementation process, both of the paste and of the solidified product. However there are a large variety of these materials that are frequently changed or taken out of the market, then it is essential to know the commercially available materials and their effects. The tests were carried out with a solution simulating the evaporator concentrate waste coming from PWR nuclear reactors. It was cemented using two formulations, A and B, incorporating higher or lower amount of waste, respectively. It was added chemical admixtures from two manufacturers (S and H), which were: accelerators, set retarders and superplasticizers. The experiments were organized by a factorial design 2 3 . The measured parameters were the viscosity, the setting time, the paste and product density and the compressive strength. In this study we performed comparative analyzes of the results of compressive strength at age of 28 and 90 days and between the densities of the samples at the same ages.The compressive strength test at age of 28 days is considered a parameter essential issues related to security handling, transport and storage of cemented waste product. The results showed that the addition of accelerators improved the compressive strength of the cemented product, but presented lower values density products. (author)

  6. Study on metal material corrosion behavior of packaging of cement solidified form

    International Nuclear Information System (INIS)

    He Zhouguo; Lin Meiqiong; Fan Xianhua

    1997-01-01

    The corrosion behavior of A3 carbon steel is studied by the specimens that are exposed to atmosphere, embedded in cement solidified form or immersed in corrosion liquid. The corrosion rate is determined by mass change of the specimens. In order to compare the corrosion resistant performance of various coatings, the specimens painted with various material such as epoxide resin, propionic acid resin, propane ether resin and Ti-white paint are tested. The results of the tests show that corrosion rate of A3 carbon steel is less than 10 -3 mm·a -1 in the atmosphere and the cement solidified from, less than 0.1 mm·a -1 in the corrosion liquids, and pH value in the corrosion liquids also affect the corrosion rate of A3 carbon steel. The corrosion resistant performance of Ti-white paint is better than that of other paints. So, A3 carbon steel as packaging material can meet the requirements during storage

  7. Metal-organic frameworks for the removal of toxic industrial chemicals and chemical warfare agents.

    Science.gov (United States)

    Bobbitt, N Scott; Mendonca, Matthew L; Howarth, Ashlee J; Islamoglu, Timur; Hupp, Joseph T; Farha, Omar K; Snurr, Randall Q

    2017-06-06

    Owing to the vast diversity of linkers, nodes, and topologies, metal-organic frameworks can be tailored for specific tasks, such as chemical separations or catalysis. Accordingly, these materials have attracted significant interest for capture and/or detoxification of toxic industrial chemicals and chemical warfare agents. In this paper, we review recent experimental and computational work pertaining to the capture of several industrially-relevant toxic chemicals, including NH 3 , SO 2 , NO 2 , H 2 S, and some volatile organic compounds, with particular emphasis on the challenging issue of designing materials that selectively adsorb these chemicals in the presence of water. We also examine recent research on the capture and catalytic degradation of chemical warfare agents such as sarin and sulfur mustard using metal-organic frameworks.

  8. A Coupled Transport and Chemical Model for Durability Predictions of Cement Based Materials

    DEFF Research Database (Denmark)

    Jensen, Mads Mønster; Johannesson, Björn; Geiker, Mette Rica

    The use of multi-physics numerical models to estimate different durability indicators and determine the service life of cement based materials is increasing. Service life documentation for concrete used in new infrastructure structures is required and the service life requirement....... The differential equations includes exchange terms between the phases and species accounting for the exchange of physical quantities which are essential for a stringent physical description of concrete. Balance postulates for, mass, momentum and energy, together with an entropy inequality are studied within...... mixture theories. Special attention is paid to the criteria for the exchange terms in the studied balance postulates. A simple case of mixture theory is used to demonstrate how constitutive assumptions are used to obtain the governing equations for a specific model. The governing equation system used...

  9. Durability of concrete: characterization and modeling of physical and chemical degradation of cement

    International Nuclear Information System (INIS)

    Adenot, Frederic

    1992-01-01

    Within the frame of nuclear waste management, and more particularly waste storage by confinement in parcels, concrete and geological environment, this research aims at predicting the durability of a concrete paste and of all concrete works. This prediction is based on a material characterization (determination of the thickness and composition of the attacked area) whatever the degradation duration is. The adopted approach is to model concrete lixiviation and to compare model results with experimental results. The model is also used to assess the influence of a great number of parameters, and to simulate non experimented cases. Thus, the author reports a bibliographical study on cement, and presents the equations of a lixiviation model. He reports experiments aimed at verifying modelling hypotheses and at acquiring necessary data. The model is then numerically solved, and applied to an experimental case. Experimental results are compared with modelling results, and a prediction is performed for a 300 year-duration [fr

  10. Chemical associations and mobilization of heavy metals in fly ash from municipal solid waste incineration.

    Science.gov (United States)

    Weibel, Gisela; Eggenberger, Urs; Schlumberger, Stefan; Mäder, Urs K

    2017-04-01

    This study focusses on chemical and mineralogical characterization of fly ash and leached filter cake and on the determination of parameters influencing metal mobilization by leaching. Three different leaching processes of fly ash from municipal solid waste incineration (MSWI) plants in Switzerland comprise neutral, acidic and optimized acidic (+ oxidizing agent) fly ash leaching have been investigated. Fly ash is characterized by refractory particles (Al-foil, unburnt carbon, quartz, feldspar) and newly formed high-temperature phases (glass, gehlenite, wollastonite) surrounded by characteristic dust rims. Metals are carried along with the flue gas (Fe-oxides, brass) and are enriched in mineral aggregates (quartz, feldspar, wollastonite, glass) or vaporized and condensed as chlorides or sulphates. Parameters controlling the mobilization of neutral and acidic fly ash leaching are pH and redox conditions, liquid to solid ratio, extraction time and temperature. Almost no depletion for Zn, Pb, Cu and Cd is achieved by performing neutral leaching. Acidic fly ash leaching results in depletion factors of 40% for Zn, 53% for Cd, 8% for Pb and 6% for Cu. The extraction of Pb and Cu are mainly limited due to a cementation process and the formation of a PbCu 0 -alloy-phase and to a minor degree due to secondary precipitation (PbCl 2 ). The addition of hydrogen peroxide during acidic fly ash leaching (optimized acidic leaching) prevents this reduction through oxidation of metallic components and thus significantly higher depletion factors for Pb (57%), Cu (30%) and Cd (92%) are achieved. The elevated metal depletion using acidic leaching in combination with hydrogen peroxide justifies the extra effort not only by reduced metal loads to the environment but also by reduced deposition costs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Chemical Speciation and Mobility of Some Heavy Metals in Soils ...

    African Journals Online (AJOL)

    The mobility of some heavy metals (Fe, Co, Ni and Mn) in soils around automobile waste dumpsites in Northern part of Niger Delta was assessed using Tessier et al. five syteps sequential chemical extraction procedure. The results showed that majority of iron and manganese were associated with the residual fraction with ...

  12. Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Henych, Jiří; Janos, P.; Skoumal, M.

    2016-01-01

    Roč. 236, č. 2016 (2016), s. 239-258 ISSN 0179-5953 R&D Projects: GA ČR(CZ) GAP106/12/1116 Institutional support: RVO:61388980 Keywords : chemical warfare agent * metal nanoparticle * unique surface- chemistry * mesoporous manganese oxide Subject RIV: CA - Inorganic Chemistry Impact factor: 3.930, year: 2016

  13. Chemical Abundances of Metal-poor stars in Dwarf Galaxies

    NARCIS (Netherlands)

    Venn, Kim A.; Jablonka, Pascale; Hill, Vanessa; Starkenburg, Else; Lemasle, Bertrand; Shetrone, Matthew; Irwin, Mike; Norris, John; Yong, David; Gilmore, Gerry; Salvadori, Stephania; Skuladottir, Asa; Tolstoy, Eline; Bragaglia, A.; Arnaboldi, M.; Rejkuba, M.; Romano, D.

    2016-01-01

    Stars in low-mass dwarf galaxies show a larger range in their chemical properties than those in the Milky Way halo. The slower star formation efficiency make dwarf galaxies ideal systems for testing nucleosynthetic yields. Not only are alpha-poor stars found at lower metallicities, and a higher

  14. Physico-chemical parameters and heavy metal contents of Ibuya ...

    African Journals Online (AJOL)

    The physico-chemical parameters and heavy metal contents of Ibuya River were investigated between September 2012 and August 2013 from four stations using standard methods to etermine acceptable water quality standards and evaluate possible sustainability of a thriving fisheries cum tourist sport fishing venture.

  15. Physico-chemical characteristics and Heavy metal levels in Drinking ...

    African Journals Online (AJOL)

    Physico-chemical characteristics and Heavy metal levels in Drinking Water sources in Sokoto metropolis in North-western Nigeria. ... Tap water samples had similar conductivity values (180 -190μS/m), sachet water samples had conductivity values ranging from 80μS/m to 260μS/m while well water samples had highest ...

  16. Comparison of electrocoagulation and chemical coagulation for heavy metal removal

    Energy Technology Data Exchange (ETDEWEB)

    Akbal, F.; Camci, S. [Ondokuz Mayis University, Engineering Faculty, Environmental Engineering Department, Kurupelit, Samsun (Turkey)

    2010-10-15

    Copper (Cu), chromium (Cr), and nickel (Ni) removal from metal plating wastewater by electrocoagulation and chemical coagulation was investigated. Chemical coagulation was performed using either aluminum sulfate or ferric chloride, whereas electrocoagulation was done in an electrolytic cell using aluminum or iron electrodes. By chemical coagulation, Cu-, Cr-, and Ni-removal of 99.9 % was achieved with aluminum sulfate and ferric chloride dosages of 500, 1000, and 2000 mg L{sup -1}, respectively. Removal of metals by electrocoagulation was affected by the electrode material, wastewater pH, current density, number of electrodes, and electrocoagulation time. Electrocoagulation with iron electrodes at a current density of 10 mA cm{sup -2}, electrocoagulation time of 20 min, and pH 3.0 resulted in 99.9 % Cu-, 99.9 % Cr-, and 98 % Ni-removal. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  17. Solidification/Stabilization of High Nitrate and Biodenitrified Heavy Metal Sludges with a Portland Cement/Flyash System

    International Nuclear Information System (INIS)

    Canonico, J.S.

    1995-01-01

    Pond 207C at Rocky Flats Environmental Technology Site (RFETS) contains process wastewaters characterized by high levels of nitrates and other salts, heavy metal contamination, and low level alpha activity. The purpose of this research was to investigate the feasibility of treating a high-nitrate waste, contaminated with heavy metals, with a coupled dewateriug and S/S process, as well as to investigate the effects of biodenitrification pretreatment on the S/S process. Pond 207C residuals served as the target waste. A bench-scale treatability study was conducted to demonstrate an S/S process that would minimize final product volume without a significant decrease in contaminant stabilization or loss of desirable physical characteristics. The process formulation recommended as a result a previous S/S treatability study conducted on Pond 207C residuals was used as the baseline formulation for this research. Because the actual waste was unavailable due to difficulties associated with radioactive waste handling and storage, a surrogate waste, of known composition and representative of Pond 207C residuals, was used throughout this research. The contaminants of regulatory concern added to the surrogate were cadmium, chromium, nickel, and silver. Product volume reduction was achieved by dewatering the waste prior to S/S treatment. The surrogate was dewatered by evaporation at 60 to 80 C to total solids contents from 43% to 78% by weight, and treated with Portland cement and fly ash. Two cement to flyash ratios were tested, 2:1 and 1:2, by weight. Contaminant leachability testing was conducted with a 0.5 water to pozzolan (the cement/flyash mixture) ratio and both cement to flyash ratios. Each product was tested for unconfined compressive strength (UCS) and for contaminant leachability by the Toxicity Characteristics Leaching Procedure (TCLP). At the highest solids content achieved by dewatering, 78% solids by weight, the predicted final waste form volume f or Pond 207C

  18. The refilling of pores in cement mortars treated by chemicals and desiccation at different temperatures

    Directory of Open Access Journals (Sweden)

    Menéndez Pazos, Ignacio

    1992-09-01

    Full Text Available Bases under the law of solubility product, the pores of the cement mortar are refilled by impregnation with two salts that form another insoluble salt. The number of treatments to be underdone and the drying temperatures more suitable in each case. The calcium salts like impregnants and urea sodium oxalate and sugar like precipitates are employed, obtained in each case the corresponding pores are occupied, which depends generally on the number of treatments and in particular the drier temperature.

    Basados en los principios del producto de solubilidad, se rellenan los poros de las probetas de mortero de cemento por impregnación con dos sales que forman otra insoluble. Se determina el número de tratamientos a realizar y las temperaturas de secado más idóneas en cada caso. Se emplean sales cálcicas como impregnantes, y urea, oxalato sódico y azúcar como precipitantes, obteniéndose en cada caso las correspondientes ocupaciones de poros que dependen, por lo general, del número de tratamientos y, en particular, de la temperatura de secado.

  19. Novel Nanotechnology of TiO2 Improves Physical-Chemical and Biological Properties of Glass Ionomer Cement

    Directory of Open Access Journals (Sweden)

    Daniela Dellosso Cibim

    2017-01-01

    Full Text Available The aim of this study was to assess the performance of glass ionomer cement (GIC added with TiO2 nanotubes. TiO2 nanotubes [3%, 5%, and 7% (w/w] were incorporated into GIC’s (Ketac Molar EasyMix™ powder component, whereas unblended powder was used as control. Physical-chemical-biological analysis included energy dispersive spectroscopy (EDS, surface roughness (SR, Knoop hardness (SH, fluoride-releasing analysis, cytotoxicity, cell morphology, and extracellular matrix (ECM composition. Parametric or nonparametric ANOVA were used for statistical comparisons (α≤0.05. Data analysis revealed that EDS only detected Ti at the 5% and 7% groups and that GIC’s physical-chemical properties were significantly improved by the addition of 5% TiO2 as compared to 3% and GIC alone. Furthermore, regardless of TiO2 concentration, no significant effect was found on SR, whereas GIC-containing 7% TiO2 presented decreased SH values. Fluoride release lasted longer for the 5% and 7% TiO2 groups, and cell morphology/spreading and ECM composition were found to be positively affected by TiO2 at 5%. In conclusion, in the current study, nanotechnology incorporated in GIC affected ECM composition and was important for the superior microhardness and fluoride release, suggesting its potential for higher stress-bearing site restorations.

  20. Chemical sensors based on molecularly modified metallic nanoparticles

    International Nuclear Information System (INIS)

    Haick, Hossam

    2007-01-01

    This paper presents a concise, although admittedly non-exhaustive, didactic review of some of the main concepts and approaches related to the use of molecularly modified metal nanoparticles in or as chemical sensors. This paper attempts to pull together different views and terminologies used in sensors based on molecularly modified metal nanoparticles, including those established upon electrochemical, optical, surface Plasmon resonance, piezoelectric and electrical transduction approaches. Finally, this paper discusses briefly the main advantages and disadvantages of each of the presented class of sensors. (review article)

  1. Metal-assisted chemical etch porous silicon formation method

    Science.gov (United States)

    Li, Xiuling; Bohn, Paul W.; Sweedler, Jonathan V.

    2004-09-14

    A thin discontinuous layer of metal such as Au, Pt, or Au/Pd is deposited on a silicon surface. The surface is then etched in a solution including HF and an oxidant for a brief period, as little as a couple seconds to one hour. A preferred oxidant is H.sub.2 O.sub.2. Morphology and light emitting properties of porous silicon can be selectively controlled as a function of the type of metal deposited, Si doping type, silicon doping level, and/or etch time. Electrical assistance is unnecessary during the chemical etching of the invention, which may be conducted in the presence or absence of illumination.

  2. State of chemical modeling modules for the degradation of concrete and cements

    Energy Technology Data Exchange (ETDEWEB)

    Meike, A.

    1997-04-15

    This report describes the conceptual framework upon which modeling activities will be needed to predict the chemistry of water in contact with concrete and its degradation products cover a broad area, from developing databases for existing abiotic codes, to developing codes that can simulate the chemical impact of microbial activities at a level of sophistication equivalent to that of the abiotic modeling codes, and ultimately, to simulating drift-scale chemical systems in support of hydrological, geochemical,a nd engineering efforts.

  3. Effect of chemical treatments on the mechanical properties of peanut shell and cement blends

    Directory of Open Access Journals (Sweden)

    Gatani, M.

    2010-06-01

    Full Text Available An abundance of agri-food waste in the area around Cordoba, Argentina, has driven the development of new construction materials. This study explored the applicability of peanut shells as additions in cement blends and the suitability of the properties of the resulting mixes for use in construction materials. The mechanical properties of the specimens were observed to improve when the shells were previously treated with quicklime (CaO or when sodium silicate and aluminium sulphate were added to the blend. While the resulting materials did not exhibit the same mechanical properties as traditional mortars and concretes, they do appear to be apt for use in lightweight and non-bearing structures.

    La abundante disponibilidad de residuos de la agroindustria local (Córdoba, Argentina, ha promovido el desarrollo de nuevos materiales para la construcción. Este trabajo de investigación se desarrolla a partir de la utilización de cáscara de maní como agregado en mezclas de cemento a fin de conocer las propiedades obtenidas en relación al tratamiento de dicho agregado, para la producción de materiales de construcción. Los ensayos demostraron mejoras en las propiedades mecánicas de las probetas realizadas con cemento y cáscaras previamente tratadas con cal viva (CaO, también en aquéllas aditivadas con silicato de sodio y sulfato de aluminio. Si bien los materiales resultantes no tienen las propiedades mecánicas de los morteros y hormigones tradicionales, parecen interesantes para ser aplicadas en componentes de construcción livianos y de uso no portante.

  4. Chemical metallization of KMPR photoresist polymer in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Zeb, Gul [MiQro Innovation Collaborative Centre (C2MI), 45, boul. de l' Aéroport, Bromont, QC, J2L 1S8 (Canada); Mining & Materials Engineering, McGill University, 3610,University Street, Montreal, QC, H3A 0C5 (Canada); Duong, Xuan Truong [Department of Mechanical Engineering, Ecole polytechnique de Montréal, Montréal, QC, H3C 3T5 (Canada); Thai Nguyen University of Technology, 3-2 Street, Thai Nguyen City (Viet Nam); Vu, Ngoc Pi; Phan, Quang The; Nguyen, Duc Tuong; Ly, Viet Anh [Thai Nguyen University of Technology, 3-2 Street, Thai Nguyen City (Viet Nam); Salimy, Siamak [ePeer Review LLC, 145 Pine Haven Shores Rd, Suite 1000-X, Shelburne, VT 05482 (United States); Le, Xuan Tuan, E-mail: xuantuan.le@teledyne.com [MiQro Innovation Collaborative Centre (C2MI), 45, boul. de l' Aéroport, Bromont, QC, J2L 1S8 (Canada); Thai Nguyen University of Technology, 3-2 Street, Thai Nguyen City (Viet Nam)

    2017-06-15

    Highlights: • Electroless deposition of Ni-B film on KMPR photoresist polymer insulator with excellent adhesion has been achieved. • This metallization has been carried out in aqueous solutions at low temperature. • Polyamine palladium complexes grafts serve as seeds for the electroless plating on KMPR. • This electroless metallization process is simple, industrially feasible, chromium-free and environment-friendly. - Abstract: While conventional methods for preparing thin films of metals and metallic alloys on insulating substrates in the field of microelectromechanical systems (MEMS) include vapor deposition techniques, we demonstrate here that electroless deposition can be considered as an alternate efficient approach to metallize the surface of insulating substrates, such as KMPR epoxy photoresist polymer. In comparison with the physical and chemical vapor deposition methods, which are well-established for metallization of photoresist polymers, our electroless nickel plating requires only immersing the substrates into aqueous solutions in open air at low temperatures. Thin films of nickel alloy have been deposited electrolessly on KMPR surface, through a cost-effective and environmental chromium-free process, mediated through direct grafting of amine palladium complexes in aqueous medium. This covalent organic coating provides excellent adhesion between KMPR and the nickel film and allows better control of the palladium catalyst content. Covalent grafting and characterization of the deposited nickel film have been carried out by means of Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy techniques.

  5. Metal accumulation by stream bryophytes, related to chemical speciation

    Energy Technology Data Exchange (ETDEWEB)

    Tipping, E. [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP (United Kingdom)], E-mail: et@ceh.ac.uk; Vincent, C.D.; Lawlor, A.J.; Lofts, S. [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP (United Kingdom)

    2008-12-15

    Metal accumulation by aquatic bryophytes was investigated using data for headwater streams of differing chemistry. The Windermere Humic Aqueous Model (WHAM) was applied to calculate chemical speciation, including competitive proton and metal interactions with external binding sites on the plants. The speciation modelling approach gives smaller deviations between observed and predicted bryophyte contents of Cu, Zn, Cd and Pb than regressions based on total filtered metal concentrations. If all four metals, and Ni, are considered together, the WHAM predictions are superior at the 1% level. Optimised constants for bryophyte binding by the trace metals are similar to those for humic substances and simple carboxylate ligands. Bryophyte contents of Na, Mg and Ca are approximately explained by binding at external sites, while most of the K is intracellular. Oxide phases account for some of the Al, and most of the Mn, Fe and Co. - Speciation modelling can be used to interpret the accumulation of Ni, Cu, Zn, Cd and Pb by bryophytes, supporting its use to quantify trace metal bioavailability in the field.

  6. Molecularly Imprinted Polymer/Metal Organic Framework Based Chemical Sensors

    Directory of Open Access Journals (Sweden)

    Zhenzhong Guo

    2016-10-01

    Full Text Available The present review describes recent advances in the concept of molecular imprinting using metal organic frameworks (MOF for development of chemical sensors. Two main strategies regarding the fabrication, performance and applications of recent sensors based on molecularly imprinted polymers associated with MOF are presented: molecularly imprinted MOF films and molecularly imprinted core-shell nanoparticles using MOF as core. The associated transduction modes are also discussed. A brief conclusion and future expectations are described herein.

  7. Electrochemical and chemical methods of metallizing plastic films

    OpenAIRE

    Chapples, J.

    1991-01-01

    This thesis describes two novel techniques for the metallization of non-electroactive polymer films and thicker sectioned polyethylene and nylon substrates. In the first approach, non-electroactive polymer substrates were impregnated with surface layers of polypyrrole and polyaniline, using electrochemical and chemical methods of polymerization. The relative merits of both these approaches are discussed and compared with other methods in the literature. The resultant composi...

  8. Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents.

    Science.gov (United States)

    Štengl, Václav; Henych, Jiří; Janoš, Pavel; Skoumal, Miroslav

    2016-01-01

    Metal oxides have very important applications in many areas of chemistry, physics and materials science; their properties are dependent on the method of preparation, the morphology and texture. Nanostructured metal oxides can exhibit unique characteristics unlike those of the bulk form depending on their morphology, with a high density of edges, corners and defect surfaces. In recent years, methods have been developed for the preparation of metal oxide powders with tunable control of the primary particle size as well as of a secondary particle size: the size of agglomerates of crystallites. One of the many ways to take advantage of unique properties of nanostructured oxide materials is stoichiometric degradation of chemical warfare agents (CWAs) and volatile organic compounds (VOC) pollutants on their surfaces.

  9. 23 Effects of Groundnut Husk Ash-blended Cement on Chemical ...

    African Journals Online (AJOL)

    Arc. Usman A. Jalam

    OPC/GHA concrete after curing in three chemical solutions (MgSO4, NaCl and H2SO4) at 14, 21 .... greatest production is in the northern parts of ..... Steel Reinforcement. ... Asia Publishing Limited, England, Longman Malaysia, VVP2000.

  10. Biomonitoring in California firefighters: metals and perfluorinated chemicals.

    Science.gov (United States)

    Dobraca, Dina; Israel, Leslie; McNeel, Sandra; Voss, Robert; Wang, Miaomiao; Gajek, Ryszard; Park, June-Soo; Harwani, Suhash; Barley, Frank; She, Jianwen; Das, Rupali

    2015-01-01

    To assess California firefighters' blood concentrations of selected chemicals and compare with a representative US population. We report laboratory methods and analytic results for cadmium, lead, mercury, and manganese in whole blood and 12 serum perfluorinated chemicals in a sample of 101 Southern California firefighters. Firefighters' blood metal concentrations were all similar to or lower than the National Health and Nutrition Examination Survey (NHANES) values, except for six participants whose mercury concentrations (range: 9.79 to 13.42 μg/L) were close to or higher than the NHANES reporting threshold of 10 μg/L. Perfluorodecanoic acid concentrations were elevated compared with NHANES and other firefighter studies. Perfluorodecanoic acid concentrations were three times higher in this firefighter group than in NHANES adult males. Firefighters may have unidentified sources of occupational exposure to perfluorinated chemicals.

  11. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Jamin M.; Catledge, Shane A., E-mail: catledge@uab.edu

    2016-02-28

    Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W{sub 2}CoB{sub 2}. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W{sub 2}CoB{sub 2} with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  12. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Johnston, Jamin M.; Catledge, Shane A.

    2016-01-01

    Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W_2CoB_2. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W_2CoB_2 with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  13. Evaluation of the chemical modifications in petroleum asphalt cement with the addition of polypropylene

    International Nuclear Information System (INIS)

    Marcondes, C.P.; Sales, M.J.A.; Resck, I.S.; Farias, M.M.; Souza, M.V.R.

    2010-01-01

    Studies show that the common distress mode in the Brazilian highway network are fatigue cracks and plastic deformation, which are associated with the type of material used in the pavement layers, structural project, excessive traffic load and weathering. To minimize these defects, research on modifiers such as polymers, added to asphalt binders have been developed to provide physical, chemical and rheological improvement. This paper investigates chemical modifications of the binders with the addition of PP by FTIR, NMR and DSC. FTIR spectra of pure and modified binder showed no differences in absorption. NMR analysis showed no strong chemical bonds between the binder and PP. DSC curve of PP showed a melting temperature of 160 deg C (ΔH = 94J/g) and the pure binder presented an endothermic transition between 20 and 40 deg C (ΔH = 2J/g). In the DSC curves of mixtures, these transitions are not significant, indicating possible interactions between asphalt binder and PP. (author)

  14. Chemical vapor deposition of refractory metals and ceramics III

    International Nuclear Information System (INIS)

    Gallois, B.M.; Lee, W.Y.; Pickering, M.A.

    1995-01-01

    The papers contained in this volume were originally presented at Symposium K on Chemical Vapor Deposition of Refractory Metals and Ceramics III, held at the Fall Meeting of the Materials Research Society in Boston, Massachusetts, on November 28--30, 1994. This symposium was sponsored by Morton International Inc., Advanced Materials, and by The Department of Energy-Oak Ridge National Laboratory. The purpose of this symposium was to exchange scientific information on the chemical vapor deposition (CVD) of metallic and ceramic materials. CVD technology is receiving much interest in the scientific community, in particular, to synthesize new materials with tailored chemical composition and physical properties that offer multiple functionality. Multiphase or multilayered films, functionally graded materials (FGMs), ''smart'' material structures and nanocomposites are some examples of new classes of materials being produced via CVD. As rapid progress is being made in many interdisciplinary research areas, this symposium is intended to provide a forum for reporting new scientific results and addressing technological issues relevant to CVD materials and processes. Thirty four papers have been processed separately for inclusion on the data base

  15. Chemical metallization of KMPR photoresist polymer in aqueous solutions

    Science.gov (United States)

    Zeb, Gul; Duong, Xuan Truong; Vu, Ngoc Pi; Phan, Quang The; Nguyen, Duc Tuong; Ly, Viet Anh; Salimy, Siamak; Le, Xuan Tuan

    2017-06-01

    While conventional methods for preparing thin films of metals and metallic alloys on insulating substrates in the field of microelectromechanical systems (MEMS) include vapor deposition techniques, we demonstrate here that electroless deposition can be considered as an alternate efficient approach to metallize the surface of insulating substrates, such as KMPR epoxy photoresist polymer. In comparison with the physical and chemical vapor deposition methods, which are well-established for metallization of photoresist polymers, our electroless nickel plating requires only immersing the substrates into aqueous solutions in open air at low temperatures. Thin films of nickel alloy have been deposited electrolessly on KMPR surface, through a cost-effective and environmental chromium-free process, mediated through direct grafting of amine palladium complexes in aqueous medium. This covalent organic coating provides excellent adhesion between KMPR and the nickel film and allows better control of the palladium catalyst content. Covalent grafting and characterization of the deposited nickel film have been carried out by means of Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy techniques.

  16. Influence of the mineralogical composition of cement in the diffusion of chemical species; Influencia de la composicion mineralogica del cemento en la difusion de especies quimicas

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, E.

    2015-07-01

    , setting time, color and others. Portland cements commonly used in the construction industry, they are based primarily on the mineral phases of limestone and silica. In conventional cement admixtures the chemical reactivity depends on the ratio of tricalcium and dicalcium silicate (C{sub 3}S/C{sub 2}S), the tricalcium aluminate (C{sub 3}A) influences in the setting time and tetra calcium ferro aluminate (C{sub 4}AF) gives a different color to the cement. In this research the mineralogical composition of two commercial cements is studied and its influence on the phenomenon of radionuclides retention. For this particular concrete discs were manufactured with water, sand and two commercial cements: Tolteca Extra CPC 30-RRS and Cruz Azul CPC Type II 30-R. The solid observation techniques used for analysis of the cement paste and concrete they are: X-ray Diffraction and Scanning Electron Microscopy, as well as the nuclear analytic techniques of Moessbauer and X-ray Fluorescence. (Author)

  17. Characterization of surrogate radioactive cemented waste: a laboratory study

    International Nuclear Information System (INIS)

    Fiset, J.F.; Lastra, R.; Bilodeau, A.; Bouzoubaa

    2011-01-01

    Portland cement is commonly used to stabilize intermediate and low level of radioactive wastes. The stabilization/solidification process needs to be well understood as waste constituents can retard or activate cement hydration. The objectives of this project were to prepare surrogate radioactive cemented waste (SRCW), develop a comminution strategy for SRCW, determine its chemical characteristics, and develop processes for long term storage. This paper emphasizes on the characterization of surrogate radioactive cemented waste. The SRCW produced showed a high degree of heterogeneity mainly due to the method used to add the solution to the host cement. Heavy metals such as uranium and mercury were not distributed uniformly in the pail. Mineralogical characterization (SEM, EDS) showed that uranium is located around the rims of hydrated cement particles. In the SRCW, uranium occurs possibly in the form of a hydrated calcium uranate.The SEM-EDS results also suggest that mercury occurs mainly in the form of HgO although some metallic mercury may be also present as a result of partial decomposition of the HgO. (author)

  18. Effects of radiant exposure and wavelength spectrum of light-curing units on chemical and physical properties of resin cements

    Directory of Open Access Journals (Sweden)

    Adriano Fonseca Lima

    2016-11-01

    Full Text Available Objectives In this study, we evaluated the influence of different radiant exposures provided by single-peak and polywave light-curing units (LCUs on the degree of conversion (DC and the mechanical properties of resin cements. Materials and Methods Six experimental groups were established for each cement (RelyX ARC, 3M ESPE; LuxaCore Dual, Ivoclar Vivadent; Variolink, DMG, according to the different radiant exposures (5, 10, and 20 J/cm2 and two LCUs (single-peak and polywave. The specimens were made (7 mm in length × 2 mm in width × 1 mm in height using silicone molds. After 24 hours of preparation, DC measurement was performed using Fourier transform infrared spectrometry. The same specimens were used for the evaluation of mechanical properties (flexural strength, FS; elastic modulus, E by a three-point bending test. Data were assessed for normality, after which two-way analysis of variance (ANOVA and post hoc Tukey's test were performed. Results No properties of the Variolink cement were influenced by any of the considered experimental conditions. In the case of the RelyX ARC cement, DC was higher when polywave LCU was used; FS and E were not influenced by the conditions evaluated. The LuxaCore cement showed greater sensitivity to the different protocols. Conclusions On the basis of these results, both the spectrum of light emitted and the radiant exposure used could affect the properties of resin cements. However, the influence was material-dependent.

  19. In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

    Science.gov (United States)

    Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

    2004-03-23

    A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

  20. Addition of bioactive glass to glass ionomer cements: Effect on the physico-chemical properties and biocompatibility.

    Science.gov (United States)

    De Caluwé, T; Vercruysse, C W J; Ladik, I; Convents, R; Declercq, H; Martens, L C; Verbeeck, R M H

    2017-04-01

    Glass ionomer cements (GICs) are a subject of research because of their inferior mechanical properties, despite their advantages such as fluoride release and direct bonding to bone and teeth. Recent research aims to improve the bioactivity of the GICs and thereby improve mechanical properties on the long term. In this study, two types of bioactive glasses (BAG) (45S5F and CF9) are combined with GICs to evaluate the physico-chemical properties and biocompatibility of the BAG-GIC combinations. The effect of the addition of Al 3+ to the BAG composition and the use of smaller BAG particles on the BAG-GIC properties was also investigated. Conventional aluminosilicate glass (ASG) and (modified) BAG were synthesized by the melt method. BAG-GIC were investigated on setting time, compressive strength and bioactivity. Surface changes were evaluated by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), EDS and PO 4 3- -and Ca 2+ uptake in SBF. Biocompatibility of selected BAG-GICs was determined by a direct toxicity assay. The addition of BAG improves the bioactivity of the GIC, which can be observed by the formation of an apatite (Ap) layer, especially in CF9-containing GICs. More BAG leads to more bioactivity but decreases strength. The addition of Al 3+ to the BAG composition improves strength, but decreases bioactivity. BAGs with smaller particle sizes have no effect on bioactivity and decrease strength. The formation of an Ap layer seems beneficial to the biocompatibility of the BAG-GICs. Bioactive GICs may have several advantages over conventional GICs, such as remineralization of demineralized tissue, adhesion and proliferation of bone- and dental cells, allowing integration in surrounding tissue. CF9 BAG-GIC combinations containing maximum 10mol% Al 3+ are most promising, when added in ≤20wt% to a GIC. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Chemical and biological properties of toxic metals and use of chelating agents for the pharmacological treatment of metal poisoning

    Energy Technology Data Exchange (ETDEWEB)

    Sinicropi, Maria Stefania; Caruso, Anna [University of Calabria, Department of Pharmaceutical Sciences, Rende (Italy); Amantea, Diana [University of Calabria, Department of Pharmacobiology, Rende (Italy); Saturnino, Carmela [University of Salerno, Department of Pharmaceutical Sciences, Fisciano (Italy)

    2010-07-15

    Exposure to toxic metals is a well-known problem in industrialized countries. Metals interfere with a number of physiological processes, including central nervous system (CNS), haematopoietic, hepatic and renal functions. In the evaluation of the toxicity of a particular metal it is crucial to consider many parameters: chemical forms (elemental, organic or inorganic), binding capability, presence of specific proteins that selectively bind metals, etc. Medical treatment of acute and chronic metal toxicity is provided by chelating agents, namely organic compounds capable of interacting with metal ions to form structures called chelates. The present review attempts to provide updated information about the mechanisms, the cellular targets and the effects of toxic metals. (orig.)

  2. Chemical Decontamination of Metallic Waste from Uranium Conversion Plant Dismantling

    International Nuclear Information System (INIS)

    Hwang, D. S.; Choi, Y. D.; Hwang, S. T.; Park, J. H.; Byun, J. I.; Jang, N. S.

    2005-01-01

    Korea Atomic Energy Research Institute (KAERI) started a decommissioning program of the uranium conversion plant. Pre-work was carried as follows; installation of the access control facility, installation of a changing room and shower room, designation of an emergency exit way and indicating signs, installation of a radiation management facility, preparation of a storage area for tools and equipments, inspection and load test of crane, distribution and packaging of existing waste, and pre-decontamination of the equipment surface and the interior. First, decommissioning work was performed in kiln room, which will be used for temporary radioactive waste storage room. Kiln room housed hydro fluorination rotary kiln for production of uranium tetra-fluoride. The kiln is about 0.8 m in diameter and 5.5 m long. The total dismantled waste was 6,690 kg, 73 % of which was metallic waste and 27 % the others such as cable, asbestos, concrete, secondary waste, etc. And effluent treatment room and filtration room were dismantled for installation of decontamination equipment and lagoon sludge treatment equipment. There were tanks and square mixer in these rooms. The total dismantled waste was 17,250 kg, 67% of which was metallic waste and 33% the others. These dismantled metallic wastes consist of stainless and carbon steel. In this paper, the stainless steel plate and pipe were decontaminated by the chemical decontamination with ultrasonic

  3. Metal organic frameworks for the catalytic detoxification of chemical warfare nerve agents

    Science.gov (United States)

    Hupp, Joseph T.; Farha, Omar K.; Katz, Michael J.; Mondloch, Joseph E.

    2017-04-18

    A method of using a metal organic framework (MOF) comprising a metal ion and an at least bidendate organic ligand to catalytically detoxify chemical warfare nerve agents including exposing the metal-organic-framework (MOF) to the chemical warfare nerve agent and catalytically decomposing the nerve agent with the MOF.

  4. Radiation chemical route for preparation of metal nanoparticles

    International Nuclear Information System (INIS)

    Kapoor, S.; Mukherjee, T.

    2006-01-01

    Nanoparticles show properties that are neither seen in the bulk or at atomic level. The unusual properties are governed by quantum size effect. Due to this various methodologies have been endeavored to control the size of the particles. In the present work we show the use of two complimentary techniques (radiation and photo) to synthesize and control the size of the metal particles. In-situ synthesis of fine silver, thallium and cadmium particles has been carried out by gamma-irradiation and electron pulse irradiation at room temperature in the pre-organized gel of polyacrylamide or cyclodextrin cavity. The role of generation of nuclei in high concentrations in stabilization of metal nanoparticles in hydrophobic cavity is shown. Similarly the importance of entrapment of metal ions in the polymer matrix during its formation is highlighted. The work is further extended to exploit the microemulsion droplets for stabilization of Cd nanoparticles. Utility of pulse radiolysis in probing the mechanism of the formation of metal nanoparticles is also shown. Ultrafast laser pulses were employed to control the morphology of the pre-prepared Pt nanoparticles. The changes in reduction of shape and size are considered to occur through melting and vaporization of the nanoparticles. Pt nanoparticles were coated on the inner walls of the tubular pyrex reactor and tested for their catalytic activity for oxidation of CO. It was observed that Pt nanoparticles prepared in the presence of a stabilizer (gelatin) showed a higher tendency to adhere to the inner walls of the pyrex reactor as compared to that prepared in the presence of silica nanoparticles. The catalyst was found to be active at ≥150 degree C giving CO 2 . Chemically reduced Pt nanoparticles stabilized on silica nanoparticles gave ∼7% CO conversion per hr. However, radiolytically prepared Pt nanoaprticles stabilized by gelatin gave ∼10% conversion per hr. The data indicates that catalytic oxidation of CO takes place

  5. Removal of Heavy Metal Ions by Using Composite of Cement Kiln Dust/Ethylene Glycol co Acrylic Acid Prepared by y-Irradiation

    International Nuclear Information System (INIS)

    Sokker, H.H.; Abdel-Rahman, H.A.; Khattab, M.M.; Ismail, M.R.

    2010-01-01

    Various composites of cement kiln dust (CKD) and poly(ethylene glycol co acrylic acid) using y-irradiation was investigated. The samples were prepared using three percentages of cement kiln dust namely, 20, 50 and 75 by wt % and mixed with an equimolar ratio (1:1) of ethylene glycol and acrylic acid then irradiated at doses; 10,20 and 30 kGy of gamma-irradiation. The results showed that (CKD) and poly(ethylene glycol co acrylic acid) composites were formed only at 30 kGy. In addition, CKD alone has the lowest degree of removal of heavy metal ions compared with the prepared composites. A composite containing 75% cement kiln dust by weight percentage, showed the highest degree of removal of cobalt ions, whereas, a composite of 20% CKD showed the highest degree for cadmium ion removal. While the composite of 75% CKD showed a higher selectivity of cobalt ion than cadmium ion in their mixed solution.

  6. Physical, chemical and radioactive characterization of co-products from titanium dioxide industry for valorization in the cement industry

    International Nuclear Information System (INIS)

    Gazquez, M.J.; Mantero, J.; Bolivar, J.P.; Garcia-Tenorio, R.; Vaca, F.

    2011-01-01

    The present study was conducted to characterize the raw materials (ilmenite and slag), waste (red gypsum) and several co-products (sulphate monohydrate and sulphate heptahydrated) form the titanium dioxide industry in relation to their elemental composition (major, minor and trace elements), granulometry, mineralogy, microscopic morphology, physical composition and radioactive content in order to apply this knowledge in the valorization of the co-products in the fields such a as construction, civil engineering, etc. In particular, the main properties of cements produced with different proportions of red gypsum were studied, and the obtained improvements, in relation to Ordinary Portland Cements (OPC) were evaluated. It was also demonstrated that the levels of pollutants and the radioactive content in the produced RG cements, remain within the regulated safety limits. (Author). 38 refs.

  7. Modeling of the interaction between chemical and mechanical behavior of ion exchange resins encapsulated into a cement-based matrix

    International Nuclear Information System (INIS)

    Neji, Mejdi

    2014-01-01

    Ion exchange resins (IER) are widely used in the nuclear industry to purge non directly storable infected effluents. IER then become a solid waste which could be stored as any classical nuclear waste. One way of conditioning consists in embedding it into a cement paste matrix. This process raises some concerns regarding the cohesiveness of the composite. Once embedded, the IER might indeed interact with the cement paste which would lead, in some cases, to the swelling of the composite. This thesis has been set up to address this potential issue, with the aim to develop a numerical tool able to predict the mechanical behavior of this kind of material. This work only focuses on the long term behavior and more specifically on the potential degradations of the cement paste/IER composite due to cationic IER. (author)

  8. Assessment of heavy metal removal technologies for biowaste by physico-chemical fractionation

    NARCIS (Netherlands)

    Veeken, A.H.M.; Hamelers, H.V.M.

