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1

Glass ionomer cements  

Microsoft Academic Search

Glass ionomer cements have been used in pediatric restorative dentistry for 20 years. Their usefulness in pediatric restorative dentistry is preferential relative to other materi- als because of their fluoride release, chemical adhesion to tooth structure, and availability to use in a variety of clinical scenarios. This paper reviews the use of glass ionomer ma- terials in pediatric restorative dentistry.

Joel H. Berg

2002-01-01

2

Thermal characterization of glass ionomer/vinyl IPN composites  

SciTech Connect

In and attempt to improve some of the disadvantages of the conventional glass ionomers such as Ketac-fil, two photocurable glass ionomer restoratives have been introduced to the dental profession. The initial objective of this study was to compare the thermal expansion coefficients on the new formulations, Vari-Glass and Fuji II ionomer to the conventional glass ionomer composites using thermal mechanical analysis and to determine the residual monomer contents after photopolymerization using differential scanning calorimetry. Results suggest that these materials exhibit multiphase morphologies. Conventional glass ionomers exhibit two distinct glass transition temperatures. While Fuji II exhibits many of the characteristics of a conventional glass ionomer, Vari-Glass behaves more as a glass-filled resin composite. Fuji II and Ketac-fil exhibit expansion coefficients which are compatible with tooth structure below body temperature, but may cause significant stress on the bond to tooth structure due to shrinkage of the materials at temperatures slightly above body temperature. In contrast, the Vari-Glass formulation exhibits an expansion coefficient which is over three times that of tooth structure and will result in significant stresses above or below body temperature.

Puckett, A.D.; Bennett, B.; Shelby, A. [Univ. of Mississippi Medical Center, Jackson, MS (United States)] Storey, R. [Univ. of Southern Mississippi, Hattiesburg, MS (United States)

1993-12-31

3

Antibacterial activity of resin adhesives, glass ionomer and resin-modified glass ionomer cements and a compomer in contact with dentin caries samples.  

PubMed

A total of 103 clinical samples of carious dentin were used to study the antibacterial action of different dental resin adhesive materials (Gluma 2000, Syntac, Prisma Universal Bond 3, Scotchbond Multi-Purpose and Prime&Bond 2.0) glass ionomer cements (Ketac-Cem, Ketac-Bond, Ketac-Silver, Ketac-Fil) resin-modified glass ionomer cements (Fuji II LC, Vitremer and Vitrebond) and a compomer (Dyract). The agar plate diffusion method was used for the microbial cultures and a chlorhexidine control. The growth of the caries-producing microorganisms was effectively inhibited by the Vitremer and Vitrebond cements, and to a lesser extent by the Scotchbond Multi-Purpose adhesive system. Overall, there were statistically significant differences in the antibacterial activity of the products tested. PMID:11203829

Herrera, M; Castillo, A; Bravo, M; Liébana, J; Carrión, P

2000-01-01

4

Antibacterial activity of glass-ionomer restorative cements exposed to cavity-producing microorganisms.  

PubMed

The antibacterial activity of the glass-ionomer restorative cements Ketac-Fil, Ketac-Silver, Fuji II LC, and Vitremer was studied in vitro, in conjunction with a total of 32 strains of five bacterial genera that may be associated with dental caries: Streptococcus spp, Lactobacillus spp, Actinomyces spp, Porphyromonas spp, and Clostridium spp. Agar plate diffusion was the method used for the bacterial cultures, which included a chlorhexidine control. All four glass-ionomer cements were found to inhibit bacterial growth, though with noteworthy differences in their spheres of action. Vitremer was the cement determined to have the greatest antibacterial effects, whereas Ketac-Silver presented the least inhibitory action. PMID:10823075

Herrera, M; Castillo, A; Baca, P; Carrión, P

1999-01-01

5

Mechanical performance of encapsulated restorative glass-ionomer cements for use with Atraumatic Restorative Treatment (ART)  

PubMed Central

The Atraumatic Restorative Treatment (ART) approach was suggested to be a suitable method to treat enamel and dentine carious lesions in patients with disabilities. The use of a restorative glass-ionomer with optimal mechanical properties is, therefore, very important. Objective: To test the null-hypotheses that no difference in diametral tensile, compressive and flexural strengths exists between: (1) The EQUIA system and (2) The Chemfil Rock (encapsulated glass-ionomers; test materials) and the Fuji 9 Gold Label and the Ketac Molar Easymix (hand-mixed conventional glass-ionomers; control materials); (3) The EQUIA system and Chemfil Rock. Material and Methods: Specimens for testing flexural (n=240) and diametral tensile (n=80) strengths were prepared according to standardized specifications; the compressive strength (n=80) was measured using a tooth-model of a class II ART restoration. ANOVA and Tukey B tests were used to test for significant differences between dependent and independent variables. Results: The EQUIA system and Chemfil Rock had significantly higher mean scores for all the three strength variables than the Fuji 9 Gold Label and Ketac Molar Easymix (?=0.05). The EQUIA system had significant higher mean scores for diametral tensile and flexural strengths than the Chemfil Rock (?=0.05). Conclusion: The two encapsulated high-viscosity glass-ionomers had significantly higher test values for diametral tensile, flexural and compressive strengths than the commonly used hand-mixed high-viscosity glass-ionomers. PMID:23857657

MOLINA, Gustavo Fabián; CABRAL, Ricardo Juan; MAZZOLA, Ignacio; BRAIN LASCANO, Laura; FRENCKEN, Jo. E.

2013-01-01

6

Influence of air abrasion preparation on microleakage in glass ionomer cement restorations.  

PubMed

The aim of this study was to assess microleakage in class V cavities prepared by air abrasion or high-speed dental bur and restored with different glass ionomer cements. Sixty bovine incisors were equally divided into 6 groups: I, II and III (preparation by high-speed) and IV, V and VI (preparation by air abrasion). Groups I and IV were restored with Fuji IX; groups II and V with Ketac Molar; and groups III and VI with Vitremer. After 24 h (37 degrees C), specimens were thermocycled, isolated with nail varnish, immersed in a 0.2% Rhodamine B solution for 24 hours, sectioned longitudinally and analyzed for microleakage using an optical microscope connected to a digital camera and a computer. The images were digitized and a software allowed the quantitative evaluation of microleakage in millimeters. Data were analyzed by Wilcoxon and Kruskal-Wallis tests. It was observed that there were significant differences (p < 0.05) between incisal (enamel) and cervical (dentine/cementum) margins, mainly for Ketac Molar; there was no difference (p > 0.05) between preparation methods, except for group II (high-speed/Ketac Molar) that showed higher infiltration; regarding the materials, Ketac Molar demonstrated the highest microleakage values (p < 0.05), and only Vitremer sealed completely both margins of restorations. It was concluded that air abrasion preparation did not influence microleakage in class V restorations with the employed glass ionomer cements. PMID:15880930

Reis, Lucia da Silva; Chinelatti, Michelle A; Corona, Silmara A M; Palma-Dibb, Regina G; Borsatto, Maria Cristina

2004-11-01

7

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements  

PubMed Central

Objective The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resin-modified glass ionomer cements (RMGICs). Material and Methods Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. Results Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. Conclusions Except for Ionoseal, all cements provided satisfactory bond strength values.

PEREIRA, Jefferson Ricardo; da ROSA, Ricardo Abreu; SÓ, Marcus Vinícius Reis; AFONSO, Daniele; KUGA, Milton Carlos; HONÓRIO, Heitor Marques; do VALLE, Accácio Lins; VIDOTTI, Hugo Alberto

2014-01-01

8

A review of glass-ionomers: From conventional glass-ionomer to bioactive glass-ionomer  

PubMed Central

Materials used in the body, especially the materials used in various oral cavity regions should be stable and passive without any interactions with the body tissues or fluids. Dental amalgam, composite resins and dental cements are the materials of choice with such properties. The first attempts to produce active materials, which could interact with the human body tissues and fluids were prompted by the concept that fluoride-releasing materials exert useful effects in the body. The concept of using the “smart” materials in dentistry has attracted a lot of attention in recent years. Conventional glass-ionomer (GI) cements have a large number of applications in dentistry. They are biocompatible with the dental pulp to some extent. GI is predominantly used as cements in dentistry; however, they have some disadvantages, the most important of which is lack of adequate strength and toughness. In an attempt to improve the mechanical properties of the conventional GI, resin-modified glass-ionomers have been marketed, with hydrophilic monomers, such as hydroxyethyl methacrylated (HEMA). Some recent studies have evaluated GI with bioactive glass in its structure to validate the claims that such a combination will improve tooth bioactivity, regeneration capacity and restoration. There is ever-increasing interest in the application of bioactive materials in the dental field in an attempt to remineralize affected dentin. The aim of this review article is to evaluate these materials and their characteristics and applications. PMID:24130573

Khoroushi, Maryam; Keshani, Fateme

2013-01-01

9

Cytotoxicity of dental glass ionomers evaluated using dimethylthiazol diphenyltetrazolium and neutral red tests.  

PubMed

The purpose of this study was to assess the cytotoxicity of some commonly used glass ionomers. Three chemically cured glass ionomers (Fuji II, Lining cement, and Ketac Silver) and one light-cured (Fuji II LC) were tested. Extracts of mixed non-polymerized materials and polymerized specimens were prepared in accordance with ISO standard 10993-12. The polymerized specimens were cured and placed either directly in the medium (freshly cured), left for 24 h (aged), or aged plus ground before being placed in the medium. The cytotoxicity of extracts was evaluated on mouse fibroblasts (L, 929), using dimethylthiazol diphenyltetrazolium (MTT) and neutral red (NR) assays. Further, the concentrations of aluminum, arsenic and lead were analyzed in aqueous extracts from freshly cured and aged samples, and the fluoride levels analyzed in aqueous extracts from freshly cured samples. All extracts except that of non-polymerized Ketac Silver were rated as severely cytotoxic in both assays. Extracts of polymerized material were significantly more cytotoxic than extracts of non-polymerized material. All freshly cured glass ionomers released aluminum and fluoride concentrations far above what is considered cytotoxic (aluminum >0.2 ppm and fluoride >20 ppm). Extracts from freshly cured Lining Cement contained the highest concentrations of aluminum and fluoride (215 ppm and 112 ppm). Extracts from freshly cured Ketac Silver had the lowest concentrations of aluminum and fluoride but the highest of lead (100 ppm). It can be concluded that all extracts from non-cured, freshly cured, and aged glass ionomers contained cytotoxic levels of substances. Curing did not reduce the toxicity significantly. PMID:11318043

Lönnroth, E C; Dahl, J E

2001-02-01

10

Comparative wear resistance of reinforced glass ionomer restorative materials.  

PubMed

This study investigated the wear resistance of three restorative reinforced glass ionomer cements (Fuji IX GP FAST [FJ], Miracle Mix [MM] and Ketac Silver [KS]). Microfilled (Silux [SX]) and mini-filled (Z100 [ZO]) composites were used for comparison. Six specimens were made for each material. The specimens were conditioned for one week in distilled water at 37 degrees C and subjected to wear testing at 20 MPa contact stress against SS304 counterbodies using a reciprocal compression-sliding wear instrumentation. Distilled water was used as lubricant. Wear depth (microm) was measured using profilometry every 2,000 cycles up to 10,000 cycles. Results were analyzed using ANOVA/Scheffe's test (p<0.05). After 10,000 cycles of wear testing, ranking was as follows: KS>ZO>MM>FJ>SX. Wear ranged from 26.1 microm for SX to 71.5 microm for KS. The wear resistance of KS was significantly lower than FJ, MM and SX at all wear intervals. Although KS had significantly more wear than ZO at 2,000 to 6,000 cycles, no significant difference in wear was observed between these two materials at 8,000 and 10,000 cycles. Sintering of silver particles to glass ionomer cement (KS) did not appear to improve wear resistance. The simple addition of amalgam alloy to glass ionomer may improve wear resistance but results in poor aesthetics (silver-black color). FJ, which relies on improved chemistry instead of metal fillers, showed comparable wear resistance to the composites evaluated and is tooth-colored. It may serve as a potential substitute for composites in low-stress situations where fluoride release is desirable and aesthetic requirements are not high. PMID:11504433

Yap, A U; Teo, J C; Teoh, S H

2001-01-01

11

In vitro fluoride release from a different kind of conventional and resin modified glass-ionomer cements.  

PubMed

Fluoride release is important characteristic of glass-ionomer cements. Quantity of fluoride ions released from the glass-ionomer cements has major importance in definition of their biological activity. The objectives of this study were to define the quantity of fluoride ions released from the experimental glass-ionomer cements and to define the effect of fluoride ions released from the experimental glass-ionomer cements on their cytotoxicity. Concentrations of the fluoride ions released in the evaluated glass-ionomer cements were measured indirectly, by the fluoride-selective WTW, F500 electrode potential, combined with reference R503/D electrode. Statistical analyses of F-ion concentrations released by all glass-ionomers evaluated at two time points, after 8 and after 24 hours, show statistically higher fluoride releases from RMGICs: Vitrebond, Fuji II LC and Fuji Plus, when compared to conventional glass-ionomer cements: Fuji Triage, Fuji IX GP Fast and Ketac Silver, both after 8 and after 24 hours. Correlation coefficient between concentrations of fluoride ion released by evaluated glass-ionomer cements and cytotoxic response of UMR-106 osteoblast cell-line are relatively high, but do not reach levels of biological significance. Correlation between concentrations of fluoride ion released and cytotoxic response of NIH3T3 mouse fibroblast cell line after 8 hours is high, positive and statistically significant for conventional GICs, Fuji Triage and Fuji IX GP Fast, and RMGIC, Fuji II LC. Statistically significant Correlation coefficient between concentrations of fluoride ion released and cytotoxic response of NIH3T3 cell line after 24 hours is defined for RMGIC Fuji II LC only. PMID:23988173

Selimovi?-Dragaš, Mediha; Hasi?-Brankovi?, Lajla; Kora?, Fehim; ?apo, Nermin; Huseinbegovi?, Amina; Kobašlija, Sedin; Leki?, Meliha; Hatibovi?-Kofman, Šahza

2013-08-01

12

Biaxial Flexural Strength of High-Viscosity Glass-Ionomer Cements Heat-Cured with an LED Lamp during Setting  

PubMed Central

Adding heat to glass ionomers during setting might improve mechanical properties. The aim was to compare the biaxial flexural strength (BFS) between and within four glass ionomers, by time of exposure to a high-intensity LED light-curing unit. Materials and methods. Samples of Fuji 9 Gold Label, Ketac Molar Easymix, ChemFil Rock, and the EQUIA system were divided into three treatment groups (n = 30): without heating (Group 1), heated with LED lamp of 1400?mW/cm2 for 30?s while setting (Group 2), and heated with LED lamp of 1400?mW/cm2 for 60?s while setting (Group 3). Samples were stored for 48 hours in distilled water at 37°C until tested. BFS was tested, using a universal testing machine at a crosshead speed of 1?mm/min. Data were analyzed, using ANOVA test with the Bonferroni correction (? = 0.05). Heating the glass-ionomer cements with an LED curing light of 1400?mW/cm2 during setting for 30?s increased the BFS value of all GICs. No statistically significant difference in mean BFS scores was found between the EQUIA system and ChemFil Rock at 30?s and 60?s. The mean BFS value was statistically significantly higher for the EQUIA system and ChemFil Rock than for Fuji 9 Gold Label and Ketac Molar Easymix at all exposure times. PMID:23841095

Fabian Molina, Gustavo; Cabral, Ricardo Juan; Mazzola, Ignacio; Brain Lascano, Laura; Frencken, Jo E.

2013-01-01

13

Effects of etching and adhesive applications on the bond strength between composite resin and glass-ionomer cements  

PubMed Central

Objective This study determined the effects of various surface treatment modalities on the bond strength of composite resins to glass-ionomer cements. Material and Methods Conventional (KetacTM Molar Quick ApplicapTM) or resin-modified (PhotacTM Fil Quick AplicapTM) glass-ionomer cements were prepared. Two-step etch-rinse & bond adhesive (AdperTM Single Bond 2) or single-step self-etching adhesive (AdperTM PromptTM L-PopTM) was applied to the set cements. In the etch-rinse & bond group, the sample surfaces were pre-treated as follows: (1) no etching, (2) 15 s of etching with 35% phosphoric acid, (3) 30 s of etching, and (4) 60 s of etching. Following the placement of the composite resin (FiltekTM Z250), the bond strength was measured in a universal testing machine and the data obtained were analyzed with the two-way analysis of variance (ANOVA) followed by the Tukey's HSD post hoc analysis (p=0.05). Then, the fractured surfaces were examined by scanning electron microscopy. Results The bond strength of the composite resin to the conventional glass-ionomer cement was significantly lower than that to the resin-modified glass-ionomer cement (p<0.001). No significant differences were determined between the self-etching and etch-rinse & bond adhesives at any etching time (p>0.05). However, a greater bond strength was obtained with 30 s of phosphoric acid application. Conclusions The resin-modified glass-ionomer cement improved the bond strength of the composite resin to the glass-ionomer cement. Both etch-rinse & bond and self-etching adhesives may be used effectively in the lamination of glass-ionomer cements. However, an etching time of at least 30 s appears to be optimal. PMID:23329245

PAMIR, Tijen; SEN, Bilge Hakan; EVCIN, Ozgur

2012-01-01

14

Influence of citric acid on the surface texture of glass ionomer restorative materials  

PubMed Central

Aim: This study determined the effectiveness of G-coat plus surface protective agent over petroleum jelly on the surface texture of conventional Glass ionomer restorative materials. Materials and Methods: Three chemically cured conventional glass ionomer restorative materials type II, type IX and ketac molar were evaluated in this study. Sixty specimens were made for each restorative material. They were divided into two groups of thirty specimens each. Of the sixty specimens, thirty were coated with G-coat plus (a nano-filler coating) and the rest with petroleum jelly. Thirty samples of both protective coating agents were randomly divided into six groups of five specimens and conditioned in citric acid solutions of differing pH (pH 2, 3, 4, 5, 6 & 7). Each specimen was kept in citric acid for three hours a day, and the rest of time stored in salivary substitute. This procedure was repeated for 8 days. After conditioning, the surface roughness (Ra, ?m) of each specimen was measured using a surface profilometer (Taylor & Habson, UK). Data was analyzed using one-way analysis of variance (ANOVA) and Tukey's HSD test at a significance level of 0.05. Results: The surface textures of all the tested glass ionomer restorative materials protected with G-coat plus were not significantly affected by acids at low pH. The surface textures of all the tested glass ionomer restorative materials protected with petroleum jelly coating were significantly affected by acids at low pH. Conclusion: The effects of pH on the surface texture of glass ionomer restoratives are material dependent. Among all the materials tested the surface texture of Type II GIC (Group I) revealed marked deterioration when conditioned in solutions of low pH and was statistically significant. Hence, a protective coating either with G-coat plus or with light polymerized low viscosity unfilled resin adhesives is mandatory for all the glass ionomer restorations to increase the wear resistance of the restorative materials.

Reddy, Dappili Swami Ranga; Kumar, Ramachandran Anil; Venkatesan, Sokkalingam Mothilal; Narayan, Gopal Shankar; Duraivel, Dasarathan; Indra, Rajamani

2014-01-01

15

Micronucleus, alkaline, and human 8-oxoguanine glycosylase 1 modified comet assays evaluation of glass-ionomer cements - in vitro.  

PubMed

The purpose of this study was to evaluate the genotoxic potential of components leached from two conventional self-curing glass-ionomer cements (Fuji IX and Ketac Molar), and light-curing, resin modified glass-ionomer cements (Vitrebond, Fuji II LC). Evaluation was performed on human lymphocytes using alkaline and hOGG1 modified comet, and micronucleus assays. Each material, polymerised and unpolymerised, was eluted in extracellular saline (1 cm2 mL-1) for 1 h, 1 day, and 5 days. Cultures were treated with eluates using final dilutions of 10(-2), 10(-3), and 10(-4). Alkaline comet assay did not detect changes in DNA migration of treated cells regardless of the ionomer tested, polymerisation state, and elution duration. Glass ionomers failed to significantly influence micronucleus frequency. No oxidative DNA damage in treated lymphocytes was observed using hOGG1 modified comet assay. Obtained results indicate high biocompatibility of all tested materials used in the study under experimental conditions. PMID:24846952

Gali?, Elizabeta; Tadin, Antonija; Gali?, Nada; Kašuba, Vilena; Mladini?, Marin; Rozgaj, Ružica; Bio?ina-Lukenda, Dolores; Gali?, Ivan; Zelježi?, Davor

2014-06-01

16

Effect of green propolis addition to physical-mechanical properties of glass ionomer cements  

PubMed Central

Objective This study investigated the mechanical properties of glass ionomer cements (GICs) combined with propolis as a natural antimicrobial substance Material and Methods Typified green propolis, as an ethanolic extract (EEP) or in the lyophilized form (powder), was incorporated to specimens of Ketac Fil Plus, ChemFlex and Ketac Molar Easymix GICs. For each test, 8 specimens of each material were prepared. For water sorption and solubility tests, specimens were subjected to dehydration, hydration and re-dehydration cycles until a constant mass was obtained for each step. Measurements were recorded using a digital balance of 10-4 g precision. For the diametral tensile strength test, specimens were tested in a universal test machine at 0.5 mm/min crosshead speed after 24 h storage in deionized water. Data were evaluated by one-way ANOVA and Tukey’s tests (p<0.05). Results The addition of propolis to GIC clearly increased water sorption compared to pure material. Solubility was material-dependent and was not clearly evident. For the diametral tensile strength test, association with propolis altered negatively only Chemflex. Conclusion It may be concluded that incorporation of propolis to GICs alters some properties in a material-dependent condition. PMID:21552709

TROCA, Valéria Barros Pereira Barbosa; FERNANDES, Karen Barros Parron; TERRILE, Amélia Elena; MARCUCCI, Maria Cristina; de ANDRADE, Flaviana Bombarda; WANG, Linda

2011-01-01

17

Microleakage Evaluation of Class V Restorations with Conventional and Resin-modified Glass Ionomer Cements.  

PubMed

The aim of this study was to evaluate in vitro the marginal microleakage of conventional Glass Ionomer Cements (GIC) and Resin Modified Glass Ionomer Cements (RMGIC). The tested materials were grouped as follows: GIC category - G1 (Vidrion R - SSWhite); G2 (Vitro Fill - DFL); G3 (Vitro Molar - DFL); G4 (Bioglass R - Biodinâmica); and G5 (Ketac Fill - 3M/ESPE); and RMGIC category - G6 (Vitremer - 3M/ESPE); G7 (Vitro Fill LC - DFL); and G8 (Resiglass - Biodinâmica). Therefore, 80 class V cavities (2.0X2.0 mm) were prepared in bovine incisors, either in the buccal face. The samples were randomly divided into 8 groups and restored using each material tested according to the manufacturer. The root apices were then sealed with acrylic resin. The teeth were stored for 24 h in 100% humidity at 37°C. After storage, the specimens were polished with extra-slim burs and silicon disc (Soft-lex - 3M/ESPE), then were isolated with cosmetic nail polish up to 1 mm around the restoration. Then, the samples were immersed in 50% AgNO3 solution for 12 h and in a developing solution for 30 min. They were rinsed and buccal-lingual sectioned. The evaluation of the microleakage followed scores from 0 to 3. The Kruskal-Wallis test and Dunn method test were applied (a=0.05). The results showed that there was no difference between the enamel and dentin margins. However, GIC materials presented more microleakage than RMGIC. PMID:25284528

Pontes, Danielson Guedes; Guedes-Neto, Manoel Valcacio; Cabral, Maria Fernanda Costa; Cohen-Carneiro, Flávia

2014-09-01

18

Interaction of Glass-ionomer Cements with Moist Dentin  

Microsoft Academic Search

Glass-ionomer cements (GICs) are regarded as aqueous gels made up of polyalkenoic acid salts containing ion-leachable glass fillers. The consequence of water permeation across the GIC-dentin interface is unknown. This study used SEM, field-emission\\/environmental SEM (FE-ESEM), and TEM to examine the ultrastructure of GIC-bonded moist dentin. Dentin surfaces bonded with 6 auto-cured GICs were examined along the fractured GIC-dentin interfaces.

C. K. Y. Yiu; F. R. Tay; N. M. King; D. H. Pashley; S. K. Sidhu; J. C. L. Neo; M. Toledano; S. L. Wong

2004-01-01

19

Comparative evaluation of microleakage of three restorative glass ionomer cements: An in vitro study  

PubMed Central

Purpose: The aim of this study was to compare the microleakage of glass ionomers (conventional and resin modified) with that of recently introduced nanoionomers. Materials and Methods: Standardized class I and class V cavities were prepared on 120 young permanent teeth. Samples were equally divided into group I (class I restorations) and group II (class V restorations), and further divided into subgroups. The subgroups were restored with Fuji IX, Fuji II LC, and newly introduced Ketac™ N 100 (KN 100). Samples were thermocycled and submerged in Acridine dye for 24 h. Samples were sectioned to view under fluorescent microscope and marginal leakage was evaluated by Chi-square and Kruskal — Wallis test. Results: Fuji IX showed the maximum leakage, followed by LC II and the least was observed in KN 100. In class I restorations, there was significant difference while comparing Fuji IX with Fuji LC II and KN 100 and nonsignificant difference between LC II and KN100. In class V restorations, Fuji IX and KN100, KN 100 and LC II showed significant difference. Fuji IX and LC II showed nonsignificant difference. Conclusion: Within the limitations of this study, Fuji IX showed the maximum microleakage. KN 100 showed minimum leakage, better sealing ability, and was more consistent. PMID:25097418

Diwanji, Amish; Dhar, Vineet; Arora, Ruchi; Madhusudan, A.; Rathore, Ambika Singh

2014-01-01

20

The erosion kinetics of conventional and resin-modified glass-ionomer luting cements in acidic buffer solutions.  

PubMed

This study investigated the erosion kinetics of conventional and resin-modified glass-ionomer luting cements in acidic buffer solutions as a function of time. Disc shaped specimens were prepared from conventional (Ketac-Cem: KTC) and resin-modified glass ionomer cements (Fuji Plus: FP) and immersed in three acidic buffer solutions (0.01 M) namely, acetic acid/sodium acetate (AA(B)), lactic acid/sodium lactate (LA(B)) and citric acid/sodium citrate (CA(B)) with a constant pH of 4.1 and stored for 1, 8, 24, 48, 80, 120 and 168 h. F concentration was determined using ion-specific electrode. Si, Ca and Al concentrations were determined by atomic absorption spectroscopy. Ca, Al, Si and F solubility rates in both FP and KTC were the highest in CA(B) solution. The erosion rates of both FP and KTC in all buffer solutions increased as a function of immersion time. The amount of F eluted from FP was more than that of KTC. The total amount of elements released from FP was less than KTC in all solutions. PMID:23207217

Hazar-Yoruc, Binnaz; Bavbek, Andac Barkin; Özcan, Mutlu

2012-01-01

21

A long term study of fluoride release from metal-containing conventional and resin-modified glass-ionomer cements.  

PubMed

The objective of this study was to determine long term release of fluoride from a resin-modified glass-ionomer cement (RMGIC) (Fuji II LC (FLC)) compared with that from two conventional acid-base setting cements (HiDense (HD) and KetacSilver (KS)) marketed for similar restorative purposes. Fluoride release from discs of cement immersed in water or artificial saliva was measured for 2.7 years using an ion selective electrode technique. The RMGIC was affected by water if immersed immediately after setting. This is similar to conventional acid-base cements and the experimental method was designed to allow for this. Over the 2.7-year period, the RMGIC and HD released similar amounts of fluoride into both water and artificial saliva. In water, the RMGIC released the most fluoride, while in artificial saliva the highest release was from HD. KS released the least amount of fluoride in both immersing liquids. In artificial saliva, release was reduced to 17-25% of that found in water, with the RMGIC showing the greatest reduction. Both acid-base cured cements showed changes in colour over the 2.7-year span, while the colour of the RMGIC was stable. It was concluded that the RMGIC released equivalent or greater amounts of fluoride than the two acid-base cure glass-ionomers over a period of 2.7 years. PMID:11298908

Williams, J A; Billington, R W; Pearson, G J

2001-01-01

22

Biodegradation of dental composites/glass-ionomer cements.  

PubMed

Studies of the degradation processes, types of tests, and measurements and analyses of substances leaching out from resin-based composite materials and glass-ionomer cements are reviewed. For both types of materials, the initial release rate rapidly decreases to a low, but nearly constant, level. For composites, various types of degradation processes have been demonstrated. Elements from filler particles and degradation products from the resin (e.g., formaldehyde) leak out. Many substances are not properly identified. It is, however, difficult for in vitro and in vivo degradation to be compared. For glass ionomers, a total disintegration of a surface layer is observed, together with a slow release of elements from the bulk. Of the elements released, fluoride is the most interesting. Marked differences have been shown between in vitro and in vivo solubility tests. PMID:1292463

Oilo, G

1992-09-01

23

Local and Systemic Responses To Dental Composites and Glass Ionomers  

Microsoft Academic Search

For many years, the dental profession worked mainly with rather inert restorative materials that had a limited contact with vital tissue, and the opportunity for local and systemic complications was minimal. However, conditions have changed in recent years where the two leading non-mercury-containing materials, resin composites and glass-ionomer cements, are chemically active compounds and can have detrimental effects on pulp

Harold R. Stanley

1992-01-01

24

Microleakage of high-strength glass ionomer: resin composite restorations in minimally invasive treatment.  

PubMed

Atraumatic Restorative Treatment (ART) has been investigated as an alternative caries treatment. The technique involves removal of loose tooth structure with a spoon excavator, followed by placement of an adhesive restorative material, often a high-strength glass ionomer. This study compares the microleakage of a high-strength glass ionomer/resin composite and two occlusal resin composite restoration techniques. PMID:12061017

Platt, J A; Rhodes, B

25

Reconsidering glass-ionomer cements for direct restorations.  

PubMed

Glass-ionomer cements (GICs) have been used in dentistry for a number of applications, primarily as a base or liner under other direct filling materials or indirect restorative materials, for crown buildup/foundation restorations, or as luting cements for indirect restorations. However, GICs have many unique attributes that make them useful for either a full-contour restoration or sandwich/hybrid restorations where they are synergistic with composite resins. This article, which includes two brief case reports, discusses the potential advantages of GIC for some direct applications where composite resin or other materials may not be the most ideal choice. PMID:24571524

Pitel, Mark L

2014-01-01

26

Fluoride release and bioactivity evaluation of glass ionomer: Forsterite nanocomposite  

PubMed Central

Background: The most important limitation of glass ionomer cements (GICs) is the weak mechanical properties. Our previous research showed that higher mechanical properties could be achieved by addition of forsterite (Mg2SiO4) nanoparticles to ceramic part of GIC. The objective of the present study was to fabricate a glass ionomer- Mg2SiO4 nanocomposite and to evaluate the effect of addition of Mg2SiO4 nanoparticles on bioactivity and fluoride release behavior of prepared nanocomposite. Materials and Methods: Forsterite nanoparticles were made by sol-gel process. X-ray diffraction (XRD) technique was used in order to phase structure characterization and determination of grain size of Mg2SiO4 nanopowder. Nanocomposite was fabricated via adding 3wt.% of Mg2SiO4 nanoparticles to ceramic part of commercial GIC (Fuji II GC). Fluoride ion release and bioactivity of nanocomposite were measured using the artificial saliva and simulated body fluid (SBF), respectively. Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and registration of the changes in pH of soaking solution at the soaking period. Statistical analysis was carried out by one Way analysis of variance and differences were considered significant if P < 0.05. Results: The results of XRD analysis confirmed that nanocrystalline and pure Mg2SiO4 powder was obtained. Fluoride ion release evaluation showed that the values of released fluoride ions from nanocomposite are somewhat less than Fuji II GC. SEM images, pH changes of the SBF and results of the ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Statistical analysis showed that the differences between the results of all groups were significant (P < 0.05). Conclusion: Glass ionomer- Mg2SiO4 nanocomposite could be a good candidate for dentistry and orthopedic applications, through of desirable fluoride ion release and bioactivity. PMID:24130579

Sayyedan, Fatemeh Sadat; Fathi, Mohammadhossein; Edris, Hossein; Doostmohammadi, Ali; Mortazavi, Vajihesadat; Shirani, Farzaneh

2013-01-01

27

Improvement of enamel bond strengths for conventional and resin-modified glass ionomers: acid-etching vs. conditioning*  

PubMed Central

Objective: This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths (?TBSs) of conventional and resin-modified glass ionomer cements (GICs/RMGICs). Methods: Forty-eight bovine incisors were prepared into rectangular blocks. Highly-polished labial enamel surfaces were either acid-etched, conditioned with liquids of cements, or not further treated (control). Subsequently, two matching pre-treated enamel surfaces were cemented together with one of four cements [two GICs: Fuji I (GC), Ketac Cem Easymix (3M ESPE); two RMGICs: Fuji Plus (GC), RelyX Luting (3M ESPE)] in preparation for ?TBS tests. Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy (SEM). Results: Phosphoric acid etching significantly increased the enamel ?TBS of GICs/RMGICs. Conditioning with the liquids of the cements produced significantly weaker or equivalent enamel ?TBS compared to the control. Regardless of etching, RMGICs yielded stronger enamel ?TBS than GICs. A visible hybrid layer was found at certain enamel-cement interfaces of the etched enamels. Conclusions: Phosphoric acid etching significantly increased the enamel ?TBSs of GICs/RMGICs. Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays, using GICs/RMGICs to improve the bond strengths. RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength. PMID:24190447

Zhang, Ling; Tang, Tian; Zhang, Zhen-liang; Liang, Bing; Wang, Xiao-miao; Fu, Bai-ping

2013-01-01

28

A preliminary clinical trial using flowable glass-ionomer cement as a liner in proximal-ART restorations: The operator effect  

PubMed Central

Objectives: This in vivo study was carried out to assess the influence of the operator experience on the survival rate of proximal-ART restorations using a two-layer technique to insert the glass-ionomer cement (GIC). Study Design: Forty five proximal cavities in primary molars were restored in a school setting according to the ART technique. The cavities were restored by two operators with Ketac Molar Easymix, and received a flowable layer of GIC prior to a second GIC layer with a regular consistency. The operators had different clinical experiences with ART (no experience or two years of experience), but both completed a one-week training to perform the restorations and the GIC mixing in this study. Results: After a 12-month follow-up, 74% of the restorations survived; the main reason for failure was bulk fracture or total loss of the restoration.There was no operator influence (log-rank test p=0.2) Conclusion: The results encourage future well designed controlled clinical trials using the two-layer technique for insertion of GIC in proximal-ART restorations, after training the operators. Key words:Atraumatic Restorative Treatment (ART), Glass-ionomer, proximal restorations. PMID:23524424

Hesse, Daniela; Bonecker, Marcelo; Van Loveren, Cor; Van Amerongen, W E.; Raggio, Daniela P.

2013-01-01

29

Glass-ionomer cement restorative materials: a sticky subject?  

PubMed

Glass-ionomer cement (GIC) materials have been in clinical use since their inception 40 years ago. They have undergone several permutations to yield different categories of these materials. Although all GICs share the same generic properties, subtle differences between commercial products may occur. They have a wide range of uses such as lining, bonding, sealing, luting or restoring a tooth. In general, GICs are useful for reasons of adhesion to tooth structure, fluoride release and being tooth-coloured although their sensitivity to moisture, inherent opacity, long-term wear and strength are not as adequate as desired. They are useful in situations where they are not disadvantaged by their comparatively lower physical properties, such as where there is adequate remaining tooth structure to support the material and where they are not subject to heavy occlusal loading. The last decade has seen the use of these materials being extended. However, they are likely to retain their specific niches of clinical application. PMID:21564113

Sidhu, S K

2011-06-01

30

Stoichiometry of the leaching process of fluoride-containing aluminosilicate glass-ionomer glasses.  

PubMed

Dental glass-ionomer cements (GIC) set by an acid-base reaction between a polyalkenoic acid and an ion-leachable glass. The exact relationship between the glass composition and the setting and final properties of GIC is not yet fully elucidated. As part of a systematic study of this relationship, we studied the leaching stoichiometry of glasses used in commercial formulations to correlate the glass composition with its leaching properties. The leaching experiments were performed in acetic acid solutions at pH = 3.4 by means of a pH-stat method. After predetermined time intervals, the suspension was filtered and the filtrate was analyzed for the glass constituents. The usefulness of the pH-stat method for the determination of glass reactivity was corroborated. The deviation of the leaching stoichiometry with respect to the pure glass stoichiometry decreased with increasing relative content of mono- and bivalent glass network dwellers and modifiers. Indications were found that the latter can be leached out independently and preferentially, while the leaching of network dwellers is coupled with the aluminum release. The F content as well as the reactivity of the glass affect the amount of fluoride available for release from a set GIC. It could be concluded that the leaching stoichiometry of GIC glasses can be correlated with their absolute and relative composition. PMID:10403458

De Maeyer, E A; Verbeeck, R M; Vercruysse, C W

1999-07-01

31

Biocompatibility of glass ionomer cements with and without chlorhexidine  

PubMed Central

Objective: The aim of the present study is to evaluate the biocompatibility of glass ionomer cements (GICs) with and without chlorhexidine (CHX) as well as coated with varnish or not using in vitro cytotoxicity test. Materials and Methods: Biocompatibility of Fuji IX, Fuji IX with varnish, Fuji IX with 1% CHX diacetate and Fuji IX with 1% CHX diacetate with varnish was determined with in vitro cytotoxicity assay by using L929 mouse connective tissue fibroblasts. After 72 h, cell viabilities were evaluated by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay to determine the effects of the cements on the mitochondrial function and microscopic images were taken by scanning electron microscopy. Results: Statistical analysis was performed by one-way analysis of variance followed by the Bonferroni post-hoc test at a significance level of P < 0.05. 72 h after treatment, there were statistically significant differences between Fuji IX and Fuji IX-CHX (P < 0.001). In addition, the reduction of the cytotoxicity by coating the GICs with varnish was indicative and increased the cell viability ratio (P < 0.001). Conclusions: Fuji IX coated with varnish was found to be the most biocompatible one among others. Thus adding CHX significantly reduced the cell viability, it is assumed that, due to the leakage of CHX and the other components of the GICs to the cell culture medium, the cell viabilities were decreased, so it is highly recommended to use varnish not only to reduce the water loss from the GICs, but also to reduce the cytotoxicity of the GICs. PMID:24966735

Iz, Sultan Gulce; Ertugrul, Fahinur; Eden, Ece; Gurhan, S. Ismet Deliloglu

2013-01-01

32

Orthodontic bracket bonding with a plasma-arc light and resin-reinforced glass ionomer cement.  

PubMed

Developments in light-curing technology have led to the introduction of a plasma-arc light-curing unit that delivers high-intensity output for faster curing. The purposes of this study were to determine the shear bond strengths of light-cured resin-reinforced glass ionomer cement cured with a plasma-arc light-curing unit and to evaluate the durability of the resultant bond strength with thermal cycling. Comparisons were made between light-cured resin-reinforced glass ionomer cement and light-cured composite resin. Two light-curing units were used in this study: a plasma-arc light-curing unit and a conventional light-curing unit. The mean shear bond strengths of light-cured resin-reinforced glass ionomer cement with the plasma-arc and the conventional light-curing units were 20.3 MPa and 26.0 MPa, respectively. An analysis of variance showed no statistically significant differences between the plasma-arc and the conventional light-curing units. Light-cured resin-reinforced glass ionomer cement and light-cured composite resin demonstrated similar bond strengths and exhibited no statistical differences. There was no statistical difference in bond strength between the teeth that were thermal cycled and those that were not. Failure sites for the brackets bonded with light-cured resin-reinforced glass ionomer cement appeared to be predominantly at the bracket-adhesive interface. The SDs of light-cured composite resin were high for both light-curing units. Whereas the coefficients of variation for light-cured resin-reinforced glass ionomer cement ranged from 20% to 30%, those of light-cured composite resin ranged from 40% to 60%. The bond strength of light-cured resin-reinforced glass ionomer cement cured with either a conventional light-curing unit or a plasma-arc light-curing unit surpassed the clinically required threshold. The plasma-arc light-curing unit may be an advantageous alternative to the conventional light-curing unit for orthodontic bracket bonding with both light-cured resin-reinforced glass ionomer cement and light-cured composite resin. PMID:11455379

Ishikawa, H; Komori, A; Kojima, I; Ando, F

2001-07-01

33

Effect of surface treatments on the bond strength of glass ionomers to enamel  

Microsoft Academic Search

Objectives: The objective of this study was to evaluate the effect of various surface treatments on the bond strength of several glass ionomers to enamel, and to examine the resulting bond interface.Methods: Ground bovine enamel specimens were divided into groups which were pretreated with one of the following: (1) no pretreatment, (2) Vitremer primer, (3) 10% polyacrylic acid or (4)

Eileen A. Glasspoole; Robert L. Erickson; Carel L. Davidson

2002-01-01

34

Water sorption characteristics of resin-modified glass-ionomer cements  

Microsoft Academic Search

When restorative materials take up water, their dimensions and structural integrity may be affected. This study determined, using gravimetric measurements, the water sorption characteristics of four resin-modified glass-ionomer cements (RMGICs) immersed in either distilled water or artificial saliva. The dimensional changes on water storage were also determined. The RMGICs exhibited differing characteristics as they absorbed water. Percentage water uptake and

Widchaya Kanchanavasita; H. M. Anstice; Gavin J. Pearson

1997-01-01

35

The Effect of Glass Ionomer and Adhesive Cements on Substance P Expression in Human Dental Pulp  

PubMed Central

Objectives: The purpose of this study was to quantify the effect of glass ionomer and adhesive cements on SP expression in healthy human dental pulp. Study Design: Forty pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. In thirty of these premolars a Class V cavity preparation was performed and teeth were equally divided in three groups: Experimental Group I: Glass Ionomer cement was placed in the cavity. Experimental Group II: Adhesive Cement was placed in the cavity. Positive control group: Class V cavities only. The remaining ten healthy premolars where extracted without treatment and served as a negative control group. All pulp samples were processed and SP was measured by radioimmunoassay. Results: Greater SP expression was found in the adhesive cement group, followed by the glass ionomer and the positive control groups. The lower SP values were for the negative control group. ANOVA showed statistically significant differences between groups (p<0.0001). Tukey HSD post hoc tests showed statistically significant differences in SP expression between negative control group and the 3 other groups (p<0.01). Differences between the cavity-only group and the two experimental groups were also statistically significant (p<0.05 and p<0.01 respectively). There is also a statistically significant difference between the two experimental groups (p<0.01). Conclusions: These findings suggest that adhesive cements provoke a greater SP expression when compared with glass ionomer. Key words:Glass Ionomer, adhesive cement, Substance P, human dental pulp. PMID:23722145

Ariza-Garcia, German; Camelo, Patricia; Mejia, Monica; Ojeda, Karyn; Azuero-Holguin, Maria M.; Abad-Coronel, Dunia; Munoz, Hugo R.

2013-01-01

36

In-vitro Comparison of the Antimicrobial Properties of Glass Ionomer Cements with Zinc Phosphate Cements  

PubMed Central

White spot lesions are observed in nearly 50% of patients undergoing orthodontic treatment. Long-lasting antibacterial properties of orthodontic cements can reduce this phenomenon. The aim of this research was to compare antimicrobial activity of three commercial glass ionomer cements with three commercial zinc phosphate cements, over time, against streptococcus mutans and candida albicans. Direct contact test (DCT) was used to evaluate the antibacterial and antifungal activity of products after 48 h and 7 days of incubation. The results demonstrated that all the cements presented antibacterial activity but the antibacterial activity of glass ionomer cements was more than that of zinc phosphate cements. Counts of C. albicans after 48 h were lower and statistically different in the GIC group in relation to the control groups. But no differences were observed between GIC and control groups at 7 days. Based on the results of this study, the antimicrobial and mainly antifungal effects of all the cements were so short.

Vahid Dastjerdie, Elaheh; Oskoui, Mahvash; Sayanjali, Elham; Tabatabaei, Fahimeh Sadat

2012-01-01

37

[IR study of the hardening and maturation of glass ionomer cement].  

PubMed

The set reaction of glass ionomer cement has been investigated by means of IR spectra. It has been found that the band intensity around 1413 cm(-1) due to the vibration of polyacrylate salt increased with aging, and the shoulder band at 950 cm(-1) due to the stretching vibration of Si-OH still appeared during the periods studied. The results are consistent with that of mechanical determination of compressive strength, which suggested that the crosslink density increase resulting from the slow diffusion of Ca2+ and Al3+ is responsible for compressive strength increasing with aging, and forming and maturing of interface layer comprising of silica gel also have a significant effect on the properties of glass ionomer cements. PMID:16329489

Cheng, Han-ting; Liu, Han-xing; Xiao, Qun

2005-08-01

38

Effects of extraction media upon fluoride release from a resin-modified glass-ionomer cement  

Microsoft Academic Search

Previous studies have shown that various factors such as ionic composition or pH of the extraction medium may significantly\\u000a influence leaching of components from restorative materials. Therefore, it was the aim of this investigation to determine\\u000a the release of fluoride from a resin-modified glass-ionomer cement (GIC) following storage in various extraction media, including\\u000a an esterase buffer. Specimens of the resin-modified

W. Geurtsen; P. Bubeck; G. Leyhausen; F. Garcia-Godoy

1998-01-01

39

Effect of water on the physical properties of resin-modified glass ionomer cements  

Microsoft Academic Search

Objectives: Resin-modified glass ionomer cements (GIC) are available for clinical use as restorative materials or as liners and bases. This work was conducted to study the effect of water sorption on the physical properties of several resin-modified GIC, by changing the samples’ storage conditions.Methods: The water sorption, the flexural strength, the flexural elastic modulus, the Vickers hardness and the dimensional

M.-A Cattani-Lorente; V Dupuis; J Payan; F Moya; J.-M Meyer

1999-01-01

40

Failure of a Glass Ionomer to Remineralize Apatite-depleted Dentin  

Microsoft Academic Search

Remineralization of demineralized dentin lesions adjacent to glass-ionomer cements (GICs) has been reported in the literature. This study tested the hypothesis that a strontium-based GIC can remineralize completely demineralized dentin by nucleation of new apatite crystallites within an apatite-free dentin matrix. Human dentin specimens were acid-etched, bonded with Fuji IXGP, and immersed in a calcium-and-phosphate-containing 1.5X simulated body fluid (SBF)

Y. K. Kim; C. K. Y. Yiu; J. R. Kim; L. Gu; S. K. Kim; R. N. Weller; D. H. Pashley; F. R. Tay

2010-01-01

41

Antimicrobial Effects of Dental Luting Glass Ionomer Cements on Streptococcus mutans  

PubMed Central

Objective. To reduce secondary caries, glass ionomer luting cements are often used for cementing of indirect restorations. This is because of their well-known antimicrobial potential through the release of fluoride ions. The aim of this in vitro study was to investigate the antimicrobial effect of five dental luting cements which were based on glass ionomer cement technology. Methods. Five different glass ionomer based luting cements were tested for their antimicrobial effects on Streptococcus mutans in two different experimental setups: (i) determination of colony-forming units (CFUs) in a plate-counting assay; (ii) live/dead staining (LDS) and fluorescence microscopy. All experiments were conducted with or without prior treatment of the materials using sterilized human saliva. Antimicrobial effects were evaluated for adherent and planktonic bacteria. Bovine enamel slabs (BES) were used as negative control. BES covered with 0.2% chlorhexidine (CHX) served as positive control. Results. Each of the tested materials significantly reduced the number of initially adhered CFUs; this reduction was even more pronounced after prior incubation in saliva. Antimicrobial effects on adherent bacteria were confirmed by live-dead staining. Conclusion. All five luting cements showed an antimicrobial potential which was increased by prior incubation with human saliva, suggesting an enhanced effect in vivo. PMID:24795539

Altenburger, Markus; Spitzmuller, Bettina; Anderson, Annette; Hellwig, Elmar

2014-01-01

42

The influence of water sorption on the development of setting shrinkage stress in traditional and resin-modified glass ionomer cements  

Microsoft Academic Search

Objectives. The aim of this study was to determine the setting stress development for some traditional and resin-modified glass ionomer cements and to assess the effect of early water exposure to this stress. Methods. The development of the setting stress of the glass ionomer cements was determined in a tensilometer set-up as described earlier by Feilzer et al. (1987). Results.

Albert J. Feilzer; Afrodite I. Kakaboura; Anton J. de Gee; Carel L. Davidson

1995-01-01

43

Surgical management of invasive cervical resorption using resin-modified glass ionomer cement.  

PubMed

Invasive cervical resorption is an external resorption that begins below the epithelial attachment. It is caused primarily by dental trauma, orthodontic treatment, or dental bleaching. This case report involved an invasive Class III cervical resorption resulting from trauma to the superior right central incisor. Root canal treatment was followed by surgical intervention. The resorptive defect was debrided, and part of the tooth was restored with resin-modified glass ionomer cement. Postoperative follow-up revealed complete healing and healthy gingival attachment. PMID:24192742

Tavares, Warley Luciano Fonseca; Lopes, Renata Carvalho Portes; Oliveira, Ricardo Reis; Souza, Rodrigo Goncalves de; Henriques, Luiz Carlos Feitosa; Ribeiro-Sobrinho, Antonio Paulino

2013-01-01

44

Evaluation of the mechanical properties of dental adhesives and glass-ionomer cements  

Microsoft Academic Search

Adhesives and lining\\/base materials should relieve the stresses concentrated at the tooth\\/restoration interface. The study\\u000a aimed at comparing the mechanical properties of eight adhesives and six glass-ionomer cements (GICs). The adhesives were applied\\u000a on dentin disks, whereas 2 mm?×?3 mm?×?2 mm GICs specimens were prepared in a teflon mold. Vicker’s hardness (VH), elastic\\u000a modulus (E), creep (Cr) and elastic work (We\\/Wtot) were measured

Elisa Magni; Marco Ferrari; Reinhard Hickel; Nicoleta Ilie

2010-01-01

45

Ultrasonically set novel NVC-containing glass-ionomer cements for applications in restorative dentistry  

Microsoft Academic Search

The objective of this study is to investigate the effects of application of ultrasound on the physical properties of a novel\\u000a NVC (N-vinylcaprolactam)-containing conventional glass-ionomer cement (GIC). Experimental GIC (EXP) samples were made from the acrylic\\u000a acid (AA)–itaconic acid (IA)–NVC synthesized terpolymer with Fuji IX powder in a 3.6:1 P\\/L ratio as recommended by the manufacturer.\\u000a Specimens were mixed and

Alireza Moshaverinia; Sahar Ansari; Maryam Moshaverinia; Scott R. Schricker; Winston W. L. Chee

46

Microleakage of glass-ionomer cement placed in association with non-setting calcium hydroxide.  

