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Sample records for rapid hardening cement

  1. Influence of Rapid Freeze-Thaw Cycling on the Mechanical Properties of Sustainable Strain-Hardening Cement Composite (2SHCC)

    PubMed Central

    Jang, Seok-Joon; Rokugo, Keitetsu; Park, Wan-Shin; Yun, Hyun-Do

    2014-01-01

    This paper provides experimental results to investigate the mechanical properties of sustainable strain-hardening cement composite (2SHCC) for infrastructures after freeze-thaw actions. To improve the sustainability of SHCC materials in this study, high energy-consumptive components—silica sand, cement, and polyvinyl alcohol (PVA) fibers—in the conventional SHCC materials are partially replaced with recycled materials such as recycled sand, fly ash, and polyethylene terephthalate (PET) fibers, respectively. To investigate the mechanical properties of green SHCC that contains recycled materials, the cement, PVA fiber and silica sand were replaced with 10% fly ash, 25% PET fiber, and 10% recycled aggregate based on preliminary experimental results for the development of 2SHCC material, respectively. The dynamic modulus of elasticity and weight for 2SHCC material were measured at every 30 cycles of freeze-thaw. The effects of freeze-thaw cycles on the mechanical properties of sustainable SHCC are evaluated by conducting compressive tests, four-point flexural tests, direct tensile tests and prism splitting tests after 90, 180, and 300 cycles of rapid freeze-thaw. Freeze-thaw testing was conducted according to ASTM C 666 Procedure A. Test results show that after 300 cycles of freezing and thawing actions, the dynamic modulus of elasticity and mass loss of damaged 2SHCC were similar to those of virgin 2SHCC, while the freeze-thaw cycles influence mechanical properties of the 2SHCC material except for compressive behavior. PMID:28788522

  2. The effects of complex glyoxal based modifiers on properties of cement paste and hardened cement paste

    NASA Astrophysics Data System (ADS)

    Simakova, A.; Kudyakov, A.; Efremova, V.; Latypov, A.

    2017-01-01

    This paper presents the results of research on the effect of organic and glyoxal containing additives on the properties of cement paste and hardened cement paste. Complex modifying additives based on liquid glyoxal increasing the strength of the cement paste by 35-63% were developed. Physico-chemical investigations showed that hardened cement paste modified by polylactic acid with glyoxal has a homogeneous and fine-grained structure. Developed complex modifying additives containing glyoxal are approved for use in production technology of heavy cement concretes with advanced properties.

  3. Temperature influence on water transport in hardened cement pastes

    SciTech Connect

    Drouet, Emeline; Poyet, Stéphane; Torrenti, Jean-Michel

    2015-10-15

    Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

  4. Spectroscopic investigation of Ni speciation in hardened cement paste.

    PubMed

    Vespa, M; Dähn, R; Grolimund, D; Wieland, E; Scheidegger, A M

    2006-04-01

    Cement-based materials play an important role in multi-barrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. Cement is used to condition and stabilize the waste materials and to construct the engineered barrier systems (container, backfill, and liner materials) of repositories for radioactive waste. In this study, Ni uptake by hardened cement paste has been investigated with the aim of improving our understanding of the immobilization process of heavy metals in cement on the molecular level. X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance spectroscopy (DRS) techniques were used to determine the local environment of Ni in cement systems. The Ni-doped samples were prepared at two different water/cement ratios (0.4, 1.3) and different hydration times (1 hour to 1 year) using a sulfate-resisting Portland cement. The metal loadings and the metal salts added to the system were varied (50 up to 5000 mg/kg; NO3(-), SO4(2-), Cl-). The XAS study showed that for all investigated systems Ni(ll) is predominantly immobilized in a layered double hydroxide (LDH) phase, which was corroborated by DRS measurements. Only a minor extent of Ni(ll) precipitates as Ni-hydroxides (alpha-Ni(OH)2 and beta-Ni(OH)2). This finding suggests that Ni-Al LDH, rather than Ni-hydroxides, is the solubility-limiting phase in the Ni-doped cement system.

  5. Preparation of in situ hardening composite microcarriers: calcium phosphate cement combined with alginate for bone regeneration.

    PubMed

    Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C; Kim, Hae-Won

    2014-03-01

    Novel microcarriers consisting of calcium phosphate cement and alginate were prepared for use as three-dimensional scaffolds for the culture and expansion of cells that are effective for bone tissue engineering. The calcium phosphate cement-alginate composite microcarriers were produced by an emulsification of the composite aqueous solutions mixed at varying ratios (calcium phosphate cement powder/alginate solution = 0.8-1.2) in an oil bath and the subsequent in situ hardening of the compositions during spherodization. Moreover, a porous structure could be easily created in the solid microcarriers by soaking the produced microcarriers in water and a subsequent freeze-drying process. Bone mineral-like apatite nanocrystallites were shown to rapidly develop on the calcium phosphate cement-alginate microcarriers under moist conditions due to the conversion of the α-tricalcium phosphate phase in the calcium phosphate cement into a carbonate-hydroxyapatite. Osteoblastic cells cultured on the microspherical scaffolds were proven to be viable, with an active proliferative potential during 14 days of culture, and their osteogenic differentiation was confirmed by the determination of alkaline phosphatase activity. The in situ hardening calcium phosphate cement-alginate microcarriers developed herein may be used as potential three-dimensional scaffolds for cell delivery and tissue engineering of bone.

  6. Open photoacoustic cell for thermal diffusivity measurements of a fast hardening cement used in dental restoring

    NASA Astrophysics Data System (ADS)

    Astrath, F. B. G.; Astrath, N. G. C.; Baesso, M. L.; Bento, A. C.; Moraes, J. C. S.; Santos, A. D.

    2012-01-01

    Thermal diffusivity and conductivity of dental cements have been studied using open photoacoustic cell (OPC). The samples consisted of fast hardening cement named CER, developed to be a root-end filling material. Thermal characterization was performed in samples with different gel/powder ratio and particle sizes and the results were compared to the ones from commercial cements. Complementary measurements of specific heat and mass density were also performed. The results showed that the thermal diffusivity of CER tends to increase smoothly with gel volume and rapidly against particle size. This behavior was linked to the pores size and their distribution in the samples. The OPC method was shown to be a valuable way in deriving thermal properties of porous material.

  7. Preparation of in situ hardening composite microcarriers: Calcium phosphate cement combined with alginate for bone regeneration

    PubMed Central

    Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C

    2014-01-01

    Novel microcarriers consisting of calcium phosphate cement and alginate were prepared for use as three-dimensional scaffolds for the culture and expansion of cells that are effective for bone tissue engineering. The calcium phosphate cement-alginate composite microcarriers were produced by an emulsification of the composite aqueous solutions mixed at varying ratios (calcium phosphate cement powder/alginate solution = 0.8–1.2) in an oil bath and the subsequent in situ hardening of the compositions during spherodization. Moreover, a porous structure could be easily created in the solid microcarriers by soaking the produced microcarriers in water and a subsequent freeze-drying process. Bone mineral-like apatite nanocrystallites were shown to rapidly develop on the calcium phosphate cement–alginate microcarriers under moist conditions due to the conversion of the α-tricalcium phosphate phase in the calcium phosphate cement into a carbonate–hydroxyapatite. Osteoblastic cells cultured on the microspherical scaffolds were proven to be viable, with an active proliferative potential during 14 days of culture, and their osteogenic differentiation was confirmed by the determination of alkaline phosphatase activity. The in situ hardening calcium phosphate cement–alginate microcarriers developed herein may be used as potential three-dimensional scaffolds for cell delivery and tissue engineering of bone. PMID:23836845

  8. Effects of porosity on leaching of Ca from hardened ordinary Portland cement paste

    SciTech Connect

    Haga, Kazuko . E-mail: Kazuko_Haga@grp.taiheiyo-cement.co.jp; Sutou, Shunkichi; Hironaga, Michihiko; Tanaka, Satoru; Nagasaki, Shinya

    2005-09-01

    Aiming at evaluating the effects of porosity in hardened cement paste on dissolution phenomena, we prepared hardened ordinary Portland cement (OPC), with variation in pore volume, and then leached them in deionized water. It was found that the bulk density and pore volume were affected by the dissolution of portlandite. The larger the pore volume of the sample, the more rapidly portlandite is dissolved. An electron probe microanalysis (EPMA) performed on the cross-section of the solid phase showed the 'portlandite (CH) dissolution front'. As the leaching period became longer, the CH dissolution front shifted towards the inner part. In addition, the movement of the CH dissolution front was described by the diffusion model, with consideration of the dissolution of portlandite. It was concluded that the transport of leached constituents is diffusion controlled, and the major leached constituents of hardened OPC are portlandite and C-S-H gel. Large pore, which was generated associated with the leaching of portlandite, was considered significantly to affect the diffusion of leached constituents.

  9. Undrained heating and anomalous pore-fluid pressurization of a hardened cement paste

    NASA Astrophysics Data System (ADS)

    Ghabezloo, S.; Sulem, J.; Saint-Marc, J.

    2009-04-01

    Temperature increase in a fluid-saturated porous material in undrained condition leads to volume change and pore pressure increase due to the discrepancy between the thermal expansion coefficients of the pore fluid and of the pore volume. This increase of the pore fluid pressure induces a reduction of the effective mean stress, and can lead to shear failure or hydraulic fracturing. This phenomenon is important is important in environmental engineering for radioactive (exothermal) waste disposal in deep clay geological formations as well as in geophysics in the studies of rapid fault slip events when shear heating tends to increase the pore pressure and to decrease the effective compressive stress and the shearing resistance of the fault material (Sulem et al. 2007). This is also important in petroleum engineering where the reservoir rock and the well cement lining undergo sudden temperature changes for example when extracting heavy oils by steam injection methods. This rapid increase of temperature could damage cement sheath integrity of wells and lead to loss of zonal isolation. The values of the thermal pressurization coefficient, defined as the pore pressure increase due to a unit temperature increase in undrained condition, is largely dependent upon the nature of the material, the state of stress, the range of temperature change, the induced damage. The large variability of the thermal pressurization coefficient reported in the literature for different porous materials with values from 0.01MPa/°C to 1.5MPa/°C highlights the necessity of laboratory studies. This phenomenon of thermal pressurization is studied experimentally for a fluid-saturated hardened cement paste in an undrained heating test. Careful analysis of the effect of the dead volume of the drainage system of the triaxial cell has been performed based on a simple correction method proposed by Ghabezloo and Sulem (2008, 2009). The drained and undrained thermal expansion coefficients of the hardened

  10. Influence of electrified surface of cementitious materials on structure formation of hardened cement paste

    NASA Astrophysics Data System (ADS)

    Alekseev, A.; Gusakov, A.

    2015-01-01

    To provide high strength and durability of concrete it is necessary to study the influence of physical and chemical and mechanical principles of dispersed cementitious systems. The experimental bench was developed to study the influence of electrified surface of cementitious materials on structure formation of hardened cement paste. The test bench allows accelerating the processes of dissolution of cementing materials in water due to influence of electric discharge on their surface. Cement activation with high-voltage corona discharge when AC current is applied allows increasing the ultimate compressive strength of hardened cement paste by 46% at the age of one day and by 20% at the age of 28 days.

  11. Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

    SciTech Connect

    Steshenko, Aleksei Kudyakov, Aleksander; Konusheva, Viktoriya

    2016-01-15

    The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significant change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.

  12. Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

    NASA Astrophysics Data System (ADS)

    Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya

    2016-01-01

    The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significant change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.

  13. IR and NMR analyses of hardening and maturation of glass-ionomer cement.

    PubMed

    Matsuya, S; Maeda, T; Ohta, M

    1996-12-01

    It has been reported that the silicate phase as well as the cross-linking of the polycarboxylic acid by aluminum and calcium ions played an important role in the hardening of glass-ionomer cement. The objective of this study was to investigate the structural change during hardening of the cements by means of infrared (IR) spectroscopy and solid-state nuclear magnetic resonance (NMR) spectroscopy and to confirm the role of the silica phase in the hardening of the cement. For that purpose, we measured the change in compressive strength of an experimental glass-ionomer cement, two commercial glass-ionomer cements, and a polycarboxylate cement and carried out 29Si and 27Al NMR analyses of the cement samples after the strength measurement. In the IR spectra during hardening, a characteristic band of the silicate network around 1000 cm-1 shifted toward high frequency with time. The spectrum after hardening was similar to that for a hydrated amorphous silica structure. The 27Al NMR analysis showed that Al3+ ion was tetrahedrally coordinated by oxygen in the original glass, but a part of the Al3+ ion was octahedrally coordinated after hardening to form Al polyacrylate gel. The chemical shift of Si in the 29Si NMR spectra also changed during hardening. The variation in the chemical shift reflected the structural change in the silicate network. The initial increase in compressive strength of the cement was mainly caused by polycarboxylate gel formation. However, it was concluded that the reconstruction of the silicate network contributed to the increase in strength with time during the period after the gelation by cross-linking was completed.

  14. Monitoring of hardening and hygroscopic induced strains in a calcium phosphate bone cement using FBG sensor.

    PubMed

    Bimis, A; Karalekas, D; Bouropoulos, N; Mouzakis, D; Zaoutsos, S

    2016-07-01

    This study initially deals with the investigation of the induced strains during hardening stage of a self-setting calcium phosphate bone cement using fiber-Bragg grating (FBG) optical sensors. A complementary Scanning Electron Microscopy (SEM) investigation was also conducted at different time intervals of the hardening period and its findings were related to the FBG recordings. From the obtained results, it is demonstrated that the FBG response is affected by the microstructural changes taking place when the bone cement is immersed into the hardening liquid media. Subsequently, the FBG sensor was used to monitor the absorption process and hygroscopic response of the hardened and dried biocement when exposed to a liquid/humid environment. From the FBG-based calculated hygric strains as a function of moisture concentration, the coefficient of moisture expansion (CME) of the examined bone cement was obtained, exhibiting two distinct linear regions.

  15. Microstructural and bulk property changes in hardened cement paste during the first drying process

    SciTech Connect

    Maruyama, Ippei; Nishioka, Yukiko; Igarashi, Go; Matsui, Kunio

    2014-04-01

    This paper reports the microstructural changes and resultant bulk physical property changes in hardened cement paste (hcp) during the first desorption process. The microstructural changes and solid-phase changes were evaluated by water vapor sorption, nitrogen sorption, ultrasonic velocity, and {sup 29}Si and {sup 27}Al nuclear magnetic resonance. Strength, Young's modulus, and drying shrinkage were also examined. The first drying process increased the volume of macropores and decreased the volume of mesopores and interlayer spaces. Furthermore, in the first drying process globule clusters were interconnected. During the first desorption, the strength increased for samples cured at 100% to 90% RH, decreased for 90% to 40% RH, and increased again for 40% to 11% RH. This behavior is explained by both microstructural changes in hcp and C–S–H globule densification. The drying shrinkage strains during rapid drying and slow drying were compared and the effects of the microstructural changes and evaporation were separated.

  16. Effects of TEA·HCl hardening accelerator on the workability of cement-based materials

    NASA Astrophysics Data System (ADS)

    Pan, Wenhao; Ding, Zhaoyang; Chen, Yanwen

    2017-03-01

    The aim of the test is to research the influence rules of TEA·HCl on the workability of cement paste and concrete. Based on the features of the new hardening accelerator, an experimental analysis system were established through different dosages of hardening accelerator, and the feasibility of such accelerator to satisfy the need of practical engineering was verified. The results show that adding of the hardening accelerator can accelerate the cement hydration, and what’s more, when the dosage was 0.04%, the setting time was the shortest while the initial setting time and final setting time were 130 min and 180 min, respectively. The initial fluidity of cement paste of adding accelerator was roughly equivalent compared with that of blank. After 30 min, fluidity loss would decrease with the dosage increasing, but fluidity may increase. The application of the hardening accelerator can make the early workability of concrete enhance, especially the slump loss of 30 min can improve more significantly. The bleeding rate of concrete significantly decreases after adding TEA·HCl. The conclusion is that the new hardening accelerator can meet the need of the workability of cement-based materials in the optimum dosage range.

  17. The hardening of Portland cement studied by ? NMR stray-field imaging

    NASA Astrophysics Data System (ADS)

    Nunes, Teresa; Randall, E. W.; Samoilenko, A. A.; Bodart, P.; Feio, G.

    1996-03-01

    Hydration and hardening processes of Portland cement (type I) were studied by analysis of the one-dimensional projections (profiles) obtained periodically with the 0022-3727/29/3/044/img8 stray-field imaging technique over two days. The influence of additives, such as gypsum, in Portland cement (type IA) was also investigated. The decay of the signal intensity as a function of time was found to be bi-exponential for type I and mono-exponential for type IA.

  18. Monitoring of sulphate attack on hardened cement paste studied by synchrotron XRD

    NASA Astrophysics Data System (ADS)

    Stroh, J.; Meng, B.; Emmerling, F.

    2015-10-01

    The complex matter of external sulphate attack on cement-based construction materials is still not completely understood. The concentration of sulphate is a crucial factor for the formation of secondary phases and phase transitions of cement hydrates due to sulphate ingress into the microstructure. The sulphate attack on building materials for high and low sulphate concentrations was monitored by laboratory experiments. Hardened cement paste consisting of ordinary Portland cement (CEM I) were exposed to aqueous solutions of sodium sulphate for 18 months. Three sample compositions were used for this research, including different supplementary cementitious materials (SCM). The phase composition was determined for different time spans by high resolution synchrotron X-ray diffraction. Cross sections of exposed cement prisms were investigated as a representation of the microstructural profile. Based on the data, a temporal and spatial determination of the stages of the sulphate attack and the deterioration course was possible. Cement matrices blended with slag showed the highest resistance against sulphate attack.

  19. Influence of silica-based hybrid material on the gas permeability of hardened cement paste

    NASA Astrophysics Data System (ADS)

    Li, R.; Hou, P.; Xie, N.; Zhou, Z.; Cheng, X.

    2017-03-01

    Surface treatment is one of the most effective ways to elongate the service life of concrete. The surface treatment agents, including organic and inorganic types, have been intensively studied. In this paper, the silica-based hybrid nanocomposite, which take advantages of both organic and inorganic treatment agents, was synthesized and used for surface treatment of hardened cement-based material. The effectiveness of organic and inorganic hybrid nanocomposite was evaluated through investigations on the gas permeability of cement-based materials. The results showed that SiO2/PMHS hybrid nanocomposite can greatly decrease the gas transport properties of hardened cement-based materials and has a great potential for surface treatment of cementitious materials.

  20. Influence of particle size on hardening and handling of a premixed calcium phosphate cement.

    PubMed

    Aberg, Jonas; Engstrand, Johanna; Engqvist, Håkan

    2013-04-01

    Premixed calcium phosphate cements (pCPC) have been developed to circumvent problems related to mixing and transfer of cements in the operating room. In addition, by using pCPC the short working times generally associated with conventional water-mixed cements are avoided. In this work, the influence of particle size on handling and hardening characteristics of a premixed monetite cement has been assessed. The cements were evaluated with respect to their injectability, setting time and compressive strength. It was found that cements with smaller particle sizes were more difficult to inject and had higher compressive strength. Regarding setting time, no clear trend could be discerned. The addition of granules made the cements easier to inject, but setting time was prolonged and lower strengths were obtained. The main findings of this work demonstrate that particle size can be used to control handling and physical properties of premixed cements and that previous knowledge from water-based CPC, regarding effects of particle size, is not directly applicable to premixed CPC.

  1. Phase development in the hardening process of two calcium phosphate bone cements: an energy dispersive X-ray diffraction study

    SciTech Connect

    Generosi, A.; Smirnov, V.V.; Rau, J.V.; Albertini, V. Rossi; Ferro, D.; Barinov, S.M.

    2008-03-04

    This work was aimed at the application of an energy dispersive X-ray diffraction technique to study the kinetics of phase development during the setting and hardening reactions in two calcium phosphate bone cements. The cements under study are based on either tricalcium phosphate or tetracalcium phosphate initial solid phase, and a magnesium carbonate-phosphoric acid liquid phase as the hardening liquid. The application of the energy dispersive X-ray diffraction method allowed to collect the diffraction patterns from the cement pastes in situ starting from 1 min of the setting and hardening process. The only crystallized phase in both cements was apatite-like phase, the primary crystallization process proceeds during a few seconds of the setting reaction. Both the compressive strength and the pH value changes during the hardening period can be attributed to the transformations occurring in the intergranular X-ray amorphous phase.

  2. Chloride diffusivity in hardened cement paste from microscale analyses and accounting for binding effects.

    PubMed

    Carrara, P; De Lorenzis, L; Bentz, D P

    2016-08-01

    The diffusion of chloride ions in hardened cement paste (HCP) under steady-state conditions and accounting for the highly heterogeneous nature of the material is investigated. The HCP microstructures are obtained through segmentation of X-ray images of real samples as well as from simulations using the cement hydration model CEMHYD3D. Moreover, the physical and chemical interactions between chloride ions and HCP phases (binding), along with their effects on the diffusive process, are explicitly taken into account. The homogenized diffusivity of the HCP is then derived through a least square homogenization technique. Comparisons between numerical results and experimental data from the literature are presented.

  3. Deteriorated hardened cement paste structure analyzed by XPS and {sup 29}Si NMR techniques

    SciTech Connect

    Kurumisawa, Kiyofumi; Nawa, Toyoharu; Owada, Hitoshi; Shibata, Masahito

    2013-10-15

    In this report, X-ray photoelectron spectroscopy (XPS) and {sup 29}Si-MAS-NMR was used for the evaluation of deteriorated hardened cement pastes. The deterioration by ammonium nitrate solution was accompanied by changes in the pore structure as well as by structural changes in the C–S–H in the hardened cement paste. The CaO/SiO{sub 2} ratio of the C–S–H decreased with the progress of deterioration, there was also polymerization of the silicate in the C–S–H. It was confirmed that the degree of polymerization of silicate of the C–S–H in hardened cement paste can be determined by XPS. It was also shown that the polymerization depends on the structure of the C–S–H. -- Highlights: •The polymerization of silicate of the C–S–H in the HCP can be observed by XPS. •The structure of C–S–H changed with the degree of calcium leaching. •The NMR result about silicate in C–S–H was in good agreement with the XPS result.

  4. Inkbottle Pore-Method: Prediction of hygroscopic water content in hardened cement paste at variable climatic conditions

    SciTech Connect

    Espinosa, Rosa Maria . E-mail: espinosa@tuhh.de; Franke, Lutz

    2006-10-15

    The aim of this work is the development of a practicable method for the reliable prediction of the equilibrium hygroscopic water content in hardened cement paste and cement mortars at changing climatic conditions. Sorption thermodynamics and multi-scale pore structure of hardened cement paste build the basis of the new computation procedure. Drying and chemical aging lead to a formation of inkbottle pores. Their influence on sorption behaviour will be considered in particular by including them into the pore model. Experimental data of adsorption, desorption and scanning-isotherms verify the new computation method, which has been called 'IBP-Method' (inkbottle pores)

  5. Reactivity of NO2 and CO2 with hardened cement paste containing activated carbon

    NASA Astrophysics Data System (ADS)

    Horgnies, M.; Dubois-Brugger, I.; Krou, N. J.; Batonneau-Gener, I.; Belin, T.; Mignard, S.

    2015-07-01

    The development of building materials to reduce the concentration of NO2 is growing interest in a world where the air quality in urban areas is affected by the car traffic. The main binder in concrete is the cement paste that is partly composed of calcium hydroxide. This alkaline hydrate composing the hardened cement paste shows a high BET surface area (close to 100 m2.g-1) and can absorb low-concentrations of NO2. However, the presence of CO2 in the atmosphere limits the de-polluting effect of reference cement paste, mainly due to carbonation of the alkaline hydrates (reaction leading to the formation of calcium carbonate). The results established in this paper demonstrate that the addition of activated carbon in the cement paste, because of its very high BET surface area (close to 800 m2.g-1) and its specific reactivity with NO2, can significantly improve and prolong the de-polluting effect in presence of CO2 and even after complete carbonation of the surface of the cement paste.

  6. Macro- and microspectroscopic study of Nd (III) uptake mechanisms in hardened cement paste.

    PubMed

    Mandaliev, Peter; Dähn, Rainer; Wehrli, Bernhard; Wieland, Erich

    2009-11-01

    Cement is an important component in repositories for low-level and intermediate-level radioactive waste. Nd uptake by hardened cement paste (HCP) has been investigated with the aim of developing a mechanistic understanding of the immobilization processes of trivalent lanthanides and actinides in HCP on the molecular level. Information on the microstructure of HCP, the Nd distribution in the cement matrix, and the coordination environment of Nd in these matrices was gained from the combined use of scanning electron microscopy (SEM), synchrotron-based micro-X-ray fluorescence (micro-XRF), micro-X-ray (micro-XAS), and bulk-X-ray absorption spectroscopy (bulk-XAS) on Nd doped cement samples. The samples were reacted over periods of time between 15 min and 200 days. SEM and micro-XRF investigations suggest preferential Nd accumulation in rims around "inner"-calcium silicate hydrates (C-S-H). The EXAFS data indicate that the coordination environment of Nd taken up by HCP was dependent on reaction time. Changes in the structural parameters derived from EXAFS support the idea of Nd incorporation into the structure of C-S-H phases. The Nd binding mechanisms proposed in this study have implication for an overall assessment of the safe disposal of trivalent actinides in cement-based repositories for radioactive waste.

  7. Co speciation in hardened cement paste: a macro- and micro-spectroscopic investigation.

    PubMed

    Vespa, M; Dähn, R; Grolimund, D; Wieland, E; Scheidegger, A M

    2007-03-15

    Cement-based materials play an important role in multi-barrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. Cement is used to condition and stabilize the waste materials and to construct the engineered barrier systems (container, backfill and liner materials) of repositories for radioactive waste. In this study, Co uptake by hardened cement paste (HCP) has been investigated with the aim of improving our understanding of the immobilization process of heavy metals in cement on the molecular level. X-ray-absorption spectroscopy (XAS) on powder material (bulk-XAS) was used to determine the local environment of Co in cement systems. Bulk-XAS investigations were complemented with micro-beam investigations to probe the inherent microscale heterogeneity of cement by using micro-X-ray-fluorescence (micro-XRF) and micro-XAS. Micro-XRF was used to gain information on the spatial heterogeneity of the Co distribution, whereas micro-XAS was employed to determine the speciation of Co on the microscale. The Co-doped HCP samples hydrated for time-scales from 1 hour up to 1 year were prepared under normal atmosphere, to simulate similar conditions as for waste packages. To investigate the role of oxygen, further samples were prepared in the absence of oxygen. The study showed that, for the samples prepared in air, Co(II) is oxidized to Co(III) after 1 hour of hydration time. Moreover, the relative amount of Co(III) increases with increasing hydration time. The study further revealed that Co(II) is predominately present as a Co-hydroxide-like phase and/or Co-phyllosilicates, whereas Co(III) tends to be incorporated into a CoOOH-like phase and/or Co-phyllomanganates. In contrast to samples prepared in air, XAS experiments with samples prepared in the absence of oxygen revealed solely the presence of Co(II). This finding indicates that oxygen plays an important role for Co oxidation in cement. Furthermore, the study suggests that Co

  8. Determining the slag fraction, water/binder ratio and degree of hydration in hardened cement pastes

    SciTech Connect

    Yio, M.H.N. Phelan, J.C.; Wong, H.S.; Buenfeld, N.R.

    2014-02-15

    A method for determining the original mix composition of hardened slag-blended cement-based materials based on analysis of backscattered electron images combined with loss on ignition measurements is presented. The method does not require comparison to reference standards or prior knowledge of the composition of the binders used. Therefore, it is well-suited for application to real structures. The method is also able to calculate the degrees of reaction of slag and cement. Results obtained from an experimental study involving sixty samples with a wide range of water/binder (w/b) ratios (0.30 to 0.50), slag/binder ratios (0 to 0.6) and curing ages (3 days to 1 year) show that the method is very promising. The mean absolute errors for the estimated slag, water and cement contents (kg/m{sup 3}), w/b and s/b ratios were 9.1%, 1.5%, 2.5%, 4.7% and 8.7%, respectively. 91% of the estimated w/b ratios were within 0.036 of the actual values. -- Highlights: •A new method for estimating w/b ratio and slag content in cement pastes is proposed. •The method is also able to calculate the degrees of reaction of slag and cement. •Reference standards or prior knowledge of the binder composition are not required. •The method was tested on samples with varying w/b ratios and slag content.

  9. Hindered water motions in hardened cement pastes investigated over broad time and length scales.

    PubMed

    Bordallo, Heloisa N; Aldridge, Laurence P; Fouquet, Peter; Pardo, Luis Carlos; Unruh, Tobias; Wuttke, Joachim; Yokaichiya, Fabiano

    2009-10-01

    We investigated the dynamics of confined water in different hydrated cement pastes with minimized contributions of capillary water. It was found that the water motions are extremely reduced compared to those of bulk water. The onset of water mobility, which was modified by the local environment, was investigated with elastic temperature scans using the high-resolution neutron backscattering instrument SPHERES. Using a Cauchy-Lorenz distribution, the quasi-elastic signal observed in the spectra obtained by the backscattering spectrometer was analyzed, leading to the identification of rotational motions with relaxation times of 0.3 ns. Additionally, neutron spin echo (NSE) spectroscopy was used to measure the water diffusion over the local network of pores. The motions observed in the NSE time scale were characterized by diffusion constants ranging from 0.6 to 1.1 x 10(-9) m(2) s(-1) most likely related to water molecules removed from the interface. In summary, our results indicate that the local diffusion observed in the gel pores of hardened cement pastes is on the order of that found in deeply supercooled water. Finally, the importance of the magnetic properties of cement pastes were discussed in relation to the observation of a quasi-elastic signal on the dried sample spectra measured using the time-of-flight spectrometer.

  10. Nuclear Spin Relaxation and Water Self-diffusion in Hardening Magnesium Oxychloride Cement

    NASA Astrophysics Data System (ADS)

    Nestle, Nikolaus; Galvosas, Petrik; Zimmermann, Christian; Dakkouri, Marwan; Kärger, Jörg

    2001-08-01

    In this contribution, we report the results of NMR studies of the behaviour of water in a hydrating Sorel cement paste with a composition close to the stoichiometric optimum. Both the transverse spin-relaxation behaviour and water self-diffusion were studied in two separate experiments performed on samples on the basis of the same formulation. While there is a very strong initial decrease in the transverse relaxation time of the water in the paste, the diffusion coefficient is found to decrease mainly at later times of the hydration process where the decrease of the transverse relaxation time has already strongly slowed down. After about 6 h of the hardening process, the signal intensity available for a pulsed gradient diffusometry experiment is not sufficient any more for reliable measurements of the diffusion coefficients

  11. Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC)

    SciTech Connect

    Paul, S.C.; Pirskawetz, S.; Zijl, G.P.A.G. van; Schmidt, W.

    2015-03-15

    This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage.

  12. Carbonation around near aggregate regions of old hardened concrete cement paste

    SciTech Connect

    Tam, Vivian W.Y. . E-mail: tam.vivian@student.cityu.edu.hk; Gao, X.F.; Tam, C.M. . E-mail: bctam@cityu.edu.hk

    2005-06-01

    Analogous with most modern cities, waste disposal is a pressing issue due to limited landfill and public filling (land reclamation) areas in Hong Kong in which construction and demolition (C and D) waste forms the major source. Concrete, apportioning the largest portion of C and D waste, has the greatest potential for recycling. However, the knowledge on micro-structural behavior of concrete waste is immature to give adequate details on the macro-behavior of concrete waste. This paper attempts to examine the problems of recycling old concrete by investigating the microstructure and phase transformation of the concrete samples collected from buildings with 46 and 37 years of services. From the results of Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) examination, it is found that there are a lot of pores at the near layers of aggregate where carbonation of the hardened cement paste (HCP) is high. The pores may be generated as a result of poor workmanship such as insufficient concrete mixing time, trapping of air voids beneath coarse aggregate, inappropriate water to cement ratio, and the microclimate conditions such as humidity that affects the demand on water from the aggregate during mixing.

  13. Microwave detection of delaminations between fiber reinforced polymer (FRP) composite and hardened cement paste

    NASA Astrophysics Data System (ADS)

    Hughes, D.; Kazemi, M.; Marler, K.; Zoughi, R.; Myers, J.; Nanni, A.

    2002-05-01

    Fiber reinforced polymer (FRP) composites are increasingly being used for the rehabilitation of concrete structures. Detection and characterization of delaminations between an FRP composite and a concrete surface are of paramount importance. Consequently, the development of a one sided, non-contact, real time and rapid nondestructive testing (NDT) technique for this purpose is of great interest. Near-field microwave NDT techniques, using open-ended rectangular waveguide probes, have shown great potential for detecting delaminations in layered composite structures such as these. The results of some theoretical and experimental investigations on a specially prepared cement paste specimen are presented here.

  14. Microscopic air void analysis of hardened Portland cement concrete by the isolated shadow technique

    NASA Astrophysics Data System (ADS)

    Harris, Basil Mark

    The Isolated Shadow Technique is an image processing and analysis procedure for identifying and characterizing surface voids dispersed on an otherwise flat plane of heterogeneous solids. The objective of the Isolated Shadow Technique is to capture, process, and analyze images of a flat surface in which all of the features, save the boundary outlines of any surface voids, are eliminated. In short, the technique utilizes a series of digital images of the subject planar surface; where each image of the series is subjected to a unique lighting condition. By positioning the lights such that the shadows cast into the craters vary between images, these variations can be sequestered and the edges of the voids can subsequently be reconstructed from the isolated shadows. The primary purpose of this work was the development of the Isolated Shadow Technique for the particular application of quantitatively describing the microscopic voids in hardened Portland cement concrete. The Isolated Shadow System was developed for this application of the technique. The hardware and software of the system are described and the function is demonstrated. The system was found to have an average accuracy of 2.7% with a maximum deviation of 5.0% when compared to physical measurements. The results of polished sections of concrete specimens characterized by the Isolated Shadow System are compared to the results obtained with the commonly used standard methods (ASTM C 457; A and B). The coefficients of variation of parameters calculated to describe the air-void system (according to the ASTM C 457 formulations) are shown to be in the neighborhood of one percent when the observed test area includes at least 7,830 mmsp2 of polished concrete (with paste contents ranging from approximately 28% to 32%). The sensitivity of the air-void system parameters (as computed by the system) to changes in magnification and mosaic size are evaluated. A critical analysis of the underlying assumptions of the ASTM C

  15. Hardening of dual-cure resin cements and a resin composite restorative cured with QTH and LED curing units.

    PubMed

    Santos, Gildo Coelho; El-Mowafy, Omar; Rubo, Jose Henrique; Santos, Maria Jacinta Moreas Coelho

    2004-05-01

    The aim of this study was to determine the effects of light intensity and type of light unit (quartztungsten-halogen [QTH] or light-emitting diode [LED]) on the hardening of various resin cements and a resin composite restorative. Disk specimens were prepared from 4 dual-cured resin cements (Variolink II, Calibra, Nexus 2 and RelyX ARC). Two QTH light-curing units (Visilux 2, at 550 mW/cm2, and Optilux 501, at 1,360 mW/cm2) and a LED unit (Elipar FreeLight, at 320 mW/cm2) were used for curing. Specimens were light-cured or dual-cured for 10, 30 or 40 seconds with 1 of the 3 light units (curing applied to upper surface only) and were tested 24 hours after curing. Additional cement specimens were self-cured and tested at 15, 30 and 60 minutes and at 24 hours. Testing consisted of measurement of Knoop hardness number (KHN) for each specimen. Six KHN values were obtained for the upper surface only of the various cement specimens in each test group. Disk specimens 2.5 mm thick were also prepared from a resin composite restorative (XRV Herculite). These were light-cured as above, and KHN measurements were obtained for both the upper and the lower surfaces. Mean KHNs were determined, and data were analyzed with analysis of variance. The groups were significantly different (p < 0.05). High-intensity light curing resulted in the highest KHN values for all materials with any of the 3 light-curing times. For the cements, LED light curing (with both dual-curing and light-curing modes) resulted in hardness values similar to those achieved with conventional QTH light curing, although there were some exceptions. However, both LED and conventional QTH light curing resulted in inferior hardening of lower surfaces of the XRV Herculite specimens at the 3 curing times. For all cements except Nexus 2, self-curing resulted in significantly lower hardness values than dual curing. The self-curing mechanism of Variolink II cement needed a longer time to activate than those of the other

  16. CHEMICAL REACTION MECHANISM AND MODELIZATION OF DETERIORATION PHENOMENON OF HARDENED CEMENT DAMAGED BY CHEMICAL EROSION DUE TO MIXED ACID AQUEOUS SOLUTION

    NASA Astrophysics Data System (ADS)

    Miyamoto, Shintaro; Minagawa, Hiroshi; Hisada, Makoto

    This study measured the mass decrease rate of the hardened cement specimens which deteriorated by sulfuric acid, hydrochloric acid, nitric acid and mixed acid which mixed these acids (i.e. sulfuric acid, hydrochloric acid, nitric acid) for the purpose of clarify the these chemical reaction mechanism. As a result, it was clarified that mass decrease rate of hardened cement is greatly dependent on concentration of sulfuric acid when mixed acids containing sulfuric acid and other acid (i.e. hydrochloric acid or nitric acid) act on hardened cement. In this study, it was apprehended that the cause of this chemical reaction mechanism is influence of molar fraction of sulfuric acid and it was indicated that this chemical reaction mechanism could be explained by Gibbs free energy and chemical kinetics. Moreover, in this study, it was proposed that prediction model of mass decrease rate based on these theories.

  17. Injectable and rapid-setting calcium phosphate bone cement with dicalcium phosphate dihydrate.

    PubMed

    Burguera, Elena F; Xu, Hockin H K; Weir, Michael D

    2006-04-01

    Calcium phosphate cement (CPC) sets in situ with intimate adaptation to the contours of defect surfaces, and forms an implant having a structure and composition similar to hydroxyapatite, the putative mineral in teeth and bones. The objective of the present study was to develop an injectable CPC using dicalcium phosphate dihydrate (DCPD) with a high solubility for rapid setting. Two agents were incorporated to impart injectability and fast-hardening to the cement: a hardening accelerator (sodium phosphate) and a gelling agent (hydroxypropyl methylcellulose, HPMC). The cement with DCPD was designated as CPC(D), and the conventional cement was referred to as CPC(A). Using water without sodium phosphate, CPC(A) had a setting time of 82 +/- 6 min. In contrast, CPC(D) exhibited rapid setting with a time of 17 +/- 1 min. At 0.2 mol/L sodium phosphate, setting time for CPC(D) was 15 +/- 1 min, significantly faster than 40 +/- 2 min for CPC(A) (Tukey's at 0.95). Sodium phosphate decreased the paste injectability (measured as the paste mass extruded from the syringe divided by the original paste mass inside the syringe). However, the addition of HPMC dramatically increased the paste injectability. For CPC(D), the injectability was increased from 65% +/- 12% without HPMC to 98% +/- 1% with 1% HPMC. Injectability of CPC(A) was also doubled to 99% +/- 1%. The injectable and rapid-setting CPC(D) possessed flexural strength and elastic modulus values overlapping the reported values for sintered porous hydroxyapatite implants and cancellous bone. In summary, the rapid setting and relatively high strength and elastic modulus of CPC(D) should help the graft to quickly attain strength and geometrical integrity within a short period of time postoperatively. Furthermore, the injectability of CPC(D) may have potential for procedures involving defects with limited accessibility or narrow cavities, when there is a need for precise placement of the paste, and when using minimally invasive

  18. Influence of water content on hardening and handling of a premixed calcium phosphate cement.

    PubMed

    Engstrand, Johanna; Aberg, Jonas; Engqvist, Håkan

    2013-01-01

    Handling of calcium phosphate cements is difficult, where problems often arise during mixing, transferring to syringes, and subsequent injection. Via the use of premixed cements the risk of handling complications is reduced. However, for premixed cements to work in a clinical situation the setting time needs to be improved. The objective of this study is to investigate the influence of the addition of water on the properties of premixed cement. Monetite-forming premixed cements with small amounts of added water (less than 6.8 wt.%) were prepared and the influence on injectability, working time, setting time and mechanical strength was evaluated. The results showed that the addition of small amounts of water had significant influence on the properties of the premixed cement. With the addition of just 1.7 wt.% water, the force needed to extrude the cement from a syringe was reduced from 107 (±15) N to 39 (±9) N, the compression strength was almost doubled, and the setting time decreased from 29 (±4) min to 19 (±2) min, while the working time remained 5 to 6h. This study demonstrates the importance of controlling the water content in premixed cement pastes and how water can be used to improve the properties of premixed cements.

  19. Post-irradiation hardening of dual-cured and light-cured resin cements through machinable ceramics.

    PubMed

    Yoshida, Keiichi; Atsuta, Mitsuru

    2006-10-01

    To evaluate the surface hardness (Knoop Hardness Number) of the thin layer in three light-cured and dual-cured resin cements irradiated through or not through 2.0 mm thick machinable ceramics. A piece of adhesive polyethylene tape with a circular hole was positioned on the surface of the ceramic plate to control the cement layer (approximately 50 microm). The cement paste was placed on the ceramic surface within the circle. The ceramic plate with resin cement paste was placed on a clear micro cover glass over a zirconia ceramic block to obtain a flat surface, and the material was polymerized using a visible-light-curing unit. The surface hardness was recorded at a series of time intervals up to 5 days, starting from the end of a light-irradiation period. The hardness steadily increased with post-irradiation time and tended towards a maximum, usually reached after 1 or 2 days. In all cases, the increase in hardness was relatively rapid over the first 30 minutes and continued at a lower rate thereafter. The dual-cured resin cement for each material showed a significantly higher hardness value than the light-cured resin cement irradiated either through or not through ceramics at all post-irradiation times. The resin cements cured through ceramic for each material were significantly less hard compared with those cured not through ceramics at all post-irradiation times.

  20. Rapid setting of portland cement by greenhouse carbon dioxide capture

    SciTech Connect

    Wagh, A.S.; Singh, D.; Knox, L.J.

    1994-04-01

    Following the work by Berger et al. on rapid setting of calcium silicates by carbonation, a method of high-volume capture of CO{sub 2} in portland cement has been developed. Typically, 10--24 wt. % of CO{sub 2} produced by the calcination of calcium carbonate during clinkering, may be captured, and the set cement acquires most of its full strength in less than a day. The approach will have economic advantages in fabrication of precast structures, in emergency development of infrastructure during natural disasters, and in defense applications. Moreover, it will help the cement industry comply with the Clean Air Act of 1990 by sequestering the greenhouse carbon dioxide.

  1. Effect of calcium carbonate on hardening, physicochemical properties, and in vitro degradation of injectable calcium phosphate cements.

    PubMed

    Sariibrahimoglu, Kemal; Leeuwenburgh, Sander C G; Wolke, Joop G C; Yubao, Li; Jansen, John A

    2012-03-01

    The main disadvantage of apatitic calcium phosphate cements (CPCs) is their slow degradation rate, which limits complete bone regeneration. Carbonate (CO₃²⁻) is the common constituent of bone and it can be used to improve the degradability of the apatitic calcium phosphate ceramics. This study aimed to examine the effect of calcite (CaCO₃) incorporation into CPCs. To this end, the CaCO₃ amount (0-4-8-12 wt %) and its particle size (12.0-μm-coarse or 2.5-μm-fine) were systematically investigated. In comparison to calcite-free CPC, the setting time of the bone substitute was delayed with increasing CaCO₃ incorporation. Reduction of the CaCO₃ particle size in the initial powder increased the injectability time of the paste. During hardening of the cements, the increase in calcium release was inversely proportional to the extent of CO₃²⁻ incorporation into apatites. The morphology of the carbonate-free product consisted of large needle-like crystals, whereas small plate-like crystals were observed for carbonated apatites. Compressive strength decreased with increasing CaCO₃ content. In vitro accelerated degradation tests demonstrated that calcium release and dissolution rate from the set cements increased with increasing the incorporation of CO₃²⁻, whereas differences in CaCO₃ particle size did not affect the in vitro degradation rate under accelerated conditions.

  2. Effects of the granularity of raw materials on the hydration and hardening process of calcium phosphate cement.

    PubMed

    Liu, Changsheng; Shao, Huifang; Chen, Feiyue; Zheng, Haiyan

    2003-10-01

    Effects of the granularity of the raw materials on the hydration and hardening process of calcium phosphate cement (CPC) composed of equimolar tetracalcium phosphate (TECP) and dicalcium phosphate anhydrous (DCPA) were investigated systematically. The variation of pH value in CPC slurry indicated that the control step of CPC hydration was the dissolution of DCPA under these experimental conditions. Reducing the particle size of DCPA could accelerate the hydration rate, and decreasing the particle size of TECP would expedite the dissolution of DCPA, which would obviously result in a faster hydration rate. The results of isothermal conduction calorimetry showed that reducing the particle size of TECP could increase the conversion ratio of starting materials to hydration products, which would lead to an increase in the compressive strength of the hardened body of CPC. The sample composed of the smallest particle size of DCPA and TECP obtained the compressive strength of 41 MPa, which would not attain the highest compressive strength, 49 MPa. The smaller the particle size of either DCPA or TECP, the shorter the setting time was. During the setting process of CPC, the microstructure progresses from a gel structure to an agglomeration-crystallization structure. The calculated values of setting time from the rheological model coincided with the experimental data very well. The parameters of AC impedance spectroscopy were closely correlated with the mean pore diameter and porosity of the CPC hardened body. The results of AC impedance spectroscopy further verified that a small particle size of raw materials could result in high hydration rate and the compressive strength of 49.1 MPa.

  3. Hardening of a dual-cure resin cement using QTH and LED curing units.

    PubMed

    Santos, Maria Jacinta Moraes Coelho; Passos, Sheila Pestana; da Encarnação, Monalisa Olga Lessa; Santos, Gildo Coelho; Bottino, Marco Antonio

    2010-01-01

    This study evaluated the surface hardness of a resin cement (RelyX ARC) photoactivated through indirect composite resin (Cristobal) disks of different thicknesses using either a light-emitting diode (LED) or quartz tungsten halogen (QTH) light source. Eighteen resin cement specimens were prepared and divided into 6 groups according to the type of curing unit and the thickness of resin disks interposed between the cement surface and light source. Three indentations (50 g for 15 s) were performed on the top and bottom surface of each specimen and a mean Vickers hardness number (VHN) was calculated for each specimen. The data were analyzed using two-way ANOVA and Tukey-Kramer test was used for post-hoc pairwise comparisons. Increased indirect resin disk thickness resulted in decreased mean VHN values. Mean VHN values for the top surfaces of the resin cement specimens ranged from 23.2 to 46.1 (QTH) and 32.3 to 41.7 (LED). The LED curing light source produced higher hardness values compared to the QTH light source for 2- and 3-mm-thick indirect resin disks. The differences were clinically, but not statistically significant. Increased indirect resin disk thickness also resulted in decreased mean VHN values for the bottom surfaces of the resin cement: 5.8 to 19.1 (QTH) and 7.5 to 32.0 (LED). For the bottom surfaces, a statistically significant interaction was also found between the type of curing light source and the indirect resin disk thickness. Mean surface hardness values of resin cement specimens decreased with the increase of indirect resin disk thickness. The LED curing light source generally produced higher surface hardness values.

  4. Hardening of a dual-cure resin cement using QTH and LED curing units

    PubMed Central

    SANTOS, Maria Jacinta Moraes Coelho; PASSOS, Sheila Pestana; da ENCARNAÇÃO, Monalisa Olga Lessa; SANTOS, Gildo Coelho; BOTTINO, Marco Antonio

    2010-01-01

    Objective This study evaluated the surface hardness of a resin cement (RelyX ARC) photoactivated through indirect composite resin (Cristobal) disks of different thicknesses using either a light-emitting diode (LED) or quartz tungsten halogen (QTH) light source. Material and Methods Eighteen resin cement specimens were prepared and divided into 6 groups according to the type of curing unit and the thickness of resin disks interposed between the cement surface and light source. Three indentations (50 g for 15 s) were performed on the top and bottom surface of each specimen and a mean Vickers hardness number (VHN) was calculated for each specimen. The data were analyzed using two-way ANOVA and Tukey-Kramer test was used for post-hoc pairwise comparisons. Results Increased indirect resin disk thickness resulted in decreased mean VHN values. Mean VHN values for the top surfaces of the resin cement specimens ranged from 23.2 to 46.1 (QTH) and 32.3 to 41.7 (LED). The LED curing light source produced higher hardness values compared to the QTH light source for 2- and 3-mm-thick indirect resin disks. The differences were clinically, but not statistically significant. Increased indirect resin disk thickness also resulted in decreased mean VHN values for the bottom surfaces of the resin cement: 5.8 to 19.1 (QTH) and 7.5 to 32.0 (LED). For the bottom surfaces, a statistically significant interaction was also found between the type of curing light source and the indirect resin disk thickness. Conclusions Mean surface hardness values of resin cement specimens decreased with the increase of indirect resin disk thickness. The LED curing light source generally produced higher surface hardness values. PMID:20485920

  5. [Responses of Arma chinensis cold tolerance to rapid cold hardening and underlying physiological mechanisms].

    PubMed

    Li, Xing-Peng; Song, Li-Wen; Zhang, Hong-Hao; Chen, Yue-Qu; Zuo, Tong-Tong; Wang, Jun; Sun, Wei

    2012-03-01

    Rapid cold hardening can enhance the cold tolerance of some insects. To explore the effects of different cold hardening induction temperature on the cold tolerance of Arma chinensis and related physiological mechanisms, the 3rd generation A. chinensis adults reared indoor were treated with cooling at 15, 10, and 4 degrees C for 4 h, respectively, or with gradual cooling from 15 degrees C for 4 h to 10 degrees C for 4 h, and finally to 4 degrees C for 4 h. The super-cooling point, water content, and the contents of low molecular carbohydrates, glycerol, and amino acids of the adults after cooling and the adults cold tolerance at 0, -5, and -10 degrees C were measured by thermocouple, high performance liquid chromatography, and other analytical techniques. When exposed at -10 degrees C after cooling, the survival rate of the adults treated with gradual cooling or treated with cooling at 4 degrees C for 4 h was averagely 58.3%, while that of the adults reared at room temperature (25 degrees C +/- 2 degrees C) or treated with cooling at 15 degrees C or 10 degrees C for 4 h decreased significantly, with an average of 8.9%. The super-cooling point of the adults treated with gradual cooling or with cooling at 4 degrees C for 4 h was -15.6 degrees C, which was averagely 1.3 degrees C lower than that of the other treatments. The water content of the adults had no significant difference among all treatments, with an average of 61.8%, but the glucose, sorbitolum, glycerol, Ala, and Glu contents in treatments gradual cooling and cooling at 4 degrees C for 4 h increased by 2.82-fold, 2.65-fold, 3.49-fold, 51.3%, and 80.2%, while the fucose, mannose, and Pro contents decreased by 68.4%, 52.2%, and 30.2%, respectively, as compared with the other treatments. The fructose content showed no significant difference among all treatments. It was suggested that rapid cool hardening had a critical temperature to induce the physiological metabolism process of adult A. chinensis, and

  6. Effects of calcium leaching on diffusion properties of hardened and altered cement pastes

    NASA Astrophysics Data System (ADS)

    Kurumisawa, Kiyofumi; Haga, Kazuko; Hayashi, Daisuke; Owada, Hitoshi

    2017-06-01

    It is very important to predict alterations in the concrete used for fabricating disposal containers for radioactive waste. Therefore, it is necessary to understand the alteration of cementitious materials caused by calcium leaching when they are in contact with ground water in the long term. To evaluate the long-term transport characteristics of cementitious materials, the microstructural behavior of these materials should be considered. However, many predictive models of transport characteristics focus on the pore structure, while only few such models consider both, the spatial distribution of calcium silicate hydrate (C-S-H), portlandite, and the pore spaces. This study focused on the spatial distribution of these cement phases. The auto-correlation function of each phase of cementitious materials was calculated from two-dimensional backscattered electron imaging, and the three-dimensional spatial image of the cementitious material was produced using these auto-correlation functions. An attempt was made to estimate the diffusion coefficient of chloride from the three-dimensional spatial image. The estimated diffusion coefficient of the altered sample from the three-dimensional spatial image was found to be comparable to the measured value. This demonstrated that it is possible to predict the diffusion coefficient of the altered cement paste by using the proposed model.

  7. Desorption of bis(2-chloroethyl) sulfide, mustard agent, from the surface of hardened cement paste (HCP) wafers.

    PubMed

    Tang, Hairong; Zhou, Xuezhi; Guan, Yingqiang; Zhou, Liming; Wang, Xinming; Yan, Huijuan

    2013-05-01

    The decontamination of surfaces exposed to chemical warfare agents is an interesting scientific topic. The desorption behavior of bis(2-chloroethyl) sulfide (sulfur mustard, HD) from the surface of the HD-contaminated hardened cement paste (HCP) was investigated under different weather conditions, which should provide scientific reference data for protection and decontamination projects involving HD-contaminated HCP in different conditions. The desorption of HD from the surface of HCP wafers was studied, and the effects of the purge air flow rate, water content, sorption temperature, and substrate age were investigated. HD desorption was detected from the surface of HD-contaminated HCP, but the desorption velocity was relatively slow. The desorption quantity remained within an order of magnitude throughout a time span of 36h (25°C at 200mL/min of purge air), and the amount of HD that was desorbed from each square meter of HCP surface was approximately 1.1g (25°C at 200mL/min of purge air), which was approximately 5.5 percent of the total HD that was initially applied. A higher flow rate of the purge air, increased water content, and longer substrate age of HCP all increased the HD desorption. In contrast, increased temperatures suppressed HD desorption.

