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Sample records for calcium aluminate cement

  1. Conduction calorimetric studies of ternary binders based on Portland cement, calcium aluminate cement and calcium sulphate

    OpenAIRE

    Torrens Martín, David; Fernández Carrasco, Lucía; Blanco Varela, M.Teresa

    2013-01-01

    Different binders of Portland cement, calcium aluminate cement and calcium sulphate (PC/CAC/CS) have been investigated to determinate the in¿uence the CAC and CS amount in the reactions mechanism. Several mixtures were studied, ratios of 100, 85/15 and 75/25 of PC/CAC with 0, 3 and 5 % of CS. Conduction calorimetric technique was used to follow the hydration during 100 h. The XRD and FTIR techniques were used as support in the analysis of the hydration products. The results have shown tha...

  2. Calcium aluminate cement hydration in a high alkalinity environment

    Directory of Open Access Journals (Sweden)

    Palomo, Á.

    2009-03-01

    Full Text Available The present paper forms part of a broader research project that aims primarily to devise new cementitious products via the alkali activation of silico-aluminous materials. This work addresses the possibility of using small percentages of calcium aluminate cement (CAC as a source of reactive aluminium. For this reason, a preliminary review was needed of the behaviour of CACs in highly alkaline media (2, 8 and 12M NaOH solutions. Two, 28- and 180-day mechanical strength was determined and the reaction products were characterized with XRD and FTIR. The water-hydrated CAC was used as the control.The results obtained showed that CAC hardening took place much more slowly in highly alkaline media than in water. Nonetheless, the 28-day compressive strength obtained, ≥80MPa. As main reaction products, to ambient temperature and from the two days of cured, cubic aluminate C3AH6, and AH3 polymorphs are formed, instead of the usual hexagonal aluminatos (CAH10 and C2AH8 that are formed in the normal hydrate with water.El presente trabajo forma parte de una amplia investigación cuyo objetivo principal es el de elaborar nuevos materiales con propiedades cementantes mediante la activación alcalina de materiales de naturaleza silito-aluminosa. En estos estudios se contempla la posibilidad de utilizar pequeños porcentajes de cemento de aluminato de calcio (CAC como fuente de aluminio reactivo. Por ello inicialmente se ha estudiado el comportamiento de los CAC en medios fuertemente alcalinos (disoluciones de NaOH 2M, 8M y 12M. Se determinaron las resistencias mecánicas a 2, 28 y 180 días y se realizó una caracterización de los productos de reacción formados por DRX, FTIR. Como sistema de referencia se consideró la hidratación del CAC con agua.Los resultados obtenidos muestran que en medios fuertemente alcalinos se retrasan los procesos de rápido endurecimiento de CAC con agua. No obstante a 28 días se obtienen valores de resistencia a compresión

  3. Development of LiCl-containing calcium aluminate cement for bone repair and remodeling applications.

    Science.gov (United States)

    Acuña-Gutiérrez, I O; Escobedo-Bocardo, J C; Almanza-Robles, J M; Cortés-Hernández, D A; Saldívar-Ramírez, M M G; Reséndiz-Hernández, P J; Zugasti-Cruz, A

    2017-01-01

    The effect of LiCl additions on the in vitro bioactivity, hemolysis, cytotoxicity, compressive strength and setting time of calcium aluminate cements was studied. Calcium aluminate clinker (AC) was obtained via solid state reaction from reagent grade chemicals of CaCO3 and Al2O3. Calcium aluminate cements (CAC) were prepared by mixing the clinker with water or aqueous LiCl solutions (0.01, 0.0125 or 0.015M (M)) using a w/c ratio of 0.4. After 21days of immersion in a simulated body fluid (SBF) at physiological conditions of temperature and pH, a Ca-P rich layer, identified as hydroxyapatite (HA), was formed on the cement without LiCl and on the cement prepared with 0.01M of LiCl solution. This indicates the high bioactivity of these cements. The cements setting times were significantly reduced using LiCl. The measured hemolysis percentages, all of them lower than 5%, indicated that the cements were not hemolytic. The compressive strength of the cements was not negatively affected by the LiCl additions. The obtained cement when a solution of LiCl 0.010M was added, presented high compressive strength, appropriated bioactivity, no cytotoxicity and low setting time, making this material a potentially bone cement.

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

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Stefanko, D.

    2011-03-10

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

  5. Poly(carboxylate ether)-based superplasticizer achieves workability retention in calcium aluminate cement

    Science.gov (United States)

    Akhlaghi, Omid; Menceloglu, Yusuf Ziya; Akbulut, Ozge

    2017-01-01

    Calcium aluminate cement (CAC) suffers from loss of workability in less than an hour (~15 minutes) after first touch of water. Current superplasticizers that are utilized to modify the viscosity of cement admixtures are designed to target ordinary Portland cement (OPC). The high affinity between these superplasticizers and cement particles were found to be detrimental in CAC systems. Utilization of a monomer that, instead, facilitates gradual adsorption of a superplasticizer provides workability retention. For the first time in literature, we report a superplasticizer that caters to the properties of CAC such as high rate of surface development and surface charge. While neat CAC was almost unworkable after 1 hour, with the addition of only 0.4% of the optimized superplasticizer, 90% fluidity retention was achieved.

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

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    SUGAMA,T.; BROTHERS, L.E.

    2005-01-01

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

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

    Science.gov (United States)

    Navarro-Blasco, I; Duran, A; Sirera, R; Fernández, J M; Alvarez, J I

    2013-09-15

    The ability of calcium aluminate cement (CAC) to encapsulate toxic metals (Pb, Zn and Cu) was assessed under two curing conditions. Changes in the consistency and in the setting time were found upon the addition of the nitrates of the target metals. Both Pb and Cu caused a delay in CAC hydration, while Zn accelerated the stiffening of the mortar. Compressive strengths of the metal-doped mortars, when initially cured at 60 °C/100% RH, were comparable with that of the free-metal mortar. Three different pore size distribution patterns were identified and related to the compounds identified by XRD and SEM. Sorbent capacities of CAC for the toxic metals were excellent: a total uptake was achieved for up to 3 wt.% loading of the three metals. In this way, CAC mortars were perfectly able to encapsulate the toxic metals, allowing the use of CAC for waste management as proved by the leaching tests.

  8. Effect of Calcium Aluminate Cement Variety on the Hydration of Portland Cement in Blended System

    Institute of Scientific and Technical Information of China (English)

    XU Linglin; WANG Peiming; Geert DE SCHUTTER; WU Guangming

    2014-01-01

    Two kinds of CACs with different monocalcium aluminate (CA) contents were used in the PC/CAC (PAC) mixtures. Effects of CA and CACs on the properties of PAC were analyzed by setting times and the compressive strength tests, and also by means of calorimetry, XRD, DTA-TG and ESEM. The experimental results show that the compressive strength of the PAC mortars decreases with increasing content of CAC while it declines sharply with a higher content of CA in CAC. Compared with neat PC paste, the content of calcium hydroxide in hydrates of PAC paste decreases significantly, and the hydration time of PC is prominently prolonged. Additionally, the higher the content of CA in CAC, the more obviously the hydration of PC is delayed, confirming that the CA phase in CAC plays an important role in the delay of PC hydration.

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

    Energy Technology Data Exchange (ETDEWEB)

    Falzone, Gabriel, E-mail: gabefalzone@gmail.com [Laboratory for the Chemistry of Construction Materials LC" 2, Department of Civil and Environmental Engineering, University of California, Los Angeles, CA (United States); Department of Materials Science and Engineering, University of California, Los Angeles, CA (United States); Balonis, Magdalena, E-mail: mbalonis@ucla.edu [Department of Materials Science and Engineering, University of California, Los Angeles, CA (United States); Institute for Technology Advancement, University of California, Los Angeles, CA (United States); Sant, Gaurav, E-mail: gsant@ucla.edu [Laboratory for the Chemistry of Construction Materials LC" 2, Department of Civil and Environmental Engineering, University of California, Los Angeles, CA (United States); California Nanosystems Institute (CNSI), University of California, Los Angeles, CA (United States)

    2015-06-15

    Phase conversion phenomena are often observed in calcium aluminate cements (CACs), when the water-rich hydrates (e.g., CAH{sub 10}, C{sub 2}AH{sub 8}) formed at early ages, at temperatures ≤ 30 °C, expel water in time to form more compact, less water-rich structures (C{sub 3}AH{sub 6}). The phase conversions follow a path regulated by the thermodynamic stabilities (solubilities) of phases. Based on this premise, it is proposed that conversion phenomena in CACs can be bypassed by provoking the precipitation of phases more preferred than those typically encountered along the conversion pathway. Therefore, X-AFm formation (where in this case, X = NO{sub 3}{sup −}) triggered by the sequential addition of calcium nitrate (Ca(NO{sub 3}){sub 2} = CN) additives is identified as a new means of bypassing conversion. A multi-method approach comprising X-ray diffraction (XRD), thermal analytics, and evaluations of the compressive strength is applied to correlate phase balances and properties of CAC systems cured at 25 °C and 45 °C. The results highlight the absence of the C{sub 3}AH{sub 6} phase across all systems and the curing conditions considered, with enhanced strengths being noted, when sufficient quantities of CN are added. The experimental outcomes are supported by insights gained from thermodynamic calculations which highlight thermodynamic selectivity as a means of regulating and controlling the evolutions of solid phase balances using inorganic salts in CACs, and more generally in cementing material systems.

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

    Energy Technology Data Exchange (ETDEWEB)

    Navarro-Blasco, I.; Duran, A.; Sirera, R.; Fernández, J.M.; Alvarez, J.I., E-mail: jalvarez@unav.es

    2013-09-15

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

  11. PROCESSING OF ZIRCONIA AND CALCIUM ALUMINATE CEMENT MIXTURES BY SPARK PLASMA SINTERING

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    Y. L. Bruni

    2015-12-01

    Full Text Available Spark Plasma sintering (SPS was applied for the densification of Calcia stabilized ZrO2 based composites obtained from mixtures of pure zirconia (m-ZrO2 and calcium aluminate cement (HAC. Two commercial powders of pure zirconia were employed as reactants. One of these powders had a coarse mean particle size (d50 = 8 μm and the other was a submicrometer sized power (d50 = 0.44 μm. Several compositions containing different proportions of HAC (5 to 30 mol. % CaO in ZrO2 were sintered by SPS at temperatures between 1200 and 1400ºC under a pressure of 100 MPa during 10 min. The effect of processing conditions on phase composition, densification, microstructure and Vickers hardness of the obtained composites was examined. SPS significantly enhanced the densification in both type of composites (relative density > 93 % as compared to those previously produced by conventional sintering. Composites with low CaO content consisted of mixtures of c-ZrO2, (Ca0.15Zr0.85O1.85, unreacted m-ZrO2 and calcium dialuminate (CaAl4O7 or CA2. The highest hardness was determined for composites sintered at 1400ºC being related to the maximum relative density (~ 99 %. High densification of composites with 30 mol. % CaO composed by similar proportions of CaAl4O7 and c-ZrO2 were obtained even at 1200ºC but led to a slightly lower hardness. In general, the use of the finer m-ZrO2 powder contributed to increase both the c-ZrO2 content and densification of composite sintered at a relatively lower temperature. For these composites, best hardness (Hv near to 10 GPa resulted when the microstructure consisted of a fine grained ZrO2 matrix surrounding the dispersed CaAl4O7 grains instead of large interconnection between grains of both phases existed.

  12. Calcium aluminate in alumina

    Science.gov (United States)

    Altay, Arzu

    The properties of ceramic materials are determined not only by the composition and structure of the phases present, but also by the distribution of impurities, intergranular films and second phases. The phase distribution and microstructure both depend on the fabrication techniques, the raw materials used, the phase-equilibrium relations, grain growth and sintering processes. In this dissertation research, various approaches have been employed to understand fundamental phenomena such as grain growth, impurity segregation, second-phase formation and crystallization. The materials system chosen was alumina intentionally doped with calcium. Atomic-scale structural analyses of grain boundaries in alumina were carried on the processed samples. It was found that above certain calcium concentrations, CA6 precipitated as a second phase at all sintering temperatures. The results also showed that abnormal grain growth can occur after precipitation and it is not only related to the calcium level, but it is also temperature dependent. In order to understand the formation mechanism of CA6 precipitates in calcium doped alumina samples, several studies have been carried out using either bulk materials or thin films The crystallization of CA2 and CA6 powders has been studied. Chemical processing techniques were used to synthesize the powders. It was observed that CA2 powders crystallized directly, however CA6 powders crystallized through gamma-Al 2O3 solid solution. The results of energy-loss near-edge spectrometry confirmed that gamma-Al2O3 can dissolve calcium. Calcium aluminate/alumina reaction couples have also been investigated. All reaction couples were heat treated following deposition. It was found that gamma-Al2O3 was formed at the interface as a result of the interfacial reaction between the film and the substrate. gamma-Al 2O3 at the interface was stable at much higher temperatures compared to the bulk gamma-Al2O3 formed prior to the CA6 crystallization. In order to

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

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    Fernanda de Carvalho Panzeri Pires-de-Souza

    2013-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Bizzozero, Julien, E-mail: julien.bizzozero@gmail.com; Scrivener, Karen L.

    2015-10-15

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

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

    Directory of Open Access Journals (Sweden)

    George, C. M.

    1992-12-01

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

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

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

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    Velazco, G.

    2014-09-01

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

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

    Indian Academy of Sciences (India)

    K Geetha; A M Umarji; T R N Kutty

    2000-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

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

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    Tatiana Pyatina

    2016-05-01

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

  20. Propriedades e bioatividade de um cimento endodôntico à base de aluminato de cálcio Properties and bioactivity of endodontic calcium aluminate cement

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    I. R. Oliveira

    2011-09-01

    Full Text Available Desde sua introdução na endodontia como um material retro-obturador e selador de defeitos da raiz dental, o agregado de trióxido mineral (MTA tem sido considerado como um material endodôntico revolucionário. Apesar disso, este material apresenta algumas propriedades limitantes, necessitando alterações em sua composição bem como desenvolvimento de novos materiais. Assim, o objetivo desse trabalho foi mostrar a influência de aditivos no desenvolvimento de um cimento endodôntico à base de cimento de aluminato de cálcio (ECAC. Além disso, foram avaliadas as propriedades do ECAC em comparação com o MTA, quando em contato com solução de fluido corporal simulado (SBF. Testes de manipulação e medidas de resistência à compressão, porosidade aparente, tempo de endurecimento, pH e condutividade iônica, foram realizados para os materiais MTA puro e ECAC contendo aditivos. Considerando as propriedades apresentadas pelo ECAC, este material alternativo pode ser indicado para múltiplas aplicações em endodontia.The mineral trioxide aggregate (MTA, a material primarily developed as a root-end filling has been extensively investigated as an innovative product for endodontic applications. However, changes in its formulation/composition involving its mineral aggregates and the development of alternatives of materials have been proposed in an attempt to overcome its negative physical-chemical characteristics. In this work, the influence of additives addition on the development of a novel endodontic cement based on calcium aluminate, has been evaluated. In addition, the properties of endodontic calcium aluminate cement (ECAC were compared with the gold standard mineral-trioxide-aggregate in contact with simulated body fluid (SBF. Manipulation tests and measurements of compressive strength, apparent porosity, setting time, pH and ionic conductivity were carried out on plain MTA and calcium aluminate cement with and without various additives

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-02-15

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

  4. SODIUM CITRATE INFLUENCE ON FORMATION OF CEMENT STONE IN THE ALUMINOUS BINDER

    Directory of Open Access Journals (Sweden)

    S. N. Leonovich

    2016-01-01

    Full Text Available The paper deals with the effect of sodium citrate on the formation of a cement stone in the aluminous binder. Formation of cement stone framework in cement hydraulic binder is accompanied with complicated physical and chemical processes of interphase interactions and dispersion, these processes are predicated on qualitative and quantitative composition of the cement mortar, continuous changes in its properties from preparation stage till curing. Addition of sodium citrate to tempering water enhances hydration of both Portland cement and calcium aluminate cement. Process pertaining to an increase of cement hydration rate is considered as a consequence of destruction in surface formations and exclusion of damping effect in respect of hydration rate and hydrolysis of products resulted from interaction of clinker material with tempering. It has been established that sodium citrate makes it possible to control processes of hydration, hydrolysis, binding and curing for cement mass. High degree of hydration of aluminous cement in the presence of sodium citrate provides fast binding and curing of binder, low porosity and rather high compression breaking strength of cement stone for all curing stages. An increase in concentration of sodium citrate in cement mixture up to 10 % of the cement mass exerts an influence not only on the process of cement mortar liquefaction, reduction of time for cement mass setting and hardening but also increases compression strength of cement stone. An analysis of the structure for cleavage surface of cement stone gives ground to declare that the addition of sodium citrate provides cement stone sealing and reduces its water absorption.

  5. Hydration of Portland cement with additions of calcium sulfoaluminates

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-01-15

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

  6. Effect of Microwave Processing on Aluminate Cement Clinkering

    Institute of Scientific and Technical Information of China (English)

    DONG Jianmiao; LONG Shizong

    2005-01-01

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

  7. Optical properties of hollow calcium aluminate glass waveguides.

    Science.gov (United States)

    Abel, T; Harrington, J A; Foy, P R

    1994-06-20

    Calcium aluminate glass has a refractive index less than 1 at 10.6 µ, and therefore it is a good candidate for a hollow fiber for the transmission of CO(2) laser energy. We have drawn hollow calcium aluminate glass fibers with inner diameters ranging from 380 to 500 µ. The loss for our 500-µm inner-diameter hollow glass fibers measured at 10.6 µm is 8.6 dB/m.

  8. Behavior of calcium silicate hydrate in aluminate solution

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

  10. 氯化镁对铝酸钙水泥结合浇注料性能的影响%Influence of magnesium chloride on properties of calcium aluminate cement bonded castables

    Institute of Scientific and Technical Information of China (English)

    王青峰; 王亚娟; 李坤鹏; 宋秀娟; 张传银; 叶国田

    2014-01-01

    为了改善铝酸钙水泥结合浇注料的高温体积稳定性,以 w (Al2 O3)≥99.5%的板状刚玉为骨料, w(Al2O3)≥99.7%的活性Al2O3微粉和板状刚玉细粉(≤0.044 mm)为基质,以铝酸钙水泥Secar 71为结合剂,添加适量氯化镁制备铝酸钙水泥结合浇注料,分别在1100℃3 h和1450℃3 h进行热处理,测定浇注料试样的常温物理性能,并分析基质试样的物相组成和显微结构。结果表明:氯化镁的加入会导致浇注料经高温处理后的体积密度下降,显气孔率升高,并降低浇注料高温处理后的力学性能;但是,含氯化镁的浇注料经高温处理后的线膨胀较小。通过显微结构分析发现,在含氯化镁的浇注料基质中有发育良好的板片状CA6,氯化镁分解所产生的孔隙可以为高温下CA6的形成提供部分可膨胀的空间,从而降低CA6形成所带来的体积膨胀,有利于改善浇注料经高温处理后的体积稳定性。%To improve the volume stability at high tempeartures,calcium aluminate cement bonded castables were prepared using tabular alumina (Al2O3≥99.5 mass%)as aggregate,reactive alumina micropowder (Al2O3≥99.7 mass%),and tabular alumina fines (≤0.044 mm)as matrix,calcium aluminate cement (Se-car 71)as binder,and magnesium chloride as additive.The castables were fired at 1 100 ℃ and 1 450 ℃for 3 h,respectively.Then physical properties of the castables were tested,and phase composition and mi-crostructure of castable matrix specimens were analyzed.The results show that the castable with magnesi-um chloride has the decreased bulk density,the increased apparent porosity and the decreased mechani-cal properties and linear expansion after firing at high temperatures.It is found in the microstructure that the well developed tabular CA6 crystals disperse in the matrix of the castable with magnesium chloride.There-fore,these voids generated from the decomposition of

  11. Cinética de hidratação de ligantes à base de alumina hidratável ou aluminato de cálcio Kinetics of hydration of binders based on hydratable alumina or calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    I. R. Oliveira

    2007-03-01

    Full Text Available O estado de dispersão da matriz de um concreto refratário apresenta uma grande influência no comportamento reológico desse material, determinando as técnicas utilizadas para a sua aplicação. Tais métodos normalmente exigem a preparação de concretos com elevada fluidez, que possam ser bombeados com facilidade e sejam capazes de preencher moldes de formato complexo sem a necessidade de aplicação de vibração. Entretanto, embora tais requisitos favoreçam uma boa trabalhabilidade do concreto, tendem a aumentar o tempo requerido para efetuar a desmoldagem do corpo conformado. Uma vez que o desenvolvimento da resistência mecânica do concreto está intimamente relacionado ao processo de hidratação do ligante hidráulico, este necessita ser controlado quando se busca a redução do tempo para a desmoldagem. Tal controle depende de um profundo conhecimento das variáveis que determinam a cinética das reações. Neste contexto, o objetivo deste trabalho foi o de avaliar a influência do tipo de ligante hidráulico, da temperatura e da presença de finos (matriz ou de aditivos inorgânicos adicionados ao concreto sobre o processo de hidratação por meio de medidas de temperatura e ensaios reológicos oscilatórios em função do tempo.The dispersion of refractory castables matrix presents a great influence on their rheological behavior, which defines the most appropriate methods for placing these materials. The growing demand for automatically transported refractory castables has promoted the use of pumpable castables, usually specified as self flow compositions. Nevertheless, castables with higher fluidity present longer workability, leading to extended demoulding times. Because the strength development is intimately linked to the hydration process of calcium aluminate cement or hydratable alumina, it needs to be controlled in order to reach the minimum time for demoulding, contributing to reducing overall costs. The control of cement

  12. Calcium Orthophosphate Cements and Concretes

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2009-03-01

    Full Text Available 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.

  13. Thermoluminescence dosimetry of rare earth doped calcium aluminate phosphors

    Indian Academy of Sciences (India)

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

    2006-04-01

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

  14. Development of Pack Cementation Aluminizing Process on Inner Surface of 316L Stainless Steel Tube

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>In order to form the FeAl coatings on the inner surface of the 316L stainless steel tube,the pack cementation aluminizing process is introduced in this paper. The outside diameter,wall thickness and

  15. 合成温度对含镁铝尖晶石的铝酸盐水泥晶粒尺寸及凝结性能的影响%Influence of synthesis temperature on crystal size and setting properties of calcium aluminate cement with magnesium aluminate spinel

    Institute of Scientific and Technical Information of China (English)

    陈平安; 李享成; 朱伯铨

    2016-01-01

    Dolomite,industrial alumina and caustic magnesite were used as starting materials to study the in-fluence of temperature on the crystal size and setting properties of aluminate cement with magnesium alu-minate spinel.The starting materials were mixed homogeneously according to the mass ratio of 71 9 20 of Al2 O3 MgO CaO,heated to 1 100,1 200,1 300,1 400,1 500 ℃,respectively,in a high temperature furnace and soaked for 3 h.After that,the cement bulk was crushed to below 50 μm.The MA bearing aluminate ce-ment was characterized by XRD and SEM,and the setting time was tested.The results show that the phases of CA,MA and CA2 can be formed at 900,1 100 and 1 200 ℃,respectively.The crystal size of spinel could be controlled from nanometer to micrometer as the synthesis temperature rises from 1 100 to 1 500 ℃,and CA as well as CA2 grows from 2 -3 μm to 5 μm,and then sinter together forming skeleton,CA and CA2 crystals are surrounded by MA crystals.Meanwhile,the setting time delays with the synthesis temperature rising due to the growth of CA or CA2 crystals,decreasing the hydration activity;and the growth of MA crystals,hindering the reactions between water and CA or CA2 ,thus obviously hindering the hydration of the cement.%为了研究合成温度对含镁铝尖晶石的铝酸盐水泥晶粒尺寸和凝结性能的影响,以白云石、工业氧化铝和轻烧镁砂为原料,按 Al2 O3、MgO、CaO 质量比为71920配料后混合均匀,并在高温炉中分别经1100、1200、1300、1400和1500℃保温3 h 煅烧并破粉碎至50μm 以下,制备了含 MA 的铝酸盐水泥,对水泥试样进行了XRD 和 SEM分析,并检测了凝结时间。研究结果表明:含 MA 的铝酸盐水泥中的 CA、MA 和 CA2相分别在900、1100和1200℃生成。当合成温度从1100℃升高至1500℃时,水泥中 MA 的晶粒尺寸从纳米到微米级可控,CA 或 CA2的粒径从2~3μm 逐渐长大至5μm 以上,并烧结在一起形成骨架,MA

  16. Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xuerun, E-mail: xuerunli@163.com; Zhang, Yu; Shen, Xiaodong, E-mail: xdshen@njut.edu.cn; Wang, Qianqian; Pan, Zhigang

    2014-01-15

    The formation kinetics of tricalcium aluminate (C{sub 3}A) and calcium sulfate yielding calcium sulfoaluminate (C{sub 4}A{sub 3}$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C{sub 3}A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca{sub 3}Al{sub 2}O{sub 6} + CaSO{sub 4} → Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 6CaO was the primary reaction < 1350 °C with and activation energy of 231 ± 42 kJ/mol; while the decomposition reaction 2Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 10CaO → 6Ca{sub 3}Al{sub 2}O{sub 6} + 2SO{sub 2} ↑ + O{sub 2} ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C{sub 4}A{sub 3}$ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C{sub 4}A{sub 3}$ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca{sup 2+} and SO{sub 4}{sup 2−} were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C{sub 3}A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion.

  17. Physical Properties of Acidic Calcium Phosphate Cements

    OpenAIRE

    2014-01-01

    The gold standard for bone replacement today, autologous bone, suffers from several disadvantages, such as the increased risk of infection due to the need for two surgeries. Degradable synthetic materials with properties similar to bone, such as calcium phosphate cements, are a promising alternative. Calcium phosphate cements are suited for a limited amount of applications and improving their physical properties could extend their use into areas previously not considered possible. For example...

  18. Effect of resorbable calcium aluminate ceramics on regulation of calcium and phosphorus in rats.

    Science.gov (United States)

    Carvalho, B A; Bajpai, P K; Graves, G A

    1976-06-01

    Ions released from resorbable ceramics could be toxic to the animal. Experiments were designed to study the effect of implanting three different weights of porous resorbable calcium aluminate ceramics (0.172, 0.332, and 0.504 g) in rats for a total duration of 300 days. Gross and microscopic examination of heart, liver, kidneys, trachea with thyroid, and muscle adjacent to the implant did not show any pathological changes. Calcium and inorganic phosphate content of bone, serum and urine were not affected by the implants. Urine hydroxyproline excretion did not change in the animals implanted with ceramics. Animals implanted with 0.332 g of ceramics had a significantly higher serum alkaline phosphatase activity than the control animals. Resorption of calcium and depositon of inorganic phosphates in the implanted ceramics suggested that ions were being exchanged with the body fluids. Implantation of 0.172 to 0.332 g porous resorbable calcium aluminate ceramic was not toxic to the animal.

  19. Frozen delivery of brushite calcium phosphate cements.

    Science.gov (United States)

    Grover, Liam M; Hofmann, Michael P; Gbureck, Uwe; Kumarasami, Balamurgan; Barralet, Jake E

    2008-11-01

    Calcium phosphate cements typically harden following the combination of a calcium phosphate powder component with an aqueous solution to form a matrix consisting of hydroxyapatite or brushite. The mixing process can be very important to the mechanical properties exhibited by cement materials and consequently when used clinically, since they are usually hand-mixed their mechanical properties are prone to operator-induced variability. It is possible to reduce this variability by pre-mixing the cement, e.g. by replacing the aqueous liquid component with non-reactive glycerol. Here, for the first time, we report the formation of three different pre-mixed brushite cement formulations formed by freezing the cement pastes following combination of the powder and liquid components. When frozen and stored at -80 degrees C or less, significant degradation in compression strength did not occur for the duration of the study (28 days). Interestingly, in the case of the brushite cement formed from the combination of beta-tricalcium phosphate with 2 M orthophosphoric acid solution, freezing the cement paste had the effect of increasing mean compressive strength fivefold (from 4 to 20 MPa). The increase in compression strength was accompanied by a reduction in the setting rate of the cement. As no differences in porosity or degree of reaction were observed, strength improvement was attributed to a modification of crystal morphology and a reduction in damage caused to the cement matrix during manipulation.

  20. Thermal desorption study of catalytic systems. Communication 20. Adsorption of water vapors on the calcium aluminate components of catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Nissenbaum, V.D.; Danyushevskii, V.Y.; Golosman, E.Z.; Rubinstein, A.M.; Yakerson, V.I.

    1985-05-01

    Ca aluminates are used as a component of catalysts of gas-phase processes, some of which take place with the participation of water. Nickel calcium aluminate catalysts are thus used for hydrogenation of CO and CO/sub 2/ to CH/sub 4/ and water; zinc calcium aluminate catalysts are used for sulfur purification of process gases, where water is liberated during sulfiding of ZnO; and copper zinc calcium aluminate catalysts are used in low-temperature conversion of CO with water vapor. It is also known that Ca aluminates undergo various transformations in aqueous media with the formation of Ca hydroaluminates. This paper discusses the adsorption of water from the gas phase on calcium aluminate systems, which was investigated by the thermal desorption method. Samples of varying phase composition, different CaO/Al/sub 2/O/sub 3/ ratios, and specific surface areas were also studied and are reported on here.

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

    OpenAIRE

    2010-01-01

    The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper...

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

    Directory of Open Access Journals (Sweden)

    Bikić Farzet H.

    2010-01-01

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

  3. Magnesium and Calcium Aluminate Liquids: In Situ High-Temperature 27Al NMR Spectroscopy.

    Science.gov (United States)

    Poe, B T; McMillan, P F; Coté, B; Massiot, D; Coutures, J P

    1993-02-05

    The use of high-temperature nuclear magnetic resonance (NMR) spectroscopy provides a means of investigating the structure of refractory aluminate liquids at temperatures up to 2500 K. Time-averaged structural information indicates that the average aluminum coordination for magnesium aluminate (MgAl(2)O(4)) liquid is slightly greater than for calcium aluminate (CaAl(2)O(4)) liquid and that in both liquids it is close to four. Ion dynamics simulations for these liquids suggest the presence of four-, five-, and six-coordinated aluminate species, in agreement with NMR experiments on fast-quenched glasses. These species undergo rapid chemical exchange in the high-temperature liquids, which is evidenced by a single Lorentzian NMR line.

  4. 含镁铝尖晶石的铝酸盐水泥的制备及其抗侵蚀性%PREPARATION AND CORROSION RESISTANCE OF ALUMINOUS CEMENT CONTAINING MAGNESIUM ALUMINATE SPINEL

    Institute of Scientific and Technical Information of China (English)

    肖国庆; 高云琴; 段锋

    2008-01-01

    以白云石和工业Al2O3为原料,采用烧结法制备了含镁铝尖晶石的铝酸盐新型水泥,利用X射线衍射检测了合成产物的物相组成,采用扫描电子显微镜观察了新型铝酸盐水泥中各物相的形貌和能谱分析了成分分布,测量了这种铝酸盐水泥的凝结时间、耐火度以及其所结合的高铝矾土制成的耐火浇注料的早期强度.选择静态坩埚法进行抗渣性实验,对比了新型铝酸盐水泥和纯铝酸钙水泥结合刚玉浇注料的抗渣性差异.结果表明:这种水泥的物相组成为镁铝尖晶石、一铝酸钙和二铝酸钙;物相分布较为均匀.与纯铝酸钙水泥比较,凝结时间正常,新型铝酸盐水泥结合刚玉浇注料与纯铝酸钙水泥结合刚玉浇注料的抗弯强度相当,耐火度较高和抗侵蚀性较好,其原因在于水泥中存在镁铝尖晶石相,而镁铝尖晶石有较高的熔点和抗熔渣侵蚀能力.%A new type of aluminous cement containing magnesium aluminate (MA) spinel was prepared from mixtures of dolomite and alumina by a sintering process. The microstructures and phase constituents of the synthesized product were inspected by X-ray diffraction and scanning electron microscope with energy dispersive X-ray spectrometry. The setting time, refractoriness and bonding strength of the new type of aluminous cement were measured by means of standard methods. The corrosion resistance property was also investigated by static crucible method. The experimental results show that the new type of aluminous cement consists of MA spinel, calcium monoaluminate and calcium dialuminate phases. Compared with aluminous cement, the prepared cement with more uniform phase distribution has a reasonable setting time, and the cement containing MA spinel bonded castables with bauxite as an aggregate have considerable bonding strength, higher refractoriness and better corrosion resistance. This is due to the introduction of MA spinel, which has a high

  5. [Study on the influence of mineralizer on the structures and spectral properties of calcium aluminates].

    Science.gov (United States)

    Zheng, Huai-Li; Liu, Jun-Yu; Li, Lin-Tao; Li, Fang

    2009-11-01

    The present paper investigated the effect of mineralizer on the structure and properties of calcium aluminates formation. Calcium aluminates powder was synthesized under high temperature calcination by mixing bauxite, limestone and a certain amount of mineralizer. The product structure, compositional information and spectral properties were carefully characterized by XRD, IR and DTA-TG, and the mineralization mechanism of mineralizer was studied during the process of calcium aluminates preparation. The results showed that calcium aluminates powder could be obtained under lower temperature calcination after adding mineralizer to the raw materials. The main products of the reaction were CaAl10 O18 and CaAl2 Si2 O8 without mineralizer, however, the main products of the reaction were CaAl3 BO7 and Ca3 Al10 O18 with mineralizer, in which Al2 O3s could be extracted easily, while CaAl2 Si2 O8 was reduced greatly in which Al2 O3 could not be extracted easily. At the same time, it is easy for calcspar to decompose after adding mineralizer. It is favorable to Al-Si bond break and Al stripping from bauxite. These facts could improve the extraction rate of Al2 O3 from raw materials. Also, in the case of adding mineralizer to the raw mixes, the crystal structure and composition are changed, which is beneficial to reducing calcination temperature.

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

    Directory of Open Access Journals (Sweden)

    R Salomão

    2010-06-01

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

  7. High-resolution /sup 27/Al NMR study of calcium aluminate catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Yakerson, V.I.; Nissenbaum, V.D.; Golosman, E.Z.; Mastikhin, V.M.

    1987-06-01

    The high-resolution /sup 27/Al NMR spectra of calcium aluminates, calcium hydroaluminates, and calcium alumina supports and catalysts have been studied. The structures of the anhydrous calcium aluminates (CaAl/sub 2/O/sub 3/, CaAl/sub 4/O/sub 7/, 3CaO x Al/sub 2/O/sub 3/, 12CaO x 7Al/sub 2/O/sub 3/, talyum) consist of aluminum-oxygen tetrahedra and contain various types of aluminum atoms, the nonequivalence of which increases in going from strongly basic to weakly basic aluminates. In the NMR spectrum the signal of octahedrally coordinated aluminum is due to disordered aluminum-oxygen structures. During the forming of the calcium-alumina catalysts and supports the process (AlO/sub 4/) ..-->.. (AlO/sub 6/) takes place during hydration, and (AlO/sub 6/) ..-->.. (AlO/sub 4/) during thermolysis; the nonequivalence of the tetrahedrally coordinated aluminum atoms decreases, while the (AlO/sub 4/):(AlO/sub 6/) ratio decreases as the degree of hydration increases.

  8. Effect of Ga2O3 on Structure and Properties of Calcium Aluminate Glasses

    Institute of Scientific and Technical Information of China (English)

    WANG Yanhang; ZU Chengkui; HE Kun; ZHAO Huifeng; LIU Yonghua

    2016-01-01

    The effect of Ga2O3 on the structure and properties of calcium aluminate glasses fabricated by vacuum melting process was investigated by Raman spectrum, differential scanning calorimeter (DSC), and infrared spectrum methods. The results show that calcium aluminate glass network only consists of [AlO4] tetrahedral units. With the gradual addition of Ga2O3, the quantity of [GaO4] tetrahedral units increases. Substitution of Ga2O3 for Al2O3 results in a decrease inTg,Tx, andTp, and an increase in the thermal stable indexΔT. Similarly, the absorption band around 3.0 μm obviously reduces and the transparency in 4.0-6.0 μm rapidly increases with increasing Ga2O3 content. However, the chemical stability of calcium aluminate glasses decreases if Ga2O3 is introduced due to the increasing of [GaO4] units in the glass network.

  9. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

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

    Science.gov (United States)

    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.

  11. Investigation of calcium aluminates by IR spectroscopy in diffusely scattered light

    Energy Technology Data Exchange (ETDEWEB)

    Medin, A.S.; Borovkov, V.Yu.; Nissenbaum, V.D.; Yakerson, V.I.; Kazanskii, V.B.

    1989-01-01

    The hydroxyl covering and the adsorption sites for CO and H/sub 2/O on aluminum-calcium catalysts and supports with developed surfaces have been studied by IR spectroscopy in diffusely scattered light. The presence of several types of surface OH groups, viz., terminal groups bonded to calcium ions with different types of coordination, bridging OH groups, and groups appearing in (CaOH)/sup +/ groupings, which perform the role of compensating cations in the zeolite-like structure of calcium aluminates, has been established. The shifts of the bands of the OH groups upon the adsorption of C/sub 6/H/sub 6/ and cyclo-C/sub 6/H/sub 12/ point out their weakly acidic or basic character. When calcium aluminates are dehydroxylated, aprotic sites appear on their surfaces, and the rehydration of such surfaces is accompanied by the formation of OH groups and the weakening of the Al-O-M bonds (M = Al, Ca) with the appearance of additional sites for the strong adsorption of water.

  12. Durability of Alite-calcium Barium Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    LU Lingchao; LU Zeye; LIU Shiquan; WANG Shoude; CHENG Xin

    2009-01-01

    The durability of the cement was mainly studied.Under 1.0 MPa of hydraulic pressure for 8 hours,water could penetrate completely through the sample made by portland cement,but could not penetrate through that by alite-barium sulphoaluminate cement.Under the condition of freezing and thawing cycle,the loss ratio of compressive strength of the cement was only about 17.3%at curing 28 d ages,but the loss of portland cement was as high as 29.5%.Alite-calcium bar-ium sulphoaluminate cement also has an excellent resistance to sulfate attack.The coefficients of resistance to sulfate attack of the cement exceeded 1.0.Meanwhile,the composition and microstructure of the hardened paste of alite-calcium barium sulphoaluminate cement were analyzed by XRD and SEM.

  13. Preparation and characterization of bioceramics produced from calcium phosphate cements

    Energy Technology Data Exchange (ETDEWEB)

    Andriotis, O.; Katsamenis, O.L. [Department of Materials Science, University of Patras, 26504, Patras (Greece); Mouzakis, D.E. [Technological Educational Institute of Larisa, Department of Mechanical Engineering, T.E.I of Larissa, 411 10, Larissa (Greece); Bouropoulos, N. [Foundation for Research and Technology, Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, FORTH/ICE-HT, P.O. Box 1414, 26504 Rio Patras (Greece)

    2010-03-15

    The present work reports a method for preparing calcium phosphate ceramics by calcination of calcium phosphate cements composed mainly of calcium deficient hydroxyapatite (CDHA). It was found that hardened cements calcinied at temperatures from to 600 to 1300 C were transformed to tricalcium phosphates. Moreover the compressive strength was determined and porosity was estimated as a function of the calcination temperature. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Calcium aluminate coated and uncoated free form fabricated CoCr implants: a comparative study in rabbit.

    Science.gov (United States)

    Palmquist, A; Jarmar, T; Hermansson, L; Emanuelsson, L; Taylor, A; Taylor, M; Engqvist, H; Thomsen, P

    2009-10-01

    The purpose of this study was to compare the integration in bone of uncoated free form fabricated cobalt chromium (CoCr) implants to the same implant with a calcium aluminate coating. The implants of cylindrical design with a pyramidal surface structure were press-fit into the limbs of New Zealand white rabbits. After 6 weeks, the rabbits were sacrificed, and samples were retrieved and embedded. Ground sections were subjected to histological analysis and histomorphometry. The section counter part was used for preparing an electron transparent transmission electron microscopy sample by focused ion beam milling. Calcium aluminate dip coating provided a significantly greater degree of bone contact than that of the native CoCr. The gibbsite hydrate formed in the hardening reaction of the calcium aluminate was found to be the exclusive crystalline phase material in direct contact with bone.

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

    Science.gov (United States)

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

    2013-10-22

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

  16. Calcium Hex aluminate reaction sintering by Spark Plasma Sintering; Sinterizacion reactiva de Hexaluminato de Calcio mediante Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, P. G. de la; Garcia-Moreno, O.; Torrecillas, R.; Menendez, J. L.

    2012-11-01

    Calcium hex aluminate (CaAl{sub 1}2O{sub 1}9) is the most alumina-rich intermediate compound of the CaO-Al{sub 2}O{sub 3} system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina with the consequent formation of intermediates compounds with lower alumina content with increasing temperature (CaAl{sub 2}O{sub 4}, CaAl4O{sub 7}). In this study we studied the variation of sintering parameters for obtaining dense and pure calcium hex aluminate by reaction sintering by Spark Plasma Sintering (SPS). A mixing of Al{sub 2}O{sub 3} and CaCO{sub 3} were used as reactive. Final densities close to the theoretical and phase transformation over 93% were achieved by this method. (Author) 22 refs.

  17. Pressure induced reactions amongst calcium aluminate hydrate phases

    KAUST Repository

    Moon, Ju-hyuk

    2011-06-01

    The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch-Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure-volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies. © 2011 Elsevier Ltd. All rights reserved.

  18. Simultaneous chromizing-aluminizing coating of low alloy steels by a halide-activated pack cementation process

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-11-01

    The simultaneous chromizing-aluminizing of low-alloy steels has achieved Kanthal-like surface compositions of 16--2lCr and 5--8 wt%Al by the use of cementation packs with a Cr-Al masteralloy and an NH{sub 4}Cl activator salt. An initial preferential deposition of Al into the alloy induces the phase transformation from austenite to ferrite at the 1150{degrees}C process temperature. The low solubility of carbon in ferrite results in the rejection of solute C into the core of the austenitic substrate, thereby preventing the formation of an external Cr-carbide layer, which would otherwise block aluminizing and chromizing. The deposition and rapid diffusion of Cr and Al into the external bcc ferrite layer follows. Parabolic cyclic oxidation kinetics for alumina growth in air were observed over a wide range of relatively low temperatures (637--923{degrees}C).

  19. Simultaneous chromizing-aluminizing coating of low alloy steels by a halide-activated pack cementation process

    Energy Technology Data Exchange (ETDEWEB)

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

    1992-11-01

    The simultaneous chromizing-aluminizing of low-alloy steels has achieved Kanthal-like surface compositions of 16--2lCr and 5--8 wt%Al by the use of cementation packs with a Cr-Al masteralloy and an NH[sub 4]Cl activator salt. An initial preferential deposition of Al into the alloy induces the phase transformation from austenite to ferrite at the 1150[degrees]C process temperature. The low solubility of carbon in ferrite results in the rejection of solute C into the core of the austenitic substrate, thereby preventing the formation of an external Cr-carbide layer, which would otherwise block aluminizing and chromizing. The deposition and rapid diffusion of Cr and Al into the external bcc ferrite layer follows. Parabolic cyclic oxidation kinetics for alumina growth in air were observed over a wide range of relatively low temperatures (637--923[degrees]C).

  20. Calcium aluminates potential for endodontics and orthopedics applications; Aluminatos de calcio e seu potencial para aplicacao em endodontia e ortopedia

    Energy Technology Data Exchange (ETDEWEB)

    Santos, G.L. dos; Andrade, T.L.; Oliveira, I.R., E-mail: ivonero@univap.br [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil); Pandolfelli, V.C. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil)

    2011-07-01

    The mostly used material in the areas of endodontics (MTA, mineral trioxide aggregate) and bone reconstruction (PMMA, polymethyl methacrylate) present some limiting properties requiring thus changes in their compositions as well as the development of alternative materials. In this context, a novel biomaterial-based calcium aluminate cement (CAC) has been studied in order to keep the positive properties and clinical applications of MTA and PMMA, overcoming some their disadvantages. Recent studies involving the use of CAC are based on commercial products consisting of a mixture of phases. Improvements can be attained by searching the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance in applications in the areas of health. By the optimization of the CAC phases production, this article aims to present their characterization based on hydration temperature; working time and setting time; pH, ions solubilization and dissolution in contact with water and different solutions of simulated body fluid. The results indicated the CA phase as the most suitable for application in the areas of health. (author)

  1. Evaluation of cytotoxicity, antimicrobial activity and physicochemical properties of a calcium aluminate-based endodontic material

    Directory of Open Access Journals (Sweden)

    Emmanuel Joao Nogueira Leal SILVA

    2014-01-01

    Full Text Available A calcium aluminate-based endodontic material, EndoBinder, has been developed in order to reduce MTA negative characteristics, preserving its biological properties and clinical applications. Objectives: The aim of this study was to evaluate the cytotoxicity, antimicrobial activity, pH, solubility and water sorption of EndoBinder and to compare them with those of white MTA (WMTA. Material and Methods: Cytotoxicity was assessed through a multiparametric analysis employing 3T3 cells. Antimicrobial activity against Enterococcus faecalis (ATCC 29212, Staphylococcus aureus. (ATCC 25923 and Candida albicans (ATCC 10556 was determined by the agar diffusion method. pH was measured at periods of 3, 24, 72 and 168 hours. Solubility and water sorption evaluation were performed following ISO requirements. Data were statistically analyzed by ANOVA and Tukey`s test with a significance level of 5%. Results: EndoBinder and WMTA were non-cytotoxic in all tested periods and with the different cell viability parameters. There was no statistical differences between both materials (P>.05. All tested materials were inhibitory by direct contact against all microbial strains tested. EndoBinder and WMTA presented alkaline pH in all tested times with higher values of pH for WMTA (P.05. Conclusion: Under these experimental conditions, we concluded that the calcium aluminate-based endodontic material EndoBinder demonstrated suitable biological and physicochemical properties, so it can be suggested as a material of choice in root resorption, perforations and root-end filling.

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

    Directory of Open Access Journals (Sweden)

    Sagrera Moreno, José Luis

    1989-06-01

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

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

  3. Recovery of iron and calcium aluminate slag from high-ferrous bauxite by high-temperature reduction and smelting process

    Institute of Scientific and Technical Information of China (English)

    Ying-yi Zhang; Wei L; Yuan-hong Qi; Zong-shu Zou

    2016-01-01

    A high-temperature reduction and smelting process was used to recover iron and calcium aluminate slag from high-ferrous bauxite. The effects of w(CaO)/w(SiO2) ratio, anthracite ratio, and reduction temperature and time on the recovery and size of iron nuggets and on the Al2O3 grade of the calcium aluminate slag were investigated through thermodynamic calculations and experiments. The optimized process conditions were the bauxite/anthracite/slaked lime weight ratio of 100:16.17:59.37, reduction temperature of 1450°C and reduction time of 20 min. Under these conditions, high-quality iron nuggets and calcium aluminate slag were obtained. The largest size and the highest recov-ery rate of iron nuggets were 11.42 mm and 92.79wt%, respectively. The calcium aluminate slag mainly comprised Ca2SiO4 and Ca12Al14O33, with small amounts of FeAl2O4, CaAl2O4, and Ca2Al2SiO7.

  4. In vivo behavior of a novel injectable calcium phosphate cement compared with two other commercially available calcium phosphate cements.

    NARCIS (Netherlands)

    Hannink, G.; Wolke, J.G.C.; Schreurs, B.W.; Buma, P.

    2008-01-01

    The aim of this study was to investigate the physicochemical and biological properties of a newly developed calcium phosphate cement (CPC). The novel cement was compared with two other commercially available CPCs. After mixing the powder and liquid phase, the CPCs were injected as a paste into a rab

  5. 温度对合成含镁铝尖晶石铝酸盐水泥的影响%Effect of temperature on synthesis of magnesium aluminate spinel containing aluminate cement

    Institute of Scientific and Technical Information of China (English)

    宋雅楠; 朱伯铨; 李享成

    2014-01-01

    The magnesium aluminate spinel containing aluminate cement was prepared with starting mate-rials of industrial alumina,light burned magnesia and heavy weight calcium carbonate.The starting mate-rials were batched according to the Al2O3 MgO CaO mass ratio of 71 16 13,ball milled,and fired at 900,1 000,1 100,1 300 and 1 500 ℃ for 3 h,respectively.Phase compositions,microstructure and setting time of the prepared cement were investigated.The results indicate that:(1 )CA,MA and CA2 form at about 900,1 000 and 1 100 ℃,respectively;CA,CA2,and MA are detected in the specimen treated at 1 300 ℃ for 3 h,indicating a complete reaction of the starting materials;(2)SEM analysis indicates that in the cement fired at 1 300 or 1 500 ℃ for 3 h,CA and CA2 are tabular,MA is granular or octahedral,and MA well distributes around CA and CA2 particles;comparatively,CA,CA2,MA particles of the cement fired at 1 500 ℃ for 3 h develop better with larger crystal size;(3 )the initial setting times of the cement fired at 1 300 and 1 500 ℃ for 3 h are 37 min and 43 min,respectively,and the final setting times are 1 15 min and 163 min,respectively.%以工业氧化铝、轻烧氧化镁及重质碳酸钙为原料,按Al2O3、MgO、CaO质量比为711613配料,球磨混合后,分别在900、1000、1100、1300和1500℃保温3 h合成含镁铝尖晶石的铝酸盐水泥,然后分析了合成试样的物相组成、显微结构和凝结时间。结果表明:1)在900℃保温3 h后合成试样中已有CA生成,1000℃保温3 h后已有MA生成,1100℃保温3 h后已有CA2生成;1300℃保温3 h后,原料已完全反应,产物全部由CA、CA2、MA组成。2)在1300和1500℃保温3 h合成的水泥中,CA和CA2呈板状,MA呈粒状或八面体状, MA均匀分布在CA和CA2周围;在1500℃保温3 h合成的水泥中,CA、CA2、MA的晶粒比1300℃保温3 h合成的发育更完整,晶粒尺寸也更大。3)1300和1500℃保温3 h合成的水

  6. Porosity prediction of calcium phosphate cements based on chemical composition.

    Science.gov (United States)

    Öhman, Caroline; Unosson, Johanna; Carlsson, Elin; Ginebra, Maria Pau; Persson, Cecilia; Engqvist, Håkan

    2015-07-01

    The porosity of calcium phosphate cements has an impact on several important parameters, such as strength, resorbability and bioactivity. A model to predict the porosity for biomedical cements would hence be a useful tool. At the moment such a model only exists for Portland cements. The aim of this study was to develop and validate a first porosity prediction model for calcium phosphate cements. On the basis of chemical reaction, molar weight and density of components, a volume-based model was developed and validated using calcium phosphate cement as model material. 60 mol% β-tricalcium phosphate and 40 mol% monocalcium phosphate monohydrate were mixed with deionized water, at different liquid-to-powder ratios. Samples were set for 24 h at 37°C and 100% relative humidity. Thereafter, samples were dried either under vacuum at room temperature for 24 h or in air at 37 °C for 7 days. Porosity and phase composition were determined. It was found that the two drying protocols led to the formation of brushite and monetite, respectively. The model was found to predict well the experimental values and also data reported in the literature for apatite cements, as deduced from the small absolute average residual errors (brushite, monetite and apatite cements. The model gives a good estimate of the final porosity and has the potential to be used as a porosity prediction tool in the biomedical cement field.

  7. A study on new type aluminous cements containing magnesium aluminate spinel%新型含镁铝尖晶石的铝酸盐水泥的研究

    Institute of Scientific and Technical Information of China (English)

    肖国庆; 高志鹏; 荆桂花; 庞锐

    2005-01-01

    A new type of calcium aluminate cement containing MA spinel was produced by sintering the raw materials of dolomite and alumina mixture. The effects of raw materials and sintering temperature and additives on the properties of cements was were investigated. X-ray diffraction (XRD) results indicate that the final products consisted of CA, CA2and MA. The microstructure of product was analyzed by means of scanning electron microscope (SEM)and energy dispersive spectrometry (EDS). The experiments results showed that the cement had the satisfied cold bonding strength and sintering properties when the light-burned dolomite and alumina were employed and fired at 1600C. The new type cements has relatively uniform microstructure The early stage strength of the refractory castables bodies was greatly improved by adding 2wt. % of CaCl2 as a strength modifier.%以白云石和工业三氧化二铝为原料,采用反应烧结技术制得了含镁铝尖晶石的铝酸盐水泥,探讨了原料及烧结温度和添加剂对含镁铝尖晶石的铝酸盐水泥性能的影响,XRD结果表明产物的物相组成为MA,CA,CA2;采用扫描电镜(SEM)及能谱(EDS)对产物的显微结构进行了观察与分析.结果表明:以轻烧白云石和工业Al2O3为原料制得的水泥具有较高的结合强度;所制得的含镁铝尖晶石的铝酸盐水泥的显微结构较为均匀,外加剂CaCl2具有明显的早强效果.

  8. Pulp response to a novel adhesive calcium hydroxide based cement.

    Science.gov (United States)

    Watts, A; Paterson, R C; Cohen, B D; Combe, E C

    1994-09-01

    This study compares pulp responses to 3 formulations of calcium hydroxide, namely: a) An experimental adhesive calcium hydroxide cement containing polyacrylic acid, b) Dycal (L.D> Caulk Co, Milford, Delaware) Batch Nos 176970/176990, c) "Analar" calcium hydroxide mixed with sterile distilled water. After 28 days dentine bridges were present in 77% of teeth capped with the test material, 64% of teeth treated with Dycal and in 62% of teeth capped with calcium hydroxide and water. Inflammatory infiltrates were observed in a number of teeth remote from the bridges. Bacteria were detected in these specimens. Exposed rat molar pulp responses to an experimental adhesive calcium hydroxide cement were similar to to those observed with 2 other calcium hydroxide formulations.

  9. In vitro studies of calcium phosphate silicate bone cements.

    Science.gov (United States)

    Zhou, Shuxin; Ma, Jingzhi; Shen, Ya; Haapasalo, Markus; Ruse, N Dorin; Yang, Quanzu; Troczynski, Tom

    2013-02-01

    A novel calcium phosphate silicate bone cement (CPSC) was synthesized in a process, in which nanocomposite forms in situ between calcium silicate hydrate (C-S-H) gel and hydroxyapatite (HAP). The cement powder consists of tricalcium silicate (C(3)S) and calcium phosphate monobasic (CPM). During cement setting, C(3)S hydrates to produce C-S-H and calcium hydroxide (CH); CPM reacts with the CH to precipitate HAP in situ within C-S-H. This process, largely removing CH from the set cement, enhances its biocompatibility and bioactivity. The testing results of cell culture confirmed that the biocompatibility of CPSC was improved as compared to pure C(3)S. The results of XRD and SEM characterizations showed that CPSC paste induced formation of HAP layer after immersion in simulated body fluid for 7 days, suggesting that CPSC was bioactive in vitro. CPSC cement, which has good biocompatibility and low/no cytotoxicity, could be a promising candidate as biomedical cement.

  10. Preparation of calcium sulphoaluminate cement using fertiliser plant wastes.

    Science.gov (United States)

    Singh, Maneesh; Kapur, P C; Pradip

    2008-08-30

    Phosphochalks from fertiliser plants contain significant amount of calcium sulphate along with P(2)O(5) and fluorine. The presence of these impurities makes them unsuitable for most applications and, hence its availability in millions of tons. We demonstrate that it is possible to prepare calcium sulphoaluminate-aluminoferrite based special cements having strength values comparable to ordinary Portland cement (OPC) using these waste chalks. Such cements are insensitive to the presence of impurities in the raw mixture, clinker at low temperatures (1,230 degrees C) and the clinkers produced are soft and friable. An empirical technique has been developed to predict the phase composition of the clinkers given the chemical composition of the starting raw mixture. The proposed low temperature clinkering route appears to be a promising method for converting waste phosphochalks into construction grade cements.

  11. Setting mechanisms of an acidic premixed calcium phosphate cement

    OpenAIRE

    2013-01-01

    Premixed calcium phosphate cements (pCPC), where glycerol is used instead of water as mixing liquid, present better handling characteristics than water-based cements. However, the setting mechanisms of pCPC have not been described thoroughly. The aim of this paper is to increase the understanding of the setting mechanism of pCPC. The investigated cement starts to set when glycerol is exchanged with water via diffusion of glycerol out to the surrounding body fluid and water into the material. ...

  12. Influence of ferrite phase in alite-calcium sulfoaluminate cements

    Science.gov (United States)

    Duvallet, Tristana Yvonne Francoise

    Since the energy crisis in 1970's, research on low energy cements with low CO2- emissions has been increasing. Numerous solutions have been investigated, and the goal of this original research is to create a viable hybrid cement with the components of both Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC), by forming a material that contains both alite and calcium sulfoaluminate clinker phases. Furthermore, this research focuses on keeping the cost of this material reasonable by reducing aluminum requirements through its substitution with iron. The aim of this work would produce a cement that can use large amounts of red mud, which is a plentiful waste material, in place of bauxite known as an expensive raw material. Modified Bogue equations were established and tested to formulate this novel cement with different amounts of ferrite, from 5% to 45% by weight. This was followed by the production of cement from reagent chemicals, and from industrial by-products as feedstocks (fly ash, red mud and slag). Hydration processes, as well as the mechanical properties, of these clinker compositions were studied, along with the addition of gypsum and the impact of a ferric iron complexing additive triisopropanolamine (TIPA). To summarize this research, the influence of the addition of 5-45% by weight of ferrite phase, was examined with the goal of introducing as much red mud as possible in the process without negatively attenuate the cement properties. Based on this PhD dissertation, the production of high-iron alite-calcium sulfoaluminateferrite cements was proven possible from the two sources of raw materials. The hydration processes and the mechanical properties seemed negatively affected by the addition of ferrite, as this phase was not hydrated entirely, even after 6 months of curing. The usage of TIPA counteracted this decline in strength by improving the ferrite hydration and increasing the optimum amount of gypsum required in each composition

  13. Cements containing by-product gypsum

    Energy Technology Data Exchange (ETDEWEB)

    Bensted, J. [University of Greenwich, London (United Kingdom). School of Biological and Chemical Sciences

    1995-12-31

    Chemical by-product gypsum can readily replace natural gypsum in Portland cements and in blended cements like Portland pfa cement and Portland blast furnace cement without technical detriment in many instances. Indeed, sometimes the technical performance of the cement can be enhanced. The hydration chemistry is often changed, in that where there is at least some retardation of setting, more AFT phase (ettringite) is formed during early hydration at the expense of calcium silicate hydrates. By-product gypsum can also replace natural gypsum in speciality products like calcium aluminate cement-Portland cement mixes for producing quick setting cements and in calcium sulphoaluminate-type expansive cements. However, by-products gypsum have proved to be less successful for utilization in API Classes of oilwell cements, because of the greater difficulty in obtaining batch-to-batch consistency in properties like thickening time and slurry rheology. 11 refs., 3 figs., 5 tabs.

  14. Formation of calcium aluminates in the lime sinter process. [Extraction of alumina from fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Chou, K.S.

    1980-03-01

    A study of the formation of several calcium aluminates from pure components in the lime sinter process was undertaken to determine the kinetics of formation and subsequent leaching using a dilute sodium carbonate solution. The composition CaO 61.98%, SiO/sub 2/ 26.67%, and Al/sub 2/O/sub 3/ 11.53% was used. Isothermal sintering runs of 0.2 to 10.0 h were carried out at 1200, 1250, 1300, and 1350/sup 0/C. When the sintering temperature was below the eutectic temperature (1335/sup 0/C), the ternary mixture behaved like two binary systems, i.e. CaO-Al/sub 2/O/sub 3/ and CaO-SiO/sub 2/. Only one compound, 3CaO.SiO/sub 2/, was formed between CaO and SiO/sub 2/. With lower sintering temperature and shorter sintering time, the ..beta..-phase was dominant. However, when both temperature and time increased, more and more of the ..beta..-C/sub 2/S was transformed into the ..gamma..-phase. Several different aluminates were formed during the sintering of CaO and Al/sub 2/O/sub 3/. The compounds CaO.Al/sub 2/O/sub 3/ and 3CaO.Al/sub 2/O/sub 3/ were observed at all tested sintering temperatures, while the 5CaO.3Al/sub 2/O/sub 3/ phase was found only at 1200/sup 0/C and 12CaO.7Al/sub 2/O/sub 3/ at 1250/sup 0/C or higher. The first compound formed between CaO and Al/sub 2/O/sub 3/ was probably 12CaO.7Al/sub 2/O/sub 3/, but the amount did not increase immediately with time. The first dominant compound between CaO and Al/sub 2/O/sub 3/ was CaO.3Al/sub 2/O/sub 3/. When the calcium ion diffused through the product layer of CaO.Al/sub 2/O/sub 3/, 3CaO.Al/sub 2/O/sub 3/ was formed. If unreacted Al/sub 2/O/sub 3/ were present after the formation of CaO.Al/sub 2/O/sub 3/, CaO.2Al/sub 2/O/sub 3/ would form. Subsequent leaching of the sinters showed that the extractable alumina in the products increased with both sintering temperature and time, reaching a max of about 90%. These extraction data corresponded very well to the quantities of aluminates in the sinters. 59 figures, 13 tables.

  15. Mechanical and fracture behavior of calcium phosphate cements

    Science.gov (United States)

    Jew, Victoria Chou

    Apatite-based calcium phosphate cements are currently employed to a limited extent in the biomedical and dental fields. They present significant potential for a much broader range of applications, particularly as a bone mineral substitute for fracture fixation. Specifically, hydroxyapatite (HA) is known for its biocompatibility and non-immunogenicity, attributed to its similarity to the mineral phase of natural bone. The advantages of a cement-based HA include injectability, greater resorbability and osteoconductivity compared to sintered HA, and an isothermal cement-forming reaction that avoids necrosis during cement setting. Although apatite cements demonstrate good compressive strength, tensile properties are very weak compared to natural bone. Applications involving normal weight-bearing require better structural integrity than apatite cements currently provide. A more thorough understanding of fracture behavior can elucidate failure mechanisms and is essential for the design of targeted strengthening methods. This study investigated a hydroxyapatite cement using a fracture mechanics approach, focusing on subcritical crack growth properties. Subcritical crack growth can lead to much lower load-bearing ability than critical strength values predict. Experiments show that HA cement is susceptible to crack growth under both cyclic fatigue-crack growth and stress corrosion cracking conditions, but only environmental, not mechanical, mechanisms contribute to crack extension. This appears to be the first evidence ever presented of stress corrosion crack growth behavior in calcium phosphate cements. Stress corrosion cracking was examined for a range of environmental conditions. Variations in pH have surprisingly little effect. Behavior in water at elevated temperature (50°C) is altered compared to water at ambient temperature (22°C), but only for crack-growth velocities below 10-7 m/s. However, fracture resistance of dried HA cement in air increases significantly

  16. Injectable calcium phosphate cement for bone repair and implant fixation.

    NARCIS (Netherlands)

    Jansen, J.; Ooms, E.M.; Verdonschot, N.J.J.; Wolke, J.G.C.

    2005-01-01

    The studies as described are aimed at determining the efficacy of newly developed calcium phosphate cement when this material is used as a bone defect filler or gap filler around metal implants. An overview is provided about bone graft substitutes and methods of metal implant fixation.