PubMed

The purpose of this investigation was to determine whether non-setting calcium hydroxide [Ca (OH)2] cement placed in the root canal system of premolar teeth would affect the subsequent microleakage of a glass-ionomer restoration (GIC). Following selection, 62 human premolar teeth extracted for orthodontic reasons were accessed and root canals prepared according to a standardized procedure. The specimens were then allocated randomly into two major groups each of 30 teeth. Two other teeth were used as a positive and a negative control. The control group was restored with glass-ionomer cement following drying of the canal and placement of a cotton wool pledget. The test group had all canals dressed with non-setting Ca(OH)2 and then was subdivided, one set (n = 22) being restored following conditioning of the access cavity margins, the other (n = 8) having the margins cleaned with a hand excavator. Samples were assessed for microleakage using a two-point scoring system (leakage or no leakage) in conjunction with a clearing technique using AgNO3. Using Fisher's exact test, a statistically significant difference was found between the control and test groups (P < 0.05) but there was no significant difference between the excavated and conditioned cavities (P=0.55). It is concluded that contamination of access cavity margins with Ca(OH)2 during medication of a root canal interferes with the bond of GIC, resulting in increased microleakage in vitro. PMID:15842248

Mahmood, S A; Wood, D J; Boyle, E L; Jarad, F D; Youngson, C C

2005-05-01

47

Effects of enamel deproteinization on bracket bonding with conventional and resin-modified glass ionomer cements.  

PubMed

The objective of this study was to test the effects of enamel deproteinization on bracket bonding with conventional and resin-modified glass ionomer cement (RMGIC). One hundred premolars, extracted for orthodontic reasons, were divided into five groups (n = 20). Group 1 (control): enamel was etched with 35 per cent phosphoric acid, a thin layer of adhesive was applied, and the brackets were bonded with Transbond XT. Group 2: enamel was etched with 10 per cent polyacrylic acid and the brackets were bonded with conventional glass ionomer cement (GIC). Group 3: enamel was treated with 5.25 per cent NaOCl, etched with 10 per cent polyacrylic acid, and the brackets were bonded with conventional GIC. Group 4: enamel was etched with 10 per cent polyacrylic acid and the brackets were bonded with RMGIC. Group 5: enamel was treated with 5.25 per cent NaOCl, etched with 10 per cent polyacrylic acid, and the brackets were bonded with RMGIC. The teeth were stored in distilled water for 24 hours before they were submitted to shear testing. The results demonstrated that bond strength values of group 1 (17.08 ± 6.39 MPa) were significantly higher in comparison with the other groups. Groups 2 (3.43 ± 1.94 MPa) and 3 (3.92 ± 1.57 MPa) presented values below the average recommended in the literature. With regard to adhesive remnant index, the groups in which the enamel was treated with NaOCl showed a behaviour similar to that of the resin composite. It is conclude with enamel treatment with NaOCl increased bonding strength of brackets bonded with GIC and RMGIC, but increased bond strength was not statistically significant when compared to the untreated groups. PMID:22379131

Pereira, Tatiana Bahia Junqueira; Jansen, Wellington Corrêa; Pithon, Matheus Melo; Souki, Bernardo Quiroga; Tanaka, Orlando Motohiro; Oliveira, Dauro Douglas

2013-08-01

48

Comparison of the push-out shear bond strength of four types of glass ionomers when used to bond amalgam: An in vitro study  

PubMed Central

Background: Dental amalgam is the primary direct posterior restorative material used worldwide, but it have certain shortcomings due to the lack of adhesiveness to the cavity. The introduction of the concept of bonded amalgam helped improve the use of amalgam as a restorative material. Aim: Evaluation of the comparative push-out shear bond strength of four types of conventional glass ionomers used to bond amalgam to tooth in simulated class I situations. Materials and Methods: Four chemical cure glass ionomers are used: GC Fuji I, GC Fuji II, GC Fuji III and GC Fuji VII, and are compared with unbonded amalgam. The push-out bond strength was tested using the Instron Universal Testing Machine at a crosshead speed of 0.5 mm/min. Statistical Analysis: One-way ANOVA and post hoc Bonferroni tests were used to analyze the data. Results: The results showed that the use of glass ionomer to bond amalgam resulted in an increase in the bond strength of amalgam. The Type VII glass ionomer showed the highest bond strength in comparison with the other glass ionomers. Conclusions: Conventional glass ionomer bonds to amalgam and shows a beneficial increase in the bond strength of the restoration in comparison with unbonded amalgam. PMID:22144798

Mathew, Vinod Babu; Ramachandran, S; Indira, R; Shankar, P

2011-01-01

49

An evaluation of microleakage of various glass ionomer based restorative materials in deciduous and permanent teeth: An in vitro study  

PubMed Central

Aim To evaluate the microleakage of recently available glass ionomer based restorative materials (GC Fuji IX GP, GC Fuji VII, and Dyract) and compare their microleakage with the previously existing glass ionomer restorative materials (GC Fuji II LC) in primary and permanent teeth. Method One hundred and fifty (75 + 75) non-carious deciduous and permanent teeth were restored with glass ionomer based restorative materials after making class I cavities. Samples were subjected to thermocycling after storing in distilled water for 24 h. Two coats of nail polish were applied 1 mm short of restorative margins and samples sectioned buccolingually after storing in methylene blue dye for 24 h. Microleakage was assessed using stereomicroscope. Result Significant differences (P < 0.05) were found when inter group comparisons were done. Except when GC Fuji VII (Group III) was compared with GC Fuji II LC (Group II) and Dyract (Group IV), non-significant differences (P > 0.05) were observed. It was found that there was no statistically significant difference when the means of microleakage of primary teeth were compared with those of permanent teeth. Conclusions GC Fuji IX GP showed maximum microleakage and GC Fuji VII showed least microleakage. PMID:23960526

Singla, Teena; Pandit, I.K.; Srivastava, Nikhil; Gugnani, Neeraj; Gupta, Monika

2011-01-01

50

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment  

PubMed Central

Summary Background Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. Aim The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Materials and methods Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. Results No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. Conclusions When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs. PMID:24611090

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

51

Mechanical behavior of glass ionomer cements as a function of loading condition and mixing procedure.  

PubMed

With a view to comparing conventional (CGIC) and resin-modified glass ionomer cements (RMGIC) in terms of mechanical properties, these materials were subjected to different loading conditions for evaluation. In addition, this study investigated the assumption that capsulated systems possess superior mechanical properties compared to the hand-mixed systems, owing to the former's better material homogeneity and a more precise adjustment of the powder-liquid ratio. In view of the aims of this study, the following mechanical properties were determined: strength and modulus of elasticity in flexural test, diametric tensile and compressive strengths, as well as variation of hardness and modulus of elasticity with depth. In all macroscopic strength tests, the RMGICs performed significantly better than the CGICs. In microhardness evaluation, the differences were levelled out. In particular, the mechanical properties of RMGICs were comparable to those of microfilled and packable composites. The effect of mixing was closely intertwined with material property. The tested CGICs performed better when they were hand-mixed, whereas RMGICs fared better in the capsulated form. PMID:17886457

Ilie, Nicoleta; Hickel, Reinhard

2007-07-01

52

Antibacterial activity and physical properties of glass-ionomer cements containing antibiotics.  

PubMed

This study evaluated the antibacterial effects, physical properties and bonding strengths of conventional glass-ionomer cements (GICs) containing antibiotics and determined the optimal concentration of antibiotics addition for use with the ART approach. Fuji IX GIC was used as a control. Three antibiotic mixtures, ciprofloxacin, metronidazole and minocycline, were added to powdered GIC (Fuji IX) to obtain concentration ratios of 1.5, 3.0 and 4.5% w/w. The antibacterial activity of each GIC was evaluated against Streptococcus mutans or Lactobacillus casei using agar-diffusion methods. The release of antibiotics was analyzed by high-performance liquid chromatography (HPLC). The compressive strength and bonding strength to dentin were measured and compared with those of control samples. The results were analyzed using the Mann-Whitney test and Wilcoxon test. All tested groups showed a significantly greater inhibition with growth of the selected bacteria in comparison to the control groups (p < 0.01). However, the 3% and 4.5% concentration ratios of antibiotics had significantly lower compressive strength and lower bond strength to dentin than the control group (p = 0.003). The GIC-containing antibiotics were effective in inhibiting S Mutans and L Casei. The addition of a 1.5% antibiotic mixture was optimal to giving appropriate physical and bonding properties. PMID:19192833

Yesilyurt, Cemal; Er, Kursat; Tasdemir, Tamer; Buruk, Kurtulus; Celik, Davut

2009-01-01

53

Inhibitory effects on selected oral bacteria of antibacterial agents incorporated in a glass ionomer cement.  

PubMed

The objectives of the study were to investigate the antimicrobial efficacy, over time, of combining antibacterial agents with a glass ionomer cement (GIC). This was assessed using an agar diffusion test. Chlorhexidine hydrochloride, cetylpyridinium chloride, cetrimide and benzalkonium chloride were added to Fuji IX GIC at 0, 1, 2 and 4% w/w. Antibacterial-GIC specimens were placed onto agar plates inoculated with one of six bacterial species (Streptococcis, Lactobacillus, and Actinomyces, two each) and the area of inhibition calculated after 24 h incubation. The experiment was repeated weekly and at week 11 the surface of the specimen was abraded prior to replacing on inoculated agar plates. Control specimens of the GIC produced no bacterial inhibition. The antibacterial-GIC combination specimens showed significant inhibition which decreased at different rates over the test period. Resurfacing of the specimens showed a dramatic increase of antibacterial action similar to levels produced on week 1. CT-GIC showed the greatest (p < 0.005) inhibitory effect throughout the experimental period for 4 out of 6 test bacteria. The addition of antibacterial agents to Fuji IX creates a GIC material with significant antimicrobial action in vitro which is dependent on concentration and type of antibacterial agent, and appears to be associated primarily with a release of the antibacterial from the surface layer of the specimen. PMID:12652048

Botelho, Michael G

2003-01-01

54

The effect of etching on a number of glass ionomer cements.  

PubMed

In view of the continuing interest in the use of glass ionomer cements as a dentine substitute or base under composite resins, further investigations were carried out on the effects of the length of time of etching of the surface of the cement prior to the placement of the resin. A number of cements are available on the Australian market which are advocated for use in this technique. Each of them was subjected to etching for periods of 15, 30, 45, or 60 seconds and then stored in water for one week. Examination under a dissecting microscope and a scanning electron microscope revealed some variation in results between the different cements. It would appear that not all those materials presently marketed for this purpose are entirely suitable. Whilst 15 seconds is the preferred time for most cements, some require times up to 60 seconds to achieve the best result. Also, some of the cements showed signs of cracking, expansion and distortion after they had been stored in water for one week to allow for maturation before being prepared for viewing under the SEM. It is suggested that this group of cements is not suitable for the 'sandwich' technique. PMID:2275652

Fuss, J; Mount, G J; Makinson, O F

1990-08-01

55

Sealing furcation perforations with silver glass ionomer cement: an in vitro evaluation.  

PubMed

Furcation perforations sealed with silver glass ionomer cement (Chelon Silver) were evaluated in vitro compared with amalgam. Access cavities were prepared in 25 extracted human molar teeth. The coronal orifices of the root canals were sealed with amalgam and varnish. Naturally occurring coronal leakage through the intact pulp chamber floor was determined quantitatively for each tooth, using a modified fluid transport model, under pressure of 1.2 Atm. Each tooth was then disconnected from the system, perforated at the furcation, and the perforation sealed with either Chelon Silver (10 teeth) or amalgam (10 teeth); five remaining teeth served as a negative control. After incubation for 24 h at 37 degrees C in 100% humidity, teeth were reconnected to the modified fluid transport system, and coronal leakage under pressure was evaluated at 1, 2, 6, 15, and 24 h. Leakage through each tooth was compared with that of its own intact pulp chamber floor before perforation and the groups compared with each other. No significant difference was found between the mean leakage of the intact pulp chamber floors of the two groups. Chelon Silver had a significantly better sealing ability than amalgam (p < 0.01): leakage rate of 0.007 and 0.017 microliter/min, respectively. It is concluded that Chelon Silver could be an adequate sealer for furcation perforations. PMID:11199781

Fuss, Z; Abramovitz, I; Metzger, Z

2000-08-01

56

Repairability of three resin-modified glass-ionomer restorative materials.  

PubMed

The purpose of this study was to evaluate the repair shear bond strengths of three resin-modified glass-ionomer restorative materials repaired at two different times. Thirty specimens of Fuji II LC, Vitremer, and Photac-Fil were prepared in cavities (2 mm x 7 mm) cut into acrylic resin cylinders. After the initial fill, half of the specimens were repaired 5 minutes later and half 1 week later. The specimens were stored in 37 degrees C distilled water when not being repaired or tested. Repairs were made without any surface preparation of the initial fill. Each specimen was mixed according to the manufacturer's directions, placed in the preparation in 1-mm increments and photocured for 40 seconds. The last increment was covered with a plastic strip and a glass slide before curing to create a smooth surface. Repairs were accomplished by drying the specimen for 10 seconds, then adding the new material to the unprepared surface using a 3-mm-thick polytetrafluoroethylene mold. The specimens were thermocycled 500 times, stored in 37 degrees C distilled water for 1 week, then loaded to failure in shear at a rate of 0.5 mm/min. Data were analyzed using a one-way ANOVA and Z-value multiple comparison test to determine significant differences at the 0.05 significance level. Vitremer showed no significant difference in shear bond strength for 5-minute and 1-week repair periods, while Fuji II LC and Photac-Fil did. Repair bond strength of Vitremer was significantly greater than Fuji II LC and Photac-Fil at both repair times. This study showed that time of repair significantly affected the bond strength of two of the materials tested. PMID:9760918

Shaffer, R A; Charlton, D G; Hermesch, C B

1998-01-01

57

Development of a novel antimicrobial-releasing glass ionomer cement functionalized with chlorhexidine hexametaphosphate nanoparticles  

PubMed Central

Background Glass ionomer cements (GICs) are a class of dental biomaterials. They have a wide range of uses including permanent restorations (fillings), cavity linings, fissure sealants and adhesives. One of the most common reasons for replacing a dental restoration is recurrent bacterial tooth decay around the margins of the biomaterial. Therefore, a dental biomaterial which creates a sustained antimicrobial environment around the restoration would be of considerable clinical benefit. In this manuscript, the formulation of a GIC containing novel antimicrobial nanoparticles composed of chlorhexidine hexametaphosphate at 1, 2, 5, 10 and 20% powder substitution by mass is reported. The aim is to create GICs which contain chlorhexidine-hexametaphosphate nanoparticles and characterize the nanoparticle size, morphology and charge and the release of chlorhexidine and fluoride, tensile strength and morphology of the GICs. Results The GICs released chlorhexidine, which is a broad spectrum antimicrobial agent effective against a wide range of oral bacteria, over the duration of the experiment in a dose-dependent manner. This was not at the expense of other properties; fluoride release was not significantly affected by the substitution of antimicrobial nanoparticles in most formulations and internal structure appeared unaffected up to and including 10% substitution. Diametral tensile strength decreased numerically with substitutions of 10 and 20% nanoparticles but this difference was not statistically significant. Conclusion A series of GICs functionalized with chlorhexidine-hexametaphosphate nanoparticles were created for the first time. These released chlorhexidine in a dose-dependent manner. These materials may find application in the development of a new generation of antimicrobial dental nanomaterials. PMID:24456793

2014-01-01

58

Effect of different root caries treatments on the sealing ability of conventional glass ionomer cement restorations.  

PubMed

In this study we compared the microleakage of conventional glass ionomer cement (GIC) restorations following the use of different methods of root caries removal. In vitro root caries were induced in 75 human root dentin samples that were divided in five groups of 15 each according to the method used for caries removal: in group 1 spherical carbide burs at low speed were used, in group 2 a hand-held excavator was used, and in groups 3 to 5 an Er,Cr:YSGG laser was used at 2.25 W, 40.18 J/cm(2) (group 3), 2.50 W, 44.64 J/cm(2) (group 4) and 2.75 W, 49.11 J/cm(2) (group 5). The air/water cooling during irradiation was set to 55%/65% respectively. All cavities were filled with GIC. Five samples from each group were evaluated by scanning electron microscopy (SEM) and the other ten samples were thermocycled and submitted to a microleakage test. The data obtained were compared by ANOVA followed by Fisher's test (p?0.05). Group 4 showed the lowest microleakage index (56.65 6.30; p<0.05). There were no significant differences among the other groups. On SEM images samples of groups 1 and 2 showed a more regular interface than the irradiated samples. Demineralized dentin below the restoration was observed, that was probably affected dentin. Group 4 showed the lowest microleakage values compared to the other experimental groups, so under the conditions of the present study the method that provided the lowest microleakage was the Er,Cr:YSGG laser with a power output of 2.5 W yielding an energy density of 44.64 J/cm(2). PMID:20886360

Geraldo-Martins, Vinicius R; Lepri, Cesar P; Palma-Dibb, Regina G

2012-01-01

59

Mechanical properties of a resin-modified glass ionomer cement for luting: effect of adding spherical silica filler.  

PubMed

This study investigated the effects of spherical silica filler (SSF) on the workability and mechanical properties of resin-modified glass ionomer cements for luting (RMGICL). Varying powder/liquid ratios (P/L=2.0, 2.2, 2.4, and 2.6) of a commercially available glass ionomer cement (Fuji Lute, GC Corp.) were mixed with SSF at different weight percentages (5, 7.5, and 10%). On film thickness, statistically significant effects of SSF addition were noted at 2.5 minutes after mixing started, notably at P/L=2.4 and 2.6 when 7.5 and 10 wt% of SSF were added. The same result was also obtained for consistency evaluation. On mechanical and bonding strengths to the tooth substrate, no statistically significant differences were observed among all the SSF weight percentages within each P/L ratio. SSF-added RMGICL at a higher powder/liquid ratio exhibited increased mechanical and bonding strengths when compared to a control without SSF addition, but nonetheless maintained the film thickness with no further increase. PMID:20484829

E, Lihua; Irie, Masao; Nagaoka, Noriyuki; Yamashiro, Takashi; Suzuki, Kazuomi

2010-05-01

60

Influence of powder/liquid ratio on the radiodensity and diametral tensile strength of glass ionomer cements  

PubMed Central

Objective To determine the influence of P/L ratio on the radiodensity and diametral tensile strength (DTS) of glass ionomer cements. Material and Methods There were 2 factors under study: P/L ratio (manufacturer's recommended P/L ratio and a 50% reduced P/L ratio), and materials (Vitro Molar, Vitro Fil, Vitro Cem conventional GICs and Vitro Fil LC, Ortho Glass LC RMGICs). Five 1-mm-thick samples of each material-P/L ratio were produced for radiodensity evaluation. Samples were x-ray exposed onto Digora phosphor plate and radiodensity was obtained using the software Digora for Windows 2.5 Rev 0. For DTS, five (4.0x8.0 mm) cylinder samples of each material were tested (0.5 mm/min). Data were subjected to one- and two-way ANOVA (5x2) followed by Tukey's HSD test, or Kruskal-Wallis and Dunn's method. For paired comparisons, t-test or Mann-Whitney test were used (a=0.05). Results There was a significant interaction (P=0.001) for the studied factors (materials vs. P/L ratio). Reduced P/L ratio resulted in significantly lower DTS for the RMGICs, but radiodensity was affected for all materials (P<0.05). Conclusions Reduced P/L ratio affected properties of the tested glass ionomer cements. RMGICs were more susceptible to lower values of DTS, but radiodensity decreased for all materials following P/L ratio reduction. PMID:21308288

FONSECA, Rodrigo Borges; BRANCO, Carolina Assaf; QUAGLIATTO, Paulo Sergio; GONCALVES, Luciano de Souza; SOARES, Carlos Jose; CARLO, Hugo Lemes; CORRER-SOBRINHO, Lourenco

2010-01-01

61

Clinical and microbiological performance of resin-modified glass-ionomer liners after incomplete dentine caries removal.  

PubMed

The aims of this study were to evaluate clinically and microbiologically the effects of two resin-modified glass-ionomer cements (RMGICs) used as liners after incomplete dentine caries removal and to identify Streptococcus mutans and Streptococcus sobrinus strains isolated from dentine samples, before and after indirect pulp treatment. Twenty-seven primary molars with deep carious lesions, but without signs and symptoms of irreversible pulpitis, were submitted to indirect pulp treatment. Treatment consisted of incomplete excavation of the carious dentine, application of one of the RMGICs (Vitrebond or Fuji Lining LC) or calcium hydroxide cement (Dycal), and sealing for 3 months. Clinical evaluation (consistency, color, and wetness of dentine) and carious dentine collects were performed before temporary sealing and after the experimental period. Microbiological samples were cultivated in specific media for subsequent counting of mutans streptococci (MS) and lactobacilli (LB). MS colonies were selected for identification of S. mutans and S. sobrinus by polymerase chain reaction. After 3 months, the remaining dentine was hard and dry, and there was a significant decrease in the number of MS and LB, in all groups, although complete elimination was not achieved in 33% and 26% of the teeth for MS and LB, respectively. From 243 MS colonies selected, 216 (88.9%) were identified as S. mutans and only 2 (0.8%) as S. sobrinus. The use of resin-modified glass-ionomer liners after incomplete caries removal, as well as a calcium hydroxide cement, promoted significant reduction of the viable residual cariogenic bacteria in addition to favorable clinical changes in the remaining carious dentine. PMID:19548010

Duque, Cristiane; Negrini, Thais de Cássia; Sacono, Nancy Tomoko; Spolidorio, Denise Madalena Palomari; de Souza Costa, Carlos Alberto; Hebling, Josimeri

2009-12-01

62

Effect of moisture protective coatings on the strength of a modern metal-reinforced glass-ionomer cement.  

PubMed

The strength of a modern, low metal:glass ratio, metal-reinforced glass-ionomer cement was measured evaluating a number of protective barriers: one light-cured resin, two solvent-based dental varnishes and petroleum jelly. The cement was exposed to water at 10 and 60 min from start of mix. The results obtained with these protecting agents were compared with those obtained where no protection was applied. A comparison of uniaxial flexural strength and biaxial flexural strength showed the latter to be more discriminating. Proprietary dental varnishes were superior to petroleum jelly, producing similar strengths of 50 MPa. Petroleum jelly was, however, preferable to no protection. Moisture protection during the first 30 min was found to be beneficial, thereafter no further strength increase was found. A second material, a cement which has a high metal:glass ratio, was found to be more moisture resistant but weaker in strength than the modern material, with a biaxial strength of 39 MPa. PMID:9722100

Williams, J A; Billington, R W; Pearson, G J

1998-07-01

63

Minimal intervention dentistry II: part 7. Minimal intervention in cariology: the role of glass-ionomer cements in the preservation of tooth structures against caries.  

PubMed

Glass-ionomer cements (GICs) are essential materials in clinical practice because of their versatility, self-adhesion to enamel and dentine, and good biocompatibility. In addition, being chemically cured, with no shrinkage stress, makes them well suited for minimally invasive restorative techniques. This article looks at some of the clinical situations where the chemical adhesion and high biocompatibility of GIC are important for clinical success: excavation of deep carious lesions, fissure sealing and protection of root surfaces against caries. PMID:24852986

Ngo, H; Opsahl-Vital, S

2014-05-01

64

Clinical Evaluation of Resin Composite and Resin Modified Glass Ionomer in Class III Restorations of Primary Maxillary Incisors: A Comparative In Vivo Study  

PubMed Central

Restoration of primary teeth continues to be an important facet of restorative dentistry. In comparison to restorations in permanent dentition, the longevity of those in primary teeth is significantly different for all materials. This makes the assessment of these fillings as a separate group meaningful. As there is lack of supporting clinical data with regard to the restoration of primary incisors, it would be judicious to consider why this is so and determine if studies can be designed to gain new information. The purpose of this study was therefore to evaluate and compare the clinical efficacy of composite resins and resin-modified glass ionomer cement restorations of primary incisors, over a period of one year. Methods: The study group consisted of 40 patients (3½- 5 ½ years of age) with at least one pair of similar sized lesions in the middle1/3 of the same proximal surface of contralateral primary maxillary incisors. Composite resin and resinmodified glass ionomer cement restorations were placed in primary maxillary incisors using split-mouth design. The restorations were evaluated at different intervals of 3,6,9, months and 1 year using Ryge’s criteria. Data obtained was analyzed using Mann-Whitney test. Results: The results revealed no statistical significance in the difference of clinical characteristics between the two restorative materials. Interpretation and conclusion: (1) Resin-modified glass ionomer cement and composite resin restorative materials showed acceptable clinical performance after 1 year in primary teeth. (2) Resin-modified glass ionomer cement and composite resin restorative materials functioned well as class III restorative materials in primary teeth.

Mohan Das, Usha; Viswanath, Deepak; Azher, Umme

2009-01-01

65

Comparative evaluation of intracanal sealing ability of mineral trioxide aggregate and glass ionomer cement: An in vitro study  

PubMed Central

Aims: The purpose of this study was to compare the sealing ability of Mineral Trioxide Aggregate (MTA) and Glass Ionomer Cement (GIC) when used over gutta-percha as intracanal sealing materials. The study also evaluated the sealing ability of Zinc oxide eugenol (ZOE) cement and Acroseal sealer. Materials and Methods: Teeth were obturated with gutta-percha using sealer ZOE (group A, C, D) and Acroseal (group B). The groups were further divided into 2 subgroups (15 premolars each) on the basis of intracanal sealing material used: GIC subgroups (A1, B1) and MTA in subgroups (A2, B2). The clearing technique was used in this study for leakage evaluation. Seventy mandibular premolars were prepared using step-back technique and divided into experimental groups A and B (30 premolars each) and the positive and negative control groups C and D (5 premolars each). Statistical analysis used: Coronal microleakage was determined under stereomicroscope using 15X magnification. Data was statistically analyzed using one-way ANOVA followed by Post-Hoc Multiple comparison (Bonferroni). Results: MTA group leaked significantly less than GIC group (P < 0.05). Acroseal exhibited better sealing ability than ZOE sealer. Teeth with no intracanal barrier showed almost complete leakage. Conclusions: MTA may be preferred over GIC as an intracanal barrier. PMID:24347890

Malik, Gauri; Bogra, Poonam; Singh, Simranjeet; Samra, Rupandeep K

2013-01-01

66

Atraumatic restorative treatment and glass-ionomer sealants in a school oral health programme in Zimbabwe: evaluation after 1 year.  

PubMed

An oral health care programme in secondary schools using the atraumatic restorative treatment (ART) technique for dental caries was started in 1993. Glass-ionomer was used as the restorative and sealant material. Sealants were placed using the "press finger' technique. Results after 1 year revealed a survival percentage for one-surface ART restorations of 93.4 whilst the complete and partial retention percentages for sealants were 60.3 and 13.4, respectively. No caries was observed in teeth restored using ART, and only 0.8% of surfaces diagnosed as having early enamel lesions at the start of the programme and sealed consequently had progressed into active dentinal lesions after 1 year. The sealant retention percentage and the survival percentage of ART restorations were influenced by an operator effect. The majority of restorations were carried out without administering local anaesthesia. The mean treatment time for one-surface ART restorations was 22.1 min (range per operator of 19.8-23.6 min), whilst the mean time for placing sealants was 9.4 min (range per operator of 8.2-10.8 min). Post-operative sensitivity was reported for 6% of the teeth restored. 95% of the students were satisfied with ART as a treatment modality. It is concluded that ART may in part be the answer to the unavailability of restorative care for many population groups globally. PMID:8946101

Frencken, J E; Makoni, F; Sithole, W D

1996-01-01

67

Fluoride release and recharge characteristics of denture base resins containing surface pre-reacted glass-ionomer filler.  

PubMed

The flexural strength, flexural modulus, and the amount of fluoride released from four experimental denture base resins containing 5, 10, 20 and 30 wt% surface pre-reacted glass-ionomer (S-PRG) filler added to the powder were evaluated. The mean flexural strength of the experimental resins, except the 30 wt%, and the flexural modulus of all the resins, complied with ISO 1567 requirements. In the 20 wt% resin, the amount of fluoride released in the initial phase was 1.88 microg/cm2/day, after which the level decreased. After recharging in a 9000 ppm fluoride solution for eight hours, the level of released fluoride increased markedly to 40.21 microg/cm2/16 hrs. Our results show that fluoride levels increased as a function of the S-PRG filler content. After the almost completely discharged resins were recharged, similar fluoride release occurred again. These results suggest that denture base resins containing S-PRG filler have great recharge and release capabilities which may assist in preventing root caries of abutment teeth. PMID:19496404

Kamijo, Kazuko; Mukai, Yoshiharu; Tominaga, Takatoshi; Iwaya, Izumi; Fujino, Fukue; Hirata, Yukio; Teranaka, Toshio

2009-03-01

68

Comparison of Shear Bond Strength of Resin-Modified Glass Ionomer and Composite Resin to Three Pulp Capping Agents  

PubMed Central

Background and aims. Present study was designed to compare the bonding strength of resin-modified glass ionomer (RMGI) and composite resin to mineral trioxide aggregate (MTA), MTA mixed with Na2HPO4 (NAMTA), and calcium-enriched mixture (CEM). Materials and methods. Thirty specimens of each CEM, NAMTA, and MTA were prepared. Composite and RMGI restorations were then placed on the samples (15 samples in six subgroups). Shear bond strength was assessed using universal testing machine. Data were analyzed with two-way ANOVA and post-hoc Tukey test. To compare the bond strength in subgroups, one-away ANOVA was applied. Significance level was set at P < 0.05. Results. Bond strength was significantly higher to composite samples compared to RMGI samples (p<0.001). The difference in bond strength of composite samples between MTA and CEM subgroups (P=0.026) as well as MTA and NAMTA subgroups (P= 0.019) was significant, but the difference between NAMTA and CEM subgroups (P=0.56) was not significant. The differences in bond strength in subgroups of RMGI group were not significant (P>0.05). Conclusion. Regarding shear bond strength to the tested substrates, composite was shown to be superior to RMGI. The bond of resin composite to MTA was weaker than that to CEM and NAMTA. PMID:24082988

Ajami, Amir Ahmad; Jafari Navimipour, Elmira; Savadi Oskoee, Siavash; Abed Kahnamoui, Mehdi; Lotfi, Mehrdad; Daneshpooy, Mehdi

2013-01-01

69

A novel star-shaped poly(carboxylic acid) for resin-modified glass-ionomer restoratives.  

PubMed

We have developed a novel glass-ionomer cement (GIC) system composed of photo-curable star-shaped poly(acrylic acid-co-itaconic acid)s. These polyacids were synthesized via a chain-transfer radical polymerization using a newly synthesized multi-arm chain-transfer agent. The star-shaped polyacids showed significantly lower viscosities in water as compared to the linear polyacids. Due to the lower viscosities, the molecular weight (MW) of the polyacids can be significantly increased for enhancing the mechanical strengths while keeping the ease of mixing and handling. The effects of MW, GM-tethering ratio, P/L ratio, and aging on the compressive properties of the experimental cements were significant. The light-cured experimental cements showed significantly improved mechanical strengths i.e. 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS, and 36% in FS, higher than commercial Fuji II LC. After aging in water for 1 month, the compressive strength of the novel light-cured experimental cement reached 343?MPa, which was 34% and 42% higher than Fuji II and Fuji II LC, respectively. This one-month aged experimental cement was also 23% higher than itself after one day aging, indicating that aging in water can significantly enhance salt-bridge formation for this novel star-shaped polyacid-comprised GIC. PMID:24865692

Weng, Y; Howard, L; Xie, D

2014-07-01

70

Enhancing glass ionomer cement features by using the HA/YSZ nanocomposite: a feed forward neural network modelling.  

PubMed

Despite brilliant properties of glass ionomer cement (GIC), its weak mechanical property poses an obstacle for its use in medical applications. The present research aims to formulate hydroxyapatite/yttria-stabilized zirconia (HA/YSZ) in the composition of GIC to enhance mechanical properties and to improve fluoride release of GIC. HA/YSZ was synthesized via a sol-gel method and characterized by applying X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photo-emission spectroscopy (XPS) and simultaneous thermal analysis (STA) along with transmission electron microscopy (TEM) methods. The synthesized nanocomposite was mixed with GIC at a fixed composition of 5wt%. The effect of different weight percentages of YSZ:HA on GIC was investigated by measuring the compressive strength, diametral tensile strength, microhardness and fluoride release. The results showed that, after 1 and 7 days of setting, the 20wt% nanohydroxyapatite/80wt% stabilized zirconia cement exhibited higher compressive strength (1857-245MPa), higher diametral tensile strength (11-14MPa) and greater microhardness (104-106MPa) as compared with the pure GIC (65-88MPa in compressive strength, 5-9.5MPa in diametral tensile strength and 70-89MPa in microhardness). The reinforced cement, also, exhibited higher fluoride release compared with pure GIC. The artificial neural network (ANN) was trained for modeling the system. Results obtained by ANN have proved to be completely in accordance with expectations. PMID:24140732

Rajabzadeh, Ghadir; Salehi, Sahar; Nemati, Ali; Tavakoli, Razeih; Solati Hashjin, Mehran

2014-01-01

71

Compound changes and tooth mineralization effects of glass ionomer cements containing bioactive glass (S53P4), an in vivo study.  

PubMed

In this study, modifications of glass ionomer cements (GICs) were made by adding bioactive glass (BAG) to GIC to obtain bioactive restorative materials. This study used SEM, EDS and visual analysis to examine the bioactivity and the ability of the study materials to mineralize dentin. Conventional cure and resin-modified light-curing GIC were used. The materials consisted of powder and liquid. Three experimental materials were made by mixing 10-30 wt% of BAG powder with GIC powders. Commercially available GIC without BAG were used as controls. Class III restorations were made in altogether 62 intact beagle dog teeth, and the operation was performed under general anesthesia. The restorations were followed clinically for 1, 3 or 6 weeks. Resin-modified GIC containing BAG showed uniform CaP surface formation on the restorations. Mineral depositions in the close vicinity of the restoration-dentin interface and in deeper parts of dentin tubules were also noticed in resin-modified GIC containing BAG particles. It can be concluded that resin-modified GIC containing BAG have good potential in clinical applications where enhanced mineralization is expected. PMID:15958240

Yli-Urpo, Helena; Närhi, Matti; Närhi, Timo

2005-10-01

72

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

PubMed

A description is give of the effect on the ASPA cement reaction of tartaric acid incorporated in the cement liquid. Tartaric acid acts as an accelerator that aids in the extraction of ions from the aluminosilicate glass and facilitates their binding to the polyanion chains. Postgelation hardening is significantly increased. Working time is unaffected possibly because cations are initially present as complexes. PMID:187629

Crisp, S; Wilson, A D

1976-01-01

73

Absence of carious lesions at margins of glass-ionomer cement and amalgam restorations: An update of systematic review evidence  

PubMed Central

Background This article aims to update the existing systematic review evidence elicited by Mickenautsch et al. up to 18 January 2008 (published in the European Journal of Paediatric Dentistry in 2009) and addressing the review question of whether, in the same dentition and same cavity class, glass-ionomer cement (GIC) restored cavities show less recurrent carious lesions on cavity margins than cavities restored with amalgam. Methods The systematic literature search was extended beyond the original search date and a further hand-search and reference check was done. The quality of accepted trials was assessed, using updated quality criteria, and the risk of bias was investigated in more depth than previously reported. In addition, the focus of quantitative synthesis was shifted to single datasets extracted from the accepted trials. Results The database search (up to 10 August 2010) identified 1 new trial, in addition to the 9 included in the original systematic review, and 11 further trials were included after a hand-search and reference check. Of these 21 trials, 11 were excluded and 10 were accepted for data extraction and quality assessment. Thirteen dichotomous datasets of primary outcomes and 4 datasets with secondary outcomes were extracted. Meta-analysis and cumulative meta-analysis were used in combining clinically homogenous datasets. The overall results of the computed datasets suggest that GIC has a higher caries-preventive effect than amalgam for restorations in permanent teeth. No difference was found for restorations in the primary dentition. Conclusion This outcome is in agreement with the conclusions of the original systematic review. Although the findings of the trials identified in this update may be considered to be less affected by attrition- and publication bias, their risk of selection- and detection/performance bias is high. Thus, verification of the currently available results requires further high-quality randomised control trials. PMID:21396097

2011-01-01

74

Microleakage after Thermocycling of Three Self-Etch Adhesives under Resin-Modified Glass-Ionomer Cement Restorations  

PubMed Central

This study was designed to evaluate microleakage that appeared on Resin-Modified Glass-Ionomer Cement (RMGIC) restorations. Sixty class V cavities (h × w × l = 2?mm × 2?mm × 3?mm) were cut on thirty extracted third molars, which were randomly allocated to three experimental groups. All the buccal cavities were pretreated with polyacrylic acid, whereas the lingual cavities were treated with three one-step Self-Etch adhesives, respectively, Xeno III (Dentsply Detrey GmbH, Konstanz, Germany), iBond exp (Heraeus Kulzer gmbH & Co. KG, Hanau, Germany), and Adper Prompt-L-Pop (3M ESPE AG, Dental products Seefeld, Germany). All cavities were completely filled with RMGIC, teeth were thermocycled for 800 cycles, and leakage was evaluated. Results were expressed as means ± standard deviations (SDs). Microleakage scores were analysed by means of generalized linear mixed models (GLMMs) assuming an ordinal logistic link function. All results were considered to be significant at the 5% critical level (P < .05). The results showed that bonding RMGIC to dentin with a Self-Etch adhesive rather than using polyacrylic acid did not influence microleakage scores (P = .091), except for one tested Self-Etch adhesive, namely, Xeno III (P < .0001). Nevertheless, our results did not show any significant difference between the three tested Self-Etch adhesive systems. In conclusion, the pretreatment of dentin with Self-Etch adhesive system, before RMGIC filling, seems to be an alternative to the conventional Dentin Conditioner for the clinicians as suggested by our results (thermocycling) and others (microtensile tests). PMID:20628510

Geerts, Sabine O.; Seidel, Laurence; Albert, Adelin I.; Gueders, Audrey M.

2010-01-01

75

Nanoclays reinforced glass ionomer cements: dispersion and interaction of polymer grade (PG) montmorillonite with poly(acrylic acid).  

PubMed

Montmorillonite nanoclays (PGV and PGN) were dispersed in poly(acrylic acid) (PAA) for utilization as reinforcing filler in glass ionomer cements (GICs). Chemical and physical interaction of PAA and nanoclay (PGV and PGN) was studied. PAA–PGV and PAA–PGN solutions were prepared in different weight percent loadings of PGV and PGN nanoclay (0.5-8.0 wt%) via exfoliation-adsorption method. Characterization was carried out by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fourier transform infrared (FTIR) spectroscopy. XRD results of PAA–PGN demonstrated that the interlayer space expanded from 12.83 to 16.03 Å indicating intercalation whereas the absence of the peak at d(001) in PAA–PGV indicated exfoliation. XPS scans of PGV and PGN nanoclays depicted the main peak of O 1s photoelectron due to Si–O–M (M = Mg, Al, Fe) whereas, Si–O–Al linkages were identified by Si 2p or Si 2s and Al 2p or Al 2s peaks. The disappearance of the Na peak confirmed that PAA molecules exchanged sodium ions present on surface of silicate layers and significantly reduced the electrostatic van-der-Waals forces between silicate plates resulting in intercalation or exfoliation. FTIR spectra of PAA–nanoclay suspensions demonstrated the presence of a new peak at 1,019 cm(-1) associated with Si–O– stretching vibrations which increased with increasing nanoclays concentration. Information concerning the dispersion of nanoclay in PAA aqueous solutions, chemical reaction and increase interlayer space in montmorillonite nanoclay is particularly useful regarding dispersion and reinforcement of nanoclay in PAA. PMID:24077996

Fareed, Muhammad A; Stamboulis, Artemis

2014-01-01

76

An in vitro comparative SEM study of marginal adaptation of IRM, light- and chemically-cured glass ionomer, and amalgam in furcation perforations.  

PubMed

The furcation regions of 30 human mandibular molars were perforated and sealed using four different materials: IRM, light- and chemically-cured glass ionomer cement (GIC), and amalgam. The materials were compared for marginal gaps in coronal, mid, and apical regions after routine SEM processing. While light-cured GIC showed the smallest gaps in the three regions, in mid and coronal regions chemically-cured GIC, and in apical regions amalgam, showed the largest gaps. IRM cases showed the highest rate of fillings with a good "fit", whereas the majority of amalgam cases and none of the chemically-cured GIC cases were overfilled. PMID:12360666

Rajablou, N; Azimi, S

2001-12-01

77

Comparison of shear bond strength of resin-modified glass ionomer to conditioned and unconditioned mineral trioxide aggregate surface: An in vitro study  

PubMed Central

Introduction: The aim of this study was to compare the shear bond strength of resin modified glass ionomer cement to conditioned and unconditioned mineral trioxide aggregate surface. Materials and Method: White Mineral Trioxide Aggregate (WMTA) and Resin Modified Glass Ionomer Cement (RMGIC) were used for the study. 60 WMTA specimens were prepared and stored in an incubator at 37° C and 100% humidity for 72 hrs. The specimens were then divided into two groups- half of the specimens were conditioned and remaining half were left unconditioned, subsequent to which RMGIC was placed over MTA. The specimens were then stored in an incubator for 24 hrs at 37° C and 100% humidity. The shear bond strength value of RMGIC to conditioned and unconditioned WMTA was measured and compared using unpaired 't ?’ test. Results: The mean shear bond strength of value of RMGIC to conditioned and unconditioned WMTA was 6.59 MPa and 7.587 MPa respectively. Statistical analysis using unpaired t-test revealed that the difference between values of two groups was not statistically significant (P > 0.05). Conclusions: During clinical procedures like pulp capping and furcal repair, if RMGIC is placed as a base over MTA, then conditioning should be done to increase the bond strength between RMGIC and dentin and any inadvertent contact of conditioner with MTA will not significantly affect the shear bond strength value of RMGIC to MTA. PMID:25298644

Gulati, Shikha; Shenoy, Vanitha Umesh; Margasahayam, Sumanthini Venkatasubramanyam

2014-01-01

78

Comparative evaluation of effect of polymerizable and non-polymerizable desensitizing agents on crown-retentive-strength of zinc-phosphate, glass-ionomer and compomer cements.  

PubMed

The Purpose of this study was to evaluate the effect of polymerizable and non-polymerizable dentine desensitizers on retention of complete cast crowns cemented with three different types of cements. Freshly extracted human molars (n = 90) were prepared for standardized crown preparation (6-degree taper 4-mm height). The axial surface area of each preparation was determined and specimens were distributed equally among groups (n = 10). Dentine desensitizers, cementing agents, glass ionomer cement and compomer cement. Teeth were prepared and individual castings were made using high noble porcelain-metal alloy. Castings were cemented, thermo-cycled and removed along the path of insertion using a universal testing machine. Tooth surface as well as inner surface of the casting was examined and nature of cement failure was determined. Compomer cement exhibited the highest retentive strength and all dentine treatments resulted in significantly different retentive values. Zinc phosphate was the least retentive. Crown retentive values of Compomer cement were improved with Prime & Bond NT and Gluma Desensitizer Retentive values of zinc phosphate cement with Prime & Bond NT were decreased and not affected with Gluma Desensitizer Retentive values of Glass ionomer cement were not affected by any of the desensitizers used in the study. PMID:23101176

Patil, P G; Parkhedkar, R D; Patil, S P; Bhowmik, H S

2012-09-01

79

Comparison of bracket debonding force between two conventional resin adhesives and a resin-reinforced glass ionomer cement: an in vitro and in vivo study.  

PubMed

The purpose of this study was to compare the debonding force of orthodontic brackets bonded with two conventional resin adhesives (Resilience L3 and Light Bond) and a resin-reinforced glass ionomer cement (Fuji Ortho LC). For the in vitro part of the study, 80 extracted premolars were randomly divided into four groups. In groups A and B, brackets were bonded to unetched enamel using Fuji Ortho LC cement in wet and dry conditions, respectively. In groups C and D, brackets were bonded to etched enamel using Resilience L3 and Light Bond, respectively. Debonding force was determined using a servohydraulic testing machine at a crosshead speed of 1 mm/min. Data was analyzed using the ANOVA and Tukey-Kramer multiple comparison test at p<0.05. A significant difference was found in debonding force between unetched Fuji Ortho LC and the two conventional resins. There was no significant difference between the two conventional resins or between unetched resin-reinforced glass ionomer in the wet and dry conditions. For the in vivo part of the study, 30 patients were randomly assigned to one of the three bonding material groups. Bracket survival rates and distributions were obtained by following these patients for 1.2 years. Data was analyzed using the Kaplan-Meier product-limit estimates of survivorship function. Bond failure interface was determined using a modified adhesive remnant index (ARI). These results showed no significant difference between survival rates and distributions among the three bonding materials with respect to the type of malocclusion, type of orthodontic treatment, or location of bracket. There were significant differences between survival distributions of males and females in the unetched Fuji Ortho LC group and among type of teeth in the conventional resin groups. The predominant mode of bracket failure for the unetched Fuji Ortho LC cement was at the enamel-adhesive interface, and for conventional resins, the enamel-adhesive interface and the bracket-adhesive interface. These results suggest that resin-reinforced glass ionomer cement can withstand occlusal and orthodontic forces despite having a bond strength lower than that of conventional resin adhesives. PMID:10515145

Shammaa, I; Ngan, P; Kim, H; Kao, E; Gladwin, M; Gunel, E; Brown, C

1999-10-01

80

A review of chemical-approach and ultramorphological studies on the development of fluoride-releasing dental adhesives comprising new pre-reacted glass ionomer (PRG) fillers.  

PubMed

This paper reviews our recent studies on fluoride-releasing adhesives and the related studies in this field based on information from original research papers, reviews, and patent literatures. A revolutionary PRG (pre-reacted glass ionomer) filler technology--where fillers were prepared by the acid-base reaction of a fluoroaluminosilicate glass with polyalkenoic acid in water, was newly developed, and a new category as "Giomer" was introduced into the market. On fluoride release capability, SIMS examination revealed in vitro fluoride ion uptake by dentin substrate from the PRG fillers in dental adhesive. On bonding durability, it was found that the improved durability of resin-dentin bonds might be achieved not only via the strengthened dentin due to fluoride ion uptake from the PRG-Ca fillers, but also due to retention of relatively insoluble 4-AETCa formed around remnant apatite crystallites within the hybrid layer in 4-AET-containing self-etching adhesives. On ultramorphological study of the resin-dentin interface, TEM images of the PRG-Ca fillers revealed that the dehydrated hydrogel was barely distinguishable from normal glass fillers, if not for the concurrent presence of remnant, incompletely reacted glass cores. In conclusion, it was expected that uptake of fluoride ions with cariostatic effect from PRG-Ca fillers would endow dentin substrates with the benefit of secondary caries prevention, together with an effective and durable adhesion to dentin. PMID:18717159

Ikemura, Kunio; Tay, Franklin R; Endo, Takeshi; Pashley, David H

2008-05-01

81

Morphological analysis of ionomers  

SciTech Connect

Anomalous small-angle x-ray scattering (SAXS) investigations were carried out on amorphous and semi-crystalline ionomers (Ni- neutralized sulfonated polystyrene ionomers, polyurethane ionomer). Ionomers with semicrystalline matrices (three-phase materials) were also studied with SAXS (poly(ethylene-co-methacrylic acid) ionomer). Ethylene oxide units were incorporated into the backbone of sulfonated polyurethane ionomers in an attempt to induce aggregate dissociation. Small-angle neutron scattering was used to study the effect of ionic aggregation on ionomer chain dimensions in telechelic and model polyurethane ionomers. Studies have been completed on carboxylated and sulfonated model polyurethane ionomers in order to determine the effect of the pendant ionic group on ionomer structure- property relationships (mechanical properties). (DLC)

Not Available

1991-01-01

82

In vitro quantitative evaluation of marginal microleakage in Class II restorations confected with a glass ionomer cement and two composite resins.  