  8. Ultrasound monitoring of the influence of different accelerating admixtures and cement types for shotcrete on setting and hardening behaviour

    SciTech Connect

    Belie, N. de . E-mail: nele.debelie@ugent.be; Grosse, C.U.; Kurz, J.; Reinhardt, H.-W.

    2005-11-15

    The possible use of ultrasound measurements for monitoring setting and hardening of mortar containing different accelerating admixtures for shotcrete was investigated. The sensitivity to accelerator type (alkaline aluminate or alkali-free) and dosage, and accelerator-cement compatibility were evaluated. Furthermore, a new automatic onset picking algorithm for ultrasound signals was tested. A stepwise increase of the accelerator dosage resulted in increasing values for the ultrasound pulse velocity at early ages. In the accelerated mortar no dormant period could be noticed before the pulse velocity started to increase sharply, indicating a quick change in solid phase connectivity. The alkaline accelerator had a larger effect than the alkali-free accelerator, especially at ages below 90 min. The effect of the alkali-free accelerator was at very early age more pronounced on mortar containing CEM I in comparison with CEM II, while the alkaline accelerator had a larger influence on mortar containing CEM II. The increase of ultrasound energy could be related to the setting phenomenon and the maximum energy was reached when the end of workability was approached. Only the alkaline accelerator caused a significant reduction in compressive strength and this for all the dosages tested.

  9. Evaluation of a low temperature hardening Inorganic Phosphate Cement for high-temperature applications

    SciTech Connect

    Alshaaer, M.; Cuypers, H.; Mosselmans, G.; Rahier, H.; Wastiels, J.

    2011-01-15

    Phase and mechanical changes of Inorganic Phosphate Cement (IPC) are identified along with changes in macro properties as functions of temperature and time. In addition to amorphous phases, the presence of significant amounts of brushite and wollastonite in the reference IPC is confirmed using X-ray diffraction. The thermal behavior of IPC up to 1000 {sup o}C shows that contraction of the solid phase in IPC due to chemical transformations causes reduction in the volume of the material. Also the ongoing meta-stable calcium phosphate transformations and reactions over a long time contribute significantly to the phase instability of the material at ambient conditions. It is found that the strength of IPC increases with ageing at ambient conditions but the formation microcracks below 105 {sup o}C causes a sharp reduction in the mechanical performance of IPC. According to the results obtained by Mercury intrusion porosimetry, the pore system of the reference IPC is dominated by mesopores.

  10. The Bone Building Blues: Self-hardening copper-doped calcium phosphate cement and its in vitro assessment against mammalian cells and bacteria.

    PubMed

    Rau, Julietta V; Wu, Victoria M; Graziani, Valerio; Fadeeva, Inna V; Fomin, Alexander S; Fosca, Marco; Uskoković, Vuk

    2017-10-01

    A blue calcium phosphate cement with optimal self-hardening properties was synthesized by doping whitlockite (β-TCP) with copper ions. The mechanism and the kinetics of the cement solidification process were studied using energy dispersive X-ray diffraction and it was found out that hardening was accompanied by the phase transition from TCP to brushite. Reduced lattice parameters in all crystallographic directions resulting from the rather low (1:180) substitution rate of copper for calcium was consistent with the higher ionic radius of the latter. The lower cationic hydration resulting from the partial Ca→Cu substitution facilitated the release of constitutive hydroxyls and lowered the energy of formation of TCP from the apatite precursor at elevated temperatures. Addition of copper thus effectively inhibited the formation of apatite as the secondary phase. The copper-doped cement exhibited an antibacterial effect, though exclusively against Gram-negative bacteria, including E. coli, P. aeruginosa and S. enteritidis. This antibacterial effect was due to copper ions, as demonstrated by an almost negligible antibacterial effect of the pure, copper-free cement. Also, the antibacterial activity of the copper-containing cement was significantly higher than that of its precursor powder. Since there was no significant difference between the kinetics of the release of copper from the precursor TCP powder and from the final, brushite phase of the hardened cement, this has suggested that the antibacterial effect was not solely due to copper ions, but due to the synergy between cationic copper and a particular phase and aggregation state of calcium phosphate. Though inhibitory to bacteria, the copper-doped cement increased the viability of human glial E297 cells, murine osteoblastic K7M2 cells and especially human primary lung fibroblasts. That this effect was also due to copper ions was evidenced by the null effect on viability increase exhibited by the copper

  11. Critical aspects of nano-indentation technique in application to hardened cement paste

    SciTech Connect

    Davydov, D. Jirasek, M.; Kopecky, L.

    2011-01-15

    Several open questions related to the experimental protocol and processing of data acquired by the nano-indentation (NI) technique are investigated. The volume fractions of mechanically different phases obtained from statistical NI (SNI) analysis are shown to be different from those obtained by back-scattered electron (BSE) image analysis and X-ray diffraction (XRD) method on the same paste. Judging from transmission electron microscope (TEM) images, the representative volume element of low-density calcium-silicate hydrates (C-S-H) can be considered to be around 500 nm, whereas for high-density C-S-H it is about 100 nm. This raises the question how the appropriate penetration depth for NI experiments should be selected. Changing the maximum load from 1 mN to 5 mN, the effect of penetration depth on the experimental results is studied. As an alternative to the SNI method, a 'manual' indentation method is proposed, which combines information from BSE and atomic-force microscopy (AFM), coupled to the NI machine. The AFM allows to precisely indent a high-density C-S-H rim around unhydrated clinkers in cement paste. Yet the results from that technique still show a big scatter.

  12. Rapid cold hardening and expression of heat shock protein genes in the B-biotype Bemisia tabaci.

    PubMed

    Wang, Haihong; Lei, Zhongren; Li, Xue; Oetting, Ronald D

    2011-02-01

    This paper describes the rapid cold hardening processes of the sweetpotato whitefly, Bemisia tabaci (Gennadius). It was found that all developmental stages of B. tabaci have the capacity of rapid cold hardening and the length of time required to induce maximal cold hardiness at 0 °C varies with stage. There was only 18.3% survival when adult whiteflies were transferred directly from 26 °C to -8.5 °C for 2 h. However, exposure to 0 °C for 1 h before transfer to -8.5 °C increased the survival to 81.2%. The whiteflies show "prefreeze" mortality when they were exposed to temperatures above the supercooling point (SCP), although the range of SCP of whiteflies is -26 °C to -29 °C. The rapid cold hardening had no effect on SCP and reduced the lower lethal temperature of adults from -9 °C to -11 °C. Rapid cold-hardened adults had a similar lifespan as the control group but deposited fewer eggs than nonhardened individuals. The expression profiles during cold hardening and recovery from this process revealed that HSP90 did not respond to cold stress. However, HSP70 and HSP20 were significantly induced by cold with different temporal expression patterns. These results suggest that the rapid cold hardening response is possibly advantageous to whiteflies that are often exposed to drastic temperature fluctuations in spring or autumn in northern China, and the expression of HSP70 and HSP20 may be associated with the cold tolerance of B. tabaci.

  13. On the use of peak-force tapping atomic force microscopy for quantification of the local elastic modulus in hardened cement paste

    SciTech Connect

    Trtik, Pavel; Kaufmann, Josef; Volz, Udo

    2012-01-15

    A surface of epoxy-impregnated hardened cement paste was investigated using a novel atomic force microscopy (AFM) imaging mode that allows for the quantitative mapping of the local elastic modulus. The analyzed surface was previously prepared using focussed ion beam milling. The same surface was also characterized by electron microscopy and energy-dispersive X-ray spectroscopy. We demonstrate the capability of this quantitative nanomechanical mapping to provide information on the local distribution of the elastic modulus (from about 1 to about 100 GPa) with a spatial resolution in the range of decananometers, that corresponds to that of low-keV back-scattered electron imaging. Despite some surface roughness which affects the measured nanomechanical properties it is shown that topography, adhesion and Young's modulus can be clearly distinguished. The quantitative mapping of the local elastic modulus is able to discriminate between phases in the cement paste microstructure that cannot be distinguished from the corresponding back-scattered electron images.

  14. Quantitative Phosphoproteomics Reveals Signaling Mechanisms Associated with Rapid Cold Hardening in a Chill-Tolerant Fly.

    PubMed

    Teets, Nicholas M; Denlinger, David L

    2016-08-05

    Rapid cold hardening (RCH) is a physiological adaptation in which brief chilling (minutes to hours) significantly enhances the cold tolerance of insects. RCH allows insects to cope with sudden cold snaps and diurnal variation in temperature, but the mechanistic basis of this rapid stress response is poorly understood. Here, we used phosphoproteomics to identify phosphorylation-mediated signaling events that are regulated by chilling that induces RCH. Phosphoproteomic changes were measured in both brain and fat bodies, two tissues that are essential for sensing cold and coordinating RCH at the organismal level. Tissues were chilled ex vivo, and changes in phosphoprotein abundance were measured using 2D electrophoresis coupled with Pro-Q diamond labeling of phosphoproteins followed by protein identification via LC-MS/MS. In both tissues, we observed an abundance of protein phosphorylation events in response to chilling. Some of the proteins regulated by RCH-inducing chilling include proteins involved in cytoskeletal reorganization, heat shock proteins, and proteins involved in the degradation of damaged cellular components via the proteasome and autophagosome. Our results suggest that phosphorylation-mediated signaling cascades are major drivers of RCH and enhance our mechanistic understanding of this complex phenotype.

  15. A specific glycerol kinase induces rapid cold hardening of the diamondback moth, Plutella xylostella.

    PubMed

    Park, Youngjin; Kim, Yonggyun

    2014-08-01

    Insects in temperate zones survive low temperatures by migrating or tolerating the cold. The diamondback moth, Plutella xylostella, is a serious insect pest on cabbage and other cruciferous crops worldwide. We showed that P. xylostella became cold-tolerant by expressing rapid cold hardiness (RCH) in response to a brief exposure to moderately low temperature (4°C) for 7h along with glycerol accumulation in hemolymph. Glycerol played a crucial role in the cold-hardening process because exogenously supplying glycerol significantly increased the cold tolerance of P. xylostella larvae without cold acclimation. To determine the genetic factor(s) responsible for RCH and the increase of glycerol, four glycerol kinases (GKs), and glycerol-3-phosphate dehydrogenase (PxGPDH) were predicted from the whole P. xylostella genome and analyzed for their function associated with glycerol biosynthesis. All predicted genes were expressed, but differed in their expression during different developmental stages and in different tissues. Expression of the predicted genes was individually suppressed by RNA interference (RNAi) using double-stranded RNAs specific to target genes. RNAi of PxGPDH expression significantly suppressed RCH and glycerol accumulation. Only PxGK1 among the four GKs was responsible for RCH and glycerol accumulation. Furthermore, PxGK1 expression was significantly enhanced during RCH. These results indicate that a specific GK, the terminal enzyme to produce glycerol, is specifically inducible during RCH to accumulate the main cryoprotectant.

  16. Rapid desiccation hardening changes the cuticular hydrocarbon profile of Drosophila melanogaster.

    PubMed

    Stinziano, Joseph R; Sové, Richard J; Rundle, Howard D; Sinclair, Brent J

    2015-02-01

    The success of insects in terrestrial environments is due in large part to their ability to resist desiccation stress. Since the majority of water is lost across the cuticle, a relatively water-impermeable cuticle is a major component of insect desiccation resistance. Cuticular permeability is affected by the properties and mixing effects of component hydrocarbons, and changes in cuticular hydrocarbons can affect desiccation tolerance. A pre-exposure to a mild desiccation stress increases duration of desiccation survival in adult female Drosophila melanogaster, via a decrease in cuticular permeability. To test whether this acute response to desiccation stress is due to a change in cuticular hydrocarbons, we treated male and female D. melanogaster to a rapid desiccation hardening (RDH) treatment and used gas chromatography to examine the effects on cuticular hydrocarbon composition. RDH led to reduced proportions of unsaturated and methylated hydrocarbons compared to controls in females, but although RDH modified the cuticular hydrocarbon profile in males, there was no coordinated pattern. These data suggest that the phenomenon of RDH leading to reduced cuticular water loss occurs via an acute change in cuticular hydrocarbons that enhances desiccation tolerance in female, but not male, D. melanogaster.

  17. Desiccation enhances rapid cold-hardening in the flesh fly Sarcophaga bullata: evidence for cross tolerance between rapid physiological responses.

    PubMed

    Yi, Shu-Xia; Gantz, J D; Lee, Richard E

    2017-01-01

    Many insects use rapid cold-hardening (RCH), a physiological response to sub-lethal exposure to stressors, such as chilling and desiccation, to enhance their cold tolerance within minutes. Recently, drought-induced RCH, triggered by brief, mild desiccation, was described in larvae of the freeze-tolerant gall fly (Eurosta solidaginis). However, its prevalence and ecological significance in other insects is not known. Consequently, we used a freeze-intolerant model, the flesh fly, Sarcophaga bullata, to investigate the effects and mechanisms of drought-induced RCH. In addition, we investigated how drought- and cold-induced RCH interact by exposing flies to both desiccation and chilling. Desiccation for 3 h increased larval pupariation after cold shock from 28 to 40 %-the first example of drought-induced RCH in both a freeze-intolerant insect and in a non-overwintering life stage. We also found that desiccation and chilling together enhanced the cold hardiness of larvae and adults more than either did separately, suggesting that drought and cold trigger distinct physiological mechanisms that interact to afford greater cold tolerance. These results suggest that drought-induced RCH is a highly conserved response used by insects with diverse life history strategies. Furthermore, the protective interaction between drought- and cold-induced RCH suggests that, in nature, insects use multiple cues and physiological mechanisms to fine-tune their response to changing ambient conditions.

  18. Rapid growth rates of syndepositional marine aragonite cements in steep marginal slope deposits, Bahamas and Belize

    SciTech Connect

    Grammer, G.M.; Ginsburg, R.N.; Swart, P.K.; McNeill, D.F. . Div. of Marine Geology); Jull, A.J.T. . NSF Accelerator Facility); Prezbindowski, D.R. )

    1993-09-01

    Growth rates of marine botryoidal aragonite cements from steep (35-45[degree]) marginal slope deposits in the Bahamas and Belize have been determined by accelerator mass spectrometer radiocarbon dating of samples taken at the base and top of individual botryoids. The pore-filling cements, which range from approximately 11,000-13,000 years old, grew at average rates of 8-10mm/100 yr with maximum rates > 25mm/100 yr. Radiocarbon dating of coexisting skeletal components indicates that cementation was syndepositional. Microsampling transects across individual botryoids for stable-isotope analyses show little variation in [delta][sup 31]C and [delta][sup 18]O, supporting the conclusion that cementation was extremely rapid. Although the cements show a progressive depletion in isotopic composition of approximately 1[per thousand]([delta][sup 13]C) and 2[per thousand]([delta][sup 18]O) from 13 ka to 11 ka, the average variation ([delta][sub 1]) within individual pore-filling cements, ranging in size 2 mm to 32 mm (bottom to top), was 0.11[per thousand]([delta][sup 13]C) and 0.14[per thousand]([delta][sup 18]O). Results of this study provide the first quantitative data on growth rates of marine carbonate cements in a marginal slope environment. The data indicate that marginal slope deposits may lithify within several tens of years and suggest that geologically instantaneous cementation may be critical in stabilizing steep carbonate slope deposits at or above angles of repose.

  19. Anoxic stress and rapid cold hardening enhance cold tolerance of the migratory locust.

    PubMed

    Cui, Feng; Wang, Hongsheng; Zhang, Hanying; Kang, Le

    2014-10-01

    Anoxia and rapid cold hardening (RCH) can increase the cold tolerance of many animals. However, mechanisms underlying these two kinds of stresses remain unclear. In this study, we aimed to explore the relationship of acclimation to cold stress with acclimation to anoxic stress in the migratory locust, Locusta migratoria. RCH at 0°C for 3h promoted the survival of cold stress-exposed locusts. Anoxic hypercapnia (CO2 anoxic treatment) for 40 min exerted an effect similar to that of RCH. Anoxic hypercapnia within 1h can all promote the cold hardiness of locusts. We investigated the transcript levels of six heat shock protein (Hsp) genes, namely, Hsp20.5, Hsp20.6, Hsp20.7, Hsp40, Hsp70, and Hsp90. Four genes, namely, Hsp90, Hsp40, Hsp20.5, and Hsp20.7, showed differential responses to RCH and anoxic hypercapnia treatments. Under cold stress, locusts exposed to the two regimens showed different responses for Hsp90, Hsp20.5, and Hsp20.7. However, the varied responses disappeared after recovery from cold stress. Compared with the control group, the transcript levels of six Hsp genes were generally downregulated in locusts subjected to anoxic hypercapnia or/and RCH. These results indicate that anoxic stress and RCH have different mechanisms of regulating the transcription of Hsp family members even if the two treatments exerted similar effects on cold tolerance of the migratory locust. However, Hsps may not play a major role in the promotion of cold hardiness by the two treatments.

  20. Shifts in the carbohydrate, polyol, and amino acid pools during rapid cold-hardening and diapause-associated cold-hardening in flesh flies (Sarcophaga crassipalpis): a metabolomic comparison.

    PubMed

    Michaud, M Robert; Denlinger, David L

    2007-10-01

    Flesh flies can enhance their cold hardiness by entering a photoperiod-induced pupal diapause or by a temperature-induced rapid cold-hardening process. To determine whether the same or different metabolites are involved in these two responses, derivatized polar extracts from flesh flies subjected to these treatments were examined using gas chromatography-mass spectrophotometry (GC-MS). This metabolomic approach demonstrated that levels of metabolites involved in glycolysis (glycerol, glucose, alanine, pyruvate) were elevated by both treatments. Metabolites elevated uniquely in response to rapid cold-hardening include glutamine, cystathionine, sorbitol, and urea while levels of beta-alanine, ornithine, trehalose, and mannose levels were reduced. Rapid cold-hardening also uniquely perturbed the urea cycle. In addition to the elevated metabolites shared with rapid cold-hardening, leucine concentrations were uniquely elevated during diapause while levels of a number of other amino acids were reduced. Pools of two aerobic metabolic intermediates, fumarate and citrate, were reduced during diapause, indicating a reduction of Krebs cycle activity. Principal component analysis demonstrated that rapid cold-hardening and diapause are metabolically distinct from their untreated, non-diapausing counterparts. We discuss the possible contribution of each altered metabolite in enhancing the overall cold hardiness of the organism, as well as the efficacy of GC-MS metabolomics for investigating insect physiological systems.

  1. Rapid cold hardening improves recovery of ion homeostasis and chill coma recovery time in the migratory locust, Locusta migratoria.

    PubMed

    Findsen, Anders; Andersen, Jonas Lembcke; Calderon, Sofia; Overgaard, Johannes

    2013-05-01

    Chill tolerance of insects is defined as the ability to tolerate low temperature under circumstances not involving freezing of intracellular or extracellular fluids. For many insects chill tolerance is crucial for their ability to persist in cold environments and mounting evidence indicates that chill tolerance is associated with the ability to maintain ion and water homeostasis, thereby ensuring muscular function and preventing chill injury at low temperature. The present study describes the relationship between muscle and haemolymph ion homeostasis and time to regain posture following cold shock (CS, 2 h at -4°C) in the chill-susceptible locust Locusta migratoria. This relationship was examined in animals with and without a prior rapid cold-hardening treatment (RCH, 2 h at 0°C) to investigate the physiological underpinnings of RCH. CS elicited a doubling of haemolymph [K(+)] and this disturbance was greater in locusts pre-exposed to RCH. Recovery of ion homeostasis was, however, markedly faster in RCH-treated animals, which correlated well with whole-organism performance as hardened individuals regained posture faster than non-hardened individuals following CS. The present study indicates that loss and recovery of muscular function are associated with the resting membrane potential of excitable membranes as attested by the changes in the equilibrium potential for K(+) (EK) following CS. Both hardened and non-hardened animals regained movement once K(+) homeostasis had recovered to a fixed level (EK≈-41 mV). RCH is therefore not associated with altered sensitivity to ion disturbance but instead is correlated to a faster recovery of haemolymph [K(+)].

  2. Manufacture and properties of fluoride cement

    NASA Astrophysics Data System (ADS)

    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

  3. Rapid surface hardening and enhanced tribological performance of 4140 steel by friction stir processing

    SciTech Connect

    Lorenzo-Martin, Cinta; Ajayi, Oyelayo O.

    2015-06-06

    Tribological performance of steel materials can be substantially enhanced by various thermal surface hardening processes. For relatively low-carbon steel alloys, case carburization is often used to improve surface performance and durability. If the carbon content of steel is high enough (>0.4%), thermal treatments such as induction, flame, laser, etc. can produce adequate surface hardening without the need for surface compositional change. This paper presents an experimental study of the use of friction stir processing (FSP) as a means to hardened surface layer in AISI 4140 steel. The impacts of this surface hardening process on the friction and wear performance were evaluated under both dry and lubricated contact conditions in reciprocating sliding. FSP produced the same level of hardening and superior tribological performance when compared to conventional thermal treatment, using only 10% of the energy and without the need for quenching treatments. With FSP surface hardness of about 7.8 GPa (62 Rc) was achieved while water quenching conventional heat treatment produced about 7.5 GPa (61 Rc) hardness. Microstructural analysis showed that both FSP and conventional heat treatment produced martensite. Although the friction behavior for FSP treated surfaces and the conventional heat treatment were about the same, the wear in FSP processed surfaces was reduced by almost 2× that of conventional heat treated surfaces. Furthermore, the superior performance is attributed to the observed grain refinement accompanying the FSP treatment in addition to the formation of martensite. As it relates to tribological performance, this study shows FSP to be an effective, highly energy efficient, and environmental friendly (green) alternative to conventional heat treatment for steel.

  4. Rapid surface hardening and enhanced tribological performance of 4140 steel by friction stir processing

    DOE PAGES

    Lorenzo-Martin, Cinta; Ajayi, Oyelayo O.

    2015-06-06

    Tribological performance of steel materials can be substantially enhanced by various thermal surface hardening processes. For relatively low-carbon steel alloys, case carburization is often used to improve surface performance and durability. If the carbon content of steel is high enough (>0.4%), thermal treatments such as induction, flame, laser, etc. can produce adequate surface hardening without the need for surface compositional change. This paper presents an experimental study of the use of friction stir processing (FSP) as a means to hardened surface layer in AISI 4140 steel. The impacts of this surface hardening process on the friction and wear performance weremore » evaluated under both dry and lubricated contact conditions in reciprocating sliding. FSP produced the same level of hardening and superior tribological performance when compared to conventional thermal treatment, using only 10% of the energy and without the need for quenching treatments. With FSP surface hardness of about 7.8 GPa (62 Rc) was achieved while water quenching conventional heat treatment produced about 7.5 GPa (61 Rc) hardness. Microstructural analysis showed that both FSP and conventional heat treatment produced martensite. Although the friction behavior for FSP treated surfaces and the conventional heat treatment were about the same, the wear in FSP processed surfaces was reduced by almost 2× that of conventional heat treated surfaces. Furthermore, the superior performance is attributed to the observed grain refinement accompanying the FSP treatment in addition to the formation of martensite. As it relates to tribological performance, this study shows FSP to be an effective, highly energy efficient, and environmental friendly (green) alternative to conventional heat treatment for steel.« less

  5. Asphalt cement poisoning

    MedlinePlus

    ... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

  6. YIELD STRENGTH PREDICTION FOR RAPID AGE-HARDENING HEAT TREATMENT OF ALUMINUM ALLOYS

    SciTech Connect

    Yin, Hebi; Sabau, Adrian S; Ludtka, Gerard Michael; Skszek, Timothy; Niu, X

    2013-01-01

    A constitutive model has been developed to predict the yield strength aging curves for aluminum casting alloys during non-isothermal age-hardening processes. The model provides the specific relationship between the process variables and yield strength. Several aging heat treatment scenarios have been investigated using the proposed model, including two-step aging recipes. Two-step aging heat treatments involve a low temperature regime to promote nucleation of secondary phases and a second step at higher temperature for the growth of the secondary phases. The predicted results show that yield strength of approximately 300MPa might be obtained in shorter aging time, of approximately 30 minutes. Thus, better mechanical properties can be obtained by optimizing the time-temperature schedules for the precipitation hardening process of heat treatable aluminum alloys.

  7. Experimental and numerical modeling of chloride diffusivity in hardened cement concrete considering the aggregate shapes and exposure-duration effects

    NASA Astrophysics Data System (ADS)

    Jie, Wu; Dassekpo, Jean-Baptiste Mawulé; Wan, Chengyong; Zha, Xiaoxiong

    This paper presents an experimental and numerical model describing the effects of the aggregate shapes and exposure duration of chloride diffusion into cement-based materials. A simple chloride diffusion test was performed on a concrete specimen composed of a mixture of cement mortar with crushed granites and round gravels. A simulation was done and the numerical model developed was applied to the matrix at the meso-scale level and the chloride diffusivity was investigated at 30, 60, and 90 days. The experimental and simulation results showed that the aggregate shape and the exposure duration of chloride diffusing into concrete are of high significance. It was indicated that the model with crushed granite presents a good resistance against chloride ingress, while the model with rounded gravels shows some sensitivity to the chloride penetration. It was also found out that when the time dependence of the diffusion coefficient is not taken into account, the diffusion rate will be overestimated. The meso-scale model developed in this study also provides a new method applied in the analysis of the chloride and water transport that causes damage to concrete considering the particle inclusion and the diffusion duration.

  8. Quantifying the distribution of paste-void spacing of hardened cement paste using X-ray computed tomography

    SciTech Connect

    Yun, Tae Sup; Kim, Kwang Yeom; Choo, Jinhyun; Kang, Dong Hun

    2012-11-15

    The distribution of paste-void spacing in cement-based materials is an important feature related to the freeze-thaw durability of these materials, but its reliable estimation remains an unresolved problem. Herein, we evaluate the capability of X-ray computed tomography (CT) for reliable quantification of the distribution of paste-void spacing. Using X-ray CT images of three mortar specimens having different air-entrainment characteristics, we calculate the distributions of paste-void spacing of the specimens by applying previously suggested methods for deriving the exact spacing of air-void systems. This methodology is assessed by comparing the 95th percentile of the cumulative distribution function of the paste-void spacing with spacing factors computed by applying the linear-traverse method to 3D air-void system and reconstructing equivalent air-void distribution in 3D. Results show that the distributions of equivalent void diameter and paste-void spacing follow lognormal and normal distributions, respectively, and the ratios between the 95th percentile paste-void spacing value and the spacing factors reside within the ranges reported by previous numerical studies. This experimental finding indicates that the distribution of paste-void spacing quantified using X-ray CT has the potential to be the basis for a statistical assessment of the freeze-thaw durability of cement-based materials. - Highlights: Black-Right-Pointing-Pointer The paste-void spacing in 3D can be quantified by X-ray CT. Black-Right-Pointing-Pointer The distribution of the paste-void spacing follows normal distribution. Black-Right-Pointing-Pointer The spacing factor and 95th percentile of CDF of paste-void spacing are correlated.

  9. Grout Impregnation of Pre-Placed Recycled Concrete Pavement (RCP) for Rapid Repair of Deteriorated Portland Cement Concrete Airfield Pavement

    DTIC Science & Technology

    2007-04-01

    aggregates in the repair hole, and the voids are filled with a rapid-setting, flowable grout. The results of this study will be used to provide...the repair of spalls involve filling the damaged area with some type of flowable substance which hardens to provide a material that has comparable... filled with Recycled Concrete Pavement (RCP)........................................................................ 53 7 Mixing Pavemend™ material

  10. Foamed well cementing compositions and methods

    SciTech Connect

    Bour, D.L.; Childs, J.D.

    1992-07-28

    This patent describes a method of cementing a well penetrating a salt containing subterranean formation. It comprises: forming a foamed cement composition; placing the foamed cement composition in contact with the salt containing formation; and permitting the foamed cement composition to set in contact with the salt containing formation to form a hardened mass of cement.

  11. Effects of bagging on volatiles and polyphenols in "Wanmi" peaches during endocarp hardening and final fruit rapid growth stages.

    PubMed

    Wang, Yiju; Yang, Chunxiang; Liu, Chunyan; Xu, Man; Li, Shaohua; Yang, Liu; Wang, Younian

    2010-01-01

    Fruits of the late-ripening peach cultivar "Wanmi" were bagged at the early period of fruit endocarp hardening, and the bags were removed 1 wk before maturity harvest. The effects of bagging on volatile compounds and polyphenols were studied. Total volatiles and the sum of C(6) compounds, esters from bagged fruits were significantly lower than from nonbagged fruits from the beginning of the final rapid fruit growth stage to maturity. As the most dominant compounds of C(6) compounds and esters, the lower contents of hexanal, trans-2-hexenal, hexyl acetate, cis-3-hexenyl acetate, and trans-2-hexenyl acetate attributed to the lower content of C(6) compounds and esters in bagged fruit. γ-Hexalactone and δ-decalactone were produced earlier in bagged fruits than in nonbagged ones, suggesting that bagging accelerates fruit maturity. Level of γ-decalactone in bagged fruits was significantly lower than in nonbagged fruits at 159 days after full blossom (DAFB), so did δ-decalactone at 166 DAFB. Bagging did not affect chlorogenic acid and catechol contents of either fruit peel or flesh, nor did it affect contents of keracyanin or quercetin-3-rutinoside in fruit flesh during fruit development. However, keracyanin and quercetin-3-rutinoside levels were significantly reduced in bagged fruit peels before ripening compared to nonbagged fruit peels. Considering the large changes in volatiles and polyphenols, the key stage for "Wanmi" fruit maturity was between 126 DAFB and 147 DAFB, about 1 mo ahead of maturity. © 2010 Institute of Food Technologists®

  12. Meat Feeding Restricts Rapid Cold Hardening Response and Increases Thermal Activity Thresholds of Adult Blow Flies, Calliphora vicina (Diptera: Calliphoridae).

    PubMed

    Coleman, Paul C; Bale, Jeffrey S; Hayward, Scott A L

    2015-01-01

    Virtually all temperate insects survive the winter by entering a physiological state of reduced metabolic activity termed diapause. However, there is increasing evidence that climate change is disrupting the diapause response resulting in non-diapause life stages encountering periods of winter cold. This is a significant problem for adult life stages in particular, as they must remain mobile, periodically feed, and potentially initiate reproductive development at a time when resources should be diverted to enhance stress tolerance. Here we present the first evidence of protein/meat feeding restricting rapid cold hardening (RCH) ability and increasing low temperature activity thresholds. No RCH response was noted in adult female blow flies (Calliphora vicina Robineau-Desvoidy) fed a sugar, water and liver (SWL) diet, while a strong RCH response was seen in females fed a diet of sugar and water (SW) only. The RCH response in SW flies was induced at temperatures as high as 10°C, but was strongest following 3h at 0°C. The CTmin (loss of coordinated movement) and chill coma (final appendage twitch) temperature of SWL females (-0.3 ± 0.5°C and -4.9 ± 0.5°C, respectively) was significantly higher than for SW females (-3.2 ± 0.8°C and -8.5 ± 0.6°C). We confirmed this was not directly the result of altered extracellular K+, as activity thresholds of alanine-fed adults were not significantly different from SW flies. Instead we suggest the loss of cold tolerance is more likely the result of diverting resource allocation to egg development. Between 2009 and 2013 winter air temperatures in Birmingham, UK, fell below the CTmin of SW and SWL flies on 63 and 195 days, respectively, suggesting differential exposure to chill injury depending on whether adults had access to meat or not. We conclude that disruption of diapause could significantly impact on winter survival through loss of synchrony in the timing of active feeding and reproductive development with favourable

  13. Meat Feeding Restricts Rapid Cold Hardening Response and Increases Thermal Activity Thresholds of Adult Blow Flies, Calliphora vicina (Diptera: Calliphoridae)

    PubMed Central

    2015-01-01

    Virtually all temperate insects survive the winter by entering a physiological state of reduced metabolic activity termed diapause. However, there is increasing evidence that climate change is disrupting the diapause response resulting in non-diapause life stages encountering periods of winter cold. This is a significant problem for adult life stages in particular, as they must remain mobile, periodically feed, and potentially initiate reproductive development at a time when resources should be diverted to enhance stress tolerance. Here we present the first evidence of protein/meat feeding restricting rapid cold hardening (RCH) ability and increasing low temperature activity thresholds. No RCH response was noted in adult female blow flies (Calliphora vicina Robineau-Desvoidy) fed a sugar, water and liver (SWL) diet, while a strong RCH response was seen in females fed a diet of sugar and water (SW) only. The RCH response in SW flies was induced at temperatures as high as 10°C, but was strongest following 3h at 0°C. The CTmin (loss of coordinated movement) and chill coma (final appendage twitch) temperature of SWL females (-0.3 ± 0.5°C and -4.9 ± 0.5°C, respectively) was significantly higher than for SW females (-3.2 ± 0.8°C and -8.5 ± 0.6°C). We confirmed this was not directly the result of altered extracellular K+, as activity thresholds of alanine-fed adults were not significantly different from SW flies. Instead we suggest the loss of cold tolerance is more likely the result of diverting resource allocation to egg development. Between 2009 and 2013 winter air temperatures in Birmingham, UK, fell below the CTmin of SW and SWL flies on 63 and 195 days, respectively, suggesting differential exposure to chill injury depending on whether adults had access to meat or not. We conclude that disruption of diapause could significantly impact on winter survival through loss of synchrony in the timing of active feeding and reproductive development with favourable

  14. Responses of the bed bug, Cimex lectularius, to temperature extremes and dehydration: levels of tolerance, rapid cold hardening and expression of heat shock proteins.

    PubMed

    Benoit, J B; Lopez-Martinez, G; Teets, N M; Phillips, S A; Denlinger, D L

    2009-12-01

    This study of the bed bug, Cimex lectularius, examines tolerance of adult females to extremes in temperature and loss of body water. Although the supercooling point (SCP) of the bed bugs was approximately -20 degrees C, all were killed by a direct 1 h exposure to -16 degrees C. Thus, this species cannot tolerate freezing and is killed at temperatures well above its SCP. Neither cold acclimation at 4 degrees C for 2 weeks nor dehydration (15% loss of water content) enhanced cold tolerance. However, bed bugs have the capacity for rapid cold hardening, i.e. a 1-h exposure to 0 degrees C improved their subsequent tolerance of -14 and -16 degrees C. In response to heat stress, fewer than 20% of the bugs survived a 1-h exposure to 46 degrees C, and nearly all were killed at 48 degrees C. Dehydration, heat acclimation at 30 degrees C for 2 weeks and rapid heat hardening at 37 degrees C for 1 h all failed to improve heat tolerance. Expression of the mRNAs encoding two heat shock proteins (Hsps), Hsp70 and Hsp90, was elevated in response to heat stress, cold stress and during dehydration and rehydration. The response of Hsp90 was more pronounced than that of Hsp70 during dehydration and rehydration. Our results define the tolerance limits for bed bugs to these commonly encountered stresses of temperature and low humidity and indicate a role for Hsps in responding to these stresses.

  15. Research of magnesium phosphosilicate cement

    NASA Astrophysics Data System (ADS)

    Ding, Zhu

    Magnesium phosphosilicate cement (MPSC) is a novel phosphate bonded cement, which consists mainly of magnesia, phosphate and silicate minerals. The traditional magnesium phosphate cements (MPCs) usually composed by ammonium phosphate, and gaseous ammonia will emit during mixing and in service. There is no noxious ammonia released from MPSC, furthermore, it can recycle a large volume of the non-hazardous waste. The goal of this research is to investigate the composition, reaction products, reaction mechanism, microstructure, properties, durability and applications of the MPSC. MPSC sets rapidly and has high early strength. It reacts better with solid industrial waste when compared to Portland cement. Many solid industrial wastes, such as fly ash, steel slag, coal gangue, red coal gangue, red mud, barium-bearing slag, copper slag, silica fume, and ground granulated blast furnace slag, have been used as the main component (40% by weight) in MPSC. The research has found that these aluminosilicate (or ironsilicate, or calciumsilicate) minerals with an amorphous or glass structure can enhance the performance of MPSC. The disorganized internal structure of amorphous materials may make it possess higher reactivity compared to the crystalline phases. Chemical reaction between phosphate and these minerals may form an amorphous gel, which is favorable to the cementing. Borax, boric acid and sodium tripolyphosphate have been used as retardants in the MPSC system. It is found that boric acid has a higher retarding effect on the setting of cement, than borax does. However, sodium polyphosphate accelerates the reaction of MPSC. The hydration of MPSC is exothermic reaction. The heat evolution may prompt hydrates formation, and shorten the setting process. Modern materials characterization techniques, XRD, DSC, TG-DTA FTIR, XPS, MAS-NMR, SEM, TEM, MIP, etc. were used to analyze the phase composition, micro morphology, and microstructure of hardened MPSC. The main hydration product

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

    SciTech Connect

    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.

  17. Developing a More Rapid Test to Assess Sulfate Resistance of Hydraulic Cements

    PubMed Central

    Ferraris, Chiara; Stutzman, Paul; Peltz, Max; Winpigler, John

    2005-01-01

    External sulfate attack of concrete is a major problem that can appear in regions where concrete is exposed to soil or water containing sulfates, leading to softening and cracking of the concrete. Therefore, it is important that materials selection and proportioning of concrete in susceptible regions be carefully considered to resist sulfate attack. American Society for Testing Materials (ASTM) limits the tricalcium aluminate phase in cements when sulfate exposure is of concern. The hydration products of tricalcium aluminate react with the sulfates resulting in expansion and cracking. While ASTM standard tests are available to determine the susceptibility of cements to sulfate attack, these tests require at least 6 months and often up to a year to perform; a delay that hinders development of new cements. This paper presents a new method for testing cement resistance to sulfate attack that is three to five times faster than the current ASTM tests. Development of the procedure was based upon insights on the degradation process by petrographic examination of sulfate-exposed specimens over time. Also key to the development was the use of smaller samples and tighter environmental control. PMID:27308177

  18. Effect of 3 cements on white spot lesion formation after full-coverage rapid maxillary expander: A comparative in-vivo study.

    PubMed

    Yagci, Ahmet; Korkmaz, Yasemin Nur; Yagci, Filiz; Atilla, Aykan Onur; Buyuk, Suleyman Kutalmiş

    2016-12-01

    The aim of this study was to assess the effects of 3 luting agents (glass ionomer cement, compomer, and polycarboxylate cement) on white spot lesion formation in patients with full-coverage bonded acrylic splint expanders. White spot lesion formation was assessed with quantitative light-induced fluorescence. Full-coverage rapid maxillary expanders were cemented with glass ionomer cement, compomer, and polycarboxylate cement in groups 1, 2, and 3, respectively. A control group comprised patients who never had orthodontic treatment. Quantitative light-induced fluorescence images taken before and after rapid maxillary expansion treatment were analyzed for these parameters: the percentages of fluorescence loss with respect to the fluorescence of sound tooth tissue (ΔF) and maximum loss of fluorescence intensity in the whole lesion; lesion area with ΔF equal to less than a -5% threshold; and the percentage of fluorescence loss with respect to the fluorescence of sound tissue times the area that indicated lesion volume. All 3 groups showed statistically significantly greater demineralization than the control group. The 3 experimental groups differed from each other in half of the parameters calculated. Teeth in the polycarboxylate group developed the most white spot lesions. With the highest rate of white spot lesion formation, polycarboxylate cements should not be used for full-coverage bonded acrylic splint expanders. Compomers may be preferred over glass ionomer cements, based on the findings of this study. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

  19. The protective effect of rapid cold-hardening develops more quickly in frozen versus supercooled larvae of the Antarctic midge, Belgica antarctica.

    PubMed

    Kawarasaki, Yuta; Teets, Nicholas M; Denlinger, David L; Lee, Richard E

    2013-10-15

    During the austral summer, larvae of the terrestrial midge Belgica antarctica (Diptera: Chironomidae) experience highly variable and often unpredictable thermal conditions. In addition to remaining freeze tolerant year-round, larvae are capable of swiftly increasing their cold tolerance through the rapid cold-hardening (RCH) response. The present study compared the induction of RCH in frozen versus supercooled larvae. At the same induction temperature, RCH occurred more rapidly and conferred a greater level of cryoprotection in frozen versus supercooled larvae. Furthermore, RCH in frozen larvae could be induced at temperatures as low as -12°C, which is the lowest temperature reported to induce RCH. Remarkably, as little as 15 min at -5°C significantly enhanced larval cold tolerance. Not only is protection from RCH acquired swiftly, but it is also quickly lost after thawing for 2 h at 2°C. Because the primary difference between frozen and supercooled larvae is cellular dehydration caused by freeze concentration of body fluids, we also compared the effects of acclimation in dehydrated versus frozen larvae. Because slow dehydration without chilling significantly increased larval survival to a subsequent cold exposure, we hypothesize that cellular dehydration caused by freeze concentration promotes the rapid acquisition of cold tolerance in frozen larvae.

  20. Mineral of the month: cement

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2006-01-01

    Hydraulic cement is a virtually ubiquitous construction material that, when mixed with water, serves as the binder in concrete and most mortars. Only about 13 percent of concrete by weight is cement (the rest being water and aggregates), but the cement contributes all of the concrete’s compressional strength. The term “hydraulic” refers to the cement’s ability to set and harden underwater through the hydration of the cement’s components.

  1. Surface Fatigue Resistance with Induction Hardening

    NASA Technical Reports Server (NTRS)

    Townsend, Dennis; Turza, Alan; Chapman, Mike

    1996-01-01

    Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

  2. In vitro degradation and cytocompatibility of dicalcium phosphate dihydrate cements prepared using the monocalcium phosphate monohydrate/hydroxyapatite system reveals rapid conversion to HA as a key mechanism.

    PubMed

    Alge, Daniel L; Goebel, W Scott; Chu, Tien-Min Gabriel

    2012-04-01

    We previously showed that dicalcium phosphate dihydrate (DCPD) cements can be prepared using monocalcium phosphate monohydrate (MCPM) and hydroxyapatite (HA). In this study, we have characterized the degradation properties and biocompatibility of these novel cements. To study the degradation properties, cements were prepared using MCPM:HA molar ratios of 4:1, 2:1, 2:3, and 2:5. Degradation was evaluated in vitro by static soaking in PBS, and changes in pH, mass, compressive strength, and composition were monitored. Conversion of DCPD to HA was noted in the 4:1 group, which initially consisted of pure DCPD. However, the 2:1 group, which initially consisted of DCPD and an intermediate amount of unreacted HA, underwent rapid conversion to HA associated with significantly greater pH drop and mass loss as well as a complete loss of mechanical integrity. On the basis of these results, we directly compared the cytocompatibility of 2:1 MCPM:HA cements to DCPD cements prepared with an equivalent percent molar excess of β-tricalcium phosphate (β-TCP) using an in vitro cell viability assay. Viability of cells co-cultured with 2:1 MCPM:HA cements was significantly reduced after just 48 h, while viability of cells cultured with the β-TCP-based cements was no different from control cells. In conclusion, this study demonstrates that conversion to HA plays an important role in the degradation of DCPD cements prepared with the MCPM/HA system, affecting both physical properties and cytocompatibility. These results could have important clinical implications for MCPM/HA cements.

  3. The limits of drought-induced rapid cold-hardening: extremely brief, mild desiccation triggers enhanced freeze-tolerance in Eurosta solidaginis larvae.

    PubMed

    Gantz, J D; Lee, Richard E

    2015-02-01

    Rapid cold-hardening (RCH) is a highly conserved response in insects that induces physiological changes within minutes to hours of exposure to low temperature and provides protection from chilling injury. Recently, a similar response, termed drought-induced RCH, was described following as little as 6h of desiccation, producing a loss of less than 10% of fresh mass. In this study, we investigated the limits and mechanisms of this response in larvae of the goldenrod gall fly Eurosta solidaginis (Diptera, Tephritidae). The cold-hardiness of larvae increased markedly after as few as 2h of desiccation and a loss of less than 1% fresh mass, as organismal survival increased from 8% to 41% following exposure to -18 °C. Tissue-level effects of desiccation were observed within 1h, as 87% of midgut cells from desiccated larvae remained viable following freezing compared to 57% of controls. We also demonstrated that drought-induced RCH occurs independently of neuroendocrine input, as midgut tissue desiccated ex vivo displayed improved freeze-tolerance relative to control tissue (78-11% survival, respectively). Finally, though there was an increase in hemolymph osmolality beyond the expected effects of the osmo-concentration of solutes during dehydration, we determined that this increase was not due to the synthesis of glycerol, glucose, sorbitol, or trehalose. Our results indicate that E. solidaginis larvae are extremely sensitive to desiccation, which is a triggering mechanism for one or more physiological pathways that confer enhanced freeze-tolerance.

  4. New steels and methods for induction hardening of bearing rings and rollers

    SciTech Connect

    Ouchakov, B.K.; Shepeljakovsky, K.Z.

    1998-12-31

    The new method of through-surface hardening (TSH) of bearing rings and rollers was developed and used in Russia and former USSR. The principles of the method include the use of special steels of low or controlled hardenability, through-the-section induction of furnace heating and intense quenching of the parts by water stream in special devices. Due to the low hardenability of applied steels, the bearing rings and rollers have high-strength martensitic surface layer, combined with a core strengthened with a troostite and sorbite structure. High compressive residual stresses are formed in the martensitic surface layers. For a long time TSH has been successfully used for inner rings of bearings for railway car boxes, large rings and rollers of bearings for cement furnaces and rolling mills. Recently TSH was used for hollow rollers of railway bearings. For bearing rings made of SAE 52100 type high-carbon, chromium-alloyed steel a new method of low-deformation hardening was developed. The method is based on self-calibration of the rings during the quenching process and is intended for through hardening by induction heating and quenching by rapidly moved water stream.

  5. [Toxicity of glass ionomer cement].

    PubMed

    Lübben, B; Geyer, G

    2001-04-01

    The hybrid bone substitute ionomeric cement achieves a stable and durable space-free bond to adjacent bone during hardening. Clinical studies have evaluated the material differently: Fully hardened ionomeric cement showed in middle ear surgery, e.g. as an ossicular prosthesis, good biocompatibility with outstanding functional results. In a few cases, freshly mixed ionomeric cement led to severe complications after contact with CSF in skull base surgery. Therefore we intended to evaluate the influence of early fluid contact on the quality of cement and to define the interval for a safe application of the material, using a cell culture model. Further we intended to investigate whether combining cement with homologous and alloplastic materials influenced its quality. 1) Ionomeric cement (Ionocem) test bodies were placed in Ringer's solution at different times after the mixing phase. 2) Ionomeric cement (Ionocem) test bodies were coated with different clinically used homologous and alloplastic materials during the setting and hardening phase. The concentrations of released cement-forming ions and the toxic effects on mouse fibroblasts within cell cultures were measured. Cytotoxic effects were observed when ionomeric cement was not carefully protected from fluid contact for the first two hours after mixing. This was due to forced fast elution of large amounts of cement-constituting fluoride ions and aluminium ions and to the development of acid valences and their interactions. A total hardening time of less than 25 min had an especially unfavourable influence on cell behaviour. Cell impairments could be reduced significantly by coating the 30-minute cured cement with PDS sheeting and significantly by covering it with viscous collagene. On the other hand, cement toxicity was intensified in part by combinations with some other coating materials. Ionomeric cement should be kept dry and protected from any fluid contact for at least 30 minutes after mixing. Contact with soft

  6. Environmentally compatible spray cement

    SciTech Connect

    Loeschnig, P.

    1995-12-31

    Within the framework of a European research project, Heidelberger Zement developed a quickly setting and hardening binder for shotcrete, called Chronolith S, which avoids the application of setting accelerators. Density and strength of the shotcrete produced with this spray cement correspond to those of an unaccelerated shotcrete. An increased hazard for the heading team and for the environment, which may occur when applying setting accelerators, can be excluded here. Owing to the special setting properties of a spray cement, the process engineering for its manufacturing is of great importance. The treatment of a spray cement as a dry concrete with kiln-dried aggregates is possible without any problems. The use of a naturally damp pre-batched mixture is possible with Chronolith S but requires special process engineering; spray cement and damp aggregate are mixed with one another immediately before entering the spraying machinery.

  7. Influence of Thermal Treatment Conditions on the Properties of Dental Silicate Cements.

    PubMed

    Voicu, Georgeta; Popa, Alexandru Mihai; Badanoiu, Alina Ioana; Iordache, Florin

    2016-02-18

    In this study the sol-gel process was used to synthesize a precursor mixture for the preparation of silicate cement, also called mineral trioxide aggregate (MTA) cement. This mixture was thermally treated under two different conditions (1400 °C/2 h and 1450 °C/3 h) followed by rapid cooling in air. The resulted material (clinker) was ground for one hour in a laboratory planetary mill (v = 150 rot/min), in order to obtain the MTA cements. The setting time and mechanical properties, in vitro induction of apatite formation by soaking in simulated body fluid (SBF) and cytocompatibility of the MTA cements were assessed in this study. The hardening processes, nature of the reaction products and the microstructural characteristics were also investigated. The anhydrous and hydrated cements were characterized by different techniques e.g., X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) and thermal analysis (DTA-DTG-TG). The setting time of the MTA cement obtained by thermal treatment at 1400 °C/2 h (MTA1) was 55 min and 15 min for the MTA cement obtained at 1450 °C/3 h (MTA2). The compressive strength values were 18.5 MPa (MTA1) and 22.9 MPa (MTA2). Both MTA cements showed good bioactivity (assessed by an in vitro test), good cytocompatibility and stimulatory effect on the proliferation of cells.

  8. Hydraulic Signals from the Roots and Rapid Cell-Wall Hardening in Growing Maize (Zea mays L.) Leaves Are Primary Responses to Polyethylene Glycol-Induced Water Deficits.

    PubMed

    Chazen, O.; Neumann, P. M.

    1994-04-01

    We investigated mechanisms involved in inhibition of maize (Zea mays L.) leaf-elongation growth following addition of non-penetrating osmolyte to the root medium. The elongation rate of the first true leaf remained inhibited for 4 h after addition of polyethylene glycol 6000 (PEG; -0.5 MPa water potential), despite progressive osmotic adjustment in the growing leaf tissues. Thus, inhibition of leaf growth did not appear to be directly related to loss of leaf capacity to maintain osmotic potential gradients. Comparative cell-wall-extension capacities of immature (still expanding) leaf tissues were measured by creep extensiometry using whole plants. Reductions in irreversible (plastic) extension capacity (i.e. wall hardening) were detected minutes and hours after addition of PEG to the roots, by both in vivo and in vitro assay. The onset of the wall-hardening response could be detected by in vitro assay only 2 min after addition of PEG. Thus, initiation of wall hardening appeared to precede transcription-regulated responses. The inhibition of both leaf growth and wall-extension capacity was reversed by removal of PEG after 4 h. Moreover, wall hardening could be induced by other osmolytes (mannitol, NaCl). Thus, the leaf responses did not appear to be related to any specific (toxic) effect of PEG. We conclude that hardening of leaf cell walls is a primary event in the chain of growth regulatory responses to PEG-induced water deficits in maize. The signaling processes by which PEG, which is not expected to penetrate root cell walls or membranes, might cause cell-wall hardening in relatively distant leaves was also investigated. Plants with live or killed roots were exposed to PEG. The killed roots were presumed to be unable to produce hormonal or electrical signals in response to addition of PEG; however, inhibition of leaf elongation and hardening of leaf cell walls were detected with both live and killed roots. Thus, neither hormonal signaling nor signaling via

  9. Hardening of the arteries

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000171.htm Hardening of the arteries To use the sharing features on this page, please enable JavaScript. Hardening of the arteries, also called atherosclerosis, occurs when ...

  10. Reactions in glass ionomer cements: V. Effect of incorporating tartaric acid in the cement liquid.

    PubMed

    Crisp, S; Wilson, A D

    1976-01-01

    A description is give of the effect on the ASPA cement reaction of tartaric acid incorporated in the cement liquid. Tartaric acid acts as an accelerator that aids in the extraction of ions from the aluminosilicate glass and facilitates their binding to the polyanion chains. Postgelation hardening is significantly increased. Working time is unaffected possibly because cations are initially present as complexes.

  11. Case hardening of steel

    SciTech Connect

    Not Available

    1987-01-01

    The first chapter lays the groundwork for an understanding by covering absorption and diffusion of carbon, and the application of equilibrium data. Gas carburizing methods are presented, followed by other gaseous case hardening methods. Then, liquid case-hardening methods are discussed. Vacuum carburizing and pack carburizing are treated in a separate chapter. The second half of the volume deals with specific topics in relation to case hardening. First, heat-treatment considerations are presented, including chapters on cleaning and handling of parts, heat treatment, and furnaces and furnace parts and fixtures used in case hardening. The next chapter presents information on instrumentation and control the first section discussing temperature measurement and the second dealing with instrumentation for controlling carbonaceous atmospheres. Testing inspection and quality control are covered in sections detailing inspection and quality control, hardness testing of case-hardened parts, and methods of measuring case depth. The final chapter is an atlas of microstructures and macrostructures of case hardened parts.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  13. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

    Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

    1973-01-01

    Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

  14. Hardening [Chapter 12

    Treesearch

    Douglass F. Jacobs; Thomas D. Landis

    2009-01-01

    To promote survival and growth following outplanting, nursery stock must undergo proper hardening. Without proper hardening, plants do not store well over winter and are likely to grow poorly or die on the outplanting site. It is important to understand that native plant nurseries are different from traditional horticultural systems in that native plants must endure an...