    2003-01-01

    In the Netherlands, the heavy metal content of biowaste-compost frequently exceeds the legal standards for heavy metals. In order to assess heavy metal removal technologies, a physico-chemical fractionation scheme was developed to gain insight into the distribution of heavy metals (Cd, Cu, Pb and

  9. Chemical effects of nuclear transformations in metal permanganates

    International Nuclear Information System (INIS)

    Lee, Byung Hun; Kim, Bong Whan

    1986-01-01

    The chemical effects resulting from the capture of the thermal neutrons by manganese in different crystalline permanganates, that is, potassium permanganate,sodium permanganate, silver permanganate, barium permanganate and ammonium permanganate, have been investigated. The distribution of radioactive manganese formed has been determined by using different absorbents and ion-exchangers, that is,manganese dioxide, alumina, Zeolite A-3, Kaolinite and Dowex-50. The distribution of radioactive manganese in various adsorbents and ion-exchangers has almost similar result for each permanganate. The affinity for radioactive manganous ion is greatest for Dewex-50. A significant increase of retention is shown through the thermal annealing and the retention depends on the first ionization potential of metal ion in permanganates. (Author)

  10. CMP [Chemicals, Metals, and Pesticides] Pits: Environmental information document

    International Nuclear Information System (INIS)

    Scott, S.C.; Kolb, N.L.; Price, V.; Bledsoe, H.W.

    1986-12-01

    This document provides environmental information on postulated closure options for the Chemicals, Metals, and Pesticides (CMP) Pits at the Savannah River Plant and was developed as background technical documentation for the Department of Energy's proposed Environmental Impact Statement (EIS) on waste management activities for groundwater protection at the plant. The results of groundwater and atmospheric pathway analyses, accident analysis, and other environmental assessments discussed in this document are based upon a conservative analysis of all foreseeable scenarios as defined by the National Environmental Policy Act (40 CFR 1500-1508). The scenarios do not necessarily represent actual environmental conditions. This document is not meant to be used as a regulatory closure plan or other regulatory document to comply with required federal or state environmental regulations

  11. EXAFS characterization of supported metal catalysts in chemically dynamic environments

    International Nuclear Information System (INIS)

    Robota, H.J.

    1991-01-01

    Characterization of catalysts focuses on the identification of an active site responsible for accelerating desirable chemical reactions. The identification, characterization, and selective modification of such sites is fundamental to the development of structure-function relationships. Unfortunately, this goal is far from realized in nearly all catalysts, and particularly in catalysts comprised of small supported metal particles. X-ray absorption spectroscopy (XAS) has had a dramatic effect on our understanding of supported metal particles in their resting state. However, the performance of a catalyst can not be assessed from such simple resting state measurements. Among the factors which influence catalyst performance are the exact catalyst composition, including the support and any modifiers; particle size; catalyst finishing and pretreatment conditions; pressure, composition, and temperature of the operating environment; time. Gaining an understanding of how the structure of a catalytic site can change with such an array of variables requires that we begin to develop measurement methods which are effective under chemically dynamic conditions. Ideally, it should be possible to obtain a full X-ray absorption spectrum of each element thought to have a causal relationship with observed catalyst properties. From these spectra, we can optimally extract only a relatively limited amount of information which we must then piece together with information derived from other characterization methods and intuition to arrive at a hypothetical structure of the operating catalyst. Information about crystallinity, homogeneity, and general disorder can be obtained from the Debye-Waller factor. Finally, through analogy with known compounds, the electronic structure of the active atoms can be inferred from near edge absorption features

  12. Evaluating the freeze-thaw durability of portland cement-stabilized-solidified heavy metal waste using acoustic measurements

    International Nuclear Information System (INIS)

    El-Korchi, T.; Gress, D.; Baldwin, K.; Bishop, P.

    1989-01-01

    The use of stress wave propagation to assess freeze-thaw resistance of portland cement solidified/stabilized waste is presented. The stress wave technique is sensitive to the internal structure of the specimens and would detect structural deterioration independent of weight loss or visual observations. The freeze-thaw resistance of a cement-solidified cadmium waste and a control was evaluated. The control and cadmium wastes both showed poor freeze-thaw resistance. However, the addition of cadmium and seawater curing increased the resistance to more cycles of freezing and thawing. This is attributed to microstructural changes

  13. The influence of prefabricated pipe cement coatings and those made during pipe renovation on drinking water quality

    Directory of Open Access Journals (Sweden)

    Młyńska Anna

    2017-01-01

    Full Text Available Nowadays, cement coatings are often used as an anticorrosion protection of the internal surfaces of manufactured ductile iron water pipes. The protective cement linings are also commonly used for old water pipe renovation. In both cases, the cement lining is an excellent anticorrosion protection of the pipelines, effectively separating the pipe wall from the flowing water. Moreover, cement linings protect the pipelines not only by a mechanical barrier, but also by a chemical barrier creating a highly alkaline environment in water contact with the metal pipe wall. In addition, cement coatings have an ability for so-called self-regeneration and provide the improvement of hydraulic conditions inside the pipelines. In turn, the differences between the analysed cement coatings mainly depend on the types of cements used and techniques of cement mortar spraying. As was expected, they influence the quality of water having contact with the coating. A comparison of the impact of cement coatings manufactured in factories and sprayed on building sites during the renovation on drinking water quality parameters was performed in the study. The experiments were conducted in laboratory conditions, using the test stands prepared for this purpose. The results include analysis of selected water quality parameters for the samples contacting with cement mortar and collected during the investigation.

  14. Chemical composition, effective atomic number and electron density study of trommel sieve waste (TSW), Portland cement, lime, pointing and their admixtures with TSW in different proportions

    International Nuclear Information System (INIS)

    Kurudirek, Murat; Aygun, Murat; Erzeneoglu, Salih Zeki

    2010-01-01

    The trommel sieve waste (TSW) which forms during the boron ore production is considered to be a promising building material with its use as an admixture with Portland cement and is considered to be an alternative radiation shielding material, also. Thus, having knowledge on the chemical composition and radiation interaction properties of TSW as compared to other building materials is of importance. In the present study, chemical compositions of the materials used have been determined using a wavelength dispersive X-ray fluorescence spectrometer (WDXRFS). Also, TSW, some commonly used building materials (Portland cement, lime and pointing) and their admixtures with TSW have been investigated in terms of total mass attenuation coefficients (μ/ρ), photon interaction cross sections (σ t ), effective atomic numbers (Z eff ) and effective electron densities (N e ) by using X-rays at 22.1, 25 keV and γ-rays at 88 keV photon energies. Possible conclusions were drawn with respect to the variations in photon energy and chemical composition.

  15. Development of high-performance blended cements

    Science.gov (United States)

    Wu, Zichao

    2000-10-01

    This thesis presents the development of high-performance blended cements from industrial by-products. To overcome the low-early strength of blended cements, several chemicals were studied as the activators for cement hydration. Sodium sulfate was discovered as the best activator. The blending proportions were optimized by Taguchi experimental design. The optimized blended cements containing up to 80% fly ash performed better than Type I cement in strength development and durability. Maintaining a constant cement content, concrete produced from the optimized blended cements had equal or higher strength and higher durability than that produced from Type I cement alone. The key for the activation mechanism was the reaction between added SO4 2- and Ca2+ dissolved from cement hydration products.

  16. Barium aluminate cement: its application

    International Nuclear Information System (INIS)

    Drozdz, M.; Wolek, W.

    1975-01-01

    The technology of manufacturing barium aluminate cement from barium sulfate and alumina, using a rotary kiln for firing the clinker is described. The method of granulation of the homogenized charge was used. Conditions of using the ''to mud'' method in industry were indicated. The physical and chemical properties of barium aluminate cement are determined and the quality of several batches of cement prepared on a semi-industrial scale and their suitability for making highly refractory concretes are tested. The optimal composition of the concretes is determined as a function of the mixing water and barium aluminate cement contents. Several experimental batches of concretes were used in the linings of furnaces in the steel industry. The suitability of these cements for use in fields other than steelmaking is examined. It is established that calcium aluminate cement has certain limited applications [fr

  17. Chemically synthesized metal-oxide-metal segmented nanowires with high ferroelectric response

    Energy Technology Data Exchange (ETDEWEB)

    Herderick, Edward D; Padture, Nitin P [Department of Materials Science and Engineering, Center for Emergent Materials, Ohio State University, Columbus, OH 43210 (United States); Polomoff, Nicholas A; Huey, Bryan D, E-mail: padture.1@osu.edu [Department of Chemical, Materials, and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States)

    2010-08-20

    A chemical synthesis method is presented for the fabrication of high-definition segmented metal-oxide-metal (MOM) nanowires in two different ferroelectric oxide systems: Au-BaTiO{sub 3}-Au and Au-PbTiO{sub 3}-Au. This method entails electrodeposition of segmented nanowires of Au-TiO{sub 2}-Au inside anodic aluminum oxide (AAO) templates, followed by topotactic hydrothermal conversion of the TiO{sub 2} segments into BaTiO{sub 3} or PbTiO{sub 3} segments. Two-terminal devices from individual MOM nanowires are fabricated, and their ferroelectric properties are measured directly, without the aid of scanning probe microscopy (SPM) methods. The MOM nanowire architecture provides high-quality end-on electrical contacts to the oxide segments, and allows direct measurement of properties of nanoscale volume, strain-free oxide segments. Unusually high ferroelectric responses, for chemically synthesized oxides, in these MOM nanowires are reported, and are attributed to the lack of residual strain in the oxides. The ability to measure directly the active properties of nanoscale volume, strain-free oxides afforded by the MOM nanowire architecture has important implications for fundamental studies of not only ferroelectric nanostructures but also nanostructures in the emerging field of multiferroics.

  18. Chemically synthesized metal-oxide-metal segmented nanowires with high ferroelectric response

    International Nuclear Information System (INIS)

    Herderick, Edward D; Padture, Nitin P; Polomoff, Nicholas A; Huey, Bryan D

    2010-01-01

    A chemical synthesis method is presented for the fabrication of high-definition segmented metal-oxide-metal (MOM) nanowires in two different ferroelectric oxide systems: Au-BaTiO 3 -Au and Au-PbTiO 3 -Au. This method entails electrodeposition of segmented nanowires of Au-TiO 2 -Au inside anodic aluminum oxide (AAO) templates, followed by topotactic hydrothermal conversion of the TiO 2 segments into BaTiO 3 or PbTiO 3 segments. Two-terminal devices from individual MOM nanowires are fabricated, and their ferroelectric properties are measured directly, without the aid of scanning probe microscopy (SPM) methods. The MOM nanowire architecture provides high-quality end-on electrical contacts to the oxide segments, and allows direct measurement of properties of nanoscale volume, strain-free oxide segments. Unusually high ferroelectric responses, for chemically synthesized oxides, in these MOM nanowires are reported, and are attributed to the lack of residual strain in the oxides. The ability to measure directly the active properties of nanoscale volume, strain-free oxides afforded by the MOM nanowire architecture has important implications for fundamental studies of not only ferroelectric nanostructures but also nanostructures in the emerging field of multiferroics.

  19. Characterization of cement-stabilized Cd wastes

    International Nuclear Information System (INIS)

    Maria Diez, J.; Madrid, J.; Macias, A.

    1996-01-01

    Portland cement affords both physical and chemical immobilization of cadmium. The immobilization has been studied analyzing the pore fluid of cement samples and characterizing the solid pastes by X-ray diffraction. The influence of cadmium on the cement hydration and on its mechanical properties has been also studied by isothermal conduction calorimetry and by the measure of strength and setting development. Finally, the effect of cement carbonation on the immobilization of cadmium has been analyzed

  20. Chemical speciation of heavy metals in sandy soils in relation to availability and mobility

    NARCIS (Netherlands)

    Temminghoff, E.J.M.

    1998-01-01

    The environmental risk of heavy metals which are present in soil at a certain total content is highly dependent on soil properties. Chemical speciation is a comprehensive term for the distribution of heavy metals over all possible chemical forms (species) in soil solution and in the solid

  1. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid......−liquid reactions are discussed, as are the influences of particles sizes on clinker phase formation. Furthermore, a mechanism for clinker phase formation in an industrial rotary kiln reactor is outlined....

  2. Natural and active chemical remediation of toxic metals and radionuclides in the aquatic environment

    International Nuclear Information System (INIS)

    McPherson, G.; Pintauro, P.; O'Connor, S.; Zhang, J.; Gonzales, R.; Flowers, G.

    1993-01-01

    The focus of this research is the non-biological, chemical remediation of toxic heavy metals and radionuclides in aquatic environments. This Tulane/Xavier group includes researchers from Chemistry, Chemical Engineering, and Geology. Active methods using novel zeolites and ion exchange membranes are currently being evaluated for use in removing heavy metals from natural waters. In addition, field and laboratory studies of metal ion exchange reactions and competitive, heavy metal adsorption on clay substrates are underway to determine sediment metal sequestering capacity. A summary of progress to date and future work is presented

  3. Performance of Cement Containing Laterite as Supplementary Cementing Material

    Directory of Open Access Journals (Sweden)

    Abbas Bukhari, Z. S.

    2013-03-01

    Full Text Available The utilization of different industrial waste, by-products or other materials such as ground granulated blast furnace slag, silica fume, fly ash, limestone, and kiln dust, etc. as supplemen- tary cementing materials has received considerable attention in recent years. A study has been conducted to look into the performance of laterite as Supplementary Cementing Materials (SCM. The study focuses on compressive strength performance of blended cement containing different percentage of laterite. The cement is replaced accordingly with percentage of 2 %, 5 %, 7 % and 10 % by weight. In addition, the effect of use of three chemically different laterites have been studied on physical performance of cement as in setting time, Le-Chatlier expansion, loss on ignition, insoluble residue, free lime and specifically compressive strength of cement cubes tested at the age of 3, 7, and 28 days. The results show that the strength of cement blended with laterite as SCM is enhanced. Key words: Portland cement, supplementary cementing materials (SCM, laterite, compressive strength KUI – 6/2013 Received January 4, 2012 Accepted February 11, 2013

  4. Size-controlled synthesis of transition metal nanoparticles through chemical and photo-chemical routes

    Science.gov (United States)

    Tangeysh, Behzad

    The central objective of this work is developing convenient general procedures for controlling the formation and stabilization of nanoscale transition metal particles. Contemporary interest in developing alternative synthetic approaches for producing nanoparticles arises in large part from expanding applications of the nanomaterials in areas such as catalysis, electronics and medicine. This research focuses on advancing the existing nanoparticle synthetic routes by using a new class of polymer colloid materials as a chemical approach, and the laser irradiation of metal salt solution as a photo-chemical method to attain size and shape selectivity. Controlled synthesis of small metal nanoparticles with sizes ranging from 1 to 5nm is still a continuing challenge in nanomaterial synthesis. This research utilizes a new class of polymer colloid materials as nano-reactors and protective agents for controlling the formation of small transition metal nanoparticles. The polymer colloid particles were formed from cross-linking of dinegatively charged metal precursors with partially protonated poly dimethylaminoethylmethacrylate (PDMAEMA). Incorporation of [PtCl6]2- species into the colloidal particles prior to the chemical reduction was effectively employed as a new strategy for synthesis of unusually small platinum nanoparticles with narrow size distributions (1.12 +/-0.25nm). To explore the generality of this approach, in a series of proof-of-concept studies, this method was successfully employed for the synthesis of small palladium (1.4 +/-0.2nm) and copper nanoparticles (1.5 +/-0.6nm). The polymer colloid materials developed in this research are pH responsive, and are designed to self-assemble and/or disassemble by varying the levels of protonation of the polymer chains. This unique feature was used to tune the size of palladium nanoparticles in a small range from 1nm to 5nm. The procedure presented in this work is a new convenient room temperature route for synthesis of

  5. On the occurrence of metallic character in the periodic table of the chemical elements.

    Science.gov (United States)

    Hensel, Friedrich; Slocombe, Daniel R; Edwards, Peter P

    2015-03-13

    The classification of a chemical element as either 'metal' or 'non-metal' continues to form the basis of an instantly recognizable, universal representation of the periodic table (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23; Poliakoff M. & Tang S. 2015 Phil. Trans. R. Soc. A 373: , 20140211). Here, we review major, pre-quantum-mechanical innovations (Goldhammer DA. 1913 Dispersion und Absorption des Lichtes; Herzfeld KF. 1927 Phys. Rev. 29: , 701-705) that allow an understanding of the metallic or non-metallic status of the chemical elements under both ambient and extreme conditions. A special emphasis will be placed on recent experimental advances that investigate how the electronic properties of chemical elements vary with temperature and density, and how this invariably relates to a changing status of the chemical elements. Thus, the prototypical non-metals, hydrogen and helium, becomes metallic at high densities; and the acknowledged metals, mercury, rubidium and caesium, transform into their non-metallic forms at low elemental densities. This reflects the fundamental fact that, at temperatures above the absolute zero of temperature, there is therefore no clear dividing line between metals and non-metals. Our conventional demarcation of chemical elements as metals or non-metals within the periodic table is of course governed by our experience of the nature of the elements under ambient conditions. Examination of these other situations helps us to examine the exact divisions of the chemical elements into metals and non-metals (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23). © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  6. Utilization of flotation wastes of copper slag as raw material in cement production

    International Nuclear Information System (INIS)

    Alp, I.; Deveci, H.; Suenguen, H.

    2008-01-01

    Copper slag wastes, even if treated via processes such as flotation for metal recovery, still contain heavy metals with hazardous properties posing environmental risks for disposal. This study reports the potential use of flotation waste of a copper slag (FWCS) as iron source in the production of Portland cement clinker. The FWCS appears a suitable raw material as iron source containing >59% Fe 2 O 3 mainly in the form of fayalite (Fe 2 SiO 4 ) and magnetite (Fe 3 O 4 ). The clinker products obtained using the FWCS from the industrial scale trial operations over a 4-month period were characterised for the conformity of its chemical composition and the physico-mechanical performance of the resultant cement products was evaluated. The data collected for the clinker products produced using an iron ore, which is currently used as the cement raw material were also included for comparison. The results have shown that the chemical compositions of all the clinker products including those of FWCS are typical of a Portland cement clinker. The mechanical performance of the standard mortars prepared from the FWCS clinkers were found to be similar to those from the iron ore clinkers with the desired specifications for the industrial cements e.g. CEM I type cements. Furthermore, the leachability tests (TCLP and SPLP) have revealed that the mortar samples obtained from the FWCS clinkers present no environmental problems while the FWCS could act as the potential source of heavy metal contamination. These findings suggest that flotation wastes of copper slag (FWCS) can be readily utilised as cement raw material due to its availability in large quantities at low cost with the further significant benefits for waste management/environmental practices of the FWCS and the reduced production and processing costs for cement raw materials

  7. Utilization of flotation wastes of copper slag as raw material in cement production.

    Science.gov (United States)

    Alp, I; Deveci, H; Süngün, H

    2008-11-30

    Copper slag wastes, even if treated via processes such as flotation for metal recovery, still contain heavy metals with hazardous properties posing environmental risks for disposal. This study reports the potential use of flotation waste of a copper slag (FWCS) as iron source in the production of Portland cement clinker. The FWCS appears a suitable raw material as iron source containing >59% Fe(2)O(3) mainly in the form of fayalite (Fe(2)SiO(4)) and magnetite (Fe(3)O(4)). The clinker products obtained using the FWCS from the industrial scale trial operations over a 4-month period were characterised for the conformity of its chemical composition and the physico-mechanical performance of the resultant cement products was evaluated. The data collected for the clinker products produced using an iron ore, which is currently used as the cement raw material were also included for comparison. The results have shown that the chemical compositions of all the clinker products including those of FWCS are typical of a Portland cement clinker. The mechanical performance of the standard mortars prepared from the FWCS clinkers were found to be similar to those from the iron ore clinkers with the desired specifications for the industrial cements e.g. CEM I type cements. Furthermore, the leachability tests (TCLP and SPLP) have revealed that the mortar samples obtained from the FWCS clinkers present no environmental problems while the FWCS could act as the potential source of heavy metal contamination. These findings suggest that flotation wastes of copper slag (FWCS) can be readily utilised as cement raw material due to its availability in large quantities at low cost with the further significant benefits for waste management/environmental practices of the FWCS and the reduced production and processing costs for cement raw materials.

  8. Environmental levels of PCDD/Fs and metals around a cement plant in Catalonia, Spain, before and after alternative fuel implementation. Assessment of human health risks

    Energy Technology Data Exchange (ETDEWEB)

    Rovira, Joaquim [Laboratory of Toxicology and Environmental Health, School of Medicine, Universitat Rovira i Virgili, Sant Llorenç 21, 43201 Reus, Catalonia (Spain); Environmental Engineering Laboratory, Departament d' Enginyeria Quimica, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007 Tarragona, Catalonia (Spain); Nadal, Martí, E-mail: marti.nadal@urv.cat [Laboratory of Toxicology and Environmental Health, School of Medicine, Universitat Rovira i Virgili, Sant Llorenç 21, 43201 Reus, Catalonia (Spain); Schuhmacher, Marta [Laboratory of Toxicology and Environmental Health, School of Medicine, Universitat Rovira i Virgili, Sant Llorenç 21, 43201 Reus, Catalonia (Spain); Environmental Engineering Laboratory, Departament d' Enginyeria Quimica, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007 Tarragona, Catalonia (Spain); Domingo, José L. [Laboratory of Toxicology and Environmental Health, School of Medicine, Universitat Rovira i Virgili, Sant Llorenç 21, 43201 Reus, Catalonia (Spain)

    2014-07-01

    The concentrations of As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Sn, Tl, V, and Zn, and the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans were determined in samples of soil, vegetation, and air, collected in the vicinity of a cement plant (Catalonia, Spain), before (January 2011 and July 2011) and after (January 2012 and June 2013) alternative fuel partial substitution (fossil fuels by sewage sludge). Seven sampling points were selected at different directions and distances to the facility including two background sampling points. The results were used to assess the health risk assessment for the population living near the facility. Only few significant differences were found before and after alternative fuel partial substitution (Mn in soils and Cd in vegetation). Non-carcinogenic risks were below the safety threshold (HQ < 1), while carcinogenic risks were below 10{sup −5}, or exceeding slightly that value, always in the range considered as assumable (10{sup −6}–10{sup −4}). - Highlights: • The environmental impact of a cement plant using alternative fuel was monitored. • No significant differences in most pollutants were noted after the fuel change. • Traffic has a notable influence on the environmental levels of PCDD/Fs and metals. • Human health risks were below safety thresholds regardless of the used fuel.

  9. Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede; Hansen, Kurt Kielsgaard

    2001-01-01

    The influence of cement particle-size distribution on autogenous strains and stresses in cement pastes of identical water-to-cement ratios is examined for cement powders of four different finenesses. Experimental measurements include chemical shrinkage, to quantify degree of hydration; internal r...

  10. Effect of addition of nano-hydroxyapatite on physico-chemical and antibiofilm properties of calcium silicate cements

    Directory of Open Access Journals (Sweden)

    Juliane Maria GUERREIRO-TANOMARU

    Full Text Available ABSTRACT Objective Mineral Trioxide Aggregate (MTA is a calcium silicate cement composed of Portland cement (PC and bismuth oxide. Hydroxyapatite has been incorporated to enhance mechanical and biological properties of dental materials. This study evaluated physicochemical and mechanical properties and antibiofilm activity of MTA and PC associated with zirconium oxide (ZrO2 and hydroxyapatite nanoparticles (HAn. Material and Methods White MTA (Angelus, Brazil; PC (70%+ZrO2 (30%; PC (60%+ZrO2 (30%+HAn (10%; PC (50%+ZrO2 (30%+HAn (20% were evaluated. The pH was assessed by a digital pH-meter and solubility by mass loss. Setting time was evaluated by using Gilmore needles. Compressive strength was analyzed by mechanical test. Samples were radiographed alongside an aluminum step wedge to evaluate radiopacity. For the antibiofilm evaluation, materials were placed in direct contact with E. faecalis biofilm induced on dentine blocks. The number of colony-forming units (CFU mL-1 in the remaining biolfilm was evaluated. The results were submitted to ANOVA and the Tukey test, with 5% significance. Results There was no difference in pH levels of PC+ZrO2, PC+ZrO2+HAn (10% and PC+ZrO2+HAn (20% (p>0.05 and these cements presented higher pH levels than MTA (p<0.05. The highest solubility was observed in PC+ZrO2+HAn (10% and PC+ZrO2+HAn (20% (p<0.05. MTA had the shortest initial setting time (p<0.05. All the materials showed radiopacity higher than 3 mmAl. PC+ZrO2 and MTA had the highest compressive strength (p<0.05. Materials did not completely neutralize the bacterial biofilm, but the association with HAn provided greater bacterial reduction than MTA and PC+ZrO2 (p<0.05 after the post-manipulation period of 2 days. Conclusions The addition of HAn to PC associated with ZrO2 harmed the compressive strength and solubility. On the other hand, HAn did not change the pH and the initial setting time, but improved the radiopacity (HAn 10%, the final setting time and

  11. Physico-chemical investigation of cement carbonation in aqueous solution in equilibrium with calcite and with a controlled CO2 partial pressure at 25 and 50 deg. C

    International Nuclear Information System (INIS)

    Chomat, Laure; Trepy, Nadia; Le Bescop, Patrick; Dauzeres, Alexandre; Monguillon, Corinne

    2012-01-01

    In the framework of radioactive waste geological disposal, structural concretes have to be adapted to underground chemical conditions. For concrete in water saturated medium, it is believed that carbonation will have a major impact on the interaction between concrete and the geological medium. So, to understand the complex degradation of the cement paste in that context, it is interesting to study a simplified system such as degradation in carbonated water solution. This solution must be at equilibrium with a CO 2 partial pressure 30 times higher than the atmospheric pCO 2 , to reproduce underground natural conditions of Callovo-Oxfordian clayey rock of Bure (France). In this study, the behaviour of a new low pH material (CEM I + silica fume + fly ashes) is compared with a CEM I cement paste, both of them being submitted to carbonation in aqueous solution in equilibrium with calcite and with a pCO 2 equal to 1.32 kPa (1.3 10 -2 atm). Two different temperatures, 25 and 50 C, are considered. To realize these experiments, two different original types of devices were developed

  12. Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

    Energy Technology Data Exchange (ETDEWEB)

    Yu Shengwang, E-mail: bkdysw@yahoo.cn; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

    2011-11-01

    SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH{sub 3}){sub 4}) diluted in H{sub 2} as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co{sub 2}Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

  13. Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

    International Nuclear Information System (INIS)

    Yu Shengwang; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

    2011-01-01

    SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH 3 ) 4 ) diluted in H 2 as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co 2 Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

  14. Spontaneous grafting of diazonium salts: chemical mechanism on metallic surfaces.

    Science.gov (United States)

    Mesnage, Alice; Lefèvre, Xavier; Jégou, Pascale; Deniau, Guy; Palacin, Serge

    2012-08-14

    The spontaneous reaction of diazonium salts on various substrates has been widely employed since it consists of a simple immersion of the substrate in the diazonium salt solution. As electrochemical processes involving the same diazonium salts, the spontaneous grafting is assumed to give covalently poly(phenylene)-like bonded films. Resistance to solvents and to ultrasonication is commonly accepted as indirect proof of the existence of a covalent bond. However, the most relevant attempts to demonstrate a metal-C interface bond have been obtained by an XPS investigation of spontaneously grafted films on copper. Similarly, our experiments give evidence of such a bond in spontaneously grafted films on nickel substrates in acetonitrile. In the case of gold substrates, the formation of a spontaneous film was unexpected but reported in the literature in parallel to our observations. Even if no interfacial bond was observed, formation of the films was explained by grafting of aryl cations or radicals on the surface arising from dediazoniation, the film growing later by azo coupling, radical addition, or cationic addition on the grafted phenyl layer. Nevertheless, none of these mechanisms fits our experimental results showing the presence of an Au-N bond. In this work, we present a fine spectroscopic analysis of the coatings obtained on gold and nickel substrates that allow us to propose a chemical structure of such films, in particular, their interface with the substrates. After testing the most probable mechanisms, we have concluded in favor of the involvement of two complementary mechanisms which are the direct reaction of diazonium salts with the gold surface that accounts for the observed Au-N interfacial bonds as well as the formation of aryl cations able to graft on the substrate through Au-C linkages.

  15. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives.

    Science.gov (United States)

    Voglar, Grega E; Leštan, Domen

    2011-08-30

    In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085mg kg(-1) of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12N mm(-2) achieved after S/S with CAC+PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC+Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Prediction of hydroxyl concentrations in cement pore water using a numerical cement hydration model

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    2000-01-01

    In this paper, a 3D numerical cement hydration model is used for predicting alkali and hydroxyl concentrations in cement pore water. First, this numerical model is calibrated for Dutch cement employing both chemical shrinkage and calorimetric experiments. Secondly, the strength development of some

  17. Modelling of the interaction between chemical and mechanical behaviour of ion exchange resins incorporated into a cement-based matrix

    Directory of Open Access Journals (Sweden)

    Le Bescop P.

    2013-07-01

    Full Text Available In this paper, we present a predictive model, based on experimental data, to determine the macroscopic mechanical behavior of a material made up of ion exchange resins solidified into a CEM III cement paste. Some observations have shown that in some cases, a significant macroscopic expansion of this composite material may be expected, due to internal pressures generated in the resin. To build the model, we made the choice to break down the problem in two scale’s studies. The first deals with the mechanical behavior of the different heterogeneities of the composite, i.e. the resin and the cement paste. The second upscales the information from the heterogeneities to the Representative Elementary Volume (REV of the composite. The heterogeneities effects are taken into account in the REV by applying a homogenization method derived from the Eshelby theory combined with an interaction coefficient drawn from the poroelasticity theory. At the first scale, from the second thermodynamic law, a formulation is developed to estimate the resin microscopic swelling. The model response is illustrated on a simple example showing the impact of the calculated internal pressure, on the macroscopic strain.

  18. Force-induced chemical reactions on the metal centre in a single metalloprotein molecule

    Science.gov (United States)

    Zheng, Peng; Arantes, Guilherme M.; Field, Martin J.; Li, Hongbin

    2015-01-01

    Metalloproteins play indispensable roles in biology owing to the versatile chemical reactivity of metal centres. However, studying their reactivity in many metalloproteins is challenging, as protein three-dimensional structure encloses labile metal centres, thus limiting their access to reactants and impeding direct measurements. Here we demonstrate the use of single-molecule atomic force microscopy to induce partial unfolding to expose metal centres in metalloproteins to aqueous solution, thus allowing for studying their chemical reactivity in aqueous solution for the first time. As a proof-of-principle, we demonstrate two chemical reactions for the FeS4 centre in rubredoxin: electrophilic protonation and nucleophilic ligand substitution. Our results show that protonation and ligand substitution result in mechanical destabilization of the FeS4 centre. Quantum chemical calculations corroborated experimental results and revealed detailed reaction mechanisms. We anticipate that this novel approach will provide insights into chemical reactivity of metal centres in metalloproteins under biologically more relevant conditions. PMID:26108369

  19. Effect of irradiation on acrylic cement with special reference to fixation of pathological fractures

    International Nuclear Information System (INIS)

    Eftekhar, N.S.; Thurston, C.W.

    1975-01-01

    Self-curing cement is generally used in conjunction with conventional metallic devices. If the acrylic cement was supplemented, the primary goal would be a rigid immobiliztion of the fracture to alleviate the pain; usually, however, the final aim is toward osteosynthesis. During the course of rehabilitation, it is often desirous to supplement the treatment by irradiation. Although the industrial, dental and surgical literature has adequately dealt with many aspects of bone cement; for example, physical and chemical properties in joint replacement, and so on, the effects of irradiation on the acrylic cement have not been previously reported. It is the purpose of this paper to analyze the experimental studies conducted to evaluate the mechanical properties of the polymethylmethacrylate when subjected to irradiation within a maximum range of a therapeutic dose

  20. Synthesis of Portland cement and calcium sulfoaluminate-belite cement for sustainable development and performance

    Science.gov (United States)

    Chen, Irvin Allen

    Portland cement concrete, the most widely used manufactured material in the world, is made primarily from water, mineral aggregates, and portland cement. The production of portland cement is energy intensive, accounting for 2% of primary energy consumption and 5% of industrial energy consumption globally. Moreover, portland cement manufacturing contributes significantly to greenhouse gases and accounts for 5% of the global CO2 emissions resulting from human activity. The primary objective of this research was to explore methods of reducing the environmental impact of cement production while maintaining or improving current performance standards. Two approaches were taken, (1) incorporation of waste materials in portland cement synthesis, and (2) optimization of an alternative environmental friendly binder, calcium sulfoaluminate-belite cement. These approaches can lead to less energy consumption, less emission of CO2, and more reuse of industrial waste materials for cement manufacturing. In the portland cement part of the research, portland cement clinkers conforming to the compositional specifications in ASTM C 150 for Type I cement were successfully synthesized from reagent-grade chemicals with 0% to 40% fly ash and 0% to 60% slag incorporation (with 10% intervals), 72.5% limestone with 27.5% fly ash, and 65% limestone with 35% slag. The synthesized portland cements had similar early-age hydration behavior to commercial portland cement. However, waste materials significantly affected cement phase formation. The C3S--C2S ratio decreased with increasing amounts of waste materials incorporated. These differences could have implications on proportioning of raw materials for cement production when using waste materials. In the calcium sulfoaluminate-belite cement part of the research, three calcium sulfoaluminate-belite cement clinkers with a range of phase compositions were successfully synthesized from reagent-grade chemicals. The synthesized calcium sulfoaluminate

  1. Physical-Chemical and Mechanical characterization of some cement products in Madagascar by using Technical Analysis X-ray Fluorescence and tests receptions

    International Nuclear Information System (INIS)

    Rasolondraibe, I.P.

    2014-01-01

    The present work is completely realized at the 'Institut National des Sciences et Techniques Nucleaires (INSTN - Madagascar)' and 'Laboratoire National des Travaux Publics et du Batiment (LNTPB)'. Its purpose is to carry out the physico - chemical and mechanical analysis of the cements products present in Madagascar in order to ensure their qualities in case of Building and Publics Works construction safety. The necessary chemical elements in cements are the loss in ignition (LOI), the insoluble residues (RI), the silica (SiO 2 ), the lime (CaO), the alumina (Al 2 O 3 ), the iron oxide (Fe 2 O 3 ), the magnesia (MgO) and the sulfate (SO 3 ). In this work, analytical laboratory in X - Ray fluorescence department of INSTN - Madagascar using the direct excitation X - Ray fluorescence technique outline their research on lime and iron oxide while L.N.T.P.B materials laboratory can make all using test method by gravimetry and titrimetry according to EN 196 - 2. The results of INSTN - Madagascar show that the concentrations of calcium oxide and iron oxide are consistent with the concentration range provided by the laboratory materials L.N.T.P.B respectively equal to 50.00 % - 65.00 % and 1.00 % - 5.00 %. The results between the two laboratories have a - 4.76 % iron oxide maximum relative deviation and 4,77 % calcium oxide maximum relative deviation. Complementary physical and mechanical tests were performed at L.N.T.P.B materials laboratory respectively in accordance with EN 196 - 3 and EN 196 - 1. The used conventional X - ray fluorescence method fulfill the scope of application needed with good correlation less than ± 5 %. [fr

  2. Interaction of Hydroxyproline with Bivalent Metal Ions in Chemical ...

    African Journals Online (AJOL)

    NICO

    The stability constants of the ML and ML2 complex species of some metal ions, namely beryllium(II) and cobalt(II), with hydroxyproline were ... metal ions have several significant applications in biological systems.3–20 Beryllium is one ... 1 filter paper for chromatography was used for the purpose of electrophoresis. An Elico ...

  3. Basic Chemistry for the Cement Industry.

    Science.gov (United States)

    Turner, Mason

    This combined student workbook and instructor's guide contains nine units for inplant classes on basic chemistry for employees in the cement industry. The nine units cover the following topics: chemical basics; measurement; history of cement; atoms; bonding and chemical formulas; solids, liquids, and gases; chemistry of Portland cement…

  4. Corrosion resistant cemented carbide

    International Nuclear Information System (INIS)

    Hong, J.

    1990-01-01

    This paper describes a corrosion resistant cemented carbide composite. It comprises: a granular tungsten carbide phase, a semi-continuous solid solution carbide phase extending closely adjacent at least a portion of the grains of tungsten carbide for enhancing corrosion resistance, and a substantially continuous metal binder phase. The cemented carbide composite consisting essentially of an effective amount of an anti-corrosion additive, from about 4 to about 16 percent by weight metal binder phase, and with the remaining portion being from about 84 to about 96 percent by weight metal carbide wherein the metal carbide consists essentially of from about 4 to about 30 percent by weight of a transition metal carbide or mixtures thereof selected from Group IVB and of the Periodic Table of Elements and from about 70 to about 96 percent tungsten carbide. The metal binder phase consists essentially of nickel and from about 10 to about 25 percent by weight chromium, the effective amount of an anti-corrosion additive being selected from the group consisting essentially of copper, silver, tine and combinations thereof

  5. A study of chemical speciation of metals in aquatic bottom sediment ...

    African Journals Online (AJOL)

    Dele Olutona

    African Journal of Environmental Science and Technology Vol. 6(8), pp. 312-321, August .... each chemical fraction and potential risk of sediment- bound metals to the aquatic ..... Water chemistry of the Amazon River. Geochim. Cosmochim.

  6. Physical and chemical characterization of pastes of bone cements with ZrO{sub 2}; Caracterizacion fisica y quimica de pastas de cementos oseos con ZrO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Quinto H, A. [Instituto Tecnologico de Zacatepec, A.P. 45, 62900 Zacatepec, Morelos (Mexico); Pina B, M.C. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A.P. 70-360, 04510 Mexico D.F. (Mexico)

    2003-07-01

    Setting times and temperature of sixteen calcium phosphate cements added with ZrO{sub 2} were evaluated. Their behaviors were analysed to be used like injectable formulations in surgery of bone. Two cements of calcium phosphates enriched with ZrO{sub 2} with the best characteristics in setting times and temperature, were mechanically tested after 1 and 7 days of prepared. Density was determined using a pycnometer, chemical composition was determined by X-ray diffraction and the molecular structure was determined by infrared spectroscopy. (Author)

  7. Biosensor and chemical sensor probes for calcium and other metal ions

    Science.gov (United States)

    Vo-Dinh, Tuan; Viallet, Pierre

    1996-01-01

    The present invention relates to chemical sensor and biosensor probes for measuring low concentration of metals and metal ions in complex samples such as biological fluids, living cells, and environmental samples. More particularly the present invention relates to a gel-based Indo-1 and Fura-2 chemical sensor probes for the measurement of low concentrations of calcium, cadmium, magnesium and the like. Also disclosed is a detector device using the sensors of the present invention.

  8. NMR determination of chemically related metals in solution as a new method of inorganic analysis

    International Nuclear Information System (INIS)

    Fedorov, L.A.

    1989-01-01

    An NMR spectroscopic method for the determination of chemically related metals in solution is suggested. The metals are determined in complexes with specially selected polydentate ligands. Structural requirements to ligands, analytical properties and general limits of the application of the method are discussed. (orig.)

  9. Metal-contaminated soil remediation by means of paper mill sludges addition: chemical and ecotoxicological evaluation

    International Nuclear Information System (INIS)

    Calace, N.; Campisi, T.; Iacondini, A.; Leoni, M.; Petronio, B.M.; Pietroletti, M.

    2005-01-01

    Metal pollution of soils is a great environmental problem. The major risks due to metal pollution of soil consist of leaching to groundwater and potential toxicity to plants and/or animals. The objective of this study is to evaluate by means of chemical and ecotoxicological approach the effects of paper mill sludge addition on the mobile metal fraction of polluted metal soils. The study was carried out on acidic soil derived from mining activities and thus polluted with heavy metals, and on two paper mill sludges having different chemical features. The results obtained by leaching experiments showed that the addition of a paper mill sludge, consisting mainly of carbonates, silicates and organic matter, to a heavy-metal polluted soil produces a decrease of available metal forms. The carbonate content seems to play a key role in the chemical stabilisation of metals and consequently in a decrease of toxicity of soil. The leached solutions have a non-toxic effect. The mild remediation by addition of sludge has moreover a lasting effect. - Paper mill sludge decreased available metals

  10. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    Laterite obtained from Ikpayongo was stabilized with 2-10 % cement and 2-10 % Calcium Carbide waste, for use .... or open dumping which have effect on surface and ... Table 1: Chemical Composition of Calcium Carbide Waste and Cement.

  11. Effects of cement particle size distribution on performance properties of Portland cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Bentz, D.P.; Garboczi, E.J.; Haecker, C.J.; Jensen, O.M.

    1999-10-01

    The original size, spatial distribution, and composition of Portland cement particles have a large influence on hydration kinetics, microstructure development, and ultimate properties of cement-based materials. In this paper, the effects of cement particle size distribution on a variety of performance properties are explored via computer simulation and a few experimental studies. Properties examined include setting time, heat release, capillary porosity percolation, diffusivity, chemical shrinkage, autogenous shrinkage, internal relative humidity evolution, and interfacial transition zone microstructure. The effects of flocculation and dispersion of the cement particles in the starting microstructures on resultant properties are also briefly evaluated. The computer simulations are conducted using two cement particle size distributions that bound those commonly in use today and three different water-to-cement ratios: 0.5, 0.3, and 0.246. For lower water-to-cement ratio systems, the use of coarser cements may offer equivalent or superior performance, as well as reducing production costs for the manufacturer.

  12. Studies on physico-chemical and mechanical properties of the irradiated latex modified mortar

    International Nuclear Information System (INIS)

    Yassene, A.A.M.A.