PubMed

This study evaluated, in vitro, marginal microleakage in class II restorations confected with the glass ionomer cement Vitremer and with the composite resins Ariston pHc and P-60. The aims of the study were to assess the effect of thermocycling on those materials and to evaluate two methods utilized in the analysis of dye penetration. Sixty premolars divided in three groups were utilized; the teeth had proximal cavities whose cervical walls were located 1 mm below the cementoenamel junction. Half of the test specimens from each group underwent thermocycling; the other half remained in deionized water, at 37 degrees C. The specimens were immersed, for 24 hours, in a basic 0.5% fuchsin solution at 37 degrees C. For the analysis of microleakage, the specimens were sectioned in a mesio-distal direction, and the observation was carried out with the software Imagetools. The results were evaluated through the 2-way ANOVA and through the Tukey's test. All groups presented marginal microleakage. The smallest values were obtained with Vitremer, followed by those obtained with the composite resins P-60 and Ariston pHc. There was no statistically significant difference caused by thermocycling, and the method of maximum infiltration was the best for detecting the extension of microleakage. PMID:11787314

Bijella, M F; Bijella, M F; da Silva, S M

2001-01-01

83

Effect of light-cure initiation time on polymerization and orthodontic bond strength with a resin-modified glass-ionomer  

NASA Astrophysics Data System (ADS)

Introduction: The polymerization and acid-base reactions in resin-modified glass-ionomers (RMGI) are thought to compete with and inhibit one another. The objective of this study was to examine the effect of visible light-cure (VLC) delay on the polymerization efficiency and orthodontic bond strength of a dual-cured RMGI. Methods: An RMGI light-cured immediately, 2.5, 5, or 10 minutes after mixing comprised the experimental groups. Isothermal and dynamic temperature scan differential scanning calorimetry (DSC) analysis of the RMGI was performed to determine extents of VLC polymerization and acid-base reaction exotherms. Human premolars (n = 18/group) were bonded with the RMGI. Shear bond strength and adhesive remnant index (ARI) scores were determined. Results: DSC results showed the 10 minute delay RMGI group experienced significantly (P <0.05) lower VLC polymerization compared to the other groups. Acid-base reaction exotherms were undetected in all groups except the 10 minute delay group. No significant differences (P >0.05) were noted among the groups for mean shear bond strength. A chi-square test showed no significant difference (P = 0.428) in ARI scores between groups. Conclusions: Delay in light-curing may reduce polymerization efficiency and alter the structure of the RMGI, but orthodontic shear bond strength does not appear to be compromised.

Thomas, Jess

84

Vinylpyridinium Ionomers. 2. Styrene-Based ABA Block Copolymers,  

National Technical Information Service (NTIS)

The thermal and dynamic mechanical behavior of styrene-4-vinylpyridinium ABA block ionomers was investigated as a function of ion content and method of preparation. Only one tg, associated with the glass transition of the polystyrene phase, was observed i...

S. Gauthier, A. Eisenberg

1987-01-01

85

Effect of different surface treatments on the shear and microtensile bond strength of resin-modified glass ionomer cement to dentin.  

PubMed

Abstract Objective. The aim of this study was to evaluate the effect of different surface treatments on the microtensile bond strength (?TBS) and shear bond strength (SBS) of resin-modified glass ionomer cement (RMGIC) to dentin. Materials and methods. Fifty-two extracted human molars were flattened to obtain dentin surfaces. For SBS assessment 40 teeth were divided into four groups according to their surface treatments (acid etching, Er:YAG laser QSP mode, Er:YAG laser MSP mode and control-SiC) (n = 10). A plastic cylinder was placed over the differently treated dentin surfaces and RMGIC was placed into the rings and polymerized. Twelve teeth were used for the ?TBS test. The treated dentin surfaces described above were restored with 4 mm high RMGIC and light cured; then, the specimens were sectioned into serial sticks (n = 15) and ?TBS and SBS were tested for failure in a testing machine with a 1 mm/min crosshead speed. The data were analyzed by one-way ANOVA and Tukey HSD tests (? = 0.05). Results. Acid etching showed significantly higher SBS than the other groups (p < 0.05). Er:YAG QSP and MSP-treated groups showed higher SBS values than the control group, but the difference was not statistically significant (p > 0.05). Er:YAG MSP showed the highest ?TBS value followed by acid etching, whereas the control group exhibited the lowest value (p < 0.05) and the differences between the control group and Er:YAG QSP were not significant (p > 0.05). Conclusions. The application of Er:YAG MSP mode and acid etching to dentin can be used for improving the bond strength of RMGIC. PMID:24844786

Altunsoy, Mustafa; Botsali, Murat Selim; Korkut, Emre; Kucukyilmaz, Ebru; Sener, Yagmur

2014-11-01

86

Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine®)  

PubMed Central

Objectives Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB) composites, silorane-based (SB) composites, and glass ionomer cement (GIC) to Biodentine® and mineral trioxide aggregate (MTA). Material and Methods Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole) were prepared. In 45 of the samples, the holes were fully filled with Biodentine® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS) test, each block was secured in a universal testing machine. Results The highest (17.7±6.2 MPa) and the lowest (5.8±3.2 MPa) bond strength values were recorded for the MB composite-Biodentine® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7±6.2) than it did to MTA (8.9±5.7) (p<0.001), the SB composite (SB and MTA=7.4±3.3; SB and Biodentine®=8.0±3,6) and GIC (GIC and MTA=5.8±3.2; GIC and Biodentine=6.7±2.6) showed similar bond strength performance with MTA compared with Biodentine (p=0.73 and p=0.38, respectively). Conclusions The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite. PMID:25141202

CANTEKIN, Kenan; AVCI, Serap

2014-01-01

87

The effects of ambient temperature and mixing time of glass ionomer cement material on the survival rate of proximal ART restorations in primary molars  

PubMed Central

Objective: Temperature fluctuations and material mixing times are likely to affect the consistency and integrity of the material mixture, and hence the restoration made out of it. The purpose of the present study was to determine the influence of the ambient temperature and the mixing time of glass ionomer cement (GIC) restorative material on the survival rate of proximal atraumatic restorative treatment (ART) restorations placed in primary molars. Materials and Methods: A total of 804 restorations were placed in the primary molars of 6-8-year-olds using the ART approach. The restorations were then followed for a period of 2 years and evaluated at given intervals. The data collected were analyzed using SPSS computer statistical program, and the results tested and compared using the Chi-square, Kaplan Meier survival analysis and Cox Proportional hazard statistical tests. Results: The cumulative survival rate of the restorations dropped from the initial 94.4% to 30.8% at the end of 2 years. The higher survival rate of the restorations was associated with the experienced operators and assistants when using the rubber dam isolation method. However, there was no statistically significant difference in the survival rate of the restorations when related to the room temperature and the mixing time of the GIC materials used in spite of the variations in the temperature recoded and the methods used in mixing the materials. Conclusion: The ambient temperature and mixing time of GIC did not have a significant effect on the survival of the proximal ART restorations. PMID:24808692

Kemoli, Arthur M

2014-01-01

88

Ionomer Design Principles for Single Ion-Conducting Energy Materials  

NASA Astrophysics Data System (ADS)

Single-ion conducting ionomers with low glass transition temperature, high dielectric constant and containing bulky ions with diffuse charge, are needed for polymer membranes that transport small counterions. Overarching design principles emerging from quantum chemistry calculations suggest that diffuse charge can be attained from simple considerations of atomic electronegativity. For lithium or sodium batteries, perfluorinated tetraphenyl borate ionomers with solvating polar comonomers are proposed. For fluoride or hydroxide batteries and for iodide transporting solar cells, tetra-alkyl phosphonium ionomers with anion receptors are proposed. First attempts to construct such ionomers to test these ideas will be discussed, with results from dielectric spectroscopy to measure conductivity, dielectric constant and number density of simultaneously conducting ions.

Colby, Ralph; Liang, Siwei; Liu, Wenjuan; Hyeok Choi, U.; Runt, James; Shiau, Huai-Suen; Janik, Michael

2012-02-01

89

Ionomics and the Study of the Plant Ionome  

SciTech Connect

The ionome is defined as the mineral nutrient and trace element composition of an organism and represents the inorganic component of cellular and organismal systems. Ionomics, the study of the ionome, involves the quantitative and simultaneous measurement of the elemental composition of living organisms and changes in this composition in response to physiological stimuli, developmental state, and genetic modifications. Ionomics requires the application of high-throughput elemental analysis technologies and their integration with both bioinformatic and genetic tools. Ionomics has the ability to capture information about the functional state of an organism under different conditions, driven by genetic and developmental differences and by biotic and abiotic factors. The relatively high throughput and low cost of ionomic analysis means that it has the potential to provide a powerful approach to not only the functional analysis of the genes and gene networks that directly control the ionome, but also to the more extended gene networks that control developmental and physiological processes that affect the ionome indirectly. In this review we describe the analytical and bioinformatics aspects of ionomics, as well as its application as a functional genomics tool.

Salt,D.; Baxter, I.; Lahner, B.

2008-01-01

90

Rheological Behavior of Oligomeric Ionomers  

SciTech Connect

The rheological behavior of the alkali metal salts of oligomeric sulfonated polystyrene (PS) ionomers was characterized using dynamic and steady shear measurements. The starting PS had a weight average molecular weight of 4000 g/mol and a narrow molecular weight distribution (1.06). Two sulfonation levels were examined, 2.5 and 4.8 mol %, which corresponded, respectively, to one and two sulfonate groups per chain on average. The ionomers exhibited nanophase separation of an ion-rich phase, and as a consequence, time-temperature superposition failed for all samples. Sulfonation increased the melt viscosity of the ionomers, as much as seven orders of magnitude. The zero shear viscosity scaled as cq/a, where c was the concentration of the ionic groups, q was the charge of the cation, and a was the cation radius, and although the molecular weight of the parent polystyrene was much lower than the entanglement molecular weight, the ionomer melts exhibited strong elastic behavior. The flow activation energy of the ionomers was similar to that of high molecular weight PS and the calculated molecular weight between 'entanglements' of the ionomers was the same as for PS.

Weiss, R.; Zhao, H

2009-01-01

91

Treatment of dentin with polyacrylic acid--a retrospective observational study of the effect upon the durability of glass ionomer restorations.  

PubMed

This paper reports on the results of a material specific, retrospective observational study. It sought to determine the consequence of pretreatment of cavity margins with the conventional glass polyalkenoate Chemfil II prior to restoration with Tooth Cleanser on restoration durability. All restorations were placed and varnished by senior dental students under the supervision of a staff member. Manufacturer recommendations were followed. Data on each restoration was collected and entered into a relational computer database. Data included details of cavity morphology and the use or non-use of Tooth Cleanser. Six years following the study start a manual search of all records was carried out to determine, for those patients continuing to attend the Dental Hospital, the number of failed and surviving restorations. This yielded a dataset of 149 restorations, of which 41 had been placed with the aid of Tooth Cleanser and 108 without. The number of failed restorations was 20 and 62, respectively. Survival analysis by the Kaplan-Meier method revealed median survival times of 2,094 days, when Tooth Cleanser was used and 1,748 days when not. Although 80% survival times of 1111.0 (SE = 6.3) (With Tooth Cleanser) and 285.0 (SE = 3.8) (Without Tooth Cleanser) days were observed, together with a Hazard Ratio of 1.49 (95% Confidence Intervals 0.92 & 2.31), a Logrank test revealed no statistically significant difference between the survival curves (p = 0.12). It was concluded that although there was a trend for the application of Tooth Cleanser to improve the chances of obtaining a dependable restoration, this effect was not statistically significant. PMID:11699176

Chadwick, R G; Bartlett, P; McCabe, J F; Woolford, M J

2001-01-01

92

Nature and properties of ionomer assemblies. II  

Microsoft Academic Search

The principle subject in the current paper is to summarize and characterize the ionomers based on polymers and copolymers such as polystyrene (PSt), polyisoprene (PIP), polybutadiene (PB), poly(styrene-b-isobutylene-b-styrene) (PSt-PIB-PSt), poly(butadiene-styrene) (PB-PSt), poly(ethylene terephthalate) (PET), poly(butylene adipate) (PBA), poly(butylene succinate) (PBSi), poly(dimethylcarbosiloxanes), polyurethane, etc. The self-assembly of ionomers, models concerning ionomer morphologies, physical and rheological properties of ionomer phase and percolation

Ignác Capek

2005-01-01

93

SYNTHESIS AND CHARACTERIZATION OF POLYURETHANE IONOMERS.  

E-print Network

??Applications such as lithium ion batteries and actuator membranes of ionconductingpolymers usually require both mechanical strength and ionic conductivitysimultaneously. Throughout this thesis, PEO-based polyurethane ionomers… (more)

Wang, Shih-Wa

2011-01-01

94

Encapsulant Material For Solar Cell Module And Laminated Glass Applications  

DOEpatents

An encapsulant material includes a layer of metallocene polyethylene disposed between two layers of ionomer. More specifically, the layer of metallocene polyethylene is disposed adjacent a rear surface of the first ionomer layer, and a second layer of ionomer is disposed adjacent a rear surface of the layer of metallocene polyethylene. The encapsulant material can be used in solar cell module and laminated glass applications.

Hanoka, Jack I. (Brookline, MA)

2000-09-05

95

Nature and properties of ionomer assemblies. II.  

PubMed

The principle subject in the current paper is to summarize and characterize the ionomers based on polymers and copolymers such as polystyrene (PSt), polyisoprene (PIP), polybutadiene (PB), poly(styrene-b-isobutylene-b-styrene) (PSt-PIB-PSt), poly(butadiene-styrene) (PB-PSt), poly(ethylene terephthalate) (PET), poly(butylene adipate) (PBA), poly(butylene succinate) (PBSi), poly(dimethylcarbosiloxanes), polyurethane, etc. The self-assembly of ionomers, models concerning ionomer morphologies, physical and rheological properties of ionomer phase and percolation behavior of ionomers were discussed. The ionomer phase materials and dispersions have been characterized by differential scanning calorimetry (DSC), small-angle X-ray catering (SAXS), small-angle neutron scattering (SANS), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), etc. The wide range of compositions, molecular architectures, and morphologies present in ionomeric disperse systems are of great interest. The research is particularly devoted to the potential application of these materials and an understanding of the fundamental principles of the ionomers. They are extremely complex systems, sensitive to changes in structure and composition, and therefore not easily amenable to modeling and to the derivation of general patterns of behavior. The reviewed data indicate that a large number of parameters are important in influencing multiplet formation and clustering in random ionomers. Among these are the ion content, size of the polyion and counterion, dielectric constant of the host, T(g) of the polymer, rigidity or persistence length of the backbone, position of the ion pair relative to the backbone, steric constraints, amount and nature of added additive (plasticizer), thermal history, etc. PMID:16076460

Capek, Ignác

2005-12-30

96

Dynamics of Sulfonated Polystyrene Copolymers and Ionomers using Broadband Dielectric Spectroscopy  

NASA Astrophysics Data System (ADS)

The dynamics of sulfonated polystyrene (SPS) copolymers in acid and neutralized forms were investigated using broadband dielectric relaxation spectroscopy. SPS copolymers were synthesized by sulfonation of a monodisperse polystyrene to 1 and 7 mol %. Neutralization was achieved by exchanging the protons of the acid functionality with Na, Cs and Zn cations. Multiple relaxation processes were observed above the glass transition temperature of the neutralized and unneutralized materials. For the unneutralized copolymers, a `chemical relaxation' was observed at temperatures above the segmental process, arising from the presence of hydrogen bonding. For the ionomers, a Maxwell-Wagner-Sillars process was observed due to the presence of ionic clusters. The `chemical relaxation' followed Arrhenius behavior and its relaxation strength decreased significantly with increasing temperature. The relaxation times of the MWS process of all ionomers followed a VFT form. A local relaxation in the glassy state was observed for unneutalized copolymers and ionomers neutralized with monovalent cations, while it was suppressed for ionomers neutralized with divalent cations.

Atorngitjawat, Pornpen; Runt, James

2006-03-01

97

Molecular mobility, morphology, and ion conduction in ionomers for electroactive devices  

NASA Astrophysics Data System (ADS)

A sequential study of ion-containing polymers capable of ion solvation with varied ion content, dielectric constant, and counterions is presented in this dissertation in order to compare ion transport properties in ionomers with various ionic interactions. Structure-property relationships in these ion containing polymers are defined using x-ray scattering, rheology and dielectric spectroscopy, enabling the quantification of ion transport dynamics. Poly(ethylene oxide), (PEO) based ionomers are investigated in order to probe the relation between ion conduction and segmental relaxation, and copolymers of PEO and Poly(tetramethylene oxide), (PTMO) further develop an understanding of the trade-off between ion solvation and segmental dynamics. Ionomers with ionic liquid counterions probe diffuse charge interactions and steric effects on ion transport, and incorporation of ionic liquids into ionomer membranes such as Nafion provides desirable thermal and ion conducting properties which extend the use of such membranes for electroactive devices. PEO ionomers exhibit a strong relation between ionic conductivity and segmental dynamics, providing insight that the glass transition temperature, Tg, dominates the ion conduction mechanism. Increasing temperature induces aggregation of ionic groups as evidenced by the static dielectric constant and X-ray scattering as a function of temperature, revealing the contribution of ionic dipoles in the measured dielectric constant. The trade-off between ion solvation and fast polymer segmental dynamics are quantified in copolymer ionomers of PEO and lower Tg PTMO. While conducting ion content remains nearly unchanged, conductivity is lowered upon incorporation of PTMO, because the vast majority of the PTMO microphase separates from the PEO-rich microdomain that remains continuous and contributes most of the ion conduction. Dielectric constants and X-ray scattering show consistent changes with temperature that suggest a cascading aggregation process in Na ionomers as ionic dipoles thermally randomize and lower the measured dielectric constant of the medium, leading to further aggregation. We observe amplified microphase-separation through ionic groups preferentially solvated by PEO chains, as seen in block copolymers with added salt. Even at 25%PEO / 75%PTMO the ionomers have VFT temperature dependence of conducting ion mobility, meaning that the 25% PEO/ion microphase is still continuous A model is developed to describe the frequency dependent storage and loss modulus and the delay in Rouse motion due to ion association lifetime, as functions of ion content and molecular weight for our low molecular weight ionomers. The ion rearrangement relaxation in dielectric spectroscopy is clearly the ion association lifetime that controls terminal dynamics in linear viscoelasticity, allowing a simple sticky Rouse model, using the most-probable distribution based on NMR Mn, to fully describe master curves of the frequency dependent storage and loss modulus. Using insight from ionic interaction strength, ionic liquids are used as counterions, effectively plasticizing the ionomers without added solvent. Ionic interactions were weakened with increasing counterion size, and with modification of cations using ether-oxygen, promoting self-solvation, which increases conducting ion density by an order of magnitude. Room temperature ionic liquids were subsequently used in combination with NafionRTM membranes as electroactive substrates to correlate ion transport to morphology as a function of volume fraction of ionic liquid. This study illuminated the critical volume uptake of ionic liquid in Nafion, identifying percolation of ionic pathways and a significant increase in dielectric constant at low frequencies, indicating an increase in the number density of ions capable of polarizing at the electrode surface. Consequently, the fundamental information obtained about the structure-property relations of ionomers can be used to predict and design advanced ion-containing polymers to be used in battery membranes and a v

Tudryn, Gregory J.

98

Fabrication technology to increase surface area of ionomer membrane material and its application towards high surface area electric double-layer capacitors  

NASA Astrophysics Data System (ADS)

An application friendly technique to increase the surface area of the ionomer membrane such as Aquivion™ has been developed. By utilizing existing micro-fabrication technologies, square pillars were fabricated onto glass and silicon substrates. In combination with a low cost heat press, the glass and silicon stamps were used to successfully hot emboss micro-features onto the ionomer membrane. Consequently, the surface area of the Aquivion™ membrane was drastically increased enabling potential improvement of sensing and energy storage technologies. Preliminary results show successful fabrication of devices with systematic higher surface area and an improved capacitance.

Chang, Alberto A.; Patel, Jasbir N.; Cordoba, Cristina; Kaminska, Bozena; Kavanagh, Karen

2014-03-01

99

Ionomer Design, Synthesis and Characterization for Ion-Conducting Energy Materials  

NASA Astrophysics Data System (ADS)

For ionic actuators and battery separators, it is vital to utilize single-ion conductors that avoid the detrimental polarization of other ions; the commonly studied dual-ion conductors simply will not be used in the next generation of materials for these applications. Ab initio quantum chemistry calculations at 0 K in vacuum characterize ion interactions and ion solvation by various functional groups, allowing identification of constituents with weak interactions to be incorporated in ionomers for facile ion transport. Simple ideas for estimating the ion interactions and solvation at practical temperatures and dielectric constants are presented that indicate the rank ordering observed at 0 K in vacuum should be preserved. Hence, such ab initio calculations are useful for screening the plethora of combinations of polymer-ion, counterion and polar functional groups, to decide which are worthy of synthesis for new ionomers. Single-ion conducting ionomers are synthesized based on these calculations, with low glass transition temperatures (facile dynamics) to prepare ion-conducting membranes for ionic actuators and battery separators. Characterization by X-ray scattering, dielectric spectroscopy, NMR and linear viscoelasticity collectively develop a coherent picture of ionic aggregation and both counterion and polymer dynamics. Examples are shown of how ab initio calculations can be used to understand experimental observations of dielectric constant, glass transition temperature and conductivity of polymerized ionic liquids with counterions being either lithium, sodium, fluoride, hydroxide (for batteries) or bulky ionic liquids (for ionic actuators).

Colby, Ralph H.

2013-03-01

100

Morphological analysis of ionomers. Progress report, August 1, 1987--December 31, 1991  

SciTech Connect

Anomalous small-angle x-ray scattering (SAXS) investigations were carried out on amorphous and semi-crystalline ionomers (Ni- neutralized sulfonated polystyrene ionomers, polyurethane ionomer). Ionomers with semicrystalline matrices (three-phase materials) were also studied with SAXS (poly(ethylene-co-methacrylic acid) ionomer). Ethylene oxide units were incorporated into the backbone of sulfonated polyurethane ionomers in an attempt to induce aggregate dissociation. Small-angle neutron scattering was used to study the effect of ionic aggregation on ionomer chain dimensions in telechelic and model polyurethane ionomers. Studies have been completed on carboxylated and sulfonated model polyurethane ionomers in order to determine the effect of the pendant ionic group on ionomer structure- property relationships (mechanical properties). (DLC)

Not Available

1991-12-31

101

Counterion effect on rheology and morphology of polydimethylsiloxane ionomers  

NASA Astrophysics Data System (ADS)

We have synthesized a series of polydimethylsiloxane ionomers with control over spacing between ions, number of ions/chain and molecular weight. Freshly precipitated transition metal zinc and cobalt ionomers with less than one mol % of ions flow at room temperature and exhibit a zero shear-rate viscosity. X-ray scattering data and scanning transmission electron microscopy (STEM) data do not show any evidence of ionic aggregates. These ionomers form a network on annealing and the time to network percolation follows an Arrhenius dependence with temperature. Annealed zinc and cobalt ionomers also do not show any evidence of ionic aggregates that could be detected by X-rays or STEM leading to the conclusion that individual ion pairs act as cross-link points. Under similar conditions of spacing between ions and number of ions, barium ionomers, on the other hand, precipitate as weak networks at room temperature and form stronger gels on annealing. STEM and X-ray scattering from these ionomers show aggregate formation. At the higher 8 mol% zinc ions, these ionomers also precipitate as gels and show rod-like aggregates with an aspect ratio of 20 and a diameter of 1nm as observed by STEM.

Coehn, Claude; Batra, Ashish; Kim, Hansoo; Winey, Karen

2005-03-01

102

Nanoscale morphologies of polystyrene and polyethylene ionomers  

NASA Astrophysics Data System (ADS)

Ionomers are highly valued for their unique properties and therefore have long been studied to characterize, understand, and improve these properties. Many studies have focused on the bulk properties of ionomers with more recent efforts using X-ray scattering to characterize the nanometer scale structure especially the ionic aggregate. Scanning transmission electron microscopy (STEM) technology has developed to the point within the past decade that direct imaging of the ionic aggregate is possible. In this dissertation, STEM techniques are refined by accounting for extensive overlap in the projected image and STEM techniques along with X-ray scattering methods are used to study a unique group of poly(ethylene-co-acrylic acid) (P(E-AA)) copolymers and ionomers. We examined poly(styrene-ran-7%-methacrylic acid) Cu (P(S-MAA0.07) Cu) ionomer with model dependant X-ray scattering and direct imaging through STEM. Using the liquid-like hard sphere X-ray scattering model proposed by Yarusso and Cooper with Fornet interference, the ionic aggregate number density indicate an extensively overlapped system for the STEM imaging. Thus, to properly interpret the STEM data, the extensive overlap must be corrected. By creating a computer model that is able to simulate STEM images from an X-ray model, the amount of overlap can be estimated and a proper number density can be calculated from the STEM images. The number density calculated from STEM agrees with the X-ray scattering. Also, despite the extensive overlap, the brightest, isolated features in the STEM are of the appropriate size and shape that would be expected from the projection of a single ionic aggregate. Therefore, the STEM and X-ray scattering are in agreement about the morphology of the ionic aggregates in these P(S-MAA0.07) Cu ionomers. These experiments are repeated for poly(styrene-ran-1.9%-sulfonated styrene) neutralized by Cu, Zn, Ba, or Cs and found that the liquid-like hard sphere X-ray model and the STEM agree on the size, shape, distribution, and number density of the ionic aggregates. We generalize our simulation method to projection of overlapping spheres. A procedure is developed to create and analyze large numbers of simulated projections through computer algorithms. To analyze the data set, it is plotted on axes chosen to reduce the number of variables that influenced the number of features counted in the simulated image (N2D) as a function of simulation thickness (t). The dependant axis is N2D normalized by the area of the simulation in units of 4 times the square of the sphere radius. The independent axis is simply the thickness in units of the sphere radius. With these axes, the important variable is the volume fraction of spheres (? R). In addition, there is a critical thickness, t c, where if t < tc, then the normalized N2D is proportional to talpha and if t > t c, the normalized N2D is independent of thickness at a value of beta. By knowing the thickness of the sample, the normalized N2D, the volume fraction can be estimated and thus the number of spheres in the volume can be calculated. Finally, we study the morphology of linear P(E-AA) copolymers with precisely-sequenced and irregularly sequenced acid groups to establish the effect that the acid group sequence has on the crystal structure. The linear irregularly-sequenced P(E-AA) copolymers behave similarly to low density poly(ethylene-acrylic acid) forming an orthorhombic polyethylene crystal structure and excluding the acid groups to the amorphous regions. The linear precisely-sequenced P(E-AA) copolymers exhibit an unique structure with the acids forming large planar layers that are incorporated into the crystal structure. The precisely-sequence linear P(E-AA) ionomers exhibit both the new acid layer structures and the traditional ionic aggregates. With increasing neutralization, the crystallinity of the P(E-AA) and the new acid layer structure decrease as the acid groups necessary are co-opted to form the ionic aggregates in the amorphous regions.

Chan, Christopher D.

103

Counterion Effect on the Rheology and Morphology of Tailored Poly(dimethylsiloxane) Ionomers  

E-print Network

of nonequilibrated freshly precipitated ionomers varies from flowing liquids to weak networks. Low mol % zinc % zinc ionomers that precipitate as gels show a diverse range of aggregates. The equilibrium state of all for different cations. Low mol % (1 mol %) barium ionomers have rod-shaped and spherical ionic aggregates

Gruner, Sol M.

104

Dynamics and Morphology of Sulfonated Polystyrene Ionomers by Dielectric Spectroscopy  

NASA Astrophysics Data System (ADS)

The dynamics of sulfonated polystyrene (SPS) ionomers, in both the acid and neutralized forms, were investigated using broadband dielectric spectroscopy. The influences of acid content, counterion type (Zn, Na and Cs), degree of neutralization, and microphase separated morphology on segmental and local dynamics, as well as on Maxwell -- Wagner -- Sillars interfacial polarization, were examined. Ionomers prepared from SPS containing 1.9 mol% sulfonic acid species exhibit a broader segmental process indicative of a considerably broader distribution of local environments, as compared to those in unneutralized SPS. Moreover, multiple segmental relaxations were identified in the dielectric spectra of Zn and Na neutralized SPS (1.9 mol%) ionomers, likely indicating two distinct environments arising from ion clustering. A combination of STEM imaging and X-ray scattering confirmed the presence of monodisperse spherical ionic aggregates that were homogeneously distributed in the polymer matrix.

Castagna, Alicia; Wang, Wenqin; Winey, Karen I.; Runt, James

2009-03-01

105

Confinement-driven increase in ionomer thin-film modulus.  

PubMed

Ion-conductive polymers, or ionomers, are critical materials for a wide range of electrochemical technologies. For optimizing the complex heterogeneous structures in which they occur, there is a need to elucidate the governing structure-property relationships, especially at nanoscale dimensions where interfacial interactions dominate the overall materials response due to confinement effects. It is widely acknowledged that polymer physical behavior can be drastically altered from the bulk when under confinement and the literature is replete with examples thereof. However, there is a deficit in the understanding of ionomers when confined to the nanoscale, although it is apparent from literature that confinement can influence ionomer properties. Herein we show that as one particular ionomer, Nafion, is confined to thin films, there is a drastic increase in the modulus over the bulk value, and we demonstrate that this stiffening can explain previously observed deviations in materials properties such as water transport and uptake upon confinement. Moreover, we provide insight into the underlying confinement-induced stiffening through the application of a simple theoretical framework based on self-consistent micromechanics. This framework can be applied to other polymer systems and assumes that as the polymer is confined the mechanical response becomes dominated by the modulus of individual polymer chains. PMID:24773397

Page, Kirt A; Kusoglu, Ahmet; Stafford, Christopher M; Kim, Sangcheol; Kline, R Joseph; Weber, Adam Z

2014-05-14

106

The Plant Ionome Revisited by the Nutrient Balance Concept  

PubMed Central

Tissue analysis is commonly used in ecology and agronomy to portray plant nutrient signatures. Nutrient concentration data, or ionomes, belong to the compositional data class, i.e., multivariate data that are proportions of some whole, hence carrying important numerical properties. Statistics computed across raw or ordinary log-transformed nutrient data are intrinsically biased, hence possibly leading to wrong inferences. Our objective was to present a sound and robust approach based on a novel nutrient balance concept to classify plant ionomes. We analyzed leaf N, P, K, Ca, and Mg of two wild and six domesticated fruit species from Canada, Brazil, and New Zealand sampled during reproductive stages. Nutrient concentrations were (1) analyzed without transformation, (2) ordinary log-transformed as commonly but incorrectly applied in practice, (3) additive log-ratio (alr) transformed as surrogate to stoichiometric rules, and (4) converted to isometric log-ratios (ilr) arranged as sound nutrient balance variables. Raw concentration and ordinary log transformation both led to biased multivariate analysis due to redundancy between interacting nutrients. The alr- and ilr-transformed data provided unbiased discriminant analyses of plant ionomes, where wild and domesticated species formed distinct groups and the ionomes of species and cultivars were differentiated without numerical bias. The ilr nutrient balance concept is preferable to alr, because the ilr technique projects the most important interactions between nutrients into a convenient Euclidean space. This novel numerical approach allows rectifying historical biases and supervising phenotypic plasticity in plant nutrition studies. PMID:23526060

Parent, Serge-Etienne; Parent, Leon Etienne; Egozcue, Juan Jose; Rozane, Danilo-Eduardo; Hernandes, Amanda; Lapointe, Line; Hebert-Gentile, Valerie; Naess, Kristine; Marchand, Sebastien; Lafond, Jean; Mattos, Dirceu; Barlow, Philip; Natale, William

2013-01-01

107

Some Recent Studies With the Solid-Ionomer Electrochemical Capacitor  

NASA Technical Reports Server (NTRS)

Giner, Inc., has developed a high-energy-density, all-solid-ionomer electro-chemical capacitor, completely free of liquid electrolyte. The novel features of this device include: (1) a three-dimensional metal oxide-particulate-ionomer composite electrode structure and (2) a unitized repeating cell element. The composite electrode structures are bonded to opposite sides of a thin sheet of a solid proton-conducting ionomer membrane and form an integrally bonded membrane and electrode assembly (MEA). Individual MEAs can be stacked in series as bipolar elements to form a multiple cell device. The discharge characteristics and energy storage properties of these devices are described. Typical capacitance measured for a unit cell is 1 F/cm. Life testing of a multicell capacitor on an intermittent basis has shown that, over a 10,000-hour period, the capacitance and resistance of the cell has remained invariant. There has been no maintenance required on the device since it was fabricated. Other multicell units of shorter life duration have exhibited similar reliable performance characteristics. Recent work has focused on increasing the capacitance of the unitized structure and improving the low-temperature characteristics. The approaches and experimental results will be presented. Some possible advanced NASA applications for these unique all-solid-ionomer devices will be discussed.

Sarangapani, S.; Forchione, J.; Griffith, A.; LaConti, A.; Baldwin, R.

1991-01-01

108

Self-Healing Behavior of Ethylene-Based Ionomers  

NASA Technical Reports Server (NTRS)

The self-healing behavior of poly(ethylene-co-methacrylic acid) (EMAA)-based ionomers holds tremendous potential for use in a wide variety of unique applications. However, to effectively utilize this self-healing behavior and to design novel materials which possess this ability, the mechanism by which they heal must first be understood ionomers are a class of polymers that can be described as copolymers containing less than 15 mol% ionic content whereby the bulk properties are governed by ionic interactions within the polymer. These ionic groups aggregate into discrete regions known as multiplets which overlap forming clusters that act as physical cross-links profoundly influencing the bulk physical properties. These clusters possess an order-disorder transition (T(sub i)) where the clustered regions may rearrange themselves given time and stimuli. Recognizing the strong influence of these ionic regions on other well understood ionomer properties, their role in self-heating behavior will be assessed. The self-healing behavior is observed following projectile puncture. It has been suggested that during impact energy is passed to the ionomer material, heating it to the melt state. After penetration, it is proposed that the ionic regions maintain their attractions and flow together patching the hole. Thus, the importance of this ionic character and is unique interaction must be established. This will be accomplished through examination of materials with varying ionic content and through the analysis of the T(sub i). The specific ionomer systems examined include a number of ethylene-based materials. Materials of varying ionic content, including the non-ionic base copolymers, will be examined by peel tests, projectile impact and DSC analysis. The information will also be compared with some basic data on LDPE material.

Kalista, Stephen J., Jr.; Ward, Thomas C.; Oyetunji, Zainab

2004-01-01

109

Simulation of Ionic Aggregation and Ion Dynamics in Model Ionomers  

NASA Astrophysics Data System (ADS)

Ionomers, polymers containing a small fraction of covalently bound ionic groups, are of interest as possible electrolytes in batteries. A single-ion conducting polymer electrolyte would be safer and have higher efficiency than the currently-used liquid electrolytes. However, to date ionomeric materials do not have sufficiently high conductivities for practical application. This is most likely because the ions tend to form aggregates, leading to slow ion transport. A key question is therefore how molecular structure affects the ionic aggregation and ion dynamics. To probe these structure-property relationships, we have performed molecular simulations of a set of recently synthesized poly(ethylene-co-acrylic acid) copolymers and ionomers, with a focus on the morphology of the ionic aggregates. The ionomers have a precise, constant spacing of charged groups, making them ideal for direct comparisons with simulations. Ab initio calculations give insight into the expected coordination of cations with fragments of the ionomers. All-atom molecular dynamics (MD) simulations of the ionomer melt show aggregation of the ionic groups into extended string-like clusters. An extensive set of coarse-grained molecular dynamics simulations extend the results to longer times and larger length scales. The structure factors calculated from the MD simulations compare favorably with x-ray scattering data. Furthermore, the simulations give a detailed picture of the sizes, shapes, and composition of the ionic aggregates, and how they depend on polymer architecture. Implications for ion transport will be discussed. [Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Frischknecht, Amalie L.

2012-02-01

110

Sulfonated polysulfone ionomer membranes for fuel cells  

Microsoft Academic Search

Sulfonated polysulfone (SPSU) membranes with different sulfonation levels have been prepared and evaluated as proton exchange membranes in polymer electrolyte fuel cells (PEFC). The membranes have been characterized by ion-exchange capacity (IEC), thermal analysis, proton conductivity and single cell performance. The introduction of sulfonic groups in the base polymer produces an increase in glass transition temperature (Tg) from 190 to

F. Lufrano; I. Gatto; P. Staiti; V. Antonucci; E. Passalacqua

2001-01-01

111

Blends of polyester ionomers with polar polymers: Interactions, reactions, and compatibilization  

NASA Astrophysics Data System (ADS)

The compatibility of amorphous and semicrystalline polyester ionomers with various polar polymers (i.e., polyesters and polyamides) has been investigated for their potential use as minor component compatibilizers. The degree of compatibility (i.e., ranging from incompatible to miscible) between the polyester ionomers and the polar polymers was determined by evaluating the effect of blend composition on the melting behavior and phase behavior of binary blends. In addition, the origin of compatibility and/or incompatibility for each of the binary blends (i.e., polyamide/ionomer and polyester/ionomer) was determined by evaluating blends prepared by both solution and melt mixed methods. Subsequent to investigation of the binary blends, the effect of polyester ionomer addition on the compatibility of polyamide/polyester blends was investigated by evaluating the mechanical properties and phase morphology of ionomer compatibilized polyamide/polyester blends. Polyester ionomers (amorphous and semicrystalline) were shown to exhibit a high degree of compatibility (even miscibility) with polyamides, such as nylon 6,6 (N66). Compatibility was attributed to specific interactions between the metal counterion of the polyester ionomer and the amide groups of N66. The degree of compatibility (or miscibility) was shown to be dependent on the counterion type of the ionomer, with the highest degree exhibited by blends containing the divalent form of the polyester ionomers. Although polyester ionomers were shown to exhibit incompatibility with both poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), increasing the time of melt processing significantly enhanced the compatibility of the polyester ionomers with both PET and PBT. The observed enhancement in compatibility was attributed to ester-ester interchange between the polyester blend components, which was confirmed by NMR spectroscopy. The addition of polyester ionomers as a minor component compatibilizer (i.e., 2 to 5 wt%) resulted in significant enhancement in the impact strength and a dramatic improvement in the tensile properties compared to uncompatibilized blends of nylon 6,6 (N66) with poly(butylene terephthalate) (PBT). This behavior was attributed to an increase in the interfacial adhesion between the phase-separated domains due to strong interactions between the polyester ionomer and N66. The placement of the ionomer compatibilizer at the N66/PBT interface was facilitated by pre-extrusion of the polyester ionomer with PBT, prior to extrusion with N66.

Boykin, Timothy Lamar

112

Mixed hydrocarbon\\/fluoropolymer membrane\\/ionomer MEAs for durability studies  

Microsoft Academic Search

The durability of polymer electrolyte membrane (PEM) fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. Commercial viability depends on improving the durability of the fuel cell components to increase the system reliability. The aim of this work is to separate ionomer degradation from membrane degradation via mixed membrane\\/ionomer MEA experiments.

Bo Li; Yu Seung Kim; Rangachary Mukundan; Rodney L Borup; Mahlon S Wilson; Cynthia Welch; James Fenton

2010-01-01

113

The effect of pressure changes during simulated diving on the pull out strength of glass fiber posts  

PubMed Central

Background: Scuba diving is one of the fastest growing sports in the world. The objective of this study was to evaluate the effect of pressure variations to which divers are exposed on the pull out strength of glass fiber post luted with different cements. Materials and Methods: In this in vitro study, 120 extracted, single-rooted lower premolars were endodontically treated. They were randomly divided into six groups and restored using the glass fiber post (Ivoclar Vivadent AG) and the following luting agents: Zinc phosphate, conventional glass ionomer, resin reinforced glass ionomer, resin cement with etch-and-rinse adhesive, resin cement with self-etching adhesive, and self-adhesive resin cement. Each group was randomly divided into two equal subgroups, one as a control, and the other to be used experimentally. After 7 days of storage, experimental groups were pressure cycled. The force required to dislodge each post was recorded in Newton (N) on Universal testing machine (Star Testing System) at a crosshead speed of 1 mm/min. Data were statistically analyzed using the ANOVA and Student's t-test (P < 0.001). Results: The pull out strength of posts cemented with zinc phosphate and conventional glass ionomer in pressure cycle group was significantly less than their control group. Although, no significant difference was found between pressure cycle and control group using resin reinforced glass ionomer cement and resin cements. Conclusion: Dentist should consider using resin reinforced glass ionomer or resin cement, for the cementation of glass fiber post, for the patients such as divers, who are likely to be exposed to pressure cycling. PMID:24379861

Gulve, Meenal Nitin; Gulve, Nitin Dilip

2013-01-01

114

Antibacterial Activity of Restorative Dental Biomaterials in vitro  

Microsoft Academic Search

This study investigated the antibacterial effects against Streptococcus mutans of a fine-hybrid resin composite (FH-RC; Tetric ceram), an ion-releasing resin composite (Ariston pHc), a self-curing glass ionomer cement (SC-GIC; Ketac-Molar), a resin-modified GIC (RM-GIC; Photac-Fil), and a zinc oxide eugenol cement (ZOE; IRM). In a novel assay, bacterial suspensions were placed into narrow 20-?l conical cavities within the materials. After

Clemens Boeckh; Eliane Schumacher; Andreas Podbielski; Bernd Haller

2002-01-01

115

Counterion Dynamics in Polyester-Sulfonate Ionomers with Ionic Liquid Counterions  

SciTech Connect

Conventional sodium cations (Na{sup +}) in sulfonated polyester ionomers were replaced with ammonium-based ionic liquid counterions. Counterion dynamics were measured by dielectric spectroscopy and linear viscoelastic response via oscillatory shear. Ion exchange from sodium counterions to ionic liquid counterions such as tetramethylammonium and tetrabutylammonium showed an order of 10{sup 4} increase in conductivity compared with sodium counterions, primarily attributed to weaker ionic interactions that lower the glass transition temperature. Electrode polarization was used in conjunction with the 1953 Macdonald model to determine the number density of conducting counterions and their mobility. Conductivity and mobility exhibit Vogel-Fulcher-Tammann (VFT) temperature dependences and both increased with counterion size. Conducting counterion concentrations showed Arrhenius temperature dependences, with activation energy reduced as counterion size increased. When ether-oxygen was incorporated into the mobile cation structure, self-solvating ability notably increased the conducting ion concentration. Weakened ion pairing interactions prove favorable for fundamental design of single-ion conductors for actuators, as ionic liquid counterions can provide both larger and faster strains, required by such electro-active devices.

Tudryn, Gregory J.; Liu, Wenjuan; Wang, Shih-Wa; Colby, Ralph H. (Penn)

2012-04-02

116

Purdue ionomics information management system. An integrated functional genomics platform.  

PubMed

The advent of high-throughput phenotyping technologies has created a deluge of information that is difficult to deal with without the appropriate data management tools. These data management tools should integrate defined workflow controls for genomic-scale data acquisition and validation, data storage and retrieval, and data analysis, indexed around the genomic information of the organism of interest. To maximize the impact of these large datasets, it is critical that they are rapidly disseminated to the broader research community, allowing open access for data mining and discovery. We describe here a system that incorporates such functionalities developed around the Purdue University high-throughput ionomics phenotyping platform. The Purdue Ionomics Information Management System (PiiMS) provides integrated workflow control, data storage, and analysis to facilitate high-throughput data acquisition, along with integrated tools for data search, retrieval, and visualization for hypothesis development. PiiMS is deployed as a World Wide Web-enabled system, allowing for integration of distributed workflow processes and open access to raw data for analysis by numerous laboratories. PiiMS currently contains data on shoot concentrations of P, Ca, K, Mg, Cu, Fe, Zn, Mn, Co, Ni, B, Se, Mo, Na, As, and Cd in over 60,000 shoot tissue samples of Arabidopsis (Arabidopsis thaliana), including ethyl methanesulfonate, fast-neutron and defined T-DNA mutants, and natural accession and populations of recombinant inbred lines from over 800 separate experiments, representing over 1,000,000 fully quantitative elemental concentrations. PiiMS is accessible at www.purdue.edu/dp/ionomics. PMID:17189337

Baxter, Ivan; Ouzzani, Mourad; Orcun, Seza; Kennedy, Brad; Jandhyala, Shrinivas S; Salt, David E

2007-02-01

117

Self-repairing systems based on ionomers and epoxidized natural rubber blends.  

PubMed

The development of materials with the ability of intrinsic self-repairing after damage in a fashion resembling that of living tissues has important scientific and technological implications, particularly in relation to cost-effective approaches toward damage management of materials. Natural rubbers with epoxy functional groups in the macromolecular chain (ENR) and ethylene-methacrylic acid ionomers having acid groups partially neutralized with metal ions possess self-repairing behavior following high energy impacts. This research investigates the self-repairing behavior of both ENR and ionomers during ballistic puncture test on the basis of their thermal and mechanical properties. Heterogeneous blending of ionomers and ENR have also been used here as a strategy to tune the thermal and mechanical properties of the materials. Interestingly, blends of sodium ion containing ionomer exhibit complete self-repairing behavior, whereas blends of zinc ion containing ionomer show limited mending. The chemical structure studied by FTIR and thermal analysis shows that both ion content of ionomer and functionality of ENR have significant influence on the self-repairing behavior of blends. The mobility of rubbery phases along with its interaction to ionomer phase in the blends significantly changes the mending capability of materials. The healing behavior of the materials has been discussed on the basis of their thermal, mechanical, and rheological tests for each materials. PMID:22087566

Rahman, Md Arifur; Penco, Maurizio; Peroni, Isabella; Ramorino, Giorgio; Grande, Antonio Mattia; Di Landro, Luca

2011-12-01

118

Radically coarse-grained approach to the modeling of chemical degradation in fuel cell ionomers.  

PubMed

We present a kinetic model of chemical degradation in perfluorosulfonic acid ionomer membranes. It accounts for pathways of radical formation along with mechanisms of ionomer degradation through radical attack. Simplifications in the set of model equations leads to analytical expressions for the concentration of hydroxyl radicals as a function of initial concentrations of iron ions and hydrogen peroxide. The coarse-grained ionomer degradation model distinguishes units that correspond to ionomer head groups, trunk segments of ionomer side chains, and backbone segments between two side chains. A set of differential equations is formulated to describe changes in concentrations of these units. The model is used to study the impact of different degradation mechanisms and ionomer chemistries on fluorine loss and change in ion exchange capacity. Comparison of the model with experimental degradation data for Nafion and Aquivion membranes allows rate constants of degradation processes to be determined. Results of these analyses are discussed in view of strategies to mitigate chemical degradation of ionomer membranes. PMID:25164106

Ghelichi, Mahdi; Melchy, Pierre-Éric Alix; Eikerling, Michael H

2014-09-25

119

Infrared spectrometric study of acid-degradable glasses.  

PubMed

The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass. PMID:12147746

De Maeyer, E A P; Verbeeck, R M H; Vercruysse, C W J

2002-08-01

120

Characterization of ionomer solutions in non-polar solvents  

NASA Astrophysics Data System (ADS)

The effect of specific interactions on polymer solution properties was studied by examining the aggregation behavior of ionomers in non-polar solvents. Temperature-concentration phase diagrams of acid form of sulfonated polystyrene (HSPS) solutions in decalin were determined using a light scattering technique. Upper Critical Solution Temperature (UCST) type phase behavior was observed and the UCST's increased with increasing sulfonation level. This indicated that aggregation of HSPS molecules was a major factor in determining the solubility of these ionomers in non-polar solvents. The association of sulfonic acid groups of HSPS in solution due to hydrogen bonding was investigated using dynamic light scattering. CONTIN analysis of the field autocorrelation functions yielded a single relaxation mode for low HSPS concentration (at temperatures away from the cloud point), and two relaxation modes for higher concentrations. The fast relaxation mode was attributed to the presence of single chains or small sized aggregates of HSPS, and the slow relaxation mode to the presence of large multi-chain aggregates. In a narrow range of temperature above the cloud point, the slow relaxation mode diffusion coefficient decreased drastically indicating that extensive aggregation occurred close to the phase boundary. This was substantiated by the appearance of a slow relaxation mode in the low concentration solutions at temperatures very close to the phase boundary. The extensive aggregation then provides the driving force for phase separation at temperatures that are much higher than the cloud point temperatures of the precursor polystyrenes from which the HSPS were synthesized.

Chakrabarty, Kaushik

121

Structure of Secondary Crystals in Ethylene-Based Ionomers  

NASA Astrophysics Data System (ADS)

A typical DSC thermogram of an ethylene-(meth)acrylic acid ionomer displays two melting endotherms: one near 100^oC reflecting the melting of primary ethylene crystals, and one at 40-60^oC which we have shown via simultaneous SAXS/WAXS/DSC to arise from the melting of interlamellar secondary crystals. Dynamic DSC (DDSC) confirms that the two peaks reflect a bimodal crystal thickness distribution, rather than a superposition of melting and recrystallization events. The melting temperature of these secondary crystals, estimated to be 2.5-3.5 nm thick, is sensitive to annealing history. DDSC also indicates that these secondary crystals melt irreversibly, as expected if each must be individually nucleated. The 2-D SAXS patterns of highly-oriented blown films of such ionomers show intense peaks, arising from the polyethylene lamellar crystallites, along the direction of principal orientation. Comparing the azimuthal variation in SAXS peak intensity at temperatures below and above the low-temperature endotherm reveals that the secondary crystallites are significantly oriented, but less so than the primary lamellae. Thus, the secondary interlamellar crystals also have a lamellar (anisotropic) habit, rather than resembling fringed micelles (isotropic).

Wakabayashi, K.; Loo, Y.-L.; Huang, Y. E.; Lee, L.-B. W.; Register, R. A.

2003-03-01

122

[Phase transition in polymer blends and structure of ionomers and copolymers  

SciTech Connect

The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

Not Available

1993-01-01

123

Artificial caries formation around fluoride-releasing restorations in roots.  

PubMed

Secondary caries is one of the most important factors leading to replacement of dental restorations. This investigation assessed the capacity of fluoride-releasing restorative materials to resist caries in vitro when used in roots. Class 5 cavities were prepared in the buccal and lingual surfaces of 30 extracted premolars. The six materials used were: glass-ionomer cement (Fuji), glass-ionomer cement with silver particles added (Ketac-silver), fluoride-containing composite resin (Tetric), composite resin (Silux plus), fluoride-containing amalgam (Fluor-Alloy) and high-copper amalgam (Dispersalloy). After 5 weeks in an acid gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that repair with glass-ionomer materials of a carious lesion may be of great importance in the prevention of secondary caries around the restorations in roots. PMID:9846901

Dionysopoulos, P; Kotsanos, N; Papadogiannis, Y; Konstantinidis, A

1998-11-01

124

Piezoelectric and mechanical properties of fatigue resistant, self-healing PZT-ionomer composites  

NASA Astrophysics Data System (ADS)

Piezoelectric ceramic-polymer composites with 0-3 connectivity were fabricated using lead zirconium titanate (PZT) powder dispersed in an ionomer (Zn ionomer) and its reference ethylene methacrylic acid copolymer (EMAA) polymer matrix. The PZT-Zn ionomer and PZT-EMAA composites were prepared by melt extrusion followed by hot pressing. The effects of poling conditions such as temperature, time and electric field on the piezoelectric properties of the composites were investigated. The experimentally observed piezoelectric charge coefficient and dielectric constant of the composites were compared with theoretical models. The results show that PZT-Zn ionomer composites have better piezoelectric properties compared to PZT-EMAA composites. The static and fatigue properties of the composites were investigated. The PZT-Zn ionomer composites were found to have excellent fatigue resistance even at strain levels of 4%. Due to the self-healing capabilities of the ionomer matrix, the loss of piezoelectric properties after high strain tensile cyclic loading could be partially recovered by thermal healing.