  15. Well cementing in permafrost

    SciTech Connect

    Wilson, W.N.

    1980-01-01

    A process for cementing a string of pipe in the permafrost region of a borehole of a well wherein aqueous drilling fluid actually used in drilling the wellbore in the permafrost region of a wellbore is employed. The drilling fluid contains or is adjusted to contain from about 2 to about 16 volume percent solids. Mixing with the drilling fluid (1) an additive selected from the group consisting of ligno-sulfonate, lignite, tannin, and mixtures thereof, (2) sufficient base to raise the pH of the drilling fluid into the range of from about 9 to about 12, and (3) cementitious material which will harden in from about 30 to about 40 hours at 40/sup 0/F. The resulting mixture is pumped into the permafrost region of a wellbore to be cemented and allowed to harden in the wellbore. There is also provided a process for treating an aqueous drilling fluid after it has been used in drilling the wellbore in permafrost, and a cementitious composition for cementing in a permafrost region of a wellbore.

  16. Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: cement hydration, strength development and volume stability.

    PubMed

    Berger, Stéphane; Cau Dit Coumes, Céline; Le Bescop, Patrick; Damidot, Denis

    2011-10-30

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl(2) mixing solution was characterized over one year as a function of the gypsum content of the binder and the thermal history of the material. Blending the CSA clinker with 20% gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, strätlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the gypsum content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes.

  17. Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

    DOEpatents

    Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

    1997-01-01

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points.

  18. Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

    DOEpatents

    Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

    1997-10-28

    The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points. 2 figs.

  19. Bone cement

    PubMed Central

    Vaishya, Raju; Chauhan, Mayank; Vaish, Abhishek

    2013-01-01

    The knowledge about the bone cement is of paramount importance to all Orthopaedic surgeons. Although the bone cement had been the gold standard in the field of joint replacement surgery, its use has somewhat decreased because of the advent of press-fit implants which encourages bone in growth. The shortcomings, side effects and toxicity of the bone cement are being addressed recently. More research is needed and continues in the field of nanoparticle additives, enhanced bone–cement interface etc. PMID:26403875

  20. An Anisotropic Hardening Model for Springback Prediction

    SciTech Connect

    Zeng, Danielle; Xia, Z. Cedric

    2005-08-05

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

  1. 42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    42. INTERIOR VIEW OF THE NAIL HARDENER USED TO HARDEN AND TEMPER THE NAILS; WEST TUBES IN FOREGRPUND AND DRAWBACK TUBE IN THE CENTER - LaBelle Iron Works, Thirtieth & Wood Streets, Wheeling, Ohio County, WV

  2. Calcium Orthophosphate Cements and Concretes

    PubMed Central

    Dorozhkin, Sergey V.

    2009-01-01

    In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone), calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  3. Squeeze cement method using coiled tubing

    SciTech Connect

    Underdown, D.R.; Ashford, J.D.; Harrison, T.W.; Eastlack, J.K.; Blount, C.G.; Herring, G.D.

    1986-12-09

    A method is described of squeeze cementing a well wherein the well has a casing throughout the wellbore, casing cement between the casing and the wellbore of the well, perforations through the casing and the casing cement to establish fluid communication between the interior of the casing and a formation adjacent the perforations, channels in the casing cement in fluid communication with at least some of the perforations, a well tubing string in the casing extending from the surface to the proximity of the perforations, and a packer means for sealing between the tubing and the casing above the perforations. The method consists of: isolating the casing adjacent the perforations; lowering a coiled tubing down the well tubing string to a point adjacent the perforations; flowing uncontaminated squeeze cement through the coiled tubing and through the perforations into the channels; flowing a cement contaminating liquid down the coiled tubing to mix with the squeeze cement remaining in the casing; allowing the uncontaminated squeeze cement in the channels to harden; and removing the contaminated squeeze cement from the casing through the coiled tubing.

  4. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  5. RHOBOT: Radiation hardened robotics

    SciTech Connect

    Bennett, P.C.; Posey, L.D.

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  6. Nuclear effects hardened shelters

    NASA Astrophysics Data System (ADS)

    Lindke, Paul

    1990-11-01

    The Houston Fearless 76 Government Projects Group has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8' x 8' x 22' nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Corrpartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters. The specific levels of hardening to which the shelters were designed are classified and will not be mentioned during this presentation.

  7. Precipitation, strength and work hardening of age hardened aluminium alloys

    NASA Astrophysics Data System (ADS)

    Ryen, Ø.; Holmedal, B.; Marthinsen, K.; Furu, T.

    2015-08-01

    The strength and work hardening of age hardened AA6063 and AA6082 alloys have been investigated in terms of a detailed characterization of precipitate and dislocation structures obtained by TEM and SEM. Tensile and compression tests were performed at as quenched, peak aged and severely aged conditions. A strong work hardening in the as quenched condition was found, similar to AlMg alloys with twice as much alloying elements in solid solution. It was found that the initial work hardening rate and the critical failure strain are both smallest at the peak aged condition. During large deformations the needle-shaped precipitates are sheared uniformly by dislocations altering their <001> orientations, which indicates extensive cross slip. In the overaged condition the early initial work hardening is larger than at the peak aged condition, but followed by a weak linear work hardening, apparently directly entering stage IV at a low strain. Cracked, needle-shaped precipitates were seen at larger strains.

  8. Thermal Shock-resistant Cement

    SciTech Connect

    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

  9. Iron oxide nanoparticles significantly enhances the injectability of apatitic bone cement for vertebroplasty.

    PubMed

    Vlad, María Daniela; del Valle, Luis J; Barracó, Marc; Torres, Ricardo; López, José; Fernández, Enrique

    2008-10-01

    Experimental study to characterize the setting and the cytocompatibility properties of apatitic bone cement. To investigate the setting, flowing, and biocompatibility properties of new iron-modified calcium phosphate bone cements. Vertebroplasty and kyphoplasty are efficient procedures for the treatment of painful vertebral compression fractures. Nowadays, calcium phosphate cements are used to treat these fractures mainly due to the similar bone apatitic phase formed after setting. However, clinicians have reported great difficulties in filling the vertebral bodies due to the high pressures needed to inject these materials. Thus, new approaches are needed to improve the initial flowing properties of these cements without affecting or even improving their short-term mechanical stability and their long-term in vivo cement transformation into bone tissue. Cement setting times were measured by the Gillmore needles method. The evolution of the compressive strength accounted for the cement hardening process. Scanning Electron Microscopy followed the evolution of the cement microstructure with hardening. Radiograph diffraction analysis confirmed the evolution of the crystalline phases underlying the setting and the hardening processes. Injectability tests were performed by using syringes filled with bone cement and recording the evolution of the injection force needed to empty the syringe. Finally, the cytocompatibility was analyzed by culturing human epithelial cells onto the cements and evaluating both the relative cell viability and the adhesion cell density. The modification of the powder phase of an alpha-tricalcium phosphate cement with iron oxide nanopar-ticles significantly enhanced, at constant liquid to powder cement mixing ratio, the resulting cement injectability by lowering the extrusion force required for cement delivery. For example, 24 wt% iron oxide addition resulted in 83% of cement injected with an extrusion force lower than 25 N. In fact, the setting

  10. Improved microstructure of cement-based composites through the addition of rock wool particles

    SciTech Connect

    Lin, Wei-Ting; Cheng, An; Huang, Ran; Zou, Si-Yu

    2013-10-15

    Rock wool is an inorganic fibrous substance produced by steam blasting and cooling molten glass. As with other industrial by-products, rock wool particles can be used as cementitious materials or ultra fine fillers in cement-based composites. This study investigated the microstructure of mortar specimens produced with cement-based composites that include various forms of rock wool particles. It conducted compressive strength testing, rapid chloride penetration tests, X-ray diffraction analysis, thermo-gravimetric analysis, and scanning electronic microscopy to evaluate the macro- and micro-properties of the cement-based composites. Test results indicate that inclusion of rock wool particles in composites improved compressive strength and reduced chloride ion penetration at the age of 91 days due to the reduction of calcium hydroxide content. Microscopic analysis confirms that the use of rock wool particles contributed to the formation of a denser, more compact microstructure within the hardened paste. In addition, X-ray diffraction analysis shows few changes in formation of pozzolanic reaction products and no new hydrations are formed with incorporating rock wool particles. - Highlights: • We report the microstructural characterization of cement-based composites. • Different mixes produced with various rock wool particles have been tested. • The influence of different mixes on macro and micro properties has been discussed. • The macro properties are included compressive strength and permeability. • XRD and SEM observations confirm the pozzolanic reaction in the resulting pastes.

  11. Optimization of fly ash as sand replacement materials (SRM) in cement composites containing coconut fiber

    NASA Astrophysics Data System (ADS)

    Nadzri, N. I. M.; Jamaludin, S. B.; Mazlee, M. N.; Jamal, Z. A. Z.

    2016-07-01

    The need of utilizing industrial and agricultural wastes is very important to maintain sustainability. These wastes are often incorporated with cement composites to improve performances in term of physical and mechanical properties. This study presents the results of the investigation of the response of cement composites containing coconut fiber as reinforcement and fly ash use as substitution of sand at different hardening days. Hardening periods of time (7, 14 and 28 days) were selected to study the properties of cement composites. Optimization result showed that 20 wt. % of fly ash (FA) is a suitable material for sand replacement (SRM). Meanwhile 14 days of hardening period gave highest compressive strength (70.12 MPa) from the cement composite containing 9 wt. % of coconut fiber and fly ash. This strength was comparable with the cement without coconut fiber (74.19 MPa) after 28 days of curing.

  12. Practical aspects of systems hardening

    SciTech Connect

    Shepherd, W.J.

    1989-01-01

    Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system.

  13. Industrial Hardening Demonstration.

    DTIC Science & Technology

    1980-09-01

    less severe conditions than thermal cracking (850’ - 950°F and 10 to 20 psi). Zeolitic or molecular sieve- base catalysts are used. Catalytic reforming...with Potential Industrial Hardening A-1 Participants B Post-Attack Petroleum Refining (and Production) B-1 from Crude Oil V List of Figures Number Page...the Key Worker Shelter 116 viii B-1 Proportions of the Products Obtained by Distillation B-2 of Six Crude Oils B-2 Generalized Flow Chart of the

  14. Effect of carbon dioxide injection on production of wood cement composites from waste medium density fiberboard (MDF).

    PubMed

    Qi, H; Cooper, P A; Wan, H

    2006-01-01

    The possibility of recycling waste medium density fiberboard (MDF) into wood-cement composites was evaluated. Both new fibers and recycled steam exploded MDF fibers had poor compatibility with cement if no treatment was applied, due to interference of the hydration process by the water soluble components of the fiber. However, this issue was resolved when a rapid hardening process with carbon dioxide injection was adopted. It appears that the rapid carbonation allowed the board to develop considerable strength before the adverse effects of the wood extractives could take effect. After 3-5 min of carbon dioxide injection, the composites reached 22-27% of total carbonation and developed 50-70% of their final (28-day) strength. Composites containing recycled MDF fibers had slightly lower splitting tensile strength and lower tensile toughness properties than those containing new fibers especially at a high fiber/cement ratio. Composites containing recycled MDF fibers also showed lower values of water absorption. Unlike composites cured conventionally, composites cured under CO(2) injection developed higher strength and toughness with increased fiber content. Incorporation of recycled MDF fibers into wood cement composites with CO(2) injection during the production stage presents a viable option for recycling of this difficult to manage waste material.

  15. Squeeze cementing

    SciTech Connect

    Ewert, D.P.; Kundert, D.P.; Dahl, J.A.; Dalrymple, E.D.; Gerke, R.R.

    1992-06-16

    This patent describes a method for terminating the flow of fluid from a portion of a subterranean formation into a wellbore. It comprises: placing within the wellbore adjacent the portion a volume of a slurry of hydraulic cement, permitting the volume to penetrate into the portion; and maintaining the slurry in the portion for a time sufficient to enable the slurry to form a rigid mass of cement in the portion.

  16. Method and composition for cementing in a wellbore

    SciTech Connect

    Carpenter, R.B.; Jones, R.R.

    1990-11-06

    This patent describes a method of cementing in a wellbore penetrating subterranean formations. It comprises: mixing a predetermined quantity of Portland cement containing at least 2 percent by weight of the predetermined quantity of Portland cement of tricalcium aluminate; at least 2 percent by weight of the predetermined quantity of the Portland cement of gypsum; and 0.3--2.0 percent by weight of the predetermined Portland cement of polyvinyl alcohol that is formed by less than 92 percent hydrolysis of the acetate moieties of polyvinyl acetate to polyvinyl alcohol; and sufficient water to form a pumpable cement slurry; and pumping the slurry to a desired location in the wellbore; and allowing the slurry to harden to a solid mass.

  17. Development of nanosilica bonded monetite cement from egg shells.

    PubMed

    Zhou, Huan; Luchini, Timothy J F; Boroujeni, Nariman Mansouri; Agarwal, Anand K; Goel, Vijay K; Bhaduri, Sarit B

    2015-05-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5±1 min. The compressive strength after 24h of incubation was approximately 8.45±1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10±1 min) process by about 2.5 min and improve compressive strength (20.16±4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics.

  18. Influence of Solids-to-liquid and Activator Ratios on Calcined Kaolin Cement Powder

    NASA Astrophysics Data System (ADS)

    Liew, Y. M.; Kamarudin, H.; Bakri, A. M. Mustafa Al; Binhussain, M.; Luqman, M.; Nizar, I. Khairul; Ruzaidi, C. M.; Heah, C. Y.

    This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolymer slurry was produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground to obtain cement powder. Ultilizing the concept of "just adding water", hardened cement paste could be produced from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing route to produce cement powder by "just adding water" was possible, and the structure became denser and fewer unreacted particles were observed.

  19. Properties and hydration products of lightweight and expansive cements. Part II: Hydration products

    SciTech Connect

    Lilkov, V.; Djabarov, N.; Bechev, G.; Petrov, O.

    1999-10-01

    The type and quantity of hydration products in cement stone (plain cement, lightweight cement with cenospheres, and cement mixed with expansive additive) hydrated at 20 and 75 C were studied. The changes in the cement stone structure under the influence of lightweight and expansive additives and raised hardening temperature were studied with complex thermal analysis, infrared spectroscopy, powder X-ray diffraction analysis, and scanning electron microscopy. In the case of raised hardening temperature, the cenospheres and the expansive additive improve the crystallization of hydration products. A chemical reaction between the cenospheres and portlandite formed from the cement hydration was observed, accompanied by a decrease of the portlandite quantity. The expansive additive stimulates the formation of hydration products, which were thermally stable and decompose at temperatures above 600 C.

  20. Physical and thermal behavior of cement composites reinforced with recycled waste paper fibers

    NASA Astrophysics Data System (ADS)

    Hospodarova, Viola; Stevulova, Nadezda; Vaclavik, Vojtech; Dvorsky, Tomas

    2017-07-01

    In this study, three types of recycled waste paper fibers were used to manufacture cement composites reinforced with recycled cellulosic fibers. Waste cellulosic fibers in quantity of 0.2, 0.3, and 0.5 wt.% were added to cement mixtures. Physical properties such as density, water capillarity, water absorbability and thermal conductivity of fiber cement composites were studied after 28 days of hardening. However, durability of composites was tested after their water storage up to 90 days. Final results of tested properties of fiber cement composites were compared with cement reference sample without cellulosic fibers.

  1. Cement Burns

    PubMed Central

    Alam, Munir; Moynagh, M.; Lawlor, C.

    2007-01-01

    Objective: Cement burns account for relatively few admissions to a burn unit; however, these burns deserve separate consideration because of special features of diagnosis and management. Cement burns, even though potentially disabling, have rarely been reported in literature. Methods: A retrospective review was performed of all patients admitted with cement burns injuries to the national burns unit at the St James's Hospital in Dublin, Ireland, over a 10-year period for the years 1996–2005. Results: A total of 46 patients with cement burns were admitted. The majority of patients were aged 16–74 years (mean age = 32 years). Eighty-seven percent of injuries occurred in an industrial and 13% in a domestic setting. The upper and lower extremities were involved in all the patients, and the mean total body surface area affected was 6.5%. The mean length of hospital stay was 21 days with a range of 1–40 days. Thirty-eight (82%) were surgically managed involving debridement and split-thickness skin graft (SSG) and four (9%) were conservatively managed. A further four did not have data available. Conclusion: Widespread inexperience in dealing with this group of cement burns patients and delays in referral to burns unit highlights the potential for greater levels of general awareness and knowledge in both prevention and treatment of these burns. As well, early debridement and split-thickness skin grafting at diagnosis constitutes the best means of reducing the high socioeconomic costs and allows for early return to work. PMID:18091981

  2. Industrial Hardening: 1980 Technical Report.

    DTIC Science & Technology

    1981-06-01

    AD-AI02 621 SCIENTIFIC SERVICE INC REDWOOD CITY CA F/6 15/3 INDUSTRIAL HARDENING: 1980 TECHNICAL REPORT . (U) JUN 81 J V ZACCOR, C WILTON. R D BERNARD...INDUSTRIAL HARDENING. 1980 TECHNICAL REPORT zFINAL REPORT OL ELTC : -. brCc -i ’ Approved for public release; Contract No. EMW-C-0154 distribution...TYPE Of REPORT & PERIOD COVERED INDUSTRIAL HARDENING: 198k TECHNICAL REPORT , Final Ppoe t *PEg 8’Wo-C"EPT UMBER 7. AUTHOR(@) S. CONTRACT OR GRANT

  3. A study of latent hardening behavior in aluminum single crystals

    SciTech Connect

    Wang Mingzhang; Lin Shi; Li Chenghua; Xiao Jimei; Wang Zhongguang

    1996-11-15

    In order to obtain a better understanding or a complete description of plastic properties of polycrystals, especially in polycrystal modelling viewpoint, investigations on latent hardening behavior of single crystals have been performed in a great number. Recently, however, Wu et al. have pointed out that the definition of the yield stress of latent system using the conventional back extrapolation is ambiguous in terms of determining the latent hardening moduli because the initial rapid work-hardening of the transient zone is neglected. They proposed a more precise measure of the yield stress of latent system based on the decrease of the tangent modulus from the linear elastic modulus, and showed that the latent hardening, which would not plus the initial work-hardening of the transient zone, is actually lower than that obtained from the backward extrapolation. Thus, in their opinion, it is considered that the hardening behavior of latent system (such as the directionality, the effects of relative orientation and prestrain) need be newly or further studied in detail. Single crystals of aluminum have been grown with high purity to investigate this behavior.

  4. [Aluminous cement for dental application (author's transl)].

    PubMed

    Takeda, S

    1982-01-01

    The various materials such as zinc oxide eugenol pastes, calcium hydroxide slurry and self hardening polymers have been used for the root canal filling and pulp capping. However, those materials have various problems in terms of biocompatibility and physical properties in clinical use. The development of root canal filling and pulp capping materials has been carried out with powder-liquid system which consisted of aluminous cement added to 20 wt% Ca (OH)2 and polyvinylalcohol solutions. The influence of polyvinylalcohol concentrations and L/P ratio on physical properties and biocompatibility were investigated. The results were as follows: 1. The initial setting time was showed between 3 and 20 minutes according to polyvinylalcohol concentration and L/P ratio and delayed linearly by increasing the L/P ratio. 2. The consistency was indicated between 18 and 51 mm with polyvinylalcohol concentration and L/P ratio. The lower the L/P ratio, the thicker was the consistency. 3. The solubilities in distilled water were 2.7-7.3% and 3.9-8.4%, respectively, after storage for 24 hours and 1 week, while those values in 199 medium were 2.9-6.2% and 4.4-9.9%, respectively, after storage for 24 hours and 1 week. 4. The pH values in distilled water were indicated high alkaline conditions of about 11.5 after storage for 24 hours and was not influenced by the repeated immersions. On the other hand, the pH values in 199 medium were showed high alkaline conditions of about 11.0 after storage for 24 hours, but decreased rapidly to the neutral conditions of about 8.0 with the repeated immersion. 5. The compressive strengths were increased by the use of higher polyvinylalcohol concentration and lower L/P ratio and indicated from 26 kg/cm2 and 278 kg/cm2. 6. By the use of the tissue culture method, mild response with the un-set cement was recognized from the morphological observation. In the case of the set cement, the cell morphological changes showed no significant difference in the

  5. Investigation on the potential of waste cooking oil as a grinding aid in Portland cement.

    PubMed

    Li, Haoxin; Zhao, Jianfeng; Huang, Yuyan; Jiang, Zhengwu; Yang, Xiaojie; Yang, Zhenghong; Chen, Qing

    2016-12-15

    Although there are several methods for managing waste cooking oil (WCO), a significant result has not been achieved in China. A new method is required for safe WCO management that minimizes the environmental threat. In this context, this work was developed in which cement clinker and gypsum were interground with various WCOs, and their properties, such as grindability, water-cement ratio required to achieve a normal consistency, setting times, compressive strength, contents of calcium hydroxide and ettringite in the hardened paste, microstructure and economic and environmental considerations, were addressed in detail. The results show that, overall, WCO favorably improves cement grinding. WCO prolonged the cement setting times and resulted in longer setting times. Additionally, more remarkable effects were found in cements in which WCO contained more unsaturated fatty acid. WCOs increased the cement strength. However, this enhancement was rated with respect to the WCO contents and components. WCOs decreased the CH and AFt contents in the cement hardened paste. Even the AFt content at later ages was reduced when WCO was used. WCO also densify microstructure of the hardened cement paste. It is economically and environmentally feasible to use WCOs as grinding aids in the cement grinding process. These results contribute to the application of WCOs as grinding aids and to the safe management of WCO. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Self-setting bioactive calcium-magnesium phosphate cement with high strength and degradability for bone regeneration.

    PubMed

    Wu, Fan; Wei, Jie; Guo, Han; Chen, Fangping; Hong, Hua; Liu, Changsheng

    2008-11-01

    Calcium phosphate cement (CPC) has been successfully used in clinics as bone repair biomaterial for many years. However, poor mechanical properties and a low biodegradation rate limit any further applications. Magnesium phosphate cement (MPC) is characterized by fast setting, high initial strength and relatively rapid degradation in vivo. In this study, MPC was combined with CPC to develop novel calcium-magnesium phosphate cement (CMPC). The setting time, compressive strength, phase composition of hardened cement, degradation in vitro, cells responses in vitro by MG-63 cell culture and tissue responses in vivo by implantation of CMPC in bone defect of rabbits were investigated. The results show that CMPC has a shorter setting time and markedly better mechanical properties than either CPC or MPC. Moreover, CMPC showed significantly improved degradability compared to CPC in simulated body fluid. Cell culture results indicate that CMPC is biocompatible and could support cell attachment and proliferation. To investigate the in vivo biocompatibility and osteogenesis, the CMPC samples were implanted into bone defects in rabbits. Histological evaluation showed that the introduction of MPC into CPC enhanced the efficiency of new bone formation. CMPC also exhibited good biocompatibility, biodegradability and osteoconductivity with host bone in vivo. The results obtained suggest that CMPC, having met the basic requirements of bone tissue engineering, might have a significant clinical advantage over CPC, and may have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery.

  7. System-Level Radiation Hardening

    NASA Technical Reports Server (NTRS)

    Ladbury, Ray

    2014-01-01

    Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.

  8. Development of fluorapatite cement for dental enamel defects repair.

    PubMed

    Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

  9. Laboratory Electrical Resistivity Studies on Cement Stabilized Soil

    PubMed Central

    Lokesh, K. N.; Jacob, Jinu Mary

    2017-01-01

    Electrical resistivity measurement of freshly prepared uncured and cured soil-cement materials is done and the correlations between the factors controlling the performance of soil-cement and electrical resistivity are discussed in this paper. Conventional quality control of soil-cement quite often involves wastage of a lot of material, if it does not meet the strength criteria. In this study, it is observed that, in soil-cement, resistivity follows a similar trend as unconfined compressive strength, with increase in cement content and time of curing. Quantitative relations developed for predicting 7-day strength of soil-cement mix, using resistivity of the soil-cement samples at freshly prepared state, after 1-hour curing help to decide whether the soil-cement mix meets the desired strength and performance criteria. This offers the option of the soil-cement mix to be upgraded (possibly with additional cement) in its fresh state itself, if it does not fulfil the performance criteria, rather than wasting the material after hardening. PMID:28540364

  10. A new method to analyze copolymer based superplasticizer traces in cement leachates.

    PubMed

    Guérandel, Cyril; Vernex-Loset, Lionel; Krier, Gabriel; De Lanève, Michel; Guillot, Xavier; Pierre, Christian; Muller, Jean François

    2011-03-15

    Enhancing the flowing properties of fresh concrete is a crucial step for cement based materials users. This is done by adding polymeric admixtures. Such additives have enabled to improve final mechanicals properties and the development of new materials like high performance or self compacting concrete. Like this, the superplasticizers are used in almost cement based materials, in particular for concrete structures that can have a potential interaction with drinking water. It is then essential to have suitable detection techniques to assess whether these organic compounds are dissolved in water after a leaching process or not. The main constituent of the last generation superplasticizer is a PolyCarboxylate-Ester copolymer (PCE), in addition this organic admixture contains polyethylene oxide (free PEO) which constitutes a synthesis residue. Numerous analytical methods are available to characterize superplasticizer content. Although these techniques work well, they do not bring suitable detection threshold to analyze superplasticizer traces in solution with high mineral content such as leachates of hardened cement based materials formulated with superplasticizers. Moreover those techniques do not enable to distinguish free PEO from PCE in the superplasticizer. Here we discuss two highly sensitive analytical methods based on mass spectrometry suitable to perform a rapid detection of superplasticizer compounds traces in CEM I cement paste leachates: MALDI-TOF mass spectrometry, is used to determine the free PEO content in the leachate. However, industrial copolymers (such as PCE) are characterized by high molecular weight and polymolecular index. These two parameters lead to limitation concerning analysis of copolymers by MALDI-TOFMS. In this study, we demonstrate how pyrolysis and a Thermally assisted Hydrolysis/Methylation coupled with a triple-quadrupole mass spectrometer, provides good results for the detection of PCE copolymer traces in CEM I cement paste

  11. Contact allergy to epoxy hardeners.

    PubMed

    Aalto-Korte, Kristiina; Suuronen, Katri; Kuuliala, Outi; Henriks-Eckerman, Maj-Len; Jolanki, Riitta

    2014-09-01

    Diglycidylether of bisphenol A resin is the most important sensitizer in epoxy systems, but a minority of patients develop concomitant or solitary contact allergy to epoxy hardeners. At the Finnish Institute of Occupational Health, several in-house test substances of epoxy hardeners have been tested in a special epoxy compound patch test series. To analyse the frequency and clinical relevance of allergic reactions to different epoxy hardeners. Test files (January 1991 to March 2013) were screened for contact allergy to different epoxy hardeners, and the clinical records of patients with allergic reactions were analysed for occupation, concomitant allergic reactions, and exposure. The most commonly positive epoxy hardeners were m-xylylenediamine (n = 24), 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP; n = 14), isophorone-diamine (n = 12), and diethylenetriamine (n = 9). Trimethylhexamethylenediamine (n = 7), tetraethylenepentamine (n = 4), and triethylenetetramine (n = 2) elicited some reactions, although most patients were found to have no specific exposure. Allergic reactions to hexamethylenetetramine, dimethylaminopropylamine and ethylenediamine dihydrochloride were not related to epoxy products. Tris-DMP is an important sensitizer in epoxy hardeners, and should be included in the patch test series of epoxy chemicals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Mesoscale texture of cement hydrates

    PubMed Central

    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

    2016-01-01

    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

  13. Case hardenability at high carbon levels

    SciTech Connect

    Walton, H.W.

    1995-02-01

    Loss of hardenability in the case was thought to be responsible for a lower than specified hardness found on a large carburized bushing. Pseudo Jominy testing on several high hardenability carburizing grades confirmed that hardenability fade was present at carbon levels above 0.65% and particularly for those steels containing molybdenum. Analysis of previous work provided a formula for calculating Jominy hardenability at various carbon levels. Again the results confirmed that the loss of hardenability was more severe in steels containing molybdenum.

  14. Experimental Study on Artificial Cemented Sand Prepared with Ordinary Portland Cement with Different Contents

    PubMed Central

    Li, Dongliang; Liu, Xinrong; Liu, Xianshan

    2015-01-01

    Artificial cemented sand test samples were prepared by using ordinary Portland cement (OPC) as the cementing agent. Through uniaxial compression tests and consolidated drained triaxial compression tests, the stress-strain curves of the artificial cemented sand with different cementing agent contents (0.01, 0.03, 0.05 and 0.08) under various confining pressures (0.00 MPa, 0.25 MPa, 0.50 MPa and 1.00 MPa) were obtained. Based on the test results, the effect of the cementing agent content (Cv) on the physical and mechanical properties of the artificial cemented sand were analyzed and the Mohr-Coulomb strength theory was modified by using Cv. The research reveals that when Cv is high (e.g., Cv = 0.03, 0.05 or 0.08), the stress-strain curves of the samples indicate a strain softening behavior; under the same confining pressure, as Cv increases, both the peak strength and residual strength of the samples show a significant increase. When Cv is low (e.g., Cv = 0.01), the stress-strain curves of the samples indicate strain hardening behavior. From the test data, a function of Cv (the cementing agent content) with c′ (the cohesion force of the sample) and Δϕ′ (the increment of the angle of shearing resistance) is obtained. Furthermore, through modification of the Mohr-Coulomb strength theory, the effect of cementing agent content on the strength of the cemented sand is demonstrated. PMID:28793418

  15. Strain Hardening in Polymer Glasses: Limitations of Network Models

    NASA Astrophysics Data System (ADS)

    Hoy, Robert S.; Robbins, Mark O.

    2007-09-01

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.

  16. Strain hardening in polymer glasses: limitations of network models.

    PubMed

    Hoy, Robert S; Robbins, Mark O

    2007-09-14

    Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic rearrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.

  17. Lunar cement

    NASA Technical Reports Server (NTRS)

    Agosto, William N.

    1992-01-01

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

  18. Cryogenics with cement microscopy redefines cement behavior

    SciTech Connect

    Mehta, S.; Jones, R. ); Caveny, B. )

    1994-10-03

    Cement microscopy (CM), cryogenics, environmental scanning microscopy (ESM), scanning electron microscopy (SEM), and other technologies are leading investigators to change their views on cement gelation, hydration, and retardation. Cement samples frozen in a nitrogen slush and viewed with an SEM present a more accurate picture of the setting process. Observations made through this technique have revolutionized ARCO Exploration and Production Technology's and Halliburton Energy Services' oil field cement procurement and slurry design. Findings from this joint study are expected to lead to: optimized waiting on cement (WOC) times; reduced planning and design time; optimized slurry retarder additions; optimized gel times to fit given situations; especially applicable to squeeze operations; improved cement selection (from vendors) for peak performance; and improved cement manufacture. The paper discusses the measuring methods and the findings on the following: cement voids, cement gelation, and retardation mechanisms. It also briefly discusses the impact these discoveries have on operations.

  19. The Use of a Simple Enzyme Assay in 'Seed-Hardening' Studies

    ERIC Educational Resources Information Center

    Ead, J.; Devonald, V. G.

    1975-01-01

    Describes a single technique for an enzyme assay of catalase. The method shows that vegetable seeds submitted to pre-sowing 'hardening' cycles of imbition and drying have greater catalase activity and more rapid germination than do the controls. (LS)

  20. The Use of a Simple Enzyme Assay in 'Seed-Hardening' Studies

    ERIC Educational Resources Information Center

    Ead, J.; Devonald, V. G.

    1975-01-01

    Describes a single technique for an enzyme assay of catalase. The method shows that vegetable seeds submitted to pre-sowing 'hardening' cycles of imbition and drying have greater catalase activity and more rapid germination than do the controls. (LS)

  1. Sculpting with Cement.

    ERIC Educational Resources Information Center

    Olson, Lynn

    1983-01-01

    Cement offers many creative possibilities for school art programs. Instructions are given for sculpting with fiber-cement and sand-cement, as well as for finishing processes and the addition of color. Safety is stressed. (IS)

  2. Sculpting with Cement.

    ERIC Educational Resources Information Center

    Olson, Lynn

    1983-01-01

    Cement offers many creative possibilities for school art programs. Instructions are given for sculpting with fiber-cement and sand-cement, as well as for finishing processes and the addition of color. Safety is stressed. (IS)

  3. Recent developments in turning hardened steels - A review

    NASA Astrophysics Data System (ADS)

    Sivaraman, V.; Prakash, S.

    2017-05-01

    Hard materials ranging from HRC 45 - 68 such as hardened AISI H13, AISI 4340, AISI 52100, D2 STL, D3 STEEL Steel etc., need super hard tool materials to machine. Turning of these hard materials is termed as hard turning. Hard turning makes possible direct machining of the hard materials and also eliminates the lubricant requirement and thus favoring dry machining. Hard turning is a finish turning process and hence conventional grinding is not required. Development of the new advanced super hard tool materials such as ceramic inserts, Cubic Boron Nitride, Polycrystalline Cubic Boron Nitride etc. enabled the turning of these materials. PVD and CVD methods of coating have made easier the production of single and multi layered coated tool inserts. Coatings of TiN, TiAlN, TiC, Al2O3, AlCrN over cemented carbide inserts has lead to the machining of difficult to machine materials. Advancement in the process of hard machining paved way for better surface finish, long tool life, reduced tool wear, cutting force and cutting temperatures. Micro and Nano coated carbide inserts, nanocomposite coated PCBN inserts, micro and nano CBN coated carbide inserts and similar developments have made machining of hardened steels much easier and economical. In this paper, broad literature review on turning of hardened steels including optimizing process parameters, cooling requirements, different tool materials etc., are done.

  4. [The effect of daily exposure to low hardening temperature on plant vital activity].

    PubMed

    Markovskaia, E F; Sysoeva, M I; Sherudilo, E G

    2008-01-01

    Phenomenological responses of plants to daily short-term exposure to low hardening temperature was studied under chamber and field conditions. Experiments were carried out on cucumber (Cucumis sativus L.), barley (Hordeum vulgare L.), marigolds (Tagetes L.), and petunia (Petunia x hybrida) plants. The obtained data demonstrated a similar pattern of response in all studied plant species to different variants of exposure to low hardening temperature. The main features of plant response to daily short-term exposure to low hardening temperature include: a higher rate of increase in cold tolerance (cf. two- or threefold increase relative to constant low hardening temperature) that peaked on day 5 (cf. day 2 at constant low hardening temperature) and was maintained for 2 weeks (cf. 3-4 days at constant low hardening temperature); a simultaneous increase in heat tolerance (cf. twofold relative to constant low hardening temperature) maintained over a long period (cf. only in the beginning of the exposure to constant low hardening temperature); a sharp drop in the subsequent cold tolerance after plant incubation in the dark (cf. a very low decrease in cold tolerance following the exposure to constant low hardening temperature); a combination of high cold tolerance and high photochemical activity of the photosynthetic apparatus (cf. a low non-photochemical quenching at constant low hardening temperature); and the capacity to rapidly increase cold tolerance in response to repeated short-term exposures to low hardening temperature in plants grown outdoors (cf. a gradual increase after repeated exposure to constant low hardening temperature). Possible methods underlying the plant response to daily short-term exposure to low temperature are proposed.

  5. Cementing multilateral wells with latex cement

    SciTech Connect

    1997-08-01

    A multilateral well is a well with one or more branches or lateral sections extending from its main wellbore. The laterals can be openhole or cased hole. When laterals are cased hole, the cement integrity for casing support and zonal isolation is very important. When cementing the lateral sections of multilateral wells, it is important to use a cement with high strength and durability to support the liner throughout the life of the well and to support the lateral section. The cement column is subjected to various stresses when the cemented inner stub is cut. High tensile strength, flexural strength, and crack resistance are required. These properties are necessary to make a clean cut through the cement sheath that does not induce cracks in the cement column. Latex cement is commonly used for its gas-migration-control property.

  6. Expansive Cements

    DTIC Science & Technology

    1970-10-01

    sulfate (C), and free lime (C) as well as other known portland cement compounds. 9. Etiite (C6AS3H3 2 ) is the phase formed during the hydration of...hydroxide (CH), required for chemical combination originates by hydration of alite (C3 S), belite (C2 S), and hydration of free lime in both the... shrinkage was also observed when the specimens were moist cured to full exparn-on for a pericd of 33 days. The data regarding the effect of aggregate size on

  7. HARDENING FROG POINTS BY EXPLOSIVE ENERGY,

    DTIC Science & Technology

    Experiments were made to determine the most efficient method of strain hardening railroad frog points in order to increase their fatigue resistance...Mechanical strain hardening with rolls 40 mm in diameter under a load of 8 tons produced in standard frogs cast from G13L high-manganese steel (AISI...Hadfield steel) a work-hardened surface layer 3-5 mm thick with a hardness of 340 HB. In other experiments, the frogs were hardened by exploding a

  8. Cement-based materials' characterization using ultrasonic attenuation

    NASA Astrophysics Data System (ADS)

    Punurai, Wonsiri

    The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct

  9. Influence of nano-dispersive modified additive on cement activity

    SciTech Connect

    Sazonova, Natalya Badenikov, Artem Ivanova, Elizaveta; Skripnikova, Nelli

    2016-01-15

    In the work the influence of single-walled carbon nanotubes (SWCNT) on the cement activity and the processes of structure formation of the hardened cement paste in different periods of hydration are studied. The changes in the kinetic curves of the sample strength growth modified with SWCNT in amount of 0.01 and 0.0005 % are stipulated by the results of differential scanning colorimetry, scanning electronic and ionic microscopy, X-ray-phase analysis. It was found that the nano-modified additive may increase in the axis compressive strength of the system by 1.4–6.3 fold relatively to the reference samples and may reach 179.6 MPa. It may intensify the hydration process of calcium silicates as well as influence on the matrix of hardened cement paste. The studies are conducted on the structural changes in the hardened cement paste, the time periods of increase and decrease of the compressive strength of the samples, the amount of the calcium hydroxide and tobermorite-like gel as well as the degree of hydration C{sub 3}S and β-C{sub 2}S.

  10. Precipitation hardening in aluminum alloy 6022

    SciTech Connect

    Miao, W.F.; Laughlin, D.E.

    1999-03-05

    Although the precipitation process in Al-Mg-Si alloys has been extensively studied, the understanding of the hardening process is still incomplete, since any change in composition, processing and aging practices, etc., could affect the precipitation hardening behavior. In this paper, hardness measurements, differential scanning calorimetry and transmission electron microscopy have been utilized to study the precipitation hardening behavior in aluminum alloy 6022.

  11. Premixed calcium phosphate cements: Synthesis, physical properties, and cell cytotoxicity

    PubMed Central

    Xu, Hockin H.K.; Carey, Lisa E.; Simon, Carl G.; Takagi, Shozo; Chow, Laurence C.

    2009-01-01

    Objectives Calcium phosphate cement (CPC) is a promising material for dental, periodontal, and craniofacial repairs. However, its use requires on-site powder–liquid mixing that increases the surgical placement time and raises concerns of insufficient and inhomogeneous mixing. The objective of this study was to determine a formulation of premixed CPC (PCPC) with rapid setting, high strength, and good in vitro cell viability. Methods PCPCs were formulated from CPC powder + non-aqueous liquid + gelling agent + hardening accelerator. Five PCPCs were thus developed: PCPC-Tartaric, PCPC-Malonic, PCPC-Citric, PCPC-Glycolic, and PCPC-Malic. Formulations and controls were compared for setting time, diametral tensile strength, and osteoblast cell compatibility. Results Setting time (mean ± S.D.; n = 4) for PCPC-Tartaric was 8.2 ± 0.8 min, significantly less than the 61.7 ± 1.5 min for the Premixed Control developed previously (p < 0.001). On 7th day immersion, the diametral tensile strength of PCPC-Tartaric reached 6.5 ± 0.8 MPa, higher than 4.5 ± 0.8 MPa of Premixed Control (p = 0.036). Osteoblast cells displayed a polygonal morphology and attached to the nano-hydroxyapatite crystals in the PCPCs. All cements had similar live cell density values (p = 0.126), indicating that the new PCPCs were as cell compatible as a non-premixed CPC control known to be biocompatible. Each of the new PCPCs had a cell viability that was not significantly different (p > 0.1) from that of the non-premixed CPC control. Significance PCPCs will eliminate the powder–liquid mixing during surgery and may also improve the cement performance. The new PCPCs supported cell attachment and yielded a high cell density and viability. Their mechanical strengths approached the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. These nano-crystalline hydroxyapatite cements may be useful in dental, periodontal, and craniofacial repairs. PMID:16678895

  12. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  13. Kinematic hardening in creep of Zircaloy

    NASA Astrophysics Data System (ADS)

    Sedláček, Radan; Deuble, Dietmar

    2016-10-01

    Results of biaxial creep tests with stress changes on Zircaloy-2 tube samples are presented. A Hollomon-type viscoplastic strain hardening model is extended by the Armstrong-Frederic nonlinear kinematic hardening law, resulting in a mixed (i.e. isotropic and kinematic) strain hardening model. The creep tests with stress changes and similar tests published in the literature are simulated by the models. It is shown that introduction of the kinematic strain hardening in the viscoplastic strain hardening model is sufficient to describe the creep transients following stress drops, stress reversals and stress removals.

  14. Cement design based on cement mechanical response

    SciTech Connect

    Thiercelin, M.J.; Dargaud, B.; Baret, J.F.; Rodriquez, W.J.

    1998-12-01

    The disappearance of cement bond log response as a result of variations of downhole conditions has been observed in numerous wells. This observation has led to concern about the loss of proper zonal isolation. Stresses induced in the cement, through deformation of the cemented casing resulting from the variation of downhole conditions, are the cause of this damage. The authors present an analysis of the mechanical response of set cement in a cased wellbore to quantify this damage and determine the key controlling parameters. The results show that the thermo-elastic properties of the casing, cement, and formation play a significant role. The type of failure, either cement debonding or cement cracking, is a function of the nature of the downhole condition variations. This analysis allows one to propose appropriate cement mechanical properties to avoid cement failure and debonding. The authors show that the use of high compressive strength cement is not always the best solution and, in some cases, flexible cements are preferred.

  15. Scintillation-Hardened GPS Receiver

    NASA Technical Reports Server (NTRS)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  16. Microwave Hardening Technology Development Program.

    DTIC Science & Technology

    1988-12-20

    FIELD GROUP SUB-GROUP Microwave Hardening Limiters Fiber’-Optic Components Varistors Cost Benefit Analyses 19. ABSTRACT (Continue an everse If... varistor paint material applied to a co-planar waveguide transmission line when injected with micro- wave pulses, as well as the impact of the paint...needed on the results of these efforts, two other unpublished reports on the fiber-optics component direct injection tests and the varistor paint limiter

  17. Characterisation of cement pastes by inverse gas chromatography.

    PubMed

    Oliva, Victor; Mrabet, Béchir; Baeta Neves, Maria Inês; Chehimi, Mohamed M; Benzarti, Karim

    2002-09-06

    Two cement pastes, commonly used in concrete formulations, were characterised by IGC at 35-80 degrees C before and after coating with an epoxy resin and a hardener. The cements are mixtures of hydrates in various proportions, such as calcium silicate hydrate (CaO-SiO2-H2O) and calcium hydroxide Ca(OH)2. Apolar and polar probes were used to determine the dispersive and acid-base characteristics of the cement pastes. These materials have high surface energy as judged from the dispersive contribution to the surface free energy (gamma(s)d) values lying in the 50-70 mJ/m2 range at 60-80 degrees C. Examination of the specific interactions permitted to show that the cement pastes are strongly amphoteric species with a substantial predominant Lewis basicity that is in line with the basic pH of their aqueous suspensions. Following coating with an epoxy resin (DGEBA) and a hardener (triethylene tetramine), the surface energy of the cements decreases substantially with the mass loading of the organic material. The surface thermodynamic properties were also correlated with the surface chemical composition as determined by X-ray photoelectron spectroscopy.

  18. Newly developed Sr-substituted alpha-TCP bone cements.

    PubMed

    Pina, S; Torres, P M; Goetz-Neunhoeffer, F; Neubauer, J; Ferreira, J M F

    2010-03-01

    New bone cements made of Sr-substituted brushite-forming alpha-tricalcium phosphate (alpha-TCP) were prepared and characterized in the present work. The quantitative phase analysis and structural refinement of the starting powders and of hardened cements were performed by X-ray powder diffraction and the Rietveld refinement technique. Isothermal calorimetry along with setting time analysis allowed a precise tracing of the setting process of the pastes. The pastes showed exothermic reactions within the first 10-15 min after mixing and further release of heat after about 1h. An apatitic phase formed upon immersion of the hardened cements in simulated body fluid for 15 and 30 days due to the conversion of brushite into apatite confirming their in vitro mineralization capability. The compressive strength of the wet cement specimens decreased with increasing curing time, being higher in the case of Sr-substituted CPC. The results suggest that the newly developed Sr-substituted brushite-forming alpha-TCP cements show promise for uses in orthopaedic and trauma surgery such as in filling bone defects.

  19. Age-hardening of grid alloys and its effect on battery manufacturing processes

    NASA Astrophysics Data System (ADS)

    Gillian, Warren F.; Rice, David M.

    The age-hardening behaviour of three generic classes of lead—antimony grid alloys commonly used in the lead/acid battery manufacturing industry were studied. The effects on age-hardening behaviour of several heat treatments devised to simulate downstream processing of battery grids in the manufacturing process were investigated together with the effect of varying cooling rate following casting. Rapid cooling (water quenching) resulted in a general acceleration and enhancement of the age-hardening behaviour of all alloys, whilst heat treatment following casting generally gave rise to a reduction in peak hardness.

  20. In Vivo Characteristics of Premixed Calcium Phosphate Cements When Implanted in Subcutaneous Tissues and Periodontal Bone Defects.

    PubMed

    Sugawara, Akiyoshi; Fujikawa, Kenji; Hirayama, Satoshi; Takagi, Shozo; Chow, Laurence C

    2010-01-01

    Previous studies showed that water-free, premixed calcium phosphate cements (Pre-CPCs) exhibited longer hardening times and lower strengths than conventional CPCs, but were stable in the package. The materials hardened only after being delivered to a wet environment and formed hydroxyapatite as the only product. Pre-CPCs also demonstrated good washout resistance and excellent biocompatibility when implanted in subcutaneous tissues in rats. The present study evaluated characteristics of Pre-CPCs when implanted in subcutaneous tissues (Study I) and used for repairing surgically created two-wall periodontal defects (Study II). Pre-CPC pastes were prepared by combining CPC powders that consisted of CPC-1: Ca(4)(PO(4))(2)O and CaHPO(4), CPC-2: α-Ca(3)(PO(4))(2) and CaCO(3) or CPC-3: DCPA and Ca(OH)(2) with a glycerol at powder-to-liquid mass ratios of 3.5, 2.5, and 2.5, respectively. In each cement mixture, the Ca to P molar ratio was 1.67. The glycerol contained Na(2)HPO(4) (30 mass %) and hydroxypropyl methylcellulose (0.55 %) to accelerate cement hardening and improve washout resistance, respectively. In Study I, the test materials were implanted subcutaneously in rats. Four weeks after the operation, the animals were sacrificed and histopathological observations were performed. The results showed that all of the implanted materials exhibited very slight or negligible inflammatory reactions in tissues contacted with the implants. In Study II, the mandibular premolar teeth of mature beagle dogs were extracted. One month later, two-wall periodontal bone defects were surgically created adjacent to the teeth of the mandibular bone. The defects were filled with the Pre-CPC pastes and the flaps replaced in the preoperative position. The dogs were sacrificed at 1, 3 and 6 months after surgery and sections of filled defects resected. Results showed that one month after surgery, the implanted Pre-CPC-1 paste was partially replaced by bone and was converted to bone at 6

  1. Sorption of radionuclides by cement-based barrier materials

    SciTech Connect

    Li, Kefei Pang, Xiaoyun

    2014-11-15

    This paper investigates the sorption of radionuclide ions, {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+}, by cement-based barrier materials for radioactive waste disposal. A mortar with ternary binder is prepared and powder samples are ground from the hardened material following a predetermined granulometry. After pre-equilibrium with an artificial pore solution, the sorption behaviors of powder samples are investigated through single sorption and blended sorption. The results show that: (1) no systematic difference is observed for single and blended sorptions thus the interaction between {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+} sorptions must be weak; (2) the sorption kinetics is rapid and all characteristic times are less than 1d; (3) the sorption capacity is enhanced by C–A–S–H hydrates and the measured K{sub d} values can be predicted from C–S–H sorption data with Ca/Si ratio equal to Ca/(Si + Al) ratio.

  2. Phosphate-bonded calcium aluminate cements

    DOEpatents

    Sugama, T.

    1993-09-21

    A method is described for making a rapid-setting phosphate-bonded cementitious material. A powdered aluminous cement is mixed with an aqueous solution of ammonium phosphate. The mixture is allowed to set to form an amorphous cementitious material which also may be hydrothermally treated at a temperature of from about 120 C to about 300 C to form a crystal-containing phosphate-bonded material. Also described are the cementitious products of this method and the cement composition which includes aluminous cement and ammonium polyphosphate. 10 figures.

  3. Phosphate-bonded calcium aluminate cements

    DOEpatents

    Sugama, Toshifumi

    1993-01-01

    A method is described for making a rapid-setting phosphate-bonded cementitious material. A powdered aluminous cement is mixed with an aqueous solution of ammonium phosphate. The mixture is allowed to set to form an amorphous cementitious material which also may be hydrothermally treated at a temperature of from about 120.degree. C. to about 300.degree. C. to form a crystal-containing phosphate-bonded material. Also described are the cementitious products of this method and the cement composition which includes aluminous cement and ammonium polyphosphate.

  4. Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

    DOEpatents

    Wallace, Steven A.

    1984-01-01

    The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness.

  5. Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

    SciTech Connect

    Wallace, S.A.

    1981-07-29

    The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness.

  6. Stabilization/solidification of hazardous and radioactive wastes with alkali-activated cements.

    PubMed

    Shi, Caijun; Fernández-Jiménez, A

    2006-10-11

    This paper reviews progresses on the use of alkali-activated cements for stabilization/solidification of hazardous and radioactive wastes. Alkali-activated cements consist of an alkaline activator and cementing components, such as blast furnace slag, coal fly ash, phosphorus slag, steel slag, metakaolin, etc., or a combination of two or more of them. Properly designed alkali-activated cements can exhibit both higher early and later strengths than conventional portland cement. The main hydration product of alkali-activated cements is calcium silicate hydrate (CSH) with low Ca/Si ratios or aluminosilicate gel at room temperature; CSH, tobmorite, xonotlite and/or zeolites under hydrothermal condition, no metastable crystalline compounds such as Ca(OH)(2) and calcium sulphoaluminates exist. Alkali-activated cements also exhibit excellent resistance to corrosive environments. The leachability of contaminants from alkali-activated cement stabilized hazardous and radioactive wastes is lower than that from hardened portland cement stabilized wastes. From all these aspects, it is concluded that alkali-activated cements are better matrix for solidification/stabilization of hazardous and radioactive wastes than Portland cement.

  7. Cement mixing with vibrator

    SciTech Connect

    Allen, T.E.

    1991-07-09

    This patent describes a method of cementing a casing string in a bore hole of a well. It comprises introducing water and dry cement material into a mixing vessel; mixing the water and dry cement material in the mixing vessel to form a cement slurry, the slurry including lumps of the dry cement material, the mixing including steps of: agitating the slurry; and while agitating the slurry, transmitting vibrational energy into the slurry and thereby aiding disintegration and subsequent wetting of the lumps of the dry cement material in the slurry; and pumping the slurry into an annulus between the casing string and the bore hole.

  8. A water setting tetracalcium phosphate-dicalcium phosphate dihydrate cement.

    PubMed

    Burguera, E F; Guitián, F; Chow, L C

    2004-11-01

    The development of a calcium phosphate cement, comprising tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD), that hardens in 14 min with water as the liquid or 6 min with a 0.25 mol/L sodium phosphate solution as the liquid, without using hydroxyapatite (HA) seeds as setting accelerator, is reported. It was postulated that reduction in porosity would increase cement strength. Thus, the effects of applied pressure during the initial stages of the cement setting reaction on cement strength and porosity were studied. The cement powder comprised an equimolar mixture of TTCP and DCPD (median particle sizes 17 and 1.7 microm, respectively). Compressive strengths (CS) of samples prepared with distilled water were 47.6 +/- 2.4 MPa, 50.7 +/- 4.2 MPa, and 52.9 +/- 4.7 MPa at applied pressures of 5 MPa, 15 MPa, and 25 MPa, respectively. When phosphate solution was used, the CS values obtained were 41.5 +/- 2.3 MPa, 37.9 +/- 1.7 MPa, and 38.1 +/- 2.3 MPa at the same pressure levels. Statistical analysis of the results showed that pressure produced an improvement in CS when water was used as liquid but not when the phosphate solution was used. Compared to previously reported TTCP-DCPD cements, the greater CS values and shorter setting times together with a simplified formulation should make the present TTCP-DCPD cement a useful material as a bone substitute for clinical applications.