    2009-01-01

    This thesis contains three chapter; chapter(I): Introduction and literature review on:- Introduction to polymer. - Mechanism of polymer-cement co-matrix formation.-Sulphate attack. - Solidification /stabilization of heavy metal in cement mortar. chapter(II): Materials and experimental techniques that include: 1- Preparation of latex polymer films from different polymer latices of styrene butadine rubber latex (SBR), poly (styrene-acrylic ester) latex (SAE) and vinylacetate /versatic -ester copolymer latex (C2A). The effect of γ-irradiation dose on the physico - chemical and mechanical properties of different latex polymer films was studied.2- Preparation of latex polymer-modified cement mortar with different ratios of cement: latex polymer and different curing method.3- Solidification /stabilization (S/S) of electroplating heavy metal precipitate in latex polymer- modified mortar with different cement /electroplating heavy metal sludge ratio. chapter(III) results and discussion

  13. Morphology evolution and nanostructure of chemical looping transition metal oxide materials upon redox processes

    International Nuclear Information System (INIS)

    Qin, Lang; Cheng, Zhuo; Guo, Mengqing; Fan, Jonathan A.; Fan, Liang-Shih

    2017-01-01

    Transition metal are heavily used in chemical looping technologies because of their high oxygen carrying capacity and high thermal reactivity. These oxygen activities result in the oxide formation and oxygen vacancy formation that affect the nanoscale crystal phase and morphology within these materials and their subsequent bulk chemical behavior. In this study, two selected earlier transition metals manganese and cobalt as well as two selected later transition metals copper and nickel that are important to chemical looping reactions are investigated when they undergo cyclic redox reactions. We found Co microparticles exhibited increased CoO impurity presence when oxidized to Co_3O_4 upon cyclic oxidation; CuO redox cycles prefer to be limited to a reduced form of Cu_2O and an oxidized form of CuO; Mn microparticles were oxidized to a mixed phases of MnO and Mn_3O_4, which causes delamination during oxidation. For Ni microparticles, a dense surface were observed during the redox reaction. The atomistic thermodynamics methods and density functional theory (DFT) calculations are carried out to elucidate the effect of oxygen dissociation and migration on the morphological evolution of nanostructures during the redox processes. Our results indicate that the earlier transition metals (Mn and Co) tend to have stronger interaction with O_2 than the later transition metals (Ni and Cu). Also, our modified Brønsted−Evans−Polanyi (BEP) relationship for reaction energies and total reaction barriers reveals that reactions of earlier transition metals are more exergonic and have lower oxygen dissociation barriers than those of later transition metals. In addition, it was found that for these transition metal oxides the oxygen vacancy formation energies increase with the depth. The oxide in the higher oxidation state of transition metal has lower vacancy formation energy, which can facilitate forming the defective nanostructures. The fundamental understanding of these metal

  14. Chemical and Molecular Characterization of Biofilm on Metal Surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.

    analytical instrumental techniques to assess the kinetics and chemical composition of the conditioning film developed on stainless steel panels deployed in seawater. These studies suggest that proteins are the first compounds to adsorb onto stainless steel...., 1990; Bott 1993; 159 stainless steel by the Time of flight secondary ion mass spectrometer (ToF-SIMS) (Poleunis et al., 2002, 2003). Further the nature of the substratum influences the chemical composition and quality of adsorbed organic matter...

  15. The influence of cement type and temperature on chloride binding in cement paste

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen

    1998-01-01

    This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

  16. Surface Modification of α-Fe Metal Particles by Chemical Surface Coating

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The structure of α-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms.

  17. Thin metal films in resistivity-based chemical sensing

    Czech Academy of Sciences Publication Activity Database

    Podešva, Pavel; Foret, František

    2013-01-01

    Roč. 9, č. 4 (2013), s. 642-652 ISSN 1573-4110 R&D Projects: GA ČR(CZ) GAP301/11/2055 Institutional support: RVO:68081715 Keywords : voltohmmetric sensing * chemiresistor * thin metal film * gas sensing Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 1.194, year: 2013

  18. Potential use of pyrite cinders as raw material in cement production: results of industrial scale trial operations.

    Science.gov (United States)

    Alp, I; Deveci, H; Yazici, E Y; Türk, T; Süngün, Y H

    2009-07-15

    Pyrite cinders, which are the waste products of sulphuric acid manufacturing plants, contain hazardous heavy metals with potential environmental risks for disposal. In this study, the potential use of pyrite cinders (PyCs) as iron source in the production of Portland cement clinker was demonstrated at the industrial scale. The chemical and mineralogical analyses of the PyC sample used in this study have revealed that it is essentially a suitable raw material for use as iron source since it contains >87% Fe(2)O(3) mainly in the form of hematite (Fe(2)O(3)) and magnetite (Fe(3)O(4)). The samples of the clinkers produced from PyC in the industrial scale trial operation of 6 months were tested for the conformity of their chemical composition and the physico-mechanical performance of the resultant cement products. The data were compared with the clinker products of the iron ore, which is used as the raw material for the production Portland cement clinker in the plant. The chemical compositions of all the clinker products of PyC appeared to conform to those of the iron ore clinker, and hence, a Portland cement clinker. The mechanical performance of the mortars prepared from the PyC clinker was found to be consistent with those of the industrial cements e.g. CEM I type cements. It can be inferred from the leachability tests (TCLP and SPLP) that PyC could be a potential source of heavy metal pollution while the mortar samples obtained from the PyC clinkers present no environmental problems. These findings suggest that the waste pyrite cinders can be readily used as iron source for the production of Portland cement. The availability of PyC in large quantities at low cost provides further significant benefits for the management/environmental practices of these wastes and for the reduction of mining and processing costs of cement raw materials.

  19. Comparative evaluation of microbial and chemical leaching processes for heavy metal removal from dewatered metal plating sludge

    International Nuclear Information System (INIS)

    Bayat, Belgin; Sari, Bulent

    2010-01-01

    The purpose of the study described in this paper was to evaluate the application of bioleaching technique involving Acidithiobacillus ferrooxidans to recover heavy metals (Zn, Cu, Ni, Pb, Cd and Cr) in dewatered metal plating sludge (with no sulfide or sulfate compounds). The effect of some conditional parameters (i.e. pH, oxidation-reduction potential (ORP), sulfate production) and operational parameters (i.e. pulp density of the sludge and agitation time) were investigated in a 3 l completely mixed batch (CMB) reactor. The metal recovery yields in bioleaching were also compared with chemical leaching of the sludge waste using commercial inorganic acids (sulfuric acids and ferric chloride). The leaching of heavy metals increased with decreasing of pH and increasing of ORP and sulfate production during the bioleaching experiment. Optimum pulp density for bioleaching was observed at 2% (w/v), and leaching efficiency decreased with increasing pulp density in bioleaching experiments. Maximum metal solubilization (97% of Zn, 96% of Cu, 93% of Ni, 84% of Pb, 67% of Cd and 34% of Cr) was achieved at pH 2, solids contents of 2% (w/v), and a reaction temperature of 25 ± 2 deg. C during the bioleaching process. The maximum removal efficiencies of 72% and 79% Zn, 70% and 75% Cu, 69% and 73% Ni, 57% and 70% Pb, 55% and 65% Cd, and 11% and 22% Cr were also attained with the chemical leaching using sulfuric acids and ferric chloride, respectively, at pH 2, solids contents of 2% (w/v), and a reaction temperature of 25 ± 2 deg. C during the acid leaching processes. The rates of metal leaching for bioleaching and chemical leaching are well described by a kinetic equation related to time. Although bioleaching generally requires a longer period of operation compared to chemical leaching, it achieves higher removal efficiency for heavy metals. The efficiency of leaching processes can be arranged in descending order as follows: bioleaching > ferric chloride leaching > sulfuric acid

  20. Comparative evaluation of microbial and chemical leaching processes for heavy metal removal from dewatered metal plating sludge

    Energy Technology Data Exchange (ETDEWEB)

    Bayat, Belgin, E-mail: bbayat@cu.edu.tr [Department of Environmental Engineering, Faculty of Engineering and Architecture, Cukurova University, Balcali, Adana 01330 (Turkey); Sari, Bulent [Department of Environmental Engineering, Faculty of Engineering and Architecture, Cukurova University, Balcali, Adana 01330 (Turkey)

    2010-02-15

    The purpose of the study described in this paper was to evaluate the application of bioleaching technique involving Acidithiobacillus ferrooxidans to recover heavy metals (Zn, Cu, Ni, Pb, Cd and Cr) in dewatered metal plating sludge (with no sulfide or sulfate compounds). The effect of some conditional parameters (i.e. pH, oxidation-reduction potential (ORP), sulfate production) and operational parameters (i.e. pulp density of the sludge and agitation time) were investigated in a 3 l completely mixed batch (CMB) reactor. The metal recovery yields in bioleaching were also compared with chemical leaching of the sludge waste using commercial inorganic acids (sulfuric acids and ferric chloride). The leaching of heavy metals increased with decreasing of pH and increasing of ORP and sulfate production during the bioleaching experiment. Optimum pulp density for bioleaching was observed at 2% (w/v), and leaching efficiency decreased with increasing pulp density in bioleaching experiments. Maximum metal solubilization (97% of Zn, 96% of Cu, 93% of Ni, 84% of Pb, 67% of Cd and 34% of Cr) was achieved at pH 2, solids contents of 2% (w/v), and a reaction temperature of 25 {+-} 2 deg. C during the bioleaching process. The maximum removal efficiencies of 72% and 79% Zn, 70% and 75% Cu, 69% and 73% Ni, 57% and 70% Pb, 55% and 65% Cd, and 11% and 22% Cr were also attained with the chemical leaching using sulfuric acids and ferric chloride, respectively, at pH 2, solids contents of 2% (w/v), and a reaction temperature of 25 {+-} 2 deg. C during the acid leaching processes. The rates of metal leaching for bioleaching and chemical leaching are well described by a kinetic equation related to time. Although bioleaching generally requires a longer period of operation compared to chemical leaching, it achieves higher removal efficiency for heavy metals. The efficiency of leaching processes can be arranged in descending order as follows: bioleaching > ferric chloride leaching > sulfuric

  1. Cement-free Binders for Radioactive Waste Produced from Blast-furnace Slag using Vortex Layer Activation Technology

    Directory of Open Access Journals (Sweden)

    Mazov Ilya

    2017-01-01

    Full Text Available The paper addresses the issue of recycling granulated blast-furnace slag (gBFS as a source for production of cement-free binder materials for further usage in rare-earth metals production for radioactive waste disposal. The use of the vortex layer activator was provided as main technique allowing to produce high-dispersed chemically activated binders. The paper examines the effect of processing conditions on the physical-chemical and mechanical properties of the resulting BFS-based cement-free materials and gBFS-based concretes.

  2. Compressive Strength and Physical Properties Behavior of Cement Mortars with addition of Cement Klin Dust

    OpenAIRE

    Auday A Mehatlaf

    2017-01-01

    Cement Klin Dust (CKD) was the waste of almost cement industry factories, so that in this paper utilization of CKD as filler in cement and/or concrete was the main objective. CKD from the Karbala cement factory had been used and analysis to know the chemical composition of the oxides was done. In this paper cement mortars with different weight percentages of CKD (0,5,10,20,30,40) had been prepared. Physical properties such as density and porosity were done in different age curing (3, 7, 28) d...

  3. Breaking Down Chemical Weapons by Metal-Organic Frameworks.

    Science.gov (United States)

    Mondal, Suvendu Sekhar; Holdt, Hans-Jürgen

    2016-01-04

    Seek and destroy: Filtration schemes and self-detoxifying protective fabrics based on the Zr(IV)-containing metal-organic frameworks (MOFs) MOF-808 and UiO-66 doped with LiOtBu have been developed that capture and hydrolytically detoxify simulants of nerve agents and mustard gas. Both MOFs function as highly catalytic elements in these applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Formation of amorphous metal alloys by chemical vapor deposition

    Science.gov (United States)

    Mullendore, A.W.

    1988-03-18

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures of organometallic compounds and metalloid hydrides,e.g., transition metal carbonyl, such as nickel carbonyl and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit. 1 fig.

  5. Electrocatalysis of chemically synthesized noble metal nanoparticles on carbon electrodes

    DEFF Research Database (Denmark)

    Zhang, Ling; Ulstrup, Jens; Zhang, Jingdong

    Noble metal nanoparticles (NPs), such as platinum (Pt) and palladium (Pd) NPs are promising catalysts for dioxygen reduction and oxidation of molecules such as formic acid and ethanol in fuel cells. Carbon nanomaterials are ideal supporting materials for electrochemical catalysts due to their good...... by electrochemical SPM. This study offers promise for development of new high-efficiency catalyst types with low-cost for fuel cell technology...

  6. Physico-chemical characteristics and Heavy metal levels in Drinking ...

    African Journals Online (AJOL)

    Michael Horsfall

    ABSTRAC: This study investigated the physico-chemical characteristics of drinking waters collected from tap, well and sachet in Sokoto metropolis in North Western Nigeria. Conductivity and pH values were determined by standard methods while elemental composition was analysed using X-ray Fluorescence spectroscopy ...

  7. Levels of Some Heavy Metals and Physico Chemical Properties of ...

    African Journals Online (AJOL)

    MICHAEL

    except the upstream samples that gave a pH value of 6.89. The dissolved Oxygen contents of all the samples fell below FEPA limit of 10mg/l. However, the highest chemical oxygen demand concentration of 93.7mg/l was obtained in the untreated effluent sample. The mean ammonia concentration of the untreated sample ...

  8. Levels of Some Heavy Metals and Physico Chemical Properties of ...

    African Journals Online (AJOL)

    In this study, the concentrations of selected heavy meyals and physico-chemical characteristics of effluents from a beverage company in Rivers State, Nigeria and those of the receiving Woji River were evaluated to ascertain the efficiency of the company's waste treatment processes. The results showed that the contents of ...

  9. Alternative Fuels in Cement Production

    DEFF Research Database (Denmark)

    Larsen, Morten Boberg

    The substitution of alternative for fossil fuels in cement production has increased significantly in the last decade. Of these new alternative fuels, solid state fuels presently account for the largest part, and in particular, meat and bone meal, plastics and tyre derived fuels (TDF) accounted...... for the most significant alternative fuel energy contributors in the German cement industry. Solid alternative fuels are typically high in volatile content and they may differ significantly in physical and chemical properties compared to traditional solid fossil fuels. From the process point of view......, considering a modern kiln system for cement production, the use of alternative fuels mainly influences 1) kiln process stability (may accelerate build up of blockages preventing gas and/or solids flow), 2) cement clinker quality, 3) emissions, and 4) decreased production capacity. Kiln process stability...

  10. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  11. A comparative evaluation of the retention of metallic brackets bonded with resin-modified glass ionomer cement under different enamel preparations: A pilot study

    Directory of Open Access Journals (Sweden)

    Padmaja Sharma

    2013-01-01

    Full Text Available Introduction: For orthodontists, the ideal bonding material should be less moisture-sensitive and should release fluoride, thereby reducing unfavorable iatrogenic decalcification. Resin-Modified Glass Ionomer Cements (RMGICs, due to their ability to bond in the presence of saliva and blood can be a very good bonding agent for orthodontic attachments especially in the areas of mouth, which are difficult to access. Moreover, their fluoride releasing property makes them an ideal bonding agent for patients with poor oral hygiene. However, their immediate bond strength is said to be too low to immediately ligate the initial wire, which could increase the total number of appointments. The effect of sandblasting and the use of sodium hypochlorite (NaOCL on the immediate bond failure of RMGIC clinically have not been reported in the literature until the date. This investigation intended to assess the effect of sandblasting (of the bracket base and enamel and NaOCL on the rate of bond failure (with immediate ligation at 30 min of Fuji Ortho LC and its comparison with that of conventional light cured composite resin over a period of 1 year. Materials and Methods: 400 sample teeth were further divided into 4 groups of 100 each and bonded as follows: (1 Group 1: Normal metallic brackets bonded with Fuji Ortho LC. (2 Group 2: Sandblasted bracket base and enamel surface, brackets bonded with Fuji Ortho LC. (3 Group 3: Deproteinized enamel surface using sodium hypochlorite and brackets bonded with Fuji Ortho LC. (4 Group 4: Normal metallic bracket bonded with Transbond XT after etching enamel with 37% phosphoric acid. This group served as control group. Results and Conclusion: Results showed that sandblasting the bracket base and enamel, can significantly reduce the bond failure rate of RMGIC.

  12. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  13. Cyclic catalytic upgrading of chemical species using metal oxide materials

    Science.gov (United States)

    White, James H; Schutte, Erick J; Rolfe, Sara L

    2013-05-07

    Processes are disclosure which comprise alternately contacting an oxygen-carrying catalyst with a reducing substance, or a lower partial pressure of an oxidizing gas, and then with the oxidizing gas or a higher partial pressure of the oxidizing gas, whereby the catalyst is alternately reduced and then regenerated to an oxygenated state. In certain embodiments, the oxygen-carrying catalyst comprises at least one metal oxide-containing material containing a composition having the following formulas: (a) Ce.sub.xB.sub.yB'.sub.zB''O.sub..delta., wherein B=Ba, Sr, Ca, or Zr; B'=Mn, Co, and/or Fe; B''=Cu; 0.01Ba, Ca, La, or K; 0.02metal oxides.

  14. Chemical bonding of hydrogen molecules to transition metal complexes

    International Nuclear Information System (INIS)

    Kubas, G.J.

    1990-01-01

    The complex W(CO) 3 (PR 3 ) 2 (H 2 ) (CO = carbonyl; PR 3 = organophosphine) was prepared and was found to be a stable crystalline solid under ambient conditions from which the hydrogen can be reversibly removed in vacuum or under an inert atmosphere. The weakly bonded H 2 exchanges easily with D 2 . This complex represents the first stable compound containing intermolecular interaction of a sigma-bond (H-H) with a metal. The primary interaction is reported to be donation of electron density from the H 2 bonding electron pair to a vacant metal d-orbital. A series of complexes of molybdenum of the type Mo(CO)(H 2 )(R 2 PCH 2 CH 2 PR 2 ) 2 were prepared by varying the organophosphine substitutent to demonstrate that it is possible to bond either dihydrogen or dihydride by adjusting the electron-donating properties of the co-ligands. Results of infrared and NMR spectroscopic studies are reported. 20 refs., 5 fig

  15. Development of chemically engineered porous metal oxides for phosphate removal

    International Nuclear Information System (INIS)

    Delaney, Paul; McManamon, Colm; Hanrahan, John P.; Copley, Mark P.; Holmes, Justin D.; Morris, Michael A.

    2011-01-01

    In this study, the application of ordered mesoporous silica (OMS) doped with various metal oxides (Zr, Ti, Fe and Al) were studied for the removal of (ortho) phosphate ions from water by adsorption. The materials were characterized by means of N 2 physisorption (BET), powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The doped materials had surface areas between 600 and 700 m 2 g -1 and exhibited pore sizes of 44-64 A. Phosphate adsorption was determined by measurement of the aqueous concentration of orthophosphate using ultraviolet-visible (UV-vis) spectroscopy before and after extraction. The effects of different metal oxide loading ratios, initial concentration of phosphate solution, temperature and pH effects on the efficiency of phosphate removal were investigated. The doped mesoporous materials were effective adsorbents of orthophosphate and up to 100% removal was observed under appropriate conditions. 'Back extracting' the phosphate from the doped silica (following water treatment) was also investigated and shown to have little adverse effect on the adsorbent.

  16. Tracing the Chemical Evolution of Metal-rich Galactic Bulge Globular Clusters

    Science.gov (United States)

    Munoz Gonzalez, Cesar; Saviane, Ivo; Geisler, Doug; Villanova, Sandro

    2018-01-01

    We present in this poster the metallicity characterization of the four metal rich Bulge Galactic Gobular Clusters, which have controversial metallicities. We analyzed our high-resolution spectra (using UVES-580nm and GIRAFFE-HR13 setups) for a large sample of RGB/AGB targets in each cluster in order to measure their metallicity and prove or discard the iron spread hypothesis. We have also characterized chemically stars with potentially different iron content by measuring light (O, Na, Mg, Al), alpha (Si, Ca, Ti), iron–peak (V, Cr, Ni, Mn) and s and r process (Y, Zr, Ba, Eu) elements. We have identified possible channels responsible for the chemical heterogeneity of the cluster populations, like AGB or massive fast-rotating stars contamination, or SN explosion. Also, we have analyzed the origin and evolution of these bulge GCs and their connection with the bulge itself.

  17. Direct conversion of radioactive and chemical waste containing metals, ceramics, amorphous solids, and organics to glass

    International Nuclear Information System (INIS)

    Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

    1994-01-01

    The Glass Material Oxidation and Dissolution System (CMODS) is a new process for direct conversion of radioactive, mixed, and chemical wastes to glass. The wastes can be in the chemical forms of metals, ceramics, amorphous solids, and organics. GMODS destroys organics and it incorporates heavy metals and radionuclides into a glass. Processable wastes may include miscellaneous spent fuels (SF), SF hulls and hardware, plutonium wastes in different forms, high-efficiency particulate air (HEPA) filters, ion-exchange resins, failed equipment, and laboratory wastes. Thermodynamic calculations indicate theoretical feasibility. Small-scale laboratory experiments (< 100 g per test) have demonstrated chemical laboratory feasibility for several metals. Additional work is needed to demonstrate engineering feasibility

  18. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs

  19. Use of rubber crumbs in cement concrete

    Science.gov (United States)

    Longvinenko, A. A.

    2018-03-01

    Rubber crumb obtained from worn out tires has been increasingly used over the last 15-20 years, especially in manufacture of asphalt and cement concrete mixtures. This review pays principal attention to application of the rubber crumb to cement concrete mixtures. Use of the rubber crumb in cement concrete is not as successful as in asphalt concrete mixtures, due to incompatibility problems linked to chemical composition and a significant difference in rigidity between the rubber crumb and concrete mixture aggregates. Different methods are proposed and studied to mitigate the adverse influence and increase the beneficial effects of the rubber crumb when added to cement concrete.

  20. An experimental study of steam explosions involving chemically reactive metal

    International Nuclear Information System (INIS)

    Cho, D.H.; Armstrong, D.R.; Gunther, W.H.; Basu, S.

    1997-01-01

    An experimental study of molten zirconium-water explosions was conducted. A 1-kg mass of zirconium melt was dropped into a column of water. Explosions took place only when an external trigger was used. In the triggered tests, the extent of oxidation of the zirconium melt was very extensive. However, the explosion energetics estimated were found to be very small compared to the potential chemical energy available from the oxidation reaction. Zirconium is of particular interest, since it is a component of the core materials of the current nuclear power reactors. This paper describes the test apparatus and summarizes the results of four tests conducted using pure zirconium melt

  1. Heavy metal recovery from contaminated biomass ashes by chemical leaching, bioleaching and biosorption

    International Nuclear Information System (INIS)

    Pirker, K.

    2000-01-01

    Ashes from biomass combustion plants contain plant nutrients which makes their application as fertilizers economically interesting. The possibility of recycling the ash can be looked upon as a contribution to obtain a sustainable energy utilization from biomass. The ash contains heavy metals which have to be removed. The possibility of decontaminating the ash by chemical and biological leaching was investigated. The leaching capacity of commercially available organic and inorganic acids and of citric acid produced by the fungus Penicillium simplicissimus were determined. A process for heavy metal recovery from biomass ashes consisting of four steps was designed. All environmentally relevant heavy metals (except lead) were removed from contaminated biomass ashes by chemical leaching. The heavy metals were recovered and enriched by precipitation and subsequent biosorption. Inactivated bacteria and fungi were used as biosorbents. The overall costs and the washing-out of plant nutrients from the ashes by chemical leaching were drawbacks of the metal recovering process. Biosorption in combination with existing processes of waste water treatment would offer another promising possibility for achieving the low Austrian limiting values for heavy metals in waste water. (author)

  2. Chemical probes of metal cluster structure--Fe, Co, Ni, and Cu

    International Nuclear Information System (INIS)

    Parks, E.K.; Zhu, L.; Ho, J.; Riley, S.J.

    1992-01-01

    Chemical reactivity is one of the few methods currently available for investigating the geometrical structure of isolated transition metal clusters. In this paper we summarize what is currently known about the structures of clusters of four transition metals, Fe, Co, Ni, and Cu, in the size range from 13 to 180 atoms. Chemical probes used to determine structural information include reactions with H 2 (D 2 ), H 2 0, NH 3 and N 2 . Measurements at both low coverage and at saturation are discussed

  3. Fabrication of GO/Cement Composites by Incorporation of Few-Layered GO Nanosheets and Characterization of Their Crystal/Chemical Structure and Properties.

    Science.gov (United States)

    Lv, Shenghua; Hu, Haoyan; Zhang, Jia; Luo, Xiaoqian; Lei, Ying; Sun, Li

    2017-12-18

    Original graphene oxide (GO) nanosheets were prepared using the Hummers method and found to easily aggregate in aqueous and cement composites. Using carboxymethyl chitosan (CCS) as a dispersant, few-layered GO nanosheets (1-2 layers) were obtained by forming CCS/GO intercalation composites. The testing results indicated that the few-layered GO nanosheets could uniformly spread, both in aqueous and cement composites. The cement composites were prepared with GO dosages of 0.03%, 0.05% and 0.07% and we found that they had a compact microstructure in the whole volume. A special feature was determined, namely that the microstructures consisted of regular-shaped crystals created by self-crosslinking. The X-ray diffraction (XRD) results indicated that there was a higher number of cement hydration crystals in GO/cement composites. Meanwhile, we also found that partially-amorphous Calcium-Silicate-Hydrate (C-S-H) gel turned into monoclinic crystals. At 28 days, the GO/cement composites reached the maximum compressive and flexural strengths at a 0.05% dosage. These strengths were 176.64 and 31.67 MPa and, compared with control samples, their increased ratios were 64.87% and 149.73%, respectively. Durability parameters, such as penetration, freeze-thaw, carbonation, drying-shrinkage value and pore structure, showed marked improvement. The results indicated that it is possible to obtain cement composites with a compact microstructure and with high performances by introducing CCS/GO intercalation composites.

  4. Cements in radioactive waste management. Characterization requirements of cement products for acceptance and quality assurance purposes

    International Nuclear Information System (INIS)

    Rahman, A.A.; Glasser, F.P.

    1987-01-01

    Cementitious materials are used as immobilizing matrices for low (LLW) and medium-level wastes (MLW) and are also components of the construction materials in the secondary barriers and the repositories. This report has concerned itself with a critical assessment of the quality assurance aspects of the immobilization and disposal of MLW and LLW cemented wastes. This report has collated the existing knowledge of the use and potential of cementitious materials in radioactive waste immobilization and highlighted the physico-chemical parameters. Subject areas include an assessment of immobilization objectives and cement as a durable material, waste stream and matrix characterization, quality assurance concepts, nature of cement-based systems, chemistry and modelling of cement hydration, role and effect of blending agents, radwaste-cement interaction, assessment of durability, degradative and radiolytic processes in cements and the behaviour of cement-based matrices and their near-field interactions with the environment and the repository conditions

  5. The Application of Metal Oxide Nanomaterials for Chemical Sensor Development

    Science.gov (United States)

    Xu, Jennifer C.; Hunter, Gary W.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.

    2007-01-01

    NASA Glenn Research Center (GRC) has been developing miniature chemical sensors for a variety of applications including fire detection, emissions monitoring, fuel leak detection, and environmental monitoring. Smart Lick and Stick sensor technology which integrates a sensor array, electronics, telemetry, and power into one microsystem are being developed. These microsystems require low power consumption for long-term aerospace applications. One approach to decreasing power consumption is the use of nanotechnology. Nanocrystalline tin oxide (SnO2) carbon monoxide (CO) sensors developed previously by this group have been successfully used for fire detection and emissions monitoring. This presentation will briefly review the overall NASA GRC chemical sensor program and discuss our further effort in nanotechnology applications. New carbon dioxide (CO2) sensing material using doped nanocrystalline SnO2 will be discussed. Nanocrystalline SnO2 coated solid electrolyte CO2 sensors and SnO2 nanorod and nanofiber hydrogen (H2) sensors operated at reduced or room temperatures will also be discussed.

  6. Physical-chemical purification of power metal optics for increasing its service life

    Science.gov (United States)

    Filin, S. A.; Rogalin, V. E.; Kaplunov, I. A.; Zingerman, K. M.

    2017-12-01

    In order to increase the resource of power metal optics, the features of the choice of solvents for its physical and chemical cleaning are investigated. During cleaning, on the contaminated surface there remain visually observed white film of alkali and alkaline earth metal salts, insoluble by this class of solvents, and iridescent bands from the interaction of hydrocarbons with metal, and this degrades optical properties and reduces the life of mirrors. It is demonstrated that, with the use of solvents, it is necessary to inhibit the interaction of hydrocarbons with mirrors by the stabilization of solvents or by selection of cleaning regimes.

  7. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    International Nuclear Information System (INIS)

    Lichtenberger, D.L.

    1991-10-01

    The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of (η 5 -C 5 H 4 X)Rh(CO) 2 complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C 60 molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C 60 reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs

  8. Bilayer–metal assisted chemical etching of silicon microwire arrays for photovoltaic applications

    Directory of Open Access Journals (Sweden)

    R. W. Wu

    2016-02-01

    Full Text Available Silicon microwires with lateral dimension from 5 μm to 20 μm and depth as long as 20 μm are prepared by bilayer metal assisted chemical etching (MaCE. A bilayer metal configuration (Metal 1 / Metal 2 was applied to assist etching of Si where metal 1 acts as direct catalyst and metal 2 provides mechanical support. Different metal types were investigated to figure out the influence of metal catalyst on morphology of etched silicon. We find that silicon microwires with vertical side wall are produced when we use Ag/Au bilayer, while cone–like and porous microwires formed when Pt/Au is applied. The different micro-/nano-structures in as-etched silicon are demonstrated to be due to the discrepancy of work function of metal catalyst relative to Si. Further, we constructed a silicon microwire arrays solar cells in a radial p–n junction configurations in a screen printed aluminum paste p–doping process.

  9. Artificial intelligence/fuzzy logic method for analysis of combined signals from heavy metal chemical sensors

    International Nuclear Information System (INIS)

    Turek, M.; Heiden, W.; Riesen, A.; Chhabda, T.A.; Schubert, J.; Zander, W.; Krueger, P.; Keusgen, M.; Schoening, M.J.

    2009-01-01

    The cross-sensitivity of chemical sensors for several metal ions resembles in a way the overlapping sensitivity of some biological sensors, like the optical colour receptors of human retinal cone cells. While it is difficult to assign crisp classification values to measurands based on complex overlapping sensory signals, fuzzy logic offers a possibility to mathematically model such systems. Current work goes into the direction of mixed heavy metal solutions and the combination of fuzzy logic with heavy metal-sensitive, silicon-based chemical sensors for training scenarios of arbitrary sensor/probe combinations in terms of an electronic tongue. Heavy metals play an important role in environmental analysis. As trace elements as well as water impurities released from industrial processes they occur in the environment. In this work, the development of a new fuzzy logic method based on potentiometric measurements performed with three different miniaturised chalcogenide glass sensors in different heavy metal solutions will be presented. The critical validation of the developed fuzzy logic program will be demonstrated by means of measurements in unknown single- and multi-component heavy metal solutions. Limitations of this program and a comparison between calculated and expected values in terms of analyte composition and heavy metal ion concentration will be shown and discussed.

  10. Artificial intelligence/fuzzy logic method for analysis of combined signals from heavy metal chemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Turek, M. [Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Campus Juelich, Juelich (Germany); Institute of Bio- and Nanosystems (IBN), Research Centre Juelich GmbH, Juelich (Germany); Heiden, W.; Riesen, A. [Bonn-Rhein-Sieg University of Applied Sciences, Sankt Augustin (Germany); Chhabda, T.A. [Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Campus Juelich, Juelich (Germany); Schubert, J.; Zander, W. [Institute of Bio- and Nanosystems (IBN), Research Centre Juelich GmbH, Juelich (Germany); Krueger, P. [Institute of Biochemistry and Molecular Biology, RWTH Aachen, Aachen (Germany); Keusgen, M. [Institute for Pharmaceutical Chemistry, Philipps-University Marburg, Marburg (Germany); Schoening, M.J. [Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Campus Juelich, Juelich (Germany); Institute of Bio- and Nanosystems (IBN), Research Centre Juelich GmbH, Juelich (Germany)], E-mail: m.j.schoening@fz-juelich.de

    2009-10-30

    The cross-sensitivity of chemical sensors for several metal ions resembles in a way the overlapping sensitivity of some biological sensors, like the optical colour receptors of human retinal cone cells. While it is difficult to assign crisp classification values to measurands based on complex overlapping sensory signals, fuzzy logic offers a possibility to mathematically model such systems. Current work goes into the direction of mixed heavy metal solutions and the combination of fuzzy logic with heavy metal-sensitive, silicon-based chemical sensors for training scenarios of arbitrary sensor/probe combinations in terms of an electronic tongue. Heavy metals play an important role in environmental analysis. As trace elements as well as water impurities released from industrial processes they occur in the environment. In this work, the development of a new fuzzy logic method based on potentiometric measurements performed with three different miniaturised chalcogenide glass sensors in different heavy metal solutions will be presented. The critical validation of the developed fuzzy logic program will be demonstrated by means of measurements in unknown single- and multi-component heavy metal solutions. Limitations of this program and a comparison between calculated and expected values in terms of analyte composition and heavy metal ion concentration will be shown and discussed.

  11. Solidification/stabilization of technetium in cement-based grouts

    International Nuclear Information System (INIS)

    Gilliam, T.M.; Bostick, W.D.; Spence, R.D.; Shoemaker, J.L.

    1990-01-01

    Mixed low-level radioactive and chemically hazardous process treatment wastes from the Portsmouth Gaseous Diffusion Plant are stabilized by solidification in cement-based grouts. Conventional portland cement and fly ash grouts have been shown to be effective for retention of hydrolyzable metals (e.g., lead, cadmium, uranium and nickel) but are marginally acceptable for retention of radioactive Tc-99, which is present in the waste as the highly mobile pertechnate anion. Addition of ground blast furnace slag to the grout is shown to reduce the leachability of technetium by several orders of magnitude. The selective effect of slag is believed to be due to its ability to reduce Tc(VII) to the less soluble Tc(IV) species. 12 refs., 4 tabs

  12. Chemical composition of extremely metal-poor stars in the Sextans dwarf spheroidal galaxy

    OpenAIRE

    Aoki, W.; Arimoto, N.; Sadakane, K.; Tolstoy, E.; Battaglia, G.; Jablonka, P.; Shetrone, M.; Letarte, B.; Irwin, M.; Hill, V.; Francois, P.; Venn, K.; Primas, F.; Helmi, A.; Kaufer, A.

    2009-01-01

    Context. Individual stars in dwarf spheroidal galaxies around the Milky Way Galaxy have been studied both photometrically and spectroscopically. Extremely metal-poor stars among them are very valuable because they should record the early enrichment in the Local Group. However, our understanding of these stars is very limited because detailed chemical abundance measurements are needed from high resolution spectroscopy. Aims. To constrain the formation and chemical evolution of dwarf galaxi...

  13. A case study to detect the leakage of underground pressureless cement sewage water pipe using GPR, electrical, and chemical data.

    Science.gov (United States)

    Liu, Guanqun; Jia, Yonggang; Liu, Hongjun; Qiu, Hanxue; Qiu, Dongling; Shan, Hongxian

    2002-03-01

    The exploration and determination of leakage of underground pressureless nonmetallic pipes is difficult to deal with. A comprehensive method combining Ground Penetrating Rader (GPR), electric potential survey and geochemical survey is introduced in the leakage detection of an underground pressureless nonmetallic sewage pipe in this paper. Theoretically, in the influencing scope of a leakage spot, the obvious changes of the electromagnetic properties and the physical-chemical properties of the underground media will be reflected as anomalies in GPR and electrical survey plots. The advantages of GPR and electrical survey are fast and accurate in detection of anomaly scope. In-situ analysis of the geophysical surveys can guide the geochemical survey. Then water and soil sampling and analyzing can be the evidence for judging the anomaly is caused by pipe leakage or not. On the basis of previous tests and practical surveys, the GPR waveforms, electric potential curves, contour maps, and chemical survey results are all classified into three types according to the extent or indexes of anomalies in orderto find out the leakage spots. When three survey methods all show their anomalies as type I in an anomalous spot, this spot is suspected as the most possible leakage location. Otherwise, it will be down grade suspected point. The suspect leakage spots should be confirmed by referring the site conditions because some anomalies are caused other factors. The excavation afterward proved that the method for determining the suspected location by anomaly type is effective and economic. Comprehensive method of GRP, electric potential survey, and geochemical survey is one of the effective methods in the leakage detection of underground nonmetallic pressureless pipe with its advantages of being fast and accurate.

  14. Novel Chemical Process for Producing Chrome Coated Metal

    Directory of Open Access Journals (Sweden)

    Christopher Pelar

    2018-01-01

    Full Text Available This work demonstrates that a version of the Reduction Expansion Synthesis (RES process, Cr-RES, can create a micron scale Cr coating on an iron wire. The process involves three steps. I. A paste consisting of a physical mix of urea, chrome nitrate or chrome oxide, and water is prepared. II. An iron wire is coated by dipping. III. The coated, and dried, wire is heated to ~800 °C for 10 min in a tube furnace under a slow flow of nitrogen gas. The processed wires were then polished and characterized, primarily with scanning electron microscopy (SEM. SEM indicates the chrome layer is uneven, but only on the scale of a fraction of a micron. The evidence of porosity is ambiguous. Elemental mapping using SEM electron microprobe that confirmed the process led to the formation of a chrome metal layer, with no evidence of alloy formation. Additionally, it was found that thickness of the final Cr layer correlated with the thickness of the precursor layer that was applied prior to the heating step. Potentially, this technique could replace electrolytic processing, a process that generates carcinogenic hexavalent chrome, but further study and development is needed.

  15. Novel Chemical Process for Producing Chrome Coated Metal.

    Science.gov (United States)

    Pelar, Christopher; Greenaway, Karima; Zea, Hugo; Wu, Chun-Hsien; Luhrs, Claudia C; Phillips, Jonathan

    2018-01-05

    This work demonstrates that a version of the Reduction Expansion Synthesis (RES) process, Cr-RES, can create a micron scale Cr coating on an iron wire. The process involves three steps. I. A paste consisting of a physical mix of urea, chrome nitrate or chrome oxide, and water is prepared. II. An iron wire is coated by dipping. III. The coated, and dried, wire is heated to ~800 °C for 10 min in a tube furnace under a slow flow of nitrogen gas. The processed wires were then polished and characterized, primarily with scanning electron microscopy (SEM). SEM indicates the chrome layer is uneven, but only on the scale of a fraction of a micron. The evidence of porosity is ambiguous. Elemental mapping using SEM electron microprobe that confirmed the process led to the formation of a chrome metal layer, with no evidence of alloy formation. Additionally, it was found that thickness of the final Cr layer correlated with the thickness of the precursor layer that was applied prior to the heating step. Potentially, this technique could replace electrolytic processing, a process that generates carcinogenic hexavalent chrome, but further study and development is needed.

  16. Observing single molecule chemical reactions on metal nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    Emory, S. R. (Steven R.); Ambrose, W. Patrick; Goodwin, P. M. (Peter M); Keller, Richard A.

    2001-01-01

    We report the study of the photodecomposition of single Rhodamine 6G (R6G) dye molecules adsorbed on silver nanoparticles. The nanoparticles were immobilized and spatially isolated on polylysine-derivatized glass coverslips, and confocal laser microspectroscopy was used to obtain surface-enhanced Raman scattering (SERS) spectra from individual R6G molecules. The photodecomposition of these molecules was observed with 150-ms temporal resolution. The photoproduct was identified as graphitic carbon based on the appearance of broad SERS vibrational bands at 1592 cm{sup -1} and 1340 cm{sup -1} observed in both bulk and averaged single-molecule photoproduct spectra. In contrast, when observed at the single-molecule level, the photoproduct yielded sharp SERS spectra. The inhomogeneous broadening of the bulk SERS spectra is due to a variety of photoproducts in different surface orientations and is a characteristic of ensemble-averaged measurements of disordered systems. These single-molecule studies indicate a photodecomposition pathway by which the R6G molecule desorbs from the metal surface, an excited-state photoreaction occurs, and the R6G photoproduct(s) readsorbs to the surface. A SERS spectrum is obtained when either the intact R6G or the R6G photoproduct(s) are adsorbed on a SERS-active site. This work further illustrates the power of single-molecule spectroscopy (SMS) to reveal unique behaviors of single molecules that are not discernable with bulk measurements.

  17. Metallization on FDM Parts Using the Chemical Deposition Technique

    Directory of Open Access Journals (Sweden)

    Azhar Equbal

    2014-08-01

    Full Text Available Metallization of ABS (acrylonitrile-butadiene-styrene parts has been studied on flat part surfaces. These parts are fabricated on an FDM (fused deposition modeling machine using the layer-wise deposition principle using ABS as a part material. Electroless copper deposition on ABS parts was performed using two different surface preparation processes, namely ABS parts prepared using chromic acid for etching and ABS parts prepared using a solution mixture of sulphuric acid and hydrogen peroxide (H2SO4/H2O2 for etching. After surface preparations using these routes, copper (Cu is deposited electrolessly using four different acidic baths. The acidic baths used are 5 wt% CuSO4 (copper sulfate with 15 wt% of individual acids, namely HF (hydrofluoric acid, H2SO4 (sulphuric acid, H3PO4 (phosphoric acid and CH3COOH (acetic acid. Cu deposition under different acidic baths used for both the routes is presented and compared based on their electrical performance, scanning electron microscopy (SEM and energy dispersive X-ray spectrometry (EDS. The result shows that chromic acid etched samples show better electrical performance and Cu deposition in comparison to samples etched via H2SO4/H2O2.

  18. Biological and chemical characterization of metal bioavailability in sediments from Lake Roosevelt, Columbia River, Washington, USA

    Science.gov (United States)

    Besser, J.M.; Brumbaugh, W.G.; Ivey, C.D.; Ingersoll, C.G.; Moran, P.W.