James, N. K.; Lafont, U.; van der Zwaag, S.; Groen, W. A.

2014-05-01

125

Dynamics of Sulfonated Polystyrene Ionomers by Dielectric Relaxation Spectroscopy  

NASA Astrophysics Data System (ADS)

Broadband dielectric spectroscopy was used to investigate the dynamics of sulfonated polystyrene (SPS) ionomers, in both the acid and neutralized form. This study seeks to elucidate the role of counter ion type (Zn, Na, and Cs), degree of sulfonation (9 and 6%), and ion cluster morphology on the relaxation phenomena of SPS. Degree of neutralization and ion type have been found to significantly impact the breadth and time scale of the segmental relaxation process. High temperature relaxation processes, tentatively proposed to arise from Maxwell-Wagner-Sillars interfacial polarization and a hydrogen bonding relaxation, have also been identified. Bands in the sulfonate stretching region of FTIR spectra reveal information about ion coordination in the local aggregate environment. A combination of scanning transmission electron microscopy imaging and X-ray scattering confirmed the presence of homogeneously distributed, nearly monodisperse spherical ionic aggregates in the polymer matrix.

Castagna, Alicia; Wang, Wenqin; Winey, Karen; Runt, James

2010-03-01

126

Investigation of the room temperature annealing peak in ionomers  

SciTech Connect

A number of studies appearing in the literature have documented an endothermic peak in differential scanning calorimetry (DSC) scans for ethylene-methacrylic acid copolymer ionomers which appears only upon annealing at room temperature. This peak has been attributed to either polyethylene crystallites, ionic crystallite, or water absorption. In a novel polyurethane cationomer with a quarternized amine contained in hard segment, the same phenomena has been found in DSC scans when the neutralizing anion is bromine or iodine. Since this material does not crystallize, the authors were able to conclusively eliminate crystallization as the cause of the endotherm. The extended x-ray absorption fine structure (EXAFS) of bromine has been measured to differentiate between water absorption and ionic crystallites. Spectra were collected above and below the temperature corresponding to the endothermic peak. The results of the EXAFS analysis will be presented.

Goddard, R.J.; Grady, B.P.; Cooper, S.L. [Univ. of Wisconsin-Madison, WI (United States)

1993-12-31

127

High-resolution genome-wide scan of genes, gene-networks and cellular systems impacting the yeast ionome  

PubMed Central

Background To balance the demand for uptake of essential elements with their potential toxicity living cells have complex regulatory mechanisms. Here, we describe a genome-wide screen to identify genes that impact the elemental composition (‘ionome’) of yeast Saccharomyces cerevisiae. Using inductively coupled plasma – mass spectrometry (ICP-MS) we quantify Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, S and Zn in 11890 mutant strains, including 4940 haploid and 1127 diploid deletion strains, and 5798 over expression strains. Results We identified 1065 strains with an altered ionome, including 584 haploid and 35 diploid deletion strains, and 446 over expression strains. Disruption of protein metabolism or trafficking has the highest likelihood of causing large ionomic changes, with gene dosage also being important. Gene over expression produced more extreme ionomic changes, but over expression and loss of function phenotypes are generally not related. Ionomic clustering revealed the existence of only a small number of possible ionomic profiles suggesting fitness tradeoffs that constrain the ionome. Clustering also identified important roles for the mitochondria, vacuole and ESCRT pathway in regulation of the ionome. Network analysis identified hub genes such as PMR1 in Mn homeostasis, novel members of ionomic networks such as SMF3 in vacuolar retrieval of Mn, and cross-talk between the mitochondria and the vacuole. All yeast ionomic data can be searched and downloaded at http://www.ionomicshub.org. Conclusions Here, we demonstrate the power of high-throughput ICP-MS analysis to functionally dissect the ionome on a genome-wide scale. The information this reveals has the potential to benefit both human health and agriculture. PMID:23151179

2012-01-01

128

Effects of ionomer content on mass transport in gas diffusion electrodes for proton exchange membrane fuel cells  

Microsoft Academic Search

The effect of the ionomer content on the mass transport ability in gas diffusion electrodes of proton exchange membrane fuel cells (PEMFCs) was investigated. The influence of the catalytic activity caused by a change in ionomer content was eliminated by adjusting the amount of the catalyst. The mass transport ability was evaluated by the current of the oxygen reduction reaction

Z Siroma; T Sasakura; K Yasuda; M Azuma; Y Miyazaki

2003-01-01

129

Temperature-dependent structure changes in Nafion ionomer studied by PCMW2D IR correlation spectroscopy  

NASA Astrophysics Data System (ADS)

Temperature-dependent infrared (IR) spectra of a Nafion membrane were measured over a temperature range from 30 to 320 °C. The obtained spectra were analyzed using perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy and quantum chemical calculations (QCC). Three-step structural changes in Nafion ionomer induced by temperature were revealed. Dehydration of the ionomer is dominant below 60 °C. Protonation of sulfonate group in the side chain terminal occurs around 100 °C. Thermal degradation of the chains starts above 280 °C.

Morita, Shigeaki; Kitagawa, Kuniyuki

2010-06-01

130

Nuclear Magnetic Resonance Investigation of Dynamics in Poly(Ethylene Oxide) Based Lithium Polyether-ester-sulfonate Ionomers  

SciTech Connect

Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies of both the polymer and lithium ions in the lower ion content samples indicate that the polymer segmental motion and lithium ion hopping motion are correlated even though their respective correlation times differ significantly. A divergent trend is observed for correlation times and activation energies of the highest ion content sample due to the presence of ionic aggregation. Details about the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments.

Roach, David J.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

2012-01-07

131

Nuclear magnetic resonance investigation of dynamics in poly(ethylene oxide)-based lithium polyether-ester-sulfonate ionomers  

Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies for motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though their respective correlation times differ significantly. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments.

Roach, David J. [Pennsylvania State University, University Park, PA (United States); Dou, Shichen [Pennsylvania State University, University Park, PA (United States); Colby, Ralph H. [Pennsylvania State University, University Park, PA (United States); Mueller, Karl T. [Pacific Northwest Lab., Richland, WA (United States)

2012-01-06

132

The Effect of Temperature on Viscoelastic Properties of Glass Ionomer Cements and Compomers  

E-print Network

of Operative Dentistry, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece 2 of Athens, School of Dentistry, Department of Biomaterials Received 14 February 2006; revised 9 April 2006.interscience.wiley.com). DOI: 10.1002/jbm.b.30618 Abstract: The objective of this study was to determine the viscoelastic

Lakes, Roderic

133

Poly(vinylidene fluoride) based anion conductive ionomer as a catalyst binder for application in anion exchange membrane fuel cell  

NASA Astrophysics Data System (ADS)

An anion conductive polymeric ionomer incorporated into the electrodes of an anion exchange membrane fuel cell (AEMFC) can help to enhance anion transport in the catalyst layer of electrode, and thus improve the catalyst efficiency and performance of AEMFC. In this work, we report the synthesis and properties of a new type of anion conductive ionomer, which is synthesized by grafting of poly(vinylidene fluoride), or PVDF with poly(vinylbenzyltrimethylammonium chloride) via atom transfer radical polymerization. The ionomer obtained shows improved hydrophilicity relative to pristine PVDF, and exhibits an ion exchange capacity of 1.59 mmol g-1. When used in a direct hydrazine hydrate fuel cell (DHFC) as a catalyst binder, the synthesized ionomer imparts the DHFC a significantly improved power density, which is 5-10 fold as much as that of the cells without using such ionomer. The method developed here for anion exchange ionomer synthesis is facile, green and does not involve the use of carcinogenic chemicals such as chloromethylmethylether and trimethylamine, which are often used for conventional anion exchange membrane or ionomer synthesis.

Zhang, Fengxiang; Zhang, Huamin; Qu, Chao; Ren, Junxia

2011-03-01

134

Langmuir-Blodgett Monolayers of Ionomer/Oligomer Heterografts  

NASA Astrophysics Data System (ADS)

The air/water interface in a Langmuir trough provides a favorable environment for fabricating polymer surface aggregates, where the amount of polymer spread on the interface can be precisely controlled and the chain density can be continuously varied by barrier compression. In the present work, we investigated the surface structures of Langmuir monolayers, transferred to a solid substrate, of ionic complexes (heterografts) composed of a lightly sulfonated polystyrene ionomer (PSSA, acid form) and butyl acrylate oligomers monofunctionalized by dimethylamine (PtBuA). The heterografts give rise to isotherms that are similar to that of PSSA but distinct from that of PtBuA. AFM images of films deposited at very low surface pressures (0.1mN/m) show separated particles (10-20 nm in diameter, <0.3nm high) surrounded by discontinuous film of ca.0.1 nm height. At intermediate pressures (2-5 mN/m), rope-like structures (2-3 nm high), apparently formed from aggregates of spherical particles, are obtained. At 10 mN/m, more condensed aggregates result. It is hypothesized that the separated spherical particles obtained at low surface pressures are single condensed PSSA chains surrounded by expanded PtBuA chains end-grafted to the PSSA particles. Compression of these monolayers at the water surface may compress the oligomer chains and favor hydrogen-bonding interactions of the ester groups with the excess sulfonic acid groups present, and lead to aggregation of the individual particles.

Lu, Qing; Bazuin, C. Geraldine

2004-03-01

135

Counterion Effects on Ion Mobility and Mobile Ion Concentration of Doped Polyphosphazenes and Polyphosphazene Ionomers  

Microsoft Academic Search

Previous investigations have shed some light on the ion conduction process in polymer electrolytes, yet ion transport is still not well understood. Here, upon the application of a physical model of electrode polarization to two systems with nearly identical chemical structure, one composed of an ionomer (MI) with a single mobile cation, and the other a salt-doped polymer (M+S) with

Jim Runt; Robert Klein; Arlin L. Weikel; Harry R. Allcock

2007-01-01

136

Synthesis and characterization of polyurethane ionomers, blends and urethane-urea aerogel hybrids  

NASA Astrophysics Data System (ADS)

The chemical and physical properties of alkali, alkaline metal and selected transition metal polyurethane ionomers were investigated. A new synthesis was developed for carboxylated polyurethane anionomers, and it was employed to synthesize a range of ionomers. Thus, a series of polyurethane ionomers was prepared in which the molecular weight of a constituent diol, the concentration of carboxylic acid sites, and the nature of the cations was varied. The analogous materials with equivalent nominal stoichiometries were synthesized by the standard method of preparing the acid-form polymer and of replacing the protons for metal ions. The novel synthesis employs a multiphase reaction between isocyanate-terminated prepolymers and solid, anhydrous microcrystalline metal salts of a carboxylic acid diol. This required the development of new synthesis of these starting materials. The materials studied are based on polyether diols, acid-containing diols and a saturated diisocyanate. The novel synthesis is more than twenty times as fast as the standard method under the same conditions. The spectroscopic and mechanical properties of the polyurethane ionomers synthesized in both ways were studied and contrasted. Those prepared by the new method have greater spatial homogeneity, resulting in lower scattering loss in the ultraviolet-visible range. They also exhibited values of E ' (the real elastic modulus) that are as much as an order of magnitude greater than those made by the standard method. In addition, the temperature dependence of Fin the -25 ˜ +75°C range is remarkably low. Studies of the structural properties by infrared spectroscopy, small angle x-ray scattering, thermal analysis, gel permeation chromatography and scanning electron microscopy were used to elucidate their molecular structures and intermolecular interactions. The rates of key synthetic reactions and the thermal stability of the metal containing polyurethane ionomers were studied by thermal analysis. The polyurethane ionomers synthesized in this work were combined with, sulfonated polystyrene, and poly(ethylene-co-acrylic or methacrylic acid) polymers, their partially neutralized ionomers, and thermoplastic polyurethanes. It was found that polyurethane anionomers synthesized by the new method were miscible with these polymers through the composition range. Several series of these blends were studied using mid- and far-infrared spectroscopy to investigate molecular interactions that lead to the miscibility. Isocyanate-containing molecules were reacted with chitosan silica aerogels. It was discovered that -NCO groups of the diisocyanate HMDI reacted selectively with amine groups in the presence of large excesses of -OH groups from alcohol, silica, and water. This study leads to the possibility of attaching nanoscale aerogel particles to substrates, to one another, and to additional molecules of interest.

Wang, Mingzhe

137

Solid state nuclear magnetic resonance investigation of polymer backbone dynamics in poly(ethylene oxide) based lithium and sodium polyether-ester-sulfonate ionomers  

NASA Astrophysics Data System (ADS)

Polymer backbone dynamics of single ion conducting poly(ethylene oxide) (PEO)-based ionomer samples with low glass transition temperatures (Tg) have been investigated using solid-state nuclear magnetic resonance. Experiments detecting 13C with 1H decoupling under magic angle spinning (MAS) conditions identified the different components of the polymer backbone (PEO spacer and isophthalate groups) and their relative mobilities for a suite of lithium- and sodium-containing ionomer samples with varying cation contents. Variable temperature (203-373 K) 1H-13C cross-polarization MAS (CP-MAS) experiments also provided qualitative assessment of the differences in the motions of the polymer backbone components as a function of cation content and identity. Each of the main backbone components exhibit distinct motions, following the trends expected for motional characteristics based on earlier Quasi Elastic Neutron Scattering and 1H spin-lattice relaxation rate measurements. Previous 1H and 7Li spin-lattice relaxation measurements focused on both the polymer backbone and cation motion on the nanosecond timescale. The studies presented here assess the slower timescale motion of the polymer backbone allowing for a more comprehensive understanding of the polymer dynamics. The temperature dependences of 13C linewidths were used to both qualitatively and quantitatively examine the effects of cation content and identity on PEO spacer mobility. Variable contact time 1H-13C CP-MAS experiments were used to further assess the motions of the polymer backbone on the microsecond timescale. The motion of the PEO spacer, reported via the rate of magnetization transfer from 1H to 13C nuclei, becomes similar for T ˜x 1{.1} Tg in all ionic samples, indicating that at similar elevated reduced temperatures the motions of the polymer backbones on the microsecond timescale become insensitive to ion interactions. These results present an improved picture, beyond those of previous findings, for the dependence of backbone dynamics on cation density (and here, cation identity as well) in these amorphous PEO-based ionomer systems.

Roach, David J.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

2013-05-01

138

[Phase transition in polymer blends and structure of ionomers and copolymers]. [Annual report, April 1, 1989--June 30, 1993  

SciTech Connect

The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

Not Available

1993-07-01

139

A polymethacrylate-based quaternary ammonium OH- ionomer binder for non-precious metal alkaline anion exchange membrane water electrolysers  

NASA Astrophysics Data System (ADS)

In order to develop the alkaline anion exchange membrane water electrolysers (AAEMWE), a quaternary OH- conductive ionomer binder based on polymethacrylate was synthesized by copolymerization of three kinds of methacrylate monomers, which was followed by quaternization. Tensile strength of this ionomer membrane was 7.629 MPa, with Young's modulus 0.229 GPa and elongation 45.8%. The conductivity of this ionomer could reach 0.059 S cm-1 at 50 °C. With this ionomer in catalyst layers of an AAEMWE, the voltage of 1.9 V gave a current density of 100 mA cm-2. Satisfactory stability of the membrane electrode assembly was observed from chronocoulometry.

Wu, Xu; Scott, Keith

2012-09-01

140

Effect of sealers on fracture resistance of endodontically treated teeth with and without smear layer removal: An in vitro study  

PubMed Central

Aim: The present study involved the in vitro comparison of root reinforcing abilities of two sealers, i.e., Ketac-Endo and Acroseal, in endodontically treated teeth in the presence and absence of smear layer. Materials and Methods: Fifty teeth were taken and sectioned at the cementoenamel junction. The teeth with faults were discarded and a total of 36 teeth were used for study. The samples were biomechanically prepared using step-back technique. In 10 teeth, the smear layer was preserved using sodium hypochlorite. Smear layers were removed from 10 teeth using 17% EDTA, and in another 10 samples, the smear layers were eliminated using 17% EGTA. The remaining samples served as controls. Samples were obturated with sealers using the lateral condensation technique. Ketac-Endo (3M) is a glass ionomer based root canal sealer, and Acroseal (Septodont) sealers were used. The teeth were then tested by using an Instron testing machine. Results: Ketac-Endo shows higher fracture resistance values in comparison to Acroseal. Other factors as the amount of tooth structure remaining, the agents used for the removal of smear layer and instrumentation techniques may alter the tooth resistance to fracture. Conclusion: Ketac-Endo shows higher fracture resistance values in comparison to Acroseal. PMID:20543918

Jhamb, Swaty; Nikhil, Vineeta; Singh, Vijay

2009-01-01

141

Interdiffusion of long alcohols into thin ionomer films; In situ Neutron Reflectivity study  

NASA Astrophysics Data System (ADS)

Transport of solvents and ions within ionic polymers controls their many current and potential applications from energy related to drug delivery systems. The transport is determined by the phase structure and the interaction of the diffusing species with the polymers, coupled with interfacial effects. The current work presents the kinetics of penetration of long chain alcohols diffusing into rigid ionomer thin films formed by a rigid polyphenylene sulfonated ionomer, using in situ neutron reflectivity. The penetration of deuterated n-octanol and n-hexanol into ˜20nm thick films was followed as a function of time for different sulfonation levels of the polymer. As for shorter molecules, the diffusion process consists of two stages, a relatively fast one in which the film thickness increases linearly with time followed by a slow phase in which structural changes take place. With increasing sulfonation levels, the diffusion first increases and then decreases; a trend that is attributed to hydrophilic/hydrophobic balance.

Etampawala, Thusitha; Ratnaweera, Dilru; Shrestha, Umesh; Perahia, Dvora; Cornelius, Christopher; Majewski, Jaroslaw

2010-03-01

142

Study of the ionome and uptake fluxes in cherry tomato plants under moderate water stress conditions  

Microsoft Academic Search

Nutritional imbalance under water-deficit conditions depresses plant growth by affecting nutrient uptake, transport, and distribution.\\u000a The present work analyses the variations in the foliar concentrations of macro- and micronutrients as well as the transport\\u000a of these nutrients in five cherry tomato cultivars under well-watered and moderately water-stressed conditions with the aim\\u000a of establishing whether the ionome of the plants is

Eva Sánchez-Rodríguez; Maria del Mar Rubio-Wilhelmi; Luis Miguel Cervilla; Begoña Blasco; Juan Jose Rios; Rocio Leyva; Luis Romero; Juan Manuel Ruiz

2010-01-01

143

Developments in Metal?Containing Polyurethanes, Co?polyurethanes and Polyurethane Ionomers  

Microsoft Academic Search

The growth of science and technology of polyurethanes leads to the development of new materials with more desirable properties. Such kinds of materials include metal?containing polyurethanes, poly(urethane?urea)s, poly(urethane?ether)s, poly(urethane?ester)s, poly(urethane?ether?ester)s, poly(urethane?imide)s, and polyurethane ionomers with isocyanate structural units combining the properties of enhanced thermal stability, fire retardancy, flexibility, and solubility. Ionic diols containing metal salts are used as important starting

R. Jayakumar; S. Nanjundan; M. Prabaharan

2005-01-01

144

Glass Artworks  

NASA Technical Reports Server (NTRS)

Several NASA technologies have played part in growth and cost containment of studio glass art, among them a foam type insulation developed to meet a need for lightweight material that would reduce flame spread in aircraft fire. Foam comes in several forms and is widely used by glass artists, chiefly as an insulator for the various types of ovens used in glass working. Another Spinoff is alumina crucibles to contain molten glass. Before alumina crucibles were used, glass tanks were made of firebrick which tended to erode under high temperatures and cause impurities; this not only improved quality but made the process more cost effective. One more NASA technology that found its way into glass art working is a material known as graphite board, a special form of graphite originally developed for rocket motor applications. This graphite is used to exact compound angles and creates molds for poured glass artworks of dramatic design.

1988-01-01

145

Dynamics and partitioning of the ionome in seeds and germinating seedlings of winter oilseed rape.  

PubMed

Germination and seedling establishment are among the most critical phases in the development of plants, and seed vigour has become an important trait for the selection of robust crop cultivars. Little is known about the potentially limiting role of mineral nutrients in early metabolic and developmental processes during germination. Therefore, we assessed the ionome and relative distribution of mineral elements in different seed and seedling tissues of oilseed rape (Brassica napus L.) and monitored the internal allocation of nutrients during germination. In seeds, cotyledons harboured the main pool of K, P, S, Mg, Fe, Mn and Zn, whereas the seed coat contained most of the Ca, Na, B, Cu and Mo. Although the early root and hypocotyl tissue expanded first, concentrations of most elements were initially low. Re-allocation of elements to the root/hypocotyl tissue from other pools set in two days after seed imbibition and was most rapid for K. Relative to the critical deficiency levels of vegetative tissues, seed tissues were particularly low in B, K and Fe. Further analyses of the ionome of seeds and seedlings, grouped according to their germination efficiency, indicated that in particular low S, Mg and Ca coincided with germination failure. This study documents highly dynamic changes in the ionome of seed and seedling tissues and provides evidence for potentially limiting elements during early germination and seedling establishment in rapeseed. PMID:23939714

Eggert, Kai; von Wirén, Nicolaus

2013-09-01

146

Toxicity testing of restorative dental materials using brine shrimp larvae (Artemia salina).  

PubMed

This study investigated the effect of extracts of different composites, glass ionomer cement (GIC)s and compomers on the viability of brine shrimp larvae. Ethanolic extracts of four dental composites (Z-100; Solitaire 2; Filtek P60 and Synergy), a conventional GIC (Ketac-Fil), a resin-modified glass ionomer cement (Vitremer), two compomers (F2000; Dyract AP), and a flowable compomer (Dyract Flow) were prepared from each material. Following evaporation of the ethanol, the extracts were resuspended in distilled water, which was then used to test the effects on the viability of brine shrimp larvae. For the composites, the extract of Synergy was the least toxic (88% viability) followed by the extracts of Solitaire 2, Z100 and P60 (75%, 67.5% and 50% viability, respectively). One-way ANOVA revealed highly significant differences between the resin composite materials (p<0.001). Follow-up comparison between the composite groups by Tukey's pairwise multiple-comparison test (alpha =0.05) showed that the extract of Synergy was significantly less toxic than the extracts of all the other materials except that of Solitaire 2. The compomers showed 100% lethality, while the percentage of viable larvae for the extracts of Ketac-Fil, and Vitremer were 32.3%, and 37.0%, respectively. One-way ANOVA revealed highly significant differences between the groups of materials (p<0.001). Follow-up comparison between the groups by Tukey's test (alpha = 0.05) showed that the toxic effect of the extracts of the compomers were significantly greater than that of Ketac-Fil, and Vitremer. The differences in the toxic effects of Vitremer and Ketac-Fil were not statistically significant. In conclusion, the toxicity of composite materials varied according to their chemical composition. Compomers were the most lethal materials to brine shrimp larvae followed by GICs and then composites. PMID:19089264

Milhem, Manar M; Al-Hiyasat, Ahmad S; Darmani, Homa

2008-01-01

147

Optimization of nafion ionomer content using synthesized Pt/carbon nanofibers catalyst in polymer electrolyte membrane fuel cell.  

PubMed

In this study, carbon nanofiber (CNF) was used as a support in which 47.5 wt% Pt/CNFs catalyst was prepared by a modified polyol method. The platinum particle size and dispersion on the CNFs are approximately 2-4 nm as determined by X-ray diffractometry and transmission electron microscopy. The specific surface area was approximated as 55.90 m2/g by BET analysis. Electrodes were prepared by the spray method and have a size of 5 cm2. A commercial catalyst (TKK, 46 wt% Pt/C) was used as the anode and the cathode was Pt/CNFs. Different amounts of Nafion ionomer (Aldrich, 5 wt% solution, in the range of 0-20 wt%) were coated on a membrane (Dupont, Nafion 212) with 0.4 mg/cm2 of Pt catalyst at the cathode side. The resulting polarization, ohmic and mass transfer resistances changed significantly based on the Nafion ionomer content. Optimum Nafion ionomer content in the 47.5 wt% Pt/CNFs was 5 wt%. The well-dispersed Nafion ionomer was observed on the catalyst surface area using SEM-EDAX analysis. A sufficient triple-phase boundary was formed by a small amount of Nation ionomer due to the BET surface area of the Pt/CNFs. PMID:22966581

Jung, Ju-Hae; Cha, Moon-Soon; Kim, Jun-Bom

2012-07-01

148

Cusp Fracture Resistance of Maxillary Premolars Restored with the Bonded Amalgam Technique Using Various Luting Agents  

PubMed Central

Objective. This in vitro study uses measurements of fracture resistance to compare maxillary premolars restored with the bonded amalgam technique using a new resin luting cement, glass ionomer, and resin-modified glass ionomer as the bonding agents. Materials. Eighty-five sound maxillary premolars were selected and randomly assigned to one of five test groups of 17 teeth each. One group of intact teeth served as the control. The remaining groups were prepared to a standard cavity form relative to the dimensions of the overall tooth and restored with amalgam alone or a bonded amalgam using one of three luting agents: RelyX Arc (a new resin luting cement), RelyX luting (a resin-modified glass ionomer), or Ketac-Cem ? (a glass ionomer) as the bonding agents. Each tooth was then subjected to compressive testing until catastrophic failure occurred. The mean loads at failure of each group were statistically compared using ANOVA with a post hoc Bonferroni test. Results. It was found that regardless of the luting cement used for the amalgam bonding technique, there was little effect on the fracture resistance of teeth. Conclusion. Cusp fracture resistance of premolars prepared with conservative MOD cavity preparations is not improved by using an amalgam-bonding technique compared to similar cavities restored with amalgam alone. PMID:20339450

Marchan, Shivaughn M.; Coldero, Larry; White, Daniel; Smith, William A. J.; Rafeek, Reisha N.

2009-01-01

149

Metallic glasses  

Microsoft Academic Search

This paper surveys the present state of knowledge concerning the production, stability and structure of metallic glasses made by rapid quenching from the melt, and outlines their principal magnetic, electrical and mechanical properties. Emphasis is placed on the influence of annealing, at temperatures below the glass transition, on a range of properties. The prospect for practical applications is examined, with

R. W. Cahn

1980-01-01

150

Frosty Glasses  

NSDL National Science Digital Library

In this activity, learners explore why frost forms. They create their own frost using a solution of ice water and salt in a glass. The salt allows the temperature of the water to drop below the normal freezing point, so that water vapor in the air turns directly into solid ice on the surface of the glass.

Cosi

2009-01-01

151

An investigation of long and short range ion motions within the cluster morphology of electrolyte-containing perfluoro-sulfonate ionomer membranes  

SciTech Connect

An equivalent circuit model was postulated for PFSI (perfluoro-sulfanate-ionomer) polymers. It successfully models three different dielectric relaxation mechanisms taking place within long and short sidechain PFSI's in an alternating electric field. The three dielectric processes are long-range ion inter-cluster hopping in the low frequency region, short-range intra-cluster polarization occurred in frequencies at about 10[sup 3] to 10[sup 6] Hz, and Debye-like orientation of water molecules taking place at very high frequencies. When membranes are annealed in the proximity of the glass transition temperature of ionic clusters, the packing of sulfonate groups becomes more efficient. This is by the fact that the symmetrical parameter of the distribution of relaxation time of the Cole-Cole equation increases with annealing time. The cluster activities of the long and short sidechain polymers act differently in different electrolyte solutions. The sidechains of the long sidechain polymer act like a spring, it contracts while the material was equilibrated in low concentration solutions and it expands as equilibrated in concentrated solutions. The cluster dimension of the long sidechain material does not vary too much. The cluster dimension of short sidechain polymers can vary significantly on different electrolyte solutions.

Su, S.

1992-01-01

152

Morphological and physical characterization of poly(styrene-isobutylene-styrene) block copolymers and ionomers thereof  

NASA Astrophysics Data System (ADS)

Poly(styrene-isobutylene-styrene) block copolymers made by living cationic polymerization using a difunctional initiator and the sequential monomer addition technique were analyzed using curve-resolution software in conjunction with high-resolution GPC. Fractional precipitation and selective solvent extraction were applied to a representative sample in order to confirm the identity of contaminating species. The latter were found to be low molecular weight polystyrene homopolymer, diblock copolymer, and higher molecular weight segmented block copolymers formed by intermolecular electrophilic aromatic substitution linking reactions occurring late in the polymerization of the styrene outer blocks. Solvent-cast films of poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers and block ionomers were analyzed using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Four block copolymer samples with center block molecular weights of 52,000 g/mol and PS volume fractions (o sbPS) ranging from 0.17 to 0.31 were studied. All samples exhibited hexagonally packed cylinders of PS within the PIB matrix. Cylinder spacing was in the range 32 to 36 nm for most samples, while cylinder diameters varied from 14 to 21 nm. Porod analysis of the scattering data indicated the presence of isolated phase mixing and sharp phase boundaries. PS-PIB-PS block copolymers and ionomers therefrom were analyzed using dynamic mechanical analysis (DMA) and tensile testing. The study encompassed five block copolymer samples with similar PIB center blocks with molecular weights of approx52,000 g/mol and PS weight fractions ranging from 0.127 to 0.337. Ionomers were prepared from two of these materials by lightly sulfonating the PS outer blocks. Sulfonation levels varied from 1.7 to 4.7 mol % and the sodium and potassium neutralized forms were compared to the parent block copolymers. Dynamic mechanical analysis (DMA) of the block copolymer films indicated the existence of a third phase attributed to PIB chains near the PS domain interface which experience reduced mobility due to their firm attachment to the hard PS domain. The relative amount of this phase decreased in samples with larger PS blocks, while the temperature of the associated transition increased. Tensile testing showed increased tensile strength but decreased elongation at break with larger PS blocks. DMA of the ionomers indicated improved dynamic modulus at temperatures above 100spcirc$C. Tensile testing of the ionomers indicated slight improvements in tensile strength with little loss in elongation at break. PS-PIB-PS block copolymer ionomer (BCP01, center block molecular weight = 53,000 g/mole; 25.5 wt % polystyrene, 4.7% sulfonation of phenyl units, 100% neutralized with KOH) was compounded with various organic and inorganic acid salts of 2-ethylhexyl-p-dimethyl aminobenzoate (ODAB) to explore the efficacy of these compounds as ionic plasticizers. (Abstract shortened by UMI.)

Baugh, Daniel Webster, III

153

Glass recycling and reuse  

Microsoft Academic Search

Methods are surveyed for recycling and\\/or reusing post-consumer glass products to determine which methods are most favorable. The following topics are included: the properties of glass, glass manufacture; analyses of alternatives to direct disposal of glass products; reuse of waste glass for glass manufacture; techniques for the separation of glass from municipal refuse; the development of degradable glass containers; returnable

H. R. Samtur

1974-01-01

154

The role of acrylonitrile in controlling the structure and properties of nanostructured ionomer films.  

PubMed

Ionomers are polymers which contain ionic groups that are covalently bound to the main chain. The presence of a small percentage of ionic groups strongly affects the polymer's mechanical properties. Here, we examine a new family of nanostructured ionomer films prepared from core-shell polymer nanoparticles containing acrylonitrile (AN), 1,3-butadiene (Bd) and methacrylic acid (MAA). Three new AN-containing dispersions were investigated in this study. The core-shell nanoparticles contained a PBd core. The shells contained copolymerised Bd, AN and MAA, i.e., PBd-AN-MAA. Three types of crosslinking were present in these films: covalent crosslinks (from Bd); strong physical crosslinks (involving ionic bonding of RCOO(-) and Zn(2+)) and weaker physical crosslinks (from AN). We examined and compared the roles of AN and ionic crosslinking (from added Zn(2+)) on the structure and mechanical properties of the films. The FTIR spectroscopy data showed evidence for RCOOH-nitrile hydrogen bonding with tetrahedral geometry. DMTA studies showed that AN copolymerised within the PBd-AN-MAA phase uniformly. Tensile stress-strain data showed that inclusion of AN increased elasticity and toughness. Analysis showed that about 33 AN groups were required to provide an elastically-effective chain. However, only 1.5 to 2 ionically bonded RCOO(-) groups were required to generate an elastically-effective chain. By contrast to ionic bonding, AN inclusion increased the modulus without compromising ductility. Our results show that AN is an attractive, versatile, monomer for increasing the toughness of nanostructured ionomers and this should also be the case for other nanostructured polymer elastomers. PMID:24852137

Tungchaiwattana, Somjit; Musa, Muhamad Sharan; Yan, Junfeng; Lovell, Peter A; Shaw, Peter; Saunders, Brian R

2014-07-14

155

Edible Glass  

NSDL National Science Digital Library

In this activity, learners discover the principles of edible glass by making a supersaturated sugar solution. The goal of this activity is to provide an interesting experiment which learners of many different levels can perform. The write-up for this activity provides explanatory information that presents the experiment from several different perspectives. This activity includes an introduction to common sugars, as well as some discussion of temperature and thermometry, basic thermodynamics, and the experimental procedure to make the candy glass.

Pomeroy, Josh

2012-01-01

156

Comparative metabolomic and ionomic approach for abundant fishes in estuarine environments of Japan.  

PubMed

Environmental metabolomics or ionomics is widely used to characterize the effects of environmental stressors on the health of aquatic organisms. However, most studies have focused on liver and muscle tissues of fish, and little is known about how the other organs are affected by environmental perturbations and effects such as metal pollutants or eutrophication. We examined the metabolic and mineral profiles of three kinds of abundant fishes in estuarine ecosystem, yellowfin goby, urohaze-goby, and juvenile Japanese seabass sampled from Tsurumi River estuary, Japan. Multivariate analyses, including nuclear magnetic resonance-based metabolomics and inductively coupled plasma optical emission spectrometry-based ionomics approaches, revealed that the profiles were clustered according to differences among body tissues rather than differences in body size, sex, and species. The metabolic and mineral profiles of the muscle and fin tissues, respectively, suggest that these tissues are most appropriate for evaluating environmental perturbations. Such analyses will be highly useful in evaluating the environmental variation and diversity in aquatic ecosystems. PMID:25387575

Yoshida, Seiji; Date, Yasuhiro; Akama, Makiko; Kikuchi, Jun

2014-01-01

157

Comparative metabolomic and ionomic approach for abundant fishes in estuarine environments of Japan  

PubMed Central

Environmental metabolomics or ionomics is widely used to characterize the effects of environmental stressors on the health of aquatic organisms. However, most studies have focused on liver and muscle tissues of fish, and little is known about how the other organs are affected by environmental perturbations and effects such as metal pollutants or eutrophication. We examined the metabolic and mineral profiles of three kinds of abundant fishes in estuarine ecosystem, yellowfin goby, urohaze-goby, and juvenile Japanese seabass sampled from Tsurumi River estuary, Japan. Multivariate analyses, including nuclear magnetic resonance-based metabolomics and inductively coupled plasma optical emission spectrometry-based ionomics approaches, revealed that the profiles were clustered according to differences among body tissues rather than differences in body size, sex, and species. The metabolic and mineral profiles of the muscle and fin tissues, respectively, suggest that these tissues are most appropriate for evaluating environmental perturbations. Such analyses will be highly useful in evaluating the environmental variation and diversity in aquatic ecosystems. PMID:25387575

Yoshida, Seiji; Date, Yasuhiro; Akama, Makiko; Kikuchi, Jun

2014-01-01

158

Surface-initiated growth of ionomer films from pt-modified gold electrodes.  

PubMed

The ability to chemically wire ionomer films to electrode surfaces can promote transport near interfaces and impact a host of energy-related applications. Here, we demonstrate proof-of-concept principles for the surface-initiated ring-opening metathesis polymerization (SI-ROMP) of norbornene (NB), 5-butylnorbornene (NBH4), and 5-perfluorobutylnorbornene (NBF4) from Pt-modified gold substrates and the subsequent sulfonation of olefins along the polymer backbones to produce ultrathin sulfonated polymer films. Prior to sulfonation, the films are hydrophobic and exhibit large barriers against ion transport, but sulfonation dramatically reduces the resistance of the films by providing pathways for proton diffusion. Sulfonated films derived from NBF4 and NBH4 yield more anodic potentials for oxygen reduction than those derived from NB or unfunctionalized electrodes. These improvements are consistent with hydrophobic structuring by the fluorocarbon or hydrocarbon side groups to minimize interfacial flooding and generate pathways for enhanced O(2) permeation near the interface. Importantly, we demonstrate that the sulfonated polymer chains remain anchored to the surface during voltammetry for oxygen reduction whereas short-chain thiolates that do not tether polymer are removed from the substrate. This approach, which we extend to unmodified gold electrodes at neutral pH, presents a method of cleaning the ionomer/electrode interface to remove molecular components that may hamper the performance of the electrode. PMID:19637878

Berron, Brad J; Faulkner, Christopher J; Fischer, Remington E; Payne, P Andrew; Jennings, G Kane

2009-11-01

159

Ionomers of intrinsic microporosity: in silico development of ionic-functionalized gas-separation membranes.  

PubMed

This work presents the predictive molecular simulations of a functionalized polymer of intrinsic microporosity (PIM) with an ionic backbone (carboxylate) and extra-framework counterions (Na(+)) for CO2 gas storage and separation applications. The CO2-philic carboxylate-functionalized polymers are predicted to contain similar degrees of free volume to PIM-1, with Brunauer-Emmett-Teller (BET) surface areas from 510 to 890 m(2)/g, depending on concentration of ionic groups from 100% to 17%. As a result of ionic groups enhancing the CO2 enthalpy of adsorption (to 42-50 kJ/mol), the uptake of the proposed polymers at 293 K exceeded 1.7 mmol/g at 10 kPa and 3.3 mmol/g at 100 kPa for the polymers containing 100% and 50% ionic functional groups, respectively. In addition, CO2/CH4 and CO2/N2 mixed-gas separation performance was evaluated under several industrially relevant conditions, where the IonomIMs are shown to increase both the working capacity and selection performance in certain pressure swing applications (e.g., natural gas separations). These simulations reveal that intrinsically microporous ionomers show great potential as the future of energy-efficient gas-separation polymeric materials. PMID:25272236

Hart, Kyle E; Colina, Coray M

2014-10-14

160

Cluster-continuum quantum mechanical models to guide the choice of anions for Li{sup +}-conducting ionomers  

SciTech Connect

A quantum-mechanical investigation on Li poly(ethylene oxide)-based ionomers was performed in the cluster-continuum solvation model (CCM) that includes specific solvation in the first shell surrounding the cation, all surrounded by a polarizable continuum. A four-state model, including a free Li cation, Li{sup +}-anion pair, triple ion, and quadrupole was used to represent the states of Li{sup +} within the ionomer in the CCM. The relative energy of each state was calculated for Li{sup +} with various anions, with dimethyl ether representing the ether oxygen solvation. The population distribution of Li{sup +} ions among states was estimated by applying Boltzmann statistics to the CCM energies. Entropy difference estimates are needed for populations to better match the true ionomer system. The total entropy change is considered to consist of four contributions: translational, rotational, electrostatic, and solvent immobilization entropies. The population of ion states is reported as a function of Bjerrum length divided by ion-pair separation with/without entropy considered to investigate the transition between states. Predicted concentrations of Li{sup +}-conducting states (free Li{sup +} and positive triple ions) are compared among a series of anions to indicate favorable features for design of an optimal Li{sup +}-conducting ionomer; the perfluorotetraphenylborate anion maximizes the conducting positive triple ion population among the series of anions considered.

Shiau, Huai-Suen; Janik, Michael J. [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Liu, Wenjuan; Colby, Ralph H. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2013-11-28

161

Lithium Polymer Electrolytes Based On PMMA / PEG And Penetrant Diffusion In Kraton Penta-Block Ionomer  

NASA Astrophysics Data System (ADS)

The study of diffusion in polymeric material is critical to many research fields and applications, such as polymer morphology, protective coatings (paints and varnishes), separation membranes, transport phenomena, polymer electrolytes, polymer melt, and controlled release of drugs from polymer carriers [1-9]. However, it is still a challenge to understand, predict and control the diffusion of molecules and ions of different sizes in polymers [2]. This work studied the medium to long range diffusion of species (i.e., ions and molecules) in solid polymer electrolytes based on poly(ethylene glycol)/poly(methyl methacrylate) (PEG/PMMA) for Li-based batteries, and polymeric permselective membranes via pulsed-field gradient NMR and a.c. impedance. Over the past decades polymer electrolytes have attracted much attention because of their promising technological application as an ion-conducting medium in solid-state batteries, fuel cells, electrochromic displays, and chemical sensors [10, 11]. However, despite numerous studies related to ionic transport in these electrolytes the understanding of the migration mechanism is still far from being complete, and progress in the field remains largely empirical [10, 12-15]. Among various candidates for solid polymer electrolyte (SPE) material, the miscible polymer pair, poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA), is an attractive one, because there is a huge difference in mobility between PEO and PMMA in their blends, and PEO chains remain exceptionally mobile in the blend even at temperature below the glass transition temperature of the blend [ 16]. Thus the mechanical strength and dimensional stability is maintained by PMMA component, while the chain motions or rearrangements of the PEO component virtually contribute to the ion transport [17]. The current work prepared two types of SPE based on poly(ethylene glycol) (PEG) /PMMA (40/60 by weight) for Li-based batteries: lithium bis(trifluoromethylsulfonylimide) (LiN(SO2CF3)2, LiTFSI) doped SPE and single-ion SPE. PEG, which is the very low molecular weight version of PEO, was used instead of PLO due to PEG's advantages of being noncrystalline, higher mobility, and having relatively high ionic conductivity when doped with alkali metal salts [18]. The medium to long range diffusion of species (i.e., ions and molecules) were studied via pulsed-field gradient NMR and a.c. impedance, along with other properties. For the LiTFSI doped system, the samples are named with their F0 to Li ratios. The order of diffusivity of ions is 16:1> 24:1> 8:1, while the order of a.c. conductivity is 24:1 > 16:1> 8:1. The largest diffusion 7Li coefficient is 1.4 x 108 cm 2/s in 16:1 at 77°C , and the largest a.c. conductivity is 1.43x 10-5S/cm for 24:1 at 68°C. The discrepancy between the diffusivity order and conductivity order is attributed to the formation of neutral contact ion pairs by a substantial fraction of ions in 16:1 . As the salt concentration is increased as 24:1?16:1?8:1, there is the transition of mostly free ions (i.e., 24:1)?free ions+contact ion pairs (i.e.. 16:1)?free ions+contact ion pairs+higher aggregates (i.e., 8:1). For the single-ion system, ion pairing of lithium PMMA ionomer is a serious problem due to the relatively low acidity of its corresponding acid and the low dielectric constant of the solvent (i.e. PEG). The Li+ diffusivity is fair (on the order of 10-8 cm2/s at 65°C, 77°C, and 89°C), but the fraction of free Li+ is only 1-2%. This severely limits the resulting a.c. conductivity, which is 2.72x 10-7 S/cm for 40P600 at 81°C. The second project involves studying the transport properties of a sulfonated pentablock copolymer, poly(para-methylstyrene)--b-hydrogenated polybutadiene-b-polystyrene-bhydrogenated polybutadiene - b-poly(para-methylstyrene) with polystyrene sulfonated in the midblock(PMS-HPB-sS-HPB-PMS), as pemrselective membranes for protective clothing, with high permeability to water and low permeability to hazardous organic chemicals. In addition, this work also contribute

Meng, Yan

162

ELECTROSPRAYING OF GLASSES—PREPARATION OF GLASS COATINGS ON GLASS  

Microsoft Academic Search

Glass coatings on ceramic or metallic substrates are prepared by two different methods. In a two-step process the glass powder is deposited on the glass substrate by methods such as airless spraying of enamel or glaze suspensions, dipping in enamel suspensions, electrospraying or electrophoretic deposition of enamel or glaze suspensions, and electrostatic powder spraying. The particle size of the glass

S. Rosenbaum; R. Clasen

1999-01-01

163

Metallic Glasses  

Microsoft Academic Search

The novel internal structures of metallic glasses lead to exceptional strength, corrosion resistance, and ease of magnetization. Combined with low manufacturing costs, these properties make glassy ribbons attractive for many applications. These materials also have scientific fascination because their compositions, structures, and properties have unexpected features.

John J. Gilman

1980-01-01

164

"Physio-Mechanical Properties of a New Zinc-Reinforced Glass Ionomer Restorative Material" "Sarah Al-Angari*1  

E-print Network

student, Department of Restorative Dentistry, Division of Dental Biomaterials,Indiana University School, Department of Restorative Dentistry, Division of Dental Biomaterials, Indiana University School of Dentistry.Norman Cook; Associate Professor, Department of Restorative Dentistry, Division of Operative Dentistry

Zhou, Yaoqi

165

Bond strength between composite resin and resin modified glass ionomer using different adhesive systems and curing techniques  

PubMed Central

Aim: To evaluate bond strength between RMGI and composite using different adhesive systems and curing techniques. Materials and Methods: Sixty prepared samples of RMGI were randomly divided into six groups according to adhesive systems (total-etch, two-step self-etch and all-in-one) and curing techniques (co-curing and pre-curing). In co-curing technique, the adhesive systems were applied on uncured RMGI samples and co-cured together. In the pre-curing technique, before application of adhesive systems, the RMGI samples were cured. Composite layers were applied and shear bond strength was measured. Two samples of each group were evaluated by SEM. Failure mode was determined by streomicroscope. Results: Both curing methods and adhesive systems had significant effect on bond strength (P-value < 0.05). There was an interaction between two factors (P-value <0.05). Both self-etch adhesives had significantly higher shear bond strength than the total-etch adhesive (P-value <0.05). The co-curing technique improved the bond strength in self-etch adhesives, but decreased the bond strength in total-etch adhesive (P-value<0.05). Conclusion: The application of self-etch adhesive systems and co-curing technique can improve the bond strength between the RMGI and composite. PMID:24778512

Boruziniat, Alireza; Gharaei, Samineh

2014-01-01

166

Structures and properties of sulfonated ionomers probed by transport and mechanical measurements: The role of solute activity  

NASA Astrophysics Data System (ADS)

This work is focused on advancing the understanding of the structures and properties of sulfonated ionomer membranes in the context of Polymer Electrolyte Membrane Fuel Cell applications by transport and mechanical measurements. Transport and mechanical properties are two critical elements of ionomer membranes that govern the performance and longevity of fuel cells. Additionally, transport and mechanical property measurements can also provide valuable information about the structure of the ionomer membranes. It is essential to develop a comprehensive understanding of them under well controlled environmental conditions. The mechanism of water transport through Nafion membranes was found to be governed by water diffusivity, swelling of the hydrophilic phase and the interfacial transport across membrane/vapor interface. A transport model incorporating these parameters was developed and successfully employed to resolve water activity profiles in the membrane and make quantitative predictions under steady state and dynamic conditions. Experimental results of diffusivity, volume of mixing and tortuosity also provided hints about the hydration shell structure around in the hydrophilic domains of Nafion. The alcohol sorption and transport was found to be qualitatively similar to the behavior of water and the quantitative differences were attributed to the difference in molecular size. The transport of alcohol water mixtures through Nafion displayed significant non-ideality which was connected to the abnormal swelling and incomplete mixing within the hydrophilic domains. The mechanical properties of several perfluoro-sulfonated ionomer (PFSI) membranes were studied as functions of temperature and solute activity. The thermal transition found between 60-100°C was described as an order-disorder transition of the ionic clusters. Water and other polar solutes were found to plasticize PFSI below the transition but stiffen PFSI above the transition. The stiffening effect was attributed to polar solute induced re-clustering of the ionic domains. Two hydrocarbon model ionomer SPS and SPEEK were studied to further understand the structural-property relationships of ionomers. Water sorption and proton conductivity were enhanced with increasing ion content but water content was independent of ion content and proton conductivity scaled with hydrophilic volume fraction. Water transport was dependent on diffusion and interfacial transport, both of which were affected by the size and shape of the hydrophilic domains.

Zhao, Qiao

167

The room temperature annealing peak in ionomers: Ionic crystallites or water absorption  

SciTech Connect

A quaternized diol, 3-(trimethylammonio)-1,2-propanediol neutralized with either bromine or iodine, was used to produce a polyurethane cationomer with a poly(tetramethylene oxide) soft segment and a 4,4[prime]-diphenylmethane diisocyanate hard segment. If those cationomers were annealed at room temperature for a period of approximately 1 month in a desiccator filled with dry CaSO[sub 4], differential scanning calorimetry (DSC) studies showed an endotherm centered near 70 C which was not present in the unannealed polymer and did not reappear upon subsequent cooling and heating cycles in the DSC. Some authors have suggested that a very similar endotherm found in other ionomers, most notably ethylene-methacrylic acid (E-MAA) copolymer ionomers, was due to an order-disorder transition within the ionic aggregates, i.e. ionic crystallite melting. In order to isolate the origin of this endotherm, the local environment around the anion in compression molded bromine neutralized samples was measured using the extended X-ray absorption fine-structure (EXAFS) technique. By measuring the change in the local environment over the temperature range corresponding to the DSC endotherm, it has been shown that this endotherm corresponds to water leaving the bromine coordination shell, rather than ionic crystallite melting. Other studies which include thoroughly drying the material in a vacuum oven below the transition temperature to remove the water suggest that the endotherm is due to the energetic change associated with water leaving the coordination environment of the anion in combination with water vaporization.

