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Sample records for aluminous cement

  1. Barium aluminate cement: its application

    International Nuclear Information System (INIS)

    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

  2. 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

  3. Hydration and dimensional stability of calcium aluminate cement based systems

    OpenAIRE

    Bizzozero, Julien

    2014-01-01

    Calcium aluminate cements (CAC) are often used in combination with calcium sulfate and Portland cement for special applications where rapid setting, rapid drying and shrinkage compensation are required. A growing fraction of the clinker, which has the highest CO2 intensity, is being replaced by supplementary cementitious materials (SCM). These SCM are usually from industrial by-products such as slag, fly ashes or can simply be raw materials such as limestone. This project aims at replacing th...

  4. Effect of Microwave Processing on Aluminate Cement Clinkering

    Institute of Scientific and Technical Information of China (English)

    DONG Jianmiao; LONG Shizong

    2005-01-01

    When raw materials were preheated to 1000-1300 ℃ by electricity and microwave was inputted for 1 min 5 s-4 mins, then alunminate clinkers were obtained. The f-CaO contents,XRD patterns and lithofacies analysis show that the microwave processing accelerates the clinkering reaction,and Fe2O3 is contributed to the aluminate cement clinkering. The appearance of liquid phase in process of microwave heating increases the microwave absorbability of materials greatly.

  5. Calcium Aluminate based Cement as Dental Restorative Materials

    OpenAIRE

    Kraft, Lars

    2002-01-01

    This thesis presents the results from the development process of a ceramic dental filling material based on calcium aluminate cement. The main focus of the work concerns dimensional changes during setting, hardening and curing and the understanding of the factors controlling the dimensional stability of the system. A range of compositions for research purposes and the composition of Doxadent™ – a dental product launched on the Swedish market in October 2000 – were evaluated. Furthermore hardn...

  6. Accelerated carbonation of Friedel's salt in calcium aluminate cement paste

    International Nuclear Information System (INIS)

    The stability of Friedel's salt with respect to carbonation has been studied in calcium aluminate cement (CAC) pastes containing NaCl (3% of Cl- by weight of cement). Carbonation was carried out on a powdered sample in flowing 5% CO2 gas at 65% relative humidity to accelerate the process. At an intermediate carbonation step, a part of the sample was washed and dried up to 10 cycles to simulate a dynamic leaching attack. The two processes were followed by means of X-ray diffraction (XRD), pH and Cl- analyses in the simulated pore solution

  7. Another look at the deterioration of calcium aluminate cement concrete

    Directory of Open Access Journals (Sweden)

    Jambor, Jaromir

    1996-03-01

    Full Text Available Potential degradation of concrete structures made of calcium aluminate cement (CAC is well known and is caused by transformation (conversion of the thermodynamically metastable into stable calcium aluminate hydrate phases. This recrystallization is influenced by temperature and humidity; the structural degradation of the concrete itself thus its loss of strength, is strongly related to the pore structure of the hydrated cement paste, the critical parameters being the total volume of pores below 15-20 nm and the median micropore radius. This constitutes a novel procedure for evaluation of existing CAC concrete structure.

    La degradación potencial de estructuras de hormigón elaboradas con cemento aluminoso (CA es bien conocida. Este deterioro está causado por la recristalización (conversión de las fases del aluminato cálcico que son termodinámicamente metastables, en fases estables. En esta recristalización influye la temperatura y la humedad. Tanto la degradación del propio hormigón, como su pérdida de resistencias están relacionadas estrechamente con la estructura porosa de la pasta del cemento hidratado, siendo parámetros críticos el volumen total de los poros inferiores a 15-20 nm y el tamaño medio de los radios de los microporos. Esto constituye un nuevo procedimiento para evaluar las estructuras existentes de hormigón de cemento aluminoso (CA.

  8. Synthesis optimization of calcium aluminate cement phases for biomedical applications

    International Nuclear Information System (INIS)

    Calcium aluminate cement (CAC) has been studied as a potential material for applications in the areas of health such as, endodontics and bone reconstruction. These studies have been based on commercial products consisting of a mixture of phases. Improvements can be attained by investigating the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance for biomedical applications. Thus, the aim of this work was to study the CAC synthesis routes in the Al2O3-CaCO3 and Al2O3-CaO systems, as well as the phase characterization attained by means of X ray analysis. The Al2O3-CaO route enabled the production of the target phases (CA, CA2, C3A and C12A7) with a higher purity compared to the Al2O3-CaCO3 one. As a result the particular properties of these phases can be evaluated to define a more suitable composition that results in better properties for an endodontic cement and other applications. (author)

  9. Calcium aluminate cements for nuclear wastes conditioning: literature review and new approaches

    International Nuclear Information System (INIS)

    Encapsulate the diverse wastes produced by nuclear activities in cementitious binders may be very complex due to the adverse cement-waste interactions. Consequences are for example: strong delay, poor mechanical strength or low resistance to leaching. In this case, pure or blended calcium aluminate cements (CACs) may be valuable alternatives. This paper summarises the properties of CAC and blended CAC system and gives some examples from literature where calcium aluminate cements are used for conventional wastes or nuclear wastes conditioning. Moreover, it proposes another approach: using CAC not only as a binder, but also as a chemical reactant. After dissolution calcium aluminates ions can combine with many chemical species (sulphates, nitrates, chlorides, alkali metals, heavy metals) to precipitate specific hydrates allowing chemical trapping of these species. An example is given for the purification of Ni and Zn nitrates solutions. (authors)

  10. Corrosion Resistance of Calcium Aluminate Cement Concrete Exposed to a Chloride Environment

    OpenAIRE

    Ki Yong Ann; Chang-Geun Cho

    2014-01-01

    The present study concerns a development of calcium aluminate cement (CAC) concrete to enhance the durability against an externally chemically aggressive environment, in particular, chloride-induced corrosion. To evaluate the inhibition effect and concrete properties, CAC was partially mixed with ordinary Portland cement (OPC), ranging from 5% to 15%, as a binder. As a result, it was found that an increase in the CAC in binder resulted in a dramatic decrease in the setting time of fresh concr...

  11. Study of belite calcium sulfo-aluminate cement potential for zinc conditioning: From hydration to durability

    International Nuclear Information System (INIS)

    Calcium silicate cements are widely used for low- and intermediate-level radioactive waste conditioning. However, wastes produced by nuclear activities are very diverse and some of their components may chemically react with cement phases. For instance, ashes resulting from the incineration of technological wastes including neoprene and polyvinylchloride may contain substantial amounts of soluble zinc chloride. This compound is known to strongly delay or inhibit Portland cement setting. One approach to limit adverse cement-waste interactions is to select a binder showing a better compatibility with the waste while keeping cement matrix advantages (low cost, simple process, hydration with water provided by the waste...). This work thus investigates the potential of calcium sulfo-aluminate cement for zinc Zn(II) immobilization. Four aspects were considered: hydration (kinetics and products formed), properties of hydrated binders, mechanisms of zinc retention and durability of the cement pastes (based on leaching experiments and modelling). The influence of three main parameters was assessed: the gypsum content of the cement, the concentration of ZnCl2 and the thermal evolution at early age. It follows that materials based on a calcium sulfo-aluminate cement containing 20% gypsum are interesting candidates for zinc Zn(II) stabilization/solidification: there is no delay in hydration, mineralogy of the hydrated phases is slightly dependent on thermal history, mechanical strength is high, dimensional changes are limited and zinc Zn(II) is well immobilized, even if the cement paste is leached by pure water during a long period (90 d). (author)

  12. CITRIC ACID AS A SET RETARDER FOR CALCIUM ALUMINATE PHOSPHATE CEMENTS.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.; BROTHERS, L.E.

    2005-01-01

    Citric acid added as set retarder significantly contributed to enhancing the setting temperature and to extending the thickening time of a calcium aluminate phosphate (CaP) geothermal cement slurry consisting of calcium aluminate cement (CAC) as the base reactant and sodium polyphosphate (NaP) solution as the acid reactant. The set-retarding activity of citric acid was due to the uptake of Ca{sup 2+} ions from the CAC by carboxylic acid groups within the citric acid. This uptake led to the precipitation of a Ca-complexed carboxylate compound as a set-retarding barrier layer on the CAC grains' surfaces. However, this barrier layer was vulnerable to disintegration by the attack of free Ca{sup 2+} ions from CAC, and also to degradation at elevated temperature, thereby promoting the generation of exothermic energy from acid-base reactions between the CAC and NaP after the barrier was broken. The exothermic reaction energy that was promoted in this way minimized the loss in strength of the citric acid-retarded cement. The phase composition assembled in both retarded and non-retarded cements after autoclaving at 180 C encompassed three reaction products, hydroxyapatite (HOAp), hydrogrossular and boehmite, which are responsible for strengthening the autoclaved cement. The first two reaction products were susceptible to reactions with sulfuric acid and sodium sulfate to form crystalline bassanite scale as the corrosion product. The boehmite phase possessed a great resistance to acid and sulfate. Although the bassanite scales clinging to the cement's surfaces were the major factor governing the loss in weight, they served in protecting the cement from further acid- and sulfate-corrosion until their spallation eventually occurred. Nevertheless, the repetitive processes of HOAp and hydrogrossular {yields} bassanite {yields} spallation played an important role in extending the useful lifetime of CaP cement in a low pH environment at 180 C.

  13. Physical and Mechanical Properties of Composites Made with Aluminous Cement and Basalt Fibers Developed for High Temperature Application

    OpenAIRE

    Pavel Reiterman; Ondřej Holčapek; Marcel Jogl; Petr Konvalinka

    2015-01-01

    Present paper deals with the experimental study of the composition of refractory fiber-reinforced aluminous cement based composites and its response to gradual thermal loading. Basalt fibers were applied in doses of 0.25, 0.5, 1.0, 2.0, and 4.0% in volume. Simultaneously, binder system based on the aluminous cement was modified by fine ground ceramic powder originated from the accurate ceramic blocks production. Ceramic powder was dosed as partial replacement of used cement of 5, 10, 15, 20, ...

  14. Reactions of fly ash with calcium aluminate cement and calcium sulphate

    OpenAIRE

    Fernández Carrasco, Lucía; Vázquez Ramonich, Enric

    2009-01-01

    The hydration processes in the ternary system fly ash/calcium aluminate cement/calcium sulphate (FA/CAC/C$) at 20 °C were investigated; six compositions from the ternary system FA/CAC/C$ were selected for this study. The nature of the reaction products in these pastes were analysed by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). At four days reaction time, the main hydration reaction product in these pastes was ettringite and the samples with major initial CAC presented minor ett...

  15. Conditioning highly concentrated borate solutions with calcium sulfo-aluminate cement

    International Nuclear Information System (INIS)

    The early age hydration by borate solution of 3 calcium sulfo-aluminate cements (CSA), containing respectively 0%, 10% and 20% of gypsum by weight of cement was studied using isothermal calorimetry and dynamic mode rheo-metry. XRD and TGA analysis were carried out on pastes with increasing hydration degrees (up to 90 days) to specify the mineralogy and to figure out the mechanisms of borate immobilisation. It has been shown that the retarding effect of borate anions is due to the precipitation of the amorphous calcium borate C2B3H8; borate anions were then incorporated in Aft-type phases. The macroscopic properties of hydrated binders (compressive strength, length change) were also followed during 180 days. It appears that the mechanical strength continuously increases with the hydration degree. Length changes under wet-curing and sealed bag remain moderate and seem to be stabilized after 180 days

  16. The effect of supplementary pulverized fuel ash on calcium aluminate phosphate cement for intermediate-level waste encapsulation

    International Nuclear Information System (INIS)

    The objective of the current study was to evaluate the effects of supplementary pulverized fuel ash on phosphate-modified calcium aluminate cement. These systems are being established as part of a wider project to develop alternative cementing systems for the encapsulation of problematic low- and intermediate- level radioactive waste in the UK. The nuclear industry has established specific processing and property criteria, which must be fulfilled to ensure suitability for industrial application. In a series of studies, pulverized fuel ash was used as a partial replacement for calcium aluminate cement, to improve the fluidity of the system and increase the setting time. Properties such as slurry pH and fluidity, setting time, mechanical properties, and porosity were investigated using Vicat, Colflow, and compressive strength testing equipment and mercury intrusion porosimetry. The hardened cement pastes were also characterised using X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. A formulation envelope was identified, which fulfilled the plant acceptance tests defined by industry to ensure suitability for industrial application. It was found that pH of calcium aluminate phosphate cements is lower than that of conventional cementing systems used to encapsulate radioactive waste in the UK. Hence, they have potential to be used as an alternative cementing system for the encapsulation of problematic radioactive metals. (authors)

  17. Impact of Nano-Cr2O3 Addition on the Properties of Aluminous Cements Containing Spinel

    Directory of Open Access Journals (Sweden)

    Sasan OTROJ

    2015-05-01

    Full Text Available In this paper, the effect of nano-Cr2O3 addition on the properties of aluminous cement containing MgAl2O4 spinel was investigated. For this reason, the raw dolomite was used as raw material along with calcined alumina for the preparation of the aluminous cement. Then, the compositions containing different amounts of nano-Cr2O3 particles were fired at 1450 °C and their mineralogical compositions and microstructures were investigated. The setting times of prepared cements were measured after grounding and ball-milling. Besides, the slag resistance of refractory castables containing prepared cements was evaluated. The results showed that nano-Cr2O3 addition has effect on the increasing of spinel and CA2 and decreasing of CA and C12A7 phases in the cement composition. The decreasing of C12A7 leads to increasing of setting times of cement. Besides, the slag resistance of refractory castables containing prepared cements is improved due to increasing of spinel and decreasing of C12A7 amount in the cement composition.

  18. Re-examining the prospects of aluminous cements based on alkali-earth and rare-earth oxides

    International Nuclear Information System (INIS)

    In the family of aluminous cements the potential of strontium aluminate, the strontium-barium aluminate and the barium aluminate cements have been sporadically and incoherently studied over several decades in various parts of the world and more particularly in the East European countries without much wide-spread commercial success. Attempts had also been made to extend the exploratory studies to the (Ca, Sr, Ba)O-Al2O3-ZrO2-HfO2 system to synthesize super-refractory binders. In fact, the above compositions, prima facie, seem to have the potential of arriving at cementitious formulations that, apart from being super-refractory, may as well be highly resistant to seawater, X-rays and gamma radiation. Looking at these potentials, quite a few experimental studies have been carried out under the guidance and supervision of the present author. The present paper is an endeavour to collate the data on some of these systems both from the published literature as well as from the author's findings. The prime motive has been to review and re-assess the prospects of manufacturing a range of new aluminous binders with superior properties.

  19. BLENDED CALCIUM ALUMINATE-CALCIUM SULFATE CEMENT-BASED GROUT FOR P-REACTOR VESSEL IN-SITU DECOMMISSIONING

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Stefanko, D.

    2011-03-10

    The objective of this report is to document laboratory testing of blended calcium aluminate - calcium hemihydrate grouts for P-Reactor vessel in-situ decommissioning. Blended calcium aluminate - calcium hemihydrate cement-based grout was identified as candidate material for filling (physically stabilizing) the 105-P Reactor vessel (RV) because it is less alkaline than portland cement-based grout which has a pH greater than 12.4. In addition, blended calcium aluminate - calcium hemihydrate cement compositions can be formulated such that the primary cementitious phase is a stable crystalline material. A less alkaline material (pH {<=} 10.5) was desired to address a potential materials compatibility issue caused by corrosion of aluminum metal in highly alkaline environments such as that encountered in portland cement grouts [Wiersma, 2009a and b, Wiersma, 2010, and Serrato and Langton, 2010]. Information concerning access points into the P-Reactor vessel and amount of aluminum metal in the vessel is provided elsewhere [Griffin, 2010, Stefanko, 2009 and Wiersma, 2009 and 2010, Bobbitt, 2010, respectively]. Radiolysis calculations are also provided in a separate document [Reyes-Jimenez, 2010].

  20. Blended Calcium Aluminate-Calcium Sulfate Cement-Based Grout For P-Reactor Vessel In-Situ Decommissioning

    International Nuclear Information System (INIS)

    The objective of this report is to document laboratory testing of blended calcium aluminate - calcium hemihydrate grouts for P-Reactor vessel in-situ decommissioning. Blended calcium aluminate - calcium hemihydrate cement-based grout was identified as candidate material for filling (physically stabilizing) the 105-P Reactor vessel (RV) because it is less alkaline than portland cement-based grout which has a pH greater than 12.4. In addition, blended calcium aluminate - calcium hemihydrate cement compositions can be formulated such that the primary cementitious phase is a stable crystalline material. A less alkaline material (pH ≤ 10.5) was desired to address a potential materials compatibility issue caused by corrosion of aluminum metal in highly alkaline environments such as that encountered in portland cement grouts (Wiersma, 2009a and b, Wiersma, 2010, and Serrato and Langton, 2010). Information concerning access points into the P-Reactor vessel and amount of aluminum metal in the vessel is provided elsewhere (Griffin, 2010, Stefanko, 2009 and Wiersma, 2009 and 2010, Bobbitt, 2010, respectively). Radiolysis calculations are also provided in a separate document (Reyes-Jimenez, 2010).

  1. X-AFm stabilization as a mechanism of bypassing conversion phenomena in calcium aluminate cements

    International Nuclear Information System (INIS)

    Phase conversion phenomena are often observed in calcium aluminate cements (CACs), when the water-rich hydrates (e.g., CAH10, C2AH8) formed at early ages, at temperatures ≤ 30 °C, expel water in time to form more compact, less water-rich structures (C3AH6). The phase conversions follow a path regulated by the thermodynamic stabilities (solubilities) of phases. Based on this premise, it is proposed that conversion phenomena in CACs can be bypassed by provoking the precipitation of phases more preferred than those typically encountered along the conversion pathway. Therefore, X-AFm formation (where in this case, X = NO3−) triggered by the sequential addition of calcium nitrate (Ca(NO3)2 = CN) additives is identified as a new means of bypassing conversion. A multi-method approach comprising X-ray diffraction (XRD), thermal analytics, and evaluations of the compressive strength is applied to correlate phase balances and properties of CAC systems cured at 25 °C and 45 °C. The results highlight the absence of the C3AH6 phase across all systems and the curing conditions considered, with enhanced strengths being noted, when sufficient quantities of CN are added. The experimental outcomes are supported by insights gained from thermodynamic calculations which highlight thermodynamic selectivity as a means of regulating and controlling the evolutions of solid phase balances using inorganic salts in CACs, and more generally in cementing material systems

  2. Contribution to the study of wastes stabilization by sulfo-aluminate cement

    International Nuclear Information System (INIS)

    Calcium sulfo-aluminate cement is mainly composed of yeelimite known to be a precursor of ettringite formation. Ettringite is able to incorporate several heavy metals by isomorphous substitutions without altering its crystalline structure. The design of a binder required for immobilizing heavy metals was undertaken. The hydration study of clinker, and cement containing 4 amounts of gypsum has been carried out by means of XRD, DTA and IR spectrometry. It was pointed out that the addition of gypsum enhances hydration. Two binders were selected: 80/20 and 70/30. The immobilisation of 7 pollutants was very successful. Nevertheless, damages appeared with the binder 70/30 containing sodium chromate and dichromate: sodium caused activation of yeelimite reactivity and important dissolution of gypsum leading to important ettringite production. With a great amount of gypsum (30 %), dissolution led to secondary ettringite formation which damaged the hardened paste. Adding polyol enhances the retention of sodium chromate. On the other hand, the immobilisation of two types of weakly radioactive wastes supplied by CEA has been made. Results obtained in terms of setting time, compressive strength and leaching were excellent. (author)

  3. Influence of a dental ceramic and a calcium aluminate cement on dental biofilm formation and gingival inflammatory response

    OpenAIRE

    Konradsson, Katarina

    2007-01-01

    Dental restorative materials interact with their surrounding oral environment. Interaction factors can be release of toxic components and/or effects on biofilm formation and gingiva. In the end of the nineties, a calcium aluminate cement (CAC) was manufactured as a “bioceramic” alternative to resin composite. Dental ceramics are considered to be chemically stable and not to favour dental biofilm formation. Since the influence of aged, resin-bonded ceramic coverages is not fully investigated a...

  4. Early age corrosion of aluminium in calcium sulfo-aluminate cement based composites

    International Nuclear Information System (INIS)

    At present, encapsulation of low level and intermediate level nuclear wastes using Portland Cement (PC) based matrices is a preferred approach. However, it is now widely accepted that the high pH of the pore solution of these PC-based matrices (usually above pH 12.5) can cause concerns over the stability of certain wastes containing reactive metals, such as aluminium and uranium. One potential low pH system for reducing the corrosion of aluminium is calcium sulfo-aluminate cement (CSA). However, significant heat could be generated from the hydration of CSA, causing another concern to the nuclear industry. In the current study, various additives, namely pulverized fuel ash (PFA), ground granulated blast furnace slag (GGBS) and limestone powder (LSP) were used to replace part of the CSA in order to reduce the heat output. The results indicated that the replacement of CSA with GGBS, PFA and LSP can reduce the heat output of 100% CSA, although it is still higher than the control GGBS/PC 9:1 system. The corrosion rate of aluminium in each of the CSA composites was slightly higher than 100% CSA, however, all the CSA systems had corrosion rates lower than GGBS/PC 9:1 after 15 hours. Therefore, the composite CSA systems investigated in this study provide a good compromise between the heat output and the resistance to the corrosion of aluminium. Hence, offers a good potential for dealing with some historical nuclear wastes where the corrosion of aluminium is a concern. (authors)

  5. Solidification/stabilization of toxic metals in calcium aluminate cement matrices

    International Nuclear Information System (INIS)

    Highlights: • Reliable encapsulation and effective sorption of Pb, Zn and Cu on CAC was proved. • Cu and Pb were fully retained in the CAC mortar, while Zn was retained in 99.99%. •A maximum sorption capacity ca. 60 mg/g CAC was attained for Cu. • Three different PSD patterns were established as a function of XRD phase assemblage. • Some metal-loaded mortars achieved suitable mechanical strengths for landfilling. -- Abstract: The ability of calcium aluminate cement (CAC) to encapsulate toxic metals (Pb, Zn and Cu) was assessed under two curing conditions. Changes in the consistency and in the setting time were found upon the addition of the nitrates of the target metals. Both Pb and Cu caused a delay in CAC hydration, while Zn accelerated the stiffening of the mortar. Compressive strengths of the metal-doped mortars, when initially cured at 60 °C/100% RH, were comparable with that of the free-metal mortar. Three different pore size distribution patterns were identified and related to the compounds identified by XRD and SEM. Sorbent capacities of CAC for the toxic metals were excellent: a total uptake was achieved for up to 3 wt.% loading of the three metals. In this way, CAC mortars were perfectly able to encapsulate the toxic metals, allowing the use of CAC for waste management as proved by the leaching tests

  6. A neutron-diffraction study of changes induced in aluminous cement paste by the application of external electric fields

    International Nuclear Information System (INIS)

    The influence of an external DC voltage in an aluminous cement paste has been studied by in situ neutron diffraction, by monitoring the evolution of CaAl2O4 and Ca3Al2(OH)12 at different distances from the electrodes. The microstructure of the whole aluminous paste becomes dramatically altered. Both phases have been more attacked in zones closer to the electrodes. Major changes took place in the zone next to the positive electrode, in which the anhydrous phase has disappeared completely and the Ca3Al2(OH)12, has decreased significantly. In the cathodic zone, a decrease is also noticed due to the aluminium amphoteric character. The noticeable background diffraction increase in the area close to the positive electrode has been attributed to the formation of an amorphous alumina-like-gel that incorporated water to its composition

  7. Photocatalytic NOx abatement by calcium aluminate cements modified with TiO2: Improved NO2 conversion

    International Nuclear Information System (INIS)

    Photocatalytic activity of TiO2 was studied in two types of calcium aluminate cement (CAC) under two different curing regimes. The effect of the TiO2 addition on the setting time, consistency and mechanical properties of the CACs was evaluated. The abatement of gaseous pollutants (NOx) under UV irradiation was also assessed. These cementitious matrices were found to successfully retain NO2: more abundant presence of aluminates in white cement (w-CAC, iron-lean) helped to better adsorb NO2, thus improving the conversion performance of the catalyst resulting in a larger NOx removal under UV irradiation. As evidenced by XRD, SEM, EDAX and zeta potential analyses, the presence of ferrite in dark cement (d-CAC, iron-reach) induced a certain chemical interaction with TiO2. The experimental findings suggest the formation of new iron titanate phases, namely pseudobrookite. The reduced band-gap energy of these compounds compared with that of TiO2 accounts for the photocatalytic activity of these samples

  8. Quantitative determination of tricalcicum aluminate in portland cement by X-ray diffraction

    Directory of Open Access Journals (Sweden)

    Sagrera Moreno, José Luis

    1989-06-01

    Full Text Available Tricalcium aluminate (C3A is one of the constitutive phase of the cement-clinker. Its concentration influences the cement behaviour in sulphate aggressive soils. Therefore its quantification is very convenient and International standards fix its content when the concrete is used in contact with soils or liquids containing sulphate compounds. There are two possibilities in order to calculate the amount of C3A in clinker phases: one consist in a mathematical calculation from the results of the chemical analysis (Bogue formulae and the order is based in X-ray diffraction, using the height of the representative peak of the C3A phase. In the present note, the experimental procedure in order to determine the C3A content from X-ray test is presented.

    El aluminato tricáicico es una de las fases constitutivas del clinker de cemento portland. Su concentración en el cemento influye en el comportamiento de éste, en las obras sometidas a la posible agresividad de diferentes sulfatos cuando entran en contacto con las estructuras que se fabrican con él. Por ello la determinación de su concentración es un dato que puede invalidar su uso en una obra. De ahí que las normas internacionales fijen la cantidad de aluminato tricáicico según se clasifique la agresividad del entorno en el que una estructura será colocada. Existen fórmulas matemáticas para calcular la concentración de cada una de las fases del clinker a partir de las concentraciones de los elementos químicos de clinker expresados en forma de óxidos. Los posibles errores en los análisis químicos producen errores en los cálculos de las concentraciones de cada fase. Para determinar la concentración de dichas fases se puede emplear también la técnica de difracción de rayos X, basándose en la medida de la altura del pico representativo de la fase que se quiere determinar.

  9. Effect of alumina film prepared by pack cementation aluminizing and thermal oxidation treatment of stainless steels on hydrogen permeation

    International Nuclear Information System (INIS)

    A technique concerned in preparing Al2O3 barrier film on the surface of stainless steels (00Cr17Ni14Mo2 and 1Cr18Ni9Ti) was studied. In order to test the permeation behavior, hydrogen was used to simulate the deuterium and tritium. Firstly, pack cementation aluminizing process was adopted to form a aluminum rich layer on the surface of stainless steels. The composition, structure and morphology of the layers were characterized by metallography, XRD and SEM. The aluminizing layer shows the compact structure and mainly FeAl phase. The layer shows multiplayer characteristics, which consists of inner layer (25 μm), external layer (5 μm) and transitional layer (30 μm). The good adherence can be seen between the sub-layers and the interface between the layer and substrate as observed by metallography. The mass fraction of the element Al in the aluminizing layer exceeds to 30%. Then the thermal oxidation processes were taken on the aluminized layer to form the Al2O3 film. The phase structure, the surface morphology, and three-dimension morphology of the Al2O3 film were characterized by the XRD, SEM/EDS and SPM. The thickness of Al2O3 film was tested by the ellipsometry technique. It shows that an even and compact Al2O3 film was grown on the aluminizing layer. The film thickness is about 0.6 μm in case of oxidization for 2 h at 900 degree C and 3 Pa oxygen pressure. In order to examine the hydrogen permeation property of the materials, the hydrogen permeation treatment were taken to both the treated and untreated alloys. Then the amount of hydrogen in the surface region of the alloys was measured by elastic recoil detection (ERD) method. It is found that the atomic content of hydrogen droppes gradually with the increasing depth of the surface. And the atomic content of hydrogen at the distance of 0.2 μm from the surface is 0.007% that is about to the hydorgen composition of the stainless steel originally. This implies that the hydrogen atoms can not be diffused

  10. Processing and characterisation of Calcium SulfoAluminate (CSA) eco-cements coated with a hybrid organo-inorganic material for photocatalytic applications

    OpenAIRE

    Morales-Cantero, Alejandro; Cabeza, Aurelio; De la Torre, Ángeles G.; Aranda, M. A. G.; Santacruz, Isabel

    2015-01-01

    On the one hand, Calcium SulfoAluminate (CSA) eco-cements are receiving increasing attention since their manufacture produces up to 40% less CO2 than ordinary Portland cement (OPC). In addition, they show interesting properties such as high early-age strengths, short setting times, impermeability, sulfate and chloride corrosion resistance and low alkalinity. On the other hand, water treatment is a key issue and it will become much more important in the decades ahead. We have developed a p...

  11. Trials to solidify a Zn-containing low level radioactive sludge with calcium sulfo-aluminate cement

    International Nuclear Information System (INIS)

    It is well-known that Zn2+ acts as a strong retarder or even an inhibitor for the setting and hardening reaction of Portland cement. Calcium sulfo-aluminate (CSA) cement was expected to be the best solution to solidify the Zn-containing sludge in this study, because it generates an Ettringite-phase during hydration in which the Zn2+ can be integrated. With a commercially available CSA cement it was possible to develop recipes with a sufficient percentage of wet waste volume and a passable range of consistency for all existent water contents. The compressive strength of these recipes varied between 20 and 40 MPa depending on how much waste was in the recipe and how much water the waste contained. With water and sulfate resistance conforming to the guideline B05, the compressive strength was above the required 10 MPa in all cases. Additionally the linear expansion incl. layers was always clearly lower than the limiting 2%. The disadvantage of the recipes was superficial disintegration of the samples during leaching. One effect is that one can easily scrape off material from the surface of the samples, another is that flakes of material from the leached samples can be found on the bottom of leach bottles. For these reasons the development of a recipe for the solidification of the Zn-sludge is still a work in progress. (author)

  12. Beneficial use of a cell coupling rheometry, conductimetry, and calorimetry to investigate the early age hydration of calcium sulfo-aluminate cement

    International Nuclear Information System (INIS)

    A specific cell was designed to monitor simultaneously the evolution of the viscoelastic properties, electrical conductivity, and temperature of a cement paste with ongoing hydration. Hydration of calcium sulfo-aluminate cement by demineralized water or by a borated solution was then investigated as an example. Borate anions acted as set retarders but to a smaller extent than with ordinary Portland cement. The delay in cement hydration resulted from the precipitation of an amorphous or poorly crystallized calcium borate, which also caused a rapid stiffening (and thus a loss of workability) of the paste after mixing. The gypsum content of the CSA cement was shown to play a key role in the control of the cement reactivity. (authors)

  13. CaO-based pellets supported by calcium aluminate cements for high-temperature CO2 capture.

    Science.gov (United States)

    Manovic, Vasilije; Anthony, Edward J

    2009-09-15

    The development of highly efficient CaO-based pellet sorbents, using inexpensive raw materials (limestones) or the spent sorbent from CO2 capture cycles, and commercially available calcium aluminate cements (CA-14, CA-25, Secar 51, and Secar 80), is described here. The pellets were prepared using untreated powdered limestones or their corresponding hydrated limes and were tested for their CO2 capture carrying capacities for 30 carbonation/calcination cycles in a thermogravimetric analyzer (TGA). Their morphology was also investigated by scanning electron microscopy (SEM) and their compositions before and after carbonation/calcination cycleswere determined by X-ray diffraction (XRD). Pellets prepared in this manner showed superior behavior during CO2 capture cycles compared to natural sorbents, with the highest conversions being > 50% after 30 cycles. This improved performance was attributed to the resulting substructure of the sorbent particles, i.e., a porous structure with nanoparticles incorporated. During carbonation/calcination cycles mayenite (Ca12Al14O33) was formed, which is believed to be responsible for the favorable performance of synthetic CaO-based sorbents doped with alumina compounds. An added advantage of the pellets produced here is their superior strength, offering the possibility of using them in fluidized bed combustion (FBC) systems with minimal sorbent loss due to attrition. PMID:19806751

  14. The reactivity of volatized silica on volatized silica-alumina-aluminous cement system

    International Nuclear Information System (INIS)

    The use of volatized silica as surface agent on the low and ultra-low cement castables, is responsible for changes in the hydration kinetics and the kind of hydrated phases, as well as leading to packing enhancement. Besides, it can be responsible or not for the alterations in the phase assembly after firing the mixes at temperatures around 1350 C. Due its amorphous character and submicrometer particle size (0.1um), it would be expected a high reactivity of this material. Apparently this is not the case contrarily to what was reported in the literature. The phases were characterized by X-ray diffraction. (author)

  15. Ceramic joining through reactive wetting of alumina with calcium aluminate refractory cements

    Indian Academy of Sciences (India)

    K Geetha; A M Umarji; T R N Kutty

    2000-08-01

    Compositions in CaO–Al2O3 system have been prepared by gel–to–crystallite conversion method. Reactive powders of 1 : 2, 1 : 1, 2 : 1 and 3 : 1 of CaO and Al2O3 compositions were obtained by calcining the product at 800–1200°C. Fine grained powders were used as refractory cement for joining alumina ceramics. An optimum temperature of 1450°C for 4 h produced joints of satisfactory strength. The microstructure and X-ray phase analysis of the fractured joint surface clearly indicate reactive wetting of the alumina ceramics. This wetting enhances the joining of alumina substrates and can be attributed to the formation of Ca12Al14O33 liquid phase. The results are explained by using CaO–Al2O3 phase diagram.

  16. Leaching of a simulated ZnCl2-rich radwaste stabilized with calcium sulfo-aluminate cement: experimental investigation and first attempt of modelling

    International Nuclear Information System (INIS)

    This paper reports the first leaching experiments performed on a simulated ZnCl2-rich waste stabilized with calcium sulfo-aluminate cement according to a standard test developed to understand and model the degradation processes of the cement paste. A simulated cemented waste form (cement paste prepared with a binder containing 20% gypsum and a 0.5 mol/L ZnCl2 mixing solution, and submitted to a thermal cycle at early age simulating the temperature rise and fall occurring in a 200 L drum of cemented waste) was submitted to leaching by pure water (fixed pH of 7) for 3 months. The cumulative quantities of Ca2+, OH-, Cl- and SO42- ions in the leachates increased linearly versus the square root of time, showing that leaching was controlled by diffusion. Zinc was never detected, showing the excellent confining properties of the cement matrix. Examination of the solid sample at the end of the experiment revealed three zones: (i) the highly porous and friable surface layer, composed of aluminum hydroxide, perovskite and probably C-(A)-S-H (thickness: 700 μm), (ii) a less porous intermediate zone in which several precipitation and dissolution fronts occurred (thickness: 1800 μm), and (iii) the sound core. The hydrated phase evolution along depth was qualitatively reproduced with a model coupling transport by diffusion and chemical reactions. (authors)

  17. Photocatalytic NO{sub x} abatement by calcium aluminate cements modified with TiO{sub 2}: Improved NO{sub 2} conversion

    Energy Technology Data Exchange (ETDEWEB)

    Pérez-Nicolás, M. [MIMED Research Group, Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, c/Irunlarrea, 1, 31008 Pamplona (Spain); Balbuena, J.; Cruz-Yusta, M.; Sánchez, L. [Department of Inorganic Chemistry, School of Sciences, University of Córdoba, Campus de Rabanales, Edificio Marie Curie, 14071 Córdoba (Spain); Navarro-Blasco, I.; Fernández, J.M. [MIMED Research Group, Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, c/Irunlarrea, 1, 31008 Pamplona (Spain); Alvarez, J.I., E-mail: jalvarez@unav.es [MIMED Research Group, Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, c/Irunlarrea, 1, 31008 Pamplona (Spain)

    2015-04-15

    Photocatalytic activity of TiO{sub 2} was studied in two types of calcium aluminate cement (CAC) under two different curing regimes. The effect of the TiO{sub 2} addition on the setting time, consistency and mechanical properties of the CACs was evaluated. The abatement of gaseous pollutants (NO{sub x}) under UV irradiation was also assessed. These cementitious matrices were found to successfully retain NO{sub 2}: more abundant presence of aluminates in white cement (w-CAC, iron-lean) helped to better adsorb NO{sub 2}, thus improving the conversion performance of the catalyst resulting in a larger NO{sub x} removal under UV irradiation. As evidenced by XRD, SEM, EDAX and zeta potential analyses, the presence of ferrite in dark cement (d-CAC, iron-reach) induced a certain chemical interaction with TiO{sub 2}. The experimental findings suggest the formation of new iron titanate phases, namely pseudobrookite. The reduced band-gap energy of these compounds compared with that of TiO{sub 2} accounts for the photocatalytic activity of these samples.

  18. Effect of the strontium aluminate and hemihydrate contents on the properties of a calcium sulphoaluminate based cement

    Directory of Open Access Journals (Sweden)

    Velazco, G.

    2014-09-01

    Full Text Available The effect of strontium aluminate (SrAl2O4 on the hydration process of a calcium sulphoaluminate (C4A3Ŝ cement was investigated. Cement pastes were prepared by mixing C4A3Ŝ , hemihydrate (CaSO4· ½H2O, CŜH0.5 and 0, 10 or 20wt% of SrAl2O4 (SrA. The amount of CŜH0.5 was 15, 20 or 25wt% based on the C4A3Ŝ quantity. The cement pastes were hydrated using water to cement ratios (w/c of 0.4 and 0.5. Samples were cured from 1 to 28 d. The compressive strength and setting time were evaluated and the hydration products were characterized. It was found that the setting time was delayed up to 42 min for the samples containing SrAl2O4 compared to samples without addition. The samples with 25wt% hemihydrate containing 20wt% SrAl2O4 developed the highest compressive strength (60 MPa after 28 d of curing. The main product after hydration was ettringite (C6AŜ3H32. The morphology of this phase consisted of thin needle-shaped crystals.Se investigó el efecto de la adición de aluminato de estroncio (SrAl2O4 sobre las propiedades de un cemento de sulfoaluminato de calcio (C4A3Ŝ. Se prepararon muestras mezclando C4A3Ŝ, hemihidrato (CaSO4· ½H2O, CŜH0.5 y 0, 10 o 20% e.p de SrAl2O4 (SrA. La cantidad de CŜH0.5 fue de 15, 20 o 25% e.p. basado en la cantidad de C4A3Ŝ. Las relaciones agua/cemento utilizadas fueron 0.4 y 0.5. Las muestras fueron curadas hasta 28 d. Se evaluó el tiempo de fraguado y la resistencia a la compresión. Los productos de hidratación se caracterizaron mediante DRX y MEB. El tiempo de fraguado se retardó hasta 42 minutos con la adición del SrAl2O4 comparado con las muestras sin adiciones. Las muestras con 25% e.p. de yeso y 20% e.p. de SrAl2O4 desarrollaron la mayor resistencia a la compresión alcanzando 60 MPa a 28 d de curado. Los análisis por MEB y DRX muestran como principal producto de hidratación a la etringita (C6AŜ3H32, cuya morfología se observa como cristales aciculares.

  19. Effect of Tartaric Acid on Hydration of a Sodium-Metasilicate-Activated Blend of Calcium Aluminate Cement and Fly Ash F

    Directory of Open Access Journals (Sweden)

    Tatiana Pyatina

    2016-05-01

    Full Text Available An alkali-activated blend of aluminum cement and class F fly ash is an attractive solution for geothermal wells where cement is exposed to significant thermal shocks and aggressive environments. Set-control additives enable the safe cement placement in a well but may compromise its mechanical properties. This work evaluates the effect of a tartaric-acid set retarder on phase composition, microstructure, and strength development of a sodium-metasilicate-activated calcium aluminate/fly ash class F blend after curing at 85 °C, 200 °C or 300 °C. The hardened materials were characterized with X-ray diffraction, thermogravimetric analysis, X-ray computed tomography, and combined scanning electron microscopy/energy-dispersive X-ray spectroscopy and tested for mechanical strength. With increasing temperature, a higher number of phase transitions in non-retarded specimens was found as a result of fast cement hydration. The differences in the phase compositions were also attributed to tartaric acid interactions with metal ions released by the blend in retarded samples. The retarded samples showed higher total porosity but reduced percentage of large pores (above 500 µm and greater compressive strength after 300 °C curing. Mechanical properties of the set cements were not compromised by the retarder.

  20. Calcium aluminate cement concrete: durablllty and conversión. A fresh look at an old subject

    Directory of Open Access Journals (Sweden)

    George, C. M.

    1992-12-01

    Full Text Available This paper re-examines the relationship between durability and conversion of calcium aluminate cement concretes, CACC. Conversion is a natural and inevitable process whereby these materials reach a stable mature condition. Numerous structures built more than half a century ago remain serviceable and in service today. Some of these are illustrated. They are the best testament to the durability of converted concrete having survived far longer in the converted than the unconverted condition. The unique rapid hardening characteristics of CACC offer a valuable selfheating capability. Conversión is immediate and this leads to better long term strengths because more cement is hydrated. Moreover, recent work has shown that the thermodynamically stable hydrates of converted CAC are intrinsically more resistant to attack from such aggressive agents as sulphuric acid. This provides an explanation of the excellent long term performance of Fondu concretes, for example in many saewer applications. Our knowledge and understanding today of the durability of calcium alumínate bonded materials has been built on close to 100 years of accumulated experience and laboratory studies. We know how to use these materials and we know what to expect from them. We can be confident that they will serve us well in the century ahead.

    Este trabajo examina de nuevo la relación entre durabilidad y conversión de hormigones de cemento aluminoso, HAC (High Alumina Cement. La conversión es un proceso natural e inevitable a través del cual este material consigue una condición definitiva y estable. Numerosas estructuras que se edificaron hace más de medio siglo siguen utilizables y utilizadas hoy en día. Algunas de estas estructuras vienen ilustradas en este trabajo. Ellas sirven como mejor ejemplo de la durabilidad del hormigón convertido, ya que han sobrevivido mucho más tiempo en el estado convertido que en el no convertido. Las singulares caracter

  1. Leaching of calcium sulfo-aluminate cement pastes by water at regulated pH and temperature: Experimental investigation and modeling

    International Nuclear Information System (INIS)

    Two cement pastes, prepared with a ye'elimite-rich calcium sulfo-aluminate binder containing 0% or 20% gypsum, were leached by water at regulated pH (7) and temperature (20 C) for three months with the aim of understanding and modeling the degradation processes. The cumulative quantities of Ca2+, OH- and SO42- ions in the leachates increased linearly versus the square root of time, showing that leaching was controlled by diffusion. The gypsum-free material exhibited the highest decalcification rate. Examination of the solid samples after three months revealed three zones: - the surface layer, highly porous and composed of AH3, perovskite and possibly C-(A)-S-H, - an intermediate zone, less porous, in which several precipitation and dissolution fronts occurred, and - the sound core. The hydrated phase evolution along depth was accurately determined and qualitatively reproduced with a model coupling transport by diffusion and chemical reactions. (authors)

  2. Study of the ultrasonic waves action on the preparation of calcium aluminates cements; Estudo da acao das ondas ultrasonicas na sintese de cimentos de aluminatos de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Lourenco, R.R.; Exposito, C.C.D.; Rodrigues, J.A., E-mail: josear@ufscar.b [Universidade Federal de Sao Carlos (DEMa/GEMM/UFScar), SP (Brazil). Dept. de Engenharia de Materiais. Grupo de Engenharia de Microestrutura de Materiais

    2009-07-01

    Calcium aluminates cements were prepared through a route that uses the sonochemical process. In this process, calcia and alumina in an aqueous suspension are put under an ultrasonic bath during some time. After that, the water is evaporated and the material is heat treated. In this work, the action of ultrasonic waves were studied on initials molar compositions calcia:alumina of 1:1. It was also verified the influence of the water on the reactivity of initial solids. SEM and X-ray diffraction were used to characterize the obtained materials. In addition, mechanical strength of the products was evaluated through splitting tensile tests. The X-ray diffractograms showed that the presence of the water was enough to form hydrated compounds. However the material subjected to the sonochemical process presented the highest mechanical strength, indicating the potential of this route of synthesis. (author)

  3. Synthesis optimization of calcium aluminate cement phases for biomedical applications; Avaliacao da sintese das fases de cimento de aluminato de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, T.L.; Santos, G.L.; Oliveira, I.R. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil); Pandolfelli, V.C. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2011-07-01

    Calcium aluminate cement (CAC) has been studied as a potential material for applications in the areas of health such as, endodontics and bone reconstruction. These studies have been based on commercial products consisting of a mixture of phases. Improvements can be attained by investigating the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance for biomedical applications. Thus, the aim of this work was to study the CAC synthesis routes in the Al{sub 2}O{sub 3}-CaCO{sub 3} and Al{sub 2}O{sub 3}-CaO systems, as well as the phase characterization attained by means of X ray analysis. The Al{sub 2}O{sub 3}-CaO route enabled the production of the target phases (CA, CA{sub 2}, C{sub 3}A and C{sub 12}A{sub 7}) with a higher purity compared to the Al2O3-CaCO3 one. As a result the particular properties of these phases can be evaluated to define a more suitable composition that results in better properties for an endodontic cement and other applications. (author)

  4. INFLUENCE OF CURING TEMPERATURE ON THE PHYSICO-MECHANICAL, CHARACTERISTICS OF CALCIUM ALUMINATE CEMENT WITH AIR-COOLED SLAG OR WATER-COOLED SLAG

    Directory of Open Access Journals (Sweden)

    M. Heikal

    2004-12-01

    Full Text Available The nature, sequence, crystallinity and microstructure of hydrated phases were analyzed using differential scanning calorimetry (DSC, X-ray diffraction (XRD and scanning electron microscopy (SEM. The results showed that the formation of different hydrated phases was temperature dependence. The physico-mechanical and microstructural characteristics were investigated after curing at 20, 40 and 60° C. The results indicated that for the substitution of calcium aluminate cement (CAC by air-cooled slag (AS or water-cooled slag (WS at 20° C, the compressive strength increases with slag content up to 10 wt.%, then followed by a decrease with further slag substitution up to 25 wt.%; but the values are still higher than those of the neat CAC pastes at different curing ages up to 60 days. After 28 days of hydration at 40-60° C, the compressive strength increases with the slag content. This is attributed to the prevention of the conversion reaction, which was confirmed by XRD, DSC and SEM techniques, and the preferential formation of stratlingite (gehleinte-like phase. The SEM micrographs showed a close texture of hydrated CAC/slag blends made with AS or WS at 40°C due to the formation of C2ASH8 and C-S-H phases.

  5. Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Eun-Hee [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 151-744 (Korea, Republic of); Yoo, Jun-Sang [Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Seoul 110-749 (Korea, Republic of); Kim, Bo-Hye; Choi, Sung-Woo [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 151-744 (Korea, Republic of); Hong, Seong-Hyeon, E-mail: shhong@snu.ac.kr [Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2014-02-15

    Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.

  6. Role of aluminous component of fly ash on the durability of Portland cement-fly ash pastes in marine environment

    International Nuclear Information System (INIS)

    The durability, of mixtures of two kinds of Spanish fly ashes from coal combustion (ASTM class F) with 0, 15 and 35% replacement of Portland cement by fly ash, in a simulated marine environment (Na2SO4+NaCl solution of equivalent concentration to that of sea water: 0.03 and 0.45 M for sulphate and chloride, respectively), has been studied for a period of 90 days. The resistance of the different mixtures to the attack was evaluated by means of the Koch-Steinegger test. The results showed that all the mixtures were resistant, in spite of the great amount of Al2O3 content of the fly ash. The diffusion of SO42-, Na+ and Cl- ions through the pore solution activated the pozzolanic reactivity of the fly ashes causing the corresponding microstructure changes, which were characterized by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). As a result, the flexural strength of the mixtures increased, principally for the fly ash of a lower particle size and 35% of addition

  7. Evaluation of pH, calcium ion release and antimicrobial activity of a new calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    Fernanda de Carvalho Panzeri Pires-de-Souza

    2013-07-01

    Full Text Available This study evaluated the pH, calcium ion release and antimicrobial activity of EndoBinder (EB, containing different radiopacifiers: bismuth oxide (Bi2O3, zinc oxide (ZnO or zirconium oxide (ZrO2, in comparison to MTA. For pH and calcium ion release tests, 5 specimens per group (n = 5 were immersed into 10 mL of distilled and deionized water at 37°C. After 2, 4, 12, 24, 48 h; 7, 14 and 28 days, the pH was measured and calcium ion release quantified in an atomic absorption spectrophotometer. For antimicrobial activity, the cements were tested against S. aureus, E. coli, E. faecalis and C. albicans, in triplicate. MTA presented higher values for pH and calcium ion release than the other groups, however, with no statistically significant difference after 28 days (p > 0.05; and the largest inhibition halos for all strains, with no significant difference (E. coli and E. faecalis for pure EB and EB + Bi2O3 (p > 0.05. EB presented similar performance to that of MTA as regards pH and calcium ion release; however, when ZnO and ZrO2 were used, EB did not present antimicrobial activity against some strains.

  8. A LOW TEMPERATURE ALUMINIZING TREATMENT OF HOT WORK TOOL STEEL

    OpenAIRE

    Matijević, Božidar

    2013-01-01

    Conventional aluminizing processes by pack cementation are typically carried out at elevated temperatures. A low temperature powder aluminizing technology was applied to the X40CrMoV5-1 hot tool steel. The aluminizing temperature was from 550 °C to 620 °C. Effects of temperature and time on the microstructure and phase evolution were investigated. Also, the intermetallic layer thickness was measured in the aluminized layer of a steel substrate. The cross-sectional microstructures, the alumini...

  9. Hydration kinetics for the alite, belite, and calcium aluminate phase in Portland cements from 27Al and 29Si MAS NMR spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Jensen, Ole Mejlhede; Jakobsen, Hans Jørgen

    1997-01-01

    29Si magic-angle spinning (MAS) NMR spectroscopy is shown to be a valuable tool for obtaining the quantities of alite and belite in hydrated Portland cements. The hydration (1-180 days) of a white Portland cement with 10 wt.% silica fume added is investigated and the degrees of hydration for alit...... belite, and silica fume are determined. It is demonstrated that 27Al MAS NMR spectra of hydrated Portland cements can give quantitative information about the formation of ettringite and the conversion of this phase to monosulphate during hydration....

  10. Cimento aluminoso e seus efeitos em concretos refratários magnesianos espinelizados in situ Calcium aluminate cement and its effects on in-situ spinel containing magnesia refractory castables

    Directory of Open Access Journals (Sweden)

    D. H Milanez

    2010-03-01

    Full Text Available O uso de concretos refratários alumina-magnésia ligados por cimento aluminoso (CAC apresenta vantagens decorrentes da presença de espinélio e de CA6 (CaO.6Al2O3, ambas formadas in-situ e acompanhadas de expansão. Estas fases possuem alta resistência a escórias básicas e ao choque térmico, propriedades estas imprescindíveis para aplicação em panelas siderúrgicas. Estudos anteriores mostraram que o teor de CAC utilizado em concretos alumina-magnésia influencia a expansão do material, principalmente devido à formação de CA6. Este trabalho visa estudar a influência do teor de cimento no sistema magnésia-alumina, utilizando-se a mesma matriz de um concreto alumina-magnésia tradicional. Os resultados indicaram que o CAC influencia na estabilidade volumétrica do sistema MgO-espinélio: quanto menor o teor de CAC, menor a retração das amostras. Isso refletiu na sinterização dos concretos e, assim, nas propriedades mecânicas após queima em temperaturas elevadas.Calcium aluminate cement (CAC bonded alumina-magnesia refractory castables present great advantages for steel ladle applications as a result of in-situ expansive formation of spinel and CA<6, which leads to high basic slag and thermal shock resistance. The CAC content in those castables strongly influences its expansive behavior mainly due to CA6 formation. In the present work, the effects of the CAC content in magnesia-alumina castables were analyzed. The results showed that calcium aluminate cement affects the volumetric stability of MgO-spinel system: the lower the CAC content, the lower the shrinkage. These effects on the sintering and in the mechanical properties after sintering at high temperatures are also presented and discussed.

  11. Microstructure and oxidation behaviour of aluminized coating of inconel 625

    International Nuclear Information System (INIS)

    Microstructural and oxidation characteristics of aluminized coated Inconel 625 have been examined using scanning electron microscopy (SEM) and fine-probe spot and linescan EDS microanalysis techniques. The formation of slowly growing adherent metallic coatings is essential for protection against the severe environments. Aluminising of the superalloy samples was carried out by pack cementation process at 900 deg. C. in an argon atmosphere. The samples were subsequently oxidized in air at various temperatures to examine performance of the pack aluminized coated alloy. The microstructural changes that occurred in the aluminized layer at various exposure temperature and time were examined to study the oxidation behavior and formation of different phases in the aluminized coating deposited on Inconel 625. (author)

  12. Magnesium Aluminate Spinel

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan

    2012-01-01

    1 ScopeThis standard specifies the terms, definitions,classifications,technical requirements,test methods,inspection rules, packing, marking, transportation,storage,and quality certificate of magnesium aluminate spinel.

  13. Improvement of Cement Strength by Induction Method

    Institute of Scientific and Technical Information of China (English)

    YANG Li-yuan; LIN Zong-shou

    2004-01-01

    The induction method of improving the strength of Portland cement by adding fine slag powder,high aluminate component and hydrated paste was investigated through determining the physical properties,hydration heat and pore size distribution,and its mechanism was discussed.The experimental results reveal that a certain content of high aluminate component,fine slag powder and hydrated paste can improve remarkably the strength of Portland cement.