  17. Novel porous calcium aluminate/phosphate nanocomposites: in situ synthesis, microstructure and permeability

    Science.gov (United States)

    Yang, Jingzhou; Hu, Xiaozhi; Huang, Juntong; Chen, Kai; Huang, Zhaohui; Liu, Yangai; Fang, Minghao; Sun, Xudong

    2016-02-01

    Permeable porous nanomaterials have extensive applications in engineering fields. Here, we report a novel system of porous calcium aluminate/phosphate (CaAl-CaP) nanocomposites fabricated by pore generator free processing. The CaAl rich samples have close micropores and are not permeable. Interestingly, the CaP rich composites have a unique three-dimensional nanosieve structure with interconnected nanopores and exhibit excellent liquid permeability and adsorbability. The pore size has a narrow distribution of 200-500 nm. The CaAl nanoplatelets in the CaP rich composite have a thickness of 202 nm, a diameter of 1600 nm and an aspect ratio of 8. The porosity is from 19% to 40%. The bending strength and compressive strength are 40.3 MPa and 195 MPa, respectively. The CaP rich nanocomposite is highly permeable so that a water droplet can completely penetrate in 10 seconds (1 mm thick disk). The blue dye can be desorbed in 45 min by ultrasonic vibration. Given the nanosieve porous structure, good permeability/adsorbability and high mechanical properties, the CaP rich nanocomposite has big potential in applications for chemical engineering, biomedical engineering and energy/environmental engineering.

  18. Cement and concrete

    Science.gov (United States)

    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. In vitro ageing of brushite calcium phosphate cement.

    Science.gov (United States)

    Grover, L M; Knowles, J C; Fleming, G J P; Barralet, J E

    2003-10-01

    In vivo studies investigating the use of brushite cements have demonstrated mixed results with one or more of dissolution, hydrolysis, fragmentation and long term stability being demonstrated. It has been suggested that sample volume, implant location, and species can affect in vivo behaviour. As few in vitro studies on this cement system have been performed, this study aimed to compare the effects of static and dynamic in vitro ageing protocols on the phase composition, weight loss and mechanical properties of brushite cement. The effects of immersion liquid to cement volume ratio (LCVR) and sample volume on phase composition were investigated and comparative in vitro experiments were also performed in foetal bovine serum. It was determined that the weight loss after 28 days was up to seven times higher in serum than in phosphate buffered saline (PBS) and that fragmentation accounted for most of the weight loss observed. Hydroxyapatite was formed in PBS but not in serum when aged in refreshed media at all LCVRs investigated. This study has highlighted that LCVR, media refresh rate and media composition are critical to brushite cement performance. It appears that brushite cement removal from an implant site may be complex and dependent on physiological processes other than simple dissolution. A better understanding of these processes could provide the means to engineer more precise calcium phosphate cement degradation profiles.

  20. Biocompatibility and resorption of a brushite calcium phosphate cement.

    Science.gov (United States)

    Theiss, Felix; Apelt, Detlef; Brand, Bastian; Kutter, Annette; Zlinszky, Katalin; Bohner, Marc; Matter, Sandro; Frei, Christian; Auer, Joerg A; von Rechenberg, Brigitte

    2005-07-01

    A hydraulic calcium phosphate cement with beta-tricalcium phosphate (TCP) granules embedded in a matrix of dicalcium phosphate dihydrate (DCPD) was implanted in experimentally created defects in sheep. One type of defect consisted of a drill hole in the medial femoral condyle. The other, partial metaphyseal defect was located in the proximal aspect of the tibia plateau and was stabilized using a 3.5 mm T-plate. The bone samples of 2 animals each per group were harvested after 2, 4, 6 and 8 weeks. Samples were evaluated for cement resorption and signs of immediate reaction, such as inflammation, caused by the cement setting in situ. Differences regarding these aspects were assessed for both types of defects using macroscopical, radiological, histological and histomorphometrical evaluations. In both defects the brushite matrix was resorbed faster than the beta-TCP granules. The resorption front was followed directly by a front of new bone formation, in which residual beta-TCP granules were embedded. Cement resorption occurred through (i) extracellular liquid dissolution with cement disintegration and particle formation, and (ii) phagocytosis of the cement particles through macrophages. Signs of inflammation or immunologic response leading to delayed new bone formation were not noticed at any time. Cement degradation and new bone formation occurred slightly faster in the femur defects.

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

    Science.gov (United States)

    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.

  2. Enhanced bioactivity of glass ionomer cement by incorporating calcium silicates.

    Science.gov (United States)

    Chen, Song; Cai, Yixiao; Engqvist, Håkan; Xia, Wei

    2016-01-01

    Glass ionomer cements (GIC) are known as a non-bioactive dental cement. During setting the GIC have an acidic pH, driven by the acrylic acid component. It is a challenge to make GIC alkaline without disturbing its mechanical properties. One strategy was to add slowly reacting systems with an alkaline pH. The aim of the present study is to investigate the possibility of forming a bioactive dental material based on the combination of glass ionomer cement and calcium silicates. Two types of GIC were used as control. Wollastonite (CS also denoted β-CaSiO3) or Mineral Trioxide Aggregate (MTA) was incorporated into the 2 types of GIC. The material formulations' setting time, compressive strength, pH and bioactivity were compared between modified GIC and GIC control. Apatite crystals were found on the surfaces of the modified cements but not on the control GIC. The compressive strength of the cement remained with the addition of 20% calcium silicate or 20% MTA after one day immersion. In addition, the compressive strength of GIC modified with 20% MTA had been increased during the 14 d immersion (p < 0 .05).

  3. Apatite bone cement reinforced with calcium silicate fibers.

    Science.gov (United States)

    Motisuke, Mariana; Santos, Verônica R; Bazanini, Naiana C; Bertran, Celso A

    2014-10-01

    Several research efforts have been made in the attempt to reinforce calcium phosphate cements (CPCs) with polymeric and carbon fibers. Due to their low compatibility with the cement matrix, results were not satisfactory. In this context, calcium silicate fibers (CaSiO3) may be an alternative material to overcome the main drawback of reinforced CPCs since, despite of their good mechanical properties, they may interact chemically with the CPC matrix. In this work CaSiO3 fibers, with aspect ratio of 9.6, were synthesized by a reactive molten salt synthesis and used as reinforcement in apatite cement. 5 wt.% of reinforcement addition has increased the compressive strength of the CPC by 250% (from 14.5 to 50.4 MPa) without preventing the cement to set. Ca and Si release in samples containing fibers could be explained by CaSiO3 partial hydrolysis which leads to a quick increase in Ca concentration and in silica gel precipitation. The latter may be responsible for apatite precipitation in needle like form during cement setting reaction. The material developed presents potential properties to be employed in bone repair treatment.

  4. Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction.

    Science.gov (United States)

    Combes, C; Bareille, R; Rey, C

    2006-11-01

    The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.

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

    Science.gov (United States)

    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.

  6. On the development of an apatitic calcium phosphate bone cement

    Indian Academy of Sciences (India)

    Manoj Komath; H K Varma; R Sivakumar

    2000-04-01

    Development of an apatitic calcium phosphate bone cement is reported. 100 Particles of tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD) were mixed in equimolar ratio to form the cement powder. The wetting medium used was distilled water with Na2HPO4 as accelerator to manipulate the setting time. The cement powder, on wetting with the medium, formed a workable putty. The setting times of the putty were measured using a Vicat type apparatus and the compressive strength was determined with a Universal Testing Machine. The nature of the precipitated cement was analyzed through X-ray diffraction (XRD), fourier transform infrared spectrometry (FTIR) and energy dispersive electron microprobe (EDAX). The results showed the phase to be apatitic with a calcium–to–phosphorous ratio close to that of hydroxyapatite. The microstructure analysis using scanning electron microscopy (SEM) showed hydroxyapatite nanocrystallite growth over particulate matrix surface. The structure has an apparent porosity of ∼ 52%. There were no appreciable dimensional or thermal changes during setting. The cement passed the in vitro toxicological screening (cytotoxicity and haemolysis) tests. Optimization of the cement was done by manipulating the accelerator concentration so that the setting time, hardening time and the compressive strength had clinically relevant values.

  7. Molecular mechanisms of crystallization impacting calcium phosphate cements

    Science.gov (United States)

    Giocondi, Jennifer L.; El-Dasher, Bassem S.; Nancollas, George H.; Orme, Christine A.

    2010-01-01

    The biomineral calcium hydrogen phosphate dihydrate (CaHPO4·2H2O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite’s excellent biocompatibility, can be used to great benefit in making resorbable biomedical cements. To optimize cements, additives are commonly used to control crystallization kinetics and phase transformation. This paper describes the use of in situ scanning probe microscopy to investigate the role of several solution parameters and additives in brushite atomic step motion. Surprisingly, this work demonstrates that the activation barrier for phosphate (rather than calcium) incorporation limits growth kinetics and that additives such as magnesium, citrate and bisphosphonates each influence step motion in distinctly different ways. Our findings provide details of how, and where, molecules inhibit or accelerate kinetics. These insights have the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives. PMID:20308110

  8. Molecular mechanisms of crystallization impacting calcium phosphate cements.

    Science.gov (United States)

    Giocondi, Jennifer L; El-Dasher, Bassem S; Nancollas, George H; Orme, Christine A

    2010-04-28

    The biomineral calcium hydrogen phosphate dihydrate (CaHPO(4).2H(2)O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite's excellent biocompatibility, can be used to great benefit in making resorbable biomedical cements. To optimize cements, additives are commonly used to control crystallization kinetics and phase transformation. This paper describes the use of in situ scanning probe microscopy to investigate the role of several solution parameters and additives in brushite atomic step motion. Surprisingly, this work demonstrates that the activation barrier for phosphate (rather than calcium) incorporation limits growth kinetics and that additives such as magnesium, citrate and bisphosphonates each influence step motion in distinctly different ways. Our findings provide details of how, and where, molecules inhibit or accelerate kinetics. These insights have the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives.

  9. Influence of Calcium Sulfate State and Fineness of Cement on Hydration of Portland Cements Using Electrical Measurement

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; LI Zongjin; XIAO Lianzhen; THONG Wangfai

    2006-01-01

    The influence of calcium sulfate state and fineness of cement on hydration of Portland cement was studied using electrical resistivity measurement. The bulk resistivity curve of the paste from the abnormal cement mainly with hemihydrate had a characteristic abnormal peak and rapid increase in early period. The resistivity measurement technique can be used to discriminate abnormal setting. For normal cement with gypsum, the increase in fineness of the Portland cement decreases the minimum resistivity due to a higher ionic concentration and increases the 24 hour resistivity due to a reduction in macroscopic pore size. Thesetting time, compressive strength, pore structure of pastes made from different cements were carried out to compare the influence of water to cement ratio, calcium sulfate state and fineness. It is found that the electrical and mechanical properties are strongly affected by the initial porosity, the presence of hemihydrate or gypsum, and the fineness of cement.

  10. Molecular Dynamics Modeling of Hydrated Calcium-Silicate-Hydrate (CSH) Cement Molecular Structure

    Science.gov (United States)

    2014-08-30

    properties of key hydrated cement constituent calcium-silicate-hydrate (CSH) at the molecular, nanometer scale level. Due to complexity, still unknown...public release; distribution is unlimited. Molecular Dynamics Modeling of Hydrated Calcium-Silicate- Hydrate (CSH) Cement Molecular Structure The views... Cement Molecular Structure Report Title Multi-scale modeling of complex material systems requires starting from fundamental building blocks to

  11. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

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

  12. Effect of carbon fiber on calcium phosphate bone cement

    Institute of Scientific and Technical Information of China (English)

    戴红莲; 王欣宇; 黄健; 闫玉华; 李世普

    2004-01-01

    The calcium phosphate cement (α-TCP/TTCP) was reinforced with oxidation-treated carbon fibers. The effect of aspect ratio and content of carbon fiber on the compression strength and bending strength of the hardened body was discussed. The results show that the reinforcing effect is optimal as the aspect ratio is 375 and the additive amount is 0.3% (mass fraction). Under this condition, the compressive strength is increased by 55% (maximum 63.46 MPa), and the bending strength is nearly increased by 100% (maximum 11.95 MPa), respectively. However, if the additive quantity and aspect ratio are too high, the effect of the carbon fibers is limited because it can not be dispersed uniformly in the hardened body. The biological evaluation indicates that the calcium phosphate cement reinforced by carbon fibers has good biocompatibility.

  13. Dentin-cement Interfacial Interaction: Calcium Silicates and Polyalkenoates

    OpenAIRE

    Atmeh, A.R.; Chong, E.Z.; Richard, G; Festy, F.; Watson, T.F.

    2012-01-01

    The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline c...

  14. Effect of B2O3 content on structure and spectroscopic properties of neodymium-doped calcium aluminate glasses

    Science.gov (United States)

    Kang, Shuai; Wang, Xue; Xu, Wenbin; Wang, Xin; He, Dongbing; Hu, Lili

    2017-04-01

    Nd2O3-doped calcium aluminate glasses was synthesized with the following compositions: (100-x)(33Al2O3-62CaO-2MgO-3BaO)-xB2O3-0.5Nd2O3 (x = 0, 2.5, 5, 7.5, 10). The Raman, absorption, and emission spectra were measured to characterize the structure and spectroscopic properties of these glasses. The glass thermal stability was studied using differential scanning calorimetry (DSC) tests. Both the Raman spectra and DSC results indicated a decrease in the non-bridging oxygens (NBOs) in the [AlO4]- network with an increase in the B2O3 content. The J-O intensity parameter Ω2, covalency degree of the Nd-O bond, and emission bandwidth of the Nd3+ ions decreased with the B2O3 content. The stimulated emission cross-section and optical gain property increased with an increase in the B2O3 content. The tunable gain property and broadband emission feature of the Nd3+-doped CaO-Al2O3-B2O3-MgO-BaO calcium aluminate glass suggested a potential application to a high-energy ultra-short-pulse laser.

  15. Novel rechargeable calcium phosphate nanoparticle-containing orthodontic cement.

    Science.gov (United States)

    Xie, Xian-Ju; Xing, Dan; Wang, Lin; Zhou, Han; Weir, Michael D; Bai, Yu-Xing; Xu, Hockin Hk

    2016-11-04

    White spot lesions (WSLs), due to enamel demineralization, occur frequently in orthodontic treatment. We recently developed a novel rechargeable dental composite containing nanoparticles of amorphous calcium phosphate (NACP) with long-term calcium (Ca) and phosphate (P) ion release and caries-inhibiting capability. The objectives of this study were to develop the first NACP-rechargeable orthodontic cement and investigate the effects of recharge duration and frequency on the efficacy of ion re-release. The rechargeable cement consisted of pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA). NACP was mixed into the resin at 40% by mass. Specimens were tested for orthodontic bracket shear bond strength (SBS) to enamel, Ca and P ion initial release, recharge and re-release. The new orthodontic cement exhibited an SBS similar to commercial orthodontic cement without CaP release (P>0.1). Specimens after one recharge treatment (e.g., 1 min immersion in recharge solution repeating three times in one day, referred to as "1 min 3 times") exhibited a substantial and continuous re-release of Ca and P ions for 14 days without further recharge. The ion re-release did not decrease with increasing the number of recharge/re-release cycles (P>0.1). The ion re-release concentrations at 14 days versus various recharge treatments were as follows: 1 min 3 times>3 min 2 times>1 min 2 times>6 min 1 time>3 min 1 time>1 min 1 time. In conclusion, although previous studies have shown that NACP nanocomposite remineralized tooth lesions and inhibited caries, the present study developed the first orthodontic cement with Ca and P ion recharge and long-term release capability. This NACP-rechargeable orthodontic cement is a promising therapy to inhibit enamel demineralization and WSLs around orthodontic brackets.International Journal of Oral Science advance online publication,4 November 2016; doi:10.1038/ijos.2016.40.

  16. New developments in calcium phosphate bone cements: approaching spinal applications

    OpenAIRE

    Vlad, Maria Daniela

    2009-01-01

    La presente tesis doctoral (i.e., “New developments in calcium phosphate bone cements: approaching spinal applications”) aporta nuevos conocimientos en el campo de los cementos óseos de fosfato de calcio (CPBCs) en relación a su aplicación clínica en el campo de la cirugía vertebral mínimamente invasiva. La hipótesis central de esta investigación fue formulada en los siguientes términos: “Los cementos apatíticos pueden ser (si se optimizan) una alternativa mejor (debido a sus propiedades d...

  17. Injectable PLGA microsphere/calcium phosphate cements: physical properties and degradation characteristics.

    NARCIS (Netherlands)

    Habraken, W.J.E.M.; Wolke, J.G.C.; Mikos, A.G.; Jansen, J.A.

    2006-01-01

    Calcium phosphate (CaP) cements show an excellent biocompatibility and often have a high mechanical strength, but in general degrade relatively slow. To increase degradation rates, macropores can be introduced into the cement, e.g., by the inclusion of biodegradable microspheres into the cement. The

  18. Removal of methyl orange from aqueous solutions through adsorption by calcium aluminate hydrates.

    Science.gov (United States)

    Zhang, Ping; Wang, Tianqi; Qian, Guangren; Wu, Daishe; Frost, Ray L

    2014-07-15

    Methyl orange (MO) is a kind of anionic dye and widely used in industry. In this study, tricalcium aluminate hydrates (Ca-Al-LDHs) are used as an adsorbent to remove methyl orange (MO) from aqueous solutions. The resulting products were studied by X-ray diffraction (XRD), infrared spectroscopy (MIR), thermal analysis (TG-DTA) and scanning electron microscope (SEM). The XRD results indicated that the MO molecules were successfully intercalated into the tricalcium aluminate hydrates, with the basal spacing of Ca-Al-LDH expanding to 2.48 nm. The MIR spectrum for CaAl-MO-LDH shows obvious bands assigned to the N=N, N=H stretching vibrations and S=O, SO3(-) group respectively, which are considered as marks to assess MO(-) ion intercalation into the interlayers of LDH. The overall morphology of CaAl-MO-LDH displayed a "honey-comb" like structure, with the adjacent layers expanded.

  19. Fracture Toughness and Thermal Shock Properties of Calcium Aluminate Composite with Controlled Duplex Structure

    Institute of Scientific and Technical Information of China (English)

    W.J.Wei; H.J.Liaw

    2004-01-01

    This study used monocalcium aluminate (CaAl2O4,CA) for producing ceramic composites with duplex microstructures by hydration and gelation reactions of the aluminate, and compared the properties with those made by a die-pressing process of mixed powders. Densification of the composite was optimized. The microstructure of sintered bodies, the fracture strengths and toughness of the composites with and without thermal shocking was characterized by different techniques. Experimental results show that the green body with the addition of CA resulted glomerated platelets or uniform distribution of platy CA6 grains. The former, which appeared a duplex microstructure consisted of dense matrix and distributed clusters of CA6 platelets, performed an improvement on toughness and thermal shock resistance. Toughness mechanisms of samples with duplex microstructure are also investigated.

  20. Development and characterisation of injectable calcium phosphate cements for use in vertebroplasty

    OpenAIRE

    2002-01-01

    The global objective of this thesis was to understand how the starting components of brushite cements influence the cement properties relevant for its use in vertebroplasty. Therefore, this work focussed on the following cement properties : mechanical strength, X-ray opacity and heat release upon setting. To carry out the global objective, a test protocol was first developed to characterise the mechanical properties of calcium phosphate cements. The Mohr's circles representation allowed to un...

  1. Development and characterisation of injectable calcium phosphate cements for use in vertebroplasty

    OpenAIRE

    2007-01-01

    The global objective of this thesis was to understand how the starting components of brushite cements influence the cement properties relevant for its use in vertebroplasty. Therefore, this work focussed on the following cement properties : mechanical strength, X-ray opacity and heat release upon setting. To carry out the global objective, a test protocol was first developed to characterise the mechanical properties of calcium phosphate cements. The Mohr's circles representation allowed to un...

  2. Experimental Research on Calcium Aluminate Desulphurizer Slags%铝酸钙脱硫渣系的实验研究

    Institute of Scientific and Technical Information of China (English)

    袁守谦; 郭强; 王伟; 梁德安

    2011-01-01

    The desulphurizer of CaO-Al2O3-CaF2 was researched in laboratory. The results show that increasing the contents of pre-melted desulphurizer can increase the velocity and ratio of desulfurization. In the meanwhile, elevating temperature of liquid steel can increase desulfurization degree; the S-content can decrease to a relative low level (0.026wt) in 10 minutes at 1620℃. The desulphurization effect using calcium aluminate desulphurizer slags with CaO is superior to that using pure 12CaO. 7Al2O3 slag, while the additive amount of CaO is 10wt , the desulphurizatien effect is best. Therefore the calcium aluminate desulphurizer slags with CaO can be used as a high efficient, high speed and an environmental friendly desulphurizer.%在实验室的条件下,对用CaO、Al2O3、CaF2为原料配制的钢水脱硫剂进行了实验研究.研究发现,增加预熔脱硫剂量,可提高脱硫速度,增大脱硫率.提高钢水温度可以增大脱硫效率,在1620℃下,10min就可将钢液中的硫降低到0.026wt%的较低水平.添加CaO的铝酸钙预熔渣的脱硫效果明显优于纯12CaO·7Al2O3渣系,加氧化钙含量为10wt%时,整体脱硫效果最好.此预熔合成渣原料将可能成为一种高效、快速、环保的脱硫剂.

  3. Evaluation of a porosity measurement method for wet calcium phosphate cements.

    Science.gov (United States)

    Ajaxon, Ingrid; Maazouz, Yassine; Ginebra, Maria-Pau; Öhman, Caroline; Persson, Cecilia

    2015-11-01

    The porosity of a calcium phosphate cement is a key parameter as it affects several important properties of the cement. However, a successful, non-destructive porosity measurement method that does not include drying has not yet been reported for calcium phosphate cements. The aim of this study was to evaluate isopropanol solvent exchange as such a method. Two different types of calcium phosphate cements were used, one basic (hydroxyapatite) and one acidic (brushite). The cements were allowed to set in an aqueous environment and then immersed in isopropanol and stored under three different conditions: at room temperature, at room temperature under vacuum (300 mbar) or at 37℃. The specimen mass was monitored regularly. Solvent exchange took much longer time to reach steady state in hydroxyapatite cements compared to brushite cements, 350 and 18 h, respectively. Furthermore, the immersion affected the quasi-static compressive strength of the hydroxyapatite cements. However, the strength and phase composition of the brushite cements were not affected by isopropanol immersion, suggesting that isopropanol solvent exchange can be used for brushite calcium phosphate cements. The main advantages with this method are that it is non-destructive, fast, easy and the porosity can be evaluated while the cements remain wet, allowing for further analysis on the same specimen.

  4. [Allergy of calcium phosphate cement material following skull reconstruction: a case report].

    Science.gov (United States)

    Mizowaki, Takashi; Miyake, Shigeru; Yoshimoto, Yuji; Matsuura, Yoshitaka; Akiyama, Sou

    2013-04-01

    The paste form of calcium phosphate cement is often used in skull reconstruction because of the biocompatibility and early handling of these cements. Although it had rarely been shown to produce a foreign body reaction, we encountered a patient who experienced an allergic reaction to calcium phosphate cements(Biopex®. A patch test was performed and a positive reaction to magnesium phosphate was obtained. Biopex® contains magnesium phosphate, so we diagnosed this case as allergic reaction. Pathological analysis revealed infiltration of plasmacytes in the bone flap around the calcium phosphate cement. The postoperative course was uneventful 3 years after surgery. Allergy to calcium phosphate cements is rare, but must be considered in differential diagnosis of its side effects.

  5. Augmentation of Pedicle Screw Fixation with Calcium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    YANG Shu-hua; FU De-hao; LI Jin; XU Wei-hua; YANG Cao; YE Zhe-wei; ZUO Xiao-yan

    2004-01-01

    To determine whether a biodegradable calcium phosphate cement(CPC) provides significant augmentation of pedicle screw fixation or not,an in vitro biomechanical study was carried out to evaluate the biomechanical effect of CPC in the restoration and augmentation of pedicle screw fixation.Axial pullout test and cyclic bending resistance test were employed in the experiment,and polymethylmethacrylate (PMMA) was chosen as control.The results demonstrate that the pullout strengths following CPC restoration and augmentation are 74% greater on an average than those of the control group,but less than those of PMMA restoration group and augmentation group respectively (increased by 126% versus control).In cyclic bending resistance test,the CPC augmented screws are found to withstand a greater number of cycles or greater loading with less displacement before loosening,but the augmentation effect of PMMA is greater than that of CPC.

  6. Hydration studies of calcium sulfoaluminate cements blended with fly ash

    Energy Technology Data Exchange (ETDEWEB)

    García-Maté, M.; De la Torre, A.G. [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga (Spain); León-Reina, L. [Servicios Centrales de Apoyo a la Investigación, Universidad de Málaga, 29071 Málaga (Spain); Aranda, M.A.G. [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga (Spain); CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain); Santacruz, I., E-mail: isantacruz@uma.es [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga (Spain)

    2013-12-15

    The main objective of this work is to study the hydration and properties of calcium sulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied parameters were: i) FA content, 0, 15 and 30 wt.%; and ii) water addition, water-to-CSA mass ratio (w/CSA = 0.50 and 0.65), and water-to-binder mass ratio (w/b = 0.50). Finally, compressive strengths after 6 months of 0 and 15 wt.% FA [w/CSA = 0.50] mortars were similar: 73 ± 2 and 72 ± 3 MPa, respectively. This is justified by the filler effect of the FA as no strong evidences of reactivity of FA with CSA were observed. These results support the partial substitution of CSA cements with FA with the economic and environmental benefits.

  7. Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids

    Science.gov (United States)

    Taddei, Paola; Modena, Enrico; Tinti, Anna; Siboni, Francesco; Prati, Carlo; Gandolfi, Maria Giovanna

    2011-05-01

    Calcium-silicate MTA (Mineral Trioxide Aggregate) cements have been recently developed for oral and endodontic surgery. This study was aimed at investigating commercial (White ProRoot MTA, White and Grey MTA-Angelus) and experimental (wTC-Bi) accelerated calcium-silicate cements with regards to composition, hydration products and bioactivity upon incubation for 1-28 days at 37 °C, in Dulbecco's Phosphate Buffered Saline (DPBS). Deposits on the surface of the cements and the composition changes during incubation were investigated by micro-Raman and ATR/FT-IR spectroscopy, and pH measurements. Vibrational techniques disclosed significant differences in composition among the unhydrated cements, which significantly affected the bioactivity as well as pH, and hydration products of the cements. After one day in DPBS, all the cements were covered by a more or less homogeneous layer of B-type carbonated apatite. The experimental cement maintained a high bioactivity, only slightly lower than the other cements and appears a valid alternative to commercial cements, in view of its adequate setting time properties. The bioactivity represents an essential property to favour bone healing and makes the calcium-silicate cements the gold standard materials for root-apical endodontic surgery.

  8. Ionic modification of calcium phosphate cement viscosity. Part II: hypodermic injection and strength improvement of brushite cement.

    Science.gov (United States)

    Barralet, J E; Grover, L M; Gbureck, U

    2004-05-01

    Brushite-forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. However, their short setting times, low mechanical strengths and limited injectability limit broad clinical application. In this study, we showed that a significant improvement of these properties of brushite cement could be achieved by the use of sodium citrate or citric acid as setting retardants, such that workable cement pastes with a powder to liquid ratio of up to 5 could be manufactured. The cement used in this study consisted of an equimolar powder mixture of beta-tricalcium phosphate and monocalcium phosphate hydrate The use of 500 mM-1M retardant solutions as liquid phase enabled initial setting times of 8-12 min. Wet compressive strength were found to be in the range between 12-18 MPa after immersion of uncompacted cement samples in serum for 24 h. A further strength improvement to 32 MPa was obtained by compaction of the cement paste during samples preparation. This is significant because high-temperature processes cannot be used to fabricate hydrated calcium phosphate materials. Cement pastes were injectable through a hypodermic needle at a powder to liquid ratio of 3.3 g/ml when a 1M citric acid was used as liquid phase, thus enabling precise controlled delivery to small defects.

  9. 3D Computational Simulation of Calcium Leaching in Cement Matrices

    Directory of Open Access Journals (Sweden)

    Gaitero, J. J.

    2014-12-01

    Full Text Available Calcium leaching is a degradation process consisting in progressive dissolution of the cement paste by migration of calcium atoms to the aggressive solution. It is therefore, a complex phenomenon involving several phases and dissolution and diffusion processes simultaneously. Along this work, a new computational scheme for the simulation of the degradation process in three dimensions was developed and tested. The toolkit was used to simulate accelerated calcium leaching by a 6M ammonium nitrate solution in cement matrices. The obtained outputs were the three dimensional representation of the matrix and the physicochemical properties of individual phases as a consequence of the degradation process. This not only makes it possible to study the evolution of such properties as a function of time but also as a function of the position within the matrix. The obtained results are in good agreement with experimental values of the elastic modulus in degraded and undegraded samples.El lixiviado de calcio es un proceso de degradación consistente en la disolución progresiva de la pasta de cemento por la migración de los átomos de calcio a la disolución agresiva. Se trata por tanto de un fenómeno complejo que involucra simultáneamente diferentes fases y procesos de disolución y difusión. En este trabajo se desarrolló y probó una nueva herramienta computacional para la simulación del proceso de degradación en tres dimensiones. Para ello se simuló el lixiviado de calcio acelerado provocado por una disolución de nitrato amónico 6M en matrices de cemento. Como resultado se obtuvieron la representación tridimensional de la matriz y las propiedades físico-químicas sus fases a lo largo del tiempo. Esto permitió estudiar la evolución de dichas propiedades a lo largo del proceso de degradación así como en función de su posición dentro de la matriz. Los resultados obtenidos coinciden con los valores experimentales del módulo elástico tanto

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

    NARCIS (Netherlands)

    Sariibrahimoglu, K.; Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Yubao, L.; Jansen, J.A.

    2012-01-01

    The main disadvantage of apatitic calcium phosphate cements (CPCs) is their slow degradation rate, which limits complete bone regeneration. Carbonate (CO(3)(2)(-)) is the common constituent of bone and it can be used to improve the degradability of the apatitic calcium phosphate ceramics. This study

  11. Balloon vetebroplasty with calcium phosphate cement augmentation for direct restoration of traumatic thoracolumbar vertebral fractures

    NARCIS (Netherlands)

    Verlaan, JJ; van Helden, WH; Oner, FC; Verbout, AJ; Dhert, WJA

    2002-01-01

    Study Design. A human cadaveric model was used to evaluate balloon vertebroplasty in traumatic vertebral fractures. Objectives. To assess the feasibility and safety of balloon vertebroplasty followed by calcium phosphate cement augmentation to prevent recurrent kyphosis. Summary of Background Data.

  12. Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement.

    Science.gov (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan

    2013-01-01

    Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37 °C, which could give a better integration between polymer microparticles and ceramic cement compared with polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared with pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications.

  13. Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement

    Science.gov (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan

    2013-01-01

    Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37 °C, which could give a better integration between polymer microparticles and ceramic cement compared with polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared with pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications. PMID:24270588

  14. Trabecular bone response to injectable calcium phosphate (Ca-P) cement.

    NARCIS (Netherlands)

    Ooms, E.M.; Wolke, J.G.C.; Waerden, J.P.C.M. van der; Jansen, J.A.

    2002-01-01

    The aim of this study was to investigate the physicochemical, biological, and handling properties of a new developed calcium phosphate (Ca-P) cement when implanted in trabecular bone. Ca-P cement consisting of a powder and a liquid phase was implanted as a paste into femoral trabecular bone of goats

  15. PLGA microsphere/calcium phosphate cement composites for tissue engineering: in vitro release and degradation characteristics.

    NARCIS (Netherlands)

    Habraken, W.J.E.M.; Wolke, J.G.C.; Mikos, A.G.; Jansen, J.A.

    2008-01-01

    Bone cements with biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres have already been proven to provide a macroporous calcium phosphate cement (CPC) during in situ microsphere degradation. Furthermore, in vitro/in vivo release studies with these PLGA microsphere/CPC composites (PLGA/CP

  16. Introduction of enzymatically degradable poly(trimethylene carbonate) microspheres into an injectable calcium phosphate cement

    NARCIS (Netherlands)

    Habraken, Wouter J. E. M.; Zhang, Zheng; Wolke, Joop G. C.; Grijpma, Dirk W.; Mikos, Antonios G.; Feijen, Jan; Jansen, John A.

    2008-01-01

    Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polyester with rubber-like properties. Introduction of this polymer into an injectable calcium phosphate bone cement can therefore be used to introduce macroporosity into the cement for tissue engineering purposes as well as to impro

  17. Introduction of enzymatically degradable poly(trimethylene carbonate) microspheres into an injectable calcium phosphate cement.

    NARCIS (Netherlands)

    Habraken, W.J.E.M.; Zhang, Z.; Wolke, J.G.C.; Grijpma, D.W.; Mikos, A.G.; Feijen, J.; Jansen, J.A.

    2008-01-01

    Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polyester with rubber-like properties. Introduction of this polymer into an injectable calcium phosphate bone cement can therefore be used to introduce macroporosity into the cement for tissue engineering purposes as well as to impro

  18. Preparation and characterization of a novel injectable strontium-containing calcium phosphate cement with collagen

    OpenAIRE

    2015-01-01

    Purpose: To develop a novel injectable strontium-containing calcium phosphate cement with collagen. Methods: A novel calcium phosphate bone cement (CPC) was prepared with the addition of strontium element, collagenⅠ, and modified starch; the injectability, solidification time, microstructure, phase composition, compressive strength, anti-collapsibility and histological properties of material were evaluated. Results: The results showed that the material could be injected with an excellen...

  19. Molecular mechanism of crystallization impacting calcium phosphate cements

    Energy Technology Data Exchange (ETDEWEB)

    Giocondi, J L; El-Dasher, B S; Nancollas, G H; Orme, C A

    2009-05-31

    In summary, SPM data has shown that (1) Mg inhibits growth on all steps but relatively high Mg/Ca ratios are needed. Extracting the mechanism of interaction requires more modeling of the kinetic data, but step morphology is consistent with incorporation. (2) Citrate has several effects depending on the citrate/Ca ratio. At the lowest concentrations, citrate increases the step free energy without altering the step kinetics; at higher concentrations, the polar step is slowed. (3) Oxalate also slows the polar step but additionally stabilizes a new facet, with a [100]{sub Cc} step. (4) Etidronate has the greatest kinetic impact of the molecules studied. At 7{micro}M concentrations, the polar step slows by 60% and a new polar step appears. However, at the same time the [10-1]{sub Cc} increases by 67%. It should be noted that all of these molecules complex calcium and can effect kinetics by altering the solution supersaturation or the Ca to HPO{sub 4}{sup 2-} ratio. For the SPM data shown, this effect was corrected for to distinguish the effect of the molecule at the crystal surface from the effect of the molecule on the solution speciation. The goal of this paper is to draw connections between fundamental studies of atomic step motion and potential strategies for materials processing. It is not our intent to promote the utility of SPM for investigating processes in cement dynamics. The conditions are spectacularly different in many ways. The data shown in this paper are fairly close to equilibrium (S=1.6) whereas the nucleation of cements is initiated at supersaturation ratios in the thousands to millions. Of course, after the initial nucleation phase, the growth will occur at more modest supersaturations and as the cement evolves towards equilibrium certainly some of the growth will occur in regimes such as shown here. In addition to the difference in supersaturation, cements tend to have lower additive to calcium ratios. As an example, the additive to Ca ratio is

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

    Science.gov (United States)

    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.

  1. Effect of SO2 and steam on CO2 capture performance of biomass-templated calcium aluminate pellets.

    Science.gov (United States)

    Erans, María; Beisheim, Theodor; Manovic, Vasilije; Jeremias, Michal; Patchigolla, Kumar; Dieter, Heiko; Duan, Lunbo; Anthony, Edward J

    2016-10-20

    Four types of synthetic sorbents were developed for high-temperature post-combustion calcium looping CO2 capture using Longcal limestone. Pellets were prepared with: lime and cement (LC); lime and flour (LF); lime, cement and flour (LCF); and lime, cement and flour doped with seawater (LCFSW). Flour was used as a templating material. All samples underwent 20 cycles in a TGA under two different calcination conditions. Moreover, the prepared sorbents were tested for 10 carbonation/calcination cycles in a 68 mm-internal-diameter bubbling fluidized bed (BFB) in three environments: with no sulphur and no steam; in the presence of sulphur; and with steam. When compared to limestone, all the synthetic sorbents exhibited enhanced CO2 capture performance in the BFB experiments, with the exception of the sample doped with seawater. In the BFB tests, the addition of cement binder during the pelletisation process resulted in the increase of CO2 capture capacity from 0.08 g CO2 per g sorbent (LF) to 0.15 g CO2 per g sorbent (LCF) by the 10(th) cycle. The CO2 uptake in the presence of SO2 dramatically declined by the 10(th) cycle; for example, from 0.22 g CO2 per g sorbent to 0.05 g CO2 per g sorbent in the case of the untemplated material (LC). However, as expected all samples showed improved performance in the presence of steam, and the decay of reactivity during the cycles was less pronounced. Nevertheless, in the BFB environment, the templated pellets showed poorer CO2 capture performance. This is presumably because of material loss due to attrition under the FB conditions. By contrast, the templated materials performed better than untemplated materials under TGA conditions. This indicates that the reduction of attrition is critical when employing templated materials in realistic systems with FB reactors.

  2. Polymeric additives to enhance the functional properties of calcium phosphate cements

    Directory of Open Access Journals (Sweden)

    Roman A Perez

    2012-12-01

    Full Text Available The vast majority of materials used in bone tissue engineering and regenerative medicine are based on calcium phosphates due to their similarity with the mineral phase of natural bone. Among them, calcium phosphate cements, which are composed of a powder and a liquid that are mixed to obtain a moldable paste, are widely used. These calcium phosphate cement pastes can be injected using minimally invasive surgery and adapt to the shape of the defect, resulting in an entangled network of calcium phosphate crystals. Adding an organic phase to the calcium phosphate cement formulation is a very powerful strategy to enhance some of the properties of these materials. Adding some water-soluble biocompatible polymers in the calcium phosphate cement liquid or powder phase improves physicochemical and mechanical properties, such as injectability, cohesion, and toughness. Moreover, adding specific polymers can enhance the biological response and the resorption rate of the material. The goal of this study is to overview the most relevant advances in this field, focusing on the different types of polymers that have been used to enhance specific calcium phosphate cement properties.

  3. The effects of citric acid on the hydration of calcium phosphate cement

    Institute of Scientific and Technical Information of China (English)

    DAI Hong-lian; YAN Yu-hua; WANG You-fa; LI Shi-pu

    2001-01-01

    @@ INTRODUCTION Calcium phosphate cements (CPC) overcome the practical disadvantages of blocks or granulesl can be handled as a paste and sit in situ. Their structure and composition close to that of HAP make them biocompatible materials. 2 The conventional calcium phosphate cement had some problems such as long setting time (30~60 min) and low compressive strength, etc. In our system, an α-TCP/TTCP powder mixture was mixed with water containing citric acid to control the setting time and compressive strength. In this paper, the effects of various concentration citric acid solutions on the properties of the cement are reported.

  4. Calcium sulphoaluminate cement made from fluidized bed combustion wastes

    Energy Technology Data Exchange (ETDEWEB)

    Bernards, G.; Marroccoli, M.; Montagnaro, F.; Valenti, G.L.

    2000-07-01

    Wastes generated in a bench-scale atmospheric fluidized bed combustor, using two different coals (one from Poland and one from South Africa) and a high-lime limestone sorbent, were employed as raw materials for the synthesis of calcium sulphoaluminate (4 CaO{sub 3} Al{sub 2}O{sub 3}.SO{sub 3})-based cements, which can be utilized for a wide range of applications. Raw mixes containing the bed material were heated in an electric oven in the temperature range 1000-1200{degree}C. The best results in terms of reactants conversion and selectivity towards 4 CaO{sub 2} Al{sub 2}O{sub 3}.SO{sub 3} were obtained at 1200{degree}C with the addition of an external source of alumina which was required to avoid melting phenomena or integrate the Al{sub 2}O{sub 3} content necessary for the 4CaO{sub 3}.Al{sub 2}O{sub 3}-SO{sub 3} formation. 7 refs., 7 tabs.

  5. The effect of porosity on drug release kinetics from vancomycin microsphere/calcium phosphate cement composites.

    Science.gov (United States)

    Schnieders, Julia; Gbureck, Uwe; Vorndran, Elke; Schossig, Michael; Kissel, Thomas

    2011-11-01

    The influence of porosity on release profiles of antibiotics from calcium phosphate composites was investigated to optimize the duration of treatment. We hypothesized, that by the encapsulation of vancomycin-HCl into biodegradable microspheres prior admixing to calcium phosphate bone cement, the influence of porosity of the cement matrix on vancomycin release could be reduced. Encapsulation of vancomycin into a biodegradable poly(lactic co-glycolic acid) copolymer (PLGA) was performed by spray drying; drug-loaded microparticles were added to calcium phosphate cement (CPC) at different powder to liquid ratios (P/L), resulting in different porosities of the cement composites. The effect of differences in P/L ratio on drug release kinetics was compared for both the direct addition of vancomycin-HCl to the cement liquid and for cement composites modified with vancomycin-HCl-loaded microspheres. Scanning electron microscopy (SEM) was used to visualize surface and cross section morphology of the different composites. Brunauer, Emmett, and Teller-plots (BET) was used to determine the specific surface area and pore size distribution of these matrices. It could be clearly shown, that variations in P/L ratio influenced both the porosity of cement and vancomycin release profiles. Antibiotic activity during release study was successfully measured using an agar diffusion assay. However, vancomycin-HCl encapsulation into PLGA polymer microspheres decreased porosity influence of cement on drug release while maintaining antibiotic activity of the embedded substance.

  6. Influence of polymeric additives on the cohesion and mechanical properties of calcium phosphate cements.

    Science.gov (United States)

    An, Jie; Wolke, Joop G C; Jansen, John A; Leeuwenburgh, Sander C G

    2016-03-01

    To expand the clinical applicability of calcium phosphate cements (CPCs) to load-bearing anatomical sites, the mechanical and setting properties of CPCs need to be improved. Specifically, organic additives need to be developed that can overcome the disintegration and brittleness of CPCs. Hence, we compared two conventional polymeric additives (i.e. carboxylmethylcellulose (CMC) and hyaluronan (HA)) with a novel organic additive that was designed to bind to calcium phosphate, i.e. hyaluronan-bisphosphonate (HABP). The unmodified cement used in this study consisted of a powder phase of α-tricalcium phosphate (α-TCP) and liquid phase of 4% NaH2PO4·2H2O, while the modified cements were fabricated by adding 0.75 or 1.5 wt% of the polymeric additive to the cement. The cohesion of α-TCP was improved considerably by the addition of CMC and HABP. None of the additives improved the compression and bending strength of the cements, but the addition of 0.75% HABP resulted into a significantly increased cement toughness as compared to the other experimental groups. The stimulatory effects of HABP on the cohesion and toughness of the cements is hypothesized to derive from the strong affinity between the polymer-grafted bisphosphonate ligands and the calcium ions in the cement matrix.

  7. Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol.

    Science.gov (United States)

    Huang, Ming-Hsien; Shen, Yu-Fang; Hsu, Tuan-Ti; Huang, Tsui-Hsien; Shie, Ming-You

    2016-08-01

    Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0-10mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic.

  8. Fabrications of zinc-releasing biocement combining zinc calcium phosphate to calcium phosphate cement.

    Science.gov (United States)

    Horiuchi, Shinya; Hiasa, Masahiro; Yasue, Akihiro; Sekine, Kazumitsu; Hamada, Kenichi; Asaoka, Kenzo; Tanaka, Eiji

    2014-01-01

    Recently, zinc-releasing bioceramics have been the focus of much attention owing to their bone-forming ability. Thus, some types of zinc-containing calcium phosphate (e.g., zinc-doped tricalcium phosphate and zinc-substituted hydroxyapatite) are examined and their osteoblastic cell responses determined. In this investigation, we studied the effects of zinc calcium phosphate (ZCP) derived from zinc phosphate incorporated into calcium phosphate cement (CPC) in terms of its setting reaction and MC3T3-E1 osteoblast-like cell responses. Compositional analysis by powder X-ray diffraction analysis revealed that HAP crystals were precipitated in the CPC containing 10 or 30wt% ZCP after successfully hardening. However, the crystal growth observed by scanning electron microscopy was delayed in the presence of additional ZCP. These findings indicate that the additional zinc inhibits crystal growth and the conversion of CPC to the HAP crystals. The proliferation of the cells and alkaline phosphatase (ALP) activity were enhanced when 10wt% ZCP was added to CPC. Taken together, ZCP added CPC at an appropriate fraction has a potent promotional effect on bone substitute biomaterials.

  9. Evaluation of Calcium Phosphate Cement As a Root Canal Sealer Filling Material

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Calcium phosphate cement for root end sealing was obtained by mixing α-tricalcium phosphate and additives with an aqueous solution of citric. Powder and liquid were mixed at a ratio of 1.25g/mL. The biocompatibility of this material was investigated primarily by subcutaneous implantation tests. Then calcium phosphate cement was used to fill three adult dogs' root canal, both calcium hydroxide paste and hydroxyapatite paste as control. The animals were killed at 4,12,20 weeks postoperatively respectively. The effects of different materials on the apical closure, restoration of periapical tissues and adaptability to the dentinal surface were examined by optical and electronic microscope. The observation at 20 weeks shows that the calcium phosphate cement has the potentialities of being a root canal sealer filling material available for pulpless teeth with open-apex and destructive periapical tissue.

  10. 硫铝酸盐-铝酸盐水泥体系高水充填材料的研制试验%Experimental study on high-moisture filling material prepared with sulphoaluminate-aluminate cement

    Institute of Scientific and Technical Information of China (English)

    李建杰; 丁全录; 佘海龙

    2012-01-01

    The properties of the high-moisture filling material prepared with sulphoaluminate-aluminate cement were studied by determing the setting time of every single slurry,setting time of the filling material,and the compressive strength of cement pastes.The results show that subsituting 5%~30% sulphoaluminate cement clinker(42.5 MPa)with the coarser aluminate cementclinker has effect on setting time of the filling material,and subtly decreases the early age(2 h) strength,and the late age strength will be largely increased,the late age(28 d) strength even exceeds that of the filling material without substitution of sulphoaluminate cement clinker to 48.9%.The high-moisture filling material prepared with subsituting 5%~30% sulphoaluminate cement clinker(42.5 MPa) with the coarser aluminate cement clinker can meet with the requirements of the standard of MT/T 420—1995.%研究了用硫铝酸盐-铝酸盐水泥体系制备高水充填材料的方法,进行了单浆凝结时间、胶凝时间、抗压强度的测试。结果表明,用细度较粗的铝酸盐水泥熟料替代5%~30%的强度级别42.5 MPa硫铝酸盐水泥的熟料制备高水充填材料,对材料的胶凝时间有所影响,使材料的2 h强度稍有降低,但可大幅度提高材料的后期强度,28 d抗压强度最大可提高48.9%,可以制备出满足MT/T 420—1995标准要求的高水充填材料。

  11. Calcium phosphate cement augmentation of cancellous bone screws can compensate for the absence of cortical fixation.

    Science.gov (United States)

    Stadelmann, Vincent A; Bretton, Elise; Terrier, Alexandre; Procter, Philip; Pioletti, Dominique P

    2010-11-16

    An obvious means to improve the fixation of a cancellous bone screw is to augment the surrounding bone with cement. Previous studies have shown that bone augmentation with Calcium Phosphate (CaP) cement significantly improves screw fixation. Nevertheless, quantitative data about the optimal distribution of CaP cement is not available. The present study aims to show the effect of cement distribution on the screw fixation strength for various cortical thicknesses and to determine the conditions at which cement augmentation can compensate for the absence of cortical fixation in osteoporotic bone. In this study, artificial bone materials were used to mimic osteoporotic cancellous bone and cortical bone of varying thickness. These bone constructs were used to test the fixation strength of cancellous bone screws in different cortical thicknesses and different cement augmentation depths. The cement distribution was measured with microCT. The maximum pullout force was measured experimentally. The microCT analysis revealed a pseudo-conic shape distribution of the cement around the screws. While the maximum pullout strength of the screws in the artificial bone only was 30±7N, it could increase up to approximately 1000N under optimal conditions. Cement augmentation significantly increased pullout force in all cases. The effect of cortical thickness on pullout force was reduced with increased cement augmentation depth. Indeed, cement augmentation without cortical fixation increased pullout forces over that of screws without cement augmentation but with cortical fixation. Since cement augmentation significantly increased pullout force in all cases, we conclude that the loss of cortical fixation can be compensated by cement augmentation.

  12. In vitro biodegradation of three brushite calcium phosphate cements by a macrophage cell-line.

    Science.gov (United States)

    Xia, Zhidao; Grover, Liam Michael; Huang, Yizhong; Adamopoulos, Iannis E; Gbureck, Uwe; Triffitt, James T; Shelton, Richard M; Barralet, Jake E

    2006-09-01

    Depending upon local conditions, brushite (CaHPO4 x 2 H2O) cements may be largely resorbed or (following hydrolysis to hydroxyapatite) remain stable in vivo. To determine which factors influence cement resorption, previous studies have investigated the solution-driven degradation of brushite cements in vitro in the absence of any cells. However, the mechanism of cell-mediated biodegradation of the brushite cement is still unknown. The aim of the current study was to observe the cell-mediated biodegradation of brushite cement formulations in vitro. The cements were aged in the presence of a murine cell line (RAW264.7), which had the potential to form osteoclasts in the presence of the receptor for nuclear factor kappa B ligand (RANKL) in vitro, independently of macrophage colony stimulating factor (M-CSF). The cytotoxicity of the cements on RAW264.7 cells and the calcium and phosphate released from materials to the culture media were analysed. Scanning electron microscopy (SEM) and focused ion beam (FIB) microscopy were used to characterise the ultrastructure of the cells. The results showed that the RAW264.7 cell line formed multinucleated TRAP positive osteoclast-like cells, capable of ruffled border formation and lacunar resorption on the brushite calcium phosphate cement in vitro. In the osteoclast-like cell cultures, ultrastructural analysis by SEM revealed phenotypic characteristics of osteoclasts including formation of a sealing zone and ruffled border. Penetration of the surface of the cement, was demonstrated using FIB, and this showed the potential demineralising effect of the cells on the cements. This study has set up a useful model to investigate the cell-mediated cement degradation in vitro.

  13. Molecular mechanisms of crystallization impacting calcium phosphate cements

    OpenAIRE

    2010-01-01

    The biomineral calcium hydrogen phosphate dihydrate (CaHPO4·2H2O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite’s excellent biocompatibility, can be used to gr...

  14. Preparation, physical-chemical characterization, and cytocompatibility of polymeric calcium phosphate cements.

    Science.gov (United States)

    Khashaba, Rania M; Moussa, Mervet; Koch, Christopher; Jurgensen, Arthur R; Missimer, David M; Rutherford, Ronny L; Chutkan, Norman B; Borke, James L

    2011-01-01

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

  15. Si-TCP synthesized from "Mg-free" reagents employed as calcium phosphate cement

    Directory of Open Access Journals (Sweden)

    Mariana Motisuke

    2012-08-01

    Full Text Available The influence of silicon doping on calcium phosphate cement were explored in this work. α-TCP and Si-α-TCP were prepared by solid state reaction employing "Mg-free" CaHPO4, CaCO3 and CaSiO3 as precursors. It was possible to obtain TCP powders with low contents of β phase as contaminant. Cement liquid phase was an aqueous solution containing 2.5 wt. (% of Na2HPO4 and 1.5 wt. (% of citric acid. The liquid-to-powder ratio was 0.6 mL.g-1. Chemical, physical and mechanical properties of the cement samples were determined by means of XRD, FTIR, XRF, compressive strength and SEM. The calcium phosphate cements obtained achieved satisfactory properties; however, Si-α-TCP presented a decrease on the rate of setting reaction.

  16. A hazardous waste from secondary aluminium metallurgy as a new raw material for calcium aluminate glasses.

    Science.gov (United States)

    López-Delgado, Aurora; Tayibi, Hanan; Pérez, Carlos; Alguacil, Francisco José; López, Félix Antonio

    2009-06-15

    A solid waste coming from the secondary aluminium industry was successfully vitrified in the ternary CaO-Al(2)O(3)-SiO(2) system at 1500 degrees C. This waste is a complex material which is considered hazardous because of its behaviour in the presence of water or moisture. In these conditions, the dust can generate gases such as H(2), NH(3), CH(4), H(2)S, along with heat and potential aluminothermy. Only silica sand and calcium carbonate were added as external raw materials to complete the glasses formula. Different nominal compositions of glasses, with Al(2)O(3) ranging between 20% and 54%, were studied to determine the glass forming area. The glasses obtained allow the immobilisation of up to 75% of waste in a multicomponent oxide system in which all the components of the waste are incorporated. The microhardness Hv values varied between 6.05 and 6.62GPa and the linear thermal expansion coefficient, alpha, varied between (62 and 139)x10(-7)K(-1). Several glasses showed a high hydrolytic resistance in deionised water at 98 degrees C.

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

    Science.gov (United States)

    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.

  18. In vitro aging of a calcium phosphate cement.

    Science.gov (United States)

    Bohner, M; Merkle, H P; Lemaître, J

    2000-03-01

    Cement samples made of beta-tricalcium phoshate (beta-TCP), phosphoric acid (PA) and water mixtures were incubated in several aqueous solutions to determine their stability over time. The effects of the cement composition and the incubating temperature were investigated in more detail. The cement samples contained mostly dicalcium phosphate dihydrate (DCPD) and remnants of beta-TCP crystals. Depending on the initial cement composition, a certain amount of dicalcium phosphate (DCP) crystals were formed. The larger the initial PA concentration, the larger the DCP amount. After setting, the cement composition was stable for at least 16 days up to 60 degrees C. Above that temperature, the DCPD crystals decomposed into DCP crystals. The latter reaction provoked a decrease of the pH of the incubation solution, phenomenon expected for a cement sample containing an excess of PA. As the cement samples contained an excess of beta-TCP, it was postulated that beta-TCP crystals became so covered by DCP or DCPD crystals during setting that the setting reaction was stopped prematurely. The latter phenomenon gave a good explanation for the low pH values measured in the incubation solutions.

  19. Effect of physicochemical properties of a cement based on silicocarnotite/calcium silicate on in vitro cell adhesion and in vivo cement degradation.

    Science.gov (United States)

    Aparicio, Julia Lucas; Rueda, Carmen; Manchón, Ángel; Ewald, Andrea; Gbureck, Uwe; Alkhraisat, Mohammad Hamdan; Jerez, Luis Blanco; Cabarcos, Enrique López

    2016-08-02

    A silicon calcium phosphate cement (Si-CPC) was developed to produce a composite of calcium phosphate and calcium silicate. The silicon cements prepared with low silicon (Si) content were composed of crystalline phases of brushite and silicocarnotite. However, the cements prepared with high Si content were mainly composed of amorphous phases of silicocarnotite, hydroxyapatite and calcium silicate. The cement porosity was about 40% with a shift of the average pore diameter to the nanometric range with increasing Si content. Interestingly, this new cement system provides a matrix with a high specific surface area of up to 29 m(2) g(-1). The cytocompatibility of the new Si-doped cements was tested with a human osteoblast-like cell line (MG-63) showing an enhancement of cell proliferation (up to threefold) when compared with unsubstituted material. Cements with a high silica content also improved the cell attachment. The in vivo results indicated that Si-CPCs induce the formation of new bone tissue, and modify cement resorption. We conclude that this cement provides an optimal environment to enhance osteoblast growth and proliferation that could be of interest in bone engineering.

  20. CALCIUM ORTHOPHOSPHATES HYDRATES: FORMATION, STABILITY AND INFLUENCE ON STANDARD PROPERTIES OF PORTLAND CEMENT

    Directory of Open Access Journals (Sweden)

    Kaziliunas A.

    2013-12-01

    Full Text Available Preparation of phosphogypsum to produce the binders requires a much higher input than preparation of natural gypsum stone. This makes it uncompetitive material. The investigations presented therein are meant to reduce this input by looking for the ways of rendering impurities harmless. Soluble acid orthophosphates are the main harmful impurity of phosphogypsum. The studies show that dry insoluble calcium orthophosphates hydrates (1.09 % and 2.18 % P2O5 in gypsum have little effect on W/C, setting times and soundness of Portland cement pastes. Insoluble calcium orthophosphates hydrates {CaHPO4∙2H2O, Ca8(HPO42(PO44∙5H2O and Ca9(HPO4(PO45(OH∙4H2O} formed in acidic medium (pH = 4.2 - 5.9 have been destroyed in alkaline medium and reduce standard compressive strength of cement up to 28 %. Calcium orthophosphates hydrates of hydroxyapatite group are stable in alcaline medium, while in dry state they reduce the standard compressive strength of cement until 10 %, but their suspensions prolong setting times of Portland cement as soluble orthophosphates – 2 - 3 times. Alkalis in cement increase pH of paste, but do not change the process of formation of calcium orthophosphates hydrates of hydroxyapatite group: it takes place through an intermediate phase - CaHPO4·2H2O, whose transformation into apatite lasts for 2 - 3 months.

  1. Incorporation of a controlled-release glass into a calcium phosphate cement.

    Science.gov (United States)

    Khairoun, I; Boltong, M G; Gil, F J; Driessens, F C; Planell, J A; Seijas, M M; Martínez, S

    1999-04-01

    A so-called controlled-release glass was synthesized occurring in the system CaO-Na2O-P2O5. A certain sieve fraction of this glass was incorporated in a calcium phosphate cement, of which the powder contained alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate (DCP) and precipitated hydroxyapatite (HA). The glass appeared to retard the cement setting slightly and it reduced considerably the compressive strength after aging in aqueous solutions which were continuously refreshed. Scanning electron microscope (SEM) pictures and X-ray diffraction (XRD) patterns of the samples after 5 weeks of aging showed that the glass was not dissolved but that large brushite crystals were formed. Thereby, aging in CaCl2 solutions resulted in more brushite formation than aging in NaCl solutions. The brushite crystals did not reinforce the cement. Neither was the aged glass-containing cement weaker than it was before the brushite formation right after complete setting. In conclusion, the incorporation of controlled-release glasses into a calcium phosphate cement and subsequent aging in aqueous solutions did not result in the formation of macropores in the cement structure, but that of brushite crystals. This incorporation reduced the compressive strength of the cement considerably.

  2. Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ming-Hsien [Institute of Oral Science, Chung Shan Medical University, Taichung City, Taiwan (China); Shen, Yu-Fang; Hsu, Tuan-Ti [3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan (China); Huang, Tsui-Hsien [School of Dentistry, Chung Shan Medical University, Taichung City, Taiwan (China); Department of Stomatology, Chung Shan Medical University Hospital, Taichung City, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan (China)

    2016-08-01

    Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0–10 mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic. - Highlights: • The hinokitiol-modified CS up-regulation of odontogenic of hDPCs. • Promoted proliferation of hDPCs on hinokitiol-modified CS. • The hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility. • The hinokitiol-modified CS up-regulation of odontogenic of hPDLs.

  3. Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone

    DEFF Research Database (Denmark)

    Moesgaard, M; Poulsen, Søren Lundsted; Herfort, D;

    2012-01-01

    M. MOESGAARD, S.L. POULSEN, D. HERFORT, M. STEENBERG, L.F. KIRKEGAARD, J. SKIBSTED, Y. YUE, Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone, Journal of the American Ceramic Society 95, 403 – 409 (2012).......M. MOESGAARD, S.L. POULSEN, D. HERFORT, M. STEENBERG, L.F. KIRKEGAARD, J. SKIBSTED, Y. YUE, Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone, Journal of the American Ceramic Society 95, 403 – 409 (2012)....

  4. Improvement of in vitro physicochemical properties and osteogenic activity of calcium sulfate cement for bone repair by dicalcium silicate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chun-Cheng [School of Dentistry, Chung Shan Medical University, Taichung City 402, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung City 402, Taiwan (China); Wang, Chien-Wen [Department of Biomedical Engineering, National Cheng Kung University, Tainan City 701, Taiwan (China); Hsueh, Nai-Shuo [Institute of Oral Science, Chung Shan Medical University, Taichung City 402, Taiwan (China); Ding, Shinn-Jyh, E-mail: sjding@csmu.edu.tw [School of Dentistry, Chung Shan Medical University, Taichung City 402, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung City 402, Taiwan (China); Institute of Oral Science, Chung Shan Medical University, Taichung City 402, Taiwan (China)

    2014-02-05

    Highlights: • Dicalcium silicate can improve osteogenic activity of calcium sulfate cement. • The higher the calcium sulfate content, the shorter the setting time in the composite cement. • The results were useful for designing calcium-based cement with optimal properties. -- Abstract: An ideal bone graft substitute should have the same speed of degradation as formation of new bone tissue. To improve the properties of calcium sulfate hemihydrate (CSH) featured for its rapid resorption, a low degradation material of dicalcium silicate (DCS) was added to the CSH cement. This study examined the effect of DCS (20, 40, 60 and 80 wt%) on the in vitro physicochemical properties and osteogenic activities of the calcium-based composite cements. The diametral tensile strength, porosity and weight loss of the composite cements were evaluated before and after soaking in a simulated body fluid (SBF). The osteogenic activities, such as proliferation, differentiation and mineralization, of human mesenchymal stem cells (hMSCs) seeded on cement surfaces were also examined. As a result, the greater the DCS amount, the higher the setting time was in the cement. Before soaking in SBF, the diametral tensile strength of the composite cements was decreased due to the introduction of DCS. On 180-day soaking, the composite cements containing 20, 40, 60 and 80 wt% DCS lost 80%, 69%, 61% and 44% in strength, respectively. Regarding in vitro bioactivity, the DCS-rich cements were covered with clusters of apatite spherulites after soaking for 7 days, while there was no formation of apatite spherulites on the CSH-rich cement surfaces. The presence of DCS could reduce the degradation of the CSH cements, as evidenced in the results of weight loss and porosity. More importantly, DCS may promote effectively the cell proliferation, proliferation and mineralization. The combination of osteogenesis of DCS and degradation of CSH made the calcium-based composite cements an attractive choice for

  5. Effect of the calcium to phosphate ratio of tetracalcium phosphate on the properties of calcium phosphate bone cement.

    Science.gov (United States)

    Burguera, Elena F; Guitian, Francisco; Chow, Laurence C

    2008-06-01

    Six different tetracalcium phosphate (TTCP) products were synthesized by solid state reaction at high temperature by varying the overall calcium to phosphate ratio of the synthesis mixture. The objective was to evaluate the effect of the calcium to phosphate ratio on a TTCP-dicalcium phosphate dihydrate (DCPD) cement. The resulting six TTCP-DCPD cement mixtures were characterized using X-ray diffraction analysis, scanning electron microscopy, and pH measurements. Setting times and compressive strength (CS) were also measured. Using the TTCP product with a Ca/P ratio of 2.0 resulted in low strength values (25.61 MPa) when distilled water was used as the setting liquid, even though conversion to hydroxyapatite was not prevented, as confirmed by X-ray diffraction. The suspected CaO presence in this TTCP may have affected the cohesiveness of the cement mixture but not the cement setting reaction, however no direct evidence of CaO presence was found. Lower Ca/P ratio products yielded cements with CS values ranging from 46.7 MPa for Ca/P ratio of 1.90 to 38.32 MPa for Ca/P ratio of 1.85. When a dilute sodium phosphate solution was used as the setting liquid, CS values were 15.3% lower than those obtained with water as the setting liquid. Setting times ranged from 18 to 22 min when water was the cement liquid and from 7 to 8 min when sodium phosphate solution was used, and the calcium to phosphate ratio did not have a marked effect on this property.