Goddard, R.J.; Grady, B.P.; Cooper, S.L. (Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemical Engineering)

1994-03-28

168

Unprecedented effect of impurity cations on the oxygen reduction kinetics at platinum electrodes covered with perfluorinated ionomer  

SciTech Connect

Platinum electrodes covered with a perfluoro-sulfonated ionomer membrane show unique behaviors in comparison with bare platinum immersed in aqueous solutions. The electrochemical interface between the metal and the polymer can be different from the interface between the metal and the solution phase. In this context, platinum electrodes covered with such a polymer membrane are an interesting system, and deserve detailed study. Here the oxygen reduction reaction at the platinum surface covered with a perfluoro-sulfonated ionomer membrane is investigated kinetically in 0.1 N H{sub 2}SO{sub 4} in the presence of 0.001 N Na{sup +}, K{sup +}, or Ca{sup 2+} ions, using rotating disk electrodes. It is discovered that the impurity ions, even in a small amount, hinder enormously the rate of the charge transfer step of oxygen reduction at the platinum covered with perfluoro-sulfonated ionomer. Especially the effect of Na{sup +} in the membrane is very serious considering the fact that there exists only 2% NA{sup +} of the exchange site in the membrane phase at this condition. Platinum covered with perfluoro-sulfonated ionomer membrane has historically attracted much research interest, based on the fact that oxygen concentration and H{sup +} ion concentration in the membrane are both larger than those in normal acidic solutions, and could show larger catalytic activity than in bare platinum. However, this expectation encountered disappointing failure. Results here indicate that such a paradox could be accounted for by the effect of the metal-polymer interface that alters the reaction conditions of oxygen reduction.

Okada, Tatsuhiro; Dale, J.; Ayato, Yuusuke; Asbjoernsen, O.A.; Yuasa, Makoto; Sekine, Isao

1999-11-23

169

Phenotypic profile linked to inhibition of the major Zn influx system in Salmonella enterica: proteomics and ionomics investigations.  

PubMed

Zinc is required for a wide variety of cellular functions and plays a key role in bacterial metabolism and virulence. However, Zn can also be toxic and, therefore, its influx is tightly regulated. The high affinity zinc uptake transporter ZnuABC is the main Zn influx system in Salmonella enterica under conditions of Zn starvation. It has been shown that deletion of the gene encoding for its periplasmic subunit ZnuA significantly affects S. Typhimurium growth rate and virulence, highlighting the importance of this system in the host-pathogen interaction. To gain further insight into the mechanisms involved in Zn influx regulation, we characterized the main alterations in the ionome and proteome of S. Typhimurium wild type and znuA mutant strains grown either under Zn starvation or under Zn-replete conditions. We found significant differences in the element profile and protein expression that were reversed by Zn supplementation. In particular, several of the differentially regulated proteins are predicted to be metal-binding proteins. Interestingly, their over-expression in the znuA mutant strain strictly depends on Zn starvation and correlates with the differences found at the ionome level. In conclusion, our data demonstrate that inhibition of Zn influx has relevant effects either on the bacterial ionome or proteome and shed new light on the role of the ZnuABC system and Zn influx in S. Typhimurium pathogenicity. PMID:20959928

Ciavardelli, Domenico; Ammendola, Serena; Ronci, Maurizio; Consalvo, Ada; Marzano, Valeria; Lipoma, Mario; Sacchetta, Paolo; Federici, Giorgio; Di Ilio, Carmine; Battistoni, Andrea; Urbani, Andrea

2011-03-01

170

Species- and genome-wide dissection of the shoot ionome in Brassica napus and its relationship to seedling development  

PubMed Central

Knowing the genetic basis of the plant ionome is essential for understanding the control of nutrient transport and accumulation. The aim of this research was to (i) study mineral nutrient concentrations in a large and diverse set of Brassica napus, (ii) describe the relationships between the shoot ionome and seedling development, and (iii) identify genetic regions associated with variation of the shoot ionome. The plant material under study was a germplasm set consisting of 509 inbred lines that was genotyped by a 6K single nucleotide polymorphism (SNP) array and phenotyped by analyzing the concentrations of eleven mineral nutrients in the shoots of 30 days old seedlings. Among mineral concentrations, positive correlations were found, whereas mineral concentrations were mainly negatively correlated with seedling development traits from earlier studies. In a genome-wide association mapping approach, altogether 29 significantly associated loci were identified across seven traits after correcting for multiple testing. The associations included a locus with effects on the concentrations of Cu, Mn, and Zn on chromosome C3, and a genetic region with multiple associations for Na concentration on chromosome A9. This region was situated within an association hotspot close to SOS1, a key gene for Na tolerance in plants. PMID:25324847

Bus, Anja; Korber, Niklas; Parkin, Isobel A. P.; Samans, Birgit; Snowdon, Rod J.; Li, Jinquan; Stich, Benjamin

2014-01-01

171

Comparison of self-healing ionomer to aluminium-alloy bumpers for protecting spacecraft equipment from space debris impacts  

NASA Astrophysics Data System (ADS)

This paper discusses the impact behavior of a self-healing ionomeric polymer and compares its protection capability against space debris impacts to that of simple aluminium-alloy bumpers. To this end, 14 impact experiments on both ionomer and Al-7075-T6 thin plates with similar surface density were made with 1.5 mm aluminium spheres at velocity between 1 and 4 km/s.First, the perforation extent in both materials was evaluated vis-à-vis the prediction of well known hole-size equations; then, attention was given to the damage potential of the cloud of fragments ejected from the rear side of the target by analysing the craters pattern and the momentum transferred to witness plates mounted on a ballistic pendulum behind the bumpers.Self-healing was completely successful in all but one ionomer samples and the primary damage on ionomeric polymers was found to be significantly lower than that on aluminium. On the other hand, aluminium plates exhibited slightly better debris fragmentation abilities, even though the protecting performance of ionomers seemed to improve at increasing impact speed.

Francesconi, A.; Giacomuzzo, C.; Grande, A. M.; Mudric, T.; Zaccariotto, M.; Etemadi, E.; Di Landro, L.; Galvanetto, U.

2013-03-01

172

Effect of soft segment crystallization and hard segment physical crosslink on shape memory function in antibacterial segmented polyurethane ionomers.  

PubMed

Shape memory polyurethane (SMPU) ionomers containing constant 75 wt.% soft segment content were synthesized using poly(epsilon-caprolactone)diol, 4,4'-diphenylmethane diisocyanate, 1,4-butanediol and/or N,N-bis(2-hydroxyethyl)-isonicotinamide. To introduce substrate bonding antibacterial activity, pyridinium was prepared through a neutralization reaction using 1-iodooctane as neutralization agent. For the SMPU ionomer film obtained, tensile testing at 70 degrees C and dynamic mechanical analysis suggests that, at temperatures>T(ms) (the melting point of soft segments), 6.72 and 29.55 mol.% pyridinium within hard segments significantly decreased the mechanical properties such as the stress at 100% elongation (70 degrees C), the initial modulus (70 degrees C) and the elastic modulus (75-110 degrees C). Cyclic tensile investigation demonstrated that the two factors, soft segment crystallization and hard segment physical crosslink, play a very important role in shape memory function in SMPU ionomers. For the each individual specimen, the fixity ratio increased, and the recovery ratio decreased with the extension of cooling time. After sufficient cooling time, the fixity ratio of all specimens can reach a high value (approximately 95%). Owing to the disrupted physical crosslink in the sample containing 29.55 mol.% pyridinium, the crystallization rate of soft segments has less effect on shape fixity. Therefore, a high fixity ratio (93.8%) can be achieved in a short cooling time (30 s). In the control sample, the fixity ratio is only 73.7% after 30 s cooling. In addition, the admirable substrate bonding antibacterial activity of prepared SMPU ionomers was verified using standards AACTT 147 and ASTM E2149 in comparison with the control sample. The antibacterial activity of SMPU ionomers on Gram-positive bacteria (Staphylococcus aureus) is significant, and the rate of reduction of bacteria is 100%; the antibacterial activity on Gram-negative bacteria (Klebsiella pneumoniae) increases from 83.6% to 90.7% with increase in pyridinium content from 6.72 to 29.55 mol.%. PMID:19460466

Zhu, Y; Hu, J; Yeung, K

2009-11-01

173

Analysis of factors affecting failure of glass cermet tunnel restorations in a multi-center study.  

PubMed

The aim of this study was to analyze factors influencing the failures of tunnel restorations performed with a glass cermet cement (Ketac Silver). Caries activity, lesion size, tunnel cavity opening size, partial or total tunnel, composite lamination or operating time showed no significant correlation to failure rate. Twelve dentists in eight clinics clinically experienced and familiar with the tunnel technique placed 374 restorations. The occlusal sections of fifty percent of the restorations were laminated with hybrid resin composite. The results of the yearly clinical and radiographic evaluations over the course of 3 years were correlated to factors that could influence the failure rate using logistic regression analysis. At the 3-year recall a cumulative number of 305 restorations were available. The cumulative replacement rate was 20%. The main reasons for replacement were marginal ridge fracture (14%) and dentin caries (3%). Another 7% of the restorations which had not been replaced were classified as failures because of untreated dentin caries. The only significant variable observed was the individual failure rate of the participating dentists varying between 9 and 50% (p=0.013). PMID:11480816

Pilebro, C E; van Dijken, J W

2001-06-01

174

Single-Kernel Ionomic Profiles Are Highly Heritable Indicators of Genetic and Environmental Influences on Elemental Accumulation in Maize Grain (Zea mays)  

PubMed Central

The ionome, or elemental profile, of a maize kernel can be viewed in at least two distinct ways. First, the collection of elements within the kernel are food and feed for people and animals. Second, the ionome of the kernel represents a developmental end point that can summarize the life history of a plant, combining genetic programs and environmental interactions. We assert that single-kernel-based phenotyping of the ionome is an effective method of analysis, as it represents a reasonable compromise between precision, efficiency, and power. Here, we evaluate potential pitfalls of this sampling strategy using several field-grown maize sample sets. We demonstrate that there is enough genetically determined diversity in accumulation of many of the elements assayed to overcome potential artifacts. Further, we demonstrate that environmental signals are detectable through their influence on the kernel ionome. We conclude that using single kernels as the sampling unit is a valid approach for understanding genetic and environmental effects on the maize kernel ionome. PMID:24489944

Baxter, Ivan R.; Ziegler, Gregory; Lahner, Brett; Mickelbart, Michael V.; Foley, Rachel; Danku, John; Armstrong, Paul; Salt, David E.; Hoekenga, Owen A.

2014-01-01

175

Temperature dependence of ion and water transport in perfluorinated ionomer membranes for fuel cells.  

PubMed

To clarify the mechanisms of transport of ions and water molecules in perfluorosulfonated ionomer membranes for fuel cells, the temperature dependence of their transport behaviors was investigated in detail. Two types of Flemion membranes having different equivalent weight values (EW) were utilized along with Nafion 117 as the perfluorinated ionomer membranes, and H-, Li-, and Na-form samples were prepared for each membrane by immersion in 0.03 M HCl, LiCl, and NaCl aqueous solutions, respectively. The ionic conductivity, water self-diffusion coefficient (D(H)(2)(O)), and DSC were measured in the fully hydrated state as a function of temperature. The ionic conductivity of the membranes was reflected by the cation transport through the intermediary of water. Clearly, H(+) transports by the Grotthuss (hopping) mechanism, and Li(+) and Na(+) transport by the vehicle mechanism. The differences of the ion transport mechanisms were observed in the activation energies through the Arrhenius plots. The D(H)(2)(O) in the membranes exhibited a tendency similar to the ionic conductivity for the cation species and the EW value. However, no remarkable difference of D(H)(2)(O) between H- and the other cation-form membranes was observed as compared with the ionic conductivity. It indicates that water in each membrane diffuses almost in a similar way; however, H(+) transports by the Grotthuss mechanism so that conductivity of H(+) is much higher than that of the other cations. Moreover, the D(H)(2)(O) and DSC curves showed that a part of water in the membranes freezes around -20 degrees C, but the nonfreezing water remains and diffuses below that temperature. This fact suggests that completely free water (bulk water) does not exist in the membranes, and water weakly interacting with the cation species and the sulfonic acid groups in secondary and higher hydration shells freezes around -20 degrees C, while strongly binding water in primary hydration shells does not freeze. The ratio of freezing and nonfreezing water was estimated from the DSC curves. The D(H)(2)(O) in the membranes was found to be influenced by the ratio of freezing and nonfreezing water. DFT calculation of the interaction (solvation) energy between the cation species and water molecules suggested that the water content and the ratio of freezing and nonfreezing water depend strongly on the cation species penetrated into the membrane. PMID:16851330

Saito, Morihiro; Hayamizu, Kikuko; Okada, Tatsuhiro

2005-03-01

176

Setting Reaction of Polyacid Modified Composite Resins or Compomers  

PubMed Central

The hardening of modified polyacid composite resins (compomers) and glass-ionomers have been studied using infrared spectroscopy. The acid-base reaction in Ketac-fil, a glass ionomer, was followed by the ratio between the COOH band located around 1715 cm-1 and that corresponding to COO- located around 1570 cm-1. The combination of infrared analysis and band narrowing treatments enable us to propose in the glass-ionomer two maturation steps. First, a very rapid equilibrium acid-base related, and second the cross-linking of polycarboxylate with the metal ions present in the cement. In compomers, a new reaction has been described involving polymerization induced by free radicals besides the two steps associated with the acid-base reaction. Using infrared spectroscopy and band narrowing techniques, it is shown that water is essential to complete the hardening process but no acid-base reaction is produced since the COO- band does not appear. The reaction associated with free radicals could be described as a polymerization of methacrylate monomers together with an aqueous dilution of the filling particles releasing different metal cations that would chelate with the polymer molecules to form a macromolecular structure. PMID:19834564

Arrondo, J.L.R; Collado, M.I; I, Soler; Triana, R; Ellacuria, J

2009-01-01

177

Setting reaction of polyacid modified composite resins or compomers.  

PubMed

The hardening of modified polyacid composite resins (compomers) and glass-ionomers have been studied using infrared spectroscopy. The acid-base reaction in Ketac-fil, a glass ionomer, was followed by the ratio between the COOH band located around 1715 cm?¹ and that corresponding to COO? located around 1570 cm?¹. The combination of infrared analysis and band narrowing treatments enable us to propose in the glass-ionomer two maturation steps. First, a very rapid equilibrium acid-base related, and second the cross-linking of polycarboxylate with the metal ions present in the cement. In compomers, a new reaction has been described involving polymerization induced by free radicals besides the two steps associated with the acid-base reaction. Using infrared spectroscopy and band narrowing techniques, it is shown that water is essential to complete the hardening process but no acid-base reaction is produced since the COO? band does not appear. The reaction associated with free radicals could be described as a polymerization of methacrylate monomers together with an aqueous dilution of the filling particles releasing different metal cations that would chelate with the polymer molecules to form a macromolecular structure. PMID:19834564

Arrondo, J L R; Collado, M I; I, Soler; Triana, R; Ellacuria, J

2009-01-01

178

Evaluation of the sealing ability of resin cement used as a root canal sealer: An in vitro study  

PubMed Central

Aim: This study was designed to evaluate the apical seal of root canals obturated with resin cement as a root canal sealer and compare with that of the glass ionomer and zinc oxide eugenol sealers using a cold lateral condensation gutta-percha technique. Background: Successful root canal treatment requires three-dimensional obturation of the root canal system with nonirritating biomaterials. None of the available materials are capable of providing a fluid tight seal. Materials and Methods: The prepared teeth were randomly divided into three groups of 15 each to be obturated using three different sealers. Group I: zinc oxide eugenol (Tubliseal), Group II: Glass ionomer (Ketac Endo), and Group III: resin cement (C & B Superbond). All the specimens were stored in 100% relative humidity at 37° for 24 h. The specimens were placed in 2% methylene blue dye for 48 h and sectioned. The dye penetration was evaluated under a stereomicroscope. Results: The “Kruskal” Wallis test was carried out to test the equality of mean. All the specimens showed dye leakage, and there was a statistically significant difference (P < 0.0001) among the groups. The specimens in Group III showed a minimal leakage and the specimens in Group I showed a maximum leakage. Conclusion: Resin cement sealed the root canals significantly better when compared with zinc oxide eugenol and glass ionomer sealers. PMID:22876018

Kumar, R Vinod; Shruthi, CS

2012-01-01

179

Surface roughness and weight loss of esthetic restorative materials related to fluoride release and uptake.  

PubMed

The objective of this study was to assess the surface roughness of eight esthetic restorative materials and the relationship with weight changes during fluoride release and uptake. Five specimens each of ChemFil Superior, Fuji IX Dyract, Fuji II LC, Vitremer, Photac-Fil, Ketac-Silver, and Z100 (control) were prepared and immersed in 2 ml of artificial saliva at 37 degrees C. The changes in specimen weight and fluoride release were monitored for 12 weeks. This protocol was repeated after recharging the specimens with 1.23% APF gel for 12 more weeks. The immersed and fresh specimens for each material were then examined with SEM and surface profilometry. There was a significant weight loss for all glass ionomer cements following APF gel application (P < 0.01), which correlated with fluoride release (r = 0.89-0.98). Mean roughness (Ra) measurements and SEM showed that roughness increased from the resin composite to the conventional glass ionomer cements. The marked erosive effect of APF gel on glass ionomer restorations could increase surface colonization by plaque micro-organisms, and reduce the longevity of the restorations. PMID:10551132

Yip, H K; Lam, W T; Smales, R J

1999-01-01

180

Impact Strength of Glass and Glass Ceramic  

NASA Astrophysics Data System (ADS)

Bar impact tests, using the techniques described elsewhere in this symposium, were used to measure compressive and tensile strengths of borosilicate glass, soda lime glass, and glass ceramic. The glass ceramic was 25% crystalline spinel, furnished by Corning, Inc. There are two measures of compressive strength: the peak stress that can be transmitted in unconfined compression and the steady-state strength. For both glasses, these values were similar, being about 1.8 and 1.5 GPa, respectively. The glass ceramic was almost 50% stronger. Tensile failure in the glass and glass ceramic takes places via surface flaws, and thus tensile strength is an extrinsic---as opposed to intrinsic---property.

Bless, Stephan; Tolman, John

2009-06-01

181

IMPACT STRENGTH OF GLASS AND GLASS CERAMIC  

SciTech Connect

Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicate glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.

Bless, S.; Tolman, J. [Institute for Advanced Technology, University of Texas at Austin, Austin, TX 78759 (United States)

2009-12-28

182

Impact Strength of Glass and Glass Ceramic  

NASA Astrophysics Data System (ADS)

Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicate glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.

Bless, S.; Tolman, J.

2009-12-01

183

A Study of the Effect of Heat-Treatment on the Morphology of Nafion Ionomer Dispersion for Use in the Passive Direct Methanol Fuel Cell (DMFC)  

PubMed Central

Aggregation in heat-treated Nafion ionomer dispersion and 117 membrane are investigated by 1H and 19F Nuclear Magnetic Resonance (NMR) spectra, spin-lattice relaxation time, and self-diffusion coefficient measurements. Results demonstrate that heat-treatment affects the average Nafion particle size in aqueous dispersions. Measurements on heat-treated Nafion 117 membrane show changes in the 1H isotropic chemical shift and no significant changes in ionic conductivity. Scanning electron microscopy (SEM) analysis of prepared cathode catalyst layer containing the heat-treated dispersions reveals that the surface of the electrode with the catalyst ink that has been pretreated at ca. 80 °C exhibits a compact and uniform morphology. The decrease of Nafion ionomer’s size results in better contact between catalyst particles and electrolyte, higher electrochemically active surface area, as well as significant improvement in the DMFC’s performance, as verified by electrochemical analysis and single cell evaluation. PMID:24958431

Yuan, Ting; Zhang, Haifeng; Zou, Zhiqing; Khatun, Sufia; Akins, Daniel; Adam, Yara; Suarez, Sophia

2012-01-01

184

Nanocrystallization of metallic glasses  

Microsoft Academic Search

The paper summarizes briefly the current status of research in the field of nanocrystallization of metallic glasses especially highlighting the influence of glass composition and conditions of devitrification process on size, morphology and composition of crystallization products. Conventional crystallization creates a nanocrystalline structure only in glasses with particular compositions. Any metallic glass, decomposing in a primary crystallization process, can be

Tadeusz Kulik

2001-01-01

185

A Comparative Ab Initio Study of the Primary Hydration and Proton Dissociation of Various Imide and Sulfonic Acid Ionomers  

SciTech Connect

We compare the role of neighboring group substitutions on proton dissociation of hydrated acidic moieties suitable for proton exchange membranes through electronic structure calculations. Three pairs of ionomers containing similar electron withdrawing groups within the pair were chosen for the study: two fully fluorinated sulfonyl imides (CF3SO2NHSO2CF3 and CF3CF2SO2NHSO2CF3), two partially fluorinated sulfonyl imides (CH3SO2NHSO2CF3 and C6H5SO2NHSO2CF2CF3), and two aromatic sulfonic acid based material s (CH3C6H4SO3H and CH3 OC6 - H3OCH3C6H4SO3H). Fully optimized counterpoise (CP) corrected geometries were obtained for each ionomer fragment with the inclusion of water molecules at the B3LYP/6-311G** level of density functional theory. Spontaneous proton dissociation was observed upon addition of three water molecules in each system, and the transition to a solvent-separated ion pair occurred when four water molecules were introduced. No considerable quantitative or qualitative differences in proton dissociation, hydrogen bond networks formed, or water binding energies were found between systems containing similar electron withdrawing groups. Each of the sulfonyl imide ionomers exhibited qualitatively similar results regarding proton dissociation and separation. The fully fluorinated sulfonyl imides, however, showed a greater propensity to exist in dissociated and ion-pair separated states at low degrees of hydration than the partially fluorinated sulfonyl imides. This effect is due to the additional electron withdrawing groups providing charge stabilization as the dissociated proton migrates away from the imide anion.

Clark II, Jeffrey K.; Paddison, Stephen J.; Eikerling, Michael; Dupuis, Michel; Zawodzinski, Jr., Thomas A.

2012-03-29

186

Synthesis and characterization of sulfonated poly(arylene ether sulfone) ionomers incorporating perfluorohexylene units for DMFC membranes  

Microsoft Academic Search

A new, sulfonated poly(arylene ether sulfone) ionomer with partially fluorinated groups (F-SPAES) was synthesized by the direct\\u000a polymerization of 1,6-bis(4-fluororphenyl)-perfluorohexane (FPPFH) and 6F-bisphenol A (6F-BPA) with 3,3?-disulfonated 4,4?-difluorodiphenyl\\u000a sulfone (SDFDPS). The effect of fluorination on the membrane properties and membrane-electrode assembly (MEA) performance\\u000a for DMFC applications were investigated comprehensively and compared with the pristine SPAES sample. Deliberate control of\\u000a the

Su-Jin Yoon; Jong-Ho Choi; Young Taik Hong; Sang-Young Lee

2010-01-01

187

Quadrupolar interaction study of various cations confined in porous charged polymer film of sPI ionomers.  

PubMed

The structure of a sulfonated polyimide (sPI) ionomer membranes was investigated via the transport properties of various confined cations (7Li+, 23Na+, 87Rb+, 133Cs+). Their NMR spectra show large residual quadrupolar splitting depending on the orientation of the film in the static magnetic field B0. This behavior is the fingerprint of a macroscopic nematic ordering of charged interfaces. This is also confirmed by the anisotropy of the self-diffusion tensor measured by 1H and 7Li PGSE experiments on N(CH3)4+ and Li+ cations, respectively. PMID:15833649

Rollet, Anne-Laure; Porion, Patrice; Delville, Alfred; Diat, Olivier; Gebel, Gérard

2005-02-01

188

Ionomic responses and correlations between elements and metabolites under salt stress in wild and cultivated barley.  

PubMed

A thorough understanding of ionic detoxification and homeostasis is imperative for improvement of salt tolerance in crops. However, the homeostasis of elements and their relationship to metabolites under salt stress have not been fully elucidated in plants. In this study, Tibetan wild barley accessions, XZ16 and XZ169, differing in salt tolerance, and a salt-tolerant cultivar CM72 were used to investigate ionomic profile changes in tissues in response to 150 and 300 mM NaCl at the germination and seedling stages. At the germination stage, the contents of Ca and Fe significantly decreased in roots, while K and S contents increased, and Ca and Mg contents decreased in shoots, after 10 d of treatment. At the seedling stage, the contents of K, Mg, P and Mn in roots and of K, Ca, Mg and S in shoots decreased significantly after 21 d of treatment. Moreover, Na had a significant negative correlation with metabolites involved in glycolysis, ?-ketoglutaric acid, maleic acid and alanine in roots, and metabolites associated with the tricarboxylic acid (TCA) cycle, sucrose, polyols and aspartate in leaves. The salt-tolerant genotypes XZ16 and CM72 showed a lower Na content in tissues, and less reduction in Zn and Cu in roots, of Ca, Mg and S in leaves, and shoot DW than the sensitive genotype XZ169, when exposed to a higher salt level. The results indicated that restriction of Na accumulation and rearrangement of nutrient elements and metabolites in barley tissues are possibly attributable to development of salt tolerance. PMID:24058150

Wu, Dezhi; Shen, Qiufang; Cai, Shengguan; Chen, Zhong-Hua; Dai, Fei; Zhang, Guoping

2013-12-01

189

Methodological approaches for using synchrotron X-ray fluorescence (SXRF) imaging as a tool in ionomics: Examples from Arabidopsis thaliana  

PubMed Central

Here we present approaches for using multi-elemental imaging (specifically synchrotron X-ray fluorescence microscopy, SXRF) in ionomics, with examples using the model plant Arabidopsis thaliana. The complexity of each approach depends on the amount of a priori information available for the gene and/or phenotype being studied. Three approaches are outlined, which apply to experimental situations where a gene of interest has been identified but has an unknown phenotype (Phenotyping), an unidentified gene is associated with a known phenotype (Gene Cloning) and finally, a Screening approach, where both gene and phenotype are unknown. These approaches make use of open-access, online databases with which plant molecular genetics researchers working in the model plant Arabidopsis will be familiar, in particular the Ionomics Hub and online transcriptomic databases such as the Arabidopsis eFP browser. The approaches and examples we describe are based on the assumption that altering the expression of ion transporters can result in changes in elemental distribution. We provide methodological details on using elemental imaging to aid or accelerate gene functional characterization by narrowing down the search for candidate genes to the tissues in which elemental distributions are altered. We use synchrotron X-ray microprobes as a technique of choice, which can now be used to image all parts of an Arabidopsis plant in a hydrated state. We present elemental images of leaves, stem, root, siliques and germinating hypocotyls. PMID:23912758

Hindt, Maria; Socha, Amanda L.; Zuber, Helene

2013-01-01

190

Comparative ionomics and metabolomics in extremophile and glycophytic Lotus species under salt stress challenge the metabolic pre-adaptation hypothesis.  

PubMed

The legume genus Lotus includes glycophytic forage crops and other species adapted to extreme environments, such as saline soils. Understanding salt tolerance mechanisms will contribute to the discovery of new traits which may enhance the breeding efforts towards improved performance of legumes in marginal agricultural environments. Here, we used a combination of ionomic and gas chromatography-mass spectrometry (GC-MS)-based metabolite profilings of complete shoots (pooling leaves, petioles and stems) to compare the extremophile Lotus creticus, adapted to highly saline coastal regions, and two cultivated glycophytic grassland forage species, Lotus corniculatus and Lotus tenuis. L. creticus exhibited better survival after exposure to long-term lethal salinity and was more efficient at excluding Cl? from the shoots than the glycophytes. In contrast, Na+ levels were higher in the extremophile under both control and salt stress, a trait often observed in halophytes. Ionomics demonstrated a differential rearrangement of shoot nutrient levels in the extremophile upon salt exposure. Metabolite profiling showed that responses to NaCl in L. creticus shoots were globally similar to those of the glycophytes, providing little evidence for metabolic pre-adaptation to salinity. This study is the first comparing salt acclimation responses between extremophile and non-extremophile legumes, and challenges the generalization of the metabolic salt pre-adaptation hypothesis. PMID:21251019

Sanchez, Diego H; Pieckenstain, Fernando L; Escaray, Francisco; Erban, Alexander; Kraemer, Ute; Udvardi, Michael K; Kopka, Joachim

2011-04-01

191

Cathode catalyst layers with ionomer to carbon mass ratios in the range 0-2 studied by electrochemical impedance spectroscopy, cyclic voltammetry, and performance measurements  

NASA Astrophysics Data System (ADS)

Characteristics of the cathode catalyst layers (CCL) containing HiSPEC 9100 Pt/C catalyst and ionomer (I) in ionomer to carbon mass ratio (I/C) range 0-2 were studied. Pt electrochemically active surface area (ECSA) and electrode low frequency capacitance were found to be independent of I/C value. Ionic resistance of CCL was found strongly dependent of I/C value. It reaches maximum value at I/C?0.3. Ionic resistance of CCL with I/C = 0.05 increased 7 fold with the shift of electrode potential (E) from 0.4 V to 1.05 vs. RHE. Ionic resistance of an imitating layer, which contained ionomer-free Ketjenblack EC-300J carbon, increased by a factor of 20 with the potential shift from 0.1 V to 1.05 V vs. RHE. Ionic conductivity in ionomer-free CCLs is ascribed to the presence of protons which originate from ionization of oxygen containing acidic surface groups of carbon support. Application to the CCL of potential positive relative to potential of zero charge of carbon support (pzc) draws protons to the counter electrode, decreasing the ionic conductivity of the CCL. Pt mass specific activity (Im) dependence on I/C mass ratio reaches maximum at I/C ? 1.

Modestov, Alexander D.; Kapustin, Alexander V.; Avakov, Veniamin B.; Landgraf, Igor K.; Tarasevich, Mikhail R.

2014-12-01

192

Simulation study of poled low-water ionomers with different architectures This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Simulation study of poled low-water ionomers with different architectures This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 J. Phys.: Condens. Matter Contact us My IOPscience #12;IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter

Taylor, Philip L.

193

Oxynitride glass fibers  

NASA Technical Reports Server (NTRS)

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

1991-01-01

194

Goodbye to Reading Glasses?  

MedlinePLUS

... on this page, please enable JavaScript. Goodbye to Reading Glasses? Implantable eye device shows promise in preliminary ... News) -- A new implantable eye device might make reading glasses a thing of the past, researchers report. ...

195

Failure in glass  

NASA Technical Reports Server (NTRS)

Review of state of the art concerning glass failure mechanisms and fatigue theories discusses brittle fracture in glass, fatigue mechanisms, fatigue behavior, environmental effects on failure rate, and aging.

Keeton, S. C.

1972-01-01

196

Technique for Machining Glass  

NASA Technical Reports Server (NTRS)

Process for machining glass with conventional carbide tools requires a small quantity of a lubricant for aluminum applied to area of glass to be machined. A carbide tool is then placed against workpiece with light pressure. Tool is raised periodically to clear work of glass dust and particles. Additional lubricant is applied as it is displaced.

Rice, S. H.

1982-01-01

197

Hot Erosion of Glass.  

National Technical Information Service (NTIS)

In this paper the effect of plastic flow on the erosion of soda-lime-silicate glass at elevated temperatures is investigated. Although the erosion of glass at 500 C and 600 C is still basically a brittle process, viscous relaxation of glass during impact ...

S. M. Wiederhorn, B. J. Hockey

1980-01-01

198

Glasses for Children  

MedlinePLUS

Why does a child need glasses? Children may need glasses for several reasons—some of which are different than for adults. Because a ... other eye has poor vision How can a child be tested for glasses, especially in infancy or ...

199

Void formation in glasses  

Microsoft Academic Search

Void formation as a result of a single tightly focused femtosecond pulse irradiation has been systematically studied in commercial optical-grade glasses of different composition. Correlations between the composition, mass density, glass transition temperature and Young modulus of glass with the void formation threshold have been revealed. The pulse energy necessary to form a void was found reciprocal to the amount

Tomohiro Hashimoto; Saulius Juodkazis; Hiroaki Misawa

2007-01-01

200

mobility in ugar glasses  

E-print Network

by the glass transition temperature 61 7. Key factors controlling the stability of glassy materials are water content, time and temperature 61 7. For example moisture uptake will decrease the glass transition temperature of a sugar glass below storage temperature and the sugars will tend to crystallize. Much research

Hemminga, Marcus A.

201

NEWS & VIEWS Glass dynamics  

E-print Network

. That the viscosity (or relaxation time) of a glass- forming liquid diverges to infinity at some finite temperature. By a systematic analysis of the temperature- dependent relaxation-time data from a range of organic glass-called Kauzmann6 temperature Tk, which itself has been linked to an ideal glass temperature, T2. Accurate

Weeks, Eric R.

202

Radiation coloration resistant glass  

DOEpatents

A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10.sup.7 rad, the coloration resistant glass does not lose transparency.

Tomozawa, Minoru (Troy, NY); Watson, E. Bruce (Troy, NY); Acocella, John (Troy, NY)

1986-01-01

203

Radiation coloration resistant glass  

DOEpatents

A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10[sup 7] rad, the coloration resistant glass does not lose transparency. 3 figs.

Tomozawa, M.; Watson, E.B.; Acocella, J.

1986-11-04

204

Oxynitride glass production procedure  

DOEpatents

The invention is a process for the preparation of high quality oxynitride glasses without resorting to high pressures. Nitrogen-containing compounds such as Si.sub.3 N.sub.4 are first encapsulated in a low melting temperature glass. Particles of the encapsulated nitrogen-containing compound are mixed with other oxide glass-formers and melted in an atmosphere of flowing nitrogen and in the presence of buffering gas to form the oxynitride glass. Glasses containing up to 15 at % nitrogen have been prepared by this method.

Weidner, Jerry R. (Idaho Falls, ID); Schuetz, Stanley T. (Idaho Falls, ID); O'Brien, Michael H. (Idaho Falls, ID)

1991-01-01

205

High-temperature glass and glass coatings  

NASA Technical Reports Server (NTRS)

Reaction-cured glasses resist thermal shock and maintain properties over range of -100 degrees Centrigrade to +1,480 degrees Centigrade. Stability makes these excellent materials for high-temperature glassware and tubing or as coatings for porous materials.

Goldstein, H. E.; Katvala, V. E.; Leiser, D. B.

1977-01-01

206

Melt crystallization of bisphenol A polycarbonate in PC/zinc sulfonated polystyrene ionomer blend  

NASA Astrophysics Data System (ADS)

The effects of zinc sulfonated polystyrene ionomer (ZnSPS) on the melt crystallization of bisphenol A polycarbonate (PC) were investigated. Melt crystallization of pure PC is extremely slow due to its rigid chain. In the blend of PC and ZnSPS (PC-ZnSPS), the melt crystallization rate of PC can be enhanced. DSC was used to study the crystallization kinetics of PC in PC-ZnSPS blend. The crystallization of PC at 190°C increased in both partially miscible and miscible blends with ZnSPS. For PC-ZnSPS blend with same PC composition as 80%, the crystallization rate was affected by the sulfonation level of ZnSPS. The induction time of crystallization for a partially miscible blend PC-ZnSPS9.98 (80/20) was 40 minutes, and the crystallization reaches 27% crystallinity within 14 hrs. The induction time for pure PC with the same thermal history was more than 24 hrs. The crystal structure of PC crystal formed in PC-ZnSPS blend was studied by WAXD, which showed no difference from the reported WAXD pattern for pure PC. Molecular weight change of PC was found during the thermal annealing of PC-ZnSPS blend at 190°C, but molecular weight alone cannot explain the change of crystallization rate of PC in PC-ZnSPS blend. Discussion was made to address the mechanisms that are responsible for the crystallization rate enhancement of PC in PC-ZnSPS blend. In order to understand and elucidate the reason for the molecular weight change of PC in PC-ZnSPS blend and its effect on the crystallization of PC, TG, GPC and GC-MS were used to investigate the stability of PC-ZnSPS blend and mixtures of PC with sodium tosylate (NaTS), zinc tosylate (ZnTS) and sodium benzoate (NaBZ). ZnSPS, NaTS and ZnTS undergo desulfonation of the sulfonate group at temperatures above 350°C. The desulfonation process can destabilize PC and lower the maximum mass loss rate temperature of PC for more than 70°C. NaTS, ZnTS and NaBZ have quite different effect on the thermal stability of PC at temperatures below 250°C. NaBZ can significantly degrade PC both at 190°C and 250°C. PC does not show any molecular weight (M w) change in the presence of NaTS at 250°C and 190°C for up to 1hr and 16 hrs respectively. ZnTS can also cause Mw change of PC at 250°C and 190°C, but the changing of Mw of PC in the presence of ZnTS is less than that in the presence of NaBZ. The reason for the molecular weight change of PC in PC-ZnSPS blend can be explained based on Davis's ionic ester exchange reaction mechanism.

Xu, Liang

207

Effects of bleaching agents on surface roughness of filling materials.  

PubMed

The aim of this study was to use a non-tactile optical measurement system to assess the effects of three bleaching agents' concentrations on the surface roughness of dental restoration materials. Two composites (Grandio, Venus) and one glass ionomer cement (Ketac Fil Plus) were used in this in vitro study. Specimens were treated with three different bleaching agents (16% and 22% carbamide peroxide (Polanight) and 38% hydrogen peroxide (Opalescence Boost)). Surface roughness was measured with an optical profilometer (Infinite Focus G3) before and after the bleaching treatment. Surface roughness increased in all tested specimens after bleaching treatment (p<0.05). Our in vitro study showed that dental bleaching agents influenced the surface roughness of different restoration materials, and the restoration material itself was shown to have an impact on alteration susceptibility. There seemed to be no clinical relevance in case of an optimal finish. PMID:24492113

Markovic, Ljubisa; Jordan, Rainer Andreas; Glasser, Marie-Claire; Arnold, Wolfgang Hermann; Nebel, Jan; Tillmann, Wolfgang; Ostermann, Thomas; Zimmer, Stefan

2014-01-01

208

Bulk Metallic Glasses  

SciTech Connect

Bulk Metallic Glasses explores an emerging field of materials known as bulk metallic glasses. It summarizes the rapid development of these materials over the last decade and includes documentation on diverse applications of bulk metallic glasses; from structural applications to microcomponents. Some of the applications covered are pressure sensors, microgears for motors, magnetic cores for power supplies, and nano-dies for replacing next generation DVDs. The chapters cover current theories and recent research including an atomistic theory of local topological fluctuations, atomistic simulations, and unique microstructures of these amorphous materials. Other topics include glass formation, glass forming ability, and the underlying mechanisms and physical insights of these criteria. The mechanical deformation of bulk metallic glasses, fatigue, fracture, and corrosion behaviors of these materials are also reviewed.

Miller, Michael K [ORNL; Liaw, Peter K [University of Tennessee, Knoxville (UTK)

2007-01-01

209

A proof of principle experiment: Structural transitions in self-healing poly (ethylene co-methacrylic acid) ionomers using acoustic and ultrasonic time dependent resonant spectroscopy  

NASA Astrophysics Data System (ADS)

We demonstrate a method for assessing structural transitions in self-healing poly (ethylene co-methacrylic acid) ionomers as a function of time, by observing the evolution of their acoustic and ultrasonic resonant spectra and associated quality factors during the post-damage healing phase. Two samples composed of EMAA-0.6Na and EMAA-0.3Na were scanned from 1 kHz to 2 MHz before and after a damage event. After damage, time varying resonances were discovered using time dependent resonant spectroscopy (TDRS), and several of these resonances continued to evolve after visible changes in the samples ceased. These time dependent resonances enable characterization of energy dissipation, relaxation and structural ordering in self-healing ionomers. In addition, TDRS may provide a method for isolating material properties that affect the healing process, such as ion content and their associated structures as well as the effect of sample aging, which may lead to improved structural models.

Pestka, K. A.; Kalista, S. J.; Ricci, A.

2013-08-01

210

Silane treated glass fibers  

Microsoft Academic Search

There is a cogent body of evidence showing that the physical properties of glass reinforced plastics (GRP) can be vastly improved,\\u000a by pre-treatment of the glass fibers with appropriate coupling agents or sizes. This is the fourth part of a research series\\u000a investigating different silanes with non-aqueous solvents and their effect upon silane deposition onto glass fibers.\\u000a \\u000a A sample of

H. Watson; A. Jokinen; P. Mikkola; J. Matisons; J. Rosenholm

211

Diamond turning of glass  

SciTech Connect

A new research initiative will be undertaken to investigate the critical cutting depth concepts for single point diamond turning of brittle, amorphous materials. Inorganic glasses and a brittle, thermoset polymer (organic glass) are the principal candidate materials. Interrupted cutting tests similar to those done in earlier research are Ge and Si crystals will be made to obtain critical depth values as a function of machining parameters. The results will provide systematic data with which to assess machining performance on glasses and amorphous materials

Blackley, W.S.; Scattergood, R.O.

1988-12-01

212

Metallic glasses: Family traits  

NASA Astrophysics Data System (ADS)

The finding that metallic glasses inherit their elastic properties from solvent atoms leads to a new understanding of the complex relationship between glassy structure, deformation and mechanical properties.

Wang, Wei Hua

2012-04-01

213

Drugstore Reading Glasses  

NASA Astrophysics Data System (ADS)

The occasion for this paper was my reading of a paper in the February 2005 issue of TPT. As one gets older the near point of the eye begins to recede.2 This is called presbyopia.3 An alternative to purchasing glasses from an optometrist is to purchase an inexpensive pair of reading glasses in a pharmacy. The pharmacy has these glasses ordered by diopters corresponding to the strength of the lens needed for a particular presbyopic eye. The glasses are, of course, not available for myopic eyes.

Erlichson, Herman

2006-03-01

214

A Simple and Efficient Synthesis of an Acid-labile Polyphosphoramidate by Organobase-catalyzed Ring-Opening Polymerization and Transformation to Polyphosphoester Ionomers by Acid Treatment  

PubMed Central

The direct synthesis of an acid-labile polyphosphoramidate by organobase-catalyzed ring-opening polymerization and an overall two-step preparation of polyphosphodiester ionomers (PPEI) by acid-assisted cleavage of the phosphoramidate bonds along the backbone of the polyphosphoramidate were developed in this study. The ultrafast organobase-catalyzed ring-opening polymerization of a cyclic phospholane methoxyethyl amidate monomer initiated by benzyl alcohol allowed for the preparation of well-defined polyphosphoramidates (PPA) with predictable molecular weights, narrow molecular weight distributions (PDI<1.10), and well-defined chain ends. Cleavage of the acid-labile phosphoramidate bonds on the polyphosphoramidate repeat units was evaluated under acidic conditions over a pH range of 1–5, and the complete hydrolysis produced polyphosphodiesters. The thermal properties of the resulting polyphosphoester ionomer acid and polyphosphoester ionomer sodium salt exhibited significant thermal stability. The parent PPA and both forms of the PPEIs showed low cytotoxicities toward HeLa cells and RAW 264.7 mouse macrophage cells. The synthetic methodology developed here has enriched the family of water-soluble polymers prepared by rapid and convenient organobase-catalyzed ring-opening polymerizations and straightforward chemical medication reactions, which are designed to be hydrolytically degradable and have promise for numerous biomedical and other applications. PMID:23997276

Zhang, Shiyi; Wang, Hai; Shen, Yuefei; Zhang, Fuwu; Seetho, Kellie; Zou, Jiong; Taylor, John-Stephen A.; Dove, Andrew P.; Wooley, Karen L.

2013-01-01

215

Rare Earth Phosphate Glass and Glass-Ceramic Proton Conductors  

SciTech Connect

The structure and conductivity of cerium and lanthanum phosphate glasses and glass-ceramics were investigated. The effects of varying the metal to phosphate ratio in the glasses, doping LaP3O9 glasses with Ce, and recrystallization of CeP3O9 glasses, on the glasses' microstructure and total conductivity were investigated using XRD, SEM, and AC impedance techniques. Strong increases in conductivity occurred when the glasses were recrystallized: the conductivity of a cerium metaphosphate glass increased conductivity after recrystallization from 10-7.5 S/cm to 10-6 S/cm at 400oC.

De Jonghe, Lutgard C.; Ray, Hannah L.; Wang, Ruigang

2008-12-03

216

Importance of glass and brass  

E-print Network

The importance of scientific instruments in the scientific revolution, especially brass and glass. Precise lenses and lens grinding, glass vessels for chemical experiments, the advances in astronomy, microscopy and many other areas due to glass...

Dugan, David

2004-08-17

217

Glass molding technology; Technical Digest  

NASA Astrophysics Data System (ADS)

We introduce various factors required for high-precision glass molding, and examples of optical element development, with explaining of the glass molding example by Toshiba Machine glass-molding machine.

Murakoshi, Hiroshi

2005-05-01

218

Bulk metallic glasses  

Microsoft Academic Search

In the last decade metallic glasses have regained considerable interest due to the fact that new glass-forming compositions have been found that have a critical cooling rate of less than 100 K\\/s and can be made glassy with dimensions of 1 cm or more. The development of such alloys with a very high resistance to crystallization of the undercooled melt

Jörg F. Löffler

2003-01-01

219

Breaking Glass with Sound  

NSDL National Science Digital Library

This video from MIT TechTV demonstrates how to break a glass using sound. The demonstrator determines the resonant frequency of the glass and plays a tone of that frequency with a function generator. The video page has a description of the phenomenon beneath the video.

2009-11-16

220

Surface Conductive Glass.  

ERIC Educational Resources Information Center

Discusses the properties of surface-conducting glass and the chemical nature of surface-conducting stannic (tin) oxide. Also provides the procedures necessary for the preparation of surface-conducting stannic oxide films on glass substrates. The experiment is suitable for the advanced inorganic chemistry laboratory. (JN)

Tanaka, John; Suib, Steven L.

1984-01-01

221

Scotland's glass industry  

Microsoft Academic Search

Initiated in the seventeenth century, the growth of Scotland's glass industry was severely restrained by taxation laws and reached a low ebb in the 1820s. Recovery after the repeal of these laws enabled developments in every branch of glass making. Big demands for containers, especially from the drink trades, assisted the setting up of numerous container works particularly in Glasgow.

Colin M. Brown

1980-01-01

222

Corning Museum of Glass  

NSDL National Science Digital Library

The Corning Museum has a website that contains images from part of their 45,000 item historical and art glass collection. The collection spans 3,500 years, and includes "The Origins of Glassmaking", "Asian Glass", "Glass in America", and "Glass After 1960". Visitors can search or browse the collection by the name of the artist or maker, the date made, location made, or the name of the object. One of the "Current Exhibitions" that has some fantastic images of glass objects is the "Medieval Glass for Popes, Princes, and Peasants" exhibit that can be found via their homepage. Visitors interested in seeing images and reading about the history behind medieval glass, should click on the "Medieval Glass Story". The first image, of a cage cup, is a stunning piece from the early fourth century. The last image of the exhibit, entitled "Nef", is Venetian and looks like an elaborate ship with a spout on top of a conical base. Visitors who would like to hear an audio tour of the exhibit should click on "Audio Tour" to listen to any of the 20 short segments explaining the exhibit.

223

Glass, Brian 1 BRIAN DANIEL GLASS, M.A.  

E-print Network

Glass, Brian 1 BRIAN DANIEL GLASS, M.A. University Department of Psychology, A8000 The University Making, The University of Texas at Austin #12;Glass, Brian 2 Duties include: Designing and constructing, constructing, and running experiments, statistical analysis. JOURNAL PUBLICATIONS Glass, B. D., Chotibut, T

Maddox, W. Todd

224

Glass, Brian 1 BRIAN DANIEL GLASS, M.A.  

E-print Network

Glass, Brian 1 BRIAN DANIEL GLASS, M.A. University Department of Psychology, A8000 The University of Categorization and Decision Making, The University of Texas at Austin #12;Glass, Brian 2 Duties include: Programming, constructing, and running experiments, statistical analysis. JOURNAL PUBLICATIONS Glass, B. D

Maddox, W. Todd

225

Glass, Brian 1 BRIAN DANIEL GLASS, M.A.  

E-print Network

Glass, Brian 1 BRIAN DANIEL GLASS, M.A. University Department of Psychology, A8000 The University of Texas at Austin Austin, TX 78712 (512) 232-2883 e-mail: glass@mail.utexas.edu EDUCATION 2006 ­ Cognitive include: Designing and constructing experiments, statistical #12;Glass, Brian 2 analysis, manuscript

Maddox, W. Todd

226

Glass electrolyte composition  

DOEpatents

An ionically conductive glass is disclosed for use as electrolyte in a high temperature electrochemical cell, particularly a cell with sodium anode and sulfur cathode. The glass includes the constituents Na/sub 2/O, ZrO/sub 2/, Al/sub 2/O/sub 3/ and SiO/sub 2/ in selected proportions to be a single phase solid solution substantially free of crystalline regions and undissolved constituents. Other advantageous properties are an ionic conductivity in excess of 2 x 10/sup -3/ (ohm-cm)/sup -1/ at 300/sup 0/C and a glass transition temperature in excess of 500/sup 0/C.

Kucera, G.H.; Roche, M.F.

1985-01-08

227

Glass Ceiling Commission  

NSDL National Science Digital Library

Existing from 1991-1996, the Glass Ceiling Commission was a federally funded commission which considered the "invisible, artificial barriers that prevent qualified individuals from advancing within their organization and reaching full potential." While the term "Glass Ceiling" originally referred to women, it was expanded to also include minorities. The Catherwood Library at the School of Industrial and Labor Relations at Cornell University has electronically archived the reports and findings of the commission, as well as a host of papers written on the Glass Ceiling Commission. The Commission summaries, reports, and findings are annotated, as are the accompanying papers.

Commission., United S.