    2008-01-01

    We studied the bioavailability and toxicity of copper, zinc, arsenic, cadmium, and lead in sediments from Lake Roosevelt (LR), a reservoir on the Columbia River in Washington, USA that receives inputs of metals from an upstream smelter facility. We characterized chronic sediment toxicity, metal bioaccumulation, and metal concentrations in sediment and pore water from eight study sites: one site upstream in the Columbia River, six sites in the reservoir, and a reference site in an uncontaminated tributary. Total recoverable metal concentrations in LR sediments generally decreased from upstream to downstream in the study area, but sediments from two sites in the reservoir had metal concentrations much lower than adjacent reservoir sites and similar to the reference site, apparently due to erosion of uncontaminated bank soils. Concentrations of acid-volatile sulfide in LR sediments were too low to provide strong controls on metal bioavailability, and selective sediment extractions indicated that metals in most LR sediments were primarily associated with iron and manganese oxides. Oligochaetes (Lumbriculus variegatus) accumulated greatest concentrations of copper from the river sediment, and greatest concentrations of arsenic, cadmium, and lead from reservoir sediments. Chronic toxic effects on amphipods (Hyalella azteca; reduced survival) and midge larvae (Chironomus dilutus; reduced growth) in whole-sediment exposures were generally consistent with predictions of metal toxicity based on empirical and equilibrium partitioning-based sediment quality guidelines. Elevated metal concentrations in pore waters of some LR sediments suggested that metals released from iron and manganese oxides under anoxic conditions contributed to metal bioaccumulation and toxicity. Results of both chemical and biological assays indicate that metals in sediments from both riverine and reservoir habitats of Lake Roosevelt are available to benthic invertebrates. These findings will be used as

  19. Substrate Vibrations as Promoters of Chemical Reactivity on Metal Surfaces.

    Science.gov (United States)

    Campbell, Victoria L; Chen, Nan; Guo, Han; Jackson, Bret; Utz, Arthur L

    2015-12-17

    Studies exploring how vibrational energy (Evib) promotes chemical reactivity most often focus on molecular reagents, leaving the role of substrate atom motion in heterogeneous interfacial chemistry underexplored. This combined theoretical and experimental study of methane dissociation on Ni(111) shows that lattice atom motion modulates the reaction barrier height during each surface atom's vibrational period, which leads to a strong variation in the reaction probability (S0) with surface temperature (Tsurf). State-resolved beam-surface scattering studies at Tsurf = 90 K show a sharp threshold in S0 at translational energy (Etrans) = 42 kJ/mol. When Etrans decreases from 42 kJ/mol to 34 kJ/mol, S0 decreases 1000-fold at Tsurf = 90 K, but only 2-fold at Tsurf = 475 K. Results highlight the mechanism for this effect, provide benchmarks for DFT calculations, and suggest the potential importance of surface atom induced barrier height modulation in heterogeneously catalyzed reactions, particularly on structurally labile nanoscale particles and defect sites.

  20. Using magnetic and chemical measurements to detect atmospherically-derived metal pollution in artificial soils and metal uptake in plants

    International Nuclear Information System (INIS)

    Sapkota, B.; Cioppa, M.T.

    2012-01-01

    Quantification of potential effects of ambient atmospheric pollution on magnetic and chemical properties of soils and plants requires precise experimental studies. A controlled growth experiment assessing magnetic and chemical parameters was conducted within (controls) and outside (exposed) a greenhouse setting. Magnetic susceptibility (MS) measurements showed that while initial MS values were similar for the sample sets, the overall MS value of exposed soil was significantly greater than in controls, suggesting an additional input of Fe-containing particles. Scanning electron microscope images of the exposed soils revealed numerous angular magnetic particles and magnetic spherules typical of vehicular exhaust and combustion processes, respectively. Similarly, chemical analysis of plant roots showed that plants grown in the exposed soil had higher concentrations of Fe and heavy (toxic) metals than controls. This evidence suggests that atmospheric deposition contributed to the MS increase in exposed soils and increased metal uptake by plants grown in this soil. - Highlights: ► Magnetic susceptibility (MS) values increased in exposed soils during the growth. ► MS values in control soils decreased from their initial values during the growth. ► Decrease in MS values due to downwards migration of Fe particles, magnetic mineral transformations and Fe uptake by plants. ► Higher metal uptake in plants grown in exposed soils than those grown in controls. ► Atmospheric particulate deposition isolated as main contributor to these effects. - Variations in atmospheric particulate levels are measurable using magnetic and chemical techniques on soils and plant biomass, and suggest pollutant levels may be higher than previously recognized.

  1. Durability of cement-based materials: modeling of the influence of physical and chemical equilibria on the microstructure and the residual mechanical properties; Durabilite des materiaux cimentaires: modelisation de l'influence des equilibres physico-chimiques sur la microstructure et les proprietes mecaniques residuelles

    Energy Technology Data Exchange (ETDEWEB)

    Guillon, E

    2004-09-15

    A large part of mechanical and durability characteristics of cement-based materials comes from the performances of the hydrated cement, cohesive matrix surrounding the granular skeleton. Experimental studies, in situ or in laboratory, associated to models, have notably enhanced knowledge on the cement material and led to adapted formulations to specific applications or particularly aggressive environments. Nevertheless, these models, developed for precise cases, do not permit to specifically conclude for other experimental conclusions. To extend its applicability domain, we propose a new evolutive approach, based on reactive transport expressed at the microstructure scale of the cement. In a general point of view, the evolution of the solid compounds of the cement matrix, by dissolutions or precipitations, during chemical aggressions can be related to the pore solution evolution, and this one relied to the ionic exchanges with the external environment. By the utilization of a geochemical code associated to a thermodynamical database and coupled to a 3D transport model, this approach authorizes the study of all aggressive solution. The approach has been validated by the comparison of experimental observations to simulated degradations for three different environments (pure water, mineralized water, seawater) and on three different materials (CEM I Portland cement with 0.25, 0.4 and 0.5 water-to cement ratio). The microstructural approach permits also to have access to mechanical properties evolutions. During chemical aggressions, the cement matrix evolution is traduced in a microstructure evolution. This one is represented from 3D images similarly to the models developed at NIST (National Institute of Standards and Technology). A new finite-element model, validated on previous tests or models, evaluates the stiffness of the cement paste, using as a mesh these microstructures. Our approach identifies and quantifies the major influence of porosity and its spatial

  2. Interim Action Proposed Plan for the Chemicals, Metals, and Pesticides (CMP) Pits Operable Unit; FINAL

    International Nuclear Information System (INIS)

    Bradley, J.

    2002-01-01

    The purpose of this Interim Action Proposed Plan (IAPP) is to describe the preferred interim remedial action for addressing the Chemicals, Metals, and Pesticides (CMP) Pits Operable Unit and to provide an opportunity for public input into the remedial action selection process

  3. Calcium Aluminate Cement Hydration Model

    Directory of Open Access Journals (Sweden)

    Matusinović, T.

    2011-01-01

    Full Text Available Calcium aluminate cement (AC is a very versatile special cement used for specific applications. As the hydration of AC is highly temperature dependent, yielding structurally different hydration products that continuously alter material properties, a good knowledge of thermal properties at early stages of hydration is essential. The kinetics of AC hydration is a complex process and the use of single mechanisms models cannot describe the rate of hydration during the whole stage.This paper examines the influence of temperature (ϑ=5–20 °C and water-to-cement mass ratio (mH /mAC = 0.4; 0.5 and 1.0 on hydration of commercial iron-rich AC ISTRA 40 (producer: Istra Cement, Pula, Croatia, which is a part of CALUCEM group, Figs 1–3. The flow rate of heat generation of cement pastes as a result of the hydration reactions was measured with differential microcalorimeter. Chemically bonded water in the hydrated cement samples was determined by thermo-gravimetry.Far less heat is liberated when cement and water come in contact for the first time, Fig. 1, than in the case for portland cement (PC. Higher water-to-cement ratio increases the heat evolved at later ages (Fig. 3 due to higher quantity of water available for hydration. A significant effect of the water-to-cement ratio on the hydration rate and hydration degree showed the importance of water as being the limiting reactant that slows down the reaction early. A simplified stoichiometric model of early age AC hydration (eq. (8 based on reaction schemes of principal minerals, nominally CA, C12A7 and C4AF (Table 1, was employed. Hydration kinetics after the induction period (ϑ < 20 °C had been successfully described (Fig. 4 and Table 2 by a proposed model (eq. (23 which simultaneously comprised three main mechanisms: nucleation and growth, interaction at phase boundary, and mass transfer. In the proposed kinetic model the nucleation and growth is proportional to the amount of reacted minerals (eq

  4. Co-treatment of flotation waste, neutralization sludge, and arsenic-containing gypsum sludge from copper smelting: solidification/stabilization of arsenic and heavy metals with minimal cement clinker.

    Science.gov (United States)

    Liu, De-Gang; Min, Xiao-Bo; Ke, Yong; Chai, Li-Yuan; Liang, Yan-Jie; Li, Yuan-Cheng; Yao, Li-Wei; Wang, Zhong-Bing

    2018-03-01

    Flotation waste of copper slag (FWCS), neutralization sludge (NS), and arsenic-containing gypsum sludge (GS), both of which are difficult to dispose of, are major solid wastes produced by the copper smelting. This study focused on the co-treatment of FWCS, NS, and GS for solidification/stabilization of arsenic and heavy metals with minimal cement clinker. Firstly, the preparation parameters of binder composed of FWCS, NS, and cement clinker were optimized to be FWCS dosage of 40%, NS dosage of 10%, cement clinker dosage of 50%, mill time of 1.5 h, and water-to-binder ratio of 0.25. On these conditions, the unconfined compressive strength (UCS) of the binder reached 43.24 MPa after hydration of 28 days. Then, the binder was used to solidify/stabilize the As-containing GS. When the mass ratio of binder-to-GS was 5:5, the UCS of matrix can reach 11.06 MPa after hydration of 28 days, meeting the required UCS level of MU10 brick in China. Moreover, arsenic and other heavy metals in FWCS, NS, and GS were effectively solidified or stabilized. The heavy metal concentrations in leachate were much lower than those in the limits of China standard leaching test (CSLT). Therefore, the matrices were potential to be used as bricks in some constructions. XRD analysis shows that the main hydration products of the matrix were portlandite and calcium silicate hydrate. These hydration products may play a significant role in the stabilization/solidification of arsenic and heavy metals.

  5. Cementation and solidification of miscellaneous mixed wastes at the Rocky Flats Environmental Technology Site

    International Nuclear Information System (INIS)

    Phillips, J.A.; Semones, G.B.

    1995-01-01

    The Rocky Flats Environmental Technology Site produces a variety of wastes which are amenable to micro-encapsulation in cement Portland cement is an inexpensive and readily available material for this application. The Waste Projects (WP) group at Rocky Flats evaluated cementation to determine its effectiveness in encapsulating several wastes. These included waste analytical laboratory solutions, incinerator ash, hydroxide precipitation sludge, and an acidic solution from the Delphi process (a chemical oxidation technology being evaluated as an alternative to incineration). WP prepared surrogate wastes and conducted designed experiments to optimize the cement formulation for the waste streams. These experiments used a Taguchi or factorial experimental design, interactions between the variables were also considered in the testing. Surrogate waste samples were spiked with various levels of each of six Resource Conservation and Recovery Act (RCRA) listed metals (Cd, Cr, Ba, Pb, Ni, and Ag), cemented using the optimized formulation, and analyzed for leach resistance using the Toxicity Characteristic Leaching Procedure (TCLP). The metal spike levels chosen were based on characterization data, and also based on an estimate of the highest levels of contaminants suspected in the waste. This paper includes laboratory test results for each waste studied. These include qualitative observations as well as quantitative data from TCLP analyses and environmental cycling studies. The results from these experiments show that cement stabilization of the different wastes can produce final waste forms which meet the current RCRA Land Disposal Restriction (LDR) requirements. Formulations that resulted in LDR compliant waste forms are provided. The volume increases associated with cementation are also lower than anticipated. Future work will include verification studies with actual mixed radioactive waste as well as additional formulation development studies on other waste streams

  6. Influence of chemical pretreatment of hard metal substrates for diamond deposition

    International Nuclear Information System (INIS)

    Buck, V.; Kluwe, H.; Schmiler, B.; Deuerler, F.

    2001-01-01

    Diamond coated cutting tools are of increasing importance in the fields of high speed cutting, dry machining or machining of special materials such as metal-matrix-composites. A well known problem is the poor adhesion of diamond films on hard metals due to the Co- or Ni-binder that catalyzes the formation of graphite. Several methods - such as the application of intermediate layers or mechanical or chemical pretreatment of the hard metal substrate - have been developed to overcome this effect. Usually chemical pretreatment is used in order to reduce the concentration of binder phase on the surface that is to be coated. Surprisingly pretreatment with agents such as Murakami's solution result in improved adhesion and nucleation of diamond films while the concentration of the binder phase on the surface is enhanced. This 'contradiction' can be explained by proving that the surface is converted into a very thin oxide/hydroxide film. (author)

  7. The effects of cement-based and cement-ash-based mortar slabs on indoor air quality

    DEFF Research Database (Denmark)

    Krejcirikova, Barbora; Kolarik, Jakub; Wargocki, Pawel

    2018-01-01

    The effects of emissions from cement-based and cement-ash-based mortar slabs were studied. In the latter, 30% of the cement content had been replaced by sewage sludge ash. They were tested singly and together with either carpet or linoleum. The air exhausted from the chambers was assessed by means...... of odour intensity and chemical characterization of emissions. Odour intensity increased with the increased exposed area of the slabs. It did not differ significantly between cement-based or cement-ash-based mortar and neither did the chemical composition of the exhaust air. A significant sink effect...

  8. Cement materials for cesium and iodine confinement

    International Nuclear Information System (INIS)

    Nicolas, G.; Lequeux, N.; Boch, P.; Prene, S.

    2001-01-01

    The following topics were dealt with: radioactive waste storage, cement materials reacting with radioactive cesium and iodine, chemical barrier formation against radioactive pollution, ceramization, long term stability, XRD, PIXE analysis

  9. Chemical and microstructural analyses for heavy metals removal from water media by ceramic membrane filtration.

    Science.gov (United States)

    Ali, Asmaa; Ahmed, Abdelkader; Gad, Ali

    2017-01-01

    This study aims to investigate the ability of low cost ceramic membrane filtration in removing three common heavy metals namely; Pb 2+ , Cu 2+ , and Cd 2+ from water media. The work includes manufacturing ceramic membranes with dimensions of 15 by 15 cm and 2 cm thickness. The membranes were made from low cost materials of local clay mixed with different sawdust percentages of 0.5%, 2.0%, and 5.0%. The used clay was characterized by X-ray diffraction (XRD) and X-ray fluorescence analysis. Aqueous solutions of heavy metals were prepared in the laboratory and filtered through the ceramic membranes. The influence of the main parameters such as pH, initial driving pressure head, and concentration of heavy metals on their removal efficiency by ceramic membranes was investigated. Water samples were collected before and after the filtration process and their heavy metal concentrations were determined by chemical analysis. Moreover, a microstructural analysis using scanning electronic microscope (SEM) was performed on ceramic membranes before and after the filtration process. The chemical analysis results showed high removal efficiency up to 99% for the concerned heavy metals. SEM images approved these results by showing adsorbed metal ions on sides of the internal pores of the ceramic membranes.

  10. Chemical potential pinning due to equilibrium electron transfer at metal/C60-doped polymer interfaces

    Science.gov (United States)

    Heller, C. M.; Campbell, I. H.; Smith, D. L.; Barashkov, N. N.; Ferraris, J. P.

    1997-04-01

    We report electroabsorption measurements of the built-in electrostatic potential in metal/C60-doped polymer/metal structures to investigate chemical potential pinning due to equilibrium electron transfer from a metal contact to the electron acceptor energy level of C60 molecules in the polymer film. The built-in potentials of a series of structures employing thin films of both undoped and C60-doped poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were measured. For undoped MEH-PPV, which has an energy gap of about 2.4 eV, the maximum built-in potential is about 2.1 eV, whereas for C60-doped MEH-PPV the maximum built-in potential decreases to 1.5 eV. Electron transfer to the C60 molecules close to the metal interface pins the chemical potential of the metal contact near the electron acceptor energy level of C60 and decreases the built-in potential of the structure. From the systematic dependence of the built-in potential on the metal work function we find that the electron acceptor energy level of C60 in MEH-PPV is about 1.7 eV above the hole polaron energy level of MEH-PPV.

  11. Removal of heavy metals from aqueous phases using chemically modified waste Lyocell fiber

    Energy Technology Data Exchange (ETDEWEB)

    Bediako, John Kwame; Wei, Wei; Kim, Sok; Yun, Yeoung-Sang, E-mail: ysyun@jbnu.ac.kr

    2015-12-15

    Highlights: • Waste Lyocell fiber was chemically modified into cellulose xanthate. • The sorbent showed high affinity for Pb(II), Cd(II) and Cu(II) ions. • The sorbent also showed strong Cu(II) selectivity in Pb(II)–Cd(II)–Cu(II) ternary metal solutions. - Abstract: In this study, an outstanding performance of chemically modified waste Lyocell for heavy metals treatment is reported. The sorbent, which was prepared by a simple and concise method, was able to bind heavy metals such as Pb(II), Cu(II) and Cd(II), with very high efficiencies. The binding mechanisms were studied through adsorption and standard characterization tests such as scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses. Adsorption kinetics was very fast and attained equilibrium within 5 min in all metals studied. The maximum single metal uptakes were 531.29 ± 0.28 mg/g, 505.64 ± 0.21 mg/g, and 123.08 ± 0.26 mg/g for Pb(II), Cd(II) and Cu(II), respectively. In ternary metal systems, Cu(II) selectivity was observed and the underlying factors were discussed. The sorbent by its nature, could be very effective in treating large volumes of wastewater with the contact of very little amount.

  12. Metal and anion composition of two biopolymeric chemical stabilizers and toxicity risk implication for the environment.

    Science.gov (United States)

    Ndibewu, P P; Mgangira, M B; Cingo, N; McCrindle, R I

    2010-01-01

    The objective of this study was to (1) measure the concentration of four anions (Cl(-), F(-), [image omitted], and [image omitted]) and nine other elements (Al, Ba, Ca, K, Mg, Mn, Fe, Ni, and Si) in two nontraditional biopolymeric chemical stabilizers (EBCS1 and EBCS2), (2) investigate consequent environmental toxicity risk implications, and (3) create awareness regarding environmental health issues associated with metal concentration levels in enzyme-based chemical stabilizers that are now gaining widespread application in road construction and other concrete materials. Potential ecotoxicity impacts were studied on aqueous extracts of EBCS1 and EBCS2 using two thermodynamic properties models: the Pitzer-Mayorga model (calculation of the electrolyte activity coefficients) and the Millero-Pitzer model (calculation of the ionic activity coefficients). Results showed not only high concentrations of a variety of metal ions and inorganic anions, but also a significant variation between two chemical stabilizing mixtures. The mixture (EBCS2) with the lower pH value was richer in all the cationic and anionic species than (EBCS1). Sulfate (SO(2-)(4)) concentrations were found to be higher in EBCS2 than in EBCS1. There was no correlation between electrolyte activity and presence of the ionic species, which may be linked to a possible high ionic environmental activity. The concentrations of trace metals found (Mn, Fe, and Ni) were low compared to those of earth metals (Ba, Ca, K, and Mg). The metal concentrations were higher in EBCS1 than in EBCS2. Data suggest that specific studies are needed to establish "zero" permissible metal ecotoxicity values for elements and anions in any such strong polyelectrolytic enzyme-based chemical stabilizers.

  13. The Role of Electronic Excitations on Chemical Reaction Dynamics at Metal, Semiconductor and Nanoparticle Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tully, John C. [Yale Univ., New Haven, CT (United States)

    2017-06-10

    Chemical reactions are often facilitated and steered when carried out on solid surfaces, essential for applications such as heterogeneous catalysis, solar energy conversion, corrosion, materials processing, and many others. A critical factor that can determine the rates and pathways of chemical reactions at surfaces is the efficiency and specificity of energy transfer; how fast does energy move around and where does it go? For reactions on insulator surfaces energy transfer generally moves in and out of vibrations of the adsorbed molecule and the underlying substrate. By contrast, on metal surfaces, metallic nanoparticles and semiconductors, another pathway for energy flow opens up, excitation and de-excitation of electrons. This so-called “nonadiabatic” mechanism often dominates the transfer of energy and can directly impact the course of a chemical reaction. Conventional computational methods such as molecular dynamics simulation do not account for this nonadiabatic behavior. The current DOE-BES funded project has focused on developing the underlying theoretical foundation and the computational methodology for the prediction of nonadiabatic chemical reaction dynamics at surfaces. The research has successfully opened up new methodology and new applications for molecular simulation. In particular, over the last three years, the “Electronic Friction” theory, pioneered by the PI, has now been developed into a stable and accurate computational method that is sufficiently practical to allow first principles “on-the-fly” simulation of chemical reaction dynamics at metal surfaces.

  14. Glass ionomer cement: literature review

    Directory of Open Access Journals (Sweden)

    Sérgio Spezzia

    2017-12-01

    Full Text Available Introduction: In the dental area preventive actions occur in an attempt to avoid the installation of caries, a disease that has an increased prevalence in the population and which is a Public Health problem. Some resources are used for such, such as: performing early diagnosis and the option for conservative treatments of minimal intervention. The glass ionomer cement (CIV, coming from its beneficial characteristics that meet current trends, is closely related to the precepts of Preventive and Minimally Invasive Dentistry and the new preservative techniques recommended. Objective: The objective of the present article was to carry out a literature review study, to determine the characteristics of CIV that has a prominent role in the Minimally Invasive Dentistry profile. Results: The dentist surgeon must be aware of the classification, according to its composition and physical-chemical nature: conventional ionomers; ionomers reinforced by metals; high viscosity and various types of resin modified glass ionomers to correctly choose the CIV that will be used in their clinical interventions, which should occur based on the properties of the material and its clinical indication. Conclusion: It was concluded that the implementation of preventive techniques with CIV in public health care, tend to minimize curative treatments, concurrently valuing the low complexity dental procedures performed in Primary Care, avoiding referrals for treatment of cases of greater complexity at the level Secondary and tertiary care, saving resources.

  15. Chemically reduced graphene contains inherent metallic impurities present in parent natural and synthetic graphite

    Science.gov (United States)

    Ambrosi, Adriano; Chua, Chun Kiang; Khezri, Bahareh; Sofer, Zdeněk; Webster, Richard D.; Pumera, Martin

    2012-01-01

    Graphene-related materials are in the forefront of nanomaterial research. One of the most common ways to prepare graphenes is to oxidize graphite (natural or synthetic) to graphite oxide and exfoliate it to graphene oxide with consequent chemical reduction to chemically reduced graphene. Here, we show that both natural and synthetic graphite contain a large amount of metallic impurities that persist in the samples of graphite oxide after the oxidative treatment, and chemically reduced graphene after the chemical reduction. We demonstrate that, despite a substantial elimination during the oxidative treatment of graphite samples, a significant amount of impurities associated to the chemically reduced graphene materials still remain and alter their electrochemical properties dramatically. We propose a method for the purification of graphenes based on thermal treatment at 1,000 °C in chlorine atmosphere to reduce the effect of such impurities on the electrochemical properties. Our findings have important implications on the whole field of graphene research. PMID:22826262

  16. Chemically reduced graphene contains inherent metallic impurities present in parent natural and synthetic graphite.

    Science.gov (United States)

    Ambrosi, Adriano; Chua, Chun Kiang; Khezri, Bahareh; Sofer, Zdeněk; Webster, Richard D; Pumera, Martin

    2012-08-07

    Graphene-related materials are in the forefront of nanomaterial research. One of the most common ways to prepare graphenes is to oxidize graphite (natural or synthetic) to graphite oxide and exfoliate it to graphene oxide with consequent chemical reduction to chemically reduced graphene. Here, we show that both natural and synthetic graphite contain a large amount of metallic impurities that persist in the samples of graphite oxide after the oxidative treatment, and chemically reduced graphene after the chemical reduction. We demonstrate that, despite a substantial elimination during the oxidative treatment of graphite samples, a significant amount of impurities associated to the chemically reduced graphene materials still remain and alter their electrochemical properties dramatically. We propose a method for the purification of graphenes based on thermal treatment at 1,000 °C in chlorine atmosphere to reduce the effect of such impurities on the electrochemical properties. Our findings have important implications on the whole field of graphene research.

  17. Physical, chemical and mineralogical characterization of water treatment plant waste for use in soil-cement brick; Caracterizacao fisica, quimica e mineralogica de residuo de estacao de tratamento de aguas para aproveitamento em tijolo solo-cimento

    Energy Technology Data Exchange (ETDEWEB)

    Pessin, L.R.; Destefani, A.Z.; Holanda, J.N.F., E-mail: larapessin@hotmail.com [Universidade Estadual do Norte Fluminense Darcy Ribeiro (CCT/PPGECM/UENF), Campos dos Goytacazes, RJ (Brazil)

    2011-07-01

    The water treatment plants (WTP) for human consumption generate huge amounts of waste in the form of sludge (sludge) that have been over the years mostly inadequately prepared in water resources and the environment. Moreover, traditional methods of disposal of waste water treatment plants commonly used are generally costly activities. An alternative method for disposal of this waste abundant is its incorporation in ceramic products. This work is focused on the physical-chemical and mineralogical composition of a sample of waste water treatment plants from the region of Campos dos Goytacazes-RJ to their use in the manufacture of soil-cement brick. Several characterization techniques were used including X-ray diffraction, X-ray fluorescence, scanning electron microscopy, picnometry, particle size analysis and plasticity. The experimental results indicate that the waste water treatment plants have the potential to be used in the manufacture of ecologic soil-cement bricks. (author)

  18. Extraction of metal ions using chemically modified silica gel: a PIXE analysis.

    Science.gov (United States)

    Jal, P K; Dutta, R K; Sudarshan, M; Saha, A; Bhattacharyya, S N; Chintalapudi, S N; K Mishra, B

    2001-08-30

    Organic ligand with carboxyhydrazide functional group was immobilised on the surface of silica gel and the metal binding capacity of the ligand-embedded silica was investigated. The functional group was covalently bonded to the silica matrix through a spacer of methylene groups by sequential reactions of silica gel with dibromobutane, malonic ester and hydrazine in different media. Surface area value of the modified silica was determined. The changes in surface area were correlated with the structural change of the silica surface due to chemical modifications. A mixture solution of metal ions [K(I),Cr(III),Co(II),Ni(II),Cu(II),Zn(II),Hg(II) and U(VI)] was treated with the ligand-embedded silica in 10(-3) M aqueous solution. The measurement of metal extraction capacity of the silica based ligand was done by multielemental analysis of the metal complexes thus formed by using Proton Induced X-ray Emission (PIXE) technique.

  19. Structural, Chemical and Biological Aspects of Antioxidants for Strategies Against Metal and Metalloid Exposure

    Directory of Open Access Journals (Sweden)

    Swaran J. S. Flora

    2009-01-01

    Full Text Available Oxidative stress contributes to the pathophysiology of exposure to heavy metals/metalloid. Beneficial renal effects of some medications, such as chelation therapy depend at least partially on the ability to alleviate oxidative stress. The administration of various natural or synthetic antioxidants has been shown to be of benefit in the prevention and attenuation of metal induced biochemical alterations. These include vitamins, N-acetylcysteine, α-lipoic acid, melatonin, dietary flavonoids and many others. Human studies are limited in this regard. Under certain conditions, surprisingly, the antioxidant supplements may exhibit pro-oxidant properties and even worsen metal induced toxic damage. To date, the evidence is insufficient to recommend antioxidant supplements in subject with exposure to metals. Prospective, controlled clinical trials on safety and effectiveness of different therapeutic antioxidant strategies either individually or in combination with chelating agent are indispensable. The present review focuses on structural, chemical and biological aspects of antioxidants particularly related to their chelating properties.

  20. Chemical principles underpinning the performance of the metal-organic framework HKUST-1.

    Science.gov (United States)

    Hendon, Christopher H; Walsh, Aron

    2015-07-15

    A common feature of multi-functional metal-organic frameworks is a metal dimer in the form of a paddlewheel, as found in the structure of Cu 3 ( btc ) 2 (HKUST-1). The HKUST-1 framework demonstrates exceptional gas storage, sensing and separation, catalytic activity and, in recent studies, unprecedented ionic and electrical conductivity. These results are a promising step towards the real-world application of metal-organic materials. In this perspective, we discuss progress in the understanding of the electronic, magnetic and physical properties of HKUST-1, representative of the larger family of Cu···Cu containing metal-organic frameworks. We highlight the chemical interactions that give rise to its favourable properties, and which make this material well suited to a range of technological applications. From this analysis, we postulate key design principles for tailoring novel high-performance hybrid frameworks.

  1. Micropore characteristics of organic matter pools in cemented and non-cemented podzolic horizons

    NARCIS (Netherlands)

    Catoni, M.; D'amico, M.E.; Mittelmeijer-Hazeleger, M.C.; Rothenberg, G.; Bonifacio, E.

    2014-01-01

    In Podzols, organic matter (OM) is stabilized mainly by interaction with minerals, as a direct consequence of pedogenic processes. Metal-organic associations strongly affect OM surface features, particularly microporosity. Cemented ortstein horizons (CM) may form during podzolization, accompanied by

  2. Encapsulation of mixed radioactive and hazardous waste contaminated incinerator ash in modified sulfur cement

    International Nuclear Information System (INIS)

    Kalb, P.D.; Heiser, J.H. III; Colombo, P.

    1990-01-01

    Some of the process waste streams incinerated at various Department of Energy (DOE) facilities contain traces of both low-level radioactive (LLW) and hazardous constituents, thus yielding ash residues that are classified as mixed waste. Work is currently being performed at Brookhaven National Laboratory (BNL) to develop new and innovative materials for encapsulation of DOE mixed wastes including incinerator ash. One such material under investigation is modified sulfur cement, a thermoplastic developed by the US Bureau of Mines. Monolithic waste forms containing as much as 55 wt % incinerator fly ash from Idaho national Engineering Laboratory (INEL) have been formulated with modified sulfur cement, whereas maximum waste loading for this waste in hydraulic cement is 16 wt %. Compressive strength of these waste forms exceeded 27.6 MPa. Wet chemical and solid phase waste characterization analyses performed on this fly ash revealed high concentrations of soluble metal salts including Pb and Cd, identified by the Environmental Protection Agency (EPA) as toxic metals. Leach testing of the ash according to the EPA Toxicity Characteristic Leaching Procedure (TCLP) resulted in concentrations of Pb and Cd above allowable limits. Encapsulation of INEL fly ash in modified sulfur cement with a small quantity of sodium sulfide added to enhance retention of soluble metal salts reduced TCLP leachate concentrations of Pb and Cd well below EPA concentration criteria for delisting as a toxic hazardous waste. 12 refs., 4 figs., 2 tabs

  3. Soil parameters are key factors to predict metal bioavailability to snails based on chemical extractant data

    International Nuclear Information System (INIS)

    Pauget, B.; Gimbert, F.; Scheifler, R.; Coeurdassier, M.; Vaufleury, A. de

    2012-01-01

    Although soil characteristics modulate metal mobility and bioavailability to organisms, they are often ignored in the risk assessment of metal transfer. This paper aims to determine the ability of chemical methods to assess and predict cadmium (Cd), lead (Pb) and zinc (Zn) environmental bioavailability to the land snail Cantareus aspersus. Snails were exposed in the laboratory for 28 days to 17 soils from around a former smelter. The soils were selected for their range of pH, organic matter, clay content, and Cd, Pb and Zn concentrations. The influence of soil properties on environmental availability (estimated using HF-HClO 4 , EDTA, CaCl 2 , NH 4 NO 3 , NaNO 3 , free ion activity and total dissolved metal concentration in soil solution) and on environmental bioavailability (modelled using accumulation kinetics) was identified. Among the seven chemical methods, only the EDTA and the total soil concentration can be used to assess Cd and Pb environmental bioavailability to snails (r² adj = 0.67 and 0.77, respectively). For Zn, none of the chemical methods were suitable. Taking into account the influence of the soil characteristics (pH and CEC) allows a better prediction of Cd and Pb environmental bioavailability (r² adj = 0.82 and 0.83, respectively). Even though alone none of the chemical methods tested could assess Zn environmental bioavailability to snails, the addition of pH, iron and aluminium oxides allowed the variation of assimilation fluxes to be predicted. A conceptual and practical method to use soil characteristics for risk assessment is proposed based on these results. We conclude that as yet there is no universal chemical method to predict metal environmental bioavailability to snails, and that the soil factors having the greatest impact depend on the metal considered. - Highlights: ► New approach to identify chemical methods able to predict metal bioavailability to snails. ► Bioavailability of cadmium, lead and zinc to snails was determined by

  4. Soil parameters are key factors to predict metal bioavailability to snails based on chemical extractant data

    Energy Technology Data Exchange (ETDEWEB)

    Pauget, B.; Gimbert, F., E-mail: frederic.gimbert@univ-fcomte.fr; Scheifler, R.; Coeurdassier, M.; Vaufleury, A. de

    2012-08-01

    Although soil characteristics modulate metal mobility and bioavailability to organisms, they are often ignored in the risk assessment of metal transfer. This paper aims to determine the ability of chemical methods to assess and predict cadmium (Cd), lead (Pb) and zinc (Zn) environmental bioavailability to the land snail Cantareus aspersus. Snails were exposed in the laboratory for 28 days to 17 soils from around a former smelter. The soils were selected for their range of pH, organic matter, clay content, and Cd, Pb and Zn concentrations. The influence of soil properties on environmental availability (estimated using HF-HClO{sub 4}, EDTA, CaCl{sub 2}, NH{sub 4}NO{sub 3}, NaNO{sub 3}, free ion activity and total dissolved metal concentration in soil solution) and on environmental bioavailability (modelled using accumulation kinetics) was identified. Among the seven chemical methods, only the EDTA and the total soil concentration can be used to assess Cd and Pb environmental bioavailability to snails (r Superscript-Two {sub adj} = 0.67 and 0.77, respectively). For Zn, none of the chemical methods were suitable. Taking into account the influence of the soil characteristics (pH and CEC) allows a better prediction of Cd and Pb environmental bioavailability (r Superscript-Two {sub adj} = 0.82 and 0.83, respectively). Even though alone none of the chemical methods tested could assess Zn environmental bioavailability to snails, the addition of pH, iron and aluminium oxides allowed the variation of assimilation fluxes to be predicted. A conceptual and practical method to use soil characteristics for risk assessment is proposed based on these results. We conclude that as yet there is no universal chemical method to predict metal environmental bioavailability to snails, and that the soil factors having the greatest impact depend on the metal considered. - Highlights: Black-Right-Pointing-Pointer New approach to identify chemical methods able to predict metal bioavailability

  5. Evaluation of trace metals bioavailability in Japanese river waters using DGT and a chemical equilibrium model.

    Science.gov (United States)

    Han, Shuping; Naito, Wataru; Hanai, Yoshimichi; Masunaga, Shigeki

    2013-09-15

    To develop efficient and effective methods of assessing and managing the risk posed by metals to aquatic life, it is important to determine the effects of water chemistry on the bioavailability of metals in surface water. In this study, we employed the diffusive gradients in thin-films (DGT) to determine the bioavailability of metals (Ni, Cu, Zn, and Pb) in Japanese water systems. The DGT results were compared with a chemical equilibrium model (WHAM 7.0) calculation to examine its robustness and utility to predict dynamic metal speciation. The DGT measurements showed that biologically available fractions of metals in the rivers impacted by mine drainage and metal industries were relatively high compared with those in urban rivers. Comparison between the DGT results and the model calculation indicated good agreement for Zn. The model calculation concentrations for Ni and Cu were higher than the DGT concentrations at most sites. As for Pb, the model calculation depended on whether the precipitated iron(III) hydroxide or precipitated aluminum(III) hydroxide was assumed to have an active surface. Our results suggest that the use of WHAM 7.0 combined with the DGT method can predict bioavailable concentrations of most metals (except for Pb) with reasonable accuracy. Copyright © 2013. Published by Elsevier Ltd.

  6. Investigation of DOTA-Metal Chelation Effects on the Chemical Shift of 129 Xe

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, K; Slack, CC; Vassiliou, CC; Dao, P; Gomes, MD; Kennedy, DJ; Truxal, AE; Sperling, LJ; Francis, MB; Wemmer, DE; Pines, A

    2015-09-17

    Recent work has shown that xenon chemical shifts in cryptophane-cage sensors are affected when tethered chelators bind to metals. Here in this paper, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) linked to cryptophane-A. The shifts induced by the binding of Ca2+, Cu2+, Ce3+, Zn2+, Cd2+, Ni2+, Co2+, Cr2+, Fe3+, and Hg2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding with a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. Lastly, these sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs.

  7. Metal ferrite oxygen carriers for chemical looping combustion of solid fuels

    Science.gov (United States)

    Siriwardane, Ranjani V.; Fan, Yueying

    2017-01-31

    The disclosure provides a metal ferrite oxygen carrier for the chemical looping combustion of solid carbonaceous fuels, such as coal, coke, coal and biomass char, and the like. The metal ferrite oxygen carrier comprises MFe.sub.xO.sub.y on an inert support, where MFe.sub.xO.sub.y is a chemical composition and M is one of Mg, Ca, Sr, Ba, Co, Mn, and combinations thereof. For example, MFe.sub.xO.sub.y may be one of MgFe.sub.2O.sub.4, CaFe.sub.2O.sub.4, SrFe.sub.2O.sub.4, BaFe.sub.2O.sub.4, CoFe.sub.2O.sub.4, MnFeO.sub.3, and combinations thereof. The MFe.sub.xO.sub.y is supported on an inert support. The inert support disperses the MFe.sub.xO.sub.y oxides to avoid agglomeration and improve performance stability. In an embodiment, the inert support comprises from about 5 wt. % to about 60 wt. % of the metal ferrite oxygen carrier and the MFe.sub.xO.sub.y comprises at least 30 wt. % of the metal ferrite oxygen carrier. The metal ferrite oxygen carriers disclosed display improved reduction rates over Fe.sub.2O.sub.3, and improved oxidation rates over CuO.

  8. Using proven, cost-effective chemical stabilization to remediate radioactive and heavy metal contaminated sites

    International Nuclear Information System (INIS)

    Jensen, R.; Sogue, A.

    1999-01-01

    Rocky Mountain Remediation Services, L.L.C. (RMRS) has deployed a cost-effective metals stabilization method which can be used to reduce the cost of remediation projects where radioactivity and heavy metals are the contaminants of concern. The Envirobond TM process employs the use of a proprietary chemical process to stabilize metals in many waste forms, and provides an excellent binding system that can easily be compacted to reduce the waste into a shippable brick called Envirobric TM . The advantages of using chemical stabilization are: (1) Low cost, due to the simplicity of the process design and inexpensive reagents. (2) Chemical stabilization is easily deployed in field applications, which limit the amount of shielding and other protective measures. (3) The process does not add volume and bulk to the treated waste; after treatment the materials may be able to remain on-site, or if transportation and disposal is required the cost will be reduced due to lower volumes. (4) No secondary waste. The simplicity of this process creates a safe environment while treating the residues, and the long-term effectiveness of this type of chemical stabilization lowers the risk of future release of hazardous elements associated with the residues. (author)

  9. Electrospun Polymer Nanofibers Decorated with Noble Metal Nanoparticles for Chemical Sensing.

    Science.gov (United States)

    Chen, Chen; Tang, Yongan; Vlahovic, Branislav; Yan, Fei

    2017-12-01

    The integration of different noble metal nanostructures, which exhibit desirable plasmonic and/or electrocatalytic properties, with electrospun polymer nanofibers, which display unique mechanical and thermodynamic properties, yields novel hybrid nanoscale systems of synergistic properties and functions. This review summarizes recent advances on how to incorporate noble metal nanoparticles into electrospun polymer nanofibers and illustrates how such integration paves the way towards chemical sensing applications with improved sensitivity, stability, flexibility, compatibility, and selectivity. It is expected that further development of this field will eventually make a wide impact on many areas of research.

  10. Speciation of heavy metals in garden soils. Evidences from selective and sequential chemical leaching

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Zhongqi; Lee, Leda; Dayan, Sara; Grinshtein, Michael [Brooklyn College of The City Univ. of New York, Brooklyn, NY (United States). Environmental Sciences Analytical Cnter; Shaw, Richard [USDA-NRCS NYC Soil Survey, Staten Island, NY (United States)

    2011-06-15

    Purpose: Gardening (especially food growing) in urban areas is becoming popular, but urban soils are often very contaminated for historical reasons. There is lack of sufficient information as to the bioavailability of soil heavy metals to plants and human in urban environments. This study examines the relative leachability of Cr, Ni, As, Cd, Zn, and Pb for soils with varying characteristics. The speciation and mobility of these metals can be qualitatively inferred from the leaching experiments. The goal is to use the data to shed some light on their bioavailability to plant and human, as well as the basis for soil remediation. Materials and methods: Selective and sequential chemical leaching methods were both used to evaluate the speciation of Cr, Ni, As, Cd, Zn, and Pb in soil samples collected from New York City residential and community gardens. The sequential leaching experiment followed a standard BCR four-step procedure, while selective leaching involved seven different chemical extractants. Results and discussion: The results from selective and sequential leaching methods are consistent. In general, very little of the heavy metals were found in the easily soluble or exchangeable fractions. Larger fractions of Cd and Zn can be leached out than other metals. Lead appears predominantly in the organic or carbonate fractions, of which {proportional_to} 30-60% is in the easily soluble organic fraction. Most As cannot be leached out by any of the extractants used, but it could have been complicated by the ineffective dissolution of oxides by ammonium hydroxylamine. Ni and Cr were mostly in the residual fractions but some released in the oxidizable fractions. Therefore, the leachability of metals follow the order Cd/Zn > Pb > Ni/Cr. Conclusions: Despite of the controversy and inaccuracy surrounding chemical leaching methods for the speciation of metals, chemical leaching data provide important, general, and easy-to-access information on the mobility of heavy metals

  11. Chelating impact assessment of biological ad chemical chelates on metal extraction from contaminated soils

    International Nuclear Information System (INIS)

    Manwar, S.; Iram, S.

    2014-01-01

    Soil contamination is the result of uncontrolled waste dumping and poor practices by humans. Of all the pollutants heavy metals are of particular concern due to their atmospheric deposition, leaching capacity and non-biodegradability. Heavy metal containing effluent is discharged into the agricultural fields and water bodies. This results in the accumulation of heavy metals in soil and the crops grown on that soil. Studies have revealed detrimental impacts on soil fertility and the poor health of animals and humans. Phytoextraction is widely researched for remediation of heavy metal contaminated soil. To enhance the effect of phytoextraction heavy metals have to be available to the plants in soluble form. In this study the potential of different chelating agents was assessed in solubilizing the heavy metals making easy for plants to uptake them. For this purpose efficient chemical and biological chelating agent had to be identified. Along with that an optimum dose and application time for chemical chelating agent was determined. Ethylenediamine tetraacetic acid (EDTA), Diethylene triamine pentaacetic acid (DTPA), Nitriloacetic acid (NTA) were applied to the soil, containing Pb, Cr, Cu and Cd, at different concentrations and application time. Aspergillus niger and Aspergillus flavus were incubated in soil for different time periods. In correspondence with findings of the study, Pb and Cr were best solubilized by 5mM EDTA. For Cd and Cu 5mM DTPA carried out efficient chelation. NTA showed relatively inadequate solubilisation, although for Cr it performed equal to EDTA. A. niger and A. flavus instead of solubilizing adsorbed the metals in their biomass. Adsorption was mainly carried out by A. niger. (author)

  12. Trace metals of an acid mine drainage stream using a chemical model (WATEQ) and sediment analysis

    International Nuclear Information System (INIS)

    West, K.A.; Wilson, T.P.

