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1

Glass-ionomers have cariostatic effect  

Microsoft Academic Search

Design A randomised controlled trial (RCT) conducted over a period of 3 years.Intervention Either conventional glass-ionomer (Ketac-bond; 3M ESPE St. Paul, MN 55144-1000) or resin-modified glass-ionomer (Vitremer; 3M ESPE St. Paul, MN 55144-1000) sealants were applied to first permanent molars, and oral hygiene education was given. Clinical evaluations were carried out at 6, 12, 24, and 36 months after the

Paul Ashley

2003-01-01

2

Effect of fluorosis on shear bond strength of glass ionomer–based restorative materials to dentin  

Microsoft Academic Search

Statement of problem. Several studies have investigated the adhesion of glass ionomer-based restorative materials to nonfluorotic teeth, but there appears to be no information on the bond strength of these restorative materials to dentin in fluorotic teeth. Purpose. This study investigated the effect of dental fluorosis on the bond strength of Ketac-fil conventional glass ionomer cement, Vitremer resin-modified glass ionomer

Wedad Y. Awliya; E. S. Akpata

1999-01-01

3

Dispersive surface properties of glass-ionomer cements determined by inverse gas chromatography  

NASA Astrophysics Data System (ADS)

The surface properties of several glass-ionomer cements (GIC), restorative dental materials, (GC-Fuji, Chemadent G-J, Ketac Fil and Ketac Molar) were investigated for the first time by means of inverse gas chromatography. This method enables characterization of surface activity in dispersive (non-polar) and acid base interactions. The ability of the surface of glass-ionomers to participate in dispersive interactions was expressed by the use of the dispersive component of surface free energy ?sd. This parameter was determined with satisfactory precision, meaning that the values of ?sd can be further used in the discussion of the influence of the type of GIC, its preparation and the storage time on the surface properties. The greatest capacity for dispersive interactions was revealed by Ketac Molar and the lowest by GC-Fuji. Dispersive interactions in the surface activity of glass-ionomers increased with increasing storage time after cement preparation.

Andrzejewska, E.; Voelkel, A.; Andrzejewski, M.; Limanowska-Shaw, H.

2005-05-01

4

Ion release by endodontic grade glass-ionomer cement  

Microsoft Academic Search

Cylindrical specimens (6 mm high × 4 mm diameter) of the endodontic grade glass-ionomer (Ketac Endo) were exposed to various\\u000a media for 1 week, after which changes in their mass, pH of storage medium, and ion release were determined. In water, this\\u000a cement was shown to release reasonable amounts of sodium, aluminium and silicon, together with smaller amounts of calcium

Beata Czarnecka; Honorata Limanowska-Shaw; Richard Hatton; John W. Nicholson

2007-01-01

5

Recharge pattern of contemporary glass ionomer restoratives  

PubMed Central

Background: As glass ionomers have the ability to reload fluoride from outside sources, the aim was to compare the recharge pattern of six glass ionomer cements after exposure to fluoride. Materials and Methods: Fuji VII, Fuji IX, Riva Pink, Riva Bleach, Ketac Fil and Fuji IX Extra were investigated. The fluoride-containing materials used were tooth paste and mouth wash (Colgate). Specimens of each material (n=15) were immersed separately in deionized water for 59 days. Then the samples of each material were divided into three groups of five each. Two groups were recharged for 2, 20 and 60 min daily during three consecutive weekly intervals and then no treatment for one week. The third group was used as control. Fluoride release measurements (?g/cm2/day) were made in every 24 h. One-way and repeated measures analysis of variance tests were used. Results: Tooth paste recharged materials showed higher level of recharge. On day 1, the difference of fluoride release from different treatment groups of different materials except for Fuji IX Extra were not significant (P>0.05). On days 7 and 14, the differences observed were significant (P<0.05) for all materials except for Fuji VII (tooth paste versus mouth wash) and Trial Fuji IX (mouth wash versus control) and on day 14 for Rvia Pink (mouth wash versus control). On days 21 and 28, the differences observed were significant for all the materials (P<0.05) except for Riva Pink (toothpaste versus mouth wash), Riva Bleach, Ketac Fil and Trial FujiI X (mouth wash versus control) on day 28. Conclusion: A time tabled schedule of application of fluoride-containing materials could help to achieve high fluoride release.

Arbabzadeh-Zavareh, Farahnaz; Gibbs, Tim; Meyers, Ian A.; Bouzari, Majid; Mortazavi, Shiva; Walsh, Laurence J.

2012-01-01

6

Longevity and Cariostatic Effects of Everyday Conventional Glass-ionomer and Amalgam Restorations in Primary Teeth: Three-year Results  

Microsoft Academic Search

The aim of this study was to compare the longevity and cariostatic effects of everyday conventional glass-ionomer and amalgam restorations in primary teeth. The materials consisted of 515 Ketac-Fil glass-ionomer restorations and 543 Dispersalloy amalgam restorations prepared in 666 children, from 3 to 13 years of age, by 14 dentists within the Danish Public Dental Health Service in the municipalities

V. Qvist; L. Laurberg; A. Poulsen; P. T. Teglers

1997-01-01

7

Microleakage of glass ionomer formulations after erbium:yttrium-aluminium-garnet laser preparation.  

PubMed

The aim of this study was to investigate the microleakage in class V cavities restored with four conventionally setting glass ionomers (CGIs) and one resin-modified glass ionomer (RMGI) following erbium:yttrium-aluminium-garnet (Er:YAG) laser or conventional preparation. Four hundred class V cavities were assigned to four groups: A and B were prepared by an Er:YAG laser; C and D were conventionally prepared. In groups B and D, the surface was additionally conditioned with Ketac conditioner. Each group was divided into five subgroups according to the glass ionomer cement (GIC) used: groups 1 (Ketac Fil), 2 (Ketac Molar), 3 (Ionofil Molar), 4 (Ionofil Molar Quick) and 5 (Photac Fil Quick). After thermocycling, a 2% methylene blue solution was used as dye. Scanning electron microscope (SEM) photographs were taken to show the conditioner's effect. Complete marginal sealing could not be reached. PhotacFil showed less microleakage than the conventionally setting glass ionomer cements (CGICs) investigated. Conditioning laser-prepared cavities did not negatively influence microleakage results except for Ionofil Molar Quick. PMID:18716828

Delmé, Katleen I M; Deman, Peter J; De Bruyne, Mieke A A; Nammour, Samir; De Moor, Roeland J G

2008-08-21

8

Acid base surface properties of glass-ionomers determined by IGC  

NASA Astrophysics Data System (ADS)

The surface properties of several glass-ionomer restorative dental materials (GC Fuji, Chemadent G-J, Ketac Fil and Ketac Molar) were investigated by means of inverse gas chromatography. The capacity of the surface of glass-ionomers to undergo specific interactions was expressed using the specific component of free energy ?Gs as well as the parameters KA and KD to describe the ability of the cement to act both as an electron acceptor and an electron donor, respectively. The character of the examined surface was expressed with the use of the SC parameter. All these parameters were determined with a high degree of precision. It was found that the surface of glass-ionomer cements had a well-marked acidic character. The ability of the cement surface to take part in specific interactions differed with the various types of commercial products. The surface activity of the glass-ionomers investigated changed with the storage time (up to 6 months) indicating an on-going setting reaction.

Voelkel, A.; Andrzejewska, E.; Limanowska-Shaw, H.; Andrzejewski, M.

2005-05-01

9

[Glass ionomer cement and "sandwich" restorations after two years of clinical service].  

PubMed

Esthetic restorations for class V lesions extending into root dentin often show marginal discoloration after some time. In this clinical study the long term quality of glass ionomer cement and "sandwich" restorations was compared with each other. In 19 patients 83 class V lesions with the apical margin in dentin were restored with glassionomer cement (I: Fuji II/G-C Dental; II: Ketac Fil/ESPE) or with a glass ionomer liner (III: Lining Cement/G-C Dental; IV: Ketac Bond/ESPE) and laminated with a composite. Where necessary the margins were prepared apically with a butt joint. The observation period between placement and last follow-up check varied between 18 and 44 months. Modified Ryge criteria were used for the clinical assessment of 77 restorations. Marginal quality was assessed in the SEM using replicas. 15.8% of the "sandwich" type and 5% of the glass ionomer cement restorations were lost. All restored teeth remained vital. Clinically the best marginal quality was found with a glass ionomer cement (II) whereas only two thirds of the sandwich restorations and the other glassionomer cement (I) had perfect margins. In the SEM the glassionomer cements had significantly less marginal openings than one of the sandwich restorations (III). PMID:1814714

Reich, E

1991-02-01

10

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.

Khoroushi, Maryam; Keshani, Fateme

2013-01-01

11

Development of glass-ionomer cement systems  

Microsoft Academic Search

In the 1960s the idea of positive physico-chemical adhesion with tooth substance resulted in the invention of polyacrylic acid-based cements, first the zinc polycarboxylate and, subsequently, the glass-ionomer cements. These materials were shown to undergo specific adhesion with hydroxyapatite and proved to have properties satisfactory for a variety of clinical applications. The key properties of the glass-ionomer cements—fluoride release over

Dennis C. Smith

1998-01-01

12

Adhesion of a glass-ionomer root canal sealer to the root canal wall.  

PubMed

Glass-ionomer root canal sealer is commonly used because of its chemical bonding and favorable physical characteristics when bonding to dentin. This study was designed to determine the tensile bond strength of a glass-ionomer sealer (Ketac Endo, Espe, Seefeld, Germany) on root canal walls after pretreatment with different conditioners. Flat inner surfaces of root canal specimens were prepared. The specimens were divided into five groups of 10 teeth, and the groups were conditioned with one of the following smear layer removal solutions: 15% EDTA/NaOCl, 10% polyacrylic acid, 35% phosphoric acid, 6% citric acid, and 5.25% NaOCl as a control. Then the exposed root canal areas were coated with Ketac-Endo. Tensile bonding was measured using a universal testing machine until ultimate failure was obtained. The groups that were treated with phosphoric acid and citric acid showed significantly higher bond strengths than the groups that were treated with 15% EDTA and polyacrylic acid (p < 0.05). Bonding to dentin without smear layer removal (NaOCl group) was too low to be measured in the testing apparatus. Scanning electron microscopy confirmed that phosphoric and citric acids were more effective in removing smear layer than EDTA or polyacrylic acid. The result supported the view that pretreatment with phosphoric acid or citric acid should be used in association with glass-ionomer root canal sealer to achieve the most effective removal of the smear layer and to provide better adhesion. PMID:11487144

Timpawat, S; Harnirattisai, C; Senawongs, P

2001-03-01

13

Microleakage at gingival dentin margins of Class V composite restorations lined with light-cured glass ionomer cement.  

PubMed

This study compared the microleakage of light-cured and auto-set glass ionomer liners used in Class V composite laminated glass ionomer restorations by determining the amount of microleakage at the gingival cementum/dentin margins. Standardized nonundercut V-shaped Class V cavities with gingival margins below the cementoenamel junction were prepared on the mesial and distal surfaces of 40 molars, establishing a total of 80 cavities, which were randomly divided into four groups. Each was lined with glass ionomers: group 1, Ketac-Bond (ESPE-Premier), which served as the control; group 2, XR-Ionomer (Kerr); group 3, XR-Ionomer with polyacrylic acid (PAA) pretreatment (Kerr); and group 4, Vitrabond (3M). Specimens were thermocycled for 300 cycles in 0.5% aqueous solution of basic fuchsin between 4 and 55 C with a 1-minute dwell time, and individually embedded in an epoxy resin. Statistical analysis indicated no differences among groups using the light-cured glass ionomer (groups 2 to 4), and they showed significantly less leakage than the control (group 1) at P less than 0.00001). Removal of the smear layer using 10% polyacrylic acid solution did not influence microleakage in restorations with light-cured glass ionomer liners. PMID:2277155

Tjan, A H; Dunn, J R

1990-12-01

14

Effect of heat application on the mechanical behaviour of glass ionomer cements.  

PubMed

OBJECTIVES: The aim of this study was to examine the long-term effect of heat on the mechanical behaviour of conventional highly viscous glass ionomer cements. Besides, the effect of storage time was evaluated. MATERIALS AND METHODS: Five cements (ChemFil Rock, Riva Self Cure, Fuji IX GP Fast, Equia and Ketac Molar Aplicap) were evaluated using three different preparation methods: no heat application, application of heat by means of a LED curing unit for 20 and 60 s. Four hundred fifty bar-shaped specimens were produced, maintained in distilled water at 37 °C and tested after 1 week, 1 month and 3 months (n?=?10). The Vickers hardness, indentation modulus and creep were measured. In addition, the amount and size of the glass fillers and voids were examined using a light and a scanning electron microscope. RESULTS: Fuji IX GP Fast showed the highest Vickers hardness, Ketac Molar Aplicap showed the highest indentation modulus and the best value of creep was measured for Riva Self Cure. Vickers hardness, modulus of elasticity and creep resistance increased most for ChemFil Rock and Equia up to 1-month storage. CONCLUSIONS: Heat application showed no effect on the mechanical behaviour of ChemFil Rock, Fuji IX GP Fast and Equia at all ageing time. The impact of storage duration was low. CLINICAL RELEVANCE: Considering the measured mechanical properties, there is no need of using heat when restoring teeth with glass ionomer cements. PMID:23740319

Menne-Happ, Ulrike; Ilie, Nicoleta

2013-06-01

15

[Glass ionomer cementing in stomatological practice].  

PubMed

Glass ionomers cements represent a cement system which develops by a reaction between a polyalchenic acid, usually a homo- or a copolymer of acrylic acid and a ion donor, usually an aluminium fluorosilicate glass. Introduction of these ionomers in the stomatological practice was determined by their remarkable adherence to dentin, by pulpal and parodontal biocompatibility, and because of the fact that they deliver continuously fluorine over a long period of time. These cements provide a good marginal sealing of the obturation. In the last years a new generation of glass ionomers cements has been introduced, that "Cormat" cements, in which the glass powder is intimately linked to a pure silver metallic powder by a synthetization process, and this provides a greatly increased resistance to abrasion, as compared to conventional glass ionomer cements. Presently glass ionomer cements have become increasingly known in the stomatological practice and they are used preferentially for base obturations, under obturations with composites on lateral teeth, in the treatment of mylolysis and for coronary erosions determined by brushing, which do not need preparation of retention cavities. They are also used for coronary reconstruction, and the treatment of atopical microcavities of occluding decay processes on the lateral teeth that have induced limited enamel losses. The perspective of these cements in the stomatological practice depends however on an improved translucency, which, for the present at least, does not match that of silicates and composites, as well as on an improved resistance to bending, and even the "Cormat" cements are inferior to silver amalgam which is used in the obturation of classical class II cavities. PMID:2101262

Andreescu, C; Iliescu, A

16

Efficiency of glass ionomer cement linings in preventing microleakage under Class V composite resin restorations.  

PubMed

The ability of glass ionomer linings to aid in the prevention of microleakage under Class V composite resin restorations has been investigated. A conventional glass ionomer lining (Ketac-bond) and two light cured linings (Vitrabond and Timeline) were evaluated with respect to their ability to reduce microleakage. Seventy two Class V cavities were restored either by a bulk fill or incremental fill technique, and following restoration, half the teeth were thermocycled in artificial saliva. Dye penetration, using a Procion orange dye was recorded along the gingival dentine wall and at the occlusal enamel margin for all teeth. The results showed significant differences in leakage along the gingival dentine wall between the various linings under all conditions. Vitrabond produced significantly less leakage than Ketac bond which in turn produced significantly less leakage than Timeline. Significant differences in microleakage were noted between the thermocycled and non-thermocycled groups. Little or no significant differences in leakage were shown between the bulk filled and incremental filled teeth. PMID:2096890

Meyers, I A

1990-01-01

17

Randomized clinical trial of two resin-modified glass ionomer materials: 1-year results.  

PubMed

With institutional review board approval, 33 patients who needed restoration of noncarious cervical lesions (NCCL) were enrolled in this study. A total of 92 NCCL were selected and randomly assigned to three groups: (1) Ambar (FGM), a two-step etch-and-rinse adhesive (control), combined with the nanofilled composite resin Filtek Supreme Plus (FSP; 3M ESPE); (2) Fuji II LC (GC America), a traditional resin-modified glass ionomer (RMGIC) restorative material; (3) Ketac Nano (3M ESPE), a nanofilled RMGIC restorative material. Restorations were evaluated at six months and one year using modified United States Public Health Service parameters. At six months after initial placement, 84 restorations (a 91.3% recall rate) were evaluated. At one year, 78 restorations (a 84.8% recall rate) were available for evaluation. The six month and one year overall retention rates were 93.1% and 92.6%, respectively, for Ambar/FSP; 100% and 100%, respectively, for Fuji II LC; and 100% and 100%, respectively, for Ketac Nano with no statistical difference between any pair of groups at each recall. Sensitivity to air decreased for all three adhesive materials from the preoperative to the postoperative stage, but the difference was not statistically significant. For Ambar/FSP, there were no statistical differences for any of the parameters from baseline to six months and from baseline to one year. For Fuji II LC, surface texture worsened significantly from baseline to six months and from baseline to one year. For Ketac Nano, enamel marginal staining increased significantly from baseline to one year and from six months to one year. Marginal adaptation was statistically worse at one year compared with baseline only for Ketac Nano. When parameters were compared for materials at each recall, Ketac Nano resulted in significantly worse color match than any of the other two materials at any evaluation period. At one year, Ketac Nano resulted in significantly worse marginal adaptation than the other two materials and worse marginal staining than Fuji II LC. Surface texture was statistically worse for Fuji II LC compared with the other two materials at all evaluation periods. The one-year retention rate was statistically similar for the three adhesive materials. Nevertheless, enamel marginal deficiencies and color mismatch were more prevalent for Ketac Nano. Surface texture of Fuji II LC restorations deteriorated quickly. PMID:22770485

Perdigão, J; Dutra-Corrêa, M; Saraceni, S H C; Ciaramicoli, M T; Kiyan, V H

2012-07-07

18

The effect of incremental versus bulk fill techniques on the microleakage of composite resin using a glass-ionomer liner.  

PubMed

Incremental placement of composite resin has been suggested to reduce microleakage, particularly at the gingival margin of class 5 cervical restorations. It has become clinically advantageous to place a glass-ionomer liner over dentin to further minimize microleakage resulting from a bond between the dentin and glass ionomer, and glass ionomer and resin. The objective of this study was to compare the microleakage behavior of three hybrid composite/bonding agent systems using bulk and incremental filling techniques utilizing a glass-ionomer liner. This was accomplished in vitro using freshly extracted bovine incisors and a Ca45 radioisotope and autoradiography. Sixty bovine incisors were divided into six experimental groups of 10 specimens per group. Class 5 preparations were cut at the cementoenamel junction and restored with the appropriate combination of Herculite XR/Bondlite, P50/Scotchbond 2, or Pertac Hybrid/Pertac Bond. All teeth were lined with the glass ionomer Ketac Bond before the final restoration was placed. The samples were finished and stored for 24 hours in distilled water before thermocycling. The samples were tested for microleakage using a Ca45 radioisotope technique and autoradiography. Incisal (enamel) and gingival (dentin) margins were scored separately for microleakage but grouped for statistical analysis. Results were analyzed using the Kruskal-Wallis H test. Pertac Hybrid exhibited more leakage than Herculite XR or P50. The difference between microleakage of bulk and incremental filling techniques was only significant for P50. PMID:1289865

Puckett, A; Fitchie, J; Hembree, J; Smith, J

19

A comparison of the in vitro cytotoxicity of conventional and resin modified glass ionomer cements.  

PubMed

To evaluate cytotoxicity of experimental conventional and resin modified glass-ionomer cements on UMR-106 osteoblast cell cultures and cell cultures of NIH(3)T(3) mouse fibroblasts specimens were prepared for every experimental material and divided into: group 1.Conventional glass-ionomer cements: GC Fuji IX GP Fast, GC Fuji Triage and Ketac Silver; group 2. Resin modified glass-ionomer cements: GC Fuji II LC, GC Fuji Plus and Vitrebond; group 3. Positive control was presented by specimens of composite Vit-l-ecence® and negative control-group 4. was presented by ?-minimum essential medium for UMR-106 - osteoblast-like cells and Dulbecco's Modified Eagle's Medium for NIH(3)T(3) mouse fibroblast cells. Both cell cultures were exposed to 10% of eluate of each single specimen of each experimental material. Experimental dishes were incubated for 24 h. Cell metabolism was evaluated using methyltetrazolium assay. Kruskal-Wallis test and Tukey-Kramer post hoc test for the materials evaluated on NIH(3)T(3) mouse fibroblast cells, as well as UMR-106 osteoblast-like cells showed significantly more cytotoxicity of RMGICs, predominantly Vitrebond to both GICs and composite- Vit-l-ecence®.The lowest influence on cell's metabolism on UMR-106 osteoblas-like cells was shown by Ketac Silver and the lowest influence on cell's metabolism on NIH(3)T(3) mouse fibroblast cells was shown by Fuji IX GP Fast. Statistical evaluation of sensitivity of cell lines UMR-106 osteoblast-like cells and NIH(3)T(3) mouse fibroblast cells, using Mann-Whitney test, showed that NIH(3)T(3) mouse fibroblast cells were more sensitive for the evaluation of cytotoxicity of dental materials. PMID:23198945

Selimovi?-Dragaš, Mediha; Huseinbegovi?, Amina; Kobašlija, Sedin; Hatibovi?-Kofman, Sahza

2012-11-01

20

Class II Amalgam Restorations, Glass-Ionomer Tunnel Restorations, and Caries Development on Adjacent Tooth Surfaces: A 3Year Clinical Study  

Microsoft Academic Search

Eighteen caries-active adolescents, each having both a class II conventional amalgam (Dispersalloy) and a glass-ionomer (Ketac Silver) tunnel restoration of the same age placed on a contralateral tooth, were part of a 3-year clinical study. At the 1- and 2-year examinations all test restorations were assessed as acceptable in all patients. At the 3-year assessment three amalgam restorations failed due

M. Svanberg

1992-01-01

21

Toughening of dental glass ionomer cements with reactive glass fibres.  

PubMed

A fibre reinforced glass ionomer cement (FRGIC) for dental applications was loaded with 20 vol% short fibres (430 microm) with a glass composition in the system SiO(2)-Al(2)O(3)-CaF(2)-Na(3)AlF(6). The fracture toughness and the total energy release rate were examined. A 20% anisotropic fibre alignment was observed, perpendicular to the loading direction. An increase of fracture toughness of 140% and of total energy release rate of 440% was achieved compared to the unreinforced glass ionomer cement. Matrix-fibre interface reaction is supposed to exert the major influence on mechanical behaviour of FRGIC by controlling fibre pull-out and thus the total energy release rate. PMID:15110473

Lohbauer, Ulrich; Frankenberger, Roland; Clare, Alexis; Petschelt, Anselm; Greil, Peter

2004-10-01

22

Dental composites/glass ionomers: the materials.  

PubMed

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1292462

Bowen, R L; Marjenhoff, W A

1992-09-01

23

Glass transition(s) of ionomers  

SciTech Connect

Ionomers are predominantly nonpolar polymers that contain a small amount of bonded salt groups. Microphase separation of ion-rich microdomains occurs as a consequence of the thermodynamic incompatibility of the salt groups and the polymer matrix and associative interactions between salt groups. Associations of the salt groups usually increase the glass transition of the continuous matrix phase, presumably as a consequence of the inhibition of chain mobility that accompanies physical crosslinking. The central question raised in this paper is whether the dispersed ion-rich microphase exhibits a glass transition. Although no glass transition for the microphase is detected by calorimetry, a dynamic mechanical relaxation is commonly observed above the T{sub g} of the matrix phase. This transition has some of the attributes of a glass transition, but it is not clear what is the actual relaxation process that is measured. This paper discusses the effect of the ionic groups on the matrix glass transition, the origin of the high-temperature dynamic mechanical transition, and the effects of the addition of plasticizers on the T{sub g} of the matrix and the higher temperature mechanical relaxation.

Weiss, R.A. [Univ. of Connecticut, Storrs, CT (United States). Inst. of Materials Science

1994-09-01

24

Microleakage under orthodontic bands cemented with nano-hydroxyapatite-modified glass ionomer.  

PubMed

Objectives: To estimate the in vivo effect of nano-hydroxyapatite (HA) modification of banding glass-ionomer cement on microleakage under orthodontic bands. Materials and Methods: Eighty noncarious premolars scheduled for extraction in 20 orthodontic patients were randomly divided into four groups. Grouping was based on the ratio of nano-HA (0%, 5%, 10%, 15% by weight) added to the luting glass-ionomer cement (GIC) Ketac-Cem, which was used for cementation of prefabricated micro-etched orthodontic bands. Dye penetration method was used for microleakage evaluation at the cement-band and cement-enamel interfaces. Statistical evaluation was performed with a Kruskal-Wallis test and a Mann-Whitney U-test, and a Bonferroni-adjusted significance level was calculated. Results: Bands cemented with conventional GIC showed the highest microleakage scores in comparison to those cemented with nano-HA-modified GIC. No significant difference was found between teeth banded with 10% and 15% modified GIC. Conclusions: Modification of the banding GIC with 15% nano-HA revealed a positive effect on reducing microleakage around orthodontic bands. PMID:23745977

Enan, Enas T; Hammad, Shaza M

2013-06-01

25

Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements.  

PubMed

The effects of devitrification of an ionomer glass with a molar composition 4.5SiO(2).3Al(2)O(3).1.5P(2)O(5).3CaO.2CaF(2) on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750 degrees C for 2h contained peaks corresponding to apatite (JCPDS 15-876), whereas for samples heat-treated at 950 degrees C for 2h apatite and mullite (JCPDS 15-776) were the major phases detected. Transmission electron microscopy (TEM) confirmed that apatite and apatite-mullite phases were present after heat treatments at 750 degrees C and 950 degrees C respectively. Glass and glass-ceramics were ground to prepare <45microm powders and glass ionomer cements were produced using a ratio of 1g powder: 0.2g PAA: 0.3g 10% m/v tartaric acid solution in water. In vitro biocompatibility was evaluated using cultured rat osteosarcoma (ROS) cells. Scanning electron microscopy (SEM) showed that cells colonised the surfaces of cements prepared using untreated ionomer glass and glass crystallised to form apatite (750 degrees C/2h). However, quantitative evaluation using MTT and total protein assays indicated that more cell growth occurred in the presence of cements prepared using ionomer glasses crystallised to apatite than cements prepared using untreated glass. The least cell growth and respiratory activity was observed on cements made with crystallised glass containing both apatite and mullite. It was concluded that the controlled devitrification of ionomer glasses could be used to produce GIC bone cements with improved biocompatibility. PMID:12895588

Hurrell-Gillingham, K; Reaney, I M; Miller, C A; Crawford, A; Hatton, P V

2003-08-01

26

Dimensional changes occurring in a glass-ionomer cement.  

PubMed

The dimensional changes occurring when glass ionomer cements are exposed both to desiccating and moist conditions were investigated. All work was done at 23 degrees C. The effect of time allowed for cements to mature before exposure to the test conditions was studied as was the effect of adding cellulose ethers. The contraction of glass ionomer cements under desiccating conditions was far greater than the expansion by water absorption. Increase of the time allowed for the cements to mature reduced the extent of this effect markedly. The addition of cellulose ethers to cement mixes was only moderately effective in reducing dimensional change. PMID:7880475

Wilson, A D; Paddon, J M

1993-12-01

27

Influence of chemo-mechanical caries removal on the surface topography of dental composite resin and glass-ionomer materials: an in vitro study.  

PubMed

The aim of the present study was to investigate the influence of a chemo-mechanical caries removal system, Carisolv gel, on the surface topography of dental filling materials. Thirty specimens of a composite resin (Spectrum) and a compomer (Dyract AP) and 60 specimens of a glass-ionomer (Ketac-Fil Plus) were prepared. The surface topography was investigated with an optical interferometer before and after chemical exposure for 5, 10, or 20 min. Each specimen acted as its own control. The topographical part of the glass-ionomer materials was performed in two series with different drying procedures, since this material exhibits a higher sensitivity to dehydration than the other materials. The surface topographical investigations were complemented with contact angle measurements. After Carisolv gel exposure the density of summits and the developed surface area ratio (3D/2D) were slightly smaller for the composite resin and the compomer. For the minimally dried glass-ionomer material, the results indicated a reduction of the height of the surface structures, as well as a surface area enlargement, after Carisolv gel exposure. No statistically significant changes of contact angles due to Carisolv gel exposure could be detected for any material investigated. If dental filling materials of composite resin or glass-ionomer materials are exposed to Carisolv gel, no or only minor surface topographical changes can be expected. n PMID:15370632

Arvidsson, Anna; Ortengren, Ulf; Wennerberg, Ann

2004-06-01

28

Influence of acid washing on the surface morphology of ionomer glasses and handling properties of glass ionomer cements.  

PubMed

Acid washing is known to influence the handling properties of ionomer glasses used in glass ionomer cements due to the production of an ion depleted-zone on the surface of the glass particles. The influence of acid washing on the particle size distribution and surface area of four glasses was examined by scanning electron microscopy (SEM), particle size analysis (PSA) and accelerated surface area porosimetry (ASAP) and the working and setting times of cements, produced from the glasses, correlated to changes in surface morphology. A linear relationship was found between the specific surface area of acid-washed SiO(2)-Al(2)O(3)-XF(2)-P(2)O(5) glasses (X being either calcium or strontium) and their cement working and setting times. These changes directly correlated with increases in the mesopore volume. However, the influence of acid washing on the surface morphology was also found to be glass composition-dependent with the addition of sodium into the glass network resulting in no significant change in the surface area or mesopore volume despite changes in the working and setting time. Through examination of the influence of acid washing and glass composition on the specific surface area improvements in the control of the working and setting times of glass ionomer cements may be achieved. PMID:17387590

Crowley, C M; Doyle, J; Towler, M R; Rushe, N; Hampshire, S

2007-03-27

29

Comparison of glass ionomer cement and incus interposition in reconstruction of incus long process defects.  

PubMed

The ossicles may be affected through the mass effect of the pathological tissue in chronic otitis media. Ossicular reconstruction may be accomplished using the patients' own ossicles or with alloplastic materials. Glass ionomer ossiculoplasty is a fast, efficient, safe and cost-effective method and it has been used more frequently in recent years. Forty-six patients who had surgery for chronic otitis media were included in this study. All patients had an incus long process defect and a normal stapes superstructure. Ossicular reconstruction was performed using glass ionomer cement (GIC) (Ketac-Cem, Espe Dental AG, Seefeld, Germany) in 23 patients (group 1), while incus interposition was performed in other 23 patients (group 2). Preoperative and postoperative air pure tone averages of the group 1 patients were 42.8 and 35.2 dB, respectively (p < 0.01). These values were 42.9 and 34.5 dB in group 2 (p < 0.01). Two groups were similar with respect to postoperative hearing gain (p > 0.05). The air bone gap of group 1 was 27 dB preoperatively and 20.7 dB postoperatively. These values were 28.7 and 20.2 dB, respectively, in group 2. The closure of air bone gap was statistically significant in both the groups (p < 0.01, p < 0.01). The comparison of the mean gains of the air bone gap revealed no difference between the groups (p > 0.05). In conclusion, the use of both GIC ossiculoplasty and incus interposition are efficient methods for reconstruction of incus long process and one is not superior to the other. A larger study population may be useful for comparison of these methods. PMID:21340562

Dere, Huseyin; Ozdogan, Fatih; Ozcan, K Murat; Selcuk, Adin; Ozcan, Ibrahim; Gokturk, Gokhan

2011-02-22

30

Mechanical properties and microstructures of glass-ionomer cements  

Microsoft Academic Search

Objective: The objective of this study was to determine the flexural strength (FS), compressive strength (CS), diametral tensile strength (DTS), Knoop hardness (KHN) and wear resistance of ten commercial glass-ionomer cements (GICs). The fracture surfaces of these cements were examined using scanning electron microscopic (SEM) techniques to ascertain relationships between the mechanical properties and microstructures of these cements.Methods: Specimens were

D. Xie; W. A. Brantley; B. M. Culbertson; G. Wang

2000-01-01

31

Advanced antibacterial glass ionomer cements for improved dental restoratives  

Microsoft Academic Search

Secondary caries that often occurs at the interface between the restoration and the cavity preparation is mainly caused by demineralization of tooth structure due to invasion of plaque bacteria (acid-producing bacteria) such as Streptococcus mutans (S. mutans) in the presence of fermentable carbohydrates. Although glass-ionomer cements (GICs) are found to be the most cariostatic and somehow antibacterial due to release

Yiming Weng

2011-01-01

32

Wear of resin-modified glass ionomers: an in vitro study.  

PubMed

The purpose of this study was to evaluate the wear resistance and clinical applicability of resin-modified glass ionomer cements as restorative or fissure-sealing materials. The in vitro wear of resin-modified glass ionomers was compared to conventional glass ionomers, a resin-based sealant, and a composite resin. A three-body wear test (enamel block--polymethylmethacrylate powder--experimental dental material) was performed by 20,000 cycles with a load of 4 kgf/cm2. The depth of wear of the experimental materials was measured and calculated using a computerized laser surface scanner. The glass ionomers generally showed more wear than the resin-based sealant and the composite resin, but there was no difference in wear between resin-modified and conventional glass ionomers. Type III ionomers (used for sealant) showed lower wear resistance than type II ionomers (used for restoration). PMID:11497010

Futatsuki, M; Nozawa, M; Ogata, T; Nakata, M

2001-01-01

33

Marginal leakage of two newer glass-ionomer-based sealant materials assessed using micro-CT  

Microsoft Academic Search

ObjectivesTo test newer glass-ionomer-based materials as sealant materials. One glass-ionomer sealant was light-cured to obtain an early setting reaction. The null-hypothesis tested was: there is no difference in marginal leakage of sealants produced with high-viscosity glass-ionomer, with and without energy supplied, and that of glass-carbomer, in comparison with resin composite sealants in vitro.

X. Chen; V. M. J. I. Cuijpers; M. Fan; J. E. F. M. Frencken

2010-01-01

34

Use of glass ionomer cement containing antibiotics to seal off infected dentin: a randomized clinical trial.  

PubMed

Dental materials with antibacterial properties can prevent the harmful effects caused by oral cariogenic bacteria. This double-blind controlled clinical trial evaluated the performance of a glass ionomer cement (GIC) added with antibiotics for sealing infected dentin in atraumatic restorations of primary molars. The study enrolled 45 children (45 teeth) between 5 and 8 years of age, of both genders, divided into two groups: GC (n=22), where cavities were lined with a conventional GIC (Vidrion F) and GA (n=23), with cavities lined with Vidrion F added with 1% each of metronidazole, ciprofloxacin and cefaclor antibiotic. Both groups were restored with Ketac Molar Easymix. Molars with carious lesions on the inner half of dentin without clinical or radiographic pulp damage were selected. Patients were evaluated clinically (pain, fistulas or mobility) and radiographically (area of caries, periapical region and furcation) after 1, 3, 6 and 12 months. For statistical analysis, chi-squared or Fisher's exact tests were used with a 5% significance level. GA (82.6-95.7%) had better results than GC (12.5-36.4%) in all evaluations (p<0.05) and the difference in the success rate was 46.2-72.5% higher for GA. The use of the antibiotic-containing GIC liner on infected dentin proved satisfactory when applied in deciduous teeth. PMID:23657417

Ferreira, Jainara Maria Soares; Pinheiro, Sérgio Luiz; Sampaio, Fábio Correia; Menezes, Valdenice Aparecida de

2013-01-01

35

Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements  

Microsoft Academic Search

The effects of devitrification of an ionomer glass with a molar composition 4.5SiO2·3Al2O3·1.5P2O5·3CaO·2CaF2 on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750°C for 2h contained peaks corresponding to

K Hurrell-Gillingham; I. M Reaney; C. A Miller; A Crawford; P. V Hatton

2003-01-01

36

Radiopacity of resin-modified glass ionomer liners and 2 bases  

Microsoft Academic Search

Statement of problem. Lining and base materials for restorations have traditionally been autopolymerized and include conventional glass ionomer cements. Light-cured resin-modified glass ionomer cements have recently become available, but a lack of information exists regarding their radiopacity.Purpose of study. In this study the radiopacity of glass ionomer cements was assessed with a standard method that related densitometric measurements to an

P. M. M. Shah; S. K. Sidhu; B. S. Chong; T. R. Pitt Ford

1997-01-01

37

[The use of glass ionomer cements in endodontics].  

PubMed

Glass ionomer cements are currently used in endodontic therapy for sealing root canals (orthogradely and retrogradely), for sealing and restoring the pulp chamber, for repairing perforations and root resorption defects, and, rarely, for treating vertically fractured teeth. The successful use of these cements is the result of their particular characteristics: a chemical bond to dentin, which enhances the seal of the root canal and the reinforcement of the tooth; a good biocompatibility in the periradicular area and a fluoride release without loss of strength of the material. The fluoride release imparts an antimicrobial effect to combat root canal infection and attributes to bone mineralization after surgery. The present paper reviews the literature regarding the various applications of glass ionomer cements in present-day endodontics. PMID:11505760

De Moor, R; De Bruyne, M

2000-01-01

38

Short-term mechanical properties of glass ionomer cement  

Microsoft Academic Search

The setting reaction of glass ionomer cement was studied by analyzing and comparing the short-tem mechanical properties of\\u000a set cement stored in silicone oil, air and distilled water respectively at different temperatures. For the set cement stored\\u000a at 37 °C, the strength of the sample in the air reached the maximum value after 24 h, then decreased to about 210

Sanbao Tang; Dongxuan Xu

2009-01-01

39

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

40

Reactivity of Fluoride-containing Calcium Aluminosilicate Glasses Used in Dental Glass-ionomer Cements  

Microsoft Academic Search

The glass component critically determines the properties of glass-ionomer cements (GIC). However, the exact relationship between the composition of the glass and these properties is not yet fully understood. To investigate this relationship, we studied the reactivity of glasses used in commercial GIC in acetic acid solutions, using a pH-stat method. Qualitative differences in the leaching behavior of these glasses

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

1998-01-01

41

Fracture properties of composite and glass ionomer dental restorative materials.  

PubMed

The double-torsion technique has been used to determine critical stress intensity factor (K1c) values for a range of composites and glass ionomer cements used in restorative dentistry. From these values and determined elastic modulus (E) and tensile strength (sigma T) values, two other fracture properties: G1c, the critical strain energy release rate and a0, the inherent flaw size, have been evaluated. Glass ionomers have low K1c and high a0 values, coarse particle composites high K1c and high a0 values, microfine materials low K1c and low a0 values and fine particle composites medium to high K1c values and medium to low a0 values. Light curing materials have K1c values according to their group but tend to have lower a0 values than their chemically curing analogues. Glass ionomers have very low G1c values; however, there is no significant difference between the G1c values of the composite groups. The K1c and a0 values have been used to predict relative performance of the materials in highly stressed restorations and wear. PMID:4077896

Goldman, M

1985-09-01

42

Fluoride Release by Glass Ionomer Cements, Compomer and Giomer  

PubMed Central

Background: To measure the amounts of fluoride released from fluoride-containing materials, four glass ionomer cements (Fuji IX, Fuji VII, Fuji IX Extra and Fuji II LC), a compomer (Dyract Extra) and a giomer (Beautifil) were used in this study. Methods: Twenty cylindrical specimens were prepared from each material. The amount of released fluoride was measured during the first week and on the days 14 and 21 by using specific fluoride electrode and an ionanalyzer. The results were statistically analyzed using analysis of variance (two-way ANOVA) and Tukey Kramer multiple comparison tests (p=0.05). Results: Significant differences were seen in fluoride release of different days and materials (p<0.05). The maximum cumulative fluoride release of days 1-7 was related to Fuji VII, followed by Fuji IX Extra, Fuji II LC, Fuji IX, Dyract Extra and Beautifil in descending order and this order remained the same until the 21st day. Conclusion: Fuji IX, Fuji VII, Fuji IX Extra, and Fuji II LC released higher amounts of fluoride compared to Beautifil and Dyract Extra in this study. It seems that the extent of the glass ionomer matrix plays an important role in determining the fluoride releasing ability of glass ionomer cement materials.

Mousavinasab, Sayed Mostafa; Meyers, Ian

2009-01-01

43

Long-term mechanical characteristics of resin-modified glass ionomer restorative materials  

Microsoft Academic Search

Objectives. The purpose of this study was to compare the effects of long-term water storage on the mechanical characteristics of four resinmodified glass ionomer restorative materials with those of a conventional glass ionomer cement and a resin composite material.Methods. Cylindrical specimens were prepared and stored in water for 1 h, 24 h, 1 wk, 1 mon, 3 mon and 6

Shigeru Uno; Werner J. Finger; Ulrike Fritz

1996-01-01

44

Dissolution behavior and fluoride release from new glass composition used in glass ionomer cements  

Microsoft Academic Search

The degradability in an acidic environment and the release of different ions, such as Na+, Ca2+, Al3+ and F? from a calcium fluoro-aluminosilicate glass (used in glass ionomer cements) during different exposure times at 37°C has been the object of this study. The formation of a leached layer on the surface of the glass has proved to be an important

Jhamak Nourmohammadi; Reza Salarian; Mehran Solati-Hashjin; Fatollah Moztarzadeh

2007-01-01

45

Investigation of glass-ionomer cements using differential scanning calorimetry.  

PubMed

Six commercial glass-ionomer cements commonly used for various dental applications have been investigated using differential scanning calorimetry (DSC). The heat-flow behaviour and heat capacity of the cements were measured during isothermal (at 37 degrees C) setting reactions. The DSC results show that all materials undergo an exothermic setting process, but with different enthalpies of reactions and different heat capacities; there are no remaining endo- or exothermic reactions after the setting of the cement. All materials examined were found to be effective thermal insulators. PMID:15348851

Khalil, S K; Atkins, E D

1998-09-01

46

Clinical Performance of Viscous Glass Ionomer Cement in Posterior Cavities over Two Years  

PubMed Central

In this controlled prospective clinical study the highly viscous glass ionomer cement Ketac Molar was clinically assessed in Class I and Class II cavities. Forty-nine subjects (mean age 32.3 years) received 108 restorations placed by six operators in conventional Black I and II type cavities with undercuts after excavating primary lesions or after removing insufficient restorations. At baseline, and after 6, 12, and 24 months, restorations were assessed by two independent investigators according to modified USPHS codes and criteria. Impressions of the restorations were taken and epoxy replicas were made. Between the baseline and the 24-month recall, 51 representative samples were analyzed at 130 × magnification by use of a stereo light microscope (SLM). Recall rates were 83% after 6 months, 50% after 12 months, and 24% after 24 months. Failure rates after 24 months were 8% for Class I and 40% for Class II fillings, mainly due to bulk fracture at occlusally loaded areas (Kaplan Meier survival analysis). Significant changes over time were found for the criteria “surface roughness”, “marginal integrity”, “restoration integrity”, and “overall judgement” (P < .05; Friedman test). SLM analysis revealed statistically significant differences for the following criteria over time (baseline/6 months/12 months (in % of entire evaluable margin length); P < .05; Friedman 2-way ANOVA): perfect margin 37/19/11, negative step formation 26/49/57, gap formation 2/7/9, and overhang 24/11/8. Replicas exhibited mainly negative step formation as main finding due to apparently inferior wear resistance (P < .05). Gap formations were more frequently observed in Class II restorations than in Class I (12% versus 3% after 12 months; P < .05, Mann-Whitney-U test). The evaluated margin lengths were not statistically different (P > .05, Friedman 2-way ANOVA).