  6. Physicochemical properties and biocompatibility of chitosan oligosaccharide/gelatin/calcium phosphate hybrid cements

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Ting-Yi [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taichung 406, Taiwan (China); Ho, Chia-Che [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Chen, David Chan-Hen [Institute of Veterinary Microbiology, National Chung-Hsing University, Taichung 402, Taiwan (China); Lai, Meng-Heng [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Ding, Shinn-Jyh, E-mail: sjding@csmu.edu.tw [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Department of Dentistry, Chung-Shan Medical University Hospital, Taichung 402, Taiwan (China)

    2010-04-15

    A bone substitute material was developed consisting of a chitosan oligosaccharide (COS) solution in a liquid phase and gelatin (GLT) containing calcium phosphate powder in a solid phase. The physicochemical and biocompatible properties of the hybrid cements were evaluated. The addition of COS to cement did not affect the setting time or diametral tensile strength of the hybrid cements, whereas GLT significantly prolonged the setting time and decreased the strength slightly. The setting reaction was inhibited by the addition of GLT to the initial mixture, but not by COS. However, the presence of GLT appreciably improved the anti-washout properties of the hybrid cement compared with COS. COS may promote the cement's biocompatibility as an approximate twofold increase in cell proliferation for 10% COS-containing cements was observed on day 3 as compared with the controls. The combination of GLT and COS was chosen due to the benefits achieved from several synergistic effects and for their clinical applications. Cement with 5% GLT and 10% COS may be a better choice among cements in terms of anti-washout properties and biological activity.

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

    Science.gov (United States)

    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.

  8. Factors influencing calcium phosphate cement shelf-life.

    Science.gov (United States)

    Gbureck, Uwe; Dembski, Sofia; Thull, Roger; Barralet, Jake E

    2005-06-01

    Long-term stability during storage (shelf-life) is one major criterion for the use of a material as medical device. This study aimed to investigate the ageing process of beta-tricalcium phosphate/monocalcium phosphate cement powders when stored in sealed containers at ambient conditions. This kind of cement type is of interest because it is forming dicalcium phosphate dihydrate (brushite) when set, which is in contrast to hydroxyapatite resorbable in physiological conditions. The stability of cements was checked by either measuring the phase composition of powders as well as the setting time and compressive strength when mixed with sodium citrate as liquid. Critical factors influencing ageing were found to be temperature, humidity and the mixing regime of the powders. Mechanically mixed cement powders which were stored in normal laboratory atmosphere (22 degrees C, 60% rel. humidity) converted to dicalcium phosphate anhydrous (monetite) within a few days; this could be mechanistically related to a dissolution/precipitation process since humidity condensed on the particles' surfaces and acted as reaction medium. Various storage conditions were found to be effective in prolonging cement stability which were in order of effectiveness: adding solid citric acid retardant>dry argon atmosphere=gentle mixing (minimal mechanical energy input) low temperature.

  9. Preparation and characterization of a novel injectable strontium-containing calcium phosphate cement with collagen

    Directory of Open Access Journals (Sweden)

    Zhou Ziqiang

    2015-07-01

    Full Text Available Purpose: To develop a novel injectable strontium-containing calcium phosphate cement with collagen. Methods: A novel calcium phosphate bone cement (CPC was prepared with the addition of strontium element, collagenⅠ, and modified starch; the injectability, solidification time, microstructure, phase composition, compressive strength, anti-collapsibility and histological properties of material were evaluated. Results: The results showed that the material could be injected with an excellent performance; the modified starch significantly improved the anti-washout property of cement; with the liquid to solid ratio of 0.3, the largest compressive strength of cement was obtained (48.0 MPa ± 2.3 MPa; histological examination of repair tissue showed that the bone was repaired after 16 weeks; the degradation of cement was consistent with the new bone growth. Conclusion: A novel injectable collagen-strontium-containing CPC with excellent compressive strength and suitable setting time was prepared, with addition of modified starch. The CPC showed a good antiwashout property and the degradation time of the cement met with the new bone growing. This material is supposed to be used in orthopedic and maxillofacial surgery for bone defects.

  10. Incorporation of biodegradable electrospun fibers into calcium phosphate cement for bone regeneration.

    NARCIS (Netherlands)

    Zuo, Y.; Yang, F.; Wolke, J.G.C.; Li, Yubao; Jansen, J.A.

    2010-01-01

    Inherent brittleness and slow degradation are the major drawbacks for the use of calcium phosphate cements (CPCs). To address these issues, biodegradable ultrafine fibers were incorporated into the CPC in this study. Four types of fibers made of poly(epsilon-caprolactone) (PCL) (PCL12: 1.1 microm, P

  11. Biocompatibility and degradation of poly(DL-lactic-co-glycolic acid)/calcium phosphate cement composites

    NARCIS (Netherlands)

    Ruhe, P.Q.; Hedberg, E.L.; Padron, N.T.; Spauwen, P.H.M.; Jansen, J.A.; Mikos, A.G.

    2005-01-01

    Injectable calcium phosphate (Ca-P) cement materials exhibit favorable osteocompatible behavior but are resorbed slowly because of a lack of a bone ingrowth-enabling macroporosity. In this study, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles (average size 66 +/- 25 microm) were incorporated

  12. Porosity distribution in root canals filled with gutta percha and calcium silicate cement

    NARCIS (Netherlands)

    Moinzadeh, A.T.; Zerbst, W.; Boutsioukis, C.; Shemesh, H.; Zaslansky, P.

    2015-01-01

    Objective Gutta percha is commonly used in conjunction with a sealer to produce a fluid-tight seal within the root canal fillings. One of the most commonly used filling methods is lateral compaction of gutta percha coupled with a sealer such as calcium silicate cement. However, this technique may re

  13. Phase composition, mechanical performance and in vitro biocompatibility of hydraulic setting calcium magnesium phosphate cement.

    Science.gov (United States)

    Klammert, Uwe; Reuther, Tobias; Blank, Melanie; Reske, Isabelle; Barralet, Jake E; Grover, Liam M; Kübler, Alexander C; Gbureck, Uwe

    2010-04-01

    Brushite (CaHPO(4) x 2H(2)O)-forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. However, their short setting times and low mechanical strengths limit broad clinical application. In this study, we showed that a significant improvement of these properties of brushite cement could be achieved by the use of magnesium-substituted beta-tricalcium phosphate with the general formula Mg(x)Ca((3-x))((PO(4))(2) with 0 cement reactants. The incorporation of magnesium ions increased the setting times of cements from 2 min for a magnesium-free matrix to 8-11 min for Mg(2.25)Ca(0.75)(PO(4))(2) as reactant. At the same time, the compressive strength of set cements was doubled from 19 MPa to more than 40 MPa after 24h wet storage. Magnesium ions were not only retarding the setting reaction to brushite but were also forming newberyite (MgHPO(4) x 3H(2)O) as a second setting product. The biocompatibility of the material was investigated in vitro using the osteoblast-like cell line MC3T3-E1. A considerable increase of cell proliferation and expression of alkaline phosphatase, indicating an osteoblastic differentiation, could be noticed. Scanning electron microscopy analysis revealed an obvious cell growth on the surface of the scaffolds. Analysis of the culture medium showed minor alterations of pH value within the physiological range. The concentrations of free calcium, magnesium and phosphate ions were altered markedly due to the chemical solubility of the scaffolds. We conclude that the calcium magnesium phosphate (newberyite) cements have a promising potential for their use as bone replacement material since they provide a suitable biocompatibility, an extended workability and improved mechanical performance compared with brushite cements.

  14. Influence of sodium borate on the early age hydration of calcium sulfoaluminate cement

    Energy Technology Data Exchange (ETDEWEB)

    Champenois, Jean-Baptiste; Dhoury, Mélanie [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France); Cau Dit Coumes, Céline, E-mail: celine.cau-dit-coumes@cea.fr [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France); Mercier, Cyrille [LMCPA, Université de Valenciennes et du Hainaut Cambrésis, 59600 Maubeuge (France); Revel, Bertrand [Centre Commun de Mesure RMN, Université Lille1 Sciences Technologies, Cité Scientifique, 59655 Villeneuve d' Ascq Cedex (France); Le Bescop, Patrick [CEA, DEN, DPC, SECR, F-91192 Gif-sur-Yvette (France); Damidot, Denis [Ecole des Mines de Douai, LGCgE-GCE, 59508 Douai (France)

    2015-04-15

    Calcium sulfoaluminate (CSA) cements are potential candidates for the conditioning of radioactive wastes with high sodium borate concentrations. This work thus investigates early age hydration of two CSA cements with different gypsum contents (0 to 20%) as a function of the mixing solution composition (borate and NaOH concentrations). Gypsum plays a key role in controlling the reactivity of cement. When the mixing solution is pure water, increasing the gypsum concentration accelerates cement hydration. However, the reverse is observed when the mixing solution contains sodium borate. Until gypsum exhaustion, the pore solution pH remains constant at ~ 10.8, and a poorly crystallized borate compound (ulexite) precipitates. A correlation is established between this transient precipitation and the hydration delay. Decreasing the gypsum content in the binder, or increasing the sodium content in the mixing solution, are two ways of reducing the stability of ulexite, thus decreasing the hydration delay.

  15. Polymeric-Calcium Phosphate Cement Composites-Material Properties: In Vitro and In Vivo Investigations

    Science.gov (United States)

    Khashaba, Rania M.; Moussa, Mervet M.; Mettenburg, Donald J.; Rueggeberg, Frederick A.; Chutkan, Norman B.; Borke, James L.

    2010-01-01

    New polymeric calcium phosphate cement composites (CPCs) were developed. Cement powder consisting of 60 wt% tetracalcium phosphate, 30 wt% dicalcium phosphate dihydrate, and 10 wt% tricalcium phosphate was combined with either 35% w/w poly methyl vinyl ether maleic acid or polyacrylic acid to obtain CPC-1 and CPC-2. The setting time and compressive and diametral tensile strength of the CPCs were evaluated and compared with that of a commercial hydroxyapatite cement. In vitro cytotoxicity and in vivo biocompatibility of the two CPCs and hydroxyapatite cement were assessed. The setting time of the cements was 5–15 min. CPC-1 and CPC-2 showed significantly higher compressive and diametral strength values compared to hydroxyapatite cement. CPC-1 and CPC-2 were equivalent to Teflon controls after 1 week. CPC-1, CPC-2, and hydroxyapatite cement elicited a moderate to intense inflammatory reaction at 7 days which decreased over time. CPC-1 and CPC-2 show promise for orthopedic applications. PMID:20811498

  16. Polymeric-Calcium Phosphate Cement Composites-Material Properties: In Vitro and In Vivo Investigations

    Directory of Open Access Journals (Sweden)

    Rania M. Khashaba

    2010-01-01

    Full Text Available New polymeric calcium phosphate cement composites (CPCs were developed. Cement powder consisting of 60 wt% tetracalcium phosphate, 30 wt% dicalcium phosphate dihydrate, and 10 wt% tricalcium phosphate was combined with either 35% w/w poly methyl vinyl ether maleic acid or polyacrylic acid to obtain CPC-1 and CPC-2. The setting time and compressive and diametral tensile strength of the CPCs were evaluated and compared with that of a commercial hydroxyapatite cement. In vitro cytotoxicity and in vivo biocompatibility of the two CPCs and hydroxyapatite cement were assessed. The setting time of the cements was 5–15 min. CPC-1 and CPC-2 showed significantly higher compressive and diametral strength values compared to hydroxyapatite cement. CPC-1 and CPC-2 were equivalent to Teflon controls after 1 week. CPC-1, CPC-2, and hydroxyapatite cement elicited a moderate to intense inflammatory reaction at 7 days which decreased over time. CPC-1 and CPC-2 show promise for orthopedic applications.

  17. Phase transformations, microstructure formation and in vitro osteoblast response in calcium silicate/brushite cement composites.

    Science.gov (United States)

    Sopcak, T; Medvecky, L; Giretova, M; Kovalcikova, A; Stulajterova, R; Durisin, J

    2016-08-10

    Self-setting simple calcium silicate/brushite (B) biocements with various Ca/P ratios were prepared by mutual mixing of both monocalcium silicate hydrate (CSH) or β-wollastonite (woll) powders with B and the addition of 2 wt% NaH2PO4 solution as a hardening liquid. The phase composition of the final composites and the texture of the surface calcium phosphate/silica layer were controlled by the starting Ca/P ratio in composites and the pH during setting. It was verified that the presence of continuous bone-like calcium phosphate coating on the surface of the samples was not essential for in vitro osteoblast proliferation. The nanocrystalline calcium deficient hydroxyapatite and amorphous silica were found as the main setting products in composite mixtures with a Ca/P ratio close to the region of the formation of deficient hydroxyapatite-like calcium phosphates. No CSH phase with a lower Ca/Si ratio was identified after transformation. The results confirmed a small effect of the monocalcium silicate addition on the compressive strength (CS) of cements up to 30 wt% (around 20-25 MPa) and a significant rise of the value in 50 woll/B cement (65 MPa). The final setting times of the cement composites varied between 5 and 43 min depending on the P/L ratio and the type of monocalcium silicate phase in the cement mixture. 10CSH/B and 50 woll/B cements with different textures but free of both the needle-like and perpendicularly-oriented hydroxyapatite particles on the surface of the samples had low cytotoxicity.

  18. Cytotoxicity of calcium enriched mixture cement compared with mineral trioxide aggregate and intermediate restorative material.

    Science.gov (United States)

    Mozayeni, Mohammad A; Milani, Amin S; Marvasti, Laleh A; Asgary, Saeed

    2012-08-01

    Calcium enriched mixture (CEM) cement has been recently invented by the last author. It is composed of calcium oxide, calcium phosphate, calcium silicate and calcium sulphate; however, it has a different chemical composition to mineral trioxide aggregate (MTA). The purpose of this ex vivo study was to investigate the cytotoxicity of CEM cement, and compare it with intermediate restorative material (IRM) and MTA. The materials were tested in fresh and set states on L929 fibroblasts to assess their cytotoxicity. The cell viability responses were evaluated with methyl-tetrazolium bromide assay and Elisa reader at 1, 24 and 168 h (7 days). The tested materials were eluted with L929 culture medium according to international standard organisation 109935 standard. Distilled water and culture medium served as positive and negative controls, respectively. Differences in cytotoxicity were evaluated by one-way anova and t-tests. The cytotoxicity of the materials was statistically different at the three time intervals (P IRM subgroups were the most cytotoxic root-end/dental material (P IRM because of lower cytotoxicity. CEM cement also has good biocompatibility as well as lower estimated cost to MTA and seems to be a promising dental material.

  19. The Mechanical Properties and Hydration Characteristics of Cement Pastes Containing Added-calcium Coal Gangue

    Institute of Scientific and Technical Information of China (English)

    LI Dongxu; SONG Xuyan

    2008-01-01

    The mechanical properties of several kinds of coal gangue calcined with limestone were Researched so as to find the optimum way of calcinations with limestone. Mierostructure and property of hydration process of cement pastes containing added-calcium coal gangue were analyzed by means of scanning electron microscope (SEM) and method of mercury in trusion poremeasurement (MIP), etc. The experiment can approve those results: when proper amounst of gypsum and fluorite were taken as mineralizers in the course of calcinations of added-calcium coal gangue, activity of coal gangue can be effectively improved. The results of mechanical property and structural characteristic such as hydration process, hydration product and microstructure etc. of cement pastes containing added-calcium coal gangue are consistent.

  20. 铝酸钙粉矿物相红外光谱及铝溶出率分析%Analysis on infra-red spectrum of mineral phase of calcium aluminate powder and Al2O3 dissolution rate

    Institute of Scientific and Technical Information of China (English)

    黄志刚; 章兴华; 陆洋; 胡智; 杨鸿波; 舒海霞; 朱守平

    2012-01-01

    铝酸钙粉的结构会受到原料变化的强烈影响.对加入活化剂与未加入活化剂生产的铝酸钙粉进行了相关的结构鉴定与溶出率测定.X射线衍射及热重分析证实,加入活化剂的铝酸钙粉矿物相中含有卤化物,其中矿物相CaAl3XO7可能部分水解形成类弗雷德盐的双羟合结构体,这种铝酸钙粉存在2 116 cm-1及1 981 cm-1两个红外光谱特征峰.矿物相不同,铝酸钙粉的三氧化二铝溶出率有较大差异.%The structure of calcium aluminate powder will be strongly affected by the changes of raw materials.The structure and dissolution rate of calcium aluminates, which were produced with activator and without activator, were identified and measured.XRD and TGA analysis showed that after adding activator, the mineral phase of calcium aluminate powder contained halide,in which the mineral phase CaAl3XO7 may be partially hydrolyzed to form Friedel's salt double hydroxide phases.Furthermore,this calcium aluminate powder had two IR spectral feature peaks at 2 116 cm-1 and 1 981 cm-1'.Different mineral phases, dissolution rates of A12O3 in the calcium aluminate powder were quite different.

  1. An experimental approach to the study of the rheology behaviour of synthetic bone calcium phosphate cements

    Energy Technology Data Exchange (ETDEWEB)

    Friberg, J.; Fernandez, E.; Sarda, S.; Nilsson, M.; Ginebra, M.P.; Planell, J.A. [Universidad Politecnica de Catalunya, Barcelona (Spain). Dept. of Materials Science and Metallurgical Engineering; Martinez, S. [Barcelona Univ. (Spain). Mineralogia i Recursos Minerals

    2001-07-01

    Calcium phosphate cements were developed to fit surgical needs in biomedical fields such as odontology or traumatology. Nowadays, a broad field of new applications have been found for this kind of materials. Drug delivery systems, tissue-engineering scaffolds and osteoporotic bone filling applications are some of the new fields that are being benefited with these materials. Looking at both, commercial and new experimental calcium phosphate cements it is found that {alpha}-tricalcium phosphate is the main reactive powder responsible for the setting and the hardening of the cement. Thus, it is important to know how {alpha}-tricalcium phosphate affects injectability of these cements. The aim of this study was to investigate the rheological behaviour of {alpha}-tricalcium phosphate slurries in order to know how the cement injectability should be modified. Factors such as liquid to powder ratio, particle size of the main reactive powder and the addition of dispersants have been considered. The results showed that viscosity decreased when particle size of reactant was increased and when liquid to powder ratio was increased. It was also found that a minimum of viscosity exists at an optimum value of the weight percentage of dispersant. (orig.)

  2. Rechargeable calcium phosphate orthodontic cement with sustained ion release and re-release

    Science.gov (United States)

    Zhang, Ling; Weir, Michael D.; Chow, Laurence C.; Reynolds, Mark A.; Xu, Hockin H. K.

    2016-11-01

    White spot lesions (WSL) due to enamel demineralization are major complications for orthodontic treatments. Calcium phosphate (CaP) dental resins with Ca and P ion releases are promising for remineralization. However, previous Ca and P releases lasted for only weeks. Experimental orthodontic cements were developed using pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA) at mass ratio of 1:1 (PE); and PE plus 10% of 2-hydroxyethyl methacrylate (HEMA) and 5% of bisphenol A glycidyl dimethacrylate (BisGMA) (PEHB). Particles of amorphous calcium phosphate (ACP) were incorporated into PE and PEHB at 40% filler level. Specimens were tested for bracket-enamel shear bond strength, water sorption, CaP release, and ion recharge and re-release. PEHB+40ACP had higher bracket-enamel bond strength and ion release and rechargeability than PE+40ACP. ACP incorporation into the novel orthodontic cement did not adversely affect the bracket-enamel bond strength. Ion release and re-release from the novel ACP orthodontic cement indicated favorable release and re-release patterns. The recharged orthodontic cement could release CaP ions continuously for four weeks without further recharge. Novel rechargeable orthodontic cement containing ACP was developed with a high bracket-enamel bond strength and the ability to be repeatedly recharged to maintain long-term high levels of CaP ion releases.

  3. Development of a fully injectable calcium phosphate cement for orthopedic and dental applications

    Indian Academy of Sciences (India)

    Manoj Komath; H K Varma

    2003-06-01

    A study on the development of a fully injectable calcium phosphate cement for orthopedic and dental applications is presented. The paper describes its characteristic properties including results of bio- compatibility studies. A conventional two-component calcium phosphate cement formulation (having a powder part containing dry mixture of acidic and basic calcium phosphate particles and a liquid part containing phosphate solution) is modified with a biocompatible gelling agent, to induce flow properties and cohesion. The quantity of the gelling agent is optimized to get a viscous paste, which is smoothly injectable through an 18-gauge needle, with clinically relevant setting parameters. The new formulation has a setting time of 20 min and a compressive strength of 11 MPa. The X-ray diffraction, Fourier transform infrared spectrometry, and energy dispersive electron microprobe analyses showed the phase to be hydroxyapatite, the basic bone mineral. Scanning electron microscopy revealed a porous structure with particle sizes of a few micrometers. The cement did not show any appreciable dimensional or thermal change during setting. The injectability is estimated by extruding through needle and the cohesive property is assessed by water contact method. The cement passed the in vitro biocompatibility screening (cytotoxicity and haemolysis) tests.

  4. Cytotoxicity and genotoxicity of calcium silicate-based cements on an osteoblast lineage

    Directory of Open Access Journals (Sweden)

    Ana Lívia GOMES-CORNÉLIO

    2016-01-01

    Full Text Available Abstract Several calcium silicate-based biomaterials have been developed in recent years, in addition to Mineral Trioxide Aggregate (MTA. The aim of this study was to evaluate the cytotoxicity, genotoxicity and apoptosis/necrosis in human osteoblast cells (SAOS-2 of pure calcium silicate-based cements (CSC and modified formulations: modified calcium silicate-based cements (CSCM and three resin-based calcium silicate cements (CSCR1 (CSCR 2 (CSCR3. The following tests were performed after 24 hours of cement extract exposure: methyl-thiazolyl tetrazolium (MTT, apoptosis/necrosis assay and comet assay. The negative control (CT- was performed with untreated cells, and the positive control (CT+ used hydrogen peroxide. The data for MTT and apoptosis were submitted to analysis of variance and Bonferroni’s posttest (p < 0.05, and the data for the comet assay analysis, to the Kruskal-Wallis and Dunn tests (p < 0.05. The MTT test showed no significant difference among the materials in 2 mg/mL and 10 mg/mL concentrations. CSCR3 showed lower cell viability at 10 mg/mL. Only CSC showed lower cell viability at 50 mg/mL. CSCR1, CSCR2 and CSCR3 showed a higher percentage of initial apoptosis than the control in the apoptosis test, after 24 hours exposure. The same cements showed no genotoxicity in the concentration of 2 mg/mL, with the comet assay. CSC and CSCR2 were also not genotoxic at 10 mg/mL. All experimental materials showed viability with MTT. CSC and CSCR2 presented a better response to apoptosis and genotoxicity evaluation in the 10 mg/mL concentration, and demonstrated a considerable potential for use as reparative materials.

  5. Si-TCP Synthesized from "Mg-free" Reagents Employed as Calcium Phosphate Cement

    OpenAIRE

    Mariana Motisuke; Raul García Carrodeguas; Cecília Amélia Carvalho Zavaglia

    2012-01-01

    The influence of silicon doping on calcium phosphate cement were explored in this work. α-TCP and Si-α-TCP were prepared by solid state reaction employing "Mg-free" CaHPO4, CaCO3 and CaSiO3 as precursors. It was possible to obtain TCP powders with low contents of β phase as contaminant. Cement liquid phase was an aqueous solution containing 2.5 wt. (%) of Na2HPO4 and 1.5 wt. (%) of citric acid. The liquid-to-powder ratio was 0.6 mL.g-1. Chemical, physical and mechanical propert...

  6. Dry reforming reaction over nickel catalysts supported on nanocrystalline calcium aluminates with different CaO/Al2O3 ratios

    Institute of Scientific and Technical Information of China (English)

    Atiyeh Ranjbar; Mehran Rezaei

    2012-01-01

    Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG,MW:5800) as a surfactant.They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide.The prepared samples were characterized by X-ray diffraction (XRD),N2 adsorption (BET),temperature-programmed reduction and oxidation (TPR-TPO),and scanning electron microscopy (SEM) techniques.Catalysts showed a relatively high catalytic activity and stability.TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced.TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C 12A7 catalysts with higher CaO amount were effective against coke deposition.

  7. Kinetic study of the setting reaction of a calcium phosphate bone cement.

    Science.gov (United States)

    Fernández, E; Ginebra, M P; Boltong, M G; Driessens, F C; Ginebra, J; De Maeyer, E A; Verbeeck, R M; Planell, J A

    1996-11-01

    The setting reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % alpha-tertiary calcium phosphate (TCP)[alpha-Ca3(PO4)2], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PHA) used as seed material] was investigated. The cement samples were prepared at a liquid-to-powder ratio of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution. After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37 degrees C. At fixed time intervals they were unmolded and then immediately frozen in liquid nitrogen at a temperature of TN = -196 degrees C, lyofilized, and examined by X-ray diffraction as powder samples. The compressive strength versus time was also measured in setting samples of this calcium phosphate bone cement. The crystal entanglement morphology was examined by scanning electron microscopy. The results showed that: 1) alpha-TCP reacted to a calcium-deficient hydroxyapatite (CDHA), Ca9(HPO4)(PO4)5O H, whereas DCP did not react significantly; 2) the reaction was nearly finished within 32 h, during which both the reaction percentage and the compressive strength increased versus time, with a strong correlation between them; and 3) the calcium phosphate bone cement showed in general a structure of groups of interconnected large plates distributed among agglomerations of small crystal plates arranged in very dense packings.

  8. A low temperature aluminizing treatment of hot work tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Matijevic, B., E-mail: bozidar.matijevic@fsb.hr [University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Zagreb (Croatia)

    2010-07-01

    Conventional aluminizing processes by pack cementation are typically carried out at elevated temperatures. A low temperature powder aluminizing technology was applied to hot tool steel H13. The aluminizing treating temperature was from 550 to 620°C. Effects of temperature and time on the microstructure and phase evolution were investigated. Also, the intermetallic layer thickness was measured in the aluminized layer of a steel substrate. The cross-sectional microstructures, the aluminized layer thickness and the oxide layer were studied. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), glow discharge optical spectroscopy (GDOS) were applied to observe the cross-sections and the distribution of elements. (author)

  9. Clogging and Cementation Caused by Calcium or Iron Biogrouts

    Science.gov (United States)

    Ivanov, V.; Chu, J.; Naeimi, M.

    2012-12-01

    Chemical grouts are often used to reduce the hydraulic conductivity of soil for seepage control purposes. However, chemical grouts can be expensive and environmentally unfriendly. Therefore, two new biogrouts were tested for their bioclogging and biocementation properties. The first was calcium-based biogrout, which contained urease-producing bacteria, calcium chloride and urea for the crystallization of calcite due to enzymatic hydrolysis of urea. The second was iron-based biogrout, which consisted of urease-producing bacteria, ferric chelate, and urea for the precipitation of ferric hydroxide and carbonate due to enzymatic hydrolysis of urea. The permeability of sand (P, 10^-5 m/s), treated with calcium-based biogrout, linearly decreased as a function of the content of precipitated calcium (C, % w/w) according to the following equation: P = 5.1 - 4.0 C. Meanwhile, the permeability of sand treated with iron-based biogrout dropped to 2.7x10^-6 m/s at content of precipitated iron (F, % w/w) about 0.35 % w/w , by the equation: P = 5.1 - 14.6 F , and then slowly decreased to 1.4x10^-7 m/s at content of precipitated iron 1.8% w/w by the following equation: P = 0.36 - 0.23F. Both biogrouts have approximately same efficiency in the reduction of permeability of sand to low values. However, the mechanisms of bioclogging are probably different because the reduction of permeability by calcium-based biogrout was described by linear function of precipitated calcium but the reduction of permeability by iron-based biogrout showed two steps of the clogging. Different functions and mechanisms were related probably to the different type of precipitates. The images of biogrouted sand samples show that calcium-based biogrout produced white amorphous or crystallised calcium carbonate, while iron-based biogrout produced gel-like brown precipitate without visible crystals. The unconfined compressive strengths of the sand treated with different biogrouts (Y, kPa) increased by power

  10. rhBMP-2 release from injectable poly(DL-lactic-co-glycolic acid)/calcium-phosphate cement composites.

    NARCIS (Netherlands)

    Ruhe, P.Q.; Hedberg, E.L.; Padron, N.T.; Spauwen, P.H.M.; Jansen, J.A.; Mikos, A.G.

    2003-01-01

    BACKGROUND: In bone tissue engineering, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles are frequently used as a delivery vehicle for bioactive molecules. Calcium phosphate cement is an injectable, osteoconductive, and degradable bone cement that sets in situ. The objective of this study was

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

    Science.gov (United States)

    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.

  12. Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone

    DEFF Research Database (Denmark)

    Moesgaard, Mette; Poulsen, S.L.; Herfort, D.;

    2012-01-01

    This work investigates the hydration of blended Portland cement containing 30 wt.% Na2O-CaO-Al2O3-SiO2 (NCAS) glass particles either as the only supplementary cementitious material (SCM) or in combination with limestone, using 29Si MAS NMR, powder XRD, and thermal analyses. The NCAS glass...... of hydration. The hydrated glass contributes to the formation of the calcium-silicate-hydrate (C-S-H) phase, consuming a part of the Portlandite (Ca(OH)2) formed during hydration of the Portland cement. Furthermore, the presence of the glass and limestone particles, alone or in combination, results...... in an accelerated hydration for alite (Ca3SiO5), the main constituent of Portland cement. A higher degree of limestone reaction has been observed in the blend containing both limestone and NCAS glass as compared to the limestone – Portland mixture. This reflects that limestone reacts with a part of the alumina...

  13. Nano clay-enhanced calcium phosphate cements and hydrogels for biomedical applications

    Science.gov (United States)

    Jammalamadaka, Udayabhanu

    Biomaterials are used as templates for drug delivery, scaffolds in tissue engineering, grafts in surgeries, and support for tissue regeneration. Novel biomaterial composites are needed to meet multifaceted requirements of compatibility, ease of fabrication and controlled drug delivery. Currently used biomaterials in orthopedics surgeries suffer limitations in toxicity and preventing infections. Polymethyl methacrylate (PMMA) used as bone cement suffers from limitations of thermal necrosis and monomer toxicity calls for development of better cementing biomaterials. A biodegradable/bioresorbable cement with good mechanical properties is needed to address this short coming. Metal implants used in fixing fractures or total joint replacement needs improvements in preventing biofilm formation and better tissue integration. This research addressed the above mentioned research gaps by formulating novel biomaterial composites. Calcium phosphate cements are the alternative bone cements that are bioresorbable and promote tissue integration. These cements lack sufficient mechanical strengths to be used in load bearing sites. The addition of nanoparticles is hypothesized to improve the mechanical properties without inducing toxicity to the tissue. This hypothesis was tested by evaluating compression and flexural strengths in addition to cytocompatibility tests. Results indicate that addition of nano-clay particles (halloysites nanotubes) improved the compressive strength and osteoinductive properties of calcium phosphate cements. To address the research need of preventing implant failure due to infection and aseptic loosening, novel coatings are needed. Hydrogels are well establish for their ability to mimic in vivo environment, promote cell viability and as drug delivery vehicles. Use of composites of hydrogels and drug-loaded nanoparticles to prevent infection was evaluated. Cytocompatibility results indicate good cell viability. Antibacterial results show sustained release

  14. Calcium phosphate holmium-166 ceramic to addition in bone cement: synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Donanzam, Blanda A.; Campos, Tarcisio P.R., E-mail: campos@nuclear.ufmg.b [Universidade do Federal de Minas Gerais (DEN/UFMG), Belo Horizonte, MG (Brazil). Escola de Engenharia. Dept. de Engenharia Nuclear; Dalmazio, Ilza; Valente, Eduardo S., E-mail: id@cdtn.b, E-mail: valente@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2011-07-01

    Spine metastases are a common and painful complication of cancer. The treatment often consists of bone cement injection (vertebroplasty or kyphoplasty) within vertebral body for vertebrae stabilization, followed by external beam radiation therapy. Recently, researchers introduced the concept of radioactive bone cement for spine tumors therapy. Then, investigations about bioactive and radioactive materials became interesting. In this study, we present the synthesis of calcium phosphate incorporated holmium (CaP-Ho) via sol-gel technique, and its characterization by XRD, FT-IR, NA and SEM. Results showed a multiphasic bioceramic composed mainly of hydroxyapatite, {beta}-tricalcium phosphate, holmium phosphate and traces of calcium pyrophosphate. Furthermore, the nuclide Ho-166 was the major radioisotope produced. Despite that, the radioactive bioceramic CaP-{sup 166}Ho must be investigated in clinical trials to assure its efficacy and safety on spine tumors treatment (author)

  15. Tridimensional quantitative porosity characterization of three set calcium silicate-based repair cements for endodontic use.

    Science.gov (United States)

    De Souza, Erika Thuanne Gonçalves; Nunes Tameirão, Michele Dias; Roter, Juliana Marins; De Assis, Joaquim Teixeira; De Almeida Neves, Aline; De-Deus, Gustavo André

    2013-10-01

    The aim of the this study was to quantitatively evaluate in three-dimensional (3D), the porosity degree of three improved silicate-based endodontic repair cements (iRoot BP Plus®, Biodentine®, and Ceramicrete) compared to a gold-standard calcium silicate bioactive cement (Pro Root® MTA). From each tested cement, four samples were prepared by a single operator following the manufacturer's instructions in terms of proportion, time, and mixing method, using cylindrical plastic split-ring moulds. The moulds were lubricated and the mixed cements were inserted with the aid of a cement spatula. The samples were scanned using a compact micro-CT device (Skyscan 1174, Bruker micro-CT, Kontich, Belgium) and the projection images were reconstructed into cross-sectional slices (NRecon v.1.6.9, Bruker micro-CT). From the stack of images, 3D models were rendered and the porosity parameters of each tested material were obtained after threshold definition by comparison with standard porosity values of Biodentine®. No statistically significant differences in the porosity parameters among the different materials were seen. Regarding total porosity, iRoot BP Plus® showed a higher percentage of total porosity (9.58%), followed by Biodentine® (7.09%), Pro Root® MTA (6.63%), and Ceramicrete (5.91%). Regarding closed porosity, Biodentine® presented a slight increase in these numbers compared to the other sealers. No significant difference in porosity between iRoot BP Plus®, Biodentine®, and Ceramicrete were seen. In addition, no significant difference in porosity between the new calcium silicate-containing repair cements and the gold-standard MTA were found.

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

    Science.gov (United States)

    Khashaba, Rania M.; Moussa, Mervet; Koch, Christopher; Jurgensen, Arthur R.; Missimer, David M.; Rutherford, Ronny L.; Chutkan, Norman B.; Borke, James L.

    2011-01-01

    Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs) were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control). Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5–12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications. PMID:21941551

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

    Directory of Open Access Journals (Sweden)

    Rania M. Khashaba

    2011-01-01

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

  18. Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone regeneration.

    Science.gov (United States)

    Sarkar, Swapan Kumar; Lee, Byung Yeol; Padalhin, Andrew Reyas; Sarker, Avik; Carpena, Nathaniel; Kim, Boram; Paul, Kallyanshish; Choi, Hwan Jun; Bae, Sang-Ho; Lee, Byong Taek

    2016-01-01

    In this work, we report brushite-based calcium phosphate cement (CPC) system to enhance the in vivo biodegradation and tissue in-growth by incorporation of micro-channeled hydroxyapatite (HAp) granule and silicon and sodium addition in calcium phosphate precursor powder. Sodium- and silicon-rich calcium phosphate powder with predominantly tri calcium phosphate (TCP) phase was synthesized by an inexpensive wet chemical route to react with mono calcium phosphate monohydrate (MCPM) for making the CPC. TCP nanopowder also served as a packing filler and moderator of the reaction kinetics of the setting mechanism. Strong sintered cylindrical HAp granules were prepared by fibrous monolithic (FM) process, which is 800 µm in diameter and have seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution was used as the liquid component which acted as a homogenizer and setting time retarder. The granules accelerated the degradation of the brushite cement matrix as well as improved the bone tissue in-growth by permitting an easy access to the interior of the CPC through the micro-channels. The addition of micro-channeled granule in the CPC introduced porosity without sacrificing much of its compressive strength. In vivo investigation by creating a critical size defect in the femur head of a rabbit model for 1 and 2 months showed excellent bone in-growth through the micro-channels. The granules enhanced the implant degradation behavior and bone regeneration in the implanted area was significantly improved after two months of implantation.

  19. Calcium phosphate cement as an alternative for formocresol in primary teeth pulpotomies

    OpenAIRE

    Bijimole Jose; Ratnakumari, N; Mira Mohanty; Varma, H. K.; Manoj Komath

    2013-01-01

    Background: Formocresol remains to be the preferred medicament in pulpotomy, despite the concerns regarding tissue devitalization and systemic toxicity. Several materials were used as alternatives, but none proved significantly advantageous. Of recent, calcium phosphate cement (CPC) has been projected as an ideal pulpotomy material considering its tissue compatibility and dentinogenic properties. This study explores the suitability of a CPC formulation for pulpotomy, in comparison with formoc...

  20. The In-situ Reinforcement of Calcium Phosphate Cement and Its Micro-structural Analysis

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Carbon nanotubes ( CNTs ) and polyacrylic acid were employed to modify the setting process and hydration products of β- TCP/ TTCP calcium phosphate cement. The micro-structure of hydration product and the fashion of how additives and hydration particles interconnected were investigated. With the modification effect of CNTs, the setting particles and CNTs got winded and interconnected and thus made the composite more compact and denser.

  1. Analysis of the color alteration and radiopacity promoted by bismuth oxide in calcium silicate cement

    Directory of Open Access Journals (Sweden)

    Marina Angelica Marciano

    2013-07-01

    Full Text Available The aim of the study was to determine if the increase in radiopacity provided by bismuth oxide is related to the color alteration of calcium silicate-based cement. Calcium silicate cement (CSC was mixed with 0%, 15%, 20%, 30% and 50% of bismuth oxide (BO, determined by weight. Mineral trioxide aggregate (MTA was the control group. The radiopacity test was performed according to ISO 6876/2001. The color was evaluated using the CIE system. The assessments were performed after 24 hours, 7 and 30 days of setting time, using a spectrophotometer to obtain the ΔE, Δa, Δb and ΔL values. The statistical analyses were performed using the Kruskal-Wallis/Dunn and ANOVA/Tukey tests (p 3 mm equivalent of Al. The MTA group was statistically similar to the CSC / 30% BO group (p > 0.05. In regard to color, the increase of bismuth oxide resulted in a decrease in the ΔE value of the calcium silicate cement. The CSC group presented statistically higher ΔE values than the CSC / 50% BO group (p < 0.05. The comparison between 24 hours and 7 days showed higher ΔE for the MTA group, with statistical differences for the CSC / 15% BO and CSC / 50% BO groups (p < 0.05. After 30 days, CSC showed statistically higher ΔE values than CSC / 30% BO and CSC / 50% BO (p < 0.05. In conclusion, the increase in radiopacity provided by bismuth oxide has no relation to the color alteration of calcium silicate-based cements.

  2. Basic properties of calcium phosphate cement containing different concentrations of citric acid solution

    Institute of Scientific and Technical Information of China (English)

    戴红莲; 闫玉华; 冯凌云; 李世普; 贺建华

    2002-01-01

    The properties of calcium phosphate cement consisting of α-tricalcium phosphate (α-TCP) and tetracalcium phosphate (TTCP) have been investigated by using a cement liquid that contained citric acid with concentration of 0.05 mol/L or higher. The relationship between the setting time of the system cement and the concentration of citric acid solution shows concave type curve. When solution concentration was 0.2 mol/L, the setting time was 8 min, which was the shortest. While the relationship between 24 h compressive strength of the cement and the citric acid concentration shows convex type curve. When solution concentration was 0.2 mol/L, the compressive strength was 39.0 MPa, which was the highest. Afterwards, the microstructure of the hardening product was observed by SEM, the effect of citric acid on the exothermic rate of hydrate reaction was studied by microcalorimeter, and the crushed specimens were subjected to X-ray diffraction. The results verified that the low citric acid concentration can accelerate the hydrate reaction rate of the α-TCP/TTCP system. However, the high citric acid concentration inhibited hydroxyapatite formation and retarded the rate of hydrate reaction of the α-TCP/TTCP cement.

  3. Experimental Calcium Silicate-Based Cement with and without Zirconium Oxide Modulates Fibroblasts Viability.

    Science.gov (United States)

    Slompo, Camila; Peres-Buzalaf, Camila; Gasque, Kellen Cristina da Silva; Damante, Carla Andreotti; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro; de Oliveira, Rodrigo Cardoso

    2015-01-01

    The aim of this study was to verify whether the use of zirconium oxide as a radiopacifier of an experimental calcium silicate-based cement (WPCZO) leads to cytotoxicity. Fibroblasts were treated with different concentrations (10 mg/mL, 1 mg/mL, and 0.1 mg/mL) of the cements diluted in Dulbecco's modified Eagle's medium (DMEM) for periods of 12, 24, and 48 h. Groups tested were white Portland cement (WPC), white Portland cement with zirconium oxide (WPCZO), and white mineral trioxide aggregate Angelus (MTA). Control group cells were not treated. The cytotoxicity was evaluated through mitochondrial-activity (MTT) and cell-density (crystal violet) assays. All cements showed low cytotoxicity. In general, at the concentration of 10 mg/mL there was an increase in viability of those groups treated with WPC and WPCZO when compared to the control group (pzirconium oxide as the radiopacifier showed low cytotoxicity as a promising material to be exploited for root-end filling.

  4. Effects of glass fiber modified with calcium silicate hydrate (C-S-H(I)) reinforced cement

    Science.gov (United States)

    Xin, M.; Zhang, L.; Ge, S.; Cheng, X.

    2017-03-01

    In this paper, calcium silicate hydrate (C-S-H(I)) and glass fiber modified with C-S-H(I) (SiF) at ambient temperature were synthesized. SiF and untreated fiber (OF) were incorporated into cement paste. Phase composition of C-S-H(I), SiF and OF was characterized by XRD. The surface morphologies were characterized by SEM. Flexural performance of fiber reinforced cement (FRC) at different curing ages was investigated. Results indicated that both SiF and OF could reinforce cement paste. SiF had a more positive effect on improving the flexural performance of FRC than OF. The strength of SiF reinforced cement was 11.48MPa after 28 days curing when fiber volume was 1.0%, 12.55% higher than that of OF reinforced cement. The flexural strength increased with the addition of fiber volume. However, the large dosage of fiber might cause a decrease in flexural strength of FRC.

  5. A New Type of Biphasic Calcium Phosphate Cement as a Gentamicin Carrier for Osteomyelitis

    Directory of Open Access Journals (Sweden)

    Wen-Yu Su

    2013-01-01

    Full Text Available Osteomyelitis therapy is a long-term and inconvenient procedure for a patient. Antibiotic-loaded bone cements are both a complementary and alternative treatment option to intravenous antibiotic therapy for the treatment of osteomyelitis. In the current study, the biphasic calcium phosphate cement (CPC, called α-TCP/HAP (α-tricalcium phosphate/hydroxyapatite biphasic cement, was prepared as an antibiotics carrier for osteomyelitis. The developed biphasic cement with a microstructure of α-TCP surrounding the HAP has a fast setting time which will fulfill the clinical demand. The X-ray diffraction and Fourier transform infrared spectrometry analyses showed the final phase to be HAP, the basic bone mineral, after setting for a period of time. Scanning electron microscopy revealed a porous structure with particle sizes of a few micrometers. The addition of gentamicin in α-TCP/HAP would delay the transition of α-TCP but would not change the final-phase HAP. The gentamicin-loaded α-TCP/HAP supplies high doses of the antibiotic during the initial 24 hours when they are soaked in phosphate buffer solution (PBS. Thereafter, a slower drug release is produced, supplying minimum inhibitory concentration until the end of the experiment (30 days. Studies of growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa in culture indicated that gentamicin released after 30 days from α-TCP/HAP biphasic cement retained antibacterial activity.

  6. In vivo resorption behavior of a high strength injectable calcium-phosphate cement

    Energy Technology Data Exchange (ETDEWEB)

    Wolke, J.G.C.; Ooms, E.M.; Jansen, J.A. [Univ. Medical Center, Nijmegen (Netherlands). Dept. Biomaterials

    2001-07-01

    A high strength calcium-phosphate-cement powder was prepared from a composition comprising of {alpha}-TCP, CaHPO{sub 4} (monetite), CaCO{sub 3} and some seeds of precipitated apatite. An aqueous solution of 4% Na{sub 2}HPO{sub 4} was used as liquid to start the setting reaction. The powder was mixed with cement liquid in three different liquid/powder ratios respectively 0.3, 0.35 and 0.4. Observation of the setting reaction versus time revealed that the maximum of compressive strength was achieved after 3 days reaching the value of 81 MPa. The X-ray diffraction pattern of the Ca-P cement measured 3 days after mixing and storage in Ringer's solution at 37 C showed that the {alpha}-TCP was transformed to hydroxylapatite with superposition of the peaks for monetite. XRD showed that after eight weeks of implantation the monetite peaks had disappeared. Further, the clinical handling properties of all three types of Ca-P cement appeared to be excellent. No problems in setting time or cavity filling were met during the application. The histological evaluation after two weeks of implantation showed abundant bone apposition on the cement surface without inflammatory reaction. At later time points the Ca-P cements were totally covered by a thin layer of bone and osteoclast-like cells in remodeling lacunae at the interface were resorbing the cement. At all implantation periods the PMMA controls showed the presence of a thin fibrous membrane. (orig.)

  7. Effects of Leaching Behavior of Calcium Ions on Compression and Durability of Cement-based Materials with Mineral Admixtures

    Directory of Open Access Journals (Sweden)

    Wei-Ting Lin

    2013-05-01

    Full Text Available Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing reinforcing steel corrosion. This study investigates the effects of leaching behavior of calcium ions on the compression and durability of cement-based materials. Since the parameters influencing the leaching behavior of cement-based materials are unclear and diverse, this paper focuses on the influence of added mineral admixtures (fly ash, slag and silica fume on the leaching behavior of calcium ions regarding compression and durability of cemented-based materials. Ammonium nitrate solution was used to accelerate the leaching process in this study. Scanning electron microscopy, X-ray diffraction analysis, and thermogravimetric analysis were employed to analyze and compare the cement-based material compositions prior to and after calcium ion leaching. The experimental results show that the mineral admixtures reduce calcium hydroxide quantity and refine pore structure through pozzolanic reaction, thus enhancing the compressive strength and durability of cement-based materials.

  8. Influence of raw powder granulometry on the mechanical properties of a calcium phosphate bone cement

    Energy Technology Data Exchange (ETDEWEB)

    Pittet, C. [Swiss Federal Inst. of Tech., Lausanne (Switzerland). Lab. de Technologie des Poudres; Hopital Orthopedique de la Suisse Romande, Lausanne (Switzerland); Grasso, P.; Lemaitre, J. [Swiss Federal Inst. of Tech., Lausanne (Switzerland). Lab. de Technologie des Poudres

    2002-07-01

    Brushite cement is a calcium phosphate cement obtained by mixing three powders with water. Starting powders are monocalcium phosphate monohydrate (MCPM), calcium sulfate hemihydrate (CSH) and {beta}-tricalcium phosphate ({beta}-TCP). The main phase obtained after setting is brushite (DCPD). The goal of this work was to mill the starting powders to obtain a finer and more homogeneous microstructure after setting, in order to enhance the mechanical properties of the cement. All three powders were milled and freeze-dried. The median diameters passed from 70.5 to 6.2 {mu}m for MCPM, 27.2 to 1.1 {mu}m for CSH, 2.4 to 1.5 {mu}m for {beta}-TCP. Specific surface areas of the powders increased on milling. Attrition of MCPM and CSH appeared to be beneficial to the maximum stresses the set cement can withstand. Cements prepared with raw powders showed 1.4 MPa indirect tensile strength and 4.4 MPa compressive strength. With milled MCPM and CSH, those values reached 4.1 and 22.1 MPa respectively. After these benefits, we tried to use the milled {beta}-TCP expecting further enhancement. To ensure wetting of all three powders and to keep the same paste rheology, the liquid/solid ratio had to be increased. The indirect tensile strength was seen to decrease by a factor of 3 when three milled powders were used at the same time. SEM of the fracture surfaces showed that milled {beta}-TCP formed clusters that did not react to form brushite. Lowering the maximum indirect tension stress is due to the fact that less brushite was formed, and to a higher porosity in the final product (mainly due to the higher liquid/solid ratio). (orig.)

  9. Cytotoxicity and Osteogenic Potential of Silicate Calcium Cements as Potential Protective Materials for Pulpal Revascularization

    Science.gov (United States)

    Bortoluzzi, Eduardo A.; Niu, Li-na; Palani, Chithra D.; El-Awady, Ahmed R.; Hammond, Barry D.; Pei, Dan-dan; Tian, Fu-cong; Cutler, Christopher W.; Pashley, David H.; Tay, Franklin R.

    2016-01-01

    Objectives In pulpal revascularization, a protective material is placed coronal to the blood clot to prevent recontamination and to facilitate osteogenic differentiation of mesenchynal stem cells to produce new dental tissues. Although mineral trioxide aggregate (MTA) has been the material of choice for clot protection, it is easily displaced into the clot during condensation. The present study evaluated the effects of recently-introduced calcium silicate cements (Biodentine and TheraCal LC) on the viability and osteogenic differentiation of human dental pulp stem cells (hDPSCs) by comparing with MTA Angelus. Methods Cell viability was assessed using XTT assay and flow cytometry. The osteogenic potential of hDPSCs exposed to calcium silicate cements was examined using qRT-PCR for osteogeic gene expressions, alkaline phosphatase enzyme activity, Alizarin red S staining and transmission electron microscopy of extracellular calcium deposits. Parametric statistical methods were employed for analyses of significant difference among groups, with α=0.05. Results The cytotoxic effects of Biodentine and TheraCal LC on hDPSCs were time- and concentration-dependent. Osteogenic differentiation of hDPSCs was enhanced after exposure to Biodentine that was depleted of its cytotoxic components. This effect was less readily observed in hDPSCs exposed to TheraCal LC, although both cements supported extracelluar mineralization better than the positive control (zinc oxide-eugenol–based cement). Significance A favorable tissue response is anticipated to occur with the use of Biodentine as a blood clot-protecting material for pulpal revascularizaiton. Further investigations with the use of in vivo animal models are required to validate the potential adverse biological effects of TheraCal LC on hDPSCs. PMID:26494267

  10. Elucidation of real-time hardening mechanisms of two novel high-strength calcium phosphate bone cements.

    Science.gov (United States)

    Smirnov, Valery V; Rau, Julietta V; Generosi, Amanda; Albertini, Valerio Rossi; Ferro, Daniela; Barinov, Sergey M

    2010-04-01

    Despite the numerous literature data available in the field of calcium phosphate bone cements, the mechanism and kinetics of their hardening, both of which are of great importance for cements application, in most cases, is unknown. In this work, the mechanism and kinetics of hardening of two novel high-strength calcium phosphate bone cements were studied using the energy dispersive X-ray diffraction technique, which allows rapid collection of the patterns. The phase transformations occurring on the setting and hardening processes were monitored in situ. Containing minimal quantity of components, whose mixing leads to the formation of cements with pH close to neutral, the cements under study are simple in handling. The main component of both formulations is tetracalcium phosphate. In both cements, the effect of the addition of high- and low-molecular weight chitosan on phase development and kinetics was investigated in detail. One of the cements has the compressive strength of about 70 MPa, whereas the strength of the other, containing Ca(3)Al(2)O(6), is much higher, about 100 MPa. This latter cement could be regarded as an alternative to the common low-strength bioresorbable brushite cements.

  11. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate.

    Science.gov (United States)

    Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

    2016-03-25

    The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

  12. Injectable PLGA microsphere/calcium phosphate cements: physical properties and degradation characteristics.

    Science.gov (United States)

    Habraken, W J E M; Wolke, J G C; Mikos, A G; Jansen, J A

    2006-01-01

    Calcium phosphate (CaP) cements show an excellent biocompatibility and often have a high mechanical strength, but in general degrade relatively slow. To increase degradation rates, macropores can be introduced into the cement, e.g., by the inclusion of biodegradable microspheres into the cement. The aim of this research is to develop an injectable PLGA microsphere/CaP cement with sufficient setting/cohesive properties and good mechanical and physical properties. PLGA microspheres were prepared using a water-in-oil-in-water double-emulsion technique. The CaP-cement used was Calcibon, a commercially available hydroxyapatite-based cement. 10:90 and 20:80 dry wt% PLGA microsphere/CaP cylindrical scaffolds were prepared as well as microporous cement (reference material). Injectability, setting time, cohesive properties and porosity were determined. Also, a 12-week degradation study in PBS (37 degree C) was performed. Results showed that injectability decreased with an increase in PLGA microsphere content. Initial and final setting time of the PLGA/CaP samples was higher than the microporous sample. Porosity of the different formulations was 40.8% (microporous), 60.2% (10:90) and 69.3% (20:80). The degradation study showed distinct mass loss and a pH decrease of the surrounding medium starting from week 6 with the 10:90 and 20:80 formulations, indicating PLGA erosion. Compression strength of the PLGA microsphere/CaP samples decreased siginificantly in time, the microporous sample remained constant. After 12 weeks both PLGA/CaP samples showed a structure of spherical micropores and had a compressive strength of 12.2 MPa (10:90) and 4.3 MPa (20:80). Signs of cement degradation were also found with the 20:80 formulation. In conclusion, all physical parameters were well within workable ranges with both 10:90 and 20:80 PLGA microsphere/CaP cements. After 12 weeks the PLGA was totally degraded and a highly porous, but strong scaffold remained.

  13. Calcium-enriched mixture cement as artificial apical barrier: A case series

    Directory of Open Access Journals (Sweden)

    Ali Nosrat

    2011-01-01

    Full Text Available In comparison to the conventional apexification using calcium hydroxide, artificial apical barrier technique is more valuable and less time consuming. This article describes successful use of calcium-enriched mixture (CEM cement as an artificial apical barrier in open apices. In this study, 13 single-rooted teeth with necrotic pulps and open apices were treated non-surgically. After copious irrigation of the root canals with NaOCl 5.25% and gentle filing, based on need for interappointment dressing, treatments were followed by CEM cement (BioniqueDent, Tehran, Iran apical plug insertion in the first or second appointment. All cases were then permanently restored. All subjects were followed until radiographic evidence of periradicular healing was seen (mean 14.5 months. Clinically, all cases were functional and asymptomatic and complete osseous healing was observed in all the teeth. Considering the biological properties of CEM cement, this new endodontic biomaterial might be appropriate to be used as artificial apical barrier in the open apex teeth.

  14. Resorption of monetite calcium phosphate cement by mouse bone marrow derived osteoclasts.

    Science.gov (United States)

    Montazerolghaem, M; Karlsson Ott, M; Engqvist, H; Melhus, H; Rasmusson, A J

    2015-01-01

    Recently the interest for monetite based biomaterials as bone grafts has increased; since in vivo studies have demonstrated that they are degradable, osteoconductive and improve bone healing. So far osteoclastic resorption of monetite has received little attention. The current study focuses on the osteoclastic resorption of monetite cement using primary mouse bone marrow macrophages, which have the potential to differentiate into resorbing osteoclasts when treated with receptor activator NF-κB ligand (RANKL). The osteoclast viability and differentiation were analysed on monetite cement and compared to cortical bovine bone discs. After seven days live/dead stain results showed no significant difference in viability between the two materials. However, the differentiation was significantly higher on the bone discs, as shown by tartrate resistant acid phosphatase (TRAP) activity and Cathepsin K gene expression. Moreover monetite samples with differentiated osteoclasts had a 1.4 fold elevated calcium ion concentration in their culture media compared to monetite samples with undifferentiated cells. This indicates active resorption of monetite in the presence of osteoclasts. In conclusion, this study suggests that osteoclasts have a crucial role in the resorption of monetite based biomaterials. It also provides a useful model for studying in vitro resorption of acidic calcium phosphate cements by primary murine cells.

  15. Introduction of enzymatically degradable poly(trimethylene carbonate) microspheres into an injectable calcium phosphate cement.

    Science.gov (United States)

    Habraken, Wouter J E M; Zhang, Zheng; Wolke, Joop G C; Grijpma, Dirk W; Mikos, Antonios G; Feijen, Jan; Jansen, John A

    2008-06-01

    Poly(trimethylene carbonate) (PTMC) is an enzymatically degradable polyester with rubber-like properties. Introduction of this polymer into an injectable calcium phosphate bone cement can therefore be used to introduce macroporosity into the cement for tissue engineering purposes as well as to improve mechanical properties. Aim of this study was to investigate calcium phosphate cements with incorporated PTMC microspheres (PTMC CPCs) on their physical/mechanical properties and in vitro degradation characteristics. Therefore, composites were tested on setting time and mechanical strength as well as subjected to phosphate buffered saline (PBS) and enzyme containing medium. PTMC CPCs (12.5 and 25 wt%) with molecular weights of 52.7 kg mol(-1) and 176.2 kg mol(-1) were prepared, which showed initial setting times similar to that of original CPC. Though compression strength decreased upon incorporation of PTMC microspheres, elastic properties were improved as strain-at-yield increased with increasing content of microspheres. Sustained degradation of the microspheres inside PTMC CPC occurred when incubated in the enzymatic environment, but not in PBS, which resulted in an interconnected macroporosity for the 25 wt% composites.

  16. CO₂ capture from cement plants using oxyfired precalcination and/or calcium looping.

    Science.gov (United States)

    Rodríguez, Nuria; Murillo, Ramón; Abanades, J Carlos

    2012-02-21

    This paper compares two alternatives to capture CO(2) from cement plants: the first is designed to exploit the material and energy synergies with calcium looping technologies, CaL, and the second implements an oxyfired circulating fluidized bed precalcination step. The necessary mass and heat integration balances for these two options are solved and compared with a common reference cement plant and a cost analysis exercise is carried out. The CaL process applied to the flue gases of a clinker kiln oven is substantially identical to those proposed for similar applications to power plants flue gases. It translates into avoided cost of of 23 $/tCO(2) capturing up to 99% of the total CO(2) emitted in the plant. The avoided cost of an equivalent system with an oxyfired CFBC precalcination only, goes down to 16 $/tCO(2) but only captures 89% of the CO(2) emitted in the plant. Both cases reveal that the application of CaL or oxyfired CFBC for precalcination of CaCO(3) in a cement plant, at scales in the order of 50 MWth (referred to the oxyfired CFB calciner) is an important early opportunity for the development of CaL processes in large scale industrial applications as well as for the development of zero emissions cement plants.

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

    Directory of Open Access Journals (Sweden)

    Hongfang Sun

    2015-02-01

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

  18. Passive and active in vitro resorption of calcium and magnesium phosphate cements by osteoclastic cells.

    Science.gov (United States)

    Grossardt, Christian; Ewald, Andrea; Grover, Liam M; Barralet, Jake E; Gbureck, Uwe

    2010-12-01

    Biocements are clinically applied materials for bone replacement in non-load-bearing defects. Depending on their final composition, cements can be either resorbed or remain stable at the implantation site. Degradation can occur by two different mechanisms, by simple dissolution (passive) or after osteoclastic bone remodeling (active). This study investigated both the passive and active in vitro resorption behavior of brushite (CaHPO₄ · 2H₂O), monetite (CaHPO₄), calcium-deficient hydroxyapatite (CDHA; Ca₉(PO₄)₅HPO₄OH), and struvite (MgNH₄PO₄ · 6H₂O) cements. Passive resorption was measured by incubating the cement samples in a cell culture medium, whereas active resorption was determined during the surface culture of multinuclear osteoclastic cells derived from RAW 264.7 macrophages. Osteoclast formation was confirmed by showing tartrate resistant acid phosphatase (TRAP) activity on CDHA, brushite, and monetite surfaces, as well as by measuring calcitonin receptor (CT-R) expression as an osteoclast-specific protein by Western blot analysis for struvite ceramics. An absence of passive degradation and only marginally active degradation of struvite cement was the most degradable with a passive (active) release of 9.26 (2.92) Mg²+ ions and a total weight loss of 4.7% over 13 days of the study.

  19. Modifications on the properties of a calcium phosphate cement by additions of sodium alginate

    Energy Technology Data Exchange (ETDEWEB)

    Coelho, W.T.; Fernandes, J.M.; Vieira, R.S.; Thurmer, M.B.; Santos, L.A., E-mail: trajano@ufrgs.br, E-mail: julianafernandes2@yahoo.com.br, E-mail: rsvieira.eng@gmail.com, E-mail: monicathurmer@yahoo.com.br, E-mail: luis.santos@ufrgs.br [Universidade Federal do Rio Grande do Sul (PPG/LABIOMAT/UFRGS), RS (Brazil)

    2012-07-01

    The Calcium Phosphate Cement (CPC) are bone substitutes with great potential for use in orthopedics, traumatology and dentistry due to its biocompatibility, bioactivity and osteoconductivity, and form a paste that can be easily shaped and placed into the surgical site. However, CPCs have low mechanical strength, which equals the maximum mechanical strength of trabecular bone. In order to assess the strength and time to handle a CPC composed primarily of alpha phase, were added sodium alginate (1%, 2% and 3% wt) and an accelerator in an aqueous solution. The cement powder was mixed with liquid of setting, shaped into specimens and evaluated for apparent density and porosity by Archimedes method, X-ray diffraction and compressive strength. A significant increase in compressive strength by adding sodium alginate was verified. (author)

  20. Intracanal management of a post traumatic perforative invasive cervical root resorption using calcium enriched matrix cement

    Directory of Open Access Journals (Sweden)

    Saeed Asgary

    2013-01-01

    Full Text Available Invasive cervical root resorption (ICR is a consequence of a resorptive soft-tissue penetrating into dentin that starts below the gingival attachment and tends to be asymptomatic unless dental pulp involvement. Prompt diagnosis is the key to retention of the involved tooth. Treatment procedure includes non-surgical elimination of the resorptive soft-tissues and restoration of the cavity. In case of pulp involvement, endodontic treatment is indicated. This is a report of a non-surgical intra canal treatment case in a maxillary central incisor, which involved the pulp and was successfully treated with calcium enriched mixture (CEM cement. Based on favorable long-term treatment outcomes, CEM cement may be a promising biomaterial in treatment of ICR cases.

  1. [Endodontics in motion: new concepts, materials and techniques 1. Hydraulic Calcium Silicate Cements].

    Science.gov (United States)

    Moinzadeh, A T; Jongsma, L; de Groot-Kuin, D; Cristescu, R; Neirynck, N; Camilleri, J

    2015-01-01

    Hydraulic Calcium Silicate Cements (HCSCs) constitute a group of materials that have become increasingly popular in endodontics since the introduction of Mineral Trioxide Aggregate (MTA) in the 1990s. MTA is Portland cement to which bismuth oxide has been added to increase its radiopacity. The most important property of MTA is its capacity to set in water or a humid environment. However, MTA also has important limitations, for example, it's difficult to work with and can discolour teeth. Recently, numerous products based on HCSC chemistry, which can be considered as modifications of MTA intended to reduce its limitations, have become available on the market. Despite their potential advantages, all of these materials have their own specific limitations that are currently insufficiently known and investigated.