    1992-01-01

    The high metal contents common to the discharge of acid-mine drainage (AMD) from mines and mine spoils is an environmental concern to both government and industry. This paper reports the results of investigation of the behavior of metals in an AMD system at a former surface coal mine in Tuscarawas County, Oh. AMD discharges from seeps travels, in respective order through a laminar flow stream; a Typha-dominated wetland; a turbulent flow stream; and a sediment retention pond. Dissolved metals (Fe, Mn, Zn, Cr, Cd, Cu, and Al) major and minor components, and other parameters (pH, dissolved oxygen and Eh) were measured in the AMD water at each sample location. A chemical mineral equilibrium model (WATEQ) was used to predict the minerals which should precipitate at each site. Results suggest that the seeps are supersaturated and should be precipitating hematite, goethite and magnetite (iron oxides), and siderite (iron carbonate), whereas water of the other downstream sites were at or below equilibrium conditions for these minerals. The hydrogeochemistry of the AMD was further studied using sequential chemical attacks on the precipitate sediment surface coatings, in order to determine metal concentrations in the exchangeable, carbonate, Fe-Mn oxyhydroxide, and oxidizable fractions. The carbonate and exchangeable fractions of the precipitate are dominated by Ca and Fe, as well as Mg in the carbonate fraction. The Fe-Mn oxyhydroxide fraction contained Fe, Al, Mn, Mg, and trace metals, and also contained the greatest concentration of total elements in the system. The Fe-Mn oxyhydroxide is therefore, the major sink for metals of this AMD system. The decrease in the concentration of metals in the sediment precipitates in the downstream locations, is consistent with WATEQ and water analysis results

  13. Improved cement solidification of low and intermediate level radioactive wastes

    International Nuclear Information System (INIS)

    1993-01-01

    Cementation was the first and is still the most widely applied technique for the conditioning of low and intermediate level radioactive wastes. Compared with other solidification techniques, cementation is relatively simple and inexpensive. However, the quality of the final cemented waste forms depends very much on the composition of the waste and the type of cement used. Different kinds of cement are used for different kinds of waste and the compatibility of a specific waste with a specific cement type should always be carefully evaluated. Cementation technology is continuously being developed in order to improve the characteristics of cemented waste in accordance with the increasing requirements for quality of the final solidified waste. Various kinds of additives and chemicals are used to improve the cemented waste forms in order to meet all safety requirements. This report is meant mainly for engineers and designers, to provide an explanation of the chemistry of cementation systems and to facilitate the choice of solidification agents and processing equipment. It reviews recent developments in cementation technology for improving the quality of cemented waste forms and provides a brief description of the various cement solidification processes in use. Refs, figs and tabs

  14. Chemical hole doping into large-area transition metal dichalcogenide monolayers using boron-based oxidant

    KAUST Repository

    Matsuoka, Hirofumi; Kanahashi, Kaito; Tanaka, Naoki; Shoji, Yoshiaki; Li, Lain-Jong; Pu, Jiang; Ito, Hiroshi; Ohta, Hiromichi; Fukushima, Takanori; Takenobu, Taishi

    2018-01-01

    Hole carrier doping into single-crystalline transition metal dichalcogenide (TMDC) films can be achieved with various chemical reagents. However, large-area polycrystalline TMDC monolayers produced by a chemical vapor deposition (CVD) growth method have yet to be chemically doped. Here, we report that a salt of a two-coordinate boron cation, Mes2B+ (Mes: 2,4,6-trimethylphenyl group), with a chemically stable tetrakis(pentafluorophenyl)borate anion, [(C6F5)4B]−, can serve as an efficient hole-doping reagent for large-area CVD-grown tungsten diselenide (WSe2) films. Upon doping, the sheet resistance of large-area polycrystalline WSe2 monolayers decreased from 90 GΩ/sq to 3.2 kΩ/sq.

  15. Chemical hole doping into large-area transition metal dichalcogenide monolayers using boron-based oxidant

    KAUST Repository

    Matsuoka, Hirofumi

    2018-01-18

    Hole carrier doping into single-crystalline transition metal dichalcogenide (TMDC) films can be achieved with various chemical reagents. However, large-area polycrystalline TMDC monolayers produced by a chemical vapor deposition (CVD) growth method have yet to be chemically doped. Here, we report that a salt of a two-coordinate boron cation, Mes2B+ (Mes: 2,4,6-trimethylphenyl group), with a chemically stable tetrakis(pentafluorophenyl)borate anion, [(C6F5)4B]−, can serve as an efficient hole-doping reagent for large-area CVD-grown tungsten diselenide (WSe2) films. Upon doping, the sheet resistance of large-area polycrystalline WSe2 monolayers decreased from 90 GΩ/sq to 3.2 kΩ/sq.

  16. Compressive Strength and Physical Properties Behavior of Cement Mortars with addition of Cement Klin Dust

    Directory of Open Access Journals (Sweden)

    Auday A Mehatlaf

    2017-12-01

    Full Text Available Cement Klin Dust (CKD was the waste of almost cement industry factories, so that in this paper utilization of CKD as filler in cement and/or concrete was the main objective. CKD from the Karbala cement factory had been used and analysis to know the chemical composition of the oxides was done. In this paper cement mortars with different weight percentages of CKD (0,5,10,20,30,40 had been prepared. Physical properties such as density and porosity were done in different age curing (3, 7, 28 day. In addition, mechanical properties included the coefficient of thermal conductivity and compressive strength had also observed with different age (3,7, and 28 for all prepared specimens. From the obtained the experimental results and their discussion, it was clear that the addition (20% of CKD had the good results in cement mortars.  

  17. Effect of Liquid Ga on Metal Surfaces: Characterization of Morphology and Chemical Composition of Metals Heated in Liquid Ga

    Directory of Open Access Journals (Sweden)

    Eun Je Lee

    2013-01-01

    Full Text Available This study investigates the effect of liquid gallium (Ga on metal foils made of titanium (Ti, niobium (Nb, and molybdenum (Mo. The Ti, Nb, and Mo foils were heated in liquid Ga at 120°C for a maximum of two weeks. After heating, the changes in the morphology and the chemical composition of the metal foils were analyzed by using a field emission scanning electron microscope, energy-dispersive X-ray spectrometer, X-ray diffractometer, and X-ray photoelectron spectrometer. The results of the analysis indicated that the Nb foil showed the minimum adhesion of liquid Ga to the surface while the maximum amount of liquid Ga was observed to adhere to the Ti foil. In addition, the Nb foil was oxidized and the Mo foil was reduced during the heating process. Considering these effects, we conclude that Mo may be used as an alternative encapsulation material for Ga in addition to Nb, which is used as the conventional encapsulation material, due to its chemical resistance against oxidation in hot liquid Ga.

  18. Chemical Separation of Fission Products in Uranium Metal Ingots from Electrolytic Reduction Process

    International Nuclear Information System (INIS)

    Lee, Chang-Heon; Kim, Min-Jae; Choi, Kwang-Soon; Jee, Kwang-Yong; Kim, Won-Ho

    2006-01-01

    Chemical characterization of various process materials is required for the optimization of the electrolytic reduction process in which uranium dioxide, a matrix of spent PWR fuels, is electrolytically reduced to uranium metal in a medium of LiCl-Li 2 O molten at 650 .deg. C. In the uranium metal ingots of interest in this study, residual process materials and corrosion products as well as fission products are involved to some extent, which further adds difficulties to the determination of trace fission products. Besides it, direct inductively coupled plasma atomic emission spectrometric (ICP-AES) analysis of uranium bearing materials such as the uranium metal ingots is not possible because a severe spectral interference is found in the intensely complex atomic emission spectra of uranium. Thus an adequate separation procedure for the fission products should be employed prior to their determinations. In present study ion exchange and extraction chromatographic methods were adopted for selective separation of the fission products from residual process materials, corrosion products and uranium matrix. The sorption behaviour of anion and tri-nbutylphosphate (TBP) extraction chromatographic resins for the metals in acidic solutions simulated for the uranium metal ingot solutions was investigated. Then the validity of the separation procedure for its reliability and applicability was evaluated by measuring recoveries of the metals added

  19. Microstructure and chemical analysis of Hf-based high-k dielectric layers in metal-insulator-metal capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Thangadurai, P. [Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Mikhelashvili, V.; Eisenstein, G. [Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Kaplan, W.D., E-mail: kaplan@tx.technion.ac.i [Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

    2010-05-31

    The microstructure and chemistry of the high-k gate dielectric significantly influences the performance of metal-insulator-metal (MIM) and metal-oxide-semiconductor devices. In particular, the local structure, chemistry, and inter-layer mixing are important phenomena to be understood. In the present study, high resolution and analytical transmission electron microscopy are combined to study the local structure, morphology, and chemistry in MIM capacitors containing a Hf-based high-k dielectric. The gate dielectric, bottom and gate electrodes were deposited on p-type Si(100) wafers by electron beam evaporation. Four chemically distinguishable sub-layers were identified within the dielectric stack. One is an unintentionally formed 4.0 nm thick interfacial layer of Ta{sub 2}O{sub 5} at the interface between the Ta electrode and the dielectric. The other three layers are based on HfN{sub x}O{sub y} and HfTiO{sub y}, and intermixing between the nearby sub-layers including deposited SiO{sub 2}. Hf-rich clusters were found in the HfN{sub x}O{sub y} layer adjacent to the Ta{sub 2}O{sub 5} layer.

  20. Micro- and Nanostructured Metal Oxide Chemical Sensors for Volatile Organic Compounds

    Science.gov (United States)

    Alim, M. A.; Penn, B. G.; Currie, J. R., Jr.; Batra, A. K.; Aggarwal, M. D.

    2008-01-01

    Aeronautic and space applications warrant the development of chemical sensors which operate in a variety of environments. This technical memorandum incorporates various kinds of chemical sensors and ways to improve their performance. The results of exploratory investigation of the binary composite polycrystalline thick-films such as SnO2-WO3, SnO2-In2O3, SnO2-ZnO for the detection of volatile organic compound (isopropanol) are reported. A short review of the present status of the new types of nanostructured sensors such as nanobelts, nanorods, nanotube, etc. based on metal oxides is presented.

  1. Chemical effects in ion mixing of a ternary system (metal-SiO2)

    Science.gov (United States)

    Banwell, T.; Nicolet, M.-A.; Sands, T.; Grunthaner, P. J.

    1987-01-01

    The mixing of Ti, Cr, and Ni thin films with SiO2 by low-temperature (- 196-25 C) irradiation with 290 keV Xe has been investigated. Comparison of the morphology of the intermixed region and the dose dependences of net metal transport into SiO2 reveals that long range motion and phase formation probably occur as separate and sequential processes. Kinetic limitations suppress chemical effects in these systems during the initial transport process. Chemical interactions influence the subsequent phase formation.

  2. Modeling heat dissipation at the nanoscale: an embedding approach for chemical reaction dynamics on metal surfaces.

    Science.gov (United States)

    Meyer, Jörg; Reuter, Karsten

    2014-04-25

    We present an embedding technique for metallic systems that makes it possible to model energy dissipation into substrate phonons during surface chemical reactions from first principles. The separation of chemical and elastic contributions to the interaction potential provides a quantitative description of both electronic and phononic band structure. Application to the dissociation of O2 at Pd(100) predicts translationally "hot" oxygen adsorbates as a consequence of the released adsorption energy (ca. 2.6 eV). This finding questions the instant thermalization of reaction enthalpies generally assumed in models of heterogeneous catalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Evaluation of fit of cement-retained implant-supported 3-unit structures fabricated with direct metal laser sintering and vacuum casting techniques.

    Science.gov (United States)

    Oyagüe, Raquel Castillo; Sánchez-Turrión, Andrés; López-Lozano, José Francisco; Montero, Javier; Albaladejo, Alberto; Suárez-García, María Jesús

    2012-07-01

    This study evaluated the vertical discrepancy of implant-fixed 3-unit structures. Frameworks were constructed with laser-sintered Co-Cr, and vacuum-cast Co-Cr, Ni-Cr-Ti, and Pd-Au. Samples of each alloy group were randomly luted in standard fashion using resin-modified glass-ionomer, self-adhesive, and acrylic/urethane-based cements (n = 12 each). Discrepancies were SEM analyzed. Three-way ANOVA and Student-Newman-Keuls tests were run (P Laser-sintered structures achieved the best fit per cement tested. Within each alloy group, resin-modified glass-ionomer and acrylic/urethane-based cements produced comparably lower discrepancies than the self-adhesive agent. The abutment position did not yield significant differences. All misfit values could be considered clinically acceptable.

  4. Low pH Cements

    International Nuclear Information System (INIS)

    Savage, David; Benbow, Steven

    2007-05-01

    speciation of silicon at pH 10 has a significant impact upon the solubility of montmorillonite and would thus constitute a logical choice of pH limit for cement-derived pore fluids, but it is unlikely that cement-based grouts could be developed to meet this limit. Control of mass transport by diffusion processes serves as a significant constraint over the amount of bentonite that can be degraded. Computer simulations indicate that porosity reduction is likely at the interface between cement and bentonite. However, it is not clear how the transport properties of bentonite may be modified due to mineral alteration processes. There are considerable uncertainties concerning the precise mechanism of the rate of montmorillonite dissolution at elevated pH. The rate of dissolution may be inhibited by the presence of dissolved Si (and perhaps Al), but this mechanism has yet to be confirmed at high pH. The type of secondary minerals assumed to form from cement-bentonite interaction will also have a significant impact upon the rate of montmorillonite dissolution. Low-pH cement systems have received little attention thus far regarding the development of models for the chemical evolution of pore fluids. Low Ca/Si CSH gels show preferential leaching of Si, which is in marked contrast with gels of greater Ca/Si ratio. Models apparently capable of predicting pore fluid composition coexisting with low Ca/Si CSH gels are a modified Berner model and a solid-solution model proposed by Sugiyama and Fujita. The solubility of silica in pore fluids coexisting with low Ca/Si gels may exceed that of amorphous silica, and may pose problems regarding the stability of montmorillonite in relation to framework silicates such as feldspars. However, the potential rate of conversion of montmorillonite to feldspar under repository conditions is uncertain. It is necessary to use additives such as super plasticiser to improve the workability of low-pH cements. These organic additives have the potential to

  5. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    speciation of silicon at pH 10 has a significant impact upon the solubility of montmorillonite and would thus constitute a logical choice of pH limit for cement-derived pore fluids, but it is unlikely that cement-based grouts could be developed to meet this limit. Control of mass transport by diffusion processes serves as a significant constraint over the amount of bentonite that can be degraded. Computer simulations indicate that porosity reduction is likely at the interface between cement and bentonite. However, it is not clear how the transport properties of bentonite may be modified due to mineral alteration processes. There are considerable uncertainties concerning the precise mechanism of the rate of montmorillonite dissolution at elevated pH. The rate of dissolution may be inhibited by the presence of dissolved Si (and perhaps Al), but this mechanism has yet to be confirmed at high pH. The type of secondary minerals assumed to form from cement-bentonite interaction will also have a significant impact upon the rate of montmorillonite dissolution. Low-pH cement systems have received little attention thus far regarding the development of models for the chemical evolution of pore fluids. Low Ca/Si CSH gels show preferential leaching of Si, which is in marked contrast with gels of greater Ca/Si ratio. Models apparently capable of predicting pore fluid composition coexisting with low Ca/Si CSH gels are a modified Berner model and a solid-solution model proposed by Sugiyama and Fujita. The solubility of silica in pore fluids coexisting with low Ca/Si gels may exceed that of amorphous silica, and may pose problems regarding the stability of montmorillonite in relation to framework silicates such as feldspars. However, the potential rate of conversion of montmorillonite to feldspar under repository conditions is uncertain. It is necessary to use additives such as super plasticiser to improve the workability of low-pH cements. These organic additives have the potential to

  6. Conditioning of radioactive waste solutions by cementation

    International Nuclear Information System (INIS)

    Vejmelka, P.; Rudolph, G.; Kluger, W.; Koester, R.

    1992-02-01

    For the cementation of the low and intermediate level evaporator concentrates resulting from the reprocessing of spent fuel numerous experiments were performed to optimize the waste form composition and to characterize the final waste form. Concerning the cementation process, properties of the waste/cement suspension were investigated. These investigations include the dependence of viscosity, bleeding, setting time and hydration heat from the waste cement slurry composition. For the characterization of the waste forms, the mechanical, thermal and chemical stability were determined. For special cases detailed investigations were performed to determine the activity release from waste packages under defined mechanical and thermal stresses. The investigations of the interaction of the waste forms with aqueous solutions include the determination of the Cs/Sr release, the corrosion resistance and the release of actinides. The Cs/Sr release was determined in dependence of the cement type, additives, setting time and sample size. (orig./DG) [de

  7. Metal fractionation of atmospheric aerosols via sequential chemical extraction: a review

    Energy Technology Data Exchange (ETDEWEB)

    Smichowski, Patricia; Gomez, Dario [Unidad de Actividad Quimica, Comision Nacional de Energia Atomica, San Martin (Argentina); Polla, Griselda [Unidad de Actividad Fisica, Comision Nacional de Energia Atomica, San Martin (Argentina)

    2005-01-01

    This review surveys schemes used to sequentially chemically fractionate metals and metalloids present in airborne particulate matter. It focuses mainly on sequential chemical fractionation schemes published over the last 15 years. These schemes have been classified into five main categories: (1) based on Tessier's procedure, (2) based on Chester's procedure, (3) based on Zatka's procedure, (4) based on BCR procedure, and (5) other procedures. The operational characteristics as well as the state of the art in metal fractionation of airborne particulate matter, fly ashes and workroom aerosols, in terms of applications, optimizations and innovations, are also described. Many references to other works in this area are provided. (orig.)

  8. Initial chemical transport of reducing elements and chemical reactions in oxide cathode base metal

    International Nuclear Information System (INIS)

    Roquais, J.M.; Poret, F.; Doze, R. le; Dufour, P.; Steinbrunn, A.

    2002-01-01

    In the present work, the formation of compounds associated to the diffusion of reducing elements (Mg and Al) to the nickel surface of a one-piece oxide cathode has been studied. Those compounds have been evidenced after the annealing steps at high temperature performed on cathode base metal prior to the emitting coating deposition. Therefore, they form the ''initial'' interface between the nickel and the coating, in other words, the interface existing at the beginning of cathode life. Extensive analysis to characterize the nickel base prior to coating deposition has been performed by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), Auger electron spectroscopy (AES), transmission electron microscopy (TEM), and glow discharge optical emission spectroscopy (GDOES). TEM and AES analysis have allowed to identify for the first time a spinel compound of MgAl 2 O 4 . The preferential distribution of the different compounds on the nickel surface has been studied by EDX mapping. Experimental profiles of diffusion of the reducing elements in the nickel have been obtained over the entire thickness of the material by GDOES. The mechanism of formation of these compounds together with a related diffusion model are proposed

  9. Catalyst and processing effects on metal-assisted chemical etching for the production of highly porous GaN

    International Nuclear Information System (INIS)

    Geng, Xuewen; Grismer, Dane A; Bohn, Paul W; Duan, Barrett K; Zhao, Liancheng

    2013-01-01

    Metal-assisted chemical etching is a facile method to produce micro-/nanostructures in the near-surface region of gallium nitride (GaN) and other semiconductors. Detailed studies of the production of porous GaN (PGaN) using different metal catalysts and GaN doping conditions have been performed in order to understand the mechanism by which metal-assisted chemical etching is accomplished in GaN. Patterned catalysts show increasing metal-assisted chemical etching activity to n-GaN in the order Ag < Au < Ir < Pt. In addition, the catalytic behavior of continuous films is compared to discontinuous island films. Continuous metal films strongly shield the surface, hindering metal-assisted chemical etching, an effect which can be overcome by using discontinuous films or increasing the irradiance of the light source. With increasing etch time or irradiance, PGaN morphologies change from uniform porous structures to ridge and valley structures. The doping type plays an important role, with metal-assisted chemical etching activity increasing in the order p-GaN < intrinsic GaN < n-GaN. Both the catalyst identity and the doping type effects are explained by the work functions and the related band offsets that affect the metal-assisted chemical etching process through a combination of different barriers to hole injection and the formation of hole accumulation/depletion layers at the metal–semiconductor interface. (paper)

  10. Metal-Poor Stars and the Chemical Enrichment of the Universe

    OpenAIRE

    Frebel, Anna; Norris, John E.

    2011-01-01

    Metal-poor stars hold the key to our understanding of the origin of the elements and the chemical evolution of the Universe. This chapter describes the process of discovery of these rare stars, the manner in which their surface abundances (produced in supernovae and other evolved stars) are determined from the analysis of their spectra, and the interpretation of their abundance patterns to elucidate questions of origin and evolution. More generally, studies of these stars contribute to other ...

  11. Formation and Chemical Development of Non-metallic Inclusions in Ladle Treatment of Steel

    OpenAIRE

    Beskow, Kristina

    2003-01-01

    The present study was carried out to investigate theformation and chemical development of non-metallic inclusionsduring ladle treatment of steel. To begin with, an investigation of the deoxidation processand the impact of aluminium addition was carried out. For thispurpose, a new experimental setup was constructed. The setupallowed the examination of the deoxidation process as afunction of time by using a quenching technique. Preliminaryexperiments showed that homogeneous nucleation of alumin...

  12. Metal oxide nanostructures: preparation, characterization and functional applications as chemical sensors.

    Science.gov (United States)

    Zappa, Dario; Bertuna, Angela; Comini, Elisabetta; Kaur, Navpreet; Poli, Nicola; Sberveglieri, Veronica; Sberveglieri, Giorgio

    2017-01-01

    Preparation and characterization of different metal oxide (NiO, WO 3 , ZnO, SnO 2 and Nb 2 O 5 ) nanostructures for chemical sensing are presented. p-Type (NiO) and n-type (WO 3 , SnO 2 , ZnO and Nb 2 O 5 ) metal oxide nanostructures were grown on alumina substrates using evaporation-condensation, thermal oxidation and hydrothermal techniques. Surface morphologies and crystal structures were investigated through scanning electron microscopy and Raman spectroscopy. Furthermore, different batches of sensors have been prepared, and their sensing performances towards carbon monoxide and nitrogen dioxide have been explored. Moreover, metal oxide nanowires have been integrated into an electronic nose and successfully applied to discriminate between drinking and contaminated water.

  13. Chemical Engineering of Photoactivity in Heterometallic Titanium-Organic Frameworks by Metal Doping.

    Science.gov (United States)

    Castells-Gil, Javier; Padial, Natalia M; Almora-Barrios, Neyvis; Albero, Josep; Ruiz-Salvador, A Rabdel; González-Platas, Javier; García, Hermenegildo; Martí-Gastaldo, Carlos

    2018-06-06

    We report a new family of titanium-organic frameworks that enlarges the limited number of crystalline, porous materials available for this metal. They are chemically robust and can be prepared as single crystals at multi-gram scale from multiple precursors. Their heterometallic structure enables engineering of their photoactivity by metal doping rather than by linker functionalization. Compared to other methodologies based on the post-synthetic metallation of MOFs, our approach is well-fitted for controlling the positioning of dopants at an atomic level to gain more precise control over the band-gap and electronic properties of the porous solid. Changes in the band-gap are also rationalized with computational modelling and experimentally confirmed by photocatalytic H 2 production. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Chemical partitioning of heavy metals in suspended particulates of Tajan River

    International Nuclear Information System (INIS)

    Nikoosepehr, E.

    2002-01-01

    In this investigation samples of river water sediments were collected at Takam bridge in Tajan River. In order to evaluate various chemical bonds ( loosely bonded ions, sulphides and organics), 120 A A S reading on Zn, Mn, Ni was carried out. The results indicates that Zn and Ni have more affinity towards sulphides while Cu and Mn are rather concentrated in loosely bonded ions. We have found out the following trends: Affinity of metals in loosely bonded ions in 63 and 40 μm fraction in Mn>Cu>Ni>Zn. Affinity of metals in organic bonds in 63 and 40 μm fraction is Zn>Ni>Mn>Cu and Zn>Ni>Cu>Mn respectively. It should be pointed out that metals do not show any regular pattern with sulphides: however in 63 μm fraction the trend is Zn>Ni>Cu>Mn

  15. The Metal And Sulphate Removal From Mine Drainage Waters By Biological-Chemical Ways

    Directory of Open Access Journals (Sweden)

    Jenčárová Jana

    2015-06-01

    Full Text Available Mine drainage waters are often characterized by high concentrations of sulphates and metals as a consequence of the mining industry of sulphide minerals. The aims of this work are to prove some biological-chemical processes utilization for the mine drainage water treatment. The studied principles of contamination elimination from these waters include sulphate reduction and metal bioprecipitation by the application of sulphate-reducing bacteria (SRB. Other studied process was metal sorption by prepared biogenic sorbent. Mine drainage waters from Slovak localities Banská Štiavnica and Smolník were used to the pollution removal examination. In Banská Štiavnica water, sulphates decreased below the legislative limit. The elimination of zinc by sorption experiments achieved 84 % and 65 %, respectively.

  16. Comparative study on the tensile bond strength and marginal fit of complete veneer cast metal crowns using various luting agents: An in vitro study

    Directory of Open Access Journals (Sweden)

    B Devi Parameswari

    2016-01-01

    Full Text Available Introduction: Several commercially available luting agents are used to cement the dental restorations such as intra-coronal, extra-coronal, and fixed partial dentures. Tensile bond strength (TBS and accurate marginal fit are the essential factors to determine the good clinical results in fixed prosthesis. The retentivity of the luting cements is assessed by their adhesive capacity over the tooth surface and metal surface. Generally, the adhesive ability has been evaluated with in vitro testing, with tensile bond tests. The failure of fixed prosthesis may be happened as a result of incomplete seating during cementation. Most research on cementation of crowns relates seating failure to the thickness of the cement film. Materials and Methods: The study is divided into four groups with 10 samples for each of the luting cement taken up for testing TBS and four groups with 5 samples for each luting agent chosen for assessing marginal fit. The results were tabulated and statistically analyzed. Results: In this in vitro study, the TBS of luting cements, and marginal fit in relation to luting cements were tested by using appropriate testing devices. The TBS of cement is measured using universal testing machine, and the results are tabulated. The marginal gap that exists between the margin of the cast metal crown, and the finish line is measured using travelling microscope before and after cementation. The difference between these two values gives the discrepancy that is due to the film thickness of cement used for luting the restoration. Summary and Conclusion: The TBS value of zinc phosphate cement and glass ionomer cement were found to be almost same. The chemical adhesiveness of the glass ionomer with calcium ions of enamel and dentin may be the attributed reason (ionic bonding. In this study, the polycarboxylate is the one that showed low TBS, and it may be attributed to the weakness of the cement due to reduced film thickness, though this cement has

  17. Application of Neutron imaging in pore structure of hydrated wellbore cement: comparison of hydration of H20 with D2O based Portland cements

    Science.gov (United States)

    Dussenova, D.; Bilheux, H.; Radonjic, M.

    2012-12-01

    Wellbore Cement studies have been ongoing for decades. The studies vary from efforts to reduce permeability and resistance to corrosive environment to issues with gas migration also known as Sustained Casing Pressure (SCP). These practical issues often lead to health and safety problems as well as huge economic loss in oil and gas industry. Several techniques have been employed to reduce the impact of gas leakage. In this study we purely focus on expandable liners, which are introduced as part of oil well reconstruction and work-overs and as well abandonment procedures that help in prevention of SCP. Expandable liner is a tube that after application of a certain tool can increase its diameter. The increase in diameter creates extra force on hydrated cement that results in reducing width of interface fractures and cement-tube de-bonding. Moreover, this also causes cement to change its microstructure and other porous medium properties, primarily hydraulic conductivity. In order to examine changes before and after operations, cement pore structure must be well characterized and correlated to cement slurry design as well as chemical and physical environmental conditions. As modern oil well pipes and tubes contain iron, it is difficult to perform X-ray tomography of a bulk measurement of the cement in its wellbore conditions, which are tube wall-cement-tube wall. Neutron imaging is a complementary technique to x-ray imaging and is well suited for detection of light elements imbedded in metallic containers. Thus, Neutron Imaging (NI) is investigated as a tool for the detection of pore structure of hydrated wellbore cement. Recent measurements were conducted at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) neutron imaging facility. NI is is highly sensitive to light elements such as Hydrogen (H). Oil well cements that have undergone a full hydration contain on average 30%-40% of free water in its pore structure. The unreacted water is the main

  18. Screening and prioritisation of chemical risks from metal mining operations, identifying exposure media of concern.

    Science.gov (United States)

    Pan, Jilang; Oates, Christopher J; Ihlenfeld, Christian; Plant, Jane A; Voulvoulis, Nikolaos

    2010-04-01

    Metals have been central to the development of human civilisation from the Bronze Age to modern times, although in the past, metal mining and smelting have been the cause of serious environmental pollution with the potential to harm human health. Despite problems from artisanal mining in some developing countries, modern mining to Western standards now uses the best available mining technology combined with environmental monitoring, mitigation and remediation measures to limit emissions to the environment. This paper develops risk screening and prioritisation methods previously used for contaminated land on military and civilian sites and engineering systems for the analysis and prioritisation of chemical risks from modern metal mining operations. It uses hierarchical holographic modelling and multi-criteria decision making to analyse and prioritise the risks from potentially hazardous inorganic chemical substances released by mining operations. A case study of an active platinum group metals mine in South Africa is used to demonstrate the potential of the method. This risk-based methodology for identifying, filtering and ranking mining-related environmental and human health risks can be used to identify exposure media of greatest concern to inform risk management. It also provides a practical decision-making tool for mine acquisition and helps to communicate risk to all members of mining operation teams.

  19. The chemical and catalytic properties of nanocrystalline metal oxides prepared through modified sol-gel synthesis

    Science.gov (United States)

    Carnes, Corrie Leigh

    The goal of this research was to synthesize, characterize and study the chemical properties of nanocrystalline metal oxides. Nanocrystalline (NC) ZnO, CuO, NiO, Al2O3, and the binary Al2O 3/MgO and ZnO/CuO were prepared through modified sol gel methods. These NC metal oxides were studied in comparison to the commercial (CM) metal oxides. The samples were characterized by XRD, TGA, FTIR, BET, and TEM. The NC samples were all accompanied by a significant increase in surface area and decrease in crystallite size. Several chemical reactions were studied to compare the NC samples to the CM samples. One of the reactions involved a high temperature reaction between carbon tetrachloride and the oxide to form carbon dioxide and the corresponding metal chloride. A similar high temperature reaction was conducted between the metal oxide and hydrogen sulfide to form water and the corresponding metal sulfide. A room temperature gas phase adsorption was studied where SO2 was adsorbed onto the oxide. A liquid phase adsorption conducted at room temperature was the destructive adsorption of paraoxon (a toxic insecticide). In all reactions the NC samples exhibited greater activity, destroying or adsorbing a larger amount of the toxins compared to the CM samples. To better study surface area effects catalytic reactions were also studied. The catalysis of methanol was studied over the nanocrystalline ZnO, CuO, NiO, and ZnO/CuO samples in comparison to their commercial counterparts. In most cases the NC samples proved to be more active catalysts, having higher percent conversions and turnover numbers. A second catalytic reaction was also studied, this reaction was investigated to look at the support effects. The catalysis of cyclopropane to propane was studied over Pt and Co catalysts. These catalysts were supported onto NC and CM alumina by impregnation. By observing differences in the catalytic behavior, support effects have become apparent.

  20. Quantitative chemical state XPS analysis of first row transition metals, oxides and hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Biesinger, M C; Payne, B P; McIntryre, N S [Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Hart, B R; Lau, L Wm [Surface Science Western, Room G1, Western Science Centre, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Grosvenor, A P [Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Smart, R StC [ACeSSS, Applied Centre for Structural and Synchrotron Studies, University of South Australia, Mawson Lakes, SA 5095 (Australia)], E-mail: biesingr@uwo.ca

    2008-03-15

    Practical quantitative chemical state X-ray photoelectron spectroscopy (XPS) analysis of first row transition metals, oxides and hydroxides is challenging due to the complexity of their M 2p spectra. Complex multiplet splitting, shake-up and plasmon loss structure can play a role in the interpretation of the chemical states present. This paper will show practical curve fitting procedures for the quantitative measurement of different chemical states for metal oxides and hydroxides from a survey of transition metals. It will also discuss some of the limitations and pitfalls present as well as give practical examples of their successful use. These curve-fitting procedures are based on 1) standard spectra from quality reference samples, 2) a survey of appropriate literature databases and/or a compilation of literature references, 3) fitting of multiplet split spectra based on spectra of numerous reference materials and theoretical modelling, 4) spectral subtractions routines, again using reference spectra, and 5) specific literature references where fitting procedures are available.

  1. Metal removal from Municipal Solid Waste Incineration fly ash: A comparison between chemical leaching and bioleaching.

    Science.gov (United States)

    Funari, V; Mäkinen, J; Salminen, J; Braga, R; Dinelli, E; Revitzer, H

    2017-02-01

    Bio- and hydrometallurgical experimental setups at 2-l reactor scale for the processing of fly ash from municipal waste incinerators were explored. We aimed to compare chemical H 2 SO 4 leaching and bioleaching; the latter involved the use of H 2 SO 4 and a mixed culture of acidophilic bacteria. The leaching yields of several elements, including some of those considered as critical (Mg, Co, Ce, Cr, Ga, Nb, Nd, Sb and Sm), are provided. At the end of the experiments, both leaching methods resulted in comparable yields for Mg and Zn (>90%), Al and Mn (>85%), Cr (∼65%), Ga (∼60%), and Ce (∼50%). Chemical leaching showed the best yields for Cu (95%), Fe (91%), and Ni (93%), whereas bioleaching was effective for Nd (76%), Pb (59%), and Co (55%). The two leaching methods generated solids of different quality with respect to the original material as we removed and significantly reduced the metals amounts, and enriched solutions where metals can be recovered for example as mixed salts for further treatment. Compared to chemical leaching the bioleaching halved the use of H 2 SO 4 , i.e., a part of agent costs, as a likely consequence of bio-produced acid and improved metal solubility. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Quantitative chemical state XPS analysis of first row transition metals, oxides and hydroxides

    International Nuclear Information System (INIS)

    Biesinger, M C; Payne, B P; McIntryre, N S; Hart, B R; Lau, L Wm; Grosvenor, A P; Smart, R StC

    2008-01-01

    Practical quantitative chemical state X-ray photoelectron spectroscopy (XPS) analysis of first row transition metals, oxides and hydroxides is challenging due to the complexity of their M 2p spectra. Complex multiplet splitting, shake-up and plasmon loss structure can play a role in the interpretation of the chemical states present. This paper will show practical curve fitting procedures for the quantitative measurement of different chemical states for metal oxides and hydroxides from a survey of transition metals. It will also discuss some of the limitations and pitfalls present as well as give practical examples of their successful use. These curve-fitting procedures are based on 1) standard spectra from quality reference samples, 2) a survey of appropriate literature databases and/or a compilation of literature references, 3) fitting of multiplet split spectra based on spectra of numerous reference materials and theoretical modelling, 4) spectral subtractions routines, again using reference spectra, and 5) specific literature references where fitting procedures are available

  3. Metal compounds in zeolites as active components of chemisorption and catalysis. Quantum chemical approach

    International Nuclear Information System (INIS)

    Zhidomirov, G.M.

    1996-01-01

    A short review of possible catalitic active sites associated with various types of metal species in zoolite is presented. The structural and electronic peculiarity of aluminum ions in zeolite lattice and their distribution in the lattice are discussed on the basis of quantum chemical calculations in connection with the formation of Broensted activity of zeolites. Various molecular models of Lewis Acid Sites associated the extra-lattice oxide-hydroxide aluminum species have been investigated by means of density functional model cluster calculations using CO molecule as a probe. Probable ways of formation of the selective oxidation center in FeZSM-5 by decomposition of dinitrogen monoxide have been studied by ab-initio quantum chemical calculations. The immediate oxidizing site is reasonably represented by the binuclear iron-hydroxide cluster with peroxo-like fragment located between iron atoms. Various probable intermediates of the selective oxidation center formation resulted from interaction of a hydroperoxide molecule with a lattice titanium ion in titanium silicalite have been investigated by quantum chemical calculations. It was concluded that this reaction requires essential structural reconstruction in the vicinity of the titanium ion. Probability of this structural reconstruction is discussed. Possible reasons of an electron-deficient and electron-enriched state of metal particles entrapped in zoolite cavities are discussed. Also, various probable molecular models of such modified metal particles in zeolite are considered

  4. Influence of carbonation on the acid neutralization capacity of cements and cement-solidified/stabilized electroplating sludge.

    Science.gov (United States)

    Chen, Quanyuan; Zhang, Lina; Ke, Yujuan; Hills, Colin; Kang, Yanming

    2009-02-01

    Portland cement (PC) and blended cements containing pulverized fuel ash (PFA) or granulated blast-furnace slag (GGBS) were used to solidify/stabilize an electroplating sludge in this work. The acid neutralization capacity (ANC) of the hydrated pastes increased in the order of PC > PC/GGBS > PC/PFA. The GGBS or PFA replacement (80 wt%) reduced the ANC of the hydrated pastes by 30-50%. The ANC of the blended cement-solidified electroplating sludge (cement/sludge 1:2) was 20-30% higher than that of the hydrated blended cement pastes. Upon carbonation, there was little difference in the ANC of the three cement pastes, but the presence of electroplating sludge (cement/sludge 1:2) increased the ANC by 20%. Blended cements were more effective binders for immobilization of Ni, Cr and Cu, compared with PC, whereas Zn was encapsulated more effectively in the latter. Accelerated carbonation improved the immobilization of Cr, Cu and Zn, but not Ni. The geochemical code PHREEQC, with the edited database from EQ3/6 and HATCHES, was used to calculate the saturation index and solubility of likely heavy metal precipitates in cement-based solidification/stabilization systems. The release of heavy metals could be related to the disruption of cement matrices and the remarkable variation of solubility of heavy metal precipitates at different pH values.

  5. Evaluation of the CDTN's cementation facility using the results obtained in two different sizes: laboratory and facility

    International Nuclear Information System (INIS)

    Haucz, Maria Judite A.; Calabria, Jaqueline A. Almeida; Tello, Cledola Cassia O.; Candido, Francisco Donizete; Seles, Sandro Rogerio Novaes

    2011-01-01

    At CDTN R and D activities generate low-level radioactive wastes, among them the aqueous liquid ones, which need special attention due to their volumes. The usual treatment for these wastes is the volume reduction process using chemicals in order to change the radionuclides of the waste to an insoluble form. The resultant sludge is incorporated into cement in 200-liter drums using an in-line batch mixing system (CDTN Cementation Facility). The process parameters and solidified product quality are evaluated at the Cementation Laboratory (LABCIM), where tests are carried out to determine the viscosity, set time and density of the paste. In addition of the visual examination, compressive strength test and density are also established in the solidified product. In the cementation facility some pastes are also prepared for the immobilization of non-compactable waste, such as dump, scrap metal, wood, and other ones. This paper aims to present the study comparing the results of tests done in the pastes and products prepared in LABCIM and the ones obtained in CDTN's cementation facility, in order to check the efficiency of the cementation system. (author)

  6. Evaluation of the CDTN cementation facility using the results obtained in two different sizes: laboratory and facility

    International Nuclear Information System (INIS)

    Haucz, Maria Judite A.; Calabria, Jaqueline A. Almeida; Tello, Cledola Cassia O.; Candido, Francisco Donizete; Seles, Sandro Rogerio Novaes

    2011-01-01

    At CDTN R and D activities generate low-level radioactive wastes, among them the aqueous liquid ones, which need special attention due to their volumes. The usual treatment for these wastes is the volume reduction process using chemicals in order to change the radionuclides of the waste to an insoluble form. The resultant sludge is incorporated into cement in 200-liter drums using an in-line batch mixing system (CDTN Cementation Facility). The process parameters and solidified product quality are evaluated at the Cementation Laboratory (LABCIM), where tests are carried out to determine the viscosity, set time and density of the paste. In addition of the visual examination, compressive strength test and density are also established in the solidified product. In the cementation facility some pastes are also prepared for the immobilization of non-compactable waste, such as dump, scrap metal, wood, and other ones. This paper aims to present the study comparing the results of tests done in the pastes and products prepared in LABCIM and the ones obtained in CDTN's cementation facility, in order to check the efficiency of the cementation system. (author)

  7. Producing cement

    Energy Technology Data Exchange (ETDEWEB)

    Stone, E G

    1923-09-12

    A process and apparatus are described for producing Portland cement in which pulverized shale is successively heated in a series of inclined rotary retorts having internal stirrers and oil gas outlets, which are connected to condensers. The partially treated shale is removed from the lowermost retort by a conveyor, then fed separately or conjointly into pipes and thence into a number of vertically disposed retorts. Each of these retorts may be fitted interiorly with vertical arranged conveyors which elevate the shale and discharge it over a lip, from whence it falls to the bottom of the retorts. The lower end of each casing is furnished with an adjustable discharge door through which the spent shale is fed to a hopper, thence into separate trucks. The oil gases generated in the retorts are exhausted through pipes to condensers. The spent shale is conveyed to a bin and mixed while hot with ground limestone. The admixed materials are then ground and fed to a rotary kiln which is fired by the incondensible gases derived from the oil gases obtained in the previous retorting of the shale. The calcined materials are then delivered from the rotary kiln to rotary coolers. The waste gases from the kiln are utilized for heating the retorts in which the ground shale is heated for the purpose of extracting therefrom the contained hydrocarbon oils and gases.