Frankenberger, Roland; Garcia-Godoy, Franklin; Kramer, Norbert

2009-01-01

47

In vitro Characteristics of a Glass Ionomer Cement  

PubMed Central

Glass ionomer cements were first described by Wilson and Kent and have been used in dentistry since 1969. It has been recommended for bridging ossicular chain defects, fixation of ossicular chain prosthesis, anchoring of cochlear implants, mastoid obliteration, and repair of tegmen and posterior canal wall defects. The biocompatability and stability of this material over time is vital to its usefulness in neurotologic surgery. The purpose of this study was to assess the stability of a glass ionomer cement in the presence of bacteria and in different pH environments. We demonstrated that bacteria readily adhere to the surface and their presence is associated with accelerated loss of matrix. We found the cement to be susceptible to low pH and to release a visible cloud of debris upon contact with fluid. Calcium concentration in the solution was elevated at all pH levels. Although we are able to demonstrate these findings in vitro the clinical relevance is unclear. There have been several cases of aseptic meningitis possibly due to intracranial release of components of the cement. Until further studies are done use of the cement in contact with cerebral spinal fluid should be avoided. This cement, or a similar material, would be useful in neurotologic surgery but prior to widespread use further testing should be done to assess safety. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 9Figure 10Figure 11

Driscoll, Colin L. W.; Green, J. Douglas; Beatty, Charles W.; McCaffrey, Thomas V.; Marrs, Christopher D.

1998-01-01

48

A comparative study of the bond strengths of amalgam and alloy-glass ionomer cores.  

PubMed

The purpose of this study was to compare the bond strengths of dental amalgam cores and dental alloy-glass ionomer cores that were luted to cast gold crowns with glass ionomer cement. Seventy-two human extracted molars were sectioned horizontally and four regular thread mate system pins were inserted into a flat pulpal floor. The teeth were restored with amalgam or alloy-glass ionomer admixture and prepared for crown preparations. Castings were produced with type III gold and cemented to the cores with Fuji type I glass ionomer cement. Thirty-six of the specimens were subjected to thermal fatigue by cycling between 4 and 50 degrees C for periods of 1, 5 and 10 weeks. The remainder of the specimens were retained in deionized water at 37 degrees C. Bond strengths of the cores, in tension, were measured with a universal testing machine. The alloy-glass ionomer cores exhibited higher bond strengths than the amalgam cores for virtually all time periods, particularly the thermocycled samples. The alloy-glass ionomer cores exclusively displayed core fractures and pin/tooth insufficiencies while the amalgam cores failed because of a deterioration of the glass ionomer luting cement. PMID:2664111

Arcoria, C J; DeWald, J P; Moody, C R; Ferracane, J L

1989-05-01

49

Curing shrinkage and volumetric changes of resin-modified glass ionomer restorative materials  

Microsoft Academic Search

Objectives. The objective of the study was to evaluate initial curing shrinkage and volumetric change during water storage of six resin-modified glass ionomer cements (Dyract, DeTrey Dentsply; Fuji II LC, GC Dental Int.; Ionosit Fil, DMG; VariGlass VLC, DeTrey Dentsply; Vitremer, 3M Dental Products; Photac-Fil, ESPE), a hybrid composite (blend-a-lux, Blendax) and a chemical-cured glass ionomer cement (ChemFil Superior, DeTrey

Thomas Attin; Wolfgang Buchalla; Andrej M. Kielbassa; Elmar Hellwig

1995-01-01

50

Ionomics  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ionomics is the study of elemental accumulation (e.g., Ca, K, P, and metal ions) in living systems using high-throughput elemental profiling. This approach has been applied extensively in plants for forward and reverse genetics, screening diversity panels and modeling of physiological states. In thi...

51

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.

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

2013-01-01

52

Evaluation of a Glass Ionomer Restoration to Treat Hypersensitive Cervical Anatomic Deficiencies.  

National Technical Information Service (NTIS)

The objective of the research will be to test the usefulness of a glass ionomer cement ot treat hypersensitive cervical anatomic deficiencies with a restorative material that required no tooth preparation for its application. Based on the findings of this...

E. B. Mandel

1983-01-01

53

Resin-Modified Glass-Ionomer Dental Cements Field of the Invention.  

National Technical Information Service (NTIS)

Resin-modified glass-ionomer cements are provided comprising polyelectrolyte-based cements and compatible vinyl monomers and/or polymers. The composites can be further crosslinked by free-radical chemical or photochemical polymerization in addition to the...

J. M. Antonucci J. E. McKinney J. W. Stansbury

1988-01-01

54

The co-cured, light-activated glass-ionomer cement-composite resin restoration.  

PubMed

The simultaneous curing of unpolymerized composite resin and inactivated light-curing glass-ionomer cement appears to offer a number of clinical improvements to the laminated glass-ionomer cement-composite resin restoration. The observation that composite resin cures before the glass-ionomer cement suggests that the polymerization shrinkage of the resin may be taken up by the uncured glass-ionomer cement, reducing the internal stress of the restoration. A procedure is described for the placement of this type of laminate restoration that reduces both technique sensitivity and placement time, by eliminating a number of the steps required for a conventional "sandwich" restoration. The apparent clinical success of this technique indicates the need for laboratory testing to evaluate the potential of this procedure. PMID:8183983

Knight, G M

1994-02-01

55

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.

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

2013-01-01

56

Microleakage of Class V resin-modified glass ionomer and compomer restorations  

Microsoft Academic Search

Statement of problem. Resin-modified glass ionomers and polyacid-modified resin composites (compomers) have been introduced to provide esthetic restorations. However, there is concern about the marginal sealing ability of these materials, especially at the dentin (cementum) aspects of restorations. Purpose. This in vitro study evaluated the microleakage of Class V restorations made with resin-modified glass ionomers or a compomer. Material and

Manuel Toledano; Estrella Osorio; Raquel Osorio; Franklin García-Godoy

1999-01-01

57

In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers  

Microsoft Academic Search

Objectives. This study was conducted to compare the rate of abrasive wear and change in surface roughness of resin-modified and conventional acid-base glass ionomers when subjected to toothbrush-dentifrice abrasion.Methods. Two resin-modified and two conventional glass ionomers were used. Samples of a high-copper amalgam and a hybrid resin composite were used as reference materials. Specimens of each material were prepared and

Yasuko Momoi; Kunitsugu Hirosaki; Atsushi Kohno; John F. McCabe

1997-01-01

58

Development of an experimental glass ionomer cement containing niobium and fluoride  

Microsoft Academic Search

Glass ionomer cements (GICs) are currently used for various dental applications such as luting cements or as restorative materials. The calcium fluoro-alumino-silicate system is the basis for degradable glasses used to obtain the GICs. The purpose of the present paper is to add niobium to conventional glass system because according to previous papers niobium addition improves the chemical resistance and

Marcio José Bertolini; Maria Aparecida Zaghete; Rossano Gimenes

2005-01-01

59

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

60

Chlorhexidine release from an experimental glass ionomer cement.  

PubMed

Glass ionomer cements (GIC) can potentially be used as matrices for the slow release of active species, as has been shown previously for fluoride ions. This study investigated the use of an experimental GIC as a carrier for the release of chlorhexidine acetate (CHA) at included concentrations ranging from 0.5% to 13.0% of CHA by weight. Release into water was examined using high-performance liquid chromatography. All measurable chlorhexidine was released within 22 h1/2, however this was less than 10% of the total mass incorporated in the specimens. An increased percentage of CHA incorporated into the powder gave an increased release into the surrounding water. The bulk of the CHA was retained within the cement. For comparison, the surface chemistry of a CHA-containing GIC was examined using X-ray photoelectron spectroscopy before and after prolonged immersion in water. This confirmed retention of a large amount of CHA. Spectra after leaching appeared very similar to those from a CHA-free GIC after immersion in a CHA solution. In order to explore the effect of CHA-inclusion on the cement properties, compressive strengths, working and setting times were also measured. In general, compressive strengths were found to be decreased in direct proportion to the quantity of CHA added, while working and setting times increased. PMID:15130727

Palmer, G; Jones, F H; Billington, R W; Pearson, G J

2004-10-01

61

Dentin Surface Treatment and Bond Strength of Glass Ionomers. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

This study evaluated the effect of dentin surface treatment on shear bond strengths of two visible light activated glass ionomer restorative materials to dentin. Cylinders of Fuji II LC and VariGlass VLC were bonded to dentin surfaces that were untreated,...

D. G. Charlton C. W. Haveman

1994-01-01

62

The processing, mechanical properties and bioactivity of zinc based glass ionomer cements  

Microsoft Academic Search

The suitability of Glass Ionomer Cements (GICs) for use in orthopaedics is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of a GIC and its absence is likely to hinder cement formation. However, zinc oxide, a bacteriocide, can act both as a network modifying

D. Boyd; M. R. Towler

2005-01-01

63

Reactivity of fluoride-containing calcium aluminosilicate glasses used in dental glass-ionomer cements.  

PubMed

The glass component critically determines the properties of glass-ionomer cements (GIC). However, the exact relationship between the composition of the glass and these properties is not yet fully understood. To investigate this relationship, we studied the reactivity of glasses used in commercial GIC in acetic acid solutions, using a pH-stat method. Qualitative differences in the leaching behavior of these glasses can be explained by different pre-treatments. Acid-washing and silanization modify the surfaces of the glass particles, thus inducing a delay of the leaching process, whereas untreated glasses exhibit a fast initial leaching, but their acid reactivity slows very soon. Quantitative differences in acid reactivity can be correlated with the mean chemical composition of the glasses. In this respect, the leaching tends to increase with an increasing ratio of network-dwelling cations to Al3+ ions. These results provide a fundamental basis for the explanation, prediction, and control of cement properties as a function of glass characteristics. PMID:9839789

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

1998-12-01

64

The effects of maturity and dehydration shrinkage on resin-modified glass-ionomer restorations.  

PubMed

The dimensional change, including hygroscopic change, of adhesive dental materials is a clinically important topic, since excessive changes could cause debonding from tooth structure. The water balance of glass-ionomer cements arises mainly from their sensitivity to the environment; depending on the surroundings, they can gain or lose water, either of which can be potentially damaging. These effects become less noticeable as the cement ages. The effects of maturity of the newer resin-modified glass-ionomer materials and their responses to changes in moisture are unknown. Using confocal microscopy, we examined the effects of dehydration stress on the glass-ionomer/tooth interface in specimens of various degrees of maturity. Wedge-shaped cervical cavities in extracted teeth were restored with one of three resin-modified glass-ionomer restorative materials. The control specimens were restored with a conventional glass ionomer. The samples were left to mature, then sectioned and examined at 1 day, 1 wk, 1 mo, 3 mos, 6 mos, and 1 yr. After being sectioned, each specimen was examined immediately with a confocal microscope with water-immersion objectives so that the subsurface interfacial characteristics could be studied. The specimen was then allowed to dehydrate under the microscope, with further examinations at 15, 30, and 60 min. Generally, gap formation at the interface occurred within 15 min of dehydration. All materials showed a different pattern of gap change with maturity, probably due to the different setting mechanisms involved. All of them were susceptible to dehydration shrinkage up to 3 mos of maturity. At 6 mos and 1 yr, Fuji II and Fuji II LC showed insensitivity to dehydration. Vitremer and Photac-Fil showed less sensitivity to dehydration at 1 yr than at 6 mos. The results of this study of the maturing polymerized resin-modified cements have potential clinical implications in the handling of these materials; the addition of resin has not significantly reduced the glass ionomer's susceptibility to dehydration problems. PMID:9240386

Sidhu, S K; Sherriff, M; Watson, T F

1997-08-01

65

Caries protection after orthodontic band cementation with glass ionomer.  

PubMed

This study evaluated the resistance of the enamel to an artificial caries challenge after removing orthodontic bands cemented with a glass ionomer cement (GIC). Ten extracted caries-free molars were cleaned with a slurry of pumice and randomly divided into 2 groups of 5 teeth each: Group 1: Cementation with GIC (Fuji) and Group 2: Cementation with a zinc phosphate cement (Mizzy). Both cements were handled according to manufacturer's instructions. Before cementing the bands, an area of S x S mm was masked with adhesive tape on the lingual surfaces of all teeth. The orthodontic bands were cemented over this adhesive tape. After band cementation, the occlusal and gingival margins of the band were delineated with a bur on the tooth surface. The teeth were thermocycled (200 cycles, 5-55 degrees C, 30-second dwell time) and stored in distilled water for 24 hours. Then, the bands and adhesive tape were removed and the teeth again stored in distilled water for a week, changing the water daily. The teeth were then varnished with the exception of a 5 x 5 mm window (including previously exposed and covered areas) on the buccal and lingual surfaces. All teeth were then placed in an acidified gel (pH 4.5) for 5 weeks to produce artificial caries. At least three sections from the exposed and covered areas were made from the buccal and lingual challenged areas. Sections were ground to approximately 100 microns. Polarized microscopy and image analysis were used to analyze the results.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8258573

Marcushamer, M; Garcia-Godoy, F; Chan, D C

66

Non metallic restorative materials based on glass ionomer cements — recent trends and developments  

Microsoft Academic Search

In this contribution to a series of papers dealing with the colloid chemistry and structure of restorative and luting material for dentistry we will present a short introduction into the state-of-the-art of applying and developing dental material based on glass ionomer cement (GIC). The basic component of glass of GIC and related material is a glass-like calcium aluminosilicate containing some

R Zimehl; M Hannig

2000-01-01

67

The structure of a glass-ionomer cement and its relationship to the setting process.  

PubMed

The G-200 glass of the glass-ionomer cement has two phases: a continuous calcium aluminosilicate matrix and partly crystalline calcium fluoride-rich droplets, the nature of which depend on the thermal history of the glass. The setting process of the cement takes place when the glass is mixed with poly(acrylic acid). It has two overlapping stages corresponding to the rapid leaching of calcium ions from the uncrystalline part of the droplets, followed by the slower release of aluminum (and some calcium) from the main glass phase. These processes are affected by the microstructure and microcomposition of the glass. PMID:284041

Barry, T I; Clinton, D J; Wilson, A D

1979-03-01

68

The role of the ionomer glass component in polyacid-modified composite resin dental restorative materials.  

PubMed

In order to model the processes that occur within polyacid-modified composite resin ("compomer") dental restoratives, a series of experiments has been carried out with silanated and silane-free ionomer glass G338, and silanated and silane-free unreactive glass (Raysorb T-4000). In an acid-base reaction with dental grade aqueous maleic acid-acrylic acid copolymer solution, the setting time of the silanted G338 was found to be 9 min, compared with 5 min for the silane-free glass. Inclusion of each glass in an experimental composite resin system showed that the formulations which contained G338 absorbed more water than the formulations which contained Raysorb T-4000, regardless of whether or not the glass was silanted. Biaxial flexure strength was superior for experimental composites containing Raysorb T-4000, with highest results being obtained with the silanated glass. Overall these results demonstrate that silanation of the filler is essential for optimal physical properties but that, for the ionomer glass, it inhibits the acid-base reaction. The presence of ionomer glass led to an increase in water uptake compared with the unreactive glass, regardless of the presence of silane. PMID:15387409

Adusei, Gabriel O; Deb, Sanjukta; Nicholson, John W

2004-07-01

69

Reactivity ofFluoride-contain ing Calcium Aluminosilicate Glasses Used inDental Glass-ionomer Cements  

Microsoft Academic Search

Theglass component critically determines the properties ofglass-ionomer cements (GIC). However, the exact relationship between thecomposition oftheglass and these properties isnotyetfully understood. Toinvestigate this relationship, westudied thereactivity ofglasses usedin commercial GICinacetic acidsolutions, usingapH-stat method. Qualitative differences intheleaching behavior of these glasses canbeexplained bydifferent pre-treatments. Acid-washing andsilanization modifythesurfaces ofthe glass particles, thusinducing adelayoftheleaching process, whereas untreated glasses exhibit afast initial leaching, buttheir

E. A. P. DeMaeyerl; R. M. H. Verbeeck; W. J. Vercruysse

70

Investigation into the Depth of Cure of Resin-Modified Glass-Ionomer Restorative Materials.  

National Technical Information Service (NTIS)

This investigation involved an attempt at delineating the depth of cure of resin-modified glass-ionomer restorative dental materials. Samples of different thicknesses using Vitremer Core Material and Restorative (3M/ESPE), Fuji II LC (GC America), and Pho...

H. W. Roberts

2006-01-01

71

Caries inhibition by a resin-modified and a conventional glass ionomer cement, in vitro  

Microsoft Academic Search

Objectives: The aim of this study was to compare inhibition, in vitro, of a resin-modified and a conventional glass ionomer cement.Methods: Standardized Class V cavities were prepared in extracted human molar teeth and restored with Fuji II LC (n = 14) or Chemfil II (n = 14) according to manufacturers' guidelines. The teeth were submerged in an acid gel (lactic

S. M. Dunne; J. S. Goolnik; B. J. Millar; R. P. Seddon

1996-01-01

72

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

PubMed

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). Conclusion. These findings suggest that adhesive cements provoke a greater SP expression when compared with glass ionomer. PMID:23722145

Caviedes-Bucheli, J; Ariza-Garcia, G; Camelo, P; Mejia, M; Ojeda, K; Azuero-Holguin, M-M; Abad-Coronel, D; Munoz, H-R

2013-05-31

73

Effects of polycarboxylate and glass ionomer cements on stainless steel crown retention  

Microsoft Academic Search

Retentive properties of three dental cements were tested using stainless steel crowns Fitted to extracted third molar teeth. No significant difference was Found between the overall mean retentive Forces of the polycarboxylate cement and the two glass ionomer cements. Mechanical retention of the crowns was not a Factor in the overall retentive value.

David P. Noffsinger; Joseph R. Jedrychowski; Angelo A. Caputo

1983-01-01

74

Gingival Reactions Around and Plaque Formation on Resin Composites and Glass-Ionomer Cements  

Microsoft Academic Search

This review covers plaque growth on and gingival reactions adjacent to composite resin and glass-ionomer cement restorations. Despite large variations in surface roughness and chemical composition of the restoratives, no clinically measurable differences in the presence or development of plaque and gingivitis were seen. However, more pronounced signs of subclinical gingivitis adjacent to resin composites, compared with non-filled surfaces, were

J. W. V. Van Dijken; S. Sjostrom

1995-01-01

75

The effect of oxalic acid incorporation on the setting time and strength of a glass-ionomer cement  

Microsoft Academic Search

Oxalic acid and its metal oxalate salts have been used extensively in dentistry in a range of applications: as desensitisers, in cavity preparation, and as bonding agents. This study investigated the influence of oxalic acid upon the working time, initial setting time, 24-h hardness and compressive strength of a glass-ionomer cement. Conventional glass-ionomer liquids were prepared from polyacrylic acid, tartaric

Leon Hugh Prentice; Martin Tyas

2006-01-01

76

Incorporation of Casein Phosphopeptide-Amorphous Calcium Phosphate into a Glass-ionomer Cement  

Microsoft Academic Search

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal and in situ caries models. The aim of this study was to determine the effect of incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation of 1.56% w\\/w CPP-ACP into the GIC significantly increased microtensile bond strength (33%) and

S. A. Mazzaoui; M. F. Burrow; M. J. Tyas; S. G. Dashper; D. Eakins; E. C. Reynolds

2003-01-01

77

Interaction of resin-modified glass-ionomer cements with moist dentine  

Microsoft Academic Search

Objectives. The objective of this study was to report on a novel phenomenon that occurs when resin-modified glass-ionomer cements (RMGICs) are bonded to moist human dentine.Methods. Dentine surfaces from extracted third molars were abraded with 180-grit SiC paper. Ten teeth were prepared for each of the two RMGICs tested (Fuji II LC, GC Corp. and Photac-Fil Quick, 3M ESPE). RMGIC

C. K. Y Yiu; F. R Tay; N. M King; D. H Pashley; R. M Carvalho; M. R. O Carrilho

2004-01-01

78

Clinical comparison of postoperative sensitivity for a glass ionomer and a zinc phosphate luting cement  

Microsoft Academic Search

In 60 patients, 120 partial and full-coverage restorations were cemented on vital abutment teeth with either a glass ionomer or a zinc phosphate luting cement. A split-mouth design and a patient blind data acquisition protocol were used. During an average observation period of 17.3 months there were no differences between the two types of luting cements in regard to subjective

Matthias Kern; Brigitte Kleimeier; Hans-Günther Schaller; Jörg Rudolf Strub

1996-01-01

79

Comparison of incus interpositioning technique versus glass ionomer cement application in type 2 tympanoplasty.  

PubMed

Objective of this study is to compare glass ionomer cement application and incus interpositioning techniques in patients who have chronic otitis media, conductive hearing loss with intact tympanic membrane and who undergo hearing reconstruction of staged surgery using a retrospective chart review in the setting of Ministry of Health Ankara Training and Research Hospital ENT Clinic, Turkey. We retrospectively evaluated patients who underwent otological surgery and hearing reconstruction with auto graft incus during 2005-2008 or glass ionomer cement during 2008-2010. Patients who had cholesteatoma, stapes fixation and tympanosclerosis were excluded. Postoperative mean follow-up time of 107 patients was 9.8 months (6-38 months, 83.2 % of them was ? 9 months). Postoperative pure tone hearing thresholds, graft status, gain scores and air bone gaps were recorded. Intact graft, dry ear on the operated side and ABG scores less than 20 dB were accepted as surgical success. Preoperative ABG score was 30.6 ± 7.93 dB in glass ionomer (group I) and 33.6 ± 11.99 dB in incus interpositioning (group II). Postoperative ABG scores were 13.6 ± 10.40 and 22.6 ± 12.39 dB, respectively, in group I and II. Success of closure in ABG scores was obtained in both groups (p < 0.001). Gain scores in group I were better (p = 0.035). Graft success (p = 0.020) correlated with gain score. Results showed that the glass ionomer cement application is a good, cost-effective technique, easy to perform and yields better hearing scores and lower complication rates compared to incus interpositioning technique. PMID:23010791

Yaz?c?, Ha?met; Uzunkulao?lu, Hakk?; Emir, Hatice Karadas; K?z?lkaya, Zeynep; Do?an, Sedat; Samim, Erdal

2012-08-04

80

Effect of sample preparation on the in vitro genotoxicity of a light curable glass ionomer cement  

Microsoft Academic Search

The glass ionomer cement Vitrebond™ showed a clear genotoxic effect in the in vitro Mammalian Cell Gene Mutation Test (HPRT Test) with CHO cells as well as in the bacterial umu-test with Salmonella typhimurium TA1535\\/pSK1002. Both DMSO and Ham's F12 cell culture medium extracts according to ISO 10993-12 (Biological evaluation of medical devices—Part 12: sample preparation and reference materials, Geneva,

B. P Müller; A Eisenträger; W Jahnen-Dechent; W Dott; J Hollender

2003-01-01

81

In vitro comparison of the shear bond strength of amalgam to tooth structure using two bonding agents--lutting glass ionomer and 4-META.  

PubMed

Bonding dental amalgam to tooth structure using 4-META has become an accepted clinical procedure. Glass ionomer cements possess the ability to bind to tooth structure as well as to the components of dental amalgam. The present in vitro study evaluates the shear bond strength of amalgam to tooth structure using luting glass ionomer as a bond mediating agent, and compares with that obtained using 4-META. Results indicate that it is possible to bond amalgam to tooth structure using a thin layer of glass ionomer cement. The shear bond strength of glass ionomer cement mediated bond is significant and may be adequate for clinical application. PMID:10530186

Sheela, K; Sudeep, P T; Hegde, V; Francis, R F; Bhat, K S; Sundeep, P T

82

The effect of glass ionomer cement Fuji IX on the hard tissues of teeth treated by sparing methods (ART and CMCR)  

Microsoft Academic Search

Purpose: The aim of the study was to assess the effect of glass ionomer fillings Fuji IX on the mineral content of the hard dental tissues of carious teeth treated by sparing methods. Material and methods: The study material consisted of 4 deciduous teeth lost due to physiological resorption. The teeth had glass ionomer fillings Fuji IX inserted after treatment

Marczuk-Kolada G; Waszkiel D; Kierklo A; Mystkowska J

2006-01-01

83

Buonocore Memorial Lecture. Glass-ionomer cements: past, present and future.  

PubMed

It was Michael Buonocore who focused the attention of the profession on adhesion in the oral cavity. He expanded the concept of adhesion of resins to enamel and investigated adhesion to dentin. The problem has been solved through the glass-ionomer cements rather than with resins, but sadly, he did not live to see them achieve maturity. The glass-ionomer cements were introduced to the profession in 1976, and they provide adhesion to both enamel and dentin through an ion exchange with the additional benefit of a continuing fluoride release throughout the life of the restoration. Solubility is low, abrasion resistance is high, and biocompatability is excellent. As a water-based material, they have an excellent chance of survival in the hostile environment of the oral cavity. Acceptance of the early versions was slow because of perceived problems with water exchange, a poor color range, and a lack of translucency. Considerable research has been carried out over the last 20 years by members of the profession and the manufacturers; at this point, the glass-ionomer cements make a very valuable contribution to everyday practice. They are now available as both an autocure and a dual-cure cement, and the color range and translucency are excellent. Problems of clinical placement have been overcome, and it is now a simple matter to take advantage of the adhesion and the fluoride release and place a restoration that is esthetic, resistant to microleakage, long lasting, and a deterent to recurrent caries. Their only limitation lies in the fact that they lack the fracture strength to rebuild marginal ridges and incisal corners. In spite of this limitation, they have opened the way for the introduction of a new range of microcavity designs that allow for conservation of remaining tooth structure to an extent never before available. In the near future physical properties will be improved still further, and the use of these cements will expand considerably. PMID:9028245

Mount, G J

84

Bond strength of resin-reinforced glass ionomer cements after enamel etching.  

PubMed

This study evaluated the shear bond strength of resin-reinforced glass ionomers to enamel etched or unetched. Human, non-carious extracted permanent molars stored in distilled water were used. Flat buccal and lingual enamel surfaces were ground wet on 600-grit silicon carbide paper. The teeth were then distributed at random into six groups of 5 teeth (10 surfaces) each: Group 1: Fuji II LC, no enamel etching; Group 2: Fuji II LC, enamel etched with 10% phosphoric acid for 10 seconds; Group 3: Dyract, no enamel etching; Group 4: Dyract, enamel etched with 10% phosphoric acid for 10 seconds; Group 5: Photac-Fil, no enamel etching; Group 6: Photac-Fil, enamel etched with 10% phosphoric acid for 10 seconds. Cylindrical samples of the glass ionomers were prepared in plastic molds and bonded to the enamel surface according to the manufacturers' instructions. All samples were placed in distilled water for 24 hours, and sheared with an Instron at a crosshead speed of 0.5 mm/minute. The results (in MPa) were: Group 1: 11.29 +/- 4.84; Group 2: 19.64 +/- 5.43; Group 3: 8.26 +/- 3.61; Group 4: 22.04 +/- 5.40; Group 5: 2.05 +/- 3.05; Group 6: 9.12 +/- 6.61. ANOVA and Student-Newman-Keuls procedure revealed that on etched enamel, Fuji II LC and Dyract had a significantly higher bond strength than all the other groups tested (P < 0.0001), but not significantly different between each other. With these two groups, cohesive failure within the material was recorded in all samples while in the unetched samples, all specimens displayed an adhesive failure (glass ionomer-enamel interface). All samples with Photac-Fil, with or without enamel etching had adhesive failures. PMID:7880480

Cortes, O; Garcia-Godoy, F; Boj, J R

1993-12-01

85

ART restorations and glass ionomer sealants in Zimbabwe: survival after 3 years.  

PubMed

Atraumatic restorative treatment (ART) consists of removing demineralised tooth tissues with hand instruments only, restoring the prepared cavity and sealing the adjacent pits and fissures with an adhesive filling material. This relatively painless, no-handpiece, minimal intervention approach to controlling dental caries is described. ART was applied in an oral health care programme in Zimbabwe that was carried out amongst secondary school students from 1994 to 1997. A new glass ionomer (Fuji IX) was used as the restorative and sealant material. Sealants were placed in high caries risk students using the 'press-finger' technique. A total of 297 one-surface ART restorations and 95 glass ionomer sealants were placed in 142 and 66 students, respectively. After 3 years, the lost-to-follow-up percentages for one-surface ART restorations and glass ionomer sealants were 30.6% and 30.5%, respectively. Actuarial (life table) analysis resulted in 3-year survival rates of one-surface ART restorations of 88.3% (95% CI: 92.4%-84.2%), ranging from 94.3% to 65.4% per operator. A total of 28 ART restorations placed in 25 students failed. Reasons for failure related to the material and the operator (11 restorations or 5.3% each), and to caries adjacent to the restoration (one restoration or 0.5%). Reasons for failure were not recorded for five restorations (2.3%). Sealants were placed on surfaces diagnosed as early enamel lesions. After 3 years, 71.4% (95% CI: 81.7%-61.1%) of the fully and partially retained sealants survived with a range of 100% to 55.6% per operator. Of the sealed surfaces 96.3% (95% CI: 100%-92.2%) survived 3 years without developing caries. Experienced operators placed better ART restorations than inexperienced operators. This study has demonstrated that ART with a glass ionomer restorative material and sealants provided high quality preventive and restorative dental care to this student population. ART has become one of the treatment modalities available to oral health workers in managing dental caries. PMID:9870536

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

1998-12-01

86

Aluminum-free glass-ionomer bone cements with enhanced bioactivity and biodegradability.  

PubMed

Al-free glasses of general composition 0.340SiO2:0.300ZnO:(0.250-a-b)CaO:aSrO:bMgO:0.050Na2O:0.060P2O5 (a, b=0.000 or 0.125) were synthesized by melt quenching and their ability to form glass-ionomer cements was evaluated using poly(acrylic acid) and water. We evaluated the influence of the poly(acrylic acid) molecular weight and glass particle size in the cement mechanical performance. Higher compressive strength (25±5 MPa) and higher compressive elastic modulus (492±17 MPa) were achieved with a poly(acrylic acid) of 50 kDa and glass particle sizes between 63 and 125 ?m. Cements prepared with glass formulation a=0.125 and b=0.000 were analyzed after immersion in simulated body fluid; they presented a surface morphology consistent with a calcium phosphate coating and a Ca/P ratio of 1.55 (similar to calcium-deficient hydroxyapatite). Addition of starch to the cement formulation induced partial degradability after 8 weeks of immersion in phosphate buffer saline containing ?-amylase. Micro-computed tomography analysis revealed that the inclusion of starch increased the cement porosity from 35% to 42%. We were able to produce partially degradable Al-free glass-ionomer bone cements with mechanical performance, bioactivity and biodegradability suitable to be applied on non-load bearing sites and with the appropriate physical characteristics for osteointegration upon partial degradation. Zn release studies (concentrations between 413 ?M and 887 ?M) evidenced the necessity to tune the cement formulations to reduce the Zn concentration in the surrounding environment. PMID:23827583

Gomes, Filipa O; Pires, Ricardo A; Reis, Rui L

2012-12-13

87

Comparison of two minimally invasive methods on the longevity of glass ionomer cement restorations: short-term results of a pilot study.  

PubMed

The purpose of this study was to evaluate the clinical performance of glass ionomer cement (GIC) restorations comparing two minimally invasive methods in permanent teeth after 12 months. Fifty pregnant women (second trimester of pregnancy), mean age 22 +/- 5.30 years, were treated by two previously trained operators. The treatment approaches tested were: chemomechanical method (Carisolv; MediTeam) and atraumatic restorative treatment (ART). A split-mouth study design was used in which the two treatments were randomly placed in 50 matched pairs of permanent teeth. The chemomechanical method (CM) was the test group and the ART was the control group. The treatments were performed in Public Health Centers. The tested restorative material was a high-strength GIC (Ketac Molar; 3M/ESPE). The restorations were placed according to the ART guidelines. Two calibrated independent examiners evaluated the restorations in accordance with ART criteria. The inter-examiner kappa was 0.97. Data were analyzed using 95% confidence interval on the binomial distribution and Fisher's exact test at 5% significance level. In a 12-month follow-up, 86% of the restorations were evaluated. In the test group (CM), 100% (CI=93.3-100%) of the restorations were considered successful. In the control group (ART) 97.6% (CI=87.4-99.9%) of the restorations were considered successful and 2.4% unsuccessful (marginal defect >0.5 mm). There was no statistically significant difference between the 12-month success rate for both groups (Fisher's exact test: P=0.49) and between the two operators (Fisher's exact test: P=1.00). Both minimally invasive methods, chemomechanical method and ART, showed a similar clinical performance after 12 months of follow up. PMID:19089209

Barata, Terezinha Jesus Esteves; Bresciani, Eduardo; Mattos, Maria Cecília Ribeiro; Lauris, José Roberto Pereira; Ericson, Dan; Navarro, Maria Fidela de Lima

88

Use of Raman spectroscopy in the characterisation of the acid–base reaction in glass-ionomer cements  

Microsoft Academic Search

Raman spectra of various combinations of glass-ionomer cement components have been compared with those of the reactants and the salts of polyacrylic and tartaric acids. The components consisted of a fast-setting acid-degradable dental glass (containing, inter alia, oxides of Si, Al, Ca, Ba and Na), polyacrylic acid (PAA) and\\/or tartaric acid (TA). On the addition of water to the glass

A. M Young; A Sherpa; G Pearson; B Schottlander; D. N Waters

2000-01-01

89

Kinetics of fluoride ion release from dental restorative glass ionomer cements: the influence of ultrasound, radiant heat and glass composition.  

PubMed

To compare the effect of ultrasonic setting with self curing on fluoride release from conventional and experimental dental glass ionomer cements. To compare hand mixed and capsule mixing and the effect of replacing some of the reactive glass with zirconia. In a novel material which advocated using radiant heat to cure it, to compare the effect of this with ultrasound. To evaluate the effect of ultrasound on a glass ionomer with fluoride in the water but not in the glass. 10 samples of each cement were ultrasonically set for 55 s; 10 controls self cured for 6 min. Each was placed in 10 ml of deionised water which was changed at 1, 3, 7, 14, 21, 28 days. The solution fluoride content was measured using a selective ion electrode. All ultrasound samples released more fluoride than the controls. Release patterns were similar; after a few days, cumulative fluoride was linear with respect to t(1/2). Slope and intercept of linear regression plots increased with ultrasound. With radiant heat the cement released less fluoride than controls. The effect of ultrasound on cement with F in water increased only slope not intercept. Zirconia addition enhances fluoride release although the cement fluorine content is reduced. Comparison of capsule and hand mixing showed no consistent effect on fluoride release. Ultrasound enhances fluoride release from GICs. As heat has an opposite effect the heat from ultrasound is not its only action. The lesser effect on cement with fluoride only in the water indicates that of ultrasound enhances fluoride release from glass. PMID:19851843

Thanjal, N K; Billington, R W; Shahid, S; Luo, J; Hill, R G; Pearson, G J

2009-10-23

90

Sealing ability of mineral trioxide aggregate, glass ionomer cement and composite resin when repairing large furcal perforations  

Microsoft Academic Search

Objective To evaluate the sealing ability of different repair materials and the pathway of bacterial penetration after closure of large pulp chamber floor perforations. Materials and methods Perforations were made in the furcation area of extracted human molars and sealed with either mineral trioxide aggregate (MTA), glass ionomer cement or resin composite. The bacterial leakage method was used with Enterococcus

M. Kleivmyr; E. Bruzell; D. Ørstavik; G. Lodiene

2011-01-01

91

Summary of: Sealing ability of mineral trioxide aggregate, glass ionomer cement and composite resin when repairing large furcal perforations  

Microsoft Academic Search

Objective To evaluate the sealing ability of different repair materials and the pathway of bacterial penetration after closure of large pulp chamber floor perforations.Materials and methods Perforations were made in the furcation area of extracted human molars and sealed with either mineral trioxide aggregate (MTA), glass ionomer cement or resin composite. The bacterial leakage method was used with Enterococcus faecalis

Asgeir Bårdsen

2011-01-01

92

Preparation of glass ionomer cement using N-acryloyl-substituted amino acid monomers — Evaluation of physical properties  

Microsoft Academic Search

Objectives. The objectives of this study were (1) to develop polyacid formulations through the incorporation of amino acid-derived monomers with carboxylic acid groups at various distances away from the polymer backbone to allow for greater flexibility, less rigid ionic cluster formation and improved solubility, and (2) to test selected physical and handling properties of experimental ionomers with a conventional glass

Elizabeth C. Kao; Bill M. Culbertson; Dong Xie

1996-01-01

93

Long-term fluoride release from a glass ionomer cement, a compomer, and from experimental resin composites.  

PubMed

The aqueous phase of glass ionomer cements enables fluoride ions to diffuse and to be released from the material. The matrix of resin composites is much less hydrophilic, and fluoride incorporated in the material is only released in small amounts. It was the purpose of the present work to study the influence of resin matrix formulation on the fluoride release from experimental, fluoride-containing resin composites. The resin composites were based on methacrylate monomers and the adduct of maleic anhydride and HEMA (2-hydroxyethyl methacrylate). The resin composites contained 1 w% or 5 w% of AlF3*3H2O. A glass ionomer cement and a compomer were used as controls. Five disks of each material were stored in distilled water at room temperature. By means of a fluoride sensitive electrode, the fluoride release from disk-shaped specimens was determined periodically over 3 years. The glass ionomer cement released the most fluoride (1.54 +/- 4 microg/cm2 after 1 year and 248 +/- 7 microg/cm2 after 3 years). The compomer released relatively little fluoride during the 1st year (30 +/- 1 microg/cm2) but after this time the rate of fluoride release became equal to that of the glass ionomer cement, resulting in a release of 122 +/- 8 microg/cm2 after 3 years. Regarding the resin composites, the fluoride release increased with the hydrophilicity and the acid character of the polymer matrix. The release, however, was significantly lower than that from the glass ionomer cement and the compomer and ranged from 1.2 +/- 0.07 to 42 +/- 3.9 microg/cm2 at 1 year and from 2.3 +/- 0.16 to 79 +/- 6 microg/cm2 at 3 years. PMID:12020121

Asmussen, Erik; Peutzfeldt, Anne

2002-03-01

94

Effect of glass-ionomer cement on the progression of proximal caries.  

PubMed

Although effective preventive strategies exist for pit and fissure caries, prevention of proximal caries remains a significant challenge. This split-mouth study was designed to investigate the effect of glass-ionomer cement (GIC) on the progression of initial proximal caries in posterior teeth, testing the hypothesis that local application of fluoride-releasing GIC would reduce this progression. GIC was applied to 41 pairs of posterior teeth after elastic band separation in 7- to 19-year-old individuals. Follow-up bitewing radiographs were taken at 6 and 12 months. Differences in ? mean lesion depth at 6 and 12 months between test and control groups were significant (p < 0.05, p < 0.000). Lesions treated with GIC were more likely to remain in or regress to the outer half of enamel (OR = 6.3; 95%CI, 1.3-30.9). GIC provides an effective approach to the clinical management of incipient proximal caries. PMID:20858776

Trairatvorakul, C; Itsaraviriyakul, S; Wiboonchan, W

2010-09-21

95

Glass ionomer cement as an occlusive barrier in Class III furcation defect.  

PubMed

Predicting the prognosis of molars that have experienced furcation invasion, is often a frustrating experience to the dental clinician and disappointing report to the patient involved. Although multiple treatment modalities have been attempted to retain teeth with severe furcation invasion, clinical success has not been predictable. A case report involving the use of glass ionomer cement (GIC) as an occlusive barrier in the management of Class III furcation defect involving mandibular first molar is presented. A literature review on the subject matter was conducted using Medline, Google search engines, and manual library search. GIC restoration of Class III furcation invasion gives a satisfactory result. Surgical and nonsurgical treatment options are available for the management of the condition. GIC as an occlusive barrier in Class III furcation invasion is an economical and less invasive treatment option. It also makes home care easy for the patient. PMID:22124057

Singhal, Rameshwari

96

N-vinylpyrrolidone modified glass-ionomer resins for improved dental restoratives  

NASA Astrophysics Data System (ADS)

The studies described in this dissertation focus on improvement of mechanical properties of current glass-ionomer cements. Thermal properties and microstructures of the cements were correlated with their mechanical strengths. The first study evaluated mechanical properties of selected commercial glass-ionomer cements and examined their microstructures. The results showed that resin-modified glass-ionomer cements (RM GICs) exhibited much higher flexural (FS) and diametral tensile strengths (DTS), compared to conventional GICs (C GICs). In addition, they exhibited comparable compressive strength (CS), relatively low microhardness and less wear resistance than C GICs. The C GICs exhibited brittle behavior, whereas the RM GICs underwent substantial plastic deformation in compression. The mechanical properties of the GICs were closely related to their microstructures. Factors such as the density of the microstructure, the integrity of the interface between the glass particles and polymer matrix, particle size and the number and size of voids have important roles in determining the mechanical properties. The second study evaluated thermal properties of these GICs. The results showed that the RM GICs exhibited higher thermal transition temperatures than those of the C GICs, thermal expansion coefficients of these cements were close to those of human teeth, and the indentation creep of the RM GICs were higher than the C GICs. The third study explored and evaluated the effect of a water-soluble monomer, N-vinylpyrrolidone (NVP), on the performance of current C GICs, indicating a significant improvement in both mechanical and working properties. The fourth study demonstrated the process of determining the optimal molar ratio of the NVP-containing copolymers, using design of experiment. The results showed that the optimal molar ratio for these copolymers was 7:1:3 for poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone), based on the FS test. The molar ratio of 8:2:1 (AA:IA:NVP) was considered as the best molar ratio for these copolymers, based on the DTS and CS tests. The fifth study formulated the NVP-containing RM GICs using a statistical design of experiment. The results indicated that the best graft ratio for 2-isocyanatoethyl methacrylate (IEM) in this system was 15% of the terpolymer by a molar ratio. The optimal formulation was found to be at the weight ratio of 55:15:30 (RM NVP-containing terpolymer: 2-hydroxyethyl methacrylate (HEMA): Hsb2O). Stress-strain curves showed that a relatively high amount of water in the formulation led to higher elastic modulus and proportional limit and lower malleability, whereas a relatively high amount of HEMA gave the opposite results. The sixth study evaluated the NVP modified GICs (NVPM GICs) with the best molar ratios and optimal formulations in the mechanical, thermal and working properties. The results showed that the effect of molecular weight on mechanical properties of the NVPM GICs were evident. Different glass powders exhibited different effects on properties of the NVPM GICs, due to different compositions, size and affinity. Powder/liquid ratios had significant effects on the mechanical properties of NVPM GICs, especially on FS. P/W ratios are only beneficial to the NVPM GICs mixed with the Fuji II glass powders. The NVPM GICs showed a higher WT than the models, due to water retention of the NVP ring. Thermal expansion coefficients for the NVPM GICs were close to those for the natural tooth. Mismatch between the glass powders used and the polymer matrix was a big concern in this study and should be solved in the future.

Xie, Dong

97

In vitro fluoride release and the antibacterial effect of glass ionomers containing chlorhexidine gluconate.  

