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Sample records for based resorbable ceramics

  1. Strength Characteristics of Resorbable Osteoconductive Ceramics Based on Diphosphates of Calcium and Alkali Metals

    NASA Astrophysics Data System (ADS)

    Putlayev, V. I.; Evdokimov, P. V.; Garshev, A. V.; Prosvirin, D. V.; Klimashina, E. S.; Safronova, T. V.; Ivanov, V. K.

    2014-02-01

    An investigation into the strength characteristics of ceramics based on diphosphates Ca(3- x)М2 x (PO4)2 ( x = 0-1 and М = Na, K) provides evidence of composition strengthening in the range х = 0.6-0.8 containing the greatest amount of the supercooled high-temperature modification α-СаМРО4. The method of high-temperature x-ray diffractometry is used to examine thermal expansion of rhenanite phases of СаМРО4.

  2. Resorbable glass-ceramic phosphate-based scaffolds for bone tissue engineering: synthesis, properties, and in vitro effects on human marrow stromal cells.

    PubMed

    Vitale-Brovarone, Chiara; Ciapetti, Gabriela; Leonardi, Elisa; Baldini, Nicola; Bretcanu, Oana; Verné, Enrica; Baino, Francesco

    2011-11-01

    Highly porous bioresorbable glass-ceramic scaffolds were prepared via sponge replication method by using an open-cell polyurethane foam as a template and phosphate-based glass powders. The glass, belonging to the P2O5-SiO2-CaO-MgO-Na2O-K2O system, was synthesized by a melting-quenching route, ground, and sieved to obtain powders with a grain size of less than 30 μm. A slurry containing glass powders, polyvinyl alcohol, and water was prepared to coat the polymeric template. The removal of the polymer and the sintering of the glass powders were performed by a thermal treatment, in order to obtain an inorganic replica of the template structure. The structure and properties of the scaffold were investigated from structural, morphological, and mechanical viewpoints by means of X-ray diffraction, scanning electron microscopy, density measurements, image analysis, and compressive tests. The scaffolds exhibited a trabecular architecture that closely mimics the structure of a natural spongy bone. The solubility of the porous structures was assessed by soaking the samples in acellular simulated body fluid (SBF) and Tris-HCl for different time frames and then by assessing the scaffold weight loss. As far as the test in SBF is concerned, the nucleation of hydroxyapatite on the scaffold trabeculae demonstrates the bioactivity of the material. Biological tests were carried out using human bone marrow stromal cells to test the osteoconductivity of the material. The cells adhered to the scaffold struts and were metabolically active; it was found that cell differentiation over proliferation occurred. Therefore, the produced scaffolds, being biocompatible, bioactive, resorbable, and structurally similar to a spongy bone, can be proposed as interesting candidates for bone grafting. PMID:20566654

  3. Negative Effect of Rapidly Resorbing Properties of Bioactive Glass-Ceramics as Bone Graft Substitute in a Rabbit Lumbar Fusion Model

    PubMed Central

    Lee, Jae Hyup; Ryu, Hyun-Seung; Seo, Jun-Hyuk; Lee, Do-Yoon; Chang, Bong-Soon

    2014-01-01

    Background Bioactive glass-ceramics have the ability to directly bind to bones and have been widely used as bone graft substitutes due to their high osteoconductivity and biocompatibility. CaO-SiO2-P2O5-B2O3 glass-ceramics are known to have good osteoconductivity and are used as bone graft extenders. Methods This study aimed to evaluate the effects of the resorbing properties of glass-ceramics in bone fusion after producing and analyzing three types of CaO-SiO2-P2O5-B2O3 glass-ceramics with high osteoconductivity that had enhanced resorption by having an increased B2O3 content. The three types of CaO-SiO2-P2O5-B2O3 glass-ceramics with B2O3 contents of 8.0, 9.0, and 9.5 weight % were designated and grouped as P20B80, P10B90, and P5B95, respectively. Glass-ceramic types were tested for fusion rates and bone formation by employing the lumbar 5-6 intertransverse process fusion model in 51 New Zealand male rabbits. Bioactivity was assessed by soaking in simulated body fluid (SBF). Results In vitro study results showed sufficient hydroxycarbonate apatite layer formation occurred for P20B80 in1 day, for P10B90 in 3 days, and for P5B95 in 5 days after soaking in SBF. For the rabbit lumbar spine posterolateral fusion model, the autograft group recorded a 100% fusion rate with levels significantly higher than those of P20B80 (29.4%), P10B90 (0%), and P5B95 (14.3%), with high resorbing properties. Resorbing property differences among the three glass-ceramic groups were not significant. Histological results showed new bone formation confirming osteoconductivity in all three types of glass-ceramics. Radiomorphometric results also confirmed the resorbing properties of the three glass-ceramic types. Conclusions The high resorbing properties and osteoconductivity of porous glass-ceramics can be advantageous as no glass-ceramics remain in the body. However, their relatively fast rate of resorption in the body negatively affects their role as an osteoconductive scaffold as glass-ceramics

  4. Silk-based resorbable electronic devices for remotely controlled therapy and in vivo infection abatement

    PubMed Central

    Tao, Hu; Hwang, Suk-Won; Marelli, Benedetto; An, Bo; Moreau, Jodie E.; Yang, Miaomiao; Brenckle, Mark A.; Kim, Stanley; Kaplan, David L.; Rogers, John A.; Omenetto, Fiorenzo G.

    2014-01-01

    A paradigm shift for implantable medical devices lies at the confluence between regenerative medicine, where materials remodel and integrate in the biological milieu, and technology, through the use of recently developed material platforms based on biomaterials and bioresorbable technologies such as optics and electronics. The union of materials and technology in this context enables a class of biomedical devices that can be optically or electronically functional and yet harmlessly degrade once their use is complete. We present here a fully degradable, remotely controlled, implantable therapeutic device operating in vivo to counter a Staphylococcus aureus infection that disappears once its function is complete. This class of device provides fully resorbable packaging and electronics that can be turned on remotely, after implantation, to provide the necessary thermal therapy or trigger drug delivery. Such externally controllable, resorbable devices not only obviate the need for secondary surgeries and retrieval, but also have extended utility as therapeutic devices that can be left behind at a surgical or suturing site, following intervention, and can be externally controlled to allow for infection management by either thermal treatment or by remote triggering of drug release when there is retardation of antibiotic diffusion, deep infections are present, or when systemic antibiotic treatment alone is insufficient due to the emergence of antibiotic-resistant strains. After completion of function, the device is safely resorbed into the body, within a programmable period. PMID:25422476

  5. Silk-based resorbable electronic devices for remotely controlled therapy and in vivo infection abatement.

    PubMed

    Tao, Hu; Hwang, Suk-Won; Marelli, Benedetto; An, Bo; Moreau, Jodie E; Yang, Miaomiao; Brenckle, Mark A; Kim, Stanley; Kaplan, David L; Rogers, John A; Omenetto, Fiorenzo G

    2014-12-01

    A paradigm shift for implantable medical devices lies at the confluence between regenerative medicine, where materials remodel and integrate in the biological milieu, and technology, through the use of recently developed material platforms based on biomaterials and bioresorbable technologies such as optics and electronics. The union of materials and technology in this context enables a class of biomedical devices that can be optically or electronically functional and yet harmlessly degrade once their use is complete. We present here a fully degradable, remotely controlled, implantable therapeutic device operating in vivo to counter a Staphylococcus aureus infection that disappears once its function is complete. This class of device provides fully resorbable packaging and electronics that can be turned on remotely, after implantation, to provide the necessary thermal therapy or trigger drug delivery. Such externally controllable, resorbable devices not only obviate the need for secondary surgeries and retrieval, but also have extended utility as therapeutic devices that can be left behind at a surgical or suturing site, following intervention, and can be externally controlled to allow for infection management by either thermal treatment or by remote triggering of drug release when there is retardation of antibiotic diffusion, deep infections are present, or when systemic antibiotic treatment alone is insufficient due to the emergence of antibiotic-resistant strains. After completion of function, the device is safely resorbed into the body, within a programmable period. PMID:25422476

  6. Outcomes and complications based on experience with resorbable plates in pediatric craniosynostosis patients.

    PubMed

    Ahmad, Nawaiz; Lyles, James; Panchal, Jayesh; Deschamps-Braly, Jordan

    2008-05-01

    The structure and functional relationship of polymers have long been the purview of engineers and polymer chemists. Bioabsorbable fixation devices have been used for decades as dissolvable suture meshes and, recently, routinely by orthopedic surgeons. During the past decade, bioabsorbable fixation systems have become available for use by craniomaxillofacial surgeons for cranial vault remodeling. This study evaluates the application of a bioabsorbable fixation system in reconstructive craniofacial procedures in a pediatric population. We reviewed 146 cases of cranial vault reconstruction including 98 boys and 48 girls ranging from 2 months to 16 years (mean, 15 months) in age. The procedures were performed for 6 years between January 1998 and June 2004. Bioabsorbable plates and screws were used in each case; most of these cases were craniosynostosis reconstructions. There were 69 cases of frontal sagittal craniosynostosis, 36 metopic, 20 unicoronal, 12 bicoronal, 5 lamboid, 2 deformational plagiocephaly, and 2 multiple fusion of sutures. Postoperative evaluation consisted of clinical examination and three-dimensional computed tomography scan reconstructions at 3, 6, and 12 months. Items specifically screened for on the clinical examination included wound healing, signs of infection, and palpability of implant through the skin. Six patients had palpable plates, 2 patients had palpable screw, and 5 patients had infection at the incision site (of which only 3 were treated with inpatient care including incision drainage and intravenous antibiotics). Our experience has been overwhelmingly positive, and we feel that our results suggest that resorbable fixation is a superior option in pediatric plastic and craniofacial surgery. PMID:18520420

  7. Aesthetic recovery of alveolar atrophy following autogenous onlay bone grafting using interconnected porous hydroxyapatite ceramics (IP-CHA) and resorbable poly-L-lactic/polyglycolic acid screws: case report

    PubMed Central

    2014-01-01

    Background Onlay bone grafting techniques have some problems related to the limited volume of autogenous grafted bone and need for surgery to remove bone fixing screws. Here, we report a case of horizontal alveolar ridge atrophy following resection of a maxillary bone cyst, in which autogenous onlay bone grafting with interconnected porous hydroxyapatite ceramics (IP-CHA) and bioresorbable poly-L-lactic/polyglycolic acid (PLLA-PGA) screws was utilized. Case presentation A 51-year-old man had aesthetic complications related to alveolar atrophy following maxillary bone cyst extraction. We performed onlay grafting for aesthetic alveolar bone recovery using IP-CHA to provide adequate horizontal bone volume and PLLA-PGA screws for bone fixing to avoid later damage to host bone during surgical removal. During the operation, an autogenous cortical bone block was collected from the ramus mandibular and fixed to the alveolar ridge with PLLA-PGA screws, then the gap between the bone block and recipient bone was filled with a granular type of IP-CHA. Post-surgery orthopantomograph and CT scan findings showed no abnormal resorption of the grafted bone, and increased radiopacity, which indicated new bone formation in the area implanted with IP-CHA. Conclusion Our results show that IP-CHA and resorbable PLLA-PGA screws are useful materials for autogenous onlay bone grafting. PMID:24889647

  8. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-04-06

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  9. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-01-01

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  10. Alumina-based ceramic composite

    DOEpatents

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

  11. Emerging Ceramic-based Materials for Dentistry

    PubMed Central

    Denry, I.; Kelly, J.R.

    2014-01-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  12. Emerging ceramic-based materials for dentistry.

    PubMed

    Denry, I; Kelly, J R

    2014-12-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  13. Alumina-based ceramic composite

    DOEpatents

    Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

    1996-07-23

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite. 5 figs.

  14. Tantalum-Based Ceramics for Refractory Composites

    NASA Technical Reports Server (NTRS)

    Stewart, David A.; Leiser, Daniel; DiFiore, Robert; Kalvala, Victor

    2006-01-01

    A family of tantalum-based ceramics has been invented as ingredients of high-temperature composite insulating tiles. These materials are suitable for coating and/or permeating the outer layers of rigid porous (foam-like or fibrous) ceramic substrates to (1) render the resulting composite ceramic tiles impervious to hot gases and (2) enable the tiles to survive high heat fluxes at temperatures that can exceed 3,000 F ( 1,600 C).

  15. Building ceramic based on sludge

    NASA Astrophysics Data System (ADS)

    Szöke, A.-M.; Muntean, M.; Dumitrescu, O.; Bartalis, I.

    2013-12-01

    Because of the rapid evolution in the last decade of science and engineering materials, development of new advanced materials, particularly in construction, we must find solutions, namely, new performed materials, with functional and aesthetic qualities. In recent years, there have been made alternative attempts to reuse various types of wastes, including the incorporation of products in ceramic clay. This theme concerning the achievement of some durable, economic and ecological materials represents a high-level preoccupation in this domain, the problems related to the ecosystem being permanent issues of the century.

  16. Degradation and Characterization of Resorbable Phosphate-Based Glass Thin-Film Coatings Applied by Radio-Frequency Magnetron Sputtering.

    PubMed

    Stuart, Bryan W; Gimeno-Fabra, Miquel; Segal, Joel; Ahmed, Ifty; Grant, David M

    2015-12-16

    Quinternary phosphate-based glasses of up to 2.67 μm, deposited by radio-frequency magnetron sputtering, were degraded in distilled water and phosphate-buffered saline (PBS) to investigate their degradation characteristics. Magnetron-sputtered coatings have been structurally compared to their compositionally equivalent melt-quenched bulk glass counterparts. The coatings were found to have structurally variable surfaces to melt-quenched glass such that the respective bridging oxygen to nonbridging oxygen bonds were 34.2% to 65.8% versus 20.5% to 79.5%, forming metaphosphate (PO3)(-) (Q(2)) versus less soluble (P2O7)(4-) (Q(1)) and (PO4)(3-) (Q(0)), respectively. This factor led to highly soluble coatings, exhibiting a t(1/2) degradation dependence in the first 2 h in distilled water, followed by a more characteristic linear profile because the subsequent layers were less soluble. Degradation was observed to preferentially occur, forming voids characteristic of pitting corrosion, which was confirmed by the use of a focused ion beam. Coating degradation in PBS precipitated a (PO3)(-) metaphosphate, an X-ray amorphous layer, which remained adherent to the substrate and seemingly formed a protective diffusion barrier, which inhibited further coating degradation. The implications are that while compositionally similar, sputter-deposited coatings and melt-quenched glasses are structurally dissimilar, most notably, with regard to the surface layer. This factor has been attributed to surface etching of the as-deposited coating layer during deposition and variation in the thermal history between the processes of magnetron sputtering and melt quenching. PMID:26523618

  17. Process for strengthening aluminum based ceramics and material

    DOEpatents

    Moorhead, Arthur J.; Kim, Hyoun-Ee

    2000-01-01

    A process for strengthening aluminum based ceramics is provided. A gaseous atmosphere consisting essentially of silicon monoxide gas is formed by exposing a source of silicon to an atmosphere consisting essentially of hydrogen and a sufficient amount of water vapor. The aluminum based ceramic is exposed to the gaseous silicon monoxide atmosphere for a period of time and at a temperature sufficient to produce a continuous, stable silicon-containing film on the surface of the aluminum based ceramic that increases the strength of the ceramic.

  18. Design and Optimization of Resorbable Silk Internal Fixation Devices

    NASA Astrophysics Data System (ADS)

    Haas, Dylan S.

    Limitations of current material options for internal fracture fixation devices have resulted in a large gap between user needs and hardware function. Metal systems offer robust mechanical strength and ease of implantation but require secondary surgery for removal and/or result in long-term complications (infection, palpability, sensitivity, etc.). Current resorbable devices eliminate the need for second surgery and long-term complications but are still associated with negative host response as well as limited functionality and more difficult implantation. There is a definitive need for orthopedic hardware that is mechanically capable of immediate fracture stabilization and fracture fixation during healing, can safely biodegrade while allowing complete bone remodeling, can be resterilized for reuse, and is easily implantable (self-tapping). Previous work investigated the use of silk protein to produce resorbable orthopedic hardware for non- load bearing fracture fixation. In this study, silk orthopedic hardware was further investigated and optimized in order to better understand the ability of silk as a fracture fixation system and more closely meet the unfulfilled market needs. Solvent-based and aqueous-based silk processing formulations were cross-linked with methanol to induce beta sheet structure, dried, autoclaved and then machined to the desired device/geometry. Silk hardware was evaluated for dry, hydrated and fatigued (cyclic) mechanical properties, in vitro degradation, resterilization, functionalization with osteoinductive molecules and implantation technique for fracture fixation. Mechanical strength showed minor improvements from previous results, but remains comparable to current resorbable fixation systems with the advantages of self-tapping ability for ease of implantation, full degradation in 10 months, ability to be resterilized and reused, and ability to release molecules for osteoinudction. In vivo assessment confirmed biocompatibility, showed

  19. Mo-Si-B-Based Coatings for Ceramic Base Substrates

    NASA Technical Reports Server (NTRS)

    Perepezko, John Harry (Inventor); Sakidja, Ridwan (Inventor); Ritt, Patrick (Inventor)

    2015-01-01

    Alumina-containing coatings based on molybdenum (Mo), silicon (Si), and boron (B) ("MoSiB coatings") that form protective, oxidation-resistant scales on ceramic substrate at high temperatures are provided. The protective scales comprise an aluminoborosilicate glass, and may additionally contain molybdenum. Two-stage deposition methods for forming the coatings are also provided.

  20. Characterization of glass-infiltrated alumina-based ceramics

    PubMed Central

    Bona, Alvaro Della; Mecholsky, John J; Barrett, Allyson A; Griggs, Jason A

    2010-01-01

    Objective characterize the microstructure, composition, and important properties of glass-infiltrated alumina-based ceramics similar to the In-Ceram system. Methods Materials used were: IA- In-Ceram Alumina (Vita); IAE- IA electrophoretically deposited (Vita); AEM- IA using a vacuum driven method (Vita); VC- Vitro-Ceram (Angelus); TC- Turkom-Cera (Turkom-Ceramic); CC- Ceramcap (Foto-Ceram); and AG- Alglass (EDG). Ceramic specimens were fabricated following manufacturers’ instructions and ISO6872 standard and polished successively through 1μm alumina abrasive. Semi-quantitative and qualitative analyses were performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and stereology (Vv). The elastic modulus (E) and Poisson’s ratio (ν) were determined using time-of-flight data measured in an ultrasonic pulser/receiver and the density (ρ) was determined using a helium pycnometer. Vicker’s indentation was used to calculate hardness (H). Bar specimens (25×4×1.2mm3) were loaded in three-point bending to fracture using a universal testing machine with cross-head speed of 1mm/min. Flexural strength (σ3P) was calculated and statistically analyzed using ANOVA, Tukey (α=0.05) and Weibull (m= modulus, σ0= characteristic strength). Results SEM and EDS analyses revealed similar microstructure for all ceramics, except for a lead-based matrix in CC and a zirconia phase in VC. TC, AG and CC showed significantly lower mean σ3P values than the other ceramics (p 0.05). AEM showed the greatest m (16). Conclusion Despite few differences in microstructure and composition, the IA, IAE, AEM and VC ceramics have similar properties. Significance The glass-infiltrated alumina-based ceramics from different manufacturers presented distinct characteristics. It is necessary to characterize new commercially available materials to understand their properties. PMID:18692231

  1. Absorption machine with desorber-resorber

    DOEpatents

    Biermann, Wendell J.

    1985-01-01

    An absorption refrigeration system utilizing a low temperature desorber and intermediate temperature resorber. The system operates at three temperatures and three pressures to increase the efficiency of the system and is capable of utilizing a lower generator temperature than previously used.

  2. Materials design of ceramic-based layer structures for crowns.

    PubMed

    Lawn, B R; Deng, Y; Lloyd, I K; Janal, M N; Rekow, E D; Thompson, V P

    2002-06-01

    Radial cracking has been identified as the primary mode of failure in all-ceramic crowns. This study investigates the hypothesis that critical loads for radial cracking in crown-like layers vary explicitly as the square of ceramic layer thickness. Experimental data from tests with spherical indenters on model flat laminates of selected dental ceramics bonded to clear polycarbonate bases (simulating crown/dentin structures) are presented. Damage initiation events are video-recorded in situ during applied loading, and critical loads are measured. The results demonstrate an increase in the resistance to radial cracking for zirconia relative to alumina and for alumina relative to porcelain. The study provides simple a priori predictions of failure in prospective ceramic/substrate bilayers and ranks ceramic materials for best clinical performance. PMID:12097438

  3. Ceramic technology for advanced heat engines program data base

    SciTech Connect

    Booker, M.K.

    1987-12-01

    A large amount and wide variety of data on the behavior of advanced ceramic materials is currently being generated within the Ceramic Technology for Advanced Heat Engines Program. This paper summarizes efforts to date to develop a computer data base system for the management of those data. The system is based on the use of desktop microcomputers, which provides a maximum of efficiency, economy, and convenience in the operation of the system. 4 refs., 8 tabs.

  4. Ceramics

    NASA Astrophysics Data System (ADS)

    Yao, Lichun; Yang, Jian; Qiu, Tai

    2014-09-01

    The effects of CuO addition on phase composition, microstructure, sintering behavior, and microwave dielectric properties of 0.80Sm(Mg0.5Ti0.5)O3-0.20 Ca0.8Sr0.2TiO3(8SMT-2CST) ceramics prepared by a conventional solid-state ceramic route have been studied. CuO addition shows no obvious influence on the phase of the 8SMT-2CST ceramics and all the samples exhibit pure perovskite structure. Appropriate CuO addition can effectively promote sintering and grain growth, and consequently improve the dielectric properties of the ceramics. The sintering temperature of the ceramics decreases by 50°C by adding 1.00 wt.%CuO. Superior microwave dielectric properties with a ɛ r of 29.8, Q × f of 85,500 GHz, and τ f of 2.4 ppm/°C are obtained for 1.00 wt.%CuO doped 8SMT-2CST ceramics sintered at 1500°C, which shows dense and uniform microstructure as well as well-developed grain growth.

  5. Self-glazing ceramic tiles based on acidic igneous glasses

    SciTech Connect

    Merkin, A.P.; Nanazashvili, V.I.

    1988-07-01

    A technology was derived to produce self-glazing ceramic tiles based on single-component systems of acidic igneous (volcanic) glasses. A weakly alkaline solution of NaOH or KOH was used as the sealing water to activate the sintering process. Tests conducted on the self-glazing ceramic tiles showed that their water absorption amounts to 2.5-8%, linear shrinkage is 3.2-7%, and frost resistance amounts to 35-70 cycles. The application of acidic igneous glasses as the main raw material for the production of ceramic facing tiles made it possible to widen the raw material base and simplify the technology for fabricating ceramic facing tiles at lower cost. The use of waste products when processing perlite-bearing rocks, when carrying out mining and cutting of tuffs, slags, and tuff breccia for recovering cut materials was recommended.

  6. Lutetium oxide-based transparent ceramic scintillators

    DOEpatents

    Seeley, Zachary; Cherepy, Nerine; Kuntz, Joshua; Payne, Stephen A.

    2016-01-19

    In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

  7. Wettable Ceramic-Based Drained Cathode Technology for Aluminum Electrolysis

    SciTech Connect

    J.N. Bruggeman; T.R. Alcorn; R. Jeltsch; T. Mroz

    2003-01-09

    The goal of the project was to develop the ceramic based materials, technology, and necessary engineering packages to retrofit existing aluminum reduction cells in order to reduce energy consumption required for making primary aluminum. The ceramic materials would be used in a drained cathode configuration which would provide a stable, molten aluminum wetted cathode surface, allowing the reduction of the anode-cathode distance, thereby reducing the energy consumption. This multi-tasked project was divided into three major tasks: (1) Manufacturing and laboratory scale testing/evaluation of the ceramic materials, (2) Pilot scale testing of qualified compositions from the first task, and (3) Designing, retrofitting, and testing the ceramic materials in industrial cells at Kaiser Mead plant in Spokane, Washington. Specific description of these major tasks can be found in Appendix A - Project Scope. Due to the power situation in the northwest, the Mead facility was closed, thus preventing the industrial cell testing.

  8. Resorbable synthetic mesh supported with omentum flap in the treatment of giant hiatal hernia.

    PubMed

    Pérez Lara, F J; Marín, R; del Rey, A; Oliva, H

    2014-01-01

    Covering a large hiatal hernia with a mesh has become a basic procedure in the last few years. However, mesh implants are associated with high complication rates (esophageal erosion, perforation, fistula, etc.). We propose using a synthetic resorbable mesh supported with an omental flap as a possible solution to this problem. A 54-year-old female patient with a large hiatal defect (9 cm) was laparoscopically implanted with a synthetic resorbable mesh supported with an omental flap. The surgical procedure was successful and the patient was discharged on postoperative day 2. On a follow-up examination 6 months after surgery, she remained free of relapse or complication signs. Supporting an implanted resorbable mesh with an omental flap may be a solution to the problems posed by large esophageal hiatus defects. However, more studies based on larger patient samples and longer follow-up periods are necessary. PMID:25216419

  9. Resorbable Synthetic Mesh Supported With Omentum Flap in the Treatment of Giant Hiatal Hernia

    PubMed Central

    Pérez Lara, F. J.; Marín, R.; del Rey, A.; Oliva, H.

    2014-01-01

    Covering a large hiatal hernia with a mesh has become a basic procedure in the last few years. However, mesh implants are associated with high complication rates (esophageal erosion, perforation, fistula, etc.). We propose using a synthetic resorbable mesh supported with an omental flap as a possible solution to this problem. A 54-year-old female patient with a large hiatal defect (9 cm) was laparoscopically implanted with a synthetic resorbable mesh supported with an omental flap. The surgical procedure was successful and the patient was discharged on postoperative day 2. On a follow-up examination 6 months after surgery, she remained free of relapse or complication signs. Supporting an implanted resorbable mesh with an omental flap may be a solution to the problems posed by large esophageal hiatus defects. However, more studies based on larger patient samples and longer follow-up periods are necessary. PMID:25216419

  10. Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Song; Zhu, De-Gui; Cai, Xu-Sheng

    2014-08-01

    The dense monoclinic-SrAl2Si2O8 ceramics have been prepared by a two-step sintering process at a sintering temperature of 1173 K (900 °C). Firstly, the pre-sintered monoclinic-SrAl2Si2O8 powders containing small SiO2·Al2O3 crystal phases were obtained by continuously sintering a powder mixture of SrCO3 and kaolin at 1223 K (950 °C) for 6 hours and 1673 K (1400 °C) for 4 hours, respectively. Subsequently, by the combination of the pre-sintered ceramic powders with the composite flux agents, which are composed of a SrO·3B2O3 flux agent and α-Al2O3, the low-temperature densification sintering of the monoclinic-SrAl2Si2O8 ceramics was accomplished at 1173 K (900 °C). The low-temperature sintering behavior and microstructure evolvement of the monoclinic-SrAl2Si2O8 ceramics have been investigated in terms of Al2O3 in addition to the composite flux agents. It shows that due to the low-meting characteristics, the SrO·3B2O3 flux agent can urge the dense microstructure formation of the monoclinic-SrAl2Si2O8 ceramics and the re-crystallization of the grains via a liquid-phase sintering. The introduction of α-Al2O3 to the SrO·3B2O3 flux agent can apparently lead to more dense microstructures for the monoclinic-SrAl2Si2O8 ceramics but also cause the re-precipitation of SiO2·Al2O3 compounds because of an excessive Al2O3 content in the SrO·3B2O3 flux agent.

  11. Development of phosphate-based ceramic membranes

    SciTech Connect

    Anderson, M.A.; Zeltner, W.A.; Hill, C.G. Jr.

    1992-11-01

    Goal was to develop microporous ceramic membranes by coating sols that contain nanoparticles onto porous ceramic supports. They could be used for either gas phase separations or liquid phase separations involving low molecular weight solutes. This required the synthesis of Sols containing particles in the range from 2 to 10 nm. Procedures for preparing nanoparticulate sols of silica, alumina, and aluminosilicates of various compositions are given. Unsupported ceramic membranes prepared from these sols had mean pore diameters of <10 [Angstrom] (silica), ca. 35 [Angstrom] (aluminosilicate). The alumina membranes display both microporosity (mean pore diameters <20 [Angstrom]) and mesoporosity (mean pore diameters >20 [Angstrom]). These nanoparticulate sols were deposited onto porous supports. Four methods of were investigated. Dip coating appeared to give the best performance of all of these techniques and was easily implemented. Deposition of particles within porous supports by permformation was also demonstrated. Critical point drying studies of membranes were initiated, but progress was limited. Slip casting could not be successfully used to produce a supported membrane free from cracks.

  12. Ceramics

    NASA Astrophysics Data System (ADS)

    Bin, Tang; Feng, Si; Ying-xiang, Li; He-tuo, Chen; Xiao, Zhang; Shu-ren, Zhang

    2014-11-01

    The effects of Ta2O5/Y2O3 codoping on the microstructure and microwave dielectric properties of Ba(Co0.56Zn0.40)1/3Nb2/3O3- xA- xB (A = 0.045 wt.% Ta2O5; B = 0.113 wt.% Y2O3) ceramics ( x = 0, 1, 2, 4, 8, 16, 32) prepared according to the conventional solid-state reaction technique were investigated. The x-ray diffraction (XRD) results showed that the main crystal phase in the sintered ceramics was BaZn0.33Nb0.67O3-Ba3CoNb2O9. The additional surface phase of Ba8CoNb6O24 and trace amounts of Ba5Nb4O15 second phase were present when Ta2O5/Y2O3 was added to the ceramics. The 1:2 B-site cation ordering was affected by the substitution of Ta5+ and Y3+ in the crystal lattice, especially for x = 4. Scanning electron microscopy (SEM) images of the optimally doped ceramics sintered at 1340°C for 20 h showed a compact microstructure with crystal grains in dense contact. Though the dielectric constant increased with the x value, appropriate addition would result in a tremendous modification of the Q × f and τ f values. Excellent microwave dielectric properties ( ɛ r = 35.4, Q × f = 62,993 GHz, and τ f = 2.6 ppm/°C) were obtained for the ceramic with x = 0.4 sintered in air at 1340°C for 20 h.

  13. Guided Cartilage Regeneration Using Resorbable Template

    PubMed Central

    Pomahac, Bohdan; Zuhaili, Baraa; Kudsi, Yusuf

    2008-01-01

    Objective: The reconstruction of a defect involving complex cartilaginous structures such as the ear and nose is a difficult problem. Cartilage donor sites are limited, and the shaping of an ear or nose is dependent upon the surgeon's skills and experience. In this report, we propose to use resorbable plates that can be shaped to serve as a template for cartilage healing. Methods: A shell composed of polylactic/polyglycolic acid copolymer sheet was molded into different shapes. Autologous ribs harvested from 2 New Zealand rabbits were slightly crushed and bent without breaking, and placed within the pre-shaped shell. The constructs were implanted into subcutaneous pockets in the flanks of the rabbits. After 8 weeks, the implanted cartilage constructs were taken out of the shell and analyzed by the gross macroscopic appearance for preservation of the shape and by histological means for analysis of cartilage viability. Results: All of the explanted cartilage constructs retained the same pre-implanted shape and contour. Upon histological examination with hematoxylin/eosin staining, the constructs were composed of a continuous layer of viable chondrocytes. Conclusions: Construction of complex cartilaginous structures is an operator-dependent, technically difficult problem. We propose to use a resorbable template for guiding the shape and healing of the desired cartilaginous construct. Preoperative scanning and precise 3-dimensional shaping of the template could achieve further improvement in the desired cartilaginous support of the reconstructed part. In this report, we document that cartilage enclosed in a resorbable template retains its shape and viability. We believe that a prefabricated shell may help simplify and standardize outcomes of ear or nose reconstruction. PMID:18213400

  14. Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Enzhu; Zou, Mengying; Duan, Shuxin; Xu, Ning; Yuan, Ying; Zhou, Xiaohua

    2014-11-01

    The effects of excess Li content on the phase structure and microwave dielectric properties, especially on the temperature coefficient, of LiNb0.6 Ti0.5O3 (LNT) ceramics were studied. The results show that small amounts of Li effectively enhanced the sintering process due to the compensation of high volatility of Li, leading to a densification and homogenous microstructure, and therefore enhanced the dielectric properties. However, too much Li leads to a secondary phase and cause abnormal grain growth. The LNT + 5 wt.% Li ceramic sintered at 1075°C in the air shows the best properties of ɛ r = 69.73, Q × f = 5543 GHz, and τ f = -4.4 ppm/°C.

  15. Structural design methodologies for ceramic-based material systems

    NASA Technical Reports Server (NTRS)

    Duffy, Stephen F.; Chulya, Abhisak; Gyekenyesi, John P.

    1991-01-01

    One of the primary pacing items for realizing the full potential of ceramic-based structural components is the development of new design methods and protocols. The focus here is on low temperature, fast-fracture analysis of monolithic, whisker-toughened, laminated, and woven ceramic composites. A number of design models and criteria are highlighted. Public domain computer algorithms, which aid engineers in predicting the fast-fracture reliability of structural components, are mentioned. Emphasis is not placed on evaluating the models, but instead is focused on the issues relevant to the current state of the art.

  16. Coating Silicon-Based Ceramics With Durable Mullite

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Jacobson, Nathan S.; Lee, Kang N.

    1996-01-01

    Improved plasma-spraying process deposits mullite on silicon carbide substrates. Prevents formation of amorphous mullite by maintaining high temperature of sprayed deposite to allow crystallization to occur. Deposited mullite adheres to substrate and exhibits little or no cracking during thermal cycling. Provides substantially greater resistance to oxidation in dry air and corrosion by molten salt. Process expected useful in depositing mullite on substrates made of other silicon-based ceramics and other ceramic substrates having coefficients of thermal expansion similar to those of mullite.

  17. High efficiency tantalum-based ceramic composite structures

    NASA Technical Reports Server (NTRS)

    Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor); DiFiore, Robert R. (Inventor); Katvala, Victor W. (Inventor)

    2010-01-01

    Tantalum-based ceramics are suitable for use in thermal protection systems. These composite structures have high efficiency surfaces (low catalytic efficiency and high emittance), thereby reducing heat flux to a spacecraft during planetary re-entry. These ceramics contain tantalum disilicide, molybdenum disilicide and borosilicate glass. The components are milled, along with a processing aid, then applied to a surface of a porous substrate, such as a fibrous silica or carbon substrate. Following application, the coating is then sintered on the substrate. The composite structure is substantially impervious to hot gas penetration and capable of surviving high heat fluxes at temperatures approaching 3000.degree. F. and above.

  18. Integrated thick-film nanostructures based on spinel ceramics

    PubMed Central

    2014-01-01

    Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

  19. Integrated thick-film nanostructures based on spinel ceramics.

    PubMed

    Klym, Halyna; Hadzaman, Ivan; Shpotyuk, Oleh; Brunner, Michael

    2014-01-01

    Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

  20. Ceramic Technology for Advanced Heat Engines Project data base: September 1988 summary report

    SciTech Connect

    Booker, B.L.P.

    1989-03-01

    A large volume and wide variety of data on the behavior of advanced ceramic materials are currently being generated within the Ceramic Technology for Advanced Heat Engines project (CTAHE). This is the second in a series of reports summarizing the data stored in the microcomputer-based CTAHE data base. Each report features a different class of ceramics, with as much information on materials in that class as has then been processed. This report concentrates on zirconia-based ceramics.

  1. Metal-ceramics based on nanostructured boron carbide

    NASA Astrophysics Data System (ADS)

    Antadze, M.; Chedia, R.; Tsagareishvili, O.; Mikeladze, A.; Gacheciladze, A.; Margiev, B.; Gabunia, D.; Tsuladze, T.; Khantadze, D.

    2012-11-01

    Boron carbide has unique physicochemical and mechanical properties such as: high modulus of elasticity, high value of a strength-to-density ratio, heightened wear-resistance in unfriendly environment, etc., however dense product of boron carbide is not widely used in the area of engineering due to low impact strength, brittleness and low thermal conductivity of this material. Recent efforts of the scientists working in this area are focused on creating the so-called hetero-modulus metal-ceramic composite materials comprised of high-modulus ceramic and a metallic phase as an elastic binder. Creation of effective boron carbide based hetero-modulus materials is possible when a) boron carbide has a high degree of dispersion; b) metallic binder has a high adhesion ability and low reactivity toward boron carbide. The technology developed for producing boron carbide based metal-ceramic materials provides pyrolysis (900-1100 °C) of the precursors comprised of amorphous boron, carbon-chain polymers and appropriate metal salts. Each particle of the obtained powder contains both - nanostructured components of boron carbide and of a binding metallic phase. The fabricated metal-ceramic product has heightened parameters of impact strength and thermal conductivity in parallel with the retained unique properties of boron carbide.

  2. Optical Ceramics Based on Yttrium Oxide Doped with Tetravalent Ions

    NASA Astrophysics Data System (ADS)

    Osipov, V. V.; Solomonov, V. I.; Shitov, V. A.; Maksimov, R. N.; Orlov, A. N.; Murzakaev, A. M.

    2015-05-01

    Optical ceramics activated by neodymium or ytterbium and based on Y2O3 with inclusions of CeO2 , ZrO2 , and HfO2 containing optical inhomogeneities in the form of an orange peel are investigated. It is indicated that in the ceramics with such inclusions not only the crystallite size and porosity, but also the transmission near the edge of the fundamental absorption band decrease, and the theoretically predicted transparency is not achieved (even in the infrared range). It is reported that in the ceramics containing Hf 4+ and Zr4+ , Hf 3+ and Zr3+ , additionally depopulating the 4 F 3/2 upper laser level of the Nd3+ ion activator, are also present. The dependences of the Nd:Y2O3 crystal lattice parameter on the Hf 4+ or Nd3+ content in it, constructed based on the results of x-ray diffraction analysis, are linear, that is, no peculiarities are observed for solid solutions of these compounds. Energy dispersion analysis with a resolution of about 1 μm also indicates the uniformity of the distribution of the chemical elements throughout the sample. At the same time, estimates based on the Rayleigh light scattering in the ceramics indicate that one of the additional phases must have sizes smaller than λ/20 = 20 nm. By the method of high-resolution transmission electron microscopy, particles with composition modulated on the nanolevel are detected in the 90(Nd0.01Y0.99)2O3 + 10HfO2 nanopowder from which the ceramics are synthesized given that the lattice period remains unchanged.

  3. Reliability of metalloceramic and zirconia-based ceramic crowns.

    PubMed

    Silva, N R F A; Bonfante, E A; Zavanelli, R A; Thompson, V P; Ferencz, J L; Coelho, P G

    2010-10-01

    Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing. PMID:20660796

  4. 'Age-hardened alloy' based on bulk polycrystalline oxide ceramic

    NASA Astrophysics Data System (ADS)

    Gurnani, Luv; Singh, Mahesh Kumar; Bhargava, Parag; Mukhopadhyay, Amartya

    2015-05-01

    We report here for the first time the development of 'age-hardened/toughened' ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a 'near-ideal' microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe2O4) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO-MgFe2O4 alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.

  5. Reliability of Metalloceramic and Zirconia-based Ceramic Crowns

    PubMed Central

    Silva, N.R.F.A.; Bonfante, E.A.; Zavanelli, R.A.; Thompson, V.P.; Ferencz, J.L.; Coelho, P.G.

    2010-01-01

    Despite the increasing utilization of all-ceramic crown systems, their mechanical performance relative to that of metal ceramic restorations (MCR) has yet to be determined. This investigation tested the hypothesis that MCR present higher reliability over two Y-TZP all-ceramic crown systems under mouth-motion fatigue conditions. A CAD-based tooth preparation with the average dimensions of a mandibular first molar was used as a master die to fabricate all restorations. One 0.5-mm Pd-Ag and two Y-TZP system cores were veneered with 1.5 mm porcelain. Crowns were cemented onto aged (60 days in water) composite (Z100, 3M/ESPE) reproductions of the die. Mouth-motion fatigue was performed, and use level probability Weibull curves were determined. Failure modes of all systems included chipping or fracture of the porcelain veneer initiating at the indentation site. Fatigue was an acceleration factor for all-ceramic systems, but not for the MCR system. The latter presented significantly higher reliability under mouth-motion cyclic mechanical testing. PMID:20660796

  6. Thermomechanical Property Data Base Developed for Ceramic Fibers

    NASA Technical Reports Server (NTRS)

    1996-01-01

    A key to the successful application of metal and ceramic composite materials in advanced propulsion and power systems is the judicious selection of continuous-length fiber reinforcement. Appropriate fibers can provide these composites with the required thermomechanical performance. To aid in this selection, researchers at the NASA Lewis Research Center, using in-house state-of-the-art test facilities, developed an extensive data base of the deformation and fracture properties of commercial and developmental ceramic fibers at elevated temperatures. Lewis' experimental focus was primarily on fiber compositions based on silicon carbide or alumina because of their oxidation resistance, low density, and high modulus. Test approaches typically included tensile and flexural measurements on single fibers or on multifilament tow fibers in controlled environments of air or argon at temperatures from 800 to 1400 C. Some fiber specimens were pretreated at composite fabrication temperatures to simulate in situ composite conditions, whereas others were precoated with potential interphase and matrix materials.

  7. Eu oxidation state in fluorozirconate-based glass ceramics

    SciTech Connect

    Henke, B.; Passlick, C.; Keil, P.; Johnson, J. A.; Schweizer, S.

    2009-12-01

    The influence of InF{sub 3} doping and remelting on Eu-doped fluorozirconate-based glass ceramics was investigated using near-edge x-ray absorption and optical spectroscopy. It was found that the addition of InF{sub 3} to the melt decreases the Eu{sup 2+}/Eu{sup 3+} mole ratio, while remelting leads to a significant change in the Eu{sup 2+}/Eu{sup 3+} ratio in favor of Eu{sup 2+}. Photoluminescence spectroscopy shows that additional annealing steps lead to the formation of BaCl{sub 2} nanoparticles in the glass. In as-made glass ceramics containing InF{sub 3}, a phase transition of the nanoparticles from hexagonal to orthorhombic structure is observed. This phase transition is not observed in the remelted glasses studied here.

  8. Environmental Barrier Coatings for Silicon-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Fox, Dennis S.; Robinson, Raymond C.; Bansal, Narottam P.

    2001-01-01

    Silicon-based ceramics, such as SiC fiber-reinforced SiC (SiC/SiC ceramic matrix composites (CMC) and monolithic silicon nitride (Si3N4), are prime candidates for hot section structural components of next generation gas turbine engines. Silicon-based ceramics, however, suffer from rapid surface recession in combustion environments due to volatilization of the silica scale via reaction with water vapor, a major product of combustion. Therefore, application of silicon-based ceramic components in the hot section of advanced gas turbine engines requires development of a reliable method to protect the ceramic from environmental attack. An external environmental barrier coating (EBC) is considered a logical approach to achieve protection and CP long-term stability. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 Wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program (5). They consist of three layers, a silicon first bond coat, a mullite or a mullite + BSAS (BaO(1-x)-SrO(x)-Al2O3-2SiO2) second bond coat, and a BSAS top coat. The EPM EBCs were applied on SiC/SiC CMC combustor liners in three Solar Turbines (San Diego, CA) Centaur 50s gas turbine engines. The combined operation of the three engines has accumulated over 24,000 hours without failure (approximately 1,250 C maximum combustor liner temperature), with the engine in Texaco, Bakersfield, CA, accumulating about 14,000 hours. As the

  9. Synthesis of Hafnium-Based Ceramic Materials for Ultra-High Temperature Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Johnson, Sylvia; Feldman, Jay

    2004-01-01

    This project involved the synthesis of hafnium (Hf)-based ceramic powders and Hf-based precursor solutions that were suitable for preparation of Hf-based ceramics. The Hf-based ceramic materials of interest in this project were hafnium carbide (with nominal composition HE) and hafnium dioxide (HfO2). The materials were prepared at Georgia Institute of Technology and then supplied to research collaborators Dr. Sylvia Johnson and Dr. Jay Feldman) at NASA Ames Research Center.

  10. Ceramic Technology Project data base: September 1992 summary report

    SciTech Connect

    Keyes, B.L.P.

    1993-06-01

    Data presented in this report represent an intense effort to improve processing methods, testing methods, and general mechanical properties (rupture modulus, tensile, creep, stress-rupture, dynamic and cyclic fatigue, fracture toughness) of candidate ceramics for use in advanced heat engines. This work was performed by many facilities and represents only a small part of the data generated by the Ceramic Technology Project (CTP) since 1986. Materials discussed include GTE PY6, GN-10, NT-154, NT-164, SN-260, SN-251, SN-252, AY6, silicon nitride combined with rare-earth oxides, Y-TZP, ZTA, NC-433, NT-230, Hexoloy SA, MgO-PSZ-to-MgO-PSZ joints, MgO-PSZ-to-cast iron, and a few whisker/fiber-reinforced ceramics. Information in this report was taken from the project`s semiannual and bimonthly progress reports and from final reports summarizing the results of individual studies. Test results are presented in tabular form and in graphs. All data, including test rig descriptions and material characterizations, are stored in the CTP data base and are available to all project participants on request. The objective of this report is to make available the test results from these studies but not to draw conclusions from those data.

  11. Separators - Technology review: Ceramic based separators for secondary batteries

    NASA Astrophysics Data System (ADS)

    Nestler, Tina; Schmid, Robert; Münchgesang, Wolfram; Bazhenov, Vasilii; Schilm, Jochen; Leisegang, Tilmann; Meyer, Dirk C.

    2014-06-01

    Besides a continuous increase of the worldwide use of electricity, the electric energy storage technology market is a growing sector. At the latest since the German energy transition ("Energiewende") was announced, technological solutions for the storage of renewable energy have been intensively studied. Storage technologies in various forms are commercially available. A widespread technology is the electrochemical cell. Here the cost per kWh, e. g. determined by energy density, production process and cycle life, is of main interest. Commonly, an electrochemical cell consists of an anode and a cathode that are separated by an ion permeable or ion conductive membrane - the separator - as one of the main components. Many applications use polymeric separators whose pores are filled with liquid electrolyte, providing high power densities. However, problems arise from different failure mechanisms during cell operation, which can affect the integrity and functionality of these separators. In the case of excessive heating or mechanical damage, the polymeric separators become an incalculable security risk. Furthermore, the growth of metallic dendrites between the electrodes leads to unwanted short circuits. In order to minimize these risks, temperature stable and non-flammable ceramic particles can be added, forming so-called composite separators. Full ceramic separators, in turn, are currently commercially used only for high-temperature operation systems, due to their comparably low ion conductivity at room temperature. However, as security and lifetime demands increase, these materials turn into focus also for future room temperature applications. Hence, growing research effort is being spent on the improvement of the ion conductivity of these ceramic solid electrolyte materials, acting as separator and electrolyte at the same time. Starting with a short overview of available separator technologies and the separator market, this review focuses on ceramic-based separators

  12. Separators - Technology review: Ceramic based separators for secondary batteries

    SciTech Connect

    Nestler, Tina; Schmid, Robert; Münchgesang, Wolfram; Bazhenov, Vasilii; Meyer, Dirk C.; Schilm, Jochen; Leisegang, Tilmann

    2014-06-16

    Besides a continuous increase of the worldwide use of electricity, the electric energy storage technology market is a growing sector. At the latest since the German energy transition ('Energiewende') was announced, technological solutions for the storage of renewable energy have been intensively studied. Storage technologies in various forms are commercially available. A widespread technology is the electrochemical cell. Here the cost per kWh, e. g. determined by energy density, production process and cycle life, is of main interest. Commonly, an electrochemical cell consists of an anode and a cathode that are separated by an ion permeable or ion conductive membrane - the separator - as one of the main components. Many applications use polymeric separators whose pores are filled with liquid electrolyte, providing high power densities. However, problems arise from different failure mechanisms during cell operation, which can affect the integrity and functionality of these separators. In the case of excessive heating or mechanical damage, the polymeric separators become an incalculable security risk. Furthermore, the growth of metallic dendrites between the electrodes leads to unwanted short circuits. In order to minimize these risks, temperature stable and non-flammable ceramic particles can be added, forming so-called composite separators. Full ceramic separators, in turn, are currently commercially used only for high-temperature operation systems, due to their comparably low ion conductivity at room temperature. However, as security and lifetime demands increase, these materials turn into focus also for future room temperature applications. Hence, growing research effort is being spent on the improvement of the ion conductivity of these ceramic solid electrolyte materials, acting as separator and electrolyte at the same time. Starting with a short overview of available separator technologies and the separator market, this review focuses on ceramic-based separators

  13. Orthopedic devices; classification for the resorbable calcium salt bone void filler device. Final rule.

    PubMed

    2003-06-01

    The Food and Drug Administration (FDA) is classifying the resorbable calcium salt bone void filler device intended to fill bony voids or gaps of the extremities, spine, and pelvis that are caused by trauma or surgery and are not intrinsic to the stability of the bony structure into class II (special controls). Elsewhere in this issue of the Federal Register, FDA is announcing the availability of a class II special controls guidance entitled "Class II Special Controls Guidance Document: Resorbable Calcium Salt Bone Void Filler Device; Guidance for Industry and FDA." This action is being undertaken based on new information submitted in a classification proposal from Wright Medical Technology under the Federal Food, Drug, and Cosmetic Act as amended by the Medical Device Amendments of 1976, the Safe Medical Devices Act of 1990, and the Food and Drug Administration Modernization Act of 1997. PMID:12784825

  14. [In vitro studies of the mechanical load capability of resorbable monofilament suture materials].

    PubMed

    Bremer, Felicia; Gellrich, Nils-Claudius; Stiesch, Meike

    2009-01-01

    In a vast spectrum of wound closures there is an indication for resorbable suture materials. For surgeons detailed knowledge of the physicochemical properties is important in order to find the right suture for each indication. For this purpose, various new monofilament polymers were employed. The objective of the present study was to investigate the effects of hydrolysis and gamma-irradiation on the linear strength. The final analysis of all tested suture materials concluded that gamma-irradiation had no effects on linear strength. However, the analysis showed significant discrepancies between individual polymers with regard to loss of tensile strength associated with hydrolysis. Polydioxanone- and caprolactone-lactid-based resorbable suture materials both displayed adequate tensile strength after a five-week period of hydrolysis. In comparison the triblock-copolymer is subject to rapid degradation. Polydioxanone- and caprolactone-lactid-based resorbable suture materials are indicated for use in tissues which require mechanical support over a longer period. Monosyn is more suitable for short-term wound support. PMID:19852206

  15. Fatigue of alumina-based ceramics and chrome carbide composites

    NASA Astrophysics Data System (ADS)

    Kireitseu, Maksim V.; Yerakhavets, Liudmila; Nemerenco, Ion; Basenuk, Vladimir L.

    2003-10-01

    The paper was revealed a fatigue in the alumina-chrome carbide composite. The trapped crack front resembles a collinear array of microcracks interspersed by grains rich in transformable precipitates. This micromechanical model provides a reasonable explanation for the observed fatigue crack growth. A numerical procedure similar to the one used in the analysis of the array of collinear cracks, based on complex potentials and dislocation formalism is also used to simulate fatigue of composite coatings based on oxide ceramics and chrome carbide. Assuming power-law crack growth, it is found that the crack growth rate decreases with the applied stress intensity factor in the initial stage of fatigue crack growth. Depending on the applied load and the amount of transformation, the growth rate either goes through a minimum before increasing to the normal crack regime, or the rate continues to decrease until the crack is arrested. A detailed parametric study of the phenomenon of fatigue crack arrest in composite coatings based on oxide ceramics and chrome carbide reveals that the combination of transformation strength parameter and applied load determines whether or not crack arrest will occur, irrespective of the initial crack length. Based on the parametric study a simple linear relationship between the applied load and the minimum transformation strength parameter necessary to cause crack arrest has been developed. it will be found useful in the design against fatigue by predicting the maximum toad at which crack arrest can be expected.

  16. Development of CVD mullite coatings for Si-based ceramics

    NASA Astrophysics Data System (ADS)

    Auger, Michael Lawrence

    1999-09-01

    To raise fuel efficiencies, the next generation of engines and fuel systems must be lighter and operate at higher temperatures. Ceramic-based materials, which are considerably lighter than metals and can withstand working temperatures of up to 1400sp°C, have been targeted to replace traditional metal-based components. The materials used in combustion environments must also be capable of withstanding erosion and corrosion caused by combustion gases, particulates, and deposit-forming corrodants. With these demanding criteria, silicon-based ceramics are the leading candidate materials for high temperature engine and heat exchanger structural components. However, these materials are limited in gaseous environments and in the presence of molten salts since they form liquid silicates on exposed surfaces at temperatures as low as 800sp°C. Protective coatings that can withstand higher operating temperatures and corrosive atmospheres must be developed for silicon-based ceramics. Mullite (3Alsb2Osb3{*}2SiOsb2) was targeted as a potential coating material due to its unique ability to resist corrosion, retain its strength, resist creep, and avoid thermal shock failure at elevated temperatures. Several attempts to deposit mullite coatings by various processing methods have met with limited success and usually resulted in coatings that have had pores, cracks, poor adherence, and required thermal post-treatments. To overcome these deficiencies, the direct formation of chemically vapor deposited (CVD) mullite coatings has been developed. CVD is a high temperature atomistic deposition technique that results in dense, adherent crystalline coatings. The object of this dissertation was to further the understanding of the CVD mullite deposition process and resultant coating. The kinetics of CVD mullite deposition were investigated as a function of the following process parameters: temperature, pressure, and the deposition reactor system. An empirical kinetic model was developed

  17. Ceramic-based fuel technologies: scope and status

    SciTech Connect

    Mcclellan, Kenneth J

    2010-12-16

    This presentation is an overview of the approach, status and path forward for ongoing tasks under the ceramic fuel development part of the program. Experimental work is focused on fundamental studies employing depleted urania-based compositions and mixed oxide (MOX) and minor actinide-bearing MOX. Contributions are included from researchers at LANL, ORNL and BNL. The audience for this presentation consists of the various participants in the FCRD program. Those participants include representatives from: DOE-NE, other national laboratories, DOE funded university researchers, DOE funded industry teams, FCRD funded advisors, and occasionally NRC.

  18. Zirconia-based sintered ceramics for biomedical applications

    NASA Astrophysics Data System (ADS)

    Kulkov, Sergey; Buyakova, Svetlana

    2016-08-01

    A porous ceramics obtained from ultra-fine powders has been studied. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials was a cellular structure. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  19. Electrical and reliability characteristics of Mn-doped nano BaTiO3-based ceramics for ultrathin multilayer ceramic capacitor application

    NASA Astrophysics Data System (ADS)

    Gong, Huiling; Wang, Xiaohui; Zhang, Shaopeng; Tian, Zhibin; Li, Longtu

    2012-12-01

    Nano BaTiO3-based dielectric ceramics were prepared by chemical coating approach, which are promising for ultrathin multilayer ceramic capacitor (MLCC) applications. The doping effects of Mn element on the microstructures and dielectric properties of the ceramics were investigated. The degradation test and impedance spectroscopy were employed to study the resistance degradation and the conduction mechanism of Mn-doped nano-BaTiO3 ceramic samples. It has been found that the reliability characteristics greatly depended on the Mn-doped content. Moreover, the BaTiO3 ceramic with grain size in nanoscale is more sensitive to the Mn-doped content than that in sub-micron scale. The addition of 0.3 mol. % Mn is beneficial for improving the reliability of the nano BaTiO3-based ceramics, which is an important parameter for MLCC applications. However, further increasing the addition amount will deteriorate the performance of the ceramic samples.

  20. Bio resorbability of the modified hydroxyapatite in Tris-HCL buffer

    NASA Astrophysics Data System (ADS)

    Golovanova, O. A.; Izmailov, R. R.; Ghyngazov, S. A.

    2016-02-01

    The solubility of carbonated hydroxyapatite powders and granulated carbonated hydroxyapatite produced from the synovial biofluid model solution has been studied. The kinetic characteristics of dissolution were determined. It was found that the solubility of carbonated hydroxyapatite is higher as compared to that of hydroxyapatite. The impact of the organic matrix on the rate of sample dissolution was revealed. For HA-gelatin composites, as the gelatin concentration grows, the dissolution rate becomes greater, and a sample of 6.0 g / L concentration has higher resorbability. The results of the research can be used to study the kinetics of dissolution and the biocompatibility of ceramic materials for medicine, namely for reconstructive surgery, dentistry, and development of drug delivery systems.

  1. Osteoclast function and bone-resorbing activity: An overview.

    PubMed

    Soysa, Niroshani Surangika; Alles, Neil

    2016-07-29

    Bone resorption is an important cellular function in skeletal development and remodeling of the adult skeleton. Most of the pathological bone disease conditions like osteoporosis reflect increased osteoclast activity; hence, increased bone resorption. Researchers have unraveled most of the intracellular mechanisms responsible for osteoclast bone-resorbing activity in last few decades. Therefore, understanding the fundamentals of osteoclast-induced bone resorption and the cytokines and other substances that modulate the osteoclast activity unequivocally provide insights into the development of drugs to ameliorate pathological bone diseases with enhanced bone resorption. The aim of this review is to examine the literature on osteoclast function and bone-resorbing activity. PMID:27157135

  2. Novel fabrication of silicon carbide based ceramics for nuclear applications

    NASA Astrophysics Data System (ADS)

    Singh, Abhishek Kumar

    Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These materials include refractory alloys based on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as SiC--SiCf; carbon--carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor components is necessary for improved efficiency. Improving thermal conductivity of the fuel can lower the center-line temperature and, thereby, enhance power production capabilities and reduce the risk of premature fuel pellet failure. Crystalline silicon carbide has superior characteristics as a structural material from the viewpoint of its thermal and mechanical properties, thermal shock resistance, chemical stability, and low radioactivation. Therefore, there have been many efforts to develop SiC based composites in various forms for use in advanced energy systems. In recent years, with the development of high yield preceramic precursors, the polymer infiltration and pyrolysis (PIP) method has aroused interest for the fabrication of ceramic based materials, for various applications ranging from disc brakes to nuclear reactor fuels. The pyrolysis of preceramic polymers allow new types of ceramic materials to be processed at relatively low temperatures. The raw materials are element-organic polymers whose composition and architecture can be tailored and varied. The primary focus of this study is to use a pyrolysis based process to fabricate a host of novel silicon carbide-metal carbide or oxide composites, and to synthesize new materials based on mixed-metal silicocarbides that cannot be processed using conventional techniques. Allylhydridopolycarbosilane (AHPCS), which is an organometal polymer, was used as the precursor for silicon carbide. Inert gas pyrolysis of AHPCS produces near-stoichiometric amorphous

  3. An ammonium soal solution based method for the preparation of ceramic/copper metal microcomposites

    SciTech Connect

    Walker, R.J.; Robinson, D.A.

    1995-12-01

    Robinson and Maginnis have developed a process for the preparation of metal ceramic composites using an ammonium soap solution based route. This current work is an extension of their patent application. Their work focused on preparing silver/YBa{sub 2}Cu{sub 3}O{sub 7-x}. We have extended their work to prepare copper ceramic microcomposites. In this method, an ammonium soap of 2-ethylhexanoate is used to prepare a metallorganic in solution that is rapidly jelled or precipitated around a suspended and dispersed ceramic. This step is followed by a low temperature heat treatment in hydrogen to produce the desired composite. Depending on the heat treatment, the composite can be varied from metal coated ceramic grains to finely dispersed metal in a ceramic matrix. System specific schemes for the preparation of copper metal/ceramics will be presented along with X-ray Diffraction data, SEM and Optical micrographs.

  4. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance...

  5. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance...

  6. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance...

  7. A study on (K, Na) NbO3 based multilayer piezoelectric ceramics micro speaker

    NASA Astrophysics Data System (ADS)

    Gao, Renlong; Chu, Xiangcheng; Huan, Yu; Sun, Yiming; Liu, Jiayi; Wang, Xiaohui; Li, Longtu

    2014-10-01

    A flat panel micro speaker was fabricated from (K, Na) NbO3 (KNN)-based multilayer piezoelectric ceramics by a tape casting and cofiring process using Ag-Pd alloys as an inner electrode. The interface between ceramic and electrode was investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). The acoustic response was characterized by a standard audio test system. We found that the micro speaker with dimensions of 23 × 27 × 0.6 mm3, using three layers of 30 μm thickness KNN-based ceramic, has a high average sound pressure level (SPL) of 87 dB, between 100 Hz-20 kHz under five voltage. This result was even better than that of lead zirconate titanate (PZT)-based ceramics under the same conditions. The experimental results show that the KNN-based multilayer ceramics could be used as lead free piezoelectric micro speakers.

  8. Improved performance of silicon nitride-based high temperature ceramics

    NASA Technical Reports Server (NTRS)

    Ashbrook, R. L.

    1977-01-01

    Recent progress in the production of Si3N4 based ceramics is reviewed: (1) high temperature strength and toughness of hot pressed Si3N4 were improved by using high purity powder and a stabilized ZrO2 additive, (2) impact resistance of hot pressed Si3N4 was increased by the use of a crushable energy absorbing layer, (3) the oxidation resistance and strength of reaction sintered Si3N4 were increased by impregnating reaction sintered silicon nitride with solutions that oxidize to Al2O3 or ZrO2, (4) beta prime SiA1ON compositions and sintering aids were developed for improved oxidation resistance or improved high temperature strength.

  9. Improved Properties of Pb Based BLZT Ferroelectric Ceramics

    SciTech Connect

    Kumar, Parveen; Singh, Sangeeta; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

    2011-11-22

    Present report is concerning with investigation of effect of different sintering profiles on Pb based BLZT ceramics. The material powder of selected composition (Ba{sub 0.795}La{sub 0.005}Pb{sub 0.20}Ti{sub 0.90}Zr{sub 0.10}O{sub 3}) was prepared by solid state reaction route and then powder was compacted in the form of circular discs. The discs were then sintered at different temperatures (1325 deg. C for 4h, 1325 deg. C for 15min+1200 deg. C for 4h). Improved dielectric and ferroelectric properties were observed for samples sintered at 1200 deg. C. Shifting in T{sub c} to higher temperature could be related to enhanced tetragonality, which was further confirmed by X-ray diffraction analysis. All these improvements evidences that there is less Pb loss in case of modified sintering profile.

  10. Advanced Environmental Barrier Coatings Development for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Choi, R. Sung; Robinson, Raymond C.; Lee, Kang N.; Bhatt, Ramakrishna T.; Miller, Robert A.

    2005-01-01

    Advanced environmental barrier coating concepts based on multi-component HfO2 (ZrO2) and modified mullite systems are developed for monolithic Si3N4 and SiC/SiC ceramic matrix composite (CMC) applications. Comprehensive testing approaches were established using the water vapor cyclic furnace, high pressure burner rig and laser heat flux steam rig to evaluate the coating water vapor stability, cyclic durability, radiation and erosion resistance under simulated engine environments. Test results demonstrated the feasibility and durability of the environmental barrier coating systems for 2700 to 3000 F monolithic Si3N4 and SiC/SiC CMC component applications. The high-temperature-capable environmental barrier coating systems are being further developed and optimized in collaboration with engine companies for advanced turbine engine applications.