  14. Impact of welan gum on tricalcium aluminate-gypsum hydration

    Energy Technology Data Exchange (ETDEWEB)

    Ma Lei, E-mail: malei198713@163.com; Zhao Qinglin, E-mail: zhaoqinglin@whut.edu.cn; Yao Chukang; Zhou Mingkai

    2012-02-15

    The retarding effect of welan gum on tricalcium aluminate-gypsum hydration, as a partial system of ordinary Portland cement (OPC) hydration, was investigated with several methods. The tricalcium aluminate-gypsum hydration behavior in the presence or absence of welan gum was researched by field emission gun scanning electron microscopy, X-ray diffraction and zeta potential analysis. Meanwhile, we studied the surface electrochemical properties and adsorption characteristics of welan gum by utilizing a zeta potential analyzer and UV-VIS absorption spectrophotometer. By adding welan gum, the morphology change of ettringite and retardation of hydration stages in tricalcium aluminate-gypsum system was observed. Moreover, we detected the adsorption behavior and zeta potential inversion of tricalcium aluminate and ettringite, as well as a rapid decrease in the zeta potential of tricalcium aluminate-gypsum system. The reduction on nucleation rate of ettringite and hydration activity of C{sub 3}A was also demonstrated. Thus, through the adsorption effect, welan gum induces a retarding behavior in tricalcium aluminate-gypsum hydration. Highlights: Black-Right-Pointing-Pointer Adsorption characteristics of welan gum on C{sub 3}A and ettringite have been studied. Black-Right-Pointing-Pointer C{sub 3}A-gypsum hydration behavior and the hydration products are examined in L/S = 3. Black-Right-Pointing-Pointer Welan gum retards the process of C{sub 3}A-gypsum hydration. Black-Right-Pointing-Pointer The addition of welan gum changes the nucleation growth of ettringite.

  15. Limestone reaction in calcium aluminate cement–calcium sulfate systems

    International Nuclear Information System (INIS)

    This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction

  16. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  17. Effect of silica fume additions on the hydration behaviour of calcium aluminates

    OpenAIRE

    Fumo, Daniel A.; Segadães, Ana M.

    1997-01-01

    In the recent refractory castables technology, the calcium aluminate cement is being replaced in increasing proportion by very fine matrix components, such as silica fume and colloidal alumina. More efficient particle packing and the resulting lower water requirements have been the proposed explanation for the improved green density and strength, without sacrificing the castable workability. However, the aluminates are still responsible for the hydraulic setting of the castable. The hydration...

  18. Carbonation of ternary building cementing materials

    OpenAIRE

    Fernández Carrasco, Lucía; Torrens Martín, David; Martínez Ramírez, Sagrario

    2012-01-01

    The carbonation processes of ettringite and calcium aluminate hydrates phases developed by hydration of calcium aluminate cement, fly ash and calcium sulphate ternary mixtures have been studied. The hydrated samples were submitted to 4% of CO2 in a carbonation chamber, and were analysed, previous carbonation and after 14 and 90 days of carbonation time, by infrared spectroscopy and X-ray diffraction; the developed morphology was performed with the 14 days carbonated samples. The results evide...

  19. Hydration of Portland cement with additions of calcium sulfoaluminates

    Energy Technology Data Exchange (ETDEWEB)

    Le Saout, Gwenn, E-mail: gwenn.le-saout@mines-ales.fr [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Lothenbach, Barbara [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hori, Akihiro [DENKA Chemicals GmbH, Wehrhahn-Center, Cantadorstr. 3, D-40211 Duesseldorf (Germany); Higuchi, Takayuki [Denki Kagaku Kogyo Kabushiki Kaisha (DENKA), Omi, Itoigawa, Niigata, 949-0393 (Japan); Winnefeld, Frank [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)

    2013-01-15

    The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C-S-H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA-OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

  20. Hydration of Portland cement with additions of calcium sulfoaluminates

    International Nuclear Information System (INIS)

    The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C–S–H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA–OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

  1. IMPACT OF INCREASED ALUMINATE CONCENTRATIONS ON PROPERTIES OF SALTSTONE MIXES

    International Nuclear Information System (INIS)

    trends observed as the aluminate concentration increased in the salt solution were decreased Bingham Plastic yield stress and plastic viscosity, greater flowability of the grout, and reduced gel times and bleed volume for SWPF based mixes. On the other hand, the set times increased significantly with increasing aluminate concentration in the salt solutions. For the SWPF mixes, the set time increased from 1 to 4 days and for the Tank 11 mixes, the set time increased from 1 to 2 days. Heat of hydration measurements were consistent with the increased set times with extended induction periods (2 to 4 days) as aluminate concentration increased in the salt solution. This extended induction period of heat evolution observed with increasing aluminate concentrations must be addressed for Saltstone operations to avoid exceeding temperature limits. It is anticipated that the induction period will be temperature dependent and should be measured for future projections and included in the thermal modeling. The overall heat generation was greater in the mixes containing higher concentrations of aluminate. In fact, for the total heat release values calculated using curve fitting for longer times, the amount of heat was increased by 33% for SWPF based solutions and by 46% for Tank 11 based solutions. The larger amount of heat from mixes containing higher aluminate concentration must be accounted for in the modeling effort which determines the pour schedule for Saltstone. The increased induction periods were shown to be associated with hydration reactions of the blast furnace slag. The rate of heat generation with high aluminate solutions and Portland cement were only accelerated whereas high aluminate mixes containing blast furnace slag only showed the characteristic increase in induction time that was observed with mixes prepared using the premix blend of cementitious materials. It was shown that fly ash does not react significantly during the first seven days of curing but then

  2. Immobilisation of radwaste in cement based matrices

    International Nuclear Information System (INIS)

    The solubilities and influence on cement pH are reported for calcium aluminate and aluminosulphate hydrates. The solubility of Ca(OH)2 is reported to 700 bars. Polymerization of C-S-H is investigated by NMR. Specific interactions of U6+ and iodine (I-, IO3-) with cement components are described. The impact of radiation on cements and the influence of higher temperature are documented. The role of dissolved Ca and CO2 in groundwaters as dissolution media for cements are reported. (author)

  3. Carbonation on ternary cement systems

    OpenAIRE

    Martínez Ramírez, Sagrario; Fernández Carrasco, Lucía

    2012-01-01

    The main hydration reaction product in the ternary system fly ash, calcium sulphate and calcium aluminate cement (40/20/40) at 20°C is a hydrated calcium sulfoaluminate compound, an AFt phase slightly different from “traditional ettringite”. The carbonation of ettringite develops gypsum but in this case rapidcreekite is formed. For the first time it has been observed that carbonation of the mentioned calcium sulfoaluminate compound (AFt), an hydrated calcium sulphate carbonated phase (Ca2(SO4...

  4. SODIUM ALUMINATE IN CASTING PAINTS

    Directory of Open Access Journals (Sweden)

    O. S. Komarov

    2016-01-01

    Full Text Available Comparative researches showed that sodium aluminate can be successfully used as a modifying addition into the foundry paints on the basis disthen-sillimanite and lignosulfonate, as well as the binder for the chill mould paints based on graphite.

  5. 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....

  6. Processo de hidratação e os mecanismos de atuação dos aditivos aceleradores e retardadores de pega do cimento de aluminato de cálcio Hidration process and the mechanisms of retarding and accelerating the setting time of calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    J. R. Garcia

    2007-03-01

    Full Text Available Um dos aspectos principais para o desenvolvimento de concretos refratários está no aprimoramento dos conhecimentos sobre o cimento de alta alumina ou cimento de aluminato de cálcio (CAC, já que esse ligante é o mais utilizado nesta classe de produtos. O objetivo desse trabalho foi o de analisar as informações disponíveis na literatura para se obter um conhecimento mais aprofundado dos mecanismos de ação dos aditivos retardadores e aceleradores da pega deste cimento. Da análise dos dados compilados pode-se concluir que os aditivos retardadores agem geralmente de duas maneiras: 1 dificultando o processo de dissolução do cimento, por meio da formação de barreiras insolúveis ao redor das suas partículas e 2 favorecendo a formação de hidratos mais solúveis, o que aumenta o tempo necessário para que se inicie a precipitação. Por outro lado, os aditivos aceleradores de pega podem atuar favorecendo a formação de hidratos menos solúveis, diminuindo assim o tempo necessário para a precipitação ou ainda pela formação de núcleos iniciadores do processo de crescimento dos cristais dos hidratos. A análise destas informações leva a constatação de que a ação de alguns aditivos retardadores e aceleradores ocorre em estágios distintos no processo de hidratação do CAC. Portanto, pode-se imaginar uma situação onde a combinação desses dois aditivos poderia conferir um tempo de trabalhabilidade adequado e seguro, aliado a um curto tempo de desmoldagem.One of the main aspects for the development of refractories castables is to master the knowledge regarding calcium aluminate cement (CAC, as this binder is the most applied in these products. The objective of this work was to analyze the available information in the literature in order to explain the understanding regarding the actions of retarder and accelerator additives in the setting mechanisms of CACs. The analysis of the compiled information pointed out that the

  7. Lithium aluminates and tritium production

    International Nuclear Information System (INIS)

    In this work it is studied the crystalline structure of lithium aluminates prepared by three different methods, namely: solid state reaction, humid reaction and sol-gel reaction. The analysis methods are the X-ray diffractometry and the scanning and transmission electron microscopy. This study is realized as in original materials as in irradiated materials at the TRIGA Mark reactor, to correlate the synthesis method with response of these materials to the mixed irradiation of nuclear reactor. (Author)

  8. Adição de cimento de aluminato de cálcio e seus efeitos na hidratação do óxido de magnésio Effects of calcium aluminate cement addition on magnesia hydration

    Directory of Open Access Journals (Sweden)

    R Salomão

    2010-06-01

    Full Text Available Cimento de aluminato de cálcio (CAC e óxido de magnésio (MgO são duas importantes matérias primas para a indústria de concretos refratários e apresentam grande tendência à hidratação. Os efeitos dessa reação em cada caso isolado são distintos e bem conhecidos: enquanto o CAC hidratado atua como ligante e garante a resistência mecânica do material antes da sinterização, a hidratação do MgO pode causar sua total desintegração em alguns casos. Devido ao interesse tecnológico nesses materiais, é importante investigar as peculiaridades desses processos e as potenciais interações entre eles. Neste trabalho, os efeitos da adição de diferentes teores de CAC na hidratação do MgO foram investigados em suspensões aquosas usando medidas de expansão volumétrica aparente, pH das suspensões e difração de raios X. Foi observado que os efeitos danosos da hidratação do MgO podem ser significativamente reduzidos com um controle adequado do teor de CAC nas formulações.Calcium aluminate cement (CAC and magnesium oxide (MgO are two of the most important raw materials for refractory castables industry and both present a high driving force for hydration. The effects of this reaction for each compound are well known: whereas the hydrated CAC behaves as a binder, hardening the castable, MgO hydration can cause the total disintegration of the material. Due to the technological interests involved, it is important to study the peculiarities in these processes and their potential interactions. In the present work, the effects of the addition of different CAC contents on MgO hydration were investigated in aqueous suspensions by means of apparent volumetric expansion, pH measurements and qualitative X-ray diffraction. It was found out that the deleterious effects of MgO hydration can be significantly reduced with a proper control of the CAC content for the formulations.

  9. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China aims to streamline the crowded cement industry Policymakers are looking to build a concrete wall around the cement-making industry as they seek to solidify the fluid cement market and cut excessive production.

  10. Development of Production Technologies for Universal Hydraulic Cement (UHC)

    OpenAIRE

    Syal, Dr. S K

    2013-01-01

    It is based on our recent approaches of Modern construction materials utilizing existing wastes such as fly ashes slags and to save energies by technological developments.The article is essential in the direction of new materials called Durable Integral polymer-pigmented cement concretes. UHC is calcium aluminate cements with natural properties of durable earth materials. It is a step towards Research for Innovation in Indian Industries

  11. Possibilities of special cements in ceramic applications

    International Nuclear Information System (INIS)

    About 25 years ago, the only way to have confinement material for high temperature applications was to prepare a ceramic by sintering or fusion at high temperature. A new technology came, with the production of Low Cement Castables. This new product was obtained by a careful choice of the granulometry of the aggregates, an optimization of the defloculation of fine particles, including the cement (Calcium Aluminate Cement) and the addition of silica fume. Silica fume brought two improvements: a) a fluidifying effect, due partly to the low sensitivity of viscosity to pH, and partly to the geometric effect of the nicely spherical particle, b) a chemical effect, brought by the reaction of silica and Calcium Aluminate Cement to give a coherent zeolithic structure, through which water could escape during the first firing. From a ceramist point of view, it is interesting to understand how this components, nearly colloidal system mixed in water can be heated up to ceramization without any noticeable change in mechanical characteristics and shrinkage. From a more practical point of view, it is also interesting to realize that some characteristics, usually attributed only to ceramics, also apply with low cement castables technology: high compressive strength, flexural strength, corrosion resistance, abrasion resistance, impact resistance. (orig.)

  12. Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

    International Nuclear Information System (INIS)

    The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength. Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A 31P/27Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium–phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system

  13. Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

    Energy Technology Data Exchange (ETDEWEB)

    Chavda, Mehul A.; Bernal, Susan A. [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Apperley, David C. [Solid-State NMR Group, Department of Chemistry, Durham University, Durham DH1 3LE (United Kingdom); Kinoshita, Hajime [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Provis, John L., E-mail: j.provis@sheffield.ac.uk [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2015-04-15

    The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength. Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A {sup 31}P/{sup 27}Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium–phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system.

  14. Immobilization of radioactive waste in cement based matrices

    International Nuclear Information System (INIS)

    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)

  15. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    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-SiO2-H2O 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 CO2-containing environments. (author)

  16. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    A solubility model of the system CaO-SiO2-H2O is developed which takes account of the state of Si polymerization in the solid. Free energies of formations of its bonding hydrogel are tabulated. The internal redox conditions in cements have been measured; in particular, slags lower the Esub(eta) relative to OPC. The fate of Sr and U in cement systems has been determined; Sr is incorporated in the aluminate phases, while U6+ is precipitated as Ca-U-O-H2O phases. Lowering the internal Esub(eta) reduces U solubility. Studies of the carbonation of slag-cement blends are reported. (author)

  17. 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...

  18. Combustion Synthesis of Magnesium Aluminate

    Science.gov (United States)

    Kale, M. A.; Joshi, C. P.; Moharil, S. V.

    2011-10-01

    In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl6O10 has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl2O4 and MgAl6O10 were formed in a single step, while MgAl26O40 was not formed by this procedure. Activation of MgAl6O10 by rare earth ions like Ce3+, Eu3+ and Tb3+ and ns2 ion Pb2+ could be achieved. Excitation bands for MgAl6O10 are at slightly shorter wavelengths compared to those reported for MgAl2O4.

  19. The effect of microsilica and refractory cement content on the properties of andalusite based Low Cement Castables used in aluminum casthouse O efeito do teor de microsílica e de cimento refratário nas propriedades de LCCs usados em moldagem de alumínio

    OpenAIRE

    E. A. Firoozjaei; Saidi, A; A. Monshi; Koshy, P.

    2010-01-01

    The bonding system in low cement castables is achieved by the use of calcium aluminate cement, microsilica and reactive alumina. The lime/silica ratio critically impacts the liquid phase formation at high temperatures and subsequently the corrosion resistance and the mechanical and physical properties of the refractory. In the current study, the effects of microsilica and cement contents on the corrosion resistance and the physical and mechanical properties of Andalusite Low Cement Castables ...

  20. 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.

  1. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    OpenAIRE

    Nediljka Gaurina-Međimurec; Davorin Matanović; Gracijan Krklec

    1994-01-01

    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...

  2. Cements in Radioactive Waste Disposal

    International Nuclear Information System (INIS)

    burden of proof because with few exceptions, much less is known about their ability chemically to immobilise waste species and their long- term durability relative to Portland cement in a range of natural environments. It is concluded that the most robust of these alternative formulations are based on calcium aluminate and sulfoaluminate cements, on magnesium phosphate and on geopolymers. (author)

  3. Recycling of red muds with the extraction of metals and special additions to cement

    Science.gov (United States)

    Zinoveev, D. V.; Diubanov, V. G.; Shutova, A. V.; Ziniaeva, M. V.

    2015-01-01

    The liquid-phase reduction of iron oxides from red mud is experimentally studied. It is shown that, in addition to a metal, a slag suitable for utilization in the construction industry can be produced as a result of pyrometallurgical processing of red mud. Portland cement is shown to be produced from this slag with mineral additions and a high-aluminate expansion addition to cement.

  4. Development of electrodialysis process for aluminous solutions

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ One of the mostly perspective method of scrapping industrial drains is electrodialysis, which is used by us for processing of low concentrated aluminous solutions (g/L: Na2Ototal - 23.2, Na2 O ic - 3.9, Al2O3 -2.7, SO3-5.8), arises by receipting of aluminum hydroxide, which goes to synthesis of aluminum hydroxochloride-high effective new generation coagulant.

  5. Development of electrodialysis process for aluminous solutions

    Institute of Scientific and Technical Information of China (English)

    Todorov; S.; A.; Lainer; Y.; A.; Medvedev; A.; S.

    2005-01-01

    One of the mostly perspective method of scrapping industrial drains is electrodialysis, which is used by us for processing of low concentrated aluminous solutions (g/L: Na2Ototal - 23.2, Na2 O ic - 3.9, Al2O3 -2.7, SO3-5.8), arises by receipting of aluminum hydroxide, which goes to synthesis of aluminum hydroxochloride-high effective new generation coagulant.……

  6. Hydration water and microstructure in calcium silicate and aluminate hydrates

    International Nuclear Information System (INIS)

    Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C3S, C2S) and aluminates (C3A, C4AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and near-infrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm-1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small angle neutron scattering (USANS) and wide angle x

  7. Corrosion of aluminium metal in OPC- and CAC-based cement matrices

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, Hajime, E-mail: h.kinoshita@sheffield.ac.uk [Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom); Swift, Paul; Utton, Claire [Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom); Carro-Mateo, Beatriz [The Public University of Navarra, C/Esquíroz, 30 trasera, Pamplona 31007 (Spain); Marchand, Geraldine [The National Institute of Applied Sciences (INSA) Lyon, 20 Avenue Albert Einstein 69621 Villeurbanne Cedex (France); Collier, Nick [National Nuclear Laboratory, Chadwick House, Birchwood Park, Warrington, WA3 6AE (United Kingdom); Milestone, Neil [Industrial Research Ltd., 69 Gracefield Road, Lower Hutt, 5040 (New Zealand)

    2013-08-15

    Corrosion of aluminium metal in ordinary Portland cement (OPC) based pastes produces hydrogen gas and expansive reaction products causing problems for the encapsulation of aluminium containing nuclear wastes. Although corrosion of aluminium in cements has been long known, the extent of aluminium corrosion in the cement matrices and effects of such reaction on the cement phases are not well established. The present study investigates the corrosion reaction of aluminium in OPC, OPC-blast furnace slag (BFS) and calcium aluminate cement (CAC) based systems. The total amount of aluminium able to corrode in an OPC and 4:1 BFS:OPC system was determined, and the correlation between the amount of calcium hydroxide in the system and the reaction of aluminium obtained. It was also shown that a CAC-based system could offer a potential matrix to incorporate aluminium metal with a further reduction of pH by introduction of phosphate, producing a calcium phosphate cement.

  8. X-ray diffractometry of steam cured ordinary Portland and blast-furnace-slag cements

    International Nuclear Information System (INIS)

    This work studies some aspects of the phases produced by hydration of ordinary and blast-furnace-slag cements, at normal conditions and steam cured (60 and 950 C), using an X-ray diffraction technique. The blast-furnace-slag cement was a mixture of 50% of ordinary Portland cement and 50% of blast-furnace-slag (separately grinding). After curing the X-ray diffraction reveals that, in relation to ordinary Portland cement, the main phases in blast-furnace-slag cement are hydrated silicates and aluminates, hydro garnet, etringitte and mono sulphate. After steam curing the hydration of blast-furnace-slag cement proceeds. This is a result of the slag activation by the curing temperature. (author). 8 refs., 3 figs., 1 tab

  9. Mobility of cations in magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Martinelli, J.R.; Sonder, E.; Weeks, R.A.; Zuhr, R.A.

    1986-04-15

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 /sup 0/C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 /sup 0/C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field.

  10. Mobility of cations in magnesium aluminate spinel

    International Nuclear Information System (INIS)

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 0C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 0C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field

  11. Mobility of cations in magnesium aluminate spinel

    Science.gov (United States)

    Martinelli, J. R.; Sonder, E.; Weeks, R. A.; Zuhr, R. A.

    1986-04-01

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 °C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 °C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field.

  12. Tritium release from irradiated lithium aluminate, can it be improved?

    International Nuclear Information System (INIS)

    Lithium aluminate is an attractive material (in terms of its chemical, mechanical and irradiation properties) for breeding tritium in fusion reactors; however, its tritium release characteristics are not as good as those of other candidate materials. To investigate whether tritium release from lithium aluminate can be improved, we have studied the tritium release from irradiated samples of pure lithium aluminate, lithium aluminate doped with Mg, and lithium aluminate with a surface deposit of platinum. The release was studied by the temperature programmed desorption (TPD) method. Both the platinum coating and magnesium doping were found to improve the tritium release characteristics, as determined by TPD. Tritium release shifted to states with lower activation energies for the altered materials

  13. Evaluation of the slag attack resistance of high alumina refractory free cement castable

    International Nuclear Information System (INIS)

    The slag attack resistance is a very important property when the life time of refractory castable needs to be improved. The substitution of calcium aluminate cement by a free calcium hydraulic blinder has show a viable way to enhance the thermomechanical performance presented by these materials. At the present very few information is found regarding the slag attack of these free cement castable. In this study the slag attack resistance of high alumina castable with and without cement was evaluated by static test. The corroded region was analyzed by SEM and EDS. (author)

  14. Effect of different retarders on the hydration of calcium sulfoaluminate eco-cement pastes

    OpenAIRE

    García-Maté, Marta; De la Torre, Ángeles G.; Aranda, Miguel A. G.; Santacruz, Isabel

    2014-01-01

    The manufacture of Calcium SulfoAluminate (CSA) cements is more environmentally friendly than that of OPC [1] as their production releases up to 40% less CO2 than the latter. The main performances of CSA cements are fast setting time, good-chemical resistance properties and high early strengths. CSA cements are prepared by mixing CSA clinker with different amounts of a calcium sulfate set regulator such as gypsum (CaSO4•2H2O), bassanite (CaSO4•½H2O), or anhydrite (CaSO4), or mixtures of th...

  15. Solidification of low-level radioactive wastes in masonry cement

    International Nuclear Information System (INIS)

    Portland cements are widely used as solidification agents for low-level radioactive wastes. However, it is known that boric acid wastes, as generated at pressurized water reactors (PWR's) are difficult to solidify using ordinary portland cements. Waste containing as little as 5 wt % boric acid inhibits the curing of the cement. For this purpose, the suitability of masonry cement was investigated. Masonry cement, in the US consists of 50 wt % slaked lime (CaOH2) and 50 wt % of portland type I cement. Addition of boric acid in molar concentrations equal to or less than the molar concentration of the alkali in the cement eliminates any inhibiting effects. Accordingly, 15 wt % boric acid can be satisfactorily incorporated into masonry cement. The suitability of masonry cement for the solidification of sodium sulfate wastes produced at boiling water reactors (BWR's) was also investigated. It was observed that although sodium sulfate - masonry cement waste forms containing as much as 40 wt % Na2SO4 can be prepared, waste forms with more than 7 wt % sodium sulfate undergo catastrophic failure when exposed to an aqueous environment. It was determined by x-ray diffraction that in the presence of water, the sulfate reacts with hydrated calcium aluminate to form calcium aluminum sulfate hydrate (ettringite). This reaction involves a volume increase resulting in failure of the waste form. Formulation data were identified to maximize volumetric efficiency for the solidification of boric acid and sodium sulfate wastes. Measurement of some of the waste form properties relevant to evaluating the potential for the release of radionuclides to the environment included leachability, compression strengths and chemical interactions between the waste components and masonry cement. 15 refs., 19 figs., 9 tabs

  16. 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.

  17. Pollution and Prevention of Pb during Cement Calcination

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Emission pollution and prevention measures of Pb during cement calcination were discussed. The content of Pb and the variation of composition were explored by means of atomic absorption spectroscopy (AAS) and X-ray diffraction. The results show that a number of Pb emits during cement calcination, F and C1 promote the emission of Pb, and Pb is enriched in kiln dust. The smaller the particle of kiln dust, the higher the content of Pb. When utilizing the raw materials with a high content of Pb, a more efficient dust collector should be used and the kiln dust should be used as the addition of cement. Pb in clinker is enriched in the intermediate phase. The reduction of silica modulus is useful to increase the solidification content of Pb in clinker. The solidification content of Pb in calcium sulphoaluminate mineral is higher than that in calcium aluminate mineral.

  18. Structural simulation of superlattices in lithium aluminates

    International Nuclear Information System (INIS)

    Among the materials to be used on the tritium generator cover of the future fusion reactors the lithium aluminate (γ - LiAlO2) is one of the more studied. In this work it is presented the superlattice structural simulation that presents to γ - LiAlO2 as main phase and to α - LiAlO2 as the secondary phase. The simulation is developed considering that as the two phases present different symmetry (γ - LiAlO2 is tetrahedral and α - LiAlO2 is hexahedral) it is had a superlattice LUCS type (Layered Ultrathin Coherent Structure) that is it presents an structure in coherent ultrathin layers since it is what implicates a lesser energy of formation. (Author)

  19. Modified Pechini synthesis of tricalcium aluminate powder

    International Nuclear Information System (INIS)

    Tricalcium aluminate (Ca3Al2O6–C3A) was obtained by a modified Pechini synthesis in order to eliminate successive thermal treatments and intermediate grinding usually performed between the two sintering steps and in order to reduce the sintering temperature. Our results indicated that pure C3A was obtained, by a single step thermal treatment at 1300 °C for 4 h and 1350 °C for 1 h. The synthesis was confirmed by XRD, FT-IR and free lime analyses. The morphology of synthesised C3A was assessed by electron microscopy (SEM and TEM, HRTEM) and it was observed a high tendency of the particles to form aggregates and the individual particles seem to be single crystals. The bioactivity was assessed by specimen soaking in simulated body fluid (SBF) for 7 days; the hydrate (i.e. 3CaO∙Al2O3∙ 6H2O formed at the C3A surface), can act as nucleation centers for the resulted phosphate phases. - Highlights: ► A modified Pechini synthesis was used for obtained of tricalcium aluminate. ► C3A was obtained at 1300 °C/4 h and 1350 °C/1 h. ► Were eliminated successive thermal treatments and intermediate grinding. ► The morphology of synthesised C3A was assessed by electron microscopy (SEM, TEM). ► Was observed a high tendency of the particles to form aggregates.

  20. Properties of lithium aluminate for application as an OSL dosimeter

    International Nuclear Information System (INIS)

    Several samples of undoped and carbon or copper doped lithium aluminate (LiAlO2) were prepared in an attempt to achieve a material, which can be applicable in optically stimulated luminescence (OSL) dosimetry. All investigated samples are highly sensitive to ionizing radiation and show good reproducibility. The undoped and copper doped samples exhibit sensitivity several times higher than that of Al2O3:C, while sensitivity of the carbon doped samples is lower. The studied samples exhibit significant fading, but dynamics of signal loss is different for differently doped samples, what indicates a possibility of improving this characteristic by optimizing dopant composition. - Highlights: • OSL properties of lithium aluminate for personal dosimetry. • Doping influence on OSL fading of lithium aluminate. • Application of lithium aluminate in thermal neutron measurements

  1. Fatigue damage analysis of aluminized glass fiber composites

    OpenAIRE

    Ferreira, J. M.; Pires, J. T. B.; Costa, J. D.; Zhang, Z. Y.; Errajhi, O. A.; Richardson, M

    2005-01-01

    Aluminized glass fiber composite with epoxy and polyester matrix were used in this work in order to study fatigue properties and its comparison to conventional glass fiber composites. Until now aluminized glass fiber materials have been only used as decoy flares in military applications. The innovative advantages of these composites, using modified fibers, are potentially the improvement of thermal and electrical conduction. The main objective of this work was to study the fatigue damage of c...

  2. Study of thermocycling effect on the bond strength between an aluminous ceramic and a resin cement Estudo do efeito da ciclagem térmica na resistência da união adesiva entre uma cerâmica aluminizada e um cimento resinoso

    Directory of Open Access Journals (Sweden)

    Osvaldo Daniel Andreatta Filho

    2005-03-01

    Full Text Available This study evaluated the effect of thermocycling on the bond strength between Procera AllCeram (Nobel-Biocare and a resin cement (Panavia F, Kuraray CO. Nine ceramic blocks with dimensions of 5x6x6mm were conditioned at one face with Rocatec System (Espe. After, they were luted with Panavia F to composite resin blocks (Clearfil AP-X, Kuraray CO. The nine groups formed by ceramic, cement and composite resin were split up obtaining 75 samples with dimensions of 12x1x1mm and adhesive surface presenting 1mm²±0.1mm² of area. The samples were divided into 3 groups (n=25: G1 - 14 days in distilled water at 37ºC; G2 - 6,000 cycles in water (5ºC - 55ºC - 30s; G3 - 12,000 cycles in water (5ºC - 55ºC - 30s. The samples were tested in a universal testing machine (EMIC at a crosshead speed of 1mm/min. Data were analyzed by ANOVA and Tukey tests. The results indicated that mean values of rupture tension (MPa of G1 (10.71 ± 3.54 did not differ statistically (p Este trabalho avaliou o efeito da ciclagem térmica sobre a resistência adesiva entre a cerâmica aluminizada (Procera AllCeram, Nobel-Biocare e um cimento resinoso (Panavia F, Kuraray CO. Nove blocos de cerâmica, com dimensões de 5x6x6mm, foram condicionados em uma de suas faces com o Sistema Rocatec (ESPE. A seguir foram cimentados a blocos de resina composta (Clearfil AP-X, Kuraray CO. Os conjuntos cerâmica-cimento-resina foram cortados em 75 corpos-de-prova com formato retangular com dimensões de 12x1x1mm e superfície adesiva apresentando 1mm² ± 0,1mm². Os corpos-de-prova foram divididos em três grupos (n=25: G1 - 14 dias em água destilada a 37ºC, G2 - 6000 ciclos em água (5ºC e 55ºC e G3 - 12000 ciclos em água (5ºC e 55ºC. Os corpos-de-prova foram ensaiados sob velocidade de 1mm/min em máquina de ensaio universal (EMIC. Os dados foram tratados estatisticamente com os testes de Anova e Tukey e indicaram que os valores médios de tensão de rupturas (MPa de G1 (10,71 ± 3

  3. Durability of pulp fiber-cement composites

    Science.gov (United States)

    Mohr, Benjamin J.

    Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness

  4. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  5. Effect of conditioning methods on the microtensile bond strength of phosphate monomer-based cement on zirconia ceramic in dry and aged conditions

    NARCIS (Netherlands)

    Amaral, Regina; Ozcan, Mutlu; Valandro, Luiz Felipe; Balducci, Ivan; Bottino, Marco Antonio

    2008-01-01

    The objective of this study was to evaluate the durability of bond strength between a resin cement and aluminous ceramic submitted to various surface conditioning methods. Twenty-four blocks (5 X 5 X 4 mm 3) of a glass-in filtrated zirconia-alumina ceramic (inCeram Zirconia Classic) were randomly di

  6. Neutron irradiation of polycrystalline yttrium aluminate garnet, magnesium aluminate spinel and α-alumina.

    Science.gov (United States)

    Neeft, E. A. C.; Konings, R. J. M.; Bakker, K.; Boshoven, J. G.; Hein, H.; Schram, R. P. C.; van Veen, A.; Conrad, R.

    1999-08-01

    Polycrystalline pellets of yttrium aluminate garnet (Y 3Al 5O 12), magnesium aluminate spinel (MgAl 2O 4) and α-alumina (α-Al 2O 3) have been irradiated in the high flux reactor (HFR) at Petten to a neutron fluence of 1.7 × 10 26 m -2 ( E>0.1 MeV) at a temperature of about 815 K. Volume changes smaller than 1% have been measured for Y 3Al 5O 12 and MgAl 2O 4. Transmission electron microscopy (TEM) results of Y 3Al 5O 12 show no difference between the unirradiated TEM samples and neutron-irradiated samples. For MgAl 2O 4, dislocation loops in some grains are found in the irradiated samples. TEM results of Al 2O 3 show a dense network of dislocation loops after neutron irradiation. The increase in volume is 4.2% for a neutron fluence of 1.7 × 10 26 m -2.

  7. Development of the Use of Alternative Cements for the Treatment of Intermediate Level Waste

    International Nuclear Information System (INIS)

    This paper describes initial development studies undertaken to investigate the potential use of alternative, non ordinary Portland cement (OPC) based encapsulation matrices to treat historic legacy wastes within the UK's Intermediate Level Waste (ILW) inventory. Currently these wastes are encapsulated in composite OPC cement systems based on high replacement with blast furnace slag of pulverised fuel ash. However, the high alkalinity of these cements can lead to high corrosion rates with reactive metals found in some wastes releasing hydrogen and forming expansive corrosion products. This paper therefore details preliminary results from studies on two commercial products, calcium sulfo-aluminate (CSA) and magnesium phosphate (MP) cement which react with a different hydration chemistry, and which may allow wastes containing these metals to be encapsulated with lower reactivity. The results indicate that grouts can be formulated from both cements over a range of water contents and reactant ratios that have significantly improved fluidity in comparison to typical OPC cements. All designed mixes set in 24 hours with zero bleed and the pH values in the plastic state were in the range 10-11 for CSA and 5-7 for MP cements. In addition, a marked reduction in aluminium corrosion rate has been observed in both types of cements compared to a composite OPC system. These results therefore provide encouragement that both cement types can provide a possible alternative to OPC in the immobilisation of reactive wastes, however further investigation is needed. (authors)

  8. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    International Nuclear Information System (INIS)

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl2–N2 flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al2O3 (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl2 atmosphere of the MgO–Al2O3 mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C

  9. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    Energy Technology Data Exchange (ETDEWEB)

    Orosco, Pablo, E-mail: porosco@unsl.edu.ar [Instituto de Investigaciones en Tecnología Química (INTEQUI), Chacabuco y Pedernera, San Luis (Argentina); Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis Chacabuco y Pedernera, San Luis (Argentina); Barbosa, Lucía [Instituto de Investigaciones en Tecnología Química (INTEQUI), Chacabuco y Pedernera, San Luis (Argentina); Instituto de Ciencias Básicas (ICB), Universidad Nacional de Cuyo Parque General San Martín, Mendoza (Argentina); Ruiz, María del Carmen [Instituto de Investigaciones en Tecnología Química (INTEQUI), Chacabuco y Pedernera, San Luis (Argentina); Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis Chacabuco y Pedernera, San Luis (Argentina)

    2014-11-15

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.

  10. Surface Modification of Nickel Foams by a Slurry Aluminizing Process

    International Nuclear Information System (INIS)

    A novel slurry-based process for aluminizing nickel foams while improving the mechanical properties and conserving the excellent ductility is reported. Cellular unalloyed nickel foams with 92% porosity and uniform pore size and distribution were used as a starting material. Several slurries of different compositions were examined to investigate the possibility of developing an aluminide-nickel intermetallic coating on a Ni foam without considerably degrading the original ductile properties of the foam. The process temperature was varying from 400 to 850 deg. C and the process holding time was ranging between 2h to 6h. Scanning electron microscopy with an energy dispersive X-ray spectrometry and X-Ray diffraction were applied to assess the effectiveness of the aluminizing process and determine both the optimum parameters of the procedure (slurry composition, holding temperature and time) and the concentration profiles across the coating cross-section. The mechanical behavior of the aluminized Ni-foams was evaluated by the conduction of micro-tension tests. The resulting Ni-foams after aluminization retain the pore structure of original Ni-foams and present a thick outer surface layer which consists of a range of aluminide phases. The mechanical properties of the Ni-foams aluminized in low process temperature were insignificantly affected.

  11. Behavior of calcium silicate hydrate in aluminate solution

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; ZHAO Zhuo; LIU Gui-hua; ZHOU Qiu-sheng; PENG Zhi-hong

    2005-01-01

    Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO · SiO2 · H2O and 2CaO · SiO2 · 1.17H2O, were hydro-thermally synthesized at 120 ℃. The reaction rule of calcium silicate hydrate in aluminate solution was investigated. The result shows that CaO · SiO2 · H2O is more stable than 2CaO · SiO2 · 1.17H2 O in aluminate solution and its stability increases with the increase of reaction temperature but decreases with the increase of caustic concentration. The reaction between calcium silicate hydrate and aluminate solution is mainly through two routes. In the first case, Al replaces partial Si in calcium silicate hydrate, meanwhile 3CaO · Al2 O3 · xSiO2 · (6-2x) H2 O (hydro-garnet) is formed and some SiO2 enters the solution. In the second case, calcium silicate hydrate can react directly with aluminate solution, forming hydro-garnet and Na2O · Al2O3 · 2SiO2 · nH2O (DSP). The desilication reaction of aluminate solution containing silicate could contribute partially to forming DSP.

  12. Chitosan-collagen biomembrane embedded with calcium-aluminate enhances dentinogenic potential of pulp cells.

    Science.gov (United States)

    Soares, Diana Gabriela; Rosseto, Hebert Luís; Basso, Fernanda Gonçalves; Scheffel, Débora Salles; Hebling, Josimeri; Costa, Carlos Alberto de Souza

    2016-01-01

    The development of biomaterials capable of driving dental pulp stem cell differentiation into odontoblast-like cells able to secrete reparative dentin is the goal of current conservative dentistry. In the present investigation, a biomembrane (BM) composed of a chitosan/collagen matrix embedded with calcium-aluminate microparticles was tested. The BM was produced by mixing collagen gel with a chitosan solution (2:1), and then adding bioactive calcium-aluminate cement as the mineral phase. An inert material (polystyrene) was used as the negative control. Human dental pulp cells were seeded onto the surface of certain materials, and the cytocompatibility was evaluated by cell proliferation and cell morphology, assessed after 1, 7, 14 and 28 days in culture. The odontoblastic differentiation was evaluated by measuring alkaline phosphatase (ALP) activity, total protein production, gene expression of DMP-1/DSPP and mineralized nodule deposition. The pulp cells were able to attach onto the BM surface and spread, displaying a faster proliferative rate at initial periods than that of the control cells. The BM also acted on the cells to induce more intense ALP activity, protein production at 14 days, and higher gene expression of DSPP and DMP-1 at 28 days, leading to the deposition of about five times more mineralized matrix than the cells in the control group. Therefore, the experimental biomembrane induced the differentiation of pulp cells into odontoblast-like cells featuring a highly secretory phenotype. This innovative bioactive material can drive other protocols for dental pulp exposure treatment by inducing the regeneration of dentin tissue mediated by resident cells. PMID:27119587

  13. Interactions between chloride and cement-paste materials.

    Science.gov (United States)

    Barberon, Fabien; Baroghel-Bouny, Véronique; Zanni, Hélène; Bresson, Bruno; d'Espinose de la Caillerie, Jean-Baptiste; Malosse, Lucie; Gan, Zehong

    2005-02-01

    The durability of cement-based materials with respect to exterior aggressions is one of the current priorities in civil engineering. Depending on their use, the cement-based materials can be exposed to different types of aggressive environments. For instance, damages to concrete structures in contact with a saline environment (sea water on bridges, deicing salts on roads, etc.) are of utmost importance. Upon exposure to saline water, Cl- ions penetrate into the structures and subsequently lead to reinforcement corrosion. Chloride attack is often combined with other aggressive influences such as temperature (e.g., freezing) or the ingress of other ions (e.g., sulfates in sea water). We therefore aim to explore the effect of sodium chloride (NaCl) on the structural chemistry of cement paste. Existing studies about reinforcement corrosion by chloride have focused on the penetration of Cl- ions and the comparison between "free" ions (water-soluble ions) and bound ones. However, little is known about the fixation mechanisms, the localization of Cl in the cement matrix and the structural interaction between Cl and the silicate and aluminate hydrate phases present in cement paste. We present here results of a multinuclear nuclear magnetic resonance study on the fixation of chloride in the hydration products and the characterization of new phases potentially appearing due to chloride ingress. PMID:15833625

  14. Irradiated microstructures of magnesium aluminate spinel and their controlling factors

    International Nuclear Information System (INIS)

    This paper reviews out recent progress in study on the strong resistance of magnesium aluminate spinel to void swelling during irradiation, along with the related characteristic features of its radiation damage. Comparative experimental results on irradiated microstructures and mechanical properties in magnesium aluminate spinel and alpha-alumina are shown in terms of controlling factors of radiation resistance of the former crystal. It is experimentally shown that structural vacancies due to non-stoichiometry provide effective recombination sites for displaced cations to suppress the formation of interstitial loops. Decreased formation of interstitial loops enhances the further recombination of interstitials and vacancies and thereby the formation of voids

  15. Thermoluminescence dosimetry of rare earth doped calcium aluminate phosphors

    Indian Academy of Sciences (India)

    K Madhukumar; K Rajendra Babu; K C Ajith Prasad; J James; T S Elias; V Padmanabhan; C M K Nair

    2006-04-01

    The thermoluminescence (TL) properties of calcium aluminate (CaAl2O4) doped with different rare earth ions have been studied and their suitability for radiation dosimetry applications is discussed. It is observed that monocalcium aluminate doped with cerium is a good dosimeter having linear response up to about 4 kGy of radiation doses. Dopant concentration of 0.25 mol% cerium gives maximum TL emission. The well-defined single peak observed at 295°C can be advantageously used for high temperature dosimetry applications.

  16. A phase-field study of the aluminizing of nickel

    Science.gov (United States)

    Philippe, T.; Erdeniz, D.; Dunand, D. C.; Voorhees, P. W.

    2015-03-01

    A quantitative phase-field approach for multiphase systems that is based upon CALPHAD free energies is used to model the aluminization of nickel wires, wherein vapour-phase alloying is used to deposit Al on the surface of the Ni wire and then the wire is annealed so that to remove all Al gradients and achieve a homogenous Ni-Al alloy. Both processes are modelled and numerical results are compared with experiments. It is found that the kinetics of both processes is controlled by bulk diffusion. During aluminization at 1273 K, formation and growth of intermetallics, Ni2Al3 NiAl and Ni3Al, are strongly dependent on the Al content in the vapour phase. Ni2Al3 growth is very fast compared with NiAl and Ni3Al. It is also found that an intermediate Al content in the vapour phase is preferable for aluminization, since the Ni2Al3 coating thickness is difficult to control. Ni2Al3 is found to disappear in a few minutes during homogenization at 1373 K. Thereafter, the NiAl phase, in which the composition is highly non-uniform after aluminization, continues growing until the supersaturation in this phase vanishes. Then, NiAl coating disappears concomitantly with the growth of Ni3Al, which disappears thereafter. Finally, the Al concentration profile in Ni(Al) homogenizes.

  17. SINTERING AND SULFATION OF CALCIUM SILICATE-ALUMINATE

    Science.gov (United States)

    The effect of sintering on the reactivity of solids at high temperature was studied. The nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C. The kinetics of the sintering and sulfation processes were measured independentl...

  18. Magnesium aluminate spinel precipitation in MgO

    Energy Technology Data Exchange (ETDEWEB)

    Berthelet, C.; Kingery, W.D.; Vandersande, J.B.

    1976-01-01

    Magnesium aluminate spinel precipitates forming in polycrystalline MgO containing 0.43 weight % Al and 0.031 weight % Al were examined by transmission electron microscopy after air quenching or rapid cooling. Precipitation in a variety of morphologies occurred at grain boundaries, low angle grain boundaries and dislocations. On reheating a virgin surface, precipitation occurs at temperatures above 730/sup 0/C.

  19. Computation of X-ray powder diffractograms of cement components and its application to phase analysis and hydration performance of OPC cement

    Indian Academy of Sciences (India)

    Rohan Jadhav; N C Debnath

    2011-08-01

    The importance of computed X-ray diffraction patterns of various polymorphs of alite (3, 1, ), belite (, ), aluminate (cubic, orthorhombic), aluminoferrite, gypsum and hemihydrate in the quantitative phase analysis of cement and its early stage hydration performance is highlighted in this work with three OPC samples. The analysis shows that the predominant silicate phases present in all the samples are 3-alite phase and -belite phase, respectively. Both cubic and orthorhombic phases of C3A, brownmillerite, gypsum and hemihydrates are present at different levels. Quantitative phase analysis of cement by Rietveld refinement method provides more accurate and comprehensive data of the phase composition compared to Bogue method. The comparative hydration performance of these samples was studied with / ratio, 0.5 and the results are interpreted in the light of difference in phase compositions viz. -C2S/C3S ratio, fraction of finer cement particles present in the samples and theoretical modeling of C3S hydration.

  20. Calcium aluminate cement as dental restorative : Mechanical properties and clinical durability

    OpenAIRE

    Sunnegårdh-Grönberg, Karin

    2004-01-01

    In 1995, the Swedish government recommended the discontinuation of amalgam as restorative in paediatric dentistry. Because the mercury content in amalgam constitutes an environmental hazard, its use has declined. The use of resin composites is increasing, but the polymerisation shrinkage of the material is still undesirably high, and the handling of uncured resin can cause contact dermatitis. A new restorative material has recently been developed in Sweden as an alternative to amalgam and res...

  1. The Hydration and Carbonation of Tricalcium Aluminate (C3A) in the Presence of Heavy Metals

    Institute of Scientific and Technical Information of China (English)

    CHEN Quanyuan; C. D. Hills; M. Tyrer; I. Slipper

    2005-01-01

    The hydration of tricalcium aluminate (C3A) has a significant effect on the effectiveness of cement-based systems. In addition, the carbonation of hydration products of C3A is particularly important in respect of durability performance. The present work investigates the hydration and carbonation reactions of C3A and the changes induced by the presence of the heavy metal ions such as Zn2+, Pb2+, Cu2+ and Cr3+ by X-ray diffractometry (XRD). During hydration of C3A, gehlenite hydrate, hydrogarnet, calcium monoaluminate (C4AHx) and calcium carboaluminate were detected in C3A pastes except the Zn2+doped paste, where hydrogarnet did not form. The examinations revealed that heavy metals coexisted with gehlenite hydrate, calcium monoaluminate (C4AHx) and calcium carboaluminate, inhibiting the formation of hydrogarnet. Hydrating C3A was liable to be carbonated on exposure to air and carbon dioxide, especially in the presence of heavy metals, resulting in the formation of carboaluminate and/or calcium carbonate. The presence of heavy metals in-fluenced the polymorphism of calcium carbonate,ndicating that heavy metals could co-precipitate with calcium to form a carbonate solid solution.

  2. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    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

  3. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    The objective of this project is to develop an improved ultra-lightweigh cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems, Task 2: Review Russian Ultra-Lightweight Cement Literature, and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary surface pipe and intermediate casing cementing conditions historically encountered in the US and establishment of average design conditions for ULHS cements. Russian literature concerning development and use of ultra-lightweight cements employing either nitrogen or ULHS was reviewed, and a summary is presented. Quality control testing of materials used to formulate ULHS cements in the laboratory was conducted to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS. This protocol is presented and discussed. finally, results of initial testing of ULHS cements is presented along with analysis to establish cement performance design criteria to be used during the remainder of the project

  4. Inorganic Corrosion-Inhibitive Pigments for High-Temperature Alkali-activated Well Casing Foam Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pyatina, T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2014-11-14

    This study evaluates inorganic pigments for improving carbon steel (CS) brine-corrosion protection by the sodium metasilicate-activated calcium aluminate cement/Fly Ash blend at 300°C. Calcium borosilicate (CBS) and zinc phosphate, significantly improved CS corrosion-protection by decreasing cement’s permeability for corrosive ions and inhibiting anodic corrosion. An amorphous Na2O-Al2O3-SiO2-H2O phase tightly attached to CS surface formed at 300oC in CBS-modified cement pore solution. The corrosion rate of the CS covered with this phase was nearly 4-fold lower than in the case of nonmodified cement pore solution where the major phase formed on the surface of CS was crystalline analcime.

  5. Inorganic Corrosion-Inhibitive Pigments for High-Temperature Alkali-activated Well Casing Foam Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pyatina, T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2014-11-01

    This study evaluates inorganic pigments for improving carbon steel (CS) brine-corrosion protection by the sodium metasilicate-activated calcium aluminate cement/Fly Ash blend at 300°C. Calcium borosilicate (CBS) and zinc phosphate, significantly improved CS corrosion-protection by decreasing cement’s permeability for corrosive ions and inhibiting anodic corrosion. An amorphous Na2O-Al2O3-SiO2-H2O phase tightly attached to CS surface formed at 300oC in CBS-modified cement pore solution. The corrosion rate of the CS covered with this phase was nearly 4-fold lower than in the case of nonmodified cement pore solution where the major phase formed on the surface of CS was crystalline analcime.

  6. Phase transformations in lithium aluminates irradiated with neutrons

    International Nuclear Information System (INIS)

    The lithium aluminate like candidate to be used in the coverings producers of tritium in the fusion nuclear reactors, presents high resistance to the corrosion to the one to be stuck to structural materials as special steels. However, the crystallographic changes that take place in the cover that is continually subjected to irradiation with neutrons, can alter its resistance to the corrosion. In this work the changes of crystalline structure are shown that they present two types of nano structures of lithium aluminates, subjected to an average total dose 7.81 x 108 Gy in the fixed irradiation system of capsules of the one TRIGA Mark lll nuclear reactor of the Nuclear Center of Mexico. The studied nano structures presented only phase transformations without formation of amorphous material. (Author)

  7. Preparation and characterization of calcium aluminate by chemical synthesis

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Saturated Ca(OH)2 and AlCl3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 m2/g. The measurement of hydraulic exotherm revealed that the exothermal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100% of the 3 days curing strength in the mortar test.

  8. A reactive flow model for heavily aluminized cyclotrimethylene-trinitramine

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bohoon; Lee, Kyung-Cheol; Yoh, Jack J., E-mail: jjyoh@snu.ac.kr [Department of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Park, Jungsu [Agency for Defense Development, Daejeon 305-600 (Korea, Republic of)

    2014-07-14

    An accurate and reliable prediction of reactive flow is a challenging task when characterizing an energetic material subjected to an external shock impact as the detonation transition time is on the order of a micro second. The present study aims at investigating the size effect behavior of a heavily aluminized cyclotrimethylene-trinitramine (RDX) which contains 35% of aluminum by using a detonation rate model that includes ignition and growth mechanisms for shock initiation and subsequent detonation. A series of unconfined rate stick tests and two-dimensional hydrodynamic simulations are conducted to construct the size effect curve which represents the relationship between detonation velocity and inverse radius of the charge. A pressure chamber test is conducted to further validate the reactive flow model for predicting the response of a heavily aluminized high explosive subjected to an external impact.

  9. Magnetic properties of some rare-earth nanostuctured aluminates

    Energy Technology Data Exchange (ETDEWEB)

    Lovchinov, V; Petrov, D; Simeonova, P; Angelov, B, E-mail: lovcinov@issp.bas.b

    2010-11-01

    Nanocrystalline single-phase RAlO{sub 3} (R = Nd, Sm, Eu, Dy, Gd) has been prepared by modified Pechini's method. Malic acid has been used for the first time as a new complexing agent in the sol-gel process. It has facilitated a low temperature synthesis of the compound. The characterization of the nanoparticles has been carried out by different methods. Using Physical Property Measurement System (PPMS-9 QD) the temperature and magnetic dependency of the susceptibility and magnetization of the nanostuctured aluminates were measured. The obtained results were compared with the existing ones for the single crystals and powder specimens of the same aluminates. The differences observed have been discussed in the framework of the molecular field theory for a two-sublattice system.

  10. Preparation of lithium aluminate via polymeric precursor routes

    International Nuclear Information System (INIS)

    Gamma lithium aluminate is a potential candidate for tritium breeding material. Various preparation routes have been proposed including solid state reaction methods and wet chemical methods such as sol-gel process. But it is still needed to develop reliable and economic preparation methods that can be used for large production. In this paper, we examined three polymeric precursor methods - amorphous citrate process, Pechini process, and polyvinyl alcohol-assisted process - by studying thermal behavior of the precursor powders by X-ray diffractometry, differential thermal analysis, infrared spectrometry, and BET surface area analysis. All these three processes produced phase pure gamma lithium aluminate powders at a relatively low temperature. The phase purity and processing temperature were comparable to the alkoxide derived sol-gel method and yet these polymeric precursor methods did not require high quality starting materials such as alkoxides. (orig.)

  11. Radiation induced optical centres in magnesium aluminate spinel ceramics

    International Nuclear Information System (INIS)

    There were investigated the optical absorption centers formation in magnesium aluminate spinel ceramics under irradiation with UV-light, X-, and gamma-rays. The lithium fluoride doped ceramics were produced by using hot-pressing technology. It was revealed that generation by irradiation changes in optical absorption spectra can be used for detection of invisible point defects in prepared ceramics, their distribution through the bulk of spinel disk, and predict the behavior of ceramics in different radiation fields.