228

Glass electrolyte composition  

DOEpatents

An ionically conductive glass is disclosed for use as electrolyte in a high temperature electrochemical cell, particularly a cell with sodium anode and sulfur cathode. The glass includes the constituents Na.sub.2 O, ZrO.sub.2, Al.sub.2 O.sub.3 and SiO.sub.2 in selected proportions to be a single phase solid solution substantially free of crystalline regions and undissolved constituents. Other advantageous properties are an ionic conductivity in excess of 2.times.10.sup.-3 (ohm-cm).sup.-1 at 300.degree. C. and a glass transition temperature in excess of 500.degree. C.

Kucera, Gene H. (Downers Grove, IL); Roche, Michael F. (Downers Grove, IL)

1985-01-01

229

The glass transition diagram in model metallic glasses  

E-print Network

We report a strain rate (equivalent to experimental observation time) induced glass transition in model SrCaYbMg(Li)Zn(Cu) metallic glasses at room temperature. A critical strain rate, equivalent to glass transition temperature, is found for the strain rate induced a glassy state to liquid-like viscoplastic state translation. The results show that the observation time, equivalent to temperature and stress, is a key parameter for the glass transition. A three-dimension glass transition phase diagram involved in time, temperature and stress in metallic glasses is established for understanding the nature of the metallic glasses.

X. Q. Gao; W. H. Wang; K. Zhao; H. Y. Bai

2013-05-22

230

Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition  

PubMed Central

Mineral malnutrition stemming from undiversified plant-based diets is a top global challenge. In C3 plants (e.g., rice, wheat), elevated concentrations of atmospheric carbon dioxide (eCO2) reduce protein and nitrogen concentrations, and can increase the total non-structural carbohydrates (TNC; mainly starch, sugars). However, contradictory findings have obscured the effect of eCO2 on the ionome—the mineral and trace-element composition—of plants. Consequently, CO2-induced shifts in plant quality have been ignored in the estimation of the impact of global change on humans. This study shows that eCO2 reduces the overall mineral concentrations (?8%, 95% confidence interval: ?9.1 to ?6.9, p<0.00001) and increases TNC:minerals > carbon:minerals in C3 plants. The meta-analysis of 7761 observations, including 2264 observations at state of the art FACE centers, covers 130 species/cultivars. The attained statistical power reveals that the shift is systemic and global. Its potential to exacerbate the prevalence of ‘hidden hunger’ and obesity is discussed. DOI: http://dx.doi.org/10.7554/eLife.02245.001 PMID:24867639

Loladze, Irakli

2014-01-01

231

Noteworthy impacts of polyurethane-urea ionomers as the efficient polar coatings on adhesion strength of plasma treated polypropylene  

NASA Astrophysics Data System (ADS)

In present research, polypropylene (PP) was selected as a model nonpolar substrate for chemical modification using plasma. In the first step, the PP samples were treated using oxygen and argon atmospheres, individually. The prepared samples were analyzed using both FTIR and AFM techniques. The output of these techniques revealed that the carbonyl, carboxylic acid and its derivatives have been formed on the surface of PP. Afterward, a series of aqueous polyurethane-urea dispersions were synthesized as the novel polar coating for modified nonpolar polymers and characterized by different techniques including FTIR, DSC, TGA, mechanical properties and contact angle. Finally, the plasma treated samples were coated by prepared polyurethane ionomer. The results of pull-off analysis confirmed the significant role of the polyurethane as an extremely polar coating to create hydrogen bonding with functional groups on the surface of treated PP. The adhesion strength of polypropylenes increased from 0.04 MPa to 0.61 MPa for neat and oxygen-based plasma treated samples, respectively.

Chashmejahanbin, Mohammad. R.; Daemi, Hamed; Barikani, Mehdi; Salimi, Ali

2014-10-01

232

Glassy states: Concentration glasses and temperature glasses compared  

Microsoft Academic Search

The behavior of glass-forming systems in the equilibrium state above the glass temperature is still a heavily investigated field. Surprisingly, the behavior of the glass itself is less widely investigated. Even less investigated is the behavior of glass-forming materials in which composition is changed. Here we look at the behavior of glasses after temperature-jumps and compare that behavior with that

Gregory B. McKenna

2007-01-01

233

Evaluation and Comparison of the Effect of Different Surface Preparations on Bond Strength of Glass Ionomer Cement with Nickel–Chrome Metal–Ceramic Alloy: A Laboratory Study  

Microsoft Academic Search

Retention of fixed partial dentures is mostly dependent upon the bond between metal and cement as well as cement and tooth\\u000a structure. However, most of the time clinical failure of bond has been observed at metal and cement interface. The treatment\\u000a of metal surface, prior to luting, plays a crucial role in bonding cement with the metal. This study is

Kalpana Hasti; H. G. Jagadeesh; Narendra P. Patil

2011-01-01

234

Caries-preventive effect of glass ionomer and resin-based fissure sealants on permanent teeth: An update of systematic review evidence  

PubMed Central

Background This article constitutes a partial update of the original systematic review evidence by Yengopal et al. from 15 January 2008 (published in the Journal of Oral Science in 2009) with primary focus on research quality in regard to bias risk in trials. Its aim is to update the existing systematic review evidence from the English literature as to whether caries occurrence on pits and fissures of teeth sealed with either GIC or resin is the same. Methods In addition to the 12 trials included during the original systematic review, 5 new trials were identified during the database search (up to 26 August 2010) and 2 further trials were included from a hand search and reference check. Of these, 3 trials were excluded and 16 were accepted for data extraction and quality assessment. The quality of accepted trials was assessed, using updated quality criteria, and the risk of bias was investigated in more depth than previously reported. In addition, the focus of quantitative synthesis was shifted to single datasets that were extracted from the accepted trials. Results Twenty-six dichotomous and 4 continuous datasets were extracted. Meta-analysis and cumulative meta-analysis were used in combining clinically homogenous datasets. The overall outcome of the computed datasets suggest no difference between the caries-preventive effects of GIC- and resin-based fissure sealants. Conclusions This overall outcome is in agreement with the conclusions of the original systematic review. Although the findings of the trials identified in this update may be considered to be less affected by attrition- and publication bias, their risk of selection- and detection-/performance bias is high. Thus, verification of the currently available results requires further high quality randomised control trials. PMID:21276215

2011-01-01

235

The effect of mechanical load cycling and polishing time on microleakage of class V glass-ionomer and composite restorations: A scanning electron microscopy evaluation  

PubMed Central

Background: Microleakage is one of the challenging concerns in direct filling restorations. Understanding of its related factors is important in clinical practice. The aim of this study was scanning electron microscopy (SEM) evaluation of marginal integrity in three types of tooth-colored restorative materials in class V cavity preparations and the effect of load cycling and polishing time on the microleakage. Materials and Methods: In this in vitro experimental study, class V cavity preparations were prepared on the buccal and lingual surfaces of 60 bovine incisors. The specimens were divided into three groups each containing 20 teeth: group 1: Filtek Z350, Group 2: Fuji IX/G Coat Plus, Group 3: Fuji II LC/GC varnish. In each group, 2 subgroups (n = 20) were established based on finishing time (immediate or delayed by 24 h). All specimens were thermocycled (×2,000, 5-50°C). In each sub groups, half of the teeth were load cycled. Epoxy resin replicas of 24 specimens were evaluated under field emission-SEM and interfacial gaps were measured. All teeth were then immersed in 0.5% basic fuchsin dye for 24 h, sectioned and observed under stereomicroscope. Data were analyzed with Kruskal-Wallis’ test and Mann-Whitney U test and a comparison between incisal and cervical microleakage was made with Wilcoxon test. P < 0.05 was considered as significant. Results: Load cycling and filling material had a significant effect on microleakage, but polishing time did not. Cervical microleakage in Z350/load cycle/immediate polish and Fuji IX/load cycle/immediate or delayed polish and Fuji IX/no load cycle/immediate polish were significantly higher than incisal microleakage. Conclusion: It was concluded that the cervical sealing ability of Fuji IX under load cycling was better than Fuji II LC. Under load cycling and immediate polishing Z350 showed better marginal integrity than both Fuji II LC and Fuji IX. The immediate polishing didn’t cause a statistically significant increase in microleakage of evaluated tooth-colored class V restorations. PMID:24688568

Mirzaie, Mansoreh; Yasini, Esmail; Kermanshah, Hamid; Omidi, Baharan Ranjbar

2014-01-01

236

The Influence of Zinc Oxide Eugenol (ZOE) and Glass Ionomer (GI) Base Materials on the Microhardness of Various Composite and GI Restorative Materials  

PubMed Central

Objective: Re-examining the well accepted concept that Zinc-Oxide-Eugenol bases (ZOE) have a negative effect on composite restoration materials microhardness, in light of the advancement in composite materials and newer publications. Methods: Five modern composite restoration materials were used, including hybrid (Xtra-fill and Z250), micro-fill hybrid (G-aenial and Gradia-direct) and methacrylate-free restorative material (Silorane- oxirane). Two base materials were used IRM (ZOE-base) and Fuji-IX (GI-base). Samples were made using a designed mold, in which composite discs were cured on top and in close relation to base materials. Micro-hardness testing was performed using a DMH-2 microhardness tester utilizing the Knoop method. Results: Statistic analysis demonstrated significantly better microhardness of three composite materials when IRM was used as base in comparison to control (G-aenial, Gradia direct and Filtek silorane), and no differences in two materials (Filtek universal Z250 and Voco Xtra-fil). Fuji-IX bases showed a significant positive effect on the microhardness of four composite materials, and a negative effect on one material (Voco Xtra-fill). In comparison with other tested restoration materials, both Voco Xtra-fill and Fuji-IX showed higher microhardness results (P<0.05). Significance: Related to microhardness, both ZOE and GI bases can be used safely as bases under composite restorations. The results of this study together with the results published recently showed that the concept of not using ZOE or GI bases under composite must be reconsidered. Fuji IX showed microhardness results similar to the best composite material and therefore it can be used as a restorative material. PMID:24624238

Itskovich, Roee; Lewinstein, Israel; Zilberman, Uri

2014-01-01

237

Google Glasses and Eyesight  

MedlinePLUS Videos and Cool Tools

... display systems like Google Glass may be cool technology, but new research indicates they may also be ... American Medical Association looked at how this wearable technology affects visual field. The researchers asked three healthy ...

238

THE COLOR GLASS CONDENSATE.  

SciTech Connect

The Color Glass Condensate is a state of high density gluonic matter which controls the high energy limit of hadronic interactions. Its properties are important for the initial conditions for matter produced at RHIC.

MCLERRAN,L.

2001-08-26

239

Glasses and Contact Lenses  

MedlinePLUS

... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ... trouble, it's often a refractive problem. Glasses or contact lenses work so well because they can correct ...

240

Pressure dependence of glass transition temperature of elastomeric glasses  

NASA Astrophysics Data System (ADS)

The pressure dependence of the glass transition temperature Tg of two elastomers, Solithane 113 and 3,3-bis(azidomethyl)oxetane/tetrahydrofuran (BAMO/THF) has been determined, employing high-pressure differential thermal analysis (HP-DTA) and dielectric techniques, up to 8.5 kbar. The glasses of the elastomers were named the specific (or Pi glass) or the general glass depending on how the glasses were formed. A Pi glass was formed by lowering temperature under a constant pressure (Pi) and the pressure dependency of the Pi glass was determined after changing pressure only in the glassy state. The general glass consists of a series of specific glasses but the Tg is determined only at pressures under which the glass is formed. The Tg for both glasses increased with increasing pressure. However, the Tg for the Pi glass appears to level off at very high pressures while the Tg does not level off for the general glass. Thermodynamic analysis was made to show that for many general glasses dTg/dP=??/(1+n)?? holds, in which n=1 for Solithane and many other glasses. It is also shown that a modified Gibbs and DiMarzio theory can be used effectively to predict the observed experimental results.

Pae, K. D.; Tang, C.-L.; Shin, E.-S.

1984-11-01

241

Baseline LAW Glass Formulation Testing  

SciTech Connect

The major objective of the baseline glass formulation work was to develop and select glass formulations that are compliant with contractual and processing requirements for each of the LAW waste streams. Other objectives of the work included preparation and characterization of glasses with respect to the properties of interest, optimization of sulfate loading in the glasses, evaluation of ability to achieve waste loading limits, testing to demonstrate compatibility of glass melts with melter materials of construction, development of glass formulations to support ILAW qualification activities, and identification of glass formulation issues with respect to contract specifications and processing requirements.

Kruger, Albert A. [USDOE Office of River Protection, Richland, WA (United States); Mooers, Cavin [The Catholic University of America, Washington, DC (United States). Vitreous State Lab.; Bazemore, Gina [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Pegg, Ian L. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Hight, Kenneth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Lai, Shan Tao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Buechele, Andrew [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Rielley, Elizabeth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Gan, Hao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Muller, Isabelle S. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Cecil, Richard [The Catholic University of America, Washington, DC (United States). Vitreous State Lab

2013-06-13

242

Metallic glass composition  

DOEpatents

A metallic glass alloy that is either iron-based or nickel-based or based on a mixture of iron and nickel, containing lesser amounts of elements selected from the group boron, silicon carbon and phosphorous to which is added an amount of a ductility enhancing element selected from the group cerium, lanthanum, praseodymium and neodymium sufficient to increase ductility of the metallic glass upon annealing.

Kroeger, Donald M. (Knoxville, TN); Koch, Carl C. (Raleigh, NC)

1986-01-01

243

Ductile Bulk Metallic Glass  

Microsoft Academic Search

We report on experimental evidence of pronounced global plasticity measured in monolithic Pt57.5Cu14.7Ni5.3P22.5 bulk metallic glass under both bending and unconfined compression loading conditions. A plastic strain of 20% is measured, never before seen in metallic glasses. Also, permanent deformation and a strain exceeding 3% before failure is observed during bending of 4mm thick samples. To date, no monolithic metallic

Jan Schroers; William L. Johnson

2004-01-01

244

8.G Glasses  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: The diagram shows three glasses (not drawn to scale). The measurements are all in centimeters. The bowl of glass 1 is cylindrical. The inside diameter ...

245

Glasses formed by hypervelocity impact  

NASA Technical Reports Server (NTRS)

This paper presents description, classification, and geological setting of impact glasses, which are formed as a result of meteorite impacts with the planetary surface, and discusses the impact-glass formation process in the context of cratering mechanics. Impact glasses can be classified as belonging to two major groups: (1) mineral glasses, which are identical in composition to a mineral, and (2) rock glasses, which have the composition of a rock or a mixture of various rocks. Rock glasses may be (1) melt ejecta, (2) parts of a coherent melt layer inside the crater cavity, or (3) dikes or veins. The composition of rock glasses at a particular crater can be matched by that of the target. In nonporous rocks, the formation of rock glasses requires peak pressures in excess of 60-80 GPa, while mineral glasses are formed in the pressure range of about 25 to 55 GPa; in porous rocks, interstitial glass forms at pressures as low as 5 GPa.

Stoeffler, D.

1984-01-01

246

Towards ultrastrong glasses.  

PubMed

The development of new glassy materials is key for addressing major global challenges in energy, medicine, and advanced communications systems. For example, thin, flexible, and large-area glass substrates will play an enabling role in the development of flexible displays, roll-to-roll processing of solar cells, next-generation touch-screen devices, and encapsulation of organic semiconductors. The main drawback of glass and its limitation for these applications is its brittle fracture behavior, especially in the presence of surface flaws, which can significantly reduce the practical strength of a glass product. Hence, the design of new ultrastrong glassy materials and strengthening techniques is of crucial importance. The main issues regarding glass strength are discussed, with an emphasis on the underlying microscopic mechanisms that are responsible for mechanical properties. The relationship among elastic properties and fracture behavior is also addressed, focusing on both oxide and metallic glasses. From a theoretical perspective, atomistic modeling of mechanical properties of glassy materials is considered. The topological origin of these properties is also discussed, including its relation to structural and chemical heterogeneities. Finally, comments are given on several toughening strategies for increasing the damage resistance of glass products. PMID:22103001

Wondraczek, Lothar; Mauro, John C; Eckert, Jürgen; Kühn, Uta; Horbach, Jürgen; Deubener, Joachim; Rouxel, Tanguy

2011-10-18

247

Volcanic Glasses: Construction Materials  

NASA Astrophysics Data System (ADS)

Natural glass is the product of rapidly cooled molten rock. Two natural sources of the melt are volcanic eruption and meteoritic impact. Pure glass is an amorphous aggregate. Volcanic glass is a material that could be utilized in the construction of extraterrestrial outposts. Pumice and perlite are volcanic glasses currently used in the building industry. Samples of natural volcanic glass found in the lunar regolith were returned to Earth as part of the Apollo and Luna programs. An alpha proton X-ray spectrometer onboard the Pathfinder recently examined martian rocks located in the vicinity of the lander craft. Preliminary results of chemical composition by weight of SiO2 50-55%, Al203 11-13%, K20 1-2%, Na20 2-5%, CaO 4-6%, MgO 3-7%, FeO 12-14%, S03 2-5%, and MnO <1% were given for two rocks. Parenthetically, the values for K and Mn were perhaps too high, and the analysis was based on X-ray data only. The appreciable amount of silica already found on Mars and empirical evidence to support the hypothesis that the planet once had water sufficient to rapidly cool magma imply the possibility of discovering natural glass of volcanic origin in subsequent missions.

Moskowitz, Samuel E.

1998-01-01

248

Containerless synthesis of interesting glasses  

NASA Technical Reports Server (NTRS)

One aspect of containerless glass experimentation was thoroughly examined: glass forming ability. It is argued that although containerless processing will abet glass formation, other ground-based methods can do the job better. However, these methods have limitations, such as sample dimensions and concomitant ability to make property measurements. Most importantly, perhaps, is the observation that glass properties are a function of preparation procedure. Thus, it seems as though there still is an argument for use of containerless processing for glass forming.

Weinberg, Michael C.

1990-01-01

249

Glass microsphere lubrication  

NASA Technical Reports Server (NTRS)

The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the manufacturing of the microspheres, while sorting entails deciphering the good microspheres from the bad ones. Each process is discussed in detail.

Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

1991-01-01

250

Fracture resistance of endodontically treated maxillary premolars restored by silorane-based composite with or without fiber or nano-ionomer  

PubMed Central

PURPOSE This in vitro study investigated the fracture resistance of endodontically treated premolars restored using silorane- or methacrylate-based composite along with or without fiber or nano-ionomer base. MATERIALS AND METHODS Ninety-six intact maxillary premolars were randomly divided into eight groups (n = 12). G1 (negative control) was the intact teeth. In Groups 2-8, root canal treatment with mesio-occlusodistal preparation was performed. G2 (positive control) was kept unrestored. The other groups were restored using composite resin as follows: G3, methacrylate-based composite (Z250); G4, methacrylate composite (Z250) with polyethylene fiber; G5 and G6, silorane-based composite (Filtek P90) without and with the fiber, respectively; G7 and G8, methacrylate- and silorane-based composite with nano-ionomer base, respectively. After aging period and thermocycling for 1000 cycles, fracture strength was tested and fracture patterns were inspected. The results were analyzed using ANOVA and Tukey HSD tests (?=0.05). RESULTS Mean fracture resistance for the eight groups (in Newton) were G1: 1200 ± 169a, G2: 360 ± 93b, G3: 632 ± 196c, G4: 692 ± 195c, G5: 917 ± 159d, G6: 1013 ± 125ad, G7: 959 ± 148d, G8: 947 ± 105d (different superscript letters revealed significant difference among groups). Most of the fractures in all the groups were restorable, except Group 3. CONCLUSION Silorane-based composite revealed significantly higher strength of the restored premolars compared to that of methacrylate one. Fiber insertion demonstrated no additional effect on the strength of both composite restorations; however, it increased the prevalence of restorable fracture of methacrylate-based composite restored teeth. Using nano-ionomer base under methacrylate-based composite had a positive effect on fracture resistance and pattern. Only fiber-reinforced silorane composite restoration resulted in a strength similar to that of the intact teeth. PMID:25006384

Shafiei, Fereshteh; Ghahramani, Yasamin; Fattah, Zahra

2014-01-01

251

A new method to prepare high performance perfluorinated sulfonic acid ionomer/porous expanded polytetrafluoroethylene composite membranes based on perfluorinated sulfonyl fluoride polymer solution  

NASA Astrophysics Data System (ADS)

Perfluorinated sulfonyl fluoride (PFSF) resin, the precursor of perfluorinated sulfonic acid (PFSA) ionomer is successfully dissolved in perfluorinated solvents, and its hydrophobic nature is utilized to resolve the difficulty of impregnating hydrophilic PFSA solution into hydrophobic porous expanded polytetrafluoroethylene (ePTFE). The composite membrane fabricated through such simple but effective method is well impregnated, leading to better ionic conductivity and lower gas permeability. The fuel cell constructed with PFSF solution based membranes shows superior performance as compared to that of its aqueous PFSA solution based counterpart, which is comparable to that of commercial Nafion® 211.

Yang, Libin; Li, Hong; Ai, Fei; Chen, Xiaoyong; Tang, Junkun; Zhu, Yan; Wang, Chaonan; Yuan, Wang Zhang; Zhang, Yongming

2013-12-01

252

Glass matrix armor  

DOEpatents

An armor system which utilizes glass. A plurality of constraint cells are mounted on a surface of a substrate, which is metal armor plate or a similar tough material, such that the cells almost completely cover the surface of the substrate. Each constraint cell has a projectile-receiving wall parallel to the substrate surface and has sides which are perpendicular to and surround the perimeter of the receiving wall. The cells are mounted such that, in one embodiment, the substrate surface serves as a sixth side or closure for each cell. Each cell has inside of it a plate, termed the front plate, which is parallel to and in contact with substantially all of the inside surface of the receiving wall. The balance of each cell is completely filled with a projectile-abrading material consisting of glass and a ceramic material and, in certain embodiments, a polymeric material. The glass may be in monolithic form or particles of ceramic may be dispersed in a glass matrix. The ceramic material may be in monolithic form or may be in the form of particles dispersed in glass or dispersed in said polymer.

Calkins, Noel C. (Los Alamos, NM)

1991-01-01

253

Fibrous glass and cancer.  

PubMed

Some argue that fibrous glass (glass wool) should not be considered as a likely human carcinogen and hence should not be listed in the Seventh Annual Report on Carcinogens (ARC) prepared by the National Toxicology Program (NTP) and mandated by the U.S. Congress. In examining this issue, data from both laboratory experiments (animal studies) and epidemiologic studies (human data) are reviewed with the results evaluated according to the criteria established by the International Agency for Research on Cancer (IARC) and adopted in slightly modified form by the NTP for classifying substances as human carcinogens or likely human carcinogens. From our comprehensive review of the available information, we conclude that fibrous glass materials are carcinogenic, and in view of the NTP and IARC definitions should be listed in the ARC. Our review then examines the carcinogenic potency of glass fibers to humans in comparison with asbestos fibers and concludes that on a fiber-per-fiber basis, glass fibers may be as potent or even more potent than asbestos. The implications of these findings are then presented for regulatory purposes in the occupational setting. PMID:7810554

Infante, P F; Schuman, L D; Dement, J; Huff, J

1994-10-01

254

Profiling the ionome of rice and its use in discriminating geographical origins at the regional scale, China.  

PubMed

Element profile was investigated for their use to trace the geographical origin of rice (Oryza sativa L.) samples. The concentrations of 13 elements (calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), boron (B), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), arsenic (As), selenium (Se), molybdenum (Mo), and cadmium (Cd)) were determined in the rice samples by inductively coupled plasma optical emission and mass spectrometry. Most of the essential elements for human health in rice were within normal ranges except for Mo and Se. Mo concentrations were twice as high as those in rice from Vietnam and Spain. Meanwhile, Se concentrations were three times lower in the whole province compared to the Chinese average level of 0.088 mg/kg. About 12% of the rice samples failed the Chinese national food safety standard of 0.2 mg/kg for Cd. Combined with the multi-elemental profile in rice, the principal component analysis (PCA), discriminant function analysis (DFA) and Fibonacci index analysis (FIA) were applied to discriminate geographical origins of the samples. Results indicated that the FIA method could achieve a more effective geographical origin classification compared with PCA and DFA, due to its efficiency in making the grouping even when the elemental variability was so high that PCA and DFA showed little discriminatory power. Furthermore, some elements were identified as the most powerful indicators of geographical origin: Ca, Ni, Fe and Cd. This suggests that the newly established methodology of FIA based on the ionome profile can be applied to determine the geographical origin of rice. PMID:23586309

Li, Gang; Nunes, Luis; Wang, Yijie; Williams, Paul N; Zheng, Maozhong; Zhang, Qiufang; Zhu, Yongguan

2013-01-01

255

Waste glass melting stages  

SciTech Connect

Three different simulated nuclear waste glass feeds, consisting of dried waste and glass frit, were heat treated for 1 hour in a gradient furnace at temperatures ranging from approximately 600[degrees]C--1000[degrees]C. Simulated melter feeds from the Hanford Waste Vitrification Plant (HWVP), the Defense Waste Processing Facility (DWPF), and Kernforschungszentrum Karlsruhe (KfK) in Germany were used. The samples were thin-sectioned and examined by optical microscopy to investigate the stages of the conversion from feed to glass. Various phenomena were seen, such as frit softening, bubble formation, foaming, bubble motion and removal, convective mixing, and homogenization. Behavior of different feeds was similar, although the degree of gas generation and melt homogenization varied.

Anderson, L.D.; Dennis, T.; Elliott, M.L.; Hrma, P.

1993-04-01

256

Waste glass melting stages  

SciTech Connect

Three different simulated nuclear waste glass feeds, consisting of dried waste and glass frit, were heat treated for 1 hour in a gradient furnace at temperatures ranging from approximately 600{degrees}C--1000{degrees}C. Simulated melter feeds from the Hanford Waste Vitrification Plant (HWVP), the Defense Waste Processing Facility (DWPF), and Kernforschungszentrum Karlsruhe (KfK) in Germany were used. The samples were thin-sectioned and examined by optical microscopy to investigate the stages of the conversion from feed to glass. Various phenomena were seen, such as frit softening, bubble formation, foaming, bubble motion and removal, convective mixing, and homogenization. Behavior of different feeds was similar, although the degree of gas generation and melt homogenization varied.

Anderson, L.D.; Dennis, T.; Elliott, M.L.; Hrma, P.

1993-04-01

257

Porous vycor glass tube joined to borosilicate glass  

NASA Astrophysics Data System (ADS)

Porous glass can absorb various size of molecules with large surface area even in high temperature. However, it is difficult to use porous glass tubes at high-temperature, for example as a separation membrane for hydrogen condensation, because adhesives at joining sites could be damaged. In this study, welding of a porous glass tube and a glass tube was attempted to develop a gas separation membrane used at 500 C. Since forms present in porous glass may cause crack at high temperature, it is necessary to remove such forms by heat processing. Such porous glass is called to be porous vycor glass, which contains quartz 6 percents, and can be joined with a quartz tube. As a result, a gas separator with porous glass membrane which is joined by this process could endure high temperature up to 600 C and could maintain high vacuum.

Abe, Shinichi; Kikuchi, Takemitsu; Onodera, Shinji

1992-09-01

258

Transient nucleation in glasses  

NASA Technical Reports Server (NTRS)

Nucleation rates in condensed systems are frequently not at their steady state values. Such time dependent (or transient) nucleation is most clearly observed in devitrification studies of metallic and silicate glasses. The origin of transient nucleation and its role in the formation and stability of desired phases and microstructures are discussed. Numerical models of nucleation in isothermal and nonisothermal situations, based on the coupled differential equations describing cluster evolution within the classical theory, are presented. The importance of transient nucleation in glass formation and crystallization is discussed.

Kelton, K. F.

1991-01-01

259

Room temperature wafer level glass\\/glass bonding  

Microsoft Academic Search

The findings of this study report the bonding of glass\\/glass wafers by using the surface activated bonding (SAB) method at room temperature (RT) without heating. In order to bond, the glass wafers were activated by a sequential plasma activation process, in which the wafers were cleaned with reactive ion etching (RIE) oxygen radio frequency (rf) plasma and nitrogen radical microwave

M. M. R. Howlader; Satoru Suehara; Tadatomo Suga

2006-01-01

260

Containerless processing of fluoride glass  

NASA Technical Reports Server (NTRS)

Ground-based experiments on glass formation, crystallization, surface tension, vaporization, and chemical durability of a zirconium-barium-lanthanum (ZBL) fluoride glass are summarized. In a container large, columnar grains grew out from the container-glass interface during cooling. The main crystalline phase was alpha BaZrF6. A ZBL glass sphere was levitated acoustically during Shuttle flight STS-11. The glass was melted and then cooled while being levitated (containerless). Crystallization in the recovered sample was very fine and mainly beta BaZr2F10, showing the influence of the container on the nucleation and microstructure of crystallization in the glass. Glass formation should be easier for a containerless glass than in a container.

Doremus, Robert H.

1990-01-01

261

Making Highly Pure Glass Rods  

NASA Technical Reports Server (NTRS)

Proposed quasi-containerless method for making glass rods or fibers minimizes contact between processing equipment and product. Method allows greater range of product sizes and shapes than achieved in experiments on containerless processing. Molten zone established in polycrystalline rod. Furnace sections separated, and glass rod solidifies between them. Clamp supports solid glass as it grows in length. Pulling clamp rapidly away from melt draws glass fiber. Fiber diameter controlled by adjustment of pulling rate.

Naumann, R. J.

1986-01-01

262

Spectroscopic studies of glass structure  

SciTech Connect

Today`s understanding of the molecular-level structure of inorganic glasses has been transformed by the availability of a wide range of sensitive spectroscopic probes. Today we can relate glass composition to quantitative distributions of glass-forming cations and to changes in oxygen bonding and modifying cation geometries. Future spectroscopic studies will result in improved descriptions of anion and cation geometries and should provide glass scientists with the capability to optimize atomic arrangements for specific optical, electrical, and thermal properties.

Brow, R.K.

1994-08-01

263

Microexplosions in Tellurite Glasses  

SciTech Connect

Femtosecond laser pulses were used to initiate microexplosions in baseline, Al2O3-doped, and La2O3-doped sodium tellurite glasses. Single or multiple-shots were used in the experiments. Writing of simple structures (periodic array of voxels as well as lines) was demonstrated. The regions of microexplosion and writing were characterized using scanning electron microscopy (SEM, energy dispersive spectrometer (EDS), and atomic force microscopy (AFM) postmortem. Fingerprints of microexplosions, concentric lines within the region and a concentric ring outside the region due to shock wave generated during the microexplosions were evident. In the case of the baseline glass, no chemistry change was observed within the region of microexplosion. But, Al2O3-doped and La2O3-doped glasses showed depletion of the dopant from the edge to the center of the region of microexplosions, indicating chemistry gradient within the regions. Interrogation of the bulk and laser-treated regions using micro-Raman spectroscopy revealed no structural change due the microexplosions and writing within these glasses. These data were attributed to the localization of the effect to small regions due to tightly focused laser pulses used in the experiments.

Sundaram, S. K.; Schaffer, C. B.; Mazur, E.

2003-03-01

264

Triad ''Metal – Enamel – Glass''  

NASA Astrophysics Data System (ADS)

This article shows how to change the color of metal and glass. Both these materials are self–sufficient, but sometimes used together. For example, enameling. In this case, the adhesion between metal substrate and stekloobraznae enamel layer, which was conducted on a stretching and a bend, was tested.

Mukhina, T.; Petrova, S.; Toporova, V.; Fedyaeva, T.

2014-10-01

265

Light Bends Glass  

NSDL National Science Digital Library

This site, from Physical Review Focus, describes a recent experiment to find out how the momentum of a photon changes when it passes from a glass fiber into air. The article describes the 100-year-old controversy on this question and explains the results of this experiment. Links are provided for more information.

2009-02-26

266

What Glass Ceiling?  

ERIC Educational Resources Information Center

A recent study drawing on data from the Census Bureau and the Bureau of Labor Statistics suggests that the wage gap between men and women has virtually disappeared, and that the so-called "glass ceiling" results more from age and qualifications than from explicit discrimination. (SLD)

Lynch, Michael; Post, Katherine

1996-01-01

267

Glass-matrix biocomposites.  

PubMed

CaO-SiO(2) base glass-matrix/Ti particle biocomposite coatings on Ti6Al4V substrates have been prepared by means of Vacuum Plasma Spray. The base glass is considered bioactive, because, when soaked in a fluid that simulates the inorganic ion concentration of human plasma (SBF), it develops a bonelike apatite layer on its surface. The aim of this research activity was to toughen this brittle bioactive material and to broaden its biomedical applications. Pure titanium was chosen as toughening phase because of its well-known biocompatibility, and Ti6Al4V alloy as substrate because of both its biocompatibility and its mechanical reliability. At first the composites were prepared as bulk materials, by means of a simple sintering process. Then, by ball-milling the sintered composite, the as-obtained "composite powders" were sprayed by Vacuum Plasma Spray (VPS) on the substrate. By means of Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC), the characteristic temperatures of the base glasses were determined. The thermal properties of mixtures of glass powders and different vol% Ti particles were studied by means of DTA, DSC, hot-stage microscopy, and dilatometry, with the aim of optimizing the sintering conditions. Both the bulk and the coated samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), compositional analysis (EDS), Vickers indentations, and leaching tests after soaking in a simulated body fluid (SBF). PMID:10898882

Verné, E; Brovarone, C V; Milanese, D

2000-01-01

268

The Political Glass Ceiling  

Microsoft Academic Search

Why has the integration of women into elective office, particularly Congress, been so slow? We argue that incumbency and the general lack of competition in American elections serve as a “political glass ceiling,” having a dampening effect on the number of women running in both primary and general U.S. House elections. With data from House elections from 1978-1998, we find

Barbara Palmer; Dennis Simon

2001-01-01

269

Disappearing Glass Rod  

NSDL National Science Digital Library

This site from the Exploratorium contains a simple demonstration of how objects can disappear when placed in a liquid. The activity uses glass objects and Wesson⢠oil. The site provides an explanation of the refraction and reflection involved along with related physics concepts and extension activities.

2006-10-12

270

The Color Glass Condensate  

E-print Network

We provide a broad overview of the theoretical status and phenomenological applications of the Color Glass Condensate effective field theory describing universal properties of saturated gluons in hadron wavefunctions that are extracted from deeply inelastic scattering and hadron-hadron collision experiments at high energies.

F. Gelis; E. Iancu; J. Jalilian-Marian; R. Venugopalan

2010-02-01

271

Barstow heliostat mirror glass characterization  

SciTech Connect

The technical analysis performed on the special run of low iron float glass procured from the Ford Glass Division for the ten megawatt solar thermal/electric pilot power plant to be constructed at Barstow, California is discussed. The topics that are addressed include the optical properties and the relative durability of the glass. Two optical parameters, solar transmittance and optical flatness, were measured as referenced in the specification and found to be better than the stated tolerances. The average solar transmittance exceeded 0.890 transmittance units. The glass also exhibited optical angular flatness deviations less than +-1.0 mrad as required. Both qualitative and quantitative accelerated weathering tests were performed on the glass in order to compare its durability to other soda lime float glass and alternate composition glasses of interest to the solar community. In both the quantitative leaching experiments and the more qualitative room temperature and elevated temperature water vapor exposure experiments the heliostat glass exhibited the same characteristics as the other soda-lime silicate float glasses. As a final test for mirroring compatability, selected samples of the production run of the glass were sent to four different commercial manufacturers for mirror coating. None of the manufacturers reported any difficulty silvering the glass. Based on the tests performed, the glass meets or exceeds all optical specifications for the Barstow heliostat field.

Lind, M.A.; Buckwalter, C.Q.

1980-09-01

272

Water's second glass transition  

PubMed Central

The glassy states of water are of common interest as the majority of H2O in space is in the glassy state and especially because a proper description of this phenomenon is considered to be the key to our understanding why liquid water shows exceptional properties, different from all other liquids. The occurrence of water’s calorimetric glass transition of low-density amorphous ice at 136 K has been discussed controversially for many years because its calorimetric signature is very feeble. Here, we report that high-density amorphous ice at ambient pressure shows a distinct calorimetric glass transitions at 116 K and present evidence that this second glass transition involves liquid-like translational mobility of water molecules. This “double Tg scenario” is related to the coexistence of two liquid phases. The calorimetric signature of the second glass transition is much less feeble, with a heat capacity increase at Tg,2 about five times as large as at Tg,1. By using broadband-dielectric spectroscopy we resolve loss peaks yielding relaxation times near 100 s at 126 K for low-density amorphous ice and at 110 K for high-density amorphous ice as signatures of these two distinct glass transitions. Temperature-dependent dielectric data and heating-rate–dependent calorimetric data allow us to construct the relaxation map for the two distinct phases of water and to extract fragility indices m = 14 for the low-density and m = 20–25 for the high-density liquid. Thus, low-density liquid is classified as the strongest of all liquids known (“superstrong”), and also high-density liquid is classified as a strong liquid. PMID:24101518

Amann-Winkel, Katrin; Gainaru, Catalin; Handle, Philip H.; Seidl, Markus; Nelson, Helge; Bohmer, Roland

2013-01-01

273

Fluoride glass: Crystallization, surface tension  

NASA Technical Reports Server (NTRS)

Fluoride glass was levitated acoustically in the ACES apparatus on STS-11, and the recovered sample had a different microstructure from samples cooled in a container. Further experiments on levitated samples of fluoride glass are proposed. These include nucleation, crystallization, melting observations, measurement of surface tension of molten glass, and observation of bubbles in the glass. Ground experiments are required on sample preparation, outgassing, and surface reactions. The results should help in the development and evaluation of containerless processing, especially of glass, in the development of a contaminent-free method of measuring surface tensions of melts, in extending knowledge of gas and bubble behavior in fluoride glasses, and in increasing insight into the processing and properties of fluoride glasses.

Doremus, R. H.

1988-01-01

274

Digitization of stained glass  

NASA Astrophysics Data System (ADS)

Digital photography was applied to the capture of images of the stained glass windows in the historic parish church in Fairford, Gloucestershire, England. Because of their size, the windows had to be photographed in 45 separate sections in order to capture all the detail present in the painting on the glass. The digital images of each section, approximately 3000 by 2300 pixels, were then mosaiced together in order to construct the very high resolution image needed for the complete window. A special backlight panel was constructed for the purpose, and techniques developed for minimizing the effects of reflected light and for calibrating the color of the images. Improvements in the technology for mounting and positioning the camera were identified as the most significant factors currently preventing the widespread adoption of this technology for virtual heritage applications.

MacDonald, Lindsay W.

1997-04-01

275

Outgassing of Glass  

Microsoft Academic Search

The gas evolved from glass at temperatures below the softening point, which is of interest in bake-out problems, is primarily water. The water evolved from unit surface at constant temperature above 300°C is linear with respect to the square root of the time of bake-out. The intercept of the linear plot, which can be altered by different surface treatments, is

B. Johnson Todd

1955-01-01

276

CCMR: Water in Glass  

NSDL National Science Digital Library

Water uptake for various compositions of the model glass (CaO·Al2O3)x (2 SiO2)1-x under fixed annealing conditions was studied via FTIR. The water saturation concentration increased with time for certain sample sets, suggesting slow equilibration of the surface with the annealing atmosphere, while the water diffusion coefficient exhibited no appreciable time dependence. The saturation concentration and diffusion coefficient were not found to vary significantly with composition.

Uspal, William

2005-08-17

277

Eyesafe erbium glass microlaser  

NASA Astrophysics Data System (ADS)

A miniature diode pumped Er,Yb:glass laser has been developed at the Night Vision and Electronic Sensors Directorate, U. S. Army CECOM (NVESD) for soldier applications. This device uses a single laser diode at 925 nm to end pump a 200?m x 3 mm volume of Er,Yb:glass gain media. A Co2+:MgAl2O4 passive Q-switch is used to produce 2 nanosecond pulses at a repetition rate from single shot to 20 Hertz. A nominal pulse energy of 100 microjoules is emitted, corresponds to a peak power of 50 kilowatts, which is sufficient for ranging to over 2 kilometer. The Eyesafe Microlaser was designed and demonstrated to operate over a wide temperature range without temperature control of the pump laser, a feature important for soldier applications. An desirable feature of Er,Yb:glass lasers is that they emit directly at 1.54 microns, which is important for eye safe operation and low cost fabrication.

Hamlin, Scott J.; Hays, Alan D.; Trussell, C. Ward; King, Vernon

2004-07-01

278

Laser Glass Frit Sealing for Encapsulation of Vacuum Insulation Glasses  

NASA Astrophysics Data System (ADS)

Laser glass frit sealing is a joining method predestined in electronics for the sealing of engineered materials housings in dimensions of some 1 mm2 to several 10 mm2. The application field ranges from encapsulation of display panels to sensor housings. Laser glass frit sealing enables a hermetical closure excluding humidity and gas penetration. But the seam quality is also interesting for other applications requiring a hermetical sealing. One application is the encapsulation of vacuum insulation glass. The gap between two panes must be evacuated for reducing the thermal conductivity. Only an efficient encapsulating technique ensures durable tight joints of two panes for years. Laser glass frit sealing is an alternative joining method even though the material properties of soda lime glass like sensitivity to thermal stresses are much higher as known from engineered materials. An adapted thermal management of the process is necessary to prevent the thermal stresses within the pane to achieve crack free and tight glass frit seams.

Kind, H.; Gehlen, E.; Aden, M.; Olowinsky, A.; Gillner, A.

279

Transferability of glass lens molding  

NASA Astrophysics Data System (ADS)

Sphere lenses have been used for long time. But it is well known that sphere lenses theoretically have spherical aberration, coma and so on. And, aspheric lenses attract attention recently. Plastic lenses are molded easily with injection machines, and are relatively low cost. They are suitable for mass production. On the other hand, glass lenses have several excellent features such as high refractive index, heat resistance and so on. Many aspheric glass lenses came to be used for the latest digital camera and mobile phone camera module. It is very difficult to produce aspheric glass lenses by conventional process of curve generating and polishing. For the solution of this problem, Glass Molding Machine was developed and is spreading through the market. High precision mold is necessary to mold glass lenses with Glass Molding Machine. The mold core is ground or turned by high precision NC aspheric generator. To obtain higher transferability of the mold core, the function of the molding machine and the conditions of molding are very important. But because of high molding temperature, there are factors of thermal expansion and contraction of the mold and glass material. And it is hard to avoid the factors. In this session, I introduce following items. [1] Technology of glass molding and the machine is introduced. [2] The transferability of glass molding is analyzed with some data of glass lenses molded. [3] Compensation of molding shape error is discussed with examples.

Katsuki, Masahide

2006-02-01

280

Mixed Glass Former Effect In Silver Molybdophosphate and Borophosphate Glasses  

NASA Astrophysics Data System (ADS)

We report the study of electrical properties of some silver ion conducting molybdophosphate and borophosphate mixed network former glasses in a wide frequency and temperature range. The dc conductivity of the mixed network former glasses is higher than that of the single network former glasses. The ac conductivity spectra show a power law type dependence on frequency. The frequency exponent obtained from ac conductivity is observed to be independent of both temperature and composition.

Deb, B.; Kabi, S.; Ghosh, A.

2011-07-01

281

On the glass transition temperature in covalent glasses  

Microsoft Academic Search

We give a simple demonstration of the formula relating the glass transition temperature, Tg, to the molar concentration x of a modifier in two types of glasses: binary glasses, whose composition can be denoted by XnYm+xMpYq, with X an element of 3rd or 4th group (e.g., B or Si, Ge), while MpYq is an alkali oxide or chalcogenide; next, the

Richard Kerner; Matthieu Micoulaut

1997-01-01

282

Mixed polyanion glass cathodes: Iron phosphate vanadate glasses  

SciTech Connect

Mixed polyanion (MP) glasses have been investigated for use as cathodes in lithium ion batteries. MP glass cathodes are similar in composition to theoretically promising crystalline polyanionic (CP) cathodes (e.g., lithium cobalt phosphate, lithium manganese silicate), but with proper polyanion substitution, they can be designed to overcome the key shortcomings of CP cathodes, such as poor electrical conductivity and irreversible phase changes. Iron phosphate/vanadate glasses were chosen as a first demonstration of the MP glass concept. Polyanion substitution with vanadate was shown to improve the intercalation capacity of an iron phosphate glass from almost zero to full theoretical capacity. In addition, the MP glass cathodes also exhibited an unexpected second high-capacity electrochemical reaction. X-ray absorption near-edge structure (XANES) and x-ray diffraction (XRD) of cathodes from cells having different states of charge suggested that this second electrochemical reaction is a glass-state conversion reaction. With a first demonstration established, MP glass materials utilizing an intercalation and/or glass-state conversion reaction are promising candidates for future high-energy cathode research.

Kercher, Andrew K [ORNL; Ramey, Joanne Oxendine [ORNL; Carroll, Kyler J [Massachusetts Institute of Technology (MIT); Kiggans Jr, James O [ORNL; Veith, Gabriel M [ORNL; Meisner, Roberta [Oak Ridge National Laboratory (ORNL); Boatner, Lynn A [ORNL; Dudney, Nancy J [ORNL

2014-01-01

283

Crystallization of bismuth borate glasses.  

PubMed

Bismuth borate glasses with Bi(2)O(3) concentration of 20-66 mol% were prepared by melt quenching and devitrified by heat treatment above their glass transition temperatures. All glasses show a strong tendency towards crystallization on annealing that increases with Bi(2)O(3) concentration. The crystalline phases formed on devitrification were characterized by FTIR absorption spectroscopy and DSC measurements. Our studies reveal that phases produced in glasses are strongly determined by initial glass composition and the two most stable crystalline phases are: Bi(3)B(5)O(12) and Bi(4)B(2)O(9). The metastable BiBO(3) phase can also be formed by devitrification of glass with 50 mol% of Bi(2)O(3). This phase is, however, unstable and decomposes into Bi(3)B(5)O(12) and Bi(4)B(2)O(9) on prolonged heat treatment. PMID:21817270

Bajaj, Anu; Khanna, Atul

2009-01-21

284

Fracture mechanics of cellular glass  

NASA Technical Reports Server (NTRS)

The fracture mechanics of cellular glasses (for the structural substrate of mirrored glass for solr concentrator reflecting panels) are discussed. Commercial and developmental cellular glasses were tested and analyzed using standard testing techniques and models developed from linear fracture mechanics. Two models describing the fracture behavior of these materials were developed. Slow crack growth behavior in cellular glass was found to be more complex than that encountered in dense glasses or ceramics. The crack velocity was found to be strongly dependent upon water vapor transport to the tip of the moving crack. The existence of a static fatigue limit was not conclusively established, however, it is speculated that slow crack growth behavior in Region 1 may be slower, by orders of magnitude, than that found in dense glasses.

Zwissler, J. G.; Adams, M. A.

1981-01-01

285

Glass corrosion in natural environments  

NASA Technical Reports Server (NTRS)

Experiments carried out during the progress period are summarized. Experiments carried out involving glass samples exposed to solutions of Tris have shown the appearance of 'spikes' upon monitoring glass dissolution as a function of time. The periodic 'spikes' observed in Tris-based media were interpreted in terms of cracking due to excessive stress in the surface region of the glass. Studies of the interactions of silicate glasses with metal ions in buffered media were extended to systems containing Al. Caps buffer was used to establish the pH. The procedures used are described and the results are given. Preliminary studies were initiated as to the feasibility of adding a slowly dissolving solid compound of the additive to the glass-water system to maintain a supply of dissolved additive. It appears that several magnesium compounds have a suitable combination of solubility and affinity towards silicate glass surfaces to have a pronounced retarding effect on the extraction of uranium from the glass. These preliminary findings raise the possibility that introducing a magnesium source into geologic repositories for nuclear waste glass in the form of a sparingly soluble Mg-based backfill material may cause a substantial reduction in the extent of long-term glass corrosion. The studies described also provide mechanistic understanding of the roles of various metal solutes in the leachant. Such understanding forms the basis for developing long-term predictions of nuclear waste glass durability under repository conditions. From what is known about natural highly reduced glasses such as tektites, it is clear that iron is dissolved as ferrous iron with little or no ferric iron. The reducing conditions were high enough to cause metallic iron to exsolve out of the glass in the form of submicroscopic spherules. As the nuclear waste glass is much less reduced, a study was initiated on other natural glasses in addition to the nuclear waste glass. Extensive measurements were carried out on these glasses in order to characterize their magnetic properties. Results of these studies are described.

Thorpe, Arthur N.; Barkatt, Aaron

1992-01-01

286

Abelian gauge glasses  

NASA Astrophysics Data System (ADS)

Gauge glasses are lattice gauge theories with quenched random couplings; in this paper, the two simplest abelian models, having Z 2 and U(1) gauge symmetries respectively, are constructed. An important extension of gauge invariance is defined and the disorder invariant under this symmetry, the frustration, is identified. Simple energetic properties of frustrations are derived using duality arguments. The question of the existence of a weakly coupled glassy phase is raised, and then addressed using replica mean field theory and real-space renormalisation group techniques, both in the context of the Z 2 model. A phase transition is found for dimension six and above. The implications for random dynamics are discussed.

Hands, Simon

1988-12-01

287

7.G Stained Glass  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: The students in Mr. Rivera's art class are designing a stained-glass window to hang in the school entryway. The window will be 2 feet tall and 5 feet w...

288

The GLASS CHAIR Edited by Manuel Heitor  

E-print Network

The GLASS CHAIR Edited by Manuel Heitor IST Press, 2000 #12;Collaborative Design of... The GLASS the glass chair, but also for the numerous discussions on glass production processes. And last · Carmo Valente Chapter 4. GLASS: BEAUTY WITH STRENGTH Sushil Kumar Mendiratta Chapter 5. The IDEA

Instituto de Sistemas e Robotica

289

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed. 5 figs.

Boaz, P.T.

1998-07-21

290

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed.