  8. Steam Gasification of Sawdust Biochar Influenced by Chemical Speciation of Alkali and Alkaline Earth Metallic Species

    Directory of Open Access Journals (Sweden)

    Dongdong Feng

    2018-01-01

    Full Text Available The effect of chemical speciation (H2O/NH4Ac/HCl-soluble and insoluble of alkali and alkaline earth metallic species on the steam gasification of sawdust biochar was investigated in a lab-scale, fixed-bed reactor, with the method of chemical fractionation analysis. The changes in biochar structures and the evolution of biochar reactivity are discussed, with a focus on the contributions of the chemical speciation of alkali and alkaline earth metallic species (AAEMs on the steam gasification of biochar. The results indicate that H2O/NH4Ac/HCl-soluble AAEMs have a significant effect on biochar gasification rates. The release of K occurs mainly in the form of inorganic salts and hydrated ions, while that of Ca occurs mainly as organic ones. The sp3-rich or sp2-sp3 structures and different chemical-speciation AAEMs function together as the preferred active sites during steam gasification. H2O/HCl-soluble AAEMs could promote the transformation of biochar surface functional groups, from ether/alkene C-O-C to carboxylate COO− in biochar, while they may both be improved by NH4Ac-soluble AAEMs. H2O-soluble AAEMs play a crucial catalytic role in biochar reactivity. The effect of NH4Ac-soluble AAEMs is mainly concentrated in the high-conversion stage (biochar conversion >30%, while that of HCl-soluble AAEMs is reflected in the whole activity-testing stage.

  9. Redox Active Transition Metal ions Make Melanin Susceptible to Chemical Degradation Induced by Organic Peroxide.

    Science.gov (United States)

    Zadlo, Andrzej; Pilat, Anna; Sarna, Michal; Pawlak, Anna; Sarna, Tadeusz

    2017-12-01

    With aging, retinal pigment epithelium melanosomes, by fusion with the age pigment lipofuscin, form complex granules called melanolipofuscin. Lipofuscin granules may contain oxidized proteins and lipid hydroperoxides, which in melanolipofuscin could chemically modify melanin polymer, while transition metal ions present in melanin can accelerate such oxidative modifications. The aim of this research was to examine the effect of selected transition metal ions on melanin susceptibility to chemical modification induced by the water-soluble tert-butyl hydroperoxide used as an oxidizing agent. Synthetic melanin obtained by DOPA autooxidation and melanosomes isolated from bovine retinal pigment epithelium were analyzed. To monitor tert-butyl hydroperoxide-induced oxidative changes of DMa and BMs, electron paramagnetic resonance spectroscopy, UV-vis absorption spectroscopy, dynamic light scattering, atomic force microscopy and electron paramagnetic resonance oximetry were employed. These measurements revealed that both copper and iron ions accelerated chemical degradation induced by tert-butyl hydroperoxide, while zinc ions had no effect. Strong prooxidant action was detected only in the case of melanosomes and melanin degraded in the presence of iron. It can be postulated that similar chemical processes, if they occur in situ in melanolipofuscin granules of the human retinal pigment epithelium, would modify antioxidant properties of melanin and its reactivity.

  10. Chemical speciation of trace metals in the industrial sludge of Dhaka City, Bangladesh.

    Science.gov (United States)

    Islam, Md Saiful; Al-Mamun, Md Habibullah; Feng, Ye; Tokumura, Masahiro; Masunaga, Shigeki

    2017-07-01

    The objective of this study was to assess total concentration and chemical fractionation of trace metals in the industrial wastewater and sludge collected from seven different types of industries in Dhaka City, Bangladesh. The sludge from industries is either dumped on landfills or reused as secondary resources in order to preserve natural resources. Metals were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The ranges of Cr, Ni, Cu, As, Cd, and Pb in the sludges were 1.4-9,470, 4.8-994, 12.8-444, 2.2-224, 1.9-46.0 and 1.3-87.0 mg/kg, respectively. As a whole, the average concentrations of trace metals in samples were in the decreasing order of Cr > Ni > Cu > As > Pb > Cd. The results of the Community Bureau of Reference (BCR) sequential extraction showed that the studied metals were predominantly associated with the residual fraction followed by the oxidizable fraction. The study revealed that the mobile fractions of trace metals are poorly predictable from the total content, and bioavailability of all fractions of elements tends to decrease.

  11. Fluorescent, MRI, and colorimetric chemical sensors for the first-row d-block metal ions.

    Science.gov (United States)

    Zhu, Hao; Fan, Jiangli; Wang, Benhua; Peng, Xiaojun

    2015-07-07

    Transition metals (d-blocks) are recognized as playing critical roles in biology, and they most often act as cofactors in diverse enzymes; however, improper regulation of transition metal stores is also connected to serious disorders. Therefore, the monitoring and imaging of transition metals are significant for biological research as well as clinical diagnosis. In this article, efforts have been made to review the chemical sensors that have been developed for the detection of the first-row d-block metals (except Cu and Zn): Cr, Mn, Fe, Co, and Ni. We focus on the development of fluorescent sensors (fall into three classes: "turn-off", "turn-on", and ratiometric), colorimetric sensors, and responsive MRI contrast agents for these transition metals (242 references). Future work will be likely to fill in the blanks: (1) sensors for Sc, Ti, and V; (2) MRI sensors for Cr, Mn, Co, Ni; (3) ratiometric fluorescent sensors for Cr(6+), Mn(2+), and Ni(2+), explore new ways of sensing Fe(3+) or Cr(3+) without the proton interference, as well as extend applications of MRI sensors to living systems.

  12. In vitro physical, chemical, and biological evaluation of commercially available metal orthodontic brackets.

    Science.gov (United States)

    Kim, Joo Hyoung; Cha, Jung Yul; Hwang, Chung Ju

    2012-12-01

    This in vitro study was undertaken to evaluate the physical, chemical, and biological properties of commercially available metal orthodontic brackets in South Korea, because national standards for these products are lacking. FOUR BRACKET BRANDS WERE TESTED FOR DIMENSIONAL ACCURACY, (MANUFACTURING ERRORS IN ANGULATION AND TORQUE), CYTOTOXICITY, COMPOSITION, ELUTION, AND CORROSION: Archist (Daeseung Medical), Victory (3M Unitek), Kosaka (Tomy), and Confidence (Shinye Odontology Materials). The tested rackets showed no significant differences in manufacturing errors in angulation, but Confidence brackets showed a significant difference in manufacturing errors in torque. None of the brackets were cytotoxic to mouse fibroblasts. The metal ion components did not show a regular increasing or decreasing trend of elution over time, but the volume of the total eluted metal ions increased: Archist brackets had the maximal Cr elution and Confidence brackets appeared to have the largest volume of total eluted metal ions because of excessive Ni elution. Confidence brackets showed the lowest corrosion resistance during potentiodynamic polarization. The results of this study could potentially be applied in establishing national standards for metal orthodontic brackets and in evaluating commercially available products.

  13. Textile/metal-organic-framework composites as self-detoxifying filters for chemical-warfare agents.

    Science.gov (United States)

    López-Maya, Elena; Montoro, Carmen; Rodríguez-Albelo, L Marleny; Aznar Cervantes, Salvador D; Lozano-Pérez, A Abel; Cenís, José Luis; Barea, Elisa; Navarro, Jorge A R

    2015-06-01

    The current technology of air-filtration materials for protection against highly toxic chemicals, that is, chemical-warfare agents, is mainly based on the broad and effective adsorptive properties of hydrophobic activated carbons. However, adsorption does not prevent these materials from behaving as secondary emitters once they are contaminated. Thus, the development of efficient self-cleaning filters is of high interest. Herein, we report how we can take advantage of the improved phosphotriesterase catalytic activity of lithium alkoxide doped zirconium(IV) metal-organic framework (MOF) materials to develop advanced self-detoxifying adsorbents of chemical-warfare agents containing hydrolysable P-F, P-O, and C-Cl bonds. Moreover, we also show that it is possible to integrate these materials onto textiles, thereby combining air-permeation properties of the textiles with the self-detoxifying properties of the MOF material. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Development of an Improved Cement for Geothermal Wells

    Energy Technology Data Exchange (ETDEWEB)

    Trabits, George [Trabits Group, LLC, Wasilla, AK (United States)

    2015-04-20

    After an oil, gas, or geothermal production well has been drilled, the well must be stabilized with a casing (sections of steel pipe that are joined together) in order to prevent the walls of the well from collapsing. The gap between the casing and the walls of the well is filled with cement, which locks the casing into place. The casing and cementing of geothermal wells is complicated by the harsh conditions of high temperature, high pressure, and a chemical environment (brines with high concentrations of carbon dioxide and sulfuric acid) that degrades conventional Portland cement. During the 1990s and early 2000s, the U.S. Department of Energy’s Geothermal Technologies Office (GTO) provided support for the development of fly-ash-modified calcium aluminate phosphate (CaP) cement, which offers improved resistance to degradation compared with conventional cement. However, the use of CaP cements involves some operational constraints that can increase the cost and complexity of well cementing. In some cases, CaP cements are incompatible with chemical additives that are commonly used to adjust cement setting time. Care must also be taken to ensure that CaP cements do not become contaminated with leftover conventional cement in pumping equipment used in conventional well cementing. With assistance from GTO, Trabits Group, LLC has developed a zeolite-containing cement that performs well in harsh geothermal conditions (thermal stability at temperatures of up to 300°C and resistance to carbonation) and is easy to use (can be easily adjusted with additives and eliminates the need to “sterilize” pumping equipment as with CaP cements). This combination of properties reduces the complexity/cost of well cementing, which will help enable the widespread development of geothermal energy in the United States.

  15. Metal Chemical and Isotope Characterisation in the Upper Loire River Basin, France

    Science.gov (United States)

    Widory, D.; Nigris, R.; Morard, A.; Gassama, N.; Poirier, A.; Bourrain, X.

    2016-12-01

    The Water Framework Directive (WFD) elaborated by the European Commission regulates water resources in the EC based on five years management plans. A new management plan that started in 2016 imposes strict water quality criteria to its member states, including good status thresholds for metallic contaminants. The Loire River, the most important river in France, flows through areas with lithologies naturally containing high metal concentrations in the upper part of its basin. Understanding these metal fluxes into the river is thus a prerequisite to understand their potential impact on the quality of its water in regards to the criteria defined by the WFD. The Massif Central, a residue of the Hercynian chain, is composed of granitic and volcanic rocks. Both its upstream position in the Loire basin and its numerous metal mineralizations made this region a good candidate for characterizing the natural metal geochemical background of its surface waters. To fulfill this objective we focused on the Pb, Cd and Zn chemical and isotope characteristics of selected non-anthropized small watersheds. The investigated small watersheds were selected for supposedly draining a single lithology and undergoing (as far as possible) negligible to no anthropogenic pressure. Results showed that although the high metal potential of the upper part of the Loire River basin has been highly exploited by humans for centuries, metal concentrations during the hydrological cycle are still under the guidelines defined by the WFD. Isotope compositions/ratios are strongly related to the corresponding lithologies along the rivers and help precisely define the local geochemical background that can then be used to identify and quantify any anthropogenic inputs downstream.

  16. Use of alternative fuels in cement manufacture. Effect on clinker and cement characteristics and properties

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    2004-06-01

    Full Text Available This paper compares industrial clinker and cement produced using conventional and alternative fuels (animal meal, tyres or a mixture of the two. The results show no relevant differences in terms of mineralogical composition between the clinker manufactured with alternative fuels and the product obtained using conventional fuel. Clinker produced with alternative fuels at any one factory have a very similar or even lower content in heavy metals than the product manufactured with conventional fuel in the same plant (with the sole exception of Zn when the alternative fuel used is shredded tyres. Mineralogical and morphological analyses reveal no significant differences between the two types of products that can be attributed to the type of fuel used in their manufacture. All six types of cement studied are compliant with the existing legislation as regards both physical and chemical properties. Cement compressive strength is found to be to legal standards regardless of the type of fuel used. Finally, the rheological properties of the cement paste are observed to be unaffected by the type of fuel.

    Se han estudiado clínkeres y cementos obtenidos en procesos industriales que han utilizado combustibles convencionales y combustibles alternativos (harinas cárnicas, neumáticos usados y mezclas de ambos. Los resultados obtenidos han demostrado que los clínkeres fabricados con los combustibles alternativos no presentan diferencias significativas en la composición mineralógica respecto a los obtenidos con combustibles convencionales. Los contenidos de metales pesados en los clínkeres procedentes de la misma fábrica (a excepción de los contenidos en Zn en aquéllos que utilizan neumáticos son muy similares o incluso inferiores a los fabricados con combustibles convencionales. Los análisis mineralógico y morfológico de los clínkeres no evidencian diferencias asignables al tipo de combustible utilizado. Todos los cementos estudiados cumplen

  17. Asphalt cement poisoning

    Science.gov (United States)

    ... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

  18. Radioactivity of bone cement

    International Nuclear Information System (INIS)

    Scherer, M.A.; Winkler, R.; Ascherl, R.; Lenz, E.

    1993-01-01

    A total of 14 samples of different types of bone cement from five different manufacturers were examined for their radioactivity. Each of the investigated bone cements showed a low radioactivity level, i.e. between [de

  19. Ultrafine portland cement performance

    Directory of Open Access Journals (Sweden)

    C. Argiz

    2018-04-01

    Full Text Available By mixing several binder materials and additions with different degrees of fineness, the packing density of the final product may be improved. In this work, ultrafine cement and silica fume mixes were studied to optimize the properties of cement-based materials. This research was performed in mortars made of two types of cement (ultrafine Portland cement and common Portland cement and two types of silica fume with different particle-size distributions. Two Portland cement replacement ratios of 4% and 10% of silica fume were selected and added by means of a mechanical blending method. The results revealed that the effect of the finer silica fume mixed with the coarse cement enhances the mechanical properties and pore structure refinement at a later age. This improvement is somewhat lower in the case of ultrafine cement with silica fume.

  20. Procedure of Destructive Chemical Recovery of Precious Metals in Nitric Acid Production

    Directory of Open Access Journals (Sweden)

    Ljubičić, M.

    2012-07-01

    Full Text Available The heart of the nitric acid production process is the chemical reactor containing a platinum-based catalyst pack and an associated catchment system, which allows the ammonia oxidation reaction to take place efficiently. Under the severe operating conditions imposed by the high-pressure ammonia oxidation process, the catalyst gauzes experience progressive deterioration, as shown by the restricted surface of the catalyst wires, the loss of catalytic activity and the loss of catalytic materials. The higher the pressure of gaseous ammonia oxidation, the greater the loss of platinum group metals from the surface of the applied selective heterogeneous catalysts. Total losses for one batch over the whole period of using selective heterogeneous catalysts may account in the range from 20 to 40 % of the total installed quantity of precious metals. An important part of the platinum removed from the platinum-rhodium alloy wires can be recovered at the outlet of the reactor by means of palladium catchment gauzes. However, this catchment process, which is based on the great ability of palladium to alloy with platinum, is not 100 % effective and a fraction of the platinum and practically all of the rhodium lost by the catalyst wires, evades the catchment package and is then deposited in other parts of the plant, especially heat exchangers. From the above mentioned operating equipment, the retained mass of precious metals can be recovered by the technical procedure of non-destructive and destructive chemical solid-liquid extraction.Shown is the technical procedure of destructive chemical recovery of preheater and boiler for preheating and production of steam by applying sulfuric acid (w = 20 % and subsequent procedure of raffination of derived sludge, to the final recovery of precious metals. The technical procedure of destructive chemical recovery of precious metals from preheater and boiler for preheating and production of steam in nitric acid production is

  1. Interactions between cement grouts and sulphate bearing ground water

    International Nuclear Information System (INIS)

    Walton, P.L.; Duerden, S.L.; Atkins, K.M.; Majumdar, A.J.

    1989-01-01

    The physical, chemical and mineralogical properties of mixtures of Ordinary Portland cement and blastfurnace slag or pulverized fuel ash, exposed to a sulphate-bearing ground water at different temperatures and pressures, were investigated in order to assess the long term durability of cements for encapsulating radioactive waste and backfilling a repository. The effect of the ground water on the chemical and mineralogical characteristics of the cements is minimal. Calcite and C-S-H are present in all the samples and are durable throughout the test. Dimensional changes in the cements during setting and curing may cause weaknesses in the materials which may increase the effects of a percolating ground water. (author)

  2. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    Science.gov (United States)

    Karamat, S.; Sonuşen, S.; Çelik, Ü.; Uysallı, Y.; Oral, A.

    2016-04-01

    In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH)2 for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and LiOH was ∼6 min and for NaOH and Ba(OH)2 it was ∼15 min. KOH and LiOH peeled off graphene very efficiently as compared to NaOH and Ba(OH)2 from the Pt electrode. In case of copper, the peeling time is ∼3-5 min. Different characterizations like optical microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were done to analyze the as grown and transferred graphene samples.

  3. Half-sandwich cobalt complexes in the metal-organic chemical vapor deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Georgi, Colin [Technische Universität Chemnitz, Faculty of Natural Science, Institute of Chemistry, Inorganic Chemistry, Chemnitz 09107 (Germany); Hapke, Marko; Thiel, Indre [Leibniz-Institut für Katalyse e.V. an der Universität Rostock (LIKAT), Albert-Einstein-Straße 29a, Rostock 18059 (Germany); Hildebrandt, Alexander [Technische Universität Chemnitz, Faculty of Natural Science, Institute of Chemistry, Inorganic Chemistry, Chemnitz 09107 (Germany); Waechtler, Thomas; Schulz, Stefan E. [Fraunhofer Institute of Electronic Nano Systems (ENAS), Technologie-Campus 3, Chemnitz 09126 (Germany); Technische Universität Chemnitz, Center for Microtechnologies (ZfM), Chemnitz 09107 (Germany); Lang, Heinrich, E-mail: heinrich.lang@chemie.tu-chemnitz.de [Technische Universität Chemnitz, Faculty of Natural Science, Institute of Chemistry, Inorganic Chemistry, Chemnitz 09107 (Germany)

    2015-03-02

    A series of cobalt half-sandwich complexes of type [Co(η{sup 5}-C{sub 5}H{sub 5})(L)(L′)] (1: L, L′ = 1,5-hexadiene; 2: L = P(OEt){sub 3}, L′ = H{sub 2}C=CHSiMe{sub 3}; 3: L = L′ = P(OEt){sub 3}) has been studied regarding their physical properties such as the vapor pressure, decomposition temperature and applicability within the metal-organic chemical vapor deposition (MOCVD) process, with a focus of the influence of the phosphite ligands. It could be shown that an increasing number of P(OEt){sub 3} ligands increases the vapor pressure and thermal stability of the respective organometallic compound. Complex 3 appeared to be a promising MOCVD precursor with a high vapor pressure and hence was deposited onto Si/SiO{sub 2} (100 nm) substrates. The resulting reflective layer is closed, dense and homogeneous, with a slightly granulated surface morphology. X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of metallic cobalt, cobalt phosphate, cobalt oxide and cobalt carbide. - Highlights: • Thermal studies and vapor pressure measurements of cobalt half-sandwich complexes was carried out. • Chemical vapor deposition with cobalt half-sandwich complexes is reported. • The use of Co-phosphites results in significant phosphorous-doped metallic layers.

  4. Expansion control for cementation of incinerated ash

    International Nuclear Information System (INIS)

    Nakayama, T.; Suzuki, S.; Hanada, K.; Tomioka, O.; Sato, J.; Irisawa, K.; Kato, J.; Kawato, Y.; Meguro, Y.

    2015-01-01

    A method, in which incinerated ash is solidified with a cement material, has been developed to dispose of radioactive incinerated ash waste. A small amount of metallic Al, which was not oxidized in the incineration, existed in the ash. When such ash was mixed with a cement material and water, alkaline components in the ash and the cement were dissolved in the mixing water and then metallic Al reaction with the alkaline compounds resulted in generation of H 2 . Because the H 2 generation began immediately just after the mixing, H 2 bubbles pushed up the mixed grout material and an expanded solidified form was obtained. The expansion leads to lowering the strength of the solidified form and making harmful void. In this study, we tried to control H 2 generation from the reaction of metallic Al in the cementation by means of following two methods, one was a method to let metallic Al react prior to the cementation and the other was a method to add an expansion inhibitor that made an oxide film on the surface of metallic Al. In the pre-treatment, the ash was soaked in water in order to let metallic Al react with it, and then the ash with the immersion solution was dried at 105 Celsius degrees. The pre-treated ash was mixed with an ordinary portland cement and water. The inhibitor of lithium nitrite, sodium nitrite, phosphoric acid, or potassium dihydrogen phosphate was added at the mixing process. The solidified forms prepared using the pre-treated ash and lithium nitrite were not expanded. Phosphoric acid and sodium nitrite were effective for expansion control, but potassium dihydrogen phosphate did not work. (authors)

  5. Concrete research using blended cements

    International Nuclear Information System (INIS)

    Butler, W.B.

    2001-01-01

    Concrete research increasingly involves the use of mixes containing one or more of the supplementary cementitious materials (SCMs), often in conjunction with chemical admixtures. The influence of materials is commonly evaluated on the basis of water/ cement or water/ binder ratio and SCM content as a percentage of total binder, with dosage level of chemical admixture varied to maintain workability. As a result, more than one variable is introduced at a time and the objectives of the research may not be achieved. The significance of water/ cement ratio and addition rates of admixtures are examined from a practical standpoint with suggestions for more appropriate means of evaluation of the influence of individual materials. Copyright (2001) The Australian Ceramic Society

  6. CONCRETE BASED ON MODIFIED DISPERSE CEMENT SYSTEM

    Directory of Open Access Journals (Sweden)

    D. V. Rudenko

    2016-08-01

    Full Text Available Purpose. The article considers definition of the bond types occurring in a modified cement concrete matrix, and the evaluation of the quality of these links in a non-uniform material to determine the geometrical and physical relationships between the structure and the cement matrix modifiers. Methodology. To achieve this purpose the studies covered the microstructure of dispersed modified concrete cement matrix, the structure formation mechanism of the modified cement concrete system of natural hardening; as well as identification of the methods of sound concrete strength assessment. Findings. The author proposed a model of the spatial structure of the concrete cement matrix, modified by particulate reinforcement crystal hydrates. The initial object of study is a set of volume elements (cells of the cement matrix and the system of the spatial distribution of reinforcing crystallohydrates in these volume elements. It is found that the most dangerous defects such as cracks in the concrete volume during hardening are formed as a result of internal stresses, mainly in the zone of cement matrix-filler contact or in the area bordering with the largest pores of the concrete. Originality. The result of the study is the defined mechanism of the process of formation of the initial strength and stiffness of the modified cement matrix due to the rapid growth of crystallohydrates in the space among the dispersed reinforcing modifier particles. Since the lack of space prevents from the free growth of crystals, the latter cross-penetrate, forming a dense structure, which contributes to the growth of strength. Practical value. Dispersed modifying cement matrix provides a durable concrete for special purposes with the design performance characteristics. The developed technology of dispersed cement system modification, the defined features of its structure formation mechanism and the use of congruence principle for the complex of technological impacts of physical

  7. PRODUCTION OF METAL CHEMICAL WELDING ADDITIVE WITH NANODISPERSED PARTICLES OF TITANIUM DIOXIDE

    Directory of Open Access Journals (Sweden)

    BOLDYREV Alexander Mikhaylovich

    2013-12-01

    Full Text Available When welding bridge structures automatic welding under a gumboil layer with metal chemical additive (MCA is widely applied in the modern bridge building. MCA consists of a chopped welding wire (granulated material, which is powdered by modifying chemical additive of titanium dioxide (TiO₂ in the cylindrical mixer «drunk cask». Chemical composition of all welding materials including welding wire, gumboil, electrodes, are strictly normalized and controlled. However, the existing technology of producing MCA doesn’t allow precise controlling of its structure under working conditions and that causes an impact on the stability of welded connections properties. Therefore the aim of this work is to develop a technology to produce stable MCA structure. The paper compares the existing and proposed manufacturing techniques of the metal chemical additive (MCA which is applied in automatic welding of butt connections for bridge structures. It is shown that production of MCA in a high-energy planetary mill provides more stable structure of the additive introduced into a welded joint. The granulometric analysis of the powder TiO₂ showed that when processing MCA in a planetary mill TiO₂ particles are crashed to nanodimensional order. This process is accompanied by crushing of granulated material too. The proposed method for production of MCA in a planetary mill provides stronger cohesion of dioxide with the granulate surface and, as a consequence, more stable MCA chemical structure. Application of MCA which has been mechanical intensified in a planetary mill, increases stability of mechanical properties, if compare with applied technology, in single-order by breaking point and almost twice by impact viscosity.

  8. Searching for chemical classes among metal-poor stars using medium-resolution spectroscopy

    Science.gov (United States)

    Cruz, Monique A.; Cogo-Moreira, Hugo; Rossi, Silvia

    2018-04-01

    Astronomy is in the era of large spectroscopy surveys, with the spectra of hundreds of thousands of stars in the Galaxy being collected. Although most of these surveys have low or medium resolution, which makes precise abundance measurements not possible, there is still important information to be extracted from the available data. Our aim is to identify chemically distinct classes among metal-poor stars, observed by the Sloan Digital Sky Survey, using line indices. The present work focused on carbon-enhanced metal-poor (CEMP) stars and their subclasses. We applied the latent profile analysis technique to line indices for carbon, barium, iron and europium, in order to separate the sample into classes with similar chemical signatures. This technique provides not only the number of possible groups but also the probability of each object to belong to each class. The method was able to distinguish at least two classes among the observed sample, with one of them being probable CEMP stars enriched in s-process elements. However, it was not able to separate CEMP-no stars from the rest of the sample. Latent profile analysis is a powerful model-based tool to be used in the identification of patterns in astrophysics. Our tests show the potential of the technique for the attainment of additional chemical information from `poor' data.

  9. Chemically assisted phytoextraction: a review of potential soil amendments for increasing plant uptake of heavy metals.

    Science.gov (United States)

    Meers, E; Tack, F M G; Van Slycken, S; Ruttens, A; Du Laing, G; Vangronsveld, J; Verloo, M G

    2008-01-01

    The contamination of soils by trace metals has been an unfortunate sideeffect of industrialization. Some of these contaminants can interfere with vulnerable enduses of soil, such as agriculture or nature, already at relatively low levels of contamination. Reversely, conventional civil-technical soil-remediation techniques are too expensive to remediate extended areas of moderately contaminated soil. Phytoextraction has been proposed as a more economic complementary approach to deal with this specific niche of soil contamination. However, phytoextraction has been shown to be a slow-working process due to the low amounts of metals that can be annually removed from the soil under normal agronomic conditions. Therefore, extensive research has been conducted on process optimization by means of chemically improving plant availability and the uptake of heavy metals. A wide range of potential amendments has been proposed in the literature, with considerable attention being spent on aminopolycarboxylic acids such as ethylenediaminetetraacetic acid (EDTA). However, these compounds have received increasing criticism due to their environmental persistence and associated risks for leaching. This review presents an overview of potential soil amendments that can be employed for enhancing metal uptake by phytoextraction crops, with a distinct focus on more degradable alternatives to persistent compounds such as EDTA.

  10. Co3O4 protective coatings prepared by Pulsed Injection Metal Organic Chemical Vapour Deposition

    DEFF Research Database (Denmark)

    Burriel, M.; Garcia, G.; Santiso, J.

    2005-01-01

    of deposition temperature. Pure Co3O4 spinel structure was found for deposition temperatures ranging from 360 to 540 degreesC. The optimum experimental parameters to prepare dense layers with a high growth rate were determined and used to prepare corrosion protective coatings for Fe-22Cr metallic interconnects......Cobalt oxide films were grown by Pulsed Injection Metal Organic Chemical Vapour Deposition (PI-MOCVD) using Co(acac)(3) (acac=acetylacetonate) precursor dissolved in toluene. The structure, morphology and growth rate of the layers deposited on silicon substrates were studied as a function......, to be used in Intermediate Temperature Solid Oxide Fuel Cells. (C) 2004 Elsevier B.V. All rights reserved....

  11. Inverse metal-assisted chemical etching produces smooth high aspect ratio InP nanostructures.

    Science.gov (United States)

    Kim, Seung Hyun; Mohseni, Parsian K; Song, Yi; Ishihara, Tatsumi; Li, Xiuling

    2015-01-14

    Creating high aspect ratio (AR) nanostructures by top-down fabrication without surface damage remains challenging for III-V semiconductors. Here, we demonstrate uniform, array-based InP nanostructures with lateral dimensions as small as sub-20 nm and AR > 35 using inverse metal-assisted chemical etching (I-MacEtch) in hydrogen peroxide (H2O2) and sulfuric acid (H2SO4), a purely solution-based yet anisotropic etching method. The mechanism of I-MacEtch, in contrast to regular MacEtch, is explored through surface characterization. Unique to I-MacEtch, the sidewall etching profile is remarkably smooth, independent of metal pattern edge roughness. The capability of this simple method to create various InP nanostructures, including high AR fins, can potentially enable the aggressive scaling of InP based transistors and optoelectronic devices with better performance and at lower cost than conventional etching methods.

  12. Structured nanocarbon on various metal foils by microwave plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Rius, G; Yoshimura, M

    2013-01-01

    We present a versatile process for the engineering of nanostructures made of crystalline carbon on metal foils. The single step process by microwave plasma-enhance chemical vapor deposition is demonstrated for various substrate materials, such as Ni or Cu. Either carbon nanotubes (CNT) or carbon nanowalls (CNW) are obtained under same growth conditions and without the need of additional catalyst. The use of spacer and insulator implies a certain control over the kind of allotropes that are obtained. High density and large surface area are morphological characteristics of the thus obtained C products. The possibility of application on many metals, and in the alloy composition, on as-delivered commercially available foils indicates that this strategy can be adapted to a bunch of specific applications, while the production of C nanostructures is of remarkable simplicity.

  13. Elaboration of strontium ruthenium oxide thin films on metal substrates by chemical solution deposition

    Energy Technology Data Exchange (ETDEWEB)

    Seveno, R. [Universite de Nantes, Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique (IREENA), 2, rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3 (France)]. E-mail: raynald.seveno@univ-nantes.fr; Braud, A. [Universite de Nantes, Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique (IREENA), 2, rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3 (France); Gundel, H.W. [Universite de Nantes, Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique (IREENA), 2, rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3 (France)

    2005-12-22

    In order to improve the structural interface between a metal substrate and a lead zirconate titanate (Pb(ZrTi)O{sub 3}, PZT) ferroelectric thin film, the elaboration of strontium ruthenium oxide (SrRuO{sub 3}) by chemical solution deposition is studied. The SrRuO{sub 3} thin films were realized by multiple spin-coating technique and the temperature of the rapid thermal annealing process was optimized. The crystallization behavior was examined by X-ray diffraction; surface analyses using scanning electron microscope and atomic force microscope techniques showed the influence of the SrRuO{sub 3} layer at the interface PZT/metal on the morphology of the ferroelectric thin film. From the electrical measurements, a coercive electric field around 25 kV/cm and a remanent polarization of approximately 30 {mu}C/cm were found.

  14. Direct Growth of Graphene on Silicon by Metal-Free Chemical Vapor Deposition

    Science.gov (United States)

    Tai, Lixuan; Zhu, Daming; Liu, Xing; Yang, Tieying; Wang, Lei; Wang, Rui; Jiang, Sheng; Chen, Zhenhua; Xu, Zhongmin; Li, Xiaolong

    2018-06-01

    The metal-free synthesis of graphene on single-crystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed, single-crystal silicon substrate using metal-free, ambient-pressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates. [Figure not available: see fulltext.

  15. Elaboration of strontium ruthenium oxide thin films on metal substrates by chemical solution deposition

    International Nuclear Information System (INIS)

    Seveno, R.; Braud, A.; Gundel, H.W.

    2005-01-01

    In order to improve the structural interface between a metal substrate and a lead zirconate titanate (Pb(ZrTi)O 3 , PZT) ferroelectric thin film, the elaboration of strontium ruthenium oxide (SrRuO 3 ) by chemical solution deposition is studied. The SrRuO 3 thin films were realized by multiple spin-coating technique and the temperature of the rapid thermal annealing process was optimized. The crystallization behavior was examined by X-ray diffraction; surface analyses using scanning electron microscope and atomic force microscope techniques showed the influence of the SrRuO 3 layer at the interface PZT/metal on the morphology of the ferroelectric thin film. From the electrical measurements, a coercive electric field around 25 kV/cm and a remanent polarization of approximately 30 μC/cm were found

  16. Development of the foremost light-curable calcium-silicate MTA cement as root-end in oral surgery. Chemical-physical properties, bioactivity and biological behavior.

    Science.gov (United States)

    Gandolfi, Maria Giovanna; Taddei, Paola; Siboni, Francesco; Modena, Enrico; Ciapetti, Gabriela; Prati, Carlo

    2011-07-01

    An innovative light-curable calcium-silicate cement containing a HEMA-TEGDMA-based resin (lc-MTA) was designed to obtain a bioactive fast setting root-end filling and root repair material. lc-MTA was tested for setting time, solubility, water absorption, calcium release, alkalinizing activity (pH of soaking water), bioactivity (apatite-forming ability) and cell growth-proliferation. The apatite-forming ability was investigated by micro-Raman, ATR-FTIR and ESEM/EDX after immersion at 37°C for 1-28 days in DPBS or DMEM+FBS. The marginal adaptation of cement in root-end cavities of extracted teeth was assessed by ESEM/EDX, and the viability of Saos-2 cell on cements was evaluated. lc-MTA demonstrated a rapid setting time (2min), low solubility, high calcium release (150-200ppm) and alkalinizing power (pH 10-12). lc-MTA proved the formation of bone-like apatite spherulites just after 1 day. Apatite precipitates completely filled the interface porosities and created a perfect marginal adaptation. lc-MTA allowed Saos-2 cell viability and growth and no compromising toxicity was exerted. HEMA-TEGDMA creates a polymeric network able to stabilize the outer surface of the cement and a hydrophilic matrix permeable enough to allow water absorption. SiO(-)/Si-OH groups from the mineral particles induce heterogeneous nucleation of apatite by sorption of calcium and phosphate ions. Oxygen-containing groups from poly-HEMA-TEGDMA provide additional apatite nucleating sites through the formation of calcium chelates. The strong novelty was that the combination of a hydraulic calcium-silicate powder and a poly-HEMA-TEGDMA hydrophilic resin creates the conditions (calcium release and functional groups able to chelate Ca ions) for a bioactive fast setting light-curable material for clinical applications in dental and maxillofacial surgery. The first and unique/exclusive light-curable calcium-silicate MTA cement for endodontics and root-end application was created, with a potential

  17. Hydration kinetics modeling of Portland cement considering the effects of curing temperature and applied pressure

    International Nuclear Information System (INIS)

    Lin Feng; Meyer, Christian

    2009-01-01

    A hydration kinetics model for Portland cement is formulated based on thermodynamics of multiphase porous media. The mechanism of cement hydration is discussed based on literature review. The model is then developed considering the effects of chemical composition and fineness of cement, water-cement ratio, curing temperature and applied pressure. The ultimate degree of hydration of Portland cement is also analyzed and a corresponding formula is established. The model is calibrated against the experimental data for eight different Portland cements. Simple relations between the model parameters and cement composition are obtained and used to predict hydration kinetics. The model is used to reproduce experimental results on hydration kinetics, adiabatic temperature rise, and chemical shrinkage of different cement pastes. The comparisons between the model reproductions and the different experimental results demonstrate the applicability of the proposed model, especially for cement hydration at elevated temperature and high pressure.

  18. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    van Eijk, R.J.; Brouwers, Jos

    2000-01-01

    Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long

  19. STOCHASTIC MODELING OF COMPRESSIVE STRENGTH OF PHOSPHORUS SLAG CONTENT CEMENT

    Directory of Open Access Journals (Sweden)

    Ali Allahverdi

    2016-07-01

    Full Text Available One of the common methods for quick determination of compressive strength as one of the most important properties for assessment of cement quality is to apply various modeling approaches. This study is aimed at finding a model for estimating the compressive strength of phosphorus slag content cements. For this purpose, the compressive strengths of chemically activated high phosphorus slag content cement prepared from phosphorus slag (80 wt.%, Portland cement (14 wt.% and a compound chemical activator containing sodium sulfate and anhydrite (6 wt.% were measured at various Blaine finenesses and curing times. Based on the obtained results, a primary stochastic model in terms of curing time and Blaine fineness has been developed. Then, another different dataset was used to incorporate composition variable including weight fractions of phosphorus slag, cement, and activator in the model. This model can be effectively used to predict the compressive strength of phosphorus slag content cements at various Blaine finenesses, curing times, and compositions.

  20. Immobilization of radioactive waste in cement based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Rahman, A.A.; Macphee, D.; McCulloch, C.E.; Angus, M.J.

    1985-06-01

    The kinetics of reaction between cement and clinoptilolite are elucidated and rate equations containing temperature dependent constants derived for this reaction. Variations in clinoptilolite particle size and their consequences to reactivity are assessed. The presence of pozzolanic agents more reactive than clinoptilolite provides sacrificial agents which are partially effective in lowering the clinoptilolite reactivity. Blast furnace slag-cements have been evaluated and the background literature summarized. Experimental studies of the pore fluid in matured slag-cements show that they provide significantly more immobilization for Cs than Portland cement. The distribution of Sr in cemented waste forms has been examined, and it is shown that most of the chemical immobilization potential in the short term is likely to be associated with the aluminate phases. The chemical and structural nature of these are described. Carbonation studies on real cements are summarized. (author)

  1. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Rahman, A.A.; Macphee, D.; McCulloch, C.E.; Angus, M.J.

    1984-01-01

    Model studies of the behaviour of cement systems have been advanced by considering the nature of the phases formed during hydration and deriving pH-composition models for the CaO-SiO 2 -H 2 O system. Preliminary results of Esub(h) measurements are also reported. Leach tests on Sr from cements are interpreted in terms of Sr retention mechanisms. Present results indicate that the aluminate phases in OPC contribute to the chemical retentivity. Studies on cement-clinoptilolite reactions, made using coarse grained clinoptilolite are reported: ferrierite also reacts chemically with cement. Two critical surveys are presented, together with new data: one on the potential of blended cements, the other on cement durability in CO 2 -containing environments. (author)

  2. Chemically assisted release of transition metals in graphite vaporizers for atomic spectrometry

    International Nuclear Information System (INIS)

    Katskov, Dmitri; Darangwa, Nicholas; Grotti, Marco

    2006-01-01

    decomposition of metal oxide, is the most probable source of chemical energy, which facilitates the vaporization. Intensity of the process depends on chemical properties of the sample and substrate and efficiency of mass and heat transfer by the protective gas. The discussed mechanism of chemically assisted vapor release signifies the energy exchange between all participants of the vaporization process in ET AAS including the matrix, modifier, purge gas and analyte. The finding contributes in the ET AAS theory regarding the mechanisms of vaporization and mass transfer in the presence of matrix and modifiers

  3. Ion transport by gating voltage to nanopores produced via metal-assisted chemical etching method

    Science.gov (United States)

    Van Toan, Nguyen; Inomata, Naoki; Toda, Masaya; Ono, Takahito

    2018-05-01

    In this work, we report a simple and low-cost way to create nanopores that can be employed for various applications in nanofluidics. Nano sized Ag particles in the range from 1 to 20 nm are formed on a silicon substrate with a de-wetting method. Then the silicon nanopores with an approximate 15 nm average diameter and 200 μm height are successfully produced by the metal-assisted chemical etching method. In addition, electrically driven ion transport in the nanopores is demonstrated for nanofluidic applications. Ion transport through the nanopores is observed and could be controlled by an application of a gating voltage to the nanopores.

  4. Chemical composition of late-type supergiants. IV. Homogeneous abundances and galactic metallicity trends

    International Nuclear Information System (INIS)

    Luck, R.E.

    1982-01-01

    In a recent series of papers by Luck and by Luck and Bond on the chemical composition of G and K lb supergiants, [Fe/H] ratios were determined from high-dispersion spectroscopic data for 54 stars. The main results were: (1) that supergiants in the solar neighborhood have about twice the iron content of the Sun ( = +0.3); and (2) that supergiants between 7.7 and 10.2 kpc from the galactic center show a steep radial metallicity gradient, d[Fe/H]/dR = -0.24 kpc -1

  5. Pulsed injection metal organic chemical vapour deposition and characterisation of thin CaO films

    International Nuclear Information System (INIS)

    Borges, R.P.; Ferreira, P.; Saraiva, A.; Goncalves, R.; Rosa, M.A.; Goncalves, A.P.; Silva, R.C. da; Magalhaes, S.; Lourenco, M.J.V.; Santos, F.J.V.; Godinho, M.

    2009-01-01

    Thin films of CaO were grown on silicon (Si) and lanthanum aluminate (LaAlO 3 ) substrates by pulsed injection metal-organic chemical vapour deposition in a vertical injection MOCVD system. Growth parameters were systematically varied to study their effect on film growth and quality and to determine the optimal growth conditions for this material. Film quality and growth rate were evaluated by atomic force microscopy, X-ray diffraction and Rutherford Backscattering Spectroscopy measurements. Optimised conditions allowed growing transparent, single phase films textured along the (0 0 l) direction.

  6. Research on the surface chemical behavior of uranium metal in hydrogen atmosphere by XPS

    International Nuclear Information System (INIS)

    Fu Xiaoguo; Wang Xiaolin; Yu Yong; Zhao Zhengping

    2001-01-01

    The surface chemical behavior clean uranium metal in hydrogen atmosphere at 100 and 200 degree C is studied by X-ray photoelectron spectroscopy (XPS), respectively. It leads to hydriding reaction when the hydrogen exposure is 12.0 Pa·s, and the U4f 7/2 binding energy of UH 3 is found to be 378.7 eV. The higher temperature (200 degree C) is beneficial to UH 3 formation at the same hydrogen exposures. XPS elemental depth profiles indicate that the distribution of uranium surface layer is UO 2 , UH 3 and U after exposure to 174.2 Pa·s hydrogen

  7. Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

    DEFF Research Database (Denmark)

    Pietro, Lura; Ye, Guang; van Breugel, Klaas

    2004-01-01

    In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag...... (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

  8. Laterally Stitched Heterostructures of Transition Metal Dichalcogenide: Chemical Vapor Deposition Growth on Lithographically Patterned Area

    KAUST Repository

    Li, Henan

    2016-10-31

    Two-dimensional transition metal dichalcogenides (TMDCs) have shown great promise in electronics and optoelectronics due to their unique electrical and optical properties. Heterostructured TMDC layers such as the laterally stitched TMDCs offer the advantages of better electronic contact and easier band offset tuning. Here, we demonstrate a photoresist-free focused ion beam (FIB) method to pattern as-grown TMDC monolayers by chemical vapor deposition, where the exposed edges from FIB etching serve as the seeds for growing a second TMDC material to form desired lateral heterostructures with arbitrary layouts. The proposed lithographic and growth processes offer better controllability for fabrication of the TMDC heterostrucuture, which enables the construction of devices based on heterostructural monolayers. © 2016 American Chemical Society.