  12. Infrared spectroscopy studies of magnesium aluminates spinel crystals

    OpenAIRE

    Kobyakov, V.A.; Patochkina, O. L.; Gritsyna, V.T.

    2012-01-01

    The reflectance and transmittance spectra for magnesium aluminates spinel single crystals MgO·nAl2O3 and ceramics in the IR spectral range were measured to investigate the nature of vibration modes of constituent ions and incorporated hydrogen. The variation of intensity of registered bands in spinel of stoichiometric and nonstoichiometric compositions and spinel ceramics was obtained and interpreted in terms of vibration modes of divalent and trivalent cations in different coordinat...

  13. Tritium extraction from neutron-irradiated lithium aluminate

    International Nuclear Information System (INIS)

    Lithium aluminate is being strongly considered as a breeder material because of its thermophysical, chemical and mechanical stability at high temperatures and its favorable irradiation behavior. Furthermore, it is compatible with other blanket and structural materials. In this work, the effects of calcination temperature during preparation, extraction temperature and sweep gas composition were observed. Lithium aluminate prepared by four different methods, was neutron irradiated for 30 minutes at a flux of 1012 -1013 n/cm2 s in the TRIGA Mark III reactor at Salazar, Mexico; and the tritium extraction rate was measured. Calcination temperature do not affect the tritium extraction rate. However, using high calcination temperature, gamma lithium aluminate was formed. The tritium extraction at 600 Centigrade degrees was lower than at 800 Centigrade degrees and the tritium amount extracted by distillation of the solid sample was higher. The sweep gas composition showed that tritium extraction was less with Ar plus 0.5 % H2 that with Ar plus 0.1 % H2. This result was contrary to expected, where the tritium extraction rate could be higher when hydrogen is added to the sweep gas. Probably this effect could be attributed to the gas purity. (Author)

  14. Morphological and microstructural studies on aluminizing coating of carbon steel

    International Nuclear Information System (INIS)

    Hot dip aluminizing is one of the most effective methods of surface protection for steels and is gradually gaining popularity. The morphology and microstructure of an inter-metallic layer form on the surface of low carbon steel by hot dip aluminization treatment had been studied in detail. This effect has been investigated using optical and scanning electron microscopy, and X-ray diffraction. The result shows that the reaction between the steel and the molten aluminium leads to the formation of Fe–Al inter-metallic compounds on the steel surface. X-ray diffraction and electron microscopic studies showed that a two layer coating was formed consisting of an external Al layer and a (Fe2Al5) inter metallic on top of the substrate after hot dip aluminizing process. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. Microhardness testing shown that the intermetallic layer has high hardness followed by steel substrate and the lowest hardness was Al layer

  15. Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry

    International Nuclear Information System (INIS)

    Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL-1. Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement-waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 deg. C by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (CSA) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, CSA cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale.

  16. In-Situ interaction between cement and clay: implications for geological disposal

    International Nuclear Information System (INIS)

    The extent and the consequences of interactions between cementitious materials used in radioactive waste management and clay host rock are described. In-situ tests were performed on seven cement formulations representing materials applied in repository construction, for backfilling or for solidification of radioactive waste. Samples were exposed to realistic repository conditions of the Boom Clay Formation in the HADES underground laboratory. Chemical, physical and mineralogical changes across the cement-clay interface were identified by combined observations from Electron Probe Microanalysis, Infrared microscopy and X-Ray powder diffraction. Significant interactions in both the cement and the clay part were found in a zone extending up to several hundreds of microns. The most prominent features are (1) leaching of cement with loss of calcium and/or silicon; (2) development of a calcium-rich zone in Boom Clay close to or at contact; (3) the formation of a contact zone marked by the precipitation of a (hydrated) magnesium aluminate phase; (4) reduction in apparent porosity of initially porous/permeable materials and (5) precipitation of calcite within the cement. This elemental exchange tends to diminish pH and reduce the buffering capacity of the cement. Although hydroxide will diffuse into the clay, the development of an extensive alkaline halo in the surrounding clay is unlikely owing to the buffering capacity of the Boom Clay pore water. Copyright (2001) Material Research Society

  17. Strength of Limestone-based Non-calcined Cement and its Properties

    Institute of Scientific and Technical Information of China (English)

    LIN Zongshou; ZHAO Qian

    2009-01-01

    A new type of cement was prepared with ground limestone powder,blastfurnace slag,steel slag and gypsum without calcination.The fraction of ground limestone powder in the cement was as high as 40 wt%-60 wt%without Portland clinker.All of its physical properties can meet the requirements of masonry cement standards.The impact of limestone content on physical properties of the cement and determined its impact on law was investigated.The steel slag can excit the aquation activity of this cement effectively,and the influence of its quantity on the strength of the materials was studied,which shows that the optimum quantity of mixing is 10%.By way of changing the different content of the lime stone by quartzy sample,the law of the compression strength and the PH value was determined,confirming that the lime stone can promote the early aquation of the slag and improve the early strength.The main hydration product of this cement is calcium aluminate hydrate, ettringite and calcium silicate hydrate,as indicated by XRD and SEM analysis.

  18. Advanced cementation concepts

    International Nuclear Information System (INIS)

    The purpose of this programme of work was to investigate whether improvements could be made to existing formulations for cement suitable for the immobilization of intermediate level radioactive waste. Two additives were selected, microsilica and limestone flour. Improvements to the cement were only slight. (author)

  19. SODIUM POLYPHOSPHATE-MODIFIED CLASS C/CLASS F FLY ASH BLEND CEMENTS FOR GEOTHERMAL WELLS.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA, T.; BROTHERS, L.E.; KASPEREIT, D.

    2006-02-01

    The authors investigated the usefulness of the coal combustion by-products, Class C fly ash (C) and Class F fly ash (F), in developing cost-effective acid-resistant phosphate-based cements for geothermal wells. In the temperature range of 20-100 C, sodium polyphosphate (NaP) as the acidic cement-forming solution preferentially reacted with calcium sulfate and lime in the C as the base solid reactant through the exothermic acid-base reaction route, rather than with the tricalcium aluminate in C. This reaction led to the formation of hydroxyapatite (HOAp). In contrast, there was no acid-base reaction between the F as the acidic solid reactant and NaP. After autoclaving the cements at 250 C, a well-crystallized HOAp phase was formed in the NaP-modified C cement that was responsible for densifying the cement's structure, thereby conferring low water permeability and good compressive strength on the cement. however, the HOAp was susceptible to hot CO{sub 2}-laden H{sub 2}SO{sub 4} solution (pH 1.1), allowing some acid erosion of the cement. On the other hand, the mullite in F hydrothermally reacted with the Na from NaP to form the analcime phase. Although this phase played a pivotal role in abating acid erosion, its generation created an undesirable porous structure in the cement. They demonstrated that blending fly ash with a C/F ratio of 70/30 resulted in the most suitable properties for acid-resistant phosphate-based cement systems.

  20. Investigation of the formation of Al, Fe, N intermetallic phases during Al pack cementation followed by plasma nitriding on plain carbon steel

    International Nuclear Information System (INIS)

    Highlights: • The surface hardness is increased about eight times. • Increasing nitriding time and temperature caused strengthening the Al diffused zone. • The inward diffusion of nitrogen and outward diffusion of iron changed aluminized zone microstructure. • Surface aluminum oxides are reduced by plasma nitriding in low pressure chamber with nitrogen and hydrogen in gas mixture. - Abstract: Plain carbon steels are not suitable for nitriding as they form an extremely brittle case that spalls off readily, and the hardness increment of the diffusion zone is small. In this research, the effect of plasma nitriding time and temperature variation on the microstructure of the pack cemented aluminized plain carbon steel is investigated. All samples were aluminized at 900 °C for 2 h; the aluminized samples were subsequently plasma nitrided at 500 °C, 550 °C and 600 °C for 2.5, 5, 7.5 and 10 h. The phases formed on the sample surface were detected by X-ray diffraction (XRD). The cross section and samples surface were investigated by optical and scanning electron microscopy (SEM). Microhardness test was conducted to determine hardness change from the surface to the sample core. Results showed that by aluminizing the steel, Fe3Al phases as well as Fe–Al solid solution were formed on the surface and some aluminum rich precipitates were formed in solid solution grain boundaries. Plasma nitriding of the aluminized layer caused the formation of aluminum and iron nitride (AlN, Fe4N) on the sample surface. Consequently, surface hardness was improved up to about eight times. By increasing the nitriding temperature and time, aluminum-rich precipitates dissociated. Moreover, due to the diffusion of nitrogen through aluminized region during ion nitriding, iron and aluminum nitrides were formed in aluminized grain boundaries. Increasing nitriding time and temperature lead to the growth of these nitrides in the grain boundaries of the substrate. This phenomenon results in

  1. Effect of rare earth (RE) on diffusion of aluminum atoms in aluminizing

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei; YE Xiao-feng; PANG Bi-jun; ZHOU Si-kai

    2006-01-01

    The RE-aluminized coating and pure aluminized coating on 20 carbons steel were prepared by hot dip aluminizing method at 740 ℃. After diffusion treatment at 850 ℃ for 4 h, the distribution of aluminum and lanthanum elements in the coating was analyzed with energy disperse spectroscopy(EDS) and electron probe microanalyses(EPMA), and the lattice parameter of α-Fe in the matrix of the coating was measured precisely by X-ray diffractometer(XRD). The results show that RE permeates into the aluminized coating, leads to lattice disturbance and increases the depth of the aluminized coating. On the basis of the results, the expression of the diffusion coefficient of Al atoms is derived from the diffusion flow, and the effect of the high vacancy concentration and high concentration gradient of vacancies on the diffusion of Al atoms was analyzed by establishing the kinetics model of the vacancy mechanism of diffusion. The results show that the high vacancy concentration and high concentration gradient of vacancies in the RE-aluminized processes are the main reason why the diffusion coefficient of Al atoms in RE-aluminizing is bigger than that in pure aluminizing.

  2. Study of damages by neutron irradiation in lithium aluminates

    International Nuclear Information System (INIS)

    Lithium aluminates proposed to the production of tritium in fusion nuclear reactors, due to the thermal stability that they present as well as the behavior of the aluminium to the irradiation. As a neutron flux with profile (≅ 14 Mev) of a fusion reactor is not available. A irradiation experiment was designed in order to know the micro and nano structure damages produced by fast and thermal neutrons in two irradiation positions of the fusion nuclear reactor Triga Mark III: CT (Thermal Column) and SIFCA (System of Irradiation Fixed of Capsules). In this work samples of lithium aluminate were characterized by XRD (X-Ray Diffraction), TEM (Transmission Electron Microscopy) and SEM (Scanning Electron Microscopy). Two samples were prepared by two methods: a) coalition method and b) peroxide method. This characterization comprised original and irradiated samples. The irradiated sample amounted to 4 in total: one for each preparation method and one for each irradiation position. The object of this analysis was to correlate with the received neutron dose the damages suffered by the samples with the neutron irradiation during long periods (440 H), in their micro and nano structure aspects; in order to understand the changes as a function of the irradiation zone (with thermal and fast neutron flux) and the preparation methods of the samples and having as an antecedent the irradiation in SIFCA position by short times (2h). The obtained results are referred to the stability of γ -aluminate phase, under given conditions of irradiation and defined nano structure arrangement. They also refer to the proposals of growth mechanism and nucleation of new phases. The error associated with the measurement of neutron dose is also discussed. (Author)

  3. Shock-induced cation disorder in magnesium aluminate spinel

    Science.gov (United States)

    Chen, Q. Y.; Meng, C. M.; Lu, T. C.; Xu, M.; Qi, J. Q.; Tan, J. J.

    2010-12-01

    An increase in lattice constants and an order-disorder phase transition were observed in the magnesium aluminate spinel (MgAl2O4) powders after shock compression. Theoretical calculations on the basis of density functional theory confirm that the remarkable volume expansion in shocked MgAl2O4 powders is closely related to the substantial site disorder in the MgAl2O4 lattice. The calculations also show that the partially inverse MgAl2O4 spinel with an inversion index of 0.7 represents the greatest disordered metastable phase and the most unstable structure.

  4. Cement substitution by a combination of metakaolin and limestone

    Energy Technology Data Exchange (ETDEWEB)

    Antoni, M., E-mail: mathieu.antoni@epfl.ch [EPFL-STI-IMX-Laboratoires des Materiaux de Construction, Station12, CH-1015 Lausanne (Switzerland); Rossen, J. [EPFL-STI-IMX-Laboratoires des Materiaux de Construction, Station12, CH-1015 Lausanne (Switzerland); Martirena, F. [CIDEM-UCLV, Universidad Las Villas, Santa Clara (Cuba); Scrivener, K. [EPFL-STI-IMX-Laboratoires des Materiaux de Construction, Station12, CH-1015 Lausanne (Switzerland)

    2012-12-15

    This study investigates the coupled substitution of metakaolin and limestone in Portland cement (PC). The mechanical properties were studied in mortars and the microstructural development in pastes by X-ray diffraction, thermogravimetry analysis, mercury intrusion porosimetry and isothermal calorimetry. We show that 45% of substitution by 30% of metakaolin and 15% of limestone gives better mechanical properties at 7 and 28 days than the 100% PC reference. Our results show that calcium carbonate reacts with alumina from the metakaolin, forming supplementary AFm phases and stabilizing ettringite. Using simple mass balance calculations derived from thermogravimetry results, we also present the thermodynamic simulation for the system, which agrees fairly well with the experimental observations. It is shown that gypsum addition should be carefully balanced when using calcined clays because it considerably influences the early age strength by controlling the very rapid reaction of aluminates.

  5. Tympanoplasty with ionomeric cement

    DEFF Research Database (Denmark)

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

    isolated erosion of the long incus process have been treated with a new surgical technique in which the ossicular chain was rebuilt with ionomeric cement. The results in hearing performance (mean pure-tone average (PTA) 0.5, 1 and 2 kHz) were evaluated pre- and post-surgery, and compared to those in a...... > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy...

  6. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2003-01-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. DOE joined the Materials Management Service (MMS)-sponsored joint industry project ''Long-Term Integrity of Deepwater Cement under Stress/Compaction Conditions.'' Results of the project contained in two progress reports are also presented in this report.

  7. High-temperature oxidation behavior of aluminized AISI 4130 steel

    Science.gov (United States)

    Badaruddin, Mohammad; Wang, Chaur Jeng; Wardono, Herry; Tarkono, Asmi, Dwi

    2016-02-01

    AISI 4130 steel was dipped into a molten aluminum bath at 700°C for 16 s to produce an aluminide coating on the steel substrate. The coating, which consisted of an Al-rich layer and an FeAl3 and Fe2Al5 intermetallic layer, strongly adhered to the steel substrate. High-temperature oxidation of the bare steel and aluminized steel was performed by thermogravimetry at 850°C for 49 h in static air. The oxidation products were characterized by scanning electron microscopy and energy-dispersive spectroscopy. The aluminide coating could increase the oxidation resistance of the bare steel by a factor of ˜19. The increase in high-temperature oxidation resistance of the aluminized steel is attributed to the formation of protective alumina scale (α-Al2O3). Although iron oxide nodules grew on the aluminide coating surface, the oxidation rate of the aluminide coatings was very low. After 49 h of oxidation, agglomerates of α-Al2O3 fine grains grew on the rod-shaped FeAl phases.

  8. Aluminizing of metallic materials for fusion power applications

    International Nuclear Information System (INIS)

    The necessity of coatings is fundamental for both liquid metal blanket concepts. In a water-cooled liquid metal blanket concept, the coating has to behave as tritium permeation barrier to minimize the tritium loss into the cooling water. An electrical insulation against the liquid metal is required in a self-cooled liquid metal blanket to reduce the MHD pressure drop. Therefore, V and V-base alloys and as well the ferritic steel MANET were coated by means of hot-dip aluminizing. The different base materials are dipped under inert atmosphere into molten Al to form aluminide layers on the surface. The nitriding of the aluminide layers on V and V-base alloys was tried in a sodium solution containing 0.15 wt% Li under N2 atmosphere. The aluminide layers on the MANET steel were oxidized at high temperature in air. The results of the hot-dip aluminizing and the following nitriding reps. oxidation will be presented in this paper. (author)

  9. Transformation of monomer aluminate ions from tetrahedron to octaheron

    Institute of Scientific and Technical Information of China (English)

    陈启元; 周俊; 李洁; 尹周澜

    2003-01-01

    During the precipitation of gibbsite from supersaturated sodium aluminate solution, the main aluminum containing species in solution will transform from tetrahedral [Al(OH)4]-to sixfold octahedral [(H2O)2Al-(OH)4]-. In order to elucidate the mechanisms responsible for above transformation, the formation Gibbs free energy as well as frontier orbits of a wide range of aluminum species are studied by ab initio method at B3LYP/6-31G** level. Based on theoretical calculation results, thermodynamic possibility and coordination possibility for aluminate ion transforming from [Al(OH)4]-to [(H2O)2Al(OH)4]-are analyzed and thermodynamic permitted reaction pathways are extracted. It is found that [Al(OH)4]-can not react directly with H2O to carry out the variation of coordination number. Transformation of tetrahedral [Al(OH)4]-to octahedral [(H2O)2Al(OH)4]-is involved in two reaction pathways, one is realized by neutral [Na(H2O)+4*Al(OH)-4] acting mediator, the other is carried by neutral [(H2O)Al(OH)3]. Though there is a strong thermodynamic trend for the transformation of [Al(OH)4]-to [(H2O)2Al(OH)4]-, the practical transformation is very slow. Thus, it can be concluded that there is a great kinetic resistance during the transformation from [Al(OH)4]-to [(H2O)2Al(OH)4]-.

  10. Asphalt cement poisoning

    Science.gov (United States)

    Asphalt; Pavement ... The substances in asphalt that can be harmful are: Hydrocarbons Industrial glues Industrial solvents Tar ... Asphalt is found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for ...

  11. Radiaton-resistant electrical insulation on the base of cement binders

    International Nuclear Information System (INIS)

    The problems of designing radiation-resistant electrical insulations on the base of BATs and Talum cements for the UNK magnets operating under constant and pulse modes are discussed. The data characterizing dielectrical ad physico-mechanical properties of 25 various compositions are given. Two variants of manufacturing coils are considered: solid and with the use of asbestos tape impregnated with aluminous cement solution. The data obtained testify to the fact that the advantages of insulation on Talum cement are raised radiation resistance, high strength (particularly compression strength), weak porosity, high elasticity modulus and high thermal conductivity. BATs cement insulation is characterized by high radiation resistance, absence of shrinkage, rather low elasticity modulus and high dielectrical characteristics under normal conditions. The qualities of the solid insulation variant are its high technological effectiveness and posibility to fill up the spaces of complex configuration. In case of using as solid insulation Talum cement, however special measures for moisture removal are required. The advantage of insulation on the base of the asbestos tape is its reliability. For complex configuration magnets, however to realize is such insulation somewhat difficult

  12. Mössbauer, XRD, and Complex Thermal Analysis of the Hydration of Cement with Fly Ash

    Directory of Open Access Journals (Sweden)

    Vili Lilkov

    2013-01-01

    Full Text Available Hydration of cement with and without fly ash is studied with Mössbauer spectroscopy, XRD, and thermal analysis. Iron in cement is present as Fe3+-ions and occupies two octahedral positions, with close isomer shifts and quadrupole splittings. Iron in fly ash is present as Fe2+ and Fe3+, and the Mössbauer spectra display three doublets—two for Fe3+ in octahedral coordination and one for Fe2+. A third doublet was registered in the hydrating plain cement pastes after the 5th day, due to Fe3+ in tetrahedral coordination in the structure of the newly formed monosulphate aluminate. In cement pastes with fly ash, the doublet of tetrahedral iron is formed earlier because the quantity of ettringite and portlandite is low and more monosulphate crystallizes. No Fe(OH3 phase forms during hydration of C4AF. The fly ash displays pozzolanic properties, which lead to lowering of the portlandite quantity in the cement mixtures and increasing of the high temperature products.

  13. Characterization of cement-based ancient building materials in support of repository seal materials studies

    International Nuclear Information System (INIS)

    Ancient mortars and plasters collected from Greek and Cypriot structures dating to about 5500 BC have been investigated because of their remarkable durability. The characteristics and performance of these and other ancient cementitious materials have been considered in the light of providing information on longevity of concrete materials for sealing nuclear waste geological repositories. The matrices of these composite materials have been characterized and classified into four categories: (1) gypsum cements; (2) hydraulic hydrated lime and hydrated-lime cements; (3) hydraulic aluminous and ferruginous hydrated-lime cements (+- siliceous components); and (4) pozzolana/hydrated-lime cements. Most of the materials investigated, including linings of ore-washing basins and cisterns used to hold water, are in categories (2) and (3). The aggregates used included carbonates, sandstones, shales, schists, volcanic and pyroclastic rocks, and ore minerals, many of which represent host rock types of stratigraphic components of a salt repository. Numerous methods were used to characterize the materials chemically, mineralogically, and microstructurally and to elucidate aspects of both the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical (mineralogical) and microstructural factors. Durability was found to be affected by matrix mineralogy, particle size and porosity, and aggregate type, grading, and proportioning, as well as method of placement and exposure conditions. Similar factors govern the potential for durability of modern portland cement-containing materials, which are candidates for repository sealing. 29 references, 29 figures, 6 tables

  14. RECYCLED WASTE-BASED CEMENT COMPOSITE PATCH MATERIALS FOR RAPID/PERMANENT ROAD RESTORATION.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2001-07-31

    Over the past year, KeySpan Energy sponsored a research program at Brookhaven National Laboratory (BNL) aimed at recycling boiler ash (BA) and waste water treatment sludge (WWTS) byproducts generated from Keyspan's power stations into potentially useful materials, and at reducing concurrent costs for their disposal. Also, KeySpan has an interest in developing strategies to explicitly integrate industrial ecology and green chemistry. From our collaborative efforts with Keyspan (Diane Blankenhom Project Manager, and Kenneth Yager), we succeeded in recycling them into two viable products; Pb-exchange adsorbents (PEAs), and high-performance cements (HpCs). These products were made from chemically bonded cement and ceramic (CBC) materials that were synthesized through two-step chemical reaction pathways, acid-base and hydration. Using this synthesis technology, both the WWTS and BA served in acting as solid base reactants, and sodium polyphosphate, [-(-NaPO{sub 3}-)-{sub n}], known as an intermediator of fertilizer, was employed as the acid solution reactant. In addition, two commercial cement additives, Secar No. 51 calcium aluminate cement (CAC) and Type I calcium silicate cement (CSC), were used to improve mechanical behavior and to promote the rate of acid-base reaction of the CBC materials.

  15. Study on the hydration and microstructure of Portland cement containing diethanol-isopropanolamine

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Suhua, E-mail: yc982@163.com; Li, Weifeng; Zhang, Shenbiao; Hu, Yueyang; Shen, Xiaodong

    2015-01-15

    Diethanol-isopropanolamine (DEIPA) is a tertiary alkanolamine used in the formulation of cement grinding-aid additives and concrete early-strength agents. In this research, isothermal calorimetry was used to study the hydration kinetics of Portland cement with DEIPA. A combination of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC)–thermogravimetric (TG) analysis and micro-Raman spectroscopy was used to investigate the phase development in the process of hydration. Mercury intrusion porosimetry was used to study the pore size distribution and porosity. The results indicate that DEIPA promotes the formation of ettringite (AFt) and enhances the second hydration rate of the aluminate and ferrite phases, the transformation of AFt into monosulfoaluminate (AFm) and the formation of microcrystalline portlandite (CH) at early stages. At later stages, DEIPA accelerates the hydration of alite and reduces the pore size and porosity.

  16. Electrical properties and thermal expansion of strontium aluminates

    International Nuclear Information System (INIS)

    Highlights: • Sr3Al2O6, SrAl2O4 and Sr4Al14O25 ceramics are semiconductors. • Electrical conductivity is as low as 10−6−4×10−5 S/cm at 1273 K in dry air. • SrAl2O4 is a mixed conductor with predominant ionic conductivity. • Sr3Al2O6 shows significant contribution of protonic transport in wet atmospheres. • Average TECs vary in the range (8.5–11.1)×10−6 K−1 and are p(O2)-independent. - Abstract: Strontium aluminate ceramics, including Sr3Al2O6, SrAl2O4 and Sr4Al14O25, synthesized by glycine–nitrate combustion and sintered at 1773 K in air, were characterized by thermal analysis, dilatometry and electrical measurements in controlled atmospheres. All studied strontium aluminates are semiconductors with electrical conductivities as low as 10−6−4×10−5 S/cm at 1273 K in dry air. Electrical measurements in controlled atmospheres in combination with ion transference number determination demonstrated that SrAl2O4 is a mixed conductor with predominant ionic conductivity and increasing n-type and p-type electronic contributions under highly reducing and oxidizing conditions, respectively. While the behavior of electrical conductivity of Sr3Al2O6 in dry atmospheres was qualitatively similar to that of SrAl2O4, a significant increase of conductivity in wet atmospheres was attributed to a protonic contribution to electrical conduction, in correlation with thermogravimetric data and the tendency of this material to form a hydrogarnet at low temperatures. The average thermal expansion coefficients of strontium aluminates, (8.5–11.1)×10−6 K−1 at 333–1373 K, increase with increasing strontium content in the sequence Sr4Al14O25 < SrAl2O4 < Sr3Al2O6 and are essentially independent of oxygen partial pressure

  17. Solubilities of sodium nitrate, sodium nitrite, and sodium aluminate in simulated nuclear waste

    International Nuclear Information System (INIS)

    Solubilities were determined for sodium nitrate, sodium nitrite, and sodium aluminate in synthetic nuclear waste liquor. Solubilities were determined as a function of temperature and solution composition (concentrations of sodium hydroxide, sodium nitrate, sodium nitrite, and sodium aluminate). Temperature had the greatest effect on the solubilities of sodium nitrate and sodium nitrite and a somewhat lesser effect on sodium aluminate solubility. Hydroxide had a great effect on the solubilities of all three salts. Other solution components had minor effects. 2 references, 8 figures, 11 tables

  18. First Synthesis of Uranyl Aluminate nano-particles

    International Nuclear Information System (INIS)

    This paper describes, for the first time, a simple method for the synthesis of uranyl aluminate (URAL) nano-particles. URAL was prepared by U(VI) hydrolytic precipitation with ammonia at pH = 11 in the presence of meso-porous alumina MSU-X under 20 kHz of sonication followed by annealing of the obtained solids at 800 C. TEM, XAFS, powder XRD, and 27Al MAS NMR studies revealed that the speciation of uranium in this system strongly depends on uranium concentration. The sample with 5 wt % of uranium yields air-stable nano-particles (similar to 5 nm) of URAL. Presumably, UO22+ cations in this compound are coordinated with bidentate AlO2- groups. The increase of uranium concentration to 30 wt % causes mostly formation of U3O8 fine particles (similar to 50 nm) and small amounts of URAL. (authors)

  19. Synthesis and optical study of barium magnesium aluminate blue phosphors

    International Nuclear Information System (INIS)

    Europium doped barium magnesium aluminate (BaMgAl10O17:Eu2+) phosphor was prepared via solution combustion method at 550°C using urea as a fuel. Morphological and optical properties of the prepared sample was studied by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Photoluminescence spectroscopy (PL). XRD result showed the formation of pure phase BaMgAl10O17(JCPDS 26-0163) along with an additional phase BaAl2O4(JCPDS 01-082-1350). TEM image indicated the formation of faceted particles with average particle size 40 nm. From PL spectra, a broad emission band obtained at about 450 nm attributes to 4f6 5d → 4f7 transition of Eu2+ which lies in the blue region of the visible spectrum

  20. Modeling of tritium transport in lithium aluminate fusion solid breeders

    Energy Technology Data Exchange (ETDEWEB)

    Billone, M.C.; Clemmer, R.G.

    1985-02-01

    Lithium aluminate is a candidate tritium-breeding material for fusion reactor blankets. One of the concerns with using LiAlO/sub 2/ is tritium recovery from this material, particularly at low operating temperatures and high fluences. The data from various tritium release experiments with ..gamma..-LiAlO/sub 2/ and related materials are reviewed and analyzed to determine under what conditions bulk diffusion is the rate-limiting mechanism for tritium transport and what the effective bulk diffusion coefficient should be. Steady-state and transient models based on bulk diffusion are developed and used to interpret the data. Design calculations are then performed with the verified models to determine the steady-state inventory and time to reach equilibrium for a full-scale fusion blanket.

  1. Lanthanum aluminate synthesis by reverse precipitation starting from pseudoboehmite

    International Nuclear Information System (INIS)

    Full text: The lanthanum aluminate (Lao) shows a thermoluminescence response thus has been proposed as a material for dosimetry; this has made have been proposed various methods for their synthesis (hydrothermal, sol-gel, combustion, precipitation, etc.) These methods are complex or expensive if part of reagent grade materials which limits its application to larger scales. Therefore is proposed to use the pseudoboehmite as a precursor of alumina for the Lao phase. Pseudoboehmite was synthesized by reverse precipitation starting from aluminum sulfate and as precipitating agent the ammonium hydroxide. Lao perovskite phase was obtained at 1500 degrees C and 10 h of calcination s, at lower temperatures the presence of other phases as lanthanum oxide was detected. Also the morphology of the powders were characterized by scanning electron microscopy, finding clusters whose sizes are in the range of ∼0.25 and 1 μm. The measurement of the density by the Archimedes method reached 94% of the theoretical. (Author)

  2. First Synthesis of Uranyl Aluminate nano-particles

    Energy Technology Data Exchange (ETDEWEB)

    Chave, T.; Nikitenko, S. I. [UMII, ICSM, CEA, CNRS, ENSCM, Ctr Marcoule, UMR 5257, F-30207 Bagnols Sur Ceze (France); Scheinost, A. C. [European Synchrotron Radiat Facil, Rossendorf Beamline CRG BM20, F-38043 Grenoble (France); Scheinost, A. C. [FZD, Inst Radiochem, D-01314 Dresden (Germany); Berthon, C.; Arab-Chapelet, B.; Moisy, Ph. [CEA Marcoule, DEN, DRCP, Ctr Marcoule, F-30207 Bagnols Sur Ceze (France)

    2010-07-01

    This paper describes, for the first time, a simple method for the synthesis of uranyl aluminate (URAL) nano-particles. URAL was prepared by U(VI) hydrolytic precipitation with ammonia at pH = 11 in the presence of meso-porous alumina MSU-X under 20 kHz of sonication followed by annealing of the obtained solids at 800 C. TEM, XAFS, powder XRD, and {sup 27}Al MAS NMR studies revealed that the speciation of uranium in this system strongly depends on uranium concentration. The sample with 5 wt % of uranium yields air-stable nano-particles (similar to 5 nm) of URAL. Presumably, UO{sub 2}{sup 2+} cations in this compound are coordinated with bidentate AlO{sub 2}{sup -} groups. The increase of uranium concentration to 30 wt % causes mostly formation of U{sub 3}O{sub 8} fine particles (similar to 50 nm) and small amounts of URAL. (authors)

  3. On the Compressive and Tensile Strength of Magnesium Aluminate Spinel

    Science.gov (United States)

    Paris, V.; Hayun, S.; Dariel, M. P.; Frage, N.; Zaretsky, E.

    2009-12-01

    Magnesium aluminate spinel is a strong polycrystalline transparent ceramic. Spinel is an attractive material for armor applications and its behavior under shock wave loading is of obvious interest. The purpose of the present study was to determine the Hugoniot elastic limit (HEL) of this material, its Hugoniot response above the HEL, and its spall strength. Planar impact experiments were performed over the 2 to 40 GPa stress range using the Velocity Interferometer System for Any Reflector (VISAR) as a principal diagnostics tool. According to these tests, spinel has a HEL of about 11.3 GPa. The spall strength of the material was found to be close to zero at low, about 2 GPa, impact stress.

  4. Lattice site of helium implanted in magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Allen, W.R. (Metals and Ceramics Div., Oak Ridge National Lab., TN (United States))

    1993-01-01

    The lattice site of helium implanted at 60 keV in magnesium aluminate spinel (MgAl[sub 2]O[sub 4]) has been investigated with channeling effect measurements that apply the ion-induced [sup 3]He(d, p)[sup 4]He nuclear reaction. Within the spinel crystal structure, numerous interstices characterized by octahedral anion coordination are intrinsically unfilled by cations. For implantation at 300 K, a typical helium atom locates centrally in one of these vacant octahedral interstices with a probability of approximately 95%. Significant occupation of other lattice sites of either high or low symmetry was rejected. In particular helium neither clusters in defect complexes nor locates in tetrahedral interstices or substitutional sites. (orig.).

  5. Lattice site of helium implanted in magnesium aluminate spinel

    International Nuclear Information System (INIS)

    The lattice site of helium implanted at 60 keV in magnesium aluminate spinel (MgAl2O4) has been investigated with channeling effect measurements that apply the ion-induced 3He(d, p)4He nuclear reaction. Within the spinel crystal structure, numerous interstices characterized by octahedral anion coordination are intrinsically unfilled by cations. For implantation at 300 K, a typical helium atom locates centrally in one of these vacant octahedral interstices with a probability of approximately 95%. Significant occupation of other lattice sites of either high or low symmetry was rejected. In particular helium neither clusters in defect complexes nor locates in tetrahedral interstices or substitutional sites. (orig.)

  6. Lattice site of helium implanted in magnesium aluminate spinel

    Science.gov (United States)

    Alien, W. R.

    1993-01-01

    The lattice site of helium implanted at 60 keV in magnesium aluminate spinel (MgAl 2O 4) has been investigated with channeling effect measurements that apply the ion-induced 3He(d, p) 4He nuclear reaction. Within the spinel crystal structure, numerous interstices characterized by octahedral anion coordination are intrinsically unfilled by cations. For implantation at 300 K, a typical helium atom locates centrally in one of these vacant octahedral interstices with a probability of approximately 95%. Significant occupation of other lattice sites of either high or low symmetry was rejected. In particular, helium neither clusters in defect complexes nor locates in tetrahedral interstices or substitutional sites.

  7. Nanosized strontium aluminate phosphors prepared via a reverse microemulsion route

    International Nuclear Information System (INIS)

    Nanosized strontium aluminate phosphors co-activated by Eu2+ and Dy3+ were prepared via a novel reverse microemulsion process. This new synthesis technique lowered the synthesis temperature of SrAl2O4: Eu2+, Dy3+ phosphors to as low as 900 deg. C, and also reduced the particle size to the nanometer scale (around 40 nm). In the microemulsion process, the constituent cations were trapped by numerous nano-scaled micelles, leading to a shortening of the inter-diffusion length and enhancement of the precursor reactivity. The excitation intensity and emission peaks of nanosized SrAl2O4: Eu2+, Dy3+ phosphors significantly increased with increasing heating temperatures

  8. Synthesis and optical study of barium magnesium aluminate blue phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Jeet, Suninder, E-mail: suninder.jeet@thapar.edu; Pandey, O. P., E-mail: oppandey@thapar.edu [School of Physics and Materials Science, Thapar University, Patiala (147003), Punjab (India); Sharma, Manoj, E-mail: manojnarad@sggswu.org [Department of Nanotechnology, Sri Guru Granth Sahib World University, Fatehgarh Sahib(146406), Punjab (India)

    2015-05-15

    Europium doped barium magnesium aluminate (BaMgAl{sub 10}O{sub 17}:Eu{sup 2+}) phosphor was prepared via solution combustion method at 550°C using urea as a fuel. Morphological and optical properties of the prepared sample was studied by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Photoluminescence spectroscopy (PL). XRD result showed the formation of pure phase BaMgAl{sub 10}O{sub 17}(JCPDS 26-0163) along with an additional phase BaAl{sub 2}O{sub 4}(JCPDS 01-082-1350). TEM image indicated the formation of faceted particles with average particle size 40 nm. From PL spectra, a broad emission band obtained at about 450 nm attributes to 4f{sup 6} 5d → 4f{sup 7} transition of Eu{sup 2+} which lies in the blue region of the visible spectrum.

  9. On structural, optical and dielectric properties of zinc aluminate nanoparticles

    Indian Academy of Sciences (India)

    E Muhammad Abdul Jamal; D Sakthi Kumar; M R Anantharaman

    2011-04-01

    Zinc aluminate nanoparticles with average particle size of 40 nm were synthesized using a sol–gel combustion method. X-ray diffractometry result was analysed by Rietveld refinement method to establish the phase purity of the material. Different stages of phase formation of the material during the synthesis were investigated using differential scanning calorimetry and differential thermogravimetric analysis. Particle size was determined with transmission electron microscopy and the optical bandgap of the nanoparticles was determined by absorption spectroscopy in the ultraviolet-visible range. Dielectric permittivity and a.c. conductivity of the material were measured for frequencies from 100 kHz to 8 MHz in the temperature range of 30–120°C. The presence of Maxwell–Wagner type interfacial polarization was found to exist in the material and hopping of electron by means of quantum mechanical tunneling is attributed as the reason for the observed a.c. conductivity.

  10. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-10-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; 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; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  11. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

    Science.gov (United States)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini

    2012-06-01

    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  12. Solubility products of tungstates, titanates and aluminates from 250C to 2000C

    International Nuclear Information System (INIS)

    The solubility products of several complex oxides (tungstates aluminates and titanates) were calculated from thermodynamic data, in the range 25 - 2000C, using a computer program. High temperature entropy for ionic species was determined using the entropy correspondence principle. (Author)

  13. Pack cementation diffusion coatings for iron-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1995-02-01

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels. The Cr-Si ferrite layers have proven to be very resistant to high temperature cyclic oxidation and to pitting in aqueous solutions. The process has been patented, and is being transferred for industrial application, e.g. for water walls of utility boilers, etc. In the proposed extension of this project, the use of mixed pure metal powders in the pack will be extended to achieve similar ferrite Fe-Cr-Al coatings with excellent oxidation resistance, with the eventual transfer of the technology to industry. In other recent studies, Ni-base alloy rods were aluminized by the halide-activated pack cementation process to bring their average composition to that for the ORNL-developed Ni{sub 3}Al, for use as a welding rod. A similar effort to develop a welding rod for the ORNL Fe{sub 3}Al alloy did not yield reproducible coating compositions or growth kinetics. The continued effort to produce Duriron-type (Fe-18Si-5Cr) coatings on steels was not successful. Literature for the intrinsic diffusion coefficients suggests that this task cannot be achieved.

  14. [Study on the Influence of Mineralizer on the Preparation of Calcium Aluminates Based on Infrared Spectroscopy].

    Science.gov (United States)

    Fan, Wei; Wang, Liang; Zheng, Huai-li; Chen, Wei; Tang, Xiao-min; Shang, Juan-fang; Qian, Li

    2015-05-01

    In this study, effect of mineralizer on the structure and spectraproperties of calcium aluminates formation was extensively studied. Medium or low-grade bauxite and calcium carbonate were used as raw material and mineralizer CaF2 as additive. Calcium aluminates can be obtained after mixing fully, calcination and grinding. The prepared calcium aluminates can be directly used for the production of polyaluminiumchloride (PAC), polymeric aluminum sulfate, sodium aluminate and some other water treatment agents. The calcium aluminates preparation technology was optimized by investigating the mass ratio of raw materials (bauxiteand calcium carbonate) and mineralizer CaF2 dosage. The structure and spectra properties of bauxite and calcium aluminates were characterized by Fourier transform infrared(FTIR) spectroscopy analysis and the mineralization mechanism of the mineralizer was studied. FTIR spectra indicated that the addition of mineralizer promoted the decomposition and transformation of the diaspore, gibbsite and kaolinite, the decomposition of calcium carbonate, and more adequately reaction between bauxite and calcium carbonate. In addition, not only Ca in calcium carbonate and Si in bauxite were more readily reacted, but also Si-O, Si-O-Al and Al-Si bonds in the bauxite were more fractured which contributed to the release of Al in bauxite, and therefore, the dissolution rate of Al2O3 could be improved. The dissolution rate of Al2O3 can be promoted effectively when the mineralizer CaF2 was added in a mass ratio amount of 3%. And the mineralizer CaF2 cannot be fully functioned, when its dosage was in a mass percent of 1. 5%. Low-grade bauxite was easier to sinter for the preparation of calcium aluminates comparing with the highgrade one. The optimum material ratio for the preparation of calcium aluminates calcium at 1 250 °C was the mass ratio between bauxite and calcium carbonate of 1 : 0. 6 and mineralizer CaF2 mass ratio percent of 3%. PMID:26415430

  15. Technology Roadmaps: Cement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    To support its roadmap work focusing on key technologies for emissions reductions, the International Energy Agency (IEA) also investigated one particular industry: cement. Cement production includes technologies that are both specific to this industry and those that are shared with other industries (e.g., grinding, fuel preparation, combustion, crushing, transport). An industry specific roadmap provides an effective mechanism to bring together several technology options. It outlines the potential for technological advancement for emissions reductions in one industry, as well as potential cross-industry collaboration.

  16. Concrete = aggregate, cement, water?

    International Nuclear Information System (INIS)

    Concrete for the Temelin nuclear power plant is produced to about 70 different formulae. For quality production, homogeneous properties of aggregates, accurate proportioning devices, technological discipline and systematic inspections and tests should be assured. The results are reported of measuring compression strength after 28 days for different concrete samples. The results of such tests allow reducing the proportion of cement, which brings about considerable savings. Reduction in cement quantities can also be achieved by adding ash to the concrete mixes. Ligoplast, a plasticizer addition is used for improving workability. (M.D). 8 figs

  17. Neutron diffraction investigation of structural deviations in cement clinker

    International Nuclear Information System (INIS)

    Full text: The effects of refining the atomic positions in cement clinker phases using Rietveld analysis of neutron powder diffraction data was investigated. Changes in phase quantification and Bragg-R factors of phases after atomic position refinement are reported. A previous x-ray study, briefly reported that less than a 1% (average) alteration to bond distances in a refinement resulted in an approximately 25% improvement in the fits of a tricalcium silicate phase. In this neutron study, relatively minor adjustments to the structures resulted in decreased R-Bragg factors of tricalcium silicate phases, with very little changes to the overall bond distances. Rietveld refinement is commonly used for the phase quantification of cement clinker, which is difficult due to the complexity of component phases. Phases typically present in cement clinker are tricalcium silicate (Ca3SiO5), dicalcium silicate (Ca2SiO4), tricalcium aluminate (Ca3AI2O6), and tetracalcium aluminoferrite (Ca2(AI2O3)x(Fe2O3)i-x. Rietveld analysis is complicated by the polymorphic modification of these phases. At least seven tricalcium silicate polymorphs exist, three of which have structures that are commonly used in the Rietveld analysis of clinkers. Only one dicalcium silicate type has been shown likely to be present. Tricalcium aluminate has three polymorphs, all found in clinker, whilst tetracalcium aluminoferrite can appear with a varying AI:Fe ratio. Full-profile Rietveld methods have the ability to define the tricalcium silicate form. It is usual to include a polymorph of tricalcium silicate in each of the three crystal systems encountered when beginning a refinement of clinker data, and then exclude the crystal system(s) not found. Care must be taken so as not to enable one crystal system to alter itself to compensate for another. Quantification by diffraction methods of the tricalcium and dicalcium silicate phases in mixtures, such as in clinker, is further complicated by the wide range of

  18. Prediction of long-term chemical evolution of a low-pH cement designed for underground radioactive waste repositories

    International Nuclear Information System (INIS)

    Low-pH cements, also referred as low-alkalinity cements, are binders with a pore solution pH ≤ 11. They can be designed by replacing significant amounts of Portland cement (OPC) (>40%) by silica fume, which can be associated in some cases to low-CaO fly ash and/or ground granulated blast furnace slag to decrease the heat output during hydration by dilution of OPC and improve the mechanical strength of the final material. With the prospect of using these materials in a geological repository, it is of main importance to estimate their long-term properties and the influence of external and internal factors (chemical composition of the binder, storage temperature) on their characteristics. For this purpose, a three-way original approach was adopted. First, the hydration of low-pH cements was accelerated by milling cement slurries with zirconia beads. Secondly, the low-pH cement pastes were mimicked from mixtures of appropriate highly reactive oxides (lime, silica, calcium aluminate and calcium sulphate) in diluted suspensions. Thirdly, thermodynamic modelling was carried out to predict the mineral assemblage and composition of the solution at equilibrium, starting from the composition of the initial low-pH cement studied. Comparing the different results showed that this three-way approach is suitable to understand and predict the long-term chemical evolution of the cements since the final states obtained in all cases were equivalent. This method was then used to investigate the influence of temperature in the range 20-80 C on the chemical evolution of a low-pH cement. (authors)

  19. Cementing a wellbore using cementing material encapsulated in a shell

    Energy Technology Data Exchange (ETDEWEB)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  20. Nanocrystallization of aluminized surface of carbon steel for enhanced resistances to corrosion and corrosive wear

    International Nuclear Information System (INIS)

    Aluminizing is often used to improve steel's resistances to corrosion, oxidation and wear. This article reports our recent attempts to further improve aluminized carbon steel through surface nanocrystallization for higher resistances to corrosion and corrosive wear. The surface nanocrystallization was achieved using a process combining sandblasting and recovery heat treatment. The entire surface modification process includes dipping carbon steel specimens into a molten Al pool to form an Al coat, subsequent diffusion treatment at elevated temperature to form an aluminized layer, sandblasting to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. The grain size of the nanocrystallized aluminized surface layer was in the range of 20-100 nm. Electrochemical properties, electron work function (EWF), and corrosive wear of the nanocrystalline alloyed surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface of carbon steel exhibited improved resistances to corrosion, wear and corrosive wear. The passive film developed on the nanocrystallized aluminized surface was also evaluated in terms of its mechanical properties and adherence to the substrate.

  1. Characterization of steel 1035 hot-dip-aluminized in pure Al and Al-Cu alloys

    International Nuclear Information System (INIS)

    Medium carbon steel strips containing 0.35% carbon were hot-dip-aluminized in pure AI and AI-Cu alloys. An iron-aluminum interlayer, which is brittle in nature, developed at the interface between the melt and the steel substrate. Cu additions (4-16% by weight) in AI affected the growth rate of interlayer as well as the hardness and oxidation resistance of the aluminized surface. These effects were examined by using scanning electron microscopy, XRD 'X-Ray Diffraction'), and TGA (Thermal Gravimetric Analysis). In HAD (Hot Dip Aluminizing) with pure aluminum, the interlayer was 'thick' and exhibited a finger-like growth into steel substrate. While aluminizing in AI-Cu alloys, the thickness of the interlayer decreased consistently by gradually increasing the addition of Cu content in AI from 4-16%. Further, the addition of Cu beyond 12% transformed finger-like interface into nearly smooth interface. XRD analysis revealed that due to Cu addition, the tetragonal phases, Al/sub 2/ Cu and AI7Cu/sub 2/ Fe formed in surface coating in addition to FeAI/sub 3/ and Fe/sub 2/ Al/sub 5/ which generally form in steel HDA in pure Al. Their formation caused to reduce the growth of interlayer. Steel surface aluminized in AI-Cu alloys exhibited better hardness than of aluminized in pure AI and AI-Si alloys and also expressed excellent oxidation resistance up to 632 degree C. (author)

  2. Nanocrystallization of aluminized surface of carbon steel for enhanced resistances to corrosion and corrosive wear

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C. [Dept. of Materials Physical and Chemical, University of Science and Technology Beijing, Beijing 100083 (China); Dept. of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); Li, D.Y., E-mail: dongyang.li@ualberta.c [Dept. of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2V4 (Canada); Shang, C.J. [Dept. of Materials Physical and Chemical, University of Science and Technology Beijing, Beijing 100083 (China)

    2009-12-15

    Aluminizing is often used to improve steel's resistances to corrosion, oxidation and wear. This article reports our recent attempts to further improve aluminized carbon steel through surface nanocrystallization for higher resistances to corrosion and corrosive wear. The surface nanocrystallization was achieved using a process combining sandblasting and recovery heat treatment. The entire surface modification process includes dipping carbon steel specimens into a molten Al pool to form an Al coat, subsequent diffusion treatment at elevated temperature to form an aluminized layer, sandblasting to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. The grain size of the nanocrystallized aluminized surface layer was in the range of 20-100 nm. Electrochemical properties, electron work function (EWF), and corrosive wear of the nanocrystalline alloyed surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface of carbon steel exhibited improved resistances to corrosion, wear and corrosive wear. The passive film developed on the nanocrystallized aluminized surface was also evaluated in terms of its mechanical properties and adherence to the substrate.

  3. The mechanical effect of the existing cement mantle on the in-cement femoral revision.

    LENUS (Irish Health Repository)

    Keeling, Parnell

    2012-08-01

    Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.

  4. Produktie van cement

    NARCIS (Netherlands)

    Smit JRK; Coenen PWHG; Matthijsen AJCM; LAE; TAUW

    1995-01-01

    This document on cement production has been published within the SPIN project. In this project information has been collected on industrial plants or industrial processes to afford support to governmental policy on emission reduction. This document contains information on the processes, emission sou

  5. Hydration of alumina cement containing ferrotitanium slag with polycarboxylate-ethers (PCE) additives

    Science.gov (United States)

    Rechkalov, Denis; Chernogorlov, Sergey; Abyzov, Victor

    2016-01-01

    The paper is discussing results of study of alumina binder containing aluminous cement and ferrotitanium slag from aluminothermic process by Kliuchevskoi Ferroalloys corp. with various additives containing polycarboxylate-ethers (PCE). Selecting ferrotitanium slag as additive is based on the fact that its content of alumina and phase composition is closest to the alumina cement. The composition of the ferrotitanium slag is displayed. In order to compensate the decrease in strength caused by addition of ferrotitanium slag having low activity, PCE additives were added. As PCE additives were used Melflux 1641F, Melflux 2651F and Melflux PP200F by BASF. The effect of additives on the hydration of the binder, depending on the amount and time of additives hardening is shown. The composition of the hydration products in the cement was studied by physico-chemical analysis: derivatography and X-ray analysis. It is found that in the early stages of hardening PCE additives have inhibitory effect on hydration processes and promote new phase amorphization. The optimal content of additives was investigated. The basic properties of the binders have been tested. It was observed that the modified binders meet the requirements of Russian National State Standard GOST 969 to the alumina cement.

  6. Mineralogy and microstructure of two Mexican Portland cements for the confinement of radioactive waste

    International Nuclear Information System (INIS)

    The cementitious materials are involved in the different stages of radioactive waste management because they are used for the waste immobilization in the container, as well as filling in the spaces between containers vaults and also as engineering barrier and construction material in civil construction site. Therefore, is necessary to have a study of commercial cement available nationwide involving solid timely analysis in order to identify which phases are responsible for confinement of radionuclides, if considered the most reactive phase -CSH- or called secondary phases. In this research the hydration products of cement are presented as well as its importance in the nuclear industry. The analysis and observation of the cement clinker and the hydration products on the manufactured pulps with two commercial cements resistant to sulphates was realized using the observation technique of solid X-ray diffraction and nuclear analytic techniques of Moessbauer spectroscopy and X-Ray Fluorescence. The results show the presence of calcium silicate hydrates in the amorphous phase and the presence of ettringite crystals and portlandite sheets is appreciated. The abundant iron phase called tetra calcium ferro aluminate has been identified by Moessbauer spectroscopy. (Author)

  7. Histological and biomechanical studies of two bone colonizable cements in rabbits.

    Science.gov (United States)

    Lu, J X; About, I; Stephan, G; Van Landuyt, P; Dejou, J; Fiocchi, M; Lemaître, J; Proust, J P

    1999-08-01

    We have developed two colonizable bone cements: the first is a partially resorbable bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based cement (PRC) and the second is a calcium phosphate cement (CPC). PRC is composed of aluminous silanized ceramic and particles of a bioresorbable polymer embedded in a matrix of Bis-GMA. CPC consisted of tricalcium phosphate, monocalcium phosphate monohydrate, dicalcium phosphate dihydrate, and xanthane. Both cements were implanted into cavities drilled in rabbit femoral and tibial condyles. After 2, 4, 12, and 24 weeks of implantation, histological observations and biomechanical tests were performed. With CPC, a progressive osteointegration with a concomitant biodegradation in the presence of macrophages were observed. The mechanical study revealed a decrease of the compressive strength until the 4th week, followed by a slight increase. There was a general decrease in the elastic modulus with time. Moreover, by week 4, the histological study showed that the new bone was in direct contact with CPC margins. No inflammation was observed during the observation period. With PRC, the osteointegration as well as the biodegradation were slight, but its compressive strength was higher than that of cancellous bone and CPC (p < 0.05) at all observation periods. Its elastic modulus was greater than that of cancellous bone and CPC until the 4th week, then fell under the values of the cancellous bone. PMID:10458273

  8. Superplasticizer function and sorption in high performance cement based grouts

    International Nuclear Information System (INIS)

    This report describes laboratory studies undertaken to determine interactions between the main components of high-performance cement-based grout. These interactions were studied with the grouts in both their unset and hardened states with the specific intention of determining the following: the mechanistic function of superplasticizer; the phase of residence of the superplasticizer in hardened materials; and the permanence of the superplasticizer in hardened grouts. In unset pastes attempts were made to extract superplasticizer by mechanical processes. In hardened grout the superplasticizer was leached from the grouts. A microautoradiographic method was developed to investigate the phases of residence of superplasticizer in hardened grouts and confirm the inferences from the leaching studies. In hardened grout the superplasticizer was located on the hydrated phases formed during the early stages of cement hydration. These include tricalcium aluminate hydrates and tricalcium silicate phases. There is some tendency for the superplasticizer to sorb on ettringite. The presence of superplasticizer did not coincide with the locations of unreacted silica fume and high silica content phases such as C2S-H. The observations explain the findings of the studies of unset pastes which also showed that the sorption of superplasticizer is likely to be enhanced with increased mixing water content and, hence, distribution in and exposure to the hydration reaction surfaces in the grout. Superplasticizer can be leached in very small quantities from the hardened grouts. Rapid release takes place from the unsorbed superplasticizer contained in the accessible pore space. Subsequent release likely occurs with dissolution of the cement phases and the exposure of isolated pores to groundwater. (au) (37 refs.)