PubMed

Fluoride release from glass-ionomers (GI) may be important for the prevention of secondary caries. The addition of chlorhexidine gluconate (CHX) to glass-ionomer cement (3%) adds an effect that enables it to be used as a varnish for the temporary coating of surfaces at risk for caries. This study investigated the fluoride release pattern and antibacterial effect of such a material. Glassionomer luting cement powder (Aqua-Cem) was mixed with water, 10% CHX or 10% CHX with 11% tartaric acid (TA), respectively, to test specimens (6 X 1.5 mm). After setting, the specimens were immersed in 10 ml deionized water and transferred to new vials after various intervals over a period of two months. The antibacterial effect towards mutans streptococci was assessed using agar diffusion. The fluoride release was measured after two hours and after shifting the specimens to new vials 10 times during the two-month period. The mean total fluoride release was 69.02, 50.64 and 48.56 microg/cm2 from each specimen in the GI, GI-CHX and the GI-CHX-TA groups, respectively. For two-hour old specimens, the mean inhibition zone was 0, 50, 36 mm2 in the GI, GI-CHX and GI-CHX-TA groups, respectively, and, after two months, 45 mm2 in the GI-CHX group and 19 mm2 in the GI-CHX-TA group. It can be concluded that the addition of CHX and CHX-TA adds antibacterial properties to GI and the release of fluoride is decreased. PMID:19051864

Hoszek, A; Ericson, D

98

In vivo bracket retention comparison of a resin-modified glass ionomer cement and a resin-based bracket adhesive system after a year  

Microsoft Academic Search

Glass ionomer orthodontic adhesives cause less enamel demineralization during fixed orthodontic appliance treatment than do traditional resin-based products. An in vivo randomized clinical trial was performed comparing the clinical performance of a resin-modified glass ionomer (RMGI) adhesive with a no-mix, resin-based (the control) adhesive over a 12-month period. The split-mouth technique was used to analyze bracket retention, bracket failure causes,

David J. Hegarty; Tatiana V. Macfarlane

2002-01-01

99

Recycling of glass fiber reinforced thermo-plastic composites. I. Ionomer and low density polyethylene based composites  

Microsoft Academic Search

Ionomer and low density polyethylene (LDPE) based composites were prepared containing 40% w\\/w glass fibers in a random in-plane orientation. These composites were then dissolved, and consequently the polymer\\/fibers solution was separated by filtration to recover the reinforcing agent and the polymer matrix. Different amounts of hot solvent were employed for washing during filtration to vary the polymer content remaining

C. D. Papaspyrides; J. G. Poulakis; C. D. Arvanitopoulos

1995-01-01

100

Chlorhexidine-containing glass ionomer cement. A clinical investigation on the fissure caries inhibiting effect in first permanent molars.  

PubMed

Glass ionomer cement with addition of chlorhexidine used as a varnish on tooth surfaces has been shown to reduce the number of interproximal mutans streptococci (ms). The effect of a single application of such a varnish containing 2.5% chlorhexidine on occlusal caries development of the first permanent molars on 6-year-old children in a high caries incidence area was investigated. The children were examined according to WHO criteria and 262 children with 2 caries free contra-lateral molars were selected for treatment. Salivary ms samples were collected using the Strip-mutans (SM) method. After brushing the occlusal surfaces with a toothbrush and pumice in water slurry, rinsing and drying with a cotton roll, glass ionomer cement containing chlorhexidine (GI-CHX) and glass ionomer (GI) were applied randomly with a micro brush and the varnish was covered with occlusal wax. At baseline, the mean defs was 18.18 and DMFS was 0.25 and after one year 18.24 and 0.83 respectively. The salivary ms scores were high or very high (SM 2 and 3) in 85.6% at baseline. At the one-year follow up, the GI-CHX and GI materials could not be detected in the fissures. Also, a large number of fissure sealants had been placed in the molars outside the study protocol; thus 4% of the GI-CHX and GI, and 70% of the untreated were sealed at year one. Overall, there was no significant difference between the caries-reducing effect of GI-CHX and GI, but a trend towards a higher effect was seen for GI-CHX. Excluding the sealed molars the reduction was 74% in the GI-CHX-group, and 71% in the GI-group. Conclusion: Addition of 2.5% chlorhexidine to glass ionomer did not seem to increase the caries-reducing effect of the varnish in this high caries incidence population. PMID:16255352

Hoszek, Anders; Struzycka, Isabel; Jozefowicz, Agata; Wojcieszek, Danuta; Wierzbicka, Maria; Wretlind, Katarina; Ericson, Dan

2005-01-01

101

Influence of powder\\/liquid mixing ratio on the performance of a restorative glass-ionomer dental cement  

Microsoft Academic Search

The influence of powder\\/liquid mixing regime on the performance of a hand-mixed restorative glass-ionomer cement (GIC) was evaluated in terms of compressive strength, working characteristics and the porosity distribution.Mean compressive fracture strengths, standard deviations and associated Weibull moduli (m) were determined from series of 20 cylindrical specimens (6mm height, 4mm diameter) prepared by hand-mixing the relative proportions of the powder

Garry J. P. Fleming; Ahmed A. Farooq; Jake E. Barralet

2003-01-01

102

Synthesis of a proline-modified acrylic acid copolymer in supercritical CO2 for glass-ionomer dental cement applications.  

PubMed

Supercritical (sc-) fluids (such as sc-CO(2)) represent interesting media for the synthesis of polymers in dental and biomedical applications. Sc-CO(2) has several advantages for polymerization reactions in comparison to conventional organic solvents. It has several advantages in comparison to conventional polymerization solvents, such as enhanced kinetics, being less harmful to the environment and simplified solvent removal process. In our previous work, we synthesized poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone) (PAA-IA-NVP) terpolymers in a supercritical CO(2)/methanol mixture for applications in glass-ionomer dental cements. In this study, proline-containing acrylic acid copolymers were synthesized, in a supercritical CO(2) mixture or in water. Subsequently, the synthesized polymers were used in commercially available glass-ionomer cement formulations (Fuji IX commercial GIC). Mechanical strength (compressive strength (CS), diametral tensile strength (DTS) and biaxial flexural strength (BFS)) and handling properties (working and setting time) of the resulting modified cements were evaluated. It was found that the polymerization reaction in an sc-CO(2)/methanol mixture was significantly faster than the corresponding polymerization reaction in water and the purification procedures were simpler for the former. Furthermore, glass-ionomer cement samples made from the terpolymer prepared in sc-CO(2)/methanol exhibited higher CS and DTS and comparable BFS compared to the same polymer synthesized in water. The working properties of glass-ionomer formulations made in sc-CO(2)/methanol were comparable and better than the values of those for polymers synthesized in water. PMID:19269267

Moshaverinia, Alireza; Roohpour, Nima; Darr, Jawwad A; Rehman, Ihtesham U

2009-02-03

103

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

Microsoft Academic Search

The aims of this study were to evaluate clinically and microbiologically the effects of two resin-modified glass-ionomer cements\\u000a (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\\u000a lesions, but without signs and symptoms of irreversible

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

2009-01-01

104

Clinical performance of Class II restorations in which resin composite is laminated over resin-modified glass-ionomer.  

PubMed

This study evaluated the one-year functioning of resin-composite/resin-modified glass-ionomer open-laminate restorations when used for restoring Class II cavities. It also investigated the effect of the thickness of the resin composite layer on the performance of such restorations. The test restorations were made of Vitremer glass ionomer, Scotchbond Multipurpose Plus and Z100 resin composite, and the control restorations were made of Z100 with Scotchbond Multipurpose Plus. Forty pairs of restorations were placed in 40 patients aged 16 years and over. The thickness of the resin composite layer was measured both clinically and in the laboratory using a reflex microscope. The completed restorations were assessed in vivo and in vitro at baseline, six-month and one-year recalls using a modified Ryge system. The reflex microscope measurements showed that the majority of restorations had a resin composite layer of more than 1.5 mm in thickness, as intended. At one year, 37 pairs of restorations were examined. Apart from a few minor problems, all performed satisfactorily. Thus, it appears that the resin composite/resin modified glass ionomer open laminate is a suitable technique for restoring Class II cavities. PMID:11203844

Aboush, Y E; Torabzadeh, H

105

Glass ionomer cement formulations: I. The preparation of novel fluoroaluminosilicate glasses high in fluorine.  

PubMed

The preparation of a large number of novel fluorine-containing aluminosilicate glasses is reported along with the properties of cements formed by their reaction to aqueous solutions of poly- (acrylic acid) (PAA). PMID:286706

Kent, B E; Lewis, B G; Wilson, A D

1979-06-01

106

Conventional glass ionomers as posterior restorations. A status report for the American Journal of Dentistry.  

PubMed

The search for a material to replace amalgam continues as a major quest in materials science. Resin composites may offer one solution but an alternative class of material, the glass ionomer cements (GICs) may have some potential for fulfilling this role. GICs were first introduced to the dental profession in 1976, and have now become an accepted part of the dental armamentarium, especially for use in low load bearing situations. They possess a low coefficient of thermal expansion similar to that of tooth structure, physicochemical bonding to both enamel and dentin, and the release of fluoride ions into the adjacent tooth tissue. These properties help to reduce marginal leakage and may contribute to a reduced incidence of recurrent decay in the restored tooth. Fluoride released into the ambient fluids has a caries-preventive effect in neighboring teeth by enhancing remineralization and inhibiting demineralization of the dental hard tissues. The main criticisms of the GICs are their brittleness, poor surface polish, porosity and surface wear. To overcome some of these deficiencies, considerable attention has been directed at improving their physical properties, especially with the addition of metal powders, the metal-modified GICs. Different metal powders have been tried, including alloys of silver and tin, pure silver, gold, titanium, palladium and stainless steel. There is conflicting data as to whether or not these materials are sufficiently strong for use in high stress restorations, especially their potential use as replacement materials for amalgam fillings. PMID:9823085

Naasan, M A; Watson, T F

1998-02-01

107

Bond strengths of two conventional glass-ionomer cements to irradiated and non-irradiated dentin.  

PubMed

This study evaluated the influence of irradiation on the dentin shear bond strength of two conventional glass ionomer cements (GICs). Thirty extracted molars were bisected in the mesio-distal direction. One-half of 20 teeth were irradiated with 60 Gy (5 days/week) for 6 weeks, and then GIC was placed on the irradiated dentin surface (Groups A1, B1). For the other halves of these tooth specimens, the GICs were first placed on their dentin surfaces and then the specimens irradiated (Groups A2, B2). The remaining 10 teeth were bisected and used as non-irradiated controls (Groups C1, C2). The GIC-dentin shear bond strengths were examined. Groups A2 and B2 had significantly lower bond strengths than groups A1, B1, C1, and C2 (p < 0.05). No significant differences were found among groups A1, B1, C1, and C2 (p > 0.05). In conclusion, irradiation may have an adverse effect on the bond strength of GICs depending on the application sequence. PMID:18972786

Yesilyurt, Cemal; Bulucu, Bilinç; Sezen, Orhan; Bulut, Güne?; Celik, Davut

2008-09-01

108

Preparation and evaluation of an experimental luting glass ionomer cement to be used in dentistry.  

PubMed

The aim of this paper is to compare the fluoride-releasing and mechanical properties of an experimental luting glass ionomer cement, which has a modified composition and a commercial luting cement. The experimental powder was obtained by sol-gel process and then, it was used to prepare the experimental cements. The properties of cement pastes, such as setting time and working time, microhardness and diametral tensile strength were determined. Fluoride release from GICs was evaluated at time intervals of 1, 7, 14, 21 and 28 days in deionized water. Atomic force microscopy (AFM) analyses showed that the surface of the experimental cements is more homogeneous than commercial GICs. The mechanical properties and the measure of liberation of fluoride of the two cements were influenced by ratio powder:liquid and chemical composition of the precursor powders. Experimental cements released less fluoride than commercial cements. However, this liberation was more constant during the analyzed period. Thus, the results obtained in this study indicated that the composition of the experimental powder modified by the niobium can lead the formation of the polysalt matrix with good mechanical properties. In other words, we can say that experimental powder offered considerable promise for exploitation in dental field. PMID:19415231

Bertolini, M J; Zaghete, M A; Gimenes, R; Padovani, G C; Cruz, C A S

2009-05-05

109

Dentin surface treatment and shear bond strength of a light-cured glass ionomer.  

PubMed

This study evaluated the effect of dentin surface treatment with polyacrylic acid on the shear bond strength of Fuji Lining LC light-cured glass ionomer lining cement (GIC). A total of 40 human, noncarious extracted permanent molars stored in distilled water were used. A flat buccal dentin surface was ground wet on 600-grit silicon carbide paper. The teeth were then randomly distributed into four groups of 10 teeth each: Group 1: dentin rinsed with distilled water, dried with oil-free compressed air, placement of cylindrical GIC samples and sheared at 15 minutes post-curing. Group 2: same as group 1, but sheared 7 days post-curing. Group 3: dentin treated with GC Conditioner for 10 seconds, rinsed with distilled water, dried with oil-free compressed air, placement of the GIC and sheared 15 minutes post-curing. Group 4: same as group 3, but sheared 7 days post-curing. The GIC was mixed in a 1:1 powder-liquid ratio. The samples were stored in distilled water until sheared with an Instron. The results revealed that dentin surface treatment with the polyacrylic acid significantly increased the shear bond strength to dentin when tested at 7 days post-curing. PMID:1299259

Garcia-Godoy, F

1992-10-01

110

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

111

Effects of N-vinylpyrrolidone (NVP) containing polyelectrolytes on surface properties of conventional glass-ionomer cements (GIC).  

PubMed

It has been found that polyacids containing an N-vinylpyrrolidinone (NVP) comonomer produces a glass inomer cement with improved mechanical and handling properties. The objective of this study was to investigate the effect of NVP modified polyelectrolytes on the surface properties and shear bond strength to dentin of glass ionomer cements. Poly(acrylic acid (AA)-co-itaconic acid (IA)-co-N-vinylpyrrolidone) was synthesized by free radical polymerization. The terpolymer was characterized using (1)H NMR, FTIR spectroscopy and viscometry for solution properties. The synthesized polymers were used in glass ionomer cement formulations (Fuji II commercial GIC). Surface properties (wettability) of modified cements were studied by water contact angle measurements as a function of time. Work of adhesion values of different surfaces was also determined. The effect of NVP modified polyacid, on bond strength of glass-ionomer cement to dentin was also investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to one- and two-way analysis of variance (ANOVA) at alpha=0.05. Results showed that NVP modified glass ionomer cements showed significantly lower contact angles (theta=47 degrees) and higher work of adhesion (WA=59.4 erg/cm(2)) in comparison to commercially available Fuji II GIC (theta=60 degrees and WA=50.3 erg/cm(2), respectively). The wettability of dentin surfaces conditioned with NVP containing terpolymer was higher (theta=21 degrees, WA=74.2 erg/cm(2)) than dentin conditioned with Fuji conditioner (theta=30 degrees, WA=69 erg/cm(2)). The experimental cement also showed higher but not statistically significant values for shear bond strength to dentin (7.8 MPa), when compared to control group (7.3 MPa). It was concluded that NVP containing polyelectrolytes are better dentin conditioners than the commercially available dentin conditioner (Fuji Cavity Conditioner, GC). NVP containing terpolymers can enhance the surface properties of GICs and also increase their bond strength to the dentin. PMID:19556000

Moshaverinia, Alireza; Roohpour, Nima; Ansari, Sahar; Moshaverinia, Maryam; Schricker, Scott; Darr, Jawwad A; Rehman, Ihtesham U

2009-06-24

112

Longevity of extensive class II open-sandwich restorations with a resin-modified glass-ionomer cement.  

PubMed

Several new techniques have been introduced for use in the esthetic restoration of posterior cavities to substitute for the presumed toxicity of amalgam. Composite-laminated glass-ionomer cement restorations, the sandwich technique, have been recommended for caries-risk patients. Clinical evaluation of the use of conventional glass-ionomer cements in the open-sandwich restoration has shown a high failure rate. The aim of this study was to evaluate the durability and cariostatic effect of a modified open-sandwich restoration utilizing a resin-modified glass-ionomer cement (RMGIC) in large cavities. The materials consisted of 274 mostly extensive Class II Vitremer/Z100 restorations performed by four dentists in 168 adults. Six experimental groups were investigated. In four groups a thick and in two groups a thin layer of cement was placed. Cavity conditioning before application of the RMGIC self-etching primer was done in 3 groups with polyacrylic acid and in one group with maleic acid; in two groups, only water rinsing was performed. The restorations were evaluated at baseline and after 6, 12, 24, and 36 months according to modified USPHS criteria (van Dijken, 1986). After 3 years, 239 restorations were evaluated. Twelve (5%) were estimated as non-acceptable. Two were replaced, and seven were repaired with resin composite. Tooth fractures were observed in 2.5%. Slight erosion of the RMGIC part was seen in 4%, and in one case operative treatment was indicated. Post-operative sensitivity was reported for 9 teeth. Forty-three percent of the patients were considered as caries-risk patients. Only one restoration showed secondary caries. The three-year results indicated that the modified open-sandwich restoration is an appropriate alternative to amalgam including extensive restorations. PMID:10403459

van Dijken, J W; Kieri, C; Carlén, M

1999-07-01

113

Surface texture of resin-modified glass ionomer cements: effects of finishing/polishing systems.  

PubMed

This study investigated the surface texture of two resin-modified glass ionomer cements (RMGICs) in the vertical and horizontal axis after treatment with different finishing/polishing systems. Class V preparations were made on the buccal and lingual/palatal surfaces of freshly extracted teeth. The cavities on each tooth were restored with Fuji II LC (GC) and Photac-Fil Quick (ESPE) according to manufacturers' instructions. Immediately after light-polymerization, gross finishing was done with 8-flute tungsten carbide burs. The teeth were then randomly divided into four groups and finished/polished with (a) Robot Carbides (RC); (b) Super-Snap system (SS); (c) OneGloss (OG) and (d) CompoSite Points (CS). The sample size for each material-finishing/polishing system combination was eight. The mean surface roughness (microm) in vertical (RaV) and horizontal (RaH) axis was measured using a profilometer. Data was subjected to ANOVA/Scheffe's tests and Independent Samples t-test at significance level 0.05. Mean RaV ranged from 0.59-1.31 and 0.83-1.52, while mean RaH ranged from 0.80-1.43 and 0.85-1.58 for Fuji II LC and Photac-Fil, respectively. Results of statistical analysis were as follows: Fuji II LC: RaV-RC, SS

Yap, Adrian U J; Tan, W S; Yeo, J C; Yap, W Y; Ong, S B

114

Degree of conversion and hardness of two different systems of the Vitrebond™ glass ionomer cement light cured with blue LED.  

PubMed

This study investigated the physicochemical properties of the new formulation of the glass ionomer cements through hardness test and degree of conversion by infrared spectroscopy (FTIR). Forty specimens (n = 40) were made in a metallic mold (4 mm diameter x 2 mm thickness) with two resin-modified glass ionomer cements, Vitrebond™ and Vitrebond™ Plus (3M/ ESPE). Each specimen was light cured with blue LED with power density of 500 mW/cm(2) during 30 s. Immediately after light curing, 24h, 48h and 7 days the hardness and degree of conversion was determined. The Vickers hardness was performed by the MMT-3 microhardness tester using load of 50 gm force for 30 seconds. For degree of conversion, the specimens were pulverized, pressed with KBr and analyzed with FT-IR (Nexus 470). The statistical analysis of the data by ANOVA showed that the Vitrebond™ and Vitrebond™ Plus were no difference significant between the same storage times (p > 0.05). For degree of conversion, the Vitrebond™ and Vitrebond™ Plus were statistically different in all storage times after light curing. The Vitrebond™ showed higher values than Vitrebond™ Plus (p < 0.05). The performance of Vitrebond™ had greater results for degree of conversion than Vitrebond™ Plus. The correlation between hardness and degree of conversion was no evidence in this study. PMID:23811653

Calixto, Luiz Rafael; Tonetto, Mateus Rodrigues; Pinto, Shelon Cristina Souza; Barros, Erico Damasceno; Borges, Alvaro Henrique; Lima, Fabricio Viana Pereira; de Andrade, Marcelo Ferrarezi; Bandéca, Matheus Coelho

2013-03-01

115

Surface finish of resin-modified and highly viscous glass ionomer cements produced by new one-step systems.  

PubMed

This study investigated the surface finish of resin-modified (Fuji II LC, GC) and highly viscous (Fuji IX GP Fast, GC) glass ionomer cements after treatment with three one-step finishing/polishing systems (One-Gloss [OG], Shofu; Pogo [PG], Dentsply; Sof-Lex Brush [SB], 3M-ESPE). The surface roughness obtained was compared to that using a matrix strip [MS], a two-step rubber abrasive (CompoSite [CS], Shofu) and a graded abrasive disk (Super Snap [SS], Shofu) system. Eight specimens (3-mm long x 3-mm wide x 2-mm deep) of each material were made for the various treatment groups. With the exception of the MS group, all groups were roughened with 320 grit grinding paper using a lapping device prior to finishing/polishing with the different systems. The mean surface roughness (microm) was measured with a profilometer. Data was subjected to ANOVA/Scheffe's tests at significance level 0.05. Mean Ra ranged from 0.13 to 1.04 microm for Fuji II LC and 0.14 to 0.81 for Fuji IX GP. For both materials, the smoothest surface was obtained with MS and the roughest with OG. Depending on the materials, the surface finish produced by PG and SB was superior or comparable to that obtained with CS and SS. The effectiveness of one-step systems, when used to finish/polish resin-modified and highly viscous glass ionomer cements, is product dependent. PMID:14753338

Yap, Adrian U J; Ng, J J; Yap, S H; Teo, C K

116

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

PubMed

The objective of this study is to investigate the effects of application of ultrasound on the physical properties of a novel NVC (N-vinylcaprolactam)-containing conventional glass-ionomer cement (GIC). Experimental GIC (EXP) samples were made from the acrylic 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. Specimens were mixed and fabricated at room temperature and were conditioned in distilled water at 37°C for 1 day up to 4 week. Ultrasound (US) was applied 20 s after mixing by placing the dental scaler tip on the top of the cement and applying light hand pressure to ensure the tip remained in contact with cement without causing any deformation. Vickers hardness was determined using a microhardness tester. The working and setting times were determined using a Gillmore needle. Water sorption was also investigated. Commercial Fuji IX was used as control for comparison (CON). The data obtained for the EXP GIC set through conventional set (CS) and ultrasonically set (US) were compared with the CON group, using one-way ANOVA and the Tukey multiple range test at ? = 0.05. Not only ultrasonic (US) application accelerated the curing process of both EXP cement and CON group but also improved the surface hardness of all the specimens. US set samples showed significantly lower water sorption values (P < 0.05) due to improved acid-base reaction within the GIC matrix and accelerated maturation process. According to the statistical analysis of data, significant increase was observed in the surface hardness properties of CS and US specimens both in EXP samples and the CON groups. It was concluded that it is possible to command set GICs by the application of ultrasound, leading to GICs with enhanced physical and handling properties. US application might be a potential way to broaden the clinical applications of conventional GICs in restorative dentistry for procedures such as class V cavity restorations. PMID:21769626

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

2011-07-19

117

Clinical attachment level gain and bone regeneration around a glass ionomer restoration on root surface wall of periodontal pocket  

PubMed Central

A case describing perio-restorative management of an accidental trauma in the mid portion of root on an upper left canine tooth following an ostectomy surgery is presented here. The traumatized root area was undergoing fast resorption and a chronic periodontal abscess had developed in relation to the lesion. The article illustrates the clinical and radiographic photo series of a periodontal flap surgery done to gain access into a subgingival region for the placement of Glass ionomer restoration on the root and its periodic follow up. The clinical condition of the area suggests 8 mm clinical attachment gain over the restoration and the review radiographs at definite intervals up to 18 months revealed evidence of consistent bone regeneration around the restoration. The article also highlights the various other possibilities, where this restorative material can be effectively used in conjunction with periodontal surgical procedures.

Biniraj, K. R.; Sagir, Mohammed; Sunil, M. M.; Janardhanan, Mahija

2012-01-01

118

Synthesis and application of novel multi-arm poly(carboxylic acid)s for glass-ionomer restoratives.  

PubMed

We have developed a novel glass-ionomer cement system composed of multi-arm poly(acrylic acid-co-itaconic acid)s. These polyacids were synthesized via a chain-transfer polymerization reaction using newly synthesized multi-arm chain-transfer agents. The cements formulated with the multi-arm polyacids showed significantly lower viscosities in water as compared to those formulated with the linear polyacids. Due to the lower viscosities, the MW of the polyacids can be significantly increased for enhanced mechanical strengths, while keeping the ease of mixing and handling. The experimental cements showed significantly improved compressive strengths as compared to Fuji II after aged in water for 3 months. PMID:19033326

Xie, Dong; Zhao, Jun; Weng, Yiming

2008-11-25

119

The use of laser-induced breakdown spectroscopy for the determination of fluorine concentration in glass ionomer cement  

NASA Astrophysics Data System (ADS)

The influence of He atmosphere and gate width in laser-induced breakdown spectroscopy (LIBS) determination of fluorine concentration was investigated in detail. The measurements were realized on two double pulse LIBS devices featuring different parameters. Calibration curves, describing the relationship between the fluorine concentration and the corresponding intensity of the LIBS signal, were constructed for both LIBS devices, with and without He flow, respectively. Detection limits achieved were in the range 1.18-0.47 wt.%. The best LOD value was obtained in He atmosphere. The LIBS measurement of fluorine content is influenced by different gate widths and the atmosphere in the working chamber. The proposed method was successfully applied to the determination of fluorine concentration in glass ionomer cements.

Kratochvíl, T.; Pouzar, M.; Novotný, K.; Havránek, V.; ?ernohorský, T.; Zvolská, M.

2013-10-01

120

A 2-year clinical study of two glass ionomer cements used in the atraumatic restorative treatment (ART) technique.  

PubMed

The purpose of the study was to evaluate, in a clinical study over 2 years, the deterioration of two glass ionomer cements used with the atraumatic restorative treatment (ART) technique or approach. Fifty-five Fuji IX and 45 ChemFil Superior restorations were placed randomly in 23 adult patients, mainly in small occlusal preparations in molar teeth. The restorations were placed in a dental hospital by one dentist using the ART technique. Photographs, radiographs and replicas were obtained at baseline and subsequent recalls. Both cements were easy to mix and place, but the radiolucency of ChemFil Superior was a disadvantage. Both cements also showed early high losses of sealant and restorative material. After 2 years, 34.5% of the sealants appeared to be completely lost, with caries recorded in 5.3% of the exposed fissures. In some instances, these small lesions may have been present, but not detected clinically, at the time of sealing. Restoration failures of 7.0% were from wear and fracture of the cements and recurrent caries. Mean cumulative wear was 83.1 microm for Fuji IX and 104.0 microm for ChemFil Superior, which was not statistically significant. The cements became darker after their placement to more closely match the restored teeth, but there were few exact matches. There was no surface staining and only minor marginal discrepancies and staining associated with the restorations. Although the short-term clinical performance of the two glass ionomer cements was reasonable, the materials require further improvements in their mechanical properties, to reduce sealant losses and wear. The cements evaluated appear suitable for restricted use only, in posterior teeth. PMID:10385357

Ho, T F; Smales, R J; Fang, D T

1999-06-01

121

Fracture patterns of glass-ionomer cement overlays versus stainless steel bands during endodontic treatment: an ex-vivo study.  

PubMed

AIM: To compare fracture patterns of posterior teeth temporized with: mesio-occlusal-distal (MOD) glass-ionomer cement (GIC) interim restorations, stainless steel (SS) bands, GIC dome overlays and GIC dome overlays with occlusal temporary restorations. METHODOLOGY: The root canals of 92 extracted human premolars and molars were prepared with rotary NiTi instruments and dressed with calcium hydroxide paste prior to cavity preparation for standardized MOD restorations. Teeth were divided into four groups (n = 23) and temporarily restored with: GIC interim restorations (GIC group), stainless steel bands (SS group), GIC dome overlays (GIC-O group) or GIC dome overlays with intermediate restorative material (IRM) in the access cavities (GIC-IRM group). Teeth were subjected to compressive axial load until fracture; fracture forces and fracture modes were recorded. Statistical analysis included Kaplan-Meier plots, Cox proportional hazards model, one-way analysis of variance, chi-square and Fisher's exact tests. RESULTS: There was a significantly higher risk of failure in the GIC group compared with the SS (P < 0.001), GIC-O (P < 0.001) and GIC-IRM (P = 0.001) groups. The mean fracture force for SS was significantly higher than GIC-O (P = 0.03) and GIC-IRM (P < 0.001). GIC fracture force was significantly lower than all other groups (P < 0.001). Significantly fewer unfavourable fractures were observed in SS compared with GIC (P = 0.001), GIC-O (P = 0.007) and GIC-IRM (P < 0.001). CONCLUSIONS: Glass-ionomer cement dome overlays with reduced cuspal height and occlusal inclines may be recommended for broken-down posterior teeth, without any risk of poor aesthetics, gingival irritation or further proximal tooth structure loss. Stainless steel bands may only need to be used in extensively broken-down teeth or in the presence of parafunctional habits. PMID:23550590

Pakdeethai, S; Abuzar, M; Parashos, P

2013-03-14

122

Evaluation of surface roughness and hardness of different glass ionomer cements  

PubMed Central

Objectives: The aim of this study was to evaluate surface roughness and hardness of a nanofiller GIC, a resin-modified GIC, three conventional GICs, and a silver-reinforced GIC. Methods: For each material, 11 spcecimens were prepared and then stored in distilled water at 37 °C for 24 h. The surface roughness of 5 specimens was measured using a surface profilometer before polishing and after polishing with coarse, medium, fine, superfine aluminum oxide abrasive Sof-Lex discs respectively. The hardness of the upper surfaces of the remaining 6 specimens was measured with a Vickers microhardness measuring instrument. Results: All tested GICs showed lower surface roughness values after the polishing procedure. Surface finish of nanofiller GIC was smoother than the other tested GICs after polishing. This was followed by resin-modified GIC, Fuji II LC; then silver-reinforced GIC, Argion Molar, conventional GICs, Aqua Ionofil Plus, Fuji IX, and Ionofil Molar, respectively. The result of the hardness test indicated that the microhardness value of silver-reinforced GIC was greater than that of the other GICs. When the hardness values of all tested GICs were compared, the differences between materials (except Aqua Ionofil Plus with Ionofil Molar and Ketac N100 with Fuji II LC (P>.05)) were found statistically significant (P<.05). Conclusions: According to the results of this study, it can be concluded that the differences in the composition of GICs may affect their surface roughness and hardness.

Bala, Oya; Arisu, Hacer Deniz; Yikilgan, Ihsan; Arslan, Seda; Gullu, Abdulkadir

2012-01-01

123

Short-term evaluation of the pulpo-dentin complex response to a resin-modified glass-ionomer cement and a bonding agent applied in deep cavities  

Microsoft Academic Search

Objectives. To evaluate the response of the pulpo-dentin complex following application of a resin-modified glass-ionomer cement or an adhesive system in deep cavities performed in human teeth.Methods. Deep class V cavities were prepared on the buccal surface of 26 premolars. In Group 1 the cavity walls (dentin) and enamel were conditioned with 32% phosphoric acid and the dentin adhesive system

Carlos Alberto de Souza Costa; Elisa Maria Aparecida Giro; Alexandre Batista Lopes do Nascimento; Hilcia Mezzalira Teixeira; Josimeri Hebling

2003-01-01

124

Three-Year Survival of One-Surface ART Restorations and Glass-Ionomer Sealants in a School Oral Health Programme in Zimbabwe  

Microsoft Academic Search

An oral health care programme in secondary schools using the atraumatic restorative treatment (ART) approach for dental caries was started in 1993. Glass ionomer (restorative type II, 1) was used as the restorative and sealant material. Sealants were placed using the ‘press-finger’ technique. Results after 3 years revealed a survival percentage for one-surface ART restorations of 85.3 (95% CL: 89.7–80.9%),

J. E. Frencken; F. Makoni; W. D. Sithole; E. Hackenitz

1998-01-01

125

[Study on disintegration of glass ionomer cements. Effect of the starting time of immersion on the dissolution of Ca, Al and Si].  

PubMed

The disintegration of glass ionomer cements was evaluated with referred to the amounts of component elements of powders dissolved into solutions at various starting times of immersion. Glass ionomer cement products, three for luting and three for filling, were used. The starting times of immersion in solutions were; setting time and 10, 30 and 60 minutes and 24 hours after start of mixing. After the immersion in 30 ml of distilled water and physiological saline solution for 1 week, these solutions were analyzed by an atomic absorption spectrophotometer to determine the amounts of Ca, Al and Si. The amount of each element dissolved was highest when immersion in the solutions was started at the setting time except for Ca dissolved in physiological saline solution, and it tended to decrease as the start of immersion in the solutions was delayed. Some products contained Sr instead of Ca. The results indicated that glass ionomer cement should be protected from exposure to oral fluids for about 30 minutes in clinical use. PMID:2135529

Nomata, H

1990-05-01

126

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.

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

2013-01-01

127

A preliminary report on the effect of storage in water on the properties of commercial light-cured glass-ionomer cements.  

PubMed

Two commercially available light-curable glass-ionomer cements, Vitrebond and XR-Ionomer, have been studied and their compressive strengths measured following storage under wet and dry conditions for varying lengths of time up to 3 months. The strongest cements were those stored in air and allowed to age. On the other hand, cements that were stored in water were found to become progressively weaker with time. Their failure mode was different from that of cements stored in air in that specimens became barrel-shaped as they were loaded and exhibited considerable plastic deformation prior to fracturing. By contrast, air-stored specimens behaved as predominantly brittle materials, the specimens essentially maintaining their integrity up to the point of catastrophic failure. Both of these findings indicate that the properties of these particular light-cured cements change markedly on exposure to moisture, a fact which is of clinical significance. PMID:1503849

Nicholson, J W; Anstice, H M; McLean, J W

128

Glass-ionomer Cement Formulations. II. The Synthesis of Novel Polycarboxylic Acids  

Microsoft Academic Search

The synthesis of many polycarboxylic acids is reported. An account is given of their stability in aqueous solution and the properties of cements formed by their reaction with ion-leachable glasses. A copolymer of acrylic and itaconic acids was found to combine several favorable characteristics.

Stephen Crisp; Brian E. Kent; Brian G. Lewis; Alan J. Ferner; Alan D. Wilson

1980-01-01

129

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

130

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.

2011-01-01

131

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

PubMed

This study was designed to evaluate microleakage that appeared on Resin-Modified Glass-Ionomer Cement (RMGIC) restorations. Sixty class V cavities (h x w x l = 2 mm x 2 mm x 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

2010-06-06

132

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).

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

2010-01-01

133

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

134

Comparative quantitative and qualitative assessment of the marginal adaptation and apposition of bonded amalgam restorations using luting glass ionomer and 4-META adhesive liner under a scanning electron microscope. An in vitro study.  

PubMed

The present invitro study was conducted to assess the marginal adaptation and apposition of amalgam restorations bonded to tooth structure, using freshly mixed luting glass ionomer cement (type 1) and compared with the much documented material--Amalgam bond (4-META). Twelve freshly extracted human premolar teeth were used and class V cavities were prepared on the buccal and lingual surfaces of twelve teeth for the experimental groups. Buccal cavities (class V) were prepared on twelve other teeth for the control group. In the control, two coats of cavity varnish was applied as the liner. The experimental groups were lined with freshly mixed luting glass ionomer in twelve buccal cavities and amalgam bond adhesive liner in twelve lingual cavities. The amalgam was then condensed before the liner sets in all the cavities. The teeth were sectioned and mounted on aluminum stubs and then placed in the scanning electron microscope and were observed. The results of the study showed that marginal interface gaps were higher with luting glass ionomer and cavity varnish than with amalgam bond as the liner. The results were statistically not significant. All the three groups were effected by the severe thermal stresses introduced by the microscopy with the glass ionomer cement suffering the worst. The present investigation confirms that glass ionomer cement (type 1) can be effectively used as a bonding agent between amalgam and the tooth when it is painted onto the cavity walls after which the amalgam is condensed immediately, prior to its setting. Its ability to bond amalgam to the tooth structure with minimal gaps is comparable to that of amalgam bond. PMID:10865391

Abraham, M M; Sudeep, P T; Bhat, K S

135

Combination Flap Surgery with Resin-Modified Glass Ionomer for the Treatment of Radicular Lesions: A Long-Term Follow-up.  

PubMed

This retrospective study evaluated the long-term clinical success of combination therapy using resin-modified glass ionomer (RMGI) with flap surgery in treating subgingival radicular defects. The study population consisted of 142 patients with 188 radicular defects. Clinical parameters (pocket depth, recession, clinical attachment level [CAL], and bleeding on probing) were evaluated. Statistically significant CAL gain was observed from baseline to follow-up in successful cases (4.3 ± 0.1 mm to 4.1 ± 0.1 mm, respectively; P < .01). RMGI with flap surgery demonstrated an overall success rate of 86.7% (77.7% with open flap debridement and 94.4% with coronally advanced flap with or without connective tissue graft), with favorable and stable clinical results over a mean period of 4.2 years (longest follow-up, 13 years). PMID:24116366

Perez, Luis A; Lee, Angie; Medina, Gioconda; Eber, Robert; Wang, Hom-Lay; Oh, Tae-Ju

136

Shear bond strength of acidic primer, light-cure glass ionomer, light-cure and self cure composite adhesive systems - an in vitro study.  

PubMed

Background: The purpose of this study was to determine shear bond strength and the effect on the bracket/ adhesive failure mode when an acidic primer and other etchants were used to condition the enamel surface before bonding. Materials & Methods: Group I: Brackets bonded with Ultimate cure-on-light Light-cure composite adhesive system. Group II: Brackets bonded with Ortho-one no-mix. Self-cure composite adhesive system. Group III: Brackets bonded with Light-cure glass ionomer adhesive system. Group IV: Brackets bonded with Transbond plus self etching primer. Results: The results of this study indicated that the shear bond strength when using Transbond plus self etching primer showed the highest bond strength Group- IV(8.69 2.54 MPa) followed by Ultimate cure-on-light Group-I (8.62 1.84 MPa), Ortho-one no-mix (Bisco Inc. USA)Group-II (8.07 1.72 MPa), and least bond strength was seen in G.C. Fuji Ortho L.C. Group-III (6.01 1.6) MPa Conclusion: Use of self etching primer saves chairside time and satisfactory high bond strength was obtained. Care should be taken during debonding of ceramic brackets How to cite this article: Reddy K D, Kishore M S V, Safeena S. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study. J Int Oral Health 2013; 5(3):73-78. PMID:24155606

D, Krishnakanth Reddy; V, Kishore M S; Safeena, Safeena

2013-06-23

137

Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study  

PubMed Central

Background: The purpose of this study was to determine shear bond strength and the effect on the bracket/ adhesive failure mode when an acidic primer and other etchants were used to condition the enamel surface before bonding. Materials & Methods: Group I: Brackets bonded with Ultimate cure-on-light Light-cure composite adhesive system. Group II: Brackets bonded with Ortho-one no-mix. Self-cure composite adhesive system. Group III: Brackets bonded with Light-cure glass ionomer adhesive system. Group IV: Brackets bonded with Transbond plus self etching primer. Results: The results of this study indicated that the shear bond strength when using Transbond plus self etching primer showed the highest bond strength Group- IV(8.69 2.54 MPa) followed by Ultimate cure-on-light Group-I (8.62 1.84 MPa), Ortho-one no-mix (Bisco Inc. USA)Group-II (8.07 1.72 MPa), and least bond strength was seen in G.C. Fuji Ortho L.C. Group-III (6.01 1.6) MPa Conclusion: Use of self etching primer saves chairside time and satisfactory high bond strength was obtained. Care should be taken during debonding of ceramic brackets How to cite this article: Reddy K D, Kishore M S V, Safeena S. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study. J Int Oral Health 2013; 5(3):73-78.

D, Krishnakanth Reddy; V, Kishore M S; Safeena, Safeena

2013-01-01

138

Synthesis and characterization of a novel N-vinylcaprolactam-containing acrylic acid terpolymer for applications in glass-ionomer dental cements.  

PubMed

In this study a novel N-vinylcaprolactam (NVC)-containing copolymer of acrylic-itaconic acid was synthesized, characterized and incorporated into Fuji IX conventional glass-ionomer cement (GIC). Subsequently, the effects of incorporation of synthesized terpolymer on the mechanical properties of GIC were studied. The synthesized terpolymer was characterized using (1)H nuclear magnetic resonance, Fourier transform infrared and Raman spectroscopy. The viscosity and molecular weight of the terpolymer were also measured. The compressive strength (CS), diametral tensile strength (DTS) and biaxial flexural strength (BFS) of the modified GICs were evaluated after 24h and 1week of immersion in distilled water at 37 degrees C. The handling properties (working and setting times) of the resulting modified cements were also evaluated. One-way analysis of variance was used to study the statistical significance of the mechanical strengths and handling properties in comparison to the control group. The results showed that NVC-containing GIC samples exhibited significantly higher (P<0.05) DTS (38.3+/-10.9MPa) and BFS (82.2+/-12.8MPa) in comparison to Fuji IX GIC (DTS=19.6+/-11.4MPa; BFS=41.3+/-10.5MPa). The experimental cement also showed higher but not statistically significant values for CS compared to the control material (CS for NVC-containing sample=303+/-32.8MPa; CS for Fuji XI=236+/-41.5MPa). Novel NVC-containing GIC has been developed in this study, with a 28% increase in CS. The presented GIC is capable of doubling the DTS and BFS in comparison to commercial Fuji IX GIC. The working properties of NVC-containing glass-ionomer formulations are comparable and are acceptable for water-based cements. PMID:19289308

Moshaverinia, Alireza; Roohpour, Nima; Darr, Jawwad A; Rehman, Ihtesham U

2009-02-20

139

Influence of storage conditions and effect of metal priming agents on bond strength of resin-modified glass ionomers to gold alloy.  

PubMed

This study evaluated the influence of water storage conditions and the effect of metal priming agents on bond strength and durability of four luting agents joined to gold alloy. Disk specimens were cast from a gold alloy (Degudent U), and the surfaces were ground flat with abrasive paper. Three surface conditions employed were: unprimed, primed with Alloy Primer, and primed with Metaltite. Three resin-modified glass ionomers (RMGIs; Vitremer Luting Cement, Fuji Lute, and Xeno Cem Plus) and a resin adhesive (Super-Bond C&B) were used for bonding the gold alloy. Unprimed specimens bonded either with Fuji Lute or with Super-Bond C&B were immersed in water at 5, 37, and 55 degrees C for 7 days, or subjected to thermocycling (5,000 cycles; 5 degrees C, 1 min and 55 degrees C, 1 min). In addition, specimens were bonded with 12 combinations comprising three surface conditions and four luting agents, and thermocycled for 20,000 cycles. Shear bond strengths were then determined and analyzed statistically. Thermocycling was useful for evaluation of the bonding durability of RMGIs. Application of two metal priming agents combined with RMGIs considerably enhanced the bond strength to the gold alloy. PMID:19325196

Oshima, Akiko

2009-03-01

140

Comparison of the Shear Bond Strength of Resin Modified Glass Ionomer to Enamel in Bur-Prepared or Lased Teeth (Er:YAG)  

PubMed Central

Objective: The purpose of this study was to evaluate the effect of Er:YAG laser on the shear bond strength of resin modified glass ionomer (RMGI) to enamel. Materials and Methods: Twenty extracted caries-free human premolars were selected. The teeth were embedded in acrylic resin. The buccal surfaces of each sample were ground to plane enamel with carbonated disc. The teeth were randomly divided in two groups. In the first group, the surfaces were treated by Er:YAG laser (350mJ/10Hz). The second group was prepared by carbide bur. Fuji IX RMGI was adhered to surfaces of the samples in both groups in rod shape. The shear bond strength of samples was measured by a universal testing machine. The results of the two groups were analyzed by T- test. Results: The means and standard deviations of shear bond strength of the laser-treated group and the bur-treated group were 6.75 ± 1.99 and 4.41 ± 1.62 Mpa, respectively. There is significant difference in the shear bond strength of RMGI between the two groups (P-value=0.01). Conclusion: The laser group showed better results. Er:YAG laser can be an alternative technology in restorative dentistry.