Boaz, Premakaran Tucker (Livonia, MI)

1998-01-01

291

Mechanical failure and glass transition in metallic glasses  

SciTech Connect

The current majority view on the phenomenon of mechanical failure in metallic glasses appears to be that it is caused by the activity of some structural defects, such as free-volumes or shear transformation zones, and the concentration of such defects is small, only of the order of 1%. However, the recent results compel us to revise this view. Through molecular dynamics simulation it has been shown that mechanical failure is the stress-induced glass transition. According to our theory the concentration of the liquid-like sites (defects) is well over 20% at the glass transition. We suggest that the defect concentration in metallic glasses is actually very high, and percolation of such defects causes atomic avalanche and mechanical failure. In this article we discuss the glass transition, mechanical failure and viscosity from such a point of view.

Egami, Takeshi [ORNL

2011-01-01

292

Aspects of the mechanics of metallic glasses  

E-print Network

Metallic glasses are amorphous materials that possess unique mechanical properties, such as high tensile strengths and good fracture toughnesses. Also, since they are amorphous, metallic glasses exhibit a glass transition, ...

Henann, David Lee

2011-01-01

293

Glasses in the D'Orbigny Angrite  

NASA Astrophysics Data System (ADS)

The D'Orbigny angrite contains abundant glasses, a phase which has not been previously reported from any other angrite. Glasses fill in part open druses and intersticial spaces between major silicates, or occur as glass inclusions in olivine.

Varela, M. E.; Kurat, G.; Brandstätter, F.; Bonnin-Mosbah, M.; Metrich, N.

2001-03-01

294

Method of determining glass durability  

DOEpatents

A process is described for determining one or more leachate concentrations of one or more components of a glass composition in an aqueous solution of the glass composition by identifying the components of the glass composition, including associated oxides, determining a preliminary glass dissolution estimator, {Delta}G{sub p}, based upon the free energies of hydration for the component reactant species, determining an accelerated glass dissolution function, {Delta}G{sub a}, based upon the free energy associated with weak acid dissociation, {Delta}G{sub a}{sup WA}, and accelerated matrix dissolution at high pH, {Delta}G{sub a}{sup SB} associated with solution strong base formation, and determining a final hydration free energy, {Delta}G{sub f}. This final hydration free energy is then used to determine leachate concentrations for elements of interest using a regression analysis and the formula log{sub 10}(N C{sub i}(g/L))=a{sub i} + b{sub i}{Delta}G{sub f}. The present invention also includes a method to determine whether a particular glass to be produced will be homogeneous or phase separated. The present invention is also directed to methods of monitoring and controlling processes for making glass using these determinations to modify the feedstock materials until a desired glass durability and homogeneity is obtained. 4 figs.

Jantzen, C.M.; Pickett, J.B.; Brown, K.G.; Edwards, T.B.

1998-12-08

295

Method of determining glass durability  

DOEpatents

A process for determining one or more leachate concentrations of one or more components of a glass composition in an aqueous solution of the glass composition by identifying the components of the glass composition, including associated oxides, determining a preliminary glass dissolution estimator, .DELTA.G.sub.p, based upon the free energies of hydration for the component reactant species, determining an accelerated glass dissolution function, .DELTA.G.sub.a, based upon the free energy associated with weak acid dissociation, .DELTA.G.sub.a.sup.WA, and accelerated matrix dissolution at high pH, .DELTA.G.sub.a.sup.SB associated with solution strong base formation, and determining a final hydration free energy, .DELTA.G.sub.f. This final hydration free energy is then used to determine leachate concentrations for elements of interest using a regression analysis and the formula log.sub.10 (N C.sub.i (g/L))=a.sub.i +b.sub.i .DELTA.G.sub.f. The present invention also includes a method to determine whether a particular glass to be produced will be homogeneous or phase separated. The present invention is also directed to methods of monitoring and controlling processes for making glass using these determinations to modify the feedstock materials until a desired glass durability and homogeneity is obtained.

Jantzen, Carol Maryanne (Aiken, SC); Pickett, John Butler (Aiken, SC); Brown, Kevin George (Augusta, GA); Edwards, Thomas Barry (Aiken, SC)

1998-01-01

296

Metallic glasses as structural materials  

Microsoft Academic Search

The potential of metallic glasses as structural materials is assessed. A wide-ranging comparison with conventional engineering materials shows metallic glasses to be restricted to niche applications, but with outstanding properties awaiting wider application, for example in micro electro-mechanical systems devices.

M. F. Ashby; A. L. Greer

2006-01-01

297

Thermal Gradient Fining of Glass  

NASA Technical Reports Server (NTRS)

Molten glass fined (cleared of bubbles) by heating with suitable temperature gradient, according to preliminary experiments. Temperature gradient produces force on gas bubbles trapped in molten glass pushing bubbles to higher temperature region where they are collected. Concept demonstrated in experiments on Earth and on rocket.

Wilcox, W.

1983-01-01

298

Laboratory Waste Disposal HAZARDOUS GLASS  

E-print Network

Laboratory Waste Disposal HAZARDOUS GLASS Items that could cut or puncture skin or trash- can of in normal trash containers. Pasteur pipettes Other pipettes and tips (glass or plastic) Slides and cover HAZARDOUS TRASH Items that are neither sharp nor contaminated. Thiswastestreamishandleddirectlybycustodians

Sheridan, Jennifer

299

Glass Ceramic Formulation Data Package  

SciTech Connect

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 waste form.

Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

2012-06-17

300

Database and Interim Glass Property Models for Hanford HLW Glasses  

SciTech Connect

The purpose of this report is to provide a methodology for an increase in the efficiency and a decrease in the cost of vitrifying high-level waste (HLW) by optimizing HLW glass formulation. This methodology consists in collecting and generating a database of glass properties that determine HLW glass processability and acceptability and relating these properties to glass composition. The report explains how the property-composition models are developed, fitted to data, used for glass formulation optimization, and continuously updated in response to changes in HLW composition estimates and changes in glass processing technology. Further, the report reviews the glass property-composition literature data and presents their preliminary critical evaluation and screening. Finally the report provides interim property-composition models for melt viscosity, for liquidus temperature (with spinel and zircon primary crystalline phases), and for the product consistency test normalized releases of B, Na, and Li. Models were fitted to a subset of the screened database deemed most relevant for the current HLW composition region.

Hrma, Pavel R.; Piepel, Gregory F.; Vienna, John D.; Cooley, Scott K.; Kim, Dong-Sang; Russell, Renee L.

2001-07-24

301

Nanophase Glass Ceramics for Capacitive Energy Storage.  

E-print Network

??Glass ceramics are candidate dielectric materials for high energy storage capacitors. Since energy density depends primarily on dielectric permittivity and breakdown strength, glass ceramics with… (more)

Rangarajan, Badri

2009-01-01

302

A Topological Glass  

E-print Network

We propose and study a model with glassy behavior. The state space of the model is given by all triangulations of a sphere with $n$ nodes, half of which are red and half are blue. Red nodes want to have 5 neighbors while blue ones want 7. Energies of nodes with different numbers of neighbors are supposed to be positive. The dynamics is that of flipping the diagonal of two adjacent triangles, with a temperature dependent probability. We show that this system has an approach to a steady state which is exponentially slow, and show that the stationary state is unordered. We also study the local energy landscape and show that it has the hierarchical structure known from spin glasses. Finally, we show that the evolution can be described as that of a rarefied gas with spontaneous generation of particles and annihilating collisions.

Jean-Pierre Eckmann

2007-04-07

303

Glass science tutorial: Lecture No. 7, Waste glass technology for Hanford  

SciTech Connect

This paper presents the details of the waste glass tutorial session that was held to promote knowledge of waste glass technology and how this can be used at the Hanford Reservation. Topics discussed include: glass properties; statistical approach to glass development; processing properties of nuclear waste glass; glass composition and the effects of composition on durability; model comparisons of free energy of hydration; LLW glass structure; glass crystallization; amorphous phase separation; corrosion of refractories and electrodes in waste glass melters; and glass formulation for maximum waste loading.

Kruger, A.A.

1995-07-01

304

Reduced glass transition temperature and glass forming ability of bulk glass forming alloys  

Microsoft Academic Search

Onset temperature (solidus) Tm and offset temperature (liquidus) Tl of melting of a series of bulk glass forming alloys based on Zr, La, Mg, Pd and rare-earth elements have been measured by studying systematically the melting behaviour of these alloys using DTA or DSC. Bulk metallic glass formation has been found to be most effective at or near their eutectic

Z. P. Lu; Y. Li; S. C. Ng

2000-01-01

305

Raman study of glass transition in iron phosphate glasses  

NASA Astrophysics Data System (ADS)

Iron phosphate (Fe2O3: P2O5) glass with 40: 60 mol% composition having glass transition temperature, Tg at 782 K, was investigated between 81-873 K using Raman spectroscopy. The spectra were corrected for thermal population factor and the Raman mode frequencies were obtained from Lorentzian peak fits. Three characteristic modes of iron phosphate glass, corresponding to asymmetric stretching of Q0, Q1 and Q2 tetrahedral units, were analyzed for temperature dependences of the mode frequencies. All the modes are found to exhibit typical anharmonic behavior below Tg, while discontinuous changes are found near Tg, thereby suggesting structural relaxations.

Chakraborty, S.; Arora, A. K.

2012-06-01

306

Fracture mechanics of cellular glass  

SciTech Connect

Cellular glasses are prime candidate materials for the structural substrate of mirrored glass for solar concentrator reflecting panels. These materials are brittle, however, and susceptible to mechanical failure from slow crack growth caused by a stress corrosion mechanism. The results are detailed of one part of a program established to develop improved cellular glasses and to characterize the behavior of these and commercially available materials. Commercial and developmental cellular glasses were tested and analyzed using standard testing techniques and models developed from linear fracture mechanics. Two models describing the fracture behavior of these materials are developed. Slow crack growth behavior in cellular glass was found to be more complex than that encountered in dense glasses or ceramics. The crack velocity was found to be strongly dependent upon water vapor transport to the tip of the moving crack. The existence of a static fatigue limit was not conclusively established, however, it is speculated that slow crack growth behavior in Region I may be slower, by orders of magnitude, than that found in dense glasses.

Zwissler, J.G.; Adams, M.A.

1981-02-01

307

Glass ceramic seals to inconel  

DOEpatents

A glass ceramic composition prepared by subjecting a glass composition comprising, by weight, 65-80% SiO.sub.2, 8-16%, Li.sub.2 O, 2-8% , Al.sub.2 O.sub.3, 1-8% K.sub.2 O, 1-5% P.sub.2 O.sub.5 and 1.5-7% B.sub.2 O.sub.3, to the following processing steps of heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein, holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii, cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein, and thermally treating the glass composition at a temperature and for a time period sufficient to cause growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient and products containing said composition.

McCollister, Howard L. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

1983-11-08

308

Thermal expansion and glass transition temperatures of synthetic glasses of plagioclase-like compositions  

Microsoft Academic Search

The glass transition temperatures and the thermal expansions both below and above the glass transition temperature region of synthetic glasses of compositions close to those of plagioclases have been determined. The linear thermal expansion coefficient of the rigid glasses decreases on average from 7.4×10-6\\/dgC for albite glass to 4.9×10-6\\/dgC for glass close to anorthite composition. The glass transition temperature of

J. Arndt; F. Häberle

1973-01-01

309

Non-platinum group metal oxgyen reduction catalysts and their mechanism in both acid and alkaline media: The effect of the catalyst precursor and the ionomer on oxygen reduction  

NASA Astrophysics Data System (ADS)

Non-platinum catalysts are an attractive strategy for lowering the cost of fuel cells, but much more development is needed in order to replace platinum, especially at the cathode where oxygen is reduced. Research groups worldwide have donated material for a study in which precursor structure to catalyst activity correlations are made. The donated samples have been divided into three classes based on their precursor; macrocyclic chelates, small molecule, and polymeric precursors. The precursor is one activity-dictating factor among many, but it is one of the most influential. It was found that macrocyclic chelates on average produced the most active catalysts, having the highest limiting, diffusion-limited, kinetic, and exchange current densities, as well as the lowest overpotentials and H2O2 production. This suggests that the M-N4 atomic structure of the precursor remains largely static throughout heat treatment, as the M-Nx motif is the accepted active site conformation. The other classes were somewhat less active, but the breadth of precursor materials that range in structure and functionality, as well as low associated costs, make them attractive precursor materials. Careful precursor selection based on this analysis was applied to a new generation of catalyst derived from iron salt and 4-aminoantipyrine. An extensive investigation of the reduction of oxygen on the material performed in both acid and alkaline media, and it was found that reduction follows a two-step pathway. While the peroxide reducing step is also very fast, the first step is so rapid that, even at low active site density, the material is almost as active as platinum if all diffusion limitations are removed. In addition to bottom-up catalyst design, the catalyst:ionomer complex, by which catalyst is incorporated into the membrane electrode assembly, also affects reductive kinetics. A series of novel anionically conductive ionomers have been evaluated using a well-described cyanamide derived catalyst, and the ionomeric influence on activity was mechanistically evaluated. It was found that the water-uptake percentage of the ionomer and the ion exchange capacity has a major role in catalyzing the reaction. The ionomer content of the complex must balance ionic and electrical charge transfer, as well as manage a certain degree of hydration at the active site. In order for a catalyst to perform optimally in an operational fuel cell, design considerations must be addressed at the precursor, support, synthesis, morphological, and ionomer-complexing levels. If any level of design is neglected, catalytic performance will be sacrificed.

Robson, Michael H.

310

Zirconia solubility in boroaluminosilicate glass  

SciTech Connect

In the Idaho Chemical Processing Plant (ICPP) waste streams, zirconia is often the waste load limiting species. It modifies the glass network, enhances durability, increases viscosity and induces crystallization. The limits of its dissolution in boroaluminosilicate glass, with magnesia and soda additions were experimentally determined. A ternary compositional surface is evolved to present the isothermal regimes of liquid, liquid + zircon, liquid + forsterite, and liquid phase sintered ceramic. The potential of partitioning the transuranics, transition elements and solutes in these regimes is discussed. The visible Raman spectroscopic results are presented to elucidate the dependence among glass composition, structure and chemical durability.

Raman, S.V.; Bopp, R.; Batcheller, T.A. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States); Yan, Q. [Univ. of Houston, TX (United States). Chemistry Dept.

1995-12-31

311

Glass microspheres for medical applications  

NASA Astrophysics Data System (ADS)

Radioactive dysprosium lithium borate glass microspheres have been developed as biodegradable radiation delivery vehicles for the radiation synovectomy treatment of rheumatoid arthritis. Once injected into a diseased joint, the microspheres deliver a potent dose of radiation to the diseased tissue, while a non-uniform chemical reaction converts the glass into an amorphous, porous, hydrated dysprosium phosphate reaction product. The non-radioactive, lithium-borate component is dissolved from the glass (up to 94% weight loss), while the radioactive 165Dy reacts with phosphate anions in the body fluids, and becomes "chemically" trapped in a solid, dysprosium phosphate reaction product that has the same size as the un-reacted glass microsphere. Ethylene diamine tetraacetate (EDTA) chelation therapy can be used to dissolve the dysprosium phosphate reaction product after the radiation delivery has subsided. The dysprosium phosphate reaction product, which formed in vivo in the joint of a Sprague-Dawley rat, was dissolved by EDTA chelation therapy in <1 week, without causing any detectable joint damage. The combination of dysprosium lithium borate glass microspheres and EDTA chelation therapy provides an unique "tool" for the medical community, which can deliver a large dose (>100 Gy) of localized beta radiation to a treatment site within the body, followed by complete biodegradability. The non-uniform reaction process is a desirable characteristic for a biodegradable radiation delivery vehicle, but it is also a novel material synthesis technique that can convert a glass to a highly porous materials with widely varying chemical composition by simple, low-temperature, glass/solution reaction. The reaction product formed by nonuniform reaction occupies the same volume as the un-reacted glass, and after drying for 1 h at 300°C, has a specific surface area of ?200 m2/g, a pore size of ?30 nm, and a nominal crushing strength of ?10 MPa. Finally, rhenium glass microspheres, composed of micron-sized, metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050°C. A 50 mg injection of radioactive rhenium glass microspheres containing 3.7 GBq of 186Re and 8.5 GBq of 188Re could be used to deliver a 100 Gy dose to a cancerous tumor, while limiting the total body dose caused by rhenium dissolution to approximately 1 mGy.

Conzone, Samuel David

312

Shock temperatures in anorthite glass  

NASA Technical Reports Server (NTRS)

Shock-temperature data and the high-pressure thermal behavior of anorthite glass are examined. Temperatures of anorthite glass shocked to pressures between 48-117 GPa were measured in the temperature range 2500-5600 K using optical pyrometry techniques. The time dependence observed in the emitted light of the glass is analyzed in terms of temperature dependence, emissivity dependences, and the time dependence of absorption or scattering of an intervening layer. The three phase transitions at pressures of about 55, 85, and 100 GPa and with transition energies of about 0.5 MJ/kg are studied.

Boslough, M. B.; Ahrens, T. J.; Mitchell, A. C.

1986-01-01

313

Galactic Hearts of Glass  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on image for larger graph

This artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.

When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.

At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.

How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.

Crystal Storm in Distant Galaxy The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.

The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.

Spitzer detected the same crystals in 20 additional galaxies, all belonging to a class called ultraluminous infrared galaxies. These extremely bright and dusty galaxies usually consist of two galaxies in the process of smashing into each other. Astronomers believe massive stars at the hearts of the galaxies are churning out clouds of silicate crystals. This phenomenon may represent a short-lived phase in the evolution of galactic mergers.

2006-01-01

314

Stress Corrosion and Static Fatigue of Glass  

Microsoft Academic Search

Stress corrosion cracking of six glasses was studied using fracture mechanics techniques. Crack velocities in water were measured as a function of applied stress intensity factor and temperature, and apparent activation energies for crack mo- tion were obtained. Data were consistent with the universal fatigue curve for static fatigue of glass, which depended on glass composition. Of the glasses tested,

S. M. WIEDERHORN; L. H. BOLZ

1970-01-01

315

Apollo applications of beta fiber glass  

NASA Technical Reports Server (NTRS)

The physical characteristics of Beta fiber glass are discussed. The application of Beta fiber glass for fireproofing the interior of spacecraft compartments is described. Tests to determine the flammability of Beta fiber glass are presented. The application of Beta fiber glass for commercial purposes is examined.

Naimer, J.

1971-01-01

316

Experimental characterization of stress relaxation in glass  

Microsoft Academic Search

Glass viscoelasticity has gained importance in recent years as glass lens molding appeared as a valuable alternative to the traditional grinding and polishing process for manufacturing glass lenses. In the precision lens molding process, knowledge of viscoelastic properties of glass in the transition region, which affect the stress relaxation behavior, is required to precisely predict the final size and shape

Hemanth C. Kadali

2009-01-01

317

Lowmelting crystallizable borophosphate glass binders  

Microsoft Academic Search

Glass ceramic materials that can be used as ceramizing binders for abrasive tools with heat treatment temperatures of 650C\\u000a have been developed and tested. Their main physicochemical properties have been investigated.

A. I. Barabanov; N. O. Tagil’tseva; N. V. Elyukova; V. D. Khalilev; G. P. Zaitsev

2005-01-01

318

All-glass solar collector  

NASA Technical Reports Server (NTRS)

Proposed all tempered glass solar collector uses black collection fluid and mirrored bottom to reduce energy loss and overall costs associated with conventional collectors. Collector is more efficient and practically maintenance-free.

Wisnewski, J. P.

1980-01-01

319

Fast Crystals and Strong Glasses  

SciTech Connect

This talk describes new results on model colloid systems that provide insight into the behavior of fundamental problems in colloid physics, and more generally, for other materials as well. By visualizing the nucleation and growth of colloid crystals, we find that the incipient crystallites are much more disordered than expected, leading to a larger diversity of crystal morphologies. When the entropic contribution of these diverse morphologies is included in the free energy, we are able to describe the behavior very well, and can predict the nucleation rate surprisingly accurately. The talk also describes the glass transition in deformable colloidal particles, and will show that when the internal elasticity of the particles is included, the colloidal glass transition mimics that of molecular glass formers much more completely. These results also suggest that the elasticity at the scale of the fundamental unit, either colloid particle or molecule, determines the nature of the glass transition, as described by the "fragility."

Weitz, David (Harvard) [Harvard

2009-11-04

320

Fiber glass pulling. [in space  

NASA Technical Reports Server (NTRS)

Experiments were conducted to determine the viability of performing containerless glass fiber pulling in space. The optical transmission properties and glass-forming capabilities of the heavy metal fluorides are reviewed and the acoustic characteristics required for a molten glass levitation system are examined. The design limitations of, and necessary modifications to the acoustic levitation furnace used in the experiments are discussed in detail. Acoustic levitator force measurements were performed and a thermal map of the furnace was generated from thermocouple data. It was determined that the thermal capability of the furnace was inadequate to melt a glass sample in the center. The substitution of a 10 KW carbon monoxide laser for the original furnace heating elements resulted in improved melt heating.

Workman, Gary L.

1987-01-01

321

High Tech Art: Chameleon Glass  

NASA Technical Reports Server (NTRS)

Dichroic Glass is a technology wherein extremely thin films of metal are vacuum deposited on a glass surface. The coated glass shields spacecraft instruments from cosmic radiation and protects human vision from unfiltered sunlight in space. Because the coating process allows some wavelengths of light and color to reflect and others to pass through, a chameleon effect is produced. Murray Schwartz, a former aerospace engineer, has based his business KROMA on this NASA optical technology. He produces dichroic stained glass windows, mobiles and jewelry. The technique involves deposition of super thin layers of metal oxides applied one layer at a time in a specific order and thickness for the desired effect. His product line is unique and has been very successful.

1993-01-01

322

Soft phonons in glasses  

NASA Astrophysics Data System (ADS)

The dynamics of glasses differs strongly from the one of crystals. Coexisting with the long wavelength phonons one finds additional low energy excitations: tunneling, soft localized variations and relaxations. The soft potential model postulates a common origin of these additional excitations. In its low temperature limit (typically T < 1 K) it is equivalent to the well-known tunneling model. From general properties of the distribution functions describing the soft potentials one derives the temperature dependencies of quantities such as the specific heat or the thermal conductivity. These universal relations hold to about T = 10 K. Fitting the parameters of the model to the experimental data one finds 20-100 atoms to participate in the excitation modes. Extensions to higher temperatures are possible by introducing material dependent distribution functions. Computer simulations are used to test the assumptions of the model and to provide some insight into the microscopic origin of the modes. One finds soft vibrational modes concentrated on 10 or more atoms. These modes are centered at structural irregularities.

Schober, H. R.

1993-12-01

323

Crystallization during processing of nuclear waste glass  

SciTech Connect

In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glassmaking are reviewed.

Hrma, Pavel R.

2010-12-01

324

Glass Transitions: Opportunities and Challenges  

Microsoft Academic Search

\\u000a Glass transition is a time-dependent change in the state of a noncrystalline material. It often explains solid–liquid transformations\\u000a in foods and it may control changes in food structure and texture as well as chemical reactions. At temperatures around the\\u000a glass transition, an amorphous solid transforms to a supercooled liquid (rubber) which contributes to changes in molecular\\u000a mobility and flow properties

Yrjö H. Roos; Nattiga Silalai

325

Luminescence of powdered uranium glasses  

NASA Technical Reports Server (NTRS)

Measurement of cathodoluminescence and photoluminescence efficiencies in powdered borosilicate glasses having different particle size and different uranium content. Excitation with 100 to 350 keV electrons and with 253.7 nm light was found to produce identical absolute radiant exitance spectra in powdered samples. The most efficient glass was one containing 29.4 wt% B2O3, 58.8 wt% SiO2, 9.8 wt% Na2O and 2.0 wt% UO2.

Eubanks, A. G.; Mcgarrity, J. M.; Silverman, J.

1974-01-01

326

Reinforced glass beamsReinforced glass beamsg Auteur Dr. Christian LOUTER 1  

E-print Network

Reinforced glass beamsReinforced glass beamsg EDCE Auteur Dr. Christian LOUTER 1 ENAC/EDCE 2011In contemporary architecture glass is increasinglyIn contemporary architecture glass is increasingly applied for structural components such as beamsapplied for structural components such as beams. However glass

327

Glass Forming Ability, Structure and Spectroscopic Properties of Silica-Free Calcium Aluminate Based Glasses  

Microsoft Academic Search

Calcium aluminate based glasses are interesting because of their unusual optical properties and the fact that they do not contain any traditional glass forming ions. A large focus of the glass literature has been concerned with the study and properties of typical glass forming ions. For this reason, comparatively little is known about the possibility of glass formation and the

Eugenie Victoria Uhlmann

1994-01-01

328

Isoconversion Analysis of the Glass Transition  

NASA Astrophysics Data System (ADS)

At temperatures below their glass transition temperatures (Tgs), glass forming materials deviate from equilibrium density and form a glass. The kinetic nature of the glass transition process is manifested in the cooling rate dependence of the glass transition temperature and by structural relaxation below Tg. Various facets of the glass transition kinetics have been well described by phenomenological models of the glass transition, such as the TNM and KAHR model. An important yet frequently questioned assumption in these models is that the apparent activation energy, which describes the temperature dependence of the relaxation time, does not vary during the glass transition process. Some recent reports suggest that the activation energy varies significantly during the glass transition process. In this work we apply an isoconversion analysis to data in the glass transition region which was obtained on cooling from capillary dilatometry and differential scanning calorimetry (DSC) in order to determine whether the apparent activation energy increases as the glassy state is approached.

Badrinarayanan, Prashanth; Zheng, Wei; Simon, Sindee

2007-03-01

329

Fabrication of glass microspheres with conducting surfaces  

DOEpatents

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming a conducting coating on the surface of the microspheres.

Elsholz, W.E.

1982-09-30

330

Glass Membrane For Controlled Diffusion Of Gases  

DOEpatents

A glass structure for controlled permeability of gases includes a glass vessel. The glass vessel has walls and a hollow center for receiving a gas. The glass vessel contains a metal oxide dopant formed with at least one metal selected from the group consisting of transition metals and rare earth metals for controlling diffusion of the gas through the walls of the glass vessel. The vessel releases the gas through its walls upon exposure to a radiation source.

Shelby, James E. (Alfred Station, NY); Kenyon, Brian E. (Pittsburgh, PA)

2001-05-15

331

Fabrication of glass microspheres with conducting surfaces  

DOEpatents

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming a conducting coating on the surface of the microspheres.

Elsholz, William E. (Acampo, CA)

1984-01-01

332

Block ionomer complexes of PEG-block-poly(4-vinylbenzylphosphonate) and cationic surfactants as highly stable, pH responsive drug delivery system.  

PubMed

A new family of block ionomer complexes (BIC) formed by poly(ethylene glycol)-block-poly(4-vinylbenzylphosphonate) (PEG-b-PVBP) and various cationic surfactants was prepared and characterized. These complexes spontaneously self-assembled in aqueous solutions into particles with average size of 40-60nm and remained soluble over the entire range of the compositions of the mixtures including stoichiometric electroneutral complexes. Solution behavior and physicochemical properties of such BIC were very sensitive to the structure of cationic surfactants. Furthermore, such complexation was used for incorporation of cationic anti-cancer drug, doxorubicin (DOX), into the core of BIC with high loading capacity and efficiency. The DOX/PEG-b-PVBP BIC also displayed high stability against dilution, changes in ionic strength. Furthermore, DOX release at the extracellular pH of DOX/PEG-b-PVBP BIC was slow. It was greatly increased at the acidic pH mimicking the endosomal/lysosomal environment. Confocal fluorescence microscopy using live MCF-7 breast cancer cells suggested that DOX/PEG-b-PVBP BICs are transported to lysosomes. Subsequently, the drugs are released and exert cytotoxic effect killing these cancer cells. These findings indicate that the obtained complexes can be attractive candidates for delivery of cationic drugs to tumors. PMID:22546682

Kamimura, Masao; Kim, Jong Oh; Kabanov, Alexander V; Bronich, Tatiana K; Nagasaki, Yukio

2012-06-28

333

The fate of arsenic, cadmium and lead in Typha latifolia: a case study on the applicability of micro-PIXE in plant ionomics.  

PubMed

Understanding the uptake, accumulation and distribution of toxic elements in plants is crucial to the design of effective phytoremediation strategies, especially in the case of complex multi-element pollution. Using micro-proton induced X-ray emission, the spatial distribution of Na, Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, Zn, As, Br, Rb, Sr, Cd and Pb have been quantitatively resolved in roots and rhizomes of an obligate wetland plant species, Typha latifolia, treated with a mixture of 100 ?M each of As, Cd and Pb, together. The highest concentrations of As, Cd and Pb were found in the roots of the T. latifolia, with tissue-specific distributions. The As was detected in the root rhizodermis, and in the rhizome the majority of the As was within the vascular tissues, which indicates the high mobility of As within T. latifolia. The Cd was detected in the root exodermis, and in the vascular bundle and epidermis of the rhizome. The highest Pb concentrations were detected in the root rhizodermis and exodermis, and in the epidermis of the rhizome. These data represent an essential step in the resolution of fundamental questions in plant ionomics. PMID:23416480

Lyubenova, Lyudmila; Pongrac, Paula; Vogel-Mikuš, Katarina; Mezek, Gašper Kukec; Vavpeti?, Primož; Grlj, Nataša; Regvar, Marjana; Pelicon, Primož; Schröder, Peter

2013-03-15

334

Understanding the fingerprint region in the infra-red spectra of perfluorinated ionomer membranes and corresponding model compounds: Experiments and theoretical calculations  

NASA Astrophysics Data System (ADS)

We present an ATR-FTIR study of three major perfluorinated ionomers that are used as proton exchange membranes in fuel cells (FCs) and that differ in their side chains: Nafion, Aquivion and 3M membrane. The choice of the following low-molecular-weight model compounds (MCs) that mimic the membrane side chains was essential for FTIR band assignment: perfluoro(3-methyl-2,4-dioxahexane)sulfonic acid for Nafion, perfluoro(2-ethoxyethane)sulfonic acid for Aquivion, and perfluoro(2-ethoxybutane)sulfonic acid for the 3M membrane. The major goal was to identify spectral bands that can be used for recognizing bonds involved in membrane fragmentation. A major focus was on the signals from the C-O-C bonds, which were assigned in some papers for Nafion and Aquivion membranes. Our ATR-FTIR results for 3M membranes did not conform to these assignments, and DFT calculations of the vibrational frequencies for the MCs were used to resolve this conundrum. The ATR-FTIR spectra of membranes and MCs and the DFT calculations led to an understanding of the fingerprint region of all membranes, and to a re-examination and re-assignment of results for Nafion and Aquivion membranes. The low intensity of the spectral bands for the ether link connected to the backbone (for all membranes) and also in the side chain (for Nafion) suggests that these bands cannot be used for the determination of the extent of degradation.

Danilczuk, Marek; Lin, Lu; Schlick, Shulamith; Hamrock, Steven J.; Schaberg, Mark S.

2011-10-01

335

Glass transition and viscosity of simple glasses and liquids  

NASA Astrophysics Data System (ADS)

The theoretical understanding of liquids and glasses at an atomistic level lags well behind that of crystalline materials, even though they are important in many fields including biology and the medical sciences. We present a simple microscopic model for the glass transition based on topological fluctuations in the bonding network. The model makes predictions for important parameters of the glassy state, such as the glass transition temperature, Tg, and the liquid fragility coefficient, m, based on microscopic variables. Excellent agreement with a number of experimental observations from metallic glasses is demonstrated. A key to this success is to focus on the dependence on Poisson's ratio, following the work of Novikov and Sokolov,^1 that characterizes the interaction between local density and shear fluctuations. To our knowledge, this is the first model to predict Tg and m quantitatively from microscopic variables. It presents a simple conceptual framework that should provide the basis for a more general microscopic understanding of liquids and glasses, including molecular systems. 1. V. N. Novikov and A. P. Sokolov, Nature, 431, 961-963 (2004).

Egami, Takeshi; Poon, S. Joseph; Levashov, Valentin; Aga, Rachel; Morris, James

2006-03-01

336

Introduction and Motivation Structural Model for Laminated Glass Beams Conclusions and Outlook of Laminated Glass Structures  

E-print Network

Introduction and Motivation Structural Model for Laminated Glass Beams Conclusions and Outlook Analysis of Laminated Glass Structures for Photovoltaic Applications Holm Altenbach Otto November 5th, 2013 Hameln, Germany November 5th, 2013 Holm Altenbach Analysis of Laminated Glass Structures

337

Glass Forming Ability and Relaxation Behavior of Zr Based Metallic Glasses  

E-print Network

metallic glasses from the liquid melt phase and how the properties of metallic glasses change due to relaxation need to be understood better. The glass forming ability (GFA) with variation in composition and inclusion of different alloying elements...

Kamath, Aravind Miyar

2012-07-16

338

Natural analogues of nuclear waste glass corrosion.  

SciTech Connect

This report reviews and summarizes studies performed to characterize the products and processes involved in the corrosion of natural glasses. Studies are also reviewed and evaluated on how well the corrosion of natural glasses in natural environments serves as an analogue for the corrosion of high-level radioactive waste glasses in an engineered geologic disposal system. A wide range of natural and experimental corrosion studies has been performed on three major groups of natural glasses: tektite, obsidian, and basalt. Studies of the corrosion of natural glass attempt to characterize both the nature of alteration products and the reaction kinetics. Information available on natural glass was then compared to corresponding information on the corrosion of nuclear waste glasses, specifically to resolve two key questions: (1) whether one or more natural glasses behave similarly to nuclear waste glasses in laboratory tests, and (2) how these similarities can be used to support projections of the long-term corrosion of nuclear waste glasses. The corrosion behavior of basaltic glasses was most similar to that of nuclear waste glasses, but the corrosion of tektite and obsidian glasses involves certain processes that also occur during the corrosion of nuclear waste glasses. The reactions and processes that control basalt glass dissolution are similar to those that are important in nuclear waste glass dissolution. The key reaction of the overall corrosion mechanism is network hydrolysis, which eventually breaks down the glass network structure that remains after the initial ion-exchange and diffusion processes. This review also highlights some unresolved issues related to the application of an analogue approach to predicting long-term behavior of nuclear waste glass corrosion, such as discrepancies between experimental and field-based estimates of kinetic parameters for basaltic glasses.

Abrajano, T.A. Jr.; Ebert, W.L.; Luo, J.S.

1999-01-06

339

Glass: Kohlrausch exponent, fragility, anharmonicity.  

PubMed

The thermodynamical and mechanical properties of (fragile and strong) glass are modeled based on a generalised activation energy relationship log( ? ) = ?G ( ? )/RTn(T') process of glass-forming liquids. This cooperative process involves 1/n(T') elementary ? motions of activation Gibbs energy ?G ( ? ) dependent on the equivalent temperature T', the temperature of the liquid in equilibrium having the volume of the glass, function of temperature and aging conditions. From this modified VFT law the relaxation of any properties (V , H , stress, creep) can be calculated and approximated by the Kohlrausch function. This model predicts consistency relationships for: a) the temperature (and aging time) variation of the Kohlrausch exponent; b) the temperature dependence of the stabilisation time domain of strong and fragile glass; c) the linear relation between the activation parameters (E (*) energy, S (*) entropy, V (*) volume) of the ? and ? transition. The Lawson and Keyes (LK) relations are recalled and it is shown that these relations (somewhat equivalant to the compensation law or Meyer-Neldel rule) are observed generally in glass. Morever the (macroscopic) ratios ?H/?V observed during aging or after a temperature jump and the (microscopic) ratio E (*)/V (*) are found equal to ?? (? compressibily, ? Grüneisen parameter), in agreement with the LK predictions. From various experiments and in agreement with predictions of this model we conclude that the Grüneisen parameter ? ( B ) (pressure derivative of the bulk modulus) and the Mean Square Displacement (MSD) characterising the anharmonicity of solids (and liquids) are the main parameters which govern the relaxation properties of the glass state. Linear relations between the parameters ? ( B ), the fragility m, and the Kohlrausch exponent n ( g ) at T ( g ) are explained. These correlations underscore a strong relationship between the fragilty of glass formers and the extent of the anharmonicity in the interatomic interactions. PMID:22526977

Rault, J

2012-04-01

340

Multiple reentrant glass transitions in confined hard-sphere glasses  

NASA Astrophysics Data System (ADS)

Glass-forming liquids exhibit a rich phenomenology upon confinement. This is often related to the effects arising from wall-fluid interactions. Here we focus on the interesting limit where the separation of the confining walls becomes of the order of a few particle diameters. For a moderately polydisperse, densely packed hard-sphere fluid confined between two smooth hard walls, we show via event-driven molecular dynamics simulations the emergence of a multiple reentrant glass transition scenario upon a variation of the wall separation. Using thermodynamic relations, this reentrant phenomenon is shown to persist also under constant chemical potential. This allows straightforward experimental investigation and opens the way to a variety of applications in micro- and nanotechnology, where channel dimensions are comparable to the size of the contained particles. The results are in line with theoretical predictions obtained by a combination of density functional theory and the mode-coupling theory of the glass transition.

Mandal, Suvendu; Lang, Simon; Gross, Markus; Oettel, Martin; Raabe, Dierk; Franosch, Thomas; Varnik, Fathollah

2014-07-01

341

Multiple reentrant glass transitions in confined hard-sphere glasses  

E-print Network

Glass forming liquids exhibit a rich phenomenology upon confinement. This is often related to the effects arising from wall-fluid interactions. Here we focus on the interesting limit where the separation of the confining walls becomes of the order of a few particle diameters. For a moderately polydisperse, densely packed hard-sphere fluid confined between two smooth hard walls, we show via event-driven molecular dynamics simulations the emergence of a multiple reentrant glass transition scenario upon a variation of the wall separation. Using thermodynamic relations, this reentrant phenomenon is shown to persist also under constant chemical potential. This allows straightforward experimental investigation and opens the way to a variety of applications in micro- and nanotechnology, where channel dimensions are comparable to the size of the contained particles. The results are in-line with theoretical predictions obtained by a combination of density functional theory and the mode-coupling theory of the glass transition.

S. Mandal; S. Lang; M. Gross; M. Oettel; D. Raabe; T. Franosch; F. Varnik

2014-06-20

342

Effects of ionization on silicate glasses. [Silicate glasses  

SciTech Connect

This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures.

Primak, W.

1982-02-01

343

Calorimetric Study of Kinetic Glass Transition in Metallic Glasses  

SciTech Connect

Differential scanning calorimetry (DSC) experiments were carried out for a bulk metallic glass (BMG), Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10.0}Be{sub 22.5}, below and above the glass transition temperature T{sub g}. The T{sub g} values were determined from the DSC curves. A wide range of heating rate, q = dT/dt = 0.1-100 K/min, was adopted for the experiment, and the q dependence of the apparent T{sub g} was investigated. As q was decreased, the value of T{sub g} decreased rapidly, then more slowly, and seemed to approach a constant value at low q. The experimental result of this kinetic glass transition phenomenon was analyzed on the basis of the relaxation process occurring in the transition temperature range.

Hiki, Y. [Faculty of Science, Tokyo Institute of Technology, 39-3-303 Motoyoyogi, Shibuya-ku, Tokyo 151-0062 (Japan); Takahashi, H. [Institute of Applied Beam Science, Graduate School of Science and Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi 316-8511 (Japan)

2008-02-21

344

Database for waste glass composition and properties  

SciTech Connect

A database of waste glass composition and properties, called the PNL Waste Glass Database, has been developed. The source of data is published literature and files from projects funded by the US Department of Energy. The glass data have been organized into categories and corresponding data files have been prepared. These categories are glass chemical composition, thermal properties, leaching data, waste composition, glass radionuclide composition and crystallinity data. The data files are compatible with commercial database software. Glass compositions are linked to properties across the various files using a unique glass code. Programs have been written in database software language to permit searches and retrievals of data. The database provides easy access to the vast quantities of glass compositions and properties that have been studied. It will be a tool for researchers and others investigating vitrification and glass waste forms.

Peters, R.D.; Chapman, C.C.; Mendel, J.E. [Pacific Northwest Lab., Richland, WA (United States); Williams, C.G. [Central Michigan Univ., Mount Pleasant (Midway Islands)

1993-12-31

345

Database for waste glass composition and properties  

SciTech Connect

A database of waste glass composition and properties, called PNL Waste Glass Database, has been developed. The source of data is published literature and files from projects funded by the US Department of Energy. The glass data have been organized into categories and corresponding data files have been prepared. These categories are glass chemical composition, thermal properties, leaching data, waste composition, glass radionuclide composition and crystallinity data. The data files are compatible with commercial database software. Glass compositions are linked to properties across the various files using a unique glass code. Programs have been written in database software language to permit searches and retrievals of data. The database provides easy access to the vast quantities of glass compositions and properties that have been studied. It will be a tool for researchers and others investigating vitrification and glass waste forms.

Peters, R.D.; Chapman, C.C.; Mendel, J.E. [Pacific Northwest Lab., Richland, WA (United States); Williams, C.G. [Central Michigan Univ., Mount Pleasant, MI (United States)

1993-09-01

346

HLW Glass Studies: Development of Crystal-Tolerant HLW Glasses  

SciTech Connect

In our study, a series of lab-scale crucible tests were performed on designed glasses of different compositions to further investigate and simulate the effect of Cr, Ni, Fe, Al, Li, and RuO2 on the accumulation rate of spinel crystals in the glass discharge riser of the HLW melter. The experimental data were used to expand the compositional region covered by an empirical model developed previously (Matyáš et al. 2010b), improving its predictive performance. We also investigated the mechanism for agglomeration of particles and impact of agglomerates on accumulation rate. In addition, the TL was measured as a function of temperature and composition.

Matyas, Josef; Huckleberry, Adam R.; Rodriguez, Carmen P.; Lang, Jesse B.; Owen, Antionette T.; Kruger, Albert A.

2012-04-02

347

Electrical conduction and glass relaxation in alkali- silicate glasses  

NASA Astrophysics Data System (ADS)

Electrical response measurements from 1 Hz to 1 MHz between 50o and 540oC were made on potassium, sodium and lithium-silicate glasses with low alkali oxide contents. Conductivity and electrical relaxation responses for both annealed and air quenched glasses of the same composition were compared. Quenching was found to lower the dc conductivity, ?dc, and activation energy as well as increase the pre-exponential term when compared to the corresponding annealed glass of the same composition. All of the glasses exhibited Arrhenius behavior in the log ?dc against 1/T plots. A sharp decrease in ?dc was observed for glasses containing alkali concentrations of 7 mol% or less. The ?dc activation energy exhibited similar behavior when plotted as a function of alkali composition and was explained in terms of a mixture of the weak and strong electrolyte models. The depression angle for fits to the complex impedance data were also measured as a function of thermal history, alkali concentration and alkali species. These results were interpreted in terms of changes in the distribution of relaxation times. Annealed samples from a single melt of a 10 mol% K2O-90SiO2 glass were reheated to temperatures ranging from 450o to 800oC, held isothermally for 20 min, and then quenched in either air or silicon oil. The complex impedance of both an annealed and the quenched samples were then measured as a function of temperature from 120o to 250oC. The ?dc was found to be remain unaffected by heat treatments below 450oC, to increase rapidly over an approximate 200oC range of temperatures that was dependent on cooling rate and to be constant for heat treatments above this range. This behavior is interpreted in terms of the mean structural relaxation time as a function of temperature and cooling rate near the glass transition temperature and glass transformation ranges. A more detailed definition for the transition and transformation temperatures and ranges was also provided.

Angel, Paul William

348

Controlled morphology of Nafion^ perflourinated ionomer membrane and poly(vinylidene-co-trifluoroethylene) blends for swelling suppression.  

NASA Astrophysics Data System (ADS)

The major objective of the present study is concerned with the swelling suppression of Nafion^ membrane upon hydration through blending with poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) copolymer. The phase diagram of the Nafion/PVDF-TrFE blend was established by differential scanning calorimetry, cloud point measurement, and optical microscopy. A theoretical phase diagram was calculated by self-consistently solving the combined Flory-Huggins free energy for liquid-liquid demixing and the phase field free energy for crystal solidification. The resulting phase diagram is the combined LCST-UCST and/or an hour glass type. Guided by the phase diagram, the phase separated domain morphology can be controlled to exhibit bicontinuous or dispersed domains via phase separation by solvent casting or thermal quenching. The blends thus prepared not only afford suppression of water uptake, but also render dimensional stability. Fourier transform infrared spectroscopy studies and water uptake measurement showed infallible evidence that modification of Nafion^ with PVDF-TrFE reduces swelling upon hydration.

Nazir, Nadzrinahamin Ahmad; Kyu, Thein

2009-03-01

349

Yttrium-silicon-aluminum oxynitride glass fibers  

SciTech Connect

This paper reports on fibers made from Y-Si-Al-O-N glasses previously shown to have excellent mechanical properties and outstanding water corrosion resistance. Fibers of glasses containing, respectively, 3.2 and 6.6 wt% N were pulled free-hand in air and from glass rods in N{sub 2}. Continuous fibers (up to several kilometers long) of the former glass were melt-drawn in N{sub 2} while being wound in air outside of the glass-melting furnace. The fibers, some as small as 10 XX in diameter, retained the desirable properties of the bulk glass.

Messier, D.R.; Gleisner, R.P.; Rich, R.E. (AMTL, Watertown, MA (US))

1989-11-01

350

Study Of Phase Separation In Glass  

NASA Technical Reports Server (NTRS)

Report describes an experimental study of effect of hydroxide content on phase separation in soda/silica glasses. Ordinary and gel glasses melted at 1,565 degree C, and melts stirred periodically. "Wet" glasses produced by passing bubbles of N2 saturated with water through melts; "dry" glasses prepared in similar manner, except N2 dried before passage through melts. Analyses of compositions of glasses performed by atomic-absorption and index-of-refraction measurements. Authors conclude hydroxide speeds up phase separation, regardless of method (gel or ordinary) by which glass prepared. Eventually helps material scientists to find ways to control morphology of phase separation.

Neilson, George F.; Weinberg, Michael C.; Smith, Gary L.

1989-01-01

351

Elastic Heterogeneity in Metallic Glasses  

SciTech Connect

When a stress is applied on a metallic glass it deforms following Hook's law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about 3/4 in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.

Dmowski, Wojciech [ORNL; Iwashita, T. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Chuang, C.-P. [University of Tennessee, Knoxville (UTK); Almer, J. [Argonne National Laboratory (ANL); Egami, T. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)

2010-01-01

352

Elastic heterogeneity in metallic glasses.  

SciTech Connect

When a stress is applied on a metallic glass it deforms following Hook's law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about 3/4 in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.

Dmowski, , W.; Iwashita, T.; Chuang, C.-P.; Almer, J. D; Egami, T.; X-Ray Science Division; Univ. of Tennessee; ORNL

2010-01-01

353

Librational fluctuations in protein glasses.  

PubMed

Librational motions in the region of the protein "glass" (or dynamic) transition are analysed for spin-labelled haemoglobin, serum albumin and ?-lactoglobulin by EPR spectroscopy. A discontinuity in the temperature dependence of the mean-square librational amplitude, , occurs in the region of 200K as found for the mean-square atomic displacement, , at the protein dynamic transition by Mössbauer spectroscopy and neutron scattering. The discontinuity in vs. T can be described by the Vogel-Tammann-Fulcher equation, implying a finite glass transition temperature. Above the dynamic transition, vs. 1/T can be approximated by the Arrhenius law with activation energies similar to those usually found for , and relaxation processes in glass-forming media and the hydration shells of proteins. Similar results are found for librational fluctuations of membranous Na,K-ATPase spin-labelled either on superficial SH groups or on those essential to activity. PMID:23669570

Marsh, Derek; Bartucci, Rosa; Guzzi, Rita; Sportelli, Luigi; Esmann, Mikael

2013-08-01

354

Processing of bulk metallic glass.  

PubMed

Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)-based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass-transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF-based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made. PMID:20496386

Schroers, Jan

2010-04-12

355

Glasses for seeing beyond visible.  

PubMed

Conventional glasses based on oxides have a transparency limited by phonon absorption in the near IR region and have a limited interest for analyzing information located far beyond the visible. The IR spectral domain is nevertheless of prime interest, since it covers fundamental wavelength ranges used for thermal imaging as well as molecular vibrational signatures. Besides spectacular advances in the field of IR detectors, the main significant progresses are related to the development of IR glass optics, such as lenses or IR optical fibres. The field of IR glasses is almost totally dominated by glasses formed from heavy atoms such as the chalcogens S, Se and Te. Their transparency extends up to 12, 16 and 28 microm for sulfide-, selenide- and the new generation of telluride-based glasses, respectively. They cover the atmospheric transparency domains, 3-5 and 8-13 microm, respectively, at which the IR radiation can propagate allowing thermal imaging and night-vision operations through thick layers of atmosphere. The development of new glass compositions will be discussed on the basis of structural consideration with the objective of moulding low-cost lenses for IR cameras used, for instance, in car-driving assistance. Additionally, multimode, single-index, optical fibres operating in the 3 to 12 microm window developed for in situ remote evanescent-wave IR spectroscopy will also be mentioned. The detection of molecular IR signatures is applied to environmental monitoring for investigating the pollution of underground water with toxic molecules. The extension of this technique to the investigation of biomolecules in three different studies devoted to liver tissues analysis, bio-film formation, and cell metabolism will also be discussed. Finally we will mention the developments in the field of single-mode fibres operating around 10 mum for the Darwin space mission, which is aiming at discovering, signs of biological life in telluric earth-like exoplanets throughout the universe. PMID:18067106

Zhang, XiangHua; Bureau, Bruno; Lucas, Pierre; Boussard-Pledel, Catherine; Lucas, Jacques

2008-01-01

356

Glass Transition in Confined Geometry  

E-print Network

Extending mode-coupling theory, we elaborate a microscopic theory for the glass transition of liquids confined between two parallel flat hard walls. The theory contains the standard MCT equations in bulk and in two dimensions as limiting cases and requires as input solely the equilibrium density profile and the structure factors of the fluid in confinement. We evaluate the phase diagram as a function of the distance of the plates for the case of a hard sphere fluid and obtain an oscillatory behavior of the glass transtion line as a result of the structural changes related to layering.