  9. Caesium immobilization in hydrated calcium-silicate-aluminate systems

    International Nuclear Information System (INIS)

    A special field of application of cementitious materials in using cements for immobilization of low and medium level radioactive wastes. Clarification of mechanisms of binding is complicated by the multicomponent nature of the solidifying matrix. In the present work, interest is turned to one of the most difficult to confine, long half-life isotopes, the caesium isotope. The cement matrix for solidification of the radioactive waste can be considered, with simplification, as a CaO-SiO2-Al2O3-H2O system. The various compositions of hydrated cementitious assemblages were investigated with respect to their Cs sorption by measuring the Cs distribution ratios (Rd) therein. Trends in sorption properties were detected, and the section of the ternary phase diagram with the best performance was identified

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

    Energy Technology Data Exchange (ETDEWEB)

    Kienzler, Bernhard; Metz, Volker; Schlieker, Martina; Bohnert, Elke [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. fuer Nukleare Entsorgung (INE)

    2015-07-01

    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){sub 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

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

    International Nuclear Information System (INIS)

    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 Germany

  12. Synthesis and characterization of pure nanocrystalline magnesium aluminate spinel powder

    Energy Technology Data Exchange (ETDEWEB)

    Tavangarian, F., E-mail: f_tavangarian@yahoo.co [Department of Materials Engineering, Isfahan University of Technology (IUT), Isfahan 84156-83111 (Iran, Islamic Republic of); Emadi, R. [Department of Materials Engineering, Isfahan University of Technology (IUT), Isfahan 84156-83111 (Iran, Islamic Republic of)

    2010-01-21

    Synthesis of nanocrystalline magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) by mechanical activation of a powder mixture containing Al{sub 2}O{sub 3} and MgCO{sub 3} with subsequent annealing was investigated. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques were utilized to characterize the as-milled and annealed samples. Results showed that pure nanocrystalline spinel could be fabricated completely by 5 h of mechanical activation with subsequent annealing at 1200 {sup o}C for 1 h with a crystallite size of about 45 nm. Further milling had no significant effects on structure or phase composition of spinel phase after subsequent annealing. The nanocrystalline spinel powder obtained after 60 h of milling and subsequent annealing at 1200 {sup o}C for 1 h had a crystallite size of about 25 nm according to Williamson-Hall approach and particle sizes smaller than 200 nm. Enhanced mechanical properties were observed in samples prepared from the powder mixture and milled for a longer period.

  13. Reducing DRIFT Backgrounds with a Submicron Aluminized-Mylar Cathode

    CERN Document Server

    Battat, James B R; Dorofeev, Alexei; Ezeribe, Anthony C; Fox, Jennifer R; Gauvreau, Jean-Luc; Gold, Michael; Harmon, Lydia; Harton, John; Lafler, Randy; Lauer, Robert J; Lee, Eric R; Loomba, Dinesh; Lumnah, Alexander; Matthews, John; Miller, Eric H; Mouton, Frederic; Murphy, Alexander St J; Phan, Nguyen; Sadler, Stephen W; Scarff, Andrew; Schuckman, Fred; Snowden-Ifft, Daniel; Spooner, Neil J C; Walker, Daniel

    2015-01-01

    Background events in the DRIFT-IId dark matter detector, mimicking potential WIMP signals, are predominantly caused by alpha decays on the central cathode in which the alpha particle is completely or partially absorbed by the cathode material. We installed a 0.9 micron thick aluminized-mylar cathode as a way to reduce the probability of producing these backgrounds. We study three generations of cathode (wire, thin-film, and radiologically clean thin-film) with a focus on the ratio of background events to alpha decays. Two independent methods of measuring the absolute alpha decay rate are used to ensure an accurate result, and agree to within $10\\%$. Using alpha range spectroscopy, we measure the radiologically cleanest cathode version to have a contamination of $3.3\\pm0.1$ ppt $^{234}$U and $73\\pm2$ ppb $^{238}$U. This cathode reduces the probability of producing an RPR from an alpha decay by a factor of $70\\pm20$ % while reducing the overall background rate by $96.5\\pm0.5\\%$ compared to the original stainles...

  14. Luminescent characteristics of praseodymium-doped zinc aluminate powders

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Perez, C.D.; Garcia-Hipolito, M.; Alvarez-Fregoso, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Coyoacan, DF (Mexico); Alvarez-Perez, M.A. [Facultad de Odontologia, Universidad Nacional Autonoma de Mexico, Coyoacan, DF (Mexico); Ramos-Brito, F. [Laboratorio de Materiales Optoelectronicos, DIDe, Centro de Ciencias de Sinaloa, Av. De las Americas No. 2771 Nte. Col. Villa Universidad, Culiacan, Sinaloa (Mexico); Falcony, C. [Centro de Investigaciones y Estudios Avanzados del IPN, Departamento de Fisica, Mexico, DF (Mexico)

    2010-02-15

    In this research, we report the cathodoluminescence (CL) and preliminary photoluminescence (PL) properties of praseodymium-doped zinc aluminate powders. ZnAl{sub 2}O{sub 4}:Pr powders were synthesized by a very simple chemical process. X-ray diffraction spectra indicated a cubic spinel crystalline structure with an average crystallite size of 15 nm. CL properties of the powders were studied as a function of the praseodymium concentration and electron-accelerating potential. In this case, all the cathodoluminescent emission spectra showed main peaks located at 494, 535, 611, 646, and 733 nm, which were associated to the electronic transitions {sup 3}P{sub 0}{yields}{sup 3}H{sub 4}, {sup 3}P{sub 0}{yields}{sup 3}H{sub 5}, {sup 3}P{sub 0}{yields}{sup 3}H{sub 6}, {sup 3}P{sub 0}{yields}{sup 3}F{sub 2}, and {sup 3}P{sub 0}{yields}{sup 3}F{sub 4} of the Pr{sup 3+} ions, respectively. A quenching of the CL, with increasing doping concentration, was observed. Also, an increment on cathodoluminescent emission intensity was observed as the accelerating voltage increased. The PL emission spectrum showed similar characteristics to those of the CL spectra. The chemical composition of the powders, as determined by energy dispersive spectroscopy, is also reported. In addition, the surface morphology characteristics of the powders are shown. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  15. Synthesis and optical property of zinc aluminate spinel cryogels

    Directory of Open Access Journals (Sweden)

    Lifen Su

    2016-06-01

    Full Text Available Zinc aluminate spinel cryogels with various molar ratio of Al/Zn are synthesized by sol–gel technology followed by vacuum freeze drying. The structures and optical properties are both found to be affected by the molar ratios of Al/Zn and annealed temperatures. The peaks of zinc oxide (ZnO and zinc dialuminum oxide (ZnAl2O4 are both obtained for the samples with more Zn content annealed at 750 °C or upward. The composites have a large surface area (137 m2/g with mesoporous structure after annealing at 750 °C. The SEM images reveal that the ZnAl2O4 crystals formed a multilayer structure with redundant ZnO particles which deposited on it. Furthermore, the maximum infrared reflectance is about 80% with an improvement of 35% in the infrared region after annealing at 950 °C compared with that of 450 °C, which indicates that these porous cryogels have a potential application as thermal insulating materials at a high temperature.

  16. Hard transparent domes and windows from magnesium aluminate spinel

    Science.gov (United States)

    DiGiovanni, Anthony A.; Fehrenbacher, Larry; Roy, Don W.

    2005-05-01

    Transparent magnesium aluminate spinel is an attractive material for use in a wide range of optical applications including windows, domes, armor, and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of ALON and sapphire in the mid-wave IR, making it especially attractive for the everincreasing performance requirements of current and next-generation IR imaging systems. Future designs in missile technology will require materials that can meet stringent performance demands in both optical and RF wavelengths. Loss characteristics for spinel are being investigated to meet those demands. Technology Assessment and Transfer Inc. (TA&T), have established a 9000 ft2 production facility for optical quality spinel based on the traditional hot-pressing followed by hot isostatic pressing (HIPing) route. Additionally, TA&T is developing pressureless sintering - a highly scalable, near net shape processing method based on traditional ceramic processing technology - to fabricate optical components. These two main processing approaches allow the widest variety of applications to be addressed using a range of optical components and configurations. The polycrystalline nature of spinel facilitates near net shape processing, which provides the potential to fabricate physically larger optical parts or larger quantities of parts at significantly lower costs compared to single crystal materials such as sapphire. Current research is focused at optimizing the processing parameters for both synthesis routes to maximize strength and transparency while minimizing the cost of fabrication.

  17. Structure and mechanical properties of irradiated magnesium aluminate spinel

    Science.gov (United States)

    Devanathan, R.; Yu, N.; Sickafus, K. E.; Nastasi, M.

    1996-09-01

    The relationship between structure and mechanical properties of MgAl 2O 4 spinel single crystals following 400 keV Xe 2+ irradiation at 100 K to doses up to 1 × 10 20 ions/m 2 was examined. The structural changes in the irradiated layer were studied using electron diffraction from cross-sectional samples. The nano-indentation technique was used to determine the mechanical properties. At low doses, the material transformed into a metastable crystalline phase characterized by the rearrangement of cations. At the onset of this transformation, the Young's modulus and hardness rose to values about 10 and 15% higher, respectively, than those of the unirradiated crystal. Upon further irradiation, the metastable crystal became amorphous. The Young's modulus and hardness of the amorphous state were about 30 and 60% less, respectively, than the corresponding values of unirradiated spinel. These results, in conjunction with the findings of a recent computer simulation study, provide important insights into the exceptional radiation resistance of magnesium aluminate spinel.

  18. Structure and mechanical properties of irradiated magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Devanathan, R. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.; Yu, N. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.; Sickafus, K.E. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.; Nastasi, M. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

    1996-09-01

    The relationship between structure and mechanical properties of MgAl{sub 2}O{sub 4} spinel single crystals following 400 keV Xe{sup 2+} irradiation at 100 K to doses up to 1.10{sup 20} ions/m{sup 2} was examined. The structural changes in the irradiated layer were studied using electron diffraction from cross-sectional samples. The nano-indentation technique was used to determine the mechanical properties. At low doses, the material transformed into a metastable crystalline phase characterized by the rearrangement of cations. At the onset of this transformation, the Young`s modulus and hardness rose to values about 10 and 15% higher, respectively, than those of the unirradiated crystal. Upon further irradiation, the metastable crystal became amorphous. The Young`s modulus and hardness of the amorphous state were about 30 and 60% less, respectively, than the corresponding values of unirradiated spinel. These results, in conjunction with the findings of a recent computer simulation study, provide important insights into the exceptional radiation resistance of magnesium aluminate spinel. (orig.).

  19. Synthesis and characterization of pure nanocrystalline magnesium aluminate spinel powder

    International Nuclear Information System (INIS)

    Synthesis of nanocrystalline magnesium aluminate spinel (MgAl2O4) by mechanical activation of a powder mixture containing Al2O3 and MgCO3 with subsequent annealing was investigated. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques were utilized to characterize the as-milled and annealed samples. Results showed that pure nanocrystalline spinel could be fabricated completely by 5 h of mechanical activation with subsequent annealing at 1200 oC for 1 h with a crystallite size of about 45 nm. Further milling had no significant effects on structure or phase composition of spinel phase after subsequent annealing. The nanocrystalline spinel powder obtained after 60 h of milling and subsequent annealing at 1200 oC for 1 h had a crystallite size of about 25 nm according to Williamson-Hall approach and particle sizes smaller than 200 nm. Enhanced mechanical properties were observed in samples prepared from the powder mixture and milled for a longer period.

  20. Structure and mechanical properties of irradiated magnesium aluminate spinel

    International Nuclear Information System (INIS)

    The relationship between structure and mechanical properties of MgAl2O4 spinel single crystals following 400 keV Xe2+ irradiation at 100 K to doses up to 1.1020 ions/m2 was examined. The structural changes in the irradiated layer were studied using electron diffraction from cross-sectional samples. The nano-indentation technique was used to determine the mechanical properties. At low doses, the material transformed into a metastable crystalline phase characterized by the rearrangement of cations. At the onset of this transformation, the Young's modulus and hardness rose to values about 10 and 15% higher, respectively, than those of the unirradiated crystal. Upon further irradiation, the metastable crystal became amorphous. The Young's modulus and hardness of the amorphous state were about 30 and 60% less, respectively, than the corresponding values of unirradiated spinel. These results, in conjunction with the findings of a recent computer simulation study, provide important insights into the exceptional radiation resistance of magnesium aluminate spinel. (orig.)

  1. Hydrogen permeation behavior of hot-dip aluminized manet steel

    International Nuclear Information System (INIS)

    A hot-dip process developed in FZK was applied to produce a hydrogen permeation barrier on MANET steel. The formation of the alumina layer is a two step process. The hot-dip aluminizing method produced first an intermetallic layer of FexAly by immersing the specimens in molten aluminium at 1073 K for 10 min. Secondly, by its exposure to an oxygen containing gas (1223 K, 10 and 30 h) the alumina layer is formed on the intermetallic layer. The last step is to form a fully martensitic phase (δ-ferritic free structure) by a specific heat treatment (1348 K, 40 min fast cool; 1023 K, 2 h). The oxide layer and bulk material were characterized by optical metallography, Vickers microhardness measurements, scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) on the surface. A permeation reduction larger than three orders of magnitude was obtained in the sample that has undergone a 30 h exposure in air at 1223 K. 14 refs., 4 figs

  2. US cement industry

    Energy Technology Data Exchange (ETDEWEB)

    Nisbet, M.A.

    1997-12-31

    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.

  3. Effects of particle size distribution on the refractory properties and corrosion mechanism of ultra-low cement castables

    Directory of Open Access Journals (Sweden)

    Y. Kutmen Kalpakli

    2008-12-01

    Full Text Available Purpose: This study examines the effects of distribution of particle size-dimensions on refractory properties ofalumina based castable refractories in which calcium aluminate cement (Secar-71 is used in low proportions as thehydraulic binder, which affects negatively properties of a refractory at high temperatures owing to its CaO content.Design/methodology/approach: In this study the effect of particle size distribution on refractory properties ofultra-low cement castables was investigated. Secar 71 cement was used as a binder. The composition of refractorycastable which consist of various particle size distribution was determined according to Andreasen packing model,with distribution coefficient (q of 0.21, 0.22, 0.23, 0.24, 0.25 and 0.26. A cold crushing strength (CCS of 93 MPa, aporosity value of 16.4% and a bulk density value of 3.12 g/cm3 were obtained via a distribution coefficient of 0.26.Findings: The mechanism of slag penetration on ULC for steel ladle was examined and the penetration layer waschemically analysed. Effects of mechanical properties on the corrosion mechanism were discussed.Research limitations/implications: Determination of effects of particle size distribustion on the refractoryproperties and corrosion mechanizm of ultra-low cement castables.Originality/value: The effects of particle size distribustion on the refractory properties and corrosion mechanizmof ultra-low cement castables were investoigated.

  4. Adsorption of polyelectrolytes and its influence on the rheology, zeta potential, and microstructure of various cement and hydrate phases.

    Science.gov (United States)

    Zingg, Anatol; Winnefeld, Frank; Holzer, Lorenz; Pakusch, Joachim; Becker, Stefan; Gauckler, Ludwig

    2008-07-15

    In this study the influence of polycarboxylate-based polyelectrolytes on the particle interaction among tricalcium silicate (C(3)S, main clinker phase), calcium silicate hydrates (CSH), and calcium aluminate sulfate hydrates (ettringite) (main hydration phases) has been examined. These phases are the constituents of major concern during early hydration of cement suspensions. The results of zeta potential measurements on single mineral phase experiments show that the phases C(3)S and CSH are positively charged in synthetic pore solution (liquid phase of hydrating cement suspension), whereas the ettringite is negatively charged. Due to these opposite charges, ettringite crystals should coagulate with CSH phases and/or deposit on surfaces of the much larger C(3)S clinker particles. This behavior was proven by cryo-microscopic analysis of high-pressure frozen cement suspensions, which illustrates the consequences of colloidal mechanisms on the microstructure of early cement suspensions. Furthermore, it is shown that the polyelectrolytes have a much higher adsorption affinity to ettringite surfaces (hydrate phase) compared to silicate surfaces. However, the results from rheology experiments reveal that the presence of polyelectrolytes has a strong impact on the suspension properties of all investigated mineral phases by decreasing yield stress and plastic viscosity. From the results it can be concluded that the ettringite is the dominant mineral phase in terms of the state of dispersion which includes particle-particle and particle-polyelectrolyte interaction in the bulk cement system. PMID:18502439

  5. 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

  6. Tympanoplasty with ionomeric cement.

    Science.gov (United States)

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

    Patients with isolated erosion of the long incus process suffer from severe hearing loss caused by lack of continuity of the ossicular chain. This study is a retrospective evaluation of the hearing results using two different surgical procedures. Since January 1993, 12 consecutive patients with isolated erosion of the long incus process have been treated with a new surgical technique in which the ossicular chain was rebuilt with ionomeric cement. The results in hearing performance (mean pure-tone average (PTA) 0.5, 1 and 2 kHz) were evaluated pre- and post-surgery, and compared to those in a group of 20 historical controls who underwent surgery in 1991 and 1992 using incus autograft interposition. Among the 12 index patients, 7 (58%) achieved improvement in PTA of > 10 dB, in 3 there was no difference and in 2 a slight decline. Among the 20 controls, 14 (70%) achieved improvement in PTA of > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy to perform, presents less risk of damage to the stapes and cochlea, requires less extensive surgery and does not exclude other surgical methods in cases of reoperation. PMID:10909000

  7. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    International Nuclear Information System (INIS)

    Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Plasma nitriding and post-aluminizing result in AlN single phase layer on the steel. • PN–Al coated steel had better corrosion resistance than Al–PN one. • Formation of oxide layer provided protection of PN–Al coated steel against corrosion. • Pitting and surface defects was the dominant corrosion mechanism in Al–PN coated steel. - Abstract: Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN–Al), while the others were pack aluminized followed by plasma nitriding (Al–PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (Rp) resistances were obtained in PN–Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al–PN specimens

  8. Improving electrochemical properties of AISI 1045 steels by duplex surface treatment of plasma nitriding and aluminizing

    Energy Technology Data Exchange (ETDEWEB)

    Haftlang, Farahnaz, E-mail: f.haftlang@students.semnan.ac.ir [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Habibolahzadeh, Ali [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Sohi, Mahmoud Heydarzadeh [School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-02-28

    Highlights: • AlN coating was applied on AISI 1045 steel via plasma nitriding and aluminizing. • Plasma nitriding and post-aluminizing result in AlN single phase layer on the steel. • PN–Al coated steel had better corrosion resistance than Al–PN one. • Formation of oxide layer provided protection of PN–Al coated steel against corrosion. • Pitting and surface defects was the dominant corrosion mechanism in Al–PN coated steel. - Abstract: Improvement in electrochemical behavior of AISI 1045 steel after applying aluminum nitride coating was investigated in 3.5% NaCl solution, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analyses. Aluminum nitride coating was applied on the steel surface by duplex treatment of pack aluminizing and plasma nitriding. Some specimens were plasma nitrided followed by aluminizing (PN–Al), while the others were pack aluminized followed by plasma nitriding (Al–PN). Topological and structural studies of the modified surfaces were conducted using scanning electron microscope (SEM) equipped by energy dispersive X-ray spectroscope (EDS), and X-ray diffractometer (XRD). The electrochemical measurements showed that the highest corrosion and polarization (R{sub p}) resistances were obtained in PN–Al specimens, having single phase superficial layer of AlN. Pitting mechanism was dominant reason of lower corrosion resistance in the Al–PN specimens.

  9. Study of the chemical species of fluorine 18 produced by neutron irradiation of lithium aluminate

    International Nuclear Information System (INIS)

    In the present work, the chemical form of fluorine-18 obtained by means of the neutron irradiated lithium aluminate was studied, in order to know its chemical behavior and to observe if it volatilizes and adheres to the walls of a tritium distillation system; for this matter paper chromatography and high voltage electrophoresis techniques were used. Lithium aluminate was synthetized, being characterized as LiAlO2 which was irradiated with neutrons in order to produce fluorine-18. Lithium aluminate is a non-soluble solid, therefore fluorine produced may not be extracted, unless it is dissolved or extracted through the solid. So as not affect in a drastic way the chemical form, it was submitted to extraction processes, agitating the irradiated samples with different acids and basic solutions in order to analyze fluorine-18. The best extraction agent was found to be HCl, where two forms of fluorine-18 were found, one at the point of application, probably as a complex hexafluoride-aluminate and the other as a characteristic Rf of the fluorine ion. In the tritium distillation with helium as a carrier of a sample irradiated and heated up to 220-250oC, no volatile types of fluorine-18 were found, thus it can be considered that in commercial production of tritium by means of neutron irradiation of lithium aluminate, fluorine-18 is not a damaging pollutant of the equipment pipe system. (Author)

  10. Structural Characterization of Spinel Zinc Aluminate Nanoparticles Prepared By Coprecipitation Method

    Science.gov (United States)

    Sunder, Shyam; Rohilla, Sunil; Kumar, Sushil; Aghamkar, Praveen

    2011-12-01

    Zinc aluminate is well known wide bandgap semiconductor with cubic spinel structure and transparent for wavelength greater than 320 nm. Therefore, ZnAl2O4 can be used for ultraviolet photoelectronic devices. Furthermore, spinel zinc aluminate is useful in many reactions as catalytic support. Moreover, zinc aluminate can be used as second phase in glaze layer of white ceramics to improve wear resistance and to preserve whiteness. In present study cubic spinel zinc aluminate nanoparticles have been synthesized from aqueous solution of Zn(NO3)2.6H2O (0.1 M) and Al(NO3)2.9H2O (0.2 M) using chemical coprecipitation technique. Ammonium hydroxide was used as precipitating agent and pH was maintained between 8 to 9. The precipitated slurry was filtered and washed several times with deionized double distilled water and dried at 110 °C. The fine powder was annealed at different temperatures from 600 °C to 900 °C for 4h in temperature controlled furnace. Structural characterization of annealed samples was carried out via X-ray Diffraction (XRD), and Fourier Transform Infrared spectroscopy (FTIR). XRD patterns reveal that zinc aluminate samples were cubic spinel nanoparticles and grain size determined by Debye-Scherrer formula is from 5 to 16 nm.

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

    International Nuclear Information System (INIS)

    , 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 (C3S/C2S), the tricalcium aluminate (C3A) influences in the setting time and tetra calcium ferro aluminate (C4AF) 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)

  12. [Haemotoxicity of dental luting cements].

    Science.gov (United States)

    Anders, A; Welker, D

    1989-06-01

    A glass ionomer luting cement (AquaCem) shows a relatively low haemolytic activity in comparison with two zinc phosphate cements. Especially the initial irritation by this cement is smaller. Although it is possible that AquaCem particularly, in unfavourable cases, may damage the pulpa dentin system; this is due to the slowly decrease of the haemolytic activity with increasing of the probes. We found that Adhesor showed in dependence of the batches a varying quality. PMID:2626769

  13. Cement penetration after patella venting.

    Science.gov (United States)

    Jones, Christopher W; Lam, Li-On; Butler, Adam; Wood, David J; Walsh, William R

    2009-01-01

    There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement. PMID:19010682

  14. MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation.

    Science.gov (United States)

    E, Yanxiong; Hao, Zhibiao; Yu, Jiadong; Wu, Chao; Liu, Runze; Wang, Lai; Xiong, Bing; Wang, Jian; Han, Yanjun; Sun, Changzheng; Luo, Yi

    2015-12-01

    By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films. PMID:26437653

  15. Fine structures in Fe3Al alloy layer of a new hot dip aluminized steel

    Indian Academy of Sciences (India)

    Li Yajiang; Wang Juan; Zhang Yonglan; X Holly

    2002-12-01

    The fine structure in the Fe–Al alloy layer of a new hot dip aluminized steel (HDA) was examined by means of X-ray diffractometry (XRD), electron diffraction technique, etc. The test results indicated that the Fe–Al alloy layer of the new aluminized steel mainly composed of Fe3Al, FeAl and -Fe (Al) solid solution. There was no brittle phase containing higher aluminum content, such as FeAl3 (59.18% Al) and Fe2Al7 (62.93% Al). The tiny cracks and embrittlement, formerly caused by these brittle phases in the conventional aluminum-coated steel, were effectively eliminated. There was no microscopic defect (such as tiny cracks, pores or loose layer) in the coating. This is favourable to resist high temperature oxidation and corrosion of the aluminized steel.

  16. Respiratory Health among Cement Workers in Ethiopia

    OpenAIRE

    Zeleke, Zeyede K.

    2011-01-01

    Background: Little is known on dust exposure and respiratory health among cement cleaners. There are only a few follow-up studies on respiratory health among cement factory workers and also studies on acute effects of cement dust exposure are limited in numbers. Objective: This study aimed at assessing cement dust exposure and adverse respiratory health effects among Ethiopian cement production workers, with particular focus on cement cleaners. Method: The first paper was...

  17. Microstructure and oxidation of hot-dip aluminized titanium at high temperature

    International Nuclear Information System (INIS)

    High-temperature diffusion of a hot-dip aluminized titanium is conducted to study microstructure changes and oxidation behavior of the aluminized titanium. After aluminizing, the titanium substrate is covered by a black layer in which tiny block-shaped TiAl3 particles are scattered in aluminum matrix. Based on the diffusion experiment results, the thickness of the aluminum diffusion layer at 800 deg. C increases with diffusion time. However, the aluminum diffusion layer at 900 deg. C grows and reaches its maximum thickness in 6 h, and then the thickness of the aluminum diffusion layer is reduced with prolonged diffusion time. An inversion of the diffusion layer thickness versus time appears for the aluminized titanium treated at 1000 deg. C, and the thickness of the diffusion layer keeps declining with diffusion time. The phases present in the outer and middle sublayers are titanium-rich TiAl3 and equilibrium TiAl3, respectively. However, the phase in inner sublayer changes from titanium-rich TiAl3 to TiAl2 and TiAl as diffusion temperature and time increase. Through energy-dispersive X-ray and X-ray diffraction analysis, the oxides formed in the oxidation process are Al2O3 and Al2TiO5. Although the oxide scale formed on the surface of the aluminized titanium has an insufficient stability and integrity, the thermal oxidation resistance of the aluminized titanium is still improved by over 5 times compared with that of the pure titanium

  18. Thermal Shock-resistant Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  19. Study of optical properties of cerium ion doped barium aluminate phosphor

    Science.gov (United States)

    Lohe, P. P.; Omanwar, S. K.; Bajaj, N. S.; Belsare, P. D.

    2016-05-01

    In the recent years due to their various optical and technological applications aluminate materials have attracted attention of several researchers. When these materials are doped with rare earth ions they show properties favorable for many optical applications such as high quantum efficiencies. These materials are used in various applications such as lamp phosphors, optically and thermoluminescence dosimeter etc Barium aluminate BaAl2O4 doped with Ce is well known long lasting phosphor. This paper reports synthesis of BaAl2O4: Ce phosphor prepared by a simple combustion synthesis. The samples were characterized for the phase purity, chemical bonds and luminescent properties.

  20. Health hazards of cement dust

    International Nuclear Information System (INIS)

    ven in the 21st century, millions of people are working daily in a dusty environment. They are exposed to different types of health hazards such as fume, gases and dust, which are risk factors in developing occupational disease. Cement industry is involved in the development of structure of this advanced and modern world but generates dust during its production. Cement dust causes lung function impairment, chronic obstructive lung disease, restrictive lung disease, pneumoconiosis and carcinoma of the lungs, stomach and colon. Other studies have shown that cement dust may enter into the systemic circulation and thereby reach the essentially all the organs of body and affects the different tissues including heart, liver, spleen, bone, muscles and hairs and ultimately affecting their micro-structure and physiological performance. Most of the studies have been previously attempted to evaluate the effects of cement dust exposure on the basis of spirometry or radiology, or both. However, collective effort describing the general effects of cement dust on different organ and systems in humans or animals, or both has not been published. Therefore, the aim of this review is to gather the potential toxic effects of cement dust and to minimize the health risks in cement mill workers by providing them with information regarding the hazards of cement dust. (author)

  1. The impact of zirconium oxide radiopacifier on the early hydration behaviour of white Portland cement

    International Nuclear Information System (INIS)

    Zirconium oxide has been identified as a candidate radiopacifying agent for use in Portland cement-based biomaterials. During this study, the impact of 20 wt.% zirconium oxide on the hydration and setting reactions of white Portland cement (WPC) was monitored by powder X-ray diffraction (XRD), 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), transmission electron microscopy (TEM) and Vicat apparatus. The presence of 20 wt.% zirconium oxide particles in the size-range of 0.2 to 5 μm was found to reduce the initial and final setting times of WPC from 172 to 147 min and 213 to 191 min, respectively. Zirconium oxide did not formally participate in the chemical reactions of the hydrating cement; however, the surface of the zirconium oxide particles presented heterogeneous nucleation sites for the precipitation and growth of the early C-S-H gel products which accelerated the initial setting reactions. The presence of zirconium oxide was found to have little impact on the development of the calcium (sulpho)aluminate hydrate phases. - Highlights: ► This is the first study of Portland cement-based biomaterials by 27Al and 29Si NMR. ► 20 wt.% ZrO2 radiopacifier accelerates the early cement hydration reactions. ► Extent of hydration after 6 h is increased from 5.7% to 15% in the presence of ZrO2. ► Initial and final setting times are reduced by 25 and 22 min, respectively. ► ZrO2 provides nucleation sites for the precipitation of early hydration products.

  2. Effect of the cement type on compatibility with carboxylate super plasticisers

    International Nuclear Information System (INIS)

    An empirical study was conducted to gain a fuller understanding of the interactions taking place in cement superplasticiser systems. To this end, two clinkers of clinkers of known chemical and phase composition were prepared in this study to gain insight into such interactions. One contained no tricalcium aluminate (C1), while the other had a 9% C3A content (C2). These clinkers were ground to approximately 340 m2/kg and blended with gypsum only or gypsum and Klein compound (3CaOx3Al2O3xCaSO4) (1, 2). Sufficient compound was added to C1 to ensure the formation of about the same amount of ettringite after 0.5 and 1 h of hydration as found in cement C2 + gypsum. The admixture used was a carboxylate superplasticiser. Rheology measurements showed that while paste yield stress was correlated to ettringite formation, no such simple relationship was observed for plastic viscosity. Plastic viscosity depended on the total hydrates formed, i.e., not only as ettringite but also as C-S-H gel. The findings revealed that in clinkers with very low sulfate and potassium contents, the rheology of carboxylate-containing cement paste is primarily controlled by ettringite formation. (Author) 15 refs.

  3. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    A K Misra; Renu Mathur

    2007-06-01

    The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, -values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0.11 and 0.20%. While alternate heating–cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing–thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

  4. Fabrication and characterization of calcium aluminate glass fibers

    Science.gov (United States)

    Foy, Paul R.

    Calcium aluminate glasses (CAG) offer excellent chemical durability, high strength, broad spectral transparency, and a refractory nature. This makes them ideal candidates for fiber optic power delivery and sensor systems in the infrared spectrum. CAG also have the potential to form ultra-low loss optical materials. The fabrication of glass optical fibers from CAG was investigated in this study. High quality bulk glasses were obtained from the best industrial sources available. These glasses included silica and baria doped CAG compositions. A preform fabrication method was developed to obtain drawing samples. An optical fiber draw furnace was specially modified to achieve fiber drawing. A novel drawing method was also developed. Solid and hollow CAG waveguides, and CAG core/silica clad waveguides were obtained from drawing preforms. This represents the first successful fiber drawing of this glass system. Teflon coating for optical cladding and strength protection was also investigated. Infrared Spectroscopy was used to assess the attenuation in the drawn fibers. 7 dB/m at 2.7 mum with the baria doped CAG solid waveguide was recorded. This represents the lowest loss documented for fibers fabricated from CAG. Laser power propagation through solid and hollow waveguides was investigated. 24 Watts of CO2 laser power was delivered into a hollow baria doped CAG waveguide. 10.13 J/mm2 of 2.94 mum Erbium YAG laser power was delivered through solid baria doped CAG waveguide. Fiber strength testing was performed on the CAG fibers through four point bend testing. The best strength obtained was 1290 MPa for baria doped CAG. Glass stability was assessed using Differential Thermal Analysis. Fiber surface crystallization products were characterized using Energy Dispersive Analysis, Scanning Electron Microscopy, a specially modified Hot Stage X-Ray, and Guinier Camera X-Ray Analysis. The surface crystallization analysis revealed the formation of Ca3Al2O6 in the silica doped CAG

  5. Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1998-03-10

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.

  6. Phase transformation of alumina coating by plasma assisted tempering of aluminized P91 steels

    Energy Technology Data Exchange (ETDEWEB)

    Jamnapara, N.I., E-mail: nirav@ipr.res.in [FCIPT Division, Institute for Plasma Research, Gandhinagar 382016 (India); Department of Met. Eng. and Mat. Sci., IIT Bombay, Powai, Mumbai 400076 (India); Mukherjee, S. [FCIPT Division, Institute for Plasma Research, Gandhinagar 382016 (India); Khanna, A.S. [Department of Met. Eng. and Mat. Sci., IIT Bombay, Powai, Mumbai 400076 (India)

    2015-09-15

    Highlights: • A novel plasma assisted heat treatment process for aluminized P91 steels is reported. • Plasma plays a vital role in phase transformation of Al{sub 2}O{sub 3} from θ to α phase. • Presence of O{sup ∗} species in plasma facilitates θ to α transformation. - Abstract: α-Al{sub 2}O{sub 3} coating on aluminized surfaces are considered candidate coatings for blanket applications in fusion reactor. In order to generate α-Al{sub 2}O{sub 3}, aluminized P91 steel samples were subjected to normalizing and tempering treatments at 980 °C and 750 °C respectively. Oxygen plasma has been used during tempering treatment of aluminized P91 steel samples at 750 °C for 1 h. The resulting alumina coating on plasma tempered samples were compared with those of thermally tempered samples. The alumina films were characterized using XRD, XPS, and SEM–EDS techniques. Results indicate that the thermally tempered samples had θ-Al{sub 2}O{sub 3} coating while the plasma tempered samples had α-Al{sub 2}O{sub 3} coating after heat treatment. Such transformation of alumina phase was not visible without plasma. A hypothesis of θ to α-Al{sub 2}O{sub 3} transformation in plasma is proposed. This paper emphasizes the role of plasma processing on generation of an improved insulation coating for TBM applications in fusion reactors.

  7. Data and properties of lithium aluminate γ LiAl02

    International Nuclear Information System (INIS)

    In this report are gathered and analysed the literature data until july 1st, 1984, concerning the properties of lithium aluminate γ LiAl02 relevant for the investigation of this compound as a tritium breeding material for a fusion reactor blanket. 67 refs

  8. Data and properties of lithium aluminate γ LiAlO2

    International Nuclear Information System (INIS)

    In this report are gathered and analysed the literature data until july 1st, 1984, concerning the properties of lithium aluminate γ LiAlO2 relevant for the investigation of this compound as a tritum breeding material for a fusion reactor blanket. A french version of this report exists

  9. Hydrolitical equilibrium of hydrates of portland cement, part 1

    International Nuclear Information System (INIS)

    Based on the basic principles of thermodynamics the present report (Part 1) provides a contribution to thermodynamically favoured stable states of the most important hydrated compounds of portland cement. An extensive literature search was made to find the related thermodynamic data for the data-base. According to our calculations even at room temperature the C-S-H-Gel is not the thermodynamically most stable end product of hydrated calcium silicates. The most stable products might be Hillebrandit, Foshagit, 11A Tobermorit or Gyrolit. It is generally agreed, that the cubic hydrate C3AH6 is the stable end product of calcium aluminate hydrates. Our calculations lead to the same results. By sulfates we have found, that at lower temperatures Ettringit is the stable phase, but at higher temperatures the corresponding monosulfate is more stable. Ettringit is not stable relative to C3AH6 even in its water solutions. Ettringit is also not stable relative to Friedl's salt. More information could be found in Part 2 of this report (in preparation). 46 figs., 13 refs., 18 tabs. (Authors)

  10. Ca stabilized zirconia based composites by wet consolidation of zirconia and high alumina cement mixtures

    International Nuclear Information System (INIS)

    Composites of the CaO-Al2O3-ZrO2 system are widely used in many industrial applications. In this study, porous Ca stabilized ZrO2 composites were developed from a starting mixture of m-ZrO2 and calcium aluminate cement. Ceramics were produced by wet consolidation of aqueous suspensions with and without corn starch as pore former agent and sintering at 1000-1500 °C. The influence of processing parameters on crystalline phases, sintering behavior and textural characteristics was examined. Stabilized c-ZrO2 formed with the composition of Ca0.15Zr0.85O1.85. The sintering of the mixtures lead to porous composites materials. Textural properties were analyzed considering the initial composition and the present crystalline phases. (author)

  11. Ca stabilized zirconia based composites by wet consolidation of zirconia and high alumina cement mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Bruni, Y.L.; Garrido, L.B.; Aglietti, E.F., E-mail: lgarrido@cetmic.unlp.edu.ar [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC/CIC-CONICET La Plata), Buenos Aires (Argentina)

    2012-07-01

    Composites of the CaO-Al{sub 2}O{sub 3}-ZrO{sub 2} system are widely used in many industrial applications. In this study, porous Ca stabilized ZrO{sub 2} composites were developed from a starting mixture of m-ZrO{sub 2} and calcium aluminate cement. Ceramics were produced by wet consolidation of aqueous suspensions with and without corn starch as pore former agent and sintering at 1000-1500 °C. The influence of processing parameters on crystalline phases, sintering behavior and textural characteristics was examined. Stabilized c-ZrO{sub 2} formed with the composition of Ca{sub 0.15}Zr{sub 0.85}O{sub 1.85}. The sintering of the mixtures lead to porous composites materials. Textural properties were analyzed considering the initial composition and the present crystalline phases. (author)

  12. Cement/slag chemistry studies

    International Nuclear Information System (INIS)

    The performance of cement-based matrices intended for radwaste immobilization is assessed. The long-term performance of the matrix is characterized by thermodynamic evaluation of experimental data. The results are presented in a general form, amenable to a range of specific formulations. The interaction of specific radwaste components with cements has been studied, using Iodine as an example. It occurs as both I- and IO3- species, but these differ sharply in sorption characteristics. The effect of ionizing radiation of the pH and Eh of cement matrices is reported. (author)

  13. 13C chemical shift anisotropies for carbonate ions in cement minerals and the use of 13C, 27Al and 29Si MAS NMR in studies of Portland cement including limestone additions

    International Nuclear Information System (INIS)

    13C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed 13C MAS or 13C(1H) CP/MAS NMR spectra (9.4 T or 14.1 T) for 13C in natural abundance. The variation in the 13C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in 13C MAS NMR spectra. However, it is shown that by combining 13C MAS and 13C(1H) CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends 29Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in 27Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate. -- Highlights: •13C chemical shift anisotropies for inorganic carbonates from 13C MAS NMR. •Narrow 13C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by 13C MAS and 13C(1H) CP/MAS NMR. •Limestone accelerates the hydration for alite in Portland – limestone cements. •Limestone reduces the amount of aluminium incorporated in the C-S-H phase

  14. Cementing porcelain-fused-to-metal crowns.

    Science.gov (United States)

    Vadachkoria, D

    2009-12-01

    The clinical success of fixed prosthodontic restorations can be complex and involve multifaceted procedures. Preparation design, oral hygiene/micro flora, mechanical forces, and restorative materials are only a few of the factors which contribute to overall success. One key factor to success is choosing the proper cement. Popular use of cements for PFM crowns has shifted from zinc phosphate and glass ionomer cements to resin-reinforced glass ionomer, or RRGI, cements. This change has been rapid and profound. Dental cements have always been less than ideal materials, but this is shift to the relatively new RRGI category justified. Resin-reinforced glass ionomer (RRGI) cements appear to be better than zinc phosphate and glass ionomer cements when placing porcelain-to-metal crowns. RRGI cements, such as RelyX Luting, Fuji Plus and Vitremer Luting Cement, satisfy more of the ideal characteristics of PFM cementation than any other previous cement. Expansion of all three cements has not caused any apparent problems with the cements when used with PFM or metal crowns, but these cements, however, should be avoided when cementing all-ceramic crowns. PMID:20090144

  15. Sliding wear of cemented carbides

    International Nuclear Information System (INIS)

    Cemented carbides are known to be very hard and wear resistant and are therefor often used in applications involving surface damage and wear. The wear rate of cemented carbides is often measured in abrasion. In such tests it has been shown that the wear rate is inversely dependent on the material hardness. The sliding wear is even more of a surface phenomenon than a abrasion, making it difficult to predict friction and wear from bulk properties. This paper concentrates on the sliding wear of cemented carbides and elucidates some wear mechanisms. It is especially shown that a fragmenting wear mechanism of WC is very important for the description of wear of cemented carbides. (author)

  16. 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 in...

  17. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    OpenAIRE

    Adriana Eštoková; Lenka Palaščáková

    2013-01-01

    The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices) of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in t...

  18. Assessment of the compatibility of wood and plastic with cement for their recycling in cement composites

    OpenAIRE

    Andrade, André De; Caldeira, Fernando

    2010-01-01

    The compatibility between maritime pine wood and cement, and between plastic (LDPE) and cement, was assessed for the recycling of wood and plastic in cement composites. Temperature vs. time profiles of cement setting were registered and compatibility indices were calculated. Results indicate that recycling of plastics in plastic-cement composites does not pose any questions regarding chemical compatibility. However, maritime pine hinders cement setting in some extent. So, in or...

  19. 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

  20. Manufacture and properties of fluoride cement

    Science.gov (United States)

    Malata-Chirwa, Charles David

    This research work aimed at characterising composition, hydration and physical properties of fluoride cement, by studying samples of the cement obtained from Malawi, and comparing them to ordinary Portland cement. By confirming the suitable characteristics of fluoride cement through this work, the results of the research work provide a good basis for the wider adoption of fluoride cement as an alternative to ordinary Portland cement, especially in developing economies. Numerous accounts have been cited regarding the production and use of fluoride cement. Since there have not been conclusive agreement as to its properties, this study was limited to the theories of successful incorporation of fluoride compounds in the manufacture of fluoride cement. Hence, the properties and characteristics reported in this study relate to the cement currently manufactured in Malawi, and, on a comparative basis only, to that manufactured in other parts of the world. Samples of the fluoride cement used in the study were obtained by synthetic manufacture of the cement using common raw materials for the manufacture of fluoride cement that is limestone, silica sand, and fluorspar. These samples were subjected to several comparative tests used to characterise cements including examination under x-ray diffractometer, scanning electron microscopy and tests for setting time and compressive strength. Under similar laboratory conditions, it was possible to prove that fluoride cement hardens more rapidly than ordinary Portland cement. Also observed during the experimental work is that fluoride cement develops higher compressive strengths than ordinary Portland cement. The hardening and setting times are significantly different between the two cements. Also the nature of the hydration products, that is the microstructural development is significantly different in the two cements. The differences brought about between the two cements are because of the presence of fluorine during the clinkering

  1. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  2. Low pH Cements

    International Nuclear Information System (INIS)

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit ≤ 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio ≤ 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  3. Effect of the addition of nanosilica on white cement hydration at 25°C

    Directory of Open Access Journals (Sweden)

    Sáez del Bosque I.F.

    2014-04-01

    Full Text Available The cement industry is keen on reducing natural resource consumption, reusing waste that would otherwise be sent to a rubbish tip and lowering its CO2 emissions. In pursuit of those objectives, the addition of materials such as silica fume, ceramic waste, rice husk and precipitated or colloidal nanosilica, in the various stages of cement manufacture has become increasingly common. That practice inspired the present study (using isothermal conduction calorimetry, 29Si and 27Al MAS NMR, XRD and DTA/TG of the effect of precipitated amorphous nanosilica (10 wt% on white portland cement (WPC hydration. The isothermal conduction calorimetry findings, which were consistent with the NMR and DTA/TG results, showed that adding amorphous nanosilica altered reaction kinetics, expediting alite and belite hydration. The addition also intensified the heat flow attributed to alumina phase hydration and brought the respective peak forward. Although no general consensus has been reached in the literature on the attribution of the third peak appearing on the calorimetric curve for WPC, based on the present findings, the main aluminate hydrate product is monosulfoaluminate. Furthermore, a pre-peak inflection point on the profile of the first exothermal peak on the WPC calorimetric curve was interpreted as the beginning of the pozzolanic reaction, which accelerates alite hydration, consuming portlandite and raising the heat released. C-S-H gel nanostructure was also modified. The results revealed a linear relationship in both the blended and the pure cement pastes between the degree of hydration and the number of Q1 and Q2 units in the gel. The presence of Q2 units was much greater and of Q1 units slightly lower in the former than in the latter.

  4. Low-temperature methods of magnesium aluminate spinel synthesis and the influence of yttrium oxide on the sintering process

    International Nuclear Information System (INIS)

    Low-temperature methods of magnesium aluminate spinel synthesis are studied: sol-gel process, co-crystallization of magnesium and aluminium nitrate solutions followed by their decomposition, and mechanochemical activation of hydrated nitrates of magnesium and aluminium. It is shown that yttrium oxide addition permits a substantial intensification of MgAl2O4 sintering and formation of a rather dense and hard ceramics on magnesium aluminate spinel base at 1300 deg C

  5. Combined effect of amino and carboxyl group in α-alanine on seeded precipitation of sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    L(U) Bao-lin; CHEN Qi-yuan; YIN Zhou-lan; HU Hui-ping

    2009-01-01

    α-alanine was adopted as a new additive to elucidate the seeded precipitation mechanism of sodium aluminate solution. α-alanine has the inhibitory effect at the initial period of reaction, but the favorable effect in subsequent reaction. The combined effect of amino and carboxyl group in α-alanine was confirmed by investigating the effect of propionic acid, ethamine and the mixture of propionic acid and ethamine (mole ratio 1:1) on the precipitation of sodium aluminate solution, respectively. The inhibitory effect derives from the adsorption of amino or carboxyl group in α-alanine on the active surface sites of gibbsite, which was confirmed by the alleviating inhibitory effects of propionic acid, ethamine and α-alanine due to the double crystal seed mass. The semi-quantitative IR spectrum analysis of the relative concentrations of Al2O(OH)62- with the band at about 550 cm-1 and polynuclear aluminate ion with the bands at about 880 cm-1 and 635 cm-1, indicates that the dynamic balance among some aluminate species present in sodium aluminate solution is broken due to the addition of α-alanine, thus resulting in the change of the seeded precipitation ratio of sodium aluminate solution.

  6. The effect of cement creep and cement fatigue damage on the micromechanics of the cement-bone interface.

    Science.gov (United States)

    Waanders, Daan; Janssen, Dennis; Mann, Kenneth A; Verdonschot, Nico

    2010-11-16

    The cement-bone interface provides fixation for the cement mantle within the bone. The cement-bone interface is affected by fatigue loading in terms of fatigue damage or microcracks and creep, both mostly in the cement. This study investigates how fatigue damage and cement creep separately affect the mechanical response of the cement-bone interface at various load levels in terms of plastic displacement and crack formation. Two FEA models were created, which were based on micro-computed tomography data of two physical cement-bone interface specimens. These models were subjected to tensile fatigue loads with four different magnitudes. Three deformation modes of the cement were considered: 'only creep', 'only damage' or 'creep and damage'. The interfacial plastic deformation, the crack reduction as a result of creep and the interfacial stresses in the bone were monitored. The results demonstrate that, although some models failed early, the majority of plastic displacement was caused by fatigue damage, rather than cement creep. However, cement creep does decrease the crack formation in the cement up to 20%. Finally, while cement creep hardly influences the stress levels in the bone, fatigue damage of the cement considerably increases the stress levels in the bone. We conclude that at low load levels the plastic displacement is mainly caused by creep. At moderate to high load levels, however, the plastic displacement is dominated by fatigue damage and is hardly affected by creep, although creep reduced the number of cracks in moderate to high load region. PMID:20692663

  7. Cementation of Loose Sand Particles based on Bio-cement

    Institute of Scientific and Technical Information of China (English)

    RONG Hui; QIAN Chunxiang

    2014-01-01

    Loose sand particles could be cemented to sandstone by bio-cement (microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.

  8. Features of the influence of carbonaceous nanoparticles on the rheological properties of cement paste and technological properties of the fine-grained concrete

    Directory of Open Access Journals (Sweden)

    TOLMACHEV Sergei Nikolaevich

    2014-10-01

    Full Text Available The article describes the technological features of the manufacture of cement concrete road with carbonaceous nanoparticles. The research was carried out to determine the influence of the carbonaceous nanoparticles (CNP on the properties of cement paste and monominerals cement clinker. The method of determination of mobility and the viscosity of the cement paste due to vibration has been developed. It is shown that the optimal content of the CNP in the cement paste leads to increase of its mobility and reduced viscosity. Introduction of CNP into the cement paste helps to prolong the life setting. The investigations of zeta potential of the suspensions of the cement and cement clinker monominerals with CNP have been done. They showed that the introduction of the CNP into suspension monominerals cement clinker tricalcium aluminate (S3A and tetracalcium alyumoferrita (S4AF leads to dramatic increase of electronegativity and the change of the sign of the potential of these monominerals to the opposite. The effect of carbonaceous nanoparticles on the mechanical and structural characteristics of the cement stone and concrete with CNP was determined. It is shown that the effectiveness of the impact of the CNP on the processes of structure decreases when shifting from submikrostructure to micro-structure and further to meso- and macrostructure. Efficacy of CNP depends on the concrete mixtures compaction method: hard mixture compression or vibropressing leads to two times larger increase in strength when introducing CNP than vibration compaction of moving mixtures. The electron-microscopic studies of the structure of vibrocompacted and pressed cement stone and concrete have been done. One can observe that in the structure of concrete with CNP there are spatial frames inside and around which tumor crystallization takes place. That intensifies the processes of structure formation. Concrete with CNP can be characterized by prevailing dense structure, the

  9. Characteristics solidified cement waste using heavy concrete and light concrete paste generated from KRR-2 and UCP

    International Nuclear Information System (INIS)

    As the number of obsolete research reactors and nuclear facilities increases, dismantling nuclear facilities has become an influential issue. During the decommissioning of nuclear plants and facilities, large quantities of slightly contaminated concrete wastes are generated. In Korea, the decontamination and decommissioning of the retired TRIGA MARK II and III research reactors and a uranium conversion plant at KAERI has been under way. By dismantling KRR-2, more than 260 tons of radioactive concrete wastes were generated among the total 2,000 tons of concrete wastes and more than 60 tons of concrete wastes contaminated with uranium compounds have been generated. Typically, the contaminated layer is only 1∼10mm thick because cement materials are porous media, the penetration of radionuclides may occur up to several centimeters from the surface of a material. Concrete is a structural material which generally consists of a binder (cement), water, and aggregate. The binder is typically a portland cement which comprises the four principal clinker phases tricalcium silicate (Ca3SiO5) and constitutes 50-70%, decalcium silicate (Ca2SiO4), tricalcium aluminate (Ca3Al2O6), and calcium aluminoferrite (Ca4Al2Fe2O10). Cement powder (anhydrous cement) created from the co-grinding of clinkers and gypsum is mixed with waster and hydrate phase are formed. The interaction between highly charged C-S-H particles in the presence of divalent calcium counter ions is strongly attractive because of ion-ion correlations and a negligible entropic repulsion. In the temperature range 100-300 .deg. C, these evolutions are mainly attributed to the loss of the bound water from the C-S-H gel. Similar consequences have been reported for mortars and concretes enhanced sometimes by the appearance of micro-cracks related to the strain incompatibilities between the aggregates and the cement paste. Concrete aggregates are combined mutually strongly by hydrated cement paste. Radionuclides may be found

  10. Coating Prospects in Corrosion Prevention of Aluminized Steel and Its Coupling with Magnesium

    Science.gov (United States)

    Sun, Fuyan

    In this study, a plasma electrolytic oxidation (PEO) process was used to form oxide coating on aluminized steel, heated aluminized steel and magnesium. A potentiodynamic polarization corrosion test was employed to investigate the general corrosion properties. Galvanic corrosion of steel samples and magnesium samples was studied by zero resistance ammeter (ZRA) tests and boiling tests. Scanning electron microscopy (SEM) and EDS were used to investigate the coating microstructure and the coating/substrate interface. In general, the PEO coatings on all three substrate can help prevent general corrosion. 6-min coated magnesium with unipolar current mode performs best in most galvanic couplings for preventing both general corrosion and galvanic corrosion. Factors which could influence galvanic corrosion behaviors of tested samples were discussed based on area ratios of anode/cathode and cell potential driving force during the ZRA corrosion tests and boiling tests.

  11. Calcium aluminates for quick cesium trapping, application for nuclear power plants

    International Nuclear Information System (INIS)

    It has recently been shown that cesium dissolved in water could be trapped in a solid structure by adding cementitious calcium aluminates and fume silica. Calcium aluminates are heat resistant and widely used as refractory products. Extensive studies on the rheological properties has been achieved. It is now possible to obtain flow properties to such an extent as to percolate a slurry through broken structures and give high mechanical strength in a short time. This along with the other properties of thermal shock resistance and cesium trapping makes a solution possible for nuclear building safety as a preventitive or a curative material. For example, at Chernobyl, this material could improve safety by remote casting techniques, construction of a structure which could serve as as ash tray under the coruim. Remotelly controlled equipment needed for this are in operation in more than 50 standardized PWR's. The equipment performs maintenance and inspection tasks with low radiation exposure

  12. Relation between silico-aluminous fly ash and its coal of origin

    Institute of Scientific and Technical Information of China (English)

    Jean-Charles Benezet; Pierre Adamiec; Ali Benhassaine

    2008-01-01

    Fly ashes are typical complex solids which incorporate at the same time intrinsic properties derived from the layers (various mineralogical and dimensional spectra) and major transformations generated during prior processing. To use fly ashes in various applications, it is necessary to characterise them completely. The first research to date carried out on silico-aluminous fly ashes in order to characterise them physically,morphologically, chemically and mineralogically, resulted in the recognition that they are relatively simple materials. In the present study, a silico-aluminous fly ash coming from the power station of Albi (France) was selected. Heat treatment at 450 and 1200 ~C together with coal simulated the treatment undergone by coal in the power station in order to mimic real coal residue. In conclusion, the diversity of the particles contained in fly ash could only be explained by the relation existing between the fly ash and its coal of origin.

  13. Preparation and characterization of magnesium aluminate spinel for FCC SOx abatement

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, A.A.; Woltermann, G.M.; Cormier, W.E. (Katalistiks International, Inc., Baltimore, MD (USA))

    1988-09-01

    Recent studies have demonstrated that cerium containing magnesium aluminate spinels such as MgAl{sub 2}O{sub 4} and Mg{sub 2}Al{sub 2}O{sub 5} are very effective SO{sub x} reduction catalysts for FCC units. These magnesium aluminate spinels can be prepared by three different techniques: (1) thermal co-condensation, (2) co-precipitation, and (3) Co-gel formation. Some of the important physical and chemical properties of a spinel depends on the preparative route used. This paper will discuss the preparation methods and characterization techniques utilized for these spinels and how the SO{sub x} abatement activity of these spinels are related to the preparative route used.

  14. Kinetics of crystal growth on seeded precipitation of sodium aluminate solutions with new device

    Institute of Scientific and Technical Information of China (English)

    陈金清; 张平民; 甘国耀; 尹周澜; 陈启元

    2004-01-01

    A new device was designed, which can effectively avoid the undesired nucleation and agglomeration of fine particles on the experimental results during the seaded precipitation of sodium aluminate solution, and moreover, the experimental conditions are nearly kept constant during the experiment. With the new device, it is proven that a good result can be obtained on the kinetics study of the crystal growth in seeded precipitation of sodium aluminate solution. Experiments were carried out with the concentration of Na2 O (Nk)170 g/L, the mole ratio of Na2 O to Al2 O3 (αk) all between 1.52 to 2.01, at 65, 70, 75 ℃, respectively. And the kinetics equation of crystal growth of gibbsite was deduced.

  15. Protection against corrosion of iron alloys by aluminized coatings produced using two different processes

    International Nuclear Information System (INIS)

    Aluminized coatings were produced on iron by means of two different processes: electron beam deposition under UHV of Al on iron samples previously covered with 57Fe films, and hot-dipping of iron samples in molten aluminium. Aluminized samples were submitted to thermal treatments in order to promote interdiffusion at the Fe-Al interface and favour the formation of Fe-Al intermetallic compounds of composition suitable to protect the underlying iron from oxidation. Phase composition, structure and morphology of both as deposited and thermally treated coatings were characterized by means of X-ray diffraction, Moessbauer spectroscopy and metallographic techniques. Significant differences among the effects of the Fe-Al interdiffusion occurring for Al layers produced with the two processes are pointed out and discussed.

  16. Effect of Coating-thickness on the formability of hot dip aluminized steel

    International Nuclear Information System (INIS)

    The influence of coating thickness on the formability and ductility of hot-dip-aluminized steel has been determined using a 3-point bend test and optical metallography. The ductility / formability was estimated from the 3-point bend test wherein the angle of bend at which the cracks start to appear on the surface of the aluminized sheet during bending, was taken as an index of the formability / ductility. It was observed that as the amount of silicon in the aluminising melt was gradually increased the measured ductility of the sheet sample also increased. Metallographic examination has shown that as the amount of silicon in the aluminising melt was increased the thickness of the intermediate compound layer, between the outer aluminum coat and the substrate steel, decreased. It was thus indicated from these experiments that the formability / ductility of the sheet was inversely related to the thickness of the interlayer. (author)

  17. Fatigue damage and environment interaction of polyester aluminized glass fiber composites

    OpenAIRE

    Ferreira, J. M.; Pires, J. T. B.; Costa, J. D.; Errajhi, O. A.; Richardson, M

    2007-01-01

    Aluminized glass fiber composites in a polyester matrix were used in this work in an attempt to study their fatigue resistance under both dry and water saturated ambient conditions (compared to conventional glass fiber composites). These composites, containing specially modified fibers, exhibit increased thermal and electrical conduction properties whilst still being potentially adequate for many structural applications. The fatigue tests were performed in tension at ambient temperature and a...

  18. Radio-luminescence of defects and impurity Ions in magnesium aluminates spinel

    OpenAIRE

    Gritsyna, V.T.; Kazarinov, Yu.G.; Moskvitin, A. O.

    2012-01-01

    The investigations of radio-luminescence (RL) in magnesium aluminates spinel crystals at variation of the time, intensity of X-irradiation and temperature of sample were provided. There were registered three prominent RL bands related to electron-hole recombination process at anti-site defects, emission of Mn2+-ions and emission of Cr3+-ions. The kinetics of the growth of indicated RL emissions show the competing processes of the capture of free charge carriers generated at irradiati...

  19. The variable resistance of magnesium aluminate spinel to point-defect aggregation during irradiation

    International Nuclear Information System (INIS)

    The formation of point-defect clusters in irradiated magnesium aluminate spinel is sensitive to composition. No dislocation loops develop in stoichiometric materials bombarded with 1 MeV electrons, but pre-existing screw dislocations climb into helices. This is attributed to difficulties in loop nucleation rather than in the generation and diffusion of point defects or their differential absorption at dislocation sinks. The bias for interstitials is calculated to be 1.6% at 1073 K. (author)

  20. Variable resistance of magnesium aluminate spinel to point-defect aggregation during irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, S.N.; Shaibani, S.J.

    1987-01-01

    The formation of point-defect clusters in irradiated magnesium aluminate spinel is sensitive to composition. No dislocation loops develop in stoichiometric materials bombarded with 1 MeV electrons, but pre-existing screw dislocations climb into helices. This is attributed to difficulties in loop nucleation rather than in the generation and diffusion of point defects or their differential absorption at dislocation sinks. The bias for interstitials is calculated to be 1.6% at 1073 K.

  1. Grain-boundary migration in nonstoichiometric solid solutions of magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Y.M.; Kingery, W.D.

    1989-02-01

    The grain-boundary mobility in magnesium aluminate spinel of magnesia-rich and alumina-rich compositions has been measured from normal grain growth in dense, hot-pressed samples. Over the temperature range 1200/sup 0/ to 1800/sup 0/C, the mobility in magnesia-rich compositions is found to be greater than that in alumina-rich compositions by a factor of 10/sup 2/ to 10/sup 3/.

  2. The effect of Y2O3 addition on thermal shock behavior of magnesium aluminate spinel

    OpenAIRE

    Pošarac Milica; Devečerski A.; Volkov-Husović T.; Matović B.; Minić D.M.

    2009-01-01

    The effect of yttria additive on the thermal shock behavior of magnesium aluminate spinel has been investigated. As a starting material we used spinel (MgAl2O4) obtained by the modified glycine nitrate procedure (MGNP). Sintered products were characterized in terms of phase analysis, densities, thermal shock, monitoring the damaged surface area in the refractory specimen during thermal shock and ultrasonic determination of the Dynamic Young modulus of elasticity. It was found that a new phase...

  3. Effect of X-Rays on the Mechanical Properties of Aluminized FEP Teflon(trademark)

    Science.gov (United States)

    Gaier, James R.; Brinkmeier, Michael R.; Gaier, Elizabeth M.

    1999-01-01

    Pieces of the multilayer insulation (MLI) that is integral to the thermal control of the Hubble Space Telescope (HST) have been returned by two servicing missions after 3.6 and 6.8 years in orbit. They reveal that the outer layer, which is made from 5 mil (0.13 mm) thick aluminized fluorinated ethylenepropylene (FEP) Teflon. has become severely embrittled. Although possible agents of this embrittlement include electromagnetic radiation across the entire solar spectrum, trapped particle radiation, atomic oxygen, and thermal cycling, intensive investigations have not yielded unambiguous causes. Previous studies utilizing monoenergetic photons in the 69-1900 eV range did not cause significant embrittlement, even at much higher doses than were experienced by the HST MLI. Neither did x-rays in the 3 to 10 keV range generated in a modified electron bean evaporator. An antidotal aluminized FEP sample that was exposed to an intensive dose from unfiltered Mo x-ray radiation from a rotating anode generator, however, did show the requisite embrittlement. Thus, a study was undertaken to determine the effects of x-ray exposure on the embrittlement of aluminized FEP in hopes that it might elucidate the HST MLI degradation mechanism. Tensile specimens of aluminized 5 mil thick FEP were exposed to a constant fluence of unfiltered x-ray radiation from a Mo target whose maximum energy ranged from 20-60 kV. Other samples were annealed, thermally cycled (100x) between 77-333 K, or cycled and irradiated. Tensile tests and density measurements were then performed on the samples. Only the samples which had been irradiated had the drastically reduced elongation-to-break, characteristic of the HST samples. Thermal cycling may accelerate the embrittlement, but the effect was near the scatter in the measurements. Annealing and thermal cycling had no apparent effect. Only the samples which had been irradiated and annealed showed significant density increases, likely implicating polymer chain

  4. In situ generation of hydrogen from water by aluminum corrosion in solutions of sodium aluminate

    OpenAIRE

    Soler Turu, Lluis; Candela Soto, Angélica Maria; Macanás de Benito, Jorge; Muñoz Tapia, Maria; Casado Giménez, Juan

    2009-01-01

    A new process to obtain hydrogen from water using aluminum in sodium aluminate solutions is described and compared with results obtained in aqueous sodium hydroxide. This process consumes only water and aluminum, which are raw materials much cheaper than other compounds used for in situ hydrogen generation, such as hydrocarbons and chemical hydrides, respectively. As a consequence, our process could be an economically feasible alternative for hydrogen to supply fuel cells. Results showed an i...

  5. Phase transformation of alumina coating by plasma assisted tempering of aluminized P91 steels

    Science.gov (United States)

    Jamnapara, N. I.; Mukherjee, S.; Khanna, A. S.

    2015-09-01

    α-Al2O3 coating on aluminized surfaces are considered candidate coatings for blanket applications in fusion reactor. In order to generate α-Al2O3, aluminized P91 steel samples were subjected to normalizing and tempering treatments at 980 °C and 750 °C respectively. Oxygen plasma has been used during tempering treatment of aluminized P91 steel samples at 750 °C for 1 h. The resulting alumina coating on plasma tempered samples were compared with those of thermally tempered samples. The alumina films were characterized using XRD, XPS, and SEM-EDS techniques. Results indicate that the thermally tempered samples had θ-Al2O3 coating while the plasma tempered samples had α-Al2O3 coating after heat treatment. Such transformation of alumina phase was not visible without plasma. A hypothesis of θ to α-Al2O3 transformation in plasma is proposed. This paper emphasizes the role of plasma processing on generation of an improved insulation coating for TBM applications in fusion reactors.

  6. Mechanical properties of aluminized CoCrAlY coatings in advanced gas turbine blades

    International Nuclear Information System (INIS)

    The microstructure/composition and mechanical properties (22-950 C) in aluminized CoCrAlY coatings of advanced gas turbine blades have been examined using scanning Auger microprobe and a small punch (SP) testing method. Aluminized coatings were made of layered structure divided into four regions; (I) Al enriched and Cr depleted region, (II) Al and Cr graded region, (III) fine grained microstructure with a mixture of Al and Cr enriched phases and (IV) Ni/Co interdifusion zone adjacent to the interface. Coating regions I and II with high microhardness showed easier formation of brittle cracks in a wide temperature range, compared to regions III and IV. The coating region III had lower room temperature ductility and conversely higher elevated temperature ductility than the region IV due to a precipitous ductility increase above 730 C. The integrity of aluminized coatings while in-service is discussed in light of the variation in the low cycle fatigue life as well as the ductility in the layered structure. (orig.)

  7. Behaviour of SS316, with and without aluminization, in stagnant Pb17Li

    Science.gov (United States)

    Schreinlechner, I.; Sattler, P.

    1992-09-01

    Austenitic SS316 sheet material, partly aluminized, was tested in static Pb17Li (83 at% Pb and 17 at% Li), at 500°C. After 1000 h of exposure polished cross sections of pieces of the sample with and without aluminization were analysed by electron microscopy and compared with the as-received sample. The unprotected surface revealed the expected depletion of alloying elements and the formation of a porous ferritic zone to a depth of ≈ 200 μm into which Pb has penetrated. The aluminized suface does not show any attack by Pb17Li nor penetration of Pb into the grain boundaries. An intermediate layer is found between the matrix and the aluminum surface layer, with distinct borders on either side, consisting of Al+Ni-rich areas, believed to be an AlNi alloy between Cr-rich areas. Quantitative analyses revealed identical concentrations of Al and Ni, for exposed as well as unexposed samples, indicating no counter diffusion to have taken place during the test.

  8. IMPACT OF ALUMINATE IONS ON THE PROPERTIES OF SALTSTONE GROUT MIXES

    International Nuclear Information System (INIS)

    It is important to identify and control the operational and compositional variables that impact the important processing and performance properties of Saltstone grout mixes. The grout that is produced at the Saltstone Production Facility (SPF) is referred to as Saltstone and is a waste form that immobilizes low concentrations of radionuclides as well as certain toxic metals. The Saltstone will be disposed of in vaults at Savannah River Site (SRS). An effort referred to as the Saltstone Variability Study has been initiated to achieve this goal. The protocols developed in this variability study are also ideally suited as a tool to assess the impact of proposed changes to the processing flow sheet for Liquid Waste Operations at SRS. One such proposal that is currently under consideration is to introduce a leaching step in the treatment of the High Level Waste (HLW) sludge to remove aluminum prior to vitrification at the Defense Waste Processing Facility (DWPF). This leachate would significantly increase the soluble aluminate concentration in the salt feed that will be processed at the SPF. Consequently, an initial study of the impact of increased aluminate concentration on the Saltstone grout properties was performed. Prior work by Lukens (1) showed that aluminate in the salt solutions increases the amount of heat generation

  9. Seepage/Cement Interactions

    International Nuclear Information System (INIS)

    The Development Plan (CRWMS M andO 1999a) pertaining to this task defines the work scopes and objectives for development of various submodels for the Physical and Chemical Environment Abstraction Model for TSPA-LA. The Development Plan (CRWMS M andO 1999a) for this specific task establishes that an evaluation be performed of the chemical reactions between seepage that has entered the drift and concrete which might be used in the repository emplacement drifts. The Development Plan (CRWMS M andO 1999a) then states that the potential effects of these water/grout reactions on chemical conditions in the drift be assessed factoring in the influence of carbonation and the relatively small amount of grout. This task is also directed at: (1) developing a conceptualization of important cement/seepage interactions and potential impacts on EBS performance, (2) performing a screening analysis to assess the importance of cement/seepage interactions. As the work progresses and evolves on other studies, specifically the Engineered Barrier System: Physical and Chemical Environment (P andCE) Model (in progress), many of the issues associated with items 1 and 2, above, will be assessed. Such issues include: (1) Describing the mineralogy of the specified cementitious grout and its evolution over time. (2) Describing the composition of the water before contacting the grout. (3) Developing reasonable upper-bound estimates for the composition of water contacting grout, emphasizing pH and concentrations for anions such as sulfate. (4) Evaluating the equilibration of cement-influenced water with backfill and gas-phase CO2. (5) Developing reasonable-bound estimates for flow rate of affected water into the drift. The concept of estimating an ''upper-bound'' range for reaction between the grout and the seepage, particularly in terms of pH is based on equilibrium being established between the seepage and the grout. For example, this analysis can be based on equilibrium being established as

  10. The Uses of Copper and Zinc Aluminates to Capture and Convert Carbon dioxide to Syn-gas at Higher Temperature

    Directory of Open Access Journals (Sweden)

    R.Y. Raskar

    2014-03-01

    Full Text Available The uses of copper and zinc aluminates to capture and convert the CO2 to syn-gas were studied at higher temperatures. The samples of copper and zinc aluminates were prepared by solid-solid fusion method by calcining in air at 900 oC for 3 h. Those samples were characterized by acidity/alkalinity, surface area, XRD pattern, IR, SEM images and screening to capture CO2 at the different temperatures. The phases Cu2O, CuO, ZnO, CuAl2O4 and ZnAl2O4 were found to be in the samples of zinc and copper aluminates. Acidity and surface area of the samples of copper and zinc aluminates were found to be in the ranges from 0.063 to 9.37 mmol g-1 and 3.04 to 11.8 m2 g-1, respectively. The captured CO2 by the samples of copper and zinc aluminates was found to be 19.92 to 31.52 wt% for the temperature range 40 to 850 oC. The captured CO2 at 550 oC by variable Zn/Al and Cu/Al mol ratio from 0.5 to 6 of the samples of copper and zinc aluminates was found to be 12.81 to 18.04 wt%. The reduction of carbon dioxide by zinc and copper aluminates was observed. The conversion of CO2 by methane over variable mol ratio of Cu/Al and Zn/Al in copper and zinc aluminates, respectively, at 500 oC showed the production of syn-gas by using the gas hourly space velocities (GHSV 12000, 12000 and 6000 ml. h-1. g-1 of helium, CO2 and methane. The conversions of CO2 by methane over the samples of zinc and copper aluminates were studied at different mol ratios of CO2 to methane.  © 2014 BCREC UNDIP. All rights reservedReceived: 13rd May 2013; Revised: 8th November 2013; Accepted: 8th November 2013[How to Cite: Raskar, R.Y., Gaikwad, A.G. (2014. The Uses of Copper and Zinc Aluminates to Cap-ture and Convert Carbon Dioxide to Syn-gas at Higher Temperature. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (1: 1-15. (doi:10.9767/bcrec.9.1.4899.1-15[Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.1.4899.1-15

  11. Effect of polycarboxylate admixture structure on cement paste rheology

    Directory of Open Access Journals (Sweden)

    Aranda, M. A. G.

    2007-06-01

    Full Text Available The purpose of the present study was to analyze the effect of the structural differences in four polycarboxylate and polyether admixtures on the rheological properties of cement pastes with different chemical and mineralogical compositions and different active additions (CEM I 42.5 R, CEM I 52.5 R, CEM I 52.5 N/SR, CEM II/AV 42.5R, CEM II/B-L 32.5 R, CEM III/B 32.5R, BL I 52.5R and CAC – European standard EN 197-1:2000. The results of the minislump test concurred with the variations observed in the values of the rheological parameters (shear stress and plastic viscosity. The structural characteristic of the admixtures found to play the most prominent role in their fluidizing effect was the proportion of carboxylate (CG and polyether (EG group components. In cements characteristics such as fineness and the C3A/calcium sulphate and C3S/C3A ratios were also observed to be essential to admixture effectiveness. In this regard, the rheological parameters varied most widely in CEM I 52.5N/SR pastes and least in BL I 52.5R cement pastes. Of the additioned cements, the CEM III/B 32.5R pastes, which contained granulated blast furnace slag, showed the highest rises in flowability. Finally, the fluidizing effect of polycarboxylate superplasticizers was much more intense in calcium aluminate cements, although flowability declined rapidly in this material.El objetivo de este trabajo ha sido estudiar el efecto de las diferencias estructurales de cuatro aditivos basados en policarboxilatos y poliéteres sobre las propiedades reológicas de pastas de cemento con diferente composición química, mineralógica y con distintas adiciones activas (CEM I 42,5 R, CEM I 52,5 R, CEM I 52,5 N/SR, CEM II/AV 42,5R, CEM II/ B-L 32,5 R, CEM III/B 32,5R, BL I 52,5R y CAC - Norma EN 197-1:2000. Los resultados obtenidos sobre la fluidez de la pasta en el ensayo del “Minislump” coinciden con la evolución de los valores de los parámetros reológicos (esfuerzo de

  12. A modified PMMA cement (Sub-cement) for accelerated fatigue testing of cemented implant constructs using cadaveric bone.

    Science.gov (United States)

    Race, Amos; Miller, Mark A; Mann, Kenneth A

    2008-10-20

    Pre-clinical screening of cemented implant systems could be improved by modeling the longer-term response of the implant/cement/bone construct to cyclic loading. We formulated bone cement with degraded fatigue fracture properties (Sub-cement) such that long-term fatigue could be simulated in short-term cadaver tests. Sub-cement was made by adding a chain-transfer agent to standard polymethylmethacrylate (PMMA) cement. This reduced the molecular weight of the inter-bead matrix without changing reaction-rate or handling characteristics. Static mechanical properties were approximately equivalent to normal cement. Over a physiologically reasonable range of stress-intensity factor, fatigue crack propagation rates for Sub-cement were higher by a factor of 25+/-19. When tested in a simplified 2 1/2-D physical model of a stem-cement-bone system, crack growth from the stem was accelerated by a factor of 100. Sub-cement accelerated both crack initiation and growth rate. Sub-cement is now being evaluated in full stem/cement/femur models. PMID:18774136

  13. Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

    LENUS (Irish Health Repository)

    Addison, Owen

    2010-09-01

    Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

  14. Retention of Root Canal Posts: Effect of Cement Film Thickness, Luting Cement, and Post Pretreatment

    DEFF Research Database (Denmark)

    Sahafi, Alireza; Benetti, Ana Raquel; Peutzfeldt, Anne; Flury, Simon

    2015-01-01

    The aim of this study was to investigate the effect of the cement film thickness of a zinc phosphate or a resin cement on retention of untreated and pretreated root canal posts. Prefabricated zirconia posts (CosmoPost: 1.4 mm) and two types of luting cements (a zinc phosphate cement [DeTrey Zinc...

  15. [Antimicrobial activity of orthodontic band cements].

    Science.gov (United States)

    Pavic, J; Arriagada, M; Elgueta, J; García, C

    1990-01-01

    The prevalence of enamel decalcification and caries beneath orthodontic bands, has indicated the need for a new enamel binding adhesive orthodontic cement. The purpose of this study was to evaluate the antimicrobial activity, in vitro, on Streptococcus mutans and Lactobacillus, acidophillus, of three materials used to cements the orthodontic bands. The cements studied were: Zinc phosphate cement, Glass-ionomer cement, and Policarboxylate cement. Thirty petri plates were seeded with S. mutans, and thirty with L. acidophillus; on each plate three pellet were placed, one of each cement studied. Petri plates were incubated under microaerophilic conditions at 37 C, and checked at 72 hrs. for Streptococcus, mutans, and four days for Lactobacillus acidophillus to evaluate the inhibition zone. The results were tabulated for each material. It was demonstrated that exists important variations in the antimicrobial properties of the materials studied, as in the microbial sensitivity to these cements. PMID:2135908

  16. Cement radwaste solidification studies third annual report

    International Nuclear Information System (INIS)

    This report summarises cement radwaste studies carried out at AEE Winfrith during 1981 on the encapsulation of medium and low active waste in cement. During the year more emphasis has been placed on the work which is directly related to the solidification of SGHWR active sludge. Information has been obtained on the properties of 220 dm3 drums of cemented waste. The use of cement grouts for the encapsulation of solid items has also been investigated during 1981. (U.K.)

  17. Cement Sheath Integrity During Thermal Cycling

    OpenAIRE

    Andrade, Jesús De

    2015-01-01

    In the construction process of oil and gas wells, primary cementing constitutes a critical procedure of placing a cement sheath in the annulus between casing and formation, or between the casing strings. The main purpose is to provide mechanical stability to the wellbore and to ensure zonal isolation through the entire well service lifetime. Failures to achieve a proper primary cementing, and to ensure long-term sealing capabilities of the cement sheath, may severely limit the abi...

  18. Neutron Scattering Studies of Cement

    Science.gov (United States)

    Allen, Andrew

    2010-03-01

    Despite more than a century of research, basic questions remain regarding both the internal structure and the role of water in Ordinary Portland cement (OPC) concrete, the world's most widely used manufactured material. Most such questions concern the primary hydration product and strength-building phase of OPC paste, the calcium silicate hydrate (C-S-H) gel. When cement and water are mixed, this phase precipitates as clusters of nanoscale (nearly amorphous) colloidal particles with an associated water-filled inter-particle pore system. Most attempts to characterize the C-S-H gel and the behavior of the associated water involve drying or other processes that, themselves, change the bound water content within and around the gel. Neutron scattering methods do not suffer from this disadvantage. Furthermore, the neutron isotope effect and the neutron's sensitivity to molecular motion have enabled considerable progress to be made in recent years by: (i) determining the C-S-H composition, density and gel structure in small-angle neutron scattering (SANS) H/D contrast variation studies; (ii) elucidating the changing state of water within cement as hydration progresses using quasielastic neutron scattering (QENS); and (iii) measuring the production and consumption of nanoscale calcium hydroxide (CH), a by-product of cement hydration that co-exists with the C-S-H gel, using inelastic neutron scattering (INS). These experiments have provided new insights into the physics and chemistry of cement hydration, and have implications for the design of new concretes with pozzolanic cement additions that are intended to address environmental concerns and sustainability issues.

  19. ADVANCED CEMENTS FOR GEOTHERMAL WELLS

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2007-01-01

    Using the conventional well cements consisting of the calcium silicate hydrates (CaO-SiO{sub 2}-H{sub 2}O system) and calcium aluminum silicate hydrates (CaO-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O system) for the integrity of geothermal wells, the serious concern confronting the cementing industries was their poor performance in mechanically supporting the metallic well casing pipes and in mitigating the pipe's corrosion in very harsh geothermal reservoirs. These difficulties are particularly acute in two geological regions: One is the deep hot downhole area ({approx} 1700 m depth at temperatures of {approx} 320 C) that contains hyper saline water with high concentrations of CO{sub 2} (> 40,000 ppm) in conjunction with {approx} 100 ppm H{sub 2}S at a mild acid of pH {approx} 5.0; the other is the upper well region between the well's surface and {approx} 1000 m depth at temperatures up to 200 C. The specific environment of the latter region is characterized by highly concentrated H{sub 2}SO{sub 4} (pH < 1.5) brine containing at least 5000 ppm CO{sub 2}. When these conventional cements are emplaced in these harsh environments, their major shortcoming is their susceptibility to reactions with hot CO{sub 2} and H{sub 2}SO4, thereby causing their deterioration brought about by CO{sub 2}-catalyzed carbonation and acid-initiated erosion. Such degradation not only reduced rapidly the strength of cements, lowering the mechanical support of casing pipes, but also increased the extent of permeability of the brine through the cement layer, promoting the rate of the pipe's corrosion. Severely carbonated and acid eroded cements often impaired the integrity of a well in less than one year; in the worst cases, casings have collapsed within three months, leading to the need for costly and time-consuming repairs or redrilling operations. These were the reasons why the geothermal well drilling and cementing industries were concerned about using conventional well

  20. Effecting factors of the emission spectral characteristics of rare-earth strontium aluminate for anti-counterfeiting application

    International Nuclear Information System (INIS)

    The rare-earth strontium aluminate phosphor with stable physical and luminescent performances is a suitable rare-earth luminescent material for spectrum-fingerprint anti-counterfeiting fiber. In order to promote further the development of variety and the improvement of anti-counterfeiting effects of spectrum-fingerprint fiber, in this research, several kinds of rare-earth strontium aluminates and spectrum-fingerprint anti-counterfeiting fiber were prepared by solid-state reaction and special spinning technique, respectively. The effects upon manufacturing elements of strontium aluminate including calcining temperature, Al/Sr ratios, the addition of H3BO3, Eu2+ and Dy3+ and external environmental factors of applications such as fiber-forming polymer on emission spectral characteristics were investigated systematically in the anti-counterfeiting application. The results showed that with the increase in the calcining temperature, the amounts of H3BO3 doping and the concentration of Eu2+ and Dy3+, the emission intensity of rare-earth strontium aluminate increased and reached to the peak at a certain point at start, and then decreased gradually beyond this point. Al/Sr molar ratios influenced not only the intensity but also the wavelength of emission. Fiber-forming polymer had little effect on the emission wavelength and the shape in the luminescence, but greatly lowered the intensity of emission. - Highlights: → Rare-earth strontium aluminate was applied to make spectrum-fingerprint fiber. → Emission spectra of strontium aluminate were studied from anti-counterfeiting angle. → Calcining temperature, H3BO3, Eu2+ and Dy3+ affected only on the emission intensity. → Al/Sr ratios influenced not only the intensity but also the wavelength of emission. → Fiber-forming polymer affected only on the emission intensity of strontium aluminate.

  1. PERFORMANCE OF PULVERIZED SLAG-SUBSTITUTED CEMENT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The Portland cement is equivalently substituted by slag micropowders with various specific areas. The workability,activity and acid-corrosion resistance of the slag-substituted cements are investigated,the activation of gypsum is discussed,also the porosity and pore distribution of mortars of the slag micropowders cement are determined by mercury intrusion porosimetry.

  2. Microscale Investigation of Arsenic Distribution and Species in Cement Product from Cement Kiln Coprocessing Wastes

    OpenAIRE

    Yufei Yang; Jingchuan Xue; Qifei Huang

    2013-01-01

    To improve the understanding of the immobilization mechanism and the leaching risk of Arsenic (As) in the cement product from coprocessing wastes using cement kiln, distribution and species of As in cement product were determined by microscale investigation methods, including electron probe microanalysis (EPMA) and X-ray absorption spectroscopy. In this study, sodium arsenate crystals (Na3AsO412H2O) were mixed with cement production raw materials and calcined to produce cement clinker. Then, ...

  3. The comparison between sulfate salt weathering of portland cement paste and calcium sulfoaluminate cement paste

    OpenAIRE

    Liu, Zanqun; Deng, Dehua; De Schutter, Geert

    2015-01-01

    In this paper, the damage performances of sulfate salt weathering of Portland cement paste and calcium sulfoaluminate (CSA) cement paste were compared according to authors' previous studies. It was found that the evaporation zone of speciments partially immersed in 10% Na2SO4 solution were both severely deteriorated for Portland cement and CSA cement. However, the differences were more significant: (1) the CSA cement paste were damaged just after 7 days exposure compared to the 5 months expos...

  4. Thoughts on the Current Cement Industry Development

    Institute of Scientific and Technical Information of China (English)

    Gan Zhihe

    2003-01-01

    According to the analysis of cement capacity andits relations with macro economy running index, the mainreasons for the present rapid development of cement capacityare the rapid development of economy and the shot up ofwhole society fixed asset investment. According to the presentspeed of economy development, cement still enjoys a po-tential increase, So here has not been an overall excessivepopularity of cement industry. The best way to prevent lowlevel repeated construction is to promote the development ofnew dry- process cement as well as try to get rid of blindness.

  5. Special recipe for cement solidification

    International Nuclear Information System (INIS)

    ABB Atom's MOSS is a compact, mobile system for immobilizing radwaste in cement. Various ''recipes'' have been developed to meet stringent end product requirements. A version of MOSS, described here, was delivered to Borssele last year and has completed two solidification campaigns to date. (author)

  6. Effect of temporary cements on the shear bond strength of luting cements

    Directory of Open Access Journals (Sweden)

    Marco Fiori-Júnior

    2010-02-01

    Full Text Available OBJECTIVE: The purpose of this study was to evaluate, by shear bond strength (SBS testing, the influence of different types of temporary cements on the final cementation using conventional and self-etching resin-based luting cements. Material and Methods: Forty human teeth divided in two halves were assigned to 8 groups (n=10: I and V (no temporary cementation; II and VI: Ca(OH2-based cement; III and VII: zinc oxide (ZO-based cement; IV and VIII: ZO-eugenol (ZOE-based cement. Final cementation was done with RelyX ARC cement (groups I to IV and RelyX Unicem cement (groups V to VIII. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. RESULTS: Means were (MPa: I - 3.80 (±1.481; II - 5.24 (±2.297; III - 6.98 (±1.885; IV - 6.54 (±1.459; V - 5.22 (±2.465; VI - 4.48 (±1.705; VII - 6.29 (±2.280; VIII - 2.47 (±2.076. Comparison of the groups that had the same temporary cementation (Groups II and VI; III and VII; IV and VIII showed statistically significant difference (p0.05 for the different luting cements (RelyX TM ARC and RelyX TM Unicem. The groups that had no temporary cementation (Groups I and V did not differ significantly from each other either (p>0.05. CONCLUSION: When temporary cementation was done with ZO- or ZOE-based cements and final cementation was done with RelyX ARC, there was an increase in the SBS compared to the control. In the groups cemented with RelyX Unicem, however, the use of a ZOE-based temporary cement affected negatively the SBS of the luting agent used for final cementation.

  7. Effect of alloying additions in al on growth and morphology of intermetallic layer in hot-dip-aluminized steel

    International Nuclear Information System (INIS)

    In hot-dip-aluminized steels, an iron-aluminum intermetallic layer develops at the interface between the melt and the steel substrate. The composition of the aluminizing-metal and carbon content of steel substrate affect growth and morphology of the intermetallic layer. In the present work, the effect of various additions Cu and Zn in Al on growth and morphology of the intermetallic layer was studied. The steel substrate containing 0.35% carbon was aluminized in these melts at temperature 750 degree C. The growth and morphology of the intermetallic layer and the phases formed in surface coating were analyzed by optical microscopy, Scanning electron microscopy, and X-ray diffraction techniques. In hot-dip aluminizing with pure aluminum, the intermetallic layer was thick and exhibited a finger-like growth into steel substrate. While aluminizing in Al-Cu alloys, the thickness of the intermetallic layer decreased whereas in Al-Zn alloys it increased. The additions of Cu in Al tended to transform interface of the intermetallic layer smoother while Zn additions did not affect the interface morphology. (author)

  8. Mineralogy and microstructure of two Mexican Portland cements for the confinement of radioactive waste; Mineralogia y microestructura de dos cementos mexicanos Portland para el confinamiento de desechos radiactivos

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, E. [Universidad Autonoma del Estado de Mexico, Facultad de Ciencias, Campus El Cerrillo, Piedras Blancas, Carretera Toluca-Ixtlahuaca Km. 15.5, Estado de Mexico (Mexico); Badillo A, V. E.; Ramirez S, J. R. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Nava E, N., E-mail: nasiega_181@hotmail.com [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, 07730 Mexico D. F. (Mexico)

    2014-10-15

    The cementitious materials are involved in the different stages of radioactive waste management because they are used for the waste immobilization in the container, as well as filling in the spaces between containers vaults and also as engineering barrier and construction material in civil construction site. Therefore, is necessary to have a study of commercial cement available nationwide involving solid timely analysis in order to identify which phases are responsible for confinement of radionuclides, if considered the most reactive phase -CSH- or called secondary phases. In this research the hydration products of cement are presented as well as its importance in the nuclear industry. The analysis and observation of the cement clinker and the hydration products on the manufactured pulps with two commercial cements resistant to sulphates was realized using the observation technique of solid X-ray diffraction and nuclear analytic techniques of Moessbauer spectroscopy and X-Ray Fluorescence. The results show the presence of calcium silicate hydrates in the amorphous phase and the presence of ettringite crystals and portlandite sheets is appreciated. The abundant iron phase called tetra calcium ferro aluminate has been identified by Moessbauer spectroscopy. (Author)

  9. Mesoscale texture of cement hydrates.

    Science.gov (United States)

    Ioannidou, Katerina; Krakowiak, Konrad J; Bauchy, Mathieu; Hoover, Christian G; Masoero, Enrico; Yip, Sidney; Ulm, Franz-Josef; Levitz, Pierre; Pellenq, Roland J-M; Del Gado, Emanuela

    2016-02-23

    Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water. Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials. PMID:26858450

  10. CO2 Capture by Cement Raw Meal

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll; Dam-Johansen, Kim; Hjuler, Klaus

    2013-01-01

    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used as the...... sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone...... capacity (Xr). This shows that raw meal could be used as a sorbent for the easy integration of the carbonate looping process into the cement pyro process for reducing CO2 emissions from the cement production process....

  11. Leaching of tritium from a cement composite

    International Nuclear Information System (INIS)

    Leaching of tritium from cement composites into an aqueous phase has been studied to evaluate the safety of incorporation of the tritiated liquid waste into cement. Leaching tests were performed by the method recommended by the International Atomic Energy Agency. The Leaching fraction was measured as functions of waste-cement ratio (Wa/C), temperature of leachant and curing time. The tritium leachability of cement in the long term test follows the order: alumina cement portland cement slag cement. The fraction of tritium leached increases with increasing Wa/C and temperature and decreasing curing period. A deionized water as a leachant gives a slightly higher leachability than synthetic sea water. The amount leached of tritium from a 200 l drum size specimen was estimated on the basis of the above results. (author)

  12. The morphology of coating/substrate interface in hot-dip-aluminized steels

    International Nuclear Information System (INIS)

    In hot-dip-aluminized (HAD) steels, the morphology and the profile of the interface between the aluminum coating and the substrate steel, are affected both by the composition of the molten aluminum as well as by the composition, and even the microstructure, of the substrate steel. This effect has been investigated using optical and scanning electron microscopy, and X-ray diffraction. The reaction between the steel and the molten aluminum leads to the formation of Fe-Al inter-metallic compounds on the steel surface. The thickness of the inter-metallic compound layer as well as the morphology of the interface between the steel and the interlayer varies with the silicon content of the molten aluminum. In hot-dip-aluminizing with pure aluminum, the interlayer is 'thick' and exhibits a finger-like growth into the steel. With a gradually increasing addition of silicon into the aluminum melt, the thickness of the interlayer decreases while the interface between the interlayer and the substrate gradually becomes 'smoother'. With an increase in the carbon content of the substrate steel the growth of the interlayer into the steel is impeded by the pearlite phase, whereas the ferrite phase appears to dissolve more readily. X-ray diffraction and electron microscopic studies showed that the interlayer formed in samples aluminized in pure aluminum, essentially consisted of orthorhombic Fe2Al5. It was further observed that the finger-like grains of Fe2Al5 phase exhibited a preferred lattice orientation. With a gradual addition of silicon into the aluminum melt, a cubic phase based on Fe3Al also started to form in the interlayer and replaced most of the Fe2Al5

  13. Methods of use of calcium hexa aluminate refractory linings and/or chemical barriers in high alkali or alkaline environments

    Science.gov (United States)

    McGowan, Kenneth A; Cullen, Robert M; Keiser, James R; Hemrick, James G; Meisner, Roberta A

    2013-10-22

    A method for improving the insulating character/and or penetration resistance of a liner in contact with at least one of an alkali and/or alkaline environments is provided. The method comprises lining a surface that is subject to wear by an alkali environment and/or an alkaline environment with a refractory composition comprising a refractory aggregate consisting essentially of a calcium hexa aluminate clinker having the formula CA.sub.6, wherein C is equal to calcium oxide, wherein A is equal to aluminum oxide, and wherein the hexa aluminate clinker has from zero to less than about fifty weight percent C.sub.12A.sub.7, and wherein greater than 98 weight percent of the calcium hexa aluminate clinker having a particle size ranging from -20 microns to +3 millimeters, for forming a liner of the surface. This method improves the insulating character/and or penetration resistance of the liner.

  14. The cement recycling of the earthquake disaster debris by Hachinohe Cement Co., Ltd

    International Nuclear Information System (INIS)

    A tremendous quantity of earthquake disaster debris and tsunami sediment was resulted by the Great East Japan Earthquake on March 11, 2011. Hachinohe Cement Co., Ltd., a Sumitomo Osaka Cement subsidiary, was the first cement industry company to receive and process such waste materials outside of their usual prefecture area, while the company is performing their treatment and recycling services locally in Hachinohe City and Aomori Prefecture. This report provides an explanation about the recycling mechanism of waste materials and by-products in cement manufacturing process, and introduces an example of actual achievements for the disaster debris treatment by utilizing the cement recycling technologies at the Hachinohe Cement Plant. (author)

  15. The inverse problem in zero linear ablation of aluminizing carbon composites under high heat flux

    Directory of Open Access Journals (Sweden)

    Huang Haiming

    2013-01-01

    Full Text Available The concept of zero linear ablation is introduced to describe the mass ablation without shape change, and it is employed to design thermal protection materials under an extreme thermal environment. Aluminizing carbon composites are used as a sample to study numerically the heat response. As indicated in the numerical results, the shape of the composites did not change under a high heat flux because the phase transition (melt or evaporation of aluminum can absorb a lot of energy before the ablation of carbon, and the zero linear ablation depends on not only the volume fraction of aluminum, but also the heating period and the heat flux.

  16. Evaluation of Bayer process gibbsite reactivity in magnesium aluminate spinel formation

    International Nuclear Information System (INIS)

    Stoichiometric magnesium aluminate spinel was synthesized by solid-state reaction of calcined magnesia with tabular alumina, calcined alumina and industrial gibbsite at 1100, 1300 and 1500 deg. C for 2 h. The pellets made from both types of alumina and magnesia expanded after the heat treatment, whereas pellets made from industrial gibbsite and magnesia contracted. It was found that shrinkage could be produced by phase transformations in gibbsite and magnesia densification process in unreacted magnesia during the sintering. The X-ray diffraction patterns indicated a minor reactivity for industrial gibbsite in comparison with the calcined alumina and tabular alumina at all firing temperatures

  17. Nucleation during gibbsites precipitation with seeds from sodium aluminate solution processed under ultrasound

    Institute of Scientific and Technical Information of China (English)

    陈国辉; 陈启元; 尹周澜; 张斌

    2004-01-01

    The secondary nucleation during gibbsite precipitation with seeds from sodium aluminate solution processed by ultrasound was examined by particle size distribution(PSD) analyses. Experiments indicate that at low temperature(<65 ℃ ) and with low frequency ultrasound, the precipitation efficiency and also the secondary nucleation can be improved. Solution processed by low frequency ultrasound has more nuclei than common liquor does at low temperature. At 55 ℃, precipitation efficiency can he improved by 5.31 %, and the effect promoted by low frequency ultrasound decreases with the increase of temperature.

  18. Characterization of irregular seeds on gibbsites precipitated from caustic aluminate solutions

    Institute of Scientific and Technical Information of China (English)

    CHEN Guo-hui; CHEN Qi-yuan; YIN Zhou-lan; YIN Zhi-min

    2006-01-01

    The irregular surface of seeds on which gibbsites are precipitated from caustic aluminate solutions, was investigated according to the fractal theory. Two kinds of fractal dimensions were used to characterize these irregularity. Box-dimension and spectral dimension are based on the SEM images of seeds and diffusive dynamic equation ofthe precipitation respectively. Both these two dimensions are affected by the reaction temperature, evolved with different reaction conditions and can reflect the influence of irregularity of seeds on the precipitation rate. Box dimension is fit for the characterization of the irregular morphology of seeds, while spectral dimension can explain the fractal dynamic behavior.

  19. Water-sensitive positron trapping modes in nanoporous magnesium aluminate ceramics

    International Nuclear Information System (INIS)

    The water-sensitive positron trapping modes in nanoporous MgAl2O4 ceramics with a spinel structure are studied. It is shown that water-sorption processes in magnesium aluminate ceramics leads to corresponding increase in positron trapping rates of extended defects located near intergranual boundaries. This catalytic affect has reversible nature, being strongly dependent on sorption water fluxes in ceramics. The fixation of all water-dependent positron trapping inputs allow to refine the most significant changes in positron trapping rate of extended defects

  20. Water-sensitive positron trapping modes in nanoporous magnesium aluminate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Filipecki, J [Institute of Physics of Jan Dlugosz University, 13/15, al. Armii Krajowej, Czestochowa, PL 42201 (Poland); Ingram, A [Opole University of Technology, 75, Ozimska str., Opole, PL 45370 (Poland); Klym, H [Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA 79031 (Ukraine); Shpotyuk, O [Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA 79031 (Ukraine); Vakiv, M [Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA 79031 (Ukraine)

    2007-08-15

    The water-sensitive positron trapping modes in nanoporous MgAl{sub 2}O{sub 4} ceramics with a spinel structure are studied. It is shown that water-sorption processes in magnesium aluminate ceramics leads to corresponding increase in positron trapping rates of extended defects located near intergranual boundaries. This catalytic affect has reversible nature, being strongly dependent on sorption water fluxes in ceramics. The fixation of all water-dependent positron trapping inputs allow to refine the most significant changes in positron trapping rate of extended defects.

  1. High-Tc thin films on low microwave loss alkaline-rare-earth-aluminate crystals

    International Nuclear Information System (INIS)

    This paper reports on the alkaline-rare-earth aluminates (K2NiF4-type perovskites) which are an excellent choice as the substrate material for the growth of high-Tc thin films suitable for microwave and far-infrared applications. The CaNdAlO4, and SrLaAlO4 single crystals have been grown by Czochralski pulling and fabricated into the form of (001) oriented wafers. The Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O films deposited on these substrates by a single-target magnetron sputtering exhibited very good superconducting and structural properties

  2. Acyl silicates and acyl aluminates as activated intermediates in peptide formation on clays

    Science.gov (United States)

    White, D. H.; Kennedy, R. M.; Macklin, J.

    1984-01-01

    Glycine reacts with heating on dried clays and other minerals to give peptides in much better yield than in the absence of mineral. This reaction was proposed to occur by way of an activated intermediate such as an acyl silicate or acyl aluminate analogous to acyl phosphates involved in several biochemical reactions including peptide bond synthesis. The proposed mechanism has been confirmed by trapping the intermediate, as well as by direct spectroscopic observation of a related intermediate. The reaction of amino acids on periodically dried mineral surfaces represents a widespead, geologically realistic setting for prebiotic peptide formation via in situ activation.

  3. The effect of Y2O3 addition on thermal shock behavior of magnesium aluminate spinel

    Directory of Open Access Journals (Sweden)

    Pošarac Milica

    2009-01-01

    Full Text Available The effect of yttria additive on the thermal shock behavior of magnesium aluminate spinel has been investigated. As a starting material we used spinel (MgAl2O4 obtained by the modified glycine nitrate procedure (MGNP. Sintered products were characterized in terms of phase analysis, densities, thermal shock, monitoring the damaged surface area in the refractory specimen during thermal shock and ultrasonic determination of the Dynamic Young modulus of elasticity. It was found that a new phase between yttria and alumina is formed, which improved thermal shock properties of the spinel refractories. Also densification of samples is enhanced by yttria addition.

  4. Evaluation of Bayer process gibbsite reactivity in magnesium aluminate spinel formation

    Energy Technology Data Exchange (ETDEWEB)

    Mora, A. [Department of Materials Science, Universidad Simon Bolivar, Caracas 1080-A (Venezuela)], E-mail: abrahanmora@hotmail.com; Gutierrez-Campos, D. [Department of Materials Science, Universidad Simon Bolivar, Caracas 1080-A (Venezuela)], E-mail: dgutierr@usb.ve; Lavelle, C. [Department of Materials Science, Universidad Simon Bolivar, Caracas 1080-A (Venezuela)], E-mail: clavelle@wanadoo.fr; Rodriguez, R.M. [Department of Chemistry, Universidad Metropolitana, Edif. Corimon, Terrazas del Avila, Distribuidor Autopista, Dto. Sucre, Caracas 1070 (Venezuela)], E-mail: rrodriguez@unimet.edu.ve

    2007-04-25

    Stoichiometric magnesium aluminate spinel was synthesized by solid-state reaction of calcined magnesia with tabular alumina, calcined alumina and industrial gibbsite at 1100, 1300 and 1500 deg. C for 2 h. The pellets made from both types of alumina and magnesia expanded after the heat treatment, whereas pellets made from industrial gibbsite and magnesia contracted. It was found that shrinkage could be produced by phase transformations in gibbsite and magnesia densification process in unreacted magnesia during the sintering. The X-ray diffraction patterns indicated a minor reactivity for industrial gibbsite in comparison with the calcined alumina and tabular alumina at all firing temperatures.

  5. Effect of X-Rays on the Mechanical Properties of Aluminized FEP Teflon(R)

    Science.gov (United States)

    Gaier, James R.; Brinkmeier, Michael R.; Gaier, Elizabeth M.

    1998-01-01

    Pieces of the multilayer insulation (MLI) that is integral to the thermal control of the Hubble Space Telescope (HST) have been returned by two servicing missions after 3.6 and 6.8 years in orbit. They reveal that the outer layer, which is made from 5 mil (0.13 mm)thick aluminized fluorinated ethylene propylene(FEP) Teflon(R), has become severely embrittled. Although possible agents of this embrittlement include electromagnetic radiation across the entire solar spectrum, trapped particle radiation, atomic oxygen, and thermal cycling, intensive investigations have not yielded unambiguous causes. Previous studies utilizing monoenergetic photons in the 69-1900 eV range did not cause significant embrittlement, even at much higher doses than were experienced by the HST MLI. Neither did x-rays in the 3 to 10 keV range generated in a modified electron beam evaporator. An antidotal aluminized FEP sample that was exposed to an intensive dose from unfiltered Mo x-ray radiation from a rotating anode generator, however, did show the requisite embrittlement. Thus, a study was undertaken to determine the effects of x-ray exposure on the embrittlement of aluminized FEP in hopes that it might elucidate the HST MLI degradation mechanism. Tensile specimens of aluminized 5 mil thick FEP were exposed to a constant fluence of unfiltered x-ray radiation from a Mo target whose maximum energy ranged from 20-60 kV. Other samples were annealed, thermally cycled (100x) between 77-333 K, or cycled and irradiated. Tensile tests and density measurements were then performed on the samples. Only the samples which had been irradiated had the drastically reduced elongation-to-break, characteristic of the HST samples. Thermal cycling may accelerate the embrittlement, but the effect was near the scatter in the measurements. Annealing and thermal cycling had no apparent effect. Only the samples which had been irradiated and annealed showed significant density increases, likely implicating polymer

  6. The Uses of Copper and Zinc Aluminates to Capture and Convert Carbon dioxide to Syn-gas at Higher Temperature

    OpenAIRE

    R. Y. Raskar; A. G. Gaikwad

    2014-01-01

    The uses of copper and zinc aluminates to capture and convert the CO2 to syn-gas were studied at higher temperatures. The samples of copper and zinc aluminates were prepared by solid-solid fusion method by calcining in air at 900 oC for 3 h. Those samples were characterized by acidity/alkalinity, surface area, XRD pattern, IR, SEM images and screening to capture CO2 at the different temperatures. The phases Cu2O, CuO, ZnO, CuAl2O4 and ZnAl2O4 were found to be in the samples of zinc and copper...

  7. Session 4: Post-synthesis aluminating of SBA-15 in aqueous solution and its performance as support in hydrocracking reaction

    Energy Technology Data Exchange (ETDEWEB)

    Shuangqin, Zeng; Blanchard, J.; Breysse, M. [Research Institute of Petroleum Processing, Beijing (China); Yahua, Shi; Xintian, Su; Hong, Nie; Dadong, Li; Shuangqin, Zeng [Universite Pierre et Marie Curie, Lab. de Reactivite de Surface UMR CNRS 7609, 75 - Paris (France)

    2004-07-01

    Al-SBA-15 was efficiently synthesised by post-synthesis aluminating of SBA-15 in aqueous aluminium chlorhydrate solution. The amount of aluminium incorporated into SBA-15 and the acidity of the resulting support depend on Al concentration in the solution. Aluminating did not damage the structural integrity of the SBA-15 and most of the inserted aluminum are tetrahedrally coordinated. Al-SBA-15 is a better support for hydrocracking catalyst aiming at middle distillates than amorphous silica-alumina due to its higher surface area and acidity. (authors)

  8. WHITE CEMENT IN SUSTAINABLE DEVELOPMENT

    OpenAIRE

    Y.C.P RAMANA BABU; B.SAI DOONDI; N. M .V .VAMSI KRISHNA; K.Prasanthi

    2013-01-01

    India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO) and carbon dioxide (CO2) are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green hous...

  9. ROTARY SCREW SYSTEMS IN CEMENT

    OpenAIRE

    Taratuta V. D.; Belokur K. A.; Serga G. V.

    2016-01-01

    The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometr...

  10. WHITE CEMENT IN SUSTAINABLE DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    Y.C.P RAMANA BABU

    2013-04-01

    Full Text Available India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO and carbon dioxide (CO2 are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green house gases (i.e., CO and CO2 and also saves lot of money in the long run process. A small amount of these gases in environment can cause major problems over time. Use of white cement in composite pavement design where there is heavy traffic loads are acting as well as number of vehicles are more such as junctions, bus stops, check posts etc., can perform better and acts asenvironment friendly. Its light colour reflects more than bituminous pavement so that it can be easily identified and avoid accidents to some extent. White cement helps to lower the average bus stop, junction temperature providing comfort to the people because it has high solar reflectance there by reducing “urban heat island” effect. In addition to this it has some more advantages which increase the sustainability, durability and workability of the pavements.

  11. 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)

  12. Cement replacement materials. Properties, durability, sustainability

    Energy Technology Data Exchange (ETDEWEB)

    Ramezanianpour, Ali Akbar [Amirkabir Univ. of Technology, Tehran (Iran, Islamic Republic of). Concrete Technology Center

    2014-04-01

    The aim of this book is to present the latest findings in the properties and application of Supplementary Cementing Materials and blended cements currently used in the world in concrete. Sustainability is an important issue all over the world. Carbon dioxide emission has been a serious problem in the world due to the greenhouse effect. Today many countries agreed to reduce the emission of CO2. Many phases of cement and concrete technology can affect sustainability. Cement and concrete industry is responsible for the production of 7% carbon dioxide of the total world CO2 emission. The use of supplementary cementing materials (SCM), design of concrete mixtures with optimum content of cement and enhancement of concrete durability are the main issues towards sustainability in concrete industry.

  13. Scanning electron microscopy analysis of dental cements

    Directory of Open Access Journals (Sweden)

    Radosavljević Radivoje D.

    2009-01-01

    Full Text Available The aim of this study was to compare in vitro the characteristics of different types of luting cements (zinc phosphate, glass-ionomer and resin based composite cement using scanning electron microscopy (SEM analysis and microleakage for the quality range of materials. Dental cements were mixed in accordance with the manufacturer's instructions and formed with posts in dental root canals of extracted teeth. The quality of cement was determined by SEM observation on horizontal sectioned roots with fixed posts according to specific pore and marginal gap diameter. The microleakage was measured on specimens immersed in Lofler (methylene blue solution. The mean values of the maximal diameter of pores, marginal gaps and microleakage of conventional cements are remarkably larger in comparison with composite luting agents. In conclusion, the quality and efficiency of composite luting agents in comparison with conventional cements are more successful in protecting the interior of tooth from penetration of oral fluids, bacteria and bacterial toxins into unprotected dentine.

  14. Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation. Revised

    Science.gov (United States)

    Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.; Hall, Rachelle L.

    1998-01-01

    Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FEP. Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

  15. Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation

    Science.gov (United States)

    Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.

    1998-01-01

    Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FER Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

  16. Synthesis and Characterization of Porous Magnesium Aluminate Spinel by Hydrothermal Process

    Institute of Scientific and Technical Information of China (English)

    WANG Xiuhui; DUAN Jinxia; LU Shengbo; YIN Jianlong; SU Zhenguo; GAO Hong; YANG Jinlong

    2015-01-01

    Magnesium aluminate spinel has a great prospect in catalyst supports due to the porousstructure, good cata-lytic activity, high thermal stability and the presence of two active centers as acid and alkaline. The magnesium alumi-nate spinel powders were synthesized by a hydrothermal process. The samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N2adsorption-desorption isotherms, respectively. The particle surface with the laminated structure increases with the increase of hydrothermal temperature and hydro-thermal time. The spinel has a worm-like porous structure, and the pores become smaller and well-distributed under hexadecyl trimethyl ammonium bromide condition. The phase of the spinel appears at 450°C and the perfect crystalline structure emerges at 600°C. The percentage of MgAl2O4spinel increases with the increase of heat treatment temperature. The spinel has a great specific surface area (i.e., 245.68–58.65 m2/g) when the calcinating temperature increases from 500 to 1200°C. Moreover, the specific surface area is 195.11 m2/g 1 at.% hexadecyl trimethyl ammonium bromide.

  17. Synthesis and characterization of nickel/barium hexa-aluminate composite coatings

    Indian Academy of Sciences (India)

    Dinesh Kumar; Sampada Gurav; Vikram Jayaram; Sanjay Kumar Biswas

    2012-11-01

    Electrodeposition of nickel/barium hexa-aluminate (Ni/BHA) composite coatings has been carried out from a Watt’s bath on mild steel substrate. BHA powders with plate habit were synthesized by solution combustion synthesis followed by heat treatment to ensure complete conversion to the hexa-aluminate phase. Heat treated material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with X-ray analysis. The dispersion behaviour and stability of BHA suspensions with cationic and anionic surfactants at room temperature were studied by dynamic light scattering under different pH. The influence of BHA concentration in the electrolytic bath, deposition temperature, pH, current density and duty cycle on particle incorporation in the coatings were studied and conditions for maximum particle incorporation were established. Coatings with a roughness of about 0.4 m were produced by using this technique. Effect of BHA content on microhardness was also investigated. A reasonably good thickness of the coatings was achieved in a given set of conditions.

  18. Hydrogen permeation through MANET II steel with hot dipping aluminized coating

    International Nuclear Information System (INIS)

    The hydrogen permeation experiment of MANET II with hot dipping aluminized coating was performed in temperature range of 300 to 450 degree C, in gas phase and in liquid Pb-17Li phase. The hydrogen permeation reduction factor (PRF) evaluated in gas phase is 620-263 and in liquid Pb-17Li phase is 45-30. But, The PRFs obtained are still not satisfied for the goal of tritium permeation barrier. The self-healing of coating is obvious and effective above 400 degree C. The pressure dependence of permeation flux indicates strong surface contribution. The way of filling hydrogen by continuous flow and/or bubble can increase permeation flux. The result of SEM-EDS shows that the microcrack is on the surface of the wetted part, but not on the not wetted part. The crack is superficial and affects only thin outside layer, not penetrate aluminized layer. The surface elemental analysis shows that Al/O atomic ratio change from about 2/3 of not wetted part to about 1/1 of wetted part. The damage of coating surface seems to be related to the interaction of outside layer with liquid Pb-17Li and thermal stress during heating sample

  19. Synchrontron VUV and Soft X-Ray Radiation Effects on Aluminized Teflon FEP

    Science.gov (United States)

    Dever, Joyce A.; Townsend, Jacqueline A.; Gaier, James R.; Jalics, Alice I.

    1998-01-01

    Surfaces of the aluminized Teflon FEP multi-layer thermal insulation on the Hubble Space Telescope (HST) were found to be cracked and curled in some areas at the time of the second servicing, mission in February 1997, 6.8 years after HST was deployed in low Earth orbit (LEO). As part of a test program to assess environmental conditions which would produce embrittlement sufficient to cause cracking of Teflon on HST, samples of Teflon FEP with a backside layer of vapor deposited aluminum were exposed to vacuum ultraviolet (VUV) and soft x-ray radiation of various energies using facilities at the National Synchrotron Light Source. Brookhaven National Laboratory. Samples were exposed to synchrotron radiation of narrow energy bands centered on energies between 69 eV and 1900 eV. Samples were analyzed for ultimate tensile strength and elongation. Results will be compared to those of aluminized Teflon FEP retrieved from HST after 3.6 years and 6.8 years on orbit and will he referenced to estimated HST mission doses of VUV and soft x-ray radiation.

  20. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    OpenAIRE

    Konstantin Sobolev

    2003-01-01

    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecologi...

  1. Global Cement Industry: Competitive and Institutional Dimensions

    OpenAIRE

    Selim, Tarek; Salem, Ahmed

    2010-01-01

    The cement industry is a capital intensive, energy consuming, and vital industry for sustaining infrastructure of nations. The international cement market –while constituting a small share of world industry output—has been growing at an increasing rate relative to local production in recent years. Attempts to protect the environment in developed countries –especially Europe—have caused cement production plants to shift to countries with less stringent environmental regulations. Along with con...

  2. Characterization of cement composites with mineral additives

    OpenAIRE

    Korat, Lidija

    2015-01-01

    Doctoral dissertation is aimed at characterizing cement composites with mineral additives representing the industrial waste material (fly ash, granulated blast furnace slag and biomass fly ash). Their usage can replace high cement shares in individual cases and is, however, favourable due to the production costs reduction and environment burden decrease, including the decreased emission of greenhouse gases as well as lower energy use. Cement composites (in fresh or hardened state)...

  3. Premixed calcium silicate cement for endodontic applications

    OpenAIRE

    Persson, Cecilia; Engqvist, Håkan

    2011-01-01

    Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and am...

  4. Water dynamics in glass ionomer cements

    Science.gov (United States)

    Berg, M. C.; Jacobsen, J.; Momsen, N. C. R.; Benetti, A. R.; Telling, M. T. F.; Seydel, T.; Bordallo, H. N.

    2016-07-01

    Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this paper, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with neutron scattering data we were able to relate the water structure in the liquids to the materials properties.

  5. Retention of Root Canal Posts: Effect of Cement Film Thickness, Luting Cement, and Post Pretreatment.

    Science.gov (United States)

    Sahafi, A; Benetti, A R; Flury, S; Peutzfeldt, A

    2015-01-01

    The aim of this study was to investigate the effect of the cement film thickness of a zinc phosphate or a resin cement on retention of untreated and pretreated root canal posts. Prefabricated zirconia posts (CosmoPost: 1.4 mm) and two types of luting cements (a zinc phosphate cement [DeTrey Zinc] and a self-etch adhesive resin cement [Panavia F2.0]) were used. After removal of the crowns of 360 extracted premolars, canines, or incisors, the root canals were prepared with a parallel-sided drill system to three different final diameters. Half the posts did not receive any pretreatment. The other half received tribochemical silicate coating according to the manufacturer's instructions. Posts were then luted in the prepared root canals (n=30 per group). Following water storage at 37°C for seven days, retention of the posts was determined by the pull-out method. Irrespective of the luting cement, pretreatment with tribochemical silicate coating significantly increased retention of the posts. Increased cement film thickness resulted in decreased retention of untreated posts and of pretreated posts luted with zinc phosphate cement. Increased cement film thickness had no influence on retention of pretreated posts luted with resin cement. Thus, retention of the posts was influenced by the type of luting cement, by the cement film thickness, and by the post pretreatment. PMID:25764045

  6. The influence of ultrasound on removal of prefabricated metal post cemented with different resin cements

    Directory of Open Access Journals (Sweden)

    Atiyeh Feiz

    2013-01-01

    Conclusion: Ultrasonic energy did not decrease the retention of posts cemented with Panavia or Maxcem Elite cements. Furthermore, it seems that there is no significant difference between removal force of self-etch (Panavia and the self-etch self-adhesive (Maxcem Elite resin cements.

  7. Case Study of the California Cement Industry

    OpenAIRE

    Coito, Fred; Powell, Frank; Worrell, Ernst; Price, Lynn; Friedmann, Rafael

    2005-01-01

    California is the largest cement producing state in the U.S., accounting for between 10 percent and 15 percent of U.S. cement production and cement industry employment. The cement industry in California consists of 31 sites that consume large amounts of energy, annually: 1,600 GWh of electricity, 22 million therms of natural gas, 2.3 million tons of coal, 0.25 tons of coke, and smaller amounts of waste materials, including tires. The case study summarized in this paper focused on providi...

  8. Acoustic evaluation of cementing quality using obliquely incident ultrasonic signals

    Institute of Scientific and Technical Information of China (English)

    Duan Wen-Xing; Qiao Wen-Xiao; Che Xiao-Hua; Xie Hui

    2014-01-01

    Ultrasonic cement bond logging is a widely used method for evaluating cementing quality. Conventional ultrasonic cement bond logging uses vertical incidence and cannot accurately evaluate lightweight cement bonding. Oblique incidence is a new technology for evaluating cement quality with improved accuracy for lightweight cements. In this study, we simulated models of acoustic impedance of cement and cementing quality using ultrasonic oblique incidence, and we obtained the relation between cementing quality, acoustic impedance of cement, and the acoustic attenuation coeffi cient of the A0-mode and S0-mode Lamb waves. Then, we simulated models of different cement thickness and we obtained the relation between cement thickness and the time difference of the arrival between the A0 and A0′ modes.

  9. Design and manufacture of Portland cement Application of statistical analysis

    OpenAIRE

    Svinning, Ketil

    2011-01-01

    The purpose of the work is to enable design and manufacture of cement with emphasis on the quality and the properties of cement. Data used in the design and manufacture were collected from predictions of properties and characteristics of cement. The properties of cement were predicted from its characteristics and from the production conditions in cement kiln and mill. The cement characteristics were in some investigations predicted from the production conditions. The design was based on sensi...

  10. Influences of ruthenium and crystallographic orientation on creep behavior of aluminized nickel-base single crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Latief, F.H., E-mail: fahamsyah78@gmail.com [Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397 (Japan); Kakehi, K. [Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397 (Japan); An-Chou Yeh, H. [Department of Materials Science and Engineering, National TsingHua University, 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); Murakami, H. [Hybrid Materials Center, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-01-13

    The influences of ruthenium and surface orientation on creep behavior of aluminized Ni-base single crystal superalloys were investigated by comparing two different types of NKH superalloys. The aluminized coated specimens were then subjected to creep rupture tests at a temperature of 900 °C and a stress of 392 MPa. The coating treatment resulted in a significant decrease in creep rupture lives for both superalloys. The diffusion zones between the coating and substrate led to changes in microstructure, which diminished the creep behavior of the aluminized superalloys. Because of the interdiffusion of Ru, Al and Ni, the solubility of some of the refractory elements, such as W, Re. Mo, Co and Cr decreased in the diffusion zone; the precipitation of topologically close-packed (TCP) phases was thus inevitable. In the present study, the addition of Ru increased the degree of Re and Cr supersaturation in the γ matrix. Consequently, the addition of Ru indirectly promoted the precipitation of TCP phases in aluminized Ni-base single crystal superalloys. Furthermore, the growth of TCP precipitates was greatly influenced by the specific surface orientations of the Ni-base single crystal superalloys. In conclusion, the {110} specimens showed shorter creep rupture life than the {100} specimens, this was due to the difference in the crystallographic geometry of {111}〈101〉 slip system and TCP precipitates between the two side-surface orientations of the specimens.

  11. Thermochemical properties of gibbsite, bayerite, boehmite, diaspore, and the aluminate ion between 0 and 350/degree/C

    Energy Technology Data Exchange (ETDEWEB)

    Apps, J.A.; Neil, J.M.; Jun, C.H.

    1989-01-01

    A requirement for modelling the chemical behavior of groundwater in a nuclear waste repository is accurate thermodynamic data pertaining to the participating minerals and aqueous species. In particular, it is important that the thermodynamic properties of the aluminate ion be accurately determined, because most rock forming minerals in the earth's crust are aluminosilicates, and most groundwaters are neutral to slightly alkaline, where the aluminate ion is the predominant aluminum species in solution. Without a precise knowledge of the thermodynamic properties of the aluminate ion aluminosilicate mineral solubilities cannot be determined. The thermochemical properties of the aluminate ion have been determined from the solubilities of the aluminum hydroxides and oxyhydroxides in alkaline solutions between 20 and 350/degree/C. An internally consistent set of thermodynamic properties have been determined for gibbsite, boehmite, diaspore and corundum. The thermodynamic properties of bayerite have been provisionally estimated and a preliminary value for ..delta..G/sub f, 298//sup 0/ of nordstrandite has been determined. 205 refs., 17 figs., 25 tabs.

  12. Thermochemical properties of gibbsite, bayerite, boehmite, diaspore, and the aluminate ion between 0 and 350/degree/C

    International Nuclear Information System (INIS)

    A requirement for modelling the chemical behavior of groundwater in a nuclear waste repository is accurate thermodynamic data pertaining to the participating minerals and aqueous species. In particular, it is important that the thermodynamic properties of the aluminate ion be accurately determined, because most rock forming minerals in the earth's crust are aluminosilicates, and most groundwaters are neutral to slightly alkaline, where the aluminate ion is the predominant aluminum species in solution. Without a precise knowledge of the thermodynamic properties of the aluminate ion aluminosilicate mineral solubilities cannot be determined. The thermochemical properties of the aluminate ion have been determined from the solubilities of the aluminum hydroxides and oxyhydroxides in alkaline solutions between 20 and 350/degree/C. An internally consistent set of thermodynamic properties have been determined for gibbsite, boehmite, diaspore and corundum. The thermodynamic properties of bayerite have been provisionally estimated and a preliminary value for ΔG/sub f, 298/0 of nordstrandite has been determined. 205 refs., 17 figs., 25 tabs

  13. Investigation of barium-calcium aluminate process to manufacture and characterize impregnated thermionic cathode for power microwave devices

    International Nuclear Information System (INIS)

    In the present work it is described the barium calcium aluminate manufacture processes employed to produce impregnated cathodes to be used in a traveling-wave tube (TWT). The cathodes were developed using a tungsten body impregnated with barium and calcium aluminate with a 5:3:2 proportion (molar). Three different processes were investigated to obtain this material: solid-state reaction, precipitation and crystallization. Thermal analysis, thermogravimetry specifically, supported to determine an adequate preparation procedure (taking into account temperature, time and pyrolysis atmosphere). It was verified that the crystallization showed a better result when compared to those investigated (solid-state reaction and precipitation techniques - formation temperature is about 1000 deg C in hydrogen atmosphere), whereas it presented the lower formation temperature (800 deg C) in oxidizing atmosphere (O2). It was used the practical work function distribution theory (PWFD) of Miram to characterize thermionic impregnated cathode. The PWFD curves were used to characterize the barium-calcium aluminate cathode. PWFD curves shown that the aluminate cathode work function is about 2,00 eV. (author)

  14. Comparison of plasma electrolytic oxidation of zirconium alloy in silicate- and aluminate-based electrolytes and wear properties of the resulting coatings

    International Nuclear Information System (INIS)

    Highlights: ► PEO processes in silicate and aluminate electrolytes are compared for Zircaloy-2. ► Significant different behaviors are observed for the PEO in the two electrolytes. ► Superior wear resistance was observed for the coating from aluminate electrolyte. ► The coatings from aluminate electrolyte possess much higher t-ZrO2 content. ► The results show that Al2O3 is a more efficient tetragonal ZrO2 stabilizer. - Abstract: Plasma electrolytic oxidation of Zircaloy-2 at constant rms current is examined in silicate and aluminate electrolytes, revealing significantly different behaviors in the growth kinetics and properties of the coatings. Coatings thicken continuously in the silicate electrolyte, while in the aluminate electrolyte, the thickness reaches a relatively constant value. The latter coincides with changing appearances of discharges and detachment of an outer coating layer. Dissolution of zirconium is faster in the silicate electrolyte in the early stage of PEO, but is faster in the aluminate electrolyte following coating breakdown. The pre-spallation coating formed in the aluminate electrolyte shows superior wear resistance, which can be ascribed to its relative compactness, associated with the presence of tetragonal zirconia stabilized by aluminium species.

  15. Microscopic evaluation regarding time behavior of orthodontic cements used for disjunctor cementing

    Directory of Open Access Journals (Sweden)

    Ruxandra Bartok

    2015-11-01

    Full Text Available In order to fulfill their function, orthodontic devices must be cemented on teeth using orthodontic rings. The retention of the orthodontic ring is influenced mainly by the type of dental-ring adhesion. This study was initiated to determine possible microleakage events while using zinc phosphate cement Adhesor (Spofa Dental, conventional glass ionomer Ketac Cem (3M ESPE and Fuji Ortho (GC and a compomer Transbond Plus (3M Unitek. The results of the study are consistent with those reported in the literature reference, the compomer is the preferred adhesive material for cementing the orthodontic rings, compared to conventional glass ionomer cements and zinc-phosphate cement.

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

    International Nuclear Information System (INIS)

    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

  17. Copper Slag Blended Cement: An Environmental Sustainable Approach for Cement Industry in India

    Directory of Open Access Journals (Sweden)

    Jagmeet Singh

    2016-04-01

    Full Text Available Indian cement industry is facing environmental issue of emission of carbon dioxide (CO2, a greenhouse gas. Blended cements including supplementary cementitious materials are substitute of Portland cement to reduce CO2 emission. The present paper investigates theappropriateness of copper slag (CS as supplementary cementitious material. Strength properties and hydration of mixes were determined at different replacement levels of CS with cement. Compressive, flexural and tensile strength of each mix was found out at different curing periods. The hydration of cement was investigated through X-ray diffraction (XRD. The strength test results showed that substitution of up to 20% of CS can significantly replace Portland cement.XRD test results were corresponding to strength test results. The present study encourages the utilization of CS as supplementary cementitious material to make economical and environmentally sustainable blended cement

  18. 21 CFR 872.3275 - Dental cement.

    Science.gov (United States)

    2010-04-01

    ... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification. Zinc oxide-eugenol is a device composed of zinc oxide-eugenol intended to serve as a temporary tooth... chapter subject to § 872.9. (b) Dental cement other than zinc oxide-eugenol—(1) Identification....

  19. A Pause for China's Cement Industry

    Institute of Scientific and Technical Information of China (English)

    Li Zhen

    2009-01-01

    @@ Cement industry suffers excess productionWith the advent of global financial crisis,the Chinese government has laid out a stimulus package on infrastructure construction.Driven by the investment spree,China's cement makers are flocking to expand output capacity,which is now leading the industry into a much-higher-thanneeded state.

  20. Pre-portland cements and geopolymers

    Czech Academy of Sciences Publication Activity Database

    Hanzlíček, Tomáš; Perná, Ivana; Ertl, Z.; Miller, S.M.

    2012-01-01

    Roč. 9, č. 1 (2012), s. 57-62. ISSN 1214-9705 Institutional research plan: CEZ:AV0Z30460519 Keywords : caementum * cement itious * calcareous cement Subject RIV: JN - Civil Engineering Impact factor: 0.530, year: 2011 http://www.irsm.cas.cz/materialy/acta_content/2012_01/5_Hanzlicek.pdf

  1. Chloride ingress in cement paste and mortar

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Coats, Alison M.; Glasser, Fred P.

    1999-01-01

    In this paper chloride ingress in cement paste and mortar is followed by electron probe microanalysis. The influence of several paste and exposure parameters on chloride ingress are examined (e.g., water-cement ratio, silica fume addition, exposure time, and temperature), The measurements are...

  2. Synthesis of pure Portland cement phases

    DEFF Research Database (Denmark)

    Wesselsky, Andreas; Jensen, Ole Mejlhede

    2009-01-01

    Pure phases commonly found in Portland cement clinkers are often used to test cement hydration behaviour in simplified experimental conditions. The synthesis of these phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases in...

  3. Investigation of a Hardened Cement Paste Grout

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  4. A note on cement in asteroids

    CERN Document Server

    Bilalbegovic, G

    2016-01-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 microns were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 microns.

  5. Effect of calcium sulfates on the early hydration of calcium sulfoaluminate cement and the stability of embedded aluminium

    International Nuclear Information System (INIS)

    Conventional Portland cement-based systems have been considered unsuitable for immobilising nuclear wastes containing reactive metals, such as aluminium, due to the high pH of the pore solution (usually around 12.5) and free moisture. On the contrary, calcium sulfo-aluminate cement (CSA) produces a lower pH (10.5-12) environment and has an excellent water binding capability as a result of the formation of its main hydration product, ettringite. Therefore, it offers a good potential to immobilise aluminium. However, the pore solution pH and ettringite formation depend largely on the raw materials used to formulate the CSA, which is usually a blend of 75%-85% of CSA clinker and 15-25% of calcium sulfate (in the form of gypsum or anhydrite). In this paper, it was found that, compared to anhydrite, gypsum (15% wt of the blend) demonstrated the highest reduction in the corrosion of embedded Al, possibly due to its lower initial pH (around 10.5) and self-desiccating nature at the early stage of hydration. Whilst the CSA/anhydrite had a higher Al corrosion rate, the initial set was more acceptable than CSA/gypsum. Nonetheless, overall, it was concluded that CSA with gypsum (15% wt) should be considered as a base formulation for the encapsulation of Al waste. The unfavorable rapid set and high heat generation, however, demonstrated that modifications are required, potentially by using mineral additions. (authors)

  6. Crystal chemistry of portland cement hydrates as radioactive waste hosts. Final report, June 15, 1983-June 14, 1984

    International Nuclear Information System (INIS)

    Portland cement hydrates have been used as encapsulant/host phases in radioactive waste management. However, their phase chemistry and stability relationships are poorly defined. Therefore, on occasion, they have not performed as well as expected. As a result, their use has been mainly limited to low-level waste disposal. Since this knowledge gap existed, we had begun to investigate the crystal chemistry of the portland cement hydrates. It was our objective to identify potential hydrate host phases which were not only suitable for isolating radioactive-waste species but also inexpensive, easily processed, low-temperature materials. Initially, we were concentrating upon two areas of interest: the fixation of iodine by the calcium aluminate hydrates and the feasibility of using Stratling's compound as a host phase for cesium and strontium fixation. In both cases, a phase equilibrium study was initiated in order to identify phase relations and consequences of adding the species of interest to the system. An iodine-containing analogue of calcium monosulfoaluminate hydrate (C3A.CaI2.xH2O) was identified as a possible host phase. CsOH was added to formulations in the neighborhood of Stratling's compound, in order to establish phase relations and identify the fixation ability of Stratling's compound and its associated hydrates. 11 figures, 9 tables

  7. Crystal chemistry of portland cement hydrates as radioactive waste hosts. Progress report, June 15, 1983-February 7, 1984

    International Nuclear Information System (INIS)

    Portland cement hydrates have been used as encapsulant/host phases in radioactive waste management. However, their phase chemistry and stability relationships are poorly defined. Therefore, on occassion, they have not performed as well as expected. As a result, their use has been mainly limited to low-level waste disposal. Since this knowledge gap exists, we have begun to investigate the crystal chemistry of the portland cement hydrates. It is our objective to identify potential hydrate host phases which are not only suitable for isolating radioactive-waste species but also inexpensive, easily processed, low-temperature materials. Initially, we have been concentrating upon two areas of interest: The fixation of iodine by the calcium aluminate hydrates and the feasibility of using Straling's compound as a host phase for cesium and strontium fixation. In both cases, a phase equilibrium study has been initiated in order to identify phase relations and consequences of adding the species of interest to the system. An iodine-containing analogue of calcium monosulfoaluminate hydrate (C3A.CaI2.xH2O) has been identified as a possible host phase. CsOH and Sr(OH)2 are being added to formulations in the neighborhood of Stratling's compound, in order to establish phase relations and identify the fixation ability of Stratling's compound and its associated hydrates. 10 figures, 6 tables

  8. Conditioning of radioactive waste solutions by cementation

    International Nuclear Information System (INIS)

    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)

  9. CO2 Capture by Cement Raw Meal

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll;

    2013-01-01

    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used as the...... sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone....... The CO2 capture capacity of limestone in the raw meal is lower than for pure limestone. The difference in the CO2 capture capacity decreases with an increase in cycle number. The calcination conditions and composition are major factors that influence the CO2 capture capacity of limestone. At 850 °C in...

  10. Energetically Modified Cement (EMC) - Performance Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement

    2003-03-01

    Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

  11. Effect of temperature on the durability of class C fly ash belite cement in simulated radioactive liquid waste: synergy of chloride and sulphate ions.

    Science.gov (United States)

    Guerrero, A; Goñi, S; Allegro, V R

    2009-06-15

    The durability of class C fly ash belite cement (FABC-2-W) in simulated radioactive liquid waste (SRLW) rich in a mixed sodium chloride and sulphate solution is presented here. The effect of the temperature and potential synergic effect of chloride and sulfate ions are discussed. This study has been carried out according to the Koch-Steinegger test, at the temperature of 20 degrees C and 40 degrees C during a period of 180 days. The durability has been evaluated by the changes of the flexural strength of mortar, fabricated with this cement, immersed in a simulated radioactive liquid waste rich in sulfate (0.5M), chloride (0.5M) and sodium (1.5M) ions--catalogued like severely aggressive for the traditional Portland cement--and demineralised water, which was used as reference. The reaction mechanism of sulphate, chloride and sodium ions with the mortar was evaluated by scanning electron microscopy (SEM), porosity and pore-size distribution, and X-ray diffraction (XRD). The results showed that the chloride binding and formation of Friedel's salt was inhibited by the presence of sulphate. Sulphate ion reacts preferentially with the calcium aluminate hydrates forming non-expansive ettringite which precipitated inside the pores; the microstructure was refined and the mechanical properties enhanced. This process was faster and more marked at 40 degrees C. PMID:19056176

  12. Effect of the cement type on compatibility with carboxylate super plasticisers; Influencia de la naturaleza del cemento en la compatibilidad con aditivos superplastificantes basados en carboxilatos

    Energy Technology Data Exchange (ETDEWEB)

    Bundyra-Oracz, G.; Kurdowski, W.

    2011-07-01

    An empirical study was conducted to gain a fuller understanding of the interactions taking place in cement superplasticiser systems. To this end, two clinkers of clinkers of known chemical and phase composition were prepared in this study to gain insight into such interactions. One contained no tricalcium aluminate (C1), while the other had a 9% C{sub 3}A content (C2). These clinkers were ground to approximately 340 m{sup 2}/kg and blended with gypsum only or gypsum and Klein compound (3CaO{center_dot}3Al{sub 2}O{sub 3}{center_dot}CaSO{sub 4}) (1, 2). Sufficient compound was added to C1 to ensure the formation of about the same amount of ettringite after 0.5 and 1 h of hydration as found in cement C2 + gypsum. The admixture used was a carboxylate superplasticiser. Rheology measurements showed that while paste yield stress was correlated to ettringite formation, no such simple relationship was observed for plastic viscosity. Plastic viscosity depended on the total hydrates formed, i.e., not only as ettringite but also as C-S-H gel. The findings revealed that in clinkers with very low sulfate and potassium contents, the rheology of carboxylate-containing cement paste is primarily controlled by ettringite formation. (Author) 15 refs.

  13. Pack cementation coatings for alloys

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States)

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  14. ROTARY SCREW SYSTEMS IN CEMENT

    Directory of Open Access Journals (Sweden)

    Taratuta V. D.

    2016-01-01

    Full Text Available The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometrical shapes with form inside the screw breaks or smooth edges, screw surfaces and screw grooves. It is shown that the housing of the rotary kiln is expedient to produce helical surfaces whose centers of curvature are located within the housing. Using the proposed constructions rotary kiln during the firing when preparing cement wedge can increase the speed of rotation of the housing, furnaces 5-10 times due to changes in the rotary-screw systems increase efficiency and reduce the size of furnaces

  15. Cements with low Clinker Content

    Science.gov (United States)

    García-Lodeiro, I.; Fernández-Jiménez, A.; Palomo, A.

    2015-11-01

    Hybrid alkaline cements are multi-component systems containing a high percentage of mineral additions (fly ash, blast furnace slag), low proportions (alkaline activators. The substantially lower amount of clinker needed to manufacture these binders in comparison to ordinary Portland cement is both economically and ecologically beneficial. Their enormous versatility in terms of the raw materials used has made them the object of considerable interest. The present study explored the mechanical strength of binary blends mixes; B1= 20% clinker (CK) + 80% fly ash (FA) and B2=20% clinker + 80% blast furnace slag (BFS), both hydrated in the presence and absence of an alkaline activator specifically designed for this purpose. The use of the activator enhanced the development of early age strength considerably. All the hydrated matrices were characterised with XRD, SEM/EDX and (29Si and 27Al) NMR. The use of the alkaline activator generated reaction products consisting primarily of a mix of gels ((N,C)-A-S-H and C-A-S-H) whose respective proportions were found to depend upon system composition and initial reactivity.

  16. Cement and concrete options paper

    International Nuclear Information System (INIS)

    Greenhouse gas emissions associated with the production of concrete are projected to increase from 10.5 million tonnes in 1990 to almost 14 million tonnes in 2010. Over half of this amount will be non-energy related emissions of carbon dioxide resulting from the conversion of limestone to lime. According to this report by industry experts, the industry has an excellent record of improving energy efficiency and there are few easy gains remaining. Nevertheless, improvements in energy efficiency and fuel use, increased use of concrete where it can be shown to result in net reduction of GHG emissions, and partial replacement of cement by supplementary cementitious materials that involve no additional generation of GHGs, could yield an approximate reduction in carbon dioxide emissions of nearly seven million tons in 2010. The industry proposes three measures to realise these benefits: (1) encouraging replacement of fossil fuels by otherwise waste material, (2) encouraging increased use of concrete in constructing houses and roads, and (3) encouraging increased use of supplementary cementing materials. The industry is opposed to carbon or energy taxes that increase the cost of doing business, on the grounds that such taxes would adversely affect the industry's competitive position internationally. tabs

  17. SEM observation of gibbsite precipitation with seeds from sodium aluminate solutions promoted by ultrasound

    Institute of Scientific and Technical Information of China (English)

    陈国辉; 陈启元; 尹周澜; 张平民

    2003-01-01

    The microstructure of gibbsite precipitated with seeds from sodium aluminate solution was studied using SEM. The results show that there are a lot of fine secondary nuclei with diameter less than 1 μm and the surfaces of seeds precipitated by low frequency ultrasound are very irregular. The new nuclei are pseudo-hexagonal slices with nanometer grade in thickness. At higher precipitation temperature, such as 75 ℃, SEM micrographs show that there exist something like colloid on joints of different small granules which have agglomerated to a large particle. It is suggested that the formation of such hexagonal crystalline units is promoted by low frequency ultrasound, while the colloids on the surface may be produced by imcompletely crystallization of the growth units.

  18. Spectrographic Determination of Impurities in Ceramic Materials for Nuclear fusion Reactors. II. Analysis of Magnesium Aluminate

    International Nuclear Information System (INIS)

    The determination of minor and trace elements in the magnesium aluminate, considered as possible material in thermonuclear fusion reactors, has been studied. The concentration ranges are 0.1 - 0.3 % for Ca, SI and Y, and at the ppm level for Co, Cr, Fe, Hf, K, Li, Mn, Na, Ni, Se, Ta, Ti, V and Zr. Atomic emission spectroscopy with direct current are excitation and photographic detection has been employed. For Hf, Ta and Zr the use of 40% of copper fluoride as a carrier and of Nb as internal standard provide suitable sensitivities and precessions, while for the rest of elements the best results are obtained with graphite powder in different proportions and Rb or Sn as internal standard. (Author)4 refs

  19. The Effect of (Ag, Ni, Zn-Addition on the Thermoelectric Properties of Copper Aluminate

    Directory of Open Access Journals (Sweden)

    Jianxiao Xu

    2010-01-01

    Full Text Available Polycrystalline bulk copper aluminate Cu1-x-yAgxByAlO2 with B = Ni or Zn were prepared by spark plasma sintering and subsequent thermal treatment. The influence of partial substitution of Ag, Ni and Zn for Cu-sites in CuAlO2 on the high temperature thermoelectric properties has been studied. The addition of Ag and Zn was found to enhance the formation of CuAlO2 phase and to increase the electrical conductivity. The addition of Ag or Ag and Ni on the other hand decreases the electrical conductivity. The highest power factor of 1.26 × 10-4 W/mK2 was obtained for the addition of Ag and Zn at 1,060 K, indicating a significant improvement compared with the non-doped CuAlO2 sample.

  20. Procedure for the preparation of lithium aluminate powder in gamma phase

    Energy Technology Data Exchange (ETDEWEB)

    Lorenzini, L.; Borello, A.; Casadio, S.; Spadoni, M.; Benicchi, P.; Alvani, C.

    1987-04-01

    This ENEA (Italian Commission for Alternative Energy Sources) patent referes to a process for the production of lithium aluminate powder. The process consists of the following phases: the preparation of a mixture of aluminium 'sol' with a solution of aluminium nitrate; the homogenization of the said mixture to obtain a 'sol' of aluminium and lithium; the atomization of the 'sol' of aluminium and lithium in a drying gaseous flow to obtain a very fine grain powder; the separation, by the use of a cyclone separator, of the said powder from the gaseous flow; the heat treatment of the powder (e.g. at 600 degrees C for 22h) to obtain ternary oxides; Li Al O/sub 2/ stoichiometry in the gamma phase. The ternary oxides may be used as tritium generators in fusion reactors or in the fabrication of ceramic supports for molten carbonate fuel cell electrolytes.

  1. Optically stimulated luminescence of magnesium aluminate (MgAl2O4) spinel

    International Nuclear Information System (INIS)

    Magnesium aluminate spinel (MgAl2O4) is a crystal studied in detail mainly because of its radiation resistance and good optical and insulating features. A new characteristic of this material is presented here, which may be applied to radiation dosimetry. Spinel crystals present a high optically stimulated luminescence (OSL) signal linearly related to the absorbed dose of ionizing radiation. The correlation of OSL with thermoluminescence (TL) shown in the paper indicates that trapped carriers connected to at least three TL glow peaks (63, 260 and 540-bar C, 1-bar Cs-1) participate in the OSL process. Part of the OSL signal emitted by spinel fades very rapidly at room temperature but a more stable component of the emission can be properly separated and used as a dose indicator with good reproducibility

  2. The preparation of lithium aluminate by the hydrolysis of lithium and aluminum alkoxides

    International Nuclear Information System (INIS)

    Lithium aluminate was prepared by heating the hydrolysis products from various combinations of lithium and aluminum alkoxides under an atmosphere of nitrogen. The product was β-LiA1O2 when aluminum iso-propoxide was a starting material, whereas γ-LiA1O2 was the product for preparations starting with aluminum n-butoxide. The results were independent of the choice of lithium alkoxide. The hydrolysis of aluminum sec-butoxide with a solution of LiOH led to the γ phase as well. The temperature at which the γ phase developed depended upon the conditions of the hydrolysis reaction and was observed at a temperature as low as 550 degrees Celcius

  3. Spectrographic determination of impurities in ceramic materials for nuclear fusion reactors. II. Analysis of magnesium aluminate

    International Nuclear Information System (INIS)

    The determination of minor and trace elements in the magnesium aluminate, considered as possible mataerial in thermonuclear fusion reactors, has been studied. The concentaration ranges are 0.1-0.3 % for Ca, Si and Y, and at the ppm level for Co, Cr, Fe, Hf, K, Li, Mn, Na, Ni, Sc, Ta, Ti, V and Zr. Atomic emission spectroscopy with direct current arc excitation and photographic detection has been employed. For Hf, Ta and Zr the use of 40% of copper fluoride as a carrier and of Nb as internal standard provide suitable sensitivities and precissions, while for the rest of elements the best results are obtained with graphite power in different proportions and Rb or Sn as internal standard. (Author). 4 refs

  4. Study of caesium adsorption on hydrated calcium-silicate-aluminate systems

    International Nuclear Information System (INIS)

    Immobilization of caesium in cementitious matrixes was studied in the present paper which is a key issue of handling radioactive caesium containig wastes for caesium does not form stabile compounds therefor it can not be readily immobilized. Model matrices were prepared to map up the calcium-silicate-aluminate system considering caesium immobilization, which were of different starting compositions. To caracterize Cs sorption, distribution ratios were determined. Based on the results obtained the model matrix compositions were prepared using industrial grade materials and their caesium retardation and trapping were examined by means of leaching and sorption experiments. In the light of the results obtained, it can be established that immobilization of caesium significantly depend on the starting composition of the used matrix. (orig.)

  5. Pre-desilication and digestion of gibbsitic bauxite with lime in sodium aluminate liquor

    Science.gov (United States)

    Pan, Xiao-lin; Yu, Hai-yan; Dong, Kai-wei; Tu, Gan-feng; Bi, Shi-wen

    2012-11-01

    The effect of lime on the pre-desilication and digestion of gibbsitic bauxite in synthetic sodium aluminate liquor at different temperatures was investigated. The bauxite is comprised of gibbsite, aluminogoethite, hematite, kaolin, quartz, and minor boehmite. Lime increases the desilication efficiency of the bauxite during the pre-desilication process by promoting the conversion of sodalite and cancrinite to hydrogarnet. Desilication reactions during the digestion process promoted by lime result in the loss of Al2O3 entering the red mud, but the amount of aluminogoethite-to-hematite conversion promoted by lime leads to the increase of aluminogoethitic Al2O3 entering the digested liquor. The alumina digestion rate at 245°C is higher than that at 145°C due to the more pronounced conversion of aluminogoethite to hematite. The soda consumption during the digestion process decreases due to lime addition, especially at higher temperatures.

  6. The aluminization of 600 k WLS fibers for the TileCal/ATLAS/LHC

    CERN Document Server

    Saraiva, J G; Maneira, M J P; Maio, A; Patriarca, J

    2004-01-01

    The TILE CALorimeter, the hadronic sampling calorimeter of ATLAS/LHC /CERN, is made of iron and polystyrene scintillating tiles. The light produced in scintillating tiles is absorbed and guided to the photomultipliers (PMTs) through wave length shifter (WLS) optical fibers. To optimize the detection of jets and muons, the top of the fibers away of the PMTs is coated with an aluminum mirror. This aluminum mirror is produced by planar magnetron sputtering. This process adds to an excellent reproducibility a minimal thermal aggression, important for a proper film adhesion to the plastic surface. To satisfy schedule and optical critical requirements, a dedicated mass production machine named SIDELO II was projected and constructed. A reflectivity of R similar to 75% is achieved and the light output uniformity improved by asymptotically equal to 10%. The aluminization of the fibers and their quality control started in August 1999 and went on continuously until May 2002. The quality control results showed a reprodu...

  7. Soft sensor for ratio of soda to aluminate based on PCA-RBF multiple network

    Institute of Scientific and Technical Information of China (English)

    GUI Wei-hua; LI Yong-gang; WANG Ya-lin

    2005-01-01

    Based on principal component analysis, a multiple neural network was proposed. The principal component analysis was firstly used to reorganize the input variables and eliminate the correlativity. Then the reorganized variables were divided into 2 groups according to the original information and 2 corresponding neural networks were established. A radial basis function network was used to depict the relationship between the output variables and the first group input variables which contain main original information. An other single-layer neural network model was used to compensate the error between the output of radial basis function network and the actual output variables. At last, The multiple network was used as soft sensor for the ratio of soda to aluminate in the process of high-pressure digestion of alumina. Simulation of industry application data shows that the prediction error of the model is less than 3%, and the model has good generalization ability.

  8. Radiation-induced disordering in magnesium aluminate spinel subjected to ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Shimada, M. E-mail: shimaq@nucl.kyushu-u.ac.jp; Matsumura, S.; Yasuda, K.; Kinoshita, C.; Chimi, Y.; Ishikawa, N.; Iwase, A

    2004-08-01

    An analytical electron microscope study was carried out on single crystal specimens of magnesium aluminate spinel irradiated with 200 MeV Xe{sup 14+} ions up to 5.0 x 10{sup 15} and 2.0 x 10{sup 16} ions/m{sup 2} at ambient temperature. Bright-field images showed structurally disordered columns of about 4-5 nm in diameter along ion tracks. Tiny pits were observed on the incident surface of the columns. Quantitative HARECXS analysis of atomic configurations revealed that disordering proceeds in more extended regions over 10 nm in diameter. The configurations of Al{sup 3+} ions are more disordered than that of Mg{sup 2+} ions. The disordered areas are appeared to overlap each other in the specimen irradiated with 2.0 x 10{sup 16} ions/m{sup 2}.

  9. Radiation-induced disordering in magnesium aluminate spinel subjected to ionizing radiation

    Science.gov (United States)

    Shimada, M.; Matsumura, S.; Yasuda, K.; Kinoshita, C.; Chimi, Y.; Ishikawa, N.; Iwase, A.

    2004-08-01

    An analytical electron microscope study was carried out on single crystal specimens of magnesium aluminate spinel irradiated with 200 MeV Xe 14+ ions up to 5.0 × 10 15 and 2.0 × 10 16 ions/m 2 at ambient temperature. Bright-field images showed structurally disordered columns of about 4-5 nm in diameter along ion tracks. Tiny pits were observed on the incident surface of the columns. Quantitative HARECXS analysis of atomic configurations revealed that disordering proceeds in more extended regions over 10 nm in diameter. The configurations of Al 3+ ions are more disordered than that of Mg 2+ ions. The disordered areas are appeared to overlap each other in the specimen irradiated with 2.0 × 10 16 ions/m 2.

  10. Structural and mechanical properties of magnesium-aluminate spinel optical ceramics

    International Nuclear Information System (INIS)

    There were investigated the mechanical and structural characteristics of magnesium aluminate spinel ceramics (MgO centre dot n Al2O3), prepared by hot pressing method of powder in dependence on the technological parameters of sintering, phase composition and deviation from stoichiometry. The optimal parameters of sintering to get reliable fracture toughness (K1C) were found: the temperature of calcinations 1200 degree C and time 1 hour. There was obtained the dependence of K1C on the degree of deviation of spinel composition from stoichiometric (n) in the range 0.96...1.05 and doping with transition metals Mn, Cr, and Fe. High-temperature annealing in oxidized atmosphere leads to diffusion of Mg cations to surface, the annealing in reduced atmosphere-diffusion of Mg from surface into the bulk of sample, causing formation of spinel structure of stoichiometric composition in subsurface layer of ceramics

  11. On the Compressive and Tensile Dynamic Strength of Magnesium Aluminate Spinel

    Science.gov (United States)

    Hayun, Shmuel; Paris, Vitaly; Dariel, Moshe; Zaretsky, Eugene; Frage, Nahum

    2009-06-01

    Polycrystalline transparent Magnesium Aluminate Spinel (MAS) is an attractive material for a wide range of optical, electronic, structural and armor applications. Transparent MAS samples of 20-30 mm diameter and 3-5 mm thickness has been successfully fabricated by means of Field Assisted Sintering Technology. The dynamic response of MAS was investigated by plate impact experiments. The values of the Hugoniot Elastic Limit (HEL) and the spall strength were derived from the VISAR records of the velocities of the free sample surface or of the sample/window (PMMA) interface. The dependence of the HEL and the spall strength on the impact stress, as well as, correlation between the spall strength and the width of the loading pulse are discussed.

  12. Fabrication of translucent magnesium aluminate spinel and its compatibility in sodium vapour

    International Nuclear Information System (INIS)

    The sintering behaviour of magnesium aluminate spinel on both sides of the stoichiometry has been investigated. It is found that the composition close to the stoichiometric composition, but slightly enriched in magnesia can be sintered to translucency in a free flowing hydrogen environment. The grain size decreases with magnesia content; the addition of yttria, however, results in a highly bimodal grain structure. Prolonged exposure of the spinel in a high temperature sodium vapour environment forms Na20.5Al2O3 and some traces of Na2O.11Al2O3 predominantly at the grain boundaries and near the surface of the specimen. Some possible sintering mechanism and factors affecting the in-line transmission are discussed. (author)

  13. Optical properties of magnesium aluminate spinel crystals implanted with He ions

    International Nuclear Information System (INIS)

    Specimens of magnesium aluminate spinel MgAl2O4 0.5 mm thick are used to study the effect of 170 keV He+ ion irradiation with doses ranging from 3 x 1016 to 3 x 1017 ion/cm2 on optical properties. A comparison is made for optical absorption spectra of the specimens before and after irradiation as well as after a 1000 K annealing. Optical microscopical examination reveals spherical gas bubbles in implanted layer which size and density increase with radiation doses. At a dose of 3 x 1017 ion/cm2 gas bubbles are becoming, opened to the surface and give rise to blistering. The results of radioluminescence spectrum study point to cationic disorder, crystal defect occurrence and phase composition variations affecting optical properties

  14. Radiation-induced disordering in magnesium aluminate spinel subjected to ionizing radiation

    International Nuclear Information System (INIS)

    An analytical electron microscope study was carried out on single crystal specimens of magnesium aluminate spinel irradiated with 200 MeV Xe14+ ions up to 5.0 x 1015 and 2.0 x 1016 ions/m2 at ambient temperature. Bright-field images showed structurally disordered columns of about 4-5 nm in diameter along ion tracks. Tiny pits were observed on the incident surface of the columns. Quantitative HARECXS analysis of atomic configurations revealed that disordering proceeds in more extended regions over 10 nm in diameter. The configurations of Al3+ ions are more disordered than that of Mg2+ ions. The disordered areas are appeared to overlap each other in the specimen irradiated with 2.0 x 1016 ions/m2

  15. Production of Magnesium by Vacuum Aluminothermic Reduction with Magnesium Aluminate Spinel as a By-Product

    Science.gov (United States)

    Wang, Yaowu; You, Jing; Peng, Jianping; Di, Yuezhong

    2016-03-01

    The Pidgeon process currently accounts for 85% of the world's magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

  16. Chemical synthesis of nanocrystalline magnesium aluminate spinel via nitrate-citrate combustion route

    Energy Technology Data Exchange (ETDEWEB)

    Saberi, Ali [Ceramic Division, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)], E-mail: ASaberi@IUST.ac.ir; Golestani-Fard, Farhad; Sarpoolaky, Hosein [Ceramic Division, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Willert-Porada, Monika; Gerdes, Thorsten [Chair of Materials Processing, University of Bayreuth, Bayreuth (Germany); Simon, Reinhard [Chair of Ceramic Materials Engineering, University of Bayreuth, Bayreuth (Germany)

    2008-08-25

    Nanocrystalline magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) was synthesized using metal nitrates, citric acid and ammonium solutions. The precursor and the calcined powders at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The combustion mechanism was also studied by a quadrupole mass spectrometer (QMS) which coupled to STA. The generated heat through the combustion of the mixture of ammonium nitrate and citrate based complexes decreased the synthesis temperature of MgAl{sub 2}O{sub 4} spinel. The synthesized MgAl{sub 2}O{sub 4} spinel at 900 deg. C has faced shape with crystallite size in the range of 18-24 nm.

  17. Chemical synthesis of nanocrystalline magnesium aluminate spinel via nitrate-citrate combustion route

    International Nuclear Information System (INIS)

    Nanocrystalline magnesium aluminate spinel (MgAl2O4) was synthesized using metal nitrates, citric acid and ammonium solutions. The precursor and the calcined powders at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The combustion mechanism was also studied by a quadrupole mass spectrometer (QMS) which coupled to STA. The generated heat through the combustion of the mixture of ammonium nitrate and citrate based complexes decreased the synthesis temperature of MgAl2O4 spinel. The synthesized MgAl2O4 spinel at 900 deg. C has faced shape with crystallite size in the range of 18-24 nm

  18. Grain-boundary migration in nonstoichiometric solid solutions of magnesium aluminate spinel 2

    International Nuclear Information System (INIS)

    The grain-boundary chemistry of magnesium aluminate spinel solid solutions MgO · nAl2O3 has been investigated in order to understand the mechanism of grain-boundary migration. It is found that although segregation of impurity Ca and Si is common, much larger deviations in grain-boundary stoichiometry are present. There is an excess of Al and O relative to Mg at grain boundaries in all compositions. Grain-boundary migration appears to be rate-limited by solute drag from intrinsic defects accommodating lattice nonstoichiometry, rather than by extrinsic solutes, consistent with the observed impurity tolerance of grain-boundary mobility. Different rate-limiting defects are proposed for magnesia-rich and alumina-rich spinels

  19. Defects and radiation induced electronic processes in magnesium aluminate spinel of different compositions

    Science.gov (United States)

    Gritsyna, V. T.; Kazarinov, Y. G.; Kobyakov, V. A.; Sickafus, K. E.

    The time dependence of the formation and decay of irradiation-induced optical absorption centers in magnesium aluminate spinel single crystals of different compositions (MgO.1.0Al(2)O(3) and MgO.2.5Al(2)O(3)) was investigated. The kinetics of accumulation of X-ray irradiation-induced absorption bands is consistent with the mechanism of trap filling with free charge carriers through the conduction band. The model includes Coulomb blocking effects on spatially correlated defects. The observed two-stage decay of absorption bands after termination of X-ray irradiation is explained by electron hole recombination between centers of two different distances and/or different potential barriers. UV-irradiation confirms the existence of charge exchange between complex spatially correlated defects.

  20. Laser-Induced Fluorescence Photogrammetry for Dynamic Characterization of Transparent and Aluminized Membrane Structures

    Science.gov (United States)

    Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.; Pappa, Richard S.

    2003-01-01

    Photogrammetry has proven to be a valuable tool for static and dynamic profiling of membrane based inflatable and ultra-lightweight space structures. However, the traditional photogrammetric targeting techniques used for solid structures, such as attached retro-reflective targets and white-light dot projection, have some disadvantages and are not ideally suited for measuring highly transparent or reflective membrane structures. In this paper, we describe a new laser-induced fluorescence based target generation technique that is more suitable for these types of structures. We also present several examples of non-contact non-invasive photogrammetric measurements of laser-dye doped polymers, including the dynamic measurement and modal analysis of a 1m-by-1m aluminized solar sail style membrane.

  1. Post-stishovite transition in hydrous aluminous SiO2

    Science.gov (United States)

    Umemoto, Koichiro; Kawamura, Katsuyuki; Hirose, Kei; Wentzcovitch, Renata M.

    2016-06-01

    Lakshtanov et al. (2007) showed that incorporation of aluminum and some water into SiO2 significantly reduces the post-stishovite transition pressure in SiO2. This discovery suggested that the ferroelastic post-stishovite transition in subducted MORB crust could be the source of reflectors/scatterers with low shear velocities observed in the mid to upper lower mantle. A few years later, a similar effect was observed in anhydrous Al-bearing silica. In this paper, we show by first principles static calculations and by molecular dynamics using inter-atomic potentials that hydrogen bonds and hydrogen mobility play a crucial role in lowering the post-stishovite transition pressure. A cooperative redistribution of hydrogen atoms is the main mechanism responsible for the transition pressure reduction in hydrous aluminous stishovite. The effect is enhanced by increasing hydrogen concentration. This perspective suggests a potential relationship between the depth of seismic scatterers and the water content in stishovite.

  2. Roles of Eu2+, Dy3+ Ions in Persistent Luminescence of Strontium Aluminates Phosphors

    Institute of Scientific and Technical Information of China (English)

    L(U) Xingdong; ZHONG Minjuan; WANG Renqin

    2008-01-01

    The polycrystalline Eu2+ and Dy3+ co-doped strontium aluminates SrAl2O4: Eu2+,Dy3+ with different compositions were prepared by solid state reactions. The UV-excited photoluminescence, persistent luminescence and thermo-luminescence were studied and compared. Results show that the doped Eu2+ ion in SrAl2O4: Eu2+, Dy3+phosphors works as not only the UV-excited luminescent center but also the persistent luminescent center. The doped Dy3+ ion can hardly yield any luminescence under UV-excitation, but effectively enhance the persistent luminescence and thermo-luminescence of SrAl2O4: Eu2+. Dy3+ co-doping can help form electron traps with appropriate depth due to its suitable electro-negativity, and increase the density and depth of electron traps. Based on above observations, a persistent luminescence mechanism, electron transfer model, is proposed and illustrated.

  3. Determination of Al, P, and Si in fruit juices stored in glass and aluminized containers

    International Nuclear Information System (INIS)

    The concentration of Al, P, and Si in 142 samples of five fruit juices, measured with neutron activation analysis and atomic absorption spectroscopy, varies from 0 to 1.44, 31 to 201, and 1.5 to 35 μg/mL, respectively. The mean concentration of Al in apple, grape, grapefruit, orange, and pineapple juices is 0.54, 0.94, 0.24, 0.29, and 0.62 μg/ml, respectively. The mean concentration of P in the same juices is 102, 115, 124, 127, and 76 μg/ml. The storage of juice in aluminized containers with internal plastic coating does not increase the concentration of Al in the juice

  4. Diffusion of Aluminum Into Steel Substrates By Means Of Hot Dip Aluminizing

    International Nuclear Information System (INIS)

    Surface coating is an efficient and economical method to obtain desirable material surfaces properties. As compared to other coating techniques, hot dip coating can be considered as the most economical way to protect steel surfaces. Hot dip aluminizing technique was investigated in this study. Experiments have been conducted on the mild steel substrates with 10 mm diameter. The substrates were dipped into the molten aluminum maintained at temperature 750 deg. C for 5, 10, 15, 20, 25 and 30 minutes. Optical microscopy, scanning electron microscope and energy dispersive X-ray spectroscopy were used in this investigation. From the microstructure observation, it showed the appearance of intermetallic layer covered by the top layer of Al on the mild steel substrate increased with the increase in dipping time. The result of EDX analysis revealed the existence of Fe and Al in form of new Al-Fe phase. This indicated the possible formation of the intermetallic layers.

  5. Electron energy-loss spectroscopy study of thin film hafnium aluminates for novel gate dielectrics.

    Science.gov (United States)

    Stemmer, S; Chen, Z Q; Zhu, W J; Ma, T P

    2003-04-01

    We have used conventional high-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) in scanning transmission electron microscopy to investigate the microstructure and electronic structure of hafnia-based thin films doped with small amounts (6.8 at.%) of Al grown on (001) Si. The as-deposited film is amorphous with a very thin (approximately 0.5 nm) interfacial SiOx layer. The film partially crystallizes after annealing at 700 degrees C and the interfacial SiO2-like layer increases in thickness by oxygen diffusion through the Hf-aluminate layer and oxidation of the silicon substrate. Oxygen K-edge EELS fine-structures are analysed for both films and interpreted in the context of the films' microstructure. We also discuss valence electron energy-loss spectra of these ultrathin films. PMID:12694419

  6. Production of Magnesium by Vacuum Aluminothermic Reduction with Magnesium Aluminate Spinel as a By-Product

    Science.gov (United States)

    Wang, Yaowu; You, Jing; Peng, Jianping; Di, Yuezhong

    2016-06-01

    The Pidgeon process currently accounts for 85% of the world's magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

  7. Water solubility in aluminous orthopyroxene and the origin of Earth's asthenosphere.

    Science.gov (United States)

    Mierdel, Katrin; Keppler, Hans; Smyth, Joseph R; Langenhorst, Falko

    2007-01-19

    Plate tectonics is based on the concept of rigid lithosphere plates sliding on a mechanically weak asthenosphere. Many models assume that the weakness of the asthenosphere is related to the presence of small amounts of hydrous melts. However, the mechanism that may cause melting in the asthenosphere is not well understood. We show that the asthenosphere coincides with a zone where the water solubility in mantle minerals has a pronounced minimum. The minimum is due to a sharp decrease of water solubility in aluminous orthopyroxene with depth, whereas the water solubility in olivine continuously increases with pressure. Melting in the asthenosphere may therefore be related not to volatile enrichment but to a minimum in water solubility, which causes excess water to form a hydrous silicate melt. PMID:17234945

  8. Effect of agglomeration during coprecipitation: Delayed spinellization of magnesium aluminate hydrate

    Indian Academy of Sciences (India)

    Soumen Pal; A K Bandyopadhyay; S Mukherjee; B N Samaddar; P G Pal

    2010-08-01

    Precipitation of magnesium aluminate hydrate with faster addition of ammonia at desired pH causes agglomeration. Agglomerated powder, without any further treatment, on calcination forms intermediate compounds at low temperatures (≤ 900°C). The intermediate compounds on further heat treatment (≥ 1000°C) decompose into MgO, MgAl2O4 and -Al2O3. Effect of agglomeration and absorption of foreign ions such as Cl–, SO$^{2-}_{4}$, and NH$^{+}_{4}$ in complex compounds probably cause loss of Al3+ and Mg2+ ions during heat treatment, and stoichiometry changes. Powders prepared by continuous method with better control of process parameters than batch process yields better spinellization.

  9. Encapsulation of strontium aluminate phosphors to enhance water resistance and luminescence

    International Nuclear Information System (INIS)

    Strontium aluminate SrAl2O4:Eu2+,Dy3+ phosphors are chemically unstable against water or even moisture. To enhance the water resistance of the phosphors, an encapsulation was performed by direct surface reactions with phosphoric acid (H3PO4). The morphology, surface structure, surface element composition, water resistance, luminescence, and photoacoustic spectrum of the phosphors before and after encapsulation were discussed. Experimental results showed that phosphors were perfectly encapsulated by amorphous layers in nanoscale and crystalline layers in microscale under different conditions. The water resistance of phosphors was greatly enhanced by the two types of layer. More importantly, the amorphous layers enhanced the luminescence of phosphors markedly. The possible mechanism for the enhancements was also proposed.

  10. Aluminizing a Ni sheet through severe plastic deformation induced by ball collisions

    International Nuclear Information System (INIS)

    Highlights: • Aluminizing a Ni sheet was performed by mechanical alloying. • Technique allows us to apply Al layer from both sides of a sheet in one operation. • The Al layer consisted of Al grains with an average size of about 40 nm. • The hardness of the fabricated Al layer was 10 times that of the initial Al plate. • The ball collisions destroyed the initial rolling texture of the Ni sheet. - Abstract: Aluminizing a Ni sheet was performed through severe plastic deformation induced by ball collisions. The Ni sheet was fixed in the center of a mechanically vibrated vial between two connected parts. The balls were loaded into the vial on both sides of the Ni disk. Al disks, which were fixed on the top and the bottom of the vial, served as the sources of Al contamination. During processing, the Ni sheet was subject to intense ball collisions. The Al fragments were transferred and alloyed to the surface of the Ni sheet by these collisions. The combined effects of deformation-induced plastic flow, mechanical intermixing, and grain refinement resulted in the formation of a dense, continuous nanostructured Al layer on the Ni surface on both sides of the sheet. The Al layer consisted of Al grains with an average size of about 40 nm. The Al layer was reinforced with nano-sized Ni flakes that were introduced from the Ni surface during processing. The local amorphization at the Ni/Al interface revealed that the bonding between Ni and Al was formed by mechanical intermixing of atomic layers at the interface. The hardness of the fabricated Al layer was 10 times that of the initial Al plate. The ball collisions destroyed the initial rolling texture of the Ni sheet and induced the formation of the mixed [1 0 0] + [1 1 1] fiber texture. The laminar rolling structure of the Ni was transformed into an ultrafine grain structure

  11. Determination of hydroxide in the presence of aluminate using a modified potentiometric titration

    International Nuclear Information System (INIS)

    A procedure for the determination of hydroxide concentration in the presence of aluminate and other interfering ions was developed using the method of standard additions (or more specifically in this case, standard subtractions). The procedure called for titration with a strong acid which was added in equal increments at regular time intervals. The potential was recorded after each addition of acid. The data was plotted on Gran's Plot Paper, which is based on work done originally by Gran, or it was entered into a computer to determine the equivalence volume of the titrant. When used on many different samples in different matrices, the method gave results that were approximately 100 +- 1 percent of the calculated value. This was shown to be true even in systems containing aluminate [Al(OH)4-], phosphate (PO43-), sulfate (SO42-), nitrate (NO3-), nitrite (NO2-), carbonate (CO32-), and other ions. The effect of these ions was shown to be negligible if the initial OH- concentration was at least 10-3 M and barium chloride (BaCl2) was added to complex the PO43- and CO32- ions. These ions were checked at levels of up to 3 M for Al(OH)4- and NO3-, 2 M for NO2-, and 1 M for SO42-, PO43-, and CO32-. The method is applicable to radioactive as well as nonradioactive samples and any heat involved with a radioactive sample is insufficient to cause an error in the determination. On the basis of the work performed it was shown that the method was general enough to be run on a routine basis

  12. Irradiation damage in gamma lithium aluminate - LiAlO2

    International Nuclear Information System (INIS)

    Single crystals of gamma lithium aluminate (of tetragonal structure) are irradiated) with various projectiles (electrons, He ions, protons, X and gamma photons) and we used (i) electronic paramagnetic resonance (EPR) and optical absorption to detect the defects produced, and (ii) transmission electron microscopy (TEM). The lithium aluminate single crystals irradiated with electrons or ions contain five different paramagnetic defects. Each of them has several anisotropic configurations whose EPR signals (i) have a Lande factor close to 2, (ii) exhibit a resolved hyperfine structure and (iii) are identical only when the static magnetic field is along /001/. In addition, four optical absorption bands appear in the range 1-6 eV in the same irradiation conditions. But only three among the five paramagnetic defects and one of the optical bands appear in X-and gamma-ray irradiated samples. Using these observations, we discuss the nature of the detected defects and we conclude about the type of their production mechanism. Particularly, we assign a six-line EPR signal and an optical band in the ultraviolet range to the F+-centre. We compare this hypothesis to a defect model based on the computation of approximate electronic wave functions using the variational method. Our TEM study shows that when gamma-LiAlO2 single crystals are irradiated with 1 MeV electrons (fluence: 1020 electrons/sqcm), tridimensional defects (of mean dimension 100 nm) appear. At lower energies, the defect production is hidden by a thermal effect that is sufficient to induce the evaporation of lithium oxyde and the formation of LiAl508

  13. Luminescence of dysprosium doped strontium aluminate phosphors by codoping with manganese ion

    International Nuclear Information System (INIS)

    Highlights: • SrAl2O4:Dy3+, Mn2+ phosphor was synthesized by solid state reaction method. • The roles of Dy3+ and Mn2+ doped into SrAl2O4 were discussed. • The nature of the emission lines is discussed. -- Abstract: The authors report here the luminescence properties of strontium aluminate doped with dysprosium and manganese. The dysprosium, manganese co-doped powders were prepared by a solid state reaction at temperatures at 1600 °C under H2 (15%)–Ar (85%) atmosphere. The dysprosium, manganese co-doped strontium aluminate phosphors have the monoclinic structure with lattice parameters a ≈ 8.440 Å, b ≈ 8.821 Å, c ≈ 5.157 Å and β ≈ 93.4°. The characteristic 4F9/2 → 6H15/2 (blue), 4F9/2 → 6H13/2 (yellow), 4F9/2 → 6H11/2 (red) and 4F9/2 → 6H9/2 (NIR) transitions of Dy3+ for different luminescence techniques (radioluminescence, photoluminescence and cathodoluminescence) were detected in the emission spectra at the room temperature. The luminescence of Mn2+ co-doped SrAl2O4:Dy3+ exhibits a broad green–orange emission band (4T1 → 6A1 transition) from the synthesized phosphor particles under different excitation sources. This corresponds to the spin-forbidden transition of the d-orbital electron associated with the Mn2+ ion. Multiple emission lines observed at each of these techniques are due to the crystal field splitting of the ground state of the emitting ions. The nature of the emission lines is discussed

  14. Advanced Nanoscale Characterization of Cement Based Materials Using X-Ray Synchrotron Radiation: A Review

    KAUST Repository

    Chae, Sejung R.

    2013-05-22

    We report various synchrotron radiation laboratory based techniques used to characterize cement based materials in nanometer scale. High resolution X-ray transmission imaging combined with a rotational axis allows for rendering of samples in three dimensions revealing volumetric details. Scanning transmission X-ray microscope combines high spatial resolution imaging with high spectral resolution of the incident beam to reveal X-ray absorption near edge structure variations in the material nanostructure. Microdiffraction scans the surface of a sample to map its high order reflection or crystallographic variations with a micron-sized incident beam. High pressure X-ray diffraction measures compressibility of pure phase materials. Unique results of studies using the above tools are discussed-a study of pores, connectivity, and morphology of a 2,000 year old concrete using nanotomography; detection of localized and varying silicate chain depolymerization in Al-substituted tobermorite, and quantification of monosulfate distribution in tricalcium aluminate hydration using scanning transmission X-ray microscopy; detection and mapping of hydration products in high volume fly ash paste using microdiffraction; and determination of mechanical properties of various AFm phases using high pressure X-ray diffraction. © 2013 The Author(s).

  15. Extraoral Cementation Technique to Minimize Cement-Associated Peri-implant Marginal Bone Loss: Can a Thin Layer of Zinc Oxide Cement Provide Sufficient Retention?

    Science.gov (United States)

    Frisch, Eberhard; Ratka-Krüger, Petra; Weigl, Paul; Woelber, Johan

    2016-01-01

    This report describes the use of laboratory-fabricated crown intaglio replicas for extraorally prepared cementation of fixed restorations to implants. This technique minimizes excess cement and may therefore reduce the risk of cement-related marginal peri-implant bone loss. It is unclear whether the remaining thin layer of luting agent provides sufficient retention if low-adhesive zinc oxide (ZnO) cement is used. In 85 consecutive patients, 113 single crowns were cemented to implants using extraoral cementation technique (ECT) and ZnO cement. All patients were followed for 6 months and investigated for decementation. Seven events of decementation (incidence: 6.19%) were found in 7 patients (8.24%). ECT may represent a viable cementation technique for implant-supported single crowns, even using low-adhesion cements. PMID:27479343

  16. Modelling Quartz Cementation of Quartzose Sandstones

    Energy Technology Data Exchange (ETDEWEB)

    Wangen, Magnus

    1999-10-01

    Porosity estimation in sandstones is an important part of oil reservoir quality estimations, as porosity is lost during burial because of mechanical compaction and quartz cementation. In this report, cementation of quartzose sandstones is modelled assuming that the main source of silica is quartz dissolved at stylolites. The cementation process is shown to operate in one of two different regimes depending on the Damkohler number for diffusion. The regime, where diffusion of silica from the stylolites is a faster process than precipitation, is characterized by a nearly constant supersaturation between the stylolites. This regime, which spans the depth interval of quartz cementation for close stylolites, allows approximate analytical expressions for the porosity evolution as a function of time and temperature. An expression is derived for the temperature where half the initial porosity is lost during constant burial along constant thermal gradient. This expression is used to study the sensitivity of all parameters which enter the cementation process. The cementation process is shown to be particularly sensitive to the activation energy for quartz dissolution. The expression for the porosity decrease under constant burial is generalized to any piecewise linear burial and temperature history. The influence of the burial histories on the cementation process is studied. 32 refs., 16 figs., 1 tab.

  17. Three big Cs: climate, cement and China

    Energy Technology Data Exchange (ETDEWEB)

    Nordqvist, Joakim [Lund Univ., Lund (Sweden); Boyd, Christopher [Lafarge (France); Klee, Howard [World Business Council for Sustainable Development (Switzerland)

    2003-09-30

    Cement is a low-cost construction material whose manufacture generates significant carbon dioxide emissions. As these emissions enter a carbon-constrained world, they may ultimately have a significant impact on the industry's financial performance. Consequently, the cement industry is developing a response to climate change management and the connected political process. Ten of the world's leading cement-producing corporations, representing more than one-third of global cement production, published a joint Agenda for Action in 2002 to address sustainability issues for the industry, including climate change. Other issues identified are emissions reduction, use of fuels and raw materials, employee health and safety, local impacts on land and communities, and internal business processes. Examining the rationale for, and the effects of, proactive climate initiatives in the cement sector, this paper elaborates on the conditions for the spread of cement-related climate action to China, where more than one-third of global cement production occurs, 80% of which involves inefficient kilns using outdated, highly polluting technology. (Author)

  18. Effect of cements on fracture resistance of monolithic zirconia crowns

    OpenAIRE

    Nakamura, Keisuke; Mouhat, Mathieu; Nergård, John Magnus; Lægreid, Solveig Jenssen; Kanno, Taro; Milleding, Percy; Örtengren, Ulf

    2016-01-01

    Abstract Objectives The present study investigated the effect of cements on fracture resistance of monolithic zirconia crowns in relation to their compressive strength. Materials and methods Four different cements were tested: zinc phosphate cement (ZPC), glass-ionomer cement (GIC), self-adhesive resin-based cement (SRC) and resin-based cement (RC). RC was used in both dual cure mode (RC-D) and chemical cure mode (RC-C). First, the compressive strength of each cement was tested according to a...

  19. Laboratory studies on the longevity of cement grouts

    International Nuclear Information System (INIS)

    This paper describes laboratory studies of the longevity of cement-based grouts being carried out as part of the International Stripa Project Phase III. The longevity properties determined for a reference grout (90% Sulphate Resistant Portland Cement, 10% silica fume, 0.4< water/cement<0.6 and superplasticizer) are compared with those of a slag cement grout. Laboratory tests have been carried out to determine the following: the mechanistic function of superplasticizer in fresh cement pastes; the leachability of the sorbed superplasticizer and its location in the structure of hardened cement paste; and the general leaching properties of selected cement-based grouts

  20. Geochemical modelling of long-term cement degradation

    International Nuclear Information System (INIS)

    The objective of this study was to investigate geochemical reactions related to long-term cement degradation caused by interaction with groundwater using a geochemical model. The results from modelling showed changes in chemical composition of pore water and cement compounds resulted from cement hydration and degradation. In this study, the volume of each cement compound was also calculated using a geochemical model. The porosity of cement caused by degradation was estimated using the change in volume of each cement compound. The results from this study provide important information to evaluate long-term durability of cement in groundwater system, which is closely related to the safety of radioactive waste disposal repository

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

    International Nuclear Information System (INIS)

    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.

  2. 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.

  3. Fracture model for cemented aggregates

    Directory of Open Access Journals (Sweden)

    Aleksander Zubelewicz

    2013-01-01

    Full Text Available A mechanisms-based fracture model applicable to a broad class of cemented aggregates and, among them, plastic-bonded explosive (PBX composites, is presented. The model is calibrated for PBX 9502 using the available experimental data under uniaxial compression and tension gathered at various strain rates and temperatures. We show that the model correctly captures inelastic stress-strain responses prior to the load peak and it predicts the post-critical macro-fracture processes, which result from the growth and coalescence of micro-cracks. In our approach, the fracture zone is embedded into elastic matrix and effectively weakens the material's strength along the plane of the dominant fracture.

  4. Thermal behavior of asphalt cements

    International Nuclear Information System (INIS)

    Asphalt cements are highly complex mixtures of hydrocarbon molecules whose thermal behavior is of prime importance for petroleum and road industry. From DSC, the determination of several thermal properties of asphalts is given, e.g. glass-transition temperature and crystallized fraction content.The dissolution of a pure n-paraffin CnH2n+2 in an asphalt, as seen by DSC, should be a single peak. For 20g of these glasses change with time and temperature. The formation of the crystallized phases is superposed to the enthalpic relaxation of the glasses, making a kinetic study very difficult. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  5. Silica Transport and Cementation in Quartz Aggregates

    Science.gov (United States)

    Pebble, C.; Farver, J.; Onasch, C.; Winslow, D.

    2008-12-01

    Silica transport and cementation in quartz aggregates have been experimentally investigated. Starting materials include a natural quartz arenite (Pocono sandstone), sized clasts of synthetic quartz, and sized grains of disaggregated natural sandstones. Experimental charges consisted of amorphous silica powder (~25 mg), AlCl3 powder (~3 mg), 25 wt% NaCl brine solution (~20 mg), and the starting material (~150 mg). The charges were weld-sealed in gold capsules and run in cold-seal pressure vessels at 300°C to 600°C at 150 MPa confining pressure for up to 4 weeks. Detailed calibrations of the furnaces indicate the maximum temperature variation across the length of the sample charges (3-7mm) was vacuum impregnated with epoxy containing a blue dye and sawn in half along the long axis of the sample charge. The nature and amount of silica transport and cementation in the samples was determined by a combination of Cathodoluminescence (CL), Light Microscopy (LM), and Scanning Electron Microscopy (SEM). Photomosaics of the samples were collected and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement was easily recognized from the quartz grains by the difference in luminescence. The experiments indicate that the presence of amorphous silica results in rapid silica cementation in quartz aggregates (e.g., up to 12% cement by volume in 4 weeks at 450°C). The amount of cementation is a function of substrate type, time, temperature, and ionic strength of the brine. The rate of silica transport through the length of the experimental charge appears to be limited by the silica solubility and its rapid depletion by cementation. Although most of the cement was derived from the amorphous silica, evidence for local dissolution-precipitation was observed. The experiments demonstrate that the mobility of silica, and consequent precipitation of cement, does not require a temperature or pressure gradient as is commonly assumed. Rather

  6. INFLUENCE OF GLASS CULLET IN CEMENT PASTES

    Institute of Scientific and Technical Information of China (English)

    A.Karamberi; E.Chaniotakis; D.Papageorgiou; A.Moutsatsou

    2006-01-01

    The present study investigates glass and cement compatibility with a view to use glass as a cement replacement. Amber, flint and green glasses were chosen due to their prevalence in the Greek market as packaging materials. The factors under investigation were the pozzolanicity of the glass cullet, the hydration rate and the mechanical strength development of the cement pastes, as well as the expansion of the specimens due to alkali-silica reaction.Moreover, the potential enhancement of glass pozzolanic activity was examined. The results of the study were encouraging to show the potentiality of utilising glass cullet in cementitious products.

  7. Shrinkage Properties of Cement Stabilized Gravel

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard

    2014-01-01

    shrinkage properties of cement stabilized gravel have been documented under various temperature and relative humidity conditions. Two cement contents corresponding to a 28-days compressive strength of 6.2 MPa and 12.3 MPa have been tested and compared. It is found that the coefficient of linear expansion...... for the two cement contents is 9.9 × 10-6 ⁰C-1 and 11.3 × 10-6 ⁰C-1, respectively. Furthermore, it is found that reflecting cracking can mainly be explained by temperature dependent shrinkage rather than moisture dependent shrinkage....

  8. Operating experience with KRAFTWERK UNION cementation line

    International Nuclear Information System (INIS)

    A facility is described designed for fixation in a cement matrix of the radioactive concentrate produced by thickening waste water from the Bohunice nuclear power plant. The cementation line output is 0.6 m3 concentrate/h. The concentrate is put in 200 l drums. The individual operating units, cement management, air conditioning, dosimetric monitoring and the building part are described. The requirements for the operators and the assessment of the quality of raw materials and the product are discussed. (M.D.). 3 figs., 4 refs

  9. Reinforcement of osteosynthesis screws with brushite cement.

    Science.gov (United States)

    Van Landuyt, P; Peter, B; Beluze, L; Lemaître, J

    1999-08-01

    The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Polymethyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being injectable and resorbable. The aim of this study is to assess the reinforcement of osteosynthesis screws with brushite cement. Polyurethane foams, whose density is close to that of cancellous bone, were used as bone model. A hole was tapped in a foam sample, then brushite cement was injected. Trabecular osteosynthesis screws were inserted. After 24 h of aging in water, the stripping force was measured by a pull-out test. Screws (4.0 and 6.5 mm diameter) and two foam densities (0.14 and 0.28 g/cm3) were compared. Cements with varying solid/liquid ratios and xanthan contents were used in order to obtain the best screw reinforcement. During the pull-out test, the stripping force first increases to a maximum, then drops to a steady-state value until complete screw extraction. Both maximum force and plateau value increase drastically in the presence of cement. The highest stripping force is observed for 6.5-mm screws reinforced with cement in low-density foams. In this case, the stripping force is multiplied by 3.3 in the presence of cement. In a second experiment, cements with solid/liquid ratio ranging from 2.0 to 3.5 g/mL were used with 6.5-mm diameter screws. In some compositions, xanthan was added to improve injectability. The best results were obtained with 2.5 g/mL cement containing xanthan and with 3.0 g/mL cements without xanthan. A 0.9-kN maximal stripping force was observed with nonreinforced screws, while 1.9 kN was reached with reinforced screws. These first results are very promising regarding screw

  10. Effect of cementing technique and cement type on thermal necrosis in hip resurfacing arthroplasty - a numerical study

    NARCIS (Netherlands)

    Janssen, D.; Srinivasan, P.; Scheerlinck, T.; Verdonschot, N.J.J.

    2012-01-01

    Femoral fractures within resurfacing implants have been associated with bone necrosis, possibly resulting from heat generated by cement polymerization. The amount of heat generated depends on cement mantle volume and type of cement. Using finite element analysis, the effect of cement type and volume

  11. Foamed cement for squeeze cementing low-pressure, highly permeable reservoirs

    International Nuclear Information System (INIS)

    Four different cement squeezing techniques have been used on wells producing from the Keg River formation in the Rainbow Lake area of Alberta, Canada. This paper evaluates 151 cement squeeze treatments performed at 96 wellsites and compares the use of foam cement vs. conventional squeeze treatments and techniques. Discussion includes key aspects, such as candidate selection, slurry design, treatment design, economic evaluation, and operational considerations

  12. Voids/Cement Ratio Controlling Tensile Strength of Cement-Treated Soils

    OpenAIRE

    Nilo Cesar Consoli; Antonio Viana da Fonseca; Rodrigo Caberlon Cruz; Sara Rios Silva

    2011-01-01

    The improvement of locally available soils with cement can provide great advantages, including avoiding the need to borrow volumes of appropriate material and disposing of the local soil in deposits. This research aims to quantify the influence of the amount of cement, the porosity, and the voids/cement ratio in the assessment of splitting tensile strength (q(t)), also known as indirect diametrical tensile (IDT) strength, of three distinct soils from Brazil and Portugal. From Brazil, clayey s...

  13. Effect of Abutment Modification and Cement Type on Retention of Cement-Retained Implant Supported Crowns

    OpenAIRE

    Mitra Farzin; Kianoosh Torabi; Ahmad Hasan Ahangari; Reza Derafshi

    2014-01-01

    Objective: Provisional cements are commonly used to facilitate retrievability of cement-retained fixed implant restorations; but compromised abutment preparation may affect the retention of implant-retained crowns.The purpose of this study was to investigate the effect of abutment design and type of luting agent on the retentive strength of cement-retained implant restorations. Materials and Method: Two prefabricated abutments were attached to their corresponding analogs and embedded in an ac...

  14. ANALYSIS OF UNCERTAINTIES IN CEMENT INDUSTRY IN TURKEY

    OpenAIRE

    Kemal Yildirim; Omer Arioz

    2013-01-01

    Cement industry having 4,5 billion Dollars revenue and 1 billion Dollar export volume plays very important role in Turkey’s economy. Turkish cement industry is very sensitive to economic crisis and involves many uncertainties. In this study, price uncertainties, technological uncertainties, and price-technological uncertainties in Turkish cement industry were analyzed. The cement demand is mostly affected by demand to ready mixed concrete. Demand to cement is also related to the picture of co...

  15. Composite cements containing natural pozzolan and granulated blast furnace slag

    OpenAIRE

    Irassar, E. F.; Rahhal, V.F.; Donza, H. A.; Menéndez, G.; Bonavetti, V. L.

    2006-01-01

    For reasons of market demand and Portland cement production,the manufacture of cements with two or more separately ground additions to produce customized cements is becoming common practice.When pozzolan or slag content in this type of cements is high, however, the initial strength of the resulting product may be adversely impacted. This problem can be minimized by activating one or both of the replacement materials. The present study analyzes the effect of Portland cement additions such as p...

  16. Preliminary study using pulsating water jet for bone cement demolition

    OpenAIRE

    S. Hloch; Kloc, J.; Foldyna, J.; Pude, F.; Smolko, I.; M. Zeleňák; Sitek, L. (Libor); Hvizdoš, P.; Monka, P.; Monková, K.; Kozak, D.; A. Stoić; A. Sedmak; Milosevic, M; Lehocká, D.

    2015-01-01

    The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of bone cement which creates the interface between femoral stem and trabecular bone tissue. For investigation, commercial bone cements were used. Bone cements were tested by nanoindentation in order to review their mechanical properties. A representative sample Palacos R+G was selected for disintegration of bone cement. Bone cements samples fixed between two plexiglass...

  17. The Effect of La on the Microstructure and Corrosion-resistance of Hot-dipped Aluminizing Steel

    Institute of Scientific and Technical Information of China (English)

    WENJiu-ba; ZHANGWei; LIXiao-yuan; LIQuan-an

    2004-01-01

    The effect of the content of rare-earth La on the microstructure and corrosion-resistance of hot-dipped aluminum was investigated in this paper. The results show that, under the same technology conditions, the thickness of hot-dipped aluminizing layer by adding the appropriate content of rare-earth La is about 2-3 times as much as that without rare-earth La, and the microstructure of hot-dipped aluminizing layer has also greatly changed ,and a great deal of phase Fe3A1 waspreci pitated along the boundary of a phase. The corrosion resistance of the hot-dipped layer with rare-earth is greatly increased.

  18. The Effect of La on the Microstructure and Corrosion-resistance of Hot-dipped Aluminizing Steel

    Institute of Scientific and Technical Information of China (English)

    WEN Jiu-ba; ZHANG Wei; LI Xiao-yuan; LI Quan-an

    2004-01-01

    The effect of the content of rare-earth La on the microstructure and corrosion-resistance of hot-dipped aluminum was investigated in this paper. The results show that, under the same technology conditions, the thickness of hot-dipped aluminizing layer by adding the appropriate content of rare-earth La is about 2~3 times as much as that without rare-earth La, and the microstructure of hot-dipped aluminizing layer has also greatly changed ,and a great deal of phase Fe3Al was precipitated along the boundary of α phase. The corrosion resistance of the hot-dipped layer with rare-earth is greatly increased.

  19. Phase transformations in lithium aluminates irradiated with neutrons; Transformaciones de fase en aluminatos de litio irradiados con neutrones

    Energy Technology Data Exchange (ETDEWEB)

    Carrera, L.M.; Delfin L, A.; Urena N, F.; Basurto, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Bosch, P. [UAM-I, 09340 Mexico D.F. (Mexico)

    2003-07-01

    The lithium aluminate like candidate to be used in the coverings producers of tritium in the fusion nuclear reactors, presents high resistance to the corrosion to the one to be stuck to structural materials as special steels. However, the crystallographic changes that take place in the cover that is continually subjected to irradiation with neutrons, can alter its resistance to the corrosion. In this work the changes of crystalline structure are shown that they present two types of nano structures of lithium aluminates, subjected to an average total dose 7.81 x 10{sup 8} Gy in the fixed irradiation system of capsules of the one TRIGA Mark lll nuclear reactor of the Nuclear Center of Mexico. The studied nano structures presented only phase transformations without formation of amorphous material. (Author)

  20. Preparation of Al(OH)3 by ion membrane electrolysis and precipitation of sodium aluminate solution with seeds

    Institute of Scientific and Technical Information of China (English)

    LI Yuan-gao; CHEN Qi-yuan; WANG Song-sen; YIN Zhou-lan; ZHANG Ping-min

    2008-01-01

    The preparation of Al(OH)3 by the ion exchange membrane electrolysis followed by the precipitation of sodium aluminate solution with seeds was made. During the process of ion membrane electrolysis, the sodium aluminate solution is rapidly acidified and the caustic ratio (aK) is decreased due to oxygen evolution in the anodic region. And the causticity of solution is increased due to hydrogen evolution in the cathode region, producing the high concentration of caustic soda solution. Regulating the acidity of the anodic solution by controlling the electric quantity in the electrolysis and subsequent decomposing the solution, Al(OH)3 could yield with very large rate and high efficiency. The experiments also indicate that the quality of aluminum hydroxide product is greatly affected by the impurity silicon.

  1. The influence of alloying elements on the hot-dip aluminizing process and on the subsequent high-temperature oxidation

    International Nuclear Information System (INIS)

    For hot dip aluminizing HDA an Al melt was doped with one of the elements Mo, W or Nb with a nominal composition of about 1 wt%. In case of W, the nominal composition was achieved, not so for Mo and Nb. The influence of these elements on the coating formed and on the following oxidation process was investigated. Hot dip aluminizing was carried out at 800 C for 5 min under dry Ar atmosphere. The oxidation experiments were performed at 950 C for 24 h in air. Compared to the HDA processes with pure Al, the addition of the alloying elements lead to thinner intermetallic layers. A change in the oxidation behavior was observed as well concerning the suppression of internal oxidation and the formation of dense and close oxide scales. (orig.)

  2. Enamel fluoride levels after orthodontic band cementation with glass ionomer cement.

    Science.gov (United States)

    Akkaya, S; Uner, O; Alaçam, A; Değim, T

    1996-02-01

    The aim of this investigation was to examine the fluoride uptake by enamel after application of glass ionomer cement for orthodontic band cementation compared with zinc phosphate cement. The study was conducted on 21 children whose mean age was 14 years. All the children were reared in the Middle Anatolian cities where the water fluoride concentration was below the level of 0.50 ppm. The subjects were randomly divided into three groups. The first experimental group, had seven subjects whose teeth were topically fluoridated with 2 per cent NaF solution, before orthodontic band cementation with zinc phosphate cement. The second experimental group also had seven subjects whose orthodontic bands were cemented with glass ionomer cement. The third group, consisted of seven control subjects and no dental procedures were performed in this group. All the participants were followed for 3 months and at the end of this period maxillary first premolars, which were in the ninth developmental stage according to Nolla (1960), were extracted for orthodontic purposes. The enamel fluoride concentrations were determined on the left maxillary first premolars at three successive etch depths by means of a fluor ion electrode, whereas the calcium concentrations were determined with an atomic absorption spectrophotometer. The results of this investigation showed that in both cementation groups enamel fluoride concentrations at three successive etch depths were highly increased compared with the control group. However, the difference between the cementation groups was not statistically significant. PMID:8746180

  3. Exposure to cement dust at a Portland cement factory and the risk of cancer.

    OpenAIRE

    Vestbo, J; Knudsen, K.M.; Raffn, E; Korsgaard, B; Rasmussen, F V

    1991-01-01

    The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 1...

  4. INFLUENCE OF WINE ACID ON RHEOLOGICAL PROPERTIES OF WELL BORE CEMENT SLURRIES AND HARDENED CEMENT PROPERTIES

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1989-12-01

    Full Text Available Adaptation of commercial types of domestic cements for use in cementing the deep wells is a process by which Yugoslav oil industry tends to solve problems of completion of those wells independently. In order to design a domestic, cheep and effective retarder, tests of applicability of wine acid on cement slurries have been carried out. Besides examining the necessary wine acid content to achieve desirable Theological properties, the influence of this additive on properties of hardened cement samples has been tested too (the paper is published in Croatian.

  5. Effect of the cement type on compatibility with carboxylate superplasticisers

    Directory of Open Access Journals (Sweden)

    Bundyra-Oracz, G.

    2011-06-01

    Full Text Available An empirical study was conducted to gain a fuller understanding of the interactions taking place in cementsuperplasticiser systems. To this end, two clinkers of known chemical and phase composition were prepared in this study to gain insight into such interactions. One contained no tricalcium aluminate (C1, while the other had a 9% C3A content (C2. These clinkers were ground to approximately 340 m2/kg and blended with gypsum only or gypsum and Klein compound (3CaO·3Al2O3·CaSO4 (1, 2. Sufficient compound was added to C1 to ensure the formation of about the same amount of ettringite after 0.5 and 1 h of hydration as found in cement C2 + gypsum. The admixture used was a carboxylate superplasticiser. Rheology measurements showed that while paste yield stress was correlated to ettringite formation, no such simple relationship was observed for plastic viscosity. Plastic viscosity depended on the total hydrates formed, i.e., not only as ettringite but also as C-S-H gel. The findings revealed that in clinkers with very low sulfate and potassium contents, the rheology of carboxylate-containing cement paste is primarily controlled by ettringite formation.

    En el presente trabajo se ha realizado un estudio empírico con el objetivo de profundizar en el conocimiento de las interacciones del sistema cemento-superplastificante. Con este fin, se prepararon dos clínkeres con una composición química y de fases conocida: el primero (C1 sin aluminato tricálcico y el segundo (C2 con un contenido en C3A del 9%. Ambos se molieron hasta obtener una superficie específica aproximada de 340 m2/kg y se emplearon con dos adiciones: yeso y el compuesto de Klein (3CaO·3Al2O3·CaSO4 (1, 2. Se añadió la cantidad necesaria del compuesto de Klein a C1 para garantizar la formación, tras 0,5 y 1ª h. de hidratación, de aproximadamente la misma cantidad de etringita en dicho

  6. Factors influencing setting time of sulpho-aluminate cement%影响硫铝酸盐水泥凝结时间的因素

    Institute of Scientific and Technical Information of China (English)

    李德栋

    2002-01-01

    熟料的化学成分、不同的烧成温度、熟料中的碱(R2O)含量和窑内还原气氛是影响硫铝酸盐水泥凝结时间的主要因素.提出了改善凝结时间的一些措施及意见.

  7. Cementation of radioactive liquid scintillator waste simulate

    International Nuclear Information System (INIS)

    Liquid scintillation counting is an important analytical tool with extensive applications in medicine and basic applied research and used in quantification of □ -particles, weak □ and x-rays. The generated spent liquid scintillator radioactive waste should be limited and controlled to protect man and his environment. In this study, the radioactive spent liquid scintillator waste simulate (SLS) was immobilized in cement matrix using a surfactant in order to facilitate and increase the amount of SLS incorporated into the cementitious materials. Mechanical properties of the final cement waste form were acceptable for blocks containing up to 20% SLS in presence of surfactant. X-ray diffraction, IR analysis and scanning electron microscope proved that the hydration of cement materials is not significantly affected by organic scintillator waste. Therefore, the cement matrix could be recommended for solidification of SLS for the acceptable mechanical, physical and chemical characterizations reached.

  8. Calcium phosphate cements properties with polymers addition

    International Nuclear Information System (INIS)

    Calcium phosphate cements (CPC) have attracted great interest to use in orthopedics and dentistry as replacements for damaged parts of the skeletal system, showing good biocompatibility and osseointegration, allowing its use as bone graft. Several studies have shown that the addition of polymer additives have a strong influence on the cement properties. The low mechanical strength is the main obstacle to greater use of CPC as an implant material. The objective of this study was to evaluate properties of a cement based on α-tricalcium phosphate (α-TCP), added polymers. PVA (10%, 8%, 6%), sodium alginate (2%) and polyacrylate ammonia (3%), all in weight, were added to the synthesized α-TCP powder. The samples were molded and evaluated for density, porosity in vitro test (Simulated Body Fluid), crystalline phases and mechanical strength. The results show increased the mechanical properties of the cement when added these polymers

  9. Approach for determination of detonation performance and aluminum percentage of aluminized-based explosives by laser-induced breakdown spectroscopy.

    Science.gov (United States)

    Rezaei, Amir Hossein; Keshavarz, Mohammad Hossein; Tehrani, Masoud Kavosh; Reza Darbani, Seyyed Mohammad; Farhadian, Amir Hossein; Mousavi, Seyyed Jabbar; Mousaviazar, Ali

    2016-04-20

    Energetic materials containing aluminum powder are hazardous compounds, which have wide applications as propellants, explosives, and pyrotechnics. This work introduces a new method on the basis of the laser-induced breakdown spectroscopy technique in air and argon atmospheres to investigate determination of aluminum content and detonation performance of 1,3,5-trinitro-1,3,5-triazine (RDX)-based aluminized explosives. Plasma emission of aluminized RDX explosives are recorded where atomic lines of Al, C, H, N, and O, as well as molecular bands of AlO and CN are identified. The formation mechanism of AlO and CN molecular bands is affected by the aluminum percentage and oxygen content present in the composition and plasma. Relative intensity of the Al/O is used to determine detonation velocity and pressure of the RDX/Al samples. The released energy in the laser-induced plasma of aluminized RDX composition is related to the heat of explosion and percentage of aluminum. PMID:27140093

  10. Study and Characterization of Expansive Cement

    Directory of Open Access Journals (Sweden)

    Hugo Guerra Menéndez

    2011-10-01

    Full Text Available The objective of this study is to characterize commercial expansive cement for subsequent development of national formulation, with consequent economic effect and independence of the international market. On the other hand the results contribute to the development of scientific and technological potential. Expansive cement is a product that enables non-explosive demolition, rock and concrete demolition. To characterize the composition of these products, techniques used infrared spectroscopy with Fourier Transforms and Scanning Electron Microscopy.

  11. Study and Characterization of Expansive Cement

    OpenAIRE

    Hugo Guerra Menéndez; Eduardo Peón Avés; Julio E. Lanza Rodríguez

    2011-01-01

    The objective of this study is to characterize commercial expansive cement for subsequent development of national formulation, with consequent economic effect and independence of the international market. On the other hand the results contribute to the development of scientific and technological potential. Expansive cement is a product that enables non-explosive demolition, rock and concrete demolition. To characterize the composition of these products, techniques used infrared spectroscopy w...

  12. Radiological changes in asbestos cement workers.

    OpenAIRE

    Jakobsson, K; Strömberg, U; Albin, M; Welinder, H; Hagmar, L

    1995-01-01

    OBJECTIVE--To explore associations between exposure to asbestos cement dust and radiographic findings in lung parenchyma and pleura. METHODS--Radiographs from 174 blue collar workers and 29 white collar workers from an asbestos cement plant formed one part of the study. Progression of small opacities was further studied in those 124 blue collar workers, for whom two radiographs taken after the end of employment were available. The median readings from five readers who used the full ILO 1980 c...

  13. Dynamic properties of composite cemented clay

    Institute of Scientific and Technical Information of China (English)

    蔡袁强; 梁旭

    2004-01-01

    In this work,the dynamic properties of composite cemented clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. A simple and practical method to estimate the dynamic elastic modulus and damping ratio is proposed in this paper and a related empirical normalized formula is also presented. The results provide useful guidelines for preliminary estimation of cement requirements to improve the dynamic properties of clays.

  14. Influence of polysaccharides on cement hydration

    OpenAIRE

    Peschard, Arnaud; Govin, Alexandre; Fredon, Emmanuel; Grosseau, Philippe; Fantozzi, Gilles

    2004-01-01

    This paper is about the influence of polysaccharides on cement hydration. Three polysaccharides were studied: a cellulose ether (CE), a starch ether (SE) and a dextrin (YD). In a concentrated media as well as in a dilute media, admixture CE only revealed a slight effect on cement hydration. Portlandite and ettringite formation and gypsum consumption were slowed down by SE adjunction. Admixture YD induced an acceleration of ettringite formation as well as gypsum consumption whereas portiandite...

  15. Microstructure Analysis of Heated Portland Cement Paste

    OpenAIRE

    Q. Zhang; Ye, G.

    2011-01-01

    When a concrete structure is exposed to high temperature, the mechanical damage and chemical transformation take place simultaneously, which will change the microstructure of material. On the other hand, the mechanical properties and transport properties depend on the development of microstructure of cement paste. In order to study the microstructure changes at high temperature, in this contribution the cement paste samples were firstly heated to varied temperatures from 100 °C to 1000 °C wit...

  16. Acrylic Bone Cements Modified with Starch

    OpenAIRE

    Krilova, V; Vītiņš, V

    2010-01-01

    The successful result of restorative and replacement surgical operation depends significantly on properties of used bone cement. Acrylic bone cements are usually based on methylmethacrylate polymer, while monomer polymerization begins after mixing of components in mixing device and terminates in living tissue. Polymerization of methylmethacrylate is exothermic process, and temperature increase might cause tissue necrosis with concomitant implant aseptic loosening. Developed non-ionogenic and ...

  17. Estimating the chloride transport in cement paste

    OpenAIRE

    Princigallo, A.

    2012-01-01

    A method was developed to measure the diffusion coefficient of chloride ions in cement paste based on an analytical solution to Fick’s 2nd law in a cylindrical coordinate system. This natural method yielded diffusivity results within as little as a month. Testing time was reduced by exploiting the three-dimensional inward flux in the specimen. In an attempt to determine the saturation concentration, dense portland cement pastes were exposed to a concentrated chloride solution. The method prov...

  18. Topics in Cement and Concrete Research

    OpenAIRE

    Brouwers, H. J. H.

    2006-01-01

    The present paper addresses several topics in regard to the sustainable design and use of concrete. First, major features concerning the sustainable aspects of the material concrete are summarised. Then the major constituent, from an environmental point of view, cement is discussed in detail, particularly the hydration and application of slag cement. The intelligent combining of mineral oxides, which are found in clinker, slag, fly ashes etc., is designated as mineral oxide engineering. It re...

  19. Tricalcium aluminate hydration in additivated systems. A crystallographic study by SR-XRPD

    International Nuclear Information System (INIS)

    Synchrotron radiation X-ray powder diffraction has been used to monitor the evolution of ettringite in C3A-gypsum synthetic mixture and in commercial cement systems during the first hours of the hydration process. The hydration of the paste was achieved using a remote controlled system, in order to collect data as soon as water is added to the system. The use of full-profile Rietveld method during the analysis of the diffractograms collected allowed us to monitor the evolution of phases weight fraction. The rigorous measurement of the lattice parameters and of the diffraction peak shape proved to be very useful to obtain information on the structural evolution of ettringite and on the mean grain size of the crystal phases. Depending on the admixture added to the system, the precipitation of well crystalline ettringite takes some hours. During this 'induction' period we observe a significant variation of a and c lattice parameter values for ettringite. In particular a increases from 11.8 A to 11.24 A, the value for pure ettringite. The c parameter decreases from 22 A to 21.48 A. The lattice parameter variation could be related to small crystallite size effect, but the large variation more likely reflects also crystallographic changes, such as defect re-organization during the nucleation and growth process or also changes in the SO3 and H2O content in the ettringite channel. Not surprisingly the amount and the grain dimensions of crystalline ettringite are affected by the chemistry of the system. We observed the same evolution trend during ettringite formation also in shrinkage-compensating commercial cements (composed by mixture of Ca-Al cements, Portland cement and bassanite), in which ettringite is the main hydrous phase present

  20. Influence of Cellulose Ethers on Hydration Products of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin

    2011-01-01

    Cellulose ethers are widely used to mortar formulations, and it is significant to understand the interaction between cellulose ethers and cement pastes. FT-IR spectra, thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article. The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste, but the major hydration products, such as CH (calcium hydroxide), ettringite and C-S-H, appeared later in the modified cement pastes than in the unmodified cement paste. The cellulose ethers decrease the outer products and increase inner products of C-S-H gels. Compared to unmodified cement pastes, no new products are found in the modified cement pastes in the present experiment. The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

  1. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Moridis, George

    2014-11-01

    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  2. Characterization of cement minerals, cements and their reaction products at the atomic and nano scale

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Hall, Christopher

    2008-01-01

    Recent advances and highlights in characterization methods are reviewed for cement minerals, cements and their reaction products. The emphasis is on X-ray and neutron diffraction, and on nuclear magnetic resonance methods, although X-ray absorption and Raman spectroscopies are discussed briefly...

  3. 76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

    Science.gov (United States)

    2011-12-08

    ... review. Background The Commission instituted this review on May 2, 2011 (76 FR 24519) and determined on August 5, 2011 that it would conduct an expedited review (76 FR 50252, August 12, 2011). The Commission... COMMISSION Gray Portland Cement and Cement Clinker From Japan Determination On the basis of the record...

  4. In situ absorption of molybdate and vanadate during precipitation of hydrotalcite from sodium aluminate solutions

    Science.gov (United States)

    Smith, Howard D.; Parkinson, Gordon M.; Hart, Robert D.

    2005-02-01

    Reaction with seawater to produce the layered double hydroxide hydrotalcite is an important means for amelioration of Bayer process wastewater prior to its disposal into the marine environment. This reaction has been synthesised under controlled conditions to elucidate the principal mechanisms involved, particularly those related to absorption of transition metals that are removed from solution. Magnesium-aluminium layered double hydroxides precipitated from reaction between magnesium chloride and synthetic sodium aluminate solution in the presence of transition metal oxyanions have been prepared and characterised using thermal, X-ray and microscopic techniques. The layered double hydroxide precipitated at pH >13 is found to consist of nano-sized hexagonal crystals of final magnesium-aluminium ratio of 2:1, while that precipitated at pHprecipitation is a pH dependent process. Transition metals are found to replace carbonate in the interlayer space but have little or no overall effect on crystal size or structure. Interlayer distance remains constant in the presence of transition metals, suggesting that these species are intercalated as simple monomeric or dimeric oxyanions, rather than larger polymeric forms.

  5. Novel porous calcium aluminate/phosphate nanocomposites: in situ synthesis, microstructure and permeability.

    Science.gov (United States)

    Yang, Jingzhou; Hu, Xiaozhi; Huang, Juntong; Chen, Kai; Huang, Zhaohui; Liu, Yangai; Fang, Minghao; Sun, Xudong

    2016-02-14

    Permeable porous nanomaterials have extensive applications in engineering fields. Here, we report a novel system of porous calcium aluminate/phosphate (CaAl-CaP) nanocomposites fabricated by pore generator free processing. The CaAl rich samples have close micropores and are not permeable. Interestingly, the CaP rich composites have a unique three-dimensional nanosieve structure with interconnected nanopores and exhibit excellent liquid permeability and adsorbability. The pore size has a narrow distribution of 200-500 nm. The CaAl nanoplatelets in the CaP rich composite have a thickness of 202 nm, a diameter of 1600 nm and an aspect ratio of 8. The porosity is from 19% to 40%. The bending strength and compressive strength are 40.3 MPa and 195 MPa, respectively. The CaP rich nanocomposite is highly permeable so that a water droplet can completely penetrate in 10 seconds (1 mm thick disk). The blue dye can be desorbed in 45 min by ultrasonic vibration. Given the nanosieve porous structure, good permeability/adsorbability and high mechanical properties, the CaP rich nanocomposite has big potential in applications for chemical engineering, biomedical engineering and energy/environmental engineering. PMID:26805036

  6. Novel porous calcium aluminate/phosphate nanocomposites: in situ synthesis, microstructure and permeability

    Science.gov (United States)

    Yang, Jingzhou; Hu, Xiaozhi; Huang, Juntong; Chen, Kai; Huang, Zhaohui; Liu, Yangai; Fang, Minghao; Sun, Xudong

    2016-02-01

    Permeable porous nanomaterials have extensive applications in engineering fields. Here, we report a novel system of porous calcium aluminate/phosphate (CaAl-CaP) nanocomposites fabricated by pore generator free processing. The CaAl rich samples have close micropores and are not permeable. Interestingly, the CaP rich composites have a unique three-dimensional nanosieve structure with interconnected nanopores and exhibit excellent liquid permeability and adsorbability. The pore size has a narrow distribution of 200-500 nm. The CaAl nanoplatelets in the CaP rich composite have a thickness of 202 nm, a diameter of 1600 nm and an aspect ratio of 8. The porosity is from 19% to 40%. The bending strength and compressive strength are 40.3 MPa and 195 MPa, respectively. The CaP rich nanocomposite is highly permeable so that a water droplet can completely penetrate in 10 seconds (1 mm thick disk). The blue dye can be desorbed in 45 min by ultrasonic vibration. Given the nanosieve porous structure, good permeability/adsorbability and high mechanical properties, the CaP rich nanocomposite has big potential in applications for chemical engineering, biomedical engineering and energy/environmental engineering.

  7. Elastic Properties of Tricalcium Aluminate from High-Pressure Experiments and First-Principles Calculations

    KAUST Repository

    Moon, Juhyuk

    2012-06-04

    The structure and elasticity of tricalcium aluminate (C 3A) have been experimentally and theoretically studied. From high-pressure X-ray diffraction experiments, the bulk modulus of 102(6) and 110(3) GPa were obtained by fitting second- and third-order finite strain equation of state, respectively. First-principles calculations with a generalized gradient approximation gave an isotropic bulk modulus of 102.1 GPa and an isothermal bulk modulus of 106.0 GPa. The static calculations using the exchange-correlation functional show an excellent agreement with the experimental measurements. Based on the agreement, accurate elastic constants and other elastic moduli were computed. The slight difference of behavior at high pressure can be explained by the infiltration of pressure-transmitting silicone oil into structural holes in C 3A. The computed elastic and mechanical properties will be useful in understanding structural and mechanical properties of cementitious materials, particularly with the increasing interest in the advanced applications at the nanoscale. © 2012 The American Ceramic Society.

  8. Nanoscale calcium aluminate coated graphite for improved performance of alumina based monolithic refractory composite

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Sol–gel Ca-doped γ-Al2O3 accomplished graphite retention. • Nanocoating considerably improved matrix-aggregate bonding. • Less porous simulated matrix upgraded slag resistance. - Abstract: The synthesis and properties of high alumina castable containing nanostructured calcium aluminate coated graphite were studied in terms of slag resistance and overall physical characteristics. Raman spectroscopy, BET surface area and field emission scanning electron microscopy (FESEM) were performed to exclusively understand the coating characteristics and its compatibility in refractory composite. The coating not only secured graphite in castable for prolonged period but also noticeably improved matrix to aggregate contact. The microstructural aspects of castables were investigated, with special emphasis on a representative matrix prepared and infiltrated with slag at elevated temperature. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of fired composite containing surface-treated graphite was quite prospective. It circumvented the problems of incorporating as-received graphite in castables and should be in the attention of refractory researchers and producers

  9. Nanoscale calcium aluminate coated graphite for improved performance of alumina based monolithic refractory composite

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, S., E-mail: msunanda_cct@yahoo.co.in

    2013-07-15

    Graphical abstract: - Highlights: • Sol–gel Ca-doped γ-Al{sub 2}O{sub 3} accomplished graphite retention. • Nanocoating considerably improved matrix-aggregate bonding. • Less porous simulated matrix upgraded slag resistance. - Abstract: The synthesis and properties of high alumina castable containing nanostructured calcium aluminate coated graphite were studied in terms of slag resistance and overall physical characteristics. Raman spectroscopy, BET surface area and field emission scanning electron microscopy (FESEM) were performed to exclusively understand the coating characteristics and its compatibility in refractory composite. The coating not only secured graphite in castable for prolonged period but also noticeably improved matrix to aggregate contact. The microstructural aspects of castables were investigated, with special emphasis on a representative matrix prepared and infiltrated with slag at elevated temperature. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of fired composite containing surface-treated graphite was quite prospective. It circumvented the problems of incorporating as-received graphite in castables and should be in the attention of refractory researchers and producers.

  10. Comparison of sol-gel and solid state prepared Eu2+ doped calcium aluminates

    International Nuclear Information System (INIS)

    The Eu2+ doped calcium aluminates (CaAl2O4:Eu2+) was prepared by the sol-gel method. The structure and luminescence properties of the title compound were studied and compared to the corresponding properties of the materials prepared by a conventional solid state reaction. The use of the sol-gel method in preparation lowered the reaction threshold temperature by c.a. 200 oC. An unusual hexagonal form of CaAl2O4:Eu2+, which cannot be prepared by the solid state reaction, was obtained by a sol-gel method. The 4 UV excited luminescence and afterglow bands of the hexagonal CaAl2O4:Eu2+ were observed at a slightly longer wavelength than that of the normal monoclinic phase due to small differences in the crystal field effect on the splitting of the excited 4f65d1 configuration of the Eu2+ ion. The afterglow lifetime of the hexagonal phase was slightly longer than that of the monoclinic one due to deeper traps. (author)

  11. In situ generation of hydrogen from water by aluminum corrosion in solutions of sodium aluminate

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Lluis; Candela, Angelica Maria; Munoz, Maria; Casado, Juan [Centre Grup de Tecniques de Separacio en Quimica (GTS), Unitat de Quimica Analitica, Departament de Quimica, Universitat Autonoma de Barcelona, Campus UAB s/n, 08193 Bellaterra, Barcelona, Catalonia (Spain); Macanas, Jorge [Laboratoire de Genie Chimique, UMR 5503 CNRS-INPT-UPS, Universite de Toulouse, Toulouse (France)

    2009-07-01

    A new process to obtain hydrogen from water using aluminum in sodium aluminate solutions is described and compared with results obtained in aqueous sodium hydroxide. This process consumes only water and aluminum, which are raw materials much cheaper than other compounds used for in situ hydrogen generation, such as hydrocarbons and chemical hydrides, respectively. As a consequence, our process could be an economically feasible alternative for hydrogen to supply fuel cells. Results showed an improvement of the maximum rates and yields of hydrogen production when NaAlO{sub 2} was used instead of NaOH in aqueous solutions. Yields of 100% have been reached using NaAlO{sub 2} concentrations higher than 0.65 M and first order kinetics at concentrations below 0.75 M has been confirmed. Two different heterogeneous kinetic models are verified for NaAlO{sub 2} aqueous solutions. The activation energy (E{sub a}) of the process with NaAlO{sub 2} is 71 kJ mol{sup -1}, confirming a control by a chemical step. A mechanism unifying the behavior of Al corrosion in NaOH and NaAlO{sub 2} solutions is presented. The application of this process could reduce costs in power sources based on fuel cells that nowadays use hydrides as raw material for hydrogen production. (author)

  12. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    International Nuclear Information System (INIS)

    Structural changes in magnesium aluminate spinel (MgO · nAl2O3) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne+ ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO · Al2O3 has a tendency to form the normal spinel configuration, where Mg2+ ions and Al3+ ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO · Al2O3. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO · Al2O3 irradiated with Ne+ ions. In contrast, cation disordering is suppressed in MgO · 2.4Al2O3 irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination

  13. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel

    International Nuclear Information System (INIS)

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  14. Damage structures in fast neutron irradiated magnesium aluminate and electron irradiated aluminum oxynitride spinels

    International Nuclear Information System (INIS)

    Single crystals of magnesium aluminate spinel, MgO(Al2O3)sub(n), n=1, 1.1, and 2, were neutron irradiated in EBR-II to a fluence of 2 x 1026 n/m2 (E > 0.111 MeV) at 680 and 815 K. Control specimens were aged 1 year at 815 K for comparison. TEM analysis of the irradiated specimens showed that they contained faulted prismatic dislocation loops with fault vectors R=a/4 on [110] planes in the n=1 and 1.1 spinels, and with R=a/6 on [111] in the n=1.1 and 2 spinels. Alumina-rich control specimens precipitated a new ordered phase. Polycrystalline aluminum oxynitride spinel, AIN(Al2O3)sub(1.8), was electron irridiated with 0.8 and 1 MeV electrons in the HVEM over the temperature range 300-1100 K. No defect aggregation was observed at any temperature, through thick or thin sections. Coherent twins developed on the facets of sintering pores open to the surface. (orig.)

  15. EFFECTS OF XE ION IRRADIATION AND SUBSEQUENT ANNEALING ON THE PROPERTIES OF MAGNESIUM-ALUMINATE SPINEL

    International Nuclear Information System (INIS)

    Single crystals of magnesium-aluminate spinel MgAl2O4 were irradiated with 340 keV Xe2 ions at minus173 C (approximately 100 K). A fluence of 1 x 1020 Xe/m2 created an amorphous layer at the surface of the samples. The samples were annealed for 1 h at different temperatures ranging from 130 C to 880 C. Recrystallization took place in the temperature interval between 610 C and 855 C. Transmission electron microscopy (TEM) images show two distinct layers near the surface: (1) a polycrystalline layer with columnar grain structure; and (2) a buried damaged layer epitaxial with the substrate. After annealing at 1100 C for 52 days, the profile of implanted Xe ions did not change, which means that Xe ions are not mobile in the spinel structure up to 1100 C. The thickness of the buried damaged layer decreased significantly in the 1100 C annealed sample comparing to the sample annealed for 1 h at 855 C

  16. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel

    Science.gov (United States)

    Gilbert, C. A.; Smith, R.; Kenny, S. D.; Murphy, S. T.; Grimes, R. W.; Ball, J. A.

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  17. Mechanical properties and microstructure of α-alumina and magnesium aluminate spinel irradiated with He ions

    International Nuclear Information System (INIS)

    Mechanical properties of α-alumina, stoichiometric- and nonstoichiometric-magnesium aluminate spinel single crystals were examined by using ultra-microhardness technique. The samples were irradiated with 100 keV He- ions at temperatures of 300-870 K and to fluences up to 2 x 1020 He-/m2. Apparent hardness, ΔH, in α-alumina increases with fluence in three stages, while that of spinel crystals increases monotonically with fluence. We have also evaluated elastic modulus, plastic and elastic energies, and plastic and elastic indentation depths through the analysis of load-displacement curves. These analyses showed that plastic and elastic hardening are responsible for the variation of ΔH of α-alumina, and that plastic hardening is the main cause of hardening in spinel crystals. Corresponding TEM observations suggested the importance of point defects and/or 'invisible' defect clusters for radiation hardening compared to 'visible' dislocation loops. The relationship between microstructure and mechanical properties is given for various ceramics. (orig.)

  18. Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions

    International Nuclear Information System (INIS)

    We have investigated the microstructure and atomic disordering of nearly stoichiometric magnesium aluminate spinel (MgO . 1.1Al2O3), irradiated with 200 MeV Xe14+ ions (S e = 25 keV/nm). Transmission electron microscopy techniques of bright-field (BF) and high-resolution (HR) imaging, as well as high angular resolution electron channeling X-ray spectroscopy (HARECXS) were employed for quantitative analysis of radiation-induced structural change. BF images of ion tracks show columnar dark contrast of ∼4 nm in diameter accompanying distinct black or white dots at the incident surface. Clear lattice fringes are observed in HR images even inside the ion tracks, indicating that the spinel crystals are not amorphized but partially disordered along the ion tracks. HARECXS analysis showed that cation disordering progresses successively with ion fluence, and the disordered regions are found to extend over 12.8 ± 0.9 nm in diameter for Al ions and 9.6 ± 0.6 nm for Mg ions along the ion tracks. This chemically disordered region is much larger than the strained volume detected by BF and HR images

  19. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    Science.gov (United States)

    Soeda, Takeshi; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J.

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO · nAl 2O 3) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne + ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO · Al 2O 3 has a tendency to form the normal spinel configuration, where Mg 2+ ions and Al 3+ ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO · Al 2O 3. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO · Al 2O 3 irradiated with Ne + ions. In contrast, cation disordering is suppressed in MgO · 2.4Al 2O 3 irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  20. Transparent magnesium aluminate spinel: a prospective biomaterial for esthetic orthodontic brackets.

    Science.gov (United States)

    Krishnan, Manu; Tiwari, Brijesh; Seema, Saraswathy; Kalra, Namitha; Biswas, Papiya; Rajeswari, Kotikalapudi; Suresh, Madireddy Buchi; Johnson, Roy; Gokhale, Nitin M; Iyer, Satish R; Londhe, Sanjay; Arora, Vimal; Tripathi, Rajendra P

    2014-11-01

    Adult orthodontics is recently gaining popularity due to its importance in esthetics, oral and general health. However, none of the currently available alumina or zirconia based ceramic orthodontic brackets meet the esthetic demands of adult patients. Inherent hexagonal lattice structure and associated birefringence limits the visible light transmission in polycrystalline alumina and make them appear white and non transparent. Hence focus of the present study was to assess the feasibility of using magnesium aluminate (MgAl2O4) spinel; a member of the transparent ceramic family for esthetic orthodontic brackets. Transparent spinel specimens were developed from commercially available white spinel powder through colloidal shaping followed by pressureless sintering and hot isostatic pressing at optimum conditions of temperature and pressure. Samples were characterized for chemical composition, phases, density, hardness, flexural strength, fracture toughness and optical transmission. Biocompatibility was evaluated with in-vitro cell line experiments for cytotoxicity, apoptosis and genotoxicity. Results showed that transparent spinel samples had requisite physico-chemical, mechanical, optical and excellent biocompatibility for fabricating orthodontic brackets. Transparent spinel developed through this method demonstrated its possibility as a prospective biomaterial for developing esthetic orthodontic brackets. PMID:25027301

  1. Mechanical properties and microstructure of {alpha}-alumina and magnesium aluminate spinel irradiated with He ions

    Energy Technology Data Exchange (ETDEWEB)

    Izumi, K.; Yasuda, K.; Kinoshita, C.; Kutsuwada, M. [Kyushu Univ., Fukuoka (Japan). Dept. of Appl. Quantum Phys. and Nucl. Eng.

    1998-10-01

    Mechanical properties of {alpha}-alumina, stoichiometric- and nonstoichiometric-magnesium aluminate spinel single crystals were examined by using ultra-microhardness technique. The samples were irradiated with 100 keV He{sup -} ions at temperatures of 300-870 K and to fluences up to 2 x 10{sup 20} He{sup -}/m{sup 2}. Apparent hardness, {Delta}H, in {alpha}-alumina increases with fluence in three stages, while that of spinel crystals increases monotonically with fluence. We have also evaluated elastic modulus, plastic and elastic energies, and plastic and elastic indentation depths through the analysis of load-displacement curves. These analyses showed that plastic and elastic hardening are responsible for the variation of {Delta}H of {alpha}-alumina, and that plastic hardening is the main cause of hardening in spinel crystals. Corresponding TEM observations suggested the importance of point defects and/or `invisible` defect clusters for radiation hardening compared to `visible` dislocation loops. The relationship between microstructure and mechanical properties is given for various ceramics. (orig.) 18 refs.

  2. Atomistic structures of metastable and amorphous phases in ion-irradiated magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Ishimaru, Manabu; Hirotsu, Yoshihiko [Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka (Japan); Afanasyev-Charkin, Ivan V.; Sickafus, Kurt E. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM (United States)

    2002-02-18

    Ion-beam-induced microstructures in magnesium aluminate (MgAl{sub 2}O{sub 4}) spinel have been examined using transmission electron microscopy (TEM). Irradiations were performed at cryogenic temperature ({approx}120 K) on MgAl{sub 2}O{sub 4} spinel single-crystal surfaces with (111) orientation, using 180 keV neon (Ne{sup +}) ions to ion fluences ranging from 10{sup 16} to 10{sup 17} Ne{sup +} cm{sup -2}. Cross-sectional TEM observations indicated that the MgAl{sub 2}O{sub 4} spinel transforms first into a metastable crystalline phase and then into an amorphous phase under these irradiation conditions. On the basis of selected-area electron diffraction and high-resolution TEM, we concluded that Ne-ion-beam irradiation induces an ordered spinel-to-disordered rock-salt-like structural phase transformation. Atomistic structures of amorphous MgAl{sub 2}O{sub 4} were also examined on the basis of atomic pair distribution functions. We compared the experimentally obtained results with previous theoretically calculated results for the metastable and amorphous phases of MgAl{sub 2}O{sub 4}, and discussed the validity of the proposed ion-beam-induced structural changes in MgAl{sub 2}O{sub 4} spinel. (author)

  3. EFFECTS OF XE ION IRRADIATION AND SUBSEQUENT ANNEALING ON THE PROPERTIES OF MAGNESIUM-ALUMINATE SPINEL

    Energy Technology Data Exchange (ETDEWEB)

    I. AFANASYEV; ET AL

    2000-04-01

    Single crystals of magnesium-aluminate spinel MgAl{sub 2}O{sub 4} were irradiated with 340 keV Xe{sup 2} ions at {minus}173 C ({approximately} 100 K). A fluence of 1 x 10{sup 20} Xe/m{sup 2} created an amorphous layer at the surface of the samples. The samples were annealed for 1 h at different temperatures ranging from 130 C to 880 C. Recrystallization took place in the temperature interval between 610 C and 855 C. Transmission electron microscopy (TEM) images show two distinct layers near the surface: (1) a polycrystalline layer with columnar grain structure; and (2) a buried damaged layer epitaxial with the substrate. After annealing at 1100 C for 52 days, the profile of implanted Xe ions did not change, which means that Xe ions are not mobile in the spinel structure up to 1100 C. The thickness of the buried damaged layer decreased significantly in the 1100 C annealed sample comparing to the sample annealed for 1 h at 855 C.

  4. Absorption and spectroscopic ellipsometry study of electron irradiated magnesium aluminate spinel

    International Nuclear Information System (INIS)

    Magnesium aluminate spinels were irradiated by electron beams with energy of 1.7 MeV and fluence from 1013 to 1017 electrons cm-2. After irradiation, the samples were annealed at different temperatures from 100 to 500 C. Spectroscopic ellipsometry and absorption were used to study the effects of optical properties in the spinel produced by irradiation and subsequent annealing. The results obtained by absorption spectra showed that many F-type absorption centers were produced in the spinels. With increasing electron fluence, we observed an increase in optical absorption, especially in the vicinity of the absorption band at 5.3 eV. The concentration of F-type absorption centers increased as the electron fluence increased. The F-type absorption centers can be destroyed by isochronal annealing. The refractive index obtained by analyzing the ellipsometric spectra changed as the irradiation fluence and subsequent annealing temperature changed. Based on our findings, an attempt has been made to explain the above mentioned phenomena. (orig.)

  5. Void formation in magnesium aluminate spinel heavily irradiated with fast neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fukumoto, Ken-ichi [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Kinoshita, Chiken; Garner, F.A.

    1995-08-01

    Single crystals of magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) were heavily irradiated to fission neutron fluences from {approx}1x10{sup 26} to {approx}2x10{sup 27} n/m{sup 2} (E>0.1 MeV) at 658 and 1,023 K in FFTF (Fast Flux Test Facility) to investigate their microstructural evolution under heavy neutron irradiation and to confirm their previously observed resistance to void swelling. At 658 K no voids were observed up to 2.29x10{sup 27} n/m{sup 2}, but 1/4[110] interstitial loops were formed. These loops changed their habit planes from (111) to (110) with increasing neutron fluence. At 1,023 K the 1/4[110] type of interstitial loops grew to form stacking fault networks composed of stacking faults on each of the six equivalent {l_brace}110{r_brace} planes. Tiny voids were also observed to form preferentially no or near stacking faults after 1.37x10{sup 27} n/m{sup 2}. A limited number of very small cavities, contributing to a volumetric swelling of only 0.07%, were also observed in the crystal matrix after 2.17x10{sup 27} n/m{sup 2}. The possible mechanisms of suppression of void formation in MgAl{sub 2}O{sub 4} are discussed. (author).

  6. Atomistic structures of metastable and amorphous phases in ion-irradiated magnesium aluminate spinel

    International Nuclear Information System (INIS)

    Ion-beam-induced microstructures in magnesium aluminate (MgAl2O4) spinel have been examined using transmission electron microscopy (TEM). Irradiations were performed at cryogenic temperature (∼120 K) on MgAl2O4 spinel single-crystal surfaces with (111) orientation, using 180 keV neon (Ne+) ions to ion fluences ranging from 1016 to 1017 Ne+ cm-2. Cross-sectional TEM observations indicated that the MgAl2O4 spinel transforms first into a metastable crystalline phase and then into an amorphous phase under these irradiation conditions. On the basis of selected-area electron diffraction and high-resolution TEM, we concluded that Ne-ion-beam irradiation induces an ordered spinel-to-disordered rock-salt-like structural phase transformation. Atomistic structures of amorphous MgAl2O4 were also examined on the basis of atomic pair distribution functions. We compared the experimentally obtained results with previous theoretically calculated results for the metastable and amorphous phases of MgAl2O4, and discussed the validity of the proposed ion-beam-induced structural changes in MgAl2O4 spinel. (author)

  7. Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions

    Science.gov (United States)

    Yamamoto, T.; Shimada, M.; Yasuda, K.; Matsumura, S.; Chimi, Y.; Ishikawa, N.

    2006-04-01

    We have investigated the microstructure and atomic disordering of nearly stoichiometric magnesium aluminate spinel (MgO · 1.1Al2O3), irradiated with 200 MeV Xe14+ ions (Se = 25 keV/nm). Transmission electron microscopy techniques of bright-field (BF) and high-resolution (HR) imaging, as well as high angular resolution electron channeling X-ray spectroscopy (HARECXS) were employed for quantitative analysis of radiation-induced structural change. BF images of ion tracks show columnar dark contrast of ∼4 nm in diameter accompanying distinct black or white dots at the incident surface. Clear lattice fringes are observed in HR images even inside the ion tracks, indicating that the spinel crystals are not amorphized but partially disordered along the ion tracks. HARECXS analysis showed that cation disordering progresses successively with ion fluence, and the disordered regions are found to extend over 12.8 ± 0.9 nm in diameter for Al ions and 9.6 ± 0.6 nm for Mg ions along the ion tracks. This chemically disordered region is much larger than the strained volume detected by BF and HR images.

  8. Void formation in magnesium aluminate spinel heavily irradiated with fast neutrons

    International Nuclear Information System (INIS)

    Single crystals of magnesium aluminate spinel (MgAl2O4) were heavily irradiated to fission neutron fluences from ∼1x1026 to ∼2x1027 n/m2 (E>0.1 MeV) at 658 and 1,023 K in FFTF (Fast Flux Test Facility) to investigate their microstructural evolution under heavy neutron irradiation and to confirm their previously observed resistance to void swelling. At 658 K no voids were observed up to 2.29x1027 n/m2, but 1/4[110] interstitial loops were formed. These loops changed their habit planes from (111) to (110) with increasing neutron fluence. At 1,023 K the 1/4[110] type of interstitial loops grew to form stacking fault networks composed of stacking faults on each of the six equivalent {110} planes. Tiny voids were also observed to form preferentially no or near stacking faults after 1.37x1027 n/m2. A limited number of very small cavities, contributing to a volumetric swelling of only 0.07%, were also observed in the crystal matrix after 2.17x1027 n/m2. The possible mechanisms of suppression of void formation in MgAl2O4 are discussed. (author)

  9. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Soeda, Takeshi E-mail: soeda@regroup5.nucl.kyushu-u.ac.jp; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO {center_dot} nAl{sub 2}O{sub 3}) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne{sup +} ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO {center_dot} Al{sub 2}O{sub 3} has a tendency to form the normal spinel configuration, where Mg{sup 2+} ions and Al{sup 3+} ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO {center_dot} Al{sub 2}O{sub 3}. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO {center_dot} Al{sub 2}O{sub 3} irradiated with Ne{sup +} ions. In contrast, cation disordering is suppressed in MgO {center_dot} 2.4Al{sub 2}O{sub 3} irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  10. Mechanical properties and microstructure of α-alumina and magnesium aluminate spinel irradiated with He ions

    Science.gov (United States)

    Izumi, Koichiro; Yasuda, Kazuhiro; Kinoshita, Chiken; Kutsuwada, Masanori

    1998-10-01

    Mechanical properties of α-alumina, stoichiometric- and nonstoichiometric-magnesium aluminate spinel single crystals were examined by using ultra-microhardness technique. The samples were irradiated with 100 keV He + ions at temperatures of 300-870 K and to fluences up to 2 × 10 20 He +/m 2. Apparent hardness, Δ H, in α-alumina increases with fluence in three stages, while that of spinel crystals increases monotonically with fluence. We have also evaluated elastic modulus, plastic and elastic energies, and plastic and elastic indentation depths through the analysis of load-displacement curves. These analyses showed that plastic and elastic hardening are responsible for the variation of Δ H of α-alumina, and that plastic hardening is the main cause of hardening in spinel crystals. Corresponding TEM observations suggested the importance of point defects and/or `invisible' defect clusters for radiation hardening compared to `visible' dislocation loops. The relationship between microstructure and mechanical properties is given for various ceramics.

  11. Coprecipitation Synthesis of Superplastic 3 Mol. % Yttria -- Stabilized Tetragonal Zirconia Polycrystalline / Magnesium Aluminate Spinel Nanocomposite

    Science.gov (United States)

    Opoku, Michael

    3 mole % Yttria-stabilized tetragonal zirconia polycrystalline/Magnesium aluminate spinel (3Y-TZP/MgAl2O4) nanocomposite have exhibited high strain rate superplasticity at 1.7x10--2 --3.3x10--1 s --1. Low strain rate superplasticity (10--5--10 --3 s--1) has been the main drawback of using superplastic ceramics in industries. Microstructural design of 3Y-TZP/MgAl2O4 composite is a key in obtaining high strain rate superplasticity within the range of 10 --2--100 s--1 ). 3Y-TZP/MgAl2O4 may experience a surge in its application at high temperature if the microstructure is designed to exhibit high strain rates at low temperatures. In the present study, the reverse coprecipitation synthesis technique was adopted to synthesize nanocomposite powders containing 70%3Y-TZP/30%MgAl 2O4 and 60%3Y-TZP/40%MgAl2O4 with microstructural characteristics suitable for superplastic application. It was expected that the coprecipitation synthesis technique route will yield highly homogeneous nanocrystalline composite powders, which could be sintered into a dense component with high thermal stability of the small grains. Microstructual features observed after processing powders of 3Y-TZP/MgAl2O4 revealed that the coprecipitation synthesis is a suitable technique for processing nanocomposite powders for superplastic application.

  12. Absorption and spectroscopic ellipsometry study of electron irradiated magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Yang Shenghong; Zhang Yueli; Mo Dang [State Key Lab. of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen Univ. Guangzhou (China)

    2010-08-15

    Magnesium aluminate spinels were irradiated by electron beams with energy of 1.7 MeV and fluence from 10{sup 13} to 10{sup 17} electrons cm{sup -2}. After irradiation, the samples were annealed at different temperatures from 100 to 500 C. Spectroscopic ellipsometry and absorption were used to study the effects of optical properties in the spinel produced by irradiation and subsequent annealing. The results obtained by absorption spectra showed that many F-type absorption centers were produced in the spinels. With increasing electron fluence, we observed an increase in optical absorption, especially in the vicinity of the absorption band at 5.3 eV. The concentration of F-type absorption centers increased as the electron fluence increased. The F-type absorption centers can be destroyed by isochronal annealing. The refractive index obtained by analyzing the ellipsometric spectra changed as the irradiation fluence and subsequent annealing temperature changed. Based on our findings, an attempt has been made to explain the above mentioned phenomena. (orig.)

  13. Atomistic structures of metastable and amorphous phases in ion-irradiated magnesium aluminate spinel

    Science.gov (United States)

    Ishimaru, Manabu; Hirotsu, Yoshihiko; Afanasyev-Charkin, Ivan V.; Sickafus, Kurt E.

    2002-02-01

    Ion-beam-induced microstructures in magnesium aluminate (MgAl2O4) spinel have been examined using transmission electron microscopy (TEM). Irradiations were performed at cryogenic temperature (~120 K) on MgAl2O4 spinel single-crystal surfaces with (111) orientation, using 180 keV neon (Ne+) ions to ion fluences ranging from 1016 to 1017 Ne+ cm-2. Cross-sectional TEM observations indicated that the MgAl2O4 spinel transforms first into a metastable crystalline phase and then into an amorphous phase under these irradiation conditions. On the basis of selected-area electron diffraction and high-resolution TEM, we concluded that Ne-ion-beam irradiation induces an ordered spinel-to-disordered rock-salt-like structural phase transformation. Atomistic structures of amorphous MgAl2O4 were also examined on the basis of atomic pair distribution functions. We compared the experimentally obtained results with previous theoretically calculated results for the metastable and amorphous phases of MgAl2O4, and discussed the validity of the proposed ion-beam-induced structural changes in MgAl2O4 spinel.

  14. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, C A; Smith, R; Kenny, S D [Department of Mathematical Sciences, Loughborough University, Loughborough LE11 3TU (United Kingdom); Murphy, S T; Grimes, R W; Ball, J A [Department of Materials, Imperial College, Prince Consort Road, London SW7 2BP (United Kingdom)

    2009-07-08

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  15. Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, T. [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581 (Japan); Shimada, M. [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581 (Japan); Yasuda, K. [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581 (Japan); Matsumura, S. [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581 (Japan)]. E-mail: syo@nucl.kyushu-u.ac.jp; Chimi, Y. [Department of Materials Science, Japan Atomic Energy Research Institute, Tokai (Japan); Ishikawa, N. [Department of Materials Science, Japan Atomic Energy Research Institute, Tokai (Japan)

    2006-04-15

    We have investigated the microstructure and atomic disordering of nearly stoichiometric magnesium aluminate spinel (MgO . 1.1Al{sub 2}O{sub 3}), irradiated with 200 MeV Xe{sup 14+} ions (S {sub e} = 25 keV/nm). Transmission electron microscopy techniques of bright-field (BF) and high-resolution (HR) imaging, as well as high angular resolution electron channeling X-ray spectroscopy (HARECXS) were employed for quantitative analysis of radiation-induced structural change. BF images of ion tracks show columnar dark contrast of {approx}4 nm in diameter accompanying distinct black or white dots at the incident surface. Clear lattice fringes are observed in HR images even inside the ion tracks, indicating that the spinel crystals are not amorphized but partially disordered along the ion tracks. HARECXS analysis showed that cation disordering progresses successively with ion fluence, and the disordered regions are found to extend over 12.8 {+-} 0.9 nm in diameter for Al ions and 9.6 {+-} 0.6 nm for Mg ions along the ion tracks. This chemically disordered region is much larger than the strained volume detected by BF and HR images.

  16. Superplastic flow in a non-stoichiometric ceramic: Magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Lappalainen, R.; Pannikkat, A.; Raj, R. (Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering)

    1993-04-01

    Tensile superplastic deformation of ceramics is often limited by their susceptibility to intergranular cavitation. However, the authors find that fine grained magnesium aluminate spinel exhibits unusual superplastic ductility at strain rates of up to 5 [times] 10[sup [minus]4]s[sup [minus]1] and at temperatures below 1,280 C. The ductility is all the more remarkable because the flow stress of the spinel was in the range of several hundred MPa. The authors propose that the unusual cavitation resistance of interfaces in spinel is related to its non-stoichiometry. They further propose that the non-linear threshold stress like rheology which they have measured is related to an electrical double (barrier) layer which is postulated to form to compensate the net charge at interfaces of non-stoichiometric ceramics. They estimate that a boundary double layer potential, [psi][sub b], of 5-50 mV can account for this threshold stress. The phenomenological characteristics of superplastic flow in the spinel are shared by other non-stoichiometric ceramics such as yttria stabilized zirconia, hydroxyapatite and zinc sulfide.

  17. Influence of mechanical activation of AL2O3 on synthesis of magnesium aluminate spinel

    Directory of Open Access Journals (Sweden)

    Zhihui Zhang

    2004-01-01

    Full Text Available Magnesium aluminate (MA spinel is synthesized by reaction sintering from alumina and magnesia. The effects of mechanical activation of Al2O3 on reaction sintering were investigated. Non-milled a - Al2O3 and a - Al2O3 high-energy ball milled for 12h, 24h and 36h were mixed with a MgO analytical reagent according to the stoichiometric MA ratio, respectively and pressed into billets with diameters of 20mm and height of 15mm. The green-body billets were then sintered at high temperature in an air atmosphere. The results show that bulk density, relative content of MA and grain size of MA increase with increasing high-energy ball milling time of Al2O3. However prolonged milling time over 24h has a small beneficial effect on the densification of MA. Bulk density and grain size of a sample of a- Al2O3 milled for 24h are 3.30g/cm3 and 4-5 mm, respectively.

  18. Effective fingerprint recognition technique using doped yttrium aluminate nano phosphor material.

    Science.gov (United States)

    Darshan, G P; Premkumar, H B; Nagabhushana, H; Sharma, S C; Prashanth, S C; Prasad, B Daruka

    2016-02-15

    First time the yttrium aluminate nanoparticles are used to improve the fingerprint quality. Eco-friendly green combustion process is used to synthesize YAlO3:Sm(3+) (0.5-11mol%) nanophosphor using green tea leaf extract as non-toxic and eco-friendly fuel. Powder X-ray diffraction study confirms the orthorhombic phase. The average sizes of the crystallites were found to be in the range 20-35nm. The emission peaks centered at 564, 601 and 647nm is attributed to 4f-4f (4)G5/2→(6)HJ=5/2,7/2,9/2 forbidden transitions of Sm(3+) ions. Judd-Ofelt theory is applied to experimental data for providing qualitative support by determining J-O intensity parameters. The Commission International De I-Eclairage chromaticity co-ordinates are very close to National Television System Committee standard value of white emission (x=0.296, y=0.237). Further, correlated color temperature is found to be ∼11,900K. A simple, fast, highly sensitive and low-cost method for the detection and enhancement of fingermarks in a broad range of surfaces is developed and constitutes an alternative to traditional luminescent powders. PMID:26619131

  19. Thermal neutron response and theoretical comparison of LiF coated aluminized Mylar

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Kyle A., E-mail: knelson1@ksu.edu; Bellinger, Steven L.; Edwards, Nathaniel S.; Montag, Benjamin W.; Schmidt, Aaron J.; Wayant, Clayton; McGregor, Douglas S.

    2014-10-21

    Thin layers of LiF were deposited on a 2.0 µm thick aluminized BoPET (i.e. Mylar) in thicknesses of 4.5, 9.9, and 14.0 µm using an electron beam evaporator. These coatings were thinner than the summed triton and alpha particle range from the {sup 6}Li(n,t){sup 4}He reaction, which allows both particles to escape a suspended absorber sheet simultaneously and measured in a proportional gas region concurrently. Each thickness of the LiF coated Mylar sheets were positioned separately in a test chamber that had a single anode wire positioned on each side of the absorber sheets. The thermal neutron response pulse-height spectra were collected for each LiF thickness and are presented and discussed. The coatings became fragile at thicknesses greater than 5.0 µm and would flake off of the Mylar sheets. Additionally, the ideal LiF coating thickness that maximizes the intrinsic thermal neutron detection efficiency is greater than 5.0 µm, which is discussed in a greater detail in the text. Overall, the detectors are capable of achieving thermal-neutron detection efficiencies greater than 30% for a 5 layer device and 60 % for 20 layers, but these devices are complex to fabricate due to flaking of the LiF coatings. Additional research is required to eliminate flaking by possibly using additional mechanical structures or adhesive materials.

  20. Isotopic and REE studies of lunar basalt 12038: Implications for petrogenesis of aluminous mare basalts

    International Nuclear Information System (INIS)

    We report Sr, Nd, and Sm isotopic studies of lunar basalt 12038, one of the so-called aluminous mare basalts. A precise internal Rb-Sr isochron yields a crystallization age of 3.35 +- 0.09 AE and initial 87Sr/86Sr = 0.69922 +- 2 (2sigma error limits, 1 AE = 109 years, lambda(87Rb) = 0.0139 AE-1). An internal Sm-Nd isochron yields an age of 3.28 +- 0.23 AE and initial 143Nd/144Nd = 0.50764 +- 28. Present-day 143Nd/144Nd is less than the 'chondritic' value, i.e. epsilon(Nd,0) = -2.3 +- O.4 where epsilon(Nd) is the deviation of 143Nd/144Nd from chondritic evolution, expressed as parts in 104. At the time of crystallization epsilon(Nd,3.2 AE) = 1.5 +- 0.6. We have successfully modeled the evolution of the Sr and Nd isotopic compositions and the REE abundances within the framework of our earlier model for Apollo 12 olivine-pigeonite and ilmenite basalts. (orig./HAE)

  1. Analyses of Hubble Space Telescope Aluminized-Teflon Insulation Retrieved After 19 Years of Space Exposure

    Science.gov (United States)

    deGroh, Kim K.; Waters, Deborah L.; Mohammed, Jelila S.; Perry, Bruce A.; Banks, Bruce A.

    2012-01-01

    Since its launch in April 1990, the Hubble Space Telescope (HST) has made many important observations from its vantage point in low Earth orbit (LEO). However, as seen during five servicing missions, the outer layer of multilayer insulation (MLI) has become successively more embrittled and has cracked in many areas. In May 2009, during the 5th servicing mission (called SM4), two MLI blankets were replaced with new insulation pieces and the space-exposed MLI blankets were retrieved for degradation analyses by teams at NASA Glenn Research Center (GRC) and NASA Goddard Space Flight Center (GSFC). The MLI blankets were from Equipment Bay 8, which received direct sunlight, and Equipment Bay 5, which received grazing sunlight. Each blanket contained a range of unique regions based on environmental exposure and/or physical appearance. The retrieved MLI blanket s aluminized-Teflon (DuPont) fluorinated ethylene propylene (Al-FEP) outer layers have been analyzed for changes in optical, physical, and mechanical properties, along with space induced chemical and morphological changes. When compared to pristine material, the analyses have shown how the Al-FEP was severely affected by the space environment. This paper reviews tensile properties, solar absorptance, thermal emittance, x-ray photoelectron spectroscopy (XPS) data and atomic oxygen erosion values of the retrieved HST blankets after 19 years of space exposure.

  2. Aluminizing a Ni sheet through severe plastic deformation induced by ball collisions

    Science.gov (United States)

    Romankov, S.; Shchetinin, I. V.; Park, Y. C.

    2015-07-01

    Aluminizing a Ni sheet was performed through severe plastic deformation induced by ball collisions. The Ni sheet was fixed in the center of a mechanically vibrated vial between two connected parts. The balls were loaded into the vial on both sides of the Ni disk. Al disks, which were fixed on the top and the bottom of the vial, served as the sources of Al contamination. During processing, the Ni sheet was subject to intense ball collisions. The Al fragments were transferred and alloyed to the surface of the Ni sheet by these collisions. The combined effects of deformation-induced plastic flow, mechanical intermixing, and grain refinement resulted in the formation of a dense, continuous nanostructured Al layer on the Ni surface on both sides of the sheet. The Al layer consisted of Al grains with an average size of about 40 nm. The Al layer was reinforced with nano-sized Ni flakes that were introduced from the Ni surface during processing. The local amorphization at the Ni/Al interface revealed that the bonding between Ni and Al was formed by mechanical intermixing of atomic layers at the interface. The hardness of the fabricated Al layer was 10 times that of the initial Al plate. The ball collisions destroyed the initial rolling texture of the Ni sheet and induced the formation of the mixed [1 0 0] + [1 1 1] fiber texture. The laminar rolling structure of the Ni was transformed into an ultrafine grain structure.

  3. Comprehensive Study of Lanthanum Aluminate High-Dielectric-Constant Gate Oxides for Advanced CMOS Devices

    Directory of Open Access Journals (Sweden)

    Masamichi Suzuki

    2012-03-01

    Full Text Available A comprehensive study of the electrical and physical characteristics of Lanthanum Aluminate (LaAlO3 high-dielectric-constant gate oxides for advanced CMOS devices was performed. The most distinctive feature of LaAlO3 as compared with Hf-based high-k materials is the thermal stability at the interface with Si, which suppresses the formation of a low-permittivity Si oxide interfacial layer. Careful selection of the film deposition conditions has enabled successful deposition of an LaAlO3 gate dielectric film with an equivalent oxide thickness (EOT of 0.31 nm. Direct contact with Si has been revealed to cause significant tensile strain to the Si in the interface region. The high stability of the effective work function with respect to the annealing conditions has been demonstrated through comparison with Hf-based dielectrics. It has also been shown that the effective work function can be tuned over a wide range by controlling the La/(La + Al atomic ratio. In addition, gate-first n-MOSFETs with ultrathin EOT that use sulfur-implanted Schottky source/drain technology have been fabricated using a low-temperature process.

  4. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    International Nuclear Information System (INIS)

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1−xOy) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1−xOy films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlOy dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm2). TFTs employing solution processed LaAlOy gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >106, subthreshold swing of ∼650 mV dec−1, and electron mobility of ∼12 cm2 V−1 s−1

  5. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Esro, M.; Adamopoulos, G., E-mail: g.adamopoulos@lancaster.ac.uk [Engineering Department, Lancaster University, Lancaster LA1 4YR (United Kingdom); Mazzocco, R.; Kolosov, O.; Krier, A. [Physics Department, Lancaster University, Lancaster, LA1 4YB (United Kingdom); Vourlias, G. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Milne, W. I. [Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Department of Electrical and Computing Engineering, University of Canterbury, 4800 Christchurch (New Zealand)

    2015-05-18

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (La{sub x}Al{sub 1−x}O{sub y}) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the La{sub x}Al{sub 1−x}O{sub y} films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlO{sub y} dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm{sup 2}). TFTs employing solution processed LaAlO{sub y} gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >10{sup 6}, subthreshold swing of ∼650 mV dec{sup −1}, and electron mobility of ∼12 cm{sup 2} V{sup −1} s{sup −1}.

  6. Alternative Fuel for Portland Cement Processing

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Anton K; Duke, Steve R; Burch, Thomas E; Davis, Edward W; Zee, Ralph H; Bransby, David I; Hopkins, Carla; Thompson, Rutherford L; Duan, Jingran; ; Venkatasubramanian, Vignesh; Stephen, Giles

    2012-06-30

    The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. The overarching project objective is to evaluate the use of alternative fuels to lessen the dependence on non-renewable resources to produce portland cement. The key objective of using alternative fuels is to continue to produce high-quality cement while decreasing the use of non-renewable fuels and minimizing the impact on the environment. Burn characteristics and thermodynamic parameters were evaluated with a laboratory burn simulator under conditions that mimic those in the preheater where the fuels are brought into a cement plant. A drop-tube furnace and visualization method were developed that show potential for evaluating time- and space-resolved temperature distributions for fuel solid particles and liquid droplets undergoing combustion in various combustion atmospheres. Downdraft gasification has been explored as a means to extract chemical energy from poultry litter while limiting the throughput of potentially deleterious components with regards to use in firing a cement kiln. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Limestone also had only a slight effect on the fusion when used to coat the pellets. However, limestone addition did display some promise in regards to chlorine capture, as ash analyses showed chlorine concentrations of more than four times greater in the limestone infused ash as compared to raw poultry litter. A reliable and convenient sampling procedure was developed to estimate the combustion quality of broiler litter that is the best compromise between convenience and reliability by means of statistical analysis. Multi-day trial burns were conducted

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

    International Nuclear Information System (INIS)

    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)

  8. Chromium content in human skin after in vitro application of ordinary cement and ferrous-sulphate-reduced cement

    DEFF Research Database (Denmark)

    Fullerton, A; Gammelgaard, Bente; Avnstorp, C;

    1993-01-01

    and unexposed skin was observed, despite a more permeable skin barrier at the alkaline pH of the cement suspensions, i.e., pH 12.5. Increased chromium levels in epidermis and dermis were seen when ordinary Portland cement was applied as a suspension with added sodium sulphate (20%) on the skin surface......The amount of chromium found in human skin after in vitro application of cement suspensions on full-thickness human skin in diffusion cells was investigated. Cement suspensions made from ordinary Portland cement or Portland cement with the chromate reduced with added ferrous sulphate were used. The...... cement suspensions were either applied on the skin surface under occlusion for 48 h or applied repeatedly every 24 h for 96 h. No statistically significant difference in chromium content of skin layers between skin exposed to ordinary Portland cement, skin exposed to cement with added ferrous sulphate...

  9. Carbonation Resistance of Sulphoaluminate Cement-based High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    ZHANG Decheng; XU Dongyu; CHENG Xin; CHEN Wen

    2009-01-01

    The influences of water/cement ratio and admixtures on carbonation resistance of sulphoaluminate cement-based high performance concrete(HPC)were investigated.The experimental results show that with the decreasing water/cement ratio,the carbonation depth of sulphoaluminate cement-based HPC is decreased remarkably,and the carbonation resistance capability is also improved with the adding admixtures.The morphologies and structure characteristics of sulphoaluminate cement hydration products before and after carbonation were analyzed using SEM and XRD.The analysis results reveal that the main hydration product of sulphoaluminate cement,that is ettringite(AFt),de-composes after carbonation.

  10. Development and field use of fiber-containing cement

    Energy Technology Data Exchange (ETDEWEB)

    Vliet, J.P.M. van; Kleef, R.P.A.R. van [Shell Research Rijswijk (Netherlands); Smith, T.R. [Shell Canada Ltd., Toronto, Ontario (Canada); Plompen, A.P.; Kuijvenhoven, C.A.T.; Quaresma, V.; Raiturkar, A.; Schoenmakers, J.M.; Arentz, B.

    1995-12-31

    Fiber-containing cement was initially developed as a high-strength material that could be used to line a borehole. During the development work several relatively simple and cheap spin-off applications of fiber cement were identified, such as the use of fiber cement in cement plugs for borehole stabilization and as a lost circulation material. A number of Shell`s operating companies are already applying fiber cement for these purposes in the field. This paper presents the development of the borehole-lining technique and also describes the other field applications of fiber cement.

  11. Immobilization of radioactive waste in cement based matrices

    International Nuclear Information System (INIS)

    Experimental and theoretical studies of hydrated cement systems are described. The behaviour of slag-based cement is described with a view to predicting their long term pH, Esub(n) and mineralogical balance. Modelling studies which enable the prediction at long ages of cement composites are advanced and a base model of the CaO-SiO2-H2O system presented. The behaviour of U and I in cements is explored. The tolerance of cement systems for a wide range of miscellaneous waste stream components and environmental hazards is described. The redox potential in cements is effectively lowered by irradiation. (author)

  12. A Blended Cement Containing Blast Furnace Slag and Phosphorous Slag

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Blended cement containing blast furnace slag(BFS) and phosphorous slag(PS) is a new kind of cement.The total content of blended materials could increase if two additives were used. Using the same admixtures, the properties of the blended cement with 70% additives could reach the standard of 525-grade slag cement according to GB.The strength of cement with 80% additives could reach the standard of 425-grade slag cement.The tests of strength, pore structure,hydration products,inhibiting alkali-aggregate reaction, resistance to sulfate corrosion of BFS-PSC were performed.

  13. Quality control of cemented waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Slate, L.J.

    1994-12-31

    To insure that cemented radwaste remains immobilized after disposal, certain standards have been set in Europe by the Commission of the European Communities. One such standard is compressive strength. If the compressive strength can be predicted during the early curing stages, time and money can be saved and the quality of the final waste form guaranteed. It was determined that the 7- and 28-day compressive strength from radwaste cementation can be predicted during the mixing and early curing stages by at least three methods. The three that were studied were maturity, rheology, and impedance. Maturity is a temperature-to-time measurement, rheology is a shear stress-to-shear rate measurement, and impedance is the opposition offered to the flow of alternating current. These three methods were employed on five different cemented radwaste concentrations with three different water-to-cement ratios; thus, a total of 15 different mix designs were considered. The results showed that the impedance was the easiest to employ for an on-line process. The results of the impedance method showed a very good relationship between impedance and water-to-cement ratio; therefore, an accurate prediction of compressive strength of cemented radwaste can be drawn from this method. The results of the theology method were very good. The method showed that concrete conforms to the Bingham plastic rheologic model, and the theology method can be used to predict the compressive strength of cemented radwaste, but may be too cumbersome. The results of the maturity method were shown to be limited in accuracy for determining compressive strength.

  14. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    Directory of Open Access Journals (Sweden)

    Adriana Eštoková

    2013-12-01

    Full Text Available The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg−1, 9.78–26.3 Bq·kg−1 and 156.5–489.4 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Raeq = 67.87 Bq·kg−1, gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h−1, external hazard index Hex = 0.182 and internal hazard index Hin was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg−1 for 226Ra, 13.1–20.5 Bq·kg−1 for 232Th and 250.4–494.4 Bq·kg−1 for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.

  15. Colorectal cancer and non-malignant respiratory disease in asbestos cement and cement workers

    International Nuclear Information System (INIS)

    Radiologically visible parenchymal changes (small opacities >= 1/0;ILO 1980 classification) were present in 20% of a sample of workers (N=174), employed for 20 years (median) in an asbestos cement plant. Exposure-response relationships were found, after controlling for age and smoking habits. In a sample of asbestos cement workers with symptoms and signs suggestive of pulmonary disease (N=33), increased lung density measured by x-ray computed tomography, and reduced static lung volumes and lung compliance was found. In a cohort of asbestos cement workers (N=1.929) with an estimated median exposure of 1.2 fibres/ml, the mortality from non-malignant respiratory disease was increased in comparison to a regional reference cohort (N=1.233). A two-to three-fold increase of non-malignant respiratory mortality was noted among workers employed for more than a decade in the asbestos cement plant, compared to cement workers (N=1.526), who in their turn did not experience and increased risk compared to the general population. In the cohorts of asbestos cement and cement workers, there was a tow-to three-fold increased incidence of cancer in the right part of the colon, compared to the general population as well as to external reference cohorts of other industrial workers (N=3.965) and fishermen (N=8.092). A causal relation with the exposure to mineral dust and fibres was supported by the findings of higher risk estimated in subgroups with high cumulated asbestos doses or longer duration of cement work. The incidence of cancer in the left part of the colon was not increased. Morbidity data, but not mortality data, disclosed the subsite-specific risk pattern. Both asbestos cement workers and cement workers has an increased incidence of rectal cancer, compared with the general population, and with the fishermen. The risk was, however, of the same magnitude among the other industrial workers. 181 refs

  16. Post cementation sensitivity evaluation of glass Ionomer, zinc phosphate and resin modified glass Ionomer luting cements under class II inlays: An in vivo comparative study

    OpenAIRE

    Chandrasekhar, V.

    2010-01-01

    Objective: This study aims to compare the patient-perceived post-cementation sensitivity of class II metal restorations preoperatively, immediately after cementation, one week after cementation and one month after cementation with (1) Glass Ionomer luting cement (2) Zinc Phosphate cement and (3) Resin-modified Glass Ionomer luting cement. Materials and Methods: A total of 60 patients, irrespective of sex, in the age group of 15-50 years were selected and the teeth were randomly divided into t...

  17. Analysis of system and methods for improved cementing of oil- and gas wells

    OpenAIRE

    Stensrud, Magnus

    2011-01-01

    Cement is a crucial part of well construction. If a good cement bond between the casing and well bore wall cannot be achieved in the primary cementing, expensive remedial cementing jobs or possible loss of the well bore can occur.When cementing casings and liners in deep waters or pressure depleted reservoirs there is often a small pressure margin between pore pressure and fracture pressure, this makes cement operations more complex. New cementing techniques and cements are being developed to...

  18. Pulmonary Artery Cement Embolism after a Vertebroplasty

    Directory of Open Access Journals (Sweden)

    Anas Nooh

    2015-01-01

    Full Text Available Background Context. Vertebroplasty is a minimally invasive procedure most commonly used for the treatment of vertebral compression fractures. Although it is relatively safe, complications have been reported over time. Among those complications, massive cement pulmonary embolism is considered a rare complication. Here we report a case of massive diffuse cement pulmonary embolism following percutaneous vertebroplasty for a vertebral compression fracture. Study Design. Case report. Methods. This is a 70-year-old female who underwent vertebroplasty for T11 and T12 vertebral compression fracture. Results. CT-scan revealed an incidental finding of cement embolism in the pulmonary trunk and both pulmonary arteries. Since the patient was asymptomatic, she was monitored closely and she did not need any intervention. Conclusion. Vertebroplasty is a minimally invasive procedure used for treatment of vertebral compression fracture. Despite the low rate of complications, a pulmonary cement embolism can occur. The consequences of cement embolism range widely from being asymptomatic to embolism that can cause paralysis, radiculopathy, or a fatal pulmonary embolism.

  19. Stimuli-responsive cement-reinforced rubber.

    Science.gov (United States)

    Musso, Simone; Robisson, Agathe; Maheshwar, Sudeep; Ulm, Franz-Josef

    2014-05-14

    In this work, we report the successful development of a cement-rubber reactive composite with reversible mechanical properties. Initially, the composite behaves like rubber containing inert filler, but when exposed to water, it increases in volume and reaches a stiffness that is intermediate between that of hydrogenated nitrile butadiene rubber (HNBR) and hydrated cement, while maintaining a relatively large ductility characteristic of rubber. After drying, the modulus increases even further up to 400 MPa. Wet/drying cycles prove that the elastic modulus can reversibly change between 150 and 400 MPa. Utilizing attenuated total reflection Fourier transform infrared spectroscopy), we demonstrate that the high pH produced by the hydration of cement triggers the hydrolysis of the rubber nitrile groups into carboxylate anions. Thus, the salt bridges, generated between the carboxylate anions of the elastomer and the cations of the filler, are responsible for the reversible variations in volume and elastic modulus of the composite as a consequence of environmental moisture exposure. These results reveal that cement nanoparticles can successfully be used to accomplish a twofold task: (a) achieve an original postpolymerization modification that allows one to work with carboxylate HNBR (HXNBR) not obtained by direct copolymerization of carboxylate monomers with butadiene, and (b) synthesize a stimuli-responsive polymeric composite. This new type of material, having an ideal behavior for sealing application, could be used as an alternative to cement for oil field zonal isolation applications. PMID:24734968

  20. Microbial-influenced cement degradation: Literature review

    International Nuclear Information System (INIS)

    The Nuclear Regulatory Commission stipulates that disposed low-level radioactive waste (LLW) be stabilized. Because of apparent ease of use and normal structural integrity, cement has been widely used as a binder to solidify LLW. However, the resulting waste forms are sometimes susceptible to failure due to the actions of waste constituents, stress, and environment. This report reviews literature which addresses the effect of microbiologically influenced chemical attack on cement-solidified LLW. Groups of microorganisms are identified, which are capable of metabolically converting organic and inorganic substrates into organic and mineral acids. Such acids aggressively react with concrete and can ultimately lead to structural failure. Mechanisms inherent in microbial-influenced degradation of cement-based material are the focus of this report. This report provides sufficient evidence of the potential for microbial-influenced deterioration of cement-solidified LLW to justify the enumeration of the conditions necessary to support the microbiological growth and population expansion, as well as the development of appropriate tests necessary to determine the resistance of cement-solidified LLW to microbiological-induced degradation that could impact the stability of the waste form