Jafari, Ahmad; Shahabi, Sima; Chiniforush, Nasim; Shariat, Ali

2013-01-01

141

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

142

Effect of the CO2 laser on the microleakage of conventional and laser apicetomized teeth retrofilled with glass ionomer: in vitro study  

NASA Astrophysics Data System (ADS)

There is a need for further improvement on the level of apical sealing. The use of lasers on apical surgery is still not fully understood, however some good results have been reported. The aim of this study was to assess the effect of the use of the CO2 laser following conventional apicoectomy and retrofilling with glass ionomer using different combinations of power and types of emission 'In Vitro.' Seventy extracted human upper anterior teeth were used on this study. The teeth after conventional apicoectomy were retrofilled with VitremerTM. The samples were randomized into seven groups of 10, Group I acted as negative control. Groups II, III and IV were lased on defocused mode with superpulsed CO2 laser on CW with power output of 0,5; 3 and 7 Watts during 5 seconds respectively. Groups V, VI e VII were lased on defocused mode with continuous emission on CW mode with power output of 1, 10 and 20 Watts during 5 seconds respectively. All specimens were immersed on 2% Methylene Blue solution during 48 h, washed in running tap water and longitudinally sectioned. Three calibrated examiners regarding apical infiltration graded the samples. The results showed difference between groups, where Group II showed smaller level of apical infiltration. It is concluded that improving on apical sealing is better achieved by using 0.5 W on superpulsed on CW.

Pinheiro, Antonio L.; Martorelli, Sergio B.

2000-03-01

143

An investigation into the structure and reactivity of calcium-zinc-silicate ionomer glasses using MAS-NMR spectroscopy  

Microsoft Academic Search

The suitability of Glass Polyalkenoate Cements (GPCs) for orthopaedic applications is retarded by the presence in the glass\\u000a phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and\\u000a its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium-free GPCs may\\u000a be formulated based on

D. Boyd; M. R. Towler; R. V. Law; R. G. Hill

2006-01-01

144

Effect of acid pre-conditioning and/or delayed light irradiation on enamel bond strength of three resin-modified glass ionomers  

PubMed Central

Background: Polymerization of resin-modified glass-ionomers (RMGIs) is mediated through two competing mechanisms: An acid-base reaction and a light-dependent resin polymerization. Furthermore, pre-conditioning with acid has resulted in an increase in enamel bond strength of some RMGIs. This in vitro study evaluated the effect of pre-conditioning and/or delayed irradiation on bond strength of three RMGIs to enamel. Materials and Methods: In this in vitro study, 144 flat enamel surfaces of human molars were ground using consecutively finer abrasives up to 600-grit silicon carbide paper. Each surface was rinsed and gently air-dried (n =12). The RMGIs (Fuji II LC Improved; Ionolux and Vitremer) were bonded to enamel surfaces using the following protocols: Groups 1: Based on manufacturers’ instructions; Groups 2: Pre-conditioning with phosphoric acid for 30 s; groups 3: A 2-min delay in irradiation; groups 4: Pre-conditioning with acid for 30 s plus a 2-min delay in light activation. After 24-h storage at 37°C and 500 rounds of thermocycling, the samples underwent shear bond strength (SBS) test. Data was analyzed with 3-way ANOVA and Tukey HSD test (? =0.05). Results: There were significant differences between the study groups (P < 0.001). Acid-pre-conditioning increased Fuji II LC SBS values; it significantly decreased SBS values of Vitremer but had no effect on SBS values of Ionolux. Ionolux and Vitremer exhibited decreased enamel bond strength after a delay in light activation (P < 0.05). A 2-min delay in light activation combined with acid pre-conditioning increased RMGI SBS values only for Fuji II LC. Conclusion: Within the limitations of the present study, the effect of acid pre-conditioning, delaying irradiation and both on enamel bond strength of RMGIs was material-dependent. Further investigations are recommended.

Khoroushi, Maryam; Hosseini-Shirazi, Moeen; Soleimani, Hojatolah

2013-01-01

145

The clinical performance of a glass polyalkenoate (glass ionomer) cement used in a 'sandwich' technique with a composite resin to restore Class II cavities.  

PubMed

The use of glass polyalkenoate (GPA) cement in conjunction with composite resin using an acid etch technique is now well known and a 'sandwich' of tooth/GPA cement/composite resin has been recommended to form the cervical seal at the base of approximal boxes in Class II cavities. This paper reports on the 2-year results of a controlled clinical trial using a commercial GPA lining cement. The trial was designed to evaluate the efficacy of this 'sandwich' technique. Sixty-four restorations in the mouths of 22 patients were evaluated during the 2.5 year period of the trial. The composite resin component of the restorations performed well. Five restorations failed, all in the region of the approximal box. Four failures were related to the exposed GPA cement component of the 'sandwich'. Failure was probably related to placement difficulties of the technique. The use of GPA cement laminated with composite resin when the GPA cement was enclosed within the final restoration appeared to be a successful technique. PMID:1739506

Knibbs, P J

1992-02-01

146

Thermoplastic ionomers based on \\  

Microsoft Academic Search

Graft copolymer of natural rubber was prepared by polymerizing styrene in natural rubber latex using tertiarybutylhydroperoxide and tetraethylenepentamine through emulsion polymerization. Natural rubber thus reinforced by grafting styrene onto the hydrocarbon backbone was further converted to the ionomer by sulfonating with acetyl sulfate, followed by neutralization of the polymersulfonic acids using zinc acetate in methanol. The \\

Thommachan Xavier; Jacob Samuel; Thomas Kurian

2003-01-01

147

Molecularly Imprinted Ionomers.  

National Technical Information Service (NTIS)

Ionomers have been defined as copolymers that have a certain proportion of ionic groups. The ionic groups have a significant effect on the mechanical properties of the copolymers. This is generally due to aggregation of ions in a low dielectric medium. Th...

G. E. Southard G. M. Murray

2002-01-01

148

PREPARATION AND EVALUATION OF ACRYLIC ACID, ITACONIC ACID, AND N-METHACRYLOYLGLUTAMIC ACID COPOLYMERS FOR USE IN GLASS-IONOMER TYPE DENTAL RESTORATIVES  

Microsoft Academic Search

A series of copolymers containing various molar ratios of acrylic acid, itaconic acid and N-methacryloylglutamic acid were prepared in aqueous solution, using standard free-radical polymerization conditions. Specimens for mechanical property studies were prepared by mixing water solutions of the copolymers (50:50, wt:wt) with a commercial, calcium-fluoroaluminosilicate glass powder, with curing or hardening achieved by salt-bridge formation. The glass powder used

Bill M. Culbertson; Minhhoa H. Dotrong

2000-01-01

149

Poly(phosphoester) ionomers as tissue-engineering scaffolds.  

PubMed

Regenerative medicine requires scaffolds of divergent physicochemical properties for different tissue-engineering applications. To this end, a series of biodegradable poly(phosphoester) ionomers of the general composition [p(BHET-EOP-HOP/TC)] was synthesized, with BHET(bis-hydroxyl ethylene phosphate):EOP(ethylene phosphate):HOP(free phosphate) ratios of 60:20:20, 70:10:20, and 75:5:20, respectively. The 60/20/20 ionomer possessed the best tensile properties, exhibiting an average tensile modulus of 68 MPa and strain at break of 31%. Calcium treatment of the ionomer films led to significantly higher hardness and elastic moduli as measured by indentation. Calcium binding was evident from the increase in glass transition and melting temperatures, and a shift in the P-->O absorption in the FTIR spectrum. Stable N-hydroxysuccinimide ester (NHS) of the ionomers could be synthesized to facilitate derivatization, as demonstrated by conjugation of GRGDS in this study. The polymers conjugated with NHS were hydrolyzed in a biphasic mode, with a fast initial phase occurring in the first few hours, followed by a slower phase in the next few days. These ionomers represent a novel class of biomaterials with readily controllable physical and chemical attributes for tissue engineering. PMID:15199588

Wan, Andrew C A; Mao, Hai-Quan; Wang, Shu; Phua, Su Hui; Lee, Gin Ping; Pan, Jisheng; Lu, Shen; Wang, Jun; Leong, Kam W

2004-07-15

150

Dynamic Mechanical Studies of the Sulfonated Butyl Rubber Ionomers and Their Blends  

Microsoft Academic Search

Dynamic mechanical properties of sulfonated butyl rubber ionomers neutralized with different amine or metallic ion (zinc or barium) and their blends with polypropylene (PP), high-density polyethylene (HDPE), or styrene-butadiene-styrene (SBS) triblock copolymer were studied using viscoelastometry. The results showed that glass transition temperatures of ion pair–containing matrix and ionic domains (Tg1 and Tg2, respectively) of amine-neutralized ionomers were lower than

HONG-QUAN XIE; JI-GENG XU; HUI-ZHEN HU

2000-01-01

151

Properties of polyamic acid ionomers  

SciTech Connect

Polymers containing amic acid units were produced by reacting an oligomer based on polytetramethylene oxide (PTMO) with 1,2,4,5-benzenetetracarboxylic dianhydride (BRDA). Neutralization by a metal salt produced amic acid ionomers. Similar to other ionomer systems, neutralization from the acid to the ionomer led to the formation of a separate ionic phase as determined by dynamic mechanical analysis. Phase separation resulted in a substantial increase in mechanical properties. The effect of neutralization level, cation, soft-segment molecular weight, and soft-segment end group on mechanical and thermal properties was investigated.

Xuehai Yu (Nanjing Univ., Jiangsu (China)); Grady, B.P.; Reiner, R.S.; Cooper, S.L. (Univ. of Wisconsin, Madison (United States))

1993-03-05

152

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

153

Polysiloxane-graft-PEG/Phosphonium Ionomer Morphology and Ion Transport  

NASA Astrophysics Data System (ADS)

A series of random polysiloxane-based copolymer single ion conductors with phosphonium and polyethylene glycol side chains have been synthesized at various compositions and counterions. Morphology is investigated via X-ray scattering, and reveals microphase separation on extremely small length scales. Despite the low molecular weight of the PEG side chain, polysiloxane and PEG assemble into microdomains with covalently bound phosphonium cations at the interface. Exceptionally low glass transition temperatures in these microphase separated ionomers allow for high ionic mobility for both bulky, charge delocalized counterions as well as small, electronegative counterions. Morphology interpretation is complemented by measurement of ion transport properties via dielectric relaxation spectroscopy.

O'Reilly, Michael; Liang, Siwei; Bartels, Joshua; Runt, James; Colby, Ralph; Winey, Karen

2013-03-01

154

Ion transport in polyacetylene ionomers  

NASA Astrophysics Data System (ADS)

Ion transport in cationically and anionically functionalized polyacetylene ionomers, PAC and PAA, respectively, was investigated by analyzing the impedance responses of thin film Au|ionomer|Au sandwich configurations. Samples were measured over a frequency range of 10-2-106 Hz and a temperature range of 298-398 K. Electrode polarization at low frequencies and dispersion due to ion hopping at higher frequencies were observed. The impedance data were analyzed first without the reliance on a specific model, then through equivalent circuit modeling, to estimate the dc (bulk) ion conductivity ?0, ion hopping rate ?h, and dielectric constant of the polymer matrix. The dispersive ion hopping conduction was best modeled by a distributed process involving the Kohlrausch-Williams-Watts stretched exponential decay function. The ionic conductivity of both ionomers exhibited an Arrhenius dependence on temperature with similar activation energies: 0.94 eV for PAC and 0.97 eV for PAA. At 308 K, the ionic conductivity of PAC was measured to be 1.1×10-11 S/cm while that of PAA was measured to be 1.3×10-12 S/cm. The dielectric constant for the polymer matrix in the absence of ionic polarization was found to be ?D=4.5 for PAC and ?D=4.2 for PAA at 308 K. The assignment of the conductivity to ionic processes implies an extremely small intrinsic electronic conductivity in these polymeric semiconductors.

Lin, Fuding; Wang, Yongjun; Lonergan, Mark

2008-11-01

155

Next-generation ionomer encapsulants for thin film technology  

NASA Astrophysics Data System (ADS)

The characteristic properties of newly developed ionomer-based encapsulants are highlighted along with an in-depth analysis of moisture ingress, electrical and mechanical properties. The mechanical properties of these encapsulants with their high stiffness and strength have been found to allow the use of thinner glass and a possible shift from tempered to annealed glass. Lower-cost mounting options may be explored through full-module stress/deflection measurement capability and competencies developed in world-class finite-element modeling of system parameters. The superior electrical and moisture properties may allow modules to be produced without the use of an additional edge seal. These new materials have improved melt flow properties when compared to other encapsulant families such as EVA or PVB. This allows for faster processing which reduces production cost by shortening the lamination cycle. During the lamination process the sheets show excellent dimensional stability and low shrinkage behavior; and there is no need for curing, thus energy costs are lower due to lower lamination temperature. As advancement of technology proceeds across the entire PV industry, next generation ionomer encapsulants have been developed to keep up with the pace.

Czyzewicz, Robin; Smith, C. Anthony

2011-09-01

156

Oxygen reduction at platimun/ionomer interface: effects of phase separation of ionomer  

SciTech Connect

Oxygen reduction reaction (ORR) at the interface between platinum and recast ionomers (Nafion EW 1100 and 950 and 6F-40) was studied at different temperatures (20--80{sup o}C) and humidities (10--100%) employing smooth Pt and Pt-black-covered ultramicroelectrodes. ORR was strongly inhibited on smooth electrodes. The inhibition increased with the reduction time, temperature and humidity, but was absent for Nafion EW 1100 in contact with liquid water. It was attributed to the hydrophobic component of ionomer blocking both active sites and oxygen transport. It was postulated that the dynamic changes in interfacial phase separation of ionomer are facilitated by the attractive interactions between the hydrophobic component of ionomer and bare platinum and between oxide-covered Pt and the hydrophilic component of ionomer. These interactions were also proposed to be responsible for the differences in ORR voltammetry for films prepared and equilibrated under different conditions. The decrease in ORR inhibition, Nafion EW 950> Nafion EW 1100> 6F-40, was correlated with physical and molecular properties of the ionomers. The lack of inhibition for Pt-black-covered electrodes was attributed to the more random distribution of ionomer chains and the high activation barriers for the ionomer restructuring at rough interfaces.

Chlistunoff, Jerzy [Los Alamos National Laboratory

2008-01-01

157

Morphological studies of sulfonated polystyrene and sulfonated EPDM ionomers  

Microsoft Academic Search

Two ionomer systems have been investigated in this research. Sulfonated polystyrene (SPS) is a typical random ionomer and is a good material for studies into the nature of phase separation in ionomers. A series of narrow molecular weight distribution (MWD) zinc neutralized SPS samples of varying sulfonation levels were prepared and analyzed through small angle x-ray scattering (SAXS). Results indicated

1992-01-01

158

Molecular dynamics simulations of ionic aggregates in a coarse%3CU%2B2010%3Egrained ionomer melt.  

SciTech Connect

Ionomers--polymers containing a small fraction of covalently bound ionic groups--have potential application as solid electrolytes in batteries. Understanding ion transport in ionomers is essential for such applications. Due to strong electrostatic interactions in these materials, the ions form aggregates, tending to slow counterion diffusion. A key question is how ionomer properties affect ionic aggregation and counterion dynamics on a molecular level. Recent experimental advances have allowed synthesis and extensive characterization of ionomers with a precise, constant spacing of charged groups, making them ideal for controlled measurement and more direct comparison with molecular simulation. We have used coarse-grained molecular dynamics to simulate such ionomers with regularly spaced charged beads. The charged beads are placed either in the polymer backbone or as pendants on the backbone. The polymers, along with the counterions, are simulated at melt densities. The ionic aggregate structure was determined as a function of the dielectric constant, spacing of the charged beads on the polymer, and the sizes of the charged beads and counterions. The pendant ion architecture can yield qualitatively different aggregate structures from those of the linear polymers. For small pendant ions, roughly spherical aggregates have been found above the glass transition temperature. The implications of these aggregates for ion diffusion will be discussed.

Hall, Lisa Michelle; Frischknecht, Amalie Lucile; Stevens, Mark Jackson

2010-11-01

159

The role of glass composition in the behaviour of glass acetic acid and glass lactic acid cements.  

PubMed

Cements have recently been described, made from glass ionomer glass reacted with acetic and lactic acid instead of polymeric carboxylic acid. From their behaviour a theory relating to a possible secondary setting mechanism of glass ionomer has been adduced. However, only one glass (G338) was used throughout. In this study a much simpler glass ionomer glass (MP4) was compared with G338. This produced very different results. With acetic acid G338 formed cement which became resistant to water over a period of hours, as previously reported, MP4 formed cement which was never stable to water. With lactic acid G338 behaved similarly to G338 with acetic acid, again as reported, but MP4 produced a cement which was completely resistant to water at early exposure and unusually became slightly less resistant if exposure was delayed for 6 h or more. These findings indicate that the theories relating to secondary setting in glass ionomer maturation may need revision. PMID:17619992

Shahid, Saroash; Billington, R W; Pearson, G J

2007-07-10

160

Microleakage of newly developed glass carbomer cement in primary teeth  

PubMed Central

Objective: Glass carbomer cement represents a new generation of dental material, which mineralizes gradually into fluorapatite. The aim of this study was to evaluate the microleakage and marginal integrity of newly developed glass carbomer cement with and without protective surface coating (SC) in primary molars. Methods: Standardized cavities were prepared on extracted human primary molars, and the teeth were randomly assigned into the following groups (n = 10/each): (1) conventional glass ionomer cement (GIC) without SC; (2) GIC with SC; (3) glass carbomer cement without SC; (4) glass carbomer cement with SC; and (5) compomer without SC. Following thermocycling (5 ± 2°C–55 ± 2°C, dwell time 15 s, 2000×), the specimens were immersed in 0.5% basic fuchsin solution, sectioned, and digitally photographed. Microleakage was evaluated quantitatively by using open-source image analysis toolkit (ImageJ), and the data were analyzed statistically by using Kruskal-Wallis and Conover’s Multiple Comparison tests (P=.05). Results: The greatest amount of dye leakage was observed in the uncoated glass carbomer specimens, followed by the uncoated glass ionomer group (P<.05). There was no significant difference between the microleakage values of coated glass ionomer, coated glass carbomer, and the compomer (P>.05). The following statistical ranking was observed among microleakage of the test materials: uncoated glass carbomer > uncoated glass ionomer > coated glass ionomer ? coated glass carbomer ? compomer. Uncoated glass carbomer exhibited severe internal ice crack-like lines. Conclusion: The use of the new glass carbomer cement without SC results in severe microleakage and catastrophic internal cracks.

Cehreli, Sevi Burcak; Tirali, R. Ebru; Yalcinkaya, Zeynep; Cehreli, Zafer C.

2013-01-01

161

Ion conduction in phosphonium-polysiloxane ionomers  

NASA Astrophysics Data System (ADS)

Low Tg ionomers with phosphonium cations covalently attached as side chains have potential application in energy conversion and storage devices. For example, alkaline fuel cells rely on membranes that transport hydroxide anions and some advanced batteries rely on membranes transporting fluoride anions. To better understand ion conduction in phosphonium-polysiloxane ionomers, allyl tributyl phosphonium bromide monomer was synthesized and, along with a vinyl ethylene oxide monomer, attached to polymethylhydrosiloxane by hydrosilylation. These ionomers maintain low Tg -74 ^oC with up to 10 mol% phosphonium and are fully water soluble, allowing easy anion exchange and purification. We report dielectric spectroscopy results for these ionomers with a variety of counter-anions. Electrode polarization at low frequencies is analyzed to determine the number density of simultaneously conducting counter ions and their mobility. This analysis reveals higher mobility and lower activation energy for conducting anions that are larger and more diffuse, such as bis(trifluoromethane sulfonyl)imide, contributing to better performance as anion-conducting membranes.

Liang, Siwei; Hyeok Choi, U.; Runt, James; Colby, Ralph

2012-02-01

162

Genotoxic and cytotoxic effects of different types of dental cement on normal cultured human lymphocytes  

Microsoft Academic Search

In this study we have investigated the genotoxic and cytotoxic effects of eluates derived from different types of commercially available dental cements, including glass ionomer cements (GICs) (Ketac Cem\\/3M ESPE and GC Fuji I\\/GC Corp), resin-modified glass ionomer cements (RM-GICs) (RelyX Luting\\/3M ESPE and Vitrebond\\/3M ESPE) and dual-cure resin cements (RCs) (Variolink II\\/ Ivoclar-Vivadent and Panavia F 2.0\\/Kuraray) on normal

A. Bakopoulou; D. Mourelatos; A. S. Tsiftsoglou; N. P. Giassin; E. Mioglou; P. Garefis

2009-01-01

163

Analysis of bioactive fluoride-containing calcium aluminosilicate glasses  

Microsoft Academic Search

Different decomposition methods in aqueous solutions were evaluated on their accuracy and reproducibility for the quantitative determination of the constituents of bioactive fluoride-containing glasses used in dental glass ionomer cements. The concentrations of metals can be determined rapidly and accurately by atomic absorption spectrophotometry after degrading the sample in hydrochloric or hydrofluoric acid. The latter degradation method is also suited

E. A. P De Maeyer; R. M. H Verbeeck

1998-01-01

164

Ionomer Degradation in Electrodes of PEM Fuel Cell  

SciTech Connect

Although PEMFC Membrane Electrode Assembly (MEA) durability related studies have increased dramatically since 2004, studies on ionomer degradation of the composite electrodes has received far less attention than that of the proton exchange membranes, electrocatalysts, and catalyst supports. The catalyst layer ionomer unavoidably gets involved in other components degradation processes since it is subjected to exposure to different operating effects, including the presence of the catalyst, catalyst support, and the porous nature of the electrode layer which includes 2-phase flow. PEMFC durability issues cannot be fully resolved without understanding the contribution of ionomer degradation in electrode to the performance decay in life time. However, addressing the impact of changes to the catalyst layer ionomer during durability tests is experimentally difficult mainly because of the need to separate the ionomer in the electrode from other components during chemical, electrical and materials characterization. The catalyst layer ionomer is essentially chemically identical to the membrane ionomeric material, and is composed of low atomic number elements, making characterization difficult. In the present work, MEAs with different Nafion ionomer types: stabilized and non-stablized ionomer in the electrode layer (Type I) and mixed membrane/ionomer MEAs (Type II) were designed to separate ionomer degradation from membrane degradation, as shown in Figure (1a) and (b) respectively. Stabilized and non stabilized ionomers were 5% Nafion{reg_sign} solutions (Ion Power, New Castle, Delaware). The non-stabilized version is the typical Nafion chemical structure with carboxylic acid (-COOH) end groups; these end groups are thought to be a susceptible point of degradative peroxide attack. The stabilized version replaces the -COOH end groups with -CF{sub 3} end groups to prevent peroxide attack at the end groups. Type I MEAs were designed to compare ionomer degradation and its effect on performance decay. Since F{sup -} ions are released only from PFSA based membranes, and not from non-PFSA based membranes, Type II MEAs use a hydrocarbon membrane with no fluorine with a PFSA (Nafion{reg_sign}) ionomer in the catalyst layer for FER measurements. Any F{sup -} ions measured will then have come only for the catalyst layer ionomer during degradation experiments. Type II MEAs allow more detailed chemical characterization exclusively of the catalyst layer ionomer to better understand its degradation.

Borup, Rodney L. [Los Alamos National Laboratory

2011-01-01

165

Drilling mud viscosification agents based on sulfonated ionomers  

SciTech Connect

A new family of viscosification agents based on sulfonated ionomers is described for oil-based drilling muds. The resultant muds display good viscosity characteristics and good stability when formulated from ionomers having an appropriate sulfonate level, cation type, and cosolvent content.

Lundberg, R.D.; Makowski, H.S.; O'Farrell, Ch.P.; Walker, Th.O.

1984-05-08

166

Enamel and Cementum Fluoride Uptake from a Glass Ionomer Cement  

Microsoft Academic Search

Class V cavities were prepared at the cemento-enamel junction on the facial surfaces of 45 extracted human central maxillary incisors. Enamel samples for analysis were obtained by means of perchloric acid etching from circular areas, 1 mm in diameter, positioned 1.5, 3.5, 5.5, and 7.5 mm from the incisal and apical margins of the restorations, respectively. The preparations were filled

D. H. Retief; E. L. Bradley; J. C. Denton; P. Switzer

1984-01-01

167

Comparison of a SiO2-CaO-ZnO-SrO glass polyalkenoate cement to commercial dental materials: ion release, biocompatibility and antibacterial properties.  

PubMed

Ion Release and biocompatibility of a CaO-SrO-ZnO-SiO2 (BT 101) based glass polyalkenoate cement (GPC) was compared against commercial GPCs, Fuji IX and Ketac Molar. The radiopacity (R) was similar for each material, 2.0-2.8. Ion release was evaluated on each material over 1, 7, 30 and 90 days. BT 101 release included Ca (23 mg/L), Sr (23 mg/L) Zn (13 mg/L), Si (203 mg/L). Fuji IX release includes Ca (0.7 mg/L), Al (3 mg/L) Si (26 mg/L), Na (60 mg/L) and P (0.5 mg/L) while Ketac Molar release includes Ca (1 mg/L), Al (0.6 mg/L) Si (23 mg/L), Na (76 mg/L) and P (0.7 mg/L). Simulated body fluid trials revealed CaP surface precipitation on BT 101. No evidence of precipitation was found on Fuji IX or Ketac Molar. Cytotoxicity testing found similar cell viability values for each material (~60 %, P = 1.000). Antibacterial testing determined a reduced CFU count with BT 101 (2.5 × 10(3)) when compared to the control bacteria (2.4 × 10(4)), Fuji IX (1.5 × 10(4)) and Ketac Molar (1.2 × 10(4)). PMID:23793491

Wren, A W; Coughlan, A; Hall, M M; German, M J; Towler, M R

2013-06-21

168

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.

169

Fractography of glasses and ceramics II  

SciTech Connect

Topics addressed include finite element stress analysis and crack path prediction of imploding CRT; fractography and fracture mechanics of combustion growth diamond thin films; the fracture behavior of machineable hydroxyapatite; a fractal approach to crack branching (bifurcation) in glass; the fracture of glass-ionomer cements; the effect of quartz particle size on the strength and toughness of whitewares; and a proposed standard practice for fractographic analysis of monolithic advanced ceramics. Also treated are thermal exposure effects on ceramic matrix composites, fractography applied to rock core analysis, fractography of flexurally fractured glass rods, the fractographic determination of K(IC) and effects of microstructural effects in ceramics.

Frechette, V.D.; Varner, J.R.

1991-01-01

170

Chemical interactions in ionomers and ionomer membranes containing metal particles and ions  

SciTech Connect

Ionomer membranes are employed in PEM fuel cells as the proton conducting element, but they also hold potential for catalytic applications in both hydrogen based and other low temperature fuel cells. In these applications the reactions of H{sub 2}, CO, O{sub 2}, H{sub 2}O and other small molecules with metal-based catalysts are important to consider. Reactions of these species with perfluorocarbonsulfonic acid based ionomers (PFSA), of which Nafions{reg_sign} are prototypical, containing Rh, Ru, Pt and other metal ions and particles are shown. Metal carbonyls form with metal ions that have been reduced in situ to reduced valence ions or to metal particles, by the combination of CO and H{sub 2}O or with H{sub 2} directly. Metal nitrogen complexes also can be formed. In addition, the interactions of dissimilar metal ions leads to distinct species with NO or CO, for example, that are different from the products with either ion separately.

Risen, W.M. Jr.

2000-07-01

171

Determination of the properties of an experimental glass polyalkenoate cement prepared from niobium silicate powder containing fluoride  

Microsoft Academic Search

ObjectivesThe purpose of this paper is to modify the conventional calcium fluoro-alumino-silicate glass, which is used in the formation of glass ionomer cements (CIGs) by the niobium addition and to study the properties of GICs obtained.

Márcio J. Bertolini; Maria A. Zaghete; Rossano Gimenes; Gislaine C. Padovani

2008-01-01

172

Electrochemical characteristics of PAN ionomer based polymer electrolytes  

Microsoft Academic Search

Polymer electrolytes composed of poly(acrylonitrile-co-lithium methacrylate) (P(AN-co-LiMA), PAN ionomer), ethylene carbonate (EC), and LiClO4 salts have been prepared. The polymer electrolytes based on the PAN ionomer with 4 mol% LiMA content exhibited ionic conductivities of 1.9×10?3 S\\/cm at 25°C and 2.4×10?4 S\\/cm at ?10°C when only EC was used as a plasticizer. The interfacial resistance behavior between the lithium electrode

Kyoung-Hee Lee; Jung-Ki Park; Whi-Joong Kim

2000-01-01

173

Damage initiated self-healing in ionomer blends  

NASA Astrophysics Data System (ADS)

The development and understanding of self-healing mechanisms have been investigated in blends of ionomers (Poly(ethyelene-co-methacrylic acid), sodium & zinc ions) (EMNa & EMZn) containing both elastomers (Epoxidized natural rubbers (ENR) and cis-1,4-Polyisoprene (PISP)) and crystalline component (Poly(vinly alcohol-co-ethylene) [PVAcE]) as secondary phases. All the blends were prepared by melt-blending and self-healing behavior was studied in ballistic puncture tests. Self-healing behavior of each material was evaluated by observing the impact zones under a stereo-optical microscope and the micrographic results were further supported by the fluid flow test in the punctured zones. Interestingly, ENR50 blends of sodium ion containing ionomers exhibited complete self-repairing behavior while zinc ion containing ionomer showed limited mending but EMNa/ENR25 and EMNa/PISP blends did not show any self-healing behavior following the damage. On the other hand, a composition dependent healing behavior was observed in the EMNa/PVAcE blends where healing was observed up to 30wt% PVAcE containing blends. The chemical structure studied by FTIR analysis showed that both ion content of ionomer and functionality of ENR have significant influence on the self-repairing behavior of blends. TEM analysis revealed that self-healing occurs in the blends when the dispersed phase has a dimension of 100 to 400 nm.

Rahman, Md. Arifur; Penco, Maurizio; Spagnoli, Gloria; Peroni, Isabella; Ramorino, Giorgio; Sartore, Luciana; Bignotti, Fabio; Landro, Luca Di

2012-07-01

174

Characterization of ionomer solutions in non-polar solvents  

Microsoft Academic Search

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

Kaushik Chakrabarty

1997-01-01

175

Molecular mobility and cation conduction in sulfonated polyester copolymer ionomers  

NASA Astrophysics Data System (ADS)

Poly(ethylene oxide) ionomers are candidate materials for electrolytes in energy storage devices due to the ability of ether oxygen to solvate cations. Copolyester ionomers are synthesized via condensation of sulfonated phthalates with mixtures of PEG and PTMG to make random copolymer ionomers with identical ion content. Variation of the PEG/PTMG composition changes Tg, dielectric constant and ionic aggregation; each with consequences for ion transport. Dielectric spectroscopy is used to determine number density of conducting ions, their mobility and extent of aggregation. Conductivity and mobility show Vogel temperature dependence and increase with PEG content; even though PTMG ionomers have lower Tg. Conducting ion densities show Arrhenius temperature dependence and are nearly identical for polymers containing PEG. SAXS confirms the extent of aggregation and temperature response from dielectric results, and exposes phase separation as PTMG content is increased. The tradeoff between ion-solvation and low Tg in this study provides fundamental understanding of ionic aggregation and ion transport in polymer electrolytes.

Tudryn, Gregory; King, Daniel; O'Reilly, Michael; Winey, Karen; Colby, Ralph

2011-03-01

176

SODIUM AND ZINC IONOMERS OF SULFONATED MALEATED EPDM RUBBER  

Microsoft Academic Search

Sulfonation of maleated EPDM (m-EPDM) rubber followed by its neutralization by sodium hydroxide or zinc acetate leads to the formation of an ionomer consisting of two types of ionic association, namely carboxylate and sulfonate anions with Na or Zn as the counterion. The products were characterized by infrared spectroscopic studies, dynamic mechanical thermal analyses, dielectric thermal analyses, and measurements of

SWAPAN K. GHOSH; P. P. DE; D. KHASTGIR; S. K. DE

2000-01-01

177

Melt-intercalation studies of polystyrene ionomers in pristine montmorillonite  

NASA Astrophysics Data System (ADS)

The main objective of this study was to examine the use of ionomers, specifically alkylamine-neutralized sulfonated polystyrene (SPS) for promoting intercalation into unmodified sodium montmorillonite clay and its use as a compatabilizer for intercalating another polymer into unmodified silicate clay. The processing parameters and chemical structure of polymers which led to the formation of partially intercalated/exfoliated morphologies were investigated. Melt-intercalated polymer layered silicate nanocomposites (PLSNs) are made by mixing polymers and organically modified silicates by the application of shear forces. However, the thermal decomposition temperatures of the organic modifications are usually comparable to the processing temperatures of most of the polymers. Hence, in this work modification of the polymer, rather than the clay, for promoting melt intercalation, specifically the introduction of alkyl ammonium salt groups along the polymer chain was considered. In this study the effects of viscosity, shear rates and mixing times on the morphology of nanocomposites were investigated. The effect of ionic content in the polymer chain of SPS in the batch mixtures of SPS and PS was researched. We also compared the effect on the extent of intercalation in these silicate clay galleries as a function of size of the counter-ions by varying the alkyl chain length and as a function of basicity of these counter-ions by varying the number of alkyl substituents that are attached on the N of the amine. The melt mixing of pristine Na-Mmt with alkyl ammonium and quaternary ammonium salts of SPS ionomers, resulted in an increase in the silicate gallery spacing consistent with intercalation. Mixtures of the ionomer with PS exhibited similar gallery spacing increases, indicating that the ionomer is an effective compatibilizing agent for the melt-intercalation of hydrophobic polymers into the clay. The extent of intercalation was independent of the melt processing conditions employed in this study and also did not change as the molecular weight of ionomer was varied. Intercalation appeared to be dependent on the charge ratio between the ionomer and the clay. The increase in gallery spacing achieved was a function of size of the alkylamine counter-ions used. The nanocomposites containing ionomers exhibited higher storage moduli compared to nanocomposites without the compatibilizer.

Bhiwankar, Nikhil N.

178

Estimation of electrode ionomer oxygen permeability and ionomer-phase oxygen transport resistance in polymer electrolyte fuel cells.  

PubMed

The oxygen permeability of perfluorinated and hydrocarbon polymer electrolyte membranes (PEMs; Nafion®, SPEEK and SPSU), which are used as electrolytes and electrode ionomers in polymer electrolyte fuel cells (PEFCs), was estimated using chronoamperometry using a modified fuel cell set-up. A thin, cylindrical microelectrode was embedded into the PEM and used as the working electrode. The PEM was sandwiched between 2 gas diffusion electrodes, one of which was catalyzed and served as the counter and pseudo-reference electrode. Independently, from fuel cell experiments, the oxygen transport resistance arising due to transport through the ionomer film covering the catalyst active sites was estimated at the limiting current and decoupled from the overall mass transport resistance. The in situ oxygen permeability measured at 80 °C and 75% RH of perfluorinated ionomers such as Nafion® (3.85 × 10(12) mol cm(-1) s(-1)) was observed to be an order of magnitude higher than that of hydrocarbon-based PEMs such as SPEEK (0.27 × 10(12) mol cm(-1) s(-1)) and SPSU (0.15 × 10(12) mol cm(-1) s(-1)). The obtained oxygen transport (through ionomer film) resistance values (Nafion® - 1.6 s cm(-1), SPEEK - 2.2 s cm(-1) and SPSU - 3.0 s cm(-1); at 80 °C and 75% RH) correlated well with the measured oxygen permeabilities in these ion-containing polymers. PMID:23912796

Sambandam, Satheesh; Parrondo, Javier; Ramani, Vijay

2013-09-28

179

Control and characterization of textured, hydrophobic ionomer surfaces  

NASA Astrophysics Data System (ADS)

Polymer thin films are of increasing interest in many industrial and technological applications. Superhydrophobic, self-cleaning surfaces have attracted a lot of attention for their application in self-cleaning, anti-sticking coatings, stain resistance, or anti-contamination surfaces in diverse technologies, including medical, transportation, textiles, electronics and paints. This thesis focuses on the preparation of nanometer to micrometer-size particle textured surfaces which are desirable for super water repellency. Textured surfaces consisting of nanometer to micrometer-sized lightly sulfonated polystyrene ionomer (SPS) particles were prepared by rapid evaporation of the solvent from a dilute polymer solution cast onto silica. The effect of the solvent used to spin coat the film, the molecular weight of the ionomer, and the rate of solvent evaporation were investigated. The nano-particle or micron-particle textured ionomer surfaces were prepared by either spin coating or solution casting ionomer solutions at controlled evaporation rates. The surface morphologies were consistent with a spinodal decomposition mechanism where the surface first existed as a percolated-like structure and then ripened into droplets if molecular mobility was retained for sufficient time. The SPS particles or particle aggregates were robust and resisted deformation even after annealing at 120°C for one week. The water contact angles on as-prepared surfaces were relatively low, ~ 90° since the polar groups in ionomer reduce the surface hydrophobicity. After chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltrichlorosilane, the surface contact angles increased to ~ 109° on smooth surfaces and ~140° on the textured surfaces. Water droplets stuck to these surfaces even when tilted 90 degrees. Superhydrophobic surfaces were prepared by spraying coating ionomer solutions and Chemical Vapor Deposition (CVD) of 1H,1H,2H,2H-perfluorooctyltrichlorosilane onto textured surfaces. The surfaces after CVD of silane exhibited water contact angle of 152° and the water droplet stuck to the surfaces without falling even when tilted upside down. This kind of sticky superhydrophobic surface would have potential applications in no-loss transport of liquid, and cleaning robots.

Wang, Xueyuan

180

Determination of the properties of an experimental glass polyalkenoate cement prepared from niobium silicate powder containing fluoride  

Microsoft Academic Search

Objectives. The purpose of this paper is to modify the conventional calcium fluoro-alumino- silicate glass, which is used in the formation of glass ionomer cements (CIGs) by the niobium addition and to study the properties of GICs obtained. Materials and methods. Sol-gel process was used to prepare the powder at lower temperature than fusion method. Glass-ceramic powder obtained in this

J. Bertolini; Maria A. Zaghete; Rossano Gimenes; Gislaine C. Padovani

181

Hierarchical Structure of Poly(ethylene) Based Ionomers  

NASA Astrophysics Data System (ADS)

The effect of chain architecture (linear vs branched), acid placement (precise vs random), acid content, neutralization extent, and crystallinity on the hierarchical structure of poly(ethylene-acrylic acid) ionomers was investigated via X-ray scattering and high angle annular dark field scanning transmission electron microscopy (HAADF STEM). HAADF STEM reveals randomly dispersed, spherical ionic aggregates in all materials. At temperatures where the ionomers are fully amorphous, the scattering at intermediate angle arises from interaggregate interference and can be described by the Kinning-Thomas model. If the acid groups are placed every 21^st carbon, the materials are semicrystalline at room temperature and contributions from acid layers associated with crystallites are convoluted with interaggregate scattering. The ionic aggregates have diameters of ˜ 1 nm for all samples; however, the number density of aggregates is strongly dependent on the acid content but weakly dependent on the extent of neutralization.

Seitz, Michelle E.; Chan, Christopher D.; Opper, Kathleen L.; Baughman, Travis W.; Wagener, Kenneth B.; Winey, Karen I.

2010-03-01

182

High mineral affinity of polyphosphoester ionomer-phospholipid vesicles.  

PubMed

Bone-specific drug delivery is important for the treatment of osteoporosis and osseous metastases. However, there have been limitations in the design of drug carriers having bone affinity. We synthesized amphiphilic polyphosphoester ionomers (CH-PHE) and modified them to 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) vesicles. The ?-potential of the vesicles was decreased by immobilization of CH-PHE; the amount was influenced by the structure and fraction of CH-PHE. The release rate of 5-carboxyfluorescein from the vesicles could be controlled by changing the fraction of DOPC and CH-PHE. In particular, the release of CF from DOPC vesicles containing 3% CH-PHE was most reduced. In addition, the enzymatic degradation of DOPC was reduced by immobilization with polyphosphoester ionomers; enzyme tolerance was increased with an increase in the molar fraction of polyphosphoester ionomers. Hemolytic activity of the phospholipid vesicles bearing CH-PHE was infrequently observed and was similar to that of the DOPC vesicles. Although a decrease in the viability of mouse osteoblastic cells (MC3T3-E1) in contact with the vesicles bearing CH-PHE was observed when the DOPC concentration of the vesicles bearing 20 mol % CH-PHE with highly ionized units was greater than 200 ?M, the cytotoxicity was diminished by sodium salt formation of the CH-PHE. The affinity of the vesicles to calcium deposits generated by MC3T3-E1 cells was significantly improved by the immobilization polyphosphoesters. PMID:22829566

Ikeuchi, Ryota; Iwasaki, Yasuhiko

2012-07-25

183

Ionomic screening of field-grown soybeans identifies mutants with altered seed elemental composition  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soybean seeds contain high levels of mineral nutrients essential for human and animal nutrition. High throughput elemental profiling (ionomics) has identified mutants in model plant species grown in controlled environments. Here, we describe a method for identifying potential soybean ionomics mutant...

184

The Biological Evaluation of Poly (Vinyl Acetate-Co-Crotonic Acid) Ionomer Hydrogel Coatings.  

National Technical Information Service (NTIS)

Poly(vinyl acetate-co-2%-crotonic acid) 60% sodium ionomer hydrogel was found to be the most thromboresistant hydrogel evaluated in our screening studies. The ionomer hydrogel was graft-coated onto substrate surfaces from an ethanol solution of its monome...

W. F. Beach D. D. Stewart

1980-01-01

185

Interfacial Nanostructure of the Polymer Electrolyte Fuel Cell Catalyst Layer Constructed with Different Ionomer Contents  

NASA Astrophysics Data System (ADS)

Fibrous carbon materials such as carbon nanotubes (CNTs) and carbon nanofilaments (CNFs) have attracted attention for use in the polymer electrolyte fuel cells (PEFCs). We have applied one type of fibrous carbon materials named Marimo carbon (MC) as the catalyst support. The modified nanocolloidal method was used preparing the Marimo carbon supported Pt catalyst (Pt/MC). And then, ionomer/carbon ratio in the cathode catalyst layer of the PEFC has been investigated for its effect on performance and structure of the membrane electrode assembly (MEA). The morphologies and cell performance of cathode catalyst layer using Marimo carbon changed dramatically with ionomer content. In case of excess ionomer, the air volume between CNFs was plugged up by ionomer, and blocked supply fuel gas diffusion caused decrease cell performance. PEFC cell performance was increase with decreasing ionomer content.

Baba, Koki; Iwasawa, Kenta; Eguchi, Mika; Kobayashi, Yoshio; Kobori, Maya; Nishitani-Gamo, Mikka; Ando, Toshihiro

2013-06-01

186

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

187

Multi-scale modeling and synthesis of polyester ionomers.  