  2. Characterization of a calcium phosphate cement based on alpha-tricalcium phosphate obtained by wet precipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Thurmer, M.B.; Diehl, C.E.; Vieira, R.S.; Coelho, W.T.G.; Santos, L.A., E-mail: monicathurmer@yahoo.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Engenharia de Materiais

    2012-07-01

    There are several systems of calcium phosphate cements being studied. Those based on alpha-tricalcium phosphate are of particular interest. After setting they produce calcium deficient hydroxyapatite similar to bone like hydroxyapatite. This work aims to obtain alpha-tricalcium phosphate powders by the wet precipitation process, using calcium nitrate and phosphoric acid as reagents. This powder was characterized by infrared spectroscopy, X-ray diffraction and particle size distribution. In order to prepare the calcium phosphate cement, the powder was mixed with an accelerator in an aqueous solution. The mechanical properties of the cement were assessed and it was evaluated by means of apparent density, X-ray diffraction and scanning electron microscopy. The described method produced crystalline alpha-tricalcium phosphate as the major phase. The calcium phosphate cement showed high values of compression strength (50 MPa). The soaking of the cement in a simulated body fluid (SBF) formed a layer of hydroxyapatite like crystals in the surface of the samples. (author)

  3. 放电等离子烧结制备刚玉-铝酸钙-镁铝尖晶石复相材料%Preparation of corundum-calcium aluminate-magnesium aluminate spinel composites by spark plasma sin-tering

    Institute of Scientific and Technical Information of China (English)

    唐海; 员文杰; 商恒; 樊希安; 邓承继; 祝洪喜

    2016-01-01

    In order to reduce the synthesis temperature of the composite material and maintain its physical properties,corundum-calcium aluminate-magnesium aluminate spinel composites were prepared using 35.16 mass% underburnt dolomite and 64.84 mass% flake alumina as raw materials by spark plasma sin-tering at different temperatures (1 050,1 100,and 1 150 ℃).The effects of the firing temperature on phase composition and strength of corundum-calcium aluminate-magnesium aluminate spinel composites were investigated.The results show that with the temperature increasing the corundum content decreases gradu-ally,while the contents of calcium aluminate and magnesium aluminate spinel gradually increase,the ap-parent porosity of composites slightly increases while the splitting tensile strength improves;flake corun-dum,formed calcium aluminate and magnesium aluminate spinel bond together at high temperatures by spark plasma sintering.The composites with the apparent porosity of 23.2% fired at 1 150 ℃ achieve the splitting tensile strength of 20 MPa.%为了降低复相材料的合成温度并保证其相应的物理性能,以质量分数分别为35.16%的欠烧白云石和64.84%的片状氧化铝为原料,在1050、1100和1150℃下利用放电等离子烧结法(SPS)制备了刚玉-铝酸钙-镁铝尖晶石复相材料,并研究了烧成温度对复相材料的物相组成及强度的影响。结果表明:随着温度的升高,复相材料中刚玉相的含量逐渐降低,而铝酸钙和镁铝尖晶石的含量逐渐上升,材料的显气孔率略有增大,但是其劈裂抗拉强度逐渐增大。放电等离子烧结使复相材料中片状刚玉、生成的铝酸钙和镁铝尖晶石在高温下相互结合。当烧成温度为1150℃时,所制备的复相材料显气孔率为23.2%,劈裂抗拉强度达到20 MPa。

  4. The progress of early phase bone healing using porous granules produced from calcium phosphate cement

    Directory of Open Access Journals (Sweden)

    Jungbluth P

    2010-05-01

    Full Text Available Abstract Objective Bone grafting is a vital component in many surgical procedures to facilitate the repair of bone defects or fusions. Autologous bone has been the gold standard to date in spite of associated donor-site morbidity and the limited amount of available donor bone. The aim of this study was to investigate the progress of bone regeneration and material degradation of calcium phosphate granules (CPG produced from a calcium phosphate self-setting cement powder compared to the use of autologous bone grafting in the treatment of "critical size defects" on load-bearing long bones of minipigs. Methods A critical size defect in the tibial metaphysis of 16 mini-pigs was filled either with autologous cancellous graft or with micro- and macroporous carbonated, apatic calcium phosphate granules (CPG produced from a calcium phosphate self-setting cement powder. After 6 weeks, the specimens were assessed by X-ray and histological evaluation. The amount of new bone formation was analysed histomorphometrically. Results The semi-quantitative analysis of the radiological results showed a complete osseous bridging of the defect in three cases for the autograft group. In the same group five animals showed a beginning, but still incomplete bridging of the defect, whereas in the CPG group just two animals developed this. All other animals of the CPG group showed only a still discontinuous new bone formation. Altogether, radiologically a better osseous bridging was observed in the autograft group compared to the CPG group. Histomorphometrical analysis after six weeks of healing revealed that the area of new bone was significantly greater in the autograft group concerning the central area of the defect zone (p Conclusions Within the limits of the present study it could be demonstrated that autologous cancellous grafts lead to a significantly better bone regeneration compared to the application of calcium phosphate granules (CPG produced from a calcium

  5. Postextraction socket grafting using calcium phosphate cement and platelet rich fibrin

    Directory of Open Access Journals (Sweden)

    Nihal Devkar

    2014-01-01

    Full Text Available This clinical case report describes and demonstrates the successful use of calcium phosphate cement (CPC in conjunction with platelet-rich fibrin (PRF for postextraction socket grafting in maxillary right first premolar area. CPC can be molded to form a scaffold. It has been used previously for regeneration in intrabony defects, but very few clinical studies in humans have reported its use for socket grafting. In this report, we have presented a novel use of CPC in conjunction with PRF for ridge preservation after tooth extraction.

  6. 合理利用资源生产铝酸钙精炼渣的研究%Study on Producing Calcium Aluminate by Optimal Use of Resources

    Institute of Scientific and Technical Information of China (English)

    张延大

    2012-01-01

    钢铁冶炼会消耗大量的优质矿产资源,本文通过分析石灰岩、矾土矿等相关资源储量形势,指出了利用工业废渣作为原材料生产铝酸钙精炼渣的可行性,并在轴承钢生产中得到了理想的应用效果,脱硫率最高达到了83.5%,钛显微夹杂物显著降低.这对合理利用资源,实现可持续发展具有重要意义.%It consumes a lot of premium resources to make iron and steel. This paper dwells on the reserve situation of limestone and bauxite, indicating the feasibility of producing calcium aluminate refining slag by taking use of industrial offscum and it has been effectively used in bearing steel with desulfurization rate reaching 83.5% and micro-titanium impurity decreasing remarkably, which has important influence on the rational use of recourses and sustainable development.

  7. Mechanical properties of calcium phosphate cements obtained by solution combustion synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Volkmer, Tiago M.; Barreiro, Oscar; Souza, Vania Caldas; Santos, Luis Alberto dos, E-mail: tiagovolkmer@gmail.com, E-mail: oscarbafer@hotmail.com, E-mail: vania.souza@ufrgs.br, E-mail: luis.santos@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Laboratorio de Biomateriais

    2009-07-01

    Bioceramics based on calcium phosphates, especially hydroxyapatite and tricalcium phosphates (TCP) are the most used biomaterials as bone substitutes. The objective of this work is to evaluate the mechanical properties of α-tricalcium phosphate (α-TCP) synthesized by the solution combustion method. The solution combustion synthesis (SCS) can be considered as faster and simpler as other methods, furthermore it allows the obtainment of high purity α-TCP. In the calcium phosphates (CPC), α-TCP reacts with water forming needle like HA, which restrain the movement of grains, increasing mechanical resistance. In the present paper the influence of particle size on mechanical properties of α-TCP cements were evaluated. The α-TCP powder were characterized by XRD, TEM, BET and laser diffraction to asses particle size while the CPC bodies by SEM, Arquimedes method and compression tests. Increasing the milling time, the particle size decreases, resulting in samples with less porosity and consequently with higher compression resistance. (author)

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

    OpenAIRE

    Matijević, Božidar

    2013-01-01

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

  9. Improved workability of injectable calcium sulfate bone cement by regulation of self-setting properties

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zonggang, E-mail: chenzg@sdu.edu.cn [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, Huanye [Department of Orthodontics, School of Stomatology, China Medical University, Shenyang 110001 (China); Liu, Xi [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Lian, Xiaojie [College of Mechanics, Taiyuan University of Technology, Taiyuan 030024 (China); Guo, Zhongwu [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Jiang, Hong-Jiang [Wendeng Hospital of Traditional Chinese Orthopedics and Traumatology, Shandong 264400 (China); Cui, Fu-Zhai, E-mail: cuifz@mail.tsinghua.edu.cn [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2013-04-01

    Calcium sulfate hemihydrate (CSH) powder as an injectable bone cement was prepared by hydrothermal synthesis of calcium sulfate dihydrate (CSD). The prepared materials showed X-ray diffraction peaks corresponding to the CSH structure without any secondary phases, implying complete conversion from CSD phase to CSH phase. Thermogravimetric (TG) analyses showed the crystal water content of CSH was about 6.0% (wt.), which is near to the theoretic crystal water value of CSH. From scanning electron microscopy (SEM) micrographs, sheet crystal structure of CSD was observed to transform into rod-like crystal structure of CSH. Most interesting and important of all, CSD as setting accelerator was also introduced into CSH powder to regulate self-setting properties of injectable CSH paste, and thus the self-setting time of CSH paste can be regulated from near 30 min to less than 5 min by adding various amounts of setting accelerator. Because CSD is not only the reactant of preparing CSH but also the final solidified product of CSH, the setting accelerator has no significant effect on the other properties of materials, such as mechanical properties. In vitro biocompatibility and in vivo histology studies have demonstrated that the materials have good biocompatibility and good efficacy in bone regeneration. All these will further improve the workability of CSH in clinic applications. Highlights: ► Calcium sulfate hemihydrate (CSH) can be an injectable bone cement. ► CSH was produced by hydrothermal synthesis of calcium sulfate dihydrate (CSD). ► CSD was introduced into CSH powder to regulate self-setting properties of CSH. ► Setting accelerator has no significant effect on the other properties of materials. ► Injectable CSH has good biocompatibility and good efficacy in bone regeneration.

  10. Microstructure and Mechanical Properties of Calcium Phosphate Cement/Gelatine Composite Scaffold with Oriented Pore Structure for Bone Tissue Engineering

    Institute of Scientific and Technical Information of China (English)

    QI Xiaopeng; HE Fupo; YE Jiandong

    2012-01-01

    The macroporous calcium phosphate(CPC) cement with oriented pore structure was prepared by freeze casting.SEM observation showed that the macropores in the porous calcium phosphate cement were interconnected aligned along the ice growth direction.The porosity of the as-prepared porous CPC was measured to be 87.6% by Archimede's principle.XRD patterns of specimens showed that poorly crystallized hydroxyapatite was the main phase present in the hydrated porous calcium phosphate cement.To improve the mechanical properties of the CPC scaffold,the 15% gelatine solution was infiltrated into the pores under vacuum and then the samples were freeze dried to form the CPC/gelatine composite scaffolds.After reinforced with gelatine,the compressive strength of CPC/gelatine composite increased to 5.12 MPa,around fifty times greater than that of the unreinforced macroporous CPC scaffold,which was only 0.1 MPa.And the toughness of the scaffold has been greatly improved via the gelatine reinforcement with a much greater fracture strain.SEM examination of the specimens indicated good bonding between the cement and gelatine.Participating the external load by the deformable gelatine,patching the defects of the CPC pores wall,and crack deflection were supposed to be the reinforcement mechanisms.In conclusion,the calcium phosphate cement/gelatine composite with oriented pore structure prepared in this work might be a potential scaffold for bone tissue engineering.

  11. Statistical Analyses of Optimum Partial Replacement of Cement by Fly Ash Based on Complete Consumption of Calcium Hydroxide

    Directory of Open Access Journals (Sweden)

    Ouypornprasert Winai

    2016-01-01

    Full Text Available The objectives of this technical paper were to propose the optimum partial replacement of cement by fly ash based on the complete consumption of calcium hydroxide from hydration reactions of cement and the long-term strength activity index based on equivalent calcium silicate hydrate as well as the propagation of uncertainty due to randomness inherent in main chemical compositions in cement and fly ash. Firstly the hydration- and pozzolanic reactions as well as stoichiometry were reviewed. Then the optimum partial replacement of cement by fly ash was formulated. After that the propagation of uncertainty due to main chemical compositions in cement and fly ash was discussed and the reliability analyses for applying the suitable replacement were reviewed. Finally an applicability of the concepts mentioned above based on statistical data of materials available was demonstrated. The results from analyses were consistent with the testing results by other researchers. The results of this study provided guidelines of suitable utilization of fly ash for partial replacement of cement. It was interesting to note that these concepts could be extended to optimize partial replacement of cement by other types of pozzolan which were described in the other papers of the authors.

  12. Calcium polyphosphate as an additive to zinc-silicate glass ionomer cements.

    Science.gov (United States)

    Valliant, Esther Mae; Gagnier, David; Dickey, Brett Thomas; Boyd, Daniel; Filiaggi, Mark Joseph

    2015-07-01

    Aluminum-free glass ionomer cements (GICs) are under development for orthopedic applications, but are limited by their insufficient handling properties. Here, the addition of calcium polyphosphate (CPP) was investigated as an additive to an experimental zinc-silicate glass ionomer cement. A 50% maximum increase in working time was observed with CPP addition, though this was not clinically significant due to the short working times of the starting zinc-silicate GIC. Surprisingly, CPP also improved the mechanical properties, especially the tensile strength which increased by ∼33% after 30 days in TRIS buffer solution upon CPP addition up to 37.5 wt%. This strengthening may have been due to the formation of ionic crosslinks between the polyphosphate chains and polyacrylic acid. Thus, CPP is a potential additive to future GIC compositions as it has been shown to improve handling and mechanical properties. In addition, CPP may stimulate new bone growth and provide the ability for drug delivery, which are desirable modifications for an orthopedic cement.

  13. Vital Pulp Therapy with Calcium-Silicate Cements: Report of Two Cases

    Science.gov (United States)

    Ashraf, Hengameh; Rahmati, Afsaneh; Amini, Neda

    2017-01-01

    This article describes successful use of calcium-enriched mixture (CEM) cement and Biodentine in apexogenesis treatment in two 8-year-old patients, one with immature permanent molar diagnosed primarily with irreversible pulpitis and the other with partially vital maxillary central incisor. After access cavity preparation, partial pulpotomy in molar and full pulpotomy in central was performed, and the remaining pulps was capped with either Biodentine or CEM cement, in each tooth. The crowns were restored with composite filling material at the following visit. The post-operative radiographic and clinical examinations (approx. average of 16 months) showed that both treated teeth remained functional, with complete root development and apex formation. A calcified bridge was produced underneath the capping material. No further endodontic intervention was necessary. Considering the healing potential of immature vital pulps, the use of CEM cement and Biodentine for apexogenesis might be an applicable choice. These new endodontic biomaterials might be appropriate for vital pulp therapies in an immature tooth. However, further clinical studies with longer follow-up periods are recommended. PMID:28179936

  14. Calcium phosphate cements for bone substitution: chemistry, handling and mechanical properties.

    Science.gov (United States)

    Zhang, Jingtao; Liu, Weizhen; Schnitzler, Verena; Tancret, Franck; Bouler, Jean-Michel

    2014-03-01

    Since their initial formulation in the 1980s, calcium phosphate cements (CPCs) have been increasingly used as bone substitutes. This article provides an overview on the chemistry, kinetics of setting and handling properties (setting time, cohesion and injectability) of CPCs for bone substitution, with a focus on their mechanical properties. Many processing parameters, such as particle size, composition of cement reactants and additives, can be adjusted to control the setting process of CPCs, concomitantly influencing their handling and mechanical performance. Moreover, this review shows that, although the mechanical strength of CPCs is generally low, it is not a critical issue for their application for bone repair--an observation not often realized by researchers and clinicians. CPCs with compressive strengths comparable to those of cortical bones can be produced through densification and/or homogenization of the cement matrix. The real limitation for CPCs appears to be their low fracture toughness and poor mechanical reliability (Weibull modulus), which have so far been only rarely studied.

  15. Incorporation of biodegradable electrospun fibers into calcium phosphate cement for bone regeneration.

    Science.gov (United States)

    Zuo, Yi; Yang, Fang; Wolke, Joop G C; Li, Yubao; Jansen, John A

    2010-04-01

    Inherent brittleness and slow degradation are the major drawbacks for the use of calcium phosphate cements (CPCs). To address these issues, biodegradable ultrafine fibers were incorporated into the CPC in this study. Four types of fibers made of poly(epsilon-caprolactone) (PCL) (PCL12: 1.1 microm, PCL15: 1.4 microm, PCL18: 1.9 microm) and poly(l-lactic acid) (PLLA4: 1.4 microm) were prepared by electrospinning using a special water pool technique, then mixed with the CPC at fiber weight fractions of 1%, 3%, 5% and 7%. After incubation of the composites in simulated body fluid for 7 days, they were characterized by a gravimetric measurement for porosity evaluation, a three-point bending test for mechanical properties, microcomputer topography and scanning electron microscopy for morphological observation. The results indicated that the incorporation of ultrafine fibers increases the fracture resistance and porosity of CPCs. The toughness of the composites increased with the fiber fraction but was not affected by the fiber diameter. It was found that the incorporated fibers formed a channel-like porous structure in the CPCs. After degradation of the fibers, the created space and high porosity of the composite cement provides inter-connective channels for bone tissue in growth and facilitates cement resorption. Therefore, we concluded that this electrospun fiber-CPC composite may be beneficial to be used as bone fillers.

  16. Long-term evaluation of the degradation behavior of three apatite-forming calcium phosphate cements.

    Science.gov (United States)

    An, Jie; Liao, Hongbing; Kucko, Nathan W; Herber, Ralf-Peter; Wolke, Joop G C; van den Beucken, Jeroen J J P; Jansen, John A; Leeuwenburgh, Sander C G

    2016-05-01

    Calcium phosphate cements (CPCs) are injectable bone substitutes with a long clinical history because of their biocompatibility and osteoconductivity. Nevertheless, their cohesion upon injection into perfused bone defects as well as their long-term degradation behavior remain major clinical challenges. Therefore, the long-term degradation behavior of two types of α-tricalcium phosphate-based, apatite-forming CPCs was compared to a commercially available apatite-forming cement, that is HydroSet™ . Carboxyl methylcellulose (CMC) was used as cohesion promotor to improve handling properties of the two experimental cements, whereas poly (d, l-lactic-co-glycolic) acid (PLGA) microparticles were added to introduce macroporosity and stimulate CPC degradation. All three CPCs were injected into defects drilled into rabbit femoral condyles and explanted after 4, 12, or 26 weeks, after which the bone response was assessed both qualitatively and quantitatively. CPCs without PLGA microparticles degraded only at the periphery of the implants, while the residual CPC volume was close to 90%. On the contrary, bone ingrowth was observed not only at the periphery of the CPC, but also throughout the center of the implants after 26 weeks of implantation for the PLGA-containing CPCs with a residual CPC volume of approximately 55%. In conclusion, it was shown that CPC containing CMC and PLGA was able to induce partial degradation of apatite-forming CPCs and concomitant replacement by bone tissue.

  17. In Vitro Cytotoxicity of Calcium Silicate-Based Endodontic Cement as Root-End Filling Materials

    Directory of Open Access Journals (Sweden)

    Selen Küçükkaya

    2016-01-01

    Full Text Available The aim of this study was to evaluate the cytotoxicity of three types of calcium silicate-based endodontic cement after different incubation periods with human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were cultured from extracted third molars and seeded in 96-well plates. MTA, calcium enriched mixture (CEM cement, and Biodentine were prepared and added to culture insert plates which were immediately placed into 96-well plates containing cultured cells. After incubation periods of 24, 48, and 72 hours, cell viability was determined with WST-1 assay. Data were analysed statistically by ANOVA with repeated measures and Bonferroni tests. There was no significant difference in cell viability amongst the test materials after each incubation period (P>0.05. MTA and CEM presented more than 90% cell viability after 24 and 48 hours of incubation and showed statistically significant decrease in cell viability after 72 hours of incubation (P<0.05. Biodentine showed significantly less cell viability (73% after 24 hours of incubation, whereas more than 90% cell viability was seen after 48 and 72 hours of incubation (P<0.05. Despite the significant changes in cell viability over time, materials presented similar cytotoxicity profile. Biodentine and CEM can be considered as alternative materials for root-end surgery procedures.

  18. In Vitro Cytotoxicity of Calcium Silicate-Based Endodontic Cement as Root-End Filling Materials.

    Science.gov (United States)

    Küçükkaya, Selen; Görduysus, Mehmet Ömer; Zeybek, Naciye Dilara; Müftüoğlu, Sevda Fatma

    2016-01-01

    The aim of this study was to evaluate the cytotoxicity of three types of calcium silicate-based endodontic cement after different incubation periods with human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were cultured from extracted third molars and seeded in 96-well plates. MTA, calcium enriched mixture (CEM) cement, and Biodentine were prepared and added to culture insert plates which were immediately placed into 96-well plates containing cultured cells. After incubation periods of 24, 48, and 72 hours, cell viability was determined with WST-1 assay. Data were analysed statistically by ANOVA with repeated measures and Bonferroni tests. There was no significant difference in cell viability amongst the test materials after each incubation period (P > 0.05). MTA and CEM presented more than 90% cell viability after 24 and 48 hours of incubation and showed statistically significant decrease in cell viability after 72 hours of incubation (P Biodentine showed significantly less cell viability (73%) after 24 hours of incubation, whereas more than 90% cell viability was seen after 48 and 72 hours of incubation (P Biodentine and CEM can be considered as alternative materials for root-end surgery procedures.

  19. Bioactive calcium sulfate/magnesium phosphate cement for bone substitute applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Guangyong [Department of Orthopaedics, Taizhou Hospital of Zhejiang Province, Linhai Zhejiang, 317000 (China); Department of Orthopaedic Surgery, Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, Zhejiang, 325000 (China); Liu, Jianli [Trauma Center, Affiliated Hospital of Hainan Medical University, Haikou, Hainan, 570206 (China); Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS), Ningbo, Zhejiang, 315201 (China); Li, Fan; Pan, Zongyou; Ni, Xiao; Shen, Yue [Department of Orthopaedic Surgery, Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, Zhejiang, 325000 (China); Xu, Huazi, E-mail: spinexu@163.com [Department of Orthopaedic Surgery, Second Affiliated Hospital of Wenzhou Medical College, Wenzhou, Zhejiang, 325000 (China); Huang, Qing, E-mail: huangqing@nimte.ac.cn [Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences (CAS), Ningbo, Zhejiang, 315201 (China)

    2014-02-01

    A novel calcium sulfate/magnesium phosphate cement (CSMPC) composite was prepared and studied in the present work. The physical properties including the phases, the microstructures, the setting properties and the compressive strengths of the CSMPCs were studied. The bio-performances of the CSMPCs were comprehensively evaluated using in vitro simulated body fluid (SBF) method and in vitro cell culture. The dependence of the physical and chemical properties of the CSMPC on its composition and microstructure was studied in detail. It is found that the CSMPC composites exhibited mediate setting times (6–12 min) compared to the calcium sulfate (CS) and the magnesium phosphate cement (MPC). They showed an encapsulation structure in which the unconverted hexagonal prism CSH particles were embedded in the xerogel-like MPC matrix. The phase compositions and the mechanical properties of the CSMPCs were closely related to the content of MPC and the hardening process. The CSMPCs exhibited excellent bioactivity and good biocompatibility to support the cells to attach and proliferate on the surface. The CSMPC composite has the potential to serve as bone grafts for the bone regeneration. - Highlights: • The mechanical strength and degradation rate of CSMPC composites are discussed. • The CSMPC composites exhibited good bioactivity to form bone-like apatite. • The CSMPC composites also show good biocompatibility.

  20. Bioactive calcium sulfate/magnesium phosphate cement for bone substitute applications.

    Science.gov (United States)

    Yang, Guangyong; Liu, Jianli; Li, Fan; Pan, Zongyou; Ni, Xiao; Shen, Yue; Xu, Huazi; Huang, Qing

    2014-02-01

    A novel calcium sulfate/magnesium phosphate cement (CSMPC) composite was prepared and studied in the present work. The physical properties including the phases, the microstructures, the setting properties and the compressive strengths of the CSMPCs were studied. The bio-performances of the CSMPCs were comprehensively evaluated using in vitro simulated body fluid (SBF) method and in vitro cell culture. The dependence of the physical and chemical properties of the CSMPC on its composition and microstructure was studied in detail. It is found that the CSMPC composites exhibited mediate setting times (6-12 min) compared to the calcium sulfate (CS) and the magnesium phosphate cement (MPC). They showed an encapsulation structure in which the unconverted hexagonal prism CSH particles were embedded in the xerogel-like MPC matrix. The phase compositions and the mechanical properties of the CSMPCs were closely related to the content of MPC and the hardening process. The CSMPCs exhibited excellent bioactivity and good biocompatibility to support the cells to attach and proliferate on the surface. The CSMPC composite has the potential to serve as bone grafts for the bone regeneration.

  1. A histological evaluation on osteogenesis and resorption of methotrexate-loaded calcium phosphate cement in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Li Dong; Yang Zhiping; Li Xin; Li Zhenfeng; Li Jianmin [Department of Orthopedics, Qilu Hospital of Shandong University, Shandong (China); Yang Jingyan, E-mail: yangzhiping@medmail.com.c [Department of Pathology, 2nd Affiliated Hospital of Shandong University, Shandong (China)

    2010-04-15

    In this study, we investigated the resorption of in vivo methotrexate-loaded calcium phosphate cement (MTX-CPC) implants and their effect on osteogenesis. MTX-CPC implants containing 1% methotrexate (MTX) (weight/weight) were preset and implanted into the femoral condyle of rabbits. Calcium phosphate cement (CPC) without MTX was used as the control. The femurs were harvested at day 1 and at 1, 3 and 6 months after implantation and radiological examination were performed. Decalcified sections were examined by hematoxylin and eosin (HE) staining, alkaline phosphatase (ALPase) immunohistochemistry and tartrate-resistant acid phosphatase (TRAPase) enzyme histochemistry. Then, we performed histomorphometric analysis, including determination of the percentage of newly formed bone and osteoblast and osteoclast counts. The results indicated that MTX-CPC implants were biocompatible, biodegradable and osteoconducive. However, MTX release from the implantation site inhibited osteogenesis in the initial period; this inhibition weakened with time, and no difference was observed between CPC and MTX-CPC at 6 months after implantation. Hence, MTX-CPC is an excellent material for filling defects and can be used for preparing effective drug delivery systems to achieve local control of invasive bone tumors.

  2. A Comprehensive Study of Osteogenic Calcium Phosphate Silicate Cement: Material Characterization and In Vitro/In Vivo Testing.

    Science.gov (United States)

    Gong, Tianxing; Wang, Zhiqin; Zhang, Yixi; Zhang, Yubiao; Hou, Mingxiao; Liu, Xinwei; Wang, Yu; Zhao, Lejun; Ruse, N Dorin; Troczynski, Tom; Häfeli, Urs O

    2016-02-18

    Vertebral compression fractures can be successfully restored by injectable bone cements. Here the as-yet unexplored in vitro cytotoxicity, in vivo biodegradation, and osteoconductivity of a new calcium phosphate silicate cements (CPSC) are studied, where monocalcium phosphate (MCP; 5, 10, and 15 wt%) is added to calcium silicate cement (CSC). Setting rate and compressive strength of CPSC decrease with the addition of MCP. The crystallinity, microstructure, and porosity of hardened CPSC are evaluated by X-ray diffractometer, Fourier transform infrared spectroscopy, and microcomputed tomography (CT). It is found that MCP reacts with calcium hydroxide, one of CSC hydration products, to precipitate apatite. While the reaction accelerates the hydration of CSC, the formation of calcium silicate hydrate gel is disturbed and highly porous microstructures form, resulting in weaker compressive strength. In vitro studies demonstrate that CPSC is noncytotoxic to osteoblast cells and promotes their proliferation. In the rabbit tibia implantation model, clinical X-ray and CT scans demonstrate that CPSC biodegrades slower and osseointegrates better than clinically used calcium phosphate cement (CPC). Histological studies demonstrate that CPSC is osteoconductive and induces higher bone formation than CPC, a finding that might warrant future clinical studies.

  3. Sustained release of small molecules from carbon nanotube-reinforced monetite calcium phosphate cement.

    Science.gov (United States)

    Lin, Boren; Zhou, Huan; Leaman, Douglas W; Goel, Vijay K; Agarwal, Anand K; Bhaduri, Sarit B

    2014-10-01

    The interest in developing calcium phosphate cement (CPC) as a drug delivery system has risen because of its capability to achieve local and controlled treatment to the site of the bone disease. The purpose of this study was to investigate the release pattern of drug-carrying carboxylic acid-functionalized multi-walled carbon nanotube (MWCNT)-reinforced monetite (DCPA, CaHPO4)-based CPC. Z-Leu-Leu-Leu-al (MG132), a small peptide molecule inhibiting NF-κB-mediated osteoclastic resorption, was used as a model drug. MG132 was added into the cement during setting and released into the medium used to culture indicator cells. Significant cell death was observed in osteoblast MC3T3-E1 cells cultured in the medium incubated with MG132-loaded CPC; however, with the presence of MWCNTs in the cement, the toxic effect was not detectable. NF-κB activation was quantified using a NF-κB promoter-driving luciferase reporter in human embryonic kidney 293 cells. The medium collected after incubation with drug-incorporated CPC with or without MWCNT inhibited TNFα-induced NF-κB activation indicating that the effective amount of MG132 was released. CPC/drug complex showed a rapid release within 24h whereas incorporation of MWCNTs attenuated this burst release effect. In addition, suppression of TNFα-induced osteoclast differentiation in RAW 264.7 cell culture also confirmed the sustained release of MWCNT/CPC/drug. Our data demonstrated the drug delivery capability of this cement composite, which can potentially be used to carry therapeutic molecules to improve bone regeneration in conjunction with its fracture stabilizing function. Furthermore, it suggested a novel approach to lessen the burst release effect of the CPC-based drug delivery system by incorporating functionalized MWCNTs.

  4. Development of strong and bioactive calcium phosphate cement as a light-cure organic-inorganic hybrid.

    Science.gov (United States)

    Barounian, M; Hesaraki, S; Kazemzadeh, A

    2012-07-01

    In this research, light cured calcium phosphate cements (LCCPCs) were developed by mixing a powder phase (P) consisting of tetracalcium phosphate and dicalcium phosphate and a photo-curable resin phase (L), mixture of hydroxyethylmethacrylate (HEMA)/poly acrylic-maleic acid at various P/L ratios of 2.0, 2.4 and 2.8 g/mL. Mechanical strength, phase composition, chemical groups and microstructure of the cured cements were evaluated at pre-set times, i.e. before and after soaking in simulated body fluid (SBF). The proliferation of Rat-derived osteoblastic cells onto the LCCPCs as well as cytotoxicity of cement extracts were determined by cell counting and 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyl-2H-tetrazolium bromide assay after different culture times. It was estimated from Fourier transforming infrared spectra of cured cements that the setting process is ruled by polymerization of HEMA monomers as well as formation of calcium poly-carboxylate salts. Microstructure of the cured cements consisted of calcium phosphate particles surrounded by polymerized resin phase. Formation of nano-sized needlelike calcium phosphate phase on surfaces of cements with P/L ratios of 2.4 and 2.8 g/mL was confirmed by scanning electron microscope images and X-ray diffractometry (XRD) of the cured specimen soaked in SBF for 21 days. Also, XRD patterns revealed that the formed calcium phosphate layer was apatite phase in a poor crystalline form. Biodegradation of the cements was confirmed by weight loss, change in molecular weight of polymer and morphology of the samples after different soaking periods. The maximum compressive strength of LCCPCs governed by resin polymerization and calcium polycarboxylate salts formation was about 80 MPa for cement with P/L ratio of 2.8 g/mL, after incubation for 24 h. The strength of all cements decreased by decreasing P/L ratio as well as increasing soaking time. The preliminary cell studies revealed that LCCPCs could support proliferation of

  5. Characterization of high-calcium fly ash and its influence on ettringite formation in portland cement pastes

    Science.gov (United States)

    Tishmack, Jody Kathleen

    High-calcium Class C fly ashes derived from Powder River Basin coal are currently used as supplementary cementing materials in portland cement concrete. These fly ashes tend to contain significant amounts of sulfur, calcium, and aluminum, thus they are potential sources of ettringite. Characterization of six high-calcium fly ashes originating from Powder River Basin coal have been carried out. The hydration products formed in pastes made from fly ash and water were investigated. The principal phases produced at room temperature were ettringite, monosulfate, and stratlingite. The relative amounts formed varied with the specific fly ash. Removal of the soluble crystalline sulfur bearing minerals indicated that approximately a third of the sulfur is located in the fly ash glass. Pore solution analyses indicated that sulfur concentrations increased at later ages. Three fly ashes were selected for further study based on their ability to form ettringite. Portland cement-fly ash pastes made with the selected fly ashes were investigated to evaluate ettringite and monosulfate formation. Each of the fly ashes were mixed with four different types of portland cements (Type I, I/II, II, and III) as well as three different Type I cements exhibiting a range of C3A and sulfate contents. The pastes had 25% or 35% fly ash by total weight of solids and a water:cement-fly ash ratio of 0.45. The samples were placed in a curing room (R.H. = 100, 23°C) and were then analyzed at various ages by x-ray diffraction (XRD) and differential scanning calorimetry (DSC) to determine the principal hydration products. The hydration products identified by XRD were portlandite, ettringite (an AFt phase), monosulfate, and generally smaller amounts of hemicarboaluminate and monocarboaluminate (all AFm phases). Although the amount of ettringite formed varied with the individual cement, only a modest correlation with cement sulfate content and no correlation with cement C3A content was observed. DSC

  6. Porous poly(DL-lactic-co-glycolic acid)/calcium phosphate cement composite for reconstruction of bone defects.

    NARCIS (Netherlands)

    Ruhe, P.Q.; Hedberg, E.L.; Padron, N.T.; Spauwen, P.H.M.; Jansen, J.A.; Mikos, A.G.

    2006-01-01

    Calcium phosphate (Ca-P) cements are injectable, self-setting ceramic pastes generally known for their favorable bone response. Ingrowth of bone and subsequent degradation rates can be enhanced by the inclusion of macropores. Initial porosity can be induced by CO(2) foaming during setting of the cem

  7. Orbital floor reconstruction using calcium phosphate cement paste: an animal study.

    Science.gov (United States)

    Tañag, Marvin A; Yano, Kenji; Hosokawa, Ko

    2004-12-01

    Orbital floor defects were created in 10 New Zealand white rabbits and were reconstructed using an injectable calcium phosphate paste. These animals were euthanized at 2, 4, 8, and 12 months after implantation and were examined for biocompatibility and osteoconductivity. Grossly, implants were found to be adherent to the floor and covered with fibrous tissues. There was no sign of infection, extrusion, or migration of implant within the orbit and maxilla. The orbital floor was completely restored. Histological examination showed active new bone formation that encroached within the implant and gradually increased in density with time. Maxillary mucosa and glands were likewise reconstituted. Thin fibrovascular tissues were seen on top of and within the surface of the implant, and few to slight inflammatory cells were seen. Microradiography showed direct apposition between the new bone and the implant. These findings compare favorably with previously published reports on the biocompatibility and osteoconductivity of calcium phosphate cement. The authors believe that, together with ease of use and structural integrity, calcium phosphate paste can be useful in orbital floor reconstruction.

  8. Calcium silicate cement-induced remineralisation of totally demineralised dentine in comparison with glass ionomer cement: tetracycline labelling and two-photon fluorescence microscopy.

    Science.gov (United States)

    Atmeh, A R; Chong, E Z; Richard, G; Boyde, A; Festy, F; Watson, T F

    2015-02-01

    Two-photon fluorescence microscopy, in combination with tetracycline labelling, was used to observe the remineralising potentials of a calcium silicate-based restorative material (Biodentine(TM) ) and a glass ionomer cement (GIC:​Fuji​IX) on totally demineralised dentine. Forty demineralised dentine discs were stored with either cement in three different solutions: phosphate buffered saline (PBS) with tetracycline, phosphate-free tetracycline, and tetracycline-free PBS. Additional samples of demineralised dentine were stored alone in the first solution. After 8-week storage at 37 °C, dentine samples were imaged using two-photon fluorescence microscopy and Raman spectroscopy. Samples were later embedded in PMMA and polished block surfaces studied by 20 kV BSE imaging in an SEM to study variations in mineral concentration. The highest fluorescence intensity was exhibited by the dentine stored with Biodentine(TM) in the PBS/tetracycline solution. These samples also showed microscopic features of matrix remineralisation including a mineralisation front and intra- and intertubular mineralisation. In the other solutions, dentine exhibited much weaker fluorescence with none of these features detectable. Raman spectra confirmed the formation of calcium phosphate mineral with Raman peaks similar to apatite, while no mineral formation was detected in the dentine stored in cement-free or PBS-free media, or with GIC. It could therefore be concluded that Biodentine(TM) induced calcium phosphate mineral formation within the dentine matrix when stored in phosphate-rich media, which was selectively detectable using the tetracycline labelling.

  9. Calcium phosphate cements properties with polymers addition; Propriedades do cimento de fosfato de calcio com adicao de polimeros

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, J.M.; Trajano, W.T.; Escobar, C.F.; Santos, L.A., E-mail: julianafernandes2@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRGS), RS (Brazil)

    2012-07-01

    Calcium phosphate cements (CPC) have attracted great interest to use in orthopedics and dentistry as replacements for damaged parts of the skeletal system, showing good biocompatibility and osseointegration, allowing its use as bone graft. Several studies have shown that the addition of polymer additives have a strong influence on the cement properties. The low mechanical strength is the main obstacle to greater use of CPC as an implant material. The objective of this study was to evaluate properties of a cement based on α-tricalcium phosphate (α-TCP), added polymers. PVA (10%, 8%, 6%), sodium alginate (2%) and polyacrylate ammonia (3%), all in weight, were added to the synthesized α-TCP powder. The samples were molded and evaluated for density, porosity in vitro test (Simulated Body Fluid), crystalline phases and mechanical strength. The results show increased the mechanical properties of the cement when added these polymers.

  10. The Effect of Premixed Schedule on the Crystal Formation of Calcium Phosphate Cement-chitosan Composite with Added Tetracycline

    Institute of Scientific and Technical Information of China (English)

    Jing MAO; Yan LIU; Bin ZHOU; Liyun YAO

    2008-01-01

    In this study, calcium phosphate cements (CPC) were prepared by mixing cement powders of tetracalcium phosphate (TTCP) with a cement liquid of phosphate acid saline solution. Tetracycline (TTC)-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal characteristics. TTCP mixed with phosphate acid saline solution had similar features of Fourier transform-infrared spectrometry (FT-IR) no matter it was mixed with chitosan or TTC or both. TTC premixed with cement liquid or powder had significant different features of FT-IR and 876 cm-1seemed to be a special peak for TTC when TTC was premixed with cement liquid. This was also supported by XRD analysis, which showed that TTC premixed with cement liquid improved phase transition of TTCP to OCP. Chitosan, as organic additive, regulates the regular crystal formation and inhibits the phase transition of TTCP to OCP, except when it is mingled with cement liquid premixed with TTC in field scanning electron microscope. It was concluded that the premixed schedule influences the crystal formation and phase transition, which may be associated with its biocompatibility and bioactivities in vivo.

  11. Influence of portland cement replacement in high calcium fly ash geopolymer paste

    Directory of Open Access Journals (Sweden)

    Tanakorn Phoo-ngernkham

    2014-03-01

    Full Text Available This article presents the influence of ordinary Portland cement (OPC replacement in high calcium fly ash (FA geopolymer paste. FA was used to replace OPC at the rate of 5, 10 and 15% by mass of binder. Sodium silicate (Na2SiO3 and 10 molar sodium hydroxide (NaOH solutions were used as the alkaline solution in the reaction. The Na2SiO3/NaOH ratio of 2.0 and the liquid/binder (L/B ratio of 0.60 were used in all mixtures. The results of increase OPC replacement, the setting time and compressive strain capacity decreased while the compressive strength and modulus of elasticity increased. The compressive strength and modulus of elasticity at 28 days of geopolymer pastes with 15% OPC replacement were 36.7 MPa and 13,300 MPa, respectively.

  12. Effects of adding resorbable chitosan microspheres to calcium phosphate cements for bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Dan [Department of Prosthodontics, Beijing Stomatological Hospital, Capital Medical University, Beijing 100050 (China); Dong, Limin [Beijing Key Lab of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Energy Science Building, Beijing 100084 (China); Wen, Ying [Department of Prosthodontics, Beijing Stomatological Hospital, Capital Medical University, Beijing 100050 (China); Xie, Qiufei, E-mail: xieqiuf@163.com [Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing 100081 (China)

    2015-02-01

    Calcium phosphate cements (CPCs) have been widely used as bone graft substitutes. However, the undesirable osteoinductivity and slow degradability of CPCs greatly hamper their clinical application. The aim of this study was to synthesize a type of injectable, bioactive cement. This was accomplished by incorporating chitosan microspheres into CPC. CPC containing chitosan microspheres was analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD showed that the hardened chitosan microsphere/CPC with different proportions of microspheres contained diffraction peaks of hydroxyapatite and chitosan. Compressive strength and dissolution in simulated body fluid were measured. The chitosan microsphere/CPC containing 10% (w/w) chitosan microspheres had a compressive strength of 14.78 ± 0.67 MPa. Cavity defects were created in both femoral condylar regions of New Zealand White rabbits. Chitosan microsphere/CPC (composite group) and α-TCP/CPC (control group) were implanted separately into the bone defects of both femurs. X-ray analysis was performed to observe the filling of these bone defects 3 days after surgery. The extent of bone substitute degradation and new bone formation were evaluated by SEM and histological examination at 8, 16, and 24 weeks after implantation. These results showed far more new bone formation and degradation of the chitosan microsphere/CPC composite in the bone defects. These data indicate that a chitosan microsphere/CPC composite might be considered as a promising injectable material for the generation of new bone tissue. - Highlights: • We synthesized an injectable, bioactive chitosan microsphere/CPC for the first time. • 100–400 μm chitosan microspheres were incorporated into the cement solid phase. • XRD showed the construct contained diffraction peaks of hydroxyapatite and chitosan. • Compressive strength of the composite was about 15 MPa comparable to cancellous bone. • The new construct shows better bone

  13. Indirect pulp therapy in a symptomatic mature molar using calcium enriched mixture cement

    Directory of Open Access Journals (Sweden)

    Hassan Torabzadeh

    2013-01-01

    Full Text Available Dental pulp has the ability of repair/regeneration. Indirect pulp therapy (IPT is recommended for pulp preservation in asymptomatic teeth with extremely deep caries as well as teeth with clinical symptoms of reversible pulpitis. In this case study, we performed IPT with calcium enriched mixture (CEM cement on a symptomatic permanent molar. After clinical/radiographic examinations the tooth was diagnosed with irreversible pulpitis and associated apical periodontitis. IPT involved partial caries removal, the placement of CEM cement pulp cap and overlying adhesive permanent restoration. At the 1 week follow-up, patient′s spontaneous symptoms had resolved. One-year follow-up demonstrated pulp vitality, clinical function, as well as the absence of pain/tenderness to percussion/palpation/cold sensitivity tests; periapical radiograph showed a healing periradicular lesion with newly formed bone, that is normal pulp with normal periodontium. These favorable results indicate that IPT/CEM may be a good treatment option in comparison to endodontic treatment in young patients. IPT of deep-caries lesion is an easier, more practical and valuable treatment plan than complete caries removal.

  14. Augmentation of screw fixation with injectable calcium sulfate bone cement in ovariectomized rats.

    Science.gov (United States)

    Yu, Xiao-Wei; Xie, Xin-Hui; Yu, Zhi-Feng; Tang, Ting-Ting

    2009-04-01

    The objective of this study was to determine the effect of augmenting screw fixation with an injectable calcium sulfate cement (CSC) in the osteoporotic bone of ovariectomized rats. The influence of the calcium sulfate (CS) on bone remodeling and screw anchorage in osteoporotic cancellous bone was systematically investigated using histomorphometric and biomechanical analyses. The femoral condyles of 55 Sprague-Dawley ovariectomized rats were implanted with screw augmented with CS, while the contralateral limb received a nonaugmented screw. At time intervals of 2, 4, 8, 12, and 16 weeks, 11 rats were euthanized. Six pair-matched samples were used for histological analysis, while five pair-matched samples were preserved for biomechanical testing. Histomorphometric data showed that CS augmented screws activated cancellous bone formation, evidenced by a statistically higher (p < 0.05) percentage of osteoid surface at 2, 4, and 8 weeks and a higher rate of bone mineral apposition at 12 weeks compared with nonaugmented screws. The amount of the bone-screw contact at 2, 8, and 12 weeks and of bone ingrowth on the threads at 4 and 8 weeks was greater in the CS group than in the nonaugmented group (p < 0.05), although these parameters increased concomitantly with time for both groups. The CS was resorbed completely at 8 weeks without stimulating fibrous encapsulation on the screw surface. Also, the cement significantly increased the screw pull-out force and the energy to failure at 2, 4, 8, and 12 weeks after implantation, when compared with the control group (p < 0.05). These results imply that augmentation of screw fixation with CS may have the potential to decrease the risk of implant failure in osteoporotic bone.

  15. Pollution and Prevention of Pb during Cement Calcination

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

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

  16. Wollastonite nanofiber–doped self-setting calcium phosphate bioactive cement for bone tissue regeneration

    Directory of Open Access Journals (Sweden)

    Guo H

    2012-07-01

    Full Text Available Han Guo,1,2 Jie Wei,2 Wenhua Song,2 Shan Zhang,2 Yonggang Yan,3 Changsheng Liu,2 Tiqiao Xiao11Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, People's Republic of China; 2Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai, People's Republic of China; 3School of Physical Science and Technology, Sichuan University, Chengdu, People's Republic of ChinaAbstract: The purpose of this study was to synthesize a self-setting bioactive cement by incorporation of wollastonite nanofibers (WNFs into calcium phosphate cement (CPC. The composition, morphology, setting time, compressive strength, hydrophilicity, and degradation of WNF-doped CPC (wnf-CPC were investigated. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy were utilized. Additionally, methyl-thiazolyl-tetrazolium bromide assay, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, and histological evaluation were used to study the cell and tissue responses to wnf-CPC, both in vitro and in vivo. The results confirmed that the addition of WNFs into CPC had no obvious effect on the setting time or the compressive strength of wnf-CPC, provided the WNF amount was not more than 10 wt%. However, the hydrophilicity and degradability of wnf-CPC were significantly improved by the addition of WNFs – this was because of the change of microstructure caused by the WNFs. The preferred dissolution of WNFs caused the formation of microporosity in wnf-CPC when soaked in tris hydrochloride solution. The microporosity enlarged the surface area of the wnf-CPC and so promoted degradation of the wnf-CPC when in contact with liquid. In addition, MG-63 cell attachment and proliferation on the wnf-CPC were superior to that on the CPC, indicating that

  17. Effect of citric acid and the hemihydrate amount on the properties of a calcium sulphoaluminate cement

    Directory of Open Access Journals (Sweden)

    Velazco, G.

    2014-12-01

    Full Text Available The influence of citric acid on the hydration and strength development of a calcium sulphoaluminate cement was investigated. Cement pastes were prepared by mixing calcium sulphoaluminate (C4A3Ŝ with 15, 20 and 25wt% of hemihydrate (CŜH0.5. Citric acid was added as a retarder at 0 and 0.5wt%. The samples were cured at 20 °C for periods of time from 1 to 28 days to evaluate their compressive strength and to characterize the hydration products by scanning electron microscopy and X-ray diffraction. Calorimetric curves showed that the retarding agent considerably decreases the heat release rate and the quantity of total heat released. The main product after the curing was ettringite (C6AŜ3H32. The morphology of this phase consisted of long and thin needles growing radially on the cement grains. Samples with 15wt% of hemihydrate and 0.5wt% of citric acid developed the highest compressive strength (70 MPa at 28 days of curing.Se investigó el efecto del ácido cítrico sobre la hidratación y propiedades mecánicas de un cemento de sulfoaluminato de calcio. El C4A3Ŝ se mezcló con 15, 20 y 25% e.p. de hemihidrato (CŜH0.5. Se agregó ácido cítrico como retardante en 0 y 0.5% e.p. Las muestras fueron curadas a 20 °C por periodos de 1 a 28 días para realizar mediciones de resistencia a la compresión y caracterizar los productos de hidratación mediante microscopía electrónica de barrido y difracción de rayos X. Las curvas de calorimetría mostraron ue el ácido cítrico disminuye la velocidad de liberación de calor y la cantidad de calor liberado durante la hidratación. La resistencia a la compresión alcanzó un máximo de 70 MPa en muestras con 15% e.p. de hemihidrato y 0,5% e.p de ácido cítrico. Los resultados muestran a la etringita (C6AŜ3H32 como principal producto de hidratación. Se observa a esta fase con morfología acicular creciendo sobre las partículas de cemento.

  18. Effects of Stirring and Fluid Perfusion on the In Vitro Degradation of Calcium Phosphate Cement/PLGA Composites.

    Science.gov (United States)

    An, Jie; Leeuwenburgh, Sander C G; Wolke, Joop G C; Jansen, John A

    2015-11-01

    In vitro degradation rates of calcium phosphate bioceramics are investigated using a large variation of soaking protocols that do not all match the dynamic conditions of the perfused physiological environment. Therefore, we studied the effect of stirring and fluid perfusion on the in vitro degradation rate of apatitic calcium phosphate cements (CPC) containing poly(lactic-co-glycolic acid) (PLGA) microspheres. The composites were soaked in phosphate-buffered saline up to 6 weeks under unstirred, stirred, or perfused conditions followed by analysis of mass loss, compression strength, porosity, crystal phase composition, and morphology of the cement composites. The results showed that fluid perfusion reduced the decrease in pH and corresponding degradation rates, while nonperfused soaking conditions (i.e., stirred and unstirred conditions) resulted into more extensive acidification, the rate of which increased with stirring. After 2 weeks, the formation of a secondary brushite phase was observed for cement composites soaked under nonperfused (i.e., stirred and unstirred) conditions, whereas this phase was not detected in cements soaked under perfused conditions. The degradation rate of cement composites decreased in the order unstirred>stirred>perfused, as evidenced by quantification of mass loss, compression strength, and pore morphology. To summarize, we have demonstrated that soaking conditions strongly affected the in vitro degradation process of CPCs. As a consequence, it can be concluded that the experimental design of current in vitro degradation studies does not allow for correlation to (pre-)clinical studies.

  19. Porous calcium phosphate-poly (lactic-co-glycolic) acid composite bone cement: A viable tunable drug delivery system.

    Science.gov (United States)

    Roy, Abhijit; Jhunjhunwala, Siddharth; Bayer, Emily; Fedorchak, Morgan; Little, Steve R; Kumta, Prashant N

    2016-02-01

    Calcium phosphate based cements (CPCs) are frequently used as bone void fillers for non-load bearing segmental bone defects due to their clinically relevant handling characteristics and ability to promote natural bone growth. Macroporous CPC scaffolds with interconnected pores are preferred for their ability to degrade faster and enable accelerated bone regeneration. Herein, a composite CPC scaffold is developed using newly developed resorbable calcium phosphate cement (ReCaPP) formulation containing degradable microspheres of bio-compatible poly (lactic-co-glycolic acid) (PLGA) serving as porogen. The present study is aimed at characterizing the effect of in-vitro degradation of PLGA microspheres on the physical, chemical and structural characteristics of the composite cements. The porosity measurements results reveal the formation of highly interconnected macroporous scaffolds after degradation of PLGA microspheres. The in-vitro characterizations also suggest that the degradation by products of PLGA reduces the pH of the local environment thereby increasing the dissolution rate of the cement. In addition, the in-vitro vancomycin release from the composite CPC scaffold suggests that the drug association with the composite scaffolds can be tuned to achieve control release kinetics. Further, the study demonstrates control release lasting for longer than 10weeks from the composite cements in which vancomycin is encapsulated in PLGA microspheres.

  20. Cementing Material From Rice Husk-Broken Bricks-Spent Bleaching Earth-Dried Calcium Carbide Residue

    Directory of Open Access Journals (Sweden)

    Muthengia Jackson Washira

    2012-10-01

    Full Text Available A cementious material, coded CSBR (Carbide residue Spent bleaching earth Broken bricks and Rice husks, was made from dried calcium carbide residue (DCCR and an incinerated mix of rice husks (RH, broken bricks (BB and spent bleaching earth (SBE. Another material, coded SBR (Spent bleaching earth Broken bricks and Rice husk ash, was made from mixing separately incinerated RH, SBE and ground BB in the same ash ratio as in CSBR. When CSBR was inter-ground with Ordinary Portland Cement (OPC, it showed a continued decrease in Ca(OH2 in the hydrating cement as a function of curing time and replacement levels of the cement. Up to 45 % replacement of the OPC by CSBR produced a Portland pozzolana cement (PPC material that passed the relevant Kenyan Standard. Incorporation of the CSBR in OPC reduces the resultant calcium hydroxide from hydrating Portland cement. The use of the waste materials in production of cementitious material would rid the environment of wastes and lead to production of low cost cementitious material.

  1. Promotion of in vivo degradability, vascularization and osteogenesis of calcium sulfate-based bone cements containing nanoporous lithium doping magnesium silicate

    Science.gov (United States)

    Cao, Liehu; Weng, Weizong; Chen, Xiao; Zhang, Jun; Zhou, Qirong; Cui, Jin; Zhao, Yuechao; Shin, Jung-Woog; Su, Jiacan

    2017-01-01

    Nanoporous lithium doping magnesium silicate (nl-MS) was introduced into calcium sulfate hemihydrate to prepare calcium sulfate composite (nl-MSC) bone cements. The introduction of nl-MS improved the in vitro degradability of nl-MSC cements, which could neutralize acidic degradable products of calcium sulfate and prevented the pH from dropping. The cements were implanted into the bone defects of femur bone of rabbits, and the results of histological and immunohistochemical analysis revealed that massive new bone tissue formed in the defects while the cements were degradable, indicating that the osteogenesis and degradability of the nl-MSC cements were much better than the control calcium sulfate dihydrate (CSD) cements. Furthermore, the positive expression of vascular endothelial growth factor and collagen type I for nl-MSC cements was higher than CSD, indicating that addition of nl-MS into the cements enhanced vascularization and osteogenic differentiation. The results suggested that the nl-MSC cements with good biocompatibility and degradability could promote vascularization and osteogenesis, and had great potential to treat bone defects. PMID:28260883

  2. 铁相组分对硫铝酸钡钙水泥的影响%Influence of Iron Phase Composition on Barium Calcium Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    袁言臣; 叶正茂; 常钧

    2012-01-01

    The influence of iron phase composition of barium calcium sulphoaluminate cement is studied using pure chemical reagents as raw materials by XRD.SEM and strength testing methods. Results show that these raw materials have a fine mineral formation at 1 350℃. From macroscopic view of these clinker minerals, they change from pale green to dark green gradually with the ratio of Al to Fe decreasing. From the microstnicture of clinker minerals, these clinker minerals mainly generate a mass of rhombic dodecahedron of C2.75Ba1.25 A3 S and round granular of dicalcium silicate. Iron phase can promote Ba2+ to replace Ca2+.The hydration products are mainly hydrated barium calcium aluminum sulfur,BaSO4 and hydration calcium aluminates. When iron phase composition is C4AF, the strength can reach up to 73.2 MPa and 97.9 MPa at 1 d and 3 d curing ages.%以纯化学试剂配料,经X射线衍射仪(XRD)、扫描电子显微镜(SEM)和强度测试,研究铁相C6A2F、C4AF、C6AF2和C2F对硫铝酸钡钙水泥熟料的煅烧及性能的影响.结果表明:各生料配比试件在1 350℃时,熟料矿物形成较好;随铁相中Al与Fe的摩尔比的减小,熟料外观颜色呈浅绿色→深绿色→黑绿色变化;熟料矿物主要生成菱形十二面体的硫铝酸钡钙和卵粒状的硅酸二钙;铁相能够促进Ba2+取代Ca2+;主要水化产物为水化硫铝酸钡钙、BaSO4和水化铝酸钙.铁相组分为C4AF时,其1d和3d抗压强度分别为73.2 MPa和97.9 MPa.

  3. Development of an Improved Cement for Geothermal Wells

    Energy Technology Data Exchange (ETDEWEB)

    Trabits, George [Trabits Group, LLC, Wasilla, AK (United States)

    2015-04-20

    After an oil, gas, or geothermal production well has been drilled, the well must be stabilized with a casing (sections of steel pipe that are joined together) in order to prevent the walls of the well from collapsing. The gap between the casing and the walls of the well is filled with cement, which locks the casing into place. The casing and cementing of geothermal wells is complicated by the harsh conditions of high temperature, high pressure, and a chemical environment (brines with high concentrations of carbon dioxide and sulfuric acid) that degrades conventional Portland cement. During the 1990s and early 2000s, the U.S. Department of Energy’s Geothermal Technologies Office (GTO) provided support for the development of fly-ash-modified calcium aluminate phosphate (CaP) cement, which offers improved resistance to degradation compared with conventional cement. However, the use of CaP cements involves some operational constraints that can increase the cost and complexity of well cementing. In some cases, CaP cements are incompatible with chemical additives that are commonly used to adjust cement setting time. Care must also be taken to ensure that CaP cements do not become contaminated with leftover conventional cement in pumping equipment used in conventional well cementing. With assistance from GTO, Trabits Group, LLC has developed a zeolite-containing cement that performs well in harsh geothermal conditions (thermal stability at temperatures of up to 300°C and resistance to carbonation) and is easy to use (can be easily adjusted with additives and eliminates the need to “sterilize” pumping equipment as with CaP cements). This combination of properties reduces the complexity/cost of well cementing, which will help enable the widespread development of geothermal energy in the United States.

  4. Synthesis and mechanical properties of a calcium sulphoaluminate cement made of industrial wastes

    Directory of Open Access Journals (Sweden)

    Gallardo, M.

    2014-09-01

    Full Text Available Environmentally-friendly calcium sulphoaluminate clinkers were obtained from a mixture of aluminium dross, fluorgypsum, fly ash and CaCO₃ at temperatures within the range of 1100 to 1400 °C. After the heat treatments Ca₄Al₆O₁₂SO₄ was the main phase. Three different cements were prepared using the clinkers synthesized at 1250, 1350 and 1400 °C; the clinker powders were mixed with 20 wt% of hemihydrate. Cement pastes were prepared using a water/cement ratio (w/c, 0.4 followed by curing at 20 or 40 °C for periods of time ranging from 1 to 28 days. Most of the samples showed high compression strengths 40–47 MPa after 28 days, which were comparable to the strength of Portland cement. Ettringite was the main hydration product and its morphology consisted of acicular and hexagonal plates, which is typical of this phase.Se fabricaron clinkers de bajo impacto ambiental a base de sulfoaluminato de calcio calcinando mezclas de escoria de aluminio, fluoryeso, ceniza volante y CaCO₃ a diferentes temperaturas dentro de un rango de 1100 a 1400 °C. Se observó la formación de Ca₄Al₆O₁₂SO₄ como fase principal. Para obtener los cementos, los clinkers obtenidos a 1250, 1350 y 1400 °C se mezclaron con 20% en peso de hemihidrato. Se prepararon pastas usando una relación agua/cemento, de 0.4 y se curaron a 20 y 40 °C por diferentes periodos de tiempo desde 1 hasta 28 días. Los valores de resistencia a la compresión a los 28 días de curado de la mayoría de las muestras estuvieron entre 40–47 MPa, equiparables a los de referencia de pastas de cemento Portland. La etringita fue el principal producto de hidratación y su morfología consistió de placas hexagonales y aciculares, típicas de esta fase.

  5. Fast in situ x-ray-diffraction studies of chemical reactions: A synchrotron view of the hydration of tricalcium aluminate

    Science.gov (United States)

    Jupe, A. C.; Turrillas, X.; Barnes, P.; Colston, S. L.; Hall, C.; Häusermann, D.; Hanfland, M.

    1996-06-01

    We report observations on the early hydration of tricalcium aluminate, the most reactive component of Portland cement, using rapid-energy dispersive diffraction on a high brilliance synchrotron source. In situ observations of the hydration process over short time scales, and through bulk samples, reveal an intermediate calcium aluminate hydrate appearing just prior to the formation of the final stable hydrate, demonstrating the nucleating role of this intermediate. The superior quality of the data is sufficient to yield concentration versus time plots for each phase over the whole hydration sequence. This improvement derives from being able to use smaller diffracting volumes and consequent removal of time smearing due to inhomogenetics, and thus now offers the possibility of extending the technique in terms of time resolution and diversity of system.

  6. Effect of Additives on the Morphology of the Hydrated Product and Physical Properties of a Calcium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    Xiupeng WANG; Jiandong YE; Yingjun WANG

    2008-01-01

    The morphology of a hydrated calcium phosphate cement (CPC) doped with several normally used additives was investigated by scanning electron microscopy (SEM) and the compressive strength of the cement was determined in this study. The hydrated products of CPC without additives was rod-like hydroxyapatite (HA) grains with around 2-5 μm in length and 100 nm in width. The addition of Sr obviously decreased the crystal size of the rod-like grains. CPCs containing carbonate, collagen and gelatin showed flake-like crystal morphology. Crylic acid-containing CPC presented flocculus-like structure. And malic acid-containing CPC exhibited oriented flake-like structure. The X-ray diffraction (XRD) analysis showed that the additives used in this study did not alter the hydration products of the cement. The compressive strength tests indicated that the compressive strength of the cement with rod-like morphology HA crystals was much higher than that of the cement with flake-like morphology HA crystals, and the cement with oriented flake-like morphology HA crystals .exhibited the poorest compressive strength.

  7. Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications: in vitro study

    Energy Technology Data Exchange (ETDEWEB)

    Vlad, M D; Lopez, J; Torres, R; Barraco, M; Fernandez, E [Interdepartment Research Group for the Applied Scientific Collaboration (IRGASC), Division of Biomaterials and Bioengineering, Technical University of Catalonia (UPC), Avda Diagonal 647, E-08028-Barcelona (Spain); Valle, L J [Centre of Molecular Biotechnology (CEBIM), Department of Agri-Food Engineering and Biotechnology, ESAB, UPC, Avda Canal Olimpico 15, E-08860-Castelldefels (Spain); Poeata, I, E-mail: enrique.fernandez@upc.ed [Faculty of Medical Bioengineering, ' Gr T Popa' University of Medicine and Pharmacy, Str. Kogalniceanu 9-13, 700454 Iasi (Romania)

    2010-04-15

    In this study, the cytocompatibility of new 'iron-modified/alpha-tricalcium phosphate (IM/alpha-TCP) and calcium sulfate dihydrate (CSD)' bone cement (IM/alpha-TCP/CSD-BC) intended for spinal applications has been approached. The objective was to investigate by direct-contact osteoblast-like cell cultures (from 1 to 14 days) the in vitro cell adhesion, proliferation, morphology and cytoskeleton organization of MG-63 cells seeded onto the new cements. The results were as follows: (a) quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion, proliferation and viability were not affected with time by the presence of iron in the cements; (b) double immunofluorescent labeling of F-actin and alpha-tubulin showed a dynamic interaction between the cell and its porous substrates sustaining the locomotion phenomenon on the cements' surface, which favored the colonization, and confirming the biocompatibility of the experimental cements; (c) SEM-cell morphology and cytoskeleton observations also evidenced that MG-63 cells were able to adhere, to spread and to attain normal morphology on the new IM/alpha-TCP/CSD-BC which offered favorable substratum properties for osteoblast-like cells proliferation and differentiation in vitro. The results showed that these new iron-modified cement-like biomaterials have cytocompatible features of interest not only as possible spinal cancellous bone replacement biomaterial but also as bone tissue engineering scaffolds.

  8. Microparticulated and nanoparticulated zirconium oxide added to calcium silicate cement: Evaluation of physicochemical and biological properties.

    Science.gov (United States)

    Silva, Guilherme F; Bosso, Roberta; Ferino, Rafael V; Tanomaru-Filho, Mário; Bernardi, Maria I B; Guerreiro-Tanomaru, Juliane M; Cerri, Paulo S

    2014-12-01

    The physicochemical and biological properties of calcium silicate-based cement (CS) associated to microparticulated (micro) or nanoparticulated (nano) zirconium oxide (ZrO2 ) were compared with CS and bismuth oxide (BO) with CS. The pH, release of calcium ions, radiopacity, setting time, and compression strength of the materials were evaluated. The tissue reaction promoted by these materials in the subcutaneous was also investigated by morphological, immunohistochemical, and quantitative analyses. For this purpose, polyethylene tubes filled with materials were implanted into rat subcutaneous. After 7, 15, 30, and 60 days, the tubes surrounded by capsules were fixed and embedded in paraffin. In the H&E-stained sections, the number of inflammatory cells (ICs) in the capsule was obtained. Moreover, detection of interleukin-6 (IL-6) by immunohistochemistry and number of IL-6 immunolabeled cells were carried out. von Kossa method was also performed. The differences among the groups were subjected to Tukey test (p ≤ 0.05). The solutions containing the materials presented an alkaline pH and released calcium ions. The addition of radiopacifiers increased setting time and radiopacity of CS. A higher compressive strength in the CS + ZrO2 (micro and nano) was found compared with CS + BO. The number of IC and IL-6 positive cells in the materials with ZrO2 was significantly reduced in comparison with CS + BO. von Kossa-positive structures were observed adjacent to implanted materials. The ZrO2 associated to the CS provides satisfactory physicochemical properties and better biological response than BO. Thus, ZrO2 may be a good alternative for use as radiopacifying agent in substitution to BO.

  9. 铁铝酸盐水泥生料配比倒推计算方法%The proportioning of the raw meal of ferro-aluminate cement by reverse calculating method

    Institute of Scientific and Technical Information of China (English)

    陈宏; 吕树合; 姜振然

    2001-01-01

    The pre- designed main mineral composition of clinker and the corresponding calculated moduli were determined as the guiding control value. The multi- factor and linear non- similar equation group for raw meal proportion was established on the basis of the balance of the compositions of clinker without coal ash and of the ignited raw materials and fuel. The proportioning plan was thus solved through the step- by- step calculation, and the proportioning of the raw meal of high early strength ferro- aluminate special cement by reverse calculating was realized.%以事先设定熟料主要矿物组成含量和计算出与之相适应熟料率值为目标控制值,在灼烧基原燃材料与无灰熟料相对应氧化物含量单项平衡的基础上,建立多元系统线性非齐次配料方程组,从中求解出配比未知量,由此逐步计算,实现早强铁铝酸盐特种水泥生料配比的倒推计算。

  10. A novel injectable calcium phosphate cement-bioactive glass composite for bone regeneration.

    Directory of Open Access Journals (Sweden)

    Long Yu

    Full Text Available BACKGROUND: Calcium phosphate cement (CPC can be molded or injected to form a scaffold in situ, which intimately conforms to complex bone defects. Bioactive glass (BG is known for its unique ability to bond to living bone and promote bone growth. However, it was not until recently that literature was available regarding CPC-BG applied as an injectable graft. In this paper, we reported a novel injectable CPC-BG composite with improved properties caused by the incorporation of BG into CPC. MATERIALS AND METHODS: The novel injectable bioactive cement was evaluated to determine its composition, microstructure, setting time, injectability, compressive strength and behavior in a simulated body fluid (SBF. The in vitro cellular responses of osteoblasts and in vivo tissue responses after the implantation of CPC-BG in femoral condyle defects of rabbits were also investigated. RESULTS: CPC-BG possessed a retarded setting time and markedly better injectability and mechanical properties than CPC. Moreover, a new Ca-deficient apatite layer was deposited on the composite surface after immersing immersion in SBF for 7 days. CPC-BG samples showed significantly improved degradability and bioactivity compared to CPC in simulated body fluid (SBF. In addition, the degrees of cell attachment, proliferation and differentiation on CPC-BG were higher than those on CPC. Macroscopic evaluation, histological evaluation, and micro-computed tomography (micro-CT analysis showed that CPC-BG enhanced the efficiency of new bone formation in comparison with CPC. CONCLUSIONS: A novel CPC-BG composite has been synthesized with improved properties exhibiting promising prospects for bone regeneration.

  11. External bone remodeling after injectable calcium-phosphate cement in benign bone tumor: two cases in the hand.

    Science.gov (United States)

    Ichihara, S; Vaiss, L; Acciaro, A L; Facca, S; Liverneaux, P

    2015-12-01

    Bone remodeling commonly occurred after fracture and curettage benign bone tumor. A lot of previous articles reported "internal" trabecular bone remodeling. There were no previous clinical reports about "external" cortical bone remodeling. We present here 2 clinical cases of "external" bone remodeling after injectable calcium-phosphate in benign bone tumor in the hand. In two cases of benign bone tumor, we performed complete removal of the tumor and immediate filling of the metacarpal bone with injectable calcium-phosphate cement Arexbone(®) from the mechanical viewpoint. With respect to the shape of the calcium-phosphate, by using an injection-type, calcium-phosphate is adhered uniformly to the bone cortex by injecting, remodeling has been promoted. After 5 and 8years, both cases were no recurrences, and the shape of the metacarpal looked close to the contralateral side. These findings supposed to be concerned with potential self-healing and self-protection mechanism in human body.

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

    Science.gov (United States)

    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.

  13. Calcium phosphate cement as a "barrier-graft" for the treatment of human periodontal intraosseous defects

    Directory of Open Access Journals (Sweden)

    Rajesh J

    2009-01-01

    Full Text Available Background : Calcium phosphate cements (CPC are apparently good candidates for periodontal treatment by virtue of their biocompatibility, mouldability and osteoconductivity. However, the clinical efficacy in this regard has not been established. This study is aimed at the evaluation of the efficacy of a formulation of CPC in healing human periodontal intraosseous defects in comparison with hydroxyapatite ceramic granules. Materials and Methods : In this clinical study, 60 patients with periodontal defects were divided into 2 test groups and 1 control group. The defect sites in the test groups were repaired with CPC and hydroxyapatite ceramic granules (HAG. Debridement alone was given in the control group. The progress was assessed at 3, 6, 9 and 12 months observation intervals through soft tissue parameters (probing depth, attachment level and gingival recession. Results: CPC showed significantly better outcome. Probing depth reduction values of CPC, HAG and Control at 6 months were 5.40 ± 1.43, 3.75 ± 1.71 and 2.90 ± 1.48, and those at 12 months were 6.20 ± 1.80, 4.5 ± 1.91 and 2.95 ± 1.73. Clinical attachment gain values of CPC, HAG and Control at 6 months were 5.15 ± 1.50, 3.45 ± 1.96 and 2.25 ± 1.52, and those at 12 months were 5.80 ± 2.02, 3.55 ± 2.06 and 2.30 ± 1.78, In both cases the P value was < 0.001 showing high significance. The gingival recession over 12 months, for the CPC group is lesser than that in the HAG group and the value for the control group is marginally higher than both. Soft-tissue measurements were appended by postoperative radiographs and surgical re-entry in selected cases. Conclusions: Calcium phosphate cement is found to be significantly better than hydroxyapatite ceramic granules. The material could be considered as a "barrier-graft".

  14. Current perspectives of bio-ceramic technology in endodontics: calcium enriched mixture cement - review of its composition, properties and applications

    OpenAIRE

    Utneja, Shivani; Nawal, Ruchika Roongta; Talwar, Sangeeta; Verma, Mahesh

    2014-01-01

    Advancements in bio-ceramic technology has revolutionised endodontic material science by enhancing the treatment outcome for patients. This class of dental materials conciliates excellent biocompatibility with high osseoconductivity that render them ideal for endodontic care. Few recently introduced bio-ceramic materials have shown considerable clinical success over their early generations in terms of good handling characteristics. Calcium enriched mixture (CEM) cement, Endosequence sealer, a...

  15. Synthesis of Ag doped calcium phosphate particles and their antibacterial effect as additives in dental glass ionomer cements

    OpenAIRE

    2016-01-01

    Developing dental restorations with enhanced antibacterial properties has been a constant quest for materials scientists. The aim of this study was to synthesize silver doped calcium phosphate particles and use them to improve antibacterial properties of conventional glass ionomer cement. The Ag doped monetite (Ag-DCPA) and hydroxyapatite (Ag-HA) were synthesized by precipitation method and characterized using X-ray diffraction, scanning electron microscope and X-ray fluorescence spectroscopy...

  16. Evaluation of the biphasic calcium composite (BCC), a novel bone cement, in a minipig model of pulmonary embolism.

    Science.gov (United States)

    Qin, Yi; Ye, Jichao; Wang, Peng; Gao, Liangbin; Jiang, Jianming; Wang, Suwei; Shen, Huiyong

    2016-01-01

    Polymethylmethacrylate (PMMA) bone cement, which is used as a filler material in vertebroplasty, is one of the major sources of pulmonary embolism in patients who have undergone vertebroplasty. In the present study, we established and evaluated two animal models of pulmonary embolism by injecting PMMA or biphasic calcium composite (BCC) bone cement with a negative surface charge. A total of 12 adults and healthy Wuzhishan minipigs were randomly divided into two groups, the PMMA and BBC groups, which received injection of PMMA bone cement and BBC bone cement with a negative surface charge in the circulation system through the pulmonary trunk, respectively, to construct animal models of pulmonary embolism. The hemodynamics, arterial blood gas, and plasma coagulation were compared between these two groups. In addition, morphological changes of the lung were examined using three-dimensional computed tomography. The results showed that both PMMA and BCC injections induced pulmonary embolisms in minipigs. Compared to the PMMA group, the BCC group exhibited significantly lower levels of arterial pressure, pulmonary artery pressure, blood oxygen pressure, blood carbon dioxide pressure, blood bicarbonate, base excess, antithrombin III and D-dimer. In conclusion, BCC bone cement with a negative surface charge is a promising filler material for vertebroplasty.

  17. CT volumetry of intravertebral cement after kyphoplasty. Comparison of polymethylmethacrylate and calcium phosphate in a 12-month follow-up

    Energy Technology Data Exchange (ETDEWEB)

    Libicher, M.; Noeldge, G.; Kauffmann, G.W. [University of Heidelberg, Department of Diagnostic Radiology, Heidelberg (Germany); Vetter, M.; Wolf, I.; Meinzer, H.P. [Deutsches Krebsforschungszentrum, Departments of Medical and Biological Informatics, Heidelberg (Germany); Kasperk, C.; Grafe, I. [University of Heidelberg, Department of Internal Medicine, Heidelberg (Germany); Fonseca, K.D.; Meeder, P.J. [University of Heidelberg, Department of Trauma Surgery, Heidelberg (Germany); Hillmeier, J. [St. Vincenz Hospital, Department of Trauma Surgery, Limburg (Germany)

    2005-08-01

    This study was intended to measure the volume of intravertebral cement after balloon kyphoplasty with high resolution computed tomography (CT) and dedicated software. Volume changes of biocompatible calcium phosphate cement (CPC) were detected during a follow-up of 12 months. Measurements were compared with a control group of patients treated with polymethylmethacrylate (PMMA). Twenty-three vertebrae (14 CPC, 9 PMMA) of 12 patients were examined with CT using an identical imaging protocol. Dedicated software was used to quantify intravertebral cement volume in subvoxel resolution by analyzing each cement implant with a density-weighted algorithm. The mean volume reduction of CPC was 0.08 ml after 12 months, which corresponds to an absorption rate of 2 vol%. However, the difference did not reach significance level (P>0.05). The mean error estimate was 0.005 ml, indicating excellent precision of the method. CT volumetry appears a precise tool for measurement of intravertebral cement volume. CT volumetry offers the possibility of in vivo measurement of CPC resorption. (orig.)

  18. Effect of polydopamine on the biomimetic mineralization of mussel-inspired calcium phosphate cement in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zongguang [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Qu, Shuxin, E-mail: qushuxin@swjtu.edu.cn [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Zheng, Xiaotong; Xiong, Xiong [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Fu, Rong; Tang, Kuangyun; Zhong, Zhendong [Department of Plastic Surgery, Academy of Medical Sciences and Sichuan Provincial People' s Hospital, Chengdu 610041 (China); Weng, Jie [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2014-11-01

    Inspired by the excellent adhesive property of mussel adhesive protein, we added polydopamine (PDA) to calcium phosphate cement (PDA–CPC) to enhance its compressive strength previously. The mineralization and mechanism on PDA–CPC were investigated by soaking it in simulated body fluid in this study. The results indicated that PDA promoted the conversion of dicalcium phosphate dihydrate and α-tricalcium phosphate to hydroxyapatite (HA) in the early stage but inhibited this conversion subsequently. PDA promoted the rapid mineralization on PDA–CPC to form a layer of nanoscale calcium phosphate (CaP) whereas there was no CaP formation on the control-CPC after 1 d of soaking. This layer of nanoscale CaP was similar to that of natural bone, which was always observed during soaking. X-ray photoelectron spectroscopy showed that the peak of C=O of PDA existed in the newly formed CaP on PDA–CPC, indicating the co-precipitation of CaP with PDA. Furthermore, the newly formed CaP on PDA–CPC was HA confirmed by transmission electron microscopy, which the newly formed HA was in association with PDA. Therefore, PDA increased the capacity of mineralization of CPC and induced the formation of nanoscale bone-like apatite on PDA–CPC. Thus, this provides the feasible route for surface modification on CPC. - Highlights: • Effect of polydopamine (PDA) on the in vitro mineralization of PDA-CPC was studied. • PDA promoted the rapid mineralization on PDA-CPC to form a nanoscale HA layer. • The precipitation of the nanoscale HA layer on PDA-CPC accompanied with PDA. • Polydopamine induced mineralization is feasible for surface modification of CaP.

  19. Effect of several additives and their admixtures on the physico-chemical properties of a calcium phosphate cement.

    Science.gov (United States)

    Bohner, M; Merkle, H P; Landuyt, P V; Trophardy, G; Lemaitre, J

    2000-02-01

    Combinations of citrate (C6H5O(7)3-), pyrophosphate (P2O(7)4-) and sulfate (SO(4)2-) ions were used to modify the physico-chemical properties of a calcium phosphate cement (CPC) composed of beta-tricalcium phosphate (beta-TCP) and phosphoric acid (PA) solution. The results obtained with only one additive at a time are similar to those previously published. New facts are: the positive effect of C6H5O(7)3- ions on cement failure strain and their negative effect on cement pH. The position of the setting time maximum measured at an SO(4)2- concentration of 0.09 M was not displaced by the addition of C6H5O(7)3- and P2O(7)4- ions. However, the effect of SO(4)2- ions on the setting time was depressed by C6H5O(7)3- ions. Moreover, no increase in tensile strength was observed when increasing amounts of SO(4)2- were added into a C6H5O(7)3--containing cement. The latter results suggest a competitive effect of C6H5O(7)3- and SO(4)2- on setting time and tensile strength. Anhydrous dicalcium phosphate (DCP; CaHPO4) appeared in cement samples dried just after setting, but not in cement samples incubated for 24 h in deionized water before the drying step. It is believed that the setting reaction is stopped by the drying step, leaving a low internal pH in the sample, hence providing favorable conditions for the transformation of dicalcium phosphate dihydrate (DCPD) into DCP. Interestingly, even though C6H5O(7)3- ions dramatically lowered the equilibrium pH of the cement with 5 ml of deionized water, they still prevented the occurrence of the transformation of DCPD into DCP.

  20. Influence of artificially-induced porosity on the compressive strength of calcium phosphate bone cements.

    Science.gov (United States)

    Mouzakis, Dionysios; Zaoutsos, Stefanos Polymeros; Bouropoulos, Nikolaos; Rokidi, Stamatia; Papanicolaou, George

    2016-07-01

    The biological and mechanical nature of calcium phosphate cements (CPC's) matches well with that of bone tissues, thus they can be considered as an appropriate environment for bone repair as bone defect fillers. The current study focuses on the experimental characterization of the mechanical properties of CPCs that are favorably used in clinical applications. Aiming on evaluation of their mechanical performance, tests in compression loading were conducted in order to determine the mechanical properties of the material under study. In this context, experimental results occurring from the above mechanical tests on porous specimens that were fabricated from three different porous additives, namely albumin, gelatin and sodium alginate, are provided, while assessment of their mechanical properties in respect to the used porous media is performed. Additionally, samples reinforced with hydroxyapatite crystals were also tested in compression and the results are compared with those of the above tested porous CPCs. The knowledge obtained allows the improvement of their biomechanical properties by controlling their structure in a micro level, and finds a way to compromise between mechanical and biological response.

  1. Properties of high calcium fly ash geopolymer pastes with Portland cement as an additive

    Science.gov (United States)

    Phoo-ngernkham, Tanakorn; Chindaprasirt, Prinya; Sata, Vanchai; Pangdaeng, Saengsuree; Sinsiri, Theerawat

    2013-02-01

    The effect of Portland cement (OPC) addition on the properties of high calcium fly ash geopolymer pastes was investigated in the paper. OPC partially replaced fly ash (FA) at the dosages of 0, 5%, 10%, and 15% by mass of binder. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions were used as the liquid portion in the mixture: NaOH 10 mol/L, Na2SiO3/NaOH with a mass ratio of 2.0, and alkaline liquid/binder (L/B) with a mass ratio of 0.6. The curing at 60°C for 24 h was used to accelerate the geopolymerization. The setting time of all fresh pastes, porosity, and compressive strength of the pastes at the stages of 1, 7, 28, and 90 d were tested. The elastic modulus and strain capacity of the pastes at the stage of 7 d were determined. It is revealed that the use of OPC as an additive to replace part of FA results in the decreases in the setting time, porosity, and strain capacity of the paste specimens, while the compressive strength and elastic modulus seem to increase.

  2. Odontogenic effects of a fast-setting calcium-silicate cement containing zirconium oxide.

    Science.gov (United States)

    Kim, Kyoung-A; Yang, Yeon-Mi; Kwon, Young-Sun; Hwang, Yun-Chan; Yu, Mi-Kyung; Min, Kyung-San

    2015-01-01

    A fast-setting calcium-silicate cement (Endocem) was introduced in the field of dentistry for use in vital pulp therapy. Similar to mineral trioxide aggregate (MTA), it contains bismuth oxide to provide radiopacity. Recently, another product, EndocemZr, which contains zirconium oxide (ZrO2) as a radiopacifier, was developed by the same company. In this study, the biological/odontogenic effects of EndocemZr were investigated in human primary dental pulp cells (hpDPCs) in vitro and on capped rat teeth in vivo. The biocompatibility of EndocemZr was similar to that of ProRoot and Endocem on the basis of cell viability tests and cell morphological analysis. The mineralization nodule formation, expression of odontogenic-related markers, and reparative dentin formation of EndocemZr group was similar to those of other material groups. Our results suggest that EndocemZr has the potential to be used as an effective material for vital pulp therapy, similar to ProRoot and Endocem.

  3. Osteoregenerative capacities of dicalcium phosphate-rich calcium phosphate bone cement.

    Science.gov (United States)

    Ko, Chia-Ling; Chen, Jian-Chih; Tien, Yin-Chun; Hung, Chun-Cheng; Wang, Jen-Chyan; Chen, Wen-Cheng

    2015-01-01

    Calcium phosphate cement (CPC) is a widely used bone substitute. However, CPC application is limited by poor bioresorption, which is attributed to apatite, the stable product. This study aims to systematically survey the biological performance of dicalcium phosphate (DCP)-rich CPC. DCP-rich CPC exhibited a twofold, surface-modified DCP anhydrous (DCPA)-to-tetracalcium phosphate (TTCP) molar ratio, whereas conventional CPC (c-CPC) showed a onefold, surface unmodified DCPA-to-TTCP molar ratio. Cell adhesion, morphology, viability, and alkaline phosphatase (ALP) activity in the two CPCs were examined with bone cell progenitor D1 cultured in vitro. Microcomputed tomography and histological observation were conducted after CPC implantation in vivo to analyze the residual implant ratio and new bone formation rate. D1 cells cultured on DCP-rich CPC surfaces exhibited higher cell viability, ALP activity, and ALP quantity than c-CPC. Histological evaluation indicated that DCP-rich CPC showed lesser residual implant and higher new bone formation rate than c-CPC. Therefore, DCP-rich CPC can improve bioresorption. The newly developed DCP-rich CPC exhibited potential therapeutic applications for bone reconstruction.

  4. Cross-linked chitosan improves the mechanical properties of calcium phosphate-chitosan cement.

    Science.gov (United States)

    Aryaei, Ashkan; Liu, Jason; Jayatissa, Ahalapitiya H; Jayasuriya, A Champa

    2015-09-01

    Calcium phosphate (CaP) cements are highly applicable and valuable materials for filling bone defects by minimally invasive procedures. The chitosan (CS) biopolymer is also considered as one of the promising biomaterial candidates in bone tissue engineering. In the present study, some key features of CaP-CS were significantly improved by developing a novel CaP-CS composite. For this purpose, CS was the first cross-linked with tripolyphosphate (TPP) and then mixed with CaP matrix. A group of CaP-CS samples without cross-linking was also prepared. Samples were fabricated and tested based on the known standards. Additionally, the effect of different powder (P) to liquid (L) ratios was also investigated. Both cross-linked and uncross-linked CaP-CS samples showed excellent washout resistance. The most significant effects were observed on Young's modulus and compressive strength in wet condition as well as surface hardness. In dry conditions, the Young's modulus of cross-linked samples was slightly improved. Based on the presented results, cross-linking does not have a significant effect on porosity. As expected, by increasing the P/L ratio of a sample, ductility and injectability were decreased. However, in the most cases, mechanical properties were enhanced. The results have shown that cross-linking can improve the mechanical properties of CaP-CS and hence it can be used for bone tissue engineering applications.

  5. Effect of an organic additive on the rheology of an aluminous cement paste and consequences on the densification of the hardened material

    Science.gov (United States)

    El Hafiane, Y.; Smith, A.; Bonnet, J. P.; Tanouti, B.

    2005-03-01

    The material used in the present work is Secar 71 (Lafarge) mixed with water containing an organic additive (acetic acid noted HOAc). The rheological behavior of these pastes is studied. The best dispersion is obtained when the mass content of the additive with respect to the cement is equal to 0.5%. The microstructural characterizations of samples aged 4 days at 20° C and 95 % relative humidity reveal a significant increase in the density and a reduction in porosity for very small percentages of additive. The remarkable effect of the acetic acid on the microstructure of hardened material is correlated with its good dispersing action.

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

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

  7. 粉煤灰对硅酸盐水泥-铝酸盐水泥-硬石膏体系性能的影响%Influence of fly ash on compressive strength with portland cement-aluminate cement-anhydrite system

    Institute of Scientific and Technical Information of China (English)

    李海南; 马保国; 张承志

    2014-01-01

    This paper studies the influence of amount of mixed fly ash (0 %, 10 %, 20 %, 30 %) on compressive strength with portland cement-aluminate cement-anhydrite system. Experimental results show that with the increase of fly ash, the compressive and transverse strength decreases; With the prolonging of curing age, the compressive and transverse strength decrease slowly.%研究了不同掺量的粉煤灰(0%,10%,20%,30%)对硅酸盐水泥-铝酸盐水泥-硬石膏三元复合体系力学性能的影响。试验结果表明:随着粉煤灰掺量的增加,该三元体系浆体的抗压、抗折强度均减小,但减小的程度不一致,与养护龄期有关。随着养护龄期的延长,砂浆抗压、抗折强度降低幅度减小。这可能是由于在浆体水化后期,粉煤灰的火山灰作用起了一定的作用。

  8. Investigation of barium-calcium aluminate process to manufacture and characterize impregnated thermionic cathode for power microwave devices; Investigacao do processo de obtencao de aluminatos de bario e calcio para construcao e caracterizacao de catodos termionicos impregnados para aplicacao em dispositivos de microondas de potencia

    Energy Technology Data Exchange (ETDEWEB)

    Higashi, Cristiane

    2006-07-01

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

  9. Current perspectives of bio-ceramic technology in endodontics: calcium enriched mixture cement - review of its composition, properties and applications.

    Science.gov (United States)

    Utneja, Shivani; Nawal, Ruchika Roongta; Talwar, Sangeeta; Verma, Mahesh

    2015-02-01

    Advancements in bio-ceramic technology has revolutionised endodontic material science by enhancing the treatment outcome for patients. This class of dental materials conciliates excellent biocompatibility with high osseoconductivity that render them ideal for endodontic care. Few recently introduced bio-ceramic materials have shown considerable clinical success over their early generations in terms of good handling characteristics. Calcium enriched mixture (CEM) cement, Endosequence sealer, and root repair materials, Biodentine and BioAggregate are the new classes of bio-ceramic materials. The aim of this literature review is to present investigations regarding properties and applications of CEM cement in endodontics. A review of the existing literature was performed by using electronic and hand searching methods for CEM cement from January 2006 to December 2013. CEM cement has a different chemical composition from that of mineral trioxide aggregate (MTA) but has similar clinical applications. It combines the biocompatibility of MTA with more efficient characteristics, such as significantly shorter setting time, good handling characteristics, no staining of tooth and effective seal against bacterial leakage.

  10. Recycling the product of thermal transformation of cement-asbestos for the preparation of calcium sulfoaluminate clinker.

    Science.gov (United States)

    Viani, Alberto; Gualtieri, Alessandro F

    2013-09-15

    According to recent resolutions of the European Parliament (2012/2065(INI)), the need for environmentally friendly alternative solutions to landfill disposal of hazardous wastes, such as asbestos-containing materials, prompts their recycling as secondary raw materials (end of waste concept). In this respect, for the first time, we report the recycling of the high temperature product of cement-asbestos, in the formulation of calcium sulfoaluminate cement clinkers (novel cementitious binders designed to reduce CO₂ emissions), as a continuation of a previous work on their systematic characterization. Up to 29 wt% of the secondary raw material was successfully introduced into the raw mix. Different clinker samples were obtained at 1250 °C and 1300 °C, reproducing the phase composition of industrial analogues. As an alternative source of Ca and Si, this secondary raw material allows for a reduction of the CO₂ emissions in cement production, mitigating the ecological impact of cement manufacturing, and reducing the need for natural resources.

  11. Effects of a discoloration-resistant calcium aluminosilicate cement on the viability and proliferation of undifferentiated human dental pulp stem cells.

    Science.gov (United States)

    Niu, Li-na; Watson, Devon; Thames, Kyle; Primus, Carolyn M; Bergeron, Brian E; Jiao, Kai; Bortoluzzi, Eduardo A; Cutler, Christopher W; Chen, Ji-hua; Pashley, David H; Tay, Franklin R

    2015-11-30

    Discoloration-resistant calcium aluminosilicate cement has been formulated to overcome the timely problem of tooth discoloration reported in the clinical application of bismuth oxide-containing hydraulic cements. The present study examined the effects of this experimental cement (Quick-Set2) on the viability and proliferation of human dental pulp stem cells (hDPSCs) by comparing the cellular responses with commercially available calcium silicate cement (white mineral trioxide aggregate; WMTA) after different aging periods. Cell viability and proliferation were examined using assays that examined plasma membrane integrity, leakage of cytosolic enzyme, caspase-3 activity for early apoptosis, oxidative stress, mitochondrial metabolic activity and intracellular DNA content. Results of the six assays indicated that both Quick-Set2 and WMTA were initially cytotoxic to hDPSCs after setting for 24 h, with Quick-Set2 being comparatively less cytotoxic than WMTA at this stage. After two aging cycles, the cytotoxicity profiles of the two hydraulic cements were not significantly different and were much less cytotoxic than the positive control (zinc oxide-eugenol cement). Based on these results, it is envisaged that any potential beneficial effect of the discoloration-resistant calcium aluminosilicate cement on osteogenesis by differentiated hDPSCs is more likely to be revealed after outward diffusion and removal of its cytotoxic components.

  12. Effects of a discoloration-resistant calcium aluminosilicate cement on the viability and proliferation of undifferentiated human dental pulp stem cells

    Science.gov (United States)

    Niu, Li-na; Watson, Devon; Thames, Kyle; Primus, Carolyn M.; Bergeron, Brian E.; Jiao, Kai; Bortoluzzi, Eduardo A.; Cutler, Christopher W.; Chen, Ji-hua; Pashley, David H.; Tay, Franklin R.

    2015-01-01

    Discoloration-resistant calcium aluminosilicate cement has been formulated to overcome the timely problem of tooth discoloration reported in the clinical application of bismuth oxide-containing hydraulic cements. The present study examined the effects of this experimental cement (Quick-Set2) on the viability and proliferation of human dental pulp stem cells (hDPSCs) by comparing the cellular responses with commercially available calcium silicate cement (white mineral trioxide aggregate; WMTA) after different aging periods. Cell viability and proliferation were examined using assays that examined plasma membrane integrity, leakage of cytosolic enzyme, caspase-3 activity for early apoptosis, oxidative stress, mitochondrial metabolic activity and intracellular DNA content. Results of the six assays indicated that both Quick-Set2 and WMTA were initially cytotoxic to hDPSCs after setting for 24 h, with Quick-Set2 being comparatively less cytotoxic than WMTA at this stage. After two aging cycles, the cytotoxicity profiles of the two hydraulic cements were not significantly different and were much less cytotoxic than the positive control (zinc oxide–eugenol cement). Based on these results, it is envisaged that any potential beneficial effect of the discoloration-resistant calcium aluminosilicate cement on osteogenesis by differentiated hDPSCs is more likely to be revealed after outward diffusion and removal of its cytotoxic components. PMID:26617338

  13. Thermodynamic variations in the decarbonation of low calcium fly ash-cement raw mix

    Directory of Open Access Journals (Sweden)

    Diouri, A.

    2005-03-01

    Full Text Available In this paper, the authors analyse the decomposition of a low lime saturation factor (LSF raw mix -obtained by adding low calcium fly ash to standard portland cement- when heated to around 1000 °C. The decarbonation temperatures and variation in enthalpy taking place during calcite decomposition were determined by DTA and isothermal calorimetric measurement. The resulting belitic clinker had a LSF factor ranging from 75 to 85%. The presence of fly ash was observed to retard the onset of decarbonation and lower the peak and final decarbonation temperatures. Decarbonation enthalpy was also found to decrease with fly ash content

    El objetivo del presente trabajo es estudiar durante su tratamiento térmico, alrededor de 1.000 °C, la evolución de la descomposición de un crudo que posee un factor de saturación de cal (LSF bajo. Este crudo se ha elaborado adicionando cenizas volantes bajas en calcio a un crudo de cemento portland ordinario. La temperatura de descarbonatación y la variación de la entalpia durante la descomposición de la calcita se determinan por ATD y calorimetría isotérmica. Los resultados muestran la formación de un clinker belítico con un LSF entre 85 y 75%. Asimismo, se demuestra que la presencia de cenizas volantes retarda el comienzo de la descarbonatación y disminuye la temperatura máxima y final del proceso de descarbonatación. El valor de la entalpia de la descarbonatación disminuye con la presencia de cenizas volantes.

  14. Calcium phosphate cement as an alternative for formocresol in primary teeth pulpotomies

    Directory of Open Access Journals (Sweden)

    Bijimole Jose

    2013-01-01

    Full Text Available Background: Formocresol remains to be the preferred medicament in pulpotomy, despite the concerns regarding tissue devitalization and systemic toxicity. Several materials were used as alternatives, but none proved significantly advantageous. Of recent, calcium phosphate cement (CPC has been projected as an ideal pulpotomy material considering its tissue compatibility and dentinogenic properties. This study explores the suitability of a CPC formulation for pulpotomy, in comparison with formocresol. Materials and Methods: This comparative case study included 10 children (8-12 age group having a pair of non-carious primary canines (both maxillary and mandibular posted for extraction. Pulpotomy was performed with CPC in the right canines and formocresol in the left and sealed with IRM ® (Dentsply. The teeth were extracted at 70 ± 5 days and sectioned and stained for the histopathological evaluation. Parameters such as pulpal inflammation, tissue reaction to material, dentine bridge formation, location of dentine bridge, quality of dentine formation in bridge, and connective tissue in bridge etc. were evaluated. Results: The histological assessment after 70 days showed no statistically significant difference between the two groups in any of the parameters. However, CPC gave more favorable results in pulpal inflammation, with a lower score of 1.6 against 2.6 for formocresol. CPC samples showed better formation of dentine bridge in quantity and quality. The mean scores for CPC for the extent of dentine bridge formation, quality of dentine bridge and connective tissue in the bridge, were 2.0, 1.4, and 1.2 respectively, whereas the corresponding values for formocresol were 0.8, 0.2, and 1.0. Conclusion: CPC is more compatible to pulp tissues than formocresol and it shows good healing potential. CPC is capable of inducing dentine formation without an area of necrosis.

  15. Calcium phosphate cement delivering zoledronate decreases bone turnover rate and restores bone architecture in ovariectomized rats.

    Science.gov (United States)

    Wu, Chang-Chin; Wang, Chen-Chie; Lu, Dai-Hua; Hsu, Li-Ho; Yang, Kai-Chiang; Lin, Feng-Huei

    2012-06-01

    Patients sustaining bony fractures frequently require the application of bone graft substitutes to fill the bone defects. In the meantime, anti-osteoporosis drugs may be added in bone fillers to treat osteoporosis, especially in postmenopausal women and the elderly. The effects of zoledronate-impregnated calcium phosphate cement (ZLN/CPC) on ovariectomized (OVX) rats were evaluated. OVX rats were implanted with ZLN/CPC, containing 0.025 mg ZLN in the greater omentum. Afterward the clinical sign of toxicity was recorded for eight weeks. The rats were sacrificed and blood samples were collected for hematology and serum bone turnover markers analyses. The four limbs of the rats were harvested and micro-computer tomography (micro-CT) scanning and bone ash analyses were performed. No clinical toxicity was observed in the treated rats. Compared to the OVX rats, levels of bone resorption markers (fragments of C-telopeptides of type I collagen) and bone formation markers (alkaline phosphatase and osteocalcin) decreased significantly in the treated rats. Osteopontin, which mediates the anchoring of osteoclasts to the mineral matrix of bones, also decreased significantly. Micro-CT scanning and histologic examinations of the distal femoral metaphyses showed that the cancellous bone architectures were restored, with a concomitant decrease in bone porosity. The bone mineral content in the bone ashes also increased significantly. This study indicates that ZLN-impregnated CPC reduces bone turnover rate and restores bone architecture in OVX rats. CPC may be an appropriate carrier to deliver drugs to treat osteoporosis, and this approach may also reduce rates of post-dosing symptoms for intravenous ZLN delivery.

  16. Gas-foaming calcium phosphate cement scaffold encapsulating human umbilical cord stem cells.

    Science.gov (United States)

    Chen, Wenchuan; Zhou, Hongzhi; Tang, Minghui; Weir, Michael D; Bao, Chongyun; Xu, Hockin H K

    2012-04-01

    Tissue engineering approaches are promising to meet the increasing need for bone regeneration. Calcium phosphate cement (CPC) can be injected and self-set to form a scaffold with excellent osteoconductivity. The objectives of this study were to develop a macroporous CPC-chitosan-fiber construct containing alginate-fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs) and to investigate hUCMSC release from the degrading microbeads and proliferation inside the porous CPC construct. The hUCMSC-encapsulated microbeads were completely wrapped inside the CPC paste, with the gas-foaming porogen creating macropores in CPC to provide for access to culture media. Increasing the porogen content in CPC significantly increased the cell viability, from 49% of live cells in CPC with 0% porogen to 86% of live cells in CPC with 15% porogen. The alginate-fibrin microbeads started to degrade and release the cells inside CPC at 7 days. The released cells started to proliferate inside the macroporous CPC construct. The live cell number inside CPC increased from 270 cells/mm(2) at 1 day to 350 cells/mm(2) at 21 days. The pore volume fraction of CPC increased from 46.8% to 78.4% using the gas-foaming method, with macropore sizes of approximately 100 to 400 μm. The strength of the CPC-chitosan-fiber scaffold at 15% porogen was 3.8 MPa, which approximated the reported 3.5 MPa for cancellous bone. In conclusion, a novel gas-foaming macroporous CPC construct containing degradable alginate-fibrin microbeads was developed that encapsulated hUCMSCs. The cells had good viability while wrapped inside the porous CPC construct. The degradable microbeads in CPC quickly released the cells, which proliferated over time inside the porous CPC. Self-setting, strong CPC with alginate-fibrin microbeads for stem cell delivery is promising for bone tissue engineering applications.

  17. Induced Pluripotent Stem Cell-derived Mesenchymal Stem Cell Seeding on Biofunctionalized Calcium Phosphate Cements

    Institute of Scientific and Technical Information of China (English)

    WahWah TheinHan; Jun Liu; Minghui Tang; Wenchuan Chen; Linzhao Cheng; Hockin H. K. Xu

    2013-01-01

    Induced pluripotent stem cells (iPSCs) have great potential due to their proliferation and differentiation capability. The objectives of this study were to generate iPSC-derived mesenchymal stem cells (iPSC-MSCs), and investigate iPSC-MSC proliferation and osteogenic differentiation on calcium phosphate cement (CPC) containing biofunctional agents for the first time. Human iPSCs were derived from marrow CD34+ cells which were reprogrammed by a single episomal vector. iPSCs were cultured to form embryoid bodies (EBs), and MSCs migrated out of EBs. Five biofunctional agents were incorporated into CPC:RGD (Arg-Gly-Asp) peptides, fibronectin (Fn), fibronectin-like engineered polymer protein (FEPP), extracellular matrix Geltrex, and platelet concentrate. iPSC-MSCs were seeded on five biofunctionalized CPCs:CPC-RGD, CPC-Fn, CPC-FEPP, CPC-Geltrex, and CPC-Platelets. iPSC-MSCs on biofunctional CPCs had enhanced proliferation, actin fiber expression, osteogenic differentiation and mineralization, compared to control. Cell proliferation was greatly increased on biofunctional CPCs. iPSC-MSCs underwent osteogenic differentiation with increased alkaline phosphatase, Runx2 and collagen-I expressions. Mineral synthesis by iPSC-MSCs on CPC-Platelets was 3-fold that of CPC control. In conclusion, iPSCs showed high potential for bone engineering. iPSC-MSCs on biofunctionalized CPCs had cell proliferation and bone mineralization that were much better than traditional CPC. iPSC-MSC-CPC constructs are promising to promote bone regeneration in craniofacial/orthopedic repairs.

  18. Effect of pH and Lidocaine on the Compressive Strength of Calcium Enriched Mixture Cement

    Directory of Open Access Journals (Sweden)

    Sobhnamayan F

    2015-12-01

    Full Text Available Statement of Problem: The pH of the human abscess has been measured as low as 5.0. This low pH could potentially inhibit setting reactions, affect adhesion, or increase the solubility of root end filling materials hence affect the compressive strength. Moreover, root end filling materials might expose or even mix with lidocaine HCL during periapical surgery. Objectives: The aim of this in vitro study was to evaluate the effect of acidic pH and lidocaine on the compressive strength of calcium-enriched mixture (CEM. Materials and Methods: CEM was mixed according to the manufacturer’s instructions or with lidocaine (L, and condensed into 6 × 4 mm split moulds. The samples were exposed to phosphate buffered saline (PBS at pH 5 or 7.4 for 7 or 28 days. Cylindrical blocks of CEM (total number = 120 and 15 for each group were subjected to compressive strength test using a universal testing machine. Data were analysed using three-factor analysis of variance (ANOVA. Results: Regardless of pH and time, significant differences were not found between lidocaine groups and the groups that were mixed according to the manufacturer’s instruction (p = 0.083. For both mixing agents, regardless of time, there were no significant differences between the two pH levels (p = 0.157. Regardless of the material and pH, there was a significant increase in the compressive strength from days 7 to 28 (p < 0.001. Conclusions: Mixtures with lidocaine and exposure to an acidic environment had no adverse effects on the compressive strength of CEM Cement.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-14

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-01

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

  1. Durability of pulp fiber-cement composites

    Science.gov (United States)

    Mohr, Benjamin J.

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

  2. Local treatment of osteoporosis with alendronate-loaded calcium phosphate cement

    Institute of Scientific and Technical Information of China (English)

    Zhao Jindong; Tang Hai; Wang Jiayang; Li Gang

    2014-01-01

    Background A new treatment strategy is to target specific areas of the skeletal system that are prone to clinically significant osteoporotic fractures.We term this strategy as the "local treatment of osteoporosis".The study was performed to investigate the effect of alendronate-loaded calcium phosphate cement (CPC) as a novel drug delivery system for local treatment of osteoorosis.Methods An in vitro study was performed using CPC fabricated with different concentrations of alendronate (ALE,0,2,5,10 weight percent (wt%)).The microstructure,setting time,infrared spectrum,biomechanics,drug release,and biocompatibility of the composite were measured in order to detect changes when mixing CPC with ALE.An in vivo study was also performed using 30 Sprague-Dawley rats randomly divided into six groups:normal,Sham (ovariectomized (OVX) + Sham),CPC with 2% ALE,5%ALE,and 10% ALE groups.At 4 months after the implantation of the composite,animals were sacrificed and the caudal vertebrae (levels 4-7) were harvested for micro-CT examination and biomechanical testing.Results The setting time and strength of CPC was significantly faster and greater than the other groups.The ALE release was sustained over 21 days,and the composite showed good biocompatibility.In micro-CT analysis,compared with the Sham group,there was a significant increase with regard to volumetric bone mineral density (BMD) and trabecular number (Tb.N) in the treated groups (P <0.05).Trabecular spacing (Tb.Sp) showed a significant increase in the Sham group compared to other groups (P <0.01).However,trabecular thickness (Tb.Th) showed no significant difference among the groups.In biomechanical testing,the maximum compression strength and stiffness of trabecular bone in the Sham group were lower than those in the experimental groups.Conclusions The ALE-loaded CPC displayed satisfactory properties in vitro,which can reverse the OVX rat vertebral trabecular bone microarchitecture and biomechanical

  3. Magnesium Aluminate Spinel

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan

    2012-01-01

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

  4. Reactive Air Aluminization

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jung-Pyung; Chou, Y. S.; Stevenson, Jeffry W.

    2011-10-28

    Ferritic stainless steels and other alloys are of great interest to SOFC developers for applications such as interconnects, cell frames, and balance of plant components. While these alloys offer significant advantages (e.g., low material and manufacturing cost, high thermal conductivity, and high temperature oxidation resistance), there are challenges which can hinder their utilization in SOFC systems; these challenges include Cr volatility and reactivity with glass seals. To overcome these challenges, protective coatings and surface treatments for the alloys are under development. In particular, aluminization of alloy surfaces offers the potential for mitigating both evaporation of Cr from the alloy surface and reaction of alloy constituents with glass seals. Commercial aluminization processes are available to SOFC developers, but they tend to be costly due to their use of exotic raw materials and/or processing conditions. As an alternative, PNNL has developed Reactive Air Aluminization (RAA), which offers a low-cost, simpler alternative to conventional aluminization methods.

  5. Push-out bond strength of MTA HP, a new high-plasticity calcium silicate-based cement.

    Science.gov (United States)

    Silva, Emmanuel Jnl; Carvalho, Nancy Kudsi; Zanon, Mayara; Senna, Plínio Mendes; DE-Deus, Gustavo; Zuolo, Mário Luis; Zaia, Alexandre Augusto

    2016-06-14

    This study was designed to investigate the resistance to dislodgment provided by MTA HP, a new high-plasticity calcium silicate-based cement. Biodentine and White MTA Angelus were used as reference materials for comparison. Three discs 1 ± 0.1 mm thick were obtained from the middle third of the roots of 5 maxillary canines. Three 0.8-mm-wide holes were drilled on the axial surface of each root disc. Standardized irrigation was performed. Then the holes were dried with paper points and filled with one of the three tested cements. The filled dental slices were immersed in a phosphate-buffered saline (PBS) solution (pH 7.2) for 7 days before the push-out assessment. The Kruskal-Wallis test was applied to assess the effect of each endodontic cement on the push-out bond strength. Mann-Whitney with Bonferroni correction was used to isolate the differences. The alpha-type error was set at 0.05. All specimens had measurable push-out values and no premature failure occurred. There were significant differences among the materials (p MTA HP had significantly higher bond strength than White MTA (p MTA HP showed better push-out bond strength than its predecessor, White MTA; however, Biodentine had higher dislodgment resistance than both MTA formulations.

  6. Effect of rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteins in vitro.

    Science.gov (United States)

    Knabe, C; Berger, G; Gildenhaar, R; Meyer, J; Howlett, C R; Markovic, B; Zreiqat, H

    2004-04-01

    The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation because it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteins by human bone-derived cells (HBDCs) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were alpha-TCP, two materials with a crystalline phase Ca(2)KNa(PO(4))(2) and with a small amorphous portion containing either magnesium potassium phosphate (material denominated GB14) or silica phosphate (material denominated GB9), and a calcium phosphate bone cement (material denominated Biocement D). HBDCs were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase, and bone sialoprotein). All substrates supported continuous cellular growth for 21 days. In the presence of GB14 and Biocement D specimens cell proliferation was reduced and cell differentiation increased. At day 21, the greatest number of cells was found on GB9 expressing significantly higher levels of bone-related proteins than cells grown on all other surfaces. Because all novel materials facilitated the expression of the osteoblastic phenotype at least as much as TCP and the polystyrene control, these biomaterials can be regarded as excellent candidate bone substitute materials. GB9 induced the highest proliferation and cellular differentiation after 21 days of incubation, suggesting that this material may possess a higher potency for enhancing osteogenesis than TCP.

  7. Magnesium modification of a calcium phosphate cement alters bone marrow stromal cell behavior via an integrin-mediated mechanism.

    Science.gov (United States)

    Zhang, Jing; Ma, Xiaoyu; Lin, Dan; Shi, Hengsong; Yuan, Yuan; Tang, Wei; Zhou, Huanjun; Guo, Han; Qian, Jiangchao; Liu, Changsheng

    2015-06-01

    The chemical composition, structure and surface characteristics of biomaterials/scaffold can affect the adsorption of proteins, and this in turn influences the subsequent cellular response and tissue regeneration. With magnesium/calcium phosphate cements (MCPC) as model, the effects of magnesium (Mg) on the initial adhesion and osteogenic differentiation of bone marrow stromal cells (BMSCs) as well as the underlying mechanism were investigated. A series of MCPCs with different magnesium phosphate cement (MPC) content (0∼20%) in calcium phosphate cement (CPC) were synthesized. MCPCs with moderate proportion of MPC (5% and 10%, referred to as 5MCPC and 10MCPC) were found to effectively modulate the orientation of the adsorbed fibronectin (Fn) to exhibit enhanced receptor binding affinity, and to up-regulate integrin α5β1 expression of BMSCs, especially for 5MCPC. As a result, the attachment, morphology, focal adhesion formation, actin filaments assembly and osteogenic differentiation of BMSCs on 5MCPC were strongly enhanced. Further in vivo experiments confirmed that 5MCPC induced promoted osteogenesis in comparison to ot her CPC/MCPCs. Our results also suggested that the Mg on the underlying substrates but not the dissolved Mg ions was the main contributor to the above positive effects. Based on these results, it can be inferred that the specific interaction of Fn and integrin α5β1 had predominant effect on the MCPC-induced enhanced cellular response of BMSCs. These results provide a new strategy to regulate BMSCs adhesion and osteogenic differentiation by adjusting the Mg/Ca content and distribution in CPC, guiding the development of osteoinductive scaffolds for bone tissue regeneration.

  8. 高铁水兑入比电炉炉盖用镁铝尖晶石浇注料的研制%Development of magnesium aluminate spinel castable for cover of EAF with high molten iron adding ratio

    Institute of Scientific and Technical Information of China (English)

    陈杨; 吴洪平; 朱冬冬; 张行

    2012-01-01

    Specimens of magnesium aluminate spinel castable and calcium aluminate cement bonded bauxite based castable were prepared using special bauxite (particle size ≤8 mm) and sintered magnesia as aggregates,SiO2 micropowder.cc-alumina micropowder and calcium aluminate cement as binders,drying, firing at 1 350 ℃ and 1 500 ℃ for 3 h,respectively. The bulk density,modulus of rupture,cold crushing strength, permanent change in dimensions on heating, thermal shock resistance and slag resistance were determined. The result shows that compared with calcium aluminate cement bonded bauxite based castable,the magnesium aluminate spinel castable has higher cold crushing strength after drying, better slag resistance but worse thermal shock resistance. Magnesium aluminate spinel based lid of EAF with high molten iron adding ratio has longer service life.%以粒度≤8 mm特级高铝矾土颗粒和烧结镁砂为骨料,SiO2微粉、α-Al2O3微粉、铝酸钙水泥作结合剂,分别制得镁铝尖晶石质浇注料和铝酸钙水泥结合高铝质浇注料.对试样分别进行烘干、1 350℃3 h和1 500℃3 h热处理并检测其体积密度、抗折强度、耐压强度、加热永久线变化、抗热震性和抗渣性.结果表明:与铝酸钙水泥结合高铝质浇注料相比,镁铝尖晶石质浇注料具有较高的烘干耐压强度,优良的抗渣性,但抗热震性较差.因此,在高铁水兑入比的电炉中,镁铝尖晶石质电炉盖表现出了更长的使用寿命.

  9. Production and characterization of setting hydraulic cements based on calcium phosphate; Obtencao e caracterizacao de cimentos de fosfato de calcio de pega hidraulica

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Luci C. de; Rigo, Eliana C.S.; Santos, Luis A dos; Boschi, Anselmo Ortega [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais; Carrodeguas, Raul G. [Universidad de La Habana, Habana (Cuba). Centro de Biomateriales

    1997-12-31

    Setting hydraulic cements based on calcium phosphate has risen great interest in scientific literature during recent years due to their total bio compatibility and to the fact that they harden `in situ`, providing easy handling and adaptation to the shape and dimensions of the defect which requires correction, differently from the predecessors, the calcium phosphate ceramics (Hydroxy apatite, {beta}-tri calcium phosphate, biphasic, etc) in the shape of dense or porous blocks and grains. In the work, three calcium-phosphate cement compositions were studied. The resulting compositions were characterized according to the following aspects: setting times, pH, mechanical resistance, crystalline phases, microstructure and solubility in SBF (Simulated Body Fluid). The results show a potential use for the compositions. (author) 6 figs., 4 tabs.

  10. Bone formation induced by strontium modified calcium phosphate cement in critical-size metaphyseal fracture defects in ovariectomized rats.

    Science.gov (United States)

    Thormann, Ulrich; Ray, Seemun; Sommer, Ursula; Elkhassawna, Thaqif; Rehling, Tanja; Hundgeburth, Marvin; Henß, Anja; Rohnke, Marcus; Janek, Jürgen; Lips, Katrin S; Heiss, Christian; Schlewitz, Gudrun; Szalay, Gabor; Schumacher, Matthias; Gelinsky, Michael; Schnettler, Reinhard; Alt, Volker

    2013-11-01

    The first objective was to investigate new bone formation in a critical-size metaphyseal defect in the femur of ovariectomized rats filled with a strontium modified calcium phosphate cement (SrCPC) compared to calcium phosphate cement (CPC) and empty defects. Second, detection of strontium release from the materials as well as calcium and collagen mass distribution in the fracture defect should be targeted by time of flight secondary ion mass spectrometry (TOF-SIMS). 45 female Sprague-Dawley rats were randomly assigned to three different treatment groups: (1) SrCPC (n = 15), (2) CPC (n = 15), and (3) empty defect (n = 15). Bilateral ovariectomy was performed and three months after multi-deficient diet, the left femur of all animals underwent a 4 mm wedge-shaped metaphyseal osteotomy that was internally fixed with a T-shaped plate. The defect was then either filled with SrCPC or CPC or was left empty. After 6 weeks, histomorphometric analysis showed a statistically significant increase in bone formation of SrCPC compared to CPC (p = 0.005) and the empty defect (p = 0.002) in the former fracture defect zone. Furthermore, there was a statistically significant higher bone formation at the tissue-implant interface in the SrCPC group compared to the CPC group (p < 0.0001). These data were confirmed by immunohistochemistry revealing an increase in bone-morphogenic protein 2, osteocalcin and osteoprotegerin expression and a statistically significant higher gene expression of alkaline phosphatase, collagen10a1 and osteocalcin in the SrCPC group compared to CPC. TOF-SIMS analysis showed a high release of Sr from the SrCPC into the interface region in this area compared to CPC suggesting that improved bone formation is attributable to the released Sr from the SrCPC.

  11. Spatial Distribution of the Increased Porosity of Cement Paste due to Calcium Leaching

    Institute of Scientific and Technical Information of China (English)

    WAN Keshu; LI Lin; XU Qiong; SUN Wei

    2015-01-01

    Using the tomography image, a method to characterize the 3D spatial distributions of increased porosity was proposed, and the increased porosity distributions of cement pastes with different leaching degrees were given using the current method. The leaching processes of CH/C-S-H and the contribution of CH/C-S-H leaching to porosity evolution were discussed. The proposed method can be applied to all cement-based materials with any leaching degrees. From the quantitative increased porosity results, we ifnd that the CH leaching ifnished quickly on the sharp CH leaching front.

  12. Tuning the Degradation Rate of Calcium Phosphate Cements by Incorporating Mixtures of Polylactic-co-Glycolic Acid Microspheres and Glucono-Delta-Lactone Microparticles

    NARCIS (Netherlands)

    Sariibrahimoglu, K.; An, J.; Oirschot, B.A.J.A. van; Nijhuis, A.W.G.; Eman, R.M.; Alblas, J.; Wolke, J.G.C.; Beucken, J.J.J.P van den; Leeuwenburgh, S.C.G.; Jansen, J.A.

    2014-01-01

    Calcium phosphate cements (CPCs) are frequently used as synthetic bone graft materials in view of their excellent osteocompatibility and clinical handling behavior. Hydroxyapatite-forming CPCs, however, degrade at very low rates, thereby limiting complete bone regeneration. The current study has inv

  13. Calcium Phosphate Cement for Drug Deliver Applications%磷酸钙骨水泥载药研究

    Institute of Scientific and Technical Information of China (English)

    张海燕; 邬伟魁; 宋伟; 李芳; 芦乾; 贺娅; 杨明

    2012-01-01

    This study investigated the applications of calcium phosphate cement ( CPC ) as drug deliver system. There is strong evidence that calcium phosphate cement is a nice drug deliver vector. Due to its unique properties, much attention has paied to CPC for drug deliver applications in both areas of research and application. In recent decades, different drugs have been loaded in CPC, including antibiotic ( tobramycin, gentamicin and clindamycin) , anti-tumor drugs (adriamycin, mitomycin, vincristine) and cell factors (bone morphogenetic protein and fibrin glue). Particularly, traditional Chinese medicines ( astraglycan, Xiangdan injection, Danhong injection, Danshen injection) used in the drug delivery system were summarized to provide the reference for the further improvement of herbal remedies loaded in CPC as a drug delivery system to treat bone disease.%对磷酸钙骨水泥(calcium phosphate cement,CPC)载药的国内外研究进行文献整理与分析.研究表明,CPC是一种优良的骨科药物载体,是近年国内外生物医学、材料学和药学领域共同的研究焦点.介绍了CPC载药系统所负载的不同药物,包括抗生素(如妥布霉素、庆大霉素和克林霉素等)、抗肿瘤药物(如阿霉素、丝裂霉素、长春新碱和5F-尿嘧啶等)和细胞因子(如骨形态发生蛋白和纤维蛋白胶等);讨论了中药(如黄芪多糖、香丹注射液、丹红注射液和复方丹参注射液等)在骨水泥载药中的应用研究现状,认为中药有望应用于CPC局部给药的临床研究,但目前相关安全性研究较少,有待加强.

  14. Calcium phosphate cements: study of the beta-tricalcium phosphate--monocalcium phosphate system.

    Science.gov (United States)

    Mirtchi, A A; Lemaitre, J; Terao, N

    1989-09-01

    The possibility of making cements based on beta-tricalcium phosphate (beta-TCP), a promising bone graft material, was investigated. Upon admixture with water, beta-TCP/monocalcium phosphate monohydrate (MCPM) mixtures were found to set and harden like conventional hydraulic cements. Beta-TCP powders with larger particle size, obtained by sintering at higher temperatures, increased the ultimate strength of the cement. Results show that setting occurs after dissolution of MCPM, as a result of the precipitation of dicalcium phosphate dihydrate (DCPD) in the paste. The ultimate tensile strength of the hardened cement is proportional to the amount of DCPD formed. Upon ageing above 40 degrees C, DCPD transforms progressively into anhydrous dicalcium phosphate (DCP), thereby decreasing the strength. Ageing of the pastes in 100% r.h. results in a decay of the mechanical properties. This can be ascribed to an intergranular dissolution of the beta-TCP aggregates as a result of the pH lowering brought about by the MCPM to DCPD conversion.

  15. Blooming gelatin: an individual additive for enhancing nanoapatite precipitation, physical properties, and osteoblastic responses of nanostructured macroporous calcium phosphate bone cements.

    Science.gov (United States)

    Orshesh, Ziba; Hesaraki, Saeed; Khanlarkhani, Ali

    2017-01-01

    In recent years, there has been a great interest in using natural polymers in the composition of calcium phosphate bone cements to enhance their physical, mechanical, and biological performance. Gelatin is a partially hydrolyzed form of collagen, a natural component of bone matrix. In this study, the effect of blooming gelatin on the nanohydroxyapatite precipitation, physical and mechanical properties, and cellular responses of a calcium phosphate bone cement (CPC) was investigated. Various concentrations of blooming gelatin (2, 5, and 8 wt.%) were used as the cement liquid and an equimolar mixture of tetracalcium phosphate and dicalcium phosphate was used as solid phase. The CPC without any gelatin additive was also evaluated as a control group. The results showed that gelatin accelerated hydraulic reactions of the cement paste, in which the reactants were immediately converted into nanostructured apatite precipitates after hardening. Gelatin molecules induced 4%-10% macropores (10-300 μm) into the cement structure, decreased initial setting time by ~190%, and improved mechanical strength of the as-set cement. Variation in the above-mentioned properties was influenced by the gelatin concentration and progressed with increasing the gelatin content. The numbers of the G-292 osteoblastic cells on gelatin-containing CPCs were higher than the control group at entire culture times (1-14 days), meanwhile better alkaline phosphatase (ALP) activity was determined using blooming gelatin additive. The observation of cell morphologies on the cement surfaces revealed an appropriate cell attachment with extended cell membranes on the cements. Overall, adding gelatin to the composition of CPC improved the handling characteristics such as setting time and mechanical properties, enhanced nanoapatite precipitation, and augmented the early cell proliferation rate and ALP activity.

  16. Effect of curing conditions on the dimensional and thermal stability of calcium phosphate cement for elevated temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Blom, Johan [Vrije Universiteit Brussel, Department of Mechanics of Materials and Constructions, Pleinlaan 2, Brussels 1050 (Belgium); Rahier, Hubert [Vrije Universiteit Brussel, Research Group of Physical Chemistry and Polymer Sciences, Pleinlaan 2, Brussels 1050 (Belgium); Wastiels, Jan, E-mail: Jan.Wastiels@vub.ac.be [Vrije Universiteit Brussel, Department of Mechanics of Materials and Constructions, Pleinlaan 2, Brussels 1050 (Belgium)

    2014-12-15

    Calcium phosphate cements (CPCs) are attractive materials for elevated temperature applications, like moulds to process thermoplastics up to 300 °C. The CPC resulting from the reaction of wollastonite with phosphoric acid cured at room temperature however contains hydrated phases like brushite, and is thus not stable when exposed to temperatures above 200 °C. A non-contact method based on digital image correlation demonstrated that isothermal curing at 60 °C reduces the thermal shrinkage up to 300 °C by 25%. This curing method results in the direct formation of the more stable monetite in a shorter curing time. The correlated results of TGA, pH of the filtration water, and DSC analysis on partially cured material indicate this. XRD diffractograms and SEM images in combination with EDX show the evolution of the transformation of wollastonite into monetite, and the structure and morphology of the formed material.

  17. Calcium enriched mixture cement for primary molars exhibiting root perforations and extensive root resorption: report of three cases.

    Science.gov (United States)

    Tavassoli-Hojjati, Sara; Kameli, Somayeh; Rahimian-Emam, Sara; Ahmadyar, Maryam; Asgary, Saeed

    2014-01-01

    In primary molars with root perforations of endodontic origin, tooth extraction and space maintainer are recommended. Calcium-enriched mixture (CEM) cement is a new biomaterial demonstrating favorable sealability/biocompatibility. This report presents a novel treatment modality for cases of primary molar teeth with root perforations associated with a periodontal lesion due to extensive inflammatory root resorption, whereby CEM was used as a perforation repair/pulpotomy biomaterial. Three cases of primary molar root perforations due to inflammatory resorption were selected; all cases were associated with furcal lesions of endodontic origin. Pulp chambers were accessed/irrigated with NaOCl; the root canal orifices were filled with CEM and restored with stainless steel crowns. Clinical/radiographic examinations up to 17 months revealed that all teeth were functional and free of signs/symptoms of infection and all had complete bone healing. Further trials are suggested to confirm CEM use for management of root perforations in primary molars exhibiting root perforation.

  18. Histological and mechanical evaluation of self-setting calcium phosphate cements in a sheep vertebral bone void model.

    Science.gov (United States)

    Kobayashi, Naomi; Ong, Kevin; Villarraga, Marta; Schwardt, Jeffrey; Wenz, Robert; Togawa, Daisuke; Fujishiro, Takaaki; Turner, A Simon; Seim, Howard B; Bauer, Thomas W

    2007-06-15

    We investigated the histological and compressive properties of three different calcium phosphate cements (CPCs) using a sheep vertebral bone void model. One of the CPCs contained barium sulfate to enhance its radiopacity. Bone voids were surgically created in the lumbar region of 23 ovine spines - L3, L4, and L5 (n = 69 total vertebral bodies) - and the voids were filled with one of the three CPCs. A fourth group consisted of whole intact vertebrae. Histologic evaluation was performed for 30 of the 69 vertebrae 2 or 4 months after surgery along with radiographic evaluation. Compressive testing was performed on 39 vertebrae 4 months after surgery along with micro-CT analysis. All three CPCs were biocompatible and extremely osteoconductive. Osteoclasts associated with adjacent bone formation suggest that each cement can undergo slow resorption and replacement by bone and bone marrow. Compressive testing did not reveal a significant difference in the ultimate strength, ultimate strain, and structural modulus, among the three CPCs and intact whole vertebrae. Micro-CT analysis revealed good osseointegration between all three CPCs and adjacent bone. The barium sulfate did not affect the CPCs biocompatibility or mechanical properties. These results suggest that CPC might be a good alternative to polymethylmethacrylate for selected indications.

  19. Fabrication and characterization of calcium phosphate cement scaffolds; Obtencao e caracterizacao de scaffolds de cimento de fosfato de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, E. de; Motisuke, M., E-mail: eliandra.sousa@unifesp.br [Universidade Federal de Sao Paulo (UNIFESP), Sao Jose dos Campos, SP (Brazil). Instituto de Ciencia e Tecnologia; Bertran, C.A. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Instituto de Quimica

    2011-07-01

    In Tissue Engineering, the need for scaffolds which are capable of guiding the organization, differentiation and growth of cells leading to the formation of new tissues is highly relevant. For the development of new scaffolds focused on bone tissue therapy, calcium phosphate cements (CPC) have great potential, because besides their resorbability, they present morphology and chemical composition similar to the bone mineral phase. Moreover, there are several processing techniques to produce ceramic scaffolds: polymeric sponge replication, incorporation of organic material into the ceramic powder, gelcasting, emulsion, among others. The aim of this work was to obtain CPCs scaffolds by using two techniques, emulsion and gelcasting. The scaffolds were characterized by their physical and mechanical properties and the crystalline phases formed after the setting reaction of cement were determined by X-ray diffraction. The samples obtained by both methods presented porosity between 61-65% and the microstructure consists of nearly spherical pores (d5o = 50-100 μm). The mechanical strength of the samples ranged from 5.5 to 1.5 MPa. The crystalline phases found were monetite (CaHPO{sub 4}) and brushite (CaHPO{sub 4} 2H{sub 2}O). (author)

  20. Effect of ultrafine poly(ε-caprolactone fibers on calcium phosphate cement: in vitro degradation and in vivo regeneration

    Directory of Open Access Journals (Sweden)

    Yang BY

    2016-01-01

    Full Text Available Boyuan Yang,1 Yi Zuo,1 Qin Zou,1 Limei Li,1 Jidong Li,1 Yi Man,2 Yubao Li1 1Research Center for Nano Biomaterials, Analytical and Testing Center, Sichuan University, Chengdu, People’s Republic of China; 2State Key Laboratory of Oral Disease, West China Hospital of Stomatology, Sichuan University, Chengdu, People’s Republic of China Abstract: We incorporated ultrafine polymer fibers into calcium phosphate cement (CPC to improve the resorption rate of CPC with fiber degradation. Different weight percentages of electrospun poly(ε-caprolactone fibers (0%, 3%, and 7%, named as ultrafine fiber-incorporated CPC0 [UFICPC0], UFICPC3, and UFICPC7 were included into preset CPC specimens for in vitro immersion in lipase phosphate-buffered solution and long-term in vivo implantation in the femoral condyle of rabbits. The effect of the ultrafine poly(ε-caprolactone fibers with a diameter ranging from nanometer to micrometer on CPC degradation was evaluated by measuring the pH of the medium, mass loss, porosity, and physiochemical properties. For the in vivo evaluation, histomorphometrical analysis as well as three-dimensional (3D reconstruction was applied to assess the osteogenic properties of the CPC composite. After in vitro immersion and in vivo implantation, the total porosity and macroporosity as well as the bone formation and ingrowth increased significantly during time in the fiber-incorporated CPC specimens. After 24 weeks of implantation, the degraded space was occupied by newly formed bone, and the UFICPC3 and UFICPC7 composites showed a ~3.5 times higher fraction of bone volume than that of the pristine CPC (UFICPC0. In vitro and in vivo results proved that the introduction of ultrafine degradable fibers within a CPC matrix can be used to improve macroporosity efficiently and enhance CPC degradation and bone ingrowth largely. Keywords: ultrafine fibers, calcium phosphate cement, macroporosity, degraded space, bone ingrowth

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

    Institute of Scientific and Technical Information of China (English)

    LIN Zongshou; ZHAO Qian

    2009-01-01

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

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

    Science.gov (United States)

    GUERREIRO-TANOMARU, Juliane Maria; VÁZQUEZ-GARCÍA, Fernando Antonio; BOSSO-MARTELO, Roberta; BERNARDI, Maria Inês Basso; FARIA, Gisele; TANOMARU, Mario

    2016-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Juliane Maria GUERREIRO-TANOMARU

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

  4. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-15

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

  5. Effect of Calcium Leaching on the Properties of Cement-based Composites

    Institute of Scientific and Technical Information of China (English)

    LLIN Weiting; CHENG An; HUANG Ran; CHEN Chuntao; ZHOU Xingang

    2011-01-01

    Leaching is one of the major factors that alter the mechanical properties of cementbased composites.This study is aimed to investigate the effect of leaching on the properties of cementbased composites.Specimens with two water/cementitious ratios and two mineral admixtures were tested.An electrical potential was applied to accelerate the leaching process.Compressive strength test,scanning electronic microscopy,thermogravimetric analysis and X-ray diffraction analysis were conducted.Test results demonstrated that the calcium leaching reduced compressive strengths of concrete specimens,and such effect was prominent on the specimens without mineral admixtures.The leaching resistance increased with a decrease in water/cementitious ratio and an increase in amount of mineral admixtures.The mineral admixtures would reduce the amount of calcium hydroxide and refine the pore structure through pozzolanic reactions.A fair relationship was found between the calcium leaching and the compressive strength.

  6. The mechanical and biological studies of calcium phosphate cement-fibrin glue for bone reconstruction of rabbit femoral defects

    Directory of Open Access Journals (Sweden)

    Dong J

    2013-03-01

    Full Text Available Jingjing Dong,1,* Geng Cui,2,* Long Bi,1,* Jie Li,3 Wei Lei11Institute of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi’an, Shaanxi, People’s Republic of China; 2Institute of Orthopedics, General Hospital of PLA, Beijing, People’s Republic of China; 3Institute of Gynecology and Obstetrics, General Hospital of PLA, Beijing, People’s Republic of China*These authors contributed equally to this workAbstract: In order to improve the mechanical and biological properties of calcium phosphate cement (CPC, nanometer-biomaterial for bone reconstruction in the rabbit femoral defect model, fibrin glue (FG, the natural product, purified from the blood was introduced at three different ratios. The CPC powder and the FG solution were mixed, respectively, at the powder/liquid (P/L ratios (g/mL of 1:1, 3:1, and 5:1 (g/mL, and pure CPC was used as a control. After being implanted into the femoral defect in rabbit, the healing process was evaluated by micro-computed tomography scan, biomechanical testing, and histological examination. By micro-computed tomography analysis, the P/L ratio of 1:1 (g/mL group indicated the largest quantity of new bone formation at 4 weeks, 8 weeks, and 12 weeks after implantation, respectively. Bone volume per trabecular volume of the 1:1 group was highest in the four groups, which was 1.45% ± 0.42%, 7.35% ± 1.45%, and 29.10% ± 1.67% at 4 weeks, 8 weeks, and 12 weeks after the operation, respectively. In the biomechanical tests, the compressive strength and the elastic modulus of the three CPC–FG groups were much higher than those of the pure CPC group at the determined time point (P < 0.05. The histological evaluation also showed the best osseointegration in the 1:1 group at 4 weeks, 8 weeks, and 12 weeks after the operation, respectively. In the 1:1 group, the bone grew into the pore of the cement in the laminar arrangement and connected with the cement tightly at the 12th week after the operation

  7. Addition of 1, 2 and 3% in mass of sodium alginate in calcium phosphate cement; Adicao de alginato de sodio a cimento de fosfato de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Coelho, W.T.; Fernandes, J.M.; Vieira, R.S.; Thurmer, M.B.; Santos, L.A., E-mail: trajano@ufrgs.br [Universidade Federal do Rio Grande do Sul (LABIOMAT/UFRS), RS (Brazil)

    2011-07-01

    The calcium phosphate cement (CFC) are bone substitutes with great potential for use in orthopedics, traumatology and dentistry because of their biocompatibility, bioactivity, osteoconductivity and osteotransdutivity, and a paste that can be easily molded and placed into the surgical site. However, CFCs have low mechanical strength, which equals the maximum mechanical strength of trabecular bone. Aiming to evaluate the strength and time to handle a CFC phase composed mainly of alpha were added to sodium alginate (1%, 2% and 3% wt) and an accelerator handle in an aqueous medium. The cement powder was mixed with liquid takes 2 minutes and resigned in specimens and assessed for apparent density and porosity by the Archimedes method, X-ray diffraction and mechanical strength. We noticed a significant increase in mechanical properties of cement added sodium alginate. (author)

  8. Apical Sealing Ability of Mineral Trioxide Aggregate, Intermediate Restorative Material and Calcium Enriched Mixture Cement: A Bacterial Leakage Study

    Science.gov (United States)

    Shahriari, Shahriar; Faramarzi, Farhad; Alikhani, Mohammad-Yousef; Farhadian, Maryam; Hendi, Seyedeh Sareh

    2016-01-01

    Introduction: This in vitro study compared the apical sealing ability of three common root end filling materials namely mineral trioxide aggregate (MTA), intermediate restorative material (IRM) and calcium-enriched mixture (CEM) cement using a bacterial leakage model. Methods and Materials: The study was conducted on 83 single-rooted human teeth. Tooth crowns were cut and root canals were prepared using the step-back technique. Apical 3 mm of the roots were cut and a three-mm-deep cavity was prepared using an ultrasonic instrument. The samples were divided into three groups (n=25) according to the root-end filling material including MTA, IRM and CEM cement. The roots were inserted into cut-end microtubes. After sterilization with ethylene oxide, microtubes were placed in sterile vials containing 10 mL of Brain Heart Infusion (BHI) broth and incubated at 37°C and 0.1 mL of Enterococcus faecalis suspension compatible with 0.5 McFarland standard (1.5×108 cell/ ml), which was refreshed daily. This procedure was continued for 70 days. The data were analyzed using the chi-square, Kruskal-Wallis and log rank tests. The level of significance was set at 0.05. Results: No significant difference was found in bacterial microleakage among three groups; MTA showed slightly (but not significantly) less microleakage than IRM and CEM. However, the difference in the mean time of microleakage was significant among the groups (P<0.04) and in MTA samples leakage occurred in a longer time than CEM (P<0.012). Conclusion: The three tested root end filling materials had equal sealing efficacy for preventing bacterial leakage. PMID:27790267

  9. 钢中高熔点钙铝酸盐类夹杂物聚集行为%Aggregation of inclusions for calcium aluminate with high-melting point

    Institute of Scientific and Technical Information of China (English)

    初仁生

    2015-01-01

    The size,area,composition,type and distribution of non-metallic inclusions with high-melting point (CA2 and CA6,which C:CaO,A:Al2O3) in inspection substandard samples were analyzed by aspex explorer automated scan-ning electron microscope. To analyze the reason that why the center is the concentrated area of the large-size inclusions, three aspects for the causes of calcium aluminate with high-melting point causing the aggregation behavior for flaw sub-standard is focused on:features of non-metallic inclusions,the characteristics of continuous casting machine and the be-havior of nonmetallic inclusions during the process of solidification. The results show that calcium aluminate with high-melting point gathered together,and is easy to aggregate. The casting speed is slow for the curved continuous casting ma-chine compared with the average arc caster. The thickness of slab is thin and the molten steel solidifies rapidly,which makes the solidification end generate early,and form an easy gathering area near the center during the steel solidification. The inclusions are pushed and engulfed in the shell and will aggregate. While the space and time of floatation is reduced, combined with the effect of promoting the capture,the center forms a concentrated area of the large-size inclusions.%利用Aspex Explorer自动扫描电镜对探伤不合格试样中非金属夹杂物CA2和CA6(C为CaO,A为Al2O3)的尺寸、面积、成分、类型及分布等进行全面分析。从非金属夹杂物本身性质、连铸机本身特性和凝固过程非金属夹杂物行为3个方面集中探讨了高熔点钙铝酸盐类非金属夹杂物聚集行为。结果表明:高熔点钙铝酸盐类非金属夹杂物本身聚集能力很强,极易聚集;弧形连铸机拉速慢,铸坯厚度较一般的中厚板薄,凝固较快,使得凝固终点提前,造成在凝固过程中夹杂物在靠近中心处形成容易聚集区,同时上浮的空间和时间减少,加上推

  10. 铝酸钙系冶金熔剂和CaF2对镁碳砖的侵蚀比较%Corrosion comparison of calcium aluminate system metallurgy flux and CaF2 to magnesia carbon brick

    Institute of Scientific and Technical Information of China (English)

    李文平; 李士明; 陈俊红; 孙加林; 吴克芳; Christoph Wohrmeyer

    2013-01-01

    为了降低精炼渣对钢包渣线镁碳砖的侵蚀,分别以20%(w)的冶金熔剂铝酸钙、铝镁酸钙和CaF2与80%(w)的初始钢渣配制成三种精炼渣,以镁碳砖为感应炉的坩埚,在坩埚内放入钢样,待钢样熔化并升温到1 600℃时,加精炼渣持续冶炼5h(期间共更换渣8次),冷却后测镁碳砖渣线部位的侵蚀(渗透)深度并进行SEM分析.结果表明:以铝酸钙和铝镁酸钙为熔剂的精炼渣都比以CaF2为熔剂的精炼渣对镁碳砖的渗透浅、侵蚀小,而以铝镁酸钙冶金熔剂为精炼渣比以铝酸钙冶金熔剂为精炼渣对镁碳砖的渗透和侵蚀性都大大降低.这是由于铝镁酸钙中含有饱和的MgO,减缓了镁碳砖中MgO向CMA渣中的溶解,从而降低了渣对镁碳砖的侵蚀.%In order to reduce the corrosion of refining slag to ladle slag line MgO-C brick,three kinds of refining slags were prepared with 20 mass% metallurgy fluxes of calcium aluminate (CA) and calcium magnesia aluminate (CMA) and CaF2 and 80 mass% original steel slag,and MgO-C bricks were made into crucibles of electric induction furnace. Add steel sample into the crucible,heat up to 1 600 ℃after the steel sample melts,then add refining slag,and hold for 5 h. In the meantime,the refining slags were replaced for 8 times. The corrosion (penetration) depth of the MgO-C brick in slag line was determined and the corroded brick was observed by SEM. The research shows that the MgO-C brick can better resist the penetration and corrosion of refining slags containing CA flux and CMA flux than those of refining slag containing CaF2; refining slag containing CMA flux penetrates and corrodes MgO-C brick obviously slightly than refining slag containing CA flux. CMA flux contains the saturated MgO which reduces the dissolving speed of MgO from MgO-C brick to refining slag containing CMA flux,corresponding decreases the corrosion of the slag.

  11. EFFECT OF MgO ON THE COMPOSITION AND PROPERTIES OF BELITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT IN THE PRESENCE OF Na2O AND K2O

    Directory of Open Access Journals (Sweden)

    Jie Zhang

    2015-06-01

    Full Text Available The purpose of this study is to explore the effect of MgO (1 - 9 wt. % on the composition and properties of belite-barium calcium sulphoaluminate cement with additions of Na2O and K2O. The results show that 1 - 5 wt. % content of MgO can stabilize crystal types of M3-C3S, R-C3S and β-C2S. Moreover, MgO can promote the formation of C3S and C4AF, but has little effect on the formation of C2.75B1.25A3$ and C3A. The C3A/C4AF ratio is reduced by 22 % at 5 wt. % MgO, which indicates that appropriate MgO can decrease the liquid viscosity. In the presence of Na2O and K2O, the highest limit of incorporated amount of MgO is about 3 wt. %, which is higher than that in Portland cement clinker of 2 wt. %. Besides, MgO favors the formation of small C3S crystals in size of 4 - 20 μm. MgO enhances the hydration rate and mechanical property of cement at an optimal dosage (1 - 5 wt. %, beyond which an adverse effect could be resulted. At a MgO dosage of 5 wt. %, the compressive strengths of the cement at 1, 3, 7 and 28 days are 15.8, 39.3, 68.6 and 97.3 MPa, which increases by 116 %, 17 %, 10 % and 6 % respectively compared to the cement without MgO dopant. This study could lead to the effective use of magnesia-rich limestone in industrial production of belite-barium calcium sulphoaluminate cement.

  12. Structure of liquid tricalcium aluminate

    Science.gov (United States)

    Drewitt, James W. E.; Barnes, Adrian C.; Jahn, Sandro; Kohn, Simon C.; Walter, Michael J.; Novikov, Alexey N.; Neuville, Daniel R.; Fischer, Henry E.; Hennet, Louis

    2017-02-01

    The atomic-scale structure of aerodynamically levitated and laser-heated liquid tricalcium aluminate (Ca3Al2O6 ) was measured at 2073(30) K by using the method of neutron diffraction with Ca isotope substitution (NDIS). The results enable the detailed resolution of the local coordination environment around calcium and aluminum atoms, including the direct determination of the liquid partial structure factor, SCaCa(Q ) , and partial pair distribution function, gCaCa(r ) . Molecular dynamics (MD) simulation and reverse Monte Carlo (RMC) refinement methods were employed to obtain a detailed atomistic model of the liquid structure. The composition Ca3Al2O6 lies at the CaO-rich limit of the CaO:Al2O3 glass-forming system. Our results show that, although significantly depolymerized, liquid Ca3Al2O6 is largely composed of AlO4 tetrahedra forming an infinite network with a slightly higher fraction of bridging oxygen atoms than expected for the composition. Calcium-centered polyhedra exhibit a wide distribution of four- to sevenfold coordinated sites, with higher coordinated calcium preferentially bonding to bridging oxygens. Analysis of the MD configuration reveals the presence of ˜10 % unconnected AlO4 monomers and Al2O7 dimers in the liquid. As the CaO concentration increases, the number of these isolated units increases, such that the upper value for the glass-forming composition of CaO:Al2O3 liquids could be described in terms of a percolation threshold at which the glass can no longer support the formation of an infinitely connected AlO4 network.

  13. Effect of Combined Calcium Hydroxide and Accelerated Portland Cement on Bone Formation and Soft Tissue Healing in Dog Bone Lesions

    Directory of Open Access Journals (Sweden)

    Khorshidi H

    2015-09-01

    Full Text Available Statement of Problem: Recent literatures show that accelerated Portland cement (APC and calcium hydroxide Ca (OH2 may have the potential to promote the bone regeneration. However, certain clinical studies reveal consistency of Ca (OH2, as one of the practical drawbacks of the material when used alone. To overcome such inconvenience, the combination of the Ca (OH2 with a bone replacement material could offer a convenient solution. Objectives: To evaluate the soft tissue healing and bone regeneration in the periodontal intrabony osseous defects using accelerated Portland cement (APC in combination with calcium hydroxide Ca (OH2, as a filling material. Materials and Methods: Five healthy adult mongrel dogs aged 2-3 years old (approximately 20 kg in weight with intact dentition and healthy periodontium were selected for this study. Two one-wall defects in both mesial and distal aspects of the 3rd premolars of both sides of the mandible were created. Therefore, four defects were prepared in each dog. Three defects in each dog were randomly filled with one of the following materials: APC alone, APC mixed with Ca (OH2, and Ca (OH2 alone. The fourth defect was left empty (control. Upon clinical examination of the sutured sites, the amount of dehiscence from the adjacent tooth was measured after two and eight weeks, using a periodontal probe mesiodistally. For histometric analysis, the degree of new bone formation was estimated at the end of the eighth postoperative week, by a differential point-counting method. The percentage of the defect volume occupied by new osteoid or trabecular bone was recorded. Results: Measurement of wound dehiscence during the second week revealed that all five APCs had an exposure of 1-2 mm and at the end of the study all samples showed 3-4 mm exposure across the surface of the graft material, whereas the Ca (OH2, control, and APC + Ca (OH2 groups did not show any exposure at the end of the eighth week of the study. The most

  14. Using calcium silicate to regulate the physicochemical and biological properties when using β-tricalcium phosphate as bone cement

    Energy Technology Data Exchange (ETDEWEB)

    Kao, Chia-Tze; Huang, Tsui-Hsien [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Chen, Yi-Jyun [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Dental Department, Taichung Hospital, Ministry of Health and Welfare, Taichung City, Taiwan (China); Hung, Chi-Jr [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Lin, Chi-Chang, E-mail: chichang31@gmail.com [Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan (China)

    2014-10-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material. For this research we have combined it with a low degradation calcium silicate (CS) to enhance its bioactive and osteostimulative properties. To check its effectiveness, a series of β-TCP/CS composites with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Regarding the formation of bone-like apatite, the diametral tensile strength as well as the ion release and weight loss of composites were compared both before and after immersions in simulated body fluid (SBF). In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on β-TCP/CS composites. The results show that the apatite deposition ability of the β-TCP/CS composites improves as the CS content is increased. For composites with more than a 60% CS content, the samples become completely covered by a dense bone-like apatite layer. At the end of the immersion period, weight losses of 24%, 32%, 34%, 38%, 41%, and 45% were observed for the composites containing 0%, 20%, 40%, 80%, 80% and 100% β-TCP cements, respectively. In addition, the antibacterial activity of CS/β-TCP composite improves as the CS-content is increased. In vitro cell experiments show that the CS-rich composites promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the CS quantity in the composite is less than 60%, the quantity of cells and osteogenesis protein of hDPCs is stimulated by Si released from the β-TCP/CS composites. The degradation of β-TCP and the osteogenesis of CS give strong reason to believe that these calcium-based composite cements will prove to be effective bone repair materials. - Highlights: • CS improved the physicochemical properties and osteogenic activity of β-TCP. • Higher CS in the composite, the shorter setting time and the higher DTS was found. • With a CS more than 40%, the osteogenesis and angiogenesis proteins were promoted by

  15. Classification and Characteristics of Alkali-Activated Cements%碱激发水泥的类型与特点(英文)

    Institute of Scientific and Technical Information of China (English)

    史才军; 何富强; A. FERNANDEZ-JIMIENEZ; V. Pavel KRIVENKO; Angel PALOMO

    2012-01-01

    The alkali-activated cements can be classified into five categories based on the composition of the cementing compo-nent(s): 1) Alkali-activated slag-based cements;2) Alkali-activated Portland blended cements;3) Alkali-activated pozzolan cements;4) Alkali-activated lime-pozzolan/slag cements;and 5) Alkali-activated calcium aluminate blended cement.Each category could include several cementing systems.The composition and characteristics of the five categories of alkali-activated cements are summarized.%基于所含胶凝组份的成分,可以将碱激发水泥分成5种类型:1)碱激发矿渣水泥;2)碱激发波特兰复合水泥;3)碱激发火山灰水泥;4)碱激发石灰-火山灰/矿渣水泥;5)碱激发铝酸钙复合水泥,每种类型碱激发水泥包含几种胶凝体系。综述了这5种碱激发水泥的成分和特征。

  16. Effect of saliva and blood contamination on the bi-axial flexural strength and setting time of two calcium-silicate based cements: Portland cement and biodentine.

    Science.gov (United States)

    Alhodiry, W; Lyons, M F; Chadwick, R G

    2014-03-01

    This study evaluated the effect of contamination with saliva and blood on the bi-axial flexural strength and setting time of pure gray Portland cement and Biodentine (Septodont, Allington, UK). A one-way ANOVA showed that contamination caused no significant difference between the cements in bi-axial flexural strength (P> 0.05). However there was a significant difference in setting time (Pcement taking longer than Biodentine, regardless of the contaminant, and contamination with blood increased the setting time of both materials. Biodentine was similar in strength to Portland cement, but had a shorter setting time for both contaminated and non-contaminated samples.

  17. 钙磷摩尔比对新型PCCP+DCPA体系骨水泥性能的影响%INFLUENCE OF CALCIUM TO PHOSPHATE MOLAR RATIO ON PERFORMANCE OF A NOVEL CALCIUM PHOSPHATE CEMENT

    Institute of Scientific and Technical Information of China (English)

    王秀鹏; 叶建东; 王迎军

    2007-01-01

    Partially crystallized calcium phosphates (PCCP) with different calcium to phosphate molar ratios (n(Ca)/n(P), the same below) and containing carbonate were synthesized by chemical precipitation method. A novel calcium phosphate cement was prepared by PCCP and dicalcium phosphate anhydrous (DCPA). The effects of n(Ca)/n(P) ratio on the properties of the PCCP-DCPA cement system were studied by X-ray diffraction, scanning electron microscope, porosity measurement, and compressive strength analysis.The results show that with the increase of n(Ca)/n(P) ratio, the compressive strength of the cement samples decreased significantly,whereas the crystallinity, porosity and pore fractions larger than 100 nm in the hydrated cement increased. The properties of the cement were greatly influenced by the n(Ca)/n(P) ratio. The n(Ca)/n(P) ratio must be carefully considered in the preparation of calcium phosphate cement.%用化学沉淀法合成了不同钙/磷摩尔比并含碳酸根的部分结晶磷酸钙(partially crystallized calcium phosphates,PCCP),用PCCP和无水磷酸氢钙(dicalcium phosphate anhydrous ,DCPA)配制了PCCP+DCPA体系磷酸钙骨水泥,用去离子水作为骨水泥的固化液.通过相组成的X射线衍射分析、扫描电子显微镜观察、孔隙率和抗压强度测定,研究了钙磷摩尔[n(Ca)/n(P)]对PCCP+DCPA磷酸钙骨水泥性能的影响.结果表明:随着部分结晶磷酸钙中n(Ca)/n(P)的提高,磷酸钙骨水泥试件的抗压强度明显下降,但磷酸钙骨水泥水化产物羟基磷灰石的结晶度提高,固化体中大于100 nm的孔隙增多、固化体的孔隙率增大,可见,n(Ca)/n(P)对磷酸钙骨水泥的性能有重要影响,在制备磷酸钙骨水泥时应选择适当的n(Ca)/n(P).

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

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2001-07-31

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

  19. Enhanced healing of rabbit segmental radius defects with surface-coated calcium phosphate cement/bone morphogenetic protein-2 scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yi; Hou, Juan; Yin, ManLi [Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Wang, Jing, E-mail: biomatwj@163.com [Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Liu, ChangSheng, E-mail: csliu@sh163.net [Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); The State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 (China); Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China)

    2014-11-01

    Large osseous defects remain a difficult clinical problem in orthopedic surgery owing to the limited effective therapeutic options, and bone morphogenetic protein-2 (BMP-2) is useful for its potent osteoinductive properties in bone regeneration. Here we build a strategy to achieve prolonged duration time and help inducting new bone formation by using water-soluble polymers as a protective film. In this study, calcium phosphate cement (CPC) scaffolds were prepared as the matrix and combined with sodium carboxymethyl cellulose (CMC-Na), hydroxypropylmethyl cellulose (HPMC), and polyvinyl alcohol (PVA) respectively to protect from the digestion of rhBMP-2. After being implanted in the mouse thigh muscles, the surface-modified composite scaffolds evidently induced ectopic bone formation. In addition, we further evaluated the in vivo effects of surface-modified scaffolds in a rabbit radius critical defect by radiography, three dimensional micro-computed tomographic (μCT) imaging, synchrotron radiation-based micro-computed tomographic (SRμCT) imaging, histological analysis, and biomechanical measurement. The HPMC-modified CPC scaffold was regarded as the best combination for segmental bone regeneration in rabbit radius. - Highlights: • A simple surface-coating method was used to fabricate composite scaffolds. • Growth factor was protected from rapid depletion via superficial coating. • Significant promotion of bone regeneration was achieved. • HPMC-modification displayed optimal effect of bone regeneration.

  20. A novel injectable, cohesive and toughened Si-HPMC (silanized-hydroxypropyl methylcellulose) composite calcium phosphate cement for bone substitution.

    Science.gov (United States)

    Liu, Weizhen; Zhang, Jingtao; Rethore, Gildas; Khairoun, Khalid; Pilet, Paul; Tancret, Franck; Bouler, Jean-Michel; Weiss, Pierre

    2014-07-01

    This study reports on the incorporation of the self-setting polysaccharide derivative hydrogel (silanized-hydroxypropyl methylcellulose, Si-HPMC) into the formulation of calcium phosphate cements (CPCs) to develop a novel injectable material for bone substitution. The effects of Si-HPMC on the handling properties (injectability, cohesion and setting time) and mechanical properties (Young's modulus, fracture toughness, flexural and compressive strength) of CPCs were systematically studied. It was found that Si-HPMC could endow composite CPC pastes with an appealing rheological behavior at the early stage of setting, promoting its application in open bone cavities. Moreover, Si-HPMC gave the composite CPC good injectability and cohesion, and reduced the setting time. Si-HPMC increased the porosity of CPCs after hardening, especially the macroporosity as a result of entrapped air bubbles; however, it improved, rather than compromised, the mechanical properties of composite CPCs, which demonstrates a strong toughening and strengthening effect. In view of the above, the Si-HPMC composite CPC may be particularly promising as bone substitute material for clinic application.

  1. Use of Fluidized Bed Combustion Ash and Other Industrial Wastes as Raw Materials for the Manufacture of Calcium Sulphoaluminate Cements

    Science.gov (United States)

    Marroccoli, M.; Montagnaro, F.; Pace, M. L.; Telesca, A.; Valenti, G. L.

    Calcium sulphoaluminate cements, mainly composed by 4CaO·3Al2O3·SO3 and 2CaO·SiO2, are special hydraulic binders which require limestone, bauxite and gypsum as natural raw materials for their manufacture. In order to save bauxite and natural gypsum, it has been explored the possibility of using, among the raw mix components, FBC waste together with pulverised coal fly ash or anodization mud and, when necessary, flue gas desulphurization gypsum. Mixtures containing limestone (29-39%), FBC waste (30-44%), pulverised coal fly ash (0-13%) or anodization mud (0-32%), bauxite (0-18%) and flue gas desulphurization gypsum (0-8%) were heated for 2 hours in a laboratory electric oven at temperatures ranging from 1150° to 1300°C. The X-ray diffraction patterns on the burnt products generally showed a good conversion of the reactants and a high selectivity degree towards 4CaO·3Al2O3·SO3, particularly at 1250°C.

  2. Dimensional evaluation of patient-specific 3D printing using calcium phosphate cement for craniofacial bone reconstruction.

    Science.gov (United States)

    Bertol, Liciane Sabadin; Schabbach, Rodrigo; Dos Santos, Luís Alberto Loureiro

    2016-12-01

    The 3D printing process is highlighted nowadays as a possibility to generate individual parts with complex geometries. Moreover, the development of 3D printing hardware, software and parameters permits the manufacture of parts that can be not only used as prototypes, but are also made from materials that are suitable for implantation. In this way, this study investigates the process involved in the production of patient-specific craniofacial implants using calcium phosphate cement, and its dimensional accuracy. The implants were previously generated in a computer-aided design environment based on the patient's tomographic data. The fabrication of the implants was carried out in a commercial 3D powder printing system using alfa-tricalcium phosphate powder and an aqueous solution of Na2HPO4 as a binder. The fit of the 3D printed implants was measured by three-dimensional laser scanning and by checking the right adjustment to the patient's anatomical biomodel. The printed parts presented a good degree of fitting and accuracy.

  3. 磷硅酸钙类骨水泥的现状与研究进展%Status and research progress of calcium phosphate bone cement

    Institute of Scientific and Technical Information of China (English)

    郑江江; 包崇云

    2012-01-01

    背景:磷硅酸钙类骨水泥是一种新型的自固化、可注射性骨替代材料.大量实验证实:该材料具有良好的生物活性、生物相容性以及物理化学性质稳定等优点在临床多个领域均有很大进展.目的:综述磷硅酸钙骨水泥材料的研究现状及进展.方法:应用计算机检索CNKI、Pubmed数据库中1999-01/2011-10 关于新型骨替代材料骨水泥的文章,在标题和摘要中以"磷酸盐类、硅酸盐类、骨水泥、骨替代材料"或"phosphates;silicates;bone cement;bone substitute"为检索词进行检索.选择文章内容与磷硅酸钙类骨水泥有关者,同一领域文献则选择近期发表或发表在权威杂志的文章.初检得到85 篇文章,根据纳入标准选择关于磷硅酸钙类骨水泥的13 篇文献进行综述.结果与结论:磷硅酸盐骨水泥作为一种新型的自固化生物材料,较传统骨水泥材料理化性能、生物学性能更为优良,但仍需运用多种方法来研究并改善材料的相关性能.改性后的材料有望发展为各式新型的钙磷硅系骨水泥材料,为骨缺损的修复提供一种新的思路.%BACKGROUND: Calcium phosphate bone cement is a new kind of self-setting and injectable bone substitute material. Plenty of experiments have proved that there is a great progress in clinical areas of this material due to its good bioactivity, biocompatible and stable physical and chemical properties.OBJECTIVE: To summarize the status and research progress of calcium phosphate bone cement.METHODS: A computer-based online search of papers published from January 1999 to October 2011 related to new bone cement was performed in CNKI database, Science direct database and Pubmed database using the key words of "phosphates, silicates, bone cement, bone substitute" by screening titles and abstracts. The documents associated with calcium phosphate bone cement were selected, and those published recently or in authoritative journals were

  4. The Properties of Cement Mortars Modified by Emulsified Epoxy and Micro-fine Slag

    Institute of Scientific and Technical Information of China (English)

    CHEN You-zhi; WANG Hong-xi; MA Zhi-yong; LI Qing-hua

    2003-01-01

    The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro-fine slag.The microstructure of the epoxy resin polymer cement materials was studied and their hydration and hardening characteristics were discussed by means of modern analysis measures such as SEM,XRD and Hg-intrusion micromeritics.The experimental results indicate that the series effects of water-reducing,density,pozzolanicity,filling and solidification crosslinking through the action together with epoxy organism and micro-fine slag endowed cement-based materials with perfect performances.The main hydration products in the system are C-S-H gel and hydrated calcium aluminate.At later age,AFt can be in existence,and no Ca(OH)2 is found.When epoxy resin is solidified,the organism is in a network structure.In the micro-pore structure of hydrated cement with modified epoxy and fine slag,big harmful pores were fewer,more harmless abundant micro pores were and the possible pore radius was smaller than that of ordinary Portland cement.

  5. New high temperature cementing materials for geothermal wells: stability and properties. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; White, E.L.; Langton, C.A.; Grutzeck, M.W.

    1980-07-01

    Potential high-temperature cements have been formulated and evaluated in terms of their properties for geothermal well cementing. Phase formation and compatibility in two major compositional regions were investigated in the temperature region between 200 and 400/sup 0/C and pressures up to 69 MPa (10,000 psi). These were followed by an evaluation of properties of the cements formed. One area in the system Ca0-Mg0-Si0/sub 2/-H/sub 2/0 centered around the xonotlite-chrysotile join while the other area of interest centered around the anorthite composition in the system Ca0-Al/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O. After numerous exploratory studies, the magnesia-containing mixtures were prepared by mixing a Class J cement with various sources of magnesia such as calcined chrysotile, or magnesium oxide. Calcium oxide and silica fine quartz powder were also added to adjust the compositions. The aluminous system cements were formulated from high-alumina cements which were mixed with various silica sources.

  6. A review of binders used in cemented paste tailings for underground and surface disposal practices.

    Science.gov (United States)

    Tariq, Amjad; Yanful, Ernest K

    2013-12-15

    Increased public awareness of environmental issues coupled with increasingly stringent environmental regulations pertaining to the disposal of sulphidic mine waste necessitates the mining industry to adopt more competent and efficient approaches to manage acid rock drainage. Cemented paste tailings (CPT) is an innovative form of amalgamated material currently available to the mining industry in developed countries. It is made usually from mill tailings mingled with a small amount of binder (customarily Portland cement) and water. The high cost associated with production and haulage of ordinary Portland cement and its alleged average performance as a sole binder in the long term (due to vulnerability to internal sulphate attack) have prompted users to appraise less expensive and technically efficient substitutes for mine tailings paste formulations. Generally, these binders include but are not limited to sulphate resistant cements, and/or as a partial replacement for Portland cement by artificial pozzolans, natural pozzolans, calcium sulphate substances and sodium silicates. The approach to designing environmentally efficient CPT is to ensure long-term stability and effective control over environmental contaminants through the use of composite binder systems with enhanced engineering properties to cater for inherit deficiencies in the individual constituents. The alkaline pore solution created by high free calcium rich cement kiln dust (CKD) (byproduct of cement manufacturing) is capable of disintegrating the solid glassy network of artificial pozzolans to produce reactive silicate and aluminate species when attacked by (OH(-)) ions. The augmented pozzolanic reactivity of CKD-slag and CKD-fly ash systems may produce resilient CPT. Since cemented paste comprising mine tailings and binders is a relatively new technology, a review of the binding materials used in such formulations and their performance evaluation in mechanical fill behaviour was considered pertinent in

  7. Human tooth germ stem cell response to calcium-silicate based endodontic cements

    Directory of Open Access Journals (Sweden)

    Esra Pamukcu Guven

    2013-07-01

    Full Text Available OBJECTIVE: The aim of this study was to compare the cytotoxic effects of endodontic cements on human tooth germ stem cells (hTGSCs. MTA Fillapex, a mineral trioxide aggregate (MTA-based, salicylate resin containing root canal sealer, was compared with iRoot SP, a bioceramic sealer, and AH Plus Jet, an epoxy resin-based root canal sealer. MATERIAL AND METHODS: To evaluate cytotoxicity, all materials were packed into Teflon rings (4 mmµ3 mm and co-cultured with hTGSCs with the aid of 24-well Transwell permeable supports, which had a pore size of 0.4 µm. Coverslips were coated with MTA Fillapex, iRoot SP and AH Plus Jet and each coverslip was placed onto the bottom of one well of a six-well plate for scanning electron microscopy (SEM analysis. Before the cytotoxicity and SEM analysis, all samples were stored at 37ºC and at 95% humidity and 5% CO2 for 24 hours to set. The cellular viability was analyzed using MTS test (3-(4,5-dimethyl-thiazol-2-yl-5-(3-carboxy-methoxy-phenyl-2-(4-sulfo-phenyl-2H-tetrazolium. The cytotoxic effects and SEM visualization of the tested materials were analyzed at 24-hour, 72-hour, one-week and two-week periods. RESULTS: On the 1st day, only MTA Fillapex caused cytotoxicity compared to negative control (NC group (p0.05. After 14 days of incubation with the test materials, MTA Fillapex exhibited significantly higher cytotoxicity compared with iRoot SP, AH Plus Jet and the NC group (P<0.008. In the SEM analysis, the highest levels of cell attachment were observed for iRoot SP and the control group. After 24 hours, MTA Fillapex reduced the number of cells attached to the surface. CONCLUSIONS: Within the limitations of this study, sealers exerted different cytotoxic effects on hTGSCs. Although all materials have exerted cellular toxicity, iRoot SP and AH Plus Jet may promote better attachment to hTGSCs.

  8. Casein Phosphopeptide-Amorphous Calcium Phosphate Reduces Streptococcus mutans Biofilm Development on Glass Ionomer Cement and Disrupts Established Biofilms

    Science.gov (United States)

    Liu, Sze-Wei; Myroforidis, Helen; Zalizniak, Ilya; Palamara, Joseph E. A.; Huq, N. Laila; Reynolds, Eric C.

    2016-01-01

    Glass ionomer cements (GIC) are dental restorative materials that are suitable for modification to help prevent dental plaque (biofilm) formation. The aim of this study was to determine the effects of incorporating casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into a GIC on the colonisation and establishment of Streptococcus mutans biofilms and the effects of aqueous CPP-ACP on established S mutans biofilms. S. mutans biofilms were either established in flow cells before a single ten min exposure to 1% w/v CPP-ACP treatment or cultured in static wells or flow cells with either GIC or GIC containing 3% w/w CPP-ACP as the substratum. The biofilms were then visualised using confocal laser scanning microscopy after BacLight LIVE/DEAD staining. A significant decrease in biovolume and average thickness of S. mutans biofilms was observed in both static and flow cell assays when 3% CPP-ACP was incorporated into the GIC substratum. A single ten min treatment with aqueous 1% CPP-ACP resulted in a 58% decrease in biofilm biomass and thickness of established S. mutans biofilms grown in a flow cell. The treatment also significantly altered the structure of these biofilms compared with controls. The incorporation of 3% CPP-ACP into GIC significantly reduced S. mutans biofilm development indicating another potential anticariogenic mechanism of this material. Additionally aqueous CPP-ACP disrupted established S. mutans biofilms. The use of CPP-ACP containing GIC combined with regular CPP-ACP treatment may lower S. mutans challenge. PMID:27589264

  9. Reinforcing effect of calcium sulfate cement bovine bone morphogenetic protein on vertebral in the rabbit model of osteoporosis

    Institute of Scientific and Technical Information of China (English)

    Jie Zhang; Yu-Ming Chen; Chen Sheng-Guo; Kaken Habaerxi; Shawuti Alimujiang; Yu Chen; Ming-Zhen Peng; Rong Yue; Yu-Lian Wu; De-Quan Wang

    2014-01-01

    Objective:To observe reinforcing effect of calcium sulfate cement(CSC) bovine bone morphogenetic protein(bBMP) on vertebral in the rabbit model of osteoporosis.Methods:A total of48NewZealand white rabbits were randomly divided into groupⅠ(blank control group), group Ⅱ(CSC injection group), group Ⅲ(CSC/bBMP injection group) and control group.White rabbit osteoporosis model was established rapidly by using castration method+methylprednisolone candidate.After modeling, groups Ⅱ, Ⅲ were given corresponding vertebral body injection material, and4 animals were sacrificed respectively at24 h,6 weeks,12 weeks after vertebral plasty.Tissue pathological status, vertebral mineral density and vertebral body bone mechanical strength were observed.Results:Vertebral body structure form was normal in the groups Ⅱand Ⅲ.Trabecular bone coarsens, connection and repair were observed in micro fracture and bone defects, bone trabecular connectivity was superior to group Ⅰ significantly; vertebral body compression strength in the groupⅠ was on the decline, vertebral compression strength in the groups Ⅱand Ⅲ was on the rise, the largest vertebra.PostoperativeBMC andBMD in groups Ⅱand Ⅲ were incresed, andsignificantly higher than group Ⅰ after6 weeks(P<0.05),BMC and BMD in group Ⅲ after12 weeks were higher than the other three groups.Conclusion:Compound bBMPCSC has good bone induction.It can improve the three-dimensional construction effect for osteoporosis vertebral trabecula, and can significantly improve the vertebral strength, as a vertebral packing material with good application prospect.

  10. Casein Phosphopeptide-Amorphous Calcium Phosphate Reduces Streptococcus mutans Biofilm Development on Glass Ionomer Cement and Disrupts Established Biofilms.

    Science.gov (United States)

    Dashper, Stuart G; Catmull, Deanne V; Liu, Sze-Wei; Myroforidis, Helen; Zalizniak, Ilya; Palamara, Joseph E A; Huq, N Laila; Reynolds, Eric C

    2016-01-01

    Glass ionomer cements (GIC) are dental restorative materials that are suitable for modification to help prevent dental plaque (biofilm) formation. The aim of this study was to determine the effects of incorporating casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into a GIC on the colonisation and establishment of Streptococcus mutans biofilms and the effects of aqueous CPP-ACP on established S mutans biofilms. S. mutans biofilms were either established in flow cells before a single ten min exposure to 1% w/v CPP-ACP treatment or cultured in static wells or flow cells with either GIC or GIC containing 3% w/w CPP-ACP as the substratum. The biofilms were then visualised using confocal laser scanning microscopy after BacLight LIVE/DEAD staining. A significant decrease in biovolume and average thickness of S. mutans biofilms was observed in both static and flow cell assays when 3% CPP-ACP was incorporated into the GIC substratum. A single ten min treatment with aqueous 1% CPP-ACP resulted in a 58% decrease in biofilm biomass and thickness of established S. mutans biofilms grown in a flow cell. The treatment also significantly altered the structure of these biofilms compared with controls. The incorporation of 3% CPP-ACP into GIC significantly reduced S. mutans biofilm development indicating another potential anticariogenic mechanism of this material. Additionally aqueous CPP-ACP disrupted established S. mutans biofilms. The use of CPP-ACP containing GIC combined with regular CPP-ACP treatment may lower S. mutans challenge.

  11. Efficiency of a blast furnace slag cement for immobilizing simulated borate radioactive liquid waste.

    Science.gov (United States)

    Guerrero, A; Goñi, S

    2002-01-01

    The efficiency of a blast furnace slag cement (Spanish CEM III/B) for immobilizing simulated radioactive borate liquid waste [containing H3BO3, NaCl, Na2SO4 and Na(OH)] has been evaluated by means of a leaching attack in de-mineralized water at the temperature of 40 degrees C over 180 days. The leaching was carried out according to the ANSI/ANS-16.1-1986 test. Moreover, changes of the matrix microstructure were characterized through porosity and pore-size distribution analysis carried out by mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and thermal analysis (TG). The results were compared with those obtained from a calcium aluminate cement matrix, previously published.

  12. Gene Expression Responses to Mechanical Stimulation of Mesenchymal Stem Cells Seeded on Calcium Phosphate Cement

    Science.gov (United States)

    Gharibi, Borzo; Cama, Giuseppe; Capurro, Marco; Thompson, Ian; Deb, Sanjukta; Di Silvio, Lucy

    2013-01-01

    Introduction The aim of the study reported here was to investigate the molecular responses of human mesenchymal stem cells (MSC) to loading with a model that attempts to closely mimic the physiological mechanical loading of bone, using monetite calcium phosphate (CaP) scaffolds to mimic the biomechanical properties of bone and a bioreactor to induce appropriate load and strain. Methods Human MSCs were seeded onto CaP scaffolds and subjected to a pulsating compressive force of 5.5±4.5 N at a frequency of 0.1 Hz. Early molecular responses to mechanical loading were assessed by microarray and quantitative reverse transcription-polymerase chain reaction and activation of signal transduction cascades was evaluated by western blotting analysis. Results The maximum mechanical strain on cell/scaffolds was calculated at around 0.4%. After 2 h of loading, a total of 100 genes were differentially expressed. The largest cluster of genes activated with 2 h stimulation was the regulator of transcription, and it included FOSB. There were also changes in genes involved in cell cycle and regulation of protein kinase cascades. When cells were rested for 6 h after mechanical stimulation, gene expression returned to normal. Further resting for a total of 22 h induced upregulation of 63 totally distinct genes that were mainly involved in cell surface receptor signal transduction and regulation of metabolic and cell division processes. In addition, the osteogenic transcription factor RUNX-2 was upregulated. Twenty-four hours of persistent loading also markedly induced osterix expression. Mechanical loading resulted in upregulation of Erk1/2 phosphorylation and the gene expression study identified a number of possible genes (SPRY2, RIPK1, SPRED2, SERTAD1, TRIB1, and RAPGEF2) that may regulate this process. Conclusion The results suggest that mechanical loading activates a small number of immediate-early response genes that are mainly associated with transcriptional

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-02-01

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

  14. Thermoluminescence and sintering of ultra-pure {alpha} alumina doped with zirconium, thorium, calcium or cerium; Thermoluminescence et frittage de l'alumine {alpha} ultra-pure dopee par le zirconium, le thorium, le calcium, ou le cerium

    Energy Technology Data Exchange (ETDEWEB)

    Ferey, F

    2002-01-01

    Thermoluminescence is a technique of identification of the point defects that appear in a solid consecutively to its fabrication. The synthesis parameters of {alpha}-alumina that will be taken into account here are the atmosphere during thermal treatment (oxidising or reducing), and the effect of the dopants: zirconium, thorium, calcium or cerium. The aim of this work is to correlate the point defects to the reactivity of the powder, especially its sintering. The TL mechanisms of the dosimetric peak of {alpha}-alumina, around 200 deg C, were clarified: the trap is an aggregate of 2 point defects (V{sub al}-V{sub O}), and the recombination centre is Cr{sup 3+}. The sensibilizing effect observed for thorium, or for cerium under reducing atmosphere, is attributed to the presence of a large emission band in the blue-green domain. Chromium is the main impurity at the origin of the E' peak (360 deg C) of {alpha}-alumina. It is acting as trap and also as recombination centre. A mechanism of transfer of energy between Cr{sup 3+} and Ti{sup 4+} is also presented in order to explain the increase of the TL intensity of the E' peak when doping by a tetravalent cation. In the case of doping by calcium, TL allows the revelation of the phase CaAl{sub 12}O{sub 19}. A quenching was observed for {alpha}Al{sub 2}O{sub 3}:Ca and {alpha}Al{sub 2}O{sub 3}:Ce under reducing atmosphere. It is attributed to oxygen vacancies for the doping by calcium, and to the presence of Ce{sup 3+} for the doping by cerium. The alumina prepared under reducing conditions exhibit a perturbation of kinetics during sintering, and also abnormal grain growth in doped samples. This unusual kinetic is explained by a decrease in the concentration of aluminium vacancies under reducing atmosphere, conducting indirectly to a greater segregation of Si{sup 4+} at the grain boundaries, and to the formation of a liquid phase at the surface of grains. This phenomenon is amplified in the case of doping by

  15. Pozzolanic Activity of Burned Coal Gangue and Its Effects on Structure of Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    ZHANG Changsen

    2006-01-01

    The pozzolanic activity of coal gangue burned at different burning temperatures was investigated. The burned coal gangue was mixed with portland cement in different proportions ( 20%-60% ). The pozzolanic activity of coal gangue burned and the hydration products were examined, the compressive strengths of the pastes of the mixtures were tested, and the mechanism of the reaction was discussed. The experimental results show that the coal gangue burned at 750 ℃ has the optimum pozzolanic activity, and the burned coal gangue with SiO2 and Al2O3 is in an active form. When the coal gangue burned at 750 ℃ is mixed into portland cement, the content of calcium hydroxide in paste is significantly reduced, while the contents of hydrated calcium silicate and hydrated calcium aluminate are increased accordingly, hence resulting in the improvement of the microstructure of mortar. The compressive strength of cement paste decreases with increasing the content of burned coal gangue. The decease in strength is small in the range of 20%- 30% coal gangue substitution and significant in 30%- 60% substitution.

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

    Energy Technology Data Exchange (ETDEWEB)

    Harbour, J; Tommy Edwards, T; Erich Hansen, E; Vickie Williams, V

    2007-10-12

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

  17. Effects of Tin Oxide on Preparation and Properties of Calcium Aluminate/Magnesium-Aluminum Spinel Composites%氧化锡对铝酸钙/镁铝尖晶石复相材料制备和性能的影响

    Institute of Scientific and Technical Information of China (English)

    商恒; 员文杰; 朱青友; 邓承继; 祝洪喜

    2016-01-01

    With the advantages of their components such as high melting point, low thermal conductivity and good corrosion resistance, calcium aluminate/magnesium-aluminum spinel composites have a very wide application prospect in high temperature industries. Calcium aluminate/magnesium-aluminum spinel composites were prepared at 1300-1600 °C by using light-burned dolomite, alumina and tin oxide as raw materials. Effects of tin oxide on the phase composition, microstructure and properties of calcium aluminate/magnesium-aluminum spinel composites were investigated by X-ray diffraction and scanning electron microscopy. The results showed that the mass loss and shrinkage of sintered samples varied due to the sublimation of tin oxide and the decomposition of light-burned dolomite. Tin oxide not only enhanced the formation of calcium hexaluminate and magnesium-aluminum spinel but also made monocalcium aluminate and CaSnO3 involved in composites as a result of the effect of SnO2 on the reaction process. Moreover, the morphology of the phases was changed because of the solution of SnO2 in calcium hexaluminate and magnesium-aluminum spinel. With the increase of SnO2 addition, the apparent porosity of composites ifrstly increased and then decreased. When the SnO2 content was 35%, the composites sintered at 1600℃achieved the highest compressive strength of 240 MPa.%结合组分高熔点、低热导率和抗侵蚀等优点,铝酸钙/镁铝尖晶石复相材料在高温工业中具有十分广泛的应用前景。以轻烧白云石、氧化铝和氧化锡为原料,在1300-1600℃烧结合成铝酸钙/镁铝尖晶石复相材料。利用X射线衍射和扫描电子显微镜等测试方法,研究添加氧化锡对铝酸钙/镁铝尖晶石复相材料的物相组成、显微结构和性能的影响。结果表明:因氧化锡的分解,反应烧结过程中试样的失重和收缩率均有明显相应变化。氧化锡不仅促进六铝酸钙和镁铝尖晶石的形成,同时

  18. Acceleration of bone regeneration by activating Wnt/β-catenin signalling pathway via lithium released from lithium chloride/calcium phosphate cement in osteoporosis

    Science.gov (United States)

    Li, Li; Peng, Xiaozhong; Qin, Yongbao; Wang, Renchong; Tang, Jingli; Cui, Xu; Wang, Ting; Liu, Wenlong; Pan, Haobo; Li, Bing

    2017-03-01

    By virtue of its excellent bioactivity and osteoconductivity, calcium phosphate cement (CPC) has been applied extensively in bone engineering. Doping a trace element into CPC can change physical characteristics and enhance osteogenesis. The trace element lithium has been demonstrated to stimulate the proliferation and differentiation of osteoblasts. We investigated the fracture-healing effect of osteoporotic defects with lithium-doped calcium phosphate cement (Li/CPC) and the underlying mechanism. Li/CPC bodies immersed in simulated body fluid converted gradually to hydroxyapatite. Li/CPC extracts stimulated the proliferation and differentiation of osteoblasts upon release of lithium ions (Li+) at 25.35 ± 0.12 to 50.74 ± 0.13 mg/l through activation of the Wnt/β-catenin pathway in vitro. We also examined the effect of locally administered Li+ on defects in rat tibia between CPC and Li/CPC in vivo. Micro-computed tomography and histological staining showed that Li/CPC had better osteogenesis by increasing bone mass and promoting repair in defects compared with CPC (P < 0.05). Li/CPC also showed better osteoconductivity and osseointegration. These findings suggest that local release of Li+ from Li/CPC may accelerate bone regeneration from injury through activation of the Wnt/β-catenin pathway in osteoporosis.

  19. Acceleration of bone regeneration by activating Wnt/β-catenin signalling pathway via lithium released from lithium chloride/calcium phosphate cement in osteoporosis

    Science.gov (United States)

    Li, Li; Peng, Xiaozhong; Qin, Yongbao; Wang, Renchong; Tang, Jingli; Cui, Xu; Wang, Ting; Liu, Wenlong; Pan, Haobo; Li, Bing

    2017-01-01

    By virtue of its excellent bioactivity and osteoconductivity, calcium phosphate cement (CPC) has been applied extensively in bone engineering. Doping a trace element into CPC can change physical characteristics and enhance osteogenesis. The trace element lithium has been demonstrated to stimulate the proliferation and differentiation of osteoblasts. We investigated the fracture-healing effect of osteoporotic defects with lithium-doped calcium phosphate cement (Li/CPC) and the underlying mechanism. Li/CPC bodies immersed in simulated body fluid converted gradually to hydroxyapatite. Li/CPC extracts stimulated the proliferation and differentiation of osteoblasts upon release of lithium ions (Li+) at 25.35 ± 0.12 to 50.74 ± 0.13 mg/l through activation of the Wnt/β-catenin pathway in vitro. We also examined the effect of locally administered Li+ on defects in rat tibia between CPC and Li/CPC in vivo. Micro-computed tomography and histological staining showed that Li/CPC had better osteogenesis by increasing bone mass and promoting repair in defects compared with CPC (P < 0.05). Li/CPC also showed better osteoconductivity and osseointegration. These findings suggest that local release of Li+ from Li/CPC may accelerate bone regeneration from injury through activation of the Wnt/β-catenin pathway in osteoporosis. PMID:28338064

  20. Microstructural and compositional change of NaOH-activated high calcium fly ash by incorporating Na-aluminate and co-existence of geopolymeric gel and C–S–H(I)

    KAUST Repository

    Oh, Jae Eun

    2012-05-01

    This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10 M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C-S-H with geopolymeric gels and strongly suggests that the C-S-H formed in the current system is C-S-H(I). The back-scattered electron images suggest that the C-S-H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel. © 2012 Elsevier Ltd.

  1. 碳纤维增强磷酸钙骨水泥%The calcium phosphate bone cement reinforced by carbon fiber

    Institute of Scientific and Technical Information of China (English)

    张睿; 张彭风; 薛润苗; 王志强

    2012-01-01

    以碳纤维为增强相,Na2HPO4/柠檬酸为调和液,α-磷酸三钙、磷酸四钙、磷酸二氢钙、羟基磷灰石和碳酸钙为原料制备骨水泥,研究不同掺杂比例的短碳纤维对其性能的影响.在磷酸钙骨水泥中掺杂碳纤维能够提高样品的致密性,缩短固化时间,提高抗压强度.当掺杂质量分数0.5%的碳纤维时,骨水泥的初凝、终凝时间分别为9.3和24.9 min,模拟体液中浸泡28 d后抗压强度最大为38.24MPa.掺杂的碳纤维对浸泡液pH影响不大,pH在小范围内浮动,均在人体安全范围内.%The effect of carbon fiber on the performance of calcium phosphate bone cement was studied. Calcium phosphate bone cement doped with carbon fiber was prepared from crtricalcium phosphate, tetracalcium phosphate, monocalcium phosphate monohydrate, hydroxyapatite and calcium carbonate, in which Na2 HPO4/citric acid was added as mixing liquid. The results show that carbon fiber doped in calcium phosphate cement can increase the density, reduce the setting time and enhance the compressive strength. When the doping amount of carbon fiber is 0.5%, the initial setting time and the final setting time is respectively 9. 3 and 24. 9 min. The compressive strength reaches up to 38. 24 MPa after immersed 28 d in the simulated body fluid. Meanwhile, the doping of carbon fiber has little influence on the change of pH, which is in the range of human security.

  2. 硫铝酸盐水泥混凝土抗高浓度硫酸镁侵蚀性能研究%Study on the Resistance to High Concentration of Magnesium Sulfate Attack on Sulfate Aluminate Cement Concrete

    Institute of Scientific and Technical Information of China (English)

    刘向楠; 唐新军; 苏建彪; 张涛; 张傲齐

    2015-01-01

    In some part of the drought and salinity region in the south of Xinjiang ,concrete buildings are confronted with double erosion problems of sulphate and magnesium salt in high concentrations .In this study ,the influence of water/ce-ment ratio ,erosion of solution concentration and erosion time on the erosion resistance of sulfate aluminium cement con-crete were studied with“the concrete resistance to sulfate erosion experiment method”(method K ) .What’s more ,both of the macroscopic and microscopic observation methods such as scanning electron microscope (SEM ) and energy spectrum analysis (EDS ) were used to analyze and reveal the mechanism of sulfate attack resistance .It is found that lowering the water/cement ratio can effectively increase the erosion resistance of sulphate aluminium cement in magnesium sulfate ero-sion environment;the double erosion damage of erosion solution to sulphate aluminium cement mortar specimens has obvi-ous correlation with the concentration of sulfate ions;gypsum which generates in large numbers is the main reason of the surface erosion on the surface of the mortar specimens .%新疆南疆部分干旱多盐碱地区混凝土建筑物面临高浓度硫酸盐、镁盐双重侵蚀破坏问题。通过水泥抗硫酸盐侵蚀试验方法(K法)研究了水灰比、侵蚀溶液浓度、侵蚀龄期等对硫铝酸盐水泥混凝土抗硫酸盐侵蚀能力的影响,并采用宏观观测和扫描电镜(SEM )、能谱(EDS )等微观观测方法,分析和揭示其抗硫酸盐侵蚀机理。结果表明,降低水胶比能有效提高硫铝酸盐水泥胶砂试件抗高浓度硫酸盐、镁盐侵蚀性能;在镁离子浓度一定时,侵蚀溶液对硫铝酸盐水泥胶砂试件的双重侵蚀破坏作用与硫酸根离子浓度具有明显的相关性;石膏的大量生成是造成胶砂试件表面剥蚀破坏的主要原因。

  3. A bioactive dental luting cement--its retentive properties and 3-year clinical findings.

    Science.gov (United States)

    Jefferies, Steven R; Pameijer, Cornelis H; Appleby, David C; Boston, Daniel; Lööf, Jesper

    2013-02-01

    A clinical validation study was conducted to determine the performance of a new bioactive dental cement (Ceramir C&B, Doxa Dental AB) for permanent cementation. The cement is a new formulation class, which is a hybrid material comprised of calcium aluminate and glass-ionomer components. A total of 38 crowns and bridges were cemented in 17 patients; 31 of the abutment teeth were vital and seven were non-vital. Six restorations were bridges with a total of 14 abutment teeth (12 vital/ two non-vital). One fixed splint comprising two abutment teeth was also included. Preparation parameters were recorded, as well as cement characteristics such as working time, setting time, seating characteristics, and ease of cement removal. Baseline data were recorded for the handling of the cement, gingival inflammation, and pre-cementation sensitivity. Post-cementation parameters included post-cementation sensitivity, gingival tissue reaction, marginal integrity, and discoloration. All patients were seen for recall examinations at 30 days and 6 months. Fifteen of 17 subjects and 13 of 17 patients were also available for subsequent comprehensive 1- and 2-year recall examination, and 13 patients were available for a 3-year recall examination. Restorations available for the 3-year recall examination included 14 single-unit full-coverage crown restorations, four three-unit bridges comprising eight abutments, and one two-unit splint. Three-year recall data yielded no loss of retention, no secondary caries, no marginal discolorations, and no subjective sensitivity. All restorations rated excellent for marginal integrity. Average visual analogue scale (VAS) score for tooth sensitivity decreased from 7.63 mm at baseline to 0.44 mm at 6-month recall, 0.20 mm at 1-year recall, and 0.00 mm at 2- and 3-year recall. Average gingival index (GI) score for gingival inflammation decreased from 0.56 at baseline to 0.11 at 6-month recall, 0.16 at 1-year recall, 0.21 at 2-year recall, and 0.07 at 3

  4. Micro-observations of different types of nano-Al₂O₃on the hydration of cement paste with sludge ash replacement.

    Science.gov (United States)

    Luo, Huan-Lin; Lin, Deng-Fong; Shieh, Show-Ing; You, Yan-Fei

    2015-01-01

    In recent years, sewer systems and wastewater treatment plants have become important in developing countries. Consequently, the amount of sewage sludge produced by these countries has been gradually increasing, and determining how to properly recycle this sludge is becoming an important topic for researchers. In this study, to expand the recyclability of sewage sludge ash (SSA) in engineering applications, two types of nano-aluminium oxides (Al₂O₃), MC2A and MC2R, were added to SSA/cement paste and mortar specimens. The MC2R type (γ phase) had a smaller particle size and larger specific surface area than the MC2A type (α phase). The results indicate that the addition of nano-Al₂O₃to SSA/cement paste can effectively improve the hydration products of the paste. Moreover, the amount of hydration products increased as the amount of nano-Al₂O₃added to the SSA/cement paste increased. The test results indicate that MC2A nano-Al₂O₃can more uniformly distribute in the paste body and improve the hydration of cement than MC2R nano-Al₂O₃. Thus, more calcium-silicate-hydrate (C-S-H) gel and calcium aluminate hydrate (C-A-H) salts were produced, and the strength of the specimens was improved. This study suggests that MC2A nano-Al₂O₃is preferable to MC2R nano- Al₂O₃for SSA/cement specimen applications.

  5. Polyelectrolyte addition effect on the properties of setting hydraulic cements based on calcium phosphate; Efeito da adicao de polieletrolitos sobre as propriedades de cimentos de fosfato de calcio de pega hidraulica

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Luis A. dos; Oliveira, Luci C. de; Rigo, Eliana C.S.; Boschi, Anselmo Ortega [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais; Carrodeguas, Raul Gracia [Universidad de La Habana, Habana, (Cuba). Centro de Biomateriales

    1997-12-31

    In the present work the effects of the addition of some poly electrolytes (sodium alginate and poly acrylic acid) on the solubility, crystalline phases, pH and mechanical strength under compression of three calcium phosphate cements were studied. (author) 10 refs., 2 figs., 4 tabs.

  6. Maxillary sinus floor elevation using a tissue-engineered bone with calcium-magnesium phosphate cement and bone marrow stromal cells in rabbits.

    Science.gov (United States)

    Zeng, Deliang; Xia, Lunguo; Zhang, Wenjie; Huang, Hui; Wei, Bin; Huang, Qingfeng; Wei, Jie; Liu, Changsheng; Jiang, Xinquan

    2012-04-01

    The objective of this study was to assess the effects of maxillary sinus floor elevation with a tissue-engineered bone constructed with bone marrow stromal cells (bMSCs) and calcium-magnesium phosphate cement (CMPC) material. The calcium (Ca), magnesium (Mg), and phosphorus (P) ions released from calcium phosphate cement (CPC), magnesium phosphate cement (MPC), and CMPC were detected by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the proliferation and osteogenic differentiation of bMSCs seeded on CPC, MPC, and CMPC or cultured in CPC, MPC, and CMPC extracts were measured by MTT analysis, alkaline phosphatase (ALP) activity assay, alizarin red mineralization assay, and real-time PCR analysis of the osteogenic genes ALP and osteocalcin (OCN). Finally, bMSCs were combined with CPC, MPC, and CMPC and used for maxillary sinus floor elevation in rabbits, while CPC, MPC, or CMPC without cells served as control groups. The new bone formation in each group was detected by histological finding and fluorochrome labeling at weeks 2 and 8 after surgical operation. It was observed that the Ca ion concentrations of the CMPC and CPC scaffolds was significantly higher than that of the MPC scaffold, while the Mg ions concentration of CMPC and MPC was significantly higher than that of CPC. The bMSCs seeded on CMPC and MPC or cultured in their extracts proliferated more quickly than the cells seeded on CPC or cultured in its extract, respectively. The osteogenic differentiation of bMSCs seeded on CMPC and CPC or cultured in the corresponding extracts was significantly enhanced compared to that of bMSCs seeded on MPC or cultured in its extract; however, there was no significant difference between CMPC and CPC. As for maxillary sinus floor elevation in vivo, CMPC could promote more new bone formation and mineralization compared to CPC and MPC, while the addition of bMSCs could further enhance its new bone formation ability significantly. Our data suggest that

  7. Dehydration kinetics of Portland cement paste at high temperature

    NARCIS (Netherlands)

    Zhang, Q.; Ye, G.

    2012-01-01

    Portland cement paste is a multiphase compound mainly consisting of calcium-silicate-hydrate (CSH) gel, calcium hydroxide (CH) crystal, and unhydrated cement core. When cement paste is exposed to high temperature, the dehydration of cement paste leads to not only the decline in strength, but also th

  8. Dealkalization of calcium silicate slag and study of using it as cement admixture%硅钙渣脱碱处理及作水泥混合材的研究

    Institute of Scientific and Technical Information of China (English)

    刘江; 张建波; 孙俊民; 王宏霞; 叶家元; 史迪

    2012-01-01

    Orthogonal experiment method is applied to research on dealkalization of calcium silicate slag, and properties of non-dealkalizated and dealkalizated calcium slag cement have been analyzed. Effects of temperature, holding time, content of lime milk and washing times were discussed, the results show that the optimum dealkalization combination of the four factors is as follows:content of lime milk is 10%,temperature 85 X. and holding time 3 hours,washing twice,then an alkali content of 0.83% will be acquired; compressive strength of non梔ealkalizated calcium slag cement is higher than dealkalizated calcium slag cement during the early hydration, the advantages of dealkalizated calcium slag cement will gradually appear as time goes and will be more significantly as calcium slag content increase; Microscopic analysis shows that non-dealkalizated calcium slag cement generates large amount of C-S-H gel during early hydration and its hydration products are more compact than dealkalizated calcium slag cement, little difference of the compactness has been found between them when the hydration time is 28 days.%采用正交试验法对硅钙渣进行脱碱处理,对脱碱前后的硅钙渣水泥性能进行了研究.通过调整温度、保温时间、石灰乳掺量和水洗次数,得出最佳脱碱组合为:石灰乳掺量10%,温度85℃,保温时间3h,水洗2次,处理后碱含量为0.83%:强度试验结果表明,水化早期未脱碱硅钙渣水泥抗压强度要高于脱碱硅钙渣水泥,但随着龄期逐渐增长,脱碱硅钙渣水泥优势逐渐显现,掺量越大优势越明显;微观形貌分析表明,未脱碱硅钙渣水泥水化早期生成大量C-S-H凝胶,水化产物较脱碱硅钙渣水泥更致密,水化28d时两者水化产物的致密性相当.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-01

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

  10. Regulation of physicochemical properties, osteogenesis activity, and fibroblast growth factor-2 release ability of β-tricalcium phosphate for bone cement by calcium silicate

    Energy Technology Data Exchange (ETDEWEB)

    Su, Ching-Chuan [Antai Medical Care Cooperation Antai Tian-Sheng Memorial Hospital, Pingtung, Taiwan (China); Kao, Chia-Tze; Hung, Chi-Jr [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Chen, Yi-Jyun [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Dental Department, Taichung Hospital, Ministry of Health and Welfare, Taichung City, Taiwan (China); Huang, Tsui-Hsien, E-mail: thh@csmu.edu.tw [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [Institute of Oral Science, Chung Shan Medical University, Taichung, Taiwan (China)

    2014-04-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material. For this research we have combined it with a low degradation calcium silicate (CS) to enhance its bioactive and osteostimulative properties. To check its effectiveness, a series of β-TCP/CS composites with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of bone-like apatite, the diametral tensile strength, and weight loss of composites were considered before and after immersion in simulated body fluid (SBF). In addition, we also examined the effects of fibroblast growth factor-2 (FGF-2) released from β-TCP/CS composites and in vitro human dental pulp cell (hDPC) and studied its behavior. The results showed that the apatite deposition ability of the β-TCP/CS composites was enhanced as the CS content was increased. For composites with more than 50% CS contents, the samples were completely covered by a dense bone-like apatite layer. At the end of the immersion point, weight losses of 19%, 24%, 33%, 42%, and 51% were observed for the composites containing 0%, 30%, 50%, 70% and 100% β-TCP cements, respectively. In vitro cell experiments show that the CS-rich composites promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the CS quantity in the composite is less than 70%, the amount of cells and osteogenesis protein of hDPCs was stimulated by FGF-2 released from β-TCP/CS composites. The combination of FGF-2 in degradation of β-TCP and osteogenesis of CS gives a strong reason to believe that these calcium-based composite cements may prove to be promising bone repair materials. - Highlights: • CS improved physicochemical properties and osteogenic activity of β-TCP. • The higher the CS in the cement, the shorter the setting time and the higher the DTS. • The cell behavior was stimulated by FGF-2 released from composite containing 50% CS. • β-TCP/CS composite with FGF-2 has optimal properties for

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

    DEFF Research Database (Denmark)

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

    1998-01-01

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

  12. Differentiation inducement of calcium phosphate / calcium silicate / bismutite cement to dental pulp cells in vitro%新型复合盖髓材料对人牙髓细胞分化的体外诱导效果

    Institute of Scientific and Technical Information of China (English)

    沈晴昳; 陈芳萍; 刘昌胜; 孙皎

    2013-01-01

    Objective The aim of this study was to investigate the effects of new calcium phosphate/calcium silicate/bismutite (CPCSBi) cement on differentiation of human dental pulp cells.Methods Dissoluble dentin matrix components (DDMCs) were extracted from powdered sound,human dentine samples by either CPCSBi saturated solution,Ca(OH)2 saturated solution,or 10% EDTA,over a 14-day period.The effects of DDMCs extracts on dentin sialophosphoprotein (DSPP),osteocalcin (OCN) and TGF-β 1 gene expression in the dental pulp cells were analysed using semi-quantitative RT-PCR following 24 h of exposure.Results All the DDMCs extracts induced DSPP,OCN and TGF-β 1 gene expression in dental pulp cells.While the DDMCs extracted from dentin powder by CPCSBi demonstrated highest inducing effect on expression of DSPP and OCN in human pulp cells.Conclusion These results suggest that CPCSBi plays an important role in the differentiation of dental pulp cells to odontoblast like cells.%目的 研究新型盖髓材料磷酸钙/硅酸钙/泡铋矿复合水门汀(Calcium phosphate-calcium silicate-bismuth compound cement,CPCSBi)诱导牙髓细胞分化的作用.方法 分别采用CPCSBi、氢氧化钙(CH)饱和溶液和10%EDTA溶液,从人牙本质粉末中提取可溶性牙本质基质(DDMCs),通过半定量RT-PCR方法,分析不同材料所提取DDMCs对人牙髓细胞的涎磷蛋白(DSPP)、骨钙素(OCN)、转化生长因子-β1(TGF-β1)基因表达的影响.结果 不同材料提取的DDMCs都能提高体外培养人牙髓细胞DSPP、OCN和TGF-β1基因的表达,其中以CPCSBi溶液提取DDMCs的促进作用最明显.结论 CPCSBi对牙髓细胞分化具有促进作用.

  13. Preparation and Construction of New Phosphorus Magnesium Aluminate Cement Road Repair Agent%新型水泥混凝土道路修补剂的制备与施工

    Institute of Scientific and Technical Information of China (English)

    王鸿非; 徐波; 代小曼; 代超; 孟祥静

    2015-01-01

    This paper prepares the high early strength magnesium phosphate repair agent on the basis of using MgO,potassium dihydrogen phosphate and borax and adding mineral admixtures and steel slag powders.The crafts-manship process of pavement repair construction was put forward and applied to practical engineering.Using fly ash, silica fume,slag powders and chromium slag powders to replace partial magnesium phosphate cement,which reduces the cost and saves resources for heavy metal solidification.The engineering application shows:the initial fluidity and setting time can be controlled with less early strength loss.Thecrack permeability is better to meet the required con-struction indicators.%采用氧化镁、磷镁酸盐和硼砂为主,添加部分矿物掺和料和钢渣粉等,制备了快硬早强磷镁酸盐快硬水泥修补剂,提出了路面修补施工工艺,并应用到了实际工程中。利用矿物掺和料(粉煤灰、硅灰、膨胀剂、钢渣粉等)和铬铁矿渣粉替代部分磷镁酸盐水泥,降低了修补剂成本,节约了资源,同时有利于重金属的固化。工程应用表明:在早期强度损失率低的情况下,该修补剂的初始流动度大,凝结时间可调控,早强强度等级高,抗裂抗渗好,满足施工设计指标要求。

  14. Mechanistic study and modeling of radionuclides retention by the hydrated calcium silicates (HCS) of cements; Etude mecanistique et modelisation de la retention de radionucleides par les silicates de calcium hydrates (CSH) des ciments

    Energy Technology Data Exchange (ETDEWEB)

    Pointeau, I

    2000-09-01

    This work attempts to investigate the modelling of radioisotopes (Cs{sup +}, Pb{sup 2+}, Eu{sup 3+}) immobilization in cement matrix, in the frame of the design of engineered barrier of a deep radwaste repository. The model development concept consists of three major steps: - surface chemistry modelling of the calcium silicate hydrate CSH, used to simulate hydrated cement behaviour; - solid analysis of the batch sorption experiments: identification of the uptake mechanism; - both previous steps are used, with isotherm data, in the modelling of the radioisotopes immobilization in the CSH matrix. Final results: (all modelling are available for all the range of studied Ca/Si ratios and have been validated with predictive calculations). - A thermodynamic modelling of the CSH surface chemistry has been developed. The labile calcium and proton sorption constants on silanol sites (>SiOH) have been extracted. - Cs{sup +} is sorbed on two sites. The silanol site (weak site) has a high site density (10 sites.nm{sup -2}), which accounts for the CSH unsaturation in high [CS{sup +}]. A strong site is also identified. - Pb{sup 2+} immobilization in CSH matrix is modelled with surface equilibria and solubility equilibrium. - Eu{sup 3+} fixation has been investigated with solid analysis: Site-Selective anti Time-Resolved Luminescence Spectroscopy, XPS and SEM-EDS. Eu{sup 3+} thus does not precipitate in CSH water but is sorbed on the CSH surface (high hydroxylated environment). Europium is also (minority site) inserted in the CSH framework. (author)

  15. Comparing the reinforcing effects of a resin modified glassionomer cement, Flowable compomer, and Flowable composite in the restoration of calcium hydroxide-treated immature roots in vitro

    Directory of Open Access Journals (Sweden)

    S Prathibha Rani

    2011-01-01

    Full Text Available One hundred and sixty human permanent central incisors were enlarged to a 120 file size after crown removal procedure to simulate immature teeth. The root canals were filled with calcium hydroxide and stored for 15 days (phase I, 30 days (phase II, 90 days (phase III, and 180 days (Phase IV. At the end of these selected time periods, calcium hydroxide was cleaned off the root canals of forty teeth that were randomly selected and obturated with gutta-percha points in the apical 2 mm of the root canals with a sealer. The specimens were further equally divided into four groups. Unrestored Group I served as control and the root canals of teeth in the other three group specimens were reinforced with resin modified glassionomer cement (RMGIC (Group II, Flowable Compomer (Group III, and Flowable Composite (Group IV, respectively, using a translucent curing post. All specimens were subjected to compressive force using an Instron Testing machine, until fracture occurred. All the materials evaluated substantially reinforced the root specimens compared to the control. At the end of 180 days, Flowable composites showed maximum reinforcement compared to the other groups; however, no significant differences were found between the reinforcement capabilities of Flowable Compomer and RMGIC.

  16. Comparing the reinforcing effects of a resin modified glassionomer cement, Flowable compomer, and Flowable composite in the restoration of calcium hydroxide-treated immature roots in vitro.

    Science.gov (United States)

    Prathibha, Rani S

    2011-01-01

    One hundred and sixty human permanent central incisors were enlarged to a 120 file size after crown removal procedure to simulate immature teeth. The root canals were filled with calcium hydroxide and stored for 15 days (phase I), 30 days (phase II), 90 days (phase III), and 180 days (Phase IV). At the end of these selected time periods, calcium hydroxide was cleaned off the root canals of forty teeth that were randomly selected and obturated with gutta-percha points in the apical 2 mm of the root canals with a sealer. The specimens were further equally divided into four groups. Unrestored Group I served as control and the root canals of teeth in the other three group specimens were reinforced with resin modified glassionomer cement (RMGIC) (Group II), Flowable Compomer (Group III), and Flowable Composite (Group IV), respectively, using a translucent curing post. All specimens were subjected to compressive force using an Instron Testing machine, until fracture occurred. All the materials evaluated substantially reinforced the root specimens compared to the control. At the end of 180 days, Flowable composites showed maximum reinforcement compared to the other groups; however, no significant differences were found between the reinforcement capabilities of Flowable Compomer and RMGIC.

  17. Sulfate Resistance of Alite-barium Calcium Sulphoaluminate Cement%阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的研究

    Institute of Scientific and Technical Information of China (English)

    李贵强; 芦令超; 王守德; 陈诚; 尹超男

    2009-01-01

    本文研究了石膏掺量对阿利特-硫铝酸钡钙水泥抗硫酸盐侵蚀性能的影响,并与硅酸盐水泥进行了比较;利用XRD,SEM-EDS等测试方法对侵蚀后水泥水化产物的物相组成和形貌进行了分析.研究结果表明:阿利特-硫铝酸钡钙水泥具有良好的抗硫酸盐侵蚀性能.当石膏掺量为5%时,阿利特-硫铝酸钡钙水泥的抗蚀系数达1.31,而硅酸盐水泥的抗蚀系数仅为0.94.石膏对阿利特-硫铝酸钡钙水泥硬化浆体的致密性有较大影响,进而影响水泥的抗硫酸盐侵蚀性能.同时,对阿利特-硫铝酸钡钙水泥的抗侵蚀机理进行了初步分析.%Effect of gypsum content on the sulfate resistance of alite-barium calcium sulphoaluminate cement was investigated. Portland cement was taken for comparison. The composition and microstructure of hardened cement pastes were analyzed by X-ray diffraction and scanning electron microscope. The results show that alite-barium calcium sulphoaluminate cement has better ability of sulfate resistance. The coefficient of resistance to sulfate attack with 5% gypsum addition in alite-barium calcium sulphoaluminate is 1.31, while that in Portland cement is only 0.94. Gypsum can affect the tightness of alite-barium calcium sulphoaluminate cement hardened pastes and further influence the ability of resistance to sulfate attack. At the same time, the mechanism of sulfate resistance of alite-barium calcium sulphoaluminate cement was discussed in this paper.

  18. Synthesis of pure Portland cement phases

    DEFF Research Database (Denmark)

    Wesselsky, Andreas; Jensen, Ole Mejlhede

    2009-01-01

    Pure phases commonly found in Portland cement clinkers are often used to test cement hydration behaviour in simplified experimental conditions. The synthesis of these phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases...... in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the The process of solid state synthesis are is described in general including practical advice on equipment and techniques. Finally In addition, some exemplary mix compositions...

  19. Calcium Sulfoaluminate Sodalite (Ca 4 Al 6 O 12 SO 4 ) Crystal Structure Evaluation and Bulk Modulus Determination

    KAUST Repository

    Hargis, Craig W.

    2013-12-12

    The predominant phase of calcium sulfoaluminate cement, Ca 4(Al6O12)SO4, was investigated using high-pressure synchrotron X-ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al 6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O 12)SO4. The compressibility of Ca4(Al 6O12)SO4 was studied using cubic, orthorhombic, and tetragonal crystal structures due to the lack of consensus on the actual space group, and all three models provided similar results of 69(6) GPa. With its divalent cage ions, the bulk modulus of Ca4(Al6O 12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H 2O. Likewise, comparing this study to previous ones shows the lattice compressibility of aluminate sodalites decreases with increasing size of the caged ions. Ca4(Al6O12)SO4 is more compressible than other cement clinker phases such as tricalcium aluminate and less compressible than hydrated cement phases such as ettringite and hemicarboaluminate. © 2013 The American Ceramic Society.

  20. Eu2+ luminescence in strontium aluminates

    NARCIS (Netherlands)

    Dutczak, D.; Juestel, T.; Ronda, C.; Meijerink, A.

    2015-01-01

    The luminescence properties of Eu2+ doped strontium aluminates are reported and reviewed for a variety of aluminates, viz. SrAl12O19, SrAl4O7, Sr4Al14O25, SrAl2O4 and Sr3Al2O6. The aim of the research is to investigate the role of local coordination and covalency of the aluminate host lattice, relat

  1. Spectra of sodium aluminate solutions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The UV spectra of sodium aluminate solutions were obtained in the sodium oxide concentration range from 59 to 409 g/L and the caustic ratio range from 1.5 to 4.0 to reveal the structure characteristics of them. It is found that a new peak appears at about 370 nm besides peaks at about 220 and 266 nm in all solutions. The new peak is strongly favored by high hydroxide concentration and high caustic ratio. And it only appears when the solutions are prepared by dissolving sodium hydroxide and aluminum hydroxide.In addition, the IR and Raman spectra of sodium aluminate solutions with high alkali concentration and high caustic ratio were measured, and the UV spectra of aqueous solutions of Al(H2O)63+ and AlF63- were measured as well. According to the crystal field theory in coordination chemistry as well as the above spectra characteristics, this new peak at about 370 nm is determined as the evidence of a new species of aluminate ion with a coordination number of 6.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-15

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

  3. Effects of Stirring and Fluid Perfusion on the In Vitro Degradation of Calcium Phosphate Cement/PLGA Composites

    NARCIS (Netherlands)

    An, J.; Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Jansen, J.A.

    2015-01-01

    In vitro degradation rates of calcium phosphate bioceramics are investigated using a large variation of soaking protocols that do not all match the dynamic conditions of the perfused physiological environment. Therefore, we studied the effect of stirring and fluid perfusion on the in vitro degradati

  4. Effect of metakaolinite on strength and chemical resistance of cement mortars

    Energy Technology Data Exchange (ETDEWEB)

    Malolepszy, J.; Pytel, Z. [Mining and Metallurgy Univ., Faculty of Materials Science and Ceramics, Cracow (Poland)

    2000-07-01

    The effect of the percentage of metakaolinite admixture and calcium aluminate content in portland cement, used as the main cementitious components, on the chemical resistance of a series of prepared standard mortars was investigated. Chemical resistance was evaluated by measuring strength, shrinkage and expansion on the samples stored in water and chemical solutions. Results showed minimal change in the standard properties of mortars by the metakaolinite. However, there was marked improvement in chemical resistance. Interest in the study of this material is related to the urgency of finding a useful application for it, in view of the fact that it is produced in large quantities as a waste-product of power generation. It is widely believed that there is a potential application for this product in improving the durability of concrete. 20 refs., 10 tabs., 9 figs.

  5. 发泡水泥用硬脂酸钙乳液的制备工艺研究%Preparation of Calcium Stearate Emulsion for Foam Cement

    Institute of Scientific and Technical Information of China (English)

    孙强强

    2015-01-01

    Two different calcium stearate emulsions were synthesized respectively by stearic acid saponification with freshly formed calsium hydroxide, and by direct emulsification with calcium stearate for improving the foam stability in the foaming process of foam cement. Then, the process of synthesis and saponification was disussed.The results indicated that calcium stearate emulsion with excellent stability and second-order dispersion was prepared at 90℃ for 100 min by saponification method.After the direct emulsification, calcium stearate emulsion with good stability and third-order dispersion was obtained with the CMC dosage of 3.5 wt%, total volume fraction of 1.5% and the proportion of 1:1 of composite emulsifier. Calcium stearate emulsion obtained by saponification for synthesis was the better foam stabilizer for foam cement,which had the longer foam stabilizing time increased for 22-23 min, compared with the direction emulsifying method for14-15 min.%为了改善发泡水泥发泡过程中泡沫的稳定性,以硬脂酸、新制氢氧化钙及轻质硬脂酸钙为原料,采用皂化合成法和直接乳化法分别制得了发泡水泥用硬脂酸钙乳液,并对合成和乳化工艺进行研究。结果表明:在反应温度为90℃,乳化时间为100 min的条件下,通过皂化合成制得了分散等级为二级,稳定性优良的硬脂酸钙乳液。在乳化温度为90℃,稳定剂羧甲基纤维素钠(CMC)用量3.5 wt%,复配乳化剂A、B总体积用量1.5%,比例为1:1时,通过直接乳化法制得了分散等级为三级,稳定性较好的硬脂酸钙乳液。对比发现,直接乳化法制得的硬脂酸钙乳液可有效增加稳泡时间14-15 min,而皂化合成法制得的硬脂酸钙乳液可有效增加稳泡时间22-23 min,更适宜用作发泡水泥的泡沫稳定剂。

  6. Study of mechanical properties of calcium phosphate cement with addition of sodium alginate and dispersant; Estudo das propriedades mecanicas de cimento de fosfato de calcio com adicao de alginato de sodio e defloculante

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, J.M.; Coelho, W.T.; Thurmer, M.B.; Vieira, P.S.; Santos, L.A., E-mail: julianafernandes2@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), RS (Brazil)

    2011-07-01

    Several studies in literature have shown that the addition of polymer additives and deflocculant has a strong influence on the mechanical properties of cements in general.The low mechanical strength is the main impediment to wider use of bone cement of calcium phosphate (CFCs) as the implant material, since they have mechanical strength which equals the maximum of trabecular bone.In order to evaluate the strength of a CFC compound alpha-tricalcium phosphate, sodium alginate were added (1%, 2% and 3% by weight) and dispersant ammonium polyacrylate (3%) in aqueous solution.Specimens were made and evaluated for density, porosity, crystalline phases and mechanical strength.The results show the increase of the mechanical properties of cement when added sodium alginate and dispersant. (author)

  7. Magnesium modification up-regulates the bioactivity of bone morphogenetic protein-2 upon calcium phosphate cement via enhanced BMP receptor recognition and Smad signaling pathway.

    Science.gov (United States)

    Ding, Sai; Zhang, Jing; Tian, Yu; Huang, Baolin; Yuan, Yuan; Liu, Changsheng

    2016-09-01

    Efficient presentation of growth factors is one of the great challenges in tissue engineering. In living systems, bioactive factors exist in soluble as well as in matrix-bound forms, both of which play an integral role in regulating cell behaviors. Herein, effect of magnesium on osteogenic bioactivity of recombinant human bone morphogenetic protein-2 (rhBMP-2) was investigated systematically with a series of Mg modified calcium phosphate cements (xMCPCs, x means the content of magnesium phosphate cement wt%) as matrix model. The results indicated that the MCPC, especially 5MCPC, could promote the rhBMP-2-induced in vitro osteogenic differentiation via Smad signaling of C2C12 cells. Further studies demonstrated that all MCPC substrates exhibited similar rhBMP-2 release rate and preserved comparable conformation and biological activity of the released rhBMP-2. Also, the ionic extracts of MCPC made little difference to the bioactivity of rhBMP-2, either in soluble or in matrix-bound forms. However, with the quartz crystal microbalance (QCM), we observed a noticeable enhancement of rhBMP-2 mass-uptake on 5MCPC as well as a better recognition of the bound rhBMP-2 to BMPR IA and BMPR II. In vivo results demonstrated a better bone regeneration capacity of 5MCPC/rhBMP-2. From the above, our results demonstrated that it was the Mg anchored on the underlying substrates that tailored the way of rhBMP-2 bound on MCPC, and thus facilitated the recognition of BMPRs to stimulate osteogenic differentiation. The study will guide the development of Mg-doped bioactive bone implants for tissue regeneration.

  8. Tuning the degradation rate of calcium phosphate cements by incorporating mixtures of polylactic-co-glycolic acid microspheres and glucono-delta-lactone microparticles.

    Science.gov (United States)

    Sariibrahimoglu, Kemal; An, Jie; van Oirschot, Bart A J A; Nijhuis, Arnold W G; Eman, Rhandy M; Alblas, Jacqueline; Wolke, Joop G C; van den Beucken, Jeroen J J P; Leeuwenburgh, Sander C G; Jansen, John A

    2014-11-01

    Calcium phosphate cements (CPCs) are frequently used as synthetic bone graft materials in view of their excellent osteocompatibility and clinical handling behavior. Hydroxyapatite-forming CPCs, however, degrade at very low rates, thereby limiting complete bone regeneration. The current study has investigated whether degradation of apatite-forming cements can be tuned by incorporating acid-producing slow-resorbing poly(D,L-lactic-co-glycolic) acid (PLGA) porogens, fast-resorbing glucono-delta-lactone (GDL) porogens, or mixtures thereof. The physicochemical, mechanical, and degradation characteristics of these CPC formulations were systematically analyzed upon soaking in phosphate-buffered saline (PBS). In parallel, various CPC formulations were implanted intramuscularly and orthotopically on top of the transverse process of goats followed by analysis of the soft tissue response and bone ingrowth after 12 weeks. In vitro degradation of GDL was almost completed after 2 weeks, as evidenced by characterization of the release of gluconic acid, while PLGA-containing CPCs released glycolic acid throughout the entire study (12 weeks), resulting in a decrease in compression strength of CPC. Extensive in vitro degradation of the CPC matrix was observed upon simultaneous incorporation of 30% PLGA-10% GDL. Histomorphometrical evaluation of the intramuscularly implanted samples revealed that all CPCs exhibited degradation, accompanied by an increase in capsule thickness. In the in vivo goat transverse process model, incorporation of 43% PLGA, 30% PLGA-5% GDL, and 30% PLGA-10% GDL in CPC significantly increased bone formation and resulted in higher bone height compared with both 10% GDL and 20% GDL-containing CPC samples.

  9. Mechanical effect of calcium polyphosphate fiber on reinforcing calcium phosphate bone cement composites%聚磷酸钙纤维增强增韧磷酸钙骨水泥的力学效应

    Institute of Scientific and Technical Information of China (English)

    徐立新; 史雪婷; 王彦平; 石宗利

    2009-01-01

    AIM: To prepare α-tricalcium phosphate (α-TCP)/calcium polyphosphate (CPP) fiber and to study the feasibility of CPP fiber to reinforce calcium phosphate bone cement composites. METHODS: Firstly,α-TCP powder was synthesized using chemical sediment method. Secondly, the α-TCP was mixed with CPP fiber according to different contents and lengths. Finally, bone cement was tempered with firming agent. Solidification time and mechanical property of the samples were measured. Microstructure of hardened sample was observed with scanning electron microscope. RESULTS: When the amount of CPP fibers was 10% and the length was 2 mm, the compressive strength reached 62.5 MPa and the rupture strength reached 12.4 MPa. Scanning electron microscope suggested that CPP fibers with great associativity were well distributed in bone cement. After immersing in Ringer fluid for two months, the CPP fibers did not biodegrade obviously and still had certain function to increase strength and toughness. CONCLUSION: To a certain extent, the CPP fiber can increase strength and toughness of bone cement. Furthermore, α-TCP/CPP composites have good mechanical properties and biocompatibility.%目的:制备α-磷酸三钙/聚磷酸钙纤维复合材料,探讨聚磷酸钙纤维增强磷酸钙骨水泥的可行性.方法:首先利用沉淀法合成出α-磷酸三钙粉末,然后将其与不同质量比、不同长度聚磷酸钙纤维混合,最后用固化液调和制得骨水泥.对样品进行凝固时间、力学性能测试,利用扫描电镜观察固化体微观结构.结果:当聚磷酸钙纤维的含量为10%、长度为2 mm时,复合材料抗压强度达到62.5 MPa,抗折强度达到12.4 MPa.扫描电镜显示适量的聚磷酸钙纤维在骨水泥基体中分布均匀,与基体结合性好.在Ringer溶液中浸泡2个月后,纤维未发生明显的降解作用,仍具有一定的增强增韧效果.结论:聚磷酸钙纤维在一定程度上可对骨水泥起到增强作用.α-磷酸三

  10. Aluminized alloy boosts turbine blade life

    Science.gov (United States)

    Gedwill, M. A.; Grisaffe, S. J.

    1974-01-01

    Description of an aluminized alloy coating technique that involves first the application of a ductile, oxidation-resistant overlay, such as NiCrAl, which is then partially aluminized. The duplex protective system has performance advantages over conventional aluminide coatings in that it provides higher-temperature hot corrosion resistance over a longer service life.

  11. Bioactive glass incorporation in calcium phosphate cement-based injectable bone substitute for improved in vitro biocompatibility and in vivo bone regeneration.

    Science.gov (United States)

    Sadiasa, Alexander; Sarkar, Swapan Kumar; Franco, Rose Ann; Min, Young Ki; Lee, Byong Taek

    2014-01-01

    In this work, we fabricated injectable bone substitutes modified with the addition of bioactive glass powders synthesized via ultrasonic energy-assisted hydrothermal method to the calcium phosphate-based bone cement to improve its biocompatibility. The injectable bone substitutes was initially composed of a powder component (tetracalcium phosphate, dicalcium phosphate dihydrate and calcium sulfate dehydrate) and a liquid component (citric acid, chitosan and hydroxyl-propyl-methyl-cellulose) upon which various concentrations of bioactive glass were added: 0%, 10%, 20% and 30%. Setting time and compressive strength of the injectable bone substitutes were evaluated and observed to improve with the increase of bioactive glass content. Surface morphologies were observed via scanning electron microscope before and after submersion of the samples to simulated body fluid and increase in apatite formation was detected using x-ray diffraction machine. In vitro biocompatibility of the injectable bone substitutes was observed to improve with the addition of bioactive glass as the proliferation/adhesion behavior of cells on the material increased. Human gene markers were successfully expressed using real time-polymerase chain reaction and the samples were found to promote cell viability and be more biocompatible as the concentration of bioactive glass increases. In vivo biocompatibility of the samples containing 0% and 30% bioactive glass were evaluated using Micro-CT and histological staining after 3 months of implantation in male rabbits' femurs. No inflammatory reaction was observed and significant bone formation was promoted by the addition of bioactive glass to the injectable bone substitute system.

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

    Science.gov (United States)

    Coleman, Nichola J; Li, Qiu

    2013-01-01

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

  13. Effects of the addition of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on mechanical properties of luting and lining glass ionomer cement

    Science.gov (United States)

    Heravi, Farzin; Bagheri, Hossein; Rangrazi, Abdolrasoul; Mojtaba Zebarjad, Seyed

    2016-07-01

    Recently, the addition of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into glass ionomer cements (GICs) has attracted interest due to its remineralization of teeth and its antibacterial effects. However, it should be investigated to ensure that the incorporation of CPP-ACP does not have significant adverse effects on its mechanical properties. The purpose of this study was to evaluate the effects of the addition of CPP-ACP on the mechanical properties of luting and lining GIC. The first step was to synthesize the CPP-ACP. Then the CPP-ACP at concentrations of 1%, 1.56% and 2% of CPP-ACP was added into a luting and lining GIC. GIC without CPP-ACP was used as a control group. The results revealed that the incorporation of CPP-ACP up to 1.56%(w/w) increased the flexural strength (29%), diametral tensile strength (36%) and microhardness (18%), followed by a reduction in these mechanical properties at 2%(w/w) CPP-ACP. The wear rate was significantly decreased (23%) in 1.56%(w/w) concentration of CPP-ACP and it was increased in 2%(w/w). Accordingly, the addition of 1.56%(w/w) CPP-ACP into luting and lining GIC had no adverse effect on the mechanical properties of luting and lining GIC and could be used in clinical practice.

  14. Immobilization of trace elements in municipal solid waste incinerator (MSWI) fly ash by producing calcium sulphoaluminate cement after carbonation and washing.

    Science.gov (United States)

    Wang, Lei; Jamro, Imtiaz Ali; Chen, Qi; Li, Shaobai; Luan, Jingde; Yang, Tianhua

    2016-03-01

    The possibility of producing calcium sulphoaluminate cement (CSA) by adding municipal solid waste incinerator (MSWI) fly ash to raw meal was investigated. After subjecting MSWI fly ash to accelerated carbonation and washing with water (ACW), various amounts (i.e., 5, 10 and 15 wt%) of the treated ash were added to raw meal composed of a mixture of bauxite, limestone and gypsum. The mixtures were sintered in a laboratory-scale muffle furnace at temperatures of 1250°, 1300°, 1325° and 1350 °C for various durations. The influence of different quantities of MSWI fly ash on the mineralogy, major phase composition and strength development of the resulting clinker was studied, as was the effect of ash treatments on leaching and volatilization of trace elements. The ACW treatment reduced the volatilization ratio of trace elements during the clinkerization process. Volatilization ratios for lead, cadmium and zinc were 21.5%, 33.6% and 16.3%, respectively, from the ACW fly ash treatment, compared with ratios of 97.5%, 93.1% and 85.2% from untreated fly ash. The volatilization ratios of trace elements were ordered as follows: untreated fly ash > carbonated fly ash > carbonated and water-washed fly ash. The ACW process also reduced the chloride content in the MSWI fly ash by 90 wt% and prevented high concentrations of trace elements in the effluents.

  15. RhBMP-2 loaded 3D-printed mesoporous silica/calcium phosphate cement porous scaffolds with enhanced vascularization and osteogenesis properties

    Science.gov (United States)

    Li, Cuidi; Jiang, Chuan; Deng, Yuan; Li, Tao; Li, Ning; Peng, Mingzheng; Wang, Jinwu

    2017-01-01

    A major limitation in the development of effective scaffolds for bone regeneration has been the limited vascularization of the regenerating tissue. Here, we propose the development of a novel calcium phosphate cement (CPC)-based scaffold combining the properties of mesoporous silica (MS) with recombinant human bone morphogenic protein-2 (rhBMP-2) to facilitate vascularization and osteogenesis. Specifically, the development of a custom MS/CPC paste allowed the three-dimensional (3D) printing of scaffolds with a defined macroporous structure and optimized silicon (Si) ions release profile to promote the ingrowth of vascular tissue at an early stage after implantation in support of tissue viability and osteogenesis. In addition, the scaffold microstructure allowed the prolonged release of rhBMP-2, which in turn significantly stimulated the osteogenesis of human bone marrow stromal cells in vitro and of bone regeneration in vivo as shown in a rabbit femur defect repair model. Thus, the combination MS/CPC/rhBMP-2 scaffolds might provide a solution to issues of tissue necrosis during the regeneration process and therefore might be able to be readily developed into a useful tool for bone repair in the clinic. PMID:28128363

  16. Evaluation of an injectable silk fibroin enhanced calcium phosphate cement loaded with human recombinant bone morphogenetic protein-2 in ovine lumbar interbody fusion.

    Science.gov (United States)

    Gu, Yong; Chen, Liang; Yang, Hui-Lin; Luo, Zong-Ping; Tang, Tian-Si

    2011-05-01

    The objective of this study was to investigate the efficacy of an injectable calcium phosphate cement/silk fibroin/human recombinant bone morphogenetic protein-2 composite (CPC/SF/rhBMP-2) in an ovine interbody fusion model. Twenty-four mature sheep underwent anterior lumbar interbody fusion at the levels of L1/2, L3/4, and L5/6 with random implantation of CPC/SF, CPC/rhBMP-2, CPC/SF/rhBMP-2, or autogenous iliac bone. After the sheep were sacrificed, the fusion segments were evaluated by manual palpation, CT scan, undestructive biomechanical testing, undecalcified histology, and histomorphology. The fusion rates of CPC/SF/rhBMP-2 were 55.56% and 77.78% at 6 and 12 months, respectively. The fusion was superior to all the biomaterial grafts in stiffness, and reached the same stiffness as the autograft at 12 months. The new bone formation was less than autograft at 6 months, but similar with that at 12 months. However, the ceramic residue volume of CPC/SF/rhBMP-2 was significantly decreased compared with CPC/SF and CPC/rhBMP-2 at both times. The results indicated that CPC/SF/rhBMP-2 composite had excellent osteoconduction and osteoinduction, and balanced degradation and osteogenesis.

  17. Characterization of the calcium-fluoroaluminosilicate glass prepared by a non-hydrolytic sol-gel route for future dental application as glass ionomer cement

    Directory of Open Access Journals (Sweden)

    Alexandre Cestari

    2009-06-01

    Full Text Available Glass ionomer cements are widely employed in dentistry due to their physical, biological and mainly anti-caries properties. Glass ionomers consist of an aluminosilicate glass matrix modified with other elements, and they contain large quantities of fluorine. In this study, we report on the preparation of calcium-fluoroaluminosilicate glasses by a nonhydrolytic sol-gel route as an alternative approach to obtaining alumina-silica matrices. The glass powders were prepared via the non-hydrolytic sol-gel method, by mixing AlCl3, SiCl4, CaF2, AlF3, NaF, and AlPO4. The powders were studied by thermal analysis (TG/DTA/DSC, photoluminescence (PL, nuclear magnetic resonance (NMR27Al-29Si, and X ray diffraction (XRD. TG/DTA/DSC analyses revealed a constant mass loss due to structural changes during the heating process, which was confirmed by NMR and PL. A stable aluminosilicate matrix with potential future application as a glass ionomer base was obtained.

  18. The use of brushite calcium phosphate cement for enhancement of bone-tendon integration in an anterior cruciate ligament reconstruction rabbit model.

    Science.gov (United States)

    Wen, Chun-Yi; Qin, Ling; Lee, Kwong-Man; Chan, Kai-Ming

    2009-05-01

    This study was designed to investigate the osteoconductivity and bioresorption of brushite calcium phosphate cement (CPC) in bone-tendon interface healing after anterior cruciate ligament (ACL) reconstruction. Surgical reconstruction using grafted tendon in bone tunnel was performed bilaterally in 28 skeletal mature rabbits. Brushite CPC was implanted between grafted tendon and bone tunnel of one limb with the contralateral one as the control. A batch of 14 rabbits was sacrificed at 6 and 12 weeks, respectively, after surgery. At each time point, six rabbits were used for micro-CT and subsequent histological examinations, whereas the remaining eight rabbits were used for pull-out testing. The components of brushite CPC-dicalcium phosphate dihydrate matrix degraded rapidly with beta-tricalcium phosphate granules left for guiding new bone formation. Brushite CPC augmented the peri-tendon bone volume and promoted bone growth into the healing interface. The ultimate strength and stiffness of the graft-tunnel complexes on experimental side was higher than that of the control by 117% and 102%, respectively, at 6 weeks postoperatively (p brushite CPC caused a paradigm shift in failure mode from intra-tunnel to intra-articular portion at 12 weeks postoperatively (p = 0.013). Brushite CPC significantly enhanced the bone-tendon integration after ACL reconstruction, which provided a scientific basis for clinical application.

  19. RhBMP-2 loaded 3D-printed mesoporous silica/calcium phosphate cement porous scaffolds with enhanced vascularization and osteogenesis properties

    Science.gov (United States)

    Li, Cuidi; Jiang, Chuan; Deng, Yuan; Li, Tao; Li, Ning; Peng, Mingzheng; Wang, Jinwu

    2017-01-01

    A major limitation in the development of effective scaffolds for bone regeneration has been the limited vascularization of the regenerating tissue. Here, we propose the development of a novel calcium phosphate cement (CPC)-based scaffold combining the properties of mesoporous silica (MS) with recombinant human bone morphogenic protein-2 (rhBMP-2) to facilitate vascularization and osteogenesis. Specifically, the development of a custom MS/CPC paste allowed the three-dimensional (3D) printing of scaffolds with a defined macroporous structure and optimized silicon (Si) ions release profile to promote the ingrowth of vascular tissue at an early stage after implantation in support of tissue viability and osteogenesis. In addition, the scaffold microstructure allowed the prolonged release of rhBMP-2, which in turn significantly stimulated the osteogenesis of human bone marrow stromal cells in vitro and of bone regeneration in vivo as shown in a rabbit femur defect repair model. Thus, the combination MS/CPC/rhBMP-2 scaffolds might provide a solution to issues of tissue necrosis during the regeneration process and therefore might be able to be readily developed into a useful tool for bone repair in the clinic.

  20. Waste brick's potential for use as a pozzolan in blended Portland cement.

    Science.gov (United States)

    Lin, Kae-Long; Chen, Bor-Yann; Chiou, Chyow-San; An Cheng

    2010-07-01

    This study investigated the pozzolanic reactions and engineering properties of waste brick-blended cements in relation to various replacement ratios (0-50%). The waste brick consisted of SiO(2) (63.21%), Al(2)O(3) (16.41%), Fe(2)O(3) (6.05%), Na(2)O (1.19%), K(2)O (2.83%) and MgO (1.11%), and had a pozzolanic activity index of 107%. The toxic characteristic leaching procedure (TCLP) results demonstrate that the heavy-metal content in waste bricks met the Environmental Protection Agency regulatory limits. Experimental results indicate that 10, 20, 30, 40 and 50% of cement can be replaced by waste brick, which causes the initial and final setting times to increase. Compressive strength development was slower in waste brick-blended cement (WBBC) pastes in the early ages; however, strength at the later ages increased significantly. Species analyses demonstrate that the hydrates in WBBC pastes primarily consisted of Ca(OH)(2) and calcium silicate hydrate (C-S-H) gel, like those found in ordinary Portland cement (OPC) paste. Pozzolanic reaction products formed in the WBBC pastes, in particular, various reaction products, including hydrates of calcium silicates (CSH), aluminates (CAH) and aluminosilicates (CASH), formed as expected, resulting in consumption of Ca(OH)(2) during the late ages of curing. The changes in the properties of WBBC pastes were significant as blend ratio increased, due to the pores of C-S-H gels and CAH filling via pozzolanic reactions. This filling of gel pores resulted in densification and subsequently enhanced the gel/space ratio and degree of hydration. Experimental results demonstrate waste brick can be supplementary cementitious material.

  1. Utilization of Phosphogypsum and Low Grade Bauxite for Belite Rich Calcium Sulphoaluminate Cement%磷石膏与低品位矾土制备高贝利特-硫铝酸盐水泥

    Institute of Scientific and Technical Information of China (English)

    梁娇; 刘娜; 刘从振; 郭清春; 李昕成; 钱觉时

    2016-01-01

    利用磷石膏和低品位矾土制备高贝利特-硫铝酸盐水泥,研究了熟料的最佳煅烧工艺制度及配入过量磷石膏对水泥性能的影响。结果表明:在1300℃保温0.5 h,烧制出性能良好的高贝利特-硫铝酸盐水泥熟料,3 d和28 d水泥净浆抗压强度分别可达54.1 MPa和59.1 MPa;过量磷石膏形成的高温硬石膏能起到后掺石膏的作用,对水泥早期力学性能无不利影响。%Belite rich calcium sulphoaluminate cement was prepared with phosphogypsum and low grade bauxite. The optimum burning process for the clinker production and the excessive amount of phosphogypsum in the clinker on the performance of the cement were investigated. The results demonstrate that belite rich calcium sulphoaluminate cement with excellent performances can be achieved. The compressive strength of the cement paste at 3 d and 28 d reaches 54.1 MPa and 59.1 MPa, separately. The excessive amount of phosphgypsum in the clinker turns into anhydrate, serving the added gypsum and satisfying the hydration of C4A3S—. And the anhydrate does not harm the strength development of the cement paste.

  2. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

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

  3. Effect of CaF2 on the Performance of Alite-strontium Calcium Sulfoaluminate Cement%CaF2对阿利特-硫铝酸锶钙水泥性能的影响

    Institute of Scientific and Technical Information of China (English)

    李秋英; 芦令超; 王守德

    2011-01-01

    Alite-strontium calcium sulphoaluminate cement, a new type of cementitious material is synthesized by combining strontium calcium sulphoaluminate with minerals of Portland cement. The influence of CaF2 on the synthesis and performance of the cement is studied by XRD, SEM-EDS, and lithofacies. The results show that suitable amount of CaF2 can benefit f-CaO combination and promote the formation of alite and strontium calcium sulphoaluminate at low temperature. The optimal mass fraction of CaF2 is 0. 6%. The compressive strength of the cement prepared under these conditions reaches to 32.8 MPa, 67.7 MPa and 120.4 MPa at 1 d,3 d and 28 d.%将硫铝酸锶钙矿物引入到硅酸盐熟料矿物体系中,合成阿利特-硫铝酸锶钙水泥.利用XRD,SEM-EDS和岩相等测试手段研究了CaF2对阿利特-硫铝酸锶钙水泥熟料矿物组成和水泥性能的影响.结果表明,CaF2能够促进固相反应使得阿利特在较低温度下形成,有利于阿利特和硫铝酸锶钙矿物的共存.当CaF2在熟料中的掺入量为0.6%时,阿利特-硫铝酸锶钙水泥的1 d、3 d和28 d抗压强度分别达到32.8 MPa、67.7 MPa和120.4 MPa,表现出良好的力学性能.

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

    Energy Technology Data Exchange (ETDEWEB)

    Min, B. Y.; Choi, W. K.; Kim, G. N.; Lee, K. W. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-10-15

    As the number of obsolete research reactors and nuclear facilities increases, dismantling nuclear facilities has become an influential issue. During the decommissioning of nuclear plants and facilities, large quantities of slightly contaminated concrete wastes are generated. In Korea, the decontamination and decommissioning of the retired TRIGA MARK II and III research reactors and a uranium conversion plant at KAERI has been under way. By dismantling KRR-2, more than 260 tons of radioactive concrete wastes were generated among the total 2,000 tons of concrete wastes and more than 60 tons of concrete wastes contaminated with uranium compounds have been generated. Typically, the contaminated layer is only 1{approx}10mm thick because cement materials are porous media, the penetration of radionuclides may occur up to several centimeters from the surface of a material. Concrete is a structural material which generally consists of a binder (cement), water, and aggregate. The binder is typically a portland cement which comprises the four principal clinker phases tricalcium silicate (Ca{sub 3}SiO{sub 5}) and constitutes 50-70%, decalcium silicate (Ca{sub 2}SiO{sub 4}), tricalcium aluminate (Ca{sub 3}Al{sub 2}O{sub 6}), and calcium aluminoferrite (Ca{sub 4}Al{sub 2}Fe{sub 2}O{sub 10}). Cement powder (anhydrous cement) created from the co-grinding of clinkers and gypsum is mixed with waster and hydrate phase are formed. The interaction between highly charged C-S-H particles in the presence of divalent calcium counter ions is strongly attractive because of ion-ion correlations and a negligible entropic repulsion. In the temperature range 100-300 .deg. C, these evolutions are mainly attributed to the loss of the bound water from the C-S-H gel. Similar consequences have been reported for mortars and concretes enhanced sometimes by the appearance of micro-cracks related to the strain incompatibilities between the aggregates and the cement paste. Concrete aggregates are combined

  5. Preparation of a Novel Calcium Phosphate Cement Using N-methylene Phosphonic Chitosan as a Gelling Agent

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A modified chitosan ( N-methylene phosphonic Chitosan, NMPC ) was synthesized to improve solubility and ability to bind calcium ion. The properties of the raw material chitosan and its derivative NMPC were characterized using FTIR, 1 H-NMR. The aim of this study was to enhance the compressive CPC by reinforcing with NMPC. A formulation consisting of CPC powder, buffer solution and gelling agent was used for preparation of the CPC. CPC powder consisted of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous ( DCPA ). NMPC which acted as the gelling agent was dissolved iuto KH2 PO4 -Na2 HPO4 buffer solution. Each specimen in the mold was sandwiched between two fritted glass sides and kept for 24 hours. Compressive strengths were determined, the setting product was identified using X-ray diffraction and scanning electron microscopy was used to investigate the hydroxyapatite particles size and porosity. The experimental results showed that the dominating influence on the compressive strengths of CPC-NMPC was the HA particle size, its uniformity and appropriate porosity.

  6. The synergistic effects of CO2 laser treatment with calcium silicate cement of antibacterial, osteogenesis and cementogenesis efficacy

    Science.gov (United States)

    Hsu, T.-T.; Kao, C.-T.; Chen, Y.-W.; Huang, T.-H.; Yang, J.-J.; Shie, M.-Y.

    2015-05-01

    Calcium silicate-based material (CS) has been successfully used in dental clinical applications. Some researches show that the antibacterial effects of CO2 laser irradiation are highly efficient when bacteria are embedded in biofilm, due to a photo-thermal mechanism. The purpose of this study was to confirm the effects of CO2 laser irradiation on CS, with regard to both material characterization and human periodontal ligament cell (hPDLs) viability. CS was irradiated with a dental CO2 laser using directly mounted fiber optics in wound healing mode with a spot area of 0.25 cm2, and then stored in an incubator at 100% relative humidity and 37 °C for 1 d to set. The hPDLs cultured on CS were analyzed, along with their proliferation and odontogenic differentiation behaviors. The results indicate that the CO2 laser irradiation increased the amount of Ca and Si ions released from the CS, and regulated cell behavior. CO2 laser-irradiated CS promoted cementogenic differentiation of hPDLs, with the increased formation of mineralized nodules on the substrate’s surface. It also up-regulated the protein expression of multiple markers of cementogenic and the expression of cementum attachment protein. The current study provides new and important data about the effects of CO2 laser irradiation on CS. Taking cell functions into account, the Si concentration released from CS with laser irradiated may be lower than a critical value, and this information could lead to the development of new regenerative therapies for dentin and periodontal tissue.

  7. Fibrin gel-immobilized primary osteoblasts in calcium phosphate bone cement: in vivo evaluation with regard to application as injectable biological bone substitute.

    Science.gov (United States)

    Kneser, U; Voogd, A; Ohnolz, J; Buettner, O; Stangenberg, L; Zhang, Y H; Stark, G B; Schaefer, D J

    2005-01-01

    Osteogenic injectable bone substitutes may be useful for many applications. We developed a novel injectable bone substitute based on osteoblast-fibrin glue suspension and calcium phosphate bone cement (BC). Human osteoblasts were isolated from trabecular bone samples and cultured under standard conditions. Osteoblasts were suspended in fibrinogen solution (FS). BC was cured with thrombin solution. 8 x 4 mm injectable bone discs were prepared using silicon molds and a custom-made applicator device. Discs containing BC, BC/FS, or BC/FS/osteoblasts were implanted subcutaneously into athymic nude mice. After 3, 9 and 24 weeks, specimens were explanted and subjected to morphologic and biomechanical evaluation. In vitro fibrin gel-embedded osteoblasts displayed a differentiated phenotype as evidenced by alkaline phosphatase, collagen type 1 and von Kossa stains. A proportion of osteoblasts appeared morphologically intact over a 3-day in vitro period following application into the BC. BC/FS and BC/FS/osteoblast discs were sparsely infiltrated with vascularized connective tissue. There was no bone formation in implants from all groups. However, positive von Kossa staining only in BC/FS/osteoblast groups suggests engraftment of at least some of the transplanted cells. Biomechanical evaluation demonstrated initial stability of the composites. Young's modulus and maximal load did not differ significantly in the BC/FS and BC/FS/osteoblast groups. The practicability of osteoblast-containing injectable bone could be demonstrated. The dense microstructure and the suboptimal initial vascularization of the composites may explain the lack of bone formation. Modifications with regard to enhanced osteoblast survival are mandatory for a possible application as injectable osteogenic bone replacement system.

  8. Structural study and crystallography of the major compound of anhydrous cement: tri-calcium silicate; Etude structurale et cristallographie du compose majoritaire du ciment anhydre: le silicate tricalcique

    Energy Technology Data Exchange (ETDEWEB)

    Noirfontaine, M.N. de

    2000-01-01

    Anhydrous (Portland) cement is mainly composed of a synthetic material, the clinker, whose major compound is tri-calcium silicate (Ca{sub 3}SiO{sub 5}), often referred as C{sub 3}S with the compact oxides notations, C = CaO et S = SiO{sub 2}. The polymorphism of C{sub 3}S, still not well known, is the main subject of the thesis. Various crystal structures (rhombohedral R, monoclinic M1, M2, M3 and triclinic T1, T2, T3) can be found, depending on temperature and impurities. The only known structures are T1, M1 and M3, involving large unit cells with an orientational disorder of silicate tetrahedra. The single crystal studies exhibit no clear relation between the various polymorphs. Starting from known results from literature single crystal experiments, we establish the metric and structural relations between the different structures. Averaged structures for the T1, M1 and M3 polymorphs are proposed, together with all the matrices of transformation between the unit cells. We also introduce new 1-D, 2-D, and 3-D structural units, which make easier the understanding of the structures of C{sub 3}S, with the result of a better description of the orientational disorder. The effects of impurities on the structure are discussed. In industrial clinkers, impurities stabilize mainly M1 and M3 monoclinic forms. We propose a space group (Pc) and two structural models (a superstructure and an approximate averaged structure) for the M1 form. All the models are validated on synthetic compounds (M3, M2, M1 et T1) and industrial clinkers analysed by X-Ray powder diffraction with Rietveld analysis. (author)

  9. In vivo evaluation of injectable calcium phosphate cement composed of Zn- and Si-incorporated β-tricalcium phosphate and monocalcium phosphate monohydrate for a critical sized defect of the rabbit femoral condyle.

    Science.gov (United States)

    Paul, Kallyanashis; Lee, Byung Yeol; Abueva, Celine; Kim, Boram; Choi, Hwan Jun; Bae, Sang Ho; Lee, Byong Taek

    2017-02-01

    Zinc (Zn) enhances bone formation with mineralization and is an essential element of osteoblastic proliferation. Silicon (Si) is important in apatite formation coupled with the promotion of osteogenesis. The primary focus of this work was the assessment of the bone healing capacity of calcium phosphate cements (CPC) composed of Zn- and Si-incorporated β-tri calcium phosphate (TCP) and mono calcium phosphate mono hydrate (MCPM). Zn- and Si-incorporated β-TCP was synthesized through a sol gel process with varying amounts of Zn: (3, 6, or 9% w/w) and 15% w/w Si. Fabricated CPC samples were characterized by scanning electron microscopy, setting time, injectability, compressive strength and initial pH change with time. Compositional analysis and the effects of Zn and Si on cellular interaction were evaluated by energy dispersive X-ray spectroscopy mapping, viability determination and F-actin assay. The data were used to optimize the CPC formulation. The efficacy of bone healing was investigated via implantation into critical sized rabbit femoral condyle defects for 4 and 8 weeks. CPC cement with 6% (w/w) Zn content was the best candidate for faster bone healing (bone to tibial volume ratio in 8 weeks: 22.78% ± 0.02). Significantly faster degradation was also revealed. Bone healing was significantly delayed when CPC cement with 9% (w/w) Zn was used. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 260-271, 2017.

  10. Key technology research on high strength low calcium Portland cement preparation%高强低钙硅酸盐水泥制备关键技术研究

    Institute of Scientific and Technical Information of China (English)

    刘松辉; 魏丽颖; 赵松海; 管学茂; 汪澜

    2014-01-01

    基于节能减排和应对气候变化的新要求,研究开发低钙水泥有多方面的重要意义。试验分别采用化学试剂和工业原料,运用化学分析、X-射线衍射、岩相分析等测试手段,初步探讨了高强低钙硅酸盐水泥制备关键技术。结果表明:工业原料中的微量元素能够解决高强低钙硅酸盐水泥的粉化问题;在试验设计的矿物组成和煅烧制度下,w(C2S)设计值在40%~45%,煅烧温度1400~1450℃时熟料性能最优。%Based on the new requirements of energy-saving emission reduction and climate change, research and development of low calcium cement has important meanings in many aspects. Using chemical reagent and industrial raw materials,by chemical analysis, X-ray diffraction and lithofacies analysis, key production technology of high-strength low-calcium Portland cement was discussed. The results show that the trace elements in industrial raw materials can solve the pulverization problem of high-strength low-calcium Port-land cement and in the system of mineral composition and calcination scheme, when w(C2S) design value is 40%~45%and firing tem-perature at 1400~1450℃, clinker performance will reach the best.

  11. Osteotransductive bone cements.

    Science.gov (United States)

    Driessens, F C; Planell, J A; Boltong, M G; Khairoun, I; Ginebra, M P

    1998-01-01

    Calcium phosphate bone cements (CPBCs) are osteotransductive, i.e. after implantation in bone they are transformed into new bone tissue. Furthermore, due to the fact that they are mouldable, their osteointegration is immediate. Their chemistry has been established previously. Some CPBCs contain amorphous calcium phosphate (ACP) and set by a sol-gel transition. The others are crystalline and can give as the reaction product dicalcium phosphate dihydrate (DCPD), calcium-deficient hydroxyapatite (CDHA), carbonated apatite (CA) or hydroxyapatite (HA). Mixed-type gypsum-DCPD cements are also described. In vivo rates of osteotransduction vary as follows: gypsum-DCPD > DCPD > CDHA approximately CA > HA. The osteotransduction of CDHA-type cements may be increased by adding dicalcium phosphate anhydrous (DCP) and/or CaCO3 to the cement powder. CPBCs can be used for healing of bone defects, bone augmentation and bone reconstruction. Incorporation of drugs like antibiotics and bone morphogenetic protein is envisaged. Load-bearing applications are allowed for CHDA-type, CA-type and HA-type CPBCs as they have a higher compressive strength than human trabecular bone (10 MPa).

  12. Research Progress in Applications of Calcium Sulphoaluminate Modified Portland Cement%硫铝酸钙改性硅酸盐水泥应用研究进展∗

    Institute of Scientific and Technical Information of China (English)

    葛大顺; 马素花; 李伟峰; 于锦; 沈晓冬; 汤国芳; 蔡建; 管娟

    2015-01-01

    Calcium sulphoaluminate modified Portland cement clinker has excellent characteristics of ordinary Portland cement clinker and sulphoaluminate cement clinker.Meanwhile this cement clinker has superior stimulating effect for fly-ash.These advantages confer SMP broad application prospects.Herein,the properties and hydration characteristics of SMP are summarized,and the composite properties of SMP with different mineral admixtures and the adaptability of this cement with chemical admixtures are also discussed.In addittion,the existing problems of SMP and improvement measures are proposed.%硫铝酸钙改性硅酸盐水泥熟料兼具硅酸盐水泥熟料和硫铝酸盐水泥熟料的优良性能,同时该种水泥熟料对粉煤灰等火山灰类材料具有超强的活性激发效果,这使得硫铝酸钙改性硅酸盐水泥具有广阔的应用前景。主要概括了硫铝酸盐改性硅酸盐水泥的性能及水化特性,综述了该种水泥与不同矿物掺合料的复合性能以及与化学外加剂的适应性,提出了硫铝酸钙改性硅酸盐水泥存在的问题及改善措施。

  13. Influence of Burning Temperature and Components on the Mineral Formation of Pure Calcium Aluminate Cement%煅烧温度及配料组成对纯铝酸钙水泥矿物形成的影响

    Institute of Scientific and Technical Information of China (English)

    孔凡营; 刘晓存; 李艳君

    2004-01-01

    依据CaO-Al2O3二元相图,以高纯石灰石和工业氧化铝为原料,研究了嫩烧温度及配料组成对纯铝酸钙水泥矿物形成的影响.结果表明,对不同配比的试样,135O℃下煅烧,则存在较多的fCaO,除形成主要矿物CA及CA2外,还有少量C12A7形成;145O℃以上温度煅烧,fCaO基本吸收完全,随煅烧温度的提高,CA2的形成量增加;各配料组成经煅烧形成的矿物与理论计算相符,掺少量ZnO、BaO不能改善生料的易烧性.

  14. 水中高铝水泥对铝粉的水合作用的影响%Effect of Calcium Aluminate Cement in Water on Hydration of Aluminium Powder

    Institute of Scientific and Technical Information of China (English)

    刘爱云

    2006-01-01

    在水中添加少量(0.25%)的高铝水泥(CAC)可大大加速铝粉的水合作用.这是由于CAC导致天然Al2O3薄膜溶解而使溶液碱度增大,并出现早期水合作用产物,以及由于Al和CAC水合作用的加速释放出额外热量的缘故.这里讨论了在CAC结合的耐火浇注料中使用铝粉的意义.

  15. PREPARATION AND CHARACTERIZATION OF MACROPOROUS CALCIUM PHOSPHATE CEMENT SCAFFOLD WITH ORIENTED PORE STRUCTURE%具有定向孔隙结构的大孔磷酸钙骨水泥支架的制备与表征

    Institute of Scientific and Technical Information of China (English)

    漆小鹏; 叶建东; 王秀鹏; 王迎军

    2007-01-01

    A macroporous calcium phosphate cement scaffold with oriented pore structure is prepared by freeze casting. The pore structure and phases formed were evaluated by scanning electron microscope(SEM)and X-ray diffraction (XRD). The photographs of SEM show that the porous calcium phosphate cements have interconnected macropores aligned along the ice growth direction and the sizes of the open interconnected macropores can reach 150μm and 200 μm in their radial dimension and 500-1 000 μmn in the axial one. The pore size could be adjusted by the freezing parameters to match the requirements for bone tissue. The XRD patterns of the specimens show that poorly crystallized hydroxyapatite (HA) was the main phase present in the porous calcium phosphate cement.The porosity of the samples could be regulated from about 70% to 90% by the adjustment of the initial liquid to powder mass ratio.The macroporous calcium phosphate cement prepared in this work might be a potential scaffold for bone tissue engineering.%利用冷冻塑形法制备了具有定向孔隙结构的大孔磷酸钙骨水泥支架.利用扫描电镜(scanning electron microscope,SEM)和x射线衍射(X-ray diffraction,XRD)对材料的孔隙结构和物相进行了研究.SEM照片显示:多孔磷酸钙骨水泥具有与冰晶生长方向一致的相互连通的大孔.开口大孔的尺寸在径向能达到150~200 μm,在轴向能达到500~1 000 μm.孔隙的大小可以通过改变冷冻参数进行调节.XRD谱显示:多孔磷酸钙骨水泥中的主要相为弱结晶的羟基磷灰石.材料的孔隙率可以通过调整液固比在70%到90%之间进行调节.实验制备的大孔磷酸钙骨水泥支架是很有希望的骨组织工程支架材料.