  9. Metal-assisted chemical etching of CIGS thin films for grain size analysis

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Chaowei [Research and Development Centre, Hanergy Thin Film Power Group Limited, Chengdu (China); Loi, Huu-Ha; Duong, Anh; Parker, Magdalena [Failure Analysis Department, MiaSole Hi-Tech Corp., Santa Clara, CA (United States)

    2016-09-15

    Grain size of the CIGS absorber is an important monitoring factor in the CIGS solar cell manufacturing. Electron backscatter diffraction (EBSD) analysis is commonly used to perform CIGS grain size analysis in the scanning electron microscope (SEM). Although direct quantification on SEM image using the average grain intercept (AGI) method is faster and simpler than EBSD, it is hardly applicable on CIGS thin films. The challenge is that, not like polycrystalline silicon, to define grain boundaries by selective chemical etching is not easily realizable for the multi-component CIGS alloy. In this Letter, we present direct quantification of CIGS thin film grain size using the AGI method by developing metal-assisted wet chemical etching process to define CIGS grain boundaries. The calculated value is similar to EBSD result. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Chemical formation of soft metal electrodes for flexible and wearable electronics.

    Science.gov (United States)

    Wang, Dongrui; Zhang, Yaokang; Lu, Xi; Ma, Zhijun; Xie, Chuan; Zheng, Zijian

    2018-06-18

    Flexible and wearable electronics is one major technology after smartphones. It shows remarkable application potential in displays and informatics, robotics, sports, energy harvesting and storage, and medicine. As an indispensable part and the cornerstone of these devices, soft metal electrodes (SMEs) are of great significance. Compared with conventional physical processes such as vacuum thermal deposition and sputtering, chemical approaches for preparing SMEs show significant advantages in terms of scalability, low-cost, and compatibility with the soft materials and substrates used for the devices. This review article provides a detailed overview on how to chemically fabricate SMEs, including the material preparation, fabrication technologies, methods to characterize their key properties, and representative studies on different wearable applications.

  11. DNA-decorated carbon-nanotube-based chemical sensors on complementary metal oxide semiconductor circuitry

    International Nuclear Information System (INIS)

    Chen, Chia-Ling; Yang, Chih-Feng; Dokmeci, Mehmet R; Agarwal, Vinay; Sonkusale, Sameer; Kim, Taehoon; Busnaina, Ahmed; Chen, Michelle

    2010-01-01

    We present integration of single-stranded DNA (ss-DNA)-decorated single-walled carbon nanotubes (SWNTs) onto complementary metal oxide semiconductor (CMOS) circuitry as nanoscale chemical sensors. SWNTs were assembled onto CMOS circuitry via a low voltage dielectrophoretic (DEP) process. Besides, bare SWNTs are reported to be sensitive to various chemicals, and functionalization of SWNTs with biomolecular complexes further enhances the sensing specificity and sensitivity. After decorating ss-DNA on SWNTs, we have found that the sensing response of the gas sensor was enhanced (up to ∼ 300% and ∼ 250% for methanol vapor and isopropanol alcohol vapor, respectively) compared with bare SWNTs. The SWNTs coupled with ss-DNA and their integration on CMOS circuitry demonstrates a step towards realizing ultra-sensitive electronic nose applications.

  12. MOFwich: Sandwiched Metal-Organic Framework-Containing Mixed Matrix Composites for Chemical Warfare Agent Removal.

    Science.gov (United States)

    Peterson, Gregory W; Lu, Annie X; Hall, Morgan G; Browe, Matthew A; Tovar, Trenton; Epps, Thomas H

    2018-02-28

    This work describes a new strategy for fabricating mixed matrix composites containing layered metal-organic framework (MOF)/polymer films as functional barriers for chemical warfare agent protection. Through the use of mechanically robust polymers as the top and bottom encasing layers, a high-MOF-loading, high-performance-core layer can be sandwiched within. We term this multifunctional composite "MOFwich". We found that the use of elastomeric encasing layers enabled core layer reformation after breakage, an important feature for composites and membranes alike. The incorporation of MOFs into the core layer led to enhanced removal of chemical warfare agents while simultaneously promoting moisture vapor transport through the composite, showcasing the promise of these composites for protection applications.

  13. Effect of plants on the bioavailability of metals and other chemical properties of biosolids in a column study.

    Science.gov (United States)

    Huynh, Trang T; Laidlaw, W Scott; Singh, Balwant; Zhang, Hao; Baker, Alan J M

    2012-10-01

    The effects of metal-accumulating plants (Salix x reichardtii and Populus balsamifera) on the chemical properties and dynamics of metals in biosolids were investigated using different techniques including diffusive gradients in thin films (DGT), sequential extraction procedures and partitioning coefficient (K(d)). Plants could effectively extract Cd, Ni, and Zn and decreased dissolved organic carbon (DOC). The presence of plants increased the potential bioavailability of these metals, as assessed by an increase in the ratio of metal measured by DGT and metals in the solution. The plants affected the Cd, Ni, and Zn pools (soluble/exchangeable; Fe/Mn oxide and organic matter bound) characterised by sequential extraction and K(d) but did not reduce the total metals in either substrate. However, plants had no effect on Cu, presumably because of the effective buffering of available Cu by organic matter in both solution and solid phases. A high density of plant roots was associated with increased leaching of metals.

  14. Stability of biogenic metal(loid) nanomaterials related to the colloidal stabilization theory of chemical nanostructures.

    Science.gov (United States)

    Piacenza, Elena; Presentato, Alessandro; Turner, Raymond J

    2018-02-25

    In the last 15 years, the exploitation of biological systems (i.e. plants, bacteria, mycelial fungi, yeasts, and algae) to produce metal(loid) (Me)-based nanomaterials has been evaluated as eco-friendly and a cost-effective alternative to the chemical synthesis processes. Although the biological mechanisms of biogenic Me-nanomaterial (Bio-Me-nanomaterials) production are not yet completely elucidated, a key advantage of such bio-nanostructures over those chemically synthesized is related to their natural thermodynamic stability, with several studies ascribed to the presence of an organic layer surrounding these Bio-Me-nanostructures. Different macromolecules (e.g. proteins, peptides, lipids, DNA, and polysaccharides) or secondary metabolites (e.g. flavonoids, terpenoids, glycosides, organic acids, and alkaloids) naturally produced by organisms have been indicated as main contributors to the stabilization of Bio-Me-nanostructures. Nevertheless, the chemical-physical mechanisms behind the ability of these molecules in providing stability to Bio-Me-nanomaterials are unknown. In this context, transposing the stabilization theory of chemically synthesized Me-nanomaterials (Ch-Me-nanomaterials) to biogenic materials can be used towards a better comprehension of macromolecules and secondary metabolites role as stabilizing agents of Bio-Me-nanomaterials. According to this theory, nanomaterials are generally featured by high thermodynamic instability in suspension, due to their high surface area and surface energy. This feature leads to the necessity to stabilize chemical nanostructures, even during or directly after their synthesis, through the development of (i) electrostatic, (ii) steric, or (iii) electrosteric interactions occurring between molecules and nanomaterials in suspension. Based on these three mechanisms, this review is focused on parallels between the stabilization of biogenic or chemical nanomaterials, suggesting which chemical-physical mechanisms may be

  15. The influence of chemical composition and fineness on the performance of alkali activated cements obtained from blast furnace slags; A influencia da composicao quimica e da finura no desempenho de cimentos alcali ativados obtidos com escorias de alto forno

    Energy Technology Data Exchange (ETDEWEB)

    Langaro, Eloise Aparecida; Matoski, Adalberto, E-mail: elolangaro@hotmail.com, E-mail: adalberto@utfpr.edu.br [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba (Brazil); Luz, Caroline Angulski da; Buth, Islas Stein; Moraes, Maryah Costa de; Pereira Filho, Jose Ilo, E-mail: angulski@utfpr.edu.br, E-mail: islas_sb@hotmail.com, E-mail: maryah_moraes@hotmail.com, E-mail: ilofilho@yahoo.com.br [Universidade Tecnologica Federal do Parana (UTFPR), Pato Branco, PR (Brazil)

    2017-01-15

    New binders are being developed for concrete in order to reduce the environmental impact mainly related to CO{sub 2} emissions. Alkali -activated cements (CATs) are obtained from lime-aluminosilicate materials and an alkali activator and can reduce by 80% the emission of CO{sub 2} compared to Portland Cement (PC). Papers have also shown physical and mechanical properties similar or higher than those presented by the PC, however, the activation of raw material is complex. Recent papers have also have showed a strong influence of the characteristics of raw material on the performance of CAT, however, little mentioned in the literature.. Therefore, this paper aimed to analyze the influence of characteristics of blast furnace slag (fineness and chemical composition) on the behavior of activated alkali cements. For this purpose, two slags were used, A and B, which were submitted to different milling times; and activated using 5% of NaOH. Mortars and pastes were prepared for compressive strength testing (7 and 28 days), measurements of heat of hydration and investigation of microstructure (XRD and DSC) were made. The results showed that the mortar made with slag A reached a very good mechanical performance, close to 48MPa at 28 days, and higher formation of CSH, in opposite of slag B. The probable hypothesis of this study is that the system formed in CAT made with slag A (containing more Al{sub 2}O{sub 3}) could provide CSH with a greater incorporation of Al and a lower crystallinity, increasing the mechanical strength. (author)

  16. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    Fred Sabins

    2001-01-01

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter

  17. An Electrochemical Investigation of the Chemical Diffusivity in Liquid Metal Alloys

    Science.gov (United States)

    Barriga, Salvador A.

    The liquid metal battery has been shown to be a viable candidate for grid-scale energy storage, due to its fast kinetics and ability to be constructed from economically feasible materials. Various of the liquid metal couples that form high stable voltages, such as the calcium chemistries, are rate limited because they tend to form solid intermetallic compounds with high melting points. In order to understand and better engineer these batteries, the kinetic properties of these liquid alloys, in particular the chemical diffusivity, must be known accurately so that it can be used as input in computational simulations to avoid the nucleation of any solids. Unfortunately, the dominant experimental methods for measuring diffusion in liquid metals today are unreliable because the measurement timescales are on the order of days, require long capillaries susceptible to buoyancy-driven flow from temperature fluctuations, and composition analysis must be done ex-situ as a solid. To counter all these problems, a new and novel method for measuring the chemical diffusivity of metals in liquid alloys derived from electrochemical principles is presented in this thesis. This new method has the advantage of operating in shorter times scales of minutes rather than days, and requires the use of small capillaries which collectively minimize the effect of convectively-driven flow caused from temperature gradients. This new method was derived by solving the same boundary conditions required by the galvanostatic intermittent titration technique for solid-state electrodes. To verify the validity of the new theoretical derivation, the method was used to measure the chemical diffusivity of calcium in liquid bismuth within the temperature range of 550 - 700 °C using a three-electrode setup with a ternary molten salt electrolyte. Three compositions where studied (5% Ca-Bi, 10% Ca-Bi, and 15% Ca-Bi) for comparison. The chemical diffusion coefficient was found to range between (6.77 +/- 0.21)x

  18. Electro-chemical deposition of nano hydroxyapatite-zinc coating on titanium metal substrate.

    Science.gov (United States)

    El-Wassefy, N A; Reicha, F M; Aref, N S

    2017-08-13

    Titanium is an inert metal that does not induce osteogenesis and has no antibacterial properties; it is proposed that hydroxyapatite coating can enhance its bioactivity, while zinc can contribute to antibacterial properties and improve osseointegration. A nano-sized hydroxyapatite-zinc coating was deposited on commercially pure titanium using an electro-chemical process, in order to increase its surface roughness and enhance adhesion properties. The hydroxyapatite-zinc coating was attained using an electro-chemical deposition in a solution composed of a naturally derived calcium carbonate, di-ammonium hydrogen phosphate, with a pure zinc metal as the anode and titanium as the cathode. The applied voltage was -2.5 for 2 h at a temperature of 85 °C. The resultant coating was characterized for its surface morphology and chemical composition using a scanning electron microscope (SEM), energy dispersive x-ray spectroscope (EDS), and Fourier transform infrared (FT-IR) spectrometer. The coated specimens were also evaluated for their surface roughness and adhesion quality. Hydroxyapatite-zinc coating had shown rosette-shaped, homogenous structure with nano-size distribution, as confirmed by SEM analysis. FT-IR and EDS proved that coatings are composed of hydroxyapatite (HA) and zinc. The surface roughness assessment revealed that the coating procedure had significantly increased average roughness (Ra) than the control, while the adhesive tape test demonstrated a high-quality adhesive coat with no laceration on tape removal. The developed in vitro electro-chemical method can be employed for the deposition of an even thickness of nano HA-Zn adhered coatings on titanium substrate and increases its surface roughness significantly.

  19. Chemicals, metals, and pesticide pits waste unit low induction number electromagnetic survey

    Energy Technology Data Exchange (ETDEWEB)

    Cumbest, R.J.; Mohon, D.

    1995-06-01

    An electromagnetic survey was conducted at the Chemicals, Metals, and Pesticide Waste Unit to identify any buried metallic objects that may be present in the materials used to fill and cover the pits after removal of pit debris. The survey was conducted with a Geonics EM-31 Terrain Conductivity Meter along north - south oriented traverses with 5-ft station intervals to produce a 5-ft by 5-ft square grid node pattern. Both conductivity and in-phase components were measured at each station for vertical dipole orientation with the common axis of the dipoles in the north - south and east - west orientations. The conductivity data clearly show elevated conductivities (2.1 to 7.0 mS/m) associated with the material over the pits, as compared with the surrounding area that is characterized by lower conductivities (1 to 2 mS/m). This is probably the result of the higher clay content of the fill material relative to the surrounding area, which has a higher sand to clay ratio and the presence of a plastic cover beneath the fill that has probably trapped water. Many metal objects are present in the survey area including manhole covers, monitoring well heads, metal, signs, drain culverts, abandoned wells, and BP waste unit marker balls. AU of these exhibit associated conductivity and in-phase anomalies of various magnitude. In addition to these anomalies that can be definitely associated with surface sources, conductivity and in-phase anomalies are also present with no obvious surface source. These anomalies are probably indicative of subsurface buried metallic objects. A high concentration of these objects appears to be present in the southwest corner of the survey area.

  20. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    Fred Sabins

    2001-01-01

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job

  1. Emissions of metals and polychlorinated dibenzo(p)dioxins and furans (PCDD/Fs) from Portland cement manufacturing plants: inter-kiln variability and dependence on fuel-types.

    Science.gov (United States)

    Zemba, Stephen; Ames, Michael; Green, Laura; Botelho, Maria João; Gossman, David; Linkov, Igor; Palma-Oliveira, José

    2011-09-15

    Emissions from Portland cement manufacturing facilities may increase health risks in nearby populations and are thus subject to stringent regulations. Direct testing of pollutant concentrations in exhaust gases provides the best basis for assessing the extent of these risks. However, these tests (i) are often conducted under stressed, rather than typical, operating conditions, (ii) may be limited in number and duration, and (iii) may be influenced by specific fuel-types and attributes of individual kilns. We report here on the results of more than 150 emissions-tests conducted of two kilns at a Portland cement manufacturing plant in Portugal. The tests measured various regulated metals and polychlorinated dibenzo(p)dioxins and furans (PCDD/Fs). Stack-gas concentrations of pollutants were found to be highly variable, with standard deviations on the order of mean values. Emission rates of many pollutants were higher when coal was used as the main kiln fuel (instead of petroleum coke). Use of various supplemental fuels, however, had little effect on stack emissions, and few statistically significant differences were observed when hazardous waste was included in the fuel mix. Significant differences in emissions for some pollutants were observed between the two kilns despite their similar designs and uses of similar fuels. All measured values were found to be within applicable regulatory limits. Published by Elsevier B.V.

  2. Thermal and Chemical Characterization of Non-Metallic Materials Using Coupled Thermogravimetric Analysis and Infrared Spectroscopy

    Science.gov (United States)

    Huff, Timothy L.

    2002-01-01

    Thermogravimetric analysis (TGA) is widely employed in the thermal characterization of non-metallic materials, yielding valuable information on decomposition characteristics of a sample over a wide temperature range. However, a potential wealth of chemical information is lost during the process, with the evolving gases generated during thermal decomposition escaping through the exhaust line. Fourier Transform-Infrared spectroscopy (FT-IR) is a powerful analytical technique for determining many chemical constituents while in any material state, in this application, the gas phase. By linking these two techniques, evolving gases generated during the TGA process are directed into an appropriately equipped infrared spectrometer for chemical speciation. Consequently, both thermal decomposition and chemical characterization of a material may be obtained in a single sample run. In practice, a heated transfer line is employed to connect the two instruments while a purge gas stream directs the evolving gases into the FT-IR. The purge gas can be either high purity air or an inert gas such as nitrogen to allow oxidative and pyrolytic processes to be examined, respectively. The FT-IR data is collected realtime, allowing continuous monitoring of chemical compositional changes over the course of thermal decomposition. Using this coupled technique, an array of diverse materials has been examined, including composites, plastics, rubber, fiberglass epoxy resins, polycarbonates, silicones, lubricants and fluorocarbon materials. The benefit of combining these two methodologies is of particular importance in the aerospace community, where newly developing materials have little available data with which to refer. By providing both thermal and chemical data simultaneously, a more definitive and comprehensive characterization of the material is possible. Additionally, this procedure has been found to be a viable screening technique for certain materials, with the generated data useful in

  3. Durability of cermet ionomer cement conditioned in different media.

    Science.gov (United States)

    el-Din, I M

    1992-01-01

    The glass ionomer cement has exhibited significant adhesion to hard tooth structures, and good cariostatic properties. The sintering of the silver alloy powder and glass ionomer cement "cermet cement" has provided additional improvement in the physical properties of the restorative material. These were flexural resistance, wear resistance, increased radio-opacity, hardness and porosity. The improvement in the physical properties of the cermet glass cements has provided an extension in their clinical use as core build up, lining for inlays, amalgam and composite restoratives, fissure filling, restoration of primary teeth, class II tunnel preparation, treatment of root caries and repair of defective metal margins in crown and inlays.

  4. Cement Types, Composition, Uses and Advantages of Nanocement, Environmental Impact on Cement Production, and Possible Solutions

    Directory of Open Access Journals (Sweden)

    S. P. Dunuweera

    2018-01-01

    Full Text Available We first discuss cement production and special nomenclature used by cement industrialists in expressing the composition of their cement products. We reveal different types of cement products, their compositions, properties, and typical uses. Wherever possible, we tend to give reasons as to why a particular cement type is more suitable for a given purpose than other types. Cement manufacturing processes are associated with emissions of large quantities of greenhouse gases and environmental pollutants. We give below quantitative and qualitative analyses of environmental impact of cement manufacturing. Controlling pollution is a mandatory legal and social requirement pertinent to any industry. As cement industry is one of the biggest CO2 emitters, it is appropriate to discuss different ways and means of CO2 capture, which will be done next. Finally, we give an account of production of nanocement and advantages associated with nanocement. Nanofillers such as nanotitania, nanosilica, and nanoalumina can be produced in large industrial scale via top-down approach of reducing size of naturally available bulk raw materials to those in the nanorange of 1 nm–100 nm. We mention the preparation of nanotitania and nanosilica from Sri Lankan mineral sands and quartz deposits, respectively, for the use as additives in cement products to improve performance and reduce the amount and cost of cement production and consequent environmental impacts. As of now, mineral sands and other treasures of minerals are exported without much value addition. Simple chemical modifications or physical treatments would add enormous value to these natural materials. Sri Lanka is gifted with highly pure quartz and graphite from which silica and graphite nanoparticles, respectively, can be prepared by simple size reduction processes. These can be used as additives in cements. Separation of constituents of mineral sands is already an ongoing process.

  5. [PVD-silicoating before cementation of zirconia-based knee prostheses effects better cement adhesion and lower aseptic loosening rates].

    Science.gov (United States)

    Marx, R; Faramarzi, R; Oberbach, T; Begand, S; Grätz, N; Wirtz, D C

    2012-02-01

    CoCrMo alloys are contraindicated for allergy patients. For these patients, cemented or uncemented prostheses made of titanium alloy are indicated. Uncemented prostheses, however, have low primary retention, particularly the tibial components of knee joint prostheses because of the lack of a positive locking. Therefore, for knee replacement cemented CoCrMo prostheses may be suitable also for allergy sufferers if these are masked by ZrN or TiNbN layers. Alternatively the CoCrMo alloy may be replaced by high-strength oxide ceramics. For adhesion of bone cement to the ceramic surface, however, only inefficient mechanical retention spots are exposed as compared with a metal surface. Undercuts generated by corundum blasting, although highly efficient on a CoCrMo surface, are not such efficient centres on a ceramic surface due to its brittleness. Therefore, the mechanical component of retention is significantly reduced. When specific adhesion between bone cement and surface does not exist due to physical and chemical forces, the hydrolytic stability will be insufficient. Micromotions are promoted and early aseptic loosening is predictable. Silicoating of the ceramic surface will allow specific adhesion and can result in better hydrolytic stability of bonding. In order to evaluate the effectiveness of silicoating the bond strengths of blasted (mean size of corundum grains 50 µm) and silicate layered alumina-toughened zirconia (ATZ) surfaces were compared with "as fired" surfaces by utilising TiAlV probes (diameter 6 mm) for traction-adhesive strength testing. Samples machined out of CoCrMo alloy were utilised for reference. After preparing the samples for traction-adhesive strength testing (sequence: substrate, silicate and silane, protective lacquer [PolyMA], bone cement, TiAlV probe) they were aged up to 360 days at 37 °C in Ringer's solution. The bond strengths observed for all ageing intervals were well above 20 MPa and much higher and more hydrolytically

  6. Nanoparticulate fillers improve the mechanical strength of bone cement.

    Science.gov (United States)

    Gomoll, Andreas H; Fitz, Wolfgang; Scott, Richard D; Thornhill, Thomas S; Bellare, Anuj

    2008-06-01

    Polymethylmethacrylate (PMMA-) based bone cement contains micrometer-size barium sulfate or zirconium oxide particles to radiopacify the cement for radiographic monitoring during follow-up. Considerable effort has been expended to improve the mechanical qualities of cements, largely through substitution of PMMA with new chemical structures. The introduction of these materials into clinical practice has been complicated by concerns over the unknown long-term risk profile of these new structures in vivo. We investigated a new composite with the well characterized chemical composition of current cements, but with nanoparticles instead of the conventional, micrometer-size barium sulfate radiopacifier. In this study, we replaced the barium sulfate microparticles that are usually present in commercial PMMA cements with barium sulfate nanoparticles. The resultant "microcomposite" and "nanocomposite" cements were then characterized through morphological investigations such as ultra-small angle X-ray scattering (USAXS) and scanning electron microscopy (SEM). Mechanical characterization included compression, tensile, compact tension, and fatigue testing. SEM and USAXS showed excellent dispersion of nanoparticles. Substitution of nanoparticles for microparticles resulted in a 41% increase in tensile strain-to-failure (p = 0.002) and a 70% increase in tensile work-of-fracture (p = 0.005). The nanocomposite cement also showed a two-fold increase in fatigue life compared to the conventional, microcomposite cement. In summary, nanoparticulate substitution of radiopacifiers substantially improved the in vitro mechanical properties of PMMA bone cement without changing the known chemical composition.

  7. Chemically Designed Metallic/Insulating Hybrid Nanostructures with Silver Nanocrystals for Highly Sensitive Wearable Pressure Sensors.

    Science.gov (United States)

    Kim, Haneun; Lee, Seung-Wook; Joh, Hyungmok; Seong, Mingi; Lee, Woo Seok; Kang, Min Su; Pyo, Jun Beom; Oh, Soong Ju

    2018-01-10

    With the increase in interest in wearable tactile pressure sensors for e-skin, researches to make nanostructures to achieve high sensitivity have been actively conducted. However, limitations such as complex fabrication processes using expensive equipment still exist. Herein, simple lithography-free techniques to develop pyramid-like metal/insulator hybrid nanostructures utilizing nanocrystals (NCs) are demonstrated. Ligand-exchanged and unexchanged silver NC thin films are used as metallic and insulating components, respectively. The interfaces of each NC layer are chemically engineered to create discontinuous insulating layers, i.e., spacers for improved sensitivity, and eventually to realize fully solution-processed pressure sensors. Device performance analysis with structural, chemical, and electronic characterization and conductive atomic force microscopy study reveals that hybrid nanostructure based pressure sensor shows an enhanced sensitivity of higher than 500 kPa -1 , reliability, and low power consumption with a wide range of pressure sensing. Nano-/micro-hierarchical structures are also designed by combining hybrid nanostructures with conventional microstructures, exhibiting further enhanced sensing range and achieving a record sensitivity of 2.72 × 10 4 kPa -1 . Finally, all-solution-processed pressure sensor arrays with high pixel density, capable of detecting delicate signals with high spatial selectivity much better than the human tactile threshold, are introduced.

  8. Chemical treatment of olive pomace: effect on acid-basic properties and metal biosorption capacity.

    Science.gov (United States)

    Martín-Lara, M A; Pagnanelli, F; Mainelli, S; Calero, M; Toro, L

    2008-08-15

    In this study, olive pomace, an agricultural waste that is very abundant in Mediterranean area, was modified by two chemical treatments in order to improve its biosorption capacity. Potentiometric titrations and IR analyses were used to characterise untreated olive pomace (OP), olive pomace treated by phosphoric acid (PAOP) and treated by hydrogen peroxide (HPOP). Acid-base properties of all investigated biosorbents were characterised by two main kinds of active sites, whose nature and concentration were determined by a mechanistic model assuming continuous distribution for the proton affinity constants. Titration modelling denoted that all investigated biosorbents (OP, PAOP and HPOP) were characterised by the same kinds of active sites (carboxylic and phenolic), but with different total concentrations with PAOP richer than OP and HPOP. Single metal equilibrium studies in batch reactors were carried out to determine the capacity of these sorbents for copper and cadmium ions at constant pH. Experimental data were analysed and compared using the Langmuir isotherm. The order of maximum uptake capacity of copper and cadmium ions on different biosorbents was PAOP>HPOP>OP. The maximum adsorption capacity of copper and cadmium, was obtained as 0.48 and 0.10 mmol/g, respectively, for PAOP. Metal biosorption tests in presence of Na(+) in solution were also carried out in order to evaluate the effect of chemical treatment on biomass selectivity. These data showed that PAOP is more selective for cadmium than the other sorbents, while similar selectivity was observed for copper.

  9. Synthesis and electronic properties of chemically functionalized graphene on metal surfaces

    International Nuclear Information System (INIS)

    Grüneis, Alexander

    2013-01-01

    A review on the electronic properties, growth and functionalization of graphene on metals is presented. Starting from the derivation of the electronic properties of an isolated graphene layer using the nearest neighbor tight-binding (TB) approximation for π and σ electrons, the TB model is then extended to third-nearest neighbors and interlayer coupling. The latter is relevant to few-layer graphene and graphite. Next, the conditions under which epitaxial graphene can be obtained by chemical vapor deposition are reviewed with a particular emphasis on the Ni(111) surface. Regarding functionalization, I first discuss the intercalation of monolayer Au into the graphene/Ni(111) interface, which renders graphene quasi-free-standing. The Au intercalated quasi-free-standing graphene is then the basis for chemical functionalization. Functionalization of graphene is classified into covalent, ionic and substitutional functionalization. As archetypical examples for these three possibilities I discuss covalent functionalization by hydrogen, ionic functionalization by alkali metals and substitutional functionalization by nitrogen heteroatoms.

  10. Chemical treatment of olive pomace: Effect on acid-basic properties and metal biosorption capacity

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Lara, M.A. [Departamento de Ingenieria Quimica, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)], E-mail: marianml@ugr.es; Pagnanelli, F. [Dipartimento di Chimica, Facolta di S.M.F.N., Universita degli Studi ' La Sapienza' , P.le A. Moro, 5, 00185 Roma (Italy)], E-mail: francesca.pagnanelli@uniroma1.it; Mainelli, S. [Dipartimento di Chimica, Facolta di S.M.F.N., Universita degli Studi ' La Sapienza' , P.le A. Moro, 5, 00185 Roma (Italy); Calero, M. [Departamento de Ingenieria Quimica, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain); Toro, L. [Dipartimento di Chimica, Facolta di S.M.F.N., Universita degli Studi ' La Sapienza' , P.le A. Moro, 5, 00185 Roma (Italy)

    2008-08-15

    In this study, olive pomace, an agricultural waste that is very abundant in Mediterranean area, was modified by two chemical treatments in order to improve its biosorption capacity. Potentiometric titrations and IR analyses were used to characterise untreated olive pomace (OP), olive pomace treated by phosphoric acid (PAOP) and treated by hydrogen peroxide (HPOP). Acid-base properties of all investigated biosorbents were characterised by two main kinds of active sites, whose nature and concentration were determined by a mechanistic model assuming continuous distribution for the proton affinity constants. Titration modelling denoted that all investigated biosorbents (OP, PAOP and HPOP) were characterised by the same kinds of active sites (carboxylic and phenolic), but with different total concentrations with PAOP richer than OP and HPOP. Single metal equilibrium studies in batch reactors were carried out to determine the capacity of these sorbents for copper and cadmium ions at constant pH. Experimental data were analysed and compared using the Langmuir isotherm. The order of maximum uptake capacity of copper and cadmium ions on different biosorbents was PAOP > HPOP > OP. The maximum adsorption capacity of copper and cadmium, was obtained as 0.48 and 0.10 mmol/g, respectively, for PAOP. Metal biosorption tests in presence of Na{sup +} in solution were also carried out in order to evaluate the effect of chemical treatment on biomass selectivity. These data showed that PAOP is more selective for cadmium than the other sorbents, while similar selectivity was observed for copper.

  11. Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects

    Science.gov (United States)

    Zhang, Jie; Sheng, Lei; Liu, Jing

    2014-11-01

    Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

  12. Backside versus frontside advanced chemical analysis of high-k/metal gate stacks

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, E., E-mail: eugenie.martinez@cea.fr [Univ Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Saidi, B. [STMicroelectronics, 850 rue Jean Monnet, 38926 Rousset Cedex, Crolles (France); Veillerot, M. [Univ Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Caubet, P. [STMicroelectronics, 850 rue Jean Monnet, 38926 Rousset Cedex, Crolles (France); Fabbri, J-M. [Univ Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Piallat, F. [STMicroelectronics, 850 rue Jean Monnet, 38926 Rousset Cedex, Crolles (France); Gassilloud, R. [Univ Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Schamm-Chardon, S. [CEMES-CNRS et Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse (France)

    2015-08-15

    Highlights: • The backside approach is a promising solution for advanced chemical characterization of future MOSFETs. • Frontside ToF-SIMS and Auger depth profiles are affected by cumulative mixing effects and thus not relevant for analyzing ultra-thin layers. • Higher in-depth resolution is possible in the backside approach for Auger and ToF-SIMS depth profiling. • Backside depth profiling allows revealing ultra-thin layers and elemental in-depth redistribution inside high-k/metal gate stacks. • Backside XPS allows preserving the full metal gate, thus enabling the analysis of real technological samples. - Abstract: Downscaling of transistors beyond the 14 nm technological node requires the implementation of new architectures and materials. Advanced characterization methods are needed to gain information about the chemical composition of buried layers and interfaces. An effective approach based on backside analysis is presented here. X-ray photoelectron spectroscopy, Auger depth profiling and time-of-flight secondary ions mass spectrometry are combined to investigate inter-diffusion phenomena. To highlight improvements related to the backside method, backside and frontside analyses are compared. Critical information regarding nitrogen, oxygen and aluminium redistribution inside the gate stacks is obtained only in the backside configuration.

  13. Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictions*†

    Science.gov (United States)

    Mishenina, T.; Pignatari, M.; Côté, B.; Thielemann, F.-K.; Soubiran, C.; Basak, N.; Gorbaneva, T.; Korotin, S. A.; Kovtyukh, V. V.; Wehmeyer, B.; Bisterzo, S.; Travaglio, C.; Gibson, B. K.; Jordan, C.; Paul, A.; Ritter, C.; Herwig, F.; NuGrid Collaboration

    2017-08-01

    Atmospheric parameters and chemical compositions for 10 stars with metallicities in the region of -2.2 LTE) and non-LTE (NLTE) approaches. In particular, differences by assuming LTE or NLTE are about 0.10 dex; depending on [Fe/H], Teff, gravity and element lines used in the analysis. We find that the O abundance has the largest error, ranging from 0.10 and 0.2 dex. The best measured elements are Cr, Fe, and Mn; with errors between 0.03 and 0.11 dex. The stars in our sample were included in previous different observational work. We provide a consistent data analysis. The data dispersion introduced in the literature by different techniques and assumptions used by the different authors is within the observational errors, excepting for HD103095. We compare these results with stellar observations from different data sets and a number of theoretical galactic chemical evolution (GCE) simulations. We find a large scatter in the GCE results, used to study the origin of the elements. Within this scatter as found in previous GCE simulations, we cannot reproduce the evolution of the elemental ratios [Sc/Fe], [Ti/Fe], and [V/Fe] at different metallicities. The stellar yields from core-collapse supernovae are likely primarily responsible for this discrepancy. Possible solutions and open problems are discussed.

  14. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Karamat, S., E-mail: shumailakaramat@gmail.com [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey); COMSATS Institute of Information Technology, Islamabad 54000 (Pakistan); Sonuşen, S. [Sabancı Üniversitesi (SUNUM), İstanbul 34956 (Turkey); Çelik, Ü. [Nanomagnetics Instruments, Ankara (Turkey); Uysallı, Y. [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey); Oral, A., E-mail: orahmet@metu.edu.tr [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey)

    2016-04-15

    Graphical abstract: - Highlights: • Graphene layers were grown on Pt and Cu foil via ambient pressure chemical vapor deposition method and for the delicate removal of graphene from metal catalysts, electrolysis method was used by using different alkaline (sodium hydroxide, potassium hydroxide, lithium hydroxide and barium hydroxide). • The delamination speed of PMMA/graphene stack was higher during the KOH and LiOH electrolysis as compare to NaOH and Ba(OH){sub 2}. Ba(OH){sub 2} is not advisable because of the residues left on the graphene surface which would further trapped in between graphene and SiO{sub 2}/Si surface after transfer. The average peeling time in case of Pt electrode is ∼6 min for KOH and LiOH and ∼15 min for NaOH and Ba(OH){sub 2}. • Electrolysis method also works for the Cu catalyst. The peeling of graphene was faster in the case of Cu foil due to small size of bubbles which moves faster between the stack and the electrode surface. The average peeling time was ∼3–5 min. • XPS analysis clearly showed that the Pt substrates can be re-used again. Graphene layer was transferred to SiO{sub 2}/Si substrates and to the flexible substrate by using the same peeling method. - Abstract: In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH){sub 2} for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and Li

  15. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    International Nuclear Information System (INIS)

    Karamat, S.; Sonuşen, S.; Çelik, Ü.; Uysallı, Y.; Oral, A.

    2016-01-01

    Graphical abstract: - Highlights: • Graphene layers were grown on Pt and Cu foil via ambient pressure chemical vapor deposition method and for the delicate removal of graphene from metal catalysts, electrolysis method was used by using different alkaline (sodium hydroxide, potassium hydroxide, lithium hydroxide and barium hydroxide). • The delamination speed of PMMA/graphene stack was higher during the KOH and LiOH electrolysis as compare to NaOH and Ba(OH)_2. Ba(OH)_2 is not advisable because of the residues left on the graphene surface which would further trapped in between graphene and SiO_2/Si surface after transfer. The average peeling time in case of Pt electrode is ∼6 min for KOH and LiOH and ∼15 min for NaOH and Ba(OH)_2. • Electrolysis method also works for the Cu catalyst. The peeling of graphene was faster in the case of Cu foil due to small size of bubbles which moves faster between the stack and the electrode surface. The average peeling time was ∼3–5 min. • XPS analysis clearly showed that the Pt substrates can be re-used again. Graphene layer was transferred to SiO_2/Si substrates and to the flexible substrate by using the same peeling method. - Abstract: In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH)_2 for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and LiOH was ∼6 min and for NaOH and

  16. Immobilisation of ion exchange resins in cement

    International Nuclear Information System (INIS)

    Howard, C.G.; Jolliffe, C.B.; Lee, D.J.

    1990-02-01

    Over the last seven years, Low Oxidation State Metal Ion reagents (LOMI) have been used to decontaminate the 100 MW(e) Steam Generating Heavy Water Ractor (SGHWR) at Winfrith. The use of these reagents has resulted in a dilute ionic solution containing activation products which are produced by corrosion of metallic components in the reactor. It has been demonstrated that the amount of activity in the solution can be reduced using organic ion exchanger resins. These resins consist of a cross linked polystyrene with sulphonic acid or quaternary ammonium function groups and can be successfully immobilised in blended cement systems. The formulation which has been developed is produced from a 9 to 1 blend of ground granulated blast furnace slag (BFS) and ordinary Portland cement (OPC) containing 28% ion exchange resin in the water saturated form. If 6% Microsilica is added to the blended cement the waste loading can be increased to 36 w/o. (author)

  17. Stress corrosion crack initiation of alloy 182 weld metal in primary coolant - Influence of chemical composition

    Energy Technology Data Exchange (ETDEWEB)

    Calonne, O.; Foucault, M.; Steltzlen, F. [AREVA (France); Amzallag, C. [EDF SEPTEN (France)

    2011-07-01

    Nickel-base alloys 182 and 82 have been used extensively for dissimilar metal welds. Typical applications are the J-groove welds of alloy 600 vessel head penetrations, pressurizer penetrations, heater sleeves and bottom mounted instrumented nozzles as well as some safe end butt welds. While the overall performance of these weld metals has been good, during the last decade, an increasing number of cases of stress corrosion cracking of Alloy 182 weld metal have been reported in PWRs. In this context, the role of weld defects has to be examined. Their contribution in the crack initiation mechanism requires laboratory investigations with small scale characterizations. In this study, the influence of both alloy composition and weld defects on PWSCC (Stress Corrosion Cracking in Primary Water) initiation was investigated using U-bend specimens in simulated primary water at 320 C. The main results are the following: -) the chemical compositions of the weld deposits leading to a large propensity to hot cracking are not the most susceptible to PWSCC initiation, -) macroscopically, superficial defects did not evolve during successive exposures. They can be included in large corrosion cracks but their role as 'precursors' is not yet established. (authors)

  18. Electron transport characteristics of silicon nanowires by metal-assisted chemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yangyang; Wang, Zhen; Zhang, Mingliang; Wang, Xiaodong, E-mail: xdwang@semi.ac.cn; Ji, An; Yang, Fuhua [Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083 (China)

    2014-03-15

    The electron transport characteristics of silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching with different doping concentrations were studied. By increasing the doping concentration of the starting Si wafer, the resulting SiNWs were prone to have a rough surface, which had important effects on the contact and the electron transport. A metal-semiconductor-metal model and a thermionic field emission theory were used to analyse the current-voltage (I-V) characteristics. Asymmetric, rectifying and symmetric I-V curves were obtained. The diversity of the I-V curves originated from the different barrier heights at the two sides of the SiNWs. For heavily doped SiNWs, the critical voltage was one order of magnitude larger than that of the lightly doped, and the resistance obtained by differentiating the I-V curves at large bias was also higher. These were attributed to the lower electron tunnelling possibility and higher contact barrier, due to the rough surface and the reduced doping concentration during the etching process.

  19. Electron transport characteristics of silicon nanowires by metal-assisted chemical etching

    Directory of Open Access Journals (Sweden)

    Yangyang Qi

    2014-02-01

    Full Text Available The electron transport characteristics of silicon nanowires (SiNWs fabricated by metal-assisted chemical etching with different doping concentrations were studied. By increasing the doping concentration of the starting Si wafer, the resulting SiNWs were prone to have a rough surface, which had important effects on the contact and the electron transport. A metal-semiconductor-metal model and a thermionic field emission theory were used to analyse the current-voltage (I-V characteristics. Asymmetric, rectifying and symmetric I-V curves were obtained. The diversity of the I-V curves originated from the different barrier heights at the two sides of the SiNWs. For heavily doped SiNWs, the critical voltage was one order of magnitude larger than that of the lightly doped, and the resistance obtained by differentiating the I-V curves at large bias was also higher. These were attributed to the lower electron tunnelling possibility and higher contact barrier, due to the rough surface and the reduced doping concentration during the etching process.

  20. Electron transport characteristics of silicon nanowires by metal-assisted chemical etching

    Science.gov (United States)

    Qi, Yangyang; Wang, Zhen; Zhang, Mingliang; Wang, Xiaodong; Ji, An; Yang, Fuhua

    2014-03-01

    The electron transport characteristics of silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching with different doping concentrations were studied. By increasing the doping concentration of the starting Si wafer, the resulting SiNWs were prone to have a rough surface, which had important effects on the contact and the electron transport. A metal-semiconductor-metal model and a thermionic field emission theory were used to analyse the current-voltage (I-V) characteristics. Asymmetric, rectifying and symmetric I-V curves were obtained. The diversity of the I-V curves originated from the different barrier heights at the two sides of the SiNWs. For heavily doped SiNWs, the critical voltage was one order of magnitude larger than that of the lightly doped, and the resistance obtained by differentiating the I-V curves at large bias was also higher. These were attributed to the lower electron tunnelling possibility and higher contact barrier, due to the rough surface and the reduced doping concentration during the etching process.