PubMed

Simulations of microphase separation are carried out using the dissipative particle dynamics (DPD). By varying the concentration and temperature of resin solutions we explore mesomorphologies supported by the all-atom models. We found that for a low degree of functionalization the homogeneously distributed ionomers self-assemble into spherical micelles at solid loads below 31 wt%, subject to the activation energy barrier for the gradual growth of pre-micellar aggregates. Computed optimum aggregation numbers exhibit sensitivity to both the temperature-dependent interfacial tension and the ionic content and compare well with the experimental observations. PMID:23507929

Nikoli?, Dragan; Moffat, Karen A; Farrugia, Valerie M; Kobryn, Alexander E; Gusarov, Sergey; Wosnick, Jordan H; Kovalenko, Andriy

2013-03-18

188

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

2011-11-30

189

Comparative evaluation of tensile bond strength and microleakage of conventional glass ionomer cement, resin modified glass ionomer cement and compomer: An in vitro study  

PubMed Central

Aim: The purpose of this study was to evaluate and compare the tensile bond strength and microleakage of Fuji IX GP, Fuji II LC, and compoglass and to compare bond strength with degree of microleakage exhibited by the same materials. Materials and Methods: Occlusal surfaces of 96 noncarious primary teeth were ground perpendicular to long axis of the tooth. Preparations were distributed into three groups consisting of Fuji IX GP, Fuji II LC and Compoglass. Specimens were tested for tensile bond strength by mounting them on Instron Universal Testing Machine. Ninety-six primary molars were treated with Fuji IX GP, Fuji II LC, and compoglass on box-only prepared proximal surface. Samples were thermocycled, stained with dye, sectioned, and scored for microleakage under stereomicroscope. ANOVA and Bonferrani correction test were done for comparisons. Pearson Chi-square test and regression analysis were done to assess the association between the parameters. Results: Compoglass showed highest tensile strength and Fuji II LC showed least microleakage. There was a significant difference between the three groups in tensile strength and microleakage levels. The correlation between tensile strength and microleakage level in each group showed that there was a significant negative correlation only in Group 3. Conclusion: Fuji II LC and compoglass can be advocated in primary teeth because of their superior physical properties when compared with Fuji IX GP.

Rekha, C. Vishnu; Varma, Balagopal; Jayanthi

2012-01-01

190

Associations between Ionomic Profile and Metabolic Abnormalities in Human Population  

PubMed Central

Background Few studies assessed effects of individual and multiple ions simultaneously on metabolic outcomes, due to methodological limitation. Methodology/Principal Findings By combining advanced ionomics and mutual information, a quantifying measurement for mutual dependence between two random variables, we investigated associations of ion modules/networks with overweight/obesity, metabolic syndrome (MetS) and type 2 diabetes (T2DM) in 976 middle-aged Chinese men and women. Fasting plasma ions were measured by inductively coupled plasma mass spectroscopy. Significant ion modules were selected by mutual information to construct disease related ion networks. Plasma copper and phosphorus always ranked the first two among three specific ion networks associated with overweight/obesity, MetS and T2DM. Comparing the ranking of ion individually and in networks, three patterns were observed (1) “Individual ion,” such as potassium and chrome, which tends to work alone; (2) “Module ion,” such as iron in T2DM, which tends to act in modules/network; and (3) “Module-individual ion,” such as copper in overweight/obesity, which seems to work equivalently in either way. Conclusions In conclusion, by using the novel approach of the ionomics strategy and the information theory, we observed potential associations of ions individually or as modules/networks with metabolic disorders. Certainly, these findings need to be confirmed in future biological studies.

An, Peng; Yu, Danxia; Yu, Zhijie; Li, Huaixing; Sheng, Hongguang; Cai, Lu; Xue, Jun; Jing, Miao; Li, Yixue; Lin, Xu; Wang, Fudi

2012-01-01

191

Silk ionomers for encapsulation and differentiation of human MSCs.  

PubMed

The response of human bone marrow derived human mesenchymal stem cells (hMSCs) encapsulated in silk ionomer hydrogels was studied. Silk aqueous solutions with silk-poly-L-lysine or silk-poly-L-glutamate were formed into hydrogels via ultrasonication in situ with different net charges. hMSCs were encapsulated within the hydrogels and the impact of matrix charge was assessed over weeks in osteogenic, adipogenic and maintenance growth media. These modified silk charged polymers supported cell viability and proliferative potential, and the hMSCs were able to differentiate toward osteogenic or adipogenic lineages in the corresponding differentiation media. The silk/silk-poly-L-lysine hydrogels exhibited a positive effect on selective osteogenesis of hMSCs, inducing differentiation toward an osteogenic lineage even in the absence of osteogenic supplements, while also inhibiting adipogenesis. In contrast, silk/silk fibroin-poly-L-glutamate hydrogels supported both osteogenic and adipogenic differentiation of hMSCs when cultured under induction conditions. The results demonstrate the potential utility of silk-based ionomers in gel formats for hMSCs encapsulation and for directing hMSCs long term functional differentiation toward specific lineages. PMID:22824008

Calabrese, Rossella; Kaplan, David L

2012-07-21

192

Silk ionomers for encapsulation and differentiation of human MSCs  

PubMed Central

The response of human bone marrow derived human mesenchymal stem cells (hMSCs) encapsulated in silk ionomer hydrogels was studied. Silk aqueous solutions with silk-poly-L-lysine or silk-poly-L-glutamate were formed into hydrogels via ultrasonication in situ with different net charges. hMSCs were encapsulated within the hydrogels and the impact of matrix charge was assessed over weeks in osteogenic, adipogenic and maintenance growth media. These modified silk charged polymers supported cell viability and proliferative potential, and the hMSCs were able to differentiate toward osteogenic or adipogenic lineages in the corresponding differentiation media. The silk/silk-poly-L-lysine hydrogels exhibited a positive effect on selective osteogenesis of hMSCs, inducing differentiation toward an osteogenic lineage even in the absence of osteogenic supplements, while also inhibiting adipogenesis. In contrast, silk/silk fibroin-poly-L-glutamate hydrogels supported both osteogenic and adipogenic differentiation of hMSCs when cultured under induction conditions. The results demonstrate the potential utility of silk-based ionomers in gel formats for hMSCs encapsulation and for directing hMSCs long term functional differentiation toward specific lineages.

Calabrese, Rossella; Kaplan, David L.

2012-01-01

193

In vivo disintegration of four different luting agents.  

PubMed

The purpose of this study was to evaluate the disintegration of luting agents. An intraoral sample holder was made having four holes of 1.4?mm diameter and 2?mm depth. The holder was soldered onto the buccal surface of an orthodontic band, which was cemented to the first upper molar in 12 patients, average age 26 years. The holes were filled with a zinc phosphate (Phosphate Kulzer), a glass ionomer (Ketac Cem), a resin-modified-glass ionomer (Fuji Plus), and a resin cement (Calibra). Impressions were made at baseline, and 6, 12, and 18 months from which epoxy replicas were made, which were scanned with an optical scanner. Total volume loss was calculated. The rank order of mean volume loss was as follows: Phosphate cement > Ketac Cem = Fuji Plus = Calibra. Cement type and time had statistically significant effects on volume loss of cements (P < 0.001). Under in vivo conditions, zinc phosphate cement disintegrated the most, whereas no significant difference was observed for glass ionomer and resin-based cements. As intraoral conditions are considerably less aggressive than experimental laboratory conditions, the erosion behavior of glass ionomer cement was found to be similar to the resin-based cements in contradiction to previous laboratory results. PMID:22007219

Gemalmaz, Deniz; Pameijer, Cornelis H; Latta, Mark; Kuybulu, Ferah; Alcan, Toros

2011-10-05

194

In Vivo Disintegration of Four Different Luting Agents  

PubMed Central

The purpose of this study was to evaluate the disintegration of luting agents. An intraoral sample holder was made having four holes of 1.4?mm diameter and 2?mm depth. The holder was soldered onto the buccal surface of an orthodontic band, which was cemented to the first upper molar in 12 patients, average age 26 years. The holes were filled with a zinc phosphate (Phosphate Kulzer), a glass ionomer (Ketac Cem), a resin-modified-glass ionomer (Fuji Plus), and a resin cement (Calibra). Impressions were made at baseline, and 6, 12, and 18 months from which epoxy replicas were made, which were scanned with an optical scanner. Total volume loss was calculated. The rank order of mean volume loss was as follows: Phosphate cement > Ketac Cem = Fuji Plus = Calibra. Cement type and time had statistically significant effects on volume loss of cements (P < 0.001). Under in vivo conditions, zinc phosphate cement disintegrated the most, whereas no significant difference was observed for glass ionomer and resin-based cements. As intraoral conditions are considerably less aggressive than experimental laboratory conditions, the erosion behavior of glass ionomer cement was found to be similar to the resin-based cements in contradiction to previous laboratory results.

Gemalmaz, Deniz; Pameijer, Cornelis H.; Latta, Mark; Kuybulu, Ferah; Alcan, Toros

2012-01-01

195

Property Control of (Perfluorinated Ionomer)/(Inorganic Oxide) Composites by Tailoring the Nanoscale Morphology.  

National Technical Information Service (NTIS)

Unique perfluoro-organic/inorganic oxide hybrid materials have been formulated by merging processes recently developed by us for the solution and melting processing of perfluorosulfonate ionomers (PFSI's) and (2) the production of nanocomposites by the in...

K. A. Mauritz R. B. Moore

1994-01-01

196

Morphological analysis of ionomers. Final report, January 1, 1992--August 31, 1995  

SciTech Connect

This report describes three studies on ion containing polymers. (A) Extended X-ray absorption fine structure studies of ionomers investigate lightly sulfonated polystyrenes and polyurethane cationomers. In the first material, the nickel, zinc and cadmium-neutralized ionomers were investigated and the details of the cation local environment was elucidated through the use of the simulation package (FEFF5{reg_sign}). For the lightly sulfonated polystyrenes, the availability of a detailed ab initio simulation package, FEFF5{reg_sign} allowed the determination of the local structure at a level of detail not previously possible. (B) Nuclear magnetic resonance of lightly sulfonated polystyrene is studying the local environment of the cation in sodium-neutralized lightly sulfonated polystyrene. (C) Solution studies of carboxy-telechelic polystyrene ionomers are using small-angle neutron scattering to explore the role of temperature in solutions of sodium-neutralized carboxy-telechelic ionomers in toluene.

NONE

1995-12-31

197

Structural evolution of water swollen perfluorosulfonated ionomers from dry membrane to solution  

Microsoft Academic Search

The structural evolution of perfluorosulfonated ionomer (PFSI) membranes from dry materials to highly swollen membranes and solutions was investigated using mainly small-angle scattering techniques. The small-angle scattering maximum (“ionomer peak”) is shown to be observable up to very large water content and shifts continuously toward small-angle as water content increases. A modification of the swelling process is observed for a

G. Gebel

2000-01-01

198

CAD\\/CAM Zirconia vs. slip-cast glass-infiltrated Alumina\\/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial  

Microsoft Academic Search

Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA) quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain

Murat Cavit Çehreli; Ali Murat Kökat; Kivanç Akça

2009-01-01

199

Evaluating acrylic and glass-ionomer cement strength using the biaxial flexure test  

Microsoft Academic Search

Frequently, bone cement strengths are evaluated from uniaxial tests, such as three- or four-point flexure. Measurement of material strength in this manner may not provide an accurate characterisation of a bone cements true load-bearing capacity. In most orthopaedic applications, there exists a state of biaxial stress and so biaxial strength information is most useful. To address this issue, the biaxial

W. A. J. Higgs; P. Lucksanasombool; R. J. E. D. Higgs; M. V. Swain

2001-01-01

200

Permeability and micromechanical properties of silk ionomer microcapsules.  

PubMed

We studied the pH-responsive behavior of layer-by-layer (LbL) microcapsules fabricated from silk fibroin chemically modified with different poly amino acid side chains: cationic (silk-poly L-lysine, SF-PL) or anionic (silk-poly-L-glutamic acid, SF-PG). We observed that stable ultrathin shell microcapsules can be assembled with a dramatic increase in swelling, thickness, and microroughness at extremely acidic (pH < 2.5) and basic (pH > 11.0) conditions without noticeable disintegration. These changes are accompanied by dramatic changes in shell permeability with a 2 orders of magnitude increase in the diffusion coefficient. Moreover, the silk ionomer shells undergo remarkable softening with a drop in Young's modulus by more than 1 order of magnitude due to the swelling, stretching, and increase in material porosity. The ability to control permeability and mechanical properties over a wide range for the silk-based microcapsules, with distinguishing stability under harsh environmental conditions, provides an important system for controlled loading and release and applications in bioengineering. PMID:22834790

Ye, Chunhong; Drachuk, Irina; Calabrese, Rossella; Dai, Hongqi; Kaplan, David L; Tsukruk, Vladimir V

2012-08-07

201

In Silico Ionomics Segregates Parasitic from Free-Living Eukaryotes  

PubMed Central

Ion transporters are fundamental to life. Due to their ancient origin and conservation in sequence, ion transporters are also particularly well suited for comparative genomics of distantly related species. Here, we perform genome-wide ion transporter profiling as a basis for comparative genomics of eukaryotes. From a given predicted proteome, we identify all bona fide ion channels, ion porters, and ion pumps. Concentrating on unicellular eukaryotes (n = 37), we demonstrate that clustering of species according to their repertoire of ion transporters segregates obligate endoparasites (n = 23) on the one hand, from free-living species and facultative parasites (n = 14) on the other hand. This surprising finding indicates strong convergent evolution of the parasites regarding the acquisition and homeostasis of inorganic ions. Random forest classification identifies transporters of ammonia, plus transporters of iron and other transition metals, as the most informative for distinguishing the obligate parasites. Thus, in silico ionomics further underscores the importance of iron in infection biology and suggests access to host sources of nitrogen and transition metals to be selective forces in the evolution of parasitism. This finding is in agreement with the phenomenon of iron withholding as a primordial antimicrobial strategy of infected mammals.

Greganova, Eva; Steinmann, Michael; Maser, Pascal; Fankhauser, Niklaus

2013-01-01

202

Block Ionomer Complex Micelles with Cross-Linked Cores for Drug Delivery1,2  

PubMed Central

Soft polymeric nanomaterials were synthesized by template-assisted method involving condensation of the poly(ethylene oxide)-b-polycarboxylate anions by metal ions into core-shell block ionomer complex micelles followed by chemical cross-linking of the polyion chains in the micelle cores. The resulting materials represent nanogels and are capable of swelling in a pH-dependent manner. The structural determinants that guide the self-assembly of the initial micelle templates and the swelling behavior of the cross-linked micelles include the block ionomer structure, the chemical nature of metal ions, the structure of the cross-links and the degree of cross-linking. The application of these materials for loading and release of a drug, cisplatin, is evaluated. These cross-linked block ionomer micelles have promise for delivery of pharmaceutical agents.

Kim, Jong Oh; Nukolova, Nataliya V.; Oberoi, Hardeep S.; Kabanov, Alexander V.; Bronich, Tatiana K.

2010-01-01

203

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

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance 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 lithium hopping is about ten times slower than the segmental motion. 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.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

2012-01-01

204

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

205

Biodegradation and abrasive wear of nano restorative materials.  

PubMed

The purpose of this study was to evaluate the biomechanical degradation of two nanofilled restorative materials (a resin-modified glass ionomer, Ketac N100 and a composite, Filtek Z350), compared with conventional materials (Vitremer and TPH Spectrum). Twenty specimens obtained from each material were divided into two storage groups (n=10): relative humidity (control) and Streptococcus mutans biofilm (biodegradation). After 7 days of storage, roughness values (Ra) and micrographs by scanning electron microscopy (SEM) were obtained. In a second experimental phase, the specimens previously subjected to biodegradation were fixed to the tooth-brushing device and abraded via toothbrushes, using dentifrice slurry (mechanical degradation). Next, these specimens were washed, dried, and reassessed by roughness and SEM. The data were submitted to repeated measures three-way analysis of variance (ANOVA) and Tukey tests (p<0.05). There was statistically significant interaction among factors: material, storage (humidity/biofilm), and abrasion (before/after). After biodegradation (S mutans biofilm storage), Ketac N100 presented the highest Ra values. Concerning bio plus mechanical challenge, TPH Spectrum, Ketac N100, and Vitremer presented the undesirable roughening of their surfaces, while the nano composite Filtek Z350 exhibited the best resistance to cumulative challenges proposed. The degraded aspect after biodegradation and the exposure of fillers after mechanical degradation were visualized in micrographs. This study demonstrated that the nanotechnology incorporated in restorative materials, as in composite resin and resin-modified glass ionomer, was important for the superior resistance to biomechanical degradation. PMID:21913859

de Paula, A B; Fucio, S B P; Ambrosano, G M B; Alonso, R C B; Sardi, J C O; Puppin-Rontani, R M

2011-09-13

206

Anhydrous solid proton conductors based on perfluorosulfonic ionomer with polymeric solvent for polymer electrolyte fuel cell  

Microsoft Academic Search

Novel anhydrous polymeric proton conductors have been prepared from perfluorosulfonic acid ionomer with polymer solvent as supplying proton pathway through the segmental motion of polymer chains for polymer electrolyte fuel cell (PEFC) application. Since the membranes do not contain liquid-state acid or solvent, the membranes may promise more stable performances during the operation of PEFC. The Nafion-based anhydrous proton conductors

Moon-Sung Kang; Myung-Jin Lee

2009-01-01

207

Carbon-13 nuclear magnetic resonance study on poly(ethylacrylate-co-sodium acrylate) ionomer  

NASA Astrophysics Data System (ADS)

The poly(ethylacrylate) (PEA) homopolymer and poly(ethylacrylate-co-sodium acrylate) ionomer that contain 8.4 mol % ionic groups (PEANa-8.4) were studied by 13C using cross polarization and magic angle spinning nuclear magnetic resonance (CP/MAS NMR). The 13C spin-lattice relaxation times in a rotating frame, T1?, were measured as functions of the temperature. Using these T1? spin-lattice relaxation times, we addressed the chain mobility, correlation time, and activation energy for carbon of the PEA homopolymer and the PEANa-8.4 ionomer. We found that the molecular motion in the PEA homopolymer needed a higher activation energy than that in the PEANa-8.4 ionomer. In addition, we observed that motion of the 1-methyl carbons in the PEANa-8.4 ionomer was distinctly different from that in the PEA homopolymer: the value of T1? for 1-methyl carbon is ascribed to stronger interactions between the polymer chains in the homopolymer.

Lim, Ae Ran; Kwark, Young-Je; Kim, Joon-Seop

2003-12-01

208

Particulate ionomer films prepared from dispersions of crosslinked polymer colloids: a structure-property study.  

PubMed

Polymers with properties that are governed by ionic interactions in discrete regions are termed ionomers. This work presents a comprehensive study of polymer films prepared from dispersions of crosslinked poly(butadiene/methacrylic acid) (poly(Bd/MAA)) particles in water. We showed recently [O. Pinprayoon, R. Groves, B.R. Saunders, J. Colloid Interface Sci. 321 (2008) 315-322] that poly(Bd/MAA) particles could be considered to have a core-shell structure with a MAA-rich shell. The poly(Bd/MAA) dispersions used here contained added ZnO particles which provided a source of Zn(2+). The films were investigated using AFM, FTIR, small-angle X-ray scattering (SAXS), dynamic mechanical thermal analysis (DMTA) and tensile stress vs. strain measurements. The films showed differences and similarities to conventional ionomers which are discussed. The FTIR data revealed that the Zn(2+) ions formed ionic crosslinks with the carboxylate groups (RCOO(-)). Mechanical property studies were conducted using DMTA and stress vs. strain measurements. The DMTA data revealed evidence of two main phases in the systems: a poly(Bd)-rich phase and a poly(MAA)-rich phase. A third phase was also found; which was ascribed to an interphase between the particle core and shell. The SAXS data showed that the films were composed of distinct poly(Bd/MAA) particles, implying that only partial coalescence occurred across the particle interfaces during formation of these particulate ionomer films. Ionic crosslinking of the particles was suggested to occur in the interfacial region (knit regions). The SAXS data also showed scattering from Zn(2+)(RCOO(-)) ionic-aggregates. These ionic aggregates had an average separation of 2.9 nm, which is much smaller than that for conventional ionomers. Interestingly, the concentration of these aggregates passed through a maximum and decreased as the degree of neutralisation of the MAA groups approached 100%. A conceptual model for the structure of these unconventional ionomers is discussed. PMID:19406420

Pinprayoon, Orawan; Saiani, Alberto; Groves, Robert; Saunders, Brian R

2009-04-08

209

Morphological manipulation of ionomers for altered transport properties in membrane applications  

NASA Astrophysics Data System (ADS)

The focus of this research project was to investigate correlations between ionomer membrane morphology and swollen state transport properties. The project can be broken into two primary foci, the impact of processing and additives on the morphology of perfluorosulfonate ionomers and the impact of morphology on the performance of ionic actuators. Perfluorosulfonate ionomers, Nafion RTM from DuPont being the most common example, are a class of commercially successful semi-crystalline ionomers that have been used in a number of membrane applications, the primary two being chlor-alkali cell and proton exchange membrane fuel cells. It has been shown that solution and melt processing of Nafion RTM alters the membrane morphology and profoundly impacts the swelling characteristics and water transport properties of the membrane. The enhanced mobility present in both solution and melt facilitate increased crystallinity relative to the as-received state. Processing also causes a change in the spatial order of ionic aggregates, the average interaggregate spacing decreasing in both solution and melt processed membranes. Processing was also found to be an effective means to produce highly aggregated materials as the stated mobility during processing facilitates rearrangement and aggregation of the neutralized sulfonate functionalities. Of greatest interest, however, is the increase in water uptake seen in processed samples. Melt processing was found to increase water content by 60% and solution processing by 80% relative to as-received ionomer. As a result, water diffusion in processed materials was found to be much higher than as-received. Only solution processed membranes, however, were found to show high proton conductivity due to enrichment of surface water content through morphological changes which present a surface that is more readily hydrated. Manipulation of solution processed membrane morphology was further explored by producing membranes containing a mixture of alkali metal and alkylammonium counterions. Analysis of the mechanical properties and aggregation behaviors suggest the existence of mixed ionic aggregates containing both sodium and tetrabutylammonium counterions. Partitioning of counterions within the aggregates and alteration of the crystalline content are proposed to cause the appearance of a new correlation length intermediate to the lamellar long spacing and the ionomer peak. The unique morphology causes a minimum in water content and a corresponding maximum in proton conductivity that reinforces the link between membrane morphology and swollen state transport properties. (Abstract shortened by UMI.)

Phillips, Alan Keith

210

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

211

Glass Electrolytes.  

National Technical Information Service (NTIS)

The objective of this research is a glass electrolyte for use in sodium/sulfur batteries that has a low resistivity (100 ohm-cm at 300 exp 0 C) and is stable in the cell environment. Experiments in this program are focussed on glasses in the quaternary sy...

1984-01-01

212

Glass Wings  

NSDL National Science Digital Library

Glass Wings has now opened its doors onto the electronic frontier. This Australian site covers a wide range of interests including news, games, entertainment, humour, travel, books and magazines, the environment, human rights, food, health, the educational, sexuality, the arts and a writers forum. Glass Wings is a companion project of Xanadu Australia.

213

Optimization of active electrodes for novel ionomer-based ionic polymer transducers  

NASA Astrophysics Data System (ADS)

This study expands the number of novel synthetic ionomers specifically designed for performance as ionic polymer transducers (IPT) membranes, specifically employing a highly branched sulfonated polysulfone. Control of the synthetic design, characterization, and application of the novel ionomer is intended to allow fundamental study of the effect of polymer branching on electromechanical transduction in IPTs. Fabrication methods were developed based upon the direct application process (DAP) to construct a series of stand-alone electrodes as well as full IPTs with corresponding electrode compositions. Specifically, the volumetric ratio of RuO2 conducting particles to the novel ionomeric matrix was varied from 0 - 45 vol % in the electrodes. Electrical impedance spectroscopy was employed to determine the electrical properties and their variation with electrode composition separate from and in the IPT. A percolation threshold was detected for increased ionic conductivity of the stand-alone electrodes and the full IPTs based on increased loading of conducting particles in the electrodes. An equivalent electrical circuit model was applied to fit the impedance data and implicated interfacial and bulk effects contributing differently to the electrical properties of the electrodes and IPT as a whole. The fabricated IPT series was further tested for bending actuation in response to applied step voltages and represents the first demonstration of IPTs constructed with the DAP process using 100 % novel ionomer in all components. The percolation behavior extended to the bending actuation responses for strain and voltage-normalized strain rate and is useful in optimizing IPT components for maximum performance regardless of the ionomer employed.

Duncan, Andrew J.; Sarles, Stephen A.; Leo, Donald J.; Long, Timothy E.; Akle, Barbar J.; Bennett, Matthew D.

2008-05-01

214

Electrical Properties of Poly(ethylene oxide)-based Ionomers as Single Ion Conductors  

Microsoft Academic Search

Polyethers, such as poly(ethylene oxide) (PEO) are of interest for development of advanced lithium batteries because Li^+ ions have facile transport in this media. We make ionomers based on PEO by reacting poly(ethylene glycol) (PEG) oligomers with the sodium salt of dimethyl 5-sulfoisophthalate. Since the sulfonate group is covalently bonded to the chain, it is essentially immobile and hence these

Ralph H. Colby; Shichen Dou; Shihai Zhang; Robert J. Klein; James P. Runt; Karl T. Mueller

2006-01-01

215

Low platinum loading electrodes for polymer electrolyte fuel cells fabricated using thermoplastic ionomers  

Microsoft Academic Search

Low platinum loading catalyst layers for polymer electrolyte fuel cells (PEFCs) consist of a thin film of highly inter-mixed ionomer and catalyst that is applied to the electrolyte membrane. High performances are achieved with loadings as low as 0.12 mg Pt cm?2 at the cathode and even lower loadings are required at the anode. However, the long-term performance of these

Mahlon S. Wilson; Judith A. Valerio; Shimshon Gottesfeld

1995-01-01

216

Novel drug delivery systems based on the complexes of block ionomers and surfactants of opposite charge  

Microsoft Academic Search

In this paper we have evaluated a novel family of polymer-surfactant complexes formed between block ionomers and oppositely charged surfactants. Complexes between cationic copolymer poly(ethylene oxide)-g-polyethyleneimine (PEO-g-PEI) and sodium salt of oleic acid, natural nontoxic surfactant, are prepared and characterized. These systems self-assemble in aqueous solutions into particles with average size of 50–60 nm, which can solubilize hydrophobic dyes (Yellow

Tatiana K. Bronich; Andrew Nehls; Adi Eisenberg; Victor A. Kabanov; Alexander V. Kabanov

1999-01-01

217

Poly(ethylene terephthalate) ionomer based clay nanocomposites produced via melt extrusion  

Microsoft Academic Search

Poly(ethylene terephthalate) ionomer (PETI)\\/organically-modified montmorillonite clay (OMC) nanocomposites were prepared via melt extrusion. Sulfonated PET containing various incorporations of ionic comonomer and clay modifications were investigated. The random incorporation of ionic functionalities along the PET backbone enhances interactions between the matrix polymer and montmorillonite clay resulting in the creation of polymer-clay nanocomposites exhibiting a predominately exfoliated morphology. The morphology is

Grant D. Barber; Bret H. Calhoun; Robert B. Moore

2005-01-01

218

Synthesis and properties of random poly(lactic acid)-based ionomers  

Microsoft Academic Search

A random poly(lactic acid), PLA, based ionomer was synthesized by copolymerizing a methacrylate-terminated PLA macromonomer and methyl methacrylate. The copolymerization kinetics were studied using 1H NMR spectroscopy and the copolymer composition was characterized by 13C NMR spectroscopy. Carboxylic acid groups were introduced into the copolymer by reacting the hydroxyl end groups of the PLA macromonomer with succinic anhydride, and the

Andrew J. Ro; Samuel J. Huang; R. A. Weiss

2009-01-01

219

Synthesis and thermal properties of telechelic poly(lactic acid) ionomers  

Microsoft Academic Search

Telechelic poly(lactic acid) (PLA) ionomers were synthesized using a chemical recycling process. A transesterification reaction between a commercial PLA and 2-hydroxyethyl methacrylate or ethylene glycol was used to produce a hydroxy-terminated PLA. The hydroxy-terminated PLA was then reacted with itaconic anhydride to produce terminal carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca-

Andrew J. Ro; Samuel J. Huang; R. A. Weiss

2008-01-01

220

Autonomous healing materials based on epoxidized natural rubber and ethylene methacrylic acid ionomers  

NASA Astrophysics Data System (ADS)

The development of autonomous healing material has an enormous scientific and technological interest. In this context, this research work deals with the investigation of autonomous healing behavior of epoxidized natural rubber (ENR) and its blends with ethylene methacrylic acid ionomers. The autonomous healing behavior of ENR and its blends containing two different ionomers [poly(ethylene-co-methacrylic acid sodium salt) (EMNa) and poly(ethylene-co-methacrylic acid zinc salt) (EMZn)] has been studied by ballistic puncture tests. Interestingly, EMNa/ENR blends exhibit complete healing just after the ballistic test but EMZn/ENR blends do not show full self-repairing. The healing efficiency has been evaluated by optical microscopy and a depressurized air-flow test. The healing mechanism has been investigated by characterizing thermal and mechanical properties of the blends. The chemical structure studied by FTIR and thermal analysis show that the ion content of ionomers and functionality of ENR has a significant influence on the self-healing behavior.

Arifur Rahman, Md; Penco, Maurizio; Peroni, Isabella; Ramorino, Giorgio; Janszen, Gerardus; Di Landro, Luca

2012-03-01

221

Vibrational analysis of side chain model compounds of perfluorinated alkyl sulfonic Acid ionomers.  

PubMed

Perfluorinated sulfonic acid ionomers have been extensively studied in particular for application to polymer electrolyte fuel cells as they show high proton conductivity at relatively low humidity. While vibrational spectroscopic methods have been successfully applied to investigate dissociation and hydration of their acid sites, the bands in the measured spectra have still been empirically assigned to local vibrations. We performed vibrational analysis of model compounds of the side chains of perfluorinated sulfonic acid ionomers by hybrid DFT calculation. On the basis of mean absolute errors in bond lengths and vibrational frequencies of triflic acid (CF(3)SO(3)H) calculated with various hybrid functionals and basis sets, PBE0/6-311G* gave the best results within affordable computational times and was applied for the model compounds. Most of the observed bands in the ATR-IR spectra of the model compounds were successfully reproduced by calculation of their dissociated sulfonate anions. New assignments were proposed for characteristic two peaks at around 970 and 1060 cm(-1) as combinations of SO(3) symmetric stretch and adjacent CCO bend in two opposite phases. Vibrational bands of doubly hydrogen-bonded acid dimer were also identified in the IR spectrum of "as-received" PFEESA which was not hydrated. These results would provide a new basis for application of vibrational spectroscopy of perfluorinated sulfonic acid ionomers on their structural changes with degree of hydration. PMID:23110345

Yamaguchi, Makoto; Ohira, Akihiro

2012-10-30

222

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

2013-08-21

223

Tempered glass  

SciTech Connect

This document describes a demonstration for making tempered glass using minimal equipment. The demonstration is intended for a typical student of materials science, at the high school level or above. (JL)

Bunnell, L.R.

1991-11-01

224

Glass electrolytes  

SciTech Connect

The objective of this research is a glass electrolyte for use in sodium/sulfur batteries that has a low resistivity (100 ohm-cm at 300/sup 0/C) and is stable in the cell environment. Experiments in this program are focussed on glasses in the quaternary system: soda, alumina, zirconia and silica. The FY 1983 research on glass analogs of NASICON, parallel thermodynamic calculations, and a review of the literature in the areas of glass conductivity and corrosion resistance led to selection of this system for more detailed investigation. The main program elements are: (1) conductivity measurements at 300 to 500/sup 0/C; (2) differential thermal analysis for determination of glass-transition and crystallization temperatures; (3) static corrosion tests at 400/sup 0/C using Na, Na/sub 2/S/sub 4/, and S; (4) mechanical strength and fracture toughness measurements; and (5) sodium/sulfur cell tests at 350/sup 0/C. Elements (1) and (2) are nearly completed; element (3) is being initiated using the glasses prepared for (1) and (2), and elements (4) and (5) will begin in the first and second quarters of FY 1985, respectively. Fourteen quaternary glasses having a broad range of compositions have been made. The resistivities of these glasses at 300/sup 0/C extended from 130 to 3704 ohm-cm; the activation energies for conduction extended from 0.488 to 0.684 eV, and the glass transition temperatures extended from 397 to 685/sup 0/C. Through a multiple linear regression analysis of these data response surfaces were generated for resistivity, activation energy for conduction, and glass transition temperature over the composition region within the quaternary system that is bounded by SiO/sub 2/, Na/sub 2/O/sub 3/, Na/sub 2/AlO/sub 4/ and Na/sub 2/ZrO/sub 3/. These response surfaces indicated a new region of high conductivity and high glass transition temperature in the neighborhood of 42% soda, 31% silica and 27% alumina plus zirconia.

Not Available

1984-06-25

225

Water, proton, and oxygen transport in high IEC, short side chain PFSA ionomer membranes: consequences of a frustrated network.  

PubMed

The effect of ion exchange capacity (IEC) on the water sorption properties of high IEC, short side chain (SSC) PFSA ionomer membranes, and the relationships between water content, proton conductivity, proton mobility, water permeation, oxygen diffusion, and oxygen permeation are investigated. SSC PFSA ionomer membranes possessing 1.3, 1.4, and 1.5 mmol g(-1) IEC are compared to a series of long side chain (LSC) PFSA ionomer membranes ranging in IEC from 0.9 to 1.13 mmol g(-1). At 25 °C, fully-hydrated SSC ionomer membranes are characterized as possessing higher water contents (56-75 vol%), moderate ? values (15-18), high analytical acid concentrations (2-2.8 M), and moderate conductivity (88-115 mS/cm); but lower than anticipated effective proton mobility. Complementary measurements of water permeability, oxygen diffusion, and oxygen permeability also yield lower than expected values given their much higher water contents. Potential benefits afforded by reducing the side chain length of PFSA ionomer membranes, such as increased crystallinity, higher IEC, and high hydrated acid concentration are offset by a less-developed, frustrated hydrophilic percolation network, which provides a motivation for future improvements of transport properties for this class of material. PMID:21915410

Luo, Xiaoyan; Holdcroft, Steven; Mani, Ana; Zhang, Yongming; Shi, Zhiqing

2011-09-13

226

Fluoride glasses  

SciTech Connect

Crystalline fluorides play a significant role in materials science, e.g. as lenses in infrared (IR) optics (CaF{sub 2}), laser hosts (LaF{sub 3}, CaF{sub 2}), fast ion conductors ({beta}PbF{sub 2}), and fluoride ion sensitive electrodes (LaF{sub 3}). Their melts, however, are very fluid, largely ionic, and unlikely candidates for glass formation. Nevertheless, many fluoride glass forming systems have been identified, with useful properties such as extended IR transmission, and the added advantage of ease of fabrication. The development of these materials, with special emphasis on optical fibers, is considered in this paper. Fluoride glasses are often referred to by acronyms based on the initial letters of the component cation chemical symbols, in a sequence based more on historical development than amounts present. Examples include ZBLAN(ZrF{sub 4}-BaF{sub 2}-LaF{sub 3}-A1F{sub 3}-NaF), CLAP (CdF{sub 2}-LiF-A1F{sub 3}-PbF{sub 2}), and BZnYbT (BaF{sub 2}-ZnF{sub 2}-YbF{sub 3}- ThF{sub 4}) glasses. ZBLAN glasses have been studied in most detail and are the basis of much of the discussion here.

Parker, J.M. (School of Materials, Univ. of Sheffield, Elmfield, Northumberland Road, Sheffield S10 2TZ (GB))

1989-01-01

227

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

228

The characterization of new fluorinated ionomers for use in polymer electrolyte membrane (PEM) fuel cells  

NASA Astrophysics Data System (ADS)

Proton exchange membrane (PEM) fuel cells were fabricated using a novel class of bis[(perfluoalkyl)sulfonyl] imide ionomer materials synthesized by Professor Darryl D. DesMarteau and coworkers at Clemson University. These imide materials were incorporated in catalyst layers and used as membranes in fuel cell membrane electrode assemblies (MEAs). Corresponding fuel cells that used the structurally related industry standard DuPont Naflon were also assembled and tested as benchmarks. Assembled MEAs were characterized on a device level using multiple techniques including voltage-current discharge curves, current output at a static load potential, and measurement of cell resistance. Characterization was performed at a number of different cell temperatures (80, 100, and 110°C) and under a range of cell humidification conditions. The performance of MEAs with imide-based catalyst layers was found to be highly dependent upon the equivalent weight of the ionomer and the operating temperature. For MEAs where membrane material was the variable, performance was observed to be highly dependent upon membrane thickness and equivalent weight of the membrane ionomer. A representative number of these fuel cells were also characterized ex situ with scanning electron microscopy (SEM) and X-ray dispersive analysis (EDX). SEM micrographs were obtained that clearly displayed the distinct layers of MEAs. The transitions between the MEA layers were also visible in EDX elemental line scans. An investigation into the effect of catalyst poisoning from low levels of carbon monoxide in the hydrogen fuel stream was undertaken at Los Alamos National Laboratory (LANL). Anodic stripping voltammetry was used to electrochemically oxidize CO from Pt, Pt-Ru, and Pt-Mo catalyst surfaces. Results from this study corroborated earlier work at LANL for CO stripping voltammetry from Pt. Pt-Mo results were similar to those seen in literature. Pt-Ru showed CO desorption at the lowest overpotential of the three materials, indicating the highest feasibility as a fuel cell catalyst in the presence of CO.

Savett, Scott Craig

229

Hydration and proton transfer in highly sulfonated poly(phenylene sulfone) ionomers: an ab initio study.  

PubMed

The need to operate proton exchange membrane fuel cells under hot and dry conditions has driven the synthesis and testing of sulfonated poly(phenylene) sulfone (sPSO(2)) ionomers. The primary hydration and energetics associated with the transfer of protons in oligomeric fragments of two sPSO(2)ionomers were evaluated through first-principles electronic structures calculations. Our results indicate that the interaction between neighboring sulfonic acid groups affect both theconformation and stability of the fragments. The number of water molecules required to affect the transfer of a proton in the first hydration shell was observed to be a function of the hydrogen bonding in proximity of the sulfonic acid groups: three H(2)O for the meta- and four H(2)O for the ortho-conformations. Calculations of the rotational energy surfaces indicate that the aromatic backbones of sPSO(2) are much stiffer than the polytetrafluoroethylene (PTFE) backbones in perfluorosulfonic acid (PFSA) ionomers: the largest energy penalty for rotating phenylene rings (i.e., 15.5 kcal/mol for ortho-ortho-sPSO(2)) is nearly twice that computed for the rotation of a CF(2) unit in a PTFE backbone. The energetics for the transfer of various protons in proximity to one or two sulfonate groups (-SO(3)(-)) was also determined. The computed energy barrier for proton transfer when only one sulfonic acid group is present is approximately 1.9 kcal/mol, which is 2.1 kcal/mol lower than similar calculations for PFSA systems. When two sulfonic acid groups are bridged by water molecules, a symmetric bidirectional transfer occurs, which gives a substantially small energy barrier of only 0.7 kcal/mol. PMID:23286778

Wang, Chen; Paddison, Stephen J

2013-01-11

230

Pinhole Glasses  

ERIC Educational Resources Information Center

Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole…

Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

2008-01-01

231

Pinhole Glasses  

ERIC Educational Resources Information Center

|Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole…

Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

2008-01-01

232

Glass: Rotary Electric Glass Furnace  

SciTech Connect

Compared to conventional gas-fired furnaces, the new rotary electric furnace will increase energy efficiency while significantly reducing air emissions, product turnaround time, and labor costs. As this informative new fact sheet explains, the thousand different types of glass optical blanks produced for the photonics industry are used for lasers, telescopes, cameras, lights, and many other products.

Recca, L.

1999-01-29

233

Orientational glasses  

NASA Astrophysics Data System (ADS)

This review summarizes experimental evidence for the freezing of reorienting moments in solids. The moments may be of dipolar or quadrupolar nature, or both; they belong to one of the constituents of a mixed-crystal solid. Extensive results are reported for the following systems: KCl doped with hydroxyl, potassium tantalate doped with Li, Na and Nb, alkali halide cyanides and alkali-alkali cyanides, rubidium ammonium dihydrogen phosphate, solid ortho-para hydrogen and argon-nitrogen mixtures. These have clearly glass-like properties. In other systems, results are limited to one or two methods hinting at glass formation; some of those are also reported. Clustering phenomena and the slowdown of reorientations at the freezing temperature are observed in susceptibility measurements and by local probing on nuclear spins. The modulation of the structure by cluster formation is revealed by diffraction experiments. These phenomena are confronted with model predictions and numerical simulations.

Höchli, U. T.; Knorr, K.; Loidl, A.

2002-03-01

234

Morphological analysis of ionomers. Progress report, January 1, 1993--December 31, 1993  

SciTech Connect

This paper reports work on the study of ion containing polymers. X-ray absorption fine structure studies have been carried out on lightly sulfonated polystyrenes and polyurethane cationomers. In the polystyrenes, nickel, zinc, and cadmium-neutralized ionomers were studied. A simulation package, FEFF5, was available to model the polystyrenes, and the experimental data was input into the simulation to arrive at an atomic arrangement which fit the experimental data. The cationomers structure is still unresolved, and the question of water absorption is a problem for this system. NMR of {sup 23}Na is also being used to study the local environment of the cation in sodium-neutralized lightly sulfonated polystyrene. Small angle neutron scattering experiments were also performed to explore the role of temperature in solution of sodium-neutralized carboxy-telechelic polystyrene ionomers in toluene. By adjusting the labelling levels and the angular range, the neutron scattering experiments probe either the aggregate structure or the single chain structure.

Not Available

1993-12-01

235

Effect of platinum loading on fuel cell cathode performance using hydrocarbon ionomers as binders.  

PubMed

The effect of platinum loading on cathode performance in hydrogen/oxygen fuel cells was investigated using perfluorosulfonic acid (Nafion), sulfonated polyimide (SPI-8) and sulfonated poly(phenylene ether ether ketone) (SPEEK) ionomers as the electrode binder. By lowering the platinum loading, the cathode polarization decreased for MEAs using SPI-8 and SPEEK binders at high humidity (90-100% RH (relative humidity)) due to an improvement of mass transport (oxygen supply and/or water discharge) in the catalyst layer. In contrast, at humidity lower than 80% RH, the effect of platinum loading on the cathode performance differed between these two hydrocarbon (HC) ionomers. When SPI-8 was used as the binder, the cathode polarization increased when lowering the platinum loading due to an increase of activation overpotential. When SPEEK was used as the binder, the effect of platinum loading on the cathode performance was smaller. Such differences can be ascribed to the specific adsorbability of these hydrocarbon binders on the platinum catalyst at low humidity. These results point to crucial factors in achieving higher performance at low platinum loadings and low humidity using HC binders. PMID:23138448

Omata, Takuya; Uchida, Makoto; Uchida, Hiroyuki; Watanabe, Masahiro; Miyatake, Kenji

2012-11-09

236

Toward Reconciliation of STEM and SAXS Data from Ionomers by Investigating Gold Nanoparticles  

NASA Astrophysics Data System (ADS)

We have recently pioneered the use of scanning transmission electron microscopy (STEM) for direct, model independent imaging of the nano-scale morphology of ionomers. To date, the sizes of ionic aggregates determined in STEM experiments are inconsistent with SAXS data interpreted by the Yarusso-Cooper model. To address this discrepancy we have investigated a pair of model nanoparticles (11 and 55 atom Au clusters) with both STEM and SAXS. Using this model system we have improved our method of measuring nanometer scale objects and evaluated the importance of STEM probe size and specimen thickness. While the size of the STEM probe was inconsequential, specimen thicker than 50 nm showed significant depreciation of image quality, which limits our ability to accurately measure particle size. SAXS was performed on dilute suspensions of nanoparticles and fit using a monodisperse, hard-sphere form factor model. For Au11, STEM finds a diameter of 1.3 nm + .14 and SAXS finds a diameter of 1.4 nm. Similarly, both STEM and SAXS determine a diameter of 1.7 nm for Au55. Analysis of these model systems have allowed us to evaluate several factors of potential importance in reconciling STEM and SAXS data from ionomers.