  16. Study on the Injectable Magnesium-calcium Phosphate Cements%可注射镁基磷酸钙骨水泥的研究

    Institute of Scientific and Technical Information of China (English)

    戴红莲; 胡付俭; 方彩萍; 李世普

    2014-01-01

    Injectable magnesium-calcium phosphate cements (IMPC) was prepared using magnesium oxide (MgO), monopotassium phosphate (KH2PO4),β-tricalcium phosphate (β-TCP), glucose and phosphoric acid solution. The ef-fects of liquid to powder ratio(LPR), contents of MgO and glucose on IMPC’s gelling and mechanical properties were investigated. The results showed that increase of LPR and glucose content resulted in increased IMPC setting time and injectability, and decreased compressive strength. With the MgO content decreasing, the setting time and the in-jectability were decreased, whereas the compressive strength was increased. To obtain optimal formula for the new IMPC, the MgO and glucose contents and LPR were selected based on orthogonal experiments, and the result was 26wt% MgO, 6wt% glucose and 0.30 mL/g LPR. The new IMPC has moderate hydration with low exothermic reac-tion and ideal hardening performance, indicating that it may be used as a novel bone adhesive material.%采用MgO、KH2PO4、β-TCP、葡萄糖作为骨水泥的固相,磷酸溶液作为液相,制备可注射镁基磷酸钙骨水泥(IMPC)。考察液固比(LPR)、MgO含量、葡萄糖含量变化对IMPC胶凝性能和力学性能的影响。实验结果显示:液固比和缓凝剂葡萄糖含量增大均会导致凝结时间变长和抗压强度下降,但有益于可注射性;随 MgO 含量增大,凝结时间缩短,可注射率降低,但抗压强度提高。采用正交实验法确定MgO含量26wt%,液固比0.30 mL/g,葡萄糖含量6wt%时得到的IMPC综合性能良好,水化过程缓和,放热量低。该IMPC有望成为一种新型骨粘结材料。

  17. Prevascularization of a gas-foaming macroporous calcium phosphate cement scaffold via coculture of human umbilical vein endothelial cells and osteoblasts.

    Science.gov (United States)

    Thein-Han, WahWah; Xu, Hockin H K

    2013-08-01

    The lack of a vasculature in tissue-engineered constructs is currently a major challenge in tissue regeneration. There has been no report of prevascularization of macroporous calcium phosphate cement (CPC) via coculture of endothelial cells and osteoblasts. The objectives of this study were to (1) investigate coculture of human umbilical vein endothelial cells (HUVEC) and human osteoblasts (HOB) on macroporous CPC for the first time; and (2) develop a new microvasculature-CPC construct with angiogenic and osteogenic potential. A gas-foaming method was used to create macropores in CPC. HUVEC and HOB were seeded with a ratio of HUVEC:HOB=4:1, at 1.5×10(5) cells/scaffold. The constructs were cultured for up to 42 days. CPC with a porosity of 83% had a flexural strength (mean±SD; n=6) of 2.6±0.2 MPa, and an elastic modulus of 340±30 MPa, approaching the reported values for cancellous bone. Reverse transcription-polymerase chain reaction showed that HUVEC+HOB coculture on CPC had much higher vascular endothelial growth factor (VEGF) and collagen I expressions than monoculture (p<0.05). Osteogenic markers alkaline phosphatase, osteocalcin (OC), and runt-related transcription factor 2 (Runx2) were also highly elevated. Immunostaining of PECAM1 (CD31) showed abundant microcapillary-like structures on CPC in coculture at 42 days, as HUVEC self-assembled into extensive branches and net-like structures. However, no microcapillary was found on CPC in monoculture. In immunohistochemical staining, the neo-vessels were strongly positive for PECAM1, the von Willebrand factor, and collagen I. Scanning electron microscopy revealed microcapillary-like structures mingling with mineral nodules on CPC. Cell-synthesized minerals increased by an order of magnitude from 4 to 42 days. In conclusion, gas-foaming macroporous CPC was fabricated and HUVEC+HOB coculture was performed for prevascularization, yielding microcapillary-like structures on CPC for the first time. The novel

  18. Decomposition of supersaturated sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    陈启元; 李洁; 尹周澜; 张平民

    2003-01-01

    The decomposition of supersaturated sodium aluminate solution in the process of alumina production was reviewed. Some fundamental problems, such as the structure of supersaturated sodium aluminate solution and the growth unit of gibbsite precipitation as well as the decomposition mechanism of sodium aluminate solution, were investigated by model analytic technique and theoretical calculation. It is found that the main Al-contained species is S4 symmetric [Al(OH)4(H2O)4]-. [Na+(H2O)4*Al(OH)-4] is found to form in intermediate concentrated solution while [Na+(H2O)2*Al(OH)-4] in highly concentrated solution. Meanwhile, it is proved that [(H2O)2Al(OH)4]- is the basic growth unit of gibbsite and [Al6(OH)18(H2O)6] is a favorable growth unit. Based on above results and ab initio quantum mechanical calculation and transition state theory, a reaction pathway of the decomposition of supersaturated sodium aluminate solution was put forward, in which the transformation of pentacoordinate aluminates ion to hexacoordinate basic growth unit as well as the formation of circled growth unit [Al6(OH)22(H2O)2]4- are the controlling steps.

  19. Calcium phosphate bone cement containing ABK and PLLA. Sustained release of ABK, the BMD of the femur in rats, and histological examination

    Energy Technology Data Exchange (ETDEWEB)

    Kusaka, T.; Tanaka, A.; Sasaki, S.; Takano, I.; Tahara, Y.; Ishii, Y. [Kyorin Univ., Tokyo (Japan). Dept. of Orhtopaedic Surgery

    2001-07-01

    Bone cement was prepared by mixing CPC95 (Mitsubishi Material Co., Ltd.), ABK, and PLLA at a ratio of 14 : 1 : 2. In vitro, Antibiotic sustained release tests were performed by the total amount exchange method. In animal experiments, the bone cement was infused into the right femur of 18-month-old female SD rats. After 1, 2, 4, or 6 months, the BMD was determined by DXA in the bilateral femoral bones. In addition, hard tissue specimens were prepared, and the state of bone formation was observed. The release of the antibiotic was 1.73 {mu}g/ml until 18 days after administration, maintaining a concentration over the MIC80 for MRSA. In the animal experiments, the BMD significantly increased after 2 - 4 months. In the hard tissue specimens, direct binding on the bone-cement interface and bone formation in the cement were observed after 1 month. (orig.)

  20. Interaction of cerium and calcium-enriched phase in the preparation process of YG6 cemented carbide%铈与YG6硬质合金制备过程中富钙相的交互作用

    Institute of Scientific and Technical Information of China (English)

    何文; 谭敦强; 朱红波; 邝海; 欧阳国霞

    2016-01-01

    在硬质合金的原材料仲钨酸铵(APT)粉末中添加Ca和稀土Ce元素,探讨稀土Ce元素与硬质合金制备过程中富钙相的交互作用。材料的物相组成、显微结构及成分分别通过X射线衍射仪、扫描电子显微镜及能谱进行检测与分析。结果表明:氧化钨还原过程中会产生CaWO4和Ca4.26W10O30两种富钙相,分布在钨颗粒内部和周围,使钨颗粒的棱角钝化,碳化后富钙相转变为Ca4.26W10O30和CaC2相,富钙相可急剧降低YG6硬质合金的性能;添加适量稀土Ce可降低富钙相对钨粉的影响,钨粉颗粒的棱角变得明显,颗粒尺寸变小且分布均匀,稀土Ce与富钙相发生反应生成Ce0.9Ca0.1O1.9三元相;稀土Ce与富钙相的交互作用效果显著,与1% Ca-YG6硬质合金相比,1% Ce+1% Ca-YG6硬质合金的致密度、硬度和断裂韧性分别提高了7.8%,34.3%和67.8%。%The elements of Ca and rare earth Ce were added in APT powder. The interaction of rare earth element Ce with calcium-enriched phase was discussed during the preparation process of cemented carbide. The phase composition, microstructure and element distribution were tested by using X-ray diffractometer, scanning electron microscope and energy disperse spectroscopy, respectively. The results show that two kinds of calcium-enriched phases, CaWO4 and Ca4.26W10O30, are generated in the process of reducing tungsten oxide, which passivate tungsten particles. After carburization, calcium-enriched phases transform into the Ca4.26W10O30 and CaC2 phases. Calcium-enriched phases can sharply reduce the property of YG6 cemented carbide. Adding a moderate amount of rare earth Ce can decrease the influence of calcium-enriched phases on tungsten particles. The edges and corners of tungsten particles become more obvious, and the particle size of tungsten powders becomes smaller and uniform. During carburization process, rare earth Ce reacts with calcium-enriched phase and forms

  1. Influence of SO3 and SrO on Performance of Alite-Strontium Calcium Sulphoaluminate Cement%SO3与SrO对阿利特-硫铝酸锶钙水泥性能的影响

    Institute of Scientific and Technical Information of China (English)

    芦令超; 李秋英; 王守德; 程新

    2011-01-01

    Alite-strontium calcium sulphoaluminate cement(ASCSC) , a new type of cementitious material was synthesized by combining strontium calcium sulphoaluminate with minerals of Portland cement. The influence of excessive SO3 and SrO on the performances of this cement was studied by XRD, SEM-EDS, and lithofacies. The results show that the optimal excessive mass fraction of SO3 and SrO are 50% and 80% (by mass). The compressive strength of the cement prepared under these conditions reaches 32. 8, 66. 8, 126. 4 Mpa at 1,3,28 d. The additions of SO3 and SrO are beneficial to increase of content of stronti um calcium sulphoaluminate and promotion of the formation of alite at low temperature.%将硫铝酸锶钙矿物引入到硅酸盐熟料矿物体系中,合成了阿利特-硫铝酸锶钙水泥,改善了硅酸盐水泥的性能.利用X射线衍射、扫描电镜-能谱仪和岩相等测试手段,研究了过量掺加SO3和SrO对阿利特-硫铝酸锶钙水泥性能的影响.结果表明:熟料中SO3和SrO最佳过掺量分别为50%和80%(质量分数),制得的阿利特-硫铝酸锶钙水泥的1,3,28 d抗压强度分别达到32.8,66.8,126.4 MPa,具有良好的力学性能.SO3和SrO的过量掺入促进了硫铝酸锶钙矿物的形成,且有利于阿利特在低温下的形成.

  2. Influence of Dopamine on Physicochemical Properties of Calcium Phosphate Cement%多巴胺对磷酸钙骨水泥性能影响的研究

    Institute of Scientific and Technical Information of China (English)

    刘宗光; 屈树新; 赵军胜; 刘宇; 翁杰

    2013-01-01

    The aim of this study is to investigate effects of dopamine (DA) on physiochemical properties of calcium phosphate cement (CPC) and in vitro degradation of DA from CPC. DA was dissolved in Tris (Hydroxymethyl) aminomethane-hydrochloric acid buffer solution and mixed the solution with CPC powders after oxidized for 2 d in air. Orthogonal test was used to optimize the preparation of CPC with respect to the DA concentration, ratio of liquid to solid and pH values. Compressive tests, Gilmore needle tests, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) were used to characterize the physiochemical properties of CPC. Scanning electron microscope (SEM) and UV-Vis spectrophotometry were used to observe the micro-morphology of CPC and ire vitro degradation of DA from CPC, respectively. Compressive test and orthogonal analysis indicated that the optimal combination CPC was DA concentration 40 rng·mL-1, ratio of liquid to solid 0.3 mL·g-1 and pH value 8.5, which had the highest compressive strength with significant difference (p<0.01) compared with that of CPC-Blank. Setting time of the optimal combination CPC decreased slight but no significant difference compared to that of CPC-Blank, which could satisfied with the clinical demands. XRD and FTIR demonstrated that the addition of DA promoted the conversion of dicalcium phosphate dehydrate (DCPD).SEM found that there were more platy structure, lots of nubbly crystals and less porosity in optimal combination CPC compared with CPC-Blank. Cumulative release of DA from CPC was 29.7% and the pH values of immersion solution were safe for human body during in vitro degradation.%本论文研究含儿茶酚的多巴胺对磷酸钙骨水泥(calcium phosphate cement,CPC)的理化性能和体外降解的影响.将多巴胺溶于Tris-HCl缓冲液于空气中氧化2d,作为液相与固相粉末混合成型.选取多巴胺浓度、液固比、pH值三因素,通过正交试验选取最

  3. Aluminizing Low Carbon Steel at Lower Temperatures

    Institute of Scientific and Technical Information of China (English)

    Xiao Si; Bining Lu; Zhenbo Wang

    2009-01-01

    This study reports the significantly enhanced aluminizing behaviors of a low carbon steel at temperatures far below the austenitizing temperature, with a nanostructured surface layer produced by surface mechanical attrition treatment (SMAT). A much thicker iron aluminide compound layer with a much enhanced growth kinetics of η-Fe2Al5 in the SMAT sample has been observed relative to the coarse-grained steel sample. Compared to the coarse-grained sample, a weakened texture is formed in the aluminide layer in the SMAT sample. The aluminizing kinetics is analyzed in terms of promoted diffusivity and nucleation frequency in the nanostructured surface layer.

  4. Cement Formation

    DEFF Research Database (Denmark)

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

    2012-01-01

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

  5. A note on cement in asteroids

    Science.gov (United States)

    Bilalbegović, G.

    2016-09-01

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

  6. A note on cement in asteroids

    CERN Document Server

    Bilalbegovic, G

    2016-01-01

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

  7. Determination of strontium and simultaneous determination of strontium oxide, magnesium oxide and calcium oxide content of Portland cement by derivative ratio spectrophotometry.

    Science.gov (United States)

    Idriss, K A; Sedaira, H; Ahmed, S S

    2009-04-15

    A derivative spectrophotometric method has been developed for the determination of strontium in Portland cement. The method is applied successfully for the simultaneous determination of SrO, MgO and CaO. It is based on the use of Alizarin Complexone (AC) as a complexing agent and measurement of the derivative ratio spectra of the analytes. Interferences of manganese(II) and zinc(II) were eliminated by precipitation. The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The strontium complex formed at pH 9.5 allows precise and accurate determination of strontium over the concentration range of 1.5-18 mg L(-1) of strontium. The MDL (at 95% confidence level) was found to be 25 ng mL(-1) for strontium in National Institute of Standards and Technology (NIST) cement samples using the proposed method.

  8. 可注射磷酸钙骨水泥的流变性能研究%Study on the Rheological Properties of Injectable Calcium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    陈芳萍; 刘昌胜

    2012-01-01

    The influence of additives on the theological properties of injectable calcium phosphate cement (ICPC) was investigated with an advanced expansion system rheometer. During the measurement of steady rheological properties, the viscosity, shear stress, and thixotropy were detected. During dynamic oscillation testing, the viscoelastic response of the ICPC under forced oscillation and the internal structure were unvailled. The results indicated that the ICPC showed both plastic and thixotropic behavior with little effect by additives. The introduction of these water-soluble polymers improved the viscosity and thixotropy of the ICPC, which are conducive to the stability of the whole system. These additives improve the recoverability and stability of the ICPC network after being sheared, in which xanthan gum and chitosan were the most obvious. On this basis, the time to form a gel was assessed to be in the range of 2 563 ~ 2 600 s for xanthan gum-ICPC system. In addition, with the increasing of xanthan gum contents, the thixotropic loop area of ICPC enlarged, but the for- mation of network structure was not stable under high shear condition.%采用高级流变扩展系统研究了添加剂种类及其含量对可注射磷酸钙骨水泥(ICPC)流变特性的影响。采用稳态流动实验表征浆体的静态粘度,用触变环面积、应力降低率和屈服应力表征ICPC浆体的触变性,并进行动态频率扫描和动态时间扫描实验动态监测ICPC的粘、弹、塑性变化规律以及水化反应过程流变参数的依时性。结果表明:添加剂并不改变ICPC的粘弹性。水溶性高分子化合物的加入提高了ICPC的粘度和触变性,利于整个体系的稳定;添加剂不同程度上提高了ICPC剪切后的网络结构恢复能力和稳定性,尤其以黄原胶和几丁糖最为明显。在此基础上,评估了加入黄原胶后ICPC形成凝胶的时间,约为2563~2600s。此外,随着黄原胶含量的增加

  9. A Controlled New Process of Pack Aluminization

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhi-rong; MA Liu-bao; LI Pei-ning; XU Hong

    2004-01-01

    Aluminum diffusion coatings are often prepared by a pack aluminization technique, which is a specific variety of chemical vapor deposition (CVD) method. The coating process takes place in a bed containing a mixed powder that serves as a source of the coatings forming element. The phase composition of the diffusion layer obtained depends on the activity of the Al during the pack aluminization processing. In this work, the proportion of Al to special additive powder in the pack and the treatment temperature are adjusted to achieve the desired surface composition of aluminized layer. The aluminized 20 plain carbon steel and HK40 austenitic steel were investigated by optical microscopy (OM) , X-ray diffraction (XRD)and microsclerometer. The results showed that the desired FeAl, Fe3Al and NiAl were respectively formed on the 20 plain carbon steel and HK40 austenitic steel, and the aluminides FeAl3, Fe2Al5 or Ni2Al3, NiAl3 could be inhibited.

  10. A Controlled New Process of Pack Aluminization

    Institute of Scientific and Technical Information of China (English)

    HUANGZhi-rong; MALiu-bao; LIPei-ning; XUHong

    2004-01-01

    Aluminum diffusion coatings are often prepared by a pack aluminization technique, which is a specific variety of chemical vapor deposition (CVD) method. The coating process takes place in a bed containing a mixed powder that serves as a source of the coatings forming element. The phase composition of the diffusion layer obtained depends on the activity of the Al during the pack aluminization processing. In this work, the proportion of Al to special additive powder in the pack and the treatment temperature are adjusted to achieve the desired surface composition of aluminized layer. The aluminized 20 plain carbon steel and HK40 austenitic steel were investigated by optical microscopy (OM) , X-ray diffraction (XRD) and microsclerometer. The results showed that the desired FeAl, Fe3Al and NiAl were respectively formed on the 20 plain carbon steel and HK40 austenitic steel, and the aluminides FeAl3, Fe2Al5 or Ni2Al3, NiAl3 could be inhibited.

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

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, A., E-mail: aguerrero@ietcc.csic.es [Eduardo Torroja Institute for Construction Science (CSIC), C/Serrano Galvache, 4, 28033 Madrid (Spain); Goni, S., E-mail: sgoni@ietcc.csic.es [Eduardo Torroja Institute for Construction Science (CSIC), C/Serrano Galvache, 4, 28033 Madrid (Spain); Allegro, V.R., E-mail: allegro@ietcc.csic.es [Eduardo Torroja Institute for Construction Science (CSIC), C/Serrano Galvache, 4, 28033 Madrid (Spain)

    2009-06-15

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

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

    Science.gov (United States)

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

    2009-06-15

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

  13. Eu(2+) luminescence in strontium aluminates.

    Science.gov (United States)

    Dutczak, D; Jüstel, T; Ronda, C; Meijerink, A

    2015-06-21

    The luminescence properties of Eu(2+) doped strontium aluminates are reported and reviewed for a variety of aluminates, viz. SrAl12O19, SrAl4O7, Sr4Al14O25, SrAl2O4 and Sr3Al2O6. The aim of the research is to investigate the role of local coordination and covalency of the aluminate host lattice, related to the Sr/Al ratio, on the optical properties of the Eu(2+) ion. The UV and VUV excited luminescence spectra as well as luminescence decay curves were recorded to characterize the luminescence properties of the investigated aluminates. The emission of Eu(2+) ions varies over a wide spectral range, from ultraviolet (UV) to red, for the series of aluminates. The variation in emission color can be related to the crystal-field splitting of the 5d levels and the covalent interaction with the surrounding oxygen anions. In the least covalent material, viz. SrAl12O19:Eu(2+), narrow line emission due to the (6)P7/2-(8)S7/2 transition occurs at 4 K, indicating that the 4f(6)5d excited state is situated above the (6)P7/2(4f(7)) excited state around 360 nm. The most alkaline material, viz. Sr3Al2O6:Eu(2+) is the most covalent host and exhibits several d-f emission bands in the yellow to red spectral range due to the Eu(2+) ions located on different crystallographic Sr(2+) sites. The Eu(2+) emission spectra in the other aluminates confirm the trend that with increasing Sr/Al ratio the Eu(2+) emission shifts to longer wavelengths. Interesting differences are observed for the Eu(2+) from different crystallographic sites which cannot always be related with apparent differences in the first oxygen coordination sphere. The discussion gives insight into how in a similar class of materials, strontium aluminates, the emission color of Eu(2+) can be tuned over a wide spectral region.

  14. Ni2+ treatment causes cement gland formation in ectoderm explants of Xenopus laevis embryo

    Institute of Scientific and Technical Information of China (English)

    HUANGYONG; XIAOYANDING

    1999-01-01

    We found T-type calcium channel blocker Ni2+ can efficiently induce the formation of cement gland in Xenopus laevis animal cap explants.Nother T-typer specific calcium channel blocker Amiloride can also induce the formation of cement gland,while L-type specific calcium channel blocker Nifedipine as no inductive effect.These results may offer us an new approach to study the differentiation of cement gland through the change of intracelluar calcium concentration.

  15. Phosphate based oil well cements

    Science.gov (United States)

    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.

  16. 新型可注射可降解磷酸钙骨水泥的生物相容性*☆%Biocompatibility of a novel injectable and degradable calcium phosphate cement

    Institute of Scientific and Technical Information of China (English)

    段昕; 廖红兴; 邹华章; 张紫机; 张浩; 张志奇; 叶建东; 廖威明

    2013-01-01

    BACKGROUND: A novel calcium phosphate bone cement has been proved to have good injectability, biomechanical properties, anti-col apsibility and in vitro degradability. OBJECTIVE: To evaluate the biocompatibility of a novel injectable and degradable calcium phosphate cement. METHODS: (1) In acute toxicity test, cement extracts were applied to mice by tail vein injection. (25) In pyrogen test, extracts were applied to rabbits by mainline. (3) In hemolysis test, extracts were added in the fresh anticoagulant blood of rabbits. (4) In delayed-type hypersensitivity test, two steps, induced and aroused were applied to guinea pigs. (5) In cytotoxicity test in vitro, extracts of cement, polyethylene, and phenol were added in L929 cells to evaluate cytotoxicity. (6) In mammal micronucleus test, extracts, normal saline and cyclophosphamide were applied to mice by intraperitoneal injection. (7) In muscular implantation test, muscle specimens were histologically evaluated. RESULTS AND CONCLUSION: The cement-extracted liquid induced no acute toxicity in mice, no pyrogenic reaction in rabbits, no genetic toxicity in mice or allergic reaction in guinea pigs. This novel cement had a great biocompatibility and biological safety.%  背景:体外实验已证实新型磷酸钙骨水泥有良好的可注射性、力学性能、抗溃散性及体外降解性能。目的:验证新型可注射、可降解磷酸钙骨水泥的生物相容性。方法:①急性毒性实验:分别向昆明小鼠尾静脉可注射新型磷酸钙骨水泥浸提液与生理盐水。②热源实验:在新西兰兔耳缘静脉注射新型磷酸钙骨水泥浸提液。③溶血实验:在兔抗凝血分别加入新型磷酸钙骨水泥浸提液、生理盐水及双蒸水。④迟发型超敏反应实验:在豚鼠肩胛骨内侧部位分别注射可注射新型磷酸钙骨水泥浸提液与生理盐水,并进行敷贴激发实验。⑤体外细胞毒性实验:在L929系小鼠成纤维细胞株

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

    Science.gov (United States)

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

    2015-01-01

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

  18. DRYING SHRINKAGE AND MECHANICAL PROPERTY OF ALITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT MORTAR%阿利特-硫铝酸钡钙水泥砂浆的力学性能和干缩性能

    Institute of Scientific and Technical Information of China (English)

    刘鹏; 周宗辉; 程新; 单立福; 张云飞

    2008-01-01

    通过与硅酸盐水泥(portland cement,PC)对比,研究了阿利特-硫铝酸钡钙水泥(alite-barium calcium sulphoaluminate cement,SABC)砂浆的力学性能和干缩性能.采用X射线衍射和扫描电镜对养护28 d SABC砂浆水化产物的物相组成、形貌以及硬化砂浆的微观结构进行了分析和观察,用压汞法对硬化砂浆的孔结构进行了分析.结果表明:SABC砂浆具有较高的早期强度,添加适量掺合料的可以提高砂浆的强度.且添加矿渣的效果更显著.由于SABC的微膨胀性能,使其砂浆的干缩性能优于pC砂浆.用≤20%(质量分数,下同)矿渣和粉煤灰取代SABC后,可以减小砂浆的干缩率,当取代量超过20%后干缩率随之增大;与掺加矿渣的SABC砂浆的干缩率相比,加入粉煤灰的SABC砂浆干缩率较小.

  19. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Y. S.; Stevenson, Jeffry W.; Singh, Prabhakar

    2008-12-01

    A novel high-temperature alkaline-earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  20. Comparative evaluation of the calcium release from mineral trioxide aggregate and its mixture with glass ionomer cement in different proportions and time intervals – An in vitro study

    Directory of Open Access Journals (Sweden)

    Surbhi Sawhney

    2015-10-01

    Conclusions: Adding GIC to improve the setting time and handling properties of the MTA powder can be detrimental to the calcium-releasing ability of the resultant mixture, depending on the proportion of GIC added. Adding MTA and GIC at a proportion of 2:1 by volume did not impact calcium release from the mixture. These findings should be verified through further clinical studies.

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

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, E.

    2015-07-01

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

  2. The aluminizing in powder technology of AISI 304 steel

    Science.gov (United States)

    Băitanu, D. B.; Găluşcă, D. G.; Achiţei, D. C.; Minciună, M. G.; Bakri Abdullah, Mohd Mustafa Al

    2016-06-01

    The paper presents a study about the aluminizing treatments applied to AISI 304 stainless steel, with the purpose to improve the corrosion resistance. The aluminizing is realized in a powder medium, composed by aluminium powder (with 99.95% purity), aluminium oxide Al2O3 and ammonium chloride NH4Cl. The structural characterization was made by scanning electronic microscopy to highlight the structure of layer after aluminizing, at different magnitudes.

  3. Development of electrodialysis process for aluminous solutions

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

  4. Development of electrodialysis process for aluminous solutions

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

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

  5. Influence of Cellulose Ethers on Hydration Products of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin

    2011-01-01

    Cellulose ethers are widely used to mortar formulations, and it is significant to understand the interaction between cellulose ethers and cement pastes. FT-IR spectra, thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article. The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste, but the major hydration products, such as CH (calcium hydroxide), ettringite and C-S-H, appeared later in the modified cement pastes than in the unmodified cement paste. The cellulose ethers decrease the outer products and increase inner products of C-S-H gels. Compared to unmodified cement pastes, no new products are found in the modified cement pastes in the present experiment. The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

  6. Interaction of calcium silicate hydrates (C-S-H), the main components of cement, with alkaline chlorides, analogy with clays; Interaction des silicates de calcium hydrates, principaux constituants du ciment, avec les chlorures d'alcalins. Analogie avec les argiles

    Energy Technology Data Exchange (ETDEWEB)

    Viallis-Terrisse, H

    2000-10-06

    This work, belonging to a more general study on the structure and reactivity of cement, deals with the experimental and theoretical analysis of the interaction of alkaline chlorides with calcium silicate hydrates (C-S-H), the main components of cement paste. The interaction of alkaline cations with C-S-H is interfacial, involving both electrostatic and surface complexation mechanisms. The C-S-H surface is constituted of silanol sites, partially dissociated due to the high pH of the interstitial solution. The calcium ions, present in large amounts in the equilibrium solution of C-S-H, constitute potential determining ions for the C-S-H surface. The alkaline ions seem to compete with calcium for the same surface sites. The adsorption isotherms show that caesium presents a better affinity than sodium and lithium for the C-S-H surface. Moreover, solid-state NMR suggests that caesium forms with the surface sites inner-sphere complexes, whereas sodium seems to keep its hydration sphere. These results are in agreement with zeta potential measurements, which let suppose a specific adsorption of caesium ions, and an indifferent behaviour of both other alkaline ions. A model for the C-S-H surface was proposed, from the electric double layer model, and mass action laws expressing the complexation of the different ionic species with the silanol sites. The whole study relies on a structural analogy with smectites, some clays presenting well-known cationic adsorption properties. The structural similarity between both minerals is enhanced by some similarities of reactivity, though significant behaviour differences could also be noted. (author)

  7. Effect of polycarboxylate admixture structure on cement paste rheology

    Directory of Open Access Journals (Sweden)

    Aranda, M. A. G.

    2007-06-01

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

  8. Structure and performance of injectable strontium-contained collagen calcium phosphate cement%一种可注射自固化含锶复合胶原磷酸钙骨水泥的结构和性能

    Institute of Scientific and Technical Information of China (English)

    叶冬平; 周子强; 梁伟国

    2009-01-01

    BACKGROUND: Orthopedic academics are committed to the modification of calcium phosphate cement (CPC) by adding different additives, including the promotion of curing agents, plasticizers, anti-water blood solvent, porogen, enhancer, or biological activity substance or drug compound to the CPC in order to enhance its physical and chemical and biological properties which is a research hotspot in the field. OBJECTIVE: To investigate the physical and chemical characteristics of a biodegradable injectable CPC. DESIGN, TIME AND SETTING: Duplicated testing study was performed at the National Key Laboratory, College of Materials, South China University of Technology from December 2008 to May 2009. MATERIALS: Calcium phosphate with partial crystallization and strontium phosphate and calcium hydrogen phosphate dehydrate with partial crystallization were added with modified starch and type I collagen to prepare a new type of self-injectable CPC. METHODS: CPC phase was analyzed using X'Pert Pro X-ray diffractometer; CPC morphology was observed using HITA2 -CHIH-800 transmission/scanning electron microscope; setting-up time was tested using Vicat apparatus according to A S TM C190203 standard; compressive strength was measured using Instron 5567 omnipotent electron apparatus; syringeability was detected using syringe apparatus with 1.6 mm of inside diameter; collapsibility was tested using soaking-shaking quantitative materials. MAIN OUTCOME MEASURES: Phase component and microstructure of CPC products, setting-up time, syringeability, compressive strength, and collapsibility. RESULTS: The material coul be injected with an excellent performance, and the modified starch significantly improved the resistance of bone cement collapsibility. As the bone cement liquid-solid ratio increased, the compressive strength of cement decreased. When the bone cement liquid-solid ratio was 0.3, the compressive strength for cement was (48.0±2.3) MPa when the bone cement liquid-solid ratio was 0

  9. Mortar and concrete based on calcium sulphate binders

    NARCIS (Netherlands)

    Bakker, J.J.F.; Brouwers, H.J.H.

    2006-01-01

    In this study both hemi-hydrate and anhydrite are tested as calcium sulphate binders for structural mortar and concrete. The advantage of using calcium sulphates instead of cement as a binder is the fact that the production of calcium sulphate is more environmental friendly than that of cement. For

  10. Comparing the reinforcing effects of a resin modified glassionomer cement, Flowable compomer, and Flowable composite in the restoration of calcium hydroxide-treated immature roots in vitro

    OpenAIRE

    S Prathibha Rani

    2011-01-01

    One hundred and sixty human permanent central incisors were enlarged to a 120 file size after crown removal procedure to simulate immature teeth. The root canals were filled with calcium hydroxide and stored for 15 days (phase I), 30 days (phase II), 90 days (phase III), and 180 days (Phase IV). At the end of these selected time periods, calcium hydroxide was cleaned off the root canals of forty teeth that were randomly selected and obturated with gutta-percha points in the apical 2 mm of the...

  11. Aluminizing Coating and Aluminizing-Y2O3 Coating Deposited by Pulsed Spark

    Institute of Scientific and Technical Information of China (English)

    何业东; 黄祖芬; 王德仁; 齐惠滨; 高 高唯

    2001-01-01

    Aluminizing coating and aluminizing-dispersed Y2O3 composite coating were prepared on 20 steel specimens by pulsed spark technique, which exhibited a micro-crystallized structure with grain size in the range of several ten to several hundred nanometers. It is shown that, after oxidation at 600 ℃ in air for 100 h, these two kinds of coatings have excellent resistance to high temperature oxidation and scale spallation, and the aluminizing-dispersed Y2O3 composite coating has even better property than the aluminizing coating. AFM, SEM, EDS and XRD were applied to analyze the surface morphology, composition and phases structure of these coatings and the oxide scale formed in oxidation. The mechanism for these coatings that how to enhance the oxidation resistance and scale spallation resistance was discussed by considering the factors, such as Al concentration on the selective oxidation of Fe-Al alloy, the effect of micro-crystallization, reactive element effect (REE) caused by dispersed Y2O3, etc.

  12. Quantitative X-ray pair distribution function analysis of nanocrystalline calcium silicate hydrates: a contribution to the understanding of cement chemistry

    Science.gov (United States)

    Grangeon, Sylvain; Baronnet, Alain; Marty, Nicolas; Poulain, Agnieszka; Elkaïm, Erik; Roosz, Cédric; Gaboreau, Stéphane; Henocq, Pierre; Claret, Francis

    2017-01-01

    The structural evolution of nanocrystalline calcium silicate hydrate (C–S–H) as a function of its calcium to silicon (Ca/Si) ratio has been probed using qualitative and quantitative X-ray atomic pair distribution function analysis of synchrotron X-ray scattering data. Whatever the Ca/Si ratio, the C–S–H structure is similar to that of tobermorite. When the Ca/Si ratio increases from ∼0.6 to ∼1.2, Si wollastonite-like chains progressively depolymerize through preferential omission of Si bridging tetrahedra. When the Ca/Si ratio approaches ∼1.5, nanosheets of portlandite are detected in samples aged for 1 d, while microcrystalline portlandite is detected in samples aged for 1 year. High-resolution transmission electron microscopy imaging shows that the tobermorite-like structure is maintained to Ca/Si > 3.

  13. Computational Material Modeling of Hydrated Cement Paste Calcium Silicate Hydrate (C-S-H) Chemistry Structure - Influence of Magnesium Exchange on Mechanical Stiffness: C-S-H Jennite

    Science.gov (United States)

    2015-04-27

    material chemistry structure are studied following a molecular dynamics (MD) computational modeling methodology. Calcium ions are replaced with... chemistry structure. Conference Name: 1st Pan-American Conference on Computational Mechanics Conference Date: April 27, 2015 1st Pan-American Congress on...MODELING OF C-S-H Material chemistry level modeling following the principles and techniques commonly grouped under Computational Material Science is

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-08-30

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

  15. The Use of Natural Pozzolan in Concrete as an Additive or Substitute for Cement

    Science.gov (United States)

    2011-12-01

    industrial processes such manufacturing steel can also take the form of a pozzolan, and this type is currently used as a concrete admixture. Another...Residue (%) 0.32 0.75 Blaine Fineness (m2/kg) 320 260 a Typical value (Mindess 1981). b When Tricalcium aluminate is more than 8%. (Tricalcium... aluminate = 2.650*% Al2O3 - 1.692 *% Fe2O3 = 2.650*5.68 - 1.692*3.98 = 8.32). Table 15. Particle size distribution of Portland cement. Cilas sieves (µm

  16. Integration of calcium and chemical looping combustion using composite CaO/CuO-based materials.

    Science.gov (United States)

    Manovic, Vasilije; Anthony, Edward J

    2011-12-15

    Calcium looping cycles (CaL) and chemical looping combustion (CLC) are two new, developing technologies for reduction of CO(2) emissions from plants using fossil fuels for energy production, which are being intensively examined. Calcium looping is a two-stage process, which includes oxy-fuel combustion for sorbent regeneration, i.e., generation of a concentrated CO(2) stream. This paper discuss the development of composite materials which can use copper(II)-oxide (CuO) as an oxygen carrier to provide oxygen for the sorbent regeneration stage of calcium looping. In other words, the work presented here involves integration of calcium looping and chemical looping into a new class of postcombustion CO(2) capture processes designated as integrated CaL and CLC (CaL-CLC or Ca-Cu looping cycles) using composite pellets containing lime (CaO) and CuO together with the addition of calcium aluminate cement as a binder. Their activity was tested in a thermogravimetric analyzer (TGA) during calcination/reduction/oxidation/carbonation cycles. The calcination/reduction typically was performed in methane (CH(4)), and the oxidation/carbonation stage was carried out using a gas mixture containing both CO(2) and O(2). It was confirmed that the material synthesized is suitable for the proposed cycles; with the very favorable finding that reduction/oxidation of the oxygen carrier is complete. Various schemes for the Ca-Cu looping process have been explored here that would be compatible with these new composite materials, along with some different possibilities for flow directions among carbonator, calciner, and air reactor.

  17. Investigation of the reactions of chlorides binding to aluminates using XRD and DTA methods

    Directory of Open Access Journals (Sweden)

    Bikić Farzet H.

    2009-01-01

    Full Text Available The reactions of chlorides binding to aluminates were investigated by analyzing the monochloroaluminate hydrate, product of the reaction. The results show that the product is formed in the fresh concrete, after adding chloride within the stage of the preparation of concrete, as well as adding chlorides by penetration from the environment into the concrete. The obtained results are significant, considering the aspect of preventing corrosion of the steel reinforcement into the concrete. It is known that only free chlorides activate corrosion processes in the steel reinforcement in concrete. The process of chloride bonding is followed by X-ray diffraction (XRD and differential thermal (DTA analysis of samples of the cement paste, which is the process of preparation and care is described in detail in this work.

  18. Development of a novel cement by conversion of hopeite in set zinc phosphate cement into biocompatible apatite.

    Science.gov (United States)

    Horiuchi, Shinya; Asaoka, Kenzo; Tanaka, Eiji

    2009-01-01

    Synthetic bone cement that has zinc oxide core particles covered with hydroxyapatite (HAP) was developed; that is, the conversion of hopeite, the traditional zinc phosphate cement, into HAP was attempted. Here, hopeite is the final product of the reaction between powders and trituration liquid of the traditional zinc phosphate cement. This cement may have many advantages not only in terms of biological functions but also the setting process of the traditional cement and the mechanical properties of the developed compact if the hopeite can be converted into calcium phosphate (CP). In this study, calcium nitrate solutions of various concentrations were used for the conversion of hopeite crystals into CP. The products after the solution treatment were analyzed by X-ray diffractometry (XRD), Fourier transform infrared spectrometry (FTIR), and scanning electron microscope (SEM) observation. These results indicated that the converted scholzite crystals could be partially detected. Several types of set zinc phosphate cement with different P/L ratios were arranged. The surface products of the set cement after the solution treatment were analyzed by XRD. However, the crystal phase such as hopeite was not detected except for zinc oxide. The set cement, which was treated with the calcium nitrate solution, was immersed in simulated body fluid (SBF). HAP-like crystals on the set cement could be detected for the specimens immersed for 4 weeks. These findings suggested that the binding phase in the set cement could be converted into HAP by immersion in SBF.

  19. 低温施工用快硬水泥的配方及性能试验研究%Low-temperature construction with rapid hardening cement formulations and performance test study

    Institute of Scientific and Technical Information of China (English)

    莫富治; 肖展瑜

    2013-01-01

      通过试验确定了一种以硫铝酸盐水泥熟料为主要成分的低温施工用快硬水泥的配方,在5℃的低温环境下试验,结果表明该配方水泥不需添加任何外加剂,按普通混凝土常温施工方法进行施工养护,不需实施任何冬期施工措施,1d抗压强度可达拆除模板要求,后期强度能继续增长。该配方水泥在低温下正常快速硬化主要机理为:硅酸盐水泥熟料和生石灰能快速释放出Ca(OH)2,天然二水石膏能快速释放出CaSO4, Ca(OH)2和CaSO4与硫铝酸盐水泥熟料中的主要矿物4(CaO)・3(Al2O3)・SO3(无水硫铝酸钙)迅速反应生成大量的钙矾石,加上硫铝酸盐水泥低温水化硬化专用催化剂——亚硝酸钠的作用,水泥奖体快速硬化。天然硬石膏溶解速度比天然二水石膏缓慢,在天然二水石膏用尽之后与无水硫铝酸钙等继续发生水化反应,使水泥硬化体后期强度不断增长。%Determined a formula of which a sulfur aluminate cement clinker as the main ingredient and low temperature construction with rapid hardening cement by experiment. At 5 ° C low-temperature environment test, the results show that the formulation of cement don’t need to add any admixtures, Construction maintenance is used by Ordinary concrete construction method at room temperature, Don’t need to implement any winter construction measures, 1d compressive strength up to the removal of the template requirements and the late strength can continue to grow. The main mechanism of the formulation normal and rapid hardening cement at low temperatures:Portland cement clinker and quicklime rapid release of Ca (OH) 2, Natural dihydrate gypsum quick release CaSO4, Ca (OH) 2 and CaSO4 sulphoaluminate cement clinker mineral 4 (CaO) 3 (Al2O3) SO3 (anhydrous calcium sulphoaluminate) rapid responsegenerate large amounts of ettringite, Plus sulfur the aluminate cement hypothermia hydration hardened special catalyst-the role of sodium

  20. The effect of pulpotomy using a calcium-enriched mixture cement versus one-visit root canal therapy on postoperative pain relief in irreversible pulpitis: a randomized clinical trial.

    Science.gov (United States)

    Asgary, Saeed; Eghbal, Mohammad Jafar

    2010-07-01

    The purpose of this noninferiority trial was to compare postoperative pain relief after one-visit root canal therapy (ORCT) with a pulpotomy performed with a new endodontic calcium-enriched mixture cement (PCEM) in human permanent molars with irreversible pulpitis. A total of 407 selected patients were randomly allocated into the ORCT group (n = 202) or the PCEM group (n = 205). Numerical Rating Scale questionnaires were used to record pain intensity (PI) by the patients during the first 7 days after treatment. While there was no statistically significant difference in the mean PI at baseline between the two study groups (P = 0.45), changes in mean PI were significantly different between them (P < 0.001). In the ORCT group, pain relief was achieved after 36 h [95% confidence interval (CI), 27.00-45.00], compared to 18 h in the PCEM group (95% CI, 15.00-21.00), a significant difference (P < 0.01). Comparison of the mean PI sum recorded over 7 days showed that patients in the ORCT group experienced significantly more pain than those in the PCEM group (P < 0.001); a similar difference was observed for pain in response to percussion tests (P < 0.001). Treatment with PCEM thus had the better pain-reducing effects than ORCT in irreversible pulpitis cases.

  1. Study on the Implantation of Nano-calcium Phosphate Bone Cement to Canine Artificial Furcation Defects%纳米骨水泥修复根分叉病变的实验研究

    Institute of Scientific and Technical Information of China (English)

    陈晓玲; 陈作良; 冯祖德; 闫福华; 程筠

    2009-01-01

    目的:研究纳米骨水泥修复犬慢性牙周组织缺损.方法:将3只成年Beagle犬形成慢性Ⅱ度根分叉病变模型,按拉丁方设计方法分成3组,每组6颗牙,分别采用引导组织再生治疗术(Guided tissue regeneration,GTR)+纳米骨水泥(nano-calcium phosphate bone cement,CPC)、GTR+珊瑚羟基磷灰石人造骨(coralline hydroxyapatite por-ous,CHAP)、GTR进行移植修复治疗.12周观察牙周组织再生情况.结果:组织学观察GTR+CPC组牙槽骨、牙骨质和牙周组织的修复再生效果明显优于GTR组(P<0.05).X线片显示:GTR+CPC组骨缺损处骨质生长情况优于其他两组.结论:应用GTR技术结合纳米骨水泥移植可显著促进狗牙根分叉处牙周组织缺损的再生.

  2. Use of a strontium-enriched calcium phosphate cement in accelerating the healing of soft-tissue tendon graft within the bone tunnel in a rabbit model of anterior cruciate ligament reconstruction.

    Science.gov (United States)

    Kuang, G M; Yau, W P; Lu, W W; Chiu, K Y

    2013-07-01

    We investigated whether strontium-enriched calcium phosphate cement (Sr-CPC)-treated soft-tissue tendon graft results in accelerated healing within the bone tunnel in reconstruction of the anterior cruciate ligament (ACL). A total of 30 single-bundle ACL reconstructions using tendo Achillis allograft were performed in 15 rabbits. The graft on the tested limb was treated with Sr-CPC, whereas that on the contralateral limb was untreated and served as a control. At timepoints three, six, nine, 12 and 24 weeks after surgery, three animals were killed for histological examination. At six weeks, the graft-bone interface in the control group was filled in with fibrovascular tissue. However, the gap in the Sr-CPC group had already been completely filled in with new bone, and there was evidence of the early formation of Sharpey fibres. At 24 weeks, remodelling into a normal ACL-bone-like insertion was found in the Sr-CPC group. Coating of Sr-CPC on soft tissue tendon allograft leads to accelerated graft healing within the bone tunnel in a rabbit model of ACL reconstruction using Achilles tendon allograft.

  3. Aluminizing and boroaluminizing treatments of Mar-M247 and their effect on hot corrosion resistance in Na2SO4-NaCl molten salt

    Science.gov (United States)

    Cho, J. H.; Kim, T. W.; Son, K. S.; Yoon, J. H.; Kim, H. S.; Leisk, G. G.; Mitton, D. B.; Latanision, R. M.

    2003-06-01

    The effect of surface modifications of Mar-M247 superalloy on hot corrosion resistance was examined in Na2SO4-NaCl molten salt. The Mar-M247 was aluminized and boroaluminized by pack cementation in Ar and underwent a cyclic hot corrosion test in Na2SO4-NaCl molten salt. The XRD results showed that a Ni2Al3 phase was formed between the aluminized layer and the substrate when the surface modification temperature was below 1273 K. However, a NiAl phase formed when the temperature was above 1273 K. The intensity of the XRD peak in the NiAl phase increased after post heat treatment. Hot corrosion resistance increased for the specimens containing NiAl rather than Ni2Al3 phase. The ductile NiAl phase suppressed the potential for crack initiation during thermal cycling. Post heat treatment increased the corrosion resistance of the aluminized layer for Mar-M247, which underwent surface modification at 1273 K and above. In the boroaluminized Mar-M247 specimens, corrosion resistance decreased as a result of the blocking of outward diffusion of Cr by boron and decreased cohesion between the oxide scale and the aluminized layer during thermal cycling.

  4. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

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

  5. Aluminate solution decomposition new technology development

    Energy Technology Data Exchange (ETDEWEB)

    Abramov, V.Ya.; Stelmakova, G.D. [Scientific Technical Centre Reactor, Moscow (Russian Federation)

    1996-10-01

    Scientific Technical Centre Reactor together with SC Aluminy carried out the number of investigations in the field of aluminum solution decomposition new technology development. It was based on large prime ratio on one hand, and liquid-solid countercurrent flow movement on the other hand. Practically the suggested technology was considered to be the result of unstationary, mass-transfer theory, which had been checked up at 100 m3 plot scale plant. Hydrate washing was accomplished at the first stage under the condition of countercurrent flow and less than 1 m3 water discharge. The experiments of 3.2--3.3 caustic module aluminate solution decomposition were carried out at the second stage. While full reactor 20 hour regime operation the caustic module increased till 4.1. Usually it accounts 3.7 under the analogous conditions and time.

  6. Influence Mechanism of High-Silicon Limestone on Belite-Barium Calcium Sulphoaluminate Cement%高硅石灰石对贝利特-硫铝酸钡钙水泥的影响机理

    Institute of Scientific and Technical Information of China (English)

    芦令超; 赵丕琪; 王守德; 王桂芸

    2012-01-01

    The influence of high-silicon limestone on mineral structure and performance of belite-barium calcium sulphoaluminate cement clinker were investigated by thermal analysis, petrographic analysis, X-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy. The results show that high-silicon limestone has low decomposition temperature, which can promote the development of C3S by adding small quantity. The formation and development of C3S is hindered by crquartz while C3S is formed easily by mixing magnesite and dolomite in high-silicon limestone at low temperature. When mass proportions of high-silicon limestone and ordinary limestone is 1. 0:5. 0, the compressive strength of this cement at 3, 7, 28 d is 37. 9, 60. 3, 87. 9 Mpa respectively, which shows excellent improvement of mechanical properties.%通过热分析、显微镜观察、X射线衍射分析和扫描电子显微镜-能谱仪测试,研究了高硅石灰石对贝利特-硫铝酸钡钙水泥熟料矿物结构和性能的影响.结果表明:高硅石灰石的分解温度低,少量掺入可以促进C3S晶体发育,提高水泥熟料质量;高硅石灰石带入的α-石英阻碍了C3S矿物的形成和发育,但高硅石灰石带入的菱镁矿和白云石能够改善水泥熟料液相性质,促进C3S矿物在低温下形成.当高硅石灰石与普通石灰石质量比为1.0∶5.0时,所制备的贝利特-硫铝酸钡钙水泥的3,7,28 d抗压强度分别为37.9,60.3,87.9 MPa,展现出了良好的力学性能.

  7. Physicochemical properties of chitosan microspheres/silk fibroin/calcium sulfate bone cement%壳聚糖微球复合丝素基硫酸钙骨水泥的理化特性

    Institute of Scientific and Technical Information of China (English)

    王鹏; 皮斌; 王金宁; 朱雪松; 杨惠林

    2014-01-01

    背景:脊柱成形和脊柱后凸成形治疗中采用的硫酸钙骨水泥理化性质好,对人体无毒性作用,同时具有降解性能,但单独使用降解较快。  目的:研制具有载药缓释功能的壳聚糖微球丝素基硫酸钙骨水泥。  方法:采用三聚磷酸钠乳化交联法制备壳聚糖微球。采用浓度分别为3%,6%,9%的丝素溶液与CaSO4•0.5H 2 O混合,通过万能力学试验机确定骨水泥力学性能最佳时的丝素浓度,在此浓度下,按壳聚糖微球占CaSO 4•0.5H 2 O的质量比分别为0.5%,1%,5%的比例制备壳聚糖微球丝素基硫酸钙骨水泥,测定其抗压强度,并通过X射线多晶衍射仪及傅里叶红外光谱明确达到最佳抗压强度组的骨水泥成分,电镜观察复合骨水泥中壳聚糖微球的形态。  结果与结论:当丝素溶液浓度为6%,壳聚糖微球含量为0.5%时,复合骨水泥的抗压强度最大,为(39.17±1.96) MPa,此时复合骨水泥的初凝时间为(12.99±1.63) min,终凝时间为(21.55±0.54) min;骨水泥中主要晶相组成为硫酸钙,傅里叶红外光谱结果证实复合骨水泥中含有丝素及壳聚糖;复合骨水泥中的微球表面稍有皱缩,但球形仍然完整,未见明显破坏,可见在制备复合骨水泥的过程中微球能保持稳定而不被破坏。%BACKGROUND:Calcium sulfate used in kyphoplasty and vertebrolplasty has good physical and chemical properties, exerts no toxic effects on human body and has the degradation performance. But its main drawback is rapid degradation. OBJECTIVE:To develop a chitosan microsphere with silk fibroin/calcium sulfate cement to prepare drug carrier system. METHODS:Chitosan microspheres were prepared by the emulsion method. Scanning electron microscopy, particle size analysis and swel ing rate were used to study the properties of the microspheres. Different silk concentrations (3%, 6%and 9%) and weight rates (0

  8. Military Specification, Mirror, Front Surfaced Aluminized: For Optical Elements

    Science.gov (United States)

    2007-11-02

    uniform magnesium fluoride or silicon monoxide or as otherwise specified on the applicable drawing. Tha film shall be free from holes, foreign...Mt] «. OATI Of IIMMIMION (YYMHDDt MIL-M-13508C AMENDMENT 1 27 May 1983 MILITARY SPECIFICATION MIRROR, FRONT SURFACED ALUMINIZED : FOR OPTICAL... ALUMINIZED : FOR OPTICAL ELEMENTS This notice should be filed in front of MIL-M-13508C, dated 19 March 1973 MIL-M-13508C dated 19 March 1973 with

  9. ADVANCED CEMENTS FOR GEOTHERMAL WELLS

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2007-01-01

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

  10. The effect of hyaluronic acid on brushite cement cohesion.

    Science.gov (United States)

    Alkhraisat, M H; Rueda, C; Mariño, F T; Torres, J; Jerez, L B; Gbureck, U; Cabarcos, E L

    2009-10-01

    The improvement of calcium phosphate cement (CPC) cohesion is essential for its application in highly blood perfused regions. This study reports the effectiveness of hyaluronic acids of different molecular weights in the enhancement of brushite cement cohesion. The cement was prepared using a powder phase composed of a mixture of beta-tricalcium phosphate and monocalcium phosphate monohydrate, whereas the liquid phase was formed by 0.5M citric acid solution modified by the addition of hyaluronic acid of different molecular weights. It was found that medium and high molecular weight hyaluronic acid enhances the cement cohesion and scarcely affects the cement mechanical properties. However, concentrations >0.5% (w/v) were less efficient to prevent the cement disintegration. It is concluded that hyaluronic acid could be applied efficiently to reduce brushite cement disintegration.

  11. 自固化磷酸钙糊剂和氢氧化钙碘仿糊剂用于乳磨牙活髓切断术后盖髓剂的临床疗效观察%Comparison study of pulpotomy with calcium phosphate cement paste vs calcium hydroxide/iodoform paste in primary molars

    Institute of Scientific and Technical Information of China (English)

    韩汉; 吴佩玲

    2014-01-01

    Objective To investigate effectiveness of calcium phosphate cement paste vs calcium hydroxide/iodoform paste,when it performed direct capping after vital pulpotomy of deciduous molars,which acci-dentally exposed pulp because treatment of deep carie,in order to that provide a reference about choicing of capping agent for clinicians.Methods Select the children 4-6 years old met the inclusion criteria totaled 9 6 (9 6 teeth),The patients were randomly divided into calcium phosphate cement paste group (ex-perimental group)and calcium hydroxide/iodoform cement paste group (control group)and informed con-sent of the parents of these children.after 3 months,6 months and 1 2 months were observed.Results All patients without any pain and other adverse reactions.The clinical efficiency in controlled group and exper-imental group were 94% and 97.8% after 3 months operation,were 92.0% and 95.7% after 6 months, were 92.0 % and 87.0%,after 12 months,respectively .There were no statistically significant (P >0.05). Conclusion Calcium phosphate cement paste,as a capping agent for primary teeth pulpotomy,after cov-ering the pulp section,can play effectively isolated from external stimuli and retain the residual activity of the purpose of pulp,It is close to the clinical efficacy of calcium hydroxide/iodoform paste,The findings provide more option of capping agent in pulpotomy surgery for dental clinicians.%目的:探讨自固化磷酸钙与氢氧化钙碘仿糊剂用于乳磨牙活髓切断术后盖髓剂的临床疗效。方法选择4~6岁因第一、第二乳磨牙龋病在治疗过程中因去除龋坏组织导致牙髓意外暴露欲行活髓切断术的96例患儿(96颗患牙),随机分为两组,试验组50颗患牙,采用自固化磷酸钙糊剂作为盖髓剂,对照组46颗患牙,采用氢氧化钙碘仿糊剂作为盖髓剂,于术后3、6、12个月复查。结果所有患儿无明显疼痛等不适,也无不良反应;术后3

  12. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

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

  13. Structural, optical and photocatalytic activity of cerium doped zinc aluminate

    Science.gov (United States)

    Sumathi, Shanmugam; Kavipriya, A.

    2017-03-01

    Zinc aluminate and cerium-doped zinc aluminate nanoparticles are synthesised by co-precipitation method. Ammonium hydroxide is used as a precipitating agent. The synthesised compounds are characterised by powder X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Surface area measurements. The photocatalytic activity of zinc aluminate and cerium doped zinc aluminate nanoparticles are studied under the UV light and visible light taking methylene blue as a model pollutant. The amount of catalyst, concentration of dye solution and time are optimised under UV-light. Degradation of methylene blue under the UV-light is found to be 99% in 20 min with 10 mg of cerium doped catalyst. Compared to visible light degradation, the degradation of dye under UV-light is higher. Cerium doping in zinc aluminate (ZnAl2O4:Ce3+) increased the photocatalytic activity of zinc aluminate.

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

    Science.gov (United States)

    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.

  15. Control of in vivo mineral bone cement degradation.

    Science.gov (United States)

    Kanter, Britta; Geffers, Martha; Ignatius, Anita; Gbureck, Uwe

    2014-07-01

    The current study aimed to prevent the formation of hydroxyapatite reprecipitates in brushite-forming biocements by minimizing the availability of free Ca(2+) ions in the cement matrix. This was achieved by both maximizing the degree of cement setting to avoid unreacted, calcium-rich cement raw materials which can deliver Ca(2+) directly to the cement matrix after dissolution, and by a reduction in porosity to reduce Ca(2+) diffusion into the set cement matrix. In addition, a biocement based on the formation of the magnesium phosphate mineral struvite (MgNH4PO4·6H2O) was tested, which should prevent the formation of low-solubility hydroxyapatite reprecipitates due to the high magnesium content. Different porosity levels were fabricated by altering the powder-to-liquid ratio at which the cements were mixed and the materials were implanted into mechanically unloaded femoral defects in sheep for up to 10 months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10 months, slowing down cement resorption, a lower-porosity brushite cement modification was found to be chemically stable with the absence of reprecipitate formation and minor cement resorption from the implant surface. In contrast, struvite-forming cements were much more degradable due to the absence of mineral reprecipitates and a nearly quantitative cement degradation was found after 10 months of implantation.

  16. Etude vibrationnelle d'aluminates et de gallates de terres rares—IV. Aluminates de samarium et d'europium

    Science.gov (United States)

    Saine, M. C.; Husson, E.

    In order to complete our studies on rare earth aluminates and gallates of perovskite structure, we have calculated a force field for orthorhombic SmAlO 3 and EuAlO 3. This force field is anisotropic with regard to the ab plane of the structure and is slightly weaker than the force field of the rhombohedral aluminates LaAlO 3 or NdAlO 3.

  17. 硫酸钙骨水泥强化骨质疏松绵羊腰椎的生物力学研究%Biomechanical study on augmentation of osteoporotic sheep vertebrae with calcium sulfate cement:in vivo study

    Institute of Scientific and Technical Information of China (English)

    张军华; 张炼

    2012-01-01

    目的 评价硫酸钙骨水泥(CSC)强化骨质疏松绵羊腰椎力学强度的效果.方法 成年雌性绵羊4只,行去势手术后饲养1年,测量去势前后腰椎骨密度.取L2~5共16个椎体,分为CSC组和对照组,每组8个椎体.CSC组经椎弓根向椎体内注射CSC(2.0 ml),对照组不给于任何处理.CSC组于术后12周测量L2~5单个椎体的骨密度,然后处死绵羊.取出椎体行压缩实验,测量各组中椎体的最大压缩应力(σult)和能量吸收值(EAV).结果 去势1年后绵羊腰椎骨密度显著下降,与去势前比较差异有统计学意义(P<0.05),骨质疏松绵羊模型建立成功.注射CSC 12周后椎体骨密度(BMD)、σult、EAV均高于对照组(P<0.05),且椎体的σult和EAV均与BMD成正相关关系(P<0.05).结论 CSC可以提高骨质疏松椎体的BMD,强化骨质疏松椎体的力学强度,有利于避免或减少骨质疏松椎体骨折的风险.%Objective To evaluate biomechanical performance of osteoporotic lumbar vertebral body augmented with calcium sulfate cement ( CSC ) in ovariectomized sheep. Methods Four female adult sheep were treated with bilateral ovariectomy. Bone mineral density ( BMD ) of lumbar vertebrae of all sheep was measured before the treatment and one year after of the treatment. L2 ~ L5 of each sheep and total 16 vertebrae were grouped into CSC and blank group with 8 vertebrae in each group. In CSC group, vertebrae were augmented with CSC( 2. 0 ml ) through transpedicular approach. There was no augmentation in blank group. Each vertebra BMD of L2 ~ L5 in CSC group was measured 12 weeks later. Then all sheep were killed and L2 ~ L5 were prepared for compression test. The ultimate compared stres-ses( (σult )and energy absorption value( EAV )of each group were recorded. Results There was a significant decrease in average BMD of lumbar one year after ovariectomy( P < 0. 05 ). The osteoporotic lumbar vertebral experiment was successful. 12 weeks after augmentation with CSC

  18. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar [K2-44, Energy Materials Department, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99354 (United States)

    2008-12-01

    A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO{sub 4} was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications. (author)

  19. Influence of silicate anions structure on desilication in silicate-bearing sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    刘桂华; 张闻; 齐天贵; 彭志宏; 周秋生; 李小斌

    2016-01-01

    The structural changes of silicate anions in the desilication process with the addition of calcium hydrate alumino-carbonate were studied by measuring Raman spectra, infrared spectra and corresponding second derivative spectra. The results show that the desilication ratio in the solution prepared by the addition of sodium silicate (solution-SS) is much greater than that in the solution by the addition of green liquor (solution-GL), and low alumina concentration in the sodium aluminate solutions facilitates the desilication process. It is also shown that alumino-silicate anions in the solution-GL, and Q3 polymeric silicate anions in solution-SS are predominant, respectively. In addition, increasing the concentration of silica favors respectively the formation of the alumino-silicate or the Q3 silicate anions in the solution-GL or the solution-SS. Therefore, it can be inferred that the low desilication ratio in the silicate-bearing aluminate solution is mainly attributed to the existence of alumino-silicate anions.

  20. 矿物掺合料对硫铝酸盐水泥基灌浆料性能的影响%Effect of mineral admixtures on performance of grout material based on sulphate aluminium cement

    Institute of Scientific and Technical Information of China (English)

    戴民; 赵慧

    2014-01-01

    为研究矿物掺合料对硫铝酸盐水泥基灌浆料力学性能及流动性能的影响,分别以硅灰、双飞粉、轻质碳酸钙为掺合料制备了硫铝酸盐水泥基灌浆料。在不同水胶比条件下,测试了灌浆料的流动度及不同龄期的抗折、抗压强度。试验结果表明:加入一定量硅灰可以提高灌浆料各龄期强度,但随着硅灰掺量增大,灌浆料流动度降低;加入一定量双飞粉对灌浆料流动度及各龄期强度均有负面影响;加入一定量轻质碳酸钙对灌浆料不同龄期抗压强度有所提高,对流动度及抗折强度没有明显影响。%In order to study mineral admixtures' impact on the mechanical and flow properties of sulfur aluminate cement-based grouting material,the author produces sulfur aluminate cement-based grouting material samples by useing silica fume ,Flying powder and light cal-cium carbonate as mineral admixtures.The author also tests and analysises fluidity ,strength index in different water cement ratio. The fl-lowing are the results that we can conclude:(1)adding a certain amount of silica fume can improve the strength of grouting material in each stage,while the grout fluidity will reduce when the dosage of silica fume increases;(2)adding a certain amount of flying powder has negative effects on the grout fluidity and the strength in each stage;(3)adding a certain amount of light calcium carbonate can improve the compressive strength of grout in ecah stage,while has no obvious effects on fluidity and flexural strength.

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

    Directory of Open Access Journals (Sweden)

    Osvaldo Daniel Andreatta Filho

    2005-03-01

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

  2. THE PREPARATION AND COMPOSITION ANALYSIS OF ALITE-YE'ELIMITE WITH INDUSTRIAL WASTES

    Open