  11. A resorbable bicomponent braided ureteral stent with improved mechanical performance.

    PubMed

    Zou, Ting; Wang, Lu; Li, Wenchao; Wang, Wenzu; Chen, Fang; King, Martin W

    2014-10-01

    Bioresorbable ureteral stents have the advantage of eliminating the need for a second removal surgery and hence avoiding certain complications. However the inadequate mechanical performance and lack of control over the rate of resorption limit the use of current prototype designs. This paper focuses on a series of resorbable millimeter-sized stents which were fabricated by a unique combination of braiding and thermal treatment processes. Their mechanical properties where optimized by varying the braided structure and different resorbable components. Five different bicomponent structures were fabricated for the stent with different areas and distributions of poly (glycolic acid) (PGA) and poly (lactic-co-glycolic acid) (PLGA) resorbable yarns. Subsequent thermal treatment then converted the PLGA yarns into areas of continuous PLGA polymer film. The morphology, applied compression resistance and recovery and tensile strength tests were conducted on these prototype stents so as to investigate the relationship between their structures and mechanical properties. By selecting the appropriate resorbable biomaterials and altering the design of the braided structure it was possible to generate different sized areas and distributions of 100% braided yarn and 100% polymer film within the same bicomponent tubular structure. The relative total area of braided yarn to polymer film coverage was different for the five different prototype stents as well as between the external and internal surfaces of the bicomponent stents. This relative coverage of the braided yarn to polymer film played an important role in determining the mechanical performance of the stents, including the compression and recovery behavior as well as the tensile properties and failure morphology. The design of Stent C appeared to have the optimal structure for a resorbable ureteral stent with superior applied compression and tensile properties. PMID:24997428

  12. Challenges of Engineering Grain Boundaries in Boron-Based Armor Ceramics

    NASA Astrophysics Data System (ADS)

    Coleman, Shawn P.; Hernandez-Rivera, Efrain; Behler, Kristopher D.; Synowczynski-Dunn, Jennifer; Tschopp, Mark A.

    2016-06-01

    Boron-based ceramics are appealing for lightweight applications in both vehicle and personnel protection, stemming from their combination of high hardness, high elastic modulus, and low density as compared to other ceramics and metal alloys. However, the performance of these ceramics and ceramic composites is lacking because of their inherent low fracture toughness and reduced strength under high-velocity threats. The objective of the present article is to briefly discuss both the challenges and the state of the art in experimental and computational approaches for engineering grain boundaries in boron-based armor ceramics, focusing mainly on boron carbide (B4C) and boron suboxide (B6O). The experimental challenges involve processing these ceramics at full density while trying to promote microstructure features such as intergranular films to improve toughness during shock. Many of the computational challenges for boron-based ceramics stem from their complex crystal structure which has hitherto complicated the exploration of grain boundaries and interfaces. However, bridging the gaps between experimental and computational studies at multiple scales to engineer grain boundaries in these boron-based ceramics may hold the key to maturing these material systems for lightweight defense applications.

  13. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    PubMed Central

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials. PMID:22619551

  14. Challenges of Engineering Grain Boundaries in Boron-Based Armor Ceramics

    NASA Astrophysics Data System (ADS)

    Coleman, Shawn P.; Hernandez-Rivera, Efrain; Behler, Kristopher D.; Synowczynski-Dunn, Jennifer; Tschopp, Mark A.

    2016-03-01

    Boron-based ceramics are appealing for lightweight applications in both vehicle and personnel protection, stemming from their combination of high hardness, high elastic modulus, and low density as compared to other ceramics and metal alloys. However, the performance of these ceramics and ceramic composites is lacking because of their inherent low fracture toughness and reduced strength under high-velocity threats. The objective of the present article is to briefly discuss both the challenges and the state of the art in experimental and computational approaches for engineering grain boundaries in boron-based armor ceramics, focusing mainly on boron carbide (B4C) and boron suboxide (B6O). The experimental challenges involve processing these ceramics at full density while trying to promote microstructure features such as intergranular films to improve toughness during shock. Many of the computational challenges for boron-based ceramics stem from their complex crystal structure which has hitherto complicated the exploration of grain boundaries and interfaces. However, bridging the gaps between experimental and computational studies at multiple scales to engineer grain boundaries in these boron-based ceramics may hold the key to maturing these material systems for lightweight defense applications.

  15. Bond strength: a comparison between chemical coated and mechanical interlock bases of ceramic and metal brackets.

    PubMed

    Wang, W N; Meng, C L; Tarng, T H

    1997-04-01

    Two types of chemically coated bases, two types of mechanical interlock base polycrystalline ceramic brackets, as well as one type of mechanical interlock base metal bracket were selected for bonding with Concise orthodontic resin on 60 extracted premolars. Bond strength was measured with an Instron testing machine and the debonded interface and enamel detachment were examined with scanning electron microscope and energy dispersive x-ray spectrometer. The results showed the greater bond strength with a chemically coated base of ceramic brackets had a greater debonded interface between enamel and resin, and the weaker bond strength of mechanical interlock base of ceramic and metal brackets had a greater debonded interfaces between bracket and resin. There was no significant statistical difference in bond strengths with mechanically interlock bases between ceramic and metal brackets. The enamel detachment was found on only the stronger bond strength in which there was a chemically coated base on the ceramic bracket. Ceramic bracket fractures were not found during debonding in this specially designed specimen with 1 mm/min speed of crosshead. The mechanical interlock base of the ceramic bracket combines the strength, durability and retention of a metal bracket along with an aesthetic advantage and no enamel detachment after debonding. PMID:9109582

  16. Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

    Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

  17. Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2004-01-01

    Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.

  18. The effect of ceramic thickness and number of firings on the color of a zirconium oxide based all ceramic system fabricated using CAD/CAM technology

    PubMed Central

    Aras, Meena Ajay

    2011-01-01

    PURPOSE Ceramics have a long history in fixed prosthodontics for achieving optimal esthetics and various materials have been used to improve ceramic core strength. However, there is a lack of information on how color is affected by fabrication procedure. The purpose of this study was to evaluate the effects of various dentin ceramic thicknesses and repeated firings on the color of zirconium oxide all-ceramic system (Lava™) fabricated using CAD/CAM technology. MATERIALS AND METHODS Thirty disc-shaped cores, 12 mm in diameter with a 1 mm thickness were fabricated from zirconium oxide based all ceramic systems (Lava™, 3M ESPE, St Paul, MN, USA) and divided into three groups (n = 10) according to veneering with dentin ceramic thicknesses: as 0.5, 1, or 1.5 mm. Repeated firings (3, 5, 7, or 9) were performed, and the color of the specimens was compared with the color after the initial firing. Color differences among ceramic specimens were measured using a spectrophotometer (VITA Easyshade, VITA Zahnfabrik, Bad Säckingen, Germany) and data were expressed in CIELAB system coordinates. A repeated measures ANOVA and Bonferroni post hoc test were used to analyze the data (n = 10, α=.05). RESULTS L*a*b* values of the ceramic systems were affected by the number of firings (3, 5, 7, or 9 firings) (P<.001) and ceramic thickness (0.5, 1, or 1.5 mm) (P<.001). Significant interactions were present in L*a*b* values between the number of firings and ceramic thickness (P<.001). An increase in number of firings resulted in significant increase in L* values for both 0.5 mm and 1.5 mm thicknesses (P<.01, P=.013); however it decreased for 1 mm thickness (P<.01). The a* values increased for 1 mm and 1.5 mm thicknesses (P<.01), while it decreased for 0.5 mm specimens. The b* values increased significantly for all thicknesses (P<.01, P=.022). As the dentin ceramic thickness increased, significant reductions in L* values (P<.01) were recorded. There were significant increases in both a

  19. Injection molding of ceramics using a polyacetal based binder system

    SciTech Connect

    Ebenhoech, J.S.

    1996-06-01

    Among the production routes to small complex ceramic parts, powder injection molding is the most attractive alternative. It combines near net shape capability with good surface finish and is easy to automate. With the development of the catalytic debinding process for polyacetal binders, the main impediments for the acceptance of ceramic injection molding as a mass production method can be overcome. The use of this system ensures short molding cycle times, high green strength and fast debinding without deformation. Ready to mold compounds are commercially available for various oxide and non-oxide ceramic materials as well as the equipment needed for this process.

  20. Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

    NASA Astrophysics Data System (ADS)

    Li, Liyang; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Zhang, Jieqiu; Qu, Shaobo; Xu, Zhuo

    2016-04-01

    Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55–4.60 GHz and 4.54–4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications.

  1. Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

    PubMed Central

    Li, Liyang; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Zhang, Jieqiu; Qu, Shaobo; Xu, Zhuo

    2016-01-01

    Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55–4.60 GHz and 4.54–4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications. PMID:27052098

  2. The preparation of ceramic nickel metal microcompostes using an ammonium soap solution-based method

    SciTech Connect

    Clark, N.A.; Robinson, D.A.

    1995-12-01

    Robinson and Maginnis have developed a process for the preparation of metal ceramic composites using an ammonium soap solution-based route. Their work focused on the preparation of silver/YBa{sub 2}Cu{sub 3}O{sub 7-x} composites. We have extended their work to prepare nickel ceramic microcomposites. In this method, an ammonium soap of 2-ethylhexanoate is used to prepare a nickel metallorganic in solution that is rapidly gelled or precipitated around a suspended and dispersed ceramic. This is followed by a low-temperature heat treatment in hydrogen to produce the desired composite. By varying the heat treatment, the composite can be altered from metal-coated ceramic grains to finely dispersed metal in a ceramic matrix. The experimental preparation of this material will be presented along with optical micrographs and spectroscopic data.

  3. Modeling of water absorption induced cracks in resin-based composite supported ceramic layer structures.

    PubMed

    Huang, Min; Thompson, V P; Rekow, E D; Soboyejo, W O

    2008-01-01

    Cracking patterns in the top ceramic layers of the modeled dental multilayers with polymer foundation are observed when they are immersed in water. This article developed a model to understand this cracking mechanism. When water diffuses into the polymer foundation of dental restorations, the foundation will expand; as a result, the stress will build up in the top ceramic layer because of the bending and stretching. A finite element model based on this mechanism is built to predict the stress build-up and the slow crack growth in the top ceramic layers during the water absorption. Our simulations show that the stress build-up by this mechanism is high enough to cause the cracking in the top ceramic layers and the cracking patterns predicted by our model are well consistent with those observed in experiments on glass/epoxy/polymer multilayers. The model is then used to discuss the life prediction of different dental ceramics. PMID:17497681

  4. Characterization of a resorbable poly(ester urethane) with biodegradable hard segments.

    PubMed

    Dempsey, David K; Robinson, Jennifer L; Iyer, Ananth V; Parakka, James P; Bezwada, Rao S; Cosgriff-Hernandez, Elizabeth M

    2014-01-01

    The rapid growth of regenerative medicine and drug delivery fields has generated a strong need for improved polymeric materials that degrade at a controlled rate into safe, non-cytotoxic by-products. Polyurethane thermoplastic elastomers offer several advantages over other polymeric materials including tunable mechanical properties, excellent fatigue strength, and versatile processing. The variable segmental chemistry in developing resorbable polyurethanes also enables fine control over the degradation profile as well as the mechanical properties. Linear aliphatic isocyanates are most commonly used in biodegradable polyurethane formulations; however, these aliphatic polyurethanes do not match the mechanical properties of their aromatic counterparts. In this study, a novel poly(ester urethane) (PEsU) synthesized with biodegradable aromatic isocyanates based on glycolic acid was characterized for potential use as a new resorbable material in medical devices. Infrared spectral analysis confirmed the aromatic and phase-separated nature of the PEsU. Uniaxial tensile testing displayed stress-strain behavior typical of a semi-crystalline polymer above its Tg, in agreement with calorimetric findings. PEsU outperformed aliphatic PCL-based polyurethanes likely due to the enhanced cohesion of the aromatic hard domains. Accelerated degradation of the PEsU using 0.1 M sodium hydroxide resulted in hydrolysis of the polyester soft segment on the surface, reduced molecular weight, surface cracking, and a 30% mass loss after four weeks. Calorimetric studies indicated a disruption of the soft segment crystallinity after incubation which corresponded with a drop in initial modulus of the PEsU. Finally, cytocompatibility testing with 3T3 mouse fibroblasts exhibited cell viability on PEsU films comparable to a commercial poly(ether urethane urea) after 24 h followed by 85% cell viability at 72 h. Overall, this new resorbable polyurethane shows strong potential for use in wide

  5. Biomechanical failure of metacarpal fracture resorbable plate fixation.

    PubMed

    Lionelli, Gerald T; Korentager, Richard A

    2002-08-01

    Metacarpal fractures are a relatively common hand injury that may require operative intervention to ensure adequate reduction and stabilization. The use of permanent hardware, although acceptable, may lead to complications and an increased number of surgical procedures. The use of resorbable hardware such as poly-L-lactic acid and polyglycolic acid copolymer plates and screws may circumvent some of these complications. In vitro studies have demonstrated that the biomechanical characteristics of these resorbable plates may provide the rigid fixation necessary to allow for union of metacarpal fractures in vivo. However, limited clinical data are available regarding the success of their use in this application. The authors present what they believe is the first reported case of the failure of a poly-L-lactic acid and polyglycolic acid copolymer miniplate after use in the fixation of a metacarpal shaft fracture. PMID:12187350

  6. In vivo assessment of new resorbable PEG-PPG-PEG copolymer/starch bone wax in bone healing and tissue reaction of bone defect in rabbit model.

    PubMed

    Suwanprateeb, J; Kiertkrittikhoon, S; Kintarak, J; Suvannapruk, W; Thammarakcharoen, F; Rukskul, P

    2014-09-01

    In this study, in vivo performance of novel resorbable bone wax based on a miscible blend between PEG-PPG-PEG copolymer mixtures and pregelatinized starch at 0 and 25 percent by weight including hemostasis, tissue reaction and bone healing in a non-critical size tibia defect model were assessed and compared with commercial non-resorbable bone wax. Systemic reaction was evaluated by blood chemistry while local reaction, bone quantity and quality were evaluated by microcomputed tomography (microCT) and histology analyses. It was observed that the resorbable bone waxes did not show any adverse systemic reaction and resorbed from the defects within approximately 2 days after application. They were as effective as the commercial bone wax in hemostasis, but provided better adherence to the bone surface. The incorporation of pre-gelatinized starch in the formulation could further help in improved molding texture and decreased glove adherence. MicroCT and histology analyses showed that the resorbable bone waxes did not inhibit the osteogenesis whereas commercial bone wax impaired bone healing and displayed inflammation and foreign body reactions. PMID:24913421

  7. Ceramic Technology for Advanced Heat Engines Program data base: A summary report

    SciTech Connect

    Booker, M.K.

    1988-01-01

    A large amount and wide variety of data on the behavior of advanced ceramic materials is currently being generated within the Ceramic Technology for Advanced Heat Engines Program. This paper summarizes efforts to date to develop a computer data base system for the management of those data. The system is based on the use of desktop microcomputers, which provides a maximum of efficiency, economy, and convenience in the operation of the system.

  8. Lithium-based oxide ceramics for tritium-breeding applications

    SciTech Connect

    Suiter, D J

    1983-06-01

    Material preparation techniques, crystallographic data, phase diagrams, metal compatibility, and thermal properties have been assembled for the lithium-based oxide ceramics designated as potential solid tritium breeders for fusion devices. The materials discussed in this report include: Li/sub 2/O, ..beta..-Li/sub 5/AlO/sub 4/, ..gamma..-LiAlO/sub 2/, Li/sub 4/SiO/sub 4/, Li/sub 2/SiO/sub 3/, Li/sub 4/TiO/sub 4/, Li/sub 2/TiO/sub 3/, Li/sub 8/ZrO/sub 6/, Li/sub 4/ZrO/sub 4/, and Li/sub 2/ZrO/sub 3/. The thermal properties covered were vaporization, thermal conductivity, specific heat, and linear thermal expansion. There has been no attempt to rank the above mentioned candidates, but rather to merely indicate points that must be considered when using the various materials as solid breeders. These encompass low lithium atom densities, destructive phase transformations, a higher thermal expansion, low thermal conductivity, excessive vaporization at low temperatures, corrosive nature toward metals and difficulty in sample preparation.

  9. Rule-based inspection of printed green ceramic tape

    SciTech Connect

    Patek, D.R.; Goddard, J.S.; Karnowski, T.; Lamond, D.; Hawkins, T.A.

    1998-01-01

    A template-based vision system for the 100% inspection of printed flaws on green ceramic tape has been developed. Design goals included a requirement for the detection of flaws as small as two thousandths of an inch on parts up to 8 by 8 inches in size. The inspection engine is a Datacube, Inc., MV200 pipeline processor. As each part is inspected, four 2K by 2K pixel quadrant images are stitched together to construct a single 4K by 4K pixel image with the aid of multiple fiducials located in each quadrant. The part fiducial locations, mask image, and punched-hole position data are generated, beforehand, from CAD designs using a defect map editor (DME), a preprocessing software package developed for the PC. The DME also generates a part ``defect map``. Each unique structure in the printed pattern is defined as an object. Objects are grouped into user-defined categories such as die pads, contact fingers, traces, and electrolysis buses. The map is used during the runtime inspection to associate each detected defect with an object group and a particular defect specification for that group. Repeat defects are optionally tracked for up to three consecutive parts.

  10. Magnetoelectric Effect in Ceramics Based on Bismuth Ferrite

    NASA Astrophysics Data System (ADS)

    Jartych, Elżbieta; Pikula, Tomasz; Kowal, Karol; Dzik, Jolanta; Guzdek, Piotr; Czekaj, Dionizy

    2016-04-01

    Solid-state sintering method was used to prepare ceramic materials based on bismuth ferrite, i.e., (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions and the Aurivillius Bi5Ti3FeO15 compound. The structure of the materials was examined using X-ray diffraction, and the Rietveld method was applied to phase analysis and structure refinement. Magnetoelectric coupling was registered in all the materials using dynamic lock-in technique. The highest value of magnetoelectric coupling coefficient α ME was obtained for the Bi5Ti3FeO15 compound ( α ME ~ 10 mVcm-1 Oe-1). In the case of (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions, the maximum α ME is of the order of 1 and 2.7 mVcm-1 Oe-1, respectively. The magnitude of magnetoelectric coupling is accompanied with structural transformation in the studied solid solutions. The relatively high magnetoelectric effect in the Aurivillius Bi5Ti3FeO15 compound is surprising, especially since the material is paramagnetic at room temperature. When the materials were subjected to a preliminary electrical poling, the magnitude of the magnetoelectric coupling increased 2-3 times.

  11. Anelastic behavior of barium-titanate-based ceramic materials

    NASA Astrophysics Data System (ADS)

    Duffy, W.; Cheng, B. L.; Gabbay, M.; Fantozzi, G.

    1995-07-01

    The internal friction ( Qsu-1) and Young’s modulus ( E) of BaTiO3-based ceramics were measured vs temperature from -100 °C to 150 °C. Rectangular bars of high-density (96 to 99 pct) ma-terials were driven electrostatically in flexural vibration at a resonance frequency of about 3 kHz, at maximum strain levels of about 10-6. The curves of Q -1( T) and E(T) allow the study of the following three phase transformations: tetragonal to cubic (about 130 °C in pure material), orthorhombic to tetragonal (about 0 °C in pure material), and rhombohedral to orthorhombic (about -80 °C in pure material). Internal friction and modulus data were obtained on pure material and on materials doped with niobium and cobalt to give semiconducting and insulating X7R behavior. Permittivity, dielectric loss, and microstructure data are given and used to aid interpretation of the mechanical measurement data.

  12. Strength and corrosion behavior of SiC - based ceramics in hot coal combustion environments

    SciTech Connect

    Breder, K.; Parten, R.J.

    1996-08-01

    As part of an effort to evaluate the use of advanced ceramics in a new generation of coal-fired power plants, four SiC-based ceramics have been exposed to corrosive coal slag in a laboratory furnace and two pilot scale combustors. Initial results indicate that the laboratory experiments are valuable additions to more expensive pilot plant experiments. The results show increased corrosive attack with increased temperature, and that only slight changes in temperature may significantly alter the degree of strength degradation due to corrosive attack. The present results are part of a larger experimental matrix evaluating the behavior of ceramics in the coal combustion environment.

  13. Current status of environmental barrier coatings for Si-Based ceramics

    NASA Technical Reports Server (NTRS)

    Lee, K. N.

    2000-01-01

    Silicon-based ceramics are the leading candidates for high temperature structural components in next generation gas turbine engines. One key drawback of silicon-based ceramics for such an application is volatilization of the protective silica scale in water vapor and the resulting rapid ceramic recession. Therefore, the realization of Si-based ceramics components in advanced gas turbine engines depends on the development of protection schemes from water vapor attack. Currently, plasma-sprayed external environmental barrier coatings (EBCs) arc the most promising approach. In the late 1980s and early 1990s a wide range of refractory oxide materials were tested as coatings on Si-based ceramics to provide protection from hot corrosion. After the discovery of silica volatilization in water vapor in the early 1990s, the focus of EBC development research has been shifted towards the protection from water vapor attack. Experience learned form the earlier coating developmental effort provided the foundation upon which more complex and advanced EBC coatings have been developed. This paper will discuss the brief history and the current status of EBC development for Si-based ceramics with the main focus on water vapor protection.

  14. Structures and properties of alumina-based ceramic for reconstructive oncology

    NASA Astrophysics Data System (ADS)

    Grigoriev, M. V.; Kulkov, S. N.

    2016-08-01

    The microstructure of alumina ceramics based on powders with a varying grain size has been investigated. Both commercial alumina powders and those fabricated by denitration of aluminum salts in high-frequency discharge plasma were used. It is shown that the variation of the sintering temperature and morphology of the initial powders of the particles leads to a change of the pore structure of ceramics from pore isolated clusters to a structure consisting of a ceramic skeleton and a large pore space. Changing the type of pore structure occurs at about 50% of porosity. The ceramic pore size distribution is bimodal. Dependencies final density vs initial density are linear; at the same time with increasing temperature, inclination of changes from positive to negative, indicating the change of sealing mechanisms. Extrapolation of these curves showed that they intersect with the values of density of about 2 g/cm3, which indicates the possibility of producing non-shrink ceramics. It is shown that the strength increases with increasing nanocrystalline alumina content in powder mixture. A change in the character the pore structure is accompanied by a sharp decrease in strength, which corresponds to the percolation transition in ceramics. These results showed that it is possible to obtain ceramic materials with the structure and properties similar to natural bone.

  15. Gas Sensors Based on Ceramic p-n Heterocontacts

    SciTech Connect

    Seymen Murat Aygun

    2004-12-19

    Ceramic p-n heterocontacts based on CuO/ZnO were successfully synthesized and a systematic study of their hydrogen sensitivity was conducted. The sensitivity and response rates of CuO/ZnO sensors were studied utilizing current-voltage, current-time, and impedance spectroscopy measurements. The heterocontacts showed well-defined rectifying characteristics and were observed to detect hydrogen via both dc and ac measurements. Surface coverage data were derived from current-time measurements which were then fit to a two-site Langmuir adsorption model quite satisfactorily. The fit suggested that there should be two energetically different adsorption sites in the system. The heterocontacts were doped in an attempt to increase the sensitivity and the response rate of the sensor. First, the effects of doping the p-type (CuO) on the sensor characteristics were investigated. Doping the p-type CuO with both acceptor and isovalent dopants greatly improved the hydrogen sensitivity. The sensitivity of pure heterocontact observed via I-V measurements was increased from {approx}2.3 to {approx}9.4 with Ni doping. Dopants also enhanced the rectifying characteristics of the heterocontacts. Small amounts of Li addition were shown to decrease the reverse bias (saturation) current to 0.2 mA at a bias level of -5V. No unambiguous trends were observed between the sensitivity, the conductivity, and the density of the samples. Comparing the two phase microstructure to the single phase microstructure there was no dramatic increase in the sensitivity. Kinetic studies also confirmed the improved sensor characteristics with doping. The dopants decreased the response time of the sensor by decreasing the response time of one of the adsorption sites. The n-type ZnO was doped with both acceptor and donor dopants. Li doping resulted in the degradation of the p-n junction and the response time of the sensor. However, the current-voltage behavior of Ga-doped heterocontacts showed the best rectifying

  16. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  17. Magnetoelectric Effect in Ceramics Based on Bismuth Ferrite.

    PubMed

    Jartych, Elżbieta; Pikula, Tomasz; Kowal, Karol; Dzik, Jolanta; Guzdek, Piotr; Czekaj, Dionizy

    2016-12-01

    Solid-state sintering method was used to prepare ceramic materials based on bismuth ferrite, i.e., (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions and the Aurivillius Bi5Ti3FeO15 compound. The structure of the materials was examined using X-ray diffraction, and the Rietveld method was applied to phase analysis and structure refinement. Magnetoelectric coupling was registered in all the materials using dynamic lock-in technique. The highest value of magnetoelectric coupling coefficient α ME was obtained for the Bi5Ti3FeO15 compound (α ME ~ 10 mVcm(-1) Oe(-1)). In the case of (BiFeO3)1 - x -(BaTiO3) x and Bi1 - x Nd x FeO3 solid solutions, the maximum α ME is of the order of 1 and 2.7 mVcm(-1) Oe(-1), respectively. The magnitude of magnetoelectric coupling is accompanied with structural transformation in the studied solid solutions. The relatively high magnetoelectric effect in the Aurivillius Bi5Ti3FeO15 compound is surprising, especially since the material is paramagnetic at room temperature. When the materials were subjected to a preliminary electrical poling, the magnitude of the magnetoelectric coupling increased 2-3 times. PMID:27129686

  18. CDTE CERAMICS BASED ON COMPRESSION OF NANOCRYSTAL POWDER.

    SciTech Connect

    KOLESNIKOV, N.N.; BORISENKO, E.B.; BORISENKO, D.N.; JAMES, R.B.; KVEDER, V.V.; GARTMAN, V.K.; GNESIN, G.A.

    2005-07-01

    Wide-gap II-VI semiconductor crystalline materials are conventionally used in laser optics, light emitting devices, and nuclear detectors. The advances made in the studies of nanocrystals and in the associated technologies have created great interest in the design of semiconductor devices based on these new materials. The objectives of this work are to study the microstructure and the properties of the new material produced through CdTe nanopowder compression and to consider the prospects of its use in the design of ionizing-radiation detectors and in laser optics. Highly dense material produced of 7-10 nm CdTe particles under pressure of 20-600 MPa at temperatures from 20 to 200 C was analyzed using x-ray diffractometry, texture analysis; light and scanning electron microscopy, and optical spectrophotometry. The mechanical and electrical properties of the compacted material were measured and compared with similar characteristics of the conventionally grown single crystals. Phase transformation from metastable to stable crystal structure caused by deformation was observed in the material. Sharp crystallographic texture {l_brace}001{r_brace} that apparently affects specific mechanical, electrical and optical characteristics of compacted CdTe was observed. The specific resistivity calculated from the linear current-voltage characteristics was about 10{sup 10} Ohm x cm, which is a promisingly high value regarding the possibility of using this material in the design of semiconductor radiation detectors. The optical spectra show that the transmittance in the infrared region is sufficient to consider the prospects of possible applications of CdTe ceramics in laser optics.

  19. Toward smart implant synthesis: bonding bioceramics of different resorbability to match bone growth rates.

    PubMed

    Comesaña, Rafael; Lusquiños, Fernando; Del Val, Jesús; Quintero, Félix; Riveiro, Antonio; Boutinguiza, Mohamed; Jones, Julian R; Hill, Robert G; Pou, Juan

    2015-01-01

    Craniofacial reconstructive surgery requires a bioactive bone implant capable to provide a gradual resorbability and to adjust to the kinetics of new bone formation during healing. Biomaterials made of calcium phosphate or bioactive glasses are currently available, mainly as bone defect fillers, but it is still required a versatile processing technique to fabricate composition-gradient bioceramics for application as controlled resorption implants. Here it is reported the application of rapid prototyping based on laser cladding to produce three-dimensional bioceramic implants comprising of a calcium phosphate inner core, with moderate in vitro degradation at physiological pH, surrounded by a bioactive glass outer layer of higher degradability. Each component of the implant is validated in terms of chemical and physical properties, and absence of toxicity. Pre-osteoblastic cell adhesion and proliferation assays reveal the adherence and growth of new bone cells on the material. This technique affords implants with gradual-resorbability for restoration of low-load-bearing bone. PMID:26032983

  20. Toward Smart Implant Synthesis: Bonding Bioceramics of Different Resorbability to Match Bone Growth Rates

    PubMed Central

    Comesaña, Rafael; Lusquiños, Fernando; del Val, Jesús; Quintero, Félix; Riveiro, Antonio; Boutinguiza, Mohamed; Jones, Julian R.; Hill, Robert G.; Pou, Juan

    2015-01-01

    Craniofacial reconstructive surgery requires a bioactive bone implant capable to provide a gradual resorbability and to adjust to the kinetics of new bone formation during healing. Biomaterials made of calcium phosphate or bioactive glasses are currently available, mainly as bone defect fillers, but it is still required a versatile processing technique to fabricate composition-gradient bioceramics for application as controlled resorption implants. Here it is reported the application of rapid prototyping based on laser cladding to produce three-dimensional bioceramic implants comprising of a calcium phosphate inner core, with moderate in vitro degradation at physiological pH, surrounded by a bioactive glass outer layer of higher degradability. Each component of the implant is validated in terms of chemical and physical properties, and absence of toxicity. Pre–osteoblastic cell adhesion and proliferation assays reveal the adherence and growth of new bone cells on the material. This technique affords implants with gradual-resorbability for restoration of low-load-bearing bone. PMID:26032983

  1. Bioactive ceramic-based materials with designed reactivity for bone tissue regeneration

    PubMed Central

    Ohtsuki, Chikara; Kamitakahara, Masanobu; Miyazaki, Toshiki

    2009-01-01

    Bioactive ceramics have been used clinically to repair bone defects owing to their biological affinity to living bone; i.e. the capability of direct bonding to living bone, their so-called bioactivity. However, currently available bioactive ceramics do not satisfy every clinical application. Therefore, the development of novel design of bioactive materials is necessary. Bioactive ceramics show osteoconduction by formation of biologically active bone-like apatite through chemical reaction of the ceramic surface with surrounding body fluid. Hence, the control of their chemical reactivity in body fluid is essential to developing novel bioactive materials as well as biodegradable materials. This paper reviews novel bioactive materials designed based on chemical reactivity in body fluid. PMID:19158015

  2. Resorbable biosynthetic mesh for crural reinforcement during hiatal hernia repair.

    PubMed

    Alicuben, Evan T; Worrell, Stephanie G; DeMeester, Steven R

    2014-10-01

    The use of mesh to reinforce crural closure during hiatal hernia repair is controversial. Although some studies suggest that using synthetic mesh can reduce recurrence, synthetic mesh can erode into the esophagus and in our opinion should be avoided. Studies with absorbable or biologic mesh have not proven to be of benefit for recurrence. The aim of this study was to evaluate the outcome of hiatal hernia repair with modern resorbable biosynthetic mesh in combination with adjunct tension reduction techniques. We retrospectively analyzed all patients who had crural reinforcement during repair of a sliding or paraesophageal hiatal hernia with Gore BioA resorbable mesh. Objective follow-up was by videoesophagram and/or esophagogastroduodenoscopy. There were 114 patients. The majority of operations (72%) were laparoscopic primary repairs with all patients receiving a fundoplication. The crura were closed primarily in all patients and reinforced with a BioA mesh patch. Excessive tension prompted a crural relaxing incision in four per cent and a Collis gastroplasty in 39 per cent of patients. Perioperative morbidity was minor and unrelated to the mesh. Median objective follow-up was one year, but 18 patients have objective follow-up at two or more years. A recurrent hernia was found in one patient (0.9%) three years after repair. The use of crural relaxing incisions and Collis gastroplasty in combination with crural reinforcement with resorbable biosynthetic mesh is associated with a low early hernia recurrence rate and no mesh-related complications. Long-term follow-up will define the role of these techniques for hiatal hernia repair. PMID:25264654

  3. Characterization of composite materials based on cement-ceramic powder blended binder

    NASA Astrophysics Data System (ADS)

    Kulovaná, Tereza; Pavlík, Zbyšek

    2016-06-01

    Characterization of newly developed composite mortars with incorporated ceramic powder coming from precise brick cutting as partial Portland cement replacement up to 40 mass% is presented in the paper. Fine ceramic powder belongs to the pozzolanic materials. Utilization of pozzolanic materials is accompanied by lower request on energy needed for Portland clinker production which generally results in lower production costs of blended binder and lower CO2 emission. In this paper, the ceramic powder is used in cement based mortar composition in amount of 8, 16, 24, 32, and 40 mass% of cement. Chemical composition of ceramic powder is analyzed by X-Ray Fluorescence and X-Ray Diffraction. The particle size distribution of ceramics is accessed on laser diffraction principle. For 28 days cured mortar samples, basic physical and mechanical properties are experimentally determined. The obtained results demonstrate that ceramic powder has potential to replace a part of Portland cement in composition of cement based composites and to reduce negative environmental impact of their production.

  4. Stability of Chromium Carbide/Chromium Oxide Based Porous Ceramics in Supercritical Water

    NASA Astrophysics Data System (ADS)

    Dong, Ziqiang

    This research was aimed at developing porous ceramics as well as ceramic-metal composites that can be potentially used in Gen-IV supercritical water reactors (SCWR). The research mainly includes two parts: 1) fabricating and engineering the porous ceramics and porous ceramic-metal composite; 2) Evaluating the stability of the porous ceramics in SCW environments. Reactive sintering in carbonaceous environments was used to fabricate porous Cr3C2/Cr2O3-based ceramic. A new process consisting of freeze casting and reactive sintering has also been successfully developed to fabricate highly porous Cr3C 2 ceramics with multiple interconnected pores. Various amounts of cobalt powders were mixed with ceramic oxides in order to modify the porous structure and property of the porous carbide obtained by reactive sintering. The hardness of the M(Cr,Co)7C3-Co composite has been evaluated and rationalized based on the solid solution of cobalt in the ceramic phase, the composite effect of soft Co metal and the porous structure of the ceramic materials. Efforts have also been made in fabricating and evaluating interpenetrating Cr3C2-Cu composites formed by infiltrating liquid copper into porous Cr3C2. The corrosion evaluation mainly focused on assessing the stability of porous Cr3C2 and Cr2O3 under various SCW conditions. The corrosion tests showed that the porous Cr3C 2 is stable in SCW at temperatures below 425°C. However, cracking and disintegrating of the porous Cr3C2 occurred when the SCW temperature increased above 425°C. Mechanisms of the corrosion attack were also investigated. The porous Cr2O3 obtained by oxidizing the porous Cr3C2 was exposed to various SCW environments. It was found that the stability of Cr 2O 3 was dependent on its morphology and the SCW testing conditions. Increasing SCW temperature increased the dissociation rate of the Cr2O 3. Adding proper amount of Y2O3 can increase the stability of the porous Cr2O3 in SCW. It was also concluded that decreasing

  5. Advanced ceramics for land-based gas turbine applications. Final report

    SciTech Connect

    Schneibel, J.H.; Ludeman, E.; Sabol, S.M.

    1997-05-23

    In order to increase the efficiency of land-based gas turbines, inlet gas temperatures have to be increased, and the amount of air which cools the turbine vanes has to be reduced, to the maximum extent possible. Presently, thermal barrier coatings (TBC`s) are the state of the art in achieving these goals. However, since TBC`s are very thin (typically 100 {mu}m), they have clearly limitations. Since all-ceramic turbine vanes would be a very large and risky development step, Westinghouse is considering to protect the leading edges of turbine vanes with high-performance ceramics. This might be done by either replacing the leading edge with a suitably shaped ceramic part, or by modifying the vanes such that they can accommodate ceramic inserts. Among the most important criteria for the success of ceramics in such applications are (a) thermodynamic compatibility with the turbine vane alloy, (b) sufficient thermal shock resistance to survive the thermal cycling during operation and in particular during emergency shut-down, and a design considering the thermal expansion mismatch of the metallic and ceramic components. This paper presents results of work performed on SiC, SiN, and aluminas.

  6. CHARACTERIZATION OF A CERIUM-RICH PYROCHLORE-BASED CERAMIC NUCLEAR WASTE FORM

    SciTech Connect

    Giere, Reto; Segvich, Susan; Buck, Edgar C.

    2003-02-11

    Titanate ceramics have been proposed as candidate materials for immobilizing excess weapons plutonium. This study focuses on the characterization of a titanate-based ceramic through X-ray diffraction (XRD), electron probe microanalysis and electron energy-loss spectroscopy (EELS). Three distinct phases have been identified, and their volume fraction was determined from element distribution maps using Scionimage-NIH Analysis software. This analysis revealed that the pyrochlore-group phase betafite (A2Ti2O7) forms the matrix of the ceramic and occupies 90.4% of the volume. Uniformly distributed in this matrix are perovskite (A2Ti2O6) and Hf-enriched rutile (TiO2), which account for 6.4 vol% and 3.1 vol%, respectively. The studied ceramic exhibits an extremely low porosity (0.3 vol%), which is characterized by small (< 6 m), rounded and isolated pores. In the studied ceramic, A-site cations are represented by Ca, rare earth elements, and Hf. The powder XRD pattern of the ceramic allowed refining the unit cell parameters for the cubic betafite, which is characterized by a cell edge of 10.132±0.003Å. The EELS data indicate that Ce is present as both Ce3+ and Ce4+ in betafite, whereas in perovskite, all Ce is trivalent.

  7. Joining of Silicon Carbide-Based Ceramics by Reaction Forming Method

    NASA Technical Reports Server (NTRS)

    Singh, M.; Kiser, J. D.

    1997-01-01

    Recently, there has been a surge of interest in the development and testing of silicon-based ceramics and composite components for a number of aerospace and ground based systems. The designs often require fabrication of complex shaped parts which can be quite expensive. One attractive way of achieving this goal is to build up complex shapes by joining together geometrically simple shapes. However, the joints should have good mechanical strength and environmental stability comparable to the bulk materials. These joints should also be able to maintain their structural integrity at high temperatures. In addition, the joining technique should be practical, reliable, and affordable. Thus, joining has been recognized as one of the enabling technologies for the successful utilization of silicon carbide based ceramic components in high temperature applications. Overviews of various joining techniques, i.e., mechanical fastening, adhesive bonding, welding, brazing, and soldering have been provided in recent publications. The majority of the techniques used today are based on the joining of monolithic ceramics with metals either by diffusion bonding, metal brazing, brazing with oxides and oxynitrides, or diffusion welding. These techniques need either very high temperatures for processing or hot pressing (high pressures). The joints produced by these techniques have different thermal expansion coefficients than the ceramic materials, which creates a stress concentration in the joint area. The use temperatures for these joints are around 700 C. Ceramic joint interlayers have been developed as a means of obtaining high temperature joints. These joint interlayers have been produced via pre-ceramic polymers, in-situ displacement reactions, and reaction bonding techniques. Joints produced by the pre-ceramic polymer approach exhibit a large amounts of porosity and poor mechanical properties. On the other hand, hot pressing or high pressures are needed for in-situ displacement

  8. Si3N4-Based Ceramic With Greater Hot Strength

    NASA Technical Reports Server (NTRS)

    Dutta, S.; Buzek, B.

    1986-01-01

    Zyttrite-doped material outperforms MgO-doped material above 1,200 degrees C. New ceramic material produced by addition of 10 weight percent zyttrite (yttria-stabilized zirconia) to (silicon nitride) offers significantly-improved high-temperature properties (those of MgO-doped Si3N4 ceramic). Work also showed that controlled Si3N4 powder with 10 weight percent zyttrite, significant improvement in room-temperature strength achieved. Variety of high-temperature structural applications are silicon nitride and silicon carbide. Potential for use in aircraft and automobile engines and in electric-power generating systems. Improved properties strongly suggest that the 10-weight percent zyttrite/Si3N4 material has strong potential for high-temperature applications.

  9. Diffusion of radionuclides in clay-based ceramics

    SciTech Connect

    Ivanov, P.A.; Gulin, A.N.; Shatkov, V.M.; Shashukov, E.A.; Kuznetsov, B.S.

    1988-09-01

    The diffusion coefficients of sodium-22, strontium-90, and cesium-134 in clay-containing ceramics of three types are determined by the method of integral residual activity. It is found that at the investigated temperatures the diffusion coefficients of the radionuclides decrease in the order sodium-22, cesium-134, strontium-90. Migration of cesium-134 in comparison with sodium-22 is characterized by substantially lower values of the preexponential factor and diffusion activation energy. It is shown that in the case of ceramic made up of 89% by mass cambrian clay and 11% by mass perlite, increase in relative moisture content of the samples from0.05 to 0.3% leads to substantial (by 2-3 orders of magnitude) growth of the diffusion coefficients of the radionuclides. Further increase in the relative moisture content has practically no effect on their diffusive mobility.

  10. Posttraumatic craniofacial reconstruction using combined resorbable and nonresorbable fixation systems.

    PubMed

    Majewski, W Tomasz; Yu, Jack C; Ewart, Chris; Aguillon, Arturo

    2002-05-01

    The facial skeleton consists of high-stress-bearing buttresses and low-stress-bearing curved surfaces. The buttresses are like trusses made of beams, struts, and columns. They resist tensile, compressive, and shear loading. The thin, curved, planar surfaces provide for the support and partitioning of the soft tissue. The trusses are strong and one-dimensional whereas the planes are weak and two-dimensional. Ideally, strong one-dimensional fixation systems should be used for the former; weaker, two-dimensional systems should be used for the latter. The authors report their clinical experience of using such combined approaches to the treatment of facial fractures using rigid, titanium mini-plates and screws for the buttresses and polymeric resorbable meshes for the curved planes. For an 11-month period (August 2000 to June 2001), nine patients (7 males and 2 females) with a mean age of 33.7 years were treated in this fashion. The resorbable meshes were deployed for the reconstitution of the orbital walls and the anterior wall of the maxillary sinus. No enophthalmos, globe dystopia, or diplopia occurred during the short mean follow-up of 10 months (4-17 months). There were no infections or sterile abscess formations. This type of combined use of fixation systems appears to be safe and effective. More patients and more extensive follow-ups are obviously needed. PMID:11981185

  11. Development of phosphate-based ceramic membranes. Final report

    SciTech Connect

    Anderson, M.A.; Zeltner, W.A.; Hill, C.G. Jr.

    1992-11-01

    Goal was to develop microporous ceramic membranes by coating sols that contain nanoparticles onto porous ceramic supports. They could be used for either gas phase separations or liquid phase separations involving low molecular weight solutes. This required the synthesis of Sols containing particles in the range from 2 to 10 nm. Procedures for preparing nanoparticulate sols of silica, alumina, and aluminosilicates of various compositions are given. Unsupported ceramic membranes prepared from these sols had mean pore diameters of <10 {Angstrom} (silica), ca. 35 {Angstrom} (aluminosilicate). The alumina membranes display both microporosity (mean pore diameters <20 {Angstrom}) and mesoporosity (mean pore diameters >20 {Angstrom}). These nanoparticulate sols were deposited onto porous supports. Four methods of were investigated. Dip coating appeared to give the best performance of all of these techniques and was easily implemented. Deposition of particles within porous supports by permformation was also demonstrated. Critical point drying studies of membranes were initiated, but progress was limited. Slip casting could not be successfully used to produce a supported membrane free from cracks.

  12. Effect of Microstructure on Reliability of Ca(TiZr)O3-Based Multilayer Ceramic Capacitors

    NASA Astrophysics Data System (ADS)

    Motoki, Tomoo; Naito, Masahiro; Sano, Harunobu; Konoike, Takehiro; Tomono, Kunisaburo

    2000-09-01

    We examined the reliability of Ca(TiZr)O3 (CTZ)-based Ni-electrode multilayer ceramic capacitors (MLCs) prepared by two different processes with particular interest in the microstructure. One process was to calcine the mixture of CaCO3 and TiO2 to prepare CaTiO3 (CT) powder and the mixture of CaCO3 and ZrO2 to prepare CaZrO3 (CZ) powder, and then mix these calcined powders and sinter them to synthesize the CTZ-based ceramics. The other was to calcine the mixture of CaCO3, TiO2 and ZrO2 powders together to prepare CTZ powder and then sinter them. These two processes of CTZ ceramic preparation resulted in a different crystallinity and distribution of the elements. We found that these factors influenced the reliability of CTZ-based MLCs.

  13. Cement-based piezoelectric ceramic composites for sensor applications in civil engineering

    NASA Astrophysics Data System (ADS)

    Dong, Biqin

    The objectives of this thesis are to develop and apply a new smart composite for the sensing and actuation application of civil engineering. Piezoelectric ceramic powder is incorporated into cement-based composite to achieve the sensing and actuation capability. The research investigates microstructure, polarization and aging, material properties and performance of cement-based piezoelectric ceramic composites both theoretically and experimentally. A hydrogen bonding is found at the interface of piezoelectric ceramic powder and cement phase by IR (Infrared Ray), XPS (X-ray Photoelectron Spectroscopy) and SIMS (Secondary Ion Mass Spectroscopy). It largely affects the material properties of composites. A simple first order model is introduced to explain the poling mechanism of composites and the dependency of polarization is discussed using electromechanical coupling coefficient kt. The mechanisms acting on the aging effect is explored in detail. Dielectrical, piezoelectric and mechanical properties of the cement-based piezoelectric ceramic composites are studied by experiment and theoretical calculation based on modified cube model (n=1) with chemical bonding . A complex circuit model is proposed to explain the unique feature of impedance spectra and the instinct of high-loss of cement-based piezoelectric ceramic composite. The sensing ability of cement-based piezoelectric ceramic composite has been evaluated by using step wave, sine wave, and random wave. It shows that the output of the composite can reflects the nature and characteristics of mechanical input. The work in this thesis opens a new direction for the current actuation/sensing technology in civil engineering. The materials and techniques, developed in this work, have a great potential in application of health monitoring of buildings and infrastructures.

  14. Corrosion of Silicon-Based Ceramics in Combustion Environments

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.

    1993-01-01

    The processes of passive oxidation, deposit-induced corrosion, active oxidation, scale/substance interactions, and scale volatility are presently studied in the case of high-purity SiC and Si3N4 in pure oxygen, giving attention to such secondary elements in the ceramics as water and CO2 oxidants, combustion environment impurities, and thermal cycling. Deposit-induced corrosion is discussed for the cases of NaSO4 as well as vanadate and oxide-slag deposits; issues associated with the active-to-passive oxidation transition are noted.

  15. Key Durability Issues with Mullite-Based Environmental Barrier Coatings for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.

    1999-01-01

    Plasma-sprayed mullite (3Al2O3 central dot 2SiO2) and mullite/yttria-stabilized-zirconia (YSZ) dual layer coatings have been developed to protect silicon-based ceramics from environmental attack. Mullite-based coating systems show excellent durability in air. However, in combustion environments, corrosive species such as molten salt or water vapor penetrate through cracks in the coating and attack the Si-based ceramics along the interface, Thus modification of the coating system for enhanced crack-resistance is necessary for long-term durability in combustion environments. Other key durability issues include interfacial contamination and coating/substrate bonding. Interfacial contamination leads to enhanced oxidation and interfacial pore formation, while weak coating/substrate bonding leads to rapid attack of the interface by corrosive species, both of which can cause premature failure of the coating. Interfacial contamination can be minimized by limiting impurities in coating and substrate materials. The interface may be modified to improve the coating/substrate bond.

  16. Key Durability Issues with Mullite-Based Environmental Barrier Coatings for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.

    2000-01-01

    Plasma-sprayed mullite (3Al2O3.2SiO2) and mullite/yttria-stabilized-zirconia (YSZ) dual layer coatings have been developed to protect silicon -based ceramics from environmental attack. Mullite-based coating systems show excellent durability in air. However, in combustion environments, corrosive species such as molten salt or water vapor penetrate through cracks in the coating and attack the Si-based ceramics along the interface. Thus the modification of the coating system for enhanced crack-resistance is necessary for long-term durability in combustion environments. Other key durability issues include interfacial contamination and coating/substrate bonding. Interfacial contamination leads to enhanced oxidation and interfacial pore formation, while a weak coating/substrate bonding leads to rapid attack of the interface by corrosive species, both of which can cause a premature failure of the coating. Interfacial contamination can be minimized by limiting impurities in coating and substrate materials. The interface may be modified to improve the coating/substrate bond.

  17. Shape-memory starch for resorbable biomedical devices.

    PubMed

    Beilvert, A; Chaubet, F; Chaunier, L; Guilois, S; Pavon-Djavid, G; Letourneur, D; Meddahi-Pellé, A; Lourdin, D

    2014-01-01

    Shape-memory resorbable materials were obtained by extrusion-cooking of potato starch with 20% glycerol under usual conditions. They presented an efficient shape-memory with a high recovery ratio (Rr>90%). Their recovery could be triggered at 37°C in water. After water immersion at 37°C, the modulus decreased from 1GPa to 2.4MPa and remained almost constant over 21 days. Gamma-ray sterilization did not have a dramatic impact on their mechanical properties, despite a large decrease of molecular mass analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering (AFFFF-MALLS). Samples implanted in a rat model exhibited normal tissue integration with a low inflammatory response. Thus, as previously investigated in the case of shape-memory synthetic polymers, natural starch, without chemical grafting, can now be considered for manufacturing innovative biodegradable devices for less-invasive surgery. PMID:24274502

  18. Current status of ceramic-based membranes for oxygen separation from air.

    PubMed

    Hashim, Salwa Meredith; Mohamed, Abdul Rahman; Bhatia, Subhash

    2010-10-15

    There has been tremendous progress in membrane technology for gas separation, in particular oxygen separation from air in the last 20 years. It provides an alternative route to the existing conventional separation processes such as cryogenic distillation and pressure swing adsorption as well as cheaper production of oxygen with high purity. This review presents the recent advances of ceramic membranes for the separation of oxygen from air at high temperature. It covers the issues and problems with respect to the selectivity and separation performance. The paper also presents different approaches applied to overcome these challenges. The future directions of ceramic-based membranes for oxygen separation from air are also presented. PMID:20813344

  19. Ceramics based on titanium nitride and silicon nitride sintered by SPS-method

    NASA Astrophysics Data System (ADS)

    Sivkov, A. A.; Gerasimov, D. Yu; Evdokimov, A. A.

    2015-10-01

    The dependences of the microstructure and physical and mechanical properties of ceramic mixtures Si3N4/TiN in the full range of mass ratios of the components. Was also investigated directly, and the process of sintering occurring during a physical or chemical processes, in particular, has been obtained and the hardness of the material density on the ratio of the conductive titanium nitride phase and a silicon nitride insulating phase with values above and below the percolation threshold. Also obtained was pure ceramics based on titanium nitride with high physical-mechanical characteristics (H = 21.5 GPa).

  20. Glass-infiltrated zirconia/alumina-based ceramic for crowns and fixed partial dentures.

    PubMed

    McLaren, E A; White, S N

    1999-10-01

    The increased demand for metal-free restorative alternatives has resulted in the proliferation of all-ceramic systems. While these materials can predictably achieve aesthetic results in the anterior, they have traditionally been contraindicated for posterior applications due to the greater stresses present in the region. This article discusses a zirconia/alumina-based ceramic system that has been developed to expand the alternatives for the aesthetic restoration of the dentition. Material properties and considerations for its use in crown restorations, fixed partial dentures, and custom implant abutments are similarly addressed. PMID:10853604

  1. A small angle neutron scattering study of mica based glass-ceramics with applications in dentistry

    NASA Astrophysics Data System (ADS)

    Kilcoyne, S. H.; Bentley, P. M.; Al-Jawad, M.; Bubb, N. L.; Al-Shammary, H. A. O.; Wood, D. J.

    2004-07-01

    We are currently developing machinable and load-bearing mica-based glass-ceramics for use in restorative dental surgery. In this paper we present the results of an ambient temperature small angle neutron scattering (SANS) study of several such ceramics with chemical compositions chosen to optimise machinability and strength. The SANS spectra are all dominated by scattering from the crystalline-amorphous phase interface and exhibit Q-4 dependence (Porod scattering) indicating that, on a 100Å scale, the surface of the crystals is smooth.

  2. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1994-01-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel-based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  3. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1993-01-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  4. Biomaterials in skull base surgery

    PubMed Central

    Maier, Wolfgang

    2011-01-01

    Reconstruction materials and techniques for the base of the skull have undergone rapid developments and differentiation in recent years. While mostly autotransplants, collagens or resorbable alloplastic materials are preferred for duraplasties, pronounced organ-specific differences can be observed in the reconstruction of hard tissues. The use of polymethylmethacryl bone cement, once wide-spread, has decreased greatly due to the release of toxic monomers. Bony autotransplants are still used primarily for smaller skull-base defects, intraoperatively formable titanium nets may be also used for larger fronto- or laterobasal reconstructions of bony defects. Defects in visible areas are increasingly closed with preformed titanium or ceramic implants, which are planned and fitted to the individual patient using preoperative CT imaging. At the skull base, this applies especially to reconstructions of the frontal sinus. For extensive reconstructions of the orbita, titanium nets and non-resorbable plastics have proven valuable; in closing smaller defects especially of the orbital floor, resorbable implants based on Polyglactin 901 are also used. PMID:22073100

  5. Performance of Nanotube-Based Ceramic Composites: Modeling and Experiment

    NASA Technical Reports Server (NTRS)

    Curtin, W. A.; Sheldon, B. W.; Xu, J.

    2004-01-01

    The excellent mechanical properties of carbon-nanotubes are driving research into the creation of new strong, tough nanocomposite systems. In this program, our initial work presented the first evidence of toughening mechanisms operating in carbon-nanotube- reinforced ceramic composites using a highly-ordered array of parallel multiwall carbon-nanotubes (CNTs) in an alumina matrix. Nanoindentation introduced controlled cracks and the damage was examined by SEM. These nanocomposites exhibit the three hallmarks of toughening in micron-scale fiber composites: crack deflection at the CNT/matrix interface; crack bridging by CNTs; and CNT pullout on the fracture surfaces. Furthermore, for certain geometries a new mechanism of nanotube collapse in shear bands was found, suggesting that these materials can have multiaxial damage tolerance. The quantitative indentation data and computational models were used to determine the multiwall CNT axial Young's modulus as 200-570 GPa, depending on the nanotube geometry and quality.

  6. Dynamic annealing of defects in irradiated zirconia-based ceramics

    SciTech Connect

    Devanathan, Ram; Weber, William J.

    2008-03-06

    We have observed self-healing behavior in large scale molecular dynamics simulations of 30 keV Zr recoils in pure zirconia and 10 mole % yttria-stabilized zirconia. Our results reveal that dynamic annealing is highly effective during the first 5 ps of damage evolution, especially in the presence of oxygen structural vacancies introduced by aliovalent doping (Y3+ substitution for Zr4+). The presence of mobile oxygen vacancies results in near complete recovery of damage. Damage recovery on the cation sublattice is assisted by the anion sublattice recovery, which explains the remarkable radiation tolerance of stabilized zirconia. Ceramics engineered to heal themselves in this fashion hold great promise for use in high-radiation environments or for safely encapsulating high-level radioactive waste over geological time scales.

  7. THE USE OF FLY ASH IN THE PRODUCTION OF SIALON BASED STRUCTURAL CERAMICS

    EPA Science Inventory

    EPA GRANT NUMBER: X832541C004
    Title: The Use of Fly Ash in the Production of SiAlON based Structural Ceramics
    Investigator: James R. Varner
    Institution: Alfred University
    EPA Project Officer: S. Bala Krishnan
    Project Perio...

  8. Method for improving the toughness of silicon carbide-based ceramics

    DOEpatents

    Tein, T.Y.; Hilmas, G.E.

    1996-12-03

    Method of improving the toughness of SiC-based ceramics is disclosed. SiC, , AlN, Al{sub 2}O{sub 3} and optionally {alpha}-Si{sub 3}N{sub 4} are hot pressed to form a material which includes AlN polytypoids within its structure. 1 fig.

  9. Method for improving the toughness of silicon carbide-based ceramics

    DOEpatents

    Tein, Tseng-Ying; Hilmas, Gregory E.

    1996-01-01

    Method of improving the toughness of SiC-based ceramics. SiC, , AlN, Al.sub.2 O.sub.3 and optionally .alpha.-Si.sub.3 N.sub.4 are hot pressed to form a material which includes AlN polytypoids within its structure.

  10. Ceramic Powders

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In developing its product line of specialty ceramic powders and related products for government and industrial customers, including companies in the oil, automotive, electronics and nuclear industries, Advanced Refractory Technologies sought technical assistance from NERAC, Inc. in specific areas of ceramic materials and silicon technology, and for assistance in identifying possible applications of these materials in government programs and in the automotive and electronics industry. NERAC conducted a computerized search of several data bases and provided extensive information in the subject areas requested. NERAC's assistance resulted in transfer of technologies that helped ART staff develop a unique method for manufacture of ceramic materials to precise customer specifications.

  11. Kinetics of in vivo bone deposition by bone marrow stromal cells within a resorbable porous calcium phosphate scaffold: an X-ray computed microtomography study.

    PubMed

    Papadimitropoulos, A; Mastrogiacomo, M; Peyrin, F; Molinari, E; Komlev, V S; Rustichelli, F; Cancedda, R

    2007-09-01

    Resorbable ceramic scaffolds based on Silicon stabilized tricalcium phosphate (Si-TCP) were seeded with bone marrow stromal cells (BMSC) and ectopically implanted for 2, 4, and 6 months in immunodeficient mice. Qualitative and quantitative evaluation of the scaffold material was performed by X-ray synchrotron radiation computed microtomography (microCT) with a spatial resolution lower than 5 microm. Unique to these experiments was that microCT data were first collected on the scaffolds before implantation and then on the same scaffolds after they were seeded with BMSC, implanted in the mice and rescued after different times. Volume fraction, mean thickness and thickness distribution were evaluated for both new bone and scaffold phases as a function of the implantation time. New bone thickness increased from week 8 to week 16. Data for the implanted scaffolds were compared with those derived from the analysis of the same scaffolds prior to implantation and with data derived from 100% hydroxyapatite (HA) scaffold treated and analyzed in the same way. At variance with findings with the 100% HA scaffolds a significant variation in the density of the different Si-TCP scaffold regions in the pre- and post-implantation samples was observed. In particular a post-implantation decrease in the density of the scaffolds, together with major changes in the scaffold phase composition, was noticeable in areas adjacent to newly formed bone. Histology confirmed a better integration between new bone and scaffold in the Si-TCP composites in comparison to 100% HA composites where new bone and scaffold phases remained well distinct. PMID:17657771

  12. Fully-Enclosed Ceramic Micro-burners Using Fugitive Phase and Powder-based Processing.

    PubMed

    Do, Truong; Shin, Changseop; Kwon, Patrick; Yeom, Junghoon

    2016-01-01

    Ceramic-based microchemical systems (μCSs) are more suitable for operation under harsh environments such as high temperature and corrosive reactants compared to the more conventional μCS materials such as silicon and polymers. With the recent renewed interests in chemical manufacturing and process intensification, simple, inexpensive, and reliable ceramic manufacturing technologies are needed. The main objective of this paper is to introduce a new powder-based fabrication framework, which is a one-pot, cost-effective, and versatile process for ceramic μCS components. The proposed approach employs the compaction of metal-oxide sub-micron powders with a graphite fugitive phase that is burned out to create internal cavities and microchannels before full sintering. Pure alumina powder has been used without any binder phase, enabling more precise dimensional control and less structure shrinkage upon sintering. The key process steps such as powder compaction, graphite burnout during partial sintering, machining in a conventional machine tool, and final densification have been studied to characterize the process. This near-full density ceramic structure with the combustion chamber and various internal channels was fabricated to be used as a micro-burner for gas sensing applications. PMID:27546059

  13. Lithography-based ceramic manufacture (LCM) of auxetic structures: present capabilities and challenges

    NASA Astrophysics Data System (ADS)

    Díaz Lantada, Andrés; de Blas Romero, Adrián; Schwentenwein, Martin; Jellinek, Christopher; Homa, Johannes

    2016-05-01

    Auxetic metamaterials are known for having a negative Poisson’s ratio (NPR) and for displaying the unexpected properties of lateral expansion when stretched and densification when compressed. Even though a wide set of micro-manufacturing resources have been used for the development of auxetic metamaterials and related devices, additional precision and an extension to other families of materials is needed for their industrial expansion. In addition, their manufacture using ceramic materials is still challenging. In this study we present a very promising approach for the development of auxetic metamaterials and devices based on the use of lithography-based ceramic manufacturing. The process stands out for its precision and complex three-dimensional geometries attainable, without the need of supporting structures, and for enabling the manufacture of ceramic auxetics with their geometry controlled from the design stage with micrometric precision. To our knowledge it represents the first example of application of this technology to the manufacture of auxetic geometries using ceramic materials. We have used a special three-dimensional auxetic design whose remarkable NPR has been previously highlighted.

  14. Fully-Enclosed Ceramic Micro-burners Using Fugitive Phase and Powder-based Processing

    PubMed Central

    Do, Truong; Shin, Changseop; Kwon, Patrick; Yeom, Junghoon

    2016-01-01

    Ceramic-based microchemical systems (μCSs) are more suitable for operation under harsh environments such as high temperature and corrosive reactants compared to the more conventional μCS materials such as silicon and polymers. With the recent renewed interests in chemical manufacturing and process intensification, simple, inexpensive, and reliable ceramic manufacturing technologies are needed. The main objective of this paper is to introduce a new powder-based fabrication framework, which is a one-pot, cost-effective, and versatile process for ceramic μCS components. The proposed approach employs the compaction of metal-oxide sub-micron powders with a graphite fugitive phase that is burned out to create internal cavities and microchannels before full sintering. Pure alumina powder has been used without any binder phase, enabling more precise dimensional control and less structure shrinkage upon sintering. The key process steps such as powder compaction, graphite burnout during partial sintering, machining in a conventional machine tool, and final densification have been studied to characterize the process. This near-full density ceramic structure with the combustion chamber and various internal channels was fabricated to be used as a micro-burner for gas sensing applications. PMID:27546059

  15. Effect of ceramic thickness and composite bases on stress distribution of inlays--a finite element analysis.

    PubMed

    Durand, Letícia Brandão; Guimarães, Jackeline Coutinho; Monteiro Junior, Sylvio; Baratieri, Luiz Narciso

    2015-01-01

    The purpose of this study was to determine the effect of cavity depth, ceramic thickness, and resin bases with different elastic modulus on von Mises stress patterns of ceramic inlays. Tridimensional geometric models were developed with SolidWorks image software. The differences between the models were: depth of pulpal wall, ceramic thickness, and presence of composite bases with different thickness and elastic modulus. The geometric models were constrained at the proximal surfaces and base of maxillary bone. A load of 100 N was applied. The stress distribution pattern was analyzed with von Mises stress diagrams. The maximum von Mises stress values ranged from 176 MPa to 263 MPa and varied among the 3D-models. The highest von Mises stress value was found on models with 1-mm-thick composite resin base and 1-mm-thick ceramic inlay. Intermediate values (249-250 MPa) occurred on models with 2-mm-thick composite resin base and 1-mm-thick ceramic inlay and 1-mm-thick composite resin base and 2-mm-thick ceramic inlay. The lowest values were observed on models restored exclusively with ceramic inlay (176 MPa to 182 MPa). It was found that thicker inlays distribute stress more favorably and bases with low elastic modulus increase stress concentrations on the internal surface of the ceramic inlay. The increase of ceramic thickness tends to present more favorable stress distribution, especially when bonded directly onto the cavity without the use of supporting materials. When the use of a composite base is required, composite resin with high elastic modulus and reduced thickness should be preferred. PMID:25831105

  16. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... a resorbable implant intended to fill bony voids or gaps of the extremities, spine, and pelvis that are caused by trauma or surgery and are not intrinsic to the stability of the bony structure....