Benetatos, Nicholas; Smith, Brian; Heiney, Paul; Winey, Karen

2005-03-01

237

Synthesis and Bulk Physical Properties of Styrene-Alkoxide Ionomers. Part 1. Sodium Salts of Polystyrene-co-4-hydroxystyrene.  

National Technical Information Service (NTIS)

This is the first of a series of three papers on the bulk physical properties of styrene-alkoxide ionomers. In this first paper, the synthesis and mechanical properties of the sodium salts of polystyrene-co-4-hydroxystyrene will be discussed. As some char...

S. D. Clas A. Eisenberg

1986-01-01

238

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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...

239

Comparative experimental study of ionic polymer-metal composites with different backbone ionomers and in various cation forms  

Microsoft Academic Search

An ionic polymer-metal composite (IPMC) consisting of a thin perfluorinated ionomer (usually, Nafion or Flemion) strip, platinum, and\\/or gold plated on both faces and neutralized by a certain amount of appropriate cations undergoes large bending motion when, in a hydrated state, a small electric field is applied across its thickness. When the same membrane is suddenly bent, a small voltage

Sia Nemat-Nasser; Yongxian Wu

2003-01-01

240

Dental glass-reinforced composite for caries inhibition: calcium phosphate ion release and mechanical properties.  

PubMed

The two main challenges facing dental composite restorations are secondary caries and bulk fracture. Previous studies developed whisker-reinforced Ca-PO(4) composites that were relatively opaque. The objective of this study was to develop an esthetic glass particle-reinforced, photo-cured calcium phosphate composite. Tetracalcium phosphate (TTCP) particles were incorporated into a resin for Ca and PO(4) release, while glass particles provided reinforcement. Ion release and mechanical properties were measured after immersion in solutions with pH of 7, 5.5, and 4. For the composite containing 40% mass fraction of TTCP, incorporating glass fillers increased the strength (p < 0.05). Flexural strength (Mean +/- SD; n = 6) at 30% glass was 99 +/- 18 MPa, higher than 54 +/- 20 MPa at 0% glass (p < 0.05). Elastic modulus was 11 GPa at 30% glass, compared to 2 GPa without glass. At 28 days, the released Ca ion concentration was 4.61 +/- 0.18 mmol/L at pH of 4, much higher than 1.14 +/- 0.07 at pH of 5.5, and 0.27 +/- 0.01 at pH of 7 (p < 0.05). PO(4) release was also dramatically increased at cariogenic, acidic pH. The TTCP-glass composite had strength 2-3 fold that of a resin-modified glass ionomer control. In conclusion, the photo-cured TTCP-glass composite was "smart" and substantially increased the Ca and PO(4) release when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit tooth caries. Its mechanical properties were significantly higher than previous Ca, PO(4), and fluoride releasing restoratives. Hence, the photo-cured TTCP-glass composite may have potential to provide the necessary combination of load-bearing and caries-inhibiting capabilities. PMID:19810118

Xu, Hockin H K; Moreau, Jennifer L

2010-02-01

241

Dental glass-reinforced composite for caries inhibition: Calcium phosphate ion release and mechanical properties  

PubMed Central

The two main challenges facing dental composite restorations are secondary caries and bulk fracture. Previous studies developed whisker-reinforced Ca-PO4 composites that were relatively opaque. The objective of this study was to develop an esthetic glass particle-reinforced, photo-cured calcium phosphate composite. Tetracalcium phosphate (TTCP) particles were incorporated into a resin for Ca and PO4 release, while glass particles provided reinforcement. Ion release and mechanical properties were measured after immersion in solutions with pH of 7, 5.5, and 4. For the composite containing 40% mass fraction of TTCP, incorporating glass fillers increased the strength (p < 0.05). Flexural strength (mean ± sd; n = 6) at 30% glass was (99 ± 18) MPa, higher than (54 ± 20) MPa at 0% glass (p < 0.05). Elastic modulus was 11 GPa at 30% glass, compared to 2 GPa without glass. At 28 d, the released Ca ion concentration was (4.61 ± 0.18) mmol/L at pH of 4, much higher than (1.14 ± 0.07) at pH of 5.5, and (0.27 ± 0.01) at pH of 7 (p < 0.05). PO4 release was also dramatically increased at cariogenic, acidic pH. The TTCP-glass composite had strength 2-3 fold that of a resin-modified glass ionomer control. In conclusion, the photo-cured TTCP-glass composite was “smart” and substantially increased the Ca and PO4 release when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit tooth caries. Its mechanical properties were significantly higher than previous Ca, PO4 and fluoride releasing restoratives. Hence, the photo-cured TTCP-glass composite may have potential to provide the necessary combination of load-bearing and caries-inhibiting capabilities.

Xu, Hockin H. K.; Moreau, Jennifer L.

2010-01-01

242

The effect of three finishing systems on four esthetic restorative materials.  

PubMed

Previous studies have investigated the finishing and smoothness of composite and traditional glass-ionomer restorations, but few have included resin-modified glass-ionomer cements or more recent finishing systems. The results of using three different finishing systems (Sof-Lex, Enhance, finishing burs) on two composites (Silux, Prisma TPH), a traditional glass ionomer (Ketac-Fil), and a resin-modified glass ionomer (Fuji II LC) were studied. Sixty samples were condensed into sectioned acrylic tubes, covered with a Mylar matrix plus a glass slide at each surface, then cured as per the manufacturers' instructions. Samples were randomized to three groups of five for each material and testing with a Surfanalyzer 4000 of unfinished samples (cured with Mylar matrix) was done to obtain baseline average surface roughness (Ra). Samples were then finished as per the manufacturers' instructions using polishing disks, abrasive impregnated disks, and finishing burs before further surface testing. Samples finished with burs and with abrasive impregnated disks were further polished using polishing paste (Prisma Gloss) and again tested. Data were analyzed with ANOVA testing and Tukey's HSD pairwise comparison. Initial testing after randomization to groups showed no significant difference in surface roughness (P = 0.24). Two-factor analysis revealed no significant difference between materials (P = 0.34), a significant difference in method of finish (P < or = 0.00), with no significant interaction between type of material and method of finish (P = 0.11). Aluminum oxide disk and impregnated disk systems provided the best finish for microfilled composite and both glass-ionomer materials (P < or = 0.00). No significant difference in method of finish existed with the hybrid composite (P = 0.07). Overall, esthetic restorative material finishing is best accomplished using abrasive impregnated disks or aluminum oxide disks. Finishing burs gave a significantly rougher surface than the former methods. PMID:9610331

Hoelscher, D C; Neme, A M; Pink, F E; Hughes, P J

243

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

244

Antibacterial Properties of Dental Luting Agents: Potential to Hinder the Development of Secondary Caries  

PubMed Central

A modified direct contact test was used to evaluate the antibacterial properties of four commercially available dental luting agents (RelyX Unicem, Ketac Cem, Ceramir Crown & Bridge and Harvard Cement) and two reference materials (glass-ionomer cement and calcium aluminate cement) compared to a negative-control material (PMMA). Streptococcus mutans bacteria were placed in direct contact with specimens that had been aged for 10?min, 1?day, and 7?days, in order to test the antibacterial properties of the materials. A metabolic assay containing resazurin was used to quantify the amount of viable bacteria remaining after the direct contact tests. The effects of pH and fluoride on bacteria proliferation were also evaluated. Strongest antibacterial properties were found for calcium aluminate cement, followed by Ceramir Crown & Bridge and RelyX Unicem. Ketac Cem, Harvard Cement, and the reference glass-ionomer cement showed bacteria content either higher than or not significantly different from the PMMA control in all instances. pH levels below 6.3 and above 9.0 were found to have negative effects on bacterial proliferation. No correlation between either acidic materials or fluoride release and antibacterial properties could be seen; rather, basic materials showed stronger antibacterial properties.

Unosson, Erik; Cai, Yanling; Jiang, Xiyuan; Loof, Jesper; Welch, Ken; Engqvist, Hakan

2012-01-01

245

Nonequilibrium viscosity of glass  

Microsoft Academic Search

Since glass is a nonequilibrium material, its properties depend on both composition and thermal history. While most prior studies have focused on equilibrium liquid viscosity, an accurate description of nonequilibrium viscosity is essential for understanding the low temperature dynamics of glass. Departure from equilibrium occurs as a glass-forming system is cooled through the glass transition range. The glass transition involves

John C. Mauro; Douglas C. Allan; Marcel Potuzak

2009-01-01

246

In vitro Comparison of Zinc Phosphate and Glass Ionomers Ability to Inhibit Decalcification under and Adjacent to Orthodontic Bands.  

National Technical Information Service (NTIS)

Forty sets of impacted third molar teeth were banded with custom fitted bands and cycled in a latic acid solution for four weeks. This solution simulates an environment that would be found only in patients with the worst oral hygiene. Each set was from th...

D. J. Copenhaver

1985-01-01

247

Effect of tooth storage and cavity cleansing on cervical gap formation in Class II glass-ionomer/composite restorations.  

PubMed

Class II cavities with the cervical margin just below the C-E junction and with two cervical retention grooves were prepared in intact human premolars, 31 cavities in teeth stored frozen and 29 cavities in teeth stored in 1% chloramine solution. The teeth from both storage conditions were assigned to two groups; in one group, the cavities were cleaned with a water spray, in the other group, with a cleaner containing 0.2% EDTA and 1% NaF. All cavities were lined with Vitrebond and restored with P50. Cervical contraction gaps were disclosed by a fluorescent resin penetration technique. The length and width of each gap were analysed. A contraction gap was revealed in 17 of the 31 cavities in teeth stored frozen (54.8%) and in 22 of the 29 restorations in the teeth stored in chloramine (75.8%). The width of the gap was significantly greater in teeth stored in chloramine (p = 0.0004). No statistical difference in gap formation was found between cavities cleaned with water or with the detergent containing 0.2% EDTA and sodium fluoride. Since the cavity cleansing procedure was not a significant factor in gap formation, apparently removing the superficial smear layer with the cavity cleaner does not impair the bonding of Vitrebond to the dentin. However, gap formation appeared to be significantly affected by the storage conditions of the extracted teeth. It is suggested that teeth to be used in bond strength and leakage experiments should be stored frozen rather than stored in 1% chloramine solution. PMID:1303376

Brännström, M; Coli, P; Blixt, M

1992-09-01

248

Metal glasses  

NASA Astrophysics Data System (ADS)

Methods of producing amorphous alloys of various systems (e.g., Pd-Si, Fe-B, Ni-P, Ni-Nb, Ni-Ta, Co-Gd, Fe-Gd, Mg-Zn,and Ca-Al) are briefly discussed, and the atomic structure and properties of such alloys are examined. In particular, attention is given to anomalies in the low-temperature behavior of amorphous alloys, their electrical and magnetic properties, strength, ductility, and corosion stability. Some aplications of metal glasses are mentioned.

Belen'kii, Aleksei Iakovlevich

1987-02-01

249

The effect of investment material and ceramming regime on the surface roughness of two castable glass–ceramic materials  

Microsoft Academic Search

Objective: To assess the surface roughness (Ra) of two castable glass–ceramic materials, cast using four different investment materials and employing different ceramming regimes.Methods: Forty discs, each 12mm diameter and 2mm thick were produced from two castable glass–ceramic materials, one a glass ionomer derivative based on 1.5SiO2–1Al2O3–0.53P2O5–1CaO–0.67CaF2 (LG112), the other a fluorcanasite material based on 0.60SiO2–0.05K2O–0.10Na2O–0.15CaO–0.10CaF2 (SG3). The discs were made

A Johnson; R van Noort; P. V Hatton; J. M Walsh

2003-01-01

250

Tissue response to experimental dental cements prepared from a modified powder glass composition.  

PubMed

The present work seeks to evaluate the biocompatibility of experimental glass ionomer cements (GIC) prepared from niobium-calcium fluoro-alumino-silicate glass powder and two commercial GICs. The GICs were implanted into the subcutaneous connective tissue of sixty rats. The rats were sacrificed during four varying time periods: 7, 15, 30, and 60 days and histopathological examinations were then performed. The Kruskal-Wallis test was performed to evaluate any significant differences between the materials. Additionally, multiple comparisons of the mean rank were also carried out using the Dunn test (p<0.05). No significant differences were observed that one GIC was superior to the other. The tissue response for all of the GICs tested was similar in all the periods examined. PMID:22864211

Boaventura, Juliana Maria Capelozza; Bertolini, Marcio José; Padovani, Gislaine Cristina; de Oliveira, Maria Rita Brancini; Zaghete, Maria Aparecida; de Oliveira Júnior, Osmir Batista; de Andrade, Marcelo Ferrarezi

2012-01-01

251

High Temperature IR Glasses.  

National Technical Information Service (NTIS)

Fields of glass formation, crystalline phases in these fields, ranges of immiscibility, and the relation of composition as well as heat treatment to the glass temperature in selected chalcogenide glass systems were investigated. The main objective of the ...

N. J. Kreidl

1971-01-01

252

Integrated Glass Ceramic Systems.  

National Technical Information Service (NTIS)

Integrated glass ceramic spacecraft include a plurality of glass ceramic components including molded, tempered, annealed, and patterned glass ceramic components coupled together for forming a support structure or frame or housing through which is communic...

H. Helvajian S. W. Janson

2003-01-01

253

CRYSTALLIZATION IN MULTICOMPONENT GLASSES  

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 glass making are reviewed.

KRUGER AA; HRMA PR

2009-10-08

254

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

255

Chemical Principles Revisited: The Chemistry of Glass.  

ERIC Educational Resources Information Center

|Presents a detailed discussion on the chemistry of glass. Topics discussed include: natural glass, early history, modern glass composition, raw materials for glass melting, chemically modified glasses, modern glass forming, glass ceramics, and new developments in glass research. (BT)|

Kolb, Doris; Kolb, Kenneth E.

1979-01-01

256

Microorganisms and Volcanic Glass  

Microsoft Academic Search

Volcanic glass is primarily found on Earth as quenched basalt magma or as high-silica ash deposits. Basalt magma is quenched to glass as it erupts into water or sediment, making pillow lavas, sheet flows, or highly fractured rocks (hyaloclastites). Silicic, explosive volcanism produces thick deposits of ash composed primarily of glass shards. Volcanic glass is unstable in the presence of

M. Fisk; C. di Meo; I. Thorseth; S. Giovannoni; M. Storrie-Lombardi

2002-01-01

257

Effect of Cation Size and Valency on the Ionic Aggregates in Poly(styrene-ran-methacrylic acid) Ionomers  

NASA Astrophysics Data System (ADS)

Previous STEM studies of fully-neutralized poly(styrene-ran-methacrylic acid) (SMAA) ionomers have shown spherical or vesicular aggregates when neutralized with Zn or Cs, respectively. The current study probes the effects of cation size and valency on the morphology of the ionic aggregates by examining SMAA neutralized with cations from Groups 1 (Na, K, Rb and Cs) and 2 (Mg, Ca, Sr and Ba) of the periodic table. In addition to the shape of the ionic aggregates, their size and number density are measured to further understand the influence of the cations on the ionomer morphology. Results to date suggest that the cation size is more significant than the cation valency. For example, fully neutralized SMAA ionomers exhibit spherical aggregates with Na+ (ionic radius 0.095 nm) and vesicular aggregates with Cs+ (ionic radius 0.169 nm). Complimentary studies are underway in our group using poly(ethylene-ran-methacrylic acid) neutralized with same range of cations, as well as computer simulations and rheological measurements.

Kirkmeyer, Brian P.; Winey, Karen I.

2003-03-01

258

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.

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

2009-01-01

259

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

260

Oriented Morphology and Anisotropic Transport in Uniaxially Stretched Perfluorosulfonate Ionomer Membranes  

SciTech Connect

Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.

J Park; J Li; G Divoux; L Madsen; R Moore

2011-12-31

261

Electrical Properties of Poly(ethylene oxide)-based Ionomers as Single Ion Conductors  

NASA Astrophysics Data System (ADS)

Polyethers, such as poly(ethylene oxide) (PEO) are of interest for development of advanced lithium batteries because Li^+ ions have facile transport in this media. We make ionomers based on PEO by reacting poly(ethylene glycol) (PEG) oligomers with the sodium salt of dimethyl 5-sulfoisophthalate. Since the sulfonate group is covalently bonded to the chain, it is essentially immobile and hence these materials are single-ion conductors. The charge spacing on the chain can be directly controlled by the molar mass of the PEG oligomers (we use M = 400, 600 and 900) used in the synthesis. Conductivity depends strongly on temperature, with nearly identical conductivities in all of our samples at the same T - Tg, suggesting that Li^+ ion transport is controlled by segmental motion of the PEO. Using the onset of electrode polarization (usually considered a nuisance in dielectric spectroscopy) we quantitatively estimate the free ion concentration and mobility, based on work of MacDonald (1952 & 1974) and Coelho (1983 & 1991). The temperature dependence of the free ion concentration is described by a simple pairing energy, which decreases in going from Li^+ to Na^+ to Cs^+, consistent with larger ions being less strongly bound to the sulfonate groups. The ion mobility shows a Vogel-Fulcher temperature dependence, as anticipated by the polymer's segmental motion controlling ion mobility.

Colby, Ralph H.; Dou, Shichen; Zhang, Shihai; Klein, Robert J.; Runt, James P.; Mueller, Karl T.

2006-03-01

262

Molecular Dynamics Simulations of a Single Chain Pentablock Ionomer in Dilute Solutions  

NASA Astrophysics Data System (ADS)

Co-polymers are in the core of many applications such as fuel cells, batteries and purification membranes that require transport across membranes. The challenge remains however that under the condition that transport is optimized, the stability of the membranes is compromised. To surmount this challenge, co-polymers with blocks targeting specific roles have been designed. Using molecular dynamics simulations we have studies the structure and dynamics of ionic single chain pentablock copolymer (A-B-C-B-A) containing randomly sulfonated polystyrene in the center, tethered to poly-ethylene-r-propylene end-capped by poly-t-butyl styrene. The ionic block facilitates transport while the A and B componenet are incorporated for mechanical stability. The conformation and dynamics of single pentablock ionomer of molecular weight Mw = 50,000g/mol in an implicit poor solvent with dielectric constant of 1 and 77.7, water, and mixture (1:1) of cyclohexane and n-heptane at 300K and 500K will be presented. The effect of solvents on conformation of a single molecule of pentablock was determined and compared with experiment, providing a stepping stone to the understanding phase behavior of this polymer.

Aryal, Dipak; Perahia, Dvora; Grest, Gary S.

2013-03-01

263

FOAM GLASS INSULATION FROM WASTE GLASS  

EPA Science Inventory

Waste glass has proven to be effective for the production of foam glass insulation both in the bulk or rigid board form and pellet form. Problems inherent with the use of water, carbon black and calcium carbonate as the foaming agents, have been identified and many have been solv...

264

Practice of Waste Glass Recovery.  

National Technical Information Service (NTIS)

Based on the slogan ''old glass is not waste, but raw material'' the glass container industry of West Germany is promoting glass recycling. Programs for encouraging individuals, civic groups, and communities to collect used glass are described. (ERA citat...

H. Knoche

1975-01-01

265

Glass in Class  

ERIC Educational Resources Information Center

|Glass is reviewed from fabrication to application, laying emphasis on the wide-ranging physics involved. This begins with liquids and solids and the way in which glasses are defined and can be demonstrated in the classroom. At the atomic level the regular structure of crystals and their irregular counterparts in glasses are explained through…

Greaves, Neville

2005-01-01

266

Strength of inorganic glass  

Microsoft Academic Search

This book presents information on the following topics: a look at the history of glass strength; atomistic theory of fracture; surface chemistry in relation to the strength and fracture of silicate glasses; high-speed photographic investigations of the dynamic localized loading of some oxide glasses; a correction for measurements of contact area using Newton's rings; envionmentally enhanced crack growth; fatigue in

Kurkjian

1985-01-01

267

Waste glass weathering  

Microsoft Academic Search

The weathering of glass is reviewed by examining processes that affect the reaction of commercial, historical, natural, and nuclear waste glass under conditions of contact with humid air and slowly dripping water, which may lead to immersion in nearly static solution. Radionuclide release data from weathered glass under conditions that may exist in an unsaturated environment are presented and compared

J. K. Bates; E. C. Buck

1993-01-01

268

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

269

Do cathedral glasses flow?  

NASA Astrophysics Data System (ADS)

A general belief among members of the scientific community is that glass articles can be bent irreversibly and that they flow at ambient temperature. This myth is mostly based on widespread stories that stained-glass windows of medieval cathedrals are thicker in the lower parts. In this paper I estimate the time periods required for glass to flow and deform at ordinary temperatures, using calculated viscosity curves for several modern and ancient glass compositions. The conclusion is that window glasses may flow at ambient temperature only over incredibly long times, which exceed the limits of human history.

Zanotto, Edgar Dutra

1998-05-01

270

Oxynitride glass production procedure  

SciTech Connect

This patent describes the invention of 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, J.R.; Schuetz, S.T.; O'Brien, M.H.

1991-04-09

271

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

272

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. 4 tabs.

Weidner, J.R.; Schuetz, S.T.; O' Brien, M.H.

1990-03-28

273

Rare Earth Phosphate Glass and Glass-Ceramic Proton Conductors  

Microsoft Academic Search

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

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

2008-01-01

274

Characterization of glass surfaces  

NASA Astrophysics Data System (ADS)

Significant advances have been made during the last 15 years in our understanding of glass surfaces and their environmental reactivity. The major reason for this advancement is the large array of surface analytical techniques that has been developed and applied to many industrial problems. One specific area of research where surface analysis has been proven valuable is glass corrosion. Until recently, the principal methods for studying degradation of glasses were weight loss measurements and solution analytical techniques. Neither of these provide information on surface alterations resulting from corrosion. Consequently, very little was known about the variety of mechanisms by which glass corrosion occurs. Currently, a multi-technique approach is being used in many laboratories around the world in order to achieve a better understanding of corrosion on glasses designed for immobilizing nuclear wastes. Similar approaches are being taken to solve problems related to conventional glass fabrication, glass preservation, and to new glass manufacturing processes based on sol-gel technology. In the present paper several techniques which are being routinely used to characterize glass surfaces are discussed. These include Fourier transform infrared reflection spectroscopy (FT-IRRS), secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy coupled with ion milling (AES-IM) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Each of these techniques provide unique information about glass surfaces, and when used in combination can yield solutions to complex industrial and scientific problems.

Lee, C. T.; Clark, D. E.

1985-02-01

275

Study of Ion-Polymer Interactions in Cationic and Anionic Ionomers from the Dependence of Conductivity on Temperature and Pressure  

NASA Astrophysics Data System (ADS)

Ionic transport in usual polymer electrolytes involves both cations and anions. In order to separate their respective contributions, cationic (Li+, Na+, K+), or anionic (Cl-, Br-, I-, BF4-, (CF3SO2)2N-) single-ion conducting ionomers (t+ or t- = 1) were synthesized. In both cases, the counter ion is grafted to the macromolecular skeleton in the same synthesis step of cross-linking of the polymer. Experimental results for conductivity variations as a function of pressure (1 - 5000 bar) and temperature (20 - 140° C) show a great similarity for cationic and anionic ionomers. To interpret qualitatively the experimental results, a microscopic model is proposed. Charge carriers formation would result from the dissociation of the grafted salts. Their mobility would proceed by a "free volume" mechanism. This model introduces two local variations in volume, namely the local variation of volume associated with the dissociation process and the critical free volume necessary for the ionic migration. The interpretation of our results according to this model shows that the volume associated to the dissociation process is negative and can be attributed to a local reorganisation of the macromolecular chains around the dissociated charged species. The critical tree volume for ionic migration is positive and larger than the "dry" ionic volume, confirming the participation of the polymer chain segments in the ionic transport.

Duclot, M.; Alloin, F.; Brylev, O.; Sanchez, J.-Y.; Souquet, J.-L.

2006-06-01

276

Thermodynamics of Glass Melting  

NASA Astrophysics Data System (ADS)

First, a model based on linear algebra is described by which the thermodynamic properties of industrial multi-component glasses and glass melts can be accurately predicted from their chemical composition. The model is applied to calculate the heat content of glass melts at high temperatures, the standard heat of formation of glasses from the elements, and the vapor pressures of individual oxides above the melt. An E-fiber glass composition is depicted as an example. Second, the role of individual raw materials in the melting process of E-glass is addressed, with a special focus on the decomposition kinetics and energetic situation of alkaline earth carriers. Finally, the heat of the batch-to-melt conversion is calculated. A simplified reaction path model comprising heat turnover, content of residual solid matter, and an approach to batch viscosity is outlined.

Conradt, Reinhard

277

Method for making glass  

DOEpatents

A method is discussed for making better quality molten borosilicate glass in a glass melter, the glass having the desired viscosity and, preferably, also the desired resistivity so that the glass melt can be established effectively and the product of the glass melter will have the desired level of quality. The method includes the adjustment of the composition of the glass constituents that are fed into the melter in accordance with certain correlations that reliably predict the viscosity and resistivity from the melter temperature and the melt composition, then heating the ingredients to the melter`s operating temperature until they melt and homogenize. The equations include the calculation of a ``non-bridging oxygen`` term from the numbers of moles of the various ingredients, and then the determination of the viscosity and resistivity from the operating temperature of the melter and the non-bridging oxygen term.

Jantzen, C.M.

1991-12-31

278

Method for making glass  

DOEpatents

A method is discussed for making better quality molten borosilicate glass in a glass melter, the glass having the desired viscosity and, preferably, also the desired resistivity so that the glass melt can be established effectively and the product of the glass melter will have the desired level of quality. The method includes the adjustment of the composition of the glass constituents that are fed into the melter in accordance with certain correlations that reliably predict the viscosity and resistivity from the melter temperature and the melt composition, then heating the ingredients to the melter's operating temperature until they melt and homogenize. The equations include the calculation of a non-bridging oxygen'' term from the numbers of moles of the various ingredients, and then the determination of the viscosity and resistivity from the operating temperature of the melter and the non-bridging oxygen term.

Jantzen, C.M.

1991-01-01

279

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

280

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

281

EXELFS of Metallic Glasses  

Microsoft Academic Search

The feasibility of using extended energy-loss fine structure (EXELFS) obtained from â¼1 nm regions of metallic glasses to study their short-range order has been examined. Ionization edges of the metallic glasses in the electron energy-loss spectrum (EELS) have been obtained from PdNiP bulk metallic glass and NiâP polycrystalline powder in a transmission electron microscope. The complexity of EXELFS analysis of

Y. Ito; F. M. Alamgir; R. B. Schwarz; H. Jain; D. B. Williams

1999-01-01

282

Nonequilibrium viscosity of glass  

NASA Astrophysics Data System (ADS)

Since glass is a nonequilibrium material, its properties depend on both composition and thermal history. While most prior studies have focused on equilibrium liquid viscosity, an accurate description of nonequilibrium viscosity is essential for understanding the low temperature dynamics of glass. Departure from equilibrium occurs as a glass-forming system is cooled through the glass transition range. The glass transition involves a continuous breakdown of ergodicity as the system gradually becomes trapped in a subset of the available configurational phase space. At very low temperatures a glass is perfectly nonergodic (or “isostructural”), and the viscosity is described well by an Arrhenius form. However, the behavior of viscosity during the glass transition range itself is not yet understood. In this paper, we address the problem of glass viscosity using the enthalpy landscape model of Mauro and Loucks [Phys. Rev. B 76, 174202 (2007)] for selenium, an elemental glass former. To study a wide range of thermal histories, we compute nonequilibrium viscosity with cooling rates from 10-12 to 1012K/s . Based on these detailed landscape calculations, we propose a simplified phenomenological model capturing the essential physics of glass viscosity. The phenomenological model incorporates an ergodicity parameter that accounts for the continuous breakdown of ergodicity at the glass transition. We show a direct relationship between the nonequilibrium viscosity parameters and the fragility of the supercooled liquid. The nonequilibrium viscosity model is validated against experimental measurements of Corning EAGLE XG™ glass. The measurements are performed using a specially designed beam-bending apparatus capable of accurate nonequilibrium viscosity measurements up to 1016Pas . Using a common set of parameters, the phenomenological model provides an accurate description of EAGLE XG™ viscosity over the full range of measured temperatures and fictive temperatures.

Mauro, John C.; Allan, Douglas C.; Potuzak, Marcel

2009-09-01

283

Scintillating Fluorohafnate Glasses  

Microsoft Academic Search

Data are presented on the roentgenoluminescence and gamma-radiation resistance of Ce3+-doped fluorohafnate glasses prepared under different redox conditions and containing different additions. The glasses are shown to contain several types of luminescence centers and radiation-induced color centers, whose concentrations are governed by the preparation conditions and the nature of the dopants. The radiation resistance and light output of the glasses

S. Kh. Batygov; M. N. Brekhovskikh; N. N. Vinogradova; L. N. Dmitruk; L. V. Moiseeva; V. A. Fedorov

2002-01-01

284

Containerless processing of glass  

Microsoft Academic Search

Ground-based research on the containerless melting of glass and experiments performed during a flight on the SPAR 6 are described. Experiments leading to selection of the flight sample composition, a silica-modified gallia\\/calcia glass, and the preparation of a one quarter inch diameter flight sample are described. During the flight experiment, a sample of the glass was containerless melted and cooled

R. A. Happe

1981-01-01

285

Containerless processing of glass  

NASA Astrophysics Data System (ADS)

Ground-based research on the containerless melting of glass and experiments performed during a flight on the SPAR 6 are described. Experiments leading to selection of the flight sample composition, a silica-modified gallia/calcia glass, and the preparation of a one quarter inch diameter flight sample are described. During the flight experiment, a sample of the glass was containerless melted and cooled to a clear glass in a single axis acoustic positioning apparatus. The functioning of the flight experimental hardware was evaluated. The evaluation of the sample is presented.

Happe, R. A.

1981-10-01

286

A study of cements formed by aqueous lactic acid and aluminosilicate glass.  

PubMed

A study is reported of the formation of cements from aqueous lactic acid and aluminosilicate glass of the type used in dental glass-ionomer cements. These cements were found to set quickly, and were shown by infrared spectroscopy to have undergone a neutralization reaction to yield mainly calcium lactate. They were very soluble in water at 1 h, but became progressively less so over time; when matured for 6 h before being placed in water, they had become almost insoluble. No spectroscopic differences could be detected between the cements at 1 h or 6 h, indicating that insolubilization arises from a reaction that does not alter the part of the infrared spectrum examined. This suggested that a wholly inorganic reaction between the ion-depleted glass fragments is responsible for the formation of the insoluble structure. After 24 h, the cements were found to have compressive strengths in the range 9-35 MPa, the actual value varying with concentration of lactic acid used to form the cement, and there was no statistically significant increase in strength for the strongest of these after one month. PMID:15348618

Nicholson, John W; Tawfik, Hamsa; Czarnecka, Beata

2002-04-01

287

Side Chain Flexibility in Perfluorosulfonic Acid Ionomers: An ab Initio Study.  

PubMed

Side chain flexibility in perfluorosulfonic acid (PFSA) ionomers has been explored through ab initio electronic structure calculations. Three different PFSA side chain fragments were considered with a CF3CFCF3 backbone representation: Nafion (-OCF2CF(CF3)O(CF2)2SO3H), Aquivion or the short side chain (SSC) (-O(CF2)2SO3H), and the 3M PFSA (-O(CF2)4SO3H). Rotational potential energy surfaces for each bond along the length of the side chains were obtained using density functional theory with the B3LYP and the dispersion-corrected B97D functionals with and without the inclusion of a solvation model. Solvent effects were found to have minimal effect on bond rotations close to the tetrafluoroethylene backbone but had greater impact near the terminal sulfonic acid group. The carbon-sulfur bond was found to be the most flexible portion of the side chain in each of the fragments which was further enhanced with the inclusion of the solvent. Complete rotation about either the O-CF2 or CF-O bond in the Nafion side chain resulted in fairly high energetic barriers, but significant portions of these rotational surfaces had energetic penalties less than 1.5 kcal/mol indicating substantial conformational freedom. Fully extended and folded conformations of the Nafion side chain exhibit considerable contraction in side chain end-to-end distance and were observed to be nearly isoenergetic using B3LYP, but the folded structures with the ether oxygen atoms in gauche conformations were ?1.5 kcal/mol lower in energy using B97D. Below the second ether linkage of the Nafion side chain, the rotational potential energy profiles were identical to that determined for the SSC side chain. The 3M side chain was generally found to be the most rigid with barriers for complete rotation about the central carbon-carbon bonds of approximately 7 kcal/mol. These results indicate that minor differences in side chain length and chemistry may have a pronounced effect on the rotational potential energy surfaces, particularly those involving rotation about different carbon-carbon bonds with distinctly different character. PMID:24041417

Clark, Jeffrey K; Paddison, Stephen J

2013-09-27

288

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

289

Phosphorus oxynitride glasses  

Microsoft Academic Search

The properties and structural role of nitrogen in phosphorus oxynitride glasses are reported. Properties summarized for several compositions include the dissolution rate in water, thermal expansion coefficient, viscosity and refractive index. The bonding and coordination number of nitrogen in the glass network has been deduced from nuclear magnetic resonance, X-ray photoelectron spectroscopy and Raman spectroscopy. The existing evidence shows that

Mary R. Reidmeyer; Delbert E. Day

1995-01-01

290

Glass Transitions in Polylactides  

Microsoft Academic Search

The review focuses on the relationship between the structure and the glass transition temperature in polylactide and its derivatives. Simple design rules for controlling the glass transition temperature are developed and illustrated using examples from homopolymers, copolymers, and polymers derived from AB glycolide monomers. These materials have important applications as structural materials and in biomedical applications for drug delivery, surgical

Gregory L. Baker; Erin B. Vogel; Milton R. Smith III

2008-01-01

291

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

292

Supercooled Liquids and Glasses  

Microsoft Academic Search

Selected aspects of recent progress in the study of supercooled liquids and glasses are presented in this review. As an introduction for nonspecialists, several basic features of the dynamics and thermodynamics of supercooled liquids and glasses are described. Among these are nonexponential relaxation functions, non-Arrhenius temperature dependences, and the Kauzmann temperature. Various theoretical models which attempt to explain these basic

M. D. Ediger; C. A. Angell; Sidney R. Nagel

1996-01-01

293

Photoprotection by window glass, automobile glass, and sunglasses.  

PubMed

In daily activity, much time is spent indoors and in vehicles. Although the adverse effect of ultraviolet (UV) radiation is now well recognized and active public education programs on photoprotection have been undertaken, the role of window glass in photoprotection has been rarely addressed. It has been known for some time that window glass filters out UVB and transmits UVA and visible light. Recent developments in the glass industry have resulted in glass that provides broad UV protection without the historically associated loss of visible light transmission. Factors affecting UV-protective properties of glass are glass type, glass color, interleave between glass, and glass coating. In this article, photoprotection by window glass, automobile glass, and sunglasses is reviewed. PMID:16635665

Tuchinda, Chanisada; Srivannaboon, Sabong; Lim, Henry W

2006-05-01

294

Defense HLW Glass Degradation Model  

SciTech Connect

The purpose of this report is to document the development of a model for calculating the release rate for radionuclides and other key elements from high-level radioactive waste (HLW) glasses under exposure conditions relevant to the performance of the repository. Several glass compositions are planned for the repository, some of which have yet to be identified (i.e., glasses from Hanford and Idaho National Engineering and Environmental Laboratory). The mechanism for glass dissolution is the same for these glasses and the glasses yet to be developed for the disposal of DOE wastes. All of these glasses will be of a quality consistent with the glasses used to develop this report.

D. Strachan

2004-10-20

295

Glass leaching performance  

SciTech Connect

Current understanding of the leaching performance of high-level nuclear waste (HLW) glass is summarized. The empirical model of waste glass leaching behavior developed shows that at high water flow rates the glass leach rate is kinetically limited to a maximum value. At intermediate water flow rates, leaching is limited by the solution concentration of silica and decreases with decreasing water flow rates. Release of soluble elements is controlled by silica dissolution because silica forms the binding network of the glass. At low water flow rates, mass loss rates reach values controlled by formation rates of alteration minerals, or by diffusion of dissolution products through essentially stagnant water. The parameters reviewed with respect to their quantifiable influence on leaching behavior include temperature, pH, leachant composition, glass composition, thermal history, and radiation. Of these, temperature is most important since the rate of mass loss approximately doubles with each 10/sup 0/C increase in dilute solutions. The pH has small effects within the 4 to 10 range. The chemical composition of the leachant is most important with regard to its influence on alteration product formation. Glass composition exhibits the largest effects at high flow rates where improved glasses leach from ten to thirty times slower than glass 76 to 68. The effects of the thermal history (devitrification) of the glass are not likely to be significant. Radiation effects are important primarily in that radiolysis can potentially drive pH values to less than 4. Radiation damage to the glass causes insignificant changes in leaching performance.

Chick, L.A.; Turcotte, R.P.

1983-05-01

296

Selective formation of hydrogen and hydroxyl radicals by electron beam irradiation and their reactivity with perfluorosulfonated Acid ionomer.  

PubMed

Selective formation and reactivity of hydrogen (H(•)) and hydroxyl (HO(•)) radicals with perfluorinated sulfonated ionomer membrane, Nafion 211, is described. Selective formation of radicals was achieved by electron beam irradiation of aqueous solutions of H2O2 or H2SO4 to form HO(•) and H(•), respectively, and confirmed by ESR spectroscopy using a spin trap. The structure of Nafion 211 after reaction with H(•) or HO(•) was determined using calibrated (19)F magic angle spinning NMR spectroscopy. Soluble residues of degradation were analyzed by liquid and solid-state NMR. NMR and ATR-FTIR spectroscopy, together with determination of ion exchange capacity, water uptake, proton conductivity, and fluoride ion release, strongly indicate that attack by H(•) occurs at the tertiary carbon C-F bond on both the main and side chain; whereas attack by HO(•) occurs solely on the side chain, specifically, the ?-O-C bond. PMID:24074044

Ghassemzadeh, Lida; Peckham, Timothy J; Weissbach, Thomas; Luo, Xiaoyan; Holdcroft, Steven

2013-10-15

297

Carbonatitic glasses and melts  

NASA Astrophysics Data System (ADS)

We perform first-principles molecular dynamics (MD) calculations to study C-bearing melts along the T=3000K isotherm up to high pressure. Then we use the melts to study the quenched glasses. We consider pure forsteritic compositions, atomic C-, CO2- and MgCO3- bearing compositions. We discuss in detail the behavior of the glass structure under compression and the changes in coordination polyhedra, and we compare the glasses to the equivalent high-temperature melts. We use several thermodynamic paths to obtain the glasses: (i) instantaneous quench at P=0GPa, then coldly compress, (ii) instantaneous quench at various high pressures and (iii) quench in 1K/MD step at various high pressures. Differences in glass structure and in equations of state develop between the different paths. They become larger at high pressure and are smoothed out by annealing. All glasses exhibit increase in Si-O and C-O coordination numbers, but at a smaller rate than the melts. Important structural rearrangements develop in all glasses around V/V0 compression of about 0.7.

Cohen, Ronald E.; Caracas, Razvan

2013-04-01

298

EB reinforced glass  

NASA Astrophysics Data System (ADS)

Effects of EB irradiation on fracture toughness were studied for soda lime glass and glass fiber. The EB irradiation improved the hardness, ductility, fracture stress and fracture toughness. The fracture stress was 1.43 GPa for the glass fiber before EB treatment. The irradiation enhanced the fracture stress. The fracture stress at Pf=0.5 was 1.89 GPa for glass fiber samples treated by 65 Mrad-irradiation. It was approximately 0.46 GPa larger than that before EB treatment. Based on ESR results, the reinforcement can be explained. The changes in fracture stress were in good agreement with the density change in dangling bonds, because a high tensile glass fiber was obtained at 65 Mrad-irradiation. Thus, we confirmed that the glassy cluster structure with high dangling bond density was obtained in high tensile glass fibers prepared by 65 Mrad-irradiation. The EB irradiation controlled the fracture toughness of glasses. To confirm the mechanism, an alpha-aluminum oxide crystal sheet was also studied.

Nishi, Yoshitake; Irisawa, Hayato; Yamaguchi, Naoki; Takahashi, Kousuke; Yamada, Kunio; Oguri, Kazuya; Tonegawa, Akira

2002-12-01

299

Ages of Darwin Glass, Macedon Glass, and Far Eastern tektites  

Microsoft Academic Search

A group of possibly related glasses from the Far East, including seven samples of Darwin Glass and the two known samples of Macedon Glass, have been dated by the fission track technique. With the exception of a lower age for one Darwin Glass sample and one Muong Nong tektite all ages are indistinguishable, suggesting that the Darwin and Macedon impact

R. L. Fleischer; P. B. Price; J. R. M. Viertl; R. T. Woods

1969-01-01

300

Residual stresses in glasses.  

PubMed

The history dependence of glasses formed from flow-melted steady states by a sudden cessation of the shear rate ?[over ?] is studied in colloidal suspensions, by molecular dynamics simulations and by mode-coupling theory. In an ideal glass, stresses relax only partially, leaving behind a finite persistent residual stress. For intermediate times, relaxation curves scale as a function of ?[over ?]t, even though no flow is present. The macroscopic stress evolution is connected to a length scale of residual liquefaction displayed by microscopic mean-squared displacements. The theory describes this history dependence of glasses sharing the same thermodynamic state variables but differing static properties. PMID:23745896

Ballauff, M; Brader, J M; Egelhaaf, S U; Fuchs, M; Horbach, J; Koumakis, N; Krüger, M; Laurati, M; Mutch, K J; Petekidis, G; Siebenbürger, M; Voigtmann, Th; Zausch, J

2013-05-24

301

Polar glass ceramics  

Microsoft Academic Search

Pyroelectric-piezoelecric glass ceramics of polar materials like Li2Si2O5, Ba2TiGe2O8, Ba2TiSi2O8, and Various compositions in the systems Li2O-B2O3, Li2O-SiO2-ZnO, Li2O-SiO2-B2O3 have been prepared by oriented recrystallization of the glasses under a strong temperature gradient, providing a simple inexpensive process for preparing piezoelectric and pyroelectric materials. High pyroelectric responses were observed in these glass-ceramics. Values of piezoelectric d33 coefficients, frequency constants, electromechanical

A. Halliyal; A. S. Bhalla; R. E. Newnham; L. E. Cross

1981-01-01

302

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

303

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

304

EXELFS of Metallic Glasses  

SciTech Connect

The feasibility of using extended energy-loss fine structure (EXELFS) obtained from {approximately}1 nm regions of metallic glasses to study their short-range order has been examined. Ionization edges of the metallic glasses in the electron energy-loss spectrum (EELS) have been obtained from PdNiP bulk metallic glass and Ni{sub 2}P polycrystalline powder in a transmission electron microscope. The complexity of EXELFS analysis of L- and M-ionization edges of heavy elements (Z>22, i.e. Ni and Pd) is addressed by theoretical calculations using an ab initio computer code, and its results are compared with the experimental data.