Simon Lang; Vitalie Botan; Martin Oettel; David Hajnal; Thomas Franosch; Rolf Schilling

2010-08-23

357

Spin Glasses: A Ghost Story  

Microsoft Academic Search

Extensive experimental and numerical studies of the non-equilibrium dynamics\\u000aof spin glasses subjected to temperature or bond perturbations have been\\u000aperformed to investigate chaos and memory effects in selected spin glass\\u000asystems. Temperature shift and cycling experiments were performed on the\\u000astrongly anisotropic Ising-like system {\\\\ising} and the weakly anisotropic\\u000aHeisenberg-like system {\\\\AgMn}, while bond shift and cycling simulations were

P. E. Jonsson; R. Mathieu; P. Nordblad; H. Yoshino; H. Aruga Katori; A. Ito

2003-01-01

358

Glass fibers as radiation detectors  

NASA Astrophysics Data System (ADS)

The applicability of fiber-optic systems as dosimeters for ionizing radiation is discussed. The radiation sensitivities of different types of fibers show that lead-glass fibers should be used, if a small-sized dosimeter based on attenuation is required. On the other hand, Ge-doped fibers may be applied if a great length of fiber is needed. A distributed radiation sensor based on the OTDR (optical time-domain reflectometry) method is proposed for the radiation surveillance of nuclear facilities. For applications in radiotherapy, a small-sized lead-glass .dosimeter was developed.

Hille, R.; Bueker, H.; Haesing, F. W.

1990-12-01

359

Molecular random tilings as glasses  

PubMed Central

We have recently shown that p-terphenyl-3,5,3?,5?-tetracarboxylic acid adsorbed on graphite self-assembles into a two-dimensional rhombus random tiling. This tiling is close to ideal, displaying long-range correlations punctuated by sparse localized tiling defects. In this article we explore the analogy between dynamic arrest in this type of random tilings and that of structural glasses. We show that the structural relaxation of these systems is via the propagation–reaction of tiling defects, giving rise to dynamic heterogeneity. We study the scaling properties of the dynamics and discuss connections with kinetically constrained models of glasses. PMID:19720990

Garrahan, Juan P.; Stannard, Andrew; Blunt, Matthew O.; Beton, Peter H.

2009-01-01

360

Manufacturing unique glasses in space  

NASA Technical Reports Server (NTRS)

An air suspension melting technique is described for making glasses from substances which to date have been observed only in the crystalline condition. A laminar flow vertical wind tunnel was constructed for suspending oxide melts that were melted using the energy from a carbon dioxide laser beam. By this method it is possible to melt many high-melting-point materials without interaction between the melt and crucible material. In addition, space melting permits cooling to suppress crystal growth. If a sufficient amount of under cooling is accompanied by a sufficient increase in viscosity, crystallization will be avoided entirely and glass will result.

Happe, R. P.

1976-01-01

361

Glass-Derived Superconductive Ceramic  

NASA Technical Reports Server (NTRS)

Critical superconducting-transition temperature of 107.2 K observed in specimen made by annealing glass of composition Bi1.5Pb0.5Sr2Ca2Cu3Ox for 243 h at 840 degrees C. PbO found to lower melting temperature and viscosity of glass, possibly by acting as fluxing agent. Suggested partial substitution of lead into bismuth oxide planes of crystalline phase having Tc of 110 K stabilizes this phase and facilitates formation of it.

Bansal, Narottam P.; Farrell, D. E.

1992-01-01

362

Antiferromagnetic inclusions in lunar glass  

USGS Publications Warehouse

The magnetic susceptibility of 11 glass spherules from the Apollo 15, 16, and 17 fines and two specimens of a relatively large glass spherical shell were studied as a function of temperature from room temperature to liquid helium temperatures. All but one specimen showed the presence of antiferromagnetic inclusions. Closely spaced temperature measurements of the magnetic susceptibility below 77 K on five of the specimens showed antiferromagnetic temperature transitions (Ne??el transitions). With the exception of ilmenite in one specimen, these transitions did not correspond to any transitions in known antiferromagnetic compounds. ?? 1974.

Thorpe, A.N.; Senftle, F.E.; Briggs, C.; Alexander, C.

1974-01-01

363

DEVELOPMENT OF CRYSTAL-TOLERANT WASTE GLASSES  

SciTech Connect

The loading of high-level waste in borosilicate glasses is limited by crystallinity constraints that cannot prevent crystal accumulation on the melter bottom and in the glass discharge riser of the melter. Pacific Northwest National Laboratory is studying variations in composition that are designed to constrain high-level waste glass compositions and develop the crystal-tolerant high-level waste glasses. These glasses will allow high waste loading without decreasing the lifetime of the melter by keeping the small spinel crystals suspended in the molten glass. Adding ~1 wt% of NiO to the baseline glass caused large spinel crystals to form up to 210 µm in size and resulted in the highest accumulation rate, ~ 227 mm/year, of all tested glasses. Noble metals that were added to high-Ni glass prevented large spinel crystals from forming and decreased the accumulation rate ~ 8.5 times. Adding ~5 wt% of Fe2O3 to the baseline glass resulted in a high number density of ~10-?m spinel crystals that remained suspended in the glass melt even after 17 days at 850°C. The accumulation rate of spinel crystals in high-chromia crucibles was only slightly higher compared with the accumulation rate in double crucibles. Only baseline glass exhibited about 2.6 times faster accumulation rate because of increased number of bigger crystals. These crystals were the result of glass enrichment with chromium that was leached out from the walls of high-chromia crucibles.

Matyas, Josef; Vienna, John D.; Kimura, Akihiko; Schaible, Micah J.; Tate, Rachel M.

2010-10-26

364

Theories of glass formation and the glass transition  

NASA Astrophysics Data System (ADS)

This key-issues review is a plea for a new focus on simpler and more realistic models of glass-forming fluids. It seems to me that we have too often been led astray by sophisticated mathematical models that beautifully capture some of the most intriguing features of glassy behavior, but are too unrealistic to provide bases for predictive theories. As illustrations of what I mean, the first part of this article is devoted to brief summaries of imaginative, sensible, but disparate and often contradictory ideas for solving glass problems. Almost all of these ideas remain alive today, with their own enthusiastic advocates. I then describe numerical simulations, mostly by H Tanaka and coworkers, in which it appears that very simple, polydisperse systems of hard disks and spheres develop long range, Ising-like, bond-orientational order as they approach glass transitions. Finally, I summarize my recent proposal that topologically ordered clusters of particles, in disordered environments, tend to become aligned with each other as if they were two-state systems, and thus produce the observed Ising-like behavior. Neither Tanaka's results nor my proposed interpretation of them fit comfortably within any of the currently popular glass theories.

Langer, J. S.

2014-04-01

365

Structure glass technology : systems and applications  

E-print Network

Glass cannot compete with steel in terms of strength or durability, but it is the only structural material that offers the highly sought after qualities of translucency and transparency. The use of glass has evolved from ...

Leitch, Katherine K. (Katherine Kristen)

2005-01-01

366

The Conservation of Seventeenth Century Archaeological Glass  

E-print Network

is the only chance for the objects survival. Though glass is considered one of the most stable archaeological materials, noninvasive, reversible treatments are not always possible given the level of deterioration glass objects undergo within the archaeological...

Arcak, Cory

2010-10-12

367

High modulus high temperature glass fibers  

NASA Technical Reports Server (NTRS)

The search for a new high-modulus, high-temperature glass fiber involved the preparation of 500 glass compositions lying in 12 glass fields. These systems consisted primarily of low atomic number oxides and rare-earth oxides. Direct optical measurements of the kinetics of crystallization of the cordierite-rare earth system, for example, showed that the addition of rare-earth oxides decreased the rate of formation of cordierite crystals. Glass samples prepared from these systems proved that the rare-earth oxides made large specific contributions to the Young's modulus of the glasses. The best glasses have moduli greater than 21 million psi, the best glass fibers have moduli greater than 18 million psi, and the best glass fiber-epoxy resin composites have tensile strengths of 298,000 psi, compressive strengths of at least 220,000 psi, flexural strengths of 290,000 psi, and short-beam shear strengths of almost 17,000 psi.

Bacon, J. F.

1973-01-01

368

Heating-induced glass-glass and glass-liquid transformations in computer simulations of water  

NASA Astrophysics Data System (ADS)

Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T "phase diagram" for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related, both being associated with the limit of kinetic stability of LDA (HDA).

Chiu, Janet; Starr, Francis W.; Giovambattista, Nicolas

2014-03-01

369

Heating-induced glass-glass and glass-liquid transformations in computer simulations of water.  

PubMed

Water exists in at least two families of glassy states, broadly categorized as the low-density (LDA) and high-density amorphous ice (HDA). Remarkably, LDA and HDA can be reversibly interconverted via appropriate thermodynamic paths, such as isothermal compression and isobaric heating, exhibiting first-order-like phase transitions. We perform out-of-equilibrium molecular dynamics simulations of glassy water using the ST2 model to study the evolution of LDA and HDA upon isobaric heating. Depending on pressure, glass-to-glass, glass-to-crystal, glass-to-vapor, as well as glass-to-liquid transformations are found. Specifically, heating LDA results in the following transformations, with increasing heating pressures: (i) LDA-to-vapor (sublimation), (ii) LDA-to-liquid (glass transition), (iii) LDA-to-HDA-to-liquid, (iv) LDA-to-HDA-to-liquid-to-crystal, and (v) LDA-to-HDA-to-crystal. Similarly, heating HDA results in the following transformations, with decreasing heating pressures: (a) HDA-to-crystal, (b) HDA-to-liquid-to-crystal, (c) HDA-to-liquid (glass transition), (d) HDA-to-LDA-to-liquid, and (e) HDA-to-LDA-to-vapor. A more complex sequence may be possible using lower heating rates. For each of these transformations, we determine the corresponding transformation temperature as function of pressure, and provide a P-T "phase diagram" for glassy water based on isobaric heating. Our results for isobaric heating dovetail with the LDA-HDA transformations reported for ST2 glassy water based on isothermal compression/decompression processes [Chiu et al., J. Chem. Phys. 139, 184504 (2013)]. The resulting phase diagram is consistent with the liquid-liquid phase transition hypothesis. At the same time, the glass phase diagram is sensitive to sample preparation, such as heating or compression rates. Interestingly, at least for the rates explored, our results suggest that the LDA-to-liquid (HDA-to-liquid) and LDA-to-HDA (HDA-to-LDA) transformation lines on heating are related, both being associated with the limit of kinetic stability of LDA (HDA). PMID:24655190

Chiu, Janet; Starr, Francis W; Giovambattista, Nicolas

2014-03-21

370

Yttrium-silicon-aluminum oxynitride glass fibers  

Microsoft Academic Search

This paper reports on fibers made from Y-Si-Al-O-N glasses previously shown to have excellent mechanical properties and outstanding water corrosion resistance. Fibers of glasses containing, respectively, 3.2 and 6.6 wt% N were pulled free-hand in air and from glass rods in Nâ. Continuous fibers (up to several kilometers long) of the former glass were melt-drawn in Nâ while being wound

Donald R. Messier; Robert P. Gleisner; Ronald E. Rich

1989-01-01

371

Inhomogeneous deformation in metallic glasses  

Microsoft Academic Search

The present study provides a theoretical framework for the inhomogeneous deformation in metallic glasses. The free volume concentration is adopted as the order parameter, which is a function of position and time. The three processes that can change the local free volume concentration are diffusion, annihilation, and stress-driven creation. The rate functions for free volume generation and plastic flow depend

R. Huang; Z. Suo; J. H. Prevost; W. D. Nix

2002-01-01

372

The Glass Transition in Basalt  

Microsoft Academic Search

The glass transition has been experimentally detected in basalt as (1) an increase in the aggregate !inear thermal expansion coefficient al:, (2) an abrupt change in the temperature dependence of Young's modulus dE\\/dT, and (3) a change in stress relaxation behavior that effectively separates the T > T G and T < TG creep regimes. Transition temperatures determined by the

Michael P. Ryan; Charles G. Sammis

1981-01-01

373

Scaling stiffness of spin glasses  

Microsoft Academic Search

The concept of a scaling stiffness for frustrated systems is introduced. Physical arguments supported by numerical calculations on a 3d Heisenberg spin glass suggest that its apparent lower critical dimensionality is time dependent, being equal to three on short time scales and bigger than three at sufficiently long times.

J. R. Banavar; M. Cieplak

1983-01-01

374

Glass Transition and the Coulomb Gap in Electron Glasses M. Muller and L. B. Ioffe  

E-print Network

Glass Transition and the Coulomb Gap in Electron Glasses M. Mu¨ller and L. B. Ioffe Department December 2004) We establish the connection between the presence of a glass phase and the appearance correlations in a systematic way, we show that in the case of strong disorder a continuous glass transition

Müller, Markus

375

Disconnected Glass-Glass Transitions and Diffusion Anomalies in a Model with Two Repulsive Length Scales  

E-print Network

Disconnected Glass-Glass Transitions and Diffusion Anomalies in a Model with Two Repulsive Length-coupling-theory calculations, we report a novel scenario for multiple glass tran- sitions in a purely repulsive spherical potential: the square shoulder. The liquid-glass transition lines exhibit both melting by cooling

Zaccarelli, Emanuela

376

Draining our Glass: An Energy and Heat Characterization of Google Glass  

E-print Network

Draining our Glass: An Energy and Heat Characterization of Google Glass Robert LiKamWa, Zhen Wang The Google Glass is a mobile device designed to be worn as eyeglasses. This form factor enables new use cases resources on a hands-free display. Recent interest has drawn to Google's spectacle- shaped device, Glass

Zhong, Lin

377

Dependence on pressure of the glass transition temperature for a prototypical glass forming liquid  

E-print Network

Dependence on pressure of the glass transition temperature for a prototypical glass forming liquid transition in the prototypic glass-former glycerol over the temperature range from 193 K, its atmospheric-pressure value, to 320 K, the glass transition temperature at 52.5 kbar. These very high pressures were obtained

Wysin, Gary

378

The corrosion behavior of DWPF glasses  

SciTech Connect

The authors analyzed the corroded surfaces of reference glasses developed for the Defense Waste Processing Facility (DWPF) to characterize their corrosion behavior. The corrosion mechanism of nuclear waste glasses must be known in order to provide source terms describing radionuclide release for performance assessment calculations. Different DWPF reference glasses were corroded under conditions that highlighted various aspects of the corrosion process and led to different extents of corrosion. The glasses corroded by similar mechanisms, and a phenomenological description of their corrosion behavior is presented here. The initial leaching of soluble glass components results in the formation of an amorphous gel layer on the glass surface. The gel layer is a transient phase that transforms into a layer of clay crystallites, which equilibrates with the solution as corrosion continues. The clay layer does not act as a barrier to either water penetration or glass dissolution, which continues beneath it, and may eventually separate from the glass. Solubility limits for glass components may be established by the eventual precipitation of secondary phases; thus, corrosion of the glass becomes controlled by the chemical equilibrium between the solution and the assemblage of secondary phases. In effect, the solution is an intermediate phase through which the glass transforms to an energetically more favorable assemblage of phases. Implications regarding the prediction of long-term glass corrosion behavior are discussed.

Ebert, W.L.; Bates, J.K. [Argonne National Lab., IL (United States). Chemical Technology Div.

1995-06-01

379

Reduction of Eu3+ in aluminoborosilicate glasses  

E-print Network

.16.Fh, 61.72.Hh, 61.80.Fe keywords : borosilicate glasses, rare-earth reduction, irradiation1 Reduction of Eu3+ to Eu2+ in aluminoborosilicate glasses under ionizing radiation E. Malchukova, France Abstract Eu2O3-doped aluminoborosilicate glasses were prepared by melting in air at high

Paris-Sud XI, Université de

380

Method for milling and drilling glass  

NASA Technical Reports Server (NTRS)

A process for machining glass by placing a rotating carbide working surface under minimum pressure against an area of glass to be worked is described. Concurrently the region between the working surface and the area of glass is wet with a lubricant consisting essentially of a petroleum carrier, a complex mixture of esters and a complex mixture of naturally occurring aromatic oils.

Rice, S. H. (inventor)

1980-01-01

381

High-Temperature Viscosity of Commercial Glasses  

SciTech Connect

Arrhenius models were developed for glass viscosity within the processing temperature of six types of commercial glasses: low-expansion-borosilicate glasses, E glasses, fiberglass wool glasses, TV panel glasses, container glasses, and float glasses. Both local models (for each of the six glass types) and a global model (for the composition region of commercial glasses, i.e., the six glass types taken together) are presented. The models are based on viscosity data previously obtained with rotating spindle viscometers within the temperature range between 900 C and 1550 C; the viscosity varied from 1 Pa?s to 750 Pa?s. First-order models were applied to relate Arrhenius coefficients to the mass fractions of 15 components: SiO2, TiO2, ZrO2, Al2O3, Fe2O3, B2O3, MgO, CaO, SrO, BaO, PbO, ZnO, Li2O, Na2O, K2O. The R2 is 0.98 for the global model and ranges from .097 to 0.99 for the six local models. The models are recommended for glasses containing 42 to 84 mass% SiO2 to estimate viscosities or temperatures at a constant viscosity for melts within both the temperature range from 1100 C to 1550 C and viscosity range from 5 to 400 Pa?s.

Hrma, Pavel R.

2006-08-31

382

Diffusion in metallic glasses and supercooled melts  

Microsoft Academic Search

Amorphous metallic alloys, also called metallic glasses, are of considerable technological importance. The metastability of these systems, which gives rise to various rearrangement processes at elevated temperatures, calls for an understanding of their diffusional behavior. From the fundamental point of view, these metallic glasses are the paradigm of dense random packing. Since the recent discovery of bulk metallic glasses it

Franz Faupel; Werner Frank; Michael-Peter Macht; Helmut Mehrer; Volkmar Naundorf; Klaus Rätzke; Herbert R. Schober; Suman K. Sharma; Helmar Teichler

2003-01-01

383

Jagged Edges of the Glass Ceiling  

ERIC Educational Resources Information Center

Although many aspiring young women might believe the glass ceiling was shattered a decade ago, they still need to understand how that glass ceiling impacted an older generation of women in educational leadership. They also must be aware that some segments of the glass ceiling might still exist. This article provides a historical overview of the…

Robinson, Victoria L.

2004-01-01

384

Extruded tellurite glass optical fiber preforms  

Microsoft Academic Search

The extrusion behavior of tellurite glass in the supercooled liquid region was investigated. Good extrusion formability was observed under low strain rates at various temperatures in the glass transformation region investigated. Tube and holey fiber (HF) preforms were fabricated from tellurite glass billets using a laboratory press. In particular, the results for three-spoke HF design and round tube preforms with

Amit Belwalkar; Hongsheng Xiao; Wojciech Z. Misiolek; Jean Toulouse

2010-01-01

385

Insulating spacer for double insulated glass  

Microsoft Academic Search

An improved insulating spacer to reduce the heat transfer between the two panes of glass of double insulated glass comprises an extruded or roll-formed metal spacer together with plastic insulating elements which thermally isolate the metal spacer from the panes of glass while permitting conventional application of the sealant to provide reliable bonding. In one embodiment the plastic insulator comprises

1977-01-01

386

Nickel-iron spherules from aouelloul glass  

USGS Publications Warehouse

Nickel-iron spherules, ranging from less than 0.2 to 50 microns in diameter and containing 1.7 to 9.0 percent Ni by weight, occur in glass associated with the Aouelloul crater. They occur in discrete bands of siliceous glass enriched in dissolved iron. Their discovery is significant tangible evidence that both crater and glass originated from terrestrial impact.

Chao, E. C. T.; Dwornik, E. J.; Merrill, C. W.

1966-01-01

387

On spin glass fluctuations C. de Dominicis  

E-print Network

the spin glass transition from the realm ofnature and rejecting it to zero temperature while shifting spinL-205 On spin glass fluctuations C. de Dominicis Service de Physique Théorique, CEN Saclay, 91191 function Q03B103B2p Q03B103B2-p> for the short range spin glass, around Parisi mean field solution

Boyer, Edmond

388

Glass transition temperature and topological constraints of sodium borophosphate glass-forming liquids  

NASA Astrophysics Data System (ADS)

Sodium borophosphate glasses exhibit intriguing mixed network former effect, with the nonlinear compositional dependence of their glass transition temperature as one of the most typical examples. In this paper, we establish the widely applicable topological constraint model of sodium borophosphate mixed network former glasses to explain the relationship between the internal structure and nonlinear changes of glass transition temperature. The application of glass topology network was discussed in detail in terms of the unified methodology for the quantitative distribution of each coordinated boron and phosphorus units and glass transition temperature dependence of atomic constraints. An accurate prediction of composition scaling of the glass transition temperature was obtained based on topological constraint model.

Jiang, Qi; Zeng, Huidan; Liu, Zhao; Ren, Jing; Chen, Guorong; Wang, Zhaofeng; Sun, Luyi; Zhao, Donghui

2013-09-01

389

The properties of glass resistive plate chambers made of different glasses  

NASA Astrophysics Data System (ADS)

Glass resistive plate chambers (GRPCs) have been proposed as the basic element for the JUNO top tracker detector. With good uniform performance and low cost, GRPCs are well suited for large area experiments. Glass RPCs used in underground experiments require specially designed cassette and gas flow systems, since the glass is fragile and easily corroded by acid generated by water entering the gas-filled chamber. High-strength and chemical-resistant glasses have been proposed for underground experiments. We present here the test results of four GRPC chambers made of different glasses: normal thin glass, two high-strength glasses, and a chemical-resistant glass. The chemical-resistant and high-strength glasses have good surface quality, but their volume resistivities are higher. Higher resistivities lead to a higher required voltage to reach plateau operation, meaning that these glasses can only work in a very low rate experiment.

Han, R.; Shi, Z.; Laktineh, I.; Chen, Y.; Zhang, J.; Qian, S.; Ning, Z.

2014-09-01

390

Design of Energy-Friendly Glass Fibers  

NASA Astrophysics Data System (ADS)

Incumbent fiberglass compositions rely on decades of commercial experience. From a compositional point of view, many of these melts require more energy than needed in their production, or emit toxic effluents into the environment. This chapter reviews the design of energy- and/or environmentally friendly E-glass, HT-glass, ECR-glass, A-glass, and C-glass compositions, which have lower viscosities or fiber-forming temperatures and therefore require less energy in a commercial furnace than the respective incumbent compositions and/or do not contain ingredients which are of environmental concern.

Wallenberger, Frederick T.

391

Dynamics of Glass Relaxation at Room Temperature  

NASA Astrophysics Data System (ADS)

The problem of glass relaxation under ambient conditions has intrigued scientists and the general public for centuries, most notably in the legend of flowing cathedral glass windows. Here we report quantitative measurement of glass relaxation at room temperature. We find that Corning® Gorilla® Glass shows measurable and reproducible relaxation at room temperature. Remarkably, this relaxation follows a stretched exponential decay rather than simple exponential relaxation, and the value of the stretching exponent (?=3/7) follows a theoretical prediction made by Phillips for homogeneous glasses.

Welch, Roger C.; Smith, John R.; Potuzak, Marcel; Guo, Xiaoju; Bowden, Bradley F.; Kiczenski, T. J.; Allan, Douglas C.; King, Ellyn A.; Ellison, Adam J.; Mauro, John C.

2013-06-01

392

Dynamics of glass relaxation at room temperature.  

PubMed

The problem of glass relaxation under ambient conditions has intrigued scientists and the general public for centuries, most notably in the legend of flowing cathedral glass windows. Here we report quantitative measurement of glass relaxation at room temperature. We find that Corning® Gorilla® Glass shows measurable and reproducible relaxation at room temperature. Remarkably, this relaxation follows a stretched exponential decay rather than simple exponential relaxation, and the value of the stretching exponent (?=3/7) follows a theoretical prediction made by Phillips for homogeneous glasses. PMID:23848901

Welch, Roger C; Smith, John R; Potuzak, Marcel; Guo, Xiaoju; Bowden, Bradley F; Kiczenski, T J; Allan, Douglas C; King, Ellyn A; Ellison, Adam J; Mauro, John C

2013-06-28

393

Extraction of Proteins Glass Bead Method For preparation of protein extracts, the glass bead method is preferred. Some researchers  

E-print Network

Extraction of Proteins ­ Glass Bead Method For preparation of protein extracts, the glass bead. glass beads (106 micron glass bead, Sigma cat. No. G4649) 7. Tabletop centrifuge 8. Vortex 9 µl glass beads (106 micron glass beads, Sigma, cat. G4649). 8. Vortex at top speed for 5 minutes. 9

394

glass chemistry: structure-property relationships  

NASA Astrophysics Data System (ADS)

Pyrex® glass was one of the first commercial boroaluminosilicate glass compositions, selected in 1915 from thousands of compositions due to its ability to sustain mechanical and thermal shock. While the microscopic structure of Pyrex® glass has recently been investigated, the microscopic origins of its macroscopic properties are not well understood, i.e., the atomic scale foundation of the original empirical invention of Pyrex® glass has yet to be established. In this work, we have tackled this problem by investigating the effects of varying Si/Al and Na/B ratios on the boron and aluminum speciation and a range of physical and rheological properties in the Pyrex® glass family. We show that the canonical Pyrex® boroaluminosilicate composition is indeed optimal for attaining relatively high values of glass transition temperature and elastic moduli and a low coefficient of thermal expansion, while simultaneously maintaining a high glass-forming ability.

Smedskjaer, Morten M.; Youngman, Randall E.; Mauro, John C.

2014-08-01

395

Glass-ceramic fiber optic sensors  

NASA Astrophysics Data System (ADS)

Optical fibers with layers of glass-ceramics are considered and tested with respect to their use in different environments as single- and multimode lightguides. Glass-ceramic optical fibers are tested that have different material compositions, cross-section topologies, and coefficients of thermal expansion (CTEs). Stress-induced optical phase-temperature effects can be studied with glass ceramics that have CTEs of around zero, and the glass ceramic sensors are compared to nontreated fibers to study the dependencies of the fibers' parameters on induced stress and temperature. The application of glass-ceramics with various values of linear CTE to the fibers is studied to scale the characteristics of a glass-ceramic fiber-optic thermometer for several temperature ranges. The sensor can be stabilized when the pure stress-temperature effect is isolated. These glass-ceramic optical fibers are shown to provide unique characteristics for the use of fiber-optic measuring devices in certain measurement environments.

Romaniuk, Ryszard S.; Stepien, Ryszard

1991-03-01

396

Characterization of Savannah River Plant waste glass  

SciTech Connect

The objective of the glass characterization programs at the Savannah River Laboratory (SRL) is to ensure that glass containing Savannah River Plant high-level waste can be permanently stored in a federal repository, in an environmentally acceptable manner. To accomplish this objective, SRL is carrying out several experimental programs, including: fundamental studies of the reactions between waste glass and water, particularly repository groundwater; experiments in which candidate repository environments are simulated as accurately as possible; burial tests of simulated waste glass in candidate repository geologies; large-scale tests of glass durability; and determination of the effects of process conditions on glass quality. In this paper, the strategy and current status of each of these programs is discussed. The results indicate that waste packages containing SRP waste glass will satisfy emerging regulatory criteria.

Plodinec, M J

1985-01-01

397

Durability of Silicate Glasses: An Historical Approach  

SciTech Connect

We present a short review of current theories of glass weathering, including glass dissolution, and hydrolysis of nuclear waste glasses, and leaching of historical glasses from an XAFS perspective. The results of various laboratory leaching experiments at different timescales (30 days to 12 years) are compared with results for historical glasses that were weathered by atmospheric gases and soil waters over 500 to 3000 years. Good agreement is found between laboratory experiments and slowly leached historical glasses, with a strong enrichment of metals at the water/gel interface. Depending on the nature of the transition elements originally dissolved in the melt, increasing elemental distributions are expected to increase with time for a given glass durability context.

Farges, Francois; /Museum Natl. Hist. Natur. /Stanford U., Geo. Environ. Sci.; Etcheverry, Marie-Pierre; /Marne la Vallee U.; Haddi, Amine; /Marne la Valle U.; Trocellier,; /Saclay; Curti, Enzo; /PSI, Villigen; Brown, Gordon E., Jr.; /SLAC, SSRL

2007-01-02

398

Durability of Silicate Glasses: An Historical Approach  

SciTech Connect

We present a short review of current theories of glass weathering, including glass dissolution, and hydrolysis of nuclear waste glasses, and leaching of historical glasses from an XAFS perspective. The results of various laboratory leaching experiments at different timescales (30 days to 12 years) are compared with results for historical glasses that were weathered by atmospheric gases and soil waters over 500 to 3000 years. Good agreement is found between laboratory experiments and slowly leached historical glasses, with a strong enrichment of metals at the water/gel interface. Depending on the nature of the transition elements originally dissolved in the melt, increasing elemental distributions are expected to increase with time for a given glass durability context.

Farges, Francois [USM 201 'Mineralogie-Petrologie', Museum National d'Histoire Naturelle, CNRS UMR 7160, Paris (France); Department of Geological and Environmental Sciences, Stanford University, Stanford, CA (United States); Etcheverry, Marie-Pierre [Laboratoire des Geomateriaux, Universite de Marne la Vallee (France); Laboratoire de Recherche des Monuments Historiques, Champs sur Marne (France); Haddi, Amine [Laboratoire des Geomateriaux, Universite de Marne la Vallee (France); Trocellier, Patrick [Service de Recherches de Metallurgie Physique, Commissariat a l' Energie Atomique (CEA), Saclay (France); Curti, Enzo [Laboratory of Waste Management, Paul Scherrer Institut (PSI), Villigen (Switzerland); Brown, Gordon E. Jr. [Department of Geological and Environmental Sciences, Stanford University, Stanford, CA (United States); Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA (United States)

2007-02-02

399

Physical aging in a hyperquenched glass  

NASA Astrophysics Data System (ADS)

We report experimental data on the enthalpy relaxation of a hyperquenched silicate glass subjected to long-time aging (annealing) below the glass-transition temperature (Tg). The relaxation of a hyperquenched glass substantially differs from that of a normally cooled glass. Two mechanisms govern the relaxation of a hyperquenched glass. During relaxation of the first hyperquenched, and afterward aged glass, a relaxation endotherm occurs followed by an exotherm. This is reflected by the occurrence of crossover. By increasing the aging temperature and time, the endotherm becomes more pronounced, while the exotherm gradually disappears. The consequence of this is the shift of the crossover point to higher temperature. The relaxation of the hyperquenched glass at 0.66Tg with the aging time is highly nonexponential.

Yue, Y. Z.; Jensen, S. L.; deC. Christiansen, J.

2002-10-01

400

Development of a glass GEM  

NASA Astrophysics Data System (ADS)

Gas electron multipliers (GEMs) apply the concept of gas amplification inside many tiny holes, realizing robust and high-gain proportional counters. However, the polyimide substrate of GEMs prevents them from being used in sealed detector applications. We have fabricated and tested glass GEMs (G-GEMs) with substrates made of photosensitive glass material from the Hoya Corporation. We fabricated G-GEMs with several different hole diameters and thicknesses and successfully operated test G-GEMs with a 100×100 mm2 effective area. The uniformity of our G-GEMs was good, and the energy resolution for 5.9 keV X-rays was 18.8% under uniform irradiation of the entire effective area. A gas gain by the G-GEMs of up to 6700 was confirmed with a gas mixture of Ar (70%)+CH4 (30%). X-ray imaging using the charge division readout method was demonstrated.

Takahashi, Hiroyuki; Mitsuya, Yuki; Fujiwara, Takeshi; Fushie, Takashi

2013-10-01

401

Integrated optics sensors on glass  

NASA Astrophysics Data System (ADS)

Integrated optics has been extensively used from the beginning for telecommunication applications. Depending on the functions to implement, different technologies have been employed. Among all of them, glass ion exchange is the cheapest, since both substrate and technological requirement are not expensive. Ion exchange technology has some advantages that can be very important for sensors applications. After a brief presentation of the different possible ion exchange, we will present some integrated optics sensors realized on glass that have been made in the past few years. We will give details about the particularity required for every applications. Then, we will give some informations about biological applications and we will conclude with some limitations of this technology.

Benech, Pierre; Schanen, Isabelle; Minier, Vincent

2005-03-01

402

Magnetic antenna using metallic glass  

NASA Technical Reports Server (NTRS)

A lightweight search-coil antenna or sensor assembly for detecting magnetic fields and including a multi-turn electromagnetic induction coil wound on a spool type coil form through which is inserted an elongated coil loading member comprised of metallic glass material wrapped around a dielectric rod. The dielectric rod consists of a plastic or a wooden dowel having a length which is relatively larger than its thickness so as to provide a large length-to-diameter ratio. A tri-axial configuration includes a housing in which is located three substantially identical mutually orthogonal electromagnetic induction coil assemblies of the type described above wherein each of the assemblies include an electromagnetic coil wound on a dielectric spool with an elongated metallic glass coil loading member projecting therethrough.

Desch, Michael D. (Inventor); Farrell, William M. (Inventor); Houser, Jeffrey G. (Inventor)

1996-01-01

403

"S" Glass Manufacturing Technology Transfer  

SciTech Connect

A glass-ceramic-to metal sealing technology patented by Sandia National Laboratories, Albuquerque (SNLA) was developed by MRC-Mound for use in the manufacture of weapon components. Successful implementation attracted increasingly widespread weapon use of this technology. "S-glass" manufacturing technology was transferred to commercial vendors to ensure that weapons production schedules would be met in the coming years. Such transfer also provided sources of this fledgling technology for the Department of Defense (DOD), aerospace and other commercial uses. The steps involved in the technology transfer are described, from the initial cooperative development work of Sandia and Mound scientists and technologists to the final phase of qualifying commercial vendors for component manufacture.

Buckner, Dean, A.; McCollister, Howard, L.

1988-06-01

404

Glass mountain geothermal exploration project  

SciTech Connect

Although often perceived as time-consuming, complex, and difficult, the environmental review process for proposed geothermal exploration projects in California can be completed in a timely, straight-forward, and cost-efficient fashion. All that is required is a well-defined project and thorough understanding of the pertinent environmental issues at the beginning of the process, close coordination with the lead agencies throughout the process, and preparation of a thorough environmental document that adequately addresses all issues. An example of this type of success is the Environmental Assessment/Initial Study for the Glass Mountain Geothermal Exploration Project. For this project, California Energy General Corporation (as Unit Operator) has proposed to implement a Plan of Operation for exploratory geothermal drilling near Glass Mountain in northeastern California. Utilizing the steps outlined above, the environmental review process for the project was completed in less than 11 months, even though multiple agencies were involved in the process.

Adams, H.; McClenahan, L. [MHA Environmental Consulting, Inc., San Mateo, CA (United States); McClain, D. [CE General Corporation, Portland, OR (United States)

1995-12-31

405

Bare Bones of Bioactive Glass  

NASA Technical Reports Server (NTRS)

Paul Ducheyne, a principal investigator in the microgravity materials science program and head of the University of Pernsylvania's Center for Bioactive Materials and Tissue Engineering, is leading the trio as they use simulated microgravity to determine the optimal characteristics of tiny glass particles for growing bone tissue. The result could make possible a much broader range of synthetic bone-grafting applications. Bioactive glass particles (left) with a microporous surface (right) are widely accepted as a synthetic material for periodontal procedures. Using the particles to grow three-dimensional tissue cultures may one day result in developing an improved, more rugged bone tissue that may be used to correct skeletal disorders and bone defects. The work is sponsored by NASA's Office of Biological and Physical Research.

2000-01-01

406

Probing the glass transition from structural and vibrational properties of zero-temperature glasses  

E-print Network

We find that the density dependence of the glass transition temperature of Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) systems can be predicted from properties of the zero-temperature ($T=0$) glasses. Below a crossover density $\\rho_s$, LJ and WCA glasses show different structures, leading to different vibrational properties and consequently making LJ glasses more stable with higher glass transition temperatures than WCA ones. Above $\\rho_s$, structural and vibrational quantities of the $T=0$ glasses show scaling collapse. From scaling relations and dimensional analysis, we predict a density scaling of the glass transition temperature, in excellent agreement with simulation results. We also propose an empirical expression of the glass transition temperature using structural and vibrational properties of the $T=0$ glasses, which works well over a wide range of densities.

Lijin Wang; Ning Xu

2014-02-10

407

Probing the glass transition from structural and vibrational properties of zero-temperature glasses.  

PubMed

We find that the density dependence of the glass transition temperature of Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) systems can be predicted from properties of the zero-temperature (T=0) glasses. Below a crossover density ?s, LJ and WCA glasses show different structures, leading to different vibrational properties and consequently making LJ glasses more stable with higher glass transition temperatures than WCA ones. Above ?s, structural and vibrational quantities of the T=0 glasses show scaling collapse. From scaling relations and dimensional analysis, we predict a density scaling of the glass transition temperature, in excellent agreement with simulation results. We also propose an empirical expression of the glass transition temperature using structural and vibrational properties of the T=0 glasses, which works well over a wide range of densities. PMID:24580613

Wang, Lijin; Xu, Ning

2014-02-01

408

Probing the Glass Transition from Structural and Vibrational Properties of Zero-Temperature Glasses  

NASA Astrophysics Data System (ADS)

We find that the density dependence of the glass transition temperature of Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) systems can be predicted from properties of the zero-temperature (T=0) glasses. Below a crossover density ?s, LJ and WCA glasses show different structures, leading to different vibrational properties and consequently making LJ glasses more stable with higher glass transition temperatures than WCA ones. Above ?s, structural and vibrational quantities of the T =0 glasses show scaling collapse. From scaling relations and dimensional analysis, we predict a density scaling of the glass transition temperature, in excellent agreement with simulation results. We also propose an empirical expression of the glass transition temperature using structural and vibrational properties of the T=0 glasses, which works well over a wide range of densities.

Wang, Lijin; Xu, Ning

2014-02-01

409

Liquid glass electrodes for nanofluidics.  

PubMed

Nanofluidic devices make use of molecular-level forces and phenomena to increase their density, speed and accuracy. However, fabrication is challenging, because dissimilar materials need to be integrated in three dimensions with nanoscale precision. Here, we report a three-dimensional nanoscale liquid glass electrode made from monolithic substrates without conductive materials by femtosecond-laser nanomachining. The electrode consists of a nanochannel terminating at a nanoscale glass tip that becomes a conductor in the presence of high electric fields through dielectric breakdown, and returns to being an insulator when this field is removed. This reversibility relies on control of nanoampere breakdown currents and extremely fast heat dissipation at nanoscale volumes. We use the nanoscale liquid glass electrode to fabricate a nano-injector that includes an electrokinetic pump, 4 microm across with 0.6 microm channels, which is capable of producing well-controlled flow rates below 1 fl s(-1). The electrode can be integrated easily into other nanodevices and fluidic systems, including actuators and sensors. PMID:20473300

Lee, Sanghyun; An, Ran; Hunt, Alan J

2010-06-01

410

Gauge glass in two dimensions  

E-print Network

The gauge glass model offers an interesting example of a randomly frustrated system with a continuous O(2) symmetry. In two dimensions, the existence of a glass phase at low temperatures has long been disputed among numerical studies. To resolve this controversy, we examine the behavior of vortices whose movement generates phase slips that destroy phase rigidity at large distances. Detailed analytical and numerical studies of the corresponding Coulomb gas problem in a random potential establish that the ground state, with a finite density of vortices, is polarizable with a scale-dependent dielectric susceptibility. Screening by vortex/antivortex pairs of arbitrarily large size is present to eliminate the logarithmic divergence of the Coulomb energy of a single vortex. The observed power-law decay of the Coulomb interaction between vortices with distance in the ground state leads to a power-law divergence of the glass correlation length with temperature $T$. It is argued that free vortices possess a bound excitation energy and a nonzero diffusion constant at any $T>0$.

Lei-Han Tang

2009-12-16

411

Mozart, dice, and glass selection  

NASA Astrophysics Data System (ADS)

In a perfect world a good starting point should not be required. A Genetic Algorithm in powerful lens design software should find an optimum solution for us. As a practical matter a good starting point does matter. Time and resources may not be sufficient to generate a good design in a global optimizer quickly. In lens design a small glass catalog combined with the Hammer algorithm in ZEMAX moves the glass selection process in a search around the glass map forcing the design to consider many radically different forms in a short amount of time. From this starting point an expanded search can be undertaken by conventional design methods or in a global search algorithm. There are precedents in other fields for a narrow search method that still yields near infinite numbers of solutions. Mozart invented a game that narrows a search from a blank sheet paper and a set of notes to a single voice minuet by rolling dice. The results can be played and the dynamics manipulated to form the starting points for future compositions. Music composition software has, like lens design software, incorporated many powerful algorithms and search techniques. A simple comparison will be made. It is a long way from a protoplasm to Christie Brinkley. A good starting point means a lot whether you are an optical designer, a composer, or running the universe.

Tesar, John C.

2000-10-01

412

Spectroscopic study of biologically active glasses  

NASA Astrophysics Data System (ADS)

It is known that the chemical activity phenomenon is characteristic for some inorganic glasses and they are able to participate in biological processes of living organisms (plants, animals and human bodies). An example here is the selective removal of silicate-phosphate glass components under the influence of biological solutions, which has been applied in designing glasses acting as ecological fertilizers of controlled release rate of the nutrients for plants. The structure of model silicate-phosphate glasses containing the different amounts of the glass network formers, i.e. Ca 2+ and Mg 2+, as a binding components were studied. These elements besides other are indispensable of the normal growth of plants. In order to establish the function and position occupied by the particular components in the glass structure, the glasses were examined by FTIR spectroscopy (with spectra decomposition) and XRD methods. It has been found that the increasing amount of MgO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes systematically from a structure of the cristobalite type to a structure corresponding to forsterite type. Whilst the increasing content of CaO in the structure of silicate-phosphate glasses causes the formation of domains the structure of which changes from a structure typical for cristobalite through one similar to the structure of calcium orthophosphate, to a structure corresponding to calcium silicates. The changing character of domains structure is the reason of different chemical activity of glasses.

Szumera, M.; Wac?awska, I.; Mozgawa, W.; Sitarz, M.

2005-06-01

413

Glass etching to bridge micro- and nanofluidics.  

PubMed

In this study, a simple and economical fabrication technique bridging micro- and nanostructures is proposed. Glass molds with micro-nanostructures are fabricated by glass microlithography. The microlithography provides flexibility for structure design, and the glass etching contributes to transform the micro glass ridge to the nanoscale. Glass ridge structures with triangular cross sections are generated by undercutting, which coupled the isotropic character of glass and the shield effect of the top Cr layer upon HF etching. Further etching induced the height of the glass ridges to shrink from micro- to nanometres due to the edge effects. At the late etching stage, the geometrical change of the glass greatly slows down, which gives better control over the size of the glass ridge. By glass structure mold-copy, well repeatable, mechanically stable and tunable polydimethylsiloxane (PDMS) channels and cones are fabricated. Scanning electron microscopy (SEM) and laser interferometry (LI) are carried out to characterize the micro-nanostructures. To demonstrate their workability, sample preconcentration to a single nanochannel level is carried out. PMID:22068964

Xu, Bi-Yi; Yan, Xiao-Na; Zhang, Jia-Dong; Xu, Jing-Juan; Chen, Hong-Yuan

2012-01-21

414

Method for heating, forming and tempering a glass sheet  

DOEpatents

A method for heating, forming and tempering a glass sheet including the steps of heating at least one glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, forming the glass sheet to a predetermined configuration, and cooling an outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet.

Boaz, Premakaran Tucker (Livonia, MI); Sitzman, Gary W. (Walled Lake, MI)

1998-01-01

415

Method for heating, forming and tempering a glass sheet  

DOEpatents

A method for heating, forming and tempering a glass sheet is disclosed including the steps of heating at least one glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, forming the glass sheet to a predetermined configuration, and cooling an outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet. 2 figs.

Boaz, P.T.; Sitzman, G.W.

1998-10-27

416

Effect of Air Abrasion Preconditioning on Microleakage in Class V Restorations Under Cyclic Loading: An In-vitro Study  

PubMed Central

Background: Microleakage in class V Glass Ionomer Cement(GIC) or composite restorations at enamel or cementum margins has been cited as a reason for their failure. Air abrasion has been used to precondition tooth surface for increasing retention of such restorations. This study is done to evaluate the effect of preconditioning with air abrasion on microleakage in class V GIC and composite restorations. Materials and Methods: Class V cavities were prepared in 40 freshly extracted teeth. They were categorised into following four groups (n=10) depending on cavity preconditioning and restoration. Group I: 10% polyacrylic acid and GI (Ketac molar TM 3M ESPE); Group II: AA and GI; Group III: 35% Phosphoric acid and micro filled composite (MC) (Heliomolar, Ivoclar Vivadent); Group IV: AA and MC. Each group was further divided into subgroups A (no loading) & B (cyclic loading). Microleakage at occlusal and gingival margins was evaluated using methylene blue dye penetration method. Statistical analysis was done using Kruskal-wallis test and Mann-Whitney U test. Results: Microleakage at cementum margins was higher than at enamel margins in all the groups. Preconditioning with AA resulted in increased micro leakage. Conclusion: AA as a preconditioning agent was ineffective in producing superior tooth-restoration bonding. PMID:24995240

Dharmani, Charan Kamal Kaur; Singh, Shamsher; Logani, Ajay; Shah, Naseem

2014-01-01

417

Comparative analysis of two measurement methods for marginal fit in metal-ceramic and zirconia posterior FPDs.  

PubMed

The purpose of this study was to compare two measurement methods for the external marginal fit of zirconia posterior fixed partial dentures (FPDs) fabricated using computer-aided design/manufacturing technology and metal-ceramic posterior FPDs fabricated using the conventional lost-wax technique. The null hypothesis was that there would be no differences between the measurement methods. Forty standardized steel specimens were prepared to receive posterior three-unit FPDs. Specimens were divided into four groups (n = 10): (1) metal-ceramic, (2) Procera Bridge Zirconia, (3) Lava AllCeramic System, and (4) Vita In-Ceram YZ 2000. All FPDs were luted with glass-ionomer cement (Ketac Cem EasyMix, 3M ESPE). Two measurement methods were used to analyze marginal fit: an image analysis (IA) program and a scanning electron microscope (SEM) (JEOL JSM-6400) with magnifications of 340 and 31,000, respectively. Marginal fit was measured at the same point on each abutment. Significant interaction was observed between measurement method and material (P = .0019). Therefore, the measurement method is not independent of the restoration material. Differences among groups were observed for IA (P = .0001) and SEM (P = .0013). Significant differences were observed for the Procera (P = .0050) and metal-ceramic (P = .0039) specimen groups when both measurement methods were evaluated separately. Accuracy of fit achieved by the four groups analyzed was within the range of clinical acceptance, yielding Procera Bridge Zirconia to have the best marginal fit using both measurement methods. PMID:19639075

Gonzalo, Esther; Suárez, María J; Serrano, Benjamin; Lozano, José F L

2009-01-01

418

Atomistic Theory of Metallic Liquids and Glasses  

SciTech Connect

Bulk Metallic Glasses explores an emerging field of materials known as bulk metallic glasses. It summarizes the rapid development of these materials over the last decade and includes documentation on diverse applications of bulk metallic glasses; from structural applications to microcomponents. Some of the applications covered are pressure sensors, microgears for motors, magnetic cores for power supplies, and nano-dies for replacing next generation DVDs. The chapters cover current theories and recent research including an atomistic theory of local topological fluctuations, atomistic simulations, and unique microstructures of these amorphous materials. Other topics include glass formation, glass forming ability, and the underlying mechanisms and physical insights of these criteria. The mechanical deformation of bulk metallic glasses, fatigue, fracture, and corrosion behaviors of these materials are also reviewed.

Egami, Takeshi [ORNL

2007-01-01

419

Evaluation of Glass-Forming Ability  

SciTech Connect

Bulk Metallic Glasses explores an emerging field of materials known as bulk metallic glasses. It summarizes the rapid development of these materials over the last decade and includes documentation on diverse applications of bulk metallic glasses; from structural applications to microcomponents. Some of the applications covered are pressure sensors, microgears for motors, magnetic cores for power supplies, and nano-dies for replacing next generation DVDs. The chapters cover current theories and recent research including an atomistic theory of local topological fluctuations, atomistic simulations, and unique microstructures of these amorphous materials. Other topics include glass formation, glass forming ability, and the underlying mechanisms and physical insights of these criteria. The mechanical deformation of bulk metallic glasses, fatigue, fracture, and corrosion behaviors of these materials are also reviewed.

Liu, Yong [ORNL; Lu, Zhao Ping [University of Science and Technology, Beijing; Liu, Chain T [ORNL

2007-01-01

420

Reactive cluster model of metallic glasses.  

PubMed

Though discovered more than a half century ago metallic glasses remain a scientific enigma. Unlike crystalline metals, characterized by short, medium, and long-range order, in metallic glasses short and medium-range order persist, though long-range order is absent. This fact has prompted research to develop structural descriptions of metallic glasses. Among these are cluster-based models that attribute amorphous structure to the existence of clusters that are incommensurate with crystalline periodicity. Not addressed, however, are the chemical factors stabilizing these clusters and promoting their interconnections. We have found that glass formers are characterized by a rich cluster chemistry that above the glass transformation temperature promotes exchange as well as static and vibronic sharing of atoms between clusters. The vibronic mechanism induces correlated motions between neighboring clusters and we hypothesize that the distance over which these motions are correlated mediates metallic glass stability and influences critical cooling rates. PMID:24588179

Jones, Travis E; Miorelli, Jonathan; Eberhart, Mark E

2014-02-28

421

Mineral soda alumina glass: occurence and meaning  

Microsoft Academic Search

Mineral soda–alumina (m-Na–Al) glass has been found across a vast area stretching from Africa to East Asia. m-Na–Al glass appears around the 5th c. B.C. and is relatively common for periods as late as the 19th c. A.D. It is particularly abundant in South Asia, where raw materials to produce m-Na–Al glass are readily available, and was likely manufactured there;

Laure Dussubieux; Bernard Gratuze; Maryse Blet-Lemarquand