  17. Fabrication and characterization of all-ceramic solid oxide fuel cells based on composite oxide anode

    NASA Astrophysics Data System (ADS)

    Kim, Jeonghee; Shin, Dongwook; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook; Je, Hae-June; Lee, Hae-Weon; Yoon, Kyung Joong

    2013-11-01

    All-ceramic solid oxide fuel cells (SOFCs), which offer advantages in carbon tolerance, sulfur resistance and redox stability, are fabricated and evaluated. The electrolyte-supported cells are composed of a La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM)-Ce0.9Gd0.1O1.95-δ (GDC) anode, an Y2O3-stabilized ZrO2 (YSZ) electrolyte, a GDC interdiffusion barrier layer, and a La0.8Sr0.2Co0.2Fe0.8O3-δ (LSCF)-GDC cathode. A particle-dispersed glycine-nitrate process is developed to synthesize extremely fine and homogeneous LSCM-GDC ceramic composite powders. The electrochemical performance of the LSCM-GDC anode is comparable to that of conventional Ni-based anodes. The impedance spectra of the all-ceramic SOFCs are successfully interpreted by the independent characterization of the individual electrodes via half-cell measurements. The impedance of the LSCM-GDC anode is dominated by a low-frequency arc originating from the “chemical capacitance”, which is associated with the variation of the oxygen nonstoichiometry in the mixed conducting ceramic electrode. In addition, the impedance arc associated with the electrode-gas interaction is observed in the LSCM-GDC anode. The rate-limiting processes for the LSCF-GDC cathode are observed to be solid-state oxygen diffusion and surface chemical exchange. Herein, the reaction mechanisms and rate-limiting processes of the all-ceramic SOFCs are discussed in detail and compared with those of conventional Ni-based SOFCs.

  18. Ni-BaTiO3-Based Base-Metal Electrode (BME) Ceramic Capacitors for Space Applications

    NASA Technical Reports Server (NTRS)

    Liu, Donhang; Fetter, Lula; Meinhold, Bruce

    2015-01-01

    A multi-layer ceramic capacitor (MLCC) is a high-temperature (1350C typical) co-fired ceramic monolithic that is composed of many layers of alternately stacked oxide-based dielectric and internal metal electrodes. To make the dielectric layers insulating and the metal electrode layers conducting, only highly oxidation-resistant precious metals, such as platinum, palladium, and silver, can be used for the co-firing of insulating MLCCs in a regular air atmosphere. MLCCs made with precious metals as internal electrodes and terminations are called precious-metal electrode (PME) capacitors. Currently, all military and space-level applications only address the use of PME capacitors.

  19. Fixation of a severely resorbed mandible for complete arch screw-retained rehabilitation: A clinical report.

    PubMed

    Fabris, Vinicius; Bacchi, Atais

    2016-05-01

    Severely resorbed mandibles with placed endosteal dental implants can fracture. Therefore, techniques to reduce the risk or minimize the consequences of these fractures are needed. This clinical report presents a technique for placing a titanium plate in a severely resorbed mandible subjected to complete-arch implant therapy. The titanium plate is placed in the same surgical procedure as the implants, allowing immediate implant loading. This technique provides safe implant-supported treatment for patients with severe mandibular resorption. PMID:26775245

  20. Measuring Fracture Times Of Ceramics

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

    1989-01-01

    Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

  1. Resorbable continuous-fibre reinforced polymers for osteosynthesis.

    PubMed

    Dauner, M; Planck, H; Caramaro, L; Missirlis, Y; Panagiotopoulos, E

    1998-03-01

    Four institutes from three countries in the European Union have collaborated under the BRITE-EURAM framework programme for the development of processing technologies for resorbable osteosynthesis devices. The devices should be continuous-fibre reinforced, and the technology should offer the possibility of orienting the fibres in the main trajectories. Poly-L-lactide and poly-L-DL-lactides have been synthesized for reinforcement fibres and matrix material, respectively. Melt-spun P-L-LA fibres of a strength of 800 MPa have been embedded in an amorphous P-L-DL-LA 70 : 30 matrix by compression moulding. Ethyleneoxide sterilized samples have been tested in vitro and in vivo. A satisfying bending modulus has been reached (6 GPa). Yet with 50% strength retention after ten weeks, fast degradation occurred that could be related to residual monomers. By this fast degradation 70% resorption after one year could be observed in the non-functional animal studies in rabbits. There was only a mild inflammatory reaction, which confirmed the good biocompatibility of the materials even during the resorption period. Further effort has to concentrate on the reduction of initial monomer content. The great advantage of the processing method to orient fibres in the device will be utilized in prototype samples, e.g. an osteosynthesis plate with fixation holes. PMID:15348907

  2. Polymethylmethacrylate-induced release of bone-resorbing factors

    SciTech Connect

    Herman, J.H.; Sowder, W.G.; Anderson, D.; Appel, A.M.; Hopson, C.N. )

    1989-12-01

    A pseudomembranous structure that has the histological characteristics of a foreign-body-like reaction invariably develops at the bone-cement interface in the proximity of resorption of bone around aseptically loosened cemented prostheses. This study was an attempt to implicate polymethylmethacrylate in this resorptive process. Unfractionated peripheral-blood mononuclear cells (consisting of lymphocytes and monocytes) and surface-adherent cells (monocyte-enriched) were prepared from control subjects who did and did not have clinical evidence of osteoarthrosis and from patients who had osteoarthrosis and were having a revision for failure of a cemented hip or knee implant. Cells were cultured for varying periods in the presence and absence of nonpolymerized methacrylate (one to two-micrometer spherules), pulverized polymerized material, or culture chambers that were pre-coated with polymerized cement. Conditioned media that were derived from both methacrylate-stimulated cell populations were shown to contain specific bone-resorbing mediators (interleukin-1, tumor necrosis factor, or prostaglandin E2) and to directly affect bone resorption in 45Ca-labeled murine limb-bone assays.

  3. The Role of Resorbable Mesh as a Fixation Device in Craniosynostosis.

    PubMed

    Konofaos, Petros; Goubran, Sameh; Wallace, Robert D

    2016-01-01

    The purpose of the study was to present our experience with endocranial fixation using the Resorb-X mesh (KLS Martin, Jacksonville, FL) in frontoorbital reconstruction. A retrospective review of all patients underwent frontoorbital advancement at our institution from 2003 to 2012 was performed. Inclusion criterion included: pediatric patients who underwent frontoorbital advancement for craniosynostosis; patients underwent treatment of the craniosynostosis only at our center; resorbable fixation devises were applied only endocranially; and follow-up was ≥ 2 years. Patients' evaluation included demographic information, postoperative complications, surgical outcomes, and postoperative computed tomographic imaging if accessible. Thirty-nine patients met the inclusion criteria. Resorbable plates were used in 16 patients and Resorb-X mesh in 23 patients. Observed complications were unrelated to the fixation system used. Resorption of fixation devices was evident in all patients after 20 months following reconstruction. There were no incidents of local reaction to the fixation system. Frontoorbital area contour was deemed good in 24 patients and excellent in 15 patients by both families and attending surgeon. There was a statistical significant difference (P = 0.030) between patients ≤ 12 months and >12 months regarding the complications rate. Endocranial fixation using the Resorb-X mesh is easily applicable, avoids material palpability, and provides stable and secure fixation. This technique is superior to the conventional endocranial osseous fixation with absorbable plates, as it avoids some of its possible complications while providing all the benefits of resorbable fixation. PMID:26674902

  4. A randomized, prospective study of total hip wound closure with resorbable subcuticular staples.

    PubMed

    Fisher, David A; Bengero, Lowell L; Clapp, Brenda C; Burgess, Mary

    2010-09-01

    Resorbable subcuticular staples are a new way to close surgical wounds and have not been reported in the orthopedic literature. This randomized, controlled study compared a resorbable subcuticular staple system with stainless steel wound stapling in patients undergoing unilateral primary total hip arthroplasty (THA). Institutional Review Board approval and patient consent was obtained for all patients. Sixty patients (30 each group) were randomized to receive either resorbable subcuticular staples or stainless steel staples after primary THA. Incision length, number of staples used, and any staple insertion problems were recorded. Subjective reports of pain levels or incision complaints were solicited, and wound photographs were obtained on days 1 and 14 and 6 weeks postoperatively. The presence of wound drainage, erythema, wound separation, or echymosis was recorded at each visit, as well as all postoperative complications. The average incision length in the resorbable group was 13.2 cm and required 16 staples for closure, compared to 15 cm and 20 staples for the metal staple group. No infections occurred in either group, although the incidence of erythema and wound drainage at 2 weeks was higher for patients in the stainless steel group. One patient with metal staples had a postoperative hematoma requiring secondary irrigation and debridement. Patient satisfaction was higher with the resorbable staples. A resorbable subcuticular staple system can provide comparable wound closure to stainless steel staples following THA and may do so with less local discomfort, wound drainage, or erythematous reaction. PMID:20839703

  5. Dental ceramics: An update

    PubMed Central

    Shenoy, Arvind; Shenoy, Nina

    2010-01-01

    In the last few decades, there have been tremendous advances in the mechanical properties and methods of fabrication of ceramic materials. While porcelain-based materials are still a major component of the market, there have been moves to replace metal ceramics systems with all ceramic systems. Advances in bonding techniques have increased the range and scope for use of ceramics in dentistry. In this brief review, we will discuss advances in ceramic materials and fabrication techniques. Examples of the microstructure property relationships for these ceramic materials will also be addressed. PMID:21217946

  6. Iron-phosphate-based chemically bonded phosphate ceramics for mixed waste stabilization

    SciTech Connect

    Wagh, A.S.; Jeong, S.Y.; Singh, D.

    1997-01-01

    In an effort to develop chemically bonded phosphate ceramics for mixed waste stabilization, a collaborative project to develop iron-phosphate based ceramics has been initiated between Argonne National Laboratory and the V. G. Khlopin Radium Institute in St. Petersburg, Russia. The starter powders are oxides of iron that are generated as inexpensive byproduct materials in the iron and steel industry. They contain iron oxides as a mixture of magnetite (Fe{sub 3}O{sub 4}) and haematite (Fe{sub 2}O{sub 3}). In this initial phase of this project, both of these compounds were investigated independently. Each was reacted with phosphoric acid solution to form iron phosphate ceramics. In the case of magnetite, the reaction was rapid. Adding ash as the waste component containing hazardous contaminants resulted in a dense and hard ceramic rich in glassy phase. On the other hand, the reaction of phosphoric acid solution with a mixture of haematite and ash waste contaminated with cesium and americium was too slow. Samples had to be molded under pressure. They were cured for 2-3 weeks and then hardened by heating at 350{degrees}C for 3 h. The resulting ceramics in both cases were subjected to physical tests for measurement of density, open porosity, compression strength, phase analyses using X-ray diffraction and differential thermal analysis, and leaching tests using toxicity characteristic leaching procedure (TCLP) and ANS 16.1 with 7 days of leaching. Using the preliminary information obtained from these tests, we evaluated these materials for stabilization of Department of Energy`s mixed waste streams.

  7. Improving adhesion between luting cement and zirconia-based ceramic with an alternative surface treatment.

    PubMed

    Martins, Aurealice Rosa Maria; Gotti, Valéria Bisinoto; Shimano, Marcos Massao; Borges, Gilberto Antônio; Gonçalves, Luciano de Souza

    2015-01-01

    This study evaluated the influence of an alternative surface treatment on the microshear bond strength (μsbs) of zirconia-based ceramic. Thirty-five zirconia disks were assigned to five groups according to the following treatments: Control (CO), glass and silane were not applied to the zirconia surface; G1, air blasted with 100μm glass beads + glaze + silane; G2, a gel containing 15% (by weight) glass beads applied to the ceramic surface + glaze + silane; G3, a gel containing 25% (by weight) glass beads applied to the ceramic surface + glaze + silane; and G4, a gel containing 50% (by weight) glass beads applied to the ceramic surface + glaze + silane. The specimens were built up using RelyX ARC®, according to the manufacturer's recommendations, and inserted in an elastomeric mold with an inner diameter of 0.8 mm. The μsbs test was performed using a testing machine at a crosshead speed of 0.5 mm/min. ANOVA and Tukey's test (p < 0.05) were applied to the bond strength values (in MPa). CO (15.6 ± 4.1) showed the lowest μsbs value. There were no statistical differences between the G1 (24.9 ± 7.4), G2 (24.9 ± 2.3), G3 (35.0 ± 10.3) and G4 (35.3 ± 6.0) experimental groups. Those groups submitted to surface treatments with higher concentrations of glass showed a lower frequency of adhesive failures. In conclusion, the glass application improved the interaction between the ceramic and the luting cement. PMID:25859635

  8. Fracture resistance of endodontically treated teeth restored with ceramic inlays and different base materials.

    PubMed

    Saridag, Serkan; Sari, Tugrul; Ozyesil, Atilla Gokhan; Ari Aydinbelge, Hale

    2015-01-01

    This study evaluated the fracture resistance of endodontically treated teeth restored with different base materials and mesioocclusal-distal (MOD) ceramic inlays. Fifty mandibular molars were assigned into five groups (n=10 per group). Group1 (control) comprised intact molar teeth without any treatment. Teeth in other groups were subjected to root canal treatment and restored with MOD ceramic inlays on different base materials. In Group 2, base material was zinc phosphate cement; Group 3's was glass ionomer cement; Group 4's was composite resin, and Group 5's was composite resin reinforced with fiber. Finally, a continuous occlusal load was applied until fracture occurred. Mean fracture resistance of Group 1 (3,027 N) was significantly higher than the other groups (890, 1,070, 1,670, 1,226 N respectively). Fracture resistance of Group 4 was statistically comparable with Group 5 and significantly higher than Groups 2 and 3 (p<0.05; Tukey's HSD). Use of different base materials under ceramic inlay restorations could affect the fracture resistance of endodontically treated teeth. PMID:25740162

  9. Feature selection for neural network based defect classification of ceramic components using high frequency ultrasound.

    PubMed

    Kesharaju, Manasa; Nagarajah, Romesh

    2015-09-01

    The motivation for this research stems from a need for providing a non-destructive testing method capable of detecting and locating any defects and microstructural variations within armour ceramic components before issuing them to the soldiers who rely on them for their survival. The development of an automated ultrasonic inspection based classification system would make possible the checking of each ceramic component and immediately alert the operator about the presence of defects. Generally, in many classification problems a choice of features or dimensionality reduction is significant and simultaneously very difficult, as a substantial computational effort is required to evaluate possible feature subsets. In this research, a combination of artificial neural networks and genetic algorithms are used to optimize the feature subset used in classification of various defects in reaction-sintered silicon carbide ceramic components. Initially wavelet based feature extraction is implemented from the region of interest. An Artificial Neural Network classifier is employed to evaluate the performance of these features. Genetic Algorithm based feature selection is performed. Principal Component Analysis is a popular technique used for feature selection and is compared with the genetic algorithm based technique in terms of classification accuracy and selection of optimal number of features. The experimental results confirm that features identified by Principal Component Analysis lead to improved performance in terms of classification percentage with 96% than Genetic algorithm with 94%. PMID:26081920

  10. Mechanochemically synthesized kalsilite based bioactive glass-ceramic composite for dental vaneering

    NASA Astrophysics Data System (ADS)

    Kumar, Pattem Hemanth; Singh, Vinay Kumar; Kumar, Pradeep

    2015-08-01

    Kalsilite glass-ceramic composites have been prepared by a mechanochemical synthesis process for dental veneering application. The aim of the present study is to prepare bioactive kalsilite composite material for application in tissue attachment and sealing of the marginal gap between fixed prosthesis and tooth. Mechanochemical synthesis is used for the preparation of microfine kalsilite glass-ceramic. Low temperature frit and bioglass have been prepared using the traditional quench method. Thermal, microstructural and bioactive properties of the composite material have been examined. The feasibility of the kalsilite to be coated on the base commercial opaque as well as the bioactive behavior of the coated specimen has been confirmed. This study indicates that the prepared kalsilite-based composites show similar structural, morphological and bioactive behavior to that of commercial VITA VMK95 Dentin 1M2.

  11. Development of a zirconia-mullite based ceramic for recuperator applications. DOE/ORNL Ceramic Technology Project

    SciTech Connect

    Gonzalez, J.M.

    1992-12-01

    GTE Products Corporation developed a compact ceramic high temperature recuperator for recovering heat from relatively clean exhaust gases at temperatures up to 2500F. The DOE program allowed GTE to improve the technical and economic characteristics of the recuperator and stimulate industrial acceptance of the recuperator as an energy-saving technology. From January 1981 to December 1984, 561 recuperators were installed by GTE on new or retrofitted furnaces. With over 1200 units sold commercially between 1981 and 1990, GTE has documented the effect (long and short term) of corrosive attack from alkalies and lead. One objective of this contract was to develop Z-1000 a zirconia-mullite mixed oxide ceramic for use in ceramic recuperator applications susceptible to corrosion. To first and second pass of the ceramic recuperator would utilize the current cordierite-mixed-oxide ceramic. A Z-1000 matrix element would be used in the preheated air side`s third pass (exhaust inlet). Thermal stresses on Z-1000 cross flow module could be minimized by selecting appropriate heat transfer surface areas for each pass. A large surface area for first and second pass (cordierite section) could provide for sufficient heat transfer for 50% effectiveness. A surface area that generates minimal heat transfer in the third pass (Z-1000) section is envisioned. Heat transferred in this section reduces the differential temperature across the matrix and the thermal stresses. Hence, thermal shock resistance of the material in the third pass becomes less critical; however, its corrosion resistance must be sufficient to withstand corrosive attack. This modular design could utilize a field repairable, disposable matrix. This report is concerned with process technology development for fabricating such a matrix, and a series of corrosion tests that established the potential corrosion resistance of the Z-1000 ceramic.

  12. Synthesis of ceramic-based porous gradient structures for applications in energy conversion and related fields

    NASA Astrophysics Data System (ADS)

    Graule, Thomas; Ozog, Paulina; Durif, Caroline; Wilkens-Heinecke, Judit; Kata, Dariusz

    2016-06-01

    Porous, graded ceramic structures are of high relevance in the field of energy conversion as well as in catalysis, and additionally in filtration technology and in biomedical applications. Among different technologies for the tailored design for such structures we demonstrate here a new environmental friendly UV curing-based concept to prepare laminated structures with pore sizes ranging from a few microns up to 50 microns in diameter and with porosities ranging from 10% up to 75 vol.% porosity.

  13. Fluorozirconate-based glass ceramic x-ray detectors for digital radiography.

    SciTech Connect

    Schweizer, S.; Johnson, J. A.; Energy Technology; Univ. of Paderborn

    2007-04-01

    Two-dimensional indirect digital X-ray detectors use either a storage phosphor or a scintillator as an imaging plate. A storage phosphor forms a latent X-ray image, which is subsequently readout by a photostimulable luminescence process. A scintillator produces a visible image during X-ray illumination. Commercial storage-phosphor image plates have relatively poor spatial resolution because of light scattering during the readout. To improve their image resolution, europium (II)-doped fluorozirconate (FZ)-based glasses containing barium chloride nanoparticles have been developed. X-ray imaging showed that these storage-phosphor plates can resolve features as small as 17 {micro}m. By using appropriate thermal-processing conditions, the FZ-based glass ceramics can also be made into transparent glass ceramic scintillators. Imaging tests showed that these scintillators have a spatial resolution and efficiency comparable to those of a single-crystal CdWO{sub 4} scintillator. These results demonstrate that FZ-based glass ceramics are good candidates for digital radiography, either for storage phosphor or scintillator applications.

  14. Volatile Reaction Products From Silicon-Based Ceramics in Combustion Environments Identified

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.

    1997-01-01

    Silicon-based ceramics and composites are prime candidates for use as components in the hot sections of advanced aircraft engines. These materials must have long-term durability in the combustion environment. Because water vapor is always present as a major product of combustion in the engine environment, its effect on the durability of silicon-based ceramics must be understood. In combustion environments, silicon-based ceramics react with water vapor to form a surface silica (SiO2) scale. This SiO2 scale, in turn, has been found to react with water vapor to form volatile hydroxides. Studies to date have focused on how water vapor reacts with high-purity silicon carbide (SiC) and SiO2 in model combustion environments. Because the combustion environment in advanced aircraft engines is expected to contain about 10-percent water vapor at 10-atm total pressure, the durability of SiC and SiO2 in gas mixtures containing 0.1- to 1-atm water vapor is of interest. The reactions of SiC and SiO2 with water vapor were monitored by measuring weight changes of sample coupons in a 0.5-atm water vapor/0.5-atm oxygen gas mixture with thermogravimetric analysis.

  15. Ceramic fiber ceramic matrix filter development

    SciTech Connect

    Judkins, R.R.; Stinton, D.P.; Smith, R.G.; Fischer, E.M.

    1994-09-01

    The objectives of this project were to develop a novel type of candle filter based on a ceramic fiber-ceramic matrix composite material, and to extend the development to full-size, 60-mm OD by 1-meter-long candle filters. The goal is to develop a ceramic filter suitable for use in a variety of fossil energy system environments such as integrated coal gasification combined cycles (IGCC), pressurized fluidized-bed combustion (PFBC), and other advanced coal combustion environments. Further, the ceramic fiber ceramic matrix composite filter, hereinafter referred to as the ceramic composite filter, was to be inherently crack resistant, a property not found in conventional monolithic ceramic candle filters, such as those fabricated from clay-bonded silicon carbide. Finally, the adequacy of the filters in the fossil energy system environments is to be proven through simulated and in-plant tests.

  16. Environmental durability of ceramics and ceramic composites

    NASA Technical Reports Server (NTRS)

    Fox, Dennis S.

    1992-01-01

    An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.

  17. Zirconia-coated carbonyl-iron-particle-based magnetorheological fluid for polishing optical glasses and ceramics

    SciTech Connect

    Shafrir, Shai N.; Romanofsky, Henry J.; Skarlinski, Michael; Wang, Mimi; Miao, Chunlin; Salzman, Sivan; Chartier, Taylor; Mici, Joni; Lambropoulos, John C.; Shen Rui; Yang Hong; Jacobs, Stephen D.

    2009-12-10

    We report on magnetorheological finishing (MRF) spotting experiments performed on glasses and ceramics using a zirconia-coated carbonyl-iron (CI)-particle-based magnetorheological (MR) fluid. The zirconia-coated magnetic CI particles were prepared via sol-gel synthesis in kilogram quantities. The coating layer was {approx}50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long-term stability against aqueous corrosion. ''Free'' nanocrystalline zirconia polishing abrasives were cogenerated in the coating process, resulting in an abrasive-charged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses and ceramics over a period of nearly three weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained.

  18. Properties of PZT-Based Piezoelectric Ceramics Between -150 and 250 C

    NASA Technical Reports Server (NTRS)

    Hooker, Matthew W.

    1998-01-01

    The properties of three PZT-based piezoelectric ceramics and one PLZT electrostrictive ceramic were measured as a function of temperature. In this work, the dielectric, ferroelectric polarization versus electric field, and piezoelectric properties of PZT-4, PZT-5A, PZT-5H, and PLZT-9/65/35 were measured over a temperature range of -150 to 250 C. In addition to these measurements, the relative thermal expansion of each composition was measured from 25 to 600 C and the modulus of rupture of each material was measured at room temperature. This report describes the experimental results and compares and contrasts the properties of these materials with respect to their applicability to intelligent aerospace systems.

  19. Yb:YAG ceramic-based laser driver for Inertial Fusion Energy (IFE)

    NASA Astrophysics Data System (ADS)

    Vetrovec, John; Copeland, Drew A.; Litt, Amardeep S.

    2016-03-01

    We report on a new class of laser amplifiers for inertial confinement fusion (ICF) drivers based on a Yb:YAG ceramic disk in an edge-pumped configuration and cooled by a high-velocity gas flow. The Yb lasant offers very high efficiency and low waste heat. The ceramic host material has a thermal conductivity nearly 15-times higher than the traditionally used glass and it is producible in sizes suitable for a typical 10- to 20-kJ driver beam line. The combination of high lasant efficiency, low waste heat, edge-pumping, and excellent thermal conductivity of the host, enable operation at 10 to 20 Hz at over 20% wall plug efficiency while being comparably smaller and less costly than recently considered face-pumped alternative drivers using Nd:glass, Yb:S-FAP, and cryogenic Yb:YAG. Scalability of the laser driver over a broad range of sizes is presented.

  20. Zirconia-coated carbonyl-iron-particle-based magnetorheological fluid for polishing optical glasses and ceramics.

    PubMed

    Shafrir, Shai N; Romanofsky, Henry J; Skarlinski, Michael; Wang, Mimi; Miao, Chunlin; Salzman, Sivan; Chartier, Taylor; Mici, Joni; Lambropoulos, John C; Shen, Rui; Yang, Hong; Jacobs, Stephen D

    2009-12-10

    We report on magnetorheological finishing (MRF) spotting experiments performed on glasses and ceramics using a zirconia-coated carbonyl-iron (CI)-particle-based magnetorheological (MR) fluid. The zirconia-coated magnetic CI particles were prepared via sol-gel synthesis in kilogram quantities. The coating layer was approximately 50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long-term stability against aqueous corrosion. "Free" nanocrystalline zirconia polishing abrasives were cogenerated in the coating process, resulting in an abrasive-charged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses and ceramics over a period of nearly three weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained. PMID:20011021

  1. Alumina ceramic based high-temperature performance of wireless passive pressure sensor

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Wu, Guozhu; Guo, Tao; Tan, Qiulin

    2016-07-01

    A wireless passive pressure sensor equivalent to inductive-capacitive (LC) resonance circuit and based on alumina ceramic is fabricated by using high temperature sintering ceramic and post-fire metallization processes. Cylindrical copper spiral reader antenna and insulation layer are designed to realize the wireless measurement for the sensor in high temperature environment. The high temperature performance of the sensor is analyzed and discussed by studying the phase-frequency and amplitude-frequency characteristics of reader antenna. The average frequency change of sensor is 0.68 kHz/°C when the temperature changes from 27°C to 700°C and the relative change of twice measurements is 2.12%, with high characteristic of repeatability. The study of temperature-drift characteristic of pressure sensor in high temperature environment lays a good basis for the temperature compensation methods and insures the pressure signal readout accurately.

  2. Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Levine, S. R.

    1995-01-01

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  3. Low cost fabrication of silicon carbide based ceramics and fiber reinforced composites

    SciTech Connect

    Singh, M.; Levine, S.R.

    1995-07-01

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC`s) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  4. Development of NZP ceramic based {open_quotes}cast-in-place{close_quotes} diesel engine port liners

    SciTech Connect

    Nagaswaran, R.; Limaye, S.Y.

    1996-02-01

    BSX (Ba{sub 1+x}Zr{sub 4}P{sub 6-2x}Si{sub 2x}O{sub 24}) and CSX (Ca{sub l-x}Sr{sub x}Zr{sub 4}P{sub 6}O{sub 24}) type NZP ceramics were fabricated and characterized for: (i) thermal properties viz., thermal conductivity, thermal expansion, thermal stability and thermal shock resistance; (ii) mechanical properties viz., flexure strength and elastic modulus; and (iii) microstructures. Results of these tests and analysis indicated that the BS-25 (x=0.25 in BSX) and CS-50 (x=0.50 in CSX) ceramics had the most desirable properties for casting metal with ceramic in place. Finite element analysis (FEA) of metal casting (with ceramic in place) was conducted to analyze thermomechanical stresses generated and determine material property requirements. Actual metal casting trials were also conducted to verify the results of finite element analysis. In initial trials, the ceramic cracked because of the large thermal expansion mismatch (hoop) stresses (predicted by FEA also). A process for introduction of a compliant layer between the metal and ceramic to alleviate such destructive stresses was developed. The compliant layer was successful in preventing cracking of either the ceramic or the metal. In addition to these achievements, pressure slip casting and gel-casting processes for fabrication of NZP components; and acoustic emission and ultrasonics-based NDE techniques for detection of microcracks and internal flaws, respectively, were successfully developed.

  5. Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic.

    PubMed

    He, Fupo; Ren, Weiwei; Tian, Xiumei; Liu, Wei; Wu, Shanghua; Chen, Xiaoming

    2016-07-01

    In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. PMID:27127035

  6. Damage formation, fatigue behavior and strength properties of ZrO2-based ceramics

    NASA Astrophysics Data System (ADS)

    Kozulin, A. A.; Narikovich, A. S.; Kulkov, S. N.; Leitsin, V. N.; Kulkov, S. S.

    2016-08-01

    It is suggested that a non-destructive testing technique using a three-dimensional X-ray tomography be applied to detecting internal structural defects and monitoring damage formation in a ceramic composite structure subjected to a bending load. Three-point bending tests are used to investigate the fatigue behavior and mechanical and physical properties of medical-grade ZrO2-based ceramics. The bending strength and flexural modulus are derived under static conditions at a loading rate of 2 mm/min. The fatigue strength and fatigue limit under dynamic loading are investigated at a frequency of 10 Hz in three stress ranges: 0.91-0.98, 0.8-0.83, and 0.73-0.77 MPa of the static bending strength. The average values of the bending strength and flexural modulus of sintered specimens are 43 MPa and 22 GPa, respectively. The mechanical properties of the ceramics are found to be similar to those of bone tissues. The testing results lead us to conclude that the fatigue limit obtained from 105 stress cycles is in the range 33-34 MPa, i.e. it accounts for about 75% of the static bending strength for the test material.

  7. High-power electro-optic switch technology based on novel transparent ceramic

    NASA Astrophysics Data System (ADS)

    Xue-Jiao, Zhang; Qing, Ye; Rong-Hui, Qu; Hai-wen, Cai

    2016-03-01

    A novel high-power polarization-independent electro-optic switch technology based on a reciprocal structure Sagnac interferometer and a transparent quadratic electro-optic ceramic is proposed and analyzed theoretically and experimentally. The electro-optic ceramic is used as a phase retarder for the clockwise and counter-clockwise polarized light, and their polarization directions are adjusted to their orthogonal positions by using two half-wave plates. The output light then becomes polarization-independent with respect to the polarization direction of the input light. The switch characteristics, including splitter ratios and polarization states, are theoretically analyzed and simulated in detail by the matrix multiplication method. An experimental setup is built to verify the analysis and experimental results. A new component ceramic is used and a non-polarizing cube beam splitter (NPBS) replaces the beam splitter (BS) to lower the ON/OFF voltage to 305 V and improve the extinction ratio by 2 dB. Finally, the laser-induced damage threshold for the proposed switch is measured and discussed. It is believed that potential applications of this novel polarization-independent electro-optic switch technology will be wide, especially for ultrafast high-power laser systems. Project supported by the National Natural Science Foundation of China (Grant Nos. 61137004, 61405218, and 61535014).

  8. Feature extraction for ultrasonic sensor based defect detection in ceramic components

    NASA Astrophysics Data System (ADS)

    Kesharaju, Manasa; Nagarajah, Romesh

    2014-02-01

    High density silicon carbide materials are commonly used as the ceramic element of hard armour inserts used in traditional body armour systems to reduce their weight, while providing improved hardness, strength and elastic response to stress. Currently, armour ceramic tiles are inspected visually offline using an X-ray technique that is time consuming and very expensive. In addition, from X-rays multiple defects are also misinterpreted as single defects. Therefore, to address these problems the ultrasonic non-destructive approach is being investigated. Ultrasound based inspection would be far more cost effective and reliable as the methodology is applicable for on-line quality control including implementation of accept/reject criteria. This paper describes a recently developed methodology to detect, locate and classify various manufacturing defects in ceramic tiles using sub band coding of ultrasonic test signals. The wavelet transform is applied to the ultrasonic signal and wavelet coefficients in the different frequency bands are extracted and used as input features to an artificial neural network (ANN) for purposes of signal classification. Two different classifiers, using artificial neural networks (supervised) and clustering (un-supervised) are supplied with features selected using Principal Component Analysis(PCA) and their classification performance compared. This investigation establishes experimentally that Principal Component Analysis(PCA) can be effectively used as a feature selection method that provides superior results for classifying various defects in the context of ultrasonic inspection in comparison with the X-ray technique.

  9. Crystal phase analysis of SnO{sub 2}-based varistor ceramic using the Rietveld method

    SciTech Connect

    Moreira, M.L.; Pianaro, S.A. . E-mail: sap@uepg.br; Andrade, A.V.C.; Zara, A.J.

    2006-09-15

    A second addition of l mol% of CoO to a pre calcined SnO{sub 2}-based ceramic doped with 1.0 mol% of CoO, 0.05 mol% of Nb{sub 2}O{sub 5} and 0.05 mol% of Cr{sub 2}O{sub 3} promotes the appearance of a secondary phase, Co{sub 2}SnO{sub 4}, besides the SnO{sub 2} cassiterite phase, when the ceramic was sintered at 1350 deg. C/2 h. This was observed using X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray techniques. Rietveld refinement was carried out to quantify the phases present in the ceramic system. The results of the quantitative analysis were 97 wt.% SnO{sub 2} and 3 wt.% Co{sub 2}SnO{sub 4}. The microstructural analysis showed that a certain amount of cobalt ion remains into cassiterite grains.

  10. Additive Manufacturing of Reactive In Situ Zr Based Ultra-High Temperature Ceramic Composites

    NASA Astrophysics Data System (ADS)

    Sahasrabudhe, Himanshu; Bandyopadhyay, Amit

    2016-03-01

    Reactive in situ multi-material additive manufacturing of ZrB2-based ultra-high-temperature ceramics in a Zr metal matrix was demonstrated using LENS™. Sound metallurgical bonding was achieved between the Zr metal and Zr-BN composites with Ti6Al4V substrate. Though the feedstock Zr power had α phase, LENS™ processing of the Zr powder and Zr-BN premix powder mixture led to the formation of some β phase of Zr. Microstructure of the Zr-BN composite showed primary grains of zirconium diboride phase in zirconium metal matrix. The presence of ZrB2 ceramic phase was confirmed by X-ray diffraction (XRD) analysis. Hardness of pure Zr was measured as 280 ± 12 HV and, by increasing the BN content in the feedstock, the hardness was found to increase. In Zr-5%BN composite, the hardness was 421 ± 10 HV and the same for Zr-10%BN composite was 562 ± 10 HV. It is envisioned that such multi-materials additive manufacturing will enable products in the future that cannot be manufactured using traditional approaches particularly in the areas of high-temperature metal-ceramic composites with compositional and functional gradation.

  11. Continuum-based FEM modeling of ceramic powder compaction using a cap-plasticity constitutive model

    SciTech Connect

    ARGUELLO JR.,JOSE G.; FOSSUM,ARLO F.; ZEUCH,DAVID H.; EWSUK,KEVIN G.

    2000-01-25

    Common ceramic component manufacturing typically involves the processing of the raw materials in powder form. Granulated powder is formed into a green body of the desired size and shape by consolidation, often by simply pressing nominally dry powder. Ceramic powders are commonly pressed in steel dies or rubber bags with the aim of producing a near-net-shape green body for subsequent sintering. Density gradients in these compacts, introduced during the pressing operation, are often severe enough to cause distortions in the shape of the part during sintering due to nonuniform shrinkage. In such cases, green machining or diamond grinding operations may be needed to obtain the desired final shape and size part. In severe cases, nonuniform shrinkage may even cause fracture in the parts during sintering. Likewise, density gradients can result in green bodies that break during ejection from the die or that are too fragile to be handled during subsequent processing. Empirical relationships currently exist to describe powder compaction but provide little understanding of how to control die design or compaction parameters to minimize density gradients thereby forcing the designer to use expensive and time consuming trial and error procedures. For this reason, interest has grown in developing computational tools to address this problem (Aydin et al., 1996 and Coube, 1998). The goal of the present work was to develop a general continuum-based finite element model for ceramic powder compaction that can be used to aid and guide the design and pressing of ceramic powders. Such a model can be used to improve both part and die/bag pressing design, resulting in more efficient and cost effective ways to make better parts.

  12. Metal-ceramic composite development based on its modelling results

    NASA Astrophysics Data System (ADS)

    Dvilis, E. S.; Khasanov, O. L.; Khasanov, A. O.; Petyukevich, M. S.

    2016-02-01

    The modeling (and its experimental verification) of packing and deformation of the composites consisted of aluminum-magnesium alloy AMg6, B4C powder and W nano-powder has been performed. The powder compositions were determined using discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders. The models of maximum mixture packing densities have been rendered.

  13. Tungsten band edge absorber/emitter based on a monolayer of ceramic microspheres.

    PubMed

    Dyachenko, P N; do Rosário, J J; Leib, E W; Petrov, A Yu; Störmer, M; Weller, H; Vossmeyer, T; Schneider, G A; Eich, M

    2015-09-21

    We report on a band edge absorber/emitter design for high-temperature applications based on an unstructured tungsten substrate and a monolayer of ceramic microspheres. The absorber was fabricated as a monolayer of ZrO(2) microparticles on a tungsten layer with a HfO(2) nanocoating. The band edge of the absorption is based on critically coupled microsphere resonances. It can be tuned from visible to near-infrared range by varying the diameter of the microparticles. The absorption properties were found to be stable up to 1000°C. PMID:26406752

  14. Plasma-Sprayed Refractory Oxide Coatings on Silicon-Base Ceramics

    NASA Technical Reports Server (NTRS)

    Tewari, Surendra

    1997-01-01

    Silicon-base ceramics are promising candidate materials for high temperature structural applications such as heat exchangers, gas turbines and advanced internal combustion engines. Composites based on these materials are leading candidates for combustor materials for HSCT gas turbine engines. These materials possess a combination of excellent physical and mechanical properties at high temperatures, for example, high strength, high toughness, high thermal shock resistance, high thermal conductivity, light weight and excellent oxidation resistance. However, environmental durability can be significantly reduced in certain conditions such as when molten salts, H2 or water vapor are present. The oxidation resistance of silicon-base materials is provided by SiO2 protective layer. Molten salt reacts with SiO2 and forms a mixture of SiO2 and liquid silicate at temperatures above 800C. Oxygen diffuses more easily through the chemically altered layer, resulting in a catastrophic degradation of the substrate. SiC and Si3N4 are not stable in pure H2 and decompose to silicon and gaseous species such as CH4, SiH, SiH4, N2, and NH3. Water vapor is known to slightly increase the oxidation rate of SiC and Si3N4. Refractory oxides such as alumina, yttria-stabilized zirconia, yttria and mullite (3Al2O3.2SiO2) possess excellent environmental durability in harsh conditions mentioned above. Therefore, refractory oxide coatings on silicon-base ceramics can substantially improve the environmental durability of these materials by acting as a chemical reaction barrier. These oxide coatings can also serve as a thermal barrier. The purpose of this research program has been to develop refractory oxide chemical/thermal barrier coatings on silicon-base ceramics to provide extended temperature range and lifetime to these materials in harsh environments.

  15. Ceramic separators based on Li+-conducting inorganic electrolyte for high-performance lithium-ion batteries with enhanced safety

    NASA Astrophysics Data System (ADS)

    Jung, Yun-Chae; Kim, Seul-Ki; Kim, Moon-Sung; Lee, Jeong-Hye; Han, Man-Seok; Kim, Duck-Hyun; Shin, Woo-Cheol; Ue, Makoto; Kim, Dong-Won

    2015-10-01

    Flexible ceramic separators based on Li+-conducting lithium lanthanum zirconium oxide are prepared as thin films and directly applied onto negative electrode to produce a separator-electrode assembly with good interfacial adhesion and low interfacial resistances. The ceramic separators show an excellent thermal stability and high ionic conductivity as compared to conventional polypropylene separator. The lithium-ion batteries assembled with graphite negative electrode, Li+-conducting ceramic separator and LiCoO2 positive electrode exhibit good cycling performance in terms of discharge capacity, capacity retention and rate capability. It is also demonstrated that the use of a ceramic separator can greatly improve safety over cells employing a polypropylene separator, which is highly desirable for lithium-ion batteries with enhanced safety.

  16. Ho:YAG transparent ceramics based on nanopowders produced by laser ablation method: Fabrication, optical properties, and laser performance

    NASA Astrophysics Data System (ADS)

    Bagayev, S. N.; Osipov, V. V.; Vatnik, S. M.; Shitov, V. A.; Vedin, I. A.; Platonov, V. V.; Steinberg, I. Sh.; Maksimov, R. N.

    2015-12-01

    We fabricate Ho:YAG transparent ceramics based on nanopowders produced by laser ablation method via two approaches. Higher transmittance (82% in the infrared region) is achieved in ceramics prepared with an additional round of pre-calcining before sintering. We evaluate the average volume of the scattering centers in the ceramics and their distribution along the sample depth by the direct count method using an optical microscope and by the novel method of collinear two-photon interband photoexcitation, respectively. The laser characteristics of the 1% Ho:YAG ceramics are investigated using an intracavity pumping scheme. The slope efficiency is ∼40% relative to the absorbed pumping power at 1.85 μm.

  17. Catalycity of Zirconia and of ZrB2-Based Ultra-High Temperature Ceramics

    NASA Astrophysics Data System (ADS)

    Balat-Pichelin, M.; Passarelli, M.; Scatteia, L.; Alfano, D.

    2009-01-01

    Catalytic recombination of dissociated atmospheric oxygen molecules on the surface of thermal protection systems located on nose and leading edges is a significant additional heat source during the atmospheric re-entry of a space vehicle. Typically, thermal protection systems (TPS) of re-entry vehicles are designed considering the constituent materials as fully catalytic, a strongly conservative assumption that can lead to marked structural over-dimensioning of the TPS overall mass required. However, mass, performance, and cost considerations in future re-usable re-entry vehicles require a more sensible design approach based upon a more realistic assumption of partial catalycity. Ground test simulation under atmospheric reentry conditions is therefore necessary to characterize and select base materials for TPS. Very high temperature and low pressure air plasma are reproduced within the MESOX facility - out of equilibrium plasma - with a degree of dissociation of oxygen reaching 80 % for an earth entry phase. In this paper, experimental results are given on the catalytic properties of Ultra-High Temperature Ceramics based on zirconium- and hafnium- diborides: these ceramic compounds represent a promising class of new TPS materials for the manufacturing of slender- shaped hot structures in hypersonic re-entry vehicles. Two different UHTC compounds, produced by hot pressing and machined into their final shape by mean of electrical discharge machining or, alternatively, by diamond-tooling were tested in the temperature range 900-2500 K. Three different kinds of zirconia (sintering additives) were also tested in the same temperature range. The effects of the crystalline structure of zirconia materials and the one of surface machining for the zirconium diboride based ceramics are underlined.

  18. An in vitro model for preclinical testing of thrombogenicity of resorbable metallic stents.

    PubMed

    Walker, Emily K; Nauman, Eric A; Allain, Jean Paul; Stanciu, Lia A

    2015-06-01

    Vascular stents that can biodegrade and disappear in time have been reported as a promising solution to the problems of late-stent thrombosis and in-stent restenosis. Iron alloys in particular have many advantages in terms of cytocompatibility and mechanical properties. Despite mechanical behavior and biocompatibility studies, little attention has been given to the thrombogenic potential of these stents. This article presents the first study that aims to close this gap by addressing the hemocompatibility of resorbable iron-based alloys and composites in an in vitro porcine blood model. The investigated braided biodegradable stents included 99.95% pure Fe (50% cold worked), Fe35Mn alloy, Fe35Mn-25% ZM21 (ZM21 is 2% Zn, 0.5% Mn, balance Mg), Fe-25% Mg, and Fe-57% Mg. All stents were formed by braiding 127 µm diameter wires into stents with an outer diameter of 6.35 mm. Inflammatory reaction and thrombocyte activation were examined by assessment of β-thromboglobulin, thrombin-antithrombin complex, and polymorphonuclear elastase levels. The potential of Fe35Mn for use in vascular stenting is demonstrated by its exhibition of the least thrombogenic potential among tested materials. All bioresorbable Fe-Mn alloy compositions showed a reduced propensity towards platelet adhesion compared to 316L stainless steel, further indicating a general positive shift towards reduced thrombogenicity compared to traditional stents. PMID:25294677

  19. Ceramic Coating Inspection Using Laser-Based Ultrasonics and Nanoindentation

    SciTech Connect

    Steen, T. L.; Murray, T. W.; Basu, S. N.; Sarin, V. K.

    2007-03-21

    A combination of laser-based ultrasonic (LBU) inspection and nanoindentation testing is used to evaluate the thickness uniformity and through-thickness mechanical property distributions in 5-20 {mu}m thick CVD environmental barrier coatings. Mullite (3Al2O3{center_dot}2SiO2) coatings grown on silicon carbide substrates are studied in order to provide feedback on the growth process under a range of operating conditions. Nanoindentation tests are performed on polished coating cross sections, and the depth dependence of the elastic modulus of each coating is found. In the LBU experiments, a modulated continuous wave (CW) source is used for surface wave generation. The source is held at a fixed temporal frequency as it is scanned over the surface of the coating. At each temporal frequency of interest, the spatial frequencies of the acoustic modes are found, allowing for phase velocities to be determined. The mean values of elastic moduli found using the LBU approach compare well with the nanoindentation results.

  20. Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

    NASA Astrophysics Data System (ADS)

    Li, Bao-wei; Li, Hong-xia; Zhang, Xue-feng; Jia, Xiao-lin; Sun, Zhi-chao

    2015-12-01

    The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment methods: conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a differential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron microscopy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the processing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.

  1. Polymer-Ceramic Nanocomposites Based on New Concepts for Embedded Capacitor

    NASA Astrophysics Data System (ADS)

    Takahashi, Akio; Kakimoto, Masa-Aki; Tsurumi, Taka-Aki; Hao, Jianjun; Li, Li; Kikuchi, Ryohei; Miwa, Takao; Ohno, Toshiyuki; Yamada, Shinji; Takezawa, Yoshitaka

    A rapid growth of mixed-signal integrated circuits is driving the needs of multifunction and miniaturization of the component in electronics applications. Polymer-ceramic composites have been of great interest as embedded capacitor materials because they enabled companies to combine the processability of polymers with the high dielectric constant of ceramics. Polymer-ceramic nanocomposites based on new concepts were developed for embedded capacitor applications. The dielectric constant was above 80 at 1 MHz and the specific capacitance was successfully achieved 8 nF/cm2. By use of this nanocomposites, multilayer printed wiring boards with embedded passive components were fabricated for prototypes. The following technologies are reported in this paper. Firstly, based on the investigation of barium titanium oxide (BaTiO3) crystallites, various particles with the sizes from 17 nm to 100 nm were prepared by the 2-step thermal decomposition method from barium titanyl oxalate (BaTiO(C2O4)2·4H2O). It was clarified that BaTiO3 particles with a size of around 70 nm exhibited a maximum dielectric constant of over 15,000 by FEM analysis from the measured dielectric constants of BaTiO3 suspensions. Secondary, the BaTiO3 surface modification based on a new concept was applied to improve the affinity between BaTiO3 particles and polymer matrix. Thirdly, the blend polymer of an aromatic polyamide (PA) and an aromatic bismaleimide (BMI) was employed as the matrix from a view-point of both the processabilty during fabricating the substrates with embedded passive components and the thermal stability during assembling LSI chips. Finally, these technologies were combined and optimized for embedded capacitor materials.

  2. Ceramics reinforced metal base composite coatings produced by CO II laser cladding

    NASA Astrophysics Data System (ADS)

    Yang, Xichen; Wang, Yu; Yang, Nan

    2008-03-01

    Due to the excellent performance in high strength, anti-temperature and anti-wear, ceramics reinforced metal base composite material was used in some important fields of aircraft, aerospace, automobile and defense. The traditional bulk metal base composite materials are the expensive cost, which is limited in its industrial application. Development of laser coating of ceramics reinforced metal base composite is very interesting in economy. This paper is focused on three laser cladding ceramics coatings of SiC particle /Al matrix , Al IIO 3 powder/ Al matrix and WC + Co/mild steel matrix. Powder particle sizes are of 10-60μm. Chemical contents of aluminum matrix are of 3.8-4.0% Cu, 1.2-1.8% Mg, 0.3-0.99% Mn and balance Al. 5KW CO II laser, 5 axes CNC table, JKF-6 type powder feeder and co-axis feeder nozzle are used in laser cladding. Microstructure and performance of laser composite coatings have been respectively examined with OM,SEM and X-ray diffraction. Its results are as follows : Microstructures of 3C-,6H- and 5H- SiC particles + Al + Al 4SiC 4 + Si in SiC/Al composite, hexagonal α-Al IIO 3 + cubic γ-Al IIO 3 + f.c.c Al in Al IIO 3 powder/ Al composite and original WC particles + separated WC particles + eutectic WC + γ-Co solid solution + W IIC particles in WC + Co/steel coatings are respectively recognized. New microstructures of 5H-SiC in SiC/Al composite, cubic γ-Al IIO 3 in Al IIO 3 composite and W IIC in WC + Co/ steel composite by laser cladding have been respectively observed.

  3. GBR using bovine bone matrix and resorbable and nonresorbable membranes. Part 2: Clinical results.

    PubMed

    Fugazzotto, Paul A

    2003-12-01

    Ninety sites were treated by sinus augmentation therapy using only Bio-Oss (31 sites) or extraction socket and ridge augmentation therapy using only Bio-Oss beneath secured resorbable or titanium-reinforced nonresorbable membranes (59 sites). The results of core biopsies taken at different intervals were discussed in part 1 of this study. A discussion of the use of resorbable versus reinforced nonresorbable membranes as a function of defect morphology is undertaken in part 2. Secured titanium-reinforced membranes were shown to be the most ideal means by which to ensure the final morphology of the regenerated hard tissues. PMID:14703764

  4. FEAMAC/CARES Stochastic-Strength-Based Damage Simulation Tool for Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Nemeth, Noel; Bednarcyk, Brett; Pineda, Evan; Arnold, Steven; Mital, Subodh; Murthy, Pappu; Bhatt, Ramakrishna

    2016-01-01

    Reported here is a coupling of two NASA developed codes: CARES (Ceramics Analysis and Reliability Evaluation of Structures) with the MAC/GMC (Micromechanics Analysis Code/ Generalized Method of Cells) composite material analysis code. The resulting code is called FEAMAC/CARES and is constructed as an Abaqus finite element analysis UMAT (user defined material). Here we describe the FEAMAC/CARES code and an example problem (taken from the open literature) of a laminated CMC in off-axis loading is shown. FEAMAC/CARES performs stochastic-strength-based damage simulation response of a CMC under multiaxial loading using elastic stiffness reduction of the failed elements.

  5. High-fidelity AFM scanning stage based on multilayer ceramic capacitors.

    PubMed

    Chen, Jian; Zhang, Lian Sheng; Feng, Zhi Hua

    2016-05-01

    A kind of multilayer ceramic capacitors (MLCCs) has been verified to have good micro-actuating properties, thus making them good candidates for nano-positioning. In this paper, we successfully employed the MLCCs as lateral scanners for a tripod scanning stage. The MLCC-based lateral scanners display hysteresis under 1.5% and a nonlinearity less than 2% even with the simplest open-loop voltage drive. The developed scanning stage was integrated into a commercial AFM to evaluate its imaging performance. Experimental results showed that sample images with high fidelities were obtained. SCANNING 38:184-190, 2016. © 2015 Wiley Periodicals, Inc. PMID:26367125

  6. Etching process for improving the strength of a laser-machined silicon-based ceramic article

    DOEpatents

    Copley, S.M.; Tao, H.; Todd-Copley, J.A.

    1991-06-11

    A process is disclosed for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength. 1 figure.

  7. Etching process for improving the strength of a laser-machined silicon-based ceramic article

    DOEpatents

    Copley, Stephen M.; Tao, Hongyi; Todd-Copley, Judith A.

    1991-01-01

    A process for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength.

  8. Re-poling process for piezoelectric-based multilayer ceramic capacitors force sensor

    NASA Astrophysics Data System (ADS)

    Lin, Keng-Ren; Chang, Chih-Han; Chiang, Cheng-Hung; Lin, Che-Hsin

    2013-04-01

    This study presents an industrial-grade piezoelectric-based multilayer ceramic capacitors (MLCCs) force sensor. In order to increase the sensitivity and reduce the variation of different MLCCs, a simple re-poling process is adopted by applying an external electric field at the Curie temperature of MLCCs. Results indicate that the re-poling treatment improved up to 100-fold for the force detection sensitivity and reduced the variation for the output force response by 10-fold in comparison with the MLCC sensors without re-poling.

  9. Zirconia-based powders and properties of sintered ceramics for biomedical applications

    NASA Astrophysics Data System (ADS)

    Kulkov, S.; Buyakova, S.

    2015-11-01

    Porous ceramics obtained from ultra-fine powders have been studied. The porosity of ceramic samples was from 15 to 80 %. The structure of the ceramic materials was a cellular structure. A distinctive feature of all the deformation diagram obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  10. A quantitative acoustic emission study on fracture processes in ceramics based on wavelet packet decomposition

    SciTech Connect

    Ning, J. G.; Chu, L.; Ren, H. L.

    2014-08-28

    We base a quantitative acoustic emission (AE) study on fracture processes in alumina ceramics on wavelet packet decomposition and AE source location. According to the frequency characteristics, as well as energy and ringdown counts of AE, the fracture process is divided into four stages: crack closure, nucleation, development, and critical failure. Each of the AE signals is decomposed by a 2-level wavelet package decomposition into four different (from-low-to-high) frequency bands (AA{sub 2}, AD{sub 2}, DA{sub 2}, and DD{sub 2}). The energy eigenvalues P{sub 0}, P{sub 1}, P{sub 2}, and P{sub 3} corresponding to these four frequency bands are calculated. By analyzing changes in P{sub 0} and P{sub 3} in the four stages, we determine the inverse relationship between AE frequency and the crack source size during ceramic fracture. AE signals with regard to crack nucleation can be expressed when P{sub 0} is less than 5 and P{sub 3} more than 60; whereas AE signals with regard to dangerous crack propagation can be expressed when more than 92% of P{sub 0} is greater than 4, and more than 95% of P{sub 3} is less than 45. Geiger location algorithm is used to locate AE sources and cracks in the sample. The results of this location algorithm are consistent with the positions of fractures in the sample when observed under a scanning electronic microscope; thus the locations of fractures located with Geiger's method can reflect the fracture process. The stage division by location results is in a good agreement with the division based on AE frequency characteristics. We find that both wavelet package decomposition and Geiger's AE source locations are suitable for the identification of the evolutionary process of cracks in alumina ceramics.

  11. Fracture toughness determination of ceramic and resin-based dental composites.

    PubMed

    Kvam, K

    1992-01-01

    A new method has been developed for Klc determinations of brittle materials with precracks introduced by indentations. A reference glass, five ceramic materials, and one resin-based composite were tested. Knoop hardness indentations were made with a load of 49 N in a line from edge to edge vertical to the long axis on one surface of four-point flexure bars, to make a continuous crack under the indentations. Five specimens of each material were fractured in a four-point bend test with the line of indentations placed in the zone of constant and maximum tensile stress. Separate unfractured specimens were ground and polished to expose and measure the preformed continuous crack. The mean of six crack-depth measurements was used together with the fracture load and the dimensions of the bend specimens to calculate the fracture toughness, Klc of each material. The determined Klc value (x +/- SD) for the reference glass was 0.81 +/- .24 MPa m1/2 and corresponds to previous studies. The resin-based composite material, Silux Plus, had a value of 1.04 +/- 0.14 MPa m1/2. The Klc values (MPa m1/2) were 0.94 +/- 0.31 for Dicor, 1.41 +/- 0.18 for Cerestore, 1.50 +/- 0.29 for NBK-1000, 1.60 +/- 0.17 for Vitadur-N and 2.14 +/- 0.14 for Hi-Ceram. Hi-Ceram had significantly higher Klc values than the other materials. The new method seemed to be of value in determining the fracture toughness of non-metallic dental materials. PMID:1550892

  12. Integration Science and Technology of Silicon-Based Ceramics and Composites:Technical Challenges and Opportunities

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2013-01-01

    Ceramic integration technologies enable hierarchical design and manufacturing of intricate ceramic and composite parts starting with geometrically simpler units that are subsequently joined to themselves and/or to metals to create components with progressively higher levels of complexity and functionality. However, for the development of robust and reliable integrated systems with optimum performance for high temperature applications, detailed understanding of various thermochemical and thermomechanical factors is critical. Different technical approaches are required for the integration of ceramic to ceramic and ceramic to metal systems. Active metal brazing, in particular, is a simple and cost-effective method to integrate ceramic to metallic components. Active braze alloys usually contain a reactive filler metal (e.g., Ti, Cr, V, Hf etc) that promotes wettability and spreading by inducing chemical reactions with the ceramics and composites. In this presentation, various examples of brazing of silicon nitride to themselves and to metallic systems are presented. Other examples of joining of ceramic composites (C/SiC and SiC/SiC) using ceramic interlayers and the resulting microstructures are also presented. Thermomechanical characterization of joints is presented for both types of systems. In addition, various challenges and opportunities in design, fabrication, and testing of integrated similar (ceramic-ceramic) and dissimilar (ceramic-metal) material systems will be discussed. Potential opportunities and need for the development of innovative design philosophies, approaches, and integrated system testing under simulated application conditions will also be presented.

  13. Portfolio: Ceramics.

    ERIC Educational Resources Information Center

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  14. Mullite+CAS Bond Coat for Environmental Barrier Coatings for Si-Based Ceramics

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Opila, Elizabeth J.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Current environmental barrier coatings (EBCs) for silicon-based ceramics consist of a bond coat and a top coat. Mullite bond coat modified by adding low CTE glass ceramics, such as BSAS (xBaO.1xSrO.Al2O3.2SiO2) or CAS (CaO.Al2O3.2SiO2), was developed in the NASA Enabling Propulsion Materials (EPM) Program. EBCs based on mullite+CAS bond coat were characterized using high steam thermal cycling test and high steam isothermal thermogravemitry (TGA) at 1225 C - 13,000 C. The Mullite+CAS bond coat showed far superior durability compared to mullite bond coat, due to enhanced crack resistance. A BSAS top coat provided further improved durability compared to EBCs with a yttria-stabilized zirconia (YSZ) top coat. Still further improvement in the durability was achieved by adding a silicon bond coat between the mullite and the substrate. However, the silicon/mullite+CAS/BSAS EBC showed inferior long-term durability compared to the current state-of-the art EBC (silicon/mullite+BSAS/BSAS EBC), presumably due to the higher CAS-silica chemical reactivity.

  15. Base-Metal Electrode-Multilayer Ceramic Capacitors: Past, Present and Future Perspectives

    NASA Astrophysics Data System (ADS)

    Kishi, Hiroshi; Mizuno, Youichi; Chazono, Hirokazu

    2003-01-01

    Multilayer ceramic capacitor (MLCC) production and sales figures are the highest among fine-ceramic products developed in the past 30 years. The total worldwide production and sales reached 550 billion pieces and 6 billion dollars, respectively in 2000. In the course of progress, the development of base-metal electrode (BME) technology played an important role in expanding the application area. In this review, the recent progress in MLCCs with BME nickel (Ni) electrodes is reviewed from the viewpoint of nonreducible dielectric materials. Using intermediate-ionic-size rare-earth ion (Dy2O3, Ho2O3, Er2O3, Y2O3) doped BaTiO3 (ABO3)-based dielectrics, highly reliable Ni-MLCCs with a very thin layer below 2 μm in thickness have been developed. The effect of site occupancy of rare-earth ions in BaTiO3 on the electrical properties and microstructure of nonreducible dielectrics is studied systematically. It appears that intermediate-ionic-size rare-earth ions occupy both A- and B-sites in the BaTiO3 lattice and effectively control the donor/acceptor dopant ratio and microstructural evolution. The relationship between the electrical properties and the microstructure of Ni-MLCCs is also presented.

  16. 21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Resorbable calcium salt bone void filler device. 888.3045 Section 888.3045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Industry and FDA.” See § 888.1(e) of this chapter for the availability of this guidance....

  17. Role of bacterial γ-glutamyltranspeptidase as a novel virulence factor in bone-resorbing pathogenesis.

    PubMed

    Kim, Jinmoon; Jang, Sungil; Kim, Aeryun; Su, Hanfu; Gunawardhana, Niluka; Jeon, Yeong-Eui; Bak, Eun Jung; Kim, Ji-Hye; Cha, Jeong-Heon

    2016-05-01

    Mammalian γ-glutamyltranspeptidase (GGT) has been identified as a bone-resorbing factor. Since GGT of Bacillus subtilis exhibits similarity in their primary structure and enzymatic characteristics with mammalian GGTs, the bone-resorbing activity of bacterial GGT was examined in this study. Osteoclastogenesis was performed in a co-culture system of mouse calvaria-derived osteoblasts and bone marrow cells. A conditioned medium from GGT-overproducing B. subtilis culture showed significantly higher activity of osteoclast formation than a conditioned medium from wild-type B. subtilis culture. Recombinant GGT (rGGT) of wild-type B. subtilis and an enzymatic activity-defected rGGT of B. subtilis 2288 mutant were expressed in Escherichia coli and purified using His tag. Both purified rGGTs induced similar levels of osteoclastogenesis, suggesting that B. subtilis GGT possesses virulent bone-resorbing activity and its activity is probably independent of its enzymatic activity. Furthermore, a recombinant protein of B. subtilis GGT heavy subunit (Bs rGGT/H) showed strong activity of osteoclastogenesis while the light subunit failed to show strong activity, suggesting that the bone-resorbing activity is mainly located at the heavy subunit. More importantly, the GGT enzymatic activity may not be required for this virulence activity since the light subunit contains the catalytic pocket. In addition, B. subtilis rGGT stimulated mRNA expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and cyclooxygenase-2 (COX-2), while an osteoprotegerin inhibited the osteoclast formation induced by Bs rGGT/H. This is the first demonstration that bacterial GGT itself is sufficient to act as a bone-resorbing virulence factor via RANKL-dependent pathway. Therefore, it can be hypothesized that GGT of periodontopathic bacteria may play an important role as a virulence factor in bone destruction. PMID:27095459

  18. Supercritical carbon dioxide-processed resorbable polymer nanocomposites for bone graft substitute applications

    NASA Astrophysics Data System (ADS)

    Baker, Kevin C.

    Numerous clinical situations necessitate the use of bone graft materials to enhance bone formation. While autologous and allogenic materials are considered the gold standards in the setting of fracture healing and spine fusion, their disadvantages, which include donor site morbidity and finite supply have stimulated research and development of novel bone graft substitute materials. Among the most promising candidate materials are resorbable polymers, composed of lactic and/or glycolic acid. While the characteristics of these materials, such as predictable degradation kinetics and biocompatibility, make them an excellent choice for bone graft substitute applications, they lack mechanical strength when synthesized with the requisite porous morphology. As such, porous resorbable polymers are often reinforced with filler materials. In the presented work, we describe the use of supercritical carbon dioxide (scCO2) processing to create porous resorbable polymeric constructs reinforced by nanostructured, organically modified Montmorillonite clay (nanoclay). scCO2 processing simultaneously disperses the nanoclay throughout the polymeric matrix, while imparting a porous morphology to the construct conducive to facilitating cellular infiltration and neoangiogenesis, which are necessary components of bone growth. With the addition of as little as 2.5wt% of nanoclay, the compressive strength of the constructs nearly doubles putting them on par with human cortico-cancellous bone. Rheological measurements indicate that the dominant mode of reinforcement of the nanocomposite constructs is the restriction of polymer chain mobility. This restriction is a function of the positive interaction between polymer chains and the nanoclay. In vivo inflammation studies indicate biocompatibility of the constructs. Ectopic osteogenesis assays have determined that the scCO2-processed nanocomposites are capable of supporting growth-factor induced bone formation. scCO 2-processed resorbable

  19. Corrosion protection of SiC-based ceramics with CVD mullite coatings

    SciTech Connect

    Sarin, V.; Mulpuri, R.; Auger, M.

    1996-04-20

    SiC based ceramics have been identified as the leading candidate materials for elevated temperature applications in harsh oxidation/corrosion environments. It has been established that a protective coating can be effectively used to avoid problems with excessive oxidation and hot corrosion. However, to date, no coating configuration has been developed that can withstand the rigorous requirements imposed by such applications. Chemical vapor deposited (CVD) mullite coatings due to their desirable properties of toughness, corrosion resistance, and good coefficient of thermal expansion match with SiC are being developed as a potential solution. Formation of mullite on ceramic substrates via chemical vapor deposition was investigated. Thermodynamic calculations performed on the AlCl{sub 3}- SiCl{sub 4}-CO{sub 2}-H{sub 2} system were used to construct equilibrium CVD phase diagrams. Through process optimization, crystalline CVD mullite coatings have been successfully grown on SiC and Si{sub 3}N{sub 4} substrates. Results from the thermodynamic analysis, process optimization, and effect of various process parameters on deposition rate and coating morphology are discussed.

  20. Broadband mid-infrared wavelength conversion laser based on Cr2+ doped ceramic materials

    NASA Astrophysics Data System (ADS)

    Shang, Yaping; Yin, Ke; Li, Xiao; Wang, Peng; Xu, Xiaojun

    2015-10-01

    Broadband mid-infrared lasers are desirable for pretty important applications in fields of environmental protection, medical treatment, military applications, scientific, and other domains. Recently, super-continuum laser sources have achieved striking development. However, limited by the substrate materials, the output power scaling of the broadband mid-infrared fiber laser sources could not be increased drastically, especially for the long wavelength region. In this paper, we reported an experimental study about the broadband mid-infrared lasers based on Cr2+ doped II-VI ceramic materials, by using of a super-continuum laser source developed by our groups operating at 1550~2130nm with 200mW output power. The result suggested that the near-infrared spectral component of the super-continuum source was deeply absorbed by transition metal doped zinc chalcogenides ceramic materials, meanwhile the mid-infrared part, however, had been enhanced significantly by this new "power amplifier." Actually single-pass amplification efficiency was very limited. The best way to solve this problem was multi-pass amplification systems. We had shown an initial proof of this assumption by a double-pass experiments, the result was consistent with expected effect. Above all, the spectrum shaping from short wavelength to long wavelength was obtained. The innovative discovery had laid a solid foundation for high power, high efficiency, broadly tunable mid-infrared solid state lasers.

  1. The Effect of Water or Wax-based Binders on the Chemical and Morphological Characteristics of the Margin Ceramic-Framework Interface.

    PubMed

    Güler, Umut; de Queiroz, José Renato Cavalcanti; de Oliveira, Luiz Fernando Cappa; Canay, Senay; Ozcan, Mutlu

    2015-09-01

    This study evaluated the effect of binder choice in mixing ceramic powder on the chemical and morphological features between the margin ceramic-framework interfaces. Titanium and zirconia frameworks (15 x 5 x 0.5 mm3) were veneered with margin ceramics prepared with two different binders, namely a) water/conventional or b) wax-based. For each zirconia framework material, four different margin ceramics were used: a- Creation Zi (Creation Willi Geller International); b- GC Initial Zr (GC America); Triceram (Dentaurum); and d- IPS emax (voclar Vivadent). For the titanium framework, three different margin ceramics were used: a- Creation Ti (Creation Willi Geller International); b- Triceram (Dentaurum); and c- VITA Titaniumkeramik (Vita Zahnfabrik). The chemical composition of the framework-margin ceramic interface was analyzed using Energy Dispersive X-ray Spectroscopy (EDS) and porosity level was quantified within the margin ceramic using an image program (ImageJ) from four random areas (100 x 100 pixels) on each SEM image. EDS analysis showed the presence of Carbon at the margin ceramic-framework interface in the groups where wax-based binder technique was used with the concentration being the highest for the IPS emax ZirCAD group. While IPS system (IPS ZirCAD and IPS Emax) presented higher porosity concentration using wax binder, in the other groups wax-based binder reduced the porosity of margin ceramic, except for Titanium - Triceram combination. PMID:26591248

  2. Novel Processing of Unique Ceramic-Based Nuclear Materials and Fuels

    SciTech Connect

    Hui Zhang; Raman P. Singh

    2008-11-30

    Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These include refractory alloys base on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as those based on silicon carbide (SiCf-SiC); carbon-carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor componets is necessary for improved efficiency. Improving thermal conductivity of the materials used in nuclear fuels and other temperature critical components can lower the center-line fuel temperature and thereby enhance durability and reduce the risk of premature failure.

  3. Process Conditions and Microstructures of Ceramic Coatings by Gas Phase Deposition Based on Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Mauer, G.; Hospach, A.; Zotov, N.; Vaßen, R.

    2013-03-01

    Plasma spraying at very low pressure (50-200 Pa) is significantly different from atmospheric plasma conditions (APS). By applying powder feedstock, it is possible to fragment the particles into very small clusters or even to evaporate the material. As a consequence, the deposition mechanisms and the resulting coating microstructures could be quite different compared to conventional APS liquid splat deposition. Thin and dense ceramic coatings as well as columnar-structured strain-tolerant coatings with low thermal conductivity can be achieved offering new possibilities for application in energy systems. To exploit the potential of such a gas phase deposition from plasma spray-based processes, the deposition mechanisms and their dependency on process conditions must be better understood. Thus, plasma conditions were investigated by optical emission spectroscopy. Coating experiments were performed, partially at extreme conditions. Based on the observed microstructures, a phenomenological model is developed to identify basic growth mechanisms.

  4. Development of a Chitosan-Based Biofoam: Application to the Processing of a Porous Ceramic Material

    PubMed Central

    Mathias, Jean-Denis; Tessier-Doyen, Nicolas; Michaud, Philippe

    2011-01-01

    Developing biofoams constitutes a challenging issue for several applications. The present study focuses on the development of a chitosan-based biofoam. Solutions of chitosan in acetic acid were dried under vacuum to generate foams with high-order structures. Chitosan concentration influenced significantly the morphology of developed porosity and the organization of pores in the material. Physico-chemical characterizations were performed to investigate the effects of chitosan concentration on density and thermal conductivity of foams. Even if chitosan-based biofoams exhibit interesting insulating properties (typically around 0.06 W·m−1·K−1), it has been shown that their durabilities are limited when submitted to a wet media. So, a way of application consists to elaborate a ceramic material with open porosity from a slurry prepared with an organic solvent infiltrating the porous network of the foam. PMID:21541051

  5. Segmental stability of resorbable P(L/DL)LA-TMC osteosynthesis versus titanium miniplates in orthognatic surgery.

    PubMed

    Ballon, Alexander; Laudemann, Katharina; Sader, Robert; Landes, Constantin Alexander

    2012-12-01

    After two decades of the use of resorbable miniplates, new polymer compositions for resorbable osteosynthesis are still being developed to make the handling and outcome of operations even more predictable and give higher stability to the repositioned segments. This study investigates a new resorbable osteosynthesis system in orthognathic patients. 50 patients were treated with P(L/DL)LA-TMC resorbable osteosynthesis and compared to a group of 50 patients treated with titanium miniplates. Segmental stability and relapse were measured comparing preoperative, postoperative and follow-up lateral cephalograms. Throughout this study, resorbables appeared to be as stable as titanium miniplates except in maxillary elongation and mandibular setback. Here, the titanium miniplates showed significantly higher stability than resorbable plates. P(L/DL)LA-TMC osteosynthesis seem to have less strength against compressive forces after maxillary elongation and they are less resistant to the forces the tongue exerts, pressing against the mandible after setback. It can therefore be concluded that the resorbable osteosynthesis can be used in the same situations as titanium miniplates except in maxillary elongation and mandibular setback. PMID:22503082

  6. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    PubMed

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties. PMID:27031536

  7. Optical thermometry based on luminescence behavior of Dy3+-doped transparent LaF3 glass ceramics

    NASA Astrophysics Data System (ADS)

    Bu, Y. Y.; Cheng, S. J.; Wang, X. F.; Yan, X. H.

    2015-11-01

    Dy3+-doped transparent LaF3 glass ceramics were fabricated, and its structures of resulting glass ceramics are studied by the X-ray diffraction and transmission electron microscopy. Optical temperature sensing of the resulting glass ceramics in the temperature range from 298 to 523 K is studied based on the down-conversion luminescence of Dy3+ ion. By using fluorescence intensity ratio method, the 4I15/2 and 4F9/2 of Dy3+ ions are verified as thermally coupled levels. A minimum S R = 1.16 × 10-4 K-1 is obtained at T = 294 K. By doping Eu3+ ion, the overall emission color of Eu3+-Dy3+ co-doped transparent glass ceramics can be tuned from white to yellow with the temperature increase through energy transfer between Eu3+ and Dy3+. Additionally, the thermal stability of the Dy3+ single-doped transparent glass ceramics becomes higher after doping Eu3+ ion.

  8. Some Aspects of the Failure Mechanisms in BaTiO3-Based Multilayer Ceramic Capacitors

    NASA Technical Reports Server (NTRS)

    Liu, David Donhang; Sampson, Michael J.

    2012-01-01

    The objective of this presentation is to gain insight into possible failure mechanisms in BaTiO3-based ceramic capacitors that may be associated with the reliability degradation that accompanies a reduction in dielectric thickness, as reported by Intel Corporation in 2010. The volumetric efficiency (microF/cm3) of a multilayer ceramic capacitor (MLCC) has been shown to not increase limitlessly due to the grain size effect on the dielectric constant of ferroelectric ceramic BaTiO3 material. The reliability of an MLCC has been discussed with respect to its structure. The MLCCs with higher numbers of dielectric layers will pose more challenges for the reliability of dielectric material, which is the case for most base-metal-electrode (BME) capacitors. A number of MLCCs manufactured using both precious-metal-electrode (PME) and BME technology, with 25 V rating and various chip sizes and capacitances, were tested at accelerated stress levels. Most of these MLCCs had a failure behavior with two mixed failure modes: the well-known rapid dielectric wearout, and so-called 'early failures." The two failure modes can be distinguished when the testing data were presented and normalized at use-level using a 2-parameter Weibull plot. The early failures had a slope parameter of Beta >1, indicating that the early failures are not infant mortalities. Early failures are triggered due to external electrical overstress and become dominant as dielectric layer thickness decreases, accompanied by a dramatic reduction in reliability. This indicates that early failures are the main cause of the reliability degradation in MLCCs as dielectric layer thickness decreases. All of the early failures are characterized by an avalanche-like breakdown leakage current. The failures have been attributed to the extrinsic minor construction defects introduced during fabrication of the capacitors. A reliability model including dielectric thickness and extrinsic defect feature size is proposed in this

  9. The preparation of ceramic/cobalt metal microcomposite using an ammonium soal solution based method

    SciTech Connect

    Strand, S.M.; Robinson, D.A.

    1995-12-01

    A process for the preparation of transition metal/ceramic composites has been developed by Robinson and Maginnis. Their work focused on the preparation of silver/YBa{sub 2}Cu{sub 3}Cr{sub 7-x} composite. We have extended their work to prepare cobalt ceramic microcomposites. In this method, an ammonium soap of 2-ethylhexanoate is used to prepare a cobalt metallorganic in solution that is rapidly gelled or precipitated around a suspended and dispersed ceramic. This step is followed by a low-temperature heat treatment in hydrogen to produce the desired composite. Depending on the heat treatment, the composite can be varied from metal coated ceramic gains to finely dispersed metal in a ceramic matrix. System specific schemes for the preparation of cobalt metal/ceramics will be presented.

  10. Tension free open inguinal hernia repair using an innovative self gripping semi-resorbable mesh

    PubMed Central

    Chastan, Philippe

    2006-01-01

    Aims: Inguinal hernia repair according to Lichtenstein technique has become the most common procedure performed by general surgeons. Heavy weight polypropylene meshes have been reported to stimulate inflammatory reaction responsible for mesh shrinkage when scar tissue evolved. Additionally, some concerns remain regarding the relationship between chronic pain and mesh fixation technique. In order to reduce those drawbacks, we have developed a new mesh for anterior tension free inguinal hernia repair which exhibits self-gripping absorbable properties. Materials and Methods: 52 patients (69 hernias) were prospectivly operated with this mesh (SOFRADIM-France) made of low-weight isoelastic large pores knitted fabric which incorporated resorbable micro hooks that provides self gripping properties to the mesh during the first months post-implantation. The fixation of the mesh onto the tissues is significantly facilitated. The mesh is secured around the cord with a self gripping flap. After complete tissular ingrowth and resorption of the PLA hooks, the low-weight (40 g/m2) polypropylene mesh insures the long term wall reinforcement. Results: Peroperativly, no complication was reported, the mesh was easy to handle and to fix. Discharge was obtained at Day 1. No perioperative complication occurred, return to daily activities was obtained at Day 5.5. At one month, no neurological pain or other complications were described. Conclusions: Based on the first results of this clinical study, this unique concept of low density self gripping mesh should allows an efficient treatment of inguinal hernia. It should reduce postoperative complications and the extent of required suture fixation, making the procedure more reproducible PMID:21187984

  11. Acute lead poisoning in nursing home and psychiatric patients from the ingestion of lead-based ceramic glazes.

    PubMed

    Vance, M V; Curry, S C; Bradley, J M; Kunkel, D B; Gerkin, R D; Bond, G R

    1990-10-01

    To our knowledge, acute inorganic lead poisoning from single ingestions of lead compounds has been only rarely reported. During a 14-month period, we were contacted regarding eight instances of acute ingestions of liquid lead-based ceramic glazes by mentally impaired residents of nursing homes or psychiatric facilities participating in ceramic arts programs. While some ingestions did not cause toxic effects, some patients developed acute lead poisoning characterized by abdominal pain, anemia, and basophilic stippling of red blood cells. In the blood of several patients, lead concentrations were far above normal (4 to 9.5 mumol/L). Urinary lead excretions were tremendously elevated during chelation therapy, with one patient excreting 535.9 mumol/L of lead during a 6-day period, the largest lead excretion ever reported in a patient suffering from acute lead poisoning, to our knowledge. All patients recovered following supportive care and appropriate use of chelating agents. Lead-based glazes are commonly found in nursing homes and psychiatric facilities. We suspect that acute or chronic lead poisoning from the ingestion(s) of lead-based ceramic glazes may be an unrecognized but not uncommon problem among such residents. We urge physicians to take ingestions of lead-based glazes seriously and to consider the diagnosis of lead poisoning in nursing home and psychiatric patients who have participated in ceramic crafts programs. PMID:2222094

  12. RECYCLING A NONIONIC AQUEOUS-BASED METAL-CLEANING SOLUTION WITH A CERAMIC MEMBRANE: PILOT SCALE EVALUATION: JOURNAL ARTICLE

    EPA Science Inventory

    NRMRL-CIN-1189 Ferguson*, T.D., Chen, A.S.C., and Stencel, N. Recycling a Nonionic Aqueous-Based Metal-Cleaning Solution with a Ceramic Membrane: Pilot Scale Evaluation. Published in: Environmental Progress 20 (2):123-132 (2001). The effectiveness of a zirconium dioxide (ZrO2) ...

  13. Physics-Based Design Tools for Lightweight Ceramic Composite Turbine Components with Durable Microstructures

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A.

    2011-01-01

    Under the Supersonics Project of the NASA Fundamental Aeronautics Program, modeling and experimental efforts are underway to develop generic physics-based tools to better implement lightweight ceramic matrix composites into supersonic engine components and to assure sufficient durability for these components in the engine environment. These activities, which have a crosscutting aspect for other areas of the Fundamental Aero program, are focusing primarily on improving the multi-directional design strength and rupture strength of high-performance SiC/SiC composites by advanced fiber architecture design. This presentation discusses progress in tool development with particular focus on the use of 2.5D-woven architectures and state-of-the-art constituents for a generic un-cooled SiC/SiC low-pressure turbine blade.

  14. Elevated Temperature Properties of Titanium Carbide Base Ceramals Containing Nickel or Iron

    NASA Technical Reports Server (NTRS)

    Cooper, A L; Colteryahn, L E

    1951-01-01

    Elevated-temperature properties of titanium carbide base ceramals containing nickel or iron were determined in oxidation, modulus of rupture, tensile strength, and thermal-shock resistance. These materials followed the general growth law and exhibited two stages in oxidation. The following tensile strengths were found at 2000 degrees F: 13.3 weight percent nickel, 16, 150 pounds per square inch; 11.8 weight percent iron, 12,500 pounds per square inch; unalloyed titanium carbide, 16,450 pounds per square inch. Nickel or iron additions to titanium carbide improved the thermal-shock resistance, nickel more. The path of fracture in tensile and thermal-shock specimens was found to progress approximately 50 percent intergranularly and 50 percent transgranularly.

  15. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Newsome, G.A.; Woods, J.J.

    1996-12-31

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1000{degree}C. The irradiation was conducted in the FBR-II to doses of 33 and 43 dpa-SiC at a nominal temperature of 1000{degree}C. The annealed specimens were held at 1010{degree}C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. 24 refs., 16 figs., 1 tab.

  16. A General Reliability Model for Ni-BaTiO3-Based Multilayer Ceramic Capacitors

    NASA Technical Reports Server (NTRS)

    Liu, Donhang

    2014-01-01

    The evaluation of multilayer ceramic capacitors (MLCCs) with Ni electrode and BaTiO3 dielectric material for potential space project applications requires an in-depth understanding of their reliability. A general reliability model for Ni-BaTiO3 MLCC is developed and discussed. The model consists of three parts: a statistical distribution; an acceleration function that describes how a capacitor's reliability life responds to the external stresses, and an empirical function that defines contribution of the structural and constructional characteristics of a multilayer capacitor device, such as the number of dielectric layers N, dielectric thickness d, average grain size, and capacitor chip size A. Application examples are also discussed based on the proposed reliability model for Ni-BaTiO3 MLCCs.

  17. Comprehensive profiling analysis of actively resorbing osteoclasts identifies critical signaling pathways regulated by bone substrate

    PubMed Central

    Purdue, P. Edward; Crotti, Tania N.; Shen, Zhenxin; Swantek, Jennifer; Li, Jun; Hill, Jonathan; Hanidu, Adedayo; Dimock, Janice; Nabozny, Gerald; Goldring, Steven R.; McHugh, Kevin P.

    2014-01-01

    As the only cells capable of efficiently resorbing bone, osteoclasts are central mediators of both normal bone remodeling and pathologies associates with excessive bone resorption. However, despite the clear evidence of interplay between osteoclasts and the bone surface in vivo, the role of the bone substrate in regulating osteoclast differentiation and activation at a molecular level has not been fully defined. Here, we present the first comprehensive expression profiles of osteoclasts differentiated on authentic resorbable bone substrates. This analysis has identified numerous critical pathways coordinately regulated by osteoclastogenic cytokines and bone substrate, including the transition from proliferation to differentiation, and sphingosine-1-phosphate signaling. Whilst, as expected, much of this program is dependent upon integrin beta 3, the pre-eminent mediator of osteoclast-bone interaction, a surprisingly significant portion of the bone substrate regulated expression signature is independent of this receptor. Together, these findings identify an important hitherto underappreciated role for bone substrate in osteoclastogenesis. PMID:25534583

  18. Wavelength tunability of laser based on Yb-doped YGAG ceramics

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Jelínková, Helena; Jambunathan, Venkatesan; Miura, Taisuke; Endo, Akira; Lucianetti, Antonio; Mocek, TomáÅ.¡

    2015-02-01

    The wavelength tunability of diode pumped laser based on Yb-doped mixed garnet Y3Ga2Al3O12 (Yb:YGAG) ceramics was investigated. The tested Yb:YGAG sample (10% Yb/Y) was in the form of 2mm thick plane-parallel face-polished plate (without AR coatings). A fiber (core diameter 100 μm, NA= 0.22) coupled laser diode (LIMO, LIMO35-F100-DL980-FG-E) with emission at wavelength 969 nm, was used for longitudinal Yb:YGAG pumping. The laser diode was operating in the pulsed regime (2 ms pulse length, 10 Hz repetition rate). The duty-cycle 2% ensured a low thermal load even under the maximum diode pumping power amplitude 20W (ceramics sample was only air-cooled). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ˜ 97% @ 1.01 - 1.09 μm. Wavelength tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The laser was continuously tunable over ˜ 58nm (from 1022nm to 1080 nm) and the tuning band was mostly limited by the free spectral range of used birefringent filter. The maximum output power amplitude 3W was obtained at wavelength 1046nm for absorbed pump power amplitude 10.6W. The laser slope efficiency was 34%.

  19. Application of non-porous alumina based ceramics as structural material for devices handling tritium at elevated temperatures

    SciTech Connect

    Yukhimchuk, A.A.; Maksimkin, I.P.; Baluev, V.V.; Boitsov, I.E.; Vertey, A.V.; Malkov, I.L.; Musyaev, R.K.; Popov, V.V.; Sitdikov, D.T.; Khapov, A.S.; Grishechkin, S.K.; Kiselev, V.G.

    2015-03-15

    The article presents results of comparative tests for the determination of deuterium fluxes permeating through walls of austenitic stainless steel AISI304 (DIN 1.4301) chamber and Al{sub 2}O{sub 3} based ceramic F99.7 chamber. Both chambers represent a piece of φ(ext)=26*φ(int)=22*117 mm{sup 3} tube with spherical bottom ending. It is shown that at 773 K and deuterium pressure of 1200 mbar the permeated deuterium flux through the stainless steel chamber constituted 8*10{sup -5} cm{sup 3}/s, while the flux through ceramic one it did not exceed the sensitivity of the measurement method threshold, namely about 1.5*10{sup -7} cm{sup 3}/s. The ceramic chamber turned out to survive more than 10{sup 3} cycles of heating up to 773 K with no damages. It did not lose its tightness up to 10 bar of internal deuterium pressure. The authors also present test results of a prototype bed for reversible tritium storage. The bed's case was made of alumina based ceramic F99.7, titanium being used as tritide making metal and high frequency induction used for heating the tritide metal. (authors)

  20. Endoscopic outcomes of resorbable nasal packing after functional endoscopic sinus surgery: a multicenter prospective randomized controlled study.

    PubMed

    Berlucchi, Marco; Castelnuovo, Paolo; Vincenzi, Andrea; Morra, Bruno; Pasquini, Ernesto

    2009-06-01

    Nasal packings can aid in control of postoperative bleeding and healing following functional endoscopic sinus surgery (FESS), but traditional non-resorbable stents have several inherent drawbacks. We performed a randomized, controlled, multicenter clinical trial to assess efficacy of resorbable nasal packing in patients undergoing FESS for chronic rhinosinusitis. A total of 66 patients for 88 nasal cavities were randomized to receive either hyaluronan resorbable packing (MeroGel) or standard non-resorbable nasal dressing after FESS. All underwent preoperative rhinoscopy, CT of sinuses, and, after surgery, were reassessed by rhinoscopy at 2, 4, and 12 weeks in blinded fashion. A total of 44 nasal cavities (MeroGel-group) received resorbable packing, whereas the remaining 44 were packed with non-resorbable nasal dressing. At follow-up endoscopic visit, the presence of nasal synechia was evaluated as primary outcome. Moreover, the tolerability and surgical handling properties of MeroGel and its comfort were assessed by surgeons and patients. Preoperative severity of rhinosinusitis was similar in both groups. No significant adverse events were observed in all patients. Follow-up endoscopy showed a lower proportion of nasal adhesions in MeroGel-group at both 4 (P = 0.041) and 12 weeks (P < 0.001). Moreover, an improvement of other endoscopic nasal findings such as re-epithelialization, presence of granulation tissue, and appearance of nasal mucosa of nasal cavities after FESS was observed in the MeroGel-group. Tolerability and surgical handling properties of MeroGel were positively rated by clinicians and the overall patient judged comfort of MeroGel was favorable. In conclusion, MeroGel can be considered a valid alternative to standard non-resorbable nasal dressings. It is safe, well-accepted, well-tolerated, and has significant advantage of being resorbable. Moreover, it may favor improved healing in patients undergoing FESS and reduce formation of adhesions. PMID

  1. Ceramic Technology Project

    SciTech Connect

    Not Available

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  2. New KNN-based lead-free piezoelectric ceramic for high-frequency ultrasound transducer applications

    NASA Astrophysics Data System (ADS)

    Ou-Yang, Jun; Zhu, Benpeng; Zhang, Yue; Chen, Shi; Yang, Xiaofei; Wei, Wei

    2015-03-01

    Based on new KNN-based piezoelectric material 0.96(K0.48Na0.52)(Nb0.95Sb0.05)O3-0.04Bi0.5(Na0.82K0.18)0.5ZrO3 with a giant d33 of 490, a 37-MHz high-frequency ultrasound needle transducer with the aperture size of 1 mm was successfully fabricated. The obtained transducer had a high electromechanical coupling factor k t of 0.55, a good bandwidth of 56.8 % at -6 dB, and a low insertion loss of -16 dB at the central frequency. Its excellent performance is comparable to lead-containing transducer and is superior to that of any other lead-free transducer. This promising result demonstrates that this new KNN-based lead-free piezoelectric ceramic is a good candidate to replace lead-based materials for high-frequency ultrasound imaging.

  3. Computer-assisted virtual technology in intracapsular condylar fracture with two resorbable long-screws.

    PubMed

    Wang, W H; Deng, J Y; Zhu, J; Li, M; Xia, B; Xu, B

    2013-03-01

    Our aim was to fix intracapsular condylar fractures (ICF) with two resorbable long screws using preoperative computer-assisted virtual technology. From February 2008 to July 2011, 19 patients with ICF were treated with two resorbable long screws. Preoperatively we took panoramic radiographs and spiral computed tomography (CT). Depending on their digital imaging and communications in medicine (DICOM) data, the dislocated condylar segments were restored using the SimPlant Pro™ software, version 11.04. The mean (SD) widths of the condylar head and neck from lateral to medial were 19.01 (1.28)mm and 13.84 (1.13)mm, respectively. In all patients, the mandibles and the ICF seen intraoperatively corresponded with the preoperative three-dimensional and virtual reposition. All patients were followed up for 6-46 months (mean 21). Occlusion and mouth opening had been restored completely in all but one patient, and absolute anatomical reduction was also achieved in most cases. Computer-assisted virtual technology plays an important part in the diagnosis of ICF, as well as in its preoperative design. Fixation with only two resorbable long screws is an effective and reliable method for fixing ICF. PMID:22546281

  4. Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

    NASA Technical Reports Server (NTRS)

    Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

    1999-01-01

    A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

  5. Chemical reactivity of nickel and nickel-based alloys with a SiAlON ceramic

    SciTech Connect

    Vleugels, J.; Van Der Biest, O.

    1995-11-01

    At the high cutting speeds typical for machining with ceramics and the concomitant high temperatures generated at the cutting edge and the rake face of the tool, chemical interaction between tool and workpiece material becomes the predominant mode of tool wear. To obtain more information concerning this chemical interaction mechanism, the chemical interaction of a {beta}{prime}-O{prime} SiAlON ceramic with pure nickel, Inconel 600, and Nimonic 105 is studied. The chemical reactivity was assessed by studying ceramic-alloy interaction couples after exposure at elevated temperatures (1,100--1,200 C) for times long enough to be able to characterize the interaction layer. At 1,200 C, the {beta}{prime}-O{prime} SiAlON ceramic dissociates in contact with pure nickel. Silicon from the dissociation of the ceramic dissolves and diffuses into the nickel, whereas Al and O form Al{sub 2}O{sub 3} particles. At the interface, a nitrogen pressure is built up. Inconel 600 is very reactive with the SiAlON ceramic, with the formation of molten silicides at 1,200 C. Cr{sub 3}Ni{sub 2}Si, Al{sub 2}O{sub 3}, and Ni{sub 31}Si{sub 12} are the major reaction products. The reactivity of Nimonic 105 is less than that of pure nickel because of the formation of a continuous protective TiN layer at the ceramic-metal interface.

  6. An ammonium soap solution based method for the preparation of ceramic/transition metal microcomposites

    SciTech Connect

    Robinson, D.A.; Maginnis, M.A.

    1995-12-01

    A process for the preparation of transition metal/ceramic composites has been developed. This method was initially used to prepare silver/Y BaCuO composites and is currently being used to prepare other transition metal/ceramic superconductors and metal nitrides. An ammonium soap of 2-ethylhexonate is used to prepare a metallorganic in solution that is rapidly gelled or precipitated around a suspended and dispersed ceramic. This step is followed by a low temperature heat treatment in hydrogen or oxygen to produce the desired composite.

  7. A Comparison of Shear Bond Strength of Ceramic and Resin Denture Teeth on Different Acrylic Resin Bases

    PubMed Central

    Corsalini, Massimo; Venere, Daniela Di; Pettini, Francesco; Stefanachi, Gianluca; Catapano, Santo; Boccaccio, Antonio; Lamberti, Luciano; Pappalettere, Carmine; Carossa, Stefano

    2014-01-01

    The purpose of this study is to compare the shear bond strength of different resin bases and artificial teeth made of ceramic or acrylic resin materials and whether tooth-base interface may be treated with aluminium oxide sandblasting. Experimental measurements were carried on 80 specimens consisting of a cylinder of acrylic resin into which a single tooth is inserted. An ad hoc metallic frame was realized to measure the shear bond strength at the tooth-base interface. A complete factorial plan was designed and a three-way ANalysis Of VAriance (ANOVA) was carried out to investigate if shear bond strength is affected by the following factors: (i) tooth material (ceramic or resin); (ii) base material (self-curing or thermal-curing resin); (iii) presence or absence of aluminium oxide sandblasting treatment at the tooth-base interface. Tukey post hoc test was also conducted to evaluate any statistically significant difference between shear strength values measured for the dif-ferently prepared samples. It was found from ANOVA that the above mentioned factors all affect shear strength. Furthermore, post hoc analysis indi-cated that there are statistically significant differences (p-value=0.000) between measured shear strength values for: (i) teeth made of ceramic material vs. teeth made of acrylic resin material; (ii) bases made of self-curing resin vs. thermal-curing resin; (iii) specimens treated with aluminium oxide sandblasting vs. untreated specimens. Shear strength values measured for acryl-ic resin teeth were on average 70% higher than those measured for ceramic teeth. The shear bond strength was maximized by preparing samples with thermal-curing resin bases and resin teeth submitted to aluminium oxide sandblasting. PMID:25614770

  8. Spacecraft ceramic protective shield

    NASA Technical Reports Server (NTRS)

    Larriva, Rene F. (Inventor); Nelson, Anne (M.); Czechanski, James G. (Inventor); Poff, Ray E. (Inventor)

    1995-01-01

    A low areal density protective shield apparatus, and method for making same, for protecting spacecraft structures from impact with hypervelocity objects, including a bumper member comprising a bumper ceramic layer, a bumper shock attenuator layer, and a bumper confining layer. The bumper ceramic layer can be SiC or B.sub.4 C; the bumper shock attenuator layer can be zirconia felt; and the bumper confining layer can be aluminum. A base armor member can be spaced from the bumper member and a ceramic fiber-based curtain can be positioned between the bumper and base armor members.

  9. Energy harvesting based on Ericsson pyroelectric cycles in a relaxor ferroelectric ceramic

    NASA Astrophysics Data System (ADS)

    Sebald, Gael; Pruvost, Sebastien; Guyomar, Daniel

    2008-02-01

    This work deals with energy harvesting from temperature variations. It is shown here that direct pyroelectric energy harvesting (connecting an adapted resistance, for example) is not effective, whereas Ericsson-based cycles give energy 100 times higher. The principle and experimental validation of the Ericsson cycle are shown with the example of 0.90Pb(Mg1/3Nb2/3)O3-0.10PbTiO3 ceramic. Harvested energy reached 186 mJ cm-3 for 50 °C temperature variation and electric field cycle of 3.5 kV mm-1. A correlation between the electrocaloric effect and pyroelectric energy harvesting is then shown. Harvested electric energy with Ericsson cycles can be simply expressed as electrocaloric heat multiplied by Carnot efficiency. Several examples are then given from materials with the highest known electrocaloric effect. This leads to energies of hundreds of mJ cm-3 for a limited 10 °C temperature variation. Compared to Carnot's efficiency, this is much higher than the best thermoelectric materials based on the Seebeck effect.

  10. Monolithic ceramics

    NASA Technical Reports Server (NTRS)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

    A development history and current development status evaluation are presented for SiC and Si3N4 monolithic ceramics. In the absence of widely sought improvements in these materials' toughness, and associated reliability in structural applications, uses will remain restricted to components in noncritical, nonman-rated aerospace applications such as cruise missile and drone gas turbine engine components. In such high temperature engine-section components, projected costs lie below those associated with superalloy-based short-life/expendable engines. Advancements are required in processing technology for the sake of fewer and smaller microstructural flaws.

  11. Joining of Silicon Carbide-Based Ceramics for MEMS-LDI Fuel Injector Applications

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay

    2012-01-01

    Deliver the benefits of ceramics in turbine engine applications- increased efficiency, performance, horsepower, range, operating temperature, and payload and reduced cooling and operation and support costs for future engines.

  12. On Ceramics.

    ERIC Educational Resources Information Center

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  13. Structure, nanohardness and photoluminescence of ZnO ceramics based on nanopowders

    NASA Astrophysics Data System (ADS)

    Muktepavela, Faina; Grigorjeva, Larisa; Kundzins, Karlis; Gorokhova, Elena; Rodnyi, Piotr

    2015-09-01

    ZnO ceramics obtained from grained powders with different grain size by hot pressing and ceramics from tetrapods nanopowders obtained by press-less sintering have been investigated under identical conditions. Ceramics obtained by hot pressing were optically transparent but were composed of large inhomogeneous grains (d = 8-35 μm) exhibiting a substructure. Decreased values of elastic modulus within a grain and a wide defect-associated (‘green’) photoluminescence (PL) band at 2.2-2.8 eV in conjunction with a weak excitonic band indicate a high concentration of residual point defects in hot pressed ZnO ceramics. Utilization of more small-grained powders contributes to the formation of more uniform microstructure (d = 5-15 μm) and extraction of point defects. This reflects as a substantially decreased defect PL band and increased excitonic band. Ceramics obtained by press-less sintering from tetrapods had fine-grained structure (d = 1-4 μm) with no signs of a substructure. PL spectrum has a narrow excitonic band with phonon replicas (1LO_ExD0), whereas the defect ‘green’ luminescence is negligible. The effects of powders morphologies have been explained in terms of a hereditary influence of interaction processes between initial particles on the formation of a microstructure and kinetic of defect distribution on the grain growth stages during the sintering of ZnO ceramics.

  14. Joining of Zirconium Diboride-Based Ceramic Composites to Metallic Systems for High-Temperature Applications

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Singh, M.

    2008-01-01

    Three types of hot-pressed zirconium diboride (ZrB2)-based ultra-high-temperature ceramic composites (UHTCC), ZrB2-SiC (ZS), ZrB2-SiC-C (ZSC), and ZrB2-SCS9-SiC (ZSS), were joined to Cu-clad-Mo using two Ag-Cu brazes (Cusil-ABA and Ticusil, T(sub L) approx.1073-1173 K) and two Pd-base brazes (Palco and Palni, T(sub L) approx.1493-1513 K). Scanning Electron Microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS) revealed greater chemical interaction in joints made using Pd-base brazes than in joints made using Ag-Cu based active brazes. The degree of densification achieved in hot pressed composites influenced the Knoop hardness of the UHTCC and the hardness distribution across the braze interlayer. The braze region in Pd-base system displayed higher hardness in joints made using fully-dense ZS composites than in joints made using partially-dense ZSS composites and the carbon-containing ZSC composites. Calculations indicate a small negative elastic strain energy and an increase in the UHTCC's fracture stress up to a critical clad layer thickness . Above this critical thickness, strain energy in the UHTCC is positive, and it increases with increasing clad layer thickness. Empirical projections show a reduction in the effective thermal resistance of the joints and highlight the potential benefits of joining the UHTCC to Cu-clad-Mo.

  15. Ceramic stove

    SciTech Connect

    Goetz, M.

    1984-12-24

    A ceramic stove that may be supplied in kit form includes a base frame, a cast iron firebox secured on the base frame, a top frame attached to and surrounding the top of the firebox, and ceramic panels extending between and held by the frames in spaced relation from the firebox. The ceramic panels are ''ship-lapped'' relative to each other and are not cemented or otherwise positively attached to each other. Logs may be fed as fuel into the fire box door from one side of the stove allowing longer logs to be burned. The logs rest on a grate which includes a ''shakable'' portion for shaking ashes onto an ash pan located below the grate. A separate, small door into the firebox is provided for starting the fire and that door is covered by another, safety door which also closes the scape through whic the ash pan is removed for emptying. An outer screen gate is provided to overlie the firebox doors and the entire side of the firebos. Products of combustion rise in the firebox and are guided by a baffle in a desired serpentine path prolonging their containment, until they reach an outlet at the top of the fire box where they are then carried downwardly by a flue formed in part by a portion of the back wall of the firebox. A heat shield covers the back wall of the firebox including the flue whose outlet extends through the heat shield at mid elevation. Other features and advantages are also disclosed.

  16. Structural Ceramics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

  17. Reliability Evaluation of Base-Metal-Electrode Multilayer Ceramic Capacitors for Potential Space Applications

    NASA Technical Reports Server (NTRS)

    Liu, David (Donhang); Sampson, Michael J.

    2011-01-01

    Base-metal-electrode (BME) ceramic capacitors are being investigated for possible use in high-reliability spacelevel applications. This paper focuses on how BME capacitors construction and microstructure affects their lifetime and reliability. Examination of the construction and microstructure of commercial off-the-shelf (COTS) BME capacitors reveals great variance in dielectric layer thickness, even among BME capacitors with the same rated voltage. Compared to PME (precious-metal-electrode) capacitors, BME capacitors exhibit a denser and more uniform microstructure, with an average grain size between 0.3 and 0.5 m, which is much less than that of most PME capacitors. BME capacitors can be fabricated with more internal electrode layers and thinner dielectric layers than PME capacitors because they have a fine-grained microstructure and do not shrink much during ceramic sintering. This makes it possible for BME capacitors to achieve a very high capacitance volumetric efficiency. The reliability of BME and PME capacitors was investigated using highly accelerated life testing (HALT). Most BME capacitors were found to fail with an early avalanche breakdown, followed by a regular dielectric wearout failure during the HALT test. When most of the early failures, characterized with avalanche breakdown, were removed, BME capacitors exhibited a minimum mean time-to-failure (MTTF) of more than 105 years at room temperature and rated voltage. Dielectric thickness was found to be a critical parameter for the reliability of BME capacitors. The number of stacked grains in a dielectric layer appears to play a significant role in determining BME capacitor reliability. Although dielectric layer thickness varies for a given rated voltage in BME capacitors, the number of stacked grains is relatively consistent, typically around 12 for a number of BME capacitors with a rated voltage of 25V. This may suggest that the number of grains per dielectric layer is more critical than the

  18. Tin dioxide-based ceramics as inert anodes for aluminum smelting: A laboratory study

    SciTech Connect

    Vecchio-Sadus, A.M.; Constable, D.C.; Dorin, R.; Frazer, E.J.; Fernandez, I.; Neal, G.S.; Lathabai, S.; Trigg, M.B.

    1996-10-01

    The behavior of tin dioxide-based ceramics as inert anodes was examined in a laboratory-scale aluminum smelting cell over a range of electrolyte compositions with operating temperatures between 830--975 C. Anodes of a nominal composition SnO{sub 2} (96 wt%), Sb{sub 2}O{sub 3} (2 wt%) and CuO (2 wt%), were electrolyzed for 90 min at a current density of {approximately}1 A cm{sup {minus}2}. The corrosion rate was determined from the tin and copper concentrations in the recovered electrolyte, aluminum metal and the fume. The corrosion rates were 12.5, 1.6 and 6.5 mg (Ah){sup {minus}1} in electrolytes with bath ratios 1.5 (975 C), 0.89 (903 C) and 0.74 (830 C), respectively. A four-fold increase in corrosion rate was obtained at open-circuit demonstrating the protection provided by oxygen evolution during electrolysis. A preliminary investigation of the dependence of corrosion rate on firing temperatures and additive (Sb{sub 2}O{sub 3} and CuO) concentrations was conducted using a part-factorial design experiment. Post-electrolysis examination of the anodes using scanning electron microscopy coupled with energy dispersive spectroscopy analysis revealed a depletion of copper from the anode and a build-up of an alumina-rich surface layer under certain conditions.

  19. Visualising phase change in a brushite-based calcium phosphate ceramic.

    PubMed

    Bannerman, A; Williams, R L; Cox, S C; Grover, L M

    2016-01-01

    The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco's - Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media. PMID:27604149

  20. Reactions of silicon-based ceramics in mixed oxidation chlorination environments

    NASA Technical Reports Server (NTRS)

    Marra, John E.; Kreidler, Eric R.; Jacobson, Nathan S.; Fox, Dennis S.

    1988-01-01

    The reaction of silicon-based ceramics with 2 percent Cl2/Ar and 1 percent Cl2/1 percent to 20 percent O2/Ar at 950 C was studied with thermogravimetric analysis and high-pressure mass spectrometry. Pure Si, SiO2, several types of SiC, and Si3N4 were examined. The primary corrosion products were SiCl4(g) and SiO2(s) with smaller amounts of volatile silicon oxychlorides. The reactions appear to occur by chlorine penetration of the SiO2 layer, and gas-phase diffusion of the silicon chlorides away from the sample appears to be rate limiting. Pure SiO2 shows very little reaction with Cl2, SiC with excess Si is more reactive than the other materials with Cl2, whereas SiC with excess carbon is more reactive than the other materials with Cl2/O2. Si3N4 shows very little reaction with Cl2. These differences are explained on the basis of thermodynamic and microstructural factors.

  1. Characterization of alumina-based ceramic nanocomposites by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmad, Kaleem; Al-Eshaikh, Mohammad A.; Kadachi, Ahmed N.

    2015-06-01

    Alumina-based hybrids containing different concentrations of carbon nanostructure and SiC nanoparticles were consolidated by the spark plasma sintering in order to obtain fully dense bulk ceramic nanocomposites. Laser-induced breakdown spectroscopy was employed to determine relationship between plasma temperature and surface hardness of the composites. The characteristic parameters of plasma generated by irradiation of laser Nd:YAG ( λ = 1064 nm) on different bulk nanocomposites were determined at different delay times and energies by assuming the LTE condition for optically thin plasma. The plasma temperatures were estimated through intensity of selected aluminum emission lines using the Boltzmann plot method. The electron density was determined using the Stark broadening of selected aluminum and silicon emission lines. The samples were mechanically characterized by the Vickers hardness test. It has been observed that the plasma temperature increases with the increase in hardness and shows a perfect linear relationship. The results suggest that calibration curve between hardness and the plasma temperature can be employed as an alternate method to estimate the hardness of nanocomposite with varying concentrations of nanostructures just by measuring the plasma temperature with better reproducibility and accuracy. Therefore, laser-induced break down spectroscopy (LIBS) offers potential applications in nuclear industry.

  2. Preparation and characterisation of ceramic-based thoron sources for thoron calibration chamber.

    PubMed

    Csordás, A; Fábián, F; Horváth, M; Hegedűs, M; Somlai, J; Kovács, T

    2015-11-01

    The aim of this study is to explore the correlations between the properties of the source's material and the thoron flux produced. This means a complex procedure that involves morphological characterisation (the determination of specific surface area and pore size distribution) and thoron emanation and exhalation measurements as well. In this work, the preparation of 27 thoron sources has been carried out. Three types of ceramics with different morphological properties were used as a matrix material with three different thorium contents. Spheres were formed from the dollop, and they were fired at different temperatures (200, 600 and 900°C). The phase analysis of the samples was performed by powder X-ray diffraction. The pore size distribution was determined by mercury penetration. The thoron emanation was measured using an accumulation chamber; the measured thoron emanation coefficients were from 0.34 ± 0.03 to 7.69 ± 0.13 %. Based on the results, the preparation parameters of the thoron source optimised for the calibration procedure have been given. PMID:25920779

  3. Ceramic thick film humidity sensor based on MgTiO{sub 3} + LiF

    SciTech Connect

    Kassas, Ahmad; Bernard, Jérôme; Lelièvre, Céline; Besq, Anthony; Guhel, Yannick; Houivet, David; Boudart, Bertrand; Lakiss, Hassan; Hamieh, Tayssir

    2013-10-15

    Graphical abstract: - Highlights: • The fabricated sensor based on MgTiO{sub 3} + LiF materials used the spin coating technology. • The response time is 70 s to detect variation between 5 and 95% relative humidity. • The addition of Scleroglucan controls the viscosity and decreases the roughness of thick film surface. • This humidity sensor is a promising, low-cost, high-quality, reliable ceramic films, that is highly sensitive to humidity. - Abstract: The feasibility of humidity sensor, consisting of a thick layer of MgTiO{sub 3}/LiF materials on alumina substrate, was studied. The thermal analysis TGA-DTGA and dilatometric analysis worked out to confirm the sintering temperature. An experimental plan was applied to describe the effects of different parameters in the development of the thick film sensor. Structural and microstructural characterizations of the developed thick film were made. Rheological study with different amounts of a thickener (scleroglucan “sclg”), showing the behavior variation, as a function of sclg weight % was illustrated and rapprochement with the results of thickness variation as a function of angular velocity applied in the spin coater. The electrical and dielectric measurements confirmed the sensitivity of the elaborated thick film against moisture, along with low response time.

  4. Visualising phase change in a brushite-based calcium phosphate ceramic

    PubMed Central

    Bannerman, A.; Williams, R. L.; Cox, S. C.; Grover, L. M.

    2016-01-01

    The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco’s – Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media. PMID:27604149

  5. Highly Efficient Tm-Doped Yttrium Aluminum Garnet Ceramic Laser Based on the Novel Fiber-Bulk Hybrid Configuration

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Shen, Deyuan; Huang, Haitao; Zhang, Xiaoqi; Tang, Dingyuan; Fan, Dianyuan

    2013-09-01

    A polycrystalline ceramic Tm3+-doped yttrium aluminum garnet (Tm:Y3Al5O12, Tm:YAG) laser based on the novel fiber-bulk hybrid configuration is demonstrated using a high-power and tunable Er,Yb co-doped fiber laser as the pump source. Lasing characteristics of a 4.0 at. % Tm:YAG ceramic are investigated at different pump wavelengths from 1617 to 1625 nm. With an output coupler of 10% transmission, a maximum output power of 3.9 W is obtained at 2013.2 nm under an 8.8 W incident pump power at the Tm:YAG absorption peak of 1620.4 nm, corresponding to a slope efficiency of 50.1% with respect to the incident pump power.

  6. DSC and TG Analysis of a Blended Binder Based on Waste Ceramic Powder and Portland Cement

    NASA Astrophysics Data System (ADS)

    Pavlík, Zbyšek; Trník, Anton; Kulovaná, Tereza; Scheinherrová, Lenka; Rahhal, Viviana; Irassar, Edgardo; Černý, Robert

    2016-03-01

    Cement industry belongs to the business sectors characteristic by high energy consumption and high {CO}2 generation. Therefore, any replacement of cement in concrete by waste materials can lead to immediate environmental benefits. In this paper, a possible use of waste ceramic powder in blended binders is studied. At first, the chemical composition of Portland cement and ceramic powder is analyzed using the X-ray fluorescence method. Then, thermal and mechanical characterization of hydrated blended binders containing up to 24 % ceramic is carried out within the time period of 2 days to 28 days. The differential scanning calorimetry and thermogravimetry measurements are performed in the temperature range of 25°C to 1000°C in an argon atmosphere. The measurement of compressive strength is done according to the European standards for cement mortars. The thermal analysis results in the identification of temperature and quantification of enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates dehydration and portlandite, vaterite and calcite decomposition. The portlandite content is found to decrease with time for all blends which provides the evidence of the pozzolanic activity of ceramic powder even within the limited monitoring time of 28 days. Taking into account the favorable results obtained in the measurement of compressive strength, it can be concluded that the applied waste ceramic powder can be successfully used as a supplementary cementing material to Portland cement in an amount of up to 24 mass%.

  7. Protective effects of myricitrin against osteoporosis via reducing reactive oxygen species and bone-resorbing cytokines

    SciTech Connect

    Huang, Qiang; Gao, Bo; Wang, Long; Hu, Ya-Qian; Lu, Wei-Guang; Yang, Liu; Luo, Zhuo-Jing; Liu, Jian

    2014-11-01

    Oxidative stress is a crucial pathogenic factor in the development of osteoporosis. Myricitrin, isolated from Myrica cerifera, is a potent antioxidant. We hypothesized that myricitrin possessed protective effects against osteoporosis by partially reducing reactive oxygen species (ROS) and bone-resorbing cytokines in osteoblastic MC3T3-E1 cells and human bone marrow stromal cells (hBMSCs). We investigated myricitrin on osteogenic differentiation under oxidative stress. Hydrogen peroxide (H{sub 2}O{sub 2}) was used to establish an oxidative cell injury model. Our results revealed that myricitrin significantly improved some osteogenic markers in these cells. Myricitrin decreased lipid production and reduced peroxisome proliferator-activated receptor gamma-2 (PPARγ2) expression in hBMSCs. Moreover, myricitrin reduced the expression of receptor activator of nuclear factor kappa-B ligand (RANKL) and IL-6 and partially suppressed ROS production. In vivo, we established a murine ovariectomized (OVX) osteoporosis model. Our results demonstrated that myricitrin supplementation reduced serum malondialdehyde (MDA) activity and increased reduced glutathione (GSH) activity. Importantly, it ameliorated the micro-architecture of trabecular bones in the 4th lumbar vertebrae (L4) and distal femur. Taken together, these results indicated that the protective effects of myricitrin against osteoporosis are linked to a reduction in ROS and bone-resorbing cytokines, suggesting that myricitrin may be useful in bone metabolism diseases, particularly osteoporosis. - Highlights: • Myricitrin protects MC3T3-E1 cells and hBMSCs from oxidative stress. • It is accompanied by a decrease in oxidative stress and bone-resorbing cytokines. • Myricitrin decreases serum reactive oxygen species to some degree. • Myricitrin partly reverses ovariectomy effects in vivo. • Myricitrin may represent a beneficial anti-osteoporosis treatment method.

  8. GBR using bovine bone matrix and resorbable and nonresorbable membranes. Part 1: histologic results.

    PubMed

    Fugazzotto, Paul A

    2003-08-01

    Ninety sites were treated with either sinus augmentation therapy using only Bio-Oss (31 sites), or extraction socket and ridge augmentation therapy using only Bio-Oss beneath secured resorbable or titanium-reinforced nonresorbable membranes (59 sites). Core biopsies were taken at intervals ranging from 4 to 13 months. The 12 core biopsies taken 12 to 13 months postoperative (five sinus augmentation sites and seven extraction socket/ridge augmentation sites) demonstrated distinct Bio-Oss particles in an average of only 0.13% of the core biopsy volume. Bone regeneration was evident in all specimens. PMID:12956480

  9. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1996-06-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation of irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD {beta}-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination.

  10. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    SciTech Connect

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1997-05-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation after irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD {beta}-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination.

  11. Light-weight ceramic insulation

    NASA Technical Reports Server (NTRS)

    Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2002-01-01

    Ultra-high temperature, light-weight, ceramic insulation such as ceramic tile is obtained by pyrolyzing a siloxane gel derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes may contain also an effective amount of a mono- or trialkoxy silane to obtain the siloxane gel. The siloxane gel is dried at ambient pressures to form a siloxane ceramic precursor without significant shrinkage. The siloxane ceramic precursor is subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation, can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C. and is particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

  12. Ultrahigh temperature Bi3Ti0.96Sc0.02Ta0.02NbO9-based piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Gai, Zhi-Gang; Wang, Jin-Feng; Sun, Wen-bin; Wang, Chun-Ming; Zhao, Ming-Lei; Sun, Shang-Qian; Ming, Bao-Quan; Qi, Peng; Zheng, Li-mei; Du, Juan; Zhang, Shujun; Shrout, Thomas R.

    2008-07-01

    The effect of (Sc,Ta,Ce) doping on the properties of Bi3TiNbO9 (BTNO)-based ceramics was investigated. The cerium modification greatly improves the piezoelectric activity of Bi3(Ti0.96Sc0.02Ta0.02)NbO9-based ceramics and significantly decreases the dielectric dissipation. The d33 of Bi3Ti0.96Sc0.02Ta0.02NbO9+x wt %CeO2 (x =0.35) was found to be 18 pC/N, the highest value among the BTNO-based ceramics and almost three times as much as the reported d33 values of the pure BTNO ceramics (˜6 pC/N). The modification increased the resistivity ρ of the samples extremely, resolving the low resistivity problem for high temperature applications. The dielectric spectroscopy shows that the TC for all the ceramics is higher than 900 °C. The mechanical quality factor Q and planar coupling factors kp and kt of Bi3Ti0.96Sc0.02Ta0.02NbO9+0.35 wt %CeO2 ceramic were found to be 2835, 9%, and 23%, respectively, and it has high TC and stable piezoelectric properties, demonstrating that the (Sc,Ta,Ce) modified BTNO-based material is a wonderful candidate for high temperature applications.

  13. Interfacial toughness of bilayer dental ceramics based on a short-bar, chevron-notch test

    PubMed Central

    Anunmana, Chuchai; Anusavice, Kenneth J.; Mecholsky, John J.

    2009-01-01

    Objective The objective of this study was to test the null hypothesis that the interfacial toughness of each of two types of bonded core-veneer bilayer ceramics is not significantly different from the apparent fracture toughness of the control monolithic glass veneer. Methods T-shaped short bars of a lithia-disilicate glass-ceramic core (LC) and yttria-stabilized polycrystalline zirconia core ceramic (ZC) were prepared according to the manufacturer's recommendations. V-shaped notches were prepared by using 25-μm-thick palladium foil, leaving the chevron notch area exposed, and the bars were veneered with a thermally compatible glass veneer (LC/GV and ZC/GV). Additionally, we also bonded the glass veneer to itself as a control group (GV/GV). Specimens were kept in distilled water for 30 days before testing in tension. Eight glass veneer bars were prepared for the analysis of fracture toughness test using the indentation-strength technique. Results The mean interfacial toughness of the LC/GV group was 0.69 [0.11] MPa·m1/2, and did not significantly differ from that of the GV/GV control group, 0.74 (0.17) MPa·m1/2 (p > 0.05). However, the difference between the mean interfacial toughness of the ZC/GV group, 0.13 (0.07) MPa·m1/2, and the LC/GV and the GV/GV groups was statistically significant (p<0.05). Significance For bilayer all-ceramic restorations with high-strength core materials, the veneering ceramics are the weakest link in the design of the structure. Since all-ceramic restorations often fail from chipping of veneer layers or crack initiation at the interface, the protective effects of thermal mismatch stresses oral prosthesis design should be investigated. PMID:19818486

  14. Development of a zirconia-mullite based ceramic for recuperator applications

    SciTech Connect

    Gonzalez, J.M. )

    1992-12-01

    GTE Products Corporation developed a compact ceramic high temperature recuperator for recovering heat from relatively clean exhaust gases at temperatures up to 2500F. The DOE program allowed GTE to improve the technical and economic characteristics of the recuperator and stimulate industrial acceptance of the recuperator as an energy-saving technology. From January 1981 to December 1984, 561 recuperators were installed by GTE on new or retrofitted furnaces. With over 1200 units sold commercially between 1981 and 1990, GTE has documented the effect (long and short term) of corrosive attack from alkalies and lead. One objective of this contract was to develop Z-1000 a zirconia-mullite mixed oxide ceramic for use in ceramic recuperator applications susceptible to corrosion. To first and second pass of the ceramic recuperator would utilize the current cordierite-mixed-oxide ceramic. A Z-1000 matrix element would be used in the preheated air side's third pass (exhaust inlet). Thermal stresses on Z-1000 cross flow module could be minimized by selecting appropriate heat transfer surface areas for each pass. A large surface area for first and second pass (cordierite section) could provide for sufficient heat transfer for 50% effectiveness. A surface area that generates minimal heat transfer in the third pass (Z-1000) section is envisioned. Heat transferred in this section reduces the differential temperature across the matrix and the thermal stresses. Hence, thermal shock resistance of the material in the third pass becomes less critical; however, its corrosion resistance must be sufficient to withstand corrosive attack. This modular design could utilize a field repairable, disposable matrix. This report is concerned with process technology development for fabricating such a matrix, and a series of corrosion tests that established the potential corrosion resistance of the Z-1000 ceramic.

  15. Low-temperature ceramic radioactive waste form characteriztion of supercalcine-based monazite-cement composites

    SciTech Connect

    Roy, D.M.; Wakeley, L.D.; Atkinson, S.D.

    1980-04-18

    Simulated radioactive waste solidification by a lower temperature ceramic (cement) process is being investigated. The monazite component (simulated by NdPO/sub 4/) of supercalcine-ceramic has been solidified in cement and found to generate a solid form with low leachability. Several types of commercial cements and modifications thereof were used. No detectable release of Nd or P was found through characterizing the products of accelerated hydrothermal leaching at 473/sup 0/K (200/sup 0/C) and 30.4 MPa (300 bars) pressure.

  16. Method for molding ceramic powders using a water-based gel casting process

    DOEpatents

    Jenny, Mark A.; Omalete, Ogbemi O.

    1992-09-08

    A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant, and a monomer solution. The monomer solution includes at least one monofunctional monomer and at least one difunctional monomer, a free-radical initiator, and a aqueous solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product may be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, whereafter the product may be sintered.

  17. Silicon-Based Ceramic-Matrix Composites for Advanced Turbine Engines: Some Degradation Issues

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, Linus U. J.

    2000-01-01

    SiC/BN/SiC composites are designed to take advantage of the high specific strengths and moduli of non-oxide ceramics, and their excellent resistance to creep, chemical attack, and oxidation, while circumventing the brittleness inherent in ceramics. Hence, these composites have the potential to take turbine engines of the future to higher operating temperatures than is achievable with metal alloys. However, these composites remain developmental and more work needs to be done to optimize processing techniques. This paper highlights the lingering issue of pest degradation in these materials and shows that it results from vestiges of processing steps and can thus be minimized or eliminated.

  18. Method for molding ceramic powders using a water-based gel casting

    DOEpatents

    Janney, Mark A.; Omatete, Ogbemi O.

    1991-07-02

    A method for molding ceramic powders comprises forming a slurry mixture including ceramic powder, a dispersant, and a monomer solution. The monomer solution includes at least one monofunctional monomer and at least one difunctional monomer, a free-radical initiator, and a aqueous solvent. The slurry mixture is transferred to a mold, and the mold containing the slurry mixture is heated to polymerize and crosslink the monomer and form a firm polymer-solvent gel matrix. The solid product any be removed from the mold and heated to first remove the solvent and subsequently remove the polymer, whereafter the product may be sintered.

  19. Using mixture design of experiments to assess the environmental impact of clay-based structural ceramics containing foundry wastes.

    PubMed

    Coronado, M; Segadães, A M; Andrés, A

    2015-12-15

    This work describes the leaching behavior of potentially hazardous metals from three different clay-based industrial ceramic products (wall bricks, roof tiles, and face bricks) containing foundry sand dust and Waelz slag as alternative raw materials. For each product, ten mixtures were defined by mixture design of experiments and the leaching of As, Ba, Cd, Cr, Cu, Mo, Ni, Pb, and Zn was evaluated in pressed specimens fired simulating the three industrial ceramic processes. The results showed that, despite the chemical, mineralogical and processing differences, only chrome and molybdenum were not fully immobilized during ceramic processing. Their leaching was modeled as polynomial equations, functions of the raw materials contents, and plotted as response surfaces. This brought to evidence that Cr and Mo leaching from the fired products is not only dependent on the corresponding contents and the basicity of the initial mixtures, but is also clearly related with the mineralogical composition of the fired products, namely the amount of the glassy phase, which depends on both the major oxides contents and the firing temperature. PMID:26252997

  20. Preparation, mechanical property and cytocompatibility of freeze-cast porous calcium phosphate ceramics reinforced by phosphate-based glass.

    PubMed

    Yang, Yanqiu; He, Fupo; Ye, Jiandong

    2016-12-01

    In this study, phosphate-based glass (PG) was used as a sintering aid for freeze-cast porous biphasic calcium phosphate (BCP) ceramic, which was sintered under a lower temperature (1000°C). The phase composition, pore structure, compressive strength, and cytocompatibility of calcium phosphate composite ceramics (PG-BCP) were evaluated. The results indicated that PG additive reacted with calcium phosphate during the sintering process, forming β-Ca2P2O7; the ions of sodium and magnesium from PG partially substituted the calcium sites of β-calcium phosphate in BCP. The PG-BCP showed good cytocompatibility. The pore width of the porous PG-BCP ceramics was around 50μm, regardless of the amount of PG sintering aid. As the content of PG increased from 0wt.% to 15wt.%, the compressive strength of PG-BCP increased from 0.02 MP to 0.28MPa. When the PG additive was 17.5wt.%, the compressive strength of PG-BCP dramatically increased to 5.66MPa. Addition of 15wt.% PG was the critical point for the properties of PG-BCP. PG is considered as an effective sintering aid for freeze-cast porous bioceramics. PMID:27612796

  1. Creep Life of Ceramic Components Using a Finite-Element-Based Integrated Design Program (CARES/CREEP)

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, J. P.; Powers, L. M.; Jadaan, O. M.

    1998-01-01

    The desirable properties of ceramics at high temperatures have generated interest in their use for structural applications such as in advanced turbine systems. Design lives for such systems can exceed 10,000 hours. The long life requirement necessitates subjecting the components to relatively low stresses. The combination of high temperatures and low stresses typically places failure for monolithic ceramics in the creep regime. The objective of this paper is to present a design methodology for predicting the lifetimes of structural components subjected to creep rupture conditions. This methodology utilized commercially available finite element packages and takes into account the time-varying creep strain distributions (stress relaxation). The creep life of a component is discretized into short time steps, during which the stress and strain distributions are assumed constant. The damage is calculated for each time step based on a modified Monkman-Grant creep rupture criterion. Failure is assumed to occur when the normalized accumulated damage at any point in the component is greater than or equal to unity. The corresponding time will be the creep rupture life for that component. Examples are chosen to demonstrate the CARES/CREEP (Ceramics Analysis and Reliability Evaluation of Structures/CREEP) integrated design programs, which is written for the ANSYS finite element package. Depending on the component size and loading conditions, it was found that in real structures one of two competing failure modes (creep or slow crack growth) will dominate. Applications to benechmark problems and engine components are included.

  2. Creep Life of Ceramic Components Using a Finite-Element-Based Integrated Design Program (CARES/CREEP)

    NASA Technical Reports Server (NTRS)

    Powers, L. M.; Jadaan, O. M.; Gyekenyesi, J. P.

    1998-01-01

    The desirable properties of ceramics at high temperatures have generated interest in their use for structural application such as in advanced turbine engine systems. Design lives for such systems can exceed 10,000 hours. The long life requirement necessitates subjecting the components to relatively low stresses. The combination of high temperatures and low stresses typically places failure for monolithic ceramics in the creep regime. The objective of this paper is to present a design methodology for predicting the lifetimes of structural components subjected to creep rupture conditions. This methodology utilizes commercially available finite element packages and takes into account the time-varying creep strain distributions (stress relaxation). The creep life, of a component is discretized into short time steps, during which the stress and strain distributions are assumed constant. The damage is calculated for each time step based on a modified Monkman-Grant creep rupture criterion. Failure is assumed to occur when the normalized accumulated damage at any point in the component is greater than or equal to unity. The corresponding time will be the creep rupture life for that component. Examples are chosen to demonstrate the Ceramics Analysis and Reliability Evaluation of Structures/CREEP (CARES/CREEP) integrated design program, which is written for the ANSYS finite element package. Depending on the component size and loading conditions, it was found that in real structures one of two competing failure modes (creep or slow crack growth) will dominate. Applications to benchmark problems and engine components are included.

  3. Effect of the shades of background substructures on the overall color of zirconia-based all-ceramic crowns

    PubMed Central

    Tulapornchai, Chantana; Mamani, Jatuphol; Kamchatphai, Wannaporn; Thongpun, Noparat

    2013-01-01

    PURPOSE The objective of this study was to determine the effect of the color of a background substructure on the overall color of a zirconia-based all-ceramic crown. MATERIALS AND METHODS Twenty one posterior zirconia crowns were made for twenty subjects. Seven premolar crowns and six molar crowns were cemented onto abutments with metal post and core in the first and second group. In the third group, eight molar crowns were cemented onto abutments with a prefabricated post and composite core build-up. The color measurements of all-ceramic crowns were made before try-in, before and after cementation. A repeated measure ANOVA was used for a statistical analysis of a color change of all-ceramic crowns at α=.05. Twenty four zirconia specimens, with different core thicknesses (0.4-1 mm) were also prepared to obtain the contrast ratio of zirconia materials after veneering. RESULTS L*, a*, and b* values of all-ceramic crowns cemented either on a metal cast post and core or on a prefabricated post did not show significant changes (P>.05). However, the slight color changes of zirconia crowns were detected and represented by ΔE*ab values, ranging from 1.2 to 3.1. The contrast ratios of zirconia specimens were 0.92-0.95 after veneering. CONCLUSION No significant differences were observed between the L*, a*, and b* values of zirconia crowns cemented either on a metal cast post and core or a prefabricated post and composite core. However, the color of a background substructure could affect the overall color of posterior zirconia restorations with clinically recommended core thickness according to ΔE*ab values. PMID:24049574

  4. Regeneration of nucleus pulposus tissue in an ovine intervertebral disc degeneration model by cell-free resorbable polymer scaffolds.

    PubMed

    Woiciechowsky, Christian; Abbushi, Alexander; Zenclussen, Maria L; Casalis, Pablo; Krüger, Jan Philipp; Freymann, Undine; Endres, Michaela; Kaps, Christian

    2014-10-01

    Degeneration of intervertebral discs (IVDs) occurs frequently and is often associated with lower back pain. Recent treatment options are limited and treat the symptoms rather than regenerate the degenerated disc. Cell-free, freeze-dried resorbable polyglycolic acid (PGA)-hyaluronan implants were used in an ovine IVD degeneration model. The nucleus pulposus of the IVD was partially removed, endoscopically. PGA-hyaluronan implants were immersed in autologous sheep serum and implanted into the disc defect. Animals with nucleotomy only served as controls. The T2-weighted/fat suppression sequence signal intensity index of the operated discs, as assessed by magnetic resonance imaging (MRI), showed that implantation of the PGA-hyaluronan implant improved (p = 0.0066) the MRI signal compared to controls at 6 months after surgery. Histological analysis by haematoxylin and eosin and safranin O staining showed the ingrowth of cells with typical chondrocytic morphology, even cell distribution, and extracellular matrix rich in proteoglycan. Histomorphometric analyses confirmed that the implantation of the PGA-hyaluronan scaffolds improved (p = 0.027) the formation of regenerated tissue after nucleotomy. Disc heights remained stable in discs with nucleotomy only as well as after implantation of the implant. In conclusion, implantation of cell-free polymer-based implants after nucleotomy induces nucleus pulposus tissue regeneration and improves disc water content in the ovine model. PMID:22865642

  5. Light emitting ceramic device

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  6. Cilengitide restrains the osteoclast-like bone resorbing activity of myeloma plasma cells.

    PubMed

    Tucci, Marco; Stucci, Stefania; Felici, Claudia; Cafforio, Paola; Resta, Leonardo; Rossi, Roberta; Silvestris, Franco

    2016-04-01

    Cilengitide (CLG) is an inhibitor of both αv β3 and αv β5 integrins, with a defined anti-tumour effect in glioblastoma. Pre-clinical studies demonstrate its ability to restrain the bone resorbing property of metastatic osteotropic tumours and we have previously shown that the disablement of αv β3 in multiple myeloma (MM) plasma cells results in exhaustion of their in vitro osteoclast (OC)-like activity on bone substrate. Here, we investigated the effect of CLG on this functional property of MM cells. Both αv β3 and αv β5 were measured on primary marrow MM cells from 19 patients, and the effect of CLG on proliferation, apoptosis and adhesion was investigated in parallel with MM cell lines and OCs from healthy donors. In addition, the effect of CLG on the capability of malignant plasma cells to produce erosive lacunae on calcium phosphate was explored in relation to the activation of intracellular kinases of molecular pathways of both integrins. Ultrastructural microscopy was used to evaluate the morphological changes in MM cells due to the effect of CLG on cell adhesion. The data from our study demonstrate that CLG restrains the bone resorbing function of MM cells by disabling their adhesion properties. Further investigations in pre-clinical studies of osteotropic tumours are warranted. PMID:26728969

  7. Modeling of the interaction between bone tissue and resorbable biomaterial as linear elastic materials with voids

    NASA Astrophysics Data System (ADS)

    Andreaus, Ugo; Giorgio, Ivan; Madeo, Angela

    2015-02-01

    In this paper, a continuum mixture model with evolving mass densities and porosity is proposed to describe the process of bone remodeling in the presence of bio-resorbable materials as driven by externally applied loads. From a mechanical point of view, both bone tissue and biomaterial are modeled as linear elastic media with voids in the sense of Cowin and Nunziato (J Elast 13:125-147, 1983). In the proposed continuum model, the change of volume fraction related to the void volume is directly accounted for by considering porosity as an independent kinematical field. The bio-mechanical coupling is ensured by the introduction of a suitable stimulus which allows for discriminating between resorption (of both bone and biomaterial) and synthesis (of the sole natural bone) depending on the level of externally applied loads. The presence of a `lazy zone' associated with intermediate deformation levels is also considered in which neither resorption nor synthesis occur. Some numerical solutions of the integro-differential equations associated with the proposed model are provided for the two-dimensional case. Ranges of values of the parameters for which different percentages of biomaterial substitution occur are proposed, namely parameters characterizing initial and maximum values of mass densities of bone tissue and of the bio-resorbable material.

  8. A hybrid technique for sinus floor elevation in the severely resorbed posterior maxilla

    PubMed Central

    Jung, Ui-Won; Hong, Ji-Youn; Lee, Jung-Seok; Kim, Chang-Sung; Cho, Kyoo-Sung

    2010-01-01

    Purpose This study aimed to evaluate the effectiveness of the modified sinus floor elevation technique described hereafter as a "hybrid technique," in 11 patients with severely resorbed posterior maxillae. Methods Eleven patients who received 22 implants in the maxillary premolar and molar areas by the hybrid technique were enrolled in this study. A slot-shaped osteotomy for access was prepared on the lateral wall along the lower border of the sinus floor. The Schneiderian membrane was fully reflected through the lateral slot. Following drilling with the membrane protected by a periosteal elevator, the bone was grafted. All implants were placed simultaneously with sinus augmentation. The cumulative success rate was calculated and clinical parameters were recorded. Radiographic measurements were performed. Results All implants were well maintained at last follow up (cumulative success rate=100%). The mean residual bone height, augmented bone height, crown-to-implant ratio, and marginal bone loss were 4.1±1.64 mm, 8.76±1.77 mm, 1.21±0.33 mm, and 0.34±0.72 mm, respectively. Conclusions Simultaneous implant placement with sinus augmentation by hybrid technique showed successful clinical results over a 2-year observation period and may be a reliable modality for reconstruction of a severely resorbed posterior maxilla. PMID:20498764

  9. Recombinant VSV G proteins reveal a novel raft-dependent endocytic pathway in resorbing osteoclasts

    SciTech Connect

    Mulari, Mika T.K. Nars, Martin; Laitala-Leinonen, Tiina; Kaisto, Tuula; Metsikkoe, Kalervo; Sun Yi; Vaeaenaenen, H. Kalervo

    2008-05-01

    Transcytotic membrane flow delivers degraded bone fragments from the ruffled border to the functional secretory domain, FSD, in bone resorbing osteoclasts. Here we show that there is also a FSD-to-ruffled border trafficking pathway that compensates for the membrane loss during the matrix uptake process and that rafts are essential for this ruffled border-targeted endosomal pathway. Replacing the cytoplasmic tail of the vesicular stomatitis virus G protein with that of CD4 resulted in partial insolubility in Triton X-100 and retargeting from the peripheral non-bone facing plasma membrane to the FSD. Recombinant G proteins were subsequently endosytosed and delivered from the FSD to the peripheral fusion zone of the ruffled border, which were both rich in lipid rafts as suggested by viral protein transport analysis and visualizing the rafts with fluorescent recombinant cholera toxin. Cholesterol depletion by methyl-{beta}-cyclodextrin impaired the ruffled border-targeted vesicle trafficking pathway and inhibited bone resorption dose-dependently as quantified by measuring the CTX and TRACP 5b secreted to the culture medium and by measuring the resorbed area visualized with a bi-phasic labeling method using sulpho-NHS-biotin and WGA-lectin. Thus, rafts are vital for membrane recycling from the FSD to the late endosomal/lysosomal ruffled border and bone resorption.

  10. Tunable delivery of niflumic acid from resorbable embolization microspheres for uterine fibroid embolization.

    PubMed

    Bédouet, Laurent; Moine, Laurence; Servais, Emeline; Beilvert, Anne; Labarre, Denis; Laurent, Alexandre

    2016-09-10

    Uterine arteries embolization (UAE) is a recent technique that aims, by means of particles injected percutaneously, to stifle fibroids (leiomyomas). This treatment is non-invasive, compared with uterine ablation, but generates pelvic pain for a few days. A strategy to reduce the post-embolization pain would be to use calibrated embolization microspheres preloaded with a non-steroidal inflammatory drug (NSAID). In this study, we first compared four drugs, all active at low concentration on cyclooxygenase-2, i.e. ketoprofen, sodium diclofenac, flurbiprofen and niflumic acid (NFA), for their capacity to be loaded on resorbable embolization microspheres (REM) 500-700μm. NFA had the highest capacity of loading (5mg/mL) on resorbable microspheres. Then, we evaluated in vitro the NFA release profiles from REM having various degradation times of one, two or five days. NFA release was biphasic, with an initial burst (about 60% of the loading) followed by a sustained release that correlated significantly to REM's hydrolysis (rho=0.761, p<0.0001). For each group of beads, the size distribution was not modified by the loading of NFA and their delivery through microcatheter was not impaired by the drug. NFA eluted from REM inhibited the synthesis of prostaglandin E2 from rabbit uterus explants. In summary, NFA is loadable on REM in significant amount and its delivery can be tuned according to the degradation rate of REM to provide an antalgic effect for a few days after UAE. PMID:27374196

  11. Tetraspanin 7 regulates sealing zone formation and the bone-resorbing activity of osteoclasts.

    PubMed

    Kwon, Jun-Oh; Lee, Yong Deok; Kim, Haemin; Kim, Min Kyung; Song, Min-Kyoung; Lee, Zang Hee; Kim, Hong-Hee

    2016-09-01

    Tetraspanin family proteins regulate morphology, motility, fusion, and signaling in various cell types. We investigated the role of the tetraspanin 7 (Tspan7) isoform in the differentiation and function of osteoclasts. Tspan7 was up-regulated during osteoclastogenesis. When Tspan7 expression was reduced in primary precursor cells by siRNA-mediated gene knock-down, the generation of multinuclear osteoclasts was not affected. However, a striking cytoskeletal abnormality was observed: the formation of the podosome belt structure was inhibited and the microtubular network were disrupted by Tspan7 knock-down. Decreases in acetylated microtubules and levels of phosphorylated Src and Pyk2 in Tspan7 knock-down cells supported the involvement of Tspan7 in cytoskeletal rearrangement signaling in osteoclasts. This cytoskeletal defect interfered with sealing zone formation and subsequently the bone-resorbing activity of mature osteoclasts on dentin surfaces. Our results suggest that Tspan7 plays an important role in cytoskeletal organization required for the bone-resorbing function of osteoclasts by regulating signaling to Src, Pyk2, and microtubules. PMID:27416754

  12. The Role of Resorbable Plate and Artificial Bone Substitute in Reconstruction of Large Orbital Floor Defect

    PubMed Central

    Kwon, Ho; Kim, Ho Jun; Jeong, Yeon Jin; Jung, Sung-No

    2016-01-01

    It is essential to reduce and reconstruct bony defects adequately in large orbital floor fracture and defect. Among many reconstructive methods, alloplastic materials have attracted attention because of their safety and ease of use. We have used resorbable plates combined with artificial bone substitutes in large orbital floor defect reconstructions and have evaluated their long-term reliability compared with porous polyethylene plate. A total of 147 patients with traumatic orbital floor fracture were included in the study. Surgical results were evaluated by clinical evaluations, exophthalmometry, and computed tomography at least 12 months postoperatively. Both orbital floor height discrepancy and orbital volume change were calculated and compared with preoperative CT findings. The average volume discrepancy and vertical height discrepancies were not different between two groups. Also, exophthalmometric measurements were not significantly different between the two groups. No significant postoperative complication including permanent diplopia, proptosis, and enophthalmos was noted. Use of a resorbable plate with an artificial bone substitute to repair orbital floor defects larger than 2.5 cm2 in size yielded long-lasting, effective reconstruction without significant complications. We therefore propose our approach as an effective alternative method for large orbital floor reconstructions. PMID:27517041

  13. Three-dimensional ceramic molding process based on microstereolithography for the production of piezoelectric energy harvesters

    NASA Astrophysics Data System (ADS)

    Maruo, Shoji; Sugiyama, Kenji; Daicho, Yuya; Monri, Kensaku

    2014-03-01

    A three-dimensional (3-D) molding process using a master polymer mold produced by microstereolithography has been developed for the production of piezoelectric ceramic elements. In this method, ceramic slurry is injected into a 3-D polymer mold via a centrifugal casting process. The polymer master mold is thermally decomposed so that complex 3-D piezoelectric ceramic elements can be produced. As an example of 3-D piezoelectric ceramic elements, we produced a spiral piezoelectric element that can convert multidirectional loads into a voltage. It was confirmed that a prototype of the spiral piezoelectric element could generate a voltage by applying a load in both parallel and lateral directions in relation to the helical axis. The power output of 123 pW was obtained by applying the maximum load of 2.8N at 2 Hz along the helical axis. In addition, to improve the performance of power generation, we utilized a two-step sintering process to obtain dense piezoelectric elements. As a result, we obtained a sintering body with relative density of 92.8%. Piezoelectric constant d31 of the sintered body attained to -40.0 pC/N. Furthermore we analyzed the open-circuit voltage of the spiral piezoelectric element using COMSOL multiphysics. As a result, it was found that use of patterned electrodes according to the surface potential distribution of the spiral piezoelectric element had a potential to provide high output voltage that was 20 times larger than that of uniform electrodes.

  14. D-depth profiling in as-implanted and annealed Li-based breeder blanket ceramics

    NASA Astrophysics Data System (ADS)

    Carella, Elisabetta; Gonzalez, Maria; Gonzalez-Arrabal, Raquel

    2013-07-01

    In future power plants (i.e. DEMO), the nuclear fusion of hydrogen isotopes will be used for energy production. The behaviour of hydrogen isotopes in lithium-enriched ceramics for breeder blankets (BBs) is one of the most important items to be understood. In this paper we present the chemical, microstructural and morphological features of Li4SiO4, Li2TiO3 and a third ceramic candidate with a higher Li:Si proportion (3:1), implanted with D at an energy of 100 keV and at room temperature at a fluence of 1 × 1017 cm-2. The D depth-profile in as-implanted and annealed ceramics (at T ⩽ 200 °C) was characterised by Resonance Nuclear Reaction Analysis (RNRA). The RNRA data indicate that the total amount of D is retained at room temperature, while annealing at 100 °C promotes D release and annealing at T ⩾ 150 °C drives D to completely desorb from all the studied ceramics. D release will be discussed as a function of the microstructurural and morphological features of each material.

  15. Corrosion protection of SiC-based ceramics with CVDMullite coatings

    SciTech Connect

    Sarin, V.; Auger, M.

    1997-05-01

    Silicon carbide ceramics are the leading candidate materials for use as heat exchangers in advanced combined cycle power plants because of their unique combination of high temperature strength, high thermal conductivity, excellent thermal shock resistance, and good high temperature stability and oxidation resistance. Ceramic coatings are being considered for diesel engine cylinder liners, piston caps, valve faces and seats, piston rings, and for turbine components such as combustors, blades, stators, seals, and bearings. Under such conditions ceramics are better suited to high temperature environments than metals. For the first time, adherent crystalline mullite coatings have been chemically vapor deposited onto SiC substrates to enhance its corrosion/oxidation resistance. Thermodynamic and kinetic considerations have been utilized to produce mullite coatings with a variety of growth rates, compositions, and morphologies. The flexibility of processing can be exploited to produce coated ceramics with properties tailored to specific applications and varied corrosive environments. These corrosive environments include thermal, Na{sub 2}SO{sub 4}, O{sub 2} and coal slag.

  16. Ceramic burner

    SciTech Connect

    Laux, W.; Hebel, R.; Artelt, P.; Esfeld, G.; Jacob, A.

    1981-03-31

    Improvements in the mixing body and supporting structure of a molded-ceramic-brick burner enable the burner to withstand the vibrations induced during its operation. Designed for the combustion chambers of air heaters, the burner has a mixing body composed of layers of shaped ceramic bricks that interlock and are held together vertically by a ceramic holding bar. The mixing body is shaped like a mushroom - the upper layers have a larger radius than the lower ones.

  17. Ceramic Processing

    SciTech Connect

    EWSUK,KEVIN G.

    1999-11-24

    Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referred to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.

  18. Ceramic joining

    SciTech Connect

    Loehman, R.E.

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  19. Effect of silica coating combined to a MDP-based primer on the resin bond to Y-TZP ceramic.

    PubMed

    May, Liliana Gressler; Passos, Sheila Pestana; Capelli, Diana Barca; Ozcan, Mutlu; Bottino, Marco Antonio; Valandro, Luiz Felipe

    2010-10-01

    The aim of this study was to evaluate the influence of silica coating and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer applications upon the bonding durability of a MDP-based resin cement to a yttrium stabilized tetragonal zirconia (Y-TZP) ceramic. Ninety-six Y-TZP tabs were embedded in an acrylic resin (free surface for adhesion: 5 × 5 mm(2)), ground finished and randomly divided into four groups (N = 24) according to the ceramic surface conditioning: (1) cleaning with isopropanol (ALC); (2) ALC + phosphoric acid etching + MDP-based primer application (MDP-primer); (3) silica coating + 3-methacryloyloxypropyl trimethoxysilane (MPS)-based coupling agent application (SiO2 + MPS-Sil); and (4) SiO2 + MDP-primer. The MDP-based resin cement was applied on the treated surface using a cylindrical mold (diameter= 3 mm). Half of the specimens from each surface conditioning were stored in distilled water (37 °C, 24 h) before testing. Another half of the specimens were stored (90 days) and thermo-cycled (12,000 x) during this period (90 d/TC) before testing. A shear bond strength (SBS) test was performed at a crosshead speed of 0.5 mm/min. Two factors composed the experimental design: ceramic conditioning strategy (in four levels) and storage condition (in two levels), totaling eight groups. After 90 d/TC (Tukey; p < 0.05), SiO2 + MDP-primer (24.40 MPa) promoted the highest SBS. The ALC and MDP-primer groups debonded spontaneously during 90 d/TC. Bonding values were higher and more stable in the SiO2 groups. The use of MDP-primer after silica coating increased the bond strength. PMID:20690176

  20. Indirect selective laser sintering of an apatite-mullite glass-ceramic for potential use in bone replacement applications.

    PubMed

    Goodridge, R D; Dalgarno, K W; Wood, D J

    2006-01-01

    The feasibility of using indirect selective laser sintering (SLS) to produce parts from glass-ceramic materials for bone replacement applications has been investigated. A castable glass based on the system SiO2 x Al2O3 x P2O5 x CaO x CaF2 that crystallizes to a glass-ceramic with apatite and mullite phases was produced, blended with an acrylic binder, and processed by SLS. Green parts with good structural integrity were produced using a wide range of processing conditions, allowing both monolayer and multilayer components to be constructed. Following SLS the parts were post-processed to remove the binder and to crystallize fully the material, evolving the apatite and mullite phases. The parts were heated to 1200 degrees C using a number of different time-temperature profiles, following which the processed material was analysed by differential thermal analysis, X-ray diffraction, and scanning electron microscopy, and tested for flexural strength. An increase in strength was achieved by infiltrating the brown parts with a resorbable phosphate glass, although this altered the crystal phases present in the material. PMID:16459446

  1. Porosity and biocompatibility study of ceramic implants based on ZrO{sub 2} and Al{sub 2}O{sub 3}

    SciTech Connect

    Litvinova, Larisa E-mail: vshupletsova@mail.ru Shupletsova, Valeria E-mail: vshupletsova@mail.ru Leitsin, Vladimir E-mail: vshupletsova@mail.ru; Vasyliev, Roman E-mail: zoubov77@yahoo.com; Zubov, Dmitry E-mail: zoubov77@yahoo.com; Buyakov, Ales E-mail: kulkov@ms.tsc.ru; Kulkov, Sergey E-mail: kulkov@ms.tsc.ru

    2014-11-14

    The work studies ZrO{sub 2}(Me{sub x}O{sub y})-based porous ceramics produced from the powders consisting of hollow spherical particles. It was shown that the structure is represented by a cellular framework with bimodal porosity consisting of sphere-like large pores and pores that were not filled with the powder particles during the compaction. For such ceramics, the increase of pore volume is accompanied by the increased strain in an elastic area. It was also shown that the porous ZrO{sub 2} ceramics had no acute or chronic cytotoxicity. At the same time, ceramics possess the following osteoconductive properties: adhesion support, spreading, proliferation and osteogenic differentiation of MSCs.

  2. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, Mark S.; Shlomo, Golan; Anderson, Marc A.

    1994-01-01

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range.

  3. Time-dependent fracture probability of bilayer, lithium-disilicate-based glass-ceramic molar crowns as a function of core/veneer thickness ratio and load orientation

    PubMed Central

    Anusavice, Kenneth J.; Jadaan, Osama M.; Esquivel–Upshaw, Josephine

    2013-01-01

    Recent reports on bilayer ceramic crown prostheses suggest that fractures of the veneering ceramic represent the most common reason for prosthesis failure. Objective The aims of this study were to test the hypotheses that: (1) an increase in core ceramic/veneer ceramic thickness ratio for a crown thickness of 1.6 mm reduces the time-dependent fracture probability (Pf) of bilayer crowns with a lithium-disilicate-based glass-ceramic core, and (2) oblique loading, within the central fossa, increases Pf for 1.6-mm-thick crowns compared with vertical loading. Materials and methods Time-dependent fracture probabilities were calculated for 1.6-mm-thick, veneered lithium-disilicate-based glass-ceramic molar crowns as a function of core/veneer thickness ratio and load orientation in the central fossa area. Time-dependent fracture probability analyses were computed by CARES/Life software and finite element analysis, using dynamic fatigue strength data for monolithic discs of a lithium-disilicate glass-ceramic core (Empress 2), and ceramic veneer (Empress 2 Veneer Ceramic). Results Predicted fracture probabilities (Pf) for centrally-loaded 1,6-mm-thick bilayer crowns over periods of 1, 5, and 10 years are 1.2%, 2.7%, and 3.5%, respectively, for a core/veneer thickness ratio of 1.0 (0.8 mm/0.8 mm), and 2.5%, 5.1%, and 7.0%, respectively, for a core/veneer thickness ratio of 0.33 (0.4 mm/1.2 mm). Conclusion CARES/Life results support the proposed crown design and load orientation hypotheses. Significance The application of dynamic fatigue data, finite element stress analysis, and CARES/Life analysis represent an optimal approach to optimize fixed dental prosthesis designs produced from dental ceramics and to predict time-dependent fracture probabilities of ceramic-based fixed dental prostheses that can minimize the risk for clinical failures. PMID:24060349

  4. Ceramic filters

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1995-12-31

    Filters were formed from ceramic fibers, organic fibers, and a ceramic bond phase using a papermaking technique. The distribution of particulate ceramic bond phase was determined using a model silicon carbide system. As the ceramic fiber increased in length and diameter the distance between particles decreased. The calculated number of particles per area showed good agreement with the observed value. After firing, the papers were characterized using a biaxial load test. The strength of papers was proportional to the amount of bond phase included in the paper. All samples exhibited strain-tolerant behavior.

  5. NEUTRONICS STUDIES OF URANIUM-BASED FULLY CERAMIC MICRO-ENCAPSULATED FUEL FOR PWRs

    SciTech Connect

    George, Nathan M; Maldonado, G Ivan; Terrani, Kurt A; Gehin, Jess C; Godfrey, Andrew T

    2012-01-01

    This study evaluates the core neutronics and fuel cycle characteristics that result from employing uranium-based fully ceramic micro-encapsulated (FCM) fuel in a pressurized water reactor (PWR). Specific PWR bundle designs with FCM fuel have been developed, which by virtue of their TRISO particle based elements, are expected to safely reach higher fuel burnups while also increasing the tolerance to fuel failures. The SCALE 6.1 code package, developed and maintained at ORNL, was the primary software employed to model these designs. Analysis was performed using the SCALE double-heterogeneous (DH) fuel modeling capabilities. For cases evaluated with the NESTLE full-core three-dimensional nodal simulator, because the feature to perform DH lattice physics branches with the SCALE/TRITON sequence is not yet available, the Reactivity-Equivalent Physical Transformation (RPT) method was used as workaround to support the full core analyses. As part of the fuel assembly design evaluations, fresh feed lattices were modeled to analyze the within-assembly pin power peaking. Also, a color-set array of assemblies was constructed to evaluate power peaking and power sharing between a once-burned and a fresh feed assembly. In addition, a parametric study was performed by varying the various TRISO particle design features; such as kernel diameter, coating layer thicknesses, and packing fractions. Also, other features such as the selection of matrix material (SiC, Zirconium) and fuel rod dimensions were perturbed. After evaluating different uranium-based fuels, the higher physical density of uranium mononitride (UN) proved to be favorable, as the parametric studies showed that the FCM particle fuel design will need roughly 12% additional fissile material in comparison to that of a standard UO2 rod in order to match the lifetime of an 18-month PWR cycle. Neutronically, the FCM fuel designs evaluated maintain acceptable design features in the areas of fuel lifetime, temperature

  6. Oxidation and Corrosion of Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Opila, Elizabeth J.; Lee, Kang N.

    2000-01-01

    Ceramics and ceramic matrix composites are candidates for numerous applications in high temperature environments with aggressive gases and possible corrosive deposits. There is a growing realization that high temperature oxidation and corrosion issues must be considered. There are many facets to these studies, which have been extensively covered in some recent reviews. The focus of this paper is on current research, over the past two years. In the authors' view, the most important oxidation and corrosion studies have focused on four major areas during this time frame. These are; (I) Oxidation of precursor-based ceramics; (II) Studies of the interphase material in ceramic matrix composites; (III) Water vapor interactions with ceramics, particularly in combustion environments; and (IV) Development of refractory oxide coatings for silicon-based ceramics. In this paper, we shall explore the most current work in each of these areas.

  7. Composition-Driven Phase Boundary and Piezoelectricity in Potassium-Sodium Niobate-Based Ceramics.

    PubMed

    Zheng, Ting; Wu, Jiagang; Xiao, Dingquan; Zhu, Jianguo; Wang, Xiangjian; Lou, Xiaojie

    2015-09-16

    The piezoelectricity of (K,Na)NbO3 ceramics strongly depends on the phase boundary types as well as the doped compositions. Here, we systematically studied the relationships between the compositions and phase boundary types in (K,Na) (Nb,Sb)O3-Bi0.5Na0.5AO3 (KNNS-BNA, A=Hf, Zr, Ti, Sn) ceramics; then their piezoelectricity can be readily modified. Their phase boundary types are determined by the doped elements. A rhombohedral-tetragonal (R-T) phase boundary can be driven in the compositions range of 0.035≤BNH≤0.040 and 0.035≤BNZ≤0.045; an orthorhombic-tetragonal (O-T) phase boundary is formed in the composition range of 0.005≤BNT≤0.02; and a pure O phase can be only observed regardless of BNS content (≤0.01). In addition, the phase boundary types strongly affect their corresponding piezoelectricities. A larger d33 (∼440-450 pC/N) and a higher d33* (∼742-834 pm/V) can be attained in KNNS-BNA (A=Zr and Hf) ceramics due to the involvement of R-T phase boundary, and unfortunately KNNS-BNA (A=Sn and Ti) ceramics possess a relatively poor piezoelectricity (d33≤200 and d33*<600 pm/V) due to the involvement of other phase structures (O-T or O). In addition, the underlying physical mechanisms for the relationships between piezoelectricity and phase boundary types were also discussed. We believe that comprehensive research can design more excellent ceramic systems concerning potassium-sodium niobate. PMID:26302094

  8. Processing, Structure and High Temperature Oxidation Properties of Polymer-Derived and Hafnium Oxide Based Ceramic Systems

    NASA Astrophysics Data System (ADS)

    Terauds, Kalvis

    Demands for hypersonic aircraft are driving the development of ultra-high temperature structural materials. These aircraft, envisioned to sustain Mach 5+, are expected to experience continuous temperatures of 1200--1800°C on the aircraft surface and temperatures as high as 2800°C in combustion zones. Breakthroughs in the development of fiber based ceramic matrix composites (CMCs) are opening the door to a new class of high-tech UHT structures for aerospace applications. One limitation with current carbon fiber or silicon carbide fiber based CMC technology is the inherent problem of material oxidation, requiring new approaches for protective environmental barrier coatings (EBC) in extreme environments. This thesis focuses on the development and characterization of SiCN-HfO2 based ceramic composite EBC systems to be used as a protective layer for silicon carbide fiber based CMCs. The presented work covers three main architectures for protection (i) multilayer films, (ii) polymer-derived HfSiCNO, and (iii) composite SiCN-HfO 2 infiltration. The scope of this thesis covers processing development, material characterization, and high temperature oxidation behavior of these three SiCN-HfO2 based systems. This work shows that the SiCN-HfO 2 composite materials react upon oxidation to form HfSiO4, offering a stable EBC in streaming air and water vapor at 1600°C.

  9. Ceramic breeder materials

    SciTech Connect

    Johnson, C.E.

    1990-01-01

    The breeding blanket is a key component of the fusion reactor because it directly involves tritium breeding and energy extraction, both of which are critical to development of fusion power. The lithium ceramics continue to show promise as candidate breeder materials. This promise was recognized by the International Thermonuclear Reactor (ITER) design team in its selection of ceramics as the first option for the ITER breeder material. Blanket design studies have indicated properties in the candidate materials data base that need further investigation. Current studies are focusing on tritium release behavior at high burnup, changes in thermophysical properties with burnup, compatibility between the ceramic breeder and beryllium multiplier, and phase changes with burnup. Laboratory and in-reactor tests, some as part of an international collaboration for development of ceramic breeder materials, are underway. 32 refs., 1 fig., 1 tab.

  10. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2002-04-01

    This report covers the following tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints; Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability; Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres; Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures; Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability; and Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  11. Effect of Inner Electrode on Electrical Properties of (Zn,Mg)TiO3-Based Multilayer Ceramic Capacitor

    NASA Astrophysics Data System (ADS)

    Lee, Wen-His; Su, Chi-Yi; Huang, Cheng-Liang; Lee, Ying-Chieh; Hu, Ching-Li; Yang, Jackey; Yang, Tong; Lin, Shih-Pin

    2005-12-01

    In this study, different proportions of silver-palladium alloy used as an inner electrode are adopted to fabricate (Zn,Mg)TiO3-based multilayer ceramic capacitors. Effects of sintering temperature, and measuring frequency on the dielectric properties of the samples with different proportions of the Pd-Ag inner electrode are investigated. The continuity of the inner electrode and the proportion of Pd-Ag of the inner electrode of samples sintered at different temperatures play important roles in determining the dielectric properties.

  12. Solution-based deposition of ceramic thin films for electronic applications

    NASA Astrophysics Data System (ADS)

    Yu, Shijun

    With the requirement of a low-temperature process which is compatible with flexible electronics, solution-based processes for ceramic thin films have received substantial attention in recent years. In this study, two different variations of solution processing were explored. Liquid phase deposition (LPD) was used to prepare for F-doped SiO2 and F-doped SnO2, and hydrothermal processing was used to prepare ZnO thin films consisting of vertically aligned nanorods. F-doped SiO2 thin films were developed from supersaturated hydrofluorosilicic acid (H2SiF6) solution with the addition of boric acid (H3BO3). The microstructure dependence of LPD SiO2 films on solution parameters and deposition temperature was systematically investigated. The dielectric constant is lower than that of thermal SiO2, resulting from the fluorine doping. The remarkably low dielectric constant, relatively low leakage current and fairly high elastic modulus make these low temperature processed LPD SiO2 films very promising for an interlayer dielectric for flexible substrates. Using the same LPD method, smooth SnO2 films were deposited on both silicon and glass substrates at 60 ºC through supersaturated solutions of SnF 2 with a concentration range from 10 mM to 40 mM. They consist of nanoscale crystallites and the degree of crystallinity increase with annealing temperature. A hydrothermal process was employed to deposit ZnO films for energy harvesting devices. A polymer mask was patterned on top of a zinc acetate seed layer to generate a regular array of open holes (200 nm in diameter) using a nanoimprint. Vertically aligned ZnO nanorod arrays were grown on these open holes that expose the seed layer. The morphology and microstrucutre of the nanorods were studied according to chemical composition of the solution. Equimolar reduce of the concentration of ZnAc and HMTA results in decrease in nanorod diameter, as well as in length. The nanorods become thinner and slightly better aligned with

  13. A neutron scintillator based on transparent nanocrystalline CaF2:Eu glass ceramic

    NASA Astrophysics Data System (ADS)

    Struebing, Christian; Chong, JooYun; Lee, Gyuhyon; Zavala, Martin; Erickson, Anna; Ding, Yong; Wang, Cai-Lin; Diawara, Yacouba; Engels, Ralf; Wagner, Brent; Kang, Zhitao

    2016-04-01

    There are no efficient Eu2+ doped glass neutron scintillators reported due to low doping concentrations of Eu2+ and the amorphous nature of the glass matrix. In this work, an efficient CaF2:Eu glass ceramic neutron scintillator was prepared by forming CaF2:Eu nanocrystals in a 6Li-containing glass matrix. Through appropriate thermal treatments, the scintillation light yield of the transparent glass ceramic was increased by a factor of at least 46 compared to the as-cast amorphous glass. This improvement was attributed to more efficient energy transfer from the CaF2 crystals to the Eu2+ emitting centers. Further light yield improvement is expected if the refractive index of the glass matrix can be matched to the CaF2 crystal.

  14. Reverse engineering the ancient ceramic technology based on X-ray fluorescence spectromicroscopy

    SciTech Connect

    Sciau, Philippe; Leon, Yoanna; Goudeau, Philippe; Fakra, Sirine C.; Webb, Sam; Mehta, Apurva

    2011-07-06

    We present results of X-ray fluorescence (XRF) microprobe analyses of ancient ceramic cross-sections aiming at deciphering the different firing protocols used for their production. Micro-focused XRF elemental mapping, Fe chemical mapping and Fe K-edge X-ray absorption near edge structure spectroscopy were performed on pre-sigillata ceramics from southern Gaul, and terra Sigillata vessels from Italy and southern Gaul. Pieces from the different workshops and regions showed significant difference in the starting clay material, clay conditioning and kiln firing condition. By contrast, sherds from the same workshop exhibited more subtle differences and possible misfirings. Understanding the precise firing conditions and protocols would allow recreation of kilns for various productions. Furthermore, evolution and modification of kiln design would shed some light on how ancient potters devised solutions to diverse technological problems they encountered.

  15. 1357 nm passively Q-switched crystalline ceramic laser based on multilayer graphene

    NASA Astrophysics Data System (ADS)

    Feng, Chao; Zhang, Huanian; Wang, Qingpu; Xu, Shicai; Fang, Jiaxiong

    2016-05-01

    1357 nm single wavelength passively Q-switched Nd:YAG ceramic lasers are demonstrated with a multilayer graphene sheets saturable absorber (SA). During an increase in the incident pump power, the laser exhibited stable Q-switched oscillation, which showed that our graphene SA provided Q-switched modulation successfully. The maximum average output power was 340 mW, and the corresponding pulse width, pulse repetition rate, single pulse energy and peak power were 380 ns, 209 kHz, 53 μJ and 139 W, respectively. Our results illustrate that graphene can be used as an SA for 1357 nm passively Q-switched Nd:YAG ceramic lasers.

  16. Friction And Wear Of Silicon Ceramics

    NASA Technical Reports Server (NTRS)

    Deadmore, Daniel L.; Sliney, Harold E.

    1990-01-01

    Report presents results of experimental study of friction and wear in unlubricated sliding of silicon-based ceramics on Inconel(R) 718 nickel-based alloy. Both monolithic and fiber-reinforced ceramics tested at temperatures from 25 to 800 degrees C. Evaluates ceramic materials for potential use as cylinder liners, piston caps, and other engine parts subjected to sliding or rubbing.

  17. Anterior Glenoid Rim Fracture Following Use of Resorbable Devices for Glenohumeral Stabilization

    PubMed Central

    Augusti, Carlo Alberto; Paladini, Paolo; Campi, Fabrizio; Merolla, Giovanni; Bigoni, Marco; Porcellini, Giuseppe

    2015-01-01

    Background Resorbable anchors are widely used in arthroscopic stabilization of the shoulder as a means of soft tissue fixation to bone. Their function is to ensure repair stability until they are replaced by host tissue. Complications include inflammatory soft tissue reactions, cyst formation, screw fragmentation in the joint, osteolytic reactions, and enhanced glenoid rim susceptibility to fracture. Purpose To evaluate resorption of biodegradable screws and determine whether they induce formation of areas with poor bone strength that may lead to glenoid rim fracture even with minor trauma. Study Design Case series; Level of evidence, 4. Methods This study evaluated 12 patients with anterior shoulder instability who had undergone arthroscopic stabilization with the Bankart technique and various resorbable anchors and subsequently experienced redislocation. The maximum interval between arthroscopic stabilization and the new dislocation was 52 months (mean, 22.16 months; range, 12-52 months). The mean patient age was 31.6 years (range, 17-61 years). The persistence or resorption of anchor holes; the number, area, and volume of osteolytic lesions; and glenoid erosion/fracture were assessed using computed tomography scans taken after redislocation occurred. Results Complete screw resorption was never documented. Osteolytic lesions were found at all sites (mean diameter, 5.64 mm; mean depth, 8.09 mm; mean area, 0.342 cm2; mean volume, 0.345 cm3), and all exceeded anchor size. Anterior glenoid rim fracture was seen in 9 patients, even without high-energy traumas (75% of all recurrences). Conclusion Arthroscopic stabilization with resorbable devices is a highly reliable procedure that is, however, not devoid of complications. In all 12 patients, none of the different implanted anchors had degraded completely, even in patients with longer follow-up, and all induced formation of osteolytic areas. Such reaction may lead to anterior glenoid rim fracture according to the

  18. Differential scanning calorimetry investigations on Eu-doped fluorozirconate-based glass ceramics

    PubMed Central

    Paßlick, C.; Ahrens, B.; Henke, B.; Johnson, J. A.; Schweizer, S.

    2010-01-01

    The properties of Eu-doped fluorochlorozirconate (FCZ) glass ceramics upon thermal processing and the influence of Eu-doping on the formation of BaCl2 nanocrystals therein have been investigated. Differential scanning calorimetry indicates that higher Eu-doping shifts the crystallization peak of the nanocrystals in the glass to lower temperatures, while the glass transition temperature remains constant. The activation energy and the thermal stability parameters for the BaCl2 crystallization are determined. PMID:21286235

  19. Corrosion protection of SiC-based ceramics with CVD mullite coatings

    SciTech Connect

    Auger, M.L.; Sarin, V.K.

    1997-12-01

    For the first time, crystalline mullite coatings have been chemically vapor deposited on SiC substrates to enhance its corrosion and oxidation resistance. Thermodynamic and kinetic considerations have been utilized to produce mullite coatings with a variety of growth rates, compositions, and morphologies. The flexibility of processing can be exploited to produce coated ceramics with properties tailored to specific applications and varied corrosive environments.

  20. QUANTITATIVE STUDIES OF THERMAL SHOCK IN CERAMICS BASED ON A NOVEL TEST TECHNIQUE

    SciTech Connect

    Faber, K. T.; Huang, M. D.; Evans, A. G.

    1981-05-01

    A thermal shock test has been designed which permits the thermal fracture resistance and the mechanical strength of brittle materials to be quantitatively correlated. Thermal shock·results for two materials, Al{sub 2}O{sub 3} and SiC, have been accurately predicted from biaxial strength measurements and a transient thermal stress analysis (performed using a finite element method). General implications for the prediction of thermal shock resistance, with special reference to ceramic components, are discussed.

  1. X-ray Diffraction, Dielectric, and Raman Spectroscopy Studies of SrTiO3-Based Microwave Ceramics

    NASA Astrophysics Data System (ADS)

    Qu, Jingjing; Liu, Fei; Wei, Xing; Yuan, Changlai; Liu, Xinyu; Chen, Guohua; Feng, Qin

    2016-01-01

    xSrTiO3-(1 - x)Ca0.61Nd0.26TiO3 (SCNT x) and xSrTiO3-(1 - x)Na1/2La1/2TiO3 (SNLT x) ceramics were studied by x-ray diffraction and Raman spectroscopy in the composition range of 0.1 ≤ x ≤ 0.4. The x-ray patterns illustrated that the SCNT x (0.1 ≤ x ≤ 0.4) solid solutions had a single orthorhombic perovskite phase, while a single phase with pseudoorthorhombic structure was identified for the SNLT x (0.1 ≤ x ≤ 0.4) ceramics. In addition, the Lorentz fitting method was applied to separate the Raman spectra into several individual peaks. Meanwhile, the line shift and width of the main phonons are also discussed based on the Lorentz fitting method. Among these, some new peaks at about 470 cm-1/483 cm-1 and 442.31 cm-1/429.20 cm-1 appeared for the SCNT x and SNLT x samples with 0.3 ≤ x ≤ 0.4 due to A-site occupation by two or more types of cation with different electrovalence. Based on the resulting Q × f value and full-width at half-maximum of the A 1g(O) stretch mode, it was found that propagation of microwave energy in the SCNT x samples showed stronger damping behavior; a smaller Q × f value was therefore expected with an increase in Sr content. Moreover, the τ f value and tolerance factor ( t) exhibited a proportional correlation because of increasing symmetry of the perovskite phase for the SNLT x (0.1 ≤ x ≤ 0.4) ceramics.

  2. Ceramics to Ti6Al4V by Ni-Based Interlayers

    NASA Astrophysics Data System (ADS)

    Valenza, F.; Artini, C.; Passerone, A.; Cirillo, P.; Muolo, M. L.

    2014-05-01

    Pure ZrB2 and ZrB2-SiC composites were joined to Ti6Al4V at 1100 °C using B-Ni50 (at.%) as a filler alloy. The brazing medium and the processing parameters were chosen on the basis of specific wetting tests which showed the good adhesion properties of the B-Ni alloy with both the ceramic and the Ti alloy; interfacial reactions were foreseen and interpreted by phase diagram analysis. A multilayer metal-ceramic interfacial structure was observed in the joints and a key role was played by Ti coming from Ti6Al4V: it worked as the active element enhancing the adhesion of the liquid to the ceramic and segregated at the interface forming TiB. A satisfactory mechanical performance was obtained for ZrB2-SiC/Ti6Al4V joints, which exhibited a room temperature shear strength of 74 MPa.

  3. Development of iron oxide and titania treated fly ash based ceramic and its bioactivity.

    PubMed

    Sultana, Parveen; Das, Sukhen; Bhattacharya, Alakananda; Basu, Ruma; Nandy, Papiya

    2012-08-01

    The increasing accumulation of fly ash from thermal power plants poses a major problem to the environment. The present work reflects the novel utilization of this profusely available industrial waste in the form of an antibacterial hard ceramic material by treating fly ash with ferric oxide (Fe2O3) and titania (TiO2) during sintering process at 1600 °C. The developed material shows more than 90% bacterial reduction against both Gram-positive and Gram-negative bacteria. The mechanism of their antibacterial action was studied by transmission electron microscopy (TEM) image analysis of the bacterial cross-section. The developed ceramic material acquires hardness due to the enhancement of the natural mullite content in the matrix. The mullite content and the crystallinity of mullite have shown their increasing trend with increasing concentration of the metal oxide during sintering process. A maximum of ~37% increase in mullite was obtained for 7% w/w Fe2O3 and TiO2. Metal oxide lowered the activation energy of the reaction and enhanced the reaction rate of alumina (Al2O3)-silica (SiO2) to form mullite which increases the hardness. The study highlights novel utilization of fly ash as a hard ceramic antibacterial product (bioceramics) for both structural and hygiene applications in an eco-friendly way. PMID:24364932

  4. Comparison of resorbable plates and titanium plates for fixation stability of combined mandibular symphysis and angle fractures

    PubMed Central

    Lim, Ho-Yong; Jung, Chang-Hwa; Kim, Seong-Yong; Cho, Jin-Yong; Ryu, Jae-Young

    2014-01-01

    Objectives We compared resorbable plates with titanium plates for treatment of combined mandibular angle and symphyseal fractures. Materials and Methods Patients with mandibular angle and symphysis fractures were divided into two groups. The control (T) group received titanium plates while the experimental (R) group received resorbable plates. All procedures were carried out under general anesthesia using standard surgical techniques. We compared the frequency of wound dehiscence, development of infection, malocclusion, malunion, screw breakage, and any other technical difficulties between the two groups. Results Thirteen patients were included in the R group, where 39 resorbable plates were applied. The T group consisted of 16 patients who received 48 titanium plates. The mean age in the R and T groups was 28.29 and 24.23 years, respectively. Primary healing of the fractured mandible was obtained in all patients in both groups. Postoperative complications were minor and transient. Moreover, there were no significant differences in the rates of various complications between the two groups. Breakage of 3 screws during the perioperative period was seen in the R group, while no screws or plates were broken in the T group. Conclusion Resorbable plates can be used to stabilize combined mandibular angle and symphysis fractures. PMID:25551093

  5. The value of ultrasound-assisted pinned resorbable osteosynthesis for cranial vault remodelling in craniosynostosis.

    PubMed

    Freudlsperger, Christian; Castrillon-Oberndorfer, Gregor; Baechli, Heidi; Hoffmann, Juergen; Mertens, Christian; Engel, Michael

    2014-07-01

    Resorbable osteosynthesis is a widespread tool in craniofacial surgery, however only a limited number of studies have focused on ultrasound-assisted pinned resorbable systems in the treatment of craniosynostosis. Thirty-eight children with various types of craniosynostosis including scaphocephaly, trigonocephaly, anterior and posterior plagiocephaly were treated using the Sonic Welding resorbable osteosynthesis system. All patients were evaluated for operation time, stability of the surgical results, rate of local infections and visibility or palpability of the osteosynthesis material in the follow-up ranging from 15 to 21 month. Mean operation time was not significantly higher compared to conventional osteosynthesis material and all remodelled cranial vaults showed immediate stability. Only one patient showed signs of an inflammatory skin reaction, which recovered spontaneously. The number of palpable or visible plates, respectively, increased during the first months with a maximum at 12 months (34 (89%) plates palpable, 26 (68%) plates visible). After this time point, the number decreased continuously until the end of the follow-up period at 21 months when 3 (20%) plates were palpable, 0 (0%) plates were visible). Ultrasound-assisted pinned resorbable systems seem to be a promising tool in craniofacial surgery providing a timesaving and stable osteosynthesis. An initial swelling of the plates during the first 12 months before the complete degradation might result in a palpable and visible bulge. PMID:24011607

  6. Use of a Smooth, Resorbable Template for Delivery of Cultured Pellets of Autologous Chondrocytes to Articular Cartilage Defects—Preliminary Report

    PubMed Central

    Pomahac, Bohdan; Zuhaili, Baraa; Kudsi, Yusef; Aflaki, Pejman; Eriksson, Elof

    2009-01-01

    Background: Autologous chondrocyte transplantation (ACT) is the most commonly used cell-based surgical procedure for repair of articular cartilage defects. The challenges of this technique include dedifferentiation of chondrocytes following several in vitro passages, invasive means of transplantation, and inadequate cell retention leading to washout of transplanted cells. To overcome these obstacles, we developed a novel technique of transplanting high-density chondrocyte pellets seeded on a prefabricated, resorbable, rigid, 2-dimensional template amenable to minimally invasive implantation. Methods: Chondrocytes were obtained from the costal cartilage of New Zealand white rabbits and expanded in vitro in monolayer culture. After 2 passages, chondrocyte suspension was centrifuged and a total of 1 × 106 cells condensed on the surface of a prefabricated, resorbable template of LactoSorb plate (0.5-mm thick, 4-mm diameter). The construct was incubated for 24 hours in a culture medium before transplantation into circular 4-mm diameter, 0.5-mm deep defects in a non–weight-bearing part of the femoral condyle. Control defects were left empty or implanted with LactoSorb alone. Macroscopic and histological evaluation was performed 4 weeks posttransplantation. Results: Macroscopically, boundaries of all defects were demarcated and distinguishable from adjacent intact cartilage. Regenerative tissue in experimental group appeared white, smooth, and uniform showing more resemblance to hyaline cartilage. Control groups revealed absent cartilaginous tissue and defects were filled with soft, fibrous tissue with an irregular surface. Histologically, the repair tissue in the control groups was fibroinflammatory with irregular surface and no evidence of continuous chondrocytic regeneration. Cartilage regeneration in the experimental defects revealed a continuous, high-density layer of chondrocytes surrounding the LactoSorb plates. Consistently with chondrocyte pellets grown for 4

  7. [Experimental study of dental implants with nanostructured non-resorbable coating integration into bone tissue].

    PubMed

    Grigor'ian, A S; Khamraev, T K; Toporkova, A K; Amirov, A R

    2010-01-01

    In 2 dogs on both sides of mandible premolars were removed. In 3 months after dental alveolus healing intraosseous screwdriver dental implants (Konmet, Russia) were installed in the place of the removed teeth. Analogous operation was done on the contralateral side: the same type of implants were installed but with new nanostructured multifunctional biocompatible non-resorbable coating (MBNC) of the Ti-Ca-P-C-O-N composition. The animals were taken out of the experiment in 4 months after implants installation and implant-bone blocks were studied by SEM-method. According to the SEM-data in the region of the contact of implant-bone without new MBNC only fibrous connective tissue was formed. In case when MBNC was used the close welding of bone tissue with implant surface was observed that was considered as sign of osteointegration. PMID:21186642

  8. Histologic analysis of resorbable blasting media surface implants retrieved from humans: a report of two cases

    PubMed Central

    2016-01-01

    The purpose of this study is to evaluate the degree of osseointegration of resorbable blasting media (RBM) surface implants retrieved from humans. Three implants in the mandibular molar region that were surface-treated with RBM were retrieved from two patients. The implants were used to manufacture specimens in order to measure the bone-implant contact (BIC) ratio. The BIC ratios of the three implants were found to be an average of 69.0%±9.1%. In conclusion, that RBM surface implants are integrated into the host environment with histological significance and the BIC ratio of the RBM surface-treated implant was not significantly different from that of other surface-treated implants. PMID:26904493

  9. Histologic analysis of resorbable blasting media surface implants retrieved from humans: a report of two cases.

    PubMed

    Jeong, Kyung-In; Kim, Young-Kyun; Moon, Sang-Woon; Kim, Su-Gwan; Lim, Sung-Chul; Yun, Pil-Young

    2016-02-01

    The purpose of this study is to evaluate the degree of osseointegration of resorbable blasting media (RBM) surface implants retrieved from humans. Three implants in the mandibular molar region that were surface-treated with RBM were retrieved from two patients. The implants were used to manufacture specimens in order to measure the bone-implant contact (BIC) ratio. The BIC ratios of the three implants were found to be an average of 69.0%±9.1%. In conclusion, that RBM surface implants are integrated into the host environment with histological significance and the BIC ratio of the RBM surface-treated implant was not significantly different from that of other surface-treated implants. PMID:26904493

  10. Preparation and photo-catalytic activity of TiO2-coated medical stone-based porous ceramics

    NASA Astrophysics Data System (ADS)

    Gao, Ru-qin; Hou, Xin-mei

    2013-06-01

    Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO2 thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO2 thin films calcined at 550°C is anatase with the average particle size about 10 nm. The specific surface area of the carrier-coated nano-TiO2 increases from 3.68 to 5.32 m2/g. The formaldehyde removal rate of the TiO2/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120 min reaches 85.6%.

  11. Synthesis and analysis of Mo-Si-B based coatings for high temperature oxidation protection of ceramic materials

    NASA Astrophysics Data System (ADS)

    Ritt, Patrick J.

    The use of Ni-based superalloys in turbine engines has all but been exhausted, with operating temperatures nearing the melting point of these materials. The use of ceramics in turbine engines, particularly ceramic matrix composites such as SiC/C and SiC/SiC, is of interest due to their low density and attractive mechanical properties at elevated temperatures. The same materials are also in consideration for leading edges on hypersonic vehicles. However, SiC-based composites degrade in high temperature environments with low partial pressures of oxygen due to active oxidation, as well as high temperature environments containing water or sand. The need for a protective external coating for SiC-based composites in service is obvious. To date, no coating investigated for SiC/C or SiC/SiC has been proven to be resistant to oxidation and corrosion at intermediate and high temperatures, as well as in environments deficient in oxygen. The Mo-Si-B coating shows great promise in this area, having been proven resistant to attack from oxidation at extreme temperatures, from water vapor and from calcia-magnesia-aluminosilicate (CMAS). The adaptation of the Mo-Si-B coating for ceramic materials is presented in detail here. Evaluation of the coating under a range of oxidation conditions as well as simulated re-entry conditions confirms the efficacy of the Mo-Si-B based coating as protection from catastrophic failure. The key to the oxidation and corrosion resistance is a robust external aluminoborosilica glass layer that forms and flows quickly to cover the substrate, even under the extreme simulated re-entry conditions. Suppression of active oxidation of SiC, which may occur during atmospheric re-entry and hypersonic flight trajectories, has also been examined. In order to adapt the Mo-Si-B based coating to low partial pressures of oxygen and elevated temperatures, controlled amounts of Al were added to the Mo-Si-B based coating. The resulting coating decreased the inward

  12. Heat treatment of pre-hydrolyzed silane increases adhesion of phosphate monomer-based resin cement to glass ceramic.

    PubMed

    de Carvalho, Rodrigo Furtado; Cotes, Caroline; Kimpara, Estevão Tomomitsu; Leite, Fabíola Pessoa Pereira; Özcan, Mutlu

    2015-01-01

    This study evaluated the influence of different forms of heat treatment on a pre-hydrolyzed silane to improve the adhesion of phosphate monomer-based (MDP) resin cement to glass ceramic. Resin and feldspathic ceramic blocks (n=48, n=6 for bond test, n=2 for microscopy) were randomly divided into 6 groups and subject to surface treatments: G1: Hydrofluoric acid (HF) 9.6% for 20 s + Silane + MDP resin cement (Panavia F); G2: HF 9.6% for 20 s + Silane + Heat Treatment (oven) + Panavia F; G3: Silane + Heat Treatment (oven) + Panavia F; G4: HF 9.6% for 20 s + Silane + Heat Treatment (hot air) + Panavia F; G5: Silane + Heat Treatment (hot air) + Panavia F; G6: Silane + Panavia F. Microtensile bond strength (MTBS) test was performed using a universal testing machine (1 mm/min). After debonding, the substrate and adherent surfaces were analyzed using stereomicroscope and scanning electron microscope (SEM) to categorize the failure types. Data were analyzed statistically using two-way test ANOVA and Tukey's test (=0.05). Heat treatment of the silane containing MDP, with prior etching with HF (G2: 13.15 ± 0.89a; G4: 12.58 ± 1.03a) presented significantly higher bond strength values than the control group (G1: 9.16 ± 0.64b). The groups without prior etching (G3: 10.47 ± 0.70b; G5: 9.47 ± 0.32b) showed statistically similar bond strength values between them and the control group (G1). The silane application without prior etching and heat treatment resulted in the lowest mean bond strength (G6: 8.05 ± 0.37c). SEM analysis showed predominantly adhesive failures and EDS analysis showed common elements of spectra (Si, Na, Al, K, O, C) characterizing the microstructure of the glass-ceramic studied. Heat treatment of the pre-hydrolyzed silane containing MDP in an oven at 100 °C for 2 min or with hot air application at 50 ± 5 ºC for 1 min, was effective in increasing the bond strength values between the ceramic and resin cement containing MDP. PMID:25672383

  13. High-speed impact of the metal projectile on the barrier containing porous corundum-based ceramics with chemically active filler

    NASA Astrophysics Data System (ADS)

    Ischenko, Alexander; Afanas'eva, Svetlana; Belov, Nikolai; Blinov, Vasiliy; Burkin, Vladimir; Korolkov, Leonid; Rogaev, Konstantin; Khabibullin, Marat; Yugov, Nikolai

    2016-01-01

    The paper presents a calculation-experimental study on high-speed interaction of the metal projectile with a combined barrier made of porous corundum-based ceramics filled with chemically active composition (sulfur, nitrate of potash) in the wide range of speeds. A mathematical behavior model of porous corundum-based ceramics with chemically active filler is developed within the scope of mechanics of continuous media taking into account the energy embedding from a possible chemical reaction between a projectile metal and filler at high-speed impact. Essential embedding of inlet heat is not observed in the considered range of impact speeds (2.5 … 8 km/s).

  14. Progress in SiC-Based Ceramic Composites for Fusion Applications

    SciTech Connect

    Katoh, Yutai; Kohyama, Akira; Hinoki, Tatsuya; Snead, Lance L.

    2003-07-15

    Silicon carbide (SiC) fiber-reinforced SiC-matrix ceramic composite (SiC/SiC composite) is an attractive material for blanket/first wall structures in fusion power devices. Recent extensive materials R and D efforts are producing advanced SiC/SiC composites substantially different from conventional materials in terms of baseline properties as well as irradiation stability. This paper provides a summary of the recent fusion-relevant progress in development and irradiation effect studies of SiC/SiC composites achieved through Japanese programs and Japan/US collaborative JUPITER(-II) program for fusion materials and blanket engineering.

  15. Guanidine based vehicle/binders for use with oxides, metals and ceramics

    NASA Technical Reports Server (NTRS)

    Philipp, Warren H. (Inventor); Weitch, Lisa C. (Inventor); Jaskowiak, Martha H. (Inventor)

    1995-01-01

    The use of guanidine salts of organic fatty acids (guanidine soaps) as vehicles and binders for coating substrate surfaces is disclosed. Being completely organic, the guanidine soaps can be burned off leaving no undesirable residue. Of special interest is the use of guanidine 2-ethyl hexanoate as the vehicle and binder for coating problematic surfaces such as in coating alumina fibers with platinum or zirconia. For this application the guanidine soap is used as a melt. For other applications the guanidine soap may be used in a solution with a variety of solvents, the solution containing chlorometalates or powdered metals, refractories or ceramics.

  16. Identification of Phase Boundaries and Electrical Properties in Ternary Potassium-Sodium Niobate-Based Ceramics.

    PubMed

    Lv, Xiang; Wu, Jiagang; Yang, Shuang; Xiao, Dingquan; Zhu, Jianguo

    2016-07-27

    A large piezoelectric constant (d33) of ∼480 pC/N was attained in new ternary (1-x-y)K0.5Na0.5Nb0.96Sb0.04O3-xBaSnO3-yBi0.5Na0.5ZrO3 ceramics by forming rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary using the variations of x and y, and such a phase boundary was successfully confirmed by the convergent beam electron diffraction (CBED) patterns. For (1-x)K0.5Na0.5Nb0.96Sb0.04O3-xBaSnO3, the orthorhombic (O) phase is well-maintained for 0 ≤ x ≤ 0.015, and both the R and T phases can be introduced to (0.99-y)K0.5Na0.5Nb0.96Sb0.04O3-0.01BaSnO3-yBi0.5Na0.5ZrO3 with y = 0.025-0.04 by simultaneously tailoring their compositions (x and y); then, R-O-T multiphases can be well-established. The CBED patterns strongly support the existence of R-O-T multiphases in the ceramics with y = 0.035. When the phase transitions endure from O to R-O-T, their piezoelectric activity endures a leapfrog development from ∼165 to ∼480 pC/N. In the region of the R-O-T phase boundary, a large d33 of ∼480 pC/N was attained in the ceramics with x = 0.01 and y = 0.035. In addition, the ceramics with x = 0.01 and y = 0.04 possess a high strain of ∼0.274% due to the multiphases coexistence. According to the variations of dielectric and ferroelectric properties, the enhancement in εr and Pr plays a part in the improved d33 except for the R-O-T phase boundary. We believe that the (K, Na)NbO3 ternary systems can be used to promote piezoelectric activity by forming new phase boundaries. PMID:27404481

  17. Effect of Rare Earth Oxide Content on Nanograined Base Metal Electrode Multilayer Ceramic Capacitor Powder Prepared by Aqueous Chemical Coating Method

    NASA Astrophysics Data System (ADS)

    Zhang, Yichi; Wang, Xiaohui; Kim, Jinyong; Li, Longtu

    2013-02-01

    The aqueous chemical coating route is highly effective in preparing BaTiO3 nanoparticles uniformly coated with additives. Such nanoparticles can be used to produce nano-grained temperature stable BaTiO3 ceramics with core-shell structure, fulfilling the need of next-generation ultrathin layer base metal electrode (BME) multilayer ceramic capacitors (MLCCs). Rare earth oxides are an important class of additives owing to their ability to fulfill both donor and acceptor roles. In this paper, the effects of Y2O3 and Ho2O3 co-dopant content on dielectric and microstructural properties were investigated. By applying chemical coating, BaTiO3-based high performance temperature stabilized ceramics with the average grain size of about 130 nm, which met the requirement of next generation BME MLCCs, were obtained.

  18. Processing ceramics

    NASA Technical Reports Server (NTRS)

    Moritoki, M.; Fujikawa, T.; Miyanaga, J.

    1984-01-01

    A method of hot hydrostatic pressing of ceramics is described. A detailed description of the invention is given. The invention is explained through an example, and a figure illustrates the temperature and pressure during the hot hydrostatic pressing treatment.

  19. Pyroelectric and dielectric properties of ceramics

    NASA Astrophysics Data System (ADS)

    Batra, A. K.; Moxon, Ryan; Guggilla, Padmaja; Aggarwal, M. D.; Edwards, M. E.

    2010-08-01

    Ferroelectric oxide ceramics have been investigated as possible alternatives to highly sensitive triglycine sulfate (TGS) crystals for their use in room temperature infrared detectors. In this paper dielectric and pyroelectric properties of some ceramics based on modified lead titanate and others are presented. The figures-of-merit of these ceramics calculated using the measured dielectric and pyroelectric data are presented. The relative advantages and disadvantages of the principal ceramic systems are also compared with existing materials reported in the literature.

  20. Improved leakage current and ferromagnetic properties in magnetic field annealed BiFeO{sub 3}-based ceramics

    SciTech Connect

    Yin, L.H.; Zhao, B.C.; Fang, J.; Zhang, R.R.; Tang, X.W.; Song, W.H.; Dai, J.M.; Sun, Y.P.

    2012-10-15

    Single-phase Bi{sub 0.85}La{sub 0.15}FeO{sub 3} ceramics were synthesized under various magnetic fields (H{sub a}=0 T, 3 T, 5 T). Substantially reduced leakage current and hence modified ferroelectric (FE) properties were obtained with magnetic field annealing (MA). The largest magnetization and lowest leakage current with large FE polarization (P{sub r}{approx}33 {mu}C/cm{sup 2}) were found in the sample annealed with H{sub a}=3 T. Great changes were also observed in the Raman spectra. All the observed features originate mainly from the different FE domain wall structures induced by MA. These results demonstrate that MA is an effective way to tune the multiferroic and magnetoelectric properties in BiFeO{sub 3}-based materials. - Graphical abstract: Bright field TEM micrograph of the representative domain structures in the samples (a) BLF0, (b) BLF3 and (c) BLF5. Highlights: Black-Right-Pointing-Pointer Bi{sub 0.85}La{sub 0.15}FeO{sub 3} ceramics were synthesized under various magnetic fields. Black-Right-Pointing-Pointer Substantially reduced leakage current with improved ferroelectricity were obtained. Black-Right-Pointing-Pointer Enhanced magnetization with moderate annealing magnetic field.

  1. Creep Life Prediction of Ceramic Components Using the Finite Element Based Integrated Design Program (CARES/Creep)

    NASA Technical Reports Server (NTRS)

    Jadaan, Osama M.; Powers, Lynn M.; Gyekenyesi, John P.

    1997-01-01

    The desirable properties of ceramics at high temperatures have generated interest in their use for structural applications such as in advanced turbine systems. Design lives for such systems can exceed 10,000 hours. Such long life requirements necessitate subjecting the components to relatively low stresses. The combination of high temperatures and low stresses typically places failure for monolithic ceramics in the creep regime. The objective of this work is to present a design methodology for predicting the lifetimes of structural components subjected to multiaxial creep loading. This methodology utilizes commercially available finite element packages and takes into account the time varying creep stress distributions (stress relaxation). In this methodology, the creep life of a component is divided into short time steps, during which, the stress and strain distributions are assumed constant. The damage, D, is calculated for each time step based on a modified Monkman-Grant creep rupture criterion. For components subjected to predominantly tensile loading, failure is assumed to occur when the normalized accumulated damage at any point in the component is greater than or equal to unity.

  2. Staged Osteotome Sinus Floor Elevation for Progressive Site Development and Immediate Implant Placement in Severely Resorbed Alveolar Bone: A Case Report

    PubMed Central

    2013-01-01

    This case report discusses osteotome sinus floor elevation (OSFE) and immediate placement in 2 stages in severely resorbed alveolar bone height in which multiple implant placement is not otherwise feasible due to a lack of initial stability. The first implant placed using OSFE without bone grafting prepares the adjacent resorbed sites for further implant placement in the sinus areas, which allows for better initial stability and early functional loading. This process avoids the conventional extensive lateral approach for sinus lifting and bone grafting procedures even in extremely resorbed alveolar bone. PMID:24251045

  3. Continuum-Based FEM Modeling of Ceramic Powder Compaction Using a Cap-Plasticity Constitutive Model

    SciTech Connect

    ARGUELLO JR.,JOSE G.; FOSSUM,ARLO F.; ZEUCH,DAVID H.; EWSUK,KEVIN G.

    2000-05-01

    Software has been developed and extended to allow finite element (FE) modeling of ceramic powder compaction using a cap-plasticity constitutive model. The underlying, general-purpose FE software can be used to model even the most complex three-dimensional (3D) geometries envisioned. Additionally, specialized software has been developed within this framework to address a general subclass of axisymmetric compacts that are common in industry. The expertise required to build the input deck, run the FE code, and post-process the results for this subclass of compacts is embedded within the specialized software. The user simply responds to a series of prompts, evaluates the quality of the FE mesh that is generated, and analyzes the graphical results that are produced. The specialized software allows users with little or no FE expertise to benefit from the tremendous power and insight that FE analysis can bring to the design cycle. The more general underlying software provides complete flexibility to model more complicated geometries and processes of interest to ceramic component manufacturers but requires significantly more user interaction and expertise.

  4. Environment Conscious Ceramics (Ecoceramics)

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Levine, Stanley R. (Technical Monitor)

    2000-01-01

    Environment conscious ceramics (Ecoceramics) are a new class of materials, which can be produced with renewable natural resources (wood) or wood wastes (wood sawdust). Silicon carbide-based ecoceramics have been fabricated by reactive infiltration of carbonaceous preforms by molten silicon or silicon-refractory metal alloys. These carbonaceous preforms have been fabricated by pyrolysis of solid wood bodies at 1000 C. The fabrication approach, microstructure, and mechanical properties of SiC-based ecoceramics are presented. Ecoceramics have tailorable properties and behave like ceramic materials manufactured by conventional approaches.

  5. Effect of Different Al/Si Ratios on the Structure and Energy Storage Properties of Strontium Barium Niobate-Based Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Xiu, Shaomei; Xiao, Shi; Xue, Shuangxi; Shen, Bo; Zhai, Jiwei

    2016-02-01

    Strontium barium niobate-based glass-ceramics (BSN-AS) with various Al/Si ratios have been prepared through melt casting followed by controlled crystallization. The effect of the various Al/Si ratios on the phase evolution, microstructure, dielectric properties, and energy storage density, and the relationship between the breakdown strength properties and the activation energy E a of BSN-AS glass-ceramics, were investigated. The results reveal that the microstructure of BSN-AS glass-ceramics gradually becomes dense and uniform, and the phenomenon of reunited grains is effectively improved in a certain range of Al/Si ratios. With the Al/Si ratios increasing, the breakdown strength increases to a maximum value and then decreases drastically. For the relationship between breakdown strength properties and activation energy E a, it was found that the various trends between breakdown properties and activation energy E a of the BSN-AS glass-ceramics are opposite. In this study, the energy storage densities reach 4.8 J/cm3 by adjusting the Al/Si ratios in the BSN-AS glass-ceramics.

  6. Immobilization of gadolinium in iron borophosphate glasses and iron borophosphate based glass-ceramics: Implications for the immobilization of plutonium(Ⅲ)

    NASA Astrophysics Data System (ADS)

    Wang, Fu; Liao, Qilong; Dai, Yunya; Zhu, Hanzhen

    2016-08-01

    Immobilization of gadolinium (Gd), a nonradioactive surrogate for Pu3+, in iron borophosphate glasses/glass-ceramics (IBP glasses/glass-ceramics) has been investigated. The IBP glass containing 4 mol% Gd2O3 is homogeneously amorphous. At higher Gd2O3 concentrations, additional Gd is retained in the glasses as crystalline inclusions of monazite GdPO4 crystalline phase detected with X-ray diffraction. Moreover, Gd2O3 addition increases the Tg of the IBP glasses in glass formation range, which is consistent with the structural modification of the glasses. The structure of the Gd2O3-loaded IBP glasses/glass-ceramics is mainly based on pyrophosphate units. The chemical durability of Gd2O3-loaded IBP glasses/glass-ceramics is comparable to widely used borosilicate glass waste forms and the existence of monazite GdPO4 crystalline phase does not degrade the aqueous chemical durability of the IBP glasses/glass-ceramics. The Gd-loading results imply that the solubility should not be a limiting factor in processing nuclide Pu3+ if the formed crystalline phase(s) have high chemical durability.

  7. Ceramic applications in turbine engines

    NASA Technical Reports Server (NTRS)

    Helms, H. E.; Heitman, P. W.; Lindgren, L. C.; Thrasher, S. R.

    1984-01-01

    The application of ceramic components to demonstrate improved cycle efficiency by raising the operating temperature of the existing Allison IGI 404 vehicular gas turbine engine is discussed. This effort was called the Ceramic Applications in Turbine Engines (CATE) program and has successfully demonstrated ceramic components. Among these components are two design configurations featuring stationary and rotating caramic components in the IGT 404 engine. A complete discussion of all phases of the program, design, materials development, fabrication of ceramic components, and testing-including rig, engine, and vehicle demonstation test are presented. During the CATE program, a ceramic technology base was established that is now being applied to automotive and other gas turbine engine programs. This technology base is outlined and also provides a description of the CATE program accomplishments.

  8. Fabrication of BaTiO3-Based Dielectrics for Ultrathin-Layer Multilayer Ceramic Capacitor Application by a Modified Coating Approach

    NASA Astrophysics Data System (ADS)

    Tian, Zhibin; Wang, Xiaohui; Zhang, Yichi; Song, Tae-Ho; Hur, Kang Heon; Li, Longtu

    2011-02-01

    The development of multilayer ceramic capacitor (MLCC) with base metal electrode (BME) requires precise controlling of the microstructure in a very thin dielectric layer (<1 µm). In this paper, a modified coating approach for high coverage of BaTiO3 powder for further MLCC application has been developed. The well dispersed and coated BaTiO3 powders are prepared and the relative mechanism has been discussed. Furthermore, the ultrafine grained X7R dielectric ceramics were produced by both conventional mixing and modified coating methods. Compared with the conventional mixing method, the ceramics prepared by the coating approach exhibited better TCC (the temperature coefficient of capacitance) performance, with dielectric constant over 2000 and grain size below 150 nm. In addition, it is found through the coating method the content of additives can be reduced to a relatively smaller amount than that required in conventional mixing method.

  9. Fine structure analysis of biocompatible ceramic materials based hydroxyapatite and metallic biomaterials 316L

    NASA Astrophysics Data System (ADS)

    Anghelina, F. V.; Ungureanu, D. N.; Bratu, V.; Popescu, I. N.; Rusanescu, C. O.

    2013-11-01

    The aim of this paper was to obtain and characterize (surface morphology and fine structure) two types of materials: Ca10(PO4)6(OH)2 hydroxyapatite powder (HAp) as biocompatible ceramic materials and AISI 316L austenitic stainless steels as metallic biomaterials, which are the components of the metal-ceramic composites used for medical implants in reconstructive surgery and prosthetic treatment. The HAp was synthesized by coprecipitation method, heat treated at 200 °C, 800 °C and 1200 °C for 4 h, analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The stainless steel 316L type was made by casting, annealing and machined with a low speed (100 mm/s) in order to obtain a smooth surface and after that has been studied from residual stresses point of view in three polishing regimes conditions: at low speed polishing (150 rpm), at high speed polishing (1500 rpm) and high speed-vibration contact polishing (1500 rpm) using wide angle X-ray diffractions (WAXD). The chemical compositions of AISI 316 steel samples were measured using a Foundry Master Spectrometer equipped with CCD detector for spectral lines and the sparking spots of AISI 316L samples were analyzed using SEM. By XRD the phases of HAp powders have been identified and also the degree of crystallinity and average size of crystallites, and with SEM, we studied the morphology of the HAp. It has been found from XRD analysis that we obtained HAp with a high degree of crystallinity at 800 °C and 1200 °C, no presence of impurity and from SEM analysis we noticed the influence of heat treatment on the ceramic particles morphology. From the study of residual stress profiles of 316L samples were observed that it differs substantially for different machining regimes and from the SEM analysis of sparking spots we revealed the rough surfaces of stainless steel rods necessary for a better adhesion of HAp on it.

  10. Structural Ceramics Database

    National Institute of Standards and Technology Data Gateway

    SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

  11. Ceramics Curriculum: What Has It Been? What Could it Be?

    ERIC Educational Resources Information Center

    Sessions, Billie

    1999-01-01

    Reviews the traditional approach to ceramics education that focuses on studio-based, formalist curriculum and Modernist concerns. Argues for a comprehensive, or contextual, ceramics education in high school classrooms that would include contextual information about ceramic objects. Discusses example ceramic objects by various artists. (CMK)

  12. Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

    PubMed Central

    Paßlick, C.; Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.; Johnson, J. A.; Schweizer, S.

    2011-01-01

    The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl2) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu3+ is more strongly reduced to Eu2+, in particular, when doped as a chloride instead of fluoride compound. The Eu2+-to-Eu3+ doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu2+ fraction leads to a BaCl2 phase transition from hexagonal to orthorhombic structure at a lower temperature. PMID:22275772

  13. Refractive index modulating Raman spectroscopy based on perovskite PMN-PT ceramics.

    PubMed

    Wei, Danzhu; Xu, Tian; Yuan, Li; Tian, Shu; Fang, Jinghuai; Jin, Yonglong; Wang, Chaonan; Ma, Xinxiang; Shi, Jianzhen

    2016-04-01

    A three-layer planar waveguide structure comprising a perovskite (1-x)Pb(Mg1/3Nb2/3Nb2/3)O3-xPbTiO3 (PMN-PT) ceramic sandwiched by two silver films is designed and called PMPW. Using the high sensitivity of ultrahigh-order modes, theoretical analysis is performed to calculate the effective refractive index (ERI) of the PMPW. A detailed analysis of the Raman spectrum of PMN-PT at 795  cm-1 is performed. A comparison of the numerical analysis and experimental results reveals that the nonlinear change in ERI plays a primary role in the Raman signal variation. Analysis of the Raman spectrum of a sample deposited on PMPW confirms that it is effective for modulating Raman signals. PMID:27139681

  14. Corrosion properties of zirconium-based ceramic coatings for micro-bearing and biomedical applications

    NASA Astrophysics Data System (ADS)

    Walkowicz, J.; Zavaleyev, V.; Dobruchowska, E.; Murzynski, D.; Donkov, N.; Zykova, A.; Safonov, V.; Yakovin, S.

    2016-03-01

    Ceramic oxide ZrO2 and oxynitride ZrON coatings are widely used as protective coatings against diffusion and corrosion. The enhancement of the coatings' mechanical properties, as well as their wear and corrosion resistance, is very important for their tribological performance. In this work, ZrO2 and ZrON coatings were deposited by magnetron sputtering on stainless steel (AISI 316) substrates. The adhesion, hardness and elastic properties were evaluated by standard methods. The surface structure of the deposited coatings was observed by electron scanning microscopy (SEM) and atomic force microscopy (AFM). The composition of the coatings was analyzed by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS). The corrosion resistance properties were evaluated using the potentiodynamic method. The results show that the corrosion parameters are significantly increased in the cases of both oxynitride and oxide coatings in comparison with the stainless steel (AISI 316) substrates.

  15. Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

    SciTech Connect

    Passlick, C.; Mueller, O.; Luetzenkirchen-Hecht, D.; Frahm, R.; Johnson, J. A.; Schweizer, S.

    2011-12-01

    The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl{sub 2}) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu{sup 3+} is more strongly reduced to Eu{sup 2+}, in particular, when doped as a chloride instead of fluoride compound. The Eu{sup 2+}-to-Eu{sup 3+} doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu{sup 2+} fraction leads to a BaCl{sub 2} phase transition from hexagonal to orthorhombic structure at a lower temperature.

  16. The Foreign Body Giant Cell Cannot Resorb Bone, But Dissolves Hydroxyapatite Like Osteoclasts

    PubMed Central

    ten Harkel, Bas; Schoenmaker, Ton; Picavet, Daisy I.; Davison, Noel L.; de Vries, Teun J.; Everts, Vincent

    2015-01-01

    Foreign body multinucleated giant cells (FBGCs) and osteoclasts share several characteristics, like a common myeloid precursor cell, multinuclearity, expression of tartrate-resistant acid phosphatase (TRAcP) and dendritic cell-specific transmembrane protein (DC-STAMP). However, there is an important difference: osteoclasts form and reside in the vicinity of bone, while FBGCs form only under pathological conditions or at the surface of foreign materials, like medical implants. Despite similarities, an important distinction between these cell types is that osteoclasts can resorb bone, but it is unknown whether FBGCs are capable of such an activity. To investigate this, we differentiated FBGCs and osteoclasts in vitro from their common CD14+ monocyte precursor cells, using different sets of cytokines. Both cell types were cultured on bovine bone slices and analyzed for typical osteoclast features, such as bone resorption, presence of actin rings, formation of a ruffled border, and characteristic gene expression over time. Additionally, both cell types were cultured on a biomimetic hydroxyapatite coating to discriminate between bone resorption and mineral dissolution independent of organic matrix proteolysis. Both cell types differentiated into multinucleated cells on bone, but FBGCs were larger and had a higher number of nuclei compared to osteoclasts. FBGCs were not able to resorb bone, yet they were able to dissolve the mineral fraction of bone at the surface. Remarkably, FBGCs also expressed actin rings, podosome belts and sealing zones—cytoskeletal organization that is considered to be osteoclast-specific. However, they did not form a ruffled border. At the gene expression level, FBGCs and osteoclasts expressed similar levels of mRNAs that are associated with the dissolution of mineral (e.g., anion exchange protein 2 (AE2), carbonic anhydrase 2 (CAII), chloride channel 7 (CIC7), and vacuolar-type H+-ATPase (v-ATPase)), in contrast the matrix degrading enzyme

  17. Negative effects of nicotine on bone-resorbing cytokines and bone histomorphometric parameters in male rats.

    PubMed

    Hapidin, Hermizi; Othman, Faizah; Soelaiman, Ima-Nirwana; Shuid, Ahmad N; Luke, Douglas A; Mohamed, Norazlina

    2007-01-01

    The effects of nicotine administration on bone-resorbing cytokines, cotinine, and bone histomorphometric parameters were studied in 21 Sprague-Dawley male rats. Rats aged 3 months and weighing 250-300 g were divided into three groups. Group 1 was the baseline control (BC), which was killed without treatment. The other two groups were the control group (C) and the nicotine-treated group (N). The N group was treated with nicotine 7 mg/kg body weight and the C group was treated with normal saline only. Treatment was given by intraperitoneal injection for 6 days/week for 4 months. The rats were injected intraperitoneally with calcein 20 mg/kg body weight at day 9 and day 2 before they were killed. ELISA test kits were used to measure the serum interleukin-1 (IL-1), interleukin-6 (IL-6), and cotinine (a metabolite of nicotine) levels at the beginning of the study and upon completion of the study. Histomorphometric analysis was done on the metaphyseal region of the trabecular bone of the left femur by using an image analyzer. Biochemical analysis revealed that nicotine treatment for 4 months significantly increased the serum IL-1, IL-6, and cotinine levels as compared to pretreatment levels. In addition, the serum cotinine level was significantly higher in the N group than in the C group after 4 months treatment. Histomorphometric analysis showed that nicotine significantly decreased the trabecular bone volume (BV/TV), trabecular thickness (Tb.Th), double-labeled surface (dLS/BS), mineralizing surface (MS/BS), mineral appositional rate (MAR), and bone formation rate (BFR/BS), while causing an increase in the single-labeled surface (sLS/BS), osteoclast surface (Oc.S/BS), and eroded surface (ES/BS) as compared to the BC and C groups. In conclusion, treatment with nicotine 7 mg/kg for 4 months was detrimental to bone by causing an increase in the bone resorbing cytokines and cotinine levels. Nicotine also exerted negative effects on the dynamic trabecular histomorphometric

  18. A new classification system for all-ceramic and ceramic-like restorative materials.

    PubMed

    Gracis, Stefano; Thompson, Van P; Ferencz, Jonathan L; Silva, Nelson R F A; Bonfante, Estevam A

    2015-01-01

    Classification systems for all-ceramic materials are useful for communication and educational purposes and warrant continuous revisions and updates to incorporate new materials. This article proposes a classification system for ceramic and ceramic-like restorative materials in an attempt to systematize and include a new class of materials. This new classification system categorizes ceramic restorative materials into three families: (1) glass-matrix ceramics, (2) polycrystalline ceramics, and (3) resin-matrix ceramics. Subfamilies are described in each group along with their composition, allowing for newly developed materials to be placed into the already existing main families. The criteria used to differentiate ceramic materials are based on the phase or phases present in their chemical composition. Thus, an all-ceramic material is classified according to whether a glass-matrix phase is present (glass-matrix ceramics) or absent (polycrystalline ceramics) or whether the material contains an organic matrix highly filled with ceramic particles (resin-matrix ceramics). Also presented are the manufacturers' clinical indications for the different materials and an overview of the different fabrication methods and whether they are used as framework materials or monolithic solutions. Current developments in ceramic materials not yet available to the dental market are discussed. PMID:25965634

  19. FATIGUE OF DENTAL CERAMICS

    PubMed Central

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-01-01

    Objectives Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. Data/sources The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Conclusions Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically-assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Clinical significance Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. PMID:24135295

  20. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  1. Textured and hierarchically structured calcium phosphate ceramic blocks through hydrothermal treatment.

    PubMed

    Galea, Laetitia; Alexeev, Dmitriy; Bohner, Marc; Doebelin, Nicola; Studart, André R; Aneziris, Christos G; Graule, Thomas

    2015-10-01

    Synthetic calcium phosphate bone graft substitutes are widely recognized for their biocompatibility and resorption characteristics in the treatment of large bone defects. However, due to their inherent brittleness, applications in load-bearing situations always require reinforcement by additional metallic implants. Improved mechanical stability would eliminate the need for non-resorbable metallic implants. In this context a new approach to obtain calcium phosphate scaffolds with improved mechanical stability by texturing the material in specific crystal orientations was evaluated. Texture and reduction of crystal size was achieved by recrystallizing α-TCP blocks into calcium deficient hydroxyapatite (CDHA) under hydrothermal conditions. SEM and XRD analysis revealed the formation of fine CDHA needles (diameter ≈ 0.1-0.5 μm), aligned over several hundreds of micrometers. The obtained microstructures were remarkably similar to the microstructures of the prismatic layer of mollusk shells or enamel, also showing organization at 5 hierarchical structure levels. Brazilian disc tests were used to determine the diametral tensile strength, σdts, and the work-of-fracture, WOF, of the textured materials. Hydrothermal incubation significantly increased σdts and WOF of the ceramic blocks as compared to sintered blocks. These improvements were attributed to the fine and entangled crystal structure obtained after incubation, which reduces the size of strength-determining critical defects and also leads to tortuous crack propagation. Rupture surfaces revealed intergranular tortuous crack paths, which dissipate much more energy than transgranular cracks as observed in the sintered samples. Hence, the refined and textured microstructure achieved through the proposed processing route is an effective way to improve the strength and particularly the toughness of calcium phosphate-based ceramics. PMID:26210176

  2. Microstructural investigations of materials for low temperature co-fired ceramic (LTCC) based fuel cell using small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Mohamed, A. A.; Ahmad, M. H.; Ibrahim, A.; Azman, A.; Alias, R.; Ambak, Z.; Shapee, S.; Putra, E. G.; Patriati, A.; Sharom, M. A.; Yazid, H.; Mamat, M. R.; Karim, J. A.; Idris, F. M.; Yazid, K.; Zin, M. R.

    2013-06-01

    The concept and the realization fuel cell based on LTCC technology require the investigations of fired LTCC microstructures. The majority of the works involved using small angle neutron scattering studies on the microstructural of LTCC ceramic tape and development of neutron tomography for future tool to visualize channels inside the fired tape. Most SANS characterization were carried out at Smarter SANS instrument at BATAN, Indonesia. Standard sample for resolving tens of micron of object size were measured using simple neutron tomography setup utilizing monochromatic SANS beam at Malaysian Nuclear Agency. The initial microstructural findings indicates that organic additives shape the final microstructural of LTCC after firing with the glassy material possibly fill the space left by the burned organic additives. The tomography results showed that 40 micron size object can be differentiated. The conductor deposited on LTCC is preliminary investigated which will later be used as support for catalyst.

  3. Effect of TiO2 ceramic filler on PEG-based composite polymer electrolytes for magnesium batteries

    NASA Astrophysics Data System (ADS)

    Polu, Anji Reddy; Kumar, Ranveer; Kumar, K. Vijaya; Jyothi, N. Krishna

    2013-02-01

    Composite polymer electrolytes based on poly(ethylene glycol) (PEG), magnesium acetate [Mg(CH3COO)2] and x wt. % of titanium oxide (TiO2) ceramic fillers (where x = 0, 5, 10, 15 and 20 respectively) have been prepared using solution casting technique. Several experimental techniques, such as composition-dependent conductivity, temperature dependent conductivity in the temperature range of 303-333 K and transport number measurements, have been employed to characterize these composite polymer electrolyte systems. The transference number data indicated the dominance of ion-type charge transport in these specimens. Using this (PEG-Mg(CH3COO)2-TiO2) (85-15-10) electrolyte, solid state electrochemical cell was fabricated and their discharge profiles were studied under a constant load of 100 kω.

  4. Joining of SiC Fiber-Bonded Ceramics using Silver, Copper, Nickel, Palladium, and Silicon-Based Alloy Interlayers

    SciTech Connect

    Asthana, Rajiv; Singh, Mrityunjay; Lin, Hua-Tay; Matsunaga, Kenji; Ishikawa, Toshihiro

    2013-01-01

    SiC fiber-bonded ceramics, SA-Tyrannohex, (SA-THX) with perpendicular and parallel fiber orientations were brazed using Ag-, Ni- and Pd-base brazes, and four Si X (X: Ti, Cr, Y, Ta) eutectics. Outcomes were variable, ranging from bonded joints through partially bonded to un-bonded joints. Prominent Ti- and Si-rich interfaces developed with Cusil-ABA, Ticusil, and Copper-ABA and Ni- and Si-rich layers with MBF-20. Stress rupture tests at 650 and 750 C on Cusil-ABA-bonded joints revealed a temperature-dependent behavior for the perpendicular joints but not for the parallel joints with failure occurring at brazed interface. Higher-use temperatures can be targeted with eutectic Si Ti and Si Cr alloys.

  5. Electrical Properties of BaTiO3-Based Multilayer Ceramic Capacitors Sintered with Plasma-Treated Glass Powder

    NASA Astrophysics Data System (ADS)

    Jeong, Dae-Yong; Lee, Soon-il; Lee, Heun-Young; Kim, Min-Kee; Yoon, Jung-Rag

    2013-10-01

    The influence of glass power morphology on the electrical and microstructural properties of BaTiO3-based multilayer ceramic capacitors (MLCCs) was investigated to enhance the reliability of MLCCs. For a sintering additive, glass particles of different sizes and shapes were prepared by jet-milling and RF plasma treatment. Plasma treatment decreased the glass particle size and transformed the irregular shape of glass particles into homogeneous spherical shapes. It was found that MLCCs sintered with plasma-treated glass powder have a more homogeneous microstructure, a clear core-shell structure, a more stable capacitance against voltage and temperature changes, and a higher degradation resistance. It is inferred that nanosized spherical glass powder prepared by plasma treatment helps so-called magic dopants such as rare-earth elements to be distributed homogeneously around the BaTiO3 particles.

  6. Nanocrystalline biphasic resorbable calcium phosphate (HAp/β-TCP) thin film prepared by electron beam evaporation technique

    NASA Astrophysics Data System (ADS)

    Elayaraja, K.; Chandra, V. Sarath; Joshy, M. I. Ahymah; Suganthi, R. V.; Asokan, K.; Kalkura, S. Narayana

    2013-06-01

    Biphasic calcium phosphate (BCP) thin film having resorbable β-tricalcium phosphate (β-TCP) and non-resorbable hydroxyapatite (HAp) phases having enhanced bioactivity was synthesized by electron beam evaporation technique. Nanosized BCP was deposited as a layer (500 nm) on (0 0 1) silicon substrate by electron beam evaporation and crystalline phase of samples were found to improve on annealing at 700 °C. Uniform deposition of calcium phosphate on silicon substrate was verified from elemental mapping using scanning electron microscope (SEM-EDX). Annealing of the samples led to a decrease in surface roughness, hydrophobicity and dissolution of the coating layer. Amoxicillin loaded thin films exhibited significant bacterial resistance. In addition, BCP thin films did not exhibit any cytotoxicity. Antibiotics incorporated BCP coated implants might prevent the post-surgical infections and could promote bone-bonding of orthopedic devices.

  7. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, M.S.; Shlomo, G.; Anderson, M.A.

    1994-08-30

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range. 2 figs.

  8. Challenges and Opportunities in Design, Fabrication, and Testing of High Temperature Joints in Ceramics and Ceramic Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Levine, S. R. (Technical Monitor)

    2001-01-01

    Ceramic joining has been recognized as an enabling technology for successful utilization of advanced ceramics and composite materials. A number of joint design and testing issues have been discussed for ceramic joints in silicon carbide-based ceramics and fiber-reinforced composites. These joints have been fabricated using an affordable, robust ceramic joining technology (ARCJoinT). The microstructure and good high temperature mechanical capability (compressive and flexural strengths) of ceramic joints in silicon carbide-based ceramics and composite materials are reported.

  9. A comparison study between periosteum and resorbable collagen membrane on iliac block bone graft resorption in the rabbit calvarium

    PubMed Central

    2014-01-01

    Background To compare the different resorption patterns between resorbable membrane barrier and periosteum after iliac block bone grafting radiographically and histologically. Methods Eighteen mature male rabbits weighing from 2.0 to 2.5 kg were used. The recipient site was the rabbit skull, and autogenous iliac bone was used as the grafting material. The harvested iliac block bones were divided in the following groups: autogenous iliac block bone with preservation of the periosteum (the periosteum group), autogenous iliac block bone covered with a resorbable collagen membrane (Biomesh®, Samyang Co, Korea) after removing the periosteum (the collagen membrane group), and autogenous iliac block bones with removal of the periosteum (the control group). In each experimental group, periosteum or resorbable collagen membrane of the donor site was fixed directed to the periosteum of the recipient site. The specimens were examined macroscopically, radiographically, histologically, and histomorphometrically at every 2, 4, and 8 weeks. Results All groups presented excellent bone graft healing state without inflammation, dehiscence, or displacement. The radiolucency increased from mild to moderate in all groups over the experiment. The mean thickness of the upper end of the cortical iliac bone graft was statistically significantly different between the control group and the periosteum group, between the four-week and eight-week control group, and between the four- week and eight-week periosteum group (p & 0.05). Conclusion This study suggests that both the periosteum and the resorbable collagen membrane may help to prevent soft tissue infiltration into the bone graft and to reduce bone graft resorption compared to block graft alone. PMID:24886656

  10. Effect of zircon-based tricolor pigments on the color, microstructure, flexural strength and translucency of a novel dental lithium disilicate glass-ceramic.

    PubMed

    Yuan, Kun; Wang, Fu; Gao, Jing; Sun, Xiang; Deng, Zai-Xi; Wang, Hui; Jin, Lei; Chen, Ji-Hua

    2014-01-01

    The purpose of this study was to investigate the effect of zircon-based tricolor pigments (praseodymium zircon yellow, ferrum zircon red, and vanadium zircon blue) on the color, thermal property, crystalline phase composition, microstructure, flexural strength, and translucency of a novel dental lithium disilicate glass-ceramic. The pigments were added to the glass frit, milled, pressed, and sintered. Ninety monochrome samples were prepared and the colors were analyzed. The effect of the pigments on thermal property, crystalline phase composition, and microstructure were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Addition of the pigments resulted in the acquisition of subtractive primary colors as well as tooth-like colors, and did not demonstrate significant effects on the thermal property, crystalline phase composition, microstructure, and flexural strength of the experimental glass-ceramic. Although significant differences (p < 0.01) were observed between the translucencies of the uncolored and 1.0 wt % zircon-based pigment colored ceramics, the translucencies of the latter were sufficient to fabricate dental restorations. These results indicate that the zircon-based tricolor pigments can be used with dental lithium disilicate glass-ceramic to produce abundant and predictable tooth-like colors without significant adverse effects, if mixed in the right proportions. PMID:23853033

  11. Inverted electro-mechanical behaviour induced by the irreversible domain configuration transformation in (K,Na)NbO3-based ceramics

    PubMed Central

    Huan, Yu; Wang, Xiaohui; Koruza, Jurij; Wang, Ke; Webber, Kyle G.; Hao, Yanan; Li, Longtu

    2016-01-01

    Miniaturization of domains to the nanometer scale has been previously reported in many piezoelectrics with two-phase coexistence. Despite the observation of nanoscale domain configuration near the polymorphic phase transition (PPT) regionin virgin (K0.5Na0.5)NbO3 (KNN) based ceramics, it remains unclear how this domain state responds to external loads and influences the macroscopic electro-mechanical properties. To this end, the electric-field-induced and stress-induced strain curves of KNN-based ceramics over a wide compositional range across PPT were characterized. It was found that the coercive field of the virgin samples was highest in PPT region, which was related to the inhibited domain wall motion due to the presence of nanodomains. However, the coercive field was found to be the lowest in the PPT region after electrical poling. This was related to the irreversible transformation of the nanodomains into micron-sized domains during the poling process. With the similar micron-sized domain configuration for all poled ceramics, the domains in the PPT region move more easily due to the additional polarization vectors. The results demonstrate that the poling process can give rise to the irreversible domain configuration transformation and then account for the inverted macroscopic piezoelectricity in the PPT region of KNN-based ceramics. PMID:26915972

  12. Ultrasonic transducers based on undoped lead-free (K0.5Na0.5)NbO3 ceramics.

    PubMed

    Bah, Micka; Giovannelli, Fabien; Schoenstein, Frederic; Brosseau, Christophe; Deschamps, Jean-Robert; Dorvaux, Frédéric; Haumesser, Lionel; Le Clezio, Emmanuel; Monot-Laffez, Isabelle

    2015-12-01

    Lead zirconate titanate (PZT) ceramics are the dominant piezoelectric elements for non-destructive evaluation (NDE) and ultrasonic transducers devices. However, the presence of lead content may impose the scientific community to develop lead-free ceramics, concerning human health and environmental safety. During the past ten years, many contributions have highlighted the potential properties of complex compositions like LiNbO3, LiTaO3 and LiSbO3 in the lead-free (K0.5Na0.5)NbO3 KNN system. In this context, for the first time, the practical applications and the effectiveness of simply undoped (K0.5Na0.5)NbO3 (KNN) ceramics are investigated. KNN powder is prepared by conventional solid state mixed oxide route. Ceramics of this material are prepared using conventional sintering (CS) and spark plasma sintering (SPS). Thickness coupling factor kt of 44-46%, planar coupling factor kp of 29-45%, relative permittivity at constant strain ε33,r(S) of 125-243 and acoustic impedance Z of 23-30 MRay are obtained for these two kinds of undoped KNN ceramics. Both ceramics are used to build single-element ultrasonic transducers. Relative bandwidth of 49-78% and insertion loss of -27 and -51dB are obtained for SPS and CS transducers, respectively. These results are suitable for use in non-destructive evaluation. The effectiveness of undoped KNN is evaluated using the KLM model, and compared to standard PZT based probe. Finally, chemical aging test of undoped KNN has demonstrated its stability in water. PMID:26117145

  13. Comparative transcriptomics reveals RhoE as a novel regulator of actin dynamics in bone-resorbing osteoclasts

    PubMed Central

    Georgess, Dan; Mazzorana, Marlène; Terrado, José; Delprat, Christine; Chamot, Christophe; Guasch, Rosa M.; Pérez-Roger, Ignacio; Jurdic, Pierre; Machuca-Gayet, Irma

    2014-01-01

    The function of osteoclasts (OCs), multinucleated giant cells (MGCs) of the monocytic lineage, is bone resorption. To resorb bone, OCs form podosomes. These are actin-rich adhesive structures that pattern into rings that drive OC migration and into “sealing-zones” (SZs) that confine the resorption lacuna. Although changes in actin dynamics during podosome patterning have been documented, the mechanisms that regulate these changes are largely unknown. From human monocytic precursors, we differentiated MGCs that express OC degradation enzymes but are unable to resorb the mineral matrix. We demonstrated that, despite exhibiting bona fide podosomes, these cells presented dysfunctional SZs. We then performed two-step differential transcriptomic profiling of bone-resorbing OCs versus nonresorbing MGCs to generate a list of genes implicated in bone resorption. From this list of candidate genes, we investigated the role of Rho/Rnd3. Using primary RhoE-deficient OCs, we demonstrated that RhoE is indispensable for OC migration and bone resorption by maintaining fast actin turnover in podosomes. We further showed that RhoE activates podosome component cofilin by inhibiting its Rock-mediated phosphorylation. We conclude that the RhoE-Rock-cofilin pathway, by promoting podosome dynamics and patterning, is central for OC migration, SZ formation, and, ultimately, bone resorption. PMID:24284899

  14. The effect of osteotomy dimension on osseointegration to resorbable media-treated implants: a study in the sheep.

    PubMed

    Galli, Silvia; Jimbo, Ryo; Tovar, Nick; Yoo, Daniel Y; Anchieta, Rodolfo B; Yamaguchi, Satoshi; Coelho, Paulo G

    2015-03-01

    The drilling technique and the surface characteristics are known to influence the healing times of oral implants. The influence of osteotomy dimension on osseointegration of microroughned implant surfaces treated with resorbable blasting media was tested in an in vivo model. Ninety-six implants (ø4.5 mm, 8 mm in length) with resorbable blasting media-treated surfaces were placed in the ileum of six sheep. The final osteotomy diameters were 4.6 mm (reamer), 4.1 mm (loose), 3.7 mm (medium), and 3.2 mm (tight). After three and six weeks of healing, the implants were biomechanically tested and histologically evaluated. Statistical analysis was performed using Page L trend test for ordered and paired sample and linear regression, with significance level at p < 0.05. An overall increase in all dependent variables was observed with the reduction of osteotomy diameter. In addition, all osseointegration scores increased over time. At three weeks, the retention was significantly higher for smaller osteotomies. The histological sections depicted intimate contact of bone with all the implant surfaces and osteoblast lines were visible in all sections. The resorbable blasting media microroughed surfaces achieved successful osseointegration for all the instrumentation procedures tested, with higher osseointegration scores for the high insertion torque group. PMID:25281647

  15. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  16. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  17. A Resorbable Calcium-Deficient Hydroxyapatite Hydrogel Composite for Osseous Regeneration

    SciTech Connect

    Hutchens, Stacy A; O'Neill, Hugh Michael; Benson, Roberto S.; Evans, Barbara R; Rawn, Claudia J

    2009-01-01

    It was previously discovered that the unique structure and chemistry of bacterial cellulose (BC) permits the formation of calcium-deficient hydroxyapatite (CdHAP) nanocrystallites under aqueous conditions at ambient pH and temperature. In this study, BC was chemically modified via a limited periodate oxidation reaction to render the composite degradable and thus more suitable for bone regeneration. While native BC does not degrade in mammalian systems, periodate oxidation yields dialdehyde cellulose which breaks down at physiological pH. The composite was characterized by tensile testing, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. X-ray diffraction showed that oxidized BC retains its structure and could biomimetically form CdHAP. Degradation behavior was analyzed by incubating the samples in simulated physiological fluid (pH 7.4) at 37 C under static and dynamic conditions. The oxidized BC and oxidized BC-CdHAP composites both lost significant mass after exposure to the simulated physiological environment. Examination of the incubation solutions by UV-Vis spectrophotometric analysis demonstrated that, while native BC released only small amounts of soluble cellulose fragments, oxidized cellulose releases carbonyl containing degradation products as well as soluble cellulose fragments. By entrapping CdHAP in a degradable hydrogel carrier, this composite should elicit bone regeneration then resorb over time to be replaced by new osseous tissue.

  18. Evaluation of silicon nitride as a wear resistant and resorbable alternative for total hip joint replacement

    PubMed Central

    Olofsson, Johanna; Grehk, T. Mikael; Berlind, Torun; Persson, Cecilia; Jacobson, Staffan; Engqvist, Håkan

    2012-01-01

    Many of the failures of total joint replacements are related to tribology, i.e., wear of the cup, head and liner. Accumulation of wear particles at the implants can be linked to osteolysis which leads to bone loss and in the end aseptic implant loosening. Therefore it is highly desirable to reduce the generation of wear particles from the implant surfaces. Silicon nitride (Si3N4) has shown to be biocompatible and have a low wear rate when sliding against itself and is therefore a good candidate as a hip joint material. Furthermore, wear particles of Si3N4 are predicted to slowly dissolve in polar liquids and they therefore have the potential to be resorbed in vivo, potentially reducing the risk for aseptic loosening. In this study, it was shown that α-Si3N4-powder dissolves in PBS. Adsorption of blood plasma indicated a good acceptance of Si3N4 in the body with relatively low immune response. Si3N4 sliding against Si3N4 showed low wear rates both in bovine serum and PBS compared with the other tested wear couples. Tribofilms were built up on the Si3N4 surfaces both in PBS and in bovine serum, controlling the friction and wear characteristics. PMID:23507807

  19. Analysis of a vinyl pyrrolidone/poly(propylene fumarate) resorbable bone cement.

    PubMed

    Gresser, J D; Hsu, S H; Nagaoka, H; Lyons, C M; Nieratko, D P; Wise, D L; Barabino, G A; Trantolo, D J

    1995-10-01

    A resorbable bone cement was formulated from N-vinyl-2-pyrrolidinone (VP), the unsaturated polyester poly(propylene fumarate) (PPF), and the inorganic filler tribasic calcium phosphate (hydroxy apatite). Cure, initiated by benzoyl peroxide and accelerated by N,N-dimethyl-p-toluidine, resulted in the formation of VP crosslinks between polyester chains. During cure the cement hardened from a viscous moldable putty to a rigid structure with a shore D hardness of 50-60. The purpose of this study was to determine the fractions of PPF and VP incorporated into the crosslinked structure. Dissolution of the cured cement in water followed by extraction of the residue in tetrahydrofuran indicated that over 90% of the PPF was crosslinked over the range of PPF/VP ratios explored, but that the fraction of VP used in formation of crosslinks depended linearly on the PPF/VP ratio. Kinetic analysis of these data suggests that k'pp/kpf (the reactivity ratio) was approximately 2.0 where k'pp is the rate constant for the addition of VP radical to VP monomer leading to formation of poly(vinyl pyrrolidone), and kpf is for the addition of VP radical to PPF unsaturation. PMID:8557726

  20. Stochastic modeling of filtrate alkalinity in water filtration devices: Transport through micro/nano porous clay based ceramic materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clay and plant materials such as wood are the raw materials used in manufacture of ceramic water filtration devices around the world. A step by step manufacturing procedure which includes initial mixing, molding and sintering is used. The manufactured ceramic filters have numerous pores which help i...

  1. Ceramics Analysis

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Lewis Research Center developed the CARES/LIFE software, which predicts the performance of brittle structures over time, such as ceramic compounds. Over 300 companies have used a version of the code, including Philips Display Components Company, AlliedSignal, Solar Turbines Incorporated, and TRW, Inc. for everything from engines to television tubes. The software enables a designer to test a variety of configurations for probability of failure and to adjust the structure's geometry to minimize the predicted failure or maximize durability for the lifetime of the ceramic component.

  2. Oxidation Characterization of Hafnium-Based Ceramics Fabricated by Hot Pressing and Electric Field-Assisted Sintering

    NASA Technical Reports Server (NTRS)

    Gasch, Matt; Johnson, Sylvia; Marschall, Jochen

    2010-01-01

    Ceramic borides, such as hafnium diboride (HfB2) and zirconium diboride (ZrB2), are members of a family of materials with extremely high melting temperatures referred to as Ultra High Temperature Ceramics (UHTCs). UHTCs constitute a class of promising materials for use in high temperature applications, such as sharp leading edges on future-generation hypersonic flight vehicles, because of their high melting points. The controlled development of microstructure has become important to the processing of UHTCs, with the prospect of improving their mechanical and thermal properties. The improved oxidation resistance of HfB2 has also become important if this material is to be successfully used at temperatures above 2000 C. Furthermore, the use of UHTCs on the leading edges of vehicles traveling at hypersonic speeds will mean exposure to a mixed oxidation environment comprised of both molecular and atomic oxygen. The current study has investigated the high-temperature oxidation behavior of HfB2-based materials in a pure O2 environment, as well as in environments containing different levels of dissociated oxygen (O/O2). Materials were processed by two techniques: conventional hot pressing (HP) and electric field-assisted sintering (FAS). Their oxidation behavior was evaluated in both a tube furnace at 1250 C for 3 hours and in a simulated re-entry environment in the Advanced Heating Facility (AHF) arcjet at NASA Ames Research Center, during a 10-minute exposure to a cold wall heat flux of 250W/sq cm and stagnation pressure of 0.1-0.2 atm. The microstructure of the different materials was characterized before and after oxidation using scanning electron microscopy (SEM).

  3. In Vitro and In Vivo Evaluation of Zinc-Modified Ca–Si-Based Ceramic Coating for Bone Implants

    PubMed Central

    Zheng, Xuebin; He, Dannong; Ye, Xiaojian; Wang, Meiyan

    2013-01-01

    The host response to calcium silicate ceramic coatings is not always favorable because of their high dissolution rates, leading to high pH within the surrounding physiological environment. Recently, a zinc-incorporated calcium silicate-based ceramic Ca2ZnSi2O7 coating, developed on a Ti-6Al-4V substrate using plasma-spray technology, was found to exhibit improved chemical stability and biocompatibility. This study aimed to investigate and compare the in vitro response of osteoblastic MC3T3-E1 cells cultured on Ca2ZnSi2O7 coating, CaSiO3 coating, and uncoated Ti-6Al-4V titanium control at cellular and molecular level. Our results showed Ca2ZnSi2O7 coating enhanced MC3T3-E1 cell attachment, proliferation, and differentiation compared to CaSiO3 coating and control. In addition, Ca2ZnSi2O7 coating increased mRNA levels of osteoblast-related genes (alkaline phosphatase, procollagen α1(I), osteocalcin), insulin-like growth factor-I (IGF-I), and transforming growth factor-β1 (TGF-β1). The in vivo osteoconductive properties of Ca2ZnSi2O7 coating, compared to CaSiO3 coating and control, was investigated using a rabbit femur defect model. Histological and histomorphometrical analysis demonstrated new bone formation in direct contact with the Ca2ZnSi2O7 coating surface in absence of fibrous tissue and higher bone-implant contact rate (BIC) in the Ca2ZnSi2O7 coating group, indicating better biocompatibility and faster osseointegration than CaSiO3 coated and control implants. These results indicate Ca2ZnSi2O7 coated implants have applications in bone tissue regeneration, since they are biocompatible and able to osseointegrate with host bone. PMID:23483914

  4. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption.

    PubMed

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%-95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  5. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

    PubMed Central

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  6. All solid state lithium batteries based on lamellar garnet-type ceramic electrolytes

    NASA Astrophysics Data System (ADS)

    Du, Fuming; Zhao, Ning; Li, Yiqiu; Chen, Cheng; Liu, Ziwei; Guo, Xiangxin

    2015-12-01

    All solid-state lithium batteries are constructed by using highly conducting Ta-doped Li7La3Zr2O12 (LLZTO) as the solid electrolytes as well as the supports, coated with composite cathodes consisting of poly(vinylidene fluoride) (PVdF):LiTFSI, Ketjen Black, and carbon-coated LiFePO4 on one side and attached with Li anode on the other side. At 60 °C, the batteries show the first discharge capacity of 150 mAh g-1 at 0.05 C and 93% capacity retention after 100 cycles. As the current density increases from 0.05 C to 1 C, the specific capacity decreases from 150 mAh g-1 to 100 mAh g-1. Further elevated temperature up to 100 °C leads to further improved performance, i.e. 126 mAh g-1 at 1 C and 99% capacity retention after 100 cycles. This good performance can be attributed to the highly conducting ceramic electrolytes, the optimum electronic and ionic conducting networks in the composite cathodes, and closely contacted cathode/LLZTO interface. These results indicate that the present strategy is promising for development of high-performance solid-state Li-ion batteries operated at medium temperature.

  7. In vitro evaluation of osteoconductivity and cellular response of zirconia and alumina based ceramics.

    PubMed

    Pandey, Ajoy Kumar; Pati, Falguni; Mandal, Debika; Dhara, Santanu; Biswas, Koushik

    2013-10-01

    Developed ceria/yttria stabilized zirconia and ceria/yttria stabilized zirconia toughened alumina supported formation of apatite layer when immersed in simulated body fluid without any prior surface treatment. The formed mineral layer was confirmed as hydroxyapatite through X-ray diffraction patterns. The calcium/phosphate atomic ratio obtained from energy dispersive X-ray spectroscopy was found to be little less (Ca/P=1.5) than that of pure hydroxyapatite (Ca/P=1.7) which indicates the probability of mixed type calcium-phosphate compound formation. The achieved thickness of apatite layer was estimated through a surface profilometer and as high as ~17 μm thickness was found after 28 days of soaking. The biocompatibility of the developed materials was ensured through in vitro human osteoblast like cell (MG63) culture on ceramic discs. The morphology of attached cells was characterized through scanning electron microscopy and fluorescent microscopy which show multilayered interconnected cell growth within 8 days of culture period. Moreover, differentiation of MG63 cells was evaluated through MTT assay, total protein content and alkaline phosphatase activity. PMID:23910297

  8. Passive Q-switching of microchip lasers based on Ho:YAG ceramics.

    PubMed

    Lan, R; Loiko, P; Mateos, X; Wang, Y; Li, J; Pan, Y; Choi, S Y; Kim, M H; Rotermund, F; Yasukevich, A; Yumashev, K; Griebner, U; Petrov, V

    2016-06-20

    A Ho:YAG ceramic microchip laser pumped by a Tm fiber laser at 1910 nm is passively Q-switched by single- and multi-layer graphene, single-walled carbon nanotubes (SWCNTs), and Cr2+:ZnSe saturable absorbers (SAs). Employing SWCNTs, this laser generated an average power of 810 mW at 2090 nm with a slope efficiency of 68% and continuous wave to Q-switching conversion efficiency of 70%. The shortest pulse duration was 85 ns at a repetition rate of 165 kHz, and the pulse energy reached 4.9 μJ. The laser performance and pulse stability were superior compared to graphene SAs even for a different number of graphene layers (n=1 to 4). A model for the description of the Ho:YAG laser Q-switched by carbon nanostructures is presented. This modeling allowed us to estimate the saturation intensity for multi-layered graphene and SWCNT SAs to be 1.2±0.2 and 7±1  MW/cm2, respectively. When using Cr2+:ZnSe, the Ho:YAG microchip laser generated 11 ns/25 μJ pulses at a repetition rate of 14.8 kHz. PMID:27409113

  9. Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

  10. Thermal Conductivity and Water Vapor Stability of HfO2-based Ceramic Coating Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2- 15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermaVenvironmenta1 barrier coating applications will also be discussed.

  11. Effect of Inner Electrode on Reliability of (Zn,Mg)TiO3-Based Multilayer Ceramic Capacitor

    NASA Astrophysics Data System (ADS)

    Lee, Wen‑His; Su, Chi‑Yi; Lee, Ying Chieh; Yang, Jackey; Yang, Tong; PinLin, Shih

    2006-07-01

    In this study, different proportions of silver-palladium alloy acting as the inner electrode were adopted to a (Zn,Mg)TiO3-based multilayer ceramic capacitor (MLCC) sintered at 925 °C for 2 h to evaluate the effect of the inner electrode on reliability. The main results show that the lifetime is inversely proportional to Ag content in the Pd/Ag inner electrode. Ag+1 diffusion into the (Zn,Mg)TiO3-based MLCC during cofiring at 925 °C for 2 h and Ag+1 migration at 140 °C against 200 V are both responsible for the short lifetime of the (Zn,Mg)TiO3-based MLCC, particularly the latter factor. A (Zn,Mg)TiO3-based MLCC with high Ag content in the inner electrode Ag/Pd=99/01 exhibits the shortest lifetime (13 h), and the effect of Ag+1 migration is markedly enhanced when the activation energy of the (Zn,Mg)TiO3 dielectric is greatly lowered due to the excessive formation of oxygen vacancies and the semiconducting Zn2TiO4 phase when Ag+ substitutes for Zn+2 during co-firing.

  12. Metal-ceramic joint assembly

    DOEpatents

    Li, Jian

    2002-01-01

    A metal-ceramic joint assembly in which a brazing alloy is situated between metallic and ceramic members. The metallic member is either an aluminum-containing stainless steel, a high chromium-content ferritic stainless steel or an iron nickel alloy with a corrosion protection coating. The brazing alloy, in turn, is either an Au-based or Ni-based alloy with a brazing temperature in the range of 9500 to 1200.degree. C.

  13. Incorporation of zinc for fabrication of low-cost spinel-based composite ceramic membrane support to achieve its stabilization.

    PubMed

    Li, Lingling; Dong, Xinfa; Dong, Yingchao; Zhu, Li; You, Sheng-Jie; Wang, Ya-Fen

    2015-04-28

    In order to reduce environment risk of zinc, a spinel-based porous membrane support was prepared by the high-temperature reaction of zinc and bauxite mineral. The phase evolution process, shrinkage, porosity, mechanical property, pore size distribution, gas permeation flux and microstructure were systematically studied. The XRD results, based on a Zn/Al stoichiometric composition of 1/2, show a formation of ZnAl2O4 structure starting from 1000°C and then accomplished at 1300°C. For spinel-based composite membrane, shrinkage and porosity are mainly influenced by a combination of an expansion induced by ZnAl2O4 formation and a general densification due to amorphous liquid SiO2. The highest porosity, as high as 44%, is observed in ZnAl4 membrane support among all the investigated compositions. Compared with pure bauxite (Al), ZnAl4 composite membrane support is reinforced by ZnAl2O4 phase and inter-locked mullite crystals, which is proved by the empirical strength-porosity relationships. Also, an increase in average pore diameter and gas flux can be observed in ZnAl4. A prolonged leaching experiment reveals the zinc can be successfully incorporated into ceramic membrane support via formation of ZnAl2O4, which has substantially better resistance toward acidic attack. PMID:25655422

  14. Development of low dielectric constant alumina-based ceramics for microelectronic substrates

    SciTech Connect

    Wu, S. J.

    1993-05-01

    The performance of high speed computers depends not only on IC chips, but also on the signal propagation speed between these chips. The signal propagation delay in a computer is determined by the dielectric constant of the substrate material to which the IC chips are attached. In this study, a ceramic substrate with a low dielectric constant (k {approx} 5.0) has been developed. When compared with the traditional alumina substrate (k {approx} 10.0), the new material corresponds to a 37% decrease in the signal propagation delay. Glass hollow spheres are used to introduce porosity (k = 1.0) to the alumina matrix in a controlled manner. A surface coating technique via heterogeneous nucleation in aqueous solution has been used to improve the high temperature stability of these spheres. After sintering at 1,400 C, isolated spherical pores are uniformly distributed in the almost fully dense alumina matrix; negligible amounts of matrix defects can be seen. All pores are isolated from each other. Detailed analyses of the chemical composition find that the sintered sample consists of {alpha}-alumina, mullite and residual glass. Mullite is the chemical reaction product of alumina and the glass spheres. Residual glass exists because current firing conditions do not complete the mullitization reaction. The dielectric constant of the sintered sample is measured and then compared with the predicted value using Maxwell`s model. Mechanical strength is evaluated by a four-point bending test. Although the flexural strength decreases exponentially with porosity, samples with 34% porosity (k {approx} 5.0) still maintain adequate mechanical strength for the proper operation of a microelectronic substrate.

  15. He-irradiation effects on glass-ceramics for joining of SiC-based materials

    NASA Astrophysics Data System (ADS)

    Gozzelino, L.; Casalegno, V.; Ghigo, G.; Moskalewicz, T.; Czyrska-Filemonowicz, A.; Ferraris, M.

    2016-04-01

    CaO-Al2O3 (CA) and SiO2-Al2O3-Y2O3 (SAY) glass-ceramics are promising candidates for SiC/SiC indirect joints. In view of their use in locations where high radiation level is expected (i.e. fusion plants) it is important to investigate how radiation-induced damage can modify the material microstructure. To this aim, pellets of both types were irradiated with 5.5 MeV 4He+ ions at an average temperature of 75 °C up to a fluence of almost 2.3·1018 cm-2. This produces a displacement defect density that increases with depth and reaches a value of about 40 displacements per atom in the ion implantation region, where the He-gas reaches a concentration of several thousands of atomic parts per million. X-ray diffractometry and scanning electron microscopy showed no change in the microstructure and in the morphology of the pellet surface. Moreover, a transmission electron microscopy investigation on cross-section lamellas revealed the occurrence of structural defects and agglomerates of He-bubbles in the implantation region for the CA sample and a more homogeneous He-bubble distribution in the SAY pellet, even outside the implantation layer. In addition, no amorphization was found in both samples, even in correspondence to the He implantation zone. The radiation damage induced only occasional micro-cracks, mainly located at grain boundaries (CA) or within the grains (SAY).

  16. dc-Electrical Degradation of the BT-Based Material for Multilayer Ceramic Capacitor with Ni internal Electrode: Impedance Analysis and Microstructure

    NASA Astrophysics Data System (ADS)

    Chazono, Hirokazu; Kishi, Hiroshi

    2001-09-01

    The impedance of a BaTiO3 (BT)-based multilayer ceramic capacitor with a nickel internal electrode (Ni-MLCC) was investigated by measuring the frequency domain at various temperatures. All the obtained impedance data could be successfully fitted to a 4-RC section electrical equivalent network. The 4-RC section electrical equivalent network was successfully correlated to the microstructure: the core, the shell, the grain boundary, and the ceramic/internal electrode interface regions. Based on this electrical equivalent network, the electrical properties including the Curie-Weiss law, the current-voltage characteristics, and dc electrical degradation, were well explained. A model for the degradation behavior for BT-based Ni-MLCC with thin active layer thickness was proposed.

  17. Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

    NASA Technical Reports Server (NTRS)

    Levine, Stanley R. (Editor)

    1992-01-01

    The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

  18. Evaluation of the Fatigue Performance and Degradability of Resorbable PLDLLA-TMC Osteofixations

    PubMed Central

    Landes, Constantin; Ballon, Alexander; Ghanaati, Shahram; Ebel, Daniel; Ulrich, Dieter; Spohn, Uwe; Heunemann, Ute; Sader, Robert; Jaeger, Raimund

    2013-01-01

    The fatigue performance of explanted in-situ degraded osteofixations/osteosyntheses, fabricated from poly (70L-lactide-co-24DL-lactide-6-trimethylane-carbonate or PLDLLA-TMC) copolymer was compared to that of virgin products. The fatigue test was performed on 21 explants retrieved from 12 women and 6 men; 16-46 years by a custom-designed three-point bend apparatus using a staircase method and a specified failure criterion (an increase of the deflection of the specimen > 1 mm) with run-out designated as “no failure” after 150,000 loading cycles. While all the virgin products showed run-out at 38N, all of the specimens fabricated from explants failed at this load level. For the explant specimens, although there was a trend of decreased failure load with increased in-situ time, this decrease was pronounced after 4 months in-situ, however, not yet statistically significant, while a 6-month in-situ explant had significantly less failure load. Three and four month in-situ explants had highly significant differences in failure load between measurements close and distant to the osteotomy line: p=0.0017 (the region of maximum load in-situ). In the virgin products, there were only traces of melt joining and cooling, left from a stage in the manufacturing process. For the implants retrieved after 4.5 months in-situ, the fracture surfaces showed signs of degradation of the implants, possibly caused by hydrolysis, and for those retrieved after 9 months in-situ, there were cracks and pores. Thus, the morphological results are consistent with those obtained in the fatigue test. The present results suggest that resorbable osteofixations fabricated from PLDLLA-TMC are stable enough to allow loading of the healing bone and degrade reliably PMID:24363786

  19. Ultrastructural analysis of apatite-degrading capability of extended invasive podosomes in resorbing osteoclasts.

    PubMed

    Akisaka, Toshitaka; Yoshida, Astushi

    2016-09-01

    Osteoclasts in culture are non-transformed cell types that spontaneously develop specific cell-adhesion devices such as podosomes. An individual podosome is a complex network of filamentous actin (F-actin) unit structure that collectively, with other proteins, self-organizes as the sealing zone. Major matrix degradation on apatite seems to proceed under the ruffled-border domain, which is an enclosed extracellular compartment tightly sealed off by this sealing zone. Presently we found that usually the top of finger-like projections of the ruffled border reached toward the plane of the apatite surface, where a shallow degradation of apatite took place. Simultaneously, we obtained several pieces of structural evidence indicating that a specific protrusion referred to as an invasive podosome (invadopodium), which was continuous with podosomes derived from the sealing zone, invaded deeply into apatite matrix and degraded it. The F-actin architecture of the invasive podosome - an active extracellular matrix-degrading, actin-rich cell protrusion - could be distinguished from that of other punctate F-actin structures including the individual podosome, sealing zone, and ruffled border projection. Invasive podosomes contained 2 different F-actin populations, i.e., an interconnected meshwork and a parallel array of bundles. The morphological variability of these protrusions was apparent, having a single cylindrical to lamella-shaped cytoskeletal organization. Our present observations strongly suggest that the degradation of apatite substrate-resorbing osteoclasts appears to have been preceded by the combined appearance of ruffled border and invasive podosomes, and also occurred simultaneously with cell migration during an alternating cycle of resorption and migration. PMID:27323283

  20. Degradation profile and preliminary clinical testing of a resorbable device for ligation of blood vessels.

    PubMed

    Aminlashgari, Nina; Höglund, Odd V; Borg, Niklas; Hakkarainen, Minna

    2013-06-01

    A resorbable device for ligation of blood vessels was developed and tested in vitro to reveal the degradation profile of the device and to predict the clinical performance in terms of adequate mechanical support during a healing period of 1week. In addition, preliminary clinical testing was performed that showed complete hemostasis and good tissue grip of renal arteries in five pigs. The device was made by injection molding of poly(glycolide-co-trimethylene carbonate) triblock copolymer, and it consisted of a case with a locking mechanism connected to a partly perforated flexible band. A hydrolytic degradation study was carried out for 7, 30 and 60days in water and buffer medium, following the changes in mass, water absorption, pH and mechanical properties. A new rapid matrix-free laser desorption ionization-mass spectrometry (LDI-MS) method was developed for direct screening of degradation products released into the degradation medium. The combination of LDI-MS and electrospray ionization-mass spectrometry analyses enabled the comparison of the degradation product patterns in water and buffer medium. The identified degradation products were rich in trimethylene carbonate units, indicating preferential hydrolysis of amorphous regions where trimethylene units are located. The crystallinity of the material was doubled after 60days of hydrolysis, additionally confirming the preferential hydrolysis of trimethylene carbonate units and the enrichment of glycolide units in the remaining solid matrix. The mechanical performance of the perforated band was followed for the first week of hydrolysis and the results suggest that sufficient strength is retained during the healing time of the blood vessels. PMID:23438863

  1. Evaluation of the Fatigue Performance and Degradability of Resorbable PLDLLA-TMC Osteofixations.

    PubMed

    Landes, Constantin; Ballon, Alexander; Ghanaati, Shahram; Ebel, Daniel; Ulrich, Dieter; Spohn, Uwe; Heunemann, Ute; Sader, Robert; Jaeger, Raimund

    2013-01-01

    The fatigue performance of explanted in-situ degraded osteofixations/osteosyntheses, fabricated from poly (70L-lactide-co-24DL-lactide-6-trimethylane-carbonate or PLDLLA-TMC) copolymer was compared to that of virgin products. The fatigue test was performed on 21 explants retrieved from 12 women and 6 men; 16-46 years by a custom-designed three-point bend apparatus using a staircase method and a specified failure criterion (an increase of the deflection of the specimen > 1 mm) with run-out designated as "no failure" after 150,000 loading cycles. While all the virgin products showed run-out at 38N, all of the specimens fabricated from explants failed at this load level. For the explant specimens, although there was a trend of decreased failure load with increased in-situ time, this decrease was pronounced after 4 months in-situ, however, not yet statistically significant, while a 6-month in-situ explant had significantly less failure load. Three and four month in-situ explants had highly significant differences in failure load between measurements close and distant to the osteotomy line: p=0.0017 (the region of maximum load in-situ). In the virgin products, there were only traces of melt joining and cooling, left from a stage in the manufacturing process. For the implants retrieved after 4.5 months in-situ, the fracture surfaces showed signs of degradation of the implants, possibly caused by hydrolysis, and for those retrieved after 9 months in-situ, there were cracks and pores. Thus, the morphological results are consistent with those obtained in the fatigue test. The present results suggest that resorbable osteofixations fabricated from PLDLLA-TMC are stable enough to allow loading of the healing bone and degrade reliably. PMID:24363786

  2. Ceramic Technology for Advanced Heat Engines Project

    SciTech Connect

    Not Available

    1990-08-01

    The Ceramic Technology For Advanced Heat Engines Project was developed by the Department of Energy's Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Advanced Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the Department of Energy (DOE), National Aeronautics and Space Administration (NASA), and Department of Defense (DOD) advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. An assessment of needs was completed, and a five year project plan was developed with extensive input from private industry. The objective of the project is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on structural ceramics for advanced gas turbine and diesel engines, ceramic hearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines.

  3. High-temperature corrosion resistance of ceramics and ceramic coatings

    SciTech Connect

    Tortorelli, P.F.

    1996-06-01

    Ceramics and ceramic composites offer the potential to operate fossil energy systems at the higher temperatures necessary for improved energy efficiency and better environmental control. However, because many fossil fuel-derived processes contain sulfur, chlorine, and carbon, as well as oxygen, degradation from high-temperature corrosion and environmental effects arising from reactions of solids with gases and condensable products is a common life-determining factor in operating systems. Ceramic-based products are not immune to such degradation; adequate corrosion resistance must be assured to exploit the technical and economic potential of such materials. This is normally accomplished by using stable, sound oxides that exist in their bulk form, that naturally grow as surface layers upon exposure to an oxidizing environment, or that are deposited as a coating on a susceptible material. It is therefore important to examine the critical issues with respect to more environmental stability of ceramics that have the potential to be corrosion resistant in particular fossil environments. Key aspects include not only chemical compatibility, but the influence of the environment on the mechanical behavior of the ceramic materials. In addition, for coatings, the mechanical reliability of the ceramic is a key issue in that an otherwise corrosion-resistant surface layer must remain sound and adherent in order to provide protection to the underlying substrate. The purpose of this work is to support the development of advanced ceramics and ceramic composites for applications in fossil environments by examining critical issues related to high-temperature corrosion resistance. More specifically, the overall objective of this task is to examine the chemical compatibility and reliability of potentially corrosion-resistant ceramics being developed as protective overcoats and/or structural materials as parts of other work elements funded by the AR&TD Program.

  4. Effect of Vanadium Addition on Reliability and Microstructure of BaTiO3-Based Multilayer Ceramic Capacitors

    NASA Astrophysics Data System (ADS)

    Natsui, Hidesada; Shibahara, Takeshi; Yonezawa, Yu; Kido, Osamu

    2012-09-01

    The vanadium distribution in multilayer ceramic capacitors (MLCCs), sintered under a reducing atmosphere, was investigated using scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS), and insulation resistance degradation was analyzed using impedance spectroscopy in highly accelerated lifetime tests to clarify the effects of vanadium on both the electrical properties and microstructure of MLCCs. Vanadium mitigated insulation resistance degradation and increased the reliability of MLCCs. Moreover, vanadium content increased and insulation resistance at the ceramic/electrode interface decreased slowly. This change in dynamics directly resulted in an improved lifetime of MLCCs. The results of STEM-EELS analysis showed that vanadium distributed along the grain boundary and grain boundary junction, but substituted into BaTiO3 at the ceramic/electrode interface. Therefore, it is considered that vanadium substitution at the ceramic/electrode interface improves the reliability of MLCCs.

  5. Synergistically toughening effect of SiC whiskers and nanoparticles in Al2O3-based composite ceramic cutting tool material

    NASA Astrophysics Data System (ADS)

    Liu, Xuefei; Liu, Hanlian; Huang, Chuanzhen; Wang, Limei; Zou, Bin; Zhao, Bin

    2016-06-01

    In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiCnp advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vol% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730±95 MPa and fracture toughness is 5.6±0.6 MPa·m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

  6. Low thermal expansion poreless ceramics

    NASA Astrophysics Data System (ADS)

    Sugawara, Jun; Abe, Kozo; Mukai, Toshio

    2003-05-01

    Low thermal expansion ceramics have been required for ultra precision nanometer positioning stage in the semiconductor equipments. Especially pore-less advanced ceramics have been playng an important part as mirror materials in the optical equipments. Nippon Steel produces Sialon and NEXCERA as the solutions for these demands. Sialon based on silicon nitride shows a thermal expansion of 1.3 x 10-6/K with a high Young's modulus of 300 GPa. Newly-developed NEXCERA based on cordierite ceramics shows near-zero thermal expansion around the room temperature with a Young's modulus of 130 GPa. For these advanced ceramics, near-net shape sintering, direct bonding and mirror polishing are available. These technologies will provide us new design possibilities in precision engineering fields like optical system.

  7. A portable high-power diode laser-based single-stage ceramic tile grout sealing system

    NASA Astrophysics Data System (ADS)

    Lawrence, J.; Schmidt, M. J. J.; Li, L.; Edwards, R. E.; Gale, A. W.

    2002-02-01

    By means of a 60 W high-power diode laser (HPDL) and a specially developed grout material the void between adjoining ceramic tiles has been successfully sealed. A single-stage process has been developed which uses a crushed ceramic tile mix to act as a tough, inexpensive bulk substrate and a glazed enamel surface to provide an impervious surface glaze. The single-stage ceramic tile grout sealing process yielded seals produced in normal atmospheric conditions that displayed no discernible cracks and porosities. The single-stage grout is simple to formulate and easy to apply. Tiles were successfully sealed with power densities as low as 200 kW/ mm2 and at rates of up to 600 mm/ min. Bonding of the enamel to the crushed ceramic tile mix was identified as being primarily due to van der Waals forces and, on a very small scale, some of the crushed ceramic tile mix material dissolving into the glaze. In terms of mechanical, physical and chemical characteristics, the single-stage ceramic tile grout was found to be far superior to the conventional epoxy tile grout and, in many instances, matched and occasionally surpassed that of the ceramic tiles themselves. What is more, the development of a hand-held HPDL beam delivery unit and the related procedures necessary to lead to the commercialisation of the single-stage ceramic tile grout sealing process are presented. Further, an appraisal of the potential hazards associated with the use of the HPDL in an industrial environment and the solutions implemented to ensure that the system complies with the relevant safety standards are given.

  8. Microwave processing of ceramics

    SciTech Connect

    Katz, J.D.

    1989-01-01

    This paper discusses the following topics on microwave processing of ceramics: Microwave-material interactions; anticipated advantage of microwave sintering; ceramic sintering; and ceramic joining. 24 refs., 4 figs. (LSP)

  9. High-temperature electrical transport behaviors in textured Ca{sub 3}Co{sub 4}O{sub 9}-based polycrystalline ceramics

    SciTech Connect

    Lin Yuanhua; Lan Jinle; Liu Yuheng; Nan Cewen; Li Jingfeng; Shen Zhijian

    2009-02-16

    Highly (00l) oriented Ca{sub 3}Co{sub 4}O{sub 9}-based ceramics were fabricated by spark plasma sintering combined with a dynamic forging process. The grain orientation is effective in lowering the electrical resistivity and enhancing the thermoelectric power factor but with little influence on the Seebeck coefficient. A metallic-to-semiconducting transition temperature can be observed and the activation energy is almost independent of the La-doping. All of the Ca{sub 3}Co{sub 4}O{sub 9}-based ceramic samples exhibit large thermoelectric power, and the figure of merit for La-doped Ca{sub 3}Co{sub 4}O{sub 9} sample can reach 0.26 at 975 K, which can be a promising candidate of p-type material for high-temperature thermoelectric application.

  10. Fatigue analysis of computer-aided design/computer-aided manufacturing resin-based composite vs. lithium disilicate glass-ceramic.

    PubMed

    Ankyu, Shuhei; Nakamura, Keisuke; Harada, Akio; Hong, Guang; Kanno, Taro; Niwano, Yoshimi; Örtengren, Ulf; Egusa, Hiroshi

    2016-08-01

    Resin-based composite molar crowns made by computer-aided design/computer-aided manufacturing (CAD/CAM) systems have been proposed as an inexpensive alternative to metal-ceramic or all-ceramic crowns. However, there is a lack of scientific information regarding fatigue resistance. This study aimed to analyze the fatigue behavior of CAD/CAM resin-based composite compared with lithium disilicate glass-ceramic. One-hundred and sixty bar-shaped specimens were fabricated using resin-based composite blocks [Lava Ultimate (LU); 3M/ESPE] and lithium disilicate glass-ceramic [IPS e.max press (EMP); Ivoclar/Vivadent]. The specimens were divided into four groups: no treatment (NT); thermal cycling (TC); mechanical cycling (MC); and thermal cycling followed by mechanical cycling (TCMC). Thermal cycling was performed by alternate immersion in water baths of 5°C and 55°C for 5 × 10(4) cycles. Mechanical cycling was performed in a three-point bending test, with a maximum load of 40 N, for 1.2 × 10(6) cycles. In addition, LU and EMP molar crowns were fabricated and subjected to fatigue treatments followed by load-to-failure testing. The flexural strength of LU was not severely reduced by the fatigue treatments. The fatigue treatments did not significantly affect the fracture resistance of LU molar crowns. The results demonstrate the potential of clinical application of CAD/CAM-generated resin-based composite molar crowns in terms of fatigue resistance. PMID:27203408

  11. Effects of microstructural defects on the performance of base-metal multilayer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Samantaray, Malay M.

    Multilayer ceramic capacitors (MLCCs), owing to their processing conditions, can exhibit microstructure defects such as electrode porosity and roughness. The effect of such extrinsic defects on the electrical performance of these devices needs to be understood in order to achieve successful miniaturization into the submicron dielectric layer thickness regime. Specifically, the presence of non-planar and discontinuous electrodes can lead to local field enhancements while the relative morphologies of two adjacent electrodes determine variations in the local dielectric thickness. To study the effects of electrode morphologies, an analytical approach is taken to calculate the electric field enhancement and leakage current with respect to an ideal parallel-plate capacitor. Idealized electrode defects are used to simulate the electric field distribution. It is shown that the electrode roughness causes both the electric field and the leakage current to increase with respect to that of the ideal flat parallel-plate capacitor. Moreover, finite element methods are used to predict electric field enhancements by as high as 100% within capacitor structures containing rough interfaces and porosity. To understand the influence of microstructural defects on field distributions and leakage current, the real three-dimensional microstructure of local regions in MLCCs are reconstructed using a serial-sectioning technique in the focused ion beam. These microstructures are then converted into a finite element model in order to simulate the perturbations in electric field due to the presence of electrode defects. The electric field is three times the average value, and this leads to increase in current density of these devices. It is also shown that increasing sintering rates of MLCCs leads to improved electrode morphology with smoother more continuous electrodes, which in turn leads to a decrease in electric field enhancement and calculated leakage current density. To simulate scaling

  12. Kilohertz high power extracavity KGW yellow raman lasers based on pulse LD side-pumped ceramic Nd: YAG

    NASA Astrophysics Data System (ADS)

    Bai, Y.; Chen, X. M.; Guo, J. X.; Zhang, H. L.; Bai, J. T.; Ren, Z. Y.

    2012-03-01

    We report an efficient operation of a kilohertz nanosecond extracavity KGd(WO4)2 (KGW) crystal Raman yellow laser, which is pumped by a 532 nm lasers based on pulse laser diode (LD) side-pumped ceramic Nd: YAG, BBO electro-optical Q-switched and LBO crystal extracavity frequency doubling. With the 5 W, 10 ns and 1 kHz output power pumped at 532 nm, we obtained 2.58 W, 7.4 ns, 1 kHz second Stokes Raman laser output at 579.54 nm for 768 cm-1 Raman shift of KGW crystal, corresponding to a conversion efficiency of 51.4%. By changing the KGW crystal orientation, we further obtained 3.18 W, 7.8 ns, 1 kHz Raman pulses at 588.33 nm for 901 cm-1 Raman shift, corresponding to a conversion efficiency of 63.3%. The beam quality factors M2 of 579.54 and 588.33 nm were ( M {/x-579.54 2} = 5.829, M {/y-579.54 2} = 6.336) and ( M {/x-588.33 2} = 6.405, M {/y-588.33 2} = 6.895), respectively.

  13. Structure and nonlinear optical properties of novel transparent glass-ceramics based on Co2+:ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Dymshits, O. S.; Vitkin, V. V.; Skoptsov, N. A.; Zhilin, A. A.; Shemchuk, D. V.; Tsenter, M. Ya; Bogdanov, K. V.; Malyarevich, A. M.; Glazunov, I. V.; Mateos, X.; Yumashev, K. V.

    2016-05-01

    Transparent glass-ceramics (GCs) based on Co2+:ZnO nanocrystals (mean diameter, 11 nm) are synthesized on the basis of cobalt-doped glasses of the K2O–ZnO–Al2O3–SiO2 system. For these GCs, the absorption band related to the 4A2(4F)  →  4T1(4F) transition of Co2+ ions in tetrahedral sites spans until ~1.73 μm. Saturation of the absorption is demonstrated at 1.54 μm, with a saturation fluence F s  =  0.8  ±  0.1 Jcm‑2 (σ GSA  =  1.7  ±  0.2  ×  10‑19 cm2) and a recovery time of 890  ±  10 ns. Passive Q-switching of an Er,Yb:glass laser is realized with the synthesized GCs. This laser generated 0.37 mJ/100 ns pulses at 1.54 μm. The developed GCs are promising as saturable absorbers for 1.6–1.7 μm crystalline erbium lasers.

  14. Grain-growth effect on dielectric nonlinearity of BaTiO3-based multi-layer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Yoon, Seok-Hyun; Kim, Mi-Yang; Nam, Chan-Hee; Seo, Jung-Wook; Wi, Sung-Kwon; Hur, Kang-Heon

    2015-08-01

    A significant difference in dielectric nonlinearity was contrasted between fine- and coarse-grained BaTiO3-based multilayer ceramic capacitors. Grain growth resulted in a decrease in dielectric constant in low field but a steep increase with increase in alternating current field, which can be associated with a decrease in reversible and a significant increase in irreversible domain wall contribution from Preisach analysis. Fine-grained specimens showed almost cubic structure despite ferroelectric domain contrasts, which is anticipated to significantly reduce strain incompatibility during domain wall motion, and clean domain boundaries with no lattice defects. However, coarse-grained specimens with high aspect ratio of the tetragonal lattice should accompany lattice distortion with increased intergranular constraints during domain wall motion, and many lattice defects were observed near domain boundaries. These results demonstrate experimentally the presence of weak pinning centers in coarse-grained specimens, which inhibit domain wall motion in low alternating current fields. Long-range motion occurs beyond the threshold field and results in an abrupt increase in dielectric constant.

  15. Field-induced domain switching in BaTiO3-based multilayer ceramic capacitors observed by polarized Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Gao, Haigen; Yue, Zhenxing; Xi, Xiaoqing; Li, Longtu

    2012-11-01

    Polarized Raman spectroscopy was employed to observe field-induced domain switching in BaTiO3-based multilayer ceramic capacitors (MLCCs). Un-polarized Raman intensities of vibration modes A1(TO2,TO3) are decreased with increasing the external field from 0 MV/m to 5 MV/m, which is caused by the decrease of c-domain volumes. This phenomenon can be visualized from the simulated image gained from the mapping results in cross polarization. It shows that the c-domains are switched to the direction of electric field (3.75 MV/m). We also found that the load to imprint Vickers indentation on the polished MLCCs surface can drive the domains out of the plane parallel to internal electrodes into in-plane textures. Meanwhile, the in-plane domains in the investigated area are switched to form a uniform orientation by the local introduced compressive stress. Due to the existence of cracks, the domains near cracks will re-orient and align with the direction of the relative tensile stress, resulting in a different orientation.

  16. Phase structure-electrical property relationships in Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3-based ceramics

    NASA Astrophysics Data System (ADS)

    Nie, Rui; Zhang, Qian; Yue, Yang; Liu, Hong; Chen, Yanbin; Chen, Qiang; Zhu, Jianguo; Yu, Ping; Xiao, Dingquan

    2016-03-01

    Generally, the phase structure change of Pb(B' B″)O3-PZT solid solutions near a morphotropic phase boundary (MPB) can be originated from composition variations. Here our results show that the excess PbO and the sintering temperature can also result in the ferroelectric phase structure change in the Pb(Ni1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PNN-PZT)-based ceramics near the MPB. The dielectric, piezoelectric, and ferroelectric properties are dependent on the tetragonal phase content (TP) which is closely associated with the excess PbO and the sintering temperature. The temperature dependence of the polarization (P)-electric field (E) hysteresis loops reveals that the tetragonal phase in the PNN-PZT-based ceramics has a lower activation energy (Ea) for domain wall movement than that of the rhombohedral phase, thus resulting in easier polarization rotation. This is responsible for the phase structure-electrical property relationships in the PNN-PZT-based ceramics, exhibiting the dependence of the tetragonal phase content (TP) on the electrical properties.

  17. A low-temperature process for the denitration of Hanford single-shell tank, nitrate-based waste utilizing the nitrate to ammonia and ceramic (NAC) process

    SciTech Connect

    Mattus, A.J.; Lee, D.D.; Dillow, T.A.; Farr, L.L.; Loghry, S.L.; Pitt, W.W.; Gibson, M.R.

    1994-12-01

    Bench-top feasibility studies with Hanford single-shell tank (SST) simulants, using a new, low-temperature (50 to 60C) process for converting nitrate to ammonia and ceramic (NAC), have conclusively shown that between 85 to 99% of the nitrate can be readily converted. In this process, aluminum powders or shot can be used to convert alkaline, nitrate-based supernate to ammonia and an aluminum oxide-sodium aluminate-based solid which might function as its own waste form. The process may actually be able to utilize already contaminated aluminum scrap metal from various DOE sites to effect the conversion. The final, nearly nitrate-free ceramic-like product can be pressed and sintered like other ceramics. Based upon the starting volumes of 6.2 and 3.1 M sodium nitrate solution, volume reductions of 50 to 55% were obtained for the waste form produced, compared to an expected 35 to 50% volume increase if the Hanford supernate were grouted. Engineering data extracted from bench-top studies indicate that the process will be very economical to operate, and data were used to cost a batch, 1,200-kg NO{sub 3}/h plant for working off Hanford SST waste over 20 years. Their total process cost analysis presented in the appendix, indicates that between $2.01 to 2.66 per kilogram of nitrate converted will be required. Additionally, data on the fate of select radioelements present in solution are presented in this report as well as kinetic, operational, and control data for a number of experiments. Additionally, if the ceramic product functions as its own waste form, it too will offer other cost savings associated with having a smaller volume of waste form as well as eliminating other process steps such as grouting.

  18. Enhanced lithium battery with polyethylene oxide-based electrolyte containing silane-Al2 O3 ceramic filler.

    PubMed

    Zewde, Berhanu W; Admassie, Shimelis; Zimmermann, Jutta; Isfort, Christian Schulze; Scrosati, Bruno; Hassoun, Jusef

    2013-08-01

    A solid polymer electrolyte prepared by using a solvent-free, scalable technique is reported. The membrane is formed by low-energy ball milling followed by hot-pressing of dry powdered polyethylene oxide polymer, LiCF3 SO3 salt, and silane-treated Al2 O3 (Al2 O3 -ST) ceramic filler. The effects of the ceramic fillers on the properties of the ionically conducting solid electrolyte membrane are characterized by using electrochemical impedance spectroscopy, XRD, differential scanning calorimeter, SEM, and galvanostatic cycling in lithium cells with a LiFePO4 cathode. We demonstrate that the membrane containing Al2 O3 -ST ceramic filler performs well in terms of ionic conductivity, thermal properties, and lithium transference number. Furthermore, we show that the lithium cells, which use the new electrolyte together with the LiFePO4 electrode, operate within 65 and 90 °C with high efficiency and long cycle life. Hence, the Al2 O3 -ST ceramic can be efficiently used as a ceramic filler to enhance the performance of solid polymer electrolytes in lithium batteries. PMID:23757331

  19. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors

    PubMed Central

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Azrin Shah, Nabila Farhana; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E′: 0.225) and glass transition temperature (Tg: −58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  20. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors.

    PubMed

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shah, Nabila Farhana Azrin; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E': 0.225) and glass transition temperature (Tg: -58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  1. Effects of neutron irradiation on glass ceramics as pressure-less joining materials for SiC based components for nuclear applications

    NASA Astrophysics Data System (ADS)

    Ferraris, M.; Casalegno, V.; Rizzo, S.; Salvo, M.; Van Staveren, T. O.; Matejicek, J.

    2012-10-01

    This paper reports on the microstructure and properties of two glass-ceramics based on SiO2-Al2O3-MgO (SAMg) and SiO2-Al2O3-Y2O3 (SAY), which have been designed to be used as pressure-less low activation joining materials for SiC/SiC and SiC based components for nuclear applications. Glass-ceramic pellets (SAY and SAMg) were irradiated for approximately 1 year in the reactor core of the LVR-15 research reactor at Nuclear Research Institute Rez, Czech Republic, at about 50 °C, 6.92 × 1024 n/m2 (E > 1 MeV, about 1 dpa in steel); SiC/SiC composites joined by SAY were irradiated about 1 year at High Flux Reactor (HFR), Petten, The Netherlands, 550 °C, 9-11 × 1024 n/m2 (E > 1 MeV, about 1.4-1.8 dpa in C), 600 °C, 16-22 × 1024 n/m2 (E > 1 MeV, about 2.6-3.3 dpa in C) and 820 °C 31-32 × 1024 n/m2(E > 1 MeV, about 5 dpa in C). Optical microscopy with image analysis and scanning electron microscopy (SEM) with X-ray microanalysis (EDS) were used to investigate the glass-ceramics morphology and composition, showing a remarkable similarity before and after neutron irradiation for both glass-ceramics. Comparison of bending strength for irradiated and non-irradiated SAY joined SiC/SiC indicate that the mechanical strength is unaffected by irradiation at these conditions.

  2. Methods of Si based ceramic components volatilization control in a gas turbine engine

    DOEpatents

    Garcia-Crespo, Andres Jose; Delvaux, John; Dion Ouellet, Noemie

    2016-09-06

    A method of controlling volatilization of silicon based components in a gas turbine engine includes measuring, estimating and/or predicting a variable related to operation of the gas turbine engine; correlating the variable to determine an amount of silicon to control volatilization of the silicon based components in the gas turbine engine; and injecting silicon into the gas turbine engine to control volatilization of the silicon based components. A gas turbine with a compressor, combustion system, turbine section and silicon injection system may be controlled by a controller that implements the control method.

  3. Inhibition of miR-21 restores RANKL/OPG ratio in multiple myeloma-derived bone marrow stromal cells and impairs the resorbing activity of mature osteoclasts.

    PubMed

    Pitari, Maria Rita; Rossi, Marco; Amodio, Nicola; Botta, Cirino; Morelli, Eugenio; Federico, Cinzia; Gullà, Annamaria; Caracciolo, Daniele; Di Martino, Maria Teresa; Arbitrio, Mariamena; Giordano, Antonio; Tagliaferri, Pierosandro; Tassone, Pierfrancesco

    2015-09-29

    miR-21 is an oncogenic microRNA (miRNA) with an emerging role as therapeutic target in human malignancies, including multiple myeloma (MM). Here we investigated whether miR-21 is involved in MM-related bone disease (BD). We found that miR-21 expression is dramatically enhanced, while osteoprotegerin (OPG) is strongly reduced, in bone marrow stromal cells (BMSCs) adherent to MM cells. On this basis, we validated the 3'UTR of OPG mRNA as miR-21 target. Constitutive miR-21 inhibition in lentiviral-transduced BMSCs adherent to MM cells restored OPG expression and secretion. Interestingly, miR-21 inhibition reduced RANKL production by BMSCs. Overexpression of protein inhibitor of activated STAT3 (PIAS3), which is a direct and validated target of miR-21, antagonized STAT3-mediated RANKL gene activation. Finally, we demonstrate that constitutive expression of miR-21 inhibitors in BMSCs restores RANKL/OPG balance and dramatically impairs the resorbing activity of mature osteoclasts. Taken together, our data provide proof-of-concept that miR-21 overexpression within MM-microenviroment plays a crucial role in bone resorption/apposition balance, supporting the design of innovative miR-21 inhibition-based strategies for MM-related BD. PMID:26160841

  4. Inhibition of miR-21 restores RANKL/OPG ratio in multiple myeloma-derived bone marrow stromal cells and impairs the resorbing activity of mature osteoclasts

    PubMed Central

    Pitari, Maria Rita; Rossi, Marco; Amodio, Nicola; Botta, Cirino; Morelli, Eugenio; Federico, Cinzia; Gullà, Annamaria; Caracciolo, Daniele; Di Martino, Maria Teresa; Arbitrio, Mariamena; Giordano, Antonio; Tagliaferri, Pierosandro; Tassone, Pierfrancesco

    2015-01-01

    miR-21 is an oncogenic microRNA (miRNA) with an emerging role as therapeutic target in human malignancies, including multiple myeloma (MM). Here we investigated whether miR-21 is involved in MM-related bone disease (BD). We found that miR-21 expression is dramatically enhanced, while osteoprotegerin (OPG) is strongly reduced, in bone marrow stromal cells (BMSCs) adherent to MM cells. On this basis, we validated the 3′UTR of OPG mRNA as miR-21 target. Constitutive miR-21 inhibition in lentiviral-transduced BMSCs adherent to MM cells restored OPG expression and secretion. Interestingly, miR-21 inhibition reduced RANKL production by BMSCs. Overexpression of protein inhibitor of activated STAT3 (PIAS3), which is a direct and validated target of miR-21, antagonized STAT3-mediated RANKL gene activation. Finally, we demonstrate that constitutive expression of miR-21 inhibitors in BMSCs restores RANKL/OPG balance and dramatically impairs the resorbing activity of mature osteoclasts. Taken together, our data provide proof-of-concept that miR-21 overexpression within MM-microenviroment plays a crucial role in bone resorption/apposition balance, supporting the design of innovative miR-21 inhibition-based strategies for MM-related BD. PMID:26160841

  5. Dispersed metal-toughened ceramics and ceramic brazing

    SciTech Connect

    Moorhead, A.J.; Tiegs, T.N.; Lauf, R.J.

    1983-01-01

    An alumina (Al/sub 2/O/sub 3/) based material that contains approximately 1 vol % finely dispersed platinum or chromium was developed for use in high temperature thermal-shock resistant electrical insulators. The work at ORNL is divided into two areas: (1) development of DMT ceramics; and (2) development of brazing filler metals suitable for making ceramic-to-ceramic and ceramic-to-metal brazements. The DMT ceramics and brazements are intended for service at elevated temperatures and at high stress levels in the dirty environments of advanced heat engines. The development and characterization of DMT ceramics includes processing (powder preparation, densification and heat treatment) and detailed measurement of mechanical and physical properties (strength, fracture toughness, and thermal conductivity). The brazing work includes: (1) the formulation and melting of small quantities of experimental brazing filler metals; (2) evaluation of the wetting and bonding behavior of these filler metals on Al/sub 2/O/sub 3/, partially stabilized zirconia and ..cap alpha..-SiC in a sessile drop apparatus; and (3) determine the short-term strength and fracture toughness of brazements.

  6. Lubricating Properties of Ceramic-Bonded Calcium Fluoride Coatings on Nickel-Base Alloys from 75 to 1900 deg F

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1962-01-01

    The endurance life and the friction coefficient of ceramic-bonded calcium fluoride (CaF2) coatings on nickel-base alloys were determined at temperatures from 75 F to 1900 F. The specimen configuration consisted of a hemispherical rider (3/16-in. rad.) sliding against the flat surface of a rotating disk. Increasing the ambient temperature (up to 1500 F) or the sliding velocity generally reduced the friction coefficient and improved coating life. Base-metal selection was critical above 1500 F. For instance, cast Inconel sliding against coated Inconel X was lubricated effectively to 1500 F, but at 1600 F severe blistering of the coatings occurred. However, good lubrication and adherence were obtained for Rene 41 sliding against coated Rene 41 at temperatures up to 1900 F; no blisters developed, coating wear life was fairly good, and the rider wear rate was significantly lower than for the unlubricated metals. Friction coefficients were 0.12 at 1500 F, 0.15 at 1700 F, and 0.17 at 1800 F and 1900 F. Because of its ready availability, Inconel X appears to be the preferred substrate alloy for applications in which the temperature does not exceed 1500 F. Rene 41 would have to be used in applications involving higher temperatures. Improved coating life was derived by either preoxidizing the substrate metals prior to the coating application or by applying a very thin (less than 0.0002 in.) burnished and sintered overlay to the surface of the coating. Preoxidation did not affect the friction coefficient. The overlay generally resulted in a higher friction coefficient than that obtained without the overlay. The combination of both modifications resulted in longer coating life and in friction coefficients intermediate between those obtained with either modification alone.

  7. Reliability Modeling Development and Its Applications for Ceramic Capacitors with Base-Metal Electrodes (BMEs)

    NASA Technical Reports Server (NTRS)

    Liu, Donhang

    2014-01-01

    This presentation includes a summary of NEPP-funded deliverables for the Base-Metal Electrodes (BMEs) capacitor task, development of a general reliability model for BME capacitors, and a summary and future work.

  8. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-12-01

    Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals. This project has the following 6 main tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  9. Ceramic processing: Experimental design and optimization

    NASA Technical Reports Server (NTRS)

    Weiser, Martin W.; Lauben, David N.; Madrid, Philip

    1992-01-01

    The objectives of this paper are to: (1) gain insight into the processing of ceramics and how green processing can affect the properties of ceramics; (2) investigate the technique of slip casting; (3) learn how heat treatment and temperature contribute to density, strength, and effects of under and over firing to ceramic properties; (4) experience some of the problems inherent in testing brittle materials and learn about the statistical nature of the strength of ceramics; (5) investigate orthogonal arrays as tools to examine the effect of many experimental parameters using a minimum number of experiments; (6) recognize appropriate uses for clay based ceramics; and (7) measure several different properties important to ceramic use and optimize them for a given application.

  10. Synthesis of Micro/Nano Crystalline Ceramics

    NASA Astrophysics Data System (ADS)

    Mathew, Philip; Isac, Sheelakumari; Abraham, Rosalin; Isac, Jayakumari

    2008-04-01

    As a matter of fact almost every industrial production line, office and home is dependant on ceramic materials. Newly designed devices incorporate ceramic materials because of their useful chemical, electrical, mechanical, thermal and structural properties. The effectiveness of a large system depends critically on its ceramic components. That is ceramics are important, first because they comprise a large basic industry and second because their properties are essential for many applications. Ceramics are more stable than metals both in chemical and thermal environments. In this work the authors describes a method for the preparation of PBT ceramics material from lead oxide (PbO), barium carbonate and titanium oxide based on pre-calcinations of oxides. The results were analyzed by X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and TGA. XRD and SEM studies revealed that its particle size is in nanometer range. Dielectric studies were conducted at a frequency range of 100 KHz to 13 MHz. Mechanical properties were calculated.

  11. Refractory Oxidative-Resistant Ceramic Carbon Insulation

    NASA Technical Reports Server (NTRS)

    Leiser, Daniel B. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2001-01-01

    High-temperature, lightweight, ceramic carbon insulation is prepared by coating or impregnating a porous carbon substrate with a siloxane gel derived from the reaction of an organodialkoxy silane and an organotrialkoxy silane in an acid or base medium in the presence of the carbon substrate. The siloxane gel is subsequently dried on the carbon substrate to form a ceramic carbon precursor. The carbon precursor is pyrolyzed, in an inert atmosphere, to form the ceramic insulation containing carbon, silicon, and oxygen. The carbon insulation is characterized as a porous, fibrous, carbon ceramic tile which is particularly useful as lightweight tiles for spacecraft.

  12. Low-cost shape-control synthesis of porous carbon film on β″-alumina ceramics for Na-based battery application

    NASA Astrophysics Data System (ADS)

    Hu, Yingying; Wen, Zhaoyin; Wu, Xiangwei; Jin, Jun

    2012-12-01

    Porous carbon films with tunable pore structure to modify the β″-alumina electrolyte surface are fabricated through a low-cost and direct wet chemistry method with glucose and poly(methyl-methacrylate) (PMMA) as precursors. FTIR analysis confirms the effective connection between the carbohydrate and the pore-forming agent PMMA through hydrogen bonds. The experimental results indicate that the structural parameters of the porous carbon films, including mean pore size and film thickness, can be tuned simply by adjusting the amount of PMMA in the glucose/PMMA composite. This soft-template-assisted method could be readily extended to modify any other ceramic surfaces. The porous carbon films are demonstrated to greatly improve the wettability of the β″-alumina ceramics by molten sodium. Na/β″-alumina/Na cells are used to investigate the interfacial properties between sodium and the β″-alumina electrolyte. The results obtained at 350 °C reveal that the polarization behavior of the cell is alleviated by the porous coating. This work represents a successful method to coat ceramics with porous carbon and offers a promising solution to overcome the polarization problems of the sodium/β″-alumina interface in Na-based batteries.

  13. CaO--P2O5--Na2O-based sintering additives for hydroxyapatite (HAp) ceramics.

    PubMed

    Kalita, S J; Bose, S; Hosick, H L; Bandyopadhyay, A

    2004-05-01

    We have assessed the effect of CaO--P2O5--Na2O-based sintering additives on mechanical and biological properties of hydroxyapatite (HAp) ceramics. Five different compositions of sintering additives were selected and prepared by mixing of CaO, P2O5, and Na2CO3 powders. 2.5 wt% of each additive was combined with commercial HAp powder, separately, followed by ball milling, and sintering at 1250 degrees C and 1300 degrees C in a muffle furnace. Green and sintered densities of the compacts were analyzed for the influence of additives on densification of HAp. Phase analyses were carried out using an X-ray diffractometer. Vickers microhardness testing was used to evaluate hardness of sintered compacts of different compositions. A maximum microhardness of 4.6 (+/- 0.28) GPa was attained for a composition with 2.5 wt% addition of CaO:P2O5:Na2O in the ratio of 3:3:4. Results from mechanical property evaluation showed that some of these sintering additives improved failure strength of HAp under compressive loading. Maximum compressive strength was observed for samples with 2.5 wt% addition of CaO. Average failure strength for this set of samples was calculated to be 220 (+/- 50) MPa. Cytotoxicity, and cell attachment studies were carried out using a modified human osteoblast cell line called OPC-1. In vitro results showed that these compositions were non-toxic. Some sintering aids enhanced cell attachment and proliferation, which was revealed from SEM examination of the scaffolds seeded with OPC-1 cells. PMID:14741598

  14. Optimization of La 2O 3-containing diopside based glass-ceramic sealants for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Goel, Ashutosh; Tulyaganov, Dilshat U.; Kharton, Vladislav V.; Yaremchenko, Aleksey A.; Eriksson, Sten; Ferreira, José M. F.

    We report on the optimization of La 2O 3-containing diopside based glass-ceramics (GCs) for sealant applications in solid oxide fuel cells (SOFC). Seven glass compositions were prepared by modifying the parent glass composition, Ca 0.8Ba 0.1MgAl 0.1La 0.1Si 1.9O 6. First five glasses were prepared by the addition of different amounts of B 2O 3 in a systematic manner (i.e. 2, 5, 10, 15, 20 wt.%) to the parent glass composition while the remaining two glasses were derived by substituting SrO for BaO in the glasses containing 2 wt.% and 5 wt.% B 2O 3. Structural and thermal behavior of the glasses was investigated by infrared spectroscopy (FTIR), density measurements, dilatometry and differential thermal analysis (DTA). Liquid-liquid amorphous phase separation was observed in B 2O 3-containing glasses. Sintering and crystallization behavior, microstructure, and properties of the GCs were investigated under different heat treatment conditions (800 and 850 °C; 1-300 h). The GCs with ≥5 wt.% B 2O 3 showed an abnormal thermal expansion behavior above 600 °C. The chemical interaction behavior of the glasses with SOFC electrolyte and metallic interconnects, has been investigated in air atmosphere at SOFC operating temperature. Thermal shock resistance and gas-tightness of GC sealants in contact with 8YSZ was evaluated in air and water. The total electrical resistance of a model cell comprising Crofer 22 APU and 8YSZ plates joined by a GC sealant has been examined by the impedance spectroscopy. Good matching of thermal expansion coefficients (CTE) and strong, but not reactive, adhesion to electrolyte and interconnect, in conjunction with a low level of electrical conductivity, indicate that the investigated GCs are suitable candidates for further experimentation as SOFC sealants.

  15. Multiferroic properties of modified BiFe O3 -PbTi O3 -based ceramics: Random-field induced release of latent magnetization and polarization

    NASA Astrophysics Data System (ADS)

    Wang, Naigang; Cheng, J.; Pyatakov, A.; Zvezdin, A. K.; Li, J. F.; Cross, L. E.; Viehland, D.

    2005-09-01

    It has been found that aliovalent-substituted BiFeO3-PbTiO3 -based polycrystalline materials have significantly enhanced multiferroic properties. Relative to unmodified BiFeO3 , our results for modified BiFeO3-PbTiO3 -based ceramics reveal: (i) a dramatic increase in the electric-field-induced polarization; and (ii) the establishment of a remanent magnetization. The results evidence the destruction of a space-modulated spin structure in bulk materials, via substituent effects, releasing a latent magnetization locked within the cycloid.

  16. Next-generation resorbable polymer scaffolds with surface-precipitated calcium phosphate coatings

    PubMed Central

    Kim, Jinku; Magno, Maria Hanshella R.; Ortiz, Ophir; McBride, Sean; Darr, Aniq; Kohn, Joachim; Hollinger, Jeffrey O.

    2015-01-01

    Next-generation synthetic bone graft therapies will most likely be composed of resorbable polymers in combination with bioactive components. In this article, we continue our exploration of E1001(1k), a tyrosine-derived polycarbonate, as an orthopedic implant material. Specifically, we use E1001(1k), which is degradable, nontoxic, and osteoconductive, to fabricate porous bone regeneration scaffolds that were enhanced by two different types of calcium phosphate (CP) coatings: in one case, pure dicalcium phosphate dihydrate was precipitated on the scaffold surface and throughout its porous structure (E1001(1k) + CP). In the other case, bone matrix minerals (BMM) such as zinc, manganese and fluoride were co-precipitated within the dicalcium phosphate dihydrate coating (E1001(1k) + BMM). These scaffold compositions were compared against each other and against ChronOS (Synthes USA, West Chester, PA, USA), a clinically used bone graft substitute (BGS), which served as the positive control in our experimental design. This BGS is composed of poly(lactide co-ε-caprolactone) and beta-tricalcium phosphate. We used the established rabbit calvaria critical-sized defect model to determine bone regeneration within the defect for each of the three scaffold compositions. New bone formation was determined after 2, 4, 6, 8 and 12 weeks by micro-computerized tomography (μCT) and histology. The experimental tyrosine-derived polycarbonate, enhanced with dicalcium phosphate dihydrate, E1001(1k) + CP, supported significant bone formation within the defects and was superior to the same scaffold containing a mix of BMM, E1001(1k) + BMM. The comparison with the commercially available BGS was complicated by the large variability in bone formation observed for the laboratory preparations of E1001(1k) scaffolds. At all time points, there was a trend for E1001(1k) + CP to be superior to the commercial BGS. However, only at the 6-week time point did this trend reach statistical significance

  17. FOREWORD: Focus on Advanced Ceramics Focus on Advanced Ceramics

    NASA Astrophysics Data System (ADS)

    Ohashi, Naoki

    2011-06-01

    Much research has been devoted recently to developing technologies for renewable energy and improving the efficiency of the processes and devices used in industry and everyday life. Efficient solutions have been found using novel materials such as platinum and palladium-based catalysts for car exhaust systems, samarium-cobalt and neodymium-iron-boron permanent magnets for electrical motors, and so on. However, their realization has resulted in an increasing demand for rare elements and in their deficit, the development of new materials based on more abundant elements and new functionalities of traditional materials. Moreover, increasing environmental and health concerns demand substitution of toxic or hazardous substances with nature-friendly alternatives. In this context, this focus issue on advanced ceramics aims to review current trends in ceramics science and technology. It is related to the International Conference on Science and Technology of Advanced Ceramics (STAC) held annually to discuss the emerging issues in the field of ceramics. An important direction of ceramic science is the collaboration between experimental and theoretical sciences. Recent developments in density functional theory and computer technology have enabled the prediction of physical and chemical properties of ceramics, thereby assisting the design of new materials. Therefore, this focus issue includes articles devoted to theory and advanced characterization techniques. As mentioned above, the potential shortage of rare elements is becoming critical to the industry and has resulted in a Japanese government initiative called the 'Ubiquitous Element Strategy'. This focus issue also includes articles related to this strategy and to the associated topics of energy conversion, such as phosphors for high-efficiency lighting and photocatalysts for solar-energy harvesting. We hope that this focus issue will provide a timely overview of current trends and problems in ceramics science and

  18. A water-based Al2O3 ceramic coating for polyethylene-based microporous separators for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Jeon, Hyunkyu; Yeon, Daeyong; Lee, Taejoo; Park, Joonam; Ryou, Myung-Hyun; Lee, Yong Min

    2016-05-01

    To develop an environmentally friendly and cost-effective water-based inorganic coating process for hydrophobic, polyolefin-based microporous separators, the effect of surfactants in an aqueous inorganic coating solution comprising alumina (Al2O3) on polyethylene (PE)-based microporous separators is investigated. By using a selected surfactant, i.e., disodium laureth sulfosuccinate (DLSS), the aqueous Al2O3 coating solution maintained a dispersed state over time and facilitated the formation of a uniform Al2O3 coating layer on PE separator surfaces. Due to the hydrophilic nature of the Al2O3 coating layers, the as-prepared, ceramic-coated PE separators had better wetting properties, greater electrolyte uptake, and larger ionic conductivities compared to those of the bare PE separators. Furthermore, half cells (LiMn2O4/Li metal) containing Al2O3-coated PE separators showed improved capacity retention over several cycles (93.6% retention after 400 cycles for Al2O3 coated PE separators, compared to 89.2% for bare PE separators operated at C/2) and rate capability compared to those containing bare PE separators. Moreover, because the Al2O3-coated layers are more thermally stable, the coated separators had improved dimensional stability at high temperatures (140 °C).

  19. Localized committed differentiation of neural stem cells based on the topographical regulation effects of TiO2 nanostructured ceramics.

    PubMed

    Mou, Xiaoning; Wang, Shu; Guo, Weibo; Ji, Shaozheng; Qiu, Jichuan; Li, Deshuai; Zhang, Xiaodi; Zhou, Jin; Tang, Wei; Wang, Changyong; Liu, Hong

    2016-07-21

    In this study, a porous-flat TiO2 micropattern was fabricated with flat and nanoporous TiO2 ceramics for investigating the effect of topography on neural stem cell (NSC) differentiation. This finding demonstrates that localized committed differentiation could be achieved in one system by integrating materials with different topographies. PMID:27346410

  20. Ceramics: Automobile industry. January 1980-March 1992 (Citations from the NTIS Data Base). Rept. for Jan 80-Mar 92

    SciTech Connect

    Not Available

    1992-02-01

    The bibliography contains citations concerning manufacturing processes, testing, design, and stress analysis of ceramics used in the automobile industry. Manufacturing processes discussed include slip casting, reaction sintering, hot isostatic pressing and plasma spraying. (Contains 153 citations with title list and subject index.)

  1. The Prediction and Simulation for the Mechanical Properties of Ceramic-Based Composites Reinforced with Nano-Micro Particles

    SciTech Connect

    Luo Dongmei; Hu Jinshan; Yang Hong; Zhou Yinglong

    2010-05-21

    The global-local homogenization method with precise period boundary conditions is applied to predict and simulate the mechanical properties of ceramic composites reinforced by spherical nano-micro particles with enwrapping and nesting arrays. The numerical simulation is performed with different size ratios of nano-micro particles, and different configurations for representative volume element. The results show that the low radius ratios of nano-micro particles produce a larger effective Young's modulus for its more uniform dispersion, and the hexagon RVE with nesting array can make an overestimation for effective elastic modulus of ceramic composites, and the interfacial damage between nano-microscopic particles and matrix degenerates the effective elastic modulus. It shows in this paper that it is significant to improve the mechanical properties of ceramic materials by mixing some nano- and micro-particles into the matrix with good designed array methods from the viewpoints of nano-microscopic crystal structure, and a rational interfacial damage model should be further proposed to investigate the toughening mechanism of ceramic-composites reinforced with nano-micro particles.

  2. Strains and polarization developed during electric field-induced antiferroelectric to ferroelectric phase transformations in lead zirconate-based ceramics

    NASA Astrophysics Data System (ADS)

    Frederick, Joshua

    .060 were observed to increase the critical field magnitude necessary to induce the ferroelectric phase, but the manners in which they suppressed the phase transformation were distinctively different. Axial pre-stresses resulted in an abrupt, uniform suppression while radial pre-stresses caused a gradual, non-uniform suppression of the phase transformation. The results were interpreted based on different textures in the ceramic developed by each pre-stress condition. In the absence of mechanical confinement, the induced ferroelectric phase in compositions y ≥ 0.069 became metastable and the ferroelectric-to-antiferroelectric phase transformation did not occur during the unloading of the applied field. This reverse phase transformation occurred partially when electric fields with reversed polarity were applied, though the extent of the antiferroelectric phase recovered diminished with increasing titanium content. Through the use of in-situ X-ray diffraction, an electric field-induced ferroelectric-to-antiferroelectric phase transformation was confirmed for the first time.

  3. Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

    NASA Technical Reports Server (NTRS)

    Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

    2001-01-01

    A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

  4. Method for thermally spraying crack-free mullite coatings on ceramic-based substrates

    NASA Technical Reports Server (NTRS)

    Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Heidorn, Raymond W. (Inventor)

    2000-01-01

    A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

  5. Roles of Poly(propylene Glycol) During Solvent-Based Lamination of Ceramic Green Tapes

    NASA Technical Reports Server (NTRS)

    Suppakarn, Nitinat; Ishida, Hatsuo; Cawley, James D.; Levine, Stanley R. (Technical Monitor)

    2000-01-01

    Solvent lamination for alumina green tapes is readily accomplished using a mixture of ethanol, toluene and poly(propylene glycol). After lamination, the PPG is clearly present as a discrete film at the interface between the laminated tapes. This condition, however, does not generate delamination during firing. Systematic sets of experiments are undertaken to determine the role of PPG in the lamination process and, specifically, the mechanism by which it is redistributed during subsequent processing. PPG slowly diffuses through the organic binder film at room temperature. The PPG diffusion rapidly increases as temperature is increased to 80 C. The key to the efficiency of adhesives during green-tape lamination is mutual solubility of the nonvolatile component of the glue and the base polymeric binder.

  6. Thermodynamics of solid electrolytes and related oxide ceramics based on the fluorite structure

    SciTech Connect

    Navrotsky, Alexandra

    2010-01-01

    Oxides based on the fluorite structure are important as electrolytes in solid oxide fuel cells, thermal barrier coatings, gate dielectrics, catalysts, and nuclear materials. Though the parent fluorite structure is simple, the substitution of trivalent for tetravalent cations, coupled with the presence of charge-balancing oxygen vacancies, leads to a wealth of short-range and long-range ordered structures and complex thermodynamic properties. The location of vacancies and the nature of clusters affect the energetics of mixing in rare earth doped zirconia, hafnia, ceria, urania, and thoria, with systematic trends in energetics as a function of cation radius. High temperature oxide melt solution calorimetry has provided direct measurement of formation enthalpies of these refractory materials. Surface and interfacial energies have also been measured in yttria stabilized zirconia (YSZ) nanomaterials. Other ionic conductors having perovskite, apatite, and mellilite structures are discussed briefly.

  7. A method based on infrared detection for determining the moisture content of ceramic plaster materials.

    PubMed

    Macias-Melo, E V; Aguilar-Castro, K M; Alvarez-Lemus, M A; Flores-Prieto, J J

    2015-09-01

    In this work, we describe a methodology for developing a mathematical model based on infrared (IR) detection to determine the moisture content (M) in solid samples. For this purpose, an experimental setup was designed, developed and calibrated against the gravimetric method. The experimental arrangement allowed for the simultaneous measurement of M and the electromotive force (EMF), fitting the experimental variables as much as possible. These variables were correlated by a mathematical model, and the obtained correlation was M=1.12×exp(3.47×EMF), ±2.54%. This finding suggests that it is feasible to measure the moisture content when it has greater values than 2.54%. The proposed methodology could be used for different conditions of temperature, relative humidity and drying rates to evaluate the influence of these variables on the amount of energy received by the IR detector. PMID:25887842

  8. Sodium potassium niobate-based lead-free piezoelectric ceramics: Bulk and freestanding thick films

    NASA Astrophysics Data System (ADS)

    Li, Huidong

    2008-10-01

    Due to the toxicity of lead, there is an urgent need to develop lead-free alternatives to replace the currently dominant lead-based piezoelectrics such as lead zirconate titanate (PZT). (Na0.5K0.5)NbO 3 (NKN)-based piezoelectrics are promising because of their relatively high Curie temperatures and piezoelectric coefficients among the non-lead piezoelectrics. However, it is difficult to sinter. In this thesis study, a colloidal coating method was developed to improve the sintering of NKN. With this coating method, NKN with good piezoelectric properties can be produced without cold isostatic pressing. To improve the piezoelectric performance of NKN, we performed antimony (Sb) doping studies for a NKN-LN solid solution using the coating approach. It was found that Sb doping greatly improved the density and the piezoelectric properties of the NKN-LiNbO3 solid solution and optimized performance was found at 4%Sb. The reasons for the improved piezoelectric properties and density were discussed. Recently, a large enhancement in the piezoelectric performance under electric fields was discovered in polycrystalline lead magnesium niobate-lead titanate (PMN-PT) when the material was made into freestanding film geometry. Here, for the first time, we show a similar effect was also observed in a lead-free system, (Na0.5K0.5)0.945Li0.055Nb 0.96Sb0.04O3. At 6-8 kV/cm, a giant --d 31 value of 1700 pm/V was achieved, 20 times higher than the value of bulk counterpart. The enhancement was found to result from the ease of domain motion imparted by the freestanding film geometry, and the magnitude of the enhancement can be affected by the electrode layer (a non-piezoelectric) thickness. The freestanding geometry provides a new approach to greatly improve the piezoelectric performance of the current lead-free systems.

  9. Ceramic technology for Advanced Heat Engines Project

    SciTech Connect

    Johnson, D.R.

    1991-07-01

    Significant accomplishments in fabricating ceramic components for advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and database and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. An assessment of needs was completed, and a five year project plan was developed with extensive input from private industry. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities. This project is managed by ORNL for the Office of Transportation Technologies, Office of Transportation Materials, and is closely coordinated with complementary ceramics tasks funded by other DOE offices, NASA, DOD, and industry.

  10. Development of Novel Polycrystalline Ceramic Scintillators

    SciTech Connect

    Wisniewska, Monika; Boatner, Lynn A; Neal, John S; Jellison Jr, Gerald Earle; Ramey, Joanne Oxendine; North, Andrea L; Wisniewski, Monica; Payzant, E Andrew; Howe, Jane Y; Lempicki, Aleksander; Brecher, Charlie; Glodo, J.

    2008-01-01

    For several decades most of the efforts to develop new scintillator materials have concentrated on high-light-yield inorganic single-crystals while polycrystalline ceramic scintillators, since their inception in the early 1980 s, have received relatively little attention. Nevertheless, transparent ceramics offer a promising approach to the fabrication of relatively inexpensive scintillators via a simple mechanical compaction and annealing process that eliminates single-crystal growth. Until recently, commonly accepted concepts restricted the polycrystalline ceramic approach to materials exhibiting a cubic crystal structure. Here, we report our results on the development of two novel ceramic scintillators based on the non-cubic crystalline materials: Lu SiO:Ce (LSO:Ce) and LaBr:Ce. While no evidence for texturing has been found in their ceramic microstructures, our LSO:Ce ceramics exhibit a surprisingly high level of transparency/ translucency and very good scintillation characteristics. The LSO:Ce ceramic scintillation reaches a light yield level of about 86% of that of a good LSO:Ce single crystal, and its decay time is even faster than in single crystals. Research on LaBr:Ce shows that translucent ceramics of the high-light-yield rare-earth halides can also be synthesized. Our LaBr:Ce ceramics have light yields above 42 000 photons/MeV (i.e., 70%of the single-crystal light yield).

  11. Structure and properties of the ceramics based on quasicrystal powders processed by plasma coating method

    NASA Astrophysics Data System (ADS)

    Ekimov, E. A.; Ivanov, A. S.; Pal, A. F.; Petrzhik, M. I.; Ryabinkin, A. N.; Serov, A. O.

    2015-11-01

    Homogeneous incorporation of a small amount of binding material or modifying agent in the batch consisting of micron size particles is a problem of a composite material production process. In this work the problem is solved by deposition of a thin coating consisting of binding material on the initial powder particles by means of high-rate magnetron sputtering. The confinement of dusty particles in plasma was used in fine powder processing procedure. Composite powders based on the Al-Cu-Fe quasicrystalline particles with nickel coating were obtained. Their investigation showed that the method provides uniform incorporation of small quantities of additives (at concentration of about 3 wt. %) to fine powders. The powders were pressed at room temperature under quasi-hydrostatic conditions at high pressures. After pressing the samples were sintered in hydrogen at normal pressure. Structure and mechanical properties of the sintered samples were studied. The conditions of sintering the composite powder, which provide producing compacts with improved performance data, were established.

  12. Surgical Management of Oro-Antral Communications Using Resorbable GTR Membrane and FDMB Sandwich Technique: A Clinical Study.

    PubMed

    Sandhya, G; Reddy, P Bal; Kumar, K A Jeevan; Sridhar Reddy, B; Prasad, N; Kiran, G

    2013-09-01

    The paper describes a new technique for closure of the oro-antral communication, in which both hard (bone) and soft tissue closure was achieved. The technique uses a Guided Tissue Regeeration (GTR) membrane and Freez Dried Mineralized Bone (FDMB) allograft for closure of the defect. Aim of the study was to assess the advantages of the surgical management of oro-antral communications using resorbable GTR membrane and FDMB sandwich technique. A total 10 patients were selected in whom dental extractions were complicated by formation of oro-antral communication (OAC). The resorbable guided tissue regeneration membrane (PERIOCOL-GTR) and freeze dried mineralized bone allograft material was used. Some cancellous granules of freeze dried bone allograft was sandwiched between sheaths of appropriately trimmed collagen membrane which was previously sutured together on three sides using 3/0 resorbable polyglycolic acid suture (vicryl). The fourth side was then adequately closed using the same suture after the bone graft had been inserted, thus creating a closed sandwich. The prepared sandwich was then tucked into the OAC in such a way that it formed a convexity towards the sinus and a concavity towards the alveolar bone. The rough surface of the sandwich is faced to the alveolar bone and additional bone graft is filled into this concavity. Suturing done without tension. Post-operative orthopantomogram was taken to radiologically quantify the amount of bone grafting/augmentation and closure of oro-antral fistula. There was an average of 11.84 mm bone formation after 6 months, the average width preserved and obtained was 6.9 mm. By the end of 4 months there was evidence of bone formation in 7 subjects and in three subjects bony trabeculae formed was almost similar to the adjacent bone. By the end of 6 months follow-up of 7 subjects showed trabeculae indistinguishable from the adjacent bone. The study was done in 10 patients with a follow-up period of 6 months and found to

  13. Nano-Ceramic Coated Plastics

    NASA Technical Reports Server (NTRS)

    Cho, Junghyun

    2013-01-01

    Plastic products, due to their durability, safety, and low manufacturing cost, are now rapidly replacing cookware items traditionally made of glass and ceramics. Despite this trend, some still prefer relatively expensive and more fragile ceramic/glassware because plastics can deteriorate over time after exposure to foods, which can generate odors, bad appearance, and/or color change. Nano-ceramic coatings can eliminate these drawbacks while still retaining the advantages of the plastic, since the coating only alters the surface of the plastic. The surface coating adds functionality to the plastics such as self-cleaning and disinfectant capabilities that result from a photocatalytic effect of certain ceramic systems. These ceramic coatings can also provide non-stick surfaces and higher temperature capabilities for the base plastics without resorting to ceramic or glass materials. Titanium dioxide (TiO2) and zinc oxide (ZnO) are the candidates for a nano-ceramic coating to deposit on the plastics or plastic films used in cookware and kitchenware. Both are wide-bandgap semiconductors (3.0 to 3.2 eV for TiO2 and 3.2 to 3.3 eV for ZnO), so they exhibit a photocatalytic property under ultraviolet (UV) light. This will lead to decomposition of organic compounds. Decomposed products can be easily washed off by water, so the use of detergents will be minimal. High-crystalline film with large surface area for the reaction is essential to guarantee good photocatalytic performance of these oxides. Low-temperature processing (<100 C) is also a key to generating these ceramic coatings on the plastics. One possible way of processing nanoceramic coatings at low temperatures (< 90 C) is to take advantage of in-situ precipitated nanoparticles and nanostructures grown from aqueous solution. These nanostructures can be tailored to ceramic film formation and the subsequent microstructure development. In addition, the process provides environment- friendly processing because of the

  14. Pediatric craniofacial osteosynthesis and distraction using an ultrasonic-assisted pinned resorbable system: a prospective report with a minimum 30 months' follow-up.

    PubMed

    Arnaud, Eric; Renier, Dominique

    2009-11-01

    Resorbable osteosynthesis is an important tool in pediatric craniofacial surgery. A prospective clinical study was carried out to evaluate the Sonic Welding resorbable osteosynthesis system. Twenty pediatric patients with craniosynostosis were operated on for craniofacial reconstruction. The techniques used were the same than usual (fronto-orbital remodeling or advancement). During the process of osteosynthesis, similar resorbable miniplates were used, but for fixation, only 2 steps were necessary (drilling and welding), tapping being unnecessary. Clinically, the hold of the pins in the bone seemed stronger, and less-than-usual osteosynthesis materials were necessary. Clearly, the pins were able to hold in a very thin bone in which no screws could hold. Subjectively, the satisfaction of the surgeon was greater owing to the avoidance of the tapping step. On follow-up, resorption took place with an initial swelling effect, like with another pure polylactic acid material. The good resistance of pins suggests that, in such a system, the resorbable plate becomes the weak point. PMID:19881368

  15. Ceramic inspection system

    DOEpatents

    Werve, Michael E.

    2006-05-16

    A system for inspecting a ceramic component. The ceramic component is positioned on a first rotary table. The first rotary table rotates the ceramic component. Light is directed toward the first rotary table and the rotating ceramic component. A detector is located on a second rotary table. The second rotary table is operably connected to the first rotary table and the rotating ceramic component. The second rotary table is used to move the detector at an angle to the first rotary table and the rotating ceramic component.

  16. Glass Ceramic Formulation Data Package

    SciTech Connect

    Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

    2012-06-17

    A glass ceramic waste form is being developed for treatment of secondary waste streams generated by aqueous reprocessing of commercial used nuclear fuel (Crum et al. 2012b). The waste stream contains a mixture of transition metals, alkali, alkaline earths, and lanthanides, several of which exceed the solubility limits of a single phase borosilicate glass (Crum et al. 2009; Caurant et al. 2007). A multi-phase glass ceramic waste form allows incorporation of insoluble components of the waste by designed crystallization into durable heat tolerant phases. The glass ceramic formulation and processing targets the formation of the following three stable crystalline phases: (1) powellite (XMoO4) where X can be (Ca, Sr, Ba, and/or Ln), (2) oxyapatite Yx,Z(10-x)Si6O26 where Y is alkaline earth, Z is Ln, and (3) lanthanide borosilicate (Ln5BSi2O13). These three phases incorporate the waste components that are above the solubility limit of a single-phase borosilicate glass. The glass ceramic is designed to be a single phase melt, just like a borosilicate glass, and then crystallize upon slow cooling to form the targeted phases. The slow cooling schedule is based on the centerline cooling profile of a 2 foot diameter canister such as the Hanford High-Level Waste canister. Up to this point, crucible testing has been used for glass ceramic development, with cold crucible induction melter (CCIM) targeted as the ultimate processing technology for the waste form. Idaho National Laboratory (INL) will conduct a scaled CCIM test in FY2012 with a glass ceramic to demonstrate the processing behavior. This Data Package documents the laboratory studies of the glass ceramic composition to support the CCIM test. Pacific Northwest National Laboratory (PNNL) measured melt viscosity, electrical conductivity, and crystallization behavior upon cooling to identify a processing window (temperature range) for melter operation and cooling profiles necessary to crystallize the targeted phases in the

  17. Tailored ceramics for laser applications

    NASA Astrophysics Data System (ADS)

    Hollingsworth, Joel Philip

    Transparent ceramics have many features that recommend them over single crystals for use as laser amplifiers. Some features, such as greater mechanical toughness and an absence of extended crystalline defects, are intrinsic to polycrystalline materials. Other advantages accrue from ceramic processing: ceramics sinter more rapidly than crystals grow from a melt, at lower temperatures. Ceramic processes are more readily scaled than Czochralski growth, facilitating larger apertures. Unlike a uniform melt, a ceramic green structure can have controlled concentration gradients, resulting in a multifunctional device upon sintering. Identifying diffusion mechanisms in a suitable host material and quantifying diffusion for a dopant with appropriate energy levels are key steps toward tailoring laser ceramics to the specifications of device designers. Toward that end, this study was the first to identify the mechanism and rate of Nd diffusion in YAG. Grain boundary diffusion was shown to dominate Nd transport under conditions relevant to laser ceramics fabrication. Based on a definition of grain boundary width as 1 A, this process occurs at a rate of DGB = 6.4 x 105 +/- 2.0 x 105 exp(-491 +/- 64 kJ/(mol K))m 2/s. Mechanism identification and the first published kinetics measurement were made possible by the introduction of a heat treatment method that isolates microstructural change from dopant diffusion: the concentration of grain boundaries was kept great enough to allow rapid diffusion, but low enough to limit the driving force for coarsening. Sintering of fine-grained and phase-pure precursor powder for 4 min at 1700 °C produced 0.8 mum grains; subsequent diffusion heat treatments at up to 1650 °C for up to 64 h caused negligible coarsening, while achieving diffusion distances of up to 23 mum.

  18. Randomized, Controlled Clinical Trial of Bilayer Ceramic and Metal-Ceramic Crown Performance

    PubMed Central

    Esquivel-Upshaw, Josephine; Rose, William; Oliveira, Erica; Yang, Mark; Clark, Arthur E.; Anusavice, Kenneth

    2013-01-01

    Purpose Analyzing the clinical performance of restorative materials is important, as there is an expectation that these materials and procedures will restore teeth and do no harm. The objective of this research study was to characterize the clinical performance of metal-ceramic crowns, core ceramic crowns, and core ceramic/veneer ceramic crowns based on 11 clinical criteria. Materials and Methods An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study. The following three types of full crowns were fabricated: (1) metal-ceramic crown (MC) made from a Pd-Au-Ag-Sn-In alloy (Argedent 62) and a glass-ceramic veneer (IPS d.SIGN veneer); (2) non-veneered (glazed) lithium disilicate glass-ceramic crown (LDC) (IPS e.max Press core and e.max Ceram Glaze); and (3) veneered lithia disilicate glass-ceramic crown (LDC/V) with glass-ceramic veneer (IPS Empress 2 core and IPS Eris). Single-unit crowns were randomly assigned. Patients were recalled for each of 3 years and were evaluated by two calibrated clinicians. Thirty-six crowns were placed in 31 patients. A total of 12 crowns of each of the three crown types were studied. Eleven criteria were evaluated: tissue health, marginal integrity, secondary caries, proximal contact, anatomic contour, occlusion, surface texture, cracks/chips (fractures), color match, tooth sensitivity, and wear (of crowns and opposing enamel). Numerical rankings ranged from 1 to 4, with 4 being excellent, and 1 indicating a need for immediate replacement. Statistical analysis of the numerical rankings was performed using a Fisher’s exact test. Results There was no statistically significant difference between performance of the core ceramic crowns and the two veneered crowns at year 1 and year 2 (p > 0.05). All crowns were rated either as excellent or good for each of the clinical criteria; however, between years 2 and 3, gradual roughening of the occlusal surface occurred in some of the ceramic-ceramic crowns

  19. Localized committed differentiation of neural stem cells based on the topographical regulation effects of TiO2 nanostructured ceramics

    NASA Astrophysics Data System (ADS)

    Mou, Xiaoning; Wang, Shu; Guo, Weibo; Ji, Shaozheng; Qiu, Jichuan; Li, Deshuai; Zhang, Xiaodi; Zhou, Jin; Tang, Wei; Wang, Changyong; Liu, Hong

    2016-07-01

    In this study, a porous-flat TiO2 micropattern was fabricated with flat and nanoporous TiO2 ceramics for investigating the effect of topography on neural stem cell (NSC) differentiation. This finding demonstrates that localized committed differentiation could be achieved in one system by integrating materials with different topographies.In this study, a porous-flat TiO2 micropattern was fabricated with flat and nanoporous TiO2 ceramics for investigating the effect of topography on neural stem cell (NSC) differentiation. This finding demonstrates that localized committed differentiation could be achieved in one system by integrating materials with different topographies. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01874b

  20. A High Temperature Capacitive Pressure Sensor Based on Alumina Ceramic for in Situ Measurement at 600 °C

    PubMed Central

    Tan, Qiulin; Li, Chen; Xiong, Jijun; Jia, Pinggang; Zhang, Wendong; Liu, Jun; Xue, Chenyang; Hong, Yingping; Ren, Zhong; Luo, Tao

    2014-01-01

    In response to the growing demand for in situ measurement of pressure in high-temperature environments, a high temperature capacitive pressure sensor is presented in this paper. A high-temperature ceramic material-alumina is used for the fabrication of the sensor, and the prototype sensor consists of an inductance, a variable capacitance, and a sealed cavity integrated in the alumina ceramic substrate using a thick-film integrated technology. The experimental results show that the proposed sensor has stability at 850 °C for more than 20 min. The characterization in high-temperature and pressure environments successfully demonstrated sensing capabilities for pressure from 1 to 5 bar up to 600 °C, limited by the sensor test setup. At 600 °C, the sensor achieves a linear characteristic response, and the repeatability error, hysteresis error and zero-point drift of the sensor are 8.3%, 5.05% and 1%, respectively. PMID:24487624

  1. Evaluation of sol-gel based magnetic 45S5 bioglass and bioglass-ceramics containing iron oxide.

    PubMed

    Shankhwar, Nisha; Srinivasan, A

    2016-05-01

    Multicomponent oxide powders with nominal compositions of (45-x)·SiO2·24.5CaO·24.5Na2O·6P2O5xFe2O3 (in wt.%) were prepared by a modified sol-gel procedure. X-ray diffraction (XRD) patterns and high resolution transmission electron microscope images of the sol-gel products show fully amorphous structure for Fe2O3 substitutions up to 2 wt.%. Sol-gel derived 43SiO2·24.5CaO·24.5Na2O·6P2O5·2Fe2O3 glass (or bioglass 45S5 with SiO2 substituted with 2 wt.% Fe2O3), exhibited magnetic behavior with a coercive field of 21 Oe, hysteresis loop area of 33.25 erg/g and saturation magnetization of 0.66 emu/g at an applied field of 15 kOe at room temperature. XRD pattern of this glass annealed at 850 °C for 1h revealed the formation of a glass-ceramic containing sodium calcium silicate and magnetite phases in nanocrystalline form. Temperature dependent magnetization and room temperature electron spin resonance data have been used to obtain information on the magnetic phase and distribution of iron ions in the sol-gel glass and glass-ceramic samples. Sol-gel derived glass and glass-ceramic exhibit in-vitro bioactivity by forming a hydroxyapatite surface layer under simulated physiological conditions and their bio-response is superior to their melt quenched bulk counterparts. This new form of magnetic bioglass and bioglass ceramics opens up new and more effective biomedical applications. PMID:26952414

  2. Crystallization and Properties of Strontium Barium Niobate-Based Glass-Ceramics for Energy-Storage Applications

    NASA Astrophysics Data System (ADS)

    Tang, Linjiang; Wang, Wei; Shen, Bo; Zhai, Jiwei; Kong, Ling Bing

    2014-09-01

    The crystallization kinetics, phase development, and electric properties of Al2O3-SiO2-SrO-BaO-Nb2O5-ZnO glass-ceramics were investigated for potential application of the materials for energy storage. Strontium barium niobate (Ba x Sr1-x Nb2O6) with the tetragonal tungsten-bronze structure was the major crystalline phase formed by both surface and bulk crystallization. The presence of ZnO made the glasses less stable, and thus promoted their crystallization, but had no significant effect on the microstructure of the resulting glass-ceramics. All glass-ceramic samples had a uniform microstructure, with a crystal size of approximately 50 nm. Optimized energy storage density of approximately 6.0 J/cm3 was achieved for the sample containing 0.5% ZnO; the average dielectric constant was 150-180 and the breakdown strength was 950-870 kV/cm over the temperature range 850-950°C.

  3. Crystallization and Properties of Strontium Barium Niobate-Based Glass-Ceramics for Energy-Storage Applications

    NASA Astrophysics Data System (ADS)

    Tang, Linjiang; Wang, Wei; Shen, Bo; Zhai, Jiwei; Kong, Ling Bing

    2015-01-01

    The crystallization kinetics, phase development, and electric properties of Al2O3-SiO2-SrO-BaO-Nb2O5-ZnO glass-ceramics were investigated for potential application of the materials for energy storage. Strontium barium niobate (Ba x Sr1- x Nb2O6) with the tetragonal tungsten-bronze structure was the major crystalline phase formed by both surface and bulk crystallization. The presence of ZnO made the glasses less stable, and thus promoted their crystallization, but had no significant effect on the microstructure of the resulting glass-ceramics. All glass-ceramic samples had a uniform microstructure, with a crystal size of approximately 50 nm. Optimized energy storage density of approximately 6.0 J/cm3 was achieved for the sample containing 0.5% ZnO; the average dielectric constant was 150-180 and the breakdown strength was 950-870 kV/cm over the temperature range 850-950°C.

  4. Tribology of ceramics: Report of the Committee on Tribology of Ceramics

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The current state of knowledge of ceramic surface structures, composition, and reactivity is reviewed. The tribological requirements of advanced mechanical systems now being deployed (in particular, heat engines) exceed the capabilities of traditional metallic-based materials because of the high temperatures encountered. Advanced ceramic materials for such applications are receiving intense scrutiny, but there is a lack of understanding of the properties and behavior of ceramic surfaces and the influence of processing on the properties of ceramics is described. The adequacy of models, ranging form atomic to macro, to describe and to predict ceramic friction and wear are discussed, as well as what is known about lubrication at elevated temperatures. From this analysis, recommendations are made for coordination, research, and development that will lead to better performance of ceramic materials in tribological systems.

  5. Joining Ceramics By Brazing

    NASA Technical Reports Server (NTRS)

    Chiaramonte, Francis P.; Sudsina, Michael W.

    1992-01-01

    Certain ceramic materials tightly bond together by brazing with suitable alloys. Enables fabrication of parts of wide variety of shapes from smaller initial pieces of ceramics produced directly in only limited variety of shapes.

  6. TCP is hardly resorbed and not osteoconductive in a non-loading calvarial model.

    PubMed

    Handschel, Jörg; Wiesmann, Hans Peter; Stratmann, Udo; Kleinheinz, Johannes; Meyer, Ulrich; Joos, Ulrich

    2002-04-01

    Tricalciumphosphate (TCP) has been used as a ceramic bone substitute material in the orthopedic field as well as in craniofacial surgery. Some controversies exist concerning the osteoconductive potential of this material in different implantation sites. This study was designed to evaluate the biological response of calvarial bone towards TCP granules under non-loading conditions to assess the potential of TCP as a biodegredable and osteoconductive bone substitue material for the cranial vault. Full-thickness non-critical size defects were made bilaterally in the calvaria of 21 adult Wistar rats. One side was filled by TCP granules, the contralateral side was left empty and used as a control. Animals were sacrified in defined time intervals up to 6 months. Bone regeneration was analyzed with special respect toward the micromorphological and microanalytical features of the material-bone interaction by electron microscopy and electron diffraction analysis. Histologic examination revealed no TCP degradation even after 6 months of implantation. In contrast, a nearly complete bone regeneration of control defects was found after 6 months. At all times TCP was surrounded by a thin fibrous layer without presence of osteoblasts and features of regular mineralization. As far as degradation and substitution are concerned, TCP is a less favourable material tinder conditions of non-loading. PMID:11922472

  7. Ceramic electrolyte coating methods

    DOEpatents

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2004-10-12

    Processes for preparing aqueous suspensions of a nanoscale ceramic electrolyte material such as yttrium-stabilized zirconia. The invention also includes a process for preparing an aqueous coating slurry of a nanoscale ceramic electrolyte material. The invention further includes a process for depositing an aqueous spray coating slurry including a ceramic electrolyte material on pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  8. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.

    1995-02-01

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.

  9. Process for making ceramic insulation

    DOEpatents

    Akash, Akash; Balakrishnan, G. Nair

    2009-12-08

    A method is provided for producing insulation materials and insulation for high temperature applications using novel castable and powder-based ceramics. The ceramic components produced using the proposed process offers (i) a fine porosity (from nano-to micro scale); (ii) a superior strength-to-weight ratio; and (iii) flexibility in designing multilayered features offering multifunctionality which will increase the service lifetime of insulation and refractory components used in the solid oxide fuel cell, direct carbon fuel cell, furnace, metal melting, glass, chemical, paper/pulp, automobile, industrial heating, coal, and power generation industries. Further, the ceramic components made using this method may have net-shape and/or net-size advantages with minimum post machining requirements.

  10. Ceramic Foams for TPS Applications

    NASA Technical Reports Server (NTRS)

    Stockpoole, Mairead

    2003-01-01

    Ceramic foams have potential in many areas of Thermal Protection Systems (TPS) including acreage and tile leading edges as well as being suitable as a repair approach for re-entry vehicles. NASA Ames is conducting ongoing research in developing lower-density foams from pre-ceramic polymer routes. One of the key factors to investigate, when developing new materials for re-entry applications, is their oxidation behavior in the appropriate re-entry environment which can be simulated using ground based arc jet (plasma jet) testing. Arc jet testing is required to provide the appropriate conditions (stagnation pressures, heat fluxes, enthalpies, heat loads and atmospheres) encountered during flight. This work looks at the response of ceramic foams (Si systems) exposed to simulated reentry environments and investigates the influence of microstructure and composition on the material? response. Other foam properties (mechanical and thermal) will also be presented.

  11. In-situ fabricated TiB2 particle-whisker synergistically toughened Ti(C, N)-based ceramic cutting tool material

    NASA Astrophysics Data System (ADS)

    Liu, Hanlian; Shi, Qiang; Huang, Chuanzhen; Zou, Bin; Xu, Liang; Wang, Jun

    2015-03-01

    The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers. However, the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration; although a new in-situ two-step sintering process can solve the above problems to some extent, yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process. In this paper, an in-situ one-step synthesis technology is proposed, which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace. A kind of Ti(C, N)-based ceramic cutting tool material synergistically toughened by TiB2 particles and whiskers is fabricated with this new process. The phase compositions, relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composite which is sintered under a pressure of 32 MPa at a temperature of 1700°C in vacuum holding for 60 min can get the optimal mechanical properties. Its flexural strength, fracture toughness and Vickers hardness are 540 MPa, 7.81 MPa · m1/2 and 20.42 GPa, respectively. The composite has relatively high density, and the in-situ synthesized TiB2 whiskers have good surface integrity, which is beneficial for the improvement of the fracture toughness. It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers, crack bridging by whiskers/particles and multi-scale particles synergistically toughening. This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.

  12. A practice-based clinical evaluation of the survival and success of metal-ceramic and zirconia molar crowns: 5-year results.

    PubMed

    Rinke, S; Kramer, K; Bürgers, R; Roediger, M

    2016-02-01

    This practice-based study evaluates the survival and success of conventionally luted metal-ceramic and zirconia molar crowns fabricated by using a prolonged cooling period for the veneering porcelain. Fifty-three patients were treated from 07/2008 to 07/2009 with either metal-ceramic crowns (MCC) or zirconia crowns (ZC). Forty-five patients (26 female) with 91 restorations (obser-vational period: 64.0 ± 4.8 months) participated in a clinical follow-up examination and were included in the study. Estimated cumulative survival (ECSv), success (ECSc) and veneering ceramic success (ECVCSc) were calculated (Kaplan-Meier) and analysed by the crown fabrication technique and the position of the restoration (Cox regression model) (P < 0.05). Five complete failures (MCC: 2, ZC: 3) were recorded (5-year ECSv: MCC: 97.6%, (95% confidence interval (95%-CI): [93%; 100%]/ZC: 94.0%, (95%-CI): [87%; 100%]). Of the MCCs (n = 41), 85.0%, [95%-CI: (77%; 96%)] remained event-free, whereas the ECSc for the ZCs (n = 50) was 74.3% (95%-CI): [61%; 87%]. No significant differences in ECSv (P = 0.51), ECSc (P = 0.43) and ECVCSc (P = 0.36) were detected between the two fabrication techniques. Restorations placed on terminal abutments (n = 44) demonstrated a significantly lower ECVCSc (P = 0.035), (5-year VCF-rate: 14.8%) than crowns placed on tooth-neighboured abutments (n = 47), (5-year VCF-rate: 4.3%). In the present study, zirconia molar crowns demonstrated a 5-year ECSv, ECSc and ECVCSc comparable to MCCs. Irrespective of the fabrication technique, crowns on terminal abutments bear a significantly increased risk for VCFs. Clinical investigations with an increased number of restorations are needed. PMID:26393865

  13. Reinforced ceramic dies for superplastic forming operations

    NASA Astrophysics Data System (ADS)

    Sanders, Daniel G.

    2004-12-01

    Ceramic dies have been developed to meet the need for a dimensionally stable tool, which can withstand the temperatures (425 to 950 °C) and high forming pressures (up to 7 MPa) that are required for superplastic forming (SPF), superplastic forming with diffusion bonding (SPF/DB), and hot sizing of metal parts. With the improvements that have been made to strengthen fused silica based ceramics, the performance of ceramic tools is slowly closing in on meeting the same forming complexity as corrosion-resistant steel (CRES) dies can achieve. Boeing has successfully superplastically formed jet engine wide chord fan blades using ceramic dies, and many production aircraft parts are being built with Boeing’s patented ceramic die technology.

  14. Brittleness of ceramics

    NASA Technical Reports Server (NTRS)

    Kroupa, F.

    1984-01-01

    The main characteristics of mechanical properties of ceramics are summarized and the causes of their brittleness, especially the limited mobility of dislocations, are discussed. The possibility of improving the fracture toughness of ceramics and the basic research needs relating to technology, structure and mechanical properties of ceramics are stressed in connection with their possible applications in engineering at high temperature.

  15. Ceramic to metal seal

    DOEpatents

    Snow, Gary S.; Wilcox, Paul D.

    1976-01-01

    Providing a high strength, hermetic ceramic to metal seal by essentially heating a wire-like metal gasket and a ceramic member, which have been chemically cleaned, while simultaneously deforming from about 50 to 95 percent the metal gasket against the ceramic member at a temperature of about 30 to 75 percent of the melting temperature of the metal gasket.

  16. Ceramic Technology Project semiannual progress report, April 1992--September 1992

    SciTech Connect

    Johnson, D.R.

    1993-07-01

    This project was developed to meet the ceramic technology requirements of the DOE Office of Transportation Systems` automotive technology programs. Significant progress in fabricating ceramic components for DOE, NASA, and DOE advanced heat engine programs show that operation of ceramic parts in high-temperature engines is feasible; however, addition research is needed in materials and processing, design, and data base and life prediction before industry will have a sufficient technology base for producing reliable cost-effective ceramic engine components commercially. A 5-yr project plan was developed, with focus on structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines.

  17. Method of making multilayered titanium ceramic composites

    DOEpatents

    Fisher, II, George T.; Hansen, Jeffrey S.; Oden, Laurance L.; Turner, Paul C.; Ochs, Thomas L.

    1998-01-01

    A method making a titanium ceramic composite involves forming a hot pressed powder body having a microstructure comprising at least one titanium metal or alloy layer and at least one ceramic particulate reinforced titanium metal or alloy layer and hot forging the hot pressed body follwed by hot rolling to substantially reduce a thickness dimension and substantially increase a lateral dimension thereof to form a composite plate or sheet that retains in the microstructure at least one titanium based layer and at least one ceramic reinforced titanium based layer in the thickness direction of the composite plate or sheet.

  18. Method of making multilayered titanium ceramic composites

    DOEpatents

    Fisher, G.T. II; Hansen, J.S.; Oden, L.L.; Turner, P.C.; Ochs, T.L.

    1998-08-25

    A method making a titanium ceramic composite involves forming a hot pressed powder body having a microstructure comprising at least one titanium metal or alloy layer and at least one ceramic particulate reinforced titanium metal or alloy layer and hot forging the hot pressed body followed by hot rolling to substantially reduce a thickness dimension and substantially increase a lateral dimension thereof to form a composite plate or sheet that retains in the microstructure at least one titanium based layer and at least one ceramic reinforced titanium based layer in the thickness direction of the composite plate or sheet. 3 figs.

  19. Method of making multilayered titanium ceramic composites

    DOEpatents

    Fisher, George T., II; Hansen; Jeffrey S.; Oden; Laurance L.; Turner; Paul C.; Ochs; Thomas L.

    1998-08-25

    A method making a titanium ceramic composite involves forming a hot pressed powder body having a microstructure comprising at least one titanium metal or alloy layer and at least one ceramic particulate reinforced titanium metal or alloy layer and hot forging the hot pressed body follwed by hot rolling to substantially reduce a thickness dimension and substantially increase a lateral dimension thereof to form a composite plate or sheet that retains in the microstructure at least one titanium based layer and at least one ceramic reinforced titanium based layer in the thickness direction of the composite plate or sheet.

  20. Microwave and infrared dielectric response of monoclinic bismuth zinc niobate based pyrochlore ceramics with ion substitution in A site

    SciTech Connect

    Wang Hong; Kamba, Stanislav; Zhang Meiling; Yao Xi; Denisov, Sergey; Kadlec, Filip; Petzelt, Jan

    2006-08-01

    It is well known that the cubic pyrochlore Bi{sub 1.5}ZnNb{sub 1.5}O{sub 7} exhibits higher permittivity and dielectric loss than monoclinic Bi{sub 2}Zn{sub 2/3}Nb{sub 4/3}O{sub 7} due to structural disorder in the A sites of Bi{sub 1.5}ZnNb{sub 1.5}O{sub 7}. We have studied systematically the impact of the ion substitution in the A site of monoclinic Bi{sub 2}Zn{sub 2/3}Nb{sub 4/3}O{sub 7} on the structure and microwave dielectric properties. It is shown that the structure and permittivity of (Bi{sub 1.92}M{sub 0.08})(Zn{sub 0.64}Nb{sub 1.36})O{sub 7} (M=Zn,Ca,Cd,Sr,Ba) ceramics remain almost the same as in Bi{sub 2}Zn{sub 2/3}Nb{sub 4/3}O{sub 7}; only the Ba substituted ceramics have higher permittivity due to multiphase structure. Microwave dielectric properties were compared with complex dielectric response in terahertz and infrared frequency range of 0.1-100 THz, which allows us to estimate intrinsic and extrinsic contributions to microwave dielectric losses. The best microwave properties were obtained in (Bi{sub 1.92}Ca{sub 0.08})(Zn{sub 0.64}Nb{sub 1.36})O{sub 7} with {epsilon}=76, Qf{>=}5000 (sintered below 950 deg.C), which is promising for microwave low temperature cofiring ceramic application.

  1. The influence of liquid crystalline structure and ceramic nanoparticles inclusion on thermal conductivity of epoxy based thermosets

    NASA Astrophysics Data System (ADS)

    Scamardella, A. M.; Iacono, S. Dello; Carfagna, C.; Ho, C. H.; Kornmann, X.; Amendola, E.

    2012-07-01

    Epoxy nanocomposites with ceramic nanoparticles and liquid crystalline epoxy thermosets have been prepared and characterized with the aim to improve thermal conductivity of polymeric networks, without sacrificing processibility of reactive mixture and electrical insulation of final products. The influence of mesogenic liquid crystalline structure and fillers addition on thermal, mechanical and dielectric properties have been investigated by means of Differential Scanning Calorimetry (DSC), Dynamic-mechanical analysis (DMA) and volume resistivity. Morphological investigations by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) has been also performed.

  2. The Use of Molybdenum-Based Ceramic-Metal (CerMet) Fuel for the Actinide Management in LWRs

    SciTech Connect

    Bakker, Klaas; Klaassen, Frodo C.; Schram, Ronald P. C.; Hogenbirk, Alfred; Meulekamp, Robin Klein; Bos, Arjan; Rakhorst, Hubert; Mol, Charles A.

    2004-06-15

    The technical and economic aspects of the use of molybdenum depleted in the isotope {sup 95}Mo (DepMo) for the transmutation of actinides in a light water reactor are discussed. DepMo has a low neutron absorption cross section and good physical and chemical properties. Therefore, DepMo is expected to be a good inert matrix in ceramic-metal fuel. The costs of the use of DepMo have been assessed, and it was concluded that these costs can be justified for the transmutation of the actinides neptunium, americium, and plutonium.

  3. Preliminary Design of a Helium-Cooled Ceramic Breeder Blanket for CFETR Based on the BIT Concept

    NASA Astrophysics Data System (ADS)

    Ma, Xuebin; Liu, Songlin; Li, Jia; Pu, Yong; Chen, Xiangcun

    2014-04-01

    CFETR is the “ITER-like” China fusion engineering test reactor. The design of the breeding blanket is one of the key issues in achieving the required tritium breeding radio for the self-sufficiency of tritium as a fuel. As one option, a BIT (breeder insider tube) type helium cooled ceramic breeder blanket (HCCB) was designed. This paper presents the design of the BIT—HCCB blanket configuration inside a reactor and its structure, along with neutronics, thermo-hydraulics and thermal stress analyses. Such preliminary performance analyses indicate that the design satisfies the requirements and the material allowable limits.

  4. Thin film ceramic thermocouples

    NASA Technical Reports Server (NTRS)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  5. Ceramic gas turbine shroud

    DOEpatents

    Shi, Jun; Green, Kevin E.

    2014-07-22

    An example gas turbine engine shroud includes a first annular ceramic wall having an inner side for resisting high temperature turbine engine gasses and an outer side with a plurality of radial slots. A second annular metallic wall is positioned radially outwardly of and enclosing the first annular ceramic wall and has a plurality of tabs in communication with the slot of the first annular ceramic wall. The tabs of the second annular metallic wall and slots of the first annular ceramic wall are in communication such that the first annular ceramic wall and second annular metallic wall are affixed.

  6. Ceramic fiber reinforced filter

    DOEpatents

    Stinton, David P.; McLaughlin, Jerry C.; Lowden, Richard A.

    1991-01-01

    A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

  7. Influence of ZnO on the crystallization kinetics and properties of diopside-Ca-Tschermak based glasses and glass-ceramics

    SciTech Connect

    Goel, Ashutosh; Ferreira, Jose M. F.; Tulyaganov, Dilshat U.; Shaaban, Essam R.; Basu, Rajendra N.

    2008-08-15

    We report on the influence of ZnO on the structural, thermal, and crystallization behavior of the diopside-Ca-Tschermak based glasses, and on the processing, microstructure, and the properties of the sintered glass ceramics. Four glasses with nominal compositions of CaMg{sub 0.8}Al{sub 0.4}Si{sub 1.8}O{sub 6}, CaMg{sub 0.75}Zn{sub 0.05}Al{sub 0.4}Si{sub 1.8}O{sub 6}, CaMg{sub 0.70}Zn{sub 0.10}Al{sub 0.4}Si{sub 1.8}O{sub 6}, and CaMg{sub 0.60}Zn{sub 0.20}Al{sub 0.4}Si{sub 1.8}O{sub 6} were obtained by melting at 1580 deg. C for 1 h. Structural and thermal behavior of the glasses was investigated by Fourier-transform infrared spectroscopy, density measurements, dilatometry, and differential thermal analysis. Nonisothermal crystallization kinetics has been employed to study the crystallization mechanism in the glasses. Sintering, crystallization, microstructure, and properties of the glass ceramics were investigated under nonisothermal heating conditions in the temperature range of 850-1000 deg. C.

  8. Microstructural variations and their influence on the performance of solid oxide fuel cells based on yttrium-substituted strontium titanate ceramic anodes

    NASA Astrophysics Data System (ADS)

    Ma, Qianli; Iwanschitz, Boris; Dashjav, Enkhtsetseg; Baumann, Stefan; Sebold, Doris; Arul Raj, Irudayam; Mai, Andreas; Tietz, Frank

    2015-04-01

    Donor-substituted strontium titanates have been widely recognised as alternative anode materials to the state-of-the-art Ni/YSZ cermets in solid oxide fuel cells (SOFCs). Electrolyte-supported SOFCs based on Y0.07Sr0.895TiO3 ceramic anodes with different microstructural designs were prepared. Ni or Ni with Ce0.8Gd0.2O1.9 (CGO) was infiltrated onto the pore walls within the ceramic anode framework as an electrocatalyst for anode reactions. Performances and electrochemical impedance spectroscopy measurements of the cells were analysed in detail to observe the influence of low ionic conductivity of Y0.07Sr0.895TiO3 to cell performance, to understand how to control the degradation of the cells, and to obtain a possible mechanism for the anode processes. The anode design containing both functional and current collecting layers with sufficient Ni-CGO infiltration is favourable for high power output and low performance degradation.

  9. Friction and wear of oxide-ceramic sliding against IN-718 nickel base alloy at 25 to 800 C in atmospheric air

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Deadmore, Daniel L.

    1989-01-01

    The friction and wear of oxide-ceramics sliding against the nickel base alloy IN-718 at 25 to 800 C were measured. The oxide materials tested were mullite (3Al2O3.2SiO2); lithium aluminum silicate (LiAlSi(x)O(y)); polycrystalline monolithic alpha alumina (alpha-Al2O3); single crystal alpha-Al2O3 (sapphire); zirconia (ZrO2); and silicon carbide (SiC) whisker-reinforced Al2O3 composites. At 25 C the mullite and zirconia had the lowest friction and the polycrystalline monolithic alumina had the lowest wear. At 800 C the Al2O3-8 vol/percent SiC whisker composite had the lowest friction and the Al2O3-25 vol/percent SiC composite had the lowest wear. The friction of the Al2O3-SiC whisker composites increased with increased whisker content while the wear decreased. In general, the wear-resistance of the ceramics improve with their hardness.

  10. Patches for Repairing Ceramics and Ceramic-Matrix Composites

    NASA Technical Reports Server (NTRS)

    Hogenson, Peter A.; Toombs, Gordon R.; Adam, Steven; Tompkins, James V.

    2006-01-01

    Patches consisting mostly of ceramic fabrics impregnated with partially cured polymers and ceramic particles are being developed as means of repairing ceramics and ceramic-matrix composites (CMCs) that must withstand temperatures above the melting points of refractory metal alloys. These patches were conceived for use by space-suited, space-walking astronauts in repairing damaged space-shuttle leading edges: as such, these patches could be applied in the field, in relatively simple procedures, and with minimal requirements for specialized tools. These design characteristics also make the patches useful for repairing ceramics and CMCs in terrestrial settings. In a typical patch as supplied to an astronaut or repair technician, the polymer would be in a tacky condition, denoted as an A stage, produced by partial polymerization of a monomeric liquid. The patch would be pressed against the ceramic or CMC object to be repaired, relying on the tackiness for temporary adhesion. The patch would then be bonded to the workpiece and cured by using a portable device to heat the polymer to a curing temperature above ambient temperature but well below the maximum operating temperature to which the workpiece is expected to be exposed. The patch would subsequently become pyrolized to a ceramic/glass condition upon initial exposure to the high operating temperature. In the original space-shuttle application, this exposure would be Earth-atmosphere-reentry heating to about 3,000 F (about 1,600 C). Patch formulations for space-shuttle applications include SiC and ZrO2 fabrics, a commercial SiC-based pre-ceramic polymer, and suitable proportions of both SiC and ZrO2 particles having sizes of the order of 1 m. These formulations have been tailored for the space-shuttle leading-edge material, atmospheric composition, and reentry temperature profile so as to enable repairs to survive re-entry heating with expected margin. Other formulations could be tailored for specific terrestrial

  11. Hip Squeaking after Ceramic-on-ceramic Total Hip Arthroplasty

    PubMed Central

    Wu, Guo-Liang; Zhu, Wei; Zhao, Yan; Ma, Qi; Weng, Xi-Sheng

    2016-01-01

    Objective: The present study aimed to review the characteristics and influencing factors of squeaking after ceramic-on-ceramic (CoC) total hip arthroplasty (THA) and to analyze the possible mechanisms of the audible noise. Data Sources: The data analyzed in this review were based on articles from PubMed and Web of Science. Study Selection: The articles selected for review were original articles and reviews found based on the following search terms: “total hip arthroplasty”, “ceramic-on-ceramic”, “hip squeaking”, and “hip noise.” Results: The mechanism of the squeaking remains unknown. The possible explanations included stripe wear, edge loading, a third body, fracture of the ceramic liner, and resonance of the prosthesis components. Squeaking occurrence is influenced by patient, surgical, and implant factors. Conclusions: Most studies indicated that squeaking after CoC THA was the consequence of increasing wear or impingement, caused by prosthesis design, patient characteristics, or surgical factors. However, as conflicts exist among different articles, the major reasons for the squeaking remain to be identified. PMID:27453238

  12. Metalloproteinase and inhibitor expression profiling of resorbing cartilage reveals pro-collagenase activation as a critical step for collagenolysis

    PubMed Central

    Milner, Jennifer M; Rowan, Andrew D; Cawston, Tim E; Young, David A

    2006-01-01

    Excess proteolysis of the extracellular matrix (ECM) of articular cartilage is a key characteristic of arthritis. The main enzymes involved belong to the metalloproteinase family, specifically the matrix metalloproteinases (MMPs) and a group of proteinases with a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS). Chondrocytes are the only cell type embedded in the cartilage ECM, and cell-matrix interactions can influence gene expression and cell behaviour. Thus, although the use of monolayer cultures can be informative, it is essential to study chondrocytes encapsulated within their native environment, cartilage, to fully assess cellular responses. The aim of this study was to profile the temporal gene expression of metalloproteinases and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), reversion-inducing cysteine-rich protein with Kazal motifs (RECK), and α2-macroglobulin (α2M), in actively resorbing cartilage. The addition of the pro-inflammatory cytokine combination of interleukin-1 (IL-1) + oncostatin M (OSM) to bovine nasal cartilage induces the synthesis and subsequent activation of pro-metalloproteinases, leading to cartilage resorption. We show that IL-1+OSM upregulated the expression of MMP-1, -2, -3, -9, 12, -13, -14, TIMP-1, and ADAMTS-4, -5, and -9. Differences in basal expression and the magnitude of induction were observed, whilst there was no significant modulation of TIMP-2, -3, RECK, or ADAMTS-15 gene expression. IL-1+OSM downregulated MMP-16,TIMP-4, and α2M expression. All IL-1+OSM-induced metalloproteinases showed marked upregulation early in the culture period, whilst inhibitor expression was reduced throughout the stimulation period such that metalloproteinase production would be in excess of inhibitors. Moreover, although pro-collagenases were upregulated and synthesized early (by day 5), collagenolysis became apparent later with the presence of active collagenases (day 10) when

  13. Integral Textile Ceramic Structures

    NASA Astrophysics Data System (ADS)

    Marshall, David B.; Cox, Brian N.

    2008-08-01

    A new paradigm for ceramic composite structural components enables functionality in heat exchange, transpiration, detailed shape, and thermal strain management that significantly exceeds the prior art. The paradigm is based on the use of three-dimensional fiber reinforcement that is tailored to the specific shape, stress, and thermal requirements of a structural application and therefore generally requires innovative textile methods for each realization. Key features include the attainment of thin skins (less than 1 mm) that are nevertheless structurally robust, transpiration holes formed without cutting fibers, double curvature, compliant integral attachment to other structures that avoids thermal stress buildup, and microcomposite ceramic matrices that minimize spalling and allow the formation of smooth surfaces. All these features can be combined into structures of very varied gross shape and function, using a wide range of materials such as all-oxide systems and SiC and carbon fibers in SiC matrices. Illustrations are drawn from rocket nozzles, thermal protection systems, and gas turbine engines. The new design challenges that arise for such material/structure systems are being met by specialized computational modeling that departs significantly in the representation of materials behavior from that used in conventional finite element methods.

  14. Affordable, Robust Ceramic Joining Technology (ARCJoinT)

    NASA Technical Reports Server (NTRS)

    Singh, M.

    1998-01-01

    Joining is recognized as one of the enabling technologies for the application of silicon carbide-based ceramic and composite components in a number of demanding and high temperature applications in aerospace and ground-based systems. An affordable, robust ceramic joining technology (ARCJoinT) for joining of silicon carbide-based ceramics and fiber reinforced composites has been developed. This technique is capable of producing joints with tailorable thickness and composition. A wide variety of silicon carbide-based ceramics and composites, in different shapes and sizes, have been joined using this technique. These joints maintain their mechanical strength up to 1350 C in air. This technology is suitable for the joining of large and complex shaped ceramic and composite components and with certain modifications, can be applied to repair ceramic components damaged in service.

  15. Porous ceramic scaffolds with complex architectures

    SciTech Connect

    Saiz, Eduardo; Munch, Etienne; Franco, Jaime; Deville, Sylvain; Hunger, Phillip; Saiz, Eduardo; Tomsia, Antoni P.

    2008-03-15

    This work compares two novel techniques for the fabrication of ceramic scaffolds for bone tissue engineering with complex porosity: robocasting and freeze casting. Both techniques are based on the preparation of concentrated ceramic suspensions with suitable properties for the process. In robocasting, the computer-guided deposition of the suspensions is used to build porous materials with designed three dimensional (3-D) geometries and microstructures. Freeze casting uses ice crystals as a template to form porous lamellar ceramic materials. Preliminary results on the compressive strengths of the materials are also reported.

  16. Scale up issues involved with the ceramic waste form : ceramic-container interactions and ceramic cracking quantification.

    SciTech Connect

    Bateman, K. J.; DiSanto, T.; Goff, K. M.; Johnson, S. G.; O'Holleran, T.; Riley, W. P., Jr.

    1999-05-03

    Argonne National Laboratory is developing a process for the conditioning of spent nuclear fuel to prepare the material for final disposal. Two waste streams will result from the treatment process, a stainless steel based form and a ceramic based form. The ceramic waste form will be enclosed in a stainless steel container. In order to assess the performance of the ceramic waste form in a repository two factors must be examined, the surface area increases caused by waste form cracking and any ceramic/canister interactions that may release toxic material. The results indicate that the surface area increases are less than the High Level Waste glass and any toxic releases are below regulatory limits.

  17. Influence of temperature on the dielectric nonlinearity of BaTiO3-based multi-layer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Yoon, Seok-Hyun; Kim, Mi-Yang

    2016-06-01

    Temperature dependence of the dielectric nonlinearity was investigated for the BaTiO3 multilayer ceramic capacitor. The decrease in temperature caused a significant increase in the degree of dielectric nonlinearity. The Preisach analysis shows that such effect corresponds to a decrease in reversible and a significant increase in irreversible domain wall contribution to polarization. The magnitude of spontaneous polarization (PS) was increased with decreasing temperature. It can be associated with phase transition from pseudo-cubic to monoclinic and its resultant change in the polar direction, which was observed through transmission electron microscopy. These results demonstrate that the increase in PS with the decrease in temperature inhibits domain wall motion in low driving field as it is anticipated to increase the degree of intergranular constraints during domain wall motion. But it results in a more steep increase in the dielectric constants beyond the threshold field where domain wall motion can occur.

  18. Strong domain configuration dependence of the nonlinear dielectric response in (K,Na)NbO{sub 3}-based ceramics

    SciTech Connect

    Huan, Yu; Wang, Xiaohui Li, Longtu; Koruza, Jurij

    2015-11-16

    The nonlinear dielectric response in (Na{sub 0.52}K{sub 0.4425}Li{sub 0.0375})(Nb{sub 0.92−x}Ta{sub x}Sb{sub 0.08})O{sub 3} ceramics with different amounts of Ta was measured using subcoercive electric fields and quantified by the Rayleigh model. The irreversible extrinsic contribution, mainly caused by the irreversible domain wall translation, was strongly dependent on the domain configuration. The irreversible extrinsic contributions remained approximately the same within the single-phase regions, either orthorhombic or tetragonal, due to the similar domain morphology. However, in the polymorphic phase transition region, the domain wall density was increased by minimized domain size, as observed by transmission electron microscopy. This resulted in constrained domain wall motion due to self-clamping and reduced the irreversible extrinsic contribution.

  19. Investigation of Interdiffusion in Ba(Ti,Zr)O3-Based Y5V Multilayer Ceramic Capacitors with Ni Electrodes

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Wang, Xiaohui; Qiao, Bin; Li, Longtu

    2007-02-01

    The interdiffusion between the Ba(Ti,Zr)O3 (BTZ) dielectric and the internal Ni electrode layers in Y5V-type multilayer ceramic capacitors (MLCCs) with an active layer thickness of 5 μm was studied by high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometry (EDS) analysis. It was found that such interdiffusion leads to the formation of some defects and the lattice distortion near the interface. The diffusion degree of Ni into BTZ was higher than that of BTZ into Ni. In the EDS analysis the chemical composition was confirmed and the different diffusion degrees were verified. The generation of the interdiffusion and the relationship between the interdiffusion and degradation of MLCCs with Ni electrodes were also studied.

  20. A novel combined surgical approach to vertical alveolar ridge augmentation with titanium mesh, resorbable membrane, and rhPDGF-BB: a retrospective consecutive case series.

    PubMed

    Funato, Akiyoshi; Ishikawa, Tomohiro; Kitajima, Hajime; Yamada, Masahiro; Moroi, Hidetada

    2013-01-01

    The purpose of this case series was to report the clinical outcomes and histologic findings of vertical ridge augmentation using a combination of titanium mesh, resorbable collagen membrane, and recombinant human platelet-derived growth factor BB (rhPDGF-BB). Nineteen patients were included, and autogenous bone and anorganic bovine bone particles were used. The bone graft was mixed with rhPDGF-BB and loaded onto the bony defect up to the level of the adjacent alveolar crest. A pre-adapted titanium mesh was placed over the grafted region and covered with a resorbable collagen membrane, leaving no areas of the grafted region exposed. Seventeen patients exhibited good soft tissue healing. Postoperative flap dehiscence occurred relatively early in the healing period in one patient, whereas the covering collagen membrane was exposed during the later phase of the healing period in another. During reentry surgery for removal of the titanium mesh, three patients with favorable soft and hard tissue healing underwent bone biopsies for histologic evaluation of the augmented tissue just below the titanium mesh. The mean vertical height of augmented bone was 8.6 ± 4.0 mm. This report demonstrates the remarkable efficacy of guided bone regeneration using a combination of titanium mesh, resorbable collagen membrane, and rhPDGF for vertical ridge augmentation, thus expanding the indications for implant therapy and allowing recovery of the three-dimensional esthetic architecture in a severely absorbed alveolar ridge. PMID:23820701

  1. Nanostructured surface modification of ceramic-based microelectrodes to enhance biocompatibility for a direct brain-machine interface.

    PubMed

    Moxon, Karen A; Kalkhoran, Nader M; Markert, Mathew; Sambito, Marisa A; McKenzie, J L; Webster, J Thomas

    2004-06-01

    Many different types of microelectrodes have been developed for use as a direct Brain-Machine Interface (BMI) to chronically recording single neuron action potentials from ensembles of neurons. Unfortunately, the recordings from these microelectrode devices are not consistent and often last for only a few weeks. For most microelectrode types, the loss of these recordings is not due to failure of the electrodes but most likely due to damage to surrounding tissue that results in the formation of nonconductive glial-scar. Since the extracellular matrix consists of nanostructured microtubules, we have postulated that neurons may prefer a more complex surface structure than the smooth surface typical of thin-film microelectrodes. We, therefore, investigated the suitability of a nano-porous silicon surface layer to increase the biocompatibility of our thin film ceramic-insulated multisite electrodes. In-vitro testing demonstrated, for the first time, decreased adhesion of astrocytes and increased extension of neurites from pheochromocytoma cells on porous silicon surfaces compared to smooth silicon sufaces. Moreover, nano-porous surfaces were more biocompatible than macroporous surfaces. Collectively, these results support our hypothesis that nano-porous silicon may be an ideal material to improve biocompatibility of chronically implanted microelectrodes. We next developed a method to apply nano-porous surfaces to ceramic insulated, thin-film, microelectrodes and tested them in vivo. Chronic testing demonstrated that the nano-porous surface modification did not alter the electrical properties of the recording sites and did not interfere with proper functioning of the microelectrodes in vivo. PMID:15188854

  2. Assessment of surface concentrations in resorbable ocular implants: controlled drug delivery devices for 5-fluorouracil (5-FU)

    NASA Astrophysics Data System (ADS)

    Milne, Peter J.; Gautier, Sandrine; Parel, Jean-Marie A.; Jallet, Valerie

    1997-05-01

    The antineoplastic drug 5-fluorouracil (5-fluoro- 2,4,(1H,3H)-pyrimidinedione; 5-FU) has been used to control proliferation of penetrating fibroblasts and to prevent channel closure following glaucoma filtration surgery (trabeculectomy) or laser sclerectomy. Because of the toxicity of the drug, administration of low dosages slowly over time, at the site of the desired treatment, is indicated for optimum efficacy. Repeated injections of low dosages of the drug represent an undesirable intervention and may also result in unwanted toxicity to the corneal epithelium. A suitable biocompatible and resorbable polymer matrix composed of a poly (D,L-lactic-co-glycolic acid: PLGA) has been admixed with varying amounts of 5-FU and cast as shapes suitable for intracorneal implantation. Slow biodegradation of this polymer over a one to two week period has been shown to result in an acceptably slow drug release mechanism. An issue arising during the clinical evaluation of the efficacy of this drug delivery system was how best to quantify the concentration of 5-FU and its distribution spatially in the solid implant. FT-IR and FT-Raman spectroscopies distinguishes between the drug and the polymer matrix and were used to differentiate and quantitate the 5-FU concentration of the implants.

  3. Mechanical and Histological Effects of Resorbable Blasting Media Surface Treatment on the Initial Stability of Orthodontic Mini-Implants

    PubMed Central

    2016-01-01

    Introduction. This study aimed to evaluate the effects of resorbable blasting media (RBM) treatment on early stability of orthodontic mini-implants by mechanical, histomorphometric, and histological analyses. Methods. Ninety-six (64 for mechanical study and 32 for histological study and histomorphometric analysis) titanium orthodontic mini-implants (OMIs) with machined (machined group) or RBM-treated (CaP) surface (RBM group) were implanted in the tibiae of 24 rabbits. Maximum initial torque (MIT) was measured during insertion, and maximum removal torque (MRT) and removal angular momentum (RAM) were measured at 2 and 4 weeks after implantation. Bone-to-implant contact (BIC) and bone area (BA) were analyzed at 4 weeks after implantation. Results. RBM group exhibited significantly lower MIT and significantly higher MRT and RAM at 2 weeks than machined group. No significant difference in MRT, RAM, and BIC between the two groups was noted at 4 weeks, although BA was significantly higher in RBM group than in machined group. RBM group showed little bone resorption, whereas machined group showed new bone formation after bone resorption. Conclusions. RBM surface treatment can provide early stability of OMIs around 2 weeks after insertion, whereas stability of machined surface OMIs may decrease in early stages because of bone resorption, although it can subsequently recover by new bone apposition. PMID:26942200

  4. Rehabilitation of resorbed mandibular ridges using mini implant retained overdentures: A case series with 3 year follow-up.

    PubMed

    Kumari, Pooja; Verma, Mahesh; Sainia, Vikrant; Gupta, Rekha; Gill, Shubhra

    2016-01-01

    With the increasing average life expectancy of human beings, the need to cater geriatric patients is ever increasing. Complete dentures are an indispensable tool in this regard. The loose and unstable lower complete denture owing to residual ridge resorption is one of the most common problems faced by edentulous patients. Dental implant retained overdentures have emerged as an efficient treatment modality for such patients. Though useful, not every patient is a suitable candidate to go for conventional implant-borne prosthesis, limitation being the available bone width. In such cases, mini implants may be used for augmenting the retention of the dentures and improving the quality of life of patients. In this case series, rehabilitation of three compromised cases with mini implant retained overdentures have been described wherein patients are experiencing instability of lower denture due to thin resorbed mandibular ridges. In one of the cases, three mini implants placed in A, C, and E position were splinted using a cemented bar to retain the mandibular denture. The other two cases were rehabilitated using unsplinted ball type one piece mini implants placed in A, C, and E position in one case and B and D position in another case. Though splinted bar design should be preferred but the lack of available vertical space precluded the utilization of bar in other two cases. The results were found to be satisfactory with no complications reported during a follow-up period of over 3 years in all the cases. PMID:27141177

  5. Preparation and characterization of PEG-PPG-PEG copolymer/pregelatinized starch blends for use as resorbable bone hemostatic wax.

    PubMed

    Suwanprateeb, J; Suvannapruk, W; Thammarakcharoen, F; Chokevivat, W; Rukskul, P

    2013-12-01

    In this study, polymer blends between PEG-PPG-PEG copolymer mixtures and pregelatinized starch at various compositions ranging from 0 to 3 % by weight were prepared and evaluated for potential use as novel resorbable bone hemostatic wax. It was found that the prepared samples had sufficient smearability for use as a bone wax. An addition of pregelatinized starch increased the hardness, smoothness and consistency of the texture while decreasing the adherence to glove. Thermal analysis indicated that the heat of fusion slightly decreased with increasing pregelatinized starch content. Compressive stiffness tended to decrease with increasing starch content for concentrations lower than 20 %, but re-increased at higher starch levels. In contrast, adherence deformation increased initially, but then decreased with increasing starch content. This behavior was related to the dependence of softening or reinforcing effect on the level of starch concentration in the samples. Adherence load and energy decreased with the addition of pregelatinized starch implying the decrease in adhesiveness of the samples. Furthermore, increasing the pregelatized starch amount also increased the liquid sealing duration of the samples at both 23 and 37 °C. Cytotoxicity tests against osteoblasts using a MTT assay revealed that the all the prepared samples and their raw materials did not show any cytotoxic potential. Formulations containing pregelatinized starch content between 20 and 30 % were found to show optimized performance. PMID:23955721

  6. Resorbable composites with bioresorbable glass fibers for load-bearing applications. In vitro degradation and degradation mechanism.

    PubMed

    Lehtonen, Timo J; Tuominen, Jukka U; Hiekkanen, Elina

    2013-01-01

    An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(α-hydroxyacids). Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past. PMID:22963847

  7. Mechanical and Histological Effects of Resorbable Blasting Media Surface Treatment on the Initial Stability of Orthodontic Mini-Implants.

    PubMed

    Gansukh, Odontuya; Jeong, Jong-Wha; Kim, Jong-Wan; Lee, Jong-Ho; Kim, Tae-Woo

    2016-01-01

    Introduction. This study aimed to evaluate the effects of resorbable blasting media (RBM) treatment on early stability of orthodontic mini-implants by mechanical, histomorphometric, and histological analyses. Methods. Ninety-six (64 for mechanical study and 32 for histological study and histomorphometric analysis) titanium orthodontic mini-implants (OMIs) with machined (machined group) or RBM-treated (CaP) surface (RBM group) were implanted in the tibiae of 24 rabbits. Maximum initial torque (MIT) was measured during insertion, and maximum removal torque (MRT) and removal angular momentum (RAM) were measured at 2 and 4 weeks after implantation. Bone-to-implant contact (BIC) and bone area (BA) were analyzed at 4 weeks after implantation. Results. RBM group exhibited significantly lower MIT and significantly higher MRT and RAM at 2 weeks than machined group. No significant difference in MRT, RAM, and BIC between the two groups was noted at 4 weeks, although BA was significantly higher in RBM group than in machined group. RBM group showed little bone resorption, whereas machined group showed new bone formation after bone resorption. Conclusions. RBM surface treatment can provide early stability of OMIs around 2 weeks after insertion, whereas stability of machined surface OMIs may decrease in early stages because of bone resorption, although it can subsequently recover by new bone apposition. PMID:26942200

  8. High-temperature structural ceramics.

    PubMed

    Katz, R N

    1980-05-23

    The unique properties of ceramics based on silicon carbide and silicon nitride make them prime candidates for use in advanced energy conversion systems. These compounds are the bases for broad families of engineering materials, whose properties are reviewed. The relationships between processing, microstructure, and properties are discussed. A review and assessment of recent progress in the use of these materials in high-temperature engineering systems, and vehicular engines in particular, is presented. PMID:17772807

  9. Ultrahigh strain response with fatigue-free behavior in (Bi0.5Na0.5)TiO3-based lead-free piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Hao, Jigong; Xu, Zhijun; Chu, Ruiqing; Li, Wei; Du, Juan; Li, Guorong

    2015-12-01

    In this letter, we report a lead-free piezoelectric ceramic system (Bi0.5Na0.5)1-x Ba x Ti0.98 (Fe0.5Sb0.5)0.02O3 which shows a surprisingly high field-induced nonlinear strain of 0.57% comparable to those obtained in Pb-based antiferroelectrics. The ultrahigh strain response of the composition stems from the composition proximity to the ferroelectric-nonpolar phase boundary, which leads to reversible transformation between a nonpolar phase and a polar ferroelectric phase under cyclic fields. In particular, this material is very attractive for its exceptionally good fatigue resistance (up to 106 cycles) and high temperature stability (25-100 °C) due to its stable nonpolar phase and lower defect density. These findings render the current material a great opportunity for novel applications in ultra-large stroke and nonlinear actuators demanding improved cycling and thermal reliabilities.

  10. An Insertable Passive LC Pressure Sensor Based on an Alumina Ceramic for In Situ Pressure Sensing in High-Temperature Environments.

    PubMed

    Xiong, Jijun; Li, Chen; Jia, Pinggang; Chen, Xiaoyong; Zhang, Wendong; Liu, Jun; Xue, Chenyang; Tan, Qiulin

    2015-01-01

    Pressure measurements in high-temperature applications, including compressors, turbines, and others, have become increasingly critical. This paper proposes an implantable passive LC pressure sensor based on an alumina ceramic material for in situ pressure sensing in high-temperature environments. The inductance and capacitance elements of the sensor were designed independently and separated by a thermally insulating material, which is conducive to reducing the influence of the temperature on the inductance element and improving the quality factor of the sensor. In addition, the sensor was fabricated using thick film integrated technology from high-temperature materials that ensure stable operation of the sensor in high-temperature environments. Experimental results showed that the sensor accurately monitored pressures from 0 bar to 2 bar at temperatures up to 800 °C. The sensitivity, linearity, repeatability error, and hysteretic error of the sensor were 0.225 MHz/bar, 95.3%, 5.5%, and 6.2%, respectively. PMID:26334279

  11. An Insertable Passive LC Pressure Sensor Based on an Alumina Ceramic for In Situ Pressure Sensing in High-Temperature Environments

    PubMed Central

    Xiong, Jijun; Li, Chen; Jia, Pinggang; Chen, Xiaoyong; Zhang, Wendong; Liu, Jun; Xue, Chenyang; Tan, Qiulin

    2015-01-01

    Pressure measurements in high-temperature applications, including compressors, turbines, and others, have become increasingly critical. This paper proposes an implantable passive LC pressure sensor based on an alumina ceramic material for in situ pressure sensing in high-temperature environments. The inductance and capacitance elements of the sensor were designed independently and separated by a thermally insulating material, which is conducive to reducing the influence of the temperature on the inductance element and improving the quality factor of the sensor. In addition, the sensor was fabricated using thick film integrated technology from high-temperature materials that ensure stable operation of the sensor in high-temperature environments. Experimental results showed that the sensor accurately monitored pressures from 0 bar to 2 bar at temperatures up to 800 °C. The sensitivity, linearity, repeatability error, and hysteretic error of the sensor were 0.225 MHz/bar, 95.3%, 5.5%, and 6.2%, respectively. PMID:26334279

  12. Highly Efficient Lasing Action of Nd3+- and Cr3+-Doped Yttrium Aluminum Garnet Ceramics Based on Phonon-Assisted Cross-Relaxation Using Solar Light Source

    NASA Astrophysics Data System (ADS)

    Saiki, Taku; Nakatsuka, Masahiro; Imasaki, Kazuo

    2010-08-01

    We constructed a theory to explain the mechanism of laser generation with a high optical-optical conversion efficiency for Nd3+- and Cr3+-doped yttrium aluminum ceramics when sunlight or lamplight sources are used for pumping. As a result, a unique mechanism of laser action was found where the solar or lamp-light power could be converted to laser power with a high efficiency close to 80%, which has not previously been observed. The high conversion efficiency was not only considered to be based on one-to-one photon conversion but on two-photon excitation by a single photon with phonon assistance. Thus, the mechanism of lasing action should include a process where thermal energy is converted to photon energy. The theoretical results we obtained were consistent with those of the experiments.

  13. Light-weight black ceramic insulation

    NASA Technical Reports Server (NTRS)

    Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2003-01-01

    Ultra-high temperature, light-weight, black ceramic insulation having a density ranging from about 0.12 g/cc. to 0.6 g/cc. such as ceramic tile is obtained by pyrolyzing siloxane gels derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes also may contain an effective amount of a mono- or trialkoxy silane to obtain the siloxane gels. The siloxane gels are dried at ambient temperatures and pressures to form siloxane ceramic precursors without significant shrinkage. The siloxane ceramic precursors are subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C., and particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

  14. Light Weight Biomorphous Cellular Ceramics from Cellulose Templates

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Yee, Bo-Moon; Gray, Hugh R. (Technical Monitor)

    2003-01-01

    Bimorphous ceramics are a new class of materials that can be fabricated from the cellulose templates derived from natural biopolymers. These biopolymers are abundantly available in nature and are produced by the photosynthesis process. The wood cellulose derived carbon templates have three- dimensional interconnectivity. A wide variety of non-oxide and oxide based ceramics have been fabricated by template conversion using infiltration and reaction-based processes. The cellular anatomy of the cellulose templates plays a key role in determining the processing parameters (pyrolysis, infiltration conditions, etc.) and resulting ceramic materials. The processing approach, microstructure, and mechanical properties of the biomorphous cellular ceramics (silicon carbide and oxide based) have been discussed.

  15. Microwave heating of ceramic composites

    NASA Astrophysics Data System (ADS)

    Pelesko, J. A.; Kriegsmann, G. A.

    2000-02-01

    The microwave heating of a ceramic composite is modelled and analysed. The composite consists of many small ceramic particles embedded in a ceramic cement. The composite is assumed to be well insulated, and each particle is assumed to be in imperfect thermal contact with the surrounding cement. Based on these two assumptions an asymptotic theory exploiting the small Biot number and small non-dimensional contact conductance is developed. Our asymptotic theory yields a set of nonlinear partial differential equations which govern the temperature in the composite. These are reduced to a set of coupled nonlinear ordinary differential equations in which the surface area of each particle enters as a parameter. Recent experiments with such composites have shown that the steady-state temperature of the composite is strongly dependent upon the radii of the embedded particles. Our model captures this effect. In fact, our analysis shows that the assumption of imperfect thermal contact between the particles and the ceramic cement is essential for this trend to be established.

  16. Superplastic forming of ceramic insulation

    NASA Technical Reports Server (NTRS)

    Nieh, T. G.; Wittenauer, J. P.; Wadsworth, J.

    1992-01-01

    Superplasticity has been demonstrated in many fine-grained structural ceramics and ceramic composites, including yttria-stabilized tetragonal zirconia polycrystal (YTZP), alumina, and Al2O3-reinforced zirconia (Al2O3/YTZ) duplex composites and SiC-reinforced Si3N4. These superplastic ceramics obviously offer the potential benefit of forming net shape or near net shape parts. This could be particularly useful for forming complicated shapes that are difficult to achieve using conventional forming techniques, or require elaborate, subsequent machining. In the present study, we successfully demonstrated the following: (1) superplastic 3Y-TXP and 20 percent Al2O3/YTZ composite have for the first time been successfully deformed into hemispherical caps via a biaxial gas-pressure forming technique; (2) no experimental difficulty was encountered in applying the required gas pressures and temperatures to achieve the results, thus, it is certain that higher rates of deformation than those presented in this study will be possible by using the current test apparatus at higher temperatures and pressures; and (3) an analytical model incorporating material parameters, such as variations during forming in the strain rate sensitivity exponent and grain growth-induced strain hardening, is needed to model accurately and therefore precisely control the biaxial gas-pressure forming of superplastic ceramics. Based on the results of this study, we propose to fabricate zirconia insulation tubes by superplastic extrusion of zirconia polycrystal. This would not only reduce the cost, but also improve the reliability of the tube products.

  17. Ceramic tamper-revealing seals

    DOEpatents

    Kupperman, David S.; Raptis, Apostolos C.; Sheen, Shuh-Haw

    1992-01-01

    A flexible metal or ceramic cable with composite ceramic ends, or a u-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting.

  18. Analyses of fine paste ceramics

    SciTech Connect

    Sabloff, J A

    1980-01-01

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

  19. NDE (nondestructive examination) development for ceramics for advanced heat engines

    SciTech Connect

    McClung, R.W. , Powell, TN ); Johnson, D.R. )

    1991-01-01

    The Department of Energy (DOE) Ceramic Technology for Advanced Heat Engines (CTAHE) project was initiated in 1983 to meet the ceramic technology needs of DOE's advanced heat engines programs (i.e., advanced gas turbines and low heat rejection diesels). The objective is to establish an industrial ceramic technology base for reliable and cost-effective high-temperature components. Reliability of ceramics was recognized as the major technology need. To increase the material reliability of current and new ceramics, advances were needed in component design methodology, materials processing technology, and data base/life prediction. Nondestructive examination (NDE) was identified as one of the key elements in the approach to high-reliability components. An assessment was made of the current status of NDE for structural ceramics, and a report was prepared containing the results and recommendations for needed development. Based on these recommendations, a long-range NDE development program has been established in the CTAHE project to address these needs.

  20. Superconductive ceramic oxide combination

    SciTech Connect

    Chatterjee, D.K.; Mehrotra, A.K.; Mir, J.M.

    1991-03-05

    This patent describes the combination of a superconductive ceramic oxide which degrades in conductivity upon contact of ambient air with its surface and, interposed between the ceramic oxide surface and ambient air in the amount of at least 1 mg per square meter of surface area of the superconductive ceramic oxide, a passivant polymer selected from the group consisting of a polyester ionomer and an alkyl cellulose.