Ito, Y.; Alamgir, F.M.; Schwarz, R.B.; Jain, H.; Williams, D.B.

1999-11-30

305

Lacerations from glass in childhood  

Microsoft Academic Search

A study of 62 glass injuries to children serious enough to warrant admission to hospital showed that 30 were due to architectural glass in doors or windows and 26 of these occurred in houses. Glass bottles caused 12 injuries. Architectural glass produced more serious injuries affecting major arteries, nerves and tendons, and internal viscera. In view of the frequency and

R H Jackson

1981-01-01

306

Structural design of sealing glasses  

Microsoft Academic Search

Requirements for enhanced component performance and reliability have led to the development of novel glass compositions for a variety of hermetic sealing applications. The development of technologically useful glass compositions was based on an understanding of the relationships between the molecular-level glass structure and important physical properties. The properties of the alkaline earth aluminoborate glasses for lithium batteries are sensitive

Richard K. Brow; David R. Tallant

1997-01-01

307

Seeing Glass Contractors Clearly.  

ERIC Educational Resources Information Center

|Offers seven tips for finding and working with an effective glass contractor. For example, schools should consider the company's reputation and longevity of service, and whether it has in-house engineering capabilities. (EV)|

Deliberato, Jerry

2003-01-01

308

Ultrastable nanostructured polymer glasses  

NASA Astrophysics Data System (ADS)

Owing to the kinetic nature of the glass transition, the ability to significantly alter the properties of amorphous solids by the typical routes to the vitreous state is restricted. For instance, an order of magnitude change in the cooling rate merely modifies the value of the glass transition temperature (Tg) by a few degrees. Here we show that matrix-assisted pulsed laser evaporation (MAPLE) can be used to form ultrastable and nanostructured glassy polymer films which, relative to the standard poly(methyl methacrylate) glass formed on cooling at standard rates, are 40% less dense, have a 40?K higher Tg, and exhibit a two orders of magnitude enhancement in kinetic stability at high temperatures. The unique set of properties of MAPLE-deposited glasses may make them attractive in technologies where weight and stability are central design issues.

Guo, Yunlong; Morozov, Anatoli; Schneider, Dirk; Chung, Jae Woo; Zhang, Chuan; Waldmann, Maike; Yao, Nan; Fytas, George; Arnold, Craig B.; Priestley, Rodney D.

2012-04-01

309

Metallic Spin Glasses  

NASA Astrophysics Data System (ADS)

Metallic Spin-glasses have drawn much experimental and theoretical attention in recent years(A. M. Sengupta and A. Georges, Phys. Rev. B52, 10295 (1995); S. Sachdev, N. Read and R. Opperman, Phys. Rev. B52, 10286 (1995); F. Steglich, et al., J. Phys. Condens. Matter 8, 99099 (1996).). One particularly interesting aspect of this system is the non-fermi-liquid behavior near the zero temperature transition between paramagnetic phase and spin-glass phase. In this talk we discuss a local mean-field theory which addresses some of the main issues. We also point out some major differences between Ising Spin-glass and Heisenberg spin-glass near the transition, within this mean field theory.(A. M. Sengupta, preprint, Cond-Mat. 9707316.)

Sengupta, Anirvan

1998-03-01

310

Whisker reinforced glass ceramic  

SciTech Connect

The process for making an in-situ whisker reinforced glass-ceramic that is up to 1.5 times as strong as conventional glass-ceramics was developed at Virginia Tech and patented in 1993. This technology has been identified as having commercial potential for use in high temperature heat exchanger applications for the electric power generation field by the National Center for Appropriate Technology (NCAT). This technology was licensed by MATVA, Inc., a small Virginia business, for further development. In particular, the goal of this project was to develop a property database and conduct initial testing of heat exchanger prototypes to demonstrate its potential application. This final report describes how the glass precursor was formed, physical properties of the glass-ceramic, techniques for making heat exchanger prototypes.

Hirschfeld, D.A.; Brown, J.J. Jr.

1996-06-03

311

Chemical Processing of Glasses.  

National Technical Information Service (NTIS)

The development of chemical processing methods for the fabrication of glass and ceramic shapes for photonic applications is frequently Edisonian in nature. In Part, this is because the numerous variables that must be optimized to obtain a given material w...

R. M. Laine

1992-01-01

312

Method for making glass nonfogging  

DOEpatents

A method for rendering glass nonfogging (to condensation fog) by sandwiching the glass between two electrodes such that the glass functions as the dielectric of a capacitor, a large alternating current (AC) voltage is applied across the electrodes for a selected time period causing the glass to absorb a charge, and the electrodes are removed. The glass absorbs a charge from the electrodes rendering it nonfogging. The glass surface is undamaged by application of the AC voltage, and normal optical properties are unaffected. This method can be applied to optical surfaces such as lenses, auto windshields, mirrors, etc., wherever condensation fog on glass is a problem.

Lord, David E. (Livermore, CA); Carter, Gary W. (Livermore, CA); Petrini, Richard R. (Livermore, CA)

1979-01-01

313

Nucleation in ZBLAN glasses  

Microsoft Academic Search

Nucleation rates were measured in a ZrFâ-BaFâ-NaF-LaFâ-AlFâ glass (ZBLAN) using an optical technique. The results were compared with a similar glass having a slightly different composition. The difference in the nucleation rate is explained by classical nucleation theory using calculated free-energy differences between the ZBLAN liquid and the BaZrFâ crystal, which is found as the precipitating phase.

Gerard de Leede; H. deWaal; Frank Hakkens

1989-01-01

314

Glass fiber insulation  

SciTech Connect

A composition for a glass fiber insulation is described comprising a loose mat of glass fibers having at least a portion of the surface coated with a water insoluble, non-hygroscopic, amorphous aluminum phosphate polymer having a molar ratio of Al[sub 2]O[sub 3] to P[sub 2]O[sub 5] of less than 1 and providing a substantial thermal resistance.

Griffith, E.J.; Ngo, T.M.

1993-06-29

315

Fluoride glass compositions  

SciTech Connect

This invention relates to Fluoride-based glasses that exhibit a high degree of transparency throughout the near ultraviolet visible and mid infrared portions of the spectrum. The glasses are composed of MgF2 and ZnF2 as essential compositional ingredients together with at least two other metallic fluorides from the group of YbF3, ThF4, PbF2, A1F3 and MnF2.

El-Bayoumi, O.

1983-08-09

316

Microstructuring of Photosensitive Glass  

NASA Astrophysics Data System (ADS)

Femtosecond laser direct writing followed by thermal treatment and successive wet etching can form three-dimensional (3D) hollow microstructures inside photosensitive glass. The principles and procedures of this process are explained. Next, the fabrication of 3D microfluidic structures and optical microcomponents is reviewed. Finally, the manufacture of functional microchip devices such as a microfluidic dye laser, optofluidics, and a nano-aquarium by integrating the microcomponents in a single glass chip is demonstrated.

Sugioka, Koji

317

Perspective: The glass transition.  

PubMed

We provide here a brief perspective on the glass transition field. It is an assessment, written from the point of view of theory, of where the field is and where it seems to be heading. We first give an overview of the main phenomenological characteristics, or "stylised facts," of the glass transition problem, i.e., the central observations that a theory of the physics of glass formation should aim to explain in a unified manner. We describe recent developments, with a particular focus on real space properties, including dynamical heterogeneity and facilitation, the search for underlying spatial or structural correlations, and the relation between the thermal glass transition and athermal jamming. We then discuss briefly how competing theories of the glass transition have adapted and evolved to account for such real space issues. We consider in detail two conceptual and methodological approaches put forward recently, that aim to access the fundamental critical phenomenon underlying the glass transition, be it thermodynamic or dynamic in origin, by means of biasing of ensembles, of configurations in the thermodynamic case, or of trajectories in the dynamic case. We end with a short outlook. PMID:23556751

Biroli, Giulio; Garrahan, Juan P

2013-03-28

318

Porous silicon oxycarbide glasses  

SciTech Connect

High-surface-area silicon oxycarbide gels and glasses were synthesized from mixtures of methyldimethoxysilane (MDMS) and tetraethoxysilane (TEOS) through acidic hydrolysis and condensation. A surface area of {approximately}275 m{sup 2}/g and an average pore size of {approximately}0 {angstrom} was obtained for a 50% MDMS-50% TEOS glass at 800 C under a flowing argon atmosphere. The average pore size was increased by aging the precursor gels in ammonium hydroxide. The increased average pore size and the higher strength of the mesoporous gel network enhanced the surface-area stability of the glasses: in this case, surface areas >200 m{sup 2}/g were retained at 1,200 C under an argon atmosphere. {sup 29}Si MAS NMR spectra revealed that an oxycarbide structure was established in the mesoporous glasses obtained after pyrolysis of the aged gels. The role of carbon was demonstrated by comparing the surface-area stability of the oxycarbide glasses with that of pure silica and that of oxycarbide glasses where all the carbon groups were removed through low-temperature plasma-oxidation treatments. In the absence of carbon, the thermal stability of the surface area decreased dramatically.

Singh, A.K.; Pantano, C.G. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1996-10-01

319

Influence of different conditioning methods on the shear bond strength of novel light-curing nano-ionomer restorative to enamel and dentin  

Microsoft Academic Search

The purpose of this study was to investigate shear bond strength (SBS) between a light-curing nano-ionomer restorative and\\u000a enamel or dentin after acid etching, after erbium:yttrium–aluminum–garnet (Er:YAG) laser etching, or after combined treatment.\\u000a Forty third molars were selected, the crowns were sectioned, and 80 tooth slabs were obtained. The specimens were assigned\\u000a to two groups, which were divided into four

Yonca Korkmaz; Emre Ozel; Nuray Attar; Ceren Ozge Bicer

2010-01-01

320

Competitive formation of glasses and glass-matrix composites  

SciTech Connect

By systematically investigating the effect of chemical composition on the competitive formation of glasses in various systems, we attempt to address two long-standing scientific puzzles upon metallic glasses, i.e., (i) which composition is the best for forming glasses and glass-matrix composites and (ii) what determines the easy glass-forming composition range in a given alloy system. Our findings have led to the construction of a qualitative microstructure selection map, which is useful for guiding the design of bulkier metallic glasses and glass-matrix composites. In addition, our analysis demonstrates that the classical kinetic treatment of glass formation is insufficient; to analyze glass formation properly, it is necessary to go beyond simple assumptions of single polymorphic solidification during crystallization.

Lu, Zhao Ping [ORNL; Ma, D. [University of Wisconsin, Madison; Liu, Chain T [ORNL; Chang, Y. Austin [University of Wisconsin, Madison

2007-01-01

321

DWPF GLASS BEADS AND GLASS FRIT TRANSPORT DEMONSTRATION  

SciTech Connect

DWPF is considering replacing irregularly shaped glass frit with spherical glass beads in the Slurry Mix Evaporator (SME) process to decrease the yield stress of the melter feed (a non-Newtonian Bingham Plastic). Pilot-scale testing was conducted on spherical glass beads and glass frit to determine how well the glass beads would transfer when compared to the glass frit. Process Engineering Development designed and constructed the test apparatus to aid in the understanding and impacts that spherical glass beads may have on the existing DWPF Frit Transfer System. Testing was conducted to determine if the lines would plug with the glass beads and the glass frit slurry and what is required to unplug the lines. The flow loop consisted of vertical and horizontal runs of clear PVC piping, similar in geometry to the existing system. Two different batches of glass slurry were tested: a batch of 50 wt% spherical glass beads and a batch of 50 wt% glass frit in process water. No chemicals such as formic acid was used in slurry, only water and glass formers. The glass beads used for this testing were commercially available borosilicate glass of mesh size -100+200. The glass frit was Frit 418 obtained from DWPF and is nominally -45+200 mesh. The spherical glass beads did not have a negative impact on the frit transfer system. The transferring of the spherical glass beads was much easier than the glass frit. It was difficult to create a plug with glass bead slurry in the pilot transfer system. When a small plug occurred from setting overnight with the spherical glass beads, the plug was easy to displace using only the pump. In the case of creating a man made plug in a vertical line, by filling the line with spherical glass beads and allowing the slurry to settle for days, the plug was easy to remove by using flush water. The glass frit proved to be much more difficult to transfer when compared to the spherical glass beads. The glass frit impacted the transfer system to the point that the test apparatus had to be disassembled to dislodge the plugs created in the system.

Adamson, D; Bradley Pickenheim, B

2008-11-24

322

Electrical properties of phosphate glasses  

NASA Astrophysics Data System (ADS)

Investigation of the electrical properties of phosphate glasses where transition metal oxide such as iron oxide is the network former and network modifier is presented. Phosphate glasses containing iron are electronically conducting glasses where the polaronic conduction is due to the electron hopping from low to high iron valence state. The identification of structural defects caused by ion/polaron migration, the analysis of dipolar states and electrical conductivity in iron phosphate glasses containing various alkali and mixed alkali ions was performed on the basis of the impedance spectroscopy (IS). The changes in electrical conductivity from as-quenched phosphate glass to fully crystallized glass (glass-ceramics) by IS are analyzed. A change in the characteristic features of IS follows the changes in glass and crystallized glass network. Using IS, the contribution of glass matrix, crystallized grains and grain boundary to the total electrical conductivity for iron phosphate glasses was analyzed. It was shown that decrease in conductivity is caused by discontinuities in the conduction pathways as a result of the disruption of crystalline network where two or more crystalline phases are formed. Also, phosphate-based glasses offer a unique range of biomaterials, as they form direct chemical bonding with hard/soft tissue. The surface charges of bioactive glasses are recognized to be the most important factors in determining biological responses. The improved bioactivity of the bioactive glasses as a result of the effects of the surface charges generated by electrical polarization is discussed.

Mogus-Milankovic, A.; Santic, A.; Reis, S. T.; Day, D. E.

2009-07-01

323

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

324

Jet penetration in glass  

SciTech Connect

We describe a phenomenological model which accounts for the mechanical response of glass to intense impulsive loading. An important aspect of this response is the dilatancy accompanying fracture. We have also conducted a number of experiments with 38.1-mm diameter precision shaped charges to establish the performance against various targets and to allow evaluation of our model. At 3 charge diameters standoff, the data indicate that both virgin and damaged glass offer better (Bernoulli-scaled) resistance to penetration than either of 4340 steel, or 6061-T6 aluminum alloy. Time-resolved measurements indicate two distinct phases of jet penetration in glass: An initial hydrodynamic phase, and a second phase characterized by a slower penetration velocity. Our calculations show that at early time, a crater is formed around the jet and only the tip of the undisturbed jet interacts with the glass. At late time the glass has collapsed on the jet and degraded penetration continues via a disturbed and fragmented jet.

Moran, B.; Glenn, L.A.; Kusubov, A.

1991-05-01

325

Museum of Glass  

NSDL National Science Digital Library

The Museum of Glass in Tacoma, Washington maintains a well crafted website for their spectacular museum. Founded in part by the famous glass artist Dale Chihuly, a Tacoma native, this museum highlights glass artists from the Pacific Northwest. Visitors won't want to miss any of the breathtaking online exhibits on this website, but one of the most spectacular is the "Chihuly Bridge of Glass" under the "Exhibitions & Collections" tab, in the "Outdoor Art" link. The slideshow of five photos shows a 500-foot pedestrian bridge that connects the Museum to downtown Tacoma. The bridge is composed of three distinct sections, one of which allows visitors to "experience a seemingly underwater world of glass shapes and forms a few feet above their heads." Also found under the "Exhibitions & Collections" tab, in the "Current Exhibitions" link, visitors will enjoy a multimedia treatment of the work "Glimmering Gone". Visitors can listen to poems by university students inspired by the exhibit, watch a "Residency" video of the artist who created the work, and view a video tour of the catalog for the exhibit.

326

Nonequilibrium thermodynamics of glasses  

NASA Astrophysics Data System (ADS)

We consider the nonequilibrium thermodynamics of glasses from various perspectives. For the commonly used equilibriumlike approach based on Gibbs’ fundamental form with an additional pair of conjugate variables, we discuss possible choices of the independent out-of-equilibrium variable and we illustrate some implications by concrete results for a well-known exactly solvable lattice model. The choice of variables is further illuminated from the complementary atomistic perspective offered by the inherent-structure formalism. A general formalism of nonequilibrium thermodynamics is employed (i) to derive the standard equilibriumlike approach, (ii) to formulate two self-contained levels to describe glassy dynamics and thermodynamics, and (iii) to offer guidance for future simulations of glasses. The thermodynamic approach suggests to introduce four-point correlation functions associated with structural rearrangements after imposed deformations, which might offer a possibility to detect a growing length scale at the glass transition without employing any dynamic information.

Christian Öttinger, Hans

2006-07-01

327

Nonequilibrium thermodynamics of glasses.  

PubMed

We consider the nonequilibrium thermodynamics of glasses from various perspectives. For the commonly used equilibriumlike approach based on Gibbs' fundamental form with an additional pair of conjugate variables, we discuss possible choices of the independent out-of-equilibrium variable and we illustrate some implications by concrete results for a well-known exactly solvable lattice model. The choice of variables is further illuminated from the complementary atomistic perspective offered by the inherent-structure formalism. A general formalism of nonequilibrium thermodynamics is employed (i) to derive the standard equilibriumlike approach, (ii) to formulate two self-contained levels to describe glassy dynamics and thermodynamics, and (iii) to offer guidance for future simulations of glasses. The thermodynamic approach suggests to introduce four-point correlation functions associated with structural rearrangements after imposed deformations, which might offer a possibility to detect a growing length scale at the glass transition without employing any dynamic information. PMID:16907066

Ottinger, Hans Christian

2006-07-21

328

Recycling of waste glasses into partially crystallized glass foams  

Microsoft Academic Search

Waste soda-lime glass, alone or mixed with wastes from the manufacturing of glass fibers, was successfully converted into\\u000a partially crystallized glass foams by a particularly simple and economic processing, consisting of a direct heating of glass\\u000a powders at temperatures from 900 to 1050 °C. The foaming operated by the oxidation of SiC, inserted as powder additive, was\\u000a found to depend on

Enrico Bernardo; Giovanni Scarinci; Paolo Bertuzzi; Piero Ercole; Ludovico Ramon

2010-01-01

329

Influence of ultrasound, with and without water spray cooling, on removal of posts cemented with resin or glass ionomer cements: An in-vitro study  

PubMed Central

Aims/objectives: To evaluate in vitro the ultrasonic vibration efficacy with and without water spray cooling on the reduction of the amount of force necessary to dislodge the cast posts cemented with resin cement and to compare it with those cemented with GIC Type I luting cement. Materials and Methods: Sixty samples were divided into six groups: groups 1, 2, 3, posts cemented with GIC; groups 4, 5, 6, posts cemented with resin; groups 1 and 4 (controls), no ultrasound; groups 2 and 5, ultrasound without water spray; and groups 3 and 6, ultrasound with water spray. Instron testing machine was used to dislodge the posts from the root canals and the data was statistically analyzed. Results: Ultrasound with water spray (group 3) among the GIC groups reduced the traction force necessary to extract posts by 53.33% whereas ultrasound without water spray (group 5) among the resin groups reduced by 59.5% compared to control. Conclusion: Ultrasound with water is more effective in removing posts cemented with GIC because of the ultrasonic energy being transferred to the post. Ultasonics without water is more effective in removing posts fixed with resin cement probably by the indirect action of heat production.

Adarsha, M S; Lata, D A

2010-01-01

330

Clinical evaluation of giomer- and resin-modified glass ionomer cement in class V noncarious cervical lesions: An in vivo study  

PubMed Central

Objectives: To evaluate and compare the clinical performance of Giomer (Beautifil II) and RMGIC (Fuji II LC) in noncarious cervical lesions. Materials and Methods: Thirty-two subjects with one or two pairs of noncarious cervical lesions were included in the study. Each pair of lesion was restored with either giomer or RMGIC assigned randomly. Clinical evaluation of restorations was done using USPHS criteria. Data was formulated in a predesigned format and subjected to statistical analysis using the chi square test. Results: Statistically significant difference was found between RMGIC and Giomer with respect to surface roughness with P value <0.001. Conclusion: Giomer showed superior surface finish compared to RMGIC. Both Giomer and RMGIC showed equal retention ability.

Jyothi, KN; Annapurna, S; Kumar, Anil S; Venugopal, P; Jayashankara, CM

2011-01-01

331

Leakage associated with intermediate restorative material and glass-ionomer cement retrograde fillings: A human and sheep teeth comparison with 2 different aging procedures  

Microsoft Academic Search

Objectives: Leakage around retrograde fillings is an important cause of endodontic surgery. This in vitro study sought to compare the following: (1) methylene blue dye leakage linked to retrofillings in human and sheep teeth with the degree of dye penetration when intermediate restorative materials and Chemfil were used as retrofillings, (2) the apical microleakage in filled with that in unfilled

Dominique Roux; Sophie Doméjean-Orliaguet; Marwan Saade

2002-01-01

332

Nucleation in ZBLAN glasses  

SciTech Connect

Nucleation rates were measured in a ZrF{sub 4}-BaF{sub 2}-NaF-LaF{sub 3}-AlF{sub 3} glass (ZBLAN) using an optical technique. The results were compared with a similar glass having a slightly different composition. The difference in the nucleation rate is explained by classical nucleation theory using calculated free-energy differences between the ZBLAN liquid and the BaZrF{sub 6} crystal, which is found as the precipitating phase.

Leede, G.d.; deWaal, H.; Hakkens, F. (Eindhoven Univ. of Technology, Eindhoven (NL))

1989-10-01

333

Crystalline fragments in glasses  

NASA Astrophysics Data System (ADS)

The nature of tetrahedral molecular fragments is investigated in SiSe2 glasses using the molecular-dynamics method. The glass consists of both edge-sharing (ES) and corner-sharing tetrahedra. The ES tetrahedra are the building blocks of chain-like-molecular fragments. The two-edge-sharing tetrahedra are the nucleus, and corner-sharing configurations provide connecting hinges between fragments. Statistics of rings and fragments reveals that threefold and eightfold rings are most abundant, chainlike fragments that are typically 10-15 Å long occur mostly in eightfold rings, and the longest fragments occur in elevenfold rings.

Antonio, Giomal A.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

1992-04-01

334

On the strength of glass  

NASA Astrophysics Data System (ADS)

Glass has been ignored by most of the structural engineering community because of its brittle nature. Glass is an indispensable material in optical systems and sometimes safety, even human safety, depends upon optical glass elements to behave in a structurally reliable manner. One such occasion is to accommodate survey cameras in transport-class aircraft. Fortunately, glass has reliable structural properties and the methods for structural analysis and testing for glass have been well developed. Unfortunately, the glass suppliers have not chosen to publish the appropriate strength properties for many of their glasses. This paper describes the physics of the strength of glass and the engineering application of that physics to an airborne survey aircraft for the safety of its inhabitants.

Hatheway, Alson E.

2013-09-01

335

Chemical Properties of Metallic Glasses.  

National Technical Information Service (NTIS)

Research into chemical properties of metallic glasses has revealed promising behavior in the areas of corosion resistance and catalysis. Metallic glasses containing a film-forming element exhibit resistance to uniform and localized corrosion that is super...

R. B. Diegle

1983-01-01

336

The Upgrading of Glass Microballoons.  

National Technical Information Service (NTIS)

The processes and mechanisms involved in producing glass microballoons of acceptable quality for laser fusion by gas jet levitation and manipulation were studied. Glass microballoons (GMBs) levitated at temperatures below, as well as above the liquidus, a...

S. Gunter S. A. Dunn

1979-01-01

337

Nuclear Waste Glass Composition Limitations.  

National Technical Information Service (NTIS)

This paper discusses the primary considerations involved in nuclear waste glass composition development, explains why the maximum content of certain elements in those glasses is limited, and suggests some possible improvements in reprocessing and waste ma...

L. A. Chick J. L. Swanson D. S. Goldman

1984-01-01

338

Fabrication of Hard Glass Plates.  

National Technical Information Service (NTIS)

This report describes the fabrication of hard glass for use in ballistic application. The work consisted of establishing optimum composition and process conditions for several different glasses. Properties such as Knoop hardness, density, flexural strengt...

A. Z. Hed M. A. Ali

1974-01-01

339

Topical fluoride application is able to reduce acid susceptibility of restorative materials.  

PubMed

This study aimed to investigate the effect of topical fluoride application on the acid susceptibility of restorative materials. Four restorative materials were investigated in this study: 2 composite resins (Tetric EvoCeram and Filtek Silorane), a polyacid-modified resin composite (Dyract Extra), and a conventional glass-ionomer cement (Ketac Fil Plus). The samples were treated once with 1 of 8 different fluoride solutions (TiF4, NaF, AmF, and SnF2, each at native pH or pH 4) for 3 min or remained untreated (control). The samples were then eroded by citric acid (pH 2.6) for 5 days (6×1 min daily). Erosive substance loss, surface topographic and compositional changes were investigated using surface profilometry, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), respectively, after fluoride pretreatment and after erosion. The results indicate high-concentrated AmF solution at native pH was effective in inhibiting erosion in the conventional glass-ionomer cement and polyacid-modified resin composite. PMID:22673456

Yu, Hao; Buchalla, Wolfgang; Cheng, Hui; Wiegand, Annette; Attin, Thomas

2012-05-14

340

A method for producing controlled fluoride release from an orthodontic bracket.  

PubMed

The aim of this study was to manufacture and test, in vitro, a novel modification to provide fluoride-releasing orthodontic brackets. Thirty-two orthodontic brackets were drilled to produce a recess (approximately 1.3 mm in diameter and 0.7 mm in depth) at the centre of the bracket base. Four materials, with and without the addition of sodium fluoride, a glass ionomer cement (Ketac Cem micro), a resin-modified glass ionomer cement (RMGIC; GC Fuji Ortho LC), a zinc phosphate (Zinc Cement Improved), and a resin (Transbond XT) were used to fill the recess in the bracket base. Fluoride release was measured daily during the first week and then weekly for 10 weeks. An ion chromatograph with suppressed conductivity was used for free fluoride ion determination. Statistical analysis to determine the amount of flouride release was undertaken using analysis of variance and Tukey's test. During the first 2 weeks, the resin group, with the addition of 38 per cent sodium fluoride added, released significantly more free fluoride (P < 0.05), but after 2 weeks the fluoride release markedly decreased. After 5 weeks, the RMGIC group, with 15 per cent added sodium fluoride, had significantly higher (P < 0.05) daily fluoride release than the other groups. The findings demonstrated that an appropriate fluoridated material can be used as a fluoride-releasing reservoir in a modified orthodontic bracket to enable it to release fluoride over the period of fixed appliance treatment. PMID:17804428

Li, Song; Hobson, Ross S; Bai, Yuxing; Yan, Zhuoqun; Carrick, Thomas E; McCabe, John F

2007-09-04

341

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

342

Shimmering Stained Glass.  

ERIC Educational Resources Information Center

|Presents an art lesson for fifth- and sixth-graders where they create a translucent design of colored cellophane on black paper inspired by the stained-glass windows of the Middle Ages and the artwork of Lewis Comfort Tiffany. Enables the students to become crafts people rather than just observers of the past. (CMK)|

Simon, Gail Murray

1998-01-01

343

CADMIUM PHOSPHATE GLASS  

DOEpatents

A method of preparing a cadmium phosphate glass that comprises providing a mixture of solid inorganic compounds of cadmuim and phosphate having vaporizable components and heating the resulting composition to a temperature of at least 850 un. Concent 85% C is presented. (AEC)

Carpenter, H.W.; Johnson, P.D.

1963-04-01

344

“Through-glass” injuries  

Microsoft Academic Search

This prospective trial collected all cases where injuries had resulted from the hand passing through or striking glass and had been referred to a hand injury service during 1 year. Eighty-seven cases were referred and the factors relating to these injuries were examined. A record was made of the structures damaged, the surgery performed and prevailing socioeconomic factors. These injuries

L. R. Irwin; J. C. Daly; J. H. James; C. L. Muwanga; L. Williams

1996-01-01

345

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

346

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

347

Glass microbubble composite foam  

Microsoft Academic Search

Composite foams have been prepared from blends of Kerimid 601 polyimide resin and different types of glass microbubbles. Kerimid 601 is an addition type polyimide that offers many processing advantages over other types of polyimides. In an addition reaction, no volatiles are evolved during cure and weight loss and shrinkage during cure are small. Also, since the resin is a

McIlroy

1978-01-01

348

Metallic Glass Composition.  

National Technical Information Service (NTIS)

This patent pertains to 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 am...

D. M. Kroeger C. C. Koch

1984-01-01

349

"Stained Glass" Landscape Windows  

ERIC Educational Resources Information Center

|Both adults and children alike marvel at the grand vivid stained-glass windows created by American artist Louis Comfort Tiffany. Today he is commonly recognized as one of America's most influential designers and artists throughout the last nineteenth and early twentieth century. In the lesson described in this article, students created their own…

Vannata, Janine

2008-01-01

350

The Glass Cockpit  

Microsoft Academic Search

In modern air craft, the cockpit is often referred to as a glass cockpit because of the replacement of traditional banks of mechanical dials with computer monitors. Behind these modern displays is a variety of interconnected computers, sensors, and actuators that constitute the avionics system. Avionics systems are technological wonders that increase our safety while flying, improve the efficiency of

John Knight

2007-01-01

351

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

352

Post-Tensioned Glass Beams  

Microsoft Academic Search

At Delft University, glass researchers have developed a revolutionary safety concept for glass beams. This safety concept\\u000a shows some analogy with reinforced concrete; glass beams are reinforced and\\/or post-tensioned by adding (stainless) steel\\u000a to the layout of the beam.

C. Louter; J. van Heusden; F. Veer; J. Vambersky; H. Boer; J. Versteegen

353

Nonsilica glasses for holey fibers  

Microsoft Academic Search

The authors of this paper investigated the thermal properties and optical properties of typical nonsilica glasses, including viscosity, surface tension, thermal conductivity, transmission, linear and nonlinear refractive index, and fiber attenuation in order to judge the feasibility of using nonsilica glasses as the background material of holey fibers (HFs). Novel techniques were presented to fabricate the nonsilica glass microstructured fiber

Xian Feng; Arshad K. Mairaj; Daniel W. Hewak; Tanya M. Monro

2005-01-01

354

Nuclear waste glass corrosion mechanisms  

Microsoft Academic Search

Dissolution of nuclear waste glass occurs by corrosion mechanisms similar to those of other solids, e.g., metallurgical and mineralogic systems. Metallurgical phenomena such as active corrosion, passivation and immunity have been observed to be a function of the glass composition and the solution pH. Hydration thermodynamics was used to quantify the role of glass composition and its effect on the

Jantzen

1987-01-01

355

Yesterday's Trash Makes Tomorrow's "Glass"  

ERIC Educational Resources Information Center

In this article, the author describes a glass art project inspired by Dale Chihuly. This project uses two-liter plastic soda bottles which are cut apart and trimmed. Applying heat using a hair dryer, the plastic curls and takes an uneven blown-glass quality. The "glass" is then painted using acrylic paint. (Contains 2 resources and 1 online…

Wayne, Dale

2010-01-01

356

Yesterday's Trash Makes Tomorrow's "Glass"  

ERIC Educational Resources Information Center

|In this article, the author describes a glass art project inspired by Dale Chihuly. This project uses two-liter plastic soda bottles which are cut apart and trimmed. Applying heat using a hair dryer, the plastic curls and takes an uneven blown-glass quality. The "glass" is then painted using acrylic paint. (Contains 2 resources and 1 online…

Wayne, Dale

2010-01-01

357

Heliostat glass survey and evaluation  

Microsoft Academic Search

The glass characterization and specification task included a comprehensive survey of both foreign and domestic sources of low distortion, low iron, .125 nominal flat glass for use in heliostat applications. PNL attempted to determine the availability of production lines, estimate industry interest, lead times, and costs for producing glass for second surface heliostat mirrors for the Barstow pilot plant and

M. A. Lind; J. M. Russin

1978-01-01

358

A macroscopic model of proton transport through the membrane-ionomer interface of a polymer electrolyte membrane fuel cell  

NASA Astrophysics Data System (ADS)

The membrane-ionomer interface is the critical interlink of the electrodes and catalyst to the polymer electrolyte membrane (PEM); together forming the membrane electrode assembly in current state-of-the-art PEM fuel cells. In this paper, proton conduction through the interface is investigated to understand its effect on the performance of a PEM fuel cell. The water containing domains at this interface were modeled as cylindrical pores/channels with the anionic groups (i.e., -SO3-) assumed to be fixed on the pore wall. The interactions of each species with all other species and an applied external field were examined. Molecular-based interaction potential energies were computed in a small test element of the pore and were scaled up in terms of macroscopic variables. Evolution equations of the density and momentum of the species (water molecules and hydronium ions) were derived within a framework of nonequilibrium thermodynamics. The resulting evolution equations for the species were solved analytically using an order-of-magnitude analysis to obtain an expression for the proton conductivity. Results show that the conductivity increases with increasing water content and pore radius, and strongly depends on the separation distance between the sulfonate groups and their distribution on the pore wall. It was also determined that the conductivity of two similar pores of different radii in series is limited by the pore with the smaller radius.

Kumar, Milan; Edwards, Brian J.; Paddison, Stephen J.

2013-02-01

359

Core cross-linked block ionomer micelles as pH-responsive carriers for cis-diamminedichloroplatinum(II).  

PubMed

Benefits of the frequently prescribed platinum (II) chemotherapy drugs are compromised by undesirable side effects, poor pharmacokinetics and development of drug resistance. Polymer micelles derived from amphiphilic block copolymers, offer a novel macromolecular platform for carrier based delivery of such compounds. Soft polymeric nanocarriers were synthesized by template-assisted method involving condensation of the poly(ethylene oxide)-b-polymethacrylate anions by metal ions into core-shell block ionomer complex micelles followed by chemical cross-linking of the polyion chains in the micelle cores. The resulting micelles can efficiently incorporate cisplatin with a high loading capacity (up to 42% w/w). Core cross-linking stabilized the micelles against structural disintegration and prevented premature drug release. The reversible cisplatin entrapment involved the carboxylate groups of the micellar core. The drug was released in a pH-responsive manner, without loss of its biological activity. The stable cross-linked polymer micelles can potentially improve platinum (II) drug disposition with improved therapeutic potential. PMID:21497174

Oberoi, Hardeep S; Laquer, Frederic C; Marky, Luis A; Kabanov, Alexander V; Bronich, Tatiana K

2011-04-08

360

Morphology and electrochemical properties of perfluorosulfonic acid ionomers for vanadium flow battery applications: effect of side-chain length.  

PubMed

Perfluorosulfonic acid ionomers (PFSI) with different side-chain lengths have been investigated with respect to their morphology and electrochemical properties in vanadium flow batteries (VFB). The results indicated that the membrane with the shortest side chains (SSC-M2) displayed small ion clusters and a low degree of hydrophobic-hydrophilic separation, which is favourable to reduce the cross-over of vanadium ions in the VFB. SSC-M2 shows a similar proton conductivity to Nafion, which carries longer ionic side chains but with much lower ion permeability. As a result, the VFB assembled with SSC-M2 exhibited a superior coulombic efficiency and a voltage efficiency close to that of Nafion115. In situ mass transfer revealed that SSC-M2 had a remarkably low degree of vanadium and water transfer across the membrane, which resulted in lower capacity fading than in the case of Nafion115. These results indicate that a membrane with short side chains is an ideal option in the fabrication of high-performance VFBs with low capacity loss. PMID:23775947

Ding, Cong; Zhang, Huamin; Li, Xianfeng; Zhang, Hongzhang; Yao, Chuan; Shi, Dingqin

2013-06-14

361

Interfacial interaction and morphology of EVOH and ionomer blends by scanning thermal microscopy and its correlation with barrier characteristics.  

PubMed

In a blend, the interfacial interaction between the component phases can be effectively utilized to bring about homogeneous mixing and unique performances. While in conventional blends, preserving the morphology of the melt mixed state is unfeasible because of the strong thermodynamic tendency of the components to phase separate, herein, we report the intermolecular interaction of two hydrogen bonded polymers such as a barrier polymer poly(ethylene-co-vinyl alcohol) (EVOH) with an ionic polymer in their blends, which work symbiotically to achieve the desirable characteristics. We demonstrate the creation of a unique ellipsoid microfibrilliar morphology and melt exfoliation of one polymer in the blends through intermolecular interaction and achieve high oxygen barrier characteristics. Scanning thermal microscopy and scanning electron microscopy investigations confirm the presence of such unique morphology. The interfacial interaction and formation of interphase was evident from the local thermal analysis results combined with photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). PA-FTIR confirms the chemical nature of the interaction, while the differential scanning calorimetry results indicate modification of the EVOH phase by the ionomer. The shift of Tg and broadening of the tan delta curve is evident from dynamic mechanical analysis confirming the interaction of the blend components. The blend B(60) with microfibrillar morphology shows fourfold drop in oxygen permeability indicating the role of interfacial interaction and desired morphology. PMID:18439030

Shelat, Kinnari J; Dutta, Naba K; Choudhury, Namita R

2008-04-26

362

Bioactive calcium pyrophosphate glasses and glass-ceramics.  

PubMed

Calcium phosphate glass-based materials in the pyrophosphate region are briefly reviewed. Calcium pyrophosphate glasses can be prepared by including a small amount of TiO(2) (glasses in simulated body fluid. By heating powder-compacts of the glasses, they are crystallized and subsequently are sintered, resulting in fabrication of high-strength glass-ceramics with machinability; they are easier to be machined using conventional tools in comparison with conventional calcium phosphate ceramics. beta-Ca(2)P(2)O(7) crystal formed in the glass-ceramics plays an important role in the machinability. Their apatite-forming ability in simulated body fluid is drastically enhanced after autoclaving in distilled water. The glass-ceramics can be easily coated on a new beta-type titanium alloy using a conventional glazing technique. PMID:16701780

Kasuga, Toshihiro

2005-01-01

363

Apollo 12 ropy glasses revisited  

NASA Astrophysics Data System (ADS)

We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and Ar-39-Ar-40 age dating. The ropy glasses have potassium rare earth elements phosphorous (KREEP)-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component. Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma. Measurements of 39-Ar-40-Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact. Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly.

Wentworth, S. J.; McKay, D. S.; Lindstrom, D. J.; Basu, A.; Martinez, R. R.; Bogard, D. D.; Garrison, D. H.

1994-05-01

364

Colloid formation in implanted glasses  

SciTech Connect

Metal colloids in glasses can yield an enhanced ([chi]([sup 3])) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in colloid formation. We have characterized Ag-colloid formation in various silicate glasses and, in addition, have studied the formation of colloids in Ag-doped phosphate glass as a function of N and H implantation. Some preliminary results for Cu-implanted glasses are presented.

Arnold, G.W. (Sandia National Labs., Albuquerque, NM (United States)); Mazzoldi, P.; Tramontin, L. (Padua Univ. (Italy)); Boscolo-Boscoletto, A. (ECP-EniChem Polimeri, Porto Marghera (Italy)); Battaglin, G. (Venice Univ. (Italy))

1992-01-01

365

Colloid formation in implanted glasses  

SciTech Connect

Metal colloids in glasses can yield an enhanced ({chi}({sup 3})) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in colloid formation. We have characterized Ag-colloid formation in various silicate glasses and, in addition, have studied the formation of colloids in Ag-doped phosphate glass as a function of N and H implantation. Some preliminary results for Cu-implanted glasses are presented.

Arnold, G.W. [Sandia National Labs., Albuquerque, NM (United States); Mazzoldi, P.; Tramontin, L. [Padua Univ. (Italy); Boscolo-Boscoletto, A. [ECP-EniChem Polimeri, Porto Marghera (Italy); Battaglin, G. [Venice Univ. (Italy)

1992-12-31

366

Commercial and Experimental Glass Fibers  

NASA Astrophysics Data System (ADS)

Continuous glass fibers can be formed from melts with a wide range of compositions and viscosities. This chapter reviews pure silica fibers which are formed from highly viscous melts, silicate glass fibers with 50-70% SiO2 which are formed from moderately viscous melts, aluminate glass fibers with 50-80% Al2O3, as well as yttria-alumina-garnet (YAG) glass fibers which are formed from inviscid (literally non-viscous) melts. Commercial glass fibers are made for a variety of applications from pure silica rods and from silicate melts containing 50-70% SiO2 and 10-25% Al2O3. Boron-free, essentially boron-free, and borosilicate E-glass are general-purpose fibers. ERC-glass offers high corrosion resistance, HS-glass offers high-strength composites, D-glass offers a low dielectric constant, and A-glass offers the possibility of using waste container glass for less demanding applications.

Wallenberger, Frederick T.

367

Profiles in garbage glass containers  

SciTech Connect

Glass containers are made from sand, limestone, soda ash, cullet (crushed bottles), and various additives, including those used to color brown, green, or blue bottles. Sixty percent of the glass used in the US is clear (flint) and one-fourth is brown (amber). Almost half of the green bottles are imported wind and beer bottles. Other glass products include flat glass such as windows; fiberglass insulation; and glassware. These products use different manufacturing processes and different additives than container glass. This profile covers only container glass. Glass bottles are commonly collected in curb-side programs. Losses due to breakage and the abrasiveness of glass during collection and processing offset their low collection and processing costs. Breakage solutions include installation of interior baffles or nets in the collection trucks, special glass-only truck compartments, and limiting the number of times glass is transferred after collection before final processing. Ten states require deposits on glass bottles for beer and soft drinks and related items.

Miller, C. [Environmental Industry Associations, Washington, DC (United States)

1997-09-01

368

Quality of glass marbles and the preparation of bubble-free glass for fiber production  

Microsoft Academic Search

Before the glass marbles are produced the glass-making process has been completed and the glass has passed through all the glass-making stages, including that of fining. A microscopic analysis of a batch of glass marbles showed that they contained no gas inclusions in the volume. To work the glass fiber it is necessary that the molten glass be at a

V. V. Ulybyshev; T. A. Vlasova; V. Vo Yurchenko

1986-01-01

369

Production of glass or glass-ceramic to metal seals with the application of pressure  

DOEpatents

In a process for preparing a glass or glass-ceramic to metal seal comprising contacting the glass with the metal and heat-treating the glass and metal under conditions whereby the glass to metal seal is effected and, optionally, the glass is converted to a glass-ceramic, an improvement comprises carrying out the heat-treating step using hot isostatic pressing.

Kelly, M.D.; Kramer, D.P.

1985-01-04

370

Production of glass or glass-ceramic to metal seals with the application of pressure  

DOEpatents

In a process for preparing a glass or glass-ceramic to metal seal comprising contacting the glass with the metal and heat-treating the glass and metal under conditions whereby the glass to metal seal is effected and, optionally, the glass is converted to a glass-ceramic, an improvement comprises carrying out the heat-treating step using hot isostatic pressing.