  1. A chemical approach toward low temperature alloying of immiscible iron and molybdenum metals

    Energy Technology Data Exchange (ETDEWEB)

    Nazir, Rabia [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Applied Chemistry Research Centre, Pakistan Council of Scientific and Industrial Research Laboratories Complex, Lahore 54600 (Pakistan); Ahmed, Sohail [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Mazhar, Muhammad, E-mail: mazhar42pk@yahoo.com [Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Akhtar, Muhammad Javed; Siddique, Muhammad [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Khan, Nawazish Ali [Material Science Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shah, Muhammad Raza [HEJ Research Institute of Chemistry, University of Karachi, Karachi 75270 (Pakistan); Nadeem, Muhammad [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

    2013-11-15

    Graphical abstract: - Highlights: • Low temperature pyrolysis of [Fe(bipy){sub 3}]Cl{sub 2} and [Mo(bipy)Cl{sub 4}] homogeneous powder. • Easy low temperature alloying of immiscible metals like Fe and Mo. • Uniform sized Fe–Mo nanoalloy with particle size of 48–68 nm. • Characterization by EDXRF, AFM, XRPD, magnetometery, {sup 57}Fe Mössbauer and impedance. • Alloy behaves as almost superparamagnetic obeying simple –R(CPE)– circuit. - Abstract: The present research is based on a low temperature operated feasible method for the synthesis of immiscible iron and molybdenum metals’ nanoalloy for technological applications. The nanoalloy has been synthesized by pyrolysis of homogeneous powder precipitated, from a common solvent, of the two complexes, trisbipyridineiron(II)chloride, [Fe(bipy){sub 3}]Cl{sub 2}, and bipyridinemolybedenum(IV) chloride, [Mo(bipy)Cl{sub 4}], followed by heating at 500 °C in an inert atmosphere of flowing argon gas. The resulting nanoalloy has been characterized by using EDXRF, AFM, XRD, magnetometery, {sup 57}Fe Mössbauer and impedance spectroscopies. These results showed that under provided experimental conditions iron and molybdenum metals, with known miscibility barrier, alloy together to give (1:1) single phase material having particle size in the range of 48–66 nm. The magnetism of iron is considerably reduced after alloy formation and shows its trend toward superparamagnetism. The designed chemical synthetic procedure is equally feasible for the fabrication of other immiscible metals.

  2. An efficient laser vaporization source for chemically modified metal clusters characterized by thermodynamics and kinetics

    Science.gov (United States)

    Masubuchi, Tsugunosuke; Eckhard, Jan F.; Lange, Kathrin; Visser, Bradley; Tschurl, Martin; Heiz, Ulrich

    2018-02-01

    A laser vaporization cluster source that has a room for cluster aggregation and a reactor volume, each equipped with a pulsed valve, is presented for the efficient gas-phase production of chemically modified metal clusters. The performance of the cluster source is evaluated through the production of Ta and Ta oxide cluster cations, TaxOy+ (y ≥ 0). It is demonstrated that the cluster source produces TaxOy+ over a wide mass range, the metal-to-oxygen ratio of which can easily be controlled by changing the pulse duration that influences the amount of reactant O2 introduced into the cluster source. Reaction kinetic modeling shows that the generation of the oxides takes place under thermalized conditions at less than 300 K, whereas metal cluster cores are presumably created with excess heat. These characteristics are also advantageous to yield "reaction intermediates" of interest via reactions between clusters and reactive molecules in the cluster source, which may subsequently be mass selected for their reactivity measurements.

  3. A chemical approach toward low temperature alloying of immiscible iron and molybdenum metals

    International Nuclear Information System (INIS)

    Nazir, Rabia; Ahmed, Sohail; Mazhar, Muhammad; Akhtar, Muhammad Javed; Siddique, Muhammad; Khan, Nawazish Ali; Shah, Muhammad Raza; Nadeem, Muhammad

    2013-01-01

    Graphical abstract: - Highlights: • Low temperature pyrolysis of [Fe(bipy) 3 ]Cl 2 and [Mo(bipy)Cl 4 ] homogeneous powder. • Easy low temperature alloying of immiscible metals like Fe and Mo. • Uniform sized Fe–Mo nanoalloy with particle size of 48–68 nm. • Characterization by EDXRF, AFM, XRPD, magnetometery, 57 Fe Mössbauer and impedance. • Alloy behaves as almost superparamagnetic obeying simple –R(CPE)– circuit. - Abstract: The present research is based on a low temperature operated feasible method for the synthesis of immiscible iron and molybdenum metals’ nanoalloy for technological applications. The nanoalloy has been synthesized by pyrolysis of homogeneous powder precipitated, from a common solvent, of the two complexes, trisbipyridineiron(II)chloride, [Fe(bipy) 3 ]Cl 2 , and bipyridinemolybedenum(IV) chloride, [Mo(bipy)Cl 4 ], followed by heating at 500 °C in an inert atmosphere of flowing argon gas. The resulting nanoalloy has been characterized by using EDXRF, AFM, XRD, magnetometery, 57 Fe Mössbauer and impedance spectroscopies. These results showed that under provided experimental conditions iron and molybdenum metals, with known miscibility barrier, alloy together to give (1:1) single phase material having particle size in the range of 48–66 nm. The magnetism of iron is considerably reduced after alloy formation and shows its trend toward superparamagnetism. The designed chemical synthetic procedure is equally feasible for the fabrication of other immiscible metals

  4. Red cabbage yield, heavy metal content, water use and soil chemical characteristics under wastewater irrigation.

    Science.gov (United States)

    Tunc, Talip; Sahin, Ustun

    2016-04-01

    The objective of this 2-year field study was to evaluate the effects of drip irrigation with urban wastewaters reclaimed using primary (filtration) and secondary (filtration and aeration) processes on red cabbage growth and fresh yield, heavy metal content, water use and efficiency and soil chemical properties. Filtered wastewater (WW1), filtered and aerated wastewater (WW2), freshwater and filtered wastewater mix (1:1 by volume) (WW3) and freshwater (FW) were investigated as irrigation water treatments. Crop evapotranspiration decreased significantly, while water use efficiency increased under wastewater treatments compared to FW. WW1 treatment had the lowest value (474.2 mm), while FW treatments had the highest value (556.7 mm). The highest water use efficiency was found in the WW1 treatment as 8.41 kg m(-3), and there was a twofold increase with regard to the FW. Wastewater irrigation increased soil fertility and therefore red cabbage yield. WW2 treatment produced the highest total fresh yield (40.02 Mg ha(-1)). However, wastewater irrigation increased the heavy metal content in crops and soil. Cd content in red cabbage heads was above the safe limit, and WW1 treatment had the highest value (0.168 mg kg(-1)). WW3 treatment among wastewater treatments is less risky in terms of soil and crop heavy metal pollution and faecal coliform contamination. Therefore, WW3 wastewater irrigation for red cabbage could be recommended for higher yield and water efficiency with regard to freshwater irrigation.

  5. Composition and Morphology Control of Metal Dichalcogenides via Chemical Vapor Deposition for Photovoltaic and Nanoelectronic Applications

    Science.gov (United States)

    Samad, Leith L. J.

    The body of work reviewed here encompasses a variety of metal dichalcogenides all synthesized using chemical vapor deposition (CVD) for solar and electronics applications. The first reported phase-pure CVD synthesis of iron pyrite thin films is presented with detailed structural and electrochemical analysis. The phase-pure thin film and improved crystal growth on a metallic backing material represents one of the best options for potential solar applications using iron pyrite. Large tin-sulfur-selenide solid solution plates with tunable bandgaps were also synthesized via CVD as single-crystals with a thin film geometry. Solid solution tin-sulfur-selenide plates were demonstrated to be a new material for solar cells with the first observed solar conversion efficiencies up to 3.1%. Finally, a low temperature molybdenum disulfide vertical heterostructure CVD synthesis with layered controlled growth was achieved with preferential growth enabled by Van der Waals epitaxy. Through recognition of additional reaction parameters, a fully regulated CVD synthesis enabled the controlled growth of 1-6 molybdenum disulfide monolayers for nanoelectronic applications. The improvements in synthesis and materials presented here were all enabled by the control afforded by CVD such that advances in phase purity, growth, and composition control of several metal dichalcogenides were achieved. Further work will be able to take full advantage of these advances for future solar and electronics technologies.

  6. Chemical Speciation and Potential Mobility of Heavy Metals in the Soil of Former Tin Mining Catchment

    Directory of Open Access Journals (Sweden)

    M. A. Ashraf

    2012-01-01

    Full Text Available This study describes the chemical speciation of Pb, Zn, Cu, Cr, As, and Sn in soil of former tin mining catchment. Total five sites were selected for sampling and subsequent subsamples were collected from each site in order to create a composite sample for analysis. Samples were analysed by the sequential extraction procedure using optical emission spectrometry (ICP OES. Small amounts of Cu, Cr, and As retrieved from the exchangeable phase, the ready available for biogeochemical cycles in the ecosystem. Low quantities of Cu and As could be taken up by plants in these kind of acidic soils. Zn not detected in the bioavailable forms while Pb is only present in negligible amounts in very few samples. The absence of mobile forms of Pb eliminates the toxic risk both in the trophic chain and its migration downwards the soil profile. The results also indicate that most of the metals have high abundance in residual fraction indicating lithogenic origin and low bioavailability of the metals in the studied soil. The average potential mobility for the metals giving the following order: Sn > Cu > Zn > Pb > Cr > As.

  7. Fundamentals of Hydrocarbon Upgrading to Liquid Fuels and Commodity Chemicals over Catalytic Metallic Nanoparticles

    Science.gov (United States)

    Chen, Tao

    Promising new technologies for biomass conversion into fuels and chemical feedstocks rely on the production of bio-oils, which need to be upgraded in order to remove oxygen-containing hydrocarbons and water. A high oxygen concentration makes bio-oils acidic and corrosive, unstable during storage, and less energetically valuable per unit weight than petroleum-derived hydrocarbons. Although there are efficient processes for the production of bio-oils, there are no efficient technologies for their upgrading. Current technologies utilize traditional petroleum refining catalysts, which are not optimized for biomass processing. New upgrading technologies are, therefore, urgently needed for development of sustainable energy resources. Development of such new technologies, however, is severely hindered by a lack of fundamental understanding of how oxygen and oxygen-containing hydrocarbons derived from biomass interact with promising noble-metal catalysts. In this study, kinetic reaction measurements, catalyst characterization and quantum chemical calculations using density functional theory were combined for determining adsorption modes and reaction mechanisms of hydrocarbons in the presence of oxygen on surfaces of catalytic noble-metal nanoparticles. The results were used for developing improved catalyst formulations and optimization of reaction conditions. The addition of molybdenum to platinum catalysts was shown to improve catalytic activity, stability, and selectivity in hydrodeoxygenation of acetic acid, which served as a model biomass compound. The fundamental results that describe interactions of oxygen and hydrocarbons with noble-metal catalysts were extended to other reactions and fields of study: evaluation of the reaction mechanism for hydrogen peroxide decomposition, development of improved hydrogenation catalysts and determination of adsorption modes of a spectroscopic probe molecule.

  8. Spectroscopic investigation of Ni speciation in hardened cement paste.

    Science.gov (United States)

    Vespa, M; Dähn, R; Grolimund, D; Wieland, E; Scheidegger, A M

    2006-04-01

    Cement-based materials play an important role in multi-barrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. Cement is used to condition and stabilize the waste materials and to construct the engineered barrier systems (container, backfill, and liner materials) of repositories for radioactive waste. In this study, Ni uptake by hardened cement paste has been investigated with the aim of improving our understanding of the immobilization process of heavy metals in cement on the molecular level. X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance spectroscopy (DRS) techniques were used to determine the local environment of Ni in cement systems. The Ni-doped samples were prepared at two different water/cement ratios (0.4, 1.3) and different hydration times (1 hour to 1 year) using a sulfate-resisting Portland cement. The metal loadings and the metal salts added to the system were varied (50 up to 5000 mg/kg; NO3(-), SO4(2-), Cl-). The XAS study showed that for all investigated systems Ni(ll) is predominantly immobilized in a layered double hydroxide (LDH) phase, which was corroborated by DRS measurements. Only a minor extent of Ni(ll) precipitates as Ni-hydroxides (alpha-Ni(OH)2 and beta-Ni(OH)2). This finding suggests that Ni-Al LDH, rather than Ni-hydroxides, is the solubility-limiting phase in the Ni-doped cement system.

  9. Metal hydride/chemical heat-pump development project. Phase I. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Argabright, T.A.

    1982-02-01

    The metal hydride/chemical heat pump (MHHP) is a chemical heat pump containing two hydrides for the storage and/or recovery of thermal energy. It utilizes the heat of reaction of hydrogen with specific metal alloys. The MHHP design can be tailored to provide heating and/or cooling or temperature upgrading over a wide range of input and ambient temperatures. The system can thus be used with a variety of heat sources including waste heat, solar energy or a fossil fuel. The conceptual design of the MHHP was developed. A national market survey including a study of applications and market sectors was conducted. The technical tasks including conceptual development, thermal and mechanical design, laboratory verification of design and material performance, cost analysis and the detailed design of the Engineering Development Test Unit (EDTU) were performed. As a result of the market study, the temperature upgrade cycle of the MHHP was chosen for development. Operating temperature ranges for the upgrader were selected to be from 70 to 110/sup 0/C (160 to 230/sup 0/F) for the source heat and 140 to 190/sup 0/C (280 to 375/sup 0/F) for the product heat. These ranges are applicable to many processes in industries such as food, textile, paper and pulp, and chemical. The hydride pair well suited for these temperatures is LaNi/sub 5//LaNi/sub 4/ /sub 5/Al/sub 0/ /sub 5/. The EDTU was designed for the upgrade cycle. It is a compact finned tube arrangement enclosed in a pressure vessel. This design incorporates high heat transfer and low thermal mass in a system which maximizes the coefficient of performance (COP). It will be constructed in Phase II. Continuation of this effort is recommended.

  10. Savannah River Site chemical, metal, and pesticide (CMP) waste vitrification treatability studies

    International Nuclear Information System (INIS)

    Cicero, C.A.

    1997-01-01

    Numerous Department of Energy (DOE) facilities, as well as Department of Defense (DOD) and commercial facilities, have used earthen pits for disposal of chemicals, organic contaminants, and other waste materials. Although this was an acceptable means of disposal in the past, direct disposal into earthen pits without liners or barriers is no longer a standard practice. At the Savannah River Site (SRS), approximately three million pounds of such material was removed from seven chemical, metal, and pesticide disposal pits. This material is known as the Chemical, Metal, and Pesticide (CMP) Pit waste and carries several different listed waste codes depending on the contaminants in the respective storage container. The waste is not classified as a mixed waste because it is believed to be non-radioactive; however, in order to treat the material in a non-radioactive facility, the waste would first have to be screened for radioactivity. The Defense Waste Processing Technology (DWPT) Section of the Savannah River Technology Center (SRTC) was requested by the DOE-Savannah River (SR) office to determine the viability of vitrification of the CMP Pit wastes. Radioactive vitrification facilities exist which would be able to process this waste, so the material would not have to be analyzed for radioactive content. Bench-scale treatability studies were performed by the DWPT to determine whether a homogeneous and durable glass could be produced from the CMP Pit wastes. Homogeneous and durable glasses were produced from the six pits sampled. The optimum composition was determined to be 68.5 wt% CMP waste, 7.2 wt% Na 2 O, 9 wt% CaO, 7.2 wt% Li 2 O and 8.1 wt% Fe 2 O 3 . This glass melted at 1,150 C and represented a two fold volume reduction

  11. Effect of modified cementation technique on marginal fit and apical spread of excess cement for implant restorations: An in vitro study

    Directory of Open Access Journals (Sweden)

    Brijesh Patel

    2016-01-01

    Full Text Available Aim: To investigate and compare the vertical marginal discrepancy and spread of excess cement after cementation with modified cementation technique and conventional technique. Materials and Methods: Ten implant analogs with prefabricated standard abutments of similar dimensions were mounted individually in self-cure acrylic blocks subcrestally. Forty ideal metal coping specimens were prepared by conventional lost wax technique. Measurement of the marginal discrepancy at the implant-crown interface was done using a stereomicroscope before cementation. Abutment replicas (ARs were prepared for twenty specimens using cast copings and pattern resin. All forty copings were cemented according to the following cementation techniques and cement types, with ten specimens in each group. (1 Group 1: Half filling (HF cementation technique using provisional cement. (2 Group 2: HF cementation technique using permanent cement. (3 Group 3: AR technique using provisional cement. (4 Group 4: AR technique using permanent cement. Specimens were subjected to measurement of marginal discrepancy and spread of excess cement using stereomicroscope after cementation procedure. Data were analyzed using paired t-test and unpaired t-test. Results: AR technique showed significantly less marginal discrepancy (P = 0.000 and apical spread of excess cement (P = 0.002 than conventional HF technique. Provisional cement showed significantly more marginal discrepancy (HF-P = 0.000 and AR-P = 0.001 and less apical spread of excess cement (HF-P = 0.023 and AR-P = 0.002 and among both technique. Statistical Analysis: Unpaired t-test. Conclusion: An alternative technique of using AR is effective technique to prevent peri-implant diseases.

  12. Magnesium-phosphate-glass cements with ceramic-type properties

    Science.gov (United States)

    Sugama, T.; Kukacka, L.E.

    1982-09-23

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate, exhibits rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  13. Magnesium phosphate glass cements with ceramic-type properties

    Science.gov (United States)

    Sugama, Toshifumi; Kukacka, Lawrence E.

    1984-03-13

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate exhibiting rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  14. Acoustic monitoring techniques for corrosion degradation in cemented waste canisters

    International Nuclear Information System (INIS)

    Naish, C.C.; Buttle, D.; Wallace-Sims, R.; O'Brien, T.M.

    1991-01-01

    This report describes work to investigate acoustic emission as a non-intrusive monitor of corrosion and degradation of cemented wasteforms where the waste is a potentially reactive metal. The acoustic data collected shows good correlation with the corrosion rate as measured by hydrogen gas evolution rates and the electrochemically measured corrosion rates post cement hardening. The technique has been shown to be sensitive in detecting stress caused by expansive corrosion product within the cemented wasteform. The attenuation of the acoustic signal by the wasteform reduced the signal received by the monitoring equipment by a factor of 10 over a distance of approximately 150-400 mm, dependent on the water level in the cement. Full size packages were successfully monitored. It is concluded that the technique offers good potential for monitoring cemented containers of the more reactive metals, for example Magnox and aluminium. (author)

  15. Chemical study of the metal-rich globular cluster NGC 5927

    Science.gov (United States)

    Mura-Guzmán, A.; Villanova, S.; Muñoz, C.; Tang, B.

    2018-03-01

    Globular clusters (GCs) are natural laboratories where stellar and chemical evolution can be studied in detail. In addition, their chemical patterns and kinematics can tell us to which Galactic structure (disc, bulge, halo or extragalactic) the cluster belongs to. NGC 5927 is one of most metal-rich GCs in the Galaxy and its kinematics links it to the thick disc. We present abundance analysis based on high-resolution spectra of seven giant stars. The data were obtained using Fibre Large Array Multi Element Spectrograph/Ultraviolet Echelle Spectrograph (UVES) spectrograph mounted on UT2 telescope of the European Southern Observatory. The principal objective of this work is to perform a wide and detailed chemical abundance analysis of the cluster and look for possible Multiple Populations (MPs). We determined stellar parameters and measured 22 elements corresponding to light (Na, Al), alpha (O, Mg, Si, Ca, Ti), iron-peak (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and heavy elements (Y, Zr, Ba, Ce, Nd, Eu). We found a mean iron content of [Fe/H] = -0.47 ± 0.02 (error on the mean). We confirm the existence of MPs in this GC with an O-Na anti-correlation, and moderate spread in Al abundances. We estimate a mean [α/Fe] = 0.25 ± 0.08. Iron-peak elements show no significant spread. The [Ba/Eu] ratios indicate a predominant contribution from SNeII for the formation of the cluster.

  16. Chemical composition dispersion in bi-metallic nanoparticles: semi-automated analysis using HAADF-STEM

    International Nuclear Information System (INIS)

    Epicier, T.; Sato, K.; Tournus, F.; Konno, T.

    2012-01-01

    We present a method using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) to determine the chemical composition of bi-metallic nanoparticles. This method, which can be applied in a semi-automated way, allows large scale analysis with a statistical number of particles (several hundreds) in a short time. Once a calibration curve has been obtained, e.g., using energy-dispersive X-ray spectroscopy (EDX) measurements on a few particles, the HAADF integrated intensity of each particle can indeed be directly related to its chemical composition. After a theoretical description, this approach is applied to the case of iron–palladium nanoparticles (expected to be nearly stoichiometric) with a mean size of 8.3 nm. It will be shown that an accurate chemical composition histogram is obtained, i.e., the Fe content has been determined to be 49.0 at.% with a dispersion of 10.4 %. HAADF-STEM analysis represents a powerful alternative to fastidious single particle EDX measurements, for the compositional dispersion in alloy nanoparticles.

  17. Heavy Metal Levels and Physico-Chemical Quality of Potable Water Supply in Warri, Nigeria

    International Nuclear Information System (INIS)

    Nduka, K.C.; Orisakwe, E.O.

    2007-01-01

    The interaction between man's activities and the environment is gaining world wide attention. Warri an oil producing community in Delta State of Nigeria is faced with environmental oil pollution. Since open and underground water bodies are regarded as final recipients of most environmental pollutants, this study sought to provide data on the levels of the physico-chemical parameters and contaminants in Warri metropolitan water supply. This study investigated the cadmium, lead and chromium using Atomic Absorption Spectrophotometer, physico - chemical properties such as pH, temperature, total suspended solid TSS, total dissolved solid TDS, electrical conductivity EC, biological oxygen demand BOD, dissolved oxygen DO, chemical oxygen demand COD, and total coliform count of potable water sources in Warri. Ekpan River was found to have 1.2 mg/L of cadmium, 1.0mg/L of chromium, 1.20 mg/L of lead and 2.0 mg/L of manganese. The heavy metals levels and the pollution parameters were lowest in the borehole water samples, except pH which is more acidic in borehole water samples and conductivity which is more in well water samples in all the sampling stations. Some of the parameters were above WHO standards

  18. The Mechanism of Disintegration of Cement Concrete at High Temperatures

    Directory of Open Access Journals (Sweden)

    Jocius Vytautas

    2016-10-01

    Full Text Available Concrete is a composite material composed of a binder, aggregates, water and additives. Mixing of cement with water results in a number of chemical reactions known as cement hydration. Heating of concrete results in dehydration processes of cement minerals and new hydration products, which disintegrate the microstructure of concrete. This article reviews results of research conducted with Portland and alumina cement with conventional and refractory concrete aggregates. In civic buildings such common fillers as gravel, granite, dolomite or expanded clay are usually used. It is important to point out the differences between fillers because they constitute the majority of the concrete volume.

  19. Utilization of waste glass in ECO-cement: Strength properties and microstructural observations

    International Nuclear Information System (INIS)

    Sobolev, Konstantin; Tuerker, Pelin; Soboleva, Svetlana; Iscioglu, Gunsel

    2007-01-01

    Waste glass creates a serious environmental problem, mainly because of the inconsistency of the waste glass streams. The use of waste glass as a finely ground mineral additive (FGMA) in cement is a promising direction for recycling. Based on the method of mechano-chemical activation, a new group of ECO-cements was developed. In ECO-cement, relatively large amounts (up to 70%) of portland cement clinker can be replaced with waste glass. This report examines the effect of waste glass on the microstructure and strength of ECO-cement based materials. Scanning electron microscopy (SEM) investigations were used to observe the changes in the cement hydrates and interface between the cement matrix and waste glass particles. According to the research results, the developed ECO-cement with 50% of waste glass possessed compressive strength properties at a level similar to normal portland cement

  20. Portland-pfa cement: a comparison between intergrinding and blending

    Energy Technology Data Exchange (ETDEWEB)

    Monk, M

    1983-09-01

    Portland-pfa cements containing 20-40% (by weight) pfa have been prepared in the laboratory both by intergrinding the ashes with clinker and by blending with cement. Cement properties have been assessed according to BS 4550 and scanning electron microscopy was used to examine the effects of grinding upon the pfa particles. The work has shown that intergrinding leads to an improvement in the water-reducing properties of coarse pfas and also in their pozzolanic activity as indicated by compressive strength development at later ages. Setting times have been found to be essentially the same for blended and interground cements, both being considerably longer than for typical ordinary Portland cements. Thus the results of this investigation indicate that, provided pfa's are chemically acceptable, they can be used for Portland-pfa cement manufacture by intergrinding irrespective of their coarseness.

  1. Effect of amendments on chemical immobilization of heavy metals in sugar mill contaminated soils

    Directory of Open Access Journals (Sweden)

    Mohammad Jamal Khan, Muhammad Tahir Azeem and Sajida Perveen1

    2012-05-01

    Full Text Available A bulk soil sample collected from the vicinity of PSM (Premier Sugar Mill Mardan was amended with diammonium phosphate (DAP, triple super phosphate (TSP, Farm Yard Manure (FYM and poultry manure (PM in 1.5 kg soil in a 2 L plastic pot. Both DAP and TSP were added at 230 mg kg 1 (460 kg ha 1 soil whereas the organic amendments (FYM and PM were added at the rate of 10% by weight of soil. The air dried samples in pots were brought to field moisture content (0.33 bar water content by the addition of either HIE (Hayatabad Industrial Estate or PSM in two separate sets of experiments. The experimental pots were arranged in randomized complete design with three replicates under laboratory conditions during March to May (Temperature varying between 25 to 30 °C. Treated and control pots were incubated for 90 days al 0.33 bar ca 25% moisture and the moisture deficit during the incubation time was adjusted by adding PSM and HIE effluents in their respective set of experimental pots. Soil samples were collected after 15, 30, 45 and 90 d to determine the effect of amendments on AB-DTPA extractable metals. The results showed that AB-DTPA extractable Cd, Or, Cu, Ni and Cd increased significantly with lime and the maximum values were noted after 90 days incubation whereas the Fe, Mn and Zn content in soil increased with time but the increase was not significant. It was further noted that the increase over time in metal was not pronounced when supplied with amendments indicating their ability to chemically stabilize it compared to unamended soils. Higher values of all the heavy metals were noted in unamended soil. By comparing the different amendments, it was observed that FYM was effective in reducing the extractability/phytoavailability of all the metals under study except Pb whereby DAP was most effective as a stabilizing agent in the soil. It was concluded that in calcareous soil, FYM and DAP can be used to reduce the risk of phytotoxicity of heavy metals in

  2. PHYSICO-CHEMICAL PROPERTIES OF THE SOLID AND LIQUID WASTE PRODUCTS FROM THE HEAVY METAL CONTAMINATED ENERGY CROPS GASIFICATION PROCESS

    Directory of Open Access Journals (Sweden)

    Sebastian Werle

    2017-02-01

    Full Text Available The paper presents the results of basic physico-chemical properties of solid (ash and liquid (tar waste products of the gasification process of the heavy metal contaminated energy crops. The gasification process has carried out in a laboratory fixed bed reactor. Three types of energy crops: Miscanthus x giganteus, Sida hermaphrodita and Spartina Pectinata were used. The experimental plots were established on heavy metal contaminated arable land located in Bytom (southern part of Poland, Silesian Voivodship.

  3. PRODUCTION OF CATHODES AND HIGH PURITY TARGETS OF CHEMICALLY ACTIVE METALS BY MEANS OF ELECTRONIC-RAY MELTING

    Directory of Open Access Journals (Sweden)

    A. V. Alifanov

    2007-01-01

    Full Text Available The technical process of production and restoration of worn cathodes and targets of chemically active metals (Ti, Zr, V and others with the help of cathode ray in vacuum is developed. Regenerating of worn cathodes, targets is carried out by means of insertion in chill of worn base and successive cathode ray deposition on certain places of required quantity of metal (from 2 till 50mm.

  4. PHYSICAL, CHEMICAL, AND HEAVY METAL CONCENTRATIONS IN WATERS OF KAFR EL-ZAYAT AREA, ROSETTA BRANCH, RIVER NILE, EGYPT.

    OpenAIRE

    Heba I. A. El-Safty; Mohammed G. A. Gad; Wafai Z. A. Mikhail.

    2018-01-01

    Five sites in the water of Rosetta Branch were selected to investigate the physical, chemical, and heavy metal concentrations. In this study there are great variations in the studied parameters according to the distance from the source of pollution. Heavy metal concentrations are strongly affected by the industrial effluents produced from each of El-Mobidat, El-Malyia and Salt and Soda companies which directly discharge industrial effluents at this area without any treatments.

  5. A systematic chemical separation for thermal neutron activation analysis of seven noble metals in rock

    International Nuclear Information System (INIS)

    Ayabe, Muneo

    1980-01-01

    A method for the systematic activation analysis of seven noble metals - ruthenium, silver, rhenium, osmium, iridium, platinum and gold - in rocks were developed and examined with radiotracers and irradiated rock samples. After the fusion of the irradiated rock sample with sodium hydroxide and sodium peroxide, 10% sodium sulfide solution is added and rhenium is extracted with pyridine-benzene mixture from 6N sodium hydroxide solution. From the hydroxide-sulfide precipitate fraction, ruthenium and osmium are distilled as tetroxides, silver is precipitated as chloride, gold is extracted with ethyl acetate, and iridium and platinum are extracted with diantipyrylmethane. Each fraction is purified and subjected to the γ-ray spectrometry. Chemical yields for the elements are more than 60%. Determination limits are given for the seven elements. (author)

  6. Glass Formation, Chemical Properties and Surface Analysis of Cu-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Akihisa Inoue

    2011-04-01

    Full Text Available This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs. In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni and Cu–Zr–Ag–Al–(Nb bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

  7. Catalyst-free growth of InN nanorods by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Kim, Min Hwa; Moon, Dae Young; Park, Jinsub; Nanishi, Yasushi; Yi, Gyu-Chul; Yoon, Euijoon

    2012-01-01

    We demonstrated the growth of catalyst-free InN nanostructures including nanorods on (0001) Al 2 O 3 substrates using metal-organic chemical vapor deposition. As the growth time increased, growth rate along c-direction increased superlinearly with decreasing c-plane area fractions and increasing side wall areas. It was also found that desorption from the sidewalls of InN nanostructures during the InN nanorods formation was one of essential key parameters of the growth mechanism. We propose a growth model to explain the InN nanostructure evolution by considering the side wall desorption and re-deposition of indium at top c-plane surfaces. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. High mobility single-crystalline-like GaAs thin films on inexpensive flexible metal substrates by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Dutta, P.; Rathi, M.; Gao, Y.; Yao, Y.; Selvamanickam, V.; Zheng, N.; Ahrenkiel, P.; Martinez, J.

    2014-01-01

    We demonstrate heteroepitaxial growth of single-crystalline-like n and p-type doped GaAs thin films on inexpensive, flexible, and light-weight metal foils by metal-organic chemical vapor deposition. Single-crystalline-like Ge thin film on biaxially textured templates made by ion beam assisted deposition on metal foil served as the epitaxy enabling substrate for GaAs growth. The GaAs films exhibited strong (004) preferred orientation, sharp in-plane texture, low grain misorientation, strong photoluminescence, and a defect density of ∼10 7  cm −2 . Furthermore, the GaAs films exhibited hole and electron mobilities as high as 66 and 300 cm 2 /V-s, respectively. High mobility single-crystalline-like GaAs thin films on inexpensive metal substrates can pave the path for roll-to-roll manufacturing of flexible III-V solar cells for the mainstream photovoltaics market.

  9. Chemical and sequential analysis of some metals in sediments from the North Coast of the Gulf of Mexico

    International Nuclear Information System (INIS)

    Trinidad Martinez; Brenda Estanol; Miguel Angel Zuniga

    2016-01-01

    Sediments collected from the North Coast of the Gulf of Mexico got carefully mixed, dried, and finally subjected to physical and chemical analysis. Metal concentration was determined by energy dispersive X-ray fluorescence (EDXRF). Sequential chemical analysis was performed by modified TESSIER technique. Results and statistical analysis (α = 0.05) show concentrations of most elements (excepting Mn, Ca, Ga, As and Pb) in the range of those of the earth crust's values, which set a sampling zone base line. Sequential extraction shows the potential risk of mobilization of metals sequestered in particulate phases by oxidation of anoxic sediments or intense organic matter degradation. (author)

  10. Evaluation of physical, chemical and heavy metal concentration of food waste composting

    Directory of Open Access Journals (Sweden)

    Abdul Kadir Aeslina

    2017-01-01

    Full Text Available In this study, food waste composting with rice husk and coconut fibre as compost medium were carried out. Two types of different fermentation liquids were prepared which were fermented liquid (banana peel and fermented liquid from fermented soybeans. During the composting process, a compost samples for a twenty week duration at an interval time of two weeks. Among the physico-chemical parameters that were tested were temperature, moisture content, pH value, Total Nitrogen, Total Phosphorous, Potassium and Total Organic Carbon and Carbon Nitrogen ratio. Heavy metals such as copper, cadmium, lead, nickel and arsenic were observed and analysed. From this study, it was found that, the temperature increased during the thermophilic phase while there was gradually increase of Total Nitrogen, Total Phosphorous and Potassium from the beginning till the end of the composting process. It was also found that the total organic carbon (TOC and the carbon nitrogen ratio decreased significantly during the decomposition process. Traces amounts of heavy metals were also detected and remains below the standard Malaysian Environmental regulations. It was concluded that, the composting process was faster with processed food waste followed by combination of processed food waste and raw. Raw food waste were demonstrated the lowest degradation rate.

  11. Effects of Chemical Applications to Metal Polluted Soils on Cadmium Uptake by Rice Plant

    Directory of Open Access Journals (Sweden)

    Yoo J. H.

    2013-04-01

    Full Text Available Pot experiment using metal polluted soils was conducted to investigate the effects of lime, iron and sulfur on changes in Cd availability and uptake by rice plant. Drainage and irrigation of water were performed to develop redox changes like field cultivation. Iron chloride and sodium sulfate solutions were applied to the pots in the middle of growth period of rice plant. Reactive metal pool in heavily polluted soils was slightly decreased after treatments with lime, iron chloride, sodium sulfate and combination of these chemicals. However, cadmium uptake by rice plant was significantly different across the treatments and the extent of Cd pollution. For highly polluted soils, more Cd reduction was observed in iron chloride treatments. Cd content in polished rice for iron chloride and (iron chloride+organic matter treatments was only 16-23% and 25-37% compared to control and liming, respectively. Treatment of (iron chloride+sulfate rather increased Cd content in rice. For moderately polluted soils, Cd reduction rate was the order of (OM+iron chloride > iron chloride > lime. Other treatments including sulfate rather increased Cd content in rice maximum 3 times than control. It was proposed to determine the optimum application rate of iron for minimizing hazardous effect on rice plant.

  12. Chemical resistance of thin film materials based on metal oxides grown by atomic layer deposition

    International Nuclear Information System (INIS)

    Sammelselg, Väino; Netšipailo, Ivan; Aidla, Aleks; Tarre, Aivar; Aarik, Lauri; Asari, Jelena; Ritslaid, Peeter; Aarik, Jaan

    2013-01-01

    Etching rate of technologically important metal oxide thin films in hot sulphuric acid was investigated. The films of Al-, Ti-, Cr-, and Ta-oxides studied were grown by atomic layer deposition (ALD) method on silicon substrates from different precursors in large ranges of growth temperatures (80–900 °C) in order to reveal process parameters that allow deposition of coatings with higher chemical resistance. The results obtained demonstrate that application of processes that yield films with lower concentration of residual impurities as well as crystallization of films in thermal ALD processes leads to significant decrease of etching rate. Crystalline films of materials studied showed etching rates down to values of < 5 pm/s. - Highlights: • Etching of atomic layer deposited thin metal oxide films in hot H 2 SO 4 was studied. • Smallest etching rates of < 5 pm/s for TiO 2 , Al 2 O 3 , and Cr 2 O 3 were reached. • Highest etching rate of 2.8 nm/s for Al 2 O 3 was occurred. • Remarkable differences in etching of non- and crystalline films were observed

  13. Availability of heavy metals in contaminated soil evidenced by chemical extractants

    Directory of Open Access Journals (Sweden)

    Maria Ligia de Souza Silva

    2012-06-01

    Full Text Available Heavy metals have been accumulating in Brazilian soils, due to natural processes, such as atmospheric deposition, or human industrial activities. For certain heavy metals, when in high concentrations in the soil, there is no specific extractant to determine the availability of these elements in the soil. The objective of the present study was to evaluate the availability of Cd, Cu, Fe, Mn, Pb and Zn for rice and soybeans, using different chemical extractants. In this study we used seven soil samples with different levels of contamination, in completely randomized experimental design with four replications. We determined the available concentrations of Cd, Cu, Fe, Mn, Pb and Zn extracted by Mehlich-1, HCl 0.1 mol L-1, DTPA, and organic acid extractants and the contents in rice and soybeans, which extracts were analyzed by ICP-OES. It was observed that Mehlich-1, HCl 0.1 mol L-1 and DTPA extractants were effective to assess the availability of Cd, Cu, Pb and Zn for rice and soybeans. However, the same was not observed for the organic acid extractant.

  14. Chemical Reactions Catalyzed by Metalloporphyrin-Based Metal-Organic Frameworks

    Directory of Open Access Journals (Sweden)

    Kelly Aparecida Dias de Freitas Castro

    2013-06-01

    Full Text Available The synthetic versatility and the potential application of metalloporphyrins (MP in different fields have aroused researchers’ interest in studying these complexes, in an attempt to mimic biological systems such as cytochrome P-450. Over the last 40 years, synthetic MPs have been mainly used as catalysts for homogeneous or heterogeneous chemical reactions. To employ them in heterogeneous catalysis, chemists have prepared new MP-based solids by immobilizing MP onto rigid inorganic supports, a strategy that affords hybrid inorganic-organic materials. More recently, materials obtained by supramolecular assembly processes and containing MPs as building blocks have been applied in a variety of areas, like gas storage, photonic devices, separation, molecular sensing, magnets, and heterogeneous catalysis, among others. These coordination polymers, known as metal-organic frameworks (MOFs, contain organic ligands or complexes connected by metal ions or clusters, which give rise to a 1-, 2- or 3-D network. These kinds of materials presents large surface areas, Brønsted or redox sites, and high porosity, all of which are desirable features in catalysts with potential use in heterogeneous phases. Building MOFs based on MP is a good way to obtain solid catalysts that offer the advantages of bioinspired systems and zeolitic materials. In this mini review, we will adopt a historical approach to present the most relevant MP-based MOFs applicable to catalytic reactions such as oxidation, reduction, insertion of functional groups, and exchange of organic functions.

  15. Direct chemical reduction of neptunium oxide to neptunium metal using calcium and calcium chloride

    International Nuclear Information System (INIS)

    Squires, Leah N.; Lessing, Paul

    2016-01-01

    A process of direct reduction of neptunium oxide to neptunium metal using calcium metal as the reducing agent is discussed. After reduction of the oxide to metal, the metal is separated by density from the other components of the reaction mixture and can be easily removed upon cooling. The direct reduction technique consistently produces high purity (98%–99% pure) neptunium metal.

  16. Fractionation analysis of oxyanion-forming metals and metalloids in leachates of cement-based materials using ion exchange solid phase extraction.

    Science.gov (United States)

    Mulugeta, Mesay; Wibetoe, Grethe; Engelsen, Christian J; Lund, Walter

    2009-05-15

    A simple and versatile solid phase extraction (SPE) method has been developed to determine the anionic species of As, Cr, Mo, Sb, Se and V in leachates of cement mortar and concrete materials in the pH range 3-13. The anionic fractions of these elements were extracted using a strong anion exchanger (SAX) and their concentrations were determined as the difference in element concentration between the sample and the SAX effluent. Inductively coupled plasma mass spectrometry (ICP-MS) was used off-line to analyse solutions before and after passing through the SAX. The extraction method has been developed by optimizing sorbent type, sorbent conditioning and sample percolation rate. Breakthrough volumes and effect of matrix constituents were also studied. It was found that a polymer-based SAX conditioned with a buffer close to the sample pH or in some cases deionised water gave the best retention of the analytes. Optimal conditions were also determined for the quantitative elution of analytes retained on the SAX. Extraction of the cement mortar and concrete leachates showed that most of the elements had similar distribution of anions in both leachate types, and that the distribution was strongly pH dependent. Cr, Mo and V exist in anionic forms in strongly basic leachates (pH>12), and significant fractions of anionic Se were also detected in these solutions. Cr, Mo, Se and V were not determined as anions by the present method in the leachates of pH<12. Anionic As and Sb were found in small fractions in most of the leachates.

  17. Heat of hydration measurements on cemented radioactive wastes. Part 1: cement-water pastes

    International Nuclear Information System (INIS)

    Lee, D.J.

    1983-12-01

    This report describes the hydration of cement pastes in terms of chemical and kinetic models. A calorimetric technique was used to measure the heat of hydration to develop these models. The effects of temperature, water/cement ratio and cement replacements, ground granulated blast furnace slag (BFS) and pulverised fuel ash (PFA) on the hydration of ordinary Portland cement (OPC) is reported. The incorporation of BFS or PFA has a marked effect on the hydration reaction. The effect of temperature is also important but changing the water/cement ratio has little effect. Results from cement pastes containing only water and cement yield total heats of reaction of 400, 200 and 100 kJ/kg for OPC, BFS and PFA respectively. Using the results from the models which have been developed, the effect of major salts present in radioactive waste streams can be assessed. Values of the total heat of reaction, the time to complete 50 percent reaction, and the energy of activation, can be compared for different waste systems. (U.K.)

  18. Research Update: Mechanical properties of metal-organic frameworks – Influence of structure and chemical bonding

    Directory of Open Access Journals (Sweden)

    Wei Li

    2014-12-01

    Full Text Available Metal-organic frameworks (MOFs, a young family of functional materials, have been attracting considerable attention from the chemistry, materials science, and physics communities. In the light of their potential applications in industry and technology, the fundamental mechanical properties of MOFs, which are of critical importance for manufacturing, processing, and performance, need to be addressed and understood. It has been widely accepted that the framework topology, which describes the overall connectivity pattern of the MOF building units, is of vital importance for the mechanical properties. However, recent advances in the area of MOF mechanics reveal that chemistry plays a major role as well. From the viewpoint of materials science, a deep understanding of the influence of chemical effects on MOF mechanics is not only highly desirable for the development of novel functional materials with targeted mechanical response, but also for a better understanding of important properties such as structural flexibility and framework breathing. The present work discus