  9. Characterization and hardening of concrete with ultrasonic testing.

    PubMed

    del Río, L M; Jiménez, A; López, F; Rosa, F J; Rufo, M M; Paniagua, J M

    2004-04-01

    In this study, we describe a technique which can be used to characterize some relevant properties of 26 cylindrical samples (15 x 30 cm2) of concrete. The characterization has been performed, according to Spanish regulations in force, by some destructive and ultrasound-based techniques using frequencies of 40 kHz. Samples were manufactured using different water/cement ratios (w/c), ranging from 0.48 to 0.80, in order to simulate different values of compressive strength at each sample. We have correlated the propagation velocity v of ultrasonic waves through the samples to compressive strength R values. As some other authors remark, there exists an exponential relationship between the two above parameters. We have found that a highly linear relationship is present between R and w/c concentration at the samples. Nevertheless, when the same linear model is adopted to describe the relationship between v and w/c, the value of r decreases significantly. Thus, we have performed a multiple regression analysis which takes into account the impact of different concrete constituents (water, cement, sand, etc.) on ultrasound propagation speed. One of the most relevant practical issues addressed in our study is the estimation of the hardening curve of concrete, which can be used to quantify the viability of applying the proposed method in a real scenario. Subsequently, we also show a detailed analysis of the temporal evolution of v and R through 61 days, beginning at the date where the samples were manufactured. After analyzing both parameters separately, a double reciprocal relationship is deduced. Using the above parameters, we develop an NDE-based model which can be used to estimate hardening time of concrete samples.

  10. Epidural application of ionomeric cement implants. Experimental and clinical results.

    PubMed

    Geyer, G; Baier, G; Helms, J

    1998-04-01

    During setting and hardening, the hybrid bone substitute ionomeric cement (Ionocem) achieves a stable and durable bond with the apatite of the adjacent bone without interpository soft tissue. Fluid contact during setting results in the release of aluminium ions which may reach critical levels as high as 3000 micrograms/l. On epidural application it is, therefore, essential to prevent cement constituents from gaining access to the intradural space. After the cement has hardened, the presence of aluminium is demonstrable in the adjacent bone to a maximum depth of 20 microns (EDX microanalysis). In rabbits, epidural placement of freshly mixed cement causes slight thickening of the dura. There is reason to believe that human dura, with a thickness 10 times greater, is impermeable to components of the cement. After epidural application of the freshly mixed cement in the frontobasal and laterobasal regions and at the skull cap and petrous apex, 76 patients in all have been followed for up to 6.5 years. During this period no complications have arisen and functional (and cosmetic) results are promising. The availability of preformed implants (Ionoroc, Ionocast) permitted the peridural placement of minimal quantities of freshly mixed cement. These implants were fixed to localized sites on the adjacent calvarial bone by use of Ionocem. Notwithstanding the stringent manufacturer guidelines, there have been reports in the literature that during the vulnerable stage of setting neurotoxic aluminium ions were released into the dural space with a fatal outcome in two cases. In view of potential intradural complications, such as may occur in case of dural leaks, it was considered that further application of the material adjacent to the dura was no longer warranted. The production of Ionocem was discontinued in May 1995.

  11. Energy-Efficient Thermomagnetic and Induction Hardening

    SciTech Connect

    2009-02-01

    This factsheet describes a research project that will develop and test a hybrid thermomagnetic and induction hardening technology to replace conventional heat treatment processes in forging applications.

  12. Radiation Hardened Electronics for Extreme Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

  13. DISPERSION HARDENING OF URANIUM METAL

    DOEpatents

    Arbiter, W.

    1963-01-15

    A method of hardening U metal involves the forming of a fine dispersion of UO/sub 2/. This method consists of first hydriding the U to form a finely divided powder and then exposing the powder to a very dilute O gas in an inert atmosphere under such pressure and temperature conditions as to cause a thin oxide film to coat each particle of the U hydride, The oxide skin prevents agglomeration of the particles as the remaining H is removed, thus preserving the small particle size. The oxide skin coatings remain as an oxide dispersion. The resulting product may be workhardened to improve its physical characteristics. (AEC)

  14. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-10-31

    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.

  15. ADVANCED CEMENTS FOR GEOTHERMAL WELLS

    SciTech Connect

    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 cements, and further

  16. Brief carbon dioxide exposure blocks heat hardening but not cold acclimation in Drosophila melanogaster.

    PubMed

    Milton, Claire C; Partridge, Linda

    2008-01-01

    Carbon dioxide is a commonly used anaesthetic in Drosophila research. While any detrimental effects of CO2 exposure on behaviour or traits are largely unknown, a recent study observed significant effects of CO2 exposure on rapid cold hardening and chill-coma recovery in Drosophila melanogaster. In this study we investigated the effect of a brief CO2 exposure on heat hardening and cold acclimation in D. melanogaster, measuring heat knockdown and chill-coma recovery times of flies exposed to CO2 for 1 min after hardening or acclimation. CO2 anaesthesia had a significant negative effect on heat hardening, with heat knockdown rates in hardened flies completely reduced to those of controls after CO2 exposure. Chill-coma recovery rates also significantly increased in acclimated flies that were exposed to CO2, although not to the same extent seen in the heat populations. CO2 exposure had no impact on heat knockdown rates of control flies, while there was a significant negative effect of the anaesthetic on chill-coma recovery rates of control flies. In light of these results, we suggest that CO2 should not be used after hardening in heat resistance assays due to the complete reversal of the heat hardening process upon exposure to CO2.

  17. Dentin bonding agents and resin cements--current status.

    PubMed

    Woolsey, G; O'Mahony, A; Hansen, P A

    2000-01-01

    Contemporary restorative dentistry is a rapidly evolving science which challenges the progressive clinician with a plethora of "new and improved" products. Sound product choices should be couched in the prudent consideration of well conducted in vitro and in vivo product research. This review shall list the most recent product developments in dentin bonding agents (fifth generation agents), resin-containing dental cements and the newest generation of dental cements i.e., resin-ionomer dental cements.

  18. COSMIC-RAY HELIUM HARDENING

    SciTech Connect

    Ohira, Yutaka; Ioka, Kunihito

    2011-03-01

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

  19. Microstructural evolution and the variation of tensile behavior after aging heat treatment of precipitation hardened martensitic steel

    SciTech Connect

    Shin, Jong-Ho; Jeong, JaeSuk; Lee, Jong-Wook

    2015-01-15

    The effects of aging temperature on the microstructural evolution and the tensile behavior of precipitation hardened martensitic steel were investigated. Microscopic analysis using transmission electron microscope (TEM) was combined with the microstructural analysis using the synchrotron X-ray diffraction (XRD) to characterize the microstructural evolution with aging temperature. Peak hardness was obtained by precipitation of the Ni{sub 3}Al ordered phase. After aging at temperature range from 420 to 590 °C, spherical Ni{sub 3}Al precipitates and ellipsoidal M{sub 23}C{sub 6} carbides were observed within laths and at lath boundaries, respectively. Strain hardening behavior was analyzed with Ludwik equation. It is observed that the plastic strain regimes can be divided into two different stages by a rapid increase in strain hardening followed by a comparatively lower increase. At the first strain hardening stage, the aged specimen exhibited higher strain hardening exponent than the as-quenched specimen, and the exponent in the aged specimen was not changed considerably with increasing aging temperature. It is revealed that the strain hardening exponents at the first and the second stages were associated with the Ni{sub 3}Al precipitates and the domain size representing the coherent scattering area, respectively. - Highlights: • All of aged specimen exhibited higher strain hardening exponent than the as-quenched specimen at the first stage. • The value of strain hardening exponent in the aged specimen was nearly constant with aging temperature. • Ni{sub 3}Al precipitation dominantly influenced to the increase of strain hardening exponent at the first strain hardening stage. • Domain size was associated with strain hardening exponent at the second strain hardening stage.

  20. Effect of mechanical grinding of MCPM and CaO mixtures on their composition and on the mechanical properties of the resulting self-setting hydraulic calcium phosphate cements.

    PubMed

    Serraj, S; Boudeville, P; Terol, A

    2001-01-01

    Calcium bis-dihydrogenophosphate monohydrate (or monocalcium phosphate monohydrate, MCPM) is often used as the acid calcium phosphate in hydraulic calcium phosphate cement formulations. But commercial MCPM is not pure; it contains a small amount of orthophosphoric acid and moisture. Consequently, MCPM is difficult to mill and the powder is sticky and presents aggregates. Because granularity influences the mechanical properties of the hardened cements, a possible way to get around this difficulty that has been proposed is to premix it with other materials before grinding. We therefore ground commercial MCPM with CaO. A rapid decrease in the amount of MCPM was observed during mechanical grinding by a solid-solid reaction with calcium oxide. The final products were anhydrous or dihydrate dicalcium phosphate and/or hydroxyapatite or calcium-deficient hydroxyapatite depending on the initial calcium-to-phosphate (Ca/P) ratio. The mechanical properties (compressive strength and setting time) of cements made from MCPM and CaO were affected whatever the Ca/P ratio as a consequence of the change in composition of the starting materials. Storage at different temperatures of MCPM and CaO mixtures manually ground in a mortar for only 2 min and without mechanical grinding did not affect their composition, but a decrease was observed in the compressive strength of cements made from these mixtures.

  1. Hydration and temperature development of concrete made with blast-furnace slag cement

    SciTech Connect

    Schutter, G. de

    1999-01-01

    In Europe, massive concrete elements often are made with blast-furnace slag cements. To better deal with the problem of early-age thermal cracking in these cases, a new hydration model for blast-furnace slag cements is developed, which is based on isothermal and adiabatic hydration tests. In the hydration model, the heat production rate is calculated as a function of the degree of hydration and the temperature. The accuracy of temperature simulations using this new hydration model is evaluated by tests on hardening massive concrete cylinders made with blast-furnace slag cement.

  2. Experimental study of self-compacted concrete in hardened state

    NASA Astrophysics Data System (ADS)

    Parra Costa, Carlos Jose

    The main aim of this work is to investigate the hardened behaviour of Self-Compacting Concrete (SCC). Self compacting Concrete is a special concrete that can flow in its gravity and fill in the formwork alone to its self-weight, passing through the bars and congested sections without the need of any internal or external vibration, while maintaining adequate homogeneity. SCC avoids most of the materials defects due to bleeding or segregation. With regard to its composition, SCC consists of the same components as traditional vibrated concrete (TC), but in different proportions. Thus, the high amount of superplasticizer and high powder content have to taken into account. The high workability of SCC does not allow to use traditional methods for measuring the fresh state properties, so new tests has developed (slump-flow, V-funnel, L-box, and others). The properties of the hardened SCC, which depend on the mix design, should be different from traditional concrete. In order to study the possible modifications of SCC hardened state properties, a review of the bibliography was done. The state of art was focused on the mechanical behaviour (compressive strength, tension strength and elastic modulus), on bond strength of reinforcement steel, and on material durability. The experimental program consisted in the production of two types of concretes: Self-Compacting Concrete and Traditional Concrete. Four different dosages was made with three different water/cement ratio and two strength types of Portland cement, in order to cover the ordinary strength used in construction. Based on this study it can be concluded that compressive strength of SCC and TC are similar (the differences are lesser than 10%), whereas the tensile strength of TC are up to 18% higher. The values of elastic modulus of both concrete are similar. On the other hand, in the ultimate state the bond strength of SCC and TC is similar, although SCC shows higher bond stiffness in the serviceability state (initial

  3. Transmission and scanning electron microscope study on the secondary cyclic hardening behavior of interstitial-free steel

    SciTech Connect

    Shih, Chia-Chang; Ho, New-Jin; Huang, Hsing-Lu

    2009-11-15

    Strain controlled fatigue experiment was employed to evaluate automotive grade interstitial-free ferrite steel. Hundreds of grains were examined by scanning electron microscope under electron channeling contrast image technique of backscattered electron image mode for comprehensive comparison of micrographs with those taken under transmission electron microscope. The cyclic stress responses clearly revealed that rapid hardening occurs at the early stage of cycling as a result of multiplication of dislocations to develop loop patches, dipolar walls and dislocation cells at various total strain amplitudes. After primary rapid hardening, stress responses varied from being saturated to further hardening according to dislocation structure evolution at various strain amplitudes. The fatigue failure was always accompanied with further hardening including secondary hardening. The corresponding dislocation structures with the three types of hardening behaviors are discussed. Once the secondary hardening starts, dislocation cells began to develop along grain boundaries in the low strain region and then extended into grain interiors as strain amplitudes increased and cycling went on. The secondary hardening rates were found to be directly proportional to their strain amplitudes.

  4. Improved hardening theory for cyclic plasticity.

    NASA Technical Reports Server (NTRS)

    Vos, R. G.; Armstrong, W. H.

    1973-01-01

    A temperature-dependent version of a combined hardening theory, including isotropic and kinematic hardening, is presented within the framework of recent plasticity formulations. This theory has been found to be especially useful in finite-element analysis of aerospace vehicle engines under conditions of large plastic strain and low-cycle fatigue.

  5. Dicalcium phosphate cements: brushite and monetite.

    PubMed

    Tamimi, Faleh; Sheikh, Zeeshan; Barralet, Jake

    2012-02-01

    Dicalcium phosphate cements were developed two decades ago and ever since there has been a substantial growth in research into improving their properties in order to satisfy the requirements needed for several clinical applications. The present paper presents an overview of the rapidly expanding research field of the two main dicalcium phosphate bioceramics: brushite and monetite. This review begins with a summary of all the different formulae developed to prepare dicalcium phosphate cements, and their setting reaction, in order to set the scene for the key cement physical and chemical properties, such as compressive and tensile strength, cohesion, injectability and shelf-life. We address the issue of brushite conversion into either monetite or apatite. Moreover, we discuss the in vivo behavior of the cements, including their ability to promote bone formation, biodegradation and potential clinical applications in drug delivery, orthopedics, craniofacial surgery, cancer therapy and biosensors.

  6. Magnesium-phosphate-glass cements with ceramic-type properties

    DOEpatents

    Sugama, T.; Kukacka, L.E.

    1982-09-23

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate, exhibits rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  7. Magnesium phosphate glass cements with ceramic-type properties

    SciTech Connect

    Sugama, T.; Kukacka, L.E.

    1984-03-13

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate exhibiting rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono-and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  8. Magnesium phosphate glass cements with ceramic-type properties

    DOEpatents

    Sugama, Toshifumi; Kukacka, Lawrence E.

    1984-03-13

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate exhibiting rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  9. [Ionomer cement as bone substitute in the middle ear of the rabbit].

    PubMed

    Geyer, G

    1997-04-01

    Ionomer-based cements are obtained by the reaction of an aluminum-fluoro-silicate glass with a polyalcenoic acid. During setting and hardening the cement bonds closely with adjacent hard tissue. The previous implantation of this material in the baboon tibia has held great promise as a possible use in bone replacement. In the present study the cement was tested concerning its biocompatibility and biostability in the middle ears of 64 rabbits. Viscid cement paste was inserted into the epitympanic space of each animal. A preformed cement strut was then placed to serve as a columella between the eardrum and stapes footplate. During a subsequent interval of 28 days up to 2 years middle ear specimens were evaluated under a surgical microscope, following which histologic sections were studied under light microscopic conditions. Findings demonstrated that after insertion of freshly mixed cement a firm adhesion to bone developed that proved to be biocompatible and biostable over time. After 28 days the preformed and fully hardened implants were overgrown by a delicate mucosa normally present in the middle ear. No evidence for any rejection of the implants could be found. The experience available to date indicates that ionomer cement is biocompatible and biostable, easy to handle and workable without splintering. With appropriate use it represents a useful implant material in surgery of the head and neck.

  10. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-04-15

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  11. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-04-29

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, and shear bond. Testing to determine the effect of temperature cycling on the shear bond properties of the cement systems was also conducted. In addition, the stress-strain behavior of the cement types was studied. This report discusses a software program that is being developed to help design ULHS cements and foamed cements.

  12. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-10-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that will be performed for analyzing the alkali-silica reactivity of ULHS in cement slurries, as well as the results of Field Tests 1 and 2.

  13. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-07-18

    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.

  14. CHEMICALLY BONDED CEMENTS FROM BOILER ASH AND SLUDGE WASTES. PHASE I REPORT AUGUST 1997 - JULY 1998

    SciTech Connect

    SUGAMA,T.; YAGER,K.A.

    2002-08-05

    In exploring methods to recycle boiler ash (BA) and waste water treatment sludge (WWTS), by-products generated from Keyspan's power plants, into commercially viable materials, we synthesized chemically bonded cements (CBC) offering the following three specific characteristics; (1) immobilization of hazardous heavy metals, such as Pb, Ni, and V, (2) rapid hardening and setting properties, and (3) development of high mechanical strength. The CBCs were prepared through an acid-base reaction between these by-products acting as the solid base reactants and the sodium polyphosphate solution as the cement-forming acid reactant, followed by a hydrating reaction. Furthermore, two additives, the calcium aluminate cements (CAC) and the calcium silicate cements (CSC) were incorporated into the CBC systems to improve their properties. Using a CBC formulation consisting of 53.8 wt% WWTS, 23.1 wt% CSC, and 23.1 wt% [40 wt% -(-NaPO{sub 3}-)-{sub n}]{sub 2} the Toxicity Characteristics Leaching Procedure (TCLP) tests showed that the concentrations of Pb, Ni, and V metals leached out from the specimens were minimal. This formulation originally contained {approx} 28800 mg/kg of Pb, {approx} 6300 mg/kg of Ni, and {approx} 11130 mg/kg of V; the amounts leaching into the acid extraction fluid were only 0.15 mg/L of Pb, 0.15 mg/L of Ni, and 4.63 mgiL of V. On the other hand, CBC specimens derived from a formulation consisting of 42 wt% BA, 18 wt% CAC and 40 wt% [40 wt% -(-NaPO{sub 3}-)-{sub n}] displayed an excellent compressive strength of 10.8 MPa at an early curing age of 2 hours after mixing at room temperature. The reason for its rapid hardening was due to a high exothermic energy evolved by the acid-base reaction. Furthermore, when these specimens were immersed for 28 days in water at 25 C, and exposed for 20 hours to steam at 80 C, a very high compressive strength of 3.32 MPa developed. Two physico-chemical factors played an important role in improving the mechanical strength of

  15. Hardening of shear band in metallic glass.

    PubMed

    Wang, J G; Hu, Y C; Guan, P F; Song, K K; Wang, L; Wang, G; Pan, Y; Sarac, B; Eckert, J

    2017-08-01

    Strain hardening, originating from defects such as the dislocation, avails conventional metals of high engineering reliability in applications. However, the hardenability of metallic glass is a long-standing concern due to the lack of similar defects. In this work, we carefully examine the stress-strain relationship in three bulk monolithic metallic glasses. The results show that hardening is surely available in metallic glasses if the effective load-bearing area is considered instantly. The hardening is proposed to result from the remelting and ensuing solidification of the shear-band material under a hydrostatic pressure imposed by the normal stress during the shear banding event. This applied-pressure quenching densifies the metallic glass by discharging the free volume. On the other hand, as validated by molecular dynamics simulations, the pressure promotes the icosahedral short-range order. The densification and icosahedral clusters both contribute to the increase of the shear strength and therefore the hardening in metallic glasses.

  16. Bone marrow modified acrylic bone cement for augmentation of osteoporotic cancellous bone.

    PubMed

    Arens, Daniel; Rothstock, Stephan; Windolf, Markus; Boger, Andreas

    2011-11-01

    The use of polymethylmethacrylate (PMMA) cement to reinforce fragile or broken vertebral bodies (vertebroplasty) leads to extensive bone stiffening. This might be one reason for fractures at the adjacent vertebrae following this procedure. PMMA with a reduced Young's modulus may be more suitable. The goal of this study was to produce and characterize PMMA bone cements with a reduced Young's modulus by adding bone marrow. Bone cements were produced by combining PMMA with various volume fractions of freshly harvested bone marrow from sheep. Porosity, Young's modulus, yield strength, polymerization temperature, setting time and cement viscosity of different cement modifications were investigated. The samples generated comprised pores with diameters in the range of 30-250 μm leading to porosity up to 51%. Compared to the control cement, Young's modulus and yield strength decreased from 1830 to 740 MPa and from 58 to 23 MPa respectively by adding 7.5 ml bone marrow to 23 ml premixed cement. The polymerization temperature decreased from 61 to 38 ∘C for cement modification with 7.5 ml of bone marrow. Setting times of the modified cements were lower in comparison to the regular cement (28 min). Setting times increased with higher amounts of added bone marrow from around 16-25 min. The initial viscosities of the modified cements were higher in comparison to the control cement leading to a lower risk of extravasation. The hardening times followed the same trend as the setting times. In conclusion, blending bone marrow with acrylic bone cement seems to be a promising method to increase the compliance of PMMA cement for use in cancellous bone augmentation in osteoporotic patients due to its modified mechanical properties, lower polymerization temperature and elevated initial viscosity.

  17. New System of Shrinkage Measurement through Cement Mortars Drying

    PubMed Central

    Morón, Carlos; Saiz, Pablo; Ferrández, Daniel; García-Fuentevilla, Luisa

    2017-01-01

    Cement mortar is used as a conglomerate in the majority of construction work. There are multiple variants of cement according to the type of aggregate used in its fabrication. One of the major problems that occurs while working with this type of material is the excessive loss of moisture during cement hydration (setting and hardening), known as shrinkage, which provokes a great number of construction pathologies that are difficult to repair. In this way, the design of a new sensor able to measure the moisture loss of mortars at different age levels is useful to establish long-term predictions concerning mortar mass volume loss. The purpose of this research is the design and fabrication of a new capacitive sensor able to measure the moisture of mortars and to relate it with the shrinkage. PMID:28272297

  18. Properties of cement based composites modified using diatomaceous earth

    NASA Astrophysics Data System (ADS)

    Pokorný, Jaroslav; Pavlíková, Milena; Záleská, Martina; Pavlík, Zbyšek

    2017-07-01

    Diatomite belongs among natural materials rich on amorphous silica (a-SiO2). When finely milled, it can potentially substitute part of cement binder and positively support formation of more dense composite structure. In this connection, two types of diatomaceous earth applied as a partial substitution of 5, 10, 15, and 20 mass% of Portland cement in the composition of cement paste were studied. In the tested mixtures with cement blends, the amount of batch water remained same, with water/binder ratio 0.5. For fresh paste mixtures, initial and final setting times were measured. First, hardened pastes cured 28 days in water were characterized by their physical properties such as bulk density, matrix density and open porosity. Then, their mechanical and thermophysical parameters were assessed. Obtained results gave clear evidence of setting time shortening for pastes with diatomite what brought negative effect with respect to the impaired workability of fresh mixtures. On the other hand, there was observed strength improvement for mixtures containing diatomite with higher amount of SiO2. Here, the increase in mechanical resistivity was distinct up to 15 mass% of cement replacement. Higher cement substitution by diatomite resulted in an increase in porosity and thus improvement of thermal insulation properties.

  19. Possibility of Using Wood Pulp in the Preparation of Cement Composites

    NASA Astrophysics Data System (ADS)

    Kidalova, Lucia; Stevulova, Nadezda; Geffert, Anton

    2014-06-01

    Sustainable building materials are based on the use of renewable materials instead of non-renewable. Large group of renewable materials composes of plant fibres having high tensile strength are used as fillers into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic fillers, such as wood pulp. Wood pulp cellulose is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. Varying the producing technology (wood pulp and cement ratio in mixture) it is possible to obtain composites with density from 940 to 1260 kgm-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. Based on the experimental results, cement composites with using unbleached wood pulp reach higher values than composites based on bleached wood pulp. Volume ratio of unbleached wood pulp in composites influences water absorbability of cement composites

  20. A novel cement-based hybrid material

    NASA Astrophysics Data System (ADS)

    Nasibulin, Albert G.; Shandakov, Sergey D.; Nasibulina, Larisa I.; Cwirzen, Andrzej; Mudimela, Prasantha R.; Habermehl-Cwirzen, Karin; Grishin, Dmitrii A.; Gavrilov, Yuriy V.; Malm, Jari E. M.; Tapper, Unto; Tian, Ying; Penttala, Vesa; Karppinen, Maarit J.; Kauppinen, Esko I.

    2009-02-01

    Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) are known to possess exceptional tensile strength, elastic modulus and electrical and thermal conductivity. They are promising candidates for the next-generation high-performance structural and multi-functional composite materials. However, one of the largest obstacles to creating strong, electrically or thermally conductive CNT/CNF composites is the difficulty of getting a good dispersion of the carbon nanomaterials in a matrix. Typically, time-consuming steps of purification and functionalization of the carbon nanomaterial are required. We propose a new approach to grow CNTs/CNFs directly on the surface of matrix particles. As the matrix we selected cement, the most important construction material. We synthesized in a simple one-step process a novel cement hybrid material (CHM), wherein CNTs and CNFs are attached to the cement particles. The CHM has been proven to increase 2 times the compressive strength and 40 times the electrical conductivity of the hardened paste, i.e. concrete without sand.

  1. Shrinkage deformation of cement foam concrete

    NASA Astrophysics Data System (ADS)

    Kudyakov, A. I.; Steshenko, A. B.

    2015-01-01

    The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

  2. Cyber situational awareness and differential hardening

    NASA Astrophysics Data System (ADS)

    Dwivedi, Anurag; Tebben, Dan

    2012-06-01

    The advent of cyber threats has created a need for a new network planning, design, architecture, operations, control, situational awareness, management, and maintenance paradigms. Primary considerations include the ability to assess cyber attack resiliency of the network, and rapidly detect, isolate, and operate during deliberate simultaneous attacks against the network nodes and links. Legacy network planning relied on automatic protection of a network in the event of a single fault or a very few simultaneous faults in mesh networks, but in the future it must be augmented to include improved network resiliency and vulnerability awareness to cyber attacks. Ability to design a resilient network requires the development of methods to define, and quantify the network resiliency to attacks, and to be able to develop new optimization strategies for maintaining operations in the midst of these newly emerging cyber threats. Ways to quantify resiliency, and its use in visualizing cyber vulnerability awareness and in identifying node or link criticality, are presented in the current work, as well as a methodology of differential network hardening based on the criticality profile of cyber network components.

  3. Hydration and leaching characteristics of cement pastes made from electroplating sludge.

    PubMed

    Chen, Ying-Liang; Ko, Ming-Sheng; Lai, Yi-Chieh; Chang, Juu-En

    2011-06-01

    The purpose of this study was to investigate the hydration and leaching characteristics of the pastes of belite-rich cements made from electroplating sludge. The compressive strength of the pastes cured for 1, 3, 7, 28, and 90 days was determined, and the condensation of silicate anions in hydrates was examined with the (29)Si nuclear magnetic resonance (NMR) technology. The leachabilities of the electroplating sludge and the hardened pastes were studied with the multiple toxicity characteristic leaching procedure (MTCLP) and the tank leaching test (NEN 7345), respectively. The results showed that the electroplating sludge continued to leach heavy metals, including nickel, copper, and zinc, and posed a serious threat to the environment. The belite-rich cement made from the electroplating sludge was abundant in hydraulic β-dicalcium silicate, and it performed well with regard to compressive-strength development when properly blended with ordinary Portland cements. The blended cement containing up to 40% the belite-rich cement can still satisfy the compressive-strength requirements of ASTM standards, and the pastes cured for 90 days had comparable compressive strength to an ordinary Portland cement paste. It was also found that the later hydration reaction of the blended cements was relatively more active, and high fractions of belite-rich cement increased the chain length of silicate hydrates. In addition, by converting the sludge into belite-rich cements, the heavy metals became stable in the hardened cement pastes. This study thus indicates a viable alternative approach to dealing with heavy metal bearing wastes, and the resulting products show good compressive strength and heavy-metal stability. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Hydration and leaching characteristics of cement pastes made from electroplating sludge

    SciTech Connect

    Chen, Ying-Liang; Ko, Ming-Sheng; Lai, Yi-Chieh; Chang, Juu-En

    2011-06-15

    The purpose of this study was to investigate the hydration and leaching characteristics of the pastes of belite-rich cements made from electroplating sludge. The compressive strength of the pastes cured for 1, 3, 7, 28, and 90 days was determined, and the condensation of silicate anions in hydrates was examined with the {sup 29}Si nuclear magnetic resonance (NMR) technology. The leachabilities of the electroplating sludge and the hardened pastes were studied with the multiple toxicity characteristic leaching procedure (MTCLP) and the tank leaching test (NEN 7345), respectively. The results showed that the electroplating sludge continued to leach heavy metals, including nickel, copper, and zinc, and posed a serious threat to the environment. The belite-rich cement made from the electroplating sludge was abundant in hydraulic {beta}-dicalcium silicate, and it performed well with regard to compressive-strength development when properly blended with ordinary Portland cements. The blended cement containing up to 40% the belite-rich cement can still satisfy the compressive-strength requirements of ASTM standards, and the pastes cured for 90 days had comparable compressive strength to an ordinary Portland cement paste. It was also found that the later hydration reaction of the blended cements was relatively more active, and high fractions of belite-rich cement increased the chain length of silicate hydrates. In addition, by converting the sludge into belite-rich cements, the heavy metals became stable in the hardened cement pastes. This study thus indicates a viable alternative approach to dealing with heavy metal bearing wastes, and the resulting products show good compressive strength and heavy-metal stability.

  5. Injectable bioactive calcium-magnesium phosphate cement for bone regeneration.

    PubMed

    Wu, Fan; Su, Jiacan; Wei, Jie; Guo, Han; Liu, Changsheng

    2008-12-01

    Novel injectable and degradable calcium-magnesium phosphate cement (CMPC) with rapid-setting characteristic was developed by the introduction of magnesium phosphate cement (MPC) into calcium phosphate cement (CPC). The calcium-magnesium phosphate cement prepared under the optimum P/L ratio exhibited good injectability and desired workability. It could set within 10 min at 37 degrees C in 100% relative humidity and the compressive strength could reach 47 MPa after setting for 48 h, indicating that the prepared cement has relatively high initial mechanical strength. The results of in vitro degradation experiments demonstrated the good degradability of the injectable CMPC, and its degradation rate occurred significantly faster than that of pure CPC in simulated body fluid (SBF) solution. It can be concluded that the novel injectable calcium-magnesium phosphate cement is highly promising for a wide variety of clinical applications, especially for the development of minimally invasive techniques.

  6. Helium-induced hardening effect in polycrystalline tungsten

    NASA Astrophysics Data System (ADS)

    Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

    2017-09-01

    In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

  7. Glass transition and physical hardening of asphalts

    NASA Astrophysics Data System (ADS)

    Kriz, Pavel

    Glass transition and physical hardening was studied in straight-run paving asphalt binders. Two methods, modulated differential scanning calorimetry and dynamic mechanical analysis, were utilized in this study. Kinetic nature of the glass transition was observed in studied asphalts. The glass transition temperature, which represents the transition, was found to be a quantity dependent on observation time and thus meaningless without observation time being specified. The glass transition of asphalts was found to be very broad on the temperature scale due to complexity of the chemical composition. Asphalts were found to be multiphase systems, with glassy amorphous, non-glassy amorphous and crystalline domains existing between approximately 10 and -45°C. Physical hardening was observed in asphalts at broad range of temperatures. Physical aging, i.e. structural relaxation of the glass, was identified as a major process contributing to physical hardening. Direct effect of crystallization was rather insignificant in the temperature range of glass transition. However, the presence of crystals was suggested to affect the molecular mobility of the amorphous phase and thus increase the hardening rate and also extent the phenomenon to higher temperatures outside the normal glass transition range. The concept of rigid amorphous phase was offered. The effect of the physical hardening could generally be reversed upon heating to higher temperature. Although for semi-crystalline asphalt, temperature higher by 50°C than the isothermal storage temperature, was found not to be sufficient to successfully reverse the hardening. Effect of thermal stress on the hardening rate was studied. It was found that the imposed stress was either not significant factor affecting the asphalt hardening or the imposed stress was too low to affect hardening rate significantly. Rheological model able to capture the dependence of relaxation times on the isothermal storage time, reference temperature

  8. Improvement of casing cementation of deep and ultradeep wells. Part 2: Oilfield cements and cement additives

    NASA Astrophysics Data System (ADS)

    Arens, K. H.; Akstinat, M.

    1982-07-01

    Oilfield cements and cement additives were investigated in order to improve the casing cementation of deep and ultradeep wells. Characterization and evaluation of the main oil field cements commercially available were studied. The testing was carried out according to American Petroleum Institute API standards and nonstandardized test methods (dynamic modulus of elasticity, expansion/shrinkage), especially the rheology, thickening time and the influence of pressure, temperature and water-cement ratio, were considered. The main emphasis in the field of cement additives was on the evaluation of cement retarders for high temperatures, accelerators, and additives for cement expansion. Furthermore oil field cements were tested, and their properties are described.

  9. Method of Hardening Glass-Reinforced Plastics,

    DTIC Science & Technology

    1988-02-09

    373 NETHOD OF HARDENING GLASS -REINFORCED PLASTICS (U) 1/i FOREIGN TECHNOLOGY DIV idRIGHT-PATTERSON NFS ON V F DOLGIKH ET AL 89 FEB 88 FTD-ID(RS)T-M49...FTD-ID(RS)T-0049-88 9 February 1988 MICROFICHE NR: FTD-tES-C-00219 METHOD OF HARDENING GLASS -REINFORCED PLASTICS By: V.F. Dolgikh, S.L. Roginskiy, et...translation were extracted from the best quality copy available. If 1 11i METHOD OF HARDENING GLASS -REINFORCED PLASTICS V. F. Dolgikh, S. L. Roginskiy, E. L

  10. Cyclic hardening mechanisms in Nimonic 80A

    NASA Technical Reports Server (NTRS)

    Lerch, B. A.; Gerold, V.

    1987-01-01

    A nickel base superalloy was fatigued under constant plastic strain range control. The hardening response was investigated as a function of plastic strain range and particle size of the gamma prime phase. Hardening was found to be a function of the slip band spacing. Numerous measurements of the slip band spacing and other statistical data on the slip band structures were obtained. Interactions between intersecting slip systems were shown to influence hardening. A Petch-Hall model was found to describe best this relationship between the response stress and the slip band spacing.

  11. Abyssal seep site cementation

    SciTech Connect

    Neumann, A.C.; Paull, C.K.; Commeau, R.; Commeau, J.

    1988-01-01

    The deepest submarine cements known so far occur along the 3,300-m deep base of the Florida escarpment and are associated with methane-bearing brine seeps, which emanate there. These deep Holocene carbonates, which occur as surficial and buried crusts, burrow fillings, and friable horizons, were sampled via ALVIN. The carbonates form irregular halos extending up to 20 m from seeps colonized by chemosynthetic fauna. Mussels, gastropods, and clams, the carbonate components of the community, produce a shell hash that is locally cemented by coarsely crystalline low-Mg calcite. Halos of palisade calcite are reminiscent of ancient examples of marine cements. Also present are carbonate hemipelagics cemented by micrite into crusts and burrow fillings. The degree of cementation varies from pervasive to light. Slabs of cemented crust up to 30 cm thick contrast with typical shallow crusts and exhibit irregular tops and smooth bottoms indicating different chemical gradients and pathways.

  12. Cementation of indirect restorations: an overview of resin cements.

    PubMed

    Stamatacos, Catherine; Simon, James F

    2013-01-01

    The process of ensuring proper retention, marginal seal, and durability of indirect restorations depends heavily on effective cementation. Careful consideration must be made when selecting an adhesive cement for a given application. This article provides information on resin cements that can guide clinicians in determining which type of cement is best suited to their clinical needs regarding cementation of indirect restorations. Emphasis is placed on successful cementation of all-ceramic restorations.

  13. Impedance methodology: A new way to characterize the setting reaction of dental cements.

    PubMed

    Villat, Cyril; Tran, Xuan-Vinh; Tran, V X; Pradelle-Plasse, Nelly; Ponthiaux, Pierre; Wenger, François; Grosgogeat, Brigitte; Colon, Pierre

    2010-12-01

    Impedance spectroscopy is a non-destructive, quantitative method, commonly used nowadays for industrial research on cement and concrete. The aim of this study is to investigate the interest of impedance spectroscopy in the characterization of setting process of dental cements. Two types of dental cements are used in this experiment: a new Calcium Silicate cement Biodentine™ (Septodont, Saint Maur-des Fossés, France) and a glass ionomer cement resin modified or not (Fuji II(®) LC Improved Capsules and Fuji IX(®) GP Fast set Capsules, GC Corp., Tokyo, Japan). The conductivity of the dental cements was determined by impedance spectroscopy measurements carried out on dental cement samples immersed in a 0.1M potassium chloride solution (KCl) in a "like-permeation" cell connected to a potentiostat and a Frequency Response Analyzer. The temperature of the solution is 37°C. From the moment of mixing of powder and liquid, the experiments lasted 2 weeks. The results obtained for each material are relevant of the setting process. For GIC, impedance values are stabilized after 5 days while at least 14 days are necessary for the calcium silicate based cement. In accordance with the literature regarding studies of cements and concrete, impedance spectroscopy can characterize ion mobility, porosity and hardening process of dental hydrogel materials. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Low Temperature Salt Bath Hardening of AISI 201 Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Luo, H. S.; Zhao, C.

    Salt bath hardening at low temperature was applied in order to enhance the surface hardness of AISI 201 stainless steel. The structure and properties of the hardened layer were investigated, such as microstructure, hardness, wear resistance and corrosion resistance. The experiment results show that the treatment temperature plays an importance role in the microstructure and properties of the hardened layer. If the treatment temperature is below 460°C, the hardened layer was a face centre tetragonal (fct) structure without chromium nitride precipitation. The corrosion resistance of hardened layer is better than the matrix and as good as AISI 316 austenitic stainless steel. If the temperature rises above 460 °C the precipitation show up and the corrosion resistance gets worse. The hardness and thickness of the layer increase as the raising of treatment temperature. The test of wear resistance shows that the amount of wear reduces rapidly after hardening treatment and the worn morphology of the surface behaves abrasive wear while that of AISI 201 stainless steel behaves adhesive wear.

  15. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    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.

  16. Influence of minor components on strength development of 2CaO/SiO/sub 2/-silica cement

    SciTech Connect

    Sasaki, S.; Kobayashi, W.; Okabayashi, S.

    1986-01-01

    The authors have been accumulating the technical data on 2CaO/SiO/sub 2/-silica cement as cementing material for deep oil wells and high-temperature geothermal wells. For this paper, they chose 21 inorganic compounds as minor components that are supposed to contaminate cement slurries at cementing and investigated their influence on strength development of 2CaO/SiO/sub 2/-silica cement. The early compressive strength of ..beta..-2CaO/SiO/sub 2/-silica cement at 662/sup 0/F (350/sup 0/C) decreased remarkably with the addition of borates and hydroxides, but the strength of hardened specimens with 0.5 to 1.0% calcium chloride and magnesium chloride increased significantly. Also, they confirmed that the effect of the addition of minor components of ..beta..-2CaO/SiO/sub 2/-silica cement was similar to that on ..gamma..-2CaO/SiO/sub 2/-silica cement. Within this work, the strength of hardened specimens cured at 350/sup 0/F (177/sup 0/C) decreased with the addition of any inorganic compounds.

  17. Physico-mechanical and physico-chemical properties of synthesized cement based on plasma- and wet technologies

    NASA Astrophysics Data System (ADS)

    Sazonova, Natalya; Skripnikova, Nelli

    2016-01-01

    In this work we studied the influence of plasma-chemical technology of cement clinker synthesis under conditions of high-concentrated heat streams on the properties of cement on fixing such factors as raw-material type (chemical and mineralogical composition), fraction composition, homogenization and module characters of the raw-material mixture. In this connection the sludge of the cement plant in town Angarsk, based on which the cement clinker synthesis using the wet- and plasma-chemical technologies was performed, was used in the studies. The results of chemical X-ray-phase analysis, petrography of cement clinkers, differential scanning colorimetry of hardened cement paste are represented in this work. The analysis of building-technical properties of inorganic viscous substances was performed. It was found that in using the identical raw-material mixture the cement produced with temperature higher by 1650 °C than the traditional one may indicate the higher activity. The hardened cement paste compressive strength at the age of 28 days was higher than the strength of the reference samples by 40.8-41.4 %.

  18. Analysis of the regimes in the scanner-based laser hardening process

    NASA Astrophysics Data System (ADS)

    Martínez, S.; Lamikiz, A.; Ukar, E.; Calleja, A.; Arrizubieta, J. A.; Lopez de Lacalle, L. N.

    2017-03-01

    Laser hardening is becoming a consolidated process in different industrial sectors such as the automotive industry or in the die and mold industry. The key to ensure the success in this process is to control the surface temperature and the hardened layer thickness. Furthermore, the development of reliable scanners, based on moving optics for guiding high power lasers at extremely fast speeds allows the rapid motion of laser spots, resulting on tailored shapes of swept areas by the laser. If a scanner is used to sweep a determined area, the laser energy density distribution can be adapted by varying parameters such us the scanning speed or laser power inside this area. Despite its advantages in terms of versatility, the use of scanners for the laser hardening process has not yet been introduced in the thermal hardening industry because of the difficulty of the temperature control and possible non-homogeneous hardness thickness layers. In the present work the laser hardening process with scanning optics applied to AISI 1045 steel has been studied, with special emphasis on the influence of the scanning speed and the results derived from its variation, the evolution of the hardened layer thickness and different strategies for the control of the process temperature. For this purpose, the hardened material has been studied by measuring microhardness at different points and the shape of the hardened layer has also been evaluated. All tests have been performed using an experimental setup designed to keep a nominal temperature value using a closed-loop control. The tests results show two different regimes depending on the scanning speed and feed rate values. The experimental results conclusions have been validated by means of thermal simulations at different conditions.

  19. A Novel Heat Treatment Process for Surface Hardening of Steel: Metal Melt Surface Hardening

    NASA Astrophysics Data System (ADS)

    Fu, Yong-sheng; Zhang, Wei; Xu, Xiaowei; Li, Jiehua; Li, Jun; Xia, Mingxu; Li, Jianguo

    2017-09-01

    A novel heat treatment process for surface hardening of steel has been demonstrated and named as "metal melt surface hardening (MMSH)." A surface layer with a thickness of about 400 μm and a hardness of about 700 HV has been achieved by ejecting AISI 304 stainless steel melt at a temperature of about 1783 K (1510 °C) onto the 40Cr steel surface. This proposed MMSH provides a very promising application for surface hardening of steel.

  20. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  1. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  2. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  3. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  4. 7 CFR 58.641 - Hardening and storage.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage. 58.641 Section 58.641... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended container it shall be placed in a hardening tunnel or hardening room to continue the freezing process....

  5. Process for hardening the surface of polymers

    DOEpatents

    Mansur, L.K.; Lee, E.H.

    1992-07-14

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

  6. Process for hardening the surface of polymers

    DOEpatents

    Mansur, Louis K.; Lee, Eal H.

    1992-01-01

    Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

  7. Extraordinary strain hardening by gradient structure.

    PubMed

    Wu, XiaoLei; Jiang, Ping; Chen, Liu; Yuan, Fuping; Zhu, Yuntian T

    2014-05-20

    Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures.

  8. Alloy solution hardening with solute pairs

    DOEpatents

    Mitchell, John W.

    1976-08-24

    Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.

  9. Electromechanical Surface Hardening of Tubing Steels

    NASA Astrophysics Data System (ADS)

    Fedorova, L. V.; Fedorov, S. K.; Serzhant, A. A.; Golovin, V. V.; Systerov, S. V.

    2017-07-01

    Results of metallographic studies of the structure of steels 38G2S and 37G2F and steels of group D after electromechanical surface hardening of tube specimens over the external diameter are presented.

  10. Hardened Dunes in Arcadia Planitia

    NASA Image and Video Library

    2014-10-29

    NASA Mars Reconnaissance Orbiter HiRISE, with its high resolution and eight years in orbit about Mars, has shown that many dunes and ripples on the planet are active. This demonstrates that in some areas sand is loose enough and winds strong enough, that significant change can occur. Nevertheless, other Martian dunes are clearly *inactive*. This image in Arcadia Planitia shows dunes in a crater. Unlike active dunes on the planet, those here are bright, and, zooming in, there are several lines of evidence indicating that the dunes have become indurated, that is, hardened into cohesive sediment or even into sandstone rock. For example, the dune field at the southern edge is cut off by a step cliff, indicating erosion of hard material. Although fine scale ripples on the original dune surface are preserved, we also see large scale fluting from southwest to northeast, a common texture associated with wind-induced sand abrasion. How these dunes became indurated is unknown. One possibility is that this area of Mars was buried and then exhumed, a process that seems to have occurred many times in the Martian past over various areas of the planet. During burial, compaction and possibly ground water circulation would have indurated the dunes, leaving them as a hard sandstone that, when exhumed, was subsequently partially eroded. http://photojournal.jpl.nasa.gov/catalog/PIA18890

  11. [Beam hardening correction method for X-ray computed tomography based on subsection beam hardening curves].

    PubMed

    Huang, Kui-dong; Zhang, Ding-hua

    2009-09-01

    After researching the forming principle of X-ray beam hardening and analyzing the usual methods of beam hardening correction, a beam hardening correction model was established, in which the independent variable was the projection gray, and so the computing difficulties in beam hardening correction can be reduced. By considering the advantage and disadvantage of fitting beam hardening curve to polynomial, a new expression method of the subsection beam hardening curves based on polynomial was proposed. In the method, the beam hardening data were fitted firstly to a polynomial curve which traverses the coordinate origin, then whether the got polynomial curve surged in the fore-part or back-part of the fitting range was judged based on the polynomial curvature change. If the polynomial fitting curve surged, the power function curve was applied to replace the surging parts of the polynomial curve, and the C1 continuity was ensured at the joints of the segment curves. The experimental results of computed tomography (CT) simulation show that the method is well stable in the beam hardening correction for the ideal CT images and CT images with added noises, and can mostly remove the beam hardening artifact at the same time.

  12. Decline in Radiation Hardened Microcircuit Infrastructure

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.

    2015-01-01

    Two areas of radiation hardened microcircuit infrastructure will be discussed: 1) The availability and performance of radiation hardened microcircuits, and, and 2) The access to radiation test facilities primarily for proton single event effects (SEE) testing. Other areas not discussed, but are a concern include: The challenge for maintaining radiation effects tool access for assurance purposes, and, the access to radiation test facilities primarily for heavy ion single event effects (SEE) testing. Status and implications will be discussed for each area.

  13. Work hardening behavior in aluminum alloy 2090

    SciTech Connect

    Tseng, Carol

    1993-12-01

    An investigation into the work hardening behavior of an aluminum alloy 2090-T81 Al-3.05Cu-2.16Li-0.12Zr at various test temperatures, heat treatment conditions and microstructures was conducted. One microstructure consisted of unrecrystallized, highly textured grains, and the other microstructure was composed of recrystallized grains. Microstructural effects on work hardening were divided into two levels of contribution: the grain structure level, which consisted of the grain size and shape, subgrains and texture, and the microconsistent level, which included the precipitates and solutes. Two heat treatments were studied: the as-received, peak-aged condition, and the solution heat treated condition where the as-received plate was resolutionized. Observations of the deformed surface of both as-received grain structures at various prestrains indicated that there was no correlation between an increase in slip homogeneity and an increase in work hardening. The increase in out-of-plane grain rotation at lower temperatures was not primarily responsible for the increase in work hardening. In addition, the fully plastic deformation microstructure for the unrecrystallized microstructure appeared very inhomogeneous as the grains deformed in bands; there were also bands of grains that had very little to no deformation. From the work hardening plots it was found that an unrecrystallized, (110)<112> textured grain structure with a homogeneous distribution of subgrains produced the highest rate of work hardening between 300 K and 77 K. When the microconstituents are added to both grain structures, both the work hardening rate in the elastic-plastic and fully plastic regimes and the level of work hardening at which the elastic-plastic to fully plastic transition occurred were affected.

  14. Properties and Commercial Application of Manual Plasma Hardening

    NASA Astrophysics Data System (ADS)

    Korotkov, V. A.

    2016-11-01

    A new method and a device for plasma hardening of various parts are considered. Installation of the new device does not require too much investment (the active mechanical productions are appropriate for its accommodation) and special choice of personnel (welders train to use it without difficulty). Plasma hardening does not deform and worsen the smoothness of the surface, which makes it possible to employ many hardened parts without finishing mechanical treatment required after bulk or induction hardening. The hardened layer (about 1 mm) produced by plasma hardening exhibits better wear resistance than after bulk hardening with tempering, which prolongs the service life of the parts.

  15. On shakedown analysis in hardening plasticity

    NASA Astrophysics Data System (ADS)

    Nguyen, Quoc-Son

    2003-01-01

    The extension of classical shakedown theorems for hardening plasticity is interesting from both theoretical and practical aspects of the theory of plasticity. This problem has been much discussed in the literature. In particular, the model of generalized standard materials gives a convenient framework to derive appropriate results for common models of plasticity with strain-hardening. This paper gives a comprehensive presentation of the subject, in particular, on general results which can be obtained in this framework. The extension of the static shakedown theorem to hardening plasticity is presented at first. It leads by min-max duality to the definition of dual static and kinematic safety coefficients in hardening plasticity. Dual static and kinematic approaches are discussed for common models of isotropic hardening of limited or unlimited kinematic hardening. The kinematic approach also suggests for these models the introduction of a relaxed kinematic coefficient following a method due to Koiter. Some models for soils such as the Cam-clay model are discussed in the same spirit for applications in geomechanics. In particular, new appropriate results concerning the variational expressions of the dual kinematic coefficients are obtained.

  16. Utilization of Palm Oil Clinker as Cement Replacement Material.

    PubMed

    Kanadasan, Jegathish; Abdul Razak, Hashim

    2015-12-16

    The utilization of waste materials from the palm oil industry provides immense benefit to various sectors of the construction industry. Palm oil clinker is a by-product from the processing stages of palm oil goods. Channelling this waste material into the building industry helps to promote sustainability besides overcoming waste disposal problems. Environmental pollution due to inappropriate waste management system can also be drastically reduced. In this study, cement was substituted with palm oil clinker powder as a binder material in self-compacting mortar. The fresh, hardened and microstructure properties were evaluated throughout this study. In addition, sustainability component analysis was also carried out to assess the environmental impact of introducing palm oil clinker powder as a replacement material for cement. It can be inferred that approximately 3.3% of cement production can be saved by substituting palm oil clinker powder with cement. Reducing the utilization of cement through a high substitution level of this waste material will also help to reduce carbon emissions by 52%. A cleaner environment free from pollutants can be created to ensure healthier living. Certain industries may benefit through the inclusion of this waste material as the cost and energy consumption of the product can be minimized.

  17. Utilization of Palm Oil Clinker as Cement Replacement Material

    PubMed Central

    Kanadasan, Jegathish; Abdul Razak, Hashim

    2015-01-01

    The utilization of waste materials from the palm oil industry provides immense benefit to various sectors of the construction industry. Palm oil clinker is a by-product from the processing stages of palm oil goods. Channelling this waste material into the building industry helps to promote sustainability besides overcoming waste disposal problems. Environmental pollution due to inappropriate waste management system can also be drastically reduced. In this study, cement was substituted with palm oil clinker powder as a binder material in self-compacting mortar. The fresh, hardened and microstructure properties were evaluated throughout this study. In addition, sustainability component analysis was also carried out to assess the environmental impact of introducing palm oil clinker powder as a replacement material for cement. It can be inferred that approximately 3.3% of cement production can be saved by substituting palm oil clinker powder with cement. Reducing the utilization of cement through a high substitution level of this waste material will also help to reduce carbon emissions by 52%. A cleaner environment free from pollutants can be created to ensure healthier living. Certain industries may benefit through the inclusion of this waste material as the cost and energy consumption of the product can be minimized. PMID:28793748

  18. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2004-01-30

    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.

  19. Solid state NMR and LVSEM studies on the hardening of latex modified tile mortar systems

    SciTech Connect

    Rottstegge, J.; Arnold, M.; Herschke, L.; Glasser, G.; Wilhelm, M.; Spiess, H.W. . E-mail: spiess@mpip-mainz.mpg.de; Hergeth, W.D.

    2005-12-15

    Construction mortars contain a broad variety of both inorganic and organic additives beside the cement powder. Here we present a study of tile mortar systems based on portland cement, quartz, methyl cellulose and different latex additives. As known, the methyl cellulose stabilizes the freshly prepared cement paste, the latex additive enhances final hydrophobicity, flexibility and adhesion. Measurements were performed by solid state nuclear magnetic resonance (NMR) and low voltage scanning electron microscopy (LVSEM) to probe the influence of the latex additives on the hydration, hardening and the final tile mortar properties. While solid state NMR enables monitoring of the bulk composition, scanning electron microscopy affords visualization of particles and textures with respect to their shape and the distribution of the different phases. Within the alkaline cement paste, the poly(vinyl acetate) (VAc)-based latex dispersions stabilized by poly(vinyl alcohol) (PVA) were found to be relatively stable against hydrolysis. The influence of the combined organic additives methyl cellulose, poly(vinyl alcohol) and latexes stabilized by poly(vinyl alcohol) on the final silicate structure of the cement hydration products is small. But even small amounts of additives result in an increased ratio of ettringite to monosulfate within the final hydrated tile mortar as monitored by {sup 27}Al NMR. The latex was found to be adsorbed to the inorganic surfaces, acting as glue to the inorganic components. For similar latex water interfaces built up by poly(vinyl alcohol), a variation in the latex polymer composition results in modified organic textures. In addition to the networks of the inorganic cement and of the latex, there is a weak network build up by thin polymer fibers, most probably originating from poly(vinyl alcohol). Besides the weak network, polymer fibers form well-ordered textures covering inorganic crystals such as portlandite.

  20. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  1. Increase in the strength characteristics of Portland cement due to introduction of the compound mineral supplements

    NASA Astrophysics Data System (ADS)

    Il'ina, Liliia; Gichko, Nikolai; Mukhina, Irina

    2016-01-01

    At the initial phase of hardening it is the limestone component that plays a major role in the hardening process, which acts as the substrate for the crystallization of hydrate tumors due to its chemical affinity with the products of Portland cement hydration. After 7 days, the diopside supplement influences the processes more significantly. Diopside has a high modulus of elasticity compared to the cement paste. As a result, stresses are redistributed within the cement paste and the whole composition is hardened. An increase in the quantity of diopside in the compound supplement to more than 66.7% does not provide a substantial increase in the strength of the cement paste. As the hardness of diopside is higher than the hardness of limestone, much more energy is required to grind it down to a usable component. Therefore, a further increase in the quantity of diopside in the compound supplement is not economically feasible. An evaluation of the optimum quantity of input compound mineral supplements can be made based on the ideas of close packing of spherical particles and the Pauling rules. The optimum content of the supplement is 8-8.5% provided that its dispersion and density are close to the dispersion and density of the binder. An increase in the dispersion of the supplement reduces its optimal quantity.

  2. Development of a strontium-containing hydroxyapatite bone cement.

    PubMed

    Guo, Dagang; Xu, Kewei; Zhao, Xiaoyun; Han, Yong

    2005-07-01

    A new route was developed to synthesis a new type of strontium-containing hydroxyapatite (Sr-HAP) bone cement with precursors of tetracalcium phosphate (TTCP), strontium hydrogen phosphate (DSPA), dicalcium phosphate (DCPA), phosphate acid and water. The processing parameters and fundamental properties including pH value, setting time, compressive strength of final hardened body and the cytotoxicity for serial extracts of each cements were investigated. The result shows that the final product of the cement after setting for 24h is nonstoichiometic Sr-containing hydroxyapatite (Ca(10-m-x)Sr(x) square(m)(HPO4)y(PO4)6-y(OH)2-2m square2m, 0cement pastes approaches to 7.0-7.6 when they are mixed with a ratio of 1:1 of powder to liquid (P/L) in weight. The setting time of the cement pastes is 4-11 min for the initial one and 10-17 min for the final one when the concentration of diluted phosphate is in a range of 0.5-1.0 mol/l. The compressive strengths of the hardened cements with different molar ratios of Sr/(Sr+Ca) after subjected an immersion in simulated body fluid (SBF) increase uniformly from 1 day to 5 days, where they get maximum values, respectively, but then decrease till to 2 weeks. Especially for the CPC-1, with a Sr/(Sr+Ca) molar ratios of 5% in cement powder composition, the largest compressive strength gained at 5 days is 66.57 MPa and the lowest one gained at 2 weeks is 44.75 MPa, which matches the value of human bones and can be expected to use in clinic application in repairing the nonloading sites on account of the positive result of cytotoxicity test of the extracts of Sr-containing calcium phosphate cement (Sr-CPC).

  3. [Dentin bonding of cements. The bonding of cements with dentin in combination with various indirect restorative materials].

    PubMed

    Peutzfeldt, Anne; Sahafi, Alireza; Flury, Simon

    2011-01-01

    The number of both luting agents and restorative materials available on the market has rapidly increased. This study compared various types of luting agents when used to bond different indirect, laboratory restorative materials to dentin. Cylinders were produced of six restorative materials (gold alloy, titanium, feldspathic porcelain, leucite-glass ceramic, zirconia, and an indirect resin composite). Following relevant pretreatment, the end surface of the cylinders were luted to ground, human dentin with eight different luting agents (DeTrey Zinc [zinc phosphate cement], Fuji I [conventional glass ionomer cement], Fuji Plus [resin-modified glass ionomer cement], Variolink II [conventional etch-and-rinse resin cement], Panavia F2.0 and Multilink [self-etch resin cements], RelyX Unicem Aplicap and Maxcem [self-adhesive resin cements]). After water storage at 37 °C for one week, the shear bond strength of the specimens was measured and the fracture mode was examined stereo-microscopically. Restorative material and luting agent both had a significant effect on bond strength and there was a significant interaction between the two variables. The zinc phosphate cement and the glass ionomer cements resulted in the lowest bond strengths, whereas the highest bond strengths were found with the two self-etch and one of the self-adhesive resin cements.

  4. Characterization of dicalcium phosphate dihydrate cements prepared using a novel hydroxyapatite-based formulation.

    PubMed

    Alge, Daniel L; Santa Cruz, Grace; Goebel, W Scott; Chu, Tien-Min Gabriel

    2009-04-01

    Dicalcium phosphate dihydrate (DCPD) cements are typically prepared using beta-tricalcium phosphate (beta-TCP) as the base component. However, hydroxyapatite (HA) is an interesting alternative because of its potential for reducing cement acidity, as well as modulating cement properties via ionic substitutions. In the present study, we have characterized DCPD cements prepared with a novel formulation based on monocalcium phosphate monohydrate (MCPM) and HA. Cements were prepared using a 4:1 MCPM:HA molar ratio. The reactivity of HA in this system was verified by showing DCPD formation using poorly crystalline HA, as well as highly crystalline HA. Evaluation of cements prepared with poorly crystalline HA revealed that setting occurs rapidly in the MCPM/HA system, and that the use of a setting regulator is necessary to maintain workability of the cement paste. Compressive testing showed that MCPM/HA cements have strengths comparable to what has previously been published for DCPD cements. However, preliminary in vitro analysis of cement degradation revealed that conversion of DCPD to HA may occur much more rapidly in the MCPM/HA system compared to cements prepared with beta-TCP. Future studies should investigate this property further, as it could have important implications for the use of HA-based DCPD cement formulations.

  5. The secondary hardening phenomenon in strain-hardened MP35N alloy

    SciTech Connect

    Asgari, S.; El-Danaf, E.; Shaji, E.; Kalidindi, S.R.; Doherty, R.D.

    1998-10-09

    Mechanical testing and microscopy techniques were used to investigate the influence of aging on the structure and strengthening of MP35N alloy. It was confirmed that aging the deformed material at 600 C for 4 h provided additional strengthening, here referred to as secondary hardening, in addition to the primary strain hardening. The secondary hardening phenomenon was shown to be distinctly different from typical age hardening processes in that it only occurred in material deformed beyond a certain cold work level. At moderate strains, aging caused a shift in the entire stress-strain curve of the annealed material to higher stresses while at high strains, it produced shear localization and limited work softening. The secondary hardening increment was also found to be grain size dependent. The magnitude of the secondary hardening appeared to be controlled by the flow stress in the strain hardened material. A model is proposed to explain the observations and is supported by direct experimental evidence. The model is based on formation of h.c.p. nuclei through the Suzuki mechanism, that is segregation of solute atoms to stacking faults, on aging the strain hardened material. The h.c.p. precipitates appear to thicken only in the presence of high dislocation density produced by prior cold work.

  6. Discoloration of dental cements and composites in a sulfide solution.

    PubMed

    Sugawara, A; Antonucci, J M; Paffenbarger, G C; Nishiyama, M

    1991-03-01

    In an early study the discoloration of certain hardened silicate cements, after exposure to an atmosphere of hydrogen sulfide (H2S) for 24 h at room temperature, was ascribed to the formation of dark-colored sulfides of base metal impurities (Paffenbarger et al. JADA 25,32,1938). A recent study noted that, in general, silicate and glass ionomer cements were more prone to color shifts than composites after exposure to H2S for 9 weeks (Sugawara, Ph. D. Thesis, Nihon Univ.). The aim of the present study was to devise a simple, aqueous sulfide exposure test for esthetic restorative materials. The general procedure was to expose specimen disks to a 0.1% (w/v) sodium sulfide solution, adjusted to pH 9, for 1-7 days at 37 degrees or 55 degrees C. The 55 degrees C-Na2S exposure was designed as an accelerated test. Materials studied included: 1 silicate and 2 silicophosphate cements of known lead content, a glass ionomer cement (FIIF), several commercial composites and an experimental, hydrophilic composite. Known amounts of base metal contaminants in the form of appropriate salt solutions were added to the liquid components of FIIF and the composites. Specimens exposed to distilled water under the same conditions served as controls. Exposure to the aqueous sulfide medium resulted in the following ranking in order of decreasing discoloration: Glass ionomer cement greater than silicophosphate cement greater than silicate cement greater than hydrophilic composite greater than hydrophobic composite. Generally, the results of the aq. Na2S test paralleled those obtained with H2S. The degree of discoloration is dependent on a number of factors: the nature, concentration and leachability of the metal impurities, and the hydrophilicity and permeability to sulfide of the esthetic restoratives.

  7. Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets.

    PubMed

    Lu, Liulei; Ouyang, Dong

    2017-07-20

    In this work, the effect of graphene oxide nanosheet (GONS) additives on the properties of cement mortar and ultra-high strength concrete (UHSC) is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0-0.03% by weight of cement). Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study.

  8. Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets

    PubMed Central

    Ouyang, Dong

    2017-01-01

    In this work, the effect of graphene oxide nanosheet (GONS) additives on the properties of cement mortar and ultra-high strength concrete (UHSC) is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0–0.03% by weight of cement). Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study. PMID:28726750

  9. Ultrasonic Characterization of the Curing Process of Polymethylmethacrylate-based Bone Cement Modified with Hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Viano, Ann; Auwarter, Julie; Hoffmeister, Brent; Rho, Jae-Young

    2000-03-01

    The use of polymethylmethacrylate (PMMA)-based bone cement for implantation of metallic prostheses is becoming increasingly common. Failure of a cemented prosthesis often occurs when there is weak bonding at the bone/cement or cement/metal interface. The addition of hydroxyapatite (HA) particles, a synthetically produced version of the natural mineral in bone, may improve the adhesion by promoting bone growth into the cement itself. The curing time of PMMA bone cement determines the speed of implant insertion, which can affect the mechanical strength of the cement. Pure PMMA has a well-characterized curing time of 9-12 minutes, depending on environmental factors such as temperature and humidity. By measuring the propagation of ultrasonic pulses through a sample of bone cement, the curing process can be monitored. As the material hardens, the velocity of an ultrasonic pulse increases, and the attenuation decreases. These parameters were measured as a function of time for PMMA mixed with 0, 10 and 30investigation of the curing process as a function of hydroxyapatite concentration.

  10. Structure, properties and animal study of a calcium phosphate/calcium sulfate composite cement.

    PubMed

    Chen, Wei-Luen; Chen, Chang-Keng; Lee, Jing-Wei; Lee, Yu-Ling; Ju, Chien-Ping; Lin, Jiin-Huey Chern

    2014-04-01

    In-vitro and in-vivo studies have been conducted on an in-house-developed tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrate (CSH)-derived composite cement. Unlike most commercial calcium-based cement pastes, the investigated cement paste can be directly injected into water and harden without dispersion. The viability value of cells incubated with a conditioned medium of cement extraction is >90% that of Al2O3 control and >80% that of blank medium. Histological examination reveals excellent bonding between host bone and cement without interposition of fibrous tissues. At 12 weeks-post implantation, significant remodeling activities are found and a new bone network is developed within the femoral defect. The 26-week samples show that the newly formed bone becomes more mature, while the interface between residual cement and the new bone appears less identifiable. Image analysis indicates that the resorption rate of the present cement is much higher than that of TTCP or TTCP/DCPA-derived cement under similar implantation conditions. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  11. Rate of CO2 attack on hydrated Class H well cement under geologic sequestration conditions.

    PubMed

    Kutchko, Barbara G; Strazisar, Brian R; Lowry, Gregory V; Dzombak, David A; Thaulow, Niels

    2008-08-15

    Experiments were conducted to study the degradation of hardened cement paste due to exposure to CO2 and brine under geologic sequestration conditions (T = 50 degrees C and 30.3 MPa). The goal was to determine the rate of reaction of hydrated cement exposed to supercritical CO2 and to CO2-saturated brine to assess the potential impact of degradation in existing wells on CO2 storage integrity. Two different forms of chemical alteration were observed. The supercritical CO2 alteration of cement was similar in process to cement in contact with atmospheric CO2 (ordinary carbonation), while alteration of cement exposed to CO2-saturated brine was typical of acid attack on cement. Extrapolation of the hydrated cement alteration rate measured for 1 year indicates a penetration depth range of 1.00 +/- 0.07 mm for the CO2-saturated brine and 1.68 +/- 0.24 mm for the supercritical CO2 after 30 years. These penetration depths are consistent with observations of field samples from an enhanced oil recovery site after 30 years of exposure to CO2-saturated brine under similar temperature and pressure conditions. These results suggest that significant degradation due to matrix diffusion of CO2 in intact Class H neat hydrated cement is unlikely on time scales of decades.

  12. Timing of syntaxial cement

    SciTech Connect

    Perkins, R.D.

    1985-02-01

    Echinodermal fragments are commonly overgrown in ancient limestones, with large single crystals growing in optical continuity over their skeletal hosts (i.e., syntaxial overgrowths). Such syntaxial cements are usually considered to have precipitated from meteoric pore waters associated with a later stage of subaerial exposure. Although several examples have been reported from ancient carbonates where petrographic relationships may indicate an early submarine formation of syntaxial cement, no occurrences have been noted in Holocene submarine-cemented rocks. Syntaxial cements of submarine origin have been found in Bermuda beachrock where isopachous high-magnesian calcite cements merge with large optically continuous crystals growing on echinodermal debris. Examination of other Holocene sediments cemented by magnesian calcite indicates that echinodermal fragments are not always overgrown syntaxially, but may be rimmed by microcrystalline calcite. The reason for this difference is not clear, although it may be a function of the spacing of nucleation sites and rates of crystal growth. A review of syntaxial cements from several localities in ancient carbonate sequences reveals that many are best interpreted as having formed in the submarine setting, whereas it is more clear that others formed from meteoric precipitation. These occurrences suggest that care should be exercised in inferring meteoric diagenesis from syntaxial overgrowths and that the possibility of submarine formation should be considered.

  13. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-07-31

    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. Laboratory testing during the eleventh quarter focused on evaluation of the alkali-silica reaction of eight different cement compositions, four of which contain ULHS. This report provides a progress summary of ASR testing. The original laboratory procedure for measuring set cement expansion resulted in unacceptable erosion of the test specimens. In subsequent tests, a different expansion procedure was implemented and an alternate curing method for cements formulated with TXI Lightweight cement was employed to prevent sample failure caused by thermal shock. The results obtained with the modified procedure showed improvement over data obtained with the original procedure, but data for some compositions were still questionable. Additional modification of test procedures for compositions containing TXI Lightweight cement were implemented and testing is ongoing.

  14. On Analytical Solutions to Beam-Hardening

    NASA Astrophysics Data System (ADS)

    Rigaud, G.

    2017-01-01

    When polychromatic X-rays propagate through a material, for instance in computerized tomography (CT), low energy photons are more attenuated resulting in a "harder" beam. The beam-hardening phenomenon breaks the monochromatic radiation model based on the Radon transform giving rise to artifacts in CT reconstructions to the detriment of visual inspection and automated segmentation algorithms. We propose first a simplified analytic representation for the beam-hardening. Besides providing a general understanding of the phenomenon, this model proposes to invert the beam-hardening effect for homogeneous objects leading to classical monochromatic data. For heterogeneous objects, no analytical reconstruction of the density can be derived without more prior information. However, the beam-hardening is shown to be a smooth operation on the data and thus to preserve the encoding of the singularities of the attenuation map within the data. A microlocal analysis encourages the use of contour extraction methods to solve partially the beam-hardening effect even for heterogeneous objects. The application of both methods, exact analytical solution for homogeneous objects and feature extraction for heterogeneous ones, on real data demonstrates their relevancy and efficiency.

  15. Determination of Diffusion Profiles in Altered Wellbore Cement Using X-ray Computed Tomography Methods

    SciTech Connect

    Mason, Harris E.; Walsh, Stuart D. C.; DuFrane, Wyatt L.; Carroll, Susan A.

    2014-06-17

    The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining “effective linear activity coefficients” (ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO2-rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment.

  16. Preparation of the saving-energy sulphoaluminate cement using MSWI fly ash.

    PubMed

    Shi, Hui-sheng; Deng, Kai; Yuan, Feng; Wu, Kai

    2009-09-30

    MSWI fly ash was used as a major cement raw material in sintering sulphoaluminate cement clinker successfully in the laboratory. Sintering system, mechanical performance, hydration process and microstructure of the clinker was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF), etc. The result shows that the clinker can be sintered properly under the temperature of 1200-1300 degrees C and sintered time of 120 min. Cl(-) content in the clinker made with MSWI fly ash is about 1.08%. However most Cl(-) cannot leach out in water solution from the hardened cement paste during curing age between 1d and 28d because of the Cl(-) being combined in clinker minerals and its hydrates. The compressive strength of the sulphoaluminate cement was high in early age while that developed smoothly in later age.

  17. Analysis of Tensile Stress-Strain and Work-Hardening Behavior in 9Cr-1Mo Ferritic Steel

    NASA Astrophysics Data System (ADS)

    Choudhary, B. K.; Palaparti, D. P. Rao; Samuel, E. Isaac

    2013-01-01

    Detailed analysis on tensile true stress ( σ)-true plastic strain ( ɛ) and work-hardening behavior of 9Cr-1Mo steel have been performed in the framework of the Voce relationship and Kocks-Mecking approach for wide range of temperatures, 300 K to 873 K (27 °C to 600 °C) and strain rates (6.33 × 10-5 to 6.33 × 10-3 s-1). At all test conditions, σ- ɛ data were adequately described by the Voce equation. 9Cr-1Mo steel exhibited two-stage work-hardening behavior characterized by a rapid decrease in instantaneous work-hardening rate ( θ = dσ/ dɛ) with stress at low stresses (transient stage) followed by a gradual decrease in θ at high stresses (stage III). The variations of work-hardening parameters and θ- σ as a function of temperature and strain rate exhibited three distinct temperature regimes. Both work-hardening parameters and θ- σ displayed signatures of dynamic strain aging at intermediate temperatures and dominance of dynamic recovery at high temperatures. Excellent correlations have been obtained between work-hardening parameters evaluated using the Voce relationship and the respective tensile properties. A comparison of work-hardening parameters obtained using the Voce equation and Kocks-Mecking approach suggested an analogy between the two for the steel.

  18. Cement and concrete

    NASA Technical Reports Server (NTRS)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  19. Stage cementing apparatus

    SciTech Connect

    Blamford, D.M.; Easter, J.H.

    1988-06-21

    A stage cementing apparatus for selectively passing cement from the interior passage of a casing to the annulus between the exterior of the casing and borehole, the casing having an upper portion and a lower portion, is described comprising: a barrel secured to the upper portion of the casing; a mandrel secured to the lower portion of the casing, and a stage cementing tool having a generally cylindrical configuration adapted for attachment to the lower end of the barrel about a portion of the mandrel.

  20. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample.

    PubMed

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-30

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  1. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

    NASA Astrophysics Data System (ADS)

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-01

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  2. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

    PubMed Central

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-01-01

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases. PMID:27357449

  3. Investigation of the effects of acid rain on the deterioration of cement concrete using accelerated tests established in laboratory

    NASA Astrophysics Data System (ADS)

    Xie, Shaodong; Qi, Li; Zhou, Ding

    Deterioration of cement concrete specimens caused by simulated acid rain was investigated by laboratory tests. Before and after cement concrete specimens were exposed to simulated acid rain, the neutralized depth, the compressive strength and the chemical compositions in the hardened cement paste were measured. The mineralogical composition of the concrete specimens was analyzed with XRD. The results lead to the following conclusions: the neutralized depth of the concrete specimens of all experiments can be described as a power function of exposure duration, CaO loss and the reduction rate of strength increased with H + and decreased with SO 42- concentration in simulated acid rain. The original mineral compounds such as [Na K]AlSi 3O 8 and [Ca Na][SiAl] 4O 8 in the hardened cement paste are converted to CaSO 4·2H 2O, CaAl 2Si 2O 8 and Ca 3Al 6O 12·CaSO 4. And these are larger in volume so that the reaction with SO 42- ions result in volume expansion and strength decrease. The reduction rate of strength has a binary linear relation to the CaO loss rate and the ratio of SO 3 content to CaO content in the hardened cement paste. So the deterioration of acid rain on the concrete specimen is caused by both H + dissolution and SO 42- expansion.

  4. Influence of slip system hardening assumptions on modeling stress dependence of work hardening

    NASA Astrophysics Data System (ADS)

    Miller, Matthew; Dawson, Paul

    1997-11-01

    Due to the discrete directional nature of processes such as crystallographic slip, the orientation of slip planes relative to a fixed set of loading axes has a direct effect on the magnitude of the external load necessary to induce dislocation motion (yielding). The effect such geometric or textural hardening has on the macroscopic flow stress can be quantified in a polycrystal by the average Taylor factor M¯. Sources of resistance to dislocation motion such as interaction with dislocation structures, precipitates, and grain boundaries, contribute to the elevation of the critically resolved shear strength τcrss. In continuum slip polycrystal formulations, material hardening phenomena are reflected in the slip system hardness equations. Depending on the model, the hardening equations and the mean field assumption can both affect geometric hardening through texture evolution. In this paper, we examine continuum slip models and focus on how the slip system hardening model and the mean field assumption affect the stress-strain response. Texture results are also presented within the context of how the texture affects geometric hardening. We explore the effect of employing slip system hardnesses averaged over different size scales. We first compare a polycrystal simulation employing a single hardness per crystal to one using a latent hardening formulation producing distinct slip system hardnesses. We find little difference between the amplitude of the single hardness and a crystal-average of the latent hardening values. The geometric hardening is different due to the differences in the textures predicted by each model. We also find that due to the high degree of symmetry in an fcc crystal, macroscopic stress-strain predictions using simulations employing crystal- and aggregateaveraged hardnesses are nearly identical. We find this to be true for several different mean field assumptions. An aggregate-averaged hardness may be preferred in light of the difficulty

  5. Phenomenological modeling of hardening and thermal recovery in metals

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.

    1988-01-01

    Modeling of hardening and thermal recovery in metals is considered within the context of unified elastic-viscoplastic theories. Specifically, the choices of internal variables and hardening measures, and the resulting hardening response obtained by incorporating saturation-type evolution equations into two general forms of the flow law are examined. Based on the analytical considerations, a procedure for delineating directional and isotropic hardening from uniaxial hardening data has been developed for the Bodner-Partom model and applied to a nickel-base superalloy, B1900 + Hf. Predictions based on the directional hardening properties deduced from the monotonic loading data are shown to be in good agreement with results of cyclic tests.

  6. Point defect concentrations and solid solution hardening in NiAl with Fe additions

    SciTech Connect

    Pike, L.M.; Chang, Y.A.; Liu, C.T.

    1997-08-01

    The solid solution hardening behavior exhibited when Fe is added to NiAl is investigated. This is an interesting problem to consider since the ternary Fe additions may choose to occupy either the Ni or the Al sublattice, affecting the hardness at differing rates. Moreover, the addition of Fe may affect the concentrations of other point defects such as vacancies and Ni anti-sites. As a result, unusual effects ranging from rapid hardening to solid solution softening are observed. Alloys with varying amounts of Fe were prepared in Ni-rich (40 at. % Al) and stoichiometric (50 at. % Al) compositions. Vacancy concentrations were measured using lattice parameter and density measurements. The site occupancy of Fe was determined using ALCHEMI. Using these two techniques the site occupancies of all species could be uniquely determined. Significant differences in the defect concentrations as well as the hardening behavior were encountered between the Ni-rich and stoichiometric regimes.

  7. Properties of Portland cement mortars incorporating high amounts of oil-fuel ashes

    SciTech Connect

    Paya, J.; Borrachero, M.V.; Monzo, J.; Bonilla, M.

    1999-06-01

    The residue of oil-fuel burned at the electrical power plant of Grao de Castellon (Spain) has been incorporated in Portland cement mortar and concrete. The used oil-fuel ash (OFA) had a high percentage of magnesium compounds because of magnesium oxide addition for removing slag and ashes from boilers and pipes. Several studies had been carried out on stabilization of toxic metals also occurring in oil-fuel ashes (particularly vanadium and nickel), by mixing with coal fly ashes and cement. In this case, the presence of magnesium compounds in the composition of the studied oil-fuel ashes could alter the mechanical and chemical properties of the cement matrix in fresh and hardened mortar and concrete. The authors present here the chemical, physical and mineralogical characterization of oil-fuel ashes and the behavior of Portland cement mortars incorporating high amounts of these oil-fuel ashes. The study includes workability, water demand, setting time, expansion and compressive strength developments. Preliminary results demonstrate a high absorption of water by oil-fuel ash particles, which promotes an increase in the water/cement ratio for a given workability. Acceleration of Portland cement/oil-fuel ash particles, which promotes an increase in the water/cement ratio for a given workability. Acceleration of Portland cement/oil-fuel ash pastes setting times was observed, due to the presence of carbonates. On the other hand, no significant expansion in specimens due to the presence of magnesium compounds was detected and, consequently, mechanical properties of hardened mortars containing oil-fuel ashes did not decrease with curing time. Compressive strengths for mortars containing OFA were much lower, however, than control mortar samples.

  8. Custom-made antibiotic cement nails: a comparative study of different fabrication techniques.

    PubMed

    Kim, Ji Wan; Cuellar, Derly O; Hao, Jiandong; Seligson, David; Mauffrey, Cyril

    2014-08-01

    The management of intramedullary long bone infections remains a challenge. Placement of antibiotic cement nails is a useful adjuvant to the antibiotic treatment of osteomyelitis. However, fabrication of antibiotic cement nails can be arduous. The purpose of this article is to introduce an easy and reproducible technique for the fabrication of antibiotics cement nails. We compared the time required to peel the chest tube off the 6 antibiotic cement nail using 2 different cement-cooling techniques and the addition of mineral oil in the chest tube. Additionally, we evaluated the optimal time to cut the chest tube (before and after cement hardening), consistency of nail's diameter, and the roughness of its surface. Cooling and peeling times were measured and failure was defined as a working time (from cement mixing to have a usable antibiotic cement nail) that exceeded 1 h. When the antibiotic cement nail was left to cool by convection (i.e. air-cooling), we failed to peel the plastic off the cement nail. When the chest tube was cut after conductive cooling (i.e. cold water-cooled), the cooling time was 10 min and the peeling time was 30 min without the use of mineral oil; the addition of mineral oil reduced peeling time to 7.5 min. Following peeling, residual adherent plastic pieces were found along the entire surface of the nail when no mineral oil was used. This was rarely seen when mineral oil was utilized to coat the inner layer of the chest tube. Conductively cooling of the cement nail (in cold water) and pre-lubricating the chest tube with mineral oil are 2 tricks that render fabrication of antibiotic nail more efficient, reliable, and practical. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Radiation Hardened DDR2 SDRAM Solution

    NASA Astrophysics Data System (ADS)

    Wang, Pierre-Xiao; Sellier, Charles

    2016-08-01

    The Radiation Hardened (RH) DDR2 SDRAM Solution is a User's Friendly, Plug-and-Play and Radiation Hardened DDR2 solution, which includes the radiation tolerant stacking DDR2 modules and a radiation intelligent memory controller (RIMC) IP core. It provides a high speed radiation hardened by design DRAM solution suitable for all space applications such as commercial or scientific geo-stationary missions, earth observation, navigation, manned space vehicles and deep space scientific exploration. The DDR2 module has been guaranteed with SEL immune and TID > 100Krad(Si), on the other hand the RIMC IP core provides a full protection against the DDR2 radiation effects such as SEFI and SEU.

  10. Modeling of Irradiation Hardening of Polycrystalline Materials

    SciTech Connect

    Li, Dongsheng; Zbib, Hussein M.; Garmestani, Hamid; Sun, Xin; Khaleel, Mohammad A.

    2011-09-14

    High energy particle irradiation of structural polycrystalline materials usually produces irradiation hardening and embrittlement. The development of predict capability for the influence of irradiation on mechanical behavior is very important in materials design for next generation reactors. In this work a multiscale approach was implemented to predict irradiation hardening of body centered cubic (bcc) alpha-iron. The effect of defect density, texture and grain boundary was investigated. In the microscale, dislocation dynamics models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent model was applied to predict the irradiation hardening in samples with changes in texture and grain boundary. This multiscale modeling can guide performance evaluation of structural materials used in next generation nuclear reactors.

  11. "Work-Hardenable" ductile bulk metallic glass.

    PubMed

    Das, Jayanta; Tang, Mei Bo; Kim, Ki Buem; Theissmann, Ralf; Baier, Falko; Wang, Wei Hua; Eckert, Jürgen

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (< 1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  12. Thermoelastic constitutive equations for chemically hardening materials

    NASA Technical Reports Server (NTRS)

    Shaffer, B. W.; Levitsky, M.

    1974-01-01

    Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

  13. Radiation Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Frazier, Donald O.; Patrick, Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

    2007-01-01

    Radiation Environmental Modeling is crucial to proper predictive modeling and electronic response to the radiation environment. When compared to on-orbit data, CREME96 has been shown to be inaccurate in predicting the radiation environment. The NEDD bases much of its radiation environment data on CREME96 output. Close coordination and partnership with DoD radiation-hardened efforts will result in leveraged - not duplicated or independently developed - technology capabilities of: a) Radiation-hardened, reconfigurable FPGA-based electronics; and b) High Performance Processors (NOT duplication or independent development).

  14. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  15. Fibre-reinforced calcium phosphate cements: a review.

    PubMed

    Canal, C; Ginebra, M P

    2011-11-01

    Calcium phosphate cements (CPC) consist of one or more calcium orthophosphate powders, which upon mixing with water or an aqueous solution, form a paste that is able to set and harden after being implanted within the body. Different issues remain still to be improved in CPC, such as their mechanical properties to more closely mimic those of natural bone, or their macroporosity to favour osteointegration of the artificial grafts. To this end, blends of CPC with polymer and ceramic fibres in different forms have been investigated. The present work aims at providing an overview of the different approaches taken and identifying the most significant achievements in the field of fibre-reinforced calcium phosphate cements for clinical applications, with special focus on their mechanical properties.

  16. Thermodynamics and cement science

    SciTech Connect

    Damidot, D.; Lothenbach, B.; Herfort, D.; Glasser, F.P.

    2011-07-15

    Thermodynamics applied to cement science has proved to be very valuable. One of the most striking findings has been the extent to which the hydrate phases, with one conspicuous exception, achieve equilibrium. The important exception is the persistence of amorphous C-S-H which is metastable with respect to crystalline calcium silicate hydrates. Nevertheless C-S-H can be included in the scope of calculations. As a consequence, from comparison of calculation and experiment, it appears that kinetics is not necessarily an insuperable barrier to engineering the phase composition of a hydrated Portland cement. Also the sensitivity of the mineralogy of the AFm and AFt phase compositions to the presence of calcite and to temperature has been reported. This knowledge gives a powerful incentive to develop links between the mineralogy and engineering properties of hydrated cement paste and, of course, anticipates improvements in its performance leading to decreasing the environmental impacts of cement production.

  17. Elastic-Plastic Constitutive Equation of WC-Co Cemented Carbides with Anisotropic Damage

    NASA Astrophysics Data System (ADS)

    Hayakawa, Kunio; Nakamura, Tamotsu; Tanaka, Shigekazu

    2007-05-01

    Elastic-plastic constitutive equation of WC-Co cemented carbides with anisotropic damage is proposed to predict a precise service life of cold forging tools. A 2nd rank symmetric tensor damage tensor is introduced in order to express the stress unilaterality; a salient difference in uniaxial behavior between tension and compression. The conventional framework of irreversible thermodynamics is used to derive the constitutive equation. The Gibbs potential is formulated as a function of stress, damage tensor, isotropic hardening variable and kinematic hardening variable. The elastic-damage constitutive equation, conjugate forces of damage, isotropic hardening and kinematic hardening variable is derived from the potential. For the kinematic hardening variable, the superposition of three kinematic hardening laws is employed in order to improve the cyclic behavior of the material. For the evolution equation of the damage tensor, the damage is assumed to progress by fracture of the Co matrix — WC particle interface and by the mechanism of fatigue, i.e. the accumulation of microscopic plastic strain in matrix and particles. By using the constitutive equations, calculation of uniaxial tensile and compressive test is performed and the results are compared with the experimental ones in the literature. Furthermore, finite element analysis on cold forward extrusion was carried out, in which the proposed constitutive equation was employed as die insert material.

  18. Self-hardening and thermoresponsive alpha tricalcium phosphate/pluronic pastes.

    PubMed

    Maazouz, Yassine; Montufar, Edgar B; Malbert, Julien; Espanol, Montserrat; Ginebra, Maria-Pau

    2017-02-01

    thermoresponsive cements studied herein open up new perspectives in the surgical field, where the sequential gelling/hardening of these novel cements could allow for a better and safer clinical application.

  19. Solidification and stabilization of asbestos waste from an automobile brake manufacturing facility using cement.

    PubMed

    Chan, Y M; Agamuthu, P; Mahalingam, R

    2000-10-02

    Currently, the generated brake lining waste dust, which contains asbestos as its major component, is disposed of into a secure landfill without any additional treatment. As an alternative to this, solidification/stabilization (S/S) disposal of the dust was investigated using Portland cement alone and Portland cement mixed with activated carbon (AC), as the binders. Toxicity Characteristics Leaching Procedure (TCLP) results on the solidified matrix showed that cement was able to immobilize the heavy metals, Ba, Zn, Cr, Pb, Cu and Fe, to within the limits set by the US EPA for TCLP. Addition of AC to the cement reduced the leaching of heavy metals by an additional 4-24% compared to cement alone. The pH of the TCLP leachate extracted from virgin cement, and from dust treated with cement with or without AC was found to increase to 10.9-12.5 as opposed to an initial value of 4.93 for the TCLP extract for the untreated dust. Results of ANS 16.1 (modified) leach protocol revealed that Ba in cement-treated samples showed the highest leach rate, followed by Zn, Pb, Cr, Cu and Fe. The leach rate of heavy metals decreased with progress in time. Cement mixed with AC exhibited similar leach characteristics, however, the leach rate was lower. The linear relationship between the cumulative fraction leached (CFL) and the square root of leaching time in all cement-based samples indicate that a diffusional process is the controlling transport mechanism for the leaching of the heavy metals. The obtained Leachability Indices (L(i)) of 7.6-9.1 and 8.3-9.5 for cement and cement with AC, respectively, were low but exceeded the guidance value of 6, which clearly indicates that all the heavy metals studied are retained well within solid matrices. Cement-based S/S hardening times increased from 30 to 96 h as the dust content increased from 40 to 70 wt.%. The resulting solid matrices exhibited a compressive strength ranging from 1 to 12 MPa, which was well above the specified limit of 414 k

  20. Self-adhesive resin cements - chemistry, properties and clinical considerations.

    PubMed

    Ferracane, J L; Stansbury, J W; Burke, F J T

    2011-04-01

    Self-adhesive resin cements were introduced to dentistry within the past decade but have gained rapidly in popularity with more than a dozen commercial brands now available. This review article explores their chemical composition and its effect on the setting reaction and adhesion to various substrates, their physical and biological properties that may help to predict their ultimate performance and their clinical performance to date and handling characteristics. The result of this review of self-adhesive resin cements would suggest that these materials may be expected to show similar clinical performance as other resin-based and non-resin based dental cements. © 2010 Blackwell Publishing Ltd.

  1. Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

    NASA Astrophysics Data System (ADS)

    Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

    2001-06-01

    Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used.

  2. Structural influences on the work hardening behavior of aluminum

    SciTech Connect

    Chu, David

    1994-12-01

    Effects of various grain and subgrain morphologies on low temperature work hardening of pure Al is studied using tensile tests. Plotting the work hardening rate as a function of true stress, the work hardening is separable into two distinct regimes. Both regimes are approximated by a line θ = θ0 - K2σ, where θ0 is theoretical work hardening rate at zero stress and K2 is related to dynamic recovery rate. The first or early deformation regime exhibits greater values of θ0 and K2 and can extend up to the first 10% strain of tensile deformation. This early deformation regime is contingent on the existence of a pre-existent dislocation substructure from previous straining. The θ0 and K2 associated with the early deformation regime are dependent on the strength and orientation of the pre-existent dislocation substructure relative to the new strain path. At high enough temperatures, this pre-existent dislocation substructure is annealed out, resulting in the near elimination of the early deformation regime. In comparison, the latter regime is dominated by the initial grain and/or subgrain morphology and exhibit lower values of θ0 and K2. The actual value of K2 in the latter regime is strongly dependent on the existence of a subgrain morphology. Recrystallized or well-annealed microstructures exhibit greater values of K2 than microstructures that remain partially or fully unrecrystallized. The higher K2 value is indicative of a more rapid dynamic recovery rate and a greater degree of strain relaxation. The ability to achieve a more relaxed state produces a low-energy cellular dislocation substructure upon deformation. The introduction of subgrains hinders the evolution of a low-energy dislocation cell network, giving way to a more random distribution of the dislocation density.

  3. Brushing abrasion of luting cements under neutral and acidic conditions.

    PubMed

    Buchalla, W; Attin, T; Hellwig, E

    2000-01-01

    Four resin based materials (Compolute Aplicap, ESPE; Variolink Ultra, Vivadent; C&B Metabond, Parkell and Panavia 21, Kuraray), two carboxylate cements (Poly-F Plus, Dentsply DeTrey and Durelon Maxicap, ESPE), two glass-ionomer cements (Fuji I, GC and Ketac-Cem Aplicap, ESPE), one resin-modified glass ionomer cement (Vitremer, 3M) one polyacid-modified resin composite (Dyract Cem, Dentsply DeTrey) and one zinc phosphate cement (Harvard, Richter & Hoffmann) were investigated according to their brushing resistance after storage in neutral and acidic buffer solutions. For this purpose 24 cylindrical acrylic molds were each filled with the materials. After hardening, the samples were stored for seven days in 100% relative humidity and at 37 degrees C. Subsequently, they were ground flat and polished. Then each specimen was covered with an adhesive tape leaving a 4 mm wide window on the cement surface. Twelve samples of each material were stored for 24 hours in a buffer solution with a pH of 6.8. The remaining 12 samples were placed in a buffer with a pH of 3.0. All specimens were then subjected to a three media brushing abrasion (2,000 strokes) in an automatic brushing machine. Storage and brushing were performed three times. After 6,000 brushing strokes per specimen, the tape was removed. Brushing abrasion was measured with a computerized laser profilometer and statistically analyzed with ANOVA and Tukey's Standardized Range Test (p < or = 0.05). The highest brushing abrasion was found for the two carboxylate cements. The lowest brushing abrasion was found for one resin based material, Compolute Aplicap. With the exception of three resin-based materials, a lower pH led to a higher brushing abrasion.

  4. Dual-setting calcium phosphate cement modified with ammonium polyacrylate.

    PubMed

    dos Santos, Luís Alberto; Carrodeguas, Raúl García; Boschi, Anselmo Ortega; de Arruda, Antônio Celso

    2003-05-01

    alpha-Tricalcium phosphate bone cement, as formerly designed and developed by Driessens et al., consists of a powder composed by alpha-tricalcium phosphate (alpha-TCP) and hydroxyapatite (HA) seeds, and an aqueous solution of Na2HPO4 as mixing liquid. After mixing powder and liquid, alpha-TCP dissolves into the liquid and calcium deficient hydroxyapatite (CDHA), more insoluble than the former, precipitates as an entanglement of crystals, which causes the setting and hardening of the cement. alpha-TCP bone cement offers several advantages in comparison to calcium phosphate bioceramics and acrylic bone cements as bone graft and repairing material, like perfect adaptability to the defect size and shape, osteotransductibility, and absence of thermal effect during setting. The main handicap is its low mechanical strength. Therefore, approaching its mechanical strength to that of human bone could considerably extend its applications. In the present work, an in situ polymerization system based on acrylamide (AA) and ammonium polyacrylate (PA) as liquid reducer was added to alpha-TCP cement to increase its mechanical strength. The results showed that the addition of 20 wt% of acrylamide and 1 wt% AP to the liquid increased the compressive and tensile strength of alpha-TCP bone cement by 149 and 69% (55 and 21 MPa), respectively. The improvement in mechanical strength seems to be caused by a decrease of porosity and the reinforcing effect of a polyacrylamide network coexisting with the entanglement of CDHA crystals. The studied additives do not affect the nature of the final product of the setting reaction, CDHA, but promote the reduction of its crystal size.

  5. Dislocation Starvation and Exhaustion Hardening in Mo-alloy Nanofibers

    SciTech Connect

    Chisholm, Claire; Bei, Hongbin; Lowry, M. B.; Oh, Jason; Asif, S.A. Syed; Warren, O.; Shan, Zhiwei; George, Easo P; Minor, Andrew

    2012-01-01

    The evolution of defects in Mo alloy nanofibers with initial dislocation densities ranging from 0 to 1.6 1014 m2 were studied using an in situ push-to-pull device in conjunction with a nanoindenter in a transmission electron microscope. Digital image correlation was used to determine stress and strain in local areas of deformation. When they had no initial dislocations the Mo alloy nanofibers suffered sudden catastrophic elongation following elastic deformation to ultrahigh stresses. At the other extreme fibers with a high dislocation density underwent sustained homogeneous deformation after yielding at much lower stresses. Between these two extremes nanofibers with intermediate dislocation densities demonstrated a clear exhaustion hardening behavior, where the progressive exhaustion of dislocations and dislocation sources increases the stress required to drive plasticity. This is consistent with the idea that mechanical size effects ( smaller is stronger ) are due to the fact that nanostructures usually have fewer defects that can operate at lower stresses. By monitoring the evolution of stress locally we find that exhaustion hardening causes the stress in the nanofibers to surpass the critical stress predicted for self-multiplication, supporting a plasticity mechanism that has been hypothesized to account for the rapid strain softening observed in nanoscale bcc materials at high stresses.

  6. [Microstructural changes in hardened beans (Phaseolus vulgaris)].

    PubMed

    Mujica, Maria Virginia; Granito, Marisela; Soto, Naudy

    2015-06-01

    (Phaseolus vulgaris). The hardening of Phaseolus vulgaris beans stored at high temperature and high relative humidity is one of the main constraints for consumption. The objective of this research was to evaluate by scanning electron microscopy, structural changes in cotyledons and testa of the hardened beans. The freshly harvested grains were stored for twelve months under two conditions: 5 ° C-34% RH and 37 ° C-75% RH, in order to promote hardening. The stored raw and cooked grains were lyophilized and fractured. The sections of testa and cotyledons were observed in an electron microscope JSM-6390. After twelve months, grains stored at 37 ° C-75% RH increased their hardness by 503%, whereas there were no significant changes in grains stored at 5 ° C-34% RH. At the microstructural level, the cotyledons of the raw grains show clear differences in appearance of the cell wall, into the intercellular space size and texture matrix protein. There were also differences in compaction of palisade and sub-epidermal layer in the testa of raw grains. After cooking, cotyledon cells of the soft grains were well separated while these ofhard grains were seldom separated. In conclusion, the found differences in hard and soft grains showed a significant participation of both structures, cotyledons and testa, in the grains hardening.

  7. Fundamentals of viscoelastoplasticity and hardening theory revisited

    NASA Astrophysics Data System (ADS)

    Khoroshun, L. P.

    2008-02-01

    Thermodynamic and statistical methods for setting up the constitutive equations describing the viscoelastoplastic deformation and hardening of materials are proposed. The thermodynamic method is based on the law of conservation of energy, the equations of entropy balance and entropy production in the presence of self-balanced internal microstresses characterized by conjugate hardening parameters. The general constitutive equations include the relationships between the thermodynamic flows and forces, which follow from nonnegative entropy production and satisfy the generalized Onsager's principle, and the thermoelastic relations and the expression for entropy, which follow from the law of conservation of energy. Specific constitutive equations are derived by representing the dissipation rate as a sum of two terms responsible for kinematic and isotropic hardening and approximated by power and hyperbolic-sinus functions. The constitutive equations describing viscoelastoplastic deformation and hardening are derived based on stochastic microstructural concepts and on the linear thermoelasticity model and nonlinear Maxwell model for the spherical and deviatoric components of microstresses and microstrains, respectively. The problem of determining the effective properties and stress-strain state of a three-component material found using the Voigt-Reuss scheme leads to constitutive equations similar in form to those produced by the thermodynamic method

  8. SEU hardening of CMOS memory circuit

    NASA Technical Reports Server (NTRS)

    Whitaker, S.; Canaris, J.; Liu, K.

    1990-01-01

    This paper reports a design technique to harden CMOS memory circuits against Single Event Upset (SEU) in the space environment. A RAM cell and Flip Flop design are presented to demonstrate the method. The Flip Flop was used in the control circuitry for a Reed Solomon encoder designed for the Space Station.

  9. Strain hardening in bent copper foils

    NASA Astrophysics Data System (ADS)

    Hayashi, Ichiro; Sato, Masumi; Kuroda, Mitsutoshi

    2011-09-01

    A series of systematic tensile and microbend tests were conducted on copper foil specimens with different thicknesses. The specimens were made of a copper foil having almost unidirectional crystal orientations that was considered to be nearly single-crystal. In order to investigate the effects of slip system interactions, two different crystal orientations relative to the tensile direction were considered in the tests: one is close to coplanar double-slip orientation, and the other is close to the ideal cube orientation (the tensile direction nearly coincides to [0 0 1]) that yields multi-planar multi-slip deformation. We extended the microbend test method to include the reversal of bending, and we attempted to divide the total amount of strain-hardening into isotropic and kinematic hardening components. In the tensile tests, no systematic tendency of size dependence was observed. In the microbend tests, size-dependent kinematic hardening behavior was observed for both the crystal orientations, while size dependence of isotropic hardening was observed only for the multi-planar multi-slip case. We introduce an extended crystal plasticity model that accounts for the effects of the geometrically necessary dislocations (GNDs), which correspond to the spatial gradients of crystallographic slips. Through numerical simulations performed using the model, the origin of the size-dependent behavior observed in the microbend tests is discussed.

  10. Extraordinary strain hardening by gradient structure

    PubMed Central

    Wu, XiaoLei; Jiang, Ping; Chen, Liu; Yuan, Fuping; Zhu, Yuntian T.

    2014-01-01

    Gradient structures have evolved over millions of years through natural selection and optimization in many biological systems such as bones and plant stems, where the structures change gradually from the surface to interior. The advantage of gradient structures is their maximization of physical and mechanical performance while minimizing material cost. Here we report that the gradient structure in engineering materials such as metals renders a unique extra strain hardening, which leads to high ductility. The grain-size gradient under uniaxial tension induces a macroscopic strain gradient and converts the applied uniaxial stress to multiaxial stresses due to the evolution of incompatible deformation along the gradient depth. Thereby the accumulation and interaction of dislocations are promoted, resulting in an extra strain hardening and an obvious strain hardening rate up-turn. Such extraordinary strain hardening, which is inherent to gradient structures and does not exist in homogeneous materials, provides a hitherto unknown strategy to develop strong and ductile materials by architecting heterogeneous nanostructures. PMID:24799688

  11. Bone cement implantation syndrome during spinal surgery requiring cardiac surgery.

    PubMed

    Sastre, José A; López, Teresa; Dalmau, María J; Cuello, Rafael E

    2013-12-15

    During a posterior segmental spinal fusion procedure, a 71-year-old woman developed cardiac and pulmonary embolism characterized by nonsustained ventricular tachycardia during cement injection, rapid and severe hypoxemia, and hemodynamic instability. Management included exploratory cardiotomy under cardiopulmonary bypass and removal of the emboli from the pulmonary vessels. Postoperative recovery was successful, and the patient was discharged without sequelae. We discuss the pathophysiology of bone cement implantation syndrome during spinal fusion, possible causative factors, and treatment alternatives.

  12. 'Fire hardening' spear wood does slightly harden it, but makes it much weaker and more brittle.

    PubMed

    Ennos, Antony Roland; Chan, Tak Lok

    2016-05-01

    It is usually assumed that 'fire hardening' the tips of spears, as practised by hunter-gatherers and early Homo spp., makes them harder and better suited for hunting. This suggestion was tested by subjecting coppiced poles of hazel to a fire-hardening process and comparing their mechanical properties to those of naturally seasoned poles. A Shore D hardness test showed that fire treatment slightly increased the hardness of the wood, but flexural and impact tests showed that it reduced the strength and work of fracture by 30% and 36%, respectively. These results suggest that though potentially slightly sharper and more durable, fire-hardened tips would actually be more likely to break off when used, as may have been the case with the earliest known wooden tool, the Clacton spear. Fire might first have been used to help sharpen the tips of spears, and fire-hardening would have been a mostly negative side effect, not its primary purpose.

  13. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

    PubMed Central

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-01

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite. PMID:25592665

  14. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

    NASA Astrophysics Data System (ADS)

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-01

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite.

  15. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste.

    PubMed

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-16

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite.

  16. O-phospho-L-serine: a modulator of bone healing in calcium-phosphate cements.

    PubMed

    Mai, Ronald; Lux, Romy; Proff, Peter; Lauer, Günter; Pradel, Winnie; Leonhardt, Henry; Reinstorf, Antje; Gelinsky, Michael; Jung, Roland; Eckelt, Uwe; Gedrange, Tomasz; Stadlinger, Bernd

    2008-10-01

    Bone substitution materials are seen as an alternative to autogenous bone transplants in the reconstruction of human bone structures. The aim of the present animal study was to evaluate the clinical handling and the conditions of bone healing after the application of a phosphoserine and collagen-I-modified calcium-phosphate cement (Biozement D). The application of phosphoserine is supposed to influence the texture of the extracellular matrix. Standardised bone defects were created in the lower jaw of 10 adult minipigs. These defects were reconstructed with a pasty calcium-phosphate cement mixture. After a healing time of 4 months, the animals were sacrificed. The mandibles of all animals were resected and non-decalcified histological sections of the areas of interest were prepared. The experiment was evaluated by means of qualitative histology and histomorphometry. The hydroxyapatite cement entirely hardened intraoperatively. Modelling and handling of the cement was facile and the margin fit to the host bone was excellent. Histology showed that resorption started in the periphery and proceeded exceptionally fast. The bony substitution, especially in phosphoserine-endowed cements, was very promising. After a healing period of 4 months, phosphoserine cements showed a bone regeneration of nearly two-thirds of the defect sizes. In the applied animal experiment, the newly developed hydroxyapatite collagen-I cement is well suited for bone substitution due to its easy handling, its excellent integration and good resorption characteristics. The addition of phosphoserine is very promising in terms of influencing resorption features and bone regeneration.

  17. Bonding material containing ashes after domestic waste incineration for cementation of radioactive waste

    SciTech Connect

    Dmitriev, S.A.; Varlakov, A.P.; Gorbunova, O.A.; Arustamov, A.E.; Barinov, A.S.

    2007-07-01

    It is known that cement minerals hydration is accompanied with heat emission. Heat of hardening influences formation of a cement compound structure and its properties. It is important to reduce the heat quantity at continuous cementation of waste and filling of compartments of a repository or containers by a cement grout. For reduction of heating, it is necessary to use cement of mineral additives (fuel ashes, slag and hydraulic silica). Properties of ashes after domestic waste incineration can be similar to ones of fly fuel ashes. However, ash after domestic waste incineration is toxic industrial waste as it contains toxic elements (As, Cd, Hg, Pb, Sb, Zn). Utilization of secondary waste (slag and ash) of combustion plants is an important environmental approach to solving cities' issues. Results of the research have shown that ashes of combustion plants can be used for radioactive waste conditioning. Co-processing of toxic and radioactive waste is ecologically and economically effective. At SIA 'Radon', experimental batches of cement compositions are used for cementation of oil containing waste. (authors)

  18. The use of glass powder as a partial Portland cement replacement

    NASA Astrophysics Data System (ADS)

    Pokorný, Jaroslav; Pavlíková, Milena; Tydlitát, Vratislav; Scheinherrová, Lenka; Rovnaníková, Pavla; Pavlík, Zbyšek

    2017-07-01

    Finely grinded waste glass powder can become material having suitable properties from the point of view of particle size and pozzolanic activity. Glass powder incorporation into cement paste and cement-based composites can bring improvement in porous structure resulting in increased mechanical strength and durability characteristics. On this account, two types of recycled glass powder are investigated in the presented paper as a possible partial Portland cement substitutes in cement blends. For raw glass powders, basic physical parameters and chemical composition are measured. The studied glass powders are applied as 5, 10 and 20 mass% of Portland cement replacement in cement paste mix composition, whereas water/binder ratio of 0.3 is used for all studied pastes. Fresh paste mixtures are characterized using initial and final setting time measurement. For hardened pastes cured 28 days in water, bulk density, matrix density, total open porosity and mechanical properties represented by flexural and compressive strength are accessed. Portlandite consumption by the pozzolanic reaction is monitored with TGA. The obtained results show effectiveness of a borosilicate glass powder that acts as a pozzolanic active admixture. This resulted in improvement of mechanical characteristics for cement substitution up to 10 mass%.

  19. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  20. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  1. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  2. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  3. 7 CFR 58.622 - Hardening and storage rooms.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage rooms. 58.622 Section 58.622 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be...

  4. Influence of various amount of diatomaceous earth used as cement substitute on mechanical properties of cement paste

    NASA Astrophysics Data System (ADS)

    Pokorný, Jaroslav; Pavlíková, Milena; Medved, Igor; Pavlík, Zbyšek; Zahálková, Jana; Rovnaníková, Pavla; Černý, Robert

    2016-06-01

    Active silica containing materials in the sub-micrometer size range are commonly used for modification of strength parameters and durability of cement based composites. In addition, these materials also assist to accelerate cement hydration. In this paper, two types of diatomaceous earths are used as partial cement replacement in composition of cement paste mixtures. For raw binders, basic physical and chemical properties are studied. The chemical composition of tested materials is determined using classical chemical analysis combined with XRD method that allowed assessment of SiO2 amorphous phase content. For all tested mixtures, initial and final setting times are measured. Basic physical and mechanical properties are measured on hardened paste samples cured 28 days in water. Here, bulk density, matrix density, total open porosity, compressive and flexural strength, are measured. Relationship between compressive strength and total open porosity is studied using several empirical models. The obtained results give evidence of high pozzolanic activity of tested diatomite earths. Their application leads to the increase of both initial and final setting times, decrease of compressive strength, and increase of flexural strength.

  5. Method of Electrolyte-Plasma Surface Hardening of 65G and 20GL Low-Alloy Steels Samples

    NASA Astrophysics Data System (ADS)

    Rakhadilov, Bauyrzhan; Zhurerova, Laila; Pavlov, Alexander

    2016-08-01

    This work is devoted to formation of modified surface layers in 65G and 20GL steels which using for the manufacture of railway transport parts, as well as the study of influence of the parametersof electrolyte-plasma surface hardening methodon the changes in structural-phase states, improving of wear-resistance. The process of electrolyte-plasma surface hardening of 65G and 20GL steels samples conducted in the electrolyte from water solution of 20% sodium carbonate, in the mode ~850°C - 2 seconds, ∼⃒1200°C - 3 seconds. It is established that in the initial state 20GL steel has ferrite-pearlite structure, and the 60G steel consists of pearlite and cement structure. After application of electrolyte-plasma surface hardening is observed the formation of carbides particles and martensite phase components in the structure of 20GL and 60G steels. It is determined that after electrolyte-plasma surface hardening with heating time - 2 seconds, the abrasive wear-resistance of 65G and 20GL steels increased to 1.3 times and 1.2 times, respectively, and the microhardness is increased to 1.6 times and 1.3 times, respectively.

  6. Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete

    PubMed Central

    Fan, Wei-Jie; Wang, Xiao-Yong; Park, Ki-Bong

    2015-01-01

    High-calcium fly ash (FH) is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found. PMID:28793543

  7. Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete.

    PubMed

    Fan, Wei-Jie; Wang, Xiao-Yong; Park, Ki-Bong

    2015-09-07

    High-calcium fly ash (FH) is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found.

  8. Continuous Hardening During Isothermal Aging at 723 K (450 °C) of a Precipitation Hardening Stainless Steel

    NASA Astrophysics Data System (ADS)

    Celada-Casero, Carola; Chao, Jesús; Urones-Garrote, Esteban; San Martin, David

    2016-11-01

    The isothermal aging behavior of a cold-rolled precipitation hardening stainless steel has been studied at 723 K (450 °C) for holding times up to 72 hours. The precipitation hardening has been investigated using microhardness Vickers (Hv), thermoelectric power (TEP) measurements, and tensile testing. Microhardness compared to TEP measurements is more sensitive to detect the initial stages of aging. Two precipitation regimes have been observed: the first one related to the formation of Cu-clusters for aging times below 1 hour and a second one associated with formation of Ni-rich precipitates. The results show that the material exhibits an outstanding continuous age strengthening response over the aging time investigated, reaching a hardness of 710 ± 4 HV1 and an ultimate tensile strength ( σ UTS) of 2.65 ± 0.02 GPa after 72 hours. Engineering stress-plastic strain curves reveal that the strength increases and the ductility decreases as the aging time increases. However, after prolonged holding times (24-72 hours) and, although small, a rise in both the strength and the total elongation is observed. The precipitation kinetics can be well predicted over the entire range of aging times by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a reliable linear hardness-yield strength correlation has been found, which enables a rapid evaluation of the strength from bulk hardness measurements.

  9. Injectability of brushite-forming Mg-substituted and Sr-substituted alpha-TCP bone cements.

    PubMed

    Pina, S; Torres, P M C; Ferreira, J M F

    2010-02-01

    The influence of magnesium- and strontium-substitutions on injectability and mechanical performance of brushite-forming alpha-TCP cements has been evaluated in the present work. The effects of Mg- and Sr-substitutions on crystalline phase composition and lattice parameters were determined through quantitative X-ray phase analysis and structural Rietveld refinement of the starting calcium phosphate powders and of the hardened cements. A noticeable dependence of injectability on the liquid-to-powder ratio (LPR), smooth plots of extrusion force versus syringe plunger displacement and the absence of filter pressing effects were observed. For LPR values up to 0.36 ml g(-1), the percentage of injectability was always higher and lower for Mg-containing cements and for Sr-containing cements, respectively, while all the pastes could be fully injected for LPR > 0.36 ml g(-1). The hardened cements exhibited relatively high wet compressive strength values (~17-25 MPa) being the Sr- and Mg-containing cements the strongest and the weakest, respectively, holding an interesting promise for uses in trauma surgery such as for filling bone defects and in minimally invasive techniques such as percutaneous vertebroplasty to fill lesions and strengthen the osteoporotic bone.

  10. High-volume use of self-cementing spray dry absorber material for structural applications

    NASA Astrophysics Data System (ADS)

    Riley, Charles E.

    Spray dry absorber (SDA) material, or spray dryer ash, is a byproduct of energy generation by coal combustion and sulfur emissions controls. Like any resource, it ought to be used to its fullest potential offsetting as many of the negative environmental impacts of coal combustion as possible throughout its lifecycle. Its cementitious and pozzolanic properties suggest it be used to augment or replace another energy and emissions intensive product: Portland cement. There is excellent potential for spray dryer ash to be used beneficially in structural applications, which will offset CO2 emissions due to Portland cement production, divert landfill waste by further utilizing a plentiful coal combustion by-product, and create more durable and sustainable structures. The research into beneficial use applications for SDA material is relatively undeveloped and the material is highly underutilized. This dissertation explored a specific self-cementing spray dryer ash for use as a binder in structural materials. Strength and stiffness properties of hydrated spray dryer ash mortars were improved by chemical activation with Portland cement and reinforcement with polymer fibers from automobile tire recycling. Portland cement at additions of five percent of the cementitious material was found to function effectively as an activating agent for spray dryer ash and had a significant impact on the hardened properties. The recycled polymer fibers improved the ductility and toughness of the material in all cases and increased the compressive strength of weak matrix materials like the pure hydrated ash. The resulting hardened materials exhibited useful properties that were sufficient to suggest that they be used in structural applications such as concrete, masonry block, or as a hydraulic cement binder. While the long-term performance characteristics remain to be investigated, from an embodied-energy and carbon emissions standpoint the material investigated here is far superior to

  11. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    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.

  12. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-06-16

    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. Laboratory testing during the tenth quarter focused on evaluation of the alkali-silica reaction of eight different cement compositions, four of which contain ULHS. The original laboratory procedure for measuring set cement expansion resulted in test specimen erosion that was unacceptable. A different expansion procedure is being evaluated. This report provides a progress summary of ASR testing. The testing program initiated in November produced questionable initial results so the procedure was modified slightly and the testing was reinitiated. The results obtained with the modified procedure showed improvement over data obtained with the original procedure, but questionable data were obtained from several of the compositions. Additional modification of test procedures for compositions containing TXI Lightweight cement are being implemented and testing is ongoing.

  13. Small-particle-size cement

    SciTech Connect

    Ewert, D.P.; Almond, S.W.; Blerhaus, W.M. II )

    1991-05-01

    Successful remedial cementing has historically been difficult in wells with large-interval, multizone, gravel-packed completions. The reason is the inability of conventional oilfield cements to penetrate gravel packs adequately. Small-particle-size cement (SPSC) was developed to penetrate gravel packs and to provide the zonal isolation required. This paper details the laboratory work, job design, and field implementation of this new cement.

  14. Structural heredity influence upon principles of strain wave hardening

    NASA Astrophysics Data System (ADS)

    Kiricheck, A. V.; Barinov, S. V.; Yashin, A. V.

    2017-02-01

    It was established experimentally that by penetration of a strain wave through material hardened not only the technological modes of processing, but also a technological heredity - the direction of the fibers of the original macrostructure have an influence upon the diagram of microhardness. By penetration of the strain wave along fibers, the degree of hardening the material is less, however, a product is hardened throughout its entire section mainly along fibers. In the direction of the strain waves across fibers of the original structure of material, the degree of material hardening is much higher, the depth of the hardened layer with the degree of hardening not less than 50% makes at least 3 mm. It was found that under certain conditions the strain wave can completely change the original structure of the material. Thus, a heterogeneously hardened structure characterized by the interchange of harder and more viscous areas is formed, which is beneficial for assurance of high operational properties of material.

  15. Reducing cement's CO2 footprint

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  16. High temperature lightweight foamed cements

    DOEpatents

    Sugama, Toshifumi.

    1989-10-03

    Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed. 3 figs.

  17. Cement Mason's Curriculum. Instructional Units.

    ERIC Educational Resources Information Center

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  18. High temperature lightweight foamed cements

    DOEpatents

    Sugama, Toshifumi

    1989-01-01

    Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed.

  19. Cement Mason's Curriculum. Instructional Units.

    ERIC Educational Resources Information Center

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

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

    DOEpatents

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael

    2017-03-14

    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.

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

    DOEpatents

    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.

  2. Laser hardening of diesel engine valve

    SciTech Connect

    Androsov, A.P.; Aleksenko, S.I.; Boyarkin, M.V.; Kusidis, V.G.; Petrov, V.I.

    1988-07-01

    Results are presented of a complex investigation of the effect of laser treatment on the structure and properties of steel 40Kh10S2M and of engine tests with diesel engine valves hardened by the newly devised technology. Results of the investigation of the microstructure of steel 40Kh10S2M, heat-treated by a laser beam, showed that when a specimen is hardened with fusion of the surface layer, it contains two distinct zones of laser action. Results of the effect of laser treatment on the fatigue limit and the wear resistance of the steel and engine tests permit the conclusion that the suggested method of treating valves of internal engine valve gear has good prospects.

  3. Cyclic hardening in bundled actin networks.

    PubMed

    Schmoller, K M; Fernández, P; Arevalo, R C; Blair, D L; Bausch, A R

    2010-01-01

    Nonlinear deformations can irreversibly alter the mechanical properties of materials. Most soft materials, such as rubber and living tissues, display pronounced softening when cyclically deformed. Here we show that, in contrast, reconstituted networks of crosslinked, bundled actin filaments harden when subject to cyclical shear. As a consequence, they exhibit a mechano-memory where a significant stress barrier is generated at the maximum of the cyclic shear strain. This unique response is crucially determined by the network architecture: at lower crosslinker concentrations networks do not harden, but soften showing the classic Mullins effect known from rubber-like materials. By simultaneously performing macrorheology and confocal microscopy, we show that cyclic shearing results in structural reorganization of the network constituents such that the maximum applied strain is encoded into the network architecture.

  4. Radiation-hardened transistor and integrated circuit

    DOEpatents

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  5. Plasma hardening of railway wheel surface

    NASA Astrophysics Data System (ADS)

    Isakaev, E. Kh.; Ivanov, P. P.; Tyuftyaev, A. S.; Paristyi, I. L.; Troitsky, A. A.; Yablonsky, A. E.; Filippov, G. A.

    1998-10-01

    A computer-controlled plasma technology was developed for the treatment of rolling stock wheels, providing the thermal hardening of tread and flange working surfaces. As a result of the plasma treatment the surface hardness of the wheel grows from 255 up to 420-450 HB. Herewith, the wear capability of the wheel metal grows 2-3 times and its resistance to the weariness-driven destruction grows 1.5 times due to the pecularities of the structural state of the steel, arising out of the thermal impact and of the alloying of the steel with nitrogen during the plasma treatment. Installation of several plants based on this technology in engine houses allowed to carry out a full scale experiment in order to assess the running characteristics of treated wheel sets in comparison with plain ones. Wheel life between mounting and truing or dismounting doubles due to plasma hardening.

  6. Terminal modeling of hardened integrated circuits

    NASA Astrophysics Data System (ADS)

    Kleiner, C. T.; Haas, R.; Peacock, M.; Mandel, G.; Messenger, G. C.; Weakley, D.; Demartino, V.

    1981-12-01

    Kleiner et al. (1979) have reported modeling and test verification techniques used to develop medium-scale, dielectrically isolated integrated circuits (DIIC). The current investigation is concerned with the approaches employed in modeling the new circuits for applications studied by design and radiation hardening engineers. The described technique improves significantly the cost-effective application of computer programs such as SYSCAP II. The terminal model offers the designer of radiation-hardened electronic circuits a method for evaluating the effects of radiation transients on single or multiple piece-part response at the circuit board level. Although the models presented were intended for TREE design and analysis, it is possible to extend the technique to EMP and SGEMP evaluations.

  7. RESIDUAL STRESS IN HARDENED STEEL CYLINDERS

    DTIC Science & Technology

    ultimate strength of the steel and in some instances caused cracking, and (4) stress patterns of interrupted quench specimens were not consistent enough to warrant a conclusion. (Author)...A study was conducted to (1) measure residual stress in hardened steel solid cylinders, (2) correlate the stress values with heat treatments, and (3...develop a dissolution technique. Residual stress patterns for 12 solid cylinders of 4160 steel, heat treated by various methods, were determined

  8. Hologram formation in hardened dichromated gelatin films.

    PubMed

    Lin, L H

    1969-05-01

    Hardened gelatin films sensitized with ammonium dichromate can be utilized to record high quality holograms. The maximum diffraction efficiency of the hologram approaches 90%. The light scattering from the hologram is so low that under ordinary light the hologram plate appears almost indistinguishable from a clear glass plate. Either a transmission or a reflection hologram can be recorded. Linear recording range of light amplitude is large. A practical method of preparing and processing the film is described, and the exposure characteristics are presented.

  9. Design of Radiation Hardened MNOS Memory

    DTIC Science & Technology

    1975-06-01

    OF BADIATION HARDENED MJ^OS MEMORY. up: is ^ u. 7^- 34 ia of o/wwiAflaw WAMB AWO ADOWKM \\ Sperry Gyroscope Great Neck, N.Y. 11020 READ...s.^<.*.:.!~^,-.,-.. ■ ■ .....ViJ^ —-T"--^ -i-.^-~^,immmmmmmmmKmmii. >-im.^. imimmmmm FOREWORD This report was prepared by the Sperry Rand...Corporation, Sperry Gyroscope Division, Great Neck, New York for the Air Force Avionics Laboratory, Wright- Patterson Air Force Base, Ohio. The

  10. Incorporation of titanium dioxide nanoparticles in mortars - Influence of microstructure in the hardened state properties and photocatalytic activity

    SciTech Connect

    Lucas, S.S.

    2013-01-15

    The environmental pollution in urban areas is one of the causes for poor indoor air quality in buildings, particularly in suburban areas. The development of photocatalytic construction materials can contribute to clean the air and improve sustainability levels. Previous studies have focused mainly in cement and concrete materials, disregarding the potential application in historic buildings. In this work, a photocatalytic additive (titanium dioxide) was added to mortars prepared with aerial lime, cement and gypsum binders. The main goal was to study the way that microstructural changes affect the photocatalytic efficiency. The photocatalytic activity was determined using a reactor developed to assess the degradation rate with a common urban pollutant, NO{sub x}. The laboratory results show that all the compositions tested exhibited high photocatalytic efficiency. It was demonstrated that photocatalytic mortars can be applied in new and old buildings, because the nanoadditives do not compromise the mortar hardened state properties.

  11. Pulsed laser surface hardening of ferrous alloys.

    SciTech Connect

    Xu, Z.; Reed, C. B.; Leong, K. H.; Hunter, B. V.

    1999-09-30

    A high power pulsed Nd:YAG laser and special optics were used to produce surface hardening on 1045 steel and gray cast iron by varying the process parameters. Unlike CO{sub 2} lasers, where absorptive coatings are required, the higher absorptivity of ferrous alloys at the Nd:YAG laser wavelength eliminates the necessity of applying a coating before processing. Metallurgical analysis of the treated tracks showed that very fine and hard martensitic microstructure (1045 steel) or inhomogeneous martensite (gray cast iron) were obtained without surface melting, giving maximum hardness of HRC 61 and HRC 40 for 1045 steel and gray cast iron respectively. The corresponding maximum case depths for both alloys at the above hardness are 0.6 mm. Gray cast iron was more difficult to harden without surface melting because of its lower melting temperature and a significantly longer time-at-temperature required to diffuse carbon atoms from the graphite flakes into the austenite matrix during laser heating. The thermal distortion was characterized in term of flatness changes after surface hardening.

  12. Helium irradiation induced hardening in MNHS steels

    NASA Astrophysics Data System (ADS)

    Cui, Minghuan; Wang, Ji; Wang, Zhiguang; Shen, Tielong; Wei, Kongfang; Yao, Cunfeng; Sun, Jianrong; Gao, Ning; Zhu, Yabin; Pang, Lilong; Wang, Dong; Zhu, Huiping; Han, Yi; Fang, Xuesong

    2017-09-01

    A recently developed reduced activation martensitic MNHS steel was irradiated with 200 keV helium (He) ions to a fluence of 1.0 × 1020 ions/m2 at 300 °C and 1.0 × 1021 ions/m2 at 300 °C and 450 °C. After irradiation, transmission electron microscopy (TEM) and nano-indentation measurements were used to investigate the hardness change and defects induced by He irradiation. Two kinds of defects including He bubbles and dislocation loops are observed by TEM. Irradiation induces hardening of MNHS steels and peak hardness values occur in all irradiated samples. Hardness increments induced by He bubbles and dislocation loops are predicted and fitted with the experimental peak hardness increment, based on the dispersed barrier-hardening (DBH) model and the size and number density of the two defects. A good agreement is got between the predicted and experimental hardness increment and the obstacle strength factor of He bubbles is a little stronger than the obstacle strength of dislocation loops. Other possible contributions to irradiation induced hardening are also discussed.

  13. Stage IV work hardening in cubic metals

    SciTech Connect

    Rollett, A.D.; Kocks, U.F.; Doherty, R.D.

    1986-01-01

    The work hardening of fcc metals at large strains is discussed with reference to the linear stress-strain behavior often observed at large strains and known as Stage IV. The experimental evidence shows that Stage IV is a work hardening phenomenon that is found quite generally, even in pure fcc metals subjected to homogeneous deformation. A simple model for Stage IV in pure metals is presented, based on the accumulation of dislocation debris. Experiments are described for large strain torsion tests on four aluminum alloys. The level and extent of Stage IV scaled with the saturation stress that would represent the end of Stage III in the absence of a Stage IV. Reversing the torsion after large prestrains produced transient reductions in the work hardening. The strain rate sensitivity was also measured before and during the transient and found not to vary significantly. The microstructure observed at large strains in an Mg alloy suggest that Stage IV can occur in the absence of microband formation. Previous proposals for the cause of Stage IV are reviewed and found to be not supported by recent experimental data.

  14. Dislocation Multi-junctions and Strain Hardening

    SciTech Connect

    Bulatov, V; Hsiung, L; Tang, M; Arsenlis, A; Bartelt, M; Cai, W; Florando, J; Hiratani, M; Rhee, M; Hommes, G; Pierce, T; Diaz de la Rubia, T

    2006-06-20

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects--dislocations. First theorized in 1934 to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed only two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening: a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions tying dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed hereafter multi-junctions. The existence of multi-junctions is first predicted by Dislocation Dynamics (DD) and atomistic simulations and then confirmed by the transmission electron microscopy (TEM) experiments in single crystal molybdenum. In large-scale Dislocation Dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in BCC crystals.

  15. Dislocation multi-junctions and strain hardening.

    PubMed

    Bulatov, Vasily V; Hsiung, Luke L; Tang, Meijie; Arsenlis, Athanasios; Bartelt, Maria C; Cai, Wei; Florando, Jeff N; Hiratani, Masato; Rhee, Moon; Hommes, Gregg; Pierce, Tim G; de la Rubia, Tomas Diaz

    2006-04-27

    At the microscopic scale, the strength of a crystal derives from the motion, multiplication and interaction of distinctive line defects called dislocations. First proposed theoretically in 1934 (refs 1-3) to explain low magnitudes of crystal strength observed experimentally, the existence of dislocations was confirmed two decades later. Much of the research in dislocation physics has since focused on dislocation interactions and their role in strain hardening, a common phenomenon in which continued deformation increases a crystal's strength. The existing theory relates strain hardening to pair-wise dislocation reactions in which two intersecting dislocations form junctions that tie the dislocations together. Here we report that interactions among three dislocations result in the formation of unusual elements of dislocation network topology, termed 'multi-junctions'. We first predict the existence of multi-junctions using dislocation dynamics and atomistic simulations and then confirm their existence by transmission electron microscopy experiments in single-crystal molybdenum. In large-scale dislocation dynamics simulations, multi-junctions present very strong, nearly indestructible, obstacles to dislocation motion and furnish new sources for dislocation multiplication, thereby playing an essential role in the evolution of dislocation microstructure and strength of deforming crystals. Simulation analyses conclude that multi-junctions are responsible for the strong orientation dependence of strain hardening in body-centred cubic crystals.

  16. Strain Hardening in Bidisperse Polymer Glasses

    NASA Astrophysics Data System (ADS)

    Robbins, Mark O.; Hoy, Robert S.

    2009-03-01

    The connections between glassy and rubbery strain hardening have been a matter of great controversy in recent years. Recent experiments and our earlier simulations have suggested that the hardening modulus GR is proportional to the entanglement density in glasses, as it is to the crosslink density in rubbers. In this work we present more extensive studies of strain hardening in bidisperse glasses and its relation to microscopic conformational changes. The mixtures contain chains of very different lengths but equivalent chemistry. GR does not scale simply with the entanglement density. Instead it obeys a simple mixing rule, with GR equal to the volume fraction weighted average of the moduli of the two pure components. As in recent studies of monodisperse systems (R. S. Hoy and M. O. Robbins, Phys. Rev. Lett. 99, 117801 (2007)), the stress is directly correlated to the degree of chain orientation. Chains of a given length undergo almost the same degree of alignment in pure systems and mixtures, explaining why the simple mixing rule applies. The connection to recent analytic theories by K. Chen and K. S. Schweizer (PRL, in press) will be discussed.

  17. Inspection of deteriorating asbestos cement force mains with georadar technique.

    PubMed

    Smolders, S; Verhoest, L; De Gueldre, G; Van De Steene, B

    2009-01-01

    Several breaks on asbestos cement force mains indicated a problem with these kind of force mains. An inspection technique that could give a good idea about the state of asbestos cement pipes was searched for. A georadar technique already existed to inspect drinking water mains and gravity sewers. The technique measures the wall thickness of cement containing materials and it can differentiate between 'healthy' and deteriorated material. The technique was applied on four wastewater force mains in Flanders. The results indicated a rapid deterioration of the asbestos cement. A deterioration mechanism called 'calcium leaching' was known from asbestos cement drinking water mains. Further it was known that H(2)S is produced in force mains and that it can attack concrete containing materials by mains of biogenic sulphuric acid attack. This research checked if both deterioration mechanisms cause the measured rapid deterioration of the asbestos cement force mains. Finally deterioration speeds and minimum required wall thickness were calculated. With the results the residual lifetimes of the force mains were calculated and these could be applied in an asset management program.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. The special radiation-hardened processors for new highly informative experiments in space

    NASA Astrophysics Data System (ADS)

    Serdin, O. V.; Antonov, A. A.; Dubrovsky, A. G.; Novogilov, E. A.; Zuev, A. L.

    2017-01-01

    The article provides a detailed description of the series of special radiation-hardened microprocessor developed by SRISA for use in space technology. The microprocessors have 32-bit and 64-bit KOMDIV architecture with embedded SpaceWire, RapidIO, Ethernet and MIL-STD-1553B interfaces. These devices are used in space telescope GAMMA-400 data acquisition system, and may also be applied to other experiments in space (such as observatory “Millimetron” etc.).

  20. Cement composition and sulfate attack

    SciTech Connect

    Shanahan, Natalya; Zayed, Abla . E-mail: zayed@eng.usf.edu

    2007-04-15

    Four cements were used to address the effect of tricalcium silicate content of cement on external sulfate attack in sodium sulfate solution. The selected cements had similar fineness and Bogue-calculated tricalcium aluminate content but variable tricalcium silicates. Durability was assessed using linear expansion and compressive strength. Phases associated with deterioration were examined using scanning electron microscopy and X-ray diffraction. Mineralogical phase content of the as-received cements was studied by X-ray diffraction using two methods: internal standard and Rietveld analysis. The results indicate that phase content of cements determined by X-ray mineralogical analysis correlates better with the mortar performance in sulfate environment than Bogue content. Additionally, it was found that in cements containing triclacium aluminate only in the cubic form, the observed deterioration is affected by tricalcium silicate content. Morphological similarities between hydration products of high tricalcium aluminate and high tricalcium silicate cements exposed to sodium sulfate environment were also observed.

  1. {sup 1}H NMR relaxometry as an indicator of setting and water depletion during cement hydration

    SciTech Connect

    Wang, Biyun; Faure, Paméla; Thiéry, Mickaël; Baroghel-Bouny, Véronique

    2013-03-15

    Proton nuclear magnetic resonance relaxometry has been used to detect setting and microstructure evolution during cement hydration. NMR measurements were performed since casting, during setting and until hardening (from 0 to 3 days). The mobility of water molecules was assessed by an analysis focused on the diagram of longitudinal relaxation time T{sub 1} generated by an Inversion Recovery sequence. The initial stiffening of the solid network was identified by an analysis of the relaxation rate 1/T{sub 1}. The kinetics of water depletion was investigated by using a simple one-pulse acquisition sequence. In parallel, conventional techniques (Vicat needle and temperature monitoring), as well as numerical simulations of hydration, were used to complement and validate these NMR results. Cement pastes and mortars with different water-to-cement ratios made of grey or white OPCs were tested. Furthermore, the effects of the addition of sand, super-plasticizer and silica fume on the hydration kinetics were investigated.

  2. Properties of cement-fly ash grout admixed with bentonite, silica fume, or organic fiber

    SciTech Connect

    Huang, W.H.

    1997-03-01

    A detailed laboratory study was conducted to investigate the properties of cement-fly ash grout mixtures as barriers for isolation of hazardous and low-level radioactive wastes. In the grout studied, fly ash was used to replace 30 percent by mass of cement. Three additives including bentonite, silica fume, and polypropylene fiber were used individually in the grout mixes to improve the properties of the grouts in different aspects. The flowability, bleeding, and setting time of freshly mixed grouts were determined; and the unconfined compressive strength, pore size distribution, and water permeability were determined for hardened grouts at various curing durations up to 120 days. Finally, the durability of cement-fly ash grouts was carefully examined in terms of the changes in their physical properties after different levels of exposure to sulfate attack and wet-dry cycles.

  3. Empirical beam hardening correction (EBHC) for CT.

    PubMed

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc

    2010-10-01

    Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (Tomo-Scope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern C-arm CT scanner

  4. Empirical beam hardening correction (EBHC) for CT.

    PubMed

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelrieß, Marc

    2010-10-01

    Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. The onlya priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern C-arm CT scanner

  5. Empirical beam hardening correction (EBHC) for CT

    SciTech Connect

    Kyriakou, Yiannis; Meyer, Esther; Prell, Daniel; Kachelriess, Marc

    2010-10-15

    Purpose: Due to x-ray beam polychromaticity and scattered radiation, attenuation measurements tend to be underestimated. Cupping and beam hardening artifacts become apparent in the reconstructed CT images. If only one material such as water, for example, is present, these artifacts can be reduced by precorrecting the rawdata. Higher order beam hardening artifacts, as they result when a mixture of materials such as water and bone, or water and bone and iodine is present, require an iterative beam hardening correction where the image is segmented into different materials and those are forward projected to obtain new rawdata. Typically, the forward projection must correctly model the beam polychromaticity and account for all physical effects, including the energy dependence of the assumed materials in the patient, the detector response, and others. We propose a new algorithm that does not require any knowledge about spectra or attenuation coefficients and that does not need to be calibrated. The proposed method corrects beam hardening in single energy CT data. Methods: The only a priori knowledge entering EBHC is the segmentation of the object into different materials. Materials other than water are segmented from the original image, e.g., by using simple thresholding. Then, a (monochromatic) forward projection of these other materials is performed. The measured rawdata and the forward projected material-specific rawdata are monomially combined (e.g., multiplied or squared) and reconstructed to yield a set of correction volumes. These are then linearly combined and added to the original volume. The combination weights are determined to maximize the flatness of the new and corrected volume. EBHC is evaluated using data acquired with a modern cone-beam dual-source spiral CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany), with a modern dual-source micro-CT scanner (TomoScope Synergy Twin, CT Imaging GmbH, Erlangen, Germany), and with a modern

  6. An ultrasonic through-transmission technique for monitoring the setting of injectable calcium phosphate cement.

    PubMed

    Rajzer, Izabella; Piekarczyk, Wojciech; Castaño, Oscar

    2016-10-01

    An ultrasound through-transmission method to monitor the setting process of injectable calcium phosphate bone cements in body fluids is presented. This method can be used to determine the acoustic properties of the bone cement as it sets, which are linked to its material properties and provide some information about changes occurring within the cement. The development of the methodology of ultrasonic testing and execution of velocity measurements of the longitudinal and transverse waves using the through-transmission method made it possible to determine the material constants of samples during the setting and hardening process of an injectable cement paste in physiological fluids (i.e. the Young's modulus (E), the Poisson ratio (ν) and the shear modulus (G)), and to determine the degree of anisotropy of wave velocity in the samples. A strong advantage of the proposed method is that it is non-destructive, and the same sample can be used to monitor the whole process of the cement setting. The testing was performed on premixed and injectable calcium phosphate (CPC)/chitosan blend, where glycerol was used as a liquid phase. Comparisons between ultrasonic velocity and empirical tests such as compressive strength, porosity measurement, FTIR, SEM and XRD analysis at different days of immersion in Ringer's solutions showed that the ultrasonic velocity can be very useful to provide in situ information about changes occurring within the cement.

  7. Smart cement modified with iron oxide nanoparticles to enhance the piezoresistive behavior and compressive strength for oil well applications

    NASA Astrophysics Data System (ADS)

    Vipulanandan, C.; Mohammed, A.

    2015-12-01

    In this study, smart cement with a 0.38 water-to-cement ratio was modified with iron oxide nanoparticles (NanoFe2O3) to have better sensing properties, so that the behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated the piezoresistive smart cement behavior with and without NanoFe2O3 in order to identify the most reliable sensing properties that can also be relatively easily monitored. Tests were performed on the smart cement from the time of mixing to a hardened state behavior. When oil well cement (Class H) was modified with 0.1% of conductive filler, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the setting properties of the cement. During the initial setting the electrical resistivity changed with time based on the amount of NanoFe2O3 used to modify the smart oil well cement. A new quantification concept has been developed to characterize the smart cement curing based on electrical resistivity changes in the first 24 h of curing. Addition of 1% NanoFe2O3 increased the compressive strength of the smart cement by 26% and 40% after 1 day and 28 days of curing respectively. The modulus of elasticity of the smart cement increased with the addition of 1% NanoFe2O3 by 29% and 28% after 1 day and 28 days of curing respectively. A nonlinear curing model was used to predict the changes in electrical resistivity with curing time. The piezoresistivity of smart cement with NanoFe2O3 was over 750 times higher than the unmodified cement depending on the curing time and nanoparticle content. Also the nonlinear stress-strain and stress-change in resistivity relationships predicated the experimental results very well. Effects of curing time and NanoFe2O3 content on the model parameters have been quantified using a nonlinear model.

  8. New cement formulation helps solve deep cementing problems

    SciTech Connect

    Brothers, L.E.; DeBlanc, F.X.

    1989-06-01

    Invert-emulsion muds are used in most deep, hot wells. The internal aqueous phase of these muds frequently contains high concentrations of salts. It is desirable to complete these wells with a cement slurry containing salt concentrations up to and including saturation to minimize compatibility problems between cement slurry and mud. Above their effective temperature range, however, saturated salt cements - though still considered desirable for their other properties - pose design difficulties regarding thickening time, fluid loss, and rheology. High salt concentrations tend to decrease the effectiveness of most common cement additives - e.g., retarders, fluid-loss additives, and dispersants. At high temperatures, concentrations of these additives can become unacceptably large, while the additives themselves are not as effective under these conditions. Development of and field experience with a new cementing formulation for deep, high-temperature, saturated-salt applications have helped resolve the cement design problems encountered in south Texas and southern and offshore Louisiana. A single synthetic-polymer additive provides cement retardation, fluid-loss control, and dispersant properties with normal design considerations as opposed to the lengthy design requirements of other cement systems. A particular benefit derived from use of the new cement system involves cementing of long liners. Such liners frequently require squeeze cementing at the liner top because the cement is designed for conditions at the bottom of the liner and is thus frequently over-retarded for the cooler temperatures encountered at the top of the liner. This over-retardation tendency is alleviated greatly by use of the new saturated-salt cement additive.

  9. Constitutive modelling of evolving flow anisotropy including distortional hardening

    SciTech Connect

    Pietryga, Michael P.; Vladimirov, Ivaylo N.; Reese, Stefanie

    2011-05-04

    The paper presents a new constitutive model for anisotropic metal plasticity that takes into account the expansion or contraction (isotropic hardening), translation (kinematic hardening) and change of shape (distortional hardening) of the yield surface. The experimentally observed region of high curvature ('nose') on the yield surface in the loading direction and flattened shape in the reverse loading direction are modelled here by means of the concept of directional distortional hardening. The modelling of directional distortional hardening is accomplished by means of an evolving fourth-order tensor. The applicability of the model is illustrated by fitting experimental subsequent yield surfaces at finite plastic deformation. Comparisons with test data for aluminium low and high work hardening alloys display a good agreement between the simulation results and the experimental data.

  10. Mineral resource of the month: hydraulic cement

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2012-01-01

    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

  11. Cement from magnesium substituted hydroxyapatite.

    PubMed

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

    2005-05-01

    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  12. Mechanical Characteristics of Hardened Concrete with Different Mineral Admixtures: A Review

    PubMed Central

    2014-01-01

    The available literature identifies that the addition of mineral admixture as partial replacement of cement improves the microstructure of the concrete (i.e., porosity and pore size distribution) as well as increasing the mechanical characteristics such as drying shrinkage and creep, compressive strength, tensile strength, flexural strength, and modulus of elasticity; however, no single document is available in which review and comparison of the influence of the addition of these mineral admixtures on the mechanical characteristics of the hardened pozzolanic concretes are presented. In this paper, based on the reported results in the literature, mechanical characteristics of hardened concrete partially containing mineral admixtures including fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA) are discussed and it is concluded that the content and particle size of mineral admixture are the parameters which significantly influence the mechanical properties of concrete. All mineral admixtures enhance the mechanical properties of concrete except FA and GGBS which do not show a significant effect on the strength of concrete at 28 days; however, gain in strength at later ages is considerable. Moreover, the comparison of the mechanical characteristics of different pozzolanic concretes suggests that RHA and SF are competitive. PMID:24688443

  13. Phase-transformation-induced hardening in Zn-22Al alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Yangming; Zeng, Xuduo; Yang, Lijing; Sun, Keqing; Song, Zhenlun

    2013-06-01

    A phase-transformation-induced hardening effect is reported in Zn-22Al (Al: 22 wt.%) alloys. The Zn-22Al specimens were held at 300 °C for 10 h and then quenched in water. A hardening effect took place in subsequent artificial aging at 100-200 °C, which was accompanied by a phase decomposition of a soft α 2 phase and a grain coarsening. The phase-transformation-induced hardening affects the hardness more than the grain-coarsening-induced softening, which leads to the age-hardening phenomenon.

  14. Technology Developments in Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Howell, Joe T.

    2008-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS, Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches. System level applications for the RHESE technology products are discussed.

  15. Radiation-hardened nonvolatile MNOS RAM

    SciTech Connect

    Wrobel, T.F.; Dodson, W.H.; Hash, G.L.; Jones, R.V.; Nasby, R.D.; Olson, R.J.

    1983-01-01

    A radiation hardened nonvolatile MNOS RAM is being developed at Sandia National Laboratories. The memory organization is 128 x 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The devices have memory retention after a dose-rate exposure of 1E12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s.

  16. A radiation hardened nonvolatile MNOS RAM

    NASA Astrophysics Data System (ADS)

    Wrobel, T. F.; Dodson, W. H.; Hash, G. L.; Jones, R. V.; Nasby, R. D.; Olson, R. J.

    1983-12-01

    A radiation hardened nonvolatile MNOS RAM (SA2998) is being developed at Sandia National Laboratories. The memory organization is 128 x 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The device requires +10 V and +25 V for operation. The devices have memory retention after a dose-rate exposure of 1E12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s.

  17. Expecting the Unexpected: Radiation Hardened Software

    NASA Technical Reports Server (NTRS)

    Penix, John; Mehlitz, Peter C.

    2005-01-01

    Radiation induced Single Event Effects (SEEs) are a serious problem for spacecraft flight software, potentially leading to a complete loss of mission. Conventional risk mitigation has been focused on hardware, leading to slow, expensive and outdated on-board computing devices, increased power consumption and launch mass. Our approach is to look at SEEs from a software perspective, and to explicitly design flight software so that it can detect and correct the majority of SEES. Radiation hardened flight software will reduce the significant residual residual risk for critical missions and flight phases, and enable more use of inexpensive and fast COTS hardware.

  18. Enabling Strain Hardening Simulations with Dislocation Dynamics

    SciTech Connect

    Arsenlis, A; Cai, W

    2006-12-20

    Numerical algorithms for discrete dislocation dynamics simulations are investigated for the purpose of enabling strain hardening simulations of single crystals on massively parallel computers. The algorithms investigated include the /(N) calculation of forces, the equations of motion, time integration, adaptive mesh refinement, the treatment of dislocation core reactions, and the dynamic distribution of work on parallel computers. A simulation integrating all of these algorithmic elements using the Parallel Dislocation Simulator (ParaDiS) code is performed to understand their behavior in concert, and evaluate the overall numerical performance of dislocation dynamics simulations and their ability to accumulate percents of plastic strain.

  19. Strain hardening of steel EP836

    SciTech Connect

    Lyadskaya, A.A.; Lappa, R.M.; Spuskanyuk, V.Z.

    1986-03-01

    The authors investigate the effect of different combinations of cold hydraulic pressing and heat treatment on the physical and mechanical properties of steel EP836 (03N17K10V10MT), containing 0.03% C, 16-17% Ni, 10-11.5% Co, 9.5-11.5% W, 1% Ti, 1% Mo, and 0.15% A1. Deformation of the unaged steel resulted in insignificant hardening without a decrease in plasticity; this agrees with the results of investigations of other steels of this class.

  20. Thermomechanical and Heat Hardening of Building Steels

    NASA Astrophysics Data System (ADS)

    Odesskii, P. D.; Rudchenko, A. V.; Shabalov, I. P.

    2005-03-01

    Hardening treatment of steels used in welded metal structures like steelwork of industrial and civil buildings, towers, poles, reservoirs, railway bridge girders, cranes, construction machines, truck bodies, etc. is considered. The structures mentioned are produced from rolled stock supplied by metallurgy in an annual amount of tens of million of tons. In the first turn these are plates, shapes, rolled bars and sections, and pipes with different wall thickness and cross section. A classification of steels for metallic structures with respect to chemical composition and microstructure is presented.

  1. Evaluation of Polyester Resin, Epoxy, and Cement Grouts for Embedding Reinforcing Steel Bars in Hardened Concrete

    DTIC Science & Technology

    1990-01-01

    Ultg IFILE COPY REPAIR, EVALUATION, MAINTENANCE, AND REHABILITATION RESEARCH PROGRAM ofEn in s TECHNICAL REPORT REMR-CS-23 EVALUATION OF POLYESTER...WESSC-85-01/TV-66369A Civil Works Research Work Unit 32303 The following two letters used a5 part of the number designating technical reports of... research publisher? under the Repair, Evaluation, Maintenance, and Rehabilitation (REMR) Research Progr-m identify the problem area under which the report

  2. US cement industry

    SciTech Connect

    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. Cement evaluation tool: a new approach to cement evaluation

    SciTech Connect

    Froelich, B.; Dumont, A.; Pittman, D.; Seeman, B.

    1982-08-01

    Cement bond logging achieves its greatest utility when it provides the production engineer with precise indications of cement strength and distribution around the casing. Zone isolation is of critical importance in production. Previous logging systems have yielded measures of cement bond that were circumferential averages of cement quality. These were difficult to interpret. Additionally, they were sensitive to the degree of shear coupling between pipe, cement, and formation and thus were affected by microannulus. The cement evaluation tool (CET) described here overcomes these difficulties. It provides a measurement of cement presence and strength, which is largely insensitive to microannulus. Its log output is interpreted easily. Tool design allows examination of the casing circumferentially at each depth. Impedance behind casing is measured. Laboratory calibration measurements allow this to be presented in terms of cement compressive strength. Cement channels are distinguished easily, and a zone isolation indicator can be presented. Additionally, casing internal diameter and distortion are displayed. European and North American field tests have been completed, and performance for a variety of well conditions is discussed. The ability of the tool to identify channels is confirmed. Sequential runs with and without excess pressure demonstrate immunity to microannulus in cases where CBL is affected but where microannulus is small enough to prohibit hydraulic communication. Geometrical measurements have been good indicators of casing deformation and have identified casing corrosion and wear.

  4. Role of Substrate on Quartz Cementation in Quartz Aggregates

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Quartz cementation in quartz aggregates has been experimentally investigated. The starting material was disaggregated detrital quartz grains from the well-sorted, mature St. Peter Sandstone. The ‘as-is’ grains have patches of iron oxide coatings and some have euhedral overgrowths that contain iron oxide dust rims. In addition a set of experiments was run using grains that were cleaned by soaking in sodium hydrosulfite and sodium bisulfate solutions to remove exposed iron oxide coatings. Experimental charges consisted of amorphous silica powder (≈30 mg) to provide a source of silica for the quartz cement, AlCl3 powder (≈3 mg) to provide a tracer for Cathodoluminescence (CL) identification of cement formed during the experiment, 25 wt% NaCl brine solution (≈25 mg) to increase the silica solubility and to better mimic oil field brines, and the natural quartz grains (100-130 mg). The charges were weld-sealed in Au capsules and run in cold-seal pressure vessels at 250°C to 450°C at 150 MPa confining pressure for up to 8 weeks. After the experiments, the samples were vacuum impregnated with a low viscosity epoxy containing a blue dye. After curing, the sample charge was sawn in half along its long axis and one half was polished (to 1 micron diamond paste) for analysis. The nature and amount of quartz cement in the samples were determined by a combination of CL, light microscopy, and scanning electron microscopy. Photomosaics of the samples were created and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement formed during the experiment was easily recognized from the quartz grains (and previous overgrowths) by the difference in luminescence. The results indicate the amorphous silica powder provides a ready source for silica for quartz cementation due to its greater solubility than the quartz. The cementation rates are rapid (>14% cement formed in 2 weeks at 450°C and >7% in 8 weeks at 250°C). Compared to

  5. Cement paste prior to setting: A rheological approach

    SciTech Connect

    Bellotto, Maurizio

    2013-10-15

    The evolution of cement paste during the dormant period is analyzed via small amplitude oscillation rheological measurements. Cement paste, from the very first moments after mixing cement and water, shows the formation of an elastic gel whose strength is rapidly increasing over time. Up to the onset of Portlandite precipitation G′(t) increases by more than 2 orders of magnitude and in the acceleratory period G′(t) continues steadily to increase. A microstructural modification is likely to occur between the dormant and the acceleratory period. At low deformations in the linearity domain the storage modulus G′(ω) exhibits a negligible frequency dependence. At higher deformations cement paste shows a yield stress which increases on increasing paste concentration. The presence of superplasticizers decreases the yield stress and increases the gelation threshold of the paste. Above the gelation threshold the evolution of cement paste with superplasticizers follows similar trends to the neat paste. -- Highlights: •The gelation of cement paste during the dormant period is analyzed via rheometry. •The observed evolution is proposed to be related to the pore structure refinement. •Similarities are observed with colloidal gels and colloidal glasses.

  6. Thermal diffusivity of glass ionomer cement systems.

    PubMed

    Brantley, W A; Kerby, R E

    1993-01-01

    The thermal diffusivity has been measured for 10 glass ionomer and resin-based materials: three conventional (water-hardened) glass ionomer cements, two silver-reinforced glass ionomers, an experimental stainless steel-reinforced glass ionomer, three visible light-cured (VLC) glass ionomer-resin hybrid materials, and a VLC resin-based product developed for the same clinical uses as the hybrid materials. Cube-shaped specimens, c. 10 x 10 x 10 mm, initially at room temperature were immersed in mercury surrounded by an ice-water bath. From the experimental cooling curve a semi-log plot of relative temperature decrease vs. time yielded a straight line whose slope is proportional to the thermal diffusivity. The values ranged from 1.74-5.16 x 10(-3) cm2 s-1, and all of the materials tested would have adequate insulating properties provided normal clinical thickness levels for lining materials are maintained. It was found that the thermal diffusivities for the three metal-reinforced glass ionomers, where composition information is available, do not follow a rule of mixtures applied to the individual components.

  7. Beam hardening and partial beam hardening of the bowtie filter: Effects on dosimetric applications in CT

    NASA Astrophysics Data System (ADS)

    Lopez-Rendon, X.; Zhang, G.; Bosmans, H.; Oyen, R.; Zanca, F.

    2014-03-01

    Purpose: To estimate the consequences on dosimetric applications when a CT bowtie filter is modeled by means of full beam hardening versus partial beam hardening. Method: A model of source and filtration for a CT scanner as developed by Turner et. al. [1] was implemented. Specific exposures were measured with the stationary CT X-ray tube in order to assess the equivalent thickness of Al of the bowtie filter as a function of the fan angle. Using these thicknesses, the primary beam attenuation factors were calculated from the energy dependent photon mass attenuation coefficients and used to include beam hardening in the spectrum. This was compared to a potentially less computationally intensive approach, which accounts only partially for beam hardening, by giving the photon spectrum a global (energy independent) fan angle specific weighting factor. Percentage differences between the two methods were quantified by calculating the dose in air after passing several water equivalent thicknesses representative for patients having different BMI. Specifically, the maximum water equivalent thickness of the lateral and anterior-posterior dimension and of the corresponding (half) effective diameter were assessed. Results: The largest percentage differences were found for the thickest part of the bowtie filter and they increased with patient size. For a normal size patient they ranged from 5.5% at half effective diameter to 16.1% for the lateral dimension; for the most obese patient they ranged from 7.7% to 19.3%, respectively. For a complete simulation of one rotation of the x-ray tube, the proposed method was 12% faster than the complete simulation of the bowtie filter. Conclusion: The need for simulating the beam hardening of the bow tie filter in Monte Carlo platforms for CT dosimetry will depend on the required accuracy.

  8. Cement penetration after patella venting.

    PubMed

    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.

  9. [Haemotoxicity of dental luting cements].

    PubMed

    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.

  10. Abrasive wear of cemented carbides

    SciTech Connect

    Hawk, Jeffrey A.; Wilson, Rick D.

    2003-10-01

    Cemented carbides are used for a wide variety of applications where wear is a problem. Usually the wear of the cemented carbides is a combination of metal-to-metal and abrasion. Wear can occur at room or elevated temperatures. This research summarizes initial research to understand the abrasive wear of various cemented carbides (various grain sizes, carbide types, carbide grain sizes and binder compositions) in terms of absolute material removal rates and material removal mechanisms.

  11. High early strength calcium phosphate bone cement: effects of dicalcium phosphate dihydrate and absorbable fibers.

    PubMed

    Burguera, Elena F; Xu, Hockin H K; Takagi, Shozo; Chow, Laurence C

    2005-12-15

    Calcium phosphate cement (CPC) sets in situ to form resorbable hydroxyapatite with chemical and crystallographic similarity to the apatite in human bones, hence it is highly promising for clinical applications. The objective of the present study was to develop a CPC that is fast setting and has high strength in the early stages of implantation. Two approaches were combined to impart high early strength to the cement: the use of dicalcium phosphate dihydrate with a high solubility (which formed the cement CPC(D)) instead of anhydrous dicalcium phosphate (which formed the conventional cement CPC(A)), and the incorporation of absorbable fibers. A 2 x 8 design was tested with two materials (CPC(A) and CPC(D)) and eight levels of cement reaction time: 15 min, 30 min, 1 h, 1.5 h, 2 h, 4 h, 8 h, and 24 h. An absorbable suture fiber was incorporated into cements at 25% volume fraction. The Gilmore needle method measured a hardening time of 15.8 min for CPC(D), five-fold faster than 81.5 min for CPC(A), at a powder:liquid ratio of 3:1. Scanning electron microscopy revealed the formation of nanosized rod-like hydroxyapatite crystals and platelet crystals in the cements. At 30 min, the flexural strength (mean +/- standard deviation; n = 5) was 0 MPa for CPC(A) (the paste did not set), (4.2 +/- 0.3) MPa for CPC(D), and (10.7 +/- 2.4) MPa for CPC(D)-fiber specimens, significantly different from each other (Tukey's at 0.95). The work of fracture (toughness) was increased by two orders of magnitude for the CPC(D)-fiber cement. The high early strength matched the reported strength for cancellous bone and sintered porous hydroxyapatite implants. The composite strength S(c) was correlated to the matrix strength S(m): S(c) = 2.16S(m). In summary, substantial early strength was imparted to a moldable, self-hardening and resorbable hydroxyapatite via two synergistic approaches: dicalcium phosphate dihydrate, and absorbable fibers. The new fast-setting and strong cement may help prevent

  12. Short term hardening effects on survival of acute and chronic cold exposure by Drosophila melanogaster larvae

    PubMed Central

    Rajamohan, Arun; Sinclair, Brent J.

    2008-01-01

    We quantified the variation and plasticity in cold tolerance among four larval stages of four laboratory strains of Drosophila melanogaster in response to both acute (<2 hours of cold exposure) and chronic (∼7 hours of cold exposure) cold exposure. We observed significant differences in basal cold tolerance between the strains and among larval stages. Early larval instars were generally more tolerant of acute cold exposures than 3rd instar larvae. However, wandering larvae were more tolerant of chronic cold exposures than the other stages. Early stages also displayed a more pronounced rapid cold-hardening response than the later stages. Heat pre-treatment did not confer a significant increase in cold tolerance to any of the strains at any stage, pointing to different mechanisms being involved in resolving heat- and cold-elicited damage. However, when heat pre-treatment was combined with rapid cold-hardening as sequential pre-treatments, both positive (heat first) and negative (heat second) effects on cold tolerance were observed. We discuss possible mechanisms underlying cold-hardening and the effects of acute and chronic cold exposures. PMID:18342328

  13. Inspection program improves bulk cement system delivery

    SciTech Connect

    O'Bannion, T. ); Guidroz, B.; Morris, G. )

    1993-12-20

    A recently implemented survey of pneumatically operated bulk cement-handling equipment offshore has improved bulk cement deliverability on several Gulf of Mexico rigs. The 30-point survey helps ensure an adequate rate of bulk cement delivery throughout the cement job. The inspection survey was developed because the source of many cement job failures was a lack of adequate, steady delivery of bulk cement to the cementing unit during the job. The job failures caused by flow interruptions, plugging of tools by chunks of set cement, and erratic flow resulted in poor primary cement jobs, many of which required remedial cementing jobs. A better-controlled flow of cement may help prevent these types of failure, thereby reducing the number of remedial cement operations. The paper describes the inspection procedures.

  14. Hardened Client Platforms for Secure Internet Banking

    NASA Astrophysics Data System (ADS)

    Ronchi, C.; Zakhidov, S.

    We review the security of e-banking platforms with particular attention to the exploitable attack vectors of three main attack categories: Man-in-the-Middle, Man-in-the-PC and Man-in-the-Browser. It will be shown that the most serious threats come from combination attacks capable of hacking any transaction without the need to control the authentication process. Using this approach, the security of any authentication system can be bypassed, including those using SecureID Tokens, OTP Tokens, Biometric Sensors and Smart Cards. We will describe and compare two recently proposed e-banking platforms, the ZTIC and the USPD, both of which are based on the use of dedicated client devices, but with diverging approaches with respect to the need of hardening the Web client application. It will be shown that the use of a Hardened Browser (or H-Browser) component is critical to force attackers to employ complex and expensive techniques and to reduce the strength and variety of social engineering attacks down to physiological fraud levels.

  15. CID25: radiation hardened color video camera

    NASA Astrophysics Data System (ADS)

    Baiko, D. A.; Bhaskaran, S. K.; Czebiniak, S. W.

    2006-02-01

    The charge injection device, CID25, is presented. The CID25 is a color video imager. The imager is compliant with the NTSC interlaced TV standard. It has 484 by 710 displayable pixels and is capable of producing 30 frames-per-second color video. The CID25 is equipped with the preamplifier-per-pixel technology combined with parallel row processing to achieve high conversion gain and low noise bandwidth. The on-chip correlated double sampling circuitry serves to reduce the low frequency noise components. The CID25 is operated by a camera system consisting of two parts, the head assembly and the camera control unit (CCU). The head assembly and the CCU can be separated by up to 150 meter long cable. The CID25 imager and the head portion of the camera are radiation hardened. They can produce color video with insignificant SNR degradation out to at least 2.85 Mrad of total dose of Co 60 γ-radiation. This represents the first in industry radiation hardened color video system, based on a semiconductor photo-detector that has an adequate sensitivity for room light operation.

  16. Nanostructured calcium silicate hydrate seeds accelerate concrete hardening: a combined assessment of benefits and risks.

    PubMed

    Bräu, Michael; Ma-Hock, Lan; Hesse, Christoph; Nicoleau, Luc; Strauss, Volker; Treumann, Silke; Wiench, Karin; Landsiedel, Robert; Wohlleben, Wendel

    2012-07-01

    Nanotechnology creates new possibilities to control and improve material properties for civil infrastructure. Special focus in this area is put on Portland cement and gypsum. Together their annual production is by far larger than for any other material worldwide. Nanomodification of these materials can be done during the few hours between dissolution and hardening, especially by nucleation of the re-crystallization with suitable colloids. Here we report first results in homogeneous seeding of the precipitation of calcium silicate hydrates within a real Portland cement composition. The occupational safety during the production phase and during mixing of concrete paste is addressed in detail by in vivo testing. We perform 5-day inhalation with 21-day recovery in rats and analyze organ-specific toxicity and 71 endpoints from bronchoalveolar lavage (BALF) and blood. In BALF parameters, no test-related changes were observed, indicating the generally low toxicity of the test material. Some mild lesions were observed in larynx level. In the lungs, all animals of the 50 mg/m³ concentration group revealed a minimal to mild increase in alveolar macrophages, which recovered back to control level.

  17. In Situ Nanoindentation Studies on Detwinning and Work Hardening in Nanotwinned Monolithic Metals

    SciTech Connect

    Liu, Y.; Li, N.; Bufford, D.; Lee, J. H.; Wang, J.; Wang, H.; Zhang, X.

    2015-07-14

    Certain nanotwinned (nt) metals have rare combinations of high mechanical strength and ductility. Here, we review recent in situ nanoindentation studies (using transmission electron microscopes) on the deformation mechanisms of nt face-centered cubic metals including Cu, Ni, and Al with a wide range of stacking fault energy (SFE). Moreover, in nt Cu with low-to-intermediate SFE, detwinning (accompanied by rapid twin boundary migration) occurs at ultralow stress. In Ni with relatively high SFE, coherent {111} twin boundaries lead to substantial work hardening. Twinned Al has abundant {112} incoherent twin boundaries, which induce significant work-hardening capability and plasticity in Al. Finally, twin boundaries in Al also migrate but at very high stresses. Furthermore, molecular dynamics simulations reveal the influence of SFE on deformation mechanisms in twinned metals.

  18. In Situ Nanoindentation Studies on Detwinning and Work Hardening in Nanotwinned Monolithic Metals

    DOE PAGES

    Liu, Y.; Li, N.; Bufford, D.; ...

    2015-07-14

    Certain nanotwinned (nt) metals have rare combinations of high mechanical strength and ductility. Here, we review recent in situ nanoindentation studies (using transmission electron microscopes) on the deformation mechanisms of nt face-centered cubic metals including Cu, Ni, and Al with a wide range of stacking fault energy (SFE). Moreover, in nt Cu with low-to-intermediate SFE, detwinning (accompanied by rapid twin boundary migration) occurs at ultralow stress. In Ni with relatively high SFE, coherent {111} twin boundaries lead to substantial work hardening. Twinned Al has abundant {112} incoherent twin boundaries, which induce significant work-hardening capability and plasticity in Al. Finally, twinmore » boundaries in Al also migrate but at very high stresses. Furthermore, molecular dynamics simulations reveal the influence of SFE on deformation mechanisms in twinned metals.« less

  19. Cross-tolerance effects due to adult heat hardening, desiccation and starvation acclimation of tropical drosophilid-Zaprionus indianus.

    PubMed

    Kalra, Bhawna; Tamang, Aditya Moktan; Parkash, Ravi

    2017-07-01

    Some insect taxa from polar or temperate habitats have shown cross-tolerance for multiple stressors but tropical insect taxa have received less attention. Accordingly, we considered adult flies of a tropical drosophilid-Zaprionus indianus for testing direct as well as cross-tolerance effects of rapid heat hardening (HH), desiccation acclimation (DA) and starvation acclimation (SA) after rearing under warmer and drier season specific simulated conditions. We observed significant direct acclimation effects of HH, DA and SA; and four cases of cross-tolerance effects but no cross-tolerance between desiccation and starvation. Cross-tolerance due to heat hardening on desiccation showed 20% higher effect than its reciprocal effect. There is greater reduction of water loss in heat hardened flies (due to increase in amount of cuticular lipids) as compared with desiccation acclimated flies. However, cross-tolerance effect of SA on heat knockdown was two times higher than its reciprocal. Heat hardened and desiccation acclimated adult flies showed substantial increase in the level of trehalose and proline while body lipids increased due to heat hardening or starvation acclimation. However, maximum increase in energy metabolites was stressor specific i.e. trehalose due to DA; proline due to HH and total body lipids due to SA. Rapid changes in energy metabolites due to heat hardening seem compensatory for possible depletion of trehalose and proline due to desiccation stress; and body lipids due to starvation stress. Thus, observed cross-tolerance effects in Z. indianus represent physiological changes to cope with multiple stressors related to warmer and drier subtropical habitats. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons

    SciTech Connect

    Z. Zak Fang, H. Y. Sohn

    2009-03-10

    This report contains detailed information of the research program entitled "Development of Bulk Nanocrystalline Cemented Tungsten Carbide Materials for Industrial Applications". The report include the processes that were developed for producing nanosized WC/Co composite powders, and an ultrahigh pressure rapid hot consolidation process for sintering of nanosized powders. The mechanical properties of consolidated materials using the nanosized powders are also reported.

  1. Phosphate based oil well cements

    NASA Astrophysics Data System (ADS)

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  2. Radiation-hardened 16K-bit MNOS EAROM

    SciTech Connect

    Knoll, M.G.; Dellin, T.A.; Jones, R.V.

    1983-01-01

    A radiation-hardened silicon-gate CMOS/NMNOS 16K-bit EAROM has been designed, fabricated, and evaluated. This memory has been designed to be used as a ROM replacement in radiation-hardened microprocessor-based systems.

  3. Radiation-Hardened Electronics for the Space Environment

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.

    2007-01-01

    RHESE covers a broad range of technology areas and products. - Radiation Hardened Electronics - High Performance Processing - Reconfigurable Computing - Radiation Environmental Effects Modeling - Low Temperature Radiation Hardened Electronics. RHESE has aligned with currently defined customer needs. RHESE is leveraging/advancing SOA space electronics, not duplicating. - Awareness of radiation-related activities through out government and industry allow advancement rather than duplication of capabilities.

  4. Hardening treatment of friction surfaces of ball journal bearings

    NASA Astrophysics Data System (ADS)

    Gorlenko, A. O.; Davidov, S. V.

    2016-04-01

    The article presents the technology of finishing plasma hardening by the application of the multi-layer nanocoating Si-O-C-N system to harden the friction surfaces of the ball journal bearings. The authors of the paper have studied the applied wear-resistant anti-friction coating tribological characteristics, which determine the increase in wear resistance of the ball journal bearings.

  5. Hardening fertilization and nutrient loading of conifer seedlings

    Treesearch

    R. Kasten Dumroese

    2003-01-01

    Continuing to fertilize bareroot and container seedlings during the hardening process (from cessation of height growth until lifting) can improve seedling viability. The process of fertilizing during hardening has many names, but in the last decade a new term, nutrient loading, has come into use. The process of nutrient loading seedlings leads to luxury consumption...

  6. Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

    Treesearch

    Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2- diaminocyclohexane (DACH), were...

  7. Radiation-Hardened Electronics for Space Environments (RHESE)

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael; Cressler, John D.

    2008-01-01

    This conference poster explores NASA's Radiation-Hardened Electronics for Space Environments project. This project aims to advance the state of the art in high performance, radiation-hardened electronics that enable the long-term, reliable operation of a spacecraft in extreme radiation and temperature of space and the lunar surface.

  8. The hardening phenomenon in irritant contact dermatitis: an interpretative update.

    PubMed

    Watkins, Shannon A; Maibach, Howard I

    2009-03-01

    Irritant contact dermatitis (ICD) is common and poses a significant problem in high-risk populations. In most cases, ICD resolves despite continued exposure in a process known as 'hardening', allowing individuals to continue with their work. Those who cannot clear ICD develop chronic ICD, which is a significant source of emotional, physical, and financial distress for affected individuals. While hardening is well known among labourers and clinicians, its mechanism remains to be elucidated. Much can be learned from the study of self-healing processes like the hardening phenomenon. This overview briefly documents the pathogenesis of ICD, focuses on the latest advances pertaining to the hardening phenomenon in ICD, and then highlights potential avenues of productive research. A better understanding of the 'hardening' process in the skin will hopefully lead to advances for the treatment of ICD.

  9. New analytical approach for neutron beam-hardening correction.

    PubMed

    Hachouf, N; Kharfi, F; Hachouf, M; Boucenna, A

    2016-01-01

    In neutron imaging, the beam-hardening effect has a significant effect on quantitative and qualitative image interpretation. This study aims to propose a linearization method for beam-hardening correction. The proposed method is based on a new analytical approach establishing the attenuation coefficient as a function of neutron energy. Spectrum energy shift due to beam hardening is studied on the basis of Monte Carlo N-Particle (MCNP) simulated data and the analytical data. Good agreement between MCNP and analytical values has been found. Indeed, the beam-hardening effect is well supported in the proposed method. A correction procedure is developed to correct the errors of beam-hardening effect in neutron transmission, and therefore for projection data correction. The effectiveness of this procedure is determined by its application in correcting reconstructed images.

  10. A review of the stages of work hardening

    SciTech Connect

    Rollett, A.D.; Kocks, U.F.

    1993-07-01

    Stages of work hardening are reviewed with emphasis on links between each stage. Simple quantitative descriptions are given for each stage. Similarities between stage I, easy glide, and stage IV, large strain hardening, are pointed out both in terms of magnitude of the hardening rate and of the underlying mechanism of dislocation debris accumulation. Stage II is described as an athermal hardening stage that occurs when statistical variations in the dislocation ``forest`` lead to geometrical storage of dislocations. The steadily decreasing hardening rate observed in stage III is characterized by the increasing rate of loss of dislocation density due to dynamic recovery. Stage III appears to have an asymptote to a saturation stress which is determined by the characteristics of the dislocation tangles, or cell walls. The imperfect nature of the dynamic recovery process, however, leads to the accumulation of dislocation debris and this, by analogy with stage 1, causes the apparent saturation stress to rise, thus causing stage IV.

  11. Stabilization of chloro-organics using organophilic bentonite in a cement-blast furnace slag matrix.

    PubMed

    Cioffi, R; Maffucci, L; Santoro, L; Glasser, F P

    2001-01-01

    The application of cement-based stabilisation/solidification treatment to organic-containing wastes is made difficult by the adverse effect of organics on cement hydration. The use of organophilic clays as pre-solidification adsorbents of the organic compounds can reduce this problem because of the high adsorption power of these clays and their compatibility with the cementitious matrix. This work presents an investigation of the effect on hydration kinetics, physico-mechanical properties and leaching behaviour of cement-based solidified waste forms containing 2-chlorophenol and 1-chloronapthalene adsorbed on organophilic bentonites. These were prepared by cation exchange with benzyldimethyloctadecylammonium chloride and trimethyloctadecylammonium chloride. The binder was a 30% pozzolanic cement, 70% granulated blast furnace slag mixture. Several binder-to-bentonite ratios and different concentrations of the organics on the bentonite were used. Kinetics of hydration were studied by measurement of chemically bound water and by means of thermal and calorimetric analyses. Microstructure and other physico-mechanical properties of the solidified forms were studied by means of mercury intrusion porosimetry, scanning electron microscopy and unconfined compressive strength measurement. Leaching was checked by two different leaching tests: one dynamic, on monolithic samples, and the other static, on powdered samples. This study indicates that the incorporation of the organic-loaded bentonite in the binder matrix causes modifications in the hardened samples by altering cement hydration. The effects of the two organic contaminants are differentiated.

  12. Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration

    NASA Astrophysics Data System (ADS)

    Wei, Jie; Wang, Jiecheng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H 3PO 4) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3 wt% after self-hardening for 2 days. The solubility of fs-AC in Tris-HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.

  13. Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

    NASA Astrophysics Data System (ADS)

    Dey, Vikram

    The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and

  14. [Technology-based emission inventory of particulate matters (PM) from cement industry].

    PubMed

    Lei, Yu; He, Ke-bin; Zhang, Qiang; Liu, Zuo-yi

    2008-08-01

    A bottom-up PM emission model was developed based on the production technologies and PM emission control devices in Chinese cement industry. Through analyzing the historical distribution of technologies in cement producing and the impact of standards on PM emission control from cement industry, emission factors of cement industry in China during 1990-2004 were generated by this technology-based model, and emission inventories were developed thereby. Emission factor decreased from 27.9 kg x t(-1) cement in 1990 to 8.05 kg x t(-1) cement in 2004. Emissions of PM from cement industry in China reached the peak value in 1997, with 1044 x 10(4) t of TSP, 716 x 10(4) t of PM10, 436 x 10(4) t of PM2.5 emitted, then decreased until 2001, and increased slowly again during 2001-2004. The distribution of PM emissions among provinces is uneven. Shandong, Guangdong, Hebei, Jiangsu, Zhejiang, and Henan contribute more than 50% of emissions of China. Rapid spread of pre-calcining kilns in China and implementation of Emission Standard of Air Pollutants for Cement Industry in 2004 will probably decrease PM emissions from cement industry to a large extent, leading to obvious variation on PM pollution characteristics in China.

  15. Jerky loads on surface-hardened gears

    NASA Technical Reports Server (NTRS)

    Rettig, H.; Wirth, X.

    1978-01-01

    Damage occurs again and again in practice in the form of transmissions with surface hardened gears which break after a very long operating time (explained by seldom occurring jerky loads). Gear drives are frequently exposed to jerky stresses which are greater than their fatigue limit. These stresses are considered in gear calculations, first, by shock factors when the transmission is to be designed as high endurance with regard to overloads and, second, in the form of operating ratios when the design is to be time enduring with regard to overloads. The size of the operating ratio depends not only on torque characteristics, drive and processing machine, but also on the material and heat treatment.

  16. Precipitation hardening in 350 grade maraging steel

    SciTech Connect

    Viswanathan, U.K. . Radiometallurgy Div.); Dey, G.K. . Metallurgy Division); Asundi, M.K. )

    1993-11-01

    Evolution of microstructure in 350 grade commercial maraging steel has been examined. In the earlier stages of aging, the strengthening phases are formed by the heterogeneous precipitation, and these phases have been identified as intermetallic compounds of the Ni[sub 3] (Ti, Mo) and Fe[sub 2]Mo types. The kinetics of precipitation are studied in terms of the activation energy by carrying out isothermal hardness measurements of aged material. The mechanical properties in the peak-aged and overaged conditions were evaluated and the flow behavior examined. The overaging behavior of the steel has been studied and the formation of austenite of different morphologies identified. The crystallography of the austenite has been examined in detail. From the microstructural examination of peak-aged and deformed samples, it could be inferred that the dislocation-precipitate interaction is by precipitate shearing. Increased work hardening of the material in the overaged condition was suggestive of looping of precipitates by dislocations.

  17. Keystroke Dynamics-Based Credential Hardening Systems

    NASA Astrophysics Data System (ADS)

    Bartlow, Nick; Cukic, Bojan

    abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.

  18. Laser hardening process simulation for mechanical parts

    NASA Astrophysics Data System (ADS)

    Tani, G.; Orazi, L.; Fortunato, A.; Campana, G.; Cuccolini, G.

    2007-02-01

    In this paper a numerical simulation of laser hardening process is presented. The Finite Difference Method (FDM) was used to solve the heat transfer and the carbon diffusion equations for a defined workpiece geometry. The model is able to predict the thermal cycle into the target material, the phase transformations and the resulting micro-structures according to the laser parameters, the workpiece dimensions and the physical properties of the workpiece. The effects of the overlapping tracks of the laser beam on the resulting micro-structures is also considered. The initial workpiece micro-structure is taken into account in the simulation by a digitized photomicrograph of the ferrite perlite distribution before the thermal cycle. Experimental tests were realized on a C43 plate and the good agreement between the theoretical and experimental results is shown.

  19. Hardened engineering test building: Conceptual design report

    SciTech Connect

    Not Available

    1984-05-01

    Both the special nuclear materials nuclear explosive-like assemblies (SNM NELA) engineering tests and the intrinsic radiation (INRAD) activity is a programmatic necessity supported by Lawrence Livermore National Laboratory (LLNL) management. A new facility conforming to DOE standards for hardening and providing adequate security is an urgent requirement. The total project cost of $3,300,000 includes site improvements, building construction, and supporting utility services, as well as engineering services. The conceptual design in this report is based on functional requirements and the applicable design criteria. The design is the result of close interaction between LLNL personnel and the conceptual design team. Siting, building configuration, structural method, material selection, and mechanical and electrical systems were considered in the course of the design process. The concepts were evaluated from the viewpoints of cost effectiveness, energy conservation, functional requirements, operational patterns, and the creation of a desirable working environment.

  20. Suitability of calcium phosphate cement for injection laryngoplasty in rabbits.

    PubMed

    Ikeda, Asako; Shiotani, Akihiro; Mori, Yuko; Fujimine, Takekatsu; Tomifuji, Masayuki; Takaoka, Takuji; Kameyama, Kaori; Ogawa, Kaoru

    2006-01-01

    Calcium phosphate cement (CPC) consists of powder and liquid, which become an injectable paste after mixing, self-hardening and recrystallizing to calcium hydroxylapatite (CaHA) after injection into a living body. In this study, we investigated the suitability of CPC as an injectable material for injection laryngoplasty using rabbits. All rabbits underwent left recurrent laryngeal nerve section and injection laryngoplasty with CPC. At 7 days, scanning electron microscopic findings revealed that complete recrystallization from CPC to CaHA was achieved in the larynx. At 1, 3, and 6 months, injected CPC stayed in the paraglottic space and did not migrate, and the average remaining CPC volume percentage was 91.7%. Focal foreign body reaction to injected CPC was almost the same as that of autologous fat for all time periods observed. These results indicated that CPC appears to be biocompatible, nonabsorbable, nonmigratory, and suitable for injection laryngoplasty. Copyright 2006 S. Karger AG, Basel.

  1. Cement Materials Based on Cellulosic Fibers for Plasters

    NASA Astrophysics Data System (ADS)

    Hospodarova, Viola; Stevulova, Nadezda; Junak, Jozef; Geffert, Anton; Kacik, Frantisek; Briancin, Jaroslav

    2017-06-01

    This paper presents physical and mechanical properties of cementitious composites/plasters containing cellulosic fibers in portion 2.0% and 5.0% of filler replacement after 28 days of hardening. Cellulosic fibers (Greencel) originated from bleached wood pulp and unbleached waste paper used in this experimental work were characterized from the point of view cellulose structure. Experimental investigations reveal that adding cellulosic fibers reduces composites density (up to 8.2 %) in comparison with composites without any fibers. Moreover, the presence of wood pulp and recycled fibers in composites cause higher values of water absorbability than sample without fibers. Also, the decrease in compressive strength values for tested fiber cement plasters was observed (14.1 - 18.0 MPa) in comparison to reference sample (26.6 MPa). But the identified compressive strength values are in accordance with European standard (5 MPa) for plasters.

  2. Long-term performance of the steel-cement interface in CO2 sequestration wells

    NASA Astrophysics Data System (ADS)

    Carey, J. W.; Han, J.

    2011-12-01

    Long-term performance of CO2 storage reservoirs will require that wells (injection, monitoring, and pre-existing) continue to provide isolation of the buoyant CO2 plume. Short-term leakage concerns are driven by the quality of the well completions, particularly placement of Portland cement. However, operational and CO2-injection induced stresses in the reservoir may introduce small defects in the well isolation system, allowing migration of small quantities of CO2 and brine. Evidence for such leaks has been observed in a CO2-enhanced oil recovery well (Carey et al. 2007) and in a natural CO2 reservoir (Crow et al. 2010). The key question in long-term performance is whether these leaks will grow as wellbore materials degrade or whether carbonate precipitation reactions will self-heal the defects. In this study, we focus on the interface between steel casing and Portland cement. In a properly completed well, Portland cement provides a protective, alkaline environment for carbon steel that precludes the possibility of external corrosion. The protective cement can be damaged either by the formation of small gaps at the interface, known as microannuli, or by the carbonation of cement which eliminates cement alkalinity. To investigate these issues, we conducted experiments on cement-steel composites at conditions ranging from atmospheric to high-pressure to determine the susceptibility of steel to corrosion in the presence of well-bonded cement, carbonated cement, and cement separated from the steel by varying gap distances. The presence of cement greatly reduces corrosion rates of steel because an iron carbonate scale forms rapidly and provides a mass-transfer barrier. Similarly, a small gap at the cement-steel interface provides a mass-transfer barrier. Our results show that scale formation provides a more significant barrier to corrosion and that even small gaps (<100 um) do not enhance protection in the cement-steel system. For steel embedded in cement, corrosion

  3. Spectral Hardening and Geoeffectiveness of Solar Flares

    NASA Astrophysics Data System (ADS)

    Jain, R.; Kumar, S.; Dave, H.; Deshpande, M. R.

    We present the results of a few typical flares that observed by the first space borne solar astronomy experiment of India namely "Solar X-ray Spectrometer (SOXS)" mission, which has completed one year of its successful operation in geostationary orbit. The SOXS mission onboard GSAT-2 Indian spacecraft was launched successfully by GSLV-D2 rocket on 08 May 2003 to study the energy release and particle acceleration in solar flares. The SOXS is composed of two independent payloads viz. SOXS Low Energy Detector (SLD) payload, and SOXS High Energy Detector (SHD) payload. We restrict our presentation to SLD payload that designed, developed and fabricated by Physical Research Laboratory (PRL) in collaboration with Space Application Centre (SAC), Ahmedabad and ISRO Satellite Centre (ISAC), Bangalore of Indian Space Research Organization (ISRO). We briefly present the scientific objectives and instrumentation of the SLD payload. The SLD payload employs the state-of-art solid state detectors viz. Si PIN and CZT detectors, which reveal sub-keV spectral and 100ms temporal resolution characteristics that are necessary to study the spectral response of the flare components. The dynamic range of Si and CZT detectors is 4-25 and 4-56 keV respectively. The SLD has observed more than 140 flares of C and M class since its commissioning in the orbit. We present the X-ray emission characteristics of a few typical flares in view of their spectral hardening and geo-effectiveness. We extend our study of these flares to optical and radio waveband observations in order to improve the relationship of X-ray spectral hardening and geo-effectiveness. The flares with harder spectra and associated with small or large CME, and radio emission at frequencies above 10 GHz are found geo-effective.

  4. Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete.

    PubMed

    Safiuddin, Md; Raman, Sudharshan N; Zain, Muhammad Fauzi Mohd

    2015-12-10

    The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete.

  5. Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete

    PubMed Central

    Safiuddin, Md.; Raman, Sudharshan N.; Zain, Muhammad Fauzi Mohd.

    2015-01-01

    The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete. PMID:28793732

  6. Finite deformation analysis of crack tip fields in plastically compressible hardening-softening-hardening solids

    NASA Astrophysics Data System (ADS)

    Khan, D.; Singh, S.; Needleman, A.

    2016-11-01

    Crack tip fields are calculated under plane strain small scale yielding conditions. The material is characterized by a finite strain elastic-viscoplastic constitutive relation with various hardening-softening-hardening hardness functions. Both plastically compressible and plastically incompressible solids are considered. Displacements corresponding to the isotropic linear elastic mode I crack field are prescribed on a remote boundary. The initial crack is taken to be a semi-circular notch and symmetry about the crack plane is imposed. Plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone size and shape are found to depend on the plastic compressibility, but not much on whether material softening occurs near the crack tip. On the other hand, the near crack tip stress and deformation fields depend sensitively on whether or not material softening occurs. The combination of plastic compressibility and softening (or softening-hardening) has a particularly strong effect on the near crack tip stress and deformation fields.

  7. Finite deformation analysis of crack tip fields in plastically compressible hardening-softening-hardening solids

    NASA Astrophysics Data System (ADS)

    Khan, D.; Singh, S.; Needleman, A.

    2017-02-01

    Crack tip fields are calculated under plane strain small scale yielding conditions. The material is characterized by a finite strain elastic-viscoplastic constitutive relation with various hardening-softening-hardening hardness functions. Both plastically compressible and plastically incompressible solids are considered. Displacements corresponding to the isotropic linear elastic mode I crack field are prescribed on a remote boundary. The initial crack is taken to be a semi-circular notch and symmetry about the crack plane is imposed. Plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone size and shape are found to depend on the plastic compressibility, but not much on whether material softening occurs near the crack tip. On the other hand, the near crack tip stress and deformation fields depend sensitively on whether or not material softening occurs. The combination of plastic compressibility and softening (or softening-hardening) has a particularly strong effect on the near crack tip stress and deformation fields.

  8. Corrosion resistant cemented carbide

    SciTech Connect

    Hong, J.

    1990-10-16

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

  9. Yield Hardening of Electrorheological Fluids in Channel Flow

    NASA Astrophysics Data System (ADS)

    Helal, Ahmed; Qian, Bian; McKinley, Gareth H.; Hosoi, A. E.

    2016-06-01

    Electrorheological fluids offer potential for developing rapidly actuated hydraulic devices where shear forces or pressure-driven flow are present. In this study, the Bingham yield stress of electrorheological fluids with different particle volume fractions is investigated experimentally in wall-driven and pressure-driven flow modes using measurements in a parallel-plate rheometer and a microfluidic channel, respectively. A modified Krieger-Dougherty model can be used to describe the effects of the particle volume fraction on the yield stress and is in good agreement with the viscometric data. However, significant yield hardening in pressure-driven channel flow is observed and attributed to an increase and eventual saturation of the particle volume fraction in the channel. A phenomenological physical model linking the densification and consequent microstructure to the ratio of the particle aggregation time scale compared to the convective time scale is presented and used to predict the enhancement in yield stress in channel flow, enabling us to reconcile discrepancies in the literature between wall-driven and pressure-driven flows.

  10. Effect of Si addition on secondary hardening of alloy steels

    NASA Astrophysics Data System (ADS)

    Cho, Ki Sub; Kwon, Hoon

    2017-07-01

    In this work, the precipitation kinetics of secondary carbides in Si-bearing steels was examined via calorimetric analysis coupled with the Johnson-Mehl-Avrami kinetic model. In particular, the properties of two commercial high-speed steels (10V and ASP 23), which contained the secondary carbides described by the formulas MC/M23C6 and MC/M23C6/M6C, respectively, were investigated and compared with those of PSD and AISI D2 steels. The obtained results revealed that the presence of Si in alloys not only inhibited the precipitation of the cementite phase, but also accelerated the precipitation kinetics of the secondary carbides. Using the obtained magnitudes of the thermodynamic driving force for complete precipitation in the metastable systems formed under para-equilibrium and ortho-equilibrium conditions, it was found that the addition of Si decreased the stability of the system produced under para-equilibrium conditions and, therefore, enabled the diffusion of interstitial carbon species at low temperatures as well as rapid aging during the secondary hardening reaction.

  11. Cements containing syringic acid esters -- o-ethoxybenzoic acid and zinc oxide.

    PubMed

    Brauer, G M; Stansbury, J W

    1984-02-01

    Fissure caries is reduced when syringic acid is incorporated into a cariogenic diet of rats. It was therefore of interest to synthesize n-hexyl and 2-ethylhexyl syringate and to evaluate the properties of cements with these compounds as ingredients. Liquids containing the esters dissolved in o-ethoxybenzoic acid (EBA) - when mixed with powders made up from zinc oxide, aluminum oxide, and hydrogenated rosin - hardened in from four to nine min. Properties of the cements were determined, when possible, according to ANSI/ADA specification tests. Depending on the powder-liquid ratio employed, we obtained compositions with varying physical properties desirable for different dental applications. The syringate cements, compared with the commonly used ZOE materials, have improved compressive and tensile strength, lower water solubility, do not inhibit polymerization, and are compatible with acrylic monomers. These cements pass, and mostly greatly exceed, the requirements for ZOE-type restorative materials. They also bond significantly to resins, composites, and non-precious metals. The bond strength is somewhat less than that of n-hexyl vanillate-EBA cement, but greatly exceeds the adhesion to various substrates of ZOE luting agents. Cements containing n-hexyl syringate were somewhat brittle. Best results were obtained with liquid compositions containing 5% 2-ethylhexyl syringate, 7% n-hexyl vanillate, and 88% EBA, which yielded non-brittle materials. These cements, because of the syringate ingredient, may possess caries-reducing properties. Thus, perhaps in conjunction with fluoride additives, they would be useful as insulating bases, pulp capping agents, root canal sealers, soft tissue packs, or intermediate restoratives.

  12. An extended crystal plasticity model for latent hardening in polycrystals

    NASA Astrophysics Data System (ADS)

    Bargmann, Swantje; Svendsen, Bob; Ekh, Magnus

    2011-12-01

    In this contribution, a computational approach to modeling size-dependent self- and latent hardening in polycrystals is presented. Latent hardening is the hardening of inactive slip systems due to active slip systems. We focus attention on the investigation of glide system interaction, latent hardening and excess dislocation development. In particular, latent hardening results in a transition to patchy slip as a first indication and expression of the development of dislocation microstructures. To this end, following Nye (Acta Metall 1:153-162, 1953), Kondo (in Proceedings of the second Japan national congress for applied mechanics. Science Council of Japan, Tokyo, pp. 41-47, 1953), and many others, local deformation incompatibility in the material is adopted as a measure of the density of geometrically necessary dislocations. Their development results in additional energy being stored in the material, leading to additional kinematic-like hardening effects. A large-deformation model for latent hardening is introduced. This approach is based on direct exploitation of the dissipation principle to derive all field relations and (sufficient) forms of the constitutive relations as based on the free energy density and dissipation potential. The numerical implementation is done via a dual-mixed finite element method. A numerical example for polycrystals is presented.

  13. Porosity and mechanically optimized PLGA based in situ hardening systems.

    PubMed

    Schloegl, W; Marschall, V; Witting, M Y; Volkmer, E; Drosse, I; Leicht, U; Schieker, M; Wiggenhorn, M; Schaubhut, F; Zahler, S; Friess, W

    2012-11-01

    Goal of the present study was to develop and to characterize in situ-hardening, porous PLGA-based systems for their future application as bone grafting materials. Therefore, we investigated the precipitation behavior of formulations containing PLGA and a water-miscible solvent, DMSO, PEG 400, and NMP. To increase porosity, a pore forming agent (NaCMC) was added and to enhance mechanical properties of the system, an inorganic filler (α-TCP) was incorporated. The behavior upon contact with water and the influence of the prior addition of aqueous media on the morphology of the corresponding hardened implants were investigated. We proved cell-compatibility by live/dead assays for the hardened porous polymer/ceramic-composite scaffolds. The IsHS formulations can therefore be used to manufacture hardened scaffolds ex vivo by using molds with the desired shape and size. Cells were further successfully incorporated into the IsHS by precultivating the cells on the α-TCP-powder prior to their admixing to the formulation. However, cell viability could not be maintained due to toxicity of the tested solvents. But, the results demonstrate that in vivo cells should well penetrate, adhere, and proliferate in the hardened scaffolds. Consequently, we consider the in situ hardening system being an excellent candidate as a filling material for non-weight-bearing orthopedic indications, as the resulting properties of the hardened implant fulfill indication-specific needs like mechanical stability, elasticity, and porosity.

  14. Design Features and Initial RF Performance of a Gradient Hardened 17 GHz TW Linac Structure

    SciTech Connect

    Haimson, J.; Mecklenburg, B.

    2009-01-22

    To avoid surface erosion damage and to assist in studying RF breakdown thresholds in 17 GHz TW linac structures, a gradient hardened structure has been fabricated with high temperature brazed and machined stainless steel surfaces located in the peak E-field region of the beam apertures and the peak H-field regions of the input coupler cavity. The microwave design parameters and physical dimensions of this 22 cavity, 120 degree phase advance structure were chosen to allow the high gradient performance to be compared against a similar design all-copper structure that has been tested in a dual ring, power recirculating amplifier system. The final design parameters of the gradient hardened structure are discussed; the influence of stainless steel RF losses on the power buildup of the resonant ring and on the structure gradient distribution are described; waveforms are shown of the unique ability of the power amplifier to rapidly quench RF breakdown discharges in the linac structure by automatically sensing and redirecting the RF source power to a matched load; and preliminary test results during high power RF processing of the gradient hardened linac structure are presented.

  15. Twinning-induced plasticity (TWIP) and work hardening in Ti-based metallic glass matrix composites.

    PubMed

    Fan, J; Qiao, J W; Wang, Z H; Rao, W; Kang, G Z

    2017-05-12

    The present study demonstrates that Ti-based metallic glass matrix composites (MGMCs) with a normal composition of Ti43Zr32Ni6Ta5Be14 containing ductile dendrites dispersed in the glass matrix has been developed, and deformation mechanisms about the tensile property have been investigated by focusing on twinning-induced plasticity (TWIP) effect. The Ti-based MGMC has excellent tensile properties and pronounced tensile work-hardening capacity, with a yield strength of 1100 MPa and homogeneous elongation of 4%. The distinguished strain hardening is ascribed to the formation of deformation twinning within the dendrites. Twinning generated in the dendrites works as an obstacle for the rapid propagation of shear bands, and then, the localized necking is avoided, which ensures the ductility of such kinds of composites. Besides, a finite-element model (FEM) has been established to explain the TWIP effect which brings out a work-hardening behavior in the present MGMC instead of a localized strain concentration. According to the plasticity theory of traditional crystal materials and some new alloys, TWIP effect is mainly controlled by stacking fault energy (SFE), which has been analyzed intensively in the present MGMC.

  16. The combination of precipitation and dispersion hardening in powder metallurgy produced Cu-Ti-Si alloy

    SciTech Connect

    Bozic, D.; Dimcic, O.; Dimcic, B. Cvijovic, I.; Rajkovic, V.

    2008-08-15

    Microstructure and microhardness properties of precipitation hardened Cu-Ti and precipitation/dispersion hardened Cu-Ti-Si alloys have been analyzed. Cu-1.2Ti and Cu-1.2Ti-3TiSi{sub 2} (wt.%) atomized powders were characterized before and after consolidation by HIP (Hot Isostatic Pressing). Rapidly solidified powders and HIP-ed compacts were subsequently subjected to thermal treatment in hydrogen at temperatures between 300 and 600 deg. C. Compared to Cu-Ti powder particles and compacts, obtained by the same procedure, the strengthening effect in Cu-1.2Ti-3TiSi{sub 2} powder particles and compacts was much greater. The binary and ternary powders both reveal properties superior to those of Cu-1.2Ti and Cu-1.2Ti-3TiSi{sub 2} compacts. Microhardness analysis as a function of the aging temperature of Cu-1.2Ti-3TiSi{sub 2} alloy shows an interaction between precipitation and dispersion hardening which offers possibilities for an application at elevated temperatures.

  17. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  18. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

  19. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

  20. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

  1. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

  2. Microwave assisted preparation of magnesium phosphate cement (MPC) for orthopedic applications: a novel solution to the exothermicity problem.

    PubMed

    Zhou, Huan; Agarwal, Anand K; Goel, Vijay K; Bhaduri, Sarit B

    2013-10-01

    There are two interesting features of this paper. First, we report herein a novel microwave assisted technique to prepare phosphate based orthopedic cements, which do not generate any exothermicity during setting. The exothermic reactions during the setting of phosphate cements can cause tissue damage during the administration of injectable compositions and hence a solution to the problem is sought via microwave processing. This solution through microwave exposure is based on a phenomenon that microwave irradiation can remove all water molecules from the alkaline earth phosphate cement paste to temporarily stop the setting reaction while preserving the active precursor phase in the formulation. The setting reaction can be initiated a second time by adding aqueous medium, but without any exothermicity. Second, a special emphasis is placed on using this technique to synthesize magnesium phosphate cements for orthopedic applications with their enhanced mechanical properties and possible uses as drug and protein delivery vehicles. The as-synthesized cements were evaluated for the occurrences of exothermic reactions, setting times, presence of Mg-phosphate phases, compressive strength levels, microstructural features before and after soaking in (simulated body fluid) SBF, and in vitro cytocompatibility responses. The major results show that exposure to microwaves solves the exothermicity problem, while simultaneously improving the mechanical performance of hardened cements and reducing the setting times. As expected, the cements are also found to be cytocompatible. Finally, it is observed that this process can be applied to calcium phosphate cements system (CPCs) as well. Based on the results, this microwave exposure provides a novel technique for the processing of injectable phosphate bone cement compositions. © 2013.

  3. Hydration of Portland cement with additions of calcium sulfoaluminates

    SciTech Connect

    Le Saout, Gwenn; Lothenbach, Barbara; Hori, Akihiro; Higuchi, Takayuki; Winnefeld, Frank

    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.

  4. Apatite formation on bioactive calcium-silicate cements for dentistry affects surface topography and human marrow stromal cells proliferation.

    PubMed

    Gandolfi, Maria Giovanna; Ciapetti, Gabriela; Taddei, Paola; Perut, Francesca; Tinti, Anna; Cardoso, Marcio Vivan; Van Meerbeek, Bart; Prati, Carlo

    2010-10-01

    The effect of ageing in phosphate-containing solution of bioactive calcium-silicate cements on the chemistry, morphology and topography of the surface, as well as on in vitro human marrow stromal cells viability and proliferation was investigated. A calcium-silicate cement (wTC) mainly based on dicalcium-silicate and tricalcium-silicate was prepared. Alpha-TCP was added to wTC to obtain wTC-TCP. Bismuth oxide was inserted in wTC to prepare a radiopaque cement (wTC-Bi). A commercial calcium-silicate cement (ProRoot MTA) was tested as control. Cement disks were aged in DPBS for 5 h ('fresh samples'), 14 and 28 days, and analyzed by ESEM/EDX, SEM/EDX, ATR-FTIR, micro-Raman techniques and scanning white-light interferometry. Proliferation, LDH release, ALP activity and collagen production of human marrow stromal cells (MSC) seeded for 1-28 days on the cements were evaluated. Fresh samples exposed a surface mainly composed of calcium-silicate hydrates CSH (from the hydration of belite and alite), calcium hydroxide, calcium carbonate, and ettringite. Apatite nano-spherulites rapidly precipitated on cement surfaces within 5 h. On wTC-TCP the Ca-P deposits appeared thicker than on the other cements. Aged cements showed an irregular porous calcium-phosphate (Ca-P) coating, formed by aggregated apatite spherulites with interspersed calcite crystals. All the experimental cements exerted no acute toxicity in the cell assay system and allowed cell growth. Using biochemical results, the scores were: fresh cements>aged cements for cell proliferation and ALP activity (except for wTC-Bi), whereas fresh cementscements for collagen synthesis. Summarizing (1) non-aged cements showed higher cell proliferation than aged cements, probably favoured by the presence of Si-OH gel and the early formation of apatite nano-spherulites; (2) the alpha-TCP doped cement aged for 28 days displayed the highest bioactivity and cell proliferation; (3) the deleterious effect of bismuth on cell

  5. High-viscosity cement significantly enhances uniformity of cement filling in vertebroplasty: an experimental model and study on cement leakage.

    PubMed

    Baroud, Gamal; Crookshank, Meghan; Bohner, Marc

    2006-10-15

    Experimental study using a laboratory leakage model. To examine the working hypothesis that high-viscosity cements will spread uniformly, thus significantly reducing the risk of leakage. In vertebroplasty, forces that govern the flow of bone cement in the trabecular bone skeleton are an essential determinant of the uniformity of cement filling. Extraosseous cement leakage has been reported to be a major complication of this procedure. Leakage occurs due to the presence of a path of least resistance caused by irregularities in the trabecular bone or shell structure. Ideally, cement uniformly infiltrates the trabecular bone skeleton and does not favor specific paths. Cement viscosity is believed to affect the infiltration forces and flow during the procedure. Clinically, altering the time between cement mixing and delivery modifies the viscosity of bone cement. An experimental model of the leakage phenomenon of vertebroplasty was developed. A path, simulating a blood vessel, was created in the model to perturb the forces underlying cement flow and to favor leakage. Cement of varying viscosities was injected in the model, and, thereafter, the filling pattern, cement mass that has leaked, time at which leakage occurred, and injection pressure were measured. A strong relationship was found between the uniformity of the filling pattern and the elapsed time from cement mixing and viscosity, respectively. Specifically, 3 distinct cement leakage patterns were observed: immediate leakage was observed when cement was injected 5-7 minutes following mixing. The cement was of a low viscosity and more than 50% of the total cement injected leaked. Moderate leakage was observed when injection occurred 7-10 minutes following mixing. Less than 10% of the cement leaked, and the viscosity was at a transient state between the low viscosity of immediate leakage and a higher viscosity, doughy cement. Cement leakage ceased completely when cement was delivered after 10 minutes. The

  6. Application of solvlent change techniques to blended cements used to immobilize low-level radioactive liquid waste

    SciTech Connect

    Kruger, A.A.

    1996-07-01

    The microstructures of hardened portland and blended cement pastes, including those being considered for use in immobilizing hazardous wastes, have a complex pore structure that changes with time. In solvent exchange, the pore structure is examined by immersing a saturated sample in a large volume of solvent that is miscible with the pore fluid. This paper reports the results of solvent replacement measurements on several blended cements mixed at a solution:solids ratio of 1.0 with alkaline solutions from the simulation of the off- gas treatment system in a vitrification facility treating low-level radioactive liquid wastes. The results show that these samples have a lower permeability than ordinary portland cement samples mixed at a water:solids ratio of 0.70, despite having a higher volume of porosity. The microstructure is changed by these alkaline solutions, and these changes have important consequences with regard to durability.

  7. Contribution to the physical-mechanical study of cement CRS basis of dune-sand powder and other minerals

    NASA Astrophysics Data System (ADS)

    Dahmani, Saci; Kriker, Abdelouahed

    2016-07-01

    The Portland cements are increasingly used for the manufacture of cement materials (mortar or concrete). Sighting the increasing demand of the cement in the field of construction, and the wealth of our country of minerals. It is time to value these local materials in construction materials and in the manufacture of cement for the manufacture of a new type of cement or for the improvement of the cement of characteristics for several reasons either technical, or ecological or economic or to improve certain properties to the State fees or hardened. The uses of mineral additions remain associated to disadvantages on the time of solidification and the development of the mechanical resistance at the young age [8]. The objective of our work is to study the effects of the incorporation of additions minerals such the pozzolan (active addition) [3], slag of blast furnace (active addition) [4] and the sand dune powder (inert addition) on the physico-mechanical properties of compositions of mortar collaborated compositions according to different binary combinations basis of these additions. This will allow selecting of optimal dosages of these combinations the more efficient, from the point of view of mechanical resistanceas well. The results of this research work confirm that the rate of 10% of pozzolan, slag or powder of dune sand contributes positively on the development of resistance in the long term, at of this proportion time,there is a decrease in the latter except for the slag (20 - 40%) [4]Seems the more effective resistors and physical properties.

  8. Effects of various adjuvants (lactic acid, glycerol, and chitosan) on the injectability of a calcium phosphate cement.

    PubMed

    Leroux, L; Hatim, Z; Frèche, M; Lacout, J L

    1999-08-01

    Calcium phosphate cements are well-known orthopedic materials for filling bone. Various formulations are proposed. The current challenge is to place the material in the surgical site by methods as least invasive as possible. One approach consists of making the cement injectable by incorporation of various adjuvants. However, the requirement properties of the cement must be preserved: setting times suited to a convenient delay with surgical intervention, limited disintegration in aqueous medium, and sufficient mechanical resistance. Various additives were studied: in particular, lactic acid, glycerol, chitosan, and sodium glycerophosphate. Injectability, setting time, disintegration, and toughness after 10 days were followed in vitro. Glycerol greatly improved injectability and increased setting time, but decreased mechanical properties. Lactic acid reduced setting time, increased toughness of the material, but limited the dissolution rate. After injection, the cement did not present any disintegration. The effects lactic acid were correlated with the formation of calcium complex. Its association with sodium glycerophosphate is particularly interesting. Chitosan alone improved injectability, increased setting time, and limited the evolution of the cement by maintaining the OCP phase. Only slight disintegration was observed. These first results show that is possible to transform the cement into an injectable paste by addition of adjuvants without fundamentally modifying the chemical reactions occurring during setting and hardening.

  9. A biomimetic gelatin-calcium phosphate bone cement.

    PubMed

    Bigi, A; Torricelli, P; Fini, M; Bracci, B; Panzavolta, S; Sturba, L; Giardino, R

    2004-08-01

    The interest in new bone substitutes is rapidly increasing in the field of orthopedic surgery. A variety of calcium phosphate bone cement has been developed and different additives have been used to improve their biocompatibility and bioactivity. Following a biomimetic strategy aimed at reproducing bone characteristics, this study investigates the biological properties of a new gelatin enriched calcium phosphate cement (GEL-CP) that exhibits improved mechanical properties with respect to cement prepared without gelatin (C-CP). Human osteoblast MG63 were cultured on the surfaces of GEL-CP and were compared to cells cultured on C-CP samples, and on polystyrene of plate culture as control (C). Cell attachment, proliferation and differentiation were evaluated up to 21 days. SEM revealed that osteoblasts grown on GEL-CP showed a normal morphology and biological tests demonstrated very good rate of proliferation and viability in every experimental time. The presence of gelatin stimulated alkaline phosphatase activity, collagen and transforming growth factor 31 production. The data indicate that the new cement GEL-CP favors osteoblast proliferation, activation of their metabolism and differentiation. The remarkable improvement of the setting properties of the calcium phosphate cement due to the presence of gelatin suggest that the biomimetic composite material could be successfully applied as bone substitute.

  10. 1H NMR spin-spin relaxation and imaging in porous systems: an application to the morphological study of white portland cement during hydration in the presence of organics.

    PubMed

    Gussoni, M; Greco, F; Bonazzi, F; Vezzoli, A; Botta, D; Dotelli, G; Natali Sora, I; Pelosato, R; Zetta, L

    2004-07-01

    Proton nuclear magnetic resonance (NMR) spin-spin relaxation and imaging have been applied to investigate white Portland cement pastes during hydration in the absence and in the presence of organic solvents. The main organic solvent investigated was methanol, alone or together with the organic waste 2-chloroaniline (2-CA), an aromatic amine representative of an important class of highly toxic compounds. For all the analysed samples, prepared with a solvent-to-cement ratio of 0.4, the decay of the echo magnetization has been fitted by adopting a model that combines an exponential component with a gaussian one. The calculated independent relaxation parameters have been discussed in terms of morphological and dynamical changes that occur during the cement hardening process and pore formation. Three kinds of water molecules: "solid-like" (chemically and physically bound), "liquid-like" (porous trapped) and "free" water, endowed with anisotropic, near isotropic and isotropic motion, respectively, were identified. Spin-echo images collected on the same samples during the hydration kinetics, allowed the changes of water and solvents spatial distribution in the porous network to be monitored, showing percolation phenomena and confirming the multimodal open channels structure of the hardened cement system. Both T(2) relaxation and imaging data indicated that a pronounced delay occurs in the cement hardening when organics are present.

  11. Assessment of bart fire-hardening programs. Final report may-sep 82

    SciTech Connect

    Hathaway, W.T.; Litant, I.

    1982-09-01

    This report presents the results of an assessment of the Bay Area Rapid Transit District (BART) vehicle fire hardening. The report assesses the overall effort to improve the fire safety of the current BART vehicles through the removal of prospective ignition sources, the substitution of more fire-resistant materials, the addition of a special fire-resistant coating on the under surface of the vehicle floor, and the placement of fire stops at strategic places in the walls and ceilings. Specifically, this assessment responds to ten concerns on these improvements that were expressed by the California Public Utilities Commission.

  12. Oxidatively Degradable Poly(thioketal urethane)/Ceramic Composite Bone Cements with Bone-Like Strength.

    PubMed

    McEnery, Madison A P; Lu, Sichang; Gupta, Mukesh K; Zienkiewicz, Katarzyna J; Wenke, Joseph C; Kalpakci, Kerem N; Shimko, Daniel; Duvall, Craig L; Guelcher, Scott A

    2016-01-01

    Synthetic bone cements are commonly used in orthopaedic procedures to aid in bone regeneration following trauma or disease. Polymeric cements like PMMA provide the mechanical strength necessary for orthopaedic applications, but they are not resorbable and do not integrate with host bone. Ceramic cements have a chemical composition similar to that of bone, but their brittle mechanical properties limit their use in weight-bearing applications. In this study, we designed oxidatively degradable, polymeric bone cements with mechanical properties suitable for bone tissue engineering applications. We synthesized a novel thioketal (TK) diol, which was crosslinked with a lysine triisocyanate (LTI) prepolymer to create hydrolytically stable poly(thioketal urethane)s (PTKUR) that degrade in the oxidative environment associated with bone defects. PTKUR films were hydrolytically stable for up to 6 months, but degraded rapidly (<1 week) under simulated oxidative conditions in vitro. When combined with ceramic micro- or nanoparticles, PTKUR cements exhibited working times comparable to calcium phosphate cements and strengths exceeding those of trabecular bone. PTKUR/ceramic composite cements supported appositional bone growth and integrated with host bone near the bone-cement interface at 6 and 12 weeks post-implantation in rabbit femoral condyle plug defects. Histological evidence of osteoclast-mediated resorption of the cements was observed at 6 and 12 weeks. These findings demonstrate that a PTKUR bone cement with bone-like strength can be selectively resorbed by cells involved in bone remodeling, and thus represent an important initial step toward the development of resorbable bone cements for weight-bearing applications.

  13. Ecological Consequences of Shoreline Hardening: A Meta-Analysis

    PubMed Central

    Gittman, Rachel K.; Scyphers, Steven B.; Smith, Carter S.; Neylan, Isabelle P.; Grabowski, Jonathan H.

    2016-01-01

    Abstract Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems. PMID:28533564

  14. Work hardening and work conditioning interventions: do they affect disability?

    PubMed

    Lechner, D E

    1994-05-01

    The purpose of this article is to review the research on the effectiveness of work hardening and work conditioning programs. Twelve studies of work hardening and work conditioning programs in the United States and abroad were reviewed. One study produced convincing evidence in a randomized study that a work conditioning program was useful in producing a higher percentage of return to work and an earlier return to work in a group of patients off work for at least 2 months. Another study demonstrated that a work hardening program increased the rate of return to work by 52% in patients off work for greater than 4 months. Most of the other studies reviewed suggested positive results, but more carefully documented, randomized, and controlled studies are needed to support the efficacy of these programs and to determine the optimum and most cost-effective work hardening and work conditioning interventions.

  15. Possible correlation between work-hardening and fatigue-failure

    NASA Technical Reports Server (NTRS)

    Kettunen, P. O.; Kocks, U. F.

    1969-01-01

    Conceptual theory proposes that cyclic hardening due to non-uniform strain and stress amplitudes during testing, especially during the initial application of stress to a specimen, may correlate positively with the ultimate strength of the specimen under test.

  16. Microscopic Origin of Strain Hardening in Methane Hydrate.

    PubMed

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-03-24

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon.

  17. Stress corrosion cracking evaluation of precipitation-hardening stainless steel

    NASA Technical Reports Server (NTRS)

    Humphries, T. S.; Nelson, E. E.

    1970-01-01

    Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

  18. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis.

    PubMed

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-06-13

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis.

  19. Ultimate bending capacity of strain hardening steel pipes

    NASA Astrophysics Data System (ADS)

    Chen, Yan-fei; Zhang, Juan; Zhang, Hong; Li, Xin; Zhou, Jing; Cao, Jing

    2016-04-01

    Based on Hencky's total strain theory of plasticity, ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material, the simplified analytical solution is proposed as well. Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes. Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes. It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material. Thus, the ignorance of strain hardening effect, as commonly assumed in current codes, may underestimate the ultimate bending capacity of steel pipes. The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes, supports of offshore platforms and other tubular structural steel members.

  20. Ecological Consequences of Shoreline Hardening: A Meta-Analysis.

    PubMed

    Gittman, Rachel K; Scyphers, Steven B; Smith, Carter S; Neylan, Isabelle P; Grabowski, Jonathan H

    2016-09-01

    Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems.

  1. Computed tomographic beam-hardening artefacts: mathematical characterization and analysis

    PubMed Central

    Park, Hyoung Suk; Chung, Yong Eun; Seo, Jin Keun

    2015-01-01

    This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. PMID:25939628

  2. Microscopic Origin of Strain Hardening in Methane Hydrate

    PubMed Central

    Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

    2016-01-01

    It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

  3. Radiation-hardened microwave communications system

    SciTech Connect

    Smith, S.F.; Crutcher, R.I.; Vandermolen, R.I. )

    1990-01-01

    The consolidated fuel reprocessing program (CFRP) at the Oak Ridge National Laboratory (ORNL) has been developing signal transmission techniques and equipment to improve the efficiency of remote handling operations for nuclear applications. These efforts have been largely directed toward the goals of (a) remotely controlling bilateral force-reflecting servomanipulators for dexterous manipulation-based operations in remote maintenance tasks and (b) providing television viewing of the work site. In September 1987, developmental microwave transceiving hardware operating with dish antennas was demonstrated in the advanced integrated maintenance system (AIMS) facility at ORNL, successfully implementing both high-quality one-way television transmissions and simultaneous bidirectional digital control data transmissions with very low error rates. Initial test results based on digital transmission at a 1.0-Mbaud data rate indicated that the error rates of the microwave system were comparable to those of a hardwired system. During these test intervals, complex manipulator operations were performed, and the AIMS transporter was moved repeatedly without adverse effects on data integrity. Results of these tests have been factored into subsequent phases of the development program, with an ultimate goal of designing a fully radiation-hardened microwave signal transmission system for use in nuclear facilities.

  4. Weldable, age hardenable, austenitic stainless steel

    DOEpatents

    Brooks, J.A.; Krenzer, R.W.

    1975-07-22

    An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere is described. It has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/ o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron. (auth)

  5. Radiation-induced segregation, hardening, and IASCC

    SciTech Connect

    Eason, E.D.; Nelson, E.E.

    1995-12-31

    Intergranular cracking has been discovered after extended radiation exposure in several boiling water reactor (BWR) internal components made of austenitic stainless steel and nickel-based alloys. There are fewer field observations of intergranular cracking in pressurized water reactors (PWR), but failures have occurred in bolts, springs, and fuel cladding. There is concern for other PWR components, some of which will receive greater radiation doses than BWR components during the plant lifetime. This paper presents the results of an investigation on the connection between radiation induced segregation, hardening and irradiation-assisted stress corrosion cracking (IASCC). A data base was developed containing the available data on austenitic stainless steel where the grain boundary composition was measured by Field Emission Gun-Scanning Transmission Election Microscopy (FEG-STEM), the stress corrosion susceptibility was measured by constant extension rate tests (CERT) in light water reactor environments, some estimate of irradiated strength was available and the irradiation was conducted in a power reactor. The data base was analyzed using advanced data analysis techniques, including tree-structured pattern recognition and transformation analysis codes. The most sensitive variables and optimal modeling forms were identified using these techniques, then preliminary models were calibrated using nonlinear least squares. The results suggest that more than one mechanism causes IASCC.

  6. Cylindrical shell buckling through strain hardening

    SciTech Connect

    Bandyopadhyay, K.; Xu, J.; Shteyngart, S.; Gupta, D.

    1995-04-01

    Recently, the authors published results of plastic buckling analysis of cylindrical shells. Ideal elastic-plastic material behavior was used for the analysis. Subsequently, the buckling analysis program was continued with the realistic stress-strain relationship of a stainless steel alloy which does not exhibit a clear yield point. The plastic buckling analysis was carried out through the initial stages of strain hardening for various internal pressure values. The computer program BOSOR5 was used for this purpose. Results were compared with those obtained from the idealized elastic-plastic relationship using the offset stress level at 0.2% strain as the yield stress. For moderate hoop stress values, the realistic stress-grain case shows a slight reduction of the buckling strength. But, a substantial gain in the buckling strength is observed as the hoop stress approaches the yield strength. Most importantly, the shell retains a residual strength to carry a small amount of axial compressive load even when the hoop stress has exceeded the offset yield strength.

  7. Design concepts for hardened communications structures

    NASA Astrophysics Data System (ADS)

    Flathau, William J.; Smith, William G.

    1990-03-01

    An important component of any hardened command and control structure is the antenna system that provides communication with the outside world. Two types of antennae were considered; i.e., the whip type and the directional. The whip type is for short range communication and the directional is for use primarily with satellites. In the super high frequency range, the use of directional antennae having parabolic dishes greater than 8 feet in diameter are common. In the very extra high frequency range, dishes that are 2 to 3 feet in diameter are used. The whip type antenna should extend up to, say, 60 feet in the air. Based on this background, a family of structures was designed that can protect whip and directional antennae from the blast and shock effects from a 1-MT device for ground surface overpressure ranging from 15,000 to 500 psi. As the antennae, transmitters, receivers, power supplies, and lifting mechanisms will be located within such structures, appropriate shock spectra plots were developed to determine if the fragility level of pertinent equipment will be exceeded and for use in designing shock isolation systems. Button up periods of 1 and 4 weeks were considered.

  8. Open Source Radiation Hardened by Design Technology

    NASA Technical Reports Server (NTRS)

    Shuler, Robert

    2016-01-01

    The proposed technology allows use of the latest microcircuit technology with lowest power and fastest speed, with minimal delay and engineering costs, through new Radiation Hardened by Design (RHBD) techniques that do not require extensive process characterization, technique evaluation and re-design at each Moore's Law generation. The separation of critical node groups is explicitly parameterized so it can be increased as microcircuit technologies shrink. The technology will be open access to radiation tolerant circuit vendors. INNOVATION: This technology would enhance computation intensive applications such as autonomy, robotics, advanced sensor and tracking processes, as well as low power applications such as wireless sensor networks. OUTCOME / RESULTS: 1) Simulation analysis indicates feasibility. 2)Compact voting latch 65 nanometer test chip designed and submitted for fabrication -7/2016. INFUSION FOR SPACE / EARTH: This technology may be used in any digital integrated circuit in which a high level of resistance to Single Event Upsets is desired, and has the greatest benefit outside low earth orbit where cosmic rays are numerous.

  9. Reactions in glass-ionomer cements: IV. Effect of chelating comonomers on setting behavior.

    PubMed

    Wilson, A D; Crisp, S; Ferner, A J

    1976-01-01

    The oscillating rheometer is a valuable instrument for studying the effects of additives on the setting behavior of a cement system. Using this instrument, it was found that certain chelating comonomers, the hydroxycarboxylic acids, could improve the setting characteristics of the glass-ionomer cement system when added to the PAA solution. The acid chelates probably assign the extraction of metal ions from the glass and also tend to hold them in solution, preventing premature ion binding of the polyanion chains. The effect is to increase the rate of hardening without reducing the working time, which may indeed by slightly increased. Tartaric acid, the most effective of the comonomers, can form a chelate bridge between aluminum atoms, and this metal complex probably acts as a flexible bridge structure linking polyanion chains. This mechanism offers some steric advantages over a simple salt bridge.

  10. Magnesium substitution in brushite cements.

    PubMed

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López

    2013-01-01

    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.

  11. Graphite-reinforced bone cement

    NASA Technical Reports Server (NTRS)

    Knoell, A. C.

    1976-01-01

    Chopped graphite fibers added to surgical bone cement form bonding agent with mechanical properties closely matched to those of bone. Curing reaction produces less heat, resulting in reduced traumatization of body tissues. Stiffness is increased without affecting flexural strength.

  12. Process for cementing geothermal wells

    SciTech Connect

    Eilers, L. H.

    1985-12-03

    A pumpable slurry of coal-filled furfuryl alcohol, furfural, and/or a low molecular weight monoor copolymer thereof containing, preferably, a catalytic amount of a soluble acid catalyst is used to cement a casing in a geothermal well.

  13. Conditioning hazardous wastes with cement

    SciTech Connect

    Glasser, F.P.

    1996-10-01

    Cementitious materials, including Ca(OH)2 and Portland cement, are widely used to condition wastes for disposal. Physical confinement is easily demonstrated, but additionally, cements have a unique chemical conditioning action. A cost-benefit analysis depends on being able to quantify this chemical conditioning action. A case study approach is used to show how this can be done, using selected inorganics (Ni, Cr, U) as examples. Laboratory data should preferably be obtained in a form suitable for thermodynamic modelling; not only does this impose rigor, but it also ensures that data are of general applicability, i.e. not site-specific. The interaction of cement with some simple, water-soluble organics are described. The future performance of cemented wastes in burial sites is site dependent; scale, local geochemistry and the kinetics and mechanisms of waste degradation are important factors which cannot be determined entirely in the laboratory. Some principles are described whereby laboratory and field studies can be related.

  14. Feasibility of Underwater Friction Stir Welding of Hardenable Alloy Steel

    DTIC Science & Technology

    2010-12-01

    bead-on-plate FSW traverses, approximately 64 inches (1.6 m) in total length, on 0.25 inch (6.4 mm) thick plates of a hardenable alloy steel . The...base plate. Based on preliminary findings, FSW of hardenable alloy steel is a feasible process and should be further researched and refined. 15...v ABSTRACT The objective of this thesis is to determine whether friction stir welding ( FSW ) is a feasible welding process for steels in an

  15. Approaches to radiation-hardened I2L technology

    NASA Astrophysics Data System (ADS)

    Bahraman, A.; Chang, S. Y.

    1980-12-01

    Design techniques are described for achieving radiation-hardened Schottky-base I2L (SBI2L) circuits. Radiation performance data are presented for this new technology and compared with results for conventional or Schottky-base I2L. This concept is extended to VLSI designs. Finally, as an application of SBI2L, a new design is presented for a radiation-hardened static random-access-memory (RAM) cell.

  16. Center for Cement Composite Materials

    DTIC Science & Technology

    1990-01-31

    displacement plots. I I 21 Table 6. Polymers used in the study of organoceramics. U I Polymer Abbreviation Structure II all Poly ( vinyl alcohol ) PVA...using commercial Portland cements and a poly ( vinyl U aclohol)/acetate copolymer. Laminations in the cured composites limited flexural strengths to...cement and partially hydrolysed 3 polyvinyl alcohol was investigated as a function of relative humidity. Unmodified and crosslinked compositions were

  17. FBC conversion of deinking residue to produce valuable cement products

    SciTech Connect

    Biermann, J.J.P.; Voogt, N.; Valk, M.

    1999-07-01

    Dutch papermills annually produce 300,000 tons deinking residue. Landfilling these residues encounters increased (governmental) disapproval. High municipal waste incineration costs will jeopardize the Dutch papermills competitive international position. Four Dutch papermills joined in CDEM Holland BV and developed a new and patented process that converts deinking residue into a high-valuable cement product using fluidized bed technology. The process has lower costs and is greener than its current alternatives. Deinking residues contain valuable minerals such as highly dispersed china clay and chalk. In the CDEM process, the china clay is dehydrated, and the chalk is partially calcined. These conversions produce a mineral product with cement-like properties. Please notice that the product is not a filler, it's cement in itself. Moreover, the product can be used as a specialty additive to increase ordinary Portland cement properties such as color and hardening. The mineral conversions require a very precise control of process conditions such as temperature, residence time, and gas-phase composition. A fluidized bed installation is used under different and very strictly controlled process-conditions, compared to normal FBC incineration. The organic fraction of the residue is incinerated, producing energy for the process and allowing for additional energy production. The throughput is relatively high (over 1,000 kg/m{sup 2}/hour); thus a small unit can convert large quantities of deinking residue. Emissions to air are low; the stringent Dutch legislation can be met without additional investments in flue-gas cleanup technology. Emissions to water are absent. The CDEM process has been developed and demonstrated using the fluidized-bed facilities of the Twente University at a 50--100 kg/hr bench-scale and a 250--500 kg/hr pilot-plant-scale. Over 100,000 kg of deinking residue has been processed. The cement product made during these trials has demonstrated its quality in

  18. Compositional changes of a dicalcium phosphate dihydrate cement after implantation in sheep.

    PubMed

    Bohner, M; Theiss, F; Apelt, D; Hirsiger, W; Houriet, R; Rizzoli, G; Gnos, E; Frei, C; Auer, J A; von Rechenberg, B

    2003-09-01

    A hydraulic calcium phosphate cement having dicalcium phosphate dihydrate (DCPD) as end-product of the setting reaction was implanted in a cylindrical defect in the diaphysis of sheep for up to 6 months. The composition of the cement was investigated as a function of time. After setting, the cement composition consisted essentially of a mixture of DCPD and beta-tricalcium phosphate (beta-TCP). In the first few weeks of implantation, the edges of the cement samples became depleted in DCPD, suggesting a selective dissolution of DCPD, possibly due to low pH conditions. The cement resorption at this stage was high. After 8 weeks, the resorption rate slowed down. Simultaneously, a change of the color and density of the cement center was observed. These changes were due to the conversion of DCPD into a poorly crystalline apatite. Precipitation started after 6-8 weeks and progressed rapidly. At 9 weeks, the colored central zone reached its maximal size. The fraction of beta-TCP in the cement was constant at all time. Therefore, this study demonstrates that the resorption rate of DCPD cement is more pronounced as long as DCPD is not transformed in vivo.

  19. In-situ hardening hydroxyapatite-based scaffold for bone repair.

    PubMed

    Zhang, Yu; Xu, Hockin H K; Takagi, Shozo; Chow, Laurence C

    2006-05-01

    Musculoskeletal conditions are becoming a major health concern because of an aging population and sports- and traffic-related injuries. While sintered hydroxyapatite implants require machining, calcium phosphate cement (CPC) bone repair material is moldable, self-hardens in situ, and has excellent osteoconductivity. In the present work, new approaches for developing strong and macroporous scaffolds of CPC were tested. Relationships were determined between scaffold porosity and strength, elastic modulus and fracture toughness. A biocompatible and biodegradable polymer (chitosan) and a water-soluble porogen (mannitol) were incorporated into CPC: Chitosan to make the material stronger, fast-setting and anti-washout; and mannitol to create macropores. Flexural strength, elastic modulus, and fracture toughness were measured as functions of mannitol mass fraction in CPC from 0% to 75%. After mannitol dissolution in a physiological solution, macropores were formed in CPC in the shapes of the original entrapped mannitol crystals, with diameters of 50 microm to 200 microm for cell infiltration and bone ingrowth. The resulting porosity in CPC ranged from 34.4% to 83.3% volume fraction. At 70.2% porosity, the hydroxyapatite scaffold possessed flexural strength (mean +/- sd; n = 6) of (2.5 +/- 0.2) MPa and elastic modulus of (0.71 +/- 0.10) GPa. These values were within the range for sintered porous hydroxyapatite and cancellous bone. Predictive equations were established by regression power-law fitting to the measured data (R(2) > 0.98) that described the relationships between scaffold porosity and strength, elastic modulus and fracture toughness. In conclusion, a new graft composition was developed that could be delivered during surgery in the form of a paste to harden in situ in the bone site to form macroporous hydroxyapatite. Compared to conventional CPC without macropores, the increased macroporosity of the new apatite scaffold may help facilitate implant fixation and

  20. Portland cement-blast furnace slag blends in oilwell cementing applications

    SciTech Connect

    Mueller, D.T.; DiLullo, G.; Hibbeler, J.

    1995-12-31

    Recent investigations of blast furnace slag cementing technologies. have been expanded to include Portland cement/blast furnace slag blends. Mixtures of Portland cement and blast furnace slag, while having a long history of use in the construction industry, have not been used extensively in oilwell cementing applications. Test results indicate that blending blast furnace slag with Portland cement produces a high quality well cementing material. Presented are the design guidelines and laboratory test data relative to mixtures of blast furnace slag and Portland cements. Case histories delineating the use of blast furnace slag - Portland cement blends infield applications are also included.

  1. Analytical considerations of beam hardening in medical accelerator photon spectra.

    PubMed

    Kleinschmidt, C

    1999-09-01

    Beam hardening is a well-known phenomenon for therapeutic accelerator beams passing through matter in narrow beam geometry. This study assesses quantitatively the magnitude of beam hardening of therapeutic beams in water. A formal concept of beam hardening is proposed which is based on the decrease of the mean attenuation coefficient with depth. On the basis of this concept calculations of beam hardening effects are easily performed by means of a commercial spreadsheet program. Published accelerator spectra and the tabulated values of attenuation coefficients serve as input for these calculations. It is shown that the mean attenuation coefficient starts at depth zero with an almost linear decrease and then slowly levels off to a limit value. A similar behavior is found for the beam hardening coefficient. A physically reasonable, semianalytical model is given which fits the data better than previously published functions. The energy dependence of the initial attenuation coefficient is evaluated and shown. It fits well to published experimental data. The initial beam hardening coefficient, however, shows no energy dependence. Its mean value (eta0) approximately 0.006 cm(-1)) is also in close agreement to the measured data.

  2. [Hardening and softening phenomena in beans: technological alternatives].

    PubMed

    Palma-Tirado, M L; Reyes-Moreno, C; Cárabez-Trejo, A; Montes-Rivera, R; Paredes-López, O

    1992-09-01

    The effect of accelerated hardening and soaking solutions on cooking time and microstructure of common bean (Phaseolus vulgaris) was studied. Two varieties (Canario and Mayocoba) were grown in the same location. Three hardening procedures were used: 1) End A. Soaking in acetate buffer, pH = 4.0 at 37 degrees C for 5 hs, 2) End B. Storage at 37 degrees C, 100% RH for 28 days and, 3) End C storage at 13-33 degrees C, 76% RH for 120 days. The salt solutions used for soaking were: Soln 1 (1% NaCl+0.75% NaHCO3) and Soln 2 (0.75% NaHCO3). Cooking times were determined using a Mattson bean cooker. In both varieties, the three hardening procedures decreased (38-50%) cotyledons water holding capacity and increased significantly (2-4 times) cooking times. During soaking in salt solutions hardened beans reached maximum water absorption in four hours. Soaking in salt solutions decreased drastically (2.6-10.6 times) cooking times. Fresh, hardened and softened seeds were examined by light microscopy, observing ultrastructural differences among them. The methods used in this research might well represent the central components of an industrial technological procedure for the utilization of hardened beans.

  3. Cement pulmonary embolism after vertebroplasty.

    PubMed

    Sifuentes Giraldo, Walter Alberto; Lamúa Riazuelo, José Ramón; Gallego Rivera, José Ignacio; Vázquez Díaz, Mónica

    2013-01-01

    In recent years, the use of vertebral cementing techniques for vertebroplasty and kyphoplasty has spread for the treatment of pain associated with osteoporotic vertebral compression fractures. This is also associated with the increased incidence of complications related with these procedures, the most frequent being originated by leakage of cementation material. Cement can escape into the vertebral venous system and reach the pulmonary circulation through the azygous system and cava vein, producing a cement embolism. This is a frequent complication, occurring in up to 26% of patients undergoing vertebroplasty but, since most patients have no clinical or hemodynamical repercussion, this event usually goes unnoticed. However, some serious, and even fatal cases, have been reported. We report the case of a 74-year-old male patient who underwent vertebroplasty for persistent pain associated with osteoporotic L3 vertebral fracture and who developed a cement leak into the cava vein and right pulmonary artery during the procedure. Although he developed a pulmonary cement embolism, the patient remained asymptomatic and did not present complications during follow-up.

  4. Synthesis and characterization of hydroxyapatite cement

    NASA Astrophysics Data System (ADS)

    Rabiee, S. M.; Moztarzadeh, F.; Solati-Hashjin, M.

    2010-04-01

    This study deals with synthesizing hydroxyapatite bone cement as a bone substitute for clinical applications. The powder part of the cement is using β-tricalcium phosphate, calcium carbonate, dicalcium phosphate and the liquid part contains NaH 2PO 4·2H 2O solution with different concentrations. The effects of liquid concentration on the setting times of the cement have been investigated. XRD analysis and FT-IR spectroscopy were used to study the phase composition of calcium phosphate cement. Morphology and chemical analysis of the synthesized cement was performed using a scanning electron microscope equipped with an energy dispersive X-ray analyser. In addition, the effect of soaking time of synthesized bone cement in simulated body fluid (SBF) on the final phase and strength has been studied. Soaking prepared cement in SBF solution for appropriate time resulted in transformation of the composition of the cement into hydroxyapatite and hence the strength of the cement has been increased.

  5. Cement evaluation; Past, present, and future

    SciTech Connect

    Pilkington, P.E. )

    1992-02-01

    Cement evaluation began with the calculation of cement tops. This calculation assumed gauge holes and no channeling of the cement through the mud. Calipers were not available at that time. In the mid-1930's, the use of temperature surveys to determine the top of cement (TOC) was documented in technical journals. Properly run temperature surveys can identify the TOC, but distribution of cement-e.g., vertical isolation through zones of interest-is difficult to ascertain. Radioactive tracer surveys were run in the late 1930's to determine cement tops. Carnotite was mixed in the lead slurry and cement tops were determined with a gamma ray log. Tracer surveys had the same limitations as temperature logs but were not time-sensitive. This paper reports on methods that have been and are currently being used for cement evaluation including temperature logs, radioactive traces, and cement bond tools.

  6. Real-time monitoring of the mechanism of poorly crystalline apatite cement conversion in the presence of chitosan, simulated body fluid and human blood.

    PubMed

    Rau, Julietta V; Generosi, Amanda; Komlev, Vladimir S; Fosca, Marco; Barinov, Sergey M; Albertini, Valerio Rossi

    2010-12-21

    In this study, the real-time monitoring of structural changes, occurring upon poorly crystalline apatite bone cement hardening in the presence of chitosan, simulated body fluid and human blood, was performed. Strong experimental evidence of octacalcium phosphate intermediate phase is provided. The energy dispersive X-ray diffraction was applied in situ to monitor the structural changes upon the transformation process, while the Fourier transform infrared spectroscopy and the scanning electron microscopy supplied information on the vibrational and morphological properties of the system. The cooperative action of chitosan and simulated body fluid induces the formation of a preferentially oriented hydroxyapatite phase, this process being similar to the oriented self-assembling process in collagen-apatite matrix in human plasma, occurring upon in vivo biomineralization. Conversely, the presence of blood does not induce any significant change in hardening kinetics and the final structure of the investigated cement.

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

    PubMed Central

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

    2015-01-01

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills. PMID:28787963

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

    PubMed

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

    2015-02-13

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

  9. Strain sensitivity of carbon nanotube cement-based composites for structural health monitoring

    NASA Astrophysics Data System (ADS)

    D'Alessandro, Antonella; Ubertini, Filippo; Laflamme, Simon; Rallini, Marco; Materazzi, Annibale L.; Kenny, Josè M.

    2016-04-01

    Cement-based smart sensors appear particularly suitable for monitoring applications, due to their self-sensing abilities, their ease of use, and their numerous possible field applications. The addition of conductive carbon nanofillers into a cementitious matrix provides the material with piezoresistive characteristics and enhanced sensitivity to mechanical alterations. The strain-sensing ability is achieved by correlating the variation of external loads or deformations with the variation of specific electrical parameters, such as the electrical resistance. Among conductive nanofillers, carbon nanotubes (CNTs) have shown promise for the fabrication of self-monitoring composites. However, some issues related to the filler dispersion and the mix design of cementitious nanoadded materials need to be further investigated. For instance, a small difference in the added quantity of a specific nanofiller in a cement-matrix composite can substantially change the quality of the dispersion and the strain sensitivity of the resulting material. The present research focuses on the strain sensitivity of concrete, mortar and cement paste sensors fabricated with different amounts of carbon nanotube inclusions. The aim of the work is to investigate the quality of dispersion of the CNTs in the aqueous solutions, the physical properties of the fresh mixtures, the electromechanical properties of the hardened materials, and the sensing properties of the obtained transducers. Results show that cement-based sensors with CNT inclusions, if properly implemented, can be favorably applied to structural health monitoring.

  10. Zinc coated sheet steel for press hardening

    NASA Astrophysics Data System (ADS)

    Ghanbari, Zahra N.

    Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time

  11. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    NASA Astrophysics Data System (ADS)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  12. Short-term contamination of luting cements by water and saliva.

    PubMed

    Mojon, P; Kaltio, R; Feduik, D; Hawbolt, E B; MacEntee, M I

    1996-03-01

    The aim of this study was to determine the effect of water, artificial saliva and natural saliva on the hardening process of three dental luting cements. Cement samples, 1 mm thick and 5 mm in diameter, were subjected to various storage conditions in an oven maintained at 37 degrees C. Some samples were aged in 100% humidity or water for up to 1 wk. The other samples were covered with water, artificial saliva or natural saliva at various times after mixing. The Knoop hardness values of the cement surfaces were measured. Differences between groups were evaluated with an ANOVA followed by a Tukey multiple comparison at the 5% level of significance. The hardness ratio of the contaminated samples was calculated using the 30 min mean KHN of the samples aged in 100% humidity as the divisor. The glass ionomer samples were significantly harder (48.3 +/- 3.8) than the zinc phosphate (38.9 +/- 7.5) or composite cements (35.4 +/- 10.2) after 1 wk in 100% humidity storage condition. When immersed in water, the hardness of both the glass ionomer and the zinc phosphate decreased to almost half that of the specimens stored in 100% humidity (26.2 +/- 2.7 and 16.9 +/- 2.5, respectively). Contamination decreased the hardness of zinc phosphate and glass ionomer (hardness ratio, water contamination at 5 min: 0.39 +/- 0.10 and 0.52 +/- 0.12, respectively) but had very little effect on the composite. Overall, water had a greater softening effect than artificial or natural saliva on the cements. In light of these results, glass ionomer cement should be protected from water and saliva for the first 15 min after mixing.

  13. Rate of CO2 Attack on Hydrated Class H Well Cement under Geologic Sequestration Conditions

    SciTech Connect

    Kutchko, Barbara G.; Strazisar, Brian R.; Lowry, Gregory V.; Dzombak, David A.; Thaulow, Niels

    2008-08-01

    Experiments were conducted to study the degradation of hardened cement paste due to exposure to CO2 and brine under geologic sequestration conditions (T = 50 degrees C and 30.3 MPa). The goal was to determine the rate of reaction of hydrated cement exposed to supercritical CO2 and to CO2-saturated brine to assess the potential impact of degradation in existing wells on CO2 storage integrity. Two different forms of chemical alteration were observed. The supercritical CO2 alteration of cement was similar in process to cement in contact with atmospheric CO2 (ordinary carbonation), while alteration of cement exposed to CO2-saturated brine was typical of acid attack on cement. Extrapolation of the hydrated cement alteration rate measured for I year indicates a penetration depth range of 1.00 +/- 0.07 mm for the CO2-saturated brine and 1.68 +/- 0.24 mm for the supercritical CO2 after 30 years. These penetration depths are consistent with observations of field samples from an enhanced oil recovery site after 30 years of exposure to CO2-saturated brine under similar temperature and pressure conditions. These results suggest that significant degradation due to matrix diffusion of CO2 in intact Class H neat hydrated cement is unlikely on time scales of decades.

  14. High-Performance, Radiation-Hardened Electronics for Space Environments

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

    2007-01-01

    The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog

  15. Dielectric measurement method for real-time monitoring of initial hardening of backfill materials used for underground construction

    NASA Astrophysics Data System (ADS)

    Karlovšek, Jurij; Schwing, Moritz; Chen, Zhen; Wagner, Norman; Williams, David J.; Scheuermann, Alexander

    2016-04-01

    The broadband dielectric measurement method based on the vector network analysis technique, in combination with an open-ended coaxial probe, was applied to the determination of the dielectric relaxation behaviour of one- and two-component backfilling grout materials in the frequency range from 40 MHz to 2 GHz. The cement hydration process and the gelling of commercial grouts was monitored in real-time to investigate the application of non-destructive testing methods in the tunnelling industry. It was found that the time-dependent dielectric relaxation behaviour can accurately reveal the different stages of the hydration process and delineate the start of gel hardening. These measurement results demonstrate the practicability of the real-time dielectric measurement method to determine the broadband dielectric parameters of conventional backfill materials used in underground construction to determine construction integrity using non-destructive testing methods.

  16. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.”...

  17. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.” ...

  18. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.” ...

  19. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.” ...

  20. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.” ...

  1. Fractional factorial design to investigate the influence of heavy metals and anions on acid neutralization behavior of cement-based products.

    PubMed

    Polettini, A; Pomi, R; Sirini, P

    2002-04-01

    A major concern of cement-based solidification/stabilization of hazardous wastes is the interaction of waste contaminants on cement properties. Literature contains many examples of studies on the interference of individual contaminants on cement properties. Conversely, little information is available on how the interactions between contaminants affectthe properties of cement/waste systems. This paper provides a discussion on the interference mechanisms exerted by seven contaminants, five heavy metals and two anions, on cement hydration. The seven contaminants were selected on the basis of the typical composition of municipal solid waste incineration (MSWI) fly ash. Spiking experiments using pure compounds were performed according to a 2IV(7-3) fractional factorial design to simulate addition of MSWI fly ash to ordinary Portland cement. The acid neutralization behavior of the laboratory cement-contaminant mixtures was studied to detect the presence of solid phases responsible for the buffering capacity of the solid matrix. The results from the experimental work showed that Zn, Cl-, and SO4(2-) were the major factors influencing, occasionally in combination with other contaminants, strength and acid neutralization capacity of the cementitious products. The release of Cd, Cr, Cu, and Pb in the eluates as a function of pH also suggested possible chemical immobilization mechanisms of such metals within the hardened matrix.

  2. Characterization and utilization of cement kiln dusts (CKDs) as partial replacements of Portland cement

    NASA Astrophysics Data System (ADS)

    Khanna, Om Shervan

    mineralogical phases within CKDs. It was found that CKDs can contain significant amounts of amorphous material (>30%) and clinker compounds (>20%) and small amounts of slag and/or flyash (<5%) and calcium langbeinite (<5%). The dissolution of ionic species and composition of the liquid phase play an important role in PC hydration. The dissolved ion contributions from CKDs were compared to PC using dilute stirred suspensions at 10 minutes and it was found that the ion contributions from CKDs are qualitatively the same as the ion contributions from PC, with the exception of chloride ions. The second objective was to utilize the material characterization analysis to determine the relationships among the composition properties of CKD-PC blends and their effects on fresh and hardened properties. The study found that CKDs from preheater/precalciner kilns have different effects on workability and heat evolution than CKDs from wet and long-dry kilns due to the presence of very reactive and high free lime contents (>20%). The blends with the two CKDs from preheater/precalciner plants had higher paste water demand, lower mortar flows, and higher heat generation during initial hydrolysis in comparison to all other CKD-PC blends and control cements. The hardened properties of CKD as a partial substitute of PC appear to be governed by the sulfate content of the CKD-PC blend (the form of the CKD sulfate is not significant). According to analysis of the ASTM expansion in limewater test results, the CKD-PC blend sulfate content should be less than ˜0.40% above the optimum sulfate content of the PC. It was also found that the sulfate contribution of CKD behaves similar to gypsum. Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a partial substitute of gypsum during the grinding process to control the early hydration of C3A. The wet and long-dry kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be used as partial replacement of

  3. Assessment of the microstructure and torsional fatigue performance of an induction hardened vanadium microalloyed medium-carbon steel

    NASA Astrophysics Data System (ADS)

    Rothleutner, Lee M.

    Vanadium microalloying of medium-carbon bar steels is a common practice in industry for a number of hot rolled as well as forged and controlled-cooled components. However, use of vanadium microalloyed steels has expanded into applications beyond their originally designed controlled-cooled processing scheme. Applications such as transmission shafts often require additional heat-treatments such as quench and tempering and/or induction hardening to meet packaging or performance requirements. As a result, there is uncertainty regarding the influence of vanadium on the properties of heat-treated components, specifically the effect of rapid heat-treating such as induction hardening. In the current study, the microstructural evolution and torsional fatigue behavior of induction hardened 1045 and 10V45 (0.08 wt pct V) steels were examined. Torsional fatigue specimens specifically designed for this research were machined from the as-received, hot rolled bars and induction hardened using both scanning (96 kHz/72 kW) and single-shot (31 kHz/128 kW) methods. Four conditions were evaluated, three scan hardened to 25, 32, and 44 pct nominal effective case depths and one single-shot hardened to 44 pct. Torsional fatigue tests were conducted at a stress ratio of 0.1 and shear stress amplitudes of 550, 600, and 650 MPa. Physical simulations using the thermal profiles from select induction hardened conditions were conducted in the GleebleRTM 3500 to augment microstructural analysis of torsional fatigue specimens. Thermal profiles were calculated by a collaborating private company using electro-thermal finite element analysis. Residual stresses were evaluated for all conditions using a strain gage hole drilling technique. The results showed that vanadium microalloying has an influence on the microstructure in the highest hardness region of the induction-hardened case as well as the total case region. Vanadium microalloyed conditions consistently exhibited a greater amount of non

  4. Process design of press hardening with gradient material property influence

    SciTech Connect

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-05-04

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  5. Marine diagenesis of Lower Ordovician carbonate sediments (Dumugol Formation), Korea: cementation in a calcite sea

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Chan; Lee, Yong Il

    1996-09-01

    The Lower Ordovician Dumugol Formation exhibits many features that indicate early lithification, such as calcite nodules, hardgrounds, mud-mounds and intraclasts. Detailed observations of these early-lithified features reveal that rapid marine cementation was instrumental in their formation. Marine lithification took place in a low-energy subtidal environmental that was influenced by intermittent storms. Marine cements include syntaxial overgrowth, bladed calcite, fibrous calcite and fine-crystalline equant calcite cements. Syntaxial overgrowths precipitated on echinoderm grains and contributed to rapid marine lithification of echinoderm-bearing sediments. Bladed, fibrous, and fine-crystalline equant calcite cements precipitated in locally suitable sites but their occurrence is limited, and thus played a minor role in marine lithification. Microcrystalline calcites also precipitated in lime mud-rich, fine-grained sediments and participated in rapid marine lithification of the Dumugol sediments. The absence of aragonite allochems and cement, and the predominance of calcite cement, suggest that the Dumugol sea was undersaturated with respect to aragonite, but supersaturated with respect to calcite, which is indicative of a 'calcite sea'.

  6. Molt-dependent transcriptomic analysis of cement proteins in the barnacle Amphibalanus amphitrite.

    PubMed

    Wang, Zheng; Leary, Dagmar H; Liu, Jinny; Settlage, Robert E; Fears, Kenan P; North, Stella H; Mostaghim, Anahita; Essock-Burns, Tara; Haynes, Sarah E; Wahl, Kathryn J; Spillmann, Christopher M

    2015-10-24

    A complete understanding of barnacle adhesion remains elusive as the process occurs within and beneath the confines of a rigid calcified shell. Barnacle cement is mainly proteinaceous and several individual proteins have been identified in the hardened cement at the barnacle-substrate interface. Little is known about the molt- and tissue-specific expression of cement protein genes but could offer valuable insight into the complex multi-step processes of barnacle growth and adhesion. The main body and sub-mantle tissue of the barnacle Amphibalanus amphitrite (basionym Balanus amphitrite) were collected in pre- and post-molt stages. RNA-seq technology was used to analyze the transcriptome for differential gene expression at these two stages and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) was used to analyze the protein content of barnacle secretions. We report on the transcriptomic analysis of barnacle cement gland tissue in pre- and post-molt growth stages and proteomic investigation of barnacle secretions. While no significant difference was found in the expression of cement proteins genes at pre- and post-molting stages, expression levels were highly elevated in the sub-mantle tissue (where the cement glands are located) compared to the main barnacle body. We report the discovery of a novel 114kD cement protein, which is identified in material secreted onto various surfaces by adult barnacles and with the encoding gene highly expressed in the sub-mantle tissue. Further differential gene expression analysis of the sub-mantle tissue samples reveals a limited number of genes highly expressed in pre-molt samples with a range of functions including cuticular development, biominerialization, and proteolytic activity. The expression of cement protein genes appears to remain constant through the molt cycle and is largely confined to the sub-mantle tissue. Our results reveal a novel and potentially prominent protein to the mix of cement

  7. Effect Of Laser Hardening On Microstructure And Wear Resistance In Medium. Carbon/Chromium Steels

    NASA Astrophysics Data System (ADS)

    Kusinski, Jan; Thomas, Gareth

    1986-11-01

    Metallographical (optical, TEM, SEM), spectroscopic, abrasive wear resistance and microhardness investiga-tions of Fe/Cr/Mn/C steels heat-treated by a continuous CO2 laser are described. Laser hardening resulted in wear resistance of 1.4 - 1.6 times better than that of conventionally hardened steels. Laser melting followed by rapid solidification allows formation of a solidified layer with high wear resistance only when the scanning velocity and mass of the samples were sufficient to realize high cooling rates. The variations in the wear resistance and microhardness with distance from the heated surface were similar. The grain refinement caused by rapid laser-heating and high stresses induced during cooling create essentially fine, highly dislocated lath and internally twinned martensites with some amount of stable, interlath retained austenite. This structure has in turn beneficial effects on wear resistance, and toughness. Laser-heat treatment for deep melting of the surface layers of the steels shows only a small improvement in wear resistance. Such heat-treatment results in delta ferrite retention (10Cr steel) and chromium segregation to cell-boundaries.

  8. Long-term cement corrosion in chloride-rich solutions relevant to radioactive waste disposal in rock salt - Leaching experiments and thermodynamic simulations

    NASA Astrophysics Data System (ADS)

    Bube, C.; Metz, V.; Bohnert, E.; Garbev, K.; Schild, D.; Kienzler, B.

    Low- and intermediate-level radioactive wastes are frequently solidified in a cement matrix. In a potential repository for nuclear wastes, the cementitious matrix is altered upon contact with solution and the resulting secondary phases may provide for significant retention of the radionuclides incorporated in the wastes. In order to assess the secondary phases formed upon corrosion in chloride-rich solutions, which are relevant for nuclear waste disposal in rock salt, leaching experiments were performed. Conventional laboratory batch experiments using powdered hardened cement paste in MgCl2-rich solutions were left to equilibrate for up to three years and full-scale cemented waste products were exposed to NaCl-rich and MgCl2-rich solutions for more than twenty years, respectively. Solid phase analyses revealed that corrosion of hardened cement in MgCl2-rich solutions advanced faster than in NaCl-rich solutions due to the extensive exchange of Mg from solution against Ca from the cementitious solid. Thermodynamic equilibrium simulations compared well to results at the final stages of the respective experiments indicating that close to equilibrium conditions were reached. At high cement product to brine ratios (>0.65 g mL-1), the solution composition in the laboratory-scale experiments was close to that of the full-scale experiments (cement to brine ratio of 2.5 g mL-1) in the MgCl2 systems. The present study demonstrates the applicability of thermodynamic methods used in this approach to adequately describe full-scale long-term experiments with cemented waste simulates.

  9. Pelvic Beam-Hardening Artifacts in Dual-Energy CT Image Reconstructions: Occurrence and Impact on Image Quality.

    PubMed

    Winklhofer, Sebastian; Lambert, Jack W; Sun, Yuxin; Wang, Zhen Jane; Sun, Derek S; Yeh, Benjamin M

    2017-01-01

    The purpose of this study was to describe the frequency and appearance of beam-hardening artifacts on rapid-kilovoltage-switching dual-energy CT (DECT) image reconstructions of the pelvis. Monochromatic (70, 52, and 120 keV) and material decomposition CT images (iodine-water and water-iodine) from consecutive pelvic rapid-kilovoltage-switching DECT scans were retrospectively evaluated. We recorded the presence, type (high versus low attenuation), and severity of beam-hardening artifacts (Likert scale from 0, barely seen, to 4, severe), clarity of anatomic delineation (Likert scale from 0, unimpaired, to 4, severely impaired) and SD of CT numbers, iodine and water concentrations, and gray-scale values for artifact-affected regions and corresponding unaffected reference tissue. A pelvic phantom was scanned and evaluated in a similar manner. Wilcoxon signed rank and paired t tests were used to compare results between the image reconstructions. Beam-hardening artifacts were seen in all image reconstructions in all 41 patients (22 men, 19 women; mean age, 57 years; range 22-86 years) who met the inclusion criteria. The median artifact severity score was worse for water-iodine and iodine-water images (score of 3 for each) than for 70-keV (score 1), 52-keV (score 2), and 120-keV (score 1) images (all p < 0.001). The anatomic delineation was worse (p < 0.001) for water-iodine and iodine-water images than for monochromatic images. Higher CT number SD values, material concentrations, and gray-scale values were found for areas affected by artifacts than for reference tissues in all datasets (all p < 0.001). Similar results were seen in the phantom study. Beam-hardening artifacts are prevalent in pelvic rapid-kilovoltage-switching DECT and more severe in material decomposition than monochromatic image reconstructions.

  10. Degradable borate glass polyalkenoate cements.

    PubMed

    Shen, L; Coughlan, A; Towler, M; Hall, M

    2014-04-01

    Glass polyalkenoate cements (GPCs) containing aluminum-free borate glasses having the general composition Ag2O-Na2O-CaO-SrO-ZnO-TiO2-B2O3 were evaluated in this work. An initial screening study of sixteen compositions was used to identify regions of glass formation and cement compositions with promising rheological properties. The results of the screening study were used to develop four model borate glass compositions for further study. A second round of rheological experiments was used to identify a preferred GPC formulation for each model glass composition. The model borate glasses containing higher levels of TiO2 (7.5 mol %) tended to have longer working times and shorter setting times. Dissolution behavior of the four model GPC formulations was evaluated by measuring ion release profiles as a function of time. All four GPC formulations showed evidence of incongruent dissolution behavior when considering the relative release profiles of sodium and boron, although the exact dissolution profile of the glass was presumably obscured by the polymeric cement matrix. Compression testing was undertaken to evaluate cement strength over time during immersion in water. The cements containing the borate glass with 7.5 mol % TiO2 had the highest initial compressive strength, ranging between 20 and 30 MPa. No beneficial aging effect was observed-instead, the strength of all four model GPC formulations was found to degrade with time.

  11. Biodeterioration of the Cement Composites

    NASA Astrophysics Data System (ADS)

    Luptáková, Alena; Eštoková, Adriana; Mačingová, Eva; Kovalčíková, Martina; Jenčárová, Jana

    2016-10-01

    The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

  12. Micro Mechanics and Microstructures of Major Subsurface Hydraulic Barriers: Shale Caprock vs Wellbore Cement

    NASA Astrophysics Data System (ADS)

    Radonjic, M.; Du, H.

    2015-12-01

    Shale caprocks and wellbore cements are two of the most common subsurface impermeable barriers in the oil and gas industry. More than 60% of effective seals for geologic hydrocarbon bearing formations as natural hydraulic barriers constitute of shale rocks. Wellbore cements provide zonal isolation as an engineered hydraulic barrier to ensure controlled fluid flow from the reservoir to the production facilities. Shale caprocks were deposited and formed by squeezing excess formation water and mineralogical transformations at different temperatures and pressures. In a similar process, wellbore cements are subjected to compression during expandable tubular operations, which lead to a rapid pore water propagation and secondary mineral precipitation within the cement. The focus of this research was to investigate the effect of wellbore cement compression on its microstructure and mechanical properties, as well as a preliminary comparison of shale caprocks and hydrated cement. The purpose of comparative evaluation of engineered vs natural hydraulic barrier materials is to further improve wellbore cement durability when in contact with geofluids. The micro-indentation was utilized to evaluate the change in cement mechanical properties caused by compression. Indentation experiments showed an overall increase in hardness and Young's modulus of compressed cement. Furthermore, SEM imaging and Electron Probe Microanalysis showed mineralogical alterations and decrease in porosity. These can be correlated with the cement rehydration caused by microstructure changes as a result of compression. The mechanical properties were also quantitatively compared to shale caprock samples in order to investigate the similarities of hydraulic barrier features that could help to improve the subsurface application of cement in zonal isolation. The comparison results showed that the poro-mechanical characteristics of wellbore cement appear to be improved when inherent pore sizes are shifted to

  13. Embryos of a moss can be hardened to desiccation tolerance: effects of rate of drying on the timeline of recovery and dehardening in Aloina ambigua (Pottiaceae)

    PubMed Central

    Brinda, John C.; Stark, Lloyd R.; Clark, Theresa A.; Greenwood, Joshua L.

    2016-01-01

    Background and Aims Embryonic sporophytes of the moss Aloina ambigua are inducibly desiccation tolerant (DT). Hardening to DT describes a condition of temporary tolerance to a rapid-drying event conferred by a previous slow-drying event. This paper aimed to determine whether sporophytic embryos of a moss can be hardened to DT, to assess how the rate of desiccation influences the post-rehydration dynamics of recovery, hardening and dehardening, and to determine the minimum rate of drying for embryos and shoots. Methods Embryos were exposed to a range of drying rates using wetted filter paper in enclosed Petri dishes, monitoring relative humidity (RH) inside the dish and equilibrating tissues with 50 % RH. Rehydrated embryos and shoots were subjected to a rapid-drying event at intervals, allowing assessments of recovery, hardening and dehardening times. Key Results The minimum rate of slow drying for embryonic survival was ∼3·5 h and for shoots ∼9 h. Hardening to DT was dependent upon the prior rate of drying. When the rate of drying was extended to 22 h, embryonic hardening was strong (>50 % survival) with survival directly proportional to the post-rehydration interval preceding rapid drying. The recovery time (repair/reassembly) was so short as to be undetectable in embryos and shoots desiccated gradually; however, embryos dried in <3·5 h exhibited a lag time in development of ∼4 d, consistent with recovery. Dehardening resulted in embryos incapable of surviving a rapid-drying event. Conclusions The ability of moss embryos to harden to DT and the influence of prior rate of drying on the dynamics of hardening are shown for the first time. The minimum rate of drying is introduced as a new metric for assessing ecological DT, defined as the minimum duration at sub-turgor during a drying event in which upon rehydration the plant organ of interest survives relatively undamaged from the desiccating event. PMID:26354931

  14. Embryos of a moss can be hardened to desiccation tolerance: effects of rate of drying on the timeline of recovery and dehardening in Aloina ambigua (Pottiaceae).

    PubMed

    Brinda, John C; Stark, Lloyd R; Clark, Theresa A; Greenwood, Joshua L

    2016-01-01

    Embryonic sporophytes of the moss Aloina ambigua are inducibly desiccation tolerant (DT). Hardening to DT describes a condition of temporary tolerance to a rapid-drying event conferred by a previous slow-drying event. This paper aimed to determine whether sporophytic embryos of a moss can be hardened to DT, to assess how the rate of desiccation influences the post-rehydration dynamics of recovery, hardening and dehardening, and to determine the minimum rate of drying for embryos and shoots. Embryos were exposed to a range of drying rates using wetted filter paper in enclosed Petri dishes, monitoring relative humidity (RH) inside the dish and equilibrating tissues with 50% RH. Rehydrated embryos and shoots were subjected to a rapid-drying event at intervals, allowing assessments of recovery, hardening and dehardening times. The minimum rate of slow drying for embryonic survival was ∼3·5 h and for shoots ∼9 h. Hardening to DT was dependent upon the prior rate of drying. When the rate of drying was extended to 22 h, embryonic hardening was strong (>50% survival) with survival directly proportional to the post-rehydration interval preceding rapid drying. The recovery time (repair/reassembly) was so short as to be undetectable in embryos and shoots desiccated gradually; however, embryos dried in <3·5 h exhibited a lag time in development of ∼4 d, consistent with recovery. Dehardening resulted in embryos incapable of surviving a rapid-drying event. The ability of moss embryos to harden to DT and the influence of prior rate of drying on the dynamics of hardening are shown for the first time. The minimum rate of drying is introduced as a new metric for assessing ecological DT, defined as the minimum duration at sub-turgor during a drying event in which upon rehydration the plant organ of interest survives relatively undamaged from the desiccating event. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All

  15. 76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-08

    ... Portland Cement and Cement Clinker From Japan Determination On the basis of the record \\1\\ developed in the... antidumping duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... the Commission are contained in USITC Publication 4281 (December 2011), entitled Gray Portland...

  16. Freezing resistance of high iron phoasphoaluminate cement

    NASA Astrophysics Data System (ADS)

    Zhang, S. X.; Lu, L. C.; Wang, S. D.; Zhao, P. Q.; Gong, C. C.

    2017-03-01

    The influence of freeze-thaw cycle on the mechanical properties of high iron phoasphoaluminate cement was investigated in the present study. The visual examination was conducted to evaluate the surface damage. The deterioration considering the weight loss, modulus loss of relative dynamic elastic and strength loss of mortar were also investigated. The morphology of hydration products were analysed by SEM. Compared with ordinary Portland cement and sulphoaluminate cement, the frost resistance of high iron phosphoraluminate cement is better. Hydration products of high iron phoasphoaluminate cement contain sheet crystals, and a lot of gel form a dense three-dimensional network structure, which results in a lower porosity. Different from ordinary Portland cement, the hydration product of high iron phoasphoaluminate cement does not contain Ca(OH)2, and low alkalinity reduces its osmotic pressure. The lower porosity and osmotic pressure are the two main reasons which causes in the higher frost resistance of high iron phoasphoaluminate cement.

  17. Solute hardening and softening effects in B2 nickel aluminides

    SciTech Connect

    Pike, L.M.; Liu, C.T.; Anderson, I.M.; Chang, Y.A.

    1998-11-01

    The effect of substitutional solute additions including Fe, Mn, and Pd on the hardness of B2-ordered NiAl alloys was investigated. The solid solution hardening behavior of intermetallics is more complex than that of typical metallic solid solutions because of complications arising from the site preference of the solute as well as the effects of the solute on the concentrations of other point defects, e.g., vacancies and anti-site defects. For this reason, care was taken to experimentally establish solute site preferences and point defect concentrations in the NiAl alloys before analyzing the hardness data. By taking these factors into account it was possible to rationalize the observed unusual hardening effects. Three distinct categories of solid solution hardening behavior were encountered. The first was hardening by the solute addition itself. This was observed in the case of Pd additions to Al-poor NiAl. However, when fe or Mn is added to Al-poor NiAl a second category is observed; these elements are seen to soften the material. The third category of behavior is observed when Fe is added to NiAl with a constant Al concentration of 50 at. %. In this case it is vacancies, rather than solute atoms, which harden the material.

  18. Computer modelling of age hardening for cast aluminium alloys

    NASA Astrophysics Data System (ADS)

    Wu, Linda; Ferguson, W. George

    2009-08-01

    Age hardening, or precipitation hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. Although various age hardening models have been developed for aluminium alloys, from the large volume of literature reviewed, it appears that the bulk of the research has been concentrated on wrought aluminium alloys, only a few of the established precipitation models have been applied to the casting aluminium alloys. In the present work, there are two modelling methods that have been developed and applied to the casting aluminium alloys A356 and A357. One is based on the Shercliff-Ashby methodology to produce a process model, by which we mean a mathematical relationship between process variables (alloy composition, ageing temperature and time) and material properties (yield strength or hardness) through microstructure evolution (precipitate radius, volume fraction). The other method is based on the Kampmann and Wagner Numerical (KWN) model which deals with concomitant nucleation, growth and coarsening and is thus capable of predicting the full evolution of the particle size distribution and then a strength model is used to evaluate the resulting change in hardness or yield strength at room temperature by taking into account contributions from lattice resistance, solid solution hardening and precipitation hardening.

  19. Reduction of work hardening rate in low-carbon steels

    NASA Astrophysics Data System (ADS)

    Yalamanchili, Bhaskar Rao

    Low carbon grades of steel rods are used to produce finished products such as fine wire, coat hangers, staples, and roofing nails. These products are subject to ductility failures during production due to excessively high work hardening rates during wire drawing. The high work hardening rates are attributed to the presence of residuals, free nitrogen, or combinations thereof. This research concludes that the most cost-effective way to reduce the work hardening rate during wire drawing is to combine boron with nitrogen to form boron nitride, and thus reducing its work hardening contribution. The results of this study also conclude the following: (1) Boron/Nitrogen ratio is the more significant factor than rod tensile strength, which affects work hardening rate. Higher ratio is better in the 0.79 to 1.19 range. (2) Maintaining this narrow B/N range requires precise process control. (3) Process conditions such as dissolved oxygen (<25 ppm), carbon (≤0.05%) and ladle refining temperature (<2930°F) are necessary for optimizing boron recovery. (4) An average of 89% boron recovery is obtained with the above controlled process conditions. (5) Use of Boron has no adverse effects on the several metallurgical properties tested except with minor difficulty with scale for descaling. North Star Steel Texas (North Star) benefited from this research by being able to provide a competitive edge in both quality and cost of its low carbon boron grades thus making North Star a preferred supplier of wire rod for these products.

  20. Vertebroplasty using bisphosphonate-loaded calcium phosphate cement in a standardized vertebral body bone defect in an osteoporotic sheep model.

    PubMed

    Verron, Elise; Pissonnier, Marie-Line; Lesoeur, Julie; Schnitzler, Verena; Fellah, Borhane Hakim; Pascal-Moussellard, Hugues; Pilet, Paul; Gauthier, Olivier; Bouler, Jean-Michel

    2014-11-01

    In the context of bone regeneration in an osteoporotic environment, the present study describes the development of an approach based on the use of calcium phosphate (CaP) bone substitutes that can promote new bone formation and locally deliver in situ bisphosphonate (BP) directly at the implantation site. The formulation of a CaP material has been optimized by designing an injectable apatitic cement that (i) hardens in situ despite the presence of BP and (ii) provides immediate mechanical properties adapted to clinical applications in an osteoporotic environment. We developed a large animal model for simulating lumbar vertebroplasty through a two-level lateral corpectomy on L3 and L4 vertebrae presenting a standardized osteopenic bone defect that was filled with cements. Both 2-D and 3-D analysis of microarchitectural parameters demonstrated that implantation of BP-loaded cement in such vertebral defects positively influenced the microarchitecture of the adjacent trabecular bone. This biological effect was dependent on the distance from the implant, emphasizing the in situ effect of the BP and its release from the cement. As a drug device combination, this BP-containing apatitic cement shows good promise as a local approach for the prevention of osteoporotic vertebral fractures through percutaneous vertebroplasty procedures.