Kelly, Michael D. (West Alexandria, OH); Kramer, Daniel P. (Dayton, OH)

1987-11-10

371

Low Temperature Sintering of P2O5Added Cordierite Glass with Borosilicate Glass  

Microsoft Academic Search

Borosilicate glass was adopted as a sintering aid to improve the sinterability of P2O5-added cordierite glass. The flux effect of borosilicate glass aids the coalescence of cordierite glass particles, which promotes the densification. Crystallization of cordierite glass is the major reaction during the sintering of cordierite glass with borosilicate glass. Besides the advantage of lower sintering temperature, the addition of

Shen-Li Fu; Lih-Shan Chen

1993-01-01

372

Low Temperature Sintering of P2O5Added Cordierite Glass with Lead Borosilicate Glass  

Microsoft Academic Search

Cordierite was prepared by the sintering of cordierite glass and lead borosilicate glass. With the addition of lead borosilicate glass, P2O5-added cordierite glass can be densified at lower sintering temperature. Owing to the flux effect of lead borosilicate glass, the coalescence of glass particles was aided by the viscous flow of the glass. Besides the advantage of lower temperature sintering,

Lih-Shan Chen; Shen-Li Fu

1992-01-01

373

Bulk metallic glass matrix composites  

SciTech Connect

Composites with a bulk metallic glass matrix were synthesized and characterized. This was made possible by the recent development of bulk metallic glasses that exhibit high resistance to crystallization in the undercooled liquid state. In this letter, experimental methods for processing metallic glass composites are introduced. Three different bulk metallic glass forming alloys were used as the matrix materials. Both ceramics and metals were introduced as reinforcement into the metallic glass. The metallic glass matrix remained amorphous after adding up to a 30 vol{percent} fraction of particles or short wires. X-ray diffraction patterns of the composites show only peaks from the second phase particles superimposed on the broad diffuse maxima from the amorphous phase. Optical micrographs reveal uniformly distributed particles in the matrix. The glass transition of the amorphous matrix and the crystallization behavior of the composites were studied by calorimetric methods. {copyright} {ital 1997 American Institute of Physics.}

Choi-Yim, H.; Johnson, W.L. [W. M. Keck Laboratory of Engineering Materials, Mail Code 138-78, California Institute of Technology, Pasadena, California 91125 (United States)

1997-12-01

374

Structural interpretations of aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

This manuscript presents a theoretical analysis of the correlation between the bulk moduli and the structure of a series of multicomponent aluminosilicate glasses in terms of the bond compression model. The main parameters in the analysis were the computed elastic moduli, the average stretching-force constant and the average atomic ring size. These parameters were calculated for every glass series and for every glass composition. The results showed that the average force constant of these glasses increases and the elastic moduli decrease with the increase in the SiO2 content (pure covalent bonds). This behaviour was attributed to the decrease in the molar volume, and the role of both CaO and Al2O3. The average atomic ring size of the studied glasses are about two-thirds of pure SiO2, whilst the elastic moduli of pure SiO2 glass are about two thirds of these glasses.

Saddeek, Yasser B.

2005-06-01

375

Chalcogenide glass bolometers.  

PubMed

The chalcogenide glass Tl(2)SeAs(2) Te(3) has been evaluated as a thermistor bolometer material for room temperature operation. Thin film bolometers were fabricated on mica, glass, and sapphire substrates by both hot-pressing and rf sputtering techniques. Best results were achieved with 10-micro thick Tl(2)SeAs(2) Te(3) elements on thin mica substrates. Using a 500 K blackbody at a 10-Hz chopping frequency, a 2.5 x10(_3)cm(2) device yielded an NEP of 2.3 x 10(_9) W Hz(_4) cm(-2) device achieved an NEP of 7.7 x 10(-10) W Hz(-1/2) The ac performance of these devices is limited by their inherently long response times (tau congruent with 1 sec). PMID:20125232

Bishop, S G; Moore, W J

1973-01-01

376

Chalcogenide glass photonic crystals  

NASA Astrophysics Data System (ADS)

All-optical switching devices are based on a material possessing a nonlinear optical response, enabling light to control light, and are enjoying renewed interest. Photonic crystals are a promising platform for realizing compact all-optical switches operating at very low power and integrated on an optical integrated circuit. In this review, we show that by making photonic crystals from a highly nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the fabrication and testing of two-dimensional Ge33As12 Se55 chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to post-tune the devices using the material photosensitivity. In one proposal we hope to introduce a double-heterostructure microcavity using the photosensitivity alone.

Freeman, Darren; Grillet, Christian; Lee, Michael W.; Smith, Cameron L. C.; Ruan, Yinlan; Rode, Andrei; Krolikowska, Maryla; Tomljenovic-Hanic, Snjezana; de Sterke, C. Martijn; Steel, Michael J.; Luther-Davies, Barry; Madden, Steve; Moss, David J.; Lee, Yong-Hee; Eggleton, Benjamin J.

2008-04-01

377

Glass matrix armor  

SciTech Connect

This patent describes 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 insides 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.

Calkins, N.C.

1991-09-03

378

Ductile bulk metallic glass.  

PubMed

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 4 mm thick samples. To date, no monolithic metallic material has exhibited such a combination of high strength, extensive ductility, and high elastic limit. The large plasticity is reflected in a high Poisson ratio of 0.42, which causes the tip of a shear band to extend rather than initiate a crack. This results in the formation of multiple shear bands and is the origin of the observed large global ductility and very high fracture toughness, approximately 80 MPa m(-1/2). PMID:15697909

Schroers, Jan; Johnson, William L

2004-12-16

379

Metallic Spin Glasses  

Microsoft Academic Search

Metallic Spin-glasses have drawn much experimental and theoretical attention in recent years(A. M. Sengupta and A. Georges, Phys. Rev. B52, 10295 (1995); S. Sachdev, N. Read and R. Opperman, Phys. Rev. B52, 10286 (1995); F. Steglich, et al., J. Phys. Condens. Matter 8, 99099 (1996).). One particularly interesting aspect of this system is the non-fermi-liquid behavior near the zero temperature

Anirvan Sengupta

1998-01-01

380

Solarization of heliostat glasses  

Microsoft Academic Search

A solar-induced decrease in Fe(2+) absorption was observed in heliostat glasses from the solar furnace at Odeillo, France. This decrease occurs throughout the sample and is of sufficient magnitude to result in an increase of 2.5% in solar transmittance in a period of nine years. Optical and ESR studies did not detect a corresponding increase in Fe(3+) concentration. The effect

J. Vitko Jr.; J. E. Shelby

1980-01-01

381

Glass microbubble composite foam  

SciTech Connect

Composite foams have been prepared from blends of Kerimid 601 polyimide resin and different types of glass microbubbles. Kerimid 601 is an addition type polyimide that offers many processing advantages over other types of polyimides. In an addition reaction, no volatiles are evolved during cure and weight loss and shrinkage during cure are small. Also, since the resin is a powder that melts and flows before curing, low density foams can be prepared. Processes were developed to blend, mold, and cure the foam formulations. The powered resin and glass microbubbles were mixed together in a twin shell blender. Three methods of molding were considered: a sintering process, vacuum bag molding, and compression molding; however, all of the foams were made by the vacuum bag method. The standard cure recommended by the manufacturer of Kerimid 601 was used to cure and postcure the foam samples. Test results show that foams with compressive strengths ranging from 500 to 26,000 psi (3.45 to 179 MPa) can be prepared depending upon the type of GMB used and the density of the foam composite. Foam made from B40A glass microbubbles had the best strength to weight ratio, but the lowest foam density possible using the B40A bubbles is only about 0.35 g/cm/sup 3/. Low density composites require low density glass microbubbles. Foams with densities of about 0.2 g/cm/sup 3/ were made with the B18A bubbles, but the compressive strength was about 500 psi (3.45 MPa).

McIlroy, H.M.

1978-02-01

382

Athermal photofluidization of glasses  

NASA Astrophysics Data System (ADS)

Azobenzene and its derivatives are among the most important organic photonic materials, with their photo-induced trans-cis isomerization leading to applications ranging from holographic data storage and photoalignment to photoactuation and nanorobotics. A key element and enduring mystery in the photophysics of azobenzenes, central to all such applications, is athermal photofluidization: illumination that produces only a sub-Kelvin increase in average temperature can reduce, by many orders of magnitude, the viscosity of an organic glassy host at temperatures more than 100?K below its thermal glass transition. Here we analyse the relaxation dynamics of a dense monolayer glass of azobenzene-based molecules to obtain a measurement of the transient local effective temperature at which a photo-isomerizing molecule attacks its orientationally confining barriers. This high temperature (Tloc~800?K) leads directly to photofluidization, as each absorbed photon generates an event in which a local glass transition temperature is exceeded, enabling collective confining barriers to be attacked with near 100% quantum efficiency.

Fang, G. J.; Maclennan, J. E.; Yi, Y.; Glaser, M. A.; Farrow, M.; Korblova, E.; Walba, D. M.; Furtak, T. E.; Clark, N. A.

2013-02-01

383

Athermal photofluidization of glasses.  

PubMed

Azobenzene and its derivatives are among the most important organic photonic materials, with their photo-induced trans-cis isomerization leading to applications ranging from holographic data storage and photoalignment to photoactuation and nanorobotics. A key element and enduring mystery in the photophysics of azobenzenes, central to all such applications, is athermal photofluidization: illumination that produces only a sub-Kelvin increase in average temperature can reduce, by many orders of magnitude, the viscosity of an organic glassy host at temperatures more than 100?K below its thermal glass transition. Here we analyse the relaxation dynamics of a dense monolayer glass of azobenzene-based molecules to obtain a measurement of the transient local effective temperature at which a photo-isomerizing molecule attacks its orientationally confining barriers. This high temperature (T(loc)~800?K) leads directly to photofluidization, as each absorbed photon generates an event in which a local glass transition temperature is exceeded, enabling collective confining barriers to be attacked with near 100% quantum efficiency. PMID:23443549

Fang, G J; Maclennan, J E; Yi, Y; Glaser, M A; Farrow, M; Korblova, E; Walba, D M; Furtak, T E; Clark, N A

2013-01-01

384

Cluster-assembled metallic glasses.  

PubMed

A bottom-up approach to nanofabricate metallic glasses from metal clusters as building blocks is presented. Considering metallic glasses as a subclass of cluster-assembled materials, the relation between the two lively fields of metal clusters and metallic glasses is pointed out. Deposition of selected clusters or collections of them, generated by state-of-the-art cluster beam sources, could lead to the production of a well-defined amorphous material. In contrast to rapidly quenched glasses where only the composition of the glass can be controlled, in cluster-assembled glasses, one can precisely control the structural building blocks. Comparing properties of glasses with similar compositions but differing in building blocks and therefore different in structure will facilitate the study of structure-property correlation in metallic glasses. This bottom-up method provides a novel alternative path to the synthesis of glassy alloys and will contribute to improving fundamental understanding in the field of metallic glasses. It may even permit the production of glassy materials for alloys that cannot be quenched rapidly enough to circumvent crystallization. Additionally, gaining deeper insight into the parameters governing the structure-property relation in metallic glasses can have a great impact on understanding and design of other cluster-assembled materials. PMID:23899019

Kartouzian, Aras

2013-07-30

385

Cluster-assembled metallic glasses  

NASA Astrophysics Data System (ADS)

A bottom-up approach to nanofabricate metallic glasses from metal clusters as building blocks is presented. Considering metallic glasses as a subclass of cluster-assembled materials, the relation between the two lively fields of metal clusters and metallic glasses is pointed out. Deposition of selected clusters or collections of them, generated by state-of-the-art cluster beam sources, could lead to the production of a well-defined amorphous material. In contrast to rapidly quenched glasses where only the composition of the glass can be controlled, in cluster-assembled glasses, one can precisely control the structural building blocks. Comparing properties of glasses with similar compositions but differing in building blocks and therefore different in structure will facilitate the study of structure-property correlation in metallic glasses. This bottom-up method provides a novel alternative path to the synthesis of glassy alloys and will contribute to improving fundamental understanding in the field of metallic glasses. It may even permit the production of glassy materials for alloys that cannot be quenched rapidly enough to circumvent crystallization. Additionally, gaining deeper insight into the parameters governing the structure-property relation in metallic glasses can have a great impact on understanding and design of other cluster-assembled materials.

Kartouzian, Aras

2013-07-01

386

Analytical Plan for Roman Glasses  

SciTech Connect

Roman glasses that have been in the sea or underground for about 1800 years can serve as the independent “experiment” that is needed for validation of codes and models that are used in performance assessment. Two sets of Roman-era glasses have been obtained for this purpose. One set comes from the sunken vessel the Iulia Felix; the second from recently excavated glasses from a Roman villa in Aquileia, Italy. The specimens contain glass artifacts and attached sediment or soil. In the case of the Iulia Felix glasses quite a lot of analytical work has been completed at the University of Padova, but from an archaeological perspective. The glasses from Aquileia have not been so carefully analyzed, but they are similar to other Roman glasses. Both glass and sediment or soil need to be analyzed and are the subject of this analytical plan. The glasses need to be analyzed with the goal of validating the model used to describe glass dissolution. The sediment and soil need to be analyzed to determine the profile of elements released from the glass. This latter need represents a significant analytical challenge because of the trace quantities that need to be analyzed. Both pieces of information will yield important information useful in the validation of the glass dissolution model and the chemical transport code(s) used to determine the migration of elements once released from the glass. In this plan, we outline the analytical techniques that should be useful in obtaining the needed information and suggest a useful starting point for this analytical effort.

Strachan, Denis M.; Buck, Edgar C.; Mueller, Karl T.; Schwantes, Jon M.; Olszta, Matthew J.; Thevuthasan, Suntharampillai; Heeren, Ronald M.

2011-01-01

387

Bioactive glass in tissue engineering  

PubMed Central

This review focuses on recent advances in the development and use of bioactive glass for tissue engineering applications. Despite its inherent brittleness, bioactive glass has several appealing characteristics as a scaffold material for bone tissue engineering. New bioactive glasses based on borate and borosilicate compositions have shown the ability to enhance new bone formation when compared to silicate bioactive glass. Borate-based bioactive glasses also have controllable degradation rates, so the degradation of the bioactive glass implant can be more closely matched to the rate of new bone formation. Bioactive glasses can be doped with trace quantities of elements such as Cu, Zn and Sr, which are known to be beneficial for healthy bone growth. In addition to the new bioactive glasses, recent advances in biomaterials processing have resulted in the creation of scaffold architectures with a range of mechanical properties suitable for the substitution of loaded as well as non-loaded bone. While bioactive glass has been extensively investigated for bone repair, there has been relatively little research on the application of bioactive glass to the repair of soft tissues. However, recent work has shown the ability of bioactive glass to promote angiogenesis, which is critical to numerous applications in tissue regeneration, such as neovascularization for bone regeneration and the healing of soft tissue wounds. Bioactive glass has also been shown to enhance neocartilage formation during in vitro culture of chondrocyte-seeded hydrogels, and to serve as a subchondral substrate for tissue-engineered osteochondral constructs. Methods used to manipulate the structure and performance of bioactive glass in these tissue engineering applications are analyzed.

Rahaman, Mohamed N.; Day, Delbert E.; Bal, B. Sonny; Fu, Qiang; Jung, Steven B.; Bonewald, Lynda F.; Tomsia, Antoni P.

2011-01-01

388

Waste product profile: Glass containers  

SciTech Connect

In 1992, Waste Age initiated the Waste Product Profile series -- brief, factual listings of the solid waste management characteristics of materials in the solid waste stream. This popular series of profiles high-lighted a product, explained how it fit into integrated waste management systems, and provided current data on recycling and markets for the product. Glass containers are made from sand, limestone, soda ash, cullet (crushed bottles), and various additives, including those used to produce green, brown, and blue glass. Other glass products include flat glass, such as windows, and fiberglass products, such as insulation and glassware. These products are manufactured using different processes and different additives than container glass. This profile covers only glass containers.

Miller, C. [Environmental Industry Associations, Washington, DC (United States)

1995-09-01

389

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

2008-12-11

390

Colloid formation in implanted glasses  

Microsoft Academic Search

Metal colloids in glasses can yield an enhanced ([chi]([sup 3])) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in colloid formation. We have characterized Ag-colloid formation in various silicate glasses and, in addition, have studied the formation of colloids in Ag-doped

G. W. Arnold; P. Mazzoldi; L. Tramontin; A. Boscolo-Boscoletto; G. Battaglin

1992-01-01

391

Colloid formation in implanted glasses  

Microsoft Academic Search

Metal colloids in glasses can yield an enhanced (Ï(³)) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in colloid formation. We have characterized Ag-colloid formation in various silicate glasses and, in addition, have studied the formation of colloids in Ag-doped phosphate

G. W. Arnold; P. Mazzoldi; L. Tramontin; A. Boscolo-Boscoletto; G. Battaglin

1992-01-01

392

Transparent Ferroelectric Glass-Ceramics  

Microsoft Academic Search

In recent years, there has been a resurgence of interest in transparent ferroelectric glass-ceramics (TFGCs), which are a special class of glass-ceramic composites that combine the low cost of fabrication and forming of transparent glass with the superior nonlinear optical and electro-optical properties of ferroelectric crystals. In this paper, we present a review of the current status, focusing on the

H. JAIN

2004-01-01

393

Chalcogenide glasses for nonlinear photonics  

Microsoft Academic Search

Chalcogenide glasses are important amorphous semiconductors used for phase-change memories, solar cells and in photonics. Here I will review their photonic applications with an emphasis on new glasses for high speed all-optical signal processing. Chalcogenide glasses (ChGs) contain one or more of the chalcogen elements (S, Se, Te) covalently bonded to network formers such as As, Ge, Sb, etc. Research

Barry Luther-Davies; Xin Gai; Amrita Prasad; Steve Madden; Duk-Yong Choi; Rongping Wang

2010-01-01

394

Rare-earth-doped transparent glass ceramics  

Microsoft Academic Search

Glass ceramics are a known class of polycrystalline ceramic materials, where, depending on the glass matrix and the particular crystalline phases, one can obtain materials with improved mechanical, thermal, electrical or optical properties. The characteristics and applications of optical glass ceramics are reviewed, with particular emphasis on rare-earth-doped transparent glass ceramics for photonics, including the search for new transparent glass

M Clara Gonçalves; Luís F Santos; Rui M Almeida

2002-01-01

395

Recycled crushed glass in road work applications  

Microsoft Academic Search

A comprehensive suite of geotechnical laboratory tests was undertaken on samples of recycled crushed glass produced in Victoria, Australia. Three types of recycled glass sources were tested being coarse, medium and fine sized glass. Laboratory testing results indicated that medium and fine sized recycled glass sources exhibit geotechnical behavior similar to natural aggregates. Coarse recycled glass was however found to

M. M. Disfani; A. Arulrajah; M. W. Bo; R. Hankour

2011-01-01

396

Testing Laminated Glass for Impact Resistance  

Microsoft Academic Search

Comparative testing of laminated glass made up by different combinations for impact resistance has been performed. The testing corroborates the possibility of using glass subjected to special thermal treatment (STT) in the production of impact-resistant laminated glass. Glasses based on STT glass satisfy the impact resistance requirements of GOST R 51136–98, and their thickness and weight are a factor of

A. I. Shutov; A. N. Frank; I. A. Novikov; A. S. Ostapko; A. S. Bonchuk; A. N. Burdov

2004-01-01

397

Glass laceration injuries and prevention.  

PubMed

Accidents involving glass in doors, sidelights, specially vulnerable windows, and shower screens are an important cause of injury, and occasionally death. Most of the injuries are superficial cuts and abrasions, but many involve deep lacerations of tendons, nerves and muscles. The accidents occur mainly in children and young adults with the highest rate being among males aged from 15 to 19 years. The number and severity of these injuries could be reduced through the wider use of appropriate forms of safety glazing: laminated glass or toughened glass in new installlations, and the application of a plastic safety film to existing glass. PMID:449776

Oliver, T I; Lawson, J S

1979-03-10

398

Failure studies of glass fibers  

NASA Astrophysics Data System (ADS)

This dissertation is divided into six sections. The first section includes a review of the literature on the mechanical properties of glass, including glass strength. Section two describes a study of the effects of composition of calcium aluminoborosilicate glasses on the inert and room temperature two-point bending failure characteristics of glass fibers, including fatigue and aging effects. Sections three and four include studies of the effects of composition and structure of alkali silicate and aluminosilicate glasses on the inert two-point bending fiber failure properties. Section five describes the inert two-point bending failure results of sodium borate glass fibers. Section six includes a study of the effects of melting time and temperature (i.e. thermal history) on the resulting two-point bending failure properties of glass fibers produced from a variety of glass compositions. Throughout the course of this work, new experimental equipment and techniques were developed so that high quality failure measurements could be obtained. When glass melts were prepared to ensure homogeneity, the failure properties were shown to be sensitive to glass composition and structure and the reproducibility of the failure data was less than for a variety of different silicate glass compositions. Fibers have also been aged under controlled humidity and temperature conditions to characterize the effects of aging time on the failure strain. With the ability to produce and test high quality fiber, a new failure property of glass has been observed. Fibers tested under liquid nitrogen produce failure strains that depend on the testing rate of the two-point bending equipment. In the case of silica glass fibers, failure strain increases with increasing testing rate, an effect attributed to 'normal' inert fatigue behavior. However, some glasses, such as the high alkali silicates and soda lime silicates, show the opposite dependence of failure strain on testing rate, where slower testing rates produce greater failure strains (i.e. an "inert delayed failure effect"). With the ability to determine the intrinsic (flaw-free) failure properties of glass and the dependence of these properties on testing rate, a new insight to the understanding of glass failure and strength with relation to composition and structure may be possible.

Lower, Nathan Paul

399

Phosphate base laser glasses  

SciTech Connect

A phosphate base laser glass comprising 55-70% P2O5, 1-15% Al2O3, 0-25% Li2O, 0-25% Na2O, 0-8% K2O, the total proportion of Li2O, Na2O, and K2O being 10-25%, 0-15% BaO, 0-15% ZnO, 0-15% CaO , 0-15%, sro, 0-15% MgO, the total proportion of BaO, ZnO, CaO, SrO, and MgO being 5-15%, 0-5% Y2O3, 0-5% La2O3, 0-5% GeO2, 0-5% CeO2, 0-3% Nb2O5, 0-3% MnO2, 0-2% Ta2O5, 0-1% Sb2O3, and 0.01-5% Nd2O3, all % being mole %. The phosphate base laser glass of this invention has a high induced emission cross section, a low non-linear refractive index coefficient, and excellent acid resistance and divitrification resistance. By replacing partially or wholely one or more of LiO2, Na2O, K2O, BaO, ZnO, CaO, SrO, MgO or Al2O3 by LiF, NaF, KF , BaF2ZnF2, CaF2, SrF2, MgF2 or AlF3, respectively, the above properties of the laser glass are further improved.

Izumitani, T.; Tsuru, M.

1980-12-16

400

Performance rating of glass windows and glass windows with films in aspect of thermal comfort and heat transmission  

Microsoft Academic Search

This article is about a study on glass window and glass window with film of different types in aspect of thermal comfort and heat transmission. Different types of glass window, clear glass, tinted glass, reflective glass, double pane glass, and low-e glass were investigated. Films with different spectral optical properties were then adhered to the glass windows of different types

Somsak Chaiyapinunt; Bunyarit Phueakphongsuriya; Khemmachart Mongkornsaksit; Nopparat Khomporn

2005-01-01

401

Glass rupture disk  

DOEpatents

A frangible rupture disk and mounting apparatus for use in blocking fluid flow, generally in a fluid conducting conduit such as a well casing, a well tubing string or other conduits within subterranean boreholes. The disk can also be utilized in above-surface pipes or tanks where temporary and controllable fluid blockage is required. The frangible rupture disk is made from a pre-stressed glass with controllable rupture properties wherein the strength distribution has a standard deviation less than approximately 5% from the mean strength. The frangible rupture disk has controllable operating pressures and rupture pressures.

Glass, S. Jill (Albuquerque, NM); Nicolaysen, Scott D. (Albuquerque, NM); Beauchamp, Edwin K. (Albuquerque, NM)

2002-01-01

402

Lightguiding in photochromic glasses.  

PubMed

Lightguiding in ion-exchanged photochromic glass layers is reported. The guides were formed by ion exchange of Ag(+) for Na(+) or by outdiffusion of F. Guide attenuation was less than 0.2 dB/cm in many cases. The attenuation in the guide was varied over a range of Deltaalpha = 30 dB/cm by illuminating the guide with (1) uv radiation to darken the guide or order of seconds. (2) visible radiation to bleach the guide. Switching times were in the order of seconds. PMID:20134933

Crow, J D; Borrelli, N F; Seward Iii, T P; Chodak, J

1975-03-01

403

Examination of glass-silicon and glass-glass bonding techniques for microfluidic systems  

SciTech Connect

We report here on the results of experiments concerning particular bonding processes potentially useful for ultimate miniaturization of microfluidic systems. Direct anodic bonding of continuous thin pyrex glass of 250 {mu}m thickness to silicon substrates gives multiple, large voids in the glass. Etchback of thick glass of 1200 {mu}m thickness bonded to silicon substrates gives thin continuous glass layers of 189 {mu}m thickness without voids over areas of 5 cm {times} 12 cm. Glass was also successfully bonded to glass by thermal bonding at 800{degrees}C over a 5 cm {times} 7 cm area. Anticipated applications include microfabricated DNA sequencing, flow injection analysis, and liquid and gas chromatography microinstruments.

Raley, N.F.; Davidson, J.C.; Balch, J.W.

1995-10-23

404

High-Level Waste Glass Formulation Model Sensitivity Study. 2009 Glass Formulation Model versus 1996 Glass Formulation Model.  

National Technical Information Service (NTIS)

This document presents the differences between two HLW glass formulation models (GFM): The 1996 GFM and 2009 GFM. A glass formulation model is a collection of glass property correlations and associated limits, as well as model validity and solubility cons...

F. L. Meinert J. D. Belsher

2009-01-01

405

Alkaline phosphatase grafting on bioactive glasses and glass ceramics  

Microsoft Academic Search

Bone integration of orthopaedic or dental implants and regeneration of damaged bone at the surgical site are still unresolved problems in prosthetic surgery. For this reason, biomimetic surfaces (i.e. both inorganic and biological bioactive surfaces) represent a challenge for bone implantation. In this research work a hydrolase enzyme (alkaline phosphatase) was covalently grafted to inorganic bioactive glass and glass ceramic

Enrica Verné; Sara Ferraris; Chiara Vitale-Brovarone; Silvia Spriano; Claudia L. Bianchi; Alberto Naldoni; Marco Morra; Clara Cassinelli

2010-01-01

406

Fabrication and characterization of 20 nm planar nanofluidic channels by glass–glass and glass–silicon bonding  

Microsoft Academic Search

We have characterized glass-glass and glass-Si bonding processes for the fabrication of wide, shallow nanofluidic channels with depths down to the nanometer scale. Nanochannels on glass or Si substrate are formed by reactive ion etching or a wet etching process, and are sealed with another flat substrate either by glass-glass fusion bonding (550 uC) or an anodic bonding process. We

Pan Maoa; Jongyoon Han

2005-01-01

407

Quinary metallic glass alloys  

DOEpatents

At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

Lin, Xianghong (Pasadena, CA); Johnson, William L. (Pasadena, CA)

1998-01-01

408

Quinary metallic glass alloys  

DOEpatents

At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

Lin, X.; Johnson, W.L.

1998-04-07

409

7 CFR 3201.30 - Glass cleaners.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Glass cleaners. 3201.30 Section 3201...PROCUREMENT Designated Items § 3201.30 Glass cleaners. (a) Definition. Cleaning...designed specifically for use in cleaning glass surfaces, such as windows,...

2013-01-01

410

ConcepTest: Glass-Rock Analogy  

NSDL National Science Digital Library

Glass is made by melting silica-rich sand. The molten glass is then formed into shapes as it cools. Glass making could be seen as an analog for the formation of a. igneous rock b. metamorphic rock c. sedimentary ...

411

Colloid formation in implanted glasses.  

National Technical Information Service (NTIS)

Metal colloids in glasses can yield an enhanced ((chi)((sup 3))) susceptibility which leads to an intensity dependent refractive index. Ion implantation is a convenient means of introducing the metal species. The host glass plays an important role in coll...

G. W. Arnold P. Mazzoldi L. Tramontin A. Boscolo-Boscoletto G. Battaglin

1992-01-01

412

Plutonium dioxide dissolution in glass  

SciTech Connect

In the aftermath of the Cold War, the U.S. Department of Energy`s (DOE) Office of Fissile Materials Disposition (OFMD) is charged with providing technical support for evaluation of disposition options for excess fissile materials manufactured for the nation`s defense. One option being considered for the disposition of excess plutonium (Pu) is immobilization by vitrification. The vitrification option entails immobilizing Pu in a host glass and waste package that are criticality-safe (immune to nuclear criticality), proliferation-resistant, and environmentally acceptable for long-term storage or disposal. To prove the technical and economic feasibility of candidate vitrification options it is necessary to demonstrate that PuO{sub 2} feedstock can be dissolved in glass in sufficient quantity. The OFMD immobilization program has set a Pu solubility goal of 10 wt% in glass. The life cycle cost of the vitrification options are strongly influenced by the rate at which PUO{sub 2} dissolves in glass. The total number of process lines needed for vitrification of 50 t of Pu in 10 years is directly dependent upon the time required for Pu dissolution in glass. The objective of this joint Pacific Northwest National Laboratory (PNNL) - Savannah River Technology Center (SRTC) study was to demonstrate a high Pu solubility in glass and to identify on a rough scale the time required for Pu dissolution in the glass. This study was conducted using a lanthanide borosilicate (LaBS) glass composition designed at the SRTC for the vitrification of actinides.

Vienna, J.D.; Alexander, D.L.; Li, Hong [and others

1996-09-01

413

Polyamorphic transitions in network glasses  

Microsoft Academic Search

We have used a combination of Brillouin and Raman scattering, and molecular dynamics computer simulations to investigate the nature of polyamorphic transitions in network glasses. The manifestation and consequence of pressure-induced structural transitions in silica and boron oxide, i.e., glasses with tetrahedral and trigonal network building blocks are contrasted. In both materials different transition mechanisms are observed depending on the

L. Huang; J. D. Nicholas; J. Kieffer; S. Sinogeikin; J. D. Bass

2004-01-01

414

Refractory Glass Seals for SOFC  

Microsoft Academic Search

One of the critical challenges facing planar solid oxide fuel cell (SOFC) technology is the need for reliable sealing technology. Seals must exhibit long-term stability and mechanical integrity in the high temperature SOFC environment during normal and transient operation. Several different approaches for sealing SOFC stacks are under development, including glass or glass-ceramic seals, metallic brazes, and compressive seals. Among

Y. S. Chou; Jeffry W. Stevenson

2011-01-01

415

Chemical properties of metallic glasses  

Microsoft Academic Search

Research into chemical properties of metallic glasses has revealed promising behavior in the areas of corosion resistance and catalysis. Metallic glasses containing a film-forming element exhibit resistance to uniform and localized corrosion that is superior to that of many crystalline stainless steels. This resistance is due to the presence of passive films that are enriched in the film-forming element. Cr

Diegle

1983-01-01

416

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

417

Heliostat glass survey and analysis  

Microsoft Academic Search

A comprehensive survey of both foreign and domestic sources of low distortion, high transmission flat glass with a nominal thickness of 3 mm was undertaken. The purpose of the survey was to determine the characteristics, availability and cost of glass for use in second surface heliostat mirrors for the Barstow pilot plant and future commercial central receiver plants. Information obtained

M. A. Lind; J. M. Rusin

1978-01-01

418

Making a Better Beer Glass.  

ERIC Educational Resources Information Center

|A class activity is detailed in which alternative designs for glasses are examined. The goal is to design a glass which is built tilted, so that beer can be poured in without creating a foam problem. The activity is viewed as one leading to interesting questions. (MP)|

Hoffer, Alan R.

1982-01-01

419

Superionic glasses: theories and applications  

Microsoft Academic Search

Applications of superionic glasses in electrochemistry include solid state batteries for which new glass compositions are being developed for their enhanced conductivity and chemical stability. The focus of fundamental investigations remains the search for a generally accepted mechanism of ion transport.

Malcolm D Ingram

1997-01-01

420

Nanocomposites glass\\/conductive polymers  

Microsoft Academic Search

We report on the preparation and characterization of two glass\\/conducting polymer nanocomposites obtained by the in situ oxidative polymerization of pyrrole and aniline inside the pores of Porous Vycor Glass (PVG). Oxidative polymerization of pyrrole was done via Cu2+ cation impregnated in the PVG pores. The polymerization of aniline was undertaken by impregnating PVG with the monomer, followed by an

Aldo J. G. Zarbin; Marco-A. De Paoli; Oswaldo L. Alves

1999-01-01

421

Dehydroxylation of phosphate laser glass  

NASA Astrophysics Data System (ADS)

Rates of dehydroxylation of two Nd-doped metaphosphate laser glasses (LG-770 and LHG-8) are measured and modeled. Glass melts ranging in size from 100 g to 2.8 kg were bubbled with O2 containing various H2O partial pressures (PH(subscript 2O)) and with O2/Cl2 mixtures at temperatures ranging from 925 - 1300 degree(s)C. The OH content in the glass was measured by monitoring the OH absorption at 3.333 micrometers at various bubbling times. The OH removal by inert gas bubbling (e.g. O2 bubbling) is governed by the transport (diffusion) of OH to the glass liquid/vapor interface and by the chemical equilibrium between OH at the surface and H2O in the gas phase. The equilibrium OH content in glass melts bubbled with O2 containing different PH(subscript 2O) varies as PH(subscript 2O)1/2.

Thorsness, C. B.; Suratwala, Tayyab I.; Steele, Rusty A.; Campbell, Jack H.; Hayden, Joseph S.; Pucilowski, S. A.; Suzuki, K.

2000-10-01

422

Glass-An Environmental Protector  

SciTech Connect

From asbestos abatement to lead paint removal to nuclear waste stabilization and even to heavy metal removal using microorganisms, glass has great potential as a solution to many environmental problems. The ability to accommodate an array of chemical elements within the glass structure has facilitated the use of glass as a medium for the stabilization of numerous hazardous substances. The resulting glasses have proven to be durable enough for direct land disposal. In many cases, the stabilized forms have been deemed suitable for re-use in other applications. As recycling and hazardous material treatment become even more important in the global materials cycle, it is a certainty that glass will assume a prominent role.

MARRA, JAMES

2004-11-01

423

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

424

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

425

The rheology of solid glass  

NASA Astrophysics Data System (ADS)

As the glass transition is approached from the high temperature side, viewed as a liquid, the properties of the ever more viscous supercooled liquid are continuous functions of temperature and pressure. The point at which we decide to classify the fluid as a solid is therefore subjective. This subjective decision does, however, have discontinuous consequences for how we determine the rheological properties of the glass. We apply the recently discovered relaxation theorem to the time independent, nondissipative, nonergodic glassy state to derive an expression for the phase space distribution of an ensemble of glass samples. This distribution is then used to construct a time dependent linear response theory for aged glassy solids. The theory is verified using molecular dynamics simulations of oscillatory shear for a realistic model glass former with excellent agreement being obtained between the response theory calculations and direct nonequilibrium molecular dynamics calculations. Our numerical results confirm that unlike all the fluid states, including supercooled liquids, a solid glass (in common with crystalline states) has a nonzero value for the zero frequency shear modulus. Of all the states of matter, a supercooled fluid approaching the glass transition has the highest value for the limiting zero frequency shear viscosity. Finally, solid glasses like dilute gases and crystals have a positive temperature coefficient for the shear viscosity whereas supercooled and normal liquids have a negative temperature coefficient.

Williams, Stephen R.; Evans, Denis J.

2010-05-01

426

Chemical properties of metallic glasses  

SciTech Connect

Research into chemical properties of metallic glasses has revealed promising behavior in the areas of corosion resistance and catalysis. Metallic glasses containing a film-forming element exhibit resistance to uniform and localized corrosion that is superior to that of many crystalline stainless steels. This resistance is due to the presence of passive films that are enriched in the film-forming element. Cr is particularly effective, especially if P is present as in transition metal-Cr-P glasses. Protective coatings are an obvious application of metallic glasses. Metallic glasses also show promise as catalysts and electrocatalysts. Some glasses containing Pd and P offer better reactivity and resistance to corrosion than crystalline noble elements for electrolytic chlorine production. Others have demonstrated an ability as catalysts to oxidize methanol for fuel cell application, and also for hydrogenation of carbon monoxide. The very uniform structure and unique meta-stable compositions characteristic of metallic glasses are keys to understanding the chemical behavior of this exciting class of materials.

Diegle, R.B.

1983-01-01

427

HIGH-LEVEL WASTE GLASS FORMULATION MODEL SENSITIVITY STUDY 2009 GLASS FORMULATION MODEL VERSUS 1996 GLASS FORMULATION MODEL  

Microsoft Academic Search

This document presents the differences between two HLW glass formulation models (GFM): The 1996 GFM and 2009 GFM. A glass formulation model is a collection of glass property correlations and associated limits, as well as model validity and solubility constraints; it uses the pretreated HLW feed composition to predict the amount and composition of glass forming additives necessary to produce

BELSHER JD; MEINERT FL

2009-01-01

428

GLASS COMPOSITION-TCLP RESPONSE MODEL FOR WASTE GLASSES  

SciTech Connect

A first-order property model for normalized Toxicity Characteristic Leaching Procedure (TCLP) release as a function of glass composition was developed using data collected from various studies. The normalized boron release is used to estimate the release of toxic elements based on the observation that the boron release represents the conservative release for those constituents of interest. The current TCLP model has two targeted application areas: (1) delisting of waste-glass product as radioactive (not mixed) waste and (2) designating the glass wastes generated from waste-glass research activities as hazardous or non-hazardous. This paper describes the data collection and model development for TCLP releases and discusses the issues related to the application of the model.

Kim, Dong-Sang; Vienna, John D.

2004-01-01

429

Glass enamel and glass-ceramic coatings for chemical apparatus  

SciTech Connect

Among the known anticorrosion coatings used in chemical engineering, glass enamel base coatings are distinguished by such advantages as a high degree of continuity and chemical resistance. The paper describes basic principles for the creation of acid and alkali resistant glass enamel and ceramic coatings for chemical apparatus. As the result of investgations, glass enamel coatings with increased electrical conductivity and also experimental production compositions of chemical, temperature and radiation resistant coatings for protection of chemical equipment of 12Kh18N10T stainless steel have been developed. The coatings have successfully passed testing under service conditions. A new type of coating is short-term glass enamel, which may be recommended for use in chemical machinery manufacturing and other branches of industry in oxidation-free heating and forming of stainless steels.

Es'kov, A.S.; Oleinik, M.I.; Shabrova, E.A.

1984-05-01

430

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

431

Glass Elasticity from Particle Trajectories  

NASA Astrophysics Data System (ADS)

Using positional data from video microscopy of a two-dimensional colloidal system and from simulations of hard disks, we determine the wave-vector-dependent elastic dispersion relations in glass. The emergence of rigidity based on the existence of a well defined displacement field in amorphous solids is demonstrated. Continuum elastic theory is recovered in the limit of long wavelengths which provides the glass elastic shear and bulk modulus as a function of temperature. The onset of a finite static shear modulus upon cooling marks the fluid-glass transition in an intuitive and unique way.

Klix, Christian L.; Ebert, Florian; Weysser, Fabian; Fuchs, Matthias; Maret, Georg; Keim, Peter

2012-10-01

432

Fermionic quantum spin glass transitions  

NASA Astrophysics Data System (ADS)

This article reviews recent progress of the analytical theory of quantum spin glasses (QSG). Exact results for infinite range and one loop renormalisation group calculations for finite range models of either insulating or metallic type are presented. We describe characteristics of fermionic spin glass transitions and of fermionic correlations which are affected by these transitions and by spin glass order. Connections between tricritical thermal- and T=0 QSG transitions are described. A general phase diagram with tricritical QSG transitions caused either by random chemical potential or by elastic electron scattering, and implying discontinuous T=0-transitions in weak and in strong filling regimes, is also derived.

Oppermann, Reinhold; Rosenow, Bernd

433

Reaction rates in hydrophilic glass  

NASA Astrophysics Data System (ADS)

Sugar-based glasses are known to stabilize proteins against aggregation and chemical degradation. It has long been supposed that, due to the long timescales involved in protein aggregation and chemical degradation in the glass, relaxation processes essentially control the rate of degradation. We have shown that, although the degradation processes occur on timescales of the alpha relaxation process, secondary relaxation processes, and not alpha relaxation seems to dominate in influencing both chemical and physical degradation. In this presentation we will discuss results from time-resolved fluorescence studies in sugar-based glasses designed to help understand the physics underlying these puzzling observations.

Cicerone, Marcus; Zhong, Qin

2010-03-01

434

Studies on glass transition of lithium-iron phosphate glasses  

Microsoft Academic Search

Amorphous analogs of lithium-iron phosphates (LFP) were prepared by standard press-quenching method and their thermal stabilities\\u000a as well as structural properties were studied for the first time. Glass transition temperature T\\u000a g determined by DTA method was observed at the temperature range 492–523°C, depending on the glass composition. The maxima\\u000a of crystallization peaks were observed in the 555–579°C range. In

I. Gorzkowska; P. Jozwiak; J. E. Garbarczyk; M. Wasiucionek; C. M. Julien

2008-01-01

435

Glass composition dependence of Eu3+ polarization in oxide glasses  

Microsoft Academic Search

Eu3+-doped borate, silicate, and phosphate glasses were prepared by the melt-quenching method. Eu LIII-edge X-ray absorption spectra were measured to study the polarization of the Eu3+ ions in the glasses. The EXAFS analysis reveals that the nearest oxygen coordination number of the Eu3+ ions is 6, but the actual coordination number of Eu3+ ions is more than 6 with the

Noriyuki Wada; Kazuo Kojima; Kazuhiko Ozutsumi

436

Turning geothermal waste into glasses and glass ceramics  

SciTech Connect

Researchers investigating the waste on the pipes at the Cerro Prieto geothermal plant in Mexico found that it contained high amounts of silica. Initial tests showed that this waste silica had a high specific surface area, contained salts that could easily be eliminated, and resisted high temperatures effectively. Further research was done to see if this waste material could be used as silica sand in the production of glass. Testing of the waste material included the following: X-ray diffraction with nickel filters; EDX spectroscopy with ultrathin window; Differential thermal analysis; IR spectroscopy analysis; Electron microscope analysis. The tests were done on the raw material itself and on four sets of glass formulated from the raw material. Two sets of glass were formulated from untreated waste material, and two sets were formulated from treated waste material. The raw material was tested for purity, and the glass was tested for hardness, toughness, and transparency. As the tests show, the silica material from the Cerro Prieto plant steam pipes is not merely useless industrial waste. It is a reproducible source of silica sand that producers can use in ceramic and glass production. The initial tests show that the properties of the raw material, and those of the glass formulated from the raw material, will meet industry requirements.

Diaz, C. (Univ. Autonoma de Baja California, Tijuana, NM (United States)); Torres-Martinez, L.M.; Garza, L. (Univ. Autonoma de Nuevo Leon, Monterrey, NM (United States)); Avalos-Borja, M. (Univ. Autonoma de Mexico, Eusenada, Baja, NM (United States)); Rincon, J.M. (Instituto de Ceramica y Vidrio, Madrid (Spain))

1993-10-01

437

Comparison of Macedon and Darwin glass  

Microsoft Academic Search

Chemical analyses are presented for major and minor elements in two specimens of natural glass reported from Macedon, Victoria, and are compared with new analyses of glass from Mt. Darwin, Tasmania. One specimen of Macedon glass is dark, the other light; both are spongy with relatively large cavities of size uncommon in Darwin glass. Some of the new analyses of

Dean R. Chapman; Klaus Keil; Charles Annell

